From 2f1fc326d0e10a576927fb96fb15979478f1c80a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Mon, 25 Sep 2023 10:48:06 +0200
Subject: [PATCH 001/298] Towards 1.14.1.

---
 ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala | 2 +-
 project/Build.scala                                           | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala b/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala
index 245ca3eee9..4d7495cf96 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala
@@ -17,7 +17,7 @@ import java.util.concurrent.ConcurrentHashMap
 import scala.util.matching.Regex
 
 object ScalaJSVersions extends VersionChecks(
-    current = "1.14.0",
+    current = "1.14.1-SNAPSHOT",
     binaryEmitted = "1.13"
 )
 
diff --git a/project/Build.scala b/project/Build.scala
index 0e69559253..796bc8e4b7 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -338,7 +338,7 @@ object Build {
   val previousVersions = List("1.0.0", "1.0.1", "1.1.0", "1.1.1", "1.2.0",
       "1.3.0", "1.3.1", "1.4.0", "1.5.0", "1.5.1", "1.6.0", "1.7.0", "1.7.1",
       "1.8.0", "1.9.0", "1.10.0", "1.10.1", "1.11.0", "1.12.0", "1.13.0",
-      "1.13.1", "1.13.2")
+      "1.13.1", "1.13.2", "1.14.0")
   val previousVersion = previousVersions.last
 
   val previousBinaryCrossVersion = CrossVersion.binaryWith("sjs1_", "")

From 1982a6b631a5b37ebbd4fe61655a45ad9b62bf93 Mon Sep 17 00:00:00 2001
From: Tobias Schlatter <tobias@meisch.ch>
Date: Sat, 7 Oct 2023 22:08:03 +0200
Subject: [PATCH 002/298] Do not (ab)use blocks for top level trees

---
 .../linker/backend/emitter/ClassEmitter.scala | 122 ++--
 .../linker/backend/emitter/CoreJSLib.scala    | 524 +++++++++---------
 .../linker/backend/emitter/Emitter.scala      |  67 +--
 .../linker/backend/emitter/JSGen.scala        |   6 +-
 .../linker/backend/emitter/VarGen.scala       |  18 +-
 .../linker/backend/emitter/WithGlobals.scala  |  14 +-
 6 files changed, 356 insertions(+), 395 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
index 0c87bd53bf..be9fc9a993 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
@@ -45,23 +45,15 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
 
   def buildClass(className: ClassName, kind: ClassKind, jsClassCaptures: Option[List[ParamDef]],
       hasClassInitializer: Boolean,
-      superClass: Option[ClassIdent], jsSuperClass: Option[Tree], useESClass: Boolean, ctor: js.Tree,
+      superClass: Option[ClassIdent], jsSuperClass: Option[Tree], useESClass: Boolean, ctorDefs: List[js.Tree],
       memberDefs: List[js.MethodDef], exportedDefs: List[js.Tree])(
       implicit moduleContext: ModuleContext,
-      globalKnowledge: GlobalKnowledge, pos: Position): WithGlobals[js.Tree] = {
+      globalKnowledge: GlobalKnowledge, pos: Position): WithGlobals[List[js.Tree]] = {
 
-    def allES6Defs = {
-      js.Block(ctor +: (memberDefs ++ exportedDefs)) match {
-        case js.Block(allDefs) => allDefs
-        case js.Skip()         => Nil
-        case oneDef            => List(oneDef)
-      }
-    }
+    def allES6Defs = ctorDefs ::: memberDefs ::: exportedDefs
 
-    def allES5Defs(classVar: js.Tree) = {
-      WithGlobals(js.Block(
-          ctor, assignES5ClassMembers(classVar, memberDefs), js.Block(exportedDefs: _*)))
-    }
+    def allES5Defs(classVar: js.Tree) =
+      WithGlobals(ctorDefs ::: assignES5ClassMembers(classVar, memberDefs) ::: exportedDefs)
 
     if (!kind.isJSClass) {
       assert(jsSuperClass.isEmpty, className)
@@ -95,7 +87,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
 
       val entireClassDefWithGlobals = if (useESClass) {
         genJSSuperCtor(superClass, jsSuperClass).map { jsSuperClass =>
-          classValueVar := js.ClassDef(Some(classValueIdent), Some(jsSuperClass), allES6Defs)
+          List(classValueVar := js.ClassDef(Some(classValueIdent), Some(jsSuperClass), allES6Defs))
         }
       } else {
         allES5Defs(classValueVar)
@@ -106,7 +98,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
         entireClassDef <- entireClassDefWithGlobals
         createStaticFields <- genCreateStaticFieldsOfJSClass(className)
       } yield {
-        optStoreJSSuperClass.toList ::: entireClassDef :: createStaticFields
+        optStoreJSSuperClass.toList ::: entireClassDef ::: createStaticFields
       }
 
       jsClassCaptures.fold {
@@ -125,7 +117,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
           )
           createAccessor <- globalFunctionDef("a", className, Nil, None, body)
         } yield {
-          js.Block(createClassValueVar, createAccessor)
+          createClassValueVar :: createAccessor
         }
       } { jsClassCaptures =>
         val captureParamDefs = for (param <- jsClassCaptures) yield {
@@ -173,7 +165,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
   def genScalaClassConstructor(className: ClassName, superClass: Option[ClassIdent],
       useESClass: Boolean, initToInline: Option[MethodDef])(
       implicit moduleContext: ModuleContext,
-      globalKnowledge: GlobalKnowledge, pos: Position): WithGlobals[js.Tree] = {
+      globalKnowledge: GlobalKnowledge, pos: Position): WithGlobals[List[js.Tree]] = {
 
     assert(superClass.isDefined || className == ObjectClass,
         s"Class $className is missing a parent class")
@@ -192,9 +184,9 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
         }
 
         if (args.isEmpty && isTrivialCtorBody)
-          js.Skip()
+          Nil
         else
-          js.MethodDef(static = false, js.Ident("constructor"), args, restParam, body)
+          js.MethodDef(static = false, js.Ident("constructor"), args, restParam, body) :: Nil
       }
     } else {
       import TreeDSL._
@@ -203,13 +195,13 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
 
       val chainProtoWithGlobals = superClass match {
         case None =>
-          WithGlobals(js.Skip())
+          WithGlobals.nil
 
         case Some(_) if shouldExtendJSError(className, superClass) =>
           untrackedGlobalRef("Error").map(chainPrototypeWithLocalCtor(className, ctorVar, _))
 
         case Some(parentIdent) =>
-          WithGlobals(ctorVar.prototype := js.New(globalVar("h", parentIdent.name), Nil))
+          WithGlobals(List(ctorVar.prototype := js.New(globalVar("h", parentIdent.name), Nil)))
       }
 
       for {
@@ -220,17 +212,17 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
             globalFunctionDef("h", className, Nil, None, js.Skip())
         chainProto <- chainProtoWithGlobals
       } yield {
-        js.Block(
-            // Real constructor
-            js.DocComment("@constructor"),
-            realCtorDef,
-            chainProto,
-            genIdentBracketSelect(ctorVar.prototype, "constructor") := ctorVar,
-
-            // Inheritable constructor
-            js.DocComment("@constructor"),
-            inheritableCtorDef,
-            globalVar("h", className).prototype := ctorVar.prototype
+        (
+          // Real constructor
+          js.DocComment("@constructor") ::
+          realCtorDef :::
+          chainProto :::
+          (genIdentBracketSelect(ctorVar.prototype, "constructor") := ctorVar) ::
+
+          // Inheritable constructor
+          js.DocComment("@constructor") ::
+          inheritableCtorDef :::
+          (globalVar("h", className).prototype := ctorVar.prototype) :: Nil
         )
       }
     }
@@ -240,7 +232,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
   def genJSConstructor(className: ClassName, superClass: Option[ClassIdent],
       jsSuperClass: Option[Tree], useESClass: Boolean, jsConstructorDef: JSConstructorDef)(
       implicit moduleContext: ModuleContext,
-      globalKnowledge: GlobalKnowledge, pos: Position): WithGlobals[js.Tree] = {
+      globalKnowledge: GlobalKnowledge, pos: Position): WithGlobals[List[js.Tree]] = {
 
     val JSConstructorDef(_, params, restParam, body) = jsConstructorDef
     val ctorFunWithGlobals = desugarToFunction(className, params, restParam, body)
@@ -248,7 +240,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
     if (useESClass) {
       for (fun <- ctorFunWithGlobals) yield {
         js.MethodDef(static = false, js.Ident("constructor"),
-            fun.args, fun.restParam, fun.body)
+            fun.args, fun.restParam, fun.body) :: Nil
       }
     } else {
       for {
@@ -259,12 +251,10 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
 
         val ctorVar = fileLevelVar("b", genName(className))
 
-        js.Block(
-            js.DocComment("@constructor"),
-            ctorVar := ctorFun,
-            chainPrototypeWithLocalCtor(className, ctorVar, superCtor),
-            genIdentBracketSelect(ctorVar.prototype, "constructor") := ctorVar
-        )
+        js.DocComment("@constructor") ::
+        (ctorVar := ctorFun) ::
+        chainPrototypeWithLocalCtor(className, ctorVar, superCtor) :::
+        (genIdentBracketSelect(ctorVar.prototype, "constructor") := ctorVar) :: Nil
       }
     }
   }
@@ -348,12 +338,12 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
   }
 
   private def chainPrototypeWithLocalCtor(className: ClassName, ctorVar: js.Tree,
-      superCtor: js.Tree)(implicit pos: Position): js.Tree = {
+      superCtor: js.Tree)(implicit pos: Position): List[js.Tree] = {
     import TreeDSL._
 
     val dummyCtor = fileLevelVar("hh", genName(className))
 
-    js.Block(
+    List(
         js.DocComment("@constructor"),
         genConst(dummyCtor.ident, js.Function(false, Nil, None, js.Skip())),
         dummyCtor.prototype := superCtor.prototype,
@@ -396,7 +386,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
         globalVarDef("t", varScope, value, origName.orElse(name))
     }
 
-    WithGlobals.list(defs)
+    WithGlobals.flatten(defs)
   }
 
   /** Generates the creation of the private JS field defs for a JavaScript
@@ -424,7 +414,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
       }
     }
 
-    WithGlobals.list(defs)
+    WithGlobals.flatten(defs)
   }
 
   /** Generates the creation of the static fields for a JavaScript class. */
@@ -497,7 +487,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
 
   def genStaticLikeMethod(className: ClassName, method: MethodDef)(
       implicit moduleContext: ModuleContext,
-      globalKnowledge: GlobalKnowledge): WithGlobals[js.Tree] = {
+      globalKnowledge: GlobalKnowledge): WithGlobals[List[js.Tree]] = {
     val methodBody = method.body.getOrElse(
         throw new AssertionError("Cannot generate an abstract method"))
 
@@ -570,11 +560,11 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
   private def genJSProperty(className: ClassName, kind: ClassKind, useESClass: Boolean,
       property: JSPropertyDef)(
       implicit moduleContext: ModuleContext,
-      globalKnowledge: GlobalKnowledge): WithGlobals[js.Tree] = {
+      globalKnowledge: GlobalKnowledge): WithGlobals[List[js.Tree]] = {
     if (useESClass)
       genJSPropertyES6(className, property)
     else
-      genJSPropertyES5(className, kind, property)
+      genJSPropertyES5(className, kind, property).map(_ :: Nil)
   }
 
   private def genJSPropertyES5(className: ClassName, kind: ClassKind, property: JSPropertyDef)(
@@ -612,31 +602,27 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
 
   private def genJSPropertyES6(className: ClassName, property: JSPropertyDef)(
       implicit moduleContext: ModuleContext,
-      globalKnowledge: GlobalKnowledge): WithGlobals[js.Tree] = {
+      globalKnowledge: GlobalKnowledge): WithGlobals[List[js.Tree]] = {
     implicit val pos = property.pos
 
     val static = property.flags.namespace.isStatic
 
     genMemberNameTree(property.name).flatMap { propName =>
-      val getterWithGlobals = property.getterBody.fold {
-        WithGlobals[js.Tree](js.Skip())
-      } { body =>
+      val getterWithGlobals = property.getterBody.map { body =>
         for (fun <- desugarToFunction(className, Nil, body, resultType = AnyType))
           yield js.GetterDef(static, propName, fun.body)
       }
 
-      val setterWithGlobals = property.setterArgAndBody.fold {
-        WithGlobals[js.Tree](js.Skip())
-      } { case (arg, body) =>
+      val setterWithGlobals = property.setterArgAndBody.map { case (arg, body) =>
         for (fun <- desugarToFunction(className, arg :: Nil, body, resultType = NoType))
           yield js.SetterDef(static, propName, fun.args.head, fun.body)
       }
 
       for {
-        getter <- getterWithGlobals
-        setter <- setterWithGlobals
+        getter <- WithGlobals.option(getterWithGlobals)
+        setter <- WithGlobals.option(setterWithGlobals)
       } yield {
-        js.Block(getter, setter)
+        getter.toList ::: setter.toList
       }
     }
   }
@@ -756,11 +742,11 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
       val createIsStatWithGlobals = if (needIsFunction) {
         globalFunctionDef("is", className, List(objParam), None, js.Return(isExpression))
       } else {
-        WithGlobals(js.Skip())
+        WithGlobals.nil
       }
 
       val createAsStatWithGlobals = if (semantics.asInstanceOfs == Unchecked) {
-        WithGlobals(js.Skip())
+        WithGlobals.nil
       } else {
         globalFunctionDef("as", className, List(objParam), None, js.Return {
           val isCond =
@@ -780,10 +766,10 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
         createIsStat <- createIsStatWithGlobals
         createAsStat <- createAsStatWithGlobals
       } yield {
-        List(createIsStat, createAsStat)
+        createIsStat ::: createAsStat
       }
     } else {
-      WithGlobals(Nil)
+      WithGlobals.nil
     }
   }
 
@@ -816,7 +802,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
     }
 
     val createAsArrayOfStatWithGlobals = if (semantics.asInstanceOfs == Unchecked) {
-      WithGlobals(js.Skip())
+      WithGlobals.nil
     } else {
       globalFunctionDef("asArrayOf", className, List(objParam, depthParam), None, {
         js.Return {
@@ -835,7 +821,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
       createIsArrayOfStat <- createIsArrayOfStatWithGlobals
       createAsArrayOfStat <- createAsArrayOfStatWithGlobals
     } yield {
-      List(createIsArrayOfStat, createAsArrayOfStat)
+      createIsArrayOfStat ::: createAsArrayOfStat
     }
   }
 
@@ -855,7 +841,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
       superClass: Option[ClassIdent], ancestors: List[ClassName],
       jsNativeLoadSpec: Option[JSNativeLoadSpec])(
       implicit moduleContext: ModuleContext,
-      globalKnowledge: GlobalKnowledge, pos: Position): WithGlobals[js.Tree] = {
+      globalKnowledge: GlobalKnowledge, pos: Position): WithGlobals[List[js.Tree]] = {
     import TreeDSL._
 
     val isObjectClass =
@@ -959,7 +945,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
 
   def genModuleAccessor(className: ClassName, kind: ClassKind)(
       implicit moduleContext: ModuleContext,
-      globalKnowledge: GlobalKnowledge, pos: Position): WithGlobals[js.Tree] = {
+      globalKnowledge: GlobalKnowledge, pos: Position): WithGlobals[List[js.Tree]] = {
     import TreeDSL._
 
     val tpe = ClassType(className)
@@ -1013,14 +999,14 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
       globalFunctionDef("m", className, Nil, None, body)
     }
 
-    createAccessor.map(js.Block(createModuleInstanceField, _))
+    createAccessor.map(createModuleInstanceField :: _)
   }
 
   def genExportedMember(className: ClassName, kind: ClassKind, useESClass: Boolean, member: JSMethodPropDef)(
       implicit moduleContext: ModuleContext,
-      globalKnowledge: GlobalKnowledge): WithGlobals[js.Tree] = {
+      globalKnowledge: GlobalKnowledge): WithGlobals[List[js.Tree]] = {
     member match {
-      case m: JSMethodDef   => genJSMethod(className, kind, useESClass, m)
+      case m: JSMethodDef   => genJSMethod(className, kind, useESClass, m).map(_ :: Nil)
       case p: JSPropertyDef => genJSProperty(className, kind, useESClass, p)
     }
   }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
index 7abc4b2396..790ccfab2f 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
@@ -53,9 +53,9 @@ private[emitter] object CoreJSLib {
    *      These must have class definitions (but not static fields) available.
    */
   final class Lib private[CoreJSLib] (
-      val preObjectDefinitions: Tree,
-      val postObjectDefinitions: Tree,
-      val initialization: Tree)
+      val preObjectDefinitions: List[Tree],
+      val postObjectDefinitions: List[Tree],
+      val initialization: List[Tree])
 
   private class CoreJSLibBuilder(sjsGen: SJSGen)(
       implicit moduleContext: ModuleContext, globalKnowledge: GlobalKnowledge) {
@@ -121,36 +121,36 @@ private[emitter] object CoreJSLib {
       WithGlobals(lib, trackedGlobalRefs)
     }
 
-    private def buildPreObjectDefinitions(): Tree = Block(
-      defineLinkingInfo(),
-      defineJSBuiltinsSnapshotsAndPolyfills(),
-      declareCachedL0(),
-      definePropertyName(),
-      defineCharClass(),
-      defineRuntimeFunctions(),
-      defineObjectGetClassFunctions(),
-      defineDispatchFunctions(),
-      defineArithmeticOps(),
-      defineES2015LikeHelpers(),
-      defineModuleHelpers(),
-      defineIntrinsics(),
-      defineIsPrimitiveFunctions(),
+    private def buildPreObjectDefinitions(): List[Tree] = {
+      defineLinkingInfo() :::
+      defineJSBuiltinsSnapshotsAndPolyfills() :::
+      declareCachedL0() :::
+      definePropertyName() :::
+      defineCharClass() :::
+      defineRuntimeFunctions() :::
+      defineObjectGetClassFunctions() :::
+      defineDispatchFunctions() :::
+      defineArithmeticOps() :::
+      defineES2015LikeHelpers() :::
+      defineModuleHelpers() :::
+      defineIntrinsics() :::
+      defineIsPrimitiveFunctions() :::
       defineBoxFunctions()
-    )
+    }
 
-    private def buildPostObjectDefinitions(): Tree = Block(
-      defineSpecializedArrayClasses(),
-      defineTypeDataClass(),
-      defineSpecializedIsArrayOfFunctions(),
-      defineSpecializedAsArrayOfFunctions(),
+    private def buildPostObjectDefinitions(): List[Tree] = {
+      defineSpecializedArrayClasses() :::
+      defineTypeDataClass() :::
+      defineSpecializedIsArrayOfFunctions() :::
+      defineSpecializedAsArrayOfFunctions() :::
       defineSpecializedTypeDatas()
-    )
+    }
 
-    private def buildInitializations(): Tree = Block(
+    private def buildInitializations(): List[Tree] = {
       assignCachedL0()
-    )
+    }
 
-    private def defineLinkingInfo(): Tree = {
+    private def defineLinkingInfo(): List[Tree] = {
       // must be in sync with scala.scalajs.runtime.LinkingInfo
 
       def objectFreeze(tree: Tree): Tree =
@@ -167,7 +167,7 @@ private[emitter] object CoreJSLib {
       extractWithGlobals(globalVarDef("linkingInfo", CoreVar, linkingInfo))
     }
 
-    private def defineJSBuiltinsSnapshotsAndPolyfills(): Tree = {
+    private def defineJSBuiltinsSnapshotsAndPolyfills(): List[Tree] = {
       def genPolyfillFor(builtin: PolyfillableBuiltin): Tree = builtin match {
         case ObjectIsBuiltin =>
           val x = varRef("x")
@@ -491,10 +491,7 @@ private[emitter] object CoreJSLib {
           Apply(funGenerator, Nil)
       }
 
-      val polyfillDefs = for {
-        builtin <- PolyfillableBuiltin.All
-        if esVersion < builtin.availableInESVersion
-      } yield {
+      PolyfillableBuiltin.All.withFilter(esVersion < _.availableInESVersion).flatMap { builtin =>
         val polyfill = genPolyfillFor(builtin)
         val rhs = builtin match {
           case builtin: GlobalVarBuiltin =>
@@ -508,24 +505,23 @@ private[emitter] object CoreJSLib {
         }
         extractWithGlobals(globalVarDef(builtin.builtinName, CoreVar, rhs))
       }
-      Block(polyfillDefs)
     }
 
-    private def declareCachedL0(): Tree = {
-      condTree(!allowBigIntsForLongs)(
+    private def declareCachedL0(): List[Tree] = {
+      condDefs(!allowBigIntsForLongs)(
         extractWithGlobals(globalVarDecl("L0", CoreVar))
       )
     }
 
-    private def assignCachedL0(): Tree = {
-      condTree(!allowBigIntsForLongs)(Block(
+    private def assignCachedL0(): List[Tree] = {
+      condDefs(!allowBigIntsForLongs)(List(
         globalVar("L0", CoreVar) := genScalaClassNew(
             LongImpl.RuntimeLongClass, LongImpl.initFromParts, 0, 0),
         genClassDataOf(LongRef) DOT "zero" := globalVar("L0", CoreVar)
       ))
     }
 
-    private def definePropertyName(): Tree = {
+    private def definePropertyName(): List[Tree] = {
       /* Encodes a property name for runtime manipulation.
        *
        * Usage:
@@ -542,7 +538,7 @@ private[emitter] object CoreJSLib {
       }
     }
 
-    private def defineCharClass(): Tree = {
+    private def defineCharClass(): List[Tree] = {
       val ctor = {
         val c = varRef("c")
         MethodDef(static = false, Ident("constructor"), paramList(c), None, {
@@ -560,15 +556,13 @@ private[emitter] object CoreJSLib {
       if (useClassesForRegularClasses) {
         extractWithGlobals(globalClassDef("Char", CoreVar, None, ctor :: toStr :: Nil))
       } else {
-        Block(
-          defineFunction("Char", ctor.args, ctor.body),
-          assignES5ClassMembers(globalVar("Char", CoreVar), List(toStr))
-        )
+        defineFunction("Char", ctor.args, ctor.body) :::
+        assignES5ClassMembers(globalVar("Char", CoreVar), List(toStr))
       }
     }
 
-    private def defineRuntimeFunctions(): Tree = Block(
-      condTree(asInstanceOfs != CheckedBehavior.Unchecked || arrayStores != CheckedBehavior.Unchecked)(
+    private def defineRuntimeFunctions(): List[Tree] = (
+      condDefs(asInstanceOfs != CheckedBehavior.Unchecked || arrayStores != CheckedBehavior.Unchecked)(
         /* Returns a safe string description of a value.
          * This helper is never called for `value === null`. As implemented,
          * it would return `"object"` if it were.
@@ -604,15 +598,15 @@ private[emitter] object CoreJSLib {
             })
           }
         }
-      ),
+      ) :::
 
-      condTree(asInstanceOfs != CheckedBehavior.Unchecked)(Block(
+      condDefs(asInstanceOfs != CheckedBehavior.Unchecked)(
         defineFunction2("throwClassCastException") { (instance, classFullName) =>
           Throw(maybeWrapInUBE(asInstanceOfs, {
             genScalaClassNew(ClassCastExceptionClass, StringArgConstructorName,
                 genCallHelper("valueDescription", instance) + str(" cannot be cast to ") + classFullName)
           }))
-        },
+        } :::
 
         defineFunction3("throwArrayCastException") { (instance, classArrayEncodedName, depth) =>
           Block(
@@ -622,9 +616,9 @@ private[emitter] object CoreJSLib {
               genCallHelper("throwClassCastException", instance, classArrayEncodedName)
           )
         }
-      )),
+      ) :::
 
-      condTree(arrayIndexOutOfBounds != CheckedBehavior.Unchecked)(
+      condDefs(arrayIndexOutOfBounds != CheckedBehavior.Unchecked)(
         defineFunction1("throwArrayIndexOutOfBoundsException") { i =>
           Throw(maybeWrapInUBE(arrayIndexOutOfBounds, {
             genScalaClassNew(ArrayIndexOutOfBoundsExceptionClass,
@@ -632,9 +626,9 @@ private[emitter] object CoreJSLib {
                 If(i === Null(), Null(), str("") + i))
           }))
         }
-      ),
+      ) :::
 
-      condTree(arrayStores != CheckedBehavior.Unchecked)(
+      condDefs(arrayStores != CheckedBehavior.Unchecked)(
         defineFunction1("throwArrayStoreException") { v =>
           Throw(maybeWrapInUBE(arrayStores, {
             genScalaClassNew(ArrayStoreExceptionClass,
@@ -642,31 +636,31 @@ private[emitter] object CoreJSLib {
                 If(v === Null(), Null(), genCallHelper("valueDescription", v)))
           }))
         }
-      ),
+      ) :::
 
-      condTree(negativeArraySizes != CheckedBehavior.Unchecked)(
+      condDefs(negativeArraySizes != CheckedBehavior.Unchecked)(
         defineFunction0("throwNegativeArraySizeException") {
           Throw(maybeWrapInUBE(negativeArraySizes, {
             genScalaClassNew(NegativeArraySizeExceptionClass,
                 NoArgConstructorName)
           }))
         }
-      ),
+      ) :::
 
-      condTree(moduleInit == CheckedBehavior.Fatal)(
+      condDefs(moduleInit == CheckedBehavior.Fatal)(
         defineFunction1("throwModuleInitError") { name =>
           Throw(genScalaClassNew(UndefinedBehaviorErrorClass,
               StringArgConstructorName, str("Initializer of ") + name +
               str(" called before completion of its super constructor")))
         }
-      ),
+      ) :::
 
-      condTree(nullPointers != CheckedBehavior.Unchecked)(Block(
+      condDefs(nullPointers != CheckedBehavior.Unchecked)(
         defineFunction0("throwNullPointerException") {
           Throw(maybeWrapInUBE(nullPointers, {
             genScalaClassNew(NullPointerExceptionClass, NoArgConstructorName)
           }))
-        },
+        } :::
 
         // "checkNotNull", but with a very short name
         defineFunction1("n") { x =>
@@ -675,16 +669,16 @@ private[emitter] object CoreJSLib {
             Return(x)
           )
         }
-      )),
+      ) :::
 
       defineFunction1("noIsInstance") { instance =>
         Throw(New(TypeErrorRef,
             str("Cannot call isInstance() on a Class representing a JS trait/object") :: Nil))
-      },
+      } :::
 
       defineFunction2("newArrayObject") { (arrayClassData, lengths) =>
         Return(genCallHelper("newArrayObjectInternal", arrayClassData, lengths, int(0)))
-      },
+      } :::
 
       defineFunction3("newArrayObjectInternal") { (arrayClassData, lengths, lengthIndex) =>
         val result = varRef("result")
@@ -707,7 +701,7 @@ private[emitter] object CoreJSLib {
           )),
           Return(result)
         )
-      },
+      } :::
 
       defineFunction1("objectClone") { instance =>
         // return Object.create(Object.getPrototypeOf(instance), $getOwnPropertyDescriptors(instance));
@@ -716,7 +710,7 @@ private[emitter] object CoreJSLib {
         Return(Apply(genIdentBracketSelect(ObjectRef, "create"), List(
             Apply(genIdentBracketSelect(ObjectRef, "getPrototypeOf"), instance :: Nil),
             callGetOwnPropertyDescriptors)))
-      },
+      } :::
 
       defineFunction1("objectOrArrayClone") { instance =>
         // return instance.$classData.isArrayClass ? instance.clone__O() : $objectClone(instance);
@@ -726,12 +720,12 @@ private[emitter] object CoreJSLib {
       }
     )
 
-    private def defineObjectGetClassFunctions(): Tree = {
+    private def defineObjectGetClassFunctions(): List[Tree] = {
       // objectGetClass and objectClassName
 
       def defineObjectGetClassBasedFun(name: String,
           constantClassResult: ClassName => Tree,
-          scalaObjectResult: VarRef => Tree, jsObjectResult: Tree): Tree = {
+          scalaObjectResult: VarRef => Tree, jsObjectResult: Tree): List[Tree] = {
         defineFunction1(name) { instance =>
           Switch(typeof(instance), List(
               str("string") -> {
@@ -794,44 +788,41 @@ private[emitter] object CoreJSLib {
       }
 
 
-      Block(
-        /* We use isClassClassInstantiated as an over-approximation of whether
-         * the program contains any `GetClass` node. If `j.l.Class` is not
-         * instantiated, then we know that there is no `GetClass` node, and it is
-         * safe to omit the definition of `objectGetClass`. However, it is
-         * possible that we generate `objectGetClass` even if it is not
-         * necessary, in the case that `j.l.Class` is otherwise instantiated
-         * (i.e., through a `ClassOf` node).
-         */
-        condTree(globalKnowledge.isClassClassInstantiated)(
-          defineObjectGetClassBasedFun("objectGetClass",
-              className => genClassOf(className),
-              instance => Apply(instance DOT classData DOT "getClassOf", Nil),
-              Null()
-          )
-        ),
-
-        defineObjectGetClassBasedFun("objectClassName",
-            { className =>
-              StringLiteral(RuntimeClassNameMapperImpl.map(
-                  semantics.runtimeClassNameMapper, className.nameString))
-            },
-            instance => genIdentBracketSelect(instance DOT classData, "name"),
-            {
-              if (nullPointers == CheckedBehavior.Unchecked)
-                Apply(Null() DOT genName(getNameMethodName), Nil)
-              else
-                genCallHelper("throwNullPointerException")
-            }
+      /* We use isClassClassInstantiated as an over-approximation of whether
+       * the program contains any `GetClass` node. If `j.l.Class` is not
+       * instantiated, then we know that there is no `GetClass` node, and it is
+       * safe to omit the definition of `objectGetClass`. However, it is
+       * possible that we generate `objectGetClass` even if it is not
+       * necessary, in the case that `j.l.Class` is otherwise instantiated
+       * (i.e., through a `ClassOf` node).
+       */
+      condDefs(globalKnowledge.isClassClassInstantiated)(
+        defineObjectGetClassBasedFun("objectGetClass",
+            className => genClassOf(className),
+            instance => Apply(instance DOT classData DOT "getClassOf", Nil),
+            Null()
         )
+      ) :::
+      defineObjectGetClassBasedFun("objectClassName",
+          { className =>
+            StringLiteral(RuntimeClassNameMapperImpl.map(
+                semantics.runtimeClassNameMapper, className.nameString))
+          },
+          instance => genIdentBracketSelect(instance DOT classData, "name"),
+          {
+            if (nullPointers == CheckedBehavior.Unchecked)
+              Apply(Null() DOT genName(getNameMethodName), Nil)
+            else
+              genCallHelper("throwNullPointerException")
+          }
       )
     }
 
-    private def defineDispatchFunctions(): Tree = {
+    private def defineDispatchFunctions(): List[Tree] = {
       val instance = varRef("instance")
 
       def defineDispatcher(methodName: MethodName, args: List[VarRef],
-          body: Tree): Tree = {
+          body: Tree): List[Tree] = {
         defineFunction("dp_" + genName(methodName),
             paramList((instance :: args): _*), body)
       }
@@ -844,7 +835,7 @@ private[emitter] object CoreJSLib {
        * - The implementation in java.lang.Object (if this is a JS object).
        */
       def defineStandardDispatcher(methodName: MethodName,
-          implementingClasses: Set[ClassName]): Tree = {
+          implementingClasses: Set[ClassName]): List[Tree] = {
 
         val args =
           methodName.paramTypeRefs.indices.map(i => varRef("x" + i)).toList
@@ -915,9 +906,7 @@ private[emitter] object CoreJSLib {
       val methodsInRepresentativeClasses =
         globalKnowledge.methodsInRepresentativeClasses()
 
-      val dispatchers = for {
-        (methodName, implementingClasses) <- methodsInRepresentativeClasses
-      } yield {
+      methodsInRepresentativeClasses.flatMap { case (methodName, implementingClasses) =>
         if (methodName == toStringMethodName) {
           // toString()java.lang.String is special as per IR spec.
           defineDispatcher(toStringMethodName, Nil, {
@@ -929,11 +918,9 @@ private[emitter] object CoreJSLib {
           defineStandardDispatcher(methodName, implementingClasses)
         }
       }
-
-      Block(dispatchers)
     }
 
-    private def defineArithmeticOps(): Tree = {
+    private def defineArithmeticOps(): List[Tree] = {
       val throwDivByZero = {
         Throw(genScalaClassNew(ArithmeticExceptionClass,
             StringArgConstructorName, str("/ by zero")))
@@ -942,91 +929,85 @@ private[emitter] object CoreJSLib {
       def wrapBigInt64(tree: Tree): Tree =
         Apply(genIdentBracketSelect(BigIntRef, "asIntN"), 64 :: tree :: Nil)
 
-      Block(
-        defineFunction2("intDiv") { (x, y) =>
-          If(y === 0, throwDivByZero, {
-            Return((x / y) | 0)
-          })
-        },
-
-        defineFunction2("intMod") { (x, y) =>
-          If(y === 0, throwDivByZero, {
-            Return((x % y) | 0)
-          })
-        },
-
-        defineFunction1("doubleToInt") { x =>
-          Return(If(x > 2147483647, 2147483647, If(x < -2147483648, -2147483648, x | 0)))
-        },
-
-        condTree(semantics.stringIndexOutOfBounds != CheckedBehavior.Unchecked)(
-          defineFunction2("charAt") { (s, i) =>
-            val r = varRef("r")
-
-            val throwStringIndexOutOfBoundsException = {
-              Throw(maybeWrapInUBE(semantics.stringIndexOutOfBounds,
-                  genScalaClassNew(StringIndexOutOfBoundsExceptionClass, IntArgConstructorName, i)))
-            }
-
-            Block(
-              const(r, Apply(genIdentBracketSelect(s, "charCodeAt"), List(i))),
-              If(r !== r, throwStringIndexOutOfBoundsException, Return(r))
-            )
+      defineFunction2("intDiv") { (x, y) =>
+        If(y === 0, throwDivByZero, {
+          Return((x / y) | 0)
+        })
+      } :::
+      defineFunction2("intMod") { (x, y) =>
+        If(y === 0, throwDivByZero, {
+          Return((x % y) | 0)
+        })
+      } :::
+      defineFunction1("doubleToInt") { x =>
+        Return(If(x > 2147483647, 2147483647, If(x < -2147483648, -2147483648, x | 0)))
+      } :::
+      condDefs(semantics.stringIndexOutOfBounds != CheckedBehavior.Unchecked)(
+        defineFunction2("charAt") { (s, i) =>
+          val r = varRef("r")
+
+          val throwStringIndexOutOfBoundsException = {
+            Throw(maybeWrapInUBE(semantics.stringIndexOutOfBounds,
+                genScalaClassNew(StringIndexOutOfBoundsExceptionClass, IntArgConstructorName, i)))
           }
-        ),
 
-        condTree(allowBigIntsForLongs)(Block(
-          defineFunction2("longDiv") { (x, y) =>
-            If(y === bigInt(0), throwDivByZero, {
-              Return(wrapBigInt64(x / y))
-            })
-          },
-          defineFunction2("longMod") { (x, y) =>
-            If(y === bigInt(0), throwDivByZero, {
-              Return(wrapBigInt64(x % y))
-            })
-          },
+          Block(
+            const(r, Apply(genIdentBracketSelect(s, "charCodeAt"), List(i))),
+            If(r !== r, throwStringIndexOutOfBoundsException, Return(r))
+          )
+        }
+      ) :::
+      condDefs(allowBigIntsForLongs)(
+        defineFunction2("longDiv") { (x, y) =>
+          If(y === bigInt(0), throwDivByZero, {
+            Return(wrapBigInt64(x / y))
+          })
+        } :::
+        defineFunction2("longMod") { (x, y) =>
+          If(y === bigInt(0), throwDivByZero, {
+            Return(wrapBigInt64(x % y))
+          })
+        } :::
 
-          defineFunction1("doubleToLong")(x => Return {
-            If(x < double(-9223372036854775808.0), { // -2^63
-              bigInt(-9223372036854775808L)
+        defineFunction1("doubleToLong")(x => Return {
+          If(x < double(-9223372036854775808.0), { // -2^63
+            bigInt(-9223372036854775808L)
+          }, {
+            If (x >= double(9223372036854775808.0), { // 2^63
+              bigInt(9223372036854775807L)
             }, {
-              If (x >= double(9223372036854775808.0), { // 2^63
-                bigInt(9223372036854775807L)
+              If (x !== x, { // NaN
+                bigInt(0L)
               }, {
-                If (x !== x, { // NaN
-                  bigInt(0L)
-                }, {
-                  Apply(BigIntRef,
-                      Apply(genIdentBracketSelect(MathRef, "trunc"), x :: Nil) :: Nil)
-                })
+                Apply(BigIntRef,
+                    Apply(genIdentBracketSelect(MathRef, "trunc"), x :: Nil) :: Nil)
               })
             })
-          }),
+          })
+        }) :::
 
-          defineFunction1("longToFloat") { x =>
-            val abs = varRef("abs")
-            val y = varRef("y")
-            val absR = varRef("absR")
+        defineFunction1("longToFloat") { x =>
+          val abs = varRef("abs")
+          val y = varRef("y")
+          val absR = varRef("absR")
 
-            // See RuntimeLong.toFloat for the strategy
-            Block(
-              const(abs, If(x < bigInt(0L), -x, x)),
-              const(y, If(abs <= bigInt(1L << 53) || (abs & bigInt(0xffffL)) === bigInt(0L), {
-                abs
-              }, {
-                (abs & bigInt(~0xffffL)) | bigInt(0x8000L)
-              })),
-              const(absR, Apply(NumberRef, y :: Nil)),
-              Return(genCallPolyfillableBuiltin(FroundBuiltin, If(x < bigInt(0L), -absR, absR)))
-            )
-          }
-        ))
+          // See RuntimeLong.toFloat for the strategy
+          Block(
+            const(abs, If(x < bigInt(0L), -x, x)),
+            const(y, If(abs <= bigInt(1L << 53) || (abs & bigInt(0xffffL)) === bigInt(0L), {
+              abs
+            }, {
+              (abs & bigInt(~0xffffL)) | bigInt(0x8000L)
+            })),
+            const(absR, Apply(NumberRef, y :: Nil)),
+            Return(genCallPolyfillableBuiltin(FroundBuiltin, If(x < bigInt(0L), -absR, absR)))
+          )
+        }
       )
     }
 
-    private def defineES2015LikeHelpers(): Tree = Block(
-      condTree(esVersion < ESVersion.ES2015)(
+    private def defineES2015LikeHelpers(): List[Tree] = (
+      condDefs(esVersion < ESVersion.ES2015)(
         defineFunction2("newJSObjectWithVarargs") { (ctor, args) =>
           val instance = varRef("instance")
           val result = varRef("result")
@@ -1041,7 +1022,7 @@ private[emitter] object CoreJSLib {
                 Return(If(result === Null(), instance, result)))
           )
         }
-      ),
+      ) :::
 
       defineFunction2("resolveSuperRef") { (superClass, propName) =>
         val getPrototypeOf = varRef("getPrototypeOf")
@@ -1059,7 +1040,7 @@ private[emitter] object CoreJSLib {
             superProto := Apply(getPrototypeOf, superProto :: Nil)
           ))
         )
-      },
+      } :::
 
       defineFunction3("superGet") { (superClass, self, propName) =>
         val desc = varRef("desc")
@@ -1074,7 +1055,7 @@ private[emitter] object CoreJSLib {
                 genIdentBracketSelect(getter, "value")))
           ))
         )
-      },
+      } :::
 
       defineFunction4("superSet") { (superClass, self, propName, value) =>
         val desc = varRef("desc")
@@ -1095,8 +1076,8 @@ private[emitter] object CoreJSLib {
       }
     )
 
-    private def defineModuleHelpers(): Tree = {
-      condTree(moduleKind == ModuleKind.CommonJSModule)(
+    private def defineModuleHelpers(): List[Tree] = {
+      condDefs(moduleKind == ModuleKind.CommonJSModule)(
         defineFunction1("moduleDefault") { m =>
           Return(If(
               m && (typeof(m) === str("object")) && (str("default") in m),
@@ -1106,8 +1087,8 @@ private[emitter] object CoreJSLib {
       )
     }
 
-    private def defineIntrinsics(): Tree = Block(
-      condTree(arrayIndexOutOfBounds != CheckedBehavior.Unchecked)(
+    private def defineIntrinsics(): List[Tree] = (
+      condDefs(arrayIndexOutOfBounds != CheckedBehavior.Unchecked)(
         defineFunction5("arraycopyCheckBounds") { (srcLen, srcPos, destLen, destPos, length) =>
           If((srcPos < 0) || (destPos < 0) || (length < 0) ||
               (srcPos > ((srcLen - length) | 0)) ||
@@ -1115,7 +1096,7 @@ private[emitter] object CoreJSLib {
             genCallHelper("throwArrayIndexOutOfBoundsException", Null())
           })
         }
-      ),
+      ) :::
 
       defineFunction5("arraycopyGeneric") { (srcArray, srcPos, destArray, destPos, length) =>
         val i = varRef("i")
@@ -1136,20 +1117,20 @@ private[emitter] object CoreJSLib {
             })
           })
         )
-      },
+      } :::
 
-      condTree(esVersion < ESVersion.ES2015)(
+      condDefs(esVersion < ESVersion.ES2015)(
         defineFunction5("systemArraycopy") { (src, srcPos, dest, destPos, length) =>
           genCallHelper("arraycopyGeneric", src.u, srcPos, dest.u, destPos, length)
         }
-      ),
-      condTree(esVersion >= ESVersion.ES2015 && nullPointers != CheckedBehavior.Unchecked)(
+      ) :::
+      condDefs(esVersion >= ESVersion.ES2015 && nullPointers != CheckedBehavior.Unchecked)(
         defineFunction5("systemArraycopy") { (src, srcPos, dest, destPos, length) =>
           Apply(src DOT "copyTo", List(srcPos, dest, destPos, length))
         }
-      ),
+      ) :::
 
-      condTree(arrayStores != CheckedBehavior.Unchecked)(Block(
+      condDefs(arrayStores != CheckedBehavior.Unchecked)(
         defineFunction5("systemArraycopyRefs") { (src, srcPos, dest, destPos, length) =>
           If(Apply(genIdentBracketSelect(dest DOT classData, "isAssignableFrom"), List(src DOT classData)), {
             /* Fast-path, no need for array store checks. This always applies
@@ -1173,7 +1154,7 @@ private[emitter] object CoreJSLib {
               })
             )
           })
-        },
+        } :::
 
         defineFunction5("systemArraycopyFull") { (src, srcPos, dest, destPos, length) =>
           val ObjectArray = globalVar("ac", ObjectClass)
@@ -1201,7 +1182,7 @@ private[emitter] object CoreJSLib {
             })
           )
         }
-      )),
+      ) :::
 
       // systemIdentityHashCode
       locally {
@@ -1334,11 +1315,12 @@ private[emitter] object CoreJSLib {
           }
         }
 
-        Block(
+        List(
           let(lastIDHash, 0),
           const(idHashCodeMap,
               if (esVersion >= ESVersion.ES2015) New(WeakMapRef, Nil)
-              else If(typeof(WeakMapRef) !== str("undefined"), New(WeakMapRef, Nil), Null())),
+              else If(typeof(WeakMapRef) !== str("undefined"), New(WeakMapRef, Nil), Null()))
+        ) ::: (
           if (esVersion >= ESVersion.ES2015) {
             val f = weakMapBasedFunction
             defineFunction("systemIdentityHashCode", f.args, f.body)
@@ -1350,43 +1332,41 @@ private[emitter] object CoreJSLib {
       }
     )
 
-    private def defineIsPrimitiveFunctions(): Tree = {
-      def defineIsIntLike(name: String, specificTest: VarRef => Tree): Tree = {
+    private def defineIsPrimitiveFunctions(): List[Tree] = {
+      def defineIsIntLike(name: String, specificTest: VarRef => Tree): List[Tree] = {
         defineFunction1(name) { v =>
           Return((typeof(v) === str("number")) && specificTest(v) &&
               ((int(1) / v) !== (int(1) / double(-0.0))))
         }
       }
 
-      Block(
-        defineIsIntLike("isByte", v => (v << 24 >> 24) === v),
-        defineIsIntLike("isShort", v => (v << 16 >> 16) === v),
-        defineIsIntLike("isInt", v => (v | 0) === v),
-        condTree(allowBigIntsForLongs)(
-          defineFunction1("isLong") { v =>
-            Return((typeof(v) === str("bigint")) &&
-                (Apply(genIdentBracketSelect(BigIntRef, "asIntN"), int(64) :: v :: Nil) === v))
-          }
-        ),
-        condTree(strictFloats)(
-          defineFunction1("isFloat") { v =>
-            Return((typeof(v) === str("number")) &&
-                ((v !== v) || (genCallPolyfillableBuiltin(FroundBuiltin, v) === v)))
-          }
-        )
+      defineIsIntLike("isByte", v => (v << 24 >> 24) === v) :::
+      defineIsIntLike("isShort", v => (v << 16 >> 16) === v) :::
+      defineIsIntLike("isInt", v => (v | 0) === v) :::
+      condDefs(allowBigIntsForLongs)(
+        defineFunction1("isLong") { v =>
+          Return((typeof(v) === str("bigint")) &&
+              (Apply(genIdentBracketSelect(BigIntRef, "asIntN"), int(64) :: v :: Nil) === v))
+        }
+      ) :::
+      condDefs(strictFloats)(
+        defineFunction1("isFloat") { v =>
+          Return((typeof(v) === str("number")) &&
+              ((v !== v) || (genCallPolyfillableBuiltin(FroundBuiltin, v) === v)))
+        }
       )
     }
 
-    private def defineBoxFunctions(): Tree = Block(
+    private def defineBoxFunctions(): List[Tree] = (
       // Boxes for Chars
       defineFunction1("bC") { c =>
         Return(New(globalVar("Char", CoreVar), c :: Nil))
-      },
-      extractWithGlobals(globalVarDef("bC0", CoreVar, genCallHelper("bC", 0))),
-
+      } :::
+      extractWithGlobals(globalVarDef("bC0", CoreVar, genCallHelper("bC", 0)))
+    ) ::: (
       if (asInstanceOfs != CheckedBehavior.Unchecked) {
         // Unboxes for everything
-        def defineUnbox(name: String, boxedClassName: ClassName, resultExpr: VarRef => Tree): Tree = {
+        def defineUnbox(name: String, boxedClassName: ClassName, resultExpr: VarRef => Tree): List[Tree] = {
           val fullName = boxedClassName.nameString
           defineFunction1(name)(v => Return {
             If(genIsInstanceOfHijackedClass(v, boxedClassName) || (v === Null()),
@@ -1395,29 +1375,29 @@ private[emitter] object CoreJSLib {
           })
         }
 
-        Block(
-          defineUnbox("uV", BoxedUnitClass, _ => Undefined()),
-          defineUnbox("uZ", BoxedBooleanClass, v => !(!v)),
-          defineUnbox("uC", BoxedCharacterClass, v => If(v === Null(), 0, v DOT "c")),
-          defineUnbox("uB", BoxedByteClass, _ | 0),
-          defineUnbox("uS", BoxedShortClass, _ | 0),
-          defineUnbox("uI", BoxedIntegerClass, _ | 0),
-          defineUnbox("uJ", BoxedLongClass, v => If(v === Null(), genLongZero(), v)),
+        (
+          defineUnbox("uV", BoxedUnitClass, _ => Undefined()) :::
+          defineUnbox("uZ", BoxedBooleanClass, v => !(!v)) :::
+          defineUnbox("uC", BoxedCharacterClass, v => If(v === Null(), 0, v DOT "c")) :::
+          defineUnbox("uB", BoxedByteClass, _ | 0) :::
+          defineUnbox("uS", BoxedShortClass, _ | 0) :::
+          defineUnbox("uI", BoxedIntegerClass, _ | 0) :::
+          defineUnbox("uJ", BoxedLongClass, v => If(v === Null(), genLongZero(), v)) :::
 
           /* Since the type test ensures that v is either null or a float, we can
            * use + instead of fround.
            */
-          defineUnbox("uF", BoxedFloatClass, v => +v),
+          defineUnbox("uF", BoxedFloatClass, v => +v) :::
 
-          defineUnbox("uD", BoxedDoubleClass, v => +v),
+          defineUnbox("uD", BoxedDoubleClass, v => +v) :::
           defineUnbox("uT", BoxedStringClass, v => If(v === Null(), StringLiteral(""), v))
         )
       } else {
         // Unboxes for Chars and Longs
-        Block(
+        (
           defineFunction1("uC") { v =>
             Return(If(v === Null(), 0, v DOT "c"))
-          },
+          } :::
           defineFunction1("uJ") { v =>
             Return(If(v === Null(), genLongZero(), v))
           }
@@ -1430,8 +1410,8 @@ private[emitter] object CoreJSLib {
      *  Other array classes are created dynamically from their TypeData's
      *  `initArray` initializer, and extend the array class for `Object`.
      */
-    private def defineSpecializedArrayClasses(): Tree = Block(
-      for (componentTypeRef <- specializedArrayTypeRefs) yield {
+    private def defineSpecializedArrayClasses(): List[Tree] = {
+      specializedArrayTypeRefs.flatMap { componentTypeRef =>
         val ArrayClass = globalVar("ac", componentTypeRef)
 
         val isArrayOfObject = componentTypeRef == ClassRef(ObjectClass)
@@ -1527,27 +1507,25 @@ private[emitter] object CoreJSLib {
           extractWithGlobals(globalClassDef("ac", componentTypeRef,
               Some(globalVar("c", ObjectClass)), ctor :: members))
         } else {
-          val clsDef = Block(
+          val clsDef = {
             extractWithGlobals(globalFunctionDef("ac", componentTypeRef,
-                ctor.args, ctor.restParam, ctor.body)),
-            (ArrayClass.prototype := New(globalVar("h", ObjectClass), Nil)),
-            (ArrayClass.prototype DOT "constructor" := ArrayClass),
+                ctor.args, ctor.restParam, ctor.body)) :::
+            (ArrayClass.prototype := New(globalVar("h", ObjectClass), Nil)) ::
+            (ArrayClass.prototype DOT "constructor" := ArrayClass) ::
             assignES5ClassMembers(ArrayClass, members)
-          )
+          }
 
           componentTypeRef match {
             case _: ClassRef =>
-              Block(
-                clsDef,
-                extractWithGlobals(globalFunctionDef("ah", ObjectClass, Nil, None, Skip())),
-                (globalVar("ah", ObjectClass).prototype := ArrayClass.prototype)
-              )
+              clsDef :::
+              extractWithGlobals(globalFunctionDef("ah", ObjectClass, Nil, None, Skip())) :::
+              (globalVar("ah", ObjectClass).prototype := ArrayClass.prototype) :: Nil
             case _: PrimRef =>
               clsDef
           }
         }
       }
-    )
+    }
 
     private def genArrayClassConstructorBody(arg: VarRef,
         componentTypeRef: NonArrayTypeRef): Tree = {
@@ -1579,7 +1557,7 @@ private[emitter] object CoreJSLib {
       })
     }
 
-    private def defineTypeDataClass(): Tree = {
+    private def defineTypeDataClass(): List[Tree] = {
       def privateFieldSet(fieldName: String, value: Tree): Tree =
         This() DOT fieldName := value
 
@@ -1836,10 +1814,10 @@ private[emitter] object CoreJSLib {
                   ctor :: members)
             } else {
               Block(
-                  FunctionDef(ArrayClass.ident, ctor.args, ctor.restParam, ctor.body),
-                  ArrayClass.prototype := New(globalVar("ah", ObjectClass), Nil),
-                  ArrayClass.prototype DOT "constructor" := ArrayClass,
-                  assignES5ClassMembers(ArrayClass, members)
+                FunctionDef(ArrayClass.ident, ctor.args, ctor.restParam, ctor.body) ::
+                (ArrayClass.prototype := New(globalVar("ah", ObjectClass), Nil)) ::
+                (ArrayClass.prototype DOT "constructor" := ArrayClass) ::
+                assignES5ClassMembers(ArrayClass, members)
               )
             }
           }
@@ -1998,14 +1976,12 @@ private[emitter] object CoreJSLib {
       if (useClassesForRegularClasses) {
         extractWithGlobals(globalClassDef("TypeData", CoreVar, None, ctor :: members))
       } else {
-        Block(
-          defineFunction("TypeData", ctor.args, ctor.body),
-          assignES5ClassMembers(globalVar("TypeData", CoreVar), members)
-        )
+        defineFunction("TypeData", ctor.args, ctor.body) :::
+        assignES5ClassMembers(globalVar("TypeData", CoreVar), members)
       }
     }
 
-    private def defineSpecializedIsArrayOfFunctions(): Tree = {
+    private def defineSpecializedIsArrayOfFunctions(): List[Tree] = {
       // isArrayOf_O
       val obj = varRef("obj")
       val depth = varRef("depth")
@@ -2030,7 +2006,7 @@ private[emitter] object CoreJSLib {
         )
       }))
 
-      val forPrims = for (primRef <- orderedPrimRefsWithoutVoid) yield {
+      val forPrims = orderedPrimRefsWithoutVoid.flatMap { primRef =>
         val obj = varRef("obj")
         val depth = varRef("depth")
         extractWithGlobals(globalFunctionDef("isArrayOf", primRef, paramList(obj, depth), None, {
@@ -2040,12 +2016,12 @@ private[emitter] object CoreJSLib {
         }))
       }
 
-      Block(forObj :: forPrims)
+      forObj ::: forPrims
     }
 
-    private def defineSpecializedAsArrayOfFunctions(): Tree = {
-      condTree(asInstanceOfs != CheckedBehavior.Unchecked)(Block(
-        for (typeRef <- specializedArrayTypeRefs) yield {
+    private def defineSpecializedAsArrayOfFunctions(): List[Tree] = {
+      condDefs(asInstanceOfs != CheckedBehavior.Unchecked)(
+        specializedArrayTypeRefs.flatMap { typeRef =>
           val encodedName = typeRef match {
             case typeRef: PrimRef => typeRef.charCode.toString()
             case _                => "L" + ObjectClass.nameString + ";"
@@ -2061,10 +2037,10 @@ private[emitter] object CoreJSLib {
             })
           }))
         }
-      ))
+      )
     }
 
-    private def defineSpecializedTypeDatas(): Tree = {
+    private def defineSpecializedTypeDatas(): List[Tree] = {
       /* d_O must be first to correctly populate the parentData of array
        * classes. Unlike all other type datas, we assign the first of d_O
        * directly in the generated code, rather than through an `initXyz`
@@ -2087,9 +2063,9 @@ private[emitter] object CoreJSLib {
         def publicFieldSet(fieldName: String, value: Tree): Tree =
           genIdentBracketSelect(typeDataVar, fieldName) := value
 
-        Block(
-          extractWithGlobals(
-              globalVarDef("d", ObjectClass, New(globalVar("TypeData", CoreVar), Nil))),
+        extractWithGlobals(
+            globalVarDef("d", ObjectClass, New(globalVar("TypeData", CoreVar), Nil))) :::
+        List(
           privateFieldSet("ancestors", ObjectConstr(List((Ident(genName(ObjectClass)) -> 1)))),
           privateFieldSet("arrayEncodedName", str("L" + fullName + ";")),
           privateFieldSet("isAssignableFromFun", {
@@ -2122,7 +2098,7 @@ private[emitter] object CoreJSLib {
         )
       }
 
-      val prims = for (primRef <- orderedPrimRefs) yield {
+      val prims = orderedPrimRefs.flatMap { primRef =>
         /* Zero value, for use by the intrinsified code of
          * `scala.collection.mutable.ArrayBuilder.genericArrayBuilderResult`.
          * This code is Scala-specific, and "unboxes" `null` as the zero of
@@ -2153,38 +2129,38 @@ private[emitter] object CoreJSLib {
         }))
       }
 
-      Block(obj :: prims)
+      obj ::: prims
     }
 
-    private def defineFunction(name: String, args: List[ParamDef], body: Tree): Tree =
+    private def defineFunction(name: String, args: List[ParamDef], body: Tree): List[Tree] =
       extractWithGlobals(globalFunctionDef(name, CoreVar, args, None, body))
 
     private val argRefs = List.tabulate(5)(i => varRef("arg" + i))
 
-    private def defineFunction0(name: String)(body: Tree): Tree =
+    private def defineFunction0(name: String)(body: Tree): List[Tree] =
       defineFunction(name, Nil, body)
 
-    private def defineFunction1(name: String)(body: VarRef => Tree): Tree = {
+    private def defineFunction1(name: String)(body: VarRef => Tree): List[Tree] = {
       val a :: _ = argRefs
       defineFunction(name, paramList(a), body(a))
     }
 
-    private def defineFunction2(name: String)(body: (VarRef, VarRef) => Tree): Tree = {
+    private def defineFunction2(name: String)(body: (VarRef, VarRef) => Tree): List[Tree] = {
       val a :: b :: _ = argRefs
       defineFunction(name, paramList(a, b), body(a, b))
     }
 
-    private def defineFunction3(name: String)(body: (VarRef, VarRef, VarRef) => Tree): Tree = {
+    private def defineFunction3(name: String)(body: (VarRef, VarRef, VarRef) => Tree): List[Tree] = {
       val a :: b :: c :: _ = argRefs
       defineFunction(name, paramList(a, b, c), body(a, b, c))
     }
 
-    private def defineFunction4(name: String)(body: (VarRef, VarRef, VarRef, VarRef) => Tree): Tree = {
+    private def defineFunction4(name: String)(body: (VarRef, VarRef, VarRef, VarRef) => Tree): List[Tree] = {
       val a :: b :: c :: d :: _ = argRefs
       defineFunction(name, paramList(a, b, c, d), body(a, b, c, d))
     }
 
-    private def defineFunction5(name: String)(body: (VarRef, VarRef, VarRef, VarRef, VarRef) => Tree): Tree = {
+    private def defineFunction5(name: String)(body: (VarRef, VarRef, VarRef, VarRef, VarRef) => Tree): List[Tree] = {
       val a :: b :: c :: d :: e :: _ = argRefs
       defineFunction(name, paramList(a, b, c, d, e), body(a, b, c, d, e))
     }
@@ -2216,6 +2192,10 @@ private[emitter] object CoreJSLib {
       if (cond) tree
       else Skip()
 
+    private def condDefs(cond: Boolean)(trees: => List[Tree]): List[Tree] =
+      if (cond) trees
+      else Nil
+
     private def varRef(name: String): VarRef = VarRef(Ident(name))
 
     private def const(ref: VarRef, rhs: Tree): LocalDef =
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala
index 0c3babc589..d5b23e4525 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala
@@ -241,11 +241,11 @@ final class Emitter(config: Emitter.Config) {
          * requires consistency between the Analyzer and the Emitter. As such,
          * it is crucial that we verify it.
          */
-        val defTreesIterator: Iterator[js.Tree] = (
+        val defTrees: List[js.Tree] = (
             /* The definitions of the CoreJSLib that come before the definition
              * of `j.l.Object`. They depend on nothing else.
              */
-            coreJSLib.map(_.preObjectDefinitions).iterator ++
+            coreJSLib.iterator.flatMap(_.preObjectDefinitions) ++
 
             /* The definition of `j.l.Object` class. Unlike other classes, this
              * does not include its instance tests nor metadata.
@@ -257,7 +257,7 @@ final class Emitter(config: Emitter.Config) {
              * definitions of the array classes, as well as type data for
              * primitive types and for `j.l.Object`.
              */
-            coreJSLib.map(_.postObjectDefinitions).iterator ++
+            coreJSLib.iterator.flatMap(_.postObjectDefinitions) ++
 
             /* All class definitions, except `j.l.Object`, which depend on
              * nothing but their superclasses.
@@ -267,7 +267,7 @@ final class Emitter(config: Emitter.Config) {
             /* The initialization of the CoreJSLib, which depends on the
              * definition of classes (n.b. the RuntimeLong class).
              */
-            coreJSLib.map(_.initialization).iterator ++
+            coreJSLib.iterator.flatMap(_.initialization) ++
 
             /* All static field definitions, which depend on nothing, except
              * those of type Long which need $L0.
@@ -288,17 +288,7 @@ final class Emitter(config: Emitter.Config) {
 
             /* Module initializers, which by spec run at the end. */
             moduleInitializers.iterator
-        )
-
-        /* Flatten all the top-level js.Block's, because we temporarily use
-         * them to gather several top-level trees under a single `js.Tree`.
-         * TODO We should improve this in the future.
-         */
-        val defTrees: List[js.Tree] = defTreesIterator.flatMap {
-          case js.Block(stats) => stats
-          case js.Skip()       => Nil
-          case stat            => stat :: Nil
-        }.toList
+        ).toList
 
         // Make sure that there is at least one non-import definition.
         assert(!defTrees.isEmpty, {
@@ -391,9 +381,6 @@ final class Emitter(config: Emitter.Config) {
 
     val main = List.newBuilder[js.Tree]
 
-    def addToMain(treeWithGlobals: WithGlobals[js.Tree]): Unit =
-      main += extractWithGlobals(treeWithGlobals)
-
     val (linkedInlineableInit, linkedMethods) =
       classEmitter.extractInlineableInit(linkedClass)(classCache)
 
@@ -420,7 +407,7 @@ final class Emitter(config: Emitter.Config) {
         val methodCache =
           classCache.getStaticLikeMethodCache(namespace, methodDef.methodName)
 
-        addToMain(methodCache.getOrElseUpdate(methodDef.version,
+        main ++= extractWithGlobals(methodCache.getOrElseUpdate(methodDef.version,
             classEmitter.genStaticLikeMethod(className, methodDef)(moduleContext, methodCache)))
       }
     }
@@ -582,7 +569,7 @@ final class Emitter(config: Emitter.Config) {
               useESClass, // invalidated by class version (depends on kind, config and ancestry only)
               ctor, // invalidated directly
               memberMethods, // invalidated directly
-              exportedMembers // invalidated directly
+              exportedMembers.flatten // invalidated directly
             )(moduleContext, fullClassCache, linkedClass.pos) // pos invalidated by class version
           } yield {
             clazz
@@ -590,7 +577,7 @@ final class Emitter(config: Emitter.Config) {
         })
       }
 
-      addToMain(fullClass)
+      main ++= extractWithGlobals(fullClass)
     }
 
     if (className != ObjectClass) {
@@ -608,12 +595,12 @@ final class Emitter(config: Emitter.Config) {
        */
 
       if (classEmitter.needInstanceTests(linkedClass)(classCache)) {
-        addToMain(classTreeCache.instanceTests.getOrElseUpdate(
+        main += extractWithGlobals(classTreeCache.instanceTests.getOrElseUpdate(
             classEmitter.genInstanceTests(className, kind)(moduleContext, classCache, linkedClass.pos)))
       }
 
       if (linkedClass.hasRuntimeTypeInfo) {
-        addToMain(classTreeCache.typeData.getOrElseUpdate(
+        main ++= extractWithGlobals(classTreeCache.typeData.getOrElseUpdate(
             classEmitter.genTypeData(
               className, // invalidated by overall class cache (part of ancestors)
               kind, // invalidated by class version
@@ -630,7 +617,7 @@ final class Emitter(config: Emitter.Config) {
     }
 
     if (linkedClass.kind.hasModuleAccessor && linkedClass.hasInstances) {
-      addToMain(classTreeCache.moduleAccessor.getOrElseUpdate(
+      main ++= extractWithGlobals(classTreeCache.moduleAccessor.getOrElseUpdate(
           classEmitter.genModuleAccessor(className, kind)(moduleContext, classCache, linkedClass.pos)))
     }
 
@@ -772,15 +759,15 @@ final class Emitter(config: Emitter.Config) {
     private[this] var _cacheUsed = false
 
     private[this] val _methodCaches =
-      Array.fill(MemberNamespace.Count)(mutable.Map.empty[MethodName, MethodCache[js.Tree]])
+      Array.fill(MemberNamespace.Count)(mutable.Map.empty[MethodName, MethodCache[List[js.Tree]]])
 
     private[this] val _memberMethodCache =
       mutable.Map.empty[MethodName, MethodCache[js.MethodDef]]
 
-    private[this] var _constructorCache: Option[MethodCache[js.Tree]] = None
+    private[this] var _constructorCache: Option[MethodCache[List[js.Tree]]] = None
 
     private[this] val _exportedMembersCache =
-      mutable.Map.empty[Int, MethodCache[js.Tree]]
+      mutable.Map.empty[Int, MethodCache[List[js.Tree]]]
 
     private[this] var _fullClassCache: Option[FullClassCache] = None
 
@@ -820,20 +807,20 @@ final class Emitter(config: Emitter.Config) {
     }
 
     def getStaticLikeMethodCache(namespace: MemberNamespace,
-        methodName: MethodName): MethodCache[js.Tree] = {
+        methodName: MethodName): MethodCache[List[js.Tree]] = {
       _methodCaches(namespace.ordinal)
         .getOrElseUpdate(methodName, new MethodCache)
     }
 
-    def getConstructorCache(): MethodCache[js.Tree] = {
+    def getConstructorCache(): MethodCache[List[js.Tree]] = {
       _constructorCache.getOrElse {
-        val cache = new MethodCache[js.Tree]
+        val cache = new MethodCache[List[js.Tree]]
         _constructorCache = Some(cache)
         cache
       }
     }
 
-    def getExportedMemberCache(idx: Int): MethodCache[js.Tree] =
+    def getExportedMemberCache(idx: Int): MethodCache[List[js.Tree]] =
       _exportedMembersCache.getOrElseUpdate(idx, new MethodCache)
 
     def getFullClassCache(): FullClassCache = {
@@ -863,7 +850,7 @@ final class Emitter(config: Emitter.Config) {
     }
   }
 
-  private final class MethodCache[T <: js.Tree] extends knowledgeGuardian.KnowledgeAccessor {
+  private final class MethodCache[T] extends knowledgeGuardian.KnowledgeAccessor {
     private[this] var _tree: WithGlobals[T] = null
     private[this] var _lastVersion: Version = Version.Unversioned
     private[this] var _cacheUsed = false
@@ -899,11 +886,11 @@ final class Emitter(config: Emitter.Config) {
   }
 
   private class FullClassCache extends knowledgeGuardian.KnowledgeAccessor {
-    private[this] var _tree: WithGlobals[js.Tree] = null
+    private[this] var _tree: WithGlobals[List[js.Tree]] = null
     private[this] var _lastVersion: Version = Version.Unversioned
-    private[this] var _lastCtor: WithGlobals[js.Tree] = null
+    private[this] var _lastCtor: WithGlobals[List[js.Tree]] = null
     private[this] var _lastMemberMethods: List[WithGlobals[js.MethodDef]] = null
-    private[this] var _lastExportedMembers: List[WithGlobals[js.Tree]] = null
+    private[this] var _lastExportedMembers: List[WithGlobals[List[js.Tree]]] = null
     private[this] var _cacheUsed = false
 
     override def invalidate(): Unit = {
@@ -917,9 +904,9 @@ final class Emitter(config: Emitter.Config) {
 
     def startRun(): Unit = _cacheUsed = false
 
-    def getOrElseUpdate(version: Version, ctor: WithGlobals[js.Tree],
-        memberMethods: List[WithGlobals[js.MethodDef]], exportedMembers: List[WithGlobals[js.Tree]],
-        compute: => WithGlobals[js.Tree]): WithGlobals[js.Tree] = {
+    def getOrElseUpdate(version: Version, ctor: WithGlobals[List[js.Tree]],
+        memberMethods: List[WithGlobals[js.MethodDef]], exportedMembers: List[WithGlobals[List[js.Tree]]],
+        compute: => WithGlobals[List[js.Tree]]): WithGlobals[List[js.Tree]] = {
 
       @tailrec
       def allSame[A <: AnyRef](xs: List[A], ys: List[A]): Boolean = {
@@ -1049,9 +1036,9 @@ object Emitter {
   private final class DesugaredClassCache {
     val privateJSFields = new OneTimeCache[WithGlobals[List[js.Tree]]]
     val instanceTests = new OneTimeCache[WithGlobals[js.Tree]]
-    val typeData = new OneTimeCache[WithGlobals[js.Tree]]
+    val typeData = new OneTimeCache[WithGlobals[List[js.Tree]]]
     val setTypeData = new OneTimeCache[js.Tree]
-    val moduleAccessor = new OneTimeCache[WithGlobals[js.Tree]]
+    val moduleAccessor = new OneTimeCache[WithGlobals[List[js.Tree]]]
     val staticInitialization = new OneTimeCache[List[js.Tree]]
     val staticFields = new OneTimeCache[WithGlobals[List[js.Tree]]]
   }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/JSGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/JSGen.scala
index 6e3c9f22d9..c5e3aba380 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/JSGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/JSGen.scala
@@ -157,17 +157,15 @@ private[emitter] final class JSGen(val config: Emitter.Config) {
   }
 
   def assignES5ClassMembers(classRef: Tree, members: List[MethodDef])(
-      implicit pos: Position): Tree = {
+      implicit pos: Position): List[Tree] = {
     import TreeDSL._
 
-    val stats = for {
+    for {
       MethodDef(static, name, args, restParam, body) <- members
     } yield {
       val target = if (static) classRef else classRef.prototype
       genPropSelect(target, name) := Function(arrow = false, args, restParam, body)
     }
-
-    Block(stats)
   }
 
   def genIIFE(captures: List[(ParamDef, Tree)], body: Tree)(
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/VarGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/VarGen.scala
index 0ca1cd3deb..cff6305663 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/VarGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/VarGen.scala
@@ -54,7 +54,7 @@ private[emitter] final class VarGen(jsGen: JSGen, nameGen: NameGen,
   def globalClassDef[T: Scope](field: String, scope: T,
       parentClass: Option[Tree], members: List[Tree],
       origName: OriginalName = NoOriginalName)(
-      implicit moduleContext: ModuleContext, pos: Position): WithGlobals[Tree] = {
+      implicit moduleContext: ModuleContext, pos: Position): WithGlobals[List[Tree]] = {
     val ident = globalVarIdent(field, scope, origName)
     maybeExport(ident, ClassDef(Some(ident), parentClass, members), mutable = false)
   }
@@ -62,14 +62,14 @@ private[emitter] final class VarGen(jsGen: JSGen, nameGen: NameGen,
   def globalFunctionDef[T: Scope](field: String, scope: T,
       args: List[ParamDef], restParam: Option[ParamDef], body: Tree,
       origName: OriginalName = NoOriginalName)(
-      implicit moduleContext: ModuleContext, pos: Position): WithGlobals[Tree] = {
+      implicit moduleContext: ModuleContext, pos: Position): WithGlobals[List[Tree]] = {
     val ident = globalVarIdent(field, scope, origName)
     maybeExport(ident, FunctionDef(ident, args, restParam, body), mutable = false)
   }
 
   def globalVarDef[T: Scope](field: String, scope: T, value: Tree,
       origName: OriginalName = NoOriginalName)(
-      implicit moduleContext: ModuleContext, pos: Position): WithGlobals[Tree] = {
+      implicit moduleContext: ModuleContext, pos: Position): WithGlobals[List[Tree]] = {
     val ident = globalVarIdent(field, scope, origName)
     maybeExport(ident, genConst(ident, value), mutable = false)
   }
@@ -77,7 +77,7 @@ private[emitter] final class VarGen(jsGen: JSGen, nameGen: NameGen,
   /** Attention: A globalVarDecl may only be modified from the module it was declared in. */
   def globalVarDecl[T: Scope](field: String, scope: T,
       origName: OriginalName = NoOriginalName)(
-      implicit moduleContext: ModuleContext, pos: Position): WithGlobals[Tree] = {
+      implicit moduleContext: ModuleContext, pos: Position): WithGlobals[List[Tree]] = {
     val ident = globalVarIdent(field, scope, origName)
     maybeExport(ident, genEmptyMutableLet(ident), mutable = true)
   }
@@ -88,7 +88,7 @@ private[emitter] final class VarGen(jsGen: JSGen, nameGen: NameGen,
    */
   def globallyMutableVarDef[T: Scope](field: String, setterField: String,
       scope: T, value: Tree, origName: OriginalName = NoOriginalName)(
-      implicit moduleContext: ModuleContext, pos: Position): WithGlobals[Tree] = {
+      implicit moduleContext: ModuleContext, pos: Position): WithGlobals[List[Tree]] = {
     val ident = globalVarIdent(field, scope, origName)
     val varDef = genLet(ident, mutable = true, value)
 
@@ -102,7 +102,7 @@ private[emitter] final class VarGen(jsGen: JSGen, nameGen: NameGen,
       val exports =
         Export(genExportIdent(ident) :: genExportIdent(setterIdent) :: Nil)
 
-      WithGlobals(Block(varDef, setter, exports))
+      WithGlobals(List(varDef, setter, exports))
     } else {
       maybeExport(ident, varDef, mutable = true)
     }
@@ -269,9 +269,9 @@ private[emitter] final class VarGen(jsGen: JSGen, nameGen: NameGen,
   }
 
   private def maybeExport(ident: Ident, tree: Tree, mutable: Boolean)(
-      implicit moduleContext: ModuleContext, pos: Position): WithGlobals[Tree] = {
+      implicit moduleContext: ModuleContext, pos: Position): WithGlobals[List[Tree]] = {
     if (moduleContext.public) {
-      WithGlobals(tree)
+      WithGlobals(tree :: Nil)
     } else {
       val exportStat = config.moduleKind match {
         case ModuleKind.NoModule =>
@@ -299,7 +299,7 @@ private[emitter] final class VarGen(jsGen: JSGen, nameGen: NameGen,
           }
       }
 
-      exportStat.map(Block(tree, _))
+      exportStat.map(tree :: _ :: Nil)
     }
   }
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/WithGlobals.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/WithGlobals.scala
index 65b10a9ed1..6ff6b02544 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/WithGlobals.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/WithGlobals.scala
@@ -98,10 +98,20 @@ private[emitter] object WithGlobals {
      * efficient.
      */
     val values = xs.map(_.value)
-    val globalVarNames = xs.foldLeft(Set.empty[String]) { (prev, x) =>
+    val globalVarNames = collectNames(xs)
+    WithGlobals(values, globalVarNames)
+  }
+
+  def flatten[A](xs: List[WithGlobals[List[A]]]): WithGlobals[List[A]] = {
+    val values = xs.flatMap(_.value)
+    val globalVarNames = collectNames(xs)
+    WithGlobals(values, globalVarNames)
+  }
+
+  private def collectNames(xs: List[WithGlobals[_]]): Set[String] = {
+    xs.foldLeft(Set.empty[String]) { (prev, x) =>
       unionPreserveEmpty(prev, x.globalVarNames)
     }
-    WithGlobals(values, globalVarNames)
   }
 
   def option[A](xs: Option[WithGlobals[A]]): WithGlobals[Option[A]] =

From 6c214241f53ed2903fbccfedbbabbb609bab56cc Mon Sep 17 00:00:00 2001
From: Tobias Schlatter <tobias@meisch.ch>
Date: Sat, 14 Oct 2023 15:11:22 +0200
Subject: [PATCH 003/298] Create a VarGen scope for dispatchers

Dispatchers are the only place where we pass a dynamically computed
string to the VarGen subsystem.
---
 .../scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala | 4 ++--
 .../org/scalajs/linker/backend/emitter/FunctionEmitter.scala | 2 +-
 .../scala/org/scalajs/linker/backend/emitter/VarGen.scala    | 5 +++++
 3 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
index 790ccfab2f..d610e8cdb8 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
@@ -823,8 +823,8 @@ private[emitter] object CoreJSLib {
 
       def defineDispatcher(methodName: MethodName, args: List[VarRef],
           body: Tree): List[Tree] = {
-        defineFunction("dp_" + genName(methodName),
-            paramList((instance :: args): _*), body)
+        val params = paramList((instance :: args): _*)
+        extractWithGlobals(globalFunctionDef("dp", methodName, params, None, body))
       }
 
       /* A standard dispatcher performs a type test on the instance and then
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
index d0cd14d62c..fa7cb5ebb1 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
@@ -2247,7 +2247,7 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
             js.Apply(newReceiver(false) DOT transformMethodIdent(method), newArgs)
 
           def genDispatchApply(): js.Tree =
-            genCallHelper("dp_" + genName(methodName), newReceiver(false) :: newArgs: _*)
+            js.Apply(globalVar("dp", methodName), newReceiver(false) :: newArgs)
 
           def genHijackedMethodApply(className: ClassName): js.Tree =
             genApplyStaticLike("f", className, method, newReceiver(className == BoxedCharacterClass) :: newArgs)
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/VarGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/VarGen.scala
index cff6305663..a2a1a12153 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/VarGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/VarGen.scala
@@ -358,6 +358,11 @@ private[emitter] final class VarGen(jsGen: JSGen, nameGen: NameGen,
       def reprClass(x: (ClassName, MethodName)): ClassName = x._1
     }
 
+    implicit object DispatcherScope extends Scope[MethodName] {
+      def subField(x: MethodName): String = genName(x)
+      def reprClass(x: MethodName): ClassName = ObjectClass
+    }
+
     implicit object CoreJSLibScope extends Scope[CoreVar.type] {
       def subField(x: CoreVar.type): String = ""
       def reprClass(x: CoreVar.type): ClassName = ObjectClass

From 414b2cda3d7edfa065e4a0044e35dfb516d1a70d Mon Sep 17 00:00:00 2001
From: Tobias Schlatter <tobias@meisch.ch>
Date: Sun, 8 Oct 2023 18:02:10 +0200
Subject: [PATCH 004/298] Allocate all emitter var field strings statically

---
 .../linker/backend/emitter/ClassEmitter.scala | 108 +++----
 .../linker/backend/emitter/CoreJSLib.scala    | 284 +++++++++---------
 .../backend/emitter/FunctionEmitter.scala     |  80 ++---
 .../backend/emitter/PolyfillableBuiltin.scala |  22 +-
 .../linker/backend/emitter/SJSGen.scala       |  90 +++---
 .../linker/backend/emitter/VarField.scala     | 277 +++++++++++++++++
 .../linker/backend/emitter/VarGen.scala       |  42 +--
 7 files changed, 590 insertions(+), 313 deletions(-)
 create mode 100644 linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/VarField.scala

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
index be9fc9a993..0701d2fd84 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
@@ -62,14 +62,14 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
         val parentVarWithGlobals = for (parentIdent <- superClass) yield {
           implicit val pos = parentIdent.pos
           if (shouldExtendJSError(className, superClass)) untrackedGlobalRef("Error")
-          else WithGlobals(globalVar("c", parentIdent.name))
+          else WithGlobals(globalVar(VarField.c, parentIdent.name))
         }
 
         WithGlobals.option(parentVarWithGlobals).flatMap { parentVar =>
-          globalClassDef("c", className, parentVar, allES6Defs)
+          globalClassDef(VarField.c, className, parentVar, allES6Defs)
         }
       } else {
-        allES5Defs(globalVar("c", className))
+        allES5Defs(globalVar(VarField.c, className))
       }
     } else {
       // Wrap the entire class def in an accessor function
@@ -77,11 +77,11 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
 
       val genStoreJSSuperClass = jsSuperClass.map { jsSuperClass =>
         for (rhs <- desugarExpr(jsSuperClass, resultType = AnyType)) yield {
-          js.VarDef(fileLevelVar("superClass").ident, Some(rhs))
+          js.VarDef(fileLevelVar(VarField.superClass).ident, Some(rhs))
         }
       }
 
-      val classValueIdent = fileLevelVarIdent("b", genName(className))
+      val classValueIdent = fileLevelVarIdent(VarField.b, genName(className))
       val classValueVar = js.VarRef(classValueIdent)
       val createClassValueVar = genEmptyMutableLet(classValueIdent)
 
@@ -115,14 +115,14 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
               }),
               js.Return(classValueVar)
           )
-          createAccessor <- globalFunctionDef("a", className, Nil, None, body)
+          createAccessor <- globalFunctionDef(VarField.a, className, Nil, None, body)
         } yield {
           createClassValueVar :: createAccessor
         }
       } { jsClassCaptures =>
         val captureParamDefs = for (param <- jsClassCaptures) yield {
           implicit val pos = param.pos
-          val ident = fileLevelVarIdent("cc", genName(param.name.name),
+          val ident = fileLevelVarIdent(VarField.cc, genName(param.name.name),
               param.originalName.orElse(param.name.name))
           js.ParamDef(ident)
         }
@@ -138,7 +138,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
               Nil
           )
 
-          globalFunctionDef("a", className, captureParamDefs, None, body)
+          globalFunctionDef(VarField.a, className, captureParamDefs, None, body)
         }
       }
     }
@@ -191,7 +191,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
     } else {
       import TreeDSL._
 
-      val ctorVar = globalVar("c", className)
+      val ctorVar = globalVar(VarField.c, className)
 
       val chainProtoWithGlobals = superClass match {
         case None =>
@@ -201,15 +201,15 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
           untrackedGlobalRef("Error").map(chainPrototypeWithLocalCtor(className, ctorVar, _))
 
         case Some(parentIdent) =>
-          WithGlobals(List(ctorVar.prototype := js.New(globalVar("h", parentIdent.name), Nil)))
+          WithGlobals(List(ctorVar.prototype := js.New(globalVar(VarField.h, parentIdent.name), Nil)))
       }
 
       for {
         ctorFun <- jsConstructorFunWithGlobals
         realCtorDef <-
-            globalFunctionDef("c", className, ctorFun.args, ctorFun.restParam, ctorFun.body)
+            globalFunctionDef(VarField.c, className, ctorFun.args, ctorFun.restParam, ctorFun.body)
         inheritableCtorDef <-
-            globalFunctionDef("h", className, Nil, None, js.Skip())
+            globalFunctionDef(VarField.h, className, Nil, None, js.Skip())
         chainProto <- chainProtoWithGlobals
       } yield {
         (
@@ -222,7 +222,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
           // Inheritable constructor
           js.DocComment("@constructor") ::
           inheritableCtorDef :::
-          (globalVar("h", className).prototype := ctorVar.prototype) :: Nil
+          (globalVar(VarField.h, className).prototype := ctorVar.prototype) :: Nil
         )
       }
     }
@@ -249,7 +249,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
       } yield {
         import TreeDSL._
 
-        val ctorVar = fileLevelVar("b", genName(className))
+        val ctorVar = fileLevelVar(VarField.b, genName(className))
 
         js.DocComment("@constructor") ::
         (ctorVar := ctorFun) ::
@@ -263,7 +263,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
       implicit moduleContext: ModuleContext, globalKnowledge: GlobalKnowledge,
       pos: Position): WithGlobals[js.Tree] = {
     if (jsSuperClass.isDefined) {
-      WithGlobals(fileLevelVar("superClass"))
+      WithGlobals(fileLevelVar(VarField.superClass))
     } else {
       genJSClassConstructor(superClass.get.name, keepOnlyDangerousVarNames = true)
     }
@@ -341,7 +341,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
       superCtor: js.Tree)(implicit pos: Position): List[js.Tree] = {
     import TreeDSL._
 
-    val dummyCtor = fileLevelVar("hh", genName(className))
+    val dummyCtor = fileLevelVar(VarField.hh, genName(className))
 
     List(
         js.DocComment("@constructor"),
@@ -381,9 +381,9 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
       val value = genZeroOf(ftpe)
 
       if (flags.isMutable)
-        globallyMutableVarDef("t", "u", varScope, value, origName.orElse(name))
+        globallyMutableVarDef(VarField.t, VarField.u, varScope, value, origName.orElse(name))
       else
-        globalVarDef("t", varScope, value, origName.orElse(name))
+        globalVarDef(VarField.t, varScope, value, origName.orElse(name))
     }
 
     WithGlobals.flatten(defs)
@@ -410,7 +410,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
       }
 
       symbolValueWithGlobals.flatMap { symbolValue =>
-        globalVarDef("r", (className, name), symbolValue, origName.orElse(name))
+        globalVarDef(VarField.r, (className, name), symbolValue, origName.orElse(name))
       }
     }
 
@@ -426,7 +426,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
       if field.flags.namespace.isStatic
     } yield {
       implicit val pos = field.pos
-      val classVarRef = fileLevelVar("b", genName(className))
+      val classVarRef = fileLevelVar(VarField.b, genName(className))
       val zero = genBoxedZeroOf(field.ftpe)
       field match {
         case FieldDef(_, name, originalName, _) =>
@@ -452,7 +452,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
   def genStaticInitialization(className: ClassName)(
       implicit moduleContext: ModuleContext,
       globalKnowledge: GlobalKnowledge, pos: Position): List[js.Tree] = {
-    val field = globalVar("sct", (className, StaticInitializerName),
+    val field = globalVar(VarField.sct, (className, StaticInitializerName),
         StaticInitializerOriginalName)
     js.Apply(field, Nil) :: Nil
   }
@@ -462,7 +462,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
       implicit moduleContext: ModuleContext,
       globalKnowledge: GlobalKnowledge, pos: Position): List[js.Tree] = {
     if (hasClassInitializer) {
-      val field = globalVar("sct", (className, ClassInitializerName),
+      val field = globalVar(VarField.sct, (className, ClassInitializerName),
           ClassInitializerOriginalName)
       js.Apply(field, Nil) :: Nil
     } else {
@@ -518,12 +518,12 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
       }
 
       val field = namespace match {
-        case MemberNamespace.Public            => "f"
-        case MemberNamespace.Private           => "p"
-        case MemberNamespace.PublicStatic      => "s"
-        case MemberNamespace.PrivateStatic     => "ps"
-        case MemberNamespace.Constructor       => "ct"
-        case MemberNamespace.StaticConstructor => "sct"
+        case MemberNamespace.Public            => VarField.f
+        case MemberNamespace.Private           => VarField.p
+        case MemberNamespace.PublicStatic      => VarField.s
+        case MemberNamespace.PrivateStatic     => VarField.ps
+        case MemberNamespace.Constructor       => VarField.ct
+        case MemberNamespace.StaticConstructor => VarField.sct
       }
 
       val methodName = method.name.name
@@ -633,8 +633,8 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
     import TreeDSL._
 
     val classVarRef =
-      if (kind.isJSClass) fileLevelVar("b", genName(className))
-      else globalVar("c", className)
+      if (kind.isJSClass) fileLevelVar(VarField.b, genName(className))
+      else globalVar(VarField.c, className)
 
     if (namespace.isStatic) classVarRef
     else classVarRef.prototype
@@ -740,7 +740,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
       }
 
       val createIsStatWithGlobals = if (needIsFunction) {
-        globalFunctionDef("is", className, List(objParam), None, js.Return(isExpression))
+        globalFunctionDef(VarField.is, className, List(objParam), None, js.Return(isExpression))
       } else {
         WithGlobals.nil
       }
@@ -748,15 +748,15 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
       val createAsStatWithGlobals = if (semantics.asInstanceOfs == Unchecked) {
         WithGlobals.nil
       } else {
-        globalFunctionDef("as", className, List(objParam), None, js.Return {
+        globalFunctionDef(VarField.as, className, List(objParam), None, js.Return {
           val isCond =
-            if (needIsFunction) js.Apply(globalVar("is", className), List(obj))
+            if (needIsFunction) js.Apply(globalVar(VarField.is, className), List(obj))
             else isExpression
 
           js.If(isCond || (obj === js.Null()), {
             obj
           }, {
-            genCallHelper("throwClassCastException",
+            genCallHelper(VarField.throwClassCastException,
                 obj, js.StringLiteral(displayName))
           })
         })
@@ -791,7 +791,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
     val depth = depthParam.ref
 
     val createIsArrayOfStatWithGlobals = {
-      globalFunctionDef("isArrayOf", className, List(objParam, depthParam), None, {
+      globalFunctionDef(VarField.isArrayOf, className, List(objParam, depthParam), None, {
         js.Return(!(!({
           genIsScalaJSObject(obj) &&
           ((obj DOT "$classData" DOT "arrayDepth") === depth) &&
@@ -804,13 +804,13 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
     val createAsArrayOfStatWithGlobals = if (semantics.asInstanceOfs == Unchecked) {
       WithGlobals.nil
     } else {
-      globalFunctionDef("asArrayOf", className, List(objParam, depthParam), None, {
+      globalFunctionDef(VarField.asArrayOf, className, List(objParam, depthParam), None, {
         js.Return {
-          js.If(js.Apply(globalVar("isArrayOf", className), List(obj, depth)) ||
+          js.If(js.Apply(globalVar(VarField.isArrayOf, className), List(obj, depth)) ||
               (obj === js.Null()), {
             obj
           }, {
-            genCallHelper("throwArrayCastException",
+            genCallHelper(VarField.throwArrayCastException,
                 obj, js.StringLiteral("L"+displayName+";"), depth)
           })
         }
@@ -858,7 +858,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
         if (isObjectClass) js.Null()
         else js.Undefined()
       } { parent =>
-        globalVar("d", parent.name)
+        globalVar(VarField.d, parent.name)
       }
     } else {
       js.Undefined()
@@ -872,7 +872,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
         /* Ancestors of hijacked classes, including java.lang.Object, have a
          * normal $is_pack_Class test but with a non-standard behavior.
          */
-        WithGlobals(globalVar("is", className))
+        WithGlobals(globalVar(VarField.is, className))
       } else if (HijackedClasses.contains(className)) {
         /* Hijacked classes have a special isInstanceOf test. */
         val xParam = js.ParamDef(js.Ident("x"))
@@ -888,7 +888,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
          * cannot be performed and must throw.
          */
         if (kind != ClassKind.JSClass && kind != ClassKind.NativeJSClass) {
-          WithGlobals(globalVar("noIsInstance", CoreVar))
+          WithGlobals(globalVar(VarField.noIsInstance, CoreVar))
         } else if (kind == ClassKind.JSClass && !globalKnowledge.hasInstances(className)) {
           /* We need to constant-fold the instance test, to avoid emitting
            * `x instanceof $a_TheClass()`, because `$a_TheClass` won't be
@@ -928,10 +928,10 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
       val prunedParams =
         allParams.reverse.dropWhile(_.isInstanceOf[js.Undefined]).reverse
 
-      val typeData = js.Apply(js.New(globalVar("TypeData", CoreVar), Nil) DOT "initClass",
+      val typeData = js.Apply(js.New(globalVar(VarField.TypeData, CoreVar), Nil) DOT "initClass",
           prunedParams)
 
-      globalVarDef("d", className, typeData)
+      globalVarDef(VarField.d, className, typeData)
     }
   }
 
@@ -940,7 +940,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
       globalKnowledge: GlobalKnowledge, pos: Position): js.Tree = {
     import TreeDSL._
 
-    globalVar("c", className).prototype DOT "$classData" := globalVar("d", className)
+    globalVar(VarField.c, className).prototype DOT "$classData" := globalVar(VarField.d, className)
   }
 
   def genModuleAccessor(className: ClassName, kind: ClassKind)(
@@ -953,7 +953,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
     require(kind.hasModuleAccessor,
         s"genModuleAccessor called with non-module class: $className")
 
-    val moduleInstance = fileLevelVarIdent("n", genName(className))
+    val moduleInstance = fileLevelVarIdent(VarField.n, genName(className))
 
     val createModuleInstanceField = genEmptyMutableLet(moduleInstance)
 
@@ -967,7 +967,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
                 genNonNativeJSClassConstructor(className),
                 Nil)
           } else {
-            js.New(globalVar("c", className), Nil)
+            js.New(globalVar(VarField.c, className), Nil)
           }
         }
       }
@@ -990,13 +990,13 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
             )
           }, js.If(moduleInstanceVar === js.Null(), {
             val decodedName = className.nameString.stripSuffix("$")
-            genCallHelper("throwModuleInitError", js.StringLiteral(decodedName))
+            genCallHelper(VarField.throwModuleInitError, js.StringLiteral(decodedName))
           }, js.Skip()))
       }
 
       val body = js.Block(initBlock, js.Return(moduleInstanceVar))
 
-      globalFunctionDef("m", className, Nil, None, body)
+      globalFunctionDef(VarField.m, className, Nil, None, body)
     }
 
     createAccessor.map(createModuleInstanceField :: _)
@@ -1062,7 +1062,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
         genAssignToNoModuleExportVar(exportName, exportedValue)
 
       case ModuleKind.ESModule =>
-        val field = fileLevelVar("e", exportName)
+        val field = fileLevelVar(VarField.e, exportName)
         val let = js.Let(field.ident, mutable = true, Some(exportedValue))
         val exportStat = js.Export((field.ident -> js.ExportName(exportName)) :: Nil)
         WithGlobals(js.Block(let, exportStat))
@@ -1103,10 +1103,10 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
         /* Initial value of the export. Updates are taken care of explicitly
          * when we assign to the static field.
          */
-        genAssignToNoModuleExportVar(exportName, globalVar("t", varScope))
+        genAssignToNoModuleExportVar(exportName, globalVar(VarField.t, varScope))
 
       case ModuleKind.ESModule =>
-        WithGlobals(globalVarExport("t", varScope, js.ExportName(exportName)))
+        WithGlobals(globalVarExport(VarField.t, varScope, js.ExportName(exportName)))
 
       case ModuleKind.CommonJSModule =>
         globalRef("exports").flatMap { exportsVarRef =>
@@ -1115,7 +1115,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
               js.StringLiteral(exportName),
               List(
                   "get" -> js.Function(arrow = false, Nil, None, {
-                    js.Return(globalVar("t", varScope))
+                    js.Return(globalVar(VarField.t, varScope))
                   }),
                   "configurable" -> js.BooleanLiteral(true)
               )
@@ -1134,14 +1134,14 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
 
     ModuleInitializerImpl.fromInitializer(initializer) match {
       case VoidMainMethod(className, mainMethodName) =>
-        WithGlobals(js.Apply(globalVar("s", (className, mainMethodName)), Nil))
+        WithGlobals(js.Apply(globalVar(VarField.s, (className, mainMethodName)), Nil))
 
       case MainMethodWithArgs(className, mainMethodName, args) =>
         val stringArrayTypeRef = ArrayTypeRef(ClassRef(BoxedStringClass), 1)
         val argsArrayWithGlobals =
           genArrayValue(stringArrayTypeRef, args.map(js.StringLiteral(_)))
         for (argsArray <- argsArrayWithGlobals) yield {
-          js.Apply(globalVar("s", (className, mainMethodName)), argsArray :: Nil)
+          js.Apply(globalVar(VarField.s, (className, mainMethodName)), argsArray :: Nil)
         }
     }
   }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
index d610e8cdb8..8a04956ad8 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
@@ -164,7 +164,7 @@ private[emitter] object CoreJSLib {
           str("fileLevelThis") -> This()
       )))
 
-      extractWithGlobals(globalVarDef("linkingInfo", CoreVar, linkingInfo))
+      extractWithGlobals(globalVarDef(VarField.linkingInfo, CoreVar, linkingInfo))
     }
 
     private def defineJSBuiltinsSnapshotsAndPolyfills(): List[Tree] = {
@@ -503,21 +503,21 @@ private[emitter] object CoreJSLib {
             // NamespaceGlobalVar.builtinName || polyfill
             genIdentBracketSelect(globalRef(builtin.namespaceGlobalVar), builtin.builtinName) || polyfill
         }
-        extractWithGlobals(globalVarDef(builtin.builtinName, CoreVar, rhs))
+        extractWithGlobals(globalVarDef(builtin.polyfillField, CoreVar, rhs))
       }
     }
 
     private def declareCachedL0(): List[Tree] = {
       condDefs(!allowBigIntsForLongs)(
-        extractWithGlobals(globalVarDecl("L0", CoreVar))
+        extractWithGlobals(globalVarDecl(VarField.L0, CoreVar))
       )
     }
 
     private def assignCachedL0(): List[Tree] = {
       condDefs(!allowBigIntsForLongs)(List(
-        globalVar("L0", CoreVar) := genScalaClassNew(
+        globalVar(VarField.L0, CoreVar) := genScalaClassNew(
             LongImpl.RuntimeLongClass, LongImpl.initFromParts, 0, 0),
-        genClassDataOf(LongRef) DOT "zero" := globalVar("L0", CoreVar)
+        genClassDataOf(LongRef) DOT "zero" := globalVar(VarField.L0, CoreVar)
       ))
     }
 
@@ -532,7 +532,7 @@ private[emitter] object CoreJSLib {
        * Closure) but we must still get hold of a string of that name for
        * runtime reflection.
        */
-      defineFunction1("propertyName") { obj =>
+      defineFunction1(VarField.propertyName) { obj =>
         val prop = varRef("prop")
         ForIn(genEmptyImmutableLet(prop.ident), obj, Return(prop))
       }
@@ -554,10 +554,10 @@ private[emitter] object CoreJSLib {
       }
 
       if (useClassesForRegularClasses) {
-        extractWithGlobals(globalClassDef("Char", CoreVar, None, ctor :: toStr :: Nil))
+        extractWithGlobals(globalClassDef(VarField.Char, CoreVar, None, ctor :: toStr :: Nil))
       } else {
-        defineFunction("Char", ctor.args, ctor.body) :::
-        assignES5ClassMembers(globalVar("Char", CoreVar), List(toStr))
+        defineFunction(VarField.Char, ctor.args, ctor.body) :::
+        assignES5ClassMembers(globalVar(VarField.Char, CoreVar), List(toStr))
       }
     }
 
@@ -567,7 +567,7 @@ private[emitter] object CoreJSLib {
          * This helper is never called for `value === null`. As implemented,
          * it would return `"object"` if it were.
          */
-        defineFunction1("valueDescription") { value =>
+        defineFunction1(VarField.valueDescription) { value =>
           Return {
             If(typeof(value) === str("number"), {
               If((value === 0) && (int(1) / value < 0), {
@@ -601,25 +601,25 @@ private[emitter] object CoreJSLib {
       ) :::
 
       condDefs(asInstanceOfs != CheckedBehavior.Unchecked)(
-        defineFunction2("throwClassCastException") { (instance, classFullName) =>
+        defineFunction2(VarField.throwClassCastException) { (instance, classFullName) =>
           Throw(maybeWrapInUBE(asInstanceOfs, {
             genScalaClassNew(ClassCastExceptionClass, StringArgConstructorName,
-                genCallHelper("valueDescription", instance) + str(" cannot be cast to ") + classFullName)
+                genCallHelper(VarField.valueDescription, instance) + str(" cannot be cast to ") + classFullName)
           }))
         } :::
 
-        defineFunction3("throwArrayCastException") { (instance, classArrayEncodedName, depth) =>
+        defineFunction3(VarField.throwArrayCastException) { (instance, classArrayEncodedName, depth) =>
           Block(
               While(depth.prefix_--, {
                 classArrayEncodedName := (str("[") + classArrayEncodedName)
               }),
-              genCallHelper("throwClassCastException", instance, classArrayEncodedName)
+              genCallHelper(VarField.throwClassCastException, instance, classArrayEncodedName)
           )
         }
       ) :::
 
       condDefs(arrayIndexOutOfBounds != CheckedBehavior.Unchecked)(
-        defineFunction1("throwArrayIndexOutOfBoundsException") { i =>
+        defineFunction1(VarField.throwArrayIndexOutOfBoundsException) { i =>
           Throw(maybeWrapInUBE(arrayIndexOutOfBounds, {
             genScalaClassNew(ArrayIndexOutOfBoundsExceptionClass,
                 StringArgConstructorName,
@@ -629,17 +629,17 @@ private[emitter] object CoreJSLib {
       ) :::
 
       condDefs(arrayStores != CheckedBehavior.Unchecked)(
-        defineFunction1("throwArrayStoreException") { v =>
+        defineFunction1(VarField.throwArrayStoreException) { v =>
           Throw(maybeWrapInUBE(arrayStores, {
             genScalaClassNew(ArrayStoreExceptionClass,
                 StringArgConstructorName,
-                If(v === Null(), Null(), genCallHelper("valueDescription", v)))
+                If(v === Null(), Null(), genCallHelper(VarField.valueDescription, v)))
           }))
         }
       ) :::
 
       condDefs(negativeArraySizes != CheckedBehavior.Unchecked)(
-        defineFunction0("throwNegativeArraySizeException") {
+        defineFunction0(VarField.throwNegativeArraySizeException) {
           Throw(maybeWrapInUBE(negativeArraySizes, {
             genScalaClassNew(NegativeArraySizeExceptionClass,
                 NoArgConstructorName)
@@ -648,7 +648,7 @@ private[emitter] object CoreJSLib {
       ) :::
 
       condDefs(moduleInit == CheckedBehavior.Fatal)(
-        defineFunction1("throwModuleInitError") { name =>
+        defineFunction1(VarField.throwModuleInitError) { name =>
           Throw(genScalaClassNew(UndefinedBehaviorErrorClass,
               StringArgConstructorName, str("Initializer of ") + name +
               str(" called before completion of its super constructor")))
@@ -656,31 +656,31 @@ private[emitter] object CoreJSLib {
       ) :::
 
       condDefs(nullPointers != CheckedBehavior.Unchecked)(
-        defineFunction0("throwNullPointerException") {
+        defineFunction0(VarField.throwNullPointerException) {
           Throw(maybeWrapInUBE(nullPointers, {
             genScalaClassNew(NullPointerExceptionClass, NoArgConstructorName)
           }))
         } :::
 
         // "checkNotNull", but with a very short name
-        defineFunction1("n") { x =>
+        defineFunction1(VarField.n) { x =>
           Block(
-            If(x === Null(), genCallHelper("throwNullPointerException")),
+            If(x === Null(), genCallHelper(VarField.throwNullPointerException)),
             Return(x)
           )
         }
       ) :::
 
-      defineFunction1("noIsInstance") { instance =>
+      defineFunction1(VarField.noIsInstance) { instance =>
         Throw(New(TypeErrorRef,
             str("Cannot call isInstance() on a Class representing a JS trait/object") :: Nil))
       } :::
 
-      defineFunction2("newArrayObject") { (arrayClassData, lengths) =>
-        Return(genCallHelper("newArrayObjectInternal", arrayClassData, lengths, int(0)))
+      defineFunction2(VarField.newArrayObject) { (arrayClassData, lengths) =>
+        Return(genCallHelper(VarField.newArrayObjectInternal, arrayClassData, lengths, int(0)))
       } :::
 
-      defineFunction3("newArrayObjectInternal") { (arrayClassData, lengths, lengthIndex) =>
+      defineFunction3(VarField.newArrayObjectInternal) { (arrayClassData, lengths, lengthIndex) =>
         val result = varRef("result")
         val subArrayClassData = varRef("subArrayClassData")
         val subLengthIndex = varRef("subLengthIndex")
@@ -696,14 +696,14 @@ private[emitter] object CoreJSLib {
             const(underlying, result.u),
             For(let(i, 0), i < underlying.length, i.++, {
               BracketSelect(underlying, i) :=
-                genCallHelper("newArrayObjectInternal", subArrayClassData, lengths, subLengthIndex)
+                genCallHelper(VarField.newArrayObjectInternal, subArrayClassData, lengths, subLengthIndex)
             })
           )),
           Return(result)
         )
       } :::
 
-      defineFunction1("objectClone") { instance =>
+      defineFunction1(VarField.objectClone) { instance =>
         // return Object.create(Object.getPrototypeOf(instance), $getOwnPropertyDescriptors(instance));
         val callGetOwnPropertyDescriptors = genCallPolyfillableBuiltin(
             GetOwnPropertyDescriptorsBuiltin, instance)
@@ -712,18 +712,18 @@ private[emitter] object CoreJSLib {
             callGetOwnPropertyDescriptors)))
       } :::
 
-      defineFunction1("objectOrArrayClone") { instance =>
+      defineFunction1(VarField.objectOrArrayClone) { instance =>
         // return instance.$classData.isArrayClass ? instance.clone__O() : $objectClone(instance);
         Return(If(genIdentBracketSelect(instance DOT classData, "isArrayClass"),
             Apply(instance DOT genName(cloneMethodName), Nil),
-            genCallHelper("objectClone", instance)))
+            genCallHelper(VarField.objectClone, instance)))
       }
     )
 
     private def defineObjectGetClassFunctions(): List[Tree] = {
       // objectGetClass and objectClassName
 
-      def defineObjectGetClassBasedFun(name: String,
+      def defineObjectGetClassBasedFun(name: VarField,
           constantClassResult: ClassName => Tree,
           scalaObjectResult: VarRef => Tree, jsObjectResult: Tree): List[Tree] = {
         defineFunction1(name) { instance =>
@@ -733,7 +733,7 @@ private[emitter] object CoreJSLib {
               },
               str("number") -> {
                 Block(
-                    If(genCallHelper("isInt", instance), {
+                    If(genCallHelper(VarField.isInt, instance), {
                       If((instance << 24 >> 24) === instance, {
                         Return(constantClassResult(BoxedByteClass))
                       }, {
@@ -745,7 +745,7 @@ private[emitter] object CoreJSLib {
                       })
                     }, {
                       if (strictFloats) {
-                        If(genCallHelper("isFloat", instance), {
+                        If(genCallHelper(VarField.isFloat, instance), {
                           Return(constantClassResult(BoxedFloatClass))
                         }, {
                           Return(constantClassResult(BoxedDoubleClass))
@@ -767,7 +767,7 @@ private[emitter] object CoreJSLib {
               if (nullPointers == CheckedBehavior.Unchecked)
                 Return(Apply(instance DOT genName(getClassMethodName), Nil))
               else
-                genCallHelper("throwNullPointerException")
+                genCallHelper(VarField.throwNullPointerException)
             }, {
               If(genIsInstanceOfHijackedClass(instance, BoxedLongClass), {
                 Return(constantClassResult(BoxedLongClass))
@@ -797,13 +797,13 @@ private[emitter] object CoreJSLib {
        * (i.e., through a `ClassOf` node).
        */
       condDefs(globalKnowledge.isClassClassInstantiated)(
-        defineObjectGetClassBasedFun("objectGetClass",
+        defineObjectGetClassBasedFun(VarField.objectGetClass,
             className => genClassOf(className),
             instance => Apply(instance DOT classData DOT "getClassOf", Nil),
             Null()
         )
       ) :::
-      defineObjectGetClassBasedFun("objectClassName",
+      defineObjectGetClassBasedFun(VarField.objectClassName,
           { className =>
             StringLiteral(RuntimeClassNameMapperImpl.map(
                 semantics.runtimeClassNameMapper, className.nameString))
@@ -813,7 +813,7 @@ private[emitter] object CoreJSLib {
             if (nullPointers == CheckedBehavior.Unchecked)
               Apply(Null() DOT genName(getNameMethodName), Nil)
             else
-              genCallHelper("throwNullPointerException")
+              genCallHelper(VarField.throwNullPointerException)
           }
       )
     }
@@ -824,7 +824,7 @@ private[emitter] object CoreJSLib {
       def defineDispatcher(methodName: MethodName, args: List[VarRef],
           body: Tree): List[Tree] = {
         val params = paramList((instance :: args): _*)
-        extractWithGlobals(globalFunctionDef("dp", methodName, params, None, body))
+        extractWithGlobals(globalFunctionDef(VarField.dp, methodName, params, None, body))
       }
 
       /* A standard dispatcher performs a type test on the instance and then
@@ -854,9 +854,9 @@ private[emitter] object CoreJSLib {
 
         def genHijackedMethodApply(className: ClassName): Tree = {
           val instanceAsPrimitive =
-            if (className == BoxedCharacterClass) genCallHelper("uC", instance)
+            if (className == BoxedCharacterClass) genCallHelper(VarField.uC, instance)
             else instance
-          Apply(globalVar("f", (className, methodName)), instanceAsPrimitive :: args)
+          Apply(globalVar(VarField.f, (className, methodName)), instanceAsPrimitive :: args)
         }
 
         def genBodyNoSwitch(hijackedClasses: List[ClassName]): Tree = {
@@ -872,7 +872,7 @@ private[emitter] object CoreJSLib {
 
           if (implementedInObject) {
             val staticObjectCall: Tree = {
-              val fun = globalVar("c", ObjectClass).prototype DOT genName(methodName)
+              val fun = globalVar(VarField.c, ObjectClass).prototype DOT genName(methodName)
               Return(Apply(fun DOT "call", instance :: args))
             }
 
@@ -929,21 +929,21 @@ private[emitter] object CoreJSLib {
       def wrapBigInt64(tree: Tree): Tree =
         Apply(genIdentBracketSelect(BigIntRef, "asIntN"), 64 :: tree :: Nil)
 
-      defineFunction2("intDiv") { (x, y) =>
+      defineFunction2(VarField.intDiv) { (x, y) =>
         If(y === 0, throwDivByZero, {
           Return((x / y) | 0)
         })
       } :::
-      defineFunction2("intMod") { (x, y) =>
+      defineFunction2(VarField.intMod) { (x, y) =>
         If(y === 0, throwDivByZero, {
           Return((x % y) | 0)
         })
       } :::
-      defineFunction1("doubleToInt") { x =>
+      defineFunction1(VarField.doubleToInt) { x =>
         Return(If(x > 2147483647, 2147483647, If(x < -2147483648, -2147483648, x | 0)))
       } :::
       condDefs(semantics.stringIndexOutOfBounds != CheckedBehavior.Unchecked)(
-        defineFunction2("charAt") { (s, i) =>
+        defineFunction2(VarField.charAt) { (s, i) =>
           val r = varRef("r")
 
           val throwStringIndexOutOfBoundsException = {
@@ -958,18 +958,18 @@ private[emitter] object CoreJSLib {
         }
       ) :::
       condDefs(allowBigIntsForLongs)(
-        defineFunction2("longDiv") { (x, y) =>
+        defineFunction2(VarField.longDiv) { (x, y) =>
           If(y === bigInt(0), throwDivByZero, {
             Return(wrapBigInt64(x / y))
           })
         } :::
-        defineFunction2("longMod") { (x, y) =>
+        defineFunction2(VarField.longMod) { (x, y) =>
           If(y === bigInt(0), throwDivByZero, {
             Return(wrapBigInt64(x % y))
           })
         } :::
 
-        defineFunction1("doubleToLong")(x => Return {
+        defineFunction1(VarField.doubleToLong)(x => Return {
           If(x < double(-9223372036854775808.0), { // -2^63
             bigInt(-9223372036854775808L)
           }, {
@@ -986,7 +986,7 @@ private[emitter] object CoreJSLib {
           })
         }) :::
 
-        defineFunction1("longToFloat") { x =>
+        defineFunction1(VarField.longToFloat) { x =>
           val abs = varRef("abs")
           val y = varRef("y")
           val absR = varRef("absR")
@@ -1008,7 +1008,7 @@ private[emitter] object CoreJSLib {
 
     private def defineES2015LikeHelpers(): List[Tree] = (
       condDefs(esVersion < ESVersion.ES2015)(
-        defineFunction2("newJSObjectWithVarargs") { (ctor, args) =>
+        defineFunction2(VarField.newJSObjectWithVarargs) { (ctor, args) =>
           val instance = varRef("instance")
           val result = varRef("result")
 
@@ -1024,7 +1024,7 @@ private[emitter] object CoreJSLib {
         }
       ) :::
 
-      defineFunction2("resolveSuperRef") { (superClass, propName) =>
+      defineFunction2(VarField.resolveSuperRef) { (superClass, propName) =>
         val getPrototypeOf = varRef("getPrototypeOf")
         val getOwnPropertyDescriptor = varRef("getOwnPropertyDescriptor")
         val superProto = varRef("superProto")
@@ -1042,12 +1042,12 @@ private[emitter] object CoreJSLib {
         )
       } :::
 
-      defineFunction3("superGet") { (superClass, self, propName) =>
+      defineFunction3(VarField.superGet) { (superClass, self, propName) =>
         val desc = varRef("desc")
         val getter = varRef("getter")
 
         Block(
-          const(desc, genCallHelper("resolveSuperRef", superClass, propName)),
+          const(desc, genCallHelper(VarField.resolveSuperRef, superClass, propName)),
           If(desc !== Undefined(), Block(
             const(getter, genIdentBracketSelect(desc, "get")),
             Return(If(getter !== Undefined(),
@@ -1057,12 +1057,12 @@ private[emitter] object CoreJSLib {
         )
       } :::
 
-      defineFunction4("superSet") { (superClass, self, propName, value) =>
+      defineFunction4(VarField.superSet) { (superClass, self, propName, value) =>
         val desc = varRef("desc")
         val setter = varRef("setter")
 
         Block(
-          const(desc, genCallHelper("resolveSuperRef", superClass, propName)),
+          const(desc, genCallHelper(VarField.resolveSuperRef, superClass, propName)),
           If(desc !== Undefined(), Block(
             const(setter, genIdentBracketSelect(desc, "set")),
             If(setter !== Undefined(), Block(
@@ -1078,7 +1078,7 @@ private[emitter] object CoreJSLib {
 
     private def defineModuleHelpers(): List[Tree] = {
       condDefs(moduleKind == ModuleKind.CommonJSModule)(
-        defineFunction1("moduleDefault") { m =>
+        defineFunction1(VarField.moduleDefault) { m =>
           Return(If(
               m && (typeof(m) === str("object")) && (str("default") in m),
               BracketSelect(m, str("default")),
@@ -1089,20 +1089,20 @@ private[emitter] object CoreJSLib {
 
     private def defineIntrinsics(): List[Tree] = (
       condDefs(arrayIndexOutOfBounds != CheckedBehavior.Unchecked)(
-        defineFunction5("arraycopyCheckBounds") { (srcLen, srcPos, destLen, destPos, length) =>
+        defineFunction5(VarField.arraycopyCheckBounds) { (srcLen, srcPos, destLen, destPos, length) =>
           If((srcPos < 0) || (destPos < 0) || (length < 0) ||
               (srcPos > ((srcLen - length) | 0)) ||
               (destPos > ((destLen - length) | 0)), {
-            genCallHelper("throwArrayIndexOutOfBoundsException", Null())
+            genCallHelper(VarField.throwArrayIndexOutOfBoundsException, Null())
           })
         }
       ) :::
 
-      defineFunction5("arraycopyGeneric") { (srcArray, srcPos, destArray, destPos, length) =>
+      defineFunction5(VarField.arraycopyGeneric) { (srcArray, srcPos, destArray, destPos, length) =>
         val i = varRef("i")
         Block(
           if (arrayIndexOutOfBounds != CheckedBehavior.Unchecked) {
-            genCallHelper("arraycopyCheckBounds", srcArray.length,
+            genCallHelper(VarField.arraycopyCheckBounds, srcArray.length,
                 srcPos, destArray.length, destPos, length)
           } else {
             Skip()
@@ -1120,23 +1120,23 @@ private[emitter] object CoreJSLib {
       } :::
 
       condDefs(esVersion < ESVersion.ES2015)(
-        defineFunction5("systemArraycopy") { (src, srcPos, dest, destPos, length) =>
-          genCallHelper("arraycopyGeneric", src.u, srcPos, dest.u, destPos, length)
+        defineFunction5(VarField.systemArraycopy) { (src, srcPos, dest, destPos, length) =>
+          genCallHelper(VarField.arraycopyGeneric, src.u, srcPos, dest.u, destPos, length)
         }
       ) :::
       condDefs(esVersion >= ESVersion.ES2015 && nullPointers != CheckedBehavior.Unchecked)(
-        defineFunction5("systemArraycopy") { (src, srcPos, dest, destPos, length) =>
+        defineFunction5(VarField.systemArraycopy) { (src, srcPos, dest, destPos, length) =>
           Apply(src DOT "copyTo", List(srcPos, dest, destPos, length))
         }
       ) :::
 
       condDefs(arrayStores != CheckedBehavior.Unchecked)(
-        defineFunction5("systemArraycopyRefs") { (src, srcPos, dest, destPos, length) =>
+        defineFunction5(VarField.systemArraycopyRefs) { (src, srcPos, dest, destPos, length) =>
           If(Apply(genIdentBracketSelect(dest DOT classData, "isAssignableFrom"), List(src DOT classData)), {
             /* Fast-path, no need for array store checks. This always applies
              * for arrays of the same type, and a fortiori, when `src eq dest`.
              */
-            genCallHelper("arraycopyGeneric", src.u, srcPos, dest.u, destPos, length)
+            genCallHelper(VarField.arraycopyGeneric, src.u, srcPos, dest.u, destPos, length)
           }, {
             /* Slow copy with "set" calls for every element. By construction,
              * we have `src ne dest` in this case.
@@ -1146,7 +1146,7 @@ private[emitter] object CoreJSLib {
             Block(
               const(srcArray, src.u),
               condTree(arrayIndexOutOfBounds != CheckedBehavior.Unchecked) {
-                genCallHelper("arraycopyCheckBounds", srcArray.length,
+                genCallHelper(VarField.arraycopyCheckBounds, srcArray.length,
                     srcPos, dest.u.length, destPos, length)
               },
               For(let(i, 0), i < length, i := ((i + 1) | 0), {
@@ -1156,8 +1156,8 @@ private[emitter] object CoreJSLib {
           })
         } :::
 
-        defineFunction5("systemArraycopyFull") { (src, srcPos, dest, destPos, length) =>
-          val ObjectArray = globalVar("ac", ObjectClass)
+        defineFunction5(VarField.systemArraycopyFull) { (src, srcPos, dest, destPos, length) =>
+          val ObjectArray = globalVar(VarField.ac, ObjectClass)
           val srcData = varRef("srcData")
 
           Block(
@@ -1168,16 +1168,16 @@ private[emitter] object CoreJSLib {
                 // Fast path: the values are array of the same type
                 genUncheckedArraycopy(List(src, srcPos, dest, destPos, length))
               }, {
-                genCallHelper("throwArrayStoreException", Null())
+                genCallHelper(VarField.throwArrayStoreException, Null())
               })
             }, {
               /* src and dest are of different types; the only situation that
                * can still be valid is if they are two reference array types.
                */
               If((src instanceof ObjectArray) && (dest instanceof ObjectArray), {
-                genCallHelper("systemArraycopyRefs", src, srcPos, dest, destPos, length)
+                genCallHelper(VarField.systemArraycopyRefs, src, srcPos, dest, destPos, length)
               }, {
-                genCallHelper("throwArrayStoreException", Null())
+                genCallHelper(VarField.throwArrayStoreException, Null())
               })
             })
           )
@@ -1188,8 +1188,8 @@ private[emitter] object CoreJSLib {
       locally {
         val WeakMapRef = globalRef("WeakMap")
 
-        val lastIDHash = fileLevelVar("lastIDHash")
-        val idHashCodeMap = fileLevelVar("idHashCodeMap")
+        val lastIDHash = fileLevelVar(VarField.lastIDHash)
+        val idHashCodeMap = fileLevelVar(VarField.idHashCodeMap)
 
         val obj = varRef("obj")
         val biHash = varRef("biHash")
@@ -1198,7 +1198,7 @@ private[emitter] object CoreJSLib {
 
         def functionSkeleton(defaultImpl: Tree): Function = {
           def genHijackedMethodApply(className: ClassName, arg: Tree): Tree =
-            Apply(globalVar("f", (className, hashCodeMethodName)), arg :: Nil)
+            Apply(globalVar(VarField.f, (className, hashCodeMethodName)), arg :: Nil)
 
           def genReturnHijackedMethodApply(className: ClassName): Tree =
             Return(genHijackedMethodApply(className, obj))
@@ -1323,9 +1323,9 @@ private[emitter] object CoreJSLib {
         ) ::: (
           if (esVersion >= ESVersion.ES2015) {
             val f = weakMapBasedFunction
-            defineFunction("systemIdentityHashCode", f.args, f.body)
+            defineFunction(VarField.systemIdentityHashCode, f.args, f.body)
           } else {
-            extractWithGlobals(globalVarDef("systemIdentityHashCode", CoreVar,
+            extractWithGlobals(globalVarDef(VarField.systemIdentityHashCode, CoreVar,
                 If(idHashCodeMap !== Null(), weakMapBasedFunction, fieldBasedFunction)))
           }
         )
@@ -1333,24 +1333,24 @@ private[emitter] object CoreJSLib {
     )
 
     private def defineIsPrimitiveFunctions(): List[Tree] = {
-      def defineIsIntLike(name: String, specificTest: VarRef => Tree): List[Tree] = {
+      def defineIsIntLike(name: VarField, specificTest: VarRef => Tree): List[Tree] = {
         defineFunction1(name) { v =>
           Return((typeof(v) === str("number")) && specificTest(v) &&
               ((int(1) / v) !== (int(1) / double(-0.0))))
         }
       }
 
-      defineIsIntLike("isByte", v => (v << 24 >> 24) === v) :::
-      defineIsIntLike("isShort", v => (v << 16 >> 16) === v) :::
-      defineIsIntLike("isInt", v => (v | 0) === v) :::
+      defineIsIntLike(VarField.isByte, v => (v << 24 >> 24) === v) :::
+      defineIsIntLike(VarField.isShort, v => (v << 16 >> 16) === v) :::
+      defineIsIntLike(VarField.isInt, v => (v | 0) === v) :::
       condDefs(allowBigIntsForLongs)(
-        defineFunction1("isLong") { v =>
+        defineFunction1(VarField.isLong) { v =>
           Return((typeof(v) === str("bigint")) &&
               (Apply(genIdentBracketSelect(BigIntRef, "asIntN"), int(64) :: v :: Nil) === v))
         }
       ) :::
       condDefs(strictFloats)(
-        defineFunction1("isFloat") { v =>
+        defineFunction1(VarField.isFloat) { v =>
           Return((typeof(v) === str("number")) &&
               ((v !== v) || (genCallPolyfillableBuiltin(FroundBuiltin, v) === v)))
         }
@@ -1359,46 +1359,46 @@ private[emitter] object CoreJSLib {
 
     private def defineBoxFunctions(): List[Tree] = (
       // Boxes for Chars
-      defineFunction1("bC") { c =>
-        Return(New(globalVar("Char", CoreVar), c :: Nil))
+      defineFunction1(VarField.bC) { c =>
+        Return(New(globalVar(VarField.Char, CoreVar), c :: Nil))
       } :::
-      extractWithGlobals(globalVarDef("bC0", CoreVar, genCallHelper("bC", 0)))
+      extractWithGlobals(globalVarDef(VarField.bC0, CoreVar, genCallHelper(VarField.bC, 0)))
     ) ::: (
       if (asInstanceOfs != CheckedBehavior.Unchecked) {
         // Unboxes for everything
-        def defineUnbox(name: String, boxedClassName: ClassName, resultExpr: VarRef => Tree): List[Tree] = {
+        def defineUnbox(name: VarField, boxedClassName: ClassName, resultExpr: VarRef => Tree): List[Tree] = {
           val fullName = boxedClassName.nameString
           defineFunction1(name)(v => Return {
             If(genIsInstanceOfHijackedClass(v, boxedClassName) || (v === Null()),
                 resultExpr(v),
-                genCallHelper("throwClassCastException", v, str(fullName)))
+                genCallHelper(VarField.throwClassCastException, v, str(fullName)))
           })
         }
 
         (
-          defineUnbox("uV", BoxedUnitClass, _ => Undefined()) :::
-          defineUnbox("uZ", BoxedBooleanClass, v => !(!v)) :::
-          defineUnbox("uC", BoxedCharacterClass, v => If(v === Null(), 0, v DOT "c")) :::
-          defineUnbox("uB", BoxedByteClass, _ | 0) :::
-          defineUnbox("uS", BoxedShortClass, _ | 0) :::
-          defineUnbox("uI", BoxedIntegerClass, _ | 0) :::
-          defineUnbox("uJ", BoxedLongClass, v => If(v === Null(), genLongZero(), v)) :::
+          defineUnbox(VarField.uV, BoxedUnitClass, _ => Undefined()) :::
+          defineUnbox(VarField.uZ, BoxedBooleanClass, v => !(!v)) :::
+          defineUnbox(VarField.uC, BoxedCharacterClass, v => If(v === Null(), 0, v DOT "c")) :::
+          defineUnbox(VarField.uB, BoxedByteClass, _ | 0) :::
+          defineUnbox(VarField.uS, BoxedShortClass, _ | 0) :::
+          defineUnbox(VarField.uI, BoxedIntegerClass, _ | 0) :::
+          defineUnbox(VarField.uJ, BoxedLongClass, v => If(v === Null(), genLongZero(), v)) :::
 
           /* Since the type test ensures that v is either null or a float, we can
            * use + instead of fround.
            */
-          defineUnbox("uF", BoxedFloatClass, v => +v) :::
+          defineUnbox(VarField.uF, BoxedFloatClass, v => +v) :::
 
-          defineUnbox("uD", BoxedDoubleClass, v => +v) :::
-          defineUnbox("uT", BoxedStringClass, v => If(v === Null(), StringLiteral(""), v))
+          defineUnbox(VarField.uD, BoxedDoubleClass, v => +v) :::
+          defineUnbox(VarField.uT, BoxedStringClass, v => If(v === Null(), StringLiteral(""), v))
         )
       } else {
         // Unboxes for Chars and Longs
         (
-          defineFunction1("uC") { v =>
+          defineFunction1(VarField.uC) { v =>
             Return(If(v === Null(), 0, v DOT "c"))
           } :::
-          defineFunction1("uJ") { v =>
+          defineFunction1(VarField.uJ) { v =>
             Return(If(v === Null(), genLongZero(), v))
           }
         )
@@ -1412,7 +1412,7 @@ private[emitter] object CoreJSLib {
      */
     private def defineSpecializedArrayClasses(): List[Tree] = {
       specializedArrayTypeRefs.flatMap { componentTypeRef =>
-        val ArrayClass = globalVar("ac", componentTypeRef)
+        val ArrayClass = globalVar(VarField.ac, componentTypeRef)
 
         val isArrayOfObject = componentTypeRef == ClassRef(ObjectClass)
         val isTypedArray = usesUnderlyingTypedArray(componentTypeRef)
@@ -1433,7 +1433,7 @@ private[emitter] object CoreJSLib {
 
           val boundsCheck = {
             If((i < 0) || (i >= This().u.length),
-                genCallHelper("throwArrayIndexOutOfBoundsException", i))
+                genCallHelper(VarField.throwArrayIndexOutOfBoundsException, i))
           }
 
           List(
@@ -1476,7 +1476,7 @@ private[emitter] object CoreJSLib {
             if (isTypedArray) {
               Block(
                   if (semantics.arrayIndexOutOfBounds != CheckedBehavior.Unchecked) {
-                    genCallHelper("arraycopyCheckBounds", This().u.length,
+                    genCallHelper(VarField.arraycopyCheckBounds, This().u.length,
                         srcPos, dest.u.length, destPos, length)
                   } else {
                     Skip()
@@ -1487,7 +1487,7 @@ private[emitter] object CoreJSLib {
                       Nil)
               )
             } else {
-              genCallHelper("arraycopyGeneric", This().u, srcPos,
+              genCallHelper(VarField.arraycopyGeneric, This().u, srcPos,
                   dest.u, destPos, length)
             }
           })
@@ -1504,13 +1504,13 @@ private[emitter] object CoreJSLib {
         val members = getAndSet ::: copyTo ::: clone :: Nil
 
         if (useClassesForRegularClasses) {
-          extractWithGlobals(globalClassDef("ac", componentTypeRef,
-              Some(globalVar("c", ObjectClass)), ctor :: members))
+          extractWithGlobals(globalClassDef(VarField.ac, componentTypeRef,
+              Some(globalVar(VarField.c, ObjectClass)), ctor :: members))
         } else {
           val clsDef = {
-            extractWithGlobals(globalFunctionDef("ac", componentTypeRef,
+            extractWithGlobals(globalFunctionDef(VarField.ac, componentTypeRef,
                 ctor.args, ctor.restParam, ctor.body)) :::
-            (ArrayClass.prototype := New(globalVar("h", ObjectClass), Nil)) ::
+            (ArrayClass.prototype := New(globalVar(VarField.h, ObjectClass), Nil)) ::
             (ArrayClass.prototype DOT "constructor" := ArrayClass) ::
             assignES5ClassMembers(ArrayClass, members)
           }
@@ -1518,8 +1518,8 @@ private[emitter] object CoreJSLib {
           componentTypeRef match {
             case _: ClassRef =>
               clsDef :::
-              extractWithGlobals(globalFunctionDef("ah", ObjectClass, Nil, None, Skip())) :::
-              (globalVar("ah", ObjectClass).prototype := ArrayClass.prototype) :: Nil
+              extractWithGlobals(globalFunctionDef(VarField.ah, ObjectClass, Nil, None, Skip())) :::
+              (globalVar(VarField.ah, ObjectClass).prototype := ArrayClass.prototype) :: Nil
             case _: PrimRef =>
               clsDef
           }
@@ -1533,7 +1533,7 @@ private[emitter] object CoreJSLib {
 
       If(typeof(arg) === str("number"), {
         val arraySizeCheck = condTree(negativeArraySizes != CheckedBehavior.Unchecked) {
-          If(arg < 0, genCallHelper("throwNegativeArraySizeException"))
+          If(arg < 0, genCallHelper(VarField.throwNegativeArraySizeException))
         }
 
         getArrayUnderlyingTypedArrayClassRef(componentTypeRef) match {
@@ -1624,7 +1624,7 @@ private[emitter] object CoreJSLib {
                   genArrowFunction(paramList(obj), Return(bool(false)))),
               If(arrayClass !== Undefined(), { // it is undefined for void
                 privateFieldSet("_arrayOf",
-                    Apply(New(globalVar("TypeData", CoreVar), Nil) DOT "initSpecializedArray",
+                    Apply(New(globalVar(VarField.TypeData, CoreVar), Nil) DOT "initSpecializedArray",
                         List(This(), arrayClass, typedArrayClass)))
               }),
               Return(This())
@@ -1648,7 +1648,7 @@ private[emitter] object CoreJSLib {
             paramList(internalNameObj, isInterface, fullName, ancestors,
                 isJSType, parentData, isInstance), None, {
           Block(
-              const(internalName, genCallHelper("propertyName", internalNameObj)),
+              const(internalName, genCallHelper(VarField.propertyName, internalNameObj)),
               if (globalKnowledge.isParentDataAccessed)
                 privateFieldSet("parentData", parentData)
               else
@@ -1765,13 +1765,13 @@ private[emitter] object CoreJSLib {
 
               val boundsCheck = condTree(arrayIndexOutOfBounds != CheckedBehavior.Unchecked) {
                 If((i < 0) || (i >= This().u.length),
-                    genCallHelper("throwArrayIndexOutOfBoundsException", i))
+                    genCallHelper(VarField.throwArrayIndexOutOfBoundsException, i))
               }
 
               val storeCheck = {
                 If((v !== Null()) && !(componentData DOT "isJSType") &&
                     !Apply(genIdentBracketSelect(componentData, "isInstance"), v :: Nil),
-                    genCallHelper("throwArrayStoreException", v))
+                    genCallHelper(VarField.throwArrayStoreException, v))
               }
 
               List(
@@ -1794,7 +1794,7 @@ private[emitter] object CoreJSLib {
               val length = varRef("length")
               val methodDef = MethodDef(static = false, Ident("copyTo"),
                   paramList(srcPos, dest, destPos, length), None, {
-                genCallHelper("arraycopyGeneric", This().u, srcPos,
+                genCallHelper(VarField.arraycopyGeneric, This().u, srcPos,
                     dest.u, destPos, length)
               })
               methodDef :: Nil
@@ -1810,12 +1810,12 @@ private[emitter] object CoreJSLib {
             val members = set ::: copyTo ::: clone :: Nil
 
             if (useClassesForRegularClasses) {
-              ClassDef(Some(ArrayClass.ident), Some(globalVar("ac", ObjectClass)),
+              ClassDef(Some(ArrayClass.ident), Some(globalVar(VarField.ac, ObjectClass)),
                   ctor :: members)
             } else {
               Block(
                 FunctionDef(ArrayClass.ident, ctor.args, ctor.restParam, ctor.body) ::
-                (ArrayClass.prototype := New(globalVar("ah", ObjectClass), Nil)) ::
+                (ArrayClass.prototype := New(globalVar(VarField.ah, ObjectClass), Nil)) ::
                 (ArrayClass.prototype DOT "constructor" := ArrayClass) ::
                 assignES5ClassMembers(ArrayClass, members)
               )
@@ -1865,7 +1865,7 @@ private[emitter] object CoreJSLib {
           Block(
               If(!(This() DOT "_arrayOf"),
                   This() DOT "_arrayOf" :=
-                    Apply(New(globalVar("TypeData", CoreVar), Nil) DOT "initArray", This() :: Nil),
+                    Apply(New(globalVar(VarField.TypeData, CoreVar), Nil) DOT "initArray", This() :: Nil),
                   Skip()),
               Return(This() DOT "_arrayOf")
           )
@@ -1908,7 +1908,7 @@ private[emitter] object CoreJSLib {
           if (asInstanceOfs != CheckedBehavior.Unchecked) {
             If((obj !== Null()) && !(This() DOT "isJSType") &&
                 !Apply(genIdentBracketSelect(This(), "isInstance"), obj :: Nil),
-              genCallHelper("throwClassCastException", obj, genIdentBracketSelect(This(), "name")),
+              genCallHelper(VarField.throwClassCastException, obj, genIdentBracketSelect(This(), "name")),
               Skip())
           } else {
             Skip()
@@ -1943,7 +1943,7 @@ private[emitter] object CoreJSLib {
               For(let(i, 0), i < lengths.length, i.++, {
                 arrayClassData := Apply(arrayClassData DOT "getArrayOf", Nil)
               }),
-              Return(genCallHelper("newArrayObject", arrayClassData, lengths))
+              Return(genCallHelper(VarField.newArrayObject, arrayClassData, lengths))
           )
         })
       }
@@ -1974,10 +1974,10 @@ private[emitter] object CoreJSLib {
       )
 
       if (useClassesForRegularClasses) {
-        extractWithGlobals(globalClassDef("TypeData", CoreVar, None, ctor :: members))
+        extractWithGlobals(globalClassDef(VarField.TypeData, CoreVar, None, ctor :: members))
       } else {
-        defineFunction("TypeData", ctor.args, ctor.body) :::
-        assignES5ClassMembers(globalVar("TypeData", CoreVar), members)
+        defineFunction(VarField.TypeData, ctor.args, ctor.body) :::
+        assignES5ClassMembers(globalVar(VarField.TypeData, CoreVar), members)
       }
     }
 
@@ -1988,7 +1988,7 @@ private[emitter] object CoreJSLib {
       val data = varRef("data")
       val arrayDepth = varRef("arrayDepth")
 
-      val forObj = extractWithGlobals(globalFunctionDef("isArrayOf", ObjectClass, paramList(obj, depth), None, {
+      val forObj = extractWithGlobals(globalFunctionDef(VarField.isArrayOf, ObjectClass, paramList(obj, depth), None, {
         Block(
             const(data, obj && (obj DOT "$classData")),
             If(!data, {
@@ -2009,7 +2009,7 @@ private[emitter] object CoreJSLib {
       val forPrims = orderedPrimRefsWithoutVoid.flatMap { primRef =>
         val obj = varRef("obj")
         val depth = varRef("depth")
-        extractWithGlobals(globalFunctionDef("isArrayOf", primRef, paramList(obj, depth), None, {
+        extractWithGlobals(globalFunctionDef(VarField.isArrayOf, primRef, paramList(obj, depth), None, {
           Return(!(!(obj && (obj DOT classData) &&
               ((obj DOT classData DOT "arrayDepth") === depth) &&
               ((obj DOT classData DOT "arrayBase") === genClassDataOf(primRef)))))
@@ -2029,11 +2029,11 @@ private[emitter] object CoreJSLib {
 
           val obj = varRef("obj")
           val depth = varRef("depth")
-          extractWithGlobals(globalFunctionDef("asArrayOf", typeRef, paramList(obj, depth), None, {
-            If(Apply(globalVar("isArrayOf", typeRef), obj :: depth :: Nil) || (obj === Null()), {
+          extractWithGlobals(globalFunctionDef(VarField.asArrayOf, typeRef, paramList(obj, depth), None, {
+            If(Apply(globalVar(VarField.isArrayOf, typeRef), obj :: depth :: Nil) || (obj === Null()), {
               Return(obj)
             }, {
-              genCallHelper("throwArrayCastException", obj, str(encodedName), depth)
+              genCallHelper(VarField.throwArrayCastException, obj, str(encodedName), depth)
             })
           }))
         }
@@ -2055,7 +2055,7 @@ private[emitter] object CoreJSLib {
         val that = varRef("that")
         val obj = varRef("obj")
 
-        val typeDataVar = globalVar("d", ObjectClass)
+        val typeDataVar = globalVar(VarField.d, ObjectClass)
 
         def privateFieldSet(fieldName: String, value: Tree): Tree =
           typeDataVar DOT fieldName := value
@@ -2064,7 +2064,7 @@ private[emitter] object CoreJSLib {
           genIdentBracketSelect(typeDataVar, fieldName) := value
 
         extractWithGlobals(
-            globalVarDef("d", ObjectClass, New(globalVar("TypeData", CoreVar), Nil))) :::
+            globalVarDef(VarField.d, ObjectClass, New(globalVar(VarField.TypeData, CoreVar), Nil))) :::
         List(
           privateFieldSet("ancestors", ObjectConstr(List((Ident(genName(ObjectClass)) -> 1)))),
           privateFieldSet("arrayEncodedName", str("L" + fullName + ";")),
@@ -2077,9 +2077,9 @@ private[emitter] object CoreJSLib {
           publicFieldSet("isInstance",
               genArrowFunction(paramList(obj), Return(obj !== Null()))),
           privateFieldSet("_arrayOf", {
-            Apply(New(globalVar("TypeData", CoreVar), Nil) DOT "initSpecializedArray", List(
+            Apply(New(globalVar(VarField.TypeData, CoreVar), Nil) DOT "initSpecializedArray", List(
               typeDataVar,
-              globalVar("ac", ObjectClass),
+              globalVar(VarField.ac, ObjectClass),
               Undefined(), // typedArray
               genArrowFunction(paramList(that), {
                 val thatDepth = varRef("thatDepth")
@@ -2094,7 +2094,7 @@ private[emitter] object CoreJSLib {
               })
             ))
           }),
-          globalVar("c", ObjectClass).prototype DOT "$classData" := typeDataVar
+          globalVar(VarField.c, ObjectClass).prototype DOT "$classData" := typeDataVar
         )
       }
 
@@ -2119,8 +2119,8 @@ private[emitter] object CoreJSLib {
             Undefined()
         }
 
-        extractWithGlobals(globalVarDef("d", primRef, {
-          Apply(New(globalVar("TypeData", CoreVar), Nil) DOT "initPrim",
+        extractWithGlobals(globalVarDef(VarField.d, primRef, {
+          Apply(New(globalVar(VarField.TypeData, CoreVar), Nil) DOT "initPrim",
               List(zero, str(primRef.charCode.toString()),
                   str(primRef.displayName),
                   if (primRef == VoidRef) Undefined()
@@ -2132,35 +2132,35 @@ private[emitter] object CoreJSLib {
       obj ::: prims
     }
 
-    private def defineFunction(name: String, args: List[ParamDef], body: Tree): List[Tree] =
+    private def defineFunction(name: VarField, args: List[ParamDef], body: Tree): List[Tree] =
       extractWithGlobals(globalFunctionDef(name, CoreVar, args, None, body))
 
     private val argRefs = List.tabulate(5)(i => varRef("arg" + i))
 
-    private def defineFunction0(name: String)(body: Tree): List[Tree] =
+    private def defineFunction0(name: VarField)(body: Tree): List[Tree] =
       defineFunction(name, Nil, body)
 
-    private def defineFunction1(name: String)(body: VarRef => Tree): List[Tree] = {
+    private def defineFunction1(name: VarField)(body: VarRef => Tree): List[Tree] = {
       val a :: _ = argRefs
       defineFunction(name, paramList(a), body(a))
     }
 
-    private def defineFunction2(name: String)(body: (VarRef, VarRef) => Tree): List[Tree] = {
+    private def defineFunction2(name: VarField)(body: (VarRef, VarRef) => Tree): List[Tree] = {
       val a :: b :: _ = argRefs
       defineFunction(name, paramList(a, b), body(a, b))
     }
 
-    private def defineFunction3(name: String)(body: (VarRef, VarRef, VarRef) => Tree): List[Tree] = {
+    private def defineFunction3(name: VarField)(body: (VarRef, VarRef, VarRef) => Tree): List[Tree] = {
       val a :: b :: c :: _ = argRefs
       defineFunction(name, paramList(a, b, c), body(a, b, c))
     }
 
-    private def defineFunction4(name: String)(body: (VarRef, VarRef, VarRef, VarRef) => Tree): List[Tree] = {
+    private def defineFunction4(name: VarField)(body: (VarRef, VarRef, VarRef, VarRef) => Tree): List[Tree] = {
       val a :: b :: c :: d :: _ = argRefs
       defineFunction(name, paramList(a, b, c, d), body(a, b, c, d))
     }
 
-    private def defineFunction5(name: String)(body: (VarRef, VarRef, VarRef, VarRef, VarRef) => Tree): List[Tree] = {
+    private def defineFunction5(name: VarField)(body: (VarRef, VarRef, VarRef, VarRef, VarRef) => Tree): List[Tree] = {
       val a :: b :: c :: d :: e :: _ = argRefs
       defineFunction(name, paramList(a, b, c, d, e), body(a, b, c, d, e))
     }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
index fa7cb5ebb1..c299d8fdd7 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
@@ -400,7 +400,7 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
 
     private def newSyntheticVar()(implicit pos: Position): js.Ident = {
       syntheticVarCounter += 1
-      fileLevelVarIdent("$x" + syntheticVarCounter)
+      fileLevelVarIdent(VarField.x, syntheticVarCounter.toString())
     }
 
     @inline
@@ -482,7 +482,7 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
         implicit pos: Position): WithGlobals[js.Function] = {
 
       performOptimisticThenPessimisticRuns {
-        val thisIdent = fileLevelVarIdent("thiz", thisOriginalName)
+        val thisIdent = fileLevelVarIdent(VarField.thiz, thisOriginalName)
         val env = env0.withExplicitThis()
         val js.Function(jsArrow, jsParams, restParam, jsBody) =
           desugarToFunctionInternal(arrow = false, params, None, body, isStat, env)
@@ -667,7 +667,7 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
               unnest(superClass, qualifier, item, rhs) {
                 (newSuperClass, newQualifier, newItem, newRhs, env0) =>
                   implicit val env = env0
-                  genCallHelper("superSet", transformExprNoChar(newSuperClass),
+                  genCallHelper(VarField.superSet, transformExprNoChar(newSuperClass),
                       transformExprNoChar(newQualifier), transformExprNoChar(item),
                       transformExprNoChar(rhs))
               }
@@ -678,7 +678,7 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
               if (needToUseGloballyMutableVarSetter(scope)) {
                 unnest(rhs) { (rhs, env0) =>
                   implicit val env = env0
-                  js.Apply(globalVar("u", scope), transformExpr(rhs, lhs.tpe) :: Nil)
+                  js.Apply(globalVar(VarField.u, scope), transformExpr(rhs, lhs.tpe) :: Nil)
                 }
               } else {
                 // Assign normally.
@@ -692,7 +692,7 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
         case StoreModule(className, value) =>
           unnest(value) { (newValue, env0) =>
             implicit val env = env0
-            js.Assign(globalVar("n", className), transformExprNoChar(newValue))
+            js.Assign(globalVar(VarField.n, className), transformExprNoChar(newValue))
           }
 
         case While(cond, body) =>
@@ -773,7 +773,7 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
             } else {
               val superCtor = {
                 if (globalKnowledge.hasStoredSuperClass(enclosingClassName)) {
-                  fileLevelVar("superClass")
+                  fileLevelVar(VarField.superClass)
                 } else {
                   val superClass =
                     globalKnowledge.getSuperClassOfJSClass(enclosingClassName)
@@ -879,9 +879,9 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
                 case (PrimArray(srcPrimRef), PrimArray(destPrimRef)) if srcPrimRef == destPrimRef =>
                   genUncheckedArraycopy(jsArgs)
                 case (RefArray(), RefArray()) =>
-                  genCallHelper("systemArraycopyRefs", jsArgs: _*)
+                  genCallHelper(VarField.systemArraycopyRefs, jsArgs: _*)
                 case _ =>
-                  genCallHelper("systemArraycopyFull", jsArgs: _*)
+                  genCallHelper(VarField.systemArraycopyFull, jsArgs: _*)
               }
             }
           }
@@ -2209,7 +2209,7 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
           genSelect(transformExprNoChar(checkNotNull(qualifier)), className, field)
 
         case SelectStatic(className, item) =>
-          globalVar("t", (className, item.name))
+          globalVar(VarField.t, (className, item.name))
 
         case SelectJSNativeMember(className, member) =>
           val jsNativeLoadSpec =
@@ -2247,10 +2247,10 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
             js.Apply(newReceiver(false) DOT transformMethodIdent(method), newArgs)
 
           def genDispatchApply(): js.Tree =
-            js.Apply(globalVar("dp", methodName), newReceiver(false) :: newArgs)
+            js.Apply(globalVar(VarField.dp, methodName), newReceiver(false) :: newArgs)
 
           def genHijackedMethodApply(className: ClassName): js.Tree =
-            genApplyStaticLike("f", className, method, newReceiver(className == BoxedCharacterClass) :: newArgs)
+            genApplyStaticLike(VarField.f, className, method, newReceiver(className == BoxedCharacterClass) :: newArgs)
 
           if (isMaybeHijackedClass(receiver.tpe) &&
               !methodName.isReflectiveProxy) {
@@ -2300,20 +2300,20 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
           val transformedArgs = newReceiver :: newArgs
 
           if (flags.isConstructor) {
-            genApplyStaticLike("ct", className, method, transformedArgs)
+            genApplyStaticLike(VarField.ct, className, method, transformedArgs)
           } else if (flags.isPrivate) {
-            genApplyStaticLike("p", className, method, transformedArgs)
+            genApplyStaticLike(VarField.p, className, method, transformedArgs)
           } else if (globalKnowledge.isInterface(className)) {
-            genApplyStaticLike("f", className, method, transformedArgs)
+            genApplyStaticLike(VarField.f, className, method, transformedArgs)
           } else {
             val fun =
-              globalVar("c", className).prototype DOT transformMethodIdent(method)
+              globalVar(VarField.c, className).prototype DOT transformMethodIdent(method)
             js.Apply(fun DOT "call", transformedArgs)
           }
 
         case ApplyStatic(flags, className, method, args) =>
           genApplyStaticLike(
-              if (flags.isPrivate) "ps" else "s",
+              if (flags.isPrivate) VarField.ps else VarField.s,
               className,
               method,
               transformTypedArgs(method.name, args))
@@ -2354,7 +2354,7 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
               else
                 genLongMethodApply(newLhs, LongImpl.toInt)
             case DoubleToInt =>
-              genCallHelper("doubleToInt", newLhs)
+              genCallHelper(VarField.doubleToInt, newLhs)
             case DoubleToFloat =>
               genFround(newLhs)
 
@@ -2366,14 +2366,14 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
                 genLongMethodApply(newLhs, LongImpl.toDouble)
             case DoubleToLong =>
               if (useBigIntForLongs)
-                genCallHelper("doubleToLong", newLhs)
+                genCallHelper(VarField.doubleToLong, newLhs)
               else
                 genLongModuleApply(LongImpl.fromDouble, newLhs)
 
             // Long -> Float (neither widening nor narrowing)
             case LongToFloat =>
               if (useBigIntForLongs)
-                genCallHelper("longToFloat", newLhs)
+                genCallHelper(VarField.longToFloat, newLhs)
               else
                 genLongMethodApply(newLhs, LongImpl.toFloat)
 
@@ -2458,14 +2458,14 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
                 case IntLiteral(r) if r != 0 =>
                   or0(js.BinaryOp(JSBinaryOp./, newLhs, newRhs))
                 case _ =>
-                  genCallHelper("intDiv", newLhs, newRhs)
+                  genCallHelper(VarField.intDiv, newLhs, newRhs)
               }
             case Int_% =>
               rhs match {
                 case IntLiteral(r) if r != 0 =>
                   or0(js.BinaryOp(JSBinaryOp.%, newLhs, newRhs))
                 case _ =>
-                  genCallHelper("intMod", newLhs, newRhs)
+                  genCallHelper(VarField.intMod, newLhs, newRhs)
               }
 
             case Int_|   => js.BinaryOp(JSBinaryOp.|, newLhs, newRhs)
@@ -2513,7 +2513,7 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
                   case LongLiteral(r) if r != 0L =>
                     wrapBigInt64(js.BinaryOp(JSBinaryOp./, newLhs, newRhs))
                   case _ =>
-                    genCallHelper("longDiv", newLhs, newRhs)
+                    genCallHelper(VarField.longDiv, newLhs, newRhs)
                 }
               } else {
                 genLongMethodApply(newLhs, LongImpl./, newRhs)
@@ -2524,7 +2524,7 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
                   case LongLiteral(r) if r != 0L =>
                     wrapBigInt64(js.BinaryOp(JSBinaryOp.%, newLhs, newRhs))
                   case _ =>
-                    genCallHelper("longMod", newLhs, newRhs)
+                    genCallHelper(VarField.longMod, newLhs, newRhs)
                 }
               } else {
                 genLongMethodApply(newLhs, LongImpl.%, newRhs)
@@ -2631,7 +2631,7 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
             case String_charAt =>
               semantics.stringIndexOutOfBounds match {
                 case CheckedBehavior.Compliant | CheckedBehavior.Fatal =>
-                  genCallHelper("charAt", newLhs, newRhs)
+                  genCallHelper(VarField.charAt, newLhs, newRhs)
                 case CheckedBehavior.Unchecked =>
                   js.Apply(genIdentBracketSelect(newLhs, "charCodeAt"), List(newRhs))
               }
@@ -2672,7 +2672,7 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
           extractWithGlobals(genAsInstanceOf(transformExprNoChar(expr), tpe))
 
         case GetClass(expr) =>
-          genCallHelper("objectGetClass", transformExprNoChar(expr))
+          genCallHelper(VarField.objectGetClass, transformExprNoChar(expr))
 
         case Clone(expr) =>
           val newExpr = transformExprNoChar(checkNotNull(expr))
@@ -2700,15 +2700,15 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
              */
             case ClassType(CloneableClass) | ClassType(SerializableClass) |
                 ClassType(ObjectClass) | AnyType =>
-              genCallHelper("objectOrArrayClone", newExpr)
+              genCallHelper(VarField.objectOrArrayClone, newExpr)
 
             // Otherwise, it is known not to be an array.
             case _ =>
-              genCallHelper("objectClone", newExpr)
+              genCallHelper(VarField.objectClone, newExpr)
           }
 
         case IdentityHashCode(expr) =>
-          genCallHelper("systemIdentityHashCode", transformExprNoChar(expr))
+          genCallHelper(VarField.systemIdentityHashCode, transformExprNoChar(expr))
 
         case WrapAsThrowable(expr) =>
           val newExpr = transformExprNoChar(expr).asInstanceOf[js.VarRef]
@@ -2727,7 +2727,7 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
         // Transients
 
         case Transient(CheckNotNull(obj)) =>
-          genCallHelper("n", transformExpr(obj, preserveChar = true))
+          genCallHelper(VarField.n, transformExpr(obj, preserveChar = true))
         case Transient(AssumeNotNull(obj)) =>
           transformExpr(obj, preserveChar = true)
 
@@ -2753,7 +2753,7 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
           }
 
         case Transient(ObjectClassName(obj)) =>
-          genCallHelper("objectClassName", transformExprNoChar(obj))
+          genCallHelper(VarField.objectClassName, transformExprNoChar(obj))
 
         case Transient(ArrayToTypedArray(expr, primRef)) =>
           val value = transformExprNoChar(checkNotNull(expr))
@@ -2800,7 +2800,7 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
 
         case Transient(JSNewVararg(constr, argsArray)) =>
           assert(!es2015, s"generated a JSNewVargs with ES 2015+ at ${tree.pos}")
-          genCallHelper("newJSObjectWithVarargs",
+          genCallHelper(VarField.newJSObjectWithVarargs,
               transformExprNoChar(constr), transformExprNoChar(argsArray))
 
         case JSPrivateSelect(qualifier, className, field) =>
@@ -2840,7 +2840,7 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
               transformExprNoChar(method)), args.map(transformJSArg))
 
         case JSSuperSelect(superClass, qualifier, item) =>
-          genCallHelper("superGet", transformExprNoChar(superClass),
+          genCallHelper(VarField.superGet, transformExprNoChar(superClass),
               transformExprNoChar(qualifier), transformExprNoChar(item))
 
         case JSImportCall(arg) =>
@@ -2902,7 +2902,7 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
           js.UnaryOp(JSUnaryOp.typeof, transformExprNoChar(globalRef))
 
         case JSLinkingInfo() =>
-          globalVar("linkingInfo", CoreVar)
+          globalVar(VarField.linkingInfo, CoreVar)
 
         // Literals
 
@@ -2943,10 +2943,10 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
               js.This()
 
             case VarKind.ExplicitThisAlias =>
-              fileLevelVar("thiz")
+              fileLevelVar(VarField.thiz)
 
             case VarKind.ClassCapture =>
-              fileLevelVar("cc", genName(name.name))
+              fileLevelVar(VarField.cc, genName(name.name))
           }
 
         case Transient(JSVarRef(name, _)) =>
@@ -2954,7 +2954,7 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
 
         case This() =>
           if (env.hasExplicitThis)
-            fileLevelVar("thiz")
+            fileLevelVar(VarField.thiz)
           else
             js.This()
 
@@ -2971,7 +2971,7 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
             for ((value, expectedType) <- captureValues.zip(expectedTypes))
               yield transformExpr(value, expectedType)
           }
-          js.Apply(globalVar("a", className), transformedArgs)
+          js.Apply(globalVar(VarField.a, className), transformedArgs)
 
         // Invalid trees
 
@@ -2984,7 +2984,7 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
       if (preserveChar || tree.tpe != CharType)
         baseResult
       else
-        genCallHelper("bC", baseResult)
+        genCallHelper(VarField.bC, baseResult)
     }
 
     private def transformApplyDynamicImport(tree: ApplyDynamicImport)(
@@ -3012,7 +3012,7 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
       }
 
       val innerCall = extractWithGlobals {
-        withDynamicGlobalVar("s", (className, method.name)) { v =>
+        withDynamicGlobalVar(VarField.s, (className, method.name)) { v =>
           js.Apply(v, newArgs)
         }
       }
@@ -3232,7 +3232,7 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
           keepOnlyDangerousVarNames = false)
     }
 
-    private def genApplyStaticLike(field: String, className: ClassName,
+    private def genApplyStaticLike(field: VarField, className: ClassName,
         method: MethodIdent, args: List[js.Tree])(
         implicit pos: Position): js.Tree = {
       js.Apply(globalVar(field, (className, method.name)), args)
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/PolyfillableBuiltin.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/PolyfillableBuiltin.scala
index 743c9b437d..908d264a9f 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/PolyfillableBuiltin.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/PolyfillableBuiltin.scala
@@ -15,7 +15,7 @@ package org.scalajs.linker.backend.emitter
 import org.scalajs.linker.interface.ESVersion
 
 private[emitter] sealed abstract class PolyfillableBuiltin(
-    val builtinName: String, val availableInESVersion: ESVersion)
+    val polyfillField: VarField, val availableInESVersion: ESVersion)
 
 private[emitter] object PolyfillableBuiltin {
   lazy val All: List[PolyfillableBuiltin] = List(
@@ -27,18 +27,18 @@ private[emitter] object PolyfillableBuiltin {
   )
 
   sealed abstract class GlobalVarBuiltin(val globalVar: String,
-      builtinName: String, availableInESVersion: ESVersion)
-      extends PolyfillableBuiltin(builtinName, availableInESVersion)
+      polyfillField: VarField, availableInESVersion: ESVersion)
+      extends PolyfillableBuiltin(polyfillField, availableInESVersion)
 
   sealed abstract class NamespacedBuiltin(val namespaceGlobalVar: String,
-      builtinName: String, availableInESVersion: ESVersion)
-      extends PolyfillableBuiltin(builtinName, availableInESVersion)
+      val builtinName: String, polyfillField: VarField, availableInESVersion: ESVersion)
+      extends PolyfillableBuiltin(polyfillField, availableInESVersion)
 
-  case object ObjectIsBuiltin extends NamespacedBuiltin("Object", "is", ESVersion.ES2015)
-  case object ImulBuiltin extends NamespacedBuiltin("Math", "imul", ESVersion.ES2015)
-  case object FroundBuiltin extends NamespacedBuiltin("Math", "fround", ESVersion.ES2015)
+  case object ObjectIsBuiltin extends NamespacedBuiltin("Object", "is", VarField.is, ESVersion.ES2015)
+  case object ImulBuiltin extends NamespacedBuiltin("Math", "imul", VarField.imul, ESVersion.ES2015)
+  case object FroundBuiltin extends NamespacedBuiltin("Math", "fround", VarField.fround, ESVersion.ES2015)
   case object PrivateSymbolBuiltin
-      extends GlobalVarBuiltin("Symbol", "privateJSFieldSymbol", ESVersion.ES2015)
-  case object GetOwnPropertyDescriptorsBuiltin
-      extends NamespacedBuiltin("Object", "getOwnPropertyDescriptors", ESVersion.ES2017)
+      extends GlobalVarBuiltin("Symbol", VarField.privateJSFieldSymbol, ESVersion.ES2015)
+  case object GetOwnPropertyDescriptorsBuiltin extends NamespacedBuiltin("Object",
+      "getOwnPropertyDescriptors", VarField.getOwnPropertyDescriptors, ESVersion.ES2017)
 }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala
index e36ee63582..0449e0ed92 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala
@@ -87,7 +87,7 @@ private[emitter] final class SJSGen(
     if (useBigIntForLongs)
       BigIntLiteral(0L)
     else
-      globalVar("L0", CoreVar)
+      globalVar(VarField.L0, CoreVar)
   }
 
   def genBoxedZeroOf(tpe: Type)(
@@ -100,7 +100,7 @@ private[emitter] final class SJSGen(
   def genBoxedCharZero()(
       implicit moduleContext: ModuleContext, globalKnowledge: GlobalKnowledge,
       pos: Position): Tree = {
-    globalVar("bC0", CoreVar)
+    globalVar(VarField.bC0, CoreVar)
   }
 
   def genLongModuleApply(methodName: MethodName, args: Tree*)(
@@ -153,7 +153,7 @@ private[emitter] final class SJSGen(
     if (esFeatures.esVersion >= ESVersion.ES2015 && semantics.nullPointers == CheckedBehavior.Unchecked)
       Apply(args.head DOT "copyTo", args.tail)
     else
-      genCallHelper("systemArraycopy", args: _*)
+      genCallHelper(VarField.systemArraycopy, args: _*)
   }
 
   def genSelect(receiver: Tree, className: ClassName, field: irt.FieldIdent)(
@@ -178,7 +178,7 @@ private[emitter] final class SJSGen(
       pos: Position): Tree = {
     val fieldName = {
       implicit val pos = field.pos
-      globalVar("r", (className, field.name))
+      globalVar(VarField.r, (className, field.name))
     }
 
     BracketSelect(receiver, fieldName)
@@ -199,7 +199,7 @@ private[emitter] final class SJSGen(
             !globalKnowledge.isInterface(className)) {
           genIsInstanceOfClass(expr, className)
         } else {
-          Apply(globalVar("is", className), List(expr))
+          Apply(globalVar(VarField.is, className), List(expr))
         }
 
       case ArrayType(arrayTypeRef) =>
@@ -207,15 +207,15 @@ private[emitter] final class SJSGen(
           case ArrayTypeRef(_:PrimRef | ClassRef(ObjectClass), 1) =>
             expr instanceof genArrayConstrOf(arrayTypeRef)
           case ArrayTypeRef(base, depth) =>
-            Apply(typeRefVar("isArrayOf", base), List(expr, IntLiteral(depth)))
+            Apply(typeRefVar(VarField.isArrayOf, base), List(expr, IntLiteral(depth)))
         }
 
       case UndefType   => expr === Undefined()
       case BooleanType => typeof(expr) === "boolean"
-      case CharType    => expr instanceof globalVar("Char", CoreVar)
-      case ByteType    => genCallHelper("isByte", expr)
-      case ShortType   => genCallHelper("isShort", expr)
-      case IntType     => genCallHelper("isInt", expr)
+      case CharType    => expr instanceof globalVar(VarField.Char, CoreVar)
+      case ByteType    => genCallHelper(VarField.isByte, expr)
+      case ShortType   => genCallHelper(VarField.isShort, expr)
+      case IntType     => genCallHelper(VarField.isInt, expr)
       case LongType    => genIsLong(expr)
       case FloatType   => genIsFloat(expr)
       case DoubleType  => typeof(expr) === "number"
@@ -239,7 +239,7 @@ private[emitter] final class SJSGen(
        */
       BooleanLiteral(false)
     } else {
-      expr instanceof globalVar("c", className)
+      expr instanceof globalVar(VarField.c, className)
     }
   }
 
@@ -251,10 +251,10 @@ private[emitter] final class SJSGen(
     className match {
       case BoxedUnitClass      => expr === Undefined()
       case BoxedBooleanClass   => typeof(expr) === "boolean"
-      case BoxedCharacterClass => expr instanceof globalVar("Char", CoreVar)
-      case BoxedByteClass      => genCallHelper("isByte", expr)
-      case BoxedShortClass     => genCallHelper("isShort", expr)
-      case BoxedIntegerClass   => genCallHelper("isInt", expr)
+      case BoxedCharacterClass => expr instanceof globalVar(VarField.Char, CoreVar)
+      case BoxedByteClass      => genCallHelper(VarField.isByte, expr)
+      case BoxedShortClass     => genCallHelper(VarField.isShort, expr)
+      case BoxedIntegerClass   => genCallHelper(VarField.isInt, expr)
       case BoxedLongClass      => genIsLong(expr)
       case BoxedFloatClass     => genIsFloat(expr)
       case BoxedDoubleClass    => typeof(expr) === "number"
@@ -267,8 +267,8 @@ private[emitter] final class SJSGen(
       pos: Position): Tree = {
     import TreeDSL._
 
-    if (useBigIntForLongs) genCallHelper("isLong", expr)
-    else expr instanceof globalVar("c", LongImpl.RuntimeLongClass)
+    if (useBigIntForLongs) genCallHelper(VarField.isLong, expr)
+    else expr instanceof globalVar(VarField.c, LongImpl.RuntimeLongClass)
   }
 
   private def genIsFloat(expr: Tree)(
@@ -276,7 +276,7 @@ private[emitter] final class SJSGen(
       pos: Position): Tree = {
     import TreeDSL._
 
-    if (semantics.strictFloats) genCallHelper("isFloat", expr)
+    if (semantics.strictFloats) genCallHelper(VarField.isFloat, expr)
     else typeof(expr) === "number"
   }
 
@@ -295,9 +295,9 @@ private[emitter] final class SJSGen(
 
         case UndefType                     => wg(Block(expr, Undefined()))
         case BooleanType                   => wg(!(!expr))
-        case CharType                      => wg(genCallHelper("uC", expr))
+        case CharType                      => wg(genCallHelper(VarField.uC, expr))
         case ByteType | ShortType| IntType => wg(expr | 0)
-        case LongType                      => wg(genCallHelper("uJ", expr))
+        case LongType                      => wg(genCallHelper(VarField.uJ, expr))
         case DoubleType                    => wg(UnaryOp(irt.JSUnaryOp.+, expr))
         case StringType                    => wg(expr || StringLiteral(""))
 
@@ -313,21 +313,21 @@ private[emitter] final class SJSGen(
         case ClassType(ObjectClass) =>
           expr
         case ClassType(className) =>
-          Apply(globalVar("as", className), List(expr))
+          Apply(globalVar(VarField.as, className), List(expr))
 
         case ArrayType(ArrayTypeRef(base, depth)) =>
-          Apply(typeRefVar("asArrayOf", base), List(expr, IntLiteral(depth)))
-
-        case UndefType   => genCallHelper("uV", expr)
-        case BooleanType => genCallHelper("uZ", expr)
-        case CharType    => genCallHelper("uC", expr)
-        case ByteType    => genCallHelper("uB", expr)
-        case ShortType   => genCallHelper("uS", expr)
-        case IntType     => genCallHelper("uI", expr)
-        case LongType    => genCallHelper("uJ", expr)
-        case FloatType   => genCallHelper("uF", expr)
-        case DoubleType  => genCallHelper("uD", expr)
-        case StringType  => genCallHelper("uT", expr)
+          Apply(typeRefVar(VarField.asArrayOf, base), List(expr, IntLiteral(depth)))
+
+        case UndefType   => genCallHelper(VarField.uV, expr)
+        case BooleanType => genCallHelper(VarField.uZ, expr)
+        case CharType    => genCallHelper(VarField.uC, expr)
+        case ByteType    => genCallHelper(VarField.uB, expr)
+        case ShortType   => genCallHelper(VarField.uS, expr)
+        case IntType     => genCallHelper(VarField.uI, expr)
+        case LongType    => genCallHelper(VarField.uJ, expr)
+        case FloatType   => genCallHelper(VarField.uF, expr)
+        case DoubleType  => genCallHelper(VarField.uD, expr)
+        case StringType  => genCallHelper(VarField.uT, expr)
         case AnyType     => expr
 
         case NoType | NullType | NothingType | _:RecordType =>
@@ -386,7 +386,7 @@ private[emitter] final class SJSGen(
     BoxedFloatClass
   ) ::: nonSmallNumberHijackedClassesOrderedForTypeTests
 
-  def genCallHelper(helperName: String, args: Tree*)(
+  def genCallHelper(helperName: VarField, args: Tree*)(
       implicit moduleContext: ModuleContext, globalKnowledge: GlobalKnowledge,
       pos: Position): Tree = {
     Apply(globalVar(helperName, CoreVar), args.toList)
@@ -405,7 +405,7 @@ private[emitter] final class SJSGen(
             Apply(genIdentBracketSelect(namespace, builtin.builtinName), args.toList)
       }
     } else {
-      WithGlobals(genCallHelper(builtin.builtinName, args: _*))
+      WithGlobals(genCallHelper(builtin.polyfillField, args: _*))
     }
   }
 
@@ -413,18 +413,18 @@ private[emitter] final class SJSGen(
       implicit moduleContext: ModuleContext, globalKnowledge: GlobalKnowledge,
       pos: Position): Tree = {
     import TreeDSL._
-    Apply(globalVar("m", moduleClass), Nil)
+    Apply(globalVar(VarField.m, moduleClass), Nil)
   }
 
   def genScalaClassNew(className: ClassName, ctor: MethodName, args: Tree*)(
       implicit moduleContext: ModuleContext, globalKnowledge: GlobalKnowledge,
       pos: Position): Tree = {
-    val encodedClassVar = globalVar("c", className)
+    val encodedClassVar = globalVar(VarField.c, className)
     val argsList = args.toList
     if (globalKnowledge.hasInlineableInit(className)) {
       New(encodedClassVar, argsList)
     } else {
-      Apply(globalVar("ct", (className, ctor)), New(encodedClassVar, Nil) :: argsList)
+      Apply(globalVar(VarField.ct, (className, ctor)), New(encodedClassVar, Nil) :: argsList)
     }
   }
 
@@ -456,7 +456,7 @@ private[emitter] final class SJSGen(
   def genNonNativeJSClassConstructor(className: ClassName)(
       implicit moduleContext: ModuleContext, globalKnowledge: GlobalKnowledge,
       pos: Position): Tree = {
-    Apply(globalVar("a", className), Nil)
+    Apply(globalVar(VarField.a, className), Nil)
   }
 
   def genLoadJSFromSpec(spec: irt.JSNativeLoadSpec,
@@ -487,7 +487,7 @@ private[emitter] final class SJSGen(
         val moduleValue = VarRef(externalModuleFieldIdent(module))
         path match {
           case "default" :: rest if moduleKind == ModuleKind.CommonJSModule =>
-            val defaultField = genCallHelper("moduleDefault", moduleValue)
+            val defaultField = genCallHelper(VarField.moduleDefault, moduleValue)
             WithGlobals(pathSelection(defaultField, rest))
           case _ =>
             WithGlobals(pathSelection(moduleValue, path))
@@ -513,7 +513,7 @@ private[emitter] final class SJSGen(
       case length :: Nil =>
         New(genArrayConstrOf(arrayTypeRef), length :: Nil)
       case _ =>
-        genCallHelper("newArrayObject", genClassDataOf(arrayTypeRef),
+        genCallHelper(VarField.newArrayObject, genClassDataOf(arrayTypeRef),
             ArrayConstr(lengths))
     }
   }
@@ -551,9 +551,9 @@ private[emitter] final class SJSGen(
 
     arrayTypeRef match {
       case ArrayTypeRef(primRef: PrimRef, 1) =>
-        globalVar("ac", primRef)
+        globalVar(VarField.ac, primRef)
       case ArrayTypeRef(ClassRef(ObjectClass), 1) =>
-        globalVar("ac", ObjectClass)
+        globalVar(VarField.ac, ObjectClass)
       case _ =>
         genClassDataOf(arrayTypeRef) DOT "constr"
     }
@@ -576,7 +576,7 @@ private[emitter] final class SJSGen(
       pos: Position): Tree = {
     typeRef match {
       case typeRef: NonArrayTypeRef =>
-        typeRefVar("d", typeRef)
+        typeRefVar(VarField.d, typeRef)
 
       case ArrayTypeRef(base, dims) =>
         val baseData = genClassDataOf(base)
@@ -598,6 +598,6 @@ private[emitter] final class SJSGen(
     if (semantics.nullPointers == CheckedBehavior.Unchecked)
       obj
     else
-      genCallHelper("n", obj)
+      genCallHelper(VarField.n, obj)
   }
 }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/VarField.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/VarField.scala
new file mode 100644
index 0000000000..2be691d96e
--- /dev/null
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/VarField.scala
@@ -0,0 +1,277 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package org.scalajs.linker.backend.emitter
+
+/** Namespace for generated fields.
+ *
+ *  Mainly to avoid duplicate strings in memory.
+ *
+ *  Also gives us additional compile-time safety against typos.
+ */
+private[emitter] final class VarField private (val str: String) extends AnyVal
+
+private[emitter] object VarField {
+  private def mk(str: String): VarField = {
+    require(str(0) == '$')
+    new VarField(str)
+  }
+
+  // Scala class related fields.
+
+  /** Scala classes (constructor functions). */
+  final val c = mk("$c")
+
+  /** Inheritable constructor functions for Scala classes. */
+  final val h = mk("$h")
+
+  /** Scala class constructors (<init>). */
+  final val ct = mk("$ct")
+
+  /** Scala class initializers (<clinit>). */
+  final val sct = mk("$sct")
+
+  /** Private (instance) methods. */
+  final val p = mk("$p")
+
+  /** Public static methods. */
+  final val s = mk("$s")
+
+  /** Private static methods. */
+  final val ps = mk("$ps")
+
+  /** Interface default and hijacked public methods. */
+  final val f = mk("$f")
+
+  /** Static fields. */
+  final val t = mk("$t")
+
+  /** Scala module accessor. */
+  final val m = mk("$m")
+
+  /** Var / let to store Scala module instance.
+   *
+   * Also used for null check in CoreJSLib.
+   */
+  final val n = mk("$n")
+
+  // JS class related fields.
+
+  /** JS Class acessor / factories. */
+  final val a = mk("$a")
+
+  /** Var / let to store (top-level) JS Class. */
+  final val b = mk("$b")
+
+  /** Names for private JS fields. */
+  final val r = mk("$r")
+
+  // Reflection
+
+  /** Class data. */
+  final val d = mk("$d")
+
+  /** isInstanceOf functions.
+   *
+   *  Also used as Object.is polyfill.
+   */
+  final val is = mk("$is")
+
+  /** asInstanceOf functions. */
+  final val as = mk("$as")
+
+  /** isInstanceOf for array functions. */
+  final val isArrayOf = mk("$isArrayOf")
+
+  /** asInstanceOf for array functions. */
+  final val asArrayOf = mk("$asArrayOf")
+
+  // Modules
+
+  /** External ES module imports. */
+  final val i = mk("$i")
+
+  /** Internal ES module imports. */
+  final val j = mk("$j")
+
+  /** ES module const export names. */
+  final val e = mk("$e")
+
+  /** Setters for globally mutable vars (for ES Modules). */
+  final val u = mk("$u")
+
+  // Local fields: Used to generate non-clashing *local* identifiers.
+
+  /** Synthetic vars for the FunctionEmitter. */
+  final val x = mk("$x")
+
+  /** Dummy inheritable constructors for JS classes. */
+  final val hh = mk("$hh")
+
+  /** Local field for class captures. */
+  final val cc = mk("$cc")
+
+  /** Local field for super class. */
+  final val superClass = mk("$superClass")
+
+  /** Local field for this replacement. */
+  final val thiz = mk("$thiz")
+
+  /** Local field for dynamic imports. */
+  final val module = mk("$module")
+
+  // Core fields: Generated by the CoreJSLib
+
+  /** The linking info object. */
+  final val linkingInfo = mk("$linkingInfo")
+
+  /** The TypeData class. */
+  final val TypeData = mk("$TypeData")
+
+  /** Long zero. */
+  final val L0 = mk("$L0")
+
+  /** Dispatchers. */
+  final val dp = mk("$dp")
+
+  // Char
+
+  /** The Char class. */
+  final val Char = mk("$Char")
+
+  /** Boxed Char zero. */
+  final val bC0 = mk("$bC0")
+
+  /** Box char. */
+  final val bC = mk("$bC")
+
+  final val charAt = mk("$charAt")
+
+  // Object helpers
+
+  final val objectClone = mk("$objectClone")
+
+  final val objectOrArrayClone = mk("$objectOrArrayClone")
+
+  final val objectGetClass = mk("$objectGetClass")
+
+  final val objectClassName = mk("$objectClassName")
+
+  final val throwNullPointerException = mk("$throwNullPointerException")
+
+  final val throwModuleInitError = mk("$throwModuleInitError")
+
+  final val valueDescription = mk("$valueDescription")
+
+  final val propertyName = mk("$propertyName")
+
+  // ID hash subsystem
+
+  final val systemIdentityHashCode = mk("$systemIdentityHashCode")
+
+  final val lastIDHash = mk("$lastIDHash")
+
+  final val idHashCodeMap = mk("$idHashCodeMap")
+
+  // Cast helpers
+
+  final val isByte = mk("$isByte")
+
+  final val isShort = mk("$isShort")
+
+  final val isInt = mk("$isInt")
+
+  final val isLong = mk("$isLong")
+
+  final val isFloat = mk("$isFloat")
+
+  final val throwClassCastException = mk("$throwClassCastException")
+
+  final val noIsInstance = mk("$noIsInstance")
+
+  // Unboxes
+  final val uV = mk("$uV")
+  final val uZ = mk("$uZ")
+  final val uC = mk("$uC")
+  final val uB = mk("$uB")
+  final val uS = mk("$uS")
+  final val uI = mk("$uI")
+  final val uJ = mk("$uJ")
+  final val uF = mk("$uF")
+  final val uD = mk("$uD")
+  final val uT = mk("$uT")
+
+  // Arrays
+
+  /** Array constructors. */
+  final val ac = mk("$ac")
+
+  /** Inheritable array constructors. */
+  final val ah = mk("$ah")
+
+  final val arraycopyGeneric = mk("$arraycopyGeneric")
+
+  final val arraycopyCheckBounds = mk("$arraycopyCheckBounds")
+
+  final val systemArraycopy = mk("$systemArraycopy")
+
+  final val systemArraycopyRefs = mk("$systemArraycopyRefs")
+
+  final val systemArraycopyFull = mk("$systemArraycopyFull")
+
+  final val newArrayObject = mk("$newArrayObject")
+
+  final val newArrayObjectInternal = mk("$newArrayObjectInternal")
+
+  final val throwArrayCastException = mk("$throwArrayCastException")
+
+  final val throwArrayIndexOutOfBoundsException = mk("$throwArrayIndexOutOFBoundsException")
+
+  final val throwArrayStoreException = mk("$throwArrayStoreException")
+
+  final val throwNegativeArraySizeException = mk("$throwNegativeArraySizeException")
+
+  // JS helpers
+
+  final val newJSObjectWithVarargs = mk("$newJSObjectWithVarargs")
+
+  final val superGet = mk("$superGet")
+
+  final val superSet = mk("$superSet")
+
+  final val resolveSuperRef = mk("$resolveSuperRef")
+
+  final val moduleDefault = mk("$moduleDefault")
+
+  // Arithmetic Call Helpers
+
+  final val intDiv = mk("$intDiv")
+
+  final val intMod = mk("$intMod")
+
+  final val longToFloat = mk("$longToFloat")
+
+  final val longDiv = mk("$longDiv")
+
+  final val longMod = mk("$longMod")
+
+  final val doubleToLong = mk("$doubleToLong")
+
+  final val doubleToInt = mk("$doubleToInt")
+
+  // Polyfills
+
+  final val imul = mk("$imul")
+  final val fround = mk("$fround")
+  final val privateJSFieldSymbol = mk("$privateJSFieldSymbol")
+  final val getOwnPropertyDescriptors = mk("$getOwnPropertyDescriptors")
+}
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/VarGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/VarGen.scala
index a2a1a12153..b58ac77235 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/VarGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/VarGen.scala
@@ -39,7 +39,7 @@ private[emitter] final class VarGen(jsGen: JSGen, nameGen: NameGen,
   import jsGen._
   import nameGen._
 
-  def globalVar[T: Scope](field: String, scope: T,
+  def globalVar[T: Scope](field: VarField, scope: T,
       origName: OriginalName = NoOriginalName)(
       implicit moduleContext: ModuleContext, globalKnowledge: GlobalKnowledge,
       pos: Position): Tree = {
@@ -51,7 +51,7 @@ private[emitter] final class VarGen(jsGen: JSGen, nameGen: NameGen,
     }
   }
 
-  def globalClassDef[T: Scope](field: String, scope: T,
+  def globalClassDef[T: Scope](field: VarField, scope: T,
       parentClass: Option[Tree], members: List[Tree],
       origName: OriginalName = NoOriginalName)(
       implicit moduleContext: ModuleContext, pos: Position): WithGlobals[List[Tree]] = {
@@ -59,7 +59,7 @@ private[emitter] final class VarGen(jsGen: JSGen, nameGen: NameGen,
     maybeExport(ident, ClassDef(Some(ident), parentClass, members), mutable = false)
   }
 
-  def globalFunctionDef[T: Scope](field: String, scope: T,
+  def globalFunctionDef[T: Scope](field: VarField, scope: T,
       args: List[ParamDef], restParam: Option[ParamDef], body: Tree,
       origName: OriginalName = NoOriginalName)(
       implicit moduleContext: ModuleContext, pos: Position): WithGlobals[List[Tree]] = {
@@ -67,7 +67,7 @@ private[emitter] final class VarGen(jsGen: JSGen, nameGen: NameGen,
     maybeExport(ident, FunctionDef(ident, args, restParam, body), mutable = false)
   }
 
-  def globalVarDef[T: Scope](field: String, scope: T, value: Tree,
+  def globalVarDef[T: Scope](field: VarField, scope: T, value: Tree,
       origName: OriginalName = NoOriginalName)(
       implicit moduleContext: ModuleContext, pos: Position): WithGlobals[List[Tree]] = {
     val ident = globalVarIdent(field, scope, origName)
@@ -75,7 +75,7 @@ private[emitter] final class VarGen(jsGen: JSGen, nameGen: NameGen,
   }
 
   /** Attention: A globalVarDecl may only be modified from the module it was declared in. */
-  def globalVarDecl[T: Scope](field: String, scope: T,
+  def globalVarDecl[T: Scope](field: VarField, scope: T,
       origName: OriginalName = NoOriginalName)(
       implicit moduleContext: ModuleContext, pos: Position): WithGlobals[List[Tree]] = {
     val ident = globalVarIdent(field, scope, origName)
@@ -86,7 +86,7 @@ private[emitter] final class VarGen(jsGen: JSGen, nameGen: NameGen,
    *  module. As such, an additional field needs to be provided for an
    *  additional setter. This is used when generating ES modules.
    */
-  def globallyMutableVarDef[T: Scope](field: String, setterField: String,
+  def globallyMutableVarDef[T: Scope](field: VarField, setterField: VarField,
       scope: T, value: Tree, origName: OriginalName = NoOriginalName)(
       implicit moduleContext: ModuleContext, pos: Position): WithGlobals[List[Tree]] = {
     val ident = globalVarIdent(field, scope, origName)
@@ -116,7 +116,7 @@ private[emitter] final class VarGen(jsGen: JSGen, nameGen: NameGen,
     globalKnowledge.getModule(scopeType.reprClass(scope)) != moduleContext.moduleID
   }
 
-  def globalVarExport[T: Scope](field: String, scope: T, exportName: ExportName,
+  def globalVarExport[T: Scope](field: VarField, scope: T, exportName: ExportName,
       origName: OriginalName = NoOriginalName)(
       implicit moduleContext: ModuleContext, globalKnowledge: GlobalKnowledge,
       pos: Position): Tree = {
@@ -133,12 +133,12 @@ private[emitter] final class VarGen(jsGen: JSGen, nameGen: NameGen,
   }
 
   /** Apply the provided body to a dynamically loaded global var */
-  def withDynamicGlobalVar[T: Scope](field: String, scope: T)(body: Tree => Tree)(
+  def withDynamicGlobalVar[T: Scope](field: VarField, scope: T)(body: Tree => Tree)(
       implicit moduleContext: ModuleContext, globalKnowledge: GlobalKnowledge,
       pos: Position): WithGlobals[Tree] = {
     val ident = globalVarIdent(field, scope)
 
-    val module = fileLevelVarIdent("$module")
+    val module = fileLevelVarIdent(VarField.module)
 
     def unitPromise = {
       globalRef("Promise").map { promise =>
@@ -186,7 +186,7 @@ private[emitter] final class VarGen(jsGen: JSGen, nameGen: NameGen,
     }
   }
 
-  private def globalVarIdent[T](field: String, scope: T,
+  private def globalVarIdent[T](field: VarField, scope: T,
       origName: OriginalName = NoOriginalName)(
       implicit pos: Position, scopeType: Scope[T]): Ident = {
     genericIdent(field, scopeType.subField(scope), origName)
@@ -205,7 +205,7 @@ private[emitter] final class VarGen(jsGen: JSGen, nameGen: NameGen,
    *
    *  Returns the relevant coreJSLibVar for primitive types, globalVar otherwise.
    */
-  def typeRefVar(field: String, typeRef: NonArrayTypeRef)(
+  def typeRefVar(field: VarField, typeRef: NonArrayTypeRef)(
       implicit moduleContext: ModuleContext, globalKnowledge: GlobalKnowledge,
       pos: Position): Tree = {
     /* Explicitly bringing `PrimRefScope` and `ClassScope` as local implicit
@@ -229,41 +229,41 @@ private[emitter] final class VarGen(jsGen: JSGen, nameGen: NameGen,
     }
   }
 
-  def fileLevelVar(field: String, subField: String,
+  def fileLevelVar(field: VarField, subField: String,
       origName: OriginalName = NoOriginalName)(
       implicit pos: Position): VarRef = {
     VarRef(fileLevelVarIdent(field, subField, origName))
   }
 
-  def fileLevelVar(field: String)(implicit pos: Position): VarRef =
+  def fileLevelVar(field: VarField)(implicit pos: Position): VarRef =
     VarRef(fileLevelVarIdent(field))
 
-  def fileLevelVarIdent(field: String, subField: String,
+  def fileLevelVarIdent(field: VarField, subField: String,
       origName: OriginalName = NoOriginalName)(
       implicit pos: Position): Ident = {
     genericIdent(field, subField, origName)
   }
 
-  def fileLevelVarIdent(field: String)(implicit pos: Position): Ident =
+  def fileLevelVarIdent(field: VarField)(implicit pos: Position): Ident =
     fileLevelVarIdent(field, NoOriginalName)
 
-  def fileLevelVarIdent(field: String, origName: OriginalName)(
+  def fileLevelVarIdent(field: VarField, origName: OriginalName)(
       implicit pos: Position): Ident = {
     genericIdent(field, "", origName)
   }
 
   def externalModuleFieldIdent(moduleName: String)(implicit pos: Position): Ident =
-    fileLevelVarIdent("i", genModuleName(moduleName), OriginalName(moduleName))
+    fileLevelVarIdent(VarField.i, genModuleName(moduleName), OriginalName(moduleName))
 
   def internalModuleFieldIdent(module: ModuleID)(implicit pos: Position): Ident =
-    fileLevelVarIdent("j", genModuleName(module.id), OriginalName(module.id))
+    fileLevelVarIdent(VarField.j, genModuleName(module.id), OriginalName(module.id))
 
-  private def genericIdent(field: String, subField: String,
+  private def genericIdent(field: VarField, subField: String,
       origName: OriginalName = NoOriginalName)(
       implicit pos: Position): Ident = {
     val name =
-      if (subField == "") "$" + field
-      else "$" + field + "_" + subField
+      if (subField == "") field.str
+      else field.str + "_" + subField
 
     Ident(avoidClashWithGlobalRef(name), origName)
   }

From 11a5e4ae597251f920f97b596cbce283218e6efd Mon Sep 17 00:00:00 2001
From: Eric K Richardson <ekrichardson@gmail.com>
Date: Wed, 1 Nov 2023 08:16:00 -0700
Subject: [PATCH 005/298] Add java.io.FilterReader and tests, move other reader
 tests to individual files

---
 .../src/main/scala/java/io/FilterReader.scala |  35 ++
 .../javalib/io/BufferedReaderTest.scala       | 166 ++++++++
 .../javalib/io/FilterReaderTest.scala         |  55 +++
 .../javalib/io/InputStreamReaderTest.scala    |  86 ++++
 .../testsuite/javalib/io/ReaderTest.scala     |  34 ++
 .../testsuite/javalib/io/ReadersTest.scala    | 366 ------------------
 .../javalib/io/StringReaderTest.scala         | 139 +++++++
 7 files changed, 515 insertions(+), 366 deletions(-)
 create mode 100644 javalib/src/main/scala/java/io/FilterReader.scala
 create mode 100644 test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/io/BufferedReaderTest.scala
 create mode 100644 test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/io/FilterReaderTest.scala
 create mode 100644 test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/io/InputStreamReaderTest.scala
 create mode 100644 test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/io/ReaderTest.scala
 delete mode 100644 test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/io/ReadersTest.scala
 create mode 100644 test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/io/StringReaderTest.scala

diff --git a/javalib/src/main/scala/java/io/FilterReader.scala b/javalib/src/main/scala/java/io/FilterReader.scala
new file mode 100644
index 0000000000..810c875dde
--- /dev/null
+++ b/javalib/src/main/scala/java/io/FilterReader.scala
@@ -0,0 +1,35 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package java.io
+
+abstract class FilterReader protected (protected val in: Reader) extends Reader {
+
+  in.getClass() // null check
+
+  override def close(): Unit = in.close()
+
+  override def mark(readLimit: Int): Unit = in.mark(readLimit)
+
+  override def markSupported(): Boolean = in.markSupported()
+
+  override def read(): Int = in.read()
+
+  override def read(buffer: Array[Char], offset: Int, count: Int): Int =
+    in.read(buffer, offset, count)
+
+  override def ready(): Boolean = in.ready()
+
+  override def reset(): Unit = in.reset()
+
+  override def skip(count: Long): Long = in.skip(count)
+}
diff --git a/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/io/BufferedReaderTest.scala b/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/io/BufferedReaderTest.scala
new file mode 100644
index 0000000000..c922ef1691
--- /dev/null
+++ b/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/io/BufferedReaderTest.scala
@@ -0,0 +1,166 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package org.scalajs.testsuite.javalib.io
+
+import java.io._
+
+import org.junit.Test
+import org.junit.Assert._
+
+import org.scalajs.testsuite.utils.AssertThrows.assertThrows
+
+class BufferedReaderTest {
+
+  val str = "line1\nline2\r\n\nline4\rline5"
+  def newReader: BufferedReader = new BufferedReader(new StringReader(str), 3)
+
+  @Test def close(): Unit = {
+    class UnderlyingReader extends StringReader(str) {
+      var closeCount: Int = 0
+
+      override def close(): Unit = {
+        closeCount += 1
+        /* Do not call super.close(), to ensure IOExceptions come from
+         * BufferedReader, and not the underlying reader.
+         */
+      }
+    }
+
+    val underlying = new UnderlyingReader
+    val r = new BufferedReader(underlying)
+    r.read()
+    assertEquals(0, underlying.closeCount)
+    r.close()
+    assertEquals(1, underlying.closeCount)
+
+    // close() actually prevents further use of the reader
+    assertThrows(classOf[IOException], r.mark(1))
+    assertThrows(classOf[IOException], r.read())
+    assertThrows(classOf[IOException], r.read(new Array[Char](1), 0, 1))
+    assertThrows(classOf[IOException], r.read(new Array[Char](1)))
+    assertThrows(classOf[IOException], r.readLine())
+    assertThrows(classOf[IOException], r.ready())
+    assertThrows(classOf[IOException], r.reset())
+    assertThrows(classOf[IOException], r.skip(1L))
+    assertThrows(classOf[IllegalArgumentException], r.skip(-1L))
+
+    // close() is idempotent
+    r.close()
+    assertEquals(1, underlying.closeCount)
+  }
+
+  @Test def read(): Unit = {
+    val r = newReader
+
+    for (c <- str) {
+      assertEquals(c, r.read().toChar)
+    }
+    assertEquals(-1, r.read())
+  }
+
+  @Test def readArrayChar(): Unit = {
+    var read = 0
+    val r = newReader
+    val buf = new Array[Char](15)
+
+    // twice to force filling internal buffer
+    for (_ <- 0 to 1) {
+      val len = r.read(buf)
+      assertTrue(len > 0)
+
+      for (i <- 0 until len)
+        assertEquals(str.charAt(i + read), buf(i))
+
+      read += len
+    }
+  }
+
+  @Test def readArrayCharIntInt(): Unit = {
+    var read = 0
+    val r = newReader
+    val buf = new Array[Char](15)
+
+    // twice to force filling internal buffer
+    for (_ <- 0 to 1) {
+      val len = r.read(buf, 1, 10)
+      assertTrue(len > 0)
+      assertTrue(len < 11)
+
+      for (i <- 0 until len)
+        assertEquals(str.charAt(i + read), buf(i + 1))
+
+      read += len
+    }
+  }
+
+  @Test def markAndReset(): Unit = {
+    val r = newReader
+    assertEquals('l': Int, r.read())
+
+    // force moving and resizing buffer
+    r.mark(10)
+
+    for (i <- 0 until 10) {
+      assertEquals(str.charAt(i + 1): Int, r.read())
+    }
+
+    r.reset()
+
+    for (i <- 1 until str.length) {
+      assertEquals(str.charAt(i): Int, r.read())
+    }
+  }
+
+  @Test def readLine(): Unit = {
+    val r = newReader
+
+    assertEquals("line1", r.readLine())
+    assertEquals("line2", r.readLine())
+    assertEquals("", r.readLine())
+    assertEquals("line4", r.readLine())
+    assertEquals("line5", r.readLine())
+    assertEquals(null, r.readLine())
+  }
+
+  @Test def readLineEmptyStream(): Unit = {
+    val r = new BufferedReader(new StringReader(""))
+
+    assertEquals(null, r.readLine())
+  }
+
+  @Test def readLineEmptyLinesOnly(): Unit = {
+    val r = new BufferedReader(new StringReader("\n\r\n\r\r\n"), 1)
+
+    for (_ <- 1 to 4)
+      assertEquals("", r.readLine())
+
+    assertEquals(null, r.readLine())
+  }
+
+  @Test def skipReturns0AfterReachingEnd(): Unit = {
+    val r = newReader
+    assertEquals(25, r.skip(100))
+    assertEquals(-1, r.read())
+
+    assertEquals(0, r.skip(100))
+    assertEquals(-1, r.read())
+  }
+
+  @Test def markSupported(): Unit = {
+    assertTrue(newReader.markSupported)
+  }
+
+  @Test def markThrowsWithNegativeLookahead(): Unit = {
+    assertThrows(classOf[IllegalArgumentException], newReader.mark(-10))
+  }
+}
diff --git a/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/io/FilterReaderTest.scala b/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/io/FilterReaderTest.scala
new file mode 100644
index 0000000000..851d8a7ff0
--- /dev/null
+++ b/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/io/FilterReaderTest.scala
@@ -0,0 +1,55 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package org.scalajs.testsuite.javalib.io
+
+import java.io._
+
+import org.junit.Test
+import org.junit.Assert._
+
+import org.scalajs.testsuite.utils.AssertThrows.{
+  assertThrows,
+  assertThrowsNPEIfCompliant
+}
+
+class FilterReaderTest {
+  // use StringReader as delegate
+  val str = "asdf"
+  def newFilterReader: FilterReader = new FilterReader(new StringReader(str)) {}
+
+  @Test def nullCtorArgThrows(): Unit = {
+    assertThrowsNPEIfCompliant(new FilterReader(null) {})
+  }
+
+  // test delegation
+  @Test def close(): Unit = {
+    val fr = newFilterReader
+
+    fr.close()
+    fr.close() // multiple is fine
+    assertThrows(classOf[IOException], fr.read())
+  }
+
+  @Test def markSupported(): Unit = {
+    assertTrue(newFilterReader.markSupported)
+  }
+
+  @Test def read(): Unit = {
+    val r = newFilterReader
+
+    for (c <- str) {
+      assertEquals(c, r.read().toChar)
+    }
+    assertEquals(-1, r.read())
+  }
+}
diff --git a/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/io/InputStreamReaderTest.scala b/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/io/InputStreamReaderTest.scala
new file mode 100644
index 0000000000..fa4ab4d4d2
--- /dev/null
+++ b/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/io/InputStreamReaderTest.scala
@@ -0,0 +1,86 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package org.scalajs.testsuite.javalib.io
+
+import scala.annotation.tailrec
+
+import java.io._
+
+import org.junit.Test
+import org.junit.Assert._
+
+import org.scalajs.testsuite.utils.AssertThrows.assertThrows
+
+class InputStreamReaderTest {
+
+  @Test def readUTF8(): Unit = {
+
+    val buf = Array[Byte](72, 101, 108, 108, 111, 32, 87, 111, 114, 108, 100,
+        46, -29, -127, -109, -29, -126, -109, -29, -127, -85, -29, -127, -95,
+        -29, -127, -81, -26, -105, -91, -26, -100, -84, -24, -86, -98, -29,
+        -126, -110, -24, -86, -83, -29, -126, -127, -29, -127, -66, -29, -127,
+        -103, -29, -127, -117, -29, -128, -126)
+
+    val r = new InputStreamReader(new ByteArrayInputStream(buf))
+
+    def expectRead(str: String): Unit = {
+      val buf = new Array[Char](str.length)
+      @tailrec
+      def readAll(readSoFar: Int): Int = {
+        if (readSoFar == buf.length) readSoFar
+        else {
+          val newlyRead = r.read(buf, readSoFar, buf.length - readSoFar)
+          if (newlyRead == -1) readSoFar
+          else readAll(readSoFar + newlyRead)
+        }
+      }
+      assertEquals(str.length, readAll(0))
+      assertEquals(str, new String(buf))
+    }
+
+    expectRead("Hello World.")
+    expectRead("こんにちは")
+    expectRead("日本語を読めますか。")
+    assertEquals(-1, r.read())
+  }
+
+  @Test def readEOFThrows(): Unit = {
+    val data = "Lorem ipsum".getBytes()
+    val streamReader = new InputStreamReader(new ByteArrayInputStream(data))
+    val bytes = new Array[Char](11)
+
+    assertEquals(11, streamReader.read(bytes))
+    // Do it twice to check for a regression where this used to throw
+    assertEquals(-1, streamReader.read(bytes))
+    assertEquals(-1, streamReader.read(bytes))
+    assertThrows(classOf[IndexOutOfBoundsException],
+        streamReader.read(bytes, 10, 3))
+    assertEquals(0, streamReader.read(new Array[Char](0)))
+  }
+
+  @Test def skipReturns0AfterReachingEnd(): Unit = {
+    val data = "Lorem ipsum".getBytes()
+    val r = new InputStreamReader(new ByteArrayInputStream(data))
+    assertTrue(r.skip(100) > 0)
+    assertEquals(-1, r.read())
+
+    assertEquals(0, r.skip(100))
+    assertEquals(-1, r.read())
+  }
+
+  @Test def markThrowsNotSupported(): Unit = {
+    val data = "Lorem ipsum".getBytes()
+    val r = new InputStreamReader(new ByteArrayInputStream(data))
+    assertThrows(classOf[IOException], r.mark(0))
+  }
+}
diff --git a/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/io/ReaderTest.scala b/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/io/ReaderTest.scala
new file mode 100644
index 0000000000..0039020c2d
--- /dev/null
+++ b/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/io/ReaderTest.scala
@@ -0,0 +1,34 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package org.scalajs.testsuite.javalib.io
+
+import java.io._
+
+import org.junit.Test
+import org.junit.Assert._
+
+/** Tests for our implementation of java.io._ reader classes */
+class ReaderTest {
+  object MyReader extends java.io.Reader {
+    def read(dbuf: Array[Char], off: Int, len: Int): Int = {
+      java.util.Arrays.fill(dbuf, off, off + len, 'A')
+      len
+    }
+    def close(): Unit = ()
+  }
+
+  @Test def skipIntIfPossible(): Unit = {
+    assertEquals(42, MyReader.skip(42))
+    assertEquals(10000, MyReader.skip(10000)) // more than the 8192 batch size
+  }
+}
diff --git a/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/io/ReadersTest.scala b/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/io/ReadersTest.scala
deleted file mode 100644
index 65eb2660a9..0000000000
--- a/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/io/ReadersTest.scala
+++ /dev/null
@@ -1,366 +0,0 @@
-/*
- * Scala.js (https://www.scala-js.org/)
- *
- * Copyright EPFL.
- *
- * Licensed under Apache License 2.0
- * (https://www.apache.org/licenses/LICENSE-2.0).
- *
- * See the NOTICE file distributed with this work for
- * additional information regarding copyright ownership.
- */
-
-package org.scalajs.testsuite.javalib.io
-
-import scala.annotation.tailrec
-
-import java.io._
-
-import org.junit.Test
-import org.junit.Assert._
-
-import org.scalajs.testsuite.utils.AssertThrows.assertThrows
-
-/** Tests for our implementation of java.io._ reader classes */
-class ReaderTest {
-  object MyReader extends java.io.Reader {
-    def read(dbuf: Array[Char], off: Int, len: Int): Int = {
-      java.util.Arrays.fill(dbuf, off, off + len, 'A')
-      len
-    }
-    def close(): Unit = ()
-  }
-
-  @Test def skipIntIfPossible(): Unit = {
-    assertEquals(42, MyReader.skip(42))
-    assertEquals(10000, MyReader.skip(10000)) // more than the 8192 batch size
-  }
-}
-
-class StringReaderTest {
-  val str = "asdf"
-  def newReader: StringReader = new StringReader(str)
-
-  @Test def read()(): Unit = {
-    val r = newReader
-
-    for (c <- str) {
-      assertEquals(c, r.read().toChar)
-    }
-
-    assertEquals(-1, r.read())
-  }
-
-  @Test def readArrayCharIntInt(): Unit = {
-    val r = newReader
-    val buf = new Array[Char](10)
-
-    assertEquals(4, r.read(buf, 2, 8))
-    assertArrayEquals(buf.map(_.toInt), Array[Int](0,0,'a','s','d','f',0,0,0,0))
-    assertEquals(-1, r.read(buf, 2, 8)) // #1560
-  }
-
-  @Test def readCharBuffer(): Unit = {
-    val r = newReader
-    val buf0 = java.nio.CharBuffer.allocate(25)
-    buf0.position(3)
-    val buf = buf0.slice()
-    buf.position(4)
-    buf.limit(14)
-
-    assertEquals(4, r.read(buf))
-    assertEquals(8, buf.position())
-    buf.flip()
-    assertArrayEquals(buf.toString().map(_.toInt).toArray,
-        Array[Int](0, 0, 0, 0, 'a', 's', 'd', 'f'))
-  }
-
-  @Test def ready(): Unit = {
-    val r = newReader
-
-    for (c <- str) {
-      assertTrue(r.ready())
-      assertEquals(c, r.read().toChar)
-    }
-
-    assertTrue(r.ready())
-    assertEquals(-1, r.read())
-
-    r.close()
-    assertThrows(classOf[IOException], r.ready())
-  }
-
-  @Test def markReset(): Unit = {
-    val r = newReader
-    r.mark(str.length)
-
-    for (c <- str) {
-      assertEquals(c, r.read().toChar)
-    }
-    assertEquals(-1, r.read())
-
-    r.reset()
-
-    for (c <- str) {
-      assertEquals(c, r.read().toChar)
-    }
-    assertEquals(-1, r.read())
-  }
-
-  @Test def skip(): Unit = {
-    val r = newReader
-
-    assertEquals('a': Int, r.read())
-    assertEquals(2, r.skip(2L).toInt)
-
-    assertEquals('f': Int, r.read())
-    assertEquals(-1, r.read())
-  }
-
-  @Test def close(): Unit = {
-    val r = newReader
-
-    r.close()
-    assertThrows(classOf[IOException], r.read())
-  }
-
-  @Test def mark(): Unit = {
-    assertTrue(newReader.markSupported)
-  }
-
-  @Test def markThrowsWithNegativeLookahead(): Unit = {
-    assertThrows(classOf[IllegalArgumentException], newReader.mark(-10))
-  }
-
-  @Test def skipAcceptsNegativeLookaheadAsLookback(): Unit = {
-    // StringReader.skip accepts negative lookahead
-    val r = newReader
-    assertEquals("already head", 0, r.skip(-1))
-    assertEquals('a', r.read())
-
-    assertEquals(1, r.skip(1))
-    assertEquals('d', r.read())
-
-    assertEquals(-2, r.skip(-2))
-    assertEquals('s', r.read())
-  }
-
-  @Test def skipReturns0AfterReachingEnd(): Unit = {
-    val r = newReader
-    assertEquals(4, r.skip(100))
-    assertEquals(-1, r.read())
-
-    assertEquals(0, r.skip(-100))
-    assertEquals(-1, r.read())
-  }
-
-}
-
-class BufferedReaderTest {
-
-  val str = "line1\nline2\r\n\nline4\rline5"
-  def newReader: BufferedReader = new BufferedReader(new StringReader(str), 3)
-
-  @Test def close(): Unit = {
-    class UnderlyingReader extends StringReader(str) {
-      var closeCount: Int = 0
-
-      override def close(): Unit = {
-        closeCount += 1
-        /* Do not call super.close(), to ensure IOExceptions come from
-         * BufferedReader, and not the underlying reader.
-         */
-      }
-    }
-
-    val underlying = new UnderlyingReader
-    val r = new BufferedReader(underlying)
-    r.read()
-    assertEquals(0, underlying.closeCount)
-    r.close()
-    assertEquals(1, underlying.closeCount)
-
-    // close() actually prevents further use of the reader
-    assertThrows(classOf[IOException], r.mark(1))
-    assertThrows(classOf[IOException], r.read())
-    assertThrows(classOf[IOException], r.read(new Array[Char](1), 0, 1))
-    assertThrows(classOf[IOException], r.read(new Array[Char](1)))
-    assertThrows(classOf[IOException], r.readLine())
-    assertThrows(classOf[IOException], r.ready())
-    assertThrows(classOf[IOException], r.reset())
-    assertThrows(classOf[IOException], r.skip(1L))
-    assertThrows(classOf[IllegalArgumentException], r.skip(-1L))
-
-    // close() is idempotent
-    r.close()
-    assertEquals(1, underlying.closeCount)
-  }
-
-  @Test def read(): Unit = {
-    val r = newReader
-
-    for (c <- str) {
-      assertEquals(c, r.read().toChar)
-    }
-    assertEquals(-1, r.read())
-  }
-
-  @Test def readArrayChar(): Unit = {
-    var read = 0
-    val r = newReader
-    val buf = new Array[Char](15)
-
-    // twice to force filling internal buffer
-    for (_ <- 0 to 1) {
-      val len = r.read(buf)
-      assertTrue(len > 0)
-
-      for (i <- 0 until len)
-        assertEquals(str.charAt(i+read), buf(i))
-
-      read += len
-    }
-  }
-
-  @Test def readArrayCharIntInt(): Unit = {
-    var read = 0
-    val r = newReader
-    val buf = new Array[Char](15)
-
-    // twice to force filling internal buffer
-    for (_ <- 0 to 1) {
-      val len = r.read(buf, 1, 10)
-      assertTrue(len > 0)
-      assertTrue(len < 11)
-
-      for (i <- 0 until len)
-        assertEquals(str.charAt(i+read), buf(i+1))
-
-      read += len
-    }
-  }
-
-  @Test def markAndReset(): Unit = {
-    val r = newReader
-    assertEquals('l': Int, r.read())
-
-    // force moving and resizing buffer
-    r.mark(10)
-
-    for (i <- 0 until 10) {
-      assertEquals(str.charAt(i+1): Int, r.read())
-    }
-
-    r.reset()
-
-    for (i <- 1 until str.length) {
-      assertEquals(str.charAt(i): Int, r.read())
-    }
-  }
-
-  @Test def readLine(): Unit = {
-    val r = newReader
-
-    assertEquals("line1", r.readLine())
-    assertEquals("line2", r.readLine())
-    assertEquals("", r.readLine())
-    assertEquals("line4", r.readLine())
-    assertEquals("line5", r.readLine())
-    assertEquals(null, r.readLine())
-  }
-
-  @Test def readLineEmptyStream(): Unit = {
-    val r = new BufferedReader(new StringReader(""))
-
-    assertEquals(null, r.readLine())
-  }
-
-  @Test def readLineEmptyLinesOnly(): Unit = {
-    val r = new BufferedReader(new StringReader("\n\r\n\r\r\n"), 1)
-
-    for (_ <- 1 to 4)
-      assertEquals("", r.readLine())
-
-    assertEquals(null, r.readLine())
-  }
-
-  @Test def skipReturns0AfterReachingEnd(): Unit = {
-    val r = newReader
-    assertEquals(25, r.skip(100))
-    assertEquals(-1, r.read())
-
-    assertEquals(0, r.skip(100))
-    assertEquals(-1, r.read())
-  }
-
-  @Test def markSupported(): Unit = {
-    assertTrue(newReader.markSupported)
-  }
-
-  @Test def markThrowsWithNegativeLookahead(): Unit = {
-    assertThrows(classOf[IllegalArgumentException], newReader.mark(-10))
-  }
-}
-
-class InputStreamReaderTest {
-
-  @Test def readUTF8(): Unit = {
-
-    val buf = Array[Byte](72, 101, 108, 108, 111, 32, 87, 111, 114, 108, 100,
-        46, -29, -127, -109, -29, -126, -109, -29, -127, -85, -29, -127, -95,
-        -29, -127, -81, -26, -105, -91, -26, -100, -84, -24, -86, -98, -29,
-        -126, -110, -24, -86, -83, -29, -126, -127, -29, -127, -66, -29, -127,
-        -103, -29, -127, -117, -29, -128, -126)
-
-    val r = new InputStreamReader(new ByteArrayInputStream(buf))
-
-    def expectRead(str: String): Unit = {
-      val buf = new Array[Char](str.length)
-      @tailrec
-      def readAll(readSoFar: Int): Int = {
-        if (readSoFar == buf.length) readSoFar
-        else {
-          val newlyRead = r.read(buf, readSoFar, buf.length - readSoFar)
-          if (newlyRead == -1) readSoFar
-          else readAll(readSoFar + newlyRead)
-        }
-      }
-      assertEquals(str.length, readAll(0))
-      assertEquals(str, new String(buf))
-    }
-
-    expectRead("Hello World.")
-    expectRead("こんにちは")
-    expectRead("日本語を読めますか。")
-    assertEquals(-1, r.read())
-  }
-
-  @Test def readEOFThrows(): Unit = {
-    val data = "Lorem ipsum".getBytes()
-    val streamReader = new InputStreamReader(new ByteArrayInputStream(data))
-    val bytes = new Array[Char](11)
-
-    assertEquals(11, streamReader.read(bytes))
-    // Do it twice to check for a regression where this used to throw
-    assertEquals(-1, streamReader.read(bytes))
-    assertEquals(-1, streamReader.read(bytes))
-    assertThrows(classOf[IndexOutOfBoundsException], streamReader.read(bytes, 10, 3))
-    assertEquals(0, streamReader.read(new Array[Char](0)))
-  }
-
-  @Test def skipReturns0AfterReachingEnd(): Unit = {
-    val data = "Lorem ipsum".getBytes()
-    val r = new InputStreamReader(new ByteArrayInputStream(data))
-    assertTrue(r.skip(100) > 0)
-    assertEquals(-1, r.read())
-
-    assertEquals(0, r.skip(100))
-    assertEquals(-1, r.read())
-  }
-
-  @Test def markThrowsNotSupported(): Unit = {
-    val data = "Lorem ipsum".getBytes()
-    val r = new InputStreamReader(new ByteArrayInputStream(data))
-    assertThrows(classOf[IOException], r.mark(0))
-  }
-}
diff --git a/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/io/StringReaderTest.scala b/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/io/StringReaderTest.scala
new file mode 100644
index 0000000000..0c23d55c7b
--- /dev/null
+++ b/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/io/StringReaderTest.scala
@@ -0,0 +1,139 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package org.scalajs.testsuite.javalib.io
+
+import java.io._
+
+import org.junit.Test
+import org.junit.Assert._
+
+import org.scalajs.testsuite.utils.AssertThrows.assertThrows
+
+class StringReaderTest {
+  val str = "asdf"
+  def newReader: StringReader = new StringReader(str)
+
+  @Test def read()(): Unit = {
+    val r = newReader
+
+    for (c <- str) {
+      assertEquals(c, r.read().toChar)
+    }
+
+    assertEquals(-1, r.read())
+  }
+
+  @Test def readArrayCharIntInt(): Unit = {
+    val r = newReader
+    val buf = new Array[Char](10)
+
+    assertEquals(4, r.read(buf, 2, 8))
+    assertArrayEquals(buf.map(_.toInt),
+        Array[Int](0, 0, 'a', 's', 'd', 'f', 0, 0, 0, 0))
+    assertEquals(-1, r.read(buf, 2, 8)) // #1560
+  }
+
+  @Test def readCharBuffer(): Unit = {
+    val r = newReader
+    val buf0 = java.nio.CharBuffer.allocate(25)
+    buf0.position(3)
+    val buf = buf0.slice()
+    buf.position(4)
+    buf.limit(14)
+
+    assertEquals(4, r.read(buf))
+    assertEquals(8, buf.position())
+    buf.flip()
+    assertArrayEquals(buf.toString().map(_.toInt).toArray,
+        Array[Int](0, 0, 0, 0, 'a', 's', 'd', 'f'))
+  }
+
+  @Test def ready(): Unit = {
+    val r = newReader
+
+    for (c <- str) {
+      assertTrue(r.ready())
+      assertEquals(c, r.read().toChar)
+    }
+
+    assertTrue(r.ready())
+    assertEquals(-1, r.read())
+
+    r.close()
+    assertThrows(classOf[IOException], r.ready())
+  }
+
+  @Test def markReset(): Unit = {
+    val r = newReader
+    r.mark(str.length)
+
+    for (c <- str) {
+      assertEquals(c, r.read().toChar)
+    }
+    assertEquals(-1, r.read())
+
+    r.reset()
+
+    for (c <- str) {
+      assertEquals(c, r.read().toChar)
+    }
+    assertEquals(-1, r.read())
+  }
+
+  @Test def skip(): Unit = {
+    val r = newReader
+
+    assertEquals('a': Int, r.read())
+    assertEquals(2, r.skip(2L).toInt)
+
+    assertEquals('f': Int, r.read())
+    assertEquals(-1, r.read())
+  }
+
+  @Test def close(): Unit = {
+    val r = newReader
+
+    r.close()
+    assertThrows(classOf[IOException], r.read())
+  }
+
+  @Test def mark(): Unit = {
+    assertTrue(newReader.markSupported)
+  }
+
+  @Test def markThrowsWithNegativeLookahead(): Unit = {
+    assertThrows(classOf[IllegalArgumentException], newReader.mark(-10))
+  }
+
+  @Test def skipAcceptsNegativeLookaheadAsLookback(): Unit = {
+    // StringReader.skip accepts negative lookahead
+    val r = newReader
+    assertEquals("already head", 0, r.skip(-1))
+    assertEquals('a', r.read())
+
+    assertEquals(1, r.skip(1))
+    assertEquals('d', r.read())
+
+    assertEquals(-2, r.skip(-2))
+    assertEquals('s', r.read())
+  }
+
+  @Test def skipReturns0AfterReachingEnd(): Unit = {
+    val r = newReader
+    assertEquals(4, r.skip(100))
+    assertEquals(-1, r.read())
+
+    assertEquals(0, r.skip(-100))
+    assertEquals(-1, r.read())
+  }
+}

From 95346cf427ea4e78e177c299bbff61b4e0efa219 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Wed, 8 Nov 2023 12:17:49 +0100
Subject: [PATCH 006/298] Bump the version to 1.15.0-SNAPSHOT for the upcoming
 changes.

---
 ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala b/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala
index 4d7495cf96..c97b15f22f 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala
@@ -17,7 +17,7 @@ import java.util.concurrent.ConcurrentHashMap
 import scala.util.matching.Regex
 
 object ScalaJSVersions extends VersionChecks(
-    current = "1.14.1-SNAPSHOT",
+    current = "1.15.0-SNAPSHOT",
     binaryEmitted = "1.13"
 )
 

From b50df89ffcea28ed1d758295a6e12348a3a9568f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Wed, 8 Nov 2023 12:26:42 +0100
Subject: [PATCH 007/298] Split the scalalib .sjsir files in a separate
 artifact scalajs-scalalib.

Previously, the `.sjsir` files of the scalalib (and libraryAux)
were bundled inside scalajs-library.jar. With the plan to drop
forward binary compatibility of the upstream scala-library.jar,
this model will not work anymore.

We now publish those `.sjsir` files in their own artifact
`scalajs-scalalib.jar`. It is versioned *both* with the Scala
version number and the Scala.js version number, in a way that will
allow Ivy resolution to pick the right one.

At the POM level, `scalajs-scalalib` depends on `scalajs-javalib`.
`scalajs-library` depends on the other two. However, in terms of
*actual* content dependencies, as is, `scalajs-scalalib` also
depends on `scalajs-library`.

If the former is present on a classpath but not (a recent enough
version of) the latter, linking errors can appear. This should
not be an issue because any real build that depends on
`scalajs-scalalib` will also depend on `scalajs-library`. Moreover,
if a more recent `scalajs-scalalib` is picked up by Ivy resolution
that implicitly depends on a more recent `scalajs-library`, the
library that introduces that dependency would also *explicitly*
depend on the more recent `scalajs-library`, and so the latter
would also be picked up by Ivy resolution.

The sbt plugin explicitly adds a dependency on the
`scalajs-scalalib` with a Scala/Scala.js version combination
that matches `scalaVersion` and `scalaJSVersion`. This way,
if it uses a Scala.js version that was built for Scala 2.13.12
but it itself uses Scala 2.13.15, it will get the back-published
`scalajs-library` built for Scala 2.13.15.
---
 build.sbt                                     |   3 +-
 project/Build.scala                           | 114 ++++++++++++------
 .../sbtplugin/ScalaJSPluginInternal.scala     |   8 ++
 scripts/publish.sh                            |   6 +-
 4 files changed, 92 insertions(+), 39 deletions(-)

diff --git a/build.sbt b/build.sbt
index e3374e3358..e9bdde6b6b 100644
--- a/build.sbt
+++ b/build.sbt
@@ -14,8 +14,9 @@ val sbtPlugin = Build.plugin
 val javalibintf = Build.javalibintf
 val javalibInternal = Build.javalibInternal
 val javalib = Build.javalib
-val scalalib = Build.scalalib
+val scalalibInternal = Build.scalalibInternal
 val libraryAux = Build.libraryAux
+val scalalib = Build.scalalib
 val library = Build.library
 val testInterface = Build.testInterface
 val testBridge = Build.testBridge
diff --git a/project/Build.scala b/project/Build.scala
index 796bc8e4b7..8deb00803d 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -197,7 +197,7 @@ object MyScalaJSPlugin extends AutoPlugin {
        */
       libraryDependencies ~= { libDeps =>
         val blacklist =
-          Set("scalajs-compiler", "scalajs-library", "scalajs-test-bridge")
+          Set("scalajs-compiler", "scalajs-library", "scalajs-scalalib", "scalajs-test-bridge")
         libDeps.filterNot(dep => blacklist.contains(dep.name))
       },
 
@@ -638,7 +638,7 @@ object Build {
    *  - `"semver-spec"` for artifacts whose public API can only break in major releases (e.g., `library`)
    *
    *  At the moment, we only set the version scheme for artifacts in the
-   *  "library ecosystem", i.e., scalajs-javalib scalajs-library,
+   *  "library ecosystem", i.e., scalajs-javalib, scalajs-scalalib, scalajs-library,
    *  scalajs-test-interface, scalajs-junit-runtime and scalajs-test-bridge.
    *  Artifacts of the "tools ecosystem" do not have a version scheme set, as
    *  the jury is still out on what is the best way to specify them.
@@ -749,7 +749,7 @@ object Build {
       }
     }
 
-    /** Depends on library and, by artificial transitivity, on the javalib. */
+    /** Depends on library and, by artificial transitivity, on the javalib and scalalib. */
     def dependsOnLibrary2_12: Project = {
       val library = LocalProject("library2_12")
 
@@ -757,9 +757,9 @@ object Build {
       val project1 = project
         .dependsOn(library)
 
-      /* Because the javalib's exportsJar is false, but its actual products are
-       * only in its jar, we must manually add the jar on the internal
-       * classpath.
+      /* Because the javalib's and scalalib's exportsJar is false, but their
+       * actual products are  only in their jar, we must manually add the jars
+       * on the internal classpath.
        * Once published, only jars are ever used, so this is fine.
        */
       if (isGeneratingForIDE) {
@@ -772,6 +772,12 @@ object Build {
             Test / internalDependencyClasspath +=
               (javalib / Compile / packageBin).value,
           )
+          .settings(
+            Compile / internalDependencyClasspath +=
+              (scalalib.v2_12 / Compile / packageBin).value,
+            Test / internalDependencyClasspath +=
+              (scalalib.v2_12 / Compile / packageBin).value,
+          )
       }
     }
 
@@ -818,21 +824,21 @@ object Build {
       }
     }
 
-    /** Depends on library and, by transitivity, on the javalib. */
+    /** Depends on library and, by artificial transitivity, on the javalib and scalalib. */
     def dependsOnLibrary: MultiScalaProject = {
       // Add a real dependency on the library
       val project1 = project
         .dependsOn(library)
 
-      /* Because the javalib's exportsJar is false, but its actual products are
-       * only in its jar, we must manually add the jar on the internal
-       * classpath.
+      /* Because the javalib's and scalalib's exportsJar is false, but their
+       * actual products are  only in their jar, we must manually add the jars
+       * on the internal classpath.
        * Once published, only jars are ever used, so this is fine.
        */
       if (isGeneratingForIDE) {
         project1
       } else {
-        // Actually add classpath dependencies on the javalib jar
+        // Actually add classpath dependencies on the javalib and scalalib jars
         project1
           .settings(
             Compile / internalDependencyClasspath +=
@@ -840,6 +846,14 @@ object Build {
             Test / internalDependencyClasspath +=
               (javalib / Compile / packageBin).value,
           )
+          .zippedSettings(scalalib) { scalalib =>
+            Def.settings(
+              Compile / internalDependencyClasspath +=
+                (scalalib / Compile / packageBin).value,
+              Test / internalDependencyClasspath +=
+                (scalalib / Compile / packageBin).value,
+            )
+          }
       }
     }
 
@@ -919,7 +933,7 @@ object Build {
             linkerInterface, linkerInterfaceJS, linker, linkerJS,
             testAdapter,
             javalibintf,
-            javalibInternal, javalib, scalalib, libraryAux, library,
+            javalibInternal, javalib, scalalibInternal, libraryAux, scalalib, library,
             testInterface, jUnitRuntime, testBridge, jUnitPlugin, jUnitAsyncJS,
             jUnitAsyncJVM, jUnitTestOutputsJS, jUnitTestOutputsJVM,
             helloworld, reversi, testingExample, testSuite, testSuiteJVM,
@@ -1358,12 +1372,14 @@ object Build {
             // JS libs
             publishLocal in javalib,
 
+            publishLocal in scalalib.v2_12,
             publishLocal in library.v2_12,
             publishLocal in testInterface.v2_12,
             publishLocal in testBridge.v2_12,
             publishLocal in jUnitRuntime.v2_12,
             publishLocal in irProjectJS.v2_12,
 
+            publishLocal in scalalib.v2_13,
             publishLocal in library.v2_13,
             publishLocal in testInterface.v2_13,
             publishLocal in testBridge.v2_13,
@@ -1478,7 +1494,7 @@ object Build {
    *  copied from `javalibInternal`.
    *
    *  This the "public" version of the javalib, as depended on by the `library`
-   *  and published on Maven.
+   *  and `scalalib`, and published on Maven.
    */
   lazy val javalib: Project = Project(
       id = "javalib", base = file("javalib-public")
@@ -1506,8 +1522,13 @@ object Build {
       },
   )
 
-  lazy val scalalib: MultiScalaProject = MultiScalaProject(
-      id = "scalalib", base = file("scalalib")
+  /** The project that actually compiles the `scalalib`, but which is not
+   *  exposed.
+   *
+   *  Instead, its products are copied in `scalalib`.
+   */
+  lazy val scalalibInternal: MultiScalaProject = MultiScalaProject(
+      id = "scalalibInternal", base = file("scalalib")
   ).enablePlugins(
       MyScalaJSPlugin
   ).settings(
@@ -1523,7 +1544,7 @@ object Build {
             s"https://raw.githubusercontent.com/scala/scala/v${scalaVersion.value}/src/library/")
         option ++ prev
       },
-      name := "Scala library for Scala.js",
+      name := "scalajs-scalalib-internal",
       publishArtifact in Compile := false,
       NoIDEExport.noIDEExportSettings,
       delambdafySetting,
@@ -1669,12 +1690,54 @@ object Build {
       recompileAllOrNothingSettings,
   ).withScalaJSCompiler.dependsOnLibraryNoJar
 
+  /** An empty project, without source nor dependencies (other than the javalib),
+   *  whose products are copied from `scalalibInternal` and `libraryAux`.
+   *
+   *  This the "public" version of the scalalib, as depended on by the `library`
+   *  and published on Maven.
+   */
+  lazy val scalalib: MultiScalaProject = MultiScalaProject(
+      id = "scalalib", base = file("scalalib-public")
+  ).dependsOn(
+    javalib,
+  ).settings(
+      commonSettings,
+      name := "scalajs-scalalib",
+      publishSettings(Some(VersionScheme.BreakOnMajor)),
+
+      /* The scalalib has a special version number that encodes both the Scala
+       * version and the Scala.js version. This allows us to back-publish for
+       * newer versions of Scala and older versions of Scala.js. The Scala
+       * version comes first so that Ivy resolution will choose 2.13.20+1.15.0
+       * over 2.13.18+1.16.0. The former might not be as optimized as the
+       * latter, but at least it will contain all the binary API that might be
+       * required.
+       */
+      version := scalaVersion.value + "+" + scalaJSVersion,
+
+      exportJars := false, // very important, otherwise there's a cycle with the `library`
+  ).zippedSettings(Seq("scalalibInternal", "libraryAux"))(localProjects =>
+      inConfig(Compile)(Seq(
+        // Use the .sjsir files from scalalibInternal and libraryAux (but not the .class files)
+        Compile / packageBin / mappings := {
+          val scalalibInternalMappings = (localProjects(0) / packageBin / mappings).value
+          val libraryAuxMappings = (localProjects(1) / packageBin / mappings).value
+          val allMappings = scalalibInternalMappings ++ libraryAuxMappings
+          allMappings.filter(_._2.endsWith(".sjsir"))
+        },
+    ))
+  )
+
   lazy val library: MultiScalaProject = MultiScalaProject(
       id = "library", base = file("library")
   ).enablePlugins(
       MyScalaJSPlugin
   ).dependsOn(
+      // Project dependencies
       javalibintf % Provided, javalib,
+  ).dependsOn(
+      // MultiScalaProject dependencies
+      scalalib,
   ).settings(
       commonSettings,
       publishSettings(Some(VersionScheme.BreakOnMajor)),
@@ -1727,25 +1790,6 @@ object Build {
            */
           dependencyClasspath in doc ++= exportedProducts.value,
       ))
-  ).zippedSettings(Seq("scalalib", "libraryAux"))(localProjects =>
-        inConfig(Compile)(Seq(
-          /* Add the .sjsir files from other lib projects
-           * (but not .class files)
-           */
-          mappings in packageBin := {
-            val libraryMappings = (mappings in packageBin).value
-
-            val filter = ("*.sjsir": NameFilter)
-
-            val otherProducts = (
-                (products in localProjects(0)).value ++
-                (products in localProjects(1)).value)
-            val otherMappings =
-              otherProducts.flatMap(base => Path.selectSubpaths(base, filter))
-
-            libraryMappings ++ otherMappings
-          },
-      ))
   ).withScalaJSCompiler
 
   // The Scala.js version of sbt-testing-interface
diff --git a/sbt-plugin/src/main/scala/org/scalajs/sbtplugin/ScalaJSPluginInternal.scala b/sbt-plugin/src/main/scala/org/scalajs/sbtplugin/ScalaJSPluginInternal.scala
index c45eabf03c..6f1d6f66a4 100644
--- a/sbt-plugin/src/main/scala/org/scalajs/sbtplugin/ScalaJSPluginInternal.scala
+++ b/sbt-plugin/src/main/scala/org/scalajs/sbtplugin/ScalaJSPluginInternal.scala
@@ -795,6 +795,8 @@ private[sbtplugin] object ScalaJSPluginInternal {
               scalaOrg %% "scala3-library_sjs1" % scalaV,
               /* scala3-library_sjs1 depends on some version of scalajs-library_2.13,
                * but we bump it to be at least scalaJSVersion.
+               * (It will also depend on some version of scalajs-scalalib_2.13,
+               * but we do not have to worry about that here.)
                */
               "org.scala-js" % "scalajs-library_2.13" % scalaJSVersion,
               "org.scala-js" % "scalajs-test-bridge_2.13" % scalaJSVersion % "test"
@@ -803,6 +805,12 @@ private[sbtplugin] object ScalaJSPluginInternal {
           prev ++ Seq(
               compilerPlugin("org.scala-js" % "scalajs-compiler" % scalaJSVersion cross CrossVersion.full),
               "org.scala-js" %% "scalajs-library" % scalaJSVersion,
+              /* scalajs-library depends on some version of scalajs-scalalib,
+               * but we want to make sure to bump it to be at least the one
+               * of our own `scalaVersion` (which would have back-published in
+               * the meantime).
+               */
+              "org.scala-js" %% "scalajs-scalalib" % s"$scalaV+$scalaJSVersion",
               "org.scala-js" %% "scalajs-test-bridge" % scalaJSVersion % "test"
           )
         }
diff --git a/scripts/publish.sh b/scripts/publish.sh
index 6a6ac44d00..1158326a4e 100755
--- a/scripts/publish.sh
+++ b/scripts/publish.sh
@@ -10,7 +10,7 @@ fi
 SUFFIXES="2_12 2_13"
 
 JAVA_LIBS="javalibintf javalib"
-COMPILER="compiler jUnitPlugin"
+FULL_SCALA_LIBS="compiler jUnitPlugin scalalib"
 JS_LIBS="library irJS linkerInterfaceJS linkerJS testInterface testBridge jUnitRuntime"
 JVM_LIBS="ir linkerInterface linker testAdapter"
 SCALA_LIBS="$JS_LIBS $JVM_LIBS"
@@ -22,10 +22,10 @@ for p in $JAVA_LIBS; do
 done
 $CMD $ARGS
 
-# Publish compiler
+# Publish artifacts built with the full Scala version
 for s in $SUFFIXES; do
     ARGS=""
-    for p in $COMPILER; do
+    for p in $FULL_SCALA_LIBS; do
         ARGS="$ARGS +$p$s/publishSigned"
     done
     $CMD $ARGS

From df42b552753fffa0759f0ad62abc72c7002074d4 Mon Sep 17 00:00:00 2001
From: Tobias Schlatter <tobias@meisch.ch>
Date: Tue, 26 Dec 2023 15:59:52 +0100
Subject: [PATCH 008/298] Version 1.15.0.

---
 ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala b/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala
index c97b15f22f..b6476e0c09 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala
@@ -17,7 +17,7 @@ import java.util.concurrent.ConcurrentHashMap
 import scala.util.matching.Regex
 
 object ScalaJSVersions extends VersionChecks(
-    current = "1.15.0-SNAPSHOT",
+    current = "1.15.0",
     binaryEmitted = "1.13"
 )
 

From a6a5597c28d2a01be43e3a240f610ae2724bcb55 Mon Sep 17 00:00:00 2001
From: Tobias Schlatter <tobias@meisch.ch>
Date: Wed, 27 Dec 2023 16:38:21 +0100
Subject: [PATCH 009/298] Towards 1.15.1.

---
 ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala | 2 +-
 project/Build.scala                                           | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala b/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala
index b6476e0c09..8dfbb764e2 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala
@@ -17,7 +17,7 @@ import java.util.concurrent.ConcurrentHashMap
 import scala.util.matching.Regex
 
 object ScalaJSVersions extends VersionChecks(
-    current = "1.15.0",
+    current = "1.15.1-SNAPSHOT",
     binaryEmitted = "1.13"
 )
 
diff --git a/project/Build.scala b/project/Build.scala
index 8deb00803d..93209c3ddb 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -338,7 +338,7 @@ object Build {
   val previousVersions = List("1.0.0", "1.0.1", "1.1.0", "1.1.1", "1.2.0",
       "1.3.0", "1.3.1", "1.4.0", "1.5.0", "1.5.1", "1.6.0", "1.7.0", "1.7.1",
       "1.8.0", "1.9.0", "1.10.0", "1.10.1", "1.11.0", "1.12.0", "1.13.0",
-      "1.13.1", "1.13.2", "1.14.0")
+      "1.13.1", "1.13.2", "1.14.0", "1.15.0")
   val previousVersion = previousVersions.last
 
   val previousBinaryCrossVersion = CrossVersion.binaryWith("sjs1_", "")

From 102cae69d8b5fbbfb14a16eabbdbdd6aa1742242 Mon Sep 17 00:00:00 2001
From: Tobias Schlatter <tobias@meisch.ch>
Date: Thu, 28 Dec 2023 13:58:49 +0100
Subject: [PATCH 010/298] Add "create a release" to release steps

---
 RELEASING.md | 1 +
 1 file changed, 1 insertion(+)

diff --git a/RELEASING.md b/RELEASING.md
index 60965a93fa..b143e9a93e 100644
--- a/RELEASING.md
+++ b/RELEASING.md
@@ -26,6 +26,7 @@
 1. When merging the release announcement PR (after proper review):
     - Update the latest/ URLs (use `~/setlatestapi.sh <full sjs version>` on
       webserver)
+    - Create a release on the core scala-js repository.
     - Announce on Twitter using the @scala_js account
     - Announce on [Gitter](https://gitter.im/scala-js/scala-js)
     - Cross-post as an Announcement in Scala Users ([example][7])

From 3572a4b53b20f5d11964cef0e95852d184ca1d52 Mon Sep 17 00:00:00 2001
From: Tobias Schlatter <tobias@meisch.ch>
Date: Tue, 2 Jan 2024 14:06:44 +0100
Subject: [PATCH 011/298] Test that we can link twice on the same linker with
 GCC

Ensures that we catch issues like this:
https://github.com/scala-js/scala-js/pull/4917#issuecomment-1873311523
---
 .../org/scalajs/linker/GCCLinkerTest.scala    | 30 +++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/linker/jvm/src/test/scala/org/scalajs/linker/GCCLinkerTest.scala b/linker/jvm/src/test/scala/org/scalajs/linker/GCCLinkerTest.scala
index a399e4588b..1872712651 100644
--- a/linker/jvm/src/test/scala/org/scalajs/linker/GCCLinkerTest.scala
+++ b/linker/jvm/src/test/scala/org/scalajs/linker/GCCLinkerTest.scala
@@ -16,9 +16,13 @@ import org.junit.Test
 
 import org.scalajs.junit.async._
 
+import org.scalajs.logging._
+
 import org.scalajs.linker.interface.StandardConfig
 
+import org.scalajs.linker.testutils.{MemClassDefIRFile, TestIRRepo}
 import org.scalajs.linker.testutils.LinkingUtils._
+import org.scalajs.linker.testutils.TestIRBuilder._
 
 class GCCLinkerTest {
   import scala.concurrent.ExecutionContext.Implicits.global
@@ -30,4 +34,30 @@ class GCCLinkerTest {
      */
     testLink(Nil, Nil, config = StandardConfig().withClosureCompiler(true))
   }
+
+  @Test
+  def linkIncrementalSmoke(): AsyncResult = await {
+    /* Check that linking twice works. GCC trees are highly mutable, so if we
+     * (re-)use them wrongly over multiple runs, things can fail unexpectedly.
+     *
+     * We change something about the code in the second run to force the linker
+     * to actually re-run.
+     */
+    def classDef(text: String) =
+      MemClassDefIRFile(mainTestClassDef(consoleLog(str(text))))
+
+    val moduleInitializers = MainTestModuleInitializers
+
+    val config = StandardConfig().withCheckIR(true).withClosureCompiler(true)
+    val linker = StandardImpl.linker(config)
+
+    val output = MemOutputDirectory()
+    val logger = new ScalaConsoleLogger(Level.Error)
+
+    for {
+      lib <- TestIRRepo.minilib
+      _ <- linker.link(lib :+ classDef("test 1"), moduleInitializers, output, logger)
+      _ <- linker.link(lib :+ classDef("test 2"), moduleInitializers, output, logger)
+    } yield ()
+  }
 }

From e55b62448b4508a13a2f28e9b0dbc4922931d8d2 Mon Sep 17 00:00:00 2001
From: Tobias Schlatter <tobias@meisch.ch>
Date: Thu, 28 Dec 2023 16:32:42 +0100
Subject: [PATCH 012/298] Basic tests for javascript.Printers

We're going to do modifications, so we add some tests.
---
 .../backend/javascript/PrintersTest.scala     | 164 ++++++++++++++++++
 1 file changed, 164 insertions(+)
 create mode 100644 linker/shared/src/test/scala/org/scalajs/linker/backend/javascript/PrintersTest.scala

diff --git a/linker/shared/src/test/scala/org/scalajs/linker/backend/javascript/PrintersTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/backend/javascript/PrintersTest.scala
new file mode 100644
index 0000000000..c43b1a28e9
--- /dev/null
+++ b/linker/shared/src/test/scala/org/scalajs/linker/backend/javascript/PrintersTest.scala
@@ -0,0 +1,164 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package org.scalajs.linker.backend.javascript
+
+import scala.language.implicitConversions
+
+import java.nio.charset.StandardCharsets
+
+import org.junit.Test
+import org.junit.Assert._
+
+import org.scalajs.ir
+
+import Trees._
+
+class PrintersTest {
+
+  private implicit val pos: ir.Position = ir.Position.NoPosition
+
+  private implicit def str2ident(name: String): Ident =
+    Ident(name, ir.OriginalName.NoOriginalName)
+
+  private def assertPrintEquals(expected: String, tree: Tree): Unit = {
+    val out = new ByteArrayWriter
+    val printer = new Printers.JSTreePrinter(out)
+    printer.printTopLevelTree(tree)
+    assertEquals(expected.stripMargin.trim + "\n",
+        new String(out.toByteArray(), StandardCharsets.UTF_8))
+  }
+
+  @Test def printFunctionDef(): Unit = {
+    assertPrintEquals(
+        """
+          |function test() {
+          |  const x = 2;
+          |  return x
+          |}
+        """,
+        FunctionDef("test", Nil, None, Block(
+          Let("x", mutable = false, Some(IntLiteral(2))),
+          Return(VarRef("x"))))
+    )
+
+    assertPrintEquals(
+        """
+          |function test() {
+          |  /*<skip>*/
+          |}
+        """,
+        FunctionDef("test", Nil, None, Skip())
+    )
+  }
+
+  @Test def printClassDef(): Unit = {
+    assertPrintEquals(
+        """
+          |class MyClass extends foo.Other {
+          |}
+        """,
+        ClassDef(Some("MyClass"), Some(DotSelect(VarRef("foo"), "Other")), Nil)
+    )
+
+    assertPrintEquals(
+        """
+          |class MyClass {
+          |  foo() {
+          |    /*<skip>*/
+          |  };
+          |  get a() {
+          |    return 1
+          |  };
+          |  set a(x) {
+          |    /*<skip>*/
+          |  };
+          |}
+        """,
+        ClassDef(Some("MyClass"), None, List(
+          MethodDef(false, "foo", Nil, None, Skip()),
+          GetterDef(false, "a", Return(IntLiteral(1))),
+          SetterDef(false, "a", ParamDef("x"), Skip())
+        ))
+    )
+  }
+
+  @Test def printDocComment(): Unit = {
+    assertPrintEquals(
+      """
+        | /** test */
+      """,
+      DocComment("test")
+    )
+  }
+
+  @Test def printFor(): Unit = {
+    assertPrintEquals(
+      """
+        |for (let x = 1; (x < 15); x = (x + 1)) {
+        |  /*<skip>*/
+        |};
+      """,
+      For(Let("x", true, Some(IntLiteral(1))),
+          BinaryOp(ir.Trees.JSBinaryOp.<, VarRef("x"), IntLiteral(15)),
+          Assign(VarRef("x"), BinaryOp(ir.Trees.JSBinaryOp.+, VarRef("x"), IntLiteral(1))),
+          Skip())
+    )
+  }
+
+  @Test def printForIn(): Unit = {
+    assertPrintEquals(
+      """
+        |for (var x in foo) {
+        |  /*<skip>*/
+        |};
+      """,
+      ForIn(VarDef("x", None), VarRef("foo"), Skip())
+    )
+  }
+
+  @Test def printIf(): Unit = {
+    assertPrintEquals(
+        """
+          |if (false) {
+          |  1
+          |};
+        """,
+        If(BooleanLiteral(false), IntLiteral(1), Skip())
+    )
+
+    assertPrintEquals(
+        """
+          |if (false) {
+          |  1
+          |} else {
+          |  2
+          |};
+        """,
+        If(BooleanLiteral(false), IntLiteral(1), IntLiteral(2))
+    )
+
+    assertPrintEquals(
+        """
+          |if (false) {
+          |  1
+          |} else if (true) {
+          |  2
+          |} else {
+          |  3
+          |};
+        """,
+        If(BooleanLiteral(false), IntLiteral(1),
+            If(BooleanLiteral(true), IntLiteral(2), IntLiteral(3)))
+    )
+  }
+}

From c2ed2bb42f4dbe7e401c9b4ee130b251fe764aad Mon Sep 17 00:00:00 2001
From: Tobias Schlatter <tobias@meisch.ch>
Date: Mon, 25 Dec 2023 20:20:25 +0100
Subject: [PATCH 013/298] Print semicolon as part of statement in javascript
 Printer

This is necesary for a subsequent change, where we pre-print
statements into byte buffers. When we later assemble the statement
into the surrounding block, we do not have type information
anymore (and hence cannot judge whether a semicolon is necessary).

Note that this now prints a semicolon after the last statement in a
block (which we didn't previously). This does increase fastopt
size (somewhat artificially), but more closely corresponds:

- to what a human would write
- the ECMAScript spec (e.g. https://tc39.es/ecma262/#sec-expression-statement)
---
 .../linker/backend/javascript/Printers.scala  | 66 +++++++++++++------
 .../org/scalajs/linker/LibrarySizeTest.scala  |  4 +-
 .../backend/javascript/PrintersTest.scala     | 32 ++++-----
 project/Build.scala                           |  4 +-
 4 files changed, 67 insertions(+), 39 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Printers.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Printers.scala
index 2df5acc9f9..e2c57c92eb 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Printers.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Printers.scala
@@ -73,17 +73,10 @@ object Printers {
           }
         case _ =>
           printStat(tree)
-          if (shouldPrintSepAfterTree(tree))
-            print(';')
           println()
       }
     }
 
-    protected def shouldPrintSepAfterTree(tree: Tree): Boolean = tree match {
-      case _:DocComment | _:FunctionDef | _:ClassDef => false
-      case _                                         => true
-    }
-
     protected def printRow(ts: List[Tree], start: Char, end: Char): Unit = {
       print(start)
       var rest = ts
@@ -105,11 +98,8 @@ object Printers {
             val x = rest.head
             rest = rest.tail
             printStat(x)
-            if (rest.nonEmpty) {
-              if (shouldPrintSepAfterTree(x))
-                print(';')
+            if (rest.nonEmpty)
               println()
-            }
           }
 
         case _ =>
@@ -146,6 +136,11 @@ object Printers {
       printTree(tree, isStat = false)
 
     def printTree(tree: Tree, isStat: Boolean): Unit = {
+      def printSeparatorIfStat() = {
+        if (isStat)
+          print(';')
+      }
+
       tree match {
         // Comments
 
@@ -178,6 +173,8 @@ object Printers {
             print(" = ")
             print(rhs)
           }
+          // VarDef is an "expr" in a "For" / "ForIn" tree
+          printSeparatorIfStat()
 
         case Let(ident, mutable, optRhs) =>
           print(if (mutable) "let " else "const ")
@@ -186,6 +183,8 @@ object Printers {
             print(" = ")
             print(rhs)
           }
+          // Let is an "expr" in a "For" / "ForIn" tree
+          printSeparatorIfStat()
 
         case ParamDef(ident) =>
           print(ident)
@@ -210,10 +209,12 @@ object Printers {
           print(lhs)
           print(" = ")
           print(rhs)
+          printSeparatorIfStat()
 
         case Return(expr) =>
           print("return ")
           print(expr)
+          print(';')
 
         case If(cond, thenp, elsep) =>
           if (isStat) {
@@ -306,19 +307,22 @@ object Printers {
         case Throw(expr) =>
           print("throw ")
           print(expr)
+          print(';')
 
         case Break(label) =>
-          if (label.isEmpty) print("break")
+          if (label.isEmpty) print("break;")
           else {
             print("break ")
             print(label.get)
+            print(';')
           }
 
         case Continue(label) =>
-          if (label.isEmpty) print("continue")
+          if (label.isEmpty) print("continue;")
           else {
             print("continue ")
             print(label.get)
+            print(';')
           }
 
         case Switch(selector, cases, default) =>
@@ -354,7 +358,7 @@ object Printers {
           print('}')
 
         case Debugger() =>
-          print("debugger")
+          print("debugger;")
 
         // Expressions
 
@@ -375,6 +379,7 @@ object Printers {
             print(')')
           }
           printArgs(args)
+          printSeparatorIfStat()
 
         case DotSelect(qualifier, item) =>
           qualifier match {
@@ -387,27 +392,33 @@ object Printers {
           }
           print(".")
           print(item)
+          printSeparatorIfStat()
 
         case BracketSelect(qualifier, item) =>
           print(qualifier)
           print('[')
           print(item)
           print(']')
+          printSeparatorIfStat()
 
         case Apply(fun, args) =>
           print(fun)
           printArgs(args)
+          printSeparatorIfStat()
 
         case ImportCall(arg) =>
           print("import(")
           print(arg)
           print(')')
+          printSeparatorIfStat()
 
         case NewTarget() =>
           print("new.target")
+          printSeparatorIfStat()
 
         case ImportMeta()  =>
           print("import.meta")
+          printSeparatorIfStat()
 
         case Spread(items) =>
           print("...")
@@ -416,6 +427,7 @@ object Printers {
         case Delete(prop) =>
           print("delete ")
           print(prop)
+          printSeparatorIfStat()
 
         case UnaryOp(op, lhs) =>
           import ir.Trees.JSUnaryOp._
@@ -433,6 +445,7 @@ object Printers {
           }
           print(lhs)
           print(')')
+          printSeparatorIfStat()
 
         case IncDec(prefix, inc, arg) =>
           val op = if (inc) "++" else "--"
@@ -443,6 +456,7 @@ object Printers {
           if (!prefix)
             print(op)
           print(')')
+          printSeparatorIfStat()
 
         case BinaryOp(op, lhs, rhs) =>
           import ir.Trees.JSBinaryOp._
@@ -482,13 +496,15 @@ object Printers {
           print(' ')
           print(rhs)
           print(')')
+          printSeparatorIfStat()
 
         case ArrayConstr(items) =>
           printRow(items, '[', ']')
+          printSeparatorIfStat()
 
         case ObjectConstr(Nil) =>
           if (isStat)
-            print("({})") // force expression position for the object literal
+            print("({});") // force expression position for the object literal
           else
             print("{}")
 
@@ -514,18 +530,21 @@ object Printers {
           println()
           print('}')
           if (isStat)
-            print(')')
+            print(");")
 
         // Literals
 
         case Undefined() =>
           print("(void 0)")
+          printSeparatorIfStat()
 
         case Null() =>
           print("null")
+          printSeparatorIfStat()
 
         case BooleanLiteral(value) =>
           print(if (value) "true" else "false")
+          printSeparatorIfStat()
 
         case IntLiteral(value) =>
           if (value >= 0) {
@@ -535,6 +554,7 @@ object Printers {
             print(value.toString)
             print(')')
           }
+          printSeparatorIfStat()
 
         case DoubleLiteral(value) =>
           if (value == 0 && 1 / value < 0) {
@@ -546,11 +566,13 @@ object Printers {
             print(value.toString)
             print(')')
           }
+          printSeparatorIfStat()
 
         case StringLiteral(value) =>
           print('\"')
           printEscapeJS(value)
           print('\"')
+          printSeparatorIfStat()
 
         case BigIntLiteral(value) =>
           if (value >= 0) {
@@ -561,14 +583,17 @@ object Printers {
             print(value.toString)
             print("n)")
           }
+          printSeparatorIfStat()
 
         // Atomic expressions
 
         case VarRef(ident) =>
           print(ident)
+          printSeparatorIfStat()
 
         case This() =>
           print("this")
+          printSeparatorIfStat()
 
         case Function(arrow, args, restParam, body) =>
           if (arrow) {
@@ -595,6 +620,7 @@ object Printers {
             printBlock(body)
             print(')')
           }
+          printSeparatorIfStat()
 
         // Named function definition
 
@@ -624,8 +650,7 @@ object Printers {
           var rest = members
           while (rest.nonEmpty) {
             println()
-            print(rest.head)
-            print(';')
+            printStat(rest.head)
             rest = rest.tail
           }
           undent(); println(); print('}')
@@ -677,12 +702,14 @@ object Printers {
           }
           print(" } from ")
           print(from: Tree)
+          print(';')
 
         case ImportNamespace(binding, from) =>
           print("import * as ")
           print(binding)
           print(" from ")
           print(from: Tree)
+          print(';')
 
         case Export(bindings) =>
           print("export { ")
@@ -699,7 +726,7 @@ object Printers {
             print(binding._2)
             rest = rest.tail
           }
-          print(" }")
+          print(" };")
 
         case ExportImport(bindings, from) =>
           print("export { ")
@@ -718,6 +745,7 @@ object Printers {
           }
           print(" } from ")
           print(from: Tree)
+          print(';')
 
         case _ =>
           throw new IllegalArgumentException(
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/LibrarySizeTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/LibrarySizeTest.scala
index a64f546d68..6695edfb35 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/LibrarySizeTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/LibrarySizeTest.scala
@@ -70,8 +70,8 @@ class LibrarySizeTest {
     )
 
     testLinkedSizes(
-      expectedFastLinkSize = 150031,
-      expectedFullLinkSizeWithoutClosure = 130655,
+      expectedFastLinkSize = 150534,
+      expectedFullLinkSizeWithoutClosure = 131079,
       expectedFullLinkSizeWithClosure = 21394,
       classDefs,
       moduleInitializers = MainTestModuleInitializers
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/backend/javascript/PrintersTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/backend/javascript/PrintersTest.scala
index c43b1a28e9..621910f9a7 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/backend/javascript/PrintersTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/backend/javascript/PrintersTest.scala
@@ -43,7 +43,7 @@ class PrintersTest {
         """
           |function test() {
           |  const x = 2;
-          |  return x
+          |  return x;
           |}
         """,
         FunctionDef("test", Nil, None, Block(
@@ -75,13 +75,13 @@ class PrintersTest {
           |class MyClass {
           |  foo() {
           |    /*<skip>*/
-          |  };
+          |  }
           |  get a() {
-          |    return 1
-          |  };
+          |    return 1;
+          |  }
           |  set a(x) {
           |    /*<skip>*/
-          |  };
+          |  }
           |}
         """,
         ClassDef(Some("MyClass"), None, List(
@@ -106,7 +106,7 @@ class PrintersTest {
       """
         |for (let x = 1; (x < 15); x = (x + 1)) {
         |  /*<skip>*/
-        |};
+        |}
       """,
       For(Let("x", true, Some(IntLiteral(1))),
           BinaryOp(ir.Trees.JSBinaryOp.<, VarRef("x"), IntLiteral(15)),
@@ -120,7 +120,7 @@ class PrintersTest {
       """
         |for (var x in foo) {
         |  /*<skip>*/
-        |};
+        |}
       """,
       ForIn(VarDef("x", None), VarRef("foo"), Skip())
     )
@@ -130,8 +130,8 @@ class PrintersTest {
     assertPrintEquals(
         """
           |if (false) {
-          |  1
-          |};
+          |  1;
+          |}
         """,
         If(BooleanLiteral(false), IntLiteral(1), Skip())
     )
@@ -139,10 +139,10 @@ class PrintersTest {
     assertPrintEquals(
         """
           |if (false) {
-          |  1
+          |  1;
           |} else {
-          |  2
-          |};
+          |  2;
+          |}
         """,
         If(BooleanLiteral(false), IntLiteral(1), IntLiteral(2))
     )
@@ -150,12 +150,12 @@ class PrintersTest {
     assertPrintEquals(
         """
           |if (false) {
-          |  1
+          |  1;
           |} else if (true) {
-          |  2
+          |  2;
           |} else {
-          |  3
-          |};
+          |  3;
+          |}
         """,
         If(BooleanLiteral(false), IntLiteral(1),
             If(BooleanLiteral(true), IntLiteral(2), IntLiteral(3)))
diff --git a/project/Build.scala b/project/Build.scala
index 93209c3ddb..da13fdd781 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -1967,7 +1967,7 @@ object Build {
         scalaVersion.value match {
           case `default212Version` =>
             Some(ExpectedSizes(
-                fastLink = 772000 to 773000,
+                fastLink = 775000 to 776000,
                 fullLink = 145000 to 146000,
                 fastLinkGz = 91000 to 92000,
                 fullLinkGz = 35000 to 36000,
@@ -1975,7 +1975,7 @@ object Build {
 
           case `default213Version` =>
             Some(ExpectedSizes(
-                fastLink = 480000 to 481000,
+                fastLink = 481000 to 483000,
                 fullLink = 102000 to 103000,
                 fastLinkGz = 62000 to 63000,
                 fullLinkGz = 27000 to 28000,

From 197af9a726414fc68345920fadc5bd77c419f0fd Mon Sep 17 00:00:00 2001
From: Tobias Schlatter <tobias@meisch.ch>
Date: Thu, 28 Dec 2023 09:13:59 +0100
Subject: [PATCH 014/298] Do not print skip's in blocks

---
 .../scalajs/linker/backend/javascript/Printers.scala | 12 +++++++-----
 .../scala/org/scalajs/linker/LibrarySizeTest.scala   |  4 ++--
 .../linker/backend/javascript/PrintersTest.scala     |  5 -----
 project/Build.scala                                  |  6 +++---
 4 files changed, 12 insertions(+), 15 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Printers.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Printers.scala
index e2c57c92eb..adf58ee214 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Printers.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Printers.scala
@@ -90,19 +90,21 @@ object Printers {
     }
 
     protected def printBlock(tree: Tree): Unit = {
-      print('{'); indent(); println()
+      print('{'); indent();
       tree match {
+        case Skip() =>
+          // do not print anything
+
         case tree: Block =>
           var rest = tree.stats
           while (rest.nonEmpty) {
-            val x = rest.head
+            println()
+            printStat(rest.head)
             rest = rest.tail
-            printStat(x)
-            if (rest.nonEmpty)
-              println()
           }
 
         case _ =>
+          println()
           printStat(tree)
       }
       undent(); println(); print('}')
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/LibrarySizeTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/LibrarySizeTest.scala
index 6695edfb35..9dcc074647 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/LibrarySizeTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/LibrarySizeTest.scala
@@ -70,8 +70,8 @@ class LibrarySizeTest {
     )
 
     testLinkedSizes(
-      expectedFastLinkSize = 150534,
-      expectedFullLinkSizeWithoutClosure = 131079,
+      expectedFastLinkSize = 150339,
+      expectedFullLinkSizeWithoutClosure = 130884,
       expectedFullLinkSizeWithClosure = 21394,
       classDefs,
       moduleInitializers = MainTestModuleInitializers
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/backend/javascript/PrintersTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/backend/javascript/PrintersTest.scala
index 621910f9a7..2397717164 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/backend/javascript/PrintersTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/backend/javascript/PrintersTest.scala
@@ -54,7 +54,6 @@ class PrintersTest {
     assertPrintEquals(
         """
           |function test() {
-          |  /*<skip>*/
           |}
         """,
         FunctionDef("test", Nil, None, Skip())
@@ -74,13 +73,11 @@ class PrintersTest {
         """
           |class MyClass {
           |  foo() {
-          |    /*<skip>*/
           |  }
           |  get a() {
           |    return 1;
           |  }
           |  set a(x) {
-          |    /*<skip>*/
           |  }
           |}
         """,
@@ -105,7 +102,6 @@ class PrintersTest {
     assertPrintEquals(
       """
         |for (let x = 1; (x < 15); x = (x + 1)) {
-        |  /*<skip>*/
         |}
       """,
       For(Let("x", true, Some(IntLiteral(1))),
@@ -119,7 +115,6 @@ class PrintersTest {
     assertPrintEquals(
       """
         |for (var x in foo) {
-        |  /*<skip>*/
         |}
       """,
       ForIn(VarDef("x", None), VarRef("foo"), Skip())
diff --git a/project/Build.scala b/project/Build.scala
index da13fdd781..758975e8f0 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -1967,15 +1967,15 @@ object Build {
         scalaVersion.value match {
           case `default212Version` =>
             Some(ExpectedSizes(
-                fastLink = 775000 to 776000,
+                fastLink = 770000 to 771000,
                 fullLink = 145000 to 146000,
-                fastLinkGz = 91000 to 92000,
+                fastLinkGz = 90000 to 91000,
                 fullLinkGz = 35000 to 36000,
             ))
 
           case `default213Version` =>
             Some(ExpectedSizes(
-                fastLink = 481000 to 483000,
+                fastLink = 479000 to 480000,
                 fullLink = 102000 to 103000,
                 fastLinkGz = 62000 to 63000,
                 fullLinkGz = 27000 to 28000,

From 7c3797d02d7194a051bc51c98299f09650134330 Mon Sep 17 00:00:00 2001
From: Tobias Schlatter <tobias@meisch.ch>
Date: Thu, 28 Dec 2023 18:22:15 +0100
Subject: [PATCH 015/298] Do not abuse a block to group instance tests

This was forgotten in 1982a6b631a5b37ebbd4fe61655a45ad9b62bf93.
---
 .../org/scalajs/linker/backend/emitter/ClassEmitter.scala     | 4 ++--
 .../scala/org/scalajs/linker/backend/emitter/Emitter.scala    | 4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
index 0701d2fd84..ca58616785 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
@@ -683,12 +683,12 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
 
   def genInstanceTests(className: ClassName, kind: ClassKind)(
       implicit moduleContext: ModuleContext,
-      globalKnowledge: GlobalKnowledge, pos: Position): WithGlobals[js.Tree] = {
+      globalKnowledge: GlobalKnowledge, pos: Position): WithGlobals[List[js.Tree]] = {
     for {
       single <- genSingleInstanceTests(className, kind)
       array <- genArrayInstanceTests(className)
     } yield {
-      js.Block(single ::: array)
+      single ::: array
     }
   }
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala
index d5b23e4525..d89de7ae4d 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala
@@ -595,7 +595,7 @@ final class Emitter(config: Emitter.Config) {
        */
 
       if (classEmitter.needInstanceTests(linkedClass)(classCache)) {
-        main += extractWithGlobals(classTreeCache.instanceTests.getOrElseUpdate(
+        main ++= extractWithGlobals(classTreeCache.instanceTests.getOrElseUpdate(
             classEmitter.genInstanceTests(className, kind)(moduleContext, classCache, linkedClass.pos)))
       }
 
@@ -1035,7 +1035,7 @@ object Emitter {
 
   private final class DesugaredClassCache {
     val privateJSFields = new OneTimeCache[WithGlobals[List[js.Tree]]]
-    val instanceTests = new OneTimeCache[WithGlobals[js.Tree]]
+    val instanceTests = new OneTimeCache[WithGlobals[List[js.Tree]]]
     val typeData = new OneTimeCache[WithGlobals[List[js.Tree]]]
     val setTypeData = new OneTimeCache[js.Tree]
     val moduleAccessor = new OneTimeCache[WithGlobals[List[js.Tree]]]

From bdea4d7ddb6ac6917bae270903c803ff5fdb3166 Mon Sep 17 00:00:00 2001
From: Tobias Schlatter <tobias@meisch.ch>
Date: Fri, 29 Dec 2023 15:55:20 +0100
Subject: [PATCH 016/298] Do not abuse a block to group const field export
 statements

This was forgotten in 1982a6b631a5b37ebbd4fe61655a45ad9b62bf93.
---
 .../linker/backend/emitter/ClassEmitter.scala      | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
index ca58616785..144672a471 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
@@ -1028,16 +1028,16 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
         case e: TopLevelMethodExportDef =>
           genTopLevelMethodExportDef(e)
         case e: TopLevelFieldExportDef =>
-          genTopLevelFieldExportDef(topLevelExport.owningClass, e)
+          genTopLevelFieldExportDef(topLevelExport.owningClass, e).map(_ :: Nil)
       }
     }
 
-    WithGlobals.list(exportsWithGlobals)
+    WithGlobals.flatten(exportsWithGlobals)
   }
 
   private def genTopLevelMethodExportDef(tree: TopLevelMethodExportDef)(
       implicit moduleContext: ModuleContext,
-      globalKnowledge: GlobalKnowledge): WithGlobals[js.Tree] = {
+      globalKnowledge: GlobalKnowledge): WithGlobals[List[js.Tree]] = {
     import TreeDSL._
 
     val JSMethodDef(flags, StringLiteral(exportName), args, restParam, body) =
@@ -1056,22 +1056,22 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
 
   private def genConstValueExportDef(exportName: String,
       exportedValue: js.Tree)(
-      implicit pos: Position): WithGlobals[js.Tree] = {
+      implicit pos: Position): WithGlobals[List[js.Tree]] = {
     moduleKind match {
       case ModuleKind.NoModule =>
-        genAssignToNoModuleExportVar(exportName, exportedValue)
+        genAssignToNoModuleExportVar(exportName, exportedValue).map(_ :: Nil)
 
       case ModuleKind.ESModule =>
         val field = fileLevelVar(VarField.e, exportName)
         val let = js.Let(field.ident, mutable = true, Some(exportedValue))
         val exportStat = js.Export((field.ident -> js.ExportName(exportName)) :: Nil)
-        WithGlobals(js.Block(let, exportStat))
+        WithGlobals(List(let, exportStat))
 
       case ModuleKind.CommonJSModule =>
         globalRef("exports").map { exportsVarRef =>
           js.Assign(
               genBracketSelect(exportsVarRef, js.StringLiteral(exportName)),
-              exportedValue)
+              exportedValue) :: Nil
         }
     }
   }

From 135932afa2601f9f2b914c1fdea806f4d3903c25 Mon Sep 17 00:00:00 2001
From: Tobias Schlatter <tobias@meisch.ch>
Date: Thu, 28 Dec 2023 18:24:23 +0100
Subject: [PATCH 017/298] Simplify printTopLevelTree in JS printer

Because it does not need to flatten blocks anymore, we can simply
print it as a statement and add a trailing newline.
---
 .../linker/backend/javascript/Printers.scala      | 15 ++-------------
 1 file changed, 2 insertions(+), 13 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Printers.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Printers.scala
index adf58ee214..c50426a5d8 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Printers.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Printers.scala
@@ -62,19 +62,8 @@ object Printers {
     }
 
     def printTopLevelTree(tree: Tree): Unit = {
-      tree match {
-        case Skip() =>
-          // do not print anything
-        case tree: Block =>
-          var rest = tree.stats
-          while (rest.nonEmpty) {
-            printTopLevelTree(rest.head)
-            rest = rest.tail
-          }
-        case _ =>
-          printStat(tree)
-          println()
-      }
+      printStat(tree)
+      println()
     }
 
     protected def printRow(ts: List[Tree], start: Char, end: Char): Unit = {

From de0d65c6df5a51a8b024363f1382723b245b1c20 Mon Sep 17 00:00:00 2001
From: Tobias Schlatter <tobias@meisch.ch>
Date: Fri, 29 Dec 2023 16:14:18 +0100
Subject: [PATCH 018/298] Restrict visibility of JS Printer methods

They were unnecessarily protected.
---
 .../linker/backend/javascript/Printers.scala       | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Printers.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Printers.scala
index c50426a5d8..035f21ef0a 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Printers.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Printers.scala
@@ -66,7 +66,7 @@ object Printers {
       println()
     }
 
-    protected def printRow(ts: List[Tree], start: Char, end: Char): Unit = {
+    private def printRow(ts: List[Tree], start: Char, end: Char): Unit = {
       print(start)
       var rest = ts
       while (rest.nonEmpty) {
@@ -78,7 +78,7 @@ object Printers {
       print(end)
     }
 
-    protected def printBlock(tree: Tree): Unit = {
+    private def printBlock(tree: Tree): Unit = {
       print('{'); indent();
       tree match {
         case Skip() =>
@@ -99,7 +99,7 @@ object Printers {
       undent(); println(); print('}')
     }
 
-    protected def printSig(args: List[ParamDef], restParam: Option[ParamDef]): Unit = {
+    private def printSig(args: List[ParamDef], restParam: Option[ParamDef]): Unit = {
       print("(")
       var rem = args
       while (rem.nonEmpty) {
@@ -117,13 +117,13 @@ object Printers {
       print(") ")
     }
 
-    protected def printArgs(args: List[Tree]): Unit =
+    private def printArgs(args: List[Tree]): Unit =
       printRow(args, '(', ')')
 
-    protected def printStat(tree: Tree): Unit =
+    private def printStat(tree: Tree): Unit =
       printTree(tree, isStat = true)
 
-    protected def print(tree: Tree): Unit =
+    private def print(tree: Tree): Unit =
       printTree(tree, isStat = false)
 
     def printTree(tree: Tree, isStat: Boolean): Unit = {
@@ -760,7 +760,7 @@ object Printers {
         print("]")
     }
 
-    protected def print(exportName: ExportName): Unit =
+    private def print(exportName: ExportName): Unit =
       printEscapeJS(exportName.name)
 
     /** Prints an ASCII string -- use for syntax strings, not for user strings. */

From bd58bbbb4e2e2cf3fb5fb2c7643f0dc0dd8940e0 Mon Sep 17 00:00:00 2001
From: Tobias Schlatter <tobias@meisch.ch>
Date: Fri, 29 Dec 2023 16:16:39 +0100
Subject: [PATCH 019/298] Print trailing newline as part of statement

This is necessary so we can partially print substatements more
easily (which we'll do in a subsequent PR). It will also allow us to
fully remove the concept of "top-level" tree.
---
 .../linker/backend/javascript/Printers.scala  | 49 +++++++++++++------
 1 file changed, 33 insertions(+), 16 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Printers.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Printers.scala
index 035f21ef0a..7d0235bed3 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Printers.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Printers.scala
@@ -44,6 +44,9 @@ object Printers {
 
     protected def println(): Unit = {
       out.write('\n')
+    }
+
+    protected def printIndent(): Unit = {
       val indentArray = this.indentArray
       val indentMargin = this.indentMargin
       val bigEnoughIndentArray =
@@ -63,7 +66,6 @@ object Printers {
 
     def printTopLevelTree(tree: Tree): Unit = {
       printStat(tree)
-      println()
     }
 
     private def printRow(ts: List[Tree], start: Char, end: Char): Unit = {
@@ -79,7 +81,7 @@ object Printers {
     }
 
     private def printBlock(tree: Tree): Unit = {
-      print('{'); indent();
+      print('{'); indent(); println()
       tree match {
         case Skip() =>
           // do not print anything
@@ -87,16 +89,14 @@ object Printers {
         case tree: Block =>
           var rest = tree.stats
           while (rest.nonEmpty) {
-            println()
             printStat(rest.head)
             rest = rest.tail
           }
 
         case _ =>
-          println()
           printStat(tree)
       }
-      undent(); println(); print('}')
+      undent(); printIndent(); print('}')
     }
 
     private def printSig(args: List[ParamDef], restParam: Option[ParamDef]): Unit = {
@@ -120,12 +120,22 @@ object Printers {
     private def printArgs(args: List[Tree]): Unit =
       printRow(args, '(', ')')
 
-    private def printStat(tree: Tree): Unit =
+    /** Prints a stat including leading indent and trailing newline. */
+    private def printStat(tree: Tree): Unit = {
+      printIndent()
       printTree(tree, isStat = true)
+      println()
+    }
 
     private def print(tree: Tree): Unit =
       printTree(tree, isStat = false)
 
+    /** Print the "meat" of a tree.
+     *
+     *  Even if it is a stat:
+     *  - No leading indent.
+     *  - No trailing newline.
+     */
     def printTree(tree: Tree, isStat: Boolean): Unit = {
       def printSeparatorIfStat() = {
         if (isStat)
@@ -144,12 +154,12 @@ object Printers {
           } else {
             print("/** ")
             print(lines.head)
-            println()
+            println(); printIndent()
             var rest = lines.tail
             while (rest.nonEmpty) {
               print(" *  ")
               print(rest.head)
-              println()
+              println(); printIndent()
               rest = rest.tail
             }
             print(" */")
@@ -326,7 +336,7 @@ object Printers {
           while (rest.nonEmpty) {
             val next = rest.head
             rest = rest.tail
-            println()
+            println(); printIndent()
             print("case ")
             print(next._1)
             print(':')
@@ -339,13 +349,13 @@ object Printers {
           default match {
             case Skip() =>
             case _ =>
-              println()
+              println(); printIndent()
               print("default: ")
               printBlock(default)
           }
 
           undent()
-          println()
+          println(); printIndent()
           print('}')
 
         case Debugger() =>
@@ -509,16 +519,17 @@ object Printers {
           while (rest.nonEmpty) {
             val x = rest.head
             rest = rest.tail
+            printIndent()
             print(x._1)
             print(": ")
             print(x._2)
             if (rest.nonEmpty) {
               print(',')
-              println()
             }
+            println()
           }
           undent()
-          println()
+          printIndent()
           print('}')
           if (isStat)
             print(");")
@@ -637,14 +648,13 @@ object Printers {
             print(" extends ")
             print(optParentClass.get)
           }
-          print(" {"); indent()
+          print(" {"); indent(); println()
           var rest = members
           while (rest.nonEmpty) {
-            println()
             printStat(rest.head)
             rest = rest.tail
           }
-          undent(); println(); print('}')
+          undent(); printIndent(); print('}')
 
         case MethodDef(static, name, params, restParam, body) =>
           if (static)
@@ -801,6 +811,13 @@ object Printers {
     override protected def println(): Unit = {
       super.println()
       sourceMap.nextLine()
+      column = 0
+    }
+
+    override protected def printIndent(): Unit = {
+      assert(column == 0)
+
+      super.printIndent()
       column = this.getIndentMargin()
     }
 

From cae909ad8d661eb6af63a6946236a5b63b9181d5 Mon Sep 17 00:00:00 2001
From: Tobias Schlatter <tobias@meisch.ch>
Date: Fri, 29 Dec 2023 16:21:36 +0100
Subject: [PATCH 020/298] Remove printTopLevelTree and replace it with
 printStat

---
 .../org/scalajs/linker/backend/BasicLinkerBackend.scala     | 4 ++--
 .../org/scalajs/linker/backend/javascript/Printers.scala    | 6 +-----
 .../scalajs/linker/backend/javascript/PrintersTest.scala    | 2 +-
 3 files changed, 4 insertions(+), 8 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/BasicLinkerBackend.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/BasicLinkerBackend.scala
index a1238e7433..564ebbb99c 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/BasicLinkerBackend.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/BasicLinkerBackend.scala
@@ -283,7 +283,7 @@ private object BasicLinkerBackend {
       val jsCodeWriter = new ByteArrayWriter()
       val printer = new Printers.JSTreePrinter(jsCodeWriter)
 
-      printer.printTopLevelTree(tree)
+      printer.printStat(tree)
 
       new PrintedTree(jsCodeWriter.toByteArray(), SourceMapWriter.Fragment.Empty)
     }
@@ -321,7 +321,7 @@ private object BasicLinkerBackend {
       val smFragmentBuilder = new SourceMapWriter.FragmentBuilder()
       val printer = new Printers.JSTreePrinterWithSourceMap(jsCodeWriter, smFragmentBuilder)
 
-      printer.printTopLevelTree(tree)
+      printer.printStat(tree)
       smFragmentBuilder.complete()
 
       new PrintedTree(jsCodeWriter.toByteArray(), smFragmentBuilder.result())
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Printers.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Printers.scala
index 7d0235bed3..9690946e69 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Printers.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Printers.scala
@@ -64,10 +64,6 @@ object Printers {
       newIndentArray
     }
 
-    def printTopLevelTree(tree: Tree): Unit = {
-      printStat(tree)
-    }
-
     private def printRow(ts: List[Tree], start: Char, end: Char): Unit = {
       print(start)
       var rest = ts
@@ -121,7 +117,7 @@ object Printers {
       printRow(args, '(', ')')
 
     /** Prints a stat including leading indent and trailing newline. */
-    private def printStat(tree: Tree): Unit = {
+    final def printStat(tree: Tree): Unit = {
       printIndent()
       printTree(tree, isStat = true)
       println()
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/backend/javascript/PrintersTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/backend/javascript/PrintersTest.scala
index 2397717164..316f2c3907 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/backend/javascript/PrintersTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/backend/javascript/PrintersTest.scala
@@ -33,7 +33,7 @@ class PrintersTest {
   private def assertPrintEquals(expected: String, tree: Tree): Unit = {
     val out = new ByteArrayWriter
     val printer = new Printers.JSTreePrinter(out)
-    printer.printTopLevelTree(tree)
+    printer.printStat(tree)
     assertEquals(expected.stripMargin.trim + "\n",
         new String(out.toByteArray(), StandardCharsets.UTF_8))
   }

From c12b25368dee2d5871ba1666277fa387f5b8f8e2 Mon Sep 17 00:00:00 2001
From: Tobias Schlatter <tobias@meisch.ch>
Date: Sat, 4 Nov 2023 13:56:54 +0100
Subject: [PATCH 021/298] Only pass isJSClass to ClassEmitter (instead of
 entire ClassKind)

This allows us to invalidate generated exported members less
often (and in following commits, also class members).
---
 .../main/scala/org/scalajs/ir/Version.scala   | 10 ++++++
 .../linker/backend/emitter/ClassEmitter.scala | 33 +++++++++----------
 .../linker/backend/emitter/Emitter.scala      | 24 +++++++++-----
 3 files changed, 41 insertions(+), 26 deletions(-)

diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Version.scala b/ir/shared/src/main/scala/org/scalajs/ir/Version.scala
index f30be5f7ee..0228d63c86 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Version.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Version.scala
@@ -80,6 +80,16 @@ object Version {
   def fromBytes(bytes: Array[Byte]): Version =
     make(Type.Ephemeral, bytes)
 
+  /** Create a non-hash version from a Byte.
+   *
+   *  Strictly equivalent to (but potentially more efficient):
+   *  {{{
+   *  fromBytes(Array[Byte](i))
+   *  }}}
+   */
+  def fromByte(i: Byte): Version =
+    new Version(Array(Type.Ephemeral, i))
+
   /** Create a non-hash version from an Int.
    *
    *  Strictly equivalent to (but potentially more efficient):
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
index 144672a471..34b69507ea 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
@@ -43,7 +43,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
   import nameGen._
   import varGen._
 
-  def buildClass(className: ClassName, kind: ClassKind, jsClassCaptures: Option[List[ParamDef]],
+  def buildClass(className: ClassName, isJSClass: Boolean, jsClassCaptures: Option[List[ParamDef]],
       hasClassInitializer: Boolean,
       superClass: Option[ClassIdent], jsSuperClass: Option[Tree], useESClass: Boolean, ctorDefs: List[js.Tree],
       memberDefs: List[js.MethodDef], exportedDefs: List[js.Tree])(
@@ -55,7 +55,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
     def allES5Defs(classVar: js.Tree) =
       WithGlobals(ctorDefs ::: assignES5ClassMembers(classVar, memberDefs) ::: exportedDefs)
 
-    if (!kind.isJSClass) {
+    if (!isJSClass) {
       assert(jsSuperClass.isEmpty, className)
 
       if (useESClass) {
@@ -534,7 +534,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
   }
 
   /** Generates a JS method. */
-  private def genJSMethod(className: ClassName, kind: ClassKind, useESClass: Boolean,
+  private def genJSMethod(className: ClassName, isJSClass: Boolean, useESClass: Boolean,
       method: JSMethodDef)(
       implicit moduleContext: ModuleContext,
       globalKnowledge: GlobalKnowledge): WithGlobals[js.Tree] = {
@@ -550,29 +550,29 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
       if (useESClass) {
         js.MethodDef(static = namespace.isStatic, propName, methodFun.args, methodFun.restParam, methodFun.body)
       } else {
-        val targetObject = exportTargetES5(className, kind, namespace)
+        val targetObject = exportTargetES5(className, isJSClass, namespace)
         js.Assign(genPropSelect(targetObject, propName), methodFun)
       }
     }
   }
 
   /** Generates a property. */
-  private def genJSProperty(className: ClassName, kind: ClassKind, useESClass: Boolean,
+  private def genJSProperty(className: ClassName, isJSClass: Boolean, useESClass: Boolean,
       property: JSPropertyDef)(
       implicit moduleContext: ModuleContext,
       globalKnowledge: GlobalKnowledge): WithGlobals[List[js.Tree]] = {
     if (useESClass)
       genJSPropertyES6(className, property)
     else
-      genJSPropertyES5(className, kind, property).map(_ :: Nil)
+      genJSPropertyES5(className, isJSClass, property).map(_ :: Nil)
   }
 
-  private def genJSPropertyES5(className: ClassName, kind: ClassKind, property: JSPropertyDef)(
+  private def genJSPropertyES5(className: ClassName, isJSClass: Boolean, property: JSPropertyDef)(
       implicit moduleContext: ModuleContext,
       globalKnowledge: GlobalKnowledge): WithGlobals[js.Tree] = {
     implicit val pos = property.pos
 
-    val targetObject = exportTargetES5(className, kind, property.flags.namespace)
+    val targetObject = exportTargetES5(className, isJSClass, property.flags.namespace)
 
     // optional getter definition
     val optGetterWithGlobals = property.getterBody map { body =>
@@ -627,13 +627,13 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
     }
   }
 
-  private def exportTargetES5(className: ClassName, kind: ClassKind, namespace: MemberNamespace)(
+  private def exportTargetES5(className: ClassName, isJSClass: Boolean, namespace: MemberNamespace)(
       implicit moduleContext: ModuleContext, globalKnowledge: GlobalKnowledge,
       pos: Position): js.Tree = {
     import TreeDSL._
 
     val classVarRef =
-      if (kind.isJSClass) fileLevelVar(VarField.b, genName(className))
+      if (isJSClass) fileLevelVar(VarField.b, genName(className))
       else globalVar(VarField.c, className)
 
     if (namespace.isStatic) classVarRef
@@ -943,16 +943,13 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
     globalVar(VarField.c, className).prototype DOT "$classData" := globalVar(VarField.d, className)
   }
 
-  def genModuleAccessor(className: ClassName, kind: ClassKind)(
+  def genModuleAccessor(className: ClassName, isJSClass: Boolean)(
       implicit moduleContext: ModuleContext,
       globalKnowledge: GlobalKnowledge, pos: Position): WithGlobals[List[js.Tree]] = {
     import TreeDSL._
 
     val tpe = ClassType(className)
 
-    require(kind.hasModuleAccessor,
-        s"genModuleAccessor called with non-module class: $className")
-
     val moduleInstance = fileLevelVarIdent(VarField.n, genName(className))
 
     val createModuleInstanceField = genEmptyMutableLet(moduleInstance)
@@ -962,7 +959,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
 
       val assignModule = {
         moduleInstanceVar := {
-          if (kind == ClassKind.JSModuleClass) {
+          if (isJSClass) {
             js.New(
                 genNonNativeJSClassConstructor(className),
                 Nil)
@@ -1002,12 +999,12 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
     createAccessor.map(createModuleInstanceField :: _)
   }
 
-  def genExportedMember(className: ClassName, kind: ClassKind, useESClass: Boolean, member: JSMethodPropDef)(
+  def genExportedMember(className: ClassName, isJSClass: Boolean, useESClass: Boolean, member: JSMethodPropDef)(
       implicit moduleContext: ModuleContext,
       globalKnowledge: GlobalKnowledge): WithGlobals[List[js.Tree]] = {
     member match {
-      case m: JSMethodDef   => genJSMethod(className, kind, useESClass, m).map(_ :: Nil)
-      case p: JSPropertyDef => genJSProperty(className, kind, useESClass, p)
+      case m: JSMethodDef   => genJSMethod(className, isJSClass, useESClass, m).map(_ :: Nil)
+      case p: JSPropertyDef => genJSProperty(className, isJSClass, useESClass, p)
     }
   }
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala
index d89de7ae4d..28c20a4a66 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala
@@ -412,8 +412,12 @@ final class Emitter(config: Emitter.Config) {
       }
     }
 
+    val isJSClass = kind.isJSClass
+
     // Class definition
     if (linkedClass.hasInstances && kind.isAnyNonNativeClass) {
+      val isJSClassVersion = Version.fromByte(if (isJSClass) 1 else 0)
+
       /* Is this class compiled as an ECMAScript `class`?
        *
        * See JSGen.useClassesForRegularClasses for the rationale here.
@@ -430,13 +434,17 @@ final class Emitter(config: Emitter.Config) {
        * observable change; whereas rewiring Throwable to extend `Error` when
        * it does not actually directly extend `Object` would break everything,
        * so we need to be more careful there.
+       *
+       * For caching, isJSClassVersion can be used to guard use of `useESClass`:
+       * it is the only "dynamic" value it depends on. The rest is configuration
+       * or part of the cache key (ancestors).
        */
       val useESClass = if (jsGen.useClassesForRegularClasses) {
         assert(jsGen.useClassesForJSClassesAndThrowables)
         true
       } else {
         jsGen.useClassesForJSClassesAndThrowables &&
-        (kind.isJSClass || linkedClass.ancestors.contains(ThrowableClass))
+        (isJSClass || linkedClass.ancestors.contains(ThrowableClass))
       }
 
       // JS constructor
@@ -448,7 +456,7 @@ final class Emitter(config: Emitter.Config) {
          */
         val ctorCache = classCache.getConstructorCache()
 
-        if (linkedClass.kind.isJSClass) {
+        if (isJSClass) {
           assert(linkedInlineableInit.isEmpty)
 
           val jsConstructorDef = linkedClass.jsConstructorDef.getOrElse {
@@ -533,13 +541,13 @@ final class Emitter(config: Emitter.Config) {
         (member, idx) <- linkedClass.exportedMembers.zipWithIndex
       } yield {
         val memberCache = classCache.getExportedMemberCache(idx)
-        val version = Version.combine(linkedClass.version, member.version)
+        val version = Version.combine(isJSClassVersion, member.version)
         memberCache.getOrElseUpdate(version,
             classEmitter.genExportedMember(
                 className, // invalidated by overall class cache
-                kind, // invalidated by class verison
-                useESClass, // invalidated by class version (combined)
-                member // invalidated by version (combined)
+                isJSClass, // invalidated by isJSClassVersion
+                useESClass, // invalidated by isJSClassVersion
+                member // invalidated by version
             )(moduleContext, memberCache))
       }
 
@@ -561,7 +569,7 @@ final class Emitter(config: Emitter.Config) {
             exportedMembers <- WithGlobals.list(exportedMembersWithGlobals)
             clazz <- classEmitter.buildClass(
               className, // invalidated by overall class cache (part of ancestors)
-              linkedClass.kind, // invalidated by class version
+              isJSClass, // invalidated by class version
               linkedClass.jsClassCaptures, // invalidated by class version
               hasClassInitializer, // invalidated by class version (optimizer cannot remove it)
               linkedClass.superClass, // invalidated by class version
@@ -618,7 +626,7 @@ final class Emitter(config: Emitter.Config) {
 
     if (linkedClass.kind.hasModuleAccessor && linkedClass.hasInstances) {
       main ++= extractWithGlobals(classTreeCache.moduleAccessor.getOrElseUpdate(
-          classEmitter.genModuleAccessor(className, kind)(moduleContext, classCache, linkedClass.pos)))
+          classEmitter.genModuleAccessor(className, isJSClass)(moduleContext, classCache, linkedClass.pos)))
     }
 
     // Static fields

From 81a235d7468c40db12d65d1684b5d31bacc53f6d Mon Sep 17 00:00:00 2001
From: Tobias Schlatter <tobias@meisch.ch>
Date: Tue, 2 Jan 2024 12:04:02 +0100
Subject: [PATCH 022/298] Use Version.fromByte in KnowledgeGuardian

Now that we have it, we might as well save some memory.
---
 .../org/scalajs/linker/backend/emitter/KnowledgeGuardian.scala  | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/KnowledgeGuardian.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/KnowledgeGuardian.scala
index cd3bd4a687..2d7f18b19c 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/KnowledgeGuardian.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/KnowledgeGuardian.scala
@@ -374,7 +374,7 @@ private[emitter] final class KnowledgeGuardian(config: Emitter.Config) {
      */
     private def computeFieldDefsVersion(linkedClass: LinkedClass): Version = {
       val hasAnyJSField = linkedClass.fields.exists(_.isInstanceOf[JSFieldDef])
-      val hasAnyJSFieldVersion = Version.fromInt(if (hasAnyJSField) 1 else 0)
+      val hasAnyJSFieldVersion = Version.fromByte(if (hasAnyJSField) 1 else 0)
       val scalaFieldNamesVersion = linkedClass.fields.collect {
         case FieldDef(_, FieldIdent(name), _, _) => Version.fromUTF8String(name.encoded)
       }

From 14144ac402c470cb65063e0d15ac0c2df0bbfea8 Mon Sep 17 00:00:00 2001
From: Tobias Schlatter <tobias@meisch.ch>
Date: Sat, 4 Nov 2023 13:59:25 +0100
Subject: [PATCH 023/298] Move member assignment from buildClass to genMember

This simplifies buildClass. Thanks to the special version for
isJSClass, this will lead to acceptable invalidations (only if the
class kind changes, which should be rare).
---
 .../linker/backend/emitter/ClassEmitter.scala | 29 ++++++++++---------
 .../linker/backend/emitter/CoreJSLib.scala    |  9 ++++++
 .../linker/backend/emitter/Emitter.scala      | 22 ++++++++------
 .../linker/backend/emitter/JSGen.scala        | 12 --------
 4 files changed, 37 insertions(+), 35 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
index 34b69507ea..1a5a965e55 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
@@ -45,16 +45,11 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
 
   def buildClass(className: ClassName, isJSClass: Boolean, jsClassCaptures: Option[List[ParamDef]],
       hasClassInitializer: Boolean,
-      superClass: Option[ClassIdent], jsSuperClass: Option[Tree], useESClass: Boolean, ctorDefs: List[js.Tree],
-      memberDefs: List[js.MethodDef], exportedDefs: List[js.Tree])(
+      superClass: Option[ClassIdent], jsSuperClass: Option[Tree], useESClass: Boolean,
+      members: List[js.Tree])(
       implicit moduleContext: ModuleContext,
       globalKnowledge: GlobalKnowledge, pos: Position): WithGlobals[List[js.Tree]] = {
 
-    def allES6Defs = ctorDefs ::: memberDefs ::: exportedDefs
-
-    def allES5Defs(classVar: js.Tree) =
-      WithGlobals(ctorDefs ::: assignES5ClassMembers(classVar, memberDefs) ::: exportedDefs)
-
     if (!isJSClass) {
       assert(jsSuperClass.isEmpty, className)
 
@@ -66,10 +61,10 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
         }
 
         WithGlobals.option(parentVarWithGlobals).flatMap { parentVar =>
-          globalClassDef(VarField.c, className, parentVar, allES6Defs)
+          globalClassDef(VarField.c, className, parentVar, members)
         }
       } else {
-        allES5Defs(globalVar(VarField.c, className))
+        WithGlobals(members)
       }
     } else {
       // Wrap the entire class def in an accessor function
@@ -87,10 +82,10 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
 
       val entireClassDefWithGlobals = if (useESClass) {
         genJSSuperCtor(superClass, jsSuperClass).map { jsSuperClass =>
-          List(classValueVar := js.ClassDef(Some(classValueIdent), Some(jsSuperClass), allES6Defs))
+          List(classValueVar := js.ClassDef(Some(classValueIdent), Some(jsSuperClass), members))
         }
       } else {
-        allES5Defs(classValueVar)
+        WithGlobals(members)
       }
 
       val classDefStatsWithGlobals = for {
@@ -470,9 +465,9 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
     }
   }
 
-  def genMemberMethod(className: ClassName, method: MethodDef)(
+  def genMemberMethod(className: ClassName, isJSClass: Boolean, useESClass: Boolean, method: MethodDef)(
       implicit moduleContext: ModuleContext,
-      globalKnowledge: GlobalKnowledge): WithGlobals[js.MethodDef] = {
+      globalKnowledge: GlobalKnowledge): WithGlobals[js.Tree] = {
     assert(method.flags.namespace == MemberNamespace.Public)
 
     implicit val pos = method.pos
@@ -481,7 +476,13 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
       methodFun <- desugarToFunction(className, method.args, method.body.get, method.resultType)
     } yield {
       val jsMethodName = genMemberMethodIdent(method.name, method.originalName)
-      js.MethodDef(static = false, jsMethodName, methodFun.args, methodFun.restParam, methodFun.body)
+
+      if (useESClass) {
+        js.MethodDef(static = false, jsMethodName, methodFun.args, methodFun.restParam, methodFun.body)
+      } else {
+        val targetObject = exportTargetES5(className, isJSClass, MemberNamespace.Public)
+        js.Assign(genPropSelect(targetObject, jsMethodName), methodFun)
+      }
     }
   }
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
index 8a04956ad8..def0d13434 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
@@ -2132,6 +2132,15 @@ private[emitter] object CoreJSLib {
       obj ::: prims
     }
 
+    private def assignES5ClassMembers(classRef: Tree, members: List[MethodDef]): List[Tree] = {
+      for {
+        MethodDef(static, name, args, restParam, body) <- members
+      } yield {
+        val target = if (static) classRef else classRef.prototype
+        genPropSelect(target, name) := Function(arrow = false, args, restParam, body)
+      }
+    }
+
     private def defineFunction(name: VarField, args: List[ParamDef], body: Tree): List[Tree] =
       extractWithGlobals(globalFunctionDef(name, CoreVar, args, None, body))
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala
index 28c20a4a66..ea5e4b09bd 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala
@@ -532,8 +532,14 @@ final class Emitter(config: Emitter.Config) {
         val methodCache =
           classCache.getMemberMethodCache(method.methodName)
 
-        methodCache.getOrElseUpdate(method.version,
-            classEmitter.genMemberMethod(className, method)(moduleContext, methodCache))
+        val version = Version.combine(isJSClassVersion, method.version)
+        methodCache.getOrElseUpdate(version,
+            classEmitter.genMemberMethod(
+                className, // invalidated by overall class cache
+                isJSClass, // invalidated by isJSClassVersion
+                useESClass, // invalidated by isJSClassVersion
+                method // invalidated by method.version
+            )(moduleContext, methodCache))
       }
 
       // Exported Members
@@ -575,9 +581,7 @@ final class Emitter(config: Emitter.Config) {
               linkedClass.superClass, // invalidated by class version
               linkedClass.jsSuperClass, // invalidated by class version
               useESClass, // invalidated by class version (depends on kind, config and ancestry only)
-              ctor, // invalidated directly
-              memberMethods, // invalidated directly
-              exportedMembers.flatten // invalidated directly
+              ctor ::: memberMethods ::: exportedMembers.flatten // all 3 invalidated directly
             )(moduleContext, fullClassCache, linkedClass.pos) // pos invalidated by class version
           } yield {
             clazz
@@ -770,7 +774,7 @@ final class Emitter(config: Emitter.Config) {
       Array.fill(MemberNamespace.Count)(mutable.Map.empty[MethodName, MethodCache[List[js.Tree]]])
 
     private[this] val _memberMethodCache =
-      mutable.Map.empty[MethodName, MethodCache[js.MethodDef]]
+      mutable.Map.empty[MethodName, MethodCache[js.Tree]]
 
     private[this] var _constructorCache: Option[MethodCache[List[js.Tree]]] = None
 
@@ -810,7 +814,7 @@ final class Emitter(config: Emitter.Config) {
     }
 
     def getMemberMethodCache(
-        methodName: MethodName): MethodCache[js.MethodDef] = {
+        methodName: MethodName): MethodCache[js.Tree] = {
       _memberMethodCache.getOrElseUpdate(methodName, new MethodCache)
     }
 
@@ -897,7 +901,7 @@ final class Emitter(config: Emitter.Config) {
     private[this] var _tree: WithGlobals[List[js.Tree]] = null
     private[this] var _lastVersion: Version = Version.Unversioned
     private[this] var _lastCtor: WithGlobals[List[js.Tree]] = null
-    private[this] var _lastMemberMethods: List[WithGlobals[js.MethodDef]] = null
+    private[this] var _lastMemberMethods: List[WithGlobals[js.Tree]] = null
     private[this] var _lastExportedMembers: List[WithGlobals[List[js.Tree]]] = null
     private[this] var _cacheUsed = false
 
@@ -913,7 +917,7 @@ final class Emitter(config: Emitter.Config) {
     def startRun(): Unit = _cacheUsed = false
 
     def getOrElseUpdate(version: Version, ctor: WithGlobals[List[js.Tree]],
-        memberMethods: List[WithGlobals[js.MethodDef]], exportedMembers: List[WithGlobals[List[js.Tree]]],
+        memberMethods: List[WithGlobals[js.Tree]], exportedMembers: List[WithGlobals[List[js.Tree]]],
         compute: => WithGlobals[List[js.Tree]]): WithGlobals[List[js.Tree]] = {
 
       @tailrec
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/JSGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/JSGen.scala
index c5e3aba380..3ed36197a5 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/JSGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/JSGen.scala
@@ -156,18 +156,6 @@ private[emitter] final class JSGen(val config: Emitter.Config) {
     }
   }
 
-  def assignES5ClassMembers(classRef: Tree, members: List[MethodDef])(
-      implicit pos: Position): List[Tree] = {
-    import TreeDSL._
-
-    for {
-      MethodDef(static, name, args, restParam, body) <- members
-    } yield {
-      val target = if (static) classRef else classRef.prototype
-      genPropSelect(target, name) := Function(arrow = false, args, restParam, body)
-    }
-  }
-
   def genIIFE(captures: List[(ParamDef, Tree)], body: Tree)(
       implicit pos: Position): Tree = {
     val (params, args) = captures.unzip

From afef6bd76984772c4e5a1902ee307678059d8c49 Mon Sep 17 00:00:00 2001
From: Tobias Schlatter <tobias@meisch.ch>
Date: Sun, 17 Dec 2023 16:08:08 +0100
Subject: [PATCH 024/298] Cache (potential) jsSuperClass tree separately

This removes the only desugarExpr call from buildClass. Since we'll
stop caching buildClass going forward, this is important.
---
 .../linker/backend/emitter/ClassEmitter.scala | 31 ++++++++++---------
 .../linker/backend/emitter/Emitter.scala      | 12 +++++--
 2 files changed, 26 insertions(+), 17 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
index 1a5a965e55..08a3bcbf20 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
@@ -45,13 +45,13 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
 
   def buildClass(className: ClassName, isJSClass: Boolean, jsClassCaptures: Option[List[ParamDef]],
       hasClassInitializer: Boolean,
-      superClass: Option[ClassIdent], jsSuperClass: Option[Tree], useESClass: Boolean,
+      superClass: Option[ClassIdent], storeJSSuperClass: Option[js.Tree], useESClass: Boolean,
       members: List[js.Tree])(
       implicit moduleContext: ModuleContext,
       globalKnowledge: GlobalKnowledge, pos: Position): WithGlobals[List[js.Tree]] = {
 
     if (!isJSClass) {
-      assert(jsSuperClass.isEmpty, className)
+      assert(storeJSSuperClass.isEmpty, className)
 
       if (useESClass) {
         val parentVarWithGlobals = for (parentIdent <- superClass) yield {
@@ -70,18 +70,12 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
       // Wrap the entire class def in an accessor function
       import TreeDSL._
 
-      val genStoreJSSuperClass = jsSuperClass.map { jsSuperClass =>
-        for (rhs <- desugarExpr(jsSuperClass, resultType = AnyType)) yield {
-          js.VarDef(fileLevelVar(VarField.superClass).ident, Some(rhs))
-        }
-      }
-
       val classValueIdent = fileLevelVarIdent(VarField.b, genName(className))
       val classValueVar = js.VarRef(classValueIdent)
       val createClassValueVar = genEmptyMutableLet(classValueIdent)
 
       val entireClassDefWithGlobals = if (useESClass) {
-        genJSSuperCtor(superClass, jsSuperClass).map { jsSuperClass =>
+        genJSSuperCtor(superClass, storeJSSuperClass.isDefined).map { jsSuperClass =>
           List(classValueVar := js.ClassDef(Some(classValueIdent), Some(jsSuperClass), members))
         }
       } else {
@@ -89,11 +83,10 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
       }
 
       val classDefStatsWithGlobals = for {
-        optStoreJSSuperClass <- WithGlobals.option(genStoreJSSuperClass)
         entireClassDef <- entireClassDefWithGlobals
         createStaticFields <- genCreateStaticFieldsOfJSClass(className)
       } yield {
-        optStoreJSSuperClass.toList ::: entireClassDef ::: createStaticFields
+        storeJSSuperClass.toList ::: entireClassDef ::: createStaticFields
       }
 
       jsClassCaptures.fold {
@@ -225,7 +218,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
 
   /** Generates the JS constructor for a JS class. */
   def genJSConstructor(className: ClassName, superClass: Option[ClassIdent],
-      jsSuperClass: Option[Tree], useESClass: Boolean, jsConstructorDef: JSConstructorDef)(
+      hasJSSuperClass: Boolean, useESClass: Boolean, jsConstructorDef: JSConstructorDef)(
       implicit moduleContext: ModuleContext,
       globalKnowledge: GlobalKnowledge, pos: Position): WithGlobals[List[js.Tree]] = {
 
@@ -240,7 +233,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
     } else {
       for {
         ctorFun <- ctorFunWithGlobals
-        superCtor <- genJSSuperCtor(superClass, jsSuperClass)
+        superCtor <- genJSSuperCtor(superClass, hasJSSuperClass)
       } yield {
         import TreeDSL._
 
@@ -254,16 +247,24 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
     }
   }
 
-  private def genJSSuperCtor(superClass: Option[ClassIdent], jsSuperClass: Option[Tree])(
+  private def genJSSuperCtor(superClass: Option[ClassIdent], hasJSSuperClass: Boolean)(
       implicit moduleContext: ModuleContext, globalKnowledge: GlobalKnowledge,
       pos: Position): WithGlobals[js.Tree] = {
-    if (jsSuperClass.isDefined) {
+    if (hasJSSuperClass) {
       WithGlobals(fileLevelVar(VarField.superClass))
     } else {
       genJSClassConstructor(superClass.get.name, keepOnlyDangerousVarNames = true)
     }
   }
 
+  def genStoreJSSuperClass(jsSuperClass: Tree)(
+      implicit moduleContext: ModuleContext, globalKnowledge: GlobalKnowledge,
+      pos: Position): WithGlobals[js.Tree] = {
+    for (rhs <- desugarExpr(jsSuperClass, resultType = AnyType)) yield {
+      js.VarDef(fileLevelVar(VarField.superClass).ident, Some(rhs))
+    }
+  }
+
   /** Generates the JavaScript constructor of a class, as a `js.Function`.
    *
    *  For ECMAScript 2015, that `js.Function` must be decomposed and reformed
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala
index ea5e4b09bd..a5191cdf8c 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala
@@ -447,6 +447,13 @@ final class Emitter(config: Emitter.Config) {
         (isJSClass || linkedClass.ancestors.contains(ThrowableClass))
       }
 
+      val hasJSSuperClass = linkedClass.jsSuperClass.isDefined
+
+      val storeJSSuperClass = linkedClass.jsSuperClass.map { jsSuperClass =>
+        extractWithGlobals(classTreeCache.storeJSSuperClass.getOrElseUpdate(
+            classEmitter.genStoreJSSuperClass(jsSuperClass)(moduleContext, classCache, linkedClass.pos)))
+      }
+
       // JS constructor
       val ctorWithGlobals = {
         /* The constructor depends both on the class version, and the version
@@ -468,7 +475,7 @@ final class Emitter(config: Emitter.Config) {
               classEmitter.genJSConstructor(
                 className, // invalidated by overall class cache (part of ancestors)
                 linkedClass.superClass, // invalidated by class version
-                linkedClass.jsSuperClass, // invalidated by class version
+                hasJSSuperClass, // invalidated by class version
                 useESClass, // invalidated by class version
                 jsConstructorDef // part of ctor version
               )(moduleContext, ctorCache, linkedClass.pos))
@@ -579,7 +586,7 @@ final class Emitter(config: Emitter.Config) {
               linkedClass.jsClassCaptures, // invalidated by class version
               hasClassInitializer, // invalidated by class version (optimizer cannot remove it)
               linkedClass.superClass, // invalidated by class version
-              linkedClass.jsSuperClass, // invalidated by class version
+              storeJSSuperClass, // invalidated by class version
               useESClass, // invalidated by class version (depends on kind, config and ancestry only)
               ctor ::: memberMethods ::: exportedMembers.flatten // all 3 invalidated directly
             )(moduleContext, fullClassCache, linkedClass.pos) // pos invalidated by class version
@@ -1047,6 +1054,7 @@ object Emitter {
 
   private final class DesugaredClassCache {
     val privateJSFields = new OneTimeCache[WithGlobals[List[js.Tree]]]
+    val storeJSSuperClass = new OneTimeCache[WithGlobals[js.Tree]]
     val instanceTests = new OneTimeCache[WithGlobals[List[js.Tree]]]
     val typeData = new OneTimeCache[WithGlobals[List[js.Tree]]]
     val setTypeData = new OneTimeCache[js.Tree]

From 4b52fa070f3a1337639f55f0253aabcfaadd18f1 Mon Sep 17 00:00:00 2001
From: Tobias Schlatter <tobias@meisch.ch>
Date: Sat, 30 Dec 2023 11:11:06 +0100
Subject: [PATCH 025/298] Replace DocComment tree with dedicated
 JSDocConstructor tree

This simplifies pretty much all usage sites.
---
 .../closure/ClosureAstTransformer.scala       | 55 ++++++-------------
 .../linker/backend/emitter/ClassEmitter.scala | 14 ++---
 .../linker/backend/javascript/Printers.scala  | 26 ++-------
 .../linker/backend/javascript/Trees.scala     |  4 +-
 .../backend/javascript/PrintersTest.scala     |  8 ++-
 5 files changed, 36 insertions(+), 71 deletions(-)

diff --git a/linker/jvm/src/main/scala/org/scalajs/linker/backend/closure/ClosureAstTransformer.scala b/linker/jvm/src/main/scala/org/scalajs/linker/backend/closure/ClosureAstTransformer.scala
index fa759a4858..79ad4562ec 100644
--- a/linker/jvm/src/main/scala/org/scalajs/linker/backend/closure/ClosureAstTransformer.scala
+++ b/linker/jvm/src/main/scala/org/scalajs/linker/backend/closure/ClosureAstTransformer.scala
@@ -43,7 +43,8 @@ private class ClosureAstTransformer(featureSet: FeatureSet,
 
   def transformScript(topLevelTrees: List[Tree]): Node = {
     val script = setNodePosition(new Node(Token.SCRIPT), NoPosition)
-    transformBlockStats(topLevelTrees)(NoPosition).foreach(script.addChildToBack(_))
+    for (stat <- topLevelTrees)
+      script.addChildToBack(transformStat(stat)(NoPosition))
     script.putProp(Node.FEATURE_SET, featureSet)
     script
   }
@@ -55,6 +56,20 @@ private class ClosureAstTransformer(featureSet: FeatureSet,
     implicit val pos = pos_in
 
     wrapTransform(tree) {
+      case JSDocConstructor(tree) =>
+        val node = transformStat(tree)
+        // The @constructor must be propagated through an ExprResult node
+        val trg =
+          if (node.isExprResult()) node.getChildAtIndex(0)
+          else node
+        val ctorDoc = {
+          val b = JSDocInfo.builder()
+          b.recordConstructor()
+          b.build()
+        }
+        trg.setJSDocInfo(ctorDoc)
+        node
+
       case VarDef(ident, optRhs) =>
         val node = transformName(ident)
         optRhs.foreach(rhs => node.addChildToFront(transformExpr(rhs)))
@@ -448,45 +463,11 @@ private class ClosureAstTransformer(featureSet: FeatureSet,
 
   def transformBlock(stats: List[Tree], blockPos: Position): Node = {
     val block = new Node(Token.BLOCK)
-    for (node <- transformBlockStats(stats)(blockPos))
-      block.addChildToBack(node)
+    for (stat <- stats)
+      block.addChildToBack(transformStat(stat)(blockPos))
     block
   }
 
-  def transformBlockStats(stats: List[Tree])(
-      implicit parentPos: Position): List[Node] = {
-
-    @inline def ctorDoc(): JSDocInfo = {
-      val b = JSDocInfo.builder()
-      b.recordConstructor()
-      b.build()
-    }
-
-    // The Rhino IR attaches DocComments to the following nodes (rather than
-    // having individual nodes). We preprocess these here.
-    @tailrec
-    def loop(ts: List[Tree], nextIsCtor: Boolean, acc: List[Node]): List[Node] = ts match {
-      case DocComment(text) :: tss =>
-        loop(tss, nextIsCtor = text.startsWith("@constructor"), acc)
-
-      case t :: tss =>
-        val node = transformStat(t)
-        if (nextIsCtor) {
-          // The @constructor must be propagated through an ExprResult node
-          val trg =
-            if (node.isExprResult()) node.getChildAtIndex(0)
-            else node
-          trg.setJSDocInfo(ctorDoc())
-        }
-        loop(tss, nextIsCtor = false, node :: acc)
-
-      case Nil =>
-        acc.reverse
-    }
-
-    loop(stats, nextIsCtor = false, Nil)
-  }
-
   @inline
   private def wrapTransform(tree: Tree)(body: Tree => Node)(
       implicit pos: Position): Node = {
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
index 144672a471..fc7054c1e6 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
@@ -214,14 +214,14 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
       } yield {
         (
           // Real constructor
-          js.DocComment("@constructor") ::
-          realCtorDef :::
+          js.JSDocConstructor(realCtorDef.head) ::
+          realCtorDef.tail :::
           chainProto :::
           (genIdentBracketSelect(ctorVar.prototype, "constructor") := ctorVar) ::
 
           // Inheritable constructor
-          js.DocComment("@constructor") ::
-          inheritableCtorDef :::
+          js.JSDocConstructor(inheritableCtorDef.head) ::
+          inheritableCtorDef.tail :::
           (globalVar(VarField.h, className).prototype := ctorVar.prototype) :: Nil
         )
       }
@@ -251,8 +251,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
 
         val ctorVar = fileLevelVar(VarField.b, genName(className))
 
-        js.DocComment("@constructor") ::
-        (ctorVar := ctorFun) ::
+        js.JSDocConstructor(ctorVar := ctorFun) ::
         chainPrototypeWithLocalCtor(className, ctorVar, superCtor) :::
         (genIdentBracketSelect(ctorVar.prototype, "constructor") := ctorVar) :: Nil
       }
@@ -344,8 +343,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
     val dummyCtor = fileLevelVar(VarField.hh, genName(className))
 
     List(
-        js.DocComment("@constructor"),
-        genConst(dummyCtor.ident, js.Function(false, Nil, None, js.Skip())),
+        js.JSDocConstructor(genConst(dummyCtor.ident, js.Function(false, Nil, None, js.Skip()))),
         dummyCtor.prototype := superCtor.prototype,
         ctorVar.prototype := js.New(dummyCtor, Nil)
     )
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Printers.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Printers.scala
index 9690946e69..4d675d4dec 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Printers.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Printers.scala
@@ -139,27 +139,11 @@ object Printers {
       }
 
       tree match {
-        // Comments
-
-        case DocComment(text) =>
-          val lines = text.split("\n").toList
-          if (lines.tail.isEmpty) {
-            print("/** ")
-            print(lines.head)
-            print(" */")
-          } else {
-            print("/** ")
-            print(lines.head)
-            println(); printIndent()
-            var rest = lines.tail
-            while (rest.nonEmpty) {
-              print(" *  ")
-              print(rest.head)
-              println(); printIndent()
-              rest = rest.tail
-            }
-            print(" */")
-          }
+        case JSDocConstructor(tree) =>
+          print("/** @constructor */")
+          println(); printIndent()
+          // not printStat: we must not print the trailing newline.
+          printTree(tree, isStat = true)
 
         // Definitions
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Trees.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Trees.scala
index 27da8e50c1..efcf98e609 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Trees.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Trees.scala
@@ -39,9 +39,9 @@ object Trees {
     }
   }
 
-  // Comments
+  // Constructor comment / annotation.
 
-  sealed case class DocComment(text: String)(implicit val pos: Position)
+  sealed case class JSDocConstructor(tree: Tree)(implicit val pos: Position)
       extends Tree
 
   // Identifiers and properties
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/backend/javascript/PrintersTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/backend/javascript/PrintersTest.scala
index 316f2c3907..86c9215f02 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/backend/javascript/PrintersTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/backend/javascript/PrintersTest.scala
@@ -89,12 +89,14 @@ class PrintersTest {
     )
   }
 
-  @Test def printDocComment(): Unit = {
+  @Test def printJSDocConstructor(): Unit = {
     assertPrintEquals(
       """
-        | /** test */
+        |/** @constructor */
+        |ctor = (function() {
+        |});
       """,
-      DocComment("test")
+      JSDocConstructor(Assign(VarRef("ctor"), Function(false, Nil, None, Skip())))
     )
   }
 

From 6d072557808220d3eedb9209cc2b90d29b34357a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Thu, 25 Jan 2024 14:51:03 +0100
Subject: [PATCH 026/298] Do not put `O` (`jl.Object`) in the `ancestors`
 dictionaries.

It is never read, because all the functions that would read it are
special-cased, so these are wasted bytes.
---
 .../org/scalajs/linker/backend/emitter/ClassEmitter.scala | 2 +-
 .../org/scalajs/linker/backend/emitter/CoreJSLib.scala    | 3 +--
 .../test/scala/org/scalajs/linker/LibrarySizeTest.scala   | 6 +++---
 project/Build.scala                                       | 8 ++++----
 4 files changed, 9 insertions(+), 10 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
index 144672a471..ad953d86ef 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
@@ -865,7 +865,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
     }
 
     val ancestorsRecord = js.ObjectConstr(
-        ancestors.map(ancestor => (js.Ident(genName(ancestor)), js.IntLiteral(1))))
+        ancestors.withFilter(_ != ObjectClass).map(ancestor => (js.Ident(genName(ancestor)), js.IntLiteral(1))))
 
     val isInstanceFunWithGlobals: WithGlobals[js.Tree] = {
       if (globalKnowledge.isAncestorOfHijackedClass(className)) {
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
index 8a04956ad8..6bfac4a983 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
@@ -1687,7 +1687,6 @@ private[emitter] object CoreJSLib {
             else
               Skip(),
             privateFieldSet("ancestors", ObjectConstr(List(
-                Ident(genName(ObjectClass)) -> 1,
                 Ident(genName(CloneableClass)) -> 1,
                 Ident(genName(SerializableClass)) -> 1
             ))),
@@ -2066,7 +2065,7 @@ private[emitter] object CoreJSLib {
         extractWithGlobals(
             globalVarDef(VarField.d, ObjectClass, New(globalVar(VarField.TypeData, CoreVar), Nil))) :::
         List(
-          privateFieldSet("ancestors", ObjectConstr(List((Ident(genName(ObjectClass)) -> 1)))),
+          privateFieldSet("ancestors", ObjectConstr(Nil)),
           privateFieldSet("arrayEncodedName", str("L" + fullName + ";")),
           privateFieldSet("isAssignableFromFun", {
             genArrowFunction(paramList(that), {
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/LibrarySizeTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/LibrarySizeTest.scala
index 9dcc074647..aa851ca438 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/LibrarySizeTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/LibrarySizeTest.scala
@@ -70,9 +70,9 @@ class LibrarySizeTest {
     )
 
     testLinkedSizes(
-      expectedFastLinkSize = 150339,
-      expectedFullLinkSizeWithoutClosure = 130884,
-      expectedFullLinkSizeWithClosure = 21394,
+      expectedFastLinkSize = 150063,
+      expectedFullLinkSizeWithoutClosure = 130664,
+      expectedFullLinkSizeWithClosure = 21325,
       classDefs,
       moduleInitializers = MainTestModuleInitializers
     )
diff --git a/project/Build.scala b/project/Build.scala
index 758975e8f0..f9d72c08e0 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -1967,16 +1967,16 @@ object Build {
         scalaVersion.value match {
           case `default212Version` =>
             Some(ExpectedSizes(
-                fastLink = 770000 to 771000,
-                fullLink = 145000 to 146000,
+                fastLink = 768000 to 769000,
+                fullLink = 144000 to 145000,
                 fastLinkGz = 90000 to 91000,
                 fullLinkGz = 35000 to 36000,
             ))
 
           case `default213Version` =>
             Some(ExpectedSizes(
-                fastLink = 479000 to 480000,
-                fullLink = 102000 to 103000,
+                fastLink = 478000 to 479000,
+                fullLink = 101000 to 102000,
                 fastLinkGz = 62000 to 63000,
                 fullLinkGz = 27000 to 28000,
             ))

From 86c18be06bfff8c0245e1ab18b404bcb238a56ba Mon Sep 17 00:00:00 2001
From: Tobias Schlatter <tobias@meisch.ch>
Date: Sun, 15 Oct 2023 20:05:42 +0200
Subject: [PATCH 027/298] Fuse emitting and printing of trees in the backend

This allows us to use the Emitter's powerful caching mechanism to
directly cache printed trees (as byte buffers) and not cache
JavaScript trees anymore at all.

This reduces in-between run memory usage on the test suite from
1.12 GB (not GiB) to 1.00 GB on my machine (roughly 10%).

Runtime performance (both batch and incremental) is unaffected.

It is worth pointing out, that due to how the Emitter caches trees,
classes that end up being ES6 classes is performed will be held twice
in memory (once the individual methods, once the entire class).

On the test suite, this is the case for 710 cases out of 6538.
---
 .../closure/ClosureLinkerBackend.scala        |   9 +-
 .../linker/backend/BasicLinkerBackend.scala   | 169 ++++++--------
 .../linker/backend/emitter/ClassEmitter.scala |   6 +-
 .../linker/backend/emitter/CoreJSLib.scala    |  22 +-
 .../linker/backend/emitter/Emitter.scala      | 213 +++++++++++-------
 .../linker/backend/javascript/Printers.scala  |  30 ++-
 .../linker/backend/javascript/Trees.scala     |  18 ++
 .../linker/BasicLinkerBackendTest.scala       |  30 +--
 .../org/scalajs/linker/EmitterTest.scala      |  94 ++++++++
 .../backend/javascript/PrintersTest.scala     |  24 +-
 10 files changed, 383 insertions(+), 232 deletions(-)

diff --git a/linker/jvm/src/main/scala/org/scalajs/linker/backend/closure/ClosureLinkerBackend.scala b/linker/jvm/src/main/scala/org/scalajs/linker/backend/closure/ClosureLinkerBackend.scala
index 003e873773..1f532767e2 100644
--- a/linker/jvm/src/main/scala/org/scalajs/linker/backend/closure/ClosureLinkerBackend.scala
+++ b/linker/jvm/src/main/scala/org/scalajs/linker/backend/closure/ClosureLinkerBackend.scala
@@ -60,7 +60,7 @@ final class ClosureLinkerBackend(config: LinkerBackendImpl.Config)
       .withTrackAllGlobalRefs(true)
       .withInternalModulePattern(m => OutputPatternsImpl.moduleName(config.outputPatterns, m.id))
 
-    new Emitter(emitterConfig)
+    new Emitter(emitterConfig, ClosureLinkerBackend.PostTransformer)
   }
 
   val symbolRequirements: SymbolRequirement = emitter.symbolRequirements
@@ -295,4 +295,11 @@ private object ClosureLinkerBackend {
     Function.prototype.apply;
     var NaN = 0.0/0.0, Infinity = 1.0/0.0, undefined = void 0;
     """
+
+  private object PostTransformer extends Emitter.PostTransformer[js.Tree] {
+    // Do not apply ClosureAstTransformer eagerly:
+    // The ASTs used by closure are highly mutable, so re-using them is non-trivial.
+    // Since closure is slow anyways, we haven't built the optimization.
+    def transformStats(trees: List[js.Tree], indent: Int): List[js.Tree] = trees
+  }
 }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/BasicLinkerBackend.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/BasicLinkerBackend.scala
index 564ebbb99c..4faef57c0a 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/BasicLinkerBackend.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/BasicLinkerBackend.scala
@@ -17,6 +17,8 @@ import scala.concurrent._
 import java.nio.ByteBuffer
 import java.nio.charset.StandardCharsets
 
+import java.util.concurrent.atomic.AtomicInteger
+
 import org.scalajs.logging.Logger
 
 import org.scalajs.linker.interface.{IRFile, OutputDirectory, Report}
@@ -36,12 +38,19 @@ final class BasicLinkerBackend(config: LinkerBackendImpl.Config)
 
   import BasicLinkerBackend._
 
+  private[this] var totalModules = 0
+  private[this] val rewrittenModules = new AtomicInteger(0)
+
   private[this] val emitter = {
     val emitterConfig = Emitter.Config(config.commonConfig.coreSpec)
       .withJSHeader(config.jsHeader)
       .withInternalModulePattern(m => OutputPatternsImpl.moduleName(config.outputPatterns, m.id))
 
-    new Emitter(emitterConfig)
+    val postTransformer =
+      if (config.sourceMap) PostTransformerWithSourceMap
+      else PostTransformerWithoutSourceMap
+
+    new Emitter(emitterConfig, postTransformer)
   }
 
   val symbolRequirements: SymbolRequirement = emitter.symbolRequirements
@@ -61,6 +70,11 @@ final class BasicLinkerBackend(config: LinkerBackendImpl.Config)
       implicit ec: ExecutionContext): Future[Report] = {
     verifyModuleSet(moduleSet)
 
+    // Reset stats.
+
+    totalModules = moduleSet.modules.size
+    rewrittenModules.set(0)
+
     val emitterResult = logger.time("Emitter") {
       emitter.emit(moduleSet, logger)
     }
@@ -68,24 +82,25 @@ final class BasicLinkerBackend(config: LinkerBackendImpl.Config)
     val skipContentCheck = !isFirstRun
     isFirstRun = false
 
-    printedModuleSetCache.startRun(moduleSet)
     val allChanged =
       printedModuleSetCache.updateGlobal(emitterResult.header, emitterResult.footer)
 
     val writer = new OutputWriter(output, config, skipContentCheck) {
       protected def writeModuleWithoutSourceMap(moduleID: ModuleID, force: Boolean): Option[ByteBuffer] = {
         val cache = printedModuleSetCache.getModuleCache(moduleID)
-        val changed = cache.update(emitterResult.body(moduleID))
+        val printedTrees = emitterResult.body(moduleID)
+
+        val changed = cache.update(printedTrees)
 
         if (force || changed || allChanged) {
-          printedModuleSetCache.incRewrittenModules()
+          rewrittenModules.incrementAndGet()
 
           val jsFileWriter = new ByteArrayWriter(sizeHintFor(cache.getPreviousFinalJSFileSize()))
 
           jsFileWriter.write(printedModuleSetCache.headerBytes)
           jsFileWriter.writeASCIIString("'use strict';\n")
 
-          for (printedTree <- cache.printedTrees)
+          for (printedTree <- printedTrees)
             jsFileWriter.write(printedTree.jsCode)
 
           jsFileWriter.write(printedModuleSetCache.footerBytes)
@@ -99,10 +114,12 @@ final class BasicLinkerBackend(config: LinkerBackendImpl.Config)
 
       protected def writeModuleWithSourceMap(moduleID: ModuleID, force: Boolean): Option[(ByteBuffer, ByteBuffer)] = {
         val cache = printedModuleSetCache.getModuleCache(moduleID)
-        val changed = cache.update(emitterResult.body(moduleID))
+        val printedTrees = emitterResult.body(moduleID)
+
+        val changed = cache.update(printedTrees)
 
         if (force || changed || allChanged) {
-          printedModuleSetCache.incRewrittenModules()
+          rewrittenModules.incrementAndGet()
 
           val jsFileWriter = new ByteArrayWriter(sizeHintFor(cache.getPreviousFinalJSFileSize()))
           val sourceMapWriter = new ByteArrayWriter(sizeHintFor(cache.getPreviousFinalSourceMapSize()))
@@ -120,7 +137,7 @@ final class BasicLinkerBackend(config: LinkerBackendImpl.Config)
           jsFileWriter.writeASCIIString("'use strict';\n")
           smWriter.nextLine()
 
-          for (printedTree <- cache.printedTrees) {
+          for (printedTree <- printedTrees) {
             jsFileWriter.write(printedTree.jsCode)
             smWriter.insertFragment(printedTree.sourceMapFragment)
           }
@@ -145,9 +162,15 @@ final class BasicLinkerBackend(config: LinkerBackendImpl.Config)
       writer.write(moduleSet)
     }.andThen { case _ =>
       printedModuleSetCache.cleanAfterRun()
-      printedModuleSetCache.logStats(logger)
+      logStats(logger)
     }
   }
+
+  private def logStats(logger: Logger): Unit = {
+    // Message extracted in BasicLinkerBackendTest
+    logger.debug(
+        s"BasicBackend: total modules: $totalModules; re-written: ${rewrittenModules.get()}")
+  }
 }
 
 private object BasicLinkerBackend {
@@ -161,20 +184,6 @@ private object BasicLinkerBackend {
 
     private val modules = new java.util.concurrent.ConcurrentHashMap[ModuleID, PrintedModuleCache]
 
-    private var totalModules = 0
-    private val rewrittenModules = new java.util.concurrent.atomic.AtomicInteger(0)
-
-    private var totalTopLevelTrees = 0
-    private var recomputedTopLevelTrees = 0
-
-    def startRun(moduleSet: ModuleSet): Unit = {
-      totalModules = moduleSet.modules.size
-      rewrittenModules.set(0)
-
-      totalTopLevelTrees = 0
-      recomputedTopLevelTrees = 0
-    }
-
     def updateGlobal(header: String, footer: String): Boolean = {
       if (header == lastHeader && footer == lastFooter) {
         false
@@ -193,61 +202,32 @@ private object BasicLinkerBackend {
     def headerNewLineCount: Int = _headerNewLineCountCache
 
     def getModuleCache(moduleID: ModuleID): PrintedModuleCache = {
-      val result = modules.computeIfAbsent(moduleID, { _ =>
-        if (withSourceMaps) new PrintedModuleCacheWithSourceMaps
-        else new PrintedModuleCache
-      })
-
+      val result = modules.computeIfAbsent(moduleID, _ => new PrintedModuleCache)
       result.startRun()
       result
     }
 
-    def incRewrittenModules(): Unit =
-      rewrittenModules.incrementAndGet()
-
     def cleanAfterRun(): Unit = {
       val iter = modules.entrySet().iterator()
       while (iter.hasNext()) {
         val moduleCache = iter.next().getValue()
-        if (moduleCache.cleanAfterRun()) {
-          totalTopLevelTrees += moduleCache.getTotalTopLevelTrees
-          recomputedTopLevelTrees += moduleCache.getRecomputedTopLevelTrees
-        } else {
+        if (!moduleCache.cleanAfterRun()) {
           iter.remove()
         }
       }
     }
-
-    def logStats(logger: Logger): Unit = {
-      /* These messages are extracted in BasicLinkerBackendTest to assert that
-       * we do not invalidate anything in a no-op second run.
-       */
-      logger.debug(
-          s"BasicBackend: total top-level trees: $totalTopLevelTrees; re-computed: $recomputedTopLevelTrees")
-      logger.debug(
-          s"BasicBackend: total modules: $totalModules; re-written: ${rewrittenModules.get()}")
-    }
-  }
-
-  private final class PrintedTree(val jsCode: Array[Byte], val sourceMapFragment: SourceMapWriter.Fragment) {
-    var cachedUsed: Boolean = false
   }
 
   private sealed class PrintedModuleCache {
     private var cacheUsed = false
     private var changed = false
-    private var lastJSTrees: List[js.Tree] = Nil
-    private var printedTreesCache: List[PrintedTree] = Nil
-    private val cache = new java.util.IdentityHashMap[js.Tree, PrintedTree]
+    private var lastPrintedTrees: List[js.PrintedTree] = Nil
 
     private var previousFinalJSFileSize: Int = 0
     private var previousFinalSourceMapSize: Int = 0
 
-    private var recomputedTopLevelTrees = 0
-
     def startRun(): Unit = {
       cacheUsed = true
-      recomputedTopLevelTrees = 0
     }
 
     def getPreviousFinalJSFileSize(): Int = previousFinalJSFileSize
@@ -259,72 +239,51 @@ private object BasicLinkerBackend {
       previousFinalSourceMapSize = finalSourceMapSize
     }
 
-    def update(newJSTrees: List[js.Tree]): Boolean = {
-      val changed = !newJSTrees.corresponds(lastJSTrees)(_ eq _)
+    def update(newPrintedTrees: List[js.PrintedTree]): Boolean = {
+      val changed = !newPrintedTrees.corresponds(lastPrintedTrees)(_ eq _)
       this.changed = changed
       if (changed) {
-        printedTreesCache = newJSTrees.map(getOrComputePrintedTree(_))
-        lastJSTrees = newJSTrees
+        lastPrintedTrees = newPrintedTrees
       }
       changed
     }
 
-    private def getOrComputePrintedTree(tree: js.Tree): PrintedTree = {
-      val result = cache.computeIfAbsent(tree, { (tree: js.Tree) =>
-        recomputedTopLevelTrees += 1
-        computePrintedTree(tree)
-      })
-
-      result.cachedUsed = true
-      result
-    }
-
-    protected def computePrintedTree(tree: js.Tree): PrintedTree = {
-      val jsCodeWriter = new ByteArrayWriter()
-      val printer = new Printers.JSTreePrinter(jsCodeWriter)
-
-      printer.printStat(tree)
-
-      new PrintedTree(jsCodeWriter.toByteArray(), SourceMapWriter.Fragment.Empty)
+    def cleanAfterRun(): Boolean = {
+      val wasUsed = cacheUsed
+      cacheUsed = false
+      wasUsed
     }
+  }
 
-    def printedTrees: List[PrintedTree] = printedTreesCache
+  private object PostTransformerWithoutSourceMap extends Emitter.PostTransformer[js.PrintedTree] {
+    def transformStats(trees: List[js.Tree], indent: Int): List[js.PrintedTree] = {
+      if (trees.isEmpty) {
+        Nil // Fast path
+      } else {
+        val jsCodeWriter = new ByteArrayWriter()
+        val printer = new Printers.JSTreePrinter(jsCodeWriter, indent)
 
-    def cleanAfterRun(): Boolean = {
-      if (cacheUsed) {
-        cacheUsed = false
-
-        if (changed) {
-          val iter = cache.entrySet().iterator()
-          while (iter.hasNext()) {
-            val printedTree = iter.next().getValue()
-            if (printedTree.cachedUsed)
-              printedTree.cachedUsed = false
-            else
-              iter.remove()
-          }
-        }
+        trees.map(printer.printStat(_))
 
-        true
-      } else {
-        false
+        js.PrintedTree(jsCodeWriter.toByteArray(), SourceMapWriter.Fragment.Empty) :: Nil
       }
     }
-
-    def getTotalTopLevelTrees: Int = lastJSTrees.size
-    def getRecomputedTopLevelTrees: Int = recomputedTopLevelTrees
   }
 
-  private final class PrintedModuleCacheWithSourceMaps extends PrintedModuleCache {
-    override protected def computePrintedTree(tree: js.Tree): PrintedTree = {
-      val jsCodeWriter = new ByteArrayWriter()
-      val smFragmentBuilder = new SourceMapWriter.FragmentBuilder()
-      val printer = new Printers.JSTreePrinterWithSourceMap(jsCodeWriter, smFragmentBuilder)
+  private object PostTransformerWithSourceMap extends Emitter.PostTransformer[js.PrintedTree] {
+    def transformStats(trees: List[js.Tree], indent: Int): List[js.PrintedTree] = {
+      if (trees.isEmpty) {
+        Nil // Fast path
+      } else {
+        val jsCodeWriter = new ByteArrayWriter()
+        val smFragmentBuilder = new SourceMapWriter.FragmentBuilder()
+        val printer = new Printers.JSTreePrinterWithSourceMap(jsCodeWriter, smFragmentBuilder, indent)
 
-      printer.printStat(tree)
-      smFragmentBuilder.complete()
+        trees.map(printer.printStat(_))
+        smFragmentBuilder.complete()
 
-      new PrintedTree(jsCodeWriter.toByteArray(), smFragmentBuilder.result())
+        js.PrintedTree(jsCodeWriter.toByteArray(), smFragmentBuilder.result()) :: Nil
+      }
     }
   }
 }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
index 424b962989..aade6c4b8a 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
@@ -45,7 +45,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
 
   def buildClass(className: ClassName, isJSClass: Boolean, jsClassCaptures: Option[List[ParamDef]],
       hasClassInitializer: Boolean,
-      superClass: Option[ClassIdent], storeJSSuperClass: Option[js.Tree], useESClass: Boolean,
+      superClass: Option[ClassIdent], storeJSSuperClass: List[js.Tree], useESClass: Boolean,
       members: List[js.Tree])(
       implicit moduleContext: ModuleContext,
       globalKnowledge: GlobalKnowledge, pos: Position): WithGlobals[List[js.Tree]] = {
@@ -75,7 +75,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
       val createClassValueVar = genEmptyMutableLet(classValueIdent)
 
       val entireClassDefWithGlobals = if (useESClass) {
-        genJSSuperCtor(superClass, storeJSSuperClass.isDefined).map { jsSuperClass =>
+        genJSSuperCtor(superClass, storeJSSuperClass.nonEmpty).map { jsSuperClass =>
           List(classValueVar := js.ClassDef(Some(classValueIdent), Some(jsSuperClass), members))
         }
       } else {
@@ -86,7 +86,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
         entireClassDef <- entireClassDefWithGlobals
         createStaticFields <- genCreateStaticFieldsOfJSClass(className)
       } yield {
-        storeJSSuperClass.toList ::: entireClassDef ::: createStaticFields
+        storeJSSuperClass ::: entireClassDef ::: createStaticFields
       }
 
       jsClassCaptures.fold {
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
index 97330e7ccf..290bb7f362 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
@@ -32,9 +32,9 @@ import PolyfillableBuiltin._
 
 private[emitter] object CoreJSLib {
 
-  def build(sjsGen: SJSGen, moduleContext: ModuleContext,
-      globalKnowledge: GlobalKnowledge): WithGlobals[Lib] = {
-    new CoreJSLibBuilder(sjsGen)(moduleContext, globalKnowledge).build()
+  def build[E](sjsGen: SJSGen, postTransform: List[Tree] => E, moduleContext: ModuleContext,
+      globalKnowledge: GlobalKnowledge): WithGlobals[Lib[E]] = {
+    new CoreJSLibBuilder(sjsGen)(moduleContext, globalKnowledge).build(postTransform)
   }
 
   /** A fully built CoreJSLib
@@ -52,10 +52,10 @@ private[emitter] object CoreJSLib {
    *  @param initialization Things that depend on Scala.js generated classes.
    *      These must have class definitions (but not static fields) available.
    */
-  final class Lib private[CoreJSLib] (
-      val preObjectDefinitions: List[Tree],
-      val postObjectDefinitions: List[Tree],
-      val initialization: List[Tree])
+  final class Lib[E] private[CoreJSLib] (
+      val preObjectDefinitions: E,
+      val postObjectDefinitions: E,
+      val initialization: E)
 
   private class CoreJSLibBuilder(sjsGen: SJSGen)(
       implicit moduleContext: ModuleContext, globalKnowledge: GlobalKnowledge) {
@@ -115,9 +115,11 @@ private[emitter] object CoreJSLib {
     private val specializedArrayTypeRefs: List[NonArrayTypeRef] =
       ClassRef(ObjectClass) :: orderedPrimRefsWithoutVoid
 
-    def build(): WithGlobals[Lib] = {
-      val lib = new Lib(buildPreObjectDefinitions(),
-          buildPostObjectDefinitions(), buildInitializations())
+    def build[E](postTransform: List[Tree] => E): WithGlobals[Lib[E]] = {
+      val lib = new Lib(
+        postTransform(buildPreObjectDefinitions()),
+        postTransform(buildPostObjectDefinitions()),
+        postTransform(buildInitializations()))
       WithGlobals(lib, trackedGlobalRefs)
     }
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala
index a5191cdf8c..6035764aca 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala
@@ -33,7 +33,8 @@ import EmitterNames._
 import GlobalRefUtils._
 
 /** Emits a desugared JS tree to a builder */
-final class Emitter(config: Emitter.Config) {
+final class Emitter[E >: Null <: js.Tree](
+    config: Emitter.Config, postTransformer: Emitter.PostTransformer[E]) {
 
   import Emitter._
   import config._
@@ -71,13 +72,16 @@ final class Emitter(config: Emitter.Config) {
   private[this] var statsClassesInvalidated: Int = 0
   private[this] var statsMethodsReused: Int = 0
   private[this] var statsMethodsInvalidated: Int = 0
+  private[this] var statsPostTransforms: Int = 0
+  private[this] var statsNestedPostTransforms: Int = 0
+  private[this] var statsNestedPostTransformsAvoided: Int = 0
 
   val symbolRequirements: SymbolRequirement =
     Emitter.symbolRequirements(config)
 
   val injectedIRFiles: Seq[IRFile] = PrivateLibHolder.files
 
-  def emit(moduleSet: ModuleSet, logger: Logger): Result = {
+  def emit(moduleSet: ModuleSet, logger: Logger): Result[E] = {
     val WithGlobals(body, globalRefs) = emitInternal(moduleSet, logger)
 
     moduleKind match {
@@ -108,12 +112,15 @@ final class Emitter(config: Emitter.Config) {
   }
 
   private def emitInternal(moduleSet: ModuleSet,
-      logger: Logger): WithGlobals[Map[ModuleID, List[js.Tree]]] = {
+      logger: Logger): WithGlobals[Map[ModuleID, List[E]]] = {
     // Reset caching stats.
     statsClassesReused = 0
     statsClassesInvalidated = 0
     statsMethodsReused = 0
     statsMethodsInvalidated = 0
+    statsPostTransforms = 0
+    statsNestedPostTransforms = 0
+    statsNestedPostTransformsAvoided = 0
 
     // Update GlobalKnowledge.
     val invalidateAll = knowledgeGuardian.update(moduleSet)
@@ -128,13 +135,17 @@ final class Emitter(config: Emitter.Config) {
     try {
       emitAvoidGlobalClash(moduleSet, logger, secondAttempt = false)
     } finally {
-      // Report caching stats.
+      // Report caching stats (extracted in EmitterTest).
       logger.debug(
           s"Emitter: Class tree cache stats: reused: $statsClassesReused -- "+
           s"invalidated: $statsClassesInvalidated")
       logger.debug(
           s"Emitter: Method tree cache stats: reused: $statsMethodsReused -- "+
           s"invalidated: $statsMethodsInvalidated")
+      logger.debug(
+          s"Emitter: Post transforms: total: $statsPostTransforms -- " +
+          s"nested: $statsNestedPostTransforms -- " +
+          s"nested avoided: $statsNestedPostTransformsAvoided")
 
       // Inform caches about run completion.
       state.moduleCaches.filterInPlace((_, c) => c.cleanAfterRun())
@@ -142,6 +153,14 @@ final class Emitter(config: Emitter.Config) {
     }
   }
 
+  private def postTransform(trees: List[js.Tree], indent: Int): List[E] = {
+    statsPostTransforms += 1
+    postTransformer.transformStats(trees, indent)
+  }
+
+  private def postTransform(tree: js.Tree, indent: Int): List[E] =
+    postTransform(tree :: Nil, indent)
+
   /** Emits all JavaScript code avoiding clashes with global refs.
    *
    *  If, at the end of the process, the set of accessed dangerous globals has
@@ -150,7 +169,7 @@ final class Emitter(config: Emitter.Config) {
    */
   @tailrec
   private def emitAvoidGlobalClash(moduleSet: ModuleSet,
-      logger: Logger, secondAttempt: Boolean): WithGlobals[Map[ModuleID, List[js.Tree]]] = {
+      logger: Logger, secondAttempt: Boolean): WithGlobals[Map[ModuleID, List[E]]] = {
     val result = emitOnce(moduleSet, logger)
 
     val mentionedDangerousGlobalRefs =
@@ -175,7 +194,7 @@ final class Emitter(config: Emitter.Config) {
   }
 
   private def emitOnce(moduleSet: ModuleSet,
-      logger: Logger): WithGlobals[Map[ModuleID, List[js.Tree]]] = {
+      logger: Logger): WithGlobals[Map[ModuleID, List[E]]] = {
     // Genreate classes first so we can measure time separately.
     val generatedClasses = logger.time("Emitter: Generate Classes") {
       moduleSet.modules.map { module =>
@@ -200,7 +219,7 @@ final class Emitter(config: Emitter.Config) {
 
         val moduleImports = extractWithGlobals {
           moduleCache.getOrComputeImports(module.externalDependencies, module.internalDependencies) {
-            genModuleImports(module)
+            genModuleImports(module).map(postTransform(_, 0))
           }
         }
 
@@ -210,7 +229,7 @@ final class Emitter(config: Emitter.Config) {
            */
           moduleCache.getOrComputeTopLevelExports(module.topLevelExports) {
             classEmitter.genTopLevelExports(module.topLevelExports)(
-                moduleContext, moduleCache)
+                moduleContext, moduleCache).map(postTransform(_, 0))
           }
         }
 
@@ -220,7 +239,7 @@ final class Emitter(config: Emitter.Config) {
             WithGlobals.list(initializers.map { initializer =>
               classEmitter.genModuleInitializer(initializer)(
                   moduleContext, moduleCache)
-            })
+            }).map(postTransform(_, 0))
           }
         }
 
@@ -241,7 +260,7 @@ final class Emitter(config: Emitter.Config) {
          * requires consistency between the Analyzer and the Emitter. As such,
          * it is crucial that we verify it.
          */
-        val defTrees: List[js.Tree] = (
+        val defTrees: List[E] = (
             /* The definitions of the CoreJSLib that come before the definition
              * of `j.l.Object`. They depend on nothing else.
              */
@@ -357,7 +376,7 @@ final class Emitter(config: Emitter.Config) {
   }
 
   private def genClass(linkedClass: LinkedClass,
-      moduleContext: ModuleContext): GeneratedClass = {
+      moduleContext: ModuleContext): GeneratedClass[E] = {
     val className = linkedClass.className
 
     val classCache = classCaches.getOrElseUpdate(
@@ -379,7 +398,7 @@ final class Emitter(config: Emitter.Config) {
 
     // Main part
 
-    val main = List.newBuilder[js.Tree]
+    val main = List.newBuilder[E]
 
     val (linkedInlineableInit, linkedMethods) =
       classEmitter.extractInlineableInit(linkedClass)(classCache)
@@ -388,7 +407,7 @@ final class Emitter(config: Emitter.Config) {
     if (kind.isJSClass) {
       val fieldDefs = classTreeCache.privateJSFields.getOrElseUpdate {
         classEmitter.genCreatePrivateJSFieldDefsOfJSClass(className)(
-            moduleContext, classCache)
+            moduleContext, classCache).map(postTransform(_, 0))
       }
       main ++= extractWithGlobals(fieldDefs)
     }
@@ -407,8 +426,10 @@ final class Emitter(config: Emitter.Config) {
         val methodCache =
           classCache.getStaticLikeMethodCache(namespace, methodDef.methodName)
 
-        main ++= extractWithGlobals(methodCache.getOrElseUpdate(methodDef.version,
-            classEmitter.genStaticLikeMethod(className, methodDef)(moduleContext, methodCache)))
+        main ++= extractWithGlobals(methodCache.getOrElseUpdate(methodDef.version, {
+          classEmitter.genStaticLikeMethod(className, methodDef)(moduleContext, methodCache)
+            .map(postTransform(_, 0))
+        }))
       }
     }
 
@@ -447,11 +468,21 @@ final class Emitter(config: Emitter.Config) {
         (isJSClass || linkedClass.ancestors.contains(ThrowableClass))
       }
 
+      val memberIndent = {
+        (if (isJSClass) 1 else 0) + // accessor function
+        (if (useESClass) 1 else 0) // nesting from class
+      }
+
       val hasJSSuperClass = linkedClass.jsSuperClass.isDefined
 
-      val storeJSSuperClass = linkedClass.jsSuperClass.map { jsSuperClass =>
-        extractWithGlobals(classTreeCache.storeJSSuperClass.getOrElseUpdate(
-            classEmitter.genStoreJSSuperClass(jsSuperClass)(moduleContext, classCache, linkedClass.pos)))
+      val storeJSSuperClass = if (hasJSSuperClass) {
+        extractWithGlobals(classTreeCache.storeJSSuperClass.getOrElseUpdate({
+          val jsSuperClass = linkedClass.jsSuperClass.get
+          classEmitter.genStoreJSSuperClass(jsSuperClass)(moduleContext, classCache, linkedClass.pos)
+            .map(postTransform(_, 1))
+        }))
+      } else {
+        Nil
       }
 
       // JS constructor
@@ -478,7 +509,7 @@ final class Emitter(config: Emitter.Config) {
                 hasJSSuperClass, // invalidated by class version
                 useESClass, // invalidated by class version
                 jsConstructorDef // part of ctor version
-              )(moduleContext, ctorCache, linkedClass.pos))
+              )(moduleContext, ctorCache, linkedClass.pos).map(postTransform(_, memberIndent)))
         } else {
           val ctorVersion = linkedInlineableInit.fold {
             Version.combine(linkedClass.version)
@@ -492,7 +523,7 @@ final class Emitter(config: Emitter.Config) {
                 linkedClass.superClass, // invalidated by class version
                 useESClass, // invalidated by class version,
                 linkedInlineableInit // part of ctor version
-              )(moduleContext, ctorCache, linkedClass.pos))
+              )(moduleContext, ctorCache, linkedClass.pos).map(postTransform(_, memberIndent)))
         }
       }
 
@@ -546,7 +577,7 @@ final class Emitter(config: Emitter.Config) {
                 isJSClass, // invalidated by isJSClassVersion
                 useESClass, // invalidated by isJSClassVersion
                 method // invalidated by method.version
-            )(moduleContext, methodCache))
+            )(moduleContext, methodCache).map(postTransform(_, memberIndent)))
       }
 
       // Exported Members
@@ -561,7 +592,7 @@ final class Emitter(config: Emitter.Config) {
                 isJSClass, // invalidated by isJSClassVersion
                 useESClass, // invalidated by isJSClassVersion
                 member // invalidated by version
-            )(moduleContext, memberCache))
+            )(moduleContext, memberCache).map(postTransform(_, memberIndent)))
       }
 
       val hasClassInitializer: Boolean = {
@@ -578,8 +609,9 @@ final class Emitter(config: Emitter.Config) {
             memberMethodsWithGlobals, exportedMembersWithGlobals, {
           for {
             ctor <- ctorWithGlobals
-            memberMethods <- WithGlobals.list(memberMethodsWithGlobals)
-            exportedMembers <- WithGlobals.list(exportedMembersWithGlobals)
+            memberMethods <- WithGlobals.flatten(memberMethodsWithGlobals)
+            exportedMembers <- WithGlobals.flatten(exportedMembersWithGlobals)
+            allMembers = ctor ::: memberMethods ::: exportedMembers
             clazz <- classEmitter.buildClass(
               className, // invalidated by overall class cache (part of ancestors)
               isJSClass, // invalidated by class version
@@ -588,10 +620,17 @@ final class Emitter(config: Emitter.Config) {
               linkedClass.superClass, // invalidated by class version
               storeJSSuperClass, // invalidated by class version
               useESClass, // invalidated by class version (depends on kind, config and ancestry only)
-              ctor ::: memberMethods ::: exportedMembers.flatten // all 3 invalidated directly
+              allMembers // invalidated directly
             )(moduleContext, fullClassCache, linkedClass.pos) // pos invalidated by class version
           } yield {
-            clazz
+            // Avoid a nested post transform if we just got the original members back.
+            if (clazz eq allMembers) {
+              statsNestedPostTransformsAvoided += 1
+              allMembers
+            } else {
+              statsNestedPostTransforms += 1
+              postTransform(clazz, 0)
+            }
           }
         })
       }
@@ -614,8 +653,10 @@ final class Emitter(config: Emitter.Config) {
        */
 
       if (classEmitter.needInstanceTests(linkedClass)(classCache)) {
-        main ++= extractWithGlobals(classTreeCache.instanceTests.getOrElseUpdate(
-            classEmitter.genInstanceTests(className, kind)(moduleContext, classCache, linkedClass.pos)))
+        main ++= extractWithGlobals(classTreeCache.instanceTests.getOrElseUpdate({
+          classEmitter.genInstanceTests(className, kind)(moduleContext, classCache, linkedClass.pos)
+            .map(postTransform(_, 0))
+        }))
       }
 
       if (linkedClass.hasRuntimeTypeInfo) {
@@ -626,18 +667,22 @@ final class Emitter(config: Emitter.Config) {
               linkedClass.superClass, // invalidated by class version
               linkedClass.ancestors, // invalidated by overall class cache (identity)
               linkedClass.jsNativeLoadSpec // invalidated by class version
-            )(moduleContext, classCache, linkedClass.pos)))
+            )(moduleContext, classCache, linkedClass.pos).map(postTransform(_, 0))))
       }
 
       if (linkedClass.hasInstances && kind.isClass && linkedClass.hasRuntimeTypeInfo) {
-        main += classTreeCache.setTypeData.getOrElseUpdate(
-            classEmitter.genSetTypeData(className)(moduleContext, classCache, linkedClass.pos))
+        main ++= classTreeCache.setTypeData.getOrElseUpdate({
+          val tree = classEmitter.genSetTypeData(className)(moduleContext, classCache, linkedClass.pos)
+          postTransform(tree, 0)
+        })
       }
     }
 
     if (linkedClass.kind.hasModuleAccessor && linkedClass.hasInstances) {
-      main ++= extractWithGlobals(classTreeCache.moduleAccessor.getOrElseUpdate(
-          classEmitter.genModuleAccessor(className, isJSClass)(moduleContext, classCache, linkedClass.pos)))
+      main ++= extractWithGlobals(classTreeCache.moduleAccessor.getOrElseUpdate({
+        classEmitter.genModuleAccessor(className, isJSClass)(moduleContext, classCache, linkedClass.pos)
+          .map(postTransform(_, 0))
+      }))
     }
 
     // Static fields
@@ -645,15 +690,19 @@ final class Emitter(config: Emitter.Config) {
     val staticFields = if (linkedClass.kind.isJSType) {
       Nil
     } else {
-      extractWithGlobals(classTreeCache.staticFields.getOrElseUpdate(
-          classEmitter.genCreateStaticFieldsOfScalaClass(className)(moduleContext, classCache)))
+      extractWithGlobals(classTreeCache.staticFields.getOrElseUpdate({
+        classEmitter.genCreateStaticFieldsOfScalaClass(className)(moduleContext, classCache)
+          .map(postTransform(_, 0))
+      }))
     }
 
     // Static initialization
 
     val staticInitialization = if (classEmitter.needStaticInitialization(linkedClass)) {
-      classTreeCache.staticInitialization.getOrElseUpdate(
-          classEmitter.genStaticInitialization(className)(moduleContext, classCache, linkedClass.pos))
+      classTreeCache.staticInitialization.getOrElseUpdate({
+        val tree = classEmitter.genStaticInitialization(className)(moduleContext, classCache, linkedClass.pos)
+        postTransform(tree, 0)
+      })
     } else {
       Nil
     }
@@ -674,14 +723,14 @@ final class Emitter(config: Emitter.Config) {
   private final class ModuleCache extends knowledgeGuardian.KnowledgeAccessor {
     private[this] var _cacheUsed: Boolean = false
 
-    private[this] var _importsCache: WithGlobals[List[js.Tree]] = WithGlobals.nil
+    private[this] var _importsCache: WithGlobals[List[E]] = WithGlobals.nil
     private[this] var _lastExternalDependencies: Set[String] = Set.empty
     private[this] var _lastInternalDependencies: Set[ModuleID] = Set.empty
 
-    private[this] var _topLevelExportsCache: WithGlobals[List[js.Tree]] = WithGlobals.nil
+    private[this] var _topLevelExportsCache: WithGlobals[List[E]] = WithGlobals.nil
     private[this] var _lastTopLevelExports: List[LinkedTopLevelExport] = Nil
 
-    private[this] var _initializersCache: WithGlobals[List[js.Tree]] = WithGlobals.nil
+    private[this] var _initializersCache: WithGlobals[List[E]] = WithGlobals.nil
     private[this] var _lastInitializers: List[ModuleInitializer.Initializer] = Nil
 
     override def invalidate(): Unit = {
@@ -702,7 +751,7 @@ final class Emitter(config: Emitter.Config) {
     }
 
     def getOrComputeImports(externalDependencies: Set[String], internalDependencies: Set[ModuleID])(
-        compute: => WithGlobals[List[js.Tree]]): WithGlobals[List[js.Tree]] = {
+        compute: => WithGlobals[List[E]]): WithGlobals[List[E]] = {
 
       _cacheUsed = true
 
@@ -715,7 +764,7 @@ final class Emitter(config: Emitter.Config) {
     }
 
     def getOrComputeTopLevelExports(topLevelExports: List[LinkedTopLevelExport])(
-        compute: => WithGlobals[List[js.Tree]]): WithGlobals[List[js.Tree]] = {
+        compute: => WithGlobals[List[E]]): WithGlobals[List[E]] = {
 
       _cacheUsed = true
 
@@ -754,7 +803,7 @@ final class Emitter(config: Emitter.Config) {
     }
 
     def getOrComputeInitializers(initializers: List[ModuleInitializer.Initializer])(
-        compute: => WithGlobals[List[js.Tree]]): WithGlobals[List[js.Tree]] = {
+        compute: => WithGlobals[List[E]]): WithGlobals[List[E]] = {
 
       _cacheUsed = true
 
@@ -773,20 +822,20 @@ final class Emitter(config: Emitter.Config) {
   }
 
   private final class ClassCache extends knowledgeGuardian.KnowledgeAccessor {
-    private[this] var _cache: DesugaredClassCache = null
+    private[this] var _cache: DesugaredClassCache[List[E]] = null
     private[this] var _lastVersion: Version = Version.Unversioned
     private[this] var _cacheUsed = false
 
     private[this] val _methodCaches =
-      Array.fill(MemberNamespace.Count)(mutable.Map.empty[MethodName, MethodCache[List[js.Tree]]])
+      Array.fill(MemberNamespace.Count)(mutable.Map.empty[MethodName, MethodCache[List[E]]])
 
     private[this] val _memberMethodCache =
-      mutable.Map.empty[MethodName, MethodCache[js.Tree]]
+      mutable.Map.empty[MethodName, MethodCache[List[E]]]
 
-    private[this] var _constructorCache: Option[MethodCache[List[js.Tree]]] = None
+    private[this] var _constructorCache: Option[MethodCache[List[E]]] = None
 
     private[this] val _exportedMembersCache =
-      mutable.Map.empty[Int, MethodCache[List[js.Tree]]]
+      mutable.Map.empty[Int, MethodCache[List[E]]]
 
     private[this] var _fullClassCache: Option[FullClassCache] = None
 
@@ -807,12 +856,12 @@ final class Emitter(config: Emitter.Config) {
       _fullClassCache.foreach(_.startRun())
     }
 
-    def getCache(version: Version): DesugaredClassCache = {
+    def getCache(version: Version): DesugaredClassCache[List[E]] = {
       if (_cache == null || !_lastVersion.sameVersion(version)) {
         invalidate()
         statsClassesInvalidated += 1
         _lastVersion = version
-        _cache = new DesugaredClassCache
+        _cache = new DesugaredClassCache[List[E]]
       } else {
         statsClassesReused += 1
       }
@@ -821,25 +870,25 @@ final class Emitter(config: Emitter.Config) {
     }
 
     def getMemberMethodCache(
-        methodName: MethodName): MethodCache[js.Tree] = {
+        methodName: MethodName): MethodCache[List[E]] = {
       _memberMethodCache.getOrElseUpdate(methodName, new MethodCache)
     }
 
     def getStaticLikeMethodCache(namespace: MemberNamespace,
-        methodName: MethodName): MethodCache[List[js.Tree]] = {
+        methodName: MethodName): MethodCache[List[E]] = {
       _methodCaches(namespace.ordinal)
         .getOrElseUpdate(methodName, new MethodCache)
     }
 
-    def getConstructorCache(): MethodCache[List[js.Tree]] = {
+    def getConstructorCache(): MethodCache[List[E]] = {
       _constructorCache.getOrElse {
-        val cache = new MethodCache[List[js.Tree]]
+        val cache = new MethodCache[List[E]]
         _constructorCache = Some(cache)
         cache
       }
     }
 
-    def getExportedMemberCache(idx: Int): MethodCache[List[js.Tree]] =
+    def getExportedMemberCache(idx: Int): MethodCache[List[E]] =
       _exportedMembersCache.getOrElseUpdate(idx, new MethodCache)
 
     def getFullClassCache(): FullClassCache = {
@@ -905,11 +954,11 @@ final class Emitter(config: Emitter.Config) {
   }
 
   private class FullClassCache extends knowledgeGuardian.KnowledgeAccessor {
-    private[this] var _tree: WithGlobals[List[js.Tree]] = null
+    private[this] var _tree: WithGlobals[List[E]] = null
     private[this] var _lastVersion: Version = Version.Unversioned
-    private[this] var _lastCtor: WithGlobals[List[js.Tree]] = null
-    private[this] var _lastMemberMethods: List[WithGlobals[js.Tree]] = null
-    private[this] var _lastExportedMembers: List[WithGlobals[List[js.Tree]]] = null
+    private[this] var _lastCtor: WithGlobals[List[E]] = null
+    private[this] var _lastMemberMethods: List[WithGlobals[List[E]]] = null
+    private[this] var _lastExportedMembers: List[WithGlobals[List[E]]] = null
     private[this] var _cacheUsed = false
 
     override def invalidate(): Unit = {
@@ -923,9 +972,9 @@ final class Emitter(config: Emitter.Config) {
 
     def startRun(): Unit = _cacheUsed = false
 
-    def getOrElseUpdate(version: Version, ctor: WithGlobals[List[js.Tree]],
-        memberMethods: List[WithGlobals[js.Tree]], exportedMembers: List[WithGlobals[List[js.Tree]]],
-        compute: => WithGlobals[List[js.Tree]]): WithGlobals[List[js.Tree]] = {
+    def getOrElseUpdate(version: Version, ctor: WithGlobals[List[E]],
+        memberMethods: List[WithGlobals[List[E]]], exportedMembers: List[WithGlobals[List[E]]],
+        compute: => WithGlobals[List[E]]): WithGlobals[List[E]] = {
 
       @tailrec
       def allSame[A <: AnyRef](xs: List[A], ys: List[A]): Boolean = {
@@ -960,11 +1009,11 @@ final class Emitter(config: Emitter.Config) {
 
   private class CoreJSLibCache extends knowledgeGuardian.KnowledgeAccessor {
     private[this] var _lastModuleContext: ModuleContext = _
-    private[this] var _lib: WithGlobals[CoreJSLib.Lib] = _
+    private[this] var _lib: WithGlobals[CoreJSLib.Lib[List[E]]] = _
 
-    def build(moduleContext: ModuleContext): WithGlobals[CoreJSLib.Lib] = {
+    def build(moduleContext: ModuleContext): WithGlobals[CoreJSLib.Lib[List[E]]] = {
       if (_lib == null || _lastModuleContext != moduleContext) {
-        _lib = CoreJSLib.build(sjsGen, moduleContext, this)
+        _lib = CoreJSLib.build(sjsGen, postTransform(_, 0), moduleContext, this)
         _lastModuleContext = moduleContext
       }
       _lib
@@ -979,9 +1028,9 @@ final class Emitter(config: Emitter.Config) {
 
 object Emitter {
   /** Result of an emitter run. */
-  final class Result private[Emitter](
+  final class Result[E] private[Emitter](
       val header: String,
-      val body: Map[ModuleID, List[js.Tree]],
+      val body: Map[ModuleID, List[E]],
       val footer: String,
       val topLevelVarDecls: List[String],
       val globalRefs: Set[String]
@@ -1052,22 +1101,26 @@ object Emitter {
       new Config(coreSpec.semantics, coreSpec.moduleKind, coreSpec.esFeatures)
   }
 
-  private final class DesugaredClassCache {
-    val privateJSFields = new OneTimeCache[WithGlobals[List[js.Tree]]]
-    val storeJSSuperClass = new OneTimeCache[WithGlobals[js.Tree]]
-    val instanceTests = new OneTimeCache[WithGlobals[List[js.Tree]]]
-    val typeData = new OneTimeCache[WithGlobals[List[js.Tree]]]
-    val setTypeData = new OneTimeCache[js.Tree]
-    val moduleAccessor = new OneTimeCache[WithGlobals[List[js.Tree]]]
-    val staticInitialization = new OneTimeCache[List[js.Tree]]
-    val staticFields = new OneTimeCache[WithGlobals[List[js.Tree]]]
+  trait PostTransformer[E] {
+    def transformStats(trees: List[js.Tree], indent: Int): List[E]
+  }
+
+  private final class DesugaredClassCache[E >: Null] {
+    val privateJSFields = new OneTimeCache[WithGlobals[E]]
+    val storeJSSuperClass = new OneTimeCache[WithGlobals[E]]
+    val instanceTests = new OneTimeCache[WithGlobals[E]]
+    val typeData = new OneTimeCache[WithGlobals[E]]
+    val setTypeData = new OneTimeCache[E]
+    val moduleAccessor = new OneTimeCache[WithGlobals[E]]
+    val staticInitialization = new OneTimeCache[E]
+    val staticFields = new OneTimeCache[WithGlobals[E]]
   }
 
-  private final class GeneratedClass(
+  private final class GeneratedClass[E](
       val className: ClassName,
-      val main: List[js.Tree],
-      val staticFields: List[js.Tree],
-      val staticInitialization: List[js.Tree],
+      val main: List[E],
+      val staticFields: List[E],
+      val staticInitialization: List[E],
       val trackedGlobalRefs: Set[String]
   )
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Printers.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Printers.scala
index 4d675d4dec..a6d632a1cd 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Printers.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Printers.scala
@@ -12,6 +12,8 @@
 
 package org.scalajs.linker.backend.javascript
 
+import java.nio.charset.StandardCharsets
+
 import scala.annotation.switch
 
 // Unimport default print and println to avoid invoking them by mistake
@@ -31,10 +33,10 @@ import Trees._
 object Printers {
   private val ReusableIndentArray = Array.fill(128)(' '.toByte)
 
-  class JSTreePrinter(protected val out: ByteArrayWriter) {
+  class JSTreePrinter(protected val out: ByteArrayWriter, initIndent: Int = 0) {
     private final val IndentStep = 2
 
-    private var indentMargin = 0
+    private var indentMargin = initIndent * IndentStep
     private var indentArray = ReusableIndentArray
 
     private def indent(): Unit = indentMargin += IndentStep
@@ -117,10 +119,15 @@ object Printers {
       printRow(args, '(', ')')
 
     /** Prints a stat including leading indent and trailing newline. */
-    final def printStat(tree: Tree): Unit = {
-      printIndent()
-      printTree(tree, isStat = true)
-      println()
+    final def printStat(tree: Tree): Unit = tree match {
+      case tree: PrintedTree =>
+        // PrintedTree already contains indent and trailing newline.
+        print(tree)
+
+      case _ =>
+        printIndent()
+        printTree(tree, isStat = true)
+        println()
     }
 
     private def print(tree: Tree): Unit =
@@ -750,6 +757,9 @@ object Printers {
         print("]")
     }
 
+    protected def print(printedTree: PrintedTree): Unit =
+      out.write(printedTree.jsCode)
+
     private def print(exportName: ExportName): Unit =
       printEscapeJS(exportName.name)
 
@@ -762,7 +772,8 @@ object Printers {
   }
 
   class JSTreePrinterWithSourceMap(_out: ByteArrayWriter,
-      sourceMap: SourceMapWriter.Builder) extends JSTreePrinter(_out) {
+      sourceMap: SourceMapWriter.Builder, initIndent: Int)
+      extends JSTreePrinter(_out, initIndent) {
 
     private var column = 0
 
@@ -788,6 +799,11 @@ object Printers {
         sourceMap.endNode(column)
     }
 
+    override protected def print(printedTree: PrintedTree): Unit = {
+      super.print(printedTree)
+      sourceMap.insertFragment(printedTree.sourceMapFragment)
+    }
+
     override protected def println(): Unit = {
       super.println()
       sourceMap.nextLine()
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Trees.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Trees.scala
index efcf98e609..ec5b72e850 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Trees.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Trees.scala
@@ -499,4 +499,22 @@ object Trees {
       from: StringLiteral)(
       implicit val pos: Position)
       extends Tree
+
+  /** An already printed tree.
+   *
+   *  This is a special purpose node to store partially transformed trees.
+   *
+   *  A cleaner abstraction would be to have something like ir.Tree.Transient
+   *  (for different output formats), but for now, we do not need this.
+   */
+  sealed case class PrintedTree(jsCode: Array[Byte],
+      sourceMapFragment: SourceMapWriter.Fragment) extends Tree {
+    val pos: Position = Position.NoPosition
+
+    override def show: String = new String(jsCode, StandardCharsets.UTF_8)
+  }
+
+  object PrintedTree {
+    def empty: PrintedTree = PrintedTree(Array(), SourceMapWriter.Fragment.Empty)
+  }
 }
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/BasicLinkerBackendTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/BasicLinkerBackendTest.scala
index 1ce36b9153..2da5fe2324 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/BasicLinkerBackendTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/BasicLinkerBackendTest.scala
@@ -20,6 +20,7 @@ import org.junit.Test
 import org.junit.Assert._
 
 import org.scalajs.ir.Trees._
+import org.scalajs.ir.Version
 
 import org.scalajs.junit.async._
 
@@ -33,17 +34,17 @@ import org.scalajs.logging._
 class BasicLinkerBackendTest {
   import scala.concurrent.ExecutionContext.Implicits.global
 
-  private val BackendInvalidatedTopLevelTreesStatsMessage =
-    raw"""BasicBackend: total top-level trees: (\d+); re-computed: (\d+)""".r
+  private val BackendInvalidatedPrintedTreesStatsMessage =
+    raw"""BasicBackend: total top-level printed trees: (\d+); re-computed: (\d+)""".r
 
   private val BackendInvalidatedModulesStatsMessage =
     raw"""BasicBackend: total modules: (\d+); re-written: (\d+)""".r
 
   /** Makes sure that linking a "substantial" program (using `println`) twice
-   *  does not invalidate any top-level tree nor module in the second run.
+   *  does not invalidate any module in the second run.
    */
   @Test
-  def noInvalidatedTopLevelTreeOrModuleInSecondRun(): AsyncResult = await {
+  def noInvalidatedModuleInSecondRun(): AsyncResult = await {
     import ModuleSplitStyle._
 
     val classDefs = List(
@@ -60,7 +61,7 @@ class BasicLinkerBackendTest {
         .withModuleSplitStyle(splitStyle)
 
       val linker = StandardImpl.linker(config)
-      val classDefsFiles = classDefs.map(MemClassDefIRFile(_))
+      val classDefsFiles = classDefs.map(MemClassDefIRFile(_, Version.fromInt(0)))
 
       val initializers = MainTestModuleInitializers
       val outputDir = MemOutputDirectory()
@@ -74,25 +75,6 @@ class BasicLinkerBackendTest {
         val lines1 = logger1.allLogLines
         val lines2 = logger2.allLogLines
 
-        // Top-level trees
-
-        val Seq(totalTrees1, recomputedTrees1) =
-          lines1.assertContainsMatch(BackendInvalidatedTopLevelTreesStatsMessage).map(_.toInt)
-
-        val Seq(totalTrees2, recomputedTrees2) =
-          lines2.assertContainsMatch(BackendInvalidatedTopLevelTreesStatsMessage).map(_.toInt)
-
-        // At the time of writing this test, totalTrees1 reports 382 trees
-        assertTrue(
-            s"Not enough total top-level trees (got $totalTrees1); extraction must have gone wrong",
-            totalTrees1 > 300)
-
-        assertEquals("First run must invalidate every top-level tree", totalTrees1, recomputedTrees1)
-        assertEquals("Second run must have the same total top-level trees as first run", totalTrees1, totalTrees2)
-        assertEquals("Second run must not invalidate any top-level tree", 0, recomputedTrees2)
-
-        // Modules
-
         val Seq(totalModules1, rewrittenModules1) =
           lines1.assertContainsMatch(BackendInvalidatedModulesStatsMessage).map(_.toInt)
 
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/EmitterTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/EmitterTest.scala
index 17512130bc..935c2a57ae 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/EmitterTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/EmitterTest.scala
@@ -20,6 +20,7 @@ import org.junit.Test
 import org.junit.Assert._
 
 import org.scalajs.ir.Trees._
+import org.scalajs.ir.Version
 
 import org.scalajs.junit.async._
 
@@ -128,6 +129,99 @@ class EmitterTest {
       logger.allLogLines.assertContains(EmitterSetOfDangerousGlobalRefsChangedMessage)
     }
   }
+
+  private val EmitterClassTreeCacheStatsMessage =
+    raw"""Emitter: Class tree cache stats: reused: (\d+) -- invalidated: (\d+)""".r
+
+  private val EmitterMethodTreeCacheStatsMessage =
+    raw"""Emitter: Method tree cache stats: reused: (\d+) -- invalidated: (\d+)""".r
+
+  private val EmitterPostTransformStatsMessage =
+    raw"""Emitter: Post transforms: total: (\d+) -- nested: (\d+) -- nested avoided: (\d+)""".r
+
+  /** Makes sure that linking a "substantial" program (using `println`) twice
+   *  does not invalidate any cache or top-level tree in the second run.
+   */
+  @Test
+  def noInvalidatedCacheOrTopLevelTreeInSecondRun(): AsyncResult = await {
+    val classDefs = List(
+      mainTestClassDef(systemOutPrintln(str("Hello world!")))
+    )
+
+    val logger1 = new CapturingLogger
+    val logger2 = new CapturingLogger
+
+    val config = StandardConfig()
+      .withCheckIR(true)
+      .withModuleKind(ModuleKind.ESModule)
+
+    val linker = StandardImpl.linker(config)
+    val classDefsFiles = classDefs.map(MemClassDefIRFile(_, Version.fromInt(0)))
+
+    val initializers = MainTestModuleInitializers
+    val outputDir = MemOutputDirectory()
+
+    for {
+      javalib <- TestIRRepo.javalib
+      allIRFiles = javalib ++ classDefsFiles
+      _ <- linker.link(allIRFiles, initializers, outputDir, logger1)
+      _ <- linker.link(allIRFiles, initializers, outputDir, logger2)
+    } yield {
+      val lines1 = logger1.allLogLines
+      val lines2 = logger2.allLogLines
+
+      // Class tree caches
+
+      val Seq(classCacheReused1, classCacheInvalidated1) =
+        lines1.assertContainsMatch(EmitterClassTreeCacheStatsMessage).map(_.toInt)
+
+      val Seq(classCacheReused2, classCacheInvalidated2) =
+        lines2.assertContainsMatch(EmitterClassTreeCacheStatsMessage).map(_.toInt)
+
+      // At the time of writing this test, classCacheInvalidated1 reports 47
+      assertTrue(
+          s"Not enough invalidated class caches (got $classCacheInvalidated1); extraction must have gone wrong",
+          classCacheInvalidated1 > 40)
+
+      assertEquals("First run must not reuse any class cache", 0, classCacheReused1)
+
+      assertEquals("Second run must reuse all class caches", classCacheReused2, classCacheInvalidated1)
+      assertEquals("Second run must not invalidate any class cache", 0, classCacheInvalidated2)
+
+      // Method tree caches
+
+      val Seq(methodCacheReused1, methodCacheInvalidated1) =
+        lines1.assertContainsMatch(EmitterMethodTreeCacheStatsMessage).map(_.toInt)
+
+      val Seq(methodCacheReused2, methodCacheInvalidated2) =
+        lines2.assertContainsMatch(EmitterMethodTreeCacheStatsMessage).map(_.toInt)
+
+      // At the time of writing this test, methodCacheInvalidated1 reports 107
+      assertTrue(
+          s"Not enough invalidated method caches (got $methodCacheInvalidated1); extraction must have gone wrong",
+          methodCacheInvalidated1 > 100)
+
+      assertEquals("First run must not reuse any method cache", 0, methodCacheReused1)
+
+      assertEquals("Second run must reuse all method caches", methodCacheReused2, methodCacheInvalidated1)
+      assertEquals("Second run must not invalidate any method cache", 0, methodCacheInvalidated2)
+
+      // Post transforms
+
+      val Seq(postTransforms1, _, _) =
+        lines1.assertContainsMatch(EmitterPostTransformStatsMessage).map(_.toInt)
+
+      val Seq(postTransforms2, _, _) =
+        lines2.assertContainsMatch(EmitterPostTransformStatsMessage).map(_.toInt)
+
+      // At the time of writing this test, postTransformsTotal1 reports 216
+      assertTrue(
+          s"Not enough post transforms (got $postTransforms1); extraction must have gone wrong",
+          postTransforms1 > 200)
+
+      assertEquals("Second run must not have any post transforms", 0, postTransforms2)
+    }
+  }
 }
 
 object EmitterTest {
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/backend/javascript/PrintersTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/backend/javascript/PrintersTest.scala
index 86c9215f02..ba4848f668 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/backend/javascript/PrintersTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/backend/javascript/PrintersTest.scala
@@ -14,7 +14,7 @@ package org.scalajs.linker.backend.javascript
 
 import scala.language.implicitConversions
 
-import java.nio.charset.StandardCharsets
+import java.nio.charset.StandardCharsets.UTF_8
 
 import org.junit.Test
 import org.junit.Assert._
@@ -35,7 +35,7 @@ class PrintersTest {
     val printer = new Printers.JSTreePrinter(out)
     printer.printStat(tree)
     assertEquals(expected.stripMargin.trim + "\n",
-        new String(out.toByteArray(), StandardCharsets.UTF_8))
+        new String(out.toByteArray(), UTF_8))
   }
 
   @Test def printFunctionDef(): Unit = {
@@ -158,4 +158,24 @@ class PrintersTest {
             If(BooleanLiteral(true), IntLiteral(2), IntLiteral(3)))
     )
   }
+
+  @Test def showPrintedTree(): Unit = {
+    val tree = PrintedTree("test".getBytes(UTF_8), SourceMapWriter.Fragment.Empty)
+
+    assertEquals("test", tree.show)
+  }
+
+  @Test def showNestedPrintedTree(): Unit = {
+    val tree = PrintedTree("  test\n".getBytes(UTF_8), SourceMapWriter.Fragment.Empty)
+
+    val str = While(BooleanLiteral(false), tree).show
+    assertEquals(
+      """
+        |while (false) {
+        |  test
+        |}
+      """.stripMargin.trim,
+      str
+    )
+  }
 }

From 5c56042c11adc6df0f830c71d35b053864bc0b66 Mon Sep 17 00:00:00 2001
From: Tobias Schlatter <tobias@meisch.ch>
Date: Sun, 17 Dec 2023 18:59:07 +0100
Subject: [PATCH 028/298] Track in Emitter whether a module changed in an
 incremental run

In the next commit, we want to avoid caching entire classes because of
the memory cost. However, the BasicLinkerBackend relies on the
identity of the generated trees to detect changes: Since that identity
will change if we stop caching them, we need to provide an explicit
"changed" signal.
---
 .../closure/ClosureLinkerBackend.scala        |  3 +-
 .../linker/backend/BasicLinkerBackend.scala   | 19 +---
 .../linker/backend/emitter/Emitter.scala      | 98 ++++++++++++-------
 3 files changed, 68 insertions(+), 52 deletions(-)

diff --git a/linker/jvm/src/main/scala/org/scalajs/linker/backend/closure/ClosureLinkerBackend.scala b/linker/jvm/src/main/scala/org/scalajs/linker/backend/closure/ClosureLinkerBackend.scala
index 1f532767e2..64160204ac 100644
--- a/linker/jvm/src/main/scala/org/scalajs/linker/backend/closure/ClosureLinkerBackend.scala
+++ b/linker/jvm/src/main/scala/org/scalajs/linker/backend/closure/ClosureLinkerBackend.scala
@@ -106,7 +106,8 @@ final class ClosureLinkerBackend(config: LinkerBackendImpl.Config)
       sjsModule <- moduleSet.modules.headOption
     } yield {
       val closureChunk = logger.time("Closure: Create trees)") {
-        buildChunk(emitterResult.body(sjsModule.id))
+        val (trees, _) = emitterResult.body(sjsModule.id)
+        buildChunk(trees)
       }
 
       logger.time("Closure: Compiler pass") {
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/BasicLinkerBackend.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/BasicLinkerBackend.scala
index 4faef57c0a..e07e31597b 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/BasicLinkerBackend.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/BasicLinkerBackend.scala
@@ -88,9 +88,7 @@ final class BasicLinkerBackend(config: LinkerBackendImpl.Config)
     val writer = new OutputWriter(output, config, skipContentCheck) {
       protected def writeModuleWithoutSourceMap(moduleID: ModuleID, force: Boolean): Option[ByteBuffer] = {
         val cache = printedModuleSetCache.getModuleCache(moduleID)
-        val printedTrees = emitterResult.body(moduleID)
-
-        val changed = cache.update(printedTrees)
+        val (printedTrees, changed) = emitterResult.body(moduleID)
 
         if (force || changed || allChanged) {
           rewrittenModules.incrementAndGet()
@@ -114,9 +112,7 @@ final class BasicLinkerBackend(config: LinkerBackendImpl.Config)
 
       protected def writeModuleWithSourceMap(moduleID: ModuleID, force: Boolean): Option[(ByteBuffer, ByteBuffer)] = {
         val cache = printedModuleSetCache.getModuleCache(moduleID)
-        val printedTrees = emitterResult.body(moduleID)
-
-        val changed = cache.update(printedTrees)
+        val (printedTrees, changed) = emitterResult.body(moduleID)
 
         if (force || changed || allChanged) {
           rewrittenModules.incrementAndGet()
@@ -220,8 +216,6 @@ private object BasicLinkerBackend {
 
   private sealed class PrintedModuleCache {
     private var cacheUsed = false
-    private var changed = false
-    private var lastPrintedTrees: List[js.PrintedTree] = Nil
 
     private var previousFinalJSFileSize: Int = 0
     private var previousFinalSourceMapSize: Int = 0
@@ -239,15 +233,6 @@ private object BasicLinkerBackend {
       previousFinalSourceMapSize = finalSourceMapSize
     }
 
-    def update(newPrintedTrees: List[js.PrintedTree]): Boolean = {
-      val changed = !newPrintedTrees.corresponds(lastPrintedTrees)(_ eq _)
-      this.changed = changed
-      if (changed) {
-        lastPrintedTrees = newPrintedTrees
-      }
-      changed
-    }
-
     def cleanAfterRun(): Boolean = {
       val wasUsed = cacheUsed
       cacheUsed = false
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala
index 6035764aca..8aafe7b745 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala
@@ -112,7 +112,7 @@ final class Emitter[E >: Null <: js.Tree](
   }
 
   private def emitInternal(moduleSet: ModuleSet,
-      logger: Logger): WithGlobals[Map[ModuleID, List[E]]] = {
+      logger: Logger): WithGlobals[Map[ModuleID, (List[E], Boolean)]] = {
     // Reset caching stats.
     statsClassesReused = 0
     statsClassesInvalidated = 0
@@ -169,7 +169,7 @@ final class Emitter[E >: Null <: js.Tree](
    */
   @tailrec
   private def emitAvoidGlobalClash(moduleSet: ModuleSet,
-      logger: Logger, secondAttempt: Boolean): WithGlobals[Map[ModuleID, List[E]]] = {
+      logger: Logger, secondAttempt: Boolean): WithGlobals[Map[ModuleID, (List[E], Boolean)]] = {
     val result = emitOnce(moduleSet, logger)
 
     val mentionedDangerousGlobalRefs =
@@ -194,7 +194,7 @@ final class Emitter[E >: Null <: js.Tree](
   }
 
   private def emitOnce(moduleSet: ModuleSet,
-      logger: Logger): WithGlobals[Map[ModuleID, List[E]]] = {
+      logger: Logger): WithGlobals[Map[ModuleID, (List[E], Boolean)]] = {
     // Genreate classes first so we can measure time separately.
     val generatedClasses = logger.time("Emitter: Generate Classes") {
       moduleSet.modules.map { module =>
@@ -212,18 +212,26 @@ final class Emitter[E >: Null <: js.Tree](
 
     val moduleTrees = logger.time("Emitter: Write trees") {
       moduleSet.modules.map { module =>
+        var changed = false
+        def extractChangedAndWithGlobals[T](x: (WithGlobals[T], Boolean)): T = {
+          changed ||= x._2
+          extractWithGlobals(x._1)
+        }
+
         val moduleContext = ModuleContext.fromModule(module)
         val moduleCache = state.moduleCaches.getOrElseUpdate(module.id, new ModuleCache)
 
         val moduleClasses = generatedClasses(module.id)
 
-        val moduleImports = extractWithGlobals {
+        changed ||= moduleClasses.exists(_.changed)
+
+        val moduleImports = extractChangedAndWithGlobals {
           moduleCache.getOrComputeImports(module.externalDependencies, module.internalDependencies) {
             genModuleImports(module).map(postTransform(_, 0))
           }
         }
 
-        val topLevelExports = extractWithGlobals {
+        val topLevelExports = extractChangedAndWithGlobals {
           /* We cache top level exports all together, rather than individually,
            * since typically there are few.
            */
@@ -233,7 +241,7 @@ final class Emitter[E >: Null <: js.Tree](
           }
         }
 
-        val moduleInitializers = extractWithGlobals {
+        val moduleInitializers = extractChangedAndWithGlobals {
           val initializers = module.initializers.toList
           moduleCache.getOrComputeInitializers(initializers) {
             WithGlobals.list(initializers.map { initializer =>
@@ -324,7 +332,7 @@ final class Emitter[E >: Null <: js.Tree](
           trackedGlobalRefs = unionPreserveEmpty(trackedGlobalRefs, genClass.trackedGlobalRefs)
         }
 
-        module.id -> allTrees
+        module.id -> (allTrees, changed)
       }
     }
 
@@ -382,8 +390,14 @@ final class Emitter[E >: Null <: js.Tree](
     val classCache = classCaches.getOrElseUpdate(
         new ClassID(linkedClass.ancestors, moduleContext), new ClassCache)
 
+    var changed = false
+    def extractChanged[T](x: (T, Boolean)): T = {
+      changed ||= x._2
+      x._1
+    }
+
     val classTreeCache =
-      classCache.getCache(linkedClass.version)
+      extractChanged(classCache.getCache(linkedClass.version))
 
     val kind = linkedClass.kind
 
@@ -396,6 +410,9 @@ final class Emitter[E >: Null <: js.Tree](
       withGlobals.value
     }
 
+    def extractWithGlobalsAndChanged[T](x: (WithGlobals[T], Boolean)): T =
+      extractWithGlobals(extractChanged(x))
+
     // Main part
 
     val main = List.newBuilder[E]
@@ -426,7 +443,7 @@ final class Emitter[E >: Null <: js.Tree](
         val methodCache =
           classCache.getStaticLikeMethodCache(namespace, methodDef.methodName)
 
-        main ++= extractWithGlobals(methodCache.getOrElseUpdate(methodDef.version, {
+        main ++= extractWithGlobalsAndChanged(methodCache.getOrElseUpdate(methodDef.version, {
           classEmitter.genStaticLikeMethod(className, methodDef)(moduleContext, methodCache)
             .map(postTransform(_, 0))
         }))
@@ -486,7 +503,7 @@ final class Emitter[E >: Null <: js.Tree](
       }
 
       // JS constructor
-      val ctorWithGlobals = {
+      val ctorWithGlobals = extractChanged {
         /* The constructor depends both on the class version, and the version
          * of the inlineable init, if there is one.
          *
@@ -571,13 +588,13 @@ final class Emitter[E >: Null <: js.Tree](
           classCache.getMemberMethodCache(method.methodName)
 
         val version = Version.combine(isJSClassVersion, method.version)
-        methodCache.getOrElseUpdate(version,
+        extractChanged(methodCache.getOrElseUpdate(version,
             classEmitter.genMemberMethod(
                 className, // invalidated by overall class cache
                 isJSClass, // invalidated by isJSClassVersion
                 useESClass, // invalidated by isJSClassVersion
                 method // invalidated by method.version
-            )(moduleContext, methodCache).map(postTransform(_, memberIndent)))
+            )(moduleContext, methodCache).map(postTransform(_, memberIndent))))
       }
 
       // Exported Members
@@ -586,13 +603,13 @@ final class Emitter[E >: Null <: js.Tree](
       } yield {
         val memberCache = classCache.getExportedMemberCache(idx)
         val version = Version.combine(isJSClassVersion, member.version)
-        memberCache.getOrElseUpdate(version,
+        extractChanged(memberCache.getOrElseUpdate(version,
             classEmitter.genExportedMember(
                 className, // invalidated by overall class cache
                 isJSClass, // invalidated by isJSClassVersion
                 useESClass, // invalidated by isJSClassVersion
                 member // invalidated by version
-            )(moduleContext, memberCache).map(postTransform(_, memberIndent)))
+            )(moduleContext, memberCache).map(postTransform(_, memberIndent))))
       }
 
       val hasClassInitializer: Boolean = {
@@ -602,7 +619,7 @@ final class Emitter[E >: Null <: js.Tree](
         }
       }
 
-      val fullClass = {
+      val fullClass = extractChanged {
         val fullClassCache = classCache.getFullClassCache()
 
         fullClassCache.getOrElseUpdate(linkedClass.version, ctorWithGlobals,
@@ -714,7 +731,8 @@ final class Emitter[E >: Null <: js.Tree](
         main.result(),
         staticFields,
         staticInitialization,
-        trackedGlobalRefs
+        trackedGlobalRefs,
+        changed
     )
   }
 
@@ -751,7 +769,7 @@ final class Emitter[E >: Null <: js.Tree](
     }
 
     def getOrComputeImports(externalDependencies: Set[String], internalDependencies: Set[ModuleID])(
-        compute: => WithGlobals[List[E]]): WithGlobals[List[E]] = {
+        compute: => WithGlobals[List[E]]): (WithGlobals[List[E]], Boolean) = {
 
       _cacheUsed = true
 
@@ -759,20 +777,25 @@ final class Emitter[E >: Null <: js.Tree](
         _importsCache = compute
         _lastExternalDependencies = externalDependencies
         _lastInternalDependencies = internalDependencies
+        (_importsCache, true)
+      } else {
+        (_importsCache, false)
       }
-      _importsCache
+
     }
 
     def getOrComputeTopLevelExports(topLevelExports: List[LinkedTopLevelExport])(
-        compute: => WithGlobals[List[E]]): WithGlobals[List[E]] = {
+        compute: => WithGlobals[List[E]]): (WithGlobals[List[E]], Boolean) = {
 
       _cacheUsed = true
 
       if (!sameTopLevelExports(topLevelExports, _lastTopLevelExports)) {
         _topLevelExportsCache = compute
         _lastTopLevelExports = topLevelExports
+        (_topLevelExportsCache, true)
+      } else {
+        (_topLevelExportsCache, false)
       }
-      _topLevelExportsCache
     }
 
     private def sameTopLevelExports(tles1: List[LinkedTopLevelExport], tles2: List[LinkedTopLevelExport]): Boolean = {
@@ -803,15 +826,17 @@ final class Emitter[E >: Null <: js.Tree](
     }
 
     def getOrComputeInitializers(initializers: List[ModuleInitializer.Initializer])(
-        compute: => WithGlobals[List[E]]): WithGlobals[List[E]] = {
+        compute: => WithGlobals[List[E]]): (WithGlobals[List[E]], Boolean) = {
 
       _cacheUsed = true
 
       if (initializers != _lastInitializers) {
         _initializersCache = compute
         _lastInitializers = initializers
+        (_initializersCache, true)
+      } else {
+        (_initializersCache, false)
       }
-      _initializersCache
     }
 
     def cleanAfterRun(): Boolean = {
@@ -856,17 +881,18 @@ final class Emitter[E >: Null <: js.Tree](
       _fullClassCache.foreach(_.startRun())
     }
 
-    def getCache(version: Version): DesugaredClassCache[List[E]] = {
+    def getCache(version: Version): (DesugaredClassCache[List[E]], Boolean) = {
+      _cacheUsed = true
       if (_cache == null || !_lastVersion.sameVersion(version)) {
         invalidate()
         statsClassesInvalidated += 1
         _lastVersion = version
         _cache = new DesugaredClassCache[List[E]]
+        (_cache, true)
       } else {
         statsClassesReused += 1
+        (_cache, false)
       }
-      _cacheUsed = true
-      _cache
     }
 
     def getMemberMethodCache(
@@ -932,17 +958,18 @@ final class Emitter[E >: Null <: js.Tree](
     def startRun(): Unit = _cacheUsed = false
 
     def getOrElseUpdate(version: Version,
-        v: => WithGlobals[T]): WithGlobals[T] = {
+        v: => WithGlobals[T]): (WithGlobals[T], Boolean) = {
+      _cacheUsed = true
       if (_tree == null || !_lastVersion.sameVersion(version)) {
         invalidate()
         statsMethodsInvalidated += 1
         _tree = v
         _lastVersion = version
+        (_tree, true)
       } else {
         statsMethodsReused += 1
+        (_tree, false)
       }
-      _cacheUsed = true
-      _tree
     }
 
     def cleanAfterRun(): Boolean = {
@@ -974,7 +1001,7 @@ final class Emitter[E >: Null <: js.Tree](
 
     def getOrElseUpdate(version: Version, ctor: WithGlobals[List[E]],
         memberMethods: List[WithGlobals[List[E]]], exportedMembers: List[WithGlobals[List[E]]],
-        compute: => WithGlobals[List[E]]): WithGlobals[List[E]] = {
+        compute: => WithGlobals[List[E]]): (WithGlobals[List[E]], Boolean) = {
 
       @tailrec
       def allSame[A <: AnyRef](xs: List[A], ys: List[A]): Boolean = {
@@ -984,6 +1011,8 @@ final class Emitter[E >: Null <: js.Tree](
         }
       }
 
+      _cacheUsed = true
+
       if (_tree == null || !version.sameVersion(_lastVersion) || (_lastCtor ne ctor) ||
           !allSame(_lastMemberMethods, memberMethods) ||
           !allSame(_lastExportedMembers, exportedMembers)) {
@@ -993,10 +1022,10 @@ final class Emitter[E >: Null <: js.Tree](
         _lastCtor = ctor
         _lastMemberMethods = memberMethods
         _lastExportedMembers = exportedMembers
+        (_tree, true)
+      } else {
+        (_tree, false)
       }
-
-      _cacheUsed = true
-      _tree
     }
 
     def cleanAfterRun(): Boolean = {
@@ -1030,7 +1059,7 @@ object Emitter {
   /** Result of an emitter run. */
   final class Result[E] private[Emitter](
       val header: String,
-      val body: Map[ModuleID, List[E]],
+      val body: Map[ModuleID, (List[E], Boolean)],
       val footer: String,
       val topLevelVarDecls: List[String],
       val globalRefs: Set[String]
@@ -1121,7 +1150,8 @@ object Emitter {
       val main: List[E],
       val staticFields: List[E],
       val staticInitialization: List[E],
-      val trackedGlobalRefs: Set[String]
+      val trackedGlobalRefs: Set[String],
+      val changed: Boolean
   )
 
   private final class OneTimeCache[A >: Null] {

From 42efb2aa153b3feea58cda36ee0d25f896e52202 Mon Sep 17 00:00:00 2001
From: Tobias Schlatter <tobias@meisch.ch>
Date: Sat, 23 Dec 2023 18:07:04 +0100
Subject: [PATCH 029/298] Do not cache overall class

This reduces some memory overhead for negligible performance cost.

Residual (post link memory) benchmarks for the test suite:
Baseline: 1.13 GB, new 1.01 GB
---
 .../linker/backend/emitter/Emitter.scala      | 119 +++++++++---------
 .../org/scalajs/linker/EmitterTest.scala      |  11 +-
 2 files changed, 70 insertions(+), 60 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala
index 8aafe7b745..1906ffe84f 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala
@@ -619,37 +619,41 @@ final class Emitter[E >: Null <: js.Tree](
         }
       }
 
-      val fullClass = extractChanged {
-        val fullClassCache = classCache.getFullClassCache()
-
-        fullClassCache.getOrElseUpdate(linkedClass.version, ctorWithGlobals,
-            memberMethodsWithGlobals, exportedMembersWithGlobals, {
-          for {
-            ctor <- ctorWithGlobals
-            memberMethods <- WithGlobals.flatten(memberMethodsWithGlobals)
-            exportedMembers <- WithGlobals.flatten(exportedMembersWithGlobals)
-            allMembers = ctor ::: memberMethods ::: exportedMembers
-            clazz <- classEmitter.buildClass(
-              className, // invalidated by overall class cache (part of ancestors)
-              isJSClass, // invalidated by class version
-              linkedClass.jsClassCaptures, // invalidated by class version
-              hasClassInitializer, // invalidated by class version (optimizer cannot remove it)
-              linkedClass.superClass, // invalidated by class version
-              storeJSSuperClass, // invalidated by class version
-              useESClass, // invalidated by class version (depends on kind, config and ancestry only)
-              allMembers // invalidated directly
-            )(moduleContext, fullClassCache, linkedClass.pos) // pos invalidated by class version
-          } yield {
-            // Avoid a nested post transform if we just got the original members back.
-            if (clazz eq allMembers) {
-              statsNestedPostTransformsAvoided += 1
-              allMembers
-            } else {
-              statsNestedPostTransforms += 1
-              postTransform(clazz, 0)
-            }
+      val fullClass = {
+        val fullClassChangeTracker = classCache.getFullClassChangeTracker()
+
+        // Put changed state into a val to avoid short circuiting behavior of ||.
+        val classChanged = fullClassChangeTracker.trackChanged(
+            linkedClass.version, ctorWithGlobals,
+            memberMethodsWithGlobals, exportedMembersWithGlobals)
+
+        changed ||= classChanged
+
+        for {
+          ctor <- ctorWithGlobals
+          memberMethods <- WithGlobals.flatten(memberMethodsWithGlobals)
+          exportedMembers <- WithGlobals.flatten(exportedMembersWithGlobals)
+          allMembers = ctor ::: memberMethods ::: exportedMembers
+          clazz <- classEmitter.buildClass(
+            className, // invalidated by overall class cache (part of ancestors)
+            isJSClass, // invalidated by class version
+            linkedClass.jsClassCaptures, // invalidated by class version
+            hasClassInitializer, // invalidated by class version (optimizer cannot remove it)
+            linkedClass.superClass, // invalidated by class version
+            storeJSSuperClass, // invalidated by class version
+            useESClass, // invalidated by class version (depends on kind, config and ancestry only)
+            allMembers // invalidated directly
+          )(moduleContext, fullClassChangeTracker, linkedClass.pos) // pos invalidated by class version
+        } yield {
+          // Avoid a nested post transform if we just got the original members back.
+          if (clazz eq allMembers) {
+            statsNestedPostTransformsAvoided += 1
+            allMembers
+          } else {
+            statsNestedPostTransforms += 1
+            postTransform(clazz, 0)
           }
-        })
+        }
       }
 
       main ++= extractWithGlobals(fullClass)
@@ -862,7 +866,7 @@ final class Emitter[E >: Null <: js.Tree](
     private[this] val _exportedMembersCache =
       mutable.Map.empty[Int, MethodCache[List[E]]]
 
-    private[this] var _fullClassCache: Option[FullClassCache] = None
+    private[this] var _fullClassChangeTracker: Option[FullClassChangeTracker] = None
 
     override def invalidate(): Unit = {
       /* Do not invalidate contained methods, as they have their own
@@ -878,7 +882,7 @@ final class Emitter[E >: Null <: js.Tree](
       _methodCaches.foreach(_.valuesIterator.foreach(_.startRun()))
       _memberMethodCache.valuesIterator.foreach(_.startRun())
       _constructorCache.foreach(_.startRun())
-      _fullClassCache.foreach(_.startRun())
+      _fullClassChangeTracker.foreach(_.startRun())
     }
 
     def getCache(version: Version): (DesugaredClassCache[List[E]], Boolean) = {
@@ -917,10 +921,10 @@ final class Emitter[E >: Null <: js.Tree](
     def getExportedMemberCache(idx: Int): MethodCache[List[E]] =
       _exportedMembersCache.getOrElseUpdate(idx, new MethodCache)
 
-    def getFullClassCache(): FullClassCache = {
-      _fullClassCache.getOrElse {
-        val cache = new FullClassCache
-        _fullClassCache = Some(cache)
+    def getFullClassChangeTracker(): FullClassChangeTracker = {
+      _fullClassChangeTracker.getOrElse {
+        val cache = new FullClassChangeTracker
+        _fullClassChangeTracker = Some(cache)
         cache
       }
     }
@@ -934,8 +938,8 @@ final class Emitter[E >: Null <: js.Tree](
 
       _exportedMembersCache.filterInPlace((_, c) => c.cleanAfterRun())
 
-      if (_fullClassCache.exists(!_.cleanAfterRun()))
-        _fullClassCache = None
+      if (_fullClassChangeTracker.exists(!_.cleanAfterRun()))
+        _fullClassChangeTracker = None
 
       if (!_cacheUsed)
         invalidate()
@@ -980,28 +984,26 @@ final class Emitter[E >: Null <: js.Tree](
     }
   }
 
-  private class FullClassCache extends knowledgeGuardian.KnowledgeAccessor {
-    private[this] var _tree: WithGlobals[List[E]] = null
+  private class FullClassChangeTracker extends knowledgeGuardian.KnowledgeAccessor {
     private[this] var _lastVersion: Version = Version.Unversioned
     private[this] var _lastCtor: WithGlobals[List[E]] = null
     private[this] var _lastMemberMethods: List[WithGlobals[List[E]]] = null
     private[this] var _lastExportedMembers: List[WithGlobals[List[E]]] = null
-    private[this] var _cacheUsed = false
+    private[this] var _trackerUsed = false
 
     override def invalidate(): Unit = {
       super.invalidate()
-      _tree = null
       _lastVersion = Version.Unversioned
       _lastCtor = null
       _lastMemberMethods = null
       _lastExportedMembers = null
     }
 
-    def startRun(): Unit = _cacheUsed = false
+    def startRun(): Unit = _trackerUsed = false
 
-    def getOrElseUpdate(version: Version, ctor: WithGlobals[List[E]],
-        memberMethods: List[WithGlobals[List[E]]], exportedMembers: List[WithGlobals[List[E]]],
-        compute: => WithGlobals[List[E]]): (WithGlobals[List[E]], Boolean) = {
+    def trackChanged(version: Version, ctor: WithGlobals[List[E]],
+        memberMethods: List[WithGlobals[List[E]]],
+        exportedMembers: List[WithGlobals[List[E]]]): Boolean = {
 
       @tailrec
       def allSame[A <: AnyRef](xs: List[A], ys: List[A]): Boolean = {
@@ -1011,28 +1013,33 @@ final class Emitter[E >: Null <: js.Tree](
         }
       }
 
-      _cacheUsed = true
+      _trackerUsed = true
 
-      if (_tree == null || !version.sameVersion(_lastVersion) || (_lastCtor ne ctor) ||
-          !allSame(_lastMemberMethods, memberMethods) ||
-          !allSame(_lastExportedMembers, exportedMembers)) {
+      val changed = {
+        !version.sameVersion(_lastVersion) ||
+        (_lastCtor ne ctor) ||
+        !allSame(_lastMemberMethods, memberMethods) ||
+        !allSame(_lastExportedMembers, exportedMembers)
+      }
+
+      if (changed) {
+        // Input has changed or we were invalidated.
+        // Clean knowledge tracking and re-track dependencies.
         invalidate()
-        _tree = compute
         _lastVersion = version
         _lastCtor = ctor
         _lastMemberMethods = memberMethods
         _lastExportedMembers = exportedMembers
-        (_tree, true)
-      } else {
-        (_tree, false)
       }
+
+      changed
     }
 
     def cleanAfterRun(): Boolean = {
-      if (!_cacheUsed)
+      if (!_trackerUsed)
         invalidate()
 
-      _cacheUsed
+      _trackerUsed
     }
   }
 
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/EmitterTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/EmitterTest.scala
index 935c2a57ae..1f7884c0f1 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/EmitterTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/EmitterTest.scala
@@ -208,18 +208,21 @@ class EmitterTest {
 
       // Post transforms
 
-      val Seq(postTransforms1, _, _) =
+      val Seq(postTransforms1, nestedPostTransforms1, _) =
         lines1.assertContainsMatch(EmitterPostTransformStatsMessage).map(_.toInt)
 
-      val Seq(postTransforms2, _, _) =
+      val Seq(postTransforms2, nestedPostTransforms2, _) =
         lines2.assertContainsMatch(EmitterPostTransformStatsMessage).map(_.toInt)
 
-      // At the time of writing this test, postTransformsTotal1 reports 216
+      // At the time of writing this test, postTransforms1 reports 216
       assertTrue(
           s"Not enough post transforms (got $postTransforms1); extraction must have gone wrong",
           postTransforms1 > 200)
 
-      assertEquals("Second run must not have any post transforms", 0, postTransforms2)
+      assertEquals("Second run must only have nested post transforms",
+          nestedPostTransforms2, postTransforms2)
+      assertEquals("Both runs must have the same number of nested post transforms",
+          nestedPostTransforms1, nestedPostTransforms2)
     }
   }
 }

From d5cef60d4f25e875d18f9b902038b67aa15daca2 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Wed, 31 Jan 2024 16:51:03 +0100
Subject: [PATCH 030/298] Fix #4934: Report errors in Analyzer only after all
 tasks are completed.

Previously, as soon as one task completed with a Failure, we let
the WorkTracker's main promise complete with that Failure. If other
tasks were still running, they would leak and potentially cause
worse errors down the line. In particular, they would cause
`NullPointerException`s, which are UBEs on Scala.js.
---
 .../scalajs/linker/analyzer/Analyzer.scala    | 31 ++++++++++++++-----
 1 file changed, 23 insertions(+), 8 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala
index 34a2be0d59..11a997ef27 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala
@@ -1572,22 +1572,30 @@ private object AnalyzerRun {
 
   private class WorkTracker(implicit ec: ExecutionContext) {
     private val pending = new AtomicInteger(0)
+    private val failures = new AtomicReference[List[Throwable]](Nil)
     @volatile private var _allowComplete = false
     private val promise = Promise[Unit]()
 
     def track(fut: Future[Unit]): Unit = {
       pending.incrementAndGet()
 
-      fut.onComplete {
-        case Success(_) =>
-          if (pending.decrementAndGet() == 0)
-            tryComplete()
-
-        case Failure(t) =>
-          promise.tryFailure(t)
+      fut.onComplete { result =>
+        result match {
+          case Success(_) => ()
+          case Failure(t) => addFailure(t)
+        }
+        if (pending.decrementAndGet() == 0)
+          tryComplete()
       }
     }
 
+    @tailrec
+    private def addFailure(t: Throwable): Unit = {
+      val prev = failures.get()
+      if (!failures.compareAndSet(prev, t :: prev))
+        addFailure(t)
+    }
+
     private def tryComplete(): Unit = {
       /* Note that after _allowComplete is true and pending == 0, we are sure
        * that no new task will be submitted concurrently:
@@ -1596,7 +1604,14 @@ private object AnalyzerRun {
        *   more tasks) are running anymore.
        */
       if (_allowComplete && pending.get() == 0) {
-        promise.trySuccess(())
+        failures.get() match {
+          case Nil =>
+            promise.success(())
+          case firstFailure :: moreFailures =>
+            for (t <- moreFailures)
+              firstFailure.addSuppressed(t)
+            promise.failure(firstFailure)
+        }
       }
     }
 

From 5de6c1d46a6e2d0aa53add1dcf1be7ebbe646693 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Wed, 31 Jan 2024 12:11:44 +0100
Subject: [PATCH 031/298] Generalize the side-effect-free analysis of
 constructors to all classes.

Previously, we only analyzed *module* class constructors for
side-effect-freedom. This allowed us to get rid of unused
`LoadModule`s.

We now generalize the same analysis to all Scala classes. We take
a little shortcut by bundling *all* the constructors of a class
together as being side-effect-free or not. This is an
over-approximation in theory, but in practice it is unlikely that
it will make a difference. This shortcut allows our analysis to
be straightforward even in the presence of constructor delegation
chains.
---
 .../frontend/optimizer/IncOptimizer.scala     | 81 ++++++++++---------
 .../frontend/optimizer/OptimizerCore.scala    | 13 +--
 project/Build.scala                           |  8 +-
 .../testsuite/compiler/NullPointersTest.scala |  3 +-
 4 files changed, 56 insertions(+), 49 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
index 8982107805..f6876b2a4e 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
@@ -380,8 +380,9 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
     var subclasses: collOps.ParIterable[Class] = collOps.emptyParIterable
     var isInstantiated: Boolean = linkedClass.hasInstances
 
-    private var hasElidableModuleAccessor: Boolean = computeHasElidableModuleAccessor(linkedClass)
-    private val hasElidableModuleAccessorAskers = collOps.emptyMap[Processable, Unit]
+    /** True if *all* constructors of this class are recursively elidable. */
+    private var hasElidableConstructors: Boolean = computeHasElidableConstructors(linkedClass)
+    private val hasElidableConstructorsAskers = collOps.emptyMap[Processable, Unit]
 
     var fields: List[AnyFieldDef] = linkedClass.fields
     var fieldsRead: Set[FieldName] = linkedClass.fieldsRead
@@ -507,12 +508,12 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
       for (methodName <- methodAttributeChanges)
         myInterface.tagStaticCallersOf(namespace, methodName)
 
-      // Module class specifics
-      val newHasElidableModuleAccessor = computeHasElidableModuleAccessor(linkedClass)
-      if (hasElidableModuleAccessor != newHasElidableModuleAccessor) {
-        hasElidableModuleAccessor = newHasElidableModuleAccessor
-        hasElidableModuleAccessorAskers.keysIterator.foreach(_.tag())
-        hasElidableModuleAccessorAskers.clear()
+      // Elidable constructors
+      val newHasElidableConstructors = computeHasElidableConstructors(linkedClass)
+      if (hasElidableConstructors != newHasElidableConstructors) {
+        hasElidableConstructors = newHasElidableConstructors
+        hasElidableConstructorsAskers.keysIterator.foreach(_.tag())
+        hasElidableConstructorsAskers.clear()
       }
 
       // Inlineable class
@@ -543,25 +544,21 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
       subclasses = collOps.finishAdd(subclassAcc)
     }
 
-    def askHasElidableModuleAccessor(asker: Processable): Boolean = {
-      hasElidableModuleAccessorAskers.put(asker, ())
+    def askHasElidableConstructors(asker: Processable): Boolean = {
+      hasElidableConstructorsAskers.put(asker, ())
       asker.registerTo(this)
-      hasElidableModuleAccessor
+      hasElidableConstructors
     }
 
     /** UPDATE PASS ONLY. */
-    private def computeHasElidableModuleAccessor(linkedClass: LinkedClass): Boolean = {
-      def lookupModuleConstructor: Option[MethodImpl] = {
-        myInterface
-          .staticLike(MemberNamespace.Constructor)
-          .methods
-          .get(NoArgConstructorName)
+    private def computeHasElidableConstructors(linkedClass: LinkedClass): Boolean = {
+      if (isAdHocElidableConstructors(className)) {
+        true
+      } else {
+        superClass.forall(_.hasElidableConstructors) && // this was always updated before myself
+        myInterface.staticLike(MemberNamespace.Constructor)
+          .methods.valuesIterator.forall(computeIsElidableConstructor)
       }
-
-      val isModuleClass = linkedClass.kind == ClassKind.ModuleClass
-
-      isAdHocElidableModuleAccessor(className) ||
-      (isModuleClass && lookupModuleConstructor.exists(isElidableModuleConstructor))
     }
 
     /** UPDATE PASS ONLY. */
@@ -624,16 +621,17 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
     }
 
     /** UPDATE PASS ONLY. */
-    private def isElidableModuleConstructor(impl: MethodImpl): Boolean = {
+    private def computeIsElidableConstructor(impl: MethodImpl): Boolean = {
       def isTriviallySideEffectFree(tree: Tree): Boolean = tree match {
         case _:VarRef | _:Literal | _:This | _:Skip => true
         case _                                      => false
       }
+
       def isElidableStat(tree: Tree): Boolean = tree match {
         case Block(stats)                      => stats.forall(isElidableStat)
         case Assign(Select(This(), _, _), rhs) => isTriviallySideEffectFree(rhs)
 
-        // Mixin constructor
+        // Mixin constructor -- test whether its body is entirely empty
         case ApplyStatically(flags, This(), className, methodName, Nil)
             if !flags.isPrivate && !classes.contains(className) =>
           // Since className is not in classes, it must be a default method call.
@@ -646,22 +644,27 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
             }
           }
 
-        // Delegation to another constructor (super or in the same class)
-        case ApplyStatically(flags, This(), className, methodName, args)
-            if flags.isConstructor =>
-          args.forall(isTriviallySideEffectFree) && {
-            getInterface(className)
-              .staticLike(MemberNamespace.Constructor)
-              .methods
-              .get(methodName.name)
-              .exists(isElidableModuleConstructor)
-          }
+        /* Delegation to another constructor (super or in the same class)
+         *
+         * - for super constructor calls, we have already checked before getting
+         *   here that the super class has elidable constructors, so by
+         *   construction they are elidable and we do not need to test them
+         * - for other constructors in the same class, we will collectively
+         *   treat them as all-elidable or non-elidable; therefore, we do not
+         *   need to check them either at this point.
+         *
+         * We only need to check the arguments to the constructor, not their
+         * bodies.
+         */
+        case ApplyStatically(flags, This(), _, _, args) if flags.isConstructor =>
+          args.forall(isTriviallySideEffectFree)
 
         case StoreModule(_, _) => true
         case _                 => isTriviallySideEffectFree(tree)
       }
+
       impl.originalDef.body.fold {
-        throw new AssertionError("Module constructor cannot be abstract")
+        throw new AssertionError("Constructor cannot be abstract")
       } { body =>
         isElidableStat(body)
       }
@@ -692,7 +695,7 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
     }
 
     def unregisterDependee(dependee: Processable): Unit = {
-      hasElidableModuleAccessorAskers.remove(dependee)
+      hasElidableConstructorsAskers.remove(dependee)
     }
   }
 
@@ -1349,8 +1352,8 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
     protected def getAncestorsOf(intfName: ClassName): List[ClassName] =
       getInterface(intfName).askAncestors(asker)
 
-    protected def hasElidableModuleAccessor(moduleClassName: ClassName): Boolean =
-      classes(moduleClassName).askHasElidableModuleAccessor(asker)
+    protected def hasElidableConstructors(className: ClassName): Boolean =
+      classes(className).askHasElidableConstructors(asker)
 
     protected def tryNewInlineableClass(
         className: ClassName): Option[OptimizerCore.InlineableClassStructure] = {
@@ -1380,6 +1383,6 @@ object IncOptimizer {
   def apply(config: CommonPhaseConfig): IncOptimizer =
     new IncOptimizer(config, SeqCollOps)
 
-  private val isAdHocElidableModuleAccessor: Set[ClassName] =
+  private val isAdHocElidableConstructors: Set[ClassName] =
     Set(ClassName("scala.Predef$"))
 }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
index d2454ea80f..6b65697fe8 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
@@ -66,11 +66,11 @@ private[optimizer] abstract class OptimizerCore(
   /** Returns the list of ancestors of a class or interface. */
   protected def getAncestorsOf(className: ClassName): List[ClassName]
 
-  /** Tests whether the given module class has an elidable accessor.
-   *  In other words, whether it is safe to discard a LoadModule of that
-   *  module class which is not used.
+  /** Tests whether *all* the constructors of the given class are elidable.
+   *  In other words, whether it is safe to discard a New or LoadModule of that
+   *  class which is not used.
    */
-  protected def hasElidableModuleAccessor(moduleClassName: ClassName): Boolean
+  protected def hasElidableConstructors(className: ClassName): Boolean
 
   /** Tests whether the given class is inlineable.
    *
@@ -1578,8 +1578,11 @@ private[optimizer] abstract class OptimizerCore(
         case Skip()      => keepOnlySideEffects(Block(init)(stat.pos))
         case lastEffects => Block(init, lastEffects)(stat.pos)
       }
+    case New(className, _, args) =>
+      if (hasElidableConstructors(className)) Block(args.map(keepOnlySideEffects(_)))(stat.pos)
+      else stat
     case LoadModule(moduleClassName) =>
-      if (hasElidableModuleAccessor(moduleClassName)) Skip()(stat.pos)
+      if (hasElidableConstructors(moduleClassName)) Skip()(stat.pos)
       else stat
     case NewArray(_, lengths) if lengths.forall(isNonNegativeIntLiteral(_)) =>
       Skip()(stat.pos)
diff --git a/project/Build.scala b/project/Build.scala
index f9d72c08e0..9ff7b777a7 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -1967,17 +1967,17 @@ object Build {
         scalaVersion.value match {
           case `default212Version` =>
             Some(ExpectedSizes(
-                fastLink = 768000 to 769000,
+                fastLink = 682000 to 683000,
                 fullLink = 144000 to 145000,
-                fastLinkGz = 90000 to 91000,
+                fastLinkGz = 82000 to 83000,
                 fullLinkGz = 35000 to 36000,
             ))
 
           case `default213Version` =>
             Some(ExpectedSizes(
-                fastLink = 478000 to 479000,
+                fastLink = 476000 to 477000,
                 fullLink = 101000 to 102000,
-                fastLinkGz = 62000 to 63000,
+                fastLinkGz = 61000 to 62000,
                 fullLinkGz = 27000 to 28000,
             ))
 
diff --git a/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/NullPointersTest.scala b/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/NullPointersTest.scala
index d76225c466..4ff13defd1 100644
--- a/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/NullPointersTest.scala
+++ b/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/NullPointersTest.scala
@@ -23,7 +23,8 @@ class NullPointersTest {
   import NullPointersTest._
 
   // Instantiate Tester somewhere, otherwise plenty of tests are moot
-  new Tester(0)
+  @noinline def keep(x: Any): Unit = ()
+  keep(new Tester(0))
 
   @noinline
   private def nullOf[T >: Null]: T = null

From 7814252c8869cae75652c4dad1e0bee4e48611ef Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Fri, 2 Feb 2024 11:28:14 +0100
Subject: [PATCH 032/298] Better codegen for the null check on outer pointers
 in constructors.

When introducing outer pointers, scalac generates a null check in
the constructor of nested classes. The null check looks like this:

    if ($outer.eq(null))
      throw null
    else
      this.$outer = $outer

This is a bad shape for our optimizations, notably because the
explicit null check cannot be considered UB at the IR level if
we compile it as is, although in the original *language*, that
would clearly fall into UB.

Therefore, we now intercept that shape and rewrite it as follows
instead:

    <getClass>($outer)   // null check subject to UB
    this.$outer = $outer // the `else` branch in general
---
 .../org/scalajs/nscplugin/GenJSCode.scala     | 49 ++++++++++++++++---
 .../frontend/optimizer/OptimizerCore.scala    |  4 +-
 project/Build.scala                           |  6 +--
 3 files changed, 49 insertions(+), 10 deletions(-)

diff --git a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
index e4c9ecadd9..2cf95451db 100644
--- a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
+++ b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
@@ -2270,13 +2270,50 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
                   toIRType(sym.tpe), sym.isMutable, rhsTree)
           }
 
-        case If(cond, thenp, elsep) =>
-          val tpe =
-            if (isStat) jstpe.NoType
-            else toIRType(tree.tpe)
+        case tree @ If(cond, thenp, elsep) =>
+          def default: js.Tree = {
+            val tpe =
+              if (isStat) jstpe.NoType
+              else toIRType(tree.tpe)
+
+            js.If(genExpr(cond), genStatOrExpr(thenp, isStat),
+                genStatOrExpr(elsep, isStat))(tpe)
+          }
 
-          js.If(genExpr(cond), genStatOrExpr(thenp, isStat),
-              genStatOrExpr(elsep, isStat))(tpe)
+          if (isStat && currentMethodSym.isClassConstructor) {
+            /* Nested classes that need an outer pointer have a weird shape for
+             * assigning it, with an explicit null check. It looks like this:
+             *
+             *   if ($outer.eq(null))
+             *     throw null
+             *   else
+             *     this.$outer = $outer
+             *
+             * This is a bad shape for our optimizations, notably because the
+             * explicit null check cannot be considered UB at the IR level if
+             * we compile it as is, although in the original *language*, that
+             * would clearly fall into UB.
+             *
+             * Therefore, we intercept that shape and rewrite it as follows
+             * instead:
+             *
+             *   <getClass>($outer)   // null check subject to UB
+             *   this.$outer = $outer // the `else` branch in general
+             */
+            tree match {
+              case If(Apply(fun @ Select(outer: Ident, nme.eq), Literal(Constant(null)) :: Nil),
+                  Throw(Literal(Constant(null))), elsep)
+                  if outer.symbol.isOuterParam && fun.symbol == definitions.Object_eq =>
+                js.Block(
+                  js.GetClass(genExpr(outer)), // null check
+                  genStat(elsep)
+                )
+              case _ =>
+                default
+            }
+          } else {
+            default
+          }
 
         case Return(expr) =>
           js.Return(toIRType(expr.tpe) match {
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
index 6b65697fe8..534fd345be 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
@@ -2791,7 +2791,9 @@ private[optimizer] abstract class OptimizerCore(
        *   if (cond) throw e
        *   else value
        *
-       * Typical shape of initialization of outer pointer of inner classes.
+       * Typical shape of initialization of outer pointer of inner classes
+       * coming from Scala.js < 1.15.1 (since 1.15.1, we intercept that shape
+       * already in the compiler back-end).
        */
       case If(cond, th: Throw, Assign(Select(This(), _, _), value)) :: rest =>
         // work around a bug of the compiler (these should be @-bindings)
diff --git a/project/Build.scala b/project/Build.scala
index 9ff7b777a7..31c63099fb 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -1967,15 +1967,15 @@ object Build {
         scalaVersion.value match {
           case `default212Version` =>
             Some(ExpectedSizes(
-                fastLink = 682000 to 683000,
-                fullLink = 144000 to 145000,
+                fastLink = 681000 to 682000,
+                fullLink = 142000 to 143000,
                 fastLinkGz = 82000 to 83000,
                 fullLinkGz = 35000 to 36000,
             ))
 
           case `default213Version` =>
             Some(ExpectedSizes(
-                fastLink = 476000 to 477000,
+                fastLink = 475000 to 476000,
                 fullLink = 101000 to 102000,
                 fastLinkGz = 61000 to 62000,
                 fullLinkGz = 27000 to 28000,

From fea064dd526433181a37ae6a967866a2131f19db Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Fri, 2 Feb 2024 13:10:23 +0100
Subject: [PATCH 033/298] Handle `GetClass` in the side-effect-free analysis of
 constructors.

When NPEs are unchecked, `GetClass` is side-effect-free. This
helps enormously the analysis, as it now allows many inner classes
to be considered to have elidable constructors.
---
 .../linker/frontend/optimizer/IncOptimizer.scala    | 13 ++++++++++---
 project/Build.scala                                 |  4 ++--
 2 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
index f6876b2a4e..2ed19a5b19 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
@@ -29,7 +29,7 @@ import org.scalajs.logging._
 import org.scalajs.linker._
 import org.scalajs.linker.backend.emitter.LongImpl
 import org.scalajs.linker.frontend.LinkingUnit
-import org.scalajs.linker.interface.ModuleKind
+import org.scalajs.linker.interface.{CheckedBehavior, ModuleKind}
 import org.scalajs.linker.standard._
 import org.scalajs.linker.CollectionsCompat._
 
@@ -623,8 +623,15 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
     /** UPDATE PASS ONLY. */
     private def computeIsElidableConstructor(impl: MethodImpl): Boolean = {
       def isTriviallySideEffectFree(tree: Tree): Boolean = tree match {
-        case _:VarRef | _:Literal | _:This | _:Skip => true
-        case _                                      => false
+        case _:VarRef | _:Literal | _:This | _:Skip =>
+          true
+
+        case GetClass(expr) =>
+          config.coreSpec.semantics.nullPointers == CheckedBehavior.Unchecked &&
+          isTriviallySideEffectFree(expr)
+
+        case _ =>
+          false
       }
 
       def isElidableStat(tree: Tree): Boolean = tree match {
diff --git a/project/Build.scala b/project/Build.scala
index 31c63099fb..85ad9026ee 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -1968,9 +1968,9 @@ object Build {
           case `default212Version` =>
             Some(ExpectedSizes(
                 fastLink = 681000 to 682000,
-                fullLink = 142000 to 143000,
+                fullLink = 111000 to 112000,
                 fastLinkGz = 82000 to 83000,
-                fullLinkGz = 35000 to 36000,
+                fullLinkGz = 28000 to 29000,
             ))
 
           case `default213Version` =>

From a99abdef340a9fdd236644c232716a81e92c0873 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Fri, 2 Feb 2024 14:29:29 +0100
Subject: [PATCH 034/298] Handle `Closure` in the side-effect-free analysis of
 constructors.

---
 .../org/scalajs/linker/frontend/optimizer/IncOptimizer.scala   | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
index 2ed19a5b19..9c433fb62c 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
@@ -626,6 +626,9 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
         case _:VarRef | _:Literal | _:This | _:Skip =>
           true
 
+        case Closure(_, _, _, _, _, captureValues) =>
+          captureValues.forall(isTriviallySideEffectFree(_))
+
         case GetClass(expr) =>
           config.coreSpec.semantics.nullPointers == CheckedBehavior.Unchecked &&
           isTriviallySideEffectFree(expr)

From e47c278ed9b7dac0850587e02daefa46cd58093d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Wed, 31 Jan 2024 18:01:38 +0100
Subject: [PATCH 035/298] Make the side-effect-free analysis of constructors
 graph-aware.

Previously, as soon as a class A's constructor instantiated another
class B (including accessing module instances), A's constructors
would be considered non-elidable. That is even if B's constructors
are elidable.

In this commit, we implement a graph-based analysis that solves the
above limitation.

First, during the incremental pass of the linker (the UDPATE pass),
we compute the "elidable constructor infos" of every class:

- whether any of its constructors contains potentially
  side-effecting code, *other than* instantiating other classes;
  if yes, it is `NotElidable`;
- otherwise, the set of classes that its constructors collectively
  instantiate, which is then `DependentOn`.

We then insert a third pass in the `IncOptimizer`: the ELIDABLE
CTORS pass. This pass computes the transitive closure of
`NotElidable` by following the reverse `DependentOn` relationships.

This pass is not incremental nor parallel. However, it is only
linear in the number of classes (`Class`es, `ModuleClass`es and
`HijackedClass`es). That makes it very fast regardless (on order of
10 ms for our test suite). Therefore, it remains acceptable even
for `fastLink`.
---
 .../frontend/optimizer/IncOptimizer.scala     | 129 ++++++++++++++++--
 project/Build.scala                           |  14 +-
 2 files changed, 122 insertions(+), 21 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
index 9c433fb62c..6ba6bca95b 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
@@ -83,6 +83,11 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
       updateAndTagEverything(unit)
     }
 
+    logger.time("Optimizer: Elidable constructors") {
+      /** ELIDABLE CTORS PASS */
+      updateElidableConstructors()
+    }
+
     logger.time("Optimizer: Optimizer part") {
       /* PROCESS PASS */
       processAllTaggedMethods(logger)
@@ -259,6 +264,47 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
 
   }
 
+  /** Elidable constructors: compute the fix point of hasElidableConstructors.
+   *
+   *  ELIDABLE CTORS PASS ONLY. (This IS the elidable ctors pass).
+   */
+  private def updateElidableConstructors(): Unit = {
+    import ElidableConstructorsInfo._
+
+    /* Invariant: when something is in the stack, its
+     * elidableConstructorsInfo was set to NotElidable.
+     */
+    val toProcessStack = mutable.ArrayBuffer.empty[Class]
+
+    // Build the graph and initial stack from the infos
+    for (cls <- classes.valuesIterator) {
+      cls.elidableConstructorsInfo match {
+        case NotElidable =>
+          toProcessStack += cls
+        case DependentOn(dependencies) =>
+          for (dependency <- dependencies)
+            classes(dependency).elidableConstructorsDependents += cls
+      }
+    }
+
+    // Propagate
+    while (toProcessStack.nonEmpty) {
+      val cls = toProcessStack.remove(toProcessStack.size - 1)
+
+      for (dependent <- cls.elidableConstructorsDependents) {
+        if (dependent.elidableConstructorsInfo != NotElidable) {
+          dependent.elidableConstructorsInfo = NotElidable
+          toProcessStack += dependent
+        }
+      }
+    }
+
+    // Set the final value of hasElidableConstructors
+    for (cls <- classes.valuesIterator) {
+      cls.setHasElidableConstructors(cls.elidableConstructorsInfo != NotElidable)
+    }
+  }
+
   /** Optimizer part: process all methods that need reoptimizing.
    *  PROCESS PASS ONLY. (This IS the process pass).
    */
@@ -380,8 +426,14 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
     var subclasses: collOps.ParIterable[Class] = collOps.emptyParIterable
     var isInstantiated: Boolean = linkedClass.hasInstances
 
+    // Temporary information used to eventually derive `hasElidableConstructors`
+    var elidableConstructorsInfo: ElidableConstructorsInfo =
+      computeElidableConstructorsInfo(linkedClass)
+    val elidableConstructorsDependents: mutable.ArrayBuffer[Class] = mutable.ArrayBuffer.empty
+
     /** True if *all* constructors of this class are recursively elidable. */
-    private var hasElidableConstructors: Boolean = computeHasElidableConstructors(linkedClass)
+    private var hasElidableConstructors: Boolean =
+      elidableConstructorsInfo != ElidableConstructorsInfo.NotElidable // initial educated guess
     private val hasElidableConstructorsAskers = collOps.emptyMap[Processable, Unit]
 
     var fields: List[AnyFieldDef] = linkedClass.fields
@@ -509,12 +561,8 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
         myInterface.tagStaticCallersOf(namespace, methodName)
 
       // Elidable constructors
-      val newHasElidableConstructors = computeHasElidableConstructors(linkedClass)
-      if (hasElidableConstructors != newHasElidableConstructors) {
-        hasElidableConstructors = newHasElidableConstructors
-        hasElidableConstructorsAskers.keysIterator.foreach(_.tag())
-        hasElidableConstructorsAskers.clear()
-      }
+      elidableConstructorsInfo = computeElidableConstructorsInfo(linkedClass)
+      elidableConstructorsDependents.clear()
 
       // Inlineable class
       if (updateTryNewInlineable(linkedClass)) {
@@ -528,6 +576,15 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
       }
     }
 
+    /** ELIDABLE CTORS PASS ONLY. */
+    def setHasElidableConstructors(newHasElidableConstructors: Boolean): Unit = {
+      if (hasElidableConstructors != newHasElidableConstructors) {
+        hasElidableConstructors = newHasElidableConstructors
+        hasElidableConstructorsAskers.keysIterator.foreach(_.tag())
+        hasElidableConstructorsAskers.clear()
+      }
+    }
+
     /** UPDATE PASS ONLY. */
     def walkForAdditions(
         getNewChildren: ClassName => collOps.ParIterable[LinkedClass]): Unit = {
@@ -551,13 +608,25 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
     }
 
     /** UPDATE PASS ONLY. */
-    private def computeHasElidableConstructors(linkedClass: LinkedClass): Boolean = {
+    private def computeElidableConstructorsInfo(linkedClass: LinkedClass): ElidableConstructorsInfo = {
+      import ElidableConstructorsInfo._
+
       if (isAdHocElidableConstructors(className)) {
-        true
+        AlwaysElidable
       } else {
-        superClass.forall(_.hasElidableConstructors) && // this was always updated before myself
-        myInterface.staticLike(MemberNamespace.Constructor)
-          .methods.valuesIterator.forall(computeIsElidableConstructor)
+        // It's OK to look at the superClass like this because it will always be updated before myself
+        var result = superClass.fold(ElidableConstructorsInfo.AlwaysElidable)(_.elidableConstructorsInfo)
+
+        if (result == NotElidable) {
+          // fast path
+          result
+        } else {
+          val ctorIterator = myInterface.staticLike(MemberNamespace.Constructor).methods.valuesIterator
+          while (result != NotElidable && ctorIterator.hasNext) {
+            result = result.mergeWith(computeCtorElidableInfo(ctorIterator.next()))
+          }
+          result
+        }
       }
     }
 
@@ -621,7 +690,9 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
     }
 
     /** UPDATE PASS ONLY. */
-    private def computeIsElidableConstructor(impl: MethodImpl): Boolean = {
+    private def computeCtorElidableInfo(impl: MethodImpl): ElidableConstructorsInfo = {
+      val dependenciesBuilder = Set.newBuilder[ClassName]
+
       def isTriviallySideEffectFree(tree: Tree): Boolean = tree match {
         case _:VarRef | _:Literal | _:This | _:Skip =>
           true
@@ -633,6 +704,14 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
           config.coreSpec.semantics.nullPointers == CheckedBehavior.Unchecked &&
           isTriviallySideEffectFree(expr)
 
+        case New(className, _, args) =>
+          dependenciesBuilder += className
+          args.forall(isTriviallySideEffectFree(_))
+
+        case LoadModule(className) =>
+          dependenciesBuilder += className
+          true
+
         case _ =>
           false
       }
@@ -676,7 +755,10 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
       impl.originalDef.body.fold {
         throw new AssertionError("Constructor cannot be abstract")
       } { body =>
-        isElidableStat(body)
+        if (isElidableStat(body))
+          ElidableConstructorsInfo.DependentOn(dependenciesBuilder.result())
+        else
+          ElidableConstructorsInfo.NotElidable
       }
     }
 
@@ -1395,4 +1477,23 @@ object IncOptimizer {
 
   private val isAdHocElidableConstructors: Set[ClassName] =
     Set(ClassName("scala.Predef$"))
+
+  sealed abstract class ElidableConstructorsInfo {
+    import ElidableConstructorsInfo._
+
+    final def mergeWith(that: ElidableConstructorsInfo): ElidableConstructorsInfo = (this, that) match {
+      case (DependentOn(deps1), DependentOn(deps2)) =>
+        DependentOn(deps1 ++ deps2)
+      case _ =>
+        NotElidable
+    }
+  }
+
+  object ElidableConstructorsInfo {
+    case object NotElidable extends ElidableConstructorsInfo
+
+    final case class DependentOn(dependencies: Set[ClassName]) extends ElidableConstructorsInfo
+
+    val AlwaysElidable: ElidableConstructorsInfo = DependentOn(Set.empty)
+  }
 }
diff --git a/project/Build.scala b/project/Build.scala
index 85ad9026ee..9bc1560729 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -1967,18 +1967,18 @@ object Build {
         scalaVersion.value match {
           case `default212Version` =>
             Some(ExpectedSizes(
-                fastLink = 681000 to 682000,
-                fullLink = 111000 to 112000,
+                fastLink = 676000 to 677000,
+                fullLink = 103000 to 104000,
                 fastLinkGz = 82000 to 83000,
-                fullLinkGz = 28000 to 29000,
+                fullLinkGz = 26000 to 27000,
             ))
 
           case `default213Version` =>
             Some(ExpectedSizes(
-                fastLink = 475000 to 476000,
-                fullLink = 101000 to 102000,
-                fastLinkGz = 61000 to 62000,
-                fullLinkGz = 27000 to 28000,
+                fastLink = 468000 to 469000,
+                fullLink = 100000 to 101000,
+                fastLinkGz = 60000 to 61000,
+                fullLinkGz = 26000 to 27000,
             ))
 
           case _ =>

From 5f3323dc16ce9adb456dc02224be370791398625 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Fri, 2 Feb 2024 18:42:12 +0100
Subject: [PATCH 036/298] Hard-code `scala.package$` as having elidable
 constructors.

Like `scala.Predef$`.
---
 .../scalajs/linker/frontend/optimizer/IncOptimizer.scala    | 2 +-
 project/Build.scala                                         | 6 +++---
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
index 6ba6bca95b..e8db94edb1 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
@@ -1476,7 +1476,7 @@ object IncOptimizer {
     new IncOptimizer(config, SeqCollOps)
 
   private val isAdHocElidableConstructors: Set[ClassName] =
-    Set(ClassName("scala.Predef$"))
+    Set(ClassName("scala.Predef$"), ClassName("scala.package$"))
 
   sealed abstract class ElidableConstructorsInfo {
     import ElidableConstructorsInfo._
diff --git a/project/Build.scala b/project/Build.scala
index 9bc1560729..263683ee52 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -1967,9 +1967,9 @@ object Build {
         scalaVersion.value match {
           case `default212Version` =>
             Some(ExpectedSizes(
-                fastLink = 676000 to 677000,
-                fullLink = 103000 to 104000,
-                fastLinkGz = 82000 to 83000,
+                fastLink = 642000 to 643000,
+                fullLink = 102000 to 103000,
+                fastLinkGz = 77000 to 78000,
                 fullLinkGz = 26000 to 27000,
             ))
 

From 26300676c8acf6bdacf1b89a12dfef1be66a49dd Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Fri, 2 Feb 2024 14:24:09 +0100
Subject: [PATCH 037/298] Use `def`s for `hashCode` in 2.13.x Manifests, like
 in 2.12.x.

Originally we made the change from the upstream `val`s to `def`s
in 7865a5d48776198fa205d882de48f930ade43e41. We then accidentally
reverted that change in the 2.13.x in
1a7f013641edd77dd427e05a50f9d38462fbd154.

This commit aligns the 2.13.x overrides with 2.12.x again.
---
 scalalib/overrides-2.13/scala/reflect/Manifest.scala | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/scalalib/overrides-2.13/scala/reflect/Manifest.scala b/scalalib/overrides-2.13/scala/reflect/Manifest.scala
index 4f84b5e639..053b0c485d 100644
--- a/scalalib/overrides-2.13/scala/reflect/Manifest.scala
+++ b/scalalib/overrides-2.13/scala/reflect/Manifest.scala
@@ -152,8 +152,7 @@ abstract class AnyValManifest[T <: AnyVal](override val toString: String) extend
     case _                    => false
   }
   override def equals(that: Any): Boolean = this eq that.asInstanceOf[AnyRef]
-  @transient
-  override val hashCode = System.identityHashCode(this)
+  override def hashCode = System.identityHashCode(this)
 }
 
 /** `ManifestFactory` defines factory methods for manifests.
@@ -402,8 +401,7 @@ object ManifestFactory {
   private abstract class PhantomManifest[T](_runtimeClass: Predef.Class[_],
                                             override val toString: String) extends ClassTypeManifest[T](None, _runtimeClass, Nil) {
     override def equals(that: Any): Boolean = this eq that.asInstanceOf[AnyRef]
-    @transient
-    override val hashCode = System.identityHashCode(this)
+    override def hashCode = System.identityHashCode(this)
   }
 
   /** Manifest for the class type `clazz[args]`, where `clazz` is

From 2e4594f0739cc58b74f1de7d5c4cc51b72a1371a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Mon, 5 Feb 2024 14:06:14 +0100
Subject: [PATCH 038/298] Fix #4929: Fix logic for moving early assignements in
 JS ctors.

Previously, we moved all statements in the constructors after the
super constructor call. However, it turns out that there are
statements that must be kept before, notably local `val`s
generated for default arguments to the super constructor.

We now keep statements where they are by default. We only move
statements of the form `C.this.field = ident;`, which are the
only ones that require access to `this`.

This requires only a little bit of special-casing for outer pointer
null checks. Fortunately, we already had some logic to identify and
decompose those, which we reuse here.
---
 .../org/scalajs/nscplugin/GenJSCode.scala     | 120 +++++++++++++++---
 .../jsinterop/NonNativeJSTypeTestScala2.scala |  43 +++++++
 .../jsinterop/NonNativeJSTypeTest.scala       |  36 ++++++
 3 files changed, 184 insertions(+), 15 deletions(-)

diff --git a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
index 2cf95451db..5d46b0617b 100644
--- a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
+++ b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
@@ -1472,18 +1472,78 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
       val sym = dd.symbol
       assert(sym.isPrimaryConstructor, s"called with non-primary ctor: $sym")
 
+      var preSuperStats = List.newBuilder[js.Tree]
       var jsSuperCall: Option[js.JSSuperConstructorCall] = None
-      val jsStats = List.newBuilder[js.Tree]
+      val postSuperStats = List.newBuilder[js.Tree]
 
-      /* Move all statements after the super constructor call since JS
-       * cannot access `this` before the super constructor call.
+      /* Move param accessor initializers and early initializers after the
+       * super constructor call since JS cannot access `this` before the super
+       * constructor call.
        *
        * scalac inserts statements before the super constructor call for early
        * initializers and param accessor initializers (including val's and var's
-       * declared in the params). We move those after the super constructor
-       * call, and are therefore executed later than for a Scala class.
+       * declared in the params). Those statements include temporary local `val`
+       * definitions (for true early initializers only) and the assignments,
+       * whose rhs'es are always simple Idents (either constructor params or the
+       * temporary local `val`s).
+       *
+       * There can also be local `val`s before the super constructor call for
+       * default arguments to the super constructor. These must remain before.
+       *
+       * Our strategy is therefore to move only the field assignments after the
+       * super constructor call. They are therefore executed later than for a
+       * Scala class (as specified for non-native JS classes semantics).
+       * However, side effects and evaluation order of all the other
+       * computations remains unchanged.
+       *
+       * For a somewhat extreme example of the shapes we can get here, consider
+       * the source code:
+       *
+       *   class Parent(output: Any = "output", callbackObject: Any = "callbackObject") extends js.Object {
+       *     println(s"Parent constructor; $output; $callbackObject")
+       *   }
+       *
+       *   class Child(val foo: Int, callbackObject: Any, val bar: Int) extends {
+       *     val xyz = foo + bar
+       *     val yz = { println(xyz); xyz + 2 }
+       *   } with Parent(callbackObject = { println(foo); xyz + bar }) {
+       *     println("Child constructor")
+       *     println(xyz)
+       *   }
+       *
+       * At this phase, for the constructor of `Child`, we receive the following
+       * scalac Tree:
+       *
+       *   def <init>(foo: Int, callbackObject: Object, bar: Int): helloworld.Child = {
+       *     Child.this.foo = foo; // param accessor assignment, moved
+       *     Child.this.bar = bar; // param accessor assignment, moved
+       *     val xyz: Int = foo.+(bar); // note that these still use the ctor params, not the fields
+       *     Child.this.xyz = xyz; // early initializer, moved
+       *     val yz: Int = {
+       *       scala.Predef.println(scala.Int.box(xyz)); // note that this uses the local val, not the field
+       *       xyz.+(2)
+       *     };
+       *     Child.this.yz = yz; // early initializer, moved
+       *     {
+       *       <artifact> val x$1: Int = {
+       *         scala.Predef.println(scala.Int.box(foo));
+       *         xyz.+(bar) // here as well, we use the local vals, not the fields
+       *       };
+       *       <artifact> val x$2: Object = helloworld.this.Parent.<init>$default$1();
+       *       Child.super.<init>(x$2, scala.Int.box(x$1))
+       *     };
+       *     scala.Predef.println("Child constructor");
+       *     scala.Predef.println(scala.Int.box(Child.this.xyz()));
+       *     ()
+       *   }
+       *
        */
       withPerMethodBodyState(sym) {
+        def isThisFieldAssignment(tree: Tree): Boolean = tree match {
+          case Assign(Select(ths: This, _), Ident(_)) => ths.symbol == currentClassSym.get
+          case _                                      => false
+        }
+
         flatStats(stats).foreach {
           case tree @ Apply(fun @ Select(Super(This(_), _), _), args)
                 if fun.symbol.isClassConstructor =>
@@ -1491,14 +1551,27 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
             implicit val pos = tree.pos
             jsSuperCall = Some(js.JSSuperConstructorCall(genPrimitiveJSArgs(fun.symbol, args)))
 
-          case stat =>
-            val jsStat = genStat(stat)
+          case tree if jsSuperCall.isDefined =>
+            // Once we're past the super constructor call, everything goes after.
+            postSuperStats += genStat(tree)
 
-            assert(jsSuperCall.isDefined || !jsStat.isInstanceOf[js.VarDef],
-                "Trying to move a local VarDef after the super constructor call " +
-                s"of a non-native JS class at ${dd.pos}")
+          case tree if isThisFieldAssignment(tree) =>
+            /* If that shape appears before the jsSuperCall, it is an early
+             * initializer or param accessor initializer. We move it.
+             */
+            postSuperStats += genStat(tree)
+
+          case tree @ OuterPointerNullCheck(outer, assign) if isThisFieldAssignment(assign) =>
+            /* Variant of the above with an outer pointer null check. The actual
+             * null check remains before the super call, while the associated
+             * assignment is moved after.
+             */
+            preSuperStats += js.GetClass(genExpr(outer))(tree.pos)
+            postSuperStats += genStat(assign)
 
-            jsStats += jsStat
+          case stat =>
+            // Other statements are left before.
+            preSuperStats += genStat(stat)
         }
       }
 
@@ -1506,7 +1579,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
           s"construtor at ${dd.pos}")
 
       new PrimaryJSCtor(sym, genParamsAndInfo(sym, vparamss),
-          js.JSConstructorBody(Nil, jsSuperCall.get, jsStats.result())(dd.pos))
+          js.JSConstructorBody(preSuperStats.result(), jsSuperCall.get, postSuperStats.result())(dd.pos))
     }
 
     private def genSecondaryJSClassCtor(dd: DefDef): SplitSecondaryJSCtor = {
@@ -2301,9 +2374,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
              *   this.$outer = $outer // the `else` branch in general
              */
             tree match {
-              case If(Apply(fun @ Select(outer: Ident, nme.eq), Literal(Constant(null)) :: Nil),
-                  Throw(Literal(Constant(null))), elsep)
-                  if outer.symbol.isOuterParam && fun.symbol == definitions.Object_eq =>
+              case OuterPointerNullCheck(outer, elsep) =>
                 js.Block(
                   js.GetClass(genExpr(outer)), // null check
                   genStat(elsep)
@@ -2566,6 +2637,25 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
       }
     } // end of GenJSCode.genExpr()
 
+    /** Extractor for the shape of outer pointer null check.
+     *
+     *  See the comment in `case If(...) =>` of `genExpr`.
+     *
+     *  When successful, returns the pair `(outer, elsep)` where `outer` is the
+     *  `Ident` of the outer constructor parameter, and `elsep` is the else
+     *  branch of the condition.
+     */
+    private object OuterPointerNullCheck {
+      def unapply(tree: If): Option[(Ident, Tree)] = tree match {
+        case If(Apply(fun @ Select(outer: Ident, nme.eq), Literal(Constant(null)) :: Nil),
+            Throw(Literal(Constant(null))), elsep)
+            if outer.symbol.isOuterParam && fun.symbol == definitions.Object_eq =>
+          Some((outer, elsep))
+        case _ =>
+          None
+      }
+    }
+
     /** Gen JS this of the current class.
      *  Normally encoded straightforwardly as a JS this.
      *  But must be replaced by the tail-jump-this local variable if there
diff --git a/test-suite/js/src/test/require-scala2/org/scalajs/testsuite/jsinterop/NonNativeJSTypeTestScala2.scala b/test-suite/js/src/test/require-scala2/org/scalajs/testsuite/jsinterop/NonNativeJSTypeTestScala2.scala
index ea1c4c3f90..c3fcc9d69b 100644
--- a/test-suite/js/src/test/require-scala2/org/scalajs/testsuite/jsinterop/NonNativeJSTypeTestScala2.scala
+++ b/test-suite/js/src/test/require-scala2/org/scalajs/testsuite/jsinterop/NonNativeJSTypeTestScala2.scala
@@ -12,6 +12,8 @@
 
 package org.scalajs.testsuite.jsinterop
 
+import scala.collection.mutable
+
 import scala.scalajs.js
 import scala.scalajs.js.annotation._
 
@@ -36,6 +38,29 @@ class NonNativeJSTypeTestScala2 {
     assertNull(obj.asInstanceOf[js.Dynamic].valueClass)
   }
 
+  @Test def callSuperConstructorWithDefaultParamsAndEarlyInitializers_Issue4929(): Unit = {
+    import ConstructorSuperCallWithDefaultParamsAndEarlyInitializers._
+
+    sideEffects.clear()
+
+    val child = new Child(4, "hello", 23)
+    assertEquals(4, child.foo)
+    assertEquals(23, child.bar)
+    assertEquals(27, child.xyz)
+    assertEquals(29, child.yz)
+
+    assertEquals(
+      List(
+        "27",
+        "4",
+        "Parent constructor; param1, 27, param1-27",
+        "Child constructor; 4, hello, 23",
+        "27, 29"
+      ),
+      sideEffects.toList
+    )
+  }
+
 }
 
 object NonNativeJSTypeTestScala2 {
@@ -46,4 +71,22 @@ object NonNativeJSTypeTestScala2 {
 
   class SomeValueClass(val i: Int) extends AnyVal
 
+  object ConstructorSuperCallWithDefaultParamsAndEarlyInitializers {
+    val sideEffects = mutable.ListBuffer.empty[String]
+
+    class Parent(parentParam1: Any = "param1", parentParam2: Any = "param2")(
+        dependentParam: String = s"$parentParam1-$parentParam2")
+        extends js.Object {
+      sideEffects += s"Parent constructor; $parentParam1, $parentParam2, $dependentParam"
+    }
+
+    class Child(val foo: Int, parentParam2: Any, val bar: Int) extends {
+      val xyz = foo + bar
+      val yz = { sideEffects += xyz.toString(); xyz + 2 }
+    } with Parent(parentParam2 = { sideEffects += foo.toString(); foo + bar })() {
+      sideEffects += s"Child constructor; $foo, $parentParam2, $bar"
+      sideEffects += s"$xyz, $yz"
+    }
+  }
+
 }
diff --git a/test-suite/js/src/test/scala/org/scalajs/testsuite/jsinterop/NonNativeJSTypeTest.scala b/test-suite/js/src/test/scala/org/scalajs/testsuite/jsinterop/NonNativeJSTypeTest.scala
index 94cdf52847..0417489023 100644
--- a/test-suite/js/src/test/scala/org/scalajs/testsuite/jsinterop/NonNativeJSTypeTest.scala
+++ b/test-suite/js/src/test/scala/org/scalajs/testsuite/jsinterop/NonNativeJSTypeTest.scala
@@ -12,6 +12,8 @@
 
 package org.scalajs.testsuite.jsinterop
 
+import scala.collection.mutable
+
 import scala.scalajs.js
 import scala.scalajs.js.annotation._
 
@@ -1306,6 +1308,25 @@ class NonNativeJSTypeTest {
     assertEquals(js.undefined, foo4.description)
   }
 
+  @Test def callSuperConstructorWithDefaultParams_Issue4929(): Unit = {
+    import ConstructorSuperCallWithDefaultParams._
+
+    sideEffects.clear()
+
+    val child = new Child(4, "hello", 23)
+    assertEquals(4, child.foo)
+    assertEquals(23, child.bar)
+
+    assertEquals(
+      List(
+        "4",
+        "Parent constructor; param1, 27, param1-27",
+        "Child constructor; 4, hello, 23"
+      ),
+      sideEffects.toList
+    )
+  }
+
   @Test def callSuperConstructorWithColonAsterisk(): Unit = {
     class CallSuperCtorWithSpread(x: Int, y: Int, z: Int)
         extends NativeParentClassWithVarargs(x, Seq(y, z): _*)
@@ -2040,6 +2061,21 @@ object NonNativeJSTypeTest {
     def this(x: Int, y: Int) = this(x)(y.toString, js.undefined)
   }
 
+  object ConstructorSuperCallWithDefaultParams {
+    val sideEffects = mutable.ListBuffer.empty[String]
+
+    class Parent(parentParam1: Any = "param1", parentParam2: Any = "param2")(
+        dependentParam: String = s"$parentParam1-$parentParam2")
+        extends js.Object {
+      sideEffects += s"Parent constructor; $parentParam1, $parentParam2, $dependentParam"
+    }
+
+    class Child(val foo: Int, parentParam2: Any, val bar: Int)
+        extends Parent(parentParam2 = { sideEffects += foo.toString(); foo + bar })() {
+      sideEffects += s"Child constructor; $foo, $parentParam2, $bar"
+    }
+  }
+
   class OverloadedConstructorParamNumber(val foo: Int) extends js.Object {
     def this(x: Int, y: Int) = this(x + y)
     def this(x: Int, y: Int, z: Int) = this(x + y, z)

From db3b3ab640910b09a5a333a437c9aa02286e2ab5 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Wed, 24 Jan 2024 13:42:20 +0100
Subject: [PATCH 039/298] Use `genSelect` in the intrinsics that access
 `jl.Class.data`.

Instead of hard-coding the `"jl_Class__f_data"` string.
---
 .../org/scalajs/linker/backend/emitter/EmitterNames.scala  | 1 +
 .../scalajs/linker/backend/emitter/FunctionEmitter.scala   | 7 ++++---
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/EmitterNames.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/EmitterNames.scala
index 17c03b75dc..4c1bcebc2b 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/EmitterNames.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/EmitterNames.scala
@@ -26,6 +26,7 @@ private[emitter] object EmitterNames {
 
   // Field names
 
+  val dataFieldName = FieldName("data")
   val exceptionFieldName = FieldName("exception")
 
   // Method names
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
index c299d8fdd7..3f8dc28427 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
@@ -2733,7 +2733,8 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
 
         case Transient(ZeroOf(runtimeClass)) =>
           js.DotSelect(
-              js.DotSelect(transformExprNoChar(checkNotNull(runtimeClass)), js.Ident("jl_Class__f_data")),
+              genSelect(transformExprNoChar(checkNotNull(runtimeClass)),
+                  ClassClass, FieldIdent(dataFieldName)),
               js.Ident("zero"))
 
         case Transient(NativeArrayWrapper(elemClass, nativeArray)) =>
@@ -2744,9 +2745,9 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
               extractWithGlobals(
                   genNativeArrayWrapper(arrayTypeRef, newNativeArray))
             case _ =>
-              val elemClassData = js.DotSelect(
+              val elemClassData = genSelect(
                   transformExprNoChar(checkNotNull(elemClass)),
-                  js.Ident("jl_Class__f_data"))
+                  ClassClass, FieldIdent(dataFieldName))
               val arrayClassData = js.Apply(
                   js.DotSelect(elemClassData, js.Ident("getArrayOf")), Nil)
               js.Apply(arrayClassData DOT "wrapArray", newNativeArray :: Nil)

From 96980516b4e8f477ca54a70f6d076678f8f94513 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Wed, 24 Jan 2024 13:46:51 +0100
Subject: [PATCH 040/298] Go through SJSGen to generate Scala method names.

This centralizes the decision on how to emit method names in one
place, like we already had for fields.
---
 .../linker/backend/emitter/ClassEmitter.scala |  2 +-
 .../linker/backend/emitter/CoreJSLib.scala    | 14 ++---
 .../backend/emitter/FunctionEmitter.scala     | 54 +++++++++----------
 .../linker/backend/emitter/SJSGen.scala       | 17 +++++-
 4 files changed, 47 insertions(+), 40 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
index aade6c4b8a..4a502b6331 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
@@ -670,7 +670,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
 
   private def genMemberMethodIdent(ident: MethodIdent,
       originalName: OriginalName): js.Ident = {
-    val jsName = genName(ident.name)
+    val jsName = genMethodName(ident.name)
     js.Ident(jsName, genOriginalName(ident.name, originalName, jsName))(
         ident.pos)
   }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
index 290bb7f362..6aff172312 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
@@ -717,7 +717,7 @@ private[emitter] object CoreJSLib {
       defineFunction1(VarField.objectOrArrayClone) { instance =>
         // return instance.$classData.isArrayClass ? instance.clone__O() : $objectClone(instance);
         Return(If(genIdentBracketSelect(instance DOT classData, "isArrayClass"),
-            Apply(instance DOT genName(cloneMethodName), Nil),
+            genApply(instance, cloneMethodName, Nil),
             genCallHelper(VarField.objectClone, instance)))
       }
     )
@@ -767,7 +767,7 @@ private[emitter] object CoreJSLib {
           ), {
             If(instance === Null(), {
               if (nullPointers == CheckedBehavior.Unchecked)
-                Return(Apply(instance DOT genName(getClassMethodName), Nil))
+                Return(genApply(instance, getClassMethodName, Nil))
               else
                 genCallHelper(VarField.throwNullPointerException)
             }, {
@@ -813,7 +813,7 @@ private[emitter] object CoreJSLib {
           instance => genIdentBracketSelect(instance DOT classData, "name"),
           {
             if (nullPointers == CheckedBehavior.Unchecked)
-              Apply(Null() DOT genName(getNameMethodName), Nil)
+              genApply(Null(), getNameMethodName, Nil)
             else
               genCallHelper(VarField.throwNullPointerException)
           }
@@ -862,7 +862,7 @@ private[emitter] object CoreJSLib {
         }
 
         def genBodyNoSwitch(hijackedClasses: List[ClassName]): Tree = {
-          val normalCall = Return(Apply(instance DOT genName(methodName), args))
+          val normalCall = Return(genApply(instance, methodName, args))
 
           def hijackedDispatch(default: Tree) = {
             hijackedClasses.foldRight(default) { (className, next) =>
@@ -874,7 +874,7 @@ private[emitter] object CoreJSLib {
 
           if (implementedInObject) {
             val staticObjectCall: Tree = {
-              val fun = globalVar(VarField.c, ObjectClass).prototype DOT genName(methodName)
+              val fun = globalVar(VarField.c, ObjectClass).prototype DOT genMethodName(methodName)
               Return(Apply(fun DOT "call", instance :: args))
             }
 
@@ -1498,7 +1498,7 @@ private[emitter] object CoreJSLib {
           Nil
         }
 
-        val clone = MethodDef(static = false, Ident(genName(cloneMethodName)), Nil, None, {
+        val clone = MethodDef(static = false, Ident(genMethodName(cloneMethodName)), Nil, None, {
           Return(New(ArrayClass,
               Apply(genIdentBracketSelect(This().u, "slice"), Nil) :: Nil))
         })
@@ -1803,7 +1803,7 @@ private[emitter] object CoreJSLib {
               Nil
             }
 
-            val clone = MethodDef(static = false, Ident(genName(cloneMethodName)), Nil, None, {
+            val clone = MethodDef(static = false, Ident(genMethodName(cloneMethodName)), Nil, None, {
               Return(New(ArrayClass,
                   Apply(genIdentBracketSelect(This().u, "slice"), Nil) :: Nil))
             })
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
index 3f8dc28427..9ee6f42ecd 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
@@ -2352,7 +2352,7 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
               if (useBigIntForLongs)
                 js.Apply(genGlobalVarRef("Number"), List(wrapBigInt32(newLhs)))
               else
-                genLongMethodApply(newLhs, LongImpl.toInt)
+                genApply(newLhs, LongImpl.toInt)
             case DoubleToInt =>
               genCallHelper(VarField.doubleToInt, newLhs)
             case DoubleToFloat =>
@@ -2363,7 +2363,7 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
               if (useBigIntForLongs)
                 js.Apply(genGlobalVarRef("Number"), List(newLhs))
               else
-                genLongMethodApply(newLhs, LongImpl.toDouble)
+                genApply(newLhs, LongImpl.toDouble)
             case DoubleToLong =>
               if (useBigIntForLongs)
                 genCallHelper(VarField.doubleToLong, newLhs)
@@ -2375,7 +2375,7 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
               if (useBigIntForLongs)
                 genCallHelper(VarField.longToFloat, newLhs)
               else
-                genLongMethodApply(newLhs, LongImpl.toFloat)
+                genApply(newLhs, LongImpl.toFloat)
 
             // String.length
             case String_length =>
@@ -2488,25 +2488,25 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
               if (useBigIntForLongs)
                 wrapBigInt64(js.BinaryOp(JSBinaryOp.+, newLhs, newRhs))
               else
-                genLongMethodApply(newLhs, LongImpl.+, newRhs)
+                genApply(newLhs, LongImpl.+, newRhs)
             case Long_- =>
               lhs match {
                 case LongLiteral(0L) =>
                   if (useBigIntForLongs)
                     wrapBigInt64(js.UnaryOp(JSUnaryOp.-, newRhs))
                   else
-                    genLongMethodApply(newRhs, LongImpl.UNARY_-)
+                    genApply(newRhs, LongImpl.UNARY_-)
                 case _ =>
                   if (useBigIntForLongs)
                     wrapBigInt64(js.BinaryOp(JSBinaryOp.-, newLhs, newRhs))
                   else
-                    genLongMethodApply(newLhs, LongImpl.-, newRhs)
+                    genApply(newLhs, LongImpl.-, newRhs)
               }
             case Long_* =>
               if (useBigIntForLongs)
                 wrapBigInt64(js.BinaryOp(JSBinaryOp.*, newLhs, newRhs))
               else
-                genLongMethodApply(newLhs, LongImpl.*, newRhs)
+                genApply(newLhs, LongImpl.*, newRhs)
             case Long_/ =>
               if (useBigIntForLongs) {
                 rhs match {
@@ -2516,7 +2516,7 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
                     genCallHelper(VarField.longDiv, newLhs, newRhs)
                 }
               } else {
-                genLongMethodApply(newLhs, LongImpl./, newRhs)
+                genApply(newLhs, LongImpl./, newRhs)
               }
             case Long_% =>
               if (useBigIntForLongs) {
@@ -2527,78 +2527,78 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
                     genCallHelper(VarField.longMod, newLhs, newRhs)
                 }
               } else {
-                genLongMethodApply(newLhs, LongImpl.%, newRhs)
+                genApply(newLhs, LongImpl.%, newRhs)
               }
 
             case Long_| =>
               if (useBigIntForLongs)
                 wrapBigInt64(js.BinaryOp(JSBinaryOp.|, newLhs, newRhs))
               else
-                genLongMethodApply(newLhs, LongImpl.|, newRhs)
+                genApply(newLhs, LongImpl.|, newRhs)
             case Long_& =>
               if (useBigIntForLongs)
                 wrapBigInt64(js.BinaryOp(JSBinaryOp.&, newLhs, newRhs))
               else
-                genLongMethodApply(newLhs, LongImpl.&, newRhs)
+                genApply(newLhs, LongImpl.&, newRhs)
             case Long_^ =>
               lhs match {
                 case LongLiteral(-1L) =>
                   if (useBigIntForLongs)
                     wrapBigInt64(js.UnaryOp(JSUnaryOp.~, newRhs))
                   else
-                    genLongMethodApply(newRhs, LongImpl.UNARY_~)
+                    genApply(newRhs, LongImpl.UNARY_~)
                 case _ =>
                   if (useBigIntForLongs)
                     wrapBigInt64(js.BinaryOp(JSBinaryOp.^, newLhs, newRhs))
                   else
-                    genLongMethodApply(newLhs, LongImpl.^, newRhs)
+                    genApply(newLhs, LongImpl.^, newRhs)
               }
             case Long_<< =>
               if (useBigIntForLongs)
                 wrapBigInt64(js.BinaryOp(JSBinaryOp.<<, newLhs, bigIntShiftRhs(newRhs)))
               else
-                genLongMethodApply(newLhs, LongImpl.<<, newRhs)
+                genApply(newLhs, LongImpl.<<, newRhs)
             case Long_>>> =>
               if (useBigIntForLongs)
                 wrapBigInt64(js.BinaryOp(JSBinaryOp.>>, wrapBigIntU64(newLhs), bigIntShiftRhs(newRhs)))
               else
-                genLongMethodApply(newLhs, LongImpl.>>>, newRhs)
+                genApply(newLhs, LongImpl.>>>, newRhs)
             case Long_>> =>
               if (useBigIntForLongs)
                 wrapBigInt64(js.BinaryOp(JSBinaryOp.>>, newLhs, bigIntShiftRhs(newRhs)))
               else
-                genLongMethodApply(newLhs, LongImpl.>>, newRhs)
+                genApply(newLhs, LongImpl.>>, newRhs)
 
             case Long_== =>
               if (useBigIntForLongs)
                 js.BinaryOp(JSBinaryOp.===, newLhs, newRhs)
               else
-                genLongMethodApply(newLhs, LongImpl.===, newRhs)
+                genApply(newLhs, LongImpl.===, newRhs)
             case Long_!= =>
               if (useBigIntForLongs)
                 js.BinaryOp(JSBinaryOp.!==, newLhs, newRhs)
               else
-                genLongMethodApply(newLhs, LongImpl.!==, newRhs)
+                genApply(newLhs, LongImpl.!==, newRhs)
             case Long_< =>
               if (useBigIntForLongs)
                 js.BinaryOp(JSBinaryOp.<, newLhs, newRhs)
               else
-                genLongMethodApply(newLhs, LongImpl.<, newRhs)
+                genApply(newLhs, LongImpl.<, newRhs)
             case Long_<= =>
               if (useBigIntForLongs)
                 js.BinaryOp(JSBinaryOp.<=, newLhs, newRhs)
               else
-                genLongMethodApply(newLhs, LongImpl.<=, newRhs)
+                genApply(newLhs, LongImpl.<=, newRhs)
             case Long_> =>
               if (useBigIntForLongs)
                 js.BinaryOp(JSBinaryOp.>, newLhs, newRhs)
               else
-                genLongMethodApply(newLhs, LongImpl.>, newRhs)
+                genApply(newLhs, LongImpl.>, newRhs)
             case Long_>= =>
               if (useBigIntForLongs)
                 js.BinaryOp(JSBinaryOp.>=, newLhs, newRhs)
               else
-                genLongMethodApply(newLhs, LongImpl.>=, newRhs)
+                genApply(newLhs, LongImpl.>=, newRhs)
 
             case Float_+ => genFround(js.BinaryOp(JSBinaryOp.+, newLhs, newRhs))
             case Float_- => genFround(js.BinaryOp(JSBinaryOp.-, newLhs, newRhs))
@@ -2684,7 +2684,7 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
              * those cases, leaving a `Clone()` node an array.
              */
             case _: ArrayType =>
-              js.Apply(newExpr DOT genName(cloneMethodName), Nil)
+              genApply(newExpr, cloneMethodName, Nil)
 
             /* Otherwise, if it might be an array, use the full dispatcher.
              * In theory, only the `CloneableClass` case is required, since
@@ -3201,7 +3201,7 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
       js.Ident(genName(ident.name))(ident.pos)
 
     private def transformMethodIdent(ident: MethodIdent): js.Ident =
-      js.Ident(genName(ident.name))(ident.pos)
+      js.Ident(genMethodName(ident.name))(ident.pos)
 
     private def transformLocalVarIdent(ident: LocalIdent): js.Ident =
       js.Ident(transformLocalName(ident.name))(ident.pos)
@@ -3268,12 +3268,6 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
       js.Apply(genIdentBracketSelect(genGlobalVarRef("BigInt"), "asUintN"),
           List(js.IntLiteral(n), tree))
     }
-
-    private def genLongMethodApply(receiver: js.Tree, methodName: MethodName,
-        args: js.Tree*)(implicit pos: Position): js.Tree = {
-      import TreeDSL._
-      js.Apply(receiver DOT genName(methodName), args.toList)
-    }
   }
 }
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala
index 0449e0ed92..6100df00eb 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala
@@ -107,8 +107,8 @@ private[emitter] final class SJSGen(
       implicit moduleContext: ModuleContext, globalKnowledge: GlobalKnowledge,
       pos: Position): Tree = {
     import TreeDSL._
-    Apply(
-        genLoadModule(LongImpl.RuntimeLongModuleClass) DOT genName(methodName),
+    genApply(
+        genLoadModule(LongImpl.RuntimeLongModuleClass), methodName,
         args.toList)
   }
 
@@ -172,6 +172,19 @@ private[emitter] final class SJSGen(
   private def genFieldJSName(className: ClassName, field: irt.FieldIdent): String =
     genName(className) + "__f_" + genName(field.name)
 
+  def genApply(receiver: Tree, methodName: MethodName, args: List[Tree])(
+      implicit pos: Position): Tree = {
+    Apply(DotSelect(receiver, Ident(genMethodName(methodName))), args)
+  }
+
+  def genApply(receiver: Tree, methodName: MethodName, args: Tree*)(
+      implicit pos: Position): Tree = {
+    genApply(receiver, methodName, args.toList)
+  }
+
+  def genMethodName(methodName: MethodName): String =
+    genName(methodName)
+
   def genJSPrivateSelect(receiver: Tree, className: ClassName,
       field: irt.FieldIdent)(
       implicit moduleContext: ModuleContext, globalKnowledge: GlobalKnowledge,

From 73ad25c7be8c8a723c8f59fd018e198b5c86a44d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Wed, 24 Jan 2024 14:24:05 +0100
Subject: [PATCH 041/298] Transform and traverse the `name` subtree of
 `JSMethodPropDef`s.

---
 ir/shared/src/main/scala/org/scalajs/ir/Transformers.scala | 4 ++--
 ir/shared/src/main/scala/org/scalajs/ir/Traversers.scala   | 6 ++++--
 2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Transformers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Transformers.scala
index 99a72aedb9..879864c047 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Transformers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Transformers.scala
@@ -267,7 +267,7 @@ object Transformers {
         case JSPropertyDef(flags, name, getterBody, setterArgAndBody) =>
           JSPropertyDef(
               flags,
-              name,
+              transformExpr(name),
               getterBody.map(transformStat),
               setterArgAndBody map { case (arg, body) =>
                 (arg, transformStat(body))
@@ -277,7 +277,7 @@ object Transformers {
 
     def transformJSMethodDef(jsMethodDef: JSMethodDef): JSMethodDef = {
       val JSMethodDef(flags, name, args, restParam, body) = jsMethodDef
-      JSMethodDef(flags, name, args, restParam, transformExpr(body))(
+      JSMethodDef(flags, transformExpr(name), args, restParam, transformExpr(body))(
           jsMethodDef.optimizerHints, Unversioned)(jsMethodDef.pos)
     }
 
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Traversers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Traversers.scala
index 7a4f5d9756..be26304b96 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Traversers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Traversers.scala
@@ -246,10 +246,12 @@ object Traversers {
 
     def traverseJSMethodPropDef(jsMethodPropDef: JSMethodPropDef): Unit = {
       jsMethodPropDef match {
-        case JSMethodDef(_, _, _, _, body) =>
+        case JSMethodDef(_, name, _, _, body) =>
+          traverse(name)
           traverse(body)
 
-        case JSPropertyDef(_, _, getterBody, setterArgAndBody) =>
+        case JSPropertyDef(_, name, getterBody, setterArgAndBody) =>
+          traverse(name)
           getterBody.foreach(traverse)
           setterArgAndBody.foreach(argAndBody => traverse(argAndBody._2))
       }

From 374b13e6e82cfe7f5f380d7de6b8be7f9245d966 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Wed, 24 Jan 2024 17:30:11 +0100
Subject: [PATCH 042/298] Use implicits to be more explicit about global refs
 tracking.

Normally, unless we track all global refs for the benefit of GCC,
we prune away non-dangerous global refs as soon as possible, to
preserve empty sets. This is done in two ways:

* Within `FunctionEmitter`, we track everything for local purposes,
  but then prune the non-dangerous global refs when escaping back
  to `ClassEmitter`.
* Everywhere else, we don't track non-dangerous global refs in
  the first place.

This policy was broken in two places, because of helper code that
is called both from inside and outside `FunctionEmitter`. In
general, the way we applied that policy was very fragile, notably
because it was not explicit what methods could be called in what
context.

We now use an `implicit GlobalRefTracking` in methods that
generate global refs. The `GlobalRefTracking` indicates which
set of global refs need to be tracked in the current context.
Ironically, these implicits make it more explicit when we need to
track what.
---
 .../linker/backend/emitter/ClassEmitter.scala | 20 +++---
 .../linker/backend/emitter/CoreJSLib.scala    |  5 +-
 .../linker/backend/emitter/Emitter.scala      | 14 ++++-
 .../backend/emitter/FunctionEmitter.scala     | 55 +++++++++--------
 .../backend/emitter/GlobalRefTracking.scala   | 47 ++++++++++++++
 .../linker/backend/emitter/JSGen.scala        | 16 +++--
 .../linker/backend/emitter/SJSGen.scala       | 61 +++++++++----------
 .../linker/backend/emitter/VarGen.scala       | 20 +++---
 8 files changed, 147 insertions(+), 91 deletions(-)
 create mode 100644 linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/GlobalRefTracking.scala

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
index 4a502b6331..dff91a1fd1 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
@@ -43,6 +43,9 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
   import nameGen._
   import varGen._
 
+  private implicit val globalRefTracking: GlobalRefTracking =
+    topLevelGlobalRefTracking
+
   def buildClass(className: ClassName, isJSClass: Boolean, jsClassCaptures: Option[List[ParamDef]],
       hasClassInitializer: Boolean,
       superClass: Option[ClassIdent], storeJSSuperClass: List[js.Tree], useESClass: Boolean,
@@ -56,7 +59,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
       if (useESClass) {
         val parentVarWithGlobals = for (parentIdent <- superClass) yield {
           implicit val pos = parentIdent.pos
-          if (shouldExtendJSError(className, superClass)) untrackedGlobalRef("Error")
+          if (shouldExtendJSError(className, superClass)) globalRef("Error")
           else WithGlobals(globalVar(VarField.c, parentIdent.name))
         }
 
@@ -186,7 +189,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
           WithGlobals.nil
 
         case Some(_) if shouldExtendJSError(className, superClass) =>
-          untrackedGlobalRef("Error").map(chainPrototypeWithLocalCtor(className, ctorVar, _))
+          globalRef("Error").map(chainPrototypeWithLocalCtor(className, ctorVar, _))
 
         case Some(parentIdent) =>
           WithGlobals(List(ctorVar.prototype := js.New(globalVar(VarField.h, parentIdent.name), Nil)))
@@ -252,7 +255,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
     if (hasJSSuperClass) {
       WithGlobals(fileLevelVar(VarField.superClass))
     } else {
-      genJSClassConstructor(superClass.get.name, keepOnlyDangerousVarNames = true)
+      genJSClassConstructor(superClass.get.name)
     }
   }
 
@@ -899,8 +902,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
           }))
         } else {
           for {
-            jsCtor <- genJSClassConstructor(className, jsNativeLoadSpec,
-                keepOnlyDangerousVarNames = true)
+            jsCtor <- genJSClassConstructor(className, jsNativeLoadSpec)
           } yield {
             genArrowFunction(List(js.ParamDef(js.Ident("x"))), None, js.Return {
               js.VarRef(js.Ident("x")) instanceof jsCtor
@@ -1075,12 +1077,8 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
 
   private def genAssignToNoModuleExportVar(exportName: String, rhs: js.Tree)(
       implicit pos: Position): WithGlobals[js.Tree] = {
-    val dangerousGlobalRefs: Set[String] =
-      if (GlobalRefUtils.isDangerousGlobalRef(exportName)) Set(exportName)
-      else Set.empty
-    WithGlobals(
-        js.Assign(js.VarRef(js.Ident(exportName)), rhs),
-        dangerousGlobalRefs)
+    for (exportVar <- globalRef(exportName)) yield
+      js.Assign(exportVar, rhs)
   }
 
   private def genTopLevelFieldExportDef(className: ClassName,
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
index 6aff172312..b36e35783d 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
@@ -71,6 +71,9 @@ private[emitter] object CoreJSLib {
 
     implicit private val noPosition: Position = Position.NoPosition
 
+    private implicit val globalRefTracking: GlobalRefTracking =
+      topLevelGlobalRefTracking
+
     private var trackedGlobalRefs = Set.empty[String]
 
     private def globalRef(name: String): VarRef = {
@@ -81,7 +84,7 @@ private[emitter] object CoreJSLib {
     private def trackGlobalRef(name: String): Unit = {
       // We never access dangerous global refs from the core JS lib
       assert(!GlobalRefUtils.isDangerousGlobalRef(name))
-      if (trackAllGlobalRefs)
+      if (globalRefTracking.shouldTrack(name))
         trackedGlobalRefs += name
     }
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala
index 1906ffe84f..1a8b9bc517 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala
@@ -39,6 +39,9 @@ final class Emitter[E >: Null <: js.Tree](
   import Emitter._
   import config._
 
+  private implicit val globalRefTracking: GlobalRefTracking =
+    config.topLevelGlobalRefTracking
+
   private val knowledgeGuardian = new KnowledgeGuardian(config)
 
   private val uncachedKnowledge = new knowledgeGuardian.KnowledgeAccessor {}
@@ -173,15 +176,16 @@ final class Emitter[E >: Null <: js.Tree](
     val result = emitOnce(moduleSet, logger)
 
     val mentionedDangerousGlobalRefs =
-      if (!trackAllGlobalRefs) result.globalVarNames
-      else GlobalRefUtils.keepOnlyDangerousGlobalRefs(result.globalVarNames)
+      GlobalRefTracking.Dangerous.refineFrom(topLevelGlobalRefTracking, result.globalVarNames)
 
     if (mentionedDangerousGlobalRefs == state.lastMentionedDangerousGlobalRefs) {
       result
     } else {
       assert(!secondAttempt,
           "Uh oh! The second attempt gave a different set of dangerous " +
-          "global refs than the first one.")
+          "global refs than the first one.\n" +
+          "Before:" + state.lastMentionedDangerousGlobalRefs.toList.sorted.mkString("\n  ", "\n  ", "\n") +
+          "After:" + mentionedDangerousGlobalRefs.toList.sorted.mkString("\n  ", "\n  ", ""))
 
       // !!! This log message is tested in EmitterTest
       logger.debug(
@@ -1096,6 +1100,10 @@ object Emitter {
           trackAllGlobalRefs = false)
     }
 
+    private[emitter] val topLevelGlobalRefTracking: GlobalRefTracking =
+      if (trackAllGlobalRefs) GlobalRefTracking.All
+      else GlobalRefTracking.Dangerous
+
     def withSemantics(f: Semantics => Semantics): Config =
       copy(semantics = f(semantics))
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
index 9ee6f42ecd..d2f83eb4a3 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
@@ -259,7 +259,7 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
   def desugarToFunction(enclosingClassName: ClassName, params: List[ParamDef],
       body: Tree, resultType: Type)(
       implicit moduleContext: ModuleContext, globalKnowledge: GlobalKnowledge,
-      pos: Position): WithGlobals[js.Function] = {
+      globalRefTracking: GlobalRefTracking, pos: Position): WithGlobals[js.Function] = {
     desugarToFunction(enclosingClassName, params, restParam = None, body,
         resultType)
   }
@@ -269,10 +269,10 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
   def desugarToFunction(enclosingClassName: ClassName, params: List[ParamDef],
       restParam: Option[ParamDef], body: JSConstructorBody)(
       implicit moduleContext: ModuleContext, globalKnowledge: GlobalKnowledge,
-      pos: Position): WithGlobals[js.Function] = {
+      globalRefTracking: GlobalRefTracking, pos: Position): WithGlobals[js.Function] = {
     val bodyBlock = Block(body.allStats)(body.pos)
-    new JSDesugar().desugarToFunction(params, restParam, bodyBlock,
-        isStat = false,
+    new JSDesugar(globalRefTracking).desugarToFunction(
+        params, restParam, bodyBlock, isStat = false,
         Env.empty(AnyType).withEnclosingClassName(Some(enclosingClassName)))
   }
 
@@ -281,9 +281,9 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
   def desugarToFunction(enclosingClassName: ClassName, params: List[ParamDef],
       restParam: Option[ParamDef], body: Tree, resultType: Type)(
       implicit moduleContext: ModuleContext, globalKnowledge: GlobalKnowledge,
-      pos: Position): WithGlobals[js.Function] = {
-    new JSDesugar().desugarToFunction(params, restParam, body,
-        isStat = resultType == NoType,
+      globalRefTracking: GlobalRefTracking, pos: Position): WithGlobals[js.Function] = {
+    new JSDesugar(globalRefTracking).desugarToFunction(
+        params, restParam, body, isStat = resultType == NoType,
         Env.empty(resultType).withEnclosingClassName(Some(enclosingClassName)))
   }
 
@@ -293,9 +293,9 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
   def desugarToFunctionWithExplicitThis(enclosingClassName: ClassName,
       params: List[ParamDef], body: Tree, resultType: Type)(
       implicit moduleContext: ModuleContext, globalKnowledge: GlobalKnowledge,
-      pos: Position): WithGlobals[js.Function] = {
-    new JSDesugar().desugarToFunctionWithExplicitThis(params, body,
-        isStat = resultType == NoType,
+      globalRefTracking: GlobalRefTracking, pos: Position): WithGlobals[js.Function] = {
+    new JSDesugar(globalRefTracking).desugarToFunctionWithExplicitThis(
+        params, body, isStat = resultType == NoType,
         Env.empty(resultType).withEnclosingClassName(Some(enclosingClassName)))
   }
 
@@ -304,15 +304,16 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
   def desugarToFunction(params: List[ParamDef], restParam: Option[ParamDef],
       body: Tree, resultType: Type)(
       implicit moduleContext: ModuleContext, globalKnowledge: GlobalKnowledge,
-      pos: Position): WithGlobals[js.Function] = {
-    new JSDesugar().desugarToFunction(params, restParam, body,
-        isStat = resultType == NoType, Env.empty(resultType))
+      globalRefTracking: GlobalRefTracking, pos: Position): WithGlobals[js.Function] = {
+    new JSDesugar(globalRefTracking).desugarToFunction(
+        params, restParam, body, isStat = resultType == NoType,
+        Env.empty(resultType))
   }
 
   /** Desugars a class-level expression. */
   def desugarExpr(expr: Tree, resultType: Type)(
-      implicit moduleContext: ModuleContext,
-      globalKnowledge: GlobalKnowledge): WithGlobals[js.Tree] = {
+      implicit moduleContext: ModuleContext, globalKnowledge: GlobalKnowledge,
+      globalRefTracking: GlobalRefTracking): WithGlobals[js.Tree] = {
     implicit val pos = expr.pos
 
     for (fun <- desugarToFunction(Nil, None, expr, resultType)) yield {
@@ -326,9 +327,13 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
     }
   }
 
-  private class JSDesugar()(
+  private class JSDesugar(outerGlobalRefTracking: GlobalRefTracking)(
       implicit moduleContext: ModuleContext, globalKnowledge: GlobalKnowledge) {
 
+    // Inside JSDesugar, we always track everything
+    private implicit val globalRefTracking: GlobalRefTracking =
+      GlobalRefTracking.All
+
     // For convenience
     private val es2015 = esFeatures.esVersion >= ESVersion.ES2015
 
@@ -410,7 +415,7 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
       val result = body
       if (!isOptimisticNamingRun || !globalVarNames.exists(localVarNames)) {
         /* At this point, filter out the global refs that do not need to be
-         * tracked across functions and classes.
+         * tracked in the outer context.
          *
          * By default, only dangerous global refs need to be tracked outside of
          * functions, to power `mentionedDangerousGlobalRefs` In that case, the
@@ -422,11 +427,10 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
          * need to track all global variables across functions and classes. This is
          * slower, but running GCC will take most of the time anyway in that case.
          */
-        val globalRefs =
-          if (trackAllGlobalRefs) globalVarNames.toSet
-          else GlobalRefUtils.keepOnlyDangerousGlobalRefs(globalVarNames.toSet)
+        val outerGlobalRefs =
+          outerGlobalRefTracking.refineFrom(globalRefTracking, globalVarNames.toSet)
 
-        WithGlobals(result, globalRefs)
+        WithGlobals(result, outerGlobalRefs)
       } else {
         /* Clear the local var names, but *not* the global var names.
          * In the pessimistic run, we will use the knowledge gathered during
@@ -2214,8 +2218,7 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
         case SelectJSNativeMember(className, member) =>
           val jsNativeLoadSpec =
             globalKnowledge.getJSNativeLoadSpec(className, member.name)
-          extractWithGlobals(genLoadJSFromSpec(
-              jsNativeLoadSpec, keepOnlyDangerousVarNames = false))
+          extractWithGlobals(genLoadJSFromSpec(jsNativeLoadSpec))
 
         case Apply(_, receiver, method, args) =>
           val methodName = method.name
@@ -2863,8 +2866,7 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
               genLoadModule(className)
 
             case Some(spec) =>
-              extractWithGlobals(
-                  genLoadJSFromSpec(spec, keepOnlyDangerousVarNames = false))
+              extractWithGlobals(genLoadJSFromSpec(spec))
           }
 
         case JSUnaryOp(op, lhs) =>
@@ -3229,8 +3231,7 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
      */
     private def genJSClassConstructor(className: ClassName)(
         implicit pos: Position): WithGlobals[js.Tree] = {
-      sjsGen.genJSClassConstructor(className,
-          keepOnlyDangerousVarNames = false)
+      sjsGen.genJSClassConstructor(className)
     }
 
     private def genApplyStaticLike(field: VarField, className: ClassName,
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/GlobalRefTracking.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/GlobalRefTracking.scala
new file mode 100644
index 0000000000..13f32d5ebc
--- /dev/null
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/GlobalRefTracking.scala
@@ -0,0 +1,47 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package org.scalajs.linker.backend.emitter
+
+/** Amount of global ref tracking that we need to do in a given context.
+ *
+ *  - When using GCC, we always track all global refs;
+ *  - Otherwise, inside the body of a function, in `FunctionEmitter`, we track
+ *    all global refs so that we can identify collisions with locally allocated
+ *    variable names;
+ *  - Otherwise, we only track dangerous global refs.
+ */
+private[emitter] sealed abstract class GlobalRefTracking {
+  import GlobalRefTracking._
+
+  def shouldTrack(globalRef: String): Boolean = this match {
+    case All       => true
+    case Dangerous => GlobalRefUtils.isDangerousGlobalRef(globalRef)
+  }
+
+  /** Given a set of global refs tracked under the rules of `fromTracking`,
+   *  keep only the ones needed according to `this`.
+   */
+  def refineFrom(fromTracking: GlobalRefTracking, globalRefs: Set[String]): Set[String] = {
+    if (this == fromTracking)
+      globalRefs
+    else if (this == Dangerous)
+      GlobalRefUtils.keepOnlyDangerousGlobalRefs(globalRefs)
+    else
+      throw new AssertionError(s"Cannot refine set of global refs from $fromTracking to $this")
+  }
+}
+
+private[emitter] object GlobalRefTracking {
+  case object All extends GlobalRefTracking
+  case object Dangerous extends GlobalRefTracking
+}
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/JSGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/JSGen.scala
index 3ed36197a5..9d0150c2c9 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/JSGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/JSGen.scala
@@ -127,7 +127,7 @@ private[emitter] final class JSGen(val config: Emitter.Config) {
   }
 
   def genDefineProperty(obj: Tree, prop: Tree, descriptor: List[(String, Tree)])(
-      implicit pos: Position): WithGlobals[Tree] = {
+      implicit tracking: GlobalRefTracking, pos: Position): WithGlobals[Tree] = {
     val descriptorTree =
         ObjectConstr(descriptor.map(x => StringLiteral(x._1) -> x._2))
 
@@ -137,14 +137,12 @@ private[emitter] final class JSGen(val config: Emitter.Config) {
     }
   }
 
-  def globalRef(name: String)(implicit pos: Position): WithGlobals[VarRef] =
-    WithGlobals(VarRef(Ident(name)), Set(name))
-
-  def untrackedGlobalRef(name: String)(implicit pos: Position): WithGlobals[VarRef] = {
-    assert(!GlobalRefUtils.isDangerousGlobalRef(name))
-
-    if (trackAllGlobalRefs) globalRef(name)
-    else WithGlobals(VarRef(Ident(name)))
+  def globalRef(name: String)(
+      implicit tracking: GlobalRefTracking, pos: Position): WithGlobals[VarRef] = {
+    val trackedSet: Set[String] =
+      if (tracking.shouldTrack(name)) Set(name)
+      else Set.empty
+    WithGlobals(VarRef(Ident(name)), trackedSet)
   }
 
   def genPropSelect(qual: Tree, item: PropertyName)(
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala
index 6100df00eb..4cc050d33c 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala
@@ -112,11 +112,18 @@ private[emitter] final class SJSGen(
         args.toList)
   }
 
-  def usesUnderlyingTypedArray(elemTypeRef: NonArrayTypeRef): Boolean =
-    getArrayUnderlyingTypedArrayClassRef(elemTypeRef)(Position.NoPosition).nonEmpty
+  def usesUnderlyingTypedArray(elemTypeRef: NonArrayTypeRef): Boolean = {
+    /* We are only interested in whether `getArrayUnderlyingTypedArrayClassRef`
+     * returns a `Some` or not. We do not keep the result, so the `Position`
+     * and the `GlobalRefTracking` are irrelevant.
+     */
+    implicit val dontCareGlobalRefTracking = GlobalRefTracking.Dangerous
+    implicit val dontCarePosition = Position.NoPosition
+    getArrayUnderlyingTypedArrayClassRef(elemTypeRef).nonEmpty
+  }
 
   def getArrayUnderlyingTypedArrayClassRef(elemTypeRef: NonArrayTypeRef)(
-      implicit pos: Position): Option[WithGlobals[VarRef]] = {
+      implicit tracking: GlobalRefTracking, pos: Position): Option[WithGlobals[VarRef]] = {
     elemTypeRef match {
       case _ if esFeatures.esVersion < ESVersion.ES2015 => None
       case primRef: PrimRef                             => typedArrayRef(primRef)
@@ -125,7 +132,7 @@ private[emitter] final class SJSGen(
   }
 
   def typedArrayRef(primRef: PrimRef)(
-      implicit pos: Position): Option[WithGlobals[VarRef]] = {
+      implicit tracking: GlobalRefTracking, pos: Position): Option[WithGlobals[VarRef]] = {
     def some(name: String) = Some(globalRef(name))
 
     primRef match {
@@ -295,7 +302,7 @@ private[emitter] final class SJSGen(
 
   def genAsInstanceOf(expr: Tree, tpe: Type)(
       implicit moduleContext: ModuleContext, globalKnowledge: GlobalKnowledge,
-      pos: Position): WithGlobals[Tree] = {
+      tracking: GlobalRefTracking, pos: Position): WithGlobals[Tree] = {
     import TreeDSL._
 
     // Local short-hand of WithGlobals(...)
@@ -407,7 +414,7 @@ private[emitter] final class SJSGen(
 
   def genCallPolyfillableBuiltin(builtin: PolyfillableBuiltin, args: Tree*)(
       implicit moduleContext: ModuleContext, globalKnowledge: GlobalKnowledge,
-      pos: Position): WithGlobals[Tree] = {
+      tracking: GlobalRefTracking, pos: Position): WithGlobals[Tree] = {
     if (esFeatures.esVersion >= builtin.availableInESVersion) {
       builtin match {
         case builtin: GlobalVarBuiltin =>
@@ -441,28 +448,25 @@ private[emitter] final class SJSGen(
     }
   }
 
-  def genJSClassConstructor(className: ClassName,
-      keepOnlyDangerousVarNames: Boolean)(
+  def genJSClassConstructor(className: ClassName)(
       implicit moduleContext: ModuleContext, globalKnowledge: GlobalKnowledge,
-      pos: Position): WithGlobals[Tree] = {
+      tracking: GlobalRefTracking, pos: Position): WithGlobals[Tree] = {
 
     genJSClassConstructor(className,
-        globalKnowledge.getJSNativeLoadSpec(className),
-        keepOnlyDangerousVarNames)
+        globalKnowledge.getJSNativeLoadSpec(className))
   }
 
   def genJSClassConstructor(className: ClassName,
-      spec: Option[irt.JSNativeLoadSpec],
-      keepOnlyDangerousVarNames: Boolean)(
+      spec: Option[irt.JSNativeLoadSpec])(
       implicit moduleContext: ModuleContext, globalKnowledge: GlobalKnowledge,
-      pos: Position): WithGlobals[Tree] = {
+      tracking: GlobalRefTracking, pos: Position): WithGlobals[Tree] = {
     spec match {
       case None =>
         // This is a non-native JS class
         WithGlobals(genNonNativeJSClassConstructor(className))
 
       case Some(spec) =>
-        genLoadJSFromSpec(spec, keepOnlyDangerousVarNames)
+        genLoadJSFromSpec(spec)
     }
   }
 
@@ -472,10 +476,9 @@ private[emitter] final class SJSGen(
     Apply(globalVar(VarField.a, className), Nil)
   }
 
-  def genLoadJSFromSpec(spec: irt.JSNativeLoadSpec,
-      keepOnlyDangerousVarNames: Boolean)(
+  def genLoadJSFromSpec(spec: irt.JSNativeLoadSpec)(
       implicit moduleContext: ModuleContext, globalKnowledge: GlobalKnowledge,
-      pos: Position): WithGlobals[Tree] = {
+      tracking: GlobalRefTracking, pos: Position): WithGlobals[Tree] = {
 
     def pathSelection(from: Tree, path: List[String]): Tree = {
       path.foldLeft(from) {
@@ -484,17 +487,9 @@ private[emitter] final class SJSGen(
     }
 
     spec match {
-      case irt.JSNativeLoadSpec.Global(globalRef, path) =>
-        val globalVarRef = VarRef(Ident(globalRef))
-        val globalVarNames = {
-          if (keepOnlyDangerousVarNames && !trackAllGlobalRefs &&
-              !GlobalRefUtils.isDangerousGlobalRef(globalRef)) {
-            Set.empty[String]
-          } else {
-            Set(globalRef)
-          }
-        }
-        WithGlobals(pathSelection(globalVarRef, path), globalVarNames)
+      case irt.JSNativeLoadSpec.Global(globalRefName, path) =>
+        for (globalVarRef <- globalRef(globalRefName)) yield
+          pathSelection(globalVarRef, path)
 
       case irt.JSNativeLoadSpec.Import(module, path) =>
         val moduleValue = VarRef(externalModuleFieldIdent(module))
@@ -509,9 +504,9 @@ private[emitter] final class SJSGen(
       case irt.JSNativeLoadSpec.ImportWithGlobalFallback(importSpec, globalSpec) =>
         moduleKind match {
           case ModuleKind.NoModule =>
-            genLoadJSFromSpec(globalSpec, keepOnlyDangerousVarNames)
+            genLoadJSFromSpec(globalSpec)
           case ModuleKind.ESModule | ModuleKind.CommonJSModule =>
-            genLoadJSFromSpec(importSpec, keepOnlyDangerousVarNames)
+            genLoadJSFromSpec(importSpec)
         }
     }
   }
@@ -533,13 +528,13 @@ private[emitter] final class SJSGen(
 
   def genArrayValue(arrayTypeRef: ArrayTypeRef, elems: List[Tree])(
       implicit moduleContext: ModuleContext, globalKnowledge: GlobalKnowledge,
-      pos: Position): WithGlobals[Tree] = {
+      tracking: GlobalRefTracking, pos: Position): WithGlobals[Tree] = {
     genNativeArrayWrapper(arrayTypeRef, ArrayConstr(elems))
   }
 
   def genNativeArrayWrapper(arrayTypeRef: ArrayTypeRef, nativeArray: Tree)(
       implicit moduleContext: ModuleContext, globalKnowledge: GlobalKnowledge,
-      pos: Position): WithGlobals[Tree] = {
+      tracking: GlobalRefTracking, pos: Position): WithGlobals[Tree] = {
     val argWithGlobals = arrayTypeRef match {
       case ArrayTypeRef(elemTypeRef, 1) =>
         getArrayUnderlyingTypedArrayClassRef(elemTypeRef) match {
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/VarGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/VarGen.scala
index b58ac77235..7b7f87859d 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/VarGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/VarGen.scala
@@ -54,7 +54,8 @@ private[emitter] final class VarGen(jsGen: JSGen, nameGen: NameGen,
   def globalClassDef[T: Scope](field: VarField, scope: T,
       parentClass: Option[Tree], members: List[Tree],
       origName: OriginalName = NoOriginalName)(
-      implicit moduleContext: ModuleContext, pos: Position): WithGlobals[List[Tree]] = {
+      implicit moduleContext: ModuleContext,
+      globalRefTracking: GlobalRefTracking, pos: Position): WithGlobals[List[Tree]] = {
     val ident = globalVarIdent(field, scope, origName)
     maybeExport(ident, ClassDef(Some(ident), parentClass, members), mutable = false)
   }
@@ -62,14 +63,16 @@ private[emitter] final class VarGen(jsGen: JSGen, nameGen: NameGen,
   def globalFunctionDef[T: Scope](field: VarField, scope: T,
       args: List[ParamDef], restParam: Option[ParamDef], body: Tree,
       origName: OriginalName = NoOriginalName)(
-      implicit moduleContext: ModuleContext, pos: Position): WithGlobals[List[Tree]] = {
+      implicit moduleContext: ModuleContext,
+      globalRefTracking: GlobalRefTracking, pos: Position): WithGlobals[List[Tree]] = {
     val ident = globalVarIdent(field, scope, origName)
     maybeExport(ident, FunctionDef(ident, args, restParam, body), mutable = false)
   }
 
   def globalVarDef[T: Scope](field: VarField, scope: T, value: Tree,
       origName: OriginalName = NoOriginalName)(
-      implicit moduleContext: ModuleContext, pos: Position): WithGlobals[List[Tree]] = {
+      implicit moduleContext: ModuleContext,
+      globalRefTracking: GlobalRefTracking, pos: Position): WithGlobals[List[Tree]] = {
     val ident = globalVarIdent(field, scope, origName)
     maybeExport(ident, genConst(ident, value), mutable = false)
   }
@@ -77,7 +80,8 @@ private[emitter] final class VarGen(jsGen: JSGen, nameGen: NameGen,
   /** Attention: A globalVarDecl may only be modified from the module it was declared in. */
   def globalVarDecl[T: Scope](field: VarField, scope: T,
       origName: OriginalName = NoOriginalName)(
-      implicit moduleContext: ModuleContext, pos: Position): WithGlobals[List[Tree]] = {
+      implicit moduleContext: ModuleContext,
+      globalRefTracking: GlobalRefTracking, pos: Position): WithGlobals[List[Tree]] = {
     val ident = globalVarIdent(field, scope, origName)
     maybeExport(ident, genEmptyMutableLet(ident), mutable = true)
   }
@@ -88,7 +92,8 @@ private[emitter] final class VarGen(jsGen: JSGen, nameGen: NameGen,
    */
   def globallyMutableVarDef[T: Scope](field: VarField, setterField: VarField,
       scope: T, value: Tree, origName: OriginalName = NoOriginalName)(
-      implicit moduleContext: ModuleContext, pos: Position): WithGlobals[List[Tree]] = {
+      implicit moduleContext: ModuleContext,
+      globalRefTracking: GlobalRefTracking, pos: Position): WithGlobals[List[Tree]] = {
     val ident = globalVarIdent(field, scope, origName)
     val varDef = genLet(ident, mutable = true, value)
 
@@ -135,7 +140,7 @@ private[emitter] final class VarGen(jsGen: JSGen, nameGen: NameGen,
   /** Apply the provided body to a dynamically loaded global var */
   def withDynamicGlobalVar[T: Scope](field: VarField, scope: T)(body: Tree => Tree)(
       implicit moduleContext: ModuleContext, globalKnowledge: GlobalKnowledge,
-      pos: Position): WithGlobals[Tree] = {
+      globalRefTracking: GlobalRefTracking, pos: Position): WithGlobals[Tree] = {
     val ident = globalVarIdent(field, scope)
 
     val module = fileLevelVarIdent(VarField.module)
@@ -269,7 +274,8 @@ private[emitter] final class VarGen(jsGen: JSGen, nameGen: NameGen,
   }
 
   private def maybeExport(ident: Ident, tree: Tree, mutable: Boolean)(
-      implicit moduleContext: ModuleContext, pos: Position): WithGlobals[List[Tree]] = {
+      implicit moduleContext: ModuleContext,
+      globalRefTracking: GlobalRefTracking, pos: Position): WithGlobals[List[Tree]] = {
     if (moduleContext.public) {
       WithGlobals(tree :: Nil)
     } else {

From 7b1fece0fb665a40aa2ed05445b8df6ec2cdc7d9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Mon, 12 Feb 2024 11:41:47 +0100
Subject: [PATCH 043/298] Bump the version to 1.16.0-SNAPSHOT for the upcoming
 changes.

As well as the IR version to 1.16-SNAPSHOT.
---
 ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala b/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala
index 8dfbb764e2..91d113055f 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala
@@ -17,8 +17,8 @@ import java.util.concurrent.ConcurrentHashMap
 import scala.util.matching.Regex
 
 object ScalaJSVersions extends VersionChecks(
-    current = "1.15.1-SNAPSHOT",
-    binaryEmitted = "1.13"
+    current = "1.16.0-SNAPSHOT",
+    binaryEmitted = "1.16-SNAPSHOT"
 )
 
 /** Helper class to allow for testing of logic. */

From 659d51808b94e46a13efd7599d6119d23ea07dfc Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Mon, 12 Feb 2024 13:12:20 +0100
Subject: [PATCH 044/298] Remove the parameters to `StoreModule` IR nodes.

`StoreModule` was always implicitly assumed to be used only in the
constructor of the corresponding module class, and with a `This()`
rhs.

We now include that assumption as a core truth of `StoreModule()`,
and therefore remove its two arguments.

A deserialization hack reads the old arguments and throws if they
do not conform to the above assumption, before discarding them.
---
 .../org/scalajs/nscplugin/GenJSCode.scala     |  5 +-
 .../main/scala/org/scalajs/ir/Hashers.scala   |  4 +-
 .../main/scala/org/scalajs/ir/Printers.scala  |  7 +--
 .../scala/org/scalajs/ir/Serializers.scala    | 22 +++++++-
 .../scala/org/scalajs/ir/Transformers.scala   | 10 ++--
 .../scala/org/scalajs/ir/Traversers.scala     | 10 ++--
 .../src/main/scala/org/scalajs/ir/Trees.scala |  3 +-
 .../scala/org/scalajs/ir/PrintersTest.scala   |  3 +-
 .../backend/emitter/FunctionEmitter.scala     |  9 +--
 .../linker/checker/ClassDefChecker.scala      | 38 ++++++++++---
 .../scalajs/linker/checker/IRChecker.scala    | 11 +---
 .../frontend/optimizer/IncOptimizer.scala     |  4 +-
 .../frontend/optimizer/OptimizerCore.scala    |  9 +--
 .../linker/checker/ClassDefCheckerTest.scala  | 56 +++++++++++++++++++
 project/BinaryIncompatibilities.scala         |  3 +
 15 files changed, 135 insertions(+), 59 deletions(-)

diff --git a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
index 5d46b0617b..2c2c0478ea 100644
--- a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
+++ b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
@@ -3191,10 +3191,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
         if (isStaticModule(currentClassSym) && !isModuleInitialized.value &&
             currentMethodSym.isClassConstructor) {
           isModuleInitialized.value = true
-          val className = encodeClassName(currentClassSym)
-          val initModule =
-            js.StoreModule(className, js.This()(jstpe.ClassType(className)))
-          js.Block(superCall, initModule)
+          js.Block(superCall, js.StoreModule())
         } else {
           superCall
         }
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Hashers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Hashers.scala
index 9246cc6874..e363efccfb 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Hashers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Hashers.scala
@@ -259,10 +259,8 @@ object Hashers {
           mixTag(TagLoadModule)
           mixName(className)
 
-        case StoreModule(className, value) =>
+        case StoreModule() =>
           mixTag(TagStoreModule)
-          mixName(className)
-          mixTree(value)
 
         case Select(qualifier, className, field) =>
           mixTag(TagSelect)
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala
index f3efeb3d52..deb6ded863 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala
@@ -296,11 +296,8 @@ object Printers {
           print("mod:")
           print(className)
 
-        case StoreModule(className, value) =>
-          print("mod:")
-          print(className)
-          print("<-")
-          print(value)
+        case StoreModule() =>
+          print("<storeModule>")
 
         case Select(qualifier, className, field) =>
           print(qualifier)
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
index a2eb58cd91..f4c02e8760 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
@@ -318,9 +318,8 @@ object Serializers {
           writeTagAndPos(TagLoadModule)
           writeName(className)
 
-        case StoreModule(className, value) =>
+        case StoreModule() =>
           writeTagAndPos(TagStoreModule)
-          writeName(className); writeTree(value)
 
         case Select(qualifier, className, field) =>
           writeTagAndPos(TagSelect)
@@ -1012,6 +1011,7 @@ object Serializers {
 
     private[this] var lastPosition: Position = Position.NoPosition
 
+    private[this] var enclosingClassName: ClassName = _
     private[this] var thisTypeForHack8: Type = NoType
 
     def deserializeEntryPointsInfo(): EntryPointsInfo = {
@@ -1156,7 +1156,18 @@ object Serializers {
 
         case TagNew          => New(readClassName(), readMethodIdent(), readTrees())
         case TagLoadModule   => LoadModule(readClassName())
-        case TagStoreModule  => StoreModule(readClassName(), readTree())
+
+        case TagStoreModule =>
+          if (hacks.use13) {
+            val cls = readClassName()
+            val rhs = readTree()
+            if (cls != enclosingClassName || !rhs.isInstanceOf[This]) {
+              throw new IOException(
+                  s"Illegal legacy StoreModule(${cls.nameString}, $rhs) " +
+                  s"found in class ${enclosingClassName.nameString}")
+            }
+          }
+          StoreModule()
 
         case TagSelect =>
           val qualifier = readTree()
@@ -1359,8 +1370,11 @@ object Serializers {
 
     def readClassDef(): ClassDef = {
       implicit val pos = readPosition()
+
       val name = readClassIdent()
       val cls = name.name
+      enclosingClassName = cls
+
       val originalName = readOriginalName()
       val kind = ClassKind.fromByte(readByte())
 
@@ -2073,6 +2087,8 @@ object Serializers {
     private val use11: Boolean = use8 || sourceVersion == "1.11"
 
     val use12: Boolean = use11 || sourceVersion == "1.12"
+
+    val use13: Boolean = use12 || sourceVersion == "1.13"
   }
 
   /** Names needed for hacks. */
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Transformers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Transformers.scala
index 879864c047..415db46f33 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Transformers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Transformers.scala
@@ -91,9 +91,6 @@ object Transformers {
         case New(className, ctor, args) =>
           New(className, ctor, args map transformExpr)
 
-        case StoreModule(className, value) =>
-          StoreModule(className, transformExpr(value))
-
         case Select(qualifier, className, field) =>
           Select(transformExpr(qualifier), className, field)(tree.tpe)
 
@@ -223,9 +220,10 @@ object Transformers {
 
         // Trees that need not be transformed
 
-        case _:Skip | _:Debugger | _:LoadModule | _:SelectStatic | _:SelectJSNativeMember |
-            _:LoadJSConstructor | _:LoadJSModule | _:JSNewTarget | _:JSImportMeta |
-            _:JSLinkingInfo | _:Literal | _:VarRef | _:This | _:JSGlobalRef  =>
+        case _:Skip | _:Debugger | _:LoadModule | _:StoreModule |
+            _:SelectStatic | _:SelectJSNativeMember | _:LoadJSConstructor |
+            _:LoadJSModule | _:JSNewTarget | _:JSImportMeta | _:JSLinkingInfo |
+            _:Literal | _:VarRef | _:This | _:JSGlobalRef  =>
           tree
       }
     }
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Traversers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Traversers.scala
index be26304b96..2040341a74 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Traversers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Traversers.scala
@@ -77,9 +77,6 @@ object Traversers {
       case New(_, _, args) =>
         args foreach traverse
 
-      case StoreModule(_, value) =>
-        traverse(value)
-
       case Select(qualifier, _, _) =>
         traverse(qualifier)
 
@@ -222,9 +219,10 @@ object Traversers {
 
       // Trees that need not be traversed
 
-      case _:Skip | _:Debugger | _:LoadModule | _:SelectStatic | _:SelectJSNativeMember |
-          _:LoadJSConstructor | _:LoadJSModule | _:JSNewTarget | _:JSImportMeta |
-          _:JSLinkingInfo | _:Literal | _:VarRef | _:This | _:JSGlobalRef =>
+      case _:Skip | _:Debugger | _:LoadModule | _:StoreModule |
+          _:SelectStatic | _:SelectJSNativeMember | _:LoadJSConstructor |
+          _:LoadJSModule | _:JSNewTarget | _:JSImportMeta | _:JSLinkingInfo |
+          _:Literal | _:VarRef | _:This | _:JSGlobalRef =>
     }
 
     def traverseClassDef(tree: ClassDef): Unit = {
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala b/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
index 25b1c54575..631e39642a 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
@@ -237,8 +237,7 @@ object Trees {
     val tpe = ClassType(className)
   }
 
-  sealed case class StoreModule(className: ClassName, value: Tree)(
-      implicit val pos: Position) extends Tree {
+  sealed case class StoreModule()(implicit val pos: Position) extends Tree {
     val tpe = NoType // cannot be in expression position
   }
 
diff --git a/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala b/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala
index b8af4c7fe0..03c1628f16 100644
--- a/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala
+++ b/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala
@@ -302,8 +302,7 @@ class PrintersTest {
   }
 
   @Test def printStoreModule(): Unit = {
-    assertPrintEquals("mod:scala.Predef$<-this",
-        StoreModule("scala.Predef$", This()("scala.Predef$")))
+    assertPrintEquals("<storeModule>", StoreModule())
   }
 
   @Test def printSelect(): Unit = {
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
index d2f83eb4a3..128e8ebeed 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
@@ -693,11 +693,12 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
               pushLhsInto(Lhs.Assign(lhs), rhs, tailPosLabels)
           }
 
-        case StoreModule(className, value) =>
-          unnest(value) { (newValue, env0) =>
-            implicit val env = env0
-            js.Assign(globalVar(VarField.n, className), transformExprNoChar(newValue))
+        case StoreModule() =>
+          val enclosingClassName = env.enclosingClassName.getOrElse {
+            throw new AssertionError(
+                "Need enclosing class for StoreModule().")
           }
+          js.Assign(globalVar(VarField.n, enclosingClassName), js.This())
 
         case While(cond, body) =>
           val loopEnv = env.withInLoopForVarCapture(true)
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala b/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
index 9ce0e7175a..ba64a3b9b1 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
@@ -292,7 +292,10 @@ private final class ClassDefChecker(classDef: ClassDef,
 
     // Body
     val thisType = if (static) NoType else instanceThisType
-    body.foreach(checkTree(_, Env.fromParams(params).withThisType(thisType)))
+    val bodyEnv = Env.fromParams(params)
+      .withThisType(thisType)
+      .withInConstructor(isConstructor)
+    body.foreach(checkTree(_, bodyEnv))
   }
 
   private def checkJSConstructorDef(ctorDef: JSConstructorDef): Unit = withPerMethodState {
@@ -311,6 +314,7 @@ private final class ClassDefChecker(classDef: ClassDef,
 
     val startEnv = Env.fromParams(classDef.jsClassCaptures.getOrElse(Nil) ++ params ++ restParam)
       .withHasNewTarget(true)
+      .withInConstructor(true)
 
     val envJustBeforeSuper = body.beforeSuper.foldLeft(startEnv) { (prevEnv, stat) =>
       checkTree(stat, prevEnv)
@@ -608,8 +612,13 @@ private final class ClassDefChecker(classDef: ClassDef,
 
       case _: LoadModule =>
 
-      case StoreModule(_, value) =>
-        checkTree(value, env)
+      case StoreModule() =>
+        if (!classDef.kind.hasModuleAccessor)
+          reportError(i"Illegal StoreModule inside class of kind ${classDef.kind}")
+        if (!env.inConstructor)
+          reportError(i"Illegal StoreModule outside of constructor")
+        if (env.thisType == NoType) // can happen before JSSuperConstructorCall in JSModuleClass
+          reportError(i"Cannot find `this` in scope for StoreModule()")
 
       case Select(qualifier, _, _) =>
         checkTree(qualifier, env)
@@ -922,7 +931,9 @@ object ClassDefChecker {
       /** Local variables in scope (including through closures). */
       val locals: Map[LocalName, LocalDef],
       /** Return types by label. */
-      val returnLabels: Set[LabelName]
+      val returnLabels: Set[LabelName],
+      /** Whether we are in a constructor of the class. */
+      val inConstructor: Boolean
   ) {
     import Env._
 
@@ -938,25 +949,36 @@ object ClassDefChecker {
     def withLabel(label: LabelName): Env =
       copy(returnLabels = returnLabels + label)
 
+    def withInConstructor(inConstructor: Boolean): Env =
+      copy(inConstructor = inConstructor)
+
     private def copy(
       hasNewTarget: Boolean = hasNewTarget,
       thisType: Type = thisType,
       locals: Map[LocalName, LocalDef] = locals,
-      returnLabels: Set[LabelName] = returnLabels
+      returnLabels: Set[LabelName] = returnLabels,
+      inConstructor: Boolean = inConstructor
     ): Env = {
-      new Env(hasNewTarget, thisType, locals, returnLabels)
+      new Env(hasNewTarget, thisType, locals, returnLabels, inConstructor)
     }
   }
 
   private object Env {
     val empty: Env =
-      new Env(hasNewTarget = false, thisType = NoType, Map.empty, Set.empty)
+      new Env(hasNewTarget = false, thisType = NoType, Map.empty, Set.empty, inConstructor = false)
 
     def fromParams(params: List[ParamDef]): Env = {
       val paramLocalDefs =
         for (p @ ParamDef(ident, _, tpe, mutable) <- params)
           yield ident.name -> LocalDef(ident.name, tpe, mutable)
-      new Env(hasNewTarget = false, thisType = NoType, paramLocalDefs.toMap, Set.empty)
+
+      new Env(
+        hasNewTarget = false,
+        thisType = NoType,
+        paramLocalDefs.toMap,
+        Set.empty,
+        inConstructor = false
+      )
     }
   }
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala b/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
index 2e3678a6d4..418629d55b 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
@@ -319,14 +319,9 @@ private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter) {
         if (clazz.kind != ClassKind.ModuleClass)
           reportError("LoadModule of non-module class $className")
 
-      case StoreModule(className, value) =>
-        val clazz = lookupClass(className)
-        if (!clazz.kind.hasModuleAccessor)
-          reportError("StoreModule of non-module class $className")
-        val expectedType =
-          if (clazz.kind == ClassKind.JSModuleClass) AnyType
-          else ClassType(className)
-        typecheckExpect(value, env, expectedType)
+      case StoreModule() =>
+        // Nothing to check; everything is checked in ClassDefChecker
+        ()
 
       case Select(qualifier, className, FieldIdent(item)) =>
         val c = lookupClass(className)
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
index e8db94edb1..05763942ff 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
@@ -748,8 +748,8 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
         case ApplyStatically(flags, This(), _, _, args) if flags.isConstructor =>
           args.forall(isTriviallySideEffectFree)
 
-        case StoreModule(_, _) => true
-        case _                 => isTriviallySideEffectFree(tree)
+        case StoreModule() => true
+        case _             => isTriviallySideEffectFree(tree)
       }
 
       impl.originalDef.body.fold {
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
index 534fd345be..a417440b22 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
@@ -171,7 +171,7 @@ private[optimizer] abstract class OptimizerCore(
   private def tryElimStoreModule(body: Tree): Tree = {
     implicit val pos = body.pos
     body match {
-      case StoreModule(_, _) =>
+      case StoreModule() =>
         Skip()
       case Block(stats) =>
         val (before, from) = stats.span(!_.isInstanceOf[StoreModule])
@@ -458,9 +458,6 @@ private[optimizer] abstract class OptimizerCore(
       case New(className, ctor, args) =>
         New(className, ctor, args map transformExpr)
 
-      case StoreModule(className, value) =>
-        StoreModule(className, transformExpr(value))
-
       case tree: Select =>
         trampoline {
           pretransformSelectCommon(tree, isLhsOfAssign = false)(
@@ -656,8 +653,8 @@ private[optimizer] abstract class OptimizerCore(
 
       // Trees that need not be transformed
 
-      case _:Skip | _:Debugger | _:LoadModule | _:SelectStatic |
-          _:JSNewTarget | _:JSImportMeta | _:JSLinkingInfo |
+      case _:Skip | _:Debugger | _:LoadModule | _:StoreModule |
+          _:SelectStatic | _:JSNewTarget | _:JSImportMeta | _:JSLinkingInfo |
           _:JSGlobalRef | _:JSTypeOfGlobalRef | _:Literal =>
         tree
 
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/checker/ClassDefCheckerTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/checker/ClassDefCheckerTest.scala
index d092a04ee4..75717babd3 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/checker/ClassDefCheckerTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/checker/ClassDefCheckerTest.scala
@@ -305,6 +305,62 @@ class ClassDefCheckerTest {
         Closure(arrow = false, Nil, Nil, None, This()(ClassType("Foo")), Nil),
         "`this` of type any typed as Foo")
   }
+
+  @Test
+  def storeModule(): Unit = {
+    val ctorFlags = EMF.withNamespace(MemberNamespace.Constructor)
+
+    val superCtorCall = ApplyStatically(EAF.withConstructor(true), This()(ClassType("Foo")),
+        ObjectClass, NoArgConstructorName, Nil)(NoType)
+
+    assertError(
+      classDef(
+        "Foo",
+        kind = ClassKind.Class,
+        superClass = Some(ObjectClass),
+        methods = List(
+          MethodDef(ctorFlags, NoArgConstructorName, NON, Nil, NoType, Some {
+            Block(
+              superCtorCall,
+              StoreModule()
+            )
+          })(EOH, UNV)
+        )
+      ),
+      "Illegal StoreModule inside class of kind Class"
+    )
+
+    assertError(
+      classDef(
+        "Foo",
+        kind = ClassKind.ModuleClass,
+        superClass = Some(ObjectClass),
+        methods = List(
+          trivialCtor("Foo"),
+          MethodDef(EMF, MethodName("foo", Nil, VoidRef), NON, Nil, NoType, Some {
+            Block(
+              StoreModule()
+            )
+          })(EOH, UNV)
+        )
+      ),
+      "Illegal StoreModule outside of constructor"
+    )
+
+    assertError(
+      classDef(
+        "Foo",
+        kind = ClassKind.JSModuleClass,
+        superClass = Some("scala.scalajs.js.Object"),
+        jsConstructor = Some(
+          JSConstructorDef(JSCtorFlags, Nil, None,
+              JSConstructorBody(StoreModule() :: Nil, JSSuperConstructorCall(Nil), Undefined() :: Nil))(
+              EOH, UNV)
+        )
+      ),
+      "Cannot find `this` in scope for StoreModule()"
+    )
+  }
 }
 
 private object ClassDefCheckerTest {
diff --git a/project/BinaryIncompatibilities.scala b/project/BinaryIncompatibilities.scala
index 4713fe6bf8..0144862b7b 100644
--- a/project/BinaryIncompatibilities.scala
+++ b/project/BinaryIncompatibilities.scala
@@ -5,6 +5,9 @@ import com.typesafe.tools.mima.core.ProblemFilters._
 
 object BinaryIncompatibilities {
   val IR = Seq(
+    // !!! Breaking, OK in minor release
+    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Trees#StoreModule.*"),
+    ProblemFilters.exclude[IncompatibleResultTypeProblem]("org.scalajs.ir.Trees#StoreModule.unapply"),
   )
 
   val Linker = Seq(

From 723663b76a4dc2775dbab12f3c268e33990b6b55 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Sat, 17 Feb 2024 11:21:05 +0100
Subject: [PATCH 045/298] Refactor: Make FieldName a composite of ClassName and
 SimpleFieldName.

Previously, `FieldName` only represented the *simple* name of a
field. It was complemented everywhere with the enclosing
`ClassName`, for namespacing purposes.

We now make `FieldName` a composite, like `MethodName`. It contains
a `ClassName` and a `SimpleFieldName`. Structurally,
`SimpleFieldName` is the same as the old `FieldName`.

This removes the need to pass additional, out-of-band `ClassName`s
everywhere a `FieldName` or `FieldIdent` was used.

In addition to the readability improvements, this might improve
performance. We previously often had to create (temporary) pairs of
`(ClassName, FieldName)` as keys of maps. Now, we can directly use
the `FieldName`s instead.

While the IR names, types and trees are significantly impacted by
this change, the `.sjsir` format is unchanged.
---
 .../org/scalajs/nscplugin/GenJSCode.scala     |  20 +--
 .../org/scalajs/nscplugin/JSEncoding.scala    |   7 +-
 .../main/scala/org/scalajs/ir/Hashers.scala   |  20 ++-
 .../src/main/scala/org/scalajs/ir/Names.scala |  84 +++++++--
 .../scala/org/scalajs/ir/OriginalName.scala   |   8 +
 .../main/scala/org/scalajs/ir/Printers.scala  |  29 +--
 .../scala/org/scalajs/ir/Serializers.scala    |  88 ++++++---
 .../scala/org/scalajs/ir/Transformers.scala   |   8 +-
 .../scala/org/scalajs/ir/Traversers.scala     |   4 +-
 .../src/main/scala/org/scalajs/ir/Trees.scala |  15 +-
 .../src/main/scala/org/scalajs/ir/Types.scala |   4 +-
 .../scala/org/scalajs/ir/PrintersTest.scala   |  34 ++--
 .../scala/org/scalajs/ir/TestIRBuilder.scala  |  10 +-
 .../org/scalajs/linker/analyzer/Infos.scala   |  48 ++---
 .../linker/backend/emitter/ClassEmitter.scala |  29 ++-
 .../linker/backend/emitter/EmitterNames.scala |   4 +-
 .../backend/emitter/FunctionEmitter.scala     |  65 ++++---
 .../backend/emitter/GlobalKnowledge.scala     |   5 +-
 .../backend/emitter/KnowledgeGuardian.scala   |  17 +-
 .../linker/backend/emitter/NameGen.scala      |  14 +-
 .../linker/backend/emitter/SJSGen.scala       |  16 +-
 .../linker/backend/emitter/VarGen.scala       |   8 +-
 .../linker/checker/ClassDefChecker.scala      |   6 +-
 .../linker/checker/ErrorReporter.scala        |   1 +
 .../scalajs/linker/checker/IRChecker.scala    |  27 +--
 .../frontend/optimizer/IncOptimizer.scala     |  14 +-
 .../frontend/optimizer/OptimizerCore.scala    | 169 ++++++++----------
 .../org/scalajs/linker/OptimizerTest.scala    |  18 +-
 .../linker/checker/ClassDefCheckerTest.scala  |  38 +++-
 .../linker/testutils/TestIRBuilder.scala      |   8 +-
 project/BinaryIncompatibilities.scala         |  13 ++
 project/JavalibIRCleaner.scala                |   5 +-
 32 files changed, 479 insertions(+), 357 deletions(-)

diff --git a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
index 2c2c0478ea..6ad055b5ee 100644
--- a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
+++ b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
@@ -27,7 +27,7 @@ import scala.reflect.internal.Flags
 
 import org.scalajs.ir
 import org.scalajs.ir.{Trees => js, Types => jstpe, ClassKind, Hashers, OriginalName}
-import org.scalajs.ir.Names.{LocalName, FieldName, SimpleMethodName, MethodName, ClassName}
+import org.scalajs.ir.Names.{LocalName, SimpleFieldName, FieldName, SimpleMethodName, MethodName, ClassName}
 import org.scalajs.ir.OriginalName.NoOriginalName
 import org.scalajs.ir.Trees.OptimizerHints
 import org.scalajs.ir.Version.Unversioned
@@ -6337,7 +6337,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
       val classType = jstpe.ClassType(className)
 
       // val f: Any
-      val fFieldIdent = js.FieldIdent(FieldName("f"))
+      val fFieldIdent = js.FieldIdent(FieldName(className, SimpleFieldName("f")))
       val fFieldDef = js.FieldDef(js.MemberFlags.empty, fFieldIdent,
           NoOriginalName, jstpe.AnyType)
 
@@ -6353,8 +6353,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
             jstpe.NoType,
             Some(js.Block(List(
                 js.Assign(
-                    js.Select(js.This()(classType), className, fFieldIdent)(
-                        jstpe.AnyType),
+                    js.Select(js.This()(classType), fFieldIdent)(jstpe.AnyType),
                     fParamDef.ref),
                 js.ApplyStatically(js.ApplyFlags.empty.withConstructor(true),
                     js.This()(classType),
@@ -6405,7 +6404,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
         }.map((ensureBoxed _).tupled)
 
         val call = js.JSFunctionApply(
-            js.Select(js.This()(classType), className, fFieldIdent)(jstpe.AnyType),
+            js.Select(js.This()(classType), fFieldIdent)(jstpe.AnyType),
             actualParams)
 
         val body = fromAny(call, enteringPhase(currentRun.posterasurePhase) {
@@ -6746,14 +6745,12 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
               js.JSSelect(qual, genPrivateFieldsSymbol()),
               encodeFieldSymAsStringLiteral(sym))
         } else {
-          js.JSPrivateSelect(qual, encodeClassName(sym.owner),
-              encodeFieldSym(sym))
+          js.JSPrivateSelect(qual, encodeFieldSym(sym))
         }
 
         (f, true)
       } else if (jsInterop.topLevelExportsOf(sym).nonEmpty) {
-        val f = js.SelectStatic(encodeClassName(sym.owner),
-            encodeFieldSym(sym))(jstpe.AnyType)
+        val f = js.SelectStatic(encodeFieldSym(sym))(jstpe.AnyType)
         (f, true)
       } else if (jsInterop.staticExportsOf(sym).nonEmpty) {
         val exportInfo = jsInterop.staticExportsOf(sym).head
@@ -6764,7 +6761,6 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
 
         (f, true)
       } else {
-        val className = encodeClassName(sym.owner)
         val fieldIdent = encodeFieldSym(sym)
 
         /* #4370 Fields cannot have type NothingType, so we box them as
@@ -6774,11 +6770,11 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
          */
         toIRType(sym.tpe) match {
           case jstpe.NothingType =>
-            val f = js.Select(qual, className, fieldIdent)(
+            val f = js.Select(qual, fieldIdent)(
                 encodeClassType(RuntimeNothingClass))
             (f, true)
           case ftpe =>
-            val f = js.Select(qual, className, fieldIdent)(ftpe)
+            val f = js.Select(qual, fieldIdent)(ftpe)
             (f, false)
         }
       }
diff --git a/compiler/src/main/scala/org/scalajs/nscplugin/JSEncoding.scala b/compiler/src/main/scala/org/scalajs/nscplugin/JSEncoding.scala
index 432abaaa7a..56f089bf1e 100644
--- a/compiler/src/main/scala/org/scalajs/nscplugin/JSEncoding.scala
+++ b/compiler/src/main/scala/org/scalajs/nscplugin/JSEncoding.scala
@@ -18,7 +18,7 @@ import scala.tools.nsc._
 
 import org.scalajs.ir
 import org.scalajs.ir.{Trees => js, Types => jstpe}
-import org.scalajs.ir.Names.{LocalName, LabelName, FieldName, SimpleMethodName, MethodName, ClassName}
+import org.scalajs.ir.Names.{LocalName, LabelName, SimpleFieldName, FieldName, SimpleMethodName, MethodName, ClassName}
 import org.scalajs.ir.OriginalName
 import org.scalajs.ir.OriginalName.NoOriginalName
 import org.scalajs.ir.UTF8String
@@ -178,8 +178,9 @@ trait JSEncoding[G <: Global with Singleton] extends SubComponent {
 
   def encodeFieldSym(sym: Symbol)(implicit pos: Position): js.FieldIdent = {
     requireSymIsField(sym)
-    val name = sym.name.dropLocal
-    js.FieldIdent(FieldName(name.toString()))
+    val className = encodeClassName(sym.owner)
+    val simpleName = SimpleFieldName(sym.name.dropLocal.toString())
+    js.FieldIdent(FieldName(className, simpleName))
   }
 
   def encodeFieldSymAsStringLiteral(sym: Symbol)(
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Hashers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Hashers.scala
index e363efccfb..bbf0b85409 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Hashers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Hashers.scala
@@ -262,16 +262,14 @@ object Hashers {
         case StoreModule() =>
           mixTag(TagStoreModule)
 
-        case Select(qualifier, className, field) =>
+        case Select(qualifier, field) =>
           mixTag(TagSelect)
           mixTree(qualifier)
-          mixName(className)
           mixFieldIdent(field)
           mixType(tree.tpe)
 
-        case SelectStatic(className, field) =>
+        case SelectStatic(field) =>
           mixTag(TagSelectStatic)
-          mixName(className)
           mixFieldIdent(field)
           mixType(tree.tpe)
 
@@ -351,7 +349,7 @@ object Hashers {
         case RecordSelect(record, field) =>
           mixTag(TagRecordSelect)
           mixTree(record)
-          mixFieldIdent(field)
+          mixSimpleFieldIdent(field)
           mixType(tree.tpe)
 
         case IsInstanceOf(expr, testType) =>
@@ -389,10 +387,9 @@ object Hashers {
           mixTree(ctor)
           mixTreeOrJSSpreads(args)
 
-        case JSPrivateSelect(qualifier, className, field) =>
+        case JSPrivateSelect(qualifier, field) =>
           mixTag(TagJSPrivateSelect)
           mixTree(qualifier)
-          mixName(className)
           mixFieldIdent(field)
 
         case JSSelect(qualifier, item) =>
@@ -651,11 +648,18 @@ object Hashers {
       mixName(ident.name)
     }
 
-    def mixFieldIdent(ident: FieldIdent): Unit = {
+    def mixSimpleFieldIdent(ident: SimpleFieldIdent): Unit = {
       mixPos(ident.pos)
       mixName(ident.name)
     }
 
+    def mixFieldIdent(ident: FieldIdent): Unit = {
+      // For historical reasons, the className comes *before* the position
+      mixName(ident.name.className)
+      mixPos(ident.pos)
+      mixName(ident.name.simpleName)
+    }
+
     def mixMethodIdent(ident: MethodIdent): Unit = {
       mixPos(ident.pos)
       mixMethodName(ident.name)
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Names.scala b/ir/shared/src/main/scala/org/scalajs/ir/Names.scala
index cee7f057cb..3e4a429e2a 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Names.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Names.scala
@@ -99,7 +99,7 @@ object Names {
     def apply(name: String): LocalName =
       LocalName(UTF8String(name))
 
-    private[Names] def fromFieldName(name: FieldName): LocalName =
+    private[Names] def fromSimpleFieldName(name: SimpleFieldName): LocalName =
       new LocalName(name.encoded)
   }
 
@@ -137,38 +137,90 @@ object Names {
       LabelName(UTF8String(name))
   }
 
-  /** The name of a field.
+  /** The simple name of a field (excluding its enclosing class).
    *
    *  Field names must be non-empty, and can contain any Unicode code point
    *  except `/ . ; [`.
    */
-  final class FieldName private (encoded: UTF8String)
-      extends Name(encoded) with Comparable[FieldName] {
+  final class SimpleFieldName private (encoded: UTF8String)
+      extends Name(encoded) with Comparable[SimpleFieldName] {
 
-    type ThisName = FieldName
+    type ThisName = SimpleFieldName
 
     override def equals(that: Any): Boolean = {
       (this eq that.asInstanceOf[AnyRef]) || (that match {
-        case that: FieldName => equalsName(that)
-        case _               => false
+        case that: SimpleFieldName => equalsName(that)
+        case _                     => false
       })
     }
 
-    protected def stringPrefix: String = "FieldName"
+    protected def stringPrefix: String = "SimpleFieldName"
 
-    final def withSuffix(suffix: String): FieldName =
-      FieldName(this.encoded ++ UTF8String(suffix))
+    final def withSuffix(suffix: String): SimpleFieldName =
+      SimpleFieldName(this.encoded ++ UTF8String(suffix))
 
     final def toLocalName: LocalName =
-      LocalName.fromFieldName(this)
+      LocalName.fromSimpleFieldName(this)
   }
 
-  object FieldName {
-    def apply(name: UTF8String): FieldName =
-      new FieldName(validateSimpleEncodedName(name))
+  object SimpleFieldName {
+    def apply(name: UTF8String): SimpleFieldName =
+      new SimpleFieldName(validateSimpleEncodedName(name))
+
+    def apply(name: String): SimpleFieldName =
+      SimpleFieldName(UTF8String(name))
+  }
 
-    def apply(name: String): FieldName =
-      FieldName(UTF8String(name))
+  /** The full name of a field, including its simple name and its enclosing
+   *  class name.
+   */
+  final class FieldName private (
+      val className: ClassName, val simpleName: SimpleFieldName)
+      extends Comparable[FieldName] {
+
+    import FieldName._
+
+    private val _hashCode: Int = {
+      import scala.util.hashing.MurmurHash3._
+      var acc = -1025990011 // "FieldName".hashCode()
+      acc = mix(acc, className.##)
+      acc = mix(acc, simpleName.##)
+      finalizeHash(acc, 2)
+    }
+
+    override def equals(that: Any): Boolean = {
+      (this eq that.asInstanceOf[AnyRef]) || (that match {
+        case that: FieldName =>
+          this._hashCode == that._hashCode && // fail fast on different hash codes
+          this.className == that.className &&
+          this.simpleName == that.simpleName
+        case _ =>
+          false
+      })
+    }
+
+    override def hashCode(): Int = _hashCode
+
+    def compareTo(that: FieldName): Int = {
+      val classNameCmp = this.className.compareTo(that.className)
+      if (classNameCmp != 0)
+        classNameCmp
+      else
+        this.simpleName.compareTo(that.simpleName)
+    }
+
+    protected def stringPrefix: String = "FieldName"
+
+    def nameString: String =
+      className.nameString + "::" + simpleName.nameString
+
+    override def toString(): String =
+      "FieldName<" + nameString + ">"
+  }
+
+  object FieldName {
+    def apply(className: ClassName, simpleName: SimpleFieldName): FieldName =
+      new FieldName(className, simpleName)
   }
 
   /** The simple name of a method (excluding its signature).
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/OriginalName.scala b/ir/shared/src/main/scala/org/scalajs/ir/OriginalName.scala
index d2211095d5..7ae6745e53 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/OriginalName.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/OriginalName.scala
@@ -53,6 +53,10 @@ final class OriginalName private (private val bytes: Array[Byte])
     if (isDefined) this
     else OriginalName(name)
 
+  // new in 1.16.0; added as last overload to preserve binary compatibility
+  def orElse(name: FieldName): OriginalName =
+    orElse(name.simpleName)
+
   def getOrElse(name: Name): UTF8String =
     getOrElse(name.encoded)
 
@@ -71,6 +75,10 @@ final class OriginalName private (private val bytes: Array[Byte])
     else UTF8String(name)
   }
 
+  // new in 1.16.0; added as last overload to preserve binary compatibility
+  def getOrElse(name: FieldName): UTF8String =
+    getOrElse(name.simpleName)
+
   override def toString(): String =
     if (isDefined) s"OriginalName($unsafeGet)"
     else "NoOriginalName"
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala
index deb6ded863..875a4e4c0b 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala
@@ -123,6 +123,7 @@ object Printers {
       node match {
         case node: LocalIdent        => print(node)
         case node: LabelIdent        => print(node)
+        case node: SimpleFieldIdent  => print(node)
         case node: FieldIdent        => print(node)
         case node: MethodIdent       => print(node)
         case node: ClassIdent        => print(node)
@@ -299,16 +300,12 @@ object Printers {
         case StoreModule() =>
           print("<storeModule>")
 
-        case Select(qualifier, className, field) =>
+        case Select(qualifier, field) =>
           print(qualifier)
           print('.')
-          print(className)
-          print("::")
           print(field)
 
-        case SelectStatic(className, field) =>
-          print(className)
-          print("::")
+        case SelectStatic(field) =>
           print(field)
 
         case SelectJSNativeMember(className, member) =>
@@ -572,11 +569,11 @@ object Printers {
 
         case JSNew(ctor, args) =>
           def containsOnlySelectsFromAtom(tree: Tree): Boolean = tree match {
-            case JSPrivateSelect(qual, _, _) => containsOnlySelectsFromAtom(qual)
-            case JSSelect(qual, _)           => containsOnlySelectsFromAtom(qual)
-            case VarRef(_)                   => true
-            case This()                      => true
-            case _                           => false // in particular, Apply
+            case JSPrivateSelect(qual, _) => containsOnlySelectsFromAtom(qual)
+            case JSSelect(qual, _)        => containsOnlySelectsFromAtom(qual)
+            case VarRef(_)                => true
+            case This()                   => true
+            case _                        => false // in particular, Apply
           }
           if (containsOnlySelectsFromAtom(ctor)) {
             print("new ")
@@ -588,11 +585,9 @@ object Printers {
           }
           printArgs(args)
 
-        case JSPrivateSelect(qualifier, className, field) =>
+        case JSPrivateSelect(qualifier, field) =>
           print(qualifier)
           print('.')
-          print(className)
-          print("::")
           print(field)
 
         case JSSelect(qualifier, item) =>
@@ -1113,6 +1108,9 @@ object Printers {
     def print(ident: LabelIdent): Unit =
       print(ident.name)
 
+    def print(ident: SimpleFieldIdent): Unit =
+      print(ident.name)
+
     def print(ident: FieldIdent): Unit =
       print(ident.name)
 
@@ -1125,6 +1123,9 @@ object Printers {
     def print(name: Name): Unit =
       printEscapeJS(name.nameString, out)
 
+    def print(name: FieldName): Unit =
+      printEscapeJS(name.nameString, out)
+
     def print(name: MethodName): Unit =
       printEscapeJS(name.nameString, out)
 
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
index f4c02e8760..9be664598a 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
@@ -321,14 +321,14 @@ object Serializers {
         case StoreModule() =>
           writeTagAndPos(TagStoreModule)
 
-        case Select(qualifier, className, field) =>
+        case Select(qualifier, field) =>
           writeTagAndPos(TagSelect)
-          writeTree(qualifier); writeName(className); writeFieldIdent(field)
+          writeTree(qualifier); writeFieldIdent(field)
           writeType(tree.tpe)
 
-        case SelectStatic(className, field) =>
+        case SelectStatic(field) =>
           writeTagAndPos(TagSelectStatic)
-          writeName(className); writeFieldIdent(field)
+          writeFieldIdent(field)
           writeType(tree.tpe)
 
         case SelectJSNativeMember(className, member) =>
@@ -385,7 +385,7 @@ object Serializers {
 
         case RecordSelect(record, field) =>
           writeTagAndPos(TagRecordSelect)
-          writeTree(record); writeFieldIdent(field)
+          writeTree(record); writeSimpleFieldIdent(field)
           writeType(tree.tpe)
 
         case IsInstanceOf(expr, testType) =>
@@ -420,9 +420,9 @@ object Serializers {
           writeTagAndPos(TagJSNew)
           writeTree(ctor); writeTreeOrJSSpreads(args)
 
-        case JSPrivateSelect(qualifier, className, field) =>
+        case JSPrivateSelect(qualifier, field) =>
           writeTagAndPos(TagJSPrivateSelect)
-          writeTree(qualifier); writeName(className); writeFieldIdent(field)
+          writeTree(qualifier); writeFieldIdent(field)
 
         case JSSelect(qualifier, item) =>
           writeTagAndPos(TagJSSelect)
@@ -632,7 +632,7 @@ object Serializers {
         case FieldDef(flags, name, originalName, ftpe) =>
           writeByte(TagFieldDef)
           writeInt(MemberFlags.toBits(flags))
-          writeFieldIdent(name)
+          writeFieldIdentForEnclosingClass(name)
           writeOriginalName(originalName)
           writeType(ftpe)
 
@@ -762,7 +762,7 @@ object Serializers {
 
         case TopLevelFieldExportDef(moduleID, exportName, field) =>
           writeByte(TagTopLevelFieldExportDef)
-          writeString(moduleID); writeString(exportName); writeFieldIdent(field)
+          writeString(moduleID); writeString(exportName); writeFieldIdentForEnclosingClass(field)
       }
     }
 
@@ -782,11 +782,23 @@ object Serializers {
       writeName(ident.name)
     }
 
-    def writeFieldIdent(ident: FieldIdent): Unit = {
+    def writeSimpleFieldIdent(ident: SimpleFieldIdent): Unit = {
       writePosition(ident.pos)
       writeName(ident.name)
     }
 
+    def writeFieldIdent(ident: FieldIdent): Unit = {
+      // For historical reasons, the className comes *before* the position
+      writeName(ident.name.className)
+      writePosition(ident.pos)
+      writeName(ident.name.simpleName)
+    }
+
+    def writeFieldIdentForEnclosingClass(ident: FieldIdent): Unit = {
+      writePosition(ident.pos)
+      writeName(ident.name.simpleName)
+    }
+
     def writeMethodIdent(ident: MethodIdent): Unit = {
       writePosition(ident.pos)
       writeMethodName(ident.name)
@@ -1003,12 +1015,23 @@ object Serializers {
     private[this] var encodedNames: Array[UTF8String] = _
     private[this] var localNames: Array[LocalName] = _
     private[this] var labelNames: Array[LabelName] = _
-    private[this] var fieldNames: Array[FieldName] = _
+    private[this] var simpleFieldNames: Array[SimpleFieldName] = _
     private[this] var simpleMethodNames: Array[SimpleMethodName] = _
     private[this] var classNames: Array[ClassName] = _
     private[this] var methodNames: Array[MethodName] = _
     private[this] var strings: Array[String] = _
 
+    /** Uniqueness cache for FieldName's.
+     *
+     *  For historical reasons, the `ClassName` and `SimpleFieldName`
+     *  components of `FieldName`s are store separately in the `.sjsir` format.
+     *  Since most if not all occurrences of any particular `FieldName`
+     *  typically come from a single `.sjsir` file, we use a uniqueness cache
+     *  to make them all `eq`, consuming less memory and speeding up equality
+     *  tests.
+     */
+    private[this] val uniqueFieldNames = mutable.AnyRefMap.empty[FieldName, FieldName]
+
     private[this] var lastPosition: Position = Position.NoPosition
 
     private[this] var enclosingClassName: ClassName = _
@@ -1031,7 +1054,7 @@ object Serializers {
       }
       localNames = new Array(encodedNames.length)
       labelNames = new Array(encodedNames.length)
-      fieldNames = new Array(encodedNames.length)
+      simpleFieldNames = new Array(encodedNames.length)
       simpleMethodNames = new Array(encodedNames.length)
       classNames = new Array(encodedNames.length)
       methodNames = Array.fill(readInt()) {
@@ -1171,7 +1194,6 @@ object Serializers {
 
         case TagSelect =>
           val qualifier = readTree()
-          val className = readClassName()
           val field = readFieldIdent()
           val tpe = readType()
 
@@ -1179,12 +1201,12 @@ object Serializers {
             /* Note [Nothing FieldDef rewrite]
              * qual.field[nothing]  -->  throw qual.field[null]
              */
-            Throw(Select(qualifier, className, field)(NullType))
+            Throw(Select(qualifier, field)(NullType))
           } else {
-            Select(qualifier, className, field)(tpe)
+            Select(qualifier, field)(tpe)
           }
 
-        case TagSelectStatic => SelectStatic(readClassName(), readFieldIdent())(readType())
+        case TagSelectStatic => SelectStatic(readFieldIdent())(readType())
         case TagSelectJSNativeMember => SelectJSNativeMember(readClassName(), readMethodIdent())
 
         case TagApply =>
@@ -1219,7 +1241,7 @@ object Serializers {
           UnwrapFromThrowable(readTree())
 
         case TagJSNew                => JSNew(readTree(), readTreeOrJSSpreads())
-        case TagJSPrivateSelect      => JSPrivateSelect(readTree(), readClassName(), readFieldIdent())
+        case TagJSPrivateSelect      => JSPrivateSelect(readTree(), readFieldIdent())
         case TagJSSelect             => JSSelect(readTree(), readTree())
         case TagJSFunctionApply      => JSFunctionApply(readTree(), readTreeOrJSSpreads())
         case TagJSMethodApply        => JSMethodApply(readTree(), readTree(), readTreeOrJSSpreads())
@@ -1495,7 +1517,7 @@ object Serializers {
 
     private def readFieldDef()(implicit pos: Position): FieldDef = {
       val flags = MemberFlags.fromBits(readInt())
-      val name = readFieldIdent()
+      val name = readFieldIdentForEnclosingClass()
       val originalName = readOriginalName()
 
       val ftpe0 = readType()
@@ -1721,7 +1743,9 @@ object Serializers {
         case TagTopLevelJSClassExportDef => TopLevelJSClassExportDef(readModuleID(), readString())
         case TagTopLevelModuleExportDef  => TopLevelModuleExportDef(readModuleID(), readString())
         case TagTopLevelMethodExportDef  => TopLevelMethodExportDef(readModuleID(), readJSMethodDef())
-        case TagTopLevelFieldExportDef   => TopLevelFieldExportDef(readModuleID(), readString(), readFieldIdent())
+
+        case TagTopLevelFieldExportDef =>
+          TopLevelFieldExportDef(readModuleID(), readString(), readFieldIdentForEnclosingClass())
       }
     }
 
@@ -1739,8 +1763,22 @@ object Serializers {
     }
 
     def readFieldIdent(): FieldIdent = {
+      // For historical reasons, the className comes *before* the position
+      val className = readClassName()
+      implicit val pos = readPosition()
+      val simpleName = readSimpleFieldName()
+      FieldIdent(makeFieldName(className, simpleName))
+    }
+
+    def readFieldIdentForEnclosingClass(): FieldIdent = {
       implicit val pos = readPosition()
-      FieldIdent(readFieldName())
+      val simpleName = readSimpleFieldName()
+      FieldIdent(makeFieldName(enclosingClassName, simpleName))
+    }
+
+    private def makeFieldName(className: ClassName, simpleName: SimpleFieldName): FieldName = {
+      val newFieldName = FieldName(className, simpleName)
+      uniqueFieldNames.getOrElseUpdate(newFieldName, newFieldName)
     }
 
     def readMethodIdent(): MethodIdent = {
@@ -1826,7 +1864,7 @@ object Serializers {
 
         case TagRecordType =>
           RecordType(List.fill(readInt()) {
-            val name = readFieldName()
+            val name = readSimpleFieldName()
             val originalName = readString()
             val tpe = readType()
             val mutable = readBoolean()
@@ -1959,14 +1997,14 @@ object Serializers {
       }
     }
 
-    private def readFieldName(): FieldName = {
+    private def readSimpleFieldName(): SimpleFieldName = {
       val i = readInt()
-      val existing = fieldNames(i)
+      val existing = simpleFieldNames(i)
       if (existing ne null) {
         existing
       } else {
-        val result = FieldName(encodedNames(i))
-        fieldNames(i) = result
+        val result = SimpleFieldName(encodedNames(i))
+        simpleFieldNames(i) = result
         result
       }
     }
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Transformers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Transformers.scala
index 415db46f33..6d30327786 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Transformers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Transformers.scala
@@ -91,8 +91,8 @@ object Transformers {
         case New(className, ctor, args) =>
           New(className, ctor, args map transformExpr)
 
-        case Select(qualifier, className, field) =>
-          Select(transformExpr(qualifier), className, field)(tree.tpe)
+        case Select(qualifier, field) =>
+          Select(transformExpr(qualifier), field)(tree.tpe)
 
         case Apply(flags, receiver, method, args) =>
           Apply(flags, transformExpr(receiver), method,
@@ -158,8 +158,8 @@ object Transformers {
         case JSNew(ctor, args) =>
           JSNew(transformExpr(ctor), args.map(transformExprOrJSSpread))
 
-        case JSPrivateSelect(qualifier, className, field) =>
-          JSPrivateSelect(transformExpr(qualifier), className, field)
+        case JSPrivateSelect(qualifier, field) =>
+          JSPrivateSelect(transformExpr(qualifier), field)
 
         case JSSelect(qualifier, item) =>
           JSSelect(transformExpr(qualifier), transformExpr(item))
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Traversers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Traversers.scala
index 2040341a74..8a8909cdce 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Traversers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Traversers.scala
@@ -77,7 +77,7 @@ object Traversers {
       case New(_, _, args) =>
         args foreach traverse
 
-      case Select(qualifier, _, _) =>
+      case Select(qualifier, _) =>
         traverse(qualifier)
 
       case Apply(_, receiver, _, args) =>
@@ -147,7 +147,7 @@ object Traversers {
         traverse(ctor)
         args.foreach(traverseTreeOrJSSpread)
 
-      case JSPrivateSelect(qualifier, _, _) =>
+      case JSPrivateSelect(qualifier, _) =>
         traverse(qualifier)
 
       case JSSelect(qualifier, item) =>
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala b/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
index 631e39642a..c3d206624a 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
@@ -59,6 +59,9 @@ object Trees {
   sealed case class LabelIdent(name: LabelName)(implicit val pos: Position)
       extends IRNode
 
+  sealed case class SimpleFieldIdent(name: SimpleFieldName)(implicit val pos: Position)
+      extends IRNode
+
   sealed case class FieldIdent(name: FieldName)(implicit val pos: Position)
       extends IRNode
 
@@ -241,13 +244,10 @@ object Trees {
     val tpe = NoType // cannot be in expression position
   }
 
-  sealed case class Select(qualifier: Tree, className: ClassName,
-      field: FieldIdent)(
-      val tpe: Type)(
+  sealed case class Select(qualifier: Tree, field: FieldIdent)(val tpe: Type)(
       implicit val pos: Position) extends AssignLhs
 
-  sealed case class SelectStatic(className: ClassName, field: FieldIdent)(
-      val tpe: Type)(
+  sealed case class SelectStatic(field: FieldIdent)(val tpe: Type)(
       implicit val pos: Position) extends AssignLhs
 
   sealed case class SelectJSNativeMember(className: ClassName, member: MethodIdent)(
@@ -465,7 +465,7 @@ object Trees {
   sealed case class RecordValue(tpe: RecordType, elems: List[Tree])(
       implicit val pos: Position) extends Tree
 
-  sealed case class RecordSelect(record: Tree, field: FieldIdent)(
+  sealed case class RecordSelect(record: Tree, field: SimpleFieldIdent)(
       val tpe: Type)(
       implicit val pos: Position)
       extends AssignLhs
@@ -512,8 +512,7 @@ object Trees {
     val tpe = AnyType
   }
 
-  sealed case class JSPrivateSelect(qualifier: Tree, className: ClassName,
-      field: FieldIdent)(
+  sealed case class JSPrivateSelect(qualifier: Tree, field: FieldIdent)(
       implicit val pos: Position) extends AssignLhs {
     val tpe = AnyType
   }
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Types.scala b/ir/shared/src/main/scala/org/scalajs/ir/Types.scala
index 459f42f457..4f91fd3319 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Types.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Types.scala
@@ -143,12 +143,12 @@ object Types {
    *  The compiler itself never generates record types.
    */
   final case class RecordType(fields: List[RecordType.Field]) extends Type {
-    def findField(name: FieldName): RecordType.Field =
+    def findField(name: SimpleFieldName): RecordType.Field =
       fields.find(_.name == name).get
   }
 
   object RecordType {
-    final case class Field(name: FieldName, originalName: OriginalName,
+    final case class Field(name: SimpleFieldName, originalName: OriginalName,
         tpe: Type, mutable: Boolean)
   }
 
diff --git a/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala b/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala
index 03c1628f16..ab3c6be098 100644
--- a/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala
+++ b/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala
@@ -307,12 +307,12 @@ class PrintersTest {
 
   @Test def printSelect(): Unit = {
     assertPrintEquals("x.test.Test::f",
-        Select(ref("x", "test.Test"), "test.Test", "f")(IntType))
+        Select(ref("x", "test.Test"), FieldName("test.Test", "f"))(IntType))
   }
 
   @Test def printSelectStatic(): Unit = {
     assertPrintEquals("test.Test::f",
-        SelectStatic("test.Test", "f")(IntType))
+        SelectStatic(FieldName("test.Test", "f"))(IntType))
   }
 
   @Test def printApply(): Unit = {
@@ -606,21 +606,21 @@ class PrintersTest {
     assertPrintEquals("new C()", JSNew(ref("C", AnyType), Nil))
     assertPrintEquals("new C(4, 5)", JSNew(ref("C", AnyType), List(i(4), i(5))))
     assertPrintEquals("new x.test.Test::C(4, 5)",
-        JSNew(JSPrivateSelect(ref("x", AnyType), "test.Test", "C"), List(i(4), i(5))))
+        JSNew(JSPrivateSelect(ref("x", AnyType), FieldName("test.Test", "C")), List(i(4), i(5))))
     assertPrintEquals("""new x["C"]()""",
         JSNew(JSSelect(ref("x", AnyType), StringLiteral("C")), Nil))
 
     val fApplied = JSFunctionApply(ref("f", AnyType), Nil)
     assertPrintEquals("new (f())()", JSNew(fApplied, Nil))
     assertPrintEquals("new (f().test.Test::C)(4, 5)",
-        JSNew(JSPrivateSelect(fApplied, "test.Test", "C"), List(i(4), i(5))))
+        JSNew(JSPrivateSelect(fApplied, FieldName("test.Test", "C")), List(i(4), i(5))))
     assertPrintEquals("""new (f()["C"])()""",
         JSNew(JSSelect(fApplied, StringLiteral("C")), Nil))
   }
 
   @Test def printJSPrivateSelect(): Unit = {
     assertPrintEquals("x.test.Test::f",
-        JSPrivateSelect(ref("x", AnyType), "test.Test", "f"))
+        JSPrivateSelect(ref("x", AnyType), FieldName("test.Test", "f")))
   }
 
   @Test def printJSSelect(): Unit = {
@@ -634,12 +634,12 @@ class PrintersTest {
         JSFunctionApply(ref("f", AnyType), List(i(3), i(4))))
 
     assertPrintEquals("(0, x.test.Test::f)()",
-        JSFunctionApply(JSPrivateSelect(ref("x", AnyType), "test.Test", "f"), Nil))
+        JSFunctionApply(JSPrivateSelect(ref("x", AnyType), FieldName("test.Test", "f")), Nil))
     assertPrintEquals("""(0, x["f"])()""",
         JSFunctionApply(JSSelect(ref("x", AnyType), StringLiteral("f")),
             Nil))
     assertPrintEquals("(0, x.test.Test::f)()",
-        JSFunctionApply(Select(ref("x", "test.Test"), "test.Test", "f")(AnyType),
+        JSFunctionApply(Select(ref("x", "test.Test"), FieldName("test.Test", "f"))(AnyType),
             Nil))
   }
 
@@ -1137,7 +1137,7 @@ class PrintersTest {
     assertPrintEquals(
         """
           |module class Test extends java.lang.Object {
-          |  val x: int
+          |  val Test::x: int
           |  def m;I(): int = <abstract>
           |  constructor def constructor(): any = {
           |    super()
@@ -1151,7 +1151,7 @@ class PrintersTest {
         """,
         ClassDef("Test", NON, ClassKind.ModuleClass, None, Some(ObjectClass),
             Nil, None, None,
-            List(FieldDef(MemberFlags.empty, "x", NON, IntType)),
+            List(FieldDef(MemberFlags.empty, FieldName("Test", "x"), NON, IntType)),
             List(MethodDef(MemberFlags.empty, MethodName("m", Nil, I), NON, Nil, IntType, None)(NoOptHints, UNV)),
             Some(JSConstructorDef(MemberFlags.empty.withNamespace(Constructor), Nil, None,
                 JSConstructorBody(Nil, JSSuperConstructorCall(Nil), Nil))(NoOptHints, UNV)),
@@ -1163,12 +1163,12 @@ class PrintersTest {
   }
 
   @Test def printFieldDef(): Unit = {
-    assertPrintEquals("val x: int",
-        FieldDef(MemberFlags.empty, "x", NON, IntType))
-    assertPrintEquals("var y: any",
-        FieldDef(MemberFlags.empty.withMutable(true), "y", NON, AnyType))
-    assertPrintEquals("val x{orig name}: int",
-        FieldDef(MemberFlags.empty, "x", TestON, IntType))
+    assertPrintEquals("val Test::x: int",
+        FieldDef(MemberFlags.empty, FieldName("Test", "x"), NON, IntType))
+    assertPrintEquals("var Test::y: any",
+        FieldDef(MemberFlags.empty.withMutable(true), FieldName("Test", "y"), NON, AnyType))
+    assertPrintEquals("val Test::x{orig name}: int",
+        FieldDef(MemberFlags.empty, FieldName("Test", "x"), TestON, IntType))
   }
 
   @Test def printJSFieldDef(): Unit = {
@@ -1428,8 +1428,8 @@ class PrintersTest {
   @Test def printTopLevelFieldExportDef(): Unit = {
     assertPrintEquals(
         """
-          |export top[moduleID="main"] static field x$1 as "x"
+          |export top[moduleID="main"] static field Test::x$1 as "x"
         """,
-        TopLevelFieldExportDef("main", "x", "x$1"))
+        TopLevelFieldExportDef("main", "x", FieldName("Test", "x$1")))
   }
 }
diff --git a/ir/shared/src/test/scala/org/scalajs/ir/TestIRBuilder.scala b/ir/shared/src/test/scala/org/scalajs/ir/TestIRBuilder.scala
index 83255c1ca2..3cc7058b8f 100644
--- a/ir/shared/src/test/scala/org/scalajs/ir/TestIRBuilder.scala
+++ b/ir/shared/src/test/scala/org/scalajs/ir/TestIRBuilder.scala
@@ -37,8 +37,8 @@ object TestIRBuilder {
   val NoOptHints = OptimizerHints.empty
 
   // String -> Name conversions
-  implicit def string2fieldName(name: String): FieldName =
-    FieldName(name)
+  implicit def string2simpleFieldName(name: String): SimpleFieldName =
+    SimpleFieldName(name)
   implicit def string2className(name: String): ClassName =
     ClassName(name)
 
@@ -47,8 +47,8 @@ object TestIRBuilder {
     LocalIdent(LocalName(name))
   implicit def string2labelIdent(name: String): LabelIdent =
     LabelIdent(LabelName(name))
-  implicit def string2fieldIdent(name: String): FieldIdent =
-    FieldIdent(FieldName(name))
+  implicit def string2simpleFieldIdent(name: String): SimpleFieldIdent =
+    SimpleFieldIdent(SimpleFieldName(name))
   implicit def string2classIdent(name: String): ClassIdent =
     ClassIdent(ClassName(name))
 
@@ -59,6 +59,8 @@ object TestIRBuilder {
     ClassRef(ClassName(className))
 
   // Name -> Ident conversions
+  implicit def fieldName2fieldIdent(name: FieldName): FieldIdent =
+    FieldIdent(name)
   implicit def methodName2methodIdent(name: MethodName): MethodIdent =
     MethodIdent(name)
   implicit def className2classRef(className: ClassName): ClassRef =
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala
index d063cd5b6a..fc57860d25 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala
@@ -194,23 +194,23 @@ object Infos {
     private def forClass(cls: ClassName): ReachabilityInfoInClassBuilder =
       byClass.getOrElseUpdate(cls, new ReachabilityInfoInClassBuilder(cls))
 
-    def addFieldRead(cls: ClassName, field: FieldName): this.type = {
-      forClass(cls).addFieldRead(field)
+    def addFieldRead(field: FieldName): this.type = {
+      forClass(field.className).addFieldRead(field)
       this
     }
 
-    def addFieldWritten(cls: ClassName, field: FieldName): this.type = {
-      forClass(cls).addFieldWritten(field)
+    def addFieldWritten(field: FieldName): this.type = {
+      forClass(field.className).addFieldWritten(field)
       this
     }
 
-    def addStaticFieldRead(cls: ClassName, field: FieldName): this.type = {
-      forClass(cls).addStaticFieldRead(field)
+    def addStaticFieldRead(field: FieldName): this.type = {
+      forClass(field.className).addStaticFieldRead(field)
       this
     }
 
-    def addStaticFieldWritten(cls: ClassName, field: FieldName): this.type = {
-      forClass(cls).addStaticFieldWritten(field)
+    def addStaticFieldWritten(field: FieldName): this.type = {
+      forClass(field.className).addStaticFieldWritten(field)
       this
     }
 
@@ -560,8 +560,8 @@ object Infos {
 
         case topLevelFieldExport: TopLevelFieldExportDef =>
           val field = topLevelFieldExport.field.name
-          builder.addStaticFieldRead(enclosingClass, field)
-          builder.addStaticFieldWritten(enclosingClass, field)
+          builder.addStaticFieldRead(field)
+          builder.addStaticFieldWritten(field)
       }
 
       builder.result()
@@ -576,14 +576,14 @@ object Infos {
          */
         case Assign(lhs, rhs) =>
           lhs match {
-            case Select(qualifier, className, field) =>
-              builder.addFieldWritten(className, field.name)
+            case Select(qualifier, field) =>
+              builder.addFieldWritten(field.name)
               traverse(qualifier)
-            case SelectStatic(className, field) =>
-              builder.addStaticFieldWritten(className, field.name)
-            case JSPrivateSelect(qualifier, className, field) =>
-              builder.addStaticallyReferencedClass(className) // for the private name of the field
-              builder.addFieldWritten(className, field.name)
+            case SelectStatic(field) =>
+              builder.addStaticFieldWritten(field.name)
+            case JSPrivateSelect(qualifier, field) =>
+              builder.addStaticallyReferencedClass(field.name.className) // for the private name of the field
+              builder.addFieldWritten(field.name)
               traverse(qualifier)
             case _ =>
               traverse(lhs)
@@ -596,10 +596,10 @@ object Infos {
             case New(className, ctor, _) =>
               builder.addInstantiatedClass(className, ctor.name)
 
-            case Select(_, className, field) =>
-              builder.addFieldRead(className, field.name)
-            case SelectStatic(className, field) =>
-              builder.addStaticFieldRead(className, field.name)
+            case Select(_, field) =>
+              builder.addFieldRead(field.name)
+            case SelectStatic(field) =>
+              builder.addStaticFieldRead(field.name)
             case SelectJSNativeMember(className, member) =>
               builder.addJSNativeMemberUsed(className, member.name)
 
@@ -687,9 +687,9 @@ object Infos {
             case UnwrapFromThrowable(_) =>
               builder.addUsedInstanceTest(JavaScriptExceptionClass)
 
-            case JSPrivateSelect(_, className, field) =>
-              builder.addStaticallyReferencedClass(className) // for the private name of the field
-              builder.addFieldRead(className, field.name)
+            case JSPrivateSelect(_, field) =>
+              builder.addStaticallyReferencedClass(field.name.className) // for the private name of the field
+              builder.addFieldRead(field.name)
 
             case JSNewTarget() =>
               builder.addAccessNewTarget()
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
index dff91a1fd1..211b335e29 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
@@ -298,18 +298,15 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
       implicit moduleContext: ModuleContext,
       globalKnowledge: GlobalKnowledge, pos: Position): WithGlobals[js.Function] = {
     val superCtorCallAndFieldDefs = if (forESClass) {
-      val fieldDefs = genFieldDefsOfScalaClass(className,
+      val fieldDefs = genFieldDefsOfScalaClass(
           globalKnowledge.getFieldDefs(className))
       if (superClass.isEmpty)
         fieldDefs
       else
         js.Apply(js.Super(), Nil) :: fieldDefs
     } else {
-      val allFields =
-        globalKnowledge.getAllScalaClassFieldDefs(className)
-      allFields.flatMap { classAndFields =>
-        genFieldDefsOfScalaClass(classAndFields._1, classAndFields._2)
-      }
+      val allFields = globalKnowledge.getAllScalaClassFieldDefs(className)
+      genFieldDefsOfScalaClass(allFields)
     }
 
     initToInline.fold {
@@ -349,8 +346,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
   }
 
   /** Generates the creation of fields for a Scala class. */
-  private def genFieldDefsOfScalaClass(className: ClassName,
-      fields: List[AnyFieldDef])(
+  private def genFieldDefsOfScalaClass(fields: List[AnyFieldDef])(
       implicit moduleContext: ModuleContext,
       globalKnowledge: GlobalKnowledge): List[js.Tree] = {
     for {
@@ -359,7 +355,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
     } yield {
       val field = anyField.asInstanceOf[FieldDef]
       implicit val pos = field.pos
-      js.Assign(genSelect(js.This(), className, field.name, field.originalName),
+      js.Assign(genSelect(js.This(), field.name, field.originalName),
           genZeroOf(field.ftpe))
     }
   }
@@ -374,13 +370,12 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
     } yield {
       implicit val pos = field.pos
 
-      val varScope = (className, name)
       val value = genZeroOf(ftpe)
 
       if (flags.isMutable)
-        globallyMutableVarDef(VarField.t, VarField.u, varScope, value, origName.orElse(name))
+        globallyMutableVarDef(VarField.t, VarField.u, name, value, origName.orElse(name))
       else
-        globalVarDef(VarField.t, varScope, value, origName.orElse(name))
+        globalVarDef(VarField.t, name, value, origName.orElse(name))
     }
 
     WithGlobals.flatten(defs)
@@ -407,7 +402,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
       }
 
       symbolValueWithGlobals.flatMap { symbolValue =>
-        globalVarDef(VarField.r, (className, name), symbolValue, origName.orElse(name))
+        globalVarDef(VarField.r, name, symbolValue, origName.orElse(name))
       }
     }
 
@@ -1091,17 +1086,15 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
 
     implicit val pos = tree.pos
 
-    val varScope = (className, field.name)
-
     moduleKind match {
       case ModuleKind.NoModule =>
         /* Initial value of the export. Updates are taken care of explicitly
          * when we assign to the static field.
          */
-        genAssignToNoModuleExportVar(exportName, globalVar(VarField.t, varScope))
+        genAssignToNoModuleExportVar(exportName, globalVar(VarField.t, field.name))
 
       case ModuleKind.ESModule =>
-        WithGlobals(globalVarExport(VarField.t, varScope, js.ExportName(exportName)))
+        WithGlobals(globalVarExport(VarField.t, field.name, js.ExportName(exportName)))
 
       case ModuleKind.CommonJSModule =>
         globalRef("exports").flatMap { exportsVarRef =>
@@ -1110,7 +1103,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
               js.StringLiteral(exportName),
               List(
                   "get" -> js.Function(arrow = false, Nil, None, {
-                    js.Return(globalVar(VarField.t, varScope))
+                    js.Return(globalVar(VarField.t, field.name))
                   }),
                   "configurable" -> js.BooleanLiteral(true)
               )
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/EmitterNames.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/EmitterNames.scala
index 4c1bcebc2b..ba31cd7019 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/EmitterNames.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/EmitterNames.scala
@@ -26,8 +26,8 @@ private[emitter] object EmitterNames {
 
   // Field names
 
-  val dataFieldName = FieldName("data")
-  val exceptionFieldName = FieldName("exception")
+  val dataFieldName = FieldName(ClassClass, SimpleFieldName("data"))
+  val exceptionFieldName = FieldName(JavaScriptExceptionClass, SimpleFieldName("exception"))
 
   // Method names
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
index 128e8ebeed..32b8baca4f 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
@@ -459,11 +459,11 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
     }
 
     def makeRecordFieldIdent(recIdent: js.Ident,
-        fieldName: FieldName, fieldOrigName: OriginalName)(
+        fieldName: SimpleFieldName, fieldOrigName: OriginalName)(
         implicit pos: Position): js.Ident = {
 
       /* "__" is a safe separator for generated names because JSGen avoids it
-       * when generating `LocalName`s and `FieldName`s.
+       * when generating `LocalName`s and `SimpleFieldName`s.
        */
       val name = recIdent.name + "__" + genName(fieldName)
       val originalName = OriginalName(
@@ -607,11 +607,11 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
 
         case Assign(lhs, rhs) =>
           lhs match {
-            case Select(qualifier, className, field) =>
+            case Select(qualifier, field) =>
               unnest(checkNotNull(qualifier), rhs) { (newQualifier, newRhs, env0) =>
                 implicit val env = env0
                 js.Assign(
-                    genSelect(transformExprNoChar(newQualifier), className, field)(lhs.pos),
+                    genSelect(transformExprNoChar(newQualifier), field)(lhs.pos),
                     transformExpr(newRhs, lhs.tpe))
               }
 
@@ -648,12 +648,12 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
                   mutable = true)(lhs.tpe))
               pushLhsInto(Lhs.Assign(newLhs), rhs, tailPosLabels)
 
-            case JSPrivateSelect(qualifier, className, field) =>
+            case JSPrivateSelect(qualifier, field) =>
               unnest(qualifier, rhs) { (newQualifier, newRhs, env0) =>
                 implicit val env = env0
                 js.Assign(
-                    genJSPrivateSelect(transformExprNoChar(newQualifier),
-                        className, field)(moduleContext, globalKnowledge, lhs.pos),
+                    genJSPrivateSelect(transformExprNoChar(newQualifier), field)(
+                        moduleContext, globalKnowledge, lhs.pos),
                     transformExprNoChar(newRhs))
               }
 
@@ -676,13 +676,11 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
                       transformExprNoChar(rhs))
               }
 
-            case SelectStatic(className, item) =>
-              val scope = (className, item.name)
-
-              if (needToUseGloballyMutableVarSetter(scope)) {
+            case SelectStatic(item) =>
+              if (needToUseGloballyMutableVarSetter(item.name)) {
                 unnest(rhs) { (rhs, env0) =>
                   implicit val env = env0
-                  js.Apply(globalVar(VarField.u, scope), transformExpr(rhs, lhs.tpe) :: Nil)
+                  js.Apply(globalVar(VarField.u, item.name), transformExpr(rhs, lhs.tpe) :: Nil)
                 }
               } else {
                 // Assign normally.
@@ -837,7 +835,7 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
               field match {
                 case FieldDef(_, name, _, _) =>
                   js.Assign(
-                      genJSPrivateSelect(js.This(), enclosingClassName, name),
+                      genJSPrivateSelect(js.This(), name),
                       zero)
 
                 case JSFieldDef(_, name, _) =>
@@ -1066,8 +1064,8 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
 
               case New(className, constr, args) if noExtractYet =>
                 New(className, constr, recs(args))
-              case Select(qualifier, className, item) if noExtractYet =>
-                Select(rec(qualifier), className, item)(arg.tpe)
+              case Select(qualifier, item) if noExtractYet =>
+                Select(rec(qualifier), item)(arg.tpe)
               case Apply(flags, receiver, method, args) if noExtractYet =>
                 val newArgs = recs(args)
                 Apply(flags, rec(receiver), method, newArgs)(arg.tpe)
@@ -1292,9 +1290,9 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
           testNPE(obj)
 
         // Expressions preserving side-effect freedom (modulo NPE)
-        case Select(qualifier, _, _) =>
+        case Select(qualifier, _) =>
           allowUnpure && testNPE(qualifier)
-        case SelectStatic(_, _) =>
+        case SelectStatic(_) =>
           allowUnpure
         case ArrayValue(tpe, elems) =>
           allowUnpure && (elems forall test)
@@ -1354,7 +1352,7 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
           allowSideEffects && test(fun) && (args.forall(testJSArg))
         case Transient(JSNewVararg(ctor, argArray)) =>
           allowSideEffects && test(ctor) && test(argArray)
-        case JSPrivateSelect(qualifier, _, _) =>
+        case JSPrivateSelect(qualifier, _) =>
           allowSideEffects && test(qualifier)
         case JSSelect(qualifier, item) =>
           allowSideEffects && test(qualifier) && test(item)
@@ -1467,10 +1465,9 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
           val base = js.Assign(transformExpr(lhs, preserveChar = true),
               transformExpr(rhs, lhs.tpe))
           lhs match {
-            case SelectStatic(className, FieldIdent(field))
+            case SelectStatic(FieldIdent(field))
                 if moduleKind == ModuleKind.NoModule =>
-              val mirrors =
-                globalKnowledge.getStaticFieldMirrors(className, field)
+              val mirrors = globalKnowledge.getStaticFieldMirrors(field)
               mirrors.foldLeft(base) { (prev, mirror) =>
                 js.Assign(genGlobalVarRef(mirror), prev)
               }
@@ -1716,9 +1713,9 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
             redo(New(className, ctor, newArgs))(env)
           }
 
-        case Select(qualifier, className, item) =>
+        case Select(qualifier, item) =>
           unnest(qualifier) { (newQualifier, env) =>
-            redo(Select(newQualifier, className, item)(rhs.tpe))(env)
+            redo(Select(newQualifier, item)(rhs.tpe))(env)
           }
 
         case Apply(flags, receiver, method, args) =>
@@ -1924,9 +1921,9 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
             redo(JSImportCall(newArg))(env)
           }
 
-        case JSPrivateSelect(qualifier, className, field) =>
+        case JSPrivateSelect(qualifier, field) =>
           unnest(qualifier) { (newQualifier, env) =>
-            redo(JSPrivateSelect(newQualifier, className, field))(env)
+            redo(JSPrivateSelect(newQualifier, field))(env)
           }
 
         case JSSelect(qualifier, item) =>
@@ -2210,11 +2207,11 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
         case LoadModule(className) =>
           genLoadModule(className)
 
-        case Select(qualifier, className, field) =>
-          genSelect(transformExprNoChar(checkNotNull(qualifier)), className, field)
+        case Select(qualifier, field) =>
+          genSelect(transformExprNoChar(checkNotNull(qualifier)), field)
 
-        case SelectStatic(className, item) =>
-          globalVar(VarField.t, (className, item.name))
+        case SelectStatic(item) =>
+          globalVar(VarField.t, item.name)
 
         case SelectJSNativeMember(className, member) =>
           val jsNativeLoadSpec =
@@ -2725,7 +2722,7 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
           val newExpr = transformExprNoChar(expr).asInstanceOf[js.VarRef]
           js.If(
               genIsInstanceOfClass(newExpr, JavaScriptExceptionClass),
-              genSelect(newExpr, JavaScriptExceptionClass, FieldIdent(exceptionFieldName)),
+              genSelect(newExpr, FieldIdent(exceptionFieldName)),
               genCheckNotNull(newExpr))
 
         // Transients
@@ -2738,7 +2735,7 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
         case Transient(ZeroOf(runtimeClass)) =>
           js.DotSelect(
               genSelect(transformExprNoChar(checkNotNull(runtimeClass)),
-                  ClassClass, FieldIdent(dataFieldName)),
+                  FieldIdent(dataFieldName)),
               js.Ident("zero"))
 
         case Transient(NativeArrayWrapper(elemClass, nativeArray)) =>
@@ -2751,7 +2748,7 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
             case _ =>
               val elemClassData = genSelect(
                   transformExprNoChar(checkNotNull(elemClass)),
-                  ClassClass, FieldIdent(dataFieldName))
+                  FieldIdent(dataFieldName))
               val arrayClassData = js.Apply(
                   js.DotSelect(elemClassData, js.Ident("getArrayOf")), Nil)
               js.Apply(arrayClassData DOT "wrapArray", newNativeArray :: Nil)
@@ -2808,8 +2805,8 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
           genCallHelper(VarField.newJSObjectWithVarargs,
               transformExprNoChar(constr), transformExprNoChar(argsArray))
 
-        case JSPrivateSelect(qualifier, className, field) =>
-          genJSPrivateSelect(transformExprNoChar(qualifier), className, field)
+        case JSPrivateSelect(qualifier, field) =>
+          genJSPrivateSelect(transformExprNoChar(qualifier), field)
 
         case JSSelect(qualifier, item) =>
           genBracketSelect(transformExprNoChar(qualifier),
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/GlobalKnowledge.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/GlobalKnowledge.scala
index 1122c4b935..84592f0ec1 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/GlobalKnowledge.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/GlobalKnowledge.scala
@@ -33,8 +33,7 @@ private[emitter] trait GlobalKnowledge {
    *  It is invalid to call this method with anything but a `Class` or
    *  `ModuleClass`.
    */
-  def getAllScalaClassFieldDefs(
-      className: ClassName): List[(ClassName, List[AnyFieldDef])]
+  def getAllScalaClassFieldDefs(className: ClassName): List[AnyFieldDef]
 
   /** Tests whether the specified class uses an inlineable init.
    *
@@ -82,7 +81,7 @@ private[emitter] trait GlobalKnowledge {
   def getFieldDefs(className: ClassName): List[AnyFieldDef]
 
   /** The global variables that mirror a given static field. */
-  def getStaticFieldMirrors(className: ClassName, field: FieldName): List[String]
+  def getStaticFieldMirrors(field: FieldName): List[String]
 
   /** The module containing this class definition.
    *
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/KnowledgeGuardian.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/KnowledgeGuardian.scala
index 2d7f18b19c..1e9f26e285 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/KnowledgeGuardian.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/KnowledgeGuardian.scala
@@ -178,7 +178,7 @@ private[emitter] final class KnowledgeGuardian(config: Emitter.Config) {
     def isInterface(className: ClassName): Boolean =
       classes(className).askIsInterface(this)
 
-    def getAllScalaClassFieldDefs(className: ClassName): List[(ClassName, List[AnyFieldDef])] =
+    def getAllScalaClassFieldDefs(className: ClassName): List[AnyFieldDef] =
       classes(className).askAllScalaClassFieldDefs(this)
 
     def hasInlineableInit(className: ClassName): Boolean =
@@ -205,8 +205,8 @@ private[emitter] final class KnowledgeGuardian(config: Emitter.Config) {
     def getFieldDefs(className: ClassName): List[AnyFieldDef] =
       classes(className).askFieldDefs(this)
 
-    def getStaticFieldMirrors(className: ClassName, field: FieldName): List[String] =
-      classes(className).askStaticFieldMirrors(this, field)
+    def getStaticFieldMirrors(field: FieldName): List[String] =
+      classes(field.className).askStaticFieldMirrors(this, field)
 
     def getModule(className: ClassName): ModuleID =
       classes(className).askModule(this)
@@ -366,8 +366,8 @@ private[emitter] final class KnowledgeGuardian(config: Emitter.Config) {
      *    which will change every time the reachability analysis of the
      *    `JSFieldDef`s changes (because we either keep all or none of
      *    them), and
-     *  - the list of names of the `FieldDef`s, which will change every time
-     *    the reachability analysis of the `FieldDef`s changes.
+     *  - the list of simple names of the `FieldDef`s, which will change every
+     *    time the reachability analysis of the `FieldDef`s changes.
      *
      *  We do not try to use the names of `JSFieldDef`s because they are
      *  `Tree`s, which are not efficiently comparable nor versionable here.
@@ -376,7 +376,7 @@ private[emitter] final class KnowledgeGuardian(config: Emitter.Config) {
       val hasAnyJSField = linkedClass.fields.exists(_.isInstanceOf[JSFieldDef])
       val hasAnyJSFieldVersion = Version.fromByte(if (hasAnyJSField) 1 else 0)
       val scalaFieldNamesVersion = linkedClass.fields.collect {
-        case FieldDef(_, FieldIdent(name), _, _) => Version.fromUTF8String(name.encoded)
+        case FieldDef(_, FieldIdent(name), _, _) => Version.fromUTF8String(name.simpleName.encoded)
       }
       Version.combine((linkedClass.version :: hasAnyJSFieldVersion :: scalaFieldNamesVersion): _*)
     }
@@ -396,15 +396,14 @@ private[emitter] final class KnowledgeGuardian(config: Emitter.Config) {
       isInterface
     }
 
-    def askAllScalaClassFieldDefs(
-        invalidatable: Invalidatable): List[(ClassName, List[AnyFieldDef])] = {
+    def askAllScalaClassFieldDefs(invalidatable: Invalidatable): List[AnyFieldDef] = {
       invalidatable.registeredTo(this)
       superClassAskers += invalidatable
       fieldDefsAskers += invalidatable
       val inheritedFieldDefs =
         if (superClass == null) Nil
         else classes(superClass).askAllScalaClassFieldDefs(invalidatable)
-      inheritedFieldDefs :+ (className -> fieldDefs)
+      inheritedFieldDefs ::: fieldDefs
     }
 
     def askHasInlineableInit(invalidatable: Invalidatable): Boolean = {
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/NameGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/NameGen.scala
index 3f21ea8adb..552dd545bd 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/NameGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/NameGen.scala
@@ -47,8 +47,8 @@ private[emitter] final class NameGen {
     cache
   }
 
-  private val genFieldNameCache =
-    mutable.Map.empty[FieldName, String]
+  private val genSimpleFieldNameCache =
+    mutable.Map.empty[SimpleFieldName, String]
 
   private val genMethodNameCache =
     mutable.Map.empty[MethodName, String]
@@ -107,7 +107,10 @@ private[emitter] final class NameGen {
   }
 
   def genName(name: LabelName): String = genNameGeneric(name, genLabelNameCache)
-  def genName(name: FieldName): String = genNameGeneric(name, genFieldNameCache)
+  def genName(name: SimpleFieldName): String = genNameGeneric(name, genSimpleFieldNameCache)
+
+  def genName(name: FieldName): String =
+    genName(name.className) + "__f_" + genName(name.simpleName)
 
   def genName(name: MethodName): String = {
     genMethodNameCache.getOrElseUpdate(name, {
@@ -210,6 +213,11 @@ private[emitter] final class NameGen {
     genOriginalName(name.encoded, originalName, jsName)
   }
 
+  def genOriginalName(name: FieldName, originalName: OriginalName,
+      jsName: String): OriginalName = {
+    genOriginalName(name.simpleName, originalName, jsName)
+  }
+
   def genOriginalName(name: MethodName, originalName: OriginalName,
       jsName: String): OriginalName = {
     genOriginalName(name.simpleName, originalName, jsName)
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala
index 4cc050d33c..4541d3a292 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala
@@ -163,22 +163,19 @@ private[emitter] final class SJSGen(
       genCallHelper(VarField.systemArraycopy, args: _*)
   }
 
-  def genSelect(receiver: Tree, className: ClassName, field: irt.FieldIdent)(
+  def genSelect(receiver: Tree, field: irt.FieldIdent)(
       implicit pos: Position): Tree = {
-    DotSelect(receiver, Ident(genFieldJSName(className, field))(field.pos))
+    DotSelect(receiver, Ident(genName(field.name))(field.pos))
   }
 
-  def genSelect(receiver: Tree, className: ClassName, field: irt.FieldIdent,
+  def genSelect(receiver: Tree, field: irt.FieldIdent,
       originalName: OriginalName)(
       implicit pos: Position): Tree = {
-    val jsName = genFieldJSName(className, field)
+    val jsName = genName(field.name)
     val jsOrigName = genOriginalName(field.name, originalName, jsName)
     DotSelect(receiver, Ident(jsName, jsOrigName)(field.pos))
   }
 
-  private def genFieldJSName(className: ClassName, field: irt.FieldIdent): String =
-    genName(className) + "__f_" + genName(field.name)
-
   def genApply(receiver: Tree, methodName: MethodName, args: List[Tree])(
       implicit pos: Position): Tree = {
     Apply(DotSelect(receiver, Ident(genMethodName(methodName))), args)
@@ -192,13 +189,12 @@ private[emitter] final class SJSGen(
   def genMethodName(methodName: MethodName): String =
     genName(methodName)
 
-  def genJSPrivateSelect(receiver: Tree, className: ClassName,
-      field: irt.FieldIdent)(
+  def genJSPrivateSelect(receiver: Tree, field: irt.FieldIdent)(
       implicit moduleContext: ModuleContext, globalKnowledge: GlobalKnowledge,
       pos: Position): Tree = {
     val fieldName = {
       implicit val pos = field.pos
-      globalVar(VarField.r, (className, field.name))
+      globalVar(VarField.r, field.name)
     }
 
     BracketSelect(receiver, fieldName)
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/VarGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/VarGen.scala
index 7b7f87859d..11d93244d9 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/VarGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/VarGen.scala
@@ -350,11 +350,11 @@ private[emitter] final class VarGen(jsGen: JSGen, nameGen: NameGen,
       def reprClass(x: ClassName): ClassName = x
     }
 
-    implicit object FieldScope extends Scope[(ClassName, FieldName)] {
-      def subField(x: (ClassName, FieldName)): String =
-        genName(x._1) + "__" + genName(x._2)
+    implicit object FieldScope extends Scope[FieldName] {
+      def subField(x: FieldName): String =
+        genName(x.className) + "__" + genName(x.simpleName)
 
-      def reprClass(x: (ClassName, FieldName)): ClassName = x._1
+      def reprClass(x: FieldName): ClassName = x.className
     }
 
     implicit object MethodScope extends Scope[(ClassName, MethodName)] {
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala b/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
index ba64a3b9b1..981d065512 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
@@ -214,6 +214,8 @@ private final class ClassDefChecker(classDef: ClassDef,
       case FieldDef(_, FieldIdent(name), _, ftpe) =>
         if (!classDef.kind.isAnyNonNativeClass)
           reportError("illegal FieldDef (only non native classes may contain fields)")
+        if (name.className != classDef.className)
+          reportError(i"illegal FieldDef with name $name in class ${classDef.className}")
         if (fields(namespace.ordinal).put(name, ftpe).isDefined)
           reportError(i"duplicate ${namespace.prefixString}field '$name'")
 
@@ -620,7 +622,7 @@ private final class ClassDefChecker(classDef: ClassDef,
         if (env.thisType == NoType) // can happen before JSSuperConstructorCall in JSModuleClass
           reportError(i"Cannot find `this` in scope for StoreModule()")
 
-      case Select(qualifier, _, _) =>
+      case Select(qualifier, _) =>
         checkTree(qualifier, env)
 
       case _: SelectStatic =>
@@ -714,7 +716,7 @@ private final class ClassDefChecker(classDef: ClassDef,
         checkTree(ctor, env)
         checkTreeOrSpreads(args, env)
 
-      case JSPrivateSelect(qualifier, className, field) =>
+      case JSPrivateSelect(qualifier, _) =>
         checkTree(qualifier, env)
 
       case JSSelect(qualifier, item) =>
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/checker/ErrorReporter.scala b/linker/shared/src/main/scala/org/scalajs/linker/checker/ErrorReporter.scala
index 35cef51bf6..18c6527d13 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/checker/ErrorReporter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/checker/ErrorReporter.scala
@@ -36,6 +36,7 @@ private[checker] object ErrorReporter {
     private def format(arg: Any): String = {
       arg match {
         case arg: Name       => arg.nameString
+        case arg: FieldName  => arg.nameString
         case arg: MethodName => arg.displayName
         case arg: IRNode     => arg.show
         case arg: TypeRef    => arg.displayName
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala b/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
index 418629d55b..8f399fa984 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
@@ -225,23 +225,23 @@ private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter) {
         typecheckExpect(body, env.withLabeledReturnType(label.name, tpe), tpe)
 
       case Assign(lhs, rhs) =>
-        def checkNonStaticField(receiver: Tree, className: ClassName, name: FieldName): Unit = {
+        def checkNonStaticField(receiver: Tree, name: FieldName): Unit = {
           receiver match {
-            case This() if env.inConstructorOf == Some(className) =>
+            case This() if env.inConstructorOf == Some(name.className) =>
               // ok
             case _ =>
-              if (lookupClass(className).lookupField(name).exists(!_.flags.isMutable))
+              if (lookupClass(name.className).lookupField(name).exists(!_.flags.isMutable))
                 reportError(i"Assignment to immutable field $name.")
           }
         }
 
         lhs match {
-          case Select(receiver, className, FieldIdent(name)) =>
-            checkNonStaticField(receiver, className, name)
-          case JSPrivateSelect(receiver, className, FieldIdent(name)) =>
-            checkNonStaticField(receiver, className, name)
-          case SelectStatic(className, FieldIdent(name)) =>
-            val c = lookupClass(className)
+          case Select(receiver, FieldIdent(name)) =>
+            checkNonStaticField(receiver, name)
+          case JSPrivateSelect(receiver, FieldIdent(name)) =>
+            checkNonStaticField(receiver, name)
+          case SelectStatic(FieldIdent(name)) =>
+            val c = lookupClass(name.className)
             for {
               f <- c.lookupStaticField(name)
               if !f.flags.isMutable
@@ -323,7 +323,8 @@ private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter) {
         // Nothing to check; everything is checked in ClassDefChecker
         ()
 
-      case Select(qualifier, className, FieldIdent(item)) =>
+      case Select(qualifier, FieldIdent(item)) =>
+        val className = item.className
         val c = lookupClass(className)
         val kind = c.kind
         if (!kind.isClass) {
@@ -354,7 +355,8 @@ private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter) {
           }
         }
 
-      case SelectStatic(className, FieldIdent(item)) =>
+      case SelectStatic(FieldIdent(item)) =>
+        val className = item.className
         val checkedClass = lookupClass(className)
         if (checkedClass.kind.isJSType) {
           reportError(i"Cannot select static $item of JS type $className")
@@ -530,8 +532,9 @@ private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter) {
         for (arg <- args)
           typecheckExprOrSpread(arg, env)
 
-      case JSPrivateSelect(qualifier, className, field) =>
+      case JSPrivateSelect(qualifier, field) =>
         typecheckExpr(qualifier, env)
+        val className = field.name.className
         val checkedClass = lookupClass(className)
         if (!checkedClass.kind.isJSClass && checkedClass.kind != ClassKind.AbstractJSType) {
           reportError(i"Cannot select JS private field $field of non-JS class $className")
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
index 05763942ff..6d8cc24f28 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
@@ -645,7 +645,7 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
           field = anyField.asInstanceOf[FieldDef]
           if parent.fieldsRead.contains(field.name.name)
         } yield {
-          parent.className -> field
+          field
         }
 
         Some(new OptimizerCore.InlineableClassStructure(allFields))
@@ -717,8 +717,8 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
       }
 
       def isElidableStat(tree: Tree): Boolean = tree match {
-        case Block(stats)                      => stats.forall(isElidableStat)
-        case Assign(Select(This(), _, _), rhs) => isTriviallySideEffectFree(rhs)
+        case Block(stats)                   => stats.forall(isElidableStat)
+        case Assign(Select(This(), _), rhs) => isTriviallySideEffectFree(rhs)
 
         // Mixin constructor -- test whether its body is entirely empty
         case ApplyStatically(flags, This(), className, methodName, Nil)
@@ -1462,11 +1462,11 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
       }
     }
 
-    protected def isFieldRead(className: ClassName, fieldName: FieldName): Boolean =
-      getInterface(className).askFieldRead(fieldName, asker)
+    protected def isFieldRead(fieldName: FieldName): Boolean =
+      getInterface(fieldName.className).askFieldRead(fieldName, asker)
 
-    protected def isStaticFieldRead(className: ClassName, fieldName: FieldName): Boolean =
-      getInterface(className).askStaticFieldRead(fieldName, asker)
+    protected def isStaticFieldRead(fieldName: FieldName): Boolean =
+      getInterface(fieldName.className).askStaticFieldRead(fieldName, asker)
   }
 
 }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
index a417440b22..2dca9842bd 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
@@ -88,10 +88,10 @@ private[optimizer] abstract class OptimizerCore(
       target: ImportTarget): Option[JSNativeLoadSpec.Import]
 
   /** Returns true if the given (non-static) field is ever read. */
-  protected def isFieldRead(className: ClassName, fieldName: FieldName): Boolean
+  protected def isFieldRead(fieldName: FieldName): Boolean
 
   /** Returns true if the given static field is ever read. */
-  protected def isStaticFieldRead(className: ClassName, fieldName: FieldName): Boolean
+  protected def isStaticFieldRead(fieldName: FieldName): Boolean
 
   private val localNameAllocator = new FreshNameAllocator.Local
 
@@ -180,9 +180,9 @@ private[optimizer] abstract class OptimizerCore(
         } else {
           val after = from.tail
           val afterIsTrivial = after.forall {
-            case Assign(Select(This(), _, _), _:Literal | _:VarRef) =>
+            case Assign(Select(This(), _), _:Literal | _:VarRef) =>
               true
-            case Assign(SelectStatic(_, _), _:Literal | _:VarRef) =>
+            case Assign(SelectStatic(_), _:Literal | _:VarRef) =>
               true
             case _ =>
               false
@@ -334,15 +334,15 @@ private[optimizer] abstract class OptimizerCore(
         }
 
         lhs match {
-          case Select(qualifier, className, FieldIdent(name)) if !isFieldRead(className, name) =>
+          case Select(qualifier, FieldIdent(name)) if !isFieldRead(name) =>
             // Field is never read. Drop assign, keep side effects only.
             Block(transformStat(qualifier), transformStat(rhs))
 
-          case SelectStatic(className, FieldIdent(name)) if !isStaticFieldRead(className, name) =>
+          case SelectStatic(FieldIdent(name)) if !isStaticFieldRead(name) =>
             // Field is never read. Drop assign, keep side effects only.
             transformStat(rhs)
 
-          case JSPrivateSelect(qualifier, className, FieldIdent(name)) if !isFieldRead(className, name) =>
+          case JSPrivateSelect(qualifier, FieldIdent(name)) if !isFieldRead(name) =>
             // Field is never read. Drop assign, keep side effects only.
             Block(transformStat(qualifier), transformStat(rhs))
 
@@ -574,8 +574,8 @@ private[optimizer] abstract class OptimizerCore(
       case JSNew(ctor, args) =>
         JSNew(transformExpr(ctor), transformExprsOrSpreads(args))
 
-      case JSPrivateSelect(qualifier, className, field) =>
-        JSPrivateSelect(transformExpr(qualifier), className, field)
+      case JSPrivateSelect(qualifier, field) =>
+        JSPrivateSelect(transformExpr(qualifier), field)
 
       case tree: JSSelect =>
         trampoline {
@@ -967,7 +967,7 @@ private[optimizer] abstract class OptimizerCore(
           } else if (baseTpe == NullType) {
             cont(checkNotNull(texpr))
           } else if (isSubtype(baseTpe, JavaScriptExceptionClassType)) {
-            pretransformSelectCommon(AnyType, texpr, JavaScriptExceptionClass,
+            pretransformSelectCommon(AnyType, texpr,
                 FieldIdent(exceptionFieldName), isLhsOfAssign = false)(cont)
           } else {
             if (texpr.tpe.isExact || !isSubtype(JavaScriptExceptionClassType, baseTpe))
@@ -1171,16 +1171,15 @@ private[optimizer] abstract class OptimizerCore(
   private def pretransformSelectCommon(tree: Select, isLhsOfAssign: Boolean)(
       cont: PreTransCont)(
       implicit scope: Scope): TailRec[Tree] = {
-    val Select(qualifier, className, field) = tree
+    val Select(qualifier, field) = tree
     pretransformExpr(qualifier) { preTransQual =>
-      pretransformSelectCommon(tree.tpe, preTransQual, className, field,
-          isLhsOfAssign)(cont)(scope, tree.pos)
+      pretransformSelectCommon(tree.tpe, preTransQual, field, isLhsOfAssign)(
+          cont)(scope, tree.pos)
     }
   }
 
   private def pretransformSelectCommon(expectedType: Type,
-      preTransQual: PreTransform, className: ClassName, field: FieldIdent,
-      isLhsOfAssign: Boolean)(
+      preTransQual: PreTransform, field: FieldIdent, isLhsOfAssign: Boolean)(
       cont: PreTransCont)(
       implicit scope: Scope, pos: Position): TailRec[Tree] = {
     /* Note: Callers are expected to have already removed writes to fields that
@@ -1190,7 +1189,7 @@ private[optimizer] abstract class OptimizerCore(
     preTransQual match {
       case PreTransLocalDef(LocalDef(_, _,
           InlineClassBeingConstructedReplacement(_, fieldLocalDefs, cancelFun))) =>
-        val fieldLocalDef = fieldLocalDefs(FieldID(className, field))
+        val fieldLocalDef = fieldLocalDefs(field.name)
         if (!isLhsOfAssign || fieldLocalDef.mutable) {
           cont(fieldLocalDef.toPreTransform)
         } else {
@@ -1205,18 +1204,18 @@ private[optimizer] abstract class OptimizerCore(
 
       case PreTransLocalDef(LocalDef(_, _,
           InlineClassInstanceReplacement(_, fieldLocalDefs, cancelFun))) =>
-        val fieldLocalDef = fieldLocalDefs(FieldID(className, field))
+        val fieldLocalDef = fieldLocalDefs(field.name)
         assert(!isLhsOfAssign || fieldLocalDef.mutable, s"assign to immutable field at $pos")
         cont(fieldLocalDef.toPreTransform)
 
       // Select the lo or hi "field" of a Long literal
       case PreTransLit(LongLiteral(value)) if useRuntimeLong =>
         val itemName = field.name
-        assert(itemName == inlinedRTLongLoField ||
-            itemName == inlinedRTLongHiField)
+        assert(itemName.simpleName == inlinedRTLongLoField ||
+            itemName.simpleName == inlinedRTLongHiField)
         assert(expectedType == IntType)
         val resultValue =
-          if (itemName == inlinedRTLongLoField) value.toInt
+          if (itemName.simpleName == inlinedRTLongLoField) value.toInt
           else (value >>> 32).toInt
         cont(PreTransLit(IntLiteral(resultValue)))
 
@@ -1224,8 +1223,13 @@ private[optimizer] abstract class OptimizerCore(
         resolveLocalDef(preTransQual) match {
           case PreTransRecordTree(newQual, origType, cancelFun) =>
             val recordType = newQual.tpe.asInstanceOf[RecordType]
-            val recordField = recordType.findField(field.name)
-            val sel = RecordSelect(newQual, field)(recordField.tpe)
+            /* FIXME How come this lookup requires only the `simpleName`?
+             * The `recordType` is created at `InlineableClassStructure.recordType`,
+             * where it uses an allocator. Something fishy is going on here.
+             * (And no, this is not dead code.)
+             */
+            val recordField = recordType.findField(field.name.simpleName)
+            val sel = RecordSelect(newQual, SimpleFieldIdent(recordField.name))(recordField.tpe)
             sel.tpe match {
               case _: RecordType =>
                 cont(PreTransRecordTree(sel, RefinedType(expectedType), cancelFun))
@@ -1235,7 +1239,7 @@ private[optimizer] abstract class OptimizerCore(
 
           case PreTransTree(newQual, newQualType) =>
             val newQual1 = maybeAssumeNotNull(newQual, newQualType)
-            cont(PreTransTree(Select(newQual1, className, field)(expectedType),
+            cont(PreTransTree(Select(newQual1, field)(expectedType),
                 RefinedType(expectedType)))
         }
     }
@@ -1332,7 +1336,7 @@ private[optimizer] abstract class OptimizerCore(
             if (!isImmutableType(recordType))
               cancelFun()
             PreTransRecordTree(
-                RecordValue(recordType, structure.fieldIDs.map(
+                RecordValue(recordType, structure.fieldNames.map(
                     id => fieldLocalDefs(id).newReplacement)),
                 tpe, cancelFun)
 
@@ -1591,7 +1595,7 @@ private[optimizer] abstract class OptimizerCore(
       checkNotNullStatement(array)(stat.pos)
     case ArraySelect(array, index) if semantics.arrayIndexOutOfBounds == CheckedBehavior.Unchecked =>
       Block(checkNotNullStatement(array)(stat.pos), keepOnlySideEffects(index))(stat.pos)
-    case Select(qualifier, _, _) =>
+    case Select(qualifier, _) =>
       checkNotNullStatement(qualifier)(stat.pos)
     case Closure(_, _, _, _, _, captureValues) =>
       Block(captureValues.map(keepOnlySideEffects))(stat.pos)
@@ -2221,13 +2225,13 @@ private[optimizer] abstract class OptimizerCore(
             "There was a This(), there should be a receiver")
         cont(checkNotNull(optReceiver.get._2))
 
-      case Select(This(), className, field) if formals.isEmpty =>
+      case Select(This(), field) if formals.isEmpty =>
         assert(optReceiver.isDefined,
             "There was a This(), there should be a receiver")
-        pretransformSelectCommon(body.tpe, optReceiver.get._2, className, field,
+        pretransformSelectCommon(body.tpe, optReceiver.get._2, field,
             isLhsOfAssign = false)(cont)
 
-      case Assign(lhs @ Select(This(), className, field), VarRef(LocalIdent(rhsName)))
+      case Assign(lhs @ Select(This(), field), VarRef(LocalIdent(rhsName)))
           if formals.size == 1 && formals.head.name.name == rhsName =>
         assert(isStat, "Found Assign in expression position")
         assert(optReceiver.isDefined,
@@ -2236,11 +2240,11 @@ private[optimizer] abstract class OptimizerCore(
         val treceiver = optReceiver.get._2
         val trhs = args.head
 
-        if (!isFieldRead(className, field.name)) {
+        if (!isFieldRead(field.name)) {
           // Field is never read, discard assign, keep side effects only.
           cont(PreTransTree(finishTransformArgsAsStat(), RefinedType.NoRefinedType))
         } else {
-          pretransformSelectCommon(lhs.tpe, treceiver, className, field,
+          pretransformSelectCommon(lhs.tpe, treceiver, field,
               isLhsOfAssign = true) { tlhs =>
             pretransformAssign(tlhs, args.head)(cont)
           }
@@ -2582,7 +2586,7 @@ private[optimizer] abstract class OptimizerCore(
                   elemLocalDef match {
                     case LocalDef(RefinedType(ClassType(Tuple2Class), _, _), false,
                         InlineClassInstanceReplacement(structure, tupleFields, _)) =>
-                      val List(key, value) = structure.fieldIDs.map(tupleFields)
+                      val List(key, value) = structure.fieldNames.map(tupleFields)
                       (key.newReplacement, value.newReplacement)
 
                     case _ =>
@@ -2658,7 +2662,7 @@ private[optimizer] abstract class OptimizerCore(
 
     withNewLocalDefs(initialFieldBindings) { (initialFieldLocalDefList, cont1) =>
       val initialFieldLocalDefs =
-        structure.fieldIDs.zip(initialFieldLocalDefList).toMap
+        structure.fieldNames.zip(initialFieldLocalDefList).toMap
 
       inlineClassConstructorBody(allocationSite, structure, initialFieldLocalDefs,
           className, className, ctor, args, cancelFun) { (finalFieldLocalDefs, cont2) =>
@@ -2674,10 +2678,10 @@ private[optimizer] abstract class OptimizerCore(
 
   private def inlineClassConstructorBody(
       allocationSite: AllocationSite, structure: InlineableClassStructure,
-      inputFieldsLocalDefs: Map[FieldID, LocalDef], className: ClassName,
+      inputFieldsLocalDefs: Map[FieldName, LocalDef], className: ClassName,
       ctorClass: ClassName, ctor: MethodIdent, args: List[PreTransform],
       cancelFun: CancelFun)(
-      buildInner: (Map[FieldID, LocalDef], PreTransCont) => TailRec[Tree])(
+      buildInner: (Map[FieldName, LocalDef], PreTransCont) => TailRec[Tree])(
       cont: PreTransCont)(
       implicit scope: Scope): TailRec[Tree] = tailcall {
 
@@ -2714,9 +2718,9 @@ private[optimizer] abstract class OptimizerCore(
 
   private def inlineClassConstructorBodyList(
       allocationSite: AllocationSite, structure: InlineableClassStructure,
-      thisLocalDef: LocalDef, inputFieldsLocalDefs: Map[FieldID, LocalDef],
+      thisLocalDef: LocalDef, inputFieldsLocalDefs: Map[FieldName, LocalDef],
       className: ClassName, stats: List[Tree], cancelFun: CancelFun)(
-      buildInner: (Map[FieldID, LocalDef], PreTransCont) => TailRec[Tree])(
+      buildInner: (Map[FieldName, LocalDef], PreTransCont) => TailRec[Tree])(
       cont: PreTransCont)(
       implicit scope: Scope): TailRec[Tree] = {
 
@@ -2745,18 +2749,17 @@ private[optimizer] abstract class OptimizerCore(
         inlineClassConstructorBodyList(allocationSite, structure, thisLocalDef,
             inputFieldsLocalDefs, className, rest, cancelFun)(buildInner)(cont)
 
-      case Assign(s @ Select(ths: This, className, field), value) :: rest
-          if !inputFieldsLocalDefs.contains(FieldID(className, field)) =>
+      case Assign(s @ Select(ths: This, field), value) :: rest
+          if !inputFieldsLocalDefs.contains(field.name) =>
         // Field is being optimized away. Only keep side effects of the write.
         withStat(value, rest)
 
-      case Assign(s @ Select(ths: This, className, field), value) :: rest
-          if !inputFieldsLocalDefs(FieldID(className, field)).mutable =>
+      case Assign(s @ Select(ths: This, field), value) :: rest
+          if !inputFieldsLocalDefs(field.name).mutable =>
         pretransformExpr(value) { tvalue =>
-          val fieldID = FieldID(className, field)
-          val originalName = structure.fieldOriginalName(fieldID)
+          val originalName = structure.fieldOriginalName(field.name)
           val binding = Binding(
-              Binding.Local(field.name.toLocalName, originalName),
+              Binding.Local(field.name.simpleName.toLocalName, originalName),
               s.tpe, false, tvalue)
           withNewLocalDef(binding) { (localDef, cont1) =>
             if (localDef.contains(thisLocalDef)) {
@@ -2766,7 +2769,7 @@ private[optimizer] abstract class OptimizerCore(
               cancelFun()
             }
             val newFieldsLocalDefs =
-              inputFieldsLocalDefs.updated(fieldID, localDef)
+              inputFieldsLocalDefs.updated(field.name, localDef)
             val newThisLocalDef = LocalDef(thisLocalDef.tpe, false,
                 InlineClassBeingConstructedReplacement(structure, newFieldsLocalDefs, cancelFun))
             val restScope =
@@ -2792,7 +2795,7 @@ private[optimizer] abstract class OptimizerCore(
        * coming from Scala.js < 1.15.1 (since 1.15.1, we intercept that shape
        * already in the compiler back-end).
        */
-      case If(cond, th: Throw, Assign(Select(This(), _, _), value)) :: rest =>
+      case If(cond, th: Throw, Assign(Select(This(), _), value)) :: rest =>
         // work around a bug of the compiler (these should be @-bindings)
         val stat = stats.head.asInstanceOf[If]
         val ass = stat.elsep.asInstanceOf[Assign]
@@ -5083,7 +5086,8 @@ private[optimizer] object OptimizerCore {
   private val JavaScriptExceptionClassType = ClassType(JavaScriptExceptionClass)
   private val ThrowableClassType = ClassType(ThrowableClass)
 
-  private val exceptionFieldName = FieldName("exception")
+  private val exceptionFieldName =
+    FieldName(JavaScriptExceptionClass, SimpleFieldName("exception"))
 
   private val AnyArgConstructorName = MethodName.constructor(List(ClassRef(ObjectClass)))
 
@@ -5092,34 +5096,31 @@ private[optimizer] object OptimizerCore {
   private val ClassTagApplyMethodName =
     MethodName("apply", List(ClassRef(ClassClass)), ClassRef(ClassName("scala.reflect.ClassTag")))
 
-  final class InlineableClassStructure(
-      /** `List[ownerClassName -> fieldDef]`. */
-      private val allFields: List[(ClassName, FieldDef)]) {
-
-    private[OptimizerCore] val fieldIDs: List[FieldID] =
-      allFields.map(field => FieldID(field._1, field._2))
+  final class InlineableClassStructure(private val allFields: List[FieldDef]) {
+    private[OptimizerCore] val fieldNames: List[FieldName] =
+      allFields.map(_.name.name)
 
     private[OptimizerCore] val recordType: RecordType = {
       val allocator = new FreshNameAllocator.Field
       val recordFields = for {
-        (className, f @ FieldDef(flags, FieldIdent(name), originalName, ftpe)) <- allFields
+        f @ FieldDef(flags, FieldIdent(name), originalName, ftpe) <- allFields
       } yield {
         assert(!flags.namespace.isStatic,
             s"unexpected static field in InlineableClassStructure at ${f.pos}")
-        RecordType.Field(allocator.freshName(name), originalName, ftpe,
+        RecordType.Field(allocator.freshName(name.simpleName), originalName, ftpe,
             flags.isMutable)
       }
       RecordType(recordFields)
     }
 
-    private val recordFieldNames: Map[FieldID, RecordType.Field] = {
-      val elems = for (((className, fieldDef), recordField) <- allFields.zip(recordType.fields))
-        yield FieldID(className, fieldDef) -> recordField
+    private val recordFieldNames: Map[FieldName, RecordType.Field] = {
+      val elems = for ((fieldDef, recordField) <- allFields.zip(recordType.fields))
+        yield fieldDef.name.name -> recordField
       elems.toMap
     }
 
-    private[OptimizerCore] def fieldOriginalName(fieldID: FieldID): OriginalName =
-      recordFieldNames(fieldID).originalName
+    private[OptimizerCore] def fieldOriginalName(fieldName: FieldName): OriginalName =
+      recordFieldNames(fieldName).originalName
 
     override def equals(that: Any): Boolean = that match {
       case that: InlineableClassStructure =>
@@ -5132,7 +5133,7 @@ private[optimizer] object OptimizerCore {
 
     override def toString(): String = {
       allFields
-        .map(f => s"${f._1.nameString}::${f._2.name.name.nameString}: ${f._2.ftpe}")
+        .map(f => s"${f.name.name.nameString}: ${f.ftpe}")
         .mkString("InlineableClassStructure(", ", ", ")")
     }
   }
@@ -5276,7 +5277,7 @@ private[optimizer] object OptimizerCore {
        */
       case InlineClassInstanceReplacement(structure, fieldLocalDefs, _)
           if tpe.base == ClassType(LongImpl.RuntimeLongClass) =>
-        val List(loField, hiField) = structure.fieldIDs
+        val List(loField, hiField) = structure.fieldNames
         val lo = fieldLocalDefs(loField).newReplacement
         val hi = fieldLocalDefs(hiField).newReplacement
         createNewLong(lo, hi)
@@ -5341,12 +5342,12 @@ private[optimizer] object OptimizerCore {
 
   private final case class InlineClassBeingConstructedReplacement(
       structure: InlineableClassStructure,
-      fieldLocalDefs: Map[FieldID, LocalDef],
+      fieldLocalDefs: Map[FieldName, LocalDef],
       cancelFun: CancelFun) extends LocalDefReplacement
 
   private final case class InlineClassInstanceReplacement(
       structure: InlineableClassStructure,
-      fieldLocalDefs: Map[FieldID, LocalDef],
+      fieldLocalDefs: Map[FieldName, LocalDef],
       cancelFun: CancelFun) extends LocalDefReplacement
 
   private final case class InlineJSArrayReplacement(
@@ -5798,8 +5799,8 @@ private[optimizer] object OptimizerCore {
 
     val RecordType(List(loField, hiField)) = recordVarRef.tpe
     createNewLong(
-        RecordSelect(recordVarRef, FieldIdent(loField.name))(IntType),
-        RecordSelect(recordVarRef, FieldIdent(hiField.name))(IntType))
+        RecordSelect(recordVarRef, SimpleFieldIdent(loField.name))(IntType),
+        RecordSelect(recordVarRef, SimpleFieldIdent(hiField.name))(IntType))
   }
 
   /** Creates a new instance of `RuntimeLong` from its `lo` and `hi` parts. */
@@ -6056,9 +6057,9 @@ private[optimizer] object OptimizerCore {
               true
 
             // Shape of accessors
-            case Select(This(), _, _) if params.isEmpty =>
+            case Select(This(), _) if params.isEmpty =>
               true
-            case Assign(Select(This(), _, _), VarRef(_)) if params.size == 1 =>
+            case Assign(Select(This(), _), VarRef(_)) if params.size == 1 =>
               true
 
             // Shape of trivial call-super constructors
@@ -6150,7 +6151,7 @@ private[optimizer] object OptimizerCore {
    */
   private def isSmallTree(tree: TreeOrJSSpread): Boolean = tree match {
     case _:VarRef | _:Literal    => true
-    case Select(This(), _, _)    => true
+    case Select(This(), _)       => true
     case UnaryOp(_, lhs)         => isSmallTree(lhs)
     case BinaryOp(_, lhs, rhs)   => isSmallTree(lhs) && isSmallTree(rhs)
     case JSUnaryOp(_, lhs)       => isSmallTree(lhs)
@@ -6165,7 +6166,7 @@ private[optimizer] object OptimizerCore {
       case Apply(_, receiver, _, args)              => areSimpleArgs(receiver :: args)
       case ApplyStatically(_, receiver, _, _, args) => areSimpleArgs(receiver :: args)
       case ApplyStatic(_, _, _, args)               => areSimpleArgs(args)
-      case Select(qual, _, _)                       => isSimpleArg(qual)
+      case Select(qual, _)                          => isSimpleArg(qual)
       case IsInstanceOf(inner, _)                   => isSimpleArg(inner)
 
       case Block(List(inner, Undefined())) =>
@@ -6319,11 +6320,11 @@ private[optimizer] object OptimizerCore {
         name.withSuffix(suffix)
     }
 
-    private val InitialFieldMap: Map[FieldName, Int] =
+    private val InitialFieldMap: Map[SimpleFieldName, Int] =
       Map.empty
 
-    final class Field extends FreshNameAllocator[FieldName](InitialFieldMap) {
-      protected def nameWithSuffix(name: FieldName, suffix: String): FieldName =
+    final class Field extends FreshNameAllocator[SimpleFieldName](InitialFieldMap) {
+      protected def nameWithSuffix(name: SimpleFieldName, suffix: String): SimpleFieldName =
         name.withSuffix(suffix)
     }
 
@@ -6337,30 +6338,6 @@ private[optimizer] object OptimizerCore {
     else OriginalName(base)
   }
 
-  final class FieldID private (val ownerClassName: ClassName, val name: FieldName) {
-    override def equals(that: Any): Boolean = that match {
-      case that: FieldID =>
-        this.ownerClassName == that.ownerClassName &&
-        this.name == that.name
-      case _ =>
-        false
-    }
-
-    override def hashCode(): Int =
-      ownerClassName.## ^ name.##
-
-    override def toString(): String =
-      s"FieldID($ownerClassName, $name)"
-  }
-
-  object FieldID {
-    def apply(ownerClassName: ClassName, field: FieldIdent): FieldID =
-      new FieldID(ownerClassName, field.name)
-
-    def apply(ownerClassName: ClassName, fieldDef: FieldDef): FieldID =
-      new FieldID(ownerClassName, fieldDef.name.name)
-  }
-
   private sealed abstract class IsUsed {
     def isUsed: Boolean
   }
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/OptimizerTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/OptimizerTest.scala
index 608005203e..441b146638 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/OptimizerTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/OptimizerTest.scala
@@ -203,14 +203,14 @@ class OptimizerTest {
             fields = List(
               // static var foo: java.lang.String
               FieldDef(EMF.withNamespace(PublicStatic).withMutable(true),
-                  "foo", NON, StringType)
+                  FieldName(MainTestClassName, "foo"), NON, StringType)
             ),
             methods = List(
                 trivialCtor(MainTestClassName),
                 // static def foo(): java.lang.String = Test::foo
                 MethodDef(EMF.withNamespace(MemberNamespace.PublicStatic),
                     fooGetter, NON, Nil, StringType, Some({
-                      SelectStatic(MainTestClassName, "foo")(StringType)
+                      SelectStatic(FieldName(MainTestClassName, "foo"))(StringType)
                     }))(EOH, UNV),
                 // static def main(args: String[]) { println(Test::foo()) }
                 mainMethodDef({
@@ -223,7 +223,7 @@ class OptimizerTest {
     for (moduleSet <- linkToModuleSet(classDefs, MainTestModuleInitializers)) yield {
       val mainClassDef = findClass(moduleSet, MainTestClassName).get
       assertTrue(mainClassDef.fields.exists {
-        case FieldDef(_, FieldIdent(name), _, _) => name == FieldName("foo")
+        case FieldDef(_, FieldIdent(name), _, _) => name == FieldName(MainTestClassName, "foo")
         case _                                   => false
       })
     }
@@ -491,10 +491,10 @@ class OptimizerTest {
       classDef("Foo", kind = ClassKind.Class, superClass = Some(ObjectClass),
           fields = List(
             // x: Witness
-            FieldDef(EMF.withMutable(witnessMutable), "x", NON, witnessType),
+            FieldDef(EMF.withMutable(witnessMutable), FieldName("Foo", "x"), NON, witnessType),
 
             // y: Int
-            FieldDef(EMF, "y", NON, IntType)
+            FieldDef(EMF, FieldName("Foo", "y"), NON, IntType)
           ),
           methods = List(
             // def this() = {
@@ -502,13 +502,13 @@ class OptimizerTest {
             //   this.y = 5
             // }
             MethodDef(EMF.withNamespace(Constructor), NoArgConstructorName, NON, Nil, NoType, Some(Block(
-              Assign(Select(This()(ClassType("Foo")), "Foo", "x")(witnessType), Null()),
-              Assign(Select(This()(ClassType("Foo")), "Foo", "y")(IntType), int(5))
+              Assign(Select(This()(ClassType("Foo")), FieldName("Foo", "x"))(witnessType), Null()),
+              Assign(Select(This()(ClassType("Foo")), FieldName("Foo", "y"))(IntType), int(5))
             )))(EOH, UNV),
 
             // def method(): Int = this.y
             MethodDef(EMF, methodName, NON, Nil, IntType, Some {
-              Select(This()(ClassType("Foo")), "Foo", "y")(IntType)
+              Select(This()(ClassType("Foo")), FieldName("Foo", "y"))(IntType)
             })(EOH, UNV)
           ),
           optimizerHints = EOH.withInline(classInline)
@@ -527,7 +527,7 @@ class OptimizerTest {
       moduleSet <- linkToModuleSet(classDefs, MainTestModuleInitializers)
     } yield {
       findClass(moduleSet, "Foo").get.fields match {
-        case List(FieldDef(_, FieldIdent(name), _, _)) if name == FieldName("y") =>
+        case List(FieldDef(_, FieldIdent(name), _, _)) if name == FieldName("Foo", "y") =>
           // ok
 
         case fields =>
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/checker/ClassDefCheckerTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/checker/ClassDefCheckerTest.scala
index 75717babd3..e9f6ba2306 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/checker/ClassDefCheckerTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/checker/ClassDefCheckerTest.scala
@@ -122,15 +122,47 @@ class ClassDefCheckerTest {
         "interfaces may not have a superClass")
   }
 
+  @Test
+  def fieldDefClassName(): Unit = {
+    assertError(
+      classDef(
+        "A",
+        superClass = Some(ObjectClass),
+        fields = List(
+          FieldDef(EMF, FieldName("B", "foo"), NON, IntType)
+        ),
+        methods = List(trivialCtor("A"))
+      ),
+      "illegal FieldDef with name B::foo in class A"
+    )
+
+    // evidence that we do not need an explicit check for top-level field exports
+    assertError(
+      classDef(
+        "A",
+        kind = ClassKind.ModuleClass,
+        superClass = Some(ObjectClass),
+        fields = List(
+          FieldDef(EMF.withNamespace(MemberNamespace.PublicStatic), FieldName("A", "foo"), NON, IntType)
+        ),
+        methods = List(trivialCtor("A")),
+        topLevelExportDefs = List(
+          TopLevelFieldExportDef("main", "foo", FieldName("B", "foo"))
+        )
+      ),
+      "Cannot export non-existent static field 'B::foo'"
+    )
+  }
+
   @Test
   def noDuplicateFields(): Unit = {
     assertError(
         classDef("A", superClass = Some(ObjectClass),
             fields = List(
-              FieldDef(EMF, "foobar", NON, IntType),
-              FieldDef(EMF, "foobar", NON, BooleanType)
+              FieldDef(EMF, FieldName("A", "foobar"), NON, IntType),
+              FieldDef(EMF, FieldName("A", "foobar"), NON, BooleanType)
             )),
-        "duplicate field 'foobar'")
+        "duplicate field 'A::foobar'")
   }
 
   @Test
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/testutils/TestIRBuilder.scala b/linker/shared/src/test/scala/org/scalajs/linker/testutils/TestIRBuilder.scala
index 8b73664dc8..be6dbb33a9 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/testutils/TestIRBuilder.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/testutils/TestIRBuilder.scala
@@ -155,8 +155,8 @@ object TestIRBuilder {
     LocalName(name)
   implicit def string2LabelName(name: String): LabelName =
     LabelName(name)
-  implicit def string2FieldName(name: String): FieldName =
-    FieldName(name)
+  implicit def string2SimpleFieldName(name: String): SimpleFieldName =
+    SimpleFieldName(name)
   implicit def string2ClassName(name: String): ClassName =
     ClassName(name)
 
@@ -164,13 +164,13 @@ object TestIRBuilder {
     LocalIdent(LocalName(name))
   implicit def string2LabelIdent(name: String): LabelIdent =
     LabelIdent(LabelName(name))
-  implicit def string2FieldIdent(name: String): FieldIdent =
-    FieldIdent(FieldName(name))
   implicit def string2ClassIdent(name: String): ClassIdent =
     ClassIdent(ClassName(name))
 
   implicit def localName2LocalIdent(name: LocalName): LocalIdent =
     LocalIdent(name)
+  implicit def fieldName2FieldIdent(name: FieldName): FieldIdent =
+    FieldIdent(name)
   implicit def methodName2MethodIdent(name: MethodName): MethodIdent =
     MethodIdent(name)
 
diff --git a/project/BinaryIncompatibilities.scala b/project/BinaryIncompatibilities.scala
index 0144862b7b..6d2c642453 100644
--- a/project/BinaryIncompatibilities.scala
+++ b/project/BinaryIncompatibilities.scala
@@ -6,8 +6,21 @@ import com.typesafe.tools.mima.core.ProblemFilters._
 object BinaryIncompatibilities {
   val IR = Seq(
     // !!! Breaking, OK in minor release
+
+    ProblemFilters.exclude[MissingTypesProblem]("org.scalajs.ir.Names$FieldName"),
+    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Names#FieldName.*"),
+    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Names#LocalName.fromFieldName"),
+
+    ProblemFilters.exclude[IncompatibleMethTypeProblem]("org.scalajs.ir.Types#RecordType.findField"),
+    ProblemFilters.exclude[MemberProblem]("org.scalajs.ir.Types#RecordType#Field.*"),
+
     ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Trees#StoreModule.*"),
     ProblemFilters.exclude[IncompatibleResultTypeProblem]("org.scalajs.ir.Trees#StoreModule.unapply"),
+
+    ProblemFilters.exclude[MemberProblem]("org.scalajs.ir.Trees#JSPrivateSelect.*"),
+    ProblemFilters.exclude[MemberProblem]("org.scalajs.ir.Trees#RecordSelect.*"),
+    ProblemFilters.exclude[MemberProblem]("org.scalajs.ir.Trees#Select.*"),
+    ProblemFilters.exclude[MemberProblem]("org.scalajs.ir.Trees#SelectStatic.*"),
   )
 
   val Linker = Seq(
diff --git a/project/JavalibIRCleaner.scala b/project/JavalibIRCleaner.scala
index 58fdc14a8a..305fc74212 100644
--- a/project/JavalibIRCleaner.scala
+++ b/project/JavalibIRCleaner.scala
@@ -439,8 +439,9 @@ final class JavalibIRCleaner(baseDirectoryURI: URI) {
 
         case New(className, ctor, args) =>
           New(transformNonJSClassName(className), transformMethodIdent(ctor), args)
-        case Select(qualifier, className, field) =>
-          Select(qualifier, transformNonJSClassName(className), field)(transformType(tree.tpe))
+        case Select(qualifier, field @ FieldIdent(fieldName)) =>
+          val newFieldName = FieldName(transformNonJSClassName(fieldName.className), fieldName.simpleName)
+          Select(qualifier, FieldIdent(newFieldName)(field.pos))(transformType(tree.tpe))
 
         case t: Apply =>
           Apply(t.flags, t.receiver, transformMethodIdent(t.method), t.args)(

From 0854041850154a62a5a265b4f14ebe1b9b2445fd Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Mon, 12 Feb 2024 18:20:01 +0100
Subject: [PATCH 046/298] Codegen: Replace LoadModule(myClass) by This() after
 StoreModule().

As the comment explains, this will help the elidable constructors
analysis to give stronger guarantees.
---
 .../org/scalajs/nscplugin/GenJSCode.scala     | 24 +++++++++++++++----
 .../nscplugin/test/OptimizationTest.scala     | 22 +++++++++++++++++
 2 files changed, 41 insertions(+), 5 deletions(-)

diff --git a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
index 6ad055b5ee..a093b718da 100644
--- a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
+++ b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
@@ -6613,11 +6613,25 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
         if (sym.hasAnnotation(JSGlobalScopeAnnotation)) {
           MaybeGlobalScope.GlobalScope(pos)
         } else {
-          val className = encodeClassName(sym)
-          val tree =
-            if (isJSType(sym)) js.LoadJSModule(className)
-            else js.LoadModule(className)
-          MaybeGlobalScope.NotGlobalScope(tree)
+          if (sym == currentClassSym.get && isModuleInitialized.get != null && isModuleInitialized.value) {
+            /* This is a LoadModule(myClass) after the StoreModule(). It is
+             * guaranteed to always return the `this` value. We eagerly replace
+             * it by a `This()` node to help the elidable constructors analysis
+             * of the linker. If we don't do this, then the analysis must
+             * tolerate `LoadModule(myClass)` after `StoreModule()` to be
+             * side-effect-free, but that would weaken the guarantees resulting
+             * from the analysis. In particular, it cannot guarantee that the
+             * result of a `LoadModule()` of a module with elidable constructors
+             * is always fully initialized.
+             */
+            MaybeGlobalScope.NotGlobalScope(genThis())
+          } else {
+            val className = encodeClassName(sym)
+            val tree =
+              if (isJSType(sym)) js.LoadJSModule(className)
+              else js.LoadModule(className)
+            MaybeGlobalScope.NotGlobalScope(tree)
+          }
         }
       }
     }
diff --git a/compiler/src/test/scala/org/scalajs/nscplugin/test/OptimizationTest.scala b/compiler/src/test/scala/org/scalajs/nscplugin/test/OptimizationTest.scala
index f3a5ab9ac9..7e140ebd38 100644
--- a/compiler/src/test/scala/org/scalajs/nscplugin/test/OptimizationTest.scala
+++ b/compiler/src/test/scala/org/scalajs/nscplugin/test/OptimizationTest.scala
@@ -560,6 +560,28 @@ class OptimizationTest extends JSASTTest {
 
     assertTrue(flags.inline)
   }
+
+  @Test
+  def loadModuleAfterStoreModuleIsThis: Unit = {
+    val testName = ClassName("Test$")
+
+    """
+    object Test {
+      private val selfPair = (Test, Test)
+    }
+    """.hasNot("LoadModule") {
+      case js.LoadModule(_) =>
+    }
+
+    // Confidence check
+    """
+    object Test {
+      private def selfPair = (Test, Test)
+    }
+    """.hasExactly(2, "LoadModule") {
+      case js.LoadModule(`testName`) =>
+    }
+  }
 }
 
 object OptimizationTest {

From b6db0f5b9d9444fc25af5ecb00378121a7e98b09 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Mon, 12 Feb 2024 19:24:52 +0100
Subject: [PATCH 047/298] New side-effect-free analysis of ctors that also
 requires acyclic init.

Previously, the inter-class side-effect-free analysis of
constructors allowed cycles in the initialization graph. For
example, `A` and `B` would be considered to have elidable
constructors in

    object A { B }
    object B { A }

To do that, the actual algorithm started from the
known-`NotElidable` classes and propagated that to the classes
depending on them.

Now, we instead also require that the initialization graph be
*acyclic* for a class to have elidable constructors. To do that,
we reverse the algorithm: we start from known-`AcyclicElidable`
classes and propagate that to classes that *only* depend on them.

Now, why would we impose *more* requirements for a class to have
elidable constructors? Because it guarantees that the result of
`LoadModule` is actually non-null *and* fully initialized. That
means we can also follow `Select`ions and `Apply`s of
getter-shaped methods on these. Counter-intuitively, that means
*more* classes can be considered to have elidable constructors.

The additional guarantee of being fully initialized will also be
used in the following commit.
---
 .../frontend/optimizer/IncOptimizer.scala     | 157 +++++++++++++++---
 project/Build.scala                           |   4 +-
 2 files changed, 135 insertions(+), 26 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
index 6d8cc24f28..6118b1153e 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
@@ -271,37 +271,93 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
   private def updateElidableConstructors(): Unit = {
     import ElidableConstructorsInfo._
 
-    /* Invariant: when something is in the stack, its
-     * elidableConstructorsInfo was set to NotElidable.
-     */
     val toProcessStack = mutable.ArrayBuffer.empty[Class]
 
-    // Build the graph and initial stack from the infos
+    /* Invariants for this algo:
+     * - when a class is in the stack, its elidableConstructorsInfo was set
+     *   to AcyclicElidable,
+     * - when a class has `DependentOn` as its info, its
+     *   `elidableConstructorsRemainingDependenciesCount` is the number of
+     *   classes in its `dependencies` that have not yet been *processed* as
+     *   AcyclicElidable.
+     *
+     * During this algorithm, the info can transition from DependentOn to
+     *
+     * - NotElidable, if its getter dependencies were not satisfied.
+     * - AcyclicElidable.
+     *
+     * Other transitions are not possible.
+     */
+
+    def isGetter(classAndMethodName: (ClassName, MethodName)): Boolean = {
+      val (className, methodName) = classAndMethodName
+      classes(className).lookupMethod(methodName).exists { m =>
+        m.originalDef.body match {
+          case Some(Select(This(), _)) => true
+          case _                          => false
+        }
+      }
+    }
+
+    /* Initialization:
+     * - Prune classes with unsatisfied getter dependencies
+     * - Build reverse dependencies
+     * - Initialize `elidableConstructorsRemainingDependenciesCount` for `DependentOn` classes
+     * - Initialize the stack with dependency-free classes
+     */
     for (cls <- classes.valuesIterator) {
       cls.elidableConstructorsInfo match {
-        case NotElidable =>
+        case DependentOn(deps, getterDeps) =>
+          if (!getterDeps.forall(isGetter(_))) {
+            cls.elidableConstructorsInfo = NotElidable
+          } else {
+            if (deps.isEmpty) {
+              cls.elidableConstructorsInfo = AcyclicElidable
+              toProcessStack += cls
+            } else {
+              cls.elidableConstructorsRemainingDependenciesCount = deps.size
+              deps.foreach(dep => classes(dep).elidableConstructorsDependents += cls)
+            }
+          }
+        case AcyclicElidable =>
           toProcessStack += cls
-        case DependentOn(dependencies) =>
-          for (dependency <- dependencies)
-            classes(dependency).elidableConstructorsDependents += cls
+        case NotElidable =>
+          ()
       }
     }
 
-    // Propagate
+    /* Propagate AcyclicElidable
+     * When a class `cls` is on the stack, it is known to be AcyclicElidable.
+     * Go to all its dependents and decrement their count of remaining
+     * dependencies. If the count reaches 0, then all the dependencies of the
+     * class are known to be AcyclicElidable, and so the new class is known to
+     * be AcyclicElidable.
+     */
     while (toProcessStack.nonEmpty) {
       val cls = toProcessStack.remove(toProcessStack.size - 1)
 
       for (dependent <- cls.elidableConstructorsDependents) {
-        if (dependent.elidableConstructorsInfo != NotElidable) {
-          dependent.elidableConstructorsInfo = NotElidable
-          toProcessStack += dependent
+        dependent.elidableConstructorsInfo match {
+          case DependentOn(_, _) =>
+            dependent.elidableConstructorsRemainingDependenciesCount -= 1
+            if (dependent.elidableConstructorsRemainingDependenciesCount == 0) {
+              dependent.elidableConstructorsInfo = AcyclicElidable
+              toProcessStack += dependent
+            }
+          case NotElidable =>
+            ()
+          case AcyclicElidable =>
+            throw new AssertionError(
+              s"Unexpected dependent link from class ${cls.className.nameString} " +
+              s"to ${dependent.className.nameString} which is AcyclicElidable"
+            )
         }
       }
     }
 
     // Set the final value of hasElidableConstructors
     for (cls <- classes.valuesIterator) {
-      cls.setHasElidableConstructors(cls.elidableConstructorsInfo != NotElidable)
+      cls.setHasElidableConstructors()
     }
   }
 
@@ -430,6 +486,7 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
     var elidableConstructorsInfo: ElidableConstructorsInfo =
       computeElidableConstructorsInfo(linkedClass)
     val elidableConstructorsDependents: mutable.ArrayBuffer[Class] = mutable.ArrayBuffer.empty
+    var elidableConstructorsRemainingDependenciesCount: Int = 0
 
     /** True if *all* constructors of this class are recursively elidable. */
     private var hasElidableConstructors: Boolean =
@@ -562,7 +619,6 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
 
       // Elidable constructors
       elidableConstructorsInfo = computeElidableConstructorsInfo(linkedClass)
-      elidableConstructorsDependents.clear()
 
       // Inlineable class
       if (updateTryNewInlineable(linkedClass)) {
@@ -577,12 +633,21 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
     }
 
     /** ELIDABLE CTORS PASS ONLY. */
-    def setHasElidableConstructors(newHasElidableConstructors: Boolean): Unit = {
+    def setHasElidableConstructors(): Unit = {
+      import ElidableConstructorsInfo._
+
+      val newHasElidableConstructors = elidableConstructorsInfo == AcyclicElidable
+
       if (hasElidableConstructors != newHasElidableConstructors) {
         hasElidableConstructors = newHasElidableConstructors
         hasElidableConstructorsAskers.keysIterator.foreach(_.tag())
         hasElidableConstructorsAskers.clear()
       }
+
+      // Release memory that we won't use anymore
+      if (!newHasElidableConstructors)
+        elidableConstructorsInfo = NotElidable // get rid of DependentOn
+      elidableConstructorsDependents.clear() // also resets state for next run
     }
 
     /** UPDATE PASS ONLY. */
@@ -612,10 +677,10 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
       import ElidableConstructorsInfo._
 
       if (isAdHocElidableConstructors(className)) {
-        AlwaysElidable
+        AcyclicElidable
       } else {
         // It's OK to look at the superClass like this because it will always be updated before myself
-        var result = superClass.fold(ElidableConstructorsInfo.AlwaysElidable)(_.elidableConstructorsInfo)
+        var result = superClass.fold[ElidableConstructorsInfo](AcyclicElidable)(_.elidableConstructorsInfo)
 
         if (result == NotElidable) {
           // fast path
@@ -691,8 +756,17 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
 
     /** UPDATE PASS ONLY. */
     private def computeCtorElidableInfo(impl: MethodImpl): ElidableConstructorsInfo = {
+      /* Dependencies on other classes to have acyclic elidable constructors
+       * It is possible for the enclosing class name to be added to this set,
+       * if the constructor depends on its own class. In that case, the
+       * analysis will naturally treat it as a cycle and will conclude that the
+       * class does not have elidable constructors.
+       */
       val dependenciesBuilder = Set.newBuilder[ClassName]
 
+      // Dependencies on certain methods to be getters
+      val getterDependenciesBuilder = Set.newBuilder[(ClassName, MethodName)]
+
       def isTriviallySideEffectFree(tree: Tree): Boolean = tree match {
         case _:VarRef | _:Literal | _:This | _:Skip =>
           true
@@ -712,6 +786,28 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
           dependenciesBuilder += className
           true
 
+        case Select(LoadModule(className), _) =>
+          /* If the given module can be loaded without cycles, it is guaranteed
+           * to be non-null, and therefore the Select is side-effect-free.
+           */
+          dependenciesBuilder += className
+          true
+
+        case Select(This(), _) =>
+          true
+
+        case Apply(_, LoadModule(className), MethodIdent(methodName), Nil)
+            if !methodName.isReflectiveProxy =>
+          // For a getter-like call, we need the method to actually be a getter.
+          dependenciesBuilder += className
+          getterDependenciesBuilder += ((className, methodName))
+          true
+
+        case Apply(_, This(), MethodIdent(methodName), Nil)
+            if !methodName.isReflectiveProxy =>
+          getterDependenciesBuilder += ((className, methodName))
+          true
+
         case _ =>
           false
       }
@@ -755,10 +851,16 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
       impl.originalDef.body.fold {
         throw new AssertionError("Constructor cannot be abstract")
       } { body =>
-        if (isElidableStat(body))
-          ElidableConstructorsInfo.DependentOn(dependenciesBuilder.result())
-        else
+        if (isElidableStat(body)) {
+          val dependencies = dependenciesBuilder.result()
+          val getterDependencies = getterDependenciesBuilder.result()
+          if (dependencies.isEmpty && getterDependencies.isEmpty)
+            ElidableConstructorsInfo.AcyclicElidable
+          else
+            ElidableConstructorsInfo.DependentOn(dependencies, getterDependencies)
+        } else {
           ElidableConstructorsInfo.NotElidable
+        }
       }
     }
 
@@ -1482,8 +1584,12 @@ object IncOptimizer {
     import ElidableConstructorsInfo._
 
     final def mergeWith(that: ElidableConstructorsInfo): ElidableConstructorsInfo = (this, that) match {
-      case (DependentOn(deps1), DependentOn(deps2)) =>
-        DependentOn(deps1 ++ deps2)
+      case (DependentOn(deps1, getterDeps1), DependentOn(deps2, getterDeps2)) =>
+        DependentOn(deps1 ++ deps2, getterDeps1 ++ getterDeps2)
+      case (AcyclicElidable, _) =>
+        that
+      case (_, AcyclicElidable) =>
+        this
       case _ =>
         NotElidable
     }
@@ -1492,8 +1598,11 @@ object IncOptimizer {
   object ElidableConstructorsInfo {
     case object NotElidable extends ElidableConstructorsInfo
 
-    final case class DependentOn(dependencies: Set[ClassName]) extends ElidableConstructorsInfo
+    case object AcyclicElidable extends ElidableConstructorsInfo
 
-    val AlwaysElidable: ElidableConstructorsInfo = DependentOn(Set.empty)
+    final case class DependentOn(
+      dependencies: Set[ClassName],
+      getterDependencies: Set[(ClassName, MethodName)]
+    ) extends ElidableConstructorsInfo
   }
 }
diff --git a/project/Build.scala b/project/Build.scala
index 263683ee52..f3c9cbedac 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -1975,8 +1975,8 @@ object Build {
 
           case `default213Version` =>
             Some(ExpectedSizes(
-                fastLink = 468000 to 469000,
-                fullLink = 100000 to 101000,
+                fastLink = 463000 to 464000,
+                fullLink = 99000 to 100000,
                 fastLinkGz = 60000 to 61000,
                 fullLinkGz = 26000 to 27000,
             ))

From 3348716c2c22f379815eaa83459dc87bb89eec6d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Fri, 9 Feb 2024 15:31:24 +0100
Subject: [PATCH 048/298] Inline the "body" of fields of modules when possible.

If a module `M` has elidable constructors, and an immutable field
`f` of `M` is initialized with an "easy" value, we can replace all
occurrences of `M.f` by that value. Easy values are literals,
loads of other modules, or accesses to fields/getters of other
modules.

We can do this because having elidable constructors implies that
the initialization of the module is acyclic. So once it is fully
initialized, all fields have indeed been initialized in a
predictable way.

This is particularly effective for all the forwarders declared in
`scala.Predef$` in `scala.package$`. They contain a series of vals
like

    val Nil = scala.collection.immutable.Nil

When typical Scala code refers to `Nil`, it means `scala.Nil`
rather than `sci.Nil` We are now able to "inline" those references
instead of going through the alias.

In addition to generating less code, this tends to give a better
type to the result. For example `sci.Nil` is known to be
non-nullable, whereas `scala.Nil` could be null.
---
 .../src/main/scala/org/scalajs/ir/Trees.scala |  20 +-
 .../frontend/optimizer/IncOptimizer.scala     | 241 ++++++++++++++++--
 .../frontend/optimizer/OptimizerCore.scala    | 155 +++++++++--
 project/Build.scala                           |   2 +-
 4 files changed, 373 insertions(+), 45 deletions(-)

diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala b/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
index c3d206624a..2dd8e43d36 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
@@ -904,7 +904,11 @@ object Trees {
 
   // Literals
 
-  /** Marker for literals. Literals are always pure. */
+  /** Marker for literals. Literals are always pure.
+   *
+   *  All `Literal`s can be compared for equality. The equality does not take
+   *  the `pos` into account.
+   */
   sealed trait Literal extends Tree
 
   /** Marker for literals that can be used in a [[Match]] case.
@@ -960,11 +964,25 @@ object Trees {
   sealed case class FloatLiteral(value: Float)(
       implicit val pos: Position) extends Literal {
     val tpe = FloatType
+
+    override def equals(that: Any): Boolean = that match {
+      case that: FloatLiteral => java.lang.Float.compare(this.value, that.value) == 0
+      case _                  => false
+    }
+
+    override def hashCode(): Int = java.lang.Float.hashCode(value)
   }
 
   sealed case class DoubleLiteral(value: Double)(
       implicit val pos: Position) extends Literal {
     val tpe = DoubleType
+
+    override def equals(that: Any): Boolean = that match {
+      case that: DoubleLiteral => java.lang.Double.compare(this.value, that.value) == 0
+      case _                   => false
+    }
+
+    override def hashCode(): Int = java.lang.Double.hashCode(value)
   }
 
   sealed case class StringLiteral(value: String)(
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
index 6118b1153e..d092397b51 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
@@ -33,6 +33,8 @@ import org.scalajs.linker.interface.{CheckedBehavior, ModuleKind}
 import org.scalajs.linker.standard._
 import org.scalajs.linker.CollectionsCompat._
 
+import OptimizerCore.InlineableFieldBodies.FieldBody
+
 /** Incremental optimizer.
  *
  *  An incremental optimizer optimizes a [[LinkingUnit]]
@@ -497,6 +499,13 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
     var fieldsRead: Set[FieldName] = linkedClass.fieldsRead
     var tryNewInlineable: Option[OptimizerCore.InlineableClassStructure] = None
 
+    /** The "bodies" of fields that can "inlined", *provided that* the enclosing
+     *  module class has elidable constructors.
+     */
+    private var inlineableFieldBodies: OptimizerCore.InlineableFieldBodies =
+      computeInlineableFieldBodies(linkedClass)
+    private val inlineableFieldBodiesAskers = collOps.emptyMap[Processable, Unit]
+
     setupAfterCreation(linkedClass)
 
     override def toString(): String =
@@ -620,6 +629,14 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
       // Elidable constructors
       elidableConstructorsInfo = computeElidableConstructorsInfo(linkedClass)
 
+      // Inlineable field bodies
+      val newInlineableFieldBodies = computeInlineableFieldBodies(linkedClass)
+      if (inlineableFieldBodies != newInlineableFieldBodies) {
+        inlineableFieldBodies = newInlineableFieldBodies
+        inlineableFieldBodiesAskers.keysIterator.foreach(_.tag())
+        inlineableFieldBodiesAskers.clear()
+      }
+
       // Inlineable class
       if (updateTryNewInlineable(linkedClass)) {
         for (method <- methods.values; if method.methodName.isConstructor)
@@ -672,6 +689,22 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
       hasElidableConstructors
     }
 
+    def askInlineableFieldBodies(asker: Processable): OptimizerCore.InlineableFieldBodies = {
+      inlineableFieldBodiesAskers.put(asker, ())
+
+      if (inlineableFieldBodies.isEmpty) {
+        // Avoid asking for `hasInlineableConstructors`; we always get here for non-ModuleClass'es
+        asker.registerTo(this)
+        inlineableFieldBodies
+      } else {
+        // No need for asker.registerTo(this) in this branch; it is done anyway in askHasElidableConstructors
+        if (askHasElidableConstructors(asker))
+          inlineableFieldBodies
+        else
+          OptimizerCore.InlineableFieldBodies.Empty
+      }
+    }
+
     /** UPDATE PASS ONLY. */
     private def computeElidableConstructorsInfo(linkedClass: LinkedClass): ElidableConstructorsInfo = {
       import ElidableConstructorsInfo._
@@ -695,6 +728,39 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
       }
     }
 
+    /** UPDATE PASS ONLY. */
+    private def computeInlineableFieldBodies(
+        linkedClass: LinkedClass): OptimizerCore.InlineableFieldBodies = {
+      import OptimizerCore.InlineableFieldBodies
+
+      if (linkedClass.kind != ClassKind.ModuleClass) {
+        InlineableFieldBodies.Empty
+      } else {
+        myInterface.staticLike(MemberNamespace.Constructor).methods.get(NoArgConstructorName) match {
+          case None =>
+            InlineableFieldBodies.Empty
+
+          case Some(ctor) =>
+            val initFieldBodies = for {
+              fieldDef <- computeAllInstanceFieldDefs()
+              if !fieldDef.flags.isMutable
+            } yield {
+              // the zero value is always a Literal because the ftpe is not a RecordType
+              val zeroValue = zeroOf(fieldDef.ftpe)(NoPosition).asInstanceOf[Literal]
+              fieldDef.name.name -> FieldBody.Literal(zeroValue)
+            }
+
+            if (initFieldBodies.isEmpty) {
+              // fast path
+              InlineableFieldBodies.Empty
+            } else {
+              val finalFieldBodies = interpretConstructor(ctor, initFieldBodies.toMap, Nil)
+              new InlineableFieldBodies(finalFieldBodies)
+            }
+        }
+      }
+    }
+
     /** UPDATE PASS ONLY. */
     def updateTryNewInlineable(linkedClass: LinkedClass): Boolean = {
       val oldTryNewInlineable = tryNewInlineable
@@ -702,23 +768,27 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
       tryNewInlineable = if (!linkedClass.optimizerHints.inline) {
         None
       } else {
-        val allFields = for {
-          parent <- reverseParentChain
-          anyField <- parent.fields
-          if !anyField.flags.namespace.isStatic
-          // non-JS class may only contain FieldDefs (no JSFieldDef)
-          field = anyField.asInstanceOf[FieldDef]
-          if parent.fieldsRead.contains(field.name.name)
-        } yield {
-          field
-        }
-
+        val allFields = computeAllInstanceFieldDefs()
         Some(new OptimizerCore.InlineableClassStructure(allFields))
       }
 
       tryNewInlineable != oldTryNewInlineable
     }
 
+    /** UPDATE PASS ONLY, used by `computeInlineableFieldBodies` and `updateTryNewInlineable`. */
+    private def computeAllInstanceFieldDefs(): List[FieldDef] = {
+      for {
+        parent <- reverseParentChain
+        anyField <- parent.fields
+        if !anyField.flags.namespace.isStatic
+        // non-JS class may only contain FieldDefs (no JSFieldDef)
+        field = anyField.asInstanceOf[FieldDef]
+        if parent.fieldsRead.contains(field.name.name)
+      } yield {
+        field
+      }
+    }
+
     /** UPDATE PASS ONLY. */
     private[this] def setupAfterCreation(linkedClass: LinkedClass): Unit = {
       if (batchMode) {
@@ -864,6 +934,128 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
       }
     }
 
+    /** UPDATE PASS ONLY. */
+    private def interpretConstructor(impl: MethodImpl,
+        fieldBodies: Map[FieldName, FieldBody],
+        paramBodies: List[Option[FieldBody]]): Map[FieldName, FieldBody] = {
+
+      /* This method performs a kind of abstract intepretation of the given
+       * given constructor `impl`. It *assumes* that the enclosing class ends
+       * up having elidable constructors. If that is not the case, the
+       * computation must not crash but its result can be arbitrary.
+       */
+
+      type FieldBodyMap = Map[FieldName, FieldBody]
+      type ParamBodyMap = Map[LocalName, FieldBody]
+
+      def interpretSelfGetter(methodName: MethodName,
+          fieldBodies: FieldBodyMap): Option[FieldBody] = {
+        methods.get(methodName).flatMap { impl =>
+          impl.originalDef.body match {
+            case Some(Select(This(), FieldIdent(fieldName))) =>
+              fieldBodies.get(fieldName)
+
+            case _ =>
+              /* If we get here, it means the class won't have elidable
+               * constructors, and therefore we can return arbitrary values
+               * from the whole method, so we don't care.
+               */
+              None
+          }
+        }
+      }
+
+      def interpretExpr(tree: Tree, fieldBodies: FieldBodyMap,
+          paramBodies: ParamBodyMap): Option[FieldBody] = {
+        tree match {
+          case lit: Literal =>
+            Some(FieldBody.Literal(lit))
+
+          case VarRef(LocalIdent(valName)) =>
+            paramBodies.get(valName)
+
+          case LoadModule(moduleClassName) =>
+            Some(FieldBody.LoadModule(moduleClassName, tree.pos))
+
+          case Select(qual @ LoadModule(moduleClassName), FieldIdent(fieldName)) =>
+            val moduleBody = FieldBody.LoadModule(moduleClassName, qual.pos)
+            Some(FieldBody.ModuleSelect(moduleBody, fieldName, tree.tpe, tree.pos))
+
+          case Select(This(), FieldIdent(fieldName)) =>
+            fieldBodies.get(fieldName)
+
+          case Apply(_, receiver @ LoadModule(moduleClassName), MethodIdent(methodName), Nil)
+              if !methodName.isReflectiveProxy =>
+            val moduleBody = FieldBody.LoadModule(moduleClassName, receiver.pos)
+            Some(FieldBody.ModuleGetter(moduleBody, methodName, tree.tpe, tree.pos))
+
+          case Apply(_, This(), MethodIdent(methodName), Nil)
+              if !methodName.isReflectiveProxy =>
+            interpretSelfGetter(methodName, fieldBodies)
+
+          case _ =>
+            None
+        }
+      }
+
+      def interpretBody(body: Tree, fieldBodies: FieldBodyMap,
+          paramBodies: ParamBodyMap): FieldBodyMap = {
+        body match {
+          case Block(stats) =>
+            stats.foldLeft(fieldBodies) { (prev, stat) =>
+              interpretBody(stat, prev, paramBodies)
+            }
+
+          case Skip() =>
+            fieldBodies
+
+          case Assign(Select(This(), FieldIdent(fieldName)), rhs) =>
+            if (!fieldBodies.contains(fieldName)) {
+              // It is a mutable field or it is dce'ed as never read, don't track it
+              fieldBodies
+            } else {
+              interpretExpr(rhs, fieldBodies, paramBodies) match {
+                case Some(newFieldBody) =>
+                  fieldBodies.updated(fieldName, newFieldBody)
+                case None =>
+                  // Unknown value; don't track it anymore
+                  fieldBodies - fieldName
+              }
+            }
+
+          // Mixin constructor -- assume it is empty
+          case ApplyStatically(flags, This(), className, methodName, Nil)
+              if !flags.isPrivate && !classes.contains(className) =>
+            fieldBodies
+
+          // Delegation to another constructor
+          case ApplyStatically(flags, This(), className, MethodIdent(methodName), args) if flags.isConstructor =>
+            val argBodies = args.map(interpretExpr(_, fieldBodies, paramBodies))
+            val ctorImpl = getInterface(className)
+              .staticLike(MemberNamespace.Constructor)
+              .methods(methodName)
+            interpretConstructor(ctorImpl, fieldBodies, argBodies)
+
+          case _ =>
+            /* Other statements cannot affect the eventual fieldBodies
+             * (assuming the class ends up having elidable constructors, as always).
+             */
+            fieldBodies
+        }
+      }
+
+      impl.originalDef.body.fold {
+        throw new AssertionError(s"Constructor $impl cannot be abstract")
+      } { body =>
+        val paramBodiesMap: ParamBodyMap =
+          impl.originalDef.args.zip(paramBodies).collect {
+            case (paramDef, Some(paramBody)) => paramDef.name.name -> paramBody
+          }.toMap
+
+        interpretBody(body, fieldBodies, paramBodiesMap)
+      }
+    }
+
     /** All the methods of this class, including inherited ones.
      *  It has () so we remember this is an expensive operation.
      *  UPDATE PASS ONLY.
@@ -890,6 +1082,7 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
 
     def unregisterDependee(dependee: Processable): Unit = {
       hasElidableConstructorsAskers.remove(dependee)
+      inlineableFieldBodiesAskers.remove(dependee)
     }
   }
 
@@ -1421,8 +1614,8 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
         throw new AssertionError("Methods to optimize must be concrete")
       }
 
-      val (newParams, newBody) = new Optimizer(this, this.toString()).optimize(
-          Some(this), owner.untrackedThisType, params, jsClassCaptures = Nil,
+      val (newParams, newBody) = new Optimizer(this, Some(this), this.toString()).optimize(
+          owner.untrackedThisType, params, jsClassCaptures = Nil,
           resultType, body, isNoArgCtor = name.name == NoArgConstructorName)
 
       MethodDef(static, name, originalName,
@@ -1446,8 +1639,8 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
         case originalDef @ JSMethodDef(flags, name, params, restParam, body) =>
           val thisType = owner.untrackedThisType(flags.namespace)
 
-          val (newParamsAndRest, newBody) = new Optimizer(this, this.toString()).optimize(
-            None, thisType, params ++ restParam.toList, owner.untrackedJSClassCaptures,
+          val (newParamsAndRest, newBody) = new Optimizer(this, None, this.toString()).optimize(
+            thisType, params ++ restParam.toList, owner.untrackedJSClassCaptures,
             AnyType, body, isNoArgCtor = false)
 
           val (newParams, newRestParam) =
@@ -1462,14 +1655,14 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
           val jsClassCaptures = owner.untrackedJSClassCaptures
 
           val newGetterBody = getterBody.map { body =>
-            val (_, newBody) = new Optimizer(this, "get " + this.toString()).optimize(
-                None, thisType, Nil, jsClassCaptures, AnyType, body, isNoArgCtor = false)
+            val (_, newBody) = new Optimizer(this, None, "get " + this.toString()).optimize(
+                thisType, Nil, jsClassCaptures, AnyType, body, isNoArgCtor = false)
             newBody
           }
 
           val newSetterArgAndBody = setterArgAndBody.map { case (param, body) =>
-            val (List(newParam), newBody) = new Optimizer(this, "set " + this.toString()).optimize(
-                None, thisType, List(param), jsClassCaptures, AnyType, body,
+            val (List(newParam), newBody) = new Optimizer(this, None, "set " + this.toString()).optimize(
+                thisType, List(param), jsClassCaptures, AnyType, body,
                 isNoArgCtor = false)
             (newParam, newBody)
           }
@@ -1494,8 +1687,8 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
 
       val thisType = owner.untrackedThisType(flags.namespace)
 
-      val (newParamsAndRest, newRawBody) = new Optimizer(this, this.toString()).optimize(
-          None, thisType, params ++ restParam.toList, owner.untrackedJSClassCaptures, AnyType,
+      val (newParamsAndRest, newRawBody) = new Optimizer(this, None, this.toString()).optimize(
+          thisType, params ++ restParam.toList, owner.untrackedJSClassCaptures, AnyType,
           Block(body.allStats)(body.pos), isNoArgCtor = false)
 
       val (newParams, newRestParam) =
@@ -1522,7 +1715,8 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
    *
    *  All methods are PROCESS PASS ONLY
    */
-  private final class Optimizer(asker: Processable, debugID: String)
+  private final class Optimizer(
+      asker: Processable, protected val myself: Option[MethodImpl], debugID: String)
       extends OptimizerCore(config, debugID) {
     import OptimizerCore.ImportTarget
 
@@ -1549,6 +1743,9 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
     protected def hasElidableConstructors(className: ClassName): Boolean =
       classes(className).askHasElidableConstructors(asker)
 
+    protected def inlineableFieldBodies(className: ClassName): OptimizerCore.InlineableFieldBodies =
+      classes.get(className).fold(OptimizerCore.InlineableFieldBodies.Empty)(_.askInlineableFieldBodies(asker))
+
     protected def tryNewInlineableClass(
         className: ClassName): Option[OptimizerCore.InlineableClassStructure] = {
       classes(className).tryNewInlineable
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
index 2dca9842bd..d9c57e3b9a 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
@@ -46,6 +46,8 @@ private[optimizer] abstract class OptimizerCore(
 
   type MethodID <: AbstractMethodID
 
+  protected val myself: Option[MethodID]
+
   private def semantics: Semantics = config.coreSpec.semantics
 
   // Uncomment and adapt to print debug messages only during one method
@@ -72,6 +74,13 @@ private[optimizer] abstract class OptimizerCore(
    */
   protected def hasElidableConstructors(className: ClassName): Boolean
 
+  /** Returns the inlineable field bodies of this module class.
+   *
+   *  If the class is not a module class, or if it does not have inlineable
+   *  accessors, the resulting `InlineableFieldBodies` is always empty.
+   */
+  protected def inlineableFieldBodies(className: ClassName): InlineableFieldBodies
+
   /** Tests whether the given class is inlineable.
    *
    *  @return
@@ -141,7 +150,7 @@ private[optimizer] abstract class OptimizerCore(
   private val intrinsics =
     Intrinsics.buildIntrinsics(config.coreSpec.esFeatures)
 
-  def optimize(myself: Option[MethodID], thisType: Type, params: List[ParamDef],
+  def optimize(thisType: Type, params: List[ParamDef],
       jsClassCaptures: List[ParamDef], resultType: Type, body: Tree,
       isNoArgCtor: Boolean): (List[ParamDef], Tree) = {
     try {
@@ -1220,28 +1229,72 @@ private[optimizer] abstract class OptimizerCore(
         cont(PreTransLit(IntLiteral(resultValue)))
 
       case _ =>
-        resolveLocalDef(preTransQual) match {
-          case PreTransRecordTree(newQual, origType, cancelFun) =>
-            val recordType = newQual.tpe.asInstanceOf[RecordType]
-            /* FIXME How come this lookup requires only the `simpleName`?
-             * The `recordType` is created at `InlineableClassStructure.recordType`,
-             * where it uses an allocator. Something fishy is going on here.
-             * (And no, this is not dead code.)
-             */
-            val recordField = recordType.findField(field.name.simpleName)
-            val sel = RecordSelect(newQual, SimpleFieldIdent(recordField.name))(recordField.tpe)
-            sel.tpe match {
-              case _: RecordType =>
-                cont(PreTransRecordTree(sel, RefinedType(expectedType), cancelFun))
-              case _ =>
-                cont(PreTransTree(sel, RefinedType(sel.tpe)))
-            }
+        def default: TailRec[Tree] = {
+          resolveLocalDef(preTransQual) match {
+            case PreTransRecordTree(newQual, origType, cancelFun) =>
+              val recordType = newQual.tpe.asInstanceOf[RecordType]
+              /* FIXME How come this lookup requires only the `simpleName`?
+               * The `recordType` is created at `InlineableClassStructure.recordType`,
+               * where it uses an allocator. Something fishy is going on here.
+               * (And no, this is not dead code.)
+               */
+              val recordField = recordType.findField(field.name.simpleName)
+              val sel = RecordSelect(newQual, SimpleFieldIdent(recordField.name))(recordField.tpe)
+              sel.tpe match {
+                case _: RecordType =>
+                  cont(PreTransRecordTree(sel, RefinedType(expectedType), cancelFun))
+                case _ =>
+                  cont(PreTransTree(sel, RefinedType(sel.tpe)))
+              }
 
-          case PreTransTree(newQual, newQualType) =>
-            val newQual1 = maybeAssumeNotNull(newQual, newQualType)
-            cont(PreTransTree(Select(newQual1, field)(expectedType),
-                RefinedType(expectedType)))
+            case PreTransTree(newQual, newQualType) =>
+              val newQual1 = maybeAssumeNotNull(newQual, newQualType)
+              cont(PreTransTree(Select(newQual1, field)(expectedType),
+                  RefinedType(expectedType)))
+          }
         }
+
+        preTransQual.tpe match {
+          // Try to inline an inlineable field body
+          case RefinedType(ClassType(qualClassName), _, _) if !isLhsOfAssign =>
+            if (myself.exists(m => m.enclosingClassName == qualClassName && m.methodName.isConstructor)) {
+              /* Within the constructor of a class, we cannot trust the
+               * inlineable field bodies of that class, since they only reflect
+               * the values of fields when the instance is fully initialized.
+               */
+              default
+            } else {
+              inlineableFieldBodies(qualClassName).fieldBodies.get(field.name) match {
+                case None =>
+                  default
+                case Some(fieldBody) =>
+                  val qualSideEffects = checkNotNullStatement(preTransQual)
+                  val fieldBodyTree = fieldBodyToTree(fieldBody)
+                  pretransformExpr(fieldBodyTree) { preTransFieldBody =>
+                    cont(PreTransBlock(qualSideEffects, preTransFieldBody))
+                  }
+              }
+            }
+          case _ =>
+            default
+        }
+    }
+  }
+
+  private def fieldBodyToTree(fieldBody: InlineableFieldBodies.FieldBody): Tree = {
+    import InlineableFieldBodies.FieldBody
+
+    implicit val pos = fieldBody.pos
+
+    fieldBody match {
+      case FieldBody.Literal(literal, _) =>
+        literal
+      case FieldBody.LoadModule(moduleClassName, _) =>
+        LoadModule(moduleClassName)
+      case FieldBody.ModuleSelect(qualifier, fieldName, tpe, _) =>
+        Select(fieldBodyToTree(qualifier), FieldIdent(fieldName))(tpe)
+      case FieldBody.ModuleGetter(qualifier, methodName, tpe, _) =>
+        Apply(ApplyFlags.empty, fieldBodyToTree(qualifier), MethodIdent(methodName), Nil)(tpe)
     }
   }
 
@@ -5138,6 +5191,66 @@ private[optimizer] object OptimizerCore {
     }
   }
 
+  final class InlineableFieldBodies(
+    val fieldBodies: Map[FieldName, InlineableFieldBodies.FieldBody]
+  ) {
+    def isEmpty: Boolean = fieldBodies.isEmpty
+
+    override def equals(that: Any): Boolean = that match {
+      case that: InlineableFieldBodies =>
+        this.fieldBodies == that.fieldBodies
+      case _ =>
+        false
+    }
+
+    override def hashCode(): Int = fieldBodies.##
+
+    override def toString(): String = {
+      fieldBodies
+        .map(f => s"${f._1.nameString}: ${f._2}")
+        .mkString("InlineableFieldBodies(", ", ", ")")
+    }
+  }
+
+  object InlineableFieldBodies {
+    /** The body of field that we can inline.
+     *
+     *  This hierarchy mirrors the small subset of `Tree`s that we need to
+     *  represent field bodies that we can inline.
+     *
+     *  Unlike `Tree`, `FieldBody` guarantees a comprehensive equality test
+     *  representing its full structure. It is generally not safe to compare
+     *  `Tree`s for equality, but for `FieldBody` it is safe. We use equality
+     *  in `IncOptimizer` to detect changes.
+     *
+     *  This is also why the members of the hierarchy contain an explicit
+     *  `Position` in their primary parameter list.
+     */
+    sealed abstract class FieldBody {
+      val pos: Position
+    }
+
+    object FieldBody {
+      final case class Literal(literal: Trees.Literal, pos: Position) extends FieldBody {
+        require(pos == literal.pos, s"TreeBody.Literal.pos must be the same as its Literal")
+      }
+
+      object Literal {
+        def apply(literal: Trees.Literal): Literal =
+          Literal(literal, literal.pos)
+      }
+
+      final case class LoadModule(moduleClassName: ClassName, pos: Position)
+          extends FieldBody
+      final case class ModuleSelect(qualifier: LoadModule,
+          fieldName: FieldName, tpe: Type, pos: Position) extends FieldBody
+      final case class ModuleGetter(qualifier: LoadModule,
+          methodName: MethodName, tpe: Type, pos: Position) extends FieldBody
+    }
+
+    val Empty: InlineableFieldBodies = new InlineableFieldBodies(Map.empty)
+  }
+
   private final val MaxRollbacksPerMethod = 256
 
   private final class TooManyRollbacksException
diff --git a/project/Build.scala b/project/Build.scala
index f3c9cbedac..25eec2454a 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -1975,7 +1975,7 @@ object Build {
 
           case `default213Version` =>
             Some(ExpectedSizes(
-                fastLink = 463000 to 464000,
+                fastLink = 462000 to 463000,
                 fullLink = 99000 to 100000,
                 fastLinkGz = 60000 to 61000,
                 fullLinkGz = 26000 to 27000,

From 31452d4b2f81ab253adb2bdfb6761ec7411fd55e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Fri, 9 Feb 2024 15:56:53 +0100
Subject: [PATCH 049/298] Turn fields of scala.reflect.* back into `val`s.

They are `val`s in the original version of the files. We previously
turned them into `def`s because it allowed our inliner to do a
better job. However, now that we can "inline" the fields of modules
with elidable constructors, that is no longer necessary.

Interestingly, this allows `scala.reflect.package$` and
`scala.reflect.ClassManifestFactory$` to have elidable constructors,
which they did not have before. That is because they referred to
the `def`s in their constructor, which now have a getter shape and
therefore can be understood by the side-effect-free analysis.
---
 project/Build.scala                           |  4 +-
 .../scala/reflect/ClassTag.scala              | 30 ++++-----
 .../scala/reflect/Manifest.scala              | 30 ++++-----
 .../scala/reflect/ClassTag.scala              | 30 ++++-----
 .../scala/reflect/Manifest.scala              | 62 +++++++++----------
 5 files changed, 78 insertions(+), 78 deletions(-)

diff --git a/project/Build.scala b/project/Build.scala
index 25eec2454a..a14202f7f9 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -1967,8 +1967,8 @@ object Build {
         scalaVersion.value match {
           case `default212Version` =>
             Some(ExpectedSizes(
-                fastLink = 642000 to 643000,
-                fullLink = 102000 to 103000,
+                fastLink = 640000 to 641000,
+                fullLink = 101000 to 102000,
                 fastLinkGz = 77000 to 78000,
                 fullLinkGz = 26000 to 27000,
             ))
diff --git a/scalalib/overrides-2.12/scala/reflect/ClassTag.scala b/scalalib/overrides-2.12/scala/reflect/ClassTag.scala
index f9dc5dd716..20fac6a392 100644
--- a/scalalib/overrides-2.12/scala/reflect/ClassTag.scala
+++ b/scalalib/overrides-2.12/scala/reflect/ClassTag.scala
@@ -133,21 +133,21 @@ trait ClassTag[T] extends ClassManifestDeprecatedApis[T] with Equals with Serial
  * Class tags corresponding to primitive types and constructor/extractor for ClassTags.
  */
 object ClassTag {
-  def Byte    : ClassTag[scala.Byte]       = ManifestFactory.Byte
-  def Short   : ClassTag[scala.Short]      = ManifestFactory.Short
-  def Char    : ClassTag[scala.Char]       = ManifestFactory.Char
-  def Int     : ClassTag[scala.Int]        = ManifestFactory.Int
-  def Long    : ClassTag[scala.Long]       = ManifestFactory.Long
-  def Float   : ClassTag[scala.Float]      = ManifestFactory.Float
-  def Double  : ClassTag[scala.Double]     = ManifestFactory.Double
-  def Boolean : ClassTag[scala.Boolean]    = ManifestFactory.Boolean
-  def Unit    : ClassTag[scala.Unit]       = ManifestFactory.Unit
-  def Any     : ClassTag[scala.Any]        = ManifestFactory.Any
-  def Object  : ClassTag[java.lang.Object] = ManifestFactory.Object
-  def AnyVal  : ClassTag[scala.AnyVal]     = ManifestFactory.AnyVal
-  def AnyRef  : ClassTag[scala.AnyRef]     = ManifestFactory.AnyRef
-  def Nothing : ClassTag[scala.Nothing]    = ManifestFactory.Nothing
-  def Null    : ClassTag[scala.Null]       = ManifestFactory.Null
+  val Byte    : ClassTag[scala.Byte]       = ManifestFactory.Byte
+  val Short   : ClassTag[scala.Short]      = ManifestFactory.Short
+  val Char    : ClassTag[scala.Char]       = ManifestFactory.Char
+  val Int     : ClassTag[scala.Int]        = ManifestFactory.Int
+  val Long    : ClassTag[scala.Long]       = ManifestFactory.Long
+  val Float   : ClassTag[scala.Float]      = ManifestFactory.Float
+  val Double  : ClassTag[scala.Double]     = ManifestFactory.Double
+  val Boolean : ClassTag[scala.Boolean]    = ManifestFactory.Boolean
+  val Unit    : ClassTag[scala.Unit]       = ManifestFactory.Unit
+  val Any     : ClassTag[scala.Any]        = ManifestFactory.Any
+  val Object  : ClassTag[java.lang.Object] = ManifestFactory.Object
+  val AnyVal  : ClassTag[scala.AnyVal]     = ManifestFactory.AnyVal
+  val AnyRef  : ClassTag[scala.AnyRef]     = ManifestFactory.AnyRef
+  val Nothing : ClassTag[scala.Nothing]    = ManifestFactory.Nothing
+  val Null    : ClassTag[scala.Null]       = ManifestFactory.Null
 
   @inline
   private class GenericClassTag[T](val runtimeClass: jClass[_]) extends ClassTag[T]
diff --git a/scalalib/overrides-2.12/scala/reflect/Manifest.scala b/scalalib/overrides-2.12/scala/reflect/Manifest.scala
index f38ce59e4d..a7b8169481 100644
--- a/scalalib/overrides-2.12/scala/reflect/Manifest.scala
+++ b/scalalib/overrides-2.12/scala/reflect/Manifest.scala
@@ -93,7 +93,7 @@ object ManifestFactory {
     override def newArrayBuilder(): ArrayBuilder[Byte] = new ArrayBuilder.ofByte()
     private def readResolve(): Any = Manifest.Byte
   }
-  def Byte: AnyValManifest[Byte] = ByteManifest
+  val Byte: AnyValManifest[Byte] = ByteManifest
 
   private object ShortManifest extends AnyValManifest[scala.Short]("Short") {
     def runtimeClass = java.lang.Short.TYPE
@@ -102,7 +102,7 @@ object ManifestFactory {
     override def newArrayBuilder(): ArrayBuilder[Short] = new ArrayBuilder.ofShort()
     private def readResolve(): Any = Manifest.Short
   }
-  def Short: AnyValManifest[Short] = ShortManifest
+  val Short: AnyValManifest[Short] = ShortManifest
 
   private object CharManifest extends AnyValManifest[scala.Char]("Char") {
     def runtimeClass = java.lang.Character.TYPE
@@ -111,7 +111,7 @@ object ManifestFactory {
     override def newArrayBuilder(): ArrayBuilder[Char] = new ArrayBuilder.ofChar()
     private def readResolve(): Any = Manifest.Char
   }
-  def Char: AnyValManifest[Char] = CharManifest
+  val Char: AnyValManifest[Char] = CharManifest
 
   private object IntManifest extends AnyValManifest[scala.Int]("Int") {
     def runtimeClass = java.lang.Integer.TYPE
@@ -120,7 +120,7 @@ object ManifestFactory {
     override def newArrayBuilder(): ArrayBuilder[Int] = new ArrayBuilder.ofInt()
     private def readResolve(): Any = Manifest.Int
   }
-  def Int: AnyValManifest[Int] = IntManifest
+  val Int: AnyValManifest[Int] = IntManifest
 
   private object LongManifest extends AnyValManifest[scala.Long]("Long") {
     def runtimeClass = java.lang.Long.TYPE
@@ -129,7 +129,7 @@ object ManifestFactory {
     override def newArrayBuilder(): ArrayBuilder[Long] = new ArrayBuilder.ofLong()
     private def readResolve(): Any = Manifest.Long
   }
-  def Long: AnyValManifest[Long] = LongManifest
+  val Long: AnyValManifest[Long] = LongManifest
 
   private object FloatManifest extends AnyValManifest[scala.Float]("Float") {
     def runtimeClass = java.lang.Float.TYPE
@@ -138,7 +138,7 @@ object ManifestFactory {
     override def newArrayBuilder(): ArrayBuilder[Float] = new ArrayBuilder.ofFloat()
     private def readResolve(): Any = Manifest.Float
   }
-  def Float: AnyValManifest[Float] = FloatManifest
+  val Float: AnyValManifest[Float] = FloatManifest
 
   private object DoubleManifest extends AnyValManifest[scala.Double]("Double") {
     def runtimeClass = java.lang.Double.TYPE
@@ -147,7 +147,7 @@ object ManifestFactory {
     override def newArrayBuilder(): ArrayBuilder[Double] = new ArrayBuilder.ofDouble()
     private def readResolve(): Any = Manifest.Double
   }
-  def Double: AnyValManifest[Double] = DoubleManifest
+  val Double: AnyValManifest[Double] = DoubleManifest
 
   private object BooleanManifest extends AnyValManifest[scala.Boolean]("Boolean") {
     def runtimeClass = java.lang.Boolean.TYPE
@@ -156,7 +156,7 @@ object ManifestFactory {
     override def newArrayBuilder(): ArrayBuilder[Boolean] = new ArrayBuilder.ofBoolean()
     private def readResolve(): Any = Manifest.Boolean
   }
-  def Boolean: AnyValManifest[Boolean] = BooleanManifest
+  val Boolean: AnyValManifest[Boolean] = BooleanManifest
 
   private object UnitManifest extends AnyValManifest[scala.Unit]("Unit") {
     def runtimeClass = java.lang.Void.TYPE
@@ -168,7 +168,7 @@ object ManifestFactory {
       else super.arrayClass(tp)
     private def readResolve(): Any = Manifest.Unit
   }
-  def Unit: AnyValManifest[Unit] = UnitManifest
+  val Unit: AnyValManifest[Unit] = UnitManifest
 
   private object AnyManifest extends PhantomManifest[scala.Any](classOf[java.lang.Object], "Any") {
     override def runtimeClass = classOf[java.lang.Object]
@@ -176,7 +176,7 @@ object ManifestFactory {
     override def <:<(that: ClassManifest[_]): Boolean = (that eq this)
     private def readResolve(): Any = Manifest.Any
   }
-  def Any: Manifest[scala.Any] = AnyManifest
+  val Any: Manifest[scala.Any] = AnyManifest
 
   private object ObjectManifest extends PhantomManifest[java.lang.Object](classOf[java.lang.Object], "Object") {
     override def runtimeClass = classOf[java.lang.Object]
@@ -184,9 +184,9 @@ object ManifestFactory {
     override def <:<(that: ClassManifest[_]): Boolean = (that eq this) || (that eq Any)
     private def readResolve(): Any = Manifest.Object
   }
-  def Object: Manifest[java.lang.Object] = ObjectManifest
+  val Object: Manifest[java.lang.Object] = ObjectManifest
 
-  def AnyRef: Manifest[scala.AnyRef] = Object.asInstanceOf[Manifest[scala.AnyRef]]
+  val AnyRef: Manifest[scala.AnyRef] = Object
 
   private object AnyValManifest extends PhantomManifest[scala.AnyVal](classOf[java.lang.Object], "AnyVal") {
     override def runtimeClass = classOf[java.lang.Object]
@@ -194,7 +194,7 @@ object ManifestFactory {
     override def <:<(that: ClassManifest[_]): Boolean = (that eq this) || (that eq Any)
     private def readResolve(): Any = Manifest.AnyVal
   }
-  def AnyVal: Manifest[scala.AnyVal] = AnyValManifest
+  val AnyVal: Manifest[scala.AnyVal] = AnyValManifest
 
   private object NullManifest extends PhantomManifest[scala.Null](classOf[scala.runtime.Null$], "Null") {
     override def runtimeClass = classOf[scala.runtime.Null$]
@@ -203,7 +203,7 @@ object ManifestFactory {
       (that ne null) && (that ne Nothing) && !(that <:< AnyVal)
     private def readResolve(): Any = Manifest.Null
   }
-  def Null: Manifest[scala.Null] = NullManifest
+  val Null: Manifest[scala.Null] = NullManifest
 
   private object NothingManifest extends PhantomManifest[scala.Nothing](classOf[scala.runtime.Nothing$], "Nothing") {
     override def runtimeClass = classOf[scala.runtime.Nothing$]
@@ -211,7 +211,7 @@ object ManifestFactory {
     override def <:<(that: ClassManifest[_]): Boolean = (that ne null)
     private def readResolve(): Any = Manifest.Nothing
   }
-  def Nothing: Manifest[scala.Nothing] = NothingManifest
+  val Nothing: Manifest[scala.Nothing] = NothingManifest
 
   private class SingletonTypeManifest[T <: AnyRef](value: AnyRef) extends Manifest[T] {
     lazy val runtimeClass = value.getClass
diff --git a/scalalib/overrides-2.13/scala/reflect/ClassTag.scala b/scalalib/overrides-2.13/scala/reflect/ClassTag.scala
index 253d55cefb..a66a1a6a8e 100644
--- a/scalalib/overrides-2.13/scala/reflect/ClassTag.scala
+++ b/scalalib/overrides-2.13/scala/reflect/ClassTag.scala
@@ -96,21 +96,21 @@ trait ClassTag[T] extends ClassManifestDeprecatedApis[T] with Equals with Serial
 object ClassTag {
   import ManifestFactory._
 
-  @uncheckedStable def Byte    : ByteManifest               = ManifestFactory.Byte
-  @uncheckedStable def Short   : ShortManifest              = ManifestFactory.Short
-  @uncheckedStable def Char    : CharManifest               = ManifestFactory.Char
-  @uncheckedStable def Int     : IntManifest                = ManifestFactory.Int
-  @uncheckedStable def Long    : LongManifest               = ManifestFactory.Long
-  @uncheckedStable def Float   : FloatManifest              = ManifestFactory.Float
-  @uncheckedStable def Double  : DoubleManifest             = ManifestFactory.Double
-  @uncheckedStable def Boolean : BooleanManifest            = ManifestFactory.Boolean
-  @uncheckedStable def Unit    : UnitManifest               = ManifestFactory.Unit
-  @uncheckedStable def Any     : ClassTag[scala.Any]        = ManifestFactory.Any
-  @uncheckedStable def Object  : ClassTag[java.lang.Object] = ManifestFactory.Object
-  @uncheckedStable def AnyVal  : ClassTag[scala.AnyVal]     = ManifestFactory.AnyVal
-  @uncheckedStable def AnyRef  : ClassTag[scala.AnyRef]     = ManifestFactory.AnyRef
-  @uncheckedStable def Nothing : ClassTag[scala.Nothing]    = ManifestFactory.Nothing
-  @uncheckedStable def Null    : ClassTag[scala.Null]       = ManifestFactory.Null
+  val Byte    : ByteManifest               = ManifestFactory.Byte
+  val Short   : ShortManifest              = ManifestFactory.Short
+  val Char    : CharManifest               = ManifestFactory.Char
+  val Int     : IntManifest                = ManifestFactory.Int
+  val Long    : LongManifest               = ManifestFactory.Long
+  val Float   : FloatManifest              = ManifestFactory.Float
+  val Double  : DoubleManifest             = ManifestFactory.Double
+  val Boolean : BooleanManifest            = ManifestFactory.Boolean
+  val Unit    : UnitManifest               = ManifestFactory.Unit
+  val Any     : ClassTag[scala.Any]        = ManifestFactory.Any
+  val Object  : ClassTag[java.lang.Object] = ManifestFactory.Object
+  val AnyVal  : ClassTag[scala.AnyVal]     = ManifestFactory.AnyVal
+  val AnyRef  : ClassTag[scala.AnyRef]     = ManifestFactory.AnyRef
+  val Nothing : ClassTag[scala.Nothing]    = ManifestFactory.Nothing
+  val Null    : ClassTag[scala.Null]       = ManifestFactory.Null
 
   @inline
   @SerialVersionUID(1L)
diff --git a/scalalib/overrides-2.13/scala/reflect/Manifest.scala b/scalalib/overrides-2.13/scala/reflect/Manifest.scala
index 053b0c485d..faa2fe6f6e 100644
--- a/scalalib/overrides-2.13/scala/reflect/Manifest.scala
+++ b/scalalib/overrides-2.13/scala/reflect/Manifest.scala
@@ -80,22 +80,22 @@ object Manifest {
   def valueManifests: List[AnyValManifest[_]] =
     ManifestFactory.valueManifests
 
-  def Byte: ManifestFactory.ByteManifest = ManifestFactory.Byte
-  def Short: ManifestFactory.ShortManifest = ManifestFactory.Short
-  def Char: ManifestFactory.CharManifest = ManifestFactory.Char
-  def Int: ManifestFactory.IntManifest = ManifestFactory.Int
-  def Long: ManifestFactory.LongManifest = ManifestFactory.Long
-  def Float: ManifestFactory.FloatManifest = ManifestFactory.Float
-  def Double: ManifestFactory.DoubleManifest = ManifestFactory.Double
-  def Boolean: ManifestFactory.BooleanManifest = ManifestFactory.Boolean
-  def Unit: ManifestFactory.UnitManifest = ManifestFactory.Unit
-
-  def Any: Manifest[scala.Any] = ManifestFactory.Any
-  def Object: Manifest[java.lang.Object] = ManifestFactory.Object
-  def AnyRef: Manifest[scala.AnyRef] = ManifestFactory.AnyRef
-  def AnyVal: Manifest[scala.AnyVal] = ManifestFactory.AnyVal
-  def Null: Manifest[scala.Null] = ManifestFactory.Null
-  def Nothing: Manifest[scala.Nothing] = ManifestFactory.Nothing
+  val Byte: ManifestFactory.ByteManifest = ManifestFactory.Byte
+  val Short: ManifestFactory.ShortManifest = ManifestFactory.Short
+  val Char: ManifestFactory.CharManifest = ManifestFactory.Char
+  val Int: ManifestFactory.IntManifest = ManifestFactory.Int
+  val Long: ManifestFactory.LongManifest = ManifestFactory.Long
+  val Float: ManifestFactory.FloatManifest = ManifestFactory.Float
+  val Double: ManifestFactory.DoubleManifest = ManifestFactory.Double
+  val Boolean: ManifestFactory.BooleanManifest = ManifestFactory.Boolean
+  val Unit: ManifestFactory.UnitManifest = ManifestFactory.Unit
+
+  val Any: Manifest[scala.Any] = ManifestFactory.Any
+  val Object: Manifest[java.lang.Object] = ManifestFactory.Object
+  val AnyRef: Manifest[scala.AnyRef] = ManifestFactory.AnyRef
+  val AnyVal: Manifest[scala.AnyVal] = ManifestFactory.AnyVal
+  val Null: Manifest[scala.Null] = ManifestFactory.Null
+  val Nothing: Manifest[scala.Nothing] = ManifestFactory.Nothing
 
   /** Manifest for the singleton type `value.type`. */
   def singleType[T <: AnyRef](value: AnyRef): Manifest[T] =
@@ -181,7 +181,7 @@ object ManifestFactory {
     private def readResolve(): Any = Manifest.Byte
   }
   private object ByteManifest extends ByteManifest
-  def Byte: ByteManifest = ByteManifest
+  val Byte: ByteManifest = ByteManifest
 
   @SerialVersionUID(1L)
   private[reflect] class ShortManifest extends AnyValManifest[scala.Short]("Short") {
@@ -198,7 +198,7 @@ object ManifestFactory {
     private def readResolve(): Any = Manifest.Short
   }
   private object ShortManifest extends ShortManifest
-  def Short: ShortManifest = ShortManifest
+  val Short: ShortManifest = ShortManifest
 
   @SerialVersionUID(1L)
   private[reflect] class CharManifest extends AnyValManifest[scala.Char]("Char") {
@@ -215,7 +215,7 @@ object ManifestFactory {
     private def readResolve(): Any = Manifest.Char
   }
   private object CharManifest extends CharManifest
-  def Char: CharManifest = CharManifest
+  val Char: CharManifest = CharManifest
 
   @SerialVersionUID(1L)
   private[reflect] class IntManifest extends AnyValManifest[scala.Int]("Int") {
@@ -232,7 +232,7 @@ object ManifestFactory {
     private def readResolve(): Any = Manifest.Int
   }
   private object IntManifest extends IntManifest
-  def Int: IntManifest = IntManifest
+  val Int: IntManifest = IntManifest
 
   @SerialVersionUID(1L)
   private[reflect] class LongManifest extends AnyValManifest[scala.Long]("Long") {
@@ -249,7 +249,7 @@ object ManifestFactory {
     private def readResolve(): Any = Manifest.Long
   }
   private object LongManifest extends LongManifest
-  def Long: LongManifest = LongManifest
+  val Long: LongManifest = LongManifest
 
   @SerialVersionUID(1L)
   private[reflect] class FloatManifest extends AnyValManifest[scala.Float]("Float") {
@@ -266,7 +266,7 @@ object ManifestFactory {
     private def readResolve(): Any = Manifest.Float
   }
   private object FloatManifest extends FloatManifest
-  def Float: FloatManifest = FloatManifest
+  val Float: FloatManifest = FloatManifest
 
   @SerialVersionUID(1L)
   private[reflect] class DoubleManifest extends AnyValManifest[scala.Double]("Double") {
@@ -284,7 +284,7 @@ object ManifestFactory {
     private def readResolve(): Any = Manifest.Double
   }
   private object DoubleManifest extends DoubleManifest
-  def Double: DoubleManifest = DoubleManifest
+  val Double: DoubleManifest = DoubleManifest
 
   @SerialVersionUID(1L)
   private[reflect] class BooleanManifest extends AnyValManifest[scala.Boolean]("Boolean") {
@@ -301,7 +301,7 @@ object ManifestFactory {
     private def readResolve(): Any = Manifest.Boolean
   }
   private object BooleanManifest extends BooleanManifest
-  def Boolean: BooleanManifest = BooleanManifest
+  val Boolean: BooleanManifest = BooleanManifest
 
   @SerialVersionUID(1L)
   private[reflect] class UnitManifest extends AnyValManifest[scala.Unit]("Unit") {
@@ -321,7 +321,7 @@ object ManifestFactory {
     private def readResolve(): Any = Manifest.Unit
   }
   private object UnitManifest extends UnitManifest
-  def Unit: UnitManifest = UnitManifest
+  val Unit: UnitManifest = UnitManifest
 
   private object AnyManifest extends PhantomManifest[scala.Any](classOf[java.lang.Object], "Any") {
     override def runtimeClass = classOf[java.lang.Object]
@@ -329,7 +329,7 @@ object ManifestFactory {
     override def <:<(that: ClassManifest[_]): Boolean = (that eq this)
     private def readResolve(): Any = Manifest.Any
   }
-  def Any: Manifest[scala.Any] = AnyManifest
+  val Any: Manifest[scala.Any] = AnyManifest
 
   private object ObjectManifest extends PhantomManifest[java.lang.Object](classOf[java.lang.Object], "Object") {
     override def runtimeClass = classOf[java.lang.Object]
@@ -337,9 +337,9 @@ object ManifestFactory {
     override def <:<(that: ClassManifest[_]): Boolean = (that eq this) || (that eq Any)
     private def readResolve(): Any = Manifest.Object
   }
-  def Object: Manifest[java.lang.Object] = ObjectManifest
+  val Object: Manifest[java.lang.Object] = ObjectManifest
 
-  def AnyRef: Manifest[scala.AnyRef] = Object.asInstanceOf[Manifest[scala.AnyRef]]
+  val AnyRef: Manifest[scala.AnyRef] = Object
 
   private object AnyValManifest extends PhantomManifest[scala.AnyVal](classOf[java.lang.Object], "AnyVal") {
     override def runtimeClass = classOf[java.lang.Object]
@@ -347,7 +347,7 @@ object ManifestFactory {
     override def <:<(that: ClassManifest[_]): Boolean = (that eq this) || (that eq Any)
     private def readResolve(): Any = Manifest.AnyVal
   }
-  def AnyVal: Manifest[scala.AnyVal] = AnyValManifest
+  val AnyVal: Manifest[scala.AnyVal] = AnyValManifest
 
   private object NullManifest extends PhantomManifest[scala.Null](classOf[scala.runtime.Null$], "Null") {
     override def runtimeClass = classOf[scala.runtime.Null$]
@@ -356,7 +356,7 @@ object ManifestFactory {
       (that ne null) && (that ne Nothing) && !(that <:< AnyVal)
     private def readResolve(): Any = Manifest.Null
   }
-  def Null: Manifest[scala.Null] = NullManifest
+  val Null: Manifest[scala.Null] = NullManifest
 
   private object NothingManifest extends PhantomManifest[scala.Nothing](classOf[scala.runtime.Nothing$], "Nothing") {
     override def runtimeClass = classOf[scala.runtime.Nothing$]
@@ -364,7 +364,7 @@ object ManifestFactory {
     override def <:<(that: ClassManifest[_]): Boolean = (that ne null)
     private def readResolve(): Any = Manifest.Nothing
   }
-  def Nothing: Manifest[scala.Nothing] = NothingManifest
+  val Nothing: Manifest[scala.Nothing] = NothingManifest
 
   @SerialVersionUID(1L)
   private class SingletonTypeManifest[T <: AnyRef](value: AnyRef) extends Manifest[T] {

From 08d0286e21020a9788d1f97e8390d5736a865ca7 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Thu, 15 Feb 2024 11:48:06 +0100
Subject: [PATCH 050/298] Inline `genUnchecked` at its two call sites.

It had been factored out in `SJSGen` because of one condition that
happens to be repeated. However, it is clearer that it does the
right thing at each of its call sites. Given the amount of
information that needed to be passed to this helper, inlining it
twice actually removes additional checks. Ultimately, it seems
simpler this way.
---
 .../scalajs/linker/backend/emitter/CoreJSLib.scala |  5 ++++-
 .../linker/backend/emitter/FunctionEmitter.scala   | 11 +++++++++--
 .../scalajs/linker/backend/emitter/SJSGen.scala    | 14 --------------
 3 files changed, 13 insertions(+), 17 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
index b36e35783d..89e4ad86df 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
@@ -1171,7 +1171,10 @@ private[emitter] object CoreJSLib {
               // Both values have the same "data" (could also be falsy values)
               If(srcData && genIdentBracketSelect(srcData, "isArrayClass"), {
                 // Fast path: the values are array of the same type
-                genUncheckedArraycopy(List(src, srcPos, dest, destPos, length))
+                if (esVersion >= ESVersion.ES2015 && nullPointers == CheckedBehavior.Unchecked)
+                  Apply(src DOT "copyTo", List(srcPos, dest, destPos, length))
+                else
+                  genCallHelper(VarField.systemArraycopy, src, srcPos, dest, destPos, length)
               }, {
                 genCallHelper(VarField.throwArrayStoreException, Null())
               })
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
index 32b8baca4f..75b4bdeb61 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
@@ -875,12 +875,19 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
             implicit val env = env0
             val jsArgs = newArgs.map(transformExprNoChar(_))
 
+            def genUnchecked(): js.Tree = {
+              if (esFeatures.esVersion >= ESVersion.ES2015 && semantics.nullPointers == CheckedBehavior.Unchecked)
+                js.Apply(jsArgs.head DOT "copyTo", jsArgs.tail)
+              else
+                genCallHelper(VarField.systemArraycopy, jsArgs: _*)
+            }
+
             if (semantics.arrayStores == Unchecked) {
-              genUncheckedArraycopy(jsArgs)
+              genUnchecked()
             } else {
               (src.tpe, dest.tpe) match {
                 case (PrimArray(srcPrimRef), PrimArray(destPrimRef)) if srcPrimRef == destPrimRef =>
-                  genUncheckedArraycopy(jsArgs)
+                  genUnchecked()
                 case (RefArray(), RefArray()) =>
                   genCallHelper(VarField.systemArraycopyRefs, jsArgs: _*)
                 case _ =>
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala
index 4541d3a292..e7ea19a9db 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala
@@ -149,20 +149,6 @@ private[emitter] final class SJSGen(
     }
   }
 
-  def genUncheckedArraycopy(args: List[Tree])(
-      implicit moduleContext: ModuleContext, globalKnowledge: GlobalKnowledge,
-      pos: Position): Tree = {
-    import TreeDSL._
-
-    assert(args.lengthCompare(5) == 0,
-        s"wrong number of args for genUncheckedArrayCopy: $args")
-
-    if (esFeatures.esVersion >= ESVersion.ES2015 && semantics.nullPointers == CheckedBehavior.Unchecked)
-      Apply(args.head DOT "copyTo", args.tail)
-    else
-      genCallHelper(VarField.systemArraycopy, args: _*)
-  }
-
   def genSelect(receiver: Tree, field: irt.FieldIdent)(
       implicit pos: Position): Tree = {
     DotSelect(receiver, Ident(genName(field.name))(field.pos))

From ec2a24e7dbc75094d122d3077fb65106db105fe9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Mon, 26 Feb 2024 16:01:18 +0100
Subject: [PATCH 051/298] Fix #4954: Count `!_allowComplete` as a fake pending
 task of WorkTracker.

---
 .../scalajs/linker/analyzer/Analyzer.scala    | 48 +++++++++++--------
 1 file changed, 27 insertions(+), 21 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala
index 11a997ef27..534a30ef85 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala
@@ -1571,9 +1571,11 @@ private object AnalyzerRun {
     MethodName("getSuperclass", Nil, ClassRef(ClassClass))
 
   private class WorkTracker(implicit ec: ExecutionContext) {
-    private val pending = new AtomicInteger(0)
+    /** The number of tasks that have started but not completed, `+ 1` until
+     *  `allowComplete()` gets called.
+     */
+    private val pending = new AtomicInteger(1)
     private val failures = new AtomicReference[List[Throwable]](Nil)
-    @volatile private var _allowComplete = false
     private val promise = Promise[Unit]()
 
     def track(fut: Future[Unit]): Unit = {
@@ -1584,8 +1586,7 @@ private object AnalyzerRun {
           case Success(_) => ()
           case Failure(t) => addFailure(t)
         }
-        if (pending.decrementAndGet() == 0)
-          tryComplete()
+        decrementPending()
       }
     }
 
@@ -1596,28 +1597,33 @@ private object AnalyzerRun {
         addFailure(t)
     }
 
-    private def tryComplete(): Unit = {
-      /* Note that after _allowComplete is true and pending == 0, we are sure
-       * that no new task will be submitted concurrently:
-       * - _allowComplete guarantees us that no external task will be added anymore
-       * - pending == 0 guarantees us that no internal task (which might create
-       *   more tasks) are running anymore.
+    private def decrementPending(): Unit = {
+      /* When `pending` reaches 0, we are sure that all started tasks have
+       * completed, and that `allowComplete()` was called. Therefore, no
+       * further task can be concurrently added, and we are done.
        */
-      if (_allowComplete && pending.get() == 0) {
-        failures.get() match {
-          case Nil =>
-            promise.success(())
-          case firstFailure :: moreFailures =>
-            for (t <- moreFailures)
-              firstFailure.addSuppressed(t)
-            promise.failure(firstFailure)
-        }
+      if (pending.decrementAndGet() == 0)
+        complete()
+    }
+
+    private def complete(): Unit = {
+      failures.get() match {
+        case Nil =>
+          promise.success(())
+        case firstFailure :: moreFailures =>
+          for (t <- moreFailures)
+            firstFailure.addSuppressed(t)
+          promise.failure(firstFailure)
       }
     }
 
+    /** Signals that no new top-level tasks will be started, and that it is
+     *  therefore OK to complete the tracker once all ongoing tasks have finished.
+     *
+     *  `allowComplete()` must not be called more than once.
+     */
     def allowComplete(): Future[Unit] = {
-      _allowComplete = true
-      tryComplete()
+      decrementPending()
       promise.future
     }
   }

From 18e1862b09bf82a2f621e4ae274aab8baf823abd Mon Sep 17 00:00:00 2001
From: Rikito Taniguchi <rikiriki1238@gmail.com>
Date: Sat, 2 Mar 2024 01:36:52 +0900
Subject: [PATCH 052/298] Fix #4957: Fix error message for
 ConflictingTopLevelExport

fix https://github.com/scala-js/scala-js/issues/4957
---
 .../src/main/scala/org/scalajs/linker/analyzer/Analysis.scala   | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analysis.scala b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analysis.scala
index 1ad5f24785..6d0a02e83c 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analysis.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analysis.scala
@@ -242,7 +242,7 @@ object Analysis {
         "is not a valid JavaScript identifier " +
         "(did you want to emit a module instead?)"
       case ConflictingTopLevelExport(moduleID, exportName, infos) =>
-        s"Conflicting top level exports for module $moduleID, name $exportName "
+        s"Conflicting top level exports for module $moduleID, name $exportName " +
         "involving " + infos.map(_.owningClass.nameString).mkString(", ")
       case ImportWithoutModuleSupport(module, info, None, _) =>
         s"${info.displayName} needs to be imported from module " +

From 44aacace31712d2abc558458db282ef7b1ef820a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Mon, 26 Feb 2024 10:03:06 +0100
Subject: [PATCH 053/298] Introduce `javascript.Trees.DelayedIdent`.

We introduce a new kind of node in JS ASTs: `DelayedIdent`. A
delayed ident is like an `Ident`, but its `name` is provided by a
resolver, to be determined later. This allows us to build a JS
AST with `DelayedIdent`s whose final names will only be known
later.

Since pretty-printing requires to resolve the name, it might throw
and is not so well suited to `show` for debugging purposes anymore.
We therefore introduce `JSTreeShowPrinter`, which avoids resolving
the names. Instead, it uses the `debugString` method of the
resolver, which can be constructed to display meaningful debugging
information.

`DelayedIdent` is not yet actually used in this commit, but will
be in a subsequent commit for minifying property names.
---
 .../closure/ClosureAstTransformer.scala       | 16 ++---
 .../linker/backend/emitter/JSGen.scala        |  6 +-
 .../linker/backend/javascript/Printers.scala  | 33 +++++++++-
 .../linker/backend/javascript/Trees.scala     | 61 ++++++++++++++++---
 .../backend/javascript/PrintersTest.scala     | 37 ++++++++++-
 5 files changed, 127 insertions(+), 26 deletions(-)

diff --git a/linker/jvm/src/main/scala/org/scalajs/linker/backend/closure/ClosureAstTransformer.scala b/linker/jvm/src/main/scala/org/scalajs/linker/backend/closure/ClosureAstTransformer.scala
index 79ad4562ec..cad0fd9434 100644
--- a/linker/jvm/src/main/scala/org/scalajs/linker/backend/closure/ClosureAstTransformer.scala
+++ b/linker/jvm/src/main/scala/org/scalajs/linker/backend/closure/ClosureAstTransformer.scala
@@ -210,9 +210,9 @@ private class ClosureAstTransformer(featureSet: FeatureSet,
   private def transformClassMember(member: Tree): Node = {
     implicit val pos = member.pos
 
-    def newFixedPropNode(token: Token, static: Boolean, name: Ident,
+    def newFixedPropNode(token: Token, static: Boolean, name: MaybeDelayedIdent,
         function: Node): Node = {
-      val node = Node.newString(token, name.name)
+      val node = Node.newString(token, name.resolveName())
       node.addChildToBack(function)
       node.setStaticMember(static)
       node
@@ -258,7 +258,7 @@ private class ClosureAstTransformer(featureSet: FeatureSet,
             val node = newComputedPropNode(static, nameExpr, function)
             node.putBooleanProp(Node.COMPUTED_PROP_METHOD, true)
             node
-          case name: Ident =>
+          case name: MaybeDelayedIdent =>
             newFixedPropNode(Token.MEMBER_FUNCTION_DEF, static, name, function)
         }
 
@@ -274,7 +274,7 @@ private class ClosureAstTransformer(featureSet: FeatureSet,
             val node = newComputedPropNode(static, nameExpr, function)
             node.putBooleanProp(Node.COMPUTED_PROP_GETTER, true)
             node
-          case name: Ident =>
+          case name: MaybeDelayedIdent =>
             newFixedPropNode(Token.GETTER_DEF, static, name, function)
         }
 
@@ -290,7 +290,7 @@ private class ClosureAstTransformer(featureSet: FeatureSet,
             val node = newComputedPropNode(static, nameExpr, function)
             node.putBooleanProp(Node.COMPUTED_PROP_SETTER, true)
             node
-          case name: Ident =>
+          case name: MaybeDelayedIdent =>
             newFixedPropNode(Token.SETTER_DEF, static, name, function)
         }
 
@@ -321,7 +321,7 @@ private class ClosureAstTransformer(featureSet: FeatureSet,
         args.foreach(arg => node.addChildToBack(transformExpr(arg)))
         node
       case DotSelect(qualifier, item) =>
-        val node = Node.newString(Token.GETPROP, item.name)
+        val node = Node.newString(Token.GETPROP, item.resolveName())
         node.addChildToBack(transformExpr(qualifier))
         setNodePosition(node, item.pos.orElse(pos))
       case BracketSelect(qualifier, item) =>
@@ -435,8 +435,8 @@ private class ClosureAstTransformer(featureSet: FeatureSet,
     val transformedValue = transformExpr(value)
 
     val node = name match {
-      case Ident(name, _) =>
-        Node.newString(Token.STRING_KEY, name)
+      case name: MaybeDelayedIdent =>
+        Node.newString(Token.STRING_KEY, name.resolveName())
 
       case StringLiteral(name) =>
         val node = Node.newString(Token.STRING_KEY, name)
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/JSGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/JSGen.scala
index 9d0150c2c9..4da09323c5 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/JSGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/JSGen.scala
@@ -148,9 +148,9 @@ private[emitter] final class JSGen(val config: Emitter.Config) {
   def genPropSelect(qual: Tree, item: PropertyName)(
       implicit pos: Position): Tree = {
     item match {
-      case item: Ident         => DotSelect(qual, item)
-      case item: StringLiteral => genBracketSelect(qual, item)
-      case ComputedName(tree)  => genBracketSelect(qual, tree)
+      case item: MaybeDelayedIdent => DotSelect(qual, item)
+      case item: StringLiteral     => genBracketSelect(qual, item)
+      case ComputedName(tree)      => genBracketSelect(qual, tree)
     }
   }
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Printers.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Printers.scala
index a6d632a1cd..2b99af7010 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Printers.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Printers.scala
@@ -747,9 +747,13 @@ object Printers {
     protected def print(ident: Ident): Unit =
       printEscapeJS(ident.name)
 
+    protected def print(ident: DelayedIdent): Unit =
+      printEscapeJS(ident.resolveName())
+
     private final def print(propName: PropertyName): Unit = propName match {
-      case lit: StringLiteral => print(lit: Tree)
-      case ident: Ident       => print(ident)
+      case lit: StringLiteral  => print(lit: Tree)
+      case ident: Ident        => print(ident)
+      case ident: DelayedIdent => print(ident)
 
       case ComputedName(tree) =>
         print("[")
@@ -799,6 +803,14 @@ object Printers {
         sourceMap.endNode(column)
     }
 
+    override protected def print(ident: DelayedIdent): Unit = {
+      if (ident.pos.isDefined)
+        sourceMap.startIdentNode(column, ident.pos, ident.originalName)
+      printEscapeJS(ident.resolveName())
+      if (ident.pos.isDefined)
+        sourceMap.endNode(column)
+    }
+
     override protected def print(printedTree: PrintedTree): Unit = {
       super.print(printedTree)
       sourceMap.insertFragment(printedTree.sourceMapFragment)
@@ -830,4 +842,21 @@ object Printers {
     }
   }
 
+  /** Shows a `Tree` for debugging purposes, not for pretty-printing. */
+  private[javascript] def showTree(tree: Tree): String = {
+    val writer = new ByteArrayWriter()
+    val printer = new Printers.JSTreeShowPrinter(writer)
+    printer.printTree(tree, isStat = true)
+    new String(writer.toByteArray(), StandardCharsets.US_ASCII)
+  }
+
+  /** A printer that shows `Tree`s for debugging, not for pretty-printing. */
+  private class JSTreeShowPrinter(_out: ByteArrayWriter, initIndent: Int = 0)
+      extends JSTreePrinter(_out, initIndent) {
+    override protected def print(ident: DelayedIdent): Unit = {
+      print("<delayed:")
+      print(ident.resolver.debugString)
+      print(">")
+    }
+  }
 }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Trees.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Trees.scala
index ec5b72e850..0c0b820e82 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Trees.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Trees.scala
@@ -31,12 +31,7 @@ object Trees {
   abstract sealed class Tree {
     val pos: Position
 
-    def show: String = {
-      val writer = new ByteArrayWriter()
-      val printer = new Printers.JSTreePrinter(writer)
-      printer.printTree(this, isStat = true)
-      new String(writer.toByteArray(), StandardCharsets.US_ASCII)
-    }
+    def show: String = Printers.showTree(this)
   }
 
   // Constructor comment / annotation.
@@ -50,16 +45,26 @@ object Trees {
     def pos: Position
   }
 
+  sealed trait MaybeDelayedIdent extends PropertyName {
+    def resolveName(): String
+  }
+
   sealed case class Ident(name: String, originalName: OriginalName)(
-      implicit val pos: Position) extends PropertyName {
-    require(Ident.isValidJSIdentifierName(name),
-        s"'$name' is not a valid JS identifier name")
+      implicit val pos: Position) extends MaybeDelayedIdent {
+    Ident.requireValidJSIdentifierName(name)
+
+    def resolveName(): String = name
   }
 
   object Ident {
     def apply(name: String)(implicit pos: Position): Ident =
       new Ident(name, NoOriginalName)
 
+    def requireValidJSIdentifierName(name: String): Unit = {
+      require(isValidJSIdentifierName(name),
+          s"'$name' is not a valid JS identifier name")
+    }
+
     /** Tests whether the given string is a valid `IdentifierName` for the
      *  ECMAScript language specification.
      *
@@ -87,6 +92,42 @@ object Trees {
     }
   }
 
+  /** An ident whose real name will be resolved later. */
+  sealed case class DelayedIdent(resolver: DelayedIdent.Resolver, originalName: OriginalName)(
+      implicit val pos: Position)
+      extends MaybeDelayedIdent {
+
+    def resolveName(): String = {
+      val name = resolver.resolve()
+      Ident.requireValidJSIdentifierName(name)
+      name
+    }
+  }
+
+  object DelayedIdent {
+    def apply(resolver: DelayedIdent.Resolver)(implicit pos: Position): DelayedIdent =
+      new DelayedIdent(resolver, NoOriginalName)
+
+    /** Resolver for the eventual name of a `DelayedIdent`. */
+    trait Resolver {
+      /** Resolves the eventual name of the delayed ident.
+       *
+       *  @throws java.lang.IllegalStateException
+       *    if this resolver is not yet ready to resolve a name
+       */
+      def resolve(): String
+
+      /** A string representing this resolver for debugging purposes.
+       *
+       *  The result of this method is used when calling `show` on the
+       *  associated `DelayedIdent`. Once the resolver is ready, this method is
+       *  encouraged to return the same string as `resolve()`, but it is not
+       *  mandatory to do so.
+       */
+      def debugString: String
+    }
+  }
+
   sealed case class ComputedName(tree: Tree) extends PropertyName {
     def pos: Position = tree.pos
   }
@@ -231,7 +272,7 @@ object Trees {
       implicit val pos: Position)
       extends Tree
 
-  sealed case class DotSelect(qualifier: Tree, item: Ident)(
+  sealed case class DotSelect(qualifier: Tree, item: MaybeDelayedIdent)(
       implicit val pos: Position)
       extends Tree
 
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/backend/javascript/PrintersTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/backend/javascript/PrintersTest.scala
index ba4848f668..a2a8108fa8 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/backend/javascript/PrintersTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/backend/javascript/PrintersTest.scala
@@ -30,12 +30,16 @@ class PrintersTest {
   private implicit def str2ident(name: String): Ident =
     Ident(name, ir.OriginalName.NoOriginalName)
 
-  private def assertPrintEquals(expected: String, tree: Tree): Unit = {
+  private def printTree(tree: Tree): String = {
     val out = new ByteArrayWriter
     val printer = new Printers.JSTreePrinter(out)
     printer.printStat(tree)
-    assertEquals(expected.stripMargin.trim + "\n",
-        new String(out.toByteArray(), UTF_8))
+    new String(out.toByteArray(), UTF_8)
+  }
+
+  private def assertPrintEquals(expected: String, tree: Tree): Unit = {
+    val printResult = printTree(tree)
+    assertEquals(expected.stripMargin.trim + "\n", printResult)
   }
 
   @Test def printFunctionDef(): Unit = {
@@ -159,6 +163,33 @@ class PrintersTest {
     )
   }
 
+  @Test def delayedIdentPrintVersusShow(): Unit = {
+    locally {
+      object resolver extends DelayedIdent.Resolver {
+        def resolve(): String = "foo"
+        def debugString: String = "bar"
+      }
+
+      val tree = DotSelect(VarRef("x"), DelayedIdent(resolver))
+
+      assertPrintEquals("x.foo;", tree)
+      assertEquals("x.<delayed:bar>;", tree.show)
+    }
+
+    // Even when `resolve()` throws, `show` still succeeds based on `debugString`.
+    locally {
+      object resolver extends DelayedIdent.Resolver {
+        def resolve(): String = throw new IllegalStateException("not ready")
+        def debugString: String = "bar"
+      }
+
+      val tree = DotSelect(VarRef("x"), DelayedIdent(resolver))
+
+      assertThrows(classOf[IllegalStateException], () => printTree(tree))
+      assertEquals("x.<delayed:bar>;", tree.show)
+    }
+  }
+
   @Test def showPrintedTree(): Unit = {
     val tree = PrintedTree("test".getBytes(UTF_8), SourceMapWriter.Fragment.Empty)
 

From 298c60a0b5817a04ffd507e6ea0a793beb0a0486 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Mon, 26 Feb 2024 10:33:22 +0100
Subject: [PATCH 054/298] Make `JSTreePrinter.printTree` protected.

The only remaining public method is now `printStat(tree: Tree)`.
---
 .../org/scalajs/linker/backend/javascript/Printers.scala | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Printers.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Printers.scala
index 2b99af7010..09a3b8648a 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Printers.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Printers.scala
@@ -139,7 +139,7 @@ object Printers {
      *  - No leading indent.
      *  - No trailing newline.
      */
-    def printTree(tree: Tree, isStat: Boolean): Unit = {
+    protected def printTree(tree: Tree, isStat: Boolean): Unit = {
       def printSeparatorIfStat() = {
         if (isStat)
           print(';')
@@ -781,7 +781,7 @@ object Printers {
 
     private var column = 0
 
-    override def printTree(tree: Tree, isStat: Boolean): Unit = {
+    override protected def printTree(tree: Tree, isStat: Boolean): Unit = {
       val pos = tree.pos
       if (pos.isDefined)
         sourceMap.startNode(column, pos)
@@ -846,13 +846,16 @@ object Printers {
   private[javascript] def showTree(tree: Tree): String = {
     val writer = new ByteArrayWriter()
     val printer = new Printers.JSTreeShowPrinter(writer)
-    printer.printTree(tree, isStat = true)
+    printer.printTreeForShow(tree)
     new String(writer.toByteArray(), StandardCharsets.US_ASCII)
   }
 
   /** A printer that shows `Tree`s for debugging, not for pretty-printing. */
   private class JSTreeShowPrinter(_out: ByteArrayWriter, initIndent: Int = 0)
       extends JSTreePrinter(_out, initIndent) {
+    def printTreeForShow(tree: Tree): Unit =
+      printTree(tree, isStat = true)
+
     override protected def print(ident: DelayedIdent): Unit = {
       print("<delayed:")
       print(ident.resolver.debugString)

From a6b7a9d64284cdf913f77bc2a660449e6ba23f87 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Mon, 26 Feb 2024 11:56:16 +0100
Subject: [PATCH 055/298] Refactoring: Restrict responsibility of gen member
 idents to SJSGen.

Previously, `SJSGen` generated `Ident`s for field members, but
only names for method members. Generating the `Ident`s for methods
was left in `ClassEmitter` and `Function`. Now, we concentrate that
responsibility in `SJSGen` only.

In addition, we make a clear distinction between idents generated
for *definitions*, which receive an `OriginalName`, and those used
for *use sites*, which never receive one.
---
 .../linker/backend/emitter/ClassEmitter.scala | 23 +++++--------------
 .../linker/backend/emitter/CoreJSLib.scala    |  8 ++++---
 .../backend/emitter/FunctionEmitter.scala     |  7 ++----
 .../linker/backend/emitter/SJSGen.scala       | 23 +++++++++++++++----
 4 files changed, 32 insertions(+), 29 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
index 211b335e29..e0154b1782 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
@@ -355,7 +355,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
     } yield {
       val field = anyField.asInstanceOf[FieldDef]
       implicit val pos = field.pos
-      js.Assign(genSelect(js.This(), field.name, field.originalName),
+      js.Assign(genSelectForDef(js.This(), field.name, field.originalName),
           genZeroOf(field.ftpe))
     }
   }
@@ -422,8 +422,11 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
       val zero = genBoxedZeroOf(field.ftpe)
       field match {
         case FieldDef(_, name, originalName, _) =>
+          /* TODO This seems to be dead code, which is somehow reassuring
+           * because I don't know what it is supposed to achieve.
+           */
           WithGlobals(
-              js.Assign(js.DotSelect(classVarRef, genMemberFieldIdent(name, originalName)), zero))
+              js.Assign(genSelectForDef(classVarRef, name, originalName), zero))
         case JSFieldDef(_, name, _) =>
           for (propName <- genMemberNameTree(name))
             yield js.Assign(genPropSelect(classVarRef, propName), zero)
@@ -472,7 +475,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
     for {
       methodFun <- desugarToFunction(className, method.args, method.body.get, method.resultType)
     } yield {
-      val jsMethodName = genMemberMethodIdent(method.name, method.originalName)
+      val jsMethodName = genMethodIdentForDef(method.name, method.originalName)
 
       if (useESClass) {
         js.MethodDef(static = false, jsMethodName, methodFun.args, methodFun.restParam, methodFun.body)
@@ -659,20 +662,6 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
     }
   }
 
-  private def genMemberFieldIdent(ident: FieldIdent,
-      originalName: OriginalName): js.Ident = {
-    val jsName = genName(ident.name)
-    js.Ident(jsName, genOriginalName(ident.name, originalName, jsName))(
-        ident.pos)
-  }
-
-  private def genMemberMethodIdent(ident: MethodIdent,
-      originalName: OriginalName): js.Ident = {
-    val jsName = genMethodName(ident.name)
-    js.Ident(jsName, genOriginalName(ident.name, originalName, jsName))(
-        ident.pos)
-  }
-
   def needInstanceTests(tree: LinkedClass)(
       implicit globalKnowledge: GlobalKnowledge): Boolean = {
     tree.hasInstanceTests || (tree.hasRuntimeTypeInfo &&
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
index 89e4ad86df..3fdefbbfb5 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
@@ -877,7 +877,7 @@ private[emitter] object CoreJSLib {
 
           if (implementedInObject) {
             val staticObjectCall: Tree = {
-              val fun = globalVar(VarField.c, ObjectClass).prototype DOT genMethodName(methodName)
+              val fun = globalVar(VarField.c, ObjectClass).prototype DOT genMethodIdent(methodName)
               Return(Apply(fun DOT "call", instance :: args))
             }
 
@@ -1504,7 +1504,8 @@ private[emitter] object CoreJSLib {
           Nil
         }
 
-        val clone = MethodDef(static = false, Ident(genMethodName(cloneMethodName)), Nil, None, {
+        val cloneMethodIdent = genMethodIdentForDef(cloneMethodName, NoOriginalName)
+        val clone = MethodDef(static = false, cloneMethodIdent, Nil, None, {
           Return(New(ArrayClass,
               Apply(genIdentBracketSelect(This().u, "slice"), Nil) :: Nil))
         })
@@ -1809,7 +1810,8 @@ private[emitter] object CoreJSLib {
               Nil
             }
 
-            val clone = MethodDef(static = false, Ident(genMethodName(cloneMethodName)), Nil, None, {
+            val cloneMethodIdent = genMethodIdentForDef(cloneMethodName, NoOriginalName)
+            val clone = MethodDef(static = false, cloneMethodIdent, Nil, None, {
               Return(New(ArrayClass,
                   Apply(genIdentBracketSelect(This().u, "slice"), Nil) :: Nil))
             })
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
index 75b4bdeb61..95cf6e1c33 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
@@ -2252,7 +2252,7 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
           val newArgs = transformTypedArgs(method.name, args)
 
           def genNormalApply(): js.Tree =
-            js.Apply(newReceiver(false) DOT transformMethodIdent(method), newArgs)
+            js.Apply(newReceiver(false) DOT genMethodIdent(method), newArgs)
 
           def genDispatchApply(): js.Tree =
             js.Apply(globalVar(VarField.dp, methodName), newReceiver(false) :: newArgs)
@@ -2315,7 +2315,7 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
             genApplyStaticLike(VarField.f, className, method, transformedArgs)
           } else {
             val fun =
-              globalVar(VarField.c, className).prototype DOT transformMethodIdent(method)
+              globalVar(VarField.c, className).prototype DOT genMethodIdent(method)
             js.Apply(fun DOT "call", transformedArgs)
           }
 
@@ -3207,9 +3207,6 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
     private def transformLabelIdent(ident: LabelIdent): js.Ident =
       js.Ident(genName(ident.name))(ident.pos)
 
-    private def transformMethodIdent(ident: MethodIdent): js.Ident =
-      js.Ident(genMethodName(ident.name))(ident.pos)
-
     private def transformLocalVarIdent(ident: LocalIdent): js.Ident =
       js.Ident(transformLocalName(ident.name))(ident.pos)
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala
index e7ea19a9db..615b1e94a0 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala
@@ -154,7 +154,7 @@ private[emitter] final class SJSGen(
     DotSelect(receiver, Ident(genName(field.name))(field.pos))
   }
 
-  def genSelect(receiver: Tree, field: irt.FieldIdent,
+  def genSelectForDef(receiver: Tree, field: irt.FieldIdent,
       originalName: OriginalName)(
       implicit pos: Position): Tree = {
     val jsName = genName(field.name)
@@ -164,7 +164,7 @@ private[emitter] final class SJSGen(
 
   def genApply(receiver: Tree, methodName: MethodName, args: List[Tree])(
       implicit pos: Position): Tree = {
-    Apply(DotSelect(receiver, Ident(genMethodName(methodName))), args)
+    Apply(DotSelect(receiver, genMethodIdent(methodName)), args)
   }
 
   def genApply(receiver: Tree, methodName: MethodName, args: Tree*)(
@@ -172,8 +172,23 @@ private[emitter] final class SJSGen(
     genApply(receiver, methodName, args.toList)
   }
 
-  def genMethodName(methodName: MethodName): String =
-    genName(methodName)
+  def genMethodIdent(methodIdent: irt.MethodIdent): Ident =
+    genMethodIdent(methodIdent.name)(methodIdent.pos)
+
+  def genMethodIdentForDef(methodIdent: irt.MethodIdent,
+      originalName: OriginalName): Ident = {
+    genMethodIdentForDef(methodIdent.name, originalName)(methodIdent.pos)
+  }
+
+  def genMethodIdent(methodName: MethodName)(implicit pos: Position): Ident =
+    Ident(genName(methodName))
+
+  def genMethodIdentForDef(methodName: MethodName, originalName: OriginalName)(
+      implicit pos: Position): Ident = {
+    val jsName = genName(methodName)
+    val jsOrigName = genOriginalName(methodName, originalName, jsName)
+    Ident(jsName, jsOrigName)
+  }
 
   def genJSPrivateSelect(receiver: Tree, field: irt.FieldIdent)(
       implicit moduleContext: ModuleContext, globalKnowledge: GlobalKnowledge,

From 41b7b9c8751087602a197fc8ad591c74809e2f20 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Wed, 24 Jan 2024 14:37:59 +0100
Subject: [PATCH 056/298] Minify property names ourselves in fullLink when we
 don't use GCC.

When emitting ES modules, we cannot use Closure because it does not
support ES modules the way we need it to. This results in files
that are much larger than with other module kinds.

Off-the-shelf JavaScript bundlers/minifier can compensate for that
to a large extent for local and file-local variables, but they do
not have enough semantic information to do it on property names.

We therefore add our own property name compressor. When enabled,
the emitter computes the frequency of every field and method name
in the entire program. It then uses those frequencies to allocate
short names to them, with the shortest ones allocated to the most
used properties.

In order to compute the frequencies, we count how many times
`genMethodName` is called for any particular `MethodName` (same
for other kinds of names) during JS AST generation. That means
that while we generate the JS AST, we do not know the final
frequencies, and therefore the eventually allocated names. We
use `DelayedIdent`s to defer the actual resolution until after
the frequencies are computed.

Obviously, this breaks any sort of incremental behavior. Since we
do not cache the frequency counts per calling method, we have to
force re-generation of the whole AST at each run to re-count.
Therefore, we invalidate all the emitter caches on every run when
the new minifier is enabled. This should not be a problem as it
is only intended to be used for fullLink.

An alternative would be to store the counts along with global
refs in `WithGlobals`, but the overhead would then leak pretty
strongly on incremental runs that do not minify.

This strategy also prevents fusing AST generation and
pretty-printing. When minifying, we demand that the
`postTransformer` be `PostTransformer.Identity`. This adds a bit
of handling to `BasicLinkerBackend` to deal with the two possible
kinds of trees received from the emitter, but nothing too invasive.

We automatically enable the new minifier under fullLink when
GCC is disabled. This can be overridden with a `scalaJSLinkerConfig`
setting.
---
 Jenkinsfile                                   | 110 +++++----
 .../linker/interface/StandardConfig.scala     |  22 ++
 .../closure/ClosureLinkerBackend.scala        |  15 +-
 .../linker/backend/BasicLinkerBackend.scala   |  85 +++++--
 .../linker/backend/LinkerBackendImpl.scala    |  21 +-
 .../backend/emitter/ArrayClassProperty.scala  |  46 ++++
 .../linker/backend/emitter/CoreJSLib.scala    |  37 ++-
 .../linker/backend/emitter/Emitter.scala      |  47 +++-
 .../backend/emitter/FunctionEmitter.scala     |  22 +-
 .../backend/emitter/NameCompressor.scala      | 230 ++++++++++++++++++
 .../linker/backend/emitter/NameGen.scala      |   4 +-
 .../linker/backend/emitter/SJSGen.scala       |  86 ++++++-
 .../linker/backend/emitter/TreeDSL.scala      |   3 +-
 .../standard/StandardLinkerBackend.scala      |   1 +
 .../org/scalajs/linker/EmitterTest.scala      |   2 +-
 .../org/scalajs/linker/LibrarySizeTest.scala  |   3 +-
 .../backend/emitter/NameCompressorTest.scala  |  53 ++++
 project/Build.scala                           |  81 ++++--
 .../sbtplugin/ScalaJSPluginInternal.scala     |   1 +
 .../scalajs/testsuite/utils/BuildInfo.scala   |   3 +-
 .../scalajs/testsuite/utils/Platform.scala    |   5 +-
 .../testsuite/compiler/OptimizerTest.scala    |   9 +-
 .../testsuite/jsinterop/MiscInteropTest.scala |   4 +-
 .../testsuite/library/StackTraceTest.scala    |   2 +-
 .../scalajs/testsuite/utils/Platform.scala    |   4 +-
 .../scalajs/testsuite/compiler/LongTest.scala |   6 +-
 .../compiler/ReflectiveCallTest.scala         |   2 +-
 27 files changed, 758 insertions(+), 146 deletions(-)
 create mode 100644 linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ArrayClassProperty.scala
 create mode 100644 linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/NameCompressor.scala
 create mode 100644 linker/shared/src/test/scala/org/scalajs/linker/backend/emitter/NameCompressorTest.scala

diff --git a/Jenkinsfile b/Jenkinsfile
index 158b73cc4e..1c9dc60c29 100644
--- a/Jenkinsfile
+++ b/Jenkinsfile
@@ -185,6 +185,9 @@ def Tasks = [
         reversi$v/fastLinkJS \
         reversi$v/fullLinkJS \
         reversi$v/checksizes &&
+    sbtretry ++$scala \
+        'set Global/enableMinifyEverywhere := true' \
+        reversi$v/checksizes &&
     sbtretry ++$scala javalibintf/compile:doc compiler$v/compile:doc library$v/compile:doc \
         testInterface$v/compile:doc testBridge$v/compile:doc &&
     sbtretry ++$scala headerCheck &&
@@ -199,68 +202,84 @@ def Tasks = [
   "test-suite-default-esversion": '''
     setJavaVersion $java
     npm install &&
-    sbtretry ++$scala jUnitTestOutputsJVM$v/test jUnitTestOutputsJS$v/test testBridge$v/test \
+    sbtretry ++$scala 'set Global/enableMinifyEverywhere := $testMinify' \
+        jUnitTestOutputsJVM$v/test jUnitTestOutputsJS$v/test testBridge$v/test \
         'set scalaJSStage in Global := FullOptStage' jUnitTestOutputsJS$v/test testBridge$v/test &&
-    sbtretry ++$scala $testSuite$v/test $testSuite$v/testHtmlJSDom &&
-    sbtretry 'set scalaJSStage in Global := FullOptStage' \
-        ++$scala $testSuite$v/test \
+    sbtretry ++$scala 'set Global/enableMinifyEverywhere := $testMinify' \
+        $testSuite$v/test $testSuite$v/testHtmlJSDom &&
+    sbtretry ++$scala 'set Global/enableMinifyEverywhere := $testMinify' \
+        'set scalaJSStage in Global := FullOptStage' \
+        $testSuite$v/test \
         $testSuite$v/testHtmlJSDom &&
-    sbtretry 'set scalaJSLinkerConfig in $testSuite.v$v ~= (_.withOptimizer(false))' \
-        ++$scala $testSuite$v/test &&
-    sbtretry 'set scalaJSLinkerConfig in $testSuite.v$v ~= (_.withOptimizer(false))' \
+    sbtretry ++$scala 'set Global/enableMinifyEverywhere := $testMinify' \
+        'set scalaJSLinkerConfig in $testSuite.v$v ~= (_.withOptimizer(false))' \
+        $testSuite$v/test &&
+    sbtretry ++$scala 'set Global/enableMinifyEverywhere := $testMinify' \
+        'set scalaJSLinkerConfig in $testSuite.v$v ~= (_.withOptimizer(false))' \
         'set scalaJSStage in Global := FullOptStage' \
-        ++$scala $testSuite$v/test &&
-    sbtretry 'set scalaJSLinkerConfig in $testSuite.v$v ~= makeCompliant' \
-        ++$scala $testSuite$v/test &&
-    sbtretry 'set scalaJSLinkerConfig in $testSuite.v$v ~= makeCompliant' \
+        $testSuite$v/test &&
+    sbtretry ++$scala 'set Global/enableMinifyEverywhere := $testMinify' \
+        'set scalaJSLinkerConfig in $testSuite.v$v ~= makeCompliant' \
+        $testSuite$v/test &&
+    sbtretry ++$scala 'set Global/enableMinifyEverywhere := $testMinify' \
+        'set scalaJSLinkerConfig in $testSuite.v$v ~= makeCompliant' \
         'set scalaJSStage in Global := FullOptStage' \
-        ++$scala $testSuite$v/test &&
-    sbtretry 'set scalaJSLinkerConfig in $testSuite.v$v ~= makeCompliant' \
+        $testSuite$v/test &&
+    sbtretry ++$scala 'set Global/enableMinifyEverywhere := $testMinify' \
+        'set scalaJSLinkerConfig in $testSuite.v$v ~= makeCompliant' \
         'set scalaJSLinkerConfig in $testSuite.v$v ~= (_.withOptimizer(false))' \
-        ++$scala $testSuite$v/test &&
-    sbtretry 'set scalaJSLinkerConfig in $testSuite.v$v ~= { _.withSemantics(_.withStrictFloats(false)) }' \
-        ++$scala $testSuite$v/test &&
-    sbtretry 'set scalaJSLinkerConfig in $testSuite.v$v ~= { _.withSemantics(_.withStrictFloats(false)) }' \
+        $testSuite$v/test &&
+    sbtretry ++$scala 'set Global/enableMinifyEverywhere := $testMinify' \
+        'set scalaJSLinkerConfig in $testSuite.v$v ~= { _.withSemantics(_.withStrictFloats(false)) }' \
+        $testSuite$v/test &&
+    sbtretry ++$scala 'set Global/enableMinifyEverywhere := $testMinify' \
+        'set scalaJSLinkerConfig in $testSuite.v$v ~= { _.withSemantics(_.withStrictFloats(false)) }' \
         'set scalaJSStage in Global := FullOptStage' \
-        ++$scala $testSuite$v/test &&
-    sbtretry 'set scalaJSLinkerConfig in $testSuite.v$v ~= { _.withSemantics(_.withStrictFloats(false)) }' \
+        $testSuite$v/test &&
+    sbtretry ++$scala 'set Global/enableMinifyEverywhere := $testMinify' \
+        'set scalaJSLinkerConfig in $testSuite.v$v ~= { _.withSemantics(_.withStrictFloats(false)) }' \
         'set scalaJSLinkerConfig in $testSuite.v$v ~= (_.withOptimizer(false))' \
-        ++$scala $testSuite$v/test &&
-    sbtretry 'set scalaJSLinkerConfig in $testSuite.v$v ~= (_.withESFeatures(_.withAllowBigIntsForLongs(true)))' \
-        ++$scala $testSuite$v/test &&
-    sbtretry 'set scalaJSLinkerConfig in $testSuite.v$v ~= (_.withESFeatures(_.withAllowBigIntsForLongs(true)).withOptimizer(false))' \
-        ++$scala $testSuite$v/test &&
-    sbtretry \
+        $testSuite$v/test &&
+    sbtretry ++$scala 'set Global/enableMinifyEverywhere := $testMinify' \
+        'set scalaJSLinkerConfig in $testSuite.v$v ~= (_.withESFeatures(_.withAllowBigIntsForLongs(true)))' \
+        $testSuite$v/test &&
+    sbtretry ++$scala 'set Global/enableMinifyEverywhere := $testMinify' \
+        'set scalaJSLinkerConfig in $testSuite.v$v ~= (_.withESFeatures(_.withAllowBigIntsForLongs(true)).withOptimizer(false))' \
+        $testSuite$v/test &&
+    sbtretry ++$scala 'set Global/enableMinifyEverywhere := $testMinify' \
         'set scalaJSLinkerConfig in $testSuite.v$v ~= (_.withESFeatures(_.withAvoidLetsAndConsts(false).withAvoidClasses(false)))' \
-        ++$scala $testSuite$v/test &&
-    sbtretry \
+        $testSuite$v/test &&
+    sbtretry ++$scala 'set Global/enableMinifyEverywhere := $testMinify' \
         'set scalaJSLinkerConfig in $testSuite.v$v ~= (_.withESFeatures(_.withAvoidLetsAndConsts(false).withAvoidClasses(false)))' \
         'set scalaJSStage in Global := FullOptStage' \
-        ++$scala $testSuite$v/test &&
-    sbtretry 'set scalaJSLinkerConfig in $testSuite.v$v ~= (_.withModuleKind(ModuleKind.CommonJSModule))' \
-        ++$scala $testSuite$v/test &&
-    sbtretry \
+        $testSuite$v/test &&
+    sbtretry ++$scala 'set Global/enableMinifyEverywhere := $testMinify' \
+        'set scalaJSLinkerConfig in $testSuite.v$v ~= (_.withModuleKind(ModuleKind.CommonJSModule))' \
+        $testSuite$v/test &&
+    sbtretry ++$scala 'set Global/enableMinifyEverywhere := $testMinify' \
         'set scalaJSLinkerConfig in $testSuite.v$v ~= (_.withModuleKind(ModuleKind.CommonJSModule))' \
         'set scalaJSLinkerConfig in $testSuite.v$v ~= (_.withModuleSplitStyle(ModuleSplitStyle.SmallestModules))' \
-        ++$scala $testSuite$v/test &&
-    sbtretry 'set scalaJSLinkerConfig in $testSuite.v$v ~= (_.withModuleKind(ModuleKind.CommonJSModule))' \
+        $testSuite$v/test &&
+    sbtretry ++$scala 'set Global/enableMinifyEverywhere := $testMinify' \
+        'set scalaJSLinkerConfig in $testSuite.v$v ~= (_.withModuleKind(ModuleKind.CommonJSModule))' \
         'set scalaJSStage in Global := FullOptStage' \
-        ++$scala $testSuite$v/test &&
-    sbtretry \
+        $testSuite$v/test &&
+    sbtretry ++$scala 'set Global/enableMinifyEverywhere := $testMinify' \
         'set scalaJSLinkerConfig in $testSuite.v$v ~= (_.withModuleKind(ModuleKind.ESModule))' \
-        ++$scala $testSuite$v/test &&
-    sbtretry \
+        $testSuite$v/test &&
+    sbtretry ++$scala 'set Global/enableMinifyEverywhere := $testMinify' \
         'set scalaJSLinkerConfig in $testSuite.v$v ~= (_.withModuleSplitStyle(ModuleSplitStyle.SmallestModules))' \
         'set scalaJSLinkerConfig in $testSuite.v$v ~= (_.withModuleKind(ModuleKind.ESModule))' \
-        ++$scala $testSuite$v/test &&
-    sbtretry \
+        $testSuite$v/test &&
+    sbtretry ++$scala 'set Global/enableMinifyEverywhere := $testMinify' \
         'set scalaJSLinkerConfig in $testSuite.v$v ~= (_.withModuleSplitStyle(ModuleSplitStyle.SmallModulesFor(List("org.scalajs.testsuite"))))' \
         'set scalaJSLinkerConfig in $testSuite.v$v ~= (_.withModuleKind(ModuleKind.ESModule))' \
-        ++$scala $testSuite$v/test &&
-    sbtretry \
+        $testSuite$v/test &&
+    # The following tests the same thing whether testMinify is true or false; we also set it for regularity.
+    sbtretry ++$scala 'set Global/enableMinifyEverywhere := $testMinify' \
         'set scalaJSLinkerConfig in $testSuite.v$v ~= (_.withModuleKind(ModuleKind.ESModule))' \
         'set scalaJSStage in Global := FullOptStage' \
-        ++$scala $testSuite$v/test
+        $testSuite$v/test
   ''',
 
   "test-suite-custom-esversion-force-polyfills": '''
@@ -504,9 +523,10 @@ mainScalaVersions.each { scalaVersion ->
     quickMatrix.add([task: "main", scala: scalaVersion, java: javaVersion])
     quickMatrix.add([task: "tools", scala: scalaVersion, java: javaVersion])
   }
-  quickMatrix.add([task: "test-suite-default-esversion", scala: scalaVersion, java: mainJavaVersion, testSuite: "testSuite"])
+  quickMatrix.add([task: "test-suite-default-esversion", scala: scalaVersion, java: mainJavaVersion, testMinify: "false", testSuite: "testSuite"])
+  quickMatrix.add([task: "test-suite-default-esversion", scala: scalaVersion, java: mainJavaVersion, testMinify: "true", testSuite: "testSuite"])
   quickMatrix.add([task: "test-suite-custom-esversion", scala: scalaVersion, java: mainJavaVersion, esVersion: "ES5_1", testSuite: "testSuite"])
-  quickMatrix.add([task: "test-suite-default-esversion", scala: scalaVersion, java: mainJavaVersion, testSuite: "scalaTestSuite"])
+  quickMatrix.add([task: "test-suite-default-esversion", scala: scalaVersion, java: mainJavaVersion, testMinify: "false", testSuite: "scalaTestSuite"])
   quickMatrix.add([task: "test-suite-custom-esversion", scala: scalaVersion, java: mainJavaVersion, esVersion: "ES5_1", testSuite: "scalaTestSuite"])
   quickMatrix.add([task: "bootstrap", scala: scalaVersion, java: mainJavaVersion])
   quickMatrix.add([task: "partest-fastopt", scala: scalaVersion, java: mainJavaVersion])
@@ -527,7 +547,7 @@ otherScalaVersions.each { scalaVersion ->
 }
 mainScalaVersions.each { scalaVersion ->
   otherJavaVersions.each { javaVersion ->
-    quickMatrix.add([task: "test-suite-default-esversion", scala: scalaVersion, java: javaVersion, testSuite: "testSuite"])
+    quickMatrix.add([task: "test-suite-default-esversion", scala: scalaVersion, java: javaVersion, testMinify: "false", testSuite: "testSuite"])
   }
   fullMatrix.add([task: "partest-noopt", scala: scalaVersion, java: mainJavaVersion])
   fullMatrix.add([task: "partest-fullopt", scala: scalaVersion, java: mainJavaVersion])
diff --git a/linker-interface/shared/src/main/scala/org/scalajs/linker/interface/StandardConfig.scala b/linker-interface/shared/src/main/scala/org/scalajs/linker/interface/StandardConfig.scala
index d867c1d1bf..40644b5b9f 100644
--- a/linker-interface/shared/src/main/scala/org/scalajs/linker/interface/StandardConfig.scala
+++ b/linker-interface/shared/src/main/scala/org/scalajs/linker/interface/StandardConfig.scala
@@ -46,6 +46,19 @@ final class StandardConfig private (
     val relativizeSourceMapBase: Option[URI],
     /** Name patterns for output. */
     val outputPatterns: OutputPatterns,
+    /** Apply Scala.js-specific minification of the produced .js files.
+     *
+     *  When enabled, the linker more aggressively reduces the size of the
+     *  generated code, at the cost of readability and debuggability. It does
+     *  not perform size optimizations that would negatively impact run-time
+     *  performance.
+     *
+     *  The focus is on optimizations that general-purpose JavaScript minifiers
+     *  cannot do on their own. For the best results, we expect the Scala.js
+     *  minifier to be used in conjunction with a general-purpose JavaScript
+     *  minifier.
+     */
+    val minify: Boolean,
     /** Whether to use the Google Closure Compiler pass, if it is available.
      *  On the JavaScript platform, this does not have any effect.
      */
@@ -80,6 +93,7 @@ final class StandardConfig private (
         sourceMap = true,
         relativizeSourceMapBase = None,
         outputPatterns = OutputPatterns.Defaults,
+        minify = false,
         closureCompilerIfAvailable = false,
         prettyPrint = false,
         batchMode = false,
@@ -148,6 +162,9 @@ final class StandardConfig private (
   def withOutputPatterns(f: OutputPatterns => OutputPatterns): StandardConfig =
     copy(outputPatterns = f(outputPatterns))
 
+  def withMinify(minify: Boolean): StandardConfig =
+    copy(minify = minify)
+
   def withClosureCompilerIfAvailable(closureCompilerIfAvailable: Boolean): StandardConfig =
     copy(closureCompilerIfAvailable = closureCompilerIfAvailable)
 
@@ -173,6 +190,7 @@ final class StandardConfig private (
        |  sourceMap                  = $sourceMap,
        |  relativizeSourceMapBase    = $relativizeSourceMapBase,
        |  outputPatterns             = $outputPatterns,
+       |  minify                     = $minify,
        |  closureCompilerIfAvailable = $closureCompilerIfAvailable,
        |  prettyPrint                = $prettyPrint,
        |  batchMode                  = $batchMode,
@@ -192,6 +210,7 @@ final class StandardConfig private (
       sourceMap: Boolean = sourceMap,
       outputPatterns: OutputPatterns = outputPatterns,
       relativizeSourceMapBase: Option[URI] = relativizeSourceMapBase,
+      minify: Boolean = minify,
       closureCompilerIfAvailable: Boolean = closureCompilerIfAvailable,
       prettyPrint: Boolean = prettyPrint,
       batchMode: Boolean = batchMode,
@@ -209,6 +228,7 @@ final class StandardConfig private (
         sourceMap,
         relativizeSourceMapBase,
         outputPatterns,
+        minify,
         closureCompilerIfAvailable,
         prettyPrint,
         batchMode,
@@ -237,6 +257,7 @@ object StandardConfig {
         .addField("relativizeSourceMapBase",
             config.relativizeSourceMapBase.map(_.toASCIIString()))
         .addField("outputPatterns", config.outputPatterns)
+        .addField("minify", config.minify)
         .addField("closureCompilerIfAvailable",
             config.closureCompilerIfAvailable)
         .addField("prettyPrint", config.prettyPrint)
@@ -264,6 +285,7 @@ object StandardConfig {
    *  - `sourceMap`: `true`
    *  - `relativizeSourceMapBase`: `None`
    *  - `outputPatterns`: [[OutputPatterns.Defaults]]
+   *  - `minify`: `false`
    *  - `closureCompilerIfAvailable`: `false`
    *  - `prettyPrint`: `false`
    *  - `batchMode`: `false`
diff --git a/linker/jvm/src/main/scala/org/scalajs/linker/backend/closure/ClosureLinkerBackend.scala b/linker/jvm/src/main/scala/org/scalajs/linker/backend/closure/ClosureLinkerBackend.scala
index 64160204ac..7532e0be47 100644
--- a/linker/jvm/src/main/scala/org/scalajs/linker/backend/closure/ClosureLinkerBackend.scala
+++ b/linker/jvm/src/main/scala/org/scalajs/linker/backend/closure/ClosureLinkerBackend.scala
@@ -54,13 +54,19 @@ final class ClosureLinkerBackend(config: LinkerBackendImpl.Config)
       s"Cannot use module kind $moduleKind with the Closure Compiler")
 
   private[this] val emitter = {
+    // Note that we do not transfer `minify` -- Closure will do its own thing anyway
     val emitterConfig = Emitter.Config(config.commonConfig.coreSpec)
       .withJSHeader(config.jsHeader)
       .withOptimizeBracketSelects(false)
       .withTrackAllGlobalRefs(true)
       .withInternalModulePattern(m => OutputPatternsImpl.moduleName(config.outputPatterns, m.id))
 
-    new Emitter(emitterConfig, ClosureLinkerBackend.PostTransformer)
+    // Do not apply ClosureAstTransformer eagerly:
+    // The ASTs used by closure are highly mutable, so re-using them is non-trivial.
+    // Since closure is slow anyways, we haven't built the optimization.
+    val postTransformer = Emitter.PostTransformer.Identity
+
+    new Emitter(emitterConfig, postTransformer)
   }
 
   val symbolRequirements: SymbolRequirement = emitter.symbolRequirements
@@ -296,11 +302,4 @@ private object ClosureLinkerBackend {
     Function.prototype.apply;
     var NaN = 0.0/0.0, Infinity = 1.0/0.0, undefined = void 0;
     """
-
-  private object PostTransformer extends Emitter.PostTransformer[js.Tree] {
-    // Do not apply ClosureAstTransformer eagerly:
-    // The ASTs used by closure are highly mutable, so re-using them is non-trivial.
-    // Since closure is slow anyways, we haven't built the optimization.
-    def transformStats(trees: List[js.Tree], indent: Int): List[js.Tree] = trees
-  }
 }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/BasicLinkerBackend.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/BasicLinkerBackend.scala
index e07e31597b..fa7e616880 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/BasicLinkerBackend.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/BasicLinkerBackend.scala
@@ -41,16 +41,19 @@ final class BasicLinkerBackend(config: LinkerBackendImpl.Config)
   private[this] var totalModules = 0
   private[this] val rewrittenModules = new AtomicInteger(0)
 
-  private[this] val emitter = {
+  private[this] val bodyPrinter: BodyPrinter = {
+    if (config.minify) IdentityPostTransformerBasedBodyPrinter
+    else if (config.sourceMap) PrintedTreeWithSourceMapBodyPrinter
+    else PrintedTreeWithoutSourceMapBodyPrinter
+  }
+
+  private[this] val emitter: Emitter[bodyPrinter.TreeType] = {
     val emitterConfig = Emitter.Config(config.commonConfig.coreSpec)
       .withJSHeader(config.jsHeader)
       .withInternalModulePattern(m => OutputPatternsImpl.moduleName(config.outputPatterns, m.id))
+      .withMinify(config.minify)
 
-    val postTransformer =
-      if (config.sourceMap) PostTransformerWithSourceMap
-      else PostTransformerWithoutSourceMap
-
-    new Emitter(emitterConfig, postTransformer)
+    new Emitter(emitterConfig, bodyPrinter.postTransformer)
   }
 
   val symbolRequirements: SymbolRequirement = emitter.symbolRequirements
@@ -82,13 +85,14 @@ final class BasicLinkerBackend(config: LinkerBackendImpl.Config)
     val skipContentCheck = !isFirstRun
     isFirstRun = false
 
-    val allChanged =
+    val allChanged0 =
       printedModuleSetCache.updateGlobal(emitterResult.header, emitterResult.footer)
+    val allChanged = allChanged0 || config.minify
 
     val writer = new OutputWriter(output, config, skipContentCheck) {
       protected def writeModuleWithoutSourceMap(moduleID: ModuleID, force: Boolean): Option[ByteBuffer] = {
         val cache = printedModuleSetCache.getModuleCache(moduleID)
-        val (printedTrees, changed) = emitterResult.body(moduleID)
+        val (trees, changed) = emitterResult.body(moduleID)
 
         if (force || changed || allChanged) {
           rewrittenModules.incrementAndGet()
@@ -98,8 +102,7 @@ final class BasicLinkerBackend(config: LinkerBackendImpl.Config)
           jsFileWriter.write(printedModuleSetCache.headerBytes)
           jsFileWriter.writeASCIIString("'use strict';\n")
 
-          for (printedTree <- printedTrees)
-            jsFileWriter.write(printedTree.jsCode)
+          bodyPrinter.printWithoutSourceMap(trees, jsFileWriter)
 
           jsFileWriter.write(printedModuleSetCache.footerBytes)
 
@@ -112,7 +115,7 @@ final class BasicLinkerBackend(config: LinkerBackendImpl.Config)
 
       protected def writeModuleWithSourceMap(moduleID: ModuleID, force: Boolean): Option[(ByteBuffer, ByteBuffer)] = {
         val cache = printedModuleSetCache.getModuleCache(moduleID)
-        val (printedTrees, changed) = emitterResult.body(moduleID)
+        val (trees, changed) = emitterResult.body(moduleID)
 
         if (force || changed || allChanged) {
           rewrittenModules.incrementAndGet()
@@ -133,10 +136,7 @@ final class BasicLinkerBackend(config: LinkerBackendImpl.Config)
           jsFileWriter.writeASCIIString("'use strict';\n")
           smWriter.nextLine()
 
-          for (printedTree <- printedTrees) {
-            jsFileWriter.write(printedTree.jsCode)
-            smWriter.insertFragment(printedTree.sourceMapFragment)
-          }
+          bodyPrinter.printWithSourceMap(trees, jsFileWriter, smWriter)
 
           jsFileWriter.write(printedModuleSetCache.footerBytes)
           jsFileWriter.write(("//# sourceMappingURL=" + sourceMapURI + "\n").getBytes(StandardCharsets.UTF_8))
@@ -240,6 +240,57 @@ private object BasicLinkerBackend {
     }
   }
 
+  private abstract class BodyPrinter {
+    type TreeType >: Null <: js.Tree
+
+    val postTransformer: Emitter.PostTransformer[TreeType]
+
+    def printWithoutSourceMap(trees: List[TreeType], jsFileWriter: ByteArrayWriter): Unit
+    def printWithSourceMap(trees: List[TreeType], jsFileWriter: ByteArrayWriter, smWriter: SourceMapWriter): Unit
+  }
+
+  private object IdentityPostTransformerBasedBodyPrinter extends BodyPrinter {
+    type TreeType = js.Tree
+
+    val postTransformer: Emitter.PostTransformer[TreeType] = Emitter.PostTransformer.Identity
+
+    def printWithoutSourceMap(trees: List[TreeType], jsFileWriter: ByteArrayWriter): Unit = {
+      val printer = new Printers.JSTreePrinter(jsFileWriter)
+      for (tree <- trees)
+        printer.printStat(tree)
+    }
+
+    def printWithSourceMap(trees: List[TreeType], jsFileWriter: ByteArrayWriter, smWriter: SourceMapWriter): Unit = {
+      val printer = new Printers.JSTreePrinterWithSourceMap(jsFileWriter, smWriter, initIndent = 0)
+      for (tree <- trees)
+        printer.printStat(tree)
+    }
+  }
+
+  private abstract class PrintedTreeBasedBodyPrinter(
+    val postTransformer: Emitter.PostTransformer[js.PrintedTree]
+  ) extends BodyPrinter {
+    type TreeType = js.PrintedTree
+
+    def printWithoutSourceMap(trees: List[TreeType], jsFileWriter: ByteArrayWriter): Unit = {
+      for (tree <- trees)
+        jsFileWriter.write(tree.jsCode)
+    }
+
+    def printWithSourceMap(trees: List[TreeType], jsFileWriter: ByteArrayWriter, smWriter: SourceMapWriter): Unit = {
+      for (tree <- trees) {
+        jsFileWriter.write(tree.jsCode)
+        smWriter.insertFragment(tree.sourceMapFragment)
+      }
+    }
+  }
+
+  private object PrintedTreeWithoutSourceMapBodyPrinter
+      extends PrintedTreeBasedBodyPrinter(PostTransformerWithoutSourceMap)
+
+  private object PrintedTreeWithSourceMapBodyPrinter
+      extends PrintedTreeBasedBodyPrinter(PostTransformerWithSourceMap)
+
   private object PostTransformerWithoutSourceMap extends Emitter.PostTransformer[js.PrintedTree] {
     def transformStats(trees: List[js.Tree], indent: Int): List[js.PrintedTree] = {
       if (trees.isEmpty) {
@@ -248,7 +299,7 @@ private object BasicLinkerBackend {
         val jsCodeWriter = new ByteArrayWriter()
         val printer = new Printers.JSTreePrinter(jsCodeWriter, indent)
 
-        trees.map(printer.printStat(_))
+        trees.foreach(printer.printStat(_))
 
         js.PrintedTree(jsCodeWriter.toByteArray(), SourceMapWriter.Fragment.Empty) :: Nil
       }
@@ -264,7 +315,7 @@ private object BasicLinkerBackend {
         val smFragmentBuilder = new SourceMapWriter.FragmentBuilder()
         val printer = new Printers.JSTreePrinterWithSourceMap(jsCodeWriter, smFragmentBuilder, indent)
 
-        trees.map(printer.printStat(_))
+        trees.foreach(printer.printStat(_))
         smFragmentBuilder.complete()
 
         js.PrintedTree(jsCodeWriter.toByteArray(), smFragmentBuilder.result()) :: Nil
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/LinkerBackendImpl.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/LinkerBackendImpl.scala
index e1795d4493..0fc8f5169b 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/LinkerBackendImpl.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/LinkerBackendImpl.scala
@@ -53,6 +53,8 @@ object LinkerBackendImpl {
       val outputPatterns: OutputPatterns,
       /** Base path to relativize paths in the source map. */
       val relativizeSourceMapBase: Option[URI],
+      /** Whether to use Scala.js' minifier for property names. */
+      val minify: Boolean,
       /** Whether to use the Google Closure Compiler pass, if it is available.
        *  On the JavaScript platform, this does not have any effect.
        */
@@ -69,6 +71,7 @@ object LinkerBackendImpl {
           sourceMap = true,
           outputPatterns = OutputPatterns.Defaults,
           relativizeSourceMapBase = None,
+          minify = false,
           closureCompilerIfAvailable = false,
           prettyPrint = false,
           maxConcurrentWrites = 50)
@@ -91,6 +94,9 @@ object LinkerBackendImpl {
     def withRelativizeSourceMapBase(relativizeSourceMapBase: Option[URI]): Config =
       copy(relativizeSourceMapBase = relativizeSourceMapBase)
 
+    def withMinify(minify: Boolean): Config =
+      copy(minify = minify)
+
     def withClosureCompilerIfAvailable(closureCompilerIfAvailable: Boolean): Config =
       copy(closureCompilerIfAvailable = closureCompilerIfAvailable)
 
@@ -106,12 +112,21 @@ object LinkerBackendImpl {
         sourceMap: Boolean = sourceMap,
         outputPatterns: OutputPatterns = outputPatterns,
         relativizeSourceMapBase: Option[URI] = relativizeSourceMapBase,
+        minify: Boolean = minify,
         closureCompilerIfAvailable: Boolean = closureCompilerIfAvailable,
         prettyPrint: Boolean = prettyPrint,
         maxConcurrentWrites: Int = maxConcurrentWrites): Config = {
-      new Config(commonConfig, jsHeader, sourceMap, outputPatterns,
-          relativizeSourceMapBase, closureCompilerIfAvailable, prettyPrint,
-          maxConcurrentWrites)
+      new Config(
+        commonConfig,
+        jsHeader,
+        sourceMap,
+        outputPatterns,
+        relativizeSourceMapBase,
+        minify,
+        closureCompilerIfAvailable,
+        prettyPrint,
+        maxConcurrentWrites
+      )
     }
   }
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ArrayClassProperty.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ArrayClassProperty.scala
new file mode 100644
index 0000000000..c33d0a99e7
--- /dev/null
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ArrayClassProperty.scala
@@ -0,0 +1,46 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package org.scalajs.linker.backend.emitter
+
+import org.scalajs.ir.OriginalName
+
+/** Represents a property of one of the special `ArrayClass`es.
+ *
+ *  These properties live in the same namespace as Scala field and method
+ *  names, because the `ArrayClass`es extend `j.l.Object`. Therefore, they
+ *  must take part in the global property minification algorithm.
+ */
+final class ArrayClassProperty(val nonMinifiedName: String)
+    extends Comparable[ArrayClassProperty] {
+
+  val originalName: OriginalName = OriginalName(nonMinifiedName)
+
+  def compareTo(that: ArrayClassProperty): Int =
+    this.nonMinifiedName.compareTo(that.nonMinifiedName)
+
+  override def toString(): String = s"ArrayClassProperty($nonMinifiedName)"
+}
+
+object ArrayClassProperty {
+  /** `ArrayClass.u`: the underlying array of typed array. */
+  val u: ArrayClassProperty = new ArrayClassProperty("u")
+
+  /** `ArrayClass.get()`: gets one element. */
+  val get: ArrayClassProperty = new ArrayClassProperty("get")
+
+  /** `ArrayClass.set()`: sets one element. */
+  val set: ArrayClassProperty = new ArrayClassProperty("set")
+
+  /** `ArrayClass.copyTo()`: copies from that array to another array. */
+  val copyTo: ArrayClassProperty = new ArrayClassProperty("copyTo")
+}
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
index 3fdefbbfb5..a96dea3018 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
@@ -1131,7 +1131,7 @@ private[emitter] object CoreJSLib {
       ) :::
       condDefs(esVersion >= ESVersion.ES2015 && nullPointers != CheckedBehavior.Unchecked)(
         defineFunction5(VarField.systemArraycopy) { (src, srcPos, dest, destPos, length) =>
-          Apply(src DOT "copyTo", List(srcPos, dest, destPos, length))
+          genArrayClassPropApply(src, ArrayClassProperty.copyTo, srcPos, dest, destPos, length)
         }
       ) :::
 
@@ -1155,7 +1155,8 @@ private[emitter] object CoreJSLib {
                     srcPos, dest.u.length, destPos, length)
               },
               For(let(i, 0), i < length, i := ((i + 1) | 0), {
-                Apply(dest DOT "set", List((destPos + i) | 0, BracketSelect(srcArray, (srcPos + i) | 0)))
+                genArrayClassPropApply(dest, ArrayClassProperty.set,
+                    (destPos + i) | 0, BracketSelect(srcArray, (srcPos + i) | 0))
               })
             )
           })
@@ -1172,7 +1173,7 @@ private[emitter] object CoreJSLib {
               If(srcData && genIdentBracketSelect(srcData, "isArrayClass"), {
                 // Fast path: the values are array of the same type
                 if (esVersion >= ESVersion.ES2015 && nullPointers == CheckedBehavior.Unchecked)
-                  Apply(src DOT "copyTo", List(srcPos, dest, destPos, length))
+                  genArrayClassPropApply(src, ArrayClassProperty.copyTo, srcPos, dest, destPos, length)
                 else
                   genCallHelper(VarField.systemArraycopy, src, srcPos, dest, destPos, length)
               }, {
@@ -1444,14 +1445,17 @@ private[emitter] object CoreJSLib {
                 genCallHelper(VarField.throwArrayIndexOutOfBoundsException, i))
           }
 
+          val getName = genArrayClassPropertyForDef(ArrayClassProperty.get)
+          val setName = genArrayClassPropertyForDef(ArrayClassProperty.set)
+
           List(
-              MethodDef(static = false, Ident("get"), paramList(i), None, {
+              MethodDef(static = false, getName, paramList(i), None, {
                 Block(
                     boundsCheck,
                     Return(BracketSelect(This().u, i))
                 )
               }),
-              MethodDef(static = false, Ident("set"), paramList(i, v), None, {
+              MethodDef(static = false, setName, paramList(i, v), None, {
                 Block(
                     boundsCheck,
                     BracketSelect(This().u, i) := v
@@ -1465,8 +1469,10 @@ private[emitter] object CoreJSLib {
           val i = varRef("i")
           val v = varRef("v")
 
+          val setName = genArrayClassPropertyForDef(ArrayClassProperty.set)
+
           List(
-            MethodDef(static = false, Ident("set"), paramList(i, v), None, {
+            MethodDef(static = false, setName, paramList(i, v), None, {
               BracketSelect(This().u, i) := v
             })
           )
@@ -1479,7 +1485,10 @@ private[emitter] object CoreJSLib {
           val dest = varRef("dest")
           val destPos = varRef("destPos")
           val length = varRef("length")
-          val methodDef = MethodDef(static = false, Ident("copyTo"),
+
+          val copyToName = genArrayClassPropertyForDef(ArrayClassProperty.copyTo)
+
+          val methodDef = MethodDef(static = false, copyToName,
               paramList(srcPos, dest, destPos, length), None, {
             if (isTypedArray) {
               Block(
@@ -1771,6 +1780,8 @@ private[emitter] object CoreJSLib {
               val i = varRef("i")
               val v = varRef("v")
 
+              val setName = genArrayClassPropertyForDef(ArrayClassProperty.set)
+
               val boundsCheck = condTree(arrayIndexOutOfBounds != CheckedBehavior.Unchecked) {
                 If((i < 0) || (i >= This().u.length),
                     genCallHelper(VarField.throwArrayIndexOutOfBoundsException, i))
@@ -1783,7 +1794,7 @@ private[emitter] object CoreJSLib {
               }
 
               List(
-                MethodDef(static = false, Ident("set"), paramList(i, v), None, {
+                MethodDef(static = false, setName, paramList(i, v), None, {
                   Block(
                       boundsCheck,
                       storeCheck,
@@ -1800,7 +1811,10 @@ private[emitter] object CoreJSLib {
               val dest = varRef("dest")
               val destPos = varRef("destPos")
               val length = varRef("length")
-              val methodDef = MethodDef(static = false, Ident("copyTo"),
+
+              val copyToName = genArrayClassPropertyForDef(ArrayClassProperty.copyTo)
+
+              val methodDef = MethodDef(static = false, copyToName,
                   paramList(srcPos, dest, destPos, length), None, {
                 genCallHelper(VarField.arraycopyGeneric, This().u, srcPos,
                     dest.u, destPos, length)
@@ -2237,5 +2251,10 @@ private[emitter] object CoreJSLib {
     private def double(d: Double): DoubleLiteral = DoubleLiteral(d)
 
     private def bigInt(i: Long): BigIntLiteral = BigIntLiteral(i)
+
+    // cannot extend AnyVal because this is not a static class
+    private implicit class CustomTreeOps(private val self: Tree) {
+      def u: Tree = genArrayClassPropSelect(self, ArrayClassProperty.u)
+    }
   }
 }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala
index 1a8b9bc517..506dec4d4a 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala
@@ -39,6 +39,9 @@ final class Emitter[E >: Null <: js.Tree](
   import Emitter._
   import config._
 
+  require(!config.minify || postTransformer == PostTransformer.Identity,
+      "When using the 'minify' option, the postTransformer must be Identity.")
+
   private implicit val globalRefTracking: GlobalRefTracking =
     config.topLevelGlobalRefTracking
 
@@ -49,10 +52,14 @@ final class Emitter[E >: Null <: js.Tree](
   private val nameGen: NameGen = new NameGen
 
   private class State(val lastMentionedDangerousGlobalRefs: Set[String]) {
+    val nameCompressor =
+      if (minify) Some(new NameCompressor(config))
+      else None
+
     val sjsGen: SJSGen = {
       val jsGen = new JSGen(config)
       val varGen = new VarGen(jsGen, nameGen, lastMentionedDangerousGlobalRefs)
-      new SJSGen(jsGen, nameGen, varGen)
+      new SJSGen(jsGen, nameGen, varGen, nameCompressor)
     }
 
     val classEmitter: ClassEmitter = new ClassEmitter(sjsGen)
@@ -87,7 +94,7 @@ final class Emitter[E >: Null <: js.Tree](
   def emit(moduleSet: ModuleSet, logger: Logger): Result[E] = {
     val WithGlobals(body, globalRefs) = emitInternal(moduleSet, logger)
 
-    moduleKind match {
+    val result = moduleKind match {
       case ModuleKind.NoModule =>
         assert(moduleSet.modules.size <= 1)
         val topLevelVars = moduleSet.modules
@@ -112,6 +119,19 @@ final class Emitter[E >: Null <: js.Tree](
       case ModuleKind.ESModule | ModuleKind.CommonJSModule =>
         new Result(config.jsHeader, body, "", Nil, globalRefs)
     }
+
+    for (compressor <- state.nameCompressor) {
+      compressor.allocateNames(moduleSet, logger)
+
+      /* Throw away the whole state, but keep the mentioned dangerous global refs.
+       * Note that instances of the name compressor's entries are still alive
+       * at this point, since they are referenced from `DelayedIdent` nodes in
+       * the result trees.
+       */
+      state = new State(state.lastMentionedDangerousGlobalRefs)
+    }
+
+    result
   }
 
   private def emitInternal(moduleSet: ModuleSet,
@@ -1084,7 +1104,8 @@ object Emitter {
       val jsHeader: String,
       val internalModulePattern: ModuleID => String,
       val optimizeBracketSelects: Boolean,
-      val trackAllGlobalRefs: Boolean
+      val trackAllGlobalRefs: Boolean,
+      val minify: Boolean
   ) {
     private def this(
         semantics: Semantics,
@@ -1097,7 +1118,9 @@ object Emitter {
           jsHeader = "",
           internalModulePattern = "./" + _.id,
           optimizeBracketSelects = true,
-          trackAllGlobalRefs = false)
+          trackAllGlobalRefs = false,
+          minify = false
+      )
     }
 
     private[emitter] val topLevelGlobalRefTracking: GlobalRefTracking =
@@ -1127,6 +1150,9 @@ object Emitter {
     def withTrackAllGlobalRefs(trackAllGlobalRefs: Boolean): Config =
       copy(trackAllGlobalRefs = trackAllGlobalRefs)
 
+    def withMinify(minify: Boolean): Config =
+      copy(minify = minify)
+
     private def copy(
         semantics: Semantics = semantics,
         moduleKind: ModuleKind = moduleKind,
@@ -1134,9 +1160,12 @@ object Emitter {
         jsHeader: String = jsHeader,
         internalModulePattern: ModuleID => String = internalModulePattern,
         optimizeBracketSelects: Boolean = optimizeBracketSelects,
-        trackAllGlobalRefs: Boolean = trackAllGlobalRefs): Config = {
+        trackAllGlobalRefs: Boolean = trackAllGlobalRefs,
+        minify: Boolean = minify
+    ): Config = {
       new Config(semantics, moduleKind, esFeatures, jsHeader,
-          internalModulePattern, optimizeBracketSelects, trackAllGlobalRefs)
+          internalModulePattern, optimizeBracketSelects, trackAllGlobalRefs,
+          minify)
     }
   }
 
@@ -1149,6 +1178,12 @@ object Emitter {
     def transformStats(trees: List[js.Tree], indent: Int): List[E]
   }
 
+  object PostTransformer {
+    object Identity extends PostTransformer[js.Tree] {
+      def transformStats(trees: List[js.Tree], indent: Int): List[js.Tree] = trees
+    }
+  }
+
   private final class DesugaredClassCache[E >: Null] {
     val privateJSFields = new OneTimeCache[WithGlobals[E]]
     val storeJSSuperClass = new OneTimeCache[WithGlobals[E]]
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
index 95cf6e1c33..6a8b9ca3dd 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
@@ -632,12 +632,11 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
                 }
 
                 if (checked) {
-                  js.Apply(js.DotSelect(genArray, js.Ident("set")),
-                      List(genIndex, genRhs))
+                  genArrayClassPropApply(genArray, ArrayClassProperty.set, genIndex, genRhs)
                 } else {
                   js.Assign(
                       js.BracketSelect(
-                          js.DotSelect(genArray, js.Ident("u"))(lhs.pos),
+                          genArrayClassPropSelect(genArray, ArrayClassProperty.u)(lhs.pos),
                           genIndex)(lhs.pos),
                       genRhs)
                 }
@@ -877,7 +876,7 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
 
             def genUnchecked(): js.Tree = {
               if (esFeatures.esVersion >= ESVersion.ES2015 && semantics.nullPointers == CheckedBehavior.Unchecked)
-                js.Apply(jsArgs.head DOT "copyTo", jsArgs.tail)
+                genArrayClassPropApply(jsArgs.head, ArrayClassProperty.copyTo, jsArgs.tail)
               else
                 genCallHelper(VarField.systemArraycopy, jsArgs: _*)
             }
@@ -2657,17 +2656,19 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
               genArrayValue(typeRef, elems.map(transformExpr(_, preserveChar))))
 
         case ArrayLength(array) =>
-          genIdentBracketSelect(js.DotSelect(transformExprNoChar(checkNotNull(array)),
-              js.Ident("u")), "length")
+          val newArray = transformExprNoChar(checkNotNull(array))
+          genIdentBracketSelect(
+              genArrayClassPropSelect(newArray, ArrayClassProperty.u),
+              "length")
 
         case ArraySelect(array, index) =>
           val newArray = transformExprNoChar(checkNotNull(array))
           val newIndex = transformExprNoChar(index)
           semantics.arrayIndexOutOfBounds match {
             case CheckedBehavior.Compliant | CheckedBehavior.Fatal =>
-              js.Apply(js.DotSelect(newArray, js.Ident("get")), List(newIndex))
+              genArrayClassPropApply(newArray, ArrayClassProperty.get, newIndex)
             case CheckedBehavior.Unchecked =>
-              js.BracketSelect(js.DotSelect(newArray, js.Ident("u")), newIndex)
+              js.BracketSelect(genArrayClassPropSelect(newArray, ArrayClassProperty.u), newIndex)
           }
 
         case tree: RecordSelect =>
@@ -2766,12 +2767,13 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
 
         case Transient(ArrayToTypedArray(expr, primRef)) =>
           val value = transformExprNoChar(checkNotNull(expr))
+          val valueUnderlying = genArrayClassPropSelect(value, ArrayClassProperty.u)
 
           if (es2015) {
-            js.Apply(genIdentBracketSelect(value.u, "slice"), Nil)
+            js.Apply(genIdentBracketSelect(valueUnderlying, "slice"), Nil)
           } else {
             val typedArrayClass = extractWithGlobals(typedArrayRef(primRef).get)
-            js.New(typedArrayClass, value.u :: Nil)
+            js.New(typedArrayClass, valueUnderlying :: Nil)
           }
 
         case Transient(TypedArrayToArray(expr, primRef)) =>
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/NameCompressor.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/NameCompressor.scala
new file mode 100644
index 0000000000..f23287c6bf
--- /dev/null
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/NameCompressor.scala
@@ -0,0 +1,230 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package org.scalajs.linker.backend.emitter
+
+import scala.annotation.{switch, tailrec}
+
+import java.util.Comparator
+
+import scala.collection.mutable
+
+import org.scalajs.ir.Names._
+import org.scalajs.linker.backend.javascript.Trees.DelayedIdent.Resolver
+import org.scalajs.linker.standard.ModuleSet
+import org.scalajs.logging.Logger
+
+private[emitter] final class NameCompressor(config: Emitter.Config) {
+  import NameCompressor._
+
+  private val entries: EntryMap = mutable.AnyRefMap.empty
+
+  private var namesAllocated: Boolean = false
+
+  def allocateNames(moduleSet: ModuleSet, logger: Logger): Unit = {
+    assert(!namesAllocated, "Cannot allocate names a second time")
+
+    val propertyNamesToAvoid = logger.time("Name compressor: Collect property names to avoid") {
+      collectPropertyNamesToAvoid(moduleSet)
+    }
+
+    logger.time("Name compressor: Allocate property names") {
+      allocatePropertyNames(entries, propertyNamesToAvoid)
+    }
+
+    namesAllocated = true
+  }
+
+  def genResolverFor(fieldName: FieldName): Resolver =
+    entries.getOrElseUpdate(fieldName, new FieldNameEntry(fieldName)).genResolver()
+
+  def genResolverFor(methodName: MethodName): Resolver =
+    entries.getOrElseUpdate(methodName, new MethodNameEntry(methodName)).genResolver()
+
+  def genResolverFor(prop: ArrayClassProperty): Resolver =
+    entries.getOrElseUpdate(prop, new ArrayClassPropEntry(prop)).genResolver()
+
+  /** Collects the property names to avoid for Scala instance members.
+   *
+   *  We collect the names of exported members in Scala classes. These live in
+   *  the same namespace as Scala methods and fields. Therefore, we must avoid
+   *  them when allocating names for that namespace.
+   */
+  private def collectPropertyNamesToAvoid(moduleSet: ModuleSet): Set[String] = {
+    import org.scalajs.ir.Trees._
+
+    val builder = Set.newBuilder[String]
+
+    builder ++= BasePropertyNamesToAvoid
+
+    for {
+      module <- moduleSet.modules
+      linkedClass <- module.classDefs
+      if linkedClass.kind.isClass
+      exportedMember <- linkedClass.exportedMembers
+    } {
+      (exportedMember: @unchecked) match {
+        case JSMethodDef(_, StringLiteral(name), _, _, _) =>
+          builder += name
+        case JSPropertyDef(_, StringLiteral(name), _, _) =>
+          builder += name
+      }
+    }
+
+    builder.result()
+  }
+}
+
+private[emitter] object NameCompressor {
+  /** Base set of names that should be avoided when allocating property names
+   *  in any namespace.
+   *
+   *  This set contains:
+   *
+   *  - the reserved JS identifiers (not technically invalid by spec, but JS
+   *    minifiers tend to avoid them anyway: `foo.if` is playing with fire),
+   *  - the `"then"` name, because it is used to identify `Thenable`s by
+   *    spec and therefore lives in the same namespace as the properties of
+   *    *all* objects,
+   */
+  private val BasePropertyNamesToAvoid: Set[String] =
+    NameGen.ReservedJSIdentifierNames + "then"
+
+  private def allocatePropertyNames(entries: EntryMap,
+      namesToAvoid: collection.Set[String]): Unit = {
+    val comparator: Comparator[PropertyNameEntry] =
+      Comparator.comparingInt[PropertyNameEntry](_.occurrences).reversed() // by decreasing order of occurrences
+        .thenComparing(Comparator.naturalOrder[PropertyNameEntry]()) // tie-break
+
+    val orderedEntries = entries.values.toArray
+    java.util.Arrays.sort(orderedEntries, comparator)
+
+    val generator = new NameGenerator(namesToAvoid)
+
+    for (entry <- orderedEntries)
+      entry.allocatedName = generator.nextString()
+  }
+
+  /** Keys of this map are `FieldName | MethodName | ArrayClassProperty`. */
+  private type EntryMap = mutable.AnyRefMap[AnyRef, PropertyNameEntry]
+
+  private sealed abstract class PropertyNameEntry extends Comparable[PropertyNameEntry] {
+    var occurrences: Int = 0
+    var allocatedName: String = null
+
+    protected def debugString: String
+
+    private object resolver extends Resolver {
+      def resolve(): String = {
+        if (allocatedName == null)
+          throw new IllegalStateException(s"Cannot resolve name before it was allocated, for $this")
+        allocatedName
+      }
+
+      def debugString: String = PropertyNameEntry.this.debugString
+
+      override def toString(): String = debugString
+    }
+
+    private def incOccurrences(): Unit = {
+      if (allocatedName != null)
+        throw new IllegalStateException(s"Cannot increase occurrences after name was allocated for $this")
+      occurrences += 1
+    }
+
+    def genResolver(): Resolver = {
+      incOccurrences()
+      resolver
+    }
+
+    def compareTo(that: PropertyNameEntry): Int = (this, that) match {
+      case (x: FieldNameEntry, y: FieldNameEntry) =>
+        x.fieldName.compareTo(y.fieldName)
+
+      case (x: MethodNameEntry, y: MethodNameEntry) =>
+        x.methodName.compareTo(y.methodName)
+
+      case (x: ArrayClassPropEntry, y: ArrayClassPropEntry) =>
+        x.property.compareTo(y.property)
+
+      case _ =>
+        def ordinalFor(x: PropertyNameEntry): Int = x match {
+          case _: FieldNameEntry      => 1
+          case _: MethodNameEntry     => 2
+          case _: ArrayClassPropEntry => 3
+        }
+        ordinalFor(this) - ordinalFor(that)
+    }
+  }
+
+  private final class FieldNameEntry(val fieldName: FieldName)
+      extends PropertyNameEntry {
+    protected def debugString: String = fieldName.nameString
+
+    override def toString(): String = s"FieldNameEntry(${fieldName.nameString})"
+  }
+
+  private final class MethodNameEntry(val methodName: MethodName)
+      extends PropertyNameEntry {
+    protected def debugString: String = methodName.nameString
+
+    override def toString(): String = s"MethodNameEntry(${methodName.nameString})"
+  }
+
+  private final class ArrayClassPropEntry(val property: ArrayClassProperty)
+      extends PropertyNameEntry {
+    protected def debugString: String = property.nonMinifiedName
+
+    override def toString(): String = s"ArrayClassPropEntry(${property.nonMinifiedName})"
+  }
+
+  // private[emitter] for tests
+  private[emitter] final class NameGenerator(namesToAvoid: collection.Set[String]) {
+    /* 6 because 52 * (62**5) > Int.MaxValue
+     * i.e., to exceed this size we would need more than Int.MaxValue different names.
+     */
+    private val charArray = new Array[Char](6)
+    charArray(0) = 'a'
+    private var charCount = 1
+
+    @tailrec
+    private def incAtIndex(idx: Int): Unit = {
+      (charArray(idx): @switch) match {
+        case '9' =>
+          charArray(idx) = 'a'
+        case 'z' =>
+          charArray(idx) = 'A'
+        case 'Z' =>
+          if (idx > 0) {
+            charArray(idx) = '0'
+            incAtIndex(idx - 1)
+          } else {
+            java.util.Arrays.fill(charArray, '0')
+            charArray(0) = 'a'
+            charCount += 1
+          }
+        case c =>
+          charArray(idx) = (c + 1).toChar
+      }
+    }
+
+    @tailrec
+    final def nextString(): String = {
+      val s = new String(charArray, 0, charCount)
+      incAtIndex(charCount - 1)
+      if (namesToAvoid.contains(s))
+        nextString()
+      else
+        s
+    }
+  }
+}
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/NameGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/NameGen.scala
index 552dd545bd..ae8502211d 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/NameGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/NameGen.scala
@@ -301,7 +301,7 @@ private[emitter] final class NameGen {
   }
 }
 
-private object NameGen {
+private[emitter] object NameGen {
 
   private final val FullwidthSpacingUnderscore = '\uff3f'
   private final val GreekSmallLetterDelta = '\u03b4'
@@ -371,7 +371,7 @@ private object NameGen {
    *    not actually mean `void 0`, and who knows what JS engine performance
    *    cliffs we can trigger with that.
    */
-  private final val ReservedJSIdentifierNames: Set[String] = Set(
+  private[emitter] final val ReservedJSIdentifierNames: Set[String] = Set(
       "arguments", "await", "break", "case", "catch", "class", "const",
       "continue", "debugger", "default", "delete", "do", "else", "enum",
       "eval", "export", "extends", "false", "finally", "for", "function", "if",
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala
index 615b1e94a0..9e8810afc3 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala
@@ -32,7 +32,8 @@ import PolyfillableBuiltin._
 private[emitter] final class SJSGen(
     val jsGen: JSGen,
     val nameGen: NameGen,
-    val varGen: VarGen
+    val varGen: VarGen,
+    val nameCompressor: Option[NameCompressor]
 ) {
 
   import jsGen._
@@ -151,15 +152,36 @@ private[emitter] final class SJSGen(
 
   def genSelect(receiver: Tree, field: irt.FieldIdent)(
       implicit pos: Position): Tree = {
-    DotSelect(receiver, Ident(genName(field.name))(field.pos))
+    DotSelect(receiver, genFieldIdent(field.name)(field.pos))
   }
 
   def genSelectForDef(receiver: Tree, field: irt.FieldIdent,
       originalName: OriginalName)(
       implicit pos: Position): Tree = {
-    val jsName = genName(field.name)
-    val jsOrigName = genOriginalName(field.name, originalName, jsName)
-    DotSelect(receiver, Ident(jsName, jsOrigName)(field.pos))
+    DotSelect(receiver, genFieldIdentForDef(field.name, originalName)(field.pos))
+  }
+
+  private def genFieldIdent(fieldName: FieldName)(
+      implicit pos: Position): MaybeDelayedIdent = {
+    nameCompressor match {
+      case None =>
+        Ident(genName(fieldName))
+      case Some(compressor) =>
+        DelayedIdent(compressor.genResolverFor(fieldName))
+    }
+  }
+
+  private def genFieldIdentForDef(fieldName: FieldName,
+      originalName: OriginalName)(
+      implicit pos: Position): MaybeDelayedIdent = {
+    nameCompressor match {
+      case None =>
+        val jsName = genName(fieldName)
+        val jsOrigName = genOriginalName(fieldName, originalName, jsName)
+        Ident(jsName, jsOrigName)
+      case Some(compressor) =>
+        DelayedIdent(compressor.genResolverFor(fieldName), originalName.orElse(fieldName))
+    }
   }
 
   def genApply(receiver: Tree, methodName: MethodName, args: List[Tree])(
@@ -172,22 +194,60 @@ private[emitter] final class SJSGen(
     genApply(receiver, methodName, args.toList)
   }
 
-  def genMethodIdent(methodIdent: irt.MethodIdent): Ident =
+  def genMethodIdent(methodIdent: irt.MethodIdent): MaybeDelayedIdent =
     genMethodIdent(methodIdent.name)(methodIdent.pos)
 
   def genMethodIdentForDef(methodIdent: irt.MethodIdent,
-      originalName: OriginalName): Ident = {
+      originalName: OriginalName): MaybeDelayedIdent = {
     genMethodIdentForDef(methodIdent.name, originalName)(methodIdent.pos)
   }
 
-  def genMethodIdent(methodName: MethodName)(implicit pos: Position): Ident =
-    Ident(genName(methodName))
+  def genMethodIdent(methodName: MethodName)(implicit pos: Position): MaybeDelayedIdent = {
+    nameCompressor match {
+      case None             => Ident(genName(methodName))
+      case Some(compressor) => DelayedIdent(compressor.genResolverFor(methodName))
+    }
+  }
 
   def genMethodIdentForDef(methodName: MethodName, originalName: OriginalName)(
-      implicit pos: Position): Ident = {
-    val jsName = genName(methodName)
-    val jsOrigName = genOriginalName(methodName, originalName, jsName)
-    Ident(jsName, jsOrigName)
+      implicit pos: Position): MaybeDelayedIdent = {
+    nameCompressor match {
+      case None =>
+        val jsName = genName(methodName)
+        val jsOrigName = genOriginalName(methodName, originalName, jsName)
+        Ident(jsName, jsOrigName)
+      case Some(compressor) =>
+        DelayedIdent(compressor.genResolverFor(methodName), originalName.orElse(methodName))
+    }
+  }
+
+  def genArrayClassPropApply(receiver: Tree, prop: ArrayClassProperty, args: Tree*)(
+      implicit pos: Position): Tree = {
+    genArrayClassPropApply(receiver, prop, args.toList)
+  }
+
+  def genArrayClassPropApply(receiver: Tree, prop: ArrayClassProperty, args: List[Tree])(
+      implicit pos: Position): Tree = {
+    Apply(genArrayClassPropSelect(receiver, prop), args)
+  }
+
+  def genArrayClassPropSelect(qualifier: Tree, prop: ArrayClassProperty)(
+      implicit pos: Position): Tree = {
+    DotSelect(qualifier, genArrayClassProperty(prop))
+  }
+
+  def genArrayClassProperty(prop: ArrayClassProperty)(implicit pos: Position): MaybeDelayedIdent = {
+    nameCompressor match {
+      case None             => Ident(prop.nonMinifiedName)
+      case Some(compressor) => DelayedIdent(compressor.genResolverFor(prop))
+    }
+  }
+
+  def genArrayClassPropertyForDef(prop: ArrayClassProperty)(implicit pos: Position): MaybeDelayedIdent = {
+    nameCompressor match {
+      case None             => Ident(prop.nonMinifiedName)
+      case Some(compressor) => DelayedIdent(compressor.genResolverFor(prop), prop.originalName)
+    }
   }
 
   def genJSPrivateSelect(receiver: Tree, field: irt.FieldIdent)(
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/TreeDSL.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/TreeDSL.scala
index 0063f17d20..540936dc78 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/TreeDSL.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/TreeDSL.scala
@@ -24,7 +24,7 @@ private[emitter] object TreeDSL {
       extends AnyVal {
 
     /** Select a member */
-    def DOT(field: Ident)(implicit pos: Position): DotSelect =
+    def DOT(field: MaybeDelayedIdent)(implicit pos: Position): DotSelect =
       DotSelect(self, field)
 
     /** Select a member */
@@ -112,7 +112,6 @@ private[emitter] object TreeDSL {
 
     def prototype(implicit pos: Position): Tree = self DOT "prototype"
     def length(implicit pos: Position): Tree = self DOT "length"
-    def u(implicit pos: Position): Tree = self DOT "u"
   }
 
   def typeof(expr: Tree)(implicit pos: Position): Tree =
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/standard/StandardLinkerBackend.scala b/linker/shared/src/main/scala/org/scalajs/linker/standard/StandardLinkerBackend.scala
index 4ea98e8679..ff27b8452f 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/standard/StandardLinkerBackend.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/standard/StandardLinkerBackend.scala
@@ -23,6 +23,7 @@ object StandardLinkerBackend {
       .withSourceMap(config.sourceMap)
       .withOutputPatterns(config.outputPatterns)
       .withRelativizeSourceMapBase(config.relativizeSourceMapBase)
+      .withMinify(config.minify)
       .withClosureCompilerIfAvailable(config.closureCompilerIfAvailable)
       .withPrettyPrint(config.prettyPrint)
       .withMaxConcurrentWrites(config.maxConcurrentWrites)
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/EmitterTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/EmitterTest.scala
index 1f7884c0f1..50e726106e 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/EmitterTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/EmitterTest.scala
@@ -63,7 +63,7 @@ class EmitterTest {
           config = config)
       fullContent <- linkToContent(classDefs,
           moduleInitializers = MainTestModuleInitializers,
-          config = config.withClosureCompilerIfAvailable(true))
+          config = config.withClosureCompilerIfAvailable(true).withMinify(true))
     } yield {
       def testContent(content: String): Unit = {
         if (!content.startsWith(header)) {
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/LibrarySizeTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/LibrarySizeTest.scala
index aa851ca438..33b1bd7ff4 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/LibrarySizeTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/LibrarySizeTest.scala
@@ -71,7 +71,7 @@ class LibrarySizeTest {
 
     testLinkedSizes(
       expectedFastLinkSize = 150063,
-      expectedFullLinkSizeWithoutClosure = 130664,
+      expectedFullLinkSizeWithoutClosure = 95680,
       expectedFullLinkSizeWithClosure = 21325,
       classDefs,
       moduleInitializers = MainTestModuleInitializers
@@ -98,6 +98,7 @@ object LibrarySizeTest {
     val fullLinkConfig = config
       .withSemantics(_.optimized)
       .withClosureCompilerIfAvailable(true)
+      .withMinify(true)
 
     val fastLinker = StandardImpl.linker(config)
     val fullLinker = StandardImpl.linker(fullLinkConfig)
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/backend/emitter/NameCompressorTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/backend/emitter/NameCompressorTest.scala
new file mode 100644
index 0000000000..db2f5e722b
--- /dev/null
+++ b/linker/shared/src/test/scala/org/scalajs/linker/backend/emitter/NameCompressorTest.scala
@@ -0,0 +1,53 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package org.scalajs.linker.backend.emitter
+
+import org.junit.Test
+import org.junit.Assert._
+
+class NameCompressorTest {
+  @Test def testNameGenerator(): Unit = {
+    // all the one-letter strings
+    val letterStrings = (('a' to 'z') ++ ('A' to 'Z')).map(_.toString())
+
+    // all the one-letter-or-digit strings
+    val letterOrDigitStrings = ('0' to '9').map(_.toString()) ++ letterStrings
+
+    val expectedOneCharIdents = letterStrings
+
+    val expectedTwoCharIdents = for {
+      firstChar <- letterStrings
+      secondChar <- letterOrDigitStrings
+      ident = firstChar + secondChar
+      if ident != "do" && ident != "if" && ident != "in" // reserved JS identifiers that will be avoided
+    } yield {
+      ident
+    }
+
+    val firstFewExpectedThreeCharIdents = {
+      letterOrDigitStrings.map("a0" + _) ++
+      letterOrDigitStrings.map("a1" + _)
+    }
+
+    val expectedSequenceStart =
+      expectedOneCharIdents ++ expectedTwoCharIdents ++ firstFewExpectedThreeCharIdents
+
+    // Now actually test
+
+    val namesToAvoid = NameGen.ReservedJSIdentifierNames
+    val generator = new NameCompressor.NameGenerator(namesToAvoid)
+
+    for (expected <- expectedSequenceStart)
+      assertEquals(expected, generator.nextString())
+  }
+}
diff --git a/project/Build.scala b/project/Build.scala
index a14202f7f9..ffcd864afe 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -53,6 +53,9 @@ object ExposedValues extends AutoPlugin {
     val default213ScalaVersion: SettingKey[String] =
       settingKey("the default Scala 2.13.x version for this build (derived from cross213ScalaVersions)")
 
+    val enableMinifyEverywhere: SettingKey[Boolean] =
+      settingKey("force usage of the `minify` option of the linker in all contexts (fast and full)")
+
     // set scalaJSLinkerConfig in someProject ~= makeCompliant
     val makeCompliant: StandardConfig => StandardConfig = {
       _.withSemantics { semantics =>
@@ -102,6 +105,8 @@ object ExposedValues extends AutoPlugin {
   }
 }
 
+import ExposedValues.autoImport.enableMinifyEverywhere
+
 final case class ExpectedSizes(fastLink: Range, fullLink: Range,
     fastLinkGz: Range, fullLinkGz: Range)
 
@@ -143,6 +148,15 @@ object MyScalaJSPlugin extends AutoPlugin {
   }
 
   override def globalSettings: Seq[Setting[_]] = Def.settings(
+      // can be overridden with a 'set' command
+      enableMinifyEverywhere := false,
+
+      scalaJSLinkerConfig := {
+        scalaJSLinkerConfig.value
+          .withCheckIR(true)
+          .withMinify(enableMinifyEverywhere.value)
+      },
+
       fullClasspath in scalaJSLinkerImpl := {
         (fullClasspath in (Build.linker.v2_12, Runtime)).value
       },
@@ -201,10 +215,24 @@ object MyScalaJSPlugin extends AutoPlugin {
         libDeps.filterNot(dep => blacklist.contains(dep.name))
       },
 
-      scalaJSLinkerConfig ~= (_.withCheckIR(true)),
-
       wantSourceMaps := true,
 
+      // If `enableMinifyEverywhere` is used, make sure to deactive GCC in fullLinkJS
+      Compile / fullLinkJS / scalaJSLinkerConfig := {
+        val prev = (Compile / fullLinkJS / scalaJSLinkerConfig).value
+        if (enableMinifyEverywhere.value)
+          prev.withClosureCompiler(false)
+        else
+          prev
+      },
+      Test / fullLinkJS / scalaJSLinkerConfig := {
+        val prev = (Test / fullLinkJS / scalaJSLinkerConfig).value
+        if (enableMinifyEverywhere.value)
+          prev.withClosureCompiler(false)
+        else
+          prev
+      },
+
       jsEnv := new NodeJSEnv(
           NodeJSEnv.Config().withSourceMap(wantSourceMaps.value)),
 
@@ -231,6 +259,7 @@ object MyScalaJSPlugin extends AutoPlugin {
       checksizes := {
         val logger = streams.value.log
 
+        val useMinifySizes = enableMinifyEverywhere.value
         val maybeExpected = expectedSizes.value
 
         /* The deprecated tasks do exactly what we want in terms of module /
@@ -239,7 +268,7 @@ object MyScalaJSPlugin extends AutoPlugin {
         val fast = (fastOptJS in Compile).value.data
         val full = (fullOptJS in Compile).value.data
 
-        val desc = s"${thisProject.value.id} Scala ${scalaVersion.value}"
+        val desc = s"${thisProject.value.id} Scala ${scalaVersion.value}, useMinifySizes = $useMinifySizes"
 
         maybeExpected.fold {
           logger.info(s"Ignoring checksizes for " + desc)
@@ -1963,23 +1992,42 @@ object Build {
       MyScalaJSPlugin.expectedSizes := {
         val default212Version = default212ScalaVersion.value
         val default213Version = default213ScalaVersion.value
+        val useMinifySizes = enableMinifyEverywhere.value
 
         scalaVersion.value match {
           case `default212Version` =>
-            Some(ExpectedSizes(
-                fastLink = 640000 to 641000,
-                fullLink = 101000 to 102000,
-                fastLinkGz = 77000 to 78000,
-                fullLinkGz = 26000 to 27000,
-            ))
+            if (!useMinifySizes) {
+              Some(ExpectedSizes(
+                  fastLink = 640000 to 641000,
+                  fullLink = 101000 to 102000,
+                  fastLinkGz = 77000 to 78000,
+                  fullLinkGz = 26000 to 27000,
+              ))
+            } else {
+              Some(ExpectedSizes(
+                  fastLink = 538000 to 539000,
+                  fullLink = 371000 to 372000,
+                  fastLinkGz = 71000 to 72000,
+                  fullLinkGz = 51000 to 52000,
+              ))
+            }
 
           case `default213Version` =>
-            Some(ExpectedSizes(
-                fastLink = 462000 to 463000,
-                fullLink = 99000 to 100000,
-                fastLinkGz = 60000 to 61000,
-                fullLinkGz = 26000 to 27000,
-            ))
+            if (!useMinifySizes) {
+              Some(ExpectedSizes(
+                  fastLink = 462000 to 463000,
+                  fullLink = 99000 to 100000,
+                  fastLinkGz = 60000 to 61000,
+                  fullLinkGz = 26000 to 27000,
+              ))
+            } else {
+              Some(ExpectedSizes(
+                  fastLink = 373000 to 374000,
+                  fullLink = 332000 to 333000,
+                  fastLinkGz = 55000 to 56000,
+                  fullLinkGz = 50000 to 51000,
+              ))
+            }
 
           case _ =>
             None
@@ -2227,7 +2275,8 @@ object Build {
           "isNoModule" -> (moduleKind == ModuleKind.NoModule),
           "isESModule" -> (moduleKind == ModuleKind.ESModule),
           "isCommonJSModule" -> (moduleKind == ModuleKind.CommonJSModule),
-          "isFullOpt" -> (stage == Stage.FullOpt),
+          "usesClosureCompiler" -> linkerConfig.closureCompiler,
+          "hasMinifiedNames" -> (linkerConfig.closureCompiler || linkerConfig.minify),
           "compliantAsInstanceOfs" -> (sems.asInstanceOfs == CheckedBehavior.Compliant),
           "compliantArrayIndexOutOfBounds" -> (sems.arrayIndexOutOfBounds == CheckedBehavior.Compliant),
           "compliantArrayStores" -> (sems.arrayStores == CheckedBehavior.Compliant),
diff --git a/sbt-plugin/src/main/scala/org/scalajs/sbtplugin/ScalaJSPluginInternal.scala b/sbt-plugin/src/main/scala/org/scalajs/sbtplugin/ScalaJSPluginInternal.scala
index 6f1d6f66a4..02d4eb89f1 100644
--- a/sbt-plugin/src/main/scala/org/scalajs/sbtplugin/ScalaJSPluginInternal.scala
+++ b/sbt-plugin/src/main/scala/org/scalajs/sbtplugin/ScalaJSPluginInternal.scala
@@ -470,6 +470,7 @@ private[sbtplugin] object ScalaJSPluginInternal {
         prevConfig
           .withSemantics(_.optimized)
           .withClosureCompiler(useClosure)
+          .withMinify(true) // ignored if we actually use Closure
           .withCheckIR(true)  // for safety, fullOpt is slow anyways.
       },
 
diff --git a/test-suite/js/src/main/scala-ide-stubs/org/scalajs/testsuite/utils/BuildInfo.scala b/test-suite/js/src/main/scala-ide-stubs/org/scalajs/testsuite/utils/BuildInfo.scala
index cbd1a4f46d..d577790522 100644
--- a/test-suite/js/src/main/scala-ide-stubs/org/scalajs/testsuite/utils/BuildInfo.scala
+++ b/test-suite/js/src/main/scala-ide-stubs/org/scalajs/testsuite/utils/BuildInfo.scala
@@ -22,7 +22,8 @@ private[utils] object BuildInfo {
   final val isNoModule = false
   final val isESModule = false
   final val isCommonJSModule = false
-  final val isFullOpt = false
+  final val usesClosureCompiler = false
+  final val hasMinifiedNames = false
   final val compliantAsInstanceOfs = false
   final val compliantArrayIndexOutOfBounds = false
   final val compliantArrayStores = false
diff --git a/test-suite/js/src/main/scala/org/scalajs/testsuite/utils/Platform.scala b/test-suite/js/src/main/scala/org/scalajs/testsuite/utils/Platform.scala
index cbf49e2d92..ac1c4132b3 100644
--- a/test-suite/js/src/main/scala/org/scalajs/testsuite/utils/Platform.scala
+++ b/test-suite/js/src/main/scala/org/scalajs/testsuite/utils/Platform.scala
@@ -68,7 +68,10 @@ object Platform {
 
   def sourceMaps: Boolean = BuildInfo.hasSourceMaps && executingInNodeJS
 
-  def isInFullOpt: Boolean = BuildInfo.isFullOpt
+  def usesClosureCompiler: Boolean = BuildInfo.usesClosureCompiler
+
+  def hasMinifiedNames: Boolean = BuildInfo.hasMinifiedNames
+
   def isInProductionMode: Boolean = BuildInfo.productionMode
 
   def hasCompliantAsInstanceOfs: Boolean = BuildInfo.compliantAsInstanceOfs
diff --git a/test-suite/js/src/test/scala/org/scalajs/testsuite/compiler/OptimizerTest.scala b/test-suite/js/src/test/scala/org/scalajs/testsuite/compiler/OptimizerTest.scala
index 2e8878cef9..833ae38e64 100644
--- a/test-suite/js/src/test/scala/org/scalajs/testsuite/compiler/OptimizerTest.scala
+++ b/test-suite/js/src/test/scala/org/scalajs/testsuite/compiler/OptimizerTest.scala
@@ -321,19 +321,22 @@ class OptimizerTest {
   }
 
   @Test def foldingDoubleWithDecimalAndString(): Unit = {
-    assumeFalse("Assumed not executing in FullOpt", isInFullOpt)
+    assumeFalse("GCC wrongly optimizes this code", usesClosureCompiler)
+
     assertEquals("1.2323919403474454e+21hello", 1.2323919403474454E21 + "hello")
     assertEquals("hello1.2323919403474454e+21", "hello" + 1.2323919403474454E21)
   }
 
   @Test def foldingDoubleThatJVMWouldPrintInScientificNotationAndString(): Unit = {
-    assumeFalse("Assumed not executing in FullOpt", isInFullOpt)
+    assumeFalse("GCC wrongly optimizes this code", usesClosureCompiler)
+
     assertEquals("123456789012345hello", 123456789012345d + "hello")
     assertEquals("hello123456789012345", "hello" + 123456789012345d)
   }
 
   @Test def foldingDoublesToString(): Unit = {
-    assumeFalse("Assumed not executing in FullOpt", isInFullOpt)
+    assumeFalse("GCC wrongly optimizes this code", usesClosureCompiler)
+
     @noinline def toStringNoInline(v: Double): String = v.toString
     @inline def test(v: Double): Unit =
       assertEquals(toStringNoInline(v), v.toString)
diff --git a/test-suite/js/src/test/scala/org/scalajs/testsuite/jsinterop/MiscInteropTest.scala b/test-suite/js/src/test/scala/org/scalajs/testsuite/jsinterop/MiscInteropTest.scala
index 2877c74ac4..f477cffcc6 100644
--- a/test-suite/js/src/test/scala/org/scalajs/testsuite/jsinterop/MiscInteropTest.scala
+++ b/test-suite/js/src/test/scala/org/scalajs/testsuite/jsinterop/MiscInteropTest.scala
@@ -42,7 +42,7 @@ class MiscInteropTest {
     assumeFalse(
         "GCC wrongly optimizes this code, " +
         "see https://github.com/google/closure-compiler/issues/3498",
-        isInFullOpt)
+        usesClosureCompiler)
 
     @noinline def nonExistentGlobalVarNoInline(): Any =
       js.Dynamic.global.thisGlobalVarDoesNotExist
@@ -197,7 +197,7 @@ class MiscInteropTest {
   // Emitted classes
 
   @Test def meaningfulNameProperty(): Unit = {
-    assumeFalse("Assumed not executing in FullOpt", isInFullOpt)
+    assumeFalse("Need non-minified names", hasMinifiedNames)
 
     def nameOf(obj: Any): js.Any =
       obj.asInstanceOf[js.Dynamic].constructor.name
diff --git a/test-suite/js/src/test/scala/org/scalajs/testsuite/library/StackTraceTest.scala b/test-suite/js/src/test/scala/org/scalajs/testsuite/library/StackTraceTest.scala
index d931b4bb0d..03315cf014 100644
--- a/test-suite/js/src/test/scala/org/scalajs/testsuite/library/StackTraceTest.scala
+++ b/test-suite/js/src/test/scala/org/scalajs/testsuite/library/StackTraceTest.scala
@@ -52,7 +52,7 @@ class StackTraceTest {
 
   @Test def decodeClassNameAndMethodName(): Unit = {
     assumeTrue("Assume Node.js", executingInNodeJS)
-    assumeFalse("Assume fullopt-stage", isInFullOpt)
+    assumeFalse("Assume non-minified names", hasMinifiedNames)
 
     val Error = js.constructorOf[js.Error]
     val oldStackTraceLimit = Error.stackTraceLimit
diff --git a/test-suite/jvm/src/main/scala/org/scalajs/testsuite/utils/Platform.scala b/test-suite/jvm/src/main/scala/org/scalajs/testsuite/utils/Platform.scala
index a3d908bf8e..6b0a9c412a 100644
--- a/test-suite/jvm/src/main/scala/org/scalajs/testsuite/utils/Platform.scala
+++ b/test-suite/jvm/src/main/scala/org/scalajs/testsuite/utils/Platform.scala
@@ -40,7 +40,9 @@ object Platform {
     else Integer.parseInt(v.takeWhile(_.isDigit))
   }
 
-  def isInFullOpt: Boolean = false
+  def usesClosureCompiler: Boolean = false
+
+  def hasMinifiedNames: Boolean = false
 
   def hasCompliantAsInstanceOfs: Boolean = true
   def hasCompliantArrayIndexOutOfBounds: Boolean = true
diff --git a/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/LongTest.scala b/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/LongTest.scala
index a21f8ff802..dd9ed7a5a6 100644
--- a/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/LongTest.scala
+++ b/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/LongTest.scala
@@ -620,7 +620,7 @@ class LongTest {
     test(-1, lg(-1))
 
     // Closure seems to incorrectly rewrite the constant on the right :-(
-    val epsilon = if (isInFullOpt) 1E4f else 0.0f
+    val epsilon = if (usesClosureCompiler) 1E4f else 0.0f
     test(9.223372E18f, MaxVal, epsilon)
     test(-9.223372E18f, MinVal, epsilon)
 
@@ -674,7 +674,7 @@ class LongTest {
     test(-1, lg(-1))
 
     // Closure seems to incorrectly rewrite the constant on the right :-(
-    val epsilon = if (isInFullOpt) 1E4 else 0.0
+    val epsilon = if (usesClosureCompiler) 1E4 else 0.0
     test(9.223372036854776E18, MaxVal, epsilon)
     test(-9.223372036854776E18, MinVal, epsilon)
 
@@ -722,7 +722,7 @@ class LongTest {
     test(lg(0), -Double.MinPositiveValue)
     test(MaxVal, twoPow63)
     test(MaxVal, twoPow63NextUp)
-    if (!isInFullOpt) {
+    if (!usesClosureCompiler) {
       // GCC incorrectly rewrites the Double constants on the rhs
       test(lg(-1024, 2147483647), twoPow63NextDown)
       test(MinVal, -twoPow63)
diff --git a/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/ReflectiveCallTest.scala b/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/ReflectiveCallTest.scala
index 1fe0250028..98bd0f275e 100644
--- a/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/ReflectiveCallTest.scala
+++ b/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/ReflectiveCallTest.scala
@@ -346,7 +346,7 @@ class ReflectiveCallTest {
 
     assumeFalse(
         "GCC is a bit too eager in its optimizations in this error case",
-        Platform.isInFullOpt)
+        Platform.usesClosureCompiler)
 
     type ObjWithAnyRefPrimitives = Any {
       def eq(that: AnyRef): Boolean

From 792866359d5cfe459e05295c680de4297c0e7cc3 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Thu, 25 Jan 2024 15:34:14 +0100
Subject: [PATCH 057/298] Compress the ancestor names used for instance tests.

---
 .../linker/backend/emitter/ClassEmitter.scala |  7 ++--
 .../linker/backend/emitter/CoreJSLib.scala    |  4 +-
 .../backend/emitter/NameCompressor.scala      | 40 +++++++++++++++----
 .../linker/backend/emitter/SJSGen.scala       |  7 ++++
 .../org/scalajs/linker/LibrarySizeTest.scala  |  2 +-
 project/Build.scala                           | 16 ++++----
 6 files changed, 55 insertions(+), 21 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
index e0154b1782..9fa8a09156 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
@@ -821,7 +821,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
       ancestors: js.Tree)(
       implicit pos: Position): js.Tree = {
     import TreeDSL._
-    ancestors DOT genName(className)
+    ancestors DOT genAncestorIdent(className)
   }
 
   def genTypeData(className: ClassName, kind: ClassKind,
@@ -852,7 +852,8 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
     }
 
     val ancestorsRecord = js.ObjectConstr(
-        ancestors.withFilter(_ != ObjectClass).map(ancestor => (js.Ident(genName(ancestor)), js.IntLiteral(1))))
+        ancestors.withFilter(_ != ObjectClass).map(ancestor => (genAncestorIdent(ancestor), js.IntLiteral(1)))
+    )
 
     val isInstanceFunWithGlobals: WithGlobals[js.Tree] = {
       if (globalKnowledge.isAncestorOfHijackedClass(className)) {
@@ -901,7 +902,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
 
     isInstanceFunWithGlobals.flatMap { isInstanceFun =>
       val allParams = List(
-          js.ObjectConstr(List(js.Ident(genName(className)) -> js.IntLiteral(0))),
+          js.ObjectConstr(List(genAncestorIdent(className) -> js.IntLiteral(0))),
           js.BooleanLiteral(kind == ClassKind.Interface),
           js.StringLiteral(RuntimeClassNameMapperImpl.map(
               semantics.runtimeClassNameMapper, className.nameString)),
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
index a96dea3018..23e3242c30 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
@@ -1705,8 +1705,8 @@ private[emitter] object CoreJSLib {
             else
               Skip(),
             privateFieldSet("ancestors", ObjectConstr(List(
-                Ident(genName(CloneableClass)) -> 1,
-                Ident(genName(SerializableClass)) -> 1
+                genAncestorIdent(CloneableClass) -> 1,
+                genAncestorIdent(SerializableClass) -> 1
             ))),
             privateFieldSet("componentData", componentData),
             privateFieldSet("arrayBase", arrayBase),
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/NameCompressor.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/NameCompressor.scala
index f23287c6bf..0db5ead5bf 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/NameCompressor.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/NameCompressor.scala
@@ -17,6 +17,7 @@ import scala.annotation.{switch, tailrec}
 import java.util.Comparator
 
 import scala.collection.mutable
+import scala.reflect.ClassTag
 
 import org.scalajs.ir.Names._
 import org.scalajs.linker.backend.javascript.Trees.DelayedIdent.Resolver
@@ -27,6 +28,7 @@ private[emitter] final class NameCompressor(config: Emitter.Config) {
   import NameCompressor._
 
   private val entries: EntryMap = mutable.AnyRefMap.empty
+  private val ancestorEntries: AncestorEntryMap = mutable.AnyRefMap.empty
 
   private var namesAllocated: Boolean = false
 
@@ -41,6 +43,10 @@ private[emitter] final class NameCompressor(config: Emitter.Config) {
       allocatePropertyNames(entries, propertyNamesToAvoid)
     }
 
+    logger.time("Name compressor: Allocate ancestor names") {
+      allocatePropertyNames(ancestorEntries, BasePropertyNamesToAvoid)
+    }
+
     namesAllocated = true
   }
 
@@ -53,6 +59,9 @@ private[emitter] final class NameCompressor(config: Emitter.Config) {
   def genResolverFor(prop: ArrayClassProperty): Resolver =
     entries.getOrElseUpdate(prop, new ArrayClassPropEntry(prop)).genResolver()
 
+  def genResolverForAncestor(ancestor: ClassName): Resolver =
+    ancestorEntries.getOrElseUpdate(ancestor, new AncestorNameEntry(ancestor)).genResolver()
+
   /** Collects the property names to avoid for Scala instance members.
    *
    *  We collect the names of exported members in Scala classes. These live in
@@ -99,11 +108,11 @@ private[emitter] object NameCompressor {
   private val BasePropertyNamesToAvoid: Set[String] =
     NameGen.ReservedJSIdentifierNames + "then"
 
-  private def allocatePropertyNames(entries: EntryMap,
-      namesToAvoid: collection.Set[String]): Unit = {
-    val comparator: Comparator[PropertyNameEntry] =
-      Comparator.comparingInt[PropertyNameEntry](_.occurrences).reversed() // by decreasing order of occurrences
-        .thenComparing(Comparator.naturalOrder[PropertyNameEntry]()) // tie-break
+  private def allocatePropertyNames[K <: AnyRef, E <: BaseEntry with Comparable[E]: ClassTag](
+      entries: mutable.AnyRefMap[K, E], namesToAvoid: collection.Set[String]): Unit = {
+    val comparator: Comparator[E] =
+      Comparator.comparingInt[E](_.occurrences).reversed() // by decreasing order of occurrences
+        .thenComparing(Comparator.naturalOrder[E]()) // tie-break
 
     val orderedEntries = entries.values.toArray
     java.util.Arrays.sort(orderedEntries, comparator)
@@ -117,7 +126,9 @@ private[emitter] object NameCompressor {
   /** Keys of this map are `FieldName | MethodName | ArrayClassProperty`. */
   private type EntryMap = mutable.AnyRefMap[AnyRef, PropertyNameEntry]
 
-  private sealed abstract class PropertyNameEntry extends Comparable[PropertyNameEntry] {
+  private type AncestorEntryMap = mutable.AnyRefMap[ClassName, AncestorNameEntry]
+
+  private sealed abstract class BaseEntry {
     var occurrences: Int = 0
     var allocatedName: String = null
 
@@ -130,7 +141,7 @@ private[emitter] object NameCompressor {
         allocatedName
       }
 
-      def debugString: String = PropertyNameEntry.this.debugString
+      def debugString: String = BaseEntry.this.debugString
 
       override def toString(): String = debugString
     }
@@ -145,6 +156,10 @@ private[emitter] object NameCompressor {
       incOccurrences()
       resolver
     }
+  }
+
+  private sealed abstract class PropertyNameEntry
+      extends BaseEntry with Comparable[PropertyNameEntry] {
 
     def compareTo(that: PropertyNameEntry): Int = (this, that) match {
       case (x: FieldNameEntry, y: FieldNameEntry) =>
@@ -187,6 +202,17 @@ private[emitter] object NameCompressor {
     override def toString(): String = s"ArrayClassPropEntry(${property.nonMinifiedName})"
   }
 
+  private final class AncestorNameEntry(val ancestor: ClassName)
+      extends BaseEntry with Comparable[AncestorNameEntry] {
+
+    def compareTo(that: AncestorNameEntry): Int =
+      this.ancestor.compareTo(that.ancestor)
+
+    protected def debugString: String = ancestor.nameString
+
+    override def toString(): String = s"AncestorNameEntry(${ancestor.nameString})"
+  }
+
   // private[emitter] for tests
   private[emitter] final class NameGenerator(namesToAvoid: collection.Set[String]) {
     /* 6 because 52 * (62**5) > Int.MaxValue
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala
index 9e8810afc3..d1c46bc023 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala
@@ -250,6 +250,13 @@ private[emitter] final class SJSGen(
     }
   }
 
+  def genAncestorIdent(ancestor: ClassName)(implicit pos: Position): MaybeDelayedIdent = {
+    nameCompressor match {
+      case None             => Ident(genName(ancestor))
+      case Some(compressor) => DelayedIdent(compressor.genResolverForAncestor(ancestor))
+    }
+  }
+
   def genJSPrivateSelect(receiver: Tree, field: irt.FieldIdent)(
       implicit moduleContext: ModuleContext, globalKnowledge: GlobalKnowledge,
       pos: Position): Tree = {
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/LibrarySizeTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/LibrarySizeTest.scala
index 33b1bd7ff4..2d9e678334 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/LibrarySizeTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/LibrarySizeTest.scala
@@ -71,7 +71,7 @@ class LibrarySizeTest {
 
     testLinkedSizes(
       expectedFastLinkSize = 150063,
-      expectedFullLinkSizeWithoutClosure = 95680,
+      expectedFullLinkSizeWithoutClosure = 93868,
       expectedFullLinkSizeWithClosure = 21325,
       classDefs,
       moduleInitializers = MainTestModuleInitializers
diff --git a/project/Build.scala b/project/Build.scala
index ffcd864afe..de6ff233a9 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -2005,10 +2005,10 @@ object Build {
               ))
             } else {
               Some(ExpectedSizes(
-                  fastLink = 538000 to 539000,
-                  fullLink = 371000 to 372000,
-                  fastLinkGz = 71000 to 72000,
-                  fullLinkGz = 51000 to 52000,
+                  fastLink = 499000 to 500000,
+                  fullLink = 341000 to 342000,
+                  fastLinkGz = 69000 to 70000,
+                  fullLinkGz = 50000 to 51000,
               ))
             }
 
@@ -2022,10 +2022,10 @@ object Build {
               ))
             } else {
               Some(ExpectedSizes(
-                  fastLink = 373000 to 374000,
-                  fullLink = 332000 to 333000,
-                  fastLinkGz = 55000 to 56000,
-                  fullLinkGz = 50000 to 51000,
+                  fastLink = 352000 to 353000,
+                  fullLink = 312000 to 313000,
+                  fastLinkGz = 54000 to 55000,
+                  fullLinkGz = 49000 to 50000,
               ))
             }
 

From 280870dec269cfe02ad14835f3affbe48f261ddd Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Thu, 25 Jan 2024 17:23:46 +0100
Subject: [PATCH 058/298] Minify core (internal) property names to one letter
 each.

---
 .../linker/backend/emitter/ClassEmitter.scala |  12 +-
 .../linker/backend/emitter/CoreJSLib.scala    | 234 +++++++++---------
 .../backend/emitter/FunctionEmitter.scala     |   6 +-
 .../linker/backend/emitter/SJSGen.scala       | 108 +++++++-
 .../org/scalajs/linker/LibrarySizeTest.scala  |   2 +-
 project/Build.scala                           |   8 +-
 6 files changed, 236 insertions(+), 134 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
index 9fa8a09156..11f8c3df33 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
@@ -705,7 +705,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
           !(!(
               genIsScalaJSObject(obj) &&
               genIsClassNameInAncestors(className,
-                  obj DOT "$classData" DOT "ancestors")
+                  obj DOT cpn.classData DOT cpn.ancestors)
           ))
         }
 
@@ -781,9 +781,9 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
       globalFunctionDef(VarField.isArrayOf, className, List(objParam, depthParam), None, {
         js.Return(!(!({
           genIsScalaJSObject(obj) &&
-          ((obj DOT "$classData" DOT "arrayDepth") === depth) &&
+          ((obj DOT cpn.classData DOT cpn.arrayDepth) === depth) &&
           genIsClassNameInAncestors(className,
-              obj DOT "$classData" DOT "arrayBase" DOT "ancestors")
+              obj DOT cpn.classData DOT cpn.arrayBase DOT cpn.ancestors)
         })))
       })
     }
@@ -814,7 +814,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
 
   private def genIsScalaJSObject(obj: js.Tree)(implicit pos: Position): js.Tree = {
     import TreeDSL._
-    obj && (obj DOT "$classData")
+    obj && (obj DOT cpn.classData)
   }
 
   private def genIsClassNameInAncestors(className: ClassName,
@@ -915,7 +915,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
       val prunedParams =
         allParams.reverse.dropWhile(_.isInstanceOf[js.Undefined]).reverse
 
-      val typeData = js.Apply(js.New(globalVar(VarField.TypeData, CoreVar), Nil) DOT "initClass",
+      val typeData = js.Apply(js.New(globalVar(VarField.TypeData, CoreVar), Nil) DOT cpn.initClass,
           prunedParams)
 
       globalVarDef(VarField.d, className, typeData)
@@ -927,7 +927,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
       globalKnowledge: GlobalKnowledge, pos: Position): js.Tree = {
     import TreeDSL._
 
-    globalVar(VarField.c, className).prototype DOT "$classData" := globalVar(VarField.d, className)
+    globalVar(VarField.c, className).prototype DOT cpn.classData := globalVar(VarField.d, className)
   }
 
   def genModuleAccessor(className: ClassName, isJSClass: Boolean)(
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
index 23e3242c30..6dc814cd87 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
@@ -106,7 +106,7 @@ private[emitter] object CoreJSLib {
     // Conditional global references that we often use
     private def ReflectRef = globalRef("Reflect")
 
-    private val classData = Ident("$classData")
+    private val classData = Ident(cpn.classData)
 
     private val orderedPrimRefsWithoutVoid = {
       List(BooleanRef, CharRef, ByteRef, ShortRef, IntRef, LongRef,
@@ -522,7 +522,7 @@ private[emitter] object CoreJSLib {
       condDefs(!allowBigIntsForLongs)(List(
         globalVar(VarField.L0, CoreVar) := genScalaClassNew(
             LongImpl.RuntimeLongClass, LongImpl.initFromParts, 0, 0),
-        genClassDataOf(LongRef) DOT "zero" := globalVar(VarField.L0, CoreVar)
+        genClassDataOf(LongRef) DOT cpn.zero := globalVar(VarField.L0, CoreVar)
       ))
     }
 
@@ -547,14 +547,14 @@ private[emitter] object CoreJSLib {
       val ctor = {
         val c = varRef("c")
         MethodDef(static = false, Ident("constructor"), paramList(c), None, {
-          This() DOT "c" := c
+          This() DOT cpn.c := c
         })
       }
 
       val toStr = {
         MethodDef(static = false, Ident("toString"), Nil, None, {
           Return(Apply(genIdentBracketSelect(StringRef, "fromCharCode"),
-              (This() DOT "c") :: Nil))
+              (This() DOT cpn.c) :: Nil))
         })
       }
 
@@ -594,7 +594,7 @@ private[emitter] object CoreJSLib {
                   str("char")
                 }, {
                   If(genIsScalaJSObject(value), {
-                    genIdentBracketSelect(value DOT classData, "name")
+                    genIdentBracketSelect(value DOT classData, cpn.name)
                   }, {
                     typeof(value)
                   })
@@ -693,10 +693,10 @@ private[emitter] object CoreJSLib {
         val i = varRef("i")
 
         Block(
-          const(result, New(arrayClassData DOT "constr",
+          const(result, New(arrayClassData DOT cpn.constr,
               BracketSelect(lengths, lengthIndex) :: Nil)),
           If(lengthIndex < (lengths.length - 1), Block(
-            const(subArrayClassData, arrayClassData DOT "componentData"),
+            const(subArrayClassData, arrayClassData DOT cpn.componentData),
             const(subLengthIndex, lengthIndex + 1),
             const(underlying, result.u),
             For(let(i, 0), i < underlying.length, i.++, {
@@ -719,7 +719,7 @@ private[emitter] object CoreJSLib {
 
       defineFunction1(VarField.objectOrArrayClone) { instance =>
         // return instance.$classData.isArrayClass ? instance.clone__O() : $objectClone(instance);
-        Return(If(genIdentBracketSelect(instance DOT classData, "isArrayClass"),
+        Return(If(genIdentBracketSelect(instance DOT classData, cpn.isArrayClass),
             genApply(instance, cloneMethodName, Nil),
             genCallHelper(VarField.objectClone, instance)))
       }
@@ -804,7 +804,7 @@ private[emitter] object CoreJSLib {
       condDefs(globalKnowledge.isClassClassInstantiated)(
         defineObjectGetClassBasedFun(VarField.objectGetClass,
             className => genClassOf(className),
-            instance => Apply(instance DOT classData DOT "getClassOf", Nil),
+            instance => Apply(instance DOT classData DOT cpn.getClassOf, Nil),
             Null()
         )
       ) :::
@@ -813,7 +813,7 @@ private[emitter] object CoreJSLib {
             StringLiteral(RuntimeClassNameMapperImpl.map(
                 semantics.runtimeClassNameMapper, className.nameString))
           },
-          instance => genIdentBracketSelect(instance DOT classData, "name"),
+          instance => genIdentBracketSelect(instance DOT classData, cpn.name),
           {
             if (nullPointers == CheckedBehavior.Unchecked)
               genApply(Null(), getNameMethodName, Nil)
@@ -1137,7 +1137,7 @@ private[emitter] object CoreJSLib {
 
       condDefs(arrayStores != CheckedBehavior.Unchecked)(
         defineFunction5(VarField.systemArraycopyRefs) { (src, srcPos, dest, destPos, length) =>
-          If(Apply(genIdentBracketSelect(dest DOT classData, "isAssignableFrom"), List(src DOT classData)), {
+          If(Apply(genIdentBracketSelect(dest DOT classData, cpn.isAssignableFrom), List(src DOT classData)), {
             /* Fast-path, no need for array store checks. This always applies
              * for arrays of the same type, and a fortiori, when `src eq dest`.
              */
@@ -1170,7 +1170,7 @@ private[emitter] object CoreJSLib {
             const(srcData, src && (src DOT classData)),
             If(srcData === (dest && (dest DOT classData)), {
               // Both values have the same "data" (could also be falsy values)
-              If(srcData && genIdentBracketSelect(srcData, "isArrayClass"), {
+              If(srcData && genIdentBracketSelect(srcData, cpn.isArrayClass), {
                 // Fast path: the values are array of the same type
                 if (esVersion >= ESVersion.ES2015 && nullPointers == CheckedBehavior.Unchecked)
                   genArrayClassPropApply(src, ArrayClassProperty.copyTo, srcPos, dest, destPos, length)
@@ -1387,7 +1387,7 @@ private[emitter] object CoreJSLib {
         (
           defineUnbox(VarField.uV, BoxedUnitClass, _ => Undefined()) :::
           defineUnbox(VarField.uZ, BoxedBooleanClass, v => !(!v)) :::
-          defineUnbox(VarField.uC, BoxedCharacterClass, v => If(v === Null(), 0, v DOT "c")) :::
+          defineUnbox(VarField.uC, BoxedCharacterClass, v => If(v === Null(), 0, v DOT cpn.c)) :::
           defineUnbox(VarField.uB, BoxedByteClass, _ | 0) :::
           defineUnbox(VarField.uS, BoxedShortClass, _ | 0) :::
           defineUnbox(VarField.uI, BoxedIntegerClass, _ | 0) :::
@@ -1405,7 +1405,7 @@ private[emitter] object CoreJSLib {
         // Unboxes for Chars and Longs
         (
           defineFunction1(VarField.uC) { v =>
-            Return(If(v === Null(), 0, v DOT "c"))
+            Return(If(v === Null(), 0, v DOT cpn.c))
           } :::
           defineFunction1(VarField.uJ) { v =>
             Return(If(v === Null(), genLongZero(), v))
@@ -1585,34 +1585,34 @@ private[emitter] object CoreJSLib {
       val ctor = {
         MethodDef(static = false, Ident("constructor"), Nil, None, {
           Block(
-              privateFieldSet("constr", Undefined()),
+              privateFieldSet(cpn.constr, Undefined()),
               if (globalKnowledge.isParentDataAccessed)
-                privateFieldSet("parentData", Undefined())
+                privateFieldSet(cpn.parentData, Undefined())
               else
                 Skip(),
-              privateFieldSet("ancestors", Null()),
-              privateFieldSet("componentData", Null()),
-              privateFieldSet("arrayBase", Null()),
-              privateFieldSet("arrayDepth", int(0)),
-              privateFieldSet("zero", Null()),
-              privateFieldSet("arrayEncodedName", str("")),
-              privateFieldSet("_classOf", Undefined()),
-              privateFieldSet("_arrayOf", Undefined()),
+              privateFieldSet(cpn.ancestors, Null()),
+              privateFieldSet(cpn.componentData, Null()),
+              privateFieldSet(cpn.arrayBase, Null()),
+              privateFieldSet(cpn.arrayDepth, int(0)),
+              privateFieldSet(cpn.zero, Null()),
+              privateFieldSet(cpn.arrayEncodedName, str("")),
+              privateFieldSet(cpn._classOf, Undefined()),
+              privateFieldSet(cpn._arrayOf, Undefined()),
 
               /* A lambda for the logic of the public `isAssignableFrom`,
                * without its fast-path. See the comment on the definition of
                * `isAssignableFrom` for the rationale of this decomposition.
                */
-              privateFieldSet("isAssignableFromFun", Undefined()),
+              privateFieldSet(cpn.isAssignableFromFun, Undefined()),
 
-              privateFieldSet("wrapArray", Undefined()),
-              privateFieldSet("isJSType", bool(false)),
+              privateFieldSet(cpn.wrapArray, Undefined()),
+              privateFieldSet(cpn.isJSType, bool(false)),
 
-              publicFieldSet("name", str("")),
-              publicFieldSet("isPrimitive", bool(false)),
-              publicFieldSet("isInterface", bool(false)),
-              publicFieldSet("isArrayClass", bool(false)),
-              publicFieldSet("isInstance", Undefined())
+              publicFieldSet(cpn.name, str("")),
+              publicFieldSet(cpn.isPrimitive, bool(false)),
+              publicFieldSet(cpn.isInterface, bool(false)),
+              publicFieldSet(cpn.isArrayClass, bool(false)),
+              publicFieldSet(cpn.isInstance, Undefined())
           )
         })
       }
@@ -1627,22 +1627,22 @@ private[emitter] object CoreJSLib {
         val that = varRef("that")
         val depth = varRef("depth")
         val obj = varRef("obj")
-        MethodDef(static = false, Ident("initPrim"),
+        MethodDef(static = false, Ident(cpn.initPrim),
             paramList(zero, arrayEncodedName, displayName, arrayClass, typedArrayClass), None, {
           Block(
-              privateFieldSet("ancestors", ObjectConstr(Nil)),
-              privateFieldSet("zero", zero),
-              privateFieldSet("arrayEncodedName", arrayEncodedName),
+              privateFieldSet(cpn.ancestors, ObjectConstr(Nil)),
+              privateFieldSet(cpn.zero, zero),
+              privateFieldSet(cpn.arrayEncodedName, arrayEncodedName),
               const(self, This()), // capture `this` for use in arrow fun
-              privateFieldSet("isAssignableFromFun",
+              privateFieldSet(cpn.isAssignableFromFun,
                   genArrowFunction(paramList(that), Return(that === self))),
-              publicFieldSet("name", displayName),
-              publicFieldSet("isPrimitive", bool(true)),
-              publicFieldSet("isInstance",
+              publicFieldSet(cpn.name, displayName),
+              publicFieldSet(cpn.isPrimitive, bool(true)),
+              publicFieldSet(cpn.isInstance,
                   genArrowFunction(paramList(obj), Return(bool(false)))),
               If(arrayClass !== Undefined(), { // it is undefined for void
-                privateFieldSet("_arrayOf",
-                    Apply(New(globalVar(VarField.TypeData, CoreVar), Nil) DOT "initSpecializedArray",
+                privateFieldSet(cpn._arrayOf,
+                    Apply(New(globalVar(VarField.TypeData, CoreVar), Nil) DOT cpn.initSpecializedArray,
                         List(This(), arrayClass, typedArrayClass)))
               }),
               Return(This())
@@ -1662,29 +1662,29 @@ private[emitter] object CoreJSLib {
         val that = varRef("that")
         val depth = varRef("depth")
         val obj = varRef("obj")
-        MethodDef(static = false, Ident("initClass"),
+        MethodDef(static = false, Ident(cpn.initClass),
             paramList(internalNameObj, isInterface, fullName, ancestors,
                 isJSType, parentData, isInstance), None, {
           Block(
               const(internalName, genCallHelper(VarField.propertyName, internalNameObj)),
               if (globalKnowledge.isParentDataAccessed)
-                privateFieldSet("parentData", parentData)
+                privateFieldSet(cpn.parentData, parentData)
               else
                 Skip(),
-              privateFieldSet("ancestors", ancestors),
-              privateFieldSet("arrayEncodedName", str("L") + fullName + str(";")),
-              privateFieldSet("isAssignableFromFun", {
+              privateFieldSet(cpn.ancestors, ancestors),
+              privateFieldSet(cpn.arrayEncodedName, str("L") + fullName + str(";")),
+              privateFieldSet(cpn.isAssignableFromFun, {
                 genArrowFunction(paramList(that), {
-                  Return(!(!(BracketSelect(that DOT "ancestors", internalName))))
+                  Return(!(!(BracketSelect(that DOT cpn.ancestors, internalName))))
                 })
               }),
-              privateFieldSet("isJSType", !(!isJSType)),
-              publicFieldSet("name", fullName),
-              publicFieldSet("isInterface", isInterface),
-              publicFieldSet("isInstance", isInstance || {
+              privateFieldSet(cpn.isJSType, !(!isJSType)),
+              publicFieldSet(cpn.name, fullName),
+              publicFieldSet(cpn.isInterface, isInterface),
+              publicFieldSet(cpn.isInstance, isInstance || {
                 genArrowFunction(paramList(obj), {
                   Return(!(!(obj && (obj DOT classData) &&
-                      BracketSelect(obj DOT classData DOT "ancestors", internalName))))
+                      BracketSelect(obj DOT classData DOT cpn.ancestors, internalName))))
                 })
               }),
               Return(This())
@@ -1698,22 +1698,22 @@ private[emitter] object CoreJSLib {
 
         Block(
             arrayClass.prototype DOT classData := This(),
-            const(name, str("[") + (componentData DOT "arrayEncodedName")),
-            privateFieldSet("constr", arrayClass),
+            const(name, str("[") + (componentData DOT cpn.arrayEncodedName)),
+            privateFieldSet(cpn.constr, arrayClass),
             if (globalKnowledge.isParentDataAccessed)
-              privateFieldSet("parentData", genClassDataOf(ObjectClass))
+              privateFieldSet(cpn.parentData, genClassDataOf(ObjectClass))
             else
               Skip(),
-            privateFieldSet("ancestors", ObjectConstr(List(
+            privateFieldSet(cpn.ancestors, ObjectConstr(List(
                 genAncestorIdent(CloneableClass) -> 1,
                 genAncestorIdent(SerializableClass) -> 1
             ))),
-            privateFieldSet("componentData", componentData),
-            privateFieldSet("arrayBase", arrayBase),
-            privateFieldSet("arrayDepth", arrayDepth),
-            privateFieldSet("arrayEncodedName", name),
-            publicFieldSet("name", name),
-            publicFieldSet("isArrayClass", bool(true))
+            privateFieldSet(cpn.componentData, componentData),
+            privateFieldSet(cpn.arrayBase, arrayBase),
+            privateFieldSet(cpn.arrayDepth, arrayDepth),
+            privateFieldSet(cpn.arrayEncodedName, name),
+            publicFieldSet(cpn.name, name),
+            publicFieldSet(cpn.isArrayClass, bool(true))
         )
       }
 
@@ -1726,15 +1726,15 @@ private[emitter] object CoreJSLib {
         val that = varRef("that")
         val obj = varRef("obj")
         val array = varRef("array")
-        MethodDef(static = false, Ident("initSpecializedArray"),
+        MethodDef(static = false, Ident(cpn.initSpecializedArray),
             paramList(componentData, arrayClass, typedArrayClass, isAssignableFromFun), None, {
           Block(
               initArrayCommonBody(arrayClass, componentData, componentData, 1),
               const(self, This()), // capture `this` for use in arrow fun
-              privateFieldSet("isAssignableFromFun", isAssignableFromFun || {
+              privateFieldSet(cpn.isAssignableFromFun, isAssignableFromFun || {
                 genArrowFunction(paramList(that), Return(self === that))
               }),
-              privateFieldSet("wrapArray", {
+              privateFieldSet(cpn.wrapArray, {
                 If(typedArrayClass, {
                   genArrowFunction(paramList(array), {
                     Return(New(arrayClass, New(typedArrayClass, array :: Nil) :: Nil))
@@ -1745,7 +1745,7 @@ private[emitter] object CoreJSLib {
                   })
                 })
               }),
-              publicFieldSet("isInstance",
+              publicFieldSet(cpn.isInstance,
                   genArrowFunction(paramList(obj), Return(obj instanceof arrayClass))),
               Return(This())
           )
@@ -1762,7 +1762,7 @@ private[emitter] object CoreJSLib {
         val self = varRef("self")
         val obj = varRef("obj")
         val array = varRef("array")
-        MethodDef(static = false, Ident("initArray"),
+        MethodDef(static = false, Ident(cpn.initArray),
             paramList(componentData), None, {
           val ArrayClassDef = {
             val ctor = {
@@ -1788,8 +1788,8 @@ private[emitter] object CoreJSLib {
               }
 
               val storeCheck = {
-                If((v !== Null()) && !(componentData DOT "isJSType") &&
-                    !Apply(genIdentBracketSelect(componentData, "isInstance"), v :: Nil),
+                If((v !== Null()) && !(componentData DOT cpn.isJSType) &&
+                    !Apply(genIdentBracketSelect(componentData, cpn.isInstance), v :: Nil),
                     genCallHelper(VarField.throwArrayStoreException, v))
               }
 
@@ -1847,28 +1847,28 @@ private[emitter] object CoreJSLib {
 
           Block(
               ArrayClassDef,
-              const(arrayBase, (componentData DOT "arrayBase") || componentData),
-              const(arrayDepth, (componentData DOT "arrayDepth") + 1),
+              const(arrayBase, (componentData DOT cpn.arrayBase) || componentData),
+              const(arrayDepth, (componentData DOT cpn.arrayDepth) + 1),
               initArrayCommonBody(ArrayClass, componentData, arrayBase, arrayDepth),
               const(isAssignableFromFun, {
                 genArrowFunction(paramList(that), {
                   val thatDepth = varRef("thatDepth")
                   Block(
-                      const(thatDepth, that DOT "arrayDepth"),
+                      const(thatDepth, that DOT cpn.arrayDepth),
                       Return(If(thatDepth === arrayDepth, {
-                        Apply(arrayBase DOT "isAssignableFromFun", (that DOT "arrayBase") :: Nil)
+                        Apply(arrayBase DOT cpn.isAssignableFromFun, (that DOT cpn.arrayBase) :: Nil)
                       }, {
                         (thatDepth > arrayDepth) && (arrayBase === genClassDataOf(ObjectClass))
                       }))
                   )
                 })
               }),
-              privateFieldSet("isAssignableFromFun", isAssignableFromFun),
-              privateFieldSet("wrapArray", genArrowFunction(paramList(array), {
+              privateFieldSet(cpn.isAssignableFromFun, isAssignableFromFun),
+              privateFieldSet(cpn.wrapArray, genArrowFunction(paramList(array), {
                 Return(New(ArrayClass, array :: Nil))
               })),
               const(self, This()), // don't rely on the lambda being called with `this` as receiver
-              publicFieldSet("isInstance", genArrowFunction(paramList(obj), {
+              publicFieldSet(cpn.isInstance, genArrowFunction(paramList(obj), {
                 val data = varRef("data")
                 Block(
                     const(data, obj && (obj DOT classData)),
@@ -1884,24 +1884,24 @@ private[emitter] object CoreJSLib {
       }
 
       val getArrayOf = {
-        MethodDef(static = false, Ident("getArrayOf"), Nil, None, {
+        MethodDef(static = false, Ident(cpn.getArrayOf), Nil, None, {
           Block(
-              If(!(This() DOT "_arrayOf"),
-                  This() DOT "_arrayOf" :=
-                    Apply(New(globalVar(VarField.TypeData, CoreVar), Nil) DOT "initArray", This() :: Nil),
+              If(!(This() DOT cpn._arrayOf),
+                  This() DOT cpn._arrayOf :=
+                    Apply(New(globalVar(VarField.TypeData, CoreVar), Nil) DOT cpn.initArray, This() :: Nil),
                   Skip()),
-              Return(This() DOT "_arrayOf")
+              Return(This() DOT cpn._arrayOf)
           )
         })
       }
 
       def getClassOf = {
-        MethodDef(static = false, Ident("getClassOf"), Nil, None, {
+        MethodDef(static = false, Ident(cpn.getClassOf), Nil, None, {
           Block(
-              If(!(This() DOT "_classOf"),
-                  This() DOT "_classOf" := genScalaClassNew(ClassClass, ObjectArgConstructorName, This()),
+              If(!(This() DOT cpn._classOf),
+                  This() DOT cpn._classOf := genScalaClassNew(ClassClass, ObjectArgConstructorName, This()),
                   Skip()),
-              Return(This() DOT "_classOf")
+              Return(This() DOT cpn._classOf)
           )
         })
       }
@@ -1917,21 +1917,21 @@ private[emitter] object CoreJSLib {
          * We only need a polymorphic dispatch in the slow path.
          */
         val that = varRef("that")
-        MethodDef(static = false, StringLiteral("isAssignableFrom"),
+        MethodDef(static = false, StringLiteral(cpn.isAssignableFrom),
             paramList(that), None, {
           Return(
               (This() === that) || // fast path
-              Apply(This() DOT "isAssignableFromFun", that :: Nil))
+              Apply(This() DOT cpn.isAssignableFromFun, that :: Nil))
         })
       }
 
       def checkCast = {
         val obj = varRef("obj")
-        MethodDef(static = false, StringLiteral("checkCast"), paramList(obj), None,
+        MethodDef(static = false, StringLiteral(cpn.checkCast), paramList(obj), None,
           if (asInstanceOfs != CheckedBehavior.Unchecked) {
-            If((obj !== Null()) && !(This() DOT "isJSType") &&
-                !Apply(genIdentBracketSelect(This(), "isInstance"), obj :: Nil),
-              genCallHelper(VarField.throwClassCastException, obj, genIdentBracketSelect(This(), "name")),
+            If((obj !== Null()) && !(This() DOT cpn.isJSType) &&
+                !Apply(genIdentBracketSelect(This(), cpn.isInstance), obj :: Nil),
+              genCallHelper(VarField.throwClassCastException, obj, genIdentBracketSelect(This(), cpn.name)),
               Skip())
           } else {
             Skip()
@@ -1940,17 +1940,17 @@ private[emitter] object CoreJSLib {
       }
 
       def getSuperclass = {
-        MethodDef(static = false, StringLiteral("getSuperclass"), Nil, None, {
-          Return(If(This() DOT "parentData",
-              Apply(This() DOT "parentData" DOT "getClassOf", Nil),
+        MethodDef(static = false, StringLiteral(cpn.getSuperclass), Nil, None, {
+          Return(If(This() DOT cpn.parentData,
+              Apply(This() DOT cpn.parentData DOT cpn.getClassOf, Nil),
               Null()))
         })
       }
 
       def getComponentType = {
-        MethodDef(static = false, StringLiteral("getComponentType"), Nil, None, {
-          Return(If(This() DOT "componentData",
-              Apply(This() DOT "componentData" DOT "getClassOf", Nil),
+        MethodDef(static = false, StringLiteral(cpn.getComponentType), Nil, None, {
+          Return(If(This() DOT cpn.componentData,
+              Apply(This() DOT cpn.componentData DOT cpn.getClassOf, Nil),
               Null()))
         })
       }
@@ -1959,12 +1959,12 @@ private[emitter] object CoreJSLib {
         val lengths = varRef("lengths")
         val arrayClassData = varRef("arrayClassData")
         val i = varRef("i")
-        MethodDef(static = false, StringLiteral("newArrayOfThisClass"),
+        MethodDef(static = false, StringLiteral(cpn.newArrayOfThisClass),
             paramList(lengths), None, {
           Block(
               let(arrayClassData, This()),
               For(let(i, 0), i < lengths.length, i.++, {
-                arrayClassData := Apply(arrayClassData DOT "getArrayOf", Nil)
+                arrayClassData := Apply(arrayClassData DOT cpn.getArrayOf, Nil)
               }),
               Return(genCallHelper(VarField.newArrayObject, arrayClassData, lengths))
           )
@@ -2013,14 +2013,14 @@ private[emitter] object CoreJSLib {
 
       val forObj = extractWithGlobals(globalFunctionDef(VarField.isArrayOf, ObjectClass, paramList(obj, depth), None, {
         Block(
-            const(data, obj && (obj DOT "$classData")),
+            const(data, obj && (obj DOT cpn.classData)),
             If(!data, {
               Return(BooleanLiteral(false))
             }, {
               Block(
-                  const(arrayDepth, data DOT "arrayDepth"),
+                  const(arrayDepth, data DOT cpn.arrayDepth),
                   Return(If(arrayDepth === depth, {
-                    !genIdentBracketSelect(data DOT "arrayBase", "isPrimitive")
+                    !genIdentBracketSelect(data DOT cpn.arrayBase, cpn.isPrimitive)
                   }, {
                     arrayDepth > depth
                   }))
@@ -2034,8 +2034,8 @@ private[emitter] object CoreJSLib {
         val depth = varRef("depth")
         extractWithGlobals(globalFunctionDef(VarField.isArrayOf, primRef, paramList(obj, depth), None, {
           Return(!(!(obj && (obj DOT classData) &&
-              ((obj DOT classData DOT "arrayDepth") === depth) &&
-              ((obj DOT classData DOT "arrayBase") === genClassDataOf(primRef)))))
+              ((obj DOT classData DOT cpn.arrayDepth) === depth) &&
+              ((obj DOT classData DOT cpn.arrayBase) === genClassDataOf(primRef)))))
         }))
       }
 
@@ -2089,27 +2089,27 @@ private[emitter] object CoreJSLib {
         extractWithGlobals(
             globalVarDef(VarField.d, ObjectClass, New(globalVar(VarField.TypeData, CoreVar), Nil))) :::
         List(
-          privateFieldSet("ancestors", ObjectConstr(Nil)),
-          privateFieldSet("arrayEncodedName", str("L" + fullName + ";")),
-          privateFieldSet("isAssignableFromFun", {
+          privateFieldSet(cpn.ancestors, ObjectConstr(Nil)),
+          privateFieldSet(cpn.arrayEncodedName, str("L" + fullName + ";")),
+          privateFieldSet(cpn.isAssignableFromFun, {
             genArrowFunction(paramList(that), {
-              Return(!genIdentBracketSelect(that, "isPrimitive"))
+              Return(!genIdentBracketSelect(that, cpn.isPrimitive))
             })
           }),
-          publicFieldSet("name", str(fullName)),
-          publicFieldSet("isInstance",
+          publicFieldSet(cpn.name, str(fullName)),
+          publicFieldSet(cpn.isInstance,
               genArrowFunction(paramList(obj), Return(obj !== Null()))),
-          privateFieldSet("_arrayOf", {
-            Apply(New(globalVar(VarField.TypeData, CoreVar), Nil) DOT "initSpecializedArray", List(
+          privateFieldSet(cpn._arrayOf, {
+            Apply(New(globalVar(VarField.TypeData, CoreVar), Nil) DOT cpn.initSpecializedArray, List(
               typeDataVar,
               globalVar(VarField.ac, ObjectClass),
               Undefined(), // typedArray
               genArrowFunction(paramList(that), {
                 val thatDepth = varRef("thatDepth")
                 Block(
-                    const(thatDepth, that DOT "arrayDepth"),
+                    const(thatDepth, that DOT cpn.arrayDepth),
                     Return(If(thatDepth === 1, {
-                      !genIdentBracketSelect(that DOT "arrayBase", "isPrimitive")
+                      !genIdentBracketSelect(that DOT cpn.arrayBase, cpn.isPrimitive)
                     }, {
                       (thatDepth > 1)
                     }))
@@ -2117,7 +2117,7 @@ private[emitter] object CoreJSLib {
               })
             ))
           }),
-          globalVar(VarField.c, ObjectClass).prototype DOT "$classData" := typeDataVar
+          globalVar(VarField.c, ObjectClass).prototype DOT cpn.classData := typeDataVar
         )
       }
 
@@ -2143,7 +2143,7 @@ private[emitter] object CoreJSLib {
         }
 
         extractWithGlobals(globalVarDef(VarField.d, primRef, {
-          Apply(New(globalVar(VarField.TypeData, CoreVar), Nil) DOT "initPrim",
+          Apply(New(globalVar(VarField.TypeData, CoreVar), Nil) DOT cpn.initPrim,
               List(zero, str(primRef.charCode.toString()),
                   str(primRef.displayName),
                   if (primRef == VoidRef) Undefined()
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
index 6a8b9ca3dd..a518948b97 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
@@ -2744,7 +2744,7 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
           js.DotSelect(
               genSelect(transformExprNoChar(checkNotNull(runtimeClass)),
                   FieldIdent(dataFieldName)),
-              js.Ident("zero"))
+              js.Ident(cpn.zero))
 
         case Transient(NativeArrayWrapper(elemClass, nativeArray)) =>
           val newNativeArray = transformExprNoChar(nativeArray)
@@ -2758,8 +2758,8 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
                   transformExprNoChar(checkNotNull(elemClass)),
                   FieldIdent(dataFieldName))
               val arrayClassData = js.Apply(
-                  js.DotSelect(elemClassData, js.Ident("getArrayOf")), Nil)
-              js.Apply(arrayClassData DOT "wrapArray", newNativeArray :: Nil)
+                  js.DotSelect(elemClassData, js.Ident(cpn.getArrayOf)), Nil)
+              js.Apply(arrayClassData DOT cpn.wrapArray, newNativeArray :: Nil)
           }
 
         case Transient(ObjectClassName(obj)) =>
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala
index d1c46bc023..b52be22348 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala
@@ -43,6 +43,108 @@ private[emitter] final class SJSGen(
 
   val useBigIntForLongs = esFeatures.allowBigIntsForLongs
 
+  /** Core Property Names. */
+  object cpn {
+    // --- Scala.js objects ---
+
+    /** The class-wide classData field of Scala.js objects, which references their TypeData. */
+    val classData = "$classData" // always in full; it is used as identification of Scala.js objects
+
+    // --- Class ---
+
+    /** `Char.c`: the int value of the character. */
+    val c = "c"
+
+    // --- TypeData private fields ---
+
+    /** `TypeData.constr`: the run-time constructor of the class. */
+    val constr = if (minify) "C" else "constr"
+
+    /** `TypeData.parentData`: the super class data. */
+    val parentData = if (minify) "P" else "parentData"
+
+    /** `TypeData.ancestors`: dictionary where keys are the ancestor names of all ancestors. */
+    val ancestors = if (minify) "n" else "ancestors"
+
+    /** `TypeData.componentData`: the `TypeData` of the component type of an array type. */
+    val componentData = if (minify) "O" else "componentData"
+
+    /** `TypeData.arrayBase`: the `TypeData` of the base type of an array type. */
+    val arrayBase = if (minify) "B" else "arrayBase"
+
+    /** `TypeData.arrayDepth`: the depth of an array type. */
+    val arrayDepth = if (minify) "D" else "arrayDepth"
+
+    /** `TypeData.zero`: the zero value of the type. */
+    val zero = if (minify) "z" else "zero"
+
+    /** `TypeData.arrayEncodedName`: the name of the type as it appears in its array type's name. */
+    val arrayEncodedName = if (minify) "E" else "arrayEncodedName"
+
+    /** `TypeData._classOf`: the field storing the `jl.Class` instance for that type. */
+    val _classOf = if (minify) "L" else "_classOf"
+
+    /** `TypeData._arrayOf`: the field storing the `TypeData` for that type's array type. */
+    val _arrayOf = if (minify) "A" else "_arrayOf"
+
+    /** `TypeData.isAssignableFromFun`: the implementation of `jl.Class.isAssignableFrom` without fast path. */
+    val isAssignableFromFun = if (minify) "F" else "isAssignableFromFun"
+
+    /** `TypeData.wrapArray`: the function to create an ArrayClass instance from a JS array of its elements. */
+    val wrapArray = if (minify) "w" else "wrapArray"
+
+    /** `TypeData.isJSType`: whether it is a JS type. */
+    val isJSType = if (minify) "J" else "isJSType"
+
+    // --- TypeData constructors ---
+
+    val initPrim = if (minify) "p" else "initPrim"
+
+    val initClass = if (minify) "i" else "initClass"
+
+    val initSpecializedArray = if (minify) "y" else "initSpecializedArray"
+
+    val initArray = if (minify) "a" else "initArray"
+
+    // --- TypeData private methods ---
+
+    /** `TypeData.getArrayOf()`: the `Type` instance for that type's array type. */
+    val getArrayOf = if (minify) "r" else "getArrayOf"
+
+    /** `TypeData.getClassOf()`: the `jl.Class` instance for that type. */
+    val getClassOf = if (minify) "l" else "getClassOf"
+
+    // --- TypeData public fields --- never minified
+
+    /** `TypeData.name`: public, the user name of the class (the result of `jl.Class.getName()`). */
+    val name = "name"
+
+    /** `TypeData.isPrimitive`: public, whether it is a primitive type. */
+    val isPrimitive = "isPrimitive"
+
+    /** `TypeData.isInterface`: public, whether it is an interface type. */
+    val isInterface = "isInterface"
+
+    /** `TypeData.isArrayClass`: public, whether it is an array type. */
+    val isArrayClass = "isArrayClass"
+
+    /** `TypeData.isInstance()`: public, implementation of `jl.Class.isInstance`. */
+    val isInstance = "isInstance"
+
+    /** `TypeData.isAssignableFrom()`: public, implementation of `jl.Class.isAssignableFrom`. */
+    val isAssignableFrom = "isAssignableFrom"
+
+    // --- TypeData public methods --- never minified
+
+    val checkCast = "checkCast"
+
+    val getSuperclass = "getSuperclass"
+
+    val getComponentType = "getComponentType"
+
+    val newArrayOfThisClass = "newArrayOfThisClass"
+  }
+
   def genZeroOf(tpe: Type)(
       implicit moduleContext: ModuleContext, globalKnowledge: GlobalKnowledge,
       pos: Position): Tree = {
@@ -627,14 +729,14 @@ private[emitter] final class SJSGen(
       case ArrayTypeRef(ClassRef(ObjectClass), 1) =>
         globalVar(VarField.ac, ObjectClass)
       case _ =>
-        genClassDataOf(arrayTypeRef) DOT "constr"
+        genClassDataOf(arrayTypeRef) DOT cpn.constr
     }
   }
 
   def genClassOf(typeRef: TypeRef)(
       implicit moduleContext: ModuleContext, globalKnowledge: GlobalKnowledge,
       pos: Position): Tree = {
-    Apply(DotSelect(genClassDataOf(typeRef), Ident("getClassOf")), Nil)
+    Apply(DotSelect(genClassDataOf(typeRef), Ident(cpn.getClassOf)), Nil)
   }
 
   def genClassOf(className: ClassName)(
@@ -653,7 +755,7 @@ private[emitter] final class SJSGen(
       case ArrayTypeRef(base, dims) =>
         val baseData = genClassDataOf(base)
         (1 to dims).foldLeft[Tree](baseData) { (prev, _) =>
-          Apply(DotSelect(prev, Ident("getArrayOf")), Nil)
+          Apply(DotSelect(prev, Ident(cpn.getArrayOf)), Nil)
         }
     }
   }
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/LibrarySizeTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/LibrarySizeTest.scala
index 2d9e678334..dca2b88b47 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/LibrarySizeTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/LibrarySizeTest.scala
@@ -71,7 +71,7 @@ class LibrarySizeTest {
 
     testLinkedSizes(
       expectedFastLinkSize = 150063,
-      expectedFullLinkSizeWithoutClosure = 93868,
+      expectedFullLinkSizeWithoutClosure = 92648,
       expectedFullLinkSizeWithClosure = 21325,
       classDefs,
       moduleInitializers = MainTestModuleInitializers
diff --git a/project/Build.scala b/project/Build.scala
index de6ff233a9..c6ae6168e5 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -2005,8 +2005,8 @@ object Build {
               ))
             } else {
               Some(ExpectedSizes(
-                  fastLink = 499000 to 500000,
-                  fullLink = 341000 to 342000,
+                  fastLink = 494000 to 495000,
+                  fullLink = 337000 to 338000,
                   fastLinkGz = 69000 to 70000,
                   fullLinkGz = 50000 to 51000,
               ))
@@ -2022,8 +2022,8 @@ object Build {
               ))
             } else {
               Some(ExpectedSizes(
-                  fastLink = 352000 to 353000,
-                  fullLink = 312000 to 313000,
+                  fastLink = 347000 to 348000,
+                  fullLink = 307000 to 308000,
                   fastLinkGz = 54000 to 55000,
                   fullLinkGz = 49000 to 50000,
               ))

From 1afad42e64cf801c7cc90a55afaf942e1a5aa25e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Sat, 24 Feb 2024 10:07:41 +0100
Subject: [PATCH 059/298] Fix #4949: Always wrap object literals with `()`.

---
 .../linker/backend/javascript/Printers.scala  | 21 ++++++++++---------
 .../org/scalajs/linker/LibrarySizeTest.scala  |  4 ++--
 project/Build.scala                           | 10 ++++-----
 .../testsuite/jsinterop/DynamicTest.scala     | 14 ++++++++++---
 4 files changed, 29 insertions(+), 20 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Printers.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Printers.scala
index 09a3b8648a..33ec9cc020 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Printers.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Printers.scala
@@ -491,15 +491,17 @@ object Printers {
           printSeparatorIfStat()
 
         case ObjectConstr(Nil) =>
-          if (isStat)
-            print("({});") // force expression position for the object literal
-          else
-            print("{}")
+          /* #4949 Always wrap object literals with () in case they end up at
+           * the start of an `ExpressionStatement`.
+           */
+          print("({})")
+          printSeparatorIfStat()
 
         case ObjectConstr(fields) =>
-          if (isStat)
-            print('(') // force expression position for the object literal
-          print('{')
+          /* #4949 Always wrap object literals with () in case they end up at
+           * the start of an `ExpressionStatement`.
+           */
+          print("({")
           indent()
           println()
           var rest = fields
@@ -517,9 +519,8 @@ object Printers {
           }
           undent()
           printIndent()
-          print('}')
-          if (isStat)
-            print(");")
+          print("})")
+          printSeparatorIfStat()
 
         // Literals
 
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/LibrarySizeTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/LibrarySizeTest.scala
index dca2b88b47..fbc5b93948 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/LibrarySizeTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/LibrarySizeTest.scala
@@ -70,8 +70,8 @@ class LibrarySizeTest {
     )
 
     testLinkedSizes(
-      expectedFastLinkSize = 150063,
-      expectedFullLinkSizeWithoutClosure = 92648,
+      expectedFastLinkSize = 150205,
+      expectedFullLinkSizeWithoutClosure = 92762,
       expectedFullLinkSizeWithClosure = 21325,
       classDefs,
       moduleInitializers = MainTestModuleInitializers
diff --git a/project/Build.scala b/project/Build.scala
index c6ae6168e5..f6d3d596ab 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -1998,14 +1998,14 @@ object Build {
           case `default212Version` =>
             if (!useMinifySizes) {
               Some(ExpectedSizes(
-                  fastLink = 640000 to 641000,
+                  fastLink = 641000 to 642000,
                   fullLink = 101000 to 102000,
                   fastLinkGz = 77000 to 78000,
                   fullLinkGz = 26000 to 27000,
               ))
             } else {
               Some(ExpectedSizes(
-                  fastLink = 494000 to 495000,
+                  fastLink = 495000 to 496000,
                   fullLink = 337000 to 338000,
                   fastLinkGz = 69000 to 70000,
                   fullLinkGz = 50000 to 51000,
@@ -2015,15 +2015,15 @@ object Build {
           case `default213Version` =>
             if (!useMinifySizes) {
               Some(ExpectedSizes(
-                  fastLink = 462000 to 463000,
+                  fastLink = 463000 to 464000,
                   fullLink = 99000 to 100000,
                   fastLinkGz = 60000 to 61000,
                   fullLinkGz = 26000 to 27000,
               ))
             } else {
               Some(ExpectedSizes(
-                  fastLink = 347000 to 348000,
-                  fullLink = 307000 to 308000,
+                  fastLink = 348000 to 349000,
+                  fullLink = 308000 to 309000,
                   fastLinkGz = 54000 to 55000,
                   fullLinkGz = 49000 to 50000,
               ))
diff --git a/test-suite/js/src/test/scala/org/scalajs/testsuite/jsinterop/DynamicTest.scala b/test-suite/js/src/test/scala/org/scalajs/testsuite/jsinterop/DynamicTest.scala
index 27b7f224c1..bd23946f2e 100644
--- a/test-suite/js/src/test/scala/org/scalajs/testsuite/jsinterop/DynamicTest.scala
+++ b/test-suite/js/src/test/scala/org/scalajs/testsuite/jsinterop/DynamicTest.scala
@@ -109,11 +109,19 @@ class DynamicTest {
     assertJSUndefined(obj_anything)
   }
 
-  @Test def objectLiteralInStatementPosition_Issue1627(): Unit = {
-    // Just make sure it does not cause a SyntaxError
+  @Test def objectLiteralInStatementPosition_Issue1627_Issue4949(): Unit = {
+    @noinline def dynProp(): String = "foo"
+
+    // Just make sure those statements do not cause a SyntaxError
     js.Dynamic.literal(foo = "bar")
-    // and also test the case without param (different code path in Printers)
     js.Dynamic.literal()
+    js.Dynamic.literal(foo = "bar").foo
+    js.Dynamic.literal(foo = () => "bar").foo()
+    js.Dynamic.literal(foo = "bar").foo = "babar"
+    js.Dynamic.literal(foo = "foo").selectDynamic(dynProp())
+    js.Dynamic.literal(foo = "foo").updateDynamic(dynProp())("babar")
+    js.Dynamic.literal(foo = () => "bar").applyDynamic(dynProp())()
+    js.Dynamic.literal(foo = "bar") + js.Dynamic.literal(foobar = "babar")
   }
 
   @Test def objectLiteralConstructionWithDynamicNaming(): Unit = {

From e8b7dd7b9f59ed47eee939b5bd8d395327b10102 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Sun, 25 Feb 2024 11:26:58 +0100
Subject: [PATCH 060/298] Add some tests for printing of `ObjectConstr` nodes.

---
 .../backend/javascript/PrintersTest.scala     | 28 +++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/linker/shared/src/test/scala/org/scalajs/linker/backend/javascript/PrintersTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/backend/javascript/PrintersTest.scala
index a2a8108fa8..2c5de62dd1 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/backend/javascript/PrintersTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/backend/javascript/PrintersTest.scala
@@ -163,6 +163,34 @@ class PrintersTest {
     )
   }
 
+  @Test def printObjectLiteral(): Unit = {
+    assertPrintEquals("({});", ObjectConstr(Nil))
+
+    assertPrintEquals(
+      """
+        |({
+        |  "foo": 1
+        |});
+      """,
+      ObjectConstr(List(StringLiteral("foo") -> IntLiteral(1)))
+    )
+
+    assertPrintEquals(
+      """
+        |({
+        |  "foo": 1,
+        |  ["bar"]: 2,
+        |  baz: 3
+        |});
+      """,
+      ObjectConstr(List(
+        StringLiteral("foo") -> IntLiteral(1),
+        ComputedName(StringLiteral("bar")) -> IntLiteral(2),
+        Ident("baz") -> IntLiteral(3)
+      ))
+    )
+  }
+
   @Test def delayedIdentPrintVersusShow(): Unit = {
     locally {
       object resolver extends DelayedIdent.Resolver {

From 8b772e219c29f1bbc0336da71b8b40c9d4d22afa Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Fri, 26 Jan 2024 17:43:51 +0100
Subject: [PATCH 061/298] Under Minify, assign prototypes temporarily through
 `$p`.

When minifying, a susprisingly large amount of bytes in the
resulting .js file are caused by the `prototype`s in:

    C.prototype.f = function(...) { ... };
    C.prototype.g = function(...) { ... };

We can get rid of them by assigning `C.prototype` once to a
temporary variable, then reusing it many times:

    $p = C.prototype;
    $p.f = function(...) { ... };
    $p.f = function(...) { ... };

This commit implements that strategy when the `minify` config
is on.
---
 .../linker/backend/emitter/ClassEmitter.scala | 20 +++++------
 .../linker/backend/emitter/CoreJSLib.scala    | 27 +++++++++------
 .../linker/backend/emitter/Emitter.scala      | 10 ++++++
 .../linker/backend/emitter/SJSGen.scala       | 33 +++++++++++++++++++
 .../linker/backend/emitter/VarField.scala     |  5 ++-
 .../org/scalajs/linker/LibrarySizeTest.scala  |  2 +-
 project/Build.scala                           | 16 ++++-----
 7 files changed, 83 insertions(+), 30 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
index 11f8c3df33..8b50efda5e 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
@@ -186,13 +186,13 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
 
       val chainProtoWithGlobals = superClass match {
         case None =>
-          WithGlobals.nil
+          WithGlobals(setPrototypeVar(ctorVar))
 
         case Some(_) if shouldExtendJSError(className, superClass) =>
-          globalRef("Error").map(chainPrototypeWithLocalCtor(className, ctorVar, _))
+          globalRef("Error").map(chainPrototypeWithLocalCtor(className, ctorVar, _, localDeclPrototypeVar = false))
 
         case Some(parentIdent) =>
-          WithGlobals(List(ctorVar.prototype := js.New(globalVar(VarField.h, parentIdent.name), Nil)))
+          WithGlobals(List(genAssignPrototype(ctorVar, js.New(globalVar(VarField.h, parentIdent.name), Nil))))
       }
 
       for {
@@ -208,12 +208,12 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
           js.JSDocConstructor(realCtorDef.head) ::
           realCtorDef.tail :::
           chainProto :::
-          (genIdentBracketSelect(ctorVar.prototype, "constructor") := ctorVar) ::
+          (genIdentBracketSelect(prototypeFor(ctorVar), "constructor") := ctorVar) ::
 
           // Inheritable constructor
           js.JSDocConstructor(inheritableCtorDef.head) ::
           inheritableCtorDef.tail :::
-          (globalVar(VarField.h, className).prototype := ctorVar.prototype) :: Nil
+          (globalVar(VarField.h, className).prototype := prototypeFor(ctorVar)) :: Nil
         )
       }
     }
@@ -243,8 +243,8 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
         val ctorVar = fileLevelVar(VarField.b, genName(className))
 
         js.JSDocConstructor(ctorVar := ctorFun) ::
-        chainPrototypeWithLocalCtor(className, ctorVar, superCtor) :::
-        (genIdentBracketSelect(ctorVar.prototype, "constructor") := ctorVar) :: Nil
+        chainPrototypeWithLocalCtor(className, ctorVar, superCtor, localDeclPrototypeVar = true) :::
+        (genIdentBracketSelect(prototypeFor(ctorVar), "constructor") := ctorVar) :: Nil
       }
     }
   }
@@ -333,7 +333,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
   }
 
   private def chainPrototypeWithLocalCtor(className: ClassName, ctorVar: js.Tree,
-      superCtor: js.Tree)(implicit pos: Position): List[js.Tree] = {
+      superCtor: js.Tree, localDeclPrototypeVar: Boolean)(implicit pos: Position): List[js.Tree] = {
     import TreeDSL._
 
     val dummyCtor = fileLevelVar(VarField.hh, genName(className))
@@ -341,7 +341,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
     List(
         js.JSDocConstructor(genConst(dummyCtor.ident, js.Function(false, Nil, None, js.Skip()))),
         dummyCtor.prototype := superCtor.prototype,
-        ctorVar.prototype := js.New(dummyCtor, Nil)
+        genAssignPrototype(ctorVar, js.New(dummyCtor, Nil), localDeclPrototypeVar)
     )
   }
 
@@ -638,7 +638,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
       else globalVar(VarField.c, className)
 
     if (namespace.isStatic) classVarRef
-    else classVarRef.prototype
+    else prototypeFor(classVarRef)
   }
 
   def genMemberNameTree(name: Tree)(
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
index 6dc814cd87..43d58795ad 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
@@ -562,6 +562,7 @@ private[emitter] object CoreJSLib {
         extractWithGlobals(globalClassDef(VarField.Char, CoreVar, None, ctor :: toStr :: Nil))
       } else {
         defineFunction(VarField.Char, ctor.args, ctor.body) :::
+        setPrototypeVar(globalVar(VarField.Char, CoreVar)) :::
         assignES5ClassMembers(globalVar(VarField.Char, CoreVar), List(toStr))
       }
     }
@@ -1528,8 +1529,8 @@ private[emitter] object CoreJSLib {
           val clsDef = {
             extractWithGlobals(globalFunctionDef(VarField.ac, componentTypeRef,
                 ctor.args, ctor.restParam, ctor.body)) :::
-            (ArrayClass.prototype := New(globalVar(VarField.h, ObjectClass), Nil)) ::
-            (ArrayClass.prototype DOT "constructor" := ArrayClass) ::
+            genAssignPrototype(ArrayClass, New(globalVar(VarField.h, ObjectClass), Nil)) ::
+            (prototypeFor(ArrayClass) DOT "constructor" := ArrayClass) ::
             assignES5ClassMembers(ArrayClass, members)
           }
 
@@ -1537,7 +1538,7 @@ private[emitter] object CoreJSLib {
             case _: ClassRef =>
               clsDef :::
               extractWithGlobals(globalFunctionDef(VarField.ah, ObjectClass, Nil, None, Skip())) :::
-              (globalVar(VarField.ah, ObjectClass).prototype := ArrayClass.prototype) :: Nil
+              (globalVar(VarField.ah, ObjectClass).prototype := prototypeFor(ArrayClass)) :: Nil
             case _: PrimRef =>
               clsDef
           }
@@ -1697,7 +1698,6 @@ private[emitter] object CoreJSLib {
         val name = varRef("name")
 
         Block(
-            arrayClass.prototype DOT classData := This(),
             const(name, str("[") + (componentData DOT cpn.arrayEncodedName)),
             privateFieldSet(cpn.constr, arrayClass),
             if (globalKnowledge.isParentDataAccessed)
@@ -1729,6 +1729,7 @@ private[emitter] object CoreJSLib {
         MethodDef(static = false, Ident(cpn.initSpecializedArray),
             paramList(componentData, arrayClass, typedArrayClass, isAssignableFromFun), None, {
           Block(
+              arrayClass.prototype DOT classData := This(),
               initArrayCommonBody(arrayClass, componentData, componentData, 1),
               const(self, This()), // capture `this` for use in arrow fun
               privateFieldSet(cpn.isAssignableFromFun, isAssignableFromFun || {
@@ -1833,14 +1834,19 @@ private[emitter] object CoreJSLib {
             val members = set ::: copyTo ::: clone :: Nil
 
             if (useClassesForRegularClasses) {
-              ClassDef(Some(ArrayClass.ident), Some(globalVar(VarField.ac, ObjectClass)),
-                  ctor :: members)
+              Block(
+                  ClassDef(Some(ArrayClass.ident), Some(globalVar(VarField.ac, ObjectClass)),
+                      ctor :: members),
+                  ArrayClass.prototype DOT cpn.classData := This()
+              )
             } else {
               Block(
                 FunctionDef(ArrayClass.ident, ctor.args, ctor.restParam, ctor.body) ::
-                (ArrayClass.prototype := New(globalVar(VarField.ah, ObjectClass), Nil)) ::
-                (ArrayClass.prototype DOT "constructor" := ArrayClass) ::
-                assignES5ClassMembers(ArrayClass, members)
+                genAssignPrototype(ArrayClass, New(globalVar(VarField.ah, ObjectClass), Nil), localDecl = true) ::
+                (prototypeFor(ArrayClass) DOT "constructor" := ArrayClass) ::
+                assignES5ClassMembers(ArrayClass, members) :::
+                (prototypeFor(ArrayClass) DOT cpn.classData := This()) ::
+                Nil
               )
             }
           }
@@ -2000,6 +2006,7 @@ private[emitter] object CoreJSLib {
         extractWithGlobals(globalClassDef(VarField.TypeData, CoreVar, None, ctor :: members))
       } else {
         defineFunction(VarField.TypeData, ctor.args, ctor.body) :::
+        setPrototypeVar(globalVar(VarField.TypeData, CoreVar)) :::
         assignES5ClassMembers(globalVar(VarField.TypeData, CoreVar), members)
       }
     }
@@ -2159,7 +2166,7 @@ private[emitter] object CoreJSLib {
       for {
         MethodDef(static, name, args, restParam, body) <- members
       } yield {
-        val target = if (static) classRef else classRef.prototype
+        val target = if (static) classRef else prototypeFor(classRef)
         genPropSelect(target, name) := Function(arrow = false, args, restParam, body)
       }
     }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala
index 506dec4d4a..c7de499363 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala
@@ -64,6 +64,11 @@ final class Emitter[E >: Null <: js.Tree](
 
     val classEmitter: ClassEmitter = new ClassEmitter(sjsGen)
 
+    val everyFileStart: List[E] = {
+      // This postTransform does not count in the statistics
+      postTransformer.transformStats(sjsGen.declarePrototypeVar, 0)
+    }
+
     val coreJSLibCache: CoreJSLibCache = new CoreJSLibCache
 
     val moduleCaches: mutable.Map[ModuleID, ModuleCache] = mutable.Map.empty
@@ -293,6 +298,11 @@ final class Emitter[E >: Null <: js.Tree](
          * it is crucial that we verify it.
          */
         val defTrees: List[E] = (
+            /* The declaration of the `$p` variable that temporarily holds
+             * prototypes.
+             */
+            state.everyFileStart.iterator ++
+
             /* The definitions of the CoreJSLib that come before the definition
              * of `j.l.Object`. They depend on nothing else.
              */
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala
index b52be22348..5b7b846b8c 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala
@@ -145,6 +145,39 @@ private[emitter] final class SJSGen(
     val newArrayOfThisClass = "newArrayOfThisClass"
   }
 
+  /* This is a `val` because it is used at the top of every file, outside of
+   * any cache. Fortunately it does not depend on any dynamic content.
+   */
+  val declarePrototypeVar: List[Tree] = {
+    implicit val pos = Position.NoPosition
+    if (minify) VarDef(fileLevelVarIdent(VarField.p), None) :: Nil
+    else Nil
+  }
+
+  def prototypeFor(classRef: Tree)(implicit pos: Position): Tree = {
+    import TreeDSL._
+    if (minify) fileLevelVar(VarField.p)
+    else classRef.prototype
+  }
+
+  def genAssignPrototype(classRef: Tree, value: Tree, localDecl: Boolean = false)(implicit pos: Position): Tree = {
+    import TreeDSL._
+    val assign = classRef.prototype := value
+    if (!minify)
+      assign
+    else if (localDecl)
+      VarDef(fileLevelVarIdent(VarField.p), Some(assign))
+    else
+      fileLevelVar(VarField.p) := assign
+  }
+
+  /** Under `minify`, set `$p` to `classRef.prototype`. */
+  def setPrototypeVar(classRef: Tree)(implicit pos: Position): List[Tree] = {
+    import TreeDSL._
+    if (minify) (fileLevelVar(VarField.p) := classRef.prototype) :: Nil
+    else Nil
+  }
+
   def genZeroOf(tpe: Type)(
       implicit moduleContext: ModuleContext, globalKnowledge: GlobalKnowledge,
       pos: Position): Tree = {
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/VarField.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/VarField.scala
index 2be691d96e..10ac75518a 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/VarField.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/VarField.scala
@@ -40,7 +40,10 @@ private[emitter] object VarField {
   /** Scala class initializers (<clinit>). */
   final val sct = mk("$sct")
 
-  /** Private (instance) methods. */
+  /** Private (instance) methods.
+   *
+   *  Also used for the `prototype` of the current class when minifying.
+   */
   final val p = mk("$p")
 
   /** Public static methods. */
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/LibrarySizeTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/LibrarySizeTest.scala
index fbc5b93948..92c572391a 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/LibrarySizeTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/LibrarySizeTest.scala
@@ -71,7 +71,7 @@ class LibrarySizeTest {
 
     testLinkedSizes(
       expectedFastLinkSize = 150205,
-      expectedFullLinkSizeWithoutClosure = 92762,
+      expectedFullLinkSizeWithoutClosure = 90108,
       expectedFullLinkSizeWithClosure = 21325,
       classDefs,
       moduleInitializers = MainTestModuleInitializers
diff --git a/project/Build.scala b/project/Build.scala
index f6d3d596ab..2be6f5a261 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -2005,10 +2005,10 @@ object Build {
               ))
             } else {
               Some(ExpectedSizes(
-                  fastLink = 495000 to 496000,
-                  fullLink = 337000 to 338000,
-                  fastLinkGz = 69000 to 70000,
-                  fullLinkGz = 50000 to 51000,
+                  fastLink = 454000 to 455000,
+                  fullLink = 306000 to 307000,
+                  fastLinkGz = 65000 to 66000,
+                  fullLinkGz = 47000 to 48000,
               ))
             }
 
@@ -2022,10 +2022,10 @@ object Build {
               ))
             } else {
               Some(ExpectedSizes(
-                  fastLink = 348000 to 349000,
-                  fullLink = 308000 to 309000,
-                  fastLinkGz = 54000 to 55000,
-                  fullLinkGz = 49000 to 50000,
+                  fastLink = 325000 to 326000,
+                  fullLink = 285000 to 286000,
+                  fastLinkGz = 51000 to 52000,
+                  fullLinkGz = 47000 to 48000,
               ))
             }
 

From 229573b5427b4b2ddfb22551154478c09a720a61 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Wed, 21 Feb 2024 13:12:45 +0100
Subject: [PATCH 062/298] Be smarter about how we use params to `initClass`.

* Merge `isInterface` and `isJSType` as a single parameter `kind`
  that is an integer.
* Use the first element of `ancestors` instead of independently
  passing the `internalName` (this is safe because ES 2015
  guarantees the order of `getOwnPropertyNames`).
* Really remove the `parentData` parameter when reachability
  analysis says it is not accessed.
---
 .../linker/backend/emitter/ClassEmitter.scala | 27 +++++------
 .../linker/backend/emitter/CoreJSLib.scala    | 46 ++++++++-----------
 .../linker/backend/emitter/VarField.scala     |  2 -
 .../scalajs/linker/standard/LinkedClass.scala |  8 ++++
 .../org/scalajs/linker/LibrarySizeTest.scala  |  6 +--
 project/Build.scala                           | 26 +++++------
 6 files changed, 56 insertions(+), 59 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
index 8b50efda5e..8af483b5ce 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
@@ -836,21 +836,26 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
     val isJSType =
       kind.isJSType
 
-    val isJSTypeParam =
-      if (isJSType) js.BooleanLiteral(true)
-      else js.Undefined()
+    val kindParam = {
+      if (isJSType) js.IntLiteral(2)
+      else if (kind == ClassKind.Interface) js.IntLiteral(1)
+      else js.IntLiteral(0)
+    }
 
-    val parentData = if (globalKnowledge.isParentDataAccessed) {
-      superClass.fold[js.Tree] {
+    val parentDataOpt = if (globalKnowledge.isParentDataAccessed) {
+      val parentData = superClass.fold[js.Tree] {
         if (isObjectClass) js.Null()
         else js.Undefined()
       } { parent =>
         globalVar(VarField.d, parent.name)
       }
+      parentData :: Nil
     } else {
-      js.Undefined()
+      Nil
     }
 
+    assert(ancestors.headOption.contains(className),
+        s"The ancestors of ${className.nameString} do not start with itself: $ancestors")
     val ancestorsRecord = js.ObjectConstr(
         ancestors.withFilter(_ != ObjectClass).map(ancestor => (genAncestorIdent(ancestor), js.IntLiteral(1)))
     )
@@ -902,15 +907,11 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
 
     isInstanceFunWithGlobals.flatMap { isInstanceFun =>
       val allParams = List(
-          js.ObjectConstr(List(genAncestorIdent(className) -> js.IntLiteral(0))),
-          js.BooleanLiteral(kind == ClassKind.Interface),
+          kindParam,
           js.StringLiteral(RuntimeClassNameMapperImpl.map(
               semantics.runtimeClassNameMapper, className.nameString)),
-          ancestorsRecord,
-          isJSTypeParam,
-          parentData,
-          isInstanceFun
-      )
+          ancestorsRecord
+      ) ::: parentDataOpt ::: isInstanceFun :: Nil
 
       val prunedParams =
         allParams.reverse.dropWhile(_.isInstanceOf[js.Undefined]).reverse
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
index 43d58795ad..75106195d2 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
@@ -130,7 +130,6 @@ private[emitter] object CoreJSLib {
       defineLinkingInfo() :::
       defineJSBuiltinsSnapshotsAndPolyfills() :::
       declareCachedL0() :::
-      definePropertyName() :::
       defineCharClass() :::
       defineRuntimeFunctions() :::
       defineObjectGetClassFunctions() :::
@@ -526,23 +525,6 @@ private[emitter] object CoreJSLib {
       ))
     }
 
-    private def definePropertyName(): List[Tree] = {
-      /* Encodes a property name for runtime manipulation.
-       *
-       * Usage:
-       *   env.propertyName({someProp:0})
-       * Returns:
-       *   "someProp"
-       * Useful when the property is renamed by a global optimizer (like
-       * Closure) but we must still get hold of a string of that name for
-       * runtime reflection.
-       */
-      defineFunction1(VarField.propertyName) { obj =>
-        val prop = varRef("prop")
-        ForIn(genEmptyImmutableLet(prop.ident), obj, Return(prop))
-      }
-    }
-
     private def defineCharClass(): List[Tree] = {
       val ctor = {
         val c = varRef("c")
@@ -1652,23 +1634,31 @@ private[emitter] object CoreJSLib {
       }
 
       val initClass = {
-        val internalNameObj = varRef("internalNameObj")
-        val isInterface = varRef("isInterface")
+        // This is an int, where 1 means isInterface; 2 means isJSType; 0 otherwise
+        val kind = varRef("kind")
+
+        val hasParentData = globalKnowledge.isParentDataAccessed
+
         val fullName = varRef("fullName")
         val ancestors = varRef("ancestors")
-        val isJSType = varRef("isJSType")
         val parentData = varRef("parentData")
         val isInstance = varRef("isInstance")
         val internalName = varRef("internalName")
         val that = varRef("that")
         val depth = varRef("depth")
         val obj = varRef("obj")
-        MethodDef(static = false, Ident(cpn.initClass),
-            paramList(internalNameObj, isInterface, fullName, ancestors,
-                isJSType, parentData, isInstance), None, {
+        val params =
+          if (hasParentData) paramList(kind, fullName, ancestors, parentData, isInstance)
+          else paramList(kind, fullName, ancestors, isInstance)
+        MethodDef(static = false, Ident(cpn.initClass), params, None, {
           Block(
-              const(internalName, genCallHelper(VarField.propertyName, internalNameObj)),
-              if (globalKnowledge.isParentDataAccessed)
+              /* Extract the internalName, which is the first property of ancestors.
+               * We use `getOwnPropertyNames()`, which since ES 2015 guarantees
+               * to return non-integer string keys in creation order.
+               */
+              const(internalName,
+                  BracketSelect(Apply(genIdentBracketSelect(ObjectRef, "getOwnPropertyNames"), List(ancestors)), 0)),
+              if (hasParentData)
                 privateFieldSet(cpn.parentData, parentData)
               else
                 Skip(),
@@ -1679,9 +1669,9 @@ private[emitter] object CoreJSLib {
                   Return(!(!(BracketSelect(that DOT cpn.ancestors, internalName))))
                 })
               }),
-              privateFieldSet(cpn.isJSType, !(!isJSType)),
+              privateFieldSet(cpn.isJSType, kind === 2),
               publicFieldSet(cpn.name, fullName),
-              publicFieldSet(cpn.isInterface, isInterface),
+              publicFieldSet(cpn.isInterface, kind === 1),
               publicFieldSet(cpn.isInstance, isInstance || {
                 genArrowFunction(paramList(obj), {
                   Return(!(!(obj && (obj DOT classData) &&
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/VarField.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/VarField.scala
index 10ac75518a..0e695a24c7 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/VarField.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/VarField.scala
@@ -175,8 +175,6 @@ private[emitter] object VarField {
 
   final val valueDescription = mk("$valueDescription")
 
-  final val propertyName = mk("$propertyName")
-
   // ID hash subsystem
 
   final val systemIdentityHashCode = mk("$systemIdentityHashCode")
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/standard/LinkedClass.scala b/linker/shared/src/main/scala/org/scalajs/linker/standard/LinkedClass.scala
index 3f796633ae..58b71fb725 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/standard/LinkedClass.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/standard/LinkedClass.scala
@@ -29,6 +29,11 @@ import org.scalajs.ir.Names.{ClassName, FieldName}
  *  P+1. The converse is not true. This guarantees that versions can be used
  *  reliably to determine at phase P+1 whether a linked class coming from phase
  *  P must be reprocessed.
+ *
+ *  @param ancestors
+ *    List of all the ancestor classes and interfaces of this class. It always
+ *    contains this class name and `java.lang.Object`. This class name is
+ *    always the first element of the list.
  */
 final class LinkedClass(
     // Stuff from Tree
@@ -61,6 +66,9 @@ final class LinkedClass(
 
     val version: Version) {
 
+  require(ancestors.headOption.contains(name.name),
+      s"ancestors for ${name.name.nameString} must start with itself: $ancestors")
+
   def className: ClassName = name.name
 
   val hasStaticInitializer: Boolean = {
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/LibrarySizeTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/LibrarySizeTest.scala
index 92c572391a..b813d24f2a 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/LibrarySizeTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/LibrarySizeTest.scala
@@ -70,9 +70,9 @@ class LibrarySizeTest {
     )
 
     testLinkedSizes(
-      expectedFastLinkSize = 150205,
-      expectedFullLinkSizeWithoutClosure = 90108,
-      expectedFullLinkSizeWithClosure = 21325,
+      expectedFastLinkSize = 148754,
+      expectedFullLinkSizeWithoutClosure = 89358,
+      expectedFullLinkSizeWithClosure = 22075,
       classDefs,
       moduleInitializers = MainTestModuleInitializers
     )
diff --git a/project/Build.scala b/project/Build.scala
index 2be6f5a261..d7db8498ca 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -1998,34 +1998,34 @@ object Build {
           case `default212Version` =>
             if (!useMinifySizes) {
               Some(ExpectedSizes(
-                  fastLink = 641000 to 642000,
-                  fullLink = 101000 to 102000,
-                  fastLinkGz = 77000 to 78000,
+                  fastLink = 634000 to 635000,
+                  fullLink = 102000 to 103000,
+                  fastLinkGz = 76000 to 77000,
                   fullLinkGz = 26000 to 27000,
               ))
             } else {
               Some(ExpectedSizes(
-                  fastLink = 454000 to 455000,
-                  fullLink = 306000 to 307000,
+                  fastLink = 450000 to 451000,
+                  fullLink = 303000 to 304000,
                   fastLinkGz = 65000 to 66000,
-                  fullLinkGz = 47000 to 48000,
+                  fullLinkGz = 46000 to 47000,
               ))
             }
 
           case `default213Version` =>
             if (!useMinifySizes) {
               Some(ExpectedSizes(
-                  fastLink = 463000 to 464000,
-                  fullLink = 99000 to 100000,
-                  fastLinkGz = 60000 to 61000,
-                  fullLinkGz = 26000 to 27000,
+                  fastLink = 458000 to 459000,
+                  fullLink = 100000 to 101000,
+                  fastLinkGz = 59000 to 60000,
+                  fullLinkGz = 27000 to 28000,
               ))
             } else {
               Some(ExpectedSizes(
-                  fastLink = 325000 to 326000,
-                  fullLink = 285000 to 286000,
+                  fastLink = 322000 to 323000,
+                  fullLink = 282000 to 283000,
                   fastLinkGz = 51000 to 52000,
-                  fullLinkGz = 47000 to 48000,
+                  fullLinkGz = 46000 to 47000,
               ))
             }
 

From 7b2708673abf5efa1ec966ccdac4ca3c54449a32 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Wed, 21 Feb 2024 17:51:39 +0100
Subject: [PATCH 063/298] Store `$c.prototype.$classData` as part of
 `$TypeData().initClass()`.

This removes the largest source of uncompressible and non-removable
occurrences of `$classData` identifiers.

It does increase the size of the GCC output in the `LibrarySizeTest`,
but it does not translate to the `reversi` checksizes, so it is
probably a small codebase artifact.
---
 .../linker/backend/emitter/ClassEmitter.scala | 23 +++++++-------
 .../linker/backend/emitter/CoreJSLib.scala    | 18 +++++++----
 .../linker/backend/emitter/Emitter.scala      | 31 +++++++++++++------
 .../org/scalajs/linker/LibrarySizeTest.scala  |  6 ++--
 project/Build.scala                           | 28 ++++++++---------
 5 files changed, 63 insertions(+), 43 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
index 8af483b5ce..e2f2419835 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
@@ -826,7 +826,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
 
   def genTypeData(className: ClassName, kind: ClassKind,
       superClass: Option[ClassIdent], ancestors: List[ClassName],
-      jsNativeLoadSpec: Option[JSNativeLoadSpec])(
+      jsNativeLoadSpec: Option[JSNativeLoadSpec], hasInstances: Boolean)(
       implicit moduleContext: ModuleContext,
       globalKnowledge: GlobalKnowledge, pos: Position): WithGlobals[List[js.Tree]] = {
     import TreeDSL._
@@ -836,9 +836,18 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
     val isJSType =
       kind.isJSType
 
-    val kindParam = {
+    /* The `kindOrCtor` param is either:
+     * - an int: 1 means isInterface; 2 means isJSType; 0 otherwise
+     * - a Scala class constructor: means 0 + assign `kindOrCtor.prototype.$classData = <this TypeData>;`
+     *
+     * We must only assign the `$classData` if the class is a regular
+     * (non-hijacked) Scala class, and if it has instances. Otherwise there is
+     * no Scala class constructor for the class at all.
+     */
+    val kindOrCtorParam = {
       if (isJSType) js.IntLiteral(2)
       else if (kind == ClassKind.Interface) js.IntLiteral(1)
+      else if (kind.isClass && hasInstances) globalVar(VarField.c, className)
       else js.IntLiteral(0)
     }
 
@@ -907,7 +916,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
 
     isInstanceFunWithGlobals.flatMap { isInstanceFun =>
       val allParams = List(
-          kindParam,
+          kindOrCtorParam,
           js.StringLiteral(RuntimeClassNameMapperImpl.map(
               semantics.runtimeClassNameMapper, className.nameString)),
           ancestorsRecord
@@ -923,14 +932,6 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
     }
   }
 
-  def genSetTypeData(className: ClassName)(
-      implicit moduleContext: ModuleContext,
-      globalKnowledge: GlobalKnowledge, pos: Position): js.Tree = {
-    import TreeDSL._
-
-    globalVar(VarField.c, className).prototype DOT cpn.classData := globalVar(VarField.d, className)
-  }
-
   def genModuleAccessor(className: ClassName, isJSClass: Boolean)(
       implicit moduleContext: ModuleContext,
       globalKnowledge: GlobalKnowledge, pos: Position): WithGlobals[List[js.Tree]] = {
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
index 75106195d2..b476811b0e 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
@@ -1634,8 +1634,11 @@ private[emitter] object CoreJSLib {
       }
 
       val initClass = {
-        // This is an int, where 1 means isInterface; 2 means isJSType; 0 otherwise
-        val kind = varRef("kind")
+        /* This is either:
+         * - an int: 1 means isInterface; 2 means isJSType; 0 otherwise
+         * - a Scala class constructor: means 0 + assign `kindOrCtor.prototype.$classData = this;`
+         */
+        val kindOrCtor = varRef("kindOrCtor")
 
         val hasParentData = globalKnowledge.isParentDataAccessed
 
@@ -1648,8 +1651,8 @@ private[emitter] object CoreJSLib {
         val depth = varRef("depth")
         val obj = varRef("obj")
         val params =
-          if (hasParentData) paramList(kind, fullName, ancestors, parentData, isInstance)
-          else paramList(kind, fullName, ancestors, isInstance)
+          if (hasParentData) paramList(kindOrCtor, fullName, ancestors, parentData, isInstance)
+          else paramList(kindOrCtor, fullName, ancestors, isInstance)
         MethodDef(static = false, Ident(cpn.initClass), params, None, {
           Block(
               /* Extract the internalName, which is the first property of ancestors.
@@ -1669,15 +1672,18 @@ private[emitter] object CoreJSLib {
                   Return(!(!(BracketSelect(that DOT cpn.ancestors, internalName))))
                 })
               }),
-              privateFieldSet(cpn.isJSType, kind === 2),
+              privateFieldSet(cpn.isJSType, kindOrCtor === 2),
               publicFieldSet(cpn.name, fullName),
-              publicFieldSet(cpn.isInterface, kind === 1),
+              publicFieldSet(cpn.isInterface, kindOrCtor === 1),
               publicFieldSet(cpn.isInstance, isInstance || {
                 genArrowFunction(paramList(obj), {
                   Return(!(!(obj && (obj DOT classData) &&
                       BracketSelect(obj DOT classData DOT cpn.ancestors, internalName))))
                 })
               }),
+              If(typeof(kindOrCtor) !== str("number"), {
+                kindOrCtor.prototype DOT cpn.classData := This()
+              }),
               Return(This())
           )
         })
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala
index c7de499363..cdf17260e8 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala
@@ -716,21 +716,16 @@ final class Emitter[E >: Null <: js.Tree](
 
       if (linkedClass.hasRuntimeTypeInfo) {
         main ++= extractWithGlobals(classTreeCache.typeData.getOrElseUpdate(
+            linkedClass.hasInstances,
             classEmitter.genTypeData(
               className, // invalidated by overall class cache (part of ancestors)
               kind, // invalidated by class version
               linkedClass.superClass, // invalidated by class version
               linkedClass.ancestors, // invalidated by overall class cache (identity)
-              linkedClass.jsNativeLoadSpec // invalidated by class version
+              linkedClass.jsNativeLoadSpec, // invalidated by class version
+              linkedClass.hasInstances // invalidated directly (it is the input to `getOrElseUpdate`)
             )(moduleContext, classCache, linkedClass.pos).map(postTransform(_, 0))))
       }
-
-      if (linkedClass.hasInstances && kind.isClass && linkedClass.hasRuntimeTypeInfo) {
-        main ++= classTreeCache.setTypeData.getOrElseUpdate({
-          val tree = classEmitter.genSetTypeData(className)(moduleContext, classCache, linkedClass.pos)
-          postTransform(tree, 0)
-        })
-      }
     }
 
     if (linkedClass.kind.hasModuleAccessor && linkedClass.hasInstances) {
@@ -1198,7 +1193,7 @@ object Emitter {
     val privateJSFields = new OneTimeCache[WithGlobals[E]]
     val storeJSSuperClass = new OneTimeCache[WithGlobals[E]]
     val instanceTests = new OneTimeCache[WithGlobals[E]]
-    val typeData = new OneTimeCache[WithGlobals[E]]
+    val typeData = new InputEqualityCache[Boolean, WithGlobals[E]]
     val setTypeData = new OneTimeCache[E]
     val moduleAccessor = new OneTimeCache[WithGlobals[E]]
     val staticInitialization = new OneTimeCache[E]
@@ -1223,6 +1218,24 @@ object Emitter {
     }
   }
 
+  /** A cache that depends on an `input: I`, testing with `==`.
+   *
+   *  @tparam I
+   *    the type of input, for which `==` must meaningful
+   */
+  private final class InputEqualityCache[I, A >: Null] {
+    private[this] var lastInput: Option[I] = None
+    private[this] var value: A = null
+
+    def getOrElseUpdate(input: I, v: => A): A = {
+      if (!lastInput.contains(input)) {
+        value = v
+        lastInput = Some(input)
+      }
+      value
+    }
+  }
+
   private case class ClassID(
       ancestors: List[ClassName], moduleContext: ModuleContext)
 
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/LibrarySizeTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/LibrarySizeTest.scala
index b813d24f2a..cfa7b749fc 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/LibrarySizeTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/LibrarySizeTest.scala
@@ -70,9 +70,9 @@ class LibrarySizeTest {
     )
 
     testLinkedSizes(
-      expectedFastLinkSize = 148754,
-      expectedFullLinkSizeWithoutClosure = 89358,
-      expectedFullLinkSizeWithClosure = 22075,
+      expectedFastLinkSize = 147707,
+      expectedFullLinkSizeWithoutClosure = 88733,
+      expectedFullLinkSizeWithClosure = 21802,
       classDefs,
       moduleInitializers = MainTestModuleInitializers
     )
diff --git a/project/Build.scala b/project/Build.scala
index d7db8498ca..bf039b251f 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -1998,16 +1998,16 @@ object Build {
           case `default212Version` =>
             if (!useMinifySizes) {
               Some(ExpectedSizes(
-                  fastLink = 634000 to 635000,
-                  fullLink = 102000 to 103000,
-                  fastLinkGz = 76000 to 77000,
-                  fullLinkGz = 26000 to 27000,
+                  fastLink = 626000 to 627000,
+                  fullLink = 98000 to 99000,
+                  fastLinkGz = 75000 to 79000,
+                  fullLinkGz = 25000 to 26000,
               ))
             } else {
               Some(ExpectedSizes(
-                  fastLink = 450000 to 451000,
-                  fullLink = 303000 to 304000,
-                  fastLinkGz = 65000 to 66000,
+                  fastLink = 442000 to 443000,
+                  fullLink = 297000 to 298000,
+                  fastLinkGz = 64000 to 65000,
                   fullLinkGz = 46000 to 47000,
               ))
             }
@@ -2015,16 +2015,16 @@ object Build {
           case `default213Version` =>
             if (!useMinifySizes) {
               Some(ExpectedSizes(
-                  fastLink = 458000 to 459000,
-                  fullLink = 100000 to 101000,
-                  fastLinkGz = 59000 to 60000,
-                  fullLinkGz = 27000 to 28000,
+                  fastLink = 452000 to 453000,
+                  fullLink = 96000 to 97000,
+                  fastLinkGz = 58000 to 59000,
+                  fullLinkGz = 26000 to 27000,
               ))
             } else {
               Some(ExpectedSizes(
-                  fastLink = 322000 to 323000,
-                  fullLink = 282000 to 283000,
-                  fastLinkGz = 51000 to 52000,
+                  fastLink = 316000 to 317000,
+                  fullLink = 276000 to 277000,
+                  fastLinkGz = 50000 to 51000,
                   fullLinkGz = 46000 to 47000,
               ))
             }

From 58bec3f5b099856d961c1544cc6bbf4249224729 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Fri, 15 Mar 2024 19:59:06 +0100
Subject: [PATCH 064/298] Optimize `String_+` for `char` at the emitter level.

Previously, our implementation of `Character.toString(c)` used JS
interop itself to produce `String.fromCharCode(c)`. This was the
only hijacked class to do so, as the other ones use `"" + c`
instead. The reason was that the function emitter used to box chars
in string concatenation to get the behavior of `$Char.toString()`,
and we wanted to avoid the boxing.

We now make `FunctionEmitter` smarter about primitive `char`s in
`String_+`: it does not box anymore, and instead calls a dedicated
helper that calls `String.fromCharCode(c)`. We replace the
user-space implementation of `Character.toString(c)` with `"" + c`,
which aligns it with the other hijacked classes.

This is better because the optimization is more widely applicable:
it applies to all string concatenations, including those generated
by string interpolators, instead of only explicit `toString()`
calls.

Moreover, it automatically allows to constant-fold `c.toString()`
when `c` is a constant character.
---
 .../src/main/scala/java/lang/Character.scala  |  2 +-
 .../linker/backend/emitter/CoreJSLib.scala    |  3 +++
 .../backend/emitter/FunctionEmitter.scala     | 19 ++++++++++++-------
 .../linker/backend/emitter/VarField.scala     |  2 ++
 4 files changed, 18 insertions(+), 8 deletions(-)

diff --git a/javalib/src/main/scala/java/lang/Character.scala b/javalib/src/main/scala/java/lang/Character.scala
index b260948a6d..e5f132fd49 100644
--- a/javalib/src/main/scala/java/lang/Character.scala
+++ b/javalib/src/main/scala/java/lang/Character.scala
@@ -118,7 +118,7 @@ object Character {
   @inline def hashCode(value: Char): Int = value.toInt
 
   @inline def toString(c: Char): String =
-    js.Dynamic.global.String.fromCharCode(c.toInt).asInstanceOf[String]
+    "" + c
 
   def toString(codePoint: Int): String = {
     if (isBmpCodePoint(codePoint)) {
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
index 6dc814cd87..3dbcbe8afb 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
@@ -947,6 +947,9 @@ private[emitter] object CoreJSLib {
       defineFunction1(VarField.doubleToInt) { x =>
         Return(If(x > 2147483647, 2147483647, If(x < -2147483648, -2147483648, x | 0)))
       } :::
+      defineFunction1(VarField.charToString) { x =>
+        Return(Apply(genIdentBracketSelect(StringRef, "fromCharCode"), x :: Nil))
+      } :::
       condDefs(semantics.stringIndexOutOfBounds != CheckedBehavior.Unchecked)(
         defineFunction2(VarField.charAt) { (s, i) =>
           val r = varRef("r")
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
index a518948b97..58979155fc 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
@@ -2391,8 +2391,8 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
 
         case BinaryOp(op, lhs, rhs) =>
           import BinaryOp._
-          val newLhs = transformExprNoChar(lhs)
-          val newRhs = transformExprNoChar(rhs)
+          val newLhs = transformExpr(lhs, preserveChar = (op == String_+))
+          val newRhs = transformExpr(rhs, preserveChar = (op == String_+))
 
           (op: @switch) match {
             case === | !== =>
@@ -2445,11 +2445,16 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
               js.BinaryOp(JSBinaryOp.!==, newLhs, newRhs)
 
             case String_+ =>
-              if (lhs.tpe == StringType || rhs.tpe == StringType) {
-                js.BinaryOp(JSBinaryOp.+, newLhs, newRhs)
-              } else {
-                js.BinaryOp(JSBinaryOp.+, js.BinaryOp(JSBinaryOp.+,
-                    js.StringLiteral(""), newLhs), newRhs)
+              def charToString(t: js.Tree): js.Tree =
+                genCallHelper(VarField.charToString, t)
+
+              (lhs.tpe, rhs.tpe) match {
+                case (CharType, CharType) => charToString(newLhs) + charToString(newRhs)
+                case (CharType, _)        => charToString(newLhs) + newRhs
+                case (_, CharType)        => newLhs + charToString(newRhs)
+                case (StringType, _)      => newLhs + newRhs
+                case (_, StringType)      => newLhs + newRhs
+                case _                    => (js.StringLiteral("") + newLhs) + newRhs
               }
 
             case Int_+ => or0(js.BinaryOp(JSBinaryOp.+, newLhs, newRhs))
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/VarField.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/VarField.scala
index 2be691d96e..b89239a63a 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/VarField.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/VarField.scala
@@ -154,6 +154,8 @@ private[emitter] object VarField {
   /** Box char. */
   final val bC = mk("$bC")
 
+  final val charToString = mk("$cToS")
+
   final val charAt = mk("$charAt")
 
   // Object helpers

From 0dd63ff17f9ad57e8c29c525e58efc8d8ca3a942 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Fri, 23 Feb 2024 17:54:42 +0100
Subject: [PATCH 065/298] Under Minify, inline `VarDef`s used only once when we
 can.

During the optimizer, when emitting a `VarDef(x, ..., rhs)`, we
try to inline it if it has been used exactly once. In order to do
that, we look at the `body` in which it will be available, and
replace its only occurrence if it occurs in the first evaluation
context following only pure subexpressions.

See the long comment in the code for more details.
---
 .../frontend/optimizer/OptimizerCore.scala    | 343 +++++++++++++++++-
 .../linker/standard/CommonPhaseConfig.scala   |   5 +-
 .../org/scalajs/linker/LibrarySizeTest.scala  |   4 +-
 project/BinaryIncompatibilities.scala         |   2 +
 project/Build.scala                           |  22 +-
 5 files changed, 343 insertions(+), 33 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
index d9c57e3b9a..7c484195b5 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
@@ -417,7 +417,7 @@ private[optimizer] abstract class OptimizerCore(
         val (newName, newOriginalName) =
           freshLocalName(name, originalName, mutable = false)
         val localDef = LocalDef(RefinedType(AnyType), mutable = false,
-            ReplaceWithVarRef(newName, newSimpleState(Used), None))
+            ReplaceWithVarRef(newName, newSimpleState(UsedAtLeastOnce), None))
         val newBody = {
           val bodyScope = scope.withEnv(scope.env.withLocalDef(name, localDef))
           transformStat(body)(bodyScope)
@@ -430,7 +430,7 @@ private[optimizer] abstract class OptimizerCore(
         val (newName, newOriginalName) =
           freshLocalName(name, originalName, mutable = false)
         val localDef = LocalDef(RefinedType(AnyType), true,
-            ReplaceWithVarRef(newName, newSimpleState(Used), None))
+            ReplaceWithVarRef(newName, newSimpleState(UsedAtLeastOnce), None))
         val newHandler = {
           val handlerScope = scope.withEnv(scope.env.withLocalDef(name, localDef))
           transform(handler, isStat)(handlerScope)
@@ -1380,7 +1380,7 @@ private[optimizer] abstract class OptimizerCore(
       case PreTransLocalDef(localDef @ LocalDef(tpe, _, replacement)) =>
         replacement match {
           case ReplaceWithRecordVarRef(name, recordType, used, cancelFun) =>
-            used.value = Used
+            used.value = used.value.inc
             PreTransRecordTree(
                 VarRef(LocalIdent(name))(recordType), tpe, cancelFun)
 
@@ -1599,18 +1599,21 @@ private[optimizer] abstract class OptimizerCore(
 
         if (used.value.isUsed) {
           val ident = LocalIdent(name)
-          val varDef = resolveLocalDef(value) match {
+          resolveLocalDef(value) match {
             case PreTransRecordTree(valueTree, valueTpe, cancelFun) =>
               val recordType = valueTree.tpe.asInstanceOf[RecordType]
               if (!isImmutableType(recordType))
                 cancelFun()
-              VarDef(ident, originalName, recordType, mutable, valueTree)
+              Block(VarDef(ident, originalName, recordType, mutable, valueTree), innerBody)
 
             case PreTransTree(valueTree, valueTpe) =>
-              VarDef(ident, originalName, tpe.base, mutable, valueTree)
+              val optimized =
+                if (used.value.count == 1 && config.minify) tryInsertAtFirstEvalContext(name, valueTree, innerBody)
+                else None
+              optimized.getOrElse {
+                Block(VarDef(ident, originalName, tpe.base, mutable, valueTree), innerBody)
+              }
           }
-
-          Block(varDef, innerBody)
         } else {
           val valueSideEffects = finishTransformStat(value)
           Block(valueSideEffects, innerBody)
@@ -1713,6 +1716,282 @@ private[optimizer] abstract class OptimizerCore(
     case _                 => false
   }
 
+  /** Tries to insert `valTree` in place of the (unique) occurrence of `valName` in `body`.
+   *
+   *  This function assumes that `valName` is used only once, and only inside
+   *  `body`. It does not assume that `valTree` or `body` are side-effect-free.
+   *
+   *  The replacement is done only if we can show that it will not affect
+   *  evaluation order. In practice, this means that we only replace if we find
+   *  the occurrence of `valName` in the first evaluation context of `body`.
+   *  In other words, we verify that all the expressions that will evaluate
+   *  before `valName` in `body` are pure.
+   *
+   *  We consider a `VarRef(y)` pure if `valTree` does not contain any
+   *  assignment to `y`.
+   *
+   *  For example, we can replace `x` in the following bodies:
+   *
+   *  {{{
+   *  x
+   *  x + e
+   *  x.foo(...)
+   *  x.f
+   *  e + x                 // if `e` is pure
+   *  e0.foo(...e1, x, ...) // if `e0` is pure and non-null, and the `...e1`s are pure
+   *  if (x) { ... } else { ... }
+   *  }}}
+   *
+   *  Why is this interesting? Mostly because of inlining.
+   *
+   *  Inlining tends to create many bindings for the receivers and arguments of
+   *  methods. We must do that to preserve evaluation order, and not to evaluate
+   *  them multiple times. However, very often, the receiver and arguments are
+   *  used exactly once in the inlined body, and in-order. Using this strategy,
+   *  we can take the right-hand-sides of the synthetic bindings and inline them
+   *  directly inside the body.
+   *
+   *  This in turn allows more trees to remain JS-level expressions, which means
+   *  that `FunctionEmitter` has to `unnest` less often, further reducing the
+   *  amount of temporary variables.
+   *
+   *  ---
+   *
+   *  Note that we can never cross any potential undefined behavior, even when
+   *  the corresponding semantics are `Unchecked`. That is because the
+   *  `valTree` could throw itself, preventing the normal behavior of the code
+   *  to reach the undefined behavior in the first place. Consider for example:
+   *
+   *  {{{
+   *  val x: Foo = ... // maybe null
+   *  val y: Int = if (x == null) throw new Exception() else 1
+   *  x.foo(y)
+   *  }}}
+   *
+   *  We cannot inline `y` in this example, because that would change
+   *  observable behavior if `x` is `null`.
+   *
+   *  It is OK to cross the potential UB if we can prove that it will not
+   *  actually trigger, for example if we know that `x` is not null.
+   *
+   *  ---
+   *
+   *  We only call this function when the `minify` option is on. This is for two
+   *  reasons:
+   *
+   *  - it can be detrimental to debuggability, as even user-written `val`s can
+   *    disappear, and their right-hand-side be evaluated out-of-order compared
+   *    to the source code;
+   *  - it is non-linear, as we can perform several traversals of the same body,
+   *    if it follows a sequence of `VarDef`s that can each be successfully
+   *    inserted.
+   */
+  private def tryInsertAtFirstEvalContext(valName: LocalName, valTree: Tree, body: Tree): Option[Tree] = {
+    import EvalContextInsertion._
+
+    object valTreeInfo extends Traversers.Traverser {
+      val mutatedLocalVars = mutable.Set.empty[LocalName]
+
+      traverse(valTree)
+
+      override def traverse(tree: Tree): Unit = {
+        super.traverse(tree)
+        tree match {
+          case Assign(VarRef(ident), _) => mutatedLocalVars += ident.name
+          case _                        => ()
+        }
+      }
+    }
+
+    def recs(bodies: List[Tree]): EvalContextInsertion[List[Tree]] = bodies match {
+      case Nil =>
+        NotFoundPureSoFar
+      case firstBody :: restBodies =>
+        rec(firstBody) match {
+          case Success(newFirstBody) => Success(newFirstBody :: restBodies)
+          case NotFoundPureSoFar     => recs(restBodies).mapOrKeepGoing(firstBody :: _)
+          case Failed                => Failed
+        }
+    }
+
+    def rec(body: Tree): EvalContextInsertion[Tree] = {
+      implicit val pos = body.pos
+
+      body match {
+        case VarRef(ident) =>
+          if (ident.name == valName)
+            Success(valTree)
+          else if (valTreeInfo.mutatedLocalVars.contains(ident.name))
+            Failed
+          else
+            NotFoundPureSoFar
+
+        case Skip() =>
+          NotFoundPureSoFar
+
+        case Block(stats) =>
+          recs(stats).mapOrKeepGoing(Block(_))
+
+        case Labeled(label, tpe, innerBody) =>
+          rec(innerBody).mapOrKeepGoing(Labeled(label, tpe, _))
+
+        case Return(expr, label) =>
+          rec(expr).mapOrFailed(Return(_, label))
+
+        case If(cond, thenp, elsep) =>
+          rec(cond).mapOrFailed(If(_, thenp, elsep)(body.tpe))
+
+        case Throw(expr) =>
+          rec(expr).mapOrFailed(Throw(_))
+
+        case Match(selector, cases, default) =>
+          rec(selector).mapOrFailed(Match(_, cases, default)(body.tpe))
+
+        case New(className, ctor, args) =>
+          recs(args).mapOrKeepGoingIf(New(className, ctor, _))(
+              keepGoingIf = hasElidableConstructors(className))
+
+        case LoadModule(className) =>
+          if (hasElidableConstructors(className)) NotFoundPureSoFar
+          else Failed
+
+        case Select(qual, field) =>
+          rec(qual).mapOrFailed(Select(_, field)(body.tpe))
+
+        case Apply(flags, receiver, method, args) =>
+          rec(receiver) match {
+            case Success(newReceiver) =>
+              Success(Apply(flags, newReceiver, method, args)(body.tpe))
+            case NotFoundPureSoFar if isNotNull(receiver) =>
+              recs(args).mapOrFailed(Apply(flags, receiver, method, _)(body.tpe))
+            case _ =>
+              Failed
+          }
+
+        case ApplyStatically(flags, receiver, className, method, args) =>
+          rec(receiver) match {
+            case Success(newReceiver) =>
+              Success(ApplyStatically(flags, newReceiver, className, method, args)(body.tpe))
+            case NotFoundPureSoFar if isNotNull(receiver) =>
+              recs(args).mapOrFailed(ApplyStatically(flags, receiver, className, method, _)(body.tpe))
+            case _ =>
+              Failed
+          }
+
+        case ApplyStatic(flags, className, method, args) =>
+          recs(args).mapOrFailed(ApplyStatic(flags, className, method, _)(body.tpe))
+
+        case UnaryOp(op, arg) =>
+          rec(arg).mapOrKeepGoing(UnaryOp(op, _))
+
+        case BinaryOp(op, lhs, rhs) =>
+          import BinaryOp._
+
+          rec(lhs) match {
+            case Success(newLhs) => Success(BinaryOp(op, newLhs, rhs))
+            case Failed          => Failed
+
+            case NotFoundPureSoFar =>
+              rec(rhs).mapOrKeepGoingIf(BinaryOp(op, lhs, _)) {
+                (op: @switch) match {
+                  case Int_/ | Int_% | Long_/ | Long_% | String_+ | String_charAt =>
+                    false
+                  case _ =>
+                    true
+                }
+              }
+          }
+
+        case NewArray(typeRef, lengths) =>
+          recs(lengths).mapOrKeepGoing(NewArray(typeRef, _))
+
+        case ArrayValue(typeRef, elems) =>
+          recs(elems).mapOrKeepGoing(ArrayValue(typeRef, _))
+
+        case ArrayLength(array) =>
+          rec(array).mapOrKeepGoingIf(ArrayLength(_))(keepGoingIf = isNotNull(array))
+
+        case ArraySelect(array, index) =>
+          rec(array) match {
+            case Success(newArray) =>
+              Success(ArraySelect(newArray, index)(body.tpe))
+            case NotFoundPureSoFar if isNotNull(array) =>
+              rec(index).mapOrFailed(ArraySelect(array, _)(body.tpe))
+            case _ =>
+              Failed
+          }
+
+        case RecordValue(tpe, elems) =>
+          recs(elems).mapOrKeepGoing(RecordValue(tpe, _))
+
+        case RecordSelect(record, field) =>
+          rec(record).mapOrKeepGoingIf(RecordSelect(_, field)(body.tpe)) {
+            // We can keep going if the selected field is immutable
+            val RecordType(fields) = record.tpe: @unchecked
+            !fields.find(_.name == field.name).get.mutable
+          }
+
+        case IsInstanceOf(expr, testType) =>
+          rec(expr).mapOrKeepGoing(IsInstanceOf(_, testType))
+
+        case AsInstanceOf(expr, tpe) =>
+          rec(expr).mapOrFailed(AsInstanceOf(_, tpe))
+
+        case GetClass(expr) =>
+          rec(expr).mapOrKeepGoingIf(GetClass(_))(keepGoingIf = isNotNull(expr))
+
+        case Clone(expr) =>
+          rec(expr).mapOrFailed(Clone(_))
+
+        case JSUnaryOp(op, arg) =>
+          rec(arg).mapOrFailed(JSUnaryOp(op, _))
+
+        case JSBinaryOp(op, lhs, rhs) =>
+          rec(lhs) match {
+            case Success(newLhs) =>
+              Success(JSBinaryOp(op, newLhs, rhs))
+            case NotFoundPureSoFar =>
+              rec(rhs).mapOrKeepGoingIf(JSBinaryOp(op, lhs, _))(
+                  keepGoingIf = op == JSBinaryOp.=== || op == JSBinaryOp.!==)
+            case Failed =>
+              Failed
+          }
+
+        case JSArrayConstr(items) =>
+          if (items.exists(_.isInstanceOf[JSSpread]))
+            Failed // in theory we could do something better here, but the complexity is not worth it
+          else
+            recs(items.asInstanceOf[List[Tree]]).mapOrKeepGoing(JSArrayConstr(_))
+
+        case _: Literal =>
+          NotFoundPureSoFar
+
+        case This() =>
+          NotFoundPureSoFar
+
+        case Closure(arrow, captureParams, params, restParam, body, captureValues) =>
+          recs(captureValues).mapOrKeepGoing(Closure(arrow, captureParams, params, restParam, body, _))
+
+        case _ =>
+          Failed
+      }
+    }
+
+    rec(body) match {
+      case Success(result) => Some(result)
+      case Failed          => None
+
+      case NotFoundPureSoFar =>
+        /* The val was never actually used. This can happen even when the
+         * variable was `used` exactly once, because `used` tracks the number
+         * of times we have generated a `VarRef` for it. In some cases, the
+         * generated `VarRef` is later discarded through `keepOnlySideEffects`
+         * somewhere else.
+         */
+        Some(Block(keepOnlySideEffects(valTree), body)(body.pos))
+    }
+  }
+
   private def pretransformApply(tree: Apply, isStat: Boolean,
       usePreTransform: Boolean)(
       cont: PreTransCont)(
@@ -2066,7 +2345,7 @@ private[optimizer] abstract class OptimizerCore(
         if (target != expectedTarget)
           cancelFun()
 
-        used.value = Used
+        used.value = used.value.inc
         val module = VarRef(LocalIdent(moduleVarName))(AnyType)
         path.foldLeft[Tree](module) { (inner, pathElem) =>
           JSSelect(inner, StringLiteral(pathElem))
@@ -2097,7 +2376,7 @@ private[optimizer] abstract class OptimizerCore(
                   captureParams, params, body, captureLocalDefs,
                   alreadyUsed, cancelFun)))
               if !alreadyUsed.value.isUsed && argsNoSpread.size <= params.size =>
-            alreadyUsed.value = Used
+            alreadyUsed.value = alreadyUsed.value.inc
             val missingArgCount = params.size - argsNoSpread.size
             val expandedArgs =
               if (missingArgCount == 0) argsNoSpread
@@ -4991,7 +5270,7 @@ private[optimizer] abstract class OptimizerCore(
         case PreTransTree(VarRef(LocalIdent(refName)), _)
             if !localIsMutable(refName) =>
           buildInner(LocalDef(computeRefinedType(), false,
-              ReplaceWithVarRef(refName, newSimpleState(Used), None)), cont)
+              ReplaceWithVarRef(refName, newSimpleState(UsedAtLeastOnce), None)), cont)
 
         case _ =>
           withDedicatedVar(computeRefinedType())
@@ -5343,7 +5622,7 @@ private[optimizer] object OptimizerCore {
 
     def newReplacement(implicit pos: Position): Tree = this.replacement match {
       case ReplaceWithVarRef(name, used, _) =>
-        used.value = Used
+        used.value = used.value.inc
         VarRef(LocalIdent(name))(tpe.base)
 
       /* Allocate an instance of RuntimeLong on the fly.
@@ -5352,7 +5631,7 @@ private[optimizer] object OptimizerCore {
        */
       case ReplaceWithRecordVarRef(name, recordType, used, _)
           if tpe.base == ClassType(LongImpl.RuntimeLongClass) =>
-        used.value = Used
+        used.value = used.value.inc
         createNewLong(VarRef(LocalIdent(name))(recordType))
 
       case ReplaceWithRecordVarRef(_, _, _, cancelFun) =>
@@ -6451,14 +6730,40 @@ private[optimizer] object OptimizerCore {
     else OriginalName(base)
   }
 
-  private sealed abstract class IsUsed {
-    def isUsed: Boolean
+  private final case class IsUsed(count: Int) {
+    def isUsed: Boolean = count > 0
+
+    lazy val inc: IsUsed = IsUsed(count + 1)
   }
-  private case object Used extends IsUsed {
-    override def isUsed: Boolean = true
+
+  private val Unused: IsUsed = IsUsed(count = 0)
+  private val UsedAtLeastOnce: IsUsed = Unused.inc
+
+  private sealed abstract class EvalContextInsertion[+A] {
+    import EvalContextInsertion._
+
+    def mapOrKeepGoing[B](f: A => B): EvalContextInsertion[B] = this match {
+      case Success(a)        => Success(f(a))
+      case NotFoundPureSoFar => NotFoundPureSoFar
+      case Failed            => Failed
+    }
+
+    def mapOrKeepGoingIf[B](f: A => B)(keepGoingIf: => Boolean): EvalContextInsertion[B] = this match {
+      case Success(a)        => Success(f(a))
+      case NotFoundPureSoFar => if (keepGoingIf) NotFoundPureSoFar else Failed
+      case Failed            => Failed
+    }
+
+    def mapOrFailed[B](f: A => B): EvalContextInsertion[B] = this match {
+      case Success(a) => Success(f(a))
+      case _          => Failed
+    }
   }
-  private case object Unused extends IsUsed {
-    override def isUsed: Boolean = false
+
+  private object EvalContextInsertion {
+    final case class Success[+A](result: A) extends EvalContextInsertion[A]
+    case object Failed extends EvalContextInsertion[Nothing]
+    case object NotFoundPureSoFar extends EvalContextInsertion[Nothing]
   }
 
 }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/standard/CommonPhaseConfig.scala b/linker/shared/src/main/scala/org/scalajs/linker/standard/CommonPhaseConfig.scala
index 700a5b1ff7..66b0c0f9ef 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/standard/CommonPhaseConfig.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/standard/CommonPhaseConfig.scala
@@ -18,6 +18,8 @@ import org.scalajs.linker.interface._
 final class CommonPhaseConfig private (
     /** Core specification. */
     val coreSpec: CoreSpec,
+    /** Apply Scala.js-specific minification of the produced .js files. */
+    val minify: Boolean,
     /** Whether things that can be parallelized should be parallelized.
      *  On the JavaScript platform, this setting is typically ignored.
      */
@@ -37,6 +39,7 @@ final class CommonPhaseConfig private (
   private def this() = {
     this(
         coreSpec = CoreSpec.Defaults,
+        minify = false,
         parallel = true,
         batchMode = false)
   }
@@ -47,6 +50,6 @@ private[linker] object CommonPhaseConfig {
 
   private[linker] def fromStandardConfig(config: StandardConfig): CommonPhaseConfig = {
     val coreSpec = CoreSpec(config.semantics, config.moduleKind, config.esFeatures)
-    new CommonPhaseConfig(coreSpec, config.parallel, config.batchMode)
+    new CommonPhaseConfig(coreSpec, config.minify, config.parallel, config.batchMode)
   }
 }
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/LibrarySizeTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/LibrarySizeTest.scala
index cfa7b749fc..c55930f74f 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/LibrarySizeTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/LibrarySizeTest.scala
@@ -71,8 +71,8 @@ class LibrarySizeTest {
 
     testLinkedSizes(
       expectedFastLinkSize = 147707,
-      expectedFullLinkSizeWithoutClosure = 88733,
-      expectedFullLinkSizeWithClosure = 21802,
+      expectedFullLinkSizeWithoutClosure = 86729,
+      expectedFullLinkSizeWithClosure = 21768,
       classDefs,
       moduleInitializers = MainTestModuleInitializers
     )
diff --git a/project/BinaryIncompatibilities.scala b/project/BinaryIncompatibilities.scala
index 6d2c642453..49cbe2d2a0 100644
--- a/project/BinaryIncompatibilities.scala
+++ b/project/BinaryIncompatibilities.scala
@@ -24,6 +24,8 @@ object BinaryIncompatibilities {
   )
 
   val Linker = Seq(
+    // private, not an issue
+    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.linker.standard.CommonPhaseConfig.this"),
   )
 
   val LinkerInterface = Seq(
diff --git a/project/Build.scala b/project/Build.scala
index bf039b251f..43f4be4847 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -1999,16 +1999,16 @@ object Build {
             if (!useMinifySizes) {
               Some(ExpectedSizes(
                   fastLink = 626000 to 627000,
-                  fullLink = 98000 to 99000,
+                  fullLink = 97000 to 98000,
                   fastLinkGz = 75000 to 79000,
                   fullLinkGz = 25000 to 26000,
               ))
             } else {
               Some(ExpectedSizes(
-                  fastLink = 442000 to 443000,
-                  fullLink = 297000 to 298000,
-                  fastLinkGz = 64000 to 65000,
-                  fullLinkGz = 46000 to 47000,
+                  fastLink = 433000 to 434000,
+                  fullLink = 288000 to 289000,
+                  fastLinkGz = 62000 to 63000,
+                  fullLinkGz = 44000 to 45000,
               ))
             }
 
@@ -2016,16 +2016,16 @@ object Build {
             if (!useMinifySizes) {
               Some(ExpectedSizes(
                   fastLink = 452000 to 453000,
-                  fullLink = 96000 to 97000,
+                  fullLink = 94000 to 95000,
                   fastLinkGz = 58000 to 59000,
-                  fullLinkGz = 26000 to 27000,
+                  fullLinkGz = 25000 to 26000,
               ))
             } else {
               Some(ExpectedSizes(
-                  fastLink = 316000 to 317000,
-                  fullLink = 276000 to 277000,
-                  fastLinkGz = 50000 to 51000,
-                  fullLinkGz = 46000 to 47000,
+                  fastLink = 309000 to 310000,
+                  fullLink = 265000 to 266000,
+                  fastLinkGz = 49000 to 50000,
+                  fullLinkGz = 43000 to 44000,
               ))
             }
 

From 8b5af310db7e7cc7b918a42b14f3f25fa91bde6d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Sat, 16 Mar 2024 10:41:40 +0100
Subject: [PATCH 066/298] Reduce the memory pressure of `BackwardsCompatTest`.

Previously, we were running the tests for *all* previous versions
in parallel, because of the behavior of `Future.traverse`. While it
can reduce the wall clock time of running that test, it comes at a
huge memory consumption cost, increasing with every new release.

It seems we have recently hit the limit of what is reasonable,
especially on JS. Even JS retains things in parallel in memory
because the IO handling concurrently overlaps.

We now ensure a completely sequential behavior for this test. For
each previous version, in sequence, we

1. create a new cache for the IR files of the version,
2. load the IR files,
3. execute the test,
4. free the cache.

This commit hopefully fixes #4961.
---
 .../scalajs/linker/BackwardsCompatTest.scala  | 23 ++++-----
 .../scalajs/linker/testutils/TestIRRepo.scala | 51 ++++++++++++++++---
 2 files changed, 56 insertions(+), 18 deletions(-)

diff --git a/linker/shared/src/test/scala/org/scalajs/linker/BackwardsCompatTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/BackwardsCompatTest.scala
index ca12a09277..54a1a0f105 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/BackwardsCompatTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/BackwardsCompatTest.scala
@@ -80,18 +80,17 @@ class BackwardsCompatTest {
     val classDefFiles = classDefs.map(MemClassDefIRFile(_))
     val logger = new ScalaConsoleLogger(Level.Error)
 
-    Future.traverse(TestIRRepo.previousLibs.toSeq) { case (version, libFuture) =>
-      libFuture.flatMap { lib =>
-        val config = StandardConfig().withCheckIR(true)
-        val linker = StandardImpl.linker(config)
-        val out = MemOutputDirectory()
-
-        linker.link(lib ++ classDefFiles, moduleInitializers, out, logger)
-      }.recover {
-        case e: Throwable =>
-          throw new AssertionError(
-              s"linking stdlib $version failed: ${e.getMessage()}", e)
-      }
+    TestIRRepo.sequentiallyForEachPreviousLib { (version, lib) =>
+      val config = StandardConfig().withCheckIR(true)
+      val linker = StandardImpl.linker(config)
+      val out = MemOutputDirectory()
+
+      linker.link(lib ++ classDefFiles, moduleInitializers, out, logger)
+        .recover {
+          case e: Throwable =>
+            throw new AssertionError(
+                s"linking stdlib $version failed: ${e.getMessage()}", e)
+        }
     }
   }
 }
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/testutils/TestIRRepo.scala b/linker/shared/src/test/scala/org/scalajs/linker/testutils/TestIRRepo.scala
index 61fa025c77..f3048d0623 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/testutils/TestIRRepo.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/testutils/TestIRRepo.scala
@@ -13,7 +13,6 @@
 package org.scalajs.linker.testutils
 
 import scala.concurrent._
-import scala.concurrent.ExecutionContext.Implicits.global
 
 import org.scalajs.linker.StandardImpl
 import org.scalajs.linker.interface.IRFile
@@ -21,14 +20,54 @@ import org.scalajs.linker.interface.IRFile
 object TestIRRepo {
   private val globalIRCache = StandardImpl.irFileCache()
 
-  val minilib: Future[Seq[IRFile]] = load(StdlibHolder.minilib)
-  val javalib: Future[Seq[IRFile]] = load(StdlibHolder.javalib)
+  val minilib: Future[Seq[IRFile]] = loadGlobal(StdlibHolder.minilib)
+  val javalib: Future[Seq[IRFile]] = loadGlobal(StdlibHolder.javalib)
   val empty: Future[Seq[IRFile]] = Future.successful(Nil)
-  val previousLibs: Map[String, Future[Seq[IRFile]]] =
-    StdlibHolder.previousLibs.map(x => x._1 -> load(x._2))
 
-  private def load(stdlibPath: String) = {
+  private def loadGlobal(stdlibPath: String): Future[Seq[IRFile]] = {
+    import scala.concurrent.ExecutionContext.Implicits.global
+
     Platform.loadJar(stdlibPath)
       .flatMap(globalIRCache.newCache.cached _)
   }
+
+  /** For each previous lib, calls `f(version, irFiles)`, and combines the result.
+   *
+   *  This method applies `f` *sequentially*. It waits until the returned
+   *  `Future` completes before moving on to the next iteration.
+   */
+  def sequentiallyForEachPreviousLib[A](f: (String, Seq[IRFile]) => Future[A])(
+      implicit ec: ExecutionContext): Future[List[A]] = {
+
+    // sort for determinism
+    val sortedPreviousLibs = StdlibHolder.previousLibs.toList.sortBy(_._1)
+
+    sequentialFutureTraverse(sortedPreviousLibs) { case (version, path) =>
+      Platform.loadJar(path).flatMap { files =>
+        val cache = globalIRCache.newCache
+        cache
+          .cached(files)
+          .flatMap(f(version, _))
+          .andThen { case _ => cache.free() }
+      }
+    }
+  }
+
+  /** Like `Future.traverse`, but waits until each `Future` has completed
+   *  before starting the next one.
+   */
+  private def sequentialFutureTraverse[A, B](items: List[A])(f: A => Future[B])(
+      implicit ec: ExecutionContext): Future[List[B]] = {
+    items match {
+      case Nil =>
+        Future.successful(Nil)
+      case head :: tail =>
+        for {
+          headResult <- f(head)
+          tailResult <- sequentialFutureTraverse(tail)(f)
+        } yield {
+          headResult :: tailResult
+        }
+    }
+  }
 }

From a00497878ed250360a27622fea29ebfbb35c3690 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Sat, 16 Mar 2024 10:47:41 +0100
Subject: [PATCH 067/298] CI: Decompose the ir/linkerInterface/linker JS tests
 in separate processes.

This should also help with the memory pressure of `linkerJS/test`.
---
 Jenkinsfile | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/Jenkinsfile b/Jenkinsfile
index 1c9dc60c29..108cd81b6b 100644
--- a/Jenkinsfile
+++ b/Jenkinsfile
@@ -402,10 +402,18 @@ def Tasks = [
     npm install &&
     sbtnoretry ++$scala linker$v/test &&
     sbtnoretry linkerPrivateLibrary/test &&
-    sbtnoretry ++$scala irJS$v/test linkerJS$v/test linkerInterfaceJS$v/test &&
+    sbtnoretry ++$scala irJS$v/test &&
+    sbtnoretry ++$scala linkerInterfaceJS$v/test &&
+    sbtnoretry ++$scala linkerJS$v/test &&
     sbtnoretry 'set scalaJSStage in Global := FullOptStage' \
         'set scalaJSStage in testSuite.v$v := FastOptStage' \
-        ++$scala irJS$v/test linkerJS$v/test linkerInterfaceJS$v/test &&
+        ++$scala irJS$v/test &&
+    sbtnoretry 'set scalaJSStage in Global := FullOptStage' \
+        'set scalaJSStage in testSuite.v$v := FastOptStage' \
+        ++$scala linkerInterfaceJS$v/test &&
+    sbtnoretry 'set scalaJSStage in Global := FullOptStage' \
+        'set scalaJSStage in testSuite.v$v := FastOptStage' \
+        ++$scala linkerJS$v/test &&
     sbtnoretry ++$scala testSuite$v/bootstrap:test &&
     sbtnoretry 'set scalaJSStage in Global := FullOptStage' \
         'set scalaJSStage in testSuite.v$v := FastOptStage' \

From af924f4d5ef381e3d26bf5044aa056e25ba215c9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Fri, 15 Mar 2024 22:33:33 +0100
Subject: [PATCH 068/298] Add LinkedClass.hasDirectInstances.

It exposes whether the given class is directly instantiated. This
is required for the WebAssembly backend, which needs to build
vtables for concrete classes only.
---
 .../main/scala/org/scalajs/linker/frontend/BaseLinker.scala    | 1 +
 .../main/scala/org/scalajs/linker/standard/LinkedClass.scala   | 1 +
 project/BinaryIncompatibilities.scala                          | 3 +++
 3 files changed, 5 insertions(+)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/BaseLinker.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/BaseLinker.scala
index 692eb8a7f1..f120dff28a 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/BaseLinker.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/BaseLinker.scala
@@ -166,6 +166,7 @@ private[frontend] object BaseLinker {
         classDef.pos,
         ancestors.toList,
         hasInstances = classInfo.isAnySubclassInstantiated,
+        hasDirectInstances = classInfo.isInstantiated,
         hasInstanceTests = classInfo.areInstanceTestsUsed,
         hasRuntimeTypeInfo = classInfo.isDataAccessed,
         fieldsRead = classInfo.fieldsRead.toSet,
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/standard/LinkedClass.scala b/linker/shared/src/main/scala/org/scalajs/linker/standard/LinkedClass.scala
index 58b71fb725..afa257b289 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/standard/LinkedClass.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/standard/LinkedClass.scala
@@ -55,6 +55,7 @@ final class LinkedClass(
     // Actual Linking info
     val ancestors: List[ClassName],
     val hasInstances: Boolean,
+    val hasDirectInstances: Boolean,
     val hasInstanceTests: Boolean,
     val hasRuntimeTypeInfo: Boolean,
     val fieldsRead: Set[FieldName],
diff --git a/project/BinaryIncompatibilities.scala b/project/BinaryIncompatibilities.scala
index 49cbe2d2a0..e37b343839 100644
--- a/project/BinaryIncompatibilities.scala
+++ b/project/BinaryIncompatibilities.scala
@@ -24,6 +24,9 @@ object BinaryIncompatibilities {
   )
 
   val Linker = Seq(
+    // !!! Breaking, OK in minor release
+    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.linker.standard.LinkedClass.this"),
+
     // private, not an issue
     ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.linker.standard.CommonPhaseConfig.this"),
   )

From f05baed4b572756dfcf3069eada2b9eeafc7b6bc Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Fri, 15 Mar 2024 22:48:47 +0100
Subject: [PATCH 069/298] Only set `$c_C.prototype.$classData` if `C` has
 *direct* instances.

It is not useful for classes that only have strict sub instances,
i.e., classes that are effectively abstract.
---
 .../org/scalajs/linker/backend/emitter/ClassEmitter.scala     | 4 ++--
 .../scala/org/scalajs/linker/backend/emitter/Emitter.scala    | 4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
index e2f2419835..2d0dd515ea 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
@@ -826,7 +826,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
 
   def genTypeData(className: ClassName, kind: ClassKind,
       superClass: Option[ClassIdent], ancestors: List[ClassName],
-      jsNativeLoadSpec: Option[JSNativeLoadSpec], hasInstances: Boolean)(
+      jsNativeLoadSpec: Option[JSNativeLoadSpec], hasDirectInstances: Boolean)(
       implicit moduleContext: ModuleContext,
       globalKnowledge: GlobalKnowledge, pos: Position): WithGlobals[List[js.Tree]] = {
     import TreeDSL._
@@ -847,7 +847,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
     val kindOrCtorParam = {
       if (isJSType) js.IntLiteral(2)
       else if (kind == ClassKind.Interface) js.IntLiteral(1)
-      else if (kind.isClass && hasInstances) globalVar(VarField.c, className)
+      else if (kind.isClass && hasDirectInstances) globalVar(VarField.c, className)
       else js.IntLiteral(0)
     }
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala
index cdf17260e8..9d49e5855b 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala
@@ -716,14 +716,14 @@ final class Emitter[E >: Null <: js.Tree](
 
       if (linkedClass.hasRuntimeTypeInfo) {
         main ++= extractWithGlobals(classTreeCache.typeData.getOrElseUpdate(
-            linkedClass.hasInstances,
+            linkedClass.hasDirectInstances,
             classEmitter.genTypeData(
               className, // invalidated by overall class cache (part of ancestors)
               kind, // invalidated by class version
               linkedClass.superClass, // invalidated by class version
               linkedClass.ancestors, // invalidated by overall class cache (identity)
               linkedClass.jsNativeLoadSpec, // invalidated by class version
-              linkedClass.hasInstances // invalidated directly (it is the input to `getOrElseUpdate`)
+              linkedClass.hasDirectInstances // invalidated directly (it is the input to `getOrElseUpdate`)
             )(moduleContext, classCache, linkedClass.pos).map(postTransform(_, 0))))
       }
     }

From e4861b0ede528c9dcf11263bc7004b5cf851af5d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Sun, 17 Mar 2024 10:24:44 +0100
Subject: [PATCH 070/298] Upgrade to Scala 2.12.19.

---
 Jenkinsfile                                   |   5 +-
 .../{2.12.18 => 2.12.19}/BlacklistedTests.txt |   0
 .../{2.12.18 => 2.12.19}/neg/choices.check    |   0
 .../neg/partestInvalidFlag.check              |   0
 .../{2.12.18 => 2.12.19}/neg/t11952b.check    |   0
 .../neg/t6446-additional.check                |   0
 .../{2.12.18 => 2.12.19}/neg/t6446-list.check |   0
 .../neg/t6446-missing.check                   |   0
 .../neg/t6446-show-phases.check               |   0
 .../neg/t7494-no-options.check                |   0
 .../run/Course-2002-01.check                  |   0
 .../run/Course-2002-02.check                  |   0
 .../run/Course-2002-04.check                  |   0
 .../run/Course-2002-08.check                  |   0
 .../run/Course-2002-09.check                  |   0
 .../run/Course-2002-10.check                  |   0
 .../{2.12.18 => 2.12.19}/run/Meter.check      |   0
 .../run/MeterCaseClass.check                  |   0
 .../run/anyval-box-types.check                |   0
 .../scalajs/{2.12.18 => 2.12.19}/run/bugs.sem |   0
 .../run/caseClassHash.check                   |   0
 .../{2.12.18 => 2.12.19}/run/classof.check    |   0
 .../{2.12.18 => 2.12.19}/run/deeps.check      |   0
 .../run/dynamic-anyval.check                  |   0
 .../{2.12.18 => 2.12.19}/run/exceptions-2.sem |   0
 .../run/exceptions-nest.check                 |   0
 .../run/exceptions-nest.sem                   |   0
 .../run/impconvtimes.check                    |   0
 .../{2.12.18 => 2.12.19}/run/imports.check    |   0
 .../run/inlineHandlers.sem                    |   0
 .../run/interpolation.check                   |   0
 .../run/interpolationMultiline1.check         |   0
 .../run/macro-bundle-static.check             |   0
 .../run/macro-bundle-toplevel.check           |   0
 .../run/macro-bundle-whitebox-decl.check      |   0
 .../{2.12.18 => 2.12.19}/run/misc.check       |   0
 .../run/optimizer-array-load.sem              |   0
 .../{2.12.18 => 2.12.19}/run/pf-catch.sem     |   0
 .../{2.12.18 => 2.12.19}/run/promotion.check  |   0
 .../{2.12.18 => 2.12.19}/run/runtime.check    |   0
 .../{2.12.18 => 2.12.19}/run/spec-self.check  |   0
 .../{2.12.18 => 2.12.19}/run/structural.check |   0
 .../{2.12.18 => 2.12.19}/run/t0421-new.check  |   0
 .../{2.12.18 => 2.12.19}/run/t0421-old.check  |   0
 .../{2.12.18 => 2.12.19}/run/t1503.sem        |   0
 .../{2.12.18 => 2.12.19}/run/t3702.check      |   0
 .../{2.12.18 => 2.12.19}/run/t4148.sem        |   0
 .../{2.12.18 => 2.12.19}/run/t4617.check      |   0
 .../{2.12.18 => 2.12.19}/run/t5356.check      |   0
 .../{2.12.18 => 2.12.19}/run/t5552.check      |   0
 .../{2.12.18 => 2.12.19}/run/t5568.check      |   0
 .../{2.12.18 => 2.12.19}/run/t5629b.check     |   0
 .../{2.12.18 => 2.12.19}/run/t5680.check      |   0
 .../{2.12.18 => 2.12.19}/run/t5866.check      |   0
 .../run/t6318_primitives.check                |   0
 .../{2.12.18 => 2.12.19}/run/t6662.check      |   0
 .../{2.12.18 => 2.12.19}/run/t6827.sem        |   0
 .../{2.12.18 => 2.12.19}/run/t7657.check      |   0
 .../{2.12.18 => 2.12.19}/run/t7763.sem        |   0
 .../{2.12.18 => 2.12.19}/run/t8570a.check     |   0
 .../{2.12.18 => 2.12.19}/run/t8601b.sem       |   0
 .../{2.12.18 => 2.12.19}/run/t8601c.sem       |   0
 .../{2.12.18 => 2.12.19}/run/t8601d.sem       |   0
 .../{2.12.18 => 2.12.19}/run/t8764.check      |   0
 .../{2.12.18 => 2.12.19}/run/t9387b.check     |   0
 .../{2.12.18 => 2.12.19}/run/t9656.check      |   0
 .../run/try-catch-unify.check                 |   0
 .../run/virtpatmat_switch.check               |   0
 .../run/virtpatmat_typetag.check              |   0
 project/Build.scala                           |   1 +
 .../change-config-and-source/build.sbt        |   2 +-
 .../incremental/change-config/build.sbt       |   2 +-
 .../incremental/fix-compile-error/build.sbt   |   2 +-
 .../linker/concurrent-linker-use/build.sbt    |   2 +-
 .../sbt-test/linker/custom-linker/build.sbt   |   4 +-
 .../no-root-dependency-resolution/build.sbt   |   2 +-
 .../linker/non-existent-classpath/build.sbt   |   2 +-
 .../sbt-test/settings/cross-version/build.sbt |   2 +-
 .../src/sbt-test/settings/env-vars/build.sbt  |   2 +-
 .../settings/legacy-link-empty/build.sbt      |   2 +-
 .../settings/legacy-link-tasks/build.sbt      |   2 +-
 .../sbt-test/settings/module-init/build.sbt   |   2 +-
 .../sbt-test/settings/source-map/build.sbt    |   2 +-
 .../testing/multi-framework/build.sbt         |   2 +-
 .../resources/2.12.19/BlacklistedTests.txt    | 197 ++++++++++++++++++
 85 files changed, 216 insertions(+), 17 deletions(-)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.18 => 2.12.19}/BlacklistedTests.txt (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.18 => 2.12.19}/neg/choices.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.18 => 2.12.19}/neg/partestInvalidFlag.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.18 => 2.12.19}/neg/t11952b.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.18 => 2.12.19}/neg/t6446-additional.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.18 => 2.12.19}/neg/t6446-list.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.18 => 2.12.19}/neg/t6446-missing.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.18 => 2.12.19}/neg/t6446-show-phases.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.18 => 2.12.19}/neg/t7494-no-options.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.18 => 2.12.19}/run/Course-2002-01.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.18 => 2.12.19}/run/Course-2002-02.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.18 => 2.12.19}/run/Course-2002-04.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.18 => 2.12.19}/run/Course-2002-08.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.18 => 2.12.19}/run/Course-2002-09.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.18 => 2.12.19}/run/Course-2002-10.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.18 => 2.12.19}/run/Meter.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.18 => 2.12.19}/run/MeterCaseClass.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.18 => 2.12.19}/run/anyval-box-types.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.18 => 2.12.19}/run/bugs.sem (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.18 => 2.12.19}/run/caseClassHash.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.18 => 2.12.19}/run/classof.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.18 => 2.12.19}/run/deeps.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.18 => 2.12.19}/run/dynamic-anyval.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.18 => 2.12.19}/run/exceptions-2.sem (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.18 => 2.12.19}/run/exceptions-nest.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.18 => 2.12.19}/run/exceptions-nest.sem (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.18 => 2.12.19}/run/impconvtimes.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.18 => 2.12.19}/run/imports.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.18 => 2.12.19}/run/inlineHandlers.sem (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.18 => 2.12.19}/run/interpolation.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.18 => 2.12.19}/run/interpolationMultiline1.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.18 => 2.12.19}/run/macro-bundle-static.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.18 => 2.12.19}/run/macro-bundle-toplevel.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.18 => 2.12.19}/run/macro-bundle-whitebox-decl.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.18 => 2.12.19}/run/misc.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.18 => 2.12.19}/run/optimizer-array-load.sem (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.18 => 2.12.19}/run/pf-catch.sem (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.18 => 2.12.19}/run/promotion.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.18 => 2.12.19}/run/runtime.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.18 => 2.12.19}/run/spec-self.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.18 => 2.12.19}/run/structural.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.18 => 2.12.19}/run/t0421-new.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.18 => 2.12.19}/run/t0421-old.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.18 => 2.12.19}/run/t1503.sem (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.18 => 2.12.19}/run/t3702.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.18 => 2.12.19}/run/t4148.sem (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.18 => 2.12.19}/run/t4617.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.18 => 2.12.19}/run/t5356.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.18 => 2.12.19}/run/t5552.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.18 => 2.12.19}/run/t5568.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.18 => 2.12.19}/run/t5629b.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.18 => 2.12.19}/run/t5680.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.18 => 2.12.19}/run/t5866.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.18 => 2.12.19}/run/t6318_primitives.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.18 => 2.12.19}/run/t6662.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.18 => 2.12.19}/run/t6827.sem (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.18 => 2.12.19}/run/t7657.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.18 => 2.12.19}/run/t7763.sem (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.18 => 2.12.19}/run/t8570a.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.18 => 2.12.19}/run/t8601b.sem (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.18 => 2.12.19}/run/t8601c.sem (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.18 => 2.12.19}/run/t8601d.sem (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.18 => 2.12.19}/run/t8764.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.18 => 2.12.19}/run/t9387b.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.18 => 2.12.19}/run/t9656.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.18 => 2.12.19}/run/try-catch-unify.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.18 => 2.12.19}/run/virtpatmat_switch.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.18 => 2.12.19}/run/virtpatmat_typetag.check (100%)
 create mode 100644 scala-test-suite/src/test/resources/2.12.19/BlacklistedTests.txt

diff --git a/Jenkinsfile b/Jenkinsfile
index 108cd81b6b..f4886117a6 100644
--- a/Jenkinsfile
+++ b/Jenkinsfile
@@ -479,8 +479,8 @@ def otherJavaVersions = ["11", "16"]
 def allJavaVersions = otherJavaVersions.clone()
 allJavaVersions << mainJavaVersion
 
-def mainScalaVersion = "2.12.18"
-def mainScalaVersions = ["2.12.18", "2.13.12"]
+def mainScalaVersion = "2.12.19"
+def mainScalaVersions = ["2.12.19", "2.13.12"]
 def otherScalaVersions = [
   "2.12.2",
   "2.12.3",
@@ -497,6 +497,7 @@ def otherScalaVersions = [
   "2.12.15",
   "2.12.16",
   "2.12.17",
+  "2.12.18",
   "2.13.0",
   "2.13.1",
   "2.13.2",
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/BlacklistedTests.txt b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/BlacklistedTests.txt
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/BlacklistedTests.txt
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/BlacklistedTests.txt
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/neg/choices.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/neg/choices.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/neg/choices.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/neg/choices.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/neg/partestInvalidFlag.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/neg/partestInvalidFlag.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/neg/partestInvalidFlag.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/neg/partestInvalidFlag.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/neg/t11952b.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/neg/t11952b.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/neg/t11952b.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/neg/t11952b.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/neg/t6446-additional.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/neg/t6446-additional.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/neg/t6446-additional.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/neg/t6446-additional.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/neg/t6446-list.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/neg/t6446-list.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/neg/t6446-list.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/neg/t6446-list.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/neg/t6446-missing.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/neg/t6446-missing.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/neg/t6446-missing.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/neg/t6446-missing.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/neg/t6446-show-phases.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/neg/t6446-show-phases.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/neg/t6446-show-phases.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/neg/t6446-show-phases.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/neg/t7494-no-options.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/neg/t7494-no-options.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/neg/t7494-no-options.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/neg/t7494-no-options.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/Course-2002-01.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/Course-2002-01.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/Course-2002-01.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/Course-2002-01.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/Course-2002-02.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/Course-2002-02.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/Course-2002-02.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/Course-2002-02.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/Course-2002-04.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/Course-2002-04.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/Course-2002-04.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/Course-2002-04.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/Course-2002-08.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/Course-2002-08.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/Course-2002-08.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/Course-2002-08.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/Course-2002-09.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/Course-2002-09.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/Course-2002-09.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/Course-2002-09.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/Course-2002-10.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/Course-2002-10.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/Course-2002-10.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/Course-2002-10.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/Meter.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/Meter.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/Meter.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/Meter.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/MeterCaseClass.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/MeterCaseClass.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/MeterCaseClass.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/MeterCaseClass.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/anyval-box-types.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/anyval-box-types.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/anyval-box-types.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/anyval-box-types.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/bugs.sem b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/bugs.sem
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/bugs.sem
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/bugs.sem
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/caseClassHash.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/caseClassHash.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/caseClassHash.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/caseClassHash.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/classof.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/classof.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/classof.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/classof.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/deeps.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/deeps.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/deeps.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/deeps.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/dynamic-anyval.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/dynamic-anyval.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/dynamic-anyval.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/dynamic-anyval.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/exceptions-2.sem b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/exceptions-2.sem
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/exceptions-2.sem
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/exceptions-2.sem
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/exceptions-nest.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/exceptions-nest.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/exceptions-nest.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/exceptions-nest.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/exceptions-nest.sem b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/exceptions-nest.sem
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/exceptions-nest.sem
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/exceptions-nest.sem
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/impconvtimes.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/impconvtimes.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/impconvtimes.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/impconvtimes.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/imports.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/imports.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/imports.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/imports.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/inlineHandlers.sem b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/inlineHandlers.sem
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/inlineHandlers.sem
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/inlineHandlers.sem
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/interpolation.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/interpolation.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/interpolation.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/interpolation.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/interpolationMultiline1.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/interpolationMultiline1.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/interpolationMultiline1.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/interpolationMultiline1.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/macro-bundle-static.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/macro-bundle-static.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/macro-bundle-static.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/macro-bundle-static.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/macro-bundle-toplevel.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/macro-bundle-toplevel.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/macro-bundle-toplevel.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/macro-bundle-toplevel.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/macro-bundle-whitebox-decl.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/macro-bundle-whitebox-decl.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/macro-bundle-whitebox-decl.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/macro-bundle-whitebox-decl.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/misc.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/misc.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/misc.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/misc.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/optimizer-array-load.sem b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/optimizer-array-load.sem
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/optimizer-array-load.sem
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/optimizer-array-load.sem
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/pf-catch.sem b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/pf-catch.sem
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/pf-catch.sem
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/pf-catch.sem
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/promotion.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/promotion.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/promotion.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/promotion.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/runtime.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/runtime.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/runtime.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/runtime.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/spec-self.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/spec-self.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/spec-self.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/spec-self.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/structural.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/structural.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/structural.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/structural.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/t0421-new.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/t0421-new.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/t0421-new.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/t0421-new.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/t0421-old.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/t0421-old.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/t0421-old.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/t0421-old.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/t1503.sem b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/t1503.sem
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/t1503.sem
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/t1503.sem
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/t3702.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/t3702.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/t3702.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/t3702.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/t4148.sem b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/t4148.sem
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/t4148.sem
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/t4148.sem
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/t4617.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/t4617.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/t4617.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/t4617.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/t5356.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/t5356.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/t5356.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/t5356.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/t5552.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/t5552.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/t5552.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/t5552.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/t5568.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/t5568.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/t5568.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/t5568.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/t5629b.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/t5629b.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/t5629b.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/t5629b.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/t5680.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/t5680.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/t5680.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/t5680.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/t5866.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/t5866.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/t5866.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/t5866.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/t6318_primitives.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/t6318_primitives.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/t6318_primitives.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/t6318_primitives.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/t6662.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/t6662.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/t6662.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/t6662.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/t6827.sem b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/t6827.sem
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/t6827.sem
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/t6827.sem
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/t7657.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/t7657.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/t7657.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/t7657.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/t7763.sem b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/t7763.sem
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/t7763.sem
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/t7763.sem
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/t8570a.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/t8570a.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/t8570a.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/t8570a.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/t8601b.sem b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/t8601b.sem
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/t8601b.sem
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/t8601b.sem
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/t8601c.sem b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/t8601c.sem
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/t8601c.sem
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/t8601c.sem
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/t8601d.sem b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/t8601d.sem
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/t8601d.sem
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/t8601d.sem
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/t8764.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/t8764.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/t8764.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/t8764.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/t9387b.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/t9387b.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/t9387b.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/t9387b.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/t9656.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/t9656.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/t9656.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/t9656.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/try-catch-unify.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/try-catch-unify.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/try-catch-unify.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/try-catch-unify.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/virtpatmat_switch.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/virtpatmat_switch.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/virtpatmat_switch.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/virtpatmat_switch.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/virtpatmat_typetag.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/virtpatmat_typetag.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.18/run/virtpatmat_typetag.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/virtpatmat_typetag.check
diff --git a/project/Build.scala b/project/Build.scala
index 43f4be4847..d392347803 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -917,6 +917,7 @@ object Build {
         "2.12.16",
         "2.12.17",
         "2.12.18",
+        "2.12.19",
       ),
       cross213ScalaVersions := Seq(
         "2.13.0",
diff --git a/sbt-plugin/src/sbt-test/incremental/change-config-and-source/build.sbt b/sbt-plugin/src/sbt-test/incremental/change-config-and-source/build.sbt
index d12712d68d..d0f231b6de 100644
--- a/sbt-plugin/src/sbt-test/incremental/change-config-and-source/build.sbt
+++ b/sbt-plugin/src/sbt-test/incremental/change-config-and-source/build.sbt
@@ -1,4 +1,4 @@
-scalaVersion := "2.12.18"
+scalaVersion := "2.12.19"
 
 enablePlugins(ScalaJSPlugin)
 
diff --git a/sbt-plugin/src/sbt-test/incremental/change-config/build.sbt b/sbt-plugin/src/sbt-test/incremental/change-config/build.sbt
index d12712d68d..d0f231b6de 100644
--- a/sbt-plugin/src/sbt-test/incremental/change-config/build.sbt
+++ b/sbt-plugin/src/sbt-test/incremental/change-config/build.sbt
@@ -1,4 +1,4 @@
-scalaVersion := "2.12.18"
+scalaVersion := "2.12.19"
 
 enablePlugins(ScalaJSPlugin)
 
diff --git a/sbt-plugin/src/sbt-test/incremental/fix-compile-error/build.sbt b/sbt-plugin/src/sbt-test/incremental/fix-compile-error/build.sbt
index d12712d68d..d0f231b6de 100644
--- a/sbt-plugin/src/sbt-test/incremental/fix-compile-error/build.sbt
+++ b/sbt-plugin/src/sbt-test/incremental/fix-compile-error/build.sbt
@@ -1,4 +1,4 @@
-scalaVersion := "2.12.18"
+scalaVersion := "2.12.19"
 
 enablePlugins(ScalaJSPlugin)
 
diff --git a/sbt-plugin/src/sbt-test/linker/concurrent-linker-use/build.sbt b/sbt-plugin/src/sbt-test/linker/concurrent-linker-use/build.sbt
index f3238517cd..0c84905ef6 100644
--- a/sbt-plugin/src/sbt-test/linker/concurrent-linker-use/build.sbt
+++ b/sbt-plugin/src/sbt-test/linker/concurrent-linker-use/build.sbt
@@ -11,7 +11,7 @@ lazy val concurrentUseOfLinkerTest = taskKey[Any]("")
 name := "Scala.js sbt test"
 
 version := scalaJSVersion
-scalaVersion := "2.12.18"
+scalaVersion := "2.12.19"
 
 enablePlugins(ScalaJSPlugin)
 
diff --git a/sbt-plugin/src/sbt-test/linker/custom-linker/build.sbt b/sbt-plugin/src/sbt-test/linker/custom-linker/build.sbt
index 2576235cf2..1d4b83961d 100644
--- a/sbt-plugin/src/sbt-test/linker/custom-linker/build.sbt
+++ b/sbt-plugin/src/sbt-test/linker/custom-linker/build.sbt
@@ -13,14 +13,14 @@
 
 inThisBuild(Def.settings(
   version := scalaJSVersion,
-  scalaVersion := "2.12.18",
+  scalaVersion := "2.12.19",
 ))
 
 lazy val check = taskKey[Any]("")
 
 lazy val customLinker = project.in(file("custom-linker"))
   .settings(
-    scalaVersion := "2.12.18", // needs to match the minor version of Scala used by sbt
+    scalaVersion := "2.12.19", // needs to match the minor version of Scala used by sbt
     libraryDependencies += "org.scala-js" %% "scalajs-linker" % scalaJSVersion,
   )
 
diff --git a/sbt-plugin/src/sbt-test/linker/no-root-dependency-resolution/build.sbt b/sbt-plugin/src/sbt-test/linker/no-root-dependency-resolution/build.sbt
index 541d53caf8..2359461fa6 100644
--- a/sbt-plugin/src/sbt-test/linker/no-root-dependency-resolution/build.sbt
+++ b/sbt-plugin/src/sbt-test/linker/no-root-dependency-resolution/build.sbt
@@ -1,7 +1,7 @@
 name := "Scala.js sbt test"
 
 version in ThisBuild := scalaJSVersion
-scalaVersion in ThisBuild := "2.12.18"
+scalaVersion in ThisBuild := "2.12.19"
 
 // Disable the IvyPlugin on the root project
 disablePlugins(sbt.plugins.IvyPlugin)
diff --git a/sbt-plugin/src/sbt-test/linker/non-existent-classpath/build.sbt b/sbt-plugin/src/sbt-test/linker/non-existent-classpath/build.sbt
index bf0b1a8bc8..a3d81f1d03 100644
--- a/sbt-plugin/src/sbt-test/linker/non-existent-classpath/build.sbt
+++ b/sbt-plugin/src/sbt-test/linker/non-existent-classpath/build.sbt
@@ -1,5 +1,5 @@
 version := scalaJSVersion
-scalaVersion := "2.12.18"
+scalaVersion := "2.12.19"
 
 enablePlugins(ScalaJSPlugin)
 
diff --git a/sbt-plugin/src/sbt-test/settings/cross-version/build.sbt b/sbt-plugin/src/sbt-test/settings/cross-version/build.sbt
index 98b9b4802a..bab1e57ecf 100644
--- a/sbt-plugin/src/sbt-test/settings/cross-version/build.sbt
+++ b/sbt-plugin/src/sbt-test/settings/cross-version/build.sbt
@@ -3,7 +3,7 @@ import org.scalajs.sbtplugin.ScalaJSCrossVersion
 val check = taskKey[Unit]("Run checks of this test")
 
 version := scalaJSVersion
-scalaVersion := "2.12.18"
+scalaVersion := "2.12.19"
 
 lazy val js = project.enablePlugins(ScalaJSPlugin).settings(
     check := {
diff --git a/sbt-plugin/src/sbt-test/settings/env-vars/build.sbt b/sbt-plugin/src/sbt-test/settings/env-vars/build.sbt
index 55967e1eb6..83878dc189 100644
--- a/sbt-plugin/src/sbt-test/settings/env-vars/build.sbt
+++ b/sbt-plugin/src/sbt-test/settings/env-vars/build.sbt
@@ -1,5 +1,5 @@
 inThisBuild(Def.settings(
-  scalaVersion := "2.12.18",
+  scalaVersion := "2.12.19",
 ))
 
 lazy val sharedSettings = Def.settings(
diff --git a/sbt-plugin/src/sbt-test/settings/legacy-link-empty/build.sbt b/sbt-plugin/src/sbt-test/settings/legacy-link-empty/build.sbt
index e8419e778a..4044def10a 100644
--- a/sbt-plugin/src/sbt-test/settings/legacy-link-empty/build.sbt
+++ b/sbt-plugin/src/sbt-test/settings/legacy-link-empty/build.sbt
@@ -1,4 +1,4 @@
 version := scalaJSVersion
-scalaVersion := "2.12.18"
+scalaVersion := "2.12.19"
 
 enablePlugins(ScalaJSPlugin)
diff --git a/sbt-plugin/src/sbt-test/settings/legacy-link-tasks/build.sbt b/sbt-plugin/src/sbt-test/settings/legacy-link-tasks/build.sbt
index 309e32ab98..001fe4b7ca 100644
--- a/sbt-plugin/src/sbt-test/settings/legacy-link-tasks/build.sbt
+++ b/sbt-plugin/src/sbt-test/settings/legacy-link-tasks/build.sbt
@@ -1,7 +1,7 @@
 val checkNoClosure = taskKey[Unit]("Check that fullOptJS wasn't run with closure")
 
 version := scalaJSVersion
-scalaVersion := "2.12.18"
+scalaVersion := "2.12.19"
 
 enablePlugins(ScalaJSPlugin)
 
diff --git a/sbt-plugin/src/sbt-test/settings/module-init/build.sbt b/sbt-plugin/src/sbt-test/settings/module-init/build.sbt
index a70d51266f..b3cb9bef50 100644
--- a/sbt-plugin/src/sbt-test/settings/module-init/build.sbt
+++ b/sbt-plugin/src/sbt-test/settings/module-init/build.sbt
@@ -3,7 +3,7 @@ import org.scalajs.linker.interface.ModuleInitializer
 val check = taskKey[Unit]("Run checks of this test")
 
 version := scalaJSVersion
-scalaVersion := "2.12.18"
+scalaVersion := "2.12.19"
 
 enablePlugins(ScalaJSPlugin)
 
diff --git a/sbt-plugin/src/sbt-test/settings/source-map/build.sbt b/sbt-plugin/src/sbt-test/settings/source-map/build.sbt
index 7bfe7a52b6..fa3901cdcc 100644
--- a/sbt-plugin/src/sbt-test/settings/source-map/build.sbt
+++ b/sbt-plugin/src/sbt-test/settings/source-map/build.sbt
@@ -3,7 +3,7 @@ import org.scalajs.linker.interface.ModuleInitializer
 val check = taskKey[Unit]("Run checks of this test")
 
 version := scalaJSVersion
-scalaVersion := "2.12.18"
+scalaVersion := "2.12.19"
 
 enablePlugins(ScalaJSPlugin)
 
diff --git a/sbt-plugin/src/sbt-test/testing/multi-framework/build.sbt b/sbt-plugin/src/sbt-test/testing/multi-framework/build.sbt
index 4b3100395b..5a8b4240c9 100644
--- a/sbt-plugin/src/sbt-test/testing/multi-framework/build.sbt
+++ b/sbt-plugin/src/sbt-test/testing/multi-framework/build.sbt
@@ -1,5 +1,5 @@
 inThisBuild(version := scalaJSVersion)
-inThisBuild(scalaVersion := "2.12.18")
+inThisBuild(scalaVersion := "2.12.19")
 
 lazy val root = project.in(file(".")).
   aggregate(multiTestJS, multiTestJVM)
diff --git a/scala-test-suite/src/test/resources/2.12.19/BlacklistedTests.txt b/scala-test-suite/src/test/resources/2.12.19/BlacklistedTests.txt
new file mode 100644
index 0000000000..6c78101e5b
--- /dev/null
+++ b/scala-test-suite/src/test/resources/2.12.19/BlacklistedTests.txt
@@ -0,0 +1,197 @@
+## Do not compile
+scala/lang/annotations/BytecodeTest.scala
+scala/lang/annotations/RunTest.scala
+scala/lang/traits/BytecodeTest.scala
+scala/lang/traits/RunTest.scala
+scala/lang/primitives/NaNTest.scala
+scala/lang/primitives/BoxUnboxTest.scala
+scala/collection/SeqTest.scala
+scala/collection/Sizes.scala
+scala/collection/immutable/HashMapTest.scala
+scala/collection/immutable/HashSetTest.scala
+scala/collection/immutable/ListMapTest.scala
+scala/collection/immutable/MapHashcodeTest.scala
+scala/collection/immutable/SetTest.scala
+scala/collection/immutable/SeqTest.scala
+scala/collection/immutable/SmallMapTest.scala
+scala/collection/immutable/SortedMapTest.scala
+scala/collection/immutable/SortedSetTest.scala
+scala/collection/immutable/TreeMapTest.scala
+scala/collection/immutable/TreeSetTest.scala
+scala/reflect/ClassOfTest.scala
+scala/reflect/QTest.scala
+scala/reflect/io/AbstractFileTest.scala
+scala/reflect/io/ZipArchiveTest.scala
+scala/reflect/internal/util/AbstractFileClassLoaderTest.scala
+scala/reflect/internal/util/FileUtilsTest.scala
+scala/reflect/internal/util/SourceFileTest.scala
+scala/reflect/internal/util/StringOpsTest.scala
+scala/reflect/internal/util/WeakHashSetTest.scala
+scala/reflect/internal/LongNamesTest.scala
+scala/reflect/internal/MirrorsTest.scala
+scala/reflect/internal/NamesTest.scala
+scala/reflect/internal/PositionsTest.scala
+scala/reflect/internal/PrintersTest.scala
+scala/reflect/internal/ScopeTest.scala
+scala/reflect/internal/TreeGenTest.scala
+scala/reflect/internal/TypesTest.scala
+scala/reflect/macros/AttachmentsTest.scala
+scala/reflect/runtime/ReflectionUtilsShowTest.scala
+scala/reflect/runtime/ThreadSafetyTest.scala
+scala/runtime/BooleanBoxingTest.scala
+scala/runtime/ByteBoxingTest.scala
+scala/runtime/CharBoxingTest.scala
+scala/runtime/DoubleBoxingTest.scala
+scala/runtime/IntBoxingTest.scala
+scala/runtime/FloatBoxingTest.scala
+scala/runtime/LongBoxingTest.scala
+scala/runtime/ShortBoxingTest.scala
+scala/tools/cmd/CommandLineParserTest.scala
+scala/tools/nsc/Build.scala
+scala/tools/nsc/DeterminismTest.scala
+scala/tools/nsc/DeterminismTester.scala
+scala/tools/nsc/FileUtils.scala
+scala/tools/nsc/GlobalCustomizeClassloaderTest.scala
+scala/tools/nsc/PickleWriteTest.scala
+scala/tools/nsc/PipelineMainTest.scala
+scala/tools/nsc/async/AnnotationDrivenAsync.scala
+scala/tools/nsc/async/CustomFuture.scala
+scala/tools/nsc/backend/jvm/BTypesTest.scala
+scala/tools/nsc/backend/jvm/BytecodeTest.scala
+scala/tools/nsc/backend/jvm/ClassfileParserTest.scala
+scala/tools/nsc/backend/jvm/DefaultMethodTest.scala
+scala/tools/nsc/backend/jvm/DirectCompileTest.scala
+scala/tools/nsc/backend/jvm/GenericSignaturesTest.scala
+scala/tools/nsc/backend/jvm/IndyLambdaDirectTest.scala
+scala/tools/nsc/backend/jvm/IndyLambdaTest.scala
+scala/tools/nsc/backend/jvm/IndySammyTest.scala
+scala/tools/nsc/backend/jvm/InnerClassAttributeTest.scala
+scala/tools/nsc/backend/jvm/LineNumberTest.scala
+scala/tools/nsc/backend/jvm/NestedClassesCollectorTest.scala
+scala/tools/nsc/backend/jvm/OptimizedBytecodeTest.scala
+scala/tools/nsc/backend/jvm/PerRunInitTest.scala
+scala/tools/nsc/backend/jvm/StringConcatTest.scala
+scala/tools/nsc/backend/jvm/analysis/NullnessAnalyzerTest.scala
+scala/tools/nsc/backend/jvm/analysis/ProdConsAnalyzerTest.scala
+scala/tools/nsc/backend/jvm/opt/AnalyzerTest.scala
+scala/tools/nsc/backend/jvm/opt/BoxUnboxAndInlineTest.scala
+scala/tools/nsc/backend/jvm/opt/BoxUnboxTest.scala
+scala/tools/nsc/backend/jvm/opt/BTypesFromClassfileTest.scala
+scala/tools/nsc/backend/jvm/opt/CallGraphTest.scala
+scala/tools/nsc/backend/jvm/opt/ClosureOptimizerTest.scala
+scala/tools/nsc/backend/jvm/opt/CompactLocalVariablesTest.scala
+scala/tools/nsc/backend/jvm/opt/EmptyExceptionHandlersTest.scala
+scala/tools/nsc/backend/jvm/opt/EmptyLabelsAndLineNumbersTest.scala
+scala/tools/nsc/backend/jvm/opt/InlineInfoTest.scala
+scala/tools/nsc/backend/jvm/opt/InlinerIllegalAccessTest.scala
+scala/tools/nsc/backend/jvm/opt/InlinerSeparateCompilationTest.scala
+scala/tools/nsc/backend/jvm/opt/InlinerTest.scala
+scala/tools/nsc/backend/jvm/opt/InlineSourceMatcherTest.scala
+scala/tools/nsc/backend/jvm/opt/InlineWarningTest.scala
+scala/tools/nsc/backend/jvm/opt/MethodLevelOptsTest.scala
+scala/tools/nsc/backend/jvm/opt/ScalaInlineInfoTest.scala
+scala/tools/nsc/backend/jvm/opt/SimplifyJumpsTest.scala
+scala/tools/nsc/backend/jvm/opt/UnreachableCodeTest.scala
+scala/tools/nsc/backend/jvm/opt/UnusedLocalVariablesTest.scala
+scala/tools/nsc/ScriptRunnerTest.scala
+scala/tools/nsc/classpath/AggregateClassPathTest.scala
+scala/tools/nsc/classpath/JrtClassPathTest.scala
+scala/tools/nsc/classpath/MultiReleaseJarTest.scala
+scala/tools/nsc/classpath/PathResolverBaseTest.scala
+scala/tools/nsc/classpath/VirtualDirectoryClassPathTest.scala
+scala/tools/nsc/classpath/ZipAndJarFileLookupFactoryTest.scala
+scala/tools/nsc/doc/html/HtmlDocletTest.scala
+scala/tools/nsc/interpreter/CompletionTest.scala
+scala/tools/nsc/interpreter/ScriptedTest.scala
+scala/tools/nsc/interpreter/TabulatorTest.scala
+scala/tools/nsc/parser/ParserTest.scala
+scala/tools/nsc/reporters/ConsoleReporterTest.scala
+scala/tools/nsc/reporters/WConfTest.scala
+scala/tools/nsc/settings/ScalaVersionTest.scala
+scala/tools/nsc/settings/SettingsTest.scala
+scala/tools/nsc/settings/TargetTest.scala
+scala/tools/nsc/symtab/CannotHaveAttrsTest.scala
+scala/tools/nsc/symtab/FlagsTest.scala
+scala/tools/nsc/symtab/FreshNameExtractorTest.scala
+scala/tools/nsc/symtab/StdNamesTest.scala
+scala/tools/nsc/symtab/SymbolLoadersAssociatedFileTest.scala
+scala/tools/nsc/symtab/SymbolTableForUnitTesting.scala
+scala/tools/nsc/symtab/SymbolTableTest.scala
+scala/tools/nsc/symtab/classfile/PicklerTest.scala
+scala/tools/nsc/transform/MixinTest.scala
+scala/tools/nsc/transform/SpecializationTest.scala
+scala/tools/nsc/transform/ThicketTransformerTest.scala
+scala/tools/nsc/transform/delambdafy/DelambdafyTest.scala
+scala/tools/nsc/transform/patmat/SolvingTest.scala
+scala/tools/nsc/transform/patmat/PatmatBytecodeTest.scala
+scala/tools/nsc/typechecker/Implicits.scala
+scala/tools/nsc/typechecker/NamerTest.scala
+scala/tools/nsc/typechecker/ParamAliasTest.scala
+scala/tools/nsc/typechecker/TreeAttachmentTest.scala
+scala/tools/nsc/typechecker/TypedTreeTest.scala
+scala/tools/nsc/util/StackTraceTest.scala
+scala/tools/testing/AllocationTest.scala
+scala/tools/testing/BytecodeTesting.scala
+scala/tools/testing/JOL.scala
+scala/tools/testing/RunTesting.scala
+scala/tools/testing/VirtualCompilerTesting.scala
+scala/util/matching/RegexTest.scala
+
+## Do not link
+scala/MatchErrorSerializationTest.scala
+scala/PartialFunctionSerializationTest.scala
+scala/lang/stringinterpol/StringContextTest.scala
+scala/collection/IteratorTest.scala
+scala/collection/NewBuilderTest.scala
+scala/collection/ParallelConsistencyTest.scala
+scala/collection/SetMapRulesTest.scala
+scala/collection/SeqViewTest.scala
+scala/collection/SetMapConsistencyTest.scala
+scala/collection/concurrent/TrieMapTest.scala
+scala/collection/convert/WrapperSerializationTest.scala
+scala/collection/immutable/ListTest.scala
+scala/collection/immutable/RedBlackTreeSerialFormat.scala
+scala/collection/immutable/StreamTest.scala
+scala/collection/immutable/StringLikeTest.scala
+scala/collection/immutable/VectorTest.scala
+scala/collection/mutable/AnyRefMapTest.scala
+scala/collection/mutable/ArrayBufferTest.scala
+scala/collection/mutable/MutableListTest.scala
+scala/collection/mutable/OpenHashMapTest.scala
+scala/collection/mutable/PriorityQueueTest.scala
+scala/collection/parallel/TaskTest.scala
+scala/collection/parallel/immutable/ParRangeTest.scala
+scala/concurrent/FutureTest.scala
+scala/concurrent/duration/SerializationTest.scala
+scala/concurrent/impl/DefaultPromiseTest.scala
+scala/io/SourceTest.scala
+scala/runtime/ScalaRunTimeTest.scala
+scala/sys/process/PipedProcessTest.scala
+scala/sys/process/ProcessTest.scala
+scala/tools/testing/AssertUtilTest.scala
+scala/tools/testing/AssertThrowsTest.scala
+scala/util/SpecVersionTest.scala
+scala/util/SystemPropertiesTest.scala
+
+## Tests fail
+
+# Reflection
+scala/reflect/ClassTagTest.scala
+
+# Require strict-floats
+scala/math/BigDecimalTest.scala
+
+# Difference of getClass() on primitive values
+scala/collection/immutable/RangeTest.scala
+
+# Test fails only some times with
+#   'set scalaJSOptimizerOptions in scalaTestSuite ~= (_.withDisableOptimizer(true))'
+#   and' 'set scalaJSUseRhino in Global := false'
+scala/collection/immutable/PagedSeqTest.scala
+
+# Bugs
+scala/collection/convert/MapWrapperTest.scala
+
+# Tests passed but are too slow (timeouts)
+scala/collection/immutable/ListSetTest.scala
+scala/util/SortingTest.scala

From 24266f98fcfa0e4133a3af1d504643b021f30c36 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Sun, 17 Mar 2024 11:05:35 +0100
Subject: [PATCH 071/298] Avoid an internal deprecation in junit-runtime.

Scala 2.13.13 starts warning about these deprecations, which we
must therefore avoid. It might have missed them before because they
are secondary constructors.
---
 junit-runtime/src/main/scala/org/junit/Assume.scala           | 4 ++--
 .../main/scala/org/junit/AssumptionViolatedException.scala    | 4 ++++
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/junit-runtime/src/main/scala/org/junit/Assume.scala b/junit-runtime/src/main/scala/org/junit/Assume.scala
index ba9bdf8011..3d44f8be5d 100644
--- a/junit-runtime/src/main/scala/org/junit/Assume.scala
+++ b/junit-runtime/src/main/scala/org/junit/Assume.scala
@@ -33,13 +33,13 @@ object Assume {
   @noinline
   def assumeThat[T](actual: T, matcher: Matcher[T]): Unit = {
     if (!matcher.matches(actual.asInstanceOf[AnyRef]))
-      throw new AssumptionViolatedException(actual, matcher)
+      throw new AssumptionViolatedException(null, matcher, actual)
   }
 
   @noinline
   def assumeThat[T](message: String, actual: T, matcher: Matcher[T]): Unit = {
     if (!matcher.matches(actual.asInstanceOf[AnyRef]))
-      throw new AssumptionViolatedException(message, actual, matcher)
+      throw new AssumptionViolatedException(message, matcher, actual)
   }
 
   @noinline
diff --git a/junit-runtime/src/main/scala/org/junit/AssumptionViolatedException.scala b/junit-runtime/src/main/scala/org/junit/AssumptionViolatedException.scala
index a2adc0db01..315bcfa0e3 100644
--- a/junit-runtime/src/main/scala/org/junit/AssumptionViolatedException.scala
+++ b/junit-runtime/src/main/scala/org/junit/AssumptionViolatedException.scala
@@ -19,6 +19,10 @@ class AssumptionViolatedException protected (fAssumption: String,
   def this(message: String, expected: Any, matcher: Matcher[_]) =
     this(message, true, fMatcher = matcher, fValue = expected.asInstanceOf[AnyRef])
 
+  // Non-deprecated access to the full constructor for use in `Assume.scala`
+  private[junit] def this(message: String, matcher: Matcher[_], actual: Any) =
+    this(message, true, fMatcher = matcher, fValue = actual.asInstanceOf[AnyRef])
+
   def this(message: String) =
     this(message, false, null, null)
 

From 10634fc03818fd2d2f84db2c4f3422d971eee769 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Sun, 17 Mar 2024 11:22:16 +0100
Subject: [PATCH 072/298] Upgrade to Scala 2.13.13.

---
 Jenkinsfile                                   |   5 +-
 .../scala/scalajs/js/WrappedDictionary.scala  |   4 +
 .../scala/scalajs/js/WrappedMap.scala         |   4 +
 .../{2.13.12 => 2.13.13}/BlacklistedTests.txt |   5 +-
 .../{2.13.12 => 2.13.13}/neg/choices.check    |   0
 .../neg/partestInvalidFlag.check              |   0
 .../{2.13.12 => 2.13.13}/neg/t11952b.check    |   0
 .../{2.13.12 => 2.13.13}/neg/t12494.check     |   0
 .../neg/t6446-additional.check                |   0
 .../{2.13.12 => 2.13.13}/neg/t6446-list.check |   0
 .../neg/t6446-missing.check                   |   0
 .../neg/t6446-show-phases.check               |   0
 .../neg/t7494-no-options.check                |   0
 .../run/Course-2002-01.check                  |   0
 .../run/Course-2002-02.check                  |   0
 .../run/Course-2002-04.check                  |   0
 .../run/Course-2002-08.check                  |   0
 .../run/Course-2002-09.check                  |   0
 .../run/Course-2002-10.check                  |   0
 .../{2.13.12 => 2.13.13}/run/Meter.check      |   0
 .../run/MeterCaseClass.check                  |   0
 .../run/anyval-box-types.check                |   0
 .../scalajs/{2.13.12 => 2.13.13}/run/bugs.sem |   0
 .../run/caseClassHash.check                   |   0
 .../{2.13.12 => 2.13.13}/run/classof.check    |   0
 .../{2.13.12 => 2.13.13}/run/deeps.check      |   0
 .../run/dynamic-anyval.check                  |   0
 .../{2.13.12 => 2.13.13}/run/exceptions-2.sem |   0
 .../run/exceptions-nest.check                 |   0
 .../run/exceptions-nest.sem                   |   0
 .../run/impconvtimes.check                    |   0
 .../{2.13.12 => 2.13.13}/run/imports.check    |   0
 .../run/inlineHandlers.sem                    |   0
 .../run/interpolation.check                   |   0
 .../run/interpolationMultiline1.check         |   0
 .../run/macro-bundle-static.check             |   0
 .../run/macro-bundle-toplevel.check           |   0
 .../run/macro-bundle-whitebox-decl.check      |   0
 ...expand-varargs-implicit-over-varargs.check |   0
 .../{2.13.12 => 2.13.13}/run/misc.check       |   0
 .../run/optimizer-array-load.sem              |   0
 .../{2.13.12 => 2.13.13}/run/pf-catch.sem     |   0
 .../{2.13.12 => 2.13.13}/run/promotion.check  |   0
 .../{2.13.12 => 2.13.13}/run/runtime.check    |   0
 .../run/sammy_vararg_cbn.check                |   0
 .../{2.13.12 => 2.13.13}/run/spec-self.check  |   0
 .../run/string-switch.check                   |   0
 .../{2.13.12 => 2.13.13}/run/structural.check |   0
 .../{2.13.12 => 2.13.13}/run/t0421-new.check  |   0
 .../{2.13.12 => 2.13.13}/run/t0421-old.check  |   0
 .../{2.13.12 => 2.13.13}/run/t12221.check     |   0
 .../{2.13.12 => 2.13.13}/run/t1503.sem        |   0
 .../{2.13.12 => 2.13.13}/run/t3702.check      |   0
 .../{2.13.12 => 2.13.13}/run/t4148.sem        |   0
 .../{2.13.12 => 2.13.13}/run/t4617.check      |   0
 .../{2.13.12 => 2.13.13}/run/t5356.check      |   0
 .../{2.13.12 => 2.13.13}/run/t5552.check      |   0
 .../{2.13.12 => 2.13.13}/run/t5568.check      |   0
 .../{2.13.12 => 2.13.13}/run/t5629b.check     |   0
 .../{2.13.12 => 2.13.13}/run/t5680.check      |   0
 .../{2.13.12 => 2.13.13}/run/t5866.check      |   0
 .../{2.13.12 => 2.13.13}/run/t5966.check      |   0
 .../{2.13.12 => 2.13.13}/run/t6265.check      |   0
 .../run/t6318_primitives.check                |   0
 .../{2.13.12 => 2.13.13}/run/t6662.check      |   0
 .../{2.13.12 => 2.13.13}/run/t6827.sem        |   0
 .../{2.13.12 => 2.13.13}/run/t7657.check      |   0
 .../{2.13.12 => 2.13.13}/run/t7763.sem        |   0
 .../{2.13.12 => 2.13.13}/run/t8570a.check     |   0
 .../{2.13.12 => 2.13.13}/run/t8601b.sem       |   0
 .../{2.13.12 => 2.13.13}/run/t8601c.sem       |   0
 .../{2.13.12 => 2.13.13}/run/t8601d.sem       |   0
 .../{2.13.12 => 2.13.13}/run/t8764.check      |   0
 .../{2.13.12 => 2.13.13}/run/t9387b.check     |   0
 .../run/try-catch-unify.check                 |   0
 .../run/virtpatmat_switch.check               |   0
 .../run/virtpatmat_typetag.check              |   0
 project/Build.scala                           |  20 +-
 .../src/sbt-test/cross-version/2.13/build.sbt |   2 +-
 .../sbt-test/scala3/tasty-reader/build.sbt    |   2 +-
 .../resources/2.13.13/BlacklistedTests.txt    | 247 ++++++++++++++++++
 81 files changed, 282 insertions(+), 7 deletions(-)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/BlacklistedTests.txt (99%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/neg/choices.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/neg/partestInvalidFlag.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/neg/t11952b.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/neg/t12494.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/neg/t6446-additional.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/neg/t6446-list.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/neg/t6446-missing.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/neg/t6446-show-phases.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/neg/t7494-no-options.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/run/Course-2002-01.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/run/Course-2002-02.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/run/Course-2002-04.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/run/Course-2002-08.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/run/Course-2002-09.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/run/Course-2002-10.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/run/Meter.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/run/MeterCaseClass.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/run/anyval-box-types.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/run/bugs.sem (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/run/caseClassHash.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/run/classof.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/run/deeps.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/run/dynamic-anyval.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/run/exceptions-2.sem (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/run/exceptions-nest.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/run/exceptions-nest.sem (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/run/impconvtimes.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/run/imports.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/run/inlineHandlers.sem (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/run/interpolation.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/run/interpolationMultiline1.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/run/macro-bundle-static.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/run/macro-bundle-toplevel.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/run/macro-bundle-whitebox-decl.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/run/macro-expand-varargs-implicit-over-varargs.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/run/misc.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/run/optimizer-array-load.sem (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/run/pf-catch.sem (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/run/promotion.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/run/runtime.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/run/sammy_vararg_cbn.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/run/spec-self.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/run/string-switch.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/run/structural.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/run/t0421-new.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/run/t0421-old.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/run/t12221.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/run/t1503.sem (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/run/t3702.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/run/t4148.sem (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/run/t4617.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/run/t5356.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/run/t5552.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/run/t5568.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/run/t5629b.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/run/t5680.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/run/t5866.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/run/t5966.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/run/t6265.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/run/t6318_primitives.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/run/t6662.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/run/t6827.sem (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/run/t7657.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/run/t7763.sem (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/run/t8570a.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/run/t8601b.sem (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/run/t8601c.sem (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/run/t8601d.sem (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/run/t8764.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/run/t9387b.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/run/try-catch-unify.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/run/virtpatmat_switch.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.12 => 2.13.13}/run/virtpatmat_typetag.check (100%)
 create mode 100644 scala-test-suite/src/test/resources/2.13.13/BlacklistedTests.txt

diff --git a/Jenkinsfile b/Jenkinsfile
index f4886117a6..9ca49c5e3c 100644
--- a/Jenkinsfile
+++ b/Jenkinsfile
@@ -480,7 +480,7 @@ def allJavaVersions = otherJavaVersions.clone()
 allJavaVersions << mainJavaVersion
 
 def mainScalaVersion = "2.12.19"
-def mainScalaVersions = ["2.12.19", "2.13.12"]
+def mainScalaVersions = ["2.12.19", "2.13.13"]
 def otherScalaVersions = [
   "2.12.2",
   "2.12.3",
@@ -509,7 +509,8 @@ def otherScalaVersions = [
   "2.13.8",
   "2.13.9",
   "2.13.10",
-  "2.13.11"
+  "2.13.11",
+  "2.13.12"
 ]
 
 def scala3Version = "3.2.1"
diff --git a/library/src/main/scala-new-collections/scala/scalajs/js/WrappedDictionary.scala b/library/src/main/scala-new-collections/scala/scalajs/js/WrappedDictionary.scala
index a7624b3e46..bd379384a9 100644
--- a/library/src/main/scala-new-collections/scala/scalajs/js/WrappedDictionary.scala
+++ b/library/src/main/scala-new-collections/scala/scalajs/js/WrappedDictionary.scala
@@ -99,6 +99,10 @@ final class WrappedDictionary[A](private val dict: js.Dictionary[A])
   def iterator: scala.collection.Iterator[(String, A)] =
     new DictionaryIterator(dict)
 
+  /* Warning silenced in build for 2.13.13+:
+   * overriding method keys in trait MapOps is deprecated (since 2.13.13):
+   * This method should be an alias for keySet
+   */
   @inline
   override def keys: scala.collection.Iterable[String] =
     js.Object.keys(dict.asInstanceOf[js.Object])
diff --git a/library/src/main/scala-new-collections/scala/scalajs/js/WrappedMap.scala b/library/src/main/scala-new-collections/scala/scalajs/js/WrappedMap.scala
index 04d2f08517..83d4ace69d 100644
--- a/library/src/main/scala-new-collections/scala/scalajs/js/WrappedMap.scala
+++ b/library/src/main/scala-new-collections/scala/scalajs/js/WrappedMap.scala
@@ -95,6 +95,10 @@ final class WrappedMap[K, V](private val underlying: js.Map[K, V])
   def iterator: scala.collection.Iterator[(K, V)] =
     underlying.jsIterator().toIterator.map(kv => (kv._1, kv._2))
 
+  /* Warning silenced in build for 2.13.13+:
+   * overriding method keys in trait MapOps is deprecated (since 2.13.13):
+   * This method should be an alias for keySet
+   */
   @inline
   override def keys: scala.collection.Iterable[K] =
     underlying.asInstanceOf[js.Map.Raw[K, V]].keys().toIterator.to(Iterable)
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.12/BlacklistedTests.txt b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/BlacklistedTests.txt
similarity index 99%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.12/BlacklistedTests.txt
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/BlacklistedTests.txt
index f91b84d6d8..72066a2706 100644
--- a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.12/BlacklistedTests.txt
+++ b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/BlacklistedTests.txt
@@ -832,6 +832,7 @@ run/t12390.scala
 run/repl-release.scala
 run/eta-dependent.scala
 run/t10655.scala
+run/repl-suspended-warnings.scala
 
 # Using Scala Script (partest.ScriptTest)
 
@@ -950,7 +951,6 @@ run/t10641.scala
 run/t10751.scala
 run/t10819.scala
 run/t11385.scala
-run/t11731.scala
 run/t11746.scala
 run/t11815.scala
 run/splain.scala
@@ -972,6 +972,7 @@ run/package-object-toolbox.scala
 run/package-object-with-inner-class-in-ancestor.scala
 run/package-object-with-inner-class-in-ancestor-simpler.scala
 run/package-object-with-inner-class-in-ancestor-simpler-still.scala
+run/t7324.scala
 run/t10171
 
 # partest.StubErrorMessageTest
@@ -994,6 +995,7 @@ run/t12597.scala
 
 # partest.ASMConverters
 run/t9403
+run/nonfatal.scala
 
 # partest.BytecodeTest
 run/t7106
@@ -1119,6 +1121,7 @@ run/t12195
 run/t12380
 run/t12523
 run/t12290
+run/t9714
 
 # Using scala-script
 run/t7791-script-linenums.scala
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.12/neg/choices.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/neg/choices.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.12/neg/choices.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/neg/choices.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.12/neg/partestInvalidFlag.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/neg/partestInvalidFlag.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.12/neg/partestInvalidFlag.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/neg/partestInvalidFlag.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.12/neg/t11952b.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/neg/t11952b.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.12/neg/t11952b.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/neg/t11952b.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.12/neg/t12494.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/neg/t12494.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.12/neg/t12494.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/neg/t12494.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.12/neg/t6446-additional.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/neg/t6446-additional.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.12/neg/t6446-additional.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/neg/t6446-additional.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.12/neg/t6446-list.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/neg/t6446-list.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.12/neg/t6446-list.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/neg/t6446-list.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.12/neg/t6446-missing.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/neg/t6446-missing.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.12/neg/t6446-missing.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/neg/t6446-missing.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.12/neg/t6446-show-phases.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/neg/t6446-show-phases.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.12/neg/t6446-show-phases.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/neg/t6446-show-phases.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.12/neg/t7494-no-options.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/neg/t7494-no-options.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.12/neg/t7494-no-options.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/neg/t7494-no-options.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.12/run/Course-2002-01.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/Course-2002-01.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.12/run/Course-2002-01.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/Course-2002-01.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.12/run/Course-2002-02.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/Course-2002-02.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.12/run/Course-2002-02.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/Course-2002-02.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.12/run/Course-2002-04.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/Course-2002-04.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.12/run/Course-2002-04.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/Course-2002-04.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.12/run/Course-2002-08.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/Course-2002-08.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.12/run/Course-2002-08.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/Course-2002-08.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.12/run/Course-2002-09.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/Course-2002-09.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.12/run/Course-2002-09.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/Course-2002-09.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.12/run/Course-2002-10.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/Course-2002-10.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.12/run/Course-2002-10.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/Course-2002-10.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.12/run/Meter.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/Meter.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.12/run/Meter.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/Meter.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.12/run/MeterCaseClass.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/MeterCaseClass.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.12/run/MeterCaseClass.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/MeterCaseClass.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.12/run/anyval-box-types.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/anyval-box-types.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.12/run/anyval-box-types.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/anyval-box-types.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.12/run/bugs.sem b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/bugs.sem
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.12/run/bugs.sem
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/bugs.sem
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.12/run/caseClassHash.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/caseClassHash.check
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similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.12/run/t8601d.sem
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/t8601d.sem
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.12/run/t8764.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/t8764.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.12/run/t8764.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/t8764.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.12/run/t9387b.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/t9387b.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.12/run/t9387b.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/t9387b.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.12/run/try-catch-unify.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/try-catch-unify.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.12/run/try-catch-unify.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/try-catch-unify.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.12/run/virtpatmat_switch.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/virtpatmat_switch.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.12/run/virtpatmat_switch.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/virtpatmat_switch.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.12/run/virtpatmat_typetag.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/virtpatmat_typetag.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.12/run/virtpatmat_typetag.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/virtpatmat_typetag.check
diff --git a/project/Build.scala b/project/Build.scala
index d392347803..fb1d1efc85 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -933,6 +933,7 @@ object Build {
         "2.13.10",
         "2.13.11",
         "2.13.12",
+        "2.13.13",
       ),
 
       default212ScalaVersion := cross212ScalaVersions.value.last,
@@ -1779,6 +1780,21 @@ object Build {
       previousArtifactSetting,
       mimaBinaryIssueFilters ++= BinaryIncompatibilities.Library,
 
+      /* Silence a Scala 2.13.13+ warning that we cannot address without breaking our API.
+       * See `js.WrappedDictionary.keys` and `js.WrappedMap.keys`.
+       */
+      scalacOptions ++= {
+        /* We only need the option in 2.13.13+, but listing all previous 2.13.x
+         * versions is cumberson. We only exclude 2.13.0 and 2.13.1 because
+         * they did not support -Wconf at all.
+         */
+        val v = scalaVersion.value
+        if (v.startsWith("2.13.") && v != "2.13.0" && v != "2.13.1")
+          List("-Wconf:msg=overriding method keys in trait MapOps is deprecated:s")
+        else
+          Nil
+      },
+
       test in Test := {
         streams.value.log.warn("Skipping library/test. Run testSuite/test to test library.")
       },
@@ -2016,14 +2032,14 @@ object Build {
           case `default213Version` =>
             if (!useMinifySizes) {
               Some(ExpectedSizes(
-                  fastLink = 452000 to 453000,
+                  fastLink = 451000 to 452000,
                   fullLink = 94000 to 95000,
                   fastLinkGz = 58000 to 59000,
                   fullLinkGz = 25000 to 26000,
               ))
             } else {
               Some(ExpectedSizes(
-                  fastLink = 309000 to 310000,
+                  fastLink = 308000 to 309000,
                   fullLink = 265000 to 266000,
                   fastLinkGz = 49000 to 50000,
                   fullLinkGz = 43000 to 44000,
diff --git a/sbt-plugin/src/sbt-test/cross-version/2.13/build.sbt b/sbt-plugin/src/sbt-test/cross-version/2.13/build.sbt
index 66419e36d6..9eaf7236fc 100644
--- a/sbt-plugin/src/sbt-test/cross-version/2.13/build.sbt
+++ b/sbt-plugin/src/sbt-test/cross-version/2.13/build.sbt
@@ -2,6 +2,6 @@ enablePlugins(ScalaJSPlugin)
 enablePlugins(ScalaJSJUnitPlugin)
 
 version := scalaJSVersion
-scalaVersion := "2.13.12"
+scalaVersion := "2.13.13"
 
 scalaJSUseMainModuleInitializer := true
diff --git a/sbt-plugin/src/sbt-test/scala3/tasty-reader/build.sbt b/sbt-plugin/src/sbt-test/scala3/tasty-reader/build.sbt
index 283968ec84..a0af60a58e 100644
--- a/sbt-plugin/src/sbt-test/scala3/tasty-reader/build.sbt
+++ b/sbt-plugin/src/sbt-test/scala3/tasty-reader/build.sbt
@@ -10,7 +10,7 @@ lazy val app = project.in(file("app"))
   .enablePlugins(ScalaJSPlugin)
   .dependsOn(testlib)
   .settings(
-    scalaVersion := "2.13.12",
+    scalaVersion := "2.13.13",
     scalacOptions += "-Ytasty-reader",
     scalaJSUseMainModuleInitializer := true
   )
diff --git a/scala-test-suite/src/test/resources/2.13.13/BlacklistedTests.txt b/scala-test-suite/src/test/resources/2.13.13/BlacklistedTests.txt
new file mode 100644
index 0000000000..c813883a16
--- /dev/null
+++ b/scala-test-suite/src/test/resources/2.13.13/BlacklistedTests.txt
@@ -0,0 +1,247 @@
+## Do not compile
+scala/ExtractorTest.scala
+scala/OptionTest.scala
+scala/SerializationStabilityTest.scala
+scala/StringTest.scala
+scala/collection/FactoriesTest.scala
+scala/collection/LazyZipOpsTest.scala
+scala/collection/SeqTest.scala
+scala/collection/immutable/HashMapTest.scala
+scala/collection/immutable/HashSetTest.scala
+scala/collection/immutable/IndexedSeqTest.scala
+scala/collection/immutable/IntMapTest.scala
+scala/collection/immutable/LazyListTest.scala
+scala/collection/immutable/ListMapTest.scala
+scala/collection/immutable/LongMapTest.scala
+scala/collection/immutable/MapHashcodeTest.scala
+scala/collection/immutable/SeqTest.scala
+scala/collection/immutable/SmallMapTest.scala
+scala/collection/immutable/SortedMapTest.scala
+scala/collection/immutable/SortedSetTest.scala
+scala/collection/immutable/TreeMapTest.scala
+scala/collection/immutable/TreeSetTest.scala
+scala/lang/annotations/BytecodeTest.scala
+scala/lang/annotations/RunTest.scala
+scala/lang/traits/BytecodeTest.scala
+scala/lang/traits/RunTest.scala
+scala/lang/primitives/NaNTest.scala
+scala/reflect/ClassOfTest.scala
+scala/reflect/FieldAccessTest.scala
+scala/reflect/QTest.scala
+scala/reflect/macros/AttachmentsTest.scala
+scala/reflect/io/ZipArchiveTest.scala
+scala/reflect/internal/InferTest.scala
+scala/reflect/internal/LongNamesTest.scala
+scala/reflect/internal/MirrorsTest.scala
+scala/reflect/internal/NamesTest.scala
+scala/reflect/internal/PositionsTest.scala
+scala/reflect/internal/PrintersTest.scala
+scala/reflect/internal/ScopeTest.scala
+scala/reflect/internal/SubstMapTest.scala
+scala/reflect/internal/TreeGenTest.scala
+scala/reflect/internal/TypesTest.scala
+scala/reflect/internal/util/AbstractFileClassLoaderTest.scala
+scala/reflect/internal/util/FileUtilsTest.scala
+scala/reflect/internal/util/SourceFileTest.scala
+scala/reflect/internal/util/StringOpsTest.scala
+scala/reflect/internal/util/WeakHashSetTest.scala
+scala/reflect/io/AbstractFileTest.scala
+scala/reflect/runtime/ReflectionUtilsShowTest.scala
+scala/reflect/runtime/ThreadSafetyTest.scala
+scala/runtime/BooleanBoxingTest.scala
+scala/runtime/ByteBoxingTest.scala
+scala/runtime/CharBoxingTest.scala
+scala/runtime/DoubleBoxingTest.scala
+scala/runtime/IntBoxingTest.scala
+scala/runtime/FloatBoxingTest.scala
+scala/runtime/LongBoxingTest.scala
+scala/runtime/ShortBoxingTest.scala
+scala/tools/nsc/Build.scala
+scala/tools/nsc/DeterminismTest.scala
+scala/tools/nsc/DeterminismTester.scala
+scala/tools/nsc/FileUtils.scala
+scala/tools/nsc/GlobalCustomizeClassloaderTest.scala
+scala/tools/nsc/MainRunnerTest.scala
+scala/tools/nsc/PhaseAssemblyTest.scala
+scala/tools/nsc/PickleWriteTest.scala
+scala/tools/nsc/PipelineMainTest.scala
+scala/tools/nsc/ScriptRunnerTest.scala
+scala/tools/nsc/async/AnnotationDrivenAsyncTest.scala
+scala/tools/nsc/async/CustomFuture.scala
+scala/tools/nsc/backend/jvm/BTypesTest.scala
+scala/tools/nsc/backend/jvm/BytecodeTest.scala
+scala/tools/nsc/backend/jvm/ClassfileParserTest.scala
+scala/tools/nsc/backend/jvm/DefaultMethodTest.scala
+scala/tools/nsc/backend/jvm/DirectCompileTest.scala
+scala/tools/nsc/backend/jvm/GenericSignaturesTest.scala
+scala/tools/nsc/backend/jvm/IndyLambdaTest.scala
+scala/tools/nsc/backend/jvm/IndySammyTest.scala
+scala/tools/nsc/backend/jvm/InnerClassAttributeTest.scala
+scala/tools/nsc/backend/jvm/LineNumberTest.scala
+scala/tools/nsc/backend/jvm/NestedClassesCollectorTest.scala
+scala/tools/nsc/backend/jvm/OptimizedBytecodeTest.scala
+scala/tools/nsc/backend/jvm/PerRunInitTest.scala
+scala/tools/nsc/backend/jvm/StringConcatTest.scala
+scala/tools/nsc/backend/jvm/analysis/NullnessAnalyzerTest.scala
+scala/tools/nsc/backend/jvm/analysis/ProdConsAnalyzerTest.scala
+scala/tools/nsc/backend/jvm/analysis/TypeFlowAnalyzerTest.scala
+scala/tools/nsc/backend/jvm/opt/AnalyzerTest.scala
+scala/tools/nsc/backend/jvm/opt/BTypesFromClassfileTest.scala
+scala/tools/nsc/backend/jvm/opt/BoxUnboxAndInlineTest.scala
+scala/tools/nsc/backend/jvm/opt/BoxUnboxTest.scala
+scala/tools/nsc/backend/jvm/opt/CallGraphTest.scala
+scala/tools/nsc/backend/jvm/opt/ClosureOptimizerTest.scala
+scala/tools/nsc/backend/jvm/opt/CompactLocalVariablesTest.scala
+scala/tools/nsc/backend/jvm/opt/EmptyExceptionHandlersTest.scala
+scala/tools/nsc/backend/jvm/opt/EmptyLabelsAndLineNumbersTest.scala
+scala/tools/nsc/backend/jvm/opt/InlineInfoTest.scala
+scala/tools/nsc/backend/jvm/opt/InlinerIllegalAccessTest.scala
+scala/tools/nsc/backend/jvm/opt/InlinerSeparateCompilationTest.scala
+scala/tools/nsc/backend/jvm/opt/InlinerTest.scala
+scala/tools/nsc/backend/jvm/opt/InlineSourceMatcherTest.scala
+scala/tools/nsc/backend/jvm/opt/InlineWarningTest.scala
+scala/tools/nsc/backend/jvm/opt/MethodLevelOptsTest.scala
+scala/tools/nsc/backend/jvm/opt/ScalaInlineInfoTest.scala
+scala/tools/nsc/backend/jvm/opt/SimplifyJumpsTest.scala
+scala/tools/nsc/backend/jvm/opt/UnreachableCodeTest.scala
+scala/tools/nsc/backend/jvm/opt/UnusedLocalVariablesTest.scala
+scala/tools/nsc/classpath/AggregateClassPathTest.scala
+scala/tools/nsc/classpath/JrtClassPathTest.scala
+scala/tools/nsc/classpath/MultiReleaseJarTest.scala
+scala/tools/nsc/classpath/PathResolverBaseTest.scala
+scala/tools/nsc/classpath/VirtualDirectoryClassPathTest.scala
+scala/tools/nsc/classpath/ZipAndJarFileLookupFactoryTest.scala
+scala/tools/nsc/doc/html/HtmlDocletTest.scala
+scala/tools/nsc/doc/html/ModelFactoryTest.scala
+scala/tools/nsc/doc/html/StringLiteralTest.scala
+scala/tools/nsc/interpreter/CompletionTest.scala
+scala/tools/nsc/interpreter/ScriptedTest.scala
+scala/tools/nsc/interpreter/TabulatorTest.scala
+scala/tools/nsc/parser/ParserTest.scala
+scala/tools/nsc/reporters/ConsoleReporterTest.scala
+scala/tools/nsc/reporters/PositionFilterTest.scala
+scala/tools/nsc/reporters/WConfTest.scala
+scala/tools/nsc/reporters/AbstractCodeActionTest.scala
+scala/tools/nsc/reporters/CodeActionXsource3Test.scala
+scala/tools/nsc/reporters/CodeActionTest.scala
+scala/tools/nsc/settings/ScalaVersionTest.scala
+scala/tools/nsc/settings/SettingsTest.scala
+scala/tools/nsc/settings/TargetTest.scala
+scala/tools/nsc/symtab/CannotHaveAttrsTest.scala
+scala/tools/nsc/symtab/FlagsTest.scala
+scala/tools/nsc/symtab/FreshNameExtractorTest.scala
+scala/tools/nsc/symtab/StdNamesTest.scala
+scala/tools/nsc/symtab/SymbolTableForUnitTesting.scala
+scala/tools/nsc/symtab/SymbolTableTest.scala
+scala/tools/nsc/symtab/classfile/PicklerTest.scala
+scala/tools/nsc/transform/ErasureTest.scala
+scala/tools/nsc/transform/MixinTest.scala
+scala/tools/nsc/transform/ReleaseFenceTest.scala
+scala/tools/nsc/transform/SpecializationTest.scala
+scala/tools/nsc/transform/ThicketTransformerTest.scala
+scala/tools/nsc/transform/UncurryTest.scala
+scala/tools/nsc/transform/delambdafy/DelambdafyTest.scala
+scala/tools/nsc/transform/patmat/SolvingTest.scala
+scala/tools/nsc/transform/patmat/PatmatBytecodeTest.scala
+scala/tools/nsc/typechecker/ConstantFolderTest.scala
+scala/tools/nsc/typechecker/ImplicitsTest.scala
+scala/tools/nsc/typechecker/InferencerTest.scala
+scala/tools/nsc/typechecker/NamerTest.scala
+scala/tools/nsc/typechecker/OverridingPairsTest.scala
+scala/tools/nsc/typechecker/ParamAliasTest.scala
+scala/tools/nsc/typechecker/TreeAttachmentTest.scala
+scala/tools/nsc/typechecker/TypedTreeTest.scala
+scala/tools/nsc/QuickfixTest.scala
+scala/tools/nsc/util/StackTraceTest.scala
+scala/tools/testkit/ReflectUtilTest.scala
+scala/tools/xsbt/BridgeTesting.scala
+scala/tools/xsbt/BasicBridgeTest.scala
+scala/tools/xsbt/ClassNameTest.scala
+scala/tools/xsbt/CodeActionTest.scala
+scala/tools/xsbt/DependencyTest.scala
+scala/tools/xsbt/ExtractAPITest.scala
+scala/tools/xsbt/ExtractUsedNamesTest.scala
+scala/tools/xsbt/InteractiveConsoleInterfaceTest.scala
+scala/tools/xsbt/SameAPI.scala
+scala/tools/xsbt/TestCallback.scala
+scala/util/ChainingOpsTest.scala
+
+## Do not link
+scala/CollectTest.scala
+scala/MatchErrorSerializationTest.scala
+scala/PartialFunctionSerializationTest.scala
+scala/lang/stringinterpol/StringContextTest.scala
+scala/collection/IterableTest.scala
+scala/collection/IteratorTest.scala
+scala/collection/NewBuilderTest.scala
+scala/collection/SeqViewTest.scala
+scala/collection/SetMapConsistencyTest.scala
+scala/collection/SetMapRulesTest.scala
+scala/collection/Sizes.scala
+scala/collection/ViewTest.scala
+scala/collection/concurrent/TrieMapTest.scala
+scala/collection/convert/EqualsTest.scala
+scala/collection/convert/JConcurrentMapWrapperTest.scala
+scala/collection/convert/WrapperSerializationTest.scala
+scala/collection/immutable/ChampMapSmokeTest.scala
+scala/collection/immutable/ChampSetSmokeTest.scala
+scala/collection/immutable/LazyListGCTest.scala
+scala/collection/immutable/LazyListLazinessTest.scala
+scala/collection/immutable/ListTest.scala
+scala/collection/immutable/SerializationTest.scala
+scala/collection/immutable/StreamTest.scala
+scala/collection/immutable/StringLikeTest.scala
+scala/collection/immutable/VectorTest.scala
+scala/collection/mutable/AnyRefMapTest.scala
+scala/collection/mutable/ArrayBufferTest.scala
+scala/collection/mutable/ListBufferTest.scala
+scala/collection/mutable/OpenHashMapTest.scala
+scala/collection/mutable/PriorityQueueTest.scala
+scala/collection/mutable/SerializationTest.scala
+scala/concurrent/FutureTest.scala
+scala/concurrent/duration/SerializationTest.scala
+scala/concurrent/impl/DefaultPromiseTest.scala
+scala/io/SourceTest.scala
+scala/jdk/AccumulatorTest.scala
+scala/jdk/DurationConvertersTest.scala
+scala/jdk/FunctionConvertersTest.scala
+scala/jdk/OptionConvertersTest.scala
+scala/jdk/StepperConversionTest.scala
+scala/jdk/StepperTest.scala
+scala/jdk/StreamConvertersTest.scala
+scala/jdk/StreamConvertersTypingTest.scala
+scala/math/OrderingTest.scala
+scala/runtime/ScalaRunTimeTest.scala
+scala/sys/env.scala
+scala/sys/process/ParserTest.scala
+scala/sys/process/PipedProcessTest.scala
+scala/sys/process/ProcessBuilderTest.scala
+scala/sys/process/ProcessTest.scala
+scala/tools/testkit/AssertUtilTest.scala
+scala/util/PropertiesTest.scala
+scala/util/SpecVersionTest.scala
+scala/util/SystemPropertiesTest.scala
+
+## Tests fail
+
+# Reflection
+scala/reflect/ClassTagTest.scala
+
+# Require strict-floats
+scala/math/BigDecimalTest.scala
+
+# Tests passed but are too slow (timeouts)
+scala/collection/immutable/ListSetTest.scala
+scala/util/SortingTest.scala
+
+# Whitebox testing of ArrayBuilder.ofUnit
+scala/collection/mutable/ArrayBuilderTest.scala
+
+# Relies on undefined behavior
+scala/collection/MapTest.scala
+scala/collection/StringOpsTest.scala
+scala/collection/StringParsersTest.scala
+scala/collection/convert/CollectionConvertersTest.scala
+scala/collection/convert/MapWrapperTest.scala
+scala/collection/immutable/NumericRangeTest.scala
+scala/math/BigIntTest.scala

From ba98bb274e910a3318fc0832fb720ab50c159e69 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Sun, 17 Mar 2024 17:11:15 +0100
Subject: [PATCH 073/298] Version 1.16.0.

---
 ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala b/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala
index 91d113055f..e932635d21 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala
@@ -17,8 +17,8 @@ import java.util.concurrent.ConcurrentHashMap
 import scala.util.matching.Regex
 
 object ScalaJSVersions extends VersionChecks(
-    current = "1.16.0-SNAPSHOT",
-    binaryEmitted = "1.16-SNAPSHOT"
+    current = "1.16.0",
+    binaryEmitted = "1.16"
 )
 
 /** Helper class to allow for testing of logic. */

From 80eafa9ecb54f6763c0df32350c9c6cd8e7343c5 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Mon, 18 Mar 2024 13:20:08 +0100
Subject: [PATCH 074/298] Towards 1.16.1.

---
 .../org/scalajs/ir/ScalaJSVersions.scala      |  2 +-
 project/BinaryIncompatibilities.scala         | 21 -------------------
 project/Build.scala                           |  2 +-
 3 files changed, 2 insertions(+), 23 deletions(-)

diff --git a/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala b/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala
index e932635d21..eb920f2071 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala
@@ -17,7 +17,7 @@ import java.util.concurrent.ConcurrentHashMap
 import scala.util.matching.Regex
 
 object ScalaJSVersions extends VersionChecks(
-    current = "1.16.0",
+    current = "1.16.1-SNAPSHOT",
     binaryEmitted = "1.16"
 )
 
diff --git a/project/BinaryIncompatibilities.scala b/project/BinaryIncompatibilities.scala
index e37b343839..4713fe6bf8 100644
--- a/project/BinaryIncompatibilities.scala
+++ b/project/BinaryIncompatibilities.scala
@@ -5,30 +5,9 @@ import com.typesafe.tools.mima.core.ProblemFilters._
 
 object BinaryIncompatibilities {
   val IR = Seq(
-    // !!! Breaking, OK in minor release
-
-    ProblemFilters.exclude[MissingTypesProblem]("org.scalajs.ir.Names$FieldName"),
-    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Names#FieldName.*"),
-    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Names#LocalName.fromFieldName"),
-
-    ProblemFilters.exclude[IncompatibleMethTypeProblem]("org.scalajs.ir.Types#RecordType.findField"),
-    ProblemFilters.exclude[MemberProblem]("org.scalajs.ir.Types#RecordType#Field.*"),
-
-    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Trees#StoreModule.*"),
-    ProblemFilters.exclude[IncompatibleResultTypeProblem]("org.scalajs.ir.Trees#StoreModule.unapply"),
-
-    ProblemFilters.exclude[MemberProblem]("org.scalajs.ir.Trees#JSPrivateSelect.*"),
-    ProblemFilters.exclude[MemberProblem]("org.scalajs.ir.Trees#RecordSelect.*"),
-    ProblemFilters.exclude[MemberProblem]("org.scalajs.ir.Trees#Select.*"),
-    ProblemFilters.exclude[MemberProblem]("org.scalajs.ir.Trees#SelectStatic.*"),
   )
 
   val Linker = Seq(
-    // !!! Breaking, OK in minor release
-    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.linker.standard.LinkedClass.this"),
-
-    // private, not an issue
-    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.linker.standard.CommonPhaseConfig.this"),
   )
 
   val LinkerInterface = Seq(
diff --git a/project/Build.scala b/project/Build.scala
index fb1d1efc85..6460bd86bf 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -367,7 +367,7 @@ object Build {
   val previousVersions = List("1.0.0", "1.0.1", "1.1.0", "1.1.1", "1.2.0",
       "1.3.0", "1.3.1", "1.4.0", "1.5.0", "1.5.1", "1.6.0", "1.7.0", "1.7.1",
       "1.8.0", "1.9.0", "1.10.0", "1.10.1", "1.11.0", "1.12.0", "1.13.0",
-      "1.13.1", "1.13.2", "1.14.0", "1.15.0")
+      "1.13.1", "1.13.2", "1.14.0", "1.15.0", "1.16.0")
   val previousVersion = previousVersions.last
 
   val previousBinaryCrossVersion = CrossVersion.binaryWith("sjs1_", "")

From c8f34b9bb4e3b3fd43a12041d80ac27207ad0432 Mon Sep 17 00:00:00 2001
From: "dependabot[bot]" <49699333+dependabot[bot]@users.noreply.github.com>
Date: Thu, 28 Mar 2024 21:51:03 +0000
Subject: [PATCH 075/298] Bump express from 4.18.2 to 4.19.2

Bumps [express](https://github.com/expressjs/express) from 4.18.2 to 4.19.2.
- [Release notes](https://github.com/expressjs/express/releases)
- [Changelog](https://github.com/expressjs/express/blob/master/History.md)
- [Commits](https://github.com/expressjs/express/compare/4.18.2...4.19.2)

---
updated-dependencies:
- dependency-name: express
  dependency-type: direct:development
...

Signed-off-by: dependabot[bot] <support@github.com>
---
 package-lock.json | 140 +++++++++++++++++++---------------------------
 package.json      |   2 +-
 2 files changed, 58 insertions(+), 84 deletions(-)

diff --git a/package-lock.json b/package-lock.json
index 9ab82aa9f1..78045751fb 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -5,7 +5,7 @@
   "packages": {
     "": {
       "devDependencies": {
-        "express": "4.18.2",
+        "express": "4.19.2",
         "jsdom": "16.7.0",
         "jszip": "3.8.0",
         "source-map-support": "0.5.19"
@@ -130,13 +130,13 @@
       "dev": true
     },
     "node_modules/body-parser": {
-      "version": "1.20.1",
-      "resolved": "https://registry.npmjs.org/body-parser/-/body-parser-1.20.1.tgz",
-      "integrity": "sha512-jWi7abTbYwajOytWCQc37VulmWiRae5RyTpaCyDcS5/lMdtwSz5lOpDE67srw/HYe35f1z3fDQw+3txg7gNtWw==",
+      "version": "1.20.2",
+      "resolved": "https://registry.npmjs.org/body-parser/-/body-parser-1.20.2.tgz",
+      "integrity": "sha512-ml9pReCu3M61kGlqoTm2umSXTlRTuGTx0bfYj+uIUKKYycG5NtSbeetV3faSU6R7ajOPw0g/J1PvK4qNy7s5bA==",
       "dev": true,
       "dependencies": {
         "bytes": "3.1.2",
-        "content-type": "~1.0.4",
+        "content-type": "~1.0.5",
         "debug": "2.6.9",
         "depd": "2.0.0",
         "destroy": "1.2.0",
@@ -144,7 +144,7 @@
         "iconv-lite": "0.4.24",
         "on-finished": "2.4.1",
         "qs": "6.11.0",
-        "raw-body": "2.5.1",
+        "raw-body": "2.5.2",
         "type-is": "~1.6.18",
         "unpipe": "1.0.0"
       },
@@ -153,21 +153,6 @@
         "npm": "1.2.8000 || >= 1.4.16"
       }
     },
-    "node_modules/body-parser/node_modules/qs": {
-      "version": "6.11.0",
-      "resolved": "https://registry.npmjs.org/qs/-/qs-6.11.0.tgz",
-      "integrity": "sha512-MvjoMCJwEarSbUYk5O+nmoSzSutSsTwF85zcHPQ9OrlFoZOYIjaqBAJIqIXjptyD5vThxGq52Xu/MaJzRkIk4Q==",
-      "dev": true,
-      "dependencies": {
-        "side-channel": "^1.0.4"
-      },
-      "engines": {
-        "node": ">=0.6"
-      },
-      "funding": {
-        "url": "https://github.com/sponsors/ljharb"
-      }
-    },
     "node_modules/browser-process-hrtime": {
       "version": "1.0.0",
       "resolved": "https://registry.npmjs.org/browser-process-hrtime/-/browser-process-hrtime-1.0.0.tgz",
@@ -256,9 +241,9 @@
       }
     },
     "node_modules/cookie": {
-      "version": "0.5.0",
-      "resolved": "https://registry.npmjs.org/cookie/-/cookie-0.5.0.tgz",
-      "integrity": "sha512-YZ3GUyn/o8gfKJlnlX7g7xq4gyO6OSuhGPKaaGssGB2qgDUS0gPgtTvoyZLTt9Ab6dC4hfc9dV5arkvc/OCmrw==",
+      "version": "0.6.0",
+      "resolved": "https://registry.npmjs.org/cookie/-/cookie-0.6.0.tgz",
+      "integrity": "sha512-U71cyTamuh1CRNCfpGY6to28lxvNwPG4Guz/EVjgf3Jmzv0vlDp1atT9eS5dDjMYHucpHbWns6Lwf3BKz6svdw==",
       "dev": true,
       "engines": {
         "node": ">= 0.6"
@@ -468,17 +453,17 @@
       }
     },
     "node_modules/express": {
-      "version": "4.18.2",
-      "resolved": "https://registry.npmjs.org/express/-/express-4.18.2.tgz",
-      "integrity": "sha512-5/PsL6iGPdfQ/lKM1UuielYgv3BUoJfz1aUwU9vHZ+J7gyvwdQXFEBIEIaxeGf0GIcreATNyBExtalisDbuMqQ==",
+      "version": "4.19.2",
+      "resolved": "https://registry.npmjs.org/express/-/express-4.19.2.tgz",
+      "integrity": "sha512-5T6nhjsT+EOMzuck8JjBHARTHfMht0POzlA60WV2pMD3gyXw2LZnZ+ueGdNxG+0calOJcWKbpFcuzLZ91YWq9Q==",
       "dev": true,
       "dependencies": {
         "accepts": "~1.3.8",
         "array-flatten": "1.1.1",
-        "body-parser": "1.20.1",
+        "body-parser": "1.20.2",
         "content-disposition": "0.5.4",
         "content-type": "~1.0.4",
-        "cookie": "0.5.0",
+        "cookie": "0.6.0",
         "cookie-signature": "1.0.6",
         "debug": "2.6.9",
         "depd": "2.0.0",
@@ -509,21 +494,6 @@
         "node": ">= 0.10.0"
       }
     },
-    "node_modules/express/node_modules/qs": {
-      "version": "6.11.0",
-      "resolved": "https://registry.npmjs.org/qs/-/qs-6.11.0.tgz",
-      "integrity": "sha512-MvjoMCJwEarSbUYk5O+nmoSzSutSsTwF85zcHPQ9OrlFoZOYIjaqBAJIqIXjptyD5vThxGq52Xu/MaJzRkIk4Q==",
-      "dev": true,
-      "dependencies": {
-        "side-channel": "^1.0.4"
-      },
-      "engines": {
-        "node": ">=0.6"
-      },
-      "funding": {
-        "url": "https://github.com/sponsors/ljharb"
-      }
-    },
     "node_modules/express/node_modules/safe-buffer": {
       "version": "5.2.1",
       "resolved": "https://registry.npmjs.org/safe-buffer/-/safe-buffer-5.2.1.tgz",
@@ -1062,6 +1032,21 @@
         "node": ">=6"
       }
     },
+    "node_modules/qs": {
+      "version": "6.11.0",
+      "resolved": "https://registry.npmjs.org/qs/-/qs-6.11.0.tgz",
+      "integrity": "sha512-MvjoMCJwEarSbUYk5O+nmoSzSutSsTwF85zcHPQ9OrlFoZOYIjaqBAJIqIXjptyD5vThxGq52Xu/MaJzRkIk4Q==",
+      "dev": true,
+      "dependencies": {
+        "side-channel": "^1.0.4"
+      },
+      "engines": {
+        "node": ">=0.6"
+      },
+      "funding": {
+        "url": "https://github.com/sponsors/ljharb"
+      }
+    },
     "node_modules/querystringify": {
       "version": "2.2.0",
       "resolved": "https://registry.npmjs.org/querystringify/-/querystringify-2.2.0.tgz",
@@ -1078,9 +1063,9 @@
       }
     },
     "node_modules/raw-body": {
-      "version": "2.5.1",
-      "resolved": "https://registry.npmjs.org/raw-body/-/raw-body-2.5.1.tgz",
-      "integrity": "sha512-qqJBtEyVgS0ZmPGdCFPWJ3FreoqvG4MVQln/kCgF7Olq95IbOp0/BWyMwbdtn4VTvkM8Y7khCQ2Xgk/tcrCXig==",
+      "version": "2.5.2",
+      "resolved": "https://registry.npmjs.org/raw-body/-/raw-body-2.5.2.tgz",
+      "integrity": "sha512-8zGqypfENjCIqGhgXToC8aB2r7YrBX+AQAfIPs/Mlk+BtPTztOvTS01NRW/3Eh60J+a48lt8qsCzirQ6loCVfA==",
       "dev": true,
       "dependencies": {
         "bytes": "3.1.2",
@@ -1562,13 +1547,13 @@
       "dev": true
     },
     "body-parser": {
-      "version": "1.20.1",
-      "resolved": "https://registry.npmjs.org/body-parser/-/body-parser-1.20.1.tgz",
-      "integrity": "sha512-jWi7abTbYwajOytWCQc37VulmWiRae5RyTpaCyDcS5/lMdtwSz5lOpDE67srw/HYe35f1z3fDQw+3txg7gNtWw==",
+      "version": "1.20.2",
+      "resolved": "https://registry.npmjs.org/body-parser/-/body-parser-1.20.2.tgz",
+      "integrity": "sha512-ml9pReCu3M61kGlqoTm2umSXTlRTuGTx0bfYj+uIUKKYycG5NtSbeetV3faSU6R7ajOPw0g/J1PvK4qNy7s5bA==",
       "dev": true,
       "requires": {
         "bytes": "3.1.2",
-        "content-type": "~1.0.4",
+        "content-type": "~1.0.5",
         "debug": "2.6.9",
         "depd": "2.0.0",
         "destroy": "1.2.0",
@@ -1576,20 +1561,9 @@
         "iconv-lite": "0.4.24",
         "on-finished": "2.4.1",
         "qs": "6.11.0",
-        "raw-body": "2.5.1",
+        "raw-body": "2.5.2",
         "type-is": "~1.6.18",
         "unpipe": "1.0.0"
-      },
-      "dependencies": {
-        "qs": {
-          "version": "6.11.0",
-          "resolved": "https://registry.npmjs.org/qs/-/qs-6.11.0.tgz",
-          "integrity": "sha512-MvjoMCJwEarSbUYk5O+nmoSzSutSsTwF85zcHPQ9OrlFoZOYIjaqBAJIqIXjptyD5vThxGq52Xu/MaJzRkIk4Q==",
-          "dev": true,
-          "requires": {
-            "side-channel": "^1.0.4"
-          }
-        }
       }
     },
     "browser-process-hrtime": {
@@ -1653,9 +1627,9 @@
       "dev": true
     },
     "cookie": {
-      "version": "0.5.0",
-      "resolved": "https://registry.npmjs.org/cookie/-/cookie-0.5.0.tgz",
-      "integrity": "sha512-YZ3GUyn/o8gfKJlnlX7g7xq4gyO6OSuhGPKaaGssGB2qgDUS0gPgtTvoyZLTt9Ab6dC4hfc9dV5arkvc/OCmrw==",
+      "version": "0.6.0",
+      "resolved": "https://registry.npmjs.org/cookie/-/cookie-0.6.0.tgz",
+      "integrity": "sha512-U71cyTamuh1CRNCfpGY6to28lxvNwPG4Guz/EVjgf3Jmzv0vlDp1atT9eS5dDjMYHucpHbWns6Lwf3BKz6svdw==",
       "dev": true
     },
     "cookie-signature": {
@@ -1816,17 +1790,17 @@
       "dev": true
     },
     "express": {
-      "version": "4.18.2",
-      "resolved": "https://registry.npmjs.org/express/-/express-4.18.2.tgz",
-      "integrity": "sha512-5/PsL6iGPdfQ/lKM1UuielYgv3BUoJfz1aUwU9vHZ+J7gyvwdQXFEBIEIaxeGf0GIcreATNyBExtalisDbuMqQ==",
+      "version": "4.19.2",
+      "resolved": "https://registry.npmjs.org/express/-/express-4.19.2.tgz",
+      "integrity": "sha512-5T6nhjsT+EOMzuck8JjBHARTHfMht0POzlA60WV2pMD3gyXw2LZnZ+ueGdNxG+0calOJcWKbpFcuzLZ91YWq9Q==",
       "dev": true,
       "requires": {
         "accepts": "~1.3.8",
         "array-flatten": "1.1.1",
-        "body-parser": "1.20.1",
+        "body-parser": "1.20.2",
         "content-disposition": "0.5.4",
         "content-type": "~1.0.4",
-        "cookie": "0.5.0",
+        "cookie": "0.6.0",
         "cookie-signature": "1.0.6",
         "debug": "2.6.9",
         "depd": "2.0.0",
@@ -1854,15 +1828,6 @@
         "vary": "~1.1.2"
       },
       "dependencies": {
-        "qs": {
-          "version": "6.11.0",
-          "resolved": "https://registry.npmjs.org/qs/-/qs-6.11.0.tgz",
-          "integrity": "sha512-MvjoMCJwEarSbUYk5O+nmoSzSutSsTwF85zcHPQ9OrlFoZOYIjaqBAJIqIXjptyD5vThxGq52Xu/MaJzRkIk4Q==",
-          "dev": true,
-          "requires": {
-            "side-channel": "^1.0.4"
-          }
-        },
         "safe-buffer": {
           "version": "5.2.1",
           "resolved": "https://registry.npmjs.org/safe-buffer/-/safe-buffer-5.2.1.tgz",
@@ -2279,6 +2244,15 @@
       "integrity": "sha512-rRV+zQD8tVFys26lAGR9WUuS4iUAngJScM+ZRSKtvl5tKeZ2t5bvdNFdNHBW9FWR4guGHlgmsZ1G7BSm2wTbuA==",
       "dev": true
     },
+    "qs": {
+      "version": "6.11.0",
+      "resolved": "https://registry.npmjs.org/qs/-/qs-6.11.0.tgz",
+      "integrity": "sha512-MvjoMCJwEarSbUYk5O+nmoSzSutSsTwF85zcHPQ9OrlFoZOYIjaqBAJIqIXjptyD5vThxGq52Xu/MaJzRkIk4Q==",
+      "dev": true,
+      "requires": {
+        "side-channel": "^1.0.4"
+      }
+    },
     "querystringify": {
       "version": "2.2.0",
       "resolved": "https://registry.npmjs.org/querystringify/-/querystringify-2.2.0.tgz",
@@ -2292,9 +2266,9 @@
       "dev": true
     },
     "raw-body": {
-      "version": "2.5.1",
-      "resolved": "https://registry.npmjs.org/raw-body/-/raw-body-2.5.1.tgz",
-      "integrity": "sha512-qqJBtEyVgS0ZmPGdCFPWJ3FreoqvG4MVQln/kCgF7Olq95IbOp0/BWyMwbdtn4VTvkM8Y7khCQ2Xgk/tcrCXig==",
+      "version": "2.5.2",
+      "resolved": "https://registry.npmjs.org/raw-body/-/raw-body-2.5.2.tgz",
+      "integrity": "sha512-8zGqypfENjCIqGhgXToC8aB2r7YrBX+AQAfIPs/Mlk+BtPTztOvTS01NRW/3Eh60J+a48lt8qsCzirQ6loCVfA==",
       "dev": true,
       "requires": {
         "bytes": "3.1.2",
diff --git a/package.json b/package.json
index 9301eea5bc..d091e07ea6 100644
--- a/package.json
+++ b/package.json
@@ -1,7 +1,7 @@
 {
   "private": true,
   "devDependencies": {
-    "express": "4.18.2",
+    "express": "4.19.2",
     "jsdom": "16.7.0",
     "jszip": "3.8.0",
     "source-map-support": "0.5.19"

From 05f39f54db00e417e3b05002af8712996a6d927c Mon Sep 17 00:00:00 2001
From: Tobias Schlatter <tobias@meisch.ch>
Date: Sun, 17 Mar 2024 10:37:44 +0100
Subject: [PATCH 076/298] Compress SourceMapWriter.Fragment data

We use a similar compression strategy than source maps themselves to
reduce the in-memory footprint.

After linking the test suite, residual memory usage is as follows:

| what              | main [MB] | PR [MB] |
|-------------------|----------:|--------:|
| sbt overall heap  |       842 |     772 |
| backend retained  |       147 |      77 |
| frontend retained |       215 |     215 |
---
 .../linker/backend/BasicLinkerBackend.scala   |  15 +-
 .../backend/javascript/SourceMapWriter.scala  | 302 +++++++++++++-----
 2 files changed, 227 insertions(+), 90 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/BasicLinkerBackend.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/BasicLinkerBackend.scala
index fa7e616880..3c1125348e 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/BasicLinkerBackend.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/BasicLinkerBackend.scala
@@ -41,9 +41,11 @@ final class BasicLinkerBackend(config: LinkerBackendImpl.Config)
   private[this] var totalModules = 0
   private[this] val rewrittenModules = new AtomicInteger(0)
 
+  private[this] val fragmentIndex = new SourceMapWriter.Index
+
   private[this] val bodyPrinter: BodyPrinter = {
     if (config.minify) IdentityPostTransformerBasedBodyPrinter
-    else if (config.sourceMap) PrintedTreeWithSourceMapBodyPrinter
+    else if (config.sourceMap) new PrintedTreeWithSourceMapBodyPrinter(fragmentIndex)
     else PrintedTreeWithoutSourceMapBodyPrinter
   }
 
@@ -127,7 +129,7 @@ final class BasicLinkerBackend(config: LinkerBackendImpl.Config)
           val sourceMapURI = OutputPatternsImpl.sourceMapURI(config.outputPatterns, moduleID.id)
 
           val smWriter = new SourceMapWriter(sourceMapWriter, jsFileURI,
-              config.relativizeSourceMapBase)
+              config.relativizeSourceMapBase, fragmentIndex)
 
           jsFileWriter.write(printedModuleSetCache.headerBytes)
           for (_ <- 0 until printedModuleSetCache.headerNewLineCount)
@@ -288,8 +290,8 @@ private object BasicLinkerBackend {
   private object PrintedTreeWithoutSourceMapBodyPrinter
       extends PrintedTreeBasedBodyPrinter(PostTransformerWithoutSourceMap)
 
-  private object PrintedTreeWithSourceMapBodyPrinter
-      extends PrintedTreeBasedBodyPrinter(PostTransformerWithSourceMap)
+  private class PrintedTreeWithSourceMapBodyPrinter(fragmentIndex: SourceMapWriter.Index)
+      extends PrintedTreeBasedBodyPrinter(new PostTransformerWithSourceMap(fragmentIndex))
 
   private object PostTransformerWithoutSourceMap extends Emitter.PostTransformer[js.PrintedTree] {
     def transformStats(trees: List[js.Tree], indent: Int): List[js.PrintedTree] = {
@@ -306,13 +308,14 @@ private object BasicLinkerBackend {
     }
   }
 
-  private object PostTransformerWithSourceMap extends Emitter.PostTransformer[js.PrintedTree] {
+  private class PostTransformerWithSourceMap(fragmentIndex: SourceMapWriter.Index)
+      extends Emitter.PostTransformer[js.PrintedTree] {
     def transformStats(trees: List[js.Tree], indent: Int): List[js.PrintedTree] = {
       if (trees.isEmpty) {
         Nil // Fast path
       } else {
         val jsCodeWriter = new ByteArrayWriter()
-        val smFragmentBuilder = new SourceMapWriter.FragmentBuilder()
+        val smFragmentBuilder = new SourceMapWriter.FragmentBuilder(fragmentIndex)
         val printer = new Printers.JSTreePrinterWithSourceMap(jsCodeWriter, smFragmentBuilder, indent)
 
         trees.foreach(printer.printStat(_))
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/SourceMapWriter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/SourceMapWriter.scala
index 17b8380891..d46b90dd6a 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/SourceMapWriter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/SourceMapWriter.scala
@@ -16,8 +16,10 @@ import java.io._
 import java.net.URI
 import java.nio.ByteBuffer
 import java.nio.charset.StandardCharsets
+import java.util.concurrent.ConcurrentHashMap
 import java.{util => ju}
 
+import scala.annotation.switch
 import scala.collection.mutable.{ArrayBuffer, ListBuffer}
 
 import org.scalajs.ir
@@ -36,6 +38,12 @@ object SourceMapWriter {
   private final val VLQBaseMask = VLQBase - 1
   private final val VLQContinuationBit = VLQBase
 
+  // Constants for fragments
+  private final val FragNewLine = 0
+  private final val FragColOnly = 1
+  private final val FragColAndPos = 2
+  private final val FragColPosName = 3
+
   private final class NodePosStack {
     private var topIndex: Int = -1
     private var posStack: Array[Position] = new Array(128)
@@ -66,24 +74,14 @@ object SourceMapWriter {
     }
   }
 
-  private sealed abstract class FragmentElement
-
-  private object FragmentElement {
-    case object NewLine extends FragmentElement
-
-    // name is nullable
-    final case class Segment(columnInGenerated: Int, pos: Position, name: String)
-        extends FragmentElement
-  }
-
   final class Fragment private[SourceMapWriter] (
-      private[SourceMapWriter] val elements: Array[FragmentElement])
+      private[SourceMapWriter] val data: Array[Byte]) extends AnyVal
 
   object Fragment {
     val Empty: Fragment = new Fragment(new Array(0))
   }
 
-  sealed abstract class Builder {
+  sealed abstract class Builder(fragmentIndex: Index) {
     // Strings are nullable in this stack
     private val nodePosStack = new SourceMapWriter.NodePosStack
     nodePosStack.push(NoPosition, null)
@@ -126,17 +124,43 @@ object SourceMapWriter {
     final def insertFragment(fragment: Fragment): Unit = {
       require(pendingColumnInGenerated < 0, s"Cannot add fragment when in the middle of a line")
 
-      val elements = fragment.elements
-      val len = elements.length
-      var i = 0
-      while (i != len) {
-        elements(i) match {
-          case FragmentElement.Segment(columnInGenerated, pos, name) =>
-            doWriteSegment(columnInGenerated, pos, name)
-          case FragmentElement.NewLine =>
+      val buf = ByteBuffer.wrap(fragment.data)
+
+      var columnInGenerated = 0
+      var sourceIndex = 0
+      var line: Int = 0
+      var column: Int = 0
+      var nameIndex: Int = 0
+
+      while (buf.hasRemaining()) {
+        (buf.get(): @switch) match {
+          case FragNewLine =>
             doWriteNewLine()
+
+          case FragColOnly =>
+            columnInGenerated += readRawVLQ(buf)
+            doWriteSegment(columnInGenerated, null, 0, 0, null)
+
+          case FragColAndPos =>
+            columnInGenerated += readRawVLQ(buf)
+            sourceIndex += readRawVLQ(buf)
+            line += readRawVLQ(buf)
+            column += readRawVLQ(buf)
+
+            val source = fragmentIndex.sources(sourceIndex)
+            doWriteSegment(columnInGenerated, source, line, column, null)
+
+          case FragColPosName =>
+            columnInGenerated += readRawVLQ(buf)
+            sourceIndex += readRawVLQ(buf)
+            line += readRawVLQ(buf)
+            column += readRawVLQ(buf)
+            nameIndex += readRawVLQ(buf)
+
+            val source = fragmentIndex.sources(sourceIndex)
+            val name = fragmentIndex.names(nameIndex)
+            doWriteSegment(columnInGenerated, source, line, column, name)
         }
-        i += 1
       }
     }
 
@@ -169,47 +193,177 @@ object SourceMapWriter {
     }
 
     private def writePendingSegment(): Unit = {
-      if (pendingColumnInGenerated >= 0)
-        doWriteSegment(pendingColumnInGenerated, pendingPos, pendingName)
+      if (pendingColumnInGenerated >= 0) {
+        if (pendingPos.isEmpty) {
+          doWriteSegment(pendingColumnInGenerated, null, 0, 0, null)
+        } else {
+          doWriteSegment(pendingColumnInGenerated,
+              pendingPos.source, pendingPos.line, pendingPos.column, pendingName)
+        }
+      }
+    }
+
+    private def readRawVLQ(buf: ByteBuffer): Int = {
+      var shift = 0
+      var value = 0
+
+      while ({
+        val i = buf.get()
+        value |= (i & 0x7f) << shift
+        (i & 0x80) != 0
+      }) {
+        shift += 7
+      }
+
+      val neg = (value & 1) != 0
+      value >>>= 1
+
+      /* technically, in the neg branch, we'd need to map
+       * value == 0 to Int.MinValue. However, given that this is not a realistic
+       * value for what we are dealing with here, we skip that check to avoid a
+       * branch.
+       */
+      if (neg) -value else value
     }
 
     protected def doWriteNewLine(): Unit
 
-    protected def doWriteSegment(columnInGenerated: Int, pos: Position, name: String): Unit
+    protected def doWriteSegment(columnInGenerated: Int, source: SourceFile, line: Int, column: Int, name: String): Unit
 
     protected def doComplete(): Unit
   }
 
-  final class FragmentBuilder extends Builder {
-    private val elements = new ArrayBuffer[FragmentElement]
+  final class FragmentBuilder(index: Index) extends Builder(index) {
+    private val data = new ByteArrayWriter()
+
+    private var lastColumnInGenerated = 0
+    private var lastSource: SourceFile = null
+    private var lastSourceIndex = 0
+    private var lastLine: Int = 0
+    private var lastColumn: Int = 0
+    private var lastNameIndex: Int = 0
 
     protected def doWriteNewLine(): Unit =
-      elements += FragmentElement.NewLine
+      data.write(FragNewLine)
+
+    protected def doWriteSegment(columnInGenerated: Int, source: SourceFile,
+        line: Int, column: Int, name: String): Unit = {
+      val MaxSegmentLength = 1 + 5 * 5 // segment type + max 5 rawVLQ of max 5 bytes each
+      val buffer = data.unsafeStartDirectWrite(maxBytes = MaxSegmentLength)
+      var offset = data.currentSize
+
+      // Write segment type
+      buffer(offset) = {
+        if (source == null) FragColOnly
+        else if (name == null) FragColAndPos
+        else FragColPosName
+      }
+      offset += 1
+
+      offset = writeRawVLQ(buffer, offset, columnInGenerated-lastColumnInGenerated)
+      lastColumnInGenerated = columnInGenerated
+
+      if (source != null) {
+        if (source eq lastSource) { // highly likely
+          buffer(offset) = 0
+          offset += 1
+        } else {
+          val sourceIndex = index.sourceToIndex(source)
+          offset = writeRawVLQ(buffer, offset, sourceIndex-lastSourceIndex)
+          lastSource = source
+          lastSourceIndex = sourceIndex
+        }
 
-    protected def doWriteSegment(columnInGenerated: Int, pos: Position, name: String): Unit =
-      elements += FragmentElement.Segment(columnInGenerated, pos, name)
+        // Line field
+        offset = writeRawVLQ(buffer, offset, line - lastLine)
+        lastLine = line
 
-    protected def doComplete(): Unit = {
-      if (elements.nonEmpty && elements.last != FragmentElement.NewLine)
-        throw new IllegalStateException("Trying to complete a fragment in the middle of a line")
+        // Column field
+        offset = writeRawVLQ(buffer, offset, column - lastColumn)
+        lastColumn = column
+
+        // Name field
+        if (name != null) {
+          val nameIndex = index.nameToIndex(name)
+          offset = writeRawVLQ(buffer, offset, nameIndex-lastNameIndex)
+          lastNameIndex = nameIndex
+        }
+      }
+      data.unsafeEndDirectWrite(offset)
+    }
+
+    protected def doComplete(): Unit = ()
+
+    private def writeRawVLQ(buffer: Array[Byte], offset0: Int, value0: Int): Int = {
+      // See comment in writeBase64VLQ
+      val signExtended = value0 >> 31
+      var value = (((value0 ^ signExtended) - signExtended) << 1) | (signExtended & 1)
+
+      var offset = offset0
+
+      while ({
+        if ((value & ~0x7f) != 0)
+          buffer(offset) = ((value & 0x7f) | 0x80).toByte
+        else
+          buffer(offset) = (value & 0x7f).toByte
+
+        offset += 1
+        value >>>= 7
+
+        value != 0
+      }) ()
+
+      offset
     }
 
     def result(): Fragment =
-      new Fragment(elements.toArray)
+      new Fragment(data.toByteArray())
+  }
+
+  final class Index {
+    private[SourceMapWriter] val sources = new ArrayBuffer[SourceFile]
+    private val _srcToIndex = new ConcurrentHashMap[SourceFile, Integer]
+
+    private[SourceMapWriter] val names = new ArrayBuffer[String]
+    private val _nameToIndex = new ConcurrentHashMap[String, Integer]
+
+    private[SourceMapWriter] def sourceToIndex(source: SourceFile): Int = {
+      val existing = _srcToIndex.get(source)
+      if (existing != null) {
+        existing.intValue()
+      } else {
+        sources.synchronized {
+          val index = sources.size
+          _srcToIndex.put(source, index)
+          sources += source
+          index
+        }
+      }
+    }
+
+    private[SourceMapWriter] def nameToIndex(name: String): Int = {
+      val existing = _nameToIndex.get(name)
+      if (existing != null) {
+        existing.intValue()
+      } else {
+        names.synchronized {
+          val index = names.size
+          _nameToIndex.put(name, index)
+          names += name
+          index
+        }
+      }
+    }
   }
 }
 
 final class SourceMapWriter(out: ByteArrayWriter, jsFileName: String,
-    relativizeBaseURI: Option[URI])
-    extends SourceMapWriter.Builder {
+    relativizeBaseURI: Option[URI], fragmentIndex: SourceMapWriter.Index)
+    extends SourceMapWriter.Builder(fragmentIndex) {
 
   import SourceMapWriter._
 
-  private val sources = new ListBuffer[SourceFile]
-  private val _srcToIndex = new ju.HashMap[SourceFile, Integer]
-
-  private val names = new ListBuffer[String]
-  private val _nameToIndex = new ju.HashMap[String, Integer]
+  private val outIndex = new Index
 
   private var lineCountInGenerated = 0
   private var lastColumnInGenerated = 0
@@ -222,30 +376,6 @@ final class SourceMapWriter(out: ByteArrayWriter, jsFileName: String,
 
   writeHeader()
 
-  private def sourceToIndex(source: SourceFile): Int = {
-    val existing = _srcToIndex.get(source)
-    if (existing != null) {
-      existing.intValue()
-    } else {
-      val index = sources.size
-      _srcToIndex.put(source, index)
-      sources += source
-      index
-    }
-  }
-
-  private def nameToIndex(name: String): Int = {
-    val existing = _nameToIndex.get(name)
-    if (existing != null) {
-      existing.intValue()
-    } else {
-      val index = names.size
-      _nameToIndex.put(name, index)
-      names += name
-      index
-    }
-  }
-
   private def writeJSONString(s: String): Unit = {
     out.write('\"')
     out.writeASCIIEscapedJSString(s)
@@ -266,7 +396,8 @@ final class SourceMapWriter(out: ByteArrayWriter, jsFileName: String,
     firstSegmentOfLine = true
   }
 
-  protected def doWriteSegment(columnInGenerated: Int, pos: Position, name: String): Unit = {
+  protected def doWriteSegment(columnInGenerated: Int, source: SourceFile,
+      line: Int, column: Int, name: String): Unit = {
     // scalastyle:off return
 
     /* This method is incredibly performance-sensitive, so we resort to
@@ -288,23 +419,18 @@ final class SourceMapWriter(out: ByteArrayWriter, jsFileName: String,
     offset = writeBase64VLQ(buffer, offset, columnInGenerated-lastColumnInGenerated)
     lastColumnInGenerated = columnInGenerated
 
-    // If the position is NoPosition, stop here
-    if (pos.isEmpty) {
+    if (source == null) {
+      // The position was NoPosition, stop here
       out.unsafeEndDirectWrite(offset)
       return
     }
 
-    // Extract relevant properties of pendingPos
-    val source = pos.source
-    val line = pos.line
-    val column = pos.column
-
     // Source index field
     if (source eq lastSource) { // highly likely
       buffer(offset) = 'A' // 0 in Base64VLQ
       offset += 1
     } else {
-      val sourceIndex = sourceToIndex(source)
+      val sourceIndex = outIndex.sourceToIndex(source)
       offset = writeBase64VLQ(buffer, offset, sourceIndex-lastSourceIndex)
       lastSource = source
       lastSourceIndex = sourceIndex
@@ -320,7 +446,7 @@ final class SourceMapWriter(out: ByteArrayWriter, jsFileName: String,
 
     // Name field
     if (name != null) {
-      val nameIndex = nameToIndex(name)
+      val nameIndex = outIndex.nameToIndex(name)
       offset = writeBase64VLQ(buffer, offset, nameIndex-lastNameIndex)
       lastNameIndex = nameIndex
     }
@@ -332,21 +458,29 @@ final class SourceMapWriter(out: ByteArrayWriter, jsFileName: String,
 
   protected def doComplete(): Unit = {
     val relativizeBaseURI = this.relativizeBaseURI // local copy
-    var restSources = sources.result()
+    val sources = outIndex.sources // local copy
+    val sourcesLen = sources.length
+
     out.writeASCIIString("\",\n\"sources\": [")
-    while (restSources.nonEmpty) {
-      writeJSONString(SourceFileUtil.webURI(relativizeBaseURI, restSources.head))
-      restSources = restSources.tail
-      if (restSources.nonEmpty)
+
+    var i = 0
+    while (i < sourcesLen) {
+      writeJSONString(SourceFileUtil.webURI(relativizeBaseURI, sources(i)))
+      i += 1
+      if (i < sourcesLen)
         out.writeASCIIString(", ")
     }
 
-    var restNames = names.result()
+    val names = outIndex.names // local copy
+    val namesLen = names.length
+
     out.writeASCIIString("],\n\"names\": [")
-    while (restNames.nonEmpty) {
-      writeJSONString(restNames.head)
-      restNames = restNames.tail
-      if (restNames.nonEmpty)
+
+    i = 0
+    while (i < namesLen) {
+      writeJSONString(names(i))
+      i += 1
+      if (i < namesLen)
         out.writeASCIIString(", ")
     }
     out.writeASCIIString("],\n\"lineCount\": ")

From 448eb1eb4f6e072863b6b3e4f8a5a5ac53d785f0 Mon Sep 17 00:00:00 2001
From: Tobias Schlatter <tobias@meisch.ch>
Date: Sun, 10 Mar 2024 16:17:23 +0100
Subject: [PATCH 077/298] Remove nested post transforms

They are not useful and only make us consume more memory.

I initially introduced them because it looked like downstream could
avoid running post transforms at all. This seems to not be the case,
so there is no point in attempting to provide it.
---
 .../linker/backend/BasicLinkerBackend.scala   |  77 ++---------
 .../linker/backend/emitter/Emitter.scala      | 129 ++++++++----------
 .../org/scalajs/linker/EmitterTest.scala      |  15 +-
 3 files changed, 78 insertions(+), 143 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/BasicLinkerBackend.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/BasicLinkerBackend.scala
index 3c1125348e..2d6feafa4f 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/BasicLinkerBackend.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/BasicLinkerBackend.scala
@@ -43,19 +43,19 @@ final class BasicLinkerBackend(config: LinkerBackendImpl.Config)
 
   private[this] val fragmentIndex = new SourceMapWriter.Index
 
-  private[this] val bodyPrinter: BodyPrinter = {
-    if (config.minify) IdentityPostTransformerBasedBodyPrinter
-    else if (config.sourceMap) new PrintedTreeWithSourceMapBodyPrinter(fragmentIndex)
-    else PrintedTreeWithoutSourceMapBodyPrinter
-  }
+  private[this] val emitter: Emitter = {
+    val postTransformer = {
+      if (config.minify) Emitter.PostTransformer.Identity
+      else if (config.sourceMap) new PostTransformerWithSourceMap(fragmentIndex)
+      else PostTransformerWithoutSourceMap
+    }
 
-  private[this] val emitter: Emitter[bodyPrinter.TreeType] = {
     val emitterConfig = Emitter.Config(config.commonConfig.coreSpec)
       .withJSHeader(config.jsHeader)
       .withInternalModulePattern(m => OutputPatternsImpl.moduleName(config.outputPatterns, m.id))
       .withMinify(config.minify)
 
-    new Emitter(emitterConfig, bodyPrinter.postTransformer)
+    new Emitter(emitterConfig, postTransformer)
   }
 
   val symbolRequirements: SymbolRequirement = emitter.symbolRequirements
@@ -104,7 +104,9 @@ final class BasicLinkerBackend(config: LinkerBackendImpl.Config)
           jsFileWriter.write(printedModuleSetCache.headerBytes)
           jsFileWriter.writeASCIIString("'use strict';\n")
 
-          bodyPrinter.printWithoutSourceMap(trees, jsFileWriter)
+          val printer = new Printers.JSTreePrinter(jsFileWriter)
+          for (tree <- trees)
+            printer.printStat(tree)
 
           jsFileWriter.write(printedModuleSetCache.footerBytes)
 
@@ -138,7 +140,9 @@ final class BasicLinkerBackend(config: LinkerBackendImpl.Config)
           jsFileWriter.writeASCIIString("'use strict';\n")
           smWriter.nextLine()
 
-          bodyPrinter.printWithSourceMap(trees, jsFileWriter, smWriter)
+          val printer = new Printers.JSTreePrinterWithSourceMap(jsFileWriter, smWriter, initIndent = 0)
+          for (tree <- trees)
+            printer.printStat(tree)
 
           jsFileWriter.write(printedModuleSetCache.footerBytes)
           jsFileWriter.write(("//# sourceMappingURL=" + sourceMapURI + "\n").getBytes(StandardCharsets.UTF_8))
@@ -242,58 +246,7 @@ private object BasicLinkerBackend {
     }
   }
 
-  private abstract class BodyPrinter {
-    type TreeType >: Null <: js.Tree
-
-    val postTransformer: Emitter.PostTransformer[TreeType]
-
-    def printWithoutSourceMap(trees: List[TreeType], jsFileWriter: ByteArrayWriter): Unit
-    def printWithSourceMap(trees: List[TreeType], jsFileWriter: ByteArrayWriter, smWriter: SourceMapWriter): Unit
-  }
-
-  private object IdentityPostTransformerBasedBodyPrinter extends BodyPrinter {
-    type TreeType = js.Tree
-
-    val postTransformer: Emitter.PostTransformer[TreeType] = Emitter.PostTransformer.Identity
-
-    def printWithoutSourceMap(trees: List[TreeType], jsFileWriter: ByteArrayWriter): Unit = {
-      val printer = new Printers.JSTreePrinter(jsFileWriter)
-      for (tree <- trees)
-        printer.printStat(tree)
-    }
-
-    def printWithSourceMap(trees: List[TreeType], jsFileWriter: ByteArrayWriter, smWriter: SourceMapWriter): Unit = {
-      val printer = new Printers.JSTreePrinterWithSourceMap(jsFileWriter, smWriter, initIndent = 0)
-      for (tree <- trees)
-        printer.printStat(tree)
-    }
-  }
-
-  private abstract class PrintedTreeBasedBodyPrinter(
-    val postTransformer: Emitter.PostTransformer[js.PrintedTree]
-  ) extends BodyPrinter {
-    type TreeType = js.PrintedTree
-
-    def printWithoutSourceMap(trees: List[TreeType], jsFileWriter: ByteArrayWriter): Unit = {
-      for (tree <- trees)
-        jsFileWriter.write(tree.jsCode)
-    }
-
-    def printWithSourceMap(trees: List[TreeType], jsFileWriter: ByteArrayWriter, smWriter: SourceMapWriter): Unit = {
-      for (tree <- trees) {
-        jsFileWriter.write(tree.jsCode)
-        smWriter.insertFragment(tree.sourceMapFragment)
-      }
-    }
-  }
-
-  private object PrintedTreeWithoutSourceMapBodyPrinter
-      extends PrintedTreeBasedBodyPrinter(PostTransformerWithoutSourceMap)
-
-  private class PrintedTreeWithSourceMapBodyPrinter(fragmentIndex: SourceMapWriter.Index)
-      extends PrintedTreeBasedBodyPrinter(new PostTransformerWithSourceMap(fragmentIndex))
-
-  private object PostTransformerWithoutSourceMap extends Emitter.PostTransformer[js.PrintedTree] {
+  private object PostTransformerWithoutSourceMap extends Emitter.PostTransformer {
     def transformStats(trees: List[js.Tree], indent: Int): List[js.PrintedTree] = {
       if (trees.isEmpty) {
         Nil // Fast path
@@ -309,7 +262,7 @@ private object BasicLinkerBackend {
   }
 
   private class PostTransformerWithSourceMap(fragmentIndex: SourceMapWriter.Index)
-      extends Emitter.PostTransformer[js.PrintedTree] {
+      extends Emitter.PostTransformer {
     def transformStats(trees: List[js.Tree], indent: Int): List[js.PrintedTree] = {
       if (trees.isEmpty) {
         Nil // Fast path
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala
index 9d49e5855b..a5f851cea0 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala
@@ -33,8 +33,7 @@ import EmitterNames._
 import GlobalRefUtils._
 
 /** Emits a desugared JS tree to a builder */
-final class Emitter[E >: Null <: js.Tree](
-    config: Emitter.Config, postTransformer: Emitter.PostTransformer[E]) {
+final class Emitter(config: Emitter.Config, postTransformer: Emitter.PostTransformer) {
 
   import Emitter._
   import config._
@@ -64,7 +63,7 @@ final class Emitter[E >: Null <: js.Tree](
 
     val classEmitter: ClassEmitter = new ClassEmitter(sjsGen)
 
-    val everyFileStart: List[E] = {
+    val everyFileStart: List[js.Tree] = {
       // This postTransform does not count in the statistics
       postTransformer.transformStats(sjsGen.declarePrototypeVar, 0)
     }
@@ -88,15 +87,13 @@ final class Emitter[E >: Null <: js.Tree](
   private[this] var statsMethodsReused: Int = 0
   private[this] var statsMethodsInvalidated: Int = 0
   private[this] var statsPostTransforms: Int = 0
-  private[this] var statsNestedPostTransforms: Int = 0
-  private[this] var statsNestedPostTransformsAvoided: Int = 0
 
   val symbolRequirements: SymbolRequirement =
     Emitter.symbolRequirements(config)
 
   val injectedIRFiles: Seq[IRFile] = PrivateLibHolder.files
 
-  def emit(moduleSet: ModuleSet, logger: Logger): Result[E] = {
+  def emit(moduleSet: ModuleSet, logger: Logger): Result = {
     val WithGlobals(body, globalRefs) = emitInternal(moduleSet, logger)
 
     val result = moduleKind match {
@@ -140,15 +137,13 @@ final class Emitter[E >: Null <: js.Tree](
   }
 
   private def emitInternal(moduleSet: ModuleSet,
-      logger: Logger): WithGlobals[Map[ModuleID, (List[E], Boolean)]] = {
+      logger: Logger): WithGlobals[Map[ModuleID, (List[js.Tree], Boolean)]] = {
     // Reset caching stats.
     statsClassesReused = 0
     statsClassesInvalidated = 0
     statsMethodsReused = 0
     statsMethodsInvalidated = 0
     statsPostTransforms = 0
-    statsNestedPostTransforms = 0
-    statsNestedPostTransformsAvoided = 0
 
     // Update GlobalKnowledge.
     val invalidateAll = knowledgeGuardian.update(moduleSet)
@@ -170,10 +165,7 @@ final class Emitter[E >: Null <: js.Tree](
       logger.debug(
           s"Emitter: Method tree cache stats: reused: $statsMethodsReused -- "+
           s"invalidated: $statsMethodsInvalidated")
-      logger.debug(
-          s"Emitter: Post transforms: total: $statsPostTransforms -- " +
-          s"nested: $statsNestedPostTransforms -- " +
-          s"nested avoided: $statsNestedPostTransformsAvoided")
+      logger.debug(s"Emitter: Post transforms: $statsPostTransforms")
 
       // Inform caches about run completion.
       state.moduleCaches.filterInPlace((_, c) => c.cleanAfterRun())
@@ -181,12 +173,12 @@ final class Emitter[E >: Null <: js.Tree](
     }
   }
 
-  private def postTransform(trees: List[js.Tree], indent: Int): List[E] = {
+  private def postTransform(trees: List[js.Tree], indent: Int): List[js.Tree] = {
     statsPostTransforms += 1
     postTransformer.transformStats(trees, indent)
   }
 
-  private def postTransform(tree: js.Tree, indent: Int): List[E] =
+  private def postTransform(tree: js.Tree, indent: Int): List[js.Tree] =
     postTransform(tree :: Nil, indent)
 
   /** Emits all JavaScript code avoiding clashes with global refs.
@@ -197,7 +189,7 @@ final class Emitter[E >: Null <: js.Tree](
    */
   @tailrec
   private def emitAvoidGlobalClash(moduleSet: ModuleSet,
-      logger: Logger, secondAttempt: Boolean): WithGlobals[Map[ModuleID, (List[E], Boolean)]] = {
+      logger: Logger, secondAttempt: Boolean): WithGlobals[Map[ModuleID, (List[js.Tree], Boolean)]] = {
     val result = emitOnce(moduleSet, logger)
 
     val mentionedDangerousGlobalRefs =
@@ -223,7 +215,7 @@ final class Emitter[E >: Null <: js.Tree](
   }
 
   private def emitOnce(moduleSet: ModuleSet,
-      logger: Logger): WithGlobals[Map[ModuleID, (List[E], Boolean)]] = {
+      logger: Logger): WithGlobals[Map[ModuleID, (List[js.Tree], Boolean)]] = {
     // Genreate classes first so we can measure time separately.
     val generatedClasses = logger.time("Emitter: Generate Classes") {
       moduleSet.modules.map { module =>
@@ -297,7 +289,7 @@ final class Emitter[E >: Null <: js.Tree](
          * requires consistency between the Analyzer and the Emitter. As such,
          * it is crucial that we verify it.
          */
-        val defTrees: List[E] = (
+        val defTrees: List[js.Tree] = (
             /* The declaration of the `$p` variable that temporarily holds
              * prototypes.
              */
@@ -418,7 +410,7 @@ final class Emitter[E >: Null <: js.Tree](
   }
 
   private def genClass(linkedClass: LinkedClass,
-      moduleContext: ModuleContext): GeneratedClass[E] = {
+      moduleContext: ModuleContext): GeneratedClass = {
     val className = linkedClass.className
 
     val classCache = classCaches.getOrElseUpdate(
@@ -449,7 +441,7 @@ final class Emitter[E >: Null <: js.Tree](
 
     // Main part
 
-    val main = List.newBuilder[E]
+    val main = List.newBuilder[js.Tree]
 
     val (linkedInlineableInit, linkedMethods) =
       classEmitter.extractInlineableInit(linkedClass)(classCache)
@@ -679,14 +671,7 @@ final class Emitter[E >: Null <: js.Tree](
             allMembers // invalidated directly
           )(moduleContext, fullClassChangeTracker, linkedClass.pos) // pos invalidated by class version
         } yield {
-          // Avoid a nested post transform if we just got the original members back.
-          if (clazz eq allMembers) {
-            statsNestedPostTransformsAvoided += 1
-            allMembers
-          } else {
-            statsNestedPostTransforms += 1
-            postTransform(clazz, 0)
-          }
+          clazz
         }
       }
 
@@ -774,14 +759,14 @@ final class Emitter[E >: Null <: js.Tree](
   private final class ModuleCache extends knowledgeGuardian.KnowledgeAccessor {
     private[this] var _cacheUsed: Boolean = false
 
-    private[this] var _importsCache: WithGlobals[List[E]] = WithGlobals.nil
+    private[this] var _importsCache: WithGlobals[List[js.Tree]] = WithGlobals.nil
     private[this] var _lastExternalDependencies: Set[String] = Set.empty
     private[this] var _lastInternalDependencies: Set[ModuleID] = Set.empty
 
-    private[this] var _topLevelExportsCache: WithGlobals[List[E]] = WithGlobals.nil
+    private[this] var _topLevelExportsCache: WithGlobals[List[js.Tree]] = WithGlobals.nil
     private[this] var _lastTopLevelExports: List[LinkedTopLevelExport] = Nil
 
-    private[this] var _initializersCache: WithGlobals[List[E]] = WithGlobals.nil
+    private[this] var _initializersCache: WithGlobals[List[js.Tree]] = WithGlobals.nil
     private[this] var _lastInitializers: List[ModuleInitializer.Initializer] = Nil
 
     override def invalidate(): Unit = {
@@ -802,7 +787,7 @@ final class Emitter[E >: Null <: js.Tree](
     }
 
     def getOrComputeImports(externalDependencies: Set[String], internalDependencies: Set[ModuleID])(
-        compute: => WithGlobals[List[E]]): (WithGlobals[List[E]], Boolean) = {
+        compute: => WithGlobals[List[js.Tree]]): (WithGlobals[List[js.Tree]], Boolean) = {
 
       _cacheUsed = true
 
@@ -818,7 +803,7 @@ final class Emitter[E >: Null <: js.Tree](
     }
 
     def getOrComputeTopLevelExports(topLevelExports: List[LinkedTopLevelExport])(
-        compute: => WithGlobals[List[E]]): (WithGlobals[List[E]], Boolean) = {
+        compute: => WithGlobals[List[js.Tree]]): (WithGlobals[List[js.Tree]], Boolean) = {
 
       _cacheUsed = true
 
@@ -859,7 +844,7 @@ final class Emitter[E >: Null <: js.Tree](
     }
 
     def getOrComputeInitializers(initializers: List[ModuleInitializer.Initializer])(
-        compute: => WithGlobals[List[E]]): (WithGlobals[List[E]], Boolean) = {
+        compute: => WithGlobals[List[js.Tree]]): (WithGlobals[List[js.Tree]], Boolean) = {
 
       _cacheUsed = true
 
@@ -880,20 +865,20 @@ final class Emitter[E >: Null <: js.Tree](
   }
 
   private final class ClassCache extends knowledgeGuardian.KnowledgeAccessor {
-    private[this] var _cache: DesugaredClassCache[List[E]] = null
+    private[this] var _cache: DesugaredClassCache = null
     private[this] var _lastVersion: Version = Version.Unversioned
     private[this] var _cacheUsed = false
 
     private[this] val _methodCaches =
-      Array.fill(MemberNamespace.Count)(mutable.Map.empty[MethodName, MethodCache[List[E]]])
+      Array.fill(MemberNamespace.Count)(mutable.Map.empty[MethodName, MethodCache[List[js.Tree]]])
 
     private[this] val _memberMethodCache =
-      mutable.Map.empty[MethodName, MethodCache[List[E]]]
+      mutable.Map.empty[MethodName, MethodCache[List[js.Tree]]]
 
-    private[this] var _constructorCache: Option[MethodCache[List[E]]] = None
+    private[this] var _constructorCache: Option[MethodCache[List[js.Tree]]] = None
 
     private[this] val _exportedMembersCache =
-      mutable.Map.empty[Int, MethodCache[List[E]]]
+      mutable.Map.empty[Int, MethodCache[List[js.Tree]]]
 
     private[this] var _fullClassChangeTracker: Option[FullClassChangeTracker] = None
 
@@ -914,13 +899,13 @@ final class Emitter[E >: Null <: js.Tree](
       _fullClassChangeTracker.foreach(_.startRun())
     }
 
-    def getCache(version: Version): (DesugaredClassCache[List[E]], Boolean) = {
+    def getCache(version: Version): (DesugaredClassCache, Boolean) = {
       _cacheUsed = true
       if (_cache == null || !_lastVersion.sameVersion(version)) {
         invalidate()
         statsClassesInvalidated += 1
         _lastVersion = version
-        _cache = new DesugaredClassCache[List[E]]
+        _cache = new DesugaredClassCache
         (_cache, true)
       } else {
         statsClassesReused += 1
@@ -929,25 +914,25 @@ final class Emitter[E >: Null <: js.Tree](
     }
 
     def getMemberMethodCache(
-        methodName: MethodName): MethodCache[List[E]] = {
+        methodName: MethodName): MethodCache[List[js.Tree]] = {
       _memberMethodCache.getOrElseUpdate(methodName, new MethodCache)
     }
 
     def getStaticLikeMethodCache(namespace: MemberNamespace,
-        methodName: MethodName): MethodCache[List[E]] = {
+        methodName: MethodName): MethodCache[List[js.Tree]] = {
       _methodCaches(namespace.ordinal)
         .getOrElseUpdate(methodName, new MethodCache)
     }
 
-    def getConstructorCache(): MethodCache[List[E]] = {
+    def getConstructorCache(): MethodCache[List[js.Tree]] = {
       _constructorCache.getOrElse {
-        val cache = new MethodCache[List[E]]
+        val cache = new MethodCache[List[js.Tree]]
         _constructorCache = Some(cache)
         cache
       }
     }
 
-    def getExportedMemberCache(idx: Int): MethodCache[List[E]] =
+    def getExportedMemberCache(idx: Int): MethodCache[List[js.Tree]] =
       _exportedMembersCache.getOrElseUpdate(idx, new MethodCache)
 
     def getFullClassChangeTracker(): FullClassChangeTracker = {
@@ -1015,9 +1000,9 @@ final class Emitter[E >: Null <: js.Tree](
 
   private class FullClassChangeTracker extends knowledgeGuardian.KnowledgeAccessor {
     private[this] var _lastVersion: Version = Version.Unversioned
-    private[this] var _lastCtor: WithGlobals[List[E]] = null
-    private[this] var _lastMemberMethods: List[WithGlobals[List[E]]] = null
-    private[this] var _lastExportedMembers: List[WithGlobals[List[E]]] = null
+    private[this] var _lastCtor: WithGlobals[List[js.Tree]] = null
+    private[this] var _lastMemberMethods: List[WithGlobals[List[js.Tree]]] = null
+    private[this] var _lastExportedMembers: List[WithGlobals[List[js.Tree]]] = null
     private[this] var _trackerUsed = false
 
     override def invalidate(): Unit = {
@@ -1030,9 +1015,9 @@ final class Emitter[E >: Null <: js.Tree](
 
     def startRun(): Unit = _trackerUsed = false
 
-    def trackChanged(version: Version, ctor: WithGlobals[List[E]],
-        memberMethods: List[WithGlobals[List[E]]],
-        exportedMembers: List[WithGlobals[List[E]]]): Boolean = {
+    def trackChanged(version: Version, ctor: WithGlobals[List[js.Tree]],
+        memberMethods: List[WithGlobals[List[js.Tree]]],
+        exportedMembers: List[WithGlobals[List[js.Tree]]]): Boolean = {
 
       @tailrec
       def allSame[A <: AnyRef](xs: List[A], ys: List[A]): Boolean = {
@@ -1074,9 +1059,9 @@ final class Emitter[E >: Null <: js.Tree](
 
   private class CoreJSLibCache extends knowledgeGuardian.KnowledgeAccessor {
     private[this] var _lastModuleContext: ModuleContext = _
-    private[this] var _lib: WithGlobals[CoreJSLib.Lib[List[E]]] = _
+    private[this] var _lib: WithGlobals[CoreJSLib.Lib[List[js.Tree]]] = _
 
-    def build(moduleContext: ModuleContext): WithGlobals[CoreJSLib.Lib[List[E]]] = {
+    def build(moduleContext: ModuleContext): WithGlobals[CoreJSLib.Lib[List[js.Tree]]] = {
       if (_lib == null || _lastModuleContext != moduleContext) {
         _lib = CoreJSLib.build(sjsGen, postTransform(_, 0), moduleContext, this)
         _lastModuleContext = moduleContext
@@ -1093,9 +1078,9 @@ final class Emitter[E >: Null <: js.Tree](
 
 object Emitter {
   /** Result of an emitter run. */
-  final class Result[E] private[Emitter](
+  final class Result private[Emitter](
       val header: String,
-      val body: Map[ModuleID, (List[E], Boolean)],
+      val body: Map[ModuleID, (List[js.Tree], Boolean)],
       val footer: String,
       val topLevelVarDecls: List[String],
       val globalRefs: Set[String]
@@ -1179,32 +1164,32 @@ object Emitter {
       new Config(coreSpec.semantics, coreSpec.moduleKind, coreSpec.esFeatures)
   }
 
-  trait PostTransformer[E] {
-    def transformStats(trees: List[js.Tree], indent: Int): List[E]
+  trait PostTransformer {
+    def transformStats(trees: List[js.Tree], indent: Int): List[js.Tree]
   }
 
   object PostTransformer {
-    object Identity extends PostTransformer[js.Tree] {
+    object Identity extends PostTransformer {
       def transformStats(trees: List[js.Tree], indent: Int): List[js.Tree] = trees
     }
   }
 
-  private final class DesugaredClassCache[E >: Null] {
-    val privateJSFields = new OneTimeCache[WithGlobals[E]]
-    val storeJSSuperClass = new OneTimeCache[WithGlobals[E]]
-    val instanceTests = new OneTimeCache[WithGlobals[E]]
-    val typeData = new InputEqualityCache[Boolean, WithGlobals[E]]
-    val setTypeData = new OneTimeCache[E]
-    val moduleAccessor = new OneTimeCache[WithGlobals[E]]
-    val staticInitialization = new OneTimeCache[E]
-    val staticFields = new OneTimeCache[WithGlobals[E]]
+  private final class DesugaredClassCache {
+    val privateJSFields = new OneTimeCache[WithGlobals[List[js.Tree]]]
+    val storeJSSuperClass = new OneTimeCache[WithGlobals[List[js.Tree]]]
+    val instanceTests = new OneTimeCache[WithGlobals[List[js.Tree]]]
+    val typeData = new InputEqualityCache[Boolean, WithGlobals[List[js.Tree]]]
+    val setTypeData = new OneTimeCache[List[js.Tree]]
+    val moduleAccessor = new OneTimeCache[WithGlobals[List[js.Tree]]]
+    val staticInitialization = new OneTimeCache[List[js.Tree]]
+    val staticFields = new OneTimeCache[WithGlobals[List[js.Tree]]]
   }
 
-  private final class GeneratedClass[E](
+  private final class GeneratedClass(
       val className: ClassName,
-      val main: List[E],
-      val staticFields: List[E],
-      val staticInitialization: List[E],
+      val main: List[js.Tree],
+      val staticFields: List[js.Tree],
+      val staticInitialization: List[js.Tree],
       val trackedGlobalRefs: Set[String],
       val changed: Boolean
   )
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/EmitterTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/EmitterTest.scala
index 50e726106e..450ff7c3fe 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/EmitterTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/EmitterTest.scala
@@ -137,7 +137,7 @@ class EmitterTest {
     raw"""Emitter: Method tree cache stats: reused: (\d+) -- invalidated: (\d+)""".r
 
   private val EmitterPostTransformStatsMessage =
-    raw"""Emitter: Post transforms: total: (\d+) -- nested: (\d+) -- nested avoided: (\d+)""".r
+    raw"""Emitter: Post transforms: (\d+)""".r
 
   /** Makes sure that linking a "substantial" program (using `println`) twice
    *  does not invalidate any cache or top-level tree in the second run.
@@ -208,21 +208,18 @@ class EmitterTest {
 
       // Post transforms
 
-      val Seq(postTransforms1, nestedPostTransforms1, _) =
+      val Seq(postTransforms1) =
         lines1.assertContainsMatch(EmitterPostTransformStatsMessage).map(_.toInt)
 
-      val Seq(postTransforms2, nestedPostTransforms2, _) =
+      val Seq(postTransforms2) =
         lines2.assertContainsMatch(EmitterPostTransformStatsMessage).map(_.toInt)
 
-      // At the time of writing this test, postTransforms1 reports 216
+      // At the time of writing this test, postTransforms1 reports 188
       assertTrue(
           s"Not enough post transforms (got $postTransforms1); extraction must have gone wrong",
-          postTransforms1 > 200)
+          postTransforms1 > 180)
 
-      assertEquals("Second run must only have nested post transforms",
-          nestedPostTransforms2, postTransforms2)
-      assertEquals("Both runs must have the same number of nested post transforms",
-          nestedPostTransforms1, nestedPostTransforms2)
+      assertEquals("Second run may not have post transforms", 0, postTransforms2)
     }
   }
 }

From 09336f33fc94aef65d60891e45916381042d6fb3 Mon Sep 17 00:00:00 2001
From: Tobias Schlatter <tobias@meisch.ch>
Date: Sun, 24 Mar 2024 13:50:31 +0100
Subject: [PATCH 078/298] Rename postTransform to prePrint in emitter

Further, we move the implementations fully into Emitter: At this point
its clear, that there won't really be any others (unless we
fundamentally change tree printing).
---
 .../closure/ClosureLinkerBackend.scala        |   8 +-
 .../linker/backend/BasicLinkerBackend.scala   |  43 +-------
 .../linker/backend/emitter/Emitter.scala      | 100 ++++++++++++------
 .../org/scalajs/linker/EmitterTest.scala      |  22 ++--
 4 files changed, 85 insertions(+), 88 deletions(-)

diff --git a/linker/jvm/src/main/scala/org/scalajs/linker/backend/closure/ClosureLinkerBackend.scala b/linker/jvm/src/main/scala/org/scalajs/linker/backend/closure/ClosureLinkerBackend.scala
index 7532e0be47..347465bf72 100644
--- a/linker/jvm/src/main/scala/org/scalajs/linker/backend/closure/ClosureLinkerBackend.scala
+++ b/linker/jvm/src/main/scala/org/scalajs/linker/backend/closure/ClosureLinkerBackend.scala
@@ -61,12 +61,10 @@ final class ClosureLinkerBackend(config: LinkerBackendImpl.Config)
       .withTrackAllGlobalRefs(true)
       .withInternalModulePattern(m => OutputPatternsImpl.moduleName(config.outputPatterns, m.id))
 
-    // Do not apply ClosureAstTransformer eagerly:
-    // The ASTs used by closure are highly mutable, so re-using them is non-trivial.
-    // Since closure is slow anyways, we haven't built the optimization.
-    val postTransformer = Emitter.PostTransformer.Identity
+    // Do not pre-print trees: We do not want the printed form.
+    val prePrinter = Emitter.PrePrinter.Off
 
-    new Emitter(emitterConfig, postTransformer)
+    new Emitter(emitterConfig, prePrinter)
   }
 
   val symbolRequirements: SymbolRequirement = emitter.symbolRequirements
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/BasicLinkerBackend.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/BasicLinkerBackend.scala
index 2d6feafa4f..74b4871503 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/BasicLinkerBackend.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/BasicLinkerBackend.scala
@@ -44,10 +44,10 @@ final class BasicLinkerBackend(config: LinkerBackendImpl.Config)
   private[this] val fragmentIndex = new SourceMapWriter.Index
 
   private[this] val emitter: Emitter = {
-    val postTransformer = {
-      if (config.minify) Emitter.PostTransformer.Identity
-      else if (config.sourceMap) new PostTransformerWithSourceMap(fragmentIndex)
-      else PostTransformerWithoutSourceMap
+    val prePrinter = {
+      if (config.minify) Emitter.PrePrinter.Off
+      else if (config.sourceMap) new Emitter.PrePrinter.WithSourceMap(fragmentIndex)
+      else Emitter.PrePrinter.WithoutSourceMap
     }
 
     val emitterConfig = Emitter.Config(config.commonConfig.coreSpec)
@@ -55,7 +55,7 @@ final class BasicLinkerBackend(config: LinkerBackendImpl.Config)
       .withInternalModulePattern(m => OutputPatternsImpl.moduleName(config.outputPatterns, m.id))
       .withMinify(config.minify)
 
-    new Emitter(emitterConfig, postTransformer)
+    new Emitter(emitterConfig, prePrinter)
   }
 
   val symbolRequirements: SymbolRequirement = emitter.symbolRequirements
@@ -245,37 +245,4 @@ private object BasicLinkerBackend {
       wasUsed
     }
   }
-
-  private object PostTransformerWithoutSourceMap extends Emitter.PostTransformer {
-    def transformStats(trees: List[js.Tree], indent: Int): List[js.PrintedTree] = {
-      if (trees.isEmpty) {
-        Nil // Fast path
-      } else {
-        val jsCodeWriter = new ByteArrayWriter()
-        val printer = new Printers.JSTreePrinter(jsCodeWriter, indent)
-
-        trees.foreach(printer.printStat(_))
-
-        js.PrintedTree(jsCodeWriter.toByteArray(), SourceMapWriter.Fragment.Empty) :: Nil
-      }
-    }
-  }
-
-  private class PostTransformerWithSourceMap(fragmentIndex: SourceMapWriter.Index)
-      extends Emitter.PostTransformer {
-    def transformStats(trees: List[js.Tree], indent: Int): List[js.PrintedTree] = {
-      if (trees.isEmpty) {
-        Nil // Fast path
-      } else {
-        val jsCodeWriter = new ByteArrayWriter()
-        val smFragmentBuilder = new SourceMapWriter.FragmentBuilder(fragmentIndex)
-        val printer = new Printers.JSTreePrinterWithSourceMap(jsCodeWriter, smFragmentBuilder, indent)
-
-        trees.foreach(printer.printStat(_))
-        smFragmentBuilder.complete()
-
-        js.PrintedTree(jsCodeWriter.toByteArray(), smFragmentBuilder.result()) :: Nil
-      }
-    }
-  }
 }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala
index a5f851cea0..279a2929d0 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala
@@ -33,13 +33,13 @@ import EmitterNames._
 import GlobalRefUtils._
 
 /** Emits a desugared JS tree to a builder */
-final class Emitter(config: Emitter.Config, postTransformer: Emitter.PostTransformer) {
+final class Emitter(config: Emitter.Config, prePrinter: Emitter.PrePrinter) {
 
   import Emitter._
   import config._
 
-  require(!config.minify || postTransformer == PostTransformer.Identity,
-      "When using the 'minify' option, the postTransformer must be Identity.")
+  require(!config.minify || prePrinter == PrePrinter.Off,
+      "When using the 'minify' option, the prePrinter must be Off.")
 
   private implicit val globalRefTracking: GlobalRefTracking =
     config.topLevelGlobalRefTracking
@@ -64,8 +64,8 @@ final class Emitter(config: Emitter.Config, postTransformer: Emitter.PostTransfo
     val classEmitter: ClassEmitter = new ClassEmitter(sjsGen)
 
     val everyFileStart: List[js.Tree] = {
-      // This postTransform does not count in the statistics
-      postTransformer.transformStats(sjsGen.declarePrototypeVar, 0)
+      // This prePrint does not count in the statistics
+      prePrinter.prePrint(sjsGen.declarePrototypeVar, 0)
     }
 
     val coreJSLibCache: CoreJSLibCache = new CoreJSLibCache
@@ -86,7 +86,7 @@ final class Emitter(config: Emitter.Config, postTransformer: Emitter.PostTransfo
   private[this] var statsClassesInvalidated: Int = 0
   private[this] var statsMethodsReused: Int = 0
   private[this] var statsMethodsInvalidated: Int = 0
-  private[this] var statsPostTransforms: Int = 0
+  private[this] var statsPrePrints: Int = 0
 
   val symbolRequirements: SymbolRequirement =
     Emitter.symbolRequirements(config)
@@ -143,7 +143,7 @@ final class Emitter(config: Emitter.Config, postTransformer: Emitter.PostTransfo
     statsClassesInvalidated = 0
     statsMethodsReused = 0
     statsMethodsInvalidated = 0
-    statsPostTransforms = 0
+    statsPrePrints = 0
 
     // Update GlobalKnowledge.
     val invalidateAll = knowledgeGuardian.update(moduleSet)
@@ -165,7 +165,7 @@ final class Emitter(config: Emitter.Config, postTransformer: Emitter.PostTransfo
       logger.debug(
           s"Emitter: Method tree cache stats: reused: $statsMethodsReused -- "+
           s"invalidated: $statsMethodsInvalidated")
-      logger.debug(s"Emitter: Post transforms: $statsPostTransforms")
+      logger.debug(s"Emitter: Pre prints: $statsPrePrints")
 
       // Inform caches about run completion.
       state.moduleCaches.filterInPlace((_, c) => c.cleanAfterRun())
@@ -173,13 +173,13 @@ final class Emitter(config: Emitter.Config, postTransformer: Emitter.PostTransfo
     }
   }
 
-  private def postTransform(trees: List[js.Tree], indent: Int): List[js.Tree] = {
-    statsPostTransforms += 1
-    postTransformer.transformStats(trees, indent)
+  private def prePrint(trees: List[js.Tree], indent: Int): List[js.Tree] = {
+    statsPrePrints += 1
+    prePrinter.prePrint(trees, indent)
   }
 
-  private def postTransform(tree: js.Tree, indent: Int): List[js.Tree] =
-    postTransform(tree :: Nil, indent)
+  private def prePrint(tree: js.Tree, indent: Int): List[js.Tree] =
+    prePrint(tree :: Nil, indent)
 
   /** Emits all JavaScript code avoiding clashes with global refs.
    *
@@ -248,7 +248,7 @@ final class Emitter(config: Emitter.Config, postTransformer: Emitter.PostTransfo
 
         val moduleImports = extractChangedAndWithGlobals {
           moduleCache.getOrComputeImports(module.externalDependencies, module.internalDependencies) {
-            genModuleImports(module).map(postTransform(_, 0))
+            genModuleImports(module).map(prePrint(_, 0))
           }
         }
 
@@ -258,7 +258,7 @@ final class Emitter(config: Emitter.Config, postTransformer: Emitter.PostTransfo
            */
           moduleCache.getOrComputeTopLevelExports(module.topLevelExports) {
             classEmitter.genTopLevelExports(module.topLevelExports)(
-                moduleContext, moduleCache).map(postTransform(_, 0))
+                moduleContext, moduleCache).map(prePrint(_, 0))
           }
         }
 
@@ -268,7 +268,7 @@ final class Emitter(config: Emitter.Config, postTransformer: Emitter.PostTransfo
             WithGlobals.list(initializers.map { initializer =>
               classEmitter.genModuleInitializer(initializer)(
                   moduleContext, moduleCache)
-            }).map(postTransform(_, 0))
+            }).map(prePrint(_, 0))
           }
         }
 
@@ -450,7 +450,7 @@ final class Emitter(config: Emitter.Config, postTransformer: Emitter.PostTransfo
     if (kind.isJSClass) {
       val fieldDefs = classTreeCache.privateJSFields.getOrElseUpdate {
         classEmitter.genCreatePrivateJSFieldDefsOfJSClass(className)(
-            moduleContext, classCache).map(postTransform(_, 0))
+            moduleContext, classCache).map(prePrint(_, 0))
       }
       main ++= extractWithGlobals(fieldDefs)
     }
@@ -471,7 +471,7 @@ final class Emitter(config: Emitter.Config, postTransformer: Emitter.PostTransfo
 
         main ++= extractWithGlobalsAndChanged(methodCache.getOrElseUpdate(methodDef.version, {
           classEmitter.genStaticLikeMethod(className, methodDef)(moduleContext, methodCache)
-            .map(postTransform(_, 0))
+            .map(prePrint(_, 0))
         }))
       }
     }
@@ -522,7 +522,7 @@ final class Emitter(config: Emitter.Config, postTransformer: Emitter.PostTransfo
         extractWithGlobals(classTreeCache.storeJSSuperClass.getOrElseUpdate({
           val jsSuperClass = linkedClass.jsSuperClass.get
           classEmitter.genStoreJSSuperClass(jsSuperClass)(moduleContext, classCache, linkedClass.pos)
-            .map(postTransform(_, 1))
+            .map(prePrint(_, 1))
         }))
       } else {
         Nil
@@ -552,7 +552,7 @@ final class Emitter(config: Emitter.Config, postTransformer: Emitter.PostTransfo
                 hasJSSuperClass, // invalidated by class version
                 useESClass, // invalidated by class version
                 jsConstructorDef // part of ctor version
-              )(moduleContext, ctorCache, linkedClass.pos).map(postTransform(_, memberIndent)))
+              )(moduleContext, ctorCache, linkedClass.pos).map(prePrint(_, memberIndent)))
         } else {
           val ctorVersion = linkedInlineableInit.fold {
             Version.combine(linkedClass.version)
@@ -566,7 +566,7 @@ final class Emitter(config: Emitter.Config, postTransformer: Emitter.PostTransfo
                 linkedClass.superClass, // invalidated by class version
                 useESClass, // invalidated by class version,
                 linkedInlineableInit // part of ctor version
-              )(moduleContext, ctorCache, linkedClass.pos).map(postTransform(_, memberIndent)))
+              )(moduleContext, ctorCache, linkedClass.pos).map(prePrint(_, memberIndent)))
         }
       }
 
@@ -620,7 +620,7 @@ final class Emitter(config: Emitter.Config, postTransformer: Emitter.PostTransfo
                 isJSClass, // invalidated by isJSClassVersion
                 useESClass, // invalidated by isJSClassVersion
                 method // invalidated by method.version
-            )(moduleContext, methodCache).map(postTransform(_, memberIndent))))
+            )(moduleContext, methodCache).map(prePrint(_, memberIndent))))
       }
 
       // Exported Members
@@ -635,7 +635,7 @@ final class Emitter(config: Emitter.Config, postTransformer: Emitter.PostTransfo
                 isJSClass, // invalidated by isJSClassVersion
                 useESClass, // invalidated by isJSClassVersion
                 member // invalidated by version
-            )(moduleContext, memberCache).map(postTransform(_, memberIndent))))
+            )(moduleContext, memberCache).map(prePrint(_, memberIndent))))
       }
 
       val hasClassInitializer: Boolean = {
@@ -695,7 +695,7 @@ final class Emitter(config: Emitter.Config, postTransformer: Emitter.PostTransfo
       if (classEmitter.needInstanceTests(linkedClass)(classCache)) {
         main ++= extractWithGlobals(classTreeCache.instanceTests.getOrElseUpdate({
           classEmitter.genInstanceTests(className, kind)(moduleContext, classCache, linkedClass.pos)
-            .map(postTransform(_, 0))
+            .map(prePrint(_, 0))
         }))
       }
 
@@ -709,14 +709,14 @@ final class Emitter(config: Emitter.Config, postTransformer: Emitter.PostTransfo
               linkedClass.ancestors, // invalidated by overall class cache (identity)
               linkedClass.jsNativeLoadSpec, // invalidated by class version
               linkedClass.hasDirectInstances // invalidated directly (it is the input to `getOrElseUpdate`)
-            )(moduleContext, classCache, linkedClass.pos).map(postTransform(_, 0))))
+            )(moduleContext, classCache, linkedClass.pos).map(prePrint(_, 0))))
       }
     }
 
     if (linkedClass.kind.hasModuleAccessor && linkedClass.hasInstances) {
       main ++= extractWithGlobals(classTreeCache.moduleAccessor.getOrElseUpdate({
         classEmitter.genModuleAccessor(className, isJSClass)(moduleContext, classCache, linkedClass.pos)
-          .map(postTransform(_, 0))
+          .map(prePrint(_, 0))
       }))
     }
 
@@ -727,7 +727,7 @@ final class Emitter(config: Emitter.Config, postTransformer: Emitter.PostTransfo
     } else {
       extractWithGlobals(classTreeCache.staticFields.getOrElseUpdate({
         classEmitter.genCreateStaticFieldsOfScalaClass(className)(moduleContext, classCache)
-          .map(postTransform(_, 0))
+          .map(prePrint(_, 0))
       }))
     }
 
@@ -736,7 +736,7 @@ final class Emitter(config: Emitter.Config, postTransformer: Emitter.PostTransfo
     val staticInitialization = if (classEmitter.needStaticInitialization(linkedClass)) {
       classTreeCache.staticInitialization.getOrElseUpdate({
         val tree = classEmitter.genStaticInitialization(className)(moduleContext, classCache, linkedClass.pos)
-        postTransform(tree, 0)
+        prePrint(tree, 0)
       })
     } else {
       Nil
@@ -1063,7 +1063,7 @@ final class Emitter(config: Emitter.Config, postTransformer: Emitter.PostTransfo
 
     def build(moduleContext: ModuleContext): WithGlobals[CoreJSLib.Lib[List[js.Tree]]] = {
       if (_lib == null || _lastModuleContext != moduleContext) {
-        _lib = CoreJSLib.build(sjsGen, postTransform(_, 0), moduleContext, this)
+        _lib = CoreJSLib.build(sjsGen, prePrint(_, 0), moduleContext, this)
         _lastModuleContext = moduleContext
       }
       _lib
@@ -1164,13 +1164,45 @@ object Emitter {
       new Config(coreSpec.semantics, coreSpec.moduleKind, coreSpec.esFeatures)
   }
 
-  trait PostTransformer {
-    def transformStats(trees: List[js.Tree], indent: Int): List[js.Tree]
+  sealed trait PrePrinter {
+    private[Emitter] def prePrint(trees: List[js.Tree], indent: Int): List[js.Tree]
   }
 
-  object PostTransformer {
-    object Identity extends PostTransformer {
-      def transformStats(trees: List[js.Tree], indent: Int): List[js.Tree] = trees
+  object PrePrinter {
+    object Off extends PrePrinter {
+      private[Emitter] def prePrint(trees: List[js.Tree], indent: Int): List[js.Tree] = trees
+    }
+
+    object WithoutSourceMap extends PrePrinter {
+      private[Emitter] def prePrint(trees: List[js.Tree], indent: Int): List[js.PrintedTree] = {
+        if (trees.isEmpty) {
+          Nil // Fast path
+        } else {
+          val jsCodeWriter = new ByteArrayWriter()
+          val printer = new Printers.JSTreePrinter(jsCodeWriter, indent)
+
+          trees.foreach(printer.printStat(_))
+
+          js.PrintedTree(jsCodeWriter.toByteArray(), SourceMapWriter.Fragment.Empty) :: Nil
+        }
+      }
+    }
+
+    final class WithSourceMap(fragmentIndex: SourceMapWriter.Index) extends PrePrinter {
+      private[Emitter] def prePrint(trees: List[js.Tree], indent: Int): List[js.PrintedTree] = {
+        if (trees.isEmpty) {
+          Nil // Fast path
+        } else {
+          val jsCodeWriter = new ByteArrayWriter()
+          val smFragmentBuilder = new SourceMapWriter.FragmentBuilder(fragmentIndex)
+          val printer = new Printers.JSTreePrinterWithSourceMap(jsCodeWriter, smFragmentBuilder, indent)
+
+          trees.foreach(printer.printStat(_))
+          smFragmentBuilder.complete()
+
+          js.PrintedTree(jsCodeWriter.toByteArray(), smFragmentBuilder.result()) :: Nil
+        }
+      }
     }
   }
 
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/EmitterTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/EmitterTest.scala
index 450ff7c3fe..2a473807ec 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/EmitterTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/EmitterTest.scala
@@ -136,8 +136,8 @@ class EmitterTest {
   private val EmitterMethodTreeCacheStatsMessage =
     raw"""Emitter: Method tree cache stats: reused: (\d+) -- invalidated: (\d+)""".r
 
-  private val EmitterPostTransformStatsMessage =
-    raw"""Emitter: Post transforms: (\d+)""".r
+  private val EmitterPrePrintsStatsMessage =
+    raw"""Emitter: Pre prints: (\d+)""".r
 
   /** Makes sure that linking a "substantial" program (using `println`) twice
    *  does not invalidate any cache or top-level tree in the second run.
@@ -206,20 +206,20 @@ class EmitterTest {
       assertEquals("Second run must reuse all method caches", methodCacheReused2, methodCacheInvalidated1)
       assertEquals("Second run must not invalidate any method cache", 0, methodCacheInvalidated2)
 
-      // Post transforms
+      // Pre prints
 
-      val Seq(postTransforms1) =
-        lines1.assertContainsMatch(EmitterPostTransformStatsMessage).map(_.toInt)
+      val Seq(prePrints1) =
+        lines1.assertContainsMatch(EmitterPrePrintsStatsMessage).map(_.toInt)
 
-      val Seq(postTransforms2) =
-        lines2.assertContainsMatch(EmitterPostTransformStatsMessage).map(_.toInt)
+      val Seq(prePrints2) =
+        lines2.assertContainsMatch(EmitterPrePrintsStatsMessage).map(_.toInt)
 
-      // At the time of writing this test, postTransforms1 reports 188
+      // At the time of writing this test, prePrints1 reports 188
       assertTrue(
-          s"Not enough post transforms (got $postTransforms1); extraction must have gone wrong",
-          postTransforms1 > 180)
+          s"Not enough pre prints (got $prePrints1); extraction must have gone wrong",
+          prePrints1 > 180)
 
-      assertEquals("Second run may not have post transforms", 0, postTransforms2)
+      assertEquals("Second run may not have pre prints", 0, prePrints2)
     }
   }
 }

From a7608172be88d121814ef23eac2445bda568fc74 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Fri, 5 Apr 2024 11:45:31 +0200
Subject: [PATCH 079/298] Make the test about method calls on non-instantiated
 classes stronger.

* Actually run the code and validate that the right exceptions
  are thrown.
* Add a variant where the target of the call is an interface, not
  a class.
---
 .../testsuite/compiler/RegressionTest.scala   | 32 +++++++++++++++----
 1 file changed, 26 insertions(+), 6 deletions(-)

diff --git a/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/RegressionTest.scala b/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/RegressionTest.scala
index 219358cecc..72319844a9 100644
--- a/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/RegressionTest.scala
+++ b/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/RegressionTest.scala
@@ -18,7 +18,7 @@ import org.junit.Test
 import org.junit.Assert._
 import org.junit.Assume._
 
-import org.scalajs.testsuite.utils.AssertThrows.assertThrows
+import org.scalajs.testsuite.utils.AssertThrows.{assertThrows, _}
 
 import org.scalajs.testsuite.utils.Platform
 import org.scalajs.testsuite.utils.Platform._
@@ -268,8 +268,6 @@ class RegressionTest {
   }
 
   @Test def irCheckerDoesNotCheckMethodSignaturesOnClassesWithNoInstance(): Unit = {
-    assumeTrue("linking only", false)
-
     class Foo // this class will be dropped by base linking
 
     class Bar {
@@ -281,10 +279,32 @@ class RegressionTest {
 
     @noinline def nullBar(): Bar = null
 
+    @noinline def nothingBar(): Bar = throw new IllegalStateException()
+
+    // the IR checker must not try to infer the signature of these calls
+    assertThrowsNPEIfCompliant(nullBar().meth(null))
+    assertThrowsNPEIfCompliant((null: Bar).meth(null))
+    assertThrows(classOf[IllegalStateException], (nothingBar(): Bar).meth(null))
+  }
+
+  @Test def irCheckerDoesNotCheckMethodSignaturesOnInterfacesWithNoInstance(): Unit = {
+    class Foo // this class will be dropped by base linking
+
+    trait Bar {
+      /* This method is called, but unreachable because there are no instances
+       * of `Bar`. It will therefore not make `Foo` reachable.
+       */
+      def meth(foo: Foo): String = foo.toString()
+    }
+
+    @noinline def nullBar(): Bar = null
+
+    @noinline def nothingBar(): Bar = throw new IllegalStateException()
+
     // the IR checker must not try to infer the signature of these calls
-    nullBar().meth(null)
-    (null: Bar).meth(null)
-    (??? : Bar).meth(null) // scalastyle:ignore
+    assertThrowsNPEIfCompliant(nullBar().meth(null))
+    assertThrowsNPEIfCompliant((null: Bar).meth(null))
+    assertThrows(classOf[IllegalStateException], (nothingBar(): Bar).meth(null))
   }
 
   @Test def orderCtorStatementsWhenInlining_Issue1369(): Unit = {

From 40482507304f19369b6c49422bedda12cea2e94b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Fri, 5 Apr 2024 13:47:25 +0200
Subject: [PATCH 080/298] Fix #4972: Mark Interfaces with
 isSubclassInstantiated/hasInstances.

---
 .../scalajs/linker/analyzer/Analyzer.scala    | 29 ++++----
 .../org/scalajs/linker/IRCheckerTest.scala    | 72 +++++++++++++++++++
 2 files changed, 86 insertions(+), 15 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala
index 534a30ef85..52a6326a01 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala
@@ -1133,23 +1133,22 @@ private class AnalyzerRun(config: CommonPhaseConfig, initial: Boolean,
     private def subclassInstantiated()(implicit from: From): Unit = {
       _instantiatedFrom ::= from
 
-      if (!(isScalaClass || isJSType)) {
-        // Ignore
-      } else if (!_isAnySubclassInstantiated.getAndSet(true)) {
-
-        if (!isNativeJSClass) {
-          for (clazz <- superClass) {
-            if (clazz.isNativeJSClass)
-              clazz.jsNativeLoadSpec.foreach(addLoadSpec(this, _))
-            else
-              addStaticDependency(clazz.className)
+      if (!_isAnySubclassInstantiated.getAndSet(true)) {
+        if (!isInterface) {
+          if (!isNativeJSClass) {
+            for (clazz <- superClass) {
+              if (clazz.isNativeJSClass)
+                clazz.jsNativeLoadSpec.foreach(addLoadSpec(this, _))
+              else
+                addStaticDependency(clazz.className)
+            }
           }
-        }
 
-        // Reach exported members
-        if (!isJSClass) {
-          for (reachabilityInfo <- data.jsMethodProps)
-            followReachabilityInfo(reachabilityInfo, this)(FromExports)
+          // Reach exported members
+          if (!isJSClass) {
+            for (reachabilityInfo <- data.jsMethodProps)
+              followReachabilityInfo(reachabilityInfo, this)(FromExports)
+          }
         }
       }
     }
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/IRCheckerTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/IRCheckerTest.scala
index f53e421b43..d9a2760c69 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/IRCheckerTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/IRCheckerTest.scala
@@ -90,6 +90,78 @@ class IRCheckerTest {
     testLinkNoIRError(classDefs, mainModuleInitializers("Test"))
   }
 
+  @Test
+  def argumentTypeMismatch(): AsyncResult = await {
+    val A = ClassName("A")
+    val B = ClassName("B")
+    val C = ClassName("C")
+    val D = ClassName("D")
+
+    val fooMethodName = m("foo", List(ClassRef(B)), V)
+
+    val results = for (receiverClassName <- List(A, B, C, D)) yield {
+      val receiverClassRef = ClassRef(receiverClassName)
+      val receiverType = ClassType(receiverClassName)
+
+      val testMethodName = m("test", List(receiverClassRef, ClassRef(C), ClassRef(D)), V)
+
+      val newD = New(D, NoArgConstructorName, Nil)
+
+      val classDefs = Seq(
+        classDef(
+          "A",
+          kind = ClassKind.Interface,
+          interfaces = Nil,
+          methods = List(
+            MethodDef(EMF, fooMethodName, NON,
+                List(paramDef("x", ClassType(B))), NoType, Some(Skip()))(EOH, UNV)
+          )
+        ),
+        classDef("B", kind = ClassKind.Interface, interfaces = List("A")),
+        classDef(
+          "C",
+          kind = ClassKind.Class,
+          superClass = Some(ObjectClass),
+          interfaces = List("A"),
+          methods = List(trivialCtor("C"))
+        ),
+
+        classDef(
+          "D",
+          kind = ClassKind.Class,
+          superClass = Some("C"),
+          interfaces = List("B"),
+          methods = List(
+            trivialCtor("D"),
+            MethodDef(
+              EMF.withNamespace(MemberNamespace.PublicStatic),
+              testMethodName,
+              NON,
+              List(paramDef("x", receiverType), paramDef("c", ClassType(C)), paramDef("d", ClassType(D))),
+              NoType,
+              Some(Block(
+                Apply(EAF, VarRef("x")(receiverType), fooMethodName, List(VarRef("c")(ClassType(C))))(NoType),
+                Apply(EAF, VarRef("x")(receiverType), fooMethodName, List(VarRef("d")(ClassType(D))))(NoType)
+              ))
+            )(EOH, UNV)
+          )
+        ),
+
+        mainTestClassDef(
+          ApplyStatic(EAF, D, testMethodName, List(newD, newD, newD))(NoType)
+        )
+      )
+
+      for (log <- testLinkIRErrors(classDefs, MainTestModuleInitializers)) yield {
+        log.assertContainsError(
+            "B expected but C found for tree of type org.scalajs.ir.Trees$VarRef")
+        log.assertNotContains("B expected but D found")
+      }
+    }
+
+    Future.sequence(results)
+  }
+
   @Test
   def missingJSNativeLoadSpec(): AsyncResult = await {
     val classDefs = Seq(

From 308236f9a04fd7cc86de101baee088c6ca47d283 Mon Sep 17 00:00:00 2001
From: Tobias Schlatter <tobias@meisch.ch>
Date: Fri, 5 Apr 2024 16:09:26 +0100
Subject: [PATCH 081/298] Implement "parallel" ConcurrentHashMap forEach
 methods

---
 .../util/concurrent/ConcurrentHashMap.scala   | 18 ++++++
 .../concurrent/ConcurrentHashMapTest.scala    | 63 +++++++++++++++++++
 2 files changed, 81 insertions(+)

diff --git a/javalib/src/main/scala/java/util/concurrent/ConcurrentHashMap.scala b/javalib/src/main/scala/java/util/concurrent/ConcurrentHashMap.scala
index 29847a2acb..49c5ac683e 100644
--- a/javalib/src/main/scala/java/util/concurrent/ConcurrentHashMap.scala
+++ b/javalib/src/main/scala/java/util/concurrent/ConcurrentHashMap.scala
@@ -12,6 +12,8 @@
 
 package java.util.concurrent
 
+import java.util.function.{BiConsumer, Consumer}
+
 import java.io.Serializable
 import java.util._
 
@@ -72,6 +74,22 @@ class ConcurrentHashMap[K, V] private (initialCapacity: Int, loadFactor: Float)
     new ConcurrentHashMap.KeySetView[K, V](this.inner, mappedValue)
   }
 
+  def forEach(parallelismThreshold: Long, action: BiConsumer[_ >: K, _ >: V]): Unit = {
+    // Note: It is tempting to simply call inner.forEach here:
+    // However, this will not have the correct snapshotting behavior.
+    val i = inner.nodeIterator()
+    while (i.hasNext()) {
+      val n = i.next()
+      action.accept(n.key, n.value)
+    }
+  }
+
+  def forEachKey(parallelismThreshold: Long, action: Consumer[_ >: K]): Unit =
+    inner.keyIterator().forEachRemaining(action)
+
+  def forEachValue(parallelismThreshold: Long, action: Consumer[_ >: V]): Unit =
+    inner.valueIterator().forEachRemaining(action)
+
   override def values(): Collection[V] =
     inner.values()
 
diff --git a/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/util/concurrent/ConcurrentHashMapTest.scala b/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/util/concurrent/ConcurrentHashMapTest.scala
index 7a98007158..459b7b9926 100644
--- a/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/util/concurrent/ConcurrentHashMapTest.scala
+++ b/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/util/concurrent/ConcurrentHashMapTest.scala
@@ -227,6 +227,69 @@ class ConcurrentHashMapTest extends MapTest {
     val str = keySet.toString
     assertTrue(s"toString should print keys, but actual: $str", str == "[a, b]" || str == "[b, a]")
   }
+
+  @Test def forEachPar(): Unit = {
+    val pairs = List("ONE" -> 1, "TWO" -> 2, "THREE" -> 3)
+    val map = factory.empty[String, Int]
+    pairs.foreach(x => map.put(x._1, x._2))
+
+    val seen = mutable.Set.empty[(String, Int)]
+
+    map.forEach(1L, { (k, v) =>
+      if (k == "TWO")
+        map.remove("TWO") // check snapshotting behavior.
+
+      seen.synchronized {
+        seen += k -> v
+      }
+    })
+
+    assertEquals(2, map.size())
+    assertFalse(map.containsKey("TWO"))
+    assertEquals(pairs.toSet, seen)
+  }
+
+  @Test def forEachKeyPar(): Unit = {
+    val pairs = List("ONE" -> 1, "TWO" -> 2, "THREE" -> 3)
+    val map = factory.empty[String, Int]
+    pairs.foreach(x => map.put(x._1, x._2))
+
+    val seen = mutable.Set.empty[String]
+
+    map.forEachKey(1L, { k =>
+      if (k == "TWO")
+        map.remove("TWO") // check snapshotting behavior.
+
+      seen.synchronized {
+        seen += k
+      }
+    })
+
+    assertEquals(2, map.size())
+    assertFalse(map.containsKey("TWO"))
+    assertEquals(Set("ONE", "TWO", "THREE"), seen)
+  }
+
+  @Test def forEachValuePar(): Unit = {
+    val pairs = List("ONE" -> 1, "TWO" -> 2, "THREE" -> 3)
+    val map = factory.empty[String, Int]
+    pairs.foreach(x => map.put(x._1, x._2))
+
+    val seen = mutable.Set.empty[Int]
+
+    map.forEachValue(1L, { v =>
+      if (v == 2)
+        map.remove("TWO") // check snapshotting behavior.
+
+      seen.synchronized {
+        seen += v
+      }
+    })
+
+    assertEquals(2, map.size())
+    assertFalse(map.containsKey("TWO"))
+    assertEquals(seen, Set(1, 2, 3))
+  }
 }
 
 class ConcurrentHashMapFactory extends ConcurrentMapFactory {

From d3c42e1370b8dd1b043061c3df2985a375691494 Mon Sep 17 00:00:00 2001
From: Tobias Schlatter <tobias@meisch.ch>
Date: Sun, 31 Mar 2024 13:25:25 +0200
Subject: [PATCH 082/298] Replace (Par)TrieMap with ConcurrentHashMap in
 IncOptimizer

- Reduces residual retained size of the IncOptimizer on the test suite
  from 166MB to 144MB.
- ~10% batch speedup on the optimizer.
---
 .../frontend/optimizer/ParCollOps.scala       |  38 +---
 .../frontend/optimizer/AbsCollOps.scala       |  24 +--
 .../frontend/optimizer/IncOptimizer.scala     | 186 ++++++++++--------
 .../frontend/optimizer/SeqCollOps.scala       |  38 +---
 4 files changed, 115 insertions(+), 171 deletions(-)

diff --git a/linker/jvm/src/main/scala/org/scalajs/linker/frontend/optimizer/ParCollOps.scala b/linker/jvm/src/main/scala/org/scalajs/linker/frontend/optimizer/ParCollOps.scala
index e9c36ead8e..30b82b2283 100644
--- a/linker/jvm/src/main/scala/org/scalajs/linker/frontend/optimizer/ParCollOps.scala
+++ b/linker/jvm/src/main/scala/org/scalajs/linker/frontend/optimizer/ParCollOps.scala
@@ -14,52 +14,20 @@ package org.scalajs.linker.frontend.optimizer
 
 import scala.annotation.tailrec
 
-import scala.collection.concurrent.TrieMap
-import scala.collection.parallel.mutable.{ParTrieMap, ParArray}
+import scala.collection.parallel.mutable.ParArray
 import scala.collection.parallel._
 
 import java.util.concurrent.atomic._
 
 private[optimizer] object ParCollOps extends AbsCollOps {
-  type Map[K, V] = TrieMap[K, V]
-  type ParMap[K, V] = ParTrieMap[K, V]
-  type AccMap[K, V] = TrieMap[K, Addable[V]]
   type ParIterable[V] = ParArray[V]
   type Addable[V] = AtomicReference[List[V]]
 
-  def emptyAccMap[K, V]: AccMap[K, V] = TrieMap.empty
-  def emptyMap[K, V]: Map[K, V] = TrieMap.empty
-  def emptyParMap[K, V]: ParMap[K, V] =  ParTrieMap.empty
+  def parThreshold: Long = 1 // max parallelism
+
   def emptyParIterable[V]: ParIterable[V] = ParArray.empty
   def emptyAddable[V]: Addable[V] = new AtomicReference[List[V]](Nil)
 
-  // Operations on ParMap
-  def isEmpty[K, V](map: ParMap[K, V]): Boolean = map.isEmpty
-  def forceGet[K, V](map: ParMap[K, V], k: K): V = map(k)
-  def get[K, V](map: ParMap[K, V], k: K): Option[V] = map.get(k)
-  def put[K, V](map: ParMap[K, V], k: K, v: V): Unit = map.put(k, v)
-  def remove[K, V](map: ParMap[K, V], k: K): Option[V] = map.remove(k)
-
-  def retain[K, V](map: ParMap[K, V])(p: (K, V) => Boolean): Unit = {
-    map.foreach { case (k, v) =>
-      if (!p(k, v))
-        map.remove(k)
-    }
-  }
-
-  def valuesForeach[K, V, U](map: ParMap[K, V])(f: V => U): Unit =
-    map.values.foreach(f)
-
-  // Operations on AccMap
-  def acc[K, V](map: AccMap[K, V], k: K, v: V): Unit =
-    add(map.getOrElseUpdate(k, emptyAddable), v)
-
-  def getAcc[K, V](map: AccMap[K, V], k: K): ParIterable[V] =
-    map.get(k).fold(emptyParIterable[V])(finishAdd(_))
-
-  def parFlatMapKeys[A, B](map: AccMap[A, _])(f: A => Option[B]): ParIterable[B] =
-    map.keys.flatMap(f(_)).toParArray
-
   // Operations on ParIterable
   def prepAdd[V](it: ParIterable[V]): Addable[V] =
     new AtomicReference(it.toList)
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/AbsCollOps.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/AbsCollOps.scala
index 30d915b657..4da8461735 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/AbsCollOps.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/AbsCollOps.scala
@@ -14,35 +14,15 @@ package org.scalajs.linker.frontend.optimizer
 
 import language.higherKinds
 
-import scala.collection.mutable
-
 private[optimizer] trait AbsCollOps {
-  type Map[K, V] <: mutable.Map[K, V]
-  type ParMap[K, V] <: AnyRef
-  type AccMap[K, V] <: AnyRef
   type ParIterable[V] <: AnyRef
   type Addable[V] <: AnyRef
 
-  def emptyAccMap[K, V]: AccMap[K, V]
-  def emptyMap[K, V]: Map[K, V]
-  def emptyParMap[K, V]: ParMap[K, V]
+  def parThreshold: Long
+
   def emptyParIterable[V]: ParIterable[V]
   def emptyAddable[V]: Addable[V]
 
-  // Operations on ParMap
-  def isEmpty[K, V](map: ParMap[K, V]): Boolean
-  def forceGet[K, V](map: ParMap[K, V], k: K): V
-  def get[K, V](map: ParMap[K, V], k: K): Option[V]
-  def put[K, V](map: ParMap[K, V], k: K, v: V): Unit
-  def remove[K, V](map: ParMap[K, V], k: K): Option[V]
-  def retain[K, V](map: ParMap[K, V])(p: (K, V) => Boolean): Unit
-  def valuesForeach[K, V, U](map: ParMap[K, V])(f: V => U): Unit
-
-  // Operations on AccMap
-  def acc[K, V](map: AccMap[K, V], k: K, v: V): Unit
-  def getAcc[K, V](map: AccMap[K, V], k: K): ParIterable[V]
-  def parFlatMapKeys[A, B](map: AccMap[A, _])(f: A => Option[B]): ParIterable[B]
-
   // Operations on ParIterable
   def prepAdd[V](it: ParIterable[V]): Addable[V]
   def add[V](addable: Addable[V], v: V): Unit
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
index d092397b51..4533ca7543 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
@@ -16,6 +16,7 @@ import scala.annotation.{switch, tailrec}
 
 import scala.collection.mutable
 
+import java.util.concurrent.ConcurrentHashMap
 import java.util.concurrent.atomic.AtomicBoolean
 
 import org.scalajs.ir._
@@ -44,6 +45,16 @@ import OptimizerCore.InlineableFieldBodies.FieldBody
  *  run, based on detecting what parts of the program must be re-optimized,
  *  and keeping optimized results from previous runs for the rest.
  *
+ *  A general note about use of ConcurrentHashMap[T, Unit] as concurrent sets:
+ *  It would seem better to use ConcurrentHashMap.newKeySet() which is
+ *  specifically designed for this purpose. However, the views alone use up 4 MB
+ *  of shallow size on the test suite at the time of writing. Therefore, we give
+ *  up on the convenience API and use the underlying ConcurrentHashMap directly.
+ *
+ *  A similar argument applies to usages of keySet(): It appears that the
+ *  implementation holds on to the key set once it is created, resulting in
+ *  unnecessary memory usage.
+ *
  *  @param semantics Required Scala.js Semantics
  *  @param esLevel ECMAScript level
  */
@@ -65,15 +76,22 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
   private var batchMode: Boolean = false
 
   private var objectClass: Class = _
-  private val classes = collOps.emptyMap[ClassName, Class]
-  private val interfaces = collOps.emptyParMap[ClassName, InterfaceType]
+  private val classes = new ConcurrentHashMap[ClassName, Class]
+  private val interfaces = new ConcurrentHashMap[ClassName, InterfaceType]
   private val topLevelExports = new JSTopLevelMethodContainer
 
   private var methodsToProcess = collOps.emptyAddable[Processable]
 
   @inline
   private def getInterface(className: ClassName): InterfaceType =
-    collOps.forceGet(interfaces, className)
+    interfaces.get(className)
+
+  @inline
+  private def classOrElse[T >: Class](className: ClassName, default: => T): T = {
+    val clazz = classes.get(className)
+    if (clazz != null) clazz
+    else default
+  }
 
   /** Update the incremental analyzer with a new run. */
   def update(unit: LinkingUnit, logger: Logger): List[(ClassDef, Version)] = {
@@ -110,7 +128,7 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
     val className = linkedClass.className
     val interface = getInterface(className)
 
-    val publicContainer = classes.get(className).getOrElse {
+    val publicContainer = classOrElse(className, {
       /* For interfaces, we need to look at default methods.
        * For other kinds of classes, the public namespace is necessarily
        * empty.
@@ -120,7 +138,7 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
           linkedClass.kind == ClassKind.Interface || container.methods.isEmpty,
           linkedClass.className -> linkedClass.kind)
       container
-    }
+    })
 
     val newMethods = for (m <- linkedClass.methods) yield {
       val namespace = m.flags.namespace
@@ -169,14 +187,14 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
   }
 
   private def updateAndTagClasses(linkedClasses: List[LinkedClass]): Unit = {
-    val neededInterfaces = collOps.emptyParMap[ClassName, LinkedClass]
-    val neededClasses = collOps.emptyParMap[ClassName, LinkedClass]
+    val neededInterfaces = new ConcurrentHashMap[ClassName, LinkedClass]
+    val neededClasses = new ConcurrentHashMap[ClassName, LinkedClass]
     for (linkedClass <- linkedClasses) {
-      collOps.put(neededInterfaces, linkedClass.className, linkedClass)
+      neededInterfaces.put(linkedClass.className, linkedClass)
 
       if (linkedClass.hasInstances &&
           (linkedClass.kind.isClass || linkedClass.kind == ClassKind.HijackedClass)) {
-        collOps.put(neededClasses, linkedClass.className, linkedClass)
+        neededClasses.put(linkedClass.className, linkedClass)
       }
     }
 
@@ -187,26 +205,26 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
      *
      * Non-batch mode only.
      */
-    assert(!batchMode || collOps.isEmpty(interfaces))
+    assert(!batchMode || interfaces.isEmpty())
     if (!batchMode) {
-      collOps.retain(interfaces) { (className, interface) =>
-        collOps.remove(neededInterfaces, className).fold {
+      interfaces.forEach(collOps.parThreshold, { (className, interface) =>
+        val linkedClass = neededInterfaces.remove(className)
+        if (linkedClass == null) {
           interface.delete()
-          false
-        } { linkedClass =>
+          interfaces.remove(className)
+        } else {
           interface.updateWith(linkedClass)
-          true
         }
-      }
+      })
     }
 
     /* Add new interfaces.
      * Easy, we don't have to notify anyone.
      */
-    collOps.valuesForeach(neededInterfaces) { linkedClass =>
+    neededInterfaces.forEachValue(collOps.parThreshold, { linkedClass =>
       val interface = new InterfaceType(linkedClass)
-      collOps.put(interfaces, interface.className, interface)
-    }
+      interfaces.put(interface.className, interface)
+    })
 
     if (!batchMode) {
       /* Class removals:
@@ -218,7 +236,7 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
        * Non-batch mode only.
        */
       val objectClassStillExists =
-        objectClass.walkClassesForDeletions(collOps.get(neededClasses, _))
+        objectClass.walkClassesForDeletions(className => Option(neededClasses.get(className)))
       assert(objectClassStillExists, "Uh oh, java.lang.Object was deleted!")
 
       /* Class changes:
@@ -228,8 +246,7 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
        *
        * Non-batch mode only.
        */
-      objectClass.walkForChanges(
-          collOps.remove(neededClasses, _).get, Set.empty)
+      objectClass.walkForChanges(neededClasses.remove(_), Set.empty)
     }
 
     /* Class additions:
@@ -238,30 +255,36 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
      */
 
     // Group children by (immediate) parent
-    val newChildrenByParent = collOps.emptyAccMap[ClassName, LinkedClass]
+    val newChildrenByParent = new ConcurrentHashMap[ClassName, collOps.Addable[LinkedClass]]
 
-    collOps.valuesForeach(neededClasses) { linkedClass =>
+    neededClasses.forEachValue(collOps.parThreshold, { linkedClass =>
       linkedClass.superClass.fold[Unit] {
         assert(batchMode, "Trying to add java.lang.Object in incremental mode")
         objectClass = new Class(None, linkedClass)
-        classes += linkedClass.className -> objectClass
+        classes.put(linkedClass.className, objectClass)
       } { superClassName =>
-        collOps.acc(newChildrenByParent, superClassName.name, linkedClass)
+        val addable = newChildrenByParent
+          .computeIfAbsent(superClassName.name, _ => collOps.emptyAddable)
+
+        collOps.add(addable, linkedClass)
       }
-    }
+    })
 
-    val getNewChildren =
-      (name: ClassName) => collOps.getAcc(newChildrenByParent, name)
+    val getNewChildren = { (name: ClassName) =>
+      val acc = newChildrenByParent.get(name)
+      if (acc == null) collOps.emptyParIterable[LinkedClass]
+      else collOps.finishAdd(acc)
+    }
 
     // Walk the tree to add children
     if (batchMode) {
       objectClass.walkForAdditions(getNewChildren)
     } else {
-      val existingParents =
-        collOps.parFlatMapKeys(newChildrenByParent)(classes.get)
-      collOps.foreach(existingParents) { parent =>
-        parent.walkForAdditions(getNewChildren)
-      }
+      newChildrenByParent.forEachKey(1, { parentName =>
+        val parent = classes.get(parentName)
+        if (parent != null)
+          parent.walkForAdditions(getNewChildren)
+      })
     }
 
   }
@@ -293,7 +316,7 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
 
     def isGetter(classAndMethodName: (ClassName, MethodName)): Boolean = {
       val (className, methodName) = classAndMethodName
-      classes(className).lookupMethod(methodName).exists { m =>
+      classes.get(className).lookupMethod(methodName).exists { m =>
         m.originalDef.body match {
           case Some(Select(This(), _)) => true
           case _                          => false
@@ -307,7 +330,7 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
      * - Initialize `elidableConstructorsRemainingDependenciesCount` for `DependentOn` classes
      * - Initialize the stack with dependency-free classes
      */
-    for (cls <- classes.valuesIterator) {
+    classes.forEachValue(Long.MaxValue, { cls =>
       cls.elidableConstructorsInfo match {
         case DependentOn(deps, getterDeps) =>
           if (!getterDeps.forall(isGetter(_))) {
@@ -318,7 +341,7 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
               toProcessStack += cls
             } else {
               cls.elidableConstructorsRemainingDependenciesCount = deps.size
-              deps.foreach(dep => classes(dep).elidableConstructorsDependents += cls)
+              deps.foreach(dep => classes.get(dep).elidableConstructorsDependents += cls)
             }
           }
         case AcyclicElidable =>
@@ -326,7 +349,7 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
         case NotElidable =>
           ()
       }
-    }
+    })
 
     /* Propagate AcyclicElidable
      * When a class `cls` is on the stack, it is known to be AcyclicElidable.
@@ -358,9 +381,7 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
     }
 
     // Set the final value of hasElidableConstructors
-    for (cls <- classes.valuesIterator) {
-      cls.setHasElidableConstructors()
-    }
+    classes.forEachValue(Long.MaxValue, _.setHasElidableConstructors())
   }
 
   /** Optimizer part: process all methods that need reoptimizing.
@@ -493,7 +514,7 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
     /** True if *all* constructors of this class are recursively elidable. */
     private var hasElidableConstructors: Boolean =
       elidableConstructorsInfo != ElidableConstructorsInfo.NotElidable // initial educated guess
-    private val hasElidableConstructorsAskers = collOps.emptyMap[Processable, Unit]
+    private val hasElidableConstructorsAskers = new ConcurrentHashMap[Processable, Unit]
 
     var fields: List[AnyFieldDef] = linkedClass.fields
     var fieldsRead: Set[FieldName] = linkedClass.fieldsRead
@@ -504,7 +525,7 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
      */
     private var inlineableFieldBodies: OptimizerCore.InlineableFieldBodies =
       computeInlineableFieldBodies(linkedClass)
-    private val inlineableFieldBodiesAskers = collOps.emptyMap[Processable, Unit]
+    private val inlineableFieldBodiesAskers = new ConcurrentHashMap[Processable, Unit]
 
     setupAfterCreation(linkedClass)
 
@@ -548,7 +569,7 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
         notInstantiatedAnymore()
       for (method <- methods.values)
         method.delete()
-      classes -= className
+      classes.remove(className)
       /* Note: no need to tag methods that call *statically* one of the methods
        * of the deleted classes, since they've got to be invalidated by
        * themselves.
@@ -633,7 +654,7 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
       val newInlineableFieldBodies = computeInlineableFieldBodies(linkedClass)
       if (inlineableFieldBodies != newInlineableFieldBodies) {
         inlineableFieldBodies = newInlineableFieldBodies
-        inlineableFieldBodiesAskers.keysIterator.foreach(_.tag())
+        inlineableFieldBodiesAskers.forEachKey(Long.MaxValue, _.tag())
         inlineableFieldBodiesAskers.clear()
       }
 
@@ -657,7 +678,7 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
 
       if (hasElidableConstructors != newHasElidableConstructors) {
         hasElidableConstructors = newHasElidableConstructors
-        hasElidableConstructorsAskers.keysIterator.foreach(_.tag())
+        hasElidableConstructorsAskers.forEachKey(Long.MaxValue, _.tag())
         hasElidableConstructorsAskers.clear()
       }
 
@@ -676,7 +697,7 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
       collOps.foreach(getNewChildren(className)) { linkedClass =>
         val cls = new Class(Some(this), linkedClass)
         collOps.add(subclassAcc, cls)
-        classes += linkedClass.className -> cls
+        classes.put(linkedClass.className, cls)
         cls.walkForAdditions(getNewChildren)
       }
 
@@ -888,7 +909,7 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
 
         // Mixin constructor -- test whether its body is entirely empty
         case ApplyStatically(flags, This(), className, methodName, Nil)
-            if !flags.isPrivate && !classes.contains(className) =>
+            if !flags.isPrivate && !classes.containsKey(className) =>
           // Since className is not in classes, it must be a default method call.
           val container =
             getInterface(className).staticLike(MemberNamespace.Public)
@@ -1025,7 +1046,7 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
 
           // Mixin constructor -- assume it is empty
           case ApplyStatically(flags, This(), className, methodName, Nil)
-              if !flags.isPrivate && !classes.contains(className) =>
+              if !flags.isPrivate && !classes.containsKey(className) =>
             fieldBodies
 
           // Delegation to another constructor
@@ -1221,21 +1242,22 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
 
     val className: ClassName = linkedClass.className
 
-    private type MethodCallers = collOps.Map[MethodName, collOps.Map[Processable, Unit]]
+    private type MethodCallers =
+      ConcurrentHashMap[MethodName, ConcurrentHashMap[Processable, Unit]]
 
-    private val ancestorsAskers = collOps.emptyMap[Processable, Unit]
-    private val dynamicCallers: MethodCallers = collOps.emptyMap
+    private val ancestorsAskers = new ConcurrentHashMap[Processable, Unit]
+    private val dynamicCallers: MethodCallers = new ConcurrentHashMap
 
     // ArrayBuffer to avoid need for ClassTag[collOps.Map[_, _]]
     private val staticCallers =
-      mutable.ArrayBuffer.fill[MethodCallers](MemberNamespace.Count)(collOps.emptyMap)
+      mutable.ArrayBuffer.fill[MethodCallers](MemberNamespace.Count)(new ConcurrentHashMap)
 
-    private val jsNativeImportsAskers = collOps.emptyMap[Processable, Unit]
-    private val fieldsReadAskers = collOps.emptyMap[Processable, Unit]
+    private val jsNativeImportsAskers = new ConcurrentHashMap[Processable, Unit]
+    private val fieldsReadAskers = new ConcurrentHashMap[Processable, Unit]
 
     private var _ancestors: List[ClassName] = linkedClass.ancestors
 
-    private val _instantiatedSubclasses = collOps.emptyMap[Class, Unit]
+    private val _instantiatedSubclasses = new ConcurrentHashMap[Class, Unit]
 
     private val staticLikes: Array[StaticLikeNamespace] = {
       Array.tabulate(MemberNamespace.Count) { ord =>
@@ -1285,17 +1307,20 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
     def askDynamicCallTargets(methodName: MethodName,
         asker: Processable): List[MethodImpl] = {
       dynamicCallers
-        .getOrElseUpdate(methodName, collOps.emptyMap)
+        .computeIfAbsent(methodName, _ => new ConcurrentHashMap())
         .put(asker, ())
       asker.registerTo(this)
-      _instantiatedSubclasses.keys.flatMap(_.lookupMethod(methodName)).toList
+
+      val res = mutable.Set.empty[MethodImpl]
+      _instantiatedSubclasses.forEachKey(Long.MaxValue, _.lookupMethod(methodName).foreach(res += _))
+      res.toList
     }
 
     /** PROCESS PASS ONLY. */
     def askStaticCallTarget(namespace: MemberNamespace, methodName: MethodName,
         asker: Processable): MethodImpl = {
       staticCallers(namespace.ordinal)
-        .getOrElseUpdate(methodName, collOps.emptyMap)
+        .computeIfAbsent(methodName, _ => new ConcurrentHashMap())
         .put(asker, ())
       asker.registerTo(this)
 
@@ -1303,7 +1328,7 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
 
       val container =
         if (namespace != MemberNamespace.Public) inStaticsLike
-        else classes.getOrElse(className, inStaticsLike)
+        else classOrElse(className, inStaticsLike)
 
       // Method must exist, otherwise it's a bug / invalid IR.
       container.lookupMethod(methodName).getOrElse {
@@ -1317,7 +1342,7 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
 
     /** UPDATE PASS ONLY. */
     def removeInstantiatedSubclass(x: Class): Unit =
-      _instantiatedSubclasses -= x
+      _instantiatedSubclasses.remove(x)
 
     /** PROCESS PASS ONLY. */
     def askAncestors(asker: Processable): List[ClassName] = {
@@ -1368,7 +1393,7 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
       // Update ancestors
       if (linkedClass.ancestors != _ancestors) {
         _ancestors = linkedClass.ancestors
-        ancestorsAskers.keysIterator.foreach(_.tag())
+        ancestorsAskers.forEachKey(Long.MaxValue, _.tag())
         ancestorsAskers.clear()
       }
 
@@ -1376,7 +1401,7 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
       val newJSNativeImports = computeJSNativeImports(linkedClass)
       if (jsNativeImports != newJSNativeImports) {
         jsNativeImports = newJSNativeImports
-        jsNativeImportsAskers.keysIterator.foreach(_.tag())
+        jsNativeImportsAskers.forEachKey(Long.MaxValue, _.tag())
         jsNativeImportsAskers.clear()
       }
 
@@ -1385,7 +1410,7 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
           staticFieldsRead != linkedClass.staticFieldsRead) {
         fieldsRead = linkedClass.fieldsRead
         staticFieldsRead = linkedClass.staticFieldsRead
-        fieldsReadAskers.keysIterator.foreach(_.tag())
+        fieldsReadAskers.forEachKey(Long.MaxValue, _.tag())
         fieldsReadAskers.clear()
       }
 
@@ -1412,8 +1437,9 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
      *  UPDATE PASS ONLY.
      */
     def tagDynamicCallersOf(methodName: MethodName): Unit = {
-      dynamicCallers.remove(methodName)
-        .foreach(_.keysIterator.foreach(_.tag()))
+      val callers = dynamicCallers.remove(methodName)
+      if (callers != null)
+        callers.forEachKey(Long.MaxValue, _.tag())
     }
 
     /** Tag the static-callers of an instance method.
@@ -1421,15 +1447,16 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
      */
     def tagStaticCallersOf(namespace: MemberNamespace,
         methodName: MethodName): Unit = {
-      staticCallers(namespace.ordinal).remove(methodName)
-        .foreach(_.keysIterator.foreach(_.tag()))
+      val callers = staticCallers(namespace.ordinal).remove(methodName)
+      if (callers != null)
+        callers.forEachKey(Long.MaxValue, _.tag())
     }
 
     /** UPDATE PASS ONLY. */
     def unregisterDependee(dependee: Processable): Unit = {
       ancestorsAskers.remove(dependee)
-      dynamicCallers.valuesIterator.foreach(_.remove(dependee))
-      staticCallers.foreach(_.valuesIterator.foreach(_.remove(dependee)))
+      dynamicCallers.forEachValue(Long.MaxValue, _.remove(dependee))
+      staticCallers.foreach(_.forEachValue(Long.MaxValue, _.remove(dependee)))
       jsNativeImportsAskers.remove(dependee)
     }
 
@@ -1468,7 +1495,7 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
   private abstract class Processable {
     type Def >: scala.Null <: VersionedMemberDef
 
-    private[this] val registeredTo = collOps.emptyMap[Unregisterable, Unit]
+    private[this] val registeredTo = new ConcurrentHashMap[Unregisterable, Unit]
     private[this] val tagged = new AtomicBoolean(false)
     private[this] var _deleted: Boolean = false
 
@@ -1510,7 +1537,7 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
     }
 
     private def unregisterFromEverywhere(): Unit = {
-      registeredTo.keysIterator.foreach(_.unregisterDependee(this))
+      registeredTo.forEachKey(Long.MaxValue, _.unregisterDependee(this))
       registeredTo.clear()
     }
 
@@ -1560,7 +1587,7 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
 
     type Def = MethodDef
 
-    private val bodyAskers = collOps.emptyMap[Processable, Unit]
+    private val bodyAskers = new ConcurrentHashMap[Processable, Unit]
 
     var attributes: OptimizerCore.MethodAttributes = _
 
@@ -1578,7 +1605,7 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
 
     /** UPDATE PASS ONLY. */
     def tagBodyAskers(): Unit = {
-      bodyAskers.keysIterator.foreach(_.tag())
+      bodyAskers.forEachKey(Long.MaxValue, _.tag())
       bodyAskers.clear()
     }
 
@@ -1741,14 +1768,17 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
       getInterface(intfName).askAncestors(asker)
 
     protected def hasElidableConstructors(className: ClassName): Boolean =
-      classes(className).askHasElidableConstructors(asker)
+      classes.get(className).askHasElidableConstructors(asker)
 
-    protected def inlineableFieldBodies(className: ClassName): OptimizerCore.InlineableFieldBodies =
-      classes.get(className).fold(OptimizerCore.InlineableFieldBodies.Empty)(_.askInlineableFieldBodies(asker))
+    protected def inlineableFieldBodies(className: ClassName): OptimizerCore.InlineableFieldBodies = {
+      val clazz = classes.get(className)
+      if (clazz == null) OptimizerCore.InlineableFieldBodies.Empty
+      else clazz.askInlineableFieldBodies(asker)
+    }
 
     protected def tryNewInlineableClass(
         className: ClassName): Option[OptimizerCore.InlineableClassStructure] = {
-      classes(className).tryNewInlineable
+      classes.get(className).tryNewInlineable
     }
 
     protected def getJSNativeImportOf(
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/SeqCollOps.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/SeqCollOps.scala
index d5874fbd49..7bdc4a0697 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/SeqCollOps.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/SeqCollOps.scala
@@ -12,51 +12,17 @@
 
 package org.scalajs.linker.frontend.optimizer
 
-import scala.collection.{GenTraversableOnce, GenIterable}
 import scala.collection.mutable
 
-import org.scalajs.ir.Names.{ClassName, MethodName}
-import org.scalajs.ir.Trees.MemberNamespace
-
-import org.scalajs.linker.standard._
-import org.scalajs.linker.CollectionsCompat.MutableMapCompatOps
-
 private[optimizer] object SeqCollOps extends AbsCollOps {
-  type Map[K, V] = mutable.Map[K, V]
-  type ParMap[K, V] = mutable.Map[K, V]
-  type AccMap[K, V] = mutable.Map[K, mutable.ListBuffer[V]]
   type ParIterable[V] = mutable.ListBuffer[V]
   type Addable[V] = mutable.ListBuffer[V]
 
-  def emptyAccMap[K, V]: AccMap[K, V] = mutable.Map.empty
-  def emptyMap[K, V]: Map[K, V] = mutable.Map.empty
-  def emptyParMap[K, V]: ParMap[K, V] = mutable.Map.empty
+  def parThreshold: Long = Long.MaxValue // no parallelism
+
   def emptyParIterable[V]: ParIterable[V] = mutable.ListBuffer.empty
   def emptyAddable[V]: Addable[V] = mutable.ListBuffer.empty
 
-  // Operations on ParMap
-  def isEmpty[K, V](map: ParMap[K, V]): Boolean = map.isEmpty
-  def forceGet[K, V](map: ParMap[K, V], k: K): V = map(k)
-  def get[K, V](map: ParMap[K, V], k: K): Option[V] = map.get(k)
-  def put[K, V](map: ParMap[K, V], k: K, v: V): Unit = map.put(k, v)
-  def remove[K, V](map: ParMap[K, V], k: K): Option[V] = map.remove(k)
-
-  def retain[K, V](map: ParMap[K, V])(p: (K, V) => Boolean): Unit =
-    map.filterInPlace(p)
-
-  def valuesForeach[K, V, U](map: ParMap[K, V])(f: V => U): Unit =
-    map.values.foreach(f)
-
-  // Operations on AccMap
-  def acc[K, V](map: AccMap[K, V], k: K, v: V): Unit =
-    map.getOrElseUpdate(k, mutable.ListBuffer.empty) += v
-
-  def getAcc[K, V](map: AccMap[K, V], k: K): ParIterable[V] =
-    map.getOrElse(k, emptyParIterable)
-
-  def parFlatMapKeys[A, B](map: AccMap[A, _])(f: A => Option[B]): ParIterable[B] =
-    emptyParIterable[B] ++= map.keys.flatMap(f(_))
-
   // Operations on ParIterable
   def prepAdd[V](it: ParIterable[V]): Addable[V] = it
   def add[V](addable: Addable[V], v: V): Unit = addable += v

From 175ec62da2c00c540822786aa39bc817564ca791 Mon Sep 17 00:00:00 2001
From: Tobias Schlatter <tobias@meisch.ch>
Date: Fri, 12 Apr 2024 13:15:55 +0100
Subject: [PATCH 083/298] Use Array for byClass reachability info

This reduces the retained size on the test suite for the infos as
follows:

BaseLinker: 26MB -> 24MB
Refiner:    22MB -> 20MB
---
 .../src/main/scala/org/scalajs/linker/analyzer/Infos.scala    | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala
index fc57860d25..9b779b2f37 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala
@@ -93,7 +93,7 @@ object Infos {
   )
 
   final class ReachabilityInfo private[Infos] (
-      val byClass: List[ReachabilityInfoInClass],
+      val byClass: Array[ReachabilityInfoInClass],
       val globalFlags: ReachabilityInfo.Flags
   )
 
@@ -374,7 +374,7 @@ object Infos {
       setFlag(ReachabilityInfo.FlagUsedExponentOperator)
 
     def result(): ReachabilityInfo =
-      new ReachabilityInfo(byClass.valuesIterator.map(_.result()).toList, flags)
+      new ReachabilityInfo(byClass.valuesIterator.map(_.result()).toArray, flags)
   }
 
   final class ReachabilityInfoInClassBuilder(val className: ClassName) {

From 6dcd1b73dcaa74d18cb7f94eb87ffde4416095b6 Mon Sep 17 00:00:00 2001
From: Tobias Schlatter <tobias@meisch.ch>
Date: Fri, 12 Apr 2024 14:48:21 +0100
Subject: [PATCH 084/298] Move static module dependency tracking to class level
 info

This avoids unnecessary calls to `addStaticDependency`, but more
importantly, it will allow us to flatten the structure of
`ReachabilityInfoInClass`.
---
 .../src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala | 4 ----
 .../src/main/scala/org/scalajs/linker/analyzer/Infos.scala    | 4 ++++
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala
index 52a6326a01..77d0ab3880 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala
@@ -1448,25 +1448,21 @@ private class AnalyzerRun(config: CommonPhaseConfig, initial: Boolean,
         }
 
         if (!dataInClass.staticFieldsRead.isEmpty) {
-          moduleUnit.addStaticDependency(className)
           dataInClass.staticFieldsRead.foreach(
               clazz._staticFieldsRead.update(_, ()))
         }
 
         if (!dataInClass.staticFieldsWritten.isEmpty) {
-          moduleUnit.addStaticDependency(className)
           dataInClass.staticFieldsWritten.foreach(
               clazz._staticFieldsWritten.update(_, ()))
         }
 
         if (!dataInClass.methodsCalled.isEmpty) {
-          // Do not add to staticDependencies: We call these on the object.
           for (methodName <- dataInClass.methodsCalled)
             clazz.callMethod(methodName)
         }
 
         if (!dataInClass.methodsCalledStatically.isEmpty) {
-          moduleUnit.addStaticDependency(className)
           for (methodName <- dataInClass.methodsCalledStatically)
             clazz.callMethodStatically(methodName)
         }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala
index 9b779b2f37..6967326919 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala
@@ -400,21 +400,25 @@ object Infos {
 
     def addStaticFieldRead(field: FieldName): this.type = {
       staticFieldsRead += field
+      setStaticallyReferenced()
       this
     }
 
     def addStaticFieldWritten(field: FieldName): this.type = {
       staticFieldsWritten += field
+      setStaticallyReferenced()
       this
     }
 
     def addMethodCalled(method: MethodName): this.type = {
       methodsCalled += method
+      // Do not call setStaticallyReferenced: We call these methods on the object.
       this
     }
 
     def addMethodCalledStatically(method: NamespacedMethodName): this.type = {
       methodsCalledStatically += method
+      setStaticallyReferenced()
       this
     }
 

From a54c022343f5f50c0cffc438f30501bb1e73f033 Mon Sep 17 00:00:00 2001
From: Tobias Schlatter <tobias@meisch.ch>
Date: Fri, 12 Apr 2024 14:53:33 +0100
Subject: [PATCH 085/298] Add a flag to class level info for dynamic import

This allows us to remove a field from `ReachabilityInfoInClass` which
reduces the retained size on the test suite for the infos as follows:

BaseLinker: 24MB -> 23MB
Refiner:    20MB -> 20MB (within rounding error)
---
 .../org/scalajs/linker/analyzer/Analyzer.scala | 18 +++++++-----------
 .../org/scalajs/linker/analyzer/Infos.scala    |  8 ++++----
 2 files changed, 11 insertions(+), 15 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala
index 77d0ab3880..48d2379f4c 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala
@@ -1432,6 +1432,13 @@ private class AnalyzerRun(config: CommonPhaseConfig, initial: Boolean,
           if ((flags & ReachabilityInfoInClass.FlagStaticallyReferenced) != 0) {
             moduleUnit.addStaticDependency(className)
           }
+
+          if ((flags & ReachabilityInfoInClass.FlagDynamicallyReferenced) != 0) {
+            if (isNoModule)
+              _errors ::= DynamicImportWithoutModuleSupport(from)
+            else
+              moduleUnit.addDynamicDependency(className)
+          }
         }
 
         /* Since many of the lists below are likely to be empty, we always
@@ -1467,17 +1474,6 @@ private class AnalyzerRun(config: CommonPhaseConfig, initial: Boolean,
             clazz.callMethodStatically(methodName)
         }
 
-        if (!dataInClass.methodsCalledDynamicImport.isEmpty) {
-          if (isNoModule) {
-            _errors ::= DynamicImportWithoutModuleSupport(from)
-          } else {
-            moduleUnit.addDynamicDependency(className)
-            // In terms of reachability, a dynamic import call is just a static call.
-            for (methodName <- dataInClass.methodsCalledDynamicImport)
-              clazz.callMethodStatically(methodName)
-          }
-        }
-
         if (!dataInClass.jsNativeMembersUsed.isEmpty) {
           for (member <- dataInClass.jsNativeMembersUsed)
             clazz.useJSNativeMember(member)
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala
index 6967326919..49b60b6a3c 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala
@@ -115,7 +115,6 @@ object Infos {
       val staticFieldsWritten: List[FieldName],
       val methodsCalled: List[MethodName],
       val methodsCalledStatically: List[NamespacedMethodName],
-      val methodsCalledDynamicImport: List[NamespacedMethodName],
       val jsNativeMembersUsed: List[MethodName],
       val flags: ReachabilityInfoInClass.Flags
   )
@@ -132,6 +131,7 @@ object Infos {
     final val FlagInstanceTestsUsed = 1 << 2
     final val FlagClassDataAccessed = 1 << 3
     final val FlagStaticallyReferenced = 1 << 4
+    final val FlagDynamicallyReferenced = 1 << 5
   }
 
   final class ClassInfoBuilder(
@@ -384,7 +384,6 @@ object Infos {
     private val staticFieldsWritten = mutable.Set.empty[FieldName]
     private val methodsCalled = mutable.Set.empty[MethodName]
     private val methodsCalledStatically = mutable.Set.empty[NamespacedMethodName]
-    private val methodsCalledDynamicImport = mutable.Set.empty[NamespacedMethodName]
     private val jsNativeMembersUsed = mutable.Set.empty[MethodName]
     private var flags: ReachabilityInfoInClass.Flags = 0
 
@@ -423,7 +422,9 @@ object Infos {
     }
 
     def addMethodCalledDynamicImport(method: NamespacedMethodName): this.type = {
-      methodsCalledDynamicImport += method
+      // In terms of reachability, a dynamic import call is just a static call.
+      methodsCalledStatically += method
+      setFlag(ReachabilityInfoInClass.FlagDynamicallyReferenced)
       this
     }
 
@@ -461,7 +462,6 @@ object Infos {
           staticFieldsWritten = toLikelyEmptyList(staticFieldsWritten),
           methodsCalled = toLikelyEmptyList(methodsCalled),
           methodsCalledStatically = toLikelyEmptyList(methodsCalledStatically),
-          methodsCalledDynamicImport = toLikelyEmptyList(methodsCalledDynamicImport),
           jsNativeMembersUsed = toLikelyEmptyList(jsNativeMembersUsed),
           flags = flags
       )

From 0d81e85e50dcb31cd5ecd552facd94314529775f Mon Sep 17 00:00:00 2001
From: Tobias Schlatter <tobias@meisch.ch>
Date: Fri, 12 Apr 2024 14:39:14 +0100
Subject: [PATCH 086/298] Store member reachability in a single field

This reduces the retained size on the test suite for the infos as
follows:

BaseLinker: 23MB -> 20MB
Refiner:    20MB -> 17MB
---
 .../scalajs/linker/analyzer/Analyzer.scala    | 78 +++++----------
 .../org/scalajs/linker/analyzer/Infos.scala   | 95 +++++++++++++------
 2 files changed, 91 insertions(+), 82 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala
index 48d2379f4c..506cde51eb 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala
@@ -1079,7 +1079,8 @@ private class AnalyzerRun(config: CommonPhaseConfig, initial: Boolean,
       } else if (!_isInstantiated.getAndSet(true)) {
 
         // TODO: Why is this not in subclassInstantiated()?
-        referenceFieldClasses(fieldsRead ++ fieldsWritten)
+        fieldsRead.foreach(referenceFieldClasses(_))
+        fieldsWritten.foreach(referenceFieldClasses(_))
 
         if (isScalaClass) {
           accessData()
@@ -1208,12 +1209,6 @@ private class AnalyzerRun(config: CommonPhaseConfig, initial: Boolean,
       }
     }
 
-    def callMethodStatically(namespacedMethodName: NamespacedMethodName)(
-        implicit from: From): Unit = {
-      callMethodStatically(namespacedMethodName.namespace,
-          namespacedMethodName.methodName)
-    }
-
     def callMethodStatically(namespace: MemberNamespace,
         methodName: MethodName)(
         implicit from: From): Unit = {
@@ -1225,16 +1220,14 @@ private class AnalyzerRun(config: CommonPhaseConfig, initial: Boolean,
         lookupMethod(methodName).reachStatic()
     }
 
-    def readFields(names: List[FieldName])(implicit from: From): Unit = {
-      names.foreach(_fieldsRead.update(_, ()))
-      if (isInstantiated)
-        referenceFieldClasses(names)
-    }
-
-    def writeFields(names: List[FieldName])(implicit from: From): Unit = {
-      names.foreach(_fieldsWritten.update(_, ()))
+    def reachField(info: Infos.FieldReachable)(implicit from: From): Unit = {
+      val fieldName = info.fieldName
+      if (info.read)
+        _fieldsRead.update(fieldName, ())
+      if (info.written)
+        _fieldsWritten.update(fieldName, ())
       if (isInstantiated)
-        referenceFieldClasses(names)
+        referenceFieldClasses(fieldName)
     }
 
     def useJSNativeMember(name: MethodName)(
@@ -1251,8 +1244,7 @@ private class AnalyzerRun(config: CommonPhaseConfig, initial: Boolean,
       maybeJSNativeLoadSpec
     }
 
-    private def referenceFieldClasses(fieldNames: Iterable[FieldName])(
-        implicit from: From): Unit = {
+    private def referenceFieldClasses(fieldName: FieldName)(implicit from: From): Unit = {
       assert(isInstantiated)
 
       /* Reach referenced classes of non-static fields
@@ -1261,7 +1253,6 @@ private class AnalyzerRun(config: CommonPhaseConfig, initial: Boolean,
        * site will not reference the classes in the final JS code.
        */
       for {
-        fieldName <- fieldNames
         className <- data.referencedFieldClasses.get(fieldName)
       } {
         lookupClass(className)(_ => ())
@@ -1441,43 +1432,26 @@ private class AnalyzerRun(config: CommonPhaseConfig, initial: Boolean,
           }
         }
 
-        /* Since many of the lists below are likely to be empty, we always
-         * test `!list.isEmpty` before calling `foreach` or any other
-         * processing, avoiding closure allocations.
-         */
+        if (dataInClass.memberInfos != null) {
+          dataInClass.memberInfos.foreach {
+            case field: Infos.FieldReachable =>
+              clazz.reachField(field)
 
-        if (!dataInClass.fieldsRead.isEmpty) {
-          clazz.readFields(dataInClass.fieldsRead)
-        }
+            case Infos.StaticFieldReachable(fieldName, read, written) =>
+              if (read)
+                clazz._staticFieldsRead.update(fieldName, ())
+              if (written)
+                clazz._staticFieldsWritten.update(fieldName, ())
 
-        if (!dataInClass.fieldsWritten.isEmpty) {
-          clazz.writeFields(dataInClass.fieldsWritten)
-        }
+            case Infos.MethodReachable(methodName) =>
+              clazz.callMethod(methodName)
 
-        if (!dataInClass.staticFieldsRead.isEmpty) {
-          dataInClass.staticFieldsRead.foreach(
-              clazz._staticFieldsRead.update(_, ()))
-        }
-
-        if (!dataInClass.staticFieldsWritten.isEmpty) {
-          dataInClass.staticFieldsWritten.foreach(
-              clazz._staticFieldsWritten.update(_, ()))
-        }
+            case Infos.MethodStaticallyReachable(namespace, methodName) =>
+              clazz.callMethodStatically(namespace, methodName)
 
-        if (!dataInClass.methodsCalled.isEmpty) {
-          for (methodName <- dataInClass.methodsCalled)
-            clazz.callMethod(methodName)
-        }
-
-        if (!dataInClass.methodsCalledStatically.isEmpty) {
-          for (methodName <- dataInClass.methodsCalledStatically)
-            clazz.callMethodStatically(methodName)
-        }
-
-        if (!dataInClass.jsNativeMembersUsed.isEmpty) {
-          for (member <- dataInClass.jsNativeMembersUsed)
-            clazz.useJSNativeMember(member)
-              .foreach(addLoadSpec(moduleUnit, _))
+            case Infos.JSNativeMemberReachable(methodName) =>
+              clazz.useJSNativeMember(methodName).foreach(addLoadSpec(moduleUnit, _))
+          }
         }
       }
     }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala
index 49b60b6a3c..c031ab3f4f 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala
@@ -109,13 +109,12 @@ object Infos {
   /** Things from a given class that are reached by one method. */
   final class ReachabilityInfoInClass private[Infos] (
       val className: ClassName,
-      val fieldsRead: List[FieldName],
-      val fieldsWritten: List[FieldName],
-      val staticFieldsRead: List[FieldName],
-      val staticFieldsWritten: List[FieldName],
-      val methodsCalled: List[MethodName],
-      val methodsCalledStatically: List[NamespacedMethodName],
-      val jsNativeMembersUsed: List[MethodName],
+      /* We use a single field for all members to reduce memory consumption:
+       * Typically, there are very few members reached in a single
+       * ReachabilityInfoInClass, so the overhead of having a field per type
+       * becomes significant in terms of memory usage.
+       */
+      val memberInfos: Array[MemberReachabilityInfo], // nullable!
       val flags: ReachabilityInfoInClass.Flags
   )
 
@@ -134,6 +133,38 @@ object Infos {
     final val FlagDynamicallyReferenced = 1 << 5
   }
 
+  sealed trait MemberReachabilityInfo
+
+  final case class FieldReachable private[Infos] (
+    val fieldName: FieldName,
+    val read: Boolean = false,
+    val written: Boolean = false
+  ) extends MemberReachabilityInfo
+
+  final case class StaticFieldReachable private[Infos] (
+    val fieldName: FieldName,
+    val read: Boolean = false,
+    val written: Boolean = false
+  ) extends MemberReachabilityInfo
+
+  final case class MethodReachable private[Infos] (
+    val methodName: MethodName
+  ) extends MemberReachabilityInfo
+
+  final case class MethodStaticallyReachable private[Infos] (
+    val namespace: MemberNamespace,
+    val methodName: MethodName
+  ) extends MemberReachabilityInfo
+
+  object MethodStaticallyReachable {
+    private[Infos] def apply(m: NamespacedMethodName): MethodStaticallyReachable =
+      MethodStaticallyReachable(m.namespace, m.methodName)
+  }
+
+  final case class JSNativeMemberReachable private[Infos] (
+    val methodName: MethodName
+  ) extends MemberReachabilityInfo
+
   final class ClassInfoBuilder(
       private val className: ClassName,
       private val kind: ClassKind,
@@ -378,33 +409,39 @@ object Infos {
   }
 
   final class ReachabilityInfoInClassBuilder(val className: ClassName) {
-    private val fieldsRead = mutable.Set.empty[FieldName]
-    private val fieldsWritten = mutable.Set.empty[FieldName]
-    private val staticFieldsRead = mutable.Set.empty[FieldName]
-    private val staticFieldsWritten = mutable.Set.empty[FieldName]
+    private val fieldsUsed = mutable.Map.empty[FieldName, FieldReachable]
+    private val staticFieldsUsed = mutable.Map.empty[FieldName, StaticFieldReachable]
     private val methodsCalled = mutable.Set.empty[MethodName]
     private val methodsCalledStatically = mutable.Set.empty[NamespacedMethodName]
     private val jsNativeMembersUsed = mutable.Set.empty[MethodName]
     private var flags: ReachabilityInfoInClass.Flags = 0
 
     def addFieldRead(field: FieldName): this.type = {
-      fieldsRead += field
+      fieldsUsed(field) = fieldsUsed
+        .getOrElse(field, FieldReachable(field))
+        .copy(read = true)
       this
     }
 
     def addFieldWritten(field: FieldName): this.type = {
-      fieldsWritten += field
+      fieldsUsed(field) = fieldsUsed
+        .getOrElse(field, FieldReachable(field))
+        .copy(written = true)
       this
     }
 
     def addStaticFieldRead(field: FieldName): this.type = {
-      staticFieldsRead += field
+      staticFieldsUsed(field) = staticFieldsUsed
+        .getOrElse(field, StaticFieldReachable(field))
+        .copy(read = true)
       setStaticallyReferenced()
       this
     }
 
     def addStaticFieldWritten(field: FieldName): this.type = {
-      staticFieldsWritten += field
+      staticFieldsUsed(field) = staticFieldsUsed
+        .getOrElse(field, StaticFieldReachable(field))
+        .copy(written = true)
       setStaticallyReferenced()
       this
     }
@@ -454,22 +491,20 @@ object Infos {
       setFlag(ReachabilityInfoInClass.FlagStaticallyReferenced)
 
     def result(): ReachabilityInfoInClass = {
-      new ReachabilityInfoInClass(
-          className,
-          fieldsRead = toLikelyEmptyList(fieldsRead),
-          fieldsWritten = toLikelyEmptyList(fieldsWritten),
-          staticFieldsRead = toLikelyEmptyList(staticFieldsRead),
-          staticFieldsWritten = toLikelyEmptyList(staticFieldsWritten),
-          methodsCalled = toLikelyEmptyList(methodsCalled),
-          methodsCalledStatically = toLikelyEmptyList(methodsCalledStatically),
-          jsNativeMembersUsed = toLikelyEmptyList(jsNativeMembersUsed),
-          flags = flags
-      )
-    }
+      val memberInfos: Array[MemberReachabilityInfo] = (
+          fieldsUsed.valuesIterator ++
+          staticFieldsUsed.valuesIterator ++
+          methodsCalled.iterator.map(MethodReachable(_)) ++
+          methodsCalledStatically.iterator.map(MethodStaticallyReachable(_)) ++
+          jsNativeMembersUsed.iterator.map(JSNativeMemberReachable(_))
+      ).toArray
+
+      val memberInfosOrNull =
+        if (memberInfos.isEmpty) null
+        else memberInfos
 
-    private def toLikelyEmptyList[A](set: mutable.Set[A]): List[A] =
-      if (set.isEmpty) Nil
-      else set.toList
+      new ReachabilityInfoInClass(className, memberInfosOrNull, flags)
+    }
   }
 
   /** Generates the [[MethodInfo]] of a

From 2448ab0921f12a328931fff125b970fb5da0440f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Tue, 23 Apr 2024 11:25:12 +0200
Subject: [PATCH 087/298] Exclude files from Scala's `library-aux` to prepare
 for 2.13.14.

Since Scala 2.13.14, the stdlib's source jar contains the files of
their `library-aux` directory. These files are not meant to be
processed by the regular compiler (only by Scaladoc). We must
therefore exclude them from the compilation of the scalalib.

In the process, we remove the exclusion of `/scala/util/parsing/`
which has been dead code since we dropped support for Scala 2.11.
---
 project/Build.scala | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/project/Build.scala b/project/Build.scala
index 6460bd86bf..0d93e05ec7 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -1681,6 +1681,12 @@ object Build {
 
         val s = streams.value
 
+        /* Exclude files coming from Scala's `library-aux` directory, as they are not
+         * meant to be compiled. They are part of the source jar since Scala 2.13.14.
+         */
+        val excludeFiles =
+          Set("Any.scala", "AnyRef.scala", "Nothing.scala", "Null.scala", "Singleton.scala")
+
         for {
           srcDir <- sourceDirectories
           normSrcDir = normPath(srcDir)
@@ -1688,10 +1694,10 @@ object Build {
         } {
           val normSrc = normPath(src)
           val path = normSrc.substring(normSrcDir.length)
-          val useless =
+          val exclude =
             path.contains("/scala/collection/parallel/") ||
-            path.contains("/scala/util/parsing/")
-          if (!useless) {
+            (src.getParentFile().getName() == "scala" && excludeFiles.contains(src.getName()))
+          if (!exclude) {
             if (paths.add(path))
               sources += src
             else

From caa3e47c1893ce1536ce50a949cbeb32a829410d Mon Sep 17 00:00:00 2001
From: Tobias Schlatter <tobias@meisch.ch>
Date: Wed, 1 May 2024 17:12:23 +0200
Subject: [PATCH 088/298] Remove Infos.ClassInfoBuilder

It was a useful abstraction when we were using Traversers to build
entire class infos. However, at this point it's mostly boilerplate.

Changeing this, will help simplify upcoming changes.
---
 .../scalajs/linker/analyzer/Analyzer.scala    | 11 +--
 .../scalajs/linker/analyzer/InfoLoader.scala  | 39 ++++-------
 .../org/scalajs/linker/analyzer/Infos.scala   | 68 +++++--------------
 3 files changed, 38 insertions(+), 80 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala
index 506cde51eb..1db858f237 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala
@@ -1507,10 +1507,13 @@ private class AnalyzerRun(config: CommonPhaseConfig, initial: Boolean,
       if (className == ObjectClass) None
       else Some(ObjectClass)
 
-    new Infos.ClassInfoBuilder(className, ClassKind.Class,
-        superClass = superClass, interfaces = Nil, jsNativeLoadSpec = None)
-      .addMethod(makeSyntheticMethodInfo(NoArgConstructorName, MemberNamespace.Constructor))
-      .result()
+    val methods =
+      List(makeSyntheticMethodInfo(NoArgConstructorName, MemberNamespace.Constructor))
+
+    new Infos.ClassInfo(className, ClassKind.Class,
+        superClass = superClass, interfaces = Nil, jsNativeLoadSpec = None,
+        referencedFieldClasses = Map.empty, methods = methods,
+        jsNativeMembers = Map.empty, jsMethodProps = Nil, topLevelExports = Nil)
   }
 
   private def makeSyntheticMethodInfo(
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/InfoLoader.scala b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/InfoLoader.scala
index c30a6c9a82..fd8620284c 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/InfoLoader.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/InfoLoader.scala
@@ -115,40 +115,27 @@ private[analyzer] object InfoLoader {
     }
 
     private def generateInfos(classDef: ClassDef): Infos.ClassInfo =  {
-      val builder = new Infos.ClassInfoBuilder(classDef.className,
-          classDef.kind, classDef.superClass.map(_.name),
-          classDef.interfaces.map(_.name), classDef.jsNativeLoadSpec)
+      val referencedFieldClasses = Infos.genReferencedFieldClasses(classDef.fields)
+      val methods = classDef.methods.map(methodsInfoCaches.getInfo(_))
 
-      classDef.fields.foreach {
-        case FieldDef(flags, FieldIdent(name), _, ftpe) =>
-          if (!flags.namespace.isStatic)
-            builder.maybeAddReferencedFieldClass(name, ftpe)
-
-        case _: JSFieldDef =>
-          // Nothing to do.
-      }
-
-      classDef.methods.foreach { method =>
-        builder.addMethod(methodsInfoCaches.getInfo(method))
+      val jsMethodProps = {
+        classDef.jsConstructor.map(jsConstructorInfoCache.getInfo(_)).toList :::
+        exportedMembersInfoCaches.getInfos(classDef.jsMethodProps)
       }
 
-      classDef.jsConstructor.foreach { jsConstructor =>
-        builder.addExportedMember(jsConstructorInfoCache.getInfo(jsConstructor))
-      }
-
-      for (info <- exportedMembersInfoCaches.getInfos(classDef.jsMethodProps))
-        builder.addExportedMember(info)
-
       /* We do not cache top-level exports, because they're quite rare,
        * and usually quite small when they exist.
        */
-      classDef.topLevelExportDefs.foreach { topLevelExportDef =>
-        builder.addTopLevelExport(Infos.generateTopLevelExportInfo(classDef.name.name, topLevelExportDef))
-      }
+      val topLevelExports = classDef.topLevelExportDefs
+        .map(Infos.generateTopLevelExportInfo(classDef.name.name, _))
 
-      classDef.jsNativeMembers.foreach(builder.addJSNativeMember(_))
+      val jsNativeMembers = classDef.jsNativeMembers
+        .map(m => m.name.name -> m.jsNativeLoadSpec).toMap
 
-      builder.result()
+      new Infos.ClassInfo(classDef.className, classDef.kind,
+          classDef.superClass.map(_.name), classDef.interfaces.map(_.name),
+          classDef.jsNativeLoadSpec, referencedFieldClasses, methods, jsNativeMembers,
+          jsMethodProps, topLevelExports)
     }
 
     /** Returns true if the cache has been used and should be kept. */
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala
index c031ab3f4f..da79bcf17d 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala
@@ -43,7 +43,7 @@ object Infos {
   final case class NamespacedMethodName(
       namespace: MemberNamespace, methodName: MethodName)
 
-  final class ClassInfo private[Infos] (
+  final class ClassInfo(
       val className: ClassName,
       val kind: ClassKind,
       val superClass: Option[ClassName], // always None for interfaces
@@ -165,57 +165,25 @@ object Infos {
     val methodName: MethodName
   ) extends MemberReachabilityInfo
 
-  final class ClassInfoBuilder(
-      private val className: ClassName,
-      private val kind: ClassKind,
-      private val superClass: Option[ClassName],
-      private val interfaces: List[ClassName],
-      private val jsNativeLoadSpec: Option[JSNativeLoadSpec]
-  ) {
-    private val referencedFieldClasses = mutable.Map.empty[FieldName, ClassName]
-    private val methods = mutable.ListBuffer.empty[MethodInfo]
-    private val jsNativeMembers = mutable.Map.empty[MethodName, JSNativeLoadSpec]
-    private val jsMethodProps = mutable.ListBuffer.empty[ReachabilityInfo]
-    private val topLevelExports = mutable.ListBuffer.empty[TopLevelExportInfo]
-
-    def maybeAddReferencedFieldClass(name: FieldName, tpe: Type): this.type = {
-      tpe match {
-        case ClassType(cls) =>
-          referencedFieldClasses.put(name, cls)
-        case ArrayType(ArrayTypeRef(ClassRef(cls), _)) =>
-          referencedFieldClasses.put(name, cls)
-        case _ =>
-      }
-
-      this
-    }
-
-    def addMethod(methodInfo: MethodInfo): this.type = {
-      methods += methodInfo
-      this
-    }
-
-    def addJSNativeMember(member: JSNativeMemberDef): this.type = {
-      jsNativeMembers.put(member.name.name, member.jsNativeLoadSpec)
-      this
-    }
-
-    def addExportedMember(reachabilityInfo: ReachabilityInfo): this.type = {
-      jsMethodProps += reachabilityInfo
-      this
-    }
-
-    def addTopLevelExport(topLevelExportInfo: TopLevelExportInfo): this.type = {
-      topLevelExports += topLevelExportInfo
-      this
+  def genReferencedFieldClasses(fields: List[AnyFieldDef]): Map[FieldName, ClassName] = {
+    val builder = Map.newBuilder[FieldName, ClassName]
+
+    fields.foreach {
+      case FieldDef(flags, FieldIdent(name), _, ftpe) =>
+        if (!flags.namespace.isStatic) {
+          ftpe match {
+            case ClassType(cls) =>
+              builder += name -> cls
+            case ArrayType(ArrayTypeRef(ClassRef(cls), _)) =>
+              builder += name -> cls
+            case _ =>
+          }
+        }
+      case _: JSFieldDef =>
+        // Nothing to do.
     }
 
-    def result(): ClassInfo = {
-      new ClassInfo(className, kind, superClass,
-          interfaces, jsNativeLoadSpec, referencedFieldClasses.toMap,
-          methods.toList, jsNativeMembers.toMap, jsMethodProps.toList,
-          topLevelExports.toList)
-    }
+    builder.result()
   }
 
   final class ReachabilityInfoBuilder {

From b2cd38f7ff409f239b324f1a9c54eccc6ee550ec Mon Sep 17 00:00:00 2001
From: Tobias Schlatter <tobias@meisch.ch>
Date: Wed, 8 May 2024 22:20:16 +0200
Subject: [PATCH 089/298] Remove unused method parameter `instantiatedClasses`

---
 .../src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala  | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala
index 1db858f237..4482ff2f4a 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala
@@ -1520,8 +1520,7 @@ private class AnalyzerRun(config: CommonPhaseConfig, initial: Boolean,
       methodName: MethodName,
       namespace: MemberNamespace,
       methodsCalled: List[(ClassName, MethodName)] = Nil,
-      methodsCalledStatically: List[(ClassName, NamespacedMethodName)] = Nil,
-      instantiatedClasses: List[ClassName] = Nil
+      methodsCalledStatically: List[(ClassName, NamespacedMethodName)] = Nil
   ): Infos.MethodInfo = {
     val reachabilityInfoBuilder = new Infos.ReachabilityInfoBuilder()
     for ((className, methodName) <- methodsCalled)

From 9264732fb49f224fdfa92df01ed7fc52f34d295f Mon Sep 17 00:00:00 2001
From: Tobias Schlatter <tobias@meisch.ch>
Date: Sat, 13 Apr 2024 17:33:54 +0100
Subject: [PATCH 090/298] Optimize Infos for caching in InfoLoader

This allows us to use the previously calculated infos themselves as
the cached values, reducing memory consumption.

Further, we reduce memory consumption by using immutable maps: Because
a lot of the maps are empty, we do not spend unecessary memory on
empty mutable maps.

This reduces the retained size on the test suite for the infos as
follows:

| Component  | Before [MB] | After [MB] |
|------------|------------:|-----------:|
| BaseLinker |          20 |         15 |
| Refiner    |          17 |         13 |

As a nice side-effect, this allows us to simplify the InfoLoader. The
simplification mainly stems from the insight, that we do not need
active cache used tracking; control flow is sufficient.

Execution times are unaffected, in fact, the incremental case might
even be a bit faster (non-significant though).
---
 .../scalajs/linker/analyzer/Analyzer.scala    |  57 +++---
 .../scalajs/linker/analyzer/InfoLoader.scala  | 172 ++++++------------
 .../org/scalajs/linker/analyzer/Infos.scala   |  74 ++++----
 3 files changed, 119 insertions(+), 184 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala
index 4482ff2f4a..3931d2ab58 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala
@@ -677,16 +677,15 @@ private class AnalyzerRun(config: CommonPhaseConfig, initial: Boolean,
      */
     private val _instantiatedSubclasses = new GrowingList[ClassInfo]
 
-    private val nsMethodInfos = {
-      val nsMethodInfos = Array.fill(MemberNamespace.Count) {
-        emptyThreadSafeMap[MethodName, MethodInfo]
-      }
-      for (methodData <- data.methods) {
-        // TODO It would be good to report duplicates as errors at this point
-        val relevantMap = nsMethodInfos(methodData.namespace.ordinal)
-        relevantMap(methodData.methodName) = new MethodInfo(this, methodData)
-      }
-      nsMethodInfos
+    private val nsMethodInfos = Array.tabulate(MemberNamespace.Count) { nsOrdinal =>
+      val namespace = MemberNamespace.fromOrdinal(nsOrdinal)
+
+      val m = emptyThreadSafeMap[MethodName, MethodInfo]
+
+      for ((name, data) <- data.methods(nsOrdinal))
+        m.put(name, new MethodInfo(this, namespace, name, data))
+
+      m
     }
 
     def methodInfos(
@@ -724,8 +723,8 @@ private class AnalyzerRun(config: CommonPhaseConfig, initial: Boolean,
        * method exists.
        */
       publicMethodInfos.getOrElseUpdate(methodName, {
-        val syntheticData = makeSyntheticMethodInfo(methodName, MemberNamespace.Public)
-        new MethodInfo(this, syntheticData, nonExistent = true)
+        val syntheticData = makeSyntheticMethodInfo()
+        new MethodInfo(this, MemberNamespace.Public, methodName, syntheticData, nonExistent = true)
       })
     }
 
@@ -812,11 +811,9 @@ private class AnalyzerRun(config: CommonPhaseConfig, initial: Boolean,
         val targetOwner = target.owner
 
         val syntheticInfo = makeSyntheticMethodInfo(
-            methodName = methodName,
-            namespace = MemberNamespace.Public,
             methodsCalledStatically = List(
                 targetOwner.className -> NamespacedMethodName(MemberNamespace.Public, methodName)))
-        new MethodInfo(this, syntheticInfo,
+        new MethodInfo(this, MemberNamespace.Public, methodName, syntheticInfo,
             syntheticKind = MethodSyntheticKind.DefaultBridge(targetOwner.className))
       })
     }
@@ -1011,10 +1008,8 @@ private class AnalyzerRun(config: CommonPhaseConfig, initial: Boolean,
 
       publicMethodInfos.getOrElseUpdate(proxyName, {
         val syntheticInfo = makeSyntheticMethodInfo(
-            methodName = proxyName,
-            namespace = MemberNamespace.Public,
             methodsCalled = List(this.className -> targetName))
-        new MethodInfo(this, syntheticInfo,
+        new MethodInfo(this, MemberNamespace.Public, proxyName, syntheticInfo,
             syntheticKind = MethodSyntheticKind.ReflectiveProxy(targetName))
       })
     }
@@ -1024,8 +1019,8 @@ private class AnalyzerRun(config: CommonPhaseConfig, initial: Boolean,
       assert(namespace != MemberNamespace.Public)
 
       methodInfos(namespace).getOrElseUpdate(methodName, {
-        val syntheticData = makeSyntheticMethodInfo(methodName, namespace)
-        new MethodInfo(this, syntheticData, nonExistent = true)
+        val syntheticData = makeSyntheticMethodInfo()
+        new MethodInfo(this, namespace, methodName, syntheticData, nonExistent = true)
       })
     }
 
@@ -1273,13 +1268,13 @@ private class AnalyzerRun(config: CommonPhaseConfig, initial: Boolean,
 
   private class MethodInfo(
     val owner: ClassInfo,
+    val namespace: MemberNamespace,
+    val methodName: MethodName,
     data: Infos.MethodInfo,
     val nonExistent: Boolean = false,
     val syntheticKind: MethodSyntheticKind = MethodSyntheticKind.None
   ) extends Analysis.MethodInfo {
 
-    val methodName = data.methodName
-    val namespace = data.namespace
     val isAbstract = data.isAbstract
 
     private[this] val _isAbstractReachable = new AtomicBoolean(false)
@@ -1357,7 +1352,7 @@ private class AnalyzerRun(config: CommonPhaseConfig, initial: Boolean,
     }
 
     private[this] def doReach(): Unit =
-      followReachabilityInfo(data.reachabilityInfo, owner)(FromMethod(this))
+      followReachabilityInfo(data, owner)(FromMethod(this))
   }
 
   private class TopLevelExportInfo(val owningClass: ClassName, data: Infos.TopLevelExportInfo)
@@ -1507,8 +1502,12 @@ private class AnalyzerRun(config: CommonPhaseConfig, initial: Boolean,
       if (className == ObjectClass) None
       else Some(ObjectClass)
 
-    val methods =
-      List(makeSyntheticMethodInfo(NoArgConstructorName, MemberNamespace.Constructor))
+    val methods = Array.tabulate[Map[MethodName, Infos.MethodInfo]](MemberNamespace.Count) { nsOrdinal =>
+      if (nsOrdinal == MemberNamespace.Constructor.ordinal)
+        Map(NoArgConstructorName -> makeSyntheticMethodInfo())
+      else
+        Map.empty
+    }
 
     new Infos.ClassInfo(className, ClassKind.Class,
         superClass = superClass, interfaces = Nil, jsNativeLoadSpec = None,
@@ -1517,18 +1516,16 @@ private class AnalyzerRun(config: CommonPhaseConfig, initial: Boolean,
   }
 
   private def makeSyntheticMethodInfo(
-      methodName: MethodName,
-      namespace: MemberNamespace,
       methodsCalled: List[(ClassName, MethodName)] = Nil,
       methodsCalledStatically: List[(ClassName, NamespacedMethodName)] = Nil
   ): Infos.MethodInfo = {
-    val reachabilityInfoBuilder = new Infos.ReachabilityInfoBuilder()
+    val reachabilityInfoBuilder = new Infos.ReachabilityInfoBuilder(ir.Version.Unversioned)
+
     for ((className, methodName) <- methodsCalled)
       reachabilityInfoBuilder.addMethodCalled(className, methodName)
     for ((className, methodName) <- methodsCalledStatically)
       reachabilityInfoBuilder.addMethodCalledStatically(className, methodName)
-    Infos.MethodInfo(methodName, namespace, isAbstract = false,
-        reachabilityInfoBuilder.result())
+    Infos.MethodInfo(isAbstract = false, reachabilityInfoBuilder.result())
   }
 
 }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/InfoLoader.scala b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/InfoLoader.scala
index fd8620284c..7eeb5d197b 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/InfoLoader.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/InfoLoader.scala
@@ -64,14 +64,16 @@ private[analyzer] object InfoLoader {
   case object InitialIRCheck extends IRCheckMode
   case object InternalIRCheck extends IRCheckMode
 
+  private type MethodInfos = Array[Map[MethodName, Infos.MethodInfo]]
+
   private class ClassInfoCache(className: ClassName, irLoader: IRLoader, irCheckMode: InfoLoader.IRCheckMode) {
     private var cacheUsed: Boolean = false
     private var version: Version = Version.Unversioned
     private var info: Future[Infos.ClassInfo] = _
 
-    private val methodsInfoCaches = MethodDefsInfosCache()
-    private val jsConstructorInfoCache = new JSConstructorDefInfoCache()
-    private val exportedMembersInfoCaches = JSMethodPropDefsInfosCache()
+    private var prevMethodInfos: MethodInfos = Array.fill(MemberNamespace.Count)(Map.empty)
+    private var prevJSCtorInfo: Option[Infos.ReachabilityInfo] = None
+    private var prevJSMethodPropDefInfos: List[Infos.ReachabilityInfo] = Nil
 
     def loadInfo(logger: Logger)(implicit ec: ExecutionContext): Future[Infos.ClassInfo] = synchronized {
       /* If the cache was already used in this run, the classDef and info are
@@ -116,12 +118,13 @@ private[analyzer] object InfoLoader {
 
     private def generateInfos(classDef: ClassDef): Infos.ClassInfo =  {
       val referencedFieldClasses = Infos.genReferencedFieldClasses(classDef.fields)
-      val methods = classDef.methods.map(methodsInfoCaches.getInfo(_))
 
-      val jsMethodProps = {
-        classDef.jsConstructor.map(jsConstructorInfoCache.getInfo(_)).toList :::
-        exportedMembersInfoCaches.getInfos(classDef.jsMethodProps)
-      }
+      prevMethodInfos = genMethodInfos(classDef.methods, prevMethodInfos)
+      prevJSCtorInfo = genJSCtorInfo(classDef.jsConstructor, prevJSCtorInfo)
+      prevJSMethodPropDefInfos =
+        genJSMethodPropDefInfos(classDef.jsMethodProps, prevJSMethodPropDefInfos)
+
+      val exportedMembers = prevJSCtorInfo.toList ::: prevJSMethodPropDefInfos
 
       /* We do not cache top-level exports, because they're quite rare,
        * and usually quite small when they exist.
@@ -134,139 +137,66 @@ private[analyzer] object InfoLoader {
 
       new Infos.ClassInfo(classDef.className, classDef.kind,
           classDef.superClass.map(_.name), classDef.interfaces.map(_.name),
-          classDef.jsNativeLoadSpec, referencedFieldClasses, methods, jsNativeMembers,
-          jsMethodProps, topLevelExports)
+          classDef.jsNativeLoadSpec, referencedFieldClasses, prevMethodInfos,
+          jsNativeMembers, exportedMembers, topLevelExports)
     }
 
     /** Returns true if the cache has been used and should be kept. */
     def cleanAfterRun(): Boolean = synchronized {
       val result = cacheUsed
       cacheUsed = false
-      if (result) {
-        // No point in cleaning the inner caches if the whole class disappears
-        methodsInfoCaches.cleanAfterRun()
-        jsConstructorInfoCache.cleanAfterRun()
-        exportedMembersInfoCaches.cleanAfterRun()
-      }
       result
     }
   }
 
-  private final class MethodDefsInfosCache private (
-      val caches: Array[mutable.Map[MethodName, MethodDefInfoCache]])
-      extends AnyVal {
-
-    def getInfo(methodDef: MethodDef): Infos.MethodInfo = {
-      val cache = caches(methodDef.flags.namespace.ordinal)
-        .getOrElseUpdate(methodDef.methodName, new MethodDefInfoCache)
-      cache.getInfo(methodDef)
-    }
+  private def genMethodInfos(methods: List[MethodDef],
+      prevMethodInfos: MethodInfos): MethodInfos = {
 
-    def cleanAfterRun(): Unit = {
-      caches.foreach(_.filterInPlace((_, cache) => cache.cleanAfterRun()))
-    }
-  }
-
-  private object MethodDefsInfosCache {
-    def apply(): MethodDefsInfosCache = {
-      new MethodDefsInfosCache(
-          Array.fill(MemberNamespace.Count)(mutable.Map.empty))
-    }
-  }
+    val builders = Array.fill(MemberNamespace.Count)(Map.newBuilder[MethodName, Infos.MethodInfo])
 
-  /* For JS method and property definitions, we use their index in the list of
-   * `linkedClass.exportedMembers` as their identity. We cannot use their name
-   * because the name itself is a `Tree`.
-   *
-   * If there is a different number of exported members than in a previous run,
-   * we always recompute everything. This is fine because, for any given class,
-   * either all JS methods and properties are reachable, or none are. So we're
-   * only missing opportunities for incrementality in the case where JS members
-   * are added or removed in the original .sjsir, which is not a big deal.
-   */
-  private final class JSMethodPropDefsInfosCache private (
-      private var caches: Array[JSMethodPropDefInfoCache]) {
-
-    def getInfos(members: List[JSMethodPropDef]): List[Infos.ReachabilityInfo] = {
-      if (members.isEmpty) {
-        caches = null
-        Nil
-      } else {
-        val membersSize = members.size
-        if (caches == null || membersSize != caches.size)
-          caches = Array.fill(membersSize)(new JSMethodPropDefInfoCache)
-
-        for ((member, i) <- members.zipWithIndex) yield {
-          caches(i).getInfo(member)
-        }
-      }
-    }
+    methods.foreach { method =>
+      val info = prevMethodInfos(method.flags.namespace.ordinal)
+        .get(method.methodName)
+        .filter(_.version.sameVersion(method.version))
+        .getOrElse(Infos.generateMethodInfo(method))
 
-    def cleanAfterRun(): Unit = {
-      if (caches != null)
-        caches.foreach(_.cleanAfterRun())
+      builders(method.flags.namespace.ordinal) += method.methodName -> info
     }
-  }
 
-  private object JSMethodPropDefsInfosCache {
-    def apply(): JSMethodPropDefsInfosCache =
-      new JSMethodPropDefsInfosCache(null)
+    builders.map(_.result())
   }
 
-  private abstract class AbstractMemberInfoCache[Def <: VersionedMemberDef, Info] {
-    private var cacheUsed: Boolean = false
-    private var lastVersion: Version = Version.Unversioned
-    private var info: Info = _
-
-    final def getInfo(member: Def): Info = {
-      update(member)
-      info
-    }
-
-    private final def update(member: Def): Unit = {
-      if (!cacheUsed) {
-        cacheUsed = true
-        val newVersion = member.version
-        if (!lastVersion.sameVersion(newVersion)) {
-          info = computeInfo(member)
-          lastVersion = newVersion
-        }
-      }
-    }
-
-    protected def computeInfo(member: Def): Info
-
-    /** Returns true if the cache has been used and should be kept. */
-    final def cleanAfterRun(): Boolean = {
-      val result = cacheUsed
-      cacheUsed = false
-      result
+  private def genJSCtorInfo(jsCtor: Option[JSConstructorDef],
+      prevJSCtorInfo: Option[Infos.ReachabilityInfo]): Option[Infos.ReachabilityInfo] = {
+    jsCtor.map { ctor =>
+      prevJSCtorInfo
+        .filter(_.version.sameVersion(ctor.version))
+        .getOrElse(Infos.generateJSConstructorInfo(ctor))
     }
   }
 
-  private final class MethodDefInfoCache
-      extends AbstractMemberInfoCache[MethodDef, Infos.MethodInfo] {
-
-    protected def computeInfo(member: MethodDef): Infos.MethodInfo =
-      Infos.generateMethodInfo(member)
-  }
-
-  private final class JSConstructorDefInfoCache
-      extends AbstractMemberInfoCache[JSConstructorDef, Infos.ReachabilityInfo] {
-
-    protected def computeInfo(member: JSConstructorDef): Infos.ReachabilityInfo =
-      Infos.generateJSConstructorInfo(member)
-  }
-
-  private final class JSMethodPropDefInfoCache
-      extends AbstractMemberInfoCache[JSMethodPropDef, Infos.ReachabilityInfo] {
-
-    protected def computeInfo(member: JSMethodPropDef): Infos.ReachabilityInfo = {
-      member match {
-        case methodDef: JSMethodDef =>
-          Infos.generateJSMethodInfo(methodDef)
-        case propertyDef: JSPropertyDef =>
-          Infos.generateJSPropertyInfo(propertyDef)
+  private def genJSMethodPropDefInfos(jsMethodProps: List[JSMethodPropDef],
+      prevJSMethodPropDefInfos: List[Infos.ReachabilityInfo]): List[Infos.ReachabilityInfo] = {
+    /* For JS method and property definitions, we use their index in the list of
+     * `linkedClass.exportedMembers` as their identity. We cannot use their name
+     * because the name itself is a `Tree`.
+     *
+     * If there is a different number of exported members than in a previous run,
+     * we always recompute everything. This is fine because, for any given class,
+     * either all JS methods and properties are reachable, or none are. So we're
+     * only missing opportunities for incrementality in the case where JS members
+     * are added or removed in the original .sjsir, which is not a big deal.
+     */
+
+    if (prevJSMethodPropDefInfos.size != jsMethodProps.size) {
+      // Regenerate everything.
+      jsMethodProps.map(Infos.generateJSMethodPropDefInfo(_))
+    } else {
+      for {
+        (prevInfo, member) <- prevJSMethodPropDefInfos.zip(jsMethodProps)
+      } yield {
+        if (prevInfo.version.sameVersion(member.version)) prevInfo
+        else Infos.generateJSMethodPropDefInfo(member)
       }
     }
   }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala
index da79bcf17d..956dcb0c15 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala
@@ -19,6 +19,7 @@ import org.scalajs.ir.Names._
 import org.scalajs.ir.Traversers._
 import org.scalajs.ir.Trees._
 import org.scalajs.ir.Types._
+import org.scalajs.ir.Version
 
 import org.scalajs.linker.backend.emitter.Transients._
 import org.scalajs.linker.standard.LinkedTopLevelExport
@@ -59,7 +60,7 @@ object Infos {
        * This happens when they have non-class type (e.g. Int)
        */
       val referencedFieldClasses: Map[FieldName, ClassName],
-      val methods: List[MethodInfo],
+      val methods: Array[Map[MethodName, MethodInfo]],
       val jsNativeMembers: Map[MethodName, JSNativeLoadSpec],
       val jsMethodProps: List[ReachabilityInfo],
       val topLevelExports: List[TopLevelExportInfo]
@@ -67,22 +68,23 @@ object Infos {
     override def toString(): String = className.nameString
   }
 
+  /* MethodInfo should contain, not be a ReachbilityInfo
+   *
+   * However, since this class is retained over multiple linker runs in the
+   * cache, the shallow size of the object shows up in memory performance
+   * profiles. Therefore, we (ab)use inheritance to lower the memory overhead.
+   */
   final class MethodInfo private (
-      val methodName: MethodName,
-      val namespace: MemberNamespace,
-      val isAbstract: Boolean,
-      val reachabilityInfo: ReachabilityInfo
-  ) {
-    override def toString(): String = methodName.nameString
-  }
+    val isAbstract: Boolean,
+    version: Version,
+    byClass: Array[ReachabilityInfoInClass],
+    globalFlags: ReachabilityInfo.Flags
+  ) extends ReachabilityInfo(version, byClass, globalFlags)
 
   object MethodInfo {
-    def apply(
-        methodName: MethodName,
-        namespace: MemberNamespace,
-        isAbstract: Boolean,
-        reachabilityInfo: ReachabilityInfo): MethodInfo = {
-      new MethodInfo(methodName, namespace, isAbstract, reachabilityInfo)
+    def apply(isAbstract: Boolean, reachabilityInfo: ReachabilityInfo): MethodInfo = {
+      import reachabilityInfo._
+      new MethodInfo(isAbstract, version, byClass, globalFlags)
     }
   }
 
@@ -92,9 +94,15 @@ object Infos {
       val exportName: String
   )
 
-  final class ReachabilityInfo private[Infos] (
-      val byClass: Array[ReachabilityInfoInClass],
-      val globalFlags: ReachabilityInfo.Flags
+  sealed class ReachabilityInfo private[Infos] (
+    /* The version field does not belong here conceptually.
+     * However, it helps the InfoLoader re-use previous infos without
+     * additional data held in memory.
+     * This reduces the memory we need to cache infos between incremental runs.
+     */
+    val version: Version,
+    val byClass: Array[ReachabilityInfoInClass],
+    val globalFlags: ReachabilityInfo.Flags
   )
 
   object ReachabilityInfo {
@@ -186,7 +194,7 @@ object Infos {
     builder.result()
   }
 
-  final class ReachabilityInfoBuilder {
+  final class ReachabilityInfoBuilder(version: Version) {
     private val byClass = mutable.Map.empty[ClassName, ReachabilityInfoInClassBuilder]
     private var flags: ReachabilityInfo.Flags = 0
 
@@ -373,7 +381,7 @@ object Infos {
       setFlag(ReachabilityInfo.FlagUsedExponentOperator)
 
     def result(): ReachabilityInfo =
-      new ReachabilityInfo(byClass.valuesIterator.map(_.result()).toArray, flags)
+      new ReachabilityInfo(version, byClass.valuesIterator.map(_.result()).toArray, flags)
   }
 
   final class ReachabilityInfoInClassBuilder(val className: ClassName) {
@@ -479,38 +487,43 @@ object Infos {
    *  [[org.scalajs.ir.Trees.MethodDef Trees.MethodDef]].
    */
   def generateMethodInfo(methodDef: MethodDef): MethodInfo =
-    new GenInfoTraverser().generateMethodInfo(methodDef)
+    new GenInfoTraverser(methodDef.version).generateMethodInfo(methodDef)
 
   /** Generates the [[ReachabilityInfo]] of a
    *  [[org.scalajs.ir.Trees.JSConstructorDef Trees.JSConstructorDef]].
    */
   def generateJSConstructorInfo(ctorDef: JSConstructorDef): ReachabilityInfo =
-    new GenInfoTraverser().generateJSConstructorInfo(ctorDef)
+    new GenInfoTraverser(ctorDef.version).generateJSConstructorInfo(ctorDef)
 
   /** Generates the [[ReachabilityInfo]] of a
    *  [[org.scalajs.ir.Trees.JSMethodDef Trees.JSMethodDef]].
    */
   def generateJSMethodInfo(methodDef: JSMethodDef): ReachabilityInfo =
-    new GenInfoTraverser().generateJSMethodInfo(methodDef)
+    new GenInfoTraverser(methodDef.version).generateJSMethodInfo(methodDef)
 
   /** Generates the [[ReachabilityInfo]] of a
    *  [[org.scalajs.ir.Trees.JSPropertyDef Trees.JSPropertyDef]].
    */
   def generateJSPropertyInfo(propertyDef: JSPropertyDef): ReachabilityInfo =
-    new GenInfoTraverser().generateJSPropertyInfo(propertyDef)
+    new GenInfoTraverser(propertyDef.version).generateJSPropertyInfo(propertyDef)
+
+  def generateJSMethodPropDefInfo(member: JSMethodPropDef): ReachabilityInfo = member match {
+    case methodDef: JSMethodDef     => generateJSMethodInfo(methodDef)
+    case propertyDef: JSPropertyDef => generateJSPropertyInfo(propertyDef)
+  }
 
   /** Generates the [[MethodInfo]] for the top-level exports. */
   def generateTopLevelExportInfo(enclosingClass: ClassName,
       topLevelExportDef: TopLevelExportDef): TopLevelExportInfo = {
-    val info = new GenInfoTraverser().generateTopLevelExportInfo(enclosingClass,
-        topLevelExportDef)
+    val info = new GenInfoTraverser(Version.Unversioned)
+        .generateTopLevelExportInfo(enclosingClass, topLevelExportDef)
     new TopLevelExportInfo(info,
         ModuleID(topLevelExportDef.moduleID),
         topLevelExportDef.topLevelExportName)
   }
 
-  private final class GenInfoTraverser extends Traverser {
-    private val builder = new ReachabilityInfoBuilder
+  private final class GenInfoTraverser(version: Version) extends Traverser {
+    private val builder = new ReachabilityInfoBuilder(version)
 
     def generateMethodInfo(methodDef: MethodDef): MethodInfo = {
       val methodName = methodDef.methodName
@@ -521,12 +534,7 @@ object Infos {
 
       val reachabilityInfo = builder.result()
 
-      MethodInfo(
-          methodName,
-          methodDef.flags.namespace,
-          methodDef.body.isEmpty,
-          reachabilityInfo
-      )
+      MethodInfo(methodDef.body.isEmpty, reachabilityInfo)
     }
 
     def generateJSConstructorInfo(ctorDef: JSConstructorDef): ReachabilityInfo = {

From c48ecc467f21f08f20ae380de5b679a2e32c67e6 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Mon, 13 May 2024 14:34:06 +0200
Subject: [PATCH 091/298] Add tests for floating point remainder operations.

They do not correspond to the IEEE-754 notion of remainder.
Instead, they corresponding to the common math function `fmod`,
which does not have a straightforward implementation. Therefore,
it is worth having dedicated tests for them, to make sure that our
platforms have consistent behaviors.

This is particularly important for the Wasm backend, which does not
have built-in access to the semantics of `fmod`.
---
 .../testsuite/compiler/DoubleTest.scala       | 102 +++++++++++++++++
 .../testsuite/compiler/FloatTest.scala        | 104 ++++++++++++++++++
 2 files changed, 206 insertions(+)

diff --git a/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/DoubleTest.scala b/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/DoubleTest.scala
index 1e75f8bb8e..6f158aa23e 100644
--- a/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/DoubleTest.scala
+++ b/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/DoubleTest.scala
@@ -203,6 +203,108 @@ class DoubleTest {
     test(-3.42e-43f)
   }
 
+  @Test
+  def testRemainder(): Unit = {
+    /* Double `%` is atypical. It does not correspond to the IEEE-754 notion
+     * of remainder/modulo. Instead, it correspond to the common math function
+     * `fmod`. Therefore, we have dedicated tests for it, to make sure that
+     * our platforms agree on the semantics. They are not much, but they are
+     * enough to rule out the naive formula that can sometimes be found on the
+     * Web, namely `x - trunc(x / y) * y`.
+     */
+
+    def test(expected: Double, n: Double, d: Double): Unit =
+      assertExactEquals(expected, n % d)
+
+    // If n is NaN, return NaN
+    test(Double.NaN, Double.NaN, Double.NaN)
+    test(Double.NaN, Double.NaN, Double.PositiveInfinity)
+    test(Double.NaN, Double.NaN, Double.NegativeInfinity)
+    test(Double.NaN, Double.NaN, +0.0)
+    test(Double.NaN, Double.NaN, -0.0)
+    test(Double.NaN, Double.NaN, 2.1)
+    test(Double.NaN, Double.NaN, 5.5)
+    test(Double.NaN, Double.NaN, -151.189)
+
+    // If d is NaN, return NaN
+    test(Double.NaN, Double.NaN, Double.NaN)
+    test(Double.NaN, Double.PositiveInfinity, Double.NaN)
+    test(Double.NaN, Double.NegativeInfinity, Double.NaN)
+    test(Double.NaN, +0.0, Double.NaN)
+    test(Double.NaN, -0.0, Double.NaN)
+    test(Double.NaN, 2.1, Double.NaN)
+    test(Double.NaN, 5.5, Double.NaN)
+    test(Double.NaN, -151.189, Double.NaN)
+
+    // If n is PositiveInfinity, return NaN
+    test(Double.NaN, Double.PositiveInfinity, Double.PositiveInfinity)
+    test(Double.NaN, Double.PositiveInfinity, Double.NegativeInfinity)
+    test(Double.NaN, Double.PositiveInfinity, +0.0)
+    test(Double.NaN, Double.PositiveInfinity, -0.0)
+    test(Double.NaN, Double.PositiveInfinity, 2.1)
+    test(Double.NaN, Double.PositiveInfinity, 5.5)
+    test(Double.NaN, Double.PositiveInfinity, -151.189)
+
+    // If n is NegativeInfinity, return NaN
+    test(Double.NaN, Double.NegativeInfinity, Double.PositiveInfinity)
+    test(Double.NaN, Double.NegativeInfinity, Double.NegativeInfinity)
+    test(Double.NaN, Double.NegativeInfinity, +0.0)
+    test(Double.NaN, Double.NegativeInfinity, -0.0)
+    test(Double.NaN, Double.NegativeInfinity, 2.1)
+    test(Double.NaN, Double.NegativeInfinity, 5.5)
+    test(Double.NaN, Double.NegativeInfinity, -151.189)
+
+    // If d is PositiveInfinity, return n
+    test(+0.0, +0.0, Double.PositiveInfinity)
+    test(-0.0, -0.0, Double.PositiveInfinity)
+    test(2.1, 2.1, Double.PositiveInfinity)
+    test(5.5, 5.5, Double.PositiveInfinity)
+    test(-151.189, -151.189, Double.PositiveInfinity)
+
+    // If d is NegativeInfinity, return n
+    test(+0.0, +0.0, Double.NegativeInfinity)
+    test(-0.0, -0.0, Double.NegativeInfinity)
+    test(2.1, 2.1, Double.NegativeInfinity)
+    test(5.5, 5.5, Double.NegativeInfinity)
+    test(-151.189, -151.189, Double.NegativeInfinity)
+
+    // If d is +0.0, return NaN
+    test(Double.NaN, +0.0, +0.0)
+    test(Double.NaN, -0.0, +0.0)
+    test(Double.NaN, 2.1, +0.0)
+    test(Double.NaN, 5.5, +0.0)
+    test(Double.NaN, -151.189, +0.0)
+
+    // If d is -0.0, return NaN
+    test(Double.NaN, +0.0, -0.0)
+    test(Double.NaN, -0.0, -0.0)
+    test(Double.NaN, 2.1, -0.0)
+    test(Double.NaN, 5.5, -0.0)
+    test(Double.NaN, -151.189, -0.0)
+
+    // If n is +0.0, return n
+    test(+0.0, +0.0, 2.1)
+    test(+0.0, +0.0, 5.5)
+    test(+0.0, +0.0, -151.189)
+
+    // If n is -0.0, return n
+    test(-0.0, -0.0, 2.1)
+    test(-0.0, -0.0, 5.5)
+    test(-0.0, -0.0, -151.189)
+
+    // Non-special values
+    // { val l = List(2.1, 5.5, -151.189); for (n <- l; d <- l) println(s"    test(${n % d}, $n, $d)") }
+    test(0.0, 2.1, 2.1)
+    test(2.1, 2.1, 5.5)
+    test(2.1, 2.1, -151.189)
+    test(1.2999999999999998, 5.5, 2.1)
+    test(0.0, 5.5, 5.5)
+    test(5.5, 5.5, -151.189)
+    test(-2.0889999999999866, -151.189, 2.1)
+    test(-2.688999999999993, -151.189, 5.5)
+    test(-0.0, -151.189, -151.189)
+  }
+
   @Test
   def noReverseComparisons_Issue3575(): Unit = {
     import Double.NaN
diff --git a/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/FloatTest.scala b/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/FloatTest.scala
index 755689397c..d4dbdee940 100644
--- a/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/FloatTest.scala
+++ b/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/FloatTest.scala
@@ -53,6 +53,110 @@ class FloatTest {
     test(-65.67f, -65)
   }
 
+  @Test
+  def testRemainder(): Unit = {
+    /* Float `%` is atypical. It does not correspond to the IEEE-754 notion
+     * of remainder/modulo. Instead, it correspond to the common math function
+     * `fmod`. Therefore, we have dedicated tests for it, to make sure that
+     * our platforms agree on the semantics. They are not much, but they are
+     * enough to rule out the naive formula that can sometimes be found on the
+     * Web, namely `x - trunc(x / y) * y`.
+     */
+
+    def test(expected: Float, x: Float, y: Float): Unit =
+      assertExactEquals(expected, x % y)
+
+    // If n is NaN, return NaN
+    test(Float.NaN, Float.NaN, Float.NaN)
+    test(Float.NaN, Float.NaN, Float.PositiveInfinity)
+    test(Float.NaN, Float.NaN, Float.NegativeInfinity)
+    test(Float.NaN, Float.NaN, +0.0f)
+    test(Float.NaN, Float.NaN, -0.0f)
+    test(Float.NaN, Float.NaN, 2.1f)
+    test(Float.NaN, Float.NaN, 5.5f)
+    test(Float.NaN, Float.NaN, -151.189f)
+
+    // If d is NaN, return NaN
+    test(Float.NaN, Float.NaN, Float.NaN)
+    test(Float.NaN, Float.PositiveInfinity, Float.NaN)
+    test(Float.NaN, Float.NegativeInfinity, Float.NaN)
+    test(Float.NaN, +0.0f, Float.NaN)
+    test(Float.NaN, -0.0f, Float.NaN)
+    test(Float.NaN, 2.1f, Float.NaN)
+    test(Float.NaN, 5.5f, Float.NaN)
+    test(Float.NaN, -151.189f, Float.NaN)
+
+    // If n is PositiveInfinity, return NaN
+    test(Float.NaN, Float.PositiveInfinity, Float.PositiveInfinity)
+    test(Float.NaN, Float.PositiveInfinity, Float.NegativeInfinity)
+    test(Float.NaN, Float.PositiveInfinity, +0.0f)
+    test(Float.NaN, Float.PositiveInfinity, -0.0f)
+    test(Float.NaN, Float.PositiveInfinity, 2.1f)
+    test(Float.NaN, Float.PositiveInfinity, 5.5f)
+    test(Float.NaN, Float.PositiveInfinity, -151.189f)
+
+    // If n is NegativeInfinity, return NaN
+    test(Float.NaN, Float.NegativeInfinity, Float.PositiveInfinity)
+    test(Float.NaN, Float.NegativeInfinity, Float.NegativeInfinity)
+    test(Float.NaN, Float.NegativeInfinity, +0.0f)
+    test(Float.NaN, Float.NegativeInfinity, -0.0f)
+    test(Float.NaN, Float.NegativeInfinity, 2.1f)
+    test(Float.NaN, Float.NegativeInfinity, 5.5f)
+    test(Float.NaN, Float.NegativeInfinity, -151.189f)
+
+    // If d is PositiveInfinity, return n
+    test(+0.0f, +0.0f, Float.PositiveInfinity)
+    test(-0.0f, -0.0f, Float.PositiveInfinity)
+    test(2.1f, 2.1f, Float.PositiveInfinity)
+    test(5.5f, 5.5f, Float.PositiveInfinity)
+    test(-151.189f, -151.189f, Float.PositiveInfinity)
+
+    // If d is NegativeInfinity, return n
+    test(+0.0f, +0.0f, Float.NegativeInfinity)
+    test(-0.0f, -0.0f, Float.NegativeInfinity)
+    test(2.1f, 2.1f, Float.NegativeInfinity)
+    test(5.5f, 5.5f, Float.NegativeInfinity)
+    test(-151.189f, -151.189f, Float.NegativeInfinity)
+
+    // If d is +0.0, return NaN
+    test(Float.NaN, +0.0f, +0.0f)
+    test(Float.NaN, -0.0f, +0.0f)
+    test(Float.NaN, 2.1f, +0.0f)
+    test(Float.NaN, 5.5f, +0.0f)
+    test(Float.NaN, -151.189f, +0.0f)
+
+    // If d is -0.0, return NaN
+    test(Float.NaN, +0.0f, -0.0f)
+    test(Float.NaN, -0.0f, -0.0f)
+    test(Float.NaN, 2.1f, -0.0f)
+    test(Float.NaN, 5.5f, -0.0f)
+    test(Float.NaN, -151.189f, -0.0f)
+
+    // If n is +0.0, return n
+    test(+0.0f, +0.0f, 2.1f)
+    test(+0.0f, +0.0f, 5.5f)
+    test(+0.0f, +0.0f, -151.189f)
+
+    // If n is -0.0, return n
+    test(-0.0f, -0.0f, 2.1f)
+    test(-0.0f, -0.0f, 5.5f)
+    test(-0.0f, -0.0f, -151.189f)
+
+    // Non-special values
+    // { val l = List(2.1f, 5.5f, -151.189f); for (n <- l; d <- l) println(s"      test(${n % d}f, ${n}f, ${d}f)") }
+    if (hasStrictFloats) {
+      test(0.0f, 2.1f, 2.1f)
+      test(2.1f, 2.1f, 5.5f)
+      test(2.1f, 2.1f, -151.189f)
+      test(1.3000002f, 5.5f, 2.1f)
+      test(0.0f, 5.5f, 5.5f)
+      test(5.5f, 5.5f, -151.189f)
+      test(-2.0890021f, -151.189f, 2.1f)
+      test(-2.6889954f, -151.189f, 5.5f)
+      test(-0.0f, -151.189f, -151.189f)
+    }
+  }
+
   @Test
   def noReverseComparisons_Issue3575(): Unit = {
     import Float.NaN

From 1242fb9128de5f908177c25347ec421fe33f6069 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Mon, 13 May 2024 14:44:44 +0200
Subject: [PATCH 092/298] Remove
 SystemJSTest.identityHashCodeIsStableIfObjectIsSealed.

This test exploited undefined behavior itself, by trying to seal
a Scala object, which is not allowed in general.

It was also pointless. If any future object model implementation
change would invalidate the current implementation of
`systemIdentityHashCode`, we would be able to adjust the latter at
the same time.

When the test was originally added, back in 2015 in
941d6d3287c228dceb8b2963623ca24d8adcc6d7, `systemIdentityHashCode`
was implemented in user space, and therefore had to be forward
compatible. This is not the case anymore.

The test actually breaks on WebAssembly, since trying to seal a
Wasm object actually throws a `TypeError`.
---
 .../testsuite/javalib/lang/SystemJSTest.scala | 19 -------------------
 1 file changed, 19 deletions(-)

diff --git a/test-suite/js/src/test/scala/org/scalajs/testsuite/javalib/lang/SystemJSTest.scala b/test-suite/js/src/test/scala/org/scalajs/testsuite/javalib/lang/SystemJSTest.scala
index 867e08de6c..12dc332f64 100644
--- a/test-suite/js/src/test/scala/org/scalajs/testsuite/javalib/lang/SystemJSTest.scala
+++ b/test-suite/js/src/test/scala/org/scalajs/testsuite/javalib/lang/SystemJSTest.scala
@@ -23,25 +23,6 @@ import org.junit.Assume._
 
 class SystemJSTest {
 
-  @Test def identityHashCodeIsStableIfObjectIsSealed(): Unit = {
-    /* This is mostly forward-checking that, should we have an implementation
-     * that seals Scala.js objects, identityHashCode() survives.
-     */
-    class HasIDHashCodeToBeSealed
-
-    // Seal before the first call to hashCode()
-    val x1 = new HasIDHashCodeToBeSealed
-    js.Object.seal(x1.asInstanceOf[js.Object])
-    val x1FirstHash = x1.hashCode()
-    assertEquals(x1FirstHash, x1.hashCode())
-
-    // Seal after the first call to hashCode()
-    val x2 = new HasIDHashCodeToBeSealed
-    val x2FirstHash = x2.hashCode()
-    js.Object.seal(x2.asInstanceOf[js.Object])
-    assertEquals(x2FirstHash, x2.hashCode())
-  }
-
   @Test def identityHashCodeForJSObjects(): Unit = {
     if (Platform.assumeES2015 || js.typeOf(js.Dynamic.global.WeakMap) != "undefined") {
       /* This test is more restrictive than the spec, but we know our

From bc19472b73a2c72870eb8212b5a941cf5083c650 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Mon, 13 May 2024 14:57:33 +0200
Subject: [PATCH 093/298] Adapt boxValueClassesGivenToJSInteropMethod not to
 rely on the toString export.

The Wasm backend will not support `@JSExport` from Scala classes,
including for `toString()`. This commit makes the test pass on
Wasm without undermining what it was meat to test. In fact, it is
now more similar to the `unbox` test just above.

In order not to weaken the overall test, we add dedicated tests
for `@JSExport` behavior inside value classes to `ExportsTest`
instead.
---
 .../compiler/InteroperabilityTest.scala       |  8 ++++---
 .../testsuite/jsinterop/ExportsTest.scala     | 21 +++++++++++++++++++
 2 files changed, 26 insertions(+), 3 deletions(-)

diff --git a/test-suite/js/src/test/scala/org/scalajs/testsuite/compiler/InteroperabilityTest.scala b/test-suite/js/src/test/scala/org/scalajs/testsuite/compiler/InteroperabilityTest.scala
index 70abe08846..cc8f62fdcc 100644
--- a/test-suite/js/src/test/scala/org/scalajs/testsuite/compiler/InteroperabilityTest.scala
+++ b/test-suite/js/src/test/scala/org/scalajs/testsuite/compiler/InteroperabilityTest.scala
@@ -630,13 +630,15 @@ class InteroperabilityTest {
   @Test def boxValueClassesGivenToJSInteropMethod(): Unit = {
     val obj = js.eval("""
       var obj = {
-        stringOf: function(vc) { return vc.toString(); }
+        test: function(vc) { return vc; }
       };
       obj;
     """).asInstanceOf[InteroperabilityTestValueClassParam]
 
     val vc = new SomeValueClass(7)
-    assertEquals("SomeValueClass(7)", obj.stringOf(vc))
+    val r = obj.test(vc)
+    assertTrue(r.isInstanceOf[SomeValueClass])
+    assertEquals(7, r.asInstanceOf[SomeValueClass].i)
   }
 
   @Test def doNotUnboxValuesReceivedFromJSMethodInStatementPosition(): Unit = {
@@ -818,7 +820,7 @@ object InteroperabilityTest {
 
   @js.native
   trait InteroperabilityTestValueClassParam extends js.Object {
-    def stringOf(vc: SomeValueClass): String = js.native
+    def test(vc: SomeValueClass): Any = js.native
   }
 
   @js.native
diff --git a/test-suite/js/src/test/scala/org/scalajs/testsuite/jsinterop/ExportsTest.scala b/test-suite/js/src/test/scala/org/scalajs/testsuite/jsinterop/ExportsTest.scala
index 2d2ce36b22..6cb3bf9481 100644
--- a/test-suite/js/src/test/scala/org/scalajs/testsuite/jsinterop/ExportsTest.scala
+++ b/test-suite/js/src/test/scala/org/scalajs/testsuite/jsinterop/ExportsTest.scala
@@ -728,6 +728,20 @@ class ExportsTest {
     assertEquals(18, bar.method(5, 6, 7))
   }
 
+  @Test def exportsInsideValueClass(): Unit = {
+    val obj = new ValueClassWithExports(5).asInstanceOf[js.Dynamic]
+
+    // Explicit export
+    assertEquals(12, obj.add(7))
+
+    // Export for toString() inherited from jl.Object
+    assertEquals("ValueClassWithExports(value = 5)", obj.toString())
+
+    // Export for toString() visible from JavaScript
+    val f = new js.Function("obj", "return '' + obj;").asInstanceOf[js.Function1[Any, String]]
+    assertEquals("ValueClassWithExports(value = 5)", f(obj))
+  }
+
   @Test def overloadingWithInheritedExports(): Unit = {
     class A {
       @JSExport
@@ -1986,6 +2000,13 @@ class ExportedDefaultArgClass(x: Int, y: Int, z: Int) {
 
 class SomeValueClass(val i: Int) extends AnyVal
 
+class ValueClassWithExports(val value: Int) extends AnyVal {
+  @JSExport("add")
+  def addToValue(x: Int): Int = value + x
+
+  override def toString(): String = s"ValueClassWithExports(value = $value)"
+}
+
 object ExportHolder {
   @JSExportTopLevel("NestedExportedClass")
   class ExportedClass

From 8e06210bd045cd4b87a787b7a79ca4b7ec13f0fb Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Mon, 13 May 2024 17:05:05 +0200
Subject: [PATCH 094/298] Extract tests for `@JSExportTopLevel` in a separate
 file/class.

`@JSExportTopLevel` originally evolved from `@JSExport`. At the
time, it made sense to have their tests in the same test class.
Nowadays, however, these features have more differences than things
in common. These differences will be even more exacerbated with
WebAssembly, since it will support `@JSExportTopLevel` but not
`@JSExport`.
---
 .../testsuite/jsinterop/ExportsTest.scala     | 632 -----------------
 .../jsinterop/TopLevelExportsTest.scala       | 662 ++++++++++++++++++
 2 files changed, 662 insertions(+), 632 deletions(-)
 create mode 100644 test-suite/js/src/test/scala/org/scalajs/testsuite/jsinterop/TopLevelExportsTest.scala

diff --git a/test-suite/js/src/test/scala/org/scalajs/testsuite/jsinterop/ExportsTest.scala b/test-suite/js/src/test/scala/org/scalajs/testsuite/jsinterop/ExportsTest.scala
index 6cb3bf9481..4c03aef61e 100644
--- a/test-suite/js/src/test/scala/org/scalajs/testsuite/jsinterop/ExportsTest.scala
+++ b/test-suite/js/src/test/scala/org/scalajs/testsuite/jsinterop/ExportsTest.scala
@@ -16,32 +16,17 @@ import scala.language.higherKinds
 
 import scala.scalajs.js
 import scala.scalajs.js.annotation._
-import scala.scalajs.js.Dynamic.global
 
 import org.scalajs.testsuite.utils.AssertThrows.assertThrows
 import org.scalajs.testsuite.utils.JSAssert._
-import org.scalajs.testsuite.utils.JSUtils
 import org.scalajs.testsuite.utils.Platform._
 
-import scala.annotation.meta
-
-import scala.concurrent._
-import scala.concurrent.ExecutionContext.Implicits.{global => globalEc}
-
 import org.junit.Assert._
 import org.junit.Assume._
 import org.junit.Test
 
-import org.scalajs.junit.async._
-
 class ExportsTest {
 
-  /** The namespace in which top-level exports are stored. */
-  private lazy val exportsNamespace: Future[js.Dynamic] =
-    ExportLoopback.exportsNamespace
-
-  // @JSExport
-
   @Test def exportsForMethodsWithImplicitName(): Unit = {
     class Foo {
       @JSExport
@@ -1093,209 +1078,6 @@ class ExportsTest {
     assertEquals(3, a.foo(vc1.asInstanceOf[js.Any], vc2.asInstanceOf[js.Any]))
   }
 
-  @Test def toplevelExportsForObjects(): AsyncResult = await {
-    val objFuture =
-      if (isNoModule) Future.successful(global.TopLevelExportedObject)
-      else exportsNamespace.map(_.TopLevelExportedObject)
-    for (obj <- objFuture) yield {
-      assertJSNotUndefined(obj)
-      assertEquals("object", js.typeOf(obj))
-      assertEquals("witness", obj.witness)
-    }
-  }
-
-  @Test def toplevelExportsForScalaJSDefinedJSObjects(): AsyncResult = await {
-    val obj1Future =
-      if (isNoModule) Future.successful(global.SJSDefinedTopLevelExportedObject)
-      else exportsNamespace.map(_.SJSDefinedTopLevelExportedObject)
-    for (obj1 <- obj1Future) yield {
-      assertJSNotUndefined(obj1)
-      assertEquals("object", js.typeOf(obj1))
-      assertEquals("witness", obj1.witness)
-
-      assertSame(obj1, SJSDefinedExportedObject)
-    }
-  }
-
-  @Test def toplevelExportsForNestedObjects(): AsyncResult = await {
-    val objFuture =
-      if (isNoModule) Future.successful(global.NestedExportedObject)
-      else exportsNamespace.map(_.NestedExportedObject)
-    for (obj <- objFuture) yield {
-      assertJSNotUndefined(obj)
-      assertEquals("object", js.typeOf(obj))
-      assertSame(obj, ExportHolder.ExportedObject)
-    }
-  }
-
-  @Test def exportsForObjectsWithConstantFoldedName(): AsyncResult = await {
-    val objFuture =
-      if (isNoModule) Future.successful(global.ConstantFoldedObjectExport)
-      else exportsNamespace.map(_.ConstantFoldedObjectExport)
-    for (obj <- objFuture) yield {
-      assertJSNotUndefined(obj)
-      assertEquals("object", js.typeOf(obj))
-      assertEquals("witness", obj.witness)
-    }
-  }
-
-  @Test def exportsForProtectedObjects(): AsyncResult = await {
-    val objFuture =
-      if (isNoModule) Future.successful(global.ProtectedExportedObject)
-      else exportsNamespace.map(_.ProtectedExportedObject)
-    for (obj <- objFuture) yield {
-      assertJSNotUndefined(obj)
-      assertEquals("object", js.typeOf(obj))
-      assertEquals("witness", obj.witness)
-    }
-  }
-
-  @Test def toplevelExportsForClasses(): AsyncResult = await {
-    val constrFuture =
-      if (isNoModule) Future.successful(global.TopLevelExportedClass)
-      else exportsNamespace.map(_.TopLevelExportedClass)
-    for (constr <- constrFuture) yield {
-      assertJSNotUndefined(constr)
-      assertEquals("function", js.typeOf(constr))
-      val obj = js.Dynamic.newInstance(constr)(5)
-      assertEquals(5, obj.x)
-    }
-  }
-
-  @Test def toplevelExportsForScalaJSDefinedJSClasses(): AsyncResult = await {
-    val constrFuture =
-      if (isNoModule) Future.successful(global.SJSDefinedTopLevelExportedClass)
-      else exportsNamespace.map(_.SJSDefinedTopLevelExportedClass)
-    for (constr <- constrFuture) yield {
-      assertJSNotUndefined(constr)
-      assertEquals("function", js.typeOf(constr))
-      val obj = js.Dynamic.newInstance(constr)(5)
-      assertTrue((obj: Any).isInstanceOf[SJSDefinedTopLevelExportedClass])
-      assertEquals(5, obj.x)
-
-      assertSame(constr, js.constructorOf[SJSDefinedTopLevelExportedClass])
-    }
-  }
-
-  @Test def toplevelExportsForAbstractJSClasses_Issue4117(): AsyncResult = await {
-    val constrFuture =
-      if (isNoModule) Future.successful(global.TopLevelExportedAbstractJSClass)
-      else exportsNamespace.map(_.TopLevelExportedAbstractJSClass)
-
-    for (constr <- constrFuture) yield {
-      assertEquals("function", js.typeOf(constr))
-
-      val body = if (useECMAScript2015Semantics) {
-        """
-        class SubClass extends constr {
-          constructor(x) {
-            super(x);
-          }
-          foo(y) {
-             return y + this.x;
-          }
-        }
-        return SubClass;
-        """
-      } else {
-        """
-        function SubClass(x) {
-          constr.call(this, x);
-        }
-        SubClass.prototype = Object.create(constr.prototype);
-        SubClass.prototype.foo = function(y) {
-          return y + this.x;
-        };
-        return SubClass;
-        """
-      }
-
-      val subclassFun = new js.Function("constr", body)
-        .asInstanceOf[js.Function1[js.Dynamic, js.Dynamic]]
-      val subclass = subclassFun(constr)
-      assertEquals("function", js.typeOf(subclass))
-
-      val obj = js.Dynamic.newInstance(subclass)(5)
-        .asInstanceOf[TopLevelExportedAbstractJSClass]
-
-      assertEquals(5, obj.x)
-      assertEquals(11, obj.foo(6))
-      assertEquals(33, obj.bar(6))
-    }
-  }
-
-  @Test def toplevelExportsForNestedClasses(): AsyncResult = await {
-    val constrFuture =
-      if (isNoModule) Future.successful(global.NestedExportedClass)
-      else exportsNamespace.map(_.NestedExportedClass)
-    for (constr <- constrFuture) yield {
-      assertJSNotUndefined(constr)
-      assertEquals("function", js.typeOf(constr))
-      val obj = js.Dynamic.newInstance(constr)()
-      assertTrue((obj: Any).isInstanceOf[ExportHolder.ExportedClass])
-    }
-  }
-
-  @Test def toplevelExportsForNestedSjsDefinedClasses(): AsyncResult = await {
-    val constrFuture =
-      if (isNoModule) Future.successful(global.NestedSJSDefinedExportedClass)
-      else exportsNamespace.map(_.NestedSJSDefinedExportedClass)
-    for (constr <- constrFuture) yield {
-      assertJSNotUndefined(constr)
-      assertEquals("function", js.typeOf(constr))
-      val obj = js.Dynamic.newInstance(constr)()
-      assertTrue((obj: Any).isInstanceOf[ExportHolder.SJSDefinedExportedClass])
-    }
-  }
-
-  @Test def exportsForClassesWithConstantFoldedName(): AsyncResult = await {
-    val constrFuture =
-      if (isNoModule) Future.successful(global.ConstantFoldedClassExport)
-      else exportsNamespace.map(_.ConstantFoldedClassExport)
-    for (constr <- constrFuture) yield {
-      assertJSNotUndefined(constr)
-      assertEquals("function", js.typeOf(constr))
-      val obj = js.Dynamic.newInstance(constr)(5)
-      assertEquals(5, obj.x)
-    }
-  }
-
-  @Test def exportsForProtectedClasses(): AsyncResult = await {
-    val constrFuture =
-      if (isNoModule) Future.successful(global.ProtectedExportedClass)
-      else exportsNamespace.map(_.ProtectedExportedClass)
-    for (constr <- constrFuture) yield {
-      assertJSNotUndefined(constr)
-      assertEquals("function", js.typeOf(constr))
-      val obj = js.Dynamic.newInstance(constr)(5)
-      assertEquals(5, obj.x)
-    }
-  }
-
-  @Test def exportForClassesWithRepeatedParametersInCtor(): AsyncResult = await {
-    val constrFuture =
-      if (isNoModule) Future.successful(global.ExportedVarArgClass)
-      else exportsNamespace.map(_.ExportedVarArgClass)
-    for (constr <- constrFuture) yield {
-      assertEquals("", js.Dynamic.newInstance(constr)().result)
-      assertEquals("a", js.Dynamic.newInstance(constr)("a").result)
-      assertEquals("a|b", js.Dynamic.newInstance(constr)("a", "b").result)
-      assertEquals("a|b|c", js.Dynamic.newInstance(constr)("a", "b", "c").result)
-      assertEquals("Number: <5>|a", js.Dynamic.newInstance(constr)(5, "a").result)
-    }
-  }
-
-  @Test def exportForClassesWithDefaultParametersInCtor(): AsyncResult = await {
-    val constrFuture =
-      if (isNoModule) Future.successful(global.ExportedDefaultArgClass)
-      else exportsNamespace.map(_.ExportedDefaultArgClass)
-    for (constr <- constrFuture) yield {
-      assertEquals(6, js.Dynamic.newInstance(constr)(1,2,3).result)
-      assertEquals(106, js.Dynamic.newInstance(constr)(1).result)
-      assertEquals(103, js.Dynamic.newInstance(constr)(1,2).result)
-    }
-  }
-
   @Test def disambiguateOverloadsInvolvingLongs(): Unit = {
 
     class Foo {
@@ -1672,332 +1454,12 @@ class ExportsTest {
     testExposure(getJSObj3())
     testExposure(getJSObj4())
   }
-
-  // @JSExportTopLevel
-
-  @Test def basicTopLevelExport(): Unit = {
-    assumeTrue("Assume NoModule", isNoModule)
-    assertEquals(1, global.TopLevelExport_basic())
-  }
-
-  @Test def basicTopLevelExportModule(): AsyncResult = await {
-    assumeFalse("Assume Module", isNoModule)
-    for (exp <- exportsNamespace) yield {
-      assertEquals(1, exp.TopLevelExport_basic())
-    }
-  }
-
-  @Test def overloadedTopLevelExport(): Unit = {
-    assumeTrue("Assume NoModule", isNoModule)
-    assertEquals("Hello World", global.TopLevelExport_overload("World"))
-    assertEquals(2, global.TopLevelExport_overload(2))
-    assertEquals(9, global.TopLevelExport_overload(2, 7))
-    assertEquals(10, global.TopLevelExport_overload(1, 2, 3, 4))
-  }
-
-  @Test def overloadedTopLevelExportModule(): AsyncResult = await {
-    assumeFalse("Assume Module", isNoModule)
-    for (exp <- exportsNamespace) yield {
-      assertEquals("Hello World", exp.TopLevelExport_overload("World"))
-      assertEquals(2, exp.TopLevelExport_overload(2))
-      assertEquals(9, exp.TopLevelExport_overload(2, 7))
-      assertEquals(10, exp.TopLevelExport_overload(1, 2, 3, 4))
-    }
-  }
-
-  @Test def defaultParamsTopLevelExport_Issue4052(): Unit = {
-    assumeTrue("Assume NoModule", isNoModule)
-    assertEquals(7, global.TopLevelExport_defaultParams(6))
-    assertEquals(11, global.TopLevelExport_defaultParams(6, 5))
-  }
-
-  @Test def defaultParamsTopLevelExportModule_Issue4052(): AsyncResult = await {
-    assumeFalse("Assume Module", isNoModule)
-    for (exp <- exportsNamespace) yield {
-      assertEquals(7, exp.TopLevelExport_defaultParams(6))
-      assertEquals(11, exp.TopLevelExport_defaultParams(6, 5))
-    }
-  }
-
-  @Test def topLevelExportUsesUniqueObject(): Unit = {
-    assumeTrue("Assume NoModule", isNoModule)
-    global.TopLevelExport_set(3)
-    assertEquals(3, TopLevelExports.myVar)
-    global.TopLevelExport_set(7)
-    assertEquals(7, TopLevelExports.myVar)
-  }
-
-  @Test def topLevelExportUsesUniqueObjectModule(): AsyncResult = await {
-    assumeFalse("Assume Module", isNoModule)
-    for (exp <- exportsNamespace) yield {
-      exp.TopLevelExport_set(3)
-      assertEquals(3, TopLevelExports.myVar)
-      exp.TopLevelExport_set(7)
-      assertEquals(7, TopLevelExports.myVar)
-    }
-  }
-
-  @Test def topLevelExportFromNestedObject(): Unit = {
-    assumeTrue("Assume NoModule", isNoModule)
-    global.TopLevelExport_setNested(28)
-    assertEquals(28, TopLevelExports.Nested.myVar)
-  }
-
-  @Test def topLevelExportFromNestedObjectModule(): AsyncResult = await {
-    assumeFalse("Assume Module", isNoModule)
-    for (exp <- exportsNamespace) yield {
-      exp.TopLevelExport_setNested(28)
-      assertEquals(28, TopLevelExports.Nested.myVar)
-    }
-  }
-
-  @Test def topLevelExportWithDoubleUnderscore(): Unit = {
-    assumeTrue("Assume NoModule", isNoModule)
-    assertEquals(true, global.__topLevelExportWithDoubleUnderscore)
-  }
-
-  @Test def topLevelExportWithDoubleUnderscoreModule(): AsyncResult = await {
-    assumeFalse("Assume Module", isNoModule)
-    for (exp <- exportsNamespace) yield {
-      assertEquals(true, exp.__topLevelExportWithDoubleUnderscore)
-    }
-  }
-
-  @Test def topLevelExportIsAlwaysReachable(): Unit = {
-    assumeTrue("Assume NoModule", isNoModule)
-    assertEquals("Hello World", global.TopLevelExport_reachability())
-  }
-
-  @Test def topLevelExportIsAlwaysReachableModule(): AsyncResult = await {
-    assumeFalse("Assume Module", isNoModule)
-    for (exp <- exportsNamespace) yield {
-      assertEquals("Hello World", exp.TopLevelExport_reachability())
-    }
-  }
-
-  // @JSExportTopLevel fields
-
-  @Test def topLevelExportBasicField(): Unit = {
-    assumeTrue("Assume NoModule", isNoModule)
-    // Initialization
-    assertEquals(5, global.TopLevelExport_basicVal)
-    assertEquals("hello", global.TopLevelExport_basicVar)
-
-    // Scala modifies var
-    TopLevelFieldExports.basicVar = "modified"
-    assertEquals("modified", TopLevelFieldExports.basicVar)
-    assertEquals("modified", global.TopLevelExport_basicVar)
-
-    // Reset var
-    TopLevelFieldExports.basicVar = "hello"
-  }
-
-  @Test def topLevelExportBasicFieldModule(): AsyncResult = await {
-    assumeFalse("Assume Module", isNoModule)
-    for (exp <- exportsNamespace) yield {
-      // Initialization
-      assertEquals(5, exp.TopLevelExport_basicVal)
-      assertEquals("hello", exp.TopLevelExport_basicVar)
-
-      // Scala modifies var
-      TopLevelFieldExports.basicVar = "modified"
-      assertEquals("modified", TopLevelFieldExports.basicVar)
-      assertEquals("modified", exp.TopLevelExport_basicVar)
-
-      // Reset var
-      TopLevelFieldExports.basicVar = "hello"
-    }
-  }
-
-  @Test def topLevelExportFieldTwice(): Unit = {
-    assumeTrue("Assume NoModule", isNoModule)
-
-    // Initialization
-    assertEquals(5, global.TopLevelExport_valExportedTwice1)
-    assertEquals("hello", global.TopLevelExport_varExportedTwice1)
-    assertEquals("hello", global.TopLevelExport_varExportedTwice2)
-
-    // Scala modifies var
-    TopLevelFieldExports.varExportedTwice = "modified"
-    assertEquals("modified", TopLevelFieldExports.varExportedTwice)
-    assertEquals("modified", global.TopLevelExport_varExportedTwice1)
-    assertEquals("modified", global.TopLevelExport_varExportedTwice2)
-
-    // Reset var
-    TopLevelFieldExports.varExportedTwice = "hello"
-  }
-
-  @Test def topLevelExportFieldTwiceModule(): AsyncResult = await {
-    assumeFalse("Assume Module", isNoModule)
-    for (exp <- exportsNamespace) yield {
-      // Initialization
-      assertEquals(5, exp.TopLevelExport_valExportedTwice1)
-      assertEquals("hello", exp.TopLevelExport_varExportedTwice1)
-      assertEquals("hello", exp.TopLevelExport_varExportedTwice2)
-
-      // Scala modifies var
-      TopLevelFieldExports.varExportedTwice = "modified"
-      assertEquals("modified", TopLevelFieldExports.varExportedTwice)
-      assertEquals("modified", exp.TopLevelExport_varExportedTwice1)
-      assertEquals("modified", exp.TopLevelExport_varExportedTwice2)
-
-      // Reset var
-      TopLevelFieldExports.varExportedTwice = "hello"
-    }
-  }
-
-  @Test def topLevelExportWriteValVarCausesTypeerror(): AsyncResult = await {
-    assumeFalse("Unchecked in Script mode", isNoModule)
-
-    for (exp <- exportsNamespace) yield {
-      assertThrows(classOf[js.JavaScriptException], {
-        exp.TopLevelExport_basicVal = 54
-      })
-
-      assertThrows(classOf[js.JavaScriptException], {
-        exp.TopLevelExport_basicVar = 54
-      })
-    }
-  }
-
-  @Test def topLevelExportUninitializedFieldsScala(): Unit = {
-    assertEquals(0, TopLevelFieldExports.uninitializedVarInt)
-    assertEquals(0L, TopLevelFieldExports.uninitializedVarLong)
-    assertEquals(null, TopLevelFieldExports.uninitializedVarString)
-    assertEquals('\u0000', TopLevelFieldExports.uninitializedVarChar)
-  }
-
-  @Test def topLevelExportUninitializedFields(): Unit = {
-    assumeTrue("Assume NoModule", isNoModule)
-    assertEquals(null, global.TopLevelExport_uninitializedVarInt)
-    assertEquals(null, global.TopLevelExport_uninitializedVarLong)
-    assertEquals(null, global.TopLevelExport_uninitializedVarString)
-    assertEquals(null, global.TopLevelExport_uninitializedVarChar)
-  }
-
-  @Test def topLevelExportUninitializedFieldsModule(): AsyncResult = await {
-    assumeFalse("Assume Module", isNoModule)
-    for (exp <- exportsNamespace) yield {
-      assertEquals(null, exp.TopLevelExport_uninitializedVarInt)
-      assertEquals(null, exp.TopLevelExport_uninitializedVarLong)
-      assertEquals(null, exp.TopLevelExport_uninitializedVarString)
-      assertEquals(null, exp.TopLevelExport_uninitializedVarChar)
-    }
-  }
-
-  @Test def topLevelExportFieldIsAlwaysReachableAndInitialized(): Unit = {
-    assumeTrue("Assume NoModule", isNoModule)
-    assertEquals("Hello World", global.TopLevelExport_fieldreachability)
-  }
-
-  @Test def topLevelExportFieldIsAlwaysReachableAndInitializedModule(): AsyncResult = await {
-    assumeFalse("Assume Module", isNoModule)
-    for (exp <- exportsNamespace) yield {
-      assertEquals("Hello World", exp.TopLevelExport_fieldreachability)
-    }
-  }
-
-  @Test def topLevelExportFieldIsWritableAccrossModules(): Unit = {
-    /* We write to basicVar exported above from a different object to test writing
-     * of static fields across module boundaries (when module splitting is
-     * enabled).
-     */
-
-    assertEquals("hello", TopLevelFieldExports.inlineVar)
-    TopLevelFieldExports.inlineVar = "hello modules"
-    assertEquals("hello modules", TopLevelFieldExports.inlineVar)
-
-    // Reset var
-    TopLevelFieldExports.inlineVar = "hello"
-  }
-
-  // @JSExportTopLevel in Script's are `let`s in ES 2015, `var`s in ES 5.1
-
-  @Test def topLevelExportsNoModuleAreOfCorrectKind(): Unit = {
-    assumeTrue("relevant only for NoModule", isNoModule)
-
-    val g = JSUtils.globalObject
-
-    // Do we expect to get undefined when looking up the exports in the global object?
-    val undefinedExpected = useECMAScript2015Semantics
-
-    assertEquals(undefinedExpected, js.isUndefined(g.TopLevelExportedObject))
-    assertEquals(undefinedExpected, js.isUndefined(g.SJSDefinedTopLevelExportedObject))
-    assertEquals(undefinedExpected, js.isUndefined(g.TopLevelExportedClass))
-    assertEquals(undefinedExpected, js.isUndefined(g.SJSDefinedTopLevelExportedClass))
-    assertEquals(undefinedExpected, js.isUndefined(g.TopLevelExport_basic))
-    assertEquals(undefinedExpected, js.isUndefined(g.TopLevelExport_basicVal))
-    assertEquals(undefinedExpected, js.isUndefined(g.TopLevelExport_basicVar))
-  }
 }
 
 object ExportNameHolder {
-  final val className = "ConstantFoldedClassExport"
-  final val objectName = "ConstantFoldedObjectExport"
   final val methodName = "myMethod"
 }
 
-@JSExportTopLevel("TopLevelExportedObject")
-@JSExportTopLevel(ExportNameHolder.objectName)
-object TopLevelExportedObject {
-  @JSExport
-  val witness: String = "witness"
-}
-
-@JSExportTopLevel("SJSDefinedTopLevelExportedObject")
-object SJSDefinedExportedObject extends js.Object {
-  val witness: String = "witness"
-}
-
-@JSExportTopLevel("ProtectedExportedObject")
-protected object ProtectedExportedObject {
-  @JSExport
-  def witness: String = "witness"
-}
-
-@JSExportTopLevel("TopLevelExportedClass")
-@JSExportTopLevel(ExportNameHolder.className)
-class TopLevelExportedClass(_x: Int) {
-  @JSExport
-  val x = _x
-}
-
-@JSExportTopLevel("SJSDefinedTopLevelExportedClass")
-class SJSDefinedTopLevelExportedClass(val x: Int) extends js.Object
-
-@JSExportTopLevel("TopLevelExportedAbstractJSClass")
-abstract class TopLevelExportedAbstractJSClass(val x: Int) extends js.Object {
-  def foo(y: Int): Int
-
-  def bar(y: Int): Int = 3 * foo(y)
-}
-
-@JSExportTopLevel("ProtectedExportedClass")
-protected class ProtectedExportedClass(_x: Int) {
-  @JSExport
-  val x = _x
-}
-
-@JSExportTopLevel("ExportedVarArgClass")
-class ExportedVarArgClass(x: String*) {
-
-  @JSExportTopLevel("ExportedVarArgClass")
-  def this(x: Int, y: String) = this(s"Number: <$x>", y)
-
-  @JSExport
-  def result: String = x.mkString("|")
-}
-
-@JSExportTopLevel("ExportedDefaultArgClass")
-class ExportedDefaultArgClass(x: Int, y: Int, z: Int) {
-
-  @JSExportTopLevel("ExportedDefaultArgClass")
-  def this(x: Int, y: Int = 5) = this(x, y, 100)
-
-  @JSExport
-  def result: Int = x + y + z
-}
-
 class SomeValueClass(val i: Int) extends AnyVal
 
 class ValueClassWithExports(val value: Int) extends AnyVal {
@@ -2007,100 +1469,6 @@ class ValueClassWithExports(val value: Int) extends AnyVal {
   override def toString(): String = s"ValueClassWithExports(value = $value)"
 }
 
-object ExportHolder {
-  @JSExportTopLevel("NestedExportedClass")
-  class ExportedClass
-
-  @JSExportTopLevel("NestedExportedObject")
-  object ExportedObject
-
-  @JSExportTopLevel("NestedSJSDefinedExportedClass")
-  class SJSDefinedExportedClass extends js.Object
-}
-
-object TopLevelExports {
-  @JSExportTopLevel("TopLevelExport_basic")
-  def basic(): Int = 1
-
-  @JSExportTopLevel("TopLevelExport_overload")
-  def overload(x: String): String = "Hello " + x
-
-  @JSExportTopLevel("TopLevelExport_overload")
-  def overload(x: Int, y: Int*): Int = x + y.sum
-
-  @JSExportTopLevel("TopLevelExport_defaultParams")
-  def defaultParams(x: Int, y: Int = 1): Int = x + y
-
-  var myVar: Int = _
-
-  @JSExportTopLevel("TopLevelExport_set")
-  def setMyVar(x: Int): Unit = myVar = x
-
-  object Nested {
-    var myVar: Int = _
-
-    @JSExportTopLevel("TopLevelExport_setNested")
-    def setMyVar(x: Int): Unit = myVar = x
-  }
-
-  @JSExportTopLevel("__topLevelExportWithDoubleUnderscore")
-  val topLevelExportWithDoubleUnderscore: Boolean = true
-}
-
-/* This object is only reachable via the top level export to make sure the
- * analyzer behaves correctly.
- */
-object TopLevelExportsReachability {
-  private val name = "World"
-
-  @JSExportTopLevel("TopLevelExport_reachability")
-  def basic(): String = "Hello " + name
-}
-
-object TopLevelFieldExports {
-  @JSExportTopLevel("TopLevelExport_basicVal")
-  val basicVal: Int = 5
-
-  @JSExportTopLevel("TopLevelExport_basicVar")
-  var basicVar: String = "hello"
-
-  @JSExportTopLevel("TopLevelExport_valExportedTwice1")
-  @JSExportTopLevel("TopLevelExport_valExportedTwice2")
-  val valExportedTwice: Int = 5
-
-  @JSExportTopLevel("TopLevelExport_varExportedTwice1")
-  @JSExportTopLevel("TopLevelExport_varExportedTwice2")
-  var varExportedTwice: String = "hello"
-
-  @JSExportTopLevel("TopLevelExport_uninitializedVarInt")
-  var uninitializedVarInt: Int = _
-
-  @JSExportTopLevel("TopLevelExport_uninitializedVarLong")
-  var uninitializedVarLong: Long = _
-
-  @JSExportTopLevel("TopLevelExport_uninitializedVarString")
-  var uninitializedVarString: String = _
-
-  @JSExportTopLevel("TopLevelExport_uninitializedVarChar")
-  var uninitializedVarChar: Char = _
-
-  // the export is only to make the field IR-static
-  @JSExportTopLevel("TopLevelExport_irrelevant")
-  @(inline @meta.getter @meta.setter)
-  var inlineVar: String = "hello"
-}
-
-/* This object and its static initializer are only reachable via the top-level
- * export of its field, to make sure the analyzer and the static initiliazer
- * behave correctly.
- */
-object TopLevelFieldExportsReachability {
-  private val name = "World"
-
-  @JSExportTopLevel("TopLevelExport_fieldreachability")
-  val greeting = "Hello " + name
-}
-
 abstract class AbstractClasstWithPropertyForExport {
   @JSExport
   def x: js.Object
diff --git a/test-suite/js/src/test/scala/org/scalajs/testsuite/jsinterop/TopLevelExportsTest.scala b/test-suite/js/src/test/scala/org/scalajs/testsuite/jsinterop/TopLevelExportsTest.scala
new file mode 100644
index 0000000000..b0d90209e6
--- /dev/null
+++ b/test-suite/js/src/test/scala/org/scalajs/testsuite/jsinterop/TopLevelExportsTest.scala
@@ -0,0 +1,662 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package org.scalajs.testsuite.jsinterop
+
+import scala.scalajs.js
+import scala.scalajs.js.annotation._
+import scala.scalajs.js.Dynamic.global
+
+import org.scalajs.testsuite.utils.AssertThrows.assertThrows
+import org.scalajs.testsuite.utils.JSAssert._
+import org.scalajs.testsuite.utils.JSUtils
+import org.scalajs.testsuite.utils.Platform._
+
+import scala.annotation.meta
+
+import scala.concurrent._
+import scala.concurrent.ExecutionContext.Implicits.{global => globalEc}
+
+import org.junit.Assert._
+import org.junit.Assume._
+import org.junit.Test
+
+import org.scalajs.junit.async._
+
+class TopLevelExportsTest {
+
+  /** The namespace in which top-level exports are stored. */
+  private lazy val exportsNamespace: Future[js.Dynamic] =
+    ExportLoopback.exportsNamespace
+
+  // @JSExportTopLevel classes and objects
+
+  @Test def toplevelExportsForObjects(): AsyncResult = await {
+    val objFuture =
+      if (isNoModule) Future.successful(global.TopLevelExportedObject)
+      else exportsNamespace.map(_.TopLevelExportedObject)
+    for (obj <- objFuture) yield {
+      assertJSNotUndefined(obj)
+      assertEquals("object", js.typeOf(obj))
+      assertEquals("witness", obj.witness)
+    }
+  }
+
+  @Test def toplevelExportsForScalaJSDefinedJSObjects(): AsyncResult = await {
+    val obj1Future =
+      if (isNoModule) Future.successful(global.SJSDefinedTopLevelExportedObject)
+      else exportsNamespace.map(_.SJSDefinedTopLevelExportedObject)
+    for (obj1 <- obj1Future) yield {
+      assertJSNotUndefined(obj1)
+      assertEquals("object", js.typeOf(obj1))
+      assertEquals("witness", obj1.witness)
+
+      assertSame(obj1, SJSDefinedExportedObject)
+    }
+  }
+
+  @Test def toplevelExportsForNestedObjects(): AsyncResult = await {
+    val objFuture =
+      if (isNoModule) Future.successful(global.NestedExportedObject)
+      else exportsNamespace.map(_.NestedExportedObject)
+    for (obj <- objFuture) yield {
+      assertJSNotUndefined(obj)
+      assertEquals("object", js.typeOf(obj))
+      assertSame(obj, ExportHolder.ExportedObject)
+    }
+  }
+
+  @Test def exportsForObjectsWithConstantFoldedName(): AsyncResult = await {
+    val objFuture =
+      if (isNoModule) Future.successful(global.ConstantFoldedObjectExport)
+      else exportsNamespace.map(_.ConstantFoldedObjectExport)
+    for (obj <- objFuture) yield {
+      assertJSNotUndefined(obj)
+      assertEquals("object", js.typeOf(obj))
+      assertEquals("witness", obj.witness)
+    }
+  }
+
+  @Test def exportsForProtectedObjects(): AsyncResult = await {
+    val objFuture =
+      if (isNoModule) Future.successful(global.ProtectedExportedObject)
+      else exportsNamespace.map(_.ProtectedExportedObject)
+    for (obj <- objFuture) yield {
+      assertJSNotUndefined(obj)
+      assertEquals("object", js.typeOf(obj))
+      assertEquals("witness", obj.witness)
+    }
+  }
+
+  @Test def toplevelExportsForClasses(): AsyncResult = await {
+    val constrFuture =
+      if (isNoModule) Future.successful(global.TopLevelExportedClass)
+      else exportsNamespace.map(_.TopLevelExportedClass)
+    for (constr <- constrFuture) yield {
+      assertJSNotUndefined(constr)
+      assertEquals("function", js.typeOf(constr))
+      val obj = js.Dynamic.newInstance(constr)(5)
+      assertEquals(5, obj.x)
+    }
+  }
+
+  @Test def toplevelExportsForScalaJSDefinedJSClasses(): AsyncResult = await {
+    val constrFuture =
+      if (isNoModule) Future.successful(global.SJSDefinedTopLevelExportedClass)
+      else exportsNamespace.map(_.SJSDefinedTopLevelExportedClass)
+    for (constr <- constrFuture) yield {
+      assertJSNotUndefined(constr)
+      assertEquals("function", js.typeOf(constr))
+      val obj = js.Dynamic.newInstance(constr)(5)
+      assertTrue((obj: Any).isInstanceOf[SJSDefinedTopLevelExportedClass])
+      assertEquals(5, obj.x)
+
+      assertSame(constr, js.constructorOf[SJSDefinedTopLevelExportedClass])
+    }
+  }
+
+  @Test def toplevelExportsForAbstractJSClasses_Issue4117(): AsyncResult = await {
+    val constrFuture =
+      if (isNoModule) Future.successful(global.TopLevelExportedAbstractJSClass)
+      else exportsNamespace.map(_.TopLevelExportedAbstractJSClass)
+
+    for (constr <- constrFuture) yield {
+      assertEquals("function", js.typeOf(constr))
+
+      val body = if (useECMAScript2015Semantics) {
+        """
+        class SubClass extends constr {
+          constructor(x) {
+            super(x);
+          }
+          foo(y) {
+             return y + this.x;
+          }
+        }
+        return SubClass;
+        """
+      } else {
+        """
+        function SubClass(x) {
+          constr.call(this, x);
+        }
+        SubClass.prototype = Object.create(constr.prototype);
+        SubClass.prototype.foo = function(y) {
+          return y + this.x;
+        };
+        return SubClass;
+        """
+      }
+
+      val subclassFun = new js.Function("constr", body)
+        .asInstanceOf[js.Function1[js.Dynamic, js.Dynamic]]
+      val subclass = subclassFun(constr)
+      assertEquals("function", js.typeOf(subclass))
+
+      val obj = js.Dynamic.newInstance(subclass)(5)
+        .asInstanceOf[TopLevelExportedAbstractJSClass]
+
+      assertEquals(5, obj.x)
+      assertEquals(11, obj.foo(6))
+      assertEquals(33, obj.bar(6))
+    }
+  }
+
+  @Test def toplevelExportsForNestedClasses(): AsyncResult = await {
+    val constrFuture =
+      if (isNoModule) Future.successful(global.NestedExportedClass)
+      else exportsNamespace.map(_.NestedExportedClass)
+    for (constr <- constrFuture) yield {
+      assertJSNotUndefined(constr)
+      assertEquals("function", js.typeOf(constr))
+      val obj = js.Dynamic.newInstance(constr)()
+      assertTrue((obj: Any).isInstanceOf[ExportHolder.ExportedClass])
+    }
+  }
+
+  @Test def toplevelExportsForNestedSjsDefinedClasses(): AsyncResult = await {
+    val constrFuture =
+      if (isNoModule) Future.successful(global.NestedSJSDefinedExportedClass)
+      else exportsNamespace.map(_.NestedSJSDefinedExportedClass)
+    for (constr <- constrFuture) yield {
+      assertJSNotUndefined(constr)
+      assertEquals("function", js.typeOf(constr))
+      val obj = js.Dynamic.newInstance(constr)()
+      assertTrue((obj: Any).isInstanceOf[ExportHolder.SJSDefinedExportedClass])
+    }
+  }
+
+  @Test def exportsForClassesWithConstantFoldedName(): AsyncResult = await {
+    val constrFuture =
+      if (isNoModule) Future.successful(global.ConstantFoldedClassExport)
+      else exportsNamespace.map(_.ConstantFoldedClassExport)
+    for (constr <- constrFuture) yield {
+      assertJSNotUndefined(constr)
+      assertEquals("function", js.typeOf(constr))
+      val obj = js.Dynamic.newInstance(constr)(5)
+      assertEquals(5, obj.x)
+    }
+  }
+
+  @Test def exportsForProtectedClasses(): AsyncResult = await {
+    val constrFuture =
+      if (isNoModule) Future.successful(global.ProtectedExportedClass)
+      else exportsNamespace.map(_.ProtectedExportedClass)
+    for (constr <- constrFuture) yield {
+      assertJSNotUndefined(constr)
+      assertEquals("function", js.typeOf(constr))
+      val obj = js.Dynamic.newInstance(constr)(5)
+      assertEquals(5, obj.x)
+    }
+  }
+
+  @Test def exportForClassesWithRepeatedParametersInCtor(): AsyncResult = await {
+    val constrFuture =
+      if (isNoModule) Future.successful(global.ExportedVarArgClass)
+      else exportsNamespace.map(_.ExportedVarArgClass)
+    for (constr <- constrFuture) yield {
+      assertEquals("", js.Dynamic.newInstance(constr)().result)
+      assertEquals("a", js.Dynamic.newInstance(constr)("a").result)
+      assertEquals("a|b", js.Dynamic.newInstance(constr)("a", "b").result)
+      assertEquals("a|b|c", js.Dynamic.newInstance(constr)("a", "b", "c").result)
+      assertEquals("Number: <5>|a", js.Dynamic.newInstance(constr)(5, "a").result)
+    }
+  }
+
+  @Test def exportForClassesWithDefaultParametersInCtor(): AsyncResult = await {
+    val constrFuture =
+      if (isNoModule) Future.successful(global.ExportedDefaultArgClass)
+      else exportsNamespace.map(_.ExportedDefaultArgClass)
+    for (constr <- constrFuture) yield {
+      assertEquals(6, js.Dynamic.newInstance(constr)(1,2,3).result)
+      assertEquals(106, js.Dynamic.newInstance(constr)(1).result)
+      assertEquals(103, js.Dynamic.newInstance(constr)(1,2).result)
+    }
+  }
+
+  // @JSExportTopLevel methods
+
+  @Test def basicTopLevelExport(): Unit = {
+    assumeTrue("Assume NoModule", isNoModule)
+    assertEquals(1, global.TopLevelExport_basic())
+  }
+
+  @Test def basicTopLevelExportModule(): AsyncResult = await {
+    assumeFalse("Assume Module", isNoModule)
+    for (exp <- exportsNamespace) yield {
+      assertEquals(1, exp.TopLevelExport_basic())
+    }
+  }
+
+  @Test def overloadedTopLevelExport(): Unit = {
+    assumeTrue("Assume NoModule", isNoModule)
+    assertEquals("Hello World", global.TopLevelExport_overload("World"))
+    assertEquals(2, global.TopLevelExport_overload(2))
+    assertEquals(9, global.TopLevelExport_overload(2, 7))
+    assertEquals(10, global.TopLevelExport_overload(1, 2, 3, 4))
+  }
+
+  @Test def overloadedTopLevelExportModule(): AsyncResult = await {
+    assumeFalse("Assume Module", isNoModule)
+    for (exp <- exportsNamespace) yield {
+      assertEquals("Hello World", exp.TopLevelExport_overload("World"))
+      assertEquals(2, exp.TopLevelExport_overload(2))
+      assertEquals(9, exp.TopLevelExport_overload(2, 7))
+      assertEquals(10, exp.TopLevelExport_overload(1, 2, 3, 4))
+    }
+  }
+
+  @Test def defaultParamsTopLevelExport_Issue4052(): Unit = {
+    assumeTrue("Assume NoModule", isNoModule)
+    assertEquals(7, global.TopLevelExport_defaultParams(6))
+    assertEquals(11, global.TopLevelExport_defaultParams(6, 5))
+  }
+
+  @Test def defaultParamsTopLevelExportModule_Issue4052(): AsyncResult = await {
+    assumeFalse("Assume Module", isNoModule)
+    for (exp <- exportsNamespace) yield {
+      assertEquals(7, exp.TopLevelExport_defaultParams(6))
+      assertEquals(11, exp.TopLevelExport_defaultParams(6, 5))
+    }
+  }
+
+  @Test def topLevelExportUsesUniqueObject(): Unit = {
+    assumeTrue("Assume NoModule", isNoModule)
+    global.TopLevelExport_set(3)
+    assertEquals(3, TopLevelExports.myVar)
+    global.TopLevelExport_set(7)
+    assertEquals(7, TopLevelExports.myVar)
+  }
+
+  @Test def topLevelExportUsesUniqueObjectModule(): AsyncResult = await {
+    assumeFalse("Assume Module", isNoModule)
+    for (exp <- exportsNamespace) yield {
+      exp.TopLevelExport_set(3)
+      assertEquals(3, TopLevelExports.myVar)
+      exp.TopLevelExport_set(7)
+      assertEquals(7, TopLevelExports.myVar)
+    }
+  }
+
+  @Test def topLevelExportFromNestedObject(): Unit = {
+    assumeTrue("Assume NoModule", isNoModule)
+    global.TopLevelExport_setNested(28)
+    assertEquals(28, TopLevelExports.Nested.myVar)
+  }
+
+  @Test def topLevelExportFromNestedObjectModule(): AsyncResult = await {
+    assumeFalse("Assume Module", isNoModule)
+    for (exp <- exportsNamespace) yield {
+      exp.TopLevelExport_setNested(28)
+      assertEquals(28, TopLevelExports.Nested.myVar)
+    }
+  }
+
+  @Test def topLevelExportWithDoubleUnderscore(): Unit = {
+    assumeTrue("Assume NoModule", isNoModule)
+    assertEquals(true, global.__topLevelExportWithDoubleUnderscore)
+  }
+
+  @Test def topLevelExportWithDoubleUnderscoreModule(): AsyncResult = await {
+    assumeFalse("Assume Module", isNoModule)
+    for (exp <- exportsNamespace) yield {
+      assertEquals(true, exp.__topLevelExportWithDoubleUnderscore)
+    }
+  }
+
+  @Test def topLevelExportIsAlwaysReachable(): Unit = {
+    assumeTrue("Assume NoModule", isNoModule)
+    assertEquals("Hello World", global.TopLevelExport_reachability())
+  }
+
+  @Test def topLevelExportIsAlwaysReachableModule(): AsyncResult = await {
+    assumeFalse("Assume Module", isNoModule)
+    for (exp <- exportsNamespace) yield {
+      assertEquals("Hello World", exp.TopLevelExport_reachability())
+    }
+  }
+
+  // @JSExportTopLevel fields
+
+  @Test def topLevelExportBasicField(): Unit = {
+    assumeTrue("Assume NoModule", isNoModule)
+    // Initialization
+    assertEquals(5, global.TopLevelExport_basicVal)
+    assertEquals("hello", global.TopLevelExport_basicVar)
+
+    // Scala modifies var
+    TopLevelFieldExports.basicVar = "modified"
+    assertEquals("modified", TopLevelFieldExports.basicVar)
+    assertEquals("modified", global.TopLevelExport_basicVar)
+
+    // Reset var
+    TopLevelFieldExports.basicVar = "hello"
+  }
+
+  @Test def topLevelExportBasicFieldModule(): AsyncResult = await {
+    assumeFalse("Assume Module", isNoModule)
+    for (exp <- exportsNamespace) yield {
+      // Initialization
+      assertEquals(5, exp.TopLevelExport_basicVal)
+      assertEquals("hello", exp.TopLevelExport_basicVar)
+
+      // Scala modifies var
+      TopLevelFieldExports.basicVar = "modified"
+      assertEquals("modified", TopLevelFieldExports.basicVar)
+      assertEquals("modified", exp.TopLevelExport_basicVar)
+
+      // Reset var
+      TopLevelFieldExports.basicVar = "hello"
+    }
+  }
+
+  @Test def topLevelExportFieldTwice(): Unit = {
+    assumeTrue("Assume NoModule", isNoModule)
+
+    // Initialization
+    assertEquals(5, global.TopLevelExport_valExportedTwice1)
+    assertEquals("hello", global.TopLevelExport_varExportedTwice1)
+    assertEquals("hello", global.TopLevelExport_varExportedTwice2)
+
+    // Scala modifies var
+    TopLevelFieldExports.varExportedTwice = "modified"
+    assertEquals("modified", TopLevelFieldExports.varExportedTwice)
+    assertEquals("modified", global.TopLevelExport_varExportedTwice1)
+    assertEquals("modified", global.TopLevelExport_varExportedTwice2)
+
+    // Reset var
+    TopLevelFieldExports.varExportedTwice = "hello"
+  }
+
+  @Test def topLevelExportFieldTwiceModule(): AsyncResult = await {
+    assumeFalse("Assume Module", isNoModule)
+    for (exp <- exportsNamespace) yield {
+      // Initialization
+      assertEquals(5, exp.TopLevelExport_valExportedTwice1)
+      assertEquals("hello", exp.TopLevelExport_varExportedTwice1)
+      assertEquals("hello", exp.TopLevelExport_varExportedTwice2)
+
+      // Scala modifies var
+      TopLevelFieldExports.varExportedTwice = "modified"
+      assertEquals("modified", TopLevelFieldExports.varExportedTwice)
+      assertEquals("modified", exp.TopLevelExport_varExportedTwice1)
+      assertEquals("modified", exp.TopLevelExport_varExportedTwice2)
+
+      // Reset var
+      TopLevelFieldExports.varExportedTwice = "hello"
+    }
+  }
+
+  @Test def topLevelExportWriteValVarCausesTypeerror(): AsyncResult = await {
+    assumeFalse("Unchecked in Script mode", isNoModule)
+
+    for (exp <- exportsNamespace) yield {
+      assertThrows(classOf[js.JavaScriptException], {
+        exp.TopLevelExport_basicVal = 54
+      })
+
+      assertThrows(classOf[js.JavaScriptException], {
+        exp.TopLevelExport_basicVar = 54
+      })
+    }
+  }
+
+  @Test def topLevelExportUninitializedFieldsScala(): Unit = {
+    assertEquals(0, TopLevelFieldExports.uninitializedVarInt)
+    assertEquals(0L, TopLevelFieldExports.uninitializedVarLong)
+    assertEquals(null, TopLevelFieldExports.uninitializedVarString)
+    assertEquals('\u0000', TopLevelFieldExports.uninitializedVarChar)
+  }
+
+  @Test def topLevelExportUninitializedFields(): Unit = {
+    assumeTrue("Assume NoModule", isNoModule)
+    assertEquals(null, global.TopLevelExport_uninitializedVarInt)
+    assertEquals(null, global.TopLevelExport_uninitializedVarLong)
+    assertEquals(null, global.TopLevelExport_uninitializedVarString)
+    assertEquals(null, global.TopLevelExport_uninitializedVarChar)
+  }
+
+  @Test def topLevelExportUninitializedFieldsModule(): AsyncResult = await {
+    assumeFalse("Assume Module", isNoModule)
+    for (exp <- exportsNamespace) yield {
+      assertEquals(null, exp.TopLevelExport_uninitializedVarInt)
+      assertEquals(null, exp.TopLevelExport_uninitializedVarLong)
+      assertEquals(null, exp.TopLevelExport_uninitializedVarString)
+      assertEquals(null, exp.TopLevelExport_uninitializedVarChar)
+    }
+  }
+
+  @Test def topLevelExportFieldIsAlwaysReachableAndInitialized(): Unit = {
+    assumeTrue("Assume NoModule", isNoModule)
+    assertEquals("Hello World", global.TopLevelExport_fieldreachability)
+  }
+
+  @Test def topLevelExportFieldIsAlwaysReachableAndInitializedModule(): AsyncResult = await {
+    assumeFalse("Assume Module", isNoModule)
+    for (exp <- exportsNamespace) yield {
+      assertEquals("Hello World", exp.TopLevelExport_fieldreachability)
+    }
+  }
+
+  @Test def topLevelExportFieldIsWritableAccrossModules(): Unit = {
+    /* We write to basicVar exported above from a different object to test writing
+     * of static fields across module boundaries (when module splitting is
+     * enabled).
+     */
+
+    assertEquals("hello", TopLevelFieldExports.inlineVar)
+    TopLevelFieldExports.inlineVar = "hello modules"
+    assertEquals("hello modules", TopLevelFieldExports.inlineVar)
+
+    // Reset var
+    TopLevelFieldExports.inlineVar = "hello"
+  }
+
+  // @JSExportTopLevel in Script's are `let`s in ES 2015, `var`s in ES 5.1
+
+  @Test def topLevelExportsNoModuleAreOfCorrectKind(): Unit = {
+    assumeTrue("relevant only for NoModule", isNoModule)
+
+    val g = JSUtils.globalObject
+
+    // Do we expect to get undefined when looking up the exports in the global object?
+    val undefinedExpected = useECMAScript2015Semantics
+
+    assertEquals(undefinedExpected, js.isUndefined(g.TopLevelExportedObject))
+    assertEquals(undefinedExpected, js.isUndefined(g.SJSDefinedTopLevelExportedObject))
+    assertEquals(undefinedExpected, js.isUndefined(g.TopLevelExportedClass))
+    assertEquals(undefinedExpected, js.isUndefined(g.SJSDefinedTopLevelExportedClass))
+    assertEquals(undefinedExpected, js.isUndefined(g.TopLevelExport_basic))
+    assertEquals(undefinedExpected, js.isUndefined(g.TopLevelExport_basicVal))
+    assertEquals(undefinedExpected, js.isUndefined(g.TopLevelExport_basicVar))
+  }
+}
+
+object TopLevelExportNameHolder {
+  final val className = "ConstantFoldedClassExport"
+  final val objectName = "ConstantFoldedObjectExport"
+}
+
+@JSExportTopLevel("TopLevelExportedObject")
+@JSExportTopLevel(TopLevelExportNameHolder.objectName)
+object TopLevelExportedObject {
+  @JSExport
+  val witness: String = "witness"
+}
+
+@JSExportTopLevel("SJSDefinedTopLevelExportedObject")
+object SJSDefinedExportedObject extends js.Object {
+  val witness: String = "witness"
+}
+
+@JSExportTopLevel("ProtectedExportedObject")
+protected object ProtectedExportedObject {
+  @JSExport
+  def witness: String = "witness"
+}
+
+@JSExportTopLevel("TopLevelExportedClass")
+@JSExportTopLevel(TopLevelExportNameHolder.className)
+class TopLevelExportedClass(_x: Int) {
+  @JSExport
+  val x = _x
+}
+
+@JSExportTopLevel("SJSDefinedTopLevelExportedClass")
+class SJSDefinedTopLevelExportedClass(val x: Int) extends js.Object
+
+@JSExportTopLevel("TopLevelExportedAbstractJSClass")
+abstract class TopLevelExportedAbstractJSClass(val x: Int) extends js.Object {
+  def foo(y: Int): Int
+
+  def bar(y: Int): Int = 3 * foo(y)
+}
+
+@JSExportTopLevel("ProtectedExportedClass")
+protected class ProtectedExportedClass(_x: Int) {
+  @JSExport
+  val x = _x
+}
+
+@JSExportTopLevel("ExportedVarArgClass")
+class ExportedVarArgClass(x: String*) {
+
+  @JSExportTopLevel("ExportedVarArgClass")
+  def this(x: Int, y: String) = this(s"Number: <$x>", y)
+
+  @JSExport
+  def result: String = x.mkString("|")
+}
+
+@JSExportTopLevel("ExportedDefaultArgClass")
+class ExportedDefaultArgClass(x: Int, y: Int, z: Int) {
+
+  @JSExportTopLevel("ExportedDefaultArgClass")
+  def this(x: Int, y: Int = 5) = this(x, y, 100)
+
+  @JSExport
+  def result: Int = x + y + z
+}
+
+object ExportHolder {
+  @JSExportTopLevel("NestedExportedClass")
+  class ExportedClass
+
+  @JSExportTopLevel("NestedExportedObject")
+  object ExportedObject
+
+  @JSExportTopLevel("NestedSJSDefinedExportedClass")
+  class SJSDefinedExportedClass extends js.Object
+}
+
+object TopLevelExports {
+  @JSExportTopLevel("TopLevelExport_basic")
+  def basic(): Int = 1
+
+  @JSExportTopLevel("TopLevelExport_overload")
+  def overload(x: String): String = "Hello " + x
+
+  @JSExportTopLevel("TopLevelExport_overload")
+  def overload(x: Int, y: Int*): Int = x + y.sum
+
+  @JSExportTopLevel("TopLevelExport_defaultParams")
+  def defaultParams(x: Int, y: Int = 1): Int = x + y
+
+  var myVar: Int = _
+
+  @JSExportTopLevel("TopLevelExport_set")
+  def setMyVar(x: Int): Unit = myVar = x
+
+  object Nested {
+    var myVar: Int = _
+
+    @JSExportTopLevel("TopLevelExport_setNested")
+    def setMyVar(x: Int): Unit = myVar = x
+  }
+
+  @JSExportTopLevel("__topLevelExportWithDoubleUnderscore")
+  val topLevelExportWithDoubleUnderscore: Boolean = true
+}
+
+/* This object is only reachable via the top level export to make sure the
+ * analyzer behaves correctly.
+ */
+object TopLevelExportsReachability {
+  private val name = "World"
+
+  @JSExportTopLevel("TopLevelExport_reachability")
+  def basic(): String = "Hello " + name
+}
+
+object TopLevelFieldExports {
+  @JSExportTopLevel("TopLevelExport_basicVal")
+  val basicVal: Int = 5
+
+  @JSExportTopLevel("TopLevelExport_basicVar")
+  var basicVar: String = "hello"
+
+  @JSExportTopLevel("TopLevelExport_valExportedTwice1")
+  @JSExportTopLevel("TopLevelExport_valExportedTwice2")
+  val valExportedTwice: Int = 5
+
+  @JSExportTopLevel("TopLevelExport_varExportedTwice1")
+  @JSExportTopLevel("TopLevelExport_varExportedTwice2")
+  var varExportedTwice: String = "hello"
+
+  @JSExportTopLevel("TopLevelExport_uninitializedVarInt")
+  var uninitializedVarInt: Int = _
+
+  @JSExportTopLevel("TopLevelExport_uninitializedVarLong")
+  var uninitializedVarLong: Long = _
+
+  @JSExportTopLevel("TopLevelExport_uninitializedVarString")
+  var uninitializedVarString: String = _
+
+  @JSExportTopLevel("TopLevelExport_uninitializedVarChar")
+  var uninitializedVarChar: Char = _
+
+  // the export is only to make the field IR-static
+  @JSExportTopLevel("TopLevelExport_irrelevant")
+  @(inline @meta.getter @meta.setter)
+  var inlineVar: String = "hello"
+}
+
+/* This object and its static initializer are only reachable via the top-level
+ * export of its field, to make sure the analyzer and the static initiliazer
+ * behave correctly.
+ */
+object TopLevelFieldExportsReachability {
+  private val name = "World"
+
+  @JSExportTopLevel("TopLevelExport_fieldreachability")
+  val greeting = "Hello " + name
+}

From 4e532afc0e4104bd67da001df7c31053ff68d743 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Mon, 13 May 2024 17:26:42 +0200
Subject: [PATCH 095/298] Make tests for `@JSExportTopLevel` independent from
 `@JSExport`.

Previously, for top-level exported Scala classes and objects, we
used `@JSExport`ed "witness" members to test the results. Because
of that, the tests for `@JSExportTopLevel` were dependent on
`@JSExport`. That would be problematic for WebAssembly, which is
going to support `@JSExportTopLevel` but not `@JSExport`.

We now use a `WitnessInterface` trait instead, to access the
witness fields/methods without requiring `@JSExport` members.
---
 .../jsinterop/TopLevelExportsTest.scala       | 64 ++++++++++---------
 1 file changed, 34 insertions(+), 30 deletions(-)

diff --git a/test-suite/js/src/test/scala/org/scalajs/testsuite/jsinterop/TopLevelExportsTest.scala b/test-suite/js/src/test/scala/org/scalajs/testsuite/jsinterop/TopLevelExportsTest.scala
index b0d90209e6..66ae05a678 100644
--- a/test-suite/js/src/test/scala/org/scalajs/testsuite/jsinterop/TopLevelExportsTest.scala
+++ b/test-suite/js/src/test/scala/org/scalajs/testsuite/jsinterop/TopLevelExportsTest.scala
@@ -38,6 +38,11 @@ class TopLevelExportsTest {
   private lazy val exportsNamespace: Future[js.Dynamic] =
     ExportLoopback.exportsNamespace
 
+  def witnessOf(obj: Any): Any = {
+    assertTrue("" + obj.getClass(), obj.isInstanceOf[WitnessInterface])
+    obj.asInstanceOf[WitnessInterface].witness
+  }
+
   // @JSExportTopLevel classes and objects
 
   @Test def toplevelExportsForObjects(): AsyncResult = await {
@@ -47,7 +52,7 @@ class TopLevelExportsTest {
     for (obj <- objFuture) yield {
       assertJSNotUndefined(obj)
       assertEquals("object", js.typeOf(obj))
-      assertEquals("witness", obj.witness)
+      assertEquals("witness", witnessOf(obj))
     }
   }
 
@@ -82,7 +87,7 @@ class TopLevelExportsTest {
     for (obj <- objFuture) yield {
       assertJSNotUndefined(obj)
       assertEquals("object", js.typeOf(obj))
-      assertEquals("witness", obj.witness)
+      assertEquals("witness", witnessOf(obj))
     }
   }
 
@@ -93,7 +98,7 @@ class TopLevelExportsTest {
     for (obj <- objFuture) yield {
       assertJSNotUndefined(obj)
       assertEquals("object", js.typeOf(obj))
-      assertEquals("witness", obj.witness)
+      assertEquals("witness", witnessOf(obj))
     }
   }
 
@@ -105,7 +110,7 @@ class TopLevelExportsTest {
       assertJSNotUndefined(constr)
       assertEquals("function", js.typeOf(constr))
       val obj = js.Dynamic.newInstance(constr)(5)
-      assertEquals(5, obj.x)
+      assertEquals(5, witnessOf(obj))
     }
   }
 
@@ -203,7 +208,7 @@ class TopLevelExportsTest {
       assertJSNotUndefined(constr)
       assertEquals("function", js.typeOf(constr))
       val obj = js.Dynamic.newInstance(constr)(5)
-      assertEquals(5, obj.x)
+      assertEquals(5, witnessOf(obj))
     }
   }
 
@@ -215,7 +220,7 @@ class TopLevelExportsTest {
       assertJSNotUndefined(constr)
       assertEquals("function", js.typeOf(constr))
       val obj = js.Dynamic.newInstance(constr)(5)
-      assertEquals(5, obj.x)
+      assertEquals(5, witnessOf(obj))
     }
   }
 
@@ -224,11 +229,11 @@ class TopLevelExportsTest {
       if (isNoModule) Future.successful(global.ExportedVarArgClass)
       else exportsNamespace.map(_.ExportedVarArgClass)
     for (constr <- constrFuture) yield {
-      assertEquals("", js.Dynamic.newInstance(constr)().result)
-      assertEquals("a", js.Dynamic.newInstance(constr)("a").result)
-      assertEquals("a|b", js.Dynamic.newInstance(constr)("a", "b").result)
-      assertEquals("a|b|c", js.Dynamic.newInstance(constr)("a", "b", "c").result)
-      assertEquals("Number: <5>|a", js.Dynamic.newInstance(constr)(5, "a").result)
+      assertEquals("", witnessOf(js.Dynamic.newInstance(constr)()))
+      assertEquals("a", witnessOf(js.Dynamic.newInstance(constr)("a")))
+      assertEquals("a|b", witnessOf(js.Dynamic.newInstance(constr)("a", "b")))
+      assertEquals("a|b|c", witnessOf(js.Dynamic.newInstance(constr)("a", "b", "c")))
+      assertEquals("Number: <5>|a", witnessOf(js.Dynamic.newInstance(constr)(5, "a")))
     }
   }
 
@@ -237,9 +242,9 @@ class TopLevelExportsTest {
       if (isNoModule) Future.successful(global.ExportedDefaultArgClass)
       else exportsNamespace.map(_.ExportedDefaultArgClass)
     for (constr <- constrFuture) yield {
-      assertEquals(6, js.Dynamic.newInstance(constr)(1,2,3).result)
-      assertEquals(106, js.Dynamic.newInstance(constr)(1).result)
-      assertEquals(103, js.Dynamic.newInstance(constr)(1,2).result)
+      assertEquals(6, witnessOf(js.Dynamic.newInstance(constr)(1, 2, 3)))
+      assertEquals(106, witnessOf(js.Dynamic.newInstance(constr)(1)))
+      assertEquals(103, witnessOf(js.Dynamic.newInstance(constr)(1, 2)))
     }
   }
 
@@ -506,10 +511,14 @@ object TopLevelExportNameHolder {
   final val objectName = "ConstantFoldedObjectExport"
 }
 
+/** Access to a `witness` property in instances of exported Scala classes. */
+trait WitnessInterface {
+  def witness: Any
+}
+
 @JSExportTopLevel("TopLevelExportedObject")
 @JSExportTopLevel(TopLevelExportNameHolder.objectName)
-object TopLevelExportedObject {
-  @JSExport
+object TopLevelExportedObject extends WitnessInterface {
   val witness: String = "witness"
 }
 
@@ -519,16 +528,14 @@ object SJSDefinedExportedObject extends js.Object {
 }
 
 @JSExportTopLevel("ProtectedExportedObject")
-protected object ProtectedExportedObject {
-  @JSExport
+protected object ProtectedExportedObject extends WitnessInterface {
   def witness: String = "witness"
 }
 
 @JSExportTopLevel("TopLevelExportedClass")
 @JSExportTopLevel(TopLevelExportNameHolder.className)
-class TopLevelExportedClass(_x: Int) {
-  @JSExport
-  val x = _x
+class TopLevelExportedClass(_x: Int) extends WitnessInterface {
+  val witness = _x
 }
 
 @JSExportTopLevel("SJSDefinedTopLevelExportedClass")
@@ -542,29 +549,26 @@ abstract class TopLevelExportedAbstractJSClass(val x: Int) extends js.Object {
 }
 
 @JSExportTopLevel("ProtectedExportedClass")
-protected class ProtectedExportedClass(_x: Int) {
-  @JSExport
-  val x = _x
+protected class ProtectedExportedClass(_x: Int) extends WitnessInterface {
+  val witness = _x
 }
 
 @JSExportTopLevel("ExportedVarArgClass")
-class ExportedVarArgClass(x: String*) {
+class ExportedVarArgClass(x: String*) extends WitnessInterface {
 
   @JSExportTopLevel("ExportedVarArgClass")
   def this(x: Int, y: String) = this(s"Number: <$x>", y)
 
-  @JSExport
-  def result: String = x.mkString("|")
+  def witness: String = x.mkString("|")
 }
 
 @JSExportTopLevel("ExportedDefaultArgClass")
-class ExportedDefaultArgClass(x: Int, y: Int, z: Int) {
+class ExportedDefaultArgClass(x: Int, y: Int, z: Int) extends WitnessInterface {
 
   @JSExportTopLevel("ExportedDefaultArgClass")
   def this(x: Int, y: Int = 5) = this(x, y, 100)
 
-  @JSExport
-  def result: Int = x + y + z
+  def witness: Int = x + y + z
 }
 
 object ExportHolder {

From 69baff142d96de1afa70bf78971e1756becbca52 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Sat, 11 May 2024 12:57:00 +0200
Subject: [PATCH 096/298] Fix #4982: Synthesize This nodes with primitive types
 in hijacked classes.

---
 .../linker/checker/ClassDefChecker.scala      | 25 +++++++++++++++++++
 .../linker/frontend/MethodSynthesizer.scala   | 10 +++++---
 .../org/scalajs/linker/BaseLinkerTest.scala   | 25 +++++++++++++++++++
 3 files changed, 56 insertions(+), 4 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala b/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
index 981d065512..728efa33dc 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
@@ -24,6 +24,7 @@ import org.scalajs.ir.Types._
 import org.scalajs.logging._
 
 import org.scalajs.linker.checker.ErrorReporter._
+import org.scalajs.linker.standard.LinkedClass
 
 /** Checker for the validity of the IR. */
 private final class ClassDefChecker(classDef: ClassDef,
@@ -925,6 +926,30 @@ object ClassDefChecker {
     reporter.errorCount
   }
 
+  def check(linkedClass: LinkedClass, postOptimizer: Boolean, logger: Logger): Int = {
+    // Rebuild a ClassDef out of the LinkedClass
+    import linkedClass._
+    implicit val pos = linkedClass.pos
+    val classDef = ClassDef(
+      name,
+      OriginalName.NoOriginalName,
+      kind,
+      jsClassCaptures,
+      superClass,
+      interfaces,
+      jsSuperClass,
+      jsNativeLoadSpec,
+      fields,
+      methods,
+      jsConstructorDef,
+      exportedMembers,
+      jsNativeMembers,
+      topLevelExportDefs = Nil
+    )(optimizerHints)
+
+    check(classDef, postBaseLinker = true, postOptimizer, logger)
+  }
+
   private class Env(
       /** Whether there is a valid `new.target` in scope. */
       val hasNewTarget: Boolean,
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/MethodSynthesizer.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/MethodSynthesizer.scala
index 68ad2893fb..eb50485d57 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/MethodSynthesizer.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/MethodSynthesizer.scala
@@ -66,9 +66,10 @@ private[frontend] final class MethodSynthesizer(
       val targetIdent = targetMDef.name.copy() // for the new pos
       val proxyIdent = MethodIdent(methodName)
       val params = targetMDef.args.map(_.copy()) // for the new pos
-      val currentClassType = ClassType(classInfo.className)
+      val instanceThisType =
+        BoxedClassToPrimType.getOrElse(classInfo.className, ClassType(classInfo.className))
 
-      val call = Apply(ApplyFlags.empty, This()(currentClassType),
+      val call = Apply(ApplyFlags.empty, This()(instanceThisType),
           targetIdent, params.map(_.ref))(targetMDef.resultType)
 
       val body = if (targetName.resultTypeRef == VoidRef) {
@@ -100,10 +101,11 @@ private[frontend] final class MethodSynthesizer(
       val targetIdent = targetMDef.name.copy() // for the new pos
       val bridgeIdent = targetIdent
       val params = targetMDef.args.map(_.copy()) // for the new pos
-      val currentClassType = ClassType(classInfo.className)
+      val instanceThisType =
+        BoxedClassToPrimType.getOrElse(classInfo.className, ClassType(classInfo.className))
 
       val body = ApplyStatically(
-          ApplyFlags.empty, This()(currentClassType), targetInterface,
+          ApplyFlags.empty, This()(instanceThisType), targetInterface,
           targetIdent, params.map(_.ref))(targetMDef.resultType)
 
       MethodDef(MemberFlags.empty, bridgeIdent, targetMDef.originalName,
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/BaseLinkerTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/BaseLinkerTest.scala
index b6870d16e5..2f4c74f00a 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/BaseLinkerTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/BaseLinkerTest.scala
@@ -22,6 +22,9 @@ import org.scalajs.ir.Types._
 
 import org.scalajs.junit.async._
 
+import org.scalajs.logging._
+
+import org.scalajs.linker.checker.ClassDefChecker
 import org.scalajs.linker.interface.StandardConfig
 import org.scalajs.linker.standard._
 
@@ -67,6 +70,28 @@ class BaseLinkerTest {
     }
   }
 
+  @Test
+  def correctThisTypeInHijackedClassReflectiveProxies_Issue4982(): AsyncResult = await {
+    val compareTo = m("compareTo", List(ClassRef(BoxedIntegerClass)), IntRef)
+    val compareToReflProxy =
+      MethodName.reflectiveProxy("compareTo", List(ClassRef(BoxedIntegerClass)))
+
+    val classDefs = Seq(
+      mainTestClassDef(
+        consoleLog(Apply(EAF, IntLiteral(5), compareToReflProxy, List(IntLiteral(6)))(AnyType))
+      )
+    )
+
+    val config = StandardConfig().withOptimizer(false)
+
+    for (moduleSet <- linkToModuleSet(classDefs, MainTestModuleInitializers, config = config)) yield {
+      val clazz = findClass(moduleSet, BoxedIntegerClass).get
+      val errorCount = ClassDefChecker.check(clazz, postOptimizer = false,
+          new ScalaConsoleLogger(Level.Error))
+      assertEquals(0, errorCount)
+    }
+  }
+
   private def findClass(moduleSet: ModuleSet, name: ClassName): Option[LinkedClass] =
     moduleSet.modules.flatMap(_.classDefs).find(_.className == name)
 }

From a62941b1aceeb2a11bd5ecbd4c64232bdfaed88c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Thu, 23 May 2024 13:18:45 +0200
Subject: [PATCH 097/298] Make the HTML test runner onLoad event more resilient
 to loading details.

If the `start` method executes after the `DOMContentLoaded` event
has fired, the `onLoad` callback was not executed. We are now more
robust against that situation, following the pattern recommended
on MDN.
---
 .../org/scalajs/testing/bridge/HTMLRunner.scala   | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/test-bridge/src/main/scala/org/scalajs/testing/bridge/HTMLRunner.scala b/test-bridge/src/main/scala/org/scalajs/testing/bridge/HTMLRunner.scala
index d2aab7f7dd..0cfd173253 100644
--- a/test-bridge/src/main/scala/org/scalajs/testing/bridge/HTMLRunner.scala
+++ b/test-bridge/src/main/scala/org/scalajs/testing/bridge/HTMLRunner.scala
@@ -55,8 +55,18 @@ protected[bridge] object HTMLRunner {
     }
   }
 
-  def start(tests: IsolatedTestSet): Unit =
-    dom.window.addEventListener("DOMContentLoaded", () => onLoad(tests))
+  def start(tests: IsolatedTestSet): Unit = {
+    // See https://developer.mozilla.org/en-US/docs/Web/API/Document/DOMContentLoaded_event
+    if (dom.document.readyState == "loading") {
+      // Loading has not finished yet; register a DOMContentLoaded event
+      dom.window.addEventListener("DOMContentLoaded", () => onLoad(tests))
+    } else {
+      // `DOMContentLoaded` has already fired; schedule `onLoad` on the next tick
+      Future {
+        onLoad(tests)
+      }
+    }
+  }
 
   private def onLoad(tests: IsolatedTestSet): Unit = {
     /* Note: Test filtering is currently done based on the fully qualified name
@@ -457,6 +467,7 @@ protected[bridge] object HTMLRunner {
     @JSGlobal
     @js.native
     object document extends js.Object {
+      def readyState: String = js.native
       def body: Element = js.native
       def createElement(tag: String): Element = js.native
       def createTextNode(tag: String): Node = js.native

From c1a4c0bcaf19c9e4c5a78dfa8cef115d3570f509 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Thu, 30 May 2024 15:49:45 +0200
Subject: [PATCH 098/298] Remove dead code identifying Scala 2.11 trait impl
 forwarders.

Since we do not support Scala 2.11 anymore, it does not make sense
to try and identify shapes of "trait impl" forwarders anymore.

Technically, the removed code was not dead code, since it could be
triggered for methods that happen to delegate to a static method
at the user code level. However, that is extremely rare, and even
when found, there is virtually no chance that it could take part
in multi-inlining.
---
 .../frontend/optimizer/OptimizerCore.scala    | 19 -------------------
 1 file changed, 19 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
index 7c484195b5..8cc5b8191b 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
@@ -2093,15 +2093,6 @@ private[optimizer] abstract class OptimizerCore(
     // TODO? Inline multiple non-forwarders with the exact same body?
     impls.forall(impl => impl.attributes.isForwarder && impl.attributes.inlineable) &&
     (getMethodBody(impls.head).body.get match {
-      // Trait impl forwarder
-      case ApplyStatic(flags, staticCls, MethodIdent(methodName), _) =>
-        impls.tail.forall(getMethodBody(_).body.get match {
-          case ApplyStatic(`flags`, `staticCls`, MethodIdent(`methodName`), _) =>
-            true
-          case _ =>
-            false
-        })
-
       // Shape of forwards to default methods
       case ApplyStatically(flags, This(), className, MethodIdent(methodName), args) =>
         impls.tail.forall(getMethodBody(_).body.get match {
@@ -6408,16 +6399,6 @@ private[optimizer] object OptimizerCore {
       val optimizerHints = methodDef.optimizerHints
 
       val isForwarder = body match {
-        // Shape of forwarders to trait impls
-        case ApplyStatic(_, impl, method, args) =>
-          ((args.size == params.size + 1) &&
-              (args.head.isInstanceOf[This]) &&
-              (args.tail.zip(params).forall {
-                case (VarRef(LocalIdent(aname)),
-                    ParamDef(LocalIdent(pname), _, _, _)) => aname == pname
-                case _ => false
-              }))
-
         // Shape of forwards to default methods
         case ApplyStatically(_, This(), className, method, args) =>
           args.size == params.size &&

From 90734e014533af23a2c3371e3914a56ea8b77fe3 Mon Sep 17 00:00:00 2001
From: "dependabot[bot]" <49699333+dependabot[bot]@users.noreply.github.com>
Date: Wed, 19 Jun 2024 05:50:00 +0000
Subject: [PATCH 099/298] Bump ws from 7.5.9 to 7.5.10

Bumps [ws](https://github.com/websockets/ws) from 7.5.9 to 7.5.10.
- [Release notes](https://github.com/websockets/ws/releases)
- [Commits](https://github.com/websockets/ws/compare/7.5.9...7.5.10)

---
updated-dependencies:
- dependency-name: ws
  dependency-type: indirect
...

Signed-off-by: dependabot[bot] <support@github.com>
---
 package-lock.json | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/package-lock.json b/package-lock.json
index 78045751fb..b7f175e7dc 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1422,9 +1422,9 @@
       }
     },
     "node_modules/ws": {
-      "version": "7.5.9",
-      "resolved": "https://registry.npmjs.org/ws/-/ws-7.5.9.tgz",
-      "integrity": "sha512-F+P9Jil7UiSKSkppIiD94dN07AwvFixvLIj1Og1Rl9GGMuNipJnV9JzjD6XuqmAeiswGvUmNLjr5cFuXwNS77Q==",
+      "version": "7.5.10",
+      "resolved": "https://registry.npmjs.org/ws/-/ws-7.5.10.tgz",
+      "integrity": "sha512-+dbF1tHwZpXcbOJdVOkzLDxZP1ailvSxM6ZweXTegylPny803bFhA+vqBYw4s31NSAk4S2Qz+AKXK9a4wkdjcQ==",
       "dev": true,
       "engines": {
         "node": ">=8.3.0"
@@ -2563,9 +2563,9 @@
       "dev": true
     },
     "ws": {
-      "version": "7.5.9",
-      "resolved": "https://registry.npmjs.org/ws/-/ws-7.5.9.tgz",
-      "integrity": "sha512-F+P9Jil7UiSKSkppIiD94dN07AwvFixvLIj1Og1Rl9GGMuNipJnV9JzjD6XuqmAeiswGvUmNLjr5cFuXwNS77Q==",
+      "version": "7.5.10",
+      "resolved": "https://registry.npmjs.org/ws/-/ws-7.5.10.tgz",
+      "integrity": "sha512-+dbF1tHwZpXcbOJdVOkzLDxZP1ailvSxM6ZweXTegylPny803bFhA+vqBYw4s31NSAk4S2Qz+AKXK9a4wkdjcQ==",
       "dev": true,
       "requires": {}
     },

From aa84f641c653fbbfc1b14378329cdf89cf1c5564 Mon Sep 17 00:00:00 2001
From: Som Snytt <som.snytt@gmail.com>
Date: Sun, 23 Jun 2024 21:27:04 -0700
Subject: [PATCH 100/298] Fix name of pickler phase constraint

---
 .../src/main/scala/org/scalajs/nscplugin/ScalaJSPlugin.scala    | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/compiler/src/main/scala/org/scalajs/nscplugin/ScalaJSPlugin.scala b/compiler/src/main/scala/org/scalajs/nscplugin/ScalaJSPlugin.scala
index 5273a84b4d..a67adbb948 100644
--- a/compiler/src/main/scala/org/scalajs/nscplugin/ScalaJSPlugin.scala
+++ b/compiler/src/main/scala/org/scalajs/nscplugin/ScalaJSPlugin.scala
@@ -77,7 +77,7 @@ class ScalaJSPlugin(val global: Global) extends NscPlugin {
     val jsAddons: ScalaJSPlugin.this.jsAddons.type = ScalaJSPlugin.this.jsAddons
     val scalaJSOpts = ScalaJSPlugin.this.scalaJSOpts
     override val runsAfter = List("typer")
-    override val runsBefore = List("pickle")
+    override val runsBefore = List("pickler")
   }
 
   object ExplicitInnerJSComponent extends ExplicitInnerJS[global.type](global) {

From 6fd932263b5f1df0ba25c063ff545068a86cd7e9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Fri, 31 May 2024 14:23:23 +0200
Subject: [PATCH 101/298] Make the optimizer type-preserving by inserting Casts
 when necessary.

Previously, the optimizer generated IR that was ill-typed, in the
sense that it would not pass the IR checker (even if it were
generalized to understand intrinsics and record types).

This happened when the receiver of a method call had a more generic
type than an inlined method. That can be the case when only there
is effectively only one possible target method for a virtual call,
or when there are multiple targets but we can apply multi-inlining.

Producing ill-typed IR is not a big deal for JavaScript, although
we had to care about some details like proper unboxing of chars.
In order to apply the optimizer to the Wasm backend, however, we
need well-typed IR to be able to produce well-typed Wasm.

In this commit, we fix the issue by introducing a new transient,
`Cast`. It performs a true, unchecked cast, doing nothing but
reassigning another type to an expression. It behaves like an
unchecked `AsInstanceOf`, except it does not convert `null` to the
zero of primitive types.

When inlining, we now introduce casts (along with explicit null
checks) to adapt the receiver to the target method. For single
inlining, it is straightforward. For multi-inlining, choosing a
correct target type, and generally producing well-typed IR,
required to significantly change the logic. Previously, we picked
an arbitrary target among the possible candidates and inlined it
in the normal way. We cannot do this anymore, since the `This`
type of any one possible target may not represent what is valid
for all the targets. Instead, we now deeply inspect the shapes
we know how to multi-inlining, and recreate calls on the fly for
the method that they call.

The explicit introduction of casts at the inlining level, along
with explicit null checks, made the logic to refine receiver
types in `withBindings` redundant. In order to completely get
rid of it without any regression, we had to make `checkNotNull`
more powerful to preserve the "it is now not-null" information
even when `nullPointers` are unchecked.

Interestingly, making the above changes retains more information
even within the optimizer. That results in fewer useless
temporary variables in the generated code. The changes are
therefore beneficial even for the JavaScript backend.

Finally, since we have proper casts, we can simplify
`AsInstanceOf`s that never require unboxing into `Cast`s, when
`asInstanceOfs` are unchecked. This changes almost nothing to the
generated code, except replacing some `$uC(expr)` by `expr.c`.
---
 .../backend/emitter/FunctionEmitter.scala     |  18 +
 .../linker/backend/emitter/Transients.scala   |  32 ++
 .../frontend/optimizer/OptimizerCore.scala    | 375 ++++++++++++------
 project/Build.scala                           |  10 +-
 4 files changed, 305 insertions(+), 130 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
index 58979155fc..871324daaf 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
@@ -1092,6 +1092,8 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
 
               case Transient(AssumeNotNull(obj)) =>
                 Transient(AssumeNotNull(rec(obj)))
+              case Transient(Cast(expr, tpe)) =>
+                Transient(Cast(rec(expr), tpe))
               case Transient(ZeroOf(runtimeClass)) =>
                 Transient(ZeroOf(rec(runtimeClass)))
               case Transient(ObjectClassName(obj)) =>
@@ -1290,6 +1292,8 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
         // Transients preserving pureness (modulo NPE)
         case Transient(AssumeNotNull(obj)) =>
           test(obj)
+        case Transient(Cast(expr, _)) =>
+          test(expr)
         case Transient(ZeroOf(runtimeClass)) =>
           test(runtimeClass) // ZeroOf *assumes* that `runtimeClass ne null`
         case Transient(ObjectClassName(obj)) =>
@@ -1831,6 +1835,11 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
             redo(Transient(AssumeNotNull(newObj)))(env)
           }
 
+        case Transient(Cast(expr, tpe)) =>
+          unnest(expr) { (newExpr, env) =>
+            redo(Transient(Cast(newExpr, tpe)))(env)
+          }
+
         case Transient(ZeroOf(runtimeClass)) =>
           unnest(runtimeClass) { (newRuntimeClass, env) =>
             redo(Transient(ZeroOf(newRuntimeClass)))(env)
@@ -2745,6 +2754,13 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
         case Transient(AssumeNotNull(obj)) =>
           transformExpr(obj, preserveChar = true)
 
+        case Transient(Cast(expr, tpe)) =>
+          val newExpr = transformExpr(expr, preserveChar = true)
+          if (tpe == CharType && expr.tpe != CharType)
+            newExpr DOT cpn.c
+          else
+            newExpr
+
         case Transient(ZeroOf(runtimeClass)) =>
           js.DotSelect(
               genSelect(transformExprNoChar(checkNotNull(runtimeClass)),
@@ -3197,6 +3213,8 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
       def isShapeNotNull(tree: Tree): Boolean = tree match {
         case Transient(CheckNotNull(_) | AssumeNotNull(_)) =>
           true
+        case Transient(Cast(expr, _)) =>
+          isShapeNotNull(expr)
         case _: This =>
           tree.tpe != AnyType
         case _:New | _:LoadModule | _:NewArray | _:ArrayValue | _:Clone | _:ClassOf =>
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Transients.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Transients.scala
index c5ee557807..f151112891 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Transients.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Transients.scala
@@ -70,6 +70,38 @@ object Transients {
     }
   }
 
+  /** Casts `expr` to the given `tpe`, without any check.
+   *
+   *  This operation is only valid if we know that `expr` is indeed a value of
+   *  the given `tpe`.
+   *
+   *  `Cast` behaves like an unchecked `AsInstanceOf`, except that it does not
+   *  convert `null` to the zero of primitive types. Attempting to cast `null`
+   *  to a primitive type (that is not `NullType`) is undefined behavior.
+   *
+   *  `Cast` is not always a no-op. In some cases, a `Cast` may still have to
+   *  be implemented using a conversion. For example, casting down from
+   *  `jl.Character` to `char` requires to extract the primitive value from the
+   *  box (although we know that the box is non-null, unlike with
+   *  `AsInstanceOf`).
+   */
+  final case class Cast(expr: Tree, val tpe: Type) extends Transient.Value {
+    def traverse(traverser: Traverser): Unit =
+      traverser.traverse(expr)
+
+    def transform(transformer: Transformer, isStat: Boolean)(
+        implicit pos: Position): Tree = {
+      Transient(Cast(transformer.transformExpr(expr), tpe))
+    }
+
+    def printIR(out: IRTreePrinter): Unit = {
+      out.print(expr)
+      out.print(".as![")
+      out.print(tpe)
+      out.print("]")
+    }
+  }
+
   /** Intrinsic for `System.arraycopy`.
    *
    *  This node *assumes* that `src` and `dest` are non-null. It is the
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
index 8cc5b8191b..c7da1c1cb4 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
@@ -976,7 +976,7 @@ private[optimizer] abstract class OptimizerCore(
           } else if (baseTpe == NullType) {
             cont(checkNotNull(texpr))
           } else if (isSubtype(baseTpe, JavaScriptExceptionClassType)) {
-            pretransformSelectCommon(AnyType, texpr,
+            pretransformSelectCommon(AnyType, texpr, optQualDeclaredType = None,
                 FieldIdent(exceptionFieldName), isLhsOfAssign = false)(cont)
           } else {
             if (texpr.tpe.isExact || !isSubtype(JavaScriptExceptionClassType, baseTpe))
@@ -1182,13 +1182,14 @@ private[optimizer] abstract class OptimizerCore(
       implicit scope: Scope): TailRec[Tree] = {
     val Select(qualifier, field) = tree
     pretransformExpr(qualifier) { preTransQual =>
-      pretransformSelectCommon(tree.tpe, preTransQual, field, isLhsOfAssign)(
+      pretransformSelectCommon(tree.tpe, preTransQual, optQualDeclaredType = None, field, isLhsOfAssign)(
           cont)(scope, tree.pos)
     }
   }
 
   private def pretransformSelectCommon(expectedType: Type,
-      preTransQual: PreTransform, field: FieldIdent, isLhsOfAssign: Boolean)(
+      preTransQual: PreTransform, optQualDeclaredType: Option[Type],
+      field: FieldIdent, isLhsOfAssign: Boolean)(
       cont: PreTransCont)(
       implicit scope: Scope, pos: Position): TailRec[Tree] = {
     /* Note: Callers are expected to have already removed writes to fields that
@@ -1249,7 +1250,13 @@ private[optimizer] abstract class OptimizerCore(
 
             case PreTransTree(newQual, newQualType) =>
               val newQual1 = maybeAssumeNotNull(newQual, newQualType)
-              cont(PreTransTree(Select(newQual1, field)(expectedType),
+              val newQual2 = optQualDeclaredType match {
+                case Some(qualDeclaredType) if !isSubtype(newQual1.tpe, qualDeclaredType) =>
+                  Transient(Cast(newQual1, qualDeclaredType))
+                case _ =>
+                  newQual1
+              }
+              cont(PreTransTree(Select(newQual2, field)(expectedType),
                   RefinedType(expectedType)))
           }
         }
@@ -1707,6 +1714,11 @@ private[optimizer] abstract class OptimizerCore(
       keepOnlySideEffects(expr)
     case UnwrapFromThrowable(expr) =>
       checkNotNullStatement(expr)(stat.pos)
+
+    // By definition, a failed cast is always UB, so it cannot have side effects
+    case Transient(Cast(expr, _)) =>
+      keepOnlySideEffects(expr)
+
     case _ =>
       stat
   }
@@ -1937,6 +1949,9 @@ private[optimizer] abstract class OptimizerCore(
         case AsInstanceOf(expr, tpe) =>
           rec(expr).mapOrFailed(AsInstanceOf(_, tpe))
 
+        case Transient(Cast(expr, tpe)) =>
+          rec(expr).mapOrKeepGoing(newExpr => Transient(Cast(newExpr, tpe)))
+
         case GetClass(expr) =>
           rec(expr).mapOrKeepGoingIf(GetClass(_))(keepGoingIf = isNotNull(expr))
 
@@ -2063,24 +2078,16 @@ private[optimizer] abstract class OptimizerCore(
           } else {
             val allocationSites =
               (treceiver :: targs).map(_.tpe.allocationSite)
-            val shouldMultiInline = {
+            val shouldTryMultiInline = {
               impls.nonEmpty && // will fail at runtime.
-              !impls.exists(impl => scope.implsBeingInlined((allocationSites, impl))) &&
-              canMultiInline(impls)
+              impls.forall(impl => impl.attributes.isForwarder && impl.attributes.inlineable) &&
+              !impls.exists(impl => scope.implsBeingInlined((allocationSites, impl)))
             }
 
-            if (shouldMultiInline) {
-              /* When multi-inlining, we cannot use the enclosing class of the
-               * target method as the declared type of the receiver, since we
-               * have no guarantee that the receiver is in fact of that
-               * particular class. It could be of any of the classes that the
-               * targets belong to. Therefore, we have to keep the receiver's
-               * static type as a declared type, which is our only safe choice.
-               */
-              val representative = impls.minBy(_.enclosingClassName) // for stability
-              val receiverType = treceiver.tpe.base
-              inline(allocationSites, Some((receiverType, treceiver)), targs,
-                  representative, isStat, usePreTransform)(cont)
+            if (shouldTryMultiInline) {
+              tryMultiInline(impls, treceiver, targs, isStat, usePreTransform)(cont) {
+                treeNotInlined
+              }
             } else {
               treeNotInlined
             }
@@ -2089,22 +2096,55 @@ private[optimizer] abstract class OptimizerCore(
     }
   }
 
-  private def canMultiInline(impls: List[MethodID]): Boolean = {
-    // TODO? Inline multiple non-forwarders with the exact same body?
-    impls.forall(impl => impl.attributes.isForwarder && impl.attributes.inlineable) &&
-    (getMethodBody(impls.head).body.get match {
-      // Shape of forwards to default methods
-      case ApplyStatically(flags, This(), className, MethodIdent(methodName), args) =>
-        impls.tail.forall(getMethodBody(_).body.get match {
+  private def tryMultiInline(impls: List[MethodID], treceiver: PreTransform,
+      targs: List[PreTransform], isStat: Boolean, usePreTransform: Boolean)(
+      cont: PreTransCont)(
+      treeNotInlined: => TailRec[Tree])(
+      implicit scope: Scope, pos: Position): TailRec[Tree] = {
+
+    val referenceMethodDef = getMethodBody(impls.head)
+
+    (referenceMethodDef.body.get match {
+      // Shape of forwarders to default methods
+      case body @ ApplyStatically(flags, This(), className, MethodIdent(methodName), args) =>
+        val allTheSame = impls.tail.forall(getMethodBody(_).body.get match {
           case ApplyStatically(`flags`, This(), `className`, MethodIdent(`methodName`), _) =>
             true
           case _ =>
             false
         })
 
+        if (!allTheSame) {
+          treeNotInlined
+        } else {
+          /* In this case, we can directly "splice in" the treceiver and targs
+           * into a made-up ApplyStatically, as evaluation order is always
+           * preserved. This potentially avoids useless bindings and keeps
+           * things simple.
+           *
+           * We only need to cast the receiver after checking that it is not null,
+           * since we need to pass it as the receiver of the `ApplyStatically`,
+           * which expects a known type.
+           */
+          val treceiverCast = foldCast(checkNotNull(treceiver), ClassType(className))
+
+          val target = staticCall(className,
+              MemberNamespace.forNonStaticCall(flags), methodName)
+
+          pretransformSingleDispatch(flags, target, Some(treceiverCast), targs,
+              isStat, usePreTransform)(cont) {
+            val newTree = ApplyStatically(flags,
+                finishTransformExprMaybeAssumeNotNull(treceiverCast),
+                className, MethodIdent(methodName),
+                targs.map(finishTransformExpr))(
+                body.tpe)
+            cont(newTree.toPreTransform)
+          }
+        }
+
       // Bridge method
-      case Apply(flags, This(), MethodIdent(methodName), referenceArgs) =>
-        impls.tail.forall(getMethodBody(_).body.get match {
+      case body @ Apply(flags, This(), MethodIdent(methodName), referenceArgs) =>
+        val allTheSame = impls.tail.forall(getMethodBody(_).body.get match {
           case Apply(`flags`, This(), MethodIdent(`methodName`), implArgs) =>
             referenceArgs.zip(implArgs) forall {
               case (MaybeUnbox(_, unboxID1), MaybeUnbox(_, unboxID2)) =>
@@ -2114,6 +2154,71 @@ private[optimizer] abstract class OptimizerCore(
             false
         })
 
+        if (!allTheSame) {
+          treeNotInlined
+        } else {
+          /* Interestingly, for this shape of multi-inlining, we do not need to
+           * cast the receiver. We can keep it as is. Virtual dispatch and
+           * reachability analysis will be happy to compute the possible targets
+           * of the generated Apply given the type of our receiver.
+           *
+           * It's a good thing too, because it would be quite hard to figure out
+           * what type to cast the receiver to!
+           */
+
+          if (!referenceArgs.exists(_.isInstanceOf[AsInstanceOf])) {
+            // Common case where where we can splice in; evaluation order is preserved
+            pretransformApply(flags, treceiver, MethodIdent(methodName), targs,
+                body.tpe, isStat, usePreTransform)(cont)
+          } else {
+            /* If there is at least one unbox, we cannot splice in; we need to
+             * use actual bindings and resolve the actual Apply tree to apply
+             * the unboxes in the correct evaluation order.
+             */
+
+            /* Generate a new, fake body that we will inline. For
+             * type-preservation, the type of its `This()` node is the type of
+             * our receiver. For stability, the parameter names are normalized
+             * (taking them from `body` would make the result depend on which
+             * method came up first in the list of targets).
+             */
+            val normalizedParams: List[(LocalName, Type)] = {
+              referenceMethodDef.args.zipWithIndex.map {
+                case (referenceParam, i) => (LocalName("x" + i), referenceParam.ptpe)
+              }
+            }
+            val normalizedBody = Apply(
+              flags,
+              This()(treceiver.tpe.base),
+              MethodIdent(methodName),
+              normalizedParams.zip(referenceArgs).map {
+                case ((name, ptpe), AsInstanceOf(_, castTpe)) =>
+                  AsInstanceOf(VarRef(LocalIdent(name))(ptpe), castTpe)
+                case ((name, ptpe), _) =>
+                  VarRef(LocalIdent(name))(ptpe)
+              }
+            )(body.tpe)
+
+            // Construct bindings; need to check null for the receiver to preserve evaluation order
+            val receiverBinding =
+              Binding(Binding.This, treceiver.tpe.base, mutable = false, checkNotNull(treceiver))
+            val argsBindings = normalizedParams.zip(targs).map {
+              case ((name, ptpe), targ) =>
+                Binding(Binding.Local(name, NoOriginalName), ptpe, mutable = false, targ)
+            }
+
+            withBindings(receiverBinding :: argsBindings) { (bodyScope, cont1) =>
+              implicit val scope = bodyScope
+              if (usePreTransform) {
+                assert(!isStat, "Cannot use pretransform in statement position")
+                pretransformExpr(normalizedBody)(cont1)
+              } else {
+                cont1(PreTransTree(transform(normalizedBody, isStat)))
+              }
+            } (cont) (scope.withEnv(OptEnv.Empty))
+          }
+        }
+
       case body =>
         throw new AssertionError("Invalid forwarder shape: " + body)
     })
@@ -2546,13 +2651,14 @@ private[optimizer] abstract class OptimizerCore(
       case This() if args.isEmpty =>
         assert(optReceiver.isDefined,
             "There was a This(), there should be a receiver")
-        cont(checkNotNull(optReceiver.get._2))
+        cont(foldCast(checkNotNull(optReceiver.get._2), optReceiver.get._1))
 
       case Select(This(), field) if formals.isEmpty =>
         assert(optReceiver.isDefined,
             "There was a This(), there should be a receiver")
-        pretransformSelectCommon(body.tpe, optReceiver.get._2, field,
-            isLhsOfAssign = false)(cont)
+        pretransformSelectCommon(body.tpe, optReceiver.get._2,
+            optQualDeclaredType = Some(optReceiver.get._1),
+            field, isLhsOfAssign = false)(cont)
 
       case Assign(lhs @ Select(This(), field), VarRef(LocalIdent(rhsName)))
           if formals.size == 1 && formals.head.name.name == rhsName =>
@@ -2567,8 +2673,9 @@ private[optimizer] abstract class OptimizerCore(
           // Field is never read, discard assign, keep side effects only.
           cont(PreTransTree(finishTransformArgsAsStat(), RefinedType.NoRefinedType))
         } else {
-          pretransformSelectCommon(lhs.tpe, treceiver, field,
-              isLhsOfAssign = true) { tlhs =>
+          pretransformSelectCommon(lhs.tpe, treceiver,
+              optQualDeclaredType = Some(optReceiver.get._1),
+              field, isLhsOfAssign = true) { tlhs =>
             pretransformAssign(tlhs, args.head)(cont)
           }
         }
@@ -2588,17 +2695,14 @@ private[optimizer] abstract class OptimizerCore(
       implicit scope: Scope, pos: Position): TailRec[Tree] = tailcall {
 
     val optReceiverBinding = optReceiver map { receiver =>
-      /* If the declaredType is CharType, we must introduce a cast, because we
-       * must communicate to the emitter that it has to unbox the value.
-       * For other primitive types, unboxes/casts are not necessary, because
-       * they would only convert `null` to the zero value of the type. However,
-       * `null` is ruled out by `checkNotNull` (or because it is UB).
+      /* Introduce an explicit null check that would be part of the semantics
+       * of `Apply` or `ApplyStatically`.
+       * Then, cast the non-null receiver to the expected receiver type. This
+       * may be required because we found a single potential call target in a
+       * subclass of the static type of the receiver.
        */
       val (declaredType, value0) = receiver
-      val value1 = checkNotNull(value0)
-      val value =
-        if (declaredType == CharType) foldAsInstanceOf(value1, declaredType)
-        else value1
+      val value = foldCast(checkNotNull(value0), declaredType)
       Binding(Binding.This, declaredType, false, value)
     }
 
@@ -4746,12 +4850,52 @@ private[optimizer] abstract class OptimizerCore(
 
   private def foldAsInstanceOf(arg: PreTransform, tpe: Type)(
       implicit pos: Position): PreTransform = {
-    if (isSubtype(arg.tpe.base, tpe))
+    def mayRequireUnboxing: Boolean =
+      arg.tpe.isNullable && !isNullableType(tpe)
+
+    if (semantics.asInstanceOfs == CheckedBehavior.Unchecked && !mayRequireUnboxing)
+      foldCast(arg, tpe)
+    else if (isSubtype(arg.tpe.base, tpe))
       arg
     else
       AsInstanceOf(finishTransformExpr(arg), tpe).toPreTransform
   }
 
+  private def foldCast(arg: PreTransform, tpe: Type)(
+      implicit pos: Position): PreTransform = {
+    def default(arg: PreTransform, newTpe: RefinedType): PreTransform =
+      PreTransTree(Transient(Cast(finishTransformExpr(arg), tpe)), newTpe)
+
+    def castLocalDef(arg: PreTransform, newTpe: RefinedType): PreTransform = arg match {
+      case PreTransMaybeBlock(bindingsAndStats, PreTransLocalDef(localDef)) =>
+        val refinedLocalDef = localDef.tryWithRefinedType(newTpe)
+        if (refinedLocalDef ne localDef)
+          PreTransBlock(bindingsAndStats, PreTransLocalDef(refinedLocalDef))
+        else
+          default(arg, newTpe)
+
+      case _ =>
+        default(arg, newTpe)
+    }
+
+    if (isSubtype(arg.tpe.base, tpe)) {
+      arg
+    } else {
+      val castTpe = RefinedType(tpe, isExact = false,
+          isNullable = arg.tpe.isNullable && isNullableType(tpe),
+          arg.tpe.allocationSite)
+
+      val isCastFreeAtRunTime = tpe != CharType
+
+      if (isCastFreeAtRunTime) {
+        // Try to push the cast down to usages of LocalDefs, in order to preserve aliases
+        castLocalDef(arg, castTpe)
+      } else {
+        default(arg, castTpe)
+      }
+    }
+  }
+
   private def foldJSSelect(qualifier: Tree, item: Tree)(
       implicit pos: Position): Tree = {
     // !!! Must be in sync with scala.scalajs.runtime.LinkingInfo
@@ -4973,16 +5117,31 @@ private[optimizer] abstract class OptimizerCore(
   }
 
   private def checkNotNull(texpr: PreTransform)(implicit pos: Position): PreTransform = {
-    val tpe = texpr.tpe
-
-    if (!tpe.isNullable || semantics.nullPointers == CheckedBehavior.Unchecked) {
+    if (!texpr.tpe.isNullable) {
       texpr
-    } else {
-      val refinedType: RefinedType = tpe.base match {
-        case NullType => RefinedType.Nothing
-        case baseType => RefinedType(baseType, isExact = tpe.isExact, isNullable = false)
+    } else if (semantics.nullPointers == CheckedBehavior.Unchecked) {
+      // If possible, improve the type of the expression to be non-nullable
+
+      val nonNullType = texpr.tpe.toNonNullable
+
+      def rec(texpr: PreTransform): PreTransform = texpr match {
+        case PreTransBlock(bindingsAndStats, result) =>
+          PreTransBlock(bindingsAndStats, rec(result).asInstanceOf[PreTransResult])
+        case PreTransLocalDef(localDef) =>
+          PreTransLocalDef(localDef.tryWithRefinedType(nonNullType))(texpr.pos)
+        case PreTransTree(tree, tpe) =>
+          PreTransTree(tree, nonNullType)
+        case _:PreTransUnaryOp | _:PreTransBinaryOp | _:PreTransJSBinaryOp | _:PreTransRecordTree =>
+          // We cannot improve the type of those
+          texpr
       }
-      PreTransTree(Transient(CheckNotNull(finishTransformExpr(texpr))), refinedType)
+
+      if (nonNullType.isNothingType)
+        texpr // things blow up otherwise
+      else
+        rec(texpr)
+    } else {
+      PreTransTree(Transient(CheckNotNull(finishTransformExpr(texpr))), texpr.tpe.toNonNullable)
     }
   }
 
@@ -5023,18 +5182,20 @@ private[optimizer] abstract class OptimizerCore(
     }
   }
 
+  private def isNullableType(tpe: Type): Boolean = tpe match {
+    case NullType    => true
+    case _: PrimType => false
+    case _           => true
+  }
+
   private def isNotNull(tree: Tree): Boolean = {
     // !!! Duplicate code with FunctionEmitter.isNotNull
 
-    def isNullableType(tpe: Type): Boolean = tpe match {
-      case NullType    => true
-      case _: PrimType => false
-      case _           => true
-    }
-
     def isShapeNotNull(tree: Tree): Boolean = tree match {
       case Transient(CheckNotNull(_) | AssumeNotNull(_)) =>
         true
+      case Transient(Cast(expr, _)) =>
+        isShapeNotNull(expr)
       case _: This =>
         tree.tpe != AnyType
       case _:New | _:LoadModule | _:NewArray | _:ArrayValue | _:Clone | _:ClassOf =>
@@ -5178,48 +5339,6 @@ private[optimizer] abstract class OptimizerCore(
     } else if (mutable) {
       withDedicatedVar(RefinedType(declaredType))
     } else {
-      def computeRefinedType(): RefinedType = bindingName match {
-        case _ if value.tpe.isExact || declaredType == AnyType =>
-          /* If the value's type is exact, or if the declared type is `AnyType`,
-           * the declared type cannot have any new information to give us, so
-           * we directly return `value.tpe`. This avoids a useless `isSubtype`
-           * call, which creates dependencies for incremental optimization.
-           *
-           * In addition, for the case `declaredType == AnyType` there is a
-           * stronger reason: we don't actually know that `this` is non-null in
-           * that case, since it could be the `this` value of a JavaScript
-           * function, which can accept `null`. (As of this writing, this is
-           * theoretical, because the only place where we use a declared type
-           * of `AnyType` is in `JSFunctionApply`, where the actual value for
-           * `this` is always `undefined`.)
-           */
-          value.tpe
-
-        case _: Binding.Local =>
-          /* When binding a something else than `this`, we do not receive the
-           * non-null information. Moreover, there is no situation where the
-           * declared type would bring any new information, since that would
-           * not be valid IR in the first place. Therefore, to avoid a useless
-           * call to `isSubtype`, we directly return `value.tpe`.
-           */
-          value.tpe
-
-        case Binding.This =>
-          /* When binding to `this`, if the declared type is not `AnyType`,
-           * we are in a situation where
-           * a) we know the value must be non-null, and
-           * b) the declaredType may bring more precise information than
-           *    value.tpe.base (typically when inlining a polymorphic method
-           *    that ends up having only one target in a subclass).
-           * We can refine the type here based on that knowledge.
-           */
-          val improvedBaseType =
-            if (isSubtype(value.tpe.base, declaredType)) value.tpe.base
-            else declaredType
-          val isExact = false // We catch the case value.tpe.isExact earlier
-          RefinedType(improvedBaseType, isExact, isNullable = false)
-      }
-
       value match {
         case PreTransBlock(bindingsAndStats, result) =>
           withNewLocalDef(binding.copy(value = result))(buildInner) { tresult =>
@@ -5230,41 +5349,19 @@ private[optimizer] abstract class OptimizerCore(
           /* Attention: the same-name optimization in transformCapturingBody
            * relies on immutable bindings to var refs not being renamed.
            */
-
-          val refinedType = computeRefinedType()
-          val newLocalDef = if (refinedType == value.tpe) {
-            localDef
-          } else {
-            /* Only adjust if the replacement if ReplaceWithThis or
-             * ReplaceWithVarRef, because other types have nothing to gain
-             * (e.g., ReplaceWithConstant) or we want to keep them unwrapped
-             * because they are examined in optimizations (notably all the
-             * types with virtualized objects).
-             */
-            localDef.replacement match {
-              case _:ReplaceWithThis | _:ReplaceWithVarRef =>
-                LocalDef(refinedType, mutable = false,
-                    ReplaceWithOtherLocalDef(localDef))
-              case _ =>
-                localDef
-            }
-          }
-          buildInner(newLocalDef, cont)
+          buildInner(localDef, cont)
 
         case PreTransTree(literal: Literal, _) =>
-          /* A `Literal` always has the most precise type it could ever have.
-           * There is no point using `computeRefinedType()`.
-           */
           buildInner(LocalDef(value.tpe, false,
               ReplaceWithConstant(literal)), cont)
 
         case PreTransTree(VarRef(LocalIdent(refName)), _)
             if !localIsMutable(refName) =>
-          buildInner(LocalDef(computeRefinedType(), false,
+          buildInner(LocalDef(value.tpe, false,
               ReplaceWithVarRef(refName, newSimpleState(UsedAtLeastOnce), None)), cont)
 
         case _ =>
-          withDedicatedVar(computeRefinedType())
+          withDedicatedVar(value.tpe)
       }
     }
   }
@@ -5535,6 +5632,12 @@ private[optimizer] object OptimizerCore {
       isNullable: Boolean)(val allocationSite: AllocationSite, dummy: Int = 0) {
 
     def isNothingType: Boolean = base == NothingType
+
+    def toNonNullable: RefinedType = {
+      if (!isNullable) this
+      else if (base == NullType) RefinedType.Nothing
+      else RefinedType(base, isExact, isNullable = false, allocationSite)
+    }
   }
 
   private object RefinedType {
@@ -5643,7 +5746,11 @@ private[optimizer] object OptimizerCore {
          * notably because it allows us to run the ClassDefChecker after the
          * optimizer.
          */
-        localDef.newReplacement
+        val underlying = localDef.newReplacement
+        if (underlying.tpe == tpe.base)
+          underlying
+        else
+          Transient(Cast(underlying, tpe.base))
 
       case ReplaceWithConstant(value) =>
         value
@@ -5690,6 +5797,23 @@ private[optimizer] object OptimizerCore {
           false
       })
     }
+
+    def tryWithRefinedType(refinedType: RefinedType): LocalDef = {
+      /* Only adjust if the replacement if ReplaceWithThis or
+       * ReplaceWithVarRef, because other types have nothing to gain
+       * (e.g., ReplaceWithConstant) or we want to keep them unwrapped
+       * because they are examined in optimizations (notably all the
+       * types with virtualized objects).
+       */
+      replacement match {
+        case _:ReplaceWithThis | _:ReplaceWithVarRef =>
+          LocalDef(refinedType, mutable, ReplaceWithOtherLocalDef(this))
+        case replacement: ReplaceWithOtherLocalDef =>
+          LocalDef(refinedType, mutable, replacement)
+        case _ =>
+          this
+      }
+    }
   }
 
   private sealed abstract class LocalDefReplacement
@@ -6411,6 +6535,7 @@ private[optimizer] object OptimizerCore {
 
         // Shape of bridges for generic methods
         case Apply(_, This(), method, args) =>
+          !method.name.isReflectiveProxy &&
           (args.size == params.size) &&
           args.zip(params).forall {
             case (MaybeUnbox(VarRef(LocalIdent(aname)), _),
diff --git a/project/Build.scala b/project/Build.scala
index 0d93e05ec7..dd86f57340 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -2021,15 +2021,15 @@ object Build {
           case `default212Version` =>
             if (!useMinifySizes) {
               Some(ExpectedSizes(
-                  fastLink = 626000 to 627000,
+                  fastLink = 625000 to 626000,
                   fullLink = 97000 to 98000,
                   fastLinkGz = 75000 to 79000,
                   fullLinkGz = 25000 to 26000,
               ))
             } else {
               Some(ExpectedSizes(
-                  fastLink = 433000 to 434000,
-                  fullLink = 288000 to 289000,
+                  fastLink = 432000 to 433000,
+                  fullLink = 283000 to 284000,
                   fastLinkGz = 62000 to 63000,
                   fullLinkGz = 44000 to 45000,
               ))
@@ -2039,14 +2039,14 @@ object Build {
             if (!useMinifySizes) {
               Some(ExpectedSizes(
                   fastLink = 451000 to 452000,
-                  fullLink = 94000 to 95000,
+                  fullLink = 95000 to 96000,
                   fastLinkGz = 58000 to 59000,
                   fullLinkGz = 25000 to 26000,
               ))
             } else {
               Some(ExpectedSizes(
                   fastLink = 308000 to 309000,
-                  fullLink = 265000 to 266000,
+                  fullLink = 263000 to 264000,
                   fastLinkGz = 49000 to 50000,
                   fullLinkGz = 43000 to 44000,
               ))

From 018e5fc4fce8578faf180ed2145a99327870fa60 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Tue, 23 Jul 2024 11:11:18 +0200
Subject: [PATCH 102/298] Fix #5005: Only emit the int-div helpers if
 ArithmeticException is instantiated.

---
 Jenkinsfile                                   |  3 +
 .../linker/backend/emitter/CoreJSLib.scala    | 34 ++++++----
 .../backend/emitter/GlobalKnowledge.scala     |  3 +
 .../backend/emitter/KnowledgeGuardian.scala   | 65 ++++++++++++++-----
 4 files changed, 77 insertions(+), 28 deletions(-)

diff --git a/Jenkinsfile b/Jenkinsfile
index 9ca49c5e3c..487f96ba53 100644
--- a/Jenkinsfile
+++ b/Jenkinsfile
@@ -125,6 +125,9 @@ def Tasks = [
         ++$scala helloworld$v/run &&
     sbtretry 'set scalaJSLinkerConfig in helloworld.v$v ~= (_.withSemantics(_.withAsInstanceOfs(CheckedBehavior.Unchecked)))' \
         ++$scala helloworld$v/run &&
+    sbtretry ++$scala \
+        'set scalaJSLinkerConfig in helloworld.v$v ~= (_.withESFeatures(_.withAllowBigIntsForLongs(true)))' \
+        helloworld$v/run &&
     sbtretry ++$scala \
         'set scalaJSLinkerConfig in helloworld.v$v ~= (_.withModuleKind(ModuleKind.CommonJSModule))' \
         helloworld$v/run &&
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
index 42862541ae..05ade75ba0 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
@@ -909,7 +909,10 @@ private[emitter] object CoreJSLib {
     }
 
     private def defineArithmeticOps(): List[Tree] = {
-      val throwDivByZero = {
+      val isArithmeticExceptionClassInstantiated =
+        globalKnowledge.isArithmeticExceptionClassInstantiated
+
+      def throwDivByZero: Tree = {
         Throw(genScalaClassNew(ArithmeticExceptionClass,
             StringArgConstructorName, str("/ by zero")))
       }
@@ -917,16 +920,19 @@ private[emitter] object CoreJSLib {
       def wrapBigInt64(tree: Tree): Tree =
         Apply(genIdentBracketSelect(BigIntRef, "asIntN"), 64 :: tree :: Nil)
 
-      defineFunction2(VarField.intDiv) { (x, y) =>
-        If(y === 0, throwDivByZero, {
-          Return((x / y) | 0)
-        })
-      } :::
-      defineFunction2(VarField.intMod) { (x, y) =>
-        If(y === 0, throwDivByZero, {
-          Return((x % y) | 0)
-        })
-      } :::
+      condDefs(isArithmeticExceptionClassInstantiated)(
+        defineFunction2(VarField.intDiv) { (x, y) =>
+          If(y === 0, throwDivByZero, {
+            Return((x / y) | 0)
+          })
+        } :::
+        defineFunction2(VarField.intMod) { (x, y) =>
+          If(y === 0, throwDivByZero, {
+            Return((x % y) | 0)
+          })
+        } :::
+        Nil
+      ) :::
       defineFunction1(VarField.doubleToInt) { x =>
         Return(If(x > 2147483647, 2147483647, If(x < -2147483648, -2147483648, x | 0)))
       } :::
@@ -948,7 +954,7 @@ private[emitter] object CoreJSLib {
           )
         }
       ) :::
-      condDefs(allowBigIntsForLongs)(
+      condDefs(allowBigIntsForLongs && isArithmeticExceptionClassInstantiated)(
         defineFunction2(VarField.longDiv) { (x, y) =>
           If(y === bigInt(0), throwDivByZero, {
             Return(wrapBigInt64(x / y))
@@ -959,7 +965,9 @@ private[emitter] object CoreJSLib {
             Return(wrapBigInt64(x % y))
           })
         } :::
-
+        Nil
+      ) :::
+      condDefs(allowBigIntsForLongs)(
         defineFunction1(VarField.doubleToLong)(x => Return {
           If(x < double(-9223372036854775808.0), { // -2^63
             bigInt(-9223372036854775808L)
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/GlobalKnowledge.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/GlobalKnowledge.scala
index 84592f0ec1..b8fec3f3ff 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/GlobalKnowledge.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/GlobalKnowledge.scala
@@ -22,6 +22,9 @@ private[emitter] trait GlobalKnowledge {
   /** Tests whether the `java.lang.Class` class is instantiated. */
   def isClassClassInstantiated: Boolean
 
+  /** Tests whether the `java.lang.ArithmeticException` class is instantiated. */
+  def isArithmeticExceptionClassInstantiated: Boolean
+
   /** Tests whether the parent class data is accessed in the linking unit. */
   def isParentDataAccessed: Boolean
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/KnowledgeGuardian.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/KnowledgeGuardian.scala
index 1e9f26e285..562ad1e519 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/KnowledgeGuardian.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/KnowledgeGuardian.scala
@@ -48,6 +48,7 @@ private[emitter] final class KnowledgeGuardian(config: Emitter.Config) {
     // Object is optional, because the module splitter might remove everything.
     var objectClass: Option[LinkedClass] = None
     var classClass: Option[LinkedClass] = None
+    var arithmeticExceptionClass: Option[LinkedClass] = None
     val hijackedClasses = Iterable.newBuilder[LinkedClass]
 
     // Update classes
@@ -81,6 +82,9 @@ private[emitter] final class KnowledgeGuardian(config: Emitter.Config) {
         case ObjectClass =>
           objectClass = Some(linkedClass)
 
+        case ArithmeticExceptionClass =>
+          arithmeticExceptionClass = Some(linkedClass)
+
         case name if HijackedClasses(name) =>
           hijackedClasses += linkedClass
 
@@ -93,10 +97,12 @@ private[emitter] final class KnowledgeGuardian(config: Emitter.Config) {
 
     val invalidateAll = {
       if (specialInfo == null) {
-        specialInfo = new SpecialInfo(objectClass, classClass, hijackedClasses.result())
+        specialInfo = new SpecialInfo(objectClass, classClass,
+            arithmeticExceptionClass, hijackedClasses.result())
         false
       } else {
-        specialInfo.update(objectClass, classClass, hijackedClasses.result())
+        specialInfo.update(objectClass, classClass, arithmeticExceptionClass,
+            hijackedClasses.result())
       }
     }
 
@@ -175,6 +181,9 @@ private[emitter] final class KnowledgeGuardian(config: Emitter.Config) {
     def isClassClassInstantiated: Boolean =
       specialInfo.askIsClassClassInstantiated(this)
 
+    def isArithmeticExceptionClassInstantiated: Boolean =
+      specialInfo.askIsArithmeticExceptionClassInstantiated(this)
+
     def isInterface(className: ClassName): Boolean =
       classes(className).askIsInterface(this)
 
@@ -502,10 +511,13 @@ private[emitter] final class KnowledgeGuardian(config: Emitter.Config) {
 
   private class SpecialInfo(initObjectClass: Option[LinkedClass],
       initClassClass: Option[LinkedClass],
+      initArithmeticExceptionClass: Option[LinkedClass],
       initHijackedClasses: Iterable[LinkedClass]) extends Unregisterable {
 
-    private var isClassClassInstantiated =
-      computeIsClassClassInstantiated(initClassClass)
+    import SpecialInfo._
+
+    private var instantiatedSpecialClassBitSet =
+      computeInstantiatedSpecialClassBitSet(initClassClass, initArithmeticExceptionClass)
 
     private var isParentDataAccessed =
       computeIsParentDataAccessed(initClassClass)
@@ -519,18 +531,22 @@ private[emitter] final class KnowledgeGuardian(config: Emitter.Config) {
     private var hijackedDescendants =
       computeHijackedDescendants(initHijackedClasses)
 
-    private val isClassClassInstantiatedAskers = mutable.Set.empty[Invalidatable]
+    // Askers of isXClassInstantiated -- merged for all X because in practice that's only the CoreJSLib
+    private val instantiatedSpecialClassAskers = mutable.Set.empty[Invalidatable]
+
     private val methodsInRepresentativeClassesAskers = mutable.Set.empty[Invalidatable]
     private val methodsInObjectAskers = mutable.Set.empty[Invalidatable]
 
     def update(objectClass: Option[LinkedClass], classClass: Option[LinkedClass],
+        arithmeticExceptionClass: Option[LinkedClass],
         hijackedClasses: Iterable[LinkedClass]): Boolean = {
       var invalidateAll = false
 
-      val newIsClassClassInstantiated = computeIsClassClassInstantiated(classClass)
-      if (newIsClassClassInstantiated != isClassClassInstantiated) {
-        isClassClassInstantiated = newIsClassClassInstantiated
-        invalidateAskers(isClassClassInstantiatedAskers)
+      val newInstantiatedSpecialClassBitSet =
+        computeInstantiatedSpecialClassBitSet(classClass, arithmeticExceptionClass)
+      if (newInstantiatedSpecialClassBitSet != instantiatedSpecialClassBitSet) {
+        instantiatedSpecialClassBitSet = newInstantiatedSpecialClassBitSet
+        invalidateAskers(instantiatedSpecialClassAskers)
       }
 
       val newIsParentDataAccessed = computeIsParentDataAccessed(classClass)
@@ -562,8 +578,16 @@ private[emitter] final class KnowledgeGuardian(config: Emitter.Config) {
       invalidateAll
     }
 
-    private def computeIsClassClassInstantiated(classClass: Option[LinkedClass]): Boolean =
-      classClass.exists(_.hasInstances)
+    private def computeInstantiatedSpecialClassBitSet(
+        classClass: Option[LinkedClass],
+        arithmeticExceptionClass: Option[LinkedClass]): Int = {
+      var bitSet: Int = 0
+      if (classClass.exists(_.hasInstances))
+        bitSet |= SpecialClassClass
+      if (arithmeticExceptionClass.exists(_.hasInstances))
+        bitSet |= SpecialClassArithmeticException
+      bitSet
+    }
 
     private def computeIsParentDataAccessed(classClass: Option[LinkedClass]): Boolean = {
       def methodExists(linkedClass: LinkedClass, methodName: MethodName): Boolean = {
@@ -619,8 +643,14 @@ private[emitter] final class KnowledgeGuardian(config: Emitter.Config) {
 
     def askIsClassClassInstantiated(invalidatable: Invalidatable): Boolean = {
       invalidatable.registeredTo(this)
-      isClassClassInstantiatedAskers += invalidatable
-      isClassClassInstantiated
+      instantiatedSpecialClassAskers += invalidatable
+      (instantiatedSpecialClassBitSet & SpecialClassClass) != 0
+    }
+
+    def askIsArithmeticExceptionClassInstantiated(invalidatable: Invalidatable): Boolean = {
+      invalidatable.registeredTo(this)
+      instantiatedSpecialClassAskers += invalidatable
+      (instantiatedSpecialClassBitSet & SpecialClassArithmeticException) != 0
     }
 
     def askIsParentDataAccessed(invalidatable: Invalidatable): Boolean =
@@ -645,19 +675,24 @@ private[emitter] final class KnowledgeGuardian(config: Emitter.Config) {
     }
 
     def unregister(invalidatable: Invalidatable): Unit = {
-      isClassClassInstantiatedAskers -= invalidatable
+      instantiatedSpecialClassAskers -= invalidatable
       methodsInRepresentativeClassesAskers -= invalidatable
       methodsInObjectAskers -= invalidatable
     }
 
     /** Call this when we invalidate all caches. */
     def unregisterAll(): Unit = {
-      isClassClassInstantiatedAskers.clear()
+      instantiatedSpecialClassAskers.clear()
       methodsInRepresentativeClassesAskers.clear()
       methodsInObjectAskers.clear()
     }
   }
 
+  private object SpecialInfo {
+    private final val SpecialClassClass = 1 << 0
+    private final val SpecialClassArithmeticException = 1 << 1
+  }
+
   private def invalidateAskers(askers: mutable.Set[Invalidatable]): Unit = {
     /* Calling `invalidate` cause the `Invalidatable` to call `unregister()` in
      * this class, which will mutate the `askers` set. Therefore, we cannot

From 2e8919f11ff030f472efaf08139026bfeaf4dc0c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Thu, 25 Jul 2024 14:35:32 +0200
Subject: [PATCH 103/298] Remove the case "exact jl.Object" when trying to
 optimize `eq` as `===`.

When performing `x eq y`, the optimizer tries to optimize it as
`x === y`. It can do so if it can prove that one of the operands
can never be a primitive number.

One of the cases that we identified was when it was an *exact*
`jl.Object`, typically if it was the result of a `new Object()`.
We now remove that specific case. It was only useful for the
reference object wrapped in a `NonLocalReturnControl` exception
by the codegen for non-local `return`s. For that code, performance
is dominated by the throwing and catching of the exception, and
using `Object.is` instead of `===` should be inconsequential.

Removing that case means that the optimization now only relies
on IR `Type`s, rather than the optimizer's `RefinedType`. That
will allow us to move the optimization to the JS backend in the
following commit.
---
 .../scalajs/linker/frontend/optimizer/OptimizerCore.scala | 8 +-------
 1 file changed, 1 insertion(+), 7 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
index c7da1c1cb4..3feff5ca2e 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
@@ -3857,13 +3857,7 @@ private[optimizer] abstract class OptimizerCore(
           case AnyType | ByteType | ShortType | IntType | FloatType | DoubleType =>
             true
           case ClassType(className) =>
-            /* If `className` is a concrete superclass of a boxed number class,
-             * then it can be exact, and in that case we know that it cannot be
-             * a primitive number. In practice this happens only for
-             * `java.lang.Object`, and especially for code generated for
-             * non-local returns in Scala.
-             */
-            !tpe.isExact && MaybeHijackedPrimNumberClasses.contains(className)
+            MaybeHijackedPrimNumberClasses.contains(className)
           case _ =>
             false
         }

From 03cf1f8396743fec4cad780f90381c4d445bdbcd Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Thu, 25 Jul 2024 15:39:47 +0200
Subject: [PATCH 104/298] Move the `eq`-to-`===` optimization to the JS
 backend.

This simplifies a number of things. In particular, all the
infrastructure for intelligently dealing with `JSBinaryOp`s
disappears from the optimizer.

Since the optimization would be detrimental to Wasm anyway, it
makes more sense to move it to the JS backend.
---
 .../backend/emitter/FunctionEmitter.scala     |  59 +++++---
 .../frontend/optimizer/OptimizerCore.scala    | 142 +++---------------
 2 files changed, 60 insertions(+), 141 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
index 871324daaf..343e01605e 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
@@ -2405,23 +2405,23 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
 
           (op: @switch) match {
             case === | !== =>
-              /** Tests whether an operand receives exemption from the
-               *  `Object.is` treatment.
+              /* Semantically, this is an `Object.is` test in JS. However, we
+               * optimize it as a primitive JS strict equality (`===`) when
+               * possible.
                *
-               *  If either operand receives an exemption, we use `===`
-               *  instead.
+               * The optimizer does not do this optimization because:
+               *
+               * - it partly relies on the specifics of how hijacked classes are encoded in JS
+               *   (see the `ClassType(ObjectClass)` case in `canBePrimitiveNum`),
+               * - if handled in the optimizer, `JSBinaryOp`s become frequent
+               *   and require additional infrastructure to optimize common patterns, and
+               * - it is very specific to *JavaScript*, and is actually detrimental in Wasm.
                */
-              def receivesExemption(tree: js.Tree): Boolean = tree match {
-                case _:js.Undefined | _:js.Null =>
-                  /* An `undefined` operand happens a lot for default
-                   * parameters in exported methods. Because exported methods
-                   * are not optimized, they survive until here.
-                   *
-                   * A `null` operand often happens in the constructor of inner
-                   * JS classes, which are not optimized either.
-                   */
+
+              def canBePrimitiveNum(tree: Tree): Boolean = tree.tpe match {
+                case AnyType | ByteType | ShortType | IntType | FloatType | DoubleType =>
                   true
-                case _:js.This =>
+                case ClassType(ObjectClass) =>
                   /* Due to how hijacked classes are encoded in JS, we know
                    * that in `java.lang.Object` itself, `this` can never be a
                    * primitive. It will always be a proper Scala.js object.
@@ -2429,16 +2429,35 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
                    * Exempting `this` in `java.lang.Object` is important so
                    * that the body of `Object.equals__O__Z` can be compiled as
                    * `this === that` instead of `Object.is(this, that)`.
-                   *
-                   * This is something that the optimizer is not supposed to be
-                   * able to do, since it doesn't know how hijacked classes are
-                   * encoded.
                    */
-                  env.enclosingClassName.exists(_ == ObjectClass)
+                  !tree.isInstanceOf[This]
+                case ClassType(BoxedByteClass | BoxedShortClass |
+                    BoxedIntegerClass | BoxedFloatClass | BoxedDoubleClass) =>
+                  true
+                case ClassType(className) =>
+                  globalKnowledge.isAncestorOfHijackedClass(BoxedDoubleClass)
+                case _ =>
+                  false
+              }
+
+              def isWhole(tree: Tree): Boolean = tree.tpe match {
+                case ByteType | ShortType | IntType =>
+                  true
+                case ClassType(className) =>
+                  className == BoxedByteClass ||
+                  className == BoxedShortClass ||
+                  className == BoxedIntegerClass
                 case _ =>
                   false
               }
-              if (receivesExemption(newLhs) || receivesExemption(newRhs)) {
+
+              val canOptimizeAsJSStrictEq = {
+                !canBePrimitiveNum(lhs) ||
+                !canBePrimitiveNum(rhs) ||
+                (isWhole(lhs) && isWhole(rhs))
+              }
+
+              if (canOptimizeAsJSStrictEq) {
                 js.BinaryOp(if (op == ===) JSBinaryOp.=== else JSBinaryOp.!==,
                     newLhs, newRhs)
               } else {
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
index 3feff5ca2e..6d973cde36 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
@@ -527,7 +527,7 @@ private[optimizer] abstract class OptimizerCore(
             val result = {
               if (isSubtype(texpr.tpe.base, testType)) {
                 if (texpr.tpe.isNullable)
-                  JSBinaryOp(JSBinaryOp.!==, finishTransformExpr(texpr), Null())
+                  BinaryOp(BinaryOp.!==, finishTransformExpr(texpr), Null())
                 else
                   Block(finishTransformStat(texpr), BooleanLiteral(true))
               } else {
@@ -1381,7 +1381,7 @@ private[optimizer] abstract class OptimizerCore(
             PreTransTree(finishTransformBindings(bindingsAndStats, tree), tpe)
         }
 
-      case _:PreTransUnaryOp | _:PreTransBinaryOp | _:PreTransJSBinaryOp =>
+      case _:PreTransUnaryOp | _:PreTransBinaryOp =>
         PreTransTree(finishTransformExpr(preTrans), preTrans.tpe)
 
       case PreTransLocalDef(localDef @ LocalDef(tpe, _, replacement)) =>
@@ -1424,7 +1424,7 @@ private[optimizer] abstract class OptimizerCore(
       case PreTransBlock(_, result) =>
         resolveRecordType(result)
 
-      case _:PreTransUnaryOp | _:PreTransBinaryOp | _:PreTransJSBinaryOp =>
+      case _:PreTransUnaryOp | _:PreTransBinaryOp =>
         None
 
       case PreTransLocalDef(localDef @ LocalDef(tpe, _, replacement)) =>
@@ -1486,8 +1486,6 @@ private[optimizer] abstract class OptimizerCore(
         UnaryOp(op, finishTransformExpr(lhs))
       case PreTransBinaryOp(op, lhs, rhs) =>
         BinaryOp(op, finishTransformExpr(lhs), finishTransformExpr(rhs))
-      case PreTransJSBinaryOp(op, lhs, rhs) =>
-        JSBinaryOp(op, finishTransformExpr(lhs), finishTransformExpr(rhs))
       case PreTransLocalDef(localDef) =>
         localDef.newReplacement
 
@@ -1568,11 +1566,6 @@ private[optimizer] abstract class OptimizerCore(
           finishNoSideEffects
       }
 
-    case PreTransJSBinaryOp(op, lhs, rhs) =>
-      if (op == JSBinaryOp.=== || op == JSBinaryOp.!==)
-        Block(finishTransformStat(lhs), finishTransformStat(rhs))(stat.pos)
-      else // other operators can have side effects that we must preserve
-        finishTransformExpr(stat)
     case PreTransLocalDef(_) =>
       Skip()(stat.pos)
     case PreTransRecordTree(tree, _, _) =>
@@ -3297,9 +3290,9 @@ private[optimizer] abstract class OptimizerCore(
              * the equals() method has been inlined as a reference
              * equality test.
              */
-            case (JSBinaryOp(JSBinaryOp.===, VarRef(lhsIdent), Null()),
-                JSBinaryOp(JSBinaryOp.===, VarRef(rhsIdent), Null()),
-                JSBinaryOp(JSBinaryOp.===, VarRef(lhsIdent2), VarRef(rhsIdent2)))
+            case (BinaryOp(BinaryOp.===, VarRef(lhsIdent), Null()),
+                BinaryOp(BinaryOp.===, VarRef(rhsIdent), Null()),
+                BinaryOp(BinaryOp.===, VarRef(lhsIdent2), VarRef(rhsIdent2)))
                 if lhsIdent2 == lhsIdent && rhsIdent2 == rhsIdent =>
               elsep
 
@@ -3546,16 +3539,6 @@ private[optimizer] abstract class OptimizerCore(
             if (newOp == -1) default
             else PreTransBinaryOp(newOp, l, r)
 
-          case PreTransJSBinaryOp(innerOp, l, r) =>
-            val newOp = innerOp match {
-              case JSBinaryOp.=== => JSBinaryOp.!==
-              case JSBinaryOp.!== => JSBinaryOp.===
-
-              case _ => -1
-            }
-            if (newOp == -1) default
-            else PreTransJSBinaryOp(newOp, l, r)
-
           case _ =>
             default
         }
@@ -3722,17 +3705,15 @@ private[optimizer] abstract class OptimizerCore(
    *  The result is always known statically.
    *
    *  Bytes, Shorts, Ints, Floats and Doubles all live in the same "space" for
-   *  `===` comparison, since they all upcast as primitive numbers. If
-   *  `isJSStrictEq` is false, they are compared with `equals()` instead of
-   *  `==` so that `NaN === NaN` and `+0.0 !== -0.0`.
+   *  `===` comparison, since they all upcast as primitive numbers. They are
+   *  compared with `equals()` instead of `==` so that `NaN === NaN` and
+   *  `+0.0 !== -0.0`.
    *
    *  Chars and Longs, however, never compare as `===`, since they are boxed
    *  chars and instances of `RuntimeLong`, respectively---unless we are using
    *  `BigInt`s for `Long`s, in which case those can be `===`.
    */
-  private def literal_===(lhs: Literal, rhs: Literal,
-      isJSStrictEq: Boolean): Boolean = {
-
+  private def literal_===(lhs: Literal, rhs: Literal): Boolean = {
     object AnyNumLiteral {
       def unapply(tree: Literal): Option[Double] = tree match {
         case ByteLiteral(v)   => Some(v.toDouble)
@@ -3748,7 +3729,7 @@ private[optimizer] abstract class OptimizerCore(
       case (BooleanLiteral(l), BooleanLiteral(r)) => l == r
       case (StringLiteral(l), StringLiteral(r))   => l == r
       case (ClassOf(l), ClassOf(r))               => l == r
-      case (AnyNumLiteral(l), AnyNumLiteral(r))   => if (isJSStrictEq) l == r else l.equals(r)
+      case (AnyNumLiteral(l), AnyNumLiteral(r))   => l.equals(r)
       case (LongLiteral(l), LongLiteral(r))       => l == r && !useRuntimeLong
       case (Undefined(), Undefined())             => true
       case (Null(), Null())                       => true
@@ -3818,16 +3799,6 @@ private[optimizer] abstract class OptimizerCore(
     }
   }
 
-  private val MaybeHijackedPrimNumberClasses = {
-    /* In theory, we could figure out the ancestors from the global knowledge,
-     * but that would be overkill.
-     */
-    Set(BoxedByteClass, BoxedShortClass, BoxedIntegerClass, BoxedFloatClass,
-        BoxedDoubleClass, ObjectClass, ClassName("java.lang.CharSequence"),
-        ClassName("java.io.Serializable"), ClassName("java.lang.Comparable"),
-        ClassName("java.lang.Number"))
-  }
-
   private def foldBinaryOp(op: BinaryOp.Code, lhs: PreTransform,
       rhs: PreTransform)(
       implicit pos: Position): PreTransform = {
@@ -3851,42 +3822,18 @@ private[optimizer] abstract class OptimizerCore(
 
     (op: @switch) match {
       case === | !== =>
-        // Try to optimize as a primitive JS strict equality
-
-        def canBePrimitiveNum(tpe: RefinedType): Boolean = tpe.base match {
-          case AnyType | ByteType | ShortType | IntType | FloatType | DoubleType =>
-            true
-          case ClassType(className) =>
-            MaybeHijackedPrimNumberClasses.contains(className)
-          case _ =>
-            false
-        }
-
-        def isWhole(tpe: RefinedType): Boolean = tpe.base match {
-          case ByteType | ShortType | IntType =>
-            true
-          case ClassType(className) =>
-            className == BoxedByteClass ||
-            className == BoxedShortClass ||
-            className == BoxedIntegerClass
-          case _ =>
-            false
-        }
-
-        def canOptimizeAsJSStrictEq(lhsTpe: RefinedType, rhsTpe: RefinedType): Boolean = (
-            !canBePrimitiveNum(lhsTpe) ||
-            !canBePrimitiveNum(rhsTpe) ||
-            (isWhole(lhsTpe) && isWhole(rhsTpe))
-        )
-
         (lhs, rhs) match {
           case (PreTransLit(l), PreTransLit(r)) =>
-            val isSame = literal_===(l, r, isJSStrictEq = false)
+            val isSame = literal_===(l, r)
             PreTransLit(BooleanLiteral(if (op == ===) isSame else !isSame))
-          case _ if canOptimizeAsJSStrictEq(lhs.tpe, rhs.tpe) =>
-            foldJSBinaryOp(
-                if (op == ===) JSBinaryOp.=== else JSBinaryOp.!==,
-                lhs, rhs)
+          case (PreTransLit(_), _) =>
+            foldBinaryOp(op, rhs, lhs)
+
+          case (_, PreTransLit(Null())) if !lhs.tpe.isNullable =>
+            Block(
+                finishTransformStat(lhs),
+                BooleanLiteral(op == !==)).toPreTransform
+
           case _ =>
             default
         }
@@ -4812,36 +4759,6 @@ private[optimizer] abstract class OptimizerCore(
     }
   }
 
-  private def foldJSBinaryOp(op: JSBinaryOp.Code, lhs: PreTransform,
-      rhs: PreTransform)(
-      implicit pos: Position): PreTransform = {
-    import JSBinaryOp._
-
-    def default: PreTransform =
-      PreTransJSBinaryOp(op, lhs, rhs)
-
-    op match {
-      case JSBinaryOp.=== | JSBinaryOp.!== =>
-        val positive = (op == JSBinaryOp.===)
-        (lhs, rhs) match {
-          case (PreTransLit(l), PreTransLit(r)) =>
-            val isEq = literal_===(l, r, isJSStrictEq = true)
-            PreTransLit(BooleanLiteral(if (positive) isEq else !isEq))
-
-          case (_, PreTransLit(Null())) if !lhs.tpe.isNullable =>
-            Block(
-                finishTransformStat(lhs),
-                BooleanLiteral(!positive)).toPreTransform
-
-          case (PreTransLit(_), _) => foldBinaryOp(op, rhs, lhs)
-          case _                   => default
-        }
-
-      case _ =>
-        default
-    }
-  }
-
   private def foldAsInstanceOf(arg: PreTransform, tpe: Type)(
       implicit pos: Position): PreTransform = {
     def mayRequireUnboxing: Boolean =
@@ -5125,7 +5042,7 @@ private[optimizer] abstract class OptimizerCore(
           PreTransLocalDef(localDef.tryWithRefinedType(nonNullType))(texpr.pos)
         case PreTransTree(tree, tpe) =>
           PreTransTree(tree, nonNullType)
-        case _:PreTransUnaryOp | _:PreTransBinaryOp | _:PreTransJSBinaryOp | _:PreTransRecordTree =>
+        case _:PreTransUnaryOp | _:PreTransBinaryOp | _:PreTransRecordTree =>
           // We cannot improve the type of those
           texpr
       }
@@ -5976,8 +5893,6 @@ private[optimizer] object OptimizerCore {
         lhs.contains(localDef)
       case PreTransBinaryOp(_, lhs, rhs) =>
         lhs.contains(localDef) || rhs.contains(localDef)
-      case PreTransJSBinaryOp(_, lhs, rhs) =>
-        lhs.contains(localDef) || rhs.contains(localDef)
       case PreTransLocalDef(thisLocalDef) =>
         thisLocalDef.contains(localDef)
       case _: PreTransGenTree =>
@@ -6118,19 +6033,6 @@ private[optimizer] object OptimizerCore {
     val tpe: RefinedType = RefinedType(BinaryOp.resultTypeOf(op))
   }
 
-  /** A `PreTransform` for a `JSBinaryOp`. */
-  private final case class PreTransJSBinaryOp(op: JSBinaryOp.Code,
-      lhs: PreTransform, rhs: PreTransform)(implicit val pos: Position)
-      extends PreTransResult {
-
-    val tpe: RefinedType = RefinedType(JSBinaryOp.resultTypeOf(op))
-  }
-
-  private object PreTransJSBinaryOp {
-    def isWorthPreTransforming(op: JSBinaryOp.Code): Boolean =
-      op == JSBinaryOp.=== || op == JSBinaryOp.!==
-  }
-
   /** A virtual reference to a `LocalDef`. */
   private final case class PreTransLocalDef(localDef: LocalDef)(
       implicit val pos: Position) extends PreTransResult {
@@ -6198,8 +6100,6 @@ private[optimizer] object OptimizerCore {
           PreTransUnaryOp(op, lhs.toPreTransform)(self.pos)
         case BinaryOp(op, lhs, rhs) =>
           PreTransBinaryOp(op, lhs.toPreTransform, rhs.toPreTransform)(self.pos)
-        case JSBinaryOp(op, lhs, rhs) if PreTransJSBinaryOp.isWorthPreTransforming(op) =>
-          PreTransJSBinaryOp(op, lhs.toPreTransform, rhs.toPreTransform)(self.pos)
         case _ =>
           PreTransTree(self)
       }

From cf9e775fe7833c227f30d20464c3cb0da63984bf Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Wed, 22 May 2024 11:16:56 +0200
Subject: [PATCH 105/298] Bump the version to 1.17.0-SNAPSHOT for the upcoming
 changes.

---
 ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala b/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala
index eb920f2071..c32a7d5b2b 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala
@@ -17,7 +17,7 @@ import java.util.concurrent.ConcurrentHashMap
 import scala.util.matching.Regex
 
 object ScalaJSVersions extends VersionChecks(
-    current = "1.16.1-SNAPSHOT",
+    current = "1.17.0-SNAPSHOT",
     binaryEmitted = "1.16"
 )
 

From 4be30c723db0ca02c80036b005af4e3d19e01165 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Thu, 23 May 2024 13:20:57 +0200
Subject: [PATCH 106/298] Make `captureJSError` tolerant to sealed `throwable`
 arguments.

If an object is sealed, `captureStackTrace` throws an exception.
This will happen for WebAssembly objects.

We now detect this case and fall back to instantiating a dedicated
`js.Error` object.
---
 javalib/src/main/scala/java/lang/StackTrace.scala | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/javalib/src/main/scala/java/lang/StackTrace.scala b/javalib/src/main/scala/java/lang/StackTrace.scala
index 4dac37591c..76b3d067e7 100644
--- a/javalib/src/main/scala/java/lang/StackTrace.scala
+++ b/javalib/src/main/scala/java/lang/StackTrace.scala
@@ -61,8 +61,12 @@ private[lang] object StackTrace {
        * prototypes.
        */
       reference
-    } else if (js.constructorOf[js.Error].captureStackTrace eq ().asInstanceOf[AnyRef]) {
-      // Create a JS Error with the current stack trace.
+    } else if ((js.constructorOf[js.Error].captureStackTrace eq ().asInstanceOf[AnyRef]) ||
+        js.Object.isSealed(throwable.asInstanceOf[js.Object])) {
+      /* If `captureStackTrace` is not available, or if the `throwable` instance
+       * is sealed (which notably happens on Wasm), create a JS `Error` with the
+       * current stack trace.
+       */
       new js.Error()
     } else {
       /* V8-specific.

From ed255d2e6ff72a21acdab519532f677512a66c52 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Thu, 23 May 2024 13:23:47 +0200
Subject: [PATCH 107/298] Make `ExportLoopback` not dependent on support for
 multiple modules.

We now directly use `import("./main.js")` or `require("./main.js")`
rather than relying on the compilation scheme of `js.dynamicImport`.

This will allow `ExportLoopback` to work under WebAssembly,
although the initial implementation will not support multiple
modules.
---
 project/Build.scala                           |  4 ++-
 .../require-commonjs/ExportLoopback.scala     | 25 +++++++++++++++++++
 .../testsuite/jsinterop/ExportLoopback.scala  |  7 +-----
 3 files changed, 29 insertions(+), 7 deletions(-)
 create mode 100644 test-suite/js/src/test/require-commonjs/ExportLoopback.scala
 rename test-suite/js/src/test/{require-modules => require-esmodule}/org/scalajs/testsuite/jsinterop/ExportLoopback.scala (70%)

diff --git a/project/Build.scala b/project/Build.scala
index dd86f57340..57cb5d0b12 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -2248,7 +2248,9 @@ object Build {
         includeIf(testDir / "require-dynamic-import",
             moduleKind == ModuleKind.ESModule) ::: // this is an approximation that works for now
         includeIf(testDir / "require-esmodule",
-            moduleKind == ModuleKind.ESModule)
+            moduleKind == ModuleKind.ESModule) :::
+        includeIf(testDir / "require-commonjs",
+            moduleKind == ModuleKind.CommonJSModule)
       },
 
       unmanagedResourceDirectories in Test ++= {
diff --git a/test-suite/js/src/test/require-commonjs/ExportLoopback.scala b/test-suite/js/src/test/require-commonjs/ExportLoopback.scala
new file mode 100644
index 0000000000..aeca2e8864
--- /dev/null
+++ b/test-suite/js/src/test/require-commonjs/ExportLoopback.scala
@@ -0,0 +1,25 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package org.scalajs.testsuite.jsinterop
+
+import scala.scalajs.js
+
+import scala.concurrent.Future
+
+object ExportLoopback {
+  val exportsNamespace: Future[js.Dynamic] = {
+    js.Promise.resolve[Unit](())
+      .`then`[js.Dynamic](_ => js.Dynamic.global.require("./main.js"))
+      .toFuture
+  }
+}
diff --git a/test-suite/js/src/test/require-modules/org/scalajs/testsuite/jsinterop/ExportLoopback.scala b/test-suite/js/src/test/require-esmodule/org/scalajs/testsuite/jsinterop/ExportLoopback.scala
similarity index 70%
rename from test-suite/js/src/test/require-modules/org/scalajs/testsuite/jsinterop/ExportLoopback.scala
rename to test-suite/js/src/test/require-esmodule/org/scalajs/testsuite/jsinterop/ExportLoopback.scala
index 6e8decdc25..b91a1bdbf8 100644
--- a/test-suite/js/src/test/require-modules/org/scalajs/testsuite/jsinterop/ExportLoopback.scala
+++ b/test-suite/js/src/test/require-esmodule/org/scalajs/testsuite/jsinterop/ExportLoopback.scala
@@ -13,15 +13,10 @@
 package org.scalajs.testsuite.jsinterop
 
 import scala.scalajs.js
-import scala.scalajs.js.annotation._
 
 import scala.concurrent.Future
 
 object ExportLoopback {
   val exportsNamespace: Future[js.Dynamic] =
-    js.dynamicImport(mainModule).toFuture
-
-  @js.native
-  @JSImport("./main.js", JSImport.Namespace)
-  private val mainModule: js.Dynamic = js.native
+    js.`import`("./main.js").toFuture
 }

From e89e1e48bced9c85ded9749ce7ef3129853a567b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Thu, 23 May 2024 15:55:51 +0200
Subject: [PATCH 108/298] Initial implementation of the WebAssembly backend.

This commit contains the initial implementation of the WebAssembly
backend. This backend is still experimental, in the sense that:

* We may remove it in a future Minor version, if we decide that it
  has a better place elsewhere, and
* Newer minor versions may produce WebAssembly code that requires
  more recent WebAssembly features.

The WebAssembly backend silently ignores `@JSExport` and
`@JSExportAll` annotations. It is otherwise supposed to support
the full Scala.js language semantics.

Currently, the backend only supports some configurations of the
linker. It requires:

* No optimizer,
* Unchecked semantics for undefined behaviors,
* Strict floats, and
* ES modules.

Some of those will be relaxed in the future, definitely including
the first two.

Co-authored-by: Rikito Taniguchi <rikiriki1238@gmail.com>
---
 Jenkinsfile                                   |   38 +
 TESTING.md                                    |   19 +
 .../scala/org/scalajs/ir/UTF8String.scala     |    5 +-
 .../linker/interface/StandardConfig.scala     |   58 +-
 .../backend/LinkerBackendImplPlatform.scala   |    2 +-
 .../backend/LinkerBackendImplPlatform.scala   |    2 +-
 .../linker/backend/LinkerBackendImpl.scala    |   26 +-
 .../backend/WebAssemblyLinkerBackend.scala    |  159 +
 .../linker/backend/javascript/Printers.scala  |    6 +
 .../linker/backend/javascript/Trees.scala     |    2 +
 .../backend/wasmemitter/ClassEmitter.scala    | 1288 +++++++
 .../backend/wasmemitter/CoreWasmLib.scala     | 2214 +++++++++++
 .../backend/wasmemitter/DerivedClasses.scala  |  151 +
 .../wasmemitter/EmbeddedConstants.scala       |   68 +
 .../linker/backend/wasmemitter/Emitter.scala  |  399 ++
 .../backend/wasmemitter/FunctionEmitter.scala | 3374 +++++++++++++++++
 .../backend/wasmemitter/LoaderContent.scala   |  328 ++
 .../backend/wasmemitter/Preprocessor.scala    |  473 +++
 .../linker/backend/wasmemitter/README.md      |  790 ++++
 .../linker/backend/wasmemitter/SWasmGen.scala |  137 +
 .../backend/wasmemitter/SpecialNames.scala    |   48 +
 .../backend/wasmemitter/StringPool.scala      |  107 +
 .../backend/wasmemitter/TypeTransformer.scala |  116 +
 .../linker/backend/wasmemitter/VarGen.scala   |  446 +++
 .../backend/wasmemitter/WasmContext.scala     |  301 ++
 .../backend/webassembly/BinaryWriter.scala    |  667 ++++
 .../backend/webassembly/FunctionBuilder.scala |  445 +++
 .../backend/webassembly/Identitities.scala    |   65 +
 .../backend/webassembly/Instructions.scala    |  408 ++
 .../backend/webassembly/ModuleBuilder.scala   |   95 +
 .../linker/backend/webassembly/Modules.scala  |  137 +
 .../backend/webassembly/TextWriter.scala      |  620 +++
 .../linker/backend/webassembly/Types.scala    |  187 +
 .../standard/StandardLinkerBackend.scala      |    1 +
 project/Build.scala                           |   51 +-
 .../testsuite/javalib/lang/ClassTestEx.scala  |    7 +
 .../scalajs/testsuite/utils/Platform.scala    |    2 +
 .../resources/SourceMapTestTemplate.scala     |    1 +
 .../compiler/RuntimeTypeTestsJSTest.scala     |   20 +-
 .../javalib/lang/ThrowableJSTest.scala        |    3 +
 .../testsuite/jsinterop/ExportsTest.scala     |   10 +-
 .../testsuite/jsinterop/MiscInteropTest.scala |    1 +
 .../testsuite/library/LinkingInfoTest.scala   |   11 +-
 .../testsuite/library/StackTraceTest.scala    |    1 +
 .../scalajs/testsuite/utils/Platform.scala    |    2 +
 45 files changed, 13263 insertions(+), 28 deletions(-)
 create mode 100644 linker/shared/src/main/scala/org/scalajs/linker/backend/WebAssemblyLinkerBackend.scala
 create mode 100644 linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/ClassEmitter.scala
 create mode 100644 linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
 create mode 100644 linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/DerivedClasses.scala
 create mode 100644 linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/EmbeddedConstants.scala
 create mode 100644 linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala
 create mode 100644 linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
 create mode 100644 linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala
 create mode 100644 linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Preprocessor.scala
 create mode 100644 linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/README.md
 create mode 100644 linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/SWasmGen.scala
 create mode 100644 linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/SpecialNames.scala
 create mode 100644 linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/StringPool.scala
 create mode 100644 linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/TypeTransformer.scala
 create mode 100644 linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
 create mode 100644 linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/WasmContext.scala
 create mode 100644 linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/BinaryWriter.scala
 create mode 100644 linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/FunctionBuilder.scala
 create mode 100644 linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/Identitities.scala
 create mode 100644 linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/Instructions.scala
 create mode 100644 linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/ModuleBuilder.scala
 create mode 100644 linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/Modules.scala
 create mode 100644 linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/TextWriter.scala
 create mode 100644 linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/Types.scala

diff --git a/Jenkinsfile b/Jenkinsfile
index 487f96ba53..70d90e83fe 100644
--- a/Jenkinsfile
+++ b/Jenkinsfile
@@ -396,6 +396,41 @@ def Tasks = [
         ++$scala $testSuite$v/test
   ''',
 
+  "test-suite-webassembly": '''
+    setJavaVersion $java
+    npm install &&
+    sbtretry ++$scala \
+        'set Global/enableWasmEverywhere := true' \
+        helloworld$v/run &&
+    sbtretry ++$scala \
+        'set Global/enableWasmEverywhere := true' \
+        'set scalaJSStage in Global := FullOptStage' \
+        'set scalaJSLinkerConfig in helloworld.v$v ~= (_.withPrettyPrint(true))' \
+        helloworld$v/run &&
+    sbtretry ++$scala \
+        'set Global/enableWasmEverywhere := true' \
+        reversi$v/fastLinkJS \
+        reversi$v/fullLinkJS &&
+    sbtretry ++$scala \
+        'set Global/enableWasmEverywhere := true' \
+        jUnitTestOutputsJVM$v/test jUnitTestOutputsJS$v/test testBridge$v/test \
+        'set scalaJSStage in Global := FullOptStage' jUnitTestOutputsJS$v/test testBridge$v/test &&
+    sbtretry ++$scala \
+        'set Global/enableWasmEverywhere := true' \
+        $testSuite$v/test &&
+    sbtretry ++$scala \
+        'set Global/enableWasmEverywhere := true' \
+        'set scalaJSStage in Global := FullOptStage' \
+        $testSuite$v/test &&
+    sbtretry ++$scala \
+        'set Global/enableWasmEverywhere := true' \
+        testingExample$v/testHtml &&
+    sbtretry ++$scala \
+        'set Global/enableWasmEverywhere := true' \
+        'set scalaJSStage in Global := FullOptStage' \
+        testingExample$v/testHtml
+  ''',
+
   /* For the bootstrap tests to be able to call
    * `testSuite/test:fastOptJS`, `scalaJSStage in testSuite` must be
    * `FastOptStage`, even when `scalaJSStage in Global` is `FullOptStage`.
@@ -539,8 +574,11 @@ mainScalaVersions.each { scalaVersion ->
   quickMatrix.add([task: "test-suite-default-esversion", scala: scalaVersion, java: mainJavaVersion, testMinify: "false", testSuite: "testSuite"])
   quickMatrix.add([task: "test-suite-default-esversion", scala: scalaVersion, java: mainJavaVersion, testMinify: "true", testSuite: "testSuite"])
   quickMatrix.add([task: "test-suite-custom-esversion", scala: scalaVersion, java: mainJavaVersion, esVersion: "ES5_1", testSuite: "testSuite"])
+  quickMatrix.add([task: "test-suite-webassembly", scala: scalaVersion, java: mainJavaVersion, testMinify: "false", testSuite: "testSuite"])
+  quickMatrix.add([task: "test-suite-webassembly", scala: scalaVersion, java: mainJavaVersion, testMinify: "false", testSuite: "testSuiteEx"])
   quickMatrix.add([task: "test-suite-default-esversion", scala: scalaVersion, java: mainJavaVersion, testMinify: "false", testSuite: "scalaTestSuite"])
   quickMatrix.add([task: "test-suite-custom-esversion", scala: scalaVersion, java: mainJavaVersion, esVersion: "ES5_1", testSuite: "scalaTestSuite"])
+  quickMatrix.add([task: "test-suite-webassembly", scala: scalaVersion, java: mainJavaVersion, testMinify: "false", testSuite: "scalaTestSuite"])
   quickMatrix.add([task: "bootstrap", scala: scalaVersion, java: mainJavaVersion])
   quickMatrix.add([task: "partest-fastopt", scala: scalaVersion, java: mainJavaVersion])
 }
diff --git a/TESTING.md b/TESTING.md
index d88cbda79c..d26fafe4c3 100644
--- a/TESTING.md
+++ b/TESTING.md
@@ -25,6 +25,25 @@ $ python3 -m http.server
 // Open http://localhost:8000/test-suite/js/.2.12/target/scala-2.12/scalajs-test-suite-fastopt-test-html/index.html
 ```
 
+## HTML-Test Runner with WebAssembly
+
+WebAssembly requires modules, so this is manual as well.
+
+This test currently requires Chrome (or another V8-based browser) with `--wasm-experimental-exnref` enabled.
+That option can be configured as "Experimental WebAssembly" at [chrome://flags/#enable-experimental-webassembly-features](chrome://flags/#enable-experimental-webassembly-features).
+
+```
+$ sbt
+> set Global/enableWasmEverywhere := true
+> testingExample2_12/testHtml
+> testSuite2_12/testHtml
+> exit
+$ python3 -m http.server
+
+// Open http://localhost:8000/examples/testing/.2.12/target/scala-2.12/testing-fastopt-test-html/index.html
+// Open http://localhost:8000/test-suite/js/.2.12/target/scala-2.12/scalajs-test-suite-fastopt-test-html/index.html
+```
+
 ## Sourcemaps
 
 To test source maps, do the following on:
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/UTF8String.scala b/ir/shared/src/main/scala/org/scalajs/ir/UTF8String.scala
index 00eb0c2f11..8e4fd87a8f 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/UTF8String.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/UTF8String.scala
@@ -12,7 +12,7 @@
 
 package org.scalajs.ir
 
-import java.nio.CharBuffer
+import java.nio.{ByteBuffer, CharBuffer}
 import java.nio.charset.CharacterCodingException
 import java.nio.charset.CodingErrorAction
 import java.nio.charset.StandardCharsets.UTF_8
@@ -48,6 +48,9 @@ final class UTF8String private (private[ir] val bytes: Array[Byte])
     System.arraycopy(that.bytes, 0, result, thisLen, thatLen)
     new UTF8String(result)
   }
+
+  def writeTo(buffer: ByteBuffer): Unit =
+    buffer.put(bytes)
 }
 
 object UTF8String {
diff --git a/linker-interface/shared/src/main/scala/org/scalajs/linker/interface/StandardConfig.scala b/linker-interface/shared/src/main/scala/org/scalajs/linker/interface/StandardConfig.scala
index 40644b5b9f..14ac9e6a1c 100644
--- a/linker-interface/shared/src/main/scala/org/scalajs/linker/interface/StandardConfig.scala
+++ b/linker-interface/shared/src/main/scala/org/scalajs/linker/interface/StandardConfig.scala
@@ -63,7 +63,13 @@ final class StandardConfig private (
      *  On the JavaScript platform, this does not have any effect.
      */
     val closureCompilerIfAvailable: Boolean,
-    /** Pretty-print the output. */
+    /** Pretty-print the output, for debugging purposes.
+     *
+     *  For the WebAssembly backend, this results in an additional `.wat` file
+     *  next to each produced `.wasm` file with the WebAssembly text format
+     *  representation of the latter. This file is never subsequently used,
+     *  but may be inspected for debugging pruposes.
+     */
     val prettyPrint: Boolean,
     /** Whether the linker should run in batch mode.
      *
@@ -78,7 +84,9 @@ final class StandardConfig private (
      */
     val batchMode: Boolean,
     /** The maximum number of (file) writes executed concurrently. */
-    val maxConcurrentWrites: Int
+    val maxConcurrentWrites: Int,
+    /** If true, use the experimental WebAssembly backend. */
+    val experimentalUseWebAssembly: Boolean
 ) {
   private def this() = {
     this(
@@ -97,7 +105,8 @@ final class StandardConfig private (
         closureCompilerIfAvailable = false,
         prettyPrint = false,
         batchMode = false,
-        maxConcurrentWrites = 50
+        maxConcurrentWrites = 50,
+        experimentalUseWebAssembly = false
     )
   }
 
@@ -177,6 +186,40 @@ final class StandardConfig private (
   def withMaxConcurrentWrites(maxConcurrentWrites: Int): StandardConfig =
     copy(maxConcurrentWrites = maxConcurrentWrites)
 
+  /** Specifies whether to use the experimental WebAssembly backend.
+   *
+   *  When using this setting, the following settings must also be set:
+   *
+   *  - `withSemantics(sems)` such that the behaviors of `sems` are all set to
+   *    `CheckedBehavior.Unchecked`
+   *  - `withModuleKind(ModuleKind.ESModule)`
+   *  - `withOptimizer(false)`
+   *  - `withStrictFloats(true)` (this is the default)
+   *
+   *  These restrictions will be lifted in the future, except for the
+   *  `ModuleKind`.
+   *
+   *  If any of these restrictions are not met, linking will eventually throw
+   *  an `IllegalArgumentException`.
+   *
+   *  @note
+   *    Currently, the WebAssembly backend silently ignores `@JSExport` and
+   *    `@JSExportAll` annotations. This behavior may change in the future,
+   *    either by making them warnings or errors, or by adding support for them.
+   *    All other language features are supported.
+   *
+   *  @note
+   *    This setting is experimental. It may be removed in an upcoming *minor*
+   *    version of Scala.js. Future minor versions may also produce code that
+   *    requires more recent versions of JS engines supporting newer WebAssembly
+   *    standards.
+   *
+   *  @throws java.lang.UnsupportedOperationException
+   *    In the future, if the feature gets removed.
+   */
+  def withExperimentalUseWebAssembly(experimentalUseWebAssembly: Boolean): StandardConfig =
+    copy(experimentalUseWebAssembly = experimentalUseWebAssembly)
+
   override def toString(): String = {
     s"""StandardConfig(
        |  semantics                  = $semantics,
@@ -195,6 +238,7 @@ final class StandardConfig private (
        |  prettyPrint                = $prettyPrint,
        |  batchMode                  = $batchMode,
        |  maxConcurrentWrites        = $maxConcurrentWrites,
+       |  experimentalUseWebAssembly = $experimentalUseWebAssembly,
        |)""".stripMargin
   }
 
@@ -214,7 +258,8 @@ final class StandardConfig private (
       closureCompilerIfAvailable: Boolean = closureCompilerIfAvailable,
       prettyPrint: Boolean = prettyPrint,
       batchMode: Boolean = batchMode,
-      maxConcurrentWrites: Int = maxConcurrentWrites
+      maxConcurrentWrites: Int = maxConcurrentWrites,
+      experimentalUseWebAssembly: Boolean = experimentalUseWebAssembly
   ): StandardConfig = {
     new StandardConfig(
         semantics,
@@ -232,7 +277,8 @@ final class StandardConfig private (
         closureCompilerIfAvailable,
         prettyPrint,
         batchMode,
-        maxConcurrentWrites
+        maxConcurrentWrites,
+        experimentalUseWebAssembly
     )
   }
 }
@@ -263,6 +309,7 @@ object StandardConfig {
         .addField("prettyPrint", config.prettyPrint)
         .addField("batchMode", config.batchMode)
         .addField("maxConcurrentWrites", config.maxConcurrentWrites)
+        .addField("experimentalUseWebAssembly", config.experimentalUseWebAssembly)
         .build()
     }
   }
@@ -290,6 +337,7 @@ object StandardConfig {
    *  - `prettyPrint`: `false`
    *  - `batchMode`: `false`
    *  - `maxConcurrentWrites`: `50`
+   *  - `experimentalUseWebAssembly`: `false`
    */
   def apply(): StandardConfig = new StandardConfig()
 
diff --git a/linker/js/src/main/scala/org/scalajs/linker/backend/LinkerBackendImplPlatform.scala b/linker/js/src/main/scala/org/scalajs/linker/backend/LinkerBackendImplPlatform.scala
index 13c3c37784..9db2923d6a 100644
--- a/linker/js/src/main/scala/org/scalajs/linker/backend/LinkerBackendImplPlatform.scala
+++ b/linker/js/src/main/scala/org/scalajs/linker/backend/LinkerBackendImplPlatform.scala
@@ -15,6 +15,6 @@ package org.scalajs.linker.backend
 private[backend] object LinkerBackendImplPlatform {
   import LinkerBackendImpl.Config
 
-  def createLinkerBackend(config: Config): LinkerBackendImpl =
+  def createJSLinkerBackend(config: Config): LinkerBackendImpl =
     new BasicLinkerBackend(config)
 }
diff --git a/linker/jvm/src/main/scala/org/scalajs/linker/backend/LinkerBackendImplPlatform.scala b/linker/jvm/src/main/scala/org/scalajs/linker/backend/LinkerBackendImplPlatform.scala
index 5abeea8403..894028d5ff 100644
--- a/linker/jvm/src/main/scala/org/scalajs/linker/backend/LinkerBackendImplPlatform.scala
+++ b/linker/jvm/src/main/scala/org/scalajs/linker/backend/LinkerBackendImplPlatform.scala
@@ -17,7 +17,7 @@ import org.scalajs.linker.backend.closure.ClosureLinkerBackend
 private[backend] object LinkerBackendImplPlatform {
   import LinkerBackendImpl.Config
 
-  def createLinkerBackend(config: Config): LinkerBackendImpl = {
+  def createJSLinkerBackend(config: Config): LinkerBackendImpl = {
     if (config.closureCompiler)
       new ClosureLinkerBackend(config)
     else
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/LinkerBackendImpl.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/LinkerBackendImpl.scala
index 0fc8f5169b..29ded7b1cf 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/LinkerBackendImpl.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/LinkerBackendImpl.scala
@@ -38,8 +38,12 @@ abstract class LinkerBackendImpl(
 }
 
 object LinkerBackendImpl {
-  def apply(config: Config): LinkerBackendImpl =
-    LinkerBackendImplPlatform.createLinkerBackend(config)
+  def apply(config: Config): LinkerBackendImpl = {
+    if (config.experimentalUseWebAssembly)
+      new WebAssemblyLinkerBackend(config)
+    else
+      LinkerBackendImplPlatform.createJSLinkerBackend(config)
+  }
 
   /** Configurations relevant to the backend */
   final class Config private (
@@ -62,7 +66,9 @@ object LinkerBackendImpl {
       /** Pretty-print the output. */
       val prettyPrint: Boolean,
       /** The maximum number of (file) writes executed concurrently. */
-      val maxConcurrentWrites: Int
+      val maxConcurrentWrites: Int,
+      /** If true, use the experimental WebAssembly backend. */
+      val experimentalUseWebAssembly: Boolean
   ) {
     private def this() = {
       this(
@@ -74,7 +80,9 @@ object LinkerBackendImpl {
           minify = false,
           closureCompilerIfAvailable = false,
           prettyPrint = false,
-          maxConcurrentWrites = 50)
+          maxConcurrentWrites = 50,
+          experimentalUseWebAssembly = false
+      )
     }
 
     def withCommonConfig(commonConfig: CommonPhaseConfig): Config =
@@ -106,6 +114,9 @@ object LinkerBackendImpl {
     def withMaxConcurrentWrites(maxConcurrentWrites: Int): Config =
       copy(maxConcurrentWrites = maxConcurrentWrites)
 
+    def withExperimentalUseWebAssembly(experimentalUseWebAssembly: Boolean): Config =
+      copy(experimentalUseWebAssembly = experimentalUseWebAssembly)
+
     private def copy(
         commonConfig: CommonPhaseConfig = commonConfig,
         jsHeader: String = jsHeader,
@@ -115,7 +126,9 @@ object LinkerBackendImpl {
         minify: Boolean = minify,
         closureCompilerIfAvailable: Boolean = closureCompilerIfAvailable,
         prettyPrint: Boolean = prettyPrint,
-        maxConcurrentWrites: Int = maxConcurrentWrites): Config = {
+        maxConcurrentWrites: Int = maxConcurrentWrites,
+        experimentalUseWebAssembly: Boolean = experimentalUseWebAssembly
+    ): Config = {
       new Config(
         commonConfig,
         jsHeader,
@@ -125,7 +138,8 @@ object LinkerBackendImpl {
         minify,
         closureCompilerIfAvailable,
         prettyPrint,
-        maxConcurrentWrites
+        maxConcurrentWrites,
+        experimentalUseWebAssembly
       )
     }
   }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/WebAssemblyLinkerBackend.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/WebAssemblyLinkerBackend.scala
new file mode 100644
index 0000000000..ef7be8c498
--- /dev/null
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/WebAssemblyLinkerBackend.scala
@@ -0,0 +1,159 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package org.scalajs.linker.backend
+
+import scala.concurrent.{ExecutionContext, Future}
+
+import java.nio.ByteBuffer
+import java.nio.charset.StandardCharsets
+
+import org.scalajs.logging.Logger
+
+import org.scalajs.linker._
+import org.scalajs.linker.interface._
+import org.scalajs.linker.interface.unstable._
+import org.scalajs.linker.standard._
+
+import org.scalajs.linker.backend.javascript.{ByteArrayWriter, SourceMapWriter}
+import org.scalajs.linker.backend.webassembly._
+
+import org.scalajs.linker.backend.wasmemitter.Emitter
+
+final class WebAssemblyLinkerBackend(config: LinkerBackendImpl.Config)
+    extends LinkerBackendImpl(config) {
+
+  require(
+    coreSpec.moduleKind == ModuleKind.ESModule,
+    s"The WebAssembly backend only supports ES modules; was ${coreSpec.moduleKind}."
+  )
+  require(
+    coreSpec.semantics.asInstanceOfs == CheckedBehavior.Unchecked &&
+    coreSpec.semantics.arrayIndexOutOfBounds == CheckedBehavior.Unchecked &&
+    coreSpec.semantics.arrayStores == CheckedBehavior.Unchecked &&
+    coreSpec.semantics.negativeArraySizes == CheckedBehavior.Unchecked &&
+    coreSpec.semantics.nullPointers == CheckedBehavior.Unchecked &&
+    coreSpec.semantics.stringIndexOutOfBounds == CheckedBehavior.Unchecked &&
+    coreSpec.semantics.moduleInit == CheckedBehavior.Unchecked,
+    "The WebAssembly backend currently only supports CheckedBehavior.Unchecked semantics; " +
+    s"was ${coreSpec.semantics}."
+  )
+  require(
+    coreSpec.semantics.strictFloats,
+    "The WebAssembly backend only supports strict float semantics."
+  )
+
+  val loaderJSFileName = OutputPatternsImpl.jsFile(config.outputPatterns, "__loader")
+
+  private val fragmentIndex = new SourceMapWriter.Index
+
+  private val emitter: Emitter = {
+    val loaderModuleName = OutputPatternsImpl.moduleName(config.outputPatterns, "__loader")
+    new Emitter(Emitter.Config(coreSpec, loaderModuleName))
+  }
+
+  val symbolRequirements: SymbolRequirement = emitter.symbolRequirements
+
+  override def injectedIRFiles: Seq[IRFile] = emitter.injectedIRFiles
+
+  def emit(moduleSet: ModuleSet, output: OutputDirectory, logger: Logger)(
+      implicit ec: ExecutionContext): Future[Report] = {
+    val onlyModule = moduleSet.modules match {
+      case onlyModule :: Nil =>
+        onlyModule
+      case modules =>
+        throw new UnsupportedOperationException(
+            "The WebAssembly backend does not support multiple modules. Found: " +
+            modules.map(_.id.id).mkString(", "))
+    }
+    val moduleID = onlyModule.id.id
+
+    val emitterResult = emitter.emit(onlyModule, logger)
+    val wasmModule = emitterResult.wasmModule
+
+    val outputImpl = OutputDirectoryImpl.fromOutputDirectory(output)
+
+    val watFileName = s"$moduleID.wat"
+    val wasmFileName = s"$moduleID.wasm"
+    val sourceMapFileName = s"$wasmFileName.map"
+    val jsFileName = OutputPatternsImpl.jsFile(config.outputPatterns, moduleID)
+
+    val filesToProduce0 = Set(
+      wasmFileName,
+      loaderJSFileName,
+      jsFileName
+    )
+    val filesToProduce1 =
+      if (config.sourceMap) filesToProduce0 + sourceMapFileName
+      else filesToProduce0
+    val filesToProduce =
+      if (config.prettyPrint) filesToProduce1 + watFileName
+      else filesToProduce1
+
+    def maybeWriteWatFile(): Future[Unit] = {
+      if (config.prettyPrint) {
+        val textOutput = TextWriter.write(wasmModule)
+        val textOutputBytes = textOutput.getBytes(StandardCharsets.UTF_8)
+        outputImpl.writeFull(watFileName, ByteBuffer.wrap(textOutputBytes))
+      } else {
+        Future.unit
+      }
+    }
+
+    def writeWasmFile(): Future[Unit] = {
+      val emitDebugInfo = !config.minify
+
+      if (config.sourceMap) {
+        val sourceMapWriter = new ByteArrayWriter
+
+        val wasmFileURI = s"./$wasmFileName"
+        val sourceMapURI = s"./$sourceMapFileName"
+
+        val smWriter = new SourceMapWriter(sourceMapWriter, wasmFileURI,
+            config.relativizeSourceMapBase, fragmentIndex)
+        val binaryOutput = BinaryWriter.writeWithSourceMap(
+            wasmModule, emitDebugInfo, smWriter, sourceMapURI)
+        smWriter.complete()
+
+        outputImpl.writeFull(wasmFileName, binaryOutput).flatMap { _ =>
+          outputImpl.writeFull(sourceMapFileName, sourceMapWriter.toByteBuffer())
+        }
+      } else {
+        val binaryOutput = BinaryWriter.write(wasmModule, emitDebugInfo)
+        outputImpl.writeFull(wasmFileName, binaryOutput)
+      }
+    }
+
+    def writeLoaderFile(): Future[Unit] =
+      outputImpl.writeFull(loaderJSFileName, ByteBuffer.wrap(emitterResult.loaderContent))
+
+    def writeJSFile(): Future[Unit] =
+      outputImpl.writeFull(jsFileName, ByteBuffer.wrap(emitterResult.jsFileContent))
+
+    for {
+      existingFiles <- outputImpl.listFiles()
+      _ <- Future.sequence(existingFiles.filterNot(filesToProduce).map(outputImpl.delete(_)))
+      _ <- maybeWriteWatFile()
+      _ <- writeWasmFile()
+      _ <- writeLoaderFile()
+      _ <- writeJSFile()
+    } yield {
+      val reportModule = new ReportImpl.ModuleImpl(
+        moduleID,
+        jsFileName,
+        None,
+        coreSpec.moduleKind
+      )
+      new ReportImpl(List(reportModule))
+    }
+  }
+}
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Printers.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Printers.scala
index 33ec9cc020..aa8045f892 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Printers.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Printers.scala
@@ -435,6 +435,12 @@ object Printers {
           print(')')
           printSeparatorIfStat()
 
+        case Await(expr) =>
+          print("(await ")
+          print(expr)
+          print(')')
+          printSeparatorIfStat()
+
         case IncDec(prefix, inc, arg) =>
           val op = if (inc) "++" else "--"
           print('(')
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Trees.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Trees.scala
index 0c0b820e82..00405e253e 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Trees.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Trees.scala
@@ -328,6 +328,8 @@ object Trees {
     type Code = ir.Trees.JSUnaryOp.Code
   }
 
+  sealed case class Await(expr: Tree)(implicit val pos: Position) extends Tree
+
   /** `++x`, `x++`, `--x` or `x--`. */
   sealed case class IncDec(prefix: Boolean, inc: Boolean, arg: Tree)(
       implicit val pos: Position)
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/ClassEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/ClassEmitter.scala
new file mode 100644
index 0000000000..7b6026c346
--- /dev/null
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/ClassEmitter.scala
@@ -0,0 +1,1288 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package org.scalajs.linker.backend.wasmemitter
+
+import scala.collection.mutable
+
+import org.scalajs.ir.{ClassKind, OriginalName, Position, UTF8String}
+import org.scalajs.ir.Names._
+import org.scalajs.ir.OriginalName.NoOriginalName
+import org.scalajs.ir.Trees._
+import org.scalajs.ir.Types._
+
+import org.scalajs.linker.interface.unstable.RuntimeClassNameMapperImpl
+import org.scalajs.linker.standard.{CoreSpec, LinkedClass, LinkedTopLevelExport}
+
+import org.scalajs.linker.backend.webassembly.FunctionBuilder
+import org.scalajs.linker.backend.webassembly.{Instructions => wa}
+import org.scalajs.linker.backend.webassembly.{Modules => wamod}
+import org.scalajs.linker.backend.webassembly.{Identitities => wanme}
+import org.scalajs.linker.backend.webassembly.{Types => watpe}
+
+import EmbeddedConstants._
+import SWasmGen._
+import VarGen._
+import TypeTransformer._
+import WasmContext._
+
+class ClassEmitter(coreSpec: CoreSpec) {
+  import ClassEmitter._
+
+  def genClassDef(clazz: LinkedClass)(implicit ctx: WasmContext): Unit = {
+    val classInfo = ctx.getClassInfo(clazz.className)
+
+    if (classInfo.hasRuntimeTypeInfo && !(clazz.kind.isClass && clazz.hasDirectInstances)) {
+      // Gen typeData -- for concrete Scala classes, we do it as part of the vtable generation instead
+      val typeDataFieldValues = genTypeDataFieldValues(clazz, Nil)
+      genTypeDataGlobal(clazz.className, genTypeID.typeData, typeDataFieldValues, Nil)
+    }
+
+    // Declare static fields
+    for {
+      field @ FieldDef(flags, name, _, ftpe) <- clazz.fields
+      if flags.namespace.isStatic
+    } {
+      val origName = makeDebugName(ns.StaticField, name.name)
+      val global = wamod.Global(
+        genGlobalID.forStaticField(name.name),
+        origName,
+        isMutable = true,
+        transformType(ftpe),
+        wa.Expr(List(genZeroOf(ftpe)))
+      )
+      ctx.addGlobal(global)
+    }
+
+    // Generate method implementations
+    for (method <- clazz.methods) {
+      if (method.body.isDefined)
+        genMethod(clazz, method)
+    }
+
+    clazz.kind match {
+      case ClassKind.Class | ClassKind.ModuleClass =>
+        genScalaClass(clazz)
+      case ClassKind.Interface =>
+        genInterface(clazz)
+      case ClassKind.JSClass | ClassKind.JSModuleClass =>
+        genJSClass(clazz)
+      case ClassKind.HijackedClass | ClassKind.AbstractJSType | ClassKind.NativeJSClass |
+          ClassKind.NativeJSModuleClass =>
+        () // nothing to do
+    }
+  }
+
+  /** Generates code for a top-level export.
+   *
+   *  It is tempting to use Wasm `export`s for top-level exports. However, that
+   *  does not work in several situations:
+   *
+   *  - for values, an `export`ed `global` is visible in JS as an instance of
+   *    `WebAssembly.Global`, of which we need to extract the `.value` field anyway
+   *  - this in turn causes issues for mutable static fields, since we need to
+   *    republish changes
+   *  - we cannot distinguish mutable static fields from immutable ones, so we
+   *    have to use the same strategy for both
+   *  - exported top-level `def`s must be seen by JS as `function` functions,
+   *    but `export`ed `func`s are JS arrow functions
+   *
+   *  Overall, the only things for which `export`s would work are for exported
+   *  JS classes and objects.
+   *
+   *  Instead, we uniformly use the following strategy for all top-level exports:
+   *
+   *  - the JS code declares a non-initialized `let` for every top-level export, and exports it
+   *    from the module with an ECMAScript `export`
+   *  - the JS code provides a setter function that we import into a Wasm, which allows to set the
+   *    value of that `let`
+   *  - the Wasm code "publishes" every update to top-level exports to the JS code via this
+   *    setter; this happens once in the `start` function for every kind of top-level export (see
+   *    `Emitter.genStartFunction`), and in addition upon each reassignment of a top-level
+   *    exported field (see `FunctionEmitter.genAssign`).
+   *
+   *  This method declares the import of the setter on the Wasm side, for all kinds of top-level
+   *  exports. In addition, for exported *methods*, it generates the implementation of the method as
+   *  a Wasm function.
+   *
+   *  The JS code is generated by `Emitter.buildJSFileContent`. Note that for fields, the JS `let`s
+   *  are only "mirrors" of the state. The source of truth for the state remains in the Wasm Global
+   *  for the static field. This is fine because, by spec of ECMAScript modules, JavaScript code
+   *  that *uses* the export cannot mutate it; it can only read it.
+   *
+   *  The calls to the setters, which actually initialize all the exported `let`s, are performed:
+   *
+   *  - in the `start` function for all kinds of exports, and
+   *  - in addition on every assignment to an exported mutable static field.
+   */
+  def genTopLevelExport(topLevelExport: LinkedTopLevelExport)(
+      implicit ctx: WasmContext): Unit = {
+    genTopLevelExportSetter(topLevelExport.exportName)
+    topLevelExport.tree match {
+      case d: TopLevelMethodExportDef => genTopLevelMethodExportDef(d)
+      case _                          => ()
+    }
+  }
+
+  private def genIsJSClassInstanceFunction(clazz: LinkedClass)(
+      implicit ctx: WasmContext): Option[wanme.FunctionID] = {
+    implicit val noPos: Position = Position.NoPosition
+
+    val hasIsJSClassInstance = clazz.kind match {
+      case ClassKind.NativeJSClass => clazz.jsNativeLoadSpec.isDefined
+      case ClassKind.JSClass       => clazz.jsClassCaptures.isEmpty
+      case _                       => false
+    }
+
+    if (hasIsJSClassInstance) {
+      val className = clazz.className
+
+      val fb = new FunctionBuilder(
+        ctx.moduleBuilder,
+        genFunctionID.isJSClassInstance(className),
+        makeDebugName(ns.IsInstance, className),
+        noPos
+      )
+      val xParam = fb.addParam("x", watpe.RefType.anyref)
+      fb.setResultType(watpe.Int32)
+      fb.setFunctionType(genTypeID.isJSClassInstanceFuncType)
+
+      if (clazz.kind == ClassKind.JSClass && !clazz.hasInstances) {
+        /* We need to constant-fold the instance test, to avoid trying to
+         * call $loadJSClass.className, since it will not exist at all.
+         */
+        fb += wa.I32Const(0) // false
+      } else {
+        fb += wa.LocalGet(xParam)
+        genLoadJSConstructor(fb, className)
+        fb += wa.Call(genFunctionID.jsBinaryOps(JSBinaryOp.instanceof))
+        fb += wa.Call(genFunctionID.unbox(BooleanRef))
+      }
+
+      val func = fb.buildAndAddToModule()
+      Some(func.id)
+    } else {
+      None
+    }
+  }
+
+  private def genTypeDataFieldValues(clazz: LinkedClass,
+      reflectiveProxies: List[ConcreteMethodInfo])(
+      implicit ctx: WasmContext): List[wa.Instr] = {
+    val className = clazz.className
+    val classInfo = ctx.getClassInfo(className)
+
+    val nameStr = RuntimeClassNameMapperImpl.map(
+      coreSpec.semantics.runtimeClassNameMapper,
+      className.nameString
+    )
+    val nameDataValue: List[wa.Instr] =
+      ctx.stringPool.getConstantStringDataInstr(nameStr)
+
+    val kind = className match {
+      case ObjectClass         => KindObject
+      case BoxedUnitClass      => KindBoxedUnit
+      case BoxedBooleanClass   => KindBoxedBoolean
+      case BoxedCharacterClass => KindBoxedCharacter
+      case BoxedByteClass      => KindBoxedByte
+      case BoxedShortClass     => KindBoxedShort
+      case BoxedIntegerClass   => KindBoxedInteger
+      case BoxedLongClass      => KindBoxedLong
+      case BoxedFloatClass     => KindBoxedFloat
+      case BoxedDoubleClass    => KindBoxedDouble
+      case BoxedStringClass    => KindBoxedString
+
+      case _ =>
+        import ClassKind._
+
+        clazz.kind match {
+          case Class | ModuleClass | HijackedClass =>
+            KindClass
+          case Interface =>
+            KindInterface
+          case JSClass | JSModuleClass | AbstractJSType | NativeJSClass | NativeJSModuleClass =>
+            KindJSType
+        }
+    }
+
+    val strictAncestorsTypeData: List[wa.Instr] = {
+      val ancestors = clazz.ancestors
+
+      // By spec, the first element of `ancestors` is always the class itself
+      assert(
+        ancestors.headOption.contains(className),
+        s"The ancestors of ${className.nameString} do not start with itself: $ancestors"
+      )
+      val strictAncestors = ancestors.tail
+
+      val elems = for {
+        ancestor <- strictAncestors
+        if ctx.getClassInfo(ancestor).hasRuntimeTypeInfo
+      } yield {
+        wa.GlobalGet(genGlobalID.forVTable(ancestor))
+      }
+      elems :+ wa.ArrayNewFixed(genTypeID.typeDataArray, elems.size)
+    }
+
+    val cloneFunction = {
+      // If the class is concrete and implements the `java.lang.Cloneable`,
+      // `genCloneFunction` should've generated the clone function
+      if (!classInfo.isAbstract && clazz.ancestors.contains(CloneableClass))
+        wa.RefFunc(genFunctionID.clone(className))
+      else
+        wa.RefNull(watpe.HeapType.NoFunc)
+    }
+
+    val isJSClassInstance = genIsJSClassInstanceFunction(clazz) match {
+      case None         => wa.RefNull(watpe.HeapType.NoFunc)
+      case Some(funcID) => wa.RefFunc(funcID)
+    }
+
+    val reflectiveProxiesInstrs: List[wa.Instr] = {
+      val elemsInstrs: List[wa.Instr] = reflectiveProxies
+        .map(proxyInfo => ctx.getReflectiveProxyId(proxyInfo.methodName) -> proxyInfo.tableEntryID)
+        .sortBy(_._1) // we will perform a binary search on the ID at run-time
+        .flatMap { case (proxyID, tableEntryID) =>
+          List(
+            wa.I32Const(proxyID),
+            wa.RefFunc(tableEntryID),
+            wa.StructNew(genTypeID.reflectiveProxy)
+          )
+        }
+      elemsInstrs :+ wa.ArrayNewFixed(genTypeID.reflectiveProxies, reflectiveProxies.size)
+    }
+
+    nameDataValue :::
+      List(
+        // kind
+        wa.I32Const(kind),
+        // specialInstanceTypes
+        wa.I32Const(classInfo.specialInstanceTypes)
+      ) ::: (
+        // strictAncestors
+        strictAncestorsTypeData
+      ) :::
+      List(
+        // componentType - always `null` since this method is not used for array types
+        wa.RefNull(watpe.HeapType(genTypeID.typeData)),
+        // name - initially `null`; filled in by the `typeDataName` helper
+        wa.RefNull(watpe.HeapType.Any),
+        // the classOf instance - initially `null`; filled in by the `createClassOf` helper
+        wa.RefNull(watpe.HeapType(genTypeID.ClassStruct)),
+        // arrayOf, the typeData of an array of this type - initially `null`; filled in by the `arrayTypeData` helper
+        wa.RefNull(watpe.HeapType(genTypeID.ObjectVTable)),
+        // clonefFunction - will be invoked from `clone()` method invokaion on the class
+        cloneFunction,
+        // isJSClassInstance - invoked from the `isInstance()` helper for JS types
+        isJSClassInstance
+      ) :::
+      // reflective proxies - used to reflective call on the class at runtime.
+      // Generated instructions create an array of reflective proxy structs, where each struct
+      // contains the ID of the reflective proxy and a reference to the actual method implementation.
+      reflectiveProxiesInstrs
+  }
+
+  private def genTypeDataGlobal(className: ClassName, typeDataTypeID: wanme.TypeID,
+      typeDataFieldValues: List[wa.Instr], vtableElems: List[wa.RefFunc])(
+      implicit ctx: WasmContext): Unit = {
+    val instrs: List[wa.Instr] =
+      typeDataFieldValues ::: vtableElems ::: wa.StructNew(typeDataTypeID) :: Nil
+    ctx.addGlobal(
+      wamod.Global(
+        genGlobalID.forVTable(className),
+        makeDebugName(ns.TypeData, className),
+        isMutable = false,
+        watpe.RefType(typeDataTypeID),
+        wa.Expr(instrs)
+      )
+    )
+  }
+
+  /** Generates a Scala class or module class. */
+  private def genScalaClass(clazz: LinkedClass)(implicit ctx: WasmContext): Unit = {
+    val className = clazz.name.name
+    val typeRef = ClassRef(className)
+    val classInfo = ctx.getClassInfo(className)
+
+    // generate vtable type, this should be done for both abstract and concrete classes
+    val vtableTypeID = genVTableType(clazz, classInfo)
+
+    val isAbstractClass = !clazz.hasDirectInstances
+
+    // Generate the vtable and itable for concrete classes
+    if (!isAbstractClass) {
+      // Generate an actual vtable, which we integrate into the typeData
+      val reflectiveProxies =
+        classInfo.resolvedMethodInfos.valuesIterator.filter(_.methodName.isReflectiveProxy).toList
+      val typeDataFieldValues = genTypeDataFieldValues(clazz, reflectiveProxies)
+      val vtableElems = classInfo.tableEntries.map { methodName =>
+        wa.RefFunc(classInfo.resolvedMethodInfos(methodName).tableEntryID)
+      }
+      genTypeDataGlobal(className, vtableTypeID, typeDataFieldValues, vtableElems)
+
+      // Generate the itable
+      genGlobalClassItable(clazz)
+    }
+
+    // Declare the struct type for the class
+    val vtableField = watpe.StructField(
+      genFieldID.objStruct.vtable,
+      vtableOriginalName,
+      watpe.RefType(vtableTypeID),
+      isMutable = false
+    )
+    val itablesField = watpe.StructField(
+      genFieldID.objStruct.itables,
+      itablesOriginalName,
+      watpe.RefType.nullable(genTypeID.itables),
+      isMutable = false
+    )
+    val fields = classInfo.allFieldDefs.map { field =>
+      watpe.StructField(
+        genFieldID.forClassInstanceField(field.name.name),
+        makeDebugName(ns.InstanceField, field.name.name),
+        transformType(field.ftpe),
+        isMutable = true // initialized by the constructors, so always mutable at the Wasm level
+      )
+    }
+    val structTypeID = genTypeID.forClass(className)
+    val superType = clazz.superClass.map(s => genTypeID.forClass(s.name))
+    val structType = watpe.StructType(vtableField :: itablesField :: fields)
+    val subType = watpe.SubType(
+      structTypeID,
+      makeDebugName(ns.ClassInstance, className),
+      isFinal = false,
+      superType,
+      structType
+    )
+    ctx.mainRecType.addSubType(subType)
+
+    // Define the `new` function and possibly the `clone` function, unless the class is abstract
+    if (!isAbstractClass) {
+      genNewDefaultFunc(clazz)
+      if (clazz.ancestors.contains(CloneableClass))
+        genCloneFunction(clazz)
+    }
+
+    // Generate the module accessor
+    if (clazz.kind == ClassKind.ModuleClass && clazz.hasInstances) {
+      val heapType = watpe.HeapType(genTypeID.forClass(clazz.className))
+
+      // global instance
+      val global = wamod.Global(
+        genGlobalID.forModuleInstance(className),
+        makeDebugName(ns.ModuleInstance, className),
+        isMutable = true,
+        watpe.RefType.nullable(heapType),
+        wa.Expr(List(wa.RefNull(heapType)))
+      )
+      ctx.addGlobal(global)
+
+      genModuleAccessor(clazz)
+    }
+  }
+
+  private def genVTableType(clazz: LinkedClass, classInfo: ClassInfo)(
+      implicit ctx: WasmContext): wanme.TypeID = {
+    val className = classInfo.name
+    val typeID = genTypeID.forVTable(className)
+    val vtableFields =
+      classInfo.tableEntries.map { methodName =>
+        watpe.StructField(
+          genFieldID.forMethodTableEntry(methodName),
+          makeDebugName(ns.TableEntry, className, methodName),
+          watpe.RefType(ctx.tableFunctionType(methodName)),
+          isMutable = false
+        )
+      }
+    val superType = clazz.superClass match {
+      case None    => genTypeID.typeData
+      case Some(s) => genTypeID.forVTable(s.name)
+    }
+    val structType = watpe.StructType(CoreWasmLib.typeDataStructFields ::: vtableFields)
+    val subType = watpe.SubType(
+      typeID,
+      makeDebugName(ns.VTable, className),
+      isFinal = false,
+      Some(superType),
+      structType
+    )
+    ctx.mainRecType.addSubType(subType)
+    typeID
+  }
+
+  /** Generate type inclusion test for interfaces.
+   *
+   *  The expression `isInstanceOf[<interface>]` will be compiled to a CALL to the function
+   *  generated by this method.
+   */
+  private def genInterfaceInstanceTest(clazz: LinkedClass)(
+      implicit ctx: WasmContext): Unit = {
+    assert(clazz.kind == ClassKind.Interface)
+
+    val className = clazz.className
+    val classInfo = ctx.getClassInfo(className)
+
+    val fb = new FunctionBuilder(
+      ctx.moduleBuilder,
+      genFunctionID.instanceTest(className),
+      makeDebugName(ns.IsInstance, className),
+      clazz.pos
+    )
+    val exprParam = fb.addParam("expr", watpe.RefType.anyref)
+    fb.setResultType(watpe.Int32)
+
+    if (!clazz.hasInstances) {
+      /* Interfaces that do not have instances do not receive an itable index,
+       * so the codegen below would not work. Return a constant false instead.
+       */
+      fb += wa.I32Const(0) // false
+    } else {
+      val itables = fb.addLocal("itables", watpe.RefType.nullable(genTypeID.itables))
+
+      fb.block(watpe.RefType.anyref) { testFail =>
+        // if expr is not an instance of Object, return false
+        fb += wa.LocalGet(exprParam)
+        fb += wa.BrOnCastFail(
+          testFail,
+          watpe.RefType.anyref,
+          watpe.RefType(genTypeID.ObjectStruct)
+        )
+
+        // get itables and store
+        fb += wa.StructGet(genTypeID.ObjectStruct, genFieldID.objStruct.itables)
+        fb += wa.LocalSet(itables)
+
+        // Dummy return value from the block
+        fb += wa.RefNull(watpe.HeapType.Any)
+
+        // if the itables is null (no interfaces are implemented)
+        fb += wa.LocalGet(itables)
+        fb += wa.BrOnNull(testFail)
+
+        fb += wa.LocalGet(itables)
+        fb += wa.I32Const(classInfo.itableIdx)
+        fb += wa.ArrayGet(genTypeID.itables)
+        fb += wa.RefTest(watpe.RefType(genTypeID.forITable(className)))
+        fb += wa.Return
+      } // test fail
+
+      if (classInfo.isAncestorOfHijackedClass) {
+        /* It could be a hijacked class instance that implements this interface.
+         * Test whether `jsValueType(expr)` is in the `specialInstanceTypes` bitset.
+         * In other words, return `((1 << jsValueType(expr)) & specialInstanceTypes) != 0`.
+         *
+         * For example, if this class is `Comparable`,
+         * `specialInstanceTypes == 0b00001111`, since `jl.Boolean`, `jl.String`
+         * and `jl.Double` implement `Comparable`, but `jl.Void` does not.
+         * If `expr` is a `number`, `jsValueType(expr) == 3`. We then test whether
+         * `(1 << 3) & 0b00001111 != 0`, which is true because `(1 << 3) == 0b00001000`.
+         * If `expr` is `undefined`, it would be `(1 << 4) == 0b00010000`, which
+         * would give `false`.
+         */
+        val anyRefToVoidSig = watpe.FunctionType(List(watpe.RefType.anyref), Nil)
+
+        val exprNonNullLocal = fb.addLocal("exprNonNull", watpe.RefType.any)
+
+        fb.block(anyRefToVoidSig) { isNullLabel =>
+          // exprNonNull := expr; branch to isNullLabel if it is null
+          fb += wa.BrOnNull(isNullLabel)
+          fb += wa.LocalSet(exprNonNullLocal)
+
+          // Load 1 << jsValueType(expr)
+          fb += wa.I32Const(1)
+          fb += wa.LocalGet(exprNonNullLocal)
+          fb += wa.Call(genFunctionID.jsValueType)
+          fb += wa.I32Shl
+
+          // return (... & specialInstanceTypes) != 0
+          fb += wa.I32Const(classInfo.specialInstanceTypes)
+          fb += wa.I32And
+          fb += wa.I32Const(0)
+          fb += wa.I32Ne
+          fb += wa.Return
+        }
+
+        fb += wa.I32Const(0) // false
+      } else {
+        fb += wa.Drop
+        fb += wa.I32Const(0) // false
+      }
+    }
+
+    fb.buildAndAddToModule()
+  }
+
+  private def genNewDefaultFunc(clazz: LinkedClass)(implicit ctx: WasmContext): Unit = {
+    val className = clazz.name.name
+    val classInfo = ctx.getClassInfo(className)
+    assert(clazz.hasDirectInstances)
+
+    val structTypeID = genTypeID.forClass(className)
+    val fb = new FunctionBuilder(
+      ctx.moduleBuilder,
+      genFunctionID.newDefault(className),
+      makeDebugName(ns.NewDefault, className),
+      clazz.pos
+    )
+    fb.setResultType(watpe.RefType(structTypeID))
+
+    fb += wa.GlobalGet(genGlobalID.forVTable(className))
+
+    if (classInfo.classImplementsAnyInterface)
+      fb += wa.GlobalGet(genGlobalID.forITable(className))
+    else
+      fb += wa.RefNull(watpe.HeapType(genTypeID.itables))
+
+    classInfo.allFieldDefs.foreach { f =>
+      fb += genZeroOf(f.ftpe)
+    }
+    fb += wa.StructNew(structTypeID)
+
+    fb.buildAndAddToModule()
+  }
+
+  /** Generates the clone function for the given class, if it is concrete and
+   *  implements the Cloneable interface.
+   *
+   *  The generated clone function will be registered in the typeData of the class (which
+   *  resides in the vtable of the class), and will be invoked for a `Clone` IR tree on
+   *  the class instance.
+   */
+  private def genCloneFunction(clazz: LinkedClass)(implicit ctx: WasmContext): Unit = {
+    val className = clazz.className
+    val info = ctx.getClassInfo(className)
+
+    val fb = new FunctionBuilder(
+      ctx.moduleBuilder,
+      genFunctionID.clone(className),
+      makeDebugName(ns.Clone, className),
+      clazz.pos
+    )
+    val fromParam = fb.addParam("from", watpe.RefType(genTypeID.ObjectStruct))
+    fb.setResultType(watpe.RefType(genTypeID.ObjectStruct))
+    fb.setFunctionType(genTypeID.cloneFunctionType)
+
+    val structTypeID = genTypeID.forClass(className)
+    val structRefType = watpe.RefType(structTypeID)
+
+    val fromTypedLocal = fb.addLocal("fromTyped", structRefType)
+
+    // Downcast fromParam to fromTyped
+    fb += wa.LocalGet(fromParam)
+    fb += wa.RefCast(structRefType)
+    fb += wa.LocalSet(fromTypedLocal)
+
+    // Push vtable and itables on the stack (there is at least Cloneable in the itables)
+    fb += wa.GlobalGet(genGlobalID.forVTable(className))
+    fb += wa.GlobalGet(genGlobalID.forITable(className))
+
+    // Push every field of `fromTyped` on the stack
+    info.allFieldDefs.foreach { field =>
+      fb += wa.LocalGet(fromTypedLocal)
+      fb += wa.StructGet(structTypeID, genFieldID.forClassInstanceField(field.name.name))
+    }
+
+    // Create the result
+    fb += wa.StructNew(structTypeID)
+
+    fb.buildAndAddToModule()
+  }
+
+  private def genModuleAccessor(clazz: LinkedClass)(implicit ctx: WasmContext): Unit = {
+    assert(clazz.kind == ClassKind.ModuleClass)
+
+    val className = clazz.className
+    val globalInstanceID = genGlobalID.forModuleInstance(className)
+    val ctorID =
+      genFunctionID.forMethod(MemberNamespace.Constructor, className, NoArgConstructorName)
+    val resultType = watpe.RefType(genTypeID.forClass(className))
+
+    val fb = new FunctionBuilder(
+      ctx.moduleBuilder,
+      genFunctionID.loadModule(clazz.className),
+      makeDebugName(ns.ModuleAccessor, className),
+      clazz.pos
+    )
+    fb.setResultType(resultType)
+
+    val instanceLocal = fb.addLocal("instance", resultType)
+
+    fb.block(resultType) { nonNullLabel =>
+      // load global, return if not null
+      fb += wa.GlobalGet(globalInstanceID)
+      fb += wa.BrOnNonNull(nonNullLabel)
+
+      // create an instance and call its constructor
+      fb += wa.Call(genFunctionID.newDefault(className))
+      fb += wa.LocalTee(instanceLocal)
+      fb += wa.Call(ctorID)
+
+      // store it in the global
+      fb += wa.LocalGet(instanceLocal)
+      fb += wa.GlobalSet(globalInstanceID)
+
+      // return it
+      fb += wa.LocalGet(instanceLocal)
+    }
+
+    fb.buildAndAddToModule()
+  }
+
+  /** Generates the global instance of the class itable.
+   *
+   *  Their init value will be an array of null refs of size = number of interfaces.
+   *  They will be initialized in start function.
+   */
+  private def genGlobalClassItable(clazz: LinkedClass)(implicit ctx: WasmContext): Unit = {
+    val className = clazz.className
+
+    if (ctx.getClassInfo(className).classImplementsAnyInterface) {
+      val globalID = genGlobalID.forITable(className)
+      val itablesInit = List(
+        wa.I32Const(ctx.itablesLength),
+        wa.ArrayNewDefault(genTypeID.itables)
+      )
+      val global = wamod.Global(
+        globalID,
+        makeDebugName(ns.ITable, className),
+        isMutable = false,
+        watpe.RefType(genTypeID.itables),
+        wa.Expr(itablesInit)
+      )
+      ctx.addGlobal(global)
+    }
+  }
+
+  private def genInterface(clazz: LinkedClass)(implicit ctx: WasmContext): Unit = {
+    assert(clazz.kind == ClassKind.Interface)
+    // gen itable type
+    val className = clazz.name.name
+    val classInfo = ctx.getClassInfo(clazz.className)
+    val itableTypeID = genTypeID.forITable(className)
+    val itableType = watpe.StructType(
+      classInfo.tableEntries.map { methodName =>
+        watpe.StructField(
+          genFieldID.forMethodTableEntry(methodName),
+          makeDebugName(ns.TableEntry, className, methodName),
+          watpe.RefType(ctx.tableFunctionType(methodName)),
+          isMutable = false
+        )
+      }
+    )
+    ctx.mainRecType.addSubType(
+      itableTypeID,
+      makeDebugName(ns.ITable, className),
+      itableType
+    )
+
+    if (clazz.hasInstanceTests)
+      genInterfaceInstanceTest(clazz)
+  }
+
+  private def genJSClass(clazz: LinkedClass)(implicit ctx: WasmContext): Unit = {
+    assert(clazz.kind.isJSClass)
+
+    // Define the globals holding the Symbols of private fields
+    for (fieldDef <- clazz.fields) {
+      fieldDef match {
+        case FieldDef(flags, name, _, _) if !flags.namespace.isStatic =>
+          ctx.addGlobal(
+            wamod.Global(
+              genGlobalID.forJSPrivateField(name.name),
+              makeDebugName(ns.PrivateJSField, name.name),
+              isMutable = true,
+              watpe.RefType.anyref,
+              wa.Expr(List(wa.RefNull(watpe.HeapType.Any)))
+            )
+          )
+        case _ =>
+          ()
+      }
+    }
+
+    if (clazz.hasInstances) {
+      genCreateJSClassFunction(clazz)
+
+      if (clazz.jsClassCaptures.isEmpty)
+        genLoadJSClassFunction(clazz)
+
+      if (clazz.kind == ClassKind.JSModuleClass)
+        genLoadJSModuleFunction(clazz)
+    }
+  }
+
+  private def genCreateJSClassFunction(clazz: LinkedClass)(implicit ctx: WasmContext): Unit = {
+    implicit val noPos: Position = Position.NoPosition
+
+    val className = clazz.className
+    val jsClassCaptures = clazz.jsClassCaptures.getOrElse(Nil)
+
+    /* We need to decompose the body of the constructor into 3 closures.
+     * Given an IR constructor of the form
+     *   constructor(...params) {
+     *     preSuperStats;
+     *     super(...superArgs);
+     *     postSuperStats;
+     *   }
+     * We will create closures for `preSuperStats`, `superArgs` and `postSuperStats`.
+     *
+     * There is one huge catch: `preSuperStats` can declare `VarDef`s at its top-level,
+     * and those vars are still visible inside `superArgs` and `postSuperStats`.
+     * The `preSuperStats` must therefore return a struct with the values of its
+     * declared vars, which will be given as an additional argument to `superArgs`
+     * and `postSuperStats`. We call that struct the `preSuperEnv`.
+     *
+     * In the future, we should optimize `preSuperEnv` to only store locals that
+     * are still used by `superArgs` and/or `postSuperArgs`.
+     */
+
+    val preSuperStatsFunctionID = genFunctionID.preSuperStats(className)
+    val superArgsFunctionID = genFunctionID.superArgs(className)
+    val postSuperStatsFunctionID = genFunctionID.postSuperStats(className)
+    val ctor = clazz.jsConstructorDef.get
+
+    FunctionEmitter.emitJSConstructorFunctions(
+      preSuperStatsFunctionID,
+      superArgsFunctionID,
+      postSuperStatsFunctionID,
+      className,
+      jsClassCaptures,
+      ctor
+    )
+
+    // Build the actual `createJSClass` function
+    val createJSClassFun = {
+      val fb = new FunctionBuilder(
+        ctx.moduleBuilder,
+        genFunctionID.createJSClassOf(className),
+        makeDebugName(ns.CreateJSClass, className),
+        clazz.pos
+      )
+      val classCaptureParams = jsClassCaptures.map { cc =>
+        fb.addParam("cc." + cc.name.name.nameString, transformLocalType(cc.ptpe))
+      }
+      fb.setResultType(watpe.RefType.any)
+
+      val dataStructTypeID = ctx.getClosureDataStructType(jsClassCaptures.map(_.ptpe))
+
+      val dataStructLocal = fb.addLocal("classCaptures", watpe.RefType(dataStructTypeID))
+      val jsClassLocal = fb.addLocal("jsClass", watpe.RefType.any)
+
+      // --- Actual start of instructions of `createJSClass`
+
+      // Bundle class captures in a capture data struct -- leave it on the stack for createJSClass
+      for (classCaptureParam <- classCaptureParams)
+        fb += wa.LocalGet(classCaptureParam)
+      fb += wa.StructNew(dataStructTypeID)
+      fb += wa.LocalTee(dataStructLocal)
+
+      val classCaptureParamsOfTypeAny: Map[LocalName, wanme.LocalID] = {
+        jsClassCaptures
+          .zip(classCaptureParams)
+          .collect { case (ParamDef(ident, _, AnyType, _), param) =>
+            ident.name -> param
+          }
+          .toMap
+      }
+
+      def genLoadIsolatedTree(tree: Tree): Unit = {
+        tree match {
+          case StringLiteral(value) =>
+            // Common shape for all the `nameTree` expressions
+            fb ++= ctx.stringPool.getConstantStringInstr(value)
+
+          case VarRef(LocalIdent(localName)) if classCaptureParamsOfTypeAny.contains(localName) =>
+            /* Common shape for the `jsSuperClass` value
+             * We can only deal with class captures of type `AnyType` in this way,
+             * since otherwise we might need `adapt` to box the values.
+             */
+            fb += wa.LocalGet(classCaptureParamsOfTypeAny(localName))
+
+          case _ =>
+            // For everything else, put the tree in its own function and call it
+            val closureFuncID = new JSClassClosureFunctionID(className)
+            FunctionEmitter.emitFunction(
+              closureFuncID,
+              NoOriginalName,
+              enclosingClassName = None,
+              Some(jsClassCaptures),
+              receiverType = None,
+              paramDefs = Nil,
+              restParam = None,
+              tree,
+              AnyType
+            )
+            fb += wa.LocalGet(dataStructLocal)
+            fb += wa.Call(closureFuncID)
+        }
+      }
+
+      /* Load super constructor; specified by
+       * https://lampwww.epfl.ch/~doeraene/sjsir-semantics/#sec-sjsir-classdef-runtime-semantics-evaluation
+       * - if `jsSuperClass` is defined, evaluate it;
+       * - otherwise load the JS constructor of the declared superClass,
+       *   as if by `LoadJSConstructor`.
+       */
+      clazz.jsSuperClass match {
+        case None =>
+          genLoadJSConstructor(fb, clazz.superClass.get.name)
+        case Some(jsSuperClassTree) =>
+          genLoadIsolatedTree(jsSuperClassTree)
+      }
+
+      // Load the references to the 3 functions that make up the constructor
+      fb += ctx.refFuncWithDeclaration(preSuperStatsFunctionID)
+      fb += ctx.refFuncWithDeclaration(superArgsFunctionID)
+      fb += ctx.refFuncWithDeclaration(postSuperStatsFunctionID)
+
+      // Load the array of field names and initial values
+      fb += wa.Call(genFunctionID.jsNewArray)
+      for (fieldDef <- clazz.fields if !fieldDef.flags.namespace.isStatic) {
+        // Append the name
+        fieldDef match {
+          case FieldDef(_, name, _, _) =>
+            fb += wa.GlobalGet(genGlobalID.forJSPrivateField(name.name))
+          case JSFieldDef(_, nameTree, _) =>
+            genLoadIsolatedTree(nameTree)
+        }
+        fb += wa.Call(genFunctionID.jsArrayPush)
+
+        // Append the boxed representation of the zero of the field
+        fb += genBoxedZeroOf(fieldDef.ftpe)
+        fb += wa.Call(genFunctionID.jsArrayPush)
+      }
+
+      // Call the createJSClass helper to bundle everything
+      if (ctor.restParam.isDefined) {
+        fb += wa.I32Const(ctor.args.size) // number of fixed params
+        fb += wa.Call(genFunctionID.createJSClassRest)
+      } else {
+        fb += wa.Call(genFunctionID.createJSClass)
+      }
+
+      // Store the result, locally in `jsClass` and possibly in the global cache
+      if (clazz.jsClassCaptures.isEmpty) {
+        /* Static JS class with a global cache. We must fill the global cache
+         * before we call the class initializer, later in the current function.
+         */
+        fb += wa.LocalTee(jsClassLocal)
+        fb += wa.GlobalSet(genGlobalID.forJSClassValue(className))
+      } else {
+        // Local or inner JS class, which is new every time
+        fb += wa.LocalSet(jsClassLocal)
+      }
+
+      // Install methods and properties
+      for (methodOrProp <- clazz.exportedMembers) {
+        val isStatic = methodOrProp.flags.namespace.isStatic
+        fb += wa.LocalGet(dataStructLocal)
+        fb += wa.LocalGet(jsClassLocal)
+
+        val receiverType = if (isStatic) None else Some(watpe.RefType.anyref)
+
+        methodOrProp match {
+          case JSMethodDef(flags, nameTree, params, restParam, body) =>
+            genLoadIsolatedTree(nameTree)
+
+            val closureFuncID = new JSClassClosureFunctionID(className)
+            FunctionEmitter.emitFunction(
+              closureFuncID,
+              NoOriginalName, // TODO Come up with something here?
+              Some(className),
+              Some(jsClassCaptures),
+              receiverType,
+              params,
+              restParam,
+              body,
+              AnyType
+            )
+            fb += ctx.refFuncWithDeclaration(closureFuncID)
+
+            fb += wa.I32Const(if (restParam.isDefined) params.size else -1)
+            if (isStatic)
+              fb += wa.Call(genFunctionID.installJSStaticMethod)
+            else
+              fb += wa.Call(genFunctionID.installJSMethod)
+
+          case JSPropertyDef(flags, nameTree, optGetter, optSetter) =>
+            genLoadIsolatedTree(nameTree)
+
+            optGetter match {
+              case None =>
+                fb += wa.RefNull(watpe.HeapType.Func)
+
+              case Some(getterBody) =>
+                val closureFuncID = new JSClassClosureFunctionID(className)
+                FunctionEmitter.emitFunction(
+                  closureFuncID,
+                  NoOriginalName, // TODO Come up with something here?
+                  Some(className),
+                  Some(jsClassCaptures),
+                  receiverType,
+                  paramDefs = Nil,
+                  restParam = None,
+                  getterBody,
+                  resultType = AnyType
+                )
+                fb += ctx.refFuncWithDeclaration(closureFuncID)
+            }
+
+            optSetter match {
+              case None =>
+                fb += wa.RefNull(watpe.HeapType.Func)
+
+              case Some((setterParamDef, setterBody)) =>
+                val closureFuncID = new JSClassClosureFunctionID(className)
+                FunctionEmitter.emitFunction(
+                  closureFuncID,
+                  NoOriginalName, // TODO Come up with something here?
+                  Some(className),
+                  Some(jsClassCaptures),
+                  receiverType,
+                  setterParamDef :: Nil,
+                  restParam = None,
+                  setterBody,
+                  resultType = NoType
+                )
+                fb += ctx.refFuncWithDeclaration(closureFuncID)
+            }
+
+            if (isStatic)
+              fb += wa.Call(genFunctionID.installJSStaticProperty)
+            else
+              fb += wa.Call(genFunctionID.installJSProperty)
+        }
+      }
+
+      // Static fields
+      for (fieldDef <- clazz.fields if fieldDef.flags.namespace.isStatic) {
+        // Load class value
+        fb += wa.LocalGet(jsClassLocal)
+
+        // Load name
+        fieldDef match {
+          case FieldDef(_, name, _, _) =>
+            throw new AssertionError(
+              s"Unexpected private static field ${name.name.nameString} "
+                + s"in JS class ${className.nameString}"
+            )
+          case JSFieldDef(_, nameTree, _) =>
+            genLoadIsolatedTree(nameTree)
+        }
+
+        // Generate boxed representation of the zero of the field
+        fb += genBoxedZeroOf(fieldDef.ftpe)
+
+        /* Note: there is no `installJSStaticField` because it would do the
+         * same as `installJSField` anyway.
+         */
+        fb += wa.Call(genFunctionID.installJSField)
+      }
+
+      // Class initializer
+      if (clazz.methods.exists(_.methodName.isClassInitializer)) {
+        assert(
+          clazz.jsClassCaptures.isEmpty,
+          s"Illegal class initializer in non-static class ${className.nameString}"
+        )
+        val namespace = MemberNamespace.StaticConstructor
+        fb += wa.Call(
+          genFunctionID.forMethod(namespace, className, ClassInitializerName)
+        )
+      }
+
+      // Final result
+      fb += wa.LocalGet(jsClassLocal)
+
+      fb.buildAndAddToModule()
+    }
+  }
+
+  private def genLoadJSClassFunction(clazz: LinkedClass)(implicit ctx: WasmContext): Unit = {
+    require(clazz.jsClassCaptures.isEmpty)
+
+    val className = clazz.className
+
+    val cachedJSClassGlobal = wamod.Global(
+      genGlobalID.forJSClassValue(className),
+      makeDebugName(ns.JSClassValueCache, className),
+      isMutable = true,
+      watpe.RefType.anyref,
+      wa.Expr(List(wa.RefNull(watpe.HeapType.Any)))
+    )
+    ctx.addGlobal(cachedJSClassGlobal)
+
+    val fb = new FunctionBuilder(
+      ctx.moduleBuilder,
+      genFunctionID.loadJSClass(className),
+      makeDebugName(ns.JSClassAccessor, className),
+      clazz.pos
+    )
+    fb.setResultType(watpe.RefType.any)
+
+    fb.block(watpe.RefType.any) { doneLabel =>
+      // Load cached JS class, return if non-null
+      fb += wa.GlobalGet(cachedJSClassGlobal.id)
+      fb += wa.BrOnNonNull(doneLabel)
+      // Otherwise, call createJSClass -- it will also store the class in the cache
+      fb += wa.Call(genFunctionID.createJSClassOf(className))
+    }
+
+    fb.buildAndAddToModule()
+  }
+
+  private def genLoadJSModuleFunction(clazz: LinkedClass)(implicit ctx: WasmContext): Unit = {
+    val className = clazz.className
+    val cacheGlobalID = genGlobalID.forModuleInstance(className)
+
+    ctx.addGlobal(
+      wamod.Global(
+        cacheGlobalID,
+        makeDebugName(ns.ModuleInstance, className),
+        isMutable = true,
+        watpe.RefType.anyref,
+        wa.Expr(List(wa.RefNull(watpe.HeapType.Any)))
+      )
+    )
+
+    val fb = new FunctionBuilder(
+      ctx.moduleBuilder,
+      genFunctionID.loadModule(className),
+      makeDebugName(ns.ModuleAccessor, className),
+      clazz.pos
+    )
+    fb.setResultType(watpe.RefType.anyref)
+
+    fb.block(watpe.RefType.anyref) { doneLabel =>
+      // Load cached instance; return if non-null
+      fb += wa.GlobalGet(cacheGlobalID)
+      fb += wa.BrOnNonNull(doneLabel)
+
+      // Get the JS class and instantiate it
+      fb += wa.Call(genFunctionID.loadJSClass(className))
+      fb += wa.Call(genFunctionID.jsNewArray)
+      fb += wa.Call(genFunctionID.jsNew)
+
+      // Store and return the result
+      fb += wa.GlobalSet(cacheGlobalID)
+      fb += wa.GlobalGet(cacheGlobalID)
+    }
+
+    fb.buildAndAddToModule()
+  }
+
+  /** Generates the function import for a top-level export setter. */
+  private def genTopLevelExportSetter(exportedName: String)(implicit ctx: WasmContext): Unit = {
+    val functionID = genFunctionID.forTopLevelExportSetter(exportedName)
+    val functionSig = watpe.FunctionType(List(watpe.RefType.anyref), Nil)
+    val functionType = ctx.moduleBuilder.functionTypeToTypeID(functionSig)
+
+    ctx.moduleBuilder.addImport(
+      wamod.Import(
+        "__scalaJSExportSetters",
+        exportedName,
+        wamod.ImportDesc.Func(
+          functionID,
+          makeDebugName(ns.TopLevelExportSetter, exportedName),
+          functionType
+        )
+      )
+    )
+  }
+
+  private def genTopLevelMethodExportDef(exportDef: TopLevelMethodExportDef)(
+      implicit ctx: WasmContext): Unit = {
+    implicit val pos = exportDef.pos
+
+    val method = exportDef.methodDef
+    val exportedName = exportDef.topLevelExportName
+    val functionID = genFunctionID.forExport(exportedName)
+
+    FunctionEmitter.emitFunction(
+      functionID,
+      makeDebugName(ns.TopLevelExport, exportedName),
+      enclosingClassName = None,
+      captureParamDefs = None,
+      receiverType = None,
+      method.args,
+      method.restParam,
+      method.body,
+      resultType = AnyType
+    )
+  }
+
+  private def genMethod(clazz: LinkedClass, method: MethodDef)(
+      implicit ctx: WasmContext): Unit = {
+    implicit val pos = method.pos
+
+    val namespace = method.flags.namespace
+    val className = clazz.className
+    val methodName = method.methodName
+
+    val functionID = genFunctionID.forMethod(namespace, className, methodName)
+
+    val namespaceUTF8String = namespace match {
+      case MemberNamespace.Public            => ns.Public
+      case MemberNamespace.PublicStatic      => ns.PublicStatic
+      case MemberNamespace.Private           => ns.Private
+      case MemberNamespace.PrivateStatic     => ns.PrivateStatic
+      case MemberNamespace.Constructor       => ns.Constructor
+      case MemberNamespace.StaticConstructor => ns.StaticConstructor
+    }
+    val originalName = makeDebugName(namespaceUTF8String, className, methodName)
+
+    val isHijackedClass = clazz.kind == ClassKind.HijackedClass
+
+    val receiverType =
+      if (namespace.isStatic)
+        None
+      else if (isHijackedClass)
+        Some(transformType(BoxedClassToPrimType(className)))
+      else
+        Some(transformClassType(className).toNonNullable)
+
+    val body = method.body.getOrElse(throw new Exception("abstract method cannot be transformed"))
+
+    // Emit the function
+    FunctionEmitter.emitFunction(
+      functionID,
+      originalName,
+      Some(className),
+      captureParamDefs = None,
+      receiverType,
+      method.args,
+      restParam = None,
+      body,
+      method.resultType
+    )
+
+    if (namespace == MemberNamespace.Public && !isHijackedClass) {
+      /* Also generate the bridge that is stored in the table entries. In table
+       * entries, the receiver type is always `(ref any)`.
+       *
+       * TODO: generate this only when the method is actually referred to from
+       * at least one table.
+       */
+
+      val fb = new FunctionBuilder(
+        ctx.moduleBuilder,
+        genFunctionID.forTableEntry(className, methodName),
+        makeDebugName(ns.TableEntry, className, methodName),
+        pos
+      )
+      val receiverParam = fb.addParam(thisOriginalName, watpe.RefType.any)
+      val argParams = method.args.map { arg =>
+        val origName = arg.originalName.orElse(arg.name.name)
+        fb.addParam(origName, TypeTransformer.transformLocalType(arg.ptpe))
+      }
+      fb.setResultTypes(TypeTransformer.transformResultType(method.resultType))
+      fb.setFunctionType(ctx.tableFunctionType(methodName))
+
+      // Load and cast down the receiver
+      fb += wa.LocalGet(receiverParam)
+      receiverType match {
+        case Some(watpe.RefType(_, watpe.HeapType.Any)) =>
+          () // no cast necessary
+        case Some(receiverType: watpe.RefType) =>
+          fb += wa.RefCast(receiverType)
+        case _ =>
+          throw new AssertionError(s"Unexpected receiver type $receiverType")
+      }
+
+      // Load the other parameters
+      for (argParam <- argParams)
+        fb += wa.LocalGet(argParam)
+
+      // Call the statically resolved method
+      fb += wa.ReturnCall(functionID)
+
+      fb.buildAndAddToModule()
+    }
+  }
+
+  private def makeDebugName(namespace: UTF8String, exportedName: String): OriginalName =
+    OriginalName(namespace ++ UTF8String(exportedName))
+
+  private def makeDebugName(namespace: UTF8String, className: ClassName): OriginalName =
+    OriginalName(namespace ++ className.encoded)
+
+  private def makeDebugName(namespace: UTF8String, fieldName: FieldName): OriginalName = {
+    OriginalName(
+      namespace ++ fieldName.className.encoded ++ dotUTF8String ++ fieldName.simpleName.encoded
+    )
+  }
+
+  private def makeDebugName(
+      namespace: UTF8String,
+      className: ClassName,
+      methodName: MethodName
+  ): OriginalName = {
+    // TODO Opt: directly encode the MethodName rather than using nameString
+    val methodNameUTF8 = UTF8String(methodName.nameString)
+    OriginalName(namespace ++ className.encoded ++ dotUTF8String ++ methodNameUTF8)
+  }
+}
+
+object ClassEmitter {
+  private final class JSClassClosureFunctionID(classNameDebug: ClassName) extends wanme.FunctionID {
+    override def toString(): String =
+      s"JSClassClosureFunctionID(${classNameDebug.nameString})"
+  }
+
+  private val dotUTF8String: UTF8String = UTF8String(".")
+
+  // These particular names are the same as in the JS backend
+  private object ns {
+    // Shared with JS backend -- className + methodName
+    val Public = UTF8String("f.")
+    val PublicStatic = UTF8String("s.")
+    val Private = UTF8String("p.")
+    val PrivateStatic = UTF8String("ps.")
+    val Constructor = UTF8String("ct.")
+    val StaticConstructor = UTF8String("sct.")
+
+    // Shared with JS backend -- fieldName
+    val StaticField = UTF8String("t.")
+    val PrivateJSField = UTF8String("r.")
+
+    // Shared with JS backend -- className
+    val ModuleAccessor = UTF8String("m.")
+    val ModuleInstance = UTF8String("n.")
+    val JSClassAccessor = UTF8String("a.")
+    val JSClassValueCache = UTF8String("b.")
+    val TypeData = UTF8String("d.")
+    val IsInstance = UTF8String("is.")
+
+    // Shared with JS backend -- string
+    val TopLevelExport = UTF8String("e.")
+    val TopLevelExportSetter = UTF8String("u.")
+
+    // Wasm only -- className + methodName
+    val TableEntry = UTF8String("m.")
+
+    // Wasm only -- fieldName
+    val InstanceField = UTF8String("f.")
+
+    // Wasm only -- className
+    val ClassInstance = UTF8String("c.")
+    val CreateJSClass = UTF8String("c.")
+    val VTable = UTF8String("v.")
+    val ITable = UTF8String("it.")
+    val Clone = UTF8String("clone.")
+    val NewDefault = UTF8String("new.")
+  }
+
+  private val thisOriginalName: OriginalName = OriginalName("this")
+  private val vtableOriginalName: OriginalName = OriginalName("vtable")
+  private val itablesOriginalName: OriginalName = OriginalName("itables")
+}
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
new file mode 100644
index 0000000000..26fb965464
--- /dev/null
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
@@ -0,0 +1,2214 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package org.scalajs.linker.backend.wasmemitter
+
+import org.scalajs.ir.Names._
+import org.scalajs.ir.Trees.{JSUnaryOp, JSBinaryOp, MemberNamespace}
+import org.scalajs.ir.Types.{Type => _, ArrayType => _, _}
+import org.scalajs.ir.{OriginalName, Position}
+
+import org.scalajs.linker.backend.webassembly._
+import org.scalajs.linker.backend.webassembly.Instructions._
+import org.scalajs.linker.backend.webassembly.Identitities._
+import org.scalajs.linker.backend.webassembly.Modules._
+import org.scalajs.linker.backend.webassembly.Types._
+
+import EmbeddedConstants._
+import VarGen._
+import TypeTransformer._
+
+object CoreWasmLib {
+  import RefType.anyref
+
+  private implicit val noPos: Position = Position.NoPosition
+
+  /** Fields of the `typeData` struct definition.
+   *
+   *  They are accessible as a public list because they must be repeated in every vtable type
+   *  definition.
+   *
+   *  @see
+   *    [[VarGen.genFieldID.typeData]], which contains documentation of what is in each field.
+   */
+  val typeDataStructFields: List[StructField] = {
+    import genFieldID.typeData._
+    import RefType.nullable
+
+    def make(id: FieldID, tpe: Type, isMutable: Boolean): StructField =
+      StructField(id, OriginalName(id.toString()), tpe, isMutable)
+
+    List(
+      make(nameOffset, Int32, isMutable = false),
+      make(nameSize, Int32, isMutable = false),
+      make(nameStringIndex, Int32, isMutable = false),
+      make(kind, Int32, isMutable = false),
+      make(specialInstanceTypes, Int32, isMutable = false),
+      make(strictAncestors, nullable(genTypeID.typeDataArray), isMutable = false),
+      make(componentType, nullable(genTypeID.typeData), isMutable = false),
+      make(name, RefType.anyref, isMutable = true),
+      make(classOfValue, nullable(genTypeID.ClassStruct), isMutable = true),
+      make(arrayOf, nullable(genTypeID.ObjectVTable), isMutable = true),
+      make(cloneFunction, nullable(genTypeID.cloneFunctionType), isMutable = false),
+      make(
+        isJSClassInstance,
+        nullable(genTypeID.isJSClassInstanceFuncType),
+        isMutable = false
+      ),
+      make(
+        reflectiveProxies,
+        RefType(genTypeID.reflectiveProxies),
+        isMutable = false
+      )
+    )
+  }
+
+  /** Generates definitions that must come *before* the code generated for regular classes.
+   *
+   *  This notably includes the `typeData` definitions, since the vtable of `jl.Object` is a subtype
+   *  of `typeData`.
+   */
+  def genPreClasses()(implicit ctx: WasmContext): Unit = {
+    genPreMainRecTypeDefinitions()
+    ctx.moduleBuilder.addRecTypeBuilder(ctx.mainRecType)
+    genCoreTypesInRecType()
+
+    genImports()
+
+    genPrimitiveTypeDataGlobals()
+
+    genHelperDefinitions()
+  }
+
+  /** Generates definitions that must come *after* the code generated for regular classes.
+   *
+   *  This notably includes the array class definitions, since they are subtypes of the `jl.Object`
+   *  struct type.
+   */
+  def genPostClasses()(implicit ctx: WasmContext): Unit = {
+    genArrayClassTypes()
+
+    genBoxedZeroGlobals()
+    genArrayClassGlobals()
+  }
+
+  // --- Type definitions ---
+
+  private def genPreMainRecTypeDefinitions()(implicit ctx: WasmContext): Unit = {
+    val b = ctx.moduleBuilder
+
+    def genUnderlyingArrayType(id: TypeID, elemType: StorageType): Unit =
+      b.addRecType(id, OriginalName(id.toString()), ArrayType(FieldType(elemType, true)))
+
+    genUnderlyingArrayType(genTypeID.i8Array, Int8)
+    genUnderlyingArrayType(genTypeID.i16Array, Int16)
+    genUnderlyingArrayType(genTypeID.i32Array, Int32)
+    genUnderlyingArrayType(genTypeID.i64Array, Int64)
+    genUnderlyingArrayType(genTypeID.f32Array, Float32)
+    genUnderlyingArrayType(genTypeID.f64Array, Float64)
+    genUnderlyingArrayType(genTypeID.anyArray, anyref)
+  }
+
+  private def genCoreTypesInRecType()(implicit ctx: WasmContext): Unit = {
+    def genCoreType(id: TypeID, compositeType: CompositeType): Unit =
+      ctx.mainRecType.addSubType(id, OriginalName(id.toString()), compositeType)
+
+    genCoreType(
+      genTypeID.cloneFunctionType,
+      FunctionType(
+        List(RefType(genTypeID.ObjectStruct)),
+        List(RefType(genTypeID.ObjectStruct))
+      )
+    )
+
+    genCoreType(
+      genTypeID.isJSClassInstanceFuncType,
+      FunctionType(List(RefType.anyref), List(Int32))
+    )
+
+    genCoreType(
+      genTypeID.typeDataArray,
+      ArrayType(FieldType(RefType(genTypeID.typeData), isMutable = false))
+    )
+    genCoreType(
+      genTypeID.itables,
+      ArrayType(FieldType(RefType.nullable(HeapType.Struct), isMutable = true))
+    )
+    genCoreType(
+      genTypeID.reflectiveProxies,
+      ArrayType(FieldType(RefType(genTypeID.reflectiveProxy), isMutable = false))
+    )
+
+    ctx.mainRecType.addSubType(
+      SubType(
+        genTypeID.typeData,
+        OriginalName(genTypeID.typeData.toString()),
+        isFinal = false,
+        None,
+        StructType(typeDataStructFields)
+      )
+    )
+
+    genCoreType(
+      genTypeID.reflectiveProxy,
+      StructType(
+        List(
+          StructField(
+            genFieldID.reflectiveProxy.methodID,
+            OriginalName(genFieldID.reflectiveProxy.methodID.toString()),
+            Int32,
+            isMutable = false
+          ),
+          StructField(
+            genFieldID.reflectiveProxy.funcRef,
+            OriginalName(genFieldID.reflectiveProxy.funcRef.toString()),
+            RefType(HeapType.Func),
+            isMutable = false
+          )
+        )
+      )
+    )
+  }
+
+  private def genArrayClassTypes()(implicit ctx: WasmContext): Unit = {
+    // The vtable type is always the same as j.l.Object
+    val vtableTypeID = genTypeID.ObjectVTable
+    val vtableField = StructField(
+      genFieldID.objStruct.vtable,
+      OriginalName(genFieldID.objStruct.vtable.toString()),
+      RefType(vtableTypeID),
+      isMutable = false
+    )
+    val itablesField = StructField(
+      genFieldID.objStruct.itables,
+      OriginalName(genFieldID.objStruct.itables.toString()),
+      RefType.nullable(genTypeID.itables),
+      isMutable = false
+    )
+
+    val typeRefsWithArrays: List[(TypeID, TypeID)] =
+      List(
+        (genTypeID.BooleanArray, genTypeID.i8Array),
+        (genTypeID.CharArray, genTypeID.i16Array),
+        (genTypeID.ByteArray, genTypeID.i8Array),
+        (genTypeID.ShortArray, genTypeID.i16Array),
+        (genTypeID.IntArray, genTypeID.i32Array),
+        (genTypeID.LongArray, genTypeID.i64Array),
+        (genTypeID.FloatArray, genTypeID.f32Array),
+        (genTypeID.DoubleArray, genTypeID.f64Array),
+        (genTypeID.ObjectArray, genTypeID.anyArray)
+      )
+
+    for ((structTypeID, underlyingArrayTypeID) <- typeRefsWithArrays) {
+      val origName = OriginalName(structTypeID.toString())
+
+      val underlyingArrayField = StructField(
+        genFieldID.objStruct.arrayUnderlying,
+        OriginalName(genFieldID.objStruct.arrayUnderlying.toString()),
+        RefType(underlyingArrayTypeID),
+        isMutable = false
+      )
+
+      val superType = genTypeID.ObjectStruct
+      val structType = StructType(
+        List(vtableField, itablesField, underlyingArrayField)
+      )
+      val subType = SubType(structTypeID, origName, isFinal = true, Some(superType), structType)
+      ctx.mainRecType.addSubType(subType)
+    }
+  }
+
+  // --- Imports ---
+
+  private def genImports()(implicit ctx: WasmContext): Unit = {
+    genTagImports()
+    genGlobalImports()
+    genHelperImports()
+  }
+
+  private def genTagImports()(implicit ctx: WasmContext): Unit = {
+    val exceptionSig = FunctionType(List(RefType.externref), Nil)
+    val typeID = ctx.moduleBuilder.functionTypeToTypeID(exceptionSig)
+    ctx.moduleBuilder.addImport(
+      Import(
+        "__scalaJSHelpers",
+        "JSTag",
+        ImportDesc.Tag(
+          genTagID.exception,
+          OriginalName(genTagID.exception.toString()),
+          typeID
+        )
+      )
+    )
+  }
+
+  private def genGlobalImports()(implicit ctx: WasmContext): Unit = {
+    def addGlobalHelperImport(id: genGlobalID.JSHelperGlobalID, tpe: Type): Unit = {
+      ctx.moduleBuilder.addImport(
+        Import(
+          "__scalaJSHelpers",
+          id.toString(), // import name, guaranteed by JSHelperGlobalID
+          ImportDesc.Global(id, OriginalName(id.toString()), isMutable = false, tpe)
+        )
+      )
+    }
+
+    addGlobalHelperImport(genGlobalID.jsLinkingInfo, RefType.any)
+    addGlobalHelperImport(genGlobalID.undef, RefType.any)
+    addGlobalHelperImport(genGlobalID.bFalse, RefType.any)
+    addGlobalHelperImport(genGlobalID.bZero, RefType.any)
+    addGlobalHelperImport(genGlobalID.emptyString, RefType.any)
+    addGlobalHelperImport(genGlobalID.idHashCodeMap, RefType.extern)
+  }
+
+  private def genHelperImports()(implicit ctx: WasmContext): Unit = {
+    def addHelperImport(id: genFunctionID.JSHelperFunctionID,
+        params: List[Type], results: List[Type]): Unit = {
+      val sig = FunctionType(params, results)
+      val typeID = ctx.moduleBuilder.functionTypeToTypeID(sig)
+      ctx.moduleBuilder.addImport(
+        Import(
+          "__scalaJSHelpers",
+          id.toString(), // import name, guaranteed by JSHelperFunctionID
+          ImportDesc.Func(id, OriginalName(id.toString()), typeID)
+        )
+      )
+    }
+
+    addHelperImport(genFunctionID.is, List(anyref, anyref), List(Int32))
+
+    addHelperImport(genFunctionID.isUndef, List(anyref), List(Int32))
+
+    for (primRef <- List(BooleanRef, ByteRef, ShortRef, IntRef, FloatRef, DoubleRef)) {
+      val wasmType = primRef match {
+        case FloatRef  => Float32
+        case DoubleRef => Float64
+        case _         => Int32
+      }
+      addHelperImport(genFunctionID.box(primRef), List(wasmType), List(anyref))
+      addHelperImport(genFunctionID.unbox(primRef), List(anyref), List(wasmType))
+      addHelperImport(genFunctionID.typeTest(primRef), List(anyref), List(Int32))
+    }
+
+    addHelperImport(genFunctionID.fmod, List(Float64, Float64), List(Float64))
+
+    addHelperImport(
+      genFunctionID.closure,
+      List(RefType.func, anyref),
+      List(RefType.any)
+    )
+    addHelperImport(
+      genFunctionID.closureThis,
+      List(RefType.func, anyref),
+      List(RefType.any)
+    )
+    addHelperImport(
+      genFunctionID.closureRest,
+      List(RefType.func, anyref, Int32),
+      List(RefType.any)
+    )
+    addHelperImport(
+      genFunctionID.closureThisRest,
+      List(RefType.func, anyref, Int32),
+      List(RefType.any)
+    )
+
+    addHelperImport(genFunctionID.makeExportedDef, List(RefType.func), List(RefType.any))
+    addHelperImport(
+      genFunctionID.makeExportedDefRest,
+      List(RefType.func, Int32),
+      List(RefType.any)
+    )
+
+    addHelperImport(genFunctionID.stringLength, List(RefType.any), List(Int32))
+    addHelperImport(genFunctionID.stringCharAt, List(RefType.any, Int32), List(Int32))
+    addHelperImport(genFunctionID.jsValueToString, List(RefType.any), List(RefType.any))
+    addHelperImport(genFunctionID.jsValueToStringForConcat, List(anyref), List(RefType.any))
+    addHelperImport(genFunctionID.booleanToString, List(Int32), List(RefType.any))
+    addHelperImport(genFunctionID.charToString, List(Int32), List(RefType.any))
+    addHelperImport(genFunctionID.intToString, List(Int32), List(RefType.any))
+    addHelperImport(genFunctionID.longToString, List(Int64), List(RefType.any))
+    addHelperImport(genFunctionID.doubleToString, List(Float64), List(RefType.any))
+    addHelperImport(
+      genFunctionID.stringConcat,
+      List(RefType.any, RefType.any),
+      List(RefType.any)
+    )
+    addHelperImport(genFunctionID.isString, List(anyref), List(Int32))
+
+    addHelperImport(genFunctionID.jsValueType, List(RefType.any), List(Int32))
+    addHelperImport(genFunctionID.bigintHashCode, List(RefType.any), List(Int32))
+    addHelperImport(
+      genFunctionID.symbolDescription,
+      List(RefType.any),
+      List(RefType.anyref)
+    )
+    addHelperImport(
+      genFunctionID.idHashCodeGet,
+      List(RefType.extern, RefType.any),
+      List(Int32)
+    )
+    addHelperImport(
+      genFunctionID.idHashCodeSet,
+      List(RefType.extern, RefType.any, Int32),
+      Nil
+    )
+
+    addHelperImport(genFunctionID.jsGlobalRefGet, List(RefType.any), List(anyref))
+    addHelperImport(genFunctionID.jsGlobalRefSet, List(RefType.any, anyref), Nil)
+    addHelperImport(genFunctionID.jsGlobalRefTypeof, List(RefType.any), List(RefType.any))
+    addHelperImport(genFunctionID.jsNewArray, Nil, List(anyref))
+    addHelperImport(genFunctionID.jsArrayPush, List(anyref, anyref), List(anyref))
+    addHelperImport(
+      genFunctionID.jsArraySpreadPush,
+      List(anyref, anyref),
+      List(anyref)
+    )
+    addHelperImport(genFunctionID.jsNewObject, Nil, List(anyref))
+    addHelperImport(
+      genFunctionID.jsObjectPush,
+      List(anyref, anyref, anyref),
+      List(anyref)
+    )
+    addHelperImport(genFunctionID.jsSelect, List(anyref, anyref), List(anyref))
+    addHelperImport(genFunctionID.jsSelectSet, List(anyref, anyref, anyref), Nil)
+    addHelperImport(genFunctionID.jsNew, List(anyref, anyref), List(anyref))
+    addHelperImport(genFunctionID.jsFunctionApply, List(anyref, anyref), List(anyref))
+    addHelperImport(
+      genFunctionID.jsMethodApply,
+      List(anyref, anyref, anyref),
+      List(anyref)
+    )
+    addHelperImport(genFunctionID.jsImportCall, List(anyref), List(anyref))
+    addHelperImport(genFunctionID.jsImportMeta, Nil, List(anyref))
+    addHelperImport(genFunctionID.jsDelete, List(anyref, anyref), Nil)
+    addHelperImport(genFunctionID.jsForInSimple, List(anyref, anyref), Nil)
+    addHelperImport(genFunctionID.jsIsTruthy, List(anyref), List(Int32))
+
+    for ((op, funcID) <- genFunctionID.jsUnaryOps)
+      addHelperImport(funcID, List(anyref), List(anyref))
+
+    for ((op, funcID) <- genFunctionID.jsBinaryOps) {
+      val resultType =
+        if (op == JSBinaryOp.=== || op == JSBinaryOp.!==) Int32
+        else anyref
+      addHelperImport(funcID, List(anyref, anyref), List(resultType))
+    }
+
+    addHelperImport(genFunctionID.newSymbol, Nil, List(anyref))
+    addHelperImport(
+      genFunctionID.createJSClass,
+      List(anyref, anyref, RefType.func, RefType.func, RefType.func, anyref),
+      List(RefType.any)
+    )
+    addHelperImport(
+      genFunctionID.createJSClassRest,
+      List(anyref, anyref, RefType.func, RefType.func, RefType.func, anyref, Int32),
+      List(RefType.any)
+    )
+    addHelperImport(
+      genFunctionID.installJSField,
+      List(anyref, anyref, anyref),
+      Nil
+    )
+    addHelperImport(
+      genFunctionID.installJSMethod,
+      List(anyref, anyref, anyref, RefType.func, Int32),
+      Nil
+    )
+    addHelperImport(
+      genFunctionID.installJSStaticMethod,
+      List(anyref, anyref, anyref, RefType.func, Int32),
+      Nil
+    )
+    addHelperImport(
+      genFunctionID.installJSProperty,
+      List(anyref, anyref, anyref, RefType.funcref, RefType.funcref),
+      Nil
+    )
+    addHelperImport(
+      genFunctionID.installJSStaticProperty,
+      List(anyref, anyref, anyref, RefType.funcref, RefType.funcref),
+      Nil
+    )
+    addHelperImport(
+      genFunctionID.jsSuperSelect,
+      List(anyref, anyref, anyref),
+      List(anyref)
+    )
+    addHelperImport(
+      genFunctionID.jsSuperSelectSet,
+      List(anyref, anyref, anyref, anyref),
+      Nil
+    )
+    addHelperImport(
+      genFunctionID.jsSuperCall,
+      List(anyref, anyref, anyref, anyref),
+      List(anyref)
+    )
+  }
+
+  // --- Global definitions ---
+
+  private def genPrimitiveTypeDataGlobals()(implicit ctx: WasmContext): Unit = {
+    import genFieldID.typeData._
+
+    val primRefsWithTypeData = List(
+      VoidRef -> KindVoid,
+      BooleanRef -> KindBoolean,
+      CharRef -> KindChar,
+      ByteRef -> KindByte,
+      ShortRef -> KindShort,
+      IntRef -> KindInt,
+      LongRef -> KindLong,
+      FloatRef -> KindFloat,
+      DoubleRef -> KindDouble
+    )
+
+    val typeDataTypeID = genTypeID.typeData
+
+    // Other than `name` and `kind`, all the fields have the same value for all primitives
+    val commonFieldValues = List(
+      // specialInstanceTypes
+      I32Const(0),
+      // strictAncestors
+      RefNull(HeapType.None),
+      // componentType
+      RefNull(HeapType.None),
+      // name - initially `null`; filled in by the `typeDataName` helper
+      RefNull(HeapType.None),
+      // the classOf instance - initially `null`; filled in by the `createClassOf` helper
+      RefNull(HeapType.None),
+      // arrayOf, the typeData of an array of this type - initially `null`; filled in by the `arrayTypeData` helper
+      RefNull(HeapType.None),
+      // cloneFunction
+      RefNull(HeapType.NoFunc),
+      // isJSClassInstance
+      RefNull(HeapType.NoFunc),
+      // reflectiveProxies
+      ArrayNewFixed(genTypeID.reflectiveProxies, 0)
+    )
+
+    for ((primRef, kind) <- primRefsWithTypeData) {
+      val nameDataValue: List[Instr] =
+        ctx.stringPool.getConstantStringDataInstr(primRef.displayName)
+
+      val instrs: List[Instr] = {
+        nameDataValue ::: I32Const(kind) :: commonFieldValues :::
+          StructNew(genTypeID.typeData) :: Nil
+      }
+
+      ctx.addGlobal(
+        Global(
+          genGlobalID.forVTable(primRef),
+          OriginalName("d." + primRef.charCode),
+          isMutable = false,
+          RefType(genTypeID.typeData),
+          Expr(instrs)
+        )
+      )
+    }
+  }
+
+  private def genBoxedZeroGlobals()(implicit ctx: WasmContext): Unit = {
+    val primTypesWithBoxClasses: List[(GlobalID, ClassName, Instr)] = List(
+      (genGlobalID.bZeroChar, SpecialNames.CharBoxClass, I32Const(0)),
+      (genGlobalID.bZeroLong, SpecialNames.LongBoxClass, I64Const(0))
+    )
+
+    for ((globalID, boxClassName, zeroValueInstr) <- primTypesWithBoxClasses) {
+      val boxStruct = genTypeID.forClass(boxClassName)
+      val instrs: List[Instr] = List(
+        GlobalGet(genGlobalID.forVTable(boxClassName)),
+        GlobalGet(genGlobalID.forITable(boxClassName)),
+        zeroValueInstr,
+        StructNew(boxStruct)
+      )
+
+      ctx.addGlobal(
+        Global(
+          globalID,
+          OriginalName(globalID.toString()),
+          isMutable = false,
+          RefType(boxStruct),
+          Expr(instrs)
+        )
+      )
+    }
+  }
+
+  private def genArrayClassGlobals()(implicit ctx: WasmContext): Unit = {
+    // Common itable global for all array classes
+    val itablesInit = List(
+      I32Const(ctx.itablesLength),
+      ArrayNewDefault(genTypeID.itables)
+    )
+    ctx.addGlobal(
+      Global(
+        genGlobalID.arrayClassITable,
+        OriginalName(genGlobalID.arrayClassITable.toString()),
+        isMutable = false,
+        RefType(genTypeID.itables),
+        init = Expr(itablesInit)
+      )
+    )
+  }
+
+  // --- Function definitions ---
+
+  /** Generates all the helper function definitions of the core Wasm lib. */
+  private def genHelperDefinitions()(implicit ctx: WasmContext): Unit = {
+    genStringLiteral()
+    genCreateStringFromData()
+    genTypeDataName()
+    genCreateClassOf()
+    genGetClassOf()
+    genArrayTypeData()
+    genIsInstance()
+    genIsAssignableFromExternal()
+    genIsAssignableFrom()
+    genCheckCast()
+    genGetComponentType()
+    genNewArrayOfThisClass()
+    genAnyGetClass()
+    genNewArrayObject()
+    genIdentityHashCode()
+    genSearchReflectiveProxy()
+    genArrayCloneFunctions()
+  }
+
+  private def newFunctionBuilder(functionID: FunctionID, originalName: OriginalName)(
+      implicit ctx: WasmContext): FunctionBuilder = {
+    new FunctionBuilder(ctx.moduleBuilder, functionID, originalName, noPos)
+  }
+
+  private def newFunctionBuilder(functionID: FunctionID)(
+      implicit ctx: WasmContext): FunctionBuilder = {
+    newFunctionBuilder(functionID, OriginalName(functionID.toString()))
+  }
+
+  private def genStringLiteral()(implicit ctx: WasmContext): Unit = {
+    val fb = newFunctionBuilder(genFunctionID.stringLiteral)
+    val offsetParam = fb.addParam("offset", Int32)
+    val sizeParam = fb.addParam("size", Int32)
+    val stringIndexParam = fb.addParam("stringIndex", Int32)
+    fb.setResultType(RefType.any)
+
+    val str = fb.addLocal("str", RefType.any)
+
+    fb.block(RefType.any) { cacheHit =>
+      fb += GlobalGet(genGlobalID.stringLiteralCache)
+      fb += LocalGet(stringIndexParam)
+      fb += ArrayGet(genTypeID.anyArray)
+
+      fb += BrOnNonNull(cacheHit)
+
+      // cache miss, create a new string and cache it
+      fb += GlobalGet(genGlobalID.stringLiteralCache)
+      fb += LocalGet(stringIndexParam)
+
+      fb += LocalGet(offsetParam)
+      fb += LocalGet(sizeParam)
+      fb += ArrayNewData(genTypeID.i16Array, genDataID.string)
+      fb += Call(genFunctionID.createStringFromData)
+      fb += LocalTee(str)
+      fb += ArraySet(genTypeID.anyArray)
+
+      fb += LocalGet(str)
+    }
+
+    fb.buildAndAddToModule()
+  }
+
+  /** `createStringFromData: (ref array u16) -> (ref any)` (representing a `string`). */
+  private def genCreateStringFromData()(implicit ctx: WasmContext): Unit = {
+    val dataType = RefType(genTypeID.i16Array)
+
+    val fb = newFunctionBuilder(genFunctionID.createStringFromData)
+    val dataParam = fb.addParam("data", dataType)
+    fb.setResultType(RefType.any)
+
+    val lenLocal = fb.addLocal("len", Int32)
+    val iLocal = fb.addLocal("i", Int32)
+    val resultLocal = fb.addLocal("result", RefType.any)
+
+    // len := data.length
+    fb += LocalGet(dataParam)
+    fb += ArrayLen
+    fb += LocalSet(lenLocal)
+
+    // i := 0
+    fb += I32Const(0)
+    fb += LocalSet(iLocal)
+
+    // result := ""
+    fb += GlobalGet(genGlobalID.emptyString)
+    fb += LocalSet(resultLocal)
+
+    fb.loop() { labelLoop =>
+      // if i == len
+      fb += LocalGet(iLocal)
+      fb += LocalGet(lenLocal)
+      fb += I32Eq
+      fb.ifThen() {
+        // then return result
+        fb += LocalGet(resultLocal)
+        fb += Return
+      }
+
+      // result := concat(result, charToString(data(i)))
+      fb += LocalGet(resultLocal)
+      fb += LocalGet(dataParam)
+      fb += LocalGet(iLocal)
+      fb += ArrayGetU(genTypeID.i16Array)
+      fb += Call(genFunctionID.charToString)
+      fb += Call(genFunctionID.stringConcat)
+      fb += LocalSet(resultLocal)
+
+      // i := i + 1
+      fb += LocalGet(iLocal)
+      fb += I32Const(1)
+      fb += I32Add
+      fb += LocalSet(iLocal)
+
+      // loop back to the beginning
+      fb += Br(labelLoop)
+    } // end loop $loop
+    fb += Unreachable
+
+    fb.buildAndAddToModule()
+  }
+
+  /** `typeDataName: (ref typeData) -> (ref any)` (representing a `string`).
+   *
+   *  Initializes the `name` field of the given `typeData` if that was not done yet, and returns its
+   *  value.
+   *
+   *  The computed value is specified by `java.lang.Class.getName()`. See also the documentation on
+   *  [[Names.StructFieldIdx.typeData.name]] for details.
+   *
+   *  @see
+   *    [[https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/lang/Class.html#getName()]]
+   */
+  private def genTypeDataName()(implicit ctx: WasmContext): Unit = {
+    val typeDataType = RefType(genTypeID.typeData)
+    val nameDataType = RefType(genTypeID.i16Array)
+
+    val fb = newFunctionBuilder(genFunctionID.typeDataName)
+    val typeDataParam = fb.addParam("typeData", typeDataType)
+    fb.setResultType(RefType.any)
+
+    val componentTypeDataLocal = fb.addLocal("componentTypeData", typeDataType)
+    val componentNameDataLocal = fb.addLocal("componentNameData", nameDataType)
+    val firstCharLocal = fb.addLocal("firstChar", Int32)
+    val nameLocal = fb.addLocal("name", RefType.any)
+
+    fb.block(RefType.any) { alreadyInitializedLabel =>
+      // br_on_non_null $alreadyInitialized typeData.name
+      fb += LocalGet(typeDataParam)
+      fb += StructGet(genTypeID.typeData, genFieldID.typeData.name)
+      fb += BrOnNonNull(alreadyInitializedLabel)
+
+      // for the STRUCT_SET typeData.name near the end
+      fb += LocalGet(typeDataParam)
+
+      // if typeData.kind == KindArray
+      fb += LocalGet(typeDataParam)
+      fb += StructGet(genTypeID.typeData, genFieldID.typeData.kind)
+      fb += I32Const(KindArray)
+      fb += I32Eq
+      fb.ifThenElse(RefType.any) {
+        // it is an array; compute its name from the component type name
+
+        // <top of stack> := "[", for the CALL to stringConcat near the end
+        fb += I32Const('['.toInt)
+        fb += Call(genFunctionID.charToString)
+
+        // componentTypeData := ref_as_non_null(typeData.componentType)
+        fb += LocalGet(typeDataParam)
+        fb += StructGet(
+          genTypeID.typeData,
+          genFieldID.typeData.componentType
+        )
+        fb += RefAsNonNull
+        fb += LocalSet(componentTypeDataLocal)
+
+        // switch (componentTypeData.kind)
+        // the result of this switch is the string that must come after "["
+        fb.switch(RefType.any) { () =>
+          // scrutinee
+          fb += LocalGet(componentTypeDataLocal)
+          fb += StructGet(genTypeID.typeData, genFieldID.typeData.kind)
+        }(
+          List(KindBoolean) -> { () =>
+            fb += I32Const('Z'.toInt)
+            fb += Call(genFunctionID.charToString)
+          },
+          List(KindChar) -> { () =>
+            fb += I32Const('C'.toInt)
+            fb += Call(genFunctionID.charToString)
+          },
+          List(KindByte) -> { () =>
+            fb += I32Const('B'.toInt)
+            fb += Call(genFunctionID.charToString)
+          },
+          List(KindShort) -> { () =>
+            fb += I32Const('S'.toInt)
+            fb += Call(genFunctionID.charToString)
+          },
+          List(KindInt) -> { () =>
+            fb += I32Const('I'.toInt)
+            fb += Call(genFunctionID.charToString)
+          },
+          List(KindLong) -> { () =>
+            fb += I32Const('J'.toInt)
+            fb += Call(genFunctionID.charToString)
+          },
+          List(KindFloat) -> { () =>
+            fb += I32Const('F'.toInt)
+            fb += Call(genFunctionID.charToString)
+          },
+          List(KindDouble) -> { () =>
+            fb += I32Const('D'.toInt)
+            fb += Call(genFunctionID.charToString)
+          },
+          List(KindArray) -> { () =>
+            // the component type is an array; get its own name
+            fb += LocalGet(componentTypeDataLocal)
+            fb += Call(genFunctionID.typeDataName)
+          }
+        ) { () =>
+          // default: the component type is neither a primitive nor an array;
+          // concatenate "L" + <its own name> + ";"
+          fb += I32Const('L'.toInt)
+          fb += Call(genFunctionID.charToString)
+          fb += LocalGet(componentTypeDataLocal)
+          fb += Call(genFunctionID.typeDataName)
+          fb += Call(genFunctionID.stringConcat)
+          fb += I32Const(';'.toInt)
+          fb += Call(genFunctionID.charToString)
+          fb += Call(genFunctionID.stringConcat)
+        }
+
+        // At this point, the stack contains "[" and the string that must be concatenated with it
+        fb += Call(genFunctionID.stringConcat)
+      } {
+        // it is not an array; its name is stored in nameData
+        for (
+          idx <- List(
+            genFieldID.typeData.nameOffset,
+            genFieldID.typeData.nameSize,
+            genFieldID.typeData.nameStringIndex
+          )
+        ) {
+          fb += LocalGet(typeDataParam)
+          fb += StructGet(genTypeID.typeData, idx)
+        }
+        fb += Call(genFunctionID.stringLiteral)
+      }
+
+      // typeData.name := <top of stack> ; leave it on the stack
+      fb += LocalTee(nameLocal)
+      fb += StructSet(genTypeID.typeData, genFieldID.typeData.name)
+      fb += LocalGet(nameLocal)
+    }
+
+    fb.buildAndAddToModule()
+  }
+
+  /** `createClassOf: (ref typeData) -> (ref jlClass)`.
+   *
+   *  Creates the unique `java.lang.Class` instance associated with the given `typeData`, stores it
+   *  in its `classOfValue` field, and returns it.
+   *
+   *  Must be called only if the `classOfValue` of the typeData is null. All call sites must deal
+   *  with the non-null case as a fast-path.
+   */
+  private def genCreateClassOf()(implicit ctx: WasmContext): Unit = {
+    val typeDataType = RefType(genTypeID.typeData)
+
+    val fb = newFunctionBuilder(genFunctionID.createClassOf)
+    val typeDataParam = fb.addParam("typeData", typeDataType)
+    fb.setResultType(RefType(genTypeID.ClassStruct))
+
+    val classInstanceLocal = fb.addLocal("classInstance", RefType(genTypeID.ClassStruct))
+
+    // classInstance := newDefault$java.lang.Class()
+    // leave it on the stack for the constructor call
+    fb += Call(genFunctionID.newDefault(ClassClass))
+    fb += LocalTee(classInstanceLocal)
+
+    /* The JS object containing metadata to pass as argument to the `jl.Class` constructor.
+     * Specified by https://lampwww.epfl.ch/~doeraene/sjsir-semantics/#sec-sjsir-createclassdataof
+     * Leave it on the stack.
+     */
+    fb += Call(genFunctionID.jsNewObject)
+    // "__typeData": typeData (TODO hide this better? although nobody will notice anyway)
+    // (this is used by `isAssignableFromExternal`)
+    fb ++= ctx.stringPool.getConstantStringInstr("__typeData")
+    fb += LocalGet(typeDataParam)
+    fb += Call(genFunctionID.jsObjectPush)
+    // "name": typeDataName(typeData)
+    fb ++= ctx.stringPool.getConstantStringInstr("name")
+    fb += LocalGet(typeDataParam)
+    fb += Call(genFunctionID.typeDataName)
+    fb += Call(genFunctionID.jsObjectPush)
+    // "isPrimitive": (typeData.kind <= KindLastPrimitive)
+    fb ++= ctx.stringPool.getConstantStringInstr("isPrimitive")
+    fb += LocalGet(typeDataParam)
+    fb += StructGet(genTypeID.typeData, genFieldID.typeData.kind)
+    fb += I32Const(KindLastPrimitive)
+    fb += I32LeU
+    fb += Call(genFunctionID.box(BooleanRef))
+    fb += Call(genFunctionID.jsObjectPush)
+    // "isArrayClass": (typeData.kind == KindArray)
+    fb ++= ctx.stringPool.getConstantStringInstr("isArrayClass")
+    fb += LocalGet(typeDataParam)
+    fb += StructGet(genTypeID.typeData, genFieldID.typeData.kind)
+    fb += I32Const(KindArray)
+    fb += I32Eq
+    fb += Call(genFunctionID.box(BooleanRef))
+    fb += Call(genFunctionID.jsObjectPush)
+    // "isInterface": (typeData.kind == KindInterface)
+    fb ++= ctx.stringPool.getConstantStringInstr("isInterface")
+    fb += LocalGet(typeDataParam)
+    fb += StructGet(genTypeID.typeData, genFieldID.typeData.kind)
+    fb += I32Const(KindInterface)
+    fb += I32Eq
+    fb += Call(genFunctionID.box(BooleanRef))
+    fb += Call(genFunctionID.jsObjectPush)
+    // "isInstance": closure(isInstance, typeData)
+    fb ++= ctx.stringPool.getConstantStringInstr("isInstance")
+    fb += ctx.refFuncWithDeclaration(genFunctionID.isInstance)
+    fb += LocalGet(typeDataParam)
+    fb += Call(genFunctionID.closure)
+    fb += Call(genFunctionID.jsObjectPush)
+    // "isAssignableFrom": closure(isAssignableFrom, typeData)
+    fb ++= ctx.stringPool.getConstantStringInstr("isAssignableFrom")
+    fb += ctx.refFuncWithDeclaration(genFunctionID.isAssignableFromExternal)
+    fb += LocalGet(typeDataParam)
+    fb += Call(genFunctionID.closure)
+    fb += Call(genFunctionID.jsObjectPush)
+    // "checkCast": closure(checkCast, typeData)
+    fb ++= ctx.stringPool.getConstantStringInstr("checkCast")
+    fb += ctx.refFuncWithDeclaration(genFunctionID.checkCast)
+    fb += LocalGet(typeDataParam)
+    fb += Call(genFunctionID.closure)
+    fb += Call(genFunctionID.jsObjectPush)
+    // "getComponentType": closure(getComponentType, typeData)
+    fb ++= ctx.stringPool.getConstantStringInstr("getComponentType")
+    fb += ctx.refFuncWithDeclaration(genFunctionID.getComponentType)
+    fb += LocalGet(typeDataParam)
+    fb += Call(genFunctionID.closure)
+    fb += Call(genFunctionID.jsObjectPush)
+    // "newArrayOfThisClass": closure(newArrayOfThisClass, typeData)
+    fb ++= ctx.stringPool.getConstantStringInstr("newArrayOfThisClass")
+    fb += ctx.refFuncWithDeclaration(genFunctionID.newArrayOfThisClass)
+    fb += LocalGet(typeDataParam)
+    fb += Call(genFunctionID.closure)
+    fb += Call(genFunctionID.jsObjectPush)
+
+    // Call java.lang.Class::<init>(dataObject)
+    fb += Call(
+      genFunctionID.forMethod(
+        MemberNamespace.Constructor,
+        ClassClass,
+        SpecialNames.AnyArgConstructorName
+      )
+    )
+
+    // typeData.classOfValue := classInstance
+    fb += LocalGet(typeDataParam)
+    fb += LocalGet(classInstanceLocal)
+    fb += StructSet(genTypeID.typeData, genFieldID.typeData.classOfValue)
+
+    // <top-of-stack> := classInstance for the implicit return
+    fb += LocalGet(classInstanceLocal)
+
+    fb.buildAndAddToModule()
+  }
+
+  /** `getClassOf: (ref typeData) -> (ref jlClass)`.
+   *
+   *  Initializes the `java.lang.Class` instance associated with the given `typeData` if not already
+   *  done, and returns it.
+   */
+  private def genGetClassOf()(implicit ctx: WasmContext): Unit = {
+    val typeDataType = RefType(genTypeID.typeData)
+
+    val fb = newFunctionBuilder(genFunctionID.getClassOf)
+    val typeDataParam = fb.addParam("typeData", typeDataType)
+    fb.setResultType(RefType(genTypeID.ClassStruct))
+
+    fb.block(RefType(genTypeID.ClassStruct)) { alreadyInitializedLabel =>
+      // fast path
+      fb += LocalGet(typeDataParam)
+      fb += StructGet(genTypeID.typeData, genFieldID.typeData.classOfValue)
+      fb += BrOnNonNull(alreadyInitializedLabel)
+      // slow path
+      fb += LocalGet(typeDataParam)
+      fb += Call(genFunctionID.createClassOf)
+    } // end bock alreadyInitializedLabel
+
+    fb.buildAndAddToModule()
+  }
+
+  /** `arrayTypeData: (ref typeData), i32 -> (ref vtable.java.lang.Object)`.
+   *
+   *  Returns the typeData/vtable of an array with `dims` dimensions over the given typeData. `dims`
+   *  must be be strictly positive.
+   */
+  private def genArrayTypeData()(implicit ctx: WasmContext): Unit = {
+    val typeDataType = RefType(genTypeID.typeData)
+    val objectVTableType = RefType(genTypeID.ObjectVTable)
+
+    /* Array classes extend Cloneable, Serializable and Object.
+     * Filter out the ones that do not have run-time type info at all, as
+     * we do for other classes.
+     */
+    val strictAncestors =
+      List(CloneableClass, SerializableClass, ObjectClass)
+        .filter(name => ctx.getClassInfoOption(name).exists(_.hasRuntimeTypeInfo))
+
+    val fb = newFunctionBuilder(genFunctionID.arrayTypeData)
+    val typeDataParam = fb.addParam("typeData", typeDataType)
+    val dimsParam = fb.addParam("dims", Int32)
+    fb.setResultType(objectVTableType)
+
+    val arrayTypeDataLocal = fb.addLocal("arrayTypeData", objectVTableType)
+
+    fb.loop() { loopLabel =>
+      fb.block(objectVTableType) { arrayOfIsNonNullLabel =>
+        // br_on_non_null $arrayOfIsNonNull typeData.arrayOf
+        fb += LocalGet(typeDataParam)
+        fb += StructGet(
+          genTypeID.typeData,
+          genFieldID.typeData.arrayOf
+        )
+        fb += BrOnNonNull(arrayOfIsNonNullLabel)
+
+        // <top-of-stack> := typeData ; for the <old typeData>.arrayOf := ... later on
+        fb += LocalGet(typeDataParam)
+
+        // typeData := new typeData(...)
+        fb += I32Const(0) // nameOffset
+        fb += I32Const(0) // nameSize
+        fb += I32Const(0) // nameStringIndex
+        fb += I32Const(KindArray) // kind = KindArray
+        fb += I32Const(0) // specialInstanceTypes = 0
+
+        // strictAncestors
+        for (strictAncestor <- strictAncestors)
+          fb += GlobalGet(genGlobalID.forVTable(strictAncestor))
+        fb += ArrayNewFixed(
+          genTypeID.typeDataArray,
+          strictAncestors.size
+        )
+
+        fb += LocalGet(typeDataParam) // componentType
+        fb += RefNull(HeapType.None) // name
+        fb += RefNull(HeapType.None) // classOf
+        fb += RefNull(HeapType.None) // arrayOf
+
+        // clone
+        fb.switch(RefType(genTypeID.cloneFunctionType)) { () =>
+          fb += LocalGet(typeDataParam)
+          fb += StructGet(genTypeID.typeData, genFieldID.typeData.kind)
+        }(
+          List(KindBoolean) -> { () =>
+            fb += ctx.refFuncWithDeclaration(genFunctionID.cloneArray(BooleanRef))
+          },
+          List(KindChar) -> { () =>
+            fb += ctx.refFuncWithDeclaration(genFunctionID.cloneArray(CharRef))
+          },
+          List(KindByte) -> { () =>
+            fb += ctx.refFuncWithDeclaration(genFunctionID.cloneArray(ByteRef))
+          },
+          List(KindShort) -> { () =>
+            fb += ctx.refFuncWithDeclaration(genFunctionID.cloneArray(ShortRef))
+          },
+          List(KindInt) -> { () =>
+            fb += ctx.refFuncWithDeclaration(genFunctionID.cloneArray(IntRef))
+          },
+          List(KindLong) -> { () =>
+            fb += ctx.refFuncWithDeclaration(genFunctionID.cloneArray(LongRef))
+          },
+          List(KindFloat) -> { () =>
+            fb += ctx.refFuncWithDeclaration(genFunctionID.cloneArray(FloatRef))
+          },
+          List(KindDouble) -> { () =>
+            fb += ctx.refFuncWithDeclaration(genFunctionID.cloneArray(DoubleRef))
+          }
+        ) { () =>
+          fb += ctx.refFuncWithDeclaration(
+            genFunctionID.cloneArray(ClassRef(ObjectClass))
+          )
+        }
+
+        // isJSClassInstance
+        fb += RefNull(HeapType.NoFunc)
+
+        // reflectiveProxies, empty since all methods of array classes exist in jl.Object
+        fb += ArrayNewFixed(genTypeID.reflectiveProxies, 0)
+
+        val objectClassInfo = ctx.getClassInfo(ObjectClass)
+        fb ++= objectClassInfo.tableEntries.map { methodName =>
+          ctx.refFuncWithDeclaration(objectClassInfo.resolvedMethodInfos(methodName).tableEntryID)
+        }
+        fb += StructNew(genTypeID.ObjectVTable)
+        fb += LocalTee(arrayTypeDataLocal)
+
+        // <old typeData>.arrayOf := typeData
+        fb += StructSet(genTypeID.typeData, genFieldID.typeData.arrayOf)
+
+        // put arrayTypeData back on the stack
+        fb += LocalGet(arrayTypeDataLocal)
+      } // end block $arrayOfIsNonNullLabel
+
+      // dims := dims - 1 -- leave dims on the stack
+      fb += LocalGet(dimsParam)
+      fb += I32Const(1)
+      fb += I32Sub
+      fb += LocalTee(dimsParam)
+
+      // if dims == 0 then
+      //   return typeData.arrayOf (which is on the stack)
+      fb += I32Eqz
+      fb.ifThen(FunctionType(List(objectVTableType), List(objectVTableType))) {
+        fb += Return
+      }
+
+      // typeData := typeData.arrayOf (which is on the stack), then loop back to the beginning
+      fb += LocalSet(typeDataParam)
+      fb += Br(loopLabel)
+    } // end loop $loop
+    fb += Unreachable
+
+    fb.buildAndAddToModule()
+  }
+
+  /** `isInstance: (ref typeData), anyref -> anyref` (a boxed boolean).
+   *
+   *  Tests whether the given value is a non-null instance of the given type.
+   *
+   *  Specified by `"isInstance"` at
+   *  [[https://lampwww.epfl.ch/~doeraene/sjsir-semantics/#sec-sjsir-createclassdataof]].
+   */
+  private def genIsInstance()(implicit ctx: WasmContext): Unit = {
+    import genFieldID.typeData._
+
+    val typeDataType = RefType(genTypeID.typeData)
+    val objectRefType = RefType(genTypeID.ObjectStruct)
+
+    val fb = newFunctionBuilder(genFunctionID.isInstance)
+    val typeDataParam = fb.addParam("typeData", typeDataType)
+    val valueParam = fb.addParam("value", RefType.anyref)
+    fb.setResultType(anyref)
+
+    val valueNonNullLocal = fb.addLocal("valueNonNull", RefType.any)
+    val specialInstanceTypesLocal = fb.addLocal("specialInstanceTypes", Int32)
+
+    // switch (typeData.kind)
+    fb.switch(Int32) { () =>
+      fb += LocalGet(typeDataParam)
+      fb += StructGet(genTypeID.typeData, kind)
+    }(
+      // case anyPrimitiveKind => false
+      (KindVoid to KindLastPrimitive).toList -> { () =>
+        fb += I32Const(0)
+      },
+      // case KindObject => value ne null
+      List(KindObject) -> { () =>
+        fb += LocalGet(valueParam)
+        fb += RefIsNull
+        fb += I32Eqz
+      },
+      // for each boxed class, the corresponding primitive type test
+      List(KindBoxedUnit) -> { () =>
+        fb += LocalGet(valueParam)
+        fb += Call(genFunctionID.isUndef)
+      },
+      List(KindBoxedBoolean) -> { () =>
+        fb += LocalGet(valueParam)
+        fb += Call(genFunctionID.typeTest(BooleanRef))
+      },
+      List(KindBoxedCharacter) -> { () =>
+        fb += LocalGet(valueParam)
+        val structTypeID = genTypeID.forClass(SpecialNames.CharBoxClass)
+        fb += RefTest(RefType(structTypeID))
+      },
+      List(KindBoxedByte) -> { () =>
+        fb += LocalGet(valueParam)
+        fb += Call(genFunctionID.typeTest(ByteRef))
+      },
+      List(KindBoxedShort) -> { () =>
+        fb += LocalGet(valueParam)
+        fb += Call(genFunctionID.typeTest(ShortRef))
+      },
+      List(KindBoxedInteger) -> { () =>
+        fb += LocalGet(valueParam)
+        fb += Call(genFunctionID.typeTest(IntRef))
+      },
+      List(KindBoxedLong) -> { () =>
+        fb += LocalGet(valueParam)
+        val structTypeID = genTypeID.forClass(SpecialNames.LongBoxClass)
+        fb += RefTest(RefType(structTypeID))
+      },
+      List(KindBoxedFloat) -> { () =>
+        fb += LocalGet(valueParam)
+        fb += Call(genFunctionID.typeTest(FloatRef))
+      },
+      List(KindBoxedDouble) -> { () =>
+        fb += LocalGet(valueParam)
+        fb += Call(genFunctionID.typeTest(DoubleRef))
+      },
+      List(KindBoxedString) -> { () =>
+        fb += LocalGet(valueParam)
+        fb += Call(genFunctionID.isString)
+      },
+      // case KindJSType => call typeData.isJSClassInstance(value) or throw if it is null
+      List(KindJSType) -> { () =>
+        fb.block(RefType.anyref) { isJSClassInstanceIsNull =>
+          // Load value as the argument to the function
+          fb += LocalGet(valueParam)
+
+          // Load the function reference; break if null
+          fb += LocalGet(typeDataParam)
+          fb += StructGet(genTypeID.typeData, isJSClassInstance)
+          fb += BrOnNull(isJSClassInstanceIsNull)
+
+          // Call the function
+          fb += CallRef(genTypeID.isJSClassInstanceFuncType)
+          fb += Call(genFunctionID.box(BooleanRef))
+          fb += Return
+        }
+        fb += Drop // drop `value` which was left on the stack
+
+        // throw new TypeError("...")
+        fb ++= ctx.stringPool.getConstantStringInstr("TypeError")
+        fb += Call(genFunctionID.jsGlobalRefGet)
+        fb += Call(genFunctionID.jsNewArray)
+        fb ++= ctx.stringPool.getConstantStringInstr(
+          "Cannot call isInstance() on a Class representing a JS trait/object"
+        )
+        fb += Call(genFunctionID.jsArrayPush)
+        fb += Call(genFunctionID.jsNew)
+        fb += ExternConvertAny
+        fb += Throw(genTagID.exception)
+      }
+    ) { () =>
+      // case _ =>
+
+      // valueNonNull := as_non_null value; return false if null
+      fb.block(RefType.any) { nonNullLabel =>
+        fb += LocalGet(valueParam)
+        fb += BrOnNonNull(nonNullLabel)
+        fb += GlobalGet(genGlobalID.bFalse)
+        fb += Return
+      }
+      fb += LocalSet(valueNonNullLocal)
+
+      /* If `typeData` represents an ancestor of a hijacked classes, we have to
+       * answer `true` if `valueNonNull` is a primitive instance of any of the
+       * hijacked classes that ancestor class/interface. For example, for
+       * `Comparable`, we have to answer `true` if `valueNonNull` is a primitive
+       * boolean, number or string.
+       *
+       * To do that, we use `jsValueType` and `typeData.specialInstanceTypes`.
+       *
+       * We test whether `jsValueType(valueNonNull)` is in the set represented by
+       * `specialInstanceTypes`. Since the latter is a bitset where the bit
+       * indices correspond to the values returned by `jsValueType`, we have to
+       * test whether
+       *
+       * ((1 << jsValueType(valueNonNull)) & specialInstanceTypes) != 0
+       *
+       * Since computing `jsValueType` is somewhat expensive, we first test
+       * whether `specialInstanceTypes != 0` before calling `jsValueType`.
+       *
+       * There is a more elaborated concrete example of this algorithm in
+       * `genInstanceTest`.
+       */
+      fb += LocalGet(typeDataParam)
+      fb += StructGet(genTypeID.typeData, specialInstanceTypes)
+      fb += LocalTee(specialInstanceTypesLocal)
+      fb += I32Const(0)
+      fb += I32Ne
+      fb.ifThen() {
+        // Load (1 << jsValueType(valueNonNull))
+        fb += I32Const(1)
+        fb += LocalGet(valueNonNullLocal)
+        fb += Call(genFunctionID.jsValueType)
+        fb += I32Shl
+
+        // if ((... & specialInstanceTypes) != 0)
+        fb += LocalGet(specialInstanceTypesLocal)
+        fb += I32And
+        fb += I32Const(0)
+        fb += I32Ne
+        fb.ifThen() {
+          // then return true
+          fb += I32Const(1)
+          fb += Call(genFunctionID.box(BooleanRef))
+          fb += Return
+        }
+      }
+
+      // Get the vtable and delegate to isAssignableFrom
+
+      // Load typeData
+      fb += LocalGet(typeDataParam)
+
+      // Load the vtable; return false if it is not one of our object
+      fb.block(objectRefType) { ourObjectLabel =>
+        // Try cast to jl.Object
+        fb += LocalGet(valueNonNullLocal)
+        fb += BrOnCast(ourObjectLabel, RefType.any, objectRefType)
+
+        // on cast fail, return false
+        fb += GlobalGet(genGlobalID.bFalse)
+        fb += Return
+      }
+      fb += StructGet(genTypeID.ObjectStruct, genFieldID.objStruct.vtable)
+
+      // Call isAssignableFrom
+      fb += Call(genFunctionID.isAssignableFrom)
+    }
+
+    fb += Call(genFunctionID.box(BooleanRef))
+
+    fb.buildAndAddToModule()
+  }
+
+  /** `isAssignableFromExternal: (ref typeData), anyref -> i32` (a boolean).
+   *
+   *  This is the underlying func for the `isAssignableFrom()` closure inside class data objects.
+   */
+  private def genIsAssignableFromExternal()(implicit ctx: WasmContext): Unit = {
+    val typeDataType = RefType(genTypeID.typeData)
+
+    val fb = newFunctionBuilder(genFunctionID.isAssignableFromExternal)
+    val typeDataParam = fb.addParam("typeData", typeDataType)
+    val fromParam = fb.addParam("from", RefType.anyref)
+    fb.setResultType(anyref)
+
+    // load typeData
+    fb += LocalGet(typeDataParam)
+
+    // load ref.cast<typeData> from["__typeData"] (as a JS selection)
+    fb += LocalGet(fromParam)
+    fb ++= ctx.stringPool.getConstantStringInstr("__typeData")
+    fb += Call(genFunctionID.jsSelect)
+    fb += RefCast(RefType(typeDataType.heapType))
+
+    // delegate to isAssignableFrom
+    fb += Call(genFunctionID.isAssignableFrom)
+    fb += Call(genFunctionID.box(BooleanRef))
+
+    fb.buildAndAddToModule()
+  }
+
+  /** `isAssignableFrom: (ref typeData), (ref typeData) -> i32` (a boolean).
+   *
+   *  Specified by `java.lang.Class.isAssignableFrom(Class)`.
+   */
+  private def genIsAssignableFrom()(implicit ctx: WasmContext): Unit = {
+    import genFieldID.typeData._
+
+    val typeDataType = RefType(genTypeID.typeData)
+
+    val fb = newFunctionBuilder(genFunctionID.isAssignableFrom)
+    val typeDataParam = fb.addParam("typeData", typeDataType)
+    val fromTypeDataParam = fb.addParam("fromTypeData", typeDataType)
+    fb.setResultType(Int32)
+
+    val fromAncestorsLocal = fb.addLocal("fromAncestors", RefType(genTypeID.typeDataArray))
+    val lenLocal = fb.addLocal("len", Int32)
+    val iLocal = fb.addLocal("i", Int32)
+
+    // if (fromTypeData eq typeData)
+    fb += LocalGet(fromTypeDataParam)
+    fb += LocalGet(typeDataParam)
+    fb += RefEq
+    fb.ifThen() {
+      // then return true
+      fb += I32Const(1)
+      fb += Return
+    }
+
+    // "Tail call" loop for diving into array component types
+    fb.loop(Int32) { loopForArrayLabel =>
+      // switch (typeData.kind)
+      fb.switch(Int32) { () =>
+        // typeData.kind
+        fb += LocalGet(typeDataParam)
+        fb += StructGet(genTypeID.typeData, kind)
+      }(
+        // case anyPrimitiveKind => return false
+        (KindVoid to KindLastPrimitive).toList -> { () =>
+          fb += I32Const(0)
+        },
+        // case KindArray => check that from is an array, recurse into component types
+        List(KindArray) -> { () =>
+          fb.block() { fromComponentTypeIsNullLabel =>
+            // fromTypeData := fromTypeData.componentType; jump out if null
+            fb += LocalGet(fromTypeDataParam)
+            fb += StructGet(genTypeID.typeData, componentType)
+            fb += BrOnNull(fromComponentTypeIsNullLabel)
+            fb += LocalSet(fromTypeDataParam)
+
+            // typeData := ref.as_non_null typeData.componentType (OK because KindArray)
+            fb += LocalGet(typeDataParam)
+            fb += StructGet(genTypeID.typeData, componentType)
+            fb += RefAsNonNull
+            fb += LocalSet(typeDataParam)
+
+            // loop back ("tail call")
+            fb += Br(loopForArrayLabel)
+          }
+
+          // return false
+          fb += I32Const(0)
+        },
+        // case KindObject => return (fromTypeData.kind > KindLastPrimitive)
+        List(KindObject) -> { () =>
+          fb += LocalGet(fromTypeDataParam)
+          fb += StructGet(genTypeID.typeData, kind)
+          fb += I32Const(KindLastPrimitive)
+          fb += I32GtU
+        }
+      ) { () =>
+        // All other cases: test whether `fromTypeData.strictAncestors` contains `typeData`
+
+        fb.block() { fromAncestorsIsNullLabel =>
+          // fromAncestors := fromTypeData.strictAncestors; go to fromAncestorsIsNull if null
+          fb += LocalGet(fromTypeDataParam)
+          fb += StructGet(genTypeID.typeData, strictAncestors)
+          fb += BrOnNull(fromAncestorsIsNullLabel)
+          fb += LocalTee(fromAncestorsLocal)
+
+          // if fromAncestors contains typeData, return true
+
+          // len := fromAncestors.length
+          fb += ArrayLen
+          fb += LocalSet(lenLocal)
+
+          // i := 0
+          fb += I32Const(0)
+          fb += LocalSet(iLocal)
+
+          // while (i != len)
+          fb.whileLoop() {
+            fb += LocalGet(iLocal)
+            fb += LocalGet(lenLocal)
+            fb += I32Ne
+          } {
+            // if (fromAncestors[i] eq typeData)
+            fb += LocalGet(fromAncestorsLocal)
+            fb += LocalGet(iLocal)
+            fb += ArrayGet(genTypeID.typeDataArray)
+            fb += LocalGet(typeDataParam)
+            fb += RefEq
+            fb.ifThen() {
+              // then return true
+              fb += I32Const(1)
+              fb += Return
+            }
+
+            // i := i + 1
+            fb += LocalGet(iLocal)
+            fb += I32Const(1)
+            fb += I32Add
+            fb += LocalSet(iLocal)
+          }
+        }
+
+        // from.strictAncestors is null or does not contain typeData
+        // return false
+        fb += I32Const(0)
+      }
+    }
+
+    fb.buildAndAddToModule()
+  }
+
+  /** `checkCast: (ref typeData), anyref -> anyref`.
+   *
+   *  Casts the given value to the given type; subject to undefined behaviors.
+   */
+  private def genCheckCast()(implicit ctx: WasmContext): Unit = {
+    val typeDataType = RefType(genTypeID.typeData)
+
+    val fb = newFunctionBuilder(genFunctionID.checkCast)
+    val typeDataParam = fb.addParam("typeData", typeDataType)
+    val valueParam = fb.addParam("value", RefType.anyref)
+    fb.setResultType(RefType.anyref)
+
+    /* Given that we only implement `CheckedBehavior.Unchecked` semantics for
+     * now, this is always the identity.
+     */
+
+    fb += LocalGet(valueParam)
+
+    fb.buildAndAddToModule()
+  }
+
+  /** `getComponentType: (ref typeData) -> (ref null jlClass)`.
+   *
+   *  This is the underlying func for the `getComponentType()` closure inside class data objects.
+   */
+  private def genGetComponentType()(implicit ctx: WasmContext): Unit = {
+    val typeDataType = RefType(genTypeID.typeData)
+
+    val fb = newFunctionBuilder(genFunctionID.getComponentType)
+    val typeDataParam = fb.addParam("typeData", typeDataType)
+    fb.setResultType(RefType.nullable(genTypeID.ClassStruct))
+
+    val componentTypeDataLocal = fb.addLocal("componentTypeData", typeDataType)
+
+    fb.block() { nullResultLabel =>
+      // Try and extract non-null component type data
+      fb += LocalGet(typeDataParam)
+      fb += StructGet(genTypeID.typeData, genFieldID.typeData.componentType)
+      fb += BrOnNull(nullResultLabel)
+      // Get the corresponding classOf
+      fb += Call(genFunctionID.getClassOf)
+      fb += Return
+    } // end block nullResultLabel
+    fb += RefNull(HeapType(genTypeID.ClassStruct))
+
+    fb.buildAndAddToModule()
+  }
+
+  /** `newArrayOfThisClass: (ref typeData), anyref -> (ref jlObject)`.
+   *
+   *  This is the underlying func for the `newArrayOfThisClass()` closure inside class data objects.
+   */
+  private def genNewArrayOfThisClass()(implicit ctx: WasmContext): Unit = {
+    val typeDataType = RefType(genTypeID.typeData)
+    val i32ArrayType = RefType(genTypeID.i32Array)
+
+    val fb = newFunctionBuilder(genFunctionID.newArrayOfThisClass)
+    val typeDataParam = fb.addParam("typeData", typeDataType)
+    val lengthsParam = fb.addParam("lengths", RefType.anyref)
+    fb.setResultType(RefType(genTypeID.ObjectStruct))
+
+    val lengthsLenLocal = fb.addLocal("lengthsLenLocal", Int32)
+    val lengthsValuesLocal = fb.addLocal("lengthsValues", i32ArrayType)
+    val iLocal = fb.addLocal("i", Int32)
+
+    // lengthsLen := lengths.length // as a JS field access
+    fb += LocalGet(lengthsParam)
+    fb ++= ctx.stringPool.getConstantStringInstr("length")
+    fb += Call(genFunctionID.jsSelect)
+    fb += Call(genFunctionID.unbox(IntRef))
+    fb += LocalTee(lengthsLenLocal)
+
+    // lengthsValues := array.new<i32Array> lengthsLen
+    fb += ArrayNewDefault(genTypeID.i32Array)
+    fb += LocalSet(lengthsValuesLocal)
+
+    // i := 0
+    fb += I32Const(0)
+    fb += LocalSet(iLocal)
+
+    // while (i != lengthsLen)
+    fb.whileLoop() {
+      fb += LocalGet(iLocal)
+      fb += LocalGet(lengthsLenLocal)
+      fb += I32Ne
+    } {
+      // lengthsValue[i] := lengths[i] (where the rhs is a JS field access)
+
+      fb += LocalGet(lengthsValuesLocal)
+      fb += LocalGet(iLocal)
+
+      fb += LocalGet(lengthsParam)
+      fb += LocalGet(iLocal)
+      fb += RefI31
+      fb += Call(genFunctionID.jsSelect)
+      fb += Call(genFunctionID.unbox(IntRef))
+
+      fb += ArraySet(genTypeID.i32Array)
+
+      // i += 1
+      fb += LocalGet(iLocal)
+      fb += I32Const(1)
+      fb += I32Add
+      fb += LocalSet(iLocal)
+    }
+
+    // return newArrayObject(arrayTypeData(typeData, lengthsLen), lengthsValues, 0)
+    fb += LocalGet(typeDataParam)
+    fb += LocalGet(lengthsLenLocal)
+    fb += Call(genFunctionID.arrayTypeData)
+    fb += LocalGet(lengthsValuesLocal)
+    fb += I32Const(0)
+    fb += Call(genFunctionID.newArrayObject)
+
+    fb.buildAndAddToModule()
+  }
+
+  /** `anyGetClass: (ref any) -> (ref null jlClass)`.
+   *
+   *  This is the implementation of `value.getClass()` when `value` can be an instance of a hijacked
+   *  class, i.e., a primitive.
+   *
+   *  For `number`s, the result is based on the actual value, as specified by
+   *  [[https://www.scala-js.org/doc/semantics.html#getclass]].
+   */
+  private def genAnyGetClass()(implicit ctx: WasmContext): Unit = {
+    val typeDataType = RefType(genTypeID.typeData)
+
+    val fb = newFunctionBuilder(genFunctionID.anyGetClass)
+    val valueParam = fb.addParam("value", RefType.any)
+    fb.setResultType(RefType.nullable(genTypeID.ClassStruct))
+
+    val typeDataLocal = fb.addLocal("typeData", typeDataType)
+    val doubleValueLocal = fb.addLocal("doubleValue", Float64)
+    val intValueLocal = fb.addLocal("intValue", Int32)
+    val ourObjectLocal = fb.addLocal("ourObject", RefType(genTypeID.ObjectStruct))
+
+    def getHijackedClassTypeDataInstr(className: ClassName): Instr =
+      GlobalGet(genGlobalID.forVTable(className))
+
+    fb.block(RefType.nullable(genTypeID.ClassStruct)) { nonNullClassOfLabel =>
+      fb.block(typeDataType) { gotTypeDataLabel =>
+        fb.block(RefType(genTypeID.ObjectStruct)) { ourObjectLabel =>
+          // if value is our object, jump to $ourObject
+          fb += LocalGet(valueParam)
+          fb += BrOnCast(
+            ourObjectLabel,
+            RefType.any,
+            RefType(genTypeID.ObjectStruct)
+          )
+
+          // switch(jsValueType(value)) { ... }
+          fb.switch(typeDataType) { () =>
+            // scrutinee
+            fb += LocalGet(valueParam)
+            fb += Call(genFunctionID.jsValueType)
+          }(
+            // case JSValueTypeFalse, JSValueTypeTrue => typeDataOf[jl.Boolean]
+            List(JSValueTypeFalse, JSValueTypeTrue) -> { () =>
+              fb += getHijackedClassTypeDataInstr(BoxedBooleanClass)
+            },
+            // case JSValueTypeString => typeDataOf[jl.String]
+            List(JSValueTypeString) -> { () =>
+              fb += getHijackedClassTypeDataInstr(BoxedStringClass)
+            },
+            // case JSValueTypeNumber => ...
+            List(JSValueTypeNumber) -> { () =>
+              /* For `number`s, the result is based on the actual value, as specified by
+               * [[https://www.scala-js.org/doc/semantics.html#getclass]].
+               */
+
+              // doubleValue := unboxDouble(value)
+              fb += LocalGet(valueParam)
+              fb += Call(genFunctionID.unbox(DoubleRef))
+              fb += LocalTee(doubleValueLocal)
+
+              // intValue := doubleValue.toInt
+              fb += I32TruncSatF64S
+              fb += LocalTee(intValueLocal)
+
+              // if same(intValue.toDouble, doubleValue) -- same bit pattern to avoid +0.0 == -0.0
+              fb += F64ConvertI32S
+              fb += I64ReinterpretF64
+              fb += LocalGet(doubleValueLocal)
+              fb += I64ReinterpretF64
+              fb += I64Eq
+              fb.ifThenElse(typeDataType) {
+                // then it is a Byte, a Short, or an Integer
+
+                // if intValue.toByte.toInt == intValue
+                fb += LocalGet(intValueLocal)
+                fb += I32Extend8S
+                fb += LocalGet(intValueLocal)
+                fb += I32Eq
+                fb.ifThenElse(typeDataType) {
+                  // then it is a Byte
+                  fb += getHijackedClassTypeDataInstr(BoxedByteClass)
+                } {
+                  // else, if intValue.toShort.toInt == intValue
+                  fb += LocalGet(intValueLocal)
+                  fb += I32Extend16S
+                  fb += LocalGet(intValueLocal)
+                  fb += I32Eq
+                  fb.ifThenElse(typeDataType) {
+                    // then it is a Short
+                    fb += getHijackedClassTypeDataInstr(BoxedShortClass)
+                  } {
+                    // else, it is an Integer
+                    fb += getHijackedClassTypeDataInstr(BoxedIntegerClass)
+                  }
+                }
+              } {
+                // else, it is a Float or a Double
+
+                // if doubleValue.toFloat.toDouble == doubleValue
+                fb += LocalGet(doubleValueLocal)
+                fb += F32DemoteF64
+                fb += F64PromoteF32
+                fb += LocalGet(doubleValueLocal)
+                fb += F64Eq
+                fb.ifThenElse(typeDataType) {
+                  // then it is a Float
+                  fb += getHijackedClassTypeDataInstr(BoxedFloatClass)
+                } {
+                  // else, if it is NaN
+                  fb += LocalGet(doubleValueLocal)
+                  fb += LocalGet(doubleValueLocal)
+                  fb += F64Ne
+                  fb.ifThenElse(typeDataType) {
+                    // then it is a Float
+                    fb += getHijackedClassTypeDataInstr(BoxedFloatClass)
+                  } {
+                    // else, it is a Double
+                    fb += getHijackedClassTypeDataInstr(BoxedDoubleClass)
+                  }
+                }
+              }
+            },
+            // case JSValueTypeUndefined => typeDataOf[jl.Void]
+            List(JSValueTypeUndefined) -> { () =>
+              fb += getHijackedClassTypeDataInstr(BoxedUnitClass)
+            }
+          ) { () =>
+            // case _ (JSValueTypeOther) => return null
+            fb += RefNull(HeapType(genTypeID.ClassStruct))
+            fb += Return
+          }
+
+          fb += Br(gotTypeDataLabel)
+        }
+
+        /* Now we have one of our objects. Normally we only have to get the
+         * vtable, but there are two exceptions. If the value is an instance of
+         * `jl.CharacterBox` or `jl.LongBox`, we must use the typeData of
+         * `jl.Character` or `jl.Long`, respectively.
+         */
+        fb += LocalTee(ourObjectLocal)
+        fb += RefTest(RefType(genTypeID.forClass(SpecialNames.CharBoxClass)))
+        fb.ifThenElse(typeDataType) {
+          fb += getHijackedClassTypeDataInstr(BoxedCharacterClass)
+        } {
+          fb += LocalGet(ourObjectLocal)
+          fb += RefTest(RefType(genTypeID.forClass(SpecialNames.LongBoxClass)))
+          fb.ifThenElse(typeDataType) {
+            fb += getHijackedClassTypeDataInstr(BoxedLongClass)
+          } {
+            fb += LocalGet(ourObjectLocal)
+            fb += StructGet(genTypeID.ObjectStruct, genFieldID.objStruct.vtable)
+          }
+        }
+      }
+
+      fb += Call(genFunctionID.getClassOf)
+    }
+
+    fb.buildAndAddToModule()
+  }
+
+  /** `newArrayObject`: `(ref typeData), (ref array i32), i32 -> (ref jl.Object)`.
+   *
+   *  The arguments are `arrayTypeData`, `lengths` and `lengthIndex`.
+   *
+   *  This recursive function creates a multi-dimensional array. The resulting array has type data
+   *  `arrayTypeData` and length `lengths(lengthIndex)`. If `lengthIndex < `lengths.length - 1`, its
+   *  elements are recursively initialized with `newArrayObject(arrayTypeData.componentType,
+   *  lengths, lengthIndex - 1)`.
+   */
+  private def genNewArrayObject()(implicit ctx: WasmContext): Unit = {
+    import genFieldID.typeData._
+
+    val typeDataType = RefType(genTypeID.typeData)
+    val i32ArrayType = RefType(genTypeID.i32Array)
+    val objectVTableType = RefType(genTypeID.ObjectVTable)
+    val arrayTypeDataType = objectVTableType
+    val itablesType = RefType.nullable(genTypeID.itables)
+    val nonNullObjectType = RefType(genTypeID.ObjectStruct)
+    val anyArrayType = RefType(genTypeID.anyArray)
+
+    val fb = newFunctionBuilder(genFunctionID.newArrayObject)
+    val arrayTypeDataParam = fb.addParam("arrayTypeData", arrayTypeDataType)
+    val lengthsParam = fb.addParam("lengths", i32ArrayType)
+    val lengthIndexParam = fb.addParam("lengthIndex", Int32)
+    fb.setResultType(nonNullObjectType)
+
+    val lenLocal = fb.addLocal("len", Int32)
+    val underlyingLocal = fb.addLocal("underlying", anyArrayType)
+    val subLengthIndexLocal = fb.addLocal("subLengthIndex", Int32)
+    val arrayComponentTypeDataLocal = fb.addLocal("arrayComponentTypeData", arrayTypeDataType)
+    val iLocal = fb.addLocal("i", Int32)
+
+    /* High-level pseudo code of what this function does:
+     *
+     * def newArrayObject(arrayTypeData, lengths, lengthIndex) {
+     *   // create an array of the right primitive type
+     *   val len = lengths(lengthIndex)
+     *   switch (arrayTypeData.componentType.kind) {
+     *     // for primitives, return without recursion
+     *     case KindBoolean => new Array[Boolean](len)
+     *     ...
+     *     case KindDouble => new Array[Double](len)
+     *
+     *     // for reference array types, maybe recursively initialize
+     *     case _ =>
+     *       val result = new Array[Object](len) // with arrayTypeData as vtable
+     *       val subLengthIndex = lengthIndex + 1
+     *       if (subLengthIndex != lengths.length) {
+     *         val arrayComponentTypeData = arrayTypeData.componentType
+     *         for (i <- 0 until len)
+     *           result(i) = newArrayObject(arrayComponentTypeData, lengths, subLengthIndex)
+     *       }
+     *       result
+     *   }
+     * }
+     */
+
+    val primRefsWithArrayTypes = List(
+      BooleanRef -> KindBoolean,
+      CharRef -> KindChar,
+      ByteRef -> KindByte,
+      ShortRef -> KindShort,
+      IntRef -> KindInt,
+      LongRef -> KindLong,
+      FloatRef -> KindFloat,
+      DoubleRef -> KindDouble
+    )
+
+    // Load the vtable and itable of the resulting array on the stack
+    fb += LocalGet(arrayTypeDataParam) // vtable
+    fb += GlobalGet(genGlobalID.arrayClassITable) // itable
+
+    // Load the first length
+    fb += LocalGet(lengthsParam)
+    fb += LocalGet(lengthIndexParam)
+    fb += ArrayGet(genTypeID.i32Array)
+
+    // componentTypeData := ref_as_non_null(arrayTypeData.componentType)
+    // switch (componentTypeData.kind)
+    val switchClauseSig = FunctionType(
+      List(arrayTypeDataType, itablesType, Int32),
+      List(nonNullObjectType)
+    )
+    fb.switch(switchClauseSig) { () =>
+      // scrutinee
+      fb += LocalGet(arrayTypeDataParam)
+      fb += StructGet(genTypeID.typeData, genFieldID.typeData.componentType)
+      fb += StructGet(genTypeID.typeData, genFieldID.typeData.kind)
+    }(
+      // For all the primitive types, by construction, this is the bottom dimension
+      // case KindPrim => array.new_default underlyingPrimArray; struct.new PrimArray
+      primRefsWithArrayTypes.map { case (primRef, kind) =>
+        List(kind) -> { () =>
+          val arrayTypeRef = ArrayTypeRef(primRef, 1)
+          fb += ArrayNewDefault(genTypeID.underlyingOf(arrayTypeRef))
+          fb += StructNew(genTypeID.forArrayClass(arrayTypeRef))
+          () // required for correct type inference
+        }
+      }: _*
+    ) { () =>
+      // default -- all non-primitive array types
+
+      // len := <top-of-stack> (which is the first length)
+      fb += LocalTee(lenLocal)
+
+      // underlying := array.new_default anyArray
+      val arrayTypeRef = ArrayTypeRef(ClassRef(ObjectClass), 1)
+      fb += ArrayNewDefault(genTypeID.underlyingOf(arrayTypeRef))
+      fb += LocalSet(underlyingLocal)
+
+      // subLengthIndex := lengthIndex + 1
+      fb += LocalGet(lengthIndexParam)
+      fb += I32Const(1)
+      fb += I32Add
+      fb += LocalTee(subLengthIndexLocal)
+
+      // if subLengthIndex != lengths.length
+      fb += LocalGet(lengthsParam)
+      fb += ArrayLen
+      fb += I32Ne
+      fb.ifThen() {
+        // then, recursively initialize all the elements
+
+        // arrayComponentTypeData := ref_cast<arrayTypeDataType> arrayTypeData.componentTypeData
+        fb += LocalGet(arrayTypeDataParam)
+        fb += StructGet(genTypeID.typeData, genFieldID.typeData.componentType)
+        fb += RefCast(RefType(arrayTypeDataType.heapType))
+        fb += LocalSet(arrayComponentTypeDataLocal)
+
+        // i := 0
+        fb += I32Const(0)
+        fb += LocalSet(iLocal)
+
+        // while (i != len)
+        fb.whileLoop() {
+          fb += LocalGet(iLocal)
+          fb += LocalGet(lenLocal)
+          fb += I32Ne
+        } {
+          // underlying[i] := newArrayObject(arrayComponentType, lengths, subLengthIndex)
+
+          fb += LocalGet(underlyingLocal)
+          fb += LocalGet(iLocal)
+
+          fb += LocalGet(arrayComponentTypeDataLocal)
+          fb += LocalGet(lengthsParam)
+          fb += LocalGet(subLengthIndexLocal)
+          fb += Call(genFunctionID.newArrayObject)
+
+          fb += ArraySet(genTypeID.anyArray)
+
+          // i += 1
+          fb += LocalGet(iLocal)
+          fb += I32Const(1)
+          fb += I32Add
+          fb += LocalSet(iLocal)
+        }
+      }
+
+      // load underlying; struct.new ObjectArray
+      fb += LocalGet(underlyingLocal)
+      fb += StructNew(genTypeID.forArrayClass(arrayTypeRef))
+    }
+
+    fb.buildAndAddToModule()
+  }
+
+  /** `identityHashCode`: `anyref -> i32`.
+   *
+   *  This is the implementation of `IdentityHashCode`. It is also used to compute the `hashCode()`
+   *  of primitive values when dispatch is required (i.e., when the receiver type is not known to be
+   *  a specific primitive or hijacked class), so it must be consistent with the implementations of
+   *  `hashCode()` in hijacked classes.
+   *
+   *  For `String` and `Double`, we actually call the hijacked class methods, as they are a bit
+   *  involved. For `Boolean` and `Void`, we hard-code a copy here.
+  */
+  private def genIdentityHashCode()(implicit ctx: WasmContext): Unit = {
+    import MemberNamespace.Public
+    import SpecialNames.hashCodeMethodName
+    import genFieldID.typeData._
+
+    // A global exclusively used by this function
+    ctx.addGlobal(
+      Global(
+        genGlobalID.lastIDHashCode,
+        OriginalName(genGlobalID.lastIDHashCode.toString()),
+        isMutable = true,
+        Int32,
+        Expr(List(I32Const(0)))
+      )
+    )
+
+    val fb = newFunctionBuilder(genFunctionID.identityHashCode)
+    val objParam = fb.addParam("obj", RefType.anyref)
+    fb.setResultType(Int32)
+
+    val objNonNullLocal = fb.addLocal("objNonNull", RefType.any)
+    val resultLocal = fb.addLocal("result", Int32)
+
+    // If `obj` is `null`, return 0 (by spec)
+    fb.block(RefType.any) { nonNullLabel =>
+      fb += LocalGet(objParam)
+      fb += BrOnNonNull(nonNullLabel)
+      fb += I32Const(0)
+      fb += Return
+    }
+    fb += LocalTee(objNonNullLocal)
+
+    // If `obj` is one of our objects, skip all the jsValueType tests
+    fb += RefTest(RefType(genTypeID.ObjectStruct))
+    fb += I32Eqz
+    fb.ifThen() {
+      fb.switch() { () =>
+        fb += LocalGet(objNonNullLocal)
+        fb += Call(genFunctionID.jsValueType)
+      }(
+        List(JSValueTypeFalse) -> { () =>
+          fb += I32Const(1237) // specified by jl.Boolean.hashCode()
+          fb += Return
+        },
+        List(JSValueTypeTrue) -> { () =>
+          fb += I32Const(1231) // specified by jl.Boolean.hashCode()
+          fb += Return
+        },
+        List(JSValueTypeString) -> { () =>
+          fb += LocalGet(objNonNullLocal)
+          fb += Call(
+            genFunctionID.forMethod(Public, BoxedStringClass, hashCodeMethodName)
+          )
+          fb += Return
+        },
+        List(JSValueTypeNumber) -> { () =>
+          fb += LocalGet(objNonNullLocal)
+          fb += Call(genFunctionID.unbox(DoubleRef))
+          fb += Call(
+            genFunctionID.forMethod(Public, BoxedDoubleClass, hashCodeMethodName)
+          )
+          fb += Return
+        },
+        List(JSValueTypeUndefined) -> { () =>
+          fb += I32Const(0) // specified by jl.Void.hashCode(), Scala.js only
+          fb += Return
+        },
+        List(JSValueTypeBigInt) -> { () =>
+          fb += LocalGet(objNonNullLocal)
+          fb += Call(genFunctionID.bigintHashCode)
+          fb += Return
+        },
+        List(JSValueTypeSymbol) -> { () =>
+          fb.block() { descriptionIsNullLabel =>
+            fb += LocalGet(objNonNullLocal)
+            fb += Call(genFunctionID.symbolDescription)
+            fb += BrOnNull(descriptionIsNullLabel)
+            fb += Call(
+              genFunctionID.forMethod(Public, BoxedStringClass, hashCodeMethodName)
+            )
+            fb += Return
+          }
+          fb += I32Const(0)
+          fb += Return
+        }
+      ) { () =>
+        // JSValueTypeOther -- fall through to using idHashCodeMap
+        ()
+      }
+    }
+
+    // If we get here, use the idHashCodeMap
+
+    // Read the existing idHashCode, if one exists
+    fb += GlobalGet(genGlobalID.idHashCodeMap)
+    fb += LocalGet(objNonNullLocal)
+    fb += Call(genFunctionID.idHashCodeGet)
+    fb += LocalTee(resultLocal)
+
+    // If it is 0, there was no recorded idHashCode yet; allocate a new one
+    fb += I32Eqz
+    fb.ifThen() {
+      // Allocate a new idHashCode
+      fb += GlobalGet(genGlobalID.lastIDHashCode)
+      fb += I32Const(1)
+      fb += I32Add
+      fb += LocalTee(resultLocal)
+      fb += GlobalSet(genGlobalID.lastIDHashCode)
+
+      // Store it for next time
+      fb += GlobalGet(genGlobalID.idHashCodeMap)
+      fb += LocalGet(objNonNullLocal)
+      fb += LocalGet(resultLocal)
+      fb += Call(genFunctionID.idHashCodeSet)
+    }
+
+    fb += LocalGet(resultLocal)
+
+    fb.buildAndAddToModule()
+  }
+
+  /** Search for a reflective proxy function with the given `methodId` in the `reflectiveProxies`
+   *  field in `typeData` and returns the corresponding function reference.
+   *
+   *  `searchReflectiveProxy`: [typeData, i32] -> [(ref func)]
+   */
+  private def genSearchReflectiveProxy()(implicit ctx: WasmContext): Unit = {
+    import genFieldID.typeData._
+
+    val typeDataType = RefType(genTypeID.typeData)
+
+    val fb = newFunctionBuilder(genFunctionID.searchReflectiveProxy)
+    val typeDataParam = fb.addParam("typeData", typeDataType)
+    val methodIDParam = fb.addParam("methodID", Int32)
+    fb.setResultType(RefType(HeapType.Func))
+
+    val reflectiveProxies =
+      fb.addLocal("reflectiveProxies", Types.RefType(genTypeID.reflectiveProxies))
+    val startLocal = fb.addLocal("start", Types.Int32)
+    val endLocal = fb.addLocal("end", Types.Int32)
+    val midLocal = fb.addLocal("mid", Types.Int32)
+    val entryLocal = fb.addLocal("entry", Types.RefType(genTypeID.reflectiveProxy))
+
+    /* This function implements a binary search. Unlike the typical binary search,
+     * it does not stop early if it happens to exactly hit the target ID.
+     * Instead, it systematically reduces the search range until it contains at
+     * most one element. At that point, it checks whether it is the ID we are
+     * looking for.
+     *
+     * We do this in the name of predictability, in order to avoid performance
+     * cliffs. It avoids the scenario where a codebase happens to be fast
+     * because a particular reflective call resolves in Θ(1), but where adding
+     * or removing something completely unrelated somewhere else in the
+     * codebase pushes it to a different slot where it resolves in Θ(log n).
+     *
+     * This function is therefore intentionally Θ(log n), not merely O(log n).
+     */
+
+    fb += LocalGet(typeDataParam)
+    fb += StructGet(genTypeID.typeData, genFieldID.typeData.reflectiveProxies)
+    fb += LocalTee(reflectiveProxies)
+
+    // end := reflectiveProxies.length
+    fb += ArrayLen
+    fb += LocalSet(endLocal)
+
+    // start := 0
+    fb += I32Const(0)
+    fb += LocalSet(startLocal)
+
+    // while (start + 1 < end)
+    fb.whileLoop() {
+      fb += LocalGet(startLocal)
+      fb += I32Const(1)
+      fb += I32Add
+      fb += LocalGet(endLocal)
+      fb += I32LtU
+    } {
+      // mid := (start + end) >>> 1
+      fb += LocalGet(startLocal)
+      fb += LocalGet(endLocal)
+      fb += I32Add
+      fb += I32Const(1)
+      fb += I32ShrU
+      fb += LocalSet(midLocal)
+
+      // if (methodID < reflectiveProxies[mid].methodID)
+      fb += LocalGet(methodIDParam)
+      fb += LocalGet(reflectiveProxies)
+      fb += LocalGet(midLocal)
+      fb += ArrayGet(genTypeID.reflectiveProxies)
+      fb += StructGet(genTypeID.reflectiveProxy, genFieldID.reflectiveProxy.methodID)
+      fb += I32LtU
+      fb.ifThenElse() {
+        // then end := mid
+        fb += LocalGet(midLocal)
+        fb += LocalSet(endLocal)
+      } {
+        // else start := mid
+        fb += LocalGet(midLocal)
+        fb += LocalSet(startLocal)
+      }
+    }
+
+    // if (start < end)
+    fb += LocalGet(startLocal)
+    fb += LocalGet(endLocal)
+    fb += I32LtU
+    fb.ifThen() {
+      // entry := reflectiveProxies[start]
+      fb += LocalGet(reflectiveProxies)
+      fb += LocalGet(startLocal)
+      fb += ArrayGet(genTypeID.reflectiveProxies)
+      fb += LocalTee(entryLocal)
+
+      // if (entry.methodID == methodID)
+      fb += StructGet(genTypeID.reflectiveProxy, genFieldID.reflectiveProxy.methodID)
+      fb += LocalGet(methodIDParam)
+      fb += I32Eq
+      fb.ifThen() {
+        // return entry.funcRef
+        fb += LocalGet(entryLocal)
+        fb += StructGet(genTypeID.reflectiveProxy, genFieldID.reflectiveProxy.funcRef)
+        fb += Return
+      }
+    }
+
+    // throw new TypeError("...")
+    fb ++= ctx.stringPool.getConstantStringInstr("TypeError")
+    fb += Call(genFunctionID.jsGlobalRefGet)
+    fb += Call(genFunctionID.jsNewArray)
+    // Originally, exception is thrown from JS saying e.g. "obj2.z1__ is not a function"
+    // TODO Improve the error message to include some information about the missing method
+    fb ++= ctx.stringPool.getConstantStringInstr("Method not found")
+    fb += Call(genFunctionID.jsArrayPush)
+    fb += Call(genFunctionID.jsNew)
+    fb += ExternConvertAny
+    fb += Throw(genTagID.exception)
+
+    fb.buildAndAddToModule()
+  }
+
+  private def genArrayCloneFunctions()(implicit ctx: WasmContext): Unit = {
+    val baseRefs = List(
+      BooleanRef,
+      CharRef,
+      ByteRef,
+      ShortRef,
+      IntRef,
+      LongRef,
+      FloatRef,
+      DoubleRef,
+      ClassRef(ObjectClass)
+    )
+
+    for (baseRef <- baseRefs)
+      genArrayCloneFunction(baseRef)
+  }
+
+  /** Generates the clone function for the array class with the given base. */
+  private def genArrayCloneFunction(baseRef: NonArrayTypeRef)(implicit ctx: WasmContext): Unit = {
+    val charCodeForOriginalName = baseRef match {
+      case baseRef: PrimRef => baseRef.charCode
+      case _: ClassRef      => 'O'
+    }
+    val originalName = OriginalName("cloneArray." + charCodeForOriginalName)
+
+    val fb = newFunctionBuilder(genFunctionID.cloneArray(baseRef), originalName)
+    val fromParam = fb.addParam("from", RefType(genTypeID.ObjectStruct))
+    fb.setResultType(RefType(genTypeID.ObjectStruct))
+    fb.setFunctionType(genTypeID.cloneFunctionType)
+
+    val arrayTypeRef = ArrayTypeRef(baseRef, 1)
+
+    val arrayStructTypeID = genTypeID.forArrayClass(arrayTypeRef)
+    val arrayClassType = RefType(arrayStructTypeID)
+
+    val underlyingArrayTypeID = genTypeID.underlyingOf(arrayTypeRef)
+    val underlyingArrayType = RefType(underlyingArrayTypeID)
+
+    val fromLocal = fb.addLocal("fromTyped", arrayClassType)
+    val fromUnderlyingLocal = fb.addLocal("fromUnderlying", underlyingArrayType)
+    val lengthLocal = fb.addLocal("length", Int32)
+    val resultUnderlyingLocal = fb.addLocal("resultUnderlying", underlyingArrayType)
+
+    // Cast down the from argument
+    fb += LocalGet(fromParam)
+    fb += RefCast(arrayClassType)
+    fb += LocalTee(fromLocal)
+
+    // Load the underlying array
+    fb += StructGet(arrayStructTypeID, genFieldID.objStruct.arrayUnderlying)
+    fb += LocalTee(fromUnderlyingLocal)
+
+    // Make a copy of the underlying array
+    fb += ArrayLen
+    fb += LocalTee(lengthLocal)
+    fb += ArrayNewDefault(underlyingArrayTypeID)
+    fb += LocalTee(resultUnderlyingLocal) // also dest for array.copy
+    fb += I32Const(0) // destOffset
+    fb += LocalGet(fromUnderlyingLocal) // src
+    fb += I32Const(0) // srcOffset
+    fb += LocalGet(lengthLocal) // length
+    fb += ArrayCopy(underlyingArrayTypeID, underlyingArrayTypeID)
+
+    // Build the result arrayStruct
+    fb += LocalGet(fromLocal)
+    fb += StructGet(arrayStructTypeID, genFieldID.objStruct.vtable) // vtable
+    fb += GlobalGet(genGlobalID.arrayClassITable) // itable
+    fb += LocalGet(resultUnderlyingLocal)
+    fb += StructNew(arrayStructTypeID)
+
+    fb.buildAndAddToModule()
+  }
+
+}
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/DerivedClasses.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/DerivedClasses.scala
new file mode 100644
index 0000000000..b7e0a3cf91
--- /dev/null
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/DerivedClasses.scala
@@ -0,0 +1,151 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package org.scalajs.linker.backend.wasmemitter
+
+import scala.concurrent.{ExecutionContext, Future}
+
+import org.scalajs.ir.ClassKind._
+import org.scalajs.ir.Names._
+import org.scalajs.ir.OriginalName
+import org.scalajs.ir.OriginalName.NoOriginalName
+import org.scalajs.ir.Position
+import org.scalajs.ir.Trees._
+import org.scalajs.ir.Types._
+import org.scalajs.ir.{EntryPointsInfo, Version}
+
+import org.scalajs.linker.interface.IRFile
+import org.scalajs.linker.interface.unstable.IRFileImpl
+
+import org.scalajs.linker.standard.LinkedClass
+
+import SpecialNames._
+
+/** Derives `CharacterBox` and `LongBox` from `jl.Character` and `jl.Long`. */
+object DerivedClasses {
+  def deriveClasses(classes: List[LinkedClass]): List[LinkedClass] = {
+    classes.collect {
+      case clazz if clazz.className == BoxedCharacterClass || clazz.className == BoxedLongClass =>
+        deriveBoxClass(clazz)
+    }
+  }
+
+  /** Generates the accompanying Box class of `Character` or `Long`.
+   *
+   *  These box classes will be used as the generic representation of `char`s and `long`s when they
+   *  are upcast to `java.lang.Character`/`java.lang.Long` or any of their supertypes.
+   *
+   *  The generated Box classes mimic the public structure of the corresponding hijacked classes.
+   *  Whereas the hijacked classes instances *are* the primitives (conceptually), the box classes
+   *  contain an explicit `value` field of the primitive type. They delegate all their instance
+   *  methods to the corresponding methods of the hijacked class, applied on the `value` primitive.
+   *
+   *  For example, given the hijacked class
+   *
+   *  {{{
+   *  hijacked class Long extends java.lang.Number with Comparable {
+   *    def longValue;J(): long = this.asInstanceOf[long]
+   *    def toString;T(): string = Long$.toString(this.longValue;J())
+   *    def compareTo;jlLong;Z(that: java.lang.Long): boolean =
+   *      Long$.compare(this.longValue;J(), that.longValue;J())
+   *  }
+   *  }}}
+   *
+   *  we generate
+   *
+   *  {{{
+   *  class LongBox extends java.lang.Number with Comparable {
+   *    val value: long
+   *    def <init>(value: long) = { this.value = value }
+   *    def longValue;J(): long = this.value.longValue;J()
+   *    def toString;T(): string = this.value.toString;J()
+   *    def compareTo;jlLong;Z(that: jlLong): boolean =
+   *      this.value.compareTo;jlLong;Z(that)
+   *  }
+   *  }}}
+   */
+  private def deriveBoxClass(clazz: LinkedClass): LinkedClass = {
+    implicit val pos: Position = clazz.pos
+
+    val EAF = ApplyFlags.empty
+    val EMF = MemberFlags.empty
+    val EOH = OptimizerHints.empty
+    val NON = NoOriginalName
+    val NOV = Version.Unversioned
+
+    val className = clazz.className
+    val derivedClassName = className.withSuffix("Box")
+    val primType = BoxedClassToPrimType(className).asInstanceOf[PrimTypeWithRef]
+    val derivedClassType = ClassType(derivedClassName)
+
+    val fieldName = FieldName(derivedClassName, valueFieldSimpleName)
+    val fieldIdent = FieldIdent(fieldName)
+
+    val derivedFields: List[FieldDef] = List(
+      FieldDef(EMF, fieldIdent, NON, primType)
+    )
+
+    val selectField = Select(This()(derivedClassType), fieldIdent)(primType)
+
+    val ctorParamDef =
+      ParamDef(LocalIdent(fieldName.simpleName.toLocalName), NON, primType, mutable = false)
+    val derivedCtor = MethodDef(
+      EMF.withNamespace(MemberNamespace.Constructor),
+      MethodIdent(MethodName.constructor(List(primType.primRef))),
+      NON,
+      List(ctorParamDef),
+      NoType,
+      Some(Assign(selectField, ctorParamDef.ref))
+    )(EOH, NOV)
+
+    val derivedMethods: List[MethodDef] = for {
+      method <- clazz.methods if method.flags.namespace == MemberNamespace.Public
+    } yield {
+      MethodDef(
+        method.flags,
+        method.name,
+        method.originalName,
+        method.args,
+        method.resultType,
+        Some(Apply(EAF, selectField, method.name, method.args.map(_.ref))(method.resultType))
+      )(method.optimizerHints, method.version)
+    }
+
+    new LinkedClass(
+      ClassIdent(derivedClassName),
+      Class,
+      jsClassCaptures = None,
+      clazz.superClass,
+      clazz.interfaces,
+      jsSuperClass = None,
+      jsNativeLoadSpec = None,
+      derivedFields,
+      derivedCtor :: derivedMethods,
+      jsConstructorDef = None,
+      exportedMembers = Nil,
+      jsNativeMembers = Nil,
+      EOH,
+      pos,
+      ancestors = derivedClassName :: clazz.ancestors.tail,
+      hasInstances = true,
+      hasDirectInstances = true,
+      hasInstanceTests = true,
+      hasRuntimeTypeInfo = true,
+      fieldsRead = Set(fieldName),
+      staticFieldsRead = Set.empty,
+      staticDependencies = Set.empty,
+      externalDependencies = Set.empty,
+      dynamicDependencies = Set.empty,
+      clazz.version
+    )
+  }
+}
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/EmbeddedConstants.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/EmbeddedConstants.scala
new file mode 100644
index 0000000000..58e5f2c82b
--- /dev/null
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/EmbeddedConstants.scala
@@ -0,0 +1,68 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package org.scalajs.linker.backend.wasmemitter
+
+object EmbeddedConstants {
+  /* Values returned by the `jsValueType` helper.
+   *
+   * 0: false
+   * 1: true
+   * 2: string
+   * 3: number
+   * 4: undefined
+   * 5: everything else
+   *
+   * This encoding has the following properties:
+   *
+   * - false and true also return their value as the appropriate i32.
+   * - the types implementing `Comparable` are consecutive from 0 to 3.
+   */
+
+  final val JSValueTypeFalse = 0
+  final val JSValueTypeTrue = 1
+  final val JSValueTypeString = 2
+  final val JSValueTypeNumber = 3
+  final val JSValueTypeUndefined = 4
+  final val JSValueTypeBigInt = 5
+  final val JSValueTypeSymbol = 6
+  final val JSValueTypeOther = 7
+
+  // Values for `typeData.kind`
+
+  final val KindVoid = 0
+  final val KindBoolean = 1
+  final val KindChar = 2
+  final val KindByte = 3
+  final val KindShort = 4
+  final val KindInt = 5
+  final val KindLong = 6
+  final val KindFloat = 7
+  final val KindDouble = 8
+  final val KindArray = 9
+  final val KindObject = 10 // j.l.Object
+  final val KindBoxedUnit = 11
+  final val KindBoxedBoolean = 12
+  final val KindBoxedCharacter = 13
+  final val KindBoxedByte = 14
+  final val KindBoxedShort = 15
+  final val KindBoxedInteger = 16
+  final val KindBoxedLong = 17
+  final val KindBoxedFloat = 18
+  final val KindBoxedDouble = 19
+  final val KindBoxedString = 20
+  final val KindClass = 21
+  final val KindInterface = 22
+  final val KindJSType = 23
+
+  final val KindLastPrimitive = KindDouble
+}
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala
new file mode 100644
index 0000000000..0a477f6a59
--- /dev/null
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala
@@ -0,0 +1,399 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package org.scalajs.linker.backend.wasmemitter
+
+import scala.concurrent.{ExecutionContext, Future}
+
+import org.scalajs.ir.Names._
+import org.scalajs.ir.Types._
+import org.scalajs.ir.OriginalName
+import org.scalajs.ir.Position
+
+import org.scalajs.linker.interface._
+import org.scalajs.linker.interface.unstable._
+import org.scalajs.linker.standard._
+import org.scalajs.linker.standard.ModuleSet.ModuleID
+
+import org.scalajs.linker.backend.emitter.PrivateLibHolder
+
+import org.scalajs.linker.backend.javascript.Printers.JSTreePrinter
+import org.scalajs.linker.backend.javascript.{Trees => js}
+
+import org.scalajs.linker.backend.webassembly.FunctionBuilder
+import org.scalajs.linker.backend.webassembly.{Instructions => wa}
+import org.scalajs.linker.backend.webassembly.{Modules => wamod}
+import org.scalajs.linker.backend.webassembly.{Identitities => wanme}
+import org.scalajs.linker.backend.webassembly.{Types => watpe}
+
+import org.scalajs.logging.Logger
+
+import SpecialNames._
+import VarGen._
+import org.scalajs.linker.backend.javascript.ByteArrayWriter
+
+final class Emitter(config: Emitter.Config) {
+  import Emitter._
+
+  private val classEmitter = new ClassEmitter(config.coreSpec)
+
+  val symbolRequirements: SymbolRequirement =
+    Emitter.symbolRequirements(config.coreSpec)
+
+  val injectedIRFiles: Seq[IRFile] = PrivateLibHolder.files
+
+  def emit(module: ModuleSet.Module, logger: Logger): Result = {
+    val wasmModule = emitWasmModule(module)
+    val loaderContent = LoaderContent.bytesContent
+    val jsFileContent = buildJSFileContent(module)
+
+    new Result(wasmModule, loaderContent, jsFileContent)
+  }
+
+  private def emitWasmModule(module: ModuleSet.Module): wamod.Module = {
+    // Inject the derived linked classes
+    val allClasses =
+      DerivedClasses.deriveClasses(module.classDefs) ::: module.classDefs
+
+    /* Sort by ancestor count so that superclasses always appear before
+     * subclasses, then tie-break by name for stability.
+     */
+    val sortedClasses = allClasses.sortWith { (a, b) =>
+      val cmp = Integer.compare(a.ancestors.size, b.ancestors.size)
+      if (cmp != 0) cmp < 0
+      else a.className.compareTo(b.className) < 0
+    }
+
+    val topLevelExports = module.topLevelExports
+    val moduleInitializers = module.initializers.toList
+
+    implicit val ctx: WasmContext =
+      Preprocessor.preprocess(sortedClasses, topLevelExports)
+
+    CoreWasmLib.genPreClasses()
+    genExternalModuleImports(module)
+    sortedClasses.foreach(classEmitter.genClassDef(_))
+    topLevelExports.foreach(classEmitter.genTopLevelExport(_))
+    CoreWasmLib.genPostClasses()
+
+    genStartFunction(sortedClasses, moduleInitializers, topLevelExports)
+
+    /* Gen the string pool and the declarative elements at the very end, since
+     * they depend on what instructions where produced by all the preceding codegen.
+     */
+    ctx.stringPool.genPool()
+    genDeclarativeElements()
+
+    ctx.moduleBuilder.build()
+  }
+
+  private def genExternalModuleImports(module: ModuleSet.Module)(
+      implicit ctx: WasmContext): Unit = {
+    // Sort for stability
+    val allImportedModules = module.externalDependencies.toList.sorted
+
+    // Gen imports of external modules on the Wasm side
+    for (moduleName <- allImportedModules) {
+      val id = genGlobalID.forImportedModule(moduleName)
+      val origName = OriginalName("import." + moduleName)
+      ctx.moduleBuilder.addImport(
+        wamod.Import(
+          "__scalaJSImports",
+          moduleName,
+          wamod.ImportDesc.Global(id, origName, isMutable = false, watpe.RefType.anyref)
+        )
+      )
+    }
+  }
+
+  private def genStartFunction(
+      sortedClasses: List[LinkedClass],
+      moduleInitializers: List[ModuleInitializer.Initializer],
+      topLevelExportDefs: List[LinkedTopLevelExport]
+  )(implicit ctx: WasmContext): Unit = {
+    import org.scalajs.ir.Trees._
+
+    implicit val pos = Position.NoPosition
+
+    val fb =
+      new FunctionBuilder(ctx.moduleBuilder, genFunctionID.start, OriginalName("start"), pos)
+
+    // Initialize itables
+
+    def genInitClassITable(classITableGlobalID: wanme.GlobalID,
+        classInfoForResolving: WasmContext.ClassInfo, ancestors: List[ClassName]): Unit = {
+      val resolvedMethodInfos = classInfoForResolving.resolvedMethodInfos
+
+      for {
+        ancestor <- ancestors
+        // Use getClassInfoOption in case the reachability analysis got rid of those interfaces
+        interfaceInfo <- ctx.getClassInfoOption(ancestor)
+        if interfaceInfo.isInterface
+      } {
+        fb += wa.GlobalGet(classITableGlobalID)
+        fb += wa.I32Const(interfaceInfo.itableIdx)
+
+        for (method <- interfaceInfo.tableEntries)
+          fb += ctx.refFuncWithDeclaration(resolvedMethodInfos(method).tableEntryID)
+        fb += wa.StructNew(genTypeID.forITable(ancestor))
+        fb += wa.ArraySet(genTypeID.itables)
+      }
+    }
+
+    // For all concrete, normal classes
+    for (clazz <- sortedClasses if clazz.kind.isClass && clazz.hasDirectInstances) {
+      val className = clazz.className
+      val classInfo = ctx.getClassInfo(className)
+      if (classInfo.classImplementsAnyInterface)
+        genInitClassITable(genGlobalID.forITable(className), classInfo, clazz.ancestors)
+    }
+
+    // For array classes
+    genInitClassITable(genGlobalID.arrayClassITable, ctx.getClassInfo(ObjectClass),
+        List(SerializableClass, CloneableClass))
+
+    // Initialize the JS private field symbols
+
+    for (clazz <- sortedClasses if clazz.kind.isJSClass) {
+      for (fieldDef <- clazz.fields) {
+        fieldDef match {
+          case FieldDef(flags, name, _, _) if !flags.namespace.isStatic =>
+            fb += wa.Call(genFunctionID.newSymbol)
+            fb += wa.GlobalSet(genGlobalID.forJSPrivateField(name.name))
+          case _ =>
+            ()
+        }
+      }
+    }
+
+    // Emit the static initializers
+
+    for (clazz <- sortedClasses if clazz.hasStaticInitializer) {
+      val funcID = genFunctionID.forMethod(
+        MemberNamespace.StaticConstructor,
+        clazz.className,
+        StaticInitializerName
+      )
+      fb += wa.Call(funcID)
+    }
+
+    // Initialize the top-level exports that require it
+
+    for (tle <- topLevelExportDefs) {
+      // Load the (initial) exported value on the stack
+      tle.tree match {
+        case TopLevelJSClassExportDef(_, exportName) =>
+          fb += wa.Call(genFunctionID.loadJSClass(tle.owningClass))
+        case TopLevelModuleExportDef(_, exportName) =>
+          fb += wa.Call(genFunctionID.loadModule(tle.owningClass))
+        case TopLevelMethodExportDef(_, methodDef) =>
+          fb += ctx.refFuncWithDeclaration(genFunctionID.forExport(tle.exportName))
+          if (methodDef.restParam.isDefined) {
+            fb += wa.I32Const(methodDef.args.size)
+            fb += wa.Call(genFunctionID.makeExportedDefRest)
+          } else {
+            fb += wa.Call(genFunctionID.makeExportedDef)
+          }
+        case TopLevelFieldExportDef(_, _, fieldIdent) =>
+          /* Usually redundant, but necessary if the static field is never
+           * explicitly set and keeps its default (zero) value instead. In that
+           * case this initial call is required to publish that zero value (as
+           * opposed to the default `undefined` value of the JS `let`).
+           */
+          fb += wa.GlobalGet(genGlobalID.forStaticField(fieldIdent.name))
+      }
+
+      // Call the export setter
+      fb += wa.Call(genFunctionID.forTopLevelExportSetter(tle.exportName))
+    }
+
+    // Emit the module initializers
+
+    moduleInitializers.foreach { init =>
+      def genCallStatic(className: ClassName, methodName: MethodName): Unit = {
+        val funcID = genFunctionID.forMethod(MemberNamespace.PublicStatic, className, methodName)
+        fb += wa.Call(funcID)
+      }
+
+      ModuleInitializerImpl.fromInitializer(init) match {
+        case ModuleInitializerImpl.MainMethodWithArgs(className, encodedMainMethodName, args) =>
+          val stringArrayTypeRef = ArrayTypeRef(ClassRef(BoxedStringClass), 1)
+          SWasmGen.genArrayValue(fb, stringArrayTypeRef, args.size) {
+            args.foreach(arg => fb ++= ctx.stringPool.getConstantStringInstr(arg))
+          }
+          genCallStatic(className, encodedMainMethodName)
+
+        case ModuleInitializerImpl.VoidMainMethod(className, encodedMainMethodName) =>
+          genCallStatic(className, encodedMainMethodName)
+      }
+    }
+
+    // Finish the start function
+
+    fb.buildAndAddToModule()
+    ctx.moduleBuilder.setStart(genFunctionID.start)
+  }
+
+  private def genDeclarativeElements()(implicit ctx: WasmContext): Unit = {
+    // Aggregated Elements
+
+    val funcDeclarations = ctx.getAllFuncDeclarations()
+
+    if (funcDeclarations.nonEmpty) {
+      /* Functions that are referred to with `ref.func` in the Code section
+       * must be declared ahead of time in one of the earlier sections
+       * (otherwise the module does not validate). It can be the Global section
+       * if they are meaningful there (which is why `ref.func` in the vtables
+       * work out of the box). In the absence of any other specific place, an
+       * Element section with the declarative mode is the recommended way to
+       * introduce these declarations.
+       */
+      val exprs = funcDeclarations.map { funcID =>
+        wa.Expr(List(wa.RefFunc(funcID)))
+      }
+      ctx.moduleBuilder.addElement(
+        wamod.Element(watpe.RefType.funcref, exprs, wamod.Element.Mode.Declarative)
+      )
+    }
+  }
+
+  private def buildJSFileContent(module: ModuleSet.Module): Array[Byte] = {
+    implicit val noPos = Position.NoPosition
+
+    // Sort for stability
+    val importedModules = module.externalDependencies.toList.sorted
+
+    val (moduleImports, importedModulesItems) = (for {
+      (moduleName, idx) <- importedModules.zipWithIndex
+    } yield {
+      val importIdent = js.Ident(s"imported$idx")
+      val moduleNameStr = js.StringLiteral(moduleName)
+      val moduleImport = js.ImportNamespace(importIdent, moduleNameStr)
+      val item = moduleNameStr -> js.VarRef(importIdent)
+      (moduleImport, item)
+    }).unzip
+
+    val importedModulesDict = js.ObjectConstr(importedModulesItems)
+
+    val (exportDecls, exportSettersItems) = (for {
+      exportName <- module.topLevelExports.map(_.exportName)
+    } yield {
+      val ident = js.Ident(s"exported$exportName")
+      val decl = js.Let(ident, mutable = true, None)
+      val exportStat = js.Export(List(ident -> js.ExportName(exportName)))
+      val xParam = js.ParamDef(js.Ident("x"))
+      val setterFun = js.Function(arrow = true, List(xParam), None, {
+        js.Assign(js.VarRef(ident), xParam.ref)
+      })
+      val setterItem = js.StringLiteral(exportName) -> setterFun
+      (List(decl, exportStat), setterItem)
+    }).unzip
+
+    val exportSettersDict = js.ObjectConstr(exportSettersItems)
+
+    val loadFunIdent = js.Ident("__load")
+    val loaderImport = js.Import(
+      List(js.ExportName("load") -> loadFunIdent),
+      js.StringLiteral(config.loaderModuleName)
+    )
+
+    val loadCall = js.Apply(
+      js.VarRef(loadFunIdent),
+      List(
+        js.StringLiteral(config.internalWasmFileURIPattern(module.id)),
+        importedModulesDict,
+        exportSettersDict
+      )
+    )
+
+    val fullTree = (
+      moduleImports :::
+      loaderImport ::
+      exportDecls.flatten :::
+      js.Await(loadCall) ::
+      Nil
+    )
+
+    val writer = new ByteArrayWriter
+    val printer = new JSTreePrinter(writer)
+    fullTree.foreach(printer.printStat(_))
+    writer.toByteArray()
+  }
+}
+
+object Emitter {
+
+  /** Configuration for the Emitter. */
+  final class Config private (
+      val coreSpec: CoreSpec,
+      val loaderModuleName: String,
+      val internalWasmFileURIPattern: ModuleID => String
+  ) {
+    private def this(coreSpec: CoreSpec, loaderModuleName: String) = {
+      this(
+        coreSpec,
+        loaderModuleName,
+        internalWasmFileURIPattern = { moduleID => s"./${moduleID.id}.wasm" }
+      )
+    }
+
+    def withInternalWasmFileURIPattern(
+        internalWasmFileURIPattern: ModuleID => String): Config = {
+      copy(internalWasmFileURIPattern = internalWasmFileURIPattern)
+    }
+
+    private def copy(
+      coreSpec: CoreSpec = coreSpec,
+      loaderModuleName: String = loaderModuleName,
+      internalWasmFileURIPattern: ModuleID => String = internalWasmFileURIPattern
+    ): Config = {
+      new Config(
+        coreSpec,
+        loaderModuleName,
+        internalWasmFileURIPattern
+      )
+    }
+  }
+
+  object Config {
+    def apply(coreSpec: CoreSpec, loaderModuleName: String): Config =
+      new Config(coreSpec, loaderModuleName)
+  }
+
+  final class Result(
+      val wasmModule: wamod.Module,
+      val loaderContent: Array[Byte],
+      val jsFileContent: Array[Byte]
+  )
+
+  /** Builds the symbol requirements of our back-end.
+   *
+   *  The symbol requirements tell the LinkerFrontend that we need these symbols to always be
+   *  reachable, even if no "user-land" IR requires them. They are roots for the reachability
+   *  analysis, together with module initializers and top-level exports. If we don't do this, the
+   *  linker frontend will dead-code eliminate our box classes.
+   */
+  private def symbolRequirements(coreSpec: CoreSpec): SymbolRequirement = {
+    val factory = SymbolRequirement.factory("wasm")
+
+    factory.multiple(
+      // TODO Ideally we should not require these, but rather adapt to their absence
+      factory.instantiateClass(ClassClass, AnyArgConstructorName),
+      factory.instantiateClass(JSExceptionClass, AnyArgConstructorName),
+
+      // See genIdentityHashCode in HelperFunctions
+      factory.callMethodStatically(BoxedDoubleClass, hashCodeMethodName),
+      factory.callMethodStatically(BoxedStringClass, hashCodeMethodName)
+    )
+  }
+
+}
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
new file mode 100644
index 0000000000..d41496cef8
--- /dev/null
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
@@ -0,0 +1,3374 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package org.scalajs.linker.backend.wasmemitter
+
+import scala.annotation.switch
+
+import scala.collection.mutable
+
+import org.scalajs.ir.{ClassKind, OriginalName, Position, UTF8String}
+import org.scalajs.ir.Names._
+import org.scalajs.ir.OriginalName.NoOriginalName
+import org.scalajs.ir.Trees._
+import org.scalajs.ir.Types._
+
+import org.scalajs.linker.backend.webassembly._
+import org.scalajs.linker.backend.webassembly.{Instructions => wa}
+import org.scalajs.linker.backend.webassembly.{Identitities => wanme}
+import org.scalajs.linker.backend.webassembly.{Types => watpe}
+import org.scalajs.linker.backend.webassembly.Types.{FunctionType => Sig}
+
+import EmbeddedConstants._
+import SWasmGen._
+import VarGen._
+import TypeTransformer._
+
+object FunctionEmitter {
+
+  /** Whether to use the legacy `try` instruction to implement `TryCatch`.
+   *
+   *  Support for catching JS exceptions was only added to `try_table` in V8 12.5 from April 2024.
+   *  While waiting for Node.js to catch up with V8, we use `try` to implement our `TryCatch`.
+   *
+   *  We use this "fixed configuration option" to keep the code that implements `TryCatch` using
+   *  `try_table` in the codebase, as code that is actually compiled, so that refactorings apply to
+   *  it as well. It also makes it easier to manually experiment with the new `try_table` encoding,
+   *  which is available in Chrome since v125.
+   *
+   *  Note that we use `try_table` regardless to implement `TryFinally`. Its `catch_all_ref` handler
+   *  is perfectly happy to catch and rethrow JavaScript exception in Node.js 22. Duplicating that
+   *  implementation for `try` would be a nightmare, given how complex it is already.
+   */
+  private final val UseLegacyExceptionsForTryCatch = true
+
+  def emitFunction(
+      functionID: wanme.FunctionID,
+      originalName: OriginalName,
+      enclosingClassName: Option[ClassName],
+      captureParamDefs: Option[List[ParamDef]],
+      receiverType: Option[watpe.Type],
+      paramDefs: List[ParamDef],
+      restParam: Option[ParamDef],
+      body: Tree,
+      resultType: Type
+  )(implicit ctx: WasmContext, pos: Position): Unit = {
+    val emitter = prepareEmitter(
+      functionID,
+      originalName,
+      enclosingClassName,
+      captureParamDefs,
+      preSuperVarDefs = None,
+      hasNewTarget = false,
+      receiverType,
+      paramDefs ::: restParam.toList,
+      transformResultType(resultType)
+    )
+    emitter.genBody(body, resultType)
+    emitter.fb.buildAndAddToModule()
+  }
+
+  def emitJSConstructorFunctions(
+      preSuperStatsFunctionID: wanme.FunctionID,
+      superArgsFunctionID: wanme.FunctionID,
+      postSuperStatsFunctionID: wanme.FunctionID,
+      enclosingClassName: ClassName,
+      jsClassCaptures: List[ParamDef],
+      ctor: JSConstructorDef
+  )(implicit ctx: WasmContext): Unit = {
+    implicit val pos = ctor.pos
+
+    val allCtorParams = ctor.args ::: ctor.restParam.toList
+    val ctorBody = ctor.body
+
+    // Compute the pre-super environment
+    val preSuperDecls = ctorBody.beforeSuper.collect { case varDef: VarDef =>
+      varDef
+    }
+
+    // Build the `preSuperStats` function
+    locally {
+      val preSuperEnvStructTypeID = ctx.getClosureDataStructType(preSuperDecls.map(_.vtpe))
+      val preSuperEnvType = watpe.RefType(preSuperEnvStructTypeID)
+
+      val emitter = prepareEmitter(
+        preSuperStatsFunctionID,
+        OriginalName(UTF8String("preSuperStats.") ++ enclosingClassName.encoded),
+        Some(enclosingClassName),
+        Some(jsClassCaptures),
+        preSuperVarDefs = None,
+        hasNewTarget = true,
+        receiverType = None,
+        allCtorParams,
+        List(preSuperEnvType)
+      )
+
+      emitter.genBlockStats(ctorBody.beforeSuper) {
+        // Build and return the preSuperEnv struct
+        for (varDef <- preSuperDecls) {
+          val localID = (emitter.lookupLocal(varDef.name.name): @unchecked) match {
+            case VarStorage.Local(localID) => localID
+          }
+          emitter.fb += wa.LocalGet(localID)
+        }
+        emitter.fb += wa.StructNew(preSuperEnvStructTypeID)
+      }
+
+      emitter.fb.buildAndAddToModule()
+    }
+
+    // Build the `superArgs` function
+    locally {
+      val emitter = prepareEmitter(
+        superArgsFunctionID,
+        OriginalName(UTF8String("superArgs.") ++ enclosingClassName.encoded),
+        Some(enclosingClassName),
+        Some(jsClassCaptures),
+        Some(preSuperDecls),
+        hasNewTarget = true,
+        receiverType = None,
+        allCtorParams,
+        List(watpe.RefType.anyref) // a js.Array
+      )
+      emitter.genBody(JSArrayConstr(ctorBody.superCall.args), AnyType)
+      emitter.fb.buildAndAddToModule()
+    }
+
+    // Build the `postSuperStats` function
+    locally {
+      val emitter = prepareEmitter(
+        postSuperStatsFunctionID,
+        OriginalName(UTF8String("postSuperStats.") ++ enclosingClassName.encoded),
+        Some(enclosingClassName),
+        Some(jsClassCaptures),
+        Some(preSuperDecls),
+        hasNewTarget = true,
+        receiverType = Some(watpe.RefType.anyref),
+        allCtorParams,
+        List(watpe.RefType.anyref)
+      )
+      emitter.genBody(Block(ctorBody.afterSuper), AnyType)
+      emitter.fb.buildAndAddToModule()
+    }
+  }
+
+  private def prepareEmitter(
+      functionID: wanme.FunctionID,
+      originalName: OriginalName,
+      enclosingClassName: Option[ClassName],
+      captureParamDefs: Option[List[ParamDef]],
+      preSuperVarDefs: Option[List[VarDef]],
+      hasNewTarget: Boolean,
+      receiverType: Option[watpe.Type],
+      paramDefs: List[ParamDef],
+      resultTypes: List[watpe.Type]
+  )(implicit ctx: WasmContext, pos: Position): FunctionEmitter = {
+    val fb = new FunctionBuilder(ctx.moduleBuilder, functionID, originalName, pos)
+
+    def addCaptureLikeParamListAndMakeEnv(
+        captureParamName: String,
+        captureLikes: List[(LocalName, Type)]
+    ): Env = {
+      val dataStructTypeID = ctx.getClosureDataStructType(captureLikes.map(_._2))
+      val param = fb.addParam(captureParamName, watpe.RefType(dataStructTypeID))
+      val env: List[(LocalName, VarStorage)] = for {
+        ((name, _), idx) <- captureLikes.zipWithIndex
+      } yield {
+        val storage = VarStorage.StructField(
+          param,
+          dataStructTypeID,
+          genFieldID.captureParam(idx)
+        )
+        name -> storage
+      }
+      env.toMap
+    }
+
+    val captureParamsEnv: Env = captureParamDefs match {
+      case None =>
+        Map.empty
+      case Some(defs) =>
+        addCaptureLikeParamListAndMakeEnv("__captureData",
+            defs.map(p => p.name.name -> p.ptpe))
+    }
+
+    val preSuperEnvEnv: Env = preSuperVarDefs match {
+      case None =>
+        Map.empty
+      case Some(defs) =>
+        addCaptureLikeParamListAndMakeEnv("__preSuperEnv",
+            defs.map(p => p.name.name -> p.vtpe))
+    }
+
+    val newTargetStorage = if (!hasNewTarget) {
+      None
+    } else {
+      val newTargetParam = fb.addParam(newTargetOriginalName, watpe.RefType.anyref)
+      Some(VarStorage.Local(newTargetParam))
+    }
+
+    val receiverStorage = receiverType.map { tpe =>
+      val receiverParam = fb.addParam(receiverOriginalName, tpe)
+      VarStorage.Local(receiverParam)
+    }
+
+    val normalParamsEnv: Env = paramDefs.map { paramDef =>
+      val param = fb.addParam(
+        paramDef.originalName.orElse(paramDef.name.name),
+        transformLocalType(paramDef.ptpe)
+      )
+      paramDef.name.name -> VarStorage.Local(param)
+    }.toMap
+
+    val fullEnv: Env = captureParamsEnv ++ preSuperEnvEnv ++ normalParamsEnv
+
+    fb.setResultTypes(resultTypes)
+
+    new FunctionEmitter(
+      fb,
+      enclosingClassName,
+      newTargetStorage,
+      receiverStorage,
+      fullEnv
+    )
+  }
+
+  private val ObjectRef = ClassRef(ObjectClass)
+  private val BoxedStringRef = ClassRef(BoxedStringClass)
+  private val toStringMethodName = MethodName("toString", Nil, BoxedStringRef)
+  private val equalsMethodName = MethodName("equals", List(ObjectRef), BooleanRef)
+  private val compareToMethodName = MethodName("compareTo", List(ObjectRef), IntRef)
+
+  private val CharSequenceClass = ClassName("java.lang.CharSequence")
+  private val ComparableClass = ClassName("java.lang.Comparable")
+  private val JLNumberClass = ClassName("java.lang.Number")
+
+  private val newTargetOriginalName = OriginalName("new.target")
+  private val receiverOriginalName = OriginalName("this")
+
+  private sealed abstract class VarStorage
+
+  private object VarStorage {
+    final case class Local(localID: wanme.LocalID) extends VarStorage
+
+    final case class StructField(structLocalID: wanme.LocalID,
+        structTypeID: wanme.TypeID, fieldID: wanme.FieldID)
+        extends VarStorage
+  }
+
+  private type Env = Map[LocalName, VarStorage]
+
+  private final class ClosureFunctionID(debugName: OriginalName) extends wanme.FunctionID {
+    override def toString(): String = s"ClosureFunctionID(${debugName.toString()})"
+  }
+}
+
+private class FunctionEmitter private (
+    val fb: FunctionBuilder,
+    enclosingClassName: Option[ClassName],
+    _newTargetStorage: Option[FunctionEmitter.VarStorage.Local],
+    _receiverStorage: Option[FunctionEmitter.VarStorage.Local],
+    paramsEnv: FunctionEmitter.Env
+)(implicit ctx: WasmContext) {
+  import FunctionEmitter._
+
+  private var closureIdx: Int = 0
+  private var currentEnv: Env = paramsEnv
+
+  private def newTargetStorage: VarStorage.Local =
+    _newTargetStorage.getOrElse(throw new Error("Cannot access new.target in this context."))
+
+  private def receiverStorage: VarStorage.Local =
+    _receiverStorage.getOrElse(throw new Error("Cannot access to the receiver in this context."))
+
+  private def withNewLocal[A](name: LocalName, originalName: OriginalName, tpe: watpe.Type)(
+      body: wanme.LocalID => A
+  ): A = {
+    val savedEnv = currentEnv
+    val local = fb.addLocal(originalName.orElse(name), tpe)
+    currentEnv = currentEnv.updated(name, VarStorage.Local(local))
+    try body(local)
+    finally currentEnv = savedEnv
+  }
+
+  private def lookupLocal(name: LocalName): VarStorage = {
+    currentEnv.getOrElse(
+      name, {
+        throw new AssertionError(s"Cannot find binding for '${name.nameString}'")
+      }
+    )
+  }
+
+  private def addSyntheticLocal(tpe: watpe.Type): wanme.LocalID =
+    fb.addLocal(NoOriginalName, tpe)
+
+  private def genClosureFuncOriginalName(): OriginalName = {
+    if (fb.functionOriginalName.isEmpty) {
+      NoOriginalName
+    } else {
+      val innerName = OriginalName(fb.functionOriginalName.get ++ UTF8String("__c" + closureIdx))
+      closureIdx += 1
+      innerName
+    }
+  }
+
+  private def markPosition(pos: Position): Unit =
+    fb += wa.PositionMark(pos)
+
+  private def markPosition(tree: Tree): Unit =
+    markPosition(tree.pos)
+
+  def genBody(tree: Tree, expectedType: Type): Unit =
+    genTree(tree, expectedType)
+
+  def genTreeAuto(tree: Tree): Unit =
+    genTree(tree, tree.tpe)
+
+  def genTree(tree: Tree, expectedType: Type): Unit = {
+    val generatedType: Type = tree match {
+      case t: Literal             => genLiteral(t, expectedType)
+      case t: UnaryOp             => genUnaryOp(t)
+      case t: BinaryOp            => genBinaryOp(t)
+      case t: VarRef              => genVarRef(t)
+      case t: LoadModule          => genLoadModule(t)
+      case t: StoreModule         => genStoreModule(t)
+      case t: This                => genThis(t)
+      case t: ApplyStatically     => genApplyStatically(t)
+      case t: Apply               => genApply(t)
+      case t: ApplyStatic         => genApplyStatic(t)
+      case t: ApplyDynamicImport  => genApplyDynamicImport(t)
+      case t: IsInstanceOf        => genIsInstanceOf(t)
+      case t: AsInstanceOf        => genAsInstanceOf(t)
+      case t: GetClass            => genGetClass(t)
+      case t: Block               => genBlock(t, expectedType)
+      case t: Labeled             => unwinding.genLabeled(t, expectedType)
+      case t: Return              => unwinding.genReturn(t)
+      case t: Select              => genSelect(t)
+      case t: SelectStatic        => genSelectStatic(t)
+      case t: Assign              => genAssign(t)
+      case t: VarDef              => genVarDef(t)
+      case t: New                 => genNew(t)
+      case t: If                  => genIf(t, expectedType)
+      case t: While               => genWhile(t)
+      case t: ForIn               => genForIn(t)
+      case t: TryCatch            => genTryCatch(t, expectedType)
+      case t: TryFinally          => unwinding.genTryFinally(t, expectedType)
+      case t: Throw               => genThrow(t)
+      case t: Match               => genMatch(t, expectedType)
+      case t: Debugger            => NoType // ignore
+      case t: Skip                => NoType
+      case t: Clone               => genClone(t)
+      case t: IdentityHashCode    => genIdentityHashCode(t)
+      case t: WrapAsThrowable     => genWrapAsThrowable(t)
+      case t: UnwrapFromThrowable => genUnwrapFromThrowable(t)
+
+      // JavaScript expressions
+      case t: JSNew                => genJSNew(t)
+      case t: JSSelect             => genJSSelect(t)
+      case t: JSFunctionApply      => genJSFunctionApply(t)
+      case t: JSMethodApply        => genJSMethodApply(t)
+      case t: JSImportCall         => genJSImportCall(t)
+      case t: JSImportMeta         => genJSImportMeta(t)
+      case t: LoadJSConstructor    => genLoadJSConstructor(t)
+      case t: LoadJSModule         => genLoadJSModule(t)
+      case t: SelectJSNativeMember => genSelectJSNativeMember(t)
+      case t: JSDelete             => genJSDelete(t)
+      case t: JSUnaryOp            => genJSUnaryOp(t)
+      case t: JSBinaryOp           => genJSBinaryOp(t)
+      case t: JSArrayConstr        => genJSArrayConstr(t)
+      case t: JSObjectConstr       => genJSObjectConstr(t)
+      case t: JSGlobalRef          => genJSGlobalRef(t)
+      case t: JSTypeOfGlobalRef    => genJSTypeOfGlobalRef(t)
+      case t: JSLinkingInfo        => genJSLinkingInfo(t)
+      case t: Closure              => genClosure(t)
+
+      // array
+      case t: ArrayLength => genArrayLength(t)
+      case t: NewArray    => genNewArray(t)
+      case t: ArraySelect => genArraySelect(t)
+      case t: ArrayValue  => genArrayValue(t)
+
+      // Non-native JS classes
+      case t: CreateJSClass     => genCreateJSClass(t)
+      case t: JSPrivateSelect   => genJSPrivateSelect(t)
+      case t: JSSuperSelect     => genJSSuperSelect(t)
+      case t: JSSuperMethodCall => genJSSuperMethodCall(t)
+      case t: JSNewTarget       => genJSNewTarget(t)
+
+      case _: RecordSelect | _: RecordValue | _: Transient | _: JSSuperConstructorCall =>
+        throw new AssertionError(s"Invalid tree: $tree")
+    }
+
+    genAdapt(generatedType, expectedType)
+  }
+
+  private def genAdapt(generatedType: Type, expectedType: Type): Unit = {
+    (generatedType, expectedType) match {
+      case _ if generatedType == expectedType =>
+        ()
+      case (NothingType, _) =>
+        ()
+      case (_, NoType) =>
+        fb += wa.Drop
+      case (primType: PrimTypeWithRef, _) =>
+        // box
+        primType match {
+          case NullType =>
+            ()
+          case CharType =>
+            /* `char` and `long` are opaque to JS in the Scala.js semantics.
+             * We implement them with real Wasm classes following the correct
+             * vtable. Upcasting wraps a primitive into the corresponding class.
+             */
+            genBox(watpe.Int32, SpecialNames.CharBoxClass)
+          case LongType =>
+            genBox(watpe.Int64, SpecialNames.LongBoxClass)
+          case NoType | NothingType =>
+            throw new AssertionError(s"Unexpected adaptation from $primType to $expectedType")
+          case _ =>
+            /* Calls a `bX` helper. Most of them are of the form
+             *   bX: (x) => x
+             * at the JavaScript level, but with a primType->anyref Wasm type.
+             * For example, for `IntType`, `bI` has type `i32 -> anyref`. This
+             * asks the JS host to turn a primitive `i32` into its generic
+             * representation, which we can store in an `anyref`.
+             */
+            fb += wa.Call(genFunctionID.box(primType.primRef))
+        }
+      case _ =>
+        ()
+    }
+  }
+
+  private def genAssign(tree: Assign): Type = {
+    val Assign(lhs, rhs) = tree
+
+    lhs match {
+      case Select(qualifier, field) =>
+        val className = field.name.className
+        val classInfo = ctx.getClassInfo(className)
+
+        // For Select, the receiver can never be a hijacked class, so we can use genTreeAuto
+        genTreeAuto(qualifier)
+
+        if (!classInfo.hasInstances) {
+          /* The field may not exist in that case, and we cannot look it up.
+           * However we necessarily have a `null` receiver if we reach this
+           * point, so we can trap as NPE.
+           */
+          markPosition(tree)
+          fb += wa.Unreachable
+        } else {
+          genTree(rhs, lhs.tpe)
+          markPosition(tree)
+          fb += wa.StructSet(
+            genTypeID.forClass(className),
+            genFieldID.forClassInstanceField(field.name)
+          )
+        }
+
+      case SelectStatic(field) =>
+        val fieldName = field.name
+        val globalID = genGlobalID.forStaticField(fieldName)
+
+        genTree(rhs, lhs.tpe)
+        markPosition(tree)
+        fb += wa.GlobalSet(globalID)
+
+        // Update top-level export mirrors
+        val classInfo = ctx.getClassInfo(fieldName.className)
+        val mirrors = classInfo.staticFieldMirrors.getOrElse(fieldName, Nil)
+        for (exportedName <- mirrors) {
+          fb += wa.GlobalGet(globalID)
+          fb += wa.Call(genFunctionID.forTopLevelExportSetter(exportedName))
+        }
+
+      case ArraySelect(array, index) =>
+        genTreeAuto(array)
+        array.tpe match {
+          case ArrayType(arrayTypeRef) =>
+            // Get the underlying array; implicit trap on null
+            markPosition(tree)
+            fb += wa.StructGet(
+              genTypeID.forArrayClass(arrayTypeRef),
+              genFieldID.objStruct.arrayUnderlying
+            )
+            genTree(index, IntType)
+            genTree(rhs, lhs.tpe)
+            markPosition(tree)
+            fb += wa.ArraySet(genTypeID.underlyingOf(arrayTypeRef))
+          case NothingType =>
+            // unreachable
+            ()
+          case NullType =>
+            markPosition(tree)
+            fb += wa.Unreachable
+          case _ =>
+            throw new IllegalArgumentException(
+                s"ArraySelect.array must be an array type, but has type ${array.tpe}")
+        }
+
+      case JSPrivateSelect(qualifier, field) =>
+        genTree(qualifier, AnyType)
+        fb += wa.GlobalGet(genGlobalID.forJSPrivateField(field.name))
+        genTree(rhs, AnyType)
+        markPosition(tree)
+        fb += wa.Call(genFunctionID.jsSelectSet)
+
+      case JSSelect(qualifier, item) =>
+        genTree(qualifier, AnyType)
+        genTree(item, AnyType)
+        genTree(rhs, AnyType)
+        markPosition(tree)
+        fb += wa.Call(genFunctionID.jsSelectSet)
+
+      case JSSuperSelect(superClass, receiver, item) =>
+        genTree(superClass, AnyType)
+        genTree(receiver, AnyType)
+        genTree(item, AnyType)
+        genTree(rhs, AnyType)
+        markPosition(tree)
+        fb += wa.Call(genFunctionID.jsSuperSelectSet)
+
+      case JSGlobalRef(name) =>
+        markPosition(tree)
+        fb ++= ctx.stringPool.getConstantStringInstr(name)
+        genTree(rhs, AnyType)
+        markPosition(tree)
+        fb += wa.Call(genFunctionID.jsGlobalRefSet)
+
+      case VarRef(ident) =>
+        lookupLocal(ident.name) match {
+          case VarStorage.Local(local) =>
+            genTree(rhs, lhs.tpe)
+            markPosition(tree)
+            fb += wa.LocalSet(local)
+          case VarStorage.StructField(structLocal, structTypeID, fieldID) =>
+            markPosition(tree)
+            fb += wa.LocalGet(structLocal)
+            genTree(rhs, lhs.tpe)
+            markPosition(tree)
+            fb += wa.StructSet(structTypeID, fieldID)
+        }
+
+      case lhs: RecordSelect =>
+        throw new AssertionError(s"Invalid tree: $tree")
+    }
+
+    NoType
+  }
+
+  private def genApply(tree: Apply): Type = {
+    val Apply(flags, receiver, method, args) = tree
+
+    receiver.tpe match {
+      case NothingType =>
+        genTree(receiver, NothingType)
+        // nothing else to do; this is unreachable
+        NothingType
+
+      case NullType =>
+        genTree(receiver, NullType)
+        fb += wa.Unreachable // trap
+        NothingType
+
+      case _ if method.name.isReflectiveProxy =>
+        genReflectiveCall(tree)
+
+      case _ =>
+        val receiverClassName = receiver.tpe match {
+          case prim: PrimType  => PrimTypeToBoxedClass(prim)
+          case ClassType(cls)  => cls
+          case AnyType         => ObjectClass
+          case ArrayType(_)    => ObjectClass
+          case tpe: RecordType => throw new AssertionError(s"Invalid receiver type $tpe")
+        }
+        val receiverClassInfo = ctx.getClassInfo(receiverClassName)
+
+        /* If possible, "optimize" this Apply node as an ApplyStatically call.
+         * We can do this if the receiver's class is a hijacked class or an
+         * array type (because they are known to be final) or if the target
+         * method is effectively final.
+         *
+         * The latter condition is nothing but an optimization, and should be
+         * done by the optimizer instead. We will remove it once we can run the
+         * optimizer with Wasm.
+         *
+         * The former condition (being a hijacked class or an array type) will
+         * also never happen after we have the optimizer. But if we do not have
+         * the optimizer, we must still do it now because the preconditions of
+         * `genApplyWithDispatch` would not be met.
+         */
+        val canUseStaticallyResolved = {
+          receiverClassInfo.kind == ClassKind.HijackedClass ||
+          receiver.tpe.isInstanceOf[ArrayType] ||
+          receiverClassInfo.resolvedMethodInfos.get(method.name).exists(_.isEffectivelyFinal)
+        }
+        if (canUseStaticallyResolved) {
+          genApplyStatically(ApplyStatically(
+              flags, receiver, receiverClassName, method, args)(tree.tpe)(tree.pos))
+        } else {
+          genApplyWithDispatch(tree, receiverClassInfo)
+        }
+    }
+  }
+
+  private def genReflectiveCall(tree: Apply): Type = {
+    val Apply(flags, receiver, MethodIdent(methodName), args) = tree
+
+    assert(methodName.isReflectiveProxy)
+
+    val receiverLocalForDispatch =
+      addSyntheticLocal(watpe.RefType.any)
+
+    val proxyId = ctx.getReflectiveProxyId(methodName)
+    val funcTypeID = ctx.tableFunctionType(methodName)
+
+    /* We only need to handle calls on non-hijacked classes. For hijacked
+     * classes, the compiler already emits the appropriate dispatch at the IR
+     * level.
+     */
+
+    // Load receiver and arguments
+    genTree(receiver, AnyType)
+    fb += wa.RefAsNonNull
+    fb += wa.LocalTee(receiverLocalForDispatch)
+    genArgs(args, methodName)
+
+    // Looks up the method to be (reflectively) called
+    markPosition(tree)
+    fb += wa.LocalGet(receiverLocalForDispatch)
+    fb += wa.RefCast(watpe.RefType(genTypeID.ObjectStruct)) // see above: cannot be a hijacked class
+    fb += wa.StructGet(genTypeID.ObjectStruct, genFieldID.objStruct.vtable)
+    fb += wa.I32Const(proxyId)
+    // `searchReflectiveProxy`: [typeData, i32] -> [(ref func)]
+    fb += wa.Call(genFunctionID.searchReflectiveProxy)
+
+    fb += wa.RefCast(watpe.RefType(watpe.HeapType(funcTypeID)))
+    fb += wa.CallRef(funcTypeID)
+
+    tree.tpe
+  }
+
+  /** Generates the code for an `Apply` tree that requires dynamic dispatch.
+   *
+   *  In that case, there is always at least a vtable/itable-based dispatch. It may also contain
+   *  primitive-based dispatch if the receiver's type is an ancestor of a hijacked class.
+   *
+   *  This method must not be used if the receiver's type is a primitive, a
+   *  hijacked class or an array type. Hijacked classes do not have dispatch
+   *  tables, so the methods that are not available in any superclass/interface
+   *  cannot be called through a table dispatch. Array types share their vtable
+   *  with jl.Object, but methods called directly on an array type are not
+   *  registered as called on jl.Object by the Analyzer. In all these cases,
+   *  we must use a statically resolved call instead.
+   */
+  private def genApplyWithDispatch(tree: Apply,
+      receiverClassInfo: WasmContext.ClassInfo): Type = {
+
+    val Apply(flags, receiver, MethodIdent(methodName), args) = tree
+
+    val receiverClassName = receiverClassInfo.name
+
+    /* Similar to transformType(t.receiver.tpe), but:
+     * - it is non-null,
+     * - ancestors of hijacked classes are not treated specially,
+     * - array types are treated as j.l.Object.
+     *
+     * This is used in the code paths where we have already ruled out `null`
+     * values and primitive values (that implement hijacked classes).
+     */
+    val refTypeForDispatch: watpe.RefType = {
+      if (receiverClassInfo.isInterface)
+        watpe.RefType(genTypeID.ObjectStruct)
+      else
+        watpe.RefType(genTypeID.forClass(receiverClassName))
+    }
+
+    // A local for a copy of the receiver that we will use to resolve dispatch
+    val receiverLocalForDispatch = addSyntheticLocal(refTypeForDispatch)
+
+    /* Gen loading of the receiver and check that it is non-null.
+     * After this codegen, the non-null receiver is on the stack.
+     */
+    def genReceiverNotNull(): Unit = {
+      genTreeAuto(receiver)
+      fb += wa.RefAsNonNull
+    }
+
+    /* Generates a resolved call to a method of a hijacked class.
+     * Before this code gen, the stack must contain the receiver and the args.
+     * After this code gen, the stack contains the result.
+     */
+    def genHijackedClassCall(hijackedClass: ClassName): Unit = {
+      val funcID = genFunctionID.forMethod(MemberNamespace.Public, hijackedClass, methodName)
+      fb += wa.Call(funcID)
+    }
+
+    if (!receiverClassInfo.hasInstances) {
+      /* If the target class info does not have any instance, the only possible
+       * value for the receiver is `null`. We can therefore immediately trap for
+       * an NPE. It is important to short-cut this path because the reachability
+       * analysis may have entirely dead-code eliminated the target method,
+       * which means we do not know its signature and therefore cannot emit the
+       * corresponding vtable/itable calls.
+       */
+      genTreeAuto(receiver)
+      markPosition(tree)
+      fb += wa.Unreachable // NPE
+    } else if (!receiverClassInfo.isAncestorOfHijackedClass) {
+      // Standard dispatch codegen
+      genReceiverNotNull()
+      fb += wa.LocalTee(receiverLocalForDispatch)
+      genArgs(args, methodName)
+
+      markPosition(tree)
+      genTableDispatch(receiverClassInfo, methodName, receiverLocalForDispatch)
+    } else {
+      /* Here the receiver's type is an ancestor of a hijacked class (or `any`,
+       * which is treated as `jl.Object`).
+       *
+       * We must emit additional dispatch for the possible primitive values.
+       *
+       * The overall structure of the generated code is as follows:
+       *
+       * block resultType $done
+       *   block (ref any) $notOurObject
+       *     load non-null receiver and args and store into locals
+       *     reload copy of receiver
+       *     br_on_cast_fail (ref any) (ref $targetRealClass) $notOurObject
+       *     reload args
+       *     generate standard table-based dispatch
+       *     br $done
+       *   end $notOurObject
+       *   choose an implementation of a single hijacked class, or a JS helper
+       *   reload args
+       *   call the chosen implementation
+       * end $done
+       */
+
+      assert(receiverClassInfo.kind != ClassKind.HijackedClass, receiverClassName)
+
+      val resultType = transformResultType(tree.tpe)
+
+      fb.block(resultType) { labelDone =>
+        def pushArgs(argsLocals: List[wanme.LocalID]): Unit =
+          argsLocals.foreach(argLocal => fb += wa.LocalGet(argLocal))
+
+        /* First try the case where the value is one of our objects.
+         * We load the receiver and arguments inside the block `notOurObject`.
+         * This helps producing good code for the no-args case, in which we do
+         * not need to store the receiver in a local at all.
+         * For the case with the args, it does not hurt either way. We could
+         * move it out, but that would make for a less consistent codegen.
+         */
+        val argsLocals = fb.block(watpe.RefType.any) { labelNotOurObject =>
+          // Load receiver and arguments and store them in temporary variables
+          genReceiverNotNull()
+          val argsLocals = if (args.isEmpty) {
+            /* When there are no arguments, we can leave the receiver directly on
+             * the stack instead of going through a local. We will still need a
+             * local for the table-based dispatch, though.
+             */
+            Nil
+          } else {
+            /* When there are arguments, we need to store them in temporary
+             * variables. This is not required for correctness of the evaluation
+             * order. It is only necessary so that we do not duplicate the
+             * codegen of the arguments. If the arguments are complex, doing so
+             * could lead to exponential blow-up of the generated code.
+             */
+            val receiverLocal = addSyntheticLocal(watpe.RefType.any)
+
+            fb += wa.LocalSet(receiverLocal)
+            val argsLocals: List[wanme.LocalID] =
+              for ((arg, typeRef) <- args.zip(methodName.paramTypeRefs)) yield {
+                val tpe = ctx.inferTypeFromTypeRef(typeRef)
+                genTree(arg, tpe)
+                val localID = addSyntheticLocal(transformLocalType(tpe))
+                fb += wa.LocalSet(localID)
+                localID
+              }
+            fb += wa.LocalGet(receiverLocal)
+            argsLocals
+          }
+
+          markPosition(tree) // main position marker for the entire hijacked class dispatch branch
+
+          fb += wa.BrOnCastFail(labelNotOurObject, watpe.RefType.any, refTypeForDispatch)
+          fb += wa.LocalTee(receiverLocalForDispatch)
+          pushArgs(argsLocals)
+          genTableDispatch(receiverClassInfo, methodName, receiverLocalForDispatch)
+          fb += wa.Br(labelDone)
+
+          argsLocals
+        } // end block labelNotOurObject
+
+        /* Now we have a value that is not one of our objects, so it must be
+         * a JavaScript value whose representative class extends/implements the
+         * receiver class. It may be a primitive instance of a hijacked class, or
+         * any other value (whose representative class is therefore `jl.Object`).
+         *
+         * It is also *not* `char` or `long`, since those would reach
+         * `genApplyNonPrim` in their boxed form, and therefore they are
+         * "ourObject".
+         *
+         * The (ref any) is still on the stack.
+         */
+
+        if (methodName == toStringMethodName) {
+          // By spec, toString() is special
+          assert(argsLocals.isEmpty)
+          fb += wa.Call(genFunctionID.jsValueToString)
+        } else if (receiverClassName == JLNumberClass) {
+          // the value must be a `number`, hence we can unbox to `double`
+          genUnbox(DoubleType)
+          pushArgs(argsLocals)
+          genHijackedClassCall(BoxedDoubleClass)
+        } else if (receiverClassName == CharSequenceClass) {
+          // the value must be a `string`; it already has the right type
+          pushArgs(argsLocals)
+          genHijackedClassCall(BoxedStringClass)
+        } else if (methodName == compareToMethodName) {
+          /* The only method of jl.Comparable. Here the value can be a boolean,
+           * a number or a string. We use `jsValueType` to dispatch to Wasm-side
+           * implementations because they have to perform casts on their arguments.
+           */
+          assert(argsLocals.size == 1)
+
+          val receiverLocal = addSyntheticLocal(watpe.RefType.any)
+          fb += wa.LocalTee(receiverLocal)
+
+          val jsValueTypeLocal = addSyntheticLocal(watpe.Int32)
+          fb += wa.Call(genFunctionID.jsValueType)
+          fb += wa.LocalTee(jsValueTypeLocal)
+
+          fb.switch(Sig(List(watpe.Int32), Nil), Sig(Nil, List(watpe.Int32))) { () =>
+            // scrutinee is already on the stack
+          }(
+            // case JSValueTypeFalse | JSValueTypeTrue =>
+            List(JSValueTypeFalse, JSValueTypeTrue) -> { () =>
+              /* The jsValueTypeLocal is the boolean value, thanks to the chosen encoding.
+               * This trick avoids an additional unbox.
+               */
+              fb += wa.LocalGet(jsValueTypeLocal)
+              pushArgs(argsLocals)
+              genHijackedClassCall(BoxedBooleanClass)
+            },
+            // case JSValueTypeString =>
+            List(JSValueTypeString) -> { () =>
+              fb += wa.LocalGet(receiverLocal)
+              // no need to unbox for string
+              pushArgs(argsLocals)
+              genHijackedClassCall(BoxedStringClass)
+            }
+          ) { () =>
+            // case _ (JSValueTypeNumber) =>
+            fb += wa.LocalGet(receiverLocal)
+            genUnbox(DoubleType)
+            pushArgs(argsLocals)
+            genHijackedClassCall(BoxedDoubleClass)
+          }
+        } else {
+          /* It must be a method of j.l.Object and it can be any value.
+           * hashCode() and equals() are overridden in all hijacked classes.
+           * We use `identityHashCode` for `hashCode` and `Object.is` for `equals`,
+           * as they coincide with the respective specifications (on purpose).
+           * The other methods are never overridden and can be statically
+           * resolved to j.l.Object.
+           */
+          pushArgs(argsLocals)
+          methodName match {
+            case SpecialNames.hashCodeMethodName =>
+              fb += wa.Call(genFunctionID.identityHashCode)
+            case `equalsMethodName` =>
+              fb += wa.Call(genFunctionID.is)
+            case _ =>
+              genHijackedClassCall(ObjectClass)
+          }
+        }
+      } // end block labelDone
+    }
+
+    if (tree.tpe == NothingType)
+      fb += wa.Unreachable
+
+    tree.tpe
+  }
+
+  /** Generates a vtable- or itable-based dispatch.
+   *
+   *  Before this code gen, the stack must contain the receiver and the args of the target method.
+   *  In addition, the receiver must be available in the local `receiverLocalForDispatch`. The two
+   *  occurrences of the receiver must have the type for dispatch.
+   *
+   *  After this code gen, the stack contains the result. If the result type is `NothingType`,
+   *  `genTableDispatch` leaves the stack in an arbitrary state. It is up to the caller to insert an
+   *  `unreachable` instruction when appropriate.
+   */
+  def genTableDispatch(receiverClassInfo: WasmContext.ClassInfo,
+      methodName: MethodName, receiverLocalForDispatch: wanme.LocalID): Unit = {
+    // Generates an itable-based dispatch.
+    def genITableDispatch(): Unit = {
+      fb += wa.LocalGet(receiverLocalForDispatch)
+      fb += wa.StructGet(genTypeID.ObjectStruct, genFieldID.objStruct.itables)
+      fb += wa.I32Const(receiverClassInfo.itableIdx)
+      fb += wa.ArrayGet(genTypeID.itables)
+      fb += wa.RefCast(watpe.RefType(genTypeID.forITable(receiverClassInfo.name)))
+      fb += wa.StructGet(
+        genTypeID.forITable(receiverClassInfo.name),
+        genFieldID.forMethodTableEntry(methodName)
+      )
+      fb += wa.CallRef(ctx.tableFunctionType(methodName))
+    }
+
+    // Generates a vtable-based dispatch.
+    def genVTableDispatch(): Unit = {
+      val receiverClassName = receiverClassInfo.name
+
+      fb += wa.LocalGet(receiverLocalForDispatch)
+      fb += wa.StructGet(
+        genTypeID.forClass(receiverClassName),
+        genFieldID.objStruct.vtable
+      )
+      fb += wa.StructGet(
+        genTypeID.forVTable(receiverClassName),
+        genFieldID.forMethodTableEntry(methodName)
+      )
+      fb += wa.CallRef(ctx.tableFunctionType(methodName))
+    }
+
+    if (receiverClassInfo.isInterface)
+      genITableDispatch()
+    else
+      genVTableDispatch()
+  }
+
+  private def genApplyStatically(tree: ApplyStatically): Type = {
+    val ApplyStatically(flags, receiver, className, MethodIdent(methodName), args) = tree
+
+    receiver.tpe match {
+      case NothingType =>
+        genTree(receiver, NothingType)
+        // nothing else to do; this is unreachable
+        NothingType
+
+      case NullType =>
+        genTree(receiver, NullType)
+        markPosition(tree)
+        fb += wa.Unreachable // trap
+        NothingType
+
+      case _ =>
+        val namespace = MemberNamespace.forNonStaticCall(flags)
+        val targetClassName = {
+          val classInfo = ctx.getClassInfo(className)
+          if (!classInfo.isInterface && namespace == MemberNamespace.Public)
+            classInfo.resolvedMethodInfos(methodName).ownerClass
+          else
+            className
+        }
+
+        BoxedClassToPrimType.get(targetClassName) match {
+          case None =>
+            genTree(receiver, ClassType(targetClassName))
+            fb += wa.RefAsNonNull
+
+          case Some(primReceiverType) =>
+            if (receiver.tpe == primReceiverType) {
+              genTreeAuto(receiver)
+            } else {
+              genTree(receiver, AnyType)
+              fb += wa.RefAsNonNull
+              genUnbox(primReceiverType)
+            }
+        }
+
+        genArgs(args, methodName)
+
+        markPosition(tree)
+        val funcID = genFunctionID.forMethod(namespace, targetClassName, methodName)
+        fb += wa.Call(funcID)
+        if (tree.tpe == NothingType)
+          fb += wa.Unreachable
+        tree.tpe
+    }
+  }
+
+  private def genApplyStatic(tree: ApplyStatic): Type = {
+    val ApplyStatic(flags, className, MethodIdent(methodName), args) = tree
+
+    genArgs(args, methodName)
+    val namespace = MemberNamespace.forStaticCall(flags)
+    val funcID = genFunctionID.forMethod(namespace, className, methodName)
+    markPosition(tree)
+    fb += wa.Call(funcID)
+    if (tree.tpe == NothingType)
+      fb += wa.Unreachable
+    tree.tpe
+  }
+
+  private def genApplyDynamicImport(tree: ApplyDynamicImport): Type = {
+    // As long as we do not support multiple modules, this cannot happen
+    throw new AssertionError(
+        s"Unexpected $tree at ${tree.pos}; multiple modules are not supported yet")
+  }
+
+  private def genArgs(args: List[Tree], methodName: MethodName): Unit = {
+    for ((arg, paramTypeRef) <- args.zip(methodName.paramTypeRefs)) {
+      val paramType = ctx.inferTypeFromTypeRef(paramTypeRef)
+      genTree(arg, paramType)
+    }
+  }
+
+  private def genLiteral(tree: Literal, expectedType: Type): Type = {
+    if (expectedType == NoType) {
+      /* Since all literals are pure, we can always get rid of them.
+       * This is mostly useful for the argument of `Return` nodes that target a
+       * `Labeled` in statement position, since they must have a non-`void`
+       * type in the IR but they get a `void` expected type.
+       */
+      expectedType
+    } else {
+      markPosition(tree)
+
+      tree match {
+        case BooleanLiteral(v) => fb += wa.I32Const(if (v) 1 else 0)
+        case ByteLiteral(v)    => fb += wa.I32Const(v)
+        case ShortLiteral(v)   => fb += wa.I32Const(v)
+        case IntLiteral(v)     => fb += wa.I32Const(v)
+        case CharLiteral(v)    => fb += wa.I32Const(v)
+        case LongLiteral(v)    => fb += wa.I64Const(v)
+        case FloatLiteral(v)   => fb += wa.F32Const(v)
+        case DoubleLiteral(v)  => fb += wa.F64Const(v)
+
+        case Undefined() =>
+          fb += wa.GlobalGet(genGlobalID.undef)
+        case Null() =>
+          fb += wa.RefNull(watpe.HeapType.None)
+
+        case StringLiteral(v) =>
+          fb ++= ctx.stringPool.getConstantStringInstr(v)
+
+        case ClassOf(typeRef) =>
+          genLoadTypeData(fb, typeRef)
+          fb += wa.Call(genFunctionID.getClassOf)
+      }
+
+      tree.tpe
+    }
+  }
+
+  private def genSelect(tree: Select): Type = {
+    val Select(qualifier, FieldIdent(fieldName)) = tree
+
+    val className = fieldName.className
+    val classInfo = ctx.getClassInfo(className)
+
+    // For Select, the receiver can never be a hijacked class, so we can use genTreeAuto
+    genTreeAuto(qualifier)
+
+    markPosition(tree)
+
+    if (!classInfo.hasInstances) {
+      /* The field may not exist in that case, and we cannot look it up.
+       * However we necessarily have a `null` receiver if we reach this point,
+       * so we can trap as NPE.
+       */
+      fb += wa.Unreachable
+    } else {
+      fb += wa.StructGet(
+        genTypeID.forClass(className),
+        genFieldID.forClassInstanceField(fieldName)
+      )
+    }
+
+    tree.tpe
+  }
+
+  private def genSelectStatic(tree: SelectStatic): Type = {
+    val SelectStatic(FieldIdent(fieldName)) = tree
+
+    markPosition(tree)
+    fb += wa.GlobalGet(genGlobalID.forStaticField(fieldName))
+    tree.tpe
+  }
+
+  private def genStoreModule(tree: StoreModule): Type = {
+    val className = enclosingClassName.getOrElse {
+      throw new AssertionError(s"Cannot emit $tree at ${tree.pos} without enclosing class name")
+    }
+
+    genTreeAuto(This()(ClassType(className))(tree.pos))
+
+    markPosition(tree)
+    fb += wa.GlobalSet(genGlobalID.forModuleInstance(className))
+    NoType
+  }
+
+  private def genLoadModule(tree: LoadModule): Type = {
+    val LoadModule(className) = tree
+
+    markPosition(tree)
+    fb += wa.Call(genFunctionID.loadModule(className))
+    tree.tpe
+  }
+
+  private def genUnaryOp(tree: UnaryOp): Type = {
+    import UnaryOp._
+
+    val UnaryOp(op, lhs) = tree
+
+    genTreeAuto(lhs)
+
+    markPosition(tree)
+
+    (op: @switch) match {
+      case Boolean_! =>
+        fb += wa.I32Eqz
+
+      // Widening conversions
+      case CharToInt | ByteToInt | ShortToInt =>
+        /* These are no-ops because they are all represented as i32's with the
+         * right mathematical value.
+         */
+        ()
+      case IntToLong =>
+        fb += wa.I64ExtendI32S
+      case IntToDouble =>
+        fb += wa.F64ConvertI32S
+      case FloatToDouble =>
+        fb += wa.F64PromoteF32
+
+      // Narrowing conversions
+      case IntToChar =>
+        fb += wa.I32Const(0xFFFF)
+        fb += wa.I32And
+      case IntToByte =>
+        fb += wa.I32Extend8S
+      case IntToShort =>
+        fb += wa.I32Extend16S
+      case LongToInt =>
+        fb += wa.I32WrapI64
+      case DoubleToInt =>
+        fb += wa.I32TruncSatF64S
+      case DoubleToFloat =>
+        fb += wa.F32DemoteF64
+
+      // Long <-> Double (neither widening nor narrowing)
+      case LongToDouble =>
+        fb += wa.F64ConvertI64S
+      case DoubleToLong =>
+        fb += wa.I64TruncSatF64S
+
+      // Long -> Float (neither widening nor narrowing)
+      case LongToFloat =>
+        fb += wa.F32ConvertI64S
+
+      // String.length
+      case String_length =>
+        fb += wa.Call(genFunctionID.stringLength)
+    }
+
+    tree.tpe
+  }
+
+  private def genBinaryOp(tree: BinaryOp): Type = {
+    import BinaryOp._
+
+    val BinaryOp(op, lhs, rhs) = tree
+
+    def genLongShiftOp(shiftInstr: wa.Instr): Type = {
+      genTree(lhs, LongType)
+      genTree(rhs, IntType)
+      markPosition(tree)
+      fb += wa.I64ExtendI32S
+      fb += shiftInstr
+      LongType
+    }
+
+    (op: @switch) match {
+      case === | !== =>
+        genEq(tree)
+
+      case String_+ =>
+        genStringConcat(tree)
+
+      case Int_/ =>
+        rhs match {
+          case IntLiteral(rhsValue) =>
+            genDivModByConstant(tree, isDiv = true, rhsValue, wa.I32Const(_), wa.I32Sub, wa.I32DivS)
+          case _ =>
+            genDivMod(tree, isDiv = true, wa.I32Const(_), wa.I32Eqz, wa.I32Eq, wa.I32Sub, wa.I32DivS)
+        }
+      case Int_% =>
+        rhs match {
+          case IntLiteral(rhsValue) =>
+            genDivModByConstant(tree, isDiv = false, rhsValue, wa.I32Const(_), wa.I32Sub, wa.I32RemS)
+          case _ =>
+            genDivMod(tree, isDiv = false, wa.I32Const(_), wa.I32Eqz, wa.I32Eq, wa.I32Sub, wa.I32RemS)
+        }
+      case Long_/ =>
+        rhs match {
+          case LongLiteral(rhsValue) =>
+            genDivModByConstant(tree, isDiv = true, rhsValue, wa.I64Const(_), wa.I64Sub, wa.I64DivS)
+          case _ =>
+            genDivMod(tree, isDiv = true, wa.I64Const(_), wa.I64Eqz, wa.I64Eq, wa.I64Sub, wa.I64DivS)
+        }
+      case Long_% =>
+        rhs match {
+          case LongLiteral(rhsValue) =>
+            genDivModByConstant(tree, isDiv = false, rhsValue, wa.I64Const(_), wa.I64Sub, wa.I64RemS)
+          case _ =>
+            genDivMod(tree, isDiv = false, wa.I64Const(_), wa.I64Eqz, wa.I64Eq, wa.I64Sub, wa.I64RemS)
+        }
+
+      case Long_<< =>
+        genLongShiftOp(wa.I64Shl)
+      case Long_>>> =>
+        genLongShiftOp(wa.I64ShrU)
+      case Long_>> =>
+        genLongShiftOp(wa.I64ShrS)
+
+      /* Floating point remainders are specified by
+       * https://262.ecma-international.org/#sec-numeric-types-number-remainder
+       * which says that it is equivalent to the C library function `fmod`.
+       * For `Float`s, we promote and demote to `Double`s.
+       * `fmod` seems quite hard to correctly implement, so we delegate to a
+       * JavaScript Helper.
+       * (The naive function `x - trunc(x / y) * y` that we can find on the
+       * Web does not work.)
+       */
+      case Float_% =>
+        genTree(lhs, FloatType)
+        fb += wa.F64PromoteF32
+        genTree(rhs, FloatType)
+        fb += wa.F64PromoteF32
+        markPosition(tree)
+        fb += wa.Call(genFunctionID.fmod)
+        fb += wa.F32DemoteF64
+        FloatType
+      case Double_% =>
+        genTree(lhs, DoubleType)
+        genTree(rhs, DoubleType)
+        markPosition(tree)
+        fb += wa.Call(genFunctionID.fmod)
+        DoubleType
+
+      case String_charAt =>
+        genTree(lhs, StringType)
+        genTree(rhs, IntType)
+        markPosition(tree)
+        fb += wa.Call(genFunctionID.stringCharAt)
+        CharType
+
+      case _ =>
+        genTreeAuto(lhs)
+        genTreeAuto(rhs)
+        markPosition(tree)
+        fb += getElementaryBinaryOpInstr(op)
+        tree.tpe
+    }
+  }
+
+  private def genEq(tree: BinaryOp): Type = {
+    import BinaryOp.{===, !==}
+
+    val BinaryOp(op, lhs, rhs) = tree
+    assert(op == === || op == !==)
+
+    // TODO Optimize this when the operands have a better type than `any`
+
+    genTree(lhs, AnyType)
+    genTree(rhs, AnyType)
+
+    markPosition(tree)
+
+    fb += wa.Call(genFunctionID.is)
+
+    if (op == !==)
+      fb += wa.I32Eqz
+
+    BooleanType
+  }
+
+  private def getElementaryBinaryOpInstr(op: BinaryOp.Code): wa.Instr = {
+    import BinaryOp._
+
+    (op: @switch) match {
+      case Boolean_== => wa.I32Eq
+      case Boolean_!= => wa.I32Ne
+      case Boolean_|  => wa.I32Or
+      case Boolean_&  => wa.I32And
+
+      case Int_+   => wa.I32Add
+      case Int_-   => wa.I32Sub
+      case Int_*   => wa.I32Mul
+      case Int_|   => wa.I32Or
+      case Int_&   => wa.I32And
+      case Int_^   => wa.I32Xor
+      case Int_<<  => wa.I32Shl
+      case Int_>>> => wa.I32ShrU
+      case Int_>>  => wa.I32ShrS
+      case Int_==  => wa.I32Eq
+      case Int_!=  => wa.I32Ne
+      case Int_<   => wa.I32LtS
+      case Int_<=  => wa.I32LeS
+      case Int_>   => wa.I32GtS
+      case Int_>=  => wa.I32GeS
+
+      case Long_+ => wa.I64Add
+      case Long_- => wa.I64Sub
+      case Long_* => wa.I64Mul
+      case Long_| => wa.I64Or
+      case Long_& => wa.I64And
+      case Long_^ => wa.I64Xor
+
+      case Long_== => wa.I64Eq
+      case Long_!= => wa.I64Ne
+      case Long_<  => wa.I64LtS
+      case Long_<= => wa.I64LeS
+      case Long_>  => wa.I64GtS
+      case Long_>= => wa.I64GeS
+
+      case Float_+ => wa.F32Add
+      case Float_- => wa.F32Sub
+      case Float_* => wa.F32Mul
+      case Float_/ => wa.F32Div
+
+      case Double_+ => wa.F64Add
+      case Double_- => wa.F64Sub
+      case Double_* => wa.F64Mul
+      case Double_/ => wa.F64Div
+
+      case Double_== => wa.F64Eq
+      case Double_!= => wa.F64Ne
+      case Double_<  => wa.F64Lt
+      case Double_<= => wa.F64Le
+      case Double_>  => wa.F64Gt
+      case Double_>= => wa.F64Ge
+    }
+  }
+
+  private def genStringConcat(tree: BinaryOp): Type = {
+    val BinaryOp(op, lhs, rhs) = tree
+    assert(op == BinaryOp.String_+)
+
+    lhs match {
+      case StringLiteral("") =>
+        // Common case where we don't actually need a concatenation
+        genToStringForConcat(rhs)
+
+      case _ =>
+        genToStringForConcat(lhs)
+        genToStringForConcat(rhs)
+        markPosition(tree)
+        fb += wa.Call(genFunctionID.stringConcat)
+    }
+
+    StringType
+  }
+
+  private def genToStringForConcat(tree: Tree): Unit = {
+    def genWithDispatch(isAncestorOfHijackedClass: Boolean): Unit = {
+      /* Somewhat duplicated from genApplyNonPrim, but specialized for
+       * `toString`, and where the handling of `null` is different.
+       *
+       * We need to return the `"null"` string in two special cases:
+       * - if the value itself is `null`, or
+       * - if the value's `toString(): String` method returns `null`!
+       */
+
+      // A local for a copy of the receiver that we will use to resolve dispatch
+      val receiverLocalForDispatch =
+        addSyntheticLocal(watpe.RefType(genTypeID.ObjectStruct))
+
+      val objectClassInfo = ctx.getClassInfo(ObjectClass)
+
+      if (!isAncestorOfHijackedClass) {
+        /* Standard dispatch codegen, with dedicated null handling.
+         *
+         * The overall structure of the generated code is as follows:
+         *
+         * block (ref any) $done
+         *   block $isNull
+         *     load receiver as (ref null java.lang.Object)
+         *     br_on_null $isNull
+         *     generate standard table-based dispatch
+         *     br_on_non_null $done
+         *   end $isNull
+         *   gen "null"
+         * end $done
+         */
+
+        fb.block(watpe.RefType.any) { labelDone =>
+          fb.block() { labelIsNull =>
+            genTreeAuto(tree)
+            markPosition(tree)
+            fb += wa.BrOnNull(labelIsNull)
+            fb += wa.LocalTee(receiverLocalForDispatch)
+            genTableDispatch(objectClassInfo, toStringMethodName, receiverLocalForDispatch)
+            fb += wa.BrOnNonNull(labelDone)
+          }
+
+          fb ++= ctx.stringPool.getConstantStringInstr("null")
+        }
+      } else {
+        /* Dispatch where the receiver can be a JS value.
+         *
+         * The overall structure of the generated code is as follows:
+         *
+         * block (ref any) $done
+         *   block anyref $notOurObject
+         *     load receiver
+         *     br_on_cast_fail anyref (ref $java.lang.Object) $notOurObject
+         *     generate standard table-based dispatch
+         *     br_on_non_null $done
+         *     ref.null any
+         *   end $notOurObject
+         *   call the JS helper, also handles `null`
+         * end $done
+         */
+
+        fb.block(watpe.RefType.any) { labelDone =>
+          // First try the case where the value is one of our objects
+          fb.block(watpe.RefType.anyref) { labelNotOurObject =>
+            // Load receiver
+            genTreeAuto(tree)
+
+            markPosition(tree)
+
+            fb += wa.BrOnCastFail(
+              labelNotOurObject,
+              watpe.RefType.anyref,
+              watpe.RefType(genTypeID.ObjectStruct)
+            )
+            fb += wa.LocalTee(receiverLocalForDispatch)
+            genTableDispatch(objectClassInfo, toStringMethodName, receiverLocalForDispatch)
+            fb += wa.BrOnNonNull(labelDone)
+            fb += wa.RefNull(watpe.HeapType.Any)
+          } // end block labelNotOurObject
+
+          // Now we have a value that is not one of our objects; the anyref is still on the stack
+          fb += wa.Call(genFunctionID.jsValueToStringForConcat)
+        } // end block labelDone
+      }
+    }
+
+    tree.tpe match {
+      case primType: PrimType =>
+        genTreeAuto(tree)
+
+        markPosition(tree)
+
+        primType match {
+          case StringType =>
+            () // no-op
+          case BooleanType =>
+            fb += wa.Call(genFunctionID.booleanToString)
+          case CharType =>
+            fb += wa.Call(genFunctionID.charToString)
+          case ByteType | ShortType | IntType =>
+            fb += wa.Call(genFunctionID.intToString)
+          case LongType =>
+            fb += wa.Call(genFunctionID.longToString)
+          case FloatType =>
+            fb += wa.F64PromoteF32
+            fb += wa.Call(genFunctionID.doubleToString)
+          case DoubleType =>
+            fb += wa.Call(genFunctionID.doubleToString)
+          case NullType | UndefType =>
+            fb += wa.Call(genFunctionID.jsValueToStringForConcat)
+          case NothingType =>
+            () // unreachable
+          case NoType =>
+            throw new AssertionError(
+                s"Found expression of type void in String_+ at ${tree.pos}: $tree")
+        }
+
+      case ClassType(BoxedStringClass) =>
+        // Common case for which we want to avoid the hijacked class dispatch
+        genTreeAuto(tree)
+        markPosition(tree)
+        fb += wa.Call(genFunctionID.jsValueToStringForConcat) // for `null`
+
+      case ClassType(className) =>
+        genWithDispatch(ctx.getClassInfo(className).isAncestorOfHijackedClass)
+
+      case AnyType =>
+        genWithDispatch(isAncestorOfHijackedClass = true)
+
+      case ArrayType(_) =>
+        genWithDispatch(isAncestorOfHijackedClass = false)
+
+      case tpe: RecordType =>
+        throw new AssertionError(
+            s"Invalid type $tpe for String_+ at ${tree.pos}: $tree")
+    }
+  }
+
+  private def genDivModByConstant[T](tree: BinaryOp, isDiv: Boolean,
+      rhsValue: T, const: T => wa.Instr, sub: wa.Instr, mainOp: wa.Instr)(
+      implicit num: Numeric[T]): Type = {
+    /* When we statically know the value of the rhs, we can avoid the
+     * dynamic tests for division by zero and overflow. This is quite
+     * common in practice.
+     */
+
+    import BinaryOp._
+
+    val BinaryOp(op, lhs, rhs) = tree
+    assert(op == Int_/ || op == Int_% || op == Long_/ || op == Long_%)
+
+    val tpe = tree.tpe
+
+    if (rhsValue == num.zero) {
+      genTree(lhs, tpe)
+      markPosition(tree)
+      genThrowArithmeticException()(tree.pos)
+      NothingType
+    } else if (isDiv && rhsValue == num.fromInt(-1)) {
+      /* MinValue / -1 overflows; it traps in Wasm but we need to wrap.
+       * We rewrite as `0 - lhs` so that we do not need any test.
+       */
+      markPosition(tree)
+      fb += const(num.zero)
+      genTree(lhs, tpe)
+      markPosition(tree)
+      fb += sub
+      tpe
+    } else {
+      genTree(lhs, tpe)
+      markPosition(rhs)
+      fb += const(rhsValue)
+      markPosition(tree)
+      fb += mainOp
+      tpe
+    }
+  }
+
+  private def genDivMod[T](tree: BinaryOp, isDiv: Boolean, const: T => wa.Instr,
+      eqz: wa.Instr, eqInstr: wa.Instr, sub: wa.Instr, mainOp: wa.Instr)(
+      implicit num: Numeric[T]): Type = {
+    /* Here we perform the same steps as in the static case, but using
+     * value tests at run-time.
+     */
+
+    import BinaryOp._
+
+    val BinaryOp(op, lhs, rhs) = tree
+    assert(op == Int_/ || op == Int_% || op == Long_/ || op == Long_%)
+
+    val tpe = tree.tpe
+    val wasmType = transformType(tpe)
+
+    val lhsLocal = addSyntheticLocal(wasmType)
+    val rhsLocal = addSyntheticLocal(wasmType)
+    genTree(lhs, tpe)
+    fb += wa.LocalSet(lhsLocal)
+    genTree(rhs, tpe)
+    fb += wa.LocalTee(rhsLocal)
+
+    markPosition(tree)
+
+    fb += eqz
+    fb.ifThen() {
+      genThrowArithmeticException()(tree.pos)
+    }
+    if (isDiv) {
+      // Handle the MinValue / -1 corner case
+      fb += wa.LocalGet(rhsLocal)
+      fb += const(num.fromInt(-1))
+      fb += eqInstr
+      fb.ifThenElse(wasmType) {
+        // 0 - lhs
+        fb += const(num.zero)
+        fb += wa.LocalGet(lhsLocal)
+        fb += sub
+      } {
+        // lhs / rhs
+        fb += wa.LocalGet(lhsLocal)
+        fb += wa.LocalGet(rhsLocal)
+        fb += mainOp
+      }
+    } else {
+      // lhs % rhs
+      fb += wa.LocalGet(lhsLocal)
+      fb += wa.LocalGet(rhsLocal)
+      fb += mainOp
+    }
+
+    tpe
+  }
+
+  private def genThrowArithmeticException()(implicit pos: Position): Unit = {
+    val ctorName = MethodName.constructor(List(ClassRef(BoxedStringClass)))
+    genNewScalaClass(ArithmeticExceptionClass, ctorName) {
+      fb ++= ctx.stringPool.getConstantStringInstr("/ by zero")
+    }
+    fb += wa.ExternConvertAny
+    fb += wa.Throw(genTagID.exception)
+  }
+
+  private def genIsInstanceOf(tree: IsInstanceOf): Type = {
+    val IsInstanceOf(expr, testType) = tree
+
+    genTree(expr, AnyType)
+
+    markPosition(tree)
+
+    def genIsPrimType(testType: PrimType): Unit = testType match {
+      case UndefType =>
+        fb += wa.Call(genFunctionID.isUndef)
+      case StringType =>
+        fb += wa.Call(genFunctionID.isString)
+      case CharType =>
+        val structTypeID = genTypeID.forClass(SpecialNames.CharBoxClass)
+        fb += wa.RefTest(watpe.RefType(structTypeID))
+      case LongType =>
+        val structTypeID = genTypeID.forClass(SpecialNames.LongBoxClass)
+        fb += wa.RefTest(watpe.RefType(structTypeID))
+      case NoType | NothingType | NullType =>
+        throw new AssertionError(s"Illegal isInstanceOf[$testType]")
+      case testType: PrimTypeWithRef =>
+        fb += wa.Call(genFunctionID.typeTest(testType.primRef))
+    }
+
+    testType match {
+      case testType: PrimType =>
+        genIsPrimType(testType)
+
+      case AnyType | ClassType(ObjectClass) =>
+        fb += wa.RefIsNull
+        fb += wa.I32Eqz
+
+      case ClassType(JLNumberClass) =>
+        /* Special case: the only non-Object *class* that is an ancestor of a
+         * hijacked class. We need to accept `number` primitives here.
+         */
+        val tempLocal = addSyntheticLocal(watpe.RefType.anyref)
+        fb += wa.LocalTee(tempLocal)
+        fb += wa.RefTest(watpe.RefType(genTypeID.forClass(JLNumberClass)))
+        fb.ifThenElse(watpe.Int32) {
+          fb += wa.I32Const(1)
+        } {
+          fb += wa.LocalGet(tempLocal)
+          fb += wa.Call(genFunctionID.typeTest(DoubleRef))
+        }
+
+      case ClassType(testClassName) =>
+        BoxedClassToPrimType.get(testClassName) match {
+          case Some(primType) =>
+            genIsPrimType(primType)
+          case None =>
+            if (ctx.getClassInfo(testClassName).isInterface)
+              fb += wa.Call(genFunctionID.instanceTest(testClassName))
+            else
+              fb += wa.RefTest(watpe.RefType(genTypeID.forClass(testClassName)))
+        }
+
+      case ArrayType(arrayTypeRef) =>
+        arrayTypeRef match {
+          case ArrayTypeRef(ClassRef(ObjectClass) | _: PrimRef, 1) =>
+            // For primitive arrays and exactly Array[Object], a wa.RefTest is enough
+            val structTypeID = genTypeID.forArrayClass(arrayTypeRef)
+            fb += wa.RefTest(watpe.RefType(structTypeID))
+
+          case _ =>
+            /* Non-Object reference array types need a sophisticated type test
+             * based on assignability of component types.
+             */
+            import watpe.RefType.anyref
+
+            fb.block(Sig(List(anyref), List(watpe.Int32))) { doneLabel =>
+              fb.block(Sig(List(anyref), List(anyref))) { notARefArrayLabel =>
+                // Try and cast to the generic representation first
+                val refArrayStructTypeID = genTypeID.forArrayClass(arrayTypeRef)
+                fb += wa.BrOnCastFail(
+                  notARefArrayLabel,
+                  watpe.RefType.anyref,
+                  watpe.RefType(refArrayStructTypeID)
+                )
+
+                // refArrayValue := the generic representation
+                val refArrayValueLocal =
+                  addSyntheticLocal(watpe.RefType(refArrayStructTypeID))
+                fb += wa.LocalSet(refArrayValueLocal)
+
+                // Load typeDataOf(arrayTypeRef)
+                genLoadArrayTypeData(fb, arrayTypeRef)
+
+                // Load refArrayValue.vtable
+                fb += wa.LocalGet(refArrayValueLocal)
+                fb += wa.StructGet(refArrayStructTypeID, genFieldID.objStruct.vtable)
+
+                // Call isAssignableFrom and return its result
+                fb += wa.Call(genFunctionID.isAssignableFrom)
+                fb += wa.Br(doneLabel)
+              }
+
+              // Here, the value is not a reference array type, so return false
+              fb += wa.Drop
+              fb += wa.I32Const(0)
+            }
+        }
+
+      case testType: RecordType =>
+        throw new AssertionError(s"Illegal type in IsInstanceOf: $testType")
+    }
+
+    BooleanType
+  }
+
+  private def genAsInstanceOf(tree: AsInstanceOf): Type = {
+    val AsInstanceOf(expr, targetTpe) = tree
+
+    val sourceTpe = expr.tpe
+
+    if (sourceTpe == NothingType) {
+      // We cannot call transformType for NothingType, so we have to handle this case separately.
+      genTree(expr, NothingType)
+      NothingType
+    } else {
+      // By IR checker rules, targetTpe is none of NothingType, NullType, NoType or RecordType
+
+      val sourceWasmType = transformType(sourceTpe)
+      val targetWasmType = transformType(targetTpe)
+
+      if (sourceWasmType == targetWasmType) {
+        /* Common case where no cast is necessary at the Wasm level.
+         * Note that this is not *obviously* correct. It is only correct
+         * because, under our choices of representation and type translation
+         * rules, there is no pair `(sourceTpe, targetTpe)` for which the Wasm
+         * types are equal but a valid cast would require a *conversion*.
+         */
+        genTreeAuto(expr)
+      } else {
+        genTree(expr, AnyType)
+
+        markPosition(tree)
+
+        targetTpe match {
+          case targetTpe: PrimType =>
+            // TODO Opt: We could do something better for things like double.asInstanceOf[int]
+            genUnbox(targetTpe)
+
+          case _ =>
+            targetWasmType match {
+              case watpe.RefType(true, watpe.HeapType.Any) =>
+                () // nothing to do
+              case targetWasmType: watpe.RefType =>
+                fb += wa.RefCast(targetWasmType)
+              case _ =>
+                throw new AssertionError(s"Unexpected type in AsInstanceOf: $targetTpe")
+            }
+        }
+      }
+
+      targetTpe
+    }
+  }
+
+  /** Unbox the `anyref` on the stack to the target `PrimType`.
+   *
+   *  `targetTpe` must not be `NothingType`, `NullType` nor `NoType`.
+   *
+   *  The type left on the stack is non-nullable.
+   */
+  private def genUnbox(targetTpe: PrimType): Unit = {
+    targetTpe match {
+      case UndefType =>
+        fb += wa.Drop
+        fb += wa.GlobalGet(genGlobalID.undef)
+
+      case StringType =>
+        fb += wa.RefAsNonNull
+
+      case CharType | LongType =>
+        // Extract the `value` field (the only field) out of the box class.
+
+        val boxClass =
+          if (targetTpe == CharType) SpecialNames.CharBoxClass
+          else SpecialNames.LongBoxClass
+        val fieldName = FieldName(boxClass, SpecialNames.valueFieldSimpleName)
+        val resultType = transformType(targetTpe)
+
+        fb.block(Sig(List(watpe.RefType.anyref), List(resultType))) { doneLabel =>
+          fb.block(Sig(List(watpe.RefType.anyref), Nil)) { isNullLabel =>
+            fb += wa.BrOnNull(isNullLabel)
+            val structTypeID = genTypeID.forClass(boxClass)
+            fb += wa.RefCast(watpe.RefType(structTypeID))
+            fb += wa.StructGet(
+              structTypeID,
+              genFieldID.forClassInstanceField(fieldName)
+            )
+            fb += wa.Br(doneLabel)
+          }
+          fb += genZeroOf(targetTpe)
+        }
+
+      case NothingType | NullType | NoType =>
+        throw new IllegalArgumentException(s"Illegal type in genUnbox: $targetTpe")
+
+      case targetTpe: PrimTypeWithRef =>
+        fb += wa.Call(genFunctionID.unbox(targetTpe.primRef))
+    }
+  }
+
+  private def genGetClass(tree: GetClass): Type = {
+    /* Unlike in `genApply` or `genStringConcat`, here we make no effort to
+     * optimize known-primitive receivers. In practice, such cases would be
+     * useless.
+     */
+
+    val GetClass(expr) = tree
+
+    val needHijackedClassDispatch = expr.tpe match {
+      case ClassType(className) =>
+        ctx.getClassInfo(className).isAncestorOfHijackedClass
+      case ArrayType(_) | NothingType | NullType =>
+        false
+      case _ =>
+        true
+    }
+
+    if (!needHijackedClassDispatch) {
+      val typeDataLocal = addSyntheticLocal(watpe.RefType(genTypeID.typeData))
+
+      genTreeAuto(expr)
+      markPosition(tree)
+      fb += wa.StructGet(genTypeID.ObjectStruct, genFieldID.objStruct.vtable) // implicit trap on null
+      fb += wa.Call(genFunctionID.getClassOf)
+    } else {
+      genTree(expr, AnyType)
+      markPosition(tree)
+      fb += wa.RefAsNonNull
+      fb += wa.Call(genFunctionID.anyGetClass)
+    }
+
+    tree.tpe
+  }
+
+  private def genReadStorage(storage: VarStorage): Unit = {
+    storage match {
+      case VarStorage.Local(localID) =>
+        fb += wa.LocalGet(localID)
+      case VarStorage.StructField(structLocal, structTypeID, fieldID) =>
+        fb += wa.LocalGet(structLocal)
+        fb += wa.StructGet(structTypeID, fieldID)
+    }
+  }
+
+  private def genVarRef(tree: VarRef): Type = {
+    val VarRef(LocalIdent(name)) = tree
+
+    markPosition(tree)
+    if (tree.tpe == NothingType)
+      fb += wa.Unreachable
+    else
+      genReadStorage(lookupLocal(name))
+    tree.tpe
+  }
+
+  private def genThis(tree: This): Type = {
+    markPosition(tree)
+    genReadStorage(receiverStorage)
+    tree.tpe
+  }
+
+  private def genVarDef(tree: VarDef): Type = {
+    /* This is an isolated VarDef that is not in a Block.
+     * Its scope is empty by construction, and therefore it need not be stored.
+     */
+    val VarDef(_, _, _, _, rhs) = tree
+    genTree(rhs, NoType)
+    NoType
+  }
+
+  private def genIf(tree: If, expectedType: Type): Type = {
+    val If(cond, thenp, elsep) = tree
+
+    val ty = transformResultType(expectedType)
+    genTree(cond, BooleanType)
+
+    markPosition(tree)
+
+    elsep match {
+      case Skip() =>
+        assert(expectedType == NoType)
+        fb.ifThen() {
+          genTree(thenp, expectedType)
+        }
+      case _ =>
+        fb.ifThenElse(ty) {
+          genTree(thenp, expectedType)
+        } {
+          genTree(elsep, expectedType)
+        }
+    }
+
+    if (expectedType == NothingType)
+      fb += wa.Unreachable
+
+    expectedType
+  }
+
+  private def genWhile(tree: While): Type = {
+    val While(cond, body) = tree
+
+    cond match {
+      case BooleanLiteral(true) =>
+        // infinite loop that must be typed as `nothing`, i.e., unreachable
+        markPosition(tree)
+        fb.loop() { label =>
+          genTree(body, NoType)
+          markPosition(tree)
+          fb += wa.Br(label)
+        }
+        fb += wa.Unreachable
+        NothingType
+
+      case _ =>
+        // normal loop typed as `void`
+        markPosition(tree)
+        fb.loop() { label =>
+          genTree(cond, BooleanType)
+          markPosition(tree)
+          fb.ifThen() {
+            genTree(body, NoType)
+            markPosition(tree)
+            fb += wa.Br(label)
+          }
+        }
+        NoType
+    }
+  }
+
+  private def genForIn(tree: ForIn): Type = {
+    /* This is tricky. In general, the body of a ForIn can be an arbitrary
+     * statement, which can refer to the enclosing scope and its locals,
+     * including for mutations. Unfortunately, there is no way to implement a
+     * ForIn other than actually doing a JS `for (var key in obj) { body }`
+     * loop. That means we need to pass the `body` as a JS closure.
+     *
+     * That is problematic for our backend because we basically need to perform
+     * lambda lifting: identifying captures ourselves, and turn references to
+     * local variables into accessing the captured environment.
+     *
+     * We side-step this issue for now by exploiting the known shape of `ForIn`
+     * generated by the Scala.js compiler. This is fine as long as we do not
+     * support the Scala.js optimizer. We will have to revisit this code when
+     * we add that support.
+     */
+
+    val ForIn(obj, LocalIdent(keyVarName), _, body) = tree
+
+    body match {
+      case JSFunctionApply(fVarRef: VarRef, List(VarRef(argIdent)))
+          if fVarRef.ident.name != keyVarName && argIdent.name == keyVarName =>
+        genTree(obj, AnyType)
+        genTree(fVarRef, AnyType)
+        markPosition(tree)
+        fb += wa.Call(genFunctionID.jsForInSimple)
+
+      case _ =>
+        throw new NotImplementedError(s"Unsupported shape of ForIn node at ${tree.pos}: $tree")
+    }
+
+    NoType
+  }
+
+  private def genTryCatch(tree: TryCatch, expectedType: Type): Type = {
+    val TryCatch(block, LocalIdent(errVarName), errVarOrigName, handler) = tree
+
+    val resultType = transformResultType(expectedType)
+
+    if (UseLegacyExceptionsForTryCatch) {
+      markPosition(tree)
+      fb += wa.Try(fb.sigToBlockType(Sig(Nil, resultType)))
+      genTree(block, expectedType)
+      markPosition(tree)
+      fb += wa.Catch(genTagID.exception)
+      withNewLocal(errVarName, errVarOrigName, watpe.RefType.anyref) { exceptionLocal =>
+        fb += wa.AnyConvertExtern
+        fb += wa.LocalSet(exceptionLocal)
+        genTree(handler, expectedType)
+      }
+      fb += wa.End
+    } else {
+      markPosition(tree)
+      fb.block(resultType) { doneLabel =>
+        fb.block(watpe.RefType.externref) { catchLabel =>
+          /* We used to have `resultType` as result of the try_table, with the
+           * `wa.BR(doneLabel)` outside of the try_table. Unfortunately it seems
+           * V8 cannot handle try_table with a result type that is `(ref ...)`.
+           * The current encoding with `externref` as result type (to match the
+           * enclosing block) and the `br` *inside* the `try_table` works.
+           */
+          fb.tryTable(watpe.RefType.externref)(
+            List(wa.CatchClause.Catch(genTagID.exception, catchLabel))
+          ) {
+            genTree(block, expectedType)
+            markPosition(tree)
+            fb += wa.Br(doneLabel)
+          }
+        } // end block $catch
+        withNewLocal(errVarName, errVarOrigName, watpe.RefType.anyref) { exceptionLocal =>
+          fb += wa.AnyConvertExtern
+          fb += wa.LocalSet(exceptionLocal)
+          genTree(handler, expectedType)
+        }
+      } // end block $done
+    }
+
+    if (expectedType == NothingType)
+      fb += wa.Unreachable
+
+    expectedType
+  }
+
+  private def genThrow(tree: Throw): Type = {
+    val Throw(expr) = tree
+
+    genTree(expr, AnyType)
+    markPosition(tree)
+    fb += wa.ExternConvertAny
+    fb += wa.Throw(genTagID.exception)
+
+    NothingType
+  }
+
+  private def genBlock(tree: Block, expectedType: Type): Type = {
+    val Block(stats) = tree
+
+    genBlockStats(stats.init) {
+      genTree(stats.last, expectedType)
+    }
+    expectedType
+  }
+
+  final def genBlockStats(stats: List[Tree])(inner: => Unit): Unit = {
+    val savedEnv = currentEnv
+
+    for (stat <- stats) {
+      stat match {
+        case VarDef(LocalIdent(name), originalName, vtpe, _, rhs) =>
+          genTree(rhs, vtpe)
+          markPosition(stat)
+          val local = fb.addLocal(originalName.orElse(name), transformLocalType(vtpe))
+          currentEnv = currentEnv.updated(name, VarStorage.Local(local))
+          fb += wa.LocalSet(local)
+        case _ =>
+          genTree(stat, NoType)
+      }
+    }
+
+    inner
+
+    currentEnv = savedEnv
+  }
+
+  private def genNew(tree: New): Type = {
+    val New(className, MethodIdent(ctorName), args) = tree
+
+    genNewScalaClass(className, ctorName) {
+      genArgs(args, ctorName)
+    } (tree.pos)
+
+    tree.tpe
+  }
+
+  private def genNewScalaClass(cls: ClassName, ctor: MethodName)(
+      genCtorArgs: => Unit)(implicit pos: Position): Unit = {
+
+    /* Do not use transformType here, because we must get the struct type even
+     * if the given class is an ancestor of hijacked classes (which in practice
+     * is only the case for j.l.Object).
+     */
+    val instanceLocal = addSyntheticLocal(watpe.RefType(genTypeID.forClass(cls)))
+
+    markPosition(pos)
+    fb += wa.Call(genFunctionID.newDefault(cls))
+    fb += wa.LocalTee(instanceLocal)
+    genCtorArgs
+    markPosition(pos)
+    fb += wa.Call(genFunctionID.forMethod(MemberNamespace.Constructor, cls, ctor))
+    fb += wa.LocalGet(instanceLocal)
+  }
+
+  /** Codegen to box a primitive `char`/`long` into a `CharacterBox`/`LongBox`. */
+  private def genBox(primType: watpe.SimpleType, boxClassName: ClassName): Type = {
+    val primLocal = addSyntheticLocal(primType)
+
+    /* We use a direct `StructNew` instead of the logical call to `newDefault`
+     * plus constructor call. We can do this because we know that this is
+     * what the constructor would do anyway (so we're basically inlining it).
+     */
+
+    fb += wa.LocalSet(primLocal)
+    fb += wa.GlobalGet(genGlobalID.forVTable(boxClassName))
+    fb += wa.GlobalGet(genGlobalID.forITable(boxClassName))
+    fb += wa.LocalGet(primLocal)
+    fb += wa.StructNew(genTypeID.forClass(boxClassName))
+
+    ClassType(boxClassName)
+  }
+
+  private def genIdentityHashCode(tree: IdentityHashCode): Type = {
+    val IdentityHashCode(expr) = tree
+
+    // TODO Avoid dispatch when we know a more precise type than any
+    genTree(expr, AnyType)
+
+    markPosition(tree)
+    fb += wa.Call(genFunctionID.identityHashCode)
+
+    IntType
+  }
+
+  private def genWrapAsThrowable(tree: WrapAsThrowable): Type = {
+    val WrapAsThrowable(expr) = tree
+
+    val nonNullThrowableType = watpe.RefType(genTypeID.ThrowableStruct)
+    val jsExceptionType = watpe.RefType(genTypeID.JSExceptionStruct)
+
+    fb.block(nonNullThrowableType) { doneLabel =>
+      genTree(expr, AnyType)
+
+      markPosition(tree)
+
+      // if expr.isInstanceOf[Throwable], then br $done
+      fb += wa.BrOnCast(doneLabel, watpe.RefType.anyref, nonNullThrowableType)
+
+      // otherwise, wrap in a new JavaScriptException
+
+      val exprLocal = addSyntheticLocal(watpe.RefType.anyref)
+      val instanceLocal = addSyntheticLocal(jsExceptionType)
+
+      fb += wa.LocalSet(exprLocal)
+      fb += wa.Call(genFunctionID.newDefault(SpecialNames.JSExceptionClass))
+      fb += wa.LocalTee(instanceLocal)
+      fb += wa.LocalGet(exprLocal)
+      fb += wa.Call(
+        genFunctionID.forMethod(
+          MemberNamespace.Constructor,
+          SpecialNames.JSExceptionClass,
+          SpecialNames.AnyArgConstructorName
+        )
+      )
+      fb += wa.LocalGet(instanceLocal)
+    }
+
+    tree.tpe
+  }
+
+  private def genUnwrapFromThrowable(tree: UnwrapFromThrowable): Type = {
+    val UnwrapFromThrowable(expr) = tree
+
+    fb.block(watpe.RefType.anyref) { doneLabel =>
+      genTree(expr, ClassType(ThrowableClass))
+
+      markPosition(tree)
+
+      fb += wa.RefAsNonNull
+
+      // if !expr.isInstanceOf[js.JavaScriptException], then br $done
+      fb += wa.BrOnCastFail(
+        doneLabel,
+        watpe.RefType(genTypeID.ThrowableStruct),
+        watpe.RefType(genTypeID.JSExceptionStruct)
+      )
+
+      // otherwise, unwrap the JavaScriptException by reading its field
+      fb += wa.StructGet(
+        genTypeID.JSExceptionStruct,
+        genFieldID.forClassInstanceField(SpecialNames.exceptionFieldName)
+      )
+    }
+
+    AnyType
+  }
+
+  private def genJSNew(tree: JSNew): Type = {
+    val JSNew(ctor, args) = tree
+
+    genTree(ctor, AnyType)
+    genJSArgsArray(args)
+    markPosition(tree)
+    fb += wa.Call(genFunctionID.jsNew)
+    AnyType
+  }
+
+  private def genJSSelect(tree: JSSelect): Type = {
+    val JSSelect(qualifier, item) = tree
+
+    genTree(qualifier, AnyType)
+    genTree(item, AnyType)
+    markPosition(tree)
+    fb += wa.Call(genFunctionID.jsSelect)
+    AnyType
+  }
+
+  private def genJSFunctionApply(tree: JSFunctionApply): Type = {
+    val JSFunctionApply(fun, args) = tree
+
+    genTree(fun, AnyType)
+    genJSArgsArray(args)
+    markPosition(tree)
+    fb += wa.Call(genFunctionID.jsFunctionApply)
+    AnyType
+  }
+
+  private def genJSMethodApply(tree: JSMethodApply): Type = {
+    val JSMethodApply(receiver, method, args) = tree
+
+    genTree(receiver, AnyType)
+    genTree(method, AnyType)
+    genJSArgsArray(args)
+    markPosition(tree)
+    fb += wa.Call(genFunctionID.jsMethodApply)
+    AnyType
+  }
+
+  private def genJSImportCall(tree: JSImportCall): Type = {
+    val JSImportCall(arg) = tree
+
+    genTree(arg, AnyType)
+    markPosition(tree)
+    fb += wa.Call(genFunctionID.jsImportCall)
+    AnyType
+  }
+
+  private def genJSImportMeta(tree: JSImportMeta): Type = {
+    markPosition(tree)
+    fb += wa.Call(genFunctionID.jsImportMeta)
+    AnyType
+  }
+
+  private def genLoadJSConstructor(tree: LoadJSConstructor): Type = {
+    val LoadJSConstructor(className) = tree
+
+    markPosition(tree)
+    SWasmGen.genLoadJSConstructor(fb, className)
+    AnyType
+  }
+
+  private def genLoadJSModule(tree: LoadJSModule): Type = {
+    val LoadJSModule(className) = tree
+
+    markPosition(tree)
+
+    ctx.getClassInfo(className).jsNativeLoadSpec match {
+      case Some(loadSpec) =>
+        genLoadJSFromSpec(fb, loadSpec)
+      case None =>
+        // This is a non-native JS module
+        fb += wa.Call(genFunctionID.loadModule(className))
+    }
+
+    AnyType
+  }
+
+  private def genSelectJSNativeMember(tree: SelectJSNativeMember): Type = {
+    val SelectJSNativeMember(className, MethodIdent(memberName)) = tree
+
+    val info = ctx.getClassInfo(className)
+    val jsNativeLoadSpec = info.jsNativeMembers.getOrElse(memberName, {
+      throw new AssertionError(
+          s"Found $tree for non-existing JS native member at ${tree.pos}")
+    })
+    markPosition(tree)
+    genLoadJSFromSpec(fb, jsNativeLoadSpec)
+    AnyType
+  }
+
+  private def genJSDelete(tree: JSDelete): Type = {
+    val JSDelete(qualifier, item) = tree
+
+    genTree(qualifier, AnyType)
+    genTree(item, AnyType)
+    markPosition(tree)
+    fb += wa.Call(genFunctionID.jsDelete)
+    NoType
+  }
+
+  private def genJSUnaryOp(tree: JSUnaryOp): Type = {
+    val JSUnaryOp(op, lhs) = tree
+
+    genTree(lhs, AnyType)
+    markPosition(tree)
+    fb += wa.Call(genFunctionID.jsUnaryOps(op))
+    AnyType
+  }
+
+  private def genJSBinaryOp(tree: JSBinaryOp): Type = {
+    val JSBinaryOp(op, lhs, rhs) = tree
+
+    op match {
+      case JSBinaryOp.|| | JSBinaryOp.&& =>
+        /* Here we need to implement the short-circuiting behavior, with a
+         * condition based on the truthy value of the left-hand-side.
+         */
+        val lhsLocal = addSyntheticLocal(watpe.RefType.anyref)
+        genTree(lhs, AnyType)
+        markPosition(tree)
+        fb += wa.LocalTee(lhsLocal)
+        fb += wa.Call(genFunctionID.jsIsTruthy)
+        if (op == JSBinaryOp.||) {
+          fb.ifThenElse(watpe.RefType.anyref) {
+            fb += wa.LocalGet(lhsLocal)
+          } {
+            genTree(rhs, AnyType)
+            markPosition(tree)
+          }
+        } else {
+          fb.ifThenElse(watpe.RefType.anyref) {
+            genTree(rhs, AnyType)
+            markPosition(tree)
+          } {
+            fb += wa.LocalGet(lhsLocal)
+          }
+        }
+
+      case _ =>
+        genTree(lhs, AnyType)
+        genTree(rhs, AnyType)
+        markPosition(tree)
+        fb += wa.Call(genFunctionID.jsBinaryOps(op))
+    }
+
+    tree.tpe
+  }
+
+  private def genJSArrayConstr(tree: JSArrayConstr): Type = {
+    val JSArrayConstr(items) = tree
+
+    markPosition(tree)
+    genJSArgsArray(items)
+    AnyType
+  }
+
+  private def genJSObjectConstr(tree: JSObjectConstr): Type = {
+    val JSObjectConstr(fields) = tree
+
+    markPosition(tree)
+    fb += wa.Call(genFunctionID.jsNewObject)
+    for ((prop, value) <- fields) {
+      genTree(prop, AnyType)
+      genTree(value, AnyType)
+      fb += wa.Call(genFunctionID.jsObjectPush)
+    }
+    AnyType
+  }
+
+  private def genJSGlobalRef(tree: JSGlobalRef): Type = {
+    val JSGlobalRef(name) = tree
+
+    markPosition(tree)
+    fb ++= ctx.stringPool.getConstantStringInstr(name)
+    fb += wa.Call(genFunctionID.jsGlobalRefGet)
+    AnyType
+  }
+
+  private def genJSTypeOfGlobalRef(tree: JSTypeOfGlobalRef): Type = {
+    val JSTypeOfGlobalRef(JSGlobalRef(name)) = tree
+
+    markPosition(tree)
+    fb ++= ctx.stringPool.getConstantStringInstr(name)
+    fb += wa.Call(genFunctionID.jsGlobalRefTypeof)
+    AnyType
+  }
+
+  private def genJSArgsArray(args: List[TreeOrJSSpread]): Unit = {
+    fb += wa.Call(genFunctionID.jsNewArray)
+    for (arg <- args) {
+      arg match {
+        case arg: Tree =>
+          genTree(arg, AnyType)
+          fb += wa.Call(genFunctionID.jsArrayPush)
+        case JSSpread(items) =>
+          genTree(items, AnyType)
+          fb += wa.Call(genFunctionID.jsArraySpreadPush)
+      }
+    }
+  }
+
+  private def genJSLinkingInfo(tree: JSLinkingInfo): Type = {
+    markPosition(tree)
+    fb += wa.GlobalGet(genGlobalID.jsLinkingInfo)
+    AnyType
+  }
+
+  private def genArrayLength(tree: ArrayLength): Type = {
+    val ArrayLength(array) = tree
+
+    genTreeAuto(array)
+
+    markPosition(tree)
+
+    array.tpe match {
+      case ArrayType(arrayTypeRef) =>
+        // Get the underlying array; implicit trap on null
+        fb += wa.StructGet(
+          genTypeID.forArrayClass(arrayTypeRef),
+          genFieldID.objStruct.arrayUnderlying
+        )
+        // Get the length
+        fb += wa.ArrayLen
+        IntType
+
+      case NothingType =>
+        // unreachable
+        NothingType
+      case NullType =>
+        fb += wa.Unreachable
+        NothingType
+      case _ =>
+        throw new IllegalArgumentException(
+            s"ArraySelect.array must be an array type, but has type ${tree.array.tpe}")
+    }
+  }
+
+  private def genNewArray(tree: NewArray): Type = {
+    val NewArray(arrayTypeRef, lengths) = tree
+
+    if (lengths.isEmpty || lengths.size > arrayTypeRef.dimensions) {
+      throw new AssertionError(
+          s"invalid lengths ${tree.lengths} for array type ${arrayTypeRef.displayName}")
+    }
+
+    markPosition(tree)
+
+    if (lengths.size == 1) {
+      genLoadVTableAndITableForArray(fb, arrayTypeRef)
+
+      // Create the underlying array
+      genTree(lengths.head, IntType)
+      markPosition(tree)
+
+      val underlyingArrayType = genTypeID.underlyingOf(arrayTypeRef)
+      fb += wa.ArrayNewDefault(underlyingArrayType)
+
+      // Create the array object
+      fb += wa.StructNew(genTypeID.forArrayClass(arrayTypeRef))
+    } else {
+      /* There is no Scala source code that produces `NewArray` with more than
+       * one specified dimension, so this branch is not tested.
+       * (The underlying function `newArrayObject` is tested as part of
+       * reflective array instantiations, though.)
+       */
+
+      // First arg to `newArrayObject`: the typeData of the array to create
+      genLoadArrayTypeData(fb, arrayTypeRef)
+
+      // Second arg: an array of the lengths
+      for (length <- lengths)
+        genTree(length, IntType)
+      markPosition(tree)
+      fb += wa.ArrayNewFixed(genTypeID.i32Array, lengths.size)
+
+      // Third arg: constant 0 (start index inside the array of lengths)
+      fb += wa.I32Const(0)
+
+      fb += wa.Call(genFunctionID.newArrayObject)
+    }
+
+    tree.tpe
+  }
+
+  private def genArraySelect(tree: ArraySelect): Type = {
+    val ArraySelect(array, index) = tree
+
+    genTreeAuto(array)
+
+    markPosition(tree)
+
+    array.tpe match {
+      case ArrayType(arrayTypeRef) =>
+        // Get the underlying array; implicit trap on null
+        fb += wa.StructGet(
+          genTypeID.forArrayClass(arrayTypeRef),
+          genFieldID.objStruct.arrayUnderlying
+        )
+
+        // Load the index
+        genTree(index, IntType)
+
+        markPosition(tree)
+
+        // Use the appropriate variant of array.get for sign extension
+        val typeIdx = genTypeID.underlyingOf(arrayTypeRef)
+        arrayTypeRef match {
+          case ArrayTypeRef(BooleanRef | CharRef, 1) =>
+            fb += wa.ArrayGetU(typeIdx)
+          case ArrayTypeRef(ByteRef | ShortRef, 1) =>
+            fb += wa.ArrayGetS(typeIdx)
+          case _ =>
+            fb += wa.ArrayGet(typeIdx)
+        }
+
+        /* If it is a reference array type whose element type does not translate
+         * to `anyref`, we must cast down the result.
+         */
+        arrayTypeRef match {
+          case ArrayTypeRef(_: PrimRef, 1) =>
+            // a primitive array always has the correct type
+            ()
+          case _ =>
+            transformType(tree.tpe) match {
+              case watpe.RefType.anyref =>
+                // nothing to do
+                ()
+              case refType: watpe.RefType =>
+                fb += wa.RefCast(refType)
+              case otherType =>
+                throw new AssertionError(s"Unexpected result type for reference array: $otherType")
+            }
+        }
+
+        tree.tpe
+
+      case NothingType =>
+        // unreachable
+        NothingType
+      case NullType =>
+        fb += wa.Unreachable
+        NothingType
+      case _ =>
+        throw new IllegalArgumentException(
+            s"ArraySelect.array must be an array type, but has type ${array.tpe}")
+    }
+  }
+
+  private def genArrayValue(tree: ArrayValue): Type = {
+    val ArrayValue(arrayTypeRef, elems) = tree
+
+    val expectedElemType = arrayTypeRef match {
+      case ArrayTypeRef(base: PrimRef, 1) => base.tpe
+      case _                              => AnyType
+    }
+
+    // Mark the position for the header of `genArrayValue`
+    markPosition(tree)
+
+    SWasmGen.genArrayValue(fb, arrayTypeRef, elems.size) {
+      // Create the underlying array
+      elems.foreach(genTree(_, expectedElemType))
+
+      // Re-mark the position for the footer of `genArrayValue`
+      markPosition(tree)
+    }
+
+    tree.tpe
+  }
+
+  private def genClosure(tree: Closure): Type = {
+    val Closure(arrow, captureParams, params, restParam, body, captureValues) = tree
+
+    val hasThis = !arrow
+    val hasRestParam = restParam.isDefined
+    val dataStructTypeID = ctx.getClosureDataStructType(captureParams.map(_.ptpe))
+
+    // Define the function where captures are reified as a `__captureData` argument.
+    val closureFuncOrigName = genClosureFuncOriginalName()
+    val closureFuncID = new ClosureFunctionID(closureFuncOrigName)
+    emitFunction(
+      closureFuncID,
+      closureFuncOrigName,
+      enclosingClassName = None,
+      Some(captureParams),
+      receiverType = if (!hasThis) None else Some(watpe.RefType.anyref),
+      params,
+      restParam,
+      body,
+      resultType = AnyType
+    )(ctx, tree.pos)
+
+    markPosition(tree)
+
+    // Put a reference to the function on the stack
+    fb += ctx.refFuncWithDeclaration(closureFuncID)
+
+    // Evaluate the capture values and instantiate the capture data struct
+    for ((param, value) <- captureParams.zip(captureValues))
+      genTree(value, param.ptpe)
+    markPosition(tree)
+    fb += wa.StructNew(dataStructTypeID)
+
+    /* If there is a ...rest param, the helper requires as third argument the
+     * number of regular arguments.
+     */
+    if (hasRestParam)
+      fb += wa.I32Const(params.size)
+
+    // Call the appropriate helper
+    val helper = (hasThis, hasRestParam) match {
+      case (false, false) => genFunctionID.closure
+      case (true, false)  => genFunctionID.closureThis
+      case (false, true)  => genFunctionID.closureRest
+      case (true, true)   => genFunctionID.closureThisRest
+    }
+    fb += wa.Call(helper)
+
+    AnyType
+  }
+
+  private def genClone(tree: Clone): Type = {
+    val Clone(expr) = tree
+
+    expr.tpe match {
+      case NothingType =>
+        genTree(expr, NothingType)
+        NothingType
+
+      case NullType =>
+        genTree(expr, NullType)
+        fb += wa.Unreachable // trap for NPE
+        NothingType
+
+      case exprType =>
+        val exprLocal = addSyntheticLocal(watpe.RefType(genTypeID.ObjectStruct))
+
+        genTree(expr, ClassType(CloneableClass))
+
+        markPosition(tree)
+
+        fb += wa.RefAsNonNull
+        fb += wa.LocalTee(exprLocal)
+
+        fb += wa.LocalGet(exprLocal)
+        fb += wa.StructGet(genTypeID.ObjectStruct, genFieldID.objStruct.vtable)
+        fb += wa.StructGet(genTypeID.typeData, genFieldID.typeData.cloneFunction)
+        // cloneFunction: (ref jl.Object) -> (ref jl.Object)
+        fb += wa.CallRef(genTypeID.cloneFunctionType)
+
+        // cast the (ref jl.Object) back down to the result type
+        transformType(exprType) match {
+          case watpe.RefType(_, watpe.HeapType.Type(genTypeID.ObjectStruct)) =>
+            // no need to cast to (ref null? jl.Object)
+          case wasmType: watpe.RefType =>
+            fb += wa.RefCast(wasmType.toNonNullable)
+          case wasmType =>
+            // Since no hijacked class extends jl.Cloneable, this case cannot happen
+            throw new AssertionError(
+                s"Unexpected type for Clone: $exprType (Wasm: $wasmType)")
+        }
+
+        exprType
+    }
+  }
+
+  private def genMatch(tree: Match, expectedType: Type): Type = {
+    val Match(selector, cases, defaultBody) = tree
+
+    val selectorLocal = addSyntheticLocal(transformType(selector.tpe))
+
+    genTreeAuto(selector)
+
+    markPosition(tree)
+
+    fb += wa.LocalSet(selectorLocal)
+
+    fb.block(transformResultType(expectedType)) { doneLabel =>
+      fb.block() { defaultLabel =>
+        val caseLabels = cases.map(c => c._1 -> fb.genLabel())
+        for (caseLabel <- caseLabels)
+          fb += wa.Block(wa.BlockType.ValueType(), Some(caseLabel._2))
+
+        for {
+          (matchableLiterals, label) <- caseLabels
+          matchableLiteral <- matchableLiterals
+        } {
+          markPosition(matchableLiteral)
+          fb += wa.LocalGet(selectorLocal)
+          matchableLiteral match {
+            case IntLiteral(value) =>
+              fb += wa.I32Const(value)
+              fb += wa.I32Eq
+              fb += wa.BrIf(label)
+            case StringLiteral(value) =>
+              fb ++= ctx.stringPool.getConstantStringInstr(value)
+              fb += wa.Call(genFunctionID.is)
+              fb += wa.BrIf(label)
+            case Null() =>
+              fb += wa.RefIsNull
+              fb += wa.BrIf(label)
+          }
+        }
+        fb += wa.Br(defaultLabel)
+
+        for {
+          (caseLabel, (_, caseBody)) <- caseLabels.zip(cases).reverse
+        } {
+          markPosition(caseBody)
+          fb += wa.End
+          genTree(caseBody, expectedType)
+          fb += wa.Br(doneLabel)
+        }
+      }
+      genTree(defaultBody, expectedType)
+    }
+
+    if (expectedType == NothingType)
+      fb += wa.Unreachable
+
+    expectedType
+  }
+
+  private def genCreateJSClass(tree: CreateJSClass): Type = {
+    val CreateJSClass(className, captureValues) = tree
+
+    val classInfo = ctx.getClassInfo(className)
+    val jsClassCaptures = classInfo.jsClassCaptures.getOrElse {
+      throw new AssertionError(
+          s"Illegal CreateJSClass of top-level class ${className.nameString}")
+    }
+
+    for ((captureValue, captureParam) <- captureValues.zip(jsClassCaptures))
+      genTree(captureValue, captureParam.ptpe)
+
+    markPosition(tree)
+
+    fb += wa.Call(genFunctionID.createJSClassOf(className))
+
+    AnyType
+  }
+
+  private def genJSPrivateSelect(tree: JSPrivateSelect): Type = {
+    val JSPrivateSelect(qualifier, FieldIdent(fieldName)) = tree
+
+    genTree(qualifier, AnyType)
+
+    markPosition(tree)
+
+    fb += wa.GlobalGet(genGlobalID.forJSPrivateField(fieldName))
+    fb += wa.Call(genFunctionID.jsSelect)
+
+    AnyType
+  }
+
+  private def genJSSuperSelect(tree: JSSuperSelect): Type = {
+    val JSSuperSelect(superClass, receiver, item) = tree
+
+    genTree(superClass, AnyType)
+    genTree(receiver, AnyType)
+    genTree(item, AnyType)
+
+    markPosition(tree)
+
+    fb += wa.Call(genFunctionID.jsSuperSelect)
+
+    AnyType
+  }
+
+  private def genJSSuperMethodCall(tree: JSSuperMethodCall): Type = {
+    val JSSuperMethodCall(superClass, receiver, method, args) = tree
+
+    genTree(superClass, AnyType)
+    genTree(receiver, AnyType)
+    genTree(method, AnyType)
+    genJSArgsArray(args)
+
+    markPosition(tree)
+
+    fb += wa.Call(genFunctionID.jsSuperCall)
+
+    AnyType
+  }
+
+  private def genJSNewTarget(tree: JSNewTarget): Type = {
+    markPosition(tree)
+
+    genReadStorage(newTargetStorage)
+
+    AnyType
+  }
+
+  /*--------------------------------------------------------------------*
+   * HERE BE DRAGONS --- Handling of TryFinally, Labeled and Return --- *
+   *--------------------------------------------------------------------*/
+
+  /* From this point onwards, and until the end of the file, you will find
+   * the infrastructure required to handle TryFinally and Labeled/Return pairs.
+   *
+   * Independently, TryFinally and Labeled/Return are not very difficult to
+   * handle. The dragons come when they interact, and in particular when a
+   * TryFinally stands in the middle of a Labeled/Return pair.
+   *
+   * For example:
+   *
+   * val foo: int = alpha[int]: {
+   *   val bar: string = try {
+   *     if (somethingHappens)
+   *       return@alpha 5
+   *     "bar"
+   *   } finally {
+   *     doTheFinally()
+   *   }
+   *   someOtherThings(bar)
+   * }
+   *
+   * In that situation, if we naively translate the `return@alpha` into
+   * `br $alpha`, we bypass the `finally` block, which goes against the spec.
+   *
+   * Instead, we must stash the result 5 in a local and jump to the finally
+   * block. The issue is that, at the end of `doTheFinally()`, we need to keep
+   * propagating further up (instead of executing `someOtherThings()`).
+   *
+   * That means that there are 3 possible outcomes after the `finally` block:
+   *
+   * - Rethrow the exception if we caught one.
+   * - Reload the stashed result and branch further to `alpha`.
+   * - Otherwise keep going to do `someOtherThings()`.
+   *
+   * Now what if there are *several* labels for which we cross that
+   * `try..finally`? Well we need to deal with all the possible labels. This
+   * means that, in general, we in fact have `2 + n` possible outcomes, where
+   * `n` is the number of labels for which we found a `Return` that crosses the
+   * boundary.
+   *
+   * In order to know whether we need to rethrow, we look at a nullable
+   * `exnref`. For the remaining cases, we use a separate `destinationTag`
+   * local. Every label gets assigned a distinct tag > 0. Fall-through is
+   * always represented by 0. Before branching to a `finally` block, we set the
+   * appropriate value to the `destinationTag` value.
+   *
+   * Since the various labels can have different result types, and since they
+   * can be different from the result of the regular flow of the `try` block,
+   * we cannot use the stack for the `try_table` itself: each label has a
+   * dedicated local for its result if it comes from such a crossing `return`.
+   *
+   * Two more complications:
+   *
+   * - If the `finally` block itself contains another `try..finally`, they may
+   *   need a `destinationTag` concurrently. Therefore, every `try..finally`
+   *   gets its own `destinationTag` local. We do not need this for another
+   *   `try..finally` inside a `try` (or elsewhere in the function), so this is
+   *   not an optimal allocation; we do it this way not to complicate this
+   *   further.
+   * - If the `try` block contains another `try..finally`, so that there are
+   *   two (or more) `try..finally` in the way between a `Return` and a
+   *   `Labeled`, we must forward to the next `finally` in line (and its own
+   *   `destinationTag` local) so that the whole chain gets executed before
+   *   reaching the `Labeled`.
+   *
+   * ---
+   *
+   * As an evil example of everything that can happen, consider:
+   *
+   * alpha[double]: { // allocated destinationTag = 1
+   *   val foo: int = try { // declare local destinationTagOuter
+   *     beta[int]: { // allocated destinationTag = 2
+   *       val bar: int = try { // declare local destinationTagInner
+   *         if (A) return@alpha 5
+   *         if (B) return@beta 10
+   *         56
+   *       } finally {
+   *         doTheFinally()
+   *         // not shown: there is another try..finally here using a third
+   *         // local destinationTagThird, since destinationTagOuter and
+   *         // destinationTagInner are alive at the same time.
+   *       }
+   *       someOtherThings(bar)
+   *     }
+   *   } finally {
+   *     doTheOuterFinally()
+   *   }
+   *   moreOtherThings(foo)
+   * }
+   *
+   * The whole compiled code is too overwhelming to be useful, so we show the
+   * important aspects piecemiel, from the bottom up.
+   *
+   * First, the compiled code for `return@alpha 5`:
+   *
+   * i32.const 5                    ; eval the argument of the return
+   * local.set $alphaResult         ; store it in $alphaResult because we are cross a try..finally
+   * i32.const 1                    ; the destination tag of alpha
+   * local.set $destinationTagInner ; store it in the destinationTag local of the inner try..finally
+   * br $innerCross                 ; branch to the cross label of the inner try..finally
+   *
+   * Second, we look at the shape generated for the inner try..finally:
+   *
+   * block $innerDone (result i32)
+   *   block $innerCatch (result exnref)
+   *     block $innerCross
+   *       try_table (catch_all_ref $innerCatch)
+   *         ; [...] body of the try
+   *
+   *         local.set $innerTryResult
+   *       end ; try_table
+   *
+   *       ; set destinationTagInner := 0 to mean fall-through
+   *       i32.const 0
+   *       local.set $destinationTagInner
+   *     end ; block $innerCross
+   *
+   *     ; no exception thrown
+   *     ref.null exn
+   *   end ; block $innerCatch
+   *
+   *   ; now we have the common code with the finally
+   *
+   *   ; [...] body of the finally
+   *
+   *   ; maybe re-throw
+   *   block $innerExnIsNull (param exnref)
+   *     br_on_null $innerExnIsNull
+   *     throw_ref
+   *   end
+   *
+   *   ; re-dispatch after the outer finally based on $destinationTagInner
+   *
+   *   ; first transfer our destination tag to the outer try's destination tag
+   *   local.get $destinationTagInner
+   *   local.set $destinationTagOuter
+   *
+   *   ; now use a br_table to jump to the appropriate destination
+   *   ; if 0, fall-through
+   *   ; if 1, go the outer try's cross label because it is still on the way to alpha
+   *   ; if 2, go to beta's cross label
+   *   ; default to fall-through (never used but br_table needs a default)
+   *   br_table $innerDone $outerCross $betaCross $innerDone
+   * end ; block $innerDone
+   *
+   * We omit the shape of beta and of the outer try. There are similar to the
+   * shape of alpha and inner try, respectively.
+   *
+   * We conclude with the shape of the alpha block:
+   *
+   * block $alpha (result f64)
+   *   block $alphaCross
+   *     ; begin body of alpha
+   *
+   *     ; [...]              ; the try..finally
+   *     local.set $foo       ; val foo =
+   *     moreOtherThings(foo)
+   *
+   *     ; end body of alpha
+   *
+   *     br $alpha ; if alpha finished normally, jump over `local.get $alphaResult`
+   *   end ; block $alphaCross
+   *
+   *   ; if we returned from alpha across a try..finally, fetch the result from the local
+   *   local.get $alphaResult
+   * end ; block $alpha
+   */
+
+  /** This object namespaces everything related to unwinding, so that we don't pollute too much the
+   *  overall internal scope of `FunctionEmitter`.
+   */
+  private object unwinding {
+
+    /** The number of enclosing `Labeled` and `TryFinally` blocks.
+     *
+     *  For `TryFinally`, it is only enclosing if we are in the `try` branch, not the `finally`
+     *  branch.
+     *
+     *  Invariant:
+     *  {{{
+     *  currentUnwindingStackDepth == enclosingTryFinallyStack.size + enclosingLabeledBlocks.size
+     *  }}}
+     */
+    private var currentUnwindingStackDepth: Int = 0
+
+    private var enclosingTryFinallyStack: List[TryFinallyEntry] = Nil
+
+    private var enclosingLabeledBlocks: Map[LabelName, LabeledEntry] = Map.empty
+
+    private def innermostTryFinally: Option[TryFinallyEntry] =
+      enclosingTryFinallyStack.headOption
+
+    private def enterTryFinally(entry: TryFinallyEntry)(body: => Unit): Unit = {
+      assert(entry.depth == currentUnwindingStackDepth)
+      enclosingTryFinallyStack ::= entry
+      currentUnwindingStackDepth += 1
+      try {
+        body
+      } finally {
+        currentUnwindingStackDepth -= 1
+        enclosingTryFinallyStack = enclosingTryFinallyStack.tail
+      }
+    }
+
+    private def enterLabeled(entry: LabeledEntry)(body: => Unit): Unit = {
+      assert(entry.depth == currentUnwindingStackDepth)
+      val savedLabeledBlocks = enclosingLabeledBlocks
+      enclosingLabeledBlocks = enclosingLabeledBlocks.updated(entry.irLabelName, entry)
+      currentUnwindingStackDepth += 1
+      try {
+        body
+      } finally {
+        currentUnwindingStackDepth -= 1
+        enclosingLabeledBlocks = savedLabeledBlocks
+      }
+    }
+
+    /** The last destination tag that was allocated to a LabeledEntry. */
+    private var lastDestinationTag: Int = 0
+
+    private def allocateDestinationTag(): Int = {
+      lastDestinationTag += 1
+      lastDestinationTag
+    }
+
+    /** Information about an enclosing `TryFinally` block. */
+    private final class TryFinallyEntry(val depth: Int) {
+      import TryFinallyEntry._
+
+      private var _crossInfo: Option[CrossInfo] = None
+
+      def isInside(labeledEntry: LabeledEntry): Boolean =
+        this.depth > labeledEntry.depth
+
+      def wasCrossed: Boolean = _crossInfo.isDefined
+
+      def requireCrossInfo(): CrossInfo = {
+        _crossInfo.getOrElse {
+          val info = CrossInfo(addSyntheticLocal(watpe.Int32), fb.genLabel())
+          _crossInfo = Some(info)
+          info
+        }
+      }
+    }
+
+    private object TryFinallyEntry {
+      /** Cross info for a `TryFinally` entry.
+       *
+       *  @param destinationTagLocal
+       *    The destinationTag local variable for this `TryFinally`.
+       *  @param crossLabel
+       *    The cross label for this `TryFinally`.
+       */
+      sealed case class CrossInfo(
+        val destinationTagLocal: wanme.LocalID,
+        val crossLabel: wanme.LabelID
+      )
+    }
+
+    /** Information about an enclosing `Labeled` block. */
+    private final class LabeledEntry(val depth: Int,
+        val irLabelName: LabelName, val expectedType: Type) {
+
+      import LabeledEntry._
+
+      /** The regular label for this `Labeled` block, used for `Return`s that
+       *  do not cross a `TryFinally`.
+       */
+      val regularWasmLabel: wanme.LabelID = fb.genLabel()
+
+      private var _crossInfo: Option[CrossInfo] = None
+
+      def wasCrossUsed: Boolean = _crossInfo.isDefined
+
+      def requireCrossInfo(): CrossInfo = {
+        _crossInfo.getOrElse {
+          val destinationTag = allocateDestinationTag()
+          val resultTypes = transformResultType(expectedType)
+          val resultLocals = resultTypes.map(addSyntheticLocal(_))
+          val crossLabel = fb.genLabel()
+          val info = CrossInfo(destinationTag, resultLocals, crossLabel)
+          _crossInfo = Some(info)
+          info
+        }
+      }
+    }
+
+    private object LabeledEntry {
+      /** Cross info for a `LabeledEntry`.
+       *
+       *  @param destinationTag
+       *    The destination tag allocated to this label, used by the `finally`
+       *    blocks to keep propagating to the right destination. Destination
+       *    tags are always `> 0`. The value `0` is reserved for fall-through.
+       *  @param resultLocals
+       *    The locals in which to store the result of the label if we have to
+       *    cross a `try..finally`.
+       *  @param crossLabel
+       *    An additional Wasm label that has a `[]` result, and which will get
+       *    its result from the `resultLocal` instead of expecting it on the stack.
+       */
+      sealed case class CrossInfo(
+        destinationTag: Int,
+        resultLocals: List[wanme.LocalID],
+        crossLabel: wanme.LabelID
+      )
+    }
+
+    def genLabeled(tree: Labeled, expectedType: Type): Type = {
+      val Labeled(LabelIdent(labelName), tpe, body) = tree
+
+      val entry = new LabeledEntry(currentUnwindingStackDepth, labelName, expectedType)
+
+      val ty = transformResultType(expectedType)
+
+      markPosition(tree)
+
+      // Manual wa.Block here because we have a specific `label`
+      fb += wa.Block(fb.sigToBlockType(Sig(Nil, ty)), Some(entry.regularWasmLabel))
+
+      /* Remember the position in the instruction stream, in case we need to
+       * come back and insert the wa.Block for the cross handling.
+       */
+      val instrsBlockBeginIndex = fb.markCurrentInstructionIndex()
+
+      // Emit the body
+      enterLabeled(entry) {
+        genTree(body, expectedType)
+      }
+
+      markPosition(tree)
+
+      // Deal with crossing behavior
+      if (entry.wasCrossUsed) {
+        assert(expectedType != NothingType,
+            "The tryFinallyCrossLabel should not have been used for label " +
+            s"${labelName.nameString} of type nothing")
+
+        /* In this case we need to handle situations where we receive the value
+         * from the label's `result` local, branching out of the label's
+         * `crossLabel`.
+         *
+         * Instead of the standard shape
+         *
+         * block $labeled (result t)
+         *   body
+         * end
+         *
+         * We need to amend the shape to become
+         *
+         * block $labeled (result t)
+         *   block $crossLabel
+         *     body            ; inside the body, jumps to this label after a
+         *                     ; `finally` are compiled as `br $crossLabel`
+         *     br $labeled
+         *   end
+         *   local.get $label.resultLocals ; (0 to many)
+         * end
+         */
+
+        val LabeledEntry.CrossInfo(_, resultLocals, crossLabel) =
+          entry.requireCrossInfo()
+
+        // Go back and insert the `block $crossLabel` right after `block $labeled`
+        fb.insert(instrsBlockBeginIndex, wa.Block(wa.BlockType.ValueType(), Some(crossLabel)))
+
+        // Add the `br`, `end` and `local.get` at the current position, as usual
+        fb += wa.Br(entry.regularWasmLabel)
+        fb += wa.End
+        for (local <- resultLocals)
+          fb += wa.LocalGet(local)
+      }
+
+      fb += wa.End
+
+      if (expectedType == NothingType)
+        fb += wa.Unreachable
+
+      expectedType
+    }
+
+    def genTryFinally(tree: TryFinally, expectedType: Type): Type = {
+      val TryFinally(tryBlock, finalizer) = tree
+
+      val entry = new TryFinallyEntry(currentUnwindingStackDepth)
+
+      val resultType = transformResultType(expectedType)
+      val resultLocals = resultType.map(addSyntheticLocal(_))
+
+      markPosition(tree)
+
+      fb.block() { doneLabel =>
+        fb.block(watpe.RefType.exnref) { catchLabel =>
+          /* Remember the position in the instruction stream, in case we need
+           * to come back and insert the wa.BLOCK for the cross handling.
+           */
+          val instrsBlockBeginIndex = fb.markCurrentInstructionIndex()
+
+          fb.tryTable()(List(wa.CatchClause.CatchAllRef(catchLabel))) {
+            // try block
+            enterTryFinally(entry) {
+              genTree(tryBlock, expectedType)
+            }
+
+            markPosition(tree)
+
+            // store the result in locals during the finally block
+            for (resultLocal <- resultLocals.reverse)
+              fb += wa.LocalSet(resultLocal)
+          }
+
+          /* If this try..finally was crossed by a `Return`, we need to amend
+           * the shape of our try part to
+           *
+           * block $catch (result exnref)
+           *   block $cross
+           *     try_table (catch_all_ref $catch)
+           *       body
+           *       set_local $results ; 0 to many
+           *     end
+           *     i32.const 0 ; 0 always means fall-through
+           *     local.set $destinationTag
+           *   end
+           *   ref.null exn
+           * end
+           */
+          if (entry.wasCrossed) {
+            val TryFinallyEntry.CrossInfo(destinationTagLocal, crossLabel) =
+              entry.requireCrossInfo()
+
+            // Go back and insert the `block $cross` right after `block $catch`
+            fb.insert(
+              instrsBlockBeginIndex,
+              wa.Block(wa.BlockType.ValueType(), Some(crossLabel))
+            )
+
+            // And the other amendments normally
+            fb += wa.I32Const(0)
+            fb += wa.LocalSet(destinationTagLocal)
+            fb += wa.End // of the inserted wa.BLOCK
+          }
+
+          // on success, push a `null_ref exn` on the stack
+          fb += wa.RefNull(watpe.HeapType.Exn)
+        } // end block $catch
+
+        // finally block (during which we leave the `(ref null exn)` on the stack)
+        genTree(finalizer, NoType)
+
+        markPosition(tree)
+
+        if (!entry.wasCrossed) {
+          // If the `exnref` is non-null, rethrow it
+          fb += wa.BrOnNull(doneLabel)
+          fb += wa.ThrowRef
+        } else {
+          /* If the `exnref` is non-null, rethrow it.
+           * Otherwise, stay within the `$done` block.
+           */
+          fb.block(Sig(List(watpe.RefType.exnref), Nil)) { exnrefIsNullLabel =>
+            fb += wa.BrOnNull(exnrefIsNullLabel)
+            fb += wa.ThrowRef
+          }
+
+          /* Otherwise, use a br_table to dispatch to the right destination
+           * based on the value of the try..finally's destinationTagLocal,
+           * which is set by `Return` or to 0 for fall-through.
+           */
+
+          // The order does not matter here because they will be "re-sorted" by emitBRTable
+          val possibleTargetEntries =
+            enclosingLabeledBlocks.valuesIterator.filter(_.wasCrossUsed).toList
+
+          val nextTryFinallyEntry = innermostTryFinally // note that we're out of ourselves already
+            .filter(nextTry => possibleTargetEntries.exists(nextTry.isInside(_)))
+
+          /* Build the destination table for `br_table`. Target Labeled's that
+           * are outside of the next try..finally in line go to the latter;
+           * for other `Labeled`'s, we go to their cross label.
+           */
+          val brTableDests: List[(Int, wanme.LabelID)] = possibleTargetEntries.map { targetEntry =>
+            val LabeledEntry.CrossInfo(destinationTag, _, crossLabel) =
+              targetEntry.requireCrossInfo()
+            val label = nextTryFinallyEntry.filter(_.isInside(targetEntry)) match {
+              case None          => crossLabel
+              case Some(nextTry) => nextTry.requireCrossInfo().crossLabel
+            }
+            destinationTag -> label
+          }
+
+          fb += wa.LocalGet(entry.requireCrossInfo().destinationTagLocal)
+          for (nextTry <- nextTryFinallyEntry) {
+            // Transfer the destinationTag to the next try..finally in line
+            fb += wa.LocalTee(nextTry.requireCrossInfo().destinationTagLocal)
+          }
+          emitBRTable(brTableDests, doneLabel)
+        }
+      } // end block $done
+
+      // reload the result onto the stack
+      for (resultLocal <- resultLocals)
+        fb += wa.LocalGet(resultLocal)
+
+      if (expectedType == NothingType)
+        fb += wa.Unreachable
+
+      expectedType
+    }
+
+    private def emitBRTable(dests: List[(Int, wanme.LabelID)],
+        defaultLabel: wanme.LabelID): Unit = {
+      dests match {
+        case Nil =>
+          fb += wa.Drop
+          fb += wa.Br(defaultLabel)
+
+        case (singleDestValue, singleDestLabel) :: Nil =>
+          /* Common case (as far as getting here in the first place is concerned):
+           * All the `Return`s that cross the current `TryFinally` have the same
+           * target destination (namely the enclosing `def` in the original program).
+           */
+          fb += wa.I32Const(singleDestValue)
+          fb += wa.I32Eq
+          fb += wa.BrIf(singleDestLabel)
+          fb += wa.Br(defaultLabel)
+
+        case _ :: _ =>
+          // `max` is safe here because the list is non-empty
+          val table = Array.fill(dests.map(_._1).max + 1)(defaultLabel)
+          for (dest <- dests)
+            table(dest._1) = dest._2
+          fb += wa.BrTable(table.toList, defaultLabel)
+      }
+    }
+
+    def genReturn(tree: Return): Type = {
+      val Return(expr, LabelIdent(labelName)) = tree
+
+      val targetEntry = enclosingLabeledBlocks(labelName)
+
+      genTree(expr, targetEntry.expectedType)
+
+      markPosition(tree)
+
+      if (targetEntry.expectedType != NothingType) {
+        innermostTryFinally.filter(_.isInside(targetEntry)) match {
+          case None =>
+            // Easy case: directly branch out of the block
+            fb += wa.Br(targetEntry.regularWasmLabel)
+
+          case Some(tryFinallyEntry) =>
+            /* Here we need to branch to the innermost enclosing `finally` block,
+             * while remembering the destination label and the result value.
+             */
+            val LabeledEntry.CrossInfo(destinationTag, resultLocals, _) =
+              targetEntry.requireCrossInfo()
+            val TryFinallyEntry.CrossInfo(destinationTagLocal, crossLabel) =
+              tryFinallyEntry.requireCrossInfo()
+
+            // 1. Store the result in the label's result locals.
+            for (local <- resultLocals.reverse)
+              fb += wa.LocalSet(local)
+
+            // 2. Store the label's destination tag into the try..finally's destination local.
+            fb += wa.I32Const(destinationTag)
+            fb += wa.LocalSet(destinationTagLocal)
+
+            // 3. Branch to the enclosing `finally` block's cross label.
+            fb += wa.Br(crossLabel)
+        }
+      }
+
+      NothingType
+    }
+  }
+}
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala
new file mode 100644
index 0000000000..48bfae78d9
--- /dev/null
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala
@@ -0,0 +1,328 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package org.scalajs.linker.backend.wasmemitter
+
+import java.nio.charset.StandardCharsets
+
+import org.scalajs.ir.ScalaJSVersions
+
+import EmbeddedConstants._
+
+/** Contents of the `__loader.js` file that we emit in every output. */
+object LoaderContent {
+  val bytesContent: Array[Byte] =
+    stringContent.getBytes(StandardCharsets.UTF_8)
+
+  private def stringContent: String = {
+    raw"""
+// This implementation follows no particular specification, but is the same as the JS backend.
+// It happens to coincide with java.lang.Long.hashCode() for common values.
+function bigintHashCode(x) {
+  var res = 0;
+  if (x < 0n)
+    x = ~x;
+  while (x !== 0n) {
+    res ^= Number(BigInt.asIntN(32, x));
+    x >>= 32n;
+  }
+  return res;
+}
+
+// JSSuperSelect support -- directly copied from the output of the JS backend
+function resolveSuperRef(superClass, propName) {
+  var getPrototypeOf = Object.getPrototyeOf;
+  var getOwnPropertyDescriptor = Object.getOwnPropertyDescriptor;
+  var superProto = superClass.prototype;
+  while (superProto !== null) {
+    var desc = getOwnPropertyDescriptor(superProto, propName);
+    if (desc !== (void 0)) {
+      return desc;
+    }
+    superProto = getPrototypeOf(superProto);
+  }
+}
+function superSelect(superClass, self, propName) {
+  var desc = resolveSuperRef(superClass, propName);
+  if (desc !== (void 0)) {
+    var getter = desc.get;
+    return getter !== (void 0) ? getter.call(self) : getter.value;
+  }
+}
+function superSelectSet(superClass, self, propName, value) {
+  var desc = resolveSuperRef(superClass, propName);
+  if (desc !== (void 0)) {
+    var setter = desc.set;
+    if (setter !== (void 0)) {
+      setter.call(self, value);
+      return;
+    }
+  }
+  throw new TypeError("super has no setter '" + propName + "'.");
+}
+
+function installJSField(instance, name, value) {
+  Object.defineProperty(instance, name, {
+    value,
+    configurable: true,
+    enumerable: true,
+    writable: true,
+  });
+}
+
+// FIXME We need to adapt this to the correct values
+const linkingInfo = Object.freeze({
+  "esVersion": 6,
+  "assumingES6": true,
+  "productionMode": false,
+  "linkerVersion": "${ScalaJSVersions.current}",
+  "fileLevelThis": this
+});
+
+const scalaJSHelpers = {
+  // JSTag
+  JSTag: WebAssembly.JSTag,
+
+  // BinaryOp.===
+  is: Object.is,
+
+  // undefined
+  undef: void 0,
+  isUndef: (x) => x === (void 0),
+
+  // Zero boxes
+  bFalse: false,
+  bZero: 0,
+
+  // Boxes (upcast) -- most are identity at the JS level but with different types in Wasm
+  bZ: (x) => x !== 0,
+  bB: (x) => x,
+  bS: (x) => x,
+  bI: (x) => x,
+  bF: (x) => x,
+  bD: (x) => x,
+
+  // Unboxes (downcast, null is converted to the zero of the type as part of ToWebAssemblyValue)
+  uZ: (x) => x, // ToInt32 turns false into 0 and true into 1, so this is also an identity
+  uB: (x) => x,
+  uS: (x) => x,
+  uI: (x) => x,
+  uF: (x) => x,
+  uD: (x) => x,
+
+  // Type tests
+  tZ: (x) => typeof x === 'boolean',
+  tB: (x) => typeof x === 'number' && Object.is((x << 24) >> 24, x),
+  tS: (x) => typeof x === 'number' && Object.is((x << 16) >> 16, x),
+  tI: (x) => typeof x === 'number' && Object.is(x | 0, x),
+  tF: (x) => typeof x === 'number' && (Math.fround(x) === x || x !== x),
+  tD: (x) => typeof x === 'number',
+
+  // fmod, to implement Float_% and Double_% (it is apparently quite hard to implement fmod otherwise)
+  fmod: (x, y) => x % y,
+
+  // Closure
+  closure: (f, data) => f.bind(void 0, data),
+  closureThis: (f, data) => function(...args) { return f(data, this, ...args); },
+  closureRest: (f, data, n) => ((...args) => f(data, ...args.slice(0, n), args.slice(n))),
+  closureThisRest: (f, data, n) => function(...args) { return f(data, this, ...args.slice(0, n), args.slice(n)); },
+
+  // Top-level exported defs -- they must be `function`s but have no actual `this` nor `data`
+  makeExportedDef: (f) => function(...args) { return f(...args); },
+  makeExportedDefRest: (f, n) => function(...args) { return f(...args.slice(0, n), args.slice(n)); },
+
+  // Strings
+  emptyString: "",
+  stringLength: (s) => s.length,
+  stringCharAt: (s, i) => s.charCodeAt(i),
+  jsValueToString: (x) => (x === void 0) ? "undefined" : x.toString(),
+  jsValueToStringForConcat: (x) => "" + x,
+  booleanToString: (b) => b ? "true" : "false",
+  charToString: (c) => String.fromCharCode(c),
+  intToString: (i) => "" + i,
+  longToString: (l) => "" + l, // l must be a bigint here
+  doubleToString: (d) => "" + d,
+  stringConcat: (x, y) => ("" + x) + y, // the added "" is for the case where x === y === null
+  isString: (x) => typeof x === 'string',
+
+  // Get the type of JS value of `x` in a single JS helper call, for the purpose of dispatch.
+  jsValueType: (x) => {
+    if (typeof x === 'number')
+      return $JSValueTypeNumber;
+    if (typeof x === 'string')
+      return $JSValueTypeString;
+    if (typeof x === 'boolean')
+      return x | 0; // JSValueTypeFalse or JSValueTypeTrue
+    if (typeof x === 'undefined')
+      return $JSValueTypeUndefined;
+    if (typeof x === 'bigint')
+      return $JSValueTypeBigInt;
+    if (typeof x === 'symbol')
+      return $JSValueTypeSymbol;
+    return $JSValueTypeOther;
+  },
+
+  // Identity hash code
+  bigintHashCode,
+  symbolDescription: (x) => {
+    var desc = x.description;
+    return (desc === void 0) ? null : desc;
+  },
+  idHashCodeGet: (map, obj) => map.get(obj) | 0, // undefined becomes 0
+  idHashCodeSet: (map, obj, value) => map.set(obj, value),
+
+  // JS interop
+  jsGlobalRefGet: (globalRefName) => (new Function("return " + globalRefName))(),
+  jsGlobalRefSet: (globalRefName, v) => {
+    var argName = globalRefName === 'v' ? 'w' : 'v';
+    (new Function(argName, globalRefName + " = " + argName))(v);
+  },
+  jsGlobalRefTypeof: (globalRefName) => (new Function("return typeof " + globalRefName))(),
+  jsNewArray: () => [],
+  jsArrayPush: (a, v) => (a.push(v), a),
+  jsArraySpreadPush: (a, vs) => (a.push(...vs), a),
+  jsNewObject: () => ({}),
+  jsObjectPush: (o, p, v) => (o[p] = v, o),
+  jsSelect: (o, p) => o[p],
+  jsSelectSet: (o, p, v) => o[p] = v,
+  jsNew: (constr, args) => new constr(...args),
+  jsFunctionApply: (f, args) => f(...args),
+  jsMethodApply: (o, m, args) => o[m](...args),
+  jsImportCall: (s) => import(s),
+  jsImportMeta: () => import.meta,
+  jsDelete: (o, p) => { delete o[p]; },
+  jsForInSimple: (o, f) => { for (var k in o) f(k); },
+  jsIsTruthy: (x) => !!x,
+  jsLinkingInfo: linkingInfo,
+
+  // Excruciating list of all the JS operators
+  jsUnaryPlus: (a) => +a,
+  jsUnaryMinus: (a) => -a,
+  jsUnaryTilde: (a) => ~a,
+  jsUnaryBang: (a) => !a,
+  jsUnaryTypeof: (a) => typeof a,
+  jsStrictEquals: (a, b) => a === b,
+  jsNotStrictEquals: (a, b) => a !== b,
+  jsPlus: (a, b) => a + b,
+  jsMinus: (a, b) => a - b,
+  jsTimes: (a, b) => a * b,
+  jsDivide: (a, b) => a / b,
+  jsModulus: (a, b) => a % b,
+  jsBinaryOr: (a, b) => a | b,
+  jsBinaryAnd: (a, b) => a & b,
+  jsBinaryXor: (a, b) => a ^ b,
+  jsShiftLeft: (a, b) => a << b,
+  jsArithmeticShiftRight: (a, b) => a >> b,
+  jsLogicalShiftRight: (a, b) => a >>> b,
+  jsLessThan: (a, b) => a < b,
+  jsLessEqual: (a, b) => a <= b,
+  jsGreaterThan: (a, b) => a > b,
+  jsGreaterEqual: (a, b) => a >= b,
+  jsIn: (a, b) => a in b,
+  jsInstanceof: (a, b) => a instanceof b,
+  jsExponent: (a, b) => a ** b,
+
+  // Non-native JS class support
+  newSymbol: Symbol,
+  createJSClass: (data, superClass, preSuperStats, superArgs, postSuperStats, fields) => {
+    // fields is an array where even indices are field names and odd indices are initial values
+    return class extends superClass {
+      constructor(...args) {
+        var preSuperEnv = preSuperStats(data, new.target, ...args);
+        super(...superArgs(data, preSuperEnv, new.target, ...args));
+        for (var i = 0; i != fields.length; i = (i + 2) | 0)
+          installJSField(this, fields[i], fields[(i + 1) | 0]);
+        postSuperStats(data, preSuperEnv, new.target, this, ...args);
+      }
+    };
+  },
+  createJSClassRest: (data, superClass, preSuperStats, superArgs, postSuperStats, fields, n) => {
+    // fields is an array where even indices are field names and odd indices are initial values
+    return class extends superClass {
+      constructor(...args) {
+        var fixedArgs = args.slice(0, n);
+        var restArg = args.slice(n);
+        var preSuperEnv = preSuperStats(data, new.target, ...fixedArgs, restArg);
+        super(...superArgs(data, preSuperEnv, new.target, ...fixedArgs, restArg));
+        for (var i = 0; i != fields.length; i = (i + 2) | 0)
+          installJSField(this, fields[i], fields[(i + 1) | 0]);
+        postSuperStats(data, preSuperEnv, new.target, this, ...fixedArgs, restArg);
+      }
+    };
+  },
+  installJSField,
+  installJSMethod: (data, jsClass, name, func, fixedArgCount) => {
+    var closure = fixedArgCount < 0
+      ? (function(...args) { return func(data, this, ...args); })
+      : (function(...args) { return func(data, this, ...args.slice(0, fixedArgCount), args.slice(fixedArgCount))});
+    jsClass.prototype[name] = closure;
+  },
+  installJSStaticMethod: (data, jsClass, name, func, fixedArgCount) => {
+    var closure = fixedArgCount < 0
+      ? (function(...args) { return func(data, ...args); })
+      : (function(...args) { return func(data, ...args.slice(0, fixedArgCount), args.slice(fixedArgCount))});
+    jsClass[name] = closure;
+  },
+  installJSProperty: (data, jsClass, name, getter, setter) => {
+    var getterClosure = getter
+      ? (function() { return getter(data, this) })
+      : (void 0);
+    var setterClosure = setter
+      ? (function(arg) { setter(data, this, arg) })
+      : (void 0);
+    Object.defineProperty(jsClass.prototype, name, {
+      get: getterClosure,
+      set: setterClosure,
+      configurable: true,
+    });
+  },
+  installJSStaticProperty: (data, jsClass, name, getter, setter) => {
+    var getterClosure = getter
+      ? (function() { return getter(data) })
+      : (void 0);
+    var setterClosure = setter
+      ? (function(arg) { setter(data, arg) })
+      : (void 0);
+    Object.defineProperty(jsClass, name, {
+      get: getterClosure,
+      set: setterClosure,
+      configurable: true,
+    });
+  },
+  jsSuperSelect: superSelect,
+  jsSuperSelectSet: superSelectSet,
+  jsSuperCall: (superClass, receiver, method, args) => {
+    return superClass.prototype[method].apply(receiver, args);
+  },
+}
+
+export async function load(wasmFileURL, importedModules, exportSetters) {
+  const myScalaJSHelpers = { ...scalaJSHelpers, idHashCodeMap: new WeakMap() };
+  const importsObj = {
+    "__scalaJSHelpers": myScalaJSHelpers,
+    "__scalaJSImports": importedModules,
+    "__scalaJSExportSetters": exportSetters,
+  };
+  const resolvedURL = new URL(wasmFileURL, import.meta.url);
+  if (resolvedURL.protocol === 'file:') {
+    const { fileURLToPath } = await import("node:url");
+    const { readFile } = await import("node:fs/promises");
+    const wasmPath = fileURLToPath(resolvedURL);
+    const body = await readFile(wasmPath);
+    return WebAssembly.instantiate(body, importsObj);
+  } else {
+    return await WebAssembly.instantiateStreaming(fetch(resolvedURL), importsObj);
+  }
+}
+    """
+  }
+}
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Preprocessor.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Preprocessor.scala
new file mode 100644
index 0000000000..5c2d76f190
--- /dev/null
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Preprocessor.scala
@@ -0,0 +1,473 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package org.scalajs.linker.backend.wasmemitter
+
+import scala.collection.mutable
+
+import org.scalajs.ir.Names._
+import org.scalajs.ir.Trees._
+import org.scalajs.ir.Types._
+import org.scalajs.ir.{ClassKind, Traversers}
+
+import org.scalajs.linker.standard.{LinkedClass, LinkedTopLevelExport}
+
+import EmbeddedConstants._
+import WasmContext._
+
+object Preprocessor {
+  def preprocess(classes: List[LinkedClass], tles: List[LinkedTopLevelExport]): WasmContext = {
+    val staticFieldMirrors = computeStaticFieldMirrors(tles)
+
+    val specialInstanceTypes = computeSpecialInstanceTypes(classes)
+
+    val abstractMethodCalls =
+      AbstractMethodCallCollector.collectAbstractMethodCalls(classes, tles)
+
+    val (itableBucketCount, itableBucketAssignments) =
+      computeItableBuckets(classes)
+
+    val classInfosBuilder = mutable.HashMap.empty[ClassName, ClassInfo]
+    val definedReflectiveProxyNames = mutable.HashSet.empty[MethodName]
+
+    for (clazz <- classes) {
+      val classInfo = preprocess(
+        clazz,
+        staticFieldMirrors.getOrElse(clazz.className, Map.empty),
+        specialInstanceTypes.getOrElse(clazz.className, 0),
+        itableBucketAssignments.getOrElse(clazz.className, -1),
+        clazz.superClass.map(sup => classInfosBuilder(sup.name))
+      )
+      classInfosBuilder += clazz.className -> classInfo
+
+      // For Scala classes, collect the reflective proxy method names that it defines
+      if (clazz.kind.isClass || clazz.kind == ClassKind.HijackedClass) {
+        for (method <- clazz.methods if method.methodName.isReflectiveProxy)
+          definedReflectiveProxyNames += method.methodName
+      }
+    }
+
+    val classInfos = classInfosBuilder.toMap
+
+    // sort for stability
+    val reflectiveProxyIDs = definedReflectiveProxyNames.toList.sorted.zipWithIndex.toMap
+
+    for (clazz <- classes) {
+      classInfos(clazz.className).buildMethodTable(
+          abstractMethodCalls.getOrElse(clazz.className, Set.empty))
+    }
+
+    new WasmContext(classInfos, reflectiveProxyIDs, itableBucketCount)
+  }
+
+  private def computeStaticFieldMirrors(
+      tles: List[LinkedTopLevelExport]): Map[ClassName, Map[FieldName, List[String]]] = {
+
+    var result = Map.empty[ClassName, Map[FieldName, List[String]]]
+    for (tle <- tles) {
+      tle.tree match {
+        case TopLevelFieldExportDef(_, exportName, FieldIdent(fieldName)) =>
+          val className = tle.owningClass
+          val mirrors = result.getOrElse(className, Map.empty)
+          val newExportNames = exportName :: mirrors.getOrElse(fieldName, Nil)
+          val newMirrors = mirrors.updated(fieldName, newExportNames)
+          result = result.updated(className, newMirrors)
+
+        case _ =>
+      }
+    }
+    result
+  }
+
+  private def computeSpecialInstanceTypes(
+      classes: List[LinkedClass]): Map[ClassName, Int] = {
+
+    val result = mutable.AnyRefMap.empty[ClassName, Int]
+
+    for {
+      clazz <- classes
+      if clazz.kind == ClassKind.HijackedClass
+    } {
+      val specialInstanceTypes = clazz.className match {
+        case BoxedBooleanClass => (1 << JSValueTypeFalse) | (1 << JSValueTypeTrue)
+        case BoxedStringClass  => 1 << JSValueTypeString
+        case BoxedDoubleClass  => 1 << JSValueTypeNumber
+        case BoxedUnitClass    => 1 << JSValueTypeUndefined
+        case _                 => 0
+      }
+
+      if (specialInstanceTypes != 0) {
+        for (ancestor <- clazz.ancestors.tail)
+          result(ancestor) = result.getOrElse(ancestor, 0) | specialInstanceTypes
+      }
+    }
+
+    result.toMap
+  }
+
+  private def preprocess(
+      clazz: LinkedClass,
+      staticFieldMirrors: Map[FieldName, List[String]],
+      specialInstanceTypes: Int,
+      itableIdx: Int,
+      superClass: Option[ClassInfo]
+  ): ClassInfo = {
+    val className = clazz.className
+    val kind = clazz.kind
+
+    val allFieldDefs: List[FieldDef] = {
+      if (kind.isClass) {
+        val inheritedFields =
+          superClass.fold[List[FieldDef]](Nil)(_.allFieldDefs)
+        val myFieldDefs = clazz.fields.collect {
+          case fd: FieldDef if !fd.flags.namespace.isStatic =>
+            fd
+          case fd: JSFieldDef =>
+            throw new AssertionError(s"Illegal $fd in Scala class $className")
+        }
+        inheritedFields ::: myFieldDefs
+      } else {
+        Nil
+      }
+    }
+
+    // Does this Scala class implement any interface?
+    val classImplementsAnyInterface = {
+      (kind.isClass || kind == ClassKind.HijackedClass) &&
+      (clazz.interfaces.nonEmpty || superClass.exists(_.classImplementsAnyInterface))
+    }
+
+    /* Should we emit a vtable/typeData global for this class?
+     *
+     * There are essentially three reasons for which we need them:
+     *
+     * - Because there is a `classOf[C]` somewhere in the program; if that is
+     *   true, then `clazz.hasRuntimeTypeInfo` is true.
+     * - Because it is the vtable of a class with direct instances; in that
+     *   case `clazz.hasRuntimeTypeInfo` is also true, as guaranteed by the
+     *   Scala.js frontend analysis.
+     * - Because we generate a test of the form `isInstanceOf[Array[C]]`. In
+     *   that case, `clazz.hasInstanceTests` is true.
+     *
+     * `clazz.hasInstanceTests` is also true if there is only `isInstanceOf[C]`,
+     * in the program, so that is not *optimal*, but it is correct.
+     */
+    val hasRuntimeTypeInfo = clazz.hasRuntimeTypeInfo || clazz.hasInstanceTests
+
+    val resolvedMethodInfos: Map[MethodName, ConcreteMethodInfo] = {
+      if (kind.isClass || kind == ClassKind.HijackedClass) {
+        val inherited =
+          superClass.fold[Map[MethodName, ConcreteMethodInfo]](Map.empty)(_.resolvedMethodInfos)
+
+        val concretePublicMethodNames = for {
+          m <- clazz.methods
+          if m.body.isDefined && m.flags.namespace == MemberNamespace.Public
+        } yield {
+          m.methodName
+        }
+
+        for (methodName <- concretePublicMethodNames)
+          inherited.get(methodName).foreach(_.markOverridden())
+
+        concretePublicMethodNames.foldLeft(inherited) { (prev, methodName) =>
+          prev.updated(methodName, new ConcreteMethodInfo(className, methodName))
+        }
+      } else {
+        Map.empty
+      }
+    }
+
+    new ClassInfo(
+      className,
+      kind,
+      clazz.jsClassCaptures,
+      allFieldDefs,
+      superClass,
+      classImplementsAnyInterface,
+      clazz.hasInstances,
+      !clazz.hasDirectInstances,
+      hasRuntimeTypeInfo,
+      clazz.jsNativeLoadSpec,
+      clazz.jsNativeMembers.map(m => m.name.name -> m.jsNativeLoadSpec).toMap,
+      staticFieldMirrors,
+      specialInstanceTypes,
+      resolvedMethodInfos,
+      itableIdx
+    )
+  }
+
+  /** Collects virtual and interface method calls.
+   *
+   *  That information will be used to decide what entries are necessary in
+   *  vtables and itables.
+   *
+   *  TODO Arguably this is a job for the `Analyzer`.
+   */
+  private object AbstractMethodCallCollector {
+    def collectAbstractMethodCalls(classes: List[LinkedClass],
+        tles: List[LinkedTopLevelExport]): Map[ClassName, Set[MethodName]] = {
+
+      val collector = new AbstractMethodCallCollector
+      for (clazz <- classes)
+        collector.collectAbstractMethodCalls(clazz)
+      for (tle <- tles)
+        collector.collectAbstractMethodCalls(tle)
+      collector.result()
+    }
+  }
+
+  private class AbstractMethodCallCollector private () extends Traversers.Traverser {
+    private val builder = new mutable.AnyRefMap[ClassName, mutable.HashSet[MethodName]]
+
+    private def registerCall(className: ClassName, methodName: MethodName): Unit =
+      builder.getOrElseUpdate(className, new mutable.HashSet) += methodName
+
+    def collectAbstractMethodCalls(clazz: LinkedClass): Unit = {
+      for (method <- clazz.methods)
+        traverseMethodDef(method)
+      for (jsConstructor <- clazz.jsConstructorDef)
+        traverseJSConstructorDef(jsConstructor)
+      for (export <- clazz.exportedMembers)
+        traverseJSMethodPropDef(export)
+    }
+
+    def collectAbstractMethodCalls(tle: LinkedTopLevelExport): Unit = {
+      tle.tree match {
+        case TopLevelMethodExportDef(_, jsMethodDef) =>
+          traverseJSMethodPropDef(jsMethodDef)
+        case _ =>
+          ()
+      }
+    }
+
+    def result(): Map[ClassName, Set[MethodName]] =
+      builder.toMap.map(kv => kv._1 -> kv._2.toSet)
+
+    override def traverse(tree: Tree): Unit = {
+      super.traverse(tree)
+
+      tree match {
+        case Apply(flags, receiver, MethodIdent(methodName), _) if !methodName.isReflectiveProxy =>
+          receiver.tpe match {
+            case ClassType(className) =>
+              registerCall(className, methodName)
+            case AnyType =>
+              registerCall(ObjectClass, methodName)
+            case _ =>
+              // For all other cases, including arrays, we will always perform a static dispatch
+              ()
+          }
+
+        case _ =>
+          ()
+      }
+    }
+  }
+
+  /** Group interface types and types that implement any interfaces into buckets,
+   *  ensuring that no two types in the same bucket have common subtypes.
+   *
+   *  For example, given the following type hierarchy (with upper types as
+   *  supertypes), types will be assigned to the following buckets:
+   *
+   *  {{{
+   *      A __
+   *    / |\  \
+   *   /  | \  \
+   *  B   C  E  G
+   *      | /| /
+   *      |/ |/
+   *      D  F
+   *  }}}
+   *
+   *  - bucket0: [A]
+   *  - bucket1: [B, C, G]
+   *  - bucket2: [D, F]
+   *  - bucket3: [E]
+   *
+   *  In the original paper, within each bucket, types are given unique indices
+   *  that are local to each bucket. A gets index 0. B, C, and G are assigned
+   *  0, 1, and 2 respectively. Similarly, D=0, F=1, and E=0.
+   *
+   *  This method (called packed encoding) compresses the interface tables
+   *  compared to a global 1-1 mapping from interface to index. With the 1-1
+   *  mapping strategy, the length of the itables would be 7 (for interfaces
+   *  A-G). In contrast, using a packed encoding strategy, the length of the
+   *  interface tables is reduced to the number of buckets, which is 4 in this
+   *  case.
+   *
+   *  Each element in the interface tables array corresponds to the interface
+   *  table of the type in the respective bucket that the object implements.
+   *  For example, an object that implements G (and A) would have an interface
+   *  table structured as: [(itable of A), (itable of G), null, null], because
+   *  A is in bucket 0 and G is in bucket 1.
+   *
+   *  {{{
+   *      Object implements G
+   *                |
+   *     +----------+---------+
+   *     |  ...class metadata |
+   *     +--------------------+             1-1 mapping strategy version
+   *     |      vtable        |  +----> [(itable of A), null, null, null, null, null, (itable of G)]
+   *     +--------------------+ /
+   *     |      itables       +/
+   *     +--------------------+\            packed encoding version
+   *     |       ...          + +-----> [(itable of A), (itable of G), null, null]
+   *     +--------------------+
+   *  }}}
+   *
+   *  To perform an interface dispatch, we can use bucket IDs and indices to
+   *  locate the appropriate interface table. For instance, suppose we need to
+   *  dispatch for interface G. Knowing that G belongs to bucket 1, we retrieve
+   *  the itable for G from i-th element of the itables.
+   *
+   *  @note
+   *    Why the types in the example are assigned to the buckets like that?
+   *    - bucket0: [A]
+   *      - A is placed alone in the first bucket.
+   *      - It cannot be grouped with any of its subtypes as that would violate
+   *        the "no common subtypes" rule.
+   *    - bucket1: [B, C, G]
+   *      - B, C, and G cannot be in the same bucket with A since they are all
+   *        direct subtypes of A.
+   *      - They are grouped together because they do not share any common subtype.
+   *    - bucket2: [D, F]
+   *      - D cannot be assigned to neither bucket 0 or 1 because it shares the
+   *        same subtype (D itself) with A (in bucket 0) and C (in bucket 1).
+   *      - D and F are grouped together because they do not share any common subtype.
+   *    - bucket3: [E]
+   *     - E shares its subtype with all the other buckets, so it gets assigned
+   *       to a new bucket.
+   *
+   *  @return
+   *    The total number of buckets and a map from interface name to
+   *    (the index of) the bucket it was assigned to.
+   *
+   *  @see
+   *    The algorithm is based on the "packed encoding" presented in the paper
+   *    "Efficient Type Inclusion Tests"
+   *    [[https://www.researchgate.net/publication/2438441_Efficient_Type_Inclusion_Tests]]
+   */
+  private def computeItableBuckets(
+      allClasses: List[LinkedClass]): (Int, Map[ClassName, Int]) = {
+
+    /* Since we only have to assign itable indices to interfaces with
+     * instances, we can filter out all parts of the hierarchy that are not
+     * Scala types with instances.
+     */
+    val classes = allClasses.filter(c => !c.kind.isJSType && c.hasInstances)
+
+    /* The algorithm separates the type hierarchy into three disjoint subsets:
+     *
+     * - join types: types with multiple parents (direct supertypes) that have
+     *   only single subtyping descendants:
+     *   `join(T) = {x ∈ multis(T) | ∄ y ∈ multis(T) : y <: x}`
+     *   where multis(T) means types with multiple direct supertypes.
+     * - spine types: all ancestors of join types:
+     *   `spine(T) = {x ∈ T | ∃ y ∈ join(T) : x ∈ ancestors(y)}`
+     * - plain types: types that are neither join nor spine types
+     *
+     * Now observe that:
+     *
+     * - we only work with types that have instances,
+     * - the only way an *interface* `I` can have instances is if there is a
+     *   *class* with instances that implements it,
+     * - there must exist such a class `C` that is a join type: one that
+     *   extends another *class* and also at least one interface that has `I`
+     *   in its ancestors (note that `jl.Object` implements no interface),
+     * - therefore, `I` must be a spine type!
+     *
+     * The bucket assignment process consists of two parts:
+     *
+     * **1. Assign buckets to spine types**
+     *
+     * Two spine types can share the same bucket only if they do not have any
+     * common join type descendants.
+     *
+     * Visit spine types in reverse topological order (from leaves to root)
+     * because when assigning a spine type to a bucket, the algorithm already
+     * has complete information about the join/spine type descendants of that
+     * spine type.
+     *
+     * Assign a bucket to a spine type if adding it does not violate the bucket
+     * assignment rule, namely: two spine types can share a bucket only if they
+     * do not have any common join type descendants. If no existing bucket
+     * satisfies the rule, create a new bucket.
+     *
+     * **2. Assign buckets to non-spine types (plain and join types)**
+     *
+     * Since we only need to assign itable indices to interfaces, and we
+     * observed that interfaces are all spine types, we can entirely skip this
+     * phase of the paper's algorithm.
+     */
+
+    val buckets = new mutable.ListBuffer[Bucket]()
+    val resultBuilder = Map.newBuilder[ClassName, Int]
+
+    def findOrCreateBucketSuchThat(p: Bucket => Boolean): Bucket = {
+      buckets.find(p).getOrElse {
+        val newBucket = new Bucket(index = buckets.size)
+        buckets += newBucket
+        newBucket
+      }
+    }
+
+    /* All join type descendants of the class.
+     * Invariant: sets are non-empty when present.
+     */
+    val joinsOf = new mutable.HashMap[ClassName, mutable.HashSet[ClassName]]()
+
+    // Phase 1: Assign buckets to spine types
+    for (clazz <- classes.reverseIterator) {
+      val className = clazz.className
+      val parents = (clazz.superClass.toList ::: clazz.interfaces.toList).map(_.name)
+
+      joinsOf.get(className) match {
+        case Some(joins) =>
+          // This type is a spine type
+          assert(joins.nonEmpty, s"Found empty joins set for $className")
+
+          /* If the spine type is an interface, look for an existing bucket to
+           * add it to. Two spine types can share a bucket only if they don't
+           * have any common join type descendants.
+           */
+          if (clazz.kind == ClassKind.Interface) {
+            val bucket = findOrCreateBucketSuchThat(!_.joins.exists(joins))
+            resultBuilder += className -> bucket.index
+            bucket.joins ++= joins
+          }
+
+          for (parent <- parents)
+            joinsOf.getOrElseUpdate(parent, new mutable.HashSet()) ++= joins
+
+        case None if parents.length > 1 =>
+          // This type is a join type: add to joins map
+          for (parent <- parents)
+            joinsOf.getOrElseUpdate(parent, new mutable.HashSet()) += className
+
+        case None =>
+          // This type is a plain type. Do nothing.
+      }
+    }
+
+    // No Phase 2 :-)
+
+    // Build the result
+    (buckets.size, resultBuilder.result())
+  }
+
+  private final class Bucket(val index: Int) {
+    /** A set of join types that are descendants of the types assigned to that bucket */
+    val joins = new mutable.HashSet[ClassName]()
+  }
+
+}
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/README.md b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/README.md
new file mode 100644
index 0000000000..f03a0452bf
--- /dev/null
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/README.md
@@ -0,0 +1,790 @@
+# WebAssembly Emitter
+
+This directory contains the WebAssembly Emitter, which takes linked IR and produces WebAssembly files.
+
+The entry point is the class `Emitter`.
+Overall, this organization of this backend is similar to that of the JavaScript backend.
+
+This readme gives an overview of the compilation scheme.
+
+## WebAssembly features that we use
+
+* The [GC extension](https://github.com/WebAssembly/gc)
+* The [exception handling proposal](https://github.com/WebAssembly/exception-handling)
+
+All our heap values are allocated as GC data structures.
+We do not use the linear memory of WebAssembly at all.
+
+## Type representation
+
+Since WebAssembly is strongly statically typed, we have to convert IR types into Wasm types.
+The full compilation pipeline must be type-preserving: a well-typed IR program compiles into a well-typed Wasm module.
+
+In most cases, we also preserve subtyping: if `S <: T` at the IR level, then `transform(S) <: transform(T)` at the Wasm level.
+This is however not true when `S` is a primitive type, or when `T = void`.
+
+* When `T = void` and `S ≠ void`, we have to `drop` the value of type `S` from the stack.
+* When `S` is a primitive and `T` is a reference type (which must be an ancestor of a hijacked class), we have to "box" the primitive.
+  We will come back to this in the [hijacked classes](#hijacked-classes) section.
+
+### Primitive types
+
+| IR type         | Wasm type   | Value representation (if non-obvious)   |
+|-----------------|-------------|-----------------------------------------|
+| `void`          | no type     | no value on the stack                   |
+| `boolean`       | `i32`       | `0` for `false`, 1 for `true`           |
+| `byte`, `short` | `i32`       | the `.toInt` value, i.e., sign extended |
+| `char`          | `i32`       | the `.toInt` value, i.e., 0-extended    |
+| `int`           | `i32`       |                                         |
+| `long`          | `i64`       |                                         |
+| `float`         | `f32`       |                                         |
+| `double`        | `f64`       |                                         |
+| `undef`         | `(ref any)` | the global JavaScript value `undefined` |
+| `string`        | `(ref any)` | a JavaScript `string`                   |
+
+### Reference types
+
+We will describe more precisely the representation of reference types in the coming sections.
+This table is for reference.
+
+| IR type                           | Wasm type                        |
+|-----------------------------------|----------------------------------|
+| `C`, a Scala class                | `(ref null $c.C)` |              |
+| `I`, a Scala interface            | `(ref null $c.jl.Object)`        |
+| all ancestors of hijacked classes | `(ref null any)` (aka `anyref`)  |
+| `PT[]`, a primitive array         | `(ref null $PTArray)`            |
+| `RT[]`, any reference array type  | `(ref null $ObjectArray)`        |
+
+### Nothing
+
+Wasm does not have a bottom type that we can express at the "user level".
+That means we cannot transform `nothing` into any single Wasm type.
+However, Wasm has a well-defined notion of [*stack polymorphism*](https://webassembly.github.io/gc/core/valid/instructions.html#polymorphism).
+As far as we are concerned, we can think of a stack polymorphic context as officially dead code.
+After a *stack-polymorphic instruction*, such as `br` (an unconditional branch), we have dead code which can automatically adapt its type (to be precise: the type of the elements on the stack) to whatever is required to typecheck the following instructions.
+
+A stack-polymorphic context is as close as Wasm gets to our notion of `nothing`.
+Our "type representation" for `nothing` is therefore to make sure that we are in a stack-polymorphic context.
+
+## Object model
+
+### Basic structure
+
+We use GC `struct`s to represent instances of classes.
+The structs start with a `vtable` reference and an `itables` reference, which are followed by user-defined fields.
+The declared supertypes of those `struct`s follow the *class* hierarchy (ignoring interfaces).
+
+The `vtable` and `itables` references are immutable.
+User-defined fields are always mutable as the WebAssembly level, since they are mutated in the constructors.
+
+For example, given the following IR classes:
+
+```scala
+class A extends jl.Object {
+  val x: int
+}
+
+class B extends A {
+  var y: double
+}
+```
+
+We define the following GC structs:
+
+```wat
+(type $c.A (sub $c.java.lang.Object (struct
+  (field $vtable (ref $v.A))
+  (field $itables (ref null $itables))
+  (field $f.A.x (mut i32)))
+))
+
+(type $c.B (sub $c.A (struct
+  (field $vtable (ref $v.B))
+  (field $itables (ref null $itables))
+  (field $f.A.x (mut i32))
+  (field $f.B.y (mut f64)))
+))
+```
+
+As required in Wasm structs, all fields are always repeated in substructs.
+Declaring a parent struct type does not imply inheritance of the fields.
+
+### Methods and statically resolved calls
+
+Methods are compiled into Wasm functions in a straightforward way, given the type transformations presented above.
+When present, the receiver comes as a first argument.
+
+Statically resolved calls are also compiled straightforwardly as:
+
+1. Push the receiver, if any, on the stack
+2. Push the arguments on the stack
+3. `call` the target function
+
+Constructors are considered instance methods with a `this` receiver for this purpose, and are always statically resolved.
+
+For example, given the IR
+
+```scala
+class A extends java.lang.Object {
+  val A::x: int
+  def x;I(): int = {
+    this.A::x
+  }
+  def plus;I;I(y: int): int = {
+    (this.x;I() +[int] y)
+  }
+  constructor def <init>;I;V(x: int) {
+    this.A::x = x;
+    this.java.lang.Object::<init>;V()
+  }
+}
+```
+
+We get the following implementing functions, assuming all method calls are statically resolved.
+
+```wat
+;; getter for x
+(func $f.A.x_I
+  (param $this (ref $c.A)) (result i32)
+  ;; field selection: push the object than `struct.get`
+  local.get $this
+  struct.get $c.A $f.A.x
+  ;; there is always an implicit `return` at the end of a Wasm function
+)
+
+;; method plus
+(func $f.A.plus_I_I
+  (param $this (ref $c.A)) (param $y i32) (result i32)
+  ;; call to the getter: push receiver, cast null away, then `call`
+  local.get $this
+  ref.as_non_null
+  call $f.A.x_I
+  ;; add `y` to the stack and `i32.add` to add it to the result of the call
+  local.get $y
+  i32.add
+)
+
+;; constructor
+(func $ct.A.<init>_I_V
+  (param $this (ref $c.A)) (param $x i32)
+  ;; this.x = x
+  local.get $this
+  local.get $x
+  struct.set $c.A $f.A.x
+  ;; call Object.<init>(this)
+  local.get $this
+  ref.as_non_null
+  call $ct.java.lang.Object.<init>_V
+)
+```
+
+In theory, the call to the getter should have been a virtual call in this case.
+In practice, the backend contains an analysis of virtual calls to methods that are never overridden, and statically resolves them instead.
+In the future, we will probably transfer this optimization to the `Optimizer`, as it already contains all the required logic to efficiently do this.
+In the absence of the optimizer, however, this one optimization was important to get decent code size.
+
+### typeData
+
+Metadata about IR classes are reified at run-time as values of the struct type `(ref typeData)`.
+Documentation for the meaning of each field can be found in `VarGen.genFieldID.typeData`.
+
+### vtable and virtual method calls
+
+The vtable of our object model follows a standard layout:
+
+* The class meta data, then
+* Function pointers for the virtual methods, from `jl.Object` down to the current class.
+
+vtable structs form a subtyping hierarchy that mirrors the class hierarchy, so that `$v.B` is a subtype of `$v.A`.
+This is required for `$c.B` to be a valid subtype of `$c.A`, since their first field is of the corresponding vtable types.
+
+The vtable of `jl.Object` is a subtype of `typeData`, which allows to generically manipulate `typeData`s even when they are not full vtables.
+For example, the `typeData` of JS types and Scala interfaces do not have a corresponding vtable.
+
+An alternative would have been to make the vtables *contain* the `(ref typeData)` as a first field.
+That would however require an additional pointer indirection on every access to the `typeData`, for no benefit in memory usage or code size.
+WebAssembly does not have a notion of "flattened" inner structs: a struct cannot contain another struct; it can only contain a *reference* to another struct.
+
+Given
+
+```scala
+class A extends Object {
+  def foo(x: int): int = x
+}
+
+class B extends A {
+  val field: int
+
+  def bar(x: double): double = x
+  override def foo(x: int): int = x + this.field
+}
+```
+
+we get
+
+```wat
+(type $v.A (sub $v.java.lang.Object (struct
+  ;; ... class metadata
+  ;; ... methods of jl.Object
+  (field $m.foo_I_I (ref $4))
+)))
+
+(type $v.helloworld.B (sub $v.A (struct
+  ;; ... class metadata
+  ;; ... methods of jl.Object
+  (field $m.foo_I_I (ref $4))
+  (field $m.bar_D_D (ref $6))
+)))
+
+(type $4 (func (param (ref any)) (param i32) (result i32)))
+(type $6 (func (param (ref any)) (param f64) (result f64)))
+```
+
+Note that the declared type of `this` in the function types is always `(ref any)`.
+If we used the enclosing class type, the type of `$m.foo_I_I` would have incompatible types in the two vtables:
+
+* In `$v.A`, it would have type `(func (param (ref $c.A)) ...)`
+* In `$v.B`, it would have type `(func (param (ref $c.B)) ...)`
+
+Since the latter is not a subtype of the former, `$v.B` cannot be a subtype of `$v.A` (recall from earlier that we need that subtyping relationship to hold).
+
+Because we use `(ref any)`, we cannot directly put a reference to the implementing functions (e.g., `$f.A.foo_I_I`) in the vtables: their receiver has a precise type.
+Instead, we generate bridge forwarders (the `forTableEntry` methods) which:
+
+1. take a receiver of type `(ref any)`,
+2. cast it down to the precise type, and
+3. call the actual implementation function (with a tail call, because why not)
+
+The table entry forwarder for `A.foo` looks as follows:
+
+```wat
+;; this function has an explicit `(type $4)` which ensures it can be put in the vtables
+(func $m.A.foo_I_I (type $4)
+  (param $this (ref any)) (param $x i32) (result i32)
+  ;; get the receiver and cast it down to the precise type
+  local.get $this
+  ref.cast (ref $c.A)
+  ;; load the other arguments and call the actual implementation function
+  local.get $x
+  return_call $f.A.foo_I_I ;; return_call is a guaranteed tail call
+)
+```
+
+A virtual call to `a.foo(1)` is compiled as you would expect: lookup the function reference in the vtable and call it.
+
+### itables and interface method calls
+
+The itables field contains the method tables for interface call dispatch.
+It is an instance of the following array type:
+
+```wat
+(type $itables (array (mut structref)))
+```
+
+As a first approximation, we assign a distinct index to every interface in the program.
+It is used to index into the itables array of the instance.
+At the index of a given interface `Intf`, we find a `(ref $it.Intf)` whose fields are the method table entries of `Intf`.
+Like for vtables, we use the "table entry bridges" in the itables, i.e., the functions where the receiver is of type `(ref any)`.
+
+For example, given
+
+```scala
+interface Intf {
+  def foo(x: int): int
+  def bar(x: double): double
+}
+
+class A extends Intf {
+  def foo(x: int): int = x
+  def bar(x: double): double = x
+}
+```
+
+the struct type for `Intf` is defined as
+
+```wat
+(type $it.Intf (struct
+  (field $m.Intf.bar_D_D (ref $6))
+  (field $m.Intf.foo_I_I (ref $4))
+))
+
+(type $4 (func (param (ref any)) (param i32) (result i32)))
+(type $6 (func (param (ref any)) (param f64) (result f64)))
+```
+
+In practice, allocating one slot for every interface in the program is wasteful.
+We can use the same slot for a set of interfaces that have no concrete class in common.
+This slot allocation is implemented in `Preprocessor.assignBuckets`.
+
+Since Wasm structs only support single inheritance in their subtyping relationships, we have to transform every interface type as `(ref null jl.Object)` (the common supertype of all interfaces).
+This does not turn out to be a problem for interface method calls, since they pass through the `itables` array anyway, and use the table entry bridges which take `(ref any)` as argument.
+
+Given the above structure, an interface method call to `intf.foo(1)` is compiled as expected: lookup the function reference in the appropriate slot of the `itables` array, then call it.
+
+### Reflective calls
+
+Calls to reflective proxies use yet another strategy.
+Instead of building arrays or structs where each reflective proxy appears at a compile-time-constant slot, we use a search-based strategy.
+
+Each reflective proxy name found in the program is allocated a unique integer ID.
+The reflective proxy table of a class is an array of pairs `(id, funcRef)`, stored in the class' `typeData`.
+In order to call a reflective proxy, we perform the following steps:
+
+
+1. Load the `typeData` of the receiver.
+2. Search the reflective proxy ID in `$reflectiveProxies` (using the `searchReflectiveProxy` helper).
+3. Call it (using `call_ref`).
+
+This strategy trades off efficiency for space.
+It is slow, but that corresponds to the fact that reflective calls are slow on the JVM as well.
+In order to have fixed slots for reflective proxy methods, we would need an `m*n` matrix where `m` is the number of concrete classes and `n` the number of distinct reflective proxy names in the entire program.
+With the compilation scheme we use, we only need an array containing the actually implemented reflective proxies per class, but we pay an `O(log n)` run-time cost for lookup (instead of `O(1)`).
+
+## Hijacked classes
+
+Due to our strong interoperability guarantees with JavaScript, the universal (boxed) representation of hijacked classes must be the appropriate JavaScript values.
+For example, a boxed `int` must be a JavaScript `number`.
+The only Wasm type that can store references to both GC structs and arbitrary JavaScript `number`s is `anyref` (an alias of `(ref null any)`).
+That is why we transform the types of ancestors of hijacked classes to the Wasm type `anyref`.
+
+### Boxing
+
+When an `int` is upcast to `jl.Integer` or higher, we must *adapt* the `i32` into `anyref`.
+Doing so is not free, since `i32` is not a subtype of `anyref`.
+Even worse, no Wasm-only instruction sequence is able to perform that conversion in a way that we always get a JavaScript `number`.
+
+Instead, we ask JavaScript for help.
+We use the following JavaScript helper function, which is defined in `LoaderContent`:
+
+```js
+__scalaJSHelpers: {
+  bI: (x) => x,
+}
+```
+
+Huh!? That's an identity function.
+How does it help?
+
+The magic is to import it into Wasm with a non-identity type.
+We import it as
+
+```wat
+(import "__scalaJSHelpers" "bI" (func $bI (param i32) (result anyref)))
+```
+
+The actual conversion happens at the boundary between Wasm and JavaScript and back.
+Conversions are specified in the [Wasm JS Interface](https://webassembly.github.io/gc/js-api/index.html).
+The relevant internal functions are [`ToJSValue`](https://webassembly.github.io/gc/js-api/index.html#tojsvalue) and [`ToWebAssemblyValue`](https://webassembly.github.io/gc/js-api/index.html#towebassemblyvalue).
+
+When calling `$bI` with an `i32` value as argument, on the Wasm spec side of things, it is an `i32.const u32` value (Wasm values carry their type from a spec point of view).
+`ToJSValue` then specifies that:
+
+> * If `w` is of the form `i32.const u32`,
+>   * Let `i32` be `signed_32(u32)`.
+>   * Return 𝔽(`i32` interpreted as a mathematical value).
+
+where 𝔽 is the JS spec function that creates a `number` from a mathematical value.
+
+When that `number` *returns* from the JavaScript "identity" function and flows back into Wasm, the spec invokes `ToWebAssemblyValue(v, anyref)`, which specifies:
+
+> * If `type` is of the form `ref null heaptype` (here `heaptype = any`),
+>   * [...]
+>   * Else,
+>     1. Let `map` be the surrounding agent's associated host value cache.
+>     2. If a host address `hostaddr` exists such that `map[hostaddr]` is the same as `v`,
+>         * Return `ref.host hostaddr`.
+>     3. Let host address `hostaddr` be the smallest address such that `map[hostaddr]` exists is `false`.
+>     4. Set `map[hostaddr]` to `v`.
+>     5. Let `r` be `ref.host hostaddr`.
+
+Therefore, from a spec point of view, we receive back a `ref.host hostaddr` for which the engine remembers that it maps to `v`.
+That `ref.host` value is a valid value of type `anyref`, and therefore we can carry it around inside Wasm.
+
+### Unboxing
+
+When we *unbox* an IR `any` into a primitive `int`, we perform perform the inverse operations.
+We also use an identity function at the JavaScript for unboxing an `int`:
+
+```js
+__scalaJSHelpers: {
+  uI: (x) => x,
+}
+```
+
+However, we swap the Wasm types of parameter and result:
+
+```wat
+(import "__scalaJSHelpers" "uI" (func $uI (param anyref) (result i32)))
+```
+
+When the `ref.host hostaddr` enters JavaScript, `ToJSValue` specifies:
+
+> * If `w` is of the form `ref.host hostaddr`,
+>   * Let `map` be the surrounding agent's associated host value cache.
+>   * Assert: `map[hostaddr]` exists.
+>   * Return `map[hostaddr]`.
+
+This recovers the JavaScript `number` value we started with.
+When it comes back into WebAssembly, the spec invokes `ToWebAssemblyValue(v, i32)`, which specifies:
+
+> * If `type` is `i32`,
+>   * Let `i32` be ? `ToInt32(v)`.
+>   * Let `u32` be the unsigned integer such that `i32` is `signed_32(u32)`.
+>   * Return `i32.const u32`.
+
+Overall, we use `bI`/`uI` as a pair of round-trip functions that perform a lossless conversion from `i32` to `anyref` and back, in a way that JavaScript code would always see the appropriate `number` value.
+
+Note: conveniently, `ToInt32(v)` also takes care of converting `null` into 0, which is a spec trivia we also exploit in the JS backend.
+
+### Efficiency
+
+How is the above not terribly inefficient?
+Because implementations do not actually use a "host value cache" map.
+Instead, they pass pointer values as is through the boundary.
+
+Concretely, `ToWebAssemblyValue(v, anyref)` and `ToJSValue(ref.host x)` are no-ops.
+The conversions involving `i32` are not free, but they are as efficient as it gets for the target JS engines.
+
+### Method dispatch
+
+When the receiver of a method call is a primitive or a hijacked class, the call can always be statically resolved by construction, hence no dispatch is necessary.
+For strict ancestors of hijacked classes, we must use a type-test-based dispatch similar to what we do in `$dp_` dispatchers in the JavaScript backend.
+
+## Arrays
+
+Like the JS backend, we define a separate `struct` type for each primitive array type: `$IntArray`, `$FloatArray`, etc.
+Unlike the JS backend, we merge all the reference array types in a single `struct` type `$ObjectArray`.
+We do not really have a choice, since there is a (practically) unbounded amount of them, and we cannot create new `struct` types at run-time.
+
+All array "classes" follow the same structure:
+
+* They actually extend `jl.Object`
+* Their vtable type is the same as `jl.Object`
+* They each have their own vtable value for the differing metadata, although the method table entries are the same as in `jl.Object`
+  * This is also true for reference types: the vtables are dynamically created at run-time on first use (they are values and share the same type, so that we can do)
+* Their `itables` field points to a common itables array with entries for `jl.Cloneable` and `j.io.Serializable`
+* They have a unique "user-land" field `$underlyingArray`, which is a Wasm array of its values:
+  * For primitives, they are primitive arrays, such as `(array mut i32)`
+  * For references, they are all the same type `(array mut anyref)`
+
+Concretely, here are the relevant Wasm definitions:
+
+```wat
+(type $i8Array (array (mut i8)))
+(type $i16Array (array (mut i16)))
+(type $i32Array (array (mut i32)))
+(type $i64Array (array (mut i64)))
+(type $f32Array (array (mut f32)))
+(type $f64Array (array (mut f64)))
+(type $anyArray (array (mut anyref)))
+
+(type $BooleanArray (sub final $c.java.lang.Object (struct
+  (field $vtable (ref $v.java.lang.Object))
+  (field $itables (ref null $itables))
+  (field $arrayUnderlying (ref $i8Array))
+)))
+(type $CharArray (sub final $c.java.lang.Object (struct
+  (field $vtable (ref $v.java.lang.Object))
+  (field $itables (ref null $itables))
+  (field $arrayUnderlying (ref $i16Array))
+)))
+...
+(type $ObjectArray (sub final $c.java.lang.Object (struct
+  (field $vtable (ref $v.java.lang.Object))
+  (field $itables (ref null $itables))
+  (field $arrayUnderlying (ref $anyArray))
+)))
+```
+
+Given the above layout, reading and writing length and elements is straightforward.
+The only catch is reading an element of a reference type that is more specific than `jl.Object[]`.
+In that case, we must `ref.cast` the element down to its transformed Wasm type to preserve typing.
+This is not great, but given the requirement that reference array types be (unsoundly) covariant in their element type, it seems to be the only viable encoding.
+
+The indirection to get at `$arrayUnderlying` elements is not ideal either, but is no different than what we do in the JS backend with the `u` field.
+In the future, Wasm might provide the ability to [nest an array in a flat layout at the end of a struct](https://github.com/WebAssembly/gc/blob/main/proposals/gc/Post-MVP.md#nested-data-structures).
+
+## Order of definitions in the Wasm module
+
+For most definitions, Wasm does not care in what order things are defined in a module.
+In particular, all functions are declared ahead of time, so that the order in which they are defined is irrelevant.
+
+There are however some exceptions.
+The ones that are relevant to our usage of Wasm are the following:
+
+* In a given recursive type group, type definitions can only refer to types defined in that group or in previous groups (recall that all type definitions are part of recursive type groups, even if they are alone).
+* Even within a recursive type group, the *supertype* of a type definition must be defined before it.
+* The initialization code of `global` definitions can only refer to other global definitions that are defined before.
+
+For type definitions, we use the following ordering:
+
+1. Definitions of the underlying array types (e.g., `(type $i8Array (array (mut i8)))`)
+2. The big recursive type group, with:
+   1. Some types referred to from `$typeData`, in no particular order.
+   2. The `$typeData` struct definition (it is a supertype of the vtable types, so it must come early).
+   3. For each Scala class or interface in increasing order of ancestor count (the same order we use in the JS backend), if applicable:
+      1. Its vtable type (e.g., `$v.java.lang.Object`)
+      2. Its object struct type (e.g., `$c.java.lang.Object`)
+      3. Its itable type (e.g., `$it.java.lang.Comparable`)
+   4. Function types appearing in vtables and itables, interspersed with the above in no particular order.
+   5. The `$XArray` struct definitions (e.g., `$BooleanArray`), which are subtypes of `$c.java.lang.Object`.
+3. All the other types, in no particular order, among which:
+   * Function types that do not appear in vtables and itables, including the method implementation types and auto-generated function types for block types
+   * Closure data struct types
+
+For global definitions, we use the following ordering:
+
+1. The typeData of the primitive types (e.g., `$d.I`)
+2. For each linked class, in the same ancestor count-based order:
+   1. In no particular order, if applicable:
+      * Its typeData/vtable global (e.g., `$d.java.lang.Object`), which may refer to the typeData of ancestors, so the order between classes is important
+      * Its itables global (e.g., `$it.java.lang.Class`)
+      * Static field definitions
+      * Definitions of `Symbol`s for the "names" of private JS fields
+      * The module instance
+      * The cached JS class value
+3. Cached values of boxed zero values (such as `$bZeroChar`), which refer to the vtable and itables globals of the box classes
+4. The itables global of array classes (namely, `$arrayClassITable`)
+
+## Miscellaneous
+
+### Object instantiation
+
+An IR `New(C, ctor, args)` embeds two steps:
+
+1. Allocate a new instance of `C` with all fields initialized to their zero
+2. Call the given `ctor` on the new instance
+
+The second step follows the compilation scheme of a statically resolved method call, which we saw above.
+The allocation itself is performed by a `$new.C` function, which we generate for every concrete class.
+It looks like the following:
+
+```wat
+(func $new.C
+  (result (ref $c.C))
+
+  global.get $d.C  ;; the global vtable for class C
+  global.get $it.C ;; the global itables for class C
+  i32.const 0      ;; zero of type int
+  f64.const 0.0    ;; zero of type double
+  struct.new $c.C  ;; allocate a $c.C initialized with all of the above
+)
+```
+
+It would be nice to do the following instead:
+
+1. Allocate a `$c.C` entirely initialized with zeros, using `struct.new_default`
+2. Set the `$vtable` and `$itables` fields
+
+This would have a constant code size cost, irrespective of the amount of fields in `C`.
+Unfortunately, we cannot do this because the `$vtable` field is immutable.
+
+We cannot make it mutable since we rely on covariance (which only applies for immutable fields) for class subtyping.
+Abandoning this would have much worse consequences.
+
+Wasm may evolve to have [a more flexible `struct.new_default`](https://github.com/WebAssembly/gc/blob/main/proposals/gc/Post-MVP.md#handle-nondefaultable-fields-in-structnew_default), which would solve this trade-off.
+
+### Clone
+
+The IR node `Clone` takes an arbitrary instance of `jl.Cloneable` and returns a shallow copy of it.
+Wasm does not have any generic way to clone a reference to a `struct`.
+We must statically know what type of `struct` we want to clone instead.
+
+To solve this issue, we add a "magic" `$clone` function pointer in every vtable.
+It is only populated for classes that actually extend `jl.Cloneable`.
+We then compile a `Clone` node similarly to any virtual method call.
+
+Each concrete implementation `$clone.C` statically knows its corresponding `$c.C` struct type.
+It can therefore allocate a new instance and copy all the fields.
+
+### Identity hash code
+
+We implement `IdentityHashCode` in the same way as the JS backend:
+
+* We allocate one global `WeakMap` to store the identity hash codes (`idHashCodeMap`)
+* We allocate identity hash codes themselves by incrementing a global counter (`lastIDHashCode`)
+* For primitives, which we cannot put in a `WeakMap`, we use their normal `hashCode()` method
+
+This is implemented in the function `identityHashCode` in `CoreWasmLib`.
+
+### Strings
+
+As mentioned above, strings are represented as JS `string`s.
+All the primitive operations on strings, including string concatenation (which embeds conversion to string) are performed by helper JS functions.
+
+String constants are gathered from the entire program and their raw bytes stored in a data segment.
+We deduplicate strings so that we do not store the same string several times, but otherwise do not attempt further compression (such as reusing prefixes).
+Since creating string values from the data segment is expensive, we cache the constructed strings in a global array.
+
+At call site, we emit the following instruction sequence:
+
+```wat
+i32.const 84  ;; start of the string content in the data segment, in bytes
+i32.const 10  ;; string length, in chars
+i32.const 9   ;; index into the cache array for that string
+call $stringLiteral
+```
+
+In the future, we may want to use one of the following two Wasm proposals to improve efficiency of strings:
+
+* [JS String Builtins](https://github.com/WebAssembly/js-string-builtins)
+* [Reference-Typed Strings, aka `stringref`](https://github.com/WebAssembly/stringref)
+
+Even before that, an alternative for string literals would be to create them upfront from the JS loader and pass them to Wasm as `import`s.
+
+## JavaScript interoperability
+
+The most difficult aspects of JavaScript interoperability are related to hijacked classes, which we already mentioned.
+Other than that, we have:
+
+* a number of IR nodes with JS operation semantics (starting with `JS...`),
+* closures, and
+* non-native JS classes.
+
+### JS operation IR nodes
+
+We use a series of helper JS functions that directly embed the operation semantics.
+For example, `JSMethodApply` is implemented as a call to the following helper:
+
+```js
+__scalaJSHelpers: {
+  jsMethodApply: (o, m, args) => o[m](...args),
+}
+```
+
+The `args` are passed a JS array, which is built one element at a time, using the following helpers:
+
+```js
+__scalaJSHelpers: {
+  jsNewArray: () => [],
+  jsArrayPush: (a, v) => (a.push(v), a),
+  jsArraySpreadPush: (a, vs) => (a.push(...vs), a),
+}
+```
+
+This is of course far from being ideal.
+In the future, we will likely want to generate a JS helper for each call site, so that it can be specialized for the method name and shape of argument list.
+
+### Closures
+
+Wasm can create a function reference to any Wasm function with `ref.func`.
+Such a function reference can be passed to JavaScript and will be seen as a JS function.
+However, it is not possible to create *closures*; all the arguments to the Wasm function must always be provided.
+
+In order to create closures, we reify captures as a `__captureData` argument to the Wasm function.
+It is a reference to a `struct` with values for all the capture params of the IR `Closure` node.
+We allocate that struct when creating the `Closure`, then pass it to a JS helper, along with the function reference.
+The JS helper then creates an actual closure from the JS side and returns it to Wasm.
+
+To accomodate the combination of `function`/`=>` and `...rest`/no-rest, we use the following four helpers:
+
+```js
+__scalaJSHelpers: {
+  closure: (f, data) => f.bind(void 0, data),
+  closureThis: (f, data) => function(...args) { return f(data, this, ...args); },
+  closureRest: (f, data, n) => ((...args) => f(data, ...args.slice(0, n), args.slice(n))),
+  closureThisRest: (f, data, n) => function(...args) { return f(data, this, ...args.slice(0, n), args.slice(n)); },
+}
+```
+
+The `n` parameter is the number of non-rest parameters to the function.
+
+They are imported into Wasm with the following signatures:
+
+```wat
+(import "__scalaJSHelpers" "closure"
+  (func $closure (param (ref func)) (param anyref) (result (ref any))))
+(import "__scalaJSHelpers" "closureThis"
+  (func $closureThis (param (ref func)) (param anyref) (result (ref any))))
+(import "__scalaJSHelpers" "closureRest"
+  (func $closureRest (param (ref func)) (param anyref) (param i32) (result (ref any))))
+(import "__scalaJSHelpers" "closureThisRest"
+  (func $closureThisRest (param (ref func)) (param anyref) (param i32) (result (ref any))))
+```
+
+### Non-native JS classes
+
+For non-native JS classes, we take the above approach to another level.
+We use a unique JS helper function to create arbitrary JavaScript classes.
+It reads as follows:
+
+```js
+__scalaJSHelpers: {
+  createJSClass: (data, superClass, preSuperStats, superArgs, postSuperStats, fields) => {
+    // fields is an array where even indices are field names and odd indices are initial values
+    return class extends superClass {
+      constructor(...args) {
+        var preSuperEnv = preSuperStats(data, new.target, ...args);
+        super(...superArgs(data, preSuperEnv, new.target, ...args));
+        for (var i = 0; i != fields.length; i = (i + 2) | 0) {
+          Object.defineProperty(this, fields[i], {
+            value: fields[(i + 1) | 0],
+            configurable: true,
+            enumerable: true,
+            writable: true,
+          });
+        }
+        postSuperStats(data, preSuperEnv, new.target, this, ...args);
+      }
+    };
+  },
+}
+```
+
+Since the `super()` call must lexically appear in the `constructor` of the class, we have to decompose the body of the constructor into 3 functions:
+
+* `preSuperStats` contains the statements before the super call, and returns an environment of the locally declared variables as a `struct` (much like capture data),
+* `superArgs` computes an array of the arguments to the super call, and
+* `postSuperStats` contains the statements after the super call.
+
+The latter two take the `preSuperEnv` environment computed by `preSuperStats` as parameter.
+All functions also receive the class captures `data` and the value of `new.target`.
+
+The helper also takes the `superClass` as argument, as well as an array describing what `fields` should be created.
+The `fields` array contains an even number of elements:
+
+* even indices are field names,
+* odd indices are the initial value of the corresponding field.
+
+The method `ClassEmitter.genCreateJSClassFunction` is responsible for generating the code that calls `createJSClass`.
+After that call, it uses more straightforward helpers to install the instance methods/properties and static methods/properties.
+Those are created as `function` closures, which mimics the run-time spec behavior of the `class` construct.
+
+In the future, we may also want to generate a specialized version of `createJSClass` for each declared non-native JS class.
+It could specialize the shape of constructor parameters, the shape of the arguments to the super constructor, and the fields.
+
+## Exceptions
+
+In Wasm, exceptions consist of a *tag* and a *payload*.
+The tag defines the signature of the payload, and must be declared upfront (either imported or defined within Wasm).
+Typically, each language defines a unique tag with a payload that matches its native exception type.
+For example, a Java-to-Wasm compiler would define a tag `$javaException` with type `[(ref jl.Throwable)]`, indicating that its payload is a unique reference to a non-null instance of `java.lang.Throwable`.
+
+In order to throw an exception, the Wasm `throw` instruction takes a tag and arguments that match its payload type.
+Exceptions can be caught in two ways:
+
+* A specific `catch` with a given tag: it only catches exceptions thrown with that tag, and extracts the payload value.
+* A catch-all: it catches all exceptions, but the payloads cannot be observed.
+
+Each of those cases comes with a variant that captures an `exnref`, which can be used to re-throw the exception with `throw_ref`.
+
+For Scala.js, our exception model says that we can throw and catch arbitrary values, i.e., `anyref`.
+Moreover, our exceptions can be caught by JavaScript, and JavaScript exceptions can be caught from Scala.js.
+
+JavaScript exceptions are reified in Wasm as exceptions with a special tag, namely `WebAssembly.JSTag`, defined in the JS API.
+Wasm itself does not know that tag, but it can be `import`ed.
+Its payload signature is a single `externref`, which is isomorphic to `anyref` (there is a pair of Wasm instructions to losslessly convert between them).
+
+Instead of defining our own exception tag, we exclusively use `JSTag`, both for throwing and catching.
+That makes our exceptions directly interoperable with JavaScript at no extra cost.
+The import reads as
+
+```wat
+(import "__scalaJSHelpers" "JSTag" (tag $exception (param externref)))
+```
+
+Given the above, `Throw` and `TryCatch` have a straightforward implementation.
+
+For `TryFinally`, we have to compile it down to a try-catch-all, because Wasm does not have any notion of `try..finally`.
+That compilation scheme is very complicated.
+It deserves an entire dedicated explanation, which is covered by the big comment in `FunctionEmitter` starting with `HERE BE DRAGONS`.
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/SWasmGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/SWasmGen.scala
new file mode 100644
index 0000000000..a1ef630952
--- /dev/null
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/SWasmGen.scala
@@ -0,0 +1,137 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package org.scalajs.linker.backend.wasmemitter
+
+import org.scalajs.ir.Names._
+import org.scalajs.ir.Trees.JSNativeLoadSpec
+import org.scalajs.ir.Types._
+
+import org.scalajs.linker.backend.webassembly._
+import org.scalajs.linker.backend.webassembly.Instructions._
+
+import VarGen._
+
+/** Scala.js-specific Wasm generators that are used across the board. */
+object SWasmGen {
+
+  def genZeroOf(tpe: Type)(implicit ctx: WasmContext): Instr = {
+    tpe match {
+      case BooleanType | CharType | ByteType | ShortType | IntType =>
+        I32Const(0)
+
+      case LongType   => I64Const(0L)
+      case FloatType  => F32Const(0.0f)
+      case DoubleType => F64Const(0.0)
+      case StringType => GlobalGet(genGlobalID.emptyString)
+      case UndefType  => GlobalGet(genGlobalID.undef)
+
+      case AnyType | ClassType(_) | ArrayType(_) | NullType =>
+        RefNull(Types.HeapType.None)
+
+      case NoType | NothingType | _: RecordType =>
+        throw new AssertionError(s"Unexpected type for field: ${tpe.show()}")
+    }
+  }
+
+  def genBoxedZeroOf(tpe: Type)(implicit ctx: WasmContext): Instr = {
+    tpe match {
+      case BooleanType =>
+        GlobalGet(genGlobalID.bFalse)
+      case CharType =>
+        GlobalGet(genGlobalID.bZeroChar)
+      case ByteType | ShortType | IntType | FloatType | DoubleType =>
+        GlobalGet(genGlobalID.bZero)
+      case LongType =>
+        GlobalGet(genGlobalID.bZeroLong)
+      case AnyType | ClassType(_) | ArrayType(_) | StringType | UndefType | NullType =>
+        RefNull(Types.HeapType.None)
+
+      case NoType | NothingType | _: RecordType =>
+        throw new AssertionError(s"Unexpected type for field: ${tpe.show()}")
+    }
+  }
+
+  def genLoadTypeData(fb: FunctionBuilder, typeRef: TypeRef): Unit = typeRef match {
+    case typeRef: NonArrayTypeRef => genLoadNonArrayTypeData(fb, typeRef)
+    case typeRef: ArrayTypeRef    => genLoadArrayTypeData(fb, typeRef)
+  }
+
+  def genLoadNonArrayTypeData(fb: FunctionBuilder, typeRef: NonArrayTypeRef): Unit = {
+    fb += GlobalGet(genGlobalID.forVTable(typeRef))
+  }
+
+  def genLoadArrayTypeData(fb: FunctionBuilder, arrayTypeRef: ArrayTypeRef): Unit = {
+    genLoadNonArrayTypeData(fb, arrayTypeRef.base)
+    fb += I32Const(arrayTypeRef.dimensions)
+    fb += Call(genFunctionID.arrayTypeData)
+  }
+
+  /** Gen code to load the vtable and the itable of the given array type. */
+  def genLoadVTableAndITableForArray(fb: FunctionBuilder, arrayTypeRef: ArrayTypeRef): Unit = {
+    // Load the typeData of the resulting array type. It is the vtable of the resulting object.
+    genLoadArrayTypeData(fb, arrayTypeRef)
+
+    // Load the itables for the array type
+    fb += GlobalGet(genGlobalID.arrayClassITable)
+  }
+
+  def genArrayValue(fb: FunctionBuilder, arrayTypeRef: ArrayTypeRef, length: Int)(
+      genElems: => Unit): Unit = {
+    genLoadVTableAndITableForArray(fb, arrayTypeRef)
+
+    // Create the underlying array
+    genElems
+    val underlyingArrayType = genTypeID.underlyingOf(arrayTypeRef)
+    fb += ArrayNewFixed(underlyingArrayType, length)
+
+    // Create the array object
+    fb += StructNew(genTypeID.forArrayClass(arrayTypeRef))
+  }
+
+  def genLoadJSConstructor(fb: FunctionBuilder, className: ClassName)(
+      implicit ctx: WasmContext): Unit = {
+    val info = ctx.getClassInfo(className)
+
+    info.jsNativeLoadSpec match {
+      case None =>
+        // This is a non-native JS class
+        fb += Call(genFunctionID.loadJSClass(className))
+
+      case Some(loadSpec) =>
+        genLoadJSFromSpec(fb, loadSpec)
+    }
+  }
+
+  def genLoadJSFromSpec(fb: FunctionBuilder, loadSpec: JSNativeLoadSpec)(
+      implicit ctx: WasmContext): Unit = {
+    def genFollowPath(path: List[String]): Unit = {
+      for (prop <- path) {
+        fb ++= ctx.stringPool.getConstantStringInstr(prop)
+        fb += Call(genFunctionID.jsSelect)
+      }
+    }
+
+    loadSpec match {
+      case JSNativeLoadSpec.Global(globalRef, path) =>
+        fb ++= ctx.stringPool.getConstantStringInstr(globalRef)
+        fb += Call(genFunctionID.jsGlobalRefGet)
+        genFollowPath(path)
+      case JSNativeLoadSpec.Import(module, path) =>
+        fb += GlobalGet(genGlobalID.forImportedModule(module))
+        genFollowPath(path)
+      case JSNativeLoadSpec.ImportWithGlobalFallback(importSpec, _) =>
+        genLoadJSFromSpec(fb, importSpec)
+    }
+  }
+
+}
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/SpecialNames.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/SpecialNames.scala
new file mode 100644
index 0000000000..9a060bc3b4
--- /dev/null
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/SpecialNames.scala
@@ -0,0 +1,48 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package org.scalajs.linker.backend.wasmemitter
+
+import org.scalajs.ir.Names._
+import org.scalajs.ir.Types._
+
+object SpecialNames {
+  // Class names
+
+  /* Our back-end-specific box classes for the generic representation of
+   * `char` and `long`. These classes are not part of the classpath. They are
+   * generated automatically by `DerivedClasses`.
+   */
+  val CharBoxClass = BoxedCharacterClass.withSuffix("Box")
+  val LongBoxClass = BoxedLongClass.withSuffix("Box")
+
+  val CharBoxCtor = MethodName.constructor(List(CharRef))
+  val LongBoxCtor = MethodName.constructor(List(LongRef))
+
+  // js.JavaScriptException, for WrapAsThrowable and UnwrapFromThrowable
+  val JSExceptionClass = ClassName("scala.scalajs.js.JavaScriptException")
+
+  // Field names
+
+  val valueFieldSimpleName = SimpleFieldName("value")
+
+  val exceptionFieldName = FieldName(JSExceptionClass, SimpleFieldName("exception"))
+
+  // Method names
+
+  val AnyArgConstructorName = MethodName.constructor(List(ClassRef(ObjectClass)))
+
+  val hashCodeMethodName = MethodName("hashCode", Nil, IntRef)
+
+  /** A unique simple method name to map all method *signatures* into `MethodName`s. */
+  val normalizedSimpleMethodName = SimpleMethodName("m")
+}
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/StringPool.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/StringPool.scala
new file mode 100644
index 0000000000..12450488cc
--- /dev/null
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/StringPool.scala
@@ -0,0 +1,107 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package org.scalajs.linker.backend.wasmemitter
+
+import scala.collection.mutable
+
+import org.scalajs.ir.OriginalName
+
+import org.scalajs.linker.backend.webassembly.Instructions._
+import org.scalajs.linker.backend.webassembly.Modules._
+import org.scalajs.linker.backend.webassembly.Types._
+
+import VarGen._
+
+private[wasmemitter] final class StringPool {
+  import StringPool._
+
+  private val registeredStrings = new mutable.AnyRefMap[String, StringData]
+  private val rawData = new mutable.ArrayBuffer[Byte]()
+  private var nextIndex: Int = 0
+
+  // Set to true by `genPool()`. When true, registering strings is illegal.
+  private var poolWasGenerated: Boolean = false
+
+  /** Registers the given constant string and returns its allocated data. */
+  private def register(str: String): StringData = {
+    if (poolWasGenerated)
+      throw new IllegalStateException("The string pool was already generated")
+
+    registeredStrings.getOrElseUpdate(str, {
+      // Compute the new entry before changing the state
+      val data = StringData(nextIndex, offset = rawData.size)
+
+      // Write the actual raw data and update the next index
+      rawData ++= str.toCharArray.flatMap { char =>
+        Array((char & 0xFF).toByte, (char >> 8).toByte)
+      }
+      nextIndex += 1
+
+      data
+    })
+  }
+
+  /** Returns the list of instructions that load the given constant string.
+   *
+   *  The resulting list is *not* a Wasm constant expression, since it includes
+   *  a `call` to the helper function `stringLiteral`.
+   */
+  def getConstantStringInstr(str: String): List[Instr] =
+    getConstantStringDataInstr(str) :+ Call(genFunctionID.stringLiteral)
+
+  /** Returns the list of 3 constant integers that must be passed to `stringLiteral`.
+   *
+   *  The resulting list is a Wasm constant expression, and hence can be used
+   *  in the initializer of globals.
+   */
+  def getConstantStringDataInstr(str: String): List[I32Const] = {
+    val data = register(str)
+    List(
+      I32Const(data.offset),
+      I32Const(str.length()),
+      I32Const(data.constantStringIndex)
+    )
+  }
+
+  def genPool()(implicit ctx: WasmContext): Unit = {
+    poolWasGenerated = true
+
+    ctx.moduleBuilder.addData(
+      Data(
+        genDataID.string,
+        OriginalName("stringPool"),
+        rawData.toArray,
+        Data.Mode.Passive
+      )
+    )
+
+    ctx.addGlobal(
+      Global(
+        genGlobalID.stringLiteralCache,
+        OriginalName("stringLiteralCache"),
+        isMutable = false,
+        RefType(genTypeID.anyArray),
+        Expr(
+          List(
+            I32Const(nextIndex), // number of entries in the pool
+            ArrayNewDefault(genTypeID.anyArray)
+          )
+        )
+      )
+    )
+  }
+}
+
+private[wasmemitter] object StringPool {
+  private final case class StringData(constantStringIndex: Int, offset: Int)
+}
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/TypeTransformer.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/TypeTransformer.scala
new file mode 100644
index 0000000000..55101a98b3
--- /dev/null
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/TypeTransformer.scala
@@ -0,0 +1,116 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package org.scalajs.linker.backend.wasmemitter
+
+import org.scalajs.ir.Names._
+import org.scalajs.ir.Types._
+
+import org.scalajs.linker.backend.webassembly.{Types => watpe}
+
+import VarGen._
+
+object TypeTransformer {
+
+  /** Transforms an IR type for a local definition (including parameters).
+   *
+   *  `void` is not a valid input for this method. It is rejected by the
+   *  `ClassDefChecker`.
+   *
+   *  `nothing` translates to `i32` in this specific case, because it is a valid
+   *  type for a `ParamDef` or `VarDef`. Obviously, assigning a value to a local
+   *  of type `nothing` (either locally or by calling the method for a param)
+   *  can never complete, and therefore reading the value of such a local is
+   *  always unreachable. It is up to the reading codegen to handle this case.
+   */
+  def transformLocalType(tpe: Type)(implicit ctx: WasmContext): watpe.Type = {
+    tpe match {
+      case NothingType => watpe.Int32
+      case _           => transformType(tpe)
+    }
+  }
+
+  /** Transforms an IR type to the Wasm result types of a function or block.
+   *
+   *  `void` translates to an empty result type list, as expected.
+   *
+   *  `nothing` translates to an empty result type list as well, because Wasm does
+   *  not have a bottom type (at least not one that can expressed at the user level).
+   *  A block or function call that returns `nothing` should typically be followed
+   *  by an extra `unreachable` statement to recover a stack-polymorphic context.
+   *
+   *  @see
+   *    https://webassembly.github.io/spec/core/syntax/types.html#result-types
+   */
+  def transformResultType(tpe: Type)(implicit ctx: WasmContext): List[watpe.Type] = {
+    tpe match {
+      case NoType      => Nil
+      case NothingType => Nil
+      case _           => List(transformType(tpe))
+    }
+  }
+
+  /** Transforms a value type to a unique Wasm type.
+   *
+   *  This method cannot be used for `void` and `nothing`, since they have no corresponding Wasm
+   *  value type.
+   */
+  def transformType(tpe: Type)(implicit ctx: WasmContext): watpe.Type = {
+    tpe match {
+      case AnyType                => watpe.RefType.anyref
+      case ClassType(className)   => transformClassType(className)
+      case StringType | UndefType => watpe.RefType.any
+      case tpe: PrimTypeWithRef   => transformPrimType(tpe)
+
+      case tpe: ArrayType =>
+        watpe.RefType.nullable(genTypeID.forArrayClass(tpe.arrayTypeRef))
+
+      case RecordType(fields) =>
+        throw new AssertionError(s"Unexpected record type $tpe")
+    }
+  }
+
+  def transformClassType(className: ClassName)(implicit ctx: WasmContext): watpe.RefType = {
+    ctx.getClassInfoOption(className) match {
+      case Some(info) =>
+        if (info.isAncestorOfHijackedClass)
+          watpe.RefType.anyref
+        else if (!info.hasInstances)
+          watpe.RefType.nullref
+        else if (info.isInterface)
+          watpe.RefType.nullable(genTypeID.ObjectStruct)
+        else
+          watpe.RefType.nullable(genTypeID.forClass(className))
+
+      case None =>
+        watpe.RefType.nullref
+    }
+  }
+
+  private def transformPrimType(tpe: PrimTypeWithRef): watpe.Type = {
+    tpe match {
+      case BooleanType => watpe.Int32
+      case ByteType    => watpe.Int32
+      case ShortType   => watpe.Int32
+      case IntType     => watpe.Int32
+      case CharType    => watpe.Int32
+      case LongType    => watpe.Int64
+      case FloatType   => watpe.Float32
+      case DoubleType  => watpe.Float64
+      case NullType    => watpe.RefType.nullref
+
+      case NoType | NothingType =>
+        throw new IllegalArgumentException(
+            s"${tpe.show()} does not have a corresponding Wasm type")
+    }
+  }
+}
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
new file mode 100644
index 0000000000..7d26398a25
--- /dev/null
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
@@ -0,0 +1,446 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package org.scalajs.linker.backend.wasmemitter
+
+import org.scalajs.ir.Names._
+import org.scalajs.ir.Trees.{JSUnaryOp, JSBinaryOp, MemberNamespace}
+import org.scalajs.ir.Types._
+
+import org.scalajs.linker.backend.webassembly.Identitities._
+
+/** Manages generation of non-local IDs.
+ *
+ *  `LocalID`s and `LabelID`s are directly managed by `FunctionBuilder` instead.
+ */
+object VarGen {
+
+  object genGlobalID {
+    final case class forImportedModule(moduleName: String) extends GlobalID
+    final case class forModuleInstance(className: ClassName) extends GlobalID
+    final case class forJSClassValue(className: ClassName) extends GlobalID
+
+    final case class forVTable(typeRef: NonArrayTypeRef) extends GlobalID
+
+    object forVTable {
+      def apply(className: ClassName): forVTable =
+        forVTable(ClassRef(className))
+    }
+
+    final case class forITable(className: ClassName) extends GlobalID
+    final case class forStaticField(fieldName: FieldName) extends GlobalID
+    final case class forJSPrivateField(fieldName: FieldName) extends GlobalID
+
+    case object bZeroChar extends GlobalID
+    case object bZeroLong extends GlobalID
+    case object stringLiteralCache extends GlobalID
+    case object arrayClassITable extends GlobalID
+    case object lastIDHashCode extends GlobalID
+
+    /** A `GlobalID` for a JS helper global.
+     *
+     *  Its `toString()` is guaranteed to correspond to the import name of the helper.
+     */
+    sealed abstract class JSHelperGlobalID extends GlobalID
+
+    case object jsLinkingInfo extends JSHelperGlobalID
+    case object undef extends JSHelperGlobalID
+    case object bFalse extends JSHelperGlobalID
+    case object bZero extends JSHelperGlobalID
+    case object emptyString extends JSHelperGlobalID
+    case object idHashCodeMap extends JSHelperGlobalID
+  }
+
+  object genFunctionID {
+    final case class forMethod(namespace: MemberNamespace,
+        className: ClassName, methodName: MethodName)
+        extends FunctionID
+
+    final case class forTableEntry(className: ClassName, methodName: MethodName)
+        extends FunctionID
+
+    final case class forExport(exportedName: String) extends FunctionID
+    final case class forTopLevelExportSetter(exportedName: String) extends FunctionID
+
+    final case class loadModule(className: ClassName) extends FunctionID
+    final case class newDefault(className: ClassName) extends FunctionID
+    final case class instanceTest(className: ClassName) extends FunctionID
+    final case class clone(className: ClassName) extends FunctionID
+    final case class cloneArray(arrayBaseRef: NonArrayTypeRef) extends FunctionID
+
+    final case class isJSClassInstance(className: ClassName) extends FunctionID
+    final case class loadJSClass(className: ClassName) extends FunctionID
+    final case class createJSClassOf(className: ClassName) extends FunctionID
+    final case class preSuperStats(className: ClassName) extends FunctionID
+    final case class superArgs(className: ClassName) extends FunctionID
+    final case class postSuperStats(className: ClassName) extends FunctionID
+
+    case object start extends FunctionID
+
+    // JS helpers
+
+    /** A `FunctionID` for a JS helper function.
+     *
+     *  Its `toString()` is guaranteed to correspond to the import name of the helper.
+     */
+    sealed abstract class JSHelperFunctionID extends FunctionID
+
+    case object is extends JSHelperFunctionID
+
+    case object isUndef extends JSHelperFunctionID
+
+    final case class box(primRef: PrimRef) extends JSHelperFunctionID {
+      override def toString(): String = "b" + primRef.charCode
+    }
+
+    final case class unbox(primRef: PrimRef) extends JSHelperFunctionID {
+      override def toString(): String = "u" + primRef.charCode
+    }
+
+    final case class typeTest(primRef: PrimRef) extends JSHelperFunctionID {
+      override def toString(): String = "t" + primRef.charCode
+    }
+
+    case object fmod extends JSHelperFunctionID
+
+    case object closure extends JSHelperFunctionID
+    case object closureThis extends JSHelperFunctionID
+    case object closureRest extends JSHelperFunctionID
+    case object closureThisRest extends JSHelperFunctionID
+
+    case object makeExportedDef extends JSHelperFunctionID
+    case object makeExportedDefRest extends JSHelperFunctionID
+
+    case object stringLength extends JSHelperFunctionID
+    case object stringCharAt extends JSHelperFunctionID
+    case object jsValueToString extends JSHelperFunctionID // for actual toString() call
+    case object jsValueToStringForConcat extends JSHelperFunctionID
+    case object booleanToString extends JSHelperFunctionID
+    case object charToString extends JSHelperFunctionID
+    case object intToString extends JSHelperFunctionID
+    case object longToString extends JSHelperFunctionID
+    case object doubleToString extends JSHelperFunctionID
+    case object stringConcat extends JSHelperFunctionID
+    case object isString extends JSHelperFunctionID
+
+    case object jsValueType extends JSHelperFunctionID
+    case object bigintHashCode extends JSHelperFunctionID
+    case object symbolDescription extends JSHelperFunctionID
+    case object idHashCodeGet extends JSHelperFunctionID
+    case object idHashCodeSet extends JSHelperFunctionID
+
+    case object jsGlobalRefGet extends JSHelperFunctionID
+    case object jsGlobalRefSet extends JSHelperFunctionID
+    case object jsGlobalRefTypeof extends JSHelperFunctionID
+    case object jsNewArray extends JSHelperFunctionID
+    case object jsArrayPush extends JSHelperFunctionID
+    case object jsArraySpreadPush extends JSHelperFunctionID
+    case object jsNewObject extends JSHelperFunctionID
+    case object jsObjectPush extends JSHelperFunctionID
+    case object jsSelect extends JSHelperFunctionID
+    case object jsSelectSet extends JSHelperFunctionID
+    case object jsNew extends JSHelperFunctionID
+    case object jsFunctionApply extends JSHelperFunctionID
+    case object jsMethodApply extends JSHelperFunctionID
+    case object jsImportCall extends JSHelperFunctionID
+    case object jsImportMeta extends JSHelperFunctionID
+    case object jsDelete extends JSHelperFunctionID
+    case object jsForInSimple extends JSHelperFunctionID
+    case object jsIsTruthy extends JSHelperFunctionID
+
+    final case class jsUnaryOp(name: String) extends JSHelperFunctionID {
+      override def toString(): String = name
+    }
+
+    val jsUnaryOps: Map[JSUnaryOp.Code, jsUnaryOp] = {
+      Map(
+        JSUnaryOp.+ -> jsUnaryOp("jsUnaryPlus"),
+        JSUnaryOp.- -> jsUnaryOp("jsUnaryMinus"),
+        JSUnaryOp.~ -> jsUnaryOp("jsUnaryTilde"),
+        JSUnaryOp.! -> jsUnaryOp("jsUnaryBang"),
+        JSUnaryOp.typeof -> jsUnaryOp("jsUnaryTypeof")
+      )
+    }
+
+    final case class jsBinaryOp(name: String) extends JSHelperFunctionID {
+      override def toString(): String = name
+    }
+
+    val jsBinaryOps: Map[JSBinaryOp.Code, jsBinaryOp] = {
+      Map(
+        JSBinaryOp.=== -> jsBinaryOp("jsStrictEquals"),
+        JSBinaryOp.!== -> jsBinaryOp("jsNotStrictEquals"),
+        JSBinaryOp.+ -> jsBinaryOp("jsPlus"),
+        JSBinaryOp.- -> jsBinaryOp("jsMinus"),
+        JSBinaryOp.* -> jsBinaryOp("jsTimes"),
+        JSBinaryOp./ -> jsBinaryOp("jsDivide"),
+        JSBinaryOp.% -> jsBinaryOp("jsModulus"),
+        JSBinaryOp.| -> jsBinaryOp("jsBinaryOr"),
+        JSBinaryOp.& -> jsBinaryOp("jsBinaryAnd"),
+        JSBinaryOp.^ -> jsBinaryOp("jsBinaryXor"),
+        JSBinaryOp.<< -> jsBinaryOp("jsShiftLeft"),
+        JSBinaryOp.>> -> jsBinaryOp("jsArithmeticShiftRight"),
+        JSBinaryOp.>>> -> jsBinaryOp("jsLogicalShiftRight"),
+        JSBinaryOp.< -> jsBinaryOp("jsLessThan"),
+        JSBinaryOp.<= -> jsBinaryOp("jsLessEqual"),
+        JSBinaryOp.> -> jsBinaryOp("jsGreaterThan"),
+        JSBinaryOp.>= -> jsBinaryOp("jsGreaterEqual"),
+        JSBinaryOp.in -> jsBinaryOp("jsIn"),
+        JSBinaryOp.instanceof -> jsBinaryOp("jsInstanceof"),
+        JSBinaryOp.** -> jsBinaryOp("jsExponent")
+      )
+    }
+
+    case object newSymbol extends JSHelperFunctionID
+    case object createJSClass extends JSHelperFunctionID
+    case object createJSClassRest extends JSHelperFunctionID
+    case object installJSField extends JSHelperFunctionID
+    case object installJSMethod extends JSHelperFunctionID
+    case object installJSStaticMethod extends JSHelperFunctionID
+    case object installJSProperty extends JSHelperFunctionID
+    case object installJSStaticProperty extends JSHelperFunctionID
+    case object jsSuperSelect extends JSHelperFunctionID
+    case object jsSuperSelectSet extends JSHelperFunctionID
+    case object jsSuperCall extends JSHelperFunctionID
+
+    // Wasm internal helpers
+
+    case object createStringFromData extends FunctionID
+    case object stringLiteral extends FunctionID
+    case object typeDataName extends FunctionID
+    case object createClassOf extends FunctionID
+    case object getClassOf extends FunctionID
+    case object arrayTypeData extends FunctionID
+    case object isInstance extends FunctionID
+    case object isAssignableFromExternal extends FunctionID
+    case object isAssignableFrom extends FunctionID
+    case object checkCast extends FunctionID
+    case object getComponentType extends FunctionID
+    case object newArrayOfThisClass extends FunctionID
+    case object anyGetClass extends FunctionID
+    case object newArrayObject extends FunctionID
+    case object identityHashCode extends FunctionID
+    case object searchReflectiveProxy extends FunctionID
+  }
+
+  object genFieldID {
+    final case class forClassInstanceField(name: FieldName) extends FieldID
+    final case class forMethodTableEntry(methodName: MethodName) extends FieldID
+    final case class captureParam(i: Int) extends FieldID
+
+    object objStruct {
+      case object vtable extends FieldID
+      case object itables extends FieldID
+      case object arrayUnderlying extends FieldID
+    }
+
+    object reflectiveProxy {
+      case object methodID extends FieldID
+      case object funcRef extends FieldID
+    }
+
+    /** Fields of the typeData structs. */
+    object typeData {
+
+      /** The name data as the 3 arguments to `stringLiteral`.
+       *
+       *  It is only meaningful for primitives and for classes. For array types, they are all 0, as
+       *  array types compute their `name` from the `name` of their component type.
+       */
+      case object nameOffset extends FieldID
+
+      /** See `nameOffset`. */
+      case object nameSize extends FieldID
+
+      /** See `nameOffset`. */
+      case object nameStringIndex extends FieldID
+
+      /** The kind of type data, an `i32`.
+       *
+       *  Possible values are the the `KindX` constants in `EmbeddedConstants`.
+       */
+      case object kind extends FieldID
+
+      /** A bitset of special (primitive) instance types that are instances of this type, an `i32`.
+       *
+       *  From 0 to 5, the bits correspond to the values returned by the helper `jsValueType`. In
+       *  addition, bits 6 and 7 represent `char` and `long`, respectively.
+       */
+      case object specialInstanceTypes extends FieldID
+
+      /** Array of the strict ancestor classes of this class.
+       *
+       *  This is `null` for primitive and array types. For all other types, including JS types, it
+       *  contains an array of the typeData of their ancestors that:
+       *
+       *  - are not themselves (hence the *strict* ancestors),
+       *  - have typeData to begin with.
+       */
+      case object strictAncestors extends FieldID
+
+      /** The typeData of a component of this array type, or `null` if this is not an array type.
+       *
+       *  For example:
+       *
+       *  - the `componentType` for class `Foo` is `null`,
+       *  - the `componentType` for the array type `Array[Foo]` is the `typeData` of `Foo`.
+       */
+      case object componentType extends FieldID
+
+      /** The name as nullable string (`anyref`), lazily initialized from the nameData.
+       *
+       *  This field is initialized by the `typeDataName` helper.
+       *
+       *  The contents of this value is specified by `java.lang.Class.getName()`. In particular, for
+       *  array types, it obeys the following rules:
+       *
+       *  - `Array[prim]` where `prim` is a one of the primitive types with `charCode` `X` is
+       *    `"[X"`, for example, `"[I"` for `Array[Int]`.
+       *  - `Array[pack.Cls]` where `Cls` is a class is `"[Lpack.Cls;"`.
+       *  - `Array[nestedArray]` where `nestedArray` is an array type with name `nested` is
+       *    `"[nested"`, for example `"⟦I"` for `Array[Array[Int]]` and `"⟦Ljava.lang.String;"`
+       *    for `Array[Array[String]]`.¹
+       *
+       *  ¹ We use the Unicode character `⟦` to represent two consecutive `[` characters in order
+       *  not to confuse Scaladoc.
+       */
+      case object name extends FieldID
+
+      /** The `classOf` value, a nullable `java.lang.Class`, lazily initialized from this typeData.
+       *
+       *  This field is initialized by the `createClassOf` helper.
+       */
+      case object classOfValue extends FieldID
+
+      /** The typeData/vtable of an array of this type, a nullable `typeData`, lazily initialized.
+       *
+       *  This field is initialized by the `arrayTypeData` helper.
+       *
+       *  For example, once initialized,
+       *
+       *  - in the `typeData` of class `Foo`, it contains the `typeData` of `Array[Foo]`,
+       *  - in the `typeData` of `Array[Int]`, it contains the `typeData` of `Array[Array[Int]]`.
+       */
+      case object arrayOf extends FieldID
+
+      /** The function to clone the object of this type, a nullable function reference.
+       *
+       *  This field is initialized only with the classes that implement java.lang.Cloneable.
+       */
+      case object cloneFunction extends FieldID
+
+      /** `isInstance` func ref for top-level JS classes. */
+      case object isJSClassInstance extends FieldID
+
+      /** The reflective proxies in this type, used for reflective call on the class at runtime.
+       *
+       *  This field contains an array of reflective proxy structs, where each struct contains the
+       *  ID of the reflective proxy and a reference to the actual method implementation. Reflective
+       *  call site should walk through the array to look up a method to call.
+       *
+       *  See `genSearchReflectivePRoxy` in `HelperFunctions`
+       */
+      case object reflectiveProxies extends FieldID
+    }
+  }
+
+  object genTypeID {
+    final case class forClass(className: ClassName) extends TypeID
+    final case class captureData(index: Int) extends TypeID
+    final case class forVTable(className: ClassName) extends TypeID
+    final case class forITable(className: ClassName) extends TypeID
+    final case class forFunction(index: Int) extends TypeID
+    final case class forTableFunctionType(methodName: MethodName) extends TypeID
+
+    val ObjectStruct = forClass(ObjectClass)
+    val ClassStruct = forClass(ClassClass)
+    val ThrowableStruct = forClass(ThrowableClass)
+    val JSExceptionStruct = forClass(SpecialNames.JSExceptionClass)
+
+    val ObjectVTable: TypeID = forVTable(ObjectClass)
+
+    case object typeData extends TypeID
+    case object reflectiveProxy extends TypeID
+
+    // Array types -- they extend j.l.Object
+    case object BooleanArray extends TypeID
+    case object CharArray extends TypeID
+    case object ByteArray extends TypeID
+    case object ShortArray extends TypeID
+    case object IntArray extends TypeID
+    case object LongArray extends TypeID
+    case object FloatArray extends TypeID
+    case object DoubleArray extends TypeID
+    case object ObjectArray extends TypeID
+
+    def forArrayClass(arrayTypeRef: ArrayTypeRef): TypeID = {
+      if (arrayTypeRef.dimensions > 1) {
+        ObjectArray
+      } else {
+        arrayTypeRef.base match {
+          case BooleanRef => BooleanArray
+          case CharRef    => CharArray
+          case ByteRef    => ByteArray
+          case ShortRef   => ShortArray
+          case IntRef     => IntArray
+          case LongRef    => LongArray
+          case FloatRef   => FloatArray
+          case DoubleRef  => DoubleArray
+          case _          => ObjectArray
+        }
+      }
+    }
+
+    case object typeDataArray extends TypeID
+    case object itables extends TypeID
+    case object reflectiveProxies extends TypeID
+
+    // primitive array types, underlying the Array[T] classes
+    case object i8Array extends TypeID
+    case object i16Array extends TypeID
+    case object i32Array extends TypeID
+    case object i64Array extends TypeID
+    case object f32Array extends TypeID
+    case object f64Array extends TypeID
+    case object anyArray extends TypeID
+
+    def underlyingOf(arrayTypeRef: ArrayTypeRef): TypeID = {
+      if (arrayTypeRef.dimensions > 1) {
+        anyArray
+      } else {
+        arrayTypeRef.base match {
+          case BooleanRef => i8Array
+          case CharRef    => i16Array
+          case ByteRef    => i8Array
+          case ShortRef   => i16Array
+          case IntRef     => i32Array
+          case LongRef    => i64Array
+          case FloatRef   => f32Array
+          case DoubleRef  => f64Array
+          case _          => anyArray
+        }
+      }
+    }
+
+    case object cloneFunctionType extends TypeID
+    case object isJSClassInstanceFuncType extends TypeID
+  }
+
+  object genTagID {
+    case object exception extends TagID
+  }
+
+  object genDataID {
+    case object string extends DataID
+  }
+
+}
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/WasmContext.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/WasmContext.scala
new file mode 100644
index 0000000000..c6c2aee99a
--- /dev/null
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/WasmContext.scala
@@ -0,0 +1,301 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package org.scalajs.linker.backend.wasmemitter
+
+import scala.annotation.tailrec
+
+import scala.collection.mutable
+import scala.collection.mutable.LinkedHashMap
+
+import org.scalajs.ir.ClassKind
+import org.scalajs.ir.Names._
+import org.scalajs.ir.OriginalName.NoOriginalName
+import org.scalajs.ir.Trees.{FieldDef, ParamDef, JSNativeLoadSpec}
+import org.scalajs.ir.Types._
+
+import org.scalajs.linker.interface.ModuleInitializer
+import org.scalajs.linker.interface.unstable.ModuleInitializerImpl
+import org.scalajs.linker.standard.LinkedTopLevelExport
+import org.scalajs.linker.standard.LinkedClass
+
+import org.scalajs.linker.backend.webassembly.ModuleBuilder
+import org.scalajs.linker.backend.webassembly.{Instructions => wa}
+import org.scalajs.linker.backend.webassembly.{Modules => wamod}
+import org.scalajs.linker.backend.webassembly.{Identitities => wanme}
+import org.scalajs.linker.backend.webassembly.{Types => watpe}
+
+import VarGen._
+import org.scalajs.ir.OriginalName
+
+final class WasmContext(
+    classInfo: Map[ClassName, WasmContext.ClassInfo],
+    reflectiveProxies: Map[MethodName, Int],
+    val itablesLength: Int
+) {
+  import WasmContext._
+
+  private val functionTypes = LinkedHashMap.empty[watpe.FunctionType, wanme.TypeID]
+  private val tableFunctionTypes = mutable.HashMap.empty[MethodName, wanme.TypeID]
+  private val closureDataTypes = LinkedHashMap.empty[List[Type], wanme.TypeID]
+
+  val moduleBuilder: ModuleBuilder = {
+    new ModuleBuilder(new ModuleBuilder.FunctionTypeProvider {
+      def functionTypeToTypeID(sig: watpe.FunctionType): wanme.TypeID = {
+        functionTypes.getOrElseUpdate(
+          sig, {
+            val typeID = genTypeID.forFunction(functionTypes.size)
+            moduleBuilder.addRecType(typeID, NoOriginalName, sig)
+            typeID
+          }
+        )
+      }
+    })
+  }
+
+  private var nextClosureDataTypeIndex: Int = 1
+
+  private val _funcDeclarations: mutable.LinkedHashSet[wanme.FunctionID] =
+    new mutable.LinkedHashSet()
+
+  val stringPool: StringPool = new StringPool
+
+  /** The main `rectype` containing the object model types. */
+  val mainRecType: ModuleBuilder.RecTypeBuilder = new ModuleBuilder.RecTypeBuilder
+
+  def getClassInfoOption(name: ClassName): Option[ClassInfo] =
+    classInfo.get(name)
+
+  def getClassInfo(name: ClassName): ClassInfo =
+    classInfo.getOrElse(name, throw new Error(s"Class not found: $name"))
+
+  def inferTypeFromTypeRef(typeRef: TypeRef): Type = typeRef match {
+    case PrimRef(tpe) =>
+      tpe
+    case ClassRef(className) =>
+      if (className == ObjectClass || getClassInfo(className).kind.isJSType)
+        AnyType
+      else
+        ClassType(className)
+    case typeRef: ArrayTypeRef =>
+      ArrayType(typeRef)
+  }
+
+  /** Retrieves a unique identifier for a reflective proxy with the given name.
+   *
+   *  If no class defines a reflective proxy with the given name, returns `-1`.
+   */
+  def getReflectiveProxyId(name: MethodName): Int =
+    reflectiveProxies.getOrElse(name, -1)
+
+  /** Adds or reuses a function type for a table function.
+   *
+   *  Table function types are part of the main `rectype`, and have names derived from the
+   *  `methodName`.
+   */
+  def tableFunctionType(methodName: MethodName): wanme.TypeID = {
+    // Project all the names with the same *signatures* onto a normalized `MethodName`
+    val normalizedName = MethodName(
+      SpecialNames.normalizedSimpleMethodName,
+      methodName.paramTypeRefs,
+      methodName.resultTypeRef,
+      methodName.isReflectiveProxy
+    )
+
+    tableFunctionTypes.getOrElseUpdate(
+      normalizedName, {
+        val typeID = genTypeID.forTableFunctionType(normalizedName)
+        val regularParamTyps = normalizedName.paramTypeRefs.map { typeRef =>
+          TypeTransformer.transformLocalType(inferTypeFromTypeRef(typeRef))(this)
+        }
+        val resultType = TypeTransformer.transformResultType(
+            inferTypeFromTypeRef(normalizedName.resultTypeRef))(this)
+        mainRecType.addSubType(
+          typeID,
+          NoOriginalName,
+          watpe.FunctionType(watpe.RefType.any :: regularParamTyps, resultType)
+        )
+        typeID
+      }
+    )
+  }
+
+  def getClosureDataStructType(captureParamTypes: List[Type]): wanme.TypeID = {
+    closureDataTypes.getOrElseUpdate(
+      captureParamTypes, {
+        val fields: List[watpe.StructField] = {
+          for ((tpe, i) <- captureParamTypes.zipWithIndex) yield {
+            watpe.StructField(
+              genFieldID.captureParam(i),
+              NoOriginalName,
+              TypeTransformer.transformLocalType(tpe)(this),
+              isMutable = false
+            )
+          }
+        }
+        val structTypeID = genTypeID.captureData(nextClosureDataTypeIndex)
+        nextClosureDataTypeIndex += 1
+        val structType = watpe.StructType(fields)
+        moduleBuilder.addRecType(structTypeID, NoOriginalName, structType)
+        structTypeID
+      }
+    )
+  }
+
+  def refFuncWithDeclaration(funcID: wanme.FunctionID): wa.RefFunc = {
+    _funcDeclarations += funcID
+    wa.RefFunc(funcID)
+  }
+
+  def addGlobal(g: wamod.Global): Unit =
+    moduleBuilder.addGlobal(g)
+
+  def getAllFuncDeclarations(): List[wanme.FunctionID] =
+    _funcDeclarations.toList
+}
+
+object WasmContext {
+  final class ClassInfo(
+      val name: ClassName,
+      val kind: ClassKind,
+      val jsClassCaptures: Option[List[ParamDef]],
+      val allFieldDefs: List[FieldDef],
+      superClass: Option[ClassInfo],
+      val classImplementsAnyInterface: Boolean,
+      val hasInstances: Boolean,
+      val isAbstract: Boolean,
+      val hasRuntimeTypeInfo: Boolean,
+      val jsNativeLoadSpec: Option[JSNativeLoadSpec],
+      val jsNativeMembers: Map[MethodName, JSNativeLoadSpec],
+      val staticFieldMirrors: Map[FieldName, List[String]],
+      _specialInstanceTypes: Int, // should be `val` but there is a large Scaladoc for it below
+      val resolvedMethodInfos: Map[MethodName, ConcreteMethodInfo],
+      _itableIdx: Int
+  ) {
+    override def toString(): String =
+      s"ClassInfo(${name.nameString})"
+
+    /** For a class or interface, its table entries in definition order. */
+    private var _tableEntries: List[MethodName] = null
+
+    /** Returns the index of this interface's itable in the classes' interface tables.
+     *
+     *  Only interfaces that have instances get an itable index.
+     */
+    def itableIdx: Int = {
+      if (_itableIdx < 0) {
+        val isInterface = kind == ClassKind.Interface
+        if (isInterface && hasInstances) {
+          // it should have received an itable idx
+          throw new IllegalStateException(
+              s"$this was not assigned an itable index although it needs one.")
+        } else {
+          throw new IllegalArgumentException(
+              s"Trying to ask the itable idx for $this, which is not supposed to have one " +
+              s"(isInterface = $isInterface; hasInstances = $hasInstances).")
+        }
+      }
+      _itableIdx
+    }
+
+    /** A bitset of the `jsValueType`s corresponding to hijacked classes that extend this class.
+     *
+     *  This value is used for instance tests against this class. A JS value `x` is an instance of
+     *  this type iff `jsValueType(x)` is a member of this bitset. Because of how a bitset works,
+     *  this means testing the following formula:
+     *
+     *  {{{
+     *  ((1 << jsValueType(x)) & specialInstanceTypes) != 0
+     *  }}}
+     *
+     *  For example, if this class is `Comparable`, we want the bitset to contain the values for
+     *  `boolean`, `string` and `number` (but not `undefined`), because `jl.Boolean`, `jl.String`
+     *  and `jl.Double` implement `Comparable`.
+     *
+     *  This field is initialized with 0, and augmented during preprocessing by calls to
+     *  `addSpecialInstanceType`.
+     *
+     *  This technique is used both for static `isInstanceOf` tests as well as reflective tests
+     *  through `Class.isInstance`. For the latter, this value is stored in
+     *  `typeData.specialInstanceTypes`. For the former, it is embedded as a constant in the
+     *  generated code.
+     *
+     *  See the `isInstance` and `genInstanceTest` helpers.
+     *
+     *  Special cases: this value remains 0 for all the numeric hijacked classes except `jl.Double`,
+     *  since `jsValueType(x) == JSValueTypeNumber` is not enough to deduce that
+     *  `x.isInstanceOf[Int]`, for example.
+     */
+    val specialInstanceTypes: Int = _specialInstanceTypes
+
+    /** Is this class an ancestor of any hijacked class?
+     *
+     *  This includes but is not limited to the hijacked classes themselves, as well as `jl.Object`.
+     */
+    def isAncestorOfHijackedClass: Boolean =
+      specialInstanceTypes != 0 || kind == ClassKind.HijackedClass
+
+    def isInterface: Boolean =
+      kind == ClassKind.Interface
+
+    def buildMethodTable(methodsCalledDynamically0: Set[MethodName]): Unit = {
+      if (_tableEntries != null)
+        throw new IllegalStateException(s"Duplicate call to buildMethodTable() for $name")
+
+      val methodsCalledDynamically: List[MethodName] =
+        if (hasInstances) methodsCalledDynamically0.toList
+        else Nil
+
+      kind match {
+        case ClassKind.Class | ClassKind.ModuleClass | ClassKind.HijackedClass =>
+          val superTableEntries = superClass.fold[List[MethodName]](Nil)(_.tableEntries)
+          val superTableEntrySet = superTableEntries.toSet
+
+          /* When computing the table entries to add for this class, exclude:
+           * - methods that are already in the super class' table entries, and
+           * - methods that are effectively final, since they will always be
+           *   statically resolved instead of using the table dispatch.
+           */
+          val newTableEntries = methodsCalledDynamically
+            .filter(!superTableEntrySet.contains(_))
+            .filterNot(m => resolvedMethodInfos.get(m).exists(_.isEffectivelyFinal))
+            .sorted // for stability
+
+          _tableEntries = superTableEntries ::: newTableEntries
+
+        case ClassKind.Interface =>
+          _tableEntries = methodsCalledDynamically.sorted // for stability
+
+        case _ =>
+          _tableEntries = Nil
+      }
+    }
+
+    def tableEntries: List[MethodName] = {
+      if (_tableEntries == null)
+        throw new IllegalStateException(s"Table not yet built for $name")
+      _tableEntries
+    }
+  }
+
+  final class ConcreteMethodInfo(val ownerClass: ClassName, val methodName: MethodName) {
+    val tableEntryID = genFunctionID.forTableEntry(ownerClass, methodName)
+
+    private var effectivelyFinal: Boolean = true
+
+    /** For use by `Preprocessor`. */
+    private[wasmemitter] def markOverridden(): Unit =
+      effectivelyFinal = false
+
+    def isEffectivelyFinal: Boolean = effectivelyFinal
+  }
+}
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/BinaryWriter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/BinaryWriter.scala
new file mode 100644
index 0000000000..1c79f6daea
--- /dev/null
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/BinaryWriter.scala
@@ -0,0 +1,667 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package org.scalajs.linker.backend.webassembly
+
+import scala.annotation.tailrec
+
+import java.nio.{ByteBuffer, ByteOrder}
+
+import org.scalajs.ir.{Position, UTF8String}
+import org.scalajs.linker.backend.javascript.SourceMapWriter
+
+import Instructions._
+import Identitities._
+import Modules._
+import Types._
+
+private sealed class BinaryWriter(module: Module, emitDebugInfo: Boolean) {
+  import BinaryWriter._
+
+  /** The big output buffer. */
+  private[BinaryWriter] val buf = new Buffer()
+
+  private val typeIdxValues: Map[TypeID, Int] =
+    module.types.flatMap(_.subTypes).map(_.id).zipWithIndex.toMap
+
+  private val dataIdxValues: Map[DataID, Int] =
+    module.datas.map(_.id).zipWithIndex.toMap
+
+  private val funcIdxValues: Map[FunctionID, Int] = {
+    val importedFunctionIDs = module.imports.collect {
+      case Import(_, _, ImportDesc.Func(id, _, _)) => id
+    }
+    val allIDs = importedFunctionIDs ::: module.funcs.map(_.id)
+    allIDs.zipWithIndex.toMap
+  }
+
+  private val tagIdxValues: Map[TagID, Int] = {
+    val importedTagIDs = module.imports.collect { case Import(_, _, ImportDesc.Tag(id, _, _)) =>
+      id
+    }
+    val allIDs = importedTagIDs ::: module.tags.map(_.id)
+    allIDs.zipWithIndex.toMap
+  }
+
+  private val globalIdxValues: Map[GlobalID, Int] = {
+    val importedGlobalIDs = module.imports.collect {
+      case Import(_, _, ImportDesc.Global(id, _, _, _)) => id
+    }
+    val allIDs = importedGlobalIDs ::: module.globals.map(_.id)
+    allIDs.zipWithIndex.toMap
+  }
+
+  private val fieldIdxValues: Map[TypeID, Map[FieldID, Int]] = {
+    (for {
+      recType <- module.types
+      SubType(typeID, _, _, _, StructType(fields)) <- recType.subTypes
+    } yield {
+      typeID -> fields.map(_.id).zipWithIndex.toMap
+    }).toMap
+  }
+
+  private var localIdxValues: Option[Map[LocalID, Int]] = None
+
+  /** A stack of the labels in scope (innermost labels are on top of the stack). */
+  private var labelsInScope: List[Option[LabelID]] = Nil
+
+  private def withLocalIdxValues(values: Map[LocalID, Int])(f: => Unit): Unit = {
+    val saved = localIdxValues
+    localIdxValues = Some(values)
+    try f
+    finally localIdxValues = saved
+  }
+
+  protected def emitStartFuncPosition(pos: Position): Unit = ()
+  protected def emitPosition(pos: Position): Unit = ()
+  protected def emitEndFuncPosition(): Unit = ()
+  protected def emitSourceMapSection(): Unit = ()
+
+  def write(): ByteBuffer = {
+    // magic header: null char + "asm"
+    buf.byte(0)
+    buf.byte('a')
+    buf.byte('s')
+    buf.byte('m')
+
+    // version
+    buf.byte(1)
+    buf.byte(0)
+    buf.byte(0)
+    buf.byte(0)
+
+    writeSection(SectionType)(writeTypeSection())
+    writeSection(SectionImport)(writeImportSection())
+    writeSection(SectionFunction)(writeFunctionSection())
+    writeSection(SectionTag)(writeTagSection())
+    writeSection(SectionGlobal)(writeGlobalSection())
+    writeSection(SectionExport)(writeExportSection())
+    if (module.start.isDefined)
+      writeSection(SectionStart)(writeStartSection())
+    writeSection(SectionElement)(writeElementSection())
+    if (module.datas.nonEmpty)
+      writeSection(SectionDataCount)(writeDataCountSection())
+    writeSection(SectionCode)(writeCodeSection())
+    writeSection(SectionData)(writeDataSection())
+
+    if (emitDebugInfo)
+      writeCustomSection("name")(writeNameCustomSection())
+
+    emitSourceMapSection()
+
+    buf.result()
+  }
+
+  private def writeSection(sectionID: Byte)(sectionContent: => Unit): Unit = {
+    buf.byte(sectionID)
+    buf.byteLengthSubSection(sectionContent)
+  }
+
+  protected final def writeCustomSection(customSectionName: String)(
+      sectionContent: => Unit): Unit = {
+    writeSection(SectionCustom) {
+      buf.name(customSectionName)
+      sectionContent
+    }
+  }
+
+  private def writeTypeSection(): Unit = {
+    buf.vec(module.types) { recType =>
+      recType.subTypes match {
+        case singleSubType :: Nil =>
+          writeSubType(singleSubType)
+        case subTypes =>
+          buf.byte(0x4E) // `rectype`
+          buf.vec(subTypes)(writeSubType(_))
+      }
+    }
+  }
+
+  private def writeSubType(subType: SubType): Unit = {
+    subType match {
+      case SubType(_, _, true, None, compositeType) =>
+        writeCompositeType(compositeType)
+      case _ =>
+        buf.byte(if (subType.isFinal) 0x4F else 0x50)
+        buf.opt(subType.superType)(writeTypeIdx(_))
+        writeCompositeType(subType.compositeType)
+    }
+  }
+
+  private def writeCompositeType(compositeType: CompositeType): Unit = {
+    def writeFieldType(fieldType: FieldType): Unit = {
+      writeType(fieldType.tpe)
+      buf.boolean(fieldType.isMutable)
+    }
+
+    compositeType match {
+      case ArrayType(fieldType) =>
+        buf.byte(0x5E) // array
+        writeFieldType(fieldType)
+      case StructType(fields) =>
+        buf.byte(0x5F) // struct
+        buf.vec(fields)(field => writeFieldType(field.fieldType))
+      case FunctionType(params, results) =>
+        buf.byte(0x60) // func
+        writeResultType(params)
+        writeResultType(results)
+    }
+  }
+
+  private def writeImportSection(): Unit = {
+    buf.vec(module.imports) { imprt =>
+      buf.name(imprt.module)
+      buf.name(imprt.name)
+
+      imprt.desc match {
+        case ImportDesc.Func(_, _, typeID) =>
+          buf.byte(0x00) // func
+          writeTypeIdx(typeID)
+        case ImportDesc.Global(_, _, isMutable, tpe) =>
+          buf.byte(0x03) // global
+          writeType(tpe)
+          buf.boolean(isMutable)
+        case ImportDesc.Tag(_, _, typeID) =>
+          buf.byte(0x04) // tag
+          buf.byte(0x00) // exception kind (that is the only valid kind for now)
+          writeTypeIdx(typeID)
+      }
+    }
+  }
+
+  private def writeFunctionSection(): Unit = {
+    buf.vec(module.funcs) { fun =>
+      writeTypeIdx(fun.typeID)
+    }
+  }
+
+  private def writeTagSection(): Unit = {
+    buf.vec(module.tags) { tag =>
+      buf.byte(0x00) // exception kind (that is the only valid kind for now)
+      writeTypeIdx(tag.typeID)
+    }
+  }
+
+  private def writeGlobalSection(): Unit = {
+    buf.vec(module.globals) { global =>
+      writeType(global.tpe)
+      buf.boolean(global.isMutable)
+      writeExpr(global.init)
+    }
+  }
+
+  private def writeExportSection(): Unit = {
+    buf.vec(module.exports) { exp =>
+      buf.name(exp.name)
+      exp.desc match {
+        case ExportDesc.Func(id) =>
+          buf.byte(0x00)
+          writeFuncIdx(id)
+        case ExportDesc.Global(id) =>
+          buf.byte(0x03)
+          writeGlobalIdx(id)
+      }
+    }
+  }
+
+  private def writeStartSection(): Unit = {
+    writeFuncIdx(module.start.get)
+  }
+
+  private def writeElementSection(): Unit = {
+    buf.vec(module.elems) { element =>
+      element.mode match {
+        case Element.Mode.Declarative => buf.u32(7)
+      }
+      writeType(element.tpe)
+      buf.vec(element.init) { expr =>
+        writeExpr(expr)
+      }
+    }
+  }
+
+  private def writeDataSection(): Unit = {
+    buf.vec(module.datas) { data =>
+      data.mode match {
+        case Data.Mode.Passive => buf.u32(1)
+      }
+      buf.vec(data.bytes)(buf.byte)
+    }
+  }
+
+  private def writeDataCountSection(): Unit =
+    buf.u32(module.datas.size)
+
+  private def writeCodeSection(): Unit = {
+    buf.vec(module.funcs) { func =>
+      buf.byteLengthSubSection(writeFunc(func))
+    }
+  }
+
+  private def writeNameCustomSection(): Unit = {
+    // Currently, we only emit the function names
+
+    val importFunctionNames = module.imports.collect {
+      case Import(_, _, ImportDesc.Func(id, origName, _)) if origName.isDefined =>
+        id -> origName
+    }
+    val definedFunctionNames =
+      module.funcs.filter(_.originalName.isDefined).map(f => f.id -> f.originalName)
+    val allFunctionNames = importFunctionNames ::: definedFunctionNames
+
+    buf.byte(0x01) // function names
+    buf.byteLengthSubSection {
+      buf.vec(allFunctionNames) { elem =>
+        writeFuncIdx(elem._1)
+        buf.name(elem._2.get)
+      }
+    }
+  }
+
+  private def writeFunc(func: Function): Unit = {
+    emitStartFuncPosition(func.pos)
+
+    buf.vec(func.locals) { local =>
+      buf.u32(1)
+      writeType(local.tpe)
+    }
+
+    withLocalIdxValues((func.params ::: func.locals).map(_.id).zipWithIndex.toMap) {
+      writeExpr(func.body)
+    }
+
+    emitEndFuncPosition()
+  }
+
+  private def writeType(tpe: StorageType): Unit = {
+    tpe match {
+      case tpe: SimpleType => buf.byte(tpe.binaryCode)
+      case tpe: PackedType => buf.byte(tpe.binaryCode)
+
+      case RefType(true, heapType: HeapType.AbsHeapType) =>
+        buf.byte(heapType.binaryCode)
+
+      case RefType(nullable, heapType) =>
+        buf.byte(if (nullable) 0x63 else 0x64)
+        writeHeapType(heapType)
+    }
+  }
+
+  private def writeHeapType(heapType: HeapType): Unit = {
+    heapType match {
+      case HeapType.Type(typeID)          => writeTypeIdxs33(typeID)
+      case heapType: HeapType.AbsHeapType => buf.byte(heapType.binaryCode)
+    }
+  }
+
+  private def writeResultType(resultType: List[Type]): Unit =
+    buf.vec(resultType)(writeType(_))
+
+  private def writeTypeIdx(typeID: TypeID): Unit =
+    buf.u32(typeIdxValues(typeID))
+
+  private def writeFieldIdx(typeID: TypeID, fieldID: FieldID): Unit =
+    buf.u32(fieldIdxValues(typeID)(fieldID))
+
+  private def writeDataIdx(dataID: DataID): Unit =
+    buf.u32(dataIdxValues(dataID))
+
+  private def writeTypeIdxs33(typeID: TypeID): Unit =
+    buf.s33OfUInt(typeIdxValues(typeID))
+
+  private def writeFuncIdx(funcID: FunctionID): Unit =
+    buf.u32(funcIdxValues(funcID))
+
+  private def writeTagIdx(tagID: TagID): Unit =
+    buf.u32(tagIdxValues(tagID))
+
+  private def writeGlobalIdx(globalID: GlobalID): Unit =
+    buf.u32(globalIdxValues(globalID))
+
+  private def writeLocalIdx(localID: LocalID): Unit = {
+    localIdxValues match {
+      case Some(values) => buf.u32(values(localID))
+      case None         => throw new IllegalStateException("Local name table is not available")
+    }
+  }
+
+  private def writeLabelIdx(labelID: LabelID): Unit = {
+    val relativeNumber = labelsInScope.indexOf(Some(labelID))
+    if (relativeNumber < 0)
+      throw new IllegalStateException(s"Cannot find $labelID in scope")
+    buf.u32(relativeNumber)
+  }
+
+  private def writeExpr(expr: Expr): Unit = {
+    for (instr <- expr.instr)
+      writeInstr(instr)
+    buf.byte(0x0B) // end
+  }
+
+  private def writeInstr(instr: Instr): Unit = {
+    instr match {
+      case PositionMark(pos) =>
+        emitPosition(pos)
+
+      case _ =>
+        val opcode = instr.opcode
+        if (opcode <= 0xFF) {
+          buf.byte(opcode.toByte)
+        } else {
+          assert(opcode <= 0xFFFF,
+              s"cannot encode an opcode longer than 2 bytes yet: ${opcode.toHexString}")
+          buf.byte((opcode >>> 8).toByte)
+          buf.byte(opcode.toByte)
+        }
+
+        writeInstrImmediates(instr)
+
+        instr match {
+          case instr: StructuredLabeledInstr =>
+            // We must register even the `None` labels, because they contribute to relative numbering
+            labelsInScope ::= instr.label
+          case End =>
+            labelsInScope = labelsInScope.tail
+          case _ =>
+            ()
+        }
+    }
+  }
+
+  private def writeInstrImmediates(instr: Instr): Unit = {
+    def writeBrOnCast(labelIdx: LabelID, from: RefType, to: RefType): Unit = {
+      val castFlags = ((if (from.nullable) 1 else 0) | (if (to.nullable) 2 else 0)).toByte
+      buf.byte(castFlags)
+      writeLabelIdx(labelIdx)
+      writeHeapType(from.heapType)
+      writeHeapType(to.heapType)
+    }
+
+    instr match {
+      // Convenience categories
+
+      case instr: SimpleInstr =>
+        ()
+      case instr: BlockTypeLabeledInstr =>
+        writeBlockType(instr.blockTypeArgument)
+      case instr: LabelInstr =>
+        writeLabelIdx(instr.labelArgument)
+      case instr: FuncInstr =>
+        writeFuncIdx(instr.funcArgument)
+      case instr: TypeInstr =>
+        writeTypeIdx(instr.typeArgument)
+      case instr: TagInstr =>
+        writeTagIdx(instr.tagArgument)
+      case instr: LocalInstr =>
+        writeLocalIdx(instr.localArgument)
+      case instr: GlobalInstr =>
+        writeGlobalIdx(instr.globalArgument)
+      case instr: HeapTypeInstr =>
+        writeHeapType(instr.heapTypeArgument)
+      case instr: RefTypeInstr =>
+        writeHeapType(instr.refTypeArgument.heapType)
+      case instr: StructFieldInstr =>
+        writeTypeIdx(instr.structTypeID)
+        writeFieldIdx(instr.structTypeID, instr.fieldID)
+
+      // Specific instructions with unique-ish shapes
+
+      case I32Const(v) => buf.i32(v)
+      case I64Const(v) => buf.i64(v)
+      case F32Const(v) => buf.f32(v)
+      case F64Const(v) => buf.f64(v)
+
+      case BrTable(labelIdxVector, defaultLabelIdx) =>
+        buf.vec(labelIdxVector)(writeLabelIdx(_))
+        writeLabelIdx(defaultLabelIdx)
+
+      case TryTable(blockType, clauses, _) =>
+        writeBlockType(blockType)
+        buf.vec(clauses)(writeCatchClause(_))
+
+      case ArrayNewData(typeIdx, dataIdx) =>
+        writeTypeIdx(typeIdx)
+        writeDataIdx(dataIdx)
+
+      case ArrayNewFixed(typeIdx, length) =>
+        writeTypeIdx(typeIdx)
+        buf.u32(length)
+
+      case ArrayCopy(destType, srcType) =>
+        writeTypeIdx(destType)
+        writeTypeIdx(srcType)
+
+      case BrOnCast(labelIdx, from, to) =>
+        writeBrOnCast(labelIdx, from, to)
+      case BrOnCastFail(labelIdx, from, to) =>
+        writeBrOnCast(labelIdx, from, to)
+
+      case PositionMark(pos) =>
+        throw new AssertionError(s"Unexpected $instr")
+    }
+  }
+
+  private def writeCatchClause(clause: CatchClause): Unit = {
+    buf.byte(clause.opcode.toByte)
+    clause.tag.foreach(tag => writeTagIdx(tag))
+    writeLabelIdx(clause.label)
+  }
+
+  private def writeBlockType(blockType: BlockType): Unit = {
+    blockType match {
+      case BlockType.ValueType(None)      => buf.byte(0x40)
+      case BlockType.ValueType(Some(tpe)) => writeType(tpe)
+      case BlockType.FunctionType(typeID) => writeTypeIdxs33(typeID)
+    }
+  }
+}
+
+object BinaryWriter {
+  private final val SectionCustom = 0x00
+  private final val SectionType = 0x01
+  private final val SectionImport = 0x02
+  private final val SectionFunction = 0x03
+  private final val SectionTable = 0x04
+  private final val SectionMemory = 0x05
+  private final val SectionGlobal = 0x06
+  private final val SectionExport = 0x07
+  private final val SectionStart = 0x08
+  private final val SectionElement = 0x09
+  private final val SectionCode = 0x0A
+  private final val SectionData = 0x0B
+  private final val SectionDataCount = 0x0C
+  private final val SectionTag = 0x0D
+
+  def write(module: Module, emitDebugInfo: Boolean): ByteBuffer =
+    new BinaryWriter(module, emitDebugInfo).write()
+
+  def writeWithSourceMap(module: Module, emitDebugInfo: Boolean,
+      sourceMapWriter: SourceMapWriter, sourceMapURI: String): ByteBuffer = {
+    new WithSourceMap(module, emitDebugInfo, sourceMapWriter, sourceMapURI).write()
+  }
+
+  private[BinaryWriter] final class Buffer {
+    private var buf: ByteBuffer =
+      ByteBuffer.allocate(1024 * 1024).order(ByteOrder.LITTLE_ENDIAN)
+
+    private def ensureRemaining(requiredRemaining: Int): Unit = {
+      if (buf.remaining() < requiredRemaining) {
+        buf.flip()
+        val newCapacity = Integer.highestOneBit(buf.capacity() + requiredRemaining) << 1
+        val newBuf = ByteBuffer.allocate(newCapacity).order(ByteOrder.LITTLE_ENDIAN)
+        newBuf.put(buf)
+        buf = newBuf
+      }
+    }
+
+    def currentGlobalOffset: Int = buf.position()
+
+    def result(): ByteBuffer = {
+      buf.flip()
+      buf
+    }
+
+    def byte(b: Byte): Unit = {
+      ensureRemaining(1)
+      buf.put(b)
+    }
+
+    def rawByteArray(array: Array[Byte]): Unit = {
+      ensureRemaining(array.length)
+      buf.put(array)
+    }
+
+    def boolean(b: Boolean): Unit =
+      byte(if (b) 1 else 0)
+
+    def u32(value: Int): Unit = unsignedLEB128(Integer.toUnsignedLong(value))
+
+    def s32(value: Int): Unit = signedLEB128(value.toLong)
+
+    def i32(value: Int): Unit = s32(value)
+
+    def s33OfUInt(value: Int): Unit = signedLEB128(Integer.toUnsignedLong(value))
+
+    def u64(value: Long): Unit = unsignedLEB128(value)
+
+    def s64(value: Long): Unit = signedLEB128(value)
+
+    def i64(value: Long): Unit = s64(value)
+
+    def f32(value: Float): Unit = {
+      ensureRemaining(4)
+      buf.putFloat(value)
+    }
+
+    def f64(value: Double): Unit = {
+      ensureRemaining(8)
+      buf.putDouble(value)
+    }
+
+    def vec[A](elems: Iterable[A])(op: A => Unit): Unit = {
+      u32(elems.size)
+      for (elem <- elems)
+        op(elem)
+    }
+
+    def opt[A](elemOpt: Option[A])(op: A => Unit): Unit =
+      vec(elemOpt.toList)(op)
+
+    def name(s: String): Unit =
+      name(UTF8String(s))
+
+    def name(utf8: UTF8String): Unit = {
+      val len = utf8.length
+      u32(len)
+      ensureRemaining(len)
+      utf8.writeTo(buf)
+    }
+
+    def byteLengthSubSection(subSectionContent: => Unit): Unit = {
+      // Reserve 4 bytes at the current offset to store the byteLength later
+      val byteLengthOffset = buf.position()
+      ensureRemaining(4)
+      val startOffset = buf.position() + 4
+      buf.position(startOffset) // do not write the 4 bytes for now
+
+      subSectionContent
+
+      // Compute byteLength
+      val endOffset = buf.position()
+      val byteLength = endOffset - startOffset
+
+      /* Because we limited ourselves to 4 bytes, we cannot represent a size
+       * greater than 2^(4*7).
+       */
+      assert(byteLength < (1 << 28),
+          s"Implementation restriction: Cannot write a subsection that large: $byteLength")
+
+      /* Write the byteLength in the reserved slot. Note that we *always* use
+       * 4 bytes to store the byteLength, even when less bytes are necessary in
+       * the unsigned LEB encoding. The WebAssembly spec specifically calls out
+       * this choice as valid. We leverage it to have predictable total offsets
+       * when we write the code section, which is important to efficiently
+       * generate source maps.
+       */
+      buf.put(byteLengthOffset, ((byteLength & 0x7F) | 0x80).toByte)
+      buf.put(byteLengthOffset + 1, (((byteLength >>> 7) & 0x7F) | 0x80).toByte)
+      buf.put(byteLengthOffset + 2, (((byteLength >>> 14) & 0x7F) | 0x80).toByte)
+      buf.put(byteLengthOffset + 3, ((byteLength >>> 21) & 0x7F).toByte)
+    }
+
+    @tailrec
+    private def unsignedLEB128(value: Long): Unit = {
+      val next = value >>> 7
+      if (next == 0) {
+        byte(value.toByte)
+      } else {
+        byte(((value.toInt & 0x7F) | 0x80).toByte)
+        unsignedLEB128(next)
+      }
+    }
+
+    @tailrec
+    private def signedLEB128(value: Long): Unit = {
+      val chunk = value.toInt & 0x7F
+      val next = value >> 7
+      if (next == (if ((chunk & 0x40) != 0) -1 else 0)) {
+        byte(chunk.toByte)
+      } else {
+        byte((chunk | 0x80).toByte)
+        signedLEB128(next)
+      }
+    }
+  }
+
+  private final class WithSourceMap(module: Module, emitDebugInfo: Boolean,
+      sourceMapWriter: SourceMapWriter, sourceMapURI: String)
+      extends BinaryWriter(module, emitDebugInfo) {
+
+    override protected def emitStartFuncPosition(pos: Position): Unit =
+      sourceMapWriter.startNode(buf.currentGlobalOffset, pos)
+
+    override protected def emitPosition(pos: Position): Unit = {
+      sourceMapWriter.endNode(buf.currentGlobalOffset)
+      sourceMapWriter.startNode(buf.currentGlobalOffset, pos)
+    }
+
+    override protected def emitEndFuncPosition(): Unit =
+      sourceMapWriter.endNode(buf.currentGlobalOffset)
+
+    override protected def emitSourceMapSection(): Unit = {
+      // See https://github.com/WebAssembly/tool-conventions/blob/main/Debugging.md#source-maps
+      writeCustomSection("sourceMappingURL") {
+        buf.name(sourceMapURI)
+      }
+    }
+  }
+}
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/FunctionBuilder.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/FunctionBuilder.scala
new file mode 100644
index 0000000000..fff0a74acd
--- /dev/null
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/FunctionBuilder.scala
@@ -0,0 +1,445 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package org.scalajs.linker.backend.webassembly
+
+import scala.collection.mutable
+
+import org.scalajs.ir.{OriginalName, Position}
+
+import Instructions._
+import Identitities._
+import Modules._
+import Types._
+
+final class FunctionBuilder(
+    moduleBuilder: ModuleBuilder,
+    val functionID: FunctionID,
+    val functionOriginalName: OriginalName,
+    functionPos: Position
+) {
+  import FunctionBuilder._
+
+  private var labelIdx = 0
+
+  private val params = mutable.ListBuffer.empty[Local]
+  private val locals = mutable.ListBuffer.empty[Local]
+  private var resultTypes: List[Type] = Nil
+
+  private var specialFunctionType: Option[TypeID] = None
+
+  /** The instructions buffer. */
+  private val instrs: mutable.ListBuffer[Instr] = mutable.ListBuffer.empty
+
+  // Signature building
+
+  /** Adds one parameter to the function with the given orignal name and type.
+   *
+   *  Returns the `LocalID` of the new parameter.
+   *
+   *  @note
+   *    This follows a builder pattern to easily and safely correlate the
+   *    definition of a parameter and extracting its `LocalID`.
+   */
+  def addParam(originalName: OriginalName, tpe: Type): LocalID = {
+    val id = new ParamIDImpl(params.size, originalName)
+    params += Local(id, originalName, tpe)
+    id
+  }
+
+  /** Adds one parameter to the function with the given orignal name and type.
+   *
+   *  Returns the `LocalID` of the new parameter.
+   *
+   *  @note
+   *    This follows a builder pattern to easily and safely correlate the
+   *    definition of a parameter and extracting its `LocalID`.
+   */
+  def addParam(name: String, tpe: Type): LocalID =
+    addParam(OriginalName(name), tpe)
+
+  /** Sets the list of result types of the function to build.
+   *
+   *  By default, the list of result types is `Nil`.
+   *
+   *  @note
+   *    This follows a builder pattern to be consistent with `addParam`.
+   */
+  def setResultTypes(tpes: List[Type]): Unit =
+    resultTypes = tpes
+
+  /** Sets the list of result types to a single type.
+   *
+   *  This method is equivalent to
+   *  {{{
+   *  setResultTypes(tpe :: Nil)
+   *  }}}
+   *
+   *  @note
+   *    This follows a builder pattern to be consistent with `addParam`.
+   */
+  def setResultType(tpe: Type): Unit =
+    setResultTypes(tpe :: Nil)
+
+  /** Specifies the function type to use for the function.
+   *
+   *  If this method is not called, a default function type will be
+   *  automatically generated. Generated function types are always alone in a
+   *  recursive type group, without supertype, and final.
+   *
+   *  Use `setFunctionType` if the function must conform to a specific function
+   *  type, such as one that is defined within a recursive type group, or that
+   *  is a subtype of other function types.
+   *
+   *  The given function type must be consistent with the params created with
+   *  `addParam` and with the result types specified by `setResultType(s)`.
+   *  Using `setFunctionType` does not implicitly set any result type or create
+   *  any parameter (it cannot, since it cannot *resolve* the `typeID` to a
+   *  `FunctionType`).
+   */
+  def setFunctionType(typeID: TypeID): Unit =
+    specialFunctionType = Some(typeID)
+
+  // Local definitions
+
+  def genLabel(): LabelID = {
+    val label = new LabelIDImpl(labelIdx)
+    labelIdx += 1
+    label
+  }
+
+  def addLocal(originalName: OriginalName, tpe: Type): LocalID = {
+    val id = new LocalIDImpl(locals.size, originalName)
+    locals += Local(id, originalName, tpe)
+    id
+  }
+
+  def addLocal(name: String, tpe: Type): LocalID =
+    addLocal(OriginalName(name), tpe)
+
+  // Instructions
+
+  def +=(instr: Instr): Unit =
+    instrs += instr
+
+  def ++=(instrs: Iterable[Instr]): Unit =
+    this.instrs ++= instrs
+
+  def markCurrentInstructionIndex(): InstructionIndex =
+    new InstructionIndex(instrs.size)
+
+  def insert(index: InstructionIndex, instr: Instr): Unit =
+    instrs.insert(index.value, instr)
+
+  // Helpers to build structured control flow
+
+  def sigToBlockType(sig: FunctionType): BlockType = sig match {
+    case FunctionType(Nil, Nil) =>
+      BlockType.ValueType()
+    case FunctionType(Nil, resultType :: Nil) =>
+      BlockType.ValueType(resultType)
+    case _ =>
+      BlockType.FunctionType(moduleBuilder.functionTypeToTypeID(sig))
+  }
+
+  private def toBlockType[BT: BlockTypeLike](blockType: BT): BlockType =
+    implicitly[BlockTypeLike[BT]].toBlockType(this, blockType)
+
+  /* Work around a bug in the Scala compiler.
+   *
+   * We force it to see `ForResultTypes` here, so that it actually typechecks
+   * it and realizes that it is a valid implicit instance of
+   * `BlockTypeLike[ForResultTypes]`. I guess this is because it appears later
+   * in the same file.
+   *
+   * If we remove this line, the invocations with `()` in this file, which
+   * desugar to `(Nil)` due to the default value, do not find the implicit value.
+   */
+  BlockTypeLike.ForResultTypes
+
+  def ifThenElse[BT: BlockTypeLike](blockType: BT = Nil)(thenp: => Unit)(elsep: => Unit): Unit = {
+    instrs += If(toBlockType(blockType))
+    thenp
+    instrs += Else
+    elsep
+    instrs += End
+  }
+
+  def ifThen[BT: BlockTypeLike](blockType: BT = Nil)(thenp: => Unit): Unit = {
+    instrs += If(toBlockType(blockType))
+    thenp
+    instrs += End
+  }
+
+  def block[BT: BlockTypeLike, A](blockType: BT = Nil)(body: LabelID => A): A = {
+    val label = genLabel()
+    instrs += Block(toBlockType(blockType), Some(label))
+    val result = body(label)
+    instrs += End
+    result
+  }
+
+  def loop[BT: BlockTypeLike, A](blockType: BT = Nil)(body: LabelID => A): A = {
+    val label = genLabel()
+    instrs += Loop(toBlockType(blockType), Some(label))
+    val result = body(label)
+    instrs += End
+    result
+  }
+
+  def whileLoop()(cond: => Unit)(body: => Unit): Unit = {
+    loop() { loopLabel =>
+      cond
+      ifThen() {
+        body
+        instrs += Br(loopLabel)
+      }
+    }
+  }
+
+  def tryTable[BT: BlockTypeLike, A](blockType: BT = Nil)(
+      clauses: List[CatchClause])(body: => A): A = {
+    instrs += TryTable(toBlockType(blockType), clauses)
+    val result = body
+    instrs += End
+    result
+  }
+
+  /** Builds a `switch` over a scrutinee using a `br_table` instruction.
+   *
+   *  This function produces code that encodes the following control-flow:
+   *
+   *  {{{
+   *  switch (scrutinee) {
+   *    case clause0_alt0 | ... | clause0_altN => clause0_body
+   *    ...
+   *    case clauseM_alt0 | ... | clauseM_altN => clauseM_body
+   *    case _ => default
+   *  }
+   *  }}}
+   *
+   *  All the alternative values must be non-negative and distinct, but they need not be
+   *  consecutive. The highest one must be strictly smaller than 128, as a safety precaution against
+   *  generating unexpectedly large tables.
+   *
+   *  @param scrutineeSig
+   *    The signature of the `scrutinee` block, *excluding* the i32 result that will be switched
+   *    over.
+   *  @param clauseSig
+   *    The signature of every `clauseI_body` block and of the `default` block. The clauses' params
+   *    must consume at least all the results of the scrutinee.
+   */
+  def switch(scrutineeSig: FunctionType, clauseSig: FunctionType)(
+      scrutinee: () => Unit)(
+      clauses: (List[Int], () => Unit)*)(
+      default: () => Unit): Unit = {
+
+    // Check prerequisites
+
+    require(clauseSig.params.size >= scrutineeSig.results.size,
+        "The clauses of a switch must consume all the results of the scrutinee " +
+        s"(scrutinee results: ${scrutineeSig.results}; clause params: ${clauseSig.params})")
+
+    val numCases = clauses.map(_._1.max).max + 1
+    require(numCases <= 128, s"Too many cases for switch: $numCases")
+
+    // Allocate all the labels we will use
+    val doneLabel = genLabel()
+    val defaultLabel = genLabel()
+    val clauseLabels = clauses.map(_ => genLabel())
+
+    // Build the dispatch vector, i.e., the array of caseValue -> target clauseLabel
+    val dispatchVector = {
+      val dv = Array.fill(numCases)(defaultLabel)
+      for {
+        ((caseValues, _), clauseLabel) <- clauses.zip(clauseLabels)
+        caseValue <- caseValues
+      } {
+        require(dv(caseValue) == defaultLabel, s"Duplicate case value for switch: $caseValue")
+        dv(caseValue) = clauseLabel
+      }
+      dv.toList
+    }
+
+    // Input parameter to the overall switch "instruction"
+    val switchInputParams =
+      clauseSig.params.drop(scrutineeSig.results.size) ::: scrutineeSig.params
+
+    // Compute the BlockType's we will need
+    val doneBlockType = sigToBlockType(FunctionType(switchInputParams, clauseSig.results))
+    val clauseBlockType = sigToBlockType(FunctionType(switchInputParams, clauseSig.params))
+
+    // Open done block
+    instrs += Block(doneBlockType, Some(doneLabel))
+    // Open case and default blocks (in reverse order: default block is outermost!)
+    for (label <- (defaultLabel +: clauseLabels.reverse)) {
+      instrs += Block(clauseBlockType, Some(label))
+    }
+
+    // Load the scrutinee and dispatch
+    scrutinee()
+    instrs += BrTable(dispatchVector, defaultLabel)
+
+    // Close all the case blocks and emit their respective bodies
+    for ((_, caseBody) <- clauses) {
+      instrs += End // close the block whose label is the corresponding label for this clause
+      caseBody() // emit the body of that clause
+      instrs += Br(doneLabel) // jump to done
+    }
+
+    // Close the default block and emit its body (no jump to done necessary)
+    instrs += End
+    default()
+
+    instrs += End // close the done block
+  }
+
+  def switch(clauseSig: FunctionType)(scrutinee: () => Unit)(
+      clauses: (List[Int], () => Unit)*)(default: () => Unit): Unit = {
+    switch(FunctionType.NilToNil, clauseSig)(scrutinee)(clauses: _*)(default)
+  }
+
+  def switch(resultType: Type)(scrutinee: () => Unit)(
+      clauses: (List[Int], () => Unit)*)(default: () => Unit): Unit = {
+    switch(FunctionType(Nil, List(resultType)))(scrutinee)(clauses: _*)(default)
+  }
+
+  def switch()(scrutinee: () => Unit)(
+      clauses: (List[Int], () => Unit)*)(default: () => Unit): Unit = {
+    switch(FunctionType.NilToNil)(scrutinee)(clauses: _*)(default)
+  }
+
+  // Final result
+
+  def buildAndAddToModule(): Function = {
+    val functionTypeID = specialFunctionType.getOrElse {
+      val sig = FunctionType(params.toList.map(_.tpe), resultTypes)
+      moduleBuilder.functionTypeToTypeID(sig)
+    }
+
+    val dcedInstrs = localDeadCodeEliminationOfInstrs()
+
+    val func = Function(
+      functionID,
+      functionOriginalName,
+      functionTypeID,
+      params.toList,
+      resultTypes,
+      locals.toList,
+      Expr(dcedInstrs),
+      functionPos
+    )
+    moduleBuilder.addFunction(func)
+    func
+  }
+
+  /** Performs local dead code elimination and produces the final list of instructions.
+   *
+   *  After a stack-polymorphic instruction, the rest of the block is unreachable. In theory,
+   *  WebAssembly specifies that the rest of the block should be type-checkeable no matter the
+   *  contents of the stack. In practice, however, it seems V8 cannot handle `throw_ref` in such a
+   *  context. It reports a validation error of the form "invalid type for throw_ref: expected
+   *  exnref, found <bot>".
+   *
+   *  We work around this issue by forcing a pass of local dead-code elimination. This is in fact
+   *  straightforwrd: after every stack-polymorphic instruction, ignore all instructions until the
+   *  next `Else` or `End`. The only tricky bit is that if we encounter nested
+   *  `StructuredLabeledInstr`s during that process, must jump over them. That means we need to
+   *  track the level of nesting at which we are.
+   */
+  private def localDeadCodeEliminationOfInstrs(): List[Instr] = {
+    val resultBuilder = List.newBuilder[Instr]
+
+    val iter = instrs.iterator
+    while (iter.hasNext) {
+      // Emit the current instruction
+      val instr = iter.next()
+      resultBuilder += instr
+
+      /* If it is a stack-polymorphic instruction, dead-code eliminate until the
+       * end of the current block.
+       */
+      if (instr.isInstanceOf[StackPolymorphicInstr]) {
+        var nestingLevel = 0
+
+        while (nestingLevel >= 0 && iter.hasNext) {
+          val deadCodeInstr = iter.next()
+          deadCodeInstr match {
+            case End | Else | _: Catch if nestingLevel == 0 =>
+              /* We have reached the end of the original block of dead code.
+               * Actually emit this END or ELSE and then drop `nestingLevel`
+               * below 0 to end the dead code processing loop.
+               */
+              resultBuilder += deadCodeInstr
+              nestingLevel = -1 // acts as a `break` instruction
+
+            case End =>
+              nestingLevel -= 1
+
+            case _: StructuredLabeledInstr =>
+              nestingLevel += 1
+
+            case _ =>
+              ()
+          }
+        }
+      }
+    }
+
+    resultBuilder.result()
+  }
+}
+
+object FunctionBuilder {
+  private final class ParamIDImpl(index: Int, originalName: OriginalName) extends LocalID {
+    override def toString(): String =
+      if (originalName.isDefined) originalName.get.toString()
+      else s"<param $index>"
+  }
+
+  private final class LocalIDImpl(index: Int, originalName: OriginalName) extends LocalID {
+    override def toString(): String =
+      if (originalName.isDefined) originalName.get.toString()
+      else s"<local $index>"
+  }
+
+  private final class LabelIDImpl(index: Int) extends LabelID {
+    override def toString(): String = s"<label $index>"
+  }
+
+  final class InstructionIndex(private[FunctionBuilder] val value: Int) extends AnyVal
+
+  sealed abstract class BlockTypeLike[-A] {
+    def toBlockType(fb: FunctionBuilder, value: A): BlockType
+  }
+
+  object BlockTypeLike {
+    implicit object ForBlockType extends BlockTypeLike[BlockType] {
+      def toBlockType(fb: FunctionBuilder, value: BlockType): BlockType = value
+    }
+
+    implicit object ForFunctionType extends BlockTypeLike[FunctionType] {
+      def toBlockType(fb: FunctionBuilder, value: FunctionType): BlockType =
+        fb.sigToBlockType(value)
+    }
+
+    implicit object ForResultTypes extends BlockTypeLike[List[Type]] {
+      def toBlockType(fb: FunctionBuilder, value: List[Type]): BlockType =
+        fb.sigToBlockType(FunctionType(Nil, value))
+    }
+
+    implicit object ForResultType extends BlockTypeLike[Type] {
+      def toBlockType(fb: FunctionBuilder, value: Type): BlockType =
+        BlockType.ValueType(value)
+    }
+  }
+}
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/Identitities.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/Identitities.scala
new file mode 100644
index 0000000000..0226fde7d6
--- /dev/null
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/Identitities.scala
@@ -0,0 +1,65 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package org.scalajs.linker.backend.webassembly
+
+/** Abstract representation of WebAssembly indices as IDs.
+ *
+ *  Concrete implementations must provide meaningful `equals` and `hashCode` semantics.
+ *
+ *  They are encouraged to have a usable `toString()` implementation for debugging purposes.
+ *
+ *  @see
+ *    [[https://webassembly.github.io/gc/core/syntax/modules.html#indices]]
+ */
+object Identitities {
+  /** ID of a type declaration.
+   *
+   *  Although type declarations are actually `subtype`s and are defined within
+   *  `rectype`s, `TypeID`s are not scoped; they are global.
+   */
+  trait TypeID
+
+  /** ID of a field within an aggregate type.
+   *
+   *  `FieldID`s are scoped by their enclosing `TypeID`.
+   */
+  trait FieldID
+
+  /** ID of a function. */
+  trait FunctionID
+
+  /** ID of a local variable within a function (including parameters).
+   *
+   *  `LocalID`s are scoped by their enclosing `FunctionID`.
+   */
+  trait LocalID
+
+  /** ID of a label within a function.
+   *
+   *  `LabelID`s are scoped by their enclosing `FunctionID`.
+   */
+  trait LabelID
+
+  /** ID of an exception tag.
+   *
+   *  @see
+   *    [[https://webassembly.github.io/exception-handling/core/syntax/modules.html#indices]]
+   */
+  trait TagID
+
+  /** ID of a global variable. */
+  trait GlobalID
+
+  /** ID of a data segment. */
+  trait DataID
+}
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/Instructions.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/Instructions.scala
new file mode 100644
index 0000000000..8b05288287
--- /dev/null
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/Instructions.scala
@@ -0,0 +1,408 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package org.scalajs.linker.backend.webassembly
+
+import org.scalajs.ir.Position
+
+import Identitities._
+import Types._
+
+/** WebAssembly instructions.
+ *
+ *  @see
+ *    [[https://webassembly.github.io/spec/core/syntax/instructions.html]]
+ */
+object Instructions {
+
+  /** A WebAssembly `expr`. */
+  final case class Expr(instr: List[Instr])
+
+  /** A WebAssembly `instr`. */
+  sealed abstract class Instr(val mnemonic: String, val opcode: Int)
+
+  // Semantic categories of instructions
+
+  /** A stack-polymorphic instruction. */
+  sealed trait StackPolymorphicInstr extends Instr
+
+  /** An instruction that opens a structured control block. */
+  sealed trait StructuredLabeledInstr extends Instr {
+    val label: Option[LabelID]
+  }
+
+  // Convenience subclasses of instructions for writing text/binary
+
+  /** An instruction without any immediate argument. */
+  sealed abstract class SimpleInstr(mnemonic: String, opcode: Int)
+      extends Instr(mnemonic, opcode)
+
+  /** A structured labeled instruction with a single `BlockType` argument. */
+  sealed abstract class BlockTypeLabeledInstr(mnemonic: String, opcode: Int,
+      val blockTypeArgument: BlockType)
+      extends Instr(mnemonic, opcode) with StructuredLabeledInstr
+
+  /** An instruction with a single `LabelIdx` argument. */
+  sealed abstract class LabelInstr(mnemonic: String, opcode: Int,
+      val labelArgument: LabelID)
+      extends Instr(mnemonic, opcode)
+
+  /** An instruction with a single `FunctionID` argument. */
+  sealed abstract class FuncInstr(mnemonic: String, opcode: Int,
+      val funcArgument: FunctionID)
+      extends Instr(mnemonic, opcode)
+
+  /** An instruction with a single `TypeID` argument. */
+  sealed abstract class TypeInstr(mnemonic: String, opcode: Int,
+      val typeArgument: TypeID)
+      extends Instr(mnemonic, opcode)
+
+  /** An instruction with a single `TagID` argument. */
+  sealed abstract class TagInstr(mnemonic: String, opcode: Int,
+      val tagArgument: TagID)
+      extends Instr(mnemonic, opcode)
+
+  /** An instruction with a single `LocalID` argument. */
+  sealed abstract class LocalInstr(mnemonic: String, opcode: Int,
+      val localArgument: LocalID)
+      extends Instr(mnemonic, opcode)
+
+  /** An instruction with a single `GlobalID` argument. */
+  sealed abstract class GlobalInstr(mnemonic: String, opcode: Int,
+      val globalArgument: GlobalID)
+      extends Instr(mnemonic, opcode)
+
+  /** An instruction with a single `HeapType` argument. */
+  sealed abstract class HeapTypeInstr(mnemonic: String, opcode: Int,
+      val heapTypeArgument: HeapType)
+      extends Instr(mnemonic, opcode)
+
+  /** An instruction with a single `RefType` argument
+   *
+   *  In the binary format, it has split opcodes for the nullable and non-nullable variants.
+   */
+  sealed abstract class RefTypeInstr(mnemonic: String, nonNullOpcode: Int,
+      nullOpcode: Int, val refTypeArgument: RefType)
+      extends Instr(mnemonic, if (refTypeArgument.nullable) nullOpcode else nonNullOpcode)
+
+  /** An instruction with a pair of `TypeID`, `FieldID` arguments. */
+  sealed abstract class StructFieldInstr(mnemonic: String, opcode: Int,
+      val structTypeID: TypeID, val fieldID: FieldID)
+      extends Instr(mnemonic, opcode)
+
+  // --- The actual instruction list -- sorted by opcode ----------------------
+
+  /** Fake instruction to mark position changes. */
+  final case class PositionMark(pos: Position) extends Instr("pos", -1)
+
+  // Control instructions
+
+  case object Unreachable extends SimpleInstr("unreachable", 0x00) with StackPolymorphicInstr
+  case object Nop extends SimpleInstr("nop", 0x01)
+
+  final case class Block(i: BlockType, label: Option[LabelID])
+      extends BlockTypeLabeledInstr("block", 0x02, i)
+
+  final case class Loop(i: BlockType, label: Option[LabelID])
+      extends BlockTypeLabeledInstr("loop", 0x03, i)
+
+  final case class If(i: BlockType, label: Option[LabelID] = None)
+      extends BlockTypeLabeledInstr("if", 0x04, i)
+
+  case object Else extends SimpleInstr("else", 0x05)
+
+  /** `try` in the legacy exception system.
+   *
+   *  @see
+   *    [[https://webassembly.github.io/exception-handling/legacy/exceptions/core/syntax.html]]
+   */
+  final case class Try(i: BlockType, label: Option[LabelID] = None)
+      extends BlockTypeLabeledInstr("try", 0x06, i)
+
+  /** `catch` in the legacy exception system. */
+  final case class Catch(i: TagID) extends TagInstr("catch", 0x07, i)
+
+  final case class Throw(i: TagID) extends TagInstr("throw", 0x08, i) with StackPolymorphicInstr
+  case object ThrowRef extends SimpleInstr("throw_ref", 0x0A) with StackPolymorphicInstr
+
+  case object End extends SimpleInstr("end", 0x0B)
+
+  final case class Br(i: LabelID) extends LabelInstr("br", 0x0C, i) with StackPolymorphicInstr
+  final case class BrIf(i: LabelID) extends LabelInstr("br_if", 0x0D, i)
+
+  final case class BrTable(table: List[LabelID], default: LabelID)
+      extends Instr("br_table", 0x0E) with StackPolymorphicInstr
+
+  case object Return extends SimpleInstr("return", 0x0F) with StackPolymorphicInstr
+
+  final case class Call(i: FunctionID) extends FuncInstr("call", 0x10, i)
+
+  final case class ReturnCall(i: FunctionID)
+      extends FuncInstr("return_call", 0x12, i) with StackPolymorphicInstr
+
+  final case class CallRef(i: TypeID) extends TypeInstr("call_ref", 0x14, i)
+
+  final case class ReturnCallRef(i: TypeID)
+      extends TypeInstr("return_call_ref", 0x15, i) with StackPolymorphicInstr
+
+  case object Drop extends SimpleInstr("drop", 0x1A)
+
+  final case class TryTable(i: BlockType, cs: List[CatchClause], label: Option[LabelID] = None)
+      extends Instr("try_table", 0x1F) with StructuredLabeledInstr
+
+  // Instructions on local and global variables
+
+  final case class LocalGet(i: LocalID) extends LocalInstr("local.get", 0x20, i)
+  final case class LocalSet(i: LocalID) extends LocalInstr("local.set", 0x21, i)
+  final case class LocalTee(i: LocalID) extends LocalInstr("local.tee", 0x22, i)
+  final case class GlobalGet(i: GlobalID) extends GlobalInstr("global.get", 0x23, i)
+  final case class GlobalSet(i: GlobalID) extends GlobalInstr("global.set", 0x24, i)
+
+  // Literals of primitive numeric types
+
+  final case class I32Const(v: Int) extends Instr("i32.const", 0x41)
+  final case class I64Const(v: Long) extends Instr("i64.const", 0x42)
+  final case class F32Const(v: Float) extends Instr("f32.const", 0x43)
+  final case class F64Const(v: Double) extends Instr("f64.const", 0x44)
+
+  // Simple operations on primitive numeric types
+
+  case object I32Eqz extends SimpleInstr("i32.eqz", 0x45)
+  case object I32Eq extends SimpleInstr("i32.eq", 0x46)
+  case object I32Ne extends SimpleInstr("i32.ne", 0x47)
+  case object I32LtS extends SimpleInstr("i32.lt_s", 0x48)
+  case object I32LtU extends SimpleInstr("i32.lt_u", 0x49)
+  case object I32GtS extends SimpleInstr("i32.gt_s", 0x4A)
+  case object I32GtU extends SimpleInstr("i32.gt_u", 0x4B)
+  case object I32LeS extends SimpleInstr("i32.le_s", 0x4C)
+  case object I32LeU extends SimpleInstr("i32.le_u", 0x4D)
+  case object I32GeS extends SimpleInstr("i32.ge_s", 0x4E)
+  case object I32GeU extends SimpleInstr("i32.ge_u", 0x4F)
+  case object I64Eqz extends SimpleInstr("i64.eqz", 0x50)
+  case object I64Eq extends SimpleInstr("i64.eq", 0x51)
+  case object I64Ne extends SimpleInstr("i64.ne", 0x52)
+  case object I64LtS extends SimpleInstr("i64.lt_s", 0x53)
+  case object I64LtU extends SimpleInstr("i64.lt_u", 0x54)
+  case object I64GtS extends SimpleInstr("i64.gt_s", 0x55)
+  case object I64GtU extends SimpleInstr("i64.gt_u", 0x56)
+  case object I64LeS extends SimpleInstr("i64.le_s", 0x57)
+  case object I64LeU extends SimpleInstr("i64.le_u", 0x58)
+  case object I64GeS extends SimpleInstr("i64.ge_s", 0x59)
+  case object I64GeU extends SimpleInstr("i64.ge_u", 0x5A)
+  case object F32Eq extends SimpleInstr("f32.eq", 0x5B)
+  case object F32Ne extends SimpleInstr("f32.ne", 0x5C)
+  case object F32Lt extends SimpleInstr("f32.lt", 0x5D)
+  case object F32Gt extends SimpleInstr("f32.gt", 0x5E)
+  case object F32Le extends SimpleInstr("f32.le", 0x5F)
+  case object F32Ge extends SimpleInstr("f32.ge", 0x60)
+  case object F64Eq extends SimpleInstr("f64.eq", 0x61)
+  case object F64Ne extends SimpleInstr("f64.ne", 0x62)
+  case object F64Lt extends SimpleInstr("f64.lt", 0x63)
+  case object F64Gt extends SimpleInstr("f64.gt", 0x64)
+  case object F64Le extends SimpleInstr("f64.le", 0x65)
+  case object F64Ge extends SimpleInstr("f64.ge", 0x66)
+  case object I32Clz extends SimpleInstr("i32.clz", 0x67)
+  case object I32Ctz extends SimpleInstr("i32.ctz", 0x68)
+  case object I32Popcnt extends SimpleInstr("i32.popcnt", 0x69)
+  case object I32Add extends SimpleInstr("i32.add", 0x6A)
+  case object I32Sub extends SimpleInstr("i32.sub", 0x6B)
+  case object I32Mul extends SimpleInstr("i32.mul", 0x6C)
+  case object I32DivS extends SimpleInstr("i32.div_s", 0x6D)
+  case object I32DivU extends SimpleInstr("i32.div_u", 0x6E)
+  case object I32RemS extends SimpleInstr("i32.rem_s", 0x6F)
+  case object I32RemU extends SimpleInstr("i32.rem_u", 0x70)
+  case object I32And extends SimpleInstr("i32.and", 0x71)
+  case object I32Or extends SimpleInstr("i32.or", 0x72)
+  case object I32Xor extends SimpleInstr("i32.xor", 0x73)
+  case object I32Shl extends SimpleInstr("i32.shl", 0x74)
+  case object I32ShrS extends SimpleInstr("i32.shr_s", 0x75)
+  case object I32ShrU extends SimpleInstr("i32.shr_u", 0x76)
+  case object I32Rotl extends SimpleInstr("i32.rotl", 0x77)
+  case object I32Rotr extends SimpleInstr("i32.rotr", 0x78)
+  case object I64Clz extends SimpleInstr("i64.clz", 0x79)
+  case object I64Ctz extends SimpleInstr("i64.ctz", 0x7A)
+  case object I64Popcnt extends SimpleInstr("i64.popcnt", 0x7B)
+  case object I64Add extends SimpleInstr("i64.add", 0x7C)
+  case object I64Sub extends SimpleInstr("i64.sub", 0x7D)
+  case object I64Mul extends SimpleInstr("i64.mul", 0x7E)
+  case object I64DivS extends SimpleInstr("i64.div_s", 0x7F)
+  case object I64DivU extends SimpleInstr("i64.div_u", 0x80)
+  case object I64RemS extends SimpleInstr("i64.rem_s", 0x81)
+  case object I64RemU extends SimpleInstr("i64.rem_u", 0x82)
+  case object I64And extends SimpleInstr("i64.and", 0x83)
+  case object I64Or extends SimpleInstr("i64.or", 0x84)
+  case object I64Xor extends SimpleInstr("i64.xor", 0x85)
+  case object I64Shl extends SimpleInstr("i64.shl", 0x86)
+  case object I64ShrS extends SimpleInstr("i64.shr_s", 0x87)
+  case object I64ShrU extends SimpleInstr("i64.shr_u", 0x88)
+  case object I64Rotl extends SimpleInstr("i64.rotl", 0x89)
+  case object I64Rotr extends SimpleInstr("i64.rotr", 0x8A)
+  case object F32Abs extends SimpleInstr("f32.abs", 0x8B)
+  case object F32Neg extends SimpleInstr("f32.neg", 0x8C)
+  case object F32Ceil extends SimpleInstr("f32.ceil", 0x8D)
+  case object F32Floor extends SimpleInstr("f32.floor", 0x8E)
+  case object F32Trunc extends SimpleInstr("f32.trunc", 0x8F)
+  case object F32Nearest extends SimpleInstr("f32.nearest", 0x90)
+  case object F32Sqrt extends SimpleInstr("f32.sqrt", 0x91)
+  case object F32Add extends SimpleInstr("f32.add", 0x92)
+  case object F32Sub extends SimpleInstr("f32.sub", 0x93)
+  case object F32Mul extends SimpleInstr("f32.mul", 0x94)
+  case object F32Div extends SimpleInstr("f32.div", 0x95)
+  case object F32Min extends SimpleInstr("f32.min", 0x96)
+  case object F32Max extends SimpleInstr("f32.max", 0x97)
+  case object F32Copysign extends SimpleInstr("f32.copysign", 0x98)
+  case object F64Abs extends SimpleInstr("f64.abs", 0x99)
+  case object F64Neg extends SimpleInstr("f64.neg", 0x9A)
+  case object F64Ceil extends SimpleInstr("f64.ceil", 0x9B)
+  case object F64Floor extends SimpleInstr("f64.floor", 0x9C)
+  case object F64Trunc extends SimpleInstr("f64.trunc", 0x9D)
+  case object F64Nearest extends SimpleInstr("f64.nearest", 0x9E)
+  case object F64Sqrt extends SimpleInstr("f64.sqrt", 0x9F)
+  case object F64Add extends SimpleInstr("f64.add", 0xA0)
+  case object F64Sub extends SimpleInstr("f64.sub", 0xA1)
+  case object F64Mul extends SimpleInstr("f64.mul", 0xA2)
+  case object F64Div extends SimpleInstr("f64.div", 0xA3)
+  case object F64Min extends SimpleInstr("f64.min", 0xA4)
+  case object F64Max extends SimpleInstr("f64.max", 0xA5)
+  case object F64Copysign extends SimpleInstr("f64.copysign", 0xA6)
+  case object I32WrapI64 extends SimpleInstr("i32.wrap_i64", 0xA7)
+  case object I32TruncF32S extends SimpleInstr("i32.trunc_f32_s", 0xA8)
+  case object I32TruncF32U extends SimpleInstr("i32.trunc_f32_u", 0xA9)
+  case object I32TruncF64S extends SimpleInstr("i32.trunc_f64_s", 0xAA)
+  case object I32TruncF64U extends SimpleInstr("i32.trunc_f64_u", 0xAB)
+  case object I64ExtendI32S extends SimpleInstr("i64.extend_i32_s", 0xAC)
+  case object I64ExtendI32U extends SimpleInstr("i64.extend_i32_u", 0xAD)
+  case object I64TruncF32S extends SimpleInstr("i64.trunc_f32_s", 0xAE)
+  case object I64TruncF32U extends SimpleInstr("i64.trunc_f32_u", 0xAF)
+  case object I64TruncF64S extends SimpleInstr("i64.trunc_f64_s", 0xB0)
+  case object I64TruncF64U extends SimpleInstr("i64.trunc_f64_u", 0xB1)
+  case object F32ConvertI32S extends SimpleInstr("f32.convert_i32_s", 0xB2)
+  case object F32ConvertI32U extends SimpleInstr("f32.convert_i32_u", 0xB3)
+  case object F32ConvertI64S extends SimpleInstr("f32.convert_i64_s", 0xB4)
+  case object F32ConvertI64U extends SimpleInstr("f32.convert_i64_u", 0xB5)
+  case object F32DemoteF64 extends SimpleInstr("f32.demote_f64", 0xB6)
+  case object F64ConvertI32S extends SimpleInstr("f64.convert_i32_s", 0xB7)
+  case object F64ConvertI32U extends SimpleInstr("f64.convert_i32_u", 0xB8)
+  case object F64ConvertI64S extends SimpleInstr("f64.convert_i64_s", 0xB9)
+  case object F64ConvertI64U extends SimpleInstr("f64.convert_i64_u", 0xBA)
+  case object F64PromoteF32 extends SimpleInstr("f64.promote_f32", 0xBB)
+  case object I32ReinterpretF32 extends SimpleInstr("i32.reinterpret_f32", 0xBC)
+  case object I64ReinterpretF64 extends SimpleInstr("i64.reinterpret_f64", 0xBD)
+  case object F32ReinterpretI32 extends SimpleInstr("f32.reinterpret_i32", 0xBE)
+  case object F64ReinterpretI64 extends SimpleInstr("f64.reinterpret_i64", 0xBF)
+  case object I32Extend8S extends SimpleInstr("i32.extend8_s", 0xC0)
+  case object I32Extend16S extends SimpleInstr("i32.extend16_s", 0xC1)
+  case object I64Extend8S extends SimpleInstr("i64.extend8_s", 0xC2)
+  case object I64Extend16S extends SimpleInstr("i64.extend16_s", 0xC3)
+  case object I64Extend32S extends SimpleInstr("i64.extend32_s", 0xC4)
+
+  // Generic reference instructions
+
+  final case class RefNull(i: HeapType) extends HeapTypeInstr("ref.null", 0xD0, i)
+  case object RefIsNull extends SimpleInstr("ref.is_null", 0xD1)
+  final case class RefFunc(i: FunctionID) extends FuncInstr("ref.func", 0xD2, i)
+  case object RefEq extends SimpleInstr("ref.eq", 0xD3)
+  case object RefAsNonNull extends SimpleInstr("ref.as_non_null", 0xD4)
+  final case class BrOnNull(i: LabelID) extends LabelInstr("br_on_null", 0xD5, i)
+  final case class BrOnNonNull(i: LabelID) extends LabelInstr("br_on_non_null", 0xD6, i)
+
+  // Struct instructions
+
+  final case class StructNew(i: TypeID) extends TypeInstr("struct.new", 0xFB00, i)
+  final case class StructNewDefault(i: TypeID) extends TypeInstr("struct.new_default", 0xFB01, i)
+  final case class StructGet(tyidx: TypeID, fidx: FieldID)
+      extends StructFieldInstr("struct.get", 0xFB02, tyidx, fidx)
+  final case class StructSet(tyidx: TypeID, fidx: FieldID)
+      extends StructFieldInstr("struct.set", 0xFB05, tyidx, fidx)
+
+  // Array instructions
+
+  final case class ArrayNew(i: TypeID) extends TypeInstr("array.new", 0xFB06, i)
+  final case class ArrayNewDefault(i: TypeID) extends TypeInstr("array.new_default", 0xFB07, i)
+  final case class ArrayNewFixed(i: TypeID, size: Int) extends Instr("array.new_fixed", 0xFB08)
+  final case class ArrayNewData(i: TypeID, d: DataID) extends Instr("array.new_data", 0xFB09)
+  final case class ArrayGet(i: TypeID) extends TypeInstr("array.get", 0xFB0B, i)
+  final case class ArrayGetS(i: TypeID) extends TypeInstr("array.get_s", 0xFB0C, i)
+  final case class ArrayGetU(i: TypeID) extends TypeInstr("array.get_u", 0xFB0D, i)
+  final case class ArraySet(i: TypeID) extends TypeInstr("array.set", 0xFB0E, i)
+  case object ArrayLen extends SimpleInstr("array.len", 0xFB0F)
+  final case class ArrayCopy(destType: TypeID, srcType: TypeID) extends Instr("array.copy", 0xFB11)
+
+  // Extended generic reference instructions
+
+  final case class RefTest(i: RefType) extends RefTypeInstr("ref.test", 0xFB14, 0xFB15, i)
+  final case class RefCast(i: RefType) extends RefTypeInstr("ref.cast", 0xFB16, 0xFB17, i)
+
+  final case class BrOnCast(label: LabelID, from: RefType, to: RefType)
+      extends Instr("br_on_cast", 0xFB18)
+  final case class BrOnCastFail(label: LabelID, from: RefType, to: RefType)
+      extends Instr("br_on_cast_fail", 0xFB19)
+
+  // Instructions for interop between externref's and anyref's
+
+  case object AnyConvertExtern extends SimpleInstr("any.convert_extern", 0xFB1A)
+  case object ExternConvertAny extends SimpleInstr("extern.convert_any", 0xFB1B)
+
+  // i31 reference instructions
+
+  case object RefI31 extends SimpleInstr("ref.i31", 0xFB1C)
+  case object I31GetS extends SimpleInstr("i31.get_s", 0xFB1D)
+  case object I31GetU extends SimpleInstr("i31.get_u", 0xFB1E)
+
+  // Extended operations on primitive types
+
+  case object I32TruncSatF64S extends SimpleInstr("i32.trunc_sat_f64_s", 0xFC02)
+  case object I64TruncSatF64S extends SimpleInstr("i64.trunc_sat_f64_s", 0xFC06)
+
+  // --- End of the instruction list ------------------------------------------
+
+  // Catch clauses for TryTable
+
+  /** Catch clause of a [[TryTable]] instruction. */
+  sealed abstract class CatchClause(
+      val mnemonic: String,
+      val opcode: Int,
+      val tag: Option[TagID],
+      val label: LabelID
+  )
+
+  object CatchClause {
+    final case class Catch(x: TagID, l: LabelID) extends CatchClause("catch", 0x00, Some(x), l)
+    final case class CatchRef(x: TagID, l: LabelID) extends CatchClause("catch_ref", 0x01, Some(x), l)
+    final case class CatchAll(l: LabelID) extends CatchClause("catch_all", 0x02, None, l)
+    final case class CatchAllRef(l: LabelID) extends CatchClause("catch_all_ref", 0x03, None, l)
+  }
+
+  // Block types
+
+  /** A structured instruction can consume input and produce output on the operand stack according
+   *  to its annotated block type.
+   *
+   *  It is given either as a type index that refers to a suitable function type,
+   *  or as an optional value type inline, which is a shorthand for the function type
+   *  `[] -> [valtype]`.
+   *
+   *  @see
+   *    https://webassembly.github.io/spec/core/syntax/instructions.html#control-instructions
+   */
+  sealed abstract class BlockType
+
+  object BlockType {
+    final case class FunctionType(ty: TypeID) extends BlockType
+    final case class ValueType(ty: Option[Type]) extends BlockType
+
+    object ValueType {
+      def apply(ty: Type): ValueType = ValueType(Some(ty))
+      def apply(): ValueType = ValueType(None)
+    }
+  }
+}
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/ModuleBuilder.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/ModuleBuilder.scala
new file mode 100644
index 0000000000..8534ee9331
--- /dev/null
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/ModuleBuilder.scala
@@ -0,0 +1,95 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package org.scalajs.linker.backend.webassembly
+
+import scala.collection.mutable
+
+import org.scalajs.ir.OriginalName
+
+import Identitities._
+import Modules._
+import Types._
+
+final class ModuleBuilder(functionSignatureProvider: ModuleBuilder.FunctionTypeProvider) {
+  import ModuleBuilder._
+
+  /** Items are `RecType | RecTypeBuilder`. */
+  private val types: mutable.ListBuffer[AnyRef] = new mutable.ListBuffer()
+
+  private val imports: mutable.ListBuffer[Import] = new mutable.ListBuffer()
+  private val funcs: mutable.ListBuffer[Function] = new mutable.ListBuffer()
+  private val tags: mutable.ListBuffer[Tag] = new mutable.ListBuffer()
+  private val globals: mutable.ListBuffer[Global] = new mutable.ListBuffer()
+  private val exports: mutable.ListBuffer[Export] = new mutable.ListBuffer()
+  private var start: Option[FunctionID] = None
+  private val elems: mutable.ListBuffer[Element] = new mutable.ListBuffer()
+  private val datas: mutable.ListBuffer[Data] = new mutable.ListBuffer()
+
+  def functionTypeToTypeID(sig: FunctionType): TypeID =
+    functionSignatureProvider.functionTypeToTypeID(sig)
+
+  def addRecType(recType: RecType): Unit = types += recType
+  def addRecType(subType: SubType): Unit = addRecType(RecType(subType))
+
+  def addRecType(id: TypeID, originalName: OriginalName, compositeType: CompositeType): Unit =
+    addRecType(SubType(id, originalName, compositeType))
+
+  def addRecTypeBuilder(recTypeBuilder: RecTypeBuilder): Unit =
+    types += recTypeBuilder
+
+  def addImport(imprt: Import): Unit = imports += imprt
+  def addFunction(function: Function): Unit = funcs += function
+  def addTag(tag: Tag): Unit = tags += tag
+  def addGlobal(global: Global): Unit = globals += global
+  def addExport(exprt: Export): Unit = exports += exprt
+  def setStart(startFunction: FunctionID): Unit = start = Some(startFunction)
+  def addElement(element: Element): Unit = elems += element
+  def addData(data: Data): Unit = datas += data
+
+  def build(): Module = {
+    val builtTypes: List[RecType] = types.toList.map {
+      case tpe: RecType            => tpe
+      case builder: RecTypeBuilder => builder.build()
+    }
+
+    new Module(
+      builtTypes,
+      imports.toList,
+      funcs.toList,
+      tags.toList,
+      globals.toList,
+      exports.toList,
+      start,
+      elems.toList,
+      datas.toList
+    )
+  }
+}
+
+object ModuleBuilder {
+  trait FunctionTypeProvider {
+    def functionTypeToTypeID(sig: FunctionType): TypeID
+  }
+
+  final class RecTypeBuilder {
+    private val subTypes = mutable.ListBuffer.empty[SubType]
+
+    def addSubType(subType: SubType): Unit =
+      subTypes += subType
+
+    def addSubType(id: TypeID, originalName: OriginalName, compositeType: CompositeType): Unit =
+      addSubType(SubType(id, originalName, compositeType))
+
+    def build(): RecType = RecType(subTypes.toList)
+  }
+}
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/Modules.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/Modules.scala
new file mode 100644
index 0000000000..365a3c10fe
--- /dev/null
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/Modules.scala
@@ -0,0 +1,137 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package org.scalajs.linker.backend.webassembly
+
+import org.scalajs.ir.{OriginalName, Position}
+
+import Instructions._
+import Identitities._
+import Types._
+
+/** WebAssembly modules and their structure.
+ *
+ *  @see
+ *    [[https://webassembly.github.io/gc/core/syntax/modules.html]]
+ *
+ *  @see
+ *    For tags:
+ *    [[https://webassembly.github.io/exception-handling/core/syntax/modules.html]]
+ */
+object Modules {
+
+  /** A WebAssembly `import`. */
+  final case class Import(module: String, name: String, desc: ImportDesc)
+
+  /** A WebAssembly `importdesc`. */
+  sealed abstract class ImportDesc
+
+  object ImportDesc {
+    final case class Func(id: FunctionID, originalName: OriginalName, typeID: TypeID)
+        extends ImportDesc
+
+    final case class Global(id: GlobalID, originalName: OriginalName, isMutable: Boolean, tpe: Type)
+        extends ImportDesc
+
+    final case class Tag(id: TagID, originalName: OriginalName, typeID: TypeID) extends ImportDesc
+  }
+
+  /** A WebAssembly `func`, including names/types for parameters, locals and results.
+   *
+   *  @note
+   *    The `params`' types and the `results` are not strictly necessary, as
+   *    they can be derived from the `typeID` by resolving it to a function
+   *    type. The binary writer ignores them. They are used by the text writer.
+   */
+  final case class Function(
+      id: FunctionID,
+      originalName: OriginalName,
+      typeID: TypeID,
+      params: List[Local],
+      results: List[Type],
+      locals: List[Local],
+      body: Expr,
+      pos: Position
+  )
+
+  /** A local variable declaration within a `Function`. */
+  final case class Local(id: LocalID, originalName: OriginalName, tpe: Type)
+
+  /** A WebAssembly `tag` definition. */
+  final case class Tag(id: TagID, originalName: OriginalName, typeID: TypeID)
+
+  /** A WebAssembly `global` definition. */
+  final case class Global(
+      id: GlobalID,
+      originalName: OriginalName,
+      isMutable: Boolean,
+      tpe: Type,
+      init: Expr
+  )
+
+  /** A WebAssembly `export`.
+   *
+   *  @note
+   *    We do not use any `export` in our current compilation scheme.
+   *    However, we used them in the past and we will likely reuse them in the
+   *    future (notably for module splitting). Therefore, we keep them in the
+   *    codebase not to lose the work done in implementing them.
+   */
+  final case class Export(name: String, desc: ExportDesc)
+
+  /** A WebAssembly `exportdesc`. */
+  sealed abstract class ExportDesc
+
+  object ExportDesc {
+    final case class Func(id: FunctionID) extends ExportDesc
+    final case class Global(id: GlobalID) extends ExportDesc
+  }
+
+  /** A WebAssembly `elem` definition. */
+  final case class Element(tpe: Type, init: List[Expr], mode: Element.Mode)
+
+  object Element {
+    sealed abstract class Mode
+
+    object Mode {
+      case object Declarative extends Mode
+    }
+  }
+
+  /** A WebAssembly `data` segment definition. */
+  final case class Data(id: DataID, originalName: OriginalName, bytes: Array[Byte], mode: Data.Mode)
+
+  object Data {
+    sealed abstract class Mode
+
+    object Mode {
+      case object Passive extends Mode
+    }
+  }
+
+  /** A WebAssembly `module`.
+   *
+   *  Fields are declared in the order of the binary format:
+   *  [[https://webassembly.github.io/gc/core/binary/modules.html#sections]]
+   */
+  final class Module(
+      val types: List[RecType],
+      val imports: List[Import],
+      val funcs: List[Function],
+      val tags: List[Tag],
+      val globals: List[Global],
+      val exports: List[Export],
+      val start: Option[FunctionID],
+      val elems: List[Element],
+      val datas: List[Data]
+  )
+}
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/TextWriter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/TextWriter.scala
new file mode 100644
index 0000000000..704524c49b
--- /dev/null
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/TextWriter.scala
@@ -0,0 +1,620 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package org.scalajs.linker.backend.webassembly
+
+import scala.collection.mutable
+
+import org.scalajs.ir.OriginalName
+import org.scalajs.ir.OriginalName.NoOriginalName
+
+import Instructions._
+import Identitities._
+import Modules._
+import Types._
+
+private class TextWriter(module: Module) {
+  import TextWriter._
+
+  private val b = new WatBuilder()
+
+  private val typeNames: Map[TypeID, String] = {
+    val nameGen = new FreshNameGenerator
+    module.types.flatMap(_.subTypes).map(st => st.id -> nameGen.genName(st.originalName)).toMap
+  }
+
+  private val dataNames: Map[DataID, String] = {
+    val nameGen = new FreshNameGenerator
+    module.datas.map(data => data.id -> nameGen.genName(data.originalName)).toMap
+  }
+
+  private val funcNames: Map[FunctionID, String] = {
+    val nameGen = new FreshNameGenerator
+    val importedFunctionNames = module.imports.collect {
+      case Import(_, _, ImportDesc.Func(id, origName, _)) => id -> nameGen.genName(origName)
+    }
+    val definedFunctionNames = module.funcs.map(f => f.id -> nameGen.genName(f.originalName))
+    (importedFunctionNames ::: definedFunctionNames).toMap
+  }
+
+  private val tagNames: Map[TagID, String] = {
+    val nameGen = new FreshNameGenerator
+    val importedTagNames = module.imports.collect {
+      case Import(_, _, ImportDesc.Tag(id, origName, _)) =>
+        id -> nameGen.genName(origName)
+    }
+    val definedTagNames = module.tags.map(t => t.id -> nameGen.genName(t.originalName))
+    (importedTagNames ::: definedTagNames).toMap
+  }
+
+  private val globalNames: Map[GlobalID, String] = {
+    val nameGen = new FreshNameGenerator
+    val importedGlobalNames = module.imports.collect {
+      case Import(_, _, ImportDesc.Global(id, origName, _, _)) => id -> nameGen.genName(origName)
+    }
+    val definedGlobalNames = module.globals.map(g => g.id -> nameGen.genName(g.originalName))
+    (importedGlobalNames ::: definedGlobalNames).toMap
+  }
+
+  private val fieldNames: Map[TypeID, Map[FieldID, String]] = {
+    (for {
+      recType <- module.types
+      SubType(typeID, _, _, _, StructType(fields)) <- recType.subTypes
+    } yield {
+      val nameGen = new FreshNameGenerator
+      typeID -> fields.map(f => f.id -> nameGen.genName(f.originalName)).toMap
+    }).toMap
+  }
+
+  private var localNames: Option[Map[LocalID, String]] = None
+  private var labelNames: Option[mutable.Map[LabelID, String]] = None
+  private var labelNameGen: Option[FreshNameGenerator] = None
+
+  def write(): String = {
+    b.topLevel("module") {
+      module.types.foreach(writeRecType)
+      module.imports.foreach(writeImport)
+      module.funcs.foreach(writeFunction)
+      module.tags.foreach(writeTag)
+      module.globals.foreach(writeGlobal)
+      module.exports.foreach(writeExport)
+      module.start.foreach(writeStart)
+      module.elems.foreach(writeElement)
+      module.datas.foreach(writeData)
+    }
+
+    b.toString()
+  }
+
+  private def appendName(typeID: TypeID): Unit =
+    b.appendElement(typeNames(typeID))
+
+  private def appendName(dataID: DataID): Unit =
+    b.appendElement(dataNames(dataID))
+
+  private def appendName(functionID: FunctionID): Unit =
+    b.appendElement(funcNames(functionID))
+
+  private def appendName(tagID: TagID): Unit =
+    b.appendElement(tagNames(tagID))
+
+  private def appendName(globalID: GlobalID): Unit =
+    b.appendElement(globalNames(globalID))
+
+  private def appendName(typeID: TypeID, fieldID: FieldID): Unit =
+    b.appendElement(fieldNames(typeID)(fieldID))
+
+  private def appendName(localID: LocalID): Unit =
+    b.appendElement(localNames.get(localID))
+
+  private def appendName(labelID: LabelID): Unit =
+    b.appendElement(labelNames.get(labelID))
+
+  private def writeRecType(recType: RecType): Unit = {
+    val RecType(subTypes) = recType
+
+    subTypes match {
+      case singleSubType :: Nil =>
+        writeTypeDefinition(singleSubType)
+      case subTypes =>
+        b.newLineList("rec") {
+          subTypes.foreach(writeTypeDefinition)
+        }
+    }
+  }
+
+  private def writeTypeDefinition(subType: SubType): Unit = {
+    val SubType(id, _, isFinal, superType, compositeType) = subType
+
+    b.newLineList("type") {
+      appendName(id)
+      subType match {
+        case SubType(_, _, true, None, _) =>
+          writeCompositeType(id, compositeType)
+        case _ =>
+          b.sameLineList("sub") {
+            if (subType.isFinal)
+              b.appendElement("final")
+            superType.foreach(appendName(_))
+            writeCompositeType(id, compositeType)
+          }
+      }
+    }
+  }
+
+  private def writeCompositeType(typeID: TypeID, t: CompositeType): Unit = {
+    def writeFieldType(fieldType: FieldType): Unit = {
+      val FieldType(tpe, isMutable) = fieldType
+
+      if (isMutable) {
+        b.sameLineList("mut") {
+          writeType(tpe)
+        }
+      } else {
+        writeType(tpe)
+      }
+    }
+
+    def writeField(field: StructField): Unit = {
+      val StructField(id, _, fieldType) = field
+
+      b.sameLineList("field") {
+        appendName(typeID, id)
+        writeFieldType(fieldType)
+      }
+    }
+
+    t match {
+      case FunctionType(params, results) =>
+        b.sameLineList("func") {
+          params.foreach { ty =>
+            b.sameLineList("param")(writeType(ty))
+          }
+          results.foreach { ty =>
+            b.sameLineList("result")(writeType(ty))
+          }
+        }
+
+      case ArrayType(fieldType) =>
+        b.sameLineList("array") {
+          writeFieldType(fieldType)
+        }
+
+      case StructType(fields) =>
+        b.sameLineList("struct") {
+          fields.foreach(writeField)
+        }
+    }
+  }
+
+  private def writeImport(i: Import): Unit = {
+    val Import(module, name, desc) = i
+
+    b.newLineList("import") {
+      b.appendStringElement(module)
+      b.appendStringElement(name)
+
+      desc match {
+        case ImportDesc.Func(id, _, typeID) =>
+          b.sameLineList("func") {
+            appendName(id)
+            writeTypeUse(typeID)
+          }
+        case ImportDesc.Global(id, _, isMutable, tpe) =>
+          b.sameLineList("global") {
+            appendName(id)
+            if (isMutable)
+              b.sameLineList("mut")(writeType(tpe))
+            else
+              writeType(tpe)
+          }
+        case ImportDesc.Tag(id, _, typeID) =>
+          b.sameLineList("tag") {
+            appendName(id)
+            writeTypeUse(typeID)
+          }
+      }
+    }
+  }
+
+  private def writeFunction(f: Function): Unit = {
+    def writeParam(l: Local): Unit = {
+      b.sameLineList("param") {
+        appendName(l.id)
+        writeType(l.tpe)
+      }
+    }
+
+    def writeLocal(l: Local): Unit = {
+      b.sameLineList("local") {
+        appendName(l.id)
+        writeType(l.tpe)
+      }
+    }
+
+    val Function(id, _, typeID, params, results, locals, body, _) = f
+
+    localNames = {
+      val nameGen = new FreshNameGenerator
+      Some((params ::: locals).map(l => l.id -> nameGen.genName(l.originalName)).toMap)
+    }
+    labelNames = Some(mutable.HashMap.empty)
+    labelNameGen = Some(new FreshNameGenerator)
+
+    b.newLineList("func") {
+      appendName(id)
+      writeTypeUse(typeID)
+
+      b.newLine()
+      params.foreach(writeParam)
+      results.foreach(r => b.sameLineList("result")(writeType(r)))
+
+      b.newLine()
+      locals.foreach(writeLocal)
+      writeExpr(body)
+    }
+
+    localNames = None
+    labelNames = None
+    labelNameGen = None
+  }
+
+  private def writeTag(tag: Tag): Unit = {
+    val Tag(id, _, typeID) = tag
+
+    b.newLineList("tag") {
+      appendName(id)
+      writeTypeUse(typeID)
+    }
+  }
+
+  private def writeGlobal(g: Global): Unit = {
+    val Global(id, _, isMutable, tpe, init) = g
+
+    b.newLineList("global") {
+      appendName(id)
+      if (isMutable)
+        b.sameLineList("mut")(writeType(tpe))
+      else
+        writeType(tpe)
+      writeExpr(init)
+    }
+  }
+
+  private def writeExport(e: Export): Unit = {
+    val Export(name, desc) = e
+
+    b.newLineList("export") {
+      b.appendStringElement(name)
+      desc match {
+        case ExportDesc.Func(id) =>
+          b.sameLineList("func") {
+            appendName(id)
+          }
+        case ExportDesc.Global(id) =>
+          b.sameLineList("global") {
+            appendName(id)
+          }
+      }
+    }
+  }
+
+  private def writeStart(startFunction: FunctionID): Unit = {
+    b.newLineList("start") {
+      appendName(startFunction)
+    }
+  }
+
+  private def writeElement(element: Element): Unit = {
+    val Element(tpe, init, mode) = element
+
+    b.newLineList("elem") {
+      mode match {
+        case Element.Mode.Declarative => b.appendElement("declare")
+      }
+      writeType(tpe)
+      init.foreach { item =>
+        b.newLineList("item") {
+          writeExpr(item)
+        }
+      }
+    }
+  }
+
+  private def writeData(data: Data): Unit = {
+    val Data(id, _, bytes, mode) = data
+
+    b.newLineList("data") {
+      appendName(id)
+      mode match {
+        case Data.Mode.Passive =>
+          // do nothing
+      }
+      b.appendElement("\"" + bytes.map("\\%02x".format(_)).mkString + "\"")
+    }
+  }
+
+  /** Writes a `typeuse`.
+   *
+   *  @see
+   *    [[https://webassembly.github.io/gc/core/text/modules.html#type-uses]]
+   */
+  private def writeTypeUse(typeID: TypeID): Unit = {
+    b.sameLineList("type")(appendName(typeID))
+  }
+
+  private def writeType(tpe: StorageType): Unit = {
+    tpe match {
+      case tpe: SimpleType => b.appendElement(tpe.textName)
+      case tpe: PackedType => b.appendElement(tpe.textName)
+
+      case RefType(true, heapType: HeapType.AbsHeapType) =>
+        b.appendElement(heapType.nullableRefTextName)
+
+      case RefType(nullable, heapType) =>
+        b.sameLineList("ref") {
+          if (nullable)
+            b.appendElement("null")
+          writeHeapType(heapType)
+        }
+    }
+  }
+
+  private def writeHeapType(heapType: HeapType): Unit = {
+    heapType match {
+      case HeapType.Type(typeID)          => appendName(typeID)
+      case heapType: HeapType.AbsHeapType => b.appendElement(heapType.textName)
+    }
+  }
+
+  private def writeFloatString(v: Double): Unit = {
+    val stringRepr = {
+      if (v.isNaN()) "nan"
+      else if (v == Double.PositiveInfinity) "inf"
+      else if (v == Double.NegativeInfinity) "-inf"
+      else if (v.equals(-0.0)) "-0.0"
+      else v.toString()
+    }
+    b.appendElement(stringRepr)
+  }
+
+  private def writeBlockType(blockType: BlockType): Unit = {
+    blockType match {
+      case BlockType.FunctionType(typeID) =>
+        writeTypeUse(typeID)
+      case BlockType.ValueType(None) =>
+        // do nothing
+      case BlockType.ValueType(Some(tpe)) =>
+        b.sameLineList("result")(writeType(tpe))
+    }
+  }
+
+  private def writeExpr(expr: Expr): Unit = {
+    val Expr(instrs) = expr
+
+    instrs.foreach(writeInstr(_))
+  }
+
+  private def writeInstr(instr: Instr): Unit = {
+    instr match {
+      case PositionMark(_) =>
+        // ignore
+
+      case _ =>
+        instr match {
+          case End | Else | _: Catch => b.deindent()
+          case _                     => // do nothing
+        }
+        b.newLine()
+        b.appendElement(instr.mnemonic)
+        instr match {
+          case instr: StructuredLabeledInstr =>
+            for (label <- instr.label) {
+              labelNames.get += label -> labelNameGen.get.genName(NoOriginalName)
+              appendName(label)
+            }
+          case _ =>
+            // do nothing
+        }
+
+        writeInstrImmediates(instr)
+
+        instr match {
+          case _: StructuredLabeledInstr | Else | _: Catch => b.indent()
+          case _                                           => // do nothing
+        }
+    }
+  }
+
+  private def writeInstrImmediates(instr: Instr): Unit = {
+    instr match {
+      // Convenience categories
+
+      case instr: SimpleInstr =>
+        // do nothing
+      case instr: BlockTypeLabeledInstr =>
+        writeBlockType(instr.blockTypeArgument)
+      case instr: LabelInstr =>
+        appendName(instr.labelArgument)
+      case instr: FuncInstr =>
+        appendName(instr.funcArgument)
+      case instr: TypeInstr =>
+        appendName(instr.typeArgument)
+      case instr: TagInstr =>
+        appendName(instr.tagArgument)
+      case instr: LocalInstr =>
+        appendName(instr.localArgument)
+      case instr: GlobalInstr =>
+        appendName(instr.globalArgument)
+      case instr: HeapTypeInstr =>
+        writeHeapType(instr.heapTypeArgument)
+      case instr: RefTypeInstr =>
+        writeType(instr.refTypeArgument)
+      case instr: StructFieldInstr =>
+        appendName(instr.structTypeID)
+        appendName(instr.structTypeID, instr.fieldID)
+
+      // Specific instructions with unique-ish shapes
+
+      case I32Const(v) => b.appendElement(v.toString())
+      case I64Const(v) => b.appendElement(v.toString())
+      case F32Const(v) => writeFloatString(v.toDouble)
+      case F64Const(v) => writeFloatString(v)
+
+      case BrTable(labelIdxVector, defaultLabelIdx) =>
+        labelIdxVector.foreach(appendName(_))
+        appendName(defaultLabelIdx)
+
+      case TryTable(blockType, clauses, _) =>
+        writeBlockType(blockType)
+        for (clause <- clauses) {
+          b.sameLineList(clause.mnemonic) {
+            clause.tag.foreach(tag => appendName(tag))
+            appendName(clause.label)
+          }
+        }
+
+      case ArrayNewData(typeIdx, dataIdx) =>
+        appendName(typeIdx)
+        appendName(dataIdx)
+
+      case ArrayNewFixed(typeIdx, length) =>
+        appendName(typeIdx)
+        b.appendElement(Integer.toUnsignedString(length))
+
+      case ArrayCopy(destType, srcType) =>
+        appendName(destType)
+        appendName(srcType)
+
+      case BrOnCast(labelIdx, from, to) =>
+        appendName(labelIdx)
+        writeType(from)
+        writeType(to)
+      case BrOnCastFail(labelIdx, from, to) =>
+        appendName(labelIdx)
+        writeType(from)
+        writeType(to)
+
+      case PositionMark(_) =>
+        throw new AssertionError(s"Unexpected $instr")
+    }
+  }
+}
+
+object TextWriter {
+  def write(module: Module): String =
+    new TextWriter(module).write()
+
+  private class FreshNameGenerator {
+    private val generated = mutable.HashSet.empty[String]
+
+    def genName(originalName: OriginalName): String = {
+      val base =
+        if (originalName.isDefined) "$" + sanitizeWatIdentifier(originalName.get.toString())
+        else "$"
+      if (originalName.isDefined && generated.add(base)) {
+        base
+      } else {
+        var index = 1
+        while (!generated.add(base + index))
+          index += 1
+        base + index
+      }
+    }
+  }
+
+  private class WatBuilder {
+    private val builder = new StringBuilder
+    private var level = 0
+    private val indentStr = "  "
+
+    private def indented(body: => Unit): Unit = {
+      indent()
+      body
+      deindent()
+    }
+
+    def indent(): Unit = level += 1
+    def deindent(): Unit = level -= 1
+
+    def newLine(): Unit = {
+      builder.append("\n")
+      builder.append(indentStr * level)
+    }
+
+    def topLevel(name: String)(body: => Unit): Unit = {
+      builder.append(s"($name")
+      indented(body)
+      builder.append(")")
+      newLine()
+    }
+
+    def newLineList(name: String)(body: => Unit): Unit = {
+      newLine()
+      builder.append(s"($name")
+      indented(body)
+      builder.append(")")
+    }
+
+    def sameLineList(name: String)(body: => Unit): Unit = {
+      builder.append(s" ($name")
+      body
+      builder.append(")")
+    }
+
+    def sameLineListOne(name: String)(value: String): Unit =
+      sameLineList(name)(appendElement(value))
+
+    def appendElement(value: String): Unit = {
+      builder.append(" ")
+      builder.append(value)
+    }
+
+    /** Appends a `string` element.
+     *
+     *  @see
+     *    [[https://webassembly.github.io/gc/core/text/values.html#strings]]
+     */
+    def appendStringElement(str: String): Unit = {
+      builder.append(" \"")
+      val len = str.length()
+      var i = 0
+      while (i != len) {
+        str.charAt(i) match {
+          case '"'                        => builder.append("\\\"")
+          case '\\'                       => builder.append("\\\\")
+          case c if c < 0x20 || c == 0x7f => builder.append("\\%02x".format(c))
+          case c                          => builder.append(c)
+        }
+        i += 1
+      }
+      builder.append("\"")
+    }
+
+    override def toString: String =
+      builder.toString()
+  }
+
+  /** @see https://webassembly.github.io/spec/core/text/values.html#text-id */
+  private def sanitizeWatIdentifier(name: String): String = {
+    if (name.isEmpty) "_"
+    else if (name.forall(isValidWatIdentifierChar)) name
+    else name.map(c => if (isValidWatIdentifierChar(c)) c else '_').mkString
+  }
+
+  private def isValidWatIdentifierChar(c: Char): Boolean = {
+    c.isDigit || c.isLetter ||
+    "!#$%&'*+-./:<=>?@\\^_`|~".contains(c) ||
+    "$.@_".contains(c)
+  }
+
+}
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/Types.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/Types.scala
new file mode 100644
index 0000000000..db8f4a0e83
--- /dev/null
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/Types.scala
@@ -0,0 +1,187 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package org.scalajs.linker.backend.webassembly
+
+import org.scalajs.ir.OriginalName
+
+import Identitities._
+
+/** WebAssembly types.
+ *
+ *  @see
+ *    [[https://webassembly.github.io/gc/core/syntax/types.html]]
+ */
+object Types {
+
+  /** A WebAssembly `storagetype`. */
+  sealed trait StorageType
+
+  /** A WebAssembly `valtype`.
+   *
+   *  We call it `Type` because it matches the concept of `Type` in the
+   *  Scala.js IR. It is the type of a term, from an "execution semantic
+   *  typing" point of view. It is also the kind of type we manipulate the most
+   *  across the backend, so it also makes sense for it to be the "default".
+   */
+  sealed abstract class Type extends StorageType
+
+  /** Convenience superclass for `Type`s that are encoded with a simple opcode. */
+  sealed abstract class SimpleType(val textName: String, val binaryCode: Byte) extends Type
+
+  case object Int32 extends SimpleType("i32", 0x7F)
+  case object Int64 extends SimpleType("i64", 0x7E)
+  case object Float32 extends SimpleType("f32", 0x7D)
+  case object Float64 extends SimpleType("f64", 0x7C)
+
+  /** A WebAssembly `packedtype`. */
+  sealed abstract class PackedType(val textName: String, val binaryCode: Byte) extends StorageType
+
+  case object Int8 extends PackedType("i8", 0x78)
+  case object Int16 extends PackedType("i16", 0x77)
+
+  /** A WebAssembly `reftype`. */
+  final case class RefType(nullable: Boolean, heapType: HeapType) extends Type {
+    def toNullable: RefType = RefType(true, heapType)
+    def toNonNullable: RefType = RefType(false, heapType)
+  }
+
+  object RefType {
+
+    /** Builds a non-nullable `(ref heapType)` for the given `heapType`. */
+    def apply(heapType: HeapType): RefType = RefType(false, heapType)
+
+    /** Builds a non-nullable `(ref typeID)` for the given `typeID`. */
+    def apply(typeID: TypeID): RefType = apply(HeapType(typeID))
+
+    /** Builds a nullable `(ref null heapType)` for the given `heapType`. */
+    def nullable(heapType: HeapType): RefType = RefType(true, heapType)
+
+    /** Builds a nullable `(ref null typeID)` for the given `typeID`. */
+    def nullable(typeID: TypeID): RefType = nullable(HeapType(typeID))
+
+    /** `(ref any)`. */
+    val any: RefType = apply(HeapType.Any)
+
+    /** `(ref null any)`, i.e., `anyref`. */
+    val anyref: RefType = nullable(HeapType.Any)
+
+    /** `(ref func)`. */
+    val func: RefType = apply(HeapType.Func)
+
+    /** `(ref null func)`, i.e., `funcref`. */
+    val funcref: RefType = nullable(HeapType.Func)
+
+    /** `(ref extern)`. */
+    val extern: RefType = apply(HeapType.Extern)
+
+    /** `(ref null extern)`, i.e., `externref`. */
+    val externref: RefType = nullable(HeapType.Extern)
+
+    /** `(ref null exn)`, i.e., `exnref`. */
+    val exnref: RefType = nullable(HeapType.Exn)
+
+    /** `(ref null none)`, i.e., `nullref`. */
+    val nullref: RefType = nullable(HeapType.None)
+  }
+
+  /** A WebAssembly `heaptype`. */
+  sealed abstract class HeapType
+
+  object HeapType {
+
+    /** Reference to a named composite type. */
+    final case class Type(typeID: TypeID) extends HeapType
+
+    /** A WebAssembly `absheaptype`. */
+    sealed abstract class AbsHeapType(val textName: String,
+        val nullableRefTextName: String, val binaryCode: Byte)
+        extends HeapType
+
+    // Ordered by decreasing value of opcodes -- matches the order in the binary format
+
+    case object NoExn extends AbsHeapType("noexn", "nullexnref", 0x74)
+    case object NoFunc extends AbsHeapType("nofunc", "nullfuncref", 0x73)
+    case object NoExtern extends AbsHeapType("noextern", "nullexternref", 0x72)
+    case object None extends AbsHeapType("none", "nullref", 0x71)
+    case object Func extends AbsHeapType("func", "funcref", 0x70)
+    case object Extern extends AbsHeapType("extern", "externref", 0x6F)
+    case object Any extends AbsHeapType("any", "anyref", 0x6E)
+    case object Eq extends AbsHeapType("eq", "eqref", 0x6D)
+    case object Struct extends AbsHeapType("struct", "structref", 0x6B)
+    case object Array extends AbsHeapType("array", "arrayref", 0x6A)
+    case object Exn extends AbsHeapType("exn", "exnref", 0x69)
+
+    def apply(typeID: TypeID): HeapType.Type =
+      HeapType.Type(typeID)
+  }
+
+  /** A WebAssembly `rectype`. */
+  final case class RecType(subTypes: List[SubType])
+
+  object RecType {
+
+    /** Builds a `rectype` with a single `subtype`. */
+    def apply(singleSubType: SubType): RecType =
+      RecType(singleSubType :: Nil)
+  }
+
+  /** A WebAssembly `subtype` with an associated name.
+   *
+   *  It has the form `sub isFinal? superType* compositeType` in the spec.
+   *  There is an additional constraint that `superType` can contain at most
+   *  one element, which we why we store it as an `Option`.
+   */
+  final case class SubType(
+      id: TypeID,
+      originalName: OriginalName,
+      isFinal: Boolean,
+      superType: Option[TypeID],
+      compositeType: CompositeType
+  )
+
+  object SubType {
+
+    /** Builds a `subtype` that is `final` and without any super type. */
+    def apply(id: TypeID, originalName: OriginalName, compositeType: CompositeType): SubType =
+      SubType(id, originalName, isFinal = true, superType = None, compositeType)
+  }
+
+  /** A WebAssembly `comptype`. */
+  sealed abstract class CompositeType
+
+  /** A WebAssembly `functype`. */
+  final case class FunctionType(params: List[Type], results: List[Type]) extends CompositeType
+
+  object FunctionType {
+    val NilToNil: FunctionType = FunctionType(Nil, Nil)
+  }
+
+  /** A WebAssembly `structtype` with associated field names. */
+  final case class StructType(fields: List[StructField]) extends CompositeType
+
+  /** A member of a `StructType`, with a field name and a WebAssembly `fieldtype`. */
+  final case class StructField(id: FieldID, originalName: OriginalName, fieldType: FieldType)
+
+  /** A WebAssembly `arraytype`. */
+  final case class ArrayType(fieldType: FieldType) extends CompositeType
+
+  /** A WebAssembly `fieldtype`. */
+  final case class FieldType(tpe: StorageType, isMutable: Boolean)
+
+  object StructField {
+    def apply(id: FieldID, originalName: OriginalName, tpe: StorageType,
+        isMutable: Boolean): StructField = {
+      StructField(id, originalName, FieldType(tpe, isMutable))
+    }
+  }
+}
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/standard/StandardLinkerBackend.scala b/linker/shared/src/main/scala/org/scalajs/linker/standard/StandardLinkerBackend.scala
index ff27b8452f..369f233847 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/standard/StandardLinkerBackend.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/standard/StandardLinkerBackend.scala
@@ -27,6 +27,7 @@ object StandardLinkerBackend {
       .withClosureCompilerIfAvailable(config.closureCompilerIfAvailable)
       .withPrettyPrint(config.prettyPrint)
       .withMaxConcurrentWrites(config.maxConcurrentWrites)
+      .withExperimentalUseWebAssembly(config.experimentalUseWebAssembly)
 
     LinkerBackendImpl(backendConfig)
   }
diff --git a/project/Build.scala b/project/Build.scala
index 57cb5d0b12..29db017cac 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -55,6 +55,8 @@ object ExposedValues extends AutoPlugin {
 
     val enableMinifyEverywhere: SettingKey[Boolean] =
       settingKey("force usage of the `minify` option of the linker in all contexts (fast and full)")
+    val enableWasmEverywhere: SettingKey[Boolean] =
+      settingKey("enable the WebAssembly backend everywhere, including additional required linker config")
 
     // set scalaJSLinkerConfig in someProject ~= makeCompliant
     val makeCompliant: StandardConfig => StandardConfig = {
@@ -105,7 +107,7 @@ object ExposedValues extends AutoPlugin {
   }
 }
 
-import ExposedValues.autoImport.enableMinifyEverywhere
+import ExposedValues.autoImport.{enableMinifyEverywhere, enableWasmEverywhere}
 
 final case class ExpectedSizes(fastLink: Range, fullLink: Range,
     fastLinkGz: Range, fullLinkGz: Range)
@@ -150,11 +152,32 @@ object MyScalaJSPlugin extends AutoPlugin {
   override def globalSettings: Seq[Setting[_]] = Def.settings(
       // can be overridden with a 'set' command
       enableMinifyEverywhere := false,
+      enableWasmEverywhere := false,
 
       scalaJSLinkerConfig := {
-        scalaJSLinkerConfig.value
+        val baseConfig = scalaJSLinkerConfig.value
           .withCheckIR(true)
           .withMinify(enableMinifyEverywhere.value)
+
+        if (enableWasmEverywhere.value) {
+          import CheckedBehavior.Unchecked
+          baseConfig
+            .withExperimentalUseWebAssembly(true)
+            .withOptimizer(false)
+            .withModuleKind(ModuleKind.ESModule)
+            .withSemantics { sems =>
+              sems
+                .withAsInstanceOfs(Unchecked)
+                .withArrayIndexOutOfBounds(Unchecked)
+                .withArrayStores(Unchecked)
+                .withNegativeArraySizes(Unchecked)
+                .withNullPointers(Unchecked)
+                .withStringIndexOutOfBounds(Unchecked)
+                .withModuleInit(Unchecked)
+            }
+        } else {
+          baseConfig
+        }
       },
 
       fullClasspath in scalaJSLinkerImpl := {
@@ -233,8 +256,22 @@ object MyScalaJSPlugin extends AutoPlugin {
           prev
       },
 
-      jsEnv := new NodeJSEnv(
-          NodeJSEnv.Config().withSourceMap(wantSourceMaps.value)),
+      jsEnv := {
+        val baseConfig = NodeJSEnv.Config().withSourceMap(wantSourceMaps.value)
+        val config = if (enableWasmEverywhere.value) {
+          baseConfig.withArgs(List(
+            "--experimental-wasm-exnref",
+            /* Force using the Turboshaft infrastructure for the optimizing compiler.
+             * It appears to be more stable for the Wasm that we throw at it.
+             * If you remove it, try running `scalaTestSuite2_13/test` with Wasm.
+             */
+            "--turboshaft-wasm",
+          ))
+        } else {
+          baseConfig
+        }
+        new NodeJSEnv(config)
+      },
 
       jsEnvInput in Compile :=
         (jsEnvInput in Compile).dependsOn(writePackageJSON).value,
@@ -2233,6 +2270,7 @@ object Build {
         val esVersion = linkerConfig.esFeatures.esVersion
         val moduleKind = linkerConfig.moduleKind
         val hasModules = moduleKind != ModuleKind.NoModule
+        val isWebAssembly = linkerConfig.experimentalUseWebAssembly
 
         collectionsEraDependentDirectory(scalaV, testDir) ::
         includeIf(testDir / "require-new-target",
@@ -2244,9 +2282,9 @@ object Build {
         includeIf(testDir / "require-no-modules",
             !hasModules) :::
         includeIf(testDir / "require-multi-modules",
-            hasModules && !linkerConfig.closureCompiler) :::
+            hasModules && !linkerConfig.closureCompiler && !isWebAssembly) :::
         includeIf(testDir / "require-dynamic-import",
-            moduleKind == ModuleKind.ESModule) ::: // this is an approximation that works for now
+            moduleKind == ModuleKind.ESModule && !isWebAssembly) ::: // this is an approximation that works for now
         includeIf(testDir / "require-esmodule",
             moduleKind == ModuleKind.ESModule) :::
         includeIf(testDir / "require-commonjs",
@@ -2313,6 +2351,7 @@ object Build {
           "productionMode" -> sems.productionMode,
           "esVersion" -> linkerConfig.esFeatures.esVersion.edition,
           "useECMAScript2015Semantics" -> linkerConfig.esFeatures.useECMAScript2015Semantics,
+          "isWebAssembly" -> linkerConfig.experimentalUseWebAssembly,
         )
       },
 
diff --git a/test-suite-ex/shared/src/test/scala/org/scalajs/testsuite/javalib/lang/ClassTestEx.scala b/test-suite-ex/shared/src/test/scala/org/scalajs/testsuite/javalib/lang/ClassTestEx.scala
index 8458479188..9174f1fee8 100644
--- a/test-suite-ex/shared/src/test/scala/org/scalajs/testsuite/javalib/lang/ClassTestEx.scala
+++ b/test-suite-ex/shared/src/test/scala/org/scalajs/testsuite/javalib/lang/ClassTestEx.scala
@@ -14,6 +14,9 @@ package org.scalajs.testsuite.javalib.lang
 
 import org.junit.Test
 import org.junit.Assert._
+import org.junit.Assume._
+
+import org.scalajs.testsuite.utils.Platform._
 
 class ClassTestEx {
   import ClassTestEx._
@@ -26,6 +29,8 @@ class ClassTestEx {
    *  pollute the whole test suite with those.
    */
   @Test def getSuperclass(): Unit = {
+    assumeFalse("Not implemented yet on WebAssembly", executingInWebAssembly)
+
     def test(parent: Class[_], child: Class[_]): Unit =
       assertSame(parent, child.getSuperclass())
 
@@ -47,6 +52,8 @@ class ClassTestEx {
   }
 
   @Test def getSuperclassWhenParentClassDataIsNotDirectlyAccessed_Issue1489(): Unit = {
+    assumeFalse("Not implemented yet on WebAssembly", executingInWebAssembly)
+
     assertEquals("org.scalajs.testsuite.javalib.lang.ClassTestEx$ParentClassWhoseDataIsNotAccessedDirectly",
         classOf[ChildClassWhoseDataIsAccessedDirectly].getSuperclass.getName)
   }
diff --git a/test-suite/js/src/main/scala/org/scalajs/testsuite/utils/Platform.scala b/test-suite/js/src/main/scala/org/scalajs/testsuite/utils/Platform.scala
index ac1c4132b3..97ad78c948 100644
--- a/test-suite/js/src/main/scala/org/scalajs/testsuite/utils/Platform.scala
+++ b/test-suite/js/src/main/scala/org/scalajs/testsuite/utils/Platform.scala
@@ -36,6 +36,8 @@ object Platform {
 
   final val executingInJVMOnLowerThanJDK17 = false
 
+  def executingInWebAssembly: Boolean = BuildInfo.isWebAssembly
+
   def executingInNodeJS: Boolean = {
     js.typeOf(js.Dynamic.global.process) != "undefined" &&
     !js.isUndefined(js.Dynamic.global.process.release) &&
diff --git a/test-suite/js/src/test/resources/SourceMapTestTemplate.scala b/test-suite/js/src/test/resources/SourceMapTestTemplate.scala
index ef9768eea2..41039449a4 100644
--- a/test-suite/js/src/test/resources/SourceMapTestTemplate.scala
+++ b/test-suite/js/src/test/resources/SourceMapTestTemplate.scala
@@ -47,6 +47,7 @@ case class TestException(lineNo: Int) extends Exception
 object SourceMapTest {
   @BeforeClass def beforeClass(): Unit = {
     assumeTrue("Assumed source-maps", sourceMaps)
+    assumeFalse("Not good enough on WebAssembly yet", executingInWebAssembly)
   }
 }
 
diff --git a/test-suite/js/src/test/scala/org/scalajs/testsuite/compiler/RuntimeTypeTestsJSTest.scala b/test-suite/js/src/test/scala/org/scalajs/testsuite/compiler/RuntimeTypeTestsJSTest.scala
index ac489636a4..c9285439c9 100644
--- a/test-suite/js/src/test/scala/org/scalajs/testsuite/compiler/RuntimeTypeTestsJSTest.scala
+++ b/test-suite/js/src/test/scala/org/scalajs/testsuite/compiler/RuntimeTypeTestsJSTest.scala
@@ -43,9 +43,14 @@ class RuntimeTypeTestsJSTest {
     testJSObject(true, new ParentJSClass)
     testJSObject(true, new ChildJSClass)
     testJSObject(true, new js.Object)
-    testJSObject(true, List(5))
-    testJSObject(true, new Throwable)
-    testJSObject(true, new Exception)
+
+    /* Testing an implementation detail -- we do not actually give a guarantee
+     * about whether Scala objects are instances of Object.
+     */
+    val expectedForScalaObj = !executingInWebAssembly
+    testJSObject(expectedForScalaObj, List(5))
+    testJSObject(expectedForScalaObj, new Throwable)
+    testJSObject(expectedForScalaObj, new Exception)
 
     testJSObject(false, 5)
     testJSObject(false, ())
@@ -60,8 +65,13 @@ class RuntimeTypeTestsJSTest {
 
     testJSError(true, new js.Error)
     testJSError(true, new js.EvalError)
-    testJSError(true, new Throwable)
-    testJSError(true, new Exception)
+
+    /* Testing an implementation detail -- we do not actually give a guarantee
+     * about whether Scala objects are instances of Error.
+     */
+    val expectedForScalaException = !executingInWebAssembly
+    testJSError(expectedForScalaException, new Throwable)
+    testJSError(expectedForScalaException, new Exception)
 
     testJSError(false, 5)
     testJSError(false, ())
diff --git a/test-suite/js/src/test/scala/org/scalajs/testsuite/javalib/lang/ThrowableJSTest.scala b/test-suite/js/src/test/scala/org/scalajs/testsuite/javalib/lang/ThrowableJSTest.scala
index 66bd5b3bde..74a9180361 100644
--- a/test-suite/js/src/test/scala/org/scalajs/testsuite/javalib/lang/ThrowableJSTest.scala
+++ b/test-suite/js/src/test/scala/org/scalajs/testsuite/javalib/lang/ThrowableJSTest.scala
@@ -23,11 +23,14 @@ import org.scalajs.testsuite.utils.Platform._
 class ThrowableJSTest {
 
   @Test def throwablesAreJSErrors(): Unit = {
+    assumeFalse("Not supported on WebAssembly", executingInWebAssembly)
+
     val t: Any = new Throwable("foo")
     assertTrue(t.isInstanceOf[js.Error])
   }
 
   @Test def throwablesAreTrueErrors(): Unit = {
+    assumeFalse("Not supported on WebAssembly", executingInWebAssembly)
     assumeTrue("Requires ECMAScript 2015 semantics", useECMAScript2015Semantics)
 
     def coreToString(x: Any): String = {
diff --git a/test-suite/js/src/test/scala/org/scalajs/testsuite/jsinterop/ExportsTest.scala b/test-suite/js/src/test/scala/org/scalajs/testsuite/jsinterop/ExportsTest.scala
index 4c03aef61e..9bb851510a 100644
--- a/test-suite/js/src/test/scala/org/scalajs/testsuite/jsinterop/ExportsTest.scala
+++ b/test-suite/js/src/test/scala/org/scalajs/testsuite/jsinterop/ExportsTest.scala
@@ -23,7 +23,7 @@ import org.scalajs.testsuite.utils.Platform._
 
 import org.junit.Assert._
 import org.junit.Assume._
-import org.junit.Test
+import org.junit.{BeforeClass, Test}
 
 class ExportsTest {
 
@@ -1456,6 +1456,14 @@ class ExportsTest {
   }
 }
 
+object ExportsTest {
+  @BeforeClass
+  def beforeClass(): Unit = {
+    assumeFalse("@JSExport and @JSExportAll are not supported on WebAssembly",
+        executingInWebAssembly)
+  }
+}
+
 object ExportNameHolder {
   final val methodName = "myMethod"
 }
diff --git a/test-suite/js/src/test/scala/org/scalajs/testsuite/jsinterop/MiscInteropTest.scala b/test-suite/js/src/test/scala/org/scalajs/testsuite/jsinterop/MiscInteropTest.scala
index f477cffcc6..bb422ac84a 100644
--- a/test-suite/js/src/test/scala/org/scalajs/testsuite/jsinterop/MiscInteropTest.scala
+++ b/test-suite/js/src/test/scala/org/scalajs/testsuite/jsinterop/MiscInteropTest.scala
@@ -197,6 +197,7 @@ class MiscInteropTest {
   // Emitted classes
 
   @Test def meaningfulNameProperty(): Unit = {
+    assumeFalse("Not supported on WebAssembly", executingInWebAssembly)
     assumeFalse("Need non-minified names", hasMinifiedNames)
 
     def nameOf(obj: Any): js.Any =
diff --git a/test-suite/js/src/test/scala/org/scalajs/testsuite/library/LinkingInfoTest.scala b/test-suite/js/src/test/scala/org/scalajs/testsuite/library/LinkingInfoTest.scala
index dc895dd36a..ee20c3417b 100644
--- a/test-suite/js/src/test/scala/org/scalajs/testsuite/library/LinkingInfoTest.scala
+++ b/test-suite/js/src/test/scala/org/scalajs/testsuite/library/LinkingInfoTest.scala
@@ -16,16 +16,23 @@ import scala.scalajs.LinkingInfo
 import scala.scalajs.LinkingInfo.ESVersion
 
 import org.junit.Assert._
+import org.junit.Assume._
 import org.junit.Test
 
 import org.scalajs.testsuite.utils.Platform
 
 class LinkingInfoTest {
-  @Test def productionMode(): Unit =
+  @Test def productionMode(): Unit = {
+    assumeFalse("Not implemented yet on WebAssembly", Platform.executingInWebAssembly)
+
     assertEquals(Platform.isInProductionMode, LinkingInfo.productionMode)
+  }
+
+  @Test def developmentMode(): Unit = {
+    assumeFalse("Not implemented yet on WebAssembly", Platform.executingInWebAssembly)
 
-  @Test def developmentMode(): Unit =
     assertEquals(!Platform.isInProductionMode, LinkingInfo.developmentMode)
+  }
 
   @Test def esVersion(): Unit =
     assertEquals(Platform.assumedESVersion, LinkingInfo.esVersion)
diff --git a/test-suite/js/src/test/scala/org/scalajs/testsuite/library/StackTraceTest.scala b/test-suite/js/src/test/scala/org/scalajs/testsuite/library/StackTraceTest.scala
index 03315cf014..af7fbd654d 100644
--- a/test-suite/js/src/test/scala/org/scalajs/testsuite/library/StackTraceTest.scala
+++ b/test-suite/js/src/test/scala/org/scalajs/testsuite/library/StackTraceTest.scala
@@ -52,6 +52,7 @@ class StackTraceTest {
 
   @Test def decodeClassNameAndMethodName(): Unit = {
     assumeTrue("Assume Node.js", executingInNodeJS)
+    assumeFalse("Not good enough on WebAssembly yet", executingInWebAssembly)
     assumeFalse("Assume non-minified names", hasMinifiedNames)
 
     val Error = js.constructorOf[js.Error]
diff --git a/test-suite/jvm/src/main/scala/org/scalajs/testsuite/utils/Platform.scala b/test-suite/jvm/src/main/scala/org/scalajs/testsuite/utils/Platform.scala
index 6b0a9c412a..ba855134c9 100644
--- a/test-suite/jvm/src/main/scala/org/scalajs/testsuite/utils/Platform.scala
+++ b/test-suite/jvm/src/main/scala/org/scalajs/testsuite/utils/Platform.scala
@@ -40,6 +40,8 @@ object Platform {
     else Integer.parseInt(v.takeWhile(_.isDigit))
   }
 
+  final val executingInWebAssembly = false
+
   def usesClosureCompiler: Boolean = false
 
   def hasMinifiedNames: Boolean = false

From 4a1e347d005262ead87379f57671a077f542f80a Mon Sep 17 00:00:00 2001
From: Daniel Moss <daniel.david.moss+git@gmail.com>
Date: Mon, 18 Mar 2024 13:51:31 +0000
Subject: [PATCH 109/298] Add `js.Symbol.asyncIterator`.

---
 .../main/scala/scala/scalajs/js/Symbol.scala  |  7 ++
 .../testsuite/jsinterop/JSSymbolTest.scala    | 78 ++++++++++++++++---
 2 files changed, 74 insertions(+), 11 deletions(-)

diff --git a/library/src/main/scala/scala/scalajs/js/Symbol.scala b/library/src/main/scala/scala/scalajs/js/Symbol.scala
index 9e6ff207e8..38251f8954 100644
--- a/library/src/main/scala/scala/scalajs/js/Symbol.scala
+++ b/library/src/main/scala/scala/scalajs/js/Symbol.scala
@@ -67,6 +67,13 @@ object Symbol extends js.Object {
    */
   def keyFor(sym: js.Symbol): js.UndefOr[String] = js.native
 
+  /** <span class="badge badge-ecma2018" style="float: right;">ECMAScript 2018</span>
+   *  The well-known symbol `@@asyncIterator`.
+   *
+   *  @group wellknownsyms
+   */
+  val asyncIterator: js.Symbol = js.native
+
   /** The well-known symbol `@@hasInstance`.
    *
    *  @group wellknownsyms
diff --git a/test-suite/js/src/test/scala/org/scalajs/testsuite/jsinterop/JSSymbolTest.scala b/test-suite/js/src/test/scala/org/scalajs/testsuite/jsinterop/JSSymbolTest.scala
index 4177792dd4..4d092be096 100644
--- a/test-suite/js/src/test/scala/org/scalajs/testsuite/jsinterop/JSSymbolTest.scala
+++ b/test-suite/js/src/test/scala/org/scalajs/testsuite/jsinterop/JSSymbolTest.scala
@@ -13,6 +13,7 @@
 package org.scalajs.testsuite.jsinterop
 
 import scala.scalajs.js
+import scala.scalajs.js.|
 import scala.scalajs.js.annotation._
 
 import org.junit.Assert._
@@ -251,6 +252,17 @@ class JSSymbolTest {
     assertArrayEquals(Array(532), content.result())
   }
 
+  @Test def sjsdefinedAsyncIterable(): Unit = {
+    PromiseMock.withMockedPromise { processQueue =>
+      val obj = new SJSDefinedAsyncIterable
+
+      val content = Array.newBuilder[Int]
+      iterateAsyncIterable(obj)(content += _)
+      processQueue()
+      assertArrayEquals(Array(278), content.result())
+    }
+  }
+
   @Test def inOperatorWithSymbols(): Unit = {
     val obj = mkObject(sym1 -> "foo")
 
@@ -304,26 +316,40 @@ object JSSymbolTest {
     def callSymbol(sym: js.Symbol)(args: js.Any*): Any = js.native
   }
 
-  def singletonIterator(singleton: Any): js.Dynamic = {
-    var first = true
+  def singletonIterator(singleton: Any): js.Dynamic =
+    js.Dynamic.literal(next = singletonIteratorLogic(singleton))
+
+  def singletonAsyncIterator(singleton: Any): js.Dynamic = {
+    val logic = singletonIteratorLogic(singleton)
     js.Dynamic.literal(
-        next = { () =>
-          if (first) {
-            first = false
-            js.Dynamic.literal(value = singleton.asInstanceOf[js.Any],
-                done = false)
-          } else {
-            js.Dynamic.literal(value = (), done = true)
-          }
-        }
+      next = { () =>
+        new js.Promise[js.Dynamic]({
+          (resolve: js.Function1[js.Dynamic | js.Thenable[js.Dynamic], _], reject: js.Function1[Any, _]) =>
+            resolve(logic())
+        })
+      }
     )
   }
 
+  def singletonIteratorLogic(singleton: Any): () => js.Dynamic = {
+    var first = true
+
+    { () =>
+      if (first) {
+        first = false
+        js.Dynamic.literal(value = singleton.asInstanceOf[js.Any], done = false)
+      } else {
+        js.Dynamic.literal(value = (), done = true)
+      }
+    }
+  }
+
   def iterableToArray[A](iterable: JSIterable[A]): js.Array[A] =
     js.constructorOf[js.Array[_]].from(iterable).asInstanceOf[js.Array[A]]
 
   def iterateIterable[A](iterable: JSIterable[A])(f: A => Any): Unit = {
     val iterator = iterable.iterator()
+
     def loop(): Unit = {
       import js.DynamicImplicits.truthValue
 
@@ -333,6 +359,26 @@ object JSSymbolTest {
         loop()
       }
     }
+
+    loop()
+  }
+
+  def iterateAsyncIterable[A](
+      iterable: JSAsyncIterable[A])(f: A => Any): Unit = {
+    val iterator = iterable.asyncIterator()
+
+    def loop(): Unit = {
+      import js.DynamicImplicits.truthValue
+
+      val pEntry = iterator.next().asInstanceOf[js.Promise[js.Dynamic]]
+      pEntry.`then`[Unit] { (entry: js.Dynamic) =>
+        if (!entry.done) {
+          f(entry.value.asInstanceOf[A])
+          loop()
+        }
+      }
+    }
+
     loop()
   }
 
@@ -512,4 +558,14 @@ object JSSymbolTest {
     @JSName(js.Symbol.iterator)
     def iterator(): js.Dynamic = singletonIterator(532)
   }
+
+  trait JSAsyncIterable[+A] extends js.Object {
+    @JSName(js.Symbol.asyncIterator)
+    def asyncIterator(): js.Dynamic
+  }
+
+  class SJSDefinedAsyncIterable extends JSAsyncIterable[Int] {
+    @JSName(js.Symbol.asyncIterator)
+    def asyncIterator(): js.Dynamic = singletonAsyncIterator(278)
+  }
 }

From 1c41a257faef09a0c306be822f84c0845a34f3e3 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Thu, 30 May 2024 11:40:33 +0200
Subject: [PATCH 110/298] Add CoreSpec.targetIsWebAssembly.

This will be used to provide that information to the optimizer as
well as to user-space through linking info. Therefore, it is an
observable piece of knowledge that belongs to the core spec.
---
 .../closure/ClosureLinkerBackend.scala        |  3 +
 .../linker/backend/BasicLinkerBackend.scala   |  3 +
 .../backend/WebAssemblyLinkerBackend.scala    |  3 +
 .../linker/standard/CommonPhaseConfig.scala   |  8 +-
 .../scalajs/linker/standard/CoreSpec.scala    | 75 +++++++++++++++----
 project/BinaryIncompatibilities.scala         |  5 ++
 6 files changed, 79 insertions(+), 18 deletions(-)

diff --git a/linker/jvm/src/main/scala/org/scalajs/linker/backend/closure/ClosureLinkerBackend.scala b/linker/jvm/src/main/scala/org/scalajs/linker/backend/closure/ClosureLinkerBackend.scala
index 347465bf72..a013049de8 100644
--- a/linker/jvm/src/main/scala/org/scalajs/linker/backend/closure/ClosureLinkerBackend.scala
+++ b/linker/jvm/src/main/scala/org/scalajs/linker/backend/closure/ClosureLinkerBackend.scala
@@ -53,6 +53,9 @@ final class ClosureLinkerBackend(config: LinkerBackendImpl.Config)
   require(moduleKind != ModuleKind.ESModule,
       s"Cannot use module kind $moduleKind with the Closure Compiler")
 
+  require(!targetIsWebAssembly,
+      s"A JavaScript backend cannot be used with CoreSpec targeting WebAssembly")
+
   private[this] val emitter = {
     // Note that we do not transfer `minify` -- Closure will do its own thing anyway
     val emitterConfig = Emitter.Config(config.commonConfig.coreSpec)
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/BasicLinkerBackend.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/BasicLinkerBackend.scala
index 74b4871503..84b01582b9 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/BasicLinkerBackend.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/BasicLinkerBackend.scala
@@ -38,6 +38,9 @@ final class BasicLinkerBackend(config: LinkerBackendImpl.Config)
 
   import BasicLinkerBackend._
 
+  require(!coreSpec.targetIsWebAssembly,
+      s"A JavaScript backend cannot be used with CoreSpec targeting WebAssembly")
+
   private[this] var totalModules = 0
   private[this] val rewrittenModules = new AtomicInteger(0)
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/WebAssemblyLinkerBackend.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/WebAssemblyLinkerBackend.scala
index ef7be8c498..2e614993f1 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/WebAssemblyLinkerBackend.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/WebAssemblyLinkerBackend.scala
@@ -52,6 +52,9 @@ final class WebAssemblyLinkerBackend(config: LinkerBackendImpl.Config)
     "The WebAssembly backend only supports strict float semantics."
   )
 
+  require(coreSpec.targetIsWebAssembly,
+      s"A WebAssembly backend cannot be used with CoreSpec targeting JavaScript")
+
   val loaderJSFileName = OutputPatternsImpl.jsFile(config.outputPatterns, "__loader")
 
   private val fragmentIndex = new SourceMapWriter.Index
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/standard/CommonPhaseConfig.scala b/linker/shared/src/main/scala/org/scalajs/linker/standard/CommonPhaseConfig.scala
index 66b0c0f9ef..c611cb6479 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/standard/CommonPhaseConfig.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/standard/CommonPhaseConfig.scala
@@ -49,7 +49,11 @@ private[linker] object CommonPhaseConfig {
   private[linker] def apply(): CommonPhaseConfig = new CommonPhaseConfig()
 
   private[linker] def fromStandardConfig(config: StandardConfig): CommonPhaseConfig = {
-    val coreSpec = CoreSpec(config.semantics, config.moduleKind, config.esFeatures)
-    new CommonPhaseConfig(coreSpec, config.minify, config.parallel, config.batchMode)
+    new CommonPhaseConfig(
+      CoreSpec.fromStandardConfig(config),
+      config.minify,
+      config.parallel,
+      config.batchMode
+    )
   }
 }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/standard/CoreSpec.scala b/linker/shared/src/main/scala/org/scalajs/linker/standard/CoreSpec.scala
index 4c87430a50..3c4c979adc 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/standard/CoreSpec.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/standard/CoreSpec.scala
@@ -21,15 +21,45 @@ final class CoreSpec private (
     /** Module kind. */
     val moduleKind: ModuleKind,
     /** ECMAScript features to use. */
-    val esFeatures: ESFeatures
+    val esFeatures: ESFeatures,
+    /** Whether we are compiling to WebAssembly. */
+    val targetIsWebAssembly: Boolean
 ) {
   import CoreSpec._
 
+  private def this() = {
+    this(
+      semantics = Semantics.Defaults,
+      moduleKind = ModuleKind.NoModule,
+      esFeatures = ESFeatures.Defaults,
+      targetIsWebAssembly = false
+    )
+  }
+
+  def withSemantics(semantics: Semantics): CoreSpec =
+    copy(semantics = semantics)
+
+  def withSemantics(f: Semantics => Semantics): CoreSpec =
+    copy(semantics = f(semantics))
+
+  def withModuleKind(moduleKind: ModuleKind): CoreSpec =
+    copy(moduleKind = moduleKind)
+
+  def withESFeatures(esFeatures: ESFeatures): CoreSpec =
+    copy(esFeatures = esFeatures)
+
+  def withESFeatures(f: ESFeatures => ESFeatures): CoreSpec =
+    copy(esFeatures = f(esFeatures))
+
+  def withTargetIsWebAssembly(targetIsWebAssembly: Boolean): CoreSpec =
+    copy(targetIsWebAssembly = targetIsWebAssembly)
+
   override def equals(that: Any): Boolean = that match {
     case that: CoreSpec =>
       this.semantics == that.semantics &&
       this.moduleKind == that.moduleKind &&
-      this.esFeatures == that.esFeatures
+      this.esFeatures == that.esFeatures &&
+      this.targetIsWebAssembly == that.targetIsWebAssembly
     case _ =>
       false
   }
@@ -39,34 +69,47 @@ final class CoreSpec private (
     var acc = HashSeed
     acc = mix(acc, semantics.##)
     acc = mix(acc, moduleKind.##)
-    acc = mixLast(acc, esFeatures.##)
-    finalizeHash(acc, 3)
+    acc = mix(acc, esFeatures.##)
+    acc = mixLast(acc, targetIsWebAssembly.##)
+    finalizeHash(acc, 4)
   }
 
   override def toString(): String = {
     s"""CoreSpec(
        |  semantics  = $semantics,
        |  moduleKind = $moduleKind,
-       |  esFeatures = $esFeatures
+       |  esFeatures = $esFeatures,
+       |  targetIsWebAssembly = $targetIsWebAssembly
        |)""".stripMargin
   }
+
+  private def copy(
+      semantics: Semantics = semantics,
+      moduleKind: ModuleKind = moduleKind,
+      esFeatures: ESFeatures = esFeatures,
+      targetIsWebAssembly: Boolean = targetIsWebAssembly
+  ): CoreSpec = {
+    new CoreSpec(
+      semantics,
+      moduleKind,
+      esFeatures,
+      targetIsWebAssembly
+    )
+  }
 }
 
 private[linker] object CoreSpec {
   private val HashSeed =
     scala.util.hashing.MurmurHash3.stringHash(classOf[CoreSpec].getName)
 
-  private[linker] val Defaults: CoreSpec = {
-    new CoreSpec(
-        semantics = Semantics.Defaults,
-        moduleKind = ModuleKind.NoModule,
-        esFeatures = ESFeatures.Defaults)
-  }
+  val Defaults: CoreSpec = new CoreSpec()
 
-  private[linker] def apply(
-      semantics: Semantics,
-      moduleKind: ModuleKind,
-      esFeatures: ESFeatures): CoreSpec = {
-    new CoreSpec(semantics, moduleKind, esFeatures)
+  private[linker] def fromStandardConfig(config: StandardConfig): CoreSpec = {
+    new CoreSpec(
+      config.semantics,
+      config.moduleKind,
+      config.esFeatures,
+      config.experimentalUseWebAssembly
+    )
   }
 }
diff --git a/project/BinaryIncompatibilities.scala b/project/BinaryIncompatibilities.scala
index 4713fe6bf8..2863b4d24c 100644
--- a/project/BinaryIncompatibilities.scala
+++ b/project/BinaryIncompatibilities.scala
@@ -8,6 +8,11 @@ object BinaryIncompatibilities {
   )
 
   val Linker = Seq(
+    // private, not an issue
+    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.linker.standard.CoreSpec.this"),
+
+    // private[linker], not an issue
+    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.linker.standard.CoreSpec.apply"),
   )
 
   val LinkerInterface = Seq(

From 7430166c8792be12f8014579d6220b226211e9bb Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Fri, 31 May 2024 20:03:01 +0200
Subject: [PATCH 111/298] Add LinkingInfo.isWebAssembly to the library.

---
 .../scala/scala/scalajs/LinkingInfo.scala     | 34 +++++++++++++++++++
 .../scala/scalajs/runtime/LinkingInfo.scala   |  7 ++++
 .../linker/backend/emitter/CoreJSLib.scala    |  1 +
 .../backend/wasmemitter/LoaderContent.scala   |  1 +
 .../frontend/optimizer/OptimizerCore.scala    |  5 +++
 project/BinaryIncompatibilities.scala         |  2 ++
 project/Build.scala                           |  2 +-
 .../testsuite/library/LinkingInfoTest.scala   |  3 ++
 8 files changed, 54 insertions(+), 1 deletion(-)

diff --git a/library/src/main/scala/scala/scalajs/LinkingInfo.scala b/library/src/main/scala/scala/scalajs/LinkingInfo.scala
index ad8c612adc..bf1bfa9c00 100644
--- a/library/src/main/scala/scala/scalajs/LinkingInfo.scala
+++ b/library/src/main/scala/scala/scalajs/LinkingInfo.scala
@@ -224,6 +224,40 @@ object LinkingInfo {
   def useECMAScript2015Semantics: Boolean =
     linkingInfo.assumingES6 // name mismatch for historical reasons
 
+  /** Whether we are linking to WebAssembly.
+   *
+   *  This property can be used to delegate to different code paths optimized
+   *  for WebAssembly rather than for JavaScript.
+   *
+   *  ---
+   *
+   *  This ends up being constant-folded to a constant at link-time. So
+   *  constant-folding, inlining, and other local optimizations can be
+   *  leveraged with this "constant" to write alternatives that can be
+   *  dead-code-eliminated.
+   *
+   *  A typical usage of this method is:
+   *  {{{
+   *  if (isWebAssembly)
+   *    implementationOptimizedForWebAssembly()
+   *  else
+   *    implementationOptimizedForJavaScript()
+   *  }}}
+   *
+   *  At link-time, `isWebAssembly` will either be a constant
+   *  true, in which case the above snippet folds into
+   *  {{{
+   *  implementationOptimizedForWebAssembly()
+   *  }}}
+   *  or a constant false, in which case it folds into
+   *  {{{
+   *  implementationOptimizedForJavaScript()
+   *  }}}
+   */
+  @inline
+  def isWebAssembly: Boolean =
+    linkingInfo.isWebAssembly
+
   /** Constants for the value of `esVersion`. */
   object ESVersion {
     /** ECMAScrîpt 5.1. */
diff --git a/library/src/main/scala/scala/scalajs/runtime/LinkingInfo.scala b/library/src/main/scala/scala/scalajs/runtime/LinkingInfo.scala
index 9a97a2b323..3dd8395202 100644
--- a/library/src/main/scala/scala/scalajs/runtime/LinkingInfo.scala
+++ b/library/src/main/scala/scala/scalajs/runtime/LinkingInfo.scala
@@ -36,6 +36,13 @@ sealed trait LinkingInfo extends js.Object {
    */
   val assumingES6: Boolean
 
+  /** Whether we are linking to WebAssembly.
+   *
+   *  This property can be used to delegate to different code paths optimized
+   *  for WebAssembly rather than for JavaScript.
+   */
+  val isWebAssembly: Boolean
+
   /** Whether we are linking in production mode. */
   val productionMode: Boolean
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
index 05ade75ba0..2c27c125b9 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
@@ -163,6 +163,7 @@ private[emitter] object CoreJSLib {
       val linkingInfo = objectFreeze(ObjectConstr(List(
           str("esVersion") -> int(esVersion.edition),
           str("assumingES6") -> bool(useECMAScript2015Semantics), // different name for historical reasons
+          str("isWebAssembly") -> bool(false),
           str("productionMode") -> bool(productionMode),
           str("linkerVersion") -> str(ScalaJSVersions.current),
           str("fileLevelThis") -> This()
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala
index 48bfae78d9..01614586c1 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala
@@ -83,6 +83,7 @@ function installJSField(instance, name, value) {
 const linkingInfo = Object.freeze({
   "esVersion": 6,
   "assumingES6": true,
+  "isWebAssembly": true,
   "productionMode": false,
   "linkerVersion": "${ScalaJSVersions.current}",
   "fileLevelThis": this
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
index 6d973cde36..7ed5bc57b5 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
@@ -50,6 +50,8 @@ private[optimizer] abstract class OptimizerCore(
 
   private def semantics: Semantics = config.coreSpec.semantics
 
+  private val isWasm: Boolean = config.coreSpec.targetIsWebAssembly
+
   // Uncomment and adapt to print debug messages only during one method
   //lazy val debugThisMethod: Boolean =
   //  debugID == "java.lang.FloatingPointBits$.numberHashCode;D;I"
@@ -4823,6 +4825,9 @@ private[optimizer] abstract class OptimizerCore(
       case (JSLinkingInfo(), StringLiteral("assumingES6")) =>
         BooleanLiteral(esFeatures.useECMAScript2015Semantics)
 
+      case (JSLinkingInfo(), StringLiteral("isWebAssembly")) =>
+        BooleanLiteral(isWasm)
+
       case (JSLinkingInfo(), StringLiteral("version")) =>
         StringLiteral(ScalaJSVersions.current)
 
diff --git a/project/BinaryIncompatibilities.scala b/project/BinaryIncompatibilities.scala
index 2863b4d24c..08a3f5b462 100644
--- a/project/BinaryIncompatibilities.scala
+++ b/project/BinaryIncompatibilities.scala
@@ -25,6 +25,8 @@ object BinaryIncompatibilities {
   )
 
   val Library = Seq(
+    // New abstract member in JS trait, not an issue
+    ProblemFilters.exclude[ReversedMissingMethodProblem]("scala.scalajs.runtime.LinkingInfo.isWebAssembly"),
   )
 
   val TestInterface = Seq(
diff --git a/project/Build.scala b/project/Build.scala
index 29db017cac..d1aeeeb5ef 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -2082,7 +2082,7 @@ object Build {
               ))
             } else {
               Some(ExpectedSizes(
-                  fastLink = 308000 to 309000,
+                  fastLink = 309000 to 310000,
                   fullLink = 263000 to 264000,
                   fastLinkGz = 49000 to 50000,
                   fullLinkGz = 43000 to 44000,
diff --git a/test-suite/js/src/test/scala/org/scalajs/testsuite/library/LinkingInfoTest.scala b/test-suite/js/src/test/scala/org/scalajs/testsuite/library/LinkingInfoTest.scala
index ee20c3417b..b2b4c89ed8 100644
--- a/test-suite/js/src/test/scala/org/scalajs/testsuite/library/LinkingInfoTest.scala
+++ b/test-suite/js/src/test/scala/org/scalajs/testsuite/library/LinkingInfoTest.scala
@@ -43,6 +43,9 @@ class LinkingInfoTest {
   @Test def useECMAScript2015Semantics(): Unit =
     assertEquals(Platform.useECMAScript2015Semantics, LinkingInfo.useECMAScript2015Semantics)
 
+  @Test def isWebAssembly(): Unit =
+    assertEquals(Platform.executingInWebAssembly, LinkingInfo.isWebAssembly)
+
   @Test def esVersionConstants(): Unit = {
     // The numeric values behind the constants are meaningful, so we test them.
     assertEquals(5, ESVersion.ES5_1)

From f0a23d3cfc7d41a005e7d32a3754b9784a3e8032 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Sun, 11 Aug 2024 13:07:23 +0200
Subject: [PATCH 112/298] Wasm: Assert that we never write to
 `VarStorage.StructField`.

`StructField` is only used for captures, which are always
immutable.
---
 .../linker/backend/wasmemitter/FunctionEmitter.scala      | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
index d41496cef8..958893dc2f 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
@@ -552,12 +552,8 @@ private class FunctionEmitter private (
             genTree(rhs, lhs.tpe)
             markPosition(tree)
             fb += wa.LocalSet(local)
-          case VarStorage.StructField(structLocal, structTypeID, fieldID) =>
-            markPosition(tree)
-            fb += wa.LocalGet(structLocal)
-            genTree(rhs, lhs.tpe)
-            markPosition(tree)
-            fb += wa.StructSet(structTypeID, fieldID)
+          case storage: VarStorage.StructField =>
+            throw new AssertionError(s"Unexpected write to capture storage $storage")
         }
 
       case lhs: RecordSelect =>

From 3aebb38fbb0aedd87934de556f666d3618e7d3aa Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Wed, 29 May 2024 13:09:36 +0200
Subject: [PATCH 113/298] Wasm: Handle RecordType's in the backend.

---
 .../backend/wasmemitter/ClassEmitter.scala    |  10 +-
 .../backend/wasmemitter/FunctionEmitter.scala | 178 +++++++++++++++---
 .../backend/wasmemitter/TypeTransformer.scala |  56 ++++--
 .../backend/wasmemitter/WasmContext.scala     |   4 +-
 4 files changed, 197 insertions(+), 51 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/ClassEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/ClassEmitter.scala
index 7b6026c346..e7c8327613 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/ClassEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/ClassEmitter.scala
@@ -57,7 +57,7 @@ class ClassEmitter(coreSpec: CoreSpec) {
         genGlobalID.forStaticField(name.name),
         origName,
         isMutable = true,
-        transformType(ftpe),
+        transformFieldType(ftpe),
         wa.Expr(List(genZeroOf(ftpe)))
       )
       ctx.addGlobal(global)
@@ -350,7 +350,7 @@ class ClassEmitter(coreSpec: CoreSpec) {
       watpe.StructField(
         genFieldID.forClassInstanceField(field.name.name),
         makeDebugName(ns.InstanceField, field.name.name),
-        transformType(field.ftpe),
+        transformFieldType(field.ftpe),
         isMutable = true // initialized by the constructors, so always mutable at the Wasm level
       )
     }
@@ -769,7 +769,7 @@ class ClassEmitter(coreSpec: CoreSpec) {
         clazz.pos
       )
       val classCaptureParams = jsClassCaptures.map { cc =>
-        fb.addParam("cc." + cc.name.name.nameString, transformLocalType(cc.ptpe))
+        fb.addParam("cc." + cc.name.name.nameString, transformParamType(cc.ptpe))
       }
       fb.setResultType(watpe.RefType.any)
 
@@ -1147,7 +1147,7 @@ class ClassEmitter(coreSpec: CoreSpec) {
       if (namespace.isStatic)
         None
       else if (isHijackedClass)
-        Some(transformType(BoxedClassToPrimType(className)))
+        Some(transformPrimType(BoxedClassToPrimType(className)))
       else
         Some(transformClassType(className).toNonNullable)
 
@@ -1183,7 +1183,7 @@ class ClassEmitter(coreSpec: CoreSpec) {
       val receiverParam = fb.addParam(thisOriginalName, watpe.RefType.any)
       val argParams = method.args.map { arg =>
         val origName = arg.originalName.orElse(arg.name.name)
-        fb.addParam(origName, TypeTransformer.transformLocalType(arg.ptpe))
+        fb.addParam(origName, TypeTransformer.transformParamType(arg.ptpe))
       }
       fb.setResultTypes(TypeTransformer.transformResultType(method.resultType))
       fb.setFunctionType(ctx.tableFunctionType(methodName))
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
index 958893dc2f..e7866fa346 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
@@ -12,7 +12,7 @@
 
 package org.scalajs.linker.backend.wasmemitter
 
-import scala.annotation.switch
+import scala.annotation.{switch, tailrec}
 
 import scala.collection.mutable
 
@@ -51,6 +51,8 @@ object FunctionEmitter {
    */
   private final val UseLegacyExceptionsForTryCatch = true
 
+  private val dotUTF8String = UTF8String(".")
+
   def emitFunction(
       functionID: wanme.FunctionID,
       originalName: OriginalName,
@@ -224,7 +226,7 @@ object FunctionEmitter {
     val normalParamsEnv: Env = paramDefs.map { paramDef =>
       val param = fb.addParam(
         paramDef.originalName.orElse(paramDef.name.name),
-        transformLocalType(paramDef.ptpe)
+        transformParamType(paramDef.ptpe)
       )
       paramDef.name.name -> VarStorage.Local(param)
     }.toMap
@@ -258,7 +260,13 @@ object FunctionEmitter {
   private sealed abstract class VarStorage
 
   private object VarStorage {
-    final case class Local(localID: wanme.LocalID) extends VarStorage
+    sealed abstract class NonStructStorage extends VarStorage
+
+    final case class Local(localID: wanme.LocalID) extends NonStructStorage
+
+    // We use Vector here because we want a decent reverseIterator
+    final case class LocalRecord(fields: Vector[(SimpleFieldName, NonStructStorage)])
+        extends NonStructStorage
 
     final case class StructField(structLocalID: wanme.LocalID,
         structTypeID: wanme.TypeID, fieldID: wanme.FieldID)
@@ -308,6 +316,37 @@ private class FunctionEmitter private (
     )
   }
 
+  private def lookupRecordSelect(tree: RecordSelect): VarStorage.NonStructStorage = {
+    val RecordSelect(record, field) = tree
+
+    val recordStorage = record match {
+      case VarRef(LocalIdent(name)) =>
+        lookupLocal(name)
+      case record: RecordSelect =>
+        lookupRecordSelect(record)
+      case _ =>
+        throw new AssertionError(s"Unexpected record tree: $record")
+    }
+
+    recordStorage match {
+      case VarStorage.LocalRecord(fields) =>
+        fields.find(_._1 == field.name).getOrElse {
+          throw new AssertionError(s"Unknown field ${field.name} of $record")
+        }._2
+      case other =>
+        throw new AssertionError(s"Unexpected storage $other for record $record")
+    }
+  }
+
+  @tailrec
+  private def canLookupRecordSelect(tree: RecordSelect): Boolean = {
+    tree.record match {
+      case _: VarRef            => true
+      case record: RecordSelect => canLookupRecordSelect(record)
+      case _                    => false
+    }
+  }
+
   private def addSyntheticLocal(tpe: watpe.Type): wanme.LocalID =
     fb.addLocal(NoOriginalName, tpe)
 
@@ -404,7 +443,11 @@ private class FunctionEmitter private (
       case t: JSSuperMethodCall => genJSSuperMethodCall(t)
       case t: JSNewTarget       => genJSNewTarget(t)
 
-      case _: RecordSelect | _: RecordValue | _: Transient | _: JSSuperConstructorCall =>
+      // Records (only generated by the optimizer)
+      case t: RecordSelect => genRecordSelect(t)
+      case t: RecordValue  => genRecordValue(t)
+
+      case _: Transient | _: JSSuperConstructorCall =>
         throw new AssertionError(s"Invalid tree: $tree")
     }
 
@@ -546,23 +589,33 @@ private class FunctionEmitter private (
         markPosition(tree)
         fb += wa.Call(genFunctionID.jsGlobalRefSet)
 
-      case VarRef(ident) =>
-        lookupLocal(ident.name) match {
-          case VarStorage.Local(local) =>
-            genTree(rhs, lhs.tpe)
-            markPosition(tree)
-            fb += wa.LocalSet(local)
-          case storage: VarStorage.StructField =>
-            throw new AssertionError(s"Unexpected write to capture storage $storage")
-        }
+      case VarRef(LocalIdent(name)) =>
+        genTree(rhs, lhs.tpe)
+        markPosition(tree)
+        genWriteToStorage(lookupLocal(name))
 
       case lhs: RecordSelect =>
-        throw new AssertionError(s"Invalid tree: $tree")
+        genTree(rhs, lhs.tpe)
+        markPosition(tree)
+        genWriteToStorage(lookupRecordSelect(lhs))
     }
 
     NoType
   }
 
+  private def genWriteToStorage(storage: VarStorage): Unit = {
+    storage match {
+      case VarStorage.Local(local) =>
+        fb += wa.LocalSet(local)
+
+      case VarStorage.LocalRecord(fields) =>
+        fields.reverseIterator.foreach(field => genWriteToStorage(field._2))
+
+      case storage: VarStorage.StructField =>
+        throw new AssertionError(s"Unexpected write to capture storage $storage")
+    }
+  }
+
   private def genApply(tree: Apply): Type = {
     val Apply(flags, receiver, method, args) = tree
 
@@ -790,7 +843,7 @@ private class FunctionEmitter private (
               for ((arg, typeRef) <- args.zip(methodName.paramTypeRefs)) yield {
                 val tpe = ctx.inferTypeFromTypeRef(typeRef)
                 genTree(arg, tpe)
-                val localID = addSyntheticLocal(transformLocalType(tpe))
+                val localID = addSyntheticLocal(transformParamType(tpe))
                 fb += wa.LocalSet(localID)
                 localID
               }
@@ -1564,8 +1617,8 @@ private class FunctionEmitter private (
     val BinaryOp(op, lhs, rhs) = tree
     assert(op == Int_/ || op == Int_% || op == Long_/ || op == Long_%)
 
-    val tpe = tree.tpe
-    val wasmType = transformType(tpe)
+    val tpe = tree.tpe.asInstanceOf[PrimType]
+    val wasmType = transformPrimType(tpe)
 
     val lhsLocal = addSyntheticLocal(wasmType)
     val rhsLocal = addSyntheticLocal(wasmType)
@@ -1737,8 +1790,8 @@ private class FunctionEmitter private (
     } else {
       // By IR checker rules, targetTpe is none of NothingType, NullType, NoType or RecordType
 
-      val sourceWasmType = transformType(sourceTpe)
-      val targetWasmType = transformType(targetTpe)
+      val sourceWasmType = transformSingleType(sourceTpe)
+      val targetWasmType = transformSingleType(targetTpe)
 
       if (sourceWasmType == targetWasmType) {
         /* Common case where no cast is necessary at the Wasm level.
@@ -1796,7 +1849,7 @@ private class FunctionEmitter private (
           if (targetTpe == CharType) SpecialNames.CharBoxClass
           else SpecialNames.LongBoxClass
         val fieldName = FieldName(boxClass, SpecialNames.valueFieldSimpleName)
-        val resultType = transformType(targetTpe)
+        val resultType = transformPrimType(targetTpe)
 
         fb.block(Sig(List(watpe.RefType.anyref), List(resultType))) { doneLabel =>
           fb.block(Sig(List(watpe.RefType.anyref), Nil)) { isNullLabel =>
@@ -1858,6 +1911,9 @@ private class FunctionEmitter private (
     storage match {
       case VarStorage.Local(localID) =>
         fb += wa.LocalGet(localID)
+      case VarStorage.LocalRecord(fields) =>
+        for ((_, fieldStorage) <- fields)
+          genReadStorage(fieldStorage)
       case VarStorage.StructField(structLocal, structTypeID, fieldID) =>
         fb += wa.LocalGet(structLocal)
         fb += wa.StructGet(structTypeID, fieldID)
@@ -2055,14 +2111,31 @@ private class FunctionEmitter private (
   final def genBlockStats(stats: List[Tree])(inner: => Unit): Unit = {
     val savedEnv = currentEnv
 
+    def buildStorage(origName: UTF8String, vtpe: Type): VarStorage.NonStructStorage = vtpe match {
+      case RecordType(fields) =>
+        val fieldStorages = fields.map { field =>
+          val fieldOrigName =
+            origName ++ dotUTF8String ++ field.originalName.getOrElse(field.name)
+          field.name -> buildStorage(fieldOrigName, field.tpe)
+        }
+        VarStorage.LocalRecord(fieldStorages.toVector)
+      case _ =>
+        val wasmType =
+          if (vtpe == NothingType) watpe.Int32
+          else transformSingleType(vtpe)
+        val local = fb.addLocal(OriginalName(origName), wasmType)
+        VarStorage.Local(local)
+    }
+
     for (stat <- stats) {
       stat match {
         case VarDef(LocalIdent(name), originalName, vtpe, _, rhs) =>
           genTree(rhs, vtpe)
           markPosition(stat)
-          val local = fb.addLocal(originalName.orElse(name), transformLocalType(vtpe))
-          currentEnv = currentEnv.updated(name, VarStorage.Local(local))
-          fb += wa.LocalSet(local)
+          val storage = buildStorage(originalName.getOrElse(name), vtpe)
+          currentEnv = currentEnv.updated(name, storage)
+          genWriteToStorage(storage)
+
         case _ =>
           genTree(stat, NoType)
       }
@@ -2520,7 +2593,7 @@ private class FunctionEmitter private (
             // a primitive array always has the correct type
             ()
           case _ =>
-            transformType(tree.tpe) match {
+            transformSingleType(tree.tpe) match {
               case watpe.RefType.anyref =>
                 // nothing to do
                 ()
@@ -2648,7 +2721,7 @@ private class FunctionEmitter private (
         fb += wa.CallRef(genTypeID.cloneFunctionType)
 
         // cast the (ref jl.Object) back down to the result type
-        transformType(exprType) match {
+        transformSingleType(exprType) match {
           case watpe.RefType(_, watpe.HeapType.Type(genTypeID.ObjectStruct)) =>
             // no need to cast to (ref null? jl.Object)
           case wasmType: watpe.RefType =>
@@ -2666,7 +2739,7 @@ private class FunctionEmitter private (
   private def genMatch(tree: Match, expectedType: Type): Type = {
     val Match(selector, cases, defaultBody) = tree
 
-    val selectorLocal = addSyntheticLocal(transformType(selector.tpe))
+    val selectorLocal = addSyntheticLocal(transformSingleType(selector.tpe))
 
     genTreeAuto(selector)
 
@@ -2789,6 +2862,59 @@ private class FunctionEmitter private (
     AnyType
   }
 
+  private def genRecordSelect(tree: RecordSelect): Type = {
+    if (canLookupRecordSelect(tree)) {
+      markPosition(tree)
+      genReadStorage(lookupRecordSelect(tree))
+    } else {
+      /* We have a record select that we cannot simplify to a direct storage,
+       * because its `record` part is neither a `VarRef` nor (recursively) a
+       * `RecordSelect`. For example, it could be an `If` whose two branches
+       * both return a different `VarRef`/`Record` of the same record type:
+       *   (if (cond) record1 else record2).recordField
+       * In that case, we must evaluate the `record` in full, then discard all
+       * the fields that are not the one we're selecting.
+       *
+       * (The JS backend avoids this situation by construction because of its
+       * unnesting logic. It always creates a temporary `VarRef` of the record
+       * type. In Wasm we can use multiple values on the stack instead.)
+       */
+
+      genTreeAuto(tree.record)
+
+      markPosition(tree)
+
+      val tempTypes = transformResultType(tree.tpe)
+      val tempLocals = tempTypes.map(addSyntheticLocal(_))
+
+      val recordType = tree.record.tpe.asInstanceOf[RecordType]
+      for (recordField <- recordType.fields.reverseIterator) {
+        if (recordField.name == tree.field.name) {
+          // Store this one in our temp locals
+          for (tempLocal <- tempLocals.reverseIterator)
+            fb += wa.LocalSet(tempLocal)
+        } else {
+          // Discard this field
+          for (_ <- transformResultType(recordField.tpe))
+            fb += wa.Drop
+        }
+      }
+
+      // Read back our locals
+      for (tempLocal <- tempLocals)
+        fb += wa.LocalGet(tempLocal)
+    }
+
+    tree.tpe
+  }
+
+  private def genRecordValue(tree: RecordValue): Type = {
+    for ((elem, field) <- tree.elems.zip(tree.tpe.fields))
+      genTree(elem, field.tpe)
+
+    tree.tpe
+  }
+
   /*--------------------------------------------------------------------*
    * HERE BE DRAGONS --- Handling of TryFinally, Labeled and Return --- *
    *--------------------------------------------------------------------*/
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/TypeTransformer.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/TypeTransformer.scala
index 55101a98b3..2deaa6a013 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/TypeTransformer.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/TypeTransformer.scala
@@ -21,21 +21,34 @@ import VarGen._
 
 object TypeTransformer {
 
-  /** Transforms an IR type for a local definition (including parameters).
+  /** Transforms an IR type for a field definition.
+   *
+   *  This method cannot be used for `void` and `nothing`, since they are not
+   *  valid types for fields.
+   */
+  def transformFieldType(tpe: Type)(implicit ctx: WasmContext): watpe.Type = {
+    transformSingleType(tpe)
+  }
+
+  /** Transforms an IR type for a parameter definition.
    *
    *  `void` is not a valid input for this method. It is rejected by the
    *  `ClassDefChecker`.
    *
-   *  `nothing` translates to `i32` in this specific case, because it is a valid
-   *  type for a `ParamDef` or `VarDef`. Obviously, assigning a value to a local
-   *  of type `nothing` (either locally or by calling the method for a param)
-   *  can never complete, and therefore reading the value of such a local is
-   *  always unreachable. It is up to the reading codegen to handle this case.
+   *  Likewise, `RecordType`s are not valid, since they cannot be used for
+   *  parameters.
+   *
+   *  `nothing` translates to `i32` in this specific case, because it is a
+   *  valid type for a `ParamDef`. Obviously, calling a method that has a
+   *  param of type `nothing` can never complete, and therefore reading the
+   *  value of such a parameter is always unreachable. It is up to the reading
+   *  codegen to handle this case.
    */
-  def transformLocalType(tpe: Type)(implicit ctx: WasmContext): watpe.Type = {
+  def transformParamType(tpe: Type)(implicit ctx: WasmContext): watpe.Type = {
     tpe match {
-      case NothingType => watpe.Int32
-      case _           => transformType(tpe)
+      case NothingType   => watpe.Int32
+      case _: RecordType => throw new AssertionError(s"Unexpected $tpe for parameter")
+      case _             => transformSingleType(tpe)
     }
   }
 
@@ -43,6 +56,8 @@ object TypeTransformer {
    *
    *  `void` translates to an empty result type list, as expected.
    *
+   *  `RecordType`s are flattened.
+   *
    *  `nothing` translates to an empty result type list as well, because Wasm does
    *  not have a bottom type (at least not one that can expressed at the user level).
    *  A block or function call that returns `nothing` should typically be followed
@@ -53,9 +68,10 @@ object TypeTransformer {
    */
   def transformResultType(tpe: Type)(implicit ctx: WasmContext): List[watpe.Type] = {
     tpe match {
-      case NoType      => Nil
-      case NothingType => Nil
-      case _           => List(transformType(tpe))
+      case NoType             => Nil
+      case NothingType        => Nil
+      case RecordType(fields) => fields.flatMap(f => transformResultType(f.tpe))
+      case _                  => List(transformSingleType(tpe))
     }
   }
 
@@ -63,13 +79,15 @@ object TypeTransformer {
    *
    *  This method cannot be used for `void` and `nothing`, since they have no corresponding Wasm
    *  value type.
+   *
+   *  Likewise, it cannot be used for `RecordType`s, since they must be
+   *  flattened into several Wasm types.
    */
-  def transformType(tpe: Type)(implicit ctx: WasmContext): watpe.Type = {
+  def transformSingleType(tpe: Type)(implicit ctx: WasmContext): watpe.Type = {
     tpe match {
-      case AnyType                => watpe.RefType.anyref
-      case ClassType(className)   => transformClassType(className)
-      case StringType | UndefType => watpe.RefType.any
-      case tpe: PrimTypeWithRef   => transformPrimType(tpe)
+      case AnyType              => watpe.RefType.anyref
+      case ClassType(className) => transformClassType(className)
+      case tpe: PrimType        => transformPrimType(tpe)
 
       case tpe: ArrayType =>
         watpe.RefType.nullable(genTypeID.forArrayClass(tpe.arrayTypeRef))
@@ -96,8 +114,9 @@ object TypeTransformer {
     }
   }
 
-  private def transformPrimType(tpe: PrimTypeWithRef): watpe.Type = {
+  def transformPrimType(tpe: PrimType): watpe.Type = {
     tpe match {
+      case UndefType   => watpe.RefType.any
       case BooleanType => watpe.Int32
       case ByteType    => watpe.Int32
       case ShortType   => watpe.Int32
@@ -106,6 +125,7 @@ object TypeTransformer {
       case LongType    => watpe.Int64
       case FloatType   => watpe.Float32
       case DoubleType  => watpe.Float64
+      case StringType  => watpe.RefType.any
       case NullType    => watpe.RefType.nullref
 
       case NoType | NothingType =>
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/WasmContext.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/WasmContext.scala
index c6c2aee99a..5d30083f97 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/WasmContext.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/WasmContext.scala
@@ -115,7 +115,7 @@ final class WasmContext(
       normalizedName, {
         val typeID = genTypeID.forTableFunctionType(normalizedName)
         val regularParamTyps = normalizedName.paramTypeRefs.map { typeRef =>
-          TypeTransformer.transformLocalType(inferTypeFromTypeRef(typeRef))(this)
+          TypeTransformer.transformParamType(inferTypeFromTypeRef(typeRef))(this)
         }
         val resultType = TypeTransformer.transformResultType(
             inferTypeFromTypeRef(normalizedName.resultTypeRef))(this)
@@ -137,7 +137,7 @@ final class WasmContext(
             watpe.StructField(
               genFieldID.captureParam(i),
               NoOriginalName,
-              TypeTransformer.transformLocalType(tpe)(this),
+              TypeTransformer.transformParamType(tpe)(this),
               isMutable = false
             )
           }

From 265d283812b1731ca7a23ec19dc2054adfc226b7 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Fri, 31 May 2024 20:10:40 +0200
Subject: [PATCH 114/298] Wasm: Handle Cast nodes coming from the optimizer.

---
 .../backend/wasmemitter/FunctionEmitter.scala | 23 +++++++++++++++++--
 1 file changed, 21 insertions(+), 2 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
index e7866fa346..3c3456022b 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
@@ -22,6 +22,8 @@ import org.scalajs.ir.OriginalName.NoOriginalName
 import org.scalajs.ir.Trees._
 import org.scalajs.ir.Types._
 
+import org.scalajs.linker.backend.emitter.Transients
+
 import org.scalajs.linker.backend.webassembly._
 import org.scalajs.linker.backend.webassembly.{Instructions => wa}
 import org.scalajs.linker.backend.webassembly.{Identitities => wanme}
@@ -447,7 +449,10 @@ private class FunctionEmitter private (
       case t: RecordSelect => genRecordSelect(t)
       case t: RecordValue  => genRecordValue(t)
 
-      case _: Transient | _: JSSuperConstructorCall =>
+      // Transients (only generated by the optimizer)
+      case t: Transient => genTransient(t)
+
+      case _: JSSuperConstructorCall =>
         throw new AssertionError(s"Invalid tree: $tree")
     }
 
@@ -1781,6 +1786,10 @@ private class FunctionEmitter private (
   private def genAsInstanceOf(tree: AsInstanceOf): Type = {
     val AsInstanceOf(expr, targetTpe) = tree
 
+    genCast(expr, targetTpe, tree.pos)
+  }
+
+  private def genCast(expr: Tree, targetTpe: Type, pos: Position): Type = {
     val sourceTpe = expr.tpe
 
     if (sourceTpe == NothingType) {
@@ -1804,7 +1813,7 @@ private class FunctionEmitter private (
       } else {
         genTree(expr, AnyType)
 
-        markPosition(tree)
+        markPosition(pos)
 
         targetTpe match {
           case targetTpe: PrimType =>
@@ -2915,6 +2924,16 @@ private class FunctionEmitter private (
     tree.tpe
   }
 
+  private def genTransient(tree: Transient): Type = {
+    tree.value match {
+      case Transients.Cast(expr, tpe) =>
+        genCast(expr, tpe, tree.pos)
+
+      case other =>
+        throw new AssertionError(s"Unknown transient: $other")
+    }
+  }
+
   /*--------------------------------------------------------------------*
    * HERE BE DRAGONS --- Handling of TryFinally, Labeled and Return --- *
    *--------------------------------------------------------------------*/

From 6be639ad6ae95ee1c07f5f6c3e2daeccc123e533 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Wed, 29 May 2024 13:27:04 +0200
Subject: [PATCH 115/298] Opt/Wasm: Take into account that Wasm never uses
 `RuntimeLong`s.

However, it does box `long`s into instances, which means that two
boxed longs are not `===`.
---
 .../scalajs/linker/frontend/optimizer/OptimizerCore.scala    | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
index 7ed5bc57b5..2279eada7e 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
@@ -135,7 +135,8 @@ private[optimizer] abstract class OptimizerCore(
 
   private var curTrampolineId = 0
 
-  private val useRuntimeLong = !config.coreSpec.esFeatures.allowBigIntsForLongs
+  private val useRuntimeLong =
+    !config.coreSpec.esFeatures.allowBigIntsForLongs && !isWasm
 
   /** The record type for inlined `RuntimeLong`. */
   private lazy val inlinedRTLongStructure =
@@ -3732,7 +3733,7 @@ private[optimizer] abstract class OptimizerCore(
       case (StringLiteral(l), StringLiteral(r))   => l == r
       case (ClassOf(l), ClassOf(r))               => l == r
       case (AnyNumLiteral(l), AnyNumLiteral(r))   => l.equals(r)
-      case (LongLiteral(l), LongLiteral(r))       => l == r && !useRuntimeLong
+      case (LongLiteral(l), LongLiteral(r))       => l == r && !useRuntimeLong && !isWasm
       case (Undefined(), Undefined())             => true
       case (Null(), Null())                       => true
       case _                                      => false

From 78d12c4a84f19d73b8d512b99ec7345abdd7d790 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Wed, 29 May 2024 13:27:59 +0200
Subject: [PATCH 116/298] Opt/Wasm: Do not destroy the only shape of ForIn that
 Wasm can handle.

---
 .../frontend/optimizer/OptimizerCore.scala       | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
index 2279eada7e..c8f864fd4e 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
@@ -421,10 +421,22 @@ private[optimizer] abstract class OptimizerCore(
           freshLocalName(name, originalName, mutable = false)
         val localDef = LocalDef(RefinedType(AnyType), mutable = false,
             ReplaceWithVarRef(newName, newSimpleState(UsedAtLeastOnce), None))
-        val newBody = {
-          val bodyScope = scope.withEnv(scope.env.withLocalDef(name, localDef))
+        val bodyScope = scope.withEnv(scope.env.withLocalDef(name, localDef))
+
+        val newBody = if (isWasm) {
+          // Avoid destroying the only shape of ForIn that the Wasm backend can handle
+          body match {
+            case JSFunctionApply(f: VarRef, List(arg: VarRef)) =>
+              JSFunctionApply(transformExpr(f)(bodyScope),
+                  List(transformExpr(arg)(bodyScope)))(body.pos)
+            case _ =>
+              // Wasm will not be able to deal with anything else, but we cannot do anything about it
+              transformStat(body)(bodyScope)
+          }
+        } else {
           transformStat(body)(bodyScope)
         }
+
         ForIn(newObj, LocalIdent(newName)(keyVar.pos), newOriginalName, newBody)
 
       case TryCatch(block, errVar @ LocalIdent(name), originalName, handler) =>

From 7bb17f15963a99991f102707f5c0985b695e5b5c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Wed, 29 May 2024 13:29:16 +0200
Subject: [PATCH 117/298] Opt/Wasm: Disable intrinsics in Wasm mode for now.

We can selectively reintroduce them later.
---
 .../scalajs/linker/frontend/optimizer/OptimizerCore.scala  | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
index c8f864fd4e..11075046c2 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
@@ -151,7 +151,7 @@ private[optimizer] abstract class OptimizerCore(
     inlinedRTLongStructure.recordType.fields(1).name
 
   private val intrinsics =
-    Intrinsics.buildIntrinsics(config.coreSpec.esFeatures)
+    Intrinsics.buildIntrinsics(config.coreSpec.esFeatures, isWasm)
 
   def optimize(thisType: Type, params: List[ParamDef],
       jsClassCaptures: List[ParamDef], resultType: Type, body: Tree,
@@ -6367,9 +6367,10 @@ private[optimizer] object OptimizerCore {
     )
     // scalastyle:on line.size.limit
 
-    def buildIntrinsics(esFeatures: ESFeatures): Intrinsics = {
+    def buildIntrinsics(esFeatures: ESFeatures, isWasm: Boolean): Intrinsics = {
       val allIntrinsics =
-        if (esFeatures.allowBigIntsForLongs) baseIntrinsics
+        if (isWasm) Nil // TODO there are some intrinsics that actually matter on Wasm
+        else if (esFeatures.allowBigIntsForLongs) baseIntrinsics
         else baseIntrinsics ++ runtimeLongIntrinsics
 
       val intrinsicsMap = (for {

From b94ee9991587736a9222d3c2bf4fdf65ad693af9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Fri, 31 May 2024 20:15:06 +0200
Subject: [PATCH 118/298] Enable the optimizer with WebAssembly.

The WebAssembly backend and the optimizer are now happy to work
together, so we can enable the latter.
---
 Jenkinsfile         | 9 +++++++++
 project/Build.scala | 1 -
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/Jenkinsfile b/Jenkinsfile
index 70d90e83fe..a217171026 100644
--- a/Jenkinsfile
+++ b/Jenkinsfile
@@ -422,6 +422,15 @@ def Tasks = [
         'set Global/enableWasmEverywhere := true' \
         'set scalaJSStage in Global := FullOptStage' \
         $testSuite$v/test &&
+    sbtretry ++$scala \
+        'set Global/enableWasmEverywhere := true' \
+        'set scalaJSLinkerConfig in $testSuite.v$v ~= (_.withOptimizer(false))' \
+        $testSuite$v/test &&
+    sbtretry ++$scala \
+        'set Global/enableWasmEverywhere := true' \
+        'set scalaJSLinkerConfig in $testSuite.v$v ~= (_.withOptimizer(false))' \
+        'set scalaJSStage in Global := FullOptStage' \
+        $testSuite$v/test &&
     sbtretry ++$scala \
         'set Global/enableWasmEverywhere := true' \
         testingExample$v/testHtml &&
diff --git a/project/Build.scala b/project/Build.scala
index d1aeeeb5ef..1903d9ace4 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -163,7 +163,6 @@ object MyScalaJSPlugin extends AutoPlugin {
           import CheckedBehavior.Unchecked
           baseConfig
             .withExperimentalUseWebAssembly(true)
-            .withOptimizer(false)
             .withModuleKind(ModuleKind.ESModule)
             .withSemantics { sems =>
               sems

From bc26f0f1eb7c0f95f53b8c3114ba6a463f504a5c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Fri, 31 May 2024 22:31:07 +0200
Subject: [PATCH 119/298] Wasm: Use the original ArrayBuilder implementations.

When compiling to Wasm, the optimized implementation we have for
`ArrayBuilder` makes no sense, as it relies on JavaScript arrays.
Therefore, we revert to using the original implementations when
linking for Wasm.
---
 .../collection/mutable/ArrayBuilder.scala     | 30 +++++++++++++++++++
 .../collection/mutable/ArrayBuilder.scala     | 28 +++++++++++++++++
 2 files changed, 58 insertions(+)

diff --git a/scalalib/overrides-2.12/scala/collection/mutable/ArrayBuilder.scala b/scalalib/overrides-2.12/scala/collection/mutable/ArrayBuilder.scala
index ce3a7d5a03..0e1c43c45e 100644
--- a/scalalib/overrides-2.12/scala/collection/mutable/ArrayBuilder.scala
+++ b/scalalib/overrides-2.12/scala/collection/mutable/ArrayBuilder.scala
@@ -14,6 +14,7 @@ import scala.reflect.ClassTag
 import scala.runtime.BoxedUnit
 
 import scala.scalajs.js
+import scala.scalajs.runtime.linkingInfo
 
 /** A builder class for arrays.
  *
@@ -36,8 +37,37 @@ object ArrayBuilder {
    */
   @inline
   def make[T: ClassTag](): ArrayBuilder[T] =
+    if (linkingInfo.isWebAssembly) makeForWasm()
+    else makeForJS()
+
+  /** Implementation of `make` for JS. */
+  @inline
+  private def makeForJS[T: ClassTag](): ArrayBuilder[T] =
     new ArrayBuilder.generic[T](implicitly[ClassTag[T]].runtimeClass)
 
+  /** Implementation of `make` for Wasm.
+   *
+   *  This is the original upstream implementation from 2.13.x. It is better
+   *  than the one for 2.12.x because it does not use `isPrimitive` as "fast"
+   *  dispatch, which we cannot constant-fold away.
+   */
+  @inline
+  private def makeForWasm[T: ClassTag](): ArrayBuilder[T] = {
+    val tag = implicitly[ClassTag[T]]
+    tag.runtimeClass match {
+      case java.lang.Byte.TYPE      => new ArrayBuilder.ofByte().asInstanceOf[ArrayBuilder[T]]
+      case java.lang.Short.TYPE     => new ArrayBuilder.ofShort().asInstanceOf[ArrayBuilder[T]]
+      case java.lang.Character.TYPE => new ArrayBuilder.ofChar().asInstanceOf[ArrayBuilder[T]]
+      case java.lang.Integer.TYPE   => new ArrayBuilder.ofInt().asInstanceOf[ArrayBuilder[T]]
+      case java.lang.Long.TYPE      => new ArrayBuilder.ofLong().asInstanceOf[ArrayBuilder[T]]
+      case java.lang.Float.TYPE     => new ArrayBuilder.ofFloat().asInstanceOf[ArrayBuilder[T]]
+      case java.lang.Double.TYPE    => new ArrayBuilder.ofDouble().asInstanceOf[ArrayBuilder[T]]
+      case java.lang.Boolean.TYPE   => new ArrayBuilder.ofBoolean().asInstanceOf[ArrayBuilder[T]]
+      case java.lang.Void.TYPE      => new ArrayBuilder.ofUnit().asInstanceOf[ArrayBuilder[T]]
+      case _                        => new ArrayBuilder.ofRef[T with AnyRef]()(tag.asInstanceOf[ClassTag[T with AnyRef]]).asInstanceOf[ArrayBuilder[T]]
+    }
+  }
+
   /** A generic ArrayBuilder optimized for Scala.js.
    *
    *  @tparam T              type of elements for the array builder.
diff --git a/scalalib/overrides-2.13/scala/collection/mutable/ArrayBuilder.scala b/scalalib/overrides-2.13/scala/collection/mutable/ArrayBuilder.scala
index 8f5e94b5e2..a49ae231c2 100644
--- a/scalalib/overrides-2.13/scala/collection/mutable/ArrayBuilder.scala
+++ b/scalalib/overrides-2.13/scala/collection/mutable/ArrayBuilder.scala
@@ -17,6 +17,7 @@ import scala.reflect.ClassTag
 import scala.runtime.BoxedUnit
 
 import scala.scalajs.js
+import scala.scalajs.runtime.linkingInfo
 
 /** A builder class for arrays.
  *
@@ -89,8 +90,35 @@ object ArrayBuilder {
    */
   @inline
   def make[T: ClassTag]: ArrayBuilder[T] =
+    if (linkingInfo.isWebAssembly) makeForWasm
+    else makeForJS
+
+  /** Implementation of `make` for JS. */
+  @inline
+  private def makeForJS[T: ClassTag]: ArrayBuilder[T] =
     new ArrayBuilder.generic[T](implicitly[ClassTag[T]].runtimeClass)
 
+  /** Implementation of `make` for Wasm.
+   *
+   *  This is the original upstream implementation.
+   */
+  @inline
+  private def makeForWasm[T: ClassTag]: ArrayBuilder[T] = {
+    val tag = implicitly[ClassTag[T]]
+    tag.runtimeClass match {
+      case java.lang.Byte.TYPE      => new ArrayBuilder.ofByte().asInstanceOf[ArrayBuilder[T]]
+      case java.lang.Short.TYPE     => new ArrayBuilder.ofShort().asInstanceOf[ArrayBuilder[T]]
+      case java.lang.Character.TYPE => new ArrayBuilder.ofChar().asInstanceOf[ArrayBuilder[T]]
+      case java.lang.Integer.TYPE   => new ArrayBuilder.ofInt().asInstanceOf[ArrayBuilder[T]]
+      case java.lang.Long.TYPE      => new ArrayBuilder.ofLong().asInstanceOf[ArrayBuilder[T]]
+      case java.lang.Float.TYPE     => new ArrayBuilder.ofFloat().asInstanceOf[ArrayBuilder[T]]
+      case java.lang.Double.TYPE    => new ArrayBuilder.ofDouble().asInstanceOf[ArrayBuilder[T]]
+      case java.lang.Boolean.TYPE   => new ArrayBuilder.ofBoolean().asInstanceOf[ArrayBuilder[T]]
+      case java.lang.Void.TYPE      => new ArrayBuilder.ofUnit().asInstanceOf[ArrayBuilder[T]]
+      case _                        => new ArrayBuilder.ofRef[T with AnyRef]()(tag.asInstanceOf[ClassTag[T with AnyRef]]).asInstanceOf[ArrayBuilder[T]]
+    }
+  }
+
   /** A generic ArrayBuilder optimized for Scala.js.
    *
    *  @tparam T              type of elements for the array builder.

From ad162ac7e1cc16f7f0be092984dc60409805bb78 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Sat, 1 Jun 2024 11:59:55 +0200
Subject: [PATCH 120/298] Opt/Wasm: Enable the intrinsics that make sense for
 Wasm.

This includes `arraycopy` and `getClass().getName()`, which produce
new `Transient` nodes that we need to handle in the Wasm backend.
---
 .../backend/wasmemitter/CoreWasmLib.scala     | 401 +++++++++++-------
 .../backend/wasmemitter/FunctionEmitter.scala |  36 ++
 .../linker/backend/wasmemitter/VarGen.scala   |  14 +
 .../frontend/optimizer/OptimizerCore.scala    |  22 +-
 4 files changed, 321 insertions(+), 152 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
index 26fb965464..9f67841cbf 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
@@ -32,6 +32,23 @@ object CoreWasmLib {
 
   private implicit val noPos: Position = Position.NoPosition
 
+  private val arrayBaseRefs: List[NonArrayTypeRef] = List(
+    BooleanRef,
+    CharRef,
+    ByteRef,
+    ShortRef,
+    IntRef,
+    LongRef,
+    FloatRef,
+    DoubleRef,
+    ClassRef(ObjectClass)
+  )
+
+  private def charCodeForOriginalName(baseRef: NonArrayTypeRef): Char = baseRef match {
+    case baseRef: PrimRef => baseRef.charCode
+    case _: ClassRef      => 'O'
+  }
+
   /** Fields of the `typeData` struct definition.
    *
    *  They are accessible as a public list because they must be repeated in every vtable type
@@ -580,10 +597,13 @@ object CoreWasmLib {
     genGetComponentType()
     genNewArrayOfThisClass()
     genAnyGetClass()
+    genAnyGetClassName()
+    genAnyGetTypeData()
     genNewArrayObject()
     genIdentityHashCode()
     genSearchReflectiveProxy()
     genArrayCloneFunctions()
+    genArrayCopyFunctions()
   }
 
   private def newFunctionBuilder(functionID: FunctionID, originalName: OriginalName)(
@@ -1567,13 +1587,50 @@ object CoreWasmLib {
    *  [[https://www.scala-js.org/doc/semantics.html#getclass]].
    */
   private def genAnyGetClass()(implicit ctx: WasmContext): Unit = {
-    val typeDataType = RefType(genTypeID.typeData)
-
     val fb = newFunctionBuilder(genFunctionID.anyGetClass)
     val valueParam = fb.addParam("value", RefType.any)
     fb.setResultType(RefType.nullable(genTypeID.ClassStruct))
 
-    val typeDataLocal = fb.addLocal("typeData", typeDataType)
+    fb.block() { typeDataIsNullLabel =>
+      fb += LocalGet(valueParam)
+      fb += Call(genFunctionID.anyGetTypeData)
+      fb += BrOnNull(typeDataIsNullLabel)
+      fb += ReturnCall(genFunctionID.getClassOf)
+    }
+    fb += RefNull(HeapType.None)
+
+    fb.buildAndAddToModule()
+  }
+
+  /** `anyGetClassName: (ref any) -> (ref any)` (a string).
+   *
+   *  This is the implementation of `value.getClass().getName()`, which comes
+   *  to the backend as the `ObjectClassName` intrinsic.
+   */
+  private def genAnyGetClassName()(implicit ctx: WasmContext): Unit = {
+    val fb = newFunctionBuilder(genFunctionID.anyGetClassName)
+    val valueParam = fb.addParam("value", RefType.any)
+    fb.setResultType(RefType.any)
+
+    fb += LocalGet(valueParam)
+    fb += Call(genFunctionID.anyGetTypeData)
+    fb += RefAsNonNull // NPE for null.getName()
+    fb += ReturnCall(genFunctionID.typeDataName)
+
+    fb.buildAndAddToModule()
+  }
+
+  /** `anyGetTypeData: (ref any) -> (ref null typeData)`.
+   *
+   *  Common code between `anyGetClass` and `anyGetClassName`.
+   */
+  private def genAnyGetTypeData()(implicit ctx: WasmContext): Unit = {
+    val typeDataType = RefType(genTypeID.typeData)
+
+    val fb = newFunctionBuilder(genFunctionID.anyGetTypeData)
+    val valueParam = fb.addParam("value", RefType.any)
+    fb.setResultType(RefType.nullable(genTypeID.typeData))
+
     val doubleValueLocal = fb.addLocal("doubleValue", Float64)
     val intValueLocal = fb.addLocal("intValue", Int32)
     val ourObjectLocal = fb.addLocal("ourObject", RefType(genTypeID.ObjectStruct))
@@ -1581,139 +1638,137 @@ object CoreWasmLib {
     def getHijackedClassTypeDataInstr(className: ClassName): Instr =
       GlobalGet(genGlobalID.forVTable(className))
 
-    fb.block(RefType.nullable(genTypeID.ClassStruct)) { nonNullClassOfLabel =>
-      fb.block(typeDataType) { gotTypeDataLabel =>
-        fb.block(RefType(genTypeID.ObjectStruct)) { ourObjectLabel =>
-          // if value is our object, jump to $ourObject
-          fb += LocalGet(valueParam)
-          fb += BrOnCast(
-            ourObjectLabel,
-            RefType.any,
-            RefType(genTypeID.ObjectStruct)
-          )
+    fb.block(RefType(genTypeID.ObjectStruct)) { ourObjectLabel =>
+      // if value is our object, jump to $ourObject
+      fb += LocalGet(valueParam)
+      fb += BrOnCast(
+        ourObjectLabel,
+        RefType.any,
+        RefType(genTypeID.ObjectStruct)
+      )
 
-          // switch(jsValueType(value)) { ... }
-          fb.switch(typeDataType) { () =>
-            // scrutinee
-            fb += LocalGet(valueParam)
-            fb += Call(genFunctionID.jsValueType)
-          }(
-            // case JSValueTypeFalse, JSValueTypeTrue => typeDataOf[jl.Boolean]
-            List(JSValueTypeFalse, JSValueTypeTrue) -> { () =>
-              fb += getHijackedClassTypeDataInstr(BoxedBooleanClass)
-            },
-            // case JSValueTypeString => typeDataOf[jl.String]
-            List(JSValueTypeString) -> { () =>
-              fb += getHijackedClassTypeDataInstr(BoxedStringClass)
-            },
-            // case JSValueTypeNumber => ...
-            List(JSValueTypeNumber) -> { () =>
-              /* For `number`s, the result is based on the actual value, as specified by
-               * [[https://www.scala-js.org/doc/semantics.html#getclass]].
-               */
-
-              // doubleValue := unboxDouble(value)
-              fb += LocalGet(valueParam)
-              fb += Call(genFunctionID.unbox(DoubleRef))
-              fb += LocalTee(doubleValueLocal)
-
-              // intValue := doubleValue.toInt
-              fb += I32TruncSatF64S
-              fb += LocalTee(intValueLocal)
-
-              // if same(intValue.toDouble, doubleValue) -- same bit pattern to avoid +0.0 == -0.0
-              fb += F64ConvertI32S
-              fb += I64ReinterpretF64
-              fb += LocalGet(doubleValueLocal)
-              fb += I64ReinterpretF64
-              fb += I64Eq
+      // switch(jsValueType(value)) { ... }
+      fb.switch() { () =>
+        // scrutinee
+        fb += LocalGet(valueParam)
+        fb += Call(genFunctionID.jsValueType)
+      }(
+        // case JSValueTypeFalse, JSValueTypeTrue => typeDataOf[jl.Boolean]
+        List(JSValueTypeFalse, JSValueTypeTrue) -> { () =>
+          fb += getHijackedClassTypeDataInstr(BoxedBooleanClass)
+          fb += Return
+        },
+        // case JSValueTypeString => typeDataOf[jl.String]
+        List(JSValueTypeString) -> { () =>
+          fb += getHijackedClassTypeDataInstr(BoxedStringClass)
+          fb += Return
+        },
+        // case JSValueTypeNumber => ...
+        List(JSValueTypeNumber) -> { () =>
+          /* For `number`s, the result is based on the actual value, as specified by
+           * [[https://www.scala-js.org/doc/semantics.html#getclass]].
+           */
+
+          // doubleValue := unboxDouble(value)
+          fb += LocalGet(valueParam)
+          fb += Call(genFunctionID.unbox(DoubleRef))
+          fb += LocalTee(doubleValueLocal)
+
+          // intValue := doubleValue.toInt
+          fb += I32TruncSatF64S
+          fb += LocalTee(intValueLocal)
+
+          // if same(intValue.toDouble, doubleValue) -- same bit pattern to avoid +0.0 == -0.0
+          fb += F64ConvertI32S
+          fb += I64ReinterpretF64
+          fb += LocalGet(doubleValueLocal)
+          fb += I64ReinterpretF64
+          fb += I64Eq
+          fb.ifThenElse(typeDataType) {
+            // then it is a Byte, a Short, or an Integer
+
+            // if intValue.toByte.toInt == intValue
+            fb += LocalGet(intValueLocal)
+            fb += I32Extend8S
+            fb += LocalGet(intValueLocal)
+            fb += I32Eq
+            fb.ifThenElse(typeDataType) {
+              // then it is a Byte
+              fb += getHijackedClassTypeDataInstr(BoxedByteClass)
+            } {
+              // else, if intValue.toShort.toInt == intValue
+              fb += LocalGet(intValueLocal)
+              fb += I32Extend16S
+              fb += LocalGet(intValueLocal)
+              fb += I32Eq
               fb.ifThenElse(typeDataType) {
-                // then it is a Byte, a Short, or an Integer
-
-                // if intValue.toByte.toInt == intValue
-                fb += LocalGet(intValueLocal)
-                fb += I32Extend8S
-                fb += LocalGet(intValueLocal)
-                fb += I32Eq
-                fb.ifThenElse(typeDataType) {
-                  // then it is a Byte
-                  fb += getHijackedClassTypeDataInstr(BoxedByteClass)
-                } {
-                  // else, if intValue.toShort.toInt == intValue
-                  fb += LocalGet(intValueLocal)
-                  fb += I32Extend16S
-                  fb += LocalGet(intValueLocal)
-                  fb += I32Eq
-                  fb.ifThenElse(typeDataType) {
-                    // then it is a Short
-                    fb += getHijackedClassTypeDataInstr(BoxedShortClass)
-                  } {
-                    // else, it is an Integer
-                    fb += getHijackedClassTypeDataInstr(BoxedIntegerClass)
-                  }
-                }
+                // then it is a Short
+                fb += getHijackedClassTypeDataInstr(BoxedShortClass)
               } {
-                // else, it is a Float or a Double
-
-                // if doubleValue.toFloat.toDouble == doubleValue
-                fb += LocalGet(doubleValueLocal)
-                fb += F32DemoteF64
-                fb += F64PromoteF32
-                fb += LocalGet(doubleValueLocal)
-                fb += F64Eq
-                fb.ifThenElse(typeDataType) {
-                  // then it is a Float
-                  fb += getHijackedClassTypeDataInstr(BoxedFloatClass)
-                } {
-                  // else, if it is NaN
-                  fb += LocalGet(doubleValueLocal)
-                  fb += LocalGet(doubleValueLocal)
-                  fb += F64Ne
-                  fb.ifThenElse(typeDataType) {
-                    // then it is a Float
-                    fb += getHijackedClassTypeDataInstr(BoxedFloatClass)
-                  } {
-                    // else, it is a Double
-                    fb += getHijackedClassTypeDataInstr(BoxedDoubleClass)
-                  }
-                }
+                // else, it is an Integer
+                fb += getHijackedClassTypeDataInstr(BoxedIntegerClass)
               }
-            },
-            // case JSValueTypeUndefined => typeDataOf[jl.Void]
-            List(JSValueTypeUndefined) -> { () =>
-              fb += getHijackedClassTypeDataInstr(BoxedUnitClass)
             }
-          ) { () =>
-            // case _ (JSValueTypeOther) => return null
-            fb += RefNull(HeapType(genTypeID.ClassStruct))
-            fb += Return
-          }
-
-          fb += Br(gotTypeDataLabel)
-        }
-
-        /* Now we have one of our objects. Normally we only have to get the
-         * vtable, but there are two exceptions. If the value is an instance of
-         * `jl.CharacterBox` or `jl.LongBox`, we must use the typeData of
-         * `jl.Character` or `jl.Long`, respectively.
-         */
-        fb += LocalTee(ourObjectLocal)
-        fb += RefTest(RefType(genTypeID.forClass(SpecialNames.CharBoxClass)))
-        fb.ifThenElse(typeDataType) {
-          fb += getHijackedClassTypeDataInstr(BoxedCharacterClass)
-        } {
-          fb += LocalGet(ourObjectLocal)
-          fb += RefTest(RefType(genTypeID.forClass(SpecialNames.LongBoxClass)))
-          fb.ifThenElse(typeDataType) {
-            fb += getHijackedClassTypeDataInstr(BoxedLongClass)
           } {
-            fb += LocalGet(ourObjectLocal)
-            fb += StructGet(genTypeID.ObjectStruct, genFieldID.objStruct.vtable)
+            // else, it is a Float or a Double
+
+            // if doubleValue.toFloat.toDouble == doubleValue
+            fb += LocalGet(doubleValueLocal)
+            fb += F32DemoteF64
+            fb += F64PromoteF32
+            fb += LocalGet(doubleValueLocal)
+            fb += F64Eq
+            fb.ifThenElse(typeDataType) {
+              // then it is a Float
+              fb += getHijackedClassTypeDataInstr(BoxedFloatClass)
+            } {
+              // else, if it is NaN
+              fb += LocalGet(doubleValueLocal)
+              fb += LocalGet(doubleValueLocal)
+              fb += F64Ne
+              fb.ifThenElse(typeDataType) {
+                // then it is a Float
+                fb += getHijackedClassTypeDataInstr(BoxedFloatClass)
+              } {
+                // else, it is a Double
+                fb += getHijackedClassTypeDataInstr(BoxedDoubleClass)
+              }
+            }
           }
+          fb += Return
+        },
+        // case JSValueTypeUndefined => typeDataOf[jl.Void]
+        List(JSValueTypeUndefined) -> { () =>
+          fb += getHijackedClassTypeDataInstr(BoxedUnitClass)
+          fb += Return
         }
+      ) { () =>
+        // case _ (JSValueTypeOther) => return null
+        fb += RefNull(HeapType.None)
+        fb += Return
       }
 
-      fb += Call(genFunctionID.getClassOf)
+      fb += Unreachable
+    }
+
+    /* Now we have one of our objects. Normally we only have to get the
+     * vtable, but there are two exceptions. If the value is an instance of
+     * `jl.CharacterBox` or `jl.LongBox`, we must use the typeData of
+     * `jl.Character` or `jl.Long`, respectively.
+     */
+    fb += LocalTee(ourObjectLocal)
+    fb += RefTest(RefType(genTypeID.forClass(SpecialNames.CharBoxClass)))
+    fb.ifThenElse(typeDataType) {
+      fb += getHijackedClassTypeDataInstr(BoxedCharacterClass)
+    } {
+      fb += LocalGet(ourObjectLocal)
+      fb += RefTest(RefType(genTypeID.forClass(SpecialNames.LongBoxClass)))
+      fb.ifThenElse(typeDataType) {
+        fb += getHijackedClassTypeDataInstr(BoxedLongClass)
+      } {
+        fb += LocalGet(ourObjectLocal)
+        fb += StructGet(genTypeID.ObjectStruct, genFieldID.objStruct.vtable)
+      }
     }
 
     fb.buildAndAddToModule()
@@ -2139,29 +2194,13 @@ object CoreWasmLib {
   }
 
   private def genArrayCloneFunctions()(implicit ctx: WasmContext): Unit = {
-    val baseRefs = List(
-      BooleanRef,
-      CharRef,
-      ByteRef,
-      ShortRef,
-      IntRef,
-      LongRef,
-      FloatRef,
-      DoubleRef,
-      ClassRef(ObjectClass)
-    )
-
-    for (baseRef <- baseRefs)
+    for (baseRef <- arrayBaseRefs)
       genArrayCloneFunction(baseRef)
   }
 
   /** Generates the clone function for the array class with the given base. */
   private def genArrayCloneFunction(baseRef: NonArrayTypeRef)(implicit ctx: WasmContext): Unit = {
-    val charCodeForOriginalName = baseRef match {
-      case baseRef: PrimRef => baseRef.charCode
-      case _: ClassRef      => 'O'
-    }
-    val originalName = OriginalName("cloneArray." + charCodeForOriginalName)
+    val originalName = OriginalName("cloneArray." + charCodeForOriginalName(baseRef))
 
     val fb = newFunctionBuilder(genFunctionID.cloneArray(baseRef), originalName)
     val fromParam = fb.addParam("from", RefType(genTypeID.ObjectStruct))
@@ -2211,4 +2250,78 @@ object CoreWasmLib {
     fb.buildAndAddToModule()
   }
 
+  private def genArrayCopyFunctions()(implicit ctx: WasmContext): Unit = {
+    for (baseRef <- arrayBaseRefs)
+      genSpecializedArrayCopy(baseRef)
+
+    genGenericArrayCopy()
+  }
+
+  /** Generates a specialized arrayCopy for the array class with the given base. */
+  private def genSpecializedArrayCopy(baseRef: NonArrayTypeRef)(implicit ctx: WasmContext): Unit = {
+    val originalName = OriginalName("arrayCopy." + charCodeForOriginalName(baseRef))
+
+    val arrayTypeRef = ArrayTypeRef(baseRef, 1)
+    val arrayStructTypeID = genTypeID.forArrayClass(arrayTypeRef)
+    val arrayClassType = RefType.nullable(arrayStructTypeID)
+    val underlyingArrayTypeID = genTypeID.underlyingOf(arrayTypeRef)
+
+    val fb = newFunctionBuilder(genFunctionID.specializedArrayCopy(arrayTypeRef), originalName)
+    val srcParam = fb.addParam("src", arrayClassType)
+    val srcPosParam = fb.addParam("srcPos", Int32)
+    val destParam = fb.addParam("dest", arrayClassType)
+    val destPosParam = fb.addParam("destPos", Int32)
+    val lengthParam = fb.addParam("length", Int32)
+
+    fb += LocalGet(destParam)
+    fb += StructGet(arrayStructTypeID, genFieldID.objStruct.arrayUnderlying)
+    fb += LocalGet(destPosParam)
+    fb += LocalGet(srcParam)
+    fb += StructGet(arrayStructTypeID, genFieldID.objStruct.arrayUnderlying)
+    fb += LocalGet(srcPosParam)
+    fb += LocalGet(lengthParam)
+    fb += ArrayCopy(underlyingArrayTypeID, underlyingArrayTypeID)
+
+    fb.buildAndAddToModule()
+  }
+
+  /** Generates the generic arrayCopy for an unknown array class. */
+  private def genGenericArrayCopy()(implicit ctx: WasmContext): Unit = {
+    val fb = newFunctionBuilder(genFunctionID.genericArrayCopy)
+    val srcParam = fb.addParam("src", RefType.anyref)
+    val srcPosParam = fb.addParam("srcPos", Int32)
+    val destParam = fb.addParam("dest", RefType.anyref)
+    val destPosParam = fb.addParam("destPos", Int32)
+    val lengthParam = fb.addParam("length", Int32)
+
+    val anyrefToAnyrefBlockType =
+      fb.sigToBlockType(FunctionType(List(RefType.anyref), List(RefType.anyref)))
+
+    // Dispatch done based on the type of src
+    fb += LocalGet(srcParam)
+
+    for (baseRef <- arrayBaseRefs) {
+      val arrayTypeRef = ArrayTypeRef(baseRef, 1)
+      val arrayStructTypeID = genTypeID.forArrayClass(arrayTypeRef)
+      val nonNullArrayClassType = RefType(arrayStructTypeID)
+
+      fb.block(anyrefToAnyrefBlockType) { notThisArrayTypeLabel =>
+        fb += BrOnCastFail(notThisArrayTypeLabel, RefType.anyref, nonNullArrayClassType)
+
+        fb += LocalGet(srcPosParam)
+        fb += LocalGet(destParam)
+        fb += RefCast(nonNullArrayClassType)
+        fb += LocalGet(destPosParam)
+        fb += LocalGet(lengthParam)
+
+        fb += ReturnCall(genFunctionID.specializedArrayCopy(arrayTypeRef))
+      }
+    }
+
+    // Trap if `src` was not an instance of any of the array class types
+    fb += Unreachable
+
+    fb.buildAndAddToModule()
+  }
+
 }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
index 3c3456022b..88f70ebdca 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
@@ -2929,11 +2929,47 @@ private class FunctionEmitter private (
       case Transients.Cast(expr, tpe) =>
         genCast(expr, tpe, tree.pos)
 
+      case value: Transients.SystemArrayCopy =>
+        genSystemArrayCopy(tree, value)
+
+      case Transients.ObjectClassName(obj) =>
+        genTree(obj, AnyType)
+        markPosition(tree)
+        fb += wa.RefAsNonNull // trap on NPE
+        fb += wa.Call(genFunctionID.anyGetClassName)
+        StringType
+
       case other =>
         throw new AssertionError(s"Unknown transient: $other")
     }
   }
 
+  private def genSystemArrayCopy(tree: Transient,
+      transientValue: Transients.SystemArrayCopy): Type = {
+    val Transients.SystemArrayCopy(src, srcPos, dest, destPos, length) = transientValue
+
+    genTreeAuto(src)
+    genTree(srcPos, IntType)
+    genTreeAuto(dest)
+    genTree(destPos, IntType)
+    genTree(length, IntType)
+
+    markPosition(tree)
+
+    (src.tpe, dest.tpe) match {
+      case (ArrayType(srcArrayTypeRef), ArrayType(destArrayTypeRef))
+          if genTypeID.forArrayClass(srcArrayTypeRef) == genTypeID.forArrayClass(destArrayTypeRef) =>
+        // Generate a specialized arrayCopyT call
+        fb += wa.Call(genFunctionID.specializedArrayCopy(srcArrayTypeRef))
+
+      case _ =>
+        // Generate a generic arrayCopy call
+        fb += wa.Call(genFunctionID.genericArrayCopy)
+    }
+
+    NoType
+  }
+
   /*--------------------------------------------------------------------*
    * HERE BE DRAGONS --- Handling of TryFinally, Labeled and Return --- *
    *--------------------------------------------------------------------*/
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
index 7d26398a25..aafdf2f98b 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
@@ -227,9 +227,23 @@ object VarGen {
     case object getComponentType extends FunctionID
     case object newArrayOfThisClass extends FunctionID
     case object anyGetClass extends FunctionID
+    case object anyGetClassName extends FunctionID
+    case object anyGetTypeData extends FunctionID
     case object newArrayObject extends FunctionID
     case object identityHashCode extends FunctionID
     case object searchReflectiveProxy extends FunctionID
+
+    private final case class SpecializedArrayCopyID(arrayBaseRef: NonArrayTypeRef) extends FunctionID
+
+    def specializedArrayCopy(arrayTypeRef: ArrayTypeRef): FunctionID = {
+      val baseRef = arrayTypeRef match {
+        case ArrayTypeRef(baseRef: PrimRef, 1) => baseRef
+        case _                                 => ClassRef(ObjectClass)
+      }
+      SpecializedArrayCopyID(baseRef)
+    }
+
+    case object genericArrayCopy extends FunctionID
   }
 
   object genFieldID {
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
index 11075046c2..40a269016e 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
@@ -6314,7 +6314,7 @@ private[optimizer] object OptimizerCore {
       ClassRef(ClassName(s"scala.scalajs.js.typedarray.${baseName}Array"))
 
     // scalastyle:off line.size.limit
-    private val baseIntrinsics: List[(ClassName, List[(MethodName, Int)])] = List(
+    private val commonIntrinsics: List[(ClassName, List[(MethodName, Int)])] = List(
         ClassName("java.lang.System$") -> List(
             m("arraycopy", List(O, I, O, I, I), V) -> ArrayCopy
         ),
@@ -6326,10 +6326,6 @@ private[optimizer] object OptimizerCore {
         ClassName("java.lang.Integer$") -> List(
             m("numberOfLeadingZeros", List(I), I) -> IntegerNLZ
         ),
-        ClassName("scala.collection.mutable.ArrayBuilder$") -> List(
-            m("scala$collection$mutable$ArrayBuilder$$zeroOf", List(ClassClassRef), O) -> ArrayBuilderZeroOf,
-            m("scala$collection$mutable$ArrayBuilder$$genericArrayBuilderResult", List(ClassClassRef, JSArrayClassRef), O) -> GenericArrayBuilderResult
-        ),
         ClassName("java.lang.Class") -> List(
             m("getComponentType", Nil, ClassClassRef) -> ClassGetComponentType,
             m("getName", Nil, StringClassRef) -> ClassGetName
@@ -6339,6 +6335,13 @@ private[optimizer] object OptimizerCore {
         ),
         ClassName("scala.scalajs.js.special.package$") -> List(
             m("objectLiteral", List(SeqClassRef), JSObjectClassRef) -> ObjectLiteral
+        )
+    )
+
+    private val baseJSIntrinsics: List[(ClassName, List[(MethodName, Int)])] = List(
+        ClassName("scala.collection.mutable.ArrayBuilder$") -> List(
+            m("scala$collection$mutable$ArrayBuilder$$zeroOf", List(ClassClassRef), O) -> ArrayBuilderZeroOf,
+            m("scala$collection$mutable$ArrayBuilder$$genericArrayBuilderResult", List(ClassClassRef, JSArrayClassRef), O) -> GenericArrayBuilderResult
         ),
         ClassName("scala.scalajs.js.typedarray.package$") -> List(
             m("byteArray2Int8Array", List(a(ByteRef)), typedarrayClassRef("Int8")) -> ByteArrayToInt8Array,
@@ -6368,10 +6371,13 @@ private[optimizer] object OptimizerCore {
     // scalastyle:on line.size.limit
 
     def buildIntrinsics(esFeatures: ESFeatures, isWasm: Boolean): Intrinsics = {
-      val allIntrinsics =
-        if (isWasm) Nil // TODO there are some intrinsics that actually matter on Wasm
-        else if (esFeatures.allowBigIntsForLongs) baseIntrinsics
+      val allIntrinsics = if (isWasm) {
+        commonIntrinsics
+      } else {
+        val baseIntrinsics = commonIntrinsics ::: baseJSIntrinsics
+        if (esFeatures.allowBigIntsForLongs) baseIntrinsics
         else baseIntrinsics ++ runtimeLongIntrinsics
+      }
 
       val intrinsicsMap = (for {
         (className, methodsAndCodes) <- allIntrinsics

From 7276564fb8277de3e22b961232d76006ed6c96a6 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Sun, 2 Jun 2024 13:46:45 +0200
Subject: [PATCH 121/298] Opt/Wasm: Add a number of Wasm-specific intrinsics
 and transients.

The motivation is mainly to get intrinsics for the bit-conversions
between integers and floating point numbers, as well as for
`numberLeadingZeros`. These are building blocks for many other
low-level operations, and their JS-builtin-based implementation is
really bad on Wasm for those use cases.

Once we have the infrastructure for those as transients in the Wasm
backend, we also take the opportunity to add a series of other
methods that have a direct Wasm opcode equivalent.
---
 javalib/src/main/scala/java/lang/Double.scala |   2 +
 javalib/src/main/scala/java/lang/Float.scala  |   2 +
 .../src/main/scala/java/lang/Integer.scala    |   7 +
 javalib/src/main/scala/java/lang/Long.scala   |   9 +-
 javalib/src/main/scala/java/lang/Math.scala   |  10 +
 .../backend/wasmemitter/FunctionEmitter.scala |  13 +
 .../backend/wasmemitter/WasmTransients.scala  | 209 +++++++++++++
 .../frontend/optimizer/OptimizerCore.scala    | 284 +++++++++++++++++-
 8 files changed, 521 insertions(+), 15 deletions(-)
 create mode 100644 linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/WasmTransients.scala

diff --git a/javalib/src/main/scala/java/lang/Double.scala b/javalib/src/main/scala/java/lang/Double.scala
index bb6626981e..ffe3381bfc 100644
--- a/javalib/src/main/scala/java/lang/Double.scala
+++ b/javalib/src/main/scala/java/lang/Double.scala
@@ -366,9 +366,11 @@ object Double {
   @inline def hashCode(value: scala.Double): Int =
     FloatingPointBits.numberHashCode(value)
 
+  // Wasm intrinsic
   @inline def longBitsToDouble(bits: scala.Long): scala.Double =
     FloatingPointBits.longBitsToDouble(bits)
 
+  // Wasm intrinsic
   @inline def doubleToLongBits(value: scala.Double): scala.Long =
     FloatingPointBits.doubleToLongBits(value)
 
diff --git a/javalib/src/main/scala/java/lang/Float.scala b/javalib/src/main/scala/java/lang/Float.scala
index 4dcd15a6c1..303b48fc3b 100644
--- a/javalib/src/main/scala/java/lang/Float.scala
+++ b/javalib/src/main/scala/java/lang/Float.scala
@@ -378,9 +378,11 @@ object Float {
   @inline def hashCode(value: scala.Float): Int =
     FloatingPointBits.numberHashCode(value)
 
+  // Wasm intrinsic
   @inline def intBitsToFloat(bits: scala.Int): scala.Float =
     FloatingPointBits.intBitsToFloat(bits)
 
+  // Wasm intrinsic
   @inline def floatToIntBits(value: scala.Float): scala.Int =
     FloatingPointBits.floatToIntBits(value)
 
diff --git a/javalib/src/main/scala/java/lang/Integer.scala b/javalib/src/main/scala/java/lang/Integer.scala
index 90c46d364f..78267337da 100644
--- a/javalib/src/main/scala/java/lang/Integer.scala
+++ b/javalib/src/main/scala/java/lang/Integer.scala
@@ -198,6 +198,7 @@ object Integer {
   @inline def toUnsignedLong(x: Int): scala.Long =
     x.toLong & 0xffffffffL
 
+  // Wasm intrinsic
   def bitCount(i: scala.Int): scala.Int = {
     /* See http://graphics.stanford.edu/~seander/bithacks.html#CountBitsSetParallel
      *
@@ -219,10 +220,12 @@ object Integer {
     (((t2 + (t2 >> 4)) & 0xF0F0F0F) * 0x1010101) >> 24
   }
 
+  // Wasm intrinsic
   @inline def divideUnsigned(dividend: Int, divisor: Int): Int =
     if (divisor == 0) 0 / 0
     else asInt(asUint(dividend) / asUint(divisor))
 
+  // Wasm intrinsic
   @inline def remainderUnsigned(dividend: Int, divisor: Int): Int =
     if (divisor == 0) 0 % 0
     else asInt(asUint(dividend) % asUint(divisor))
@@ -263,15 +266,18 @@ object Integer {
     reverseBytes((k & 0x0F0F0F0F) << 4 | (k >> 4) & 0x0F0F0F0F)
   }
 
+  // Wasm intrinsic
   @inline def rotateLeft(i: scala.Int, distance: scala.Int): scala.Int =
     (i << distance) | (i >>> -distance)
 
+  // Wasm intrinsic
   @inline def rotateRight(i: scala.Int, distance: scala.Int): scala.Int =
     (i >>> distance) | (i << -distance)
 
   @inline def signum(i: scala.Int): scala.Int =
     if (i == 0) 0 else if (i < 0) -1 else 1
 
+  // Intrinsic, fallback on actual code for non-literal in JS
   @inline def numberOfLeadingZeros(i: scala.Int): scala.Int = {
     if (linkingInfo.esVersion >= ESVersion.ES2015) js.Math.clz32(i)
     else clz32Dynamic(i)
@@ -296,6 +302,7 @@ object Integer {
     }
   }
 
+  // Wasm intrinsic
   @inline def numberOfTrailingZeros(i: scala.Int): scala.Int =
     if (i == 0) 32
     else 31 - numberOfLeadingZeros(i & -i)
diff --git a/javalib/src/main/scala/java/lang/Long.scala b/javalib/src/main/scala/java/lang/Long.scala
index e6bf36ac1c..0413372acf 100644
--- a/javalib/src/main/scala/java/lang/Long.scala
+++ b/javalib/src/main/scala/java/lang/Long.scala
@@ -348,11 +348,11 @@ object Long {
   @inline def compareUnsigned(x: scala.Long, y: scala.Long): scala.Int =
     compare(x ^ SignBit, y ^ SignBit)
 
-  // Intrinsic
+  // Intrinsic, except for JS when using bigint's for longs
   def divideUnsigned(dividend: scala.Long, divisor: scala.Long): scala.Long =
     divModUnsigned(dividend, divisor, isDivide = true)
 
-  // Intrinsic
+  // Intrinsic, except for JS when using bigint's for longs
   def remainderUnsigned(dividend: scala.Long, divisor: scala.Long): scala.Long =
     divModUnsigned(dividend, divisor, isDivide = false)
 
@@ -408,6 +408,7 @@ object Long {
         if (lo != 0) 0 else Integer.lowestOneBit(hi))
   }
 
+  // Wasm intrinsic
   @inline
   def bitCount(i: scala.Long): scala.Int = {
     val lo = i.toInt
@@ -436,10 +437,12 @@ object Long {
   private def makeLongFromLoHi(lo: Int, hi: Int): scala.Long =
     (lo.toLong & 0xffffffffL) | (hi.toLong << 32)
 
+  // Wasm intrinsic
   @inline
   def rotateLeft(i: scala.Long, distance: scala.Int): scala.Long =
     (i << distance) | (i >>> -distance)
 
+  // Wasm intrinsic
   @inline
   def rotateRight(i: scala.Long, distance: scala.Int): scala.Long =
     (i >>> distance) | (i << -distance)
@@ -452,6 +455,7 @@ object Long {
     else 1
   }
 
+  // Wasm intrinsic
   @inline
   def numberOfLeadingZeros(l: scala.Long): Int = {
     val hi = (l >>> 32).toInt
@@ -459,6 +463,7 @@ object Long {
     else         Integer.numberOfLeadingZeros(l.toInt) + 32
   }
 
+  // Wasm intrinsic
   @inline
   def numberOfTrailingZeros(l: scala.Long): Int = {
     val lo = l.toInt
diff --git a/javalib/src/main/scala/java/lang/Math.scala b/javalib/src/main/scala/java/lang/Math.scala
index eebe0d67e4..42262255f3 100644
--- a/javalib/src/main/scala/java/lang/Math.scala
+++ b/javalib/src/main/scala/java/lang/Math.scala
@@ -28,22 +28,30 @@ object Math {
 
   @inline def abs(a: scala.Int): scala.Int = if (a < 0) -a else a
   @inline def abs(a: scala.Long): scala.Long = if (a < 0) -a else a
+
+  // Wasm intrinsics
   @inline def abs(a: scala.Float): scala.Float = js.Math.abs(a).toFloat
   @inline def abs(a: scala.Double): scala.Double = js.Math.abs(a)
 
   @inline def max(a: scala.Int, b: scala.Int): scala.Int = if (a > b) a else b
   @inline def max(a: scala.Long, b: scala.Long): scala.Long = if (a > b) a else b
+
+  // Wasm intrinsics
   @inline def max(a: scala.Float, b: scala.Float): scala.Float = js.Math.max(a, b).toFloat
   @inline def max(a: scala.Double, b: scala.Double): scala.Double = js.Math.max(a, b)
 
   @inline def min(a: scala.Int, b: scala.Int): scala.Int = if (a < b) a else b
   @inline def min(a: scala.Long, b: scala.Long): scala.Long = if (a < b) a else b
+
+  // Wasm intrinsics
   @inline def min(a: scala.Float, b: scala.Float): scala.Float = js.Math.min(a, b).toFloat
   @inline def min(a: scala.Double, b: scala.Double): scala.Double = js.Math.min(a, b)
 
+  // Wasm intrinsics
   @inline def ceil(a: scala.Double): scala.Double = js.Math.ceil(a)
   @inline def floor(a: scala.Double): scala.Double = js.Math.floor(a)
 
+  // Wasm intrinsic
   def rint(a: scala.Double): scala.Double = {
     val rounded = js.Math.round(a)
     val mod = a % 1.0
@@ -60,7 +68,9 @@ object Math {
   @inline def round(a: scala.Float): scala.Int = js.Math.round(a).toInt
   @inline def round(a: scala.Double): scala.Long = js.Math.round(a).toLong
 
+  // Wasm intrinsic
   @inline def sqrt(a: scala.Double): scala.Double = js.Math.sqrt(a)
+
   @inline def pow(a: scala.Double, b: scala.Double): scala.Double = js.Math.pow(a, b)
 
   @inline def exp(a: scala.Double): scala.Double = js.Math.exp(a)
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
index 88f70ebdca..abb6b50905 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
@@ -2939,6 +2939,19 @@ private class FunctionEmitter private (
         fb += wa.Call(genFunctionID.anyGetClassName)
         StringType
 
+      case value @ WasmTransients.WasmUnaryOp(_, lhs) =>
+        genTreeAuto(lhs)
+        markPosition(tree)
+        fb += value.wasmInstr
+        value.tpe
+
+      case value @ WasmTransients.WasmBinaryOp(_, lhs, rhs) =>
+        genTreeAuto(lhs)
+        genTreeAuto(rhs)
+        markPosition(tree)
+        fb += value.wasmInstr
+        value.tpe
+
       case other =>
         throw new AssertionError(s"Unknown transient: $other")
     }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/WasmTransients.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/WasmTransients.scala
new file mode 100644
index 0000000000..b58c06e025
--- /dev/null
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/WasmTransients.scala
@@ -0,0 +1,209 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package org.scalajs.linker.backend.wasmemitter
+
+import scala.annotation.switch
+
+import org.scalajs.ir.Position
+import org.scalajs.ir.Printers._
+import org.scalajs.ir.Transformers._
+import org.scalajs.ir.Traversers._
+import org.scalajs.ir.Trees._
+import org.scalajs.ir.Types._
+
+import org.scalajs.linker.backend.webassembly.{Instructions => wa}
+
+/** Transients generated by the optimizer that only makes sense in Wasm. */
+object WasmTransients {
+
+  /** Wasm unary op.
+   *
+   *  Wasm features a number of dedicated opcodes for operations that are not
+   *  in the IR, but only implemented in user space. We can see `WasmUnaryOp`
+   *  as an extension of `ir.Trees.UnaryOp` that covers those.
+   *
+   *  Wasm unary ops always preserve pureness.
+   */
+  final case class WasmUnaryOp(op: WasmUnaryOp.Code, lhs: Tree)
+      extends Transient.Value {
+    import WasmUnaryOp._
+
+    val tpe: Type = resultTypeOf(op)
+
+    def traverse(traverser: Traverser): Unit =
+      traverser.traverse(lhs)
+
+    def transform(transformer: Transformer, isStat: Boolean)(
+        implicit pos: Position): Tree = {
+      Transient(WasmUnaryOp(op, transformer.transformExpr(lhs)))
+    }
+
+    def wasmInstr: wa.SimpleInstr = (op: @switch) match {
+      case I32Clz    => wa.I32Clz
+      case I32Ctz    => wa.I32Ctz
+      case I32Popcnt => wa.I32Popcnt
+
+      case I64Clz    => wa.I64Clz
+      case I64Ctz    => wa.I64Ctz
+      case I64Popcnt => wa.I64Popcnt
+
+      case F32Abs => wa.F32Abs
+
+      case F64Abs     => wa.F64Abs
+      case F64Ceil    => wa.F64Ceil
+      case F64Floor   => wa.F64Floor
+      case F64Nearest => wa.F64Nearest
+      case F64Sqrt    => wa.F64Sqrt
+
+      case I32ReinterpretF32 => wa.I32ReinterpretF32
+      case I64ReinterpretF64 => wa.I64ReinterpretF64
+      case F32ReinterpretI32 => wa.F32ReinterpretI32
+      case F64ReinterpretI64 => wa.F64ReinterpretI64
+    }
+
+    def printIR(out: IRTreePrinter): Unit = {
+      out.print("$")
+      out.print(wasmInstr.mnemonic)
+      out.printArgs(List(lhs))
+    }
+  }
+
+  object WasmUnaryOp {
+    /** Codes are raw Ints to be able to write switch matches on them. */
+    type Code = Int
+
+    final val I32Clz = 1
+    final val I32Ctz = 2
+    final val I32Popcnt = 3
+
+    final val I64Clz = 4
+    final val I64Ctz = 5
+    final val I64Popcnt = 6
+
+    final val F32Abs = 7
+
+    final val F64Abs = 8
+    final val F64Ceil = 9
+    final val F64Floor = 10
+    final val F64Nearest = 11
+    final val F64Sqrt = 12
+
+    final val I32ReinterpretF32 = 13
+    final val I64ReinterpretF64 = 14
+    final val F32ReinterpretI32 = 15
+    final val F64ReinterpretI64 = 16
+
+    def resultTypeOf(op: Code): Type = (op: @switch) match {
+      case I32Clz | I32Ctz | I32Popcnt | I32ReinterpretF32 =>
+        IntType
+
+      case I64Clz | I64Ctz | I64Popcnt | I64ReinterpretF64 =>
+        LongType
+
+      case F32Abs | F32ReinterpretI32 =>
+        FloatType
+
+      case F64Abs | F64Ceil | F64Floor | F64Nearest | F64Sqrt | F64ReinterpretI64 =>
+        DoubleType
+    }
+  }
+
+  /** Wasm binary op.
+   *
+   *  Wasm features a number of dedicated opcodes for operations that are not
+   *  in the IR, but only implemented in user space. We can see `WasmBinaryOp`
+   *  as an extension of `ir.Trees.BinaryOp` that covers those.
+   *
+   *  Unsigned divisions and remainders exhibit always-unchecked undefined
+   *  behavior when their rhs is 0. It is up to code generating those transient
+   *  nodes to check for 0 themselves if necessary.
+   *
+   *  All other Wasm binary ops preserve pureness.
+   */
+  final case class WasmBinaryOp(op: WasmBinaryOp.Code, lhs: Tree, rhs: Tree)
+      extends Transient.Value {
+    import WasmBinaryOp._
+
+    val tpe: Type = resultTypeOf(op)
+
+    def traverse(traverser: Traverser): Unit = {
+      traverser.traverse(lhs)
+      traverser.traverse(rhs)
+    }
+
+    def transform(transformer: Transformer, isStat: Boolean)(
+        implicit pos: Position): Tree = {
+      Transient(WasmBinaryOp(op, transformer.transformExpr(lhs),
+          transformer.transformExpr(rhs)))
+    }
+
+    def wasmInstr: wa.SimpleInstr = (op: @switch) match {
+      case I32DivU => wa.I32DivU
+      case I32RemU => wa.I32RemU
+      case I32Rotl => wa.I32Rotl
+      case I32Rotr => wa.I32Rotr
+
+      case I64DivU => wa.I64DivU
+      case I64RemU => wa.I64RemU
+      case I64Rotl => wa.I64Rotl
+      case I64Rotr => wa.I64Rotr
+
+      case F32Min => wa.F32Min
+      case F32Max => wa.F32Max
+
+      case F64Min => wa.F64Min
+      case F64Max => wa.F64Max
+    }
+
+    def printIR(out: IRTreePrinter): Unit = {
+      out.print("$")
+      out.print(wasmInstr.mnemonic)
+      out.printArgs(List(lhs, rhs))
+    }
+  }
+
+  object WasmBinaryOp {
+    /** Codes are raw Ints to be able to write switch matches on them. */
+    type Code = Int
+
+    final val I32DivU = 1
+    final val I32RemU = 2
+    final val I32Rotl = 3
+    final val I32Rotr = 4
+
+    final val I64DivU = 5
+    final val I64RemU = 6
+    final val I64Rotl = 7
+    final val I64Rotr = 8
+
+    final val F32Min = 9
+    final val F32Max = 10
+
+    final val F64Min = 11
+    final val F64Max = 12
+
+    def resultTypeOf(op: Code): Type = (op: @switch) match {
+      case I32DivU | I32RemU | I32Rotl | I32Rotr =>
+        IntType
+
+      case I64DivU | I64RemU | I64Rotl | I64Rotr =>
+        LongType
+
+      case F32Min | F32Max =>
+        FloatType
+
+      case F64Min | F64Max =>
+        DoubleType
+    }
+  }
+}
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
index 40a269016e..80a46c1413 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
@@ -33,6 +33,7 @@ import org.scalajs.linker.interface.unstable.RuntimeClassNameMapperImpl
 import org.scalajs.linker.standard._
 import org.scalajs.linker.backend.emitter.LongImpl
 import org.scalajs.linker.backend.emitter.Transients._
+import org.scalajs.linker.backend.wasmemitter.WasmTransients._
 
 /** Optimizer core.
  *  Designed to be "mixed in" [[IncOptimizer#MethodImpl#Optimizer]].
@@ -2779,6 +2780,35 @@ private[optimizer] abstract class OptimizerCore(
       })
     }
 
+    def longToInt(longExpr: Tree): Tree =
+      UnaryOp(UnaryOp.LongToInt, longExpr)
+    def wasmUnaryOp(op: WasmUnaryOp.Code, lhs: PreTransform): Tree =
+      Transient(WasmUnaryOp(op, finishTransformExpr(lhs)))
+    def wasmBinaryOp(op: WasmBinaryOp.Code, lhs: PreTransform, rhs: PreTransform): Tree =
+      Transient(WasmBinaryOp(op, finishTransformExpr(lhs), finishTransformExpr(rhs)))
+
+    def genericWasmDivModUnsigned(wasmOp: WasmBinaryOp.Code, signedOp: BinaryOp.Code,
+        equalsOp: BinaryOp.Code, zeroLiteral: Literal): TailRec[Tree] = {
+      targs(1) match {
+        case PreTransLit(IntLiteral(r)) if r != 0 =>
+          contTree(wasmBinaryOp(wasmOp, targs(0), targs(1)))
+        case PreTransLit(LongLiteral(r)) if r != 0L =>
+          contTree(wasmBinaryOp(wasmOp, targs(0), targs(1)))
+        case _ =>
+          withNewTempLocalDefs(targs) { (localDefs, cont1) =>
+            val List(lhsLocalDef, rhsLocalDef) = localDefs
+            cont1 {
+              If(BinaryOp(equalsOp, rhsLocalDef.newReplacement, zeroLiteral), {
+                // trigger the appropriate ArithmeticException
+                BinaryOp(signedOp, zeroLiteral, zeroLiteral)
+              }, {
+                wasmBinaryOp(wasmOp, lhsLocalDef.toPreTransform, rhsLocalDef.toPreTransform)
+              })(zeroLiteral.tpe).toPreTransform
+            }
+          } (cont)
+      }
+    }
+
     (intrinsicCode: @switch) match {
       // Not an intrisic
 
@@ -2882,11 +2912,98 @@ private[optimizer] abstract class OptimizerCore(
           case PreTransLit(IntLiteral(value)) =>
             contTree(IntLiteral(Integer.numberOfLeadingZeros(value)))
           case _ =>
-            default
+            if (isWasm)
+              contTree(wasmUnaryOp(WasmUnaryOp.I32Clz, tvalue))
+            else
+              default
+        }
+      case IntegerNTZ =>
+        val tvalue = targs.head
+        tvalue match {
+          case PreTransLit(IntLiteral(value)) =>
+            contTree(IntLiteral(Integer.numberOfTrailingZeros(value)))
+          case _ =>
+            contTree(wasmUnaryOp(WasmUnaryOp.I32Ctz, tvalue))
+        }
+      case IntegerBitCount =>
+        val tvalue = targs.head
+        tvalue match {
+          case PreTransLit(IntLiteral(value)) =>
+            contTree(IntLiteral(Integer.bitCount(value)))
+          case _ =>
+            contTree(wasmUnaryOp(WasmUnaryOp.I32Popcnt, tvalue))
         }
 
+      case IntegerRotateLeft =>
+        val List(tvalue, tdistance) = targs
+        (tvalue, tdistance) match {
+          case (PreTransLit(IntLiteral(value)), PreTransLit(IntLiteral(distance))) =>
+            contTree(IntLiteral(Integer.rotateLeft(value, distance)))
+          case _ =>
+            contTree(wasmBinaryOp(WasmBinaryOp.I32Rotl, tvalue, tdistance))
+        }
+      case IntegerRotateRight =>
+        val List(tvalue, tdistance) = targs
+        (tvalue, tdistance) match {
+          case (PreTransLit(IntLiteral(value)), PreTransLit(IntLiteral(distance))) =>
+            contTree(IntLiteral(Integer.rotateRight(value, distance)))
+          case _ =>
+            contTree(wasmBinaryOp(WasmBinaryOp.I32Rotr, tvalue, tdistance))
+        }
+
+      case IntegerDivideUnsigned =>
+        genericWasmDivModUnsigned(WasmBinaryOp.I32DivU, BinaryOp.Int_/,
+            BinaryOp.Int_==, IntLiteral(0))
+      case IntegerRemainderUnsigned =>
+        genericWasmDivModUnsigned(WasmBinaryOp.I32RemU, BinaryOp.Int_%,
+            BinaryOp.Int_==, IntLiteral(0))
+
       // java.lang.Long
 
+      case LongNLZ =>
+        val tvalue = targs.head
+        tvalue match {
+          case PreTransLit(LongLiteral(value)) =>
+            contTree(IntLiteral(java.lang.Long.numberOfLeadingZeros(value)))
+          case _ =>
+            contTree(longToInt(wasmUnaryOp(WasmUnaryOp.I64Clz, tvalue)))
+        }
+      case LongNTZ =>
+        val tvalue = targs.head
+        tvalue match {
+          case PreTransLit(LongLiteral(value)) =>
+            contTree(IntLiteral(java.lang.Long.numberOfTrailingZeros(value)))
+          case _ =>
+            contTree(longToInt(wasmUnaryOp(WasmUnaryOp.I64Ctz, tvalue)))
+        }
+      case LongBitCount =>
+        val tvalue = targs.head
+        tvalue match {
+          case PreTransLit(LongLiteral(value)) =>
+            contTree(IntLiteral(java.lang.Long.bitCount(value)))
+          case _ =>
+            contTree(longToInt(wasmUnaryOp(WasmUnaryOp.I64Popcnt, tvalue)))
+        }
+
+      case LongRotateLeft =>
+        val List(tvalue, tdistance) = targs
+        (tvalue, tdistance) match {
+          case (PreTransLit(LongLiteral(value)), PreTransLit(IntLiteral(distance))) =>
+            contTree(LongLiteral(java.lang.Long.rotateLeft(value, distance)))
+          case _ =>
+            contTree(wasmBinaryOp(WasmBinaryOp.I64Rotl, tvalue,
+                PreTransUnaryOp(UnaryOp.IntToLong, tdistance)))
+        }
+      case LongRotateRight =>
+        val List(tvalue, tdistance) = targs
+        (tvalue, tdistance) match {
+          case (PreTransLit(LongLiteral(value)), PreTransLit(IntLiteral(distance))) =>
+            contTree(LongLiteral(java.lang.Long.rotateRight(value, distance)))
+          case _ =>
+            contTree(wasmBinaryOp(WasmBinaryOp.I64Rotr, tvalue,
+                PreTransUnaryOp(UnaryOp.IntToLong, tdistance)))
+        }
+
       case LongToString =>
         pretransformApply(ApplyFlags.empty, targs.head,
             MethodIdent(LongImpl.toString_), Nil, StringClassType,
@@ -2897,16 +3014,86 @@ private[optimizer] abstract class OptimizerCore(
             MethodIdent(LongImpl.compareToRTLong), targs.tail, IntType,
             isStat, usePreTransform)(
             cont)
+
       case LongDivideUnsigned =>
-        pretransformApply(ApplyFlags.empty, targs.head,
-            MethodIdent(LongImpl.divideUnsigned), targs.tail,
-            ClassType(LongImpl.RuntimeLongClass), isStat, usePreTransform)(
-            cont)
+        if (isWasm) {
+          genericWasmDivModUnsigned(WasmBinaryOp.I64DivU, BinaryOp.Long_/,
+              BinaryOp.Long_==, LongLiteral(0L))
+        } else {
+          pretransformApply(ApplyFlags.empty, targs.head,
+              MethodIdent(LongImpl.divideUnsigned), targs.tail,
+              ClassType(LongImpl.RuntimeLongClass), isStat, usePreTransform)(
+              cont)
+        }
       case LongRemainderUnsigned =>
-        pretransformApply(ApplyFlags.empty, targs.head,
-            MethodIdent(LongImpl.remainderUnsigned), targs.tail,
-            ClassType(LongImpl.RuntimeLongClass), isStat, usePreTransform)(
-            cont)
+        if (isWasm) {
+          genericWasmDivModUnsigned(WasmBinaryOp.I64RemU, BinaryOp.Long_%,
+              BinaryOp.Long_==, LongLiteral(0L))
+        } else {
+          pretransformApply(ApplyFlags.empty, targs.head,
+              MethodIdent(LongImpl.remainderUnsigned), targs.tail,
+              ClassType(LongImpl.RuntimeLongClass), isStat, usePreTransform)(
+              cont)
+        }
+
+      // java.lang.Float
+
+      case FloatToIntBits =>
+        // The Wasm I32ReinterpretF32 is the *raw* version; we need to normalize NaNs
+        withNewTempLocalDefs(targs) { (localDefs, cont1) =>
+          val argLocalDef = localDefs.head
+          def argToDouble = UnaryOp(UnaryOp.FloatToDouble, argLocalDef.newReplacement)
+          cont1 {
+            If(BinaryOp(BinaryOp.Double_!=, argToDouble, argToDouble),
+                IntLiteral(java.lang.Float.floatToIntBits(Float.NaN)),
+                wasmUnaryOp(WasmUnaryOp.I32ReinterpretF32, argLocalDef.toPreTransform))(
+                IntType).toPreTransform
+          }
+        } (cont)
+
+      case IntBitsToFloat =>
+        contTree(wasmUnaryOp(WasmUnaryOp.F32ReinterpretI32, targs.head))
+
+      // java.lang.Double
+
+      case DoubleToLongBits =>
+        // The Wasm I64ReinterpretF64 is the *raw* version; we need to normalize NaNs
+        withNewTempLocalDefs(targs) { (localDefs, cont1) =>
+          val argLocalDef = localDefs.head
+          cont1 {
+            If(BinaryOp(BinaryOp.Double_!=, argLocalDef.newReplacement, argLocalDef.newReplacement),
+                LongLiteral(java.lang.Double.doubleToLongBits(Double.NaN)),
+                wasmUnaryOp(WasmUnaryOp.I64ReinterpretF64, argLocalDef.toPreTransform))(
+                LongType).toPreTransform
+          }
+        } (cont)
+
+      case LongBitsToDouble =>
+        contTree(wasmUnaryOp(WasmUnaryOp.F64ReinterpretI64, targs.head))
+
+      // java.lang.Math
+
+      case MathAbsFloat =>
+        contTree(wasmUnaryOp(WasmUnaryOp.F32Abs, targs.head))
+      case MathAbsDouble =>
+        contTree(wasmUnaryOp(WasmUnaryOp.F64Abs, targs.head))
+      case MathCeil =>
+        contTree(wasmUnaryOp(WasmUnaryOp.F64Ceil, targs.head))
+      case MathFloor =>
+        contTree(wasmUnaryOp(WasmUnaryOp.F64Floor, targs.head))
+      case MathRint =>
+        contTree(wasmUnaryOp(WasmUnaryOp.F64Nearest, targs.head))
+      case MathSqrt =>
+        contTree(wasmUnaryOp(WasmUnaryOp.F64Sqrt, targs.head))
+
+      case MathMinFloat =>
+        contTree(wasmBinaryOp(WasmBinaryOp.F32Min, targs.head, targs.tail.head))
+      case MathMinDouble =>
+        contTree(wasmBinaryOp(WasmBinaryOp.F64Min, targs.head, targs.tail.head))
+      case MathMaxFloat =>
+        contTree(wasmBinaryOp(WasmBinaryOp.F32Max, targs.head, targs.tail.head))
+      case MathMaxDouble =>
+        contTree(wasmBinaryOp(WasmBinaryOp.F64Max, targs.head, targs.tail.head))
 
       // scala.collection.mutable.ArrayBuilder
 
@@ -6263,13 +6450,41 @@ private[optimizer] object OptimizerCore {
     final val ArrayLength = ArrayUpdate      + 1
 
     final val IntegerNLZ = ArrayLength + 1
-
-    final val LongToString = IntegerNLZ + 1
+    final val IntegerNTZ = IntegerNLZ + 1
+    final val IntegerBitCount = IntegerNTZ + 1
+    final val IntegerRotateLeft = IntegerBitCount + 1
+    final val IntegerRotateRight = IntegerRotateLeft + 1
+    final val IntegerDivideUnsigned = IntegerRotateRight + 1
+    final val IntegerRemainderUnsigned = IntegerDivideUnsigned + 1
+
+    final val LongNLZ = IntegerRemainderUnsigned + 1
+    final val LongNTZ = LongNLZ + 1
+    final val LongBitCount = LongNTZ + 1
+    final val LongRotateLeft = LongBitCount + 1
+    final val LongRotateRight = LongRotateLeft + 1
+    final val LongToString = LongRotateRight + 1
     final val LongCompare = LongToString + 1
     final val LongDivideUnsigned = LongCompare + 1
     final val LongRemainderUnsigned = LongDivideUnsigned + 1
 
-    final val ArrayBuilderZeroOf = LongRemainderUnsigned + 1
+    final val FloatToIntBits = LongRemainderUnsigned + 1
+    final val IntBitsToFloat = FloatToIntBits + 1
+
+    final val DoubleToLongBits = IntBitsToFloat + 1
+    final val LongBitsToDouble = DoubleToLongBits + 1
+
+    final val MathAbsFloat = LongBitsToDouble + 1
+    final val MathAbsDouble = MathAbsFloat + 1
+    final val MathCeil = MathAbsDouble + 1
+    final val MathFloor = MathCeil + 1
+    final val MathRint = MathFloor + 1
+    final val MathSqrt = MathRint + 1
+    final val MathMinFloat = MathSqrt + 1
+    final val MathMinDouble = MathMinFloat + 1
+    final val MathMaxFloat = MathMinDouble + 1
+    final val MathMaxDouble = MathMaxFloat + 1
+
+    final val ArrayBuilderZeroOf = MathMaxDouble + 1
     final val GenericArrayBuilderResult = ArrayBuilderZeroOf + 1
 
     final val ClassGetComponentType = GenericArrayBuilderResult + 1
@@ -6301,6 +6516,8 @@ private[optimizer] object OptimizerCore {
     private val V = VoidRef
     private val I = IntRef
     private val J = LongRef
+    private val F = FloatRef
+    private val D = DoubleRef
     private val O = ClassRef(ObjectClass)
     private val ClassClassRef = ClassRef(ClassClass)
     private val StringClassRef = ClassRef(BoxedStringClass)
@@ -6368,11 +6585,52 @@ private[optimizer] object OptimizerCore {
             m("remainderUnsigned", List(J, J), J) -> LongRemainderUnsigned
         )
     )
+
+    private val wasmIntrinsics: List[(ClassName, List[(MethodName, Int)])] = List(
+        ClassName("java.lang.Integer$") -> List(
+            // note: numberOfLeadingZeros in already in the commonIntrinsics
+            m("numberOfTrailingZeros", List(I), I) -> IntegerNTZ,
+            m("bitCount", List(I), I) -> IntegerBitCount,
+            m("rotateLeft", List(I, I), I) -> IntegerRotateLeft,
+            m("rotateRight", List(I, I), I) -> IntegerRotateRight,
+            m("divideUnsigned", List(I, I), I) -> IntegerDivideUnsigned,
+            m("remainderUnsigned", List(I, I), I) -> IntegerRemainderUnsigned
+        ),
+        ClassName("java.lang.Long$") -> List(
+            m("numberOfLeadingZeros", List(J), I) -> LongNLZ,
+            m("numberOfTrailingZeros", List(J), I) -> LongNTZ,
+            m("bitCount", List(J), I) -> LongBitCount,
+            m("rotateLeft", List(J, I), J) -> LongRotateLeft,
+            m("rotateRight", List(J, I), J) -> LongRotateRight,
+            m("divideUnsigned", List(J, J), J) -> LongDivideUnsigned,
+            m("remainderUnsigned", List(J, J), J) -> LongRemainderUnsigned
+        ),
+        ClassName("java.lang.Float$") -> List(
+            m("floatToIntBits", List(F), I) -> FloatToIntBits,
+            m("intBitsToFloat", List(I), F) -> IntBitsToFloat
+        ),
+        ClassName("java.lang.Double$") -> List(
+            m("doubleToLongBits", List(D), J) -> DoubleToLongBits,
+            m("longBitsToDouble", List(J), D) -> LongBitsToDouble
+        ),
+        ClassName("java.lang.Math$") -> List(
+            m("abs", List(F), F) -> MathAbsFloat,
+            m("abs", List(D), D) -> MathAbsDouble,
+            m("ceil", List(D), D) -> MathCeil,
+            m("floor", List(D), D) -> MathFloor,
+            m("rint", List(D), D) -> MathRint,
+            m("sqrt", List(D), D) -> MathSqrt,
+            m("min", List(F, F), F) -> MathMinFloat,
+            m("min", List(D, D), D) -> MathMinDouble,
+            m("max", List(F, F), F) -> MathMaxFloat,
+            m("max", List(D, D), D) -> MathMaxDouble
+        )
+    )
     // scalastyle:on line.size.limit
 
     def buildIntrinsics(esFeatures: ESFeatures, isWasm: Boolean): Intrinsics = {
       val allIntrinsics = if (isWasm) {
-        commonIntrinsics
+        commonIntrinsics ::: wasmIntrinsics
       } else {
         val baseIntrinsics = commonIntrinsics ::: baseJSIntrinsics
         if (esFeatures.allowBigIntsForLongs) baseIntrinsics

From 08d7f97ebbab71ba67b54fd8f39d5284a9ca3d57 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Sun, 2 Jun 2024 14:11:52 +0200
Subject: [PATCH 122/298] Wasm: Dedicated implementation of `Double.hashCode`.

The implementation based on `FloatingPointBits` is poor for a Wasm
output, as it uses JS interop. Given that we have an intrinsic for
`doubleToLongBits`, we can implement it much more efficiently for
Wasm.

This is important because this function is called to compute the
hash code of all JS `number`s, including those that originate as
`Int`s.
---
 javalib/src/main/scala/java/lang/Double.scala | 20 +++++++++++++++++--
 javalib/src/main/scala/java/lang/Float.scala  |  2 +-
 project/Build.scala                           |  4 ++--
 3 files changed, 21 insertions(+), 5 deletions(-)

diff --git a/javalib/src/main/scala/java/lang/Double.scala b/javalib/src/main/scala/java/lang/Double.scala
index ffe3381bfc..e2768f8aca 100644
--- a/javalib/src/main/scala/java/lang/Double.scala
+++ b/javalib/src/main/scala/java/lang/Double.scala
@@ -15,6 +15,7 @@ package java.lang
 import java.lang.constant.{Constable, ConstantDesc}
 
 import scala.scalajs.js
+import scala.scalajs.runtime.linkingInfo
 
 import Utils._
 
@@ -363,8 +364,23 @@ object Double {
   @inline def isFinite(d: scala.Double): scala.Boolean =
     !isNaN(d) && !isInfinite(d)
 
-  @inline def hashCode(value: scala.Double): Int =
-    FloatingPointBits.numberHashCode(value)
+  @inline def hashCode(value: scala.Double): Int = {
+    if (linkingInfo.isWebAssembly)
+      hashCodeForWasm(value)
+    else
+      FloatingPointBits.numberHashCode(value)
+  }
+
+  // See FloatingPointBits for the spec of this computation
+  @inline
+  private def hashCodeForWasm(value: scala.Double): Int = {
+    val bits = doubleToLongBits(value)
+    val valueInt = value.toInt
+    if (doubleToLongBits(valueInt.toDouble) == bits)
+      valueInt
+    else
+      Long.hashCode(bits)
+  }
 
   // Wasm intrinsic
   @inline def longBitsToDouble(bits: scala.Long): scala.Double =
diff --git a/javalib/src/main/scala/java/lang/Float.scala b/javalib/src/main/scala/java/lang/Float.scala
index 303b48fc3b..6bb6bb4565 100644
--- a/javalib/src/main/scala/java/lang/Float.scala
+++ b/javalib/src/main/scala/java/lang/Float.scala
@@ -376,7 +376,7 @@ object Float {
     !isNaN(f) && !isInfinite(f)
 
   @inline def hashCode(value: scala.Float): Int =
-    FloatingPointBits.numberHashCode(value)
+    Double.hashCode(value.toDouble)
 
   // Wasm intrinsic
   @inline def intBitsToFloat(bits: scala.Int): scala.Float =
diff --git a/project/Build.scala b/project/Build.scala
index 1903d9ace4..d56961696d 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -2057,14 +2057,14 @@ object Build {
           case `default212Version` =>
             if (!useMinifySizes) {
               Some(ExpectedSizes(
-                  fastLink = 625000 to 626000,
+                  fastLink = 626000 to 627000,
                   fullLink = 97000 to 98000,
                   fastLinkGz = 75000 to 79000,
                   fullLinkGz = 25000 to 26000,
               ))
             } else {
               Some(ExpectedSizes(
-                  fastLink = 432000 to 433000,
+                  fastLink = 433000 to 434000,
                   fullLink = 283000 to 284000,
                   fastLinkGz = 62000 to 63000,
                   fullLinkGz = 44000 to 45000,

From b7af05f717a23ff7d24243a484ea88e217bd5bfa Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Sun, 2 Jun 2024 23:31:34 +0200
Subject: [PATCH 123/298] Opt/Wasm: Replace `Apply` by `ApplyStatically` when
 possible.

When we resolve a dynamic call to a single possible target, but we
do not inline it, we now replace the `Apply` by an `ApplyStatically`.
This communicates the result of the resolution to the backend, which
can emit a static `call` instead of a vtable or itable-based dispatch.
---
 .../frontend/optimizer/OptimizerCore.scala      | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
index 80a46c1413..6688cfe6a4 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
@@ -2082,7 +2082,22 @@ private[optimizer] abstract class OptimizerCore(
             else dynamicCall(className, methodName)
           if (impls.size == 1) {
             pretransformSingleDispatch(flags, impls.head, Some(treceiver), targs, isStat, usePreTransform)(cont) {
-              treeNotInlined
+              if (isWasm) {
+                // Replace by an ApplyStatically to guarantee static dispatch
+                val targetClassName = impls.head.enclosingClassName
+                val castTReceiver = foldCast(treceiver, ClassType(targetClassName))
+                cont(PreTransTree(ApplyStatically(flags,
+                    finishTransformExprMaybeAssumeNotNull(castTReceiver),
+                    targetClassName, methodIdent,
+                    targs.map(finishTransformExpr))(resultType), RefinedType(resultType)))
+              } else {
+                /* In case you get tempted to perform the same optimization on
+                 * JS, we tried it before (in a much more involved way) and we
+                 * found that it was not better or even worse:
+                 * https://github.com/scala-js/scala-js/pull/4337
+                 */
+                treeNotInlined
+              }
             }
           } else {
             val allocationSites =

From bae4c823f45297055c624fda9749f11c86b09241 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Mon, 3 Jun 2024 10:08:59 +0200
Subject: [PATCH 124/298] Wasm: Use `ApplyStatically` in the derived classes.

These were one of two remaining sources of `Apply` nodes that the
backend could turn into `ApplyStatically` but that the optimizer
could not (because they are created after the optimizer).
---
 .../scalajs/linker/backend/wasmemitter/DerivedClasses.scala    | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/DerivedClasses.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/DerivedClasses.scala
index b7e0a3cf91..d30d4504b9 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/DerivedClasses.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/DerivedClasses.scala
@@ -116,7 +116,8 @@ object DerivedClasses {
         method.originalName,
         method.args,
         method.resultType,
-        Some(Apply(EAF, selectField, method.name, method.args.map(_.ref))(method.resultType))
+        Some(ApplyStatically(EAF, selectField, className, method.name,
+            method.args.map(_.ref))(method.resultType))
       )(method.optimizerHints, method.version)
     }
 

From 2cbe367b16c026e9d6a20e2c2af5f60a2704157e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Mon, 3 Jun 2024 10:51:29 +0200
Subject: [PATCH 125/298] Wasm: Remove the isEffectivelyFinal analysis and its
 use for `Apply`.

The optimizer already replaces `Apply` nodes that can be statically
resolved by `ApplyStatically`. The `isEffectivelyFinal` analysis is
therefore not useful anymore.

Technically, it was still applicable to JS property/method *names*
that are not string constants, but that is too niche to justify
keeping the analysis. Also, arguably the correct fix for that would
be to make the optimizer also optimize JS property/method names,
since it would also benefit the JS backend.
---
 .../backend/wasmemitter/FunctionEmitter.scala | 26 +++++++------------
 .../backend/wasmemitter/Preprocessor.scala    |  3 ---
 .../backend/wasmemitter/WasmContext.scala     | 15 ++---------
 3 files changed, 12 insertions(+), 32 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
index abb6b50905..15cd22c174 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
@@ -648,26 +648,20 @@ private class FunctionEmitter private (
         }
         val receiverClassInfo = ctx.getClassInfo(receiverClassName)
 
-        /* If possible, "optimize" this Apply node as an ApplyStatically call.
-         * We can do this if the receiver's class is a hijacked class or an
-         * array type (because they are known to be final) or if the target
-         * method is effectively final.
+        /* Hijacked classes do not receive tables at all, and `Apply`s on array
+         * types are considered to be statically resolved by the `Analyzer`.
+         * Therefore, if the receiver's static type is a prim type, hijacked
+         * class or array type, we must use static dispatch instead.
          *
-         * The latter condition is nothing but an optimization, and should be
-         * done by the optimizer instead. We will remove it once we can run the
-         * optimizer with Wasm.
-         *
-         * The former condition (being a hijacked class or an array type) will
-         * also never happen after we have the optimizer. But if we do not have
-         * the optimizer, we must still do it now because the preconditions of
-         * `genApplyWithDispatch` would not be met.
+         * This never happens when we use the optimizer, since it already turns
+         * any such `Apply` into an `ApplyStatically` (when it does not inline
+         * it altogether).
          */
-        val canUseStaticallyResolved = {
+        val useStaticDispatch = {
           receiverClassInfo.kind == ClassKind.HijackedClass ||
-          receiver.tpe.isInstanceOf[ArrayType] ||
-          receiverClassInfo.resolvedMethodInfos.get(method.name).exists(_.isEffectivelyFinal)
+          receiver.tpe.isInstanceOf[ArrayType]
         }
-        if (canUseStaticallyResolved) {
+        if (useStaticDispatch) {
           genApplyStatically(ApplyStatically(
               flags, receiver, receiverClassName, method, args)(tree.tpe)(tree.pos))
         } else {
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Preprocessor.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Preprocessor.scala
index 5c2d76f190..588f3f9fb9 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Preprocessor.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Preprocessor.scala
@@ -175,9 +175,6 @@ object Preprocessor {
           m.methodName
         }
 
-        for (methodName <- concretePublicMethodNames)
-          inherited.get(methodName).foreach(_.markOverridden())
-
         concretePublicMethodNames.foldLeft(inherited) { (prev, methodName) =>
           prev.updated(methodName, new ConcreteMethodInfo(className, methodName))
         }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/WasmContext.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/WasmContext.scala
index 5d30083f97..41ec679322 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/WasmContext.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/WasmContext.scala
@@ -260,14 +260,11 @@ object WasmContext {
           val superTableEntries = superClass.fold[List[MethodName]](Nil)(_.tableEntries)
           val superTableEntrySet = superTableEntries.toSet
 
-          /* When computing the table entries to add for this class, exclude:
-           * - methods that are already in the super class' table entries, and
-           * - methods that are effectively final, since they will always be
-           *   statically resolved instead of using the table dispatch.
+          /* When computing the table entries to add for this class, exclude
+           * methods that are already in the super class' table entries.
            */
           val newTableEntries = methodsCalledDynamically
             .filter(!superTableEntrySet.contains(_))
-            .filterNot(m => resolvedMethodInfos.get(m).exists(_.isEffectivelyFinal))
             .sorted // for stability
 
           _tableEntries = superTableEntries ::: newTableEntries
@@ -289,13 +286,5 @@ object WasmContext {
 
   final class ConcreteMethodInfo(val ownerClass: ClassName, val methodName: MethodName) {
     val tableEntryID = genFunctionID.forTableEntry(ownerClass, methodName)
-
-    private var effectivelyFinal: Boolean = true
-
-    /** For use by `Preprocessor`. */
-    private[wasmemitter] def markOverridden(): Unit =
-      effectivelyFinal = false
-
-    def isEffectivelyFinal: Boolean = effectivelyFinal
   }
 }

From 828f90b847b5eb44b1241e57667fc21a7dc89d63 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Mon, 5 Aug 2024 10:18:42 +0200
Subject: [PATCH 126/298] Wasm: Compute tableEntries in Preprocessor.

`ClassInfo` is now completely immutable.
---
 .../backend/wasmemitter/Preprocessor.scala    | 36 +++++++++++++---
 .../backend/wasmemitter/WasmContext.scala     | 41 +------------------
 2 files changed, 31 insertions(+), 46 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Preprocessor.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Preprocessor.scala
index 588f3f9fb9..ed480cf00c 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Preprocessor.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Preprocessor.scala
@@ -44,6 +44,7 @@ object Preprocessor {
         clazz,
         staticFieldMirrors.getOrElse(clazz.className, Map.empty),
         specialInstanceTypes.getOrElse(clazz.className, 0),
+        abstractMethodCalls.getOrElse(clazz.className, Set.empty),
         itableBucketAssignments.getOrElse(clazz.className, -1),
         clazz.superClass.map(sup => classInfosBuilder(sup.name))
       )
@@ -61,11 +62,6 @@ object Preprocessor {
     // sort for stability
     val reflectiveProxyIDs = definedReflectiveProxyNames.toList.sorted.zipWithIndex.toMap
 
-    for (clazz <- classes) {
-      classInfos(clazz.className).buildMethodTable(
-          abstractMethodCalls.getOrElse(clazz.className, Set.empty))
-    }
-
     new WasmContext(classInfos, reflectiveProxyIDs, itableBucketCount)
   }
 
@@ -118,6 +114,7 @@ object Preprocessor {
       clazz: LinkedClass,
       staticFieldMirrors: Map[FieldName, List[String]],
       specialInstanceTypes: Int,
+      methodsCalledDynamically0: Set[MethodName],
       itableIdx: Int,
       superClass: Option[ClassInfo]
   ): ClassInfo = {
@@ -183,12 +180,38 @@ object Preprocessor {
       }
     }
 
+    val tableEntries: List[MethodName] = {
+      val methodsCalledDynamically: List[MethodName] =
+        if (clazz.hasInstances) methodsCalledDynamically0.toList
+        else Nil
+
+      kind match {
+        case ClassKind.Class | ClassKind.ModuleClass | ClassKind.HijackedClass =>
+          val superTableEntries = superClass.fold[List[MethodName]](Nil)(_.tableEntries)
+          val superTableEntrySet = superTableEntries.toSet
+
+          /* When computing the table entries to add for this class, exclude
+           * methods that are already in the super class' table entries.
+           */
+          val newTableEntries = methodsCalledDynamically
+            .filter(!superTableEntrySet.contains(_))
+            .sorted // for stability
+
+          superTableEntries ::: newTableEntries
+
+        case ClassKind.Interface =>
+          methodsCalledDynamically.sorted // for stability
+
+        case _ =>
+          Nil
+      }
+    }
+
     new ClassInfo(
       className,
       kind,
       clazz.jsClassCaptures,
       allFieldDefs,
-      superClass,
       classImplementsAnyInterface,
       clazz.hasInstances,
       !clazz.hasDirectInstances,
@@ -198,6 +221,7 @@ object Preprocessor {
       staticFieldMirrors,
       specialInstanceTypes,
       resolvedMethodInfos,
+      tableEntries,
       itableIdx
     )
   }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/WasmContext.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/WasmContext.scala
index 41ec679322..1eb5cecef1 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/WasmContext.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/WasmContext.scala
@@ -169,7 +169,6 @@ object WasmContext {
       val kind: ClassKind,
       val jsClassCaptures: Option[List[ParamDef]],
       val allFieldDefs: List[FieldDef],
-      superClass: Option[ClassInfo],
       val classImplementsAnyInterface: Boolean,
       val hasInstances: Boolean,
       val isAbstract: Boolean,
@@ -179,14 +178,12 @@ object WasmContext {
       val staticFieldMirrors: Map[FieldName, List[String]],
       _specialInstanceTypes: Int, // should be `val` but there is a large Scaladoc for it below
       val resolvedMethodInfos: Map[MethodName, ConcreteMethodInfo],
+      val tableEntries: List[MethodName],
       _itableIdx: Int
   ) {
     override def toString(): String =
       s"ClassInfo(${name.nameString})"
 
-    /** For a class or interface, its table entries in definition order. */
-    private var _tableEntries: List[MethodName] = null
-
     /** Returns the index of this interface's itable in the classes' interface tables.
      *
      *  Only interfaces that have instances get an itable index.
@@ -246,42 +243,6 @@ object WasmContext {
 
     def isInterface: Boolean =
       kind == ClassKind.Interface
-
-    def buildMethodTable(methodsCalledDynamically0: Set[MethodName]): Unit = {
-      if (_tableEntries != null)
-        throw new IllegalStateException(s"Duplicate call to buildMethodTable() for $name")
-
-      val methodsCalledDynamically: List[MethodName] =
-        if (hasInstances) methodsCalledDynamically0.toList
-        else Nil
-
-      kind match {
-        case ClassKind.Class | ClassKind.ModuleClass | ClassKind.HijackedClass =>
-          val superTableEntries = superClass.fold[List[MethodName]](Nil)(_.tableEntries)
-          val superTableEntrySet = superTableEntries.toSet
-
-          /* When computing the table entries to add for this class, exclude
-           * methods that are already in the super class' table entries.
-           */
-          val newTableEntries = methodsCalledDynamically
-            .filter(!superTableEntrySet.contains(_))
-            .sorted // for stability
-
-          _tableEntries = superTableEntries ::: newTableEntries
-
-        case ClassKind.Interface =>
-          _tableEntries = methodsCalledDynamically.sorted // for stability
-
-        case _ =>
-          _tableEntries = Nil
-      }
-    }
-
-    def tableEntries: List[MethodName] = {
-      if (_tableEntries == null)
-        throw new IllegalStateException(s"Table not yet built for $name")
-      _tableEntries
-    }
   }
 
   final class ConcreteMethodInfo(val ownerClass: ClassName, val methodName: MethodName) {

From cd4cf248dec6c6a5f3f4cc94cdf01484d083ca6d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Tue, 11 Jun 2024 11:56:04 +0200
Subject: [PATCH 127/298] Bump the IR version to 1.17-SNAPSHOT for the upcoming
 changes.

---
 ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala b/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala
index c32a7d5b2b..7b68d93faa 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala
@@ -18,7 +18,7 @@ import scala.util.matching.Regex
 
 object ScalaJSVersions extends VersionChecks(
     current = "1.17.0-SNAPSHOT",
-    binaryEmitted = "1.16"
+    binaryEmitted = "1.17-SNAPSHOT"
 )
 
 /** Helper class to allow for testing of logic. */

From 1aabf39dc0dad3854f88b4b7062d0a2ae3bee0b0 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Thu, 22 Aug 2024 16:12:13 +0200
Subject: [PATCH 128/298] Give useful `toString`s to
 `IncOptimizer.JSMethodContainer`s.

---
 .../org/scalajs/linker/frontend/optimizer/IncOptimizer.scala  | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
index 4533ca7543..b16b13d39d 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
@@ -1127,6 +1127,8 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
 
     val className: ClassName = linkedClass.className
 
+    override def toString(): String = className.nameString
+
     private[this] val exportedMembers = mutable.ArrayBuffer.empty[JSMethodImpl]
     private[this] var jsConstructorDef: Option[JSCtorImpl] = None
     private[this] var _jsClassCaptures: List[ParamDef] = Nil
@@ -1203,6 +1205,8 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
     val untrackedJSClassCaptures: List[ParamDef] = Nil
     def untrackedThisType(namespace: MemberNamespace): Type = NoType
 
+    override def toString(): String = "<top-level>"
+
     def updateWith(topLevelExports: List[LinkedTopLevelExport]): Unit = {
       val newMethods = topLevelExports.map(_.tree).collect {
         case m: TopLevelMethodExportDef =>

From a79ce3f945968b77d2d7815e3be096e4a8fc3ceb Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Thu, 22 Aug 2024 22:30:26 +0200
Subject: [PATCH 129/298] Do not fold `jlr.Array.newInstance(classOf[Unit],
 ...)`.

If we do, we generate code that statically refers to the array type
`void[]`, which is not a valid type.

With the following commit, the optimizer will have enough knowledge
to enter in this case when optimizing `ClassTag`s, resulting in
ClassDef checking errors after the optimizer.
---
 .../org/scalajs/linker/frontend/optimizer/OptimizerCore.scala   | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
index 6688cfe6a4..3f6c71d8cb 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
@@ -3195,7 +3195,7 @@ private[optimizer] abstract class OptimizerCore(
       case ArrayNewInstance =>
         val List(tcomponentType, tlength) = targs
         tcomponentType match {
-          case PreTransTree(ClassOf(elementTypeRef), _) =>
+          case PreTransTree(ClassOf(elementTypeRef), _) if elementTypeRef != VoidRef =>
             val arrayTypeRef = ArrayTypeRef.of(elementTypeRef)
             contTree(NewArray(arrayTypeRef, List(finishTransformExpr(tlength))))
           case _ =>

From 043cfc86abcb8c24d553e670bc5909a2224d824a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Thu, 22 Aug 2024 16:20:18 +0200
Subject: [PATCH 130/298] Introduce non-nullable reference types in the IR.

`ClassType`s and `ArrayType`s now carry a `nullable: Boolean` flag.
When `nullable` is false, the type does not admit `null` values.
We also introduce `AnyNotNullType` to be the non-nullable variant
of `AnyType`.

This way, every non-void type `tpe` has a non-nullable variant,
which we can get with `tpe.toNonNullable`.

There are a few sources of non-nullable values, such as `New`
nodes, and, most importantly, `This` nodes.

Since non-nullable reference types have no corresponding `TypeRef`,
they cannot appear in the signature of methods. They only live
locally within method bodies.

---

The optimizer already had dedicated tracking of non-nullable
`PreTransform`s. We now replace that tracking by the actual `tpe`
of the trees.

In order to be type-preserving, we must now insert most `Cast`s,
to non-nullable types. Before, at the IR level everything became
nullable again, so even if the optimizer had determined that a tree
could not be null, that did not influence the produced IR.

On the plus side, since IR nodes track their nullability, we do not
need `AssumeNotNull` anymore. The `Cast`s to non-nullable types
achieve the same result in a more consistent way.

In fact, the new non-nullable types allow the optimizer to better
keep track of nullability, resulting in fewer `$n` calls to check
for nulls. This is the main source of code side reduction.

---

Since we now have non-nullable reference types, we change
`IsInstanceOf` to require non-nullable test types. This makes more
sense, since `IsInstanceOf` always answers `false` when the value
is `null`.

---

We introduce deserialization hacks to:

* adapt the type of `This` nodes, and
* adapt the test type of `IsInstanceOf` nodes.

In this commit, we do not change the compiler nor the hard-coded IR
of `jl.Object` yet, in order to test the deserialization hacks.
---
 .../org/scalajs/nscplugin/GenJSCode.scala     |  12 +-
 .../org/scalajs/nscplugin/GenJSExports.scala  |  10 +-
 .../org/scalajs/nscplugin/JSEncoding.scala    |   2 +-
 .../scalajs/nscplugin/TypeConversions.scala   |   2 +-
 .../main/scala/org/scalajs/ir/Hashers.scala   |  39 +-
 .../main/scala/org/scalajs/ir/Printers.scala  |  41 +-
 .../scala/org/scalajs/ir/Serializers.scala    | 140 ++---
 .../src/main/scala/org/scalajs/ir/Tags.scala  |   6 +
 .../src/main/scala/org/scalajs/ir/Trees.scala |  28 +-
 .../src/main/scala/org/scalajs/ir/Types.scala | 123 +++--
 .../scala/org/scalajs/ir/PrintersTest.scala   |  17 +-
 .../scala/org/scalajs/ir/TestIRBuilder.scala  |   4 +-
 .../scala/org/scalajs/linker/RunTest.scala    |   9 +-
 .../org/scalajs/linker/analyzer/Infos.scala   |  40 +-
 .../linker/backend/emitter/ClassEmitter.scala |   2 -
 .../linker/backend/emitter/Emitter.scala      |   4 +-
 .../backend/emitter/FunctionEmitter.scala     |  90 +---
 .../linker/backend/emitter/SJSGen.scala       |  24 +-
 .../linker/backend/emitter/Transients.scala   |  29 +-
 .../backend/wasmemitter/ClassEmitter.scala    |   2 +-
 .../backend/wasmemitter/CoreWasmLib.scala     |  16 +-
 .../backend/wasmemitter/DerivedClasses.scala  |   4 +-
 .../backend/wasmemitter/FunctionEmitter.scala | 133 +++--
 .../backend/wasmemitter/Preprocessor.scala    |   2 +-
 .../linker/backend/wasmemitter/SWasmGen.scala |  10 +-
 .../backend/wasmemitter/TypeTransformer.scala |  28 +-
 .../backend/wasmemitter/WasmContext.scala     |   4 +-
 .../linker/backend/webassembly/Types.scala    |   2 +
 .../linker/checker/ClassDefChecker.scala      |  47 +-
 .../scalajs/linker/checker/IRChecker.scala    |  20 +-
 .../linker/frontend/MethodSynthesizer.scala   |   8 +-
 .../frontend/optimizer/IncOptimizer.scala     |   2 +-
 .../frontend/optimizer/OptimizerCore.scala    | 491 +++++++++---------
 .../org/scalajs/linker/AnalyzerTest.scala     |   6 +-
 .../org/scalajs/linker/IRCheckerTest.scala    |  23 +-
 .../org/scalajs/linker/IncrementalTest.scala  |  11 +-
 .../linker/LibraryReachabilityTest.scala      |   4 +-
 .../org/scalajs/linker/LibrarySizeTest.scala  |   4 +-
 .../org/scalajs/linker/OptimizerTest.scala    |  33 +-
 .../linker/SmallModulesForSplittingTest.scala |   2 +-
 .../linker/SmallestModulesSplittingTest.scala |   2 +-
 .../linker/checker/ClassDefCheckerTest.scala  |  86 ++-
 .../linker/testutils/TestIRBuilder.scala      |  10 +-
 project/BinaryIncompatibilities.scala         |  16 +
 project/Build.scala                           |  14 +-
 project/JavaLangObject.scala                  |  20 +-
 project/JavalibIRCleaner.scala                |  14 +-
 47 files changed, 898 insertions(+), 738 deletions(-)

diff --git a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
index a093b718da..42718ce041 100644
--- a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
+++ b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
@@ -154,7 +154,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
 
     def currentThisType: jstpe.Type = {
       encodeClassType(currentClassSym) match {
-        case tpe @ jstpe.ClassType(cls) =>
+        case tpe @ jstpe.ClassType(cls, _) =>
           jstpe.BoxedClassToPrimType.getOrElse(cls, tpe)
         case tpe =>
           tpe
@@ -1259,7 +1259,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
            * Anyway, scalac also has problems with uninitialized value
            * class values, if they come from a generic context.
            */
-          jstpe.ClassType(encodeClassName(tpe.valueClazz))
+          jstpe.ClassType(encodeClassName(tpe.valueClazz), nullable = true)
 
         case _ =>
           /* Other types are not boxed, so we can initialize them to
@@ -3622,7 +3622,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
       val newMethodIdent = js.MethodIdent(newName)
 
       js.ApplyStatic(flags, className, newMethodIdent, args)(
-          jstpe.ClassType(className))
+          jstpe.ClassType(className, nullable = true))
     }
 
     /** Gen JS code for creating a new Array: new Array[T](length)
@@ -4562,8 +4562,8 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
               def genAnyEquality(eqeq: Boolean, not: Boolean): js.Tree = {
                 // Arrays, Null, Nothing never have a custom equals() method
                 def canHaveCustomEquals(tpe: jstpe.Type): Boolean = tpe match {
-                  case jstpe.AnyType | jstpe.ClassType(_) => true
-                  case _                                  => false
+                  case jstpe.AnyType | _:jstpe.ClassType => true
+                  case _                                 => false
                 }
                 if (eqeq &&
                     // don't call equals if we have a literal null at either side
@@ -6334,7 +6334,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
       }
       val className = encodeClassName(currentClassSym).withSuffix(suffix)
 
-      val classType = jstpe.ClassType(className)
+      val classType = jstpe.ClassType(className, nullable = true)
 
       // val f: Any
       val fFieldIdent = js.FieldIdent(FieldName(className, SimpleFieldName("f")))
diff --git a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSExports.scala b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSExports.scala
index e37ce3a1ef..e0c32d1d81 100644
--- a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSExports.scala
+++ b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSExports.scala
@@ -973,7 +973,7 @@ trait GenJSExports[G <: Global with Singleton] extends SubComponent {
         import org.scalajs.ir.Names
 
         (toIRType(tpe): @unchecked) match {
-          case jstpe.AnyType => NoTypeTest
+          case jstpe.AnyType | jstpe.AnyNotNullType => NoTypeTest
 
           case jstpe.NoType      => PrimitiveTypeTest(jstpe.UndefType, 0)
           case jstpe.BooleanType => PrimitiveTypeTest(jstpe.BooleanType, 1)
@@ -985,11 +985,11 @@ trait GenJSExports[G <: Global with Singleton] extends SubComponent {
           case jstpe.FloatType   => PrimitiveTypeTest(jstpe.FloatType, 7)
           case jstpe.DoubleType  => PrimitiveTypeTest(jstpe.DoubleType, 8)
 
-          case jstpe.ClassType(Names.BoxedUnitClass)   => PrimitiveTypeTest(jstpe.UndefType, 0)
-          case jstpe.ClassType(Names.BoxedStringClass) => PrimitiveTypeTest(jstpe.StringType, 9)
-          case jstpe.ClassType(_)                      => InstanceOfTypeTest(tpe)
+          case jstpe.ClassType(Names.BoxedUnitClass, _)   => PrimitiveTypeTest(jstpe.UndefType, 0)
+          case jstpe.ClassType(Names.BoxedStringClass, _) => PrimitiveTypeTest(jstpe.StringType, 9)
+          case jstpe.ClassType(_, _)                      => InstanceOfTypeTest(tpe)
 
-          case jstpe.ArrayType(_) => InstanceOfTypeTest(tpe)
+          case jstpe.ArrayType(_, _) => InstanceOfTypeTest(tpe)
         }
     }
   }
diff --git a/compiler/src/main/scala/org/scalajs/nscplugin/JSEncoding.scala b/compiler/src/main/scala/org/scalajs/nscplugin/JSEncoding.scala
index 56f089bf1e..51ec7de709 100644
--- a/compiler/src/main/scala/org/scalajs/nscplugin/JSEncoding.scala
+++ b/compiler/src/main/scala/org/scalajs/nscplugin/JSEncoding.scala
@@ -275,7 +275,7 @@ trait JSEncoding[G <: Global with Singleton] extends SubComponent {
     else {
       assert(sym != definitions.ArrayClass,
           "encodeClassType() cannot be called with ArrayClass")
-      jstpe.ClassType(encodeClassName(sym))
+      jstpe.ClassType(encodeClassName(sym), nullable = true)
     }
   }
 
diff --git a/compiler/src/main/scala/org/scalajs/nscplugin/TypeConversions.scala b/compiler/src/main/scala/org/scalajs/nscplugin/TypeConversions.scala
index 93a4a3a5db..97db07f24f 100644
--- a/compiler/src/main/scala/org/scalajs/nscplugin/TypeConversions.scala
+++ b/compiler/src/main/scala/org/scalajs/nscplugin/TypeConversions.scala
@@ -60,7 +60,7 @@ trait TypeConversions[G <: Global with Singleton] extends SubComponent {
     if (arrayDepth == 0)
       primitiveIRTypeMap.getOrElse(base, encodeClassType(base))
     else
-      Types.ArrayType(makeArrayTypeRef(base, arrayDepth))
+      Types.ArrayType(makeArrayTypeRef(base, arrayDepth), nullable = true)
   }
 
   def toTypeRef(t: Type): Types.TypeRef = {
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Hashers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Hashers.scala
index bbf0b85409..b1f69595a3 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Hashers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Hashers.scala
@@ -605,27 +605,28 @@ object Hashers {
     }
 
     def mixType(tpe: Type): Unit = tpe match {
-      case AnyType     => mixTag(TagAnyType)
-      case NothingType => mixTag(TagNothingType)
-      case UndefType   => mixTag(TagUndefType)
-      case BooleanType => mixTag(TagBooleanType)
-      case CharType    => mixTag(TagCharType)
-      case ByteType    => mixTag(TagByteType)
-      case ShortType   => mixTag(TagShortType)
-      case IntType     => mixTag(TagIntType)
-      case LongType    => mixTag(TagLongType)
-      case FloatType   => mixTag(TagFloatType)
-      case DoubleType  => mixTag(TagDoubleType)
-      case StringType  => mixTag(TagStringType)
-      case NullType    => mixTag(TagNullType)
-      case NoType      => mixTag(TagNoType)
-
-      case ClassType(className) =>
-        mixTag(TagClassType)
+      case AnyType        => mixTag(TagAnyType)
+      case AnyNotNullType => mixTag(TagAnyNotNullType)
+      case NothingType    => mixTag(TagNothingType)
+      case UndefType      => mixTag(TagUndefType)
+      case BooleanType    => mixTag(TagBooleanType)
+      case CharType       => mixTag(TagCharType)
+      case ByteType       => mixTag(TagByteType)
+      case ShortType      => mixTag(TagShortType)
+      case IntType        => mixTag(TagIntType)
+      case LongType       => mixTag(TagLongType)
+      case FloatType      => mixTag(TagFloatType)
+      case DoubleType     => mixTag(TagDoubleType)
+      case StringType     => mixTag(TagStringType)
+      case NullType       => mixTag(TagNullType)
+      case NoType         => mixTag(TagNoType)
+
+      case ClassType(className, nullable) =>
+        mixTag(if (nullable) TagClassType else TagNonNullClassType)
         mixName(className)
 
-      case ArrayType(arrayTypeRef) =>
-        mixTag(TagArrayType)
+      case ArrayType(arrayTypeRef, nullable) =>
+        mixTag(if (nullable) TagArrayType else TagNonNullArrayType)
         mixArrayTypeRef(arrayTypeRef)
 
       case RecordType(fields) =>
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala
index 875a4e4c0b..318d69355f 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala
@@ -1066,24 +1066,31 @@ object Printers {
     }
 
     def print(tpe: Type): Unit = tpe match {
-      case AnyType              => print("any")
-      case NothingType          => print("nothing")
-      case UndefType            => print("void")
-      case BooleanType          => print("boolean")
-      case CharType             => print("char")
-      case ByteType             => print("byte")
-      case ShortType            => print("short")
-      case IntType              => print("int")
-      case LongType             => print("long")
-      case FloatType            => print("float")
-      case DoubleType           => print("double")
-      case StringType           => print("string")
-      case NullType             => print("null")
-      case ClassType(className) => print(className)
-      case NoType               => print("<notype>")
-
-      case ArrayType(arrayTypeRef) =>
+      case AnyType        => print("any")
+      case AnyNotNullType => print("any!")
+      case NothingType    => print("nothing")
+      case UndefType      => print("void")
+      case BooleanType    => print("boolean")
+      case CharType       => print("char")
+      case ByteType       => print("byte")
+      case ShortType      => print("short")
+      case IntType        => print("int")
+      case LongType       => print("long")
+      case FloatType      => print("float")
+      case DoubleType     => print("double")
+      case StringType     => print("string")
+      case NullType       => print("null")
+      case NoType         => print("<notype>")
+
+      case ClassType(className, nullable) =>
+        print(className)
+        if (!nullable)
+          print("!")
+
+      case ArrayType(arrayTypeRef, nullable) =>
         print(arrayTypeRef)
+        if (!nullable)
+          print("!")
 
       case RecordType(fields) =>
         print('(')
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
index 9be664598a..0ba241bbac 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
@@ -851,27 +851,28 @@ object Serializers {
 
     def writeType(tpe: Type): Unit = {
       tpe match {
-        case AnyType     => buffer.write(TagAnyType)
-        case NothingType => buffer.write(TagNothingType)
-        case UndefType   => buffer.write(TagUndefType)
-        case BooleanType => buffer.write(TagBooleanType)
-        case CharType    => buffer.write(TagCharType)
-        case ByteType    => buffer.write(TagByteType)
-        case ShortType   => buffer.write(TagShortType)
-        case IntType     => buffer.write(TagIntType)
-        case LongType    => buffer.write(TagLongType)
-        case FloatType   => buffer.write(TagFloatType)
-        case DoubleType  => buffer.write(TagDoubleType)
-        case StringType  => buffer.write(TagStringType)
-        case NullType    => buffer.write(TagNullType)
-        case NoType      => buffer.write(TagNoType)
-
-        case ClassType(className) =>
-          buffer.write(TagClassType)
+        case AnyType        => buffer.write(TagAnyType)
+        case AnyNotNullType => buffer.write(TagAnyNotNullType)
+        case NothingType    => buffer.write(TagNothingType)
+        case UndefType      => buffer.write(TagUndefType)
+        case BooleanType    => buffer.write(TagBooleanType)
+        case CharType       => buffer.write(TagCharType)
+        case ByteType       => buffer.write(TagByteType)
+        case ShortType      => buffer.write(TagShortType)
+        case IntType        => buffer.write(TagIntType)
+        case LongType       => buffer.write(TagLongType)
+        case FloatType      => buffer.write(TagFloatType)
+        case DoubleType     => buffer.write(TagDoubleType)
+        case StringType     => buffer.write(TagStringType)
+        case NullType       => buffer.write(TagNullType)
+        case NoType         => buffer.write(TagNoType)
+
+        case ClassType(className, nullable) =>
+          buffer.write(if (nullable) TagClassType else TagNonNullClassType)
           writeName(className)
 
-        case ArrayType(arrayTypeRef) =>
-          buffer.write(TagArrayType)
+        case ArrayType(arrayTypeRef, nullable) =>
+          buffer.write(if (nullable) TagArrayType else TagNonNullArrayType)
           writeArrayTypeRef(arrayTypeRef)
 
         case RecordType(fields) =>
@@ -1035,7 +1036,7 @@ object Serializers {
     private[this] var lastPosition: Position = Position.NoPosition
 
     private[this] var enclosingClassName: ClassName = _
-    private[this] var thisTypeForHack8: Type = NoType
+    private[this] var thisTypeForHack: Option[Type] = None
 
     def deserializeEntryPointsInfo(): EntryPointsInfo = {
       hacks = new Hacks(sourceVersion = readHeader())
@@ -1229,7 +1230,22 @@ object Serializers {
         case TagArrayLength      => ArrayLength(readTree())
         case TagArraySelect      => ArraySelect(readTree(), readTree())(readType())
         case TagRecordValue      => RecordValue(readType().asInstanceOf[RecordType], readTrees())
-        case TagIsInstanceOf     => IsInstanceOf(readTree(), readType())
+
+        case TagIsInstanceOf =>
+          val expr = readTree()
+          val testType0 = readType()
+          val testType = if (true /* hacks.use16 */) { // scalastyle:ignore
+            testType0 match {
+              case ClassType(className, true)    => ClassType(className, nullable = false)
+              case ArrayType(arrayTypeRef, true) => ArrayType(arrayTypeRef, nullable = false)
+              case AnyType                       => AnyNotNullType
+              case _                             => testType0
+            }
+          } else {
+            testType0
+          }
+          IsInstanceOf(expr, testType)
+
         case TagAsInstanceOf     => AsInstanceOf(readTree(), readType())
         case TagGetClass         => GetClass(readTree())
         case TagClone            => Clone(readTree())
@@ -1282,24 +1298,22 @@ object Serializers {
 
         case TagThis =>
           val tpe = readType()
-          if (hacks.use8)
-            This()(thisTypeForHack8)
-          else
-            This()(tpe)
+          This()(thisTypeForHack.getOrElse(tpe))
 
         case TagClosure =>
           val arrow = readBoolean()
           val captureParams = readParamDefs()
           val (params, restParam) = readParamDefsWithRest()
-          val body = if (!hacks.use8) {
+          val body = if (thisTypeForHack.isEmpty) {
+            // Fast path; always taken for IR >= 1.17
             readTree()
           } else {
-            val prevThisTypeForHack8 = thisTypeForHack8
-            thisTypeForHack8 = if (arrow) NoType else AnyType
+            val prevThisTypeForHack = thisTypeForHack
+            thisTypeForHack = None
             try {
               readTree()
             } finally {
-              thisTypeForHack8 = prevThisTypeForHack8
+              thisTypeForHack = prevThisTypeForHack
             }
           }
           val captureValues = readTrees()
@@ -1358,7 +1372,7 @@ object Serializers {
           // Evaluate the expression then definitely run into an NPE UB
           UnwrapFromThrowable(expr)
 
-        case ClassType(_) =>
+        case ClassType(_, _) =>
           expr match {
             case New(_, _, _) =>
               // Common case (`throw new SomeException(...)`) that is known not to be `null`
@@ -1400,14 +1414,15 @@ object Serializers {
       val originalName = readOriginalName()
       val kind = ClassKind.fromByte(readByte())
 
-      if (hacks.use8) {
-        thisTypeForHack8 = {
-          if (kind.isJSType)
-            AnyType
-          else if (kind == ClassKind.HijackedClass)
-            BoxedClassToPrimType.getOrElse(cls, ClassType(cls)) // getOrElse as safety guard
-          else
-            ClassType(cls)
+      if (true /* hacks.use16 */) { // scalastyle:ignore
+        thisTypeForHack = kind match {
+          case ClassKind.Class | ClassKind.ModuleClass | ClassKind.Interface =>
+            Some(ClassType(cls, nullable = false))
+          case ClassKind.HijackedClass if hacks.use8 =>
+            // Use getOrElse as safety guard for otherwise invalid inputs
+            Some(BoxedClassToPrimType.getOrElse(cls, ClassType(cls, nullable = false)))
+          case _ =>
+            None
         }
       }
 
@@ -1599,11 +1614,11 @@ object Serializers {
          */
         assert(args.isEmpty)
 
-        val thisValue = This()(ClassType(ObjectClass))
-        val cloneableClassType = ClassType(CloneableClass)
+        val thisValue = This()(ClassType(ObjectClass, nullable = false))
+        val cloneableClassType = ClassType(CloneableClass, nullable = true)
 
         val patchedBody = Some {
-          If(IsInstanceOf(thisValue, cloneableClassType),
+          If(IsInstanceOf(thisValue, cloneableClassType.toNonNullable),
               Clone(AsInstanceOf(thisValue, cloneableClassType)),
               Throw(New(
                   HackNames.CloneNotSupportedExceptionClass,
@@ -1844,23 +1859,27 @@ object Serializers {
     def readType(): Type = {
       val tag = readByte()
       (tag: @switch) match {
-        case TagAnyType     => AnyType
-        case TagNothingType => NothingType
-        case TagUndefType   => UndefType
-        case TagBooleanType => BooleanType
-        case TagCharType    => CharType
-        case TagByteType    => ByteType
-        case TagShortType   => ShortType
-        case TagIntType     => IntType
-        case TagLongType    => LongType
-        case TagFloatType   => FloatType
-        case TagDoubleType  => DoubleType
-        case TagStringType  => StringType
-        case TagNullType    => NullType
-        case TagNoType      => NoType
-
-        case TagClassType => ClassType(readClassName())
-        case TagArrayType => ArrayType(readArrayTypeRef())
+        case TagAnyType        => AnyType
+        case TagAnyNotNullType => AnyNotNullType
+        case TagNothingType    => NothingType
+        case TagUndefType      => UndefType
+        case TagBooleanType    => BooleanType
+        case TagCharType       => CharType
+        case TagByteType       => ByteType
+        case TagShortType      => ShortType
+        case TagIntType        => IntType
+        case TagLongType       => LongType
+        case TagFloatType      => FloatType
+        case TagDoubleType     => DoubleType
+        case TagStringType     => StringType
+        case TagNullType       => NullType
+        case TagNoType         => NoType
+
+        case TagClassType => ClassType(readClassName(), nullable = true)
+        case TagArrayType => ArrayType(readArrayTypeRef(), nullable = true)
+
+        case TagNonNullClassType => ClassType(readClassName(), nullable = false)
+        case TagNonNullArrayType => ArrayType(readArrayTypeRef(), nullable = false)
 
         case TagRecordType =>
           RecordType(List.fill(readInt()) {
@@ -2127,6 +2146,11 @@ object Serializers {
     val use12: Boolean = use11 || sourceVersion == "1.12"
 
     val use13: Boolean = use12 || sourceVersion == "1.13"
+
+    assert(sourceVersion != "1.14", "source version 1.14 does not exist")
+    assert(sourceVersion != "1.15", "source version 1.15 does not exist")
+
+    val use16: Boolean = use13 || sourceVersion == "1.16"
   }
 
   /** Names needed for hacks. */
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Tags.scala b/ir/shared/src/main/scala/org/scalajs/ir/Tags.scala
index 80b0774f31..3c3162245b 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Tags.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Tags.scala
@@ -170,6 +170,12 @@ private[ir] object Tags {
   final val TagRecordType = TagArrayType + 1
   final val TagNoType = TagRecordType + 1
 
+  // New in 1.17
+
+  final val TagAnyNotNullType = TagNoType + 1
+  final val TagNonNullClassType = TagAnyNotNullType + 1
+  final val TagNonNullArrayType = TagNonNullClassType + 1
+
   // Tags for TypeRefs
 
   final val TagVoidRef = 1
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala b/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
index 2dd8e43d36..411f6b9a95 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
@@ -232,12 +232,17 @@ object Trees {
   sealed case class New(className: ClassName, ctor: MethodIdent,
       args: List[Tree])(
       implicit val pos: Position) extends Tree {
-    val tpe = ClassType(className)
+    val tpe = ClassType(className, nullable = false)
   }
 
   sealed case class LoadModule(className: ClassName)(
       implicit val pos: Position) extends Tree {
-    val tpe = ClassType(className)
+    /* With Compliant moduleInits, `LoadModule`s are nullable!
+     * The linker components have dedicated code to consider `LoadModule`s as
+     * non-nullable depending on the semantics, but the `tpe` here must be
+     * nullable in the general case.
+     */
+    val tpe = ClassType(className, nullable = true)
   }
 
   sealed case class StoreModule()(implicit val pos: Position) extends Tree {
@@ -446,12 +451,12 @@ object Trees {
 
   sealed case class NewArray(typeRef: ArrayTypeRef, lengths: List[Tree])(
       implicit val pos: Position) extends Tree {
-    val tpe = ArrayType(typeRef)
+    val tpe = ArrayType(typeRef, nullable = false)
   }
 
   sealed case class ArrayValue(typeRef: ArrayTypeRef, elems: List[Tree])(
       implicit val pos: Position) extends Tree {
-    val tpe = ArrayType(typeRef)
+    val tpe = ArrayType(typeRef, nullable = false)
   }
 
   sealed case class ArrayLength(array: Tree)(implicit val pos: Position)
@@ -482,12 +487,13 @@ object Trees {
 
   sealed case class GetClass(expr: Tree)(implicit val pos: Position)
       extends Tree {
-    val tpe = ClassType(ClassClass)
+    val tpe = ClassType(ClassClass, nullable = true)
   }
 
   sealed case class Clone(expr: Tree)(implicit val pos: Position)
       extends Tree {
-    val tpe: Type = expr.tpe // this is OK because our type system does not have singleton types
+    // this is OK because our type system does not have singleton types
+    val tpe: Type = expr.tpe.toNonNullable
   }
 
   sealed case class IdentityHashCode(expr: Tree)(implicit val pos: Position)
@@ -497,7 +503,7 @@ object Trees {
 
   sealed case class WrapAsThrowable(expr: Tree)(implicit val pos: Position)
       extends Tree {
-    val tpe = ClassType(ThrowableClass)
+    val tpe = ClassType(ThrowableClass, nullable = false)
   }
 
   sealed case class UnwrapFromThrowable(expr: Tree)(implicit val pos: Position)
@@ -837,12 +843,12 @@ object Trees {
 
   sealed case class JSArrayConstr(items: List[TreeOrJSSpread])(
       implicit val pos: Position) extends Tree {
-    val tpe = AnyType
+    val tpe = AnyNotNullType
   }
 
   sealed case class JSObjectConstr(fields: List[(Tree, Tree)])(
       implicit val pos: Position) extends Tree {
-    val tpe = AnyType
+    val tpe = AnyNotNullType
   }
 
   sealed case class JSGlobalRef(name: String)(
@@ -992,7 +998,7 @@ object Trees {
 
   sealed case class ClassOf(typeRef: TypeRef)(
       implicit val pos: Position) extends Literal {
-    val tpe = ClassType(ClassClass)
+    val tpe = ClassType(ClassClass, nullable = false)
   }
 
   // Atomic expressions
@@ -1014,7 +1020,7 @@ object Trees {
       params: List[ParamDef], restParam: Option[ParamDef], body: Tree,
       captureValues: List[Tree])(
       implicit val pos: Position) extends Tree {
-    val tpe = AnyType
+    val tpe = AnyNotNullType
   }
 
   /** Creates a JavaScript class value.
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Types.scala b/ir/shared/src/main/scala/org/scalajs/ir/Types.scala
index 4f91fd3319..000583a135 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Types.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Types.scala
@@ -36,9 +36,31 @@ object Types {
       printer.print(this)
       writer.toString()
     }
+
+    /** Is `null` an admissible value of this type? */
+    def isNullable: Boolean = this match {
+      case AnyType | NullType     => true
+      case ClassType(_, nullable) => nullable
+      case ArrayType(_, nullable) => nullable
+      case _                      => false
+    }
+
+    /** A type that accepts the same values as this type except `null`, unless
+     *  this type is `NoType`.
+     *
+     *  If `this` is `NoType`, returns this type.
+     *
+     *  For all other types `tpe`, `tpe.toNonNullable.isNullable` is `false`.
+     */
+    def toNonNullable: Type
   }
 
-  sealed abstract class PrimType extends Type
+  sealed abstract class PrimType extends Type {
+    final def toNonNullable: PrimType = this match {
+      case NullType => NothingType
+      case _        => this
+    }
+  }
 
   sealed abstract class PrimTypeWithRef extends PrimType {
     def primRef: PrimRef = this match {
@@ -66,7 +88,14 @@ object Types {
    *  The type java.lang.Object in the back-end maps to [[AnyType]] because it
    *  can hold JS values (not only instances of Scala.js classes).
    */
-  case object AnyType extends Type
+  case object AnyType extends Type {
+    def toNonNullable: AnyNotNullType.type = AnyNotNullType
+  }
+
+  /** Any type except `null`. */
+  case object AnyNotNullType extends Type {
+    def toNonNullable: this.type = this
+  }
 
   // Can't link to Nothing - #1969
   /** Nothing type (the bottom type of this type system).
@@ -130,10 +159,24 @@ object Types {
   case object NullType extends PrimTypeWithRef
 
   /** Class (or interface) type. */
-  final case class ClassType(className: ClassName) extends Type
+  final case class ClassType(className: ClassName, nullable: Boolean) extends Type {
+    def toNullable: ClassType = ClassType(className, nullable = true)
 
-  /** Array type. */
-  final case class ArrayType(arrayTypeRef: ArrayTypeRef) extends Type
+    def toNonNullable: ClassType = ClassType(className, nullable = false)
+  }
+
+  /** Array type.
+   *
+   *  Although the array type itself may be non-nullable, the *elements* of an
+   *  array are always nullable for non-primitive types. This is unavoidable,
+   *  since arrays can be created with their elements initialized with the zero
+   *  of the element type.
+   */
+  final case class ArrayType(arrayTypeRef: ArrayTypeRef, nullable: Boolean) extends Type {
+    def toNullable: ArrayType = ArrayType(arrayTypeRef, nullable = true)
+
+    def toNonNullable: ArrayType = ArrayType(arrayTypeRef, nullable = false)
+  }
 
   /** Record type.
    *  Used by the optimizer to inline classes as records with multiple fields.
@@ -145,6 +188,8 @@ object Types {
   final case class RecordType(fields: List[RecordType.Field]) extends Type {
     def findField(name: SimpleFieldName): RecordType.Field =
       fields.find(_.name == name).get
+
+    def toNonNullable: this.type = this
   }
 
   object RecordType {
@@ -310,12 +355,13 @@ object Types {
     case StringType  => StringLiteral("")
     case UndefType   => Undefined()
 
-    case NullType | AnyType | _:ClassType | _:ArrayType => Null()
+    case NullType | AnyType | ClassType(_, true) | ArrayType(_, true) => Null()
 
     case tpe: RecordType =>
       RecordValue(tpe, tpe.fields.map(f => zeroOf(f.tpe)))
 
-    case NothingType | NoType =>
+    case NothingType | NoType | ClassType(_, false) | ArrayType(_, false) |
+        AnyNotNullType =>
       throw new IllegalArgumentException(s"cannot generate a zero for $tpe")
   }
 
@@ -341,6 +387,10 @@ object Types {
    */
   def isSubtype(lhs: Type, rhs: Type)(
       isSubclass: (ClassName, ClassName) => Boolean): Boolean = {
+
+    def isSubnullable(lhs: Boolean, rhs: Boolean): Boolean =
+      rhs || !lhs
+
     (lhs == rhs) ||
     ((lhs, rhs) match {
       case (_, NoType)      => true
@@ -348,44 +398,47 @@ object Types {
       case (_, AnyType)     => true
       case (NothingType, _) => true
 
-      case (ClassType(lhsClass), ClassType(rhsClass)) =>
-        isSubclass(lhsClass, rhsClass)
+      case (NullType, _)       => rhs.isNullable
+      case (_, AnyNotNullType) => !lhs.isNullable
 
-      case (NullType, ClassType(_)) => true
-      case (NullType, ArrayType(_)) => true
+      case (ClassType(lhsClass, lhsNullable), ClassType(rhsClass, rhsNullable)) =>
+        isSubnullable(lhsNullable, rhsNullable) && isSubclass(lhsClass, rhsClass)
 
-      case (primType: PrimType, ClassType(rhsClass)) =>
+      case (primType: PrimType, ClassType(rhsClass, _)) =>
         val lhsClass = PrimTypeToBoxedClass.getOrElse(primType, {
           throw new AssertionError(s"unreachable case for isSubtype($lhs, $rhs)")
         })
         isSubclass(lhsClass, rhsClass)
 
-      case (ArrayType(ArrayTypeRef(lhsBase, lhsDims)),
-          ArrayType(ArrayTypeRef(rhsBase, rhsDims))) =>
-        if (lhsDims < rhsDims) {
-          false // because Array[A] </: Array[Array[A]]
-        } else if (lhsDims > rhsDims) {
-          rhsBase match {
-            case ClassRef(ObjectClass) =>
-              true // because Array[Array[A]] <: Array[Object]
-            case _ =>
-              false
-          }
-        } else { // lhsDims == rhsDims
-          // lhsBase must be <: rhsBase
-          (lhsBase, rhsBase) match {
-            case (ClassRef(lhsBaseName), ClassRef(rhsBaseName)) =>
-              /* All things must be considered subclasses of Object for this
-               * purpose, even JS types and interfaces, which do not have
-               * Object in their ancestors.
-               */
-              rhsBaseName == ObjectClass || isSubclass(lhsBaseName, rhsBaseName)
-            case _ =>
-              lhsBase eq rhsBase
+      case (ArrayType(ArrayTypeRef(lhsBase, lhsDims), lhsNullable),
+          ArrayType(ArrayTypeRef(rhsBase, rhsDims), rhsNullable)) =>
+        isSubnullable(lhsNullable, rhsNullable) && {
+          if (lhsDims < rhsDims) {
+            false // because Array[A] </: Array[Array[A]]
+          } else if (lhsDims > rhsDims) {
+            rhsBase match {
+              case ClassRef(ObjectClass) =>
+                true // because Array[Array[A]] <: Array[Object]
+              case _ =>
+                false
+            }
+          } else { // lhsDims == rhsDims
+            // lhsBase must be <: rhsBase
+            (lhsBase, rhsBase) match {
+              case (ClassRef(lhsBaseName), ClassRef(rhsBaseName)) =>
+                /* All things must be considered subclasses of Object for this
+                 * purpose, even JS types and interfaces, which do not have
+                 * Object in their ancestors.
+                 */
+                rhsBaseName == ObjectClass || isSubclass(lhsBaseName, rhsBaseName)
+              case _ =>
+                lhsBase eq rhsBase
+            }
           }
         }
 
-      case (ArrayType(_), ClassType(className)) =>
+      case (ArrayType(_, lhsNullable), ClassType(className, rhsNullable)) =>
+        isSubnullable(lhsNullable, rhsNullable) &&
         AncestorsOfPseudoArrayClass.contains(className)
 
       case _ =>
diff --git a/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala b/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala
index ab3c6be098..590a24c209 100644
--- a/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala
+++ b/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala
@@ -50,6 +50,7 @@ class PrintersTest {
 
   @Test def printType(): Unit = {
     assertPrintEquals("any", AnyType)
+    assertPrintEquals("any!", AnyNotNullType)
     assertPrintEquals("nothing", NothingType)
     assertPrintEquals("void", UndefType)
     assertPrintEquals("boolean", BooleanType)
@@ -64,10 +65,14 @@ class PrintersTest {
     assertPrintEquals("null", NullType)
     assertPrintEquals("<notype>", NoType)
 
-    assertPrintEquals("java.lang.Object", ClassType(ObjectClass))
+    assertPrintEquals("java.lang.Object", ClassType(ObjectClass, nullable = true))
+    assertPrintEquals("java.lang.String!",
+        ClassType(BoxedStringClass, nullable = false))
 
     assertPrintEquals("java.lang.Object[]", arrayType(ObjectClass, 1))
     assertPrintEquals("int[][]", arrayType(IntRef, 2))
+    assertPrintEquals("java.lang.String[]!",
+        ArrayType(ArrayTypeRef(BoxedStringClass, 1), nullable = false))
 
     assertPrintEquals("(x: int, var y: any)",
         RecordType(List(
@@ -570,13 +575,15 @@ class PrintersTest {
   }
 
   @Test def printIsInstanceOf(): Unit = {
-    assertPrintEquals("x.isInstanceOf[java.lang.String]",
-        IsInstanceOf(ref("x", AnyType), ClassType(BoxedStringClass)))
+    assertPrintEquals("x.isInstanceOf[java.lang.String!]",
+        IsInstanceOf(ref("x", AnyType), ClassType(BoxedStringClass, nullable = false)))
+    assertPrintEquals("x.isInstanceOf[int]",
+        IsInstanceOf(ref("x", AnyType), IntType))
   }
 
   @Test def printAsInstanceOf(): Unit = {
     assertPrintEquals("x.asInstanceOf[java.lang.String]",
-        AsInstanceOf(ref("x", AnyType), ClassType(BoxedStringClass)))
+        AsInstanceOf(ref("x", AnyType), ClassType(BoxedStringClass, nullable = true)))
     assertPrintEquals("x.asInstanceOf[int]",
         AsInstanceOf(ref("x", AnyType), IntType))
   }
@@ -599,7 +606,7 @@ class PrintersTest {
 
   @Test def printUnwrapFromThrowable(): Unit = {
     assertPrintEquals("<unwrapFromThrowable>(e)",
-        UnwrapFromThrowable(ref("e", ClassType(ThrowableClass))))
+        UnwrapFromThrowable(ref("e", ClassType(ThrowableClass, nullable = true))))
   }
 
   @Test def printJSNew(): Unit = {
diff --git a/ir/shared/src/test/scala/org/scalajs/ir/TestIRBuilder.scala b/ir/shared/src/test/scala/org/scalajs/ir/TestIRBuilder.scala
index 3cc7058b8f..d89d8050a7 100644
--- a/ir/shared/src/test/scala/org/scalajs/ir/TestIRBuilder.scala
+++ b/ir/shared/src/test/scala/org/scalajs/ir/TestIRBuilder.scala
@@ -54,7 +54,7 @@ object TestIRBuilder {
 
   // String -> Type and TypeRef conversions
   implicit def string2classType(className: String): ClassType =
-    ClassType(ClassName(className))
+    ClassType(ClassName(className), nullable = true)
   implicit def string2classRef(className: String): ClassRef =
     ClassRef(ClassName(className))
 
@@ -82,6 +82,6 @@ object TestIRBuilder {
   def ref(ident: LocalIdent, tpe: Type): VarRef = VarRef(ident)(tpe)
 
   def arrayType(base: NonArrayTypeRef, dimensions: Int): ArrayType =
-    ArrayType(ArrayTypeRef(base, dimensions))
+    ArrayType(ArrayTypeRef(base, dimensions), nullable = true)
 
 }
diff --git a/linker/jvm/src/test/scala/org/scalajs/linker/RunTest.scala b/linker/jvm/src/test/scala/org/scalajs/linker/RunTest.scala
index 7a4088a616..9adde311f8 100644
--- a/linker/jvm/src/test/scala/org/scalajs/linker/RunTest.scala
+++ b/linker/jvm/src/test/scala/org/scalajs/linker/RunTest.scala
@@ -66,14 +66,15 @@ class RunTest {
 
     val getMessage = MethodName("getMessage", Nil, T)
 
-    val e = VarRef("e")(ClassType(ThrowableClass))
+    val e = VarRef("e")(ClassType(ThrowableClass, nullable = true))
 
     val classDefs = Seq(
       mainTestClassDef(Block(
-        VarDef("e", NON, ClassType(ThrowableClass), mutable = false,
+        VarDef("e", NON, ClassType(ThrowableClass, nullable = true), mutable = false,
             WrapAsThrowable(JSNew(JSGlobalRef("RangeError"), List(str("boom"))))),
-        genAssert(IsInstanceOf(e, ClassType("java.lang.Exception"))),
-        genAssertEquals(str("RangeError: boom"), Apply(EAF, e, getMessage, Nil)(ClassType(BoxedStringClass)))
+        genAssert(IsInstanceOf(e, ClassType("java.lang.Exception", nullable = false))),
+        genAssertEquals(str("RangeError: boom"),
+            Apply(EAF, e, getMessage, Nil)(ClassType(BoxedStringClass, nullable = true)))
       ))
     )
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala
index 956dcb0c15..a6ed3f6a6e 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala
@@ -180,9 +180,9 @@ object Infos {
       case FieldDef(flags, FieldIdent(name), _, ftpe) =>
         if (!flags.namespace.isStatic) {
           ftpe match {
-            case ClassType(cls) =>
+            case ClassType(cls, _) =>
               builder += name -> cls
-            case ArrayType(ArrayTypeRef(ClassRef(cls), _)) =>
+            case ArrayType(ArrayTypeRef(ClassRef(cls), _), _) =>
               builder += name -> cls
             case _ =>
           }
@@ -223,20 +223,20 @@ object Infos {
 
     def addMethodCalled(receiverTpe: Type, method: MethodName): this.type = {
       receiverTpe match {
-        case ClassType(cls) => addMethodCalled(cls, method)
-        case AnyType        => addMethodCalled(ObjectClass, method)
-        case UndefType      => addMethodCalled(BoxedUnitClass, method)
-        case BooleanType    => addMethodCalled(BoxedBooleanClass, method)
-        case CharType       => addMethodCalled(BoxedCharacterClass, method)
-        case ByteType       => addMethodCalled(BoxedByteClass, method)
-        case ShortType      => addMethodCalled(BoxedShortClass, method)
-        case IntType        => addMethodCalled(BoxedIntegerClass, method)
-        case LongType       => addMethodCalled(BoxedLongClass, method)
-        case FloatType      => addMethodCalled(BoxedFloatClass, method)
-        case DoubleType     => addMethodCalled(BoxedDoubleClass, method)
-        case StringType     => addMethodCalled(BoxedStringClass, method)
-
-        case ArrayType(_) =>
+        case ClassType(cls, _)        => addMethodCalled(cls, method)
+        case AnyType | AnyNotNullType => addMethodCalled(ObjectClass, method)
+        case UndefType                => addMethodCalled(BoxedUnitClass, method)
+        case BooleanType              => addMethodCalled(BoxedBooleanClass, method)
+        case CharType                 => addMethodCalled(BoxedCharacterClass, method)
+        case ByteType                 => addMethodCalled(BoxedByteClass, method)
+        case ShortType                => addMethodCalled(BoxedShortClass, method)
+        case IntType                  => addMethodCalled(BoxedIntegerClass, method)
+        case LongType                 => addMethodCalled(BoxedLongClass, method)
+        case FloatType                => addMethodCalled(BoxedFloatClass, method)
+        case DoubleType               => addMethodCalled(BoxedDoubleClass, method)
+        case StringType               => addMethodCalled(BoxedStringClass, method)
+
+        case ArrayType(_, _) =>
           /* The pseudo Array class is not reified in our analyzer/analysis,
            * so we need to cheat here. Since the Array[T] classes do not define
            * any method themselves--they are all inherited from j.l.Object--,
@@ -297,9 +297,9 @@ object Infos {
 
     def maybeAddUsedInstanceTest(tpe: Type): this.type = {
       tpe match {
-        case ClassType(className) =>
+        case ClassType(className, _) =>
           addUsedInstanceTest(className)
-        case ArrayType(ArrayTypeRef(ClassRef(baseClassName), _)) =>
+        case ArrayType(ArrayTypeRef(ClassRef(baseClassName), _), _) =>
           addUsedInstanceTest(baseClassName)
         case _ =>
       }
@@ -354,9 +354,9 @@ object Infos {
 
     def maybeAddReferencedClass(tpe: Type): this.type = {
       tpe match {
-        case ClassType(cls) =>
+        case ClassType(cls, _) =>
           addReferencedClass(cls)
-        case ArrayType(ArrayTypeRef(ClassRef(cls), _)) =>
+        case ArrayType(ArrayTypeRef(ClassRef(cls), _), _) =>
           addReferencedClass(cls)
         case _ =>
       }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
index 2d0dd515ea..6351e43614 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
@@ -937,8 +937,6 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
       globalKnowledge: GlobalKnowledge, pos: Position): WithGlobals[List[js.Tree]] = {
     import TreeDSL._
 
-    val tpe = ClassType(className)
-
     val moduleInstance = fileLevelVarIdent(VarField.n, genName(className))
 
     val createModuleInstanceField = genEmptyMutableLet(moduleInstance)
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala
index 279a2929d0..07e4dee5f8 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala
@@ -591,8 +591,8 @@ final class Emitter(config: Emitter.Config, prePrinter: Emitter.PrePrinter) {
 
           val methodName = methodDef.name
           val newBody = ApplyStatically(ApplyFlags.empty,
-              This()(ClassType(className)), ObjectClass, methodName,
-              methodDef.args.map(_.ref))(
+              This()(ClassType(className, nullable = false)),
+              ObjectClass, methodName, methodDef.args.map(_.ref))(
               methodDef.resultType)
           MethodDef(MemberFlags.empty, methodName,
               methodDef.originalName, methodDef.args, methodDef.resultType,
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
index 343e01605e..953a54241f 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
@@ -1090,8 +1090,6 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
               case RecordSelect(record, field) if noExtractYet =>
                 RecordSelect(rec(record), field)(arg.tpe)
 
-              case Transient(AssumeNotNull(obj)) =>
-                Transient(AssumeNotNull(rec(obj)))
               case Transient(Cast(expr, tpe)) =>
                 Transient(Cast(rec(expr), tpe))
               case Transient(ZeroOf(runtimeClass)) =>
@@ -1241,7 +1239,7 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
       }
 
       def testNPE(tree: Tree): Boolean = {
-        val npeOK = allowBehavior(semantics.nullPointers) || isNotNull(tree)
+        val npeOK = allowBehavior(semantics.nullPointers) || !tree.tpe.isNullable
         npeOK && test(tree)
       }
 
@@ -1290,8 +1288,6 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
         case UnwrapFromThrowable(expr @ (VarRef(_) | Transient(JSVarRef(_, _)))) => testNPE(expr)
 
         // Transients preserving pureness (modulo NPE)
-        case Transient(AssumeNotNull(obj)) =>
-          test(obj)
         case Transient(Cast(expr, _)) =>
           test(expr)
         case Transient(ZeroOf(runtimeClass)) =>
@@ -1830,11 +1826,6 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
             redo(Transient(CheckNotNull(newObj)))(env)
           }
 
-        case Transient(AssumeNotNull(obj)) =>
-          unnest(obj) { (newObj, env) =>
-            redo(Transient(AssumeNotNull(newObj)))(env)
-          }
-
         case Transient(Cast(expr, tpe)) =>
           unnest(expr) { (newExpr, env) =>
             redo(Transient(Cast(newExpr, tpe)))(env)
@@ -2271,10 +2262,10 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
           if (isMaybeHijackedClass(receiver.tpe) &&
               !methodName.isReflectiveProxy) {
             receiver.tpe match {
-              case AnyType =>
+              case AnyType | AnyNotNullType =>
                 genDispatchApply()
 
-              case LongType | ClassType(BoxedLongClass) if !useBigIntForLongs =>
+              case LongType | ClassType(BoxedLongClass, _) if !useBigIntForLongs =>
                 // All methods of java.lang.Long are also in RuntimeLong
                 genNormalApply()
 
@@ -2292,7 +2283,7 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
                  */
                 genDispatchApply()
 
-              case ClassType(className) if !HijackedClasses.contains(className) =>
+              case ClassType(className, _) if !HijackedClasses.contains(className) =>
                 /* This is a strict ancestor of a hijacked class. We need to
                  * use the dispatcher available in the helper method.
                  */
@@ -2421,7 +2412,7 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
               def canBePrimitiveNum(tree: Tree): Boolean = tree.tpe match {
                 case AnyType | ByteType | ShortType | IntType | FloatType | DoubleType =>
                   true
-                case ClassType(ObjectClass) =>
+                case ClassType(ObjectClass, _) =>
                   /* Due to how hijacked classes are encoded in JS, we know
                    * that in `java.lang.Object` itself, `this` can never be a
                    * primitive. It will always be a proper Scala.js object.
@@ -2432,9 +2423,9 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
                    */
                   !tree.isInstanceOf[This]
                 case ClassType(BoxedByteClass | BoxedShortClass |
-                    BoxedIntegerClass | BoxedFloatClass | BoxedDoubleClass) =>
+                    BoxedIntegerClass | BoxedFloatClass | BoxedDoubleClass, _) =>
                   true
-                case ClassType(className) =>
+                case ClassType(className, _) =>
                   globalKnowledge.isAncestorOfHijackedClass(BoxedDoubleClass)
                 case _ =>
                   false
@@ -2443,7 +2434,7 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
               def isWhole(tree: Tree): Boolean = tree.tpe match {
                 case ByteType | ShortType | IntType =>
                   true
-                case ClassType(className) =>
+                case ClassType(className, _) =>
                   className == BoxedByteClass ||
                   className == BoxedShortClass ||
                   className == BoxedIntegerClass
@@ -2735,13 +2726,16 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
              * also account for other supertypes of array types. There is a
              * similar issue for CharSequenceClass in `Apply` nodes.
              *
+             * TODO Is the above comment still relevant now that the optimizer
+             * is type-preserving?
+             *
              * In practice, this only happens in the (non-inlined) definition
              * of `java.lang.Object.clone()` itself, since everywhere else it
              * is inlined in contexts where the receiver has a more precise
              * type.
              */
-            case ClassType(CloneableClass) | ClassType(SerializableClass) |
-                ClassType(ObjectClass) | AnyType =>
+            case ClassType(CloneableClass, _) | ClassType(SerializableClass, _) |
+                ClassType(ObjectClass, _) | AnyType | AnyNotNullType =>
               genCallHelper(VarField.objectOrArrayClone, newExpr)
 
             // Otherwise, it is known not to be an array.
@@ -2770,8 +2764,6 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
 
         case Transient(CheckNotNull(obj)) =>
           genCallHelper(VarField.n, transformExpr(obj, preserveChar = true))
-        case Transient(AssumeNotNull(obj)) =>
-          transformExpr(obj, preserveChar = true)
 
         case Transient(Cast(expr, tpe)) =>
           val newExpr = transformExpr(expr, preserveChar = true)
@@ -3174,30 +3166,29 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
     }
 
     def isMaybeHijackedClass(tpe: Type): Boolean = tpe match {
-      case ClassType(className) =>
+      case ClassType(className, _) =>
         HijackedClasses.contains(className) ||
         className != ObjectClass && globalKnowledge.isAncestorOfHijackedClass(className)
 
-      case AnyType | UndefType | BooleanType | CharType | ByteType | ShortType |
-          IntType | LongType | FloatType | DoubleType | StringType =>
+      case AnyType | AnyNotNullType | UndefType | BooleanType | CharType | ByteType |
+          ShortType | IntType | LongType | FloatType | DoubleType | StringType =>
         true
       case _ =>
         false
     }
 
     def typeToBoxedHijackedClass(tpe: Type): ClassName = (tpe: @unchecked) match {
-      case ClassType(className) => className
-      case AnyType              => ObjectClass
-      case UndefType            => BoxedUnitClass
-      case BooleanType          => BoxedBooleanClass
-      case CharType             => BoxedCharacterClass
-      case ByteType             => BoxedByteClass
-      case ShortType            => BoxedShortClass
-      case IntType              => BoxedIntegerClass
-      case LongType             => BoxedLongClass
-      case FloatType            => BoxedFloatClass
-      case DoubleType           => BoxedDoubleClass
-      case StringType           => BoxedStringClass
+      case ClassType(className, _) => className
+      case UndefType               => BoxedUnitClass
+      case BooleanType             => BoxedBooleanClass
+      case CharType                => BoxedCharacterClass
+      case ByteType                => BoxedByteClass
+      case ShortType               => BoxedShortClass
+      case IntType                 => BoxedIntegerClass
+      case LongType                => BoxedLongClass
+      case FloatType               => BoxedFloatClass
+      case DoubleType              => BoxedDoubleClass
+      case StringType              => BoxedStringClass
     }
 
     /* Ideally, we should dynamically figure out this set. We should test
@@ -3214,37 +3205,12 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
     )
 
     private def checkNotNull(tree: Tree)(implicit pos: Position): Tree = {
-      if (semantics.nullPointers == CheckedBehavior.Unchecked || isNotNull(tree))
+      if (semantics.nullPointers == CheckedBehavior.Unchecked || !tree.tpe.isNullable)
         tree
       else
         Transient(CheckNotNull(tree))
     }
 
-    private def isNotNull(tree: Tree): Boolean = {
-      // !!! Duplicate code with OptimizerCore.isNotNull
-
-      def isNullableType(tpe: Type): Boolean = tpe match {
-        case NullType    => true
-        case _: PrimType => false
-        case _           => true
-      }
-
-      def isShapeNotNull(tree: Tree): Boolean = tree match {
-        case Transient(CheckNotNull(_) | AssumeNotNull(_)) =>
-          true
-        case Transient(Cast(expr, _)) =>
-          isShapeNotNull(expr)
-        case _: This =>
-          tree.tpe != AnyType
-        case _:New | _:LoadModule | _:NewArray | _:ArrayValue | _:Clone | _:ClassOf =>
-          true
-        case _ =>
-          false
-      }
-
-      !isNullableType(tree.tpe) || isShapeNotNull(tree)
-    }
-
     private def transformParamDef(paramDef: ParamDef): js.ParamDef =
       js.ParamDef(transformLocalVarIdent(paramDef.name, paramDef.originalName))(paramDef.pos)
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala
index 5b7b846b8c..2a9b3cf93e 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala
@@ -409,7 +409,7 @@ private[emitter] final class SJSGen(
     import TreeDSL._
 
     tpe match {
-      case ClassType(className) =>
+      case ClassType(className, false) =>
         if (HijackedClasses.contains(className)) {
           genIsInstanceOfHijackedClass(expr, className)
         } else if (className == ObjectClass) {
@@ -421,7 +421,7 @@ private[emitter] final class SJSGen(
           Apply(globalVar(VarField.is, className), List(expr))
         }
 
-      case ArrayType(arrayTypeRef) =>
+      case ArrayType(arrayTypeRef, false) =>
         arrayTypeRef match {
           case ArrayTypeRef(_:PrimRef | ClassRef(ObjectClass), 1) =>
             expr instanceof genArrayConstrOf(arrayTypeRef)
@@ -439,9 +439,11 @@ private[emitter] final class SJSGen(
       case FloatType   => genIsFloat(expr)
       case DoubleType  => typeof(expr) === "number"
       case StringType  => typeof(expr) === "string"
-      case AnyType     => expr !== Null()
 
-      case NoType | NullType | NothingType | _:RecordType =>
+      case AnyNotNullType => expr !== Null()
+
+      case NoType | NullType | NothingType | AnyType |
+          ClassType(_, true) | ArrayType(_, true) | _:RecordType =>
         throw new AssertionError(s"Unexpected type $tpe in genIsInstanceOf")
     }
   }
@@ -509,7 +511,7 @@ private[emitter] final class SJSGen(
 
     if (semantics.asInstanceOfs == CheckedBehavior.Unchecked) {
       tpe match {
-        case _:ClassType | _:ArrayType | AnyType =>
+        case ClassType(_, true) | ArrayType(_, true) | AnyType =>
           wg(expr)
 
         case UndefType                     => wg(Block(expr, Undefined()))
@@ -524,17 +526,18 @@ private[emitter] final class SJSGen(
           if (semantics.strictFloats) genCallPolyfillableBuiltin(FroundBuiltin, expr)
           else wg(UnaryOp(irt.JSUnaryOp.+, expr))
 
-        case NoType | NullType | NothingType | _:RecordType =>
+        case NoType | NullType | NothingType | AnyNotNullType |
+            ClassType(_, false) | ArrayType(_, false) | _:RecordType =>
           throw new AssertionError(s"Unexpected type $tpe in genAsInstanceOf")
       }
     } else {
       val resultTree = tpe match {
-        case ClassType(ObjectClass) =>
+        case ClassType(ObjectClass, true) =>
           expr
-        case ClassType(className) =>
+        case ClassType(className, true) =>
           Apply(globalVar(VarField.as, className), List(expr))
 
-        case ArrayType(ArrayTypeRef(base, depth)) =>
+        case ArrayType(ArrayTypeRef(base, depth), true) =>
           Apply(typeRefVar(VarField.asArrayOf, base), List(expr, IntLiteral(depth)))
 
         case UndefType   => genCallHelper(VarField.uV, expr)
@@ -549,7 +552,8 @@ private[emitter] final class SJSGen(
         case StringType  => genCallHelper(VarField.uT, expr)
         case AnyType     => expr
 
-        case NoType | NullType | NothingType | _:RecordType =>
+        case NoType | NullType | NothingType | AnyNotNullType |
+            ClassType(_, false) | ArrayType(_, false) | _:RecordType =>
           throw new AssertionError(s"Unexpected type $tpe in genAsInstanceOf")
       }
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Transients.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Transients.scala
index f151112891..bf0aa319ae 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Transients.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Transients.scala
@@ -29,7 +29,7 @@ object Transients {
    *  This node must not be used when NPEs are Unchecked.
    */
   final case class CheckNotNull(obj: Tree) extends Transient.Value {
-    val tpe: Type = if (obj.tpe == NullType) NothingType else obj.tpe
+    val tpe: Type = obj.tpe.toNonNullable
 
     def traverse(traverser: Traverser): Unit =
       traverser.traverse(obj)
@@ -45,31 +45,6 @@ object Transients {
     }
   }
 
-  /** Assumes that `obj ne null`, and always returns `obj`.
-   *
-   *  This is used by the optimizer to communicate to the emitter that an
-   *  expression is known not to be `null`, so that it doesn't insert useless
-   *  `null` checks.
-   *
-   *  This node should not be used when NPEs are Unchecked.
-   */
-  final case class AssumeNotNull(obj: Tree) extends Transient.Value {
-    val tpe: Type = obj.tpe
-
-    def traverse(traverser: Traverser): Unit =
-      traverser.traverse(obj)
-
-    def transform(transformer: Transformer, isStat: Boolean)(
-        implicit pos: Position): Tree = {
-      Transient(CheckNotNull(transformer.transformExpr(obj)))
-    }
-
-    def printIR(out: IRTreePrinter): Unit = {
-      out.print(obj)
-      out.print("!")
-    }
-  }
-
   /** Casts `expr` to the given `tpe`, without any check.
    *
    *  This operation is only valid if we know that `expr` is indeed a value of
@@ -242,7 +217,7 @@ object Transients {
    *  actual typed arrays.
    */
   final case class TypedArrayToArray(expr: Tree, primRef: PrimRef) extends Transient.Value {
-    val tpe: Type = ArrayType(ArrayTypeRef.of(primRef))
+    val tpe: Type = ArrayType(ArrayTypeRef.of(primRef), nullable = false)
 
     def traverse(traverser: Traverser): Unit =
       traverser.traverse(expr)
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/ClassEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/ClassEmitter.scala
index e7c8327613..f669847fe2 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/ClassEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/ClassEmitter.scala
@@ -1149,7 +1149,7 @@ class ClassEmitter(coreSpec: CoreSpec) {
       else if (isHijackedClass)
         Some(transformPrimType(BoxedClassToPrimType(className)))
       else
-        Some(transformClassType(className).toNonNullable)
+        Some(transformClassType(className, nullable = false))
 
     val body = method.body.getOrElse(throw new Exception("abstract method cannot be transformed"))
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
index 9f67841cbf..855c37f888 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
@@ -311,7 +311,7 @@ object CoreWasmLib {
         case DoubleRef => Float64
         case _         => Int32
       }
-      addHelperImport(genFunctionID.box(primRef), List(wasmType), List(anyref))
+      addHelperImport(genFunctionID.box(primRef), List(wasmType), List(RefType.any))
       addHelperImport(genFunctionID.unbox(primRef), List(anyref), List(wasmType))
       addHelperImport(genFunctionID.typeTest(primRef), List(anyref), List(Int32))
     }
@@ -383,18 +383,18 @@ object CoreWasmLib {
     addHelperImport(genFunctionID.jsGlobalRefGet, List(RefType.any), List(anyref))
     addHelperImport(genFunctionID.jsGlobalRefSet, List(RefType.any, anyref), Nil)
     addHelperImport(genFunctionID.jsGlobalRefTypeof, List(RefType.any), List(RefType.any))
-    addHelperImport(genFunctionID.jsNewArray, Nil, List(anyref))
-    addHelperImport(genFunctionID.jsArrayPush, List(anyref, anyref), List(anyref))
+    addHelperImport(genFunctionID.jsNewArray, Nil, List(RefType.any))
+    addHelperImport(genFunctionID.jsArrayPush, List(RefType.any, anyref), List(RefType.any))
     addHelperImport(
       genFunctionID.jsArraySpreadPush,
-      List(anyref, anyref),
-      List(anyref)
+      List(RefType.any, anyref),
+      List(RefType.any)
     )
-    addHelperImport(genFunctionID.jsNewObject, Nil, List(anyref))
+    addHelperImport(genFunctionID.jsNewObject, Nil, List(RefType.any))
     addHelperImport(
       genFunctionID.jsObjectPush,
-      List(anyref, anyref, anyref),
-      List(anyref)
+      List(RefType.any, anyref, anyref),
+      List(RefType.any)
     )
     addHelperImport(genFunctionID.jsSelect, List(anyref, anyref), List(anyref))
     addHelperImport(genFunctionID.jsSelectSet, List(anyref, anyref, anyref), Nil)
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/DerivedClasses.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/DerivedClasses.scala
index d30d4504b9..02a3d34bea 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/DerivedClasses.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/DerivedClasses.scala
@@ -85,7 +85,7 @@ object DerivedClasses {
     val className = clazz.className
     val derivedClassName = className.withSuffix("Box")
     val primType = BoxedClassToPrimType(className).asInstanceOf[PrimTypeWithRef]
-    val derivedClassType = ClassType(derivedClassName)
+    val derivedThisType = ClassType(derivedClassName, nullable = false)
 
     val fieldName = FieldName(derivedClassName, valueFieldSimpleName)
     val fieldIdent = FieldIdent(fieldName)
@@ -94,7 +94,7 @@ object DerivedClasses {
       FieldDef(EMF, fieldIdent, NON, primType)
     )
 
-    val selectField = Select(This()(derivedClassType), fieldIdent)(primType)
+    val selectField = Select(This()(derivedThisType), fieldIdent)(primType)
 
     val ctorParamDef =
       ParamDef(LocalIdent(fieldName.simpleName.toLocalName), NON, primType, mutable = false)
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
index 15cd22c174..5fecd5dbd2 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
@@ -543,7 +543,7 @@ private class FunctionEmitter private (
       case ArraySelect(array, index) =>
         genTreeAuto(array)
         array.tpe match {
-          case ArrayType(arrayTypeRef) =>
+          case ArrayType(arrayTypeRef, _) =>
             // Get the underlying array; implicit trap on null
             markPosition(tree)
             fb += wa.StructGet(
@@ -640,11 +640,14 @@ private class FunctionEmitter private (
 
       case _ =>
         val receiverClassName = receiver.tpe match {
-          case prim: PrimType  => PrimTypeToBoxedClass(prim)
-          case ClassType(cls)  => cls
-          case AnyType         => ObjectClass
-          case ArrayType(_)    => ObjectClass
-          case tpe: RecordType => throw new AssertionError(s"Invalid receiver type $tpe")
+          case prim: PrimType =>
+            PrimTypeToBoxedClass(prim)
+          case ClassType(cls, _) =>
+            cls
+          case AnyType | AnyNotNullType | ArrayType(_, _) =>
+            ObjectClass
+          case tpe: RecordType =>
+            throw new AssertionError(s"Invalid receiver type $tpe")
         }
         val receiverClassInfo = ctx.getClassInfo(receiverClassName)
 
@@ -1028,7 +1031,7 @@ private class FunctionEmitter private (
 
         BoxedClassToPrimType.get(targetClassName) match {
           case None =>
-            genTree(receiver, ClassType(targetClassName))
+            genTree(receiver, ClassType(targetClassName, nullable = true))
             fb += wa.RefAsNonNull
 
           case Some(primReceiverType) =>
@@ -1156,7 +1159,7 @@ private class FunctionEmitter private (
       throw new AssertionError(s"Cannot emit $tree at ${tree.pos} without enclosing class name")
     }
 
-    genTreeAuto(This()(ClassType(className))(tree.pos))
+    genTreeAuto(This()(ClassType(className, nullable = false))(tree.pos))
 
     markPosition(tree)
     fb += wa.GlobalSet(genGlobalID.forModuleInstance(className))
@@ -1428,6 +1431,8 @@ private class FunctionEmitter private (
 
   private def genToStringForConcat(tree: Tree): Unit = {
     def genWithDispatch(isAncestorOfHijackedClass: Boolean): Unit = {
+      // TODO Better codegen when non-nullable
+
       /* Somewhat duplicated from genApplyNonPrim, but specialized for
        * `toString`, and where the handling of `null` is different.
        *
@@ -1543,19 +1548,20 @@ private class FunctionEmitter private (
                 s"Found expression of type void in String_+ at ${tree.pos}: $tree")
         }
 
-      case ClassType(BoxedStringClass) =>
+      case ClassType(BoxedStringClass, nullable) =>
         // Common case for which we want to avoid the hijacked class dispatch
         genTreeAuto(tree)
         markPosition(tree)
-        fb += wa.Call(genFunctionID.jsValueToStringForConcat) // for `null`
+        if (nullable)
+          fb += wa.Call(genFunctionID.jsValueToStringForConcat)
 
-      case ClassType(className) =>
+      case ClassType(className, _) =>
         genWithDispatch(ctx.getClassInfo(className).isAncestorOfHijackedClass)
 
-      case AnyType =>
+      case AnyType | AnyNotNullType =>
         genWithDispatch(isAncestorOfHijackedClass = true)
 
-      case ArrayType(_) =>
+      case ArrayType(_, _) =>
         genWithDispatch(isAncestorOfHijackedClass = false)
 
       case tpe: RecordType =>
@@ -1695,11 +1701,11 @@ private class FunctionEmitter private (
       case testType: PrimType =>
         genIsPrimType(testType)
 
-      case AnyType | ClassType(ObjectClass) =>
+      case AnyNotNullType | ClassType(ObjectClass, false) =>
         fb += wa.RefIsNull
         fb += wa.I32Eqz
 
-      case ClassType(JLNumberClass) =>
+      case ClassType(JLNumberClass, false) =>
         /* Special case: the only non-Object *class* that is an ancestor of a
          * hijacked class. We need to accept `number` primitives here.
          */
@@ -1713,7 +1719,7 @@ private class FunctionEmitter private (
           fb += wa.Call(genFunctionID.typeTest(DoubleRef))
         }
 
-      case ClassType(testClassName) =>
+      case ClassType(testClassName, false) =>
         BoxedClassToPrimType.get(testClassName) match {
           case Some(primType) =>
             genIsPrimType(primType)
@@ -1724,7 +1730,7 @@ private class FunctionEmitter private (
               fb += wa.RefTest(watpe.RefType(genTypeID.forClass(testClassName)))
         }
 
-      case ArrayType(arrayTypeRef) =>
+      case ArrayType(arrayTypeRef, false) =>
         arrayTypeRef match {
           case ArrayTypeRef(ClassRef(ObjectClass) | _: PrimRef, 1) =>
             // For primitive arrays and exactly Array[Object], a wa.RefTest is enough
@@ -1770,7 +1776,7 @@ private class FunctionEmitter private (
             }
         }
 
-      case testType: RecordType =>
+      case AnyType | ClassType(_, true) | ArrayType(_, true) | _:RecordType =>
         throw new AssertionError(s"Illegal type in IsInstanceOf: $testType")
     }
 
@@ -1786,44 +1792,65 @@ private class FunctionEmitter private (
   private def genCast(expr: Tree, targetTpe: Type, pos: Position): Type = {
     val sourceTpe = expr.tpe
 
+    /* We cannot call `transformSingleType` for NothingType, so we have to
+     * handle these cases separately.
+     */
+
     if (sourceTpe == NothingType) {
-      // We cannot call transformType for NothingType, so we have to handle this case separately.
       genTree(expr, NothingType)
       NothingType
+    } else if (targetTpe == NothingType) {
+      genTree(expr, NoType)
+      fb += wa.Unreachable
+      NothingType
     } else {
-      // By IR checker rules, targetTpe is none of NothingType, NullType, NoType or RecordType
+      /* At this point, neither sourceTpe nor targetTpe can be NothingType,
+       * NoType or RecordType, so we can use `transformSingleType`.
+       */
 
       val sourceWasmType = transformSingleType(sourceTpe)
       val targetWasmType = transformSingleType(targetTpe)
 
-      if (sourceWasmType == targetWasmType) {
-        /* Common case where no cast is necessary at the Wasm level.
-         * Note that this is not *obviously* correct. It is only correct
-         * because, under our choices of representation and type translation
-         * rules, there is no pair `(sourceTpe, targetTpe)` for which the Wasm
-         * types are equal but a valid cast would require a *conversion*.
-         */
-        genTreeAuto(expr)
-      } else {
-        genTree(expr, AnyType)
+      (sourceWasmType, targetWasmType) match {
+        case _ if sourceWasmType == targetWasmType =>
+          /* Common case where no cast is necessary at the Wasm level.
+           * Note that this is not *obviously* correct. It is only correct
+           * because, under our choices of representation and type translation
+           * rules, there is no pair `(sourceTpe, targetTpe)` for which the Wasm
+           * types are equal but a valid cast would require a *conversion*.
+           */
+          genTreeAuto(expr)
 
-        markPosition(pos)
+        case (watpe.RefType(true, sourceHeapType), watpe.RefType(false, targetHeapType))
+            if sourceHeapType == targetHeapType =>
+          /* Similar but here we need to cast away nullability. This shape of
+           * Cast is a common case for checkNotNull's inserted by the optimizer
+           * when null pointers are unchecked.
+           */
+          genTreeAuto(expr)
+          markPosition(pos)
+          fb += wa.RefAsNonNull
 
-        targetTpe match {
-          case targetTpe: PrimType =>
-            // TODO Opt: We could do something better for things like double.asInstanceOf[int]
-            genUnbox(targetTpe)
+        case _ =>
+          genTree(expr, AnyType)
 
-          case _ =>
-            targetWasmType match {
-              case watpe.RefType(true, watpe.HeapType.Any) =>
-                () // nothing to do
-              case targetWasmType: watpe.RefType =>
-                fb += wa.RefCast(targetWasmType)
-              case _ =>
-                throw new AssertionError(s"Unexpected type in AsInstanceOf: $targetTpe")
-            }
-        }
+          markPosition(pos)
+
+          targetTpe match {
+            case targetTpe: PrimType =>
+              // TODO Opt: We could do something better for things like double.asInstanceOf[int]
+              genUnbox(targetTpe)
+
+            case _ =>
+              targetWasmType match {
+                case watpe.RefType(true, watpe.HeapType.Any) =>
+                  () // nothing to do
+                case targetWasmType: watpe.RefType =>
+                  fb += wa.RefCast(targetWasmType)
+                case _ =>
+                  throw new AssertionError(s"Unexpected type in AsInstanceOf: $targetTpe")
+              }
+          }
       }
 
       targetTpe
@@ -1885,9 +1912,9 @@ private class FunctionEmitter private (
     val GetClass(expr) = tree
 
     val needHijackedClassDispatch = expr.tpe match {
-      case ClassType(className) =>
+      case ClassType(className, _) =>
         ctx.getClassInfo(className).isAncestorOfHijackedClass
-      case ArrayType(_) | NothingType | NullType =>
+      case ArrayType(_, _) | NothingType | NullType =>
         false
       case _ =>
         true
@@ -2192,7 +2219,7 @@ private class FunctionEmitter private (
     fb += wa.LocalGet(primLocal)
     fb += wa.StructNew(genTypeID.forClass(boxClassName))
 
-    ClassType(boxClassName)
+    ClassType(boxClassName, nullable = false)
   }
 
   private def genIdentityHashCode(tree: IdentityHashCode): Type = {
@@ -2247,7 +2274,7 @@ private class FunctionEmitter private (
     val UnwrapFromThrowable(expr) = tree
 
     fb.block(watpe.RefType.anyref) { doneLabel =>
-      genTree(expr, ClassType(ThrowableClass))
+      genTree(expr, ClassType(ThrowableClass, nullable = true))
 
       markPosition(tree)
 
@@ -2488,7 +2515,7 @@ private class FunctionEmitter private (
     markPosition(tree)
 
     array.tpe match {
-      case ArrayType(arrayTypeRef) =>
+      case ArrayType(arrayTypeRef, _) =>
         // Get the underlying array; implicit trap on null
         fb += wa.StructGet(
           genTypeID.forArrayClass(arrayTypeRef),
@@ -2565,7 +2592,7 @@ private class FunctionEmitter private (
     markPosition(tree)
 
     array.tpe match {
-      case ArrayType(arrayTypeRef) =>
+      case ArrayType(arrayTypeRef, _) =>
         // Get the underlying array; implicit trap on null
         fb += wa.StructGet(
           genTypeID.forArrayClass(arrayTypeRef),
@@ -2710,7 +2737,7 @@ private class FunctionEmitter private (
       case exprType =>
         val exprLocal = addSyntheticLocal(watpe.RefType(genTypeID.ObjectStruct))
 
-        genTree(expr, ClassType(CloneableClass))
+        genTree(expr, ClassType(CloneableClass, nullable = true))
 
         markPosition(tree)
 
@@ -2964,7 +2991,7 @@ private class FunctionEmitter private (
     markPosition(tree)
 
     (src.tpe, dest.tpe) match {
-      case (ArrayType(srcArrayTypeRef), ArrayType(destArrayTypeRef))
+      case (ArrayType(srcArrayTypeRef, _), ArrayType(destArrayTypeRef, _))
           if genTypeID.forArrayClass(srcArrayTypeRef) == genTypeID.forArrayClass(destArrayTypeRef) =>
         // Generate a specialized arrayCopyT call
         fb += wa.Call(genFunctionID.specializedArrayCopy(srcArrayTypeRef))
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Preprocessor.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Preprocessor.scala
index ed480cf00c..1aa1ea6f2f 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Preprocessor.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Preprocessor.scala
@@ -279,7 +279,7 @@ object Preprocessor {
       tree match {
         case Apply(flags, receiver, MethodIdent(methodName), _) if !methodName.isReflectiveProxy =>
           receiver.tpe match {
-            case ClassType(className) =>
+            case ClassType(className, _) =>
               registerCall(className, methodName)
             case AnyType =>
               registerCall(ObjectClass, methodName)
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/SWasmGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/SWasmGen.scala
index a1ef630952..b4b73a1556 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/SWasmGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/SWasmGen.scala
@@ -35,10 +35,11 @@ object SWasmGen {
       case StringType => GlobalGet(genGlobalID.emptyString)
       case UndefType  => GlobalGet(genGlobalID.undef)
 
-      case AnyType | ClassType(_) | ArrayType(_) | NullType =>
+      case AnyType | ClassType(_, true) | ArrayType(_, true) | NullType =>
         RefNull(Types.HeapType.None)
 
-      case NoType | NothingType | _: RecordType =>
+      case NothingType | NoType | ClassType(_, false) | ArrayType(_, false) |
+          AnyNotNullType | _:RecordType =>
         throw new AssertionError(s"Unexpected type for field: ${tpe.show()}")
     }
   }
@@ -53,10 +54,11 @@ object SWasmGen {
         GlobalGet(genGlobalID.bZero)
       case LongType =>
         GlobalGet(genGlobalID.bZeroLong)
-      case AnyType | ClassType(_) | ArrayType(_) | StringType | UndefType | NullType =>
+      case AnyType | ClassType(_, true) | ArrayType(_, true) | StringType | UndefType | NullType =>
         RefNull(Types.HeapType.None)
 
-      case NoType | NothingType | _: RecordType =>
+      case NothingType | NoType | ClassType(_, false) | ArrayType(_, false) |
+          AnyNotNullType | _:RecordType =>
         throw new AssertionError(s"Unexpected type for field: ${tpe.show()}")
     }
   }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/TypeTransformer.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/TypeTransformer.scala
index 2deaa6a013..6535f352ab 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/TypeTransformer.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/TypeTransformer.scala
@@ -85,33 +85,37 @@ object TypeTransformer {
    */
   def transformSingleType(tpe: Type)(implicit ctx: WasmContext): watpe.Type = {
     tpe match {
-      case AnyType              => watpe.RefType.anyref
-      case ClassType(className) => transformClassType(className)
-      case tpe: PrimType        => transformPrimType(tpe)
+      case AnyType                        => watpe.RefType.anyref
+      case AnyNotNullType                 => watpe.RefType.any
+      case ClassType(className, nullable) => transformClassType(className, nullable)
+      case tpe: PrimType                  => transformPrimType(tpe)
 
-      case tpe: ArrayType =>
-        watpe.RefType.nullable(genTypeID.forArrayClass(tpe.arrayTypeRef))
+      case ArrayType(arrayTypeRef, nullable) =>
+        watpe.RefType(nullable, genTypeID.forArrayClass(arrayTypeRef))
 
       case RecordType(fields) =>
         throw new AssertionError(s"Unexpected record type $tpe")
     }
   }
 
-  def transformClassType(className: ClassName)(implicit ctx: WasmContext): watpe.RefType = {
-    ctx.getClassInfoOption(className) match {
+  def transformClassType(className: ClassName, nullable: Boolean)(
+      implicit ctx: WasmContext): watpe.RefType = {
+    val heapType: watpe.HeapType = ctx.getClassInfoOption(className) match {
       case Some(info) =>
         if (info.isAncestorOfHijackedClass)
-          watpe.RefType.anyref
+          watpe.HeapType.Any
         else if (!info.hasInstances)
-          watpe.RefType.nullref
+          watpe.HeapType.None
         else if (info.isInterface)
-          watpe.RefType.nullable(genTypeID.ObjectStruct)
+          watpe.HeapType(genTypeID.ObjectStruct)
         else
-          watpe.RefType.nullable(genTypeID.forClass(className))
+          watpe.HeapType(genTypeID.forClass(className))
 
       case None =>
-        watpe.RefType.nullref
+        watpe.HeapType.None
     }
+
+    watpe.RefType(nullable, heapType)
   }
 
   def transformPrimType(tpe: PrimType): watpe.Type = {
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/WasmContext.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/WasmContext.scala
index 1eb5cecef1..aa230752a3 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/WasmContext.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/WasmContext.scala
@@ -85,9 +85,9 @@ final class WasmContext(
       if (className == ObjectClass || getClassInfo(className).kind.isJSType)
         AnyType
       else
-        ClassType(className)
+        ClassType(className, nullable = true)
     case typeRef: ArrayTypeRef =>
-      ArrayType(typeRef)
+      ArrayType(typeRef, nullable = true)
   }
 
   /** Retrieves a unique identifier for a reflective proxy with the given name.
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/Types.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/Types.scala
index db8f4a0e83..36b4b5cad4 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/Types.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/Types.scala
@@ -56,6 +56,8 @@ object Types {
   }
 
   object RefType {
+    def apply(nullable: Boolean, typeID: TypeID): RefType =
+      RefType(nullable, HeapType(typeID))
 
     /** Builds a non-nullable `(ref heapType)` for the given `heapType`. */
     def apply(heapType: HeapType): RefType = RefType(false, heapType)
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala b/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
index 728efa33dc..5da8ba0a6f 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
@@ -40,9 +40,9 @@ private final class ClassDefChecker(classDef: ClassDef,
     if (classDef.kind.isJSType)
       AnyType
     else if (classDef.kind == ClassKind.HijackedClass)
-      BoxedClassToPrimType.getOrElse(cls, ClassType(cls)) // getOrElse not to crash on invalid ClassDef
+      BoxedClassToPrimType.getOrElse(cls, ClassType(cls, nullable = false)) // getOrElse not to crash on invalid input
     else
-      ClassType(cls)
+      ClassType(cls, nullable = false)
   }
 
   private[this] val fields =
@@ -226,8 +226,13 @@ private final class ClassDefChecker(classDef: ClassDef,
         checkTree(name, Env.empty)
     }
 
-    if (fieldDef.ftpe == NoType || fieldDef.ftpe == NothingType)
-      reportError(i"FieldDef cannot have type ${fieldDef.ftpe}")
+    fieldDef.ftpe match {
+      case NoType | NothingType | AnyNotNullType | ClassType(_, false) |
+          ArrayType(_, false) | _:RecordType =>
+        reportError(i"FieldDef cannot have type ${fieldDef.ftpe}")
+      case _ =>
+        // ok
+    }
   }
 
   private def checkMethodDef(methodDef: MethodDef): Unit = withPerMethodState {
@@ -690,11 +695,27 @@ private final class ClassDefChecker(classDef: ClassDef,
 
       case IsInstanceOf(expr, testType) =>
         checkTree(expr, env)
-        checkIsAsInstanceTargetType(testType)
+        testType match {
+          case NoType | NullType | NothingType | AnyType |
+              ClassType(_, true) | ArrayType(_, true) | _:RecordType =>
+            reportError(i"$testType is not a valid test type for IsInstanceOf")
+          case testType: ArrayType =>
+            checkArrayType(testType)
+          case _ =>
+            // ok
+        }
 
       case AsInstanceOf(expr, tpe) =>
         checkTree(expr, env)
-        checkIsAsInstanceTargetType(tpe)
+        tpe match {
+          case NoType | NullType | NothingType | AnyNotNullType |
+              ClassType(_, false) | ArrayType(_, false) | _:RecordType =>
+            reportError(i"$tpe is not a valid target type for AsInstanceOf")
+          case tpe: ArrayType =>
+            checkArrayType(tpe)
+          case _ =>
+            // ok
+        }
 
       case GetClass(expr) =>
         checkTree(expr, env)
@@ -866,20 +887,6 @@ private final class ClassDefChecker(classDef: ClassDef,
       reportError("invalid transient tree")
   }
 
-  private def checkIsAsInstanceTargetType(tpe: Type)(
-      implicit ctx: ErrorContext): Unit = {
-    tpe match {
-      case NoType | NullType | NothingType | _:RecordType =>
-        reportError(i"$tpe is not a valid target type for Is/AsInstanceOf")
-
-      case tpe: ArrayType =>
-        checkArrayType(tpe)
-
-      case _ =>
-        // ok
-    }
-  }
-
   private def checkArrayReceiverType(tpe: Type)(
       implicit ctx: ErrorContext): Unit = tpe match {
     case tpe: ArrayType         => checkArrayType(tpe)
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala b/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
index 8f399fa984..eb12a06b3a 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
@@ -331,7 +331,7 @@ private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter) {
           reportError(i"Cannot select $item of non-class $className")
           typecheckExpr(qualifier, env)
         } else {
-          typecheckExpect(qualifier, env, ClassType(className))
+          typecheckExpect(qualifier, env, ClassType(className, nullable = true))
 
           /* Actually checking the field is done only if the class has
            * instances (including instances of subclasses).
@@ -380,7 +380,7 @@ private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter) {
           reportError("Illegal flag for Apply: Private")
         typecheckExpr(receiver, env)
         val fullCheck = receiver.tpe match {
-          case ClassType(className) =>
+          case ClassType(className, _) =>
             /* For class types, we only perform full checks if the class has
              * instances. This is necessary because the BaseLinker can
              * completely get rid of all the method *definitions* for the call
@@ -406,7 +406,7 @@ private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter) {
         }
 
       case ApplyStatically(_, receiver, className, MethodIdent(method), args) =>
-        typecheckExpect(receiver, env, ClassType(className))
+        typecheckExpect(receiver, env, ClassType(className, nullable = true))
         checkApplyGeneric(className, method, args, tree.tpe, isStatic = false)
 
       case ApplyStatic(_, className, MethodIdent(method), args) =>
@@ -514,7 +514,7 @@ private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter) {
         typecheckExpr(expr, env)
 
       case Clone(expr) =>
-        typecheckExpect(expr, env, ClassType(CloneableClass))
+        typecheckExpect(expr, env, ClassType(CloneableClass, nullable = true))
 
       case IdentityHashCode(expr) =>
         typecheckExpr(expr, env)
@@ -523,7 +523,7 @@ private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter) {
         typecheckExpr(expr, env)
 
       case UnwrapFromThrowable(expr) =>
-        typecheckExpect(expr, env, ClassType(ThrowableClass))
+        typecheckExpect(expr, env, ClassType(ThrowableClass, nullable = true))
 
       // JavaScript expressions
 
@@ -677,7 +677,7 @@ private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter) {
   private def checkIsAsInstanceTargetType(tpe: Type)(
       implicit ctx: ErrorContext): Unit = {
     tpe match {
-      case ClassType(className) =>
+      case ClassType(className, _) =>
         val kind = lookupClass(className).kind
         if (kind.isJSType) {
           reportError(
@@ -703,7 +703,7 @@ private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter) {
     typeRef match {
       case PrimRef(tpe)               => tpe
       case ClassRef(className)        => classNameToType(className)
-      case arrayTypeRef: ArrayTypeRef => ArrayType(arrayTypeRef)
+      case arrayTypeRef: ArrayTypeRef => ArrayType(arrayTypeRef, nullable = true)
     }
   }
 
@@ -714,7 +714,7 @@ private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter) {
     } else {
       val kind = lookupClass(className).kind
       if (kind.isJSType) AnyType
-      else ClassType(className)
+      else ClassType(className, nullable = true)
     }
   }
 
@@ -729,7 +729,7 @@ private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter) {
     if (dimensions == 1)
       typeRefToType(base)
     else
-      ArrayType(ArrayTypeRef(base, dimensions - 1))
+      ArrayType(ArrayTypeRef(base, dimensions - 1), nullable = true)
   }
 
   private def lookupClass(className: ClassName)(
@@ -831,7 +831,7 @@ private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter) {
 }
 
 object IRChecker {
-  private val BoxedStringType = ClassType(BoxedStringClass)
+  private val BoxedStringType = ClassType(BoxedStringClass, nullable = true)
 
   /** Checks that the IR in a [[frontend.LinkingUnit LinkingUnit]] is correct.
    *
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/MethodSynthesizer.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/MethodSynthesizer.scala
index eb50485d57..79d31dc8ab 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/MethodSynthesizer.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/MethodSynthesizer.scala
@@ -66,8 +66,8 @@ private[frontend] final class MethodSynthesizer(
       val targetIdent = targetMDef.name.copy() // for the new pos
       val proxyIdent = MethodIdent(methodName)
       val params = targetMDef.args.map(_.copy()) // for the new pos
-      val instanceThisType =
-        BoxedClassToPrimType.getOrElse(classInfo.className, ClassType(classInfo.className))
+      val instanceThisType = BoxedClassToPrimType.getOrElse(classInfo.className,
+          ClassType(classInfo.className, nullable = false))
 
       val call = Apply(ApplyFlags.empty, This()(instanceThisType),
           targetIdent, params.map(_.ref))(targetMDef.resultType)
@@ -101,8 +101,8 @@ private[frontend] final class MethodSynthesizer(
       val targetIdent = targetMDef.name.copy() // for the new pos
       val bridgeIdent = targetIdent
       val params = targetMDef.args.map(_.copy()) // for the new pos
-      val instanceThisType =
-        BoxedClassToPrimType.getOrElse(classInfo.className, ClassType(classInfo.className))
+      val instanceThisType = BoxedClassToPrimType.getOrElse(classInfo.className,
+          ClassType(classInfo.className, nullable = false))
 
       val body = ApplyStatically(
           ApplyFlags.empty, This()(instanceThisType), targetInterface,
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
index b16b13d39d..74255c7ed7 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
@@ -1491,7 +1491,7 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
     private def computeInstanceThisType(linkedClass: LinkedClass): Type = {
       if (linkedClass.kind.isJSType) AnyType
       else if (linkedClass.kind == ClassKind.HijackedClass) BoxedClassToPrimType(className)
-      else ClassType(className)
+      else ClassType(className, nullable = false)
     }
   }
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
index 3f6c71d8cb..06f62a2007 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
@@ -275,13 +275,15 @@ private[optimizer] abstract class OptimizerCore(
 
     Types.isSubtype(lhs, rhs)(isSubclassFun) || {
       (lhs, rhs) match {
-        case (LongType | ClassType(BoxedLongClass),
-            ClassType(LongImpl.RuntimeLongClass)) =>
+        case (LongType, ClassType(LongImpl.RuntimeLongClass, _)) =>
           true
+        case (ClassType(BoxedLongClass, lhsNullable),
+            ClassType(LongImpl.RuntimeLongClass, rhsNullable)) =>
+          rhsNullable || !lhsNullable
 
-        case (ClassType(LongImpl.RuntimeLongClass),
-            ClassType(BoxedLongClass)) =>
-          true
+        case (ClassType(LongImpl.RuntimeLongClass, lhsNullable),
+            ClassType(BoxedLongClass, rhsNullable)) =>
+          rhsNullable || !lhsNullable
 
         case _ =>
           false
@@ -483,6 +485,12 @@ private[optimizer] abstract class OptimizerCore(
       case New(className, ctor, args) =>
         New(className, ctor, args map transformExpr)
 
+      case LoadModule(className) =>
+        if (semantics.moduleInit == CheckedBehavior.Compliant)
+          tree
+        else // cast away nullability to enable downstream optimizations
+          makeCast(tree, ClassType(className, nullable = false))
+
       case tree: Select =>
         trampoline {
           pretransformSelectCommon(tree, isLhsOfAssign = false)(
@@ -541,7 +549,7 @@ private[optimizer] abstract class OptimizerCore(
         trampoline {
           pretransformExpr(expr) { texpr =>
             val result = {
-              if (isSubtype(texpr.tpe.base, testType)) {
+              if (isSubtype(texpr.tpe.base.toNonNullable, testType)) {
                 if (texpr.tpe.isNullable)
                   BinaryOp(BinaryOp.!==, finishTransformExpr(texpr), Null())
                 else
@@ -571,14 +579,22 @@ private[optimizer] abstract class OptimizerCore(
               TailCalls.done(Block(checkNotNullStatement(texpr), ClassOf(typeRef)))
 
             texpr.tpe match {
-              case RefinedType(ClassType(LongImpl.RuntimeLongClass), true, false) =>
+              case RefinedType(ClassType(LongImpl.RuntimeLongClass, false), true) =>
                 constant(ClassRef(BoxedLongClass))
-              case RefinedType(ClassType(className), true, false) =>
+              case RefinedType(ClassType(className, false), true) =>
                 constant(ClassRef(className))
-              case RefinedType(ArrayType(arrayTypeRef), true, false) =>
+              case RefinedType(ArrayType(arrayTypeRef, false), true) =>
                 constant(arrayTypeRef)
+              case RefinedType(AnyType | AnyNotNullType | ClassType(ObjectClass, _), _) =>
+                // The result can be anything, including null
+                TailCalls.done(GetClass(finishTransformExpr(texpr)))
               case _ =>
-                TailCalls.done(GetClass(finishTransformExprMaybeAssumeNotNull(texpr)))
+                /* If texpr.tpe is neither AnyType nor j.l.Object, it cannot be
+                 * a JS object, so its getClass() cannot be null. Cast away
+                 * nullability to help downstream optimizations.
+                 */
+                val newGetClass = GetClass(finishTransformExpr(texpr))
+                TailCalls.done(makeCast(newGetClass, newGetClass.tpe.toNonNullable))
             }
           }
         }
@@ -678,7 +694,7 @@ private[optimizer] abstract class OptimizerCore(
 
       // Trees that need not be transformed
 
-      case _:Skip | _:Debugger | _:LoadModule | _:StoreModule |
+      case _:Skip | _:Debugger | _:StoreModule |
           _:SelectStatic | _:JSNewTarget | _:JSImportMeta | _:JSLinkingInfo |
           _:JSGlobalRef | _:JSTypeOfGlobalRef | _:Literal =>
         tree
@@ -718,8 +734,8 @@ private[optimizer] abstract class OptimizerCore(
 
     transformCapturingBody(captureParams, tcaptureValues, body, innerEnv) {
       (newCaptureParams, newCaptureValues, newBody) =>
-        val newClosure = Closure(arrow, newCaptureParams, newParams, newRestParam, newBody, newCaptureValues)
-        PreTransTree(newClosure, RefinedType(AnyType, isExact = false, isNullable = false))
+        PreTransTree(Closure(arrow, newCaptureParams, newParams, newRestParam,
+            newBody, newCaptureValues))
     } (cont)
   }
 
@@ -816,7 +832,7 @@ private[optimizer] abstract class OptimizerCore(
             withBinding(Binding(nameIdent, originalName, vtpe, mutable, trhs)) {
               (restScope, cont1) =>
                 val newRest = transformList(rest)(restScope)
-                cont1(PreTransTree(newRest, RefinedType(newRest.tpe)))
+                cont1(PreTransTree(newRest))
             } (finishTransform(isStat))
           }
         }
@@ -960,22 +976,14 @@ private[optimizer] abstract class OptimizerCore(
 
       case WrapAsThrowable(expr) =>
         pretransformExpr(expr) { texpr =>
-          def default = {
-            val refinedType: RefinedType = RefinedType(ThrowableClassType, isExact = false, isNullable = false)
-            cont(PreTransTree(WrapAsThrowable(finishTransformExpr(texpr)), refinedType))
-          }
-
-          if (isSubtype(texpr.tpe.base, ThrowableClassType)) {
-            if (texpr.tpe.isNullable)
-              default
-            else
-              cont(texpr)
+          if (isSubtype(texpr.tpe.base, ThrowableClassType.toNonNullable)) {
+            cont(texpr)
           } else {
             if (texpr.tpe.isExact) {
               pretransformNew(AllocationSite.Tree(tree), JavaScriptExceptionClass,
                   MethodIdent(AnyArgConstructorName), texpr :: Nil)(cont)
             } else {
-              default
+              cont(PreTransTree(WrapAsThrowable(finishTransformExpr(texpr))))
             }
           }
         }
@@ -995,7 +1003,7 @@ private[optimizer] abstract class OptimizerCore(
             pretransformSelectCommon(AnyType, texpr, optQualDeclaredType = None,
                 FieldIdent(exceptionFieldName), isLhsOfAssign = false)(cont)
           } else {
-            if (texpr.tpe.isExact || !isSubtype(JavaScriptExceptionClassType, baseTpe))
+            if (texpr.tpe.isExact || !isSubtype(JavaScriptExceptionClassType.toNonNullable, baseTpe))
               cont(checkNotNull(texpr))
             else
               default
@@ -1029,14 +1037,13 @@ private[optimizer] abstract class OptimizerCore(
                 val replacement = InlineJSArrayReplacement(
                     itemLocalDefs.toVector, cancelFun)
                 val localDef = LocalDef(
-                    RefinedType(AnyType, isExact = false, isNullable = false),
+                    RefinedType(AnyNotNullType),
                     mutable = false,
                     replacement)
                 cont1(localDef.toPreTransform)
               } (cont)
             } { () =>
-              cont(PreTransTree(JSArrayConstr(titems.map(finishTransformExpr)),
-                  RefinedType(AnyType, isExact = false, isNullable = false)))
+              cont(PreTransTree(JSArrayConstr(titems.map(finishTransformExpr))))
             }
           }
         }
@@ -1074,7 +1081,7 @@ private[optimizer] abstract class OptimizerCore(
                     captureParams, params, body, captureLocalDefs,
                     alreadyUsed = newSimpleState(Unused), cancelFun)
                 val localDef = LocalDef(
-                    RefinedType(AnyType, isExact = false, isNullable = false),
+                    RefinedType(AnyNotNullType),
                     mutable = false,
                     replacement)
                 cont1(localDef.toPreTransform)
@@ -1115,7 +1122,7 @@ private[optimizer] abstract class OptimizerCore(
             pretransformList(rest)(cont)
           case _ =>
             if (transformedStat.tpe == NothingType)
-              cont(PreTransTree(transformedStat, RefinedType.Nothing))
+              cont(PreTransTree(transformedStat))
             else {
               pretransformList(rest) { trest =>
                 cont(PreTransBlock(transformedStat, trest))
@@ -1261,25 +1268,24 @@ private[optimizer] abstract class OptimizerCore(
                 case _: RecordType =>
                   cont(PreTransRecordTree(sel, RefinedType(expectedType), cancelFun))
                 case _ =>
-                  cont(PreTransTree(sel, RefinedType(sel.tpe)))
+                  cont(PreTransTree(sel))
               }
 
-            case PreTransTree(newQual, newQualType) =>
-              val newQual1 = maybeAssumeNotNull(newQual, newQualType)
-              val newQual2 = optQualDeclaredType match {
-                case Some(qualDeclaredType) if !isSubtype(newQual1.tpe, qualDeclaredType) =>
-                  Transient(Cast(newQual1, qualDeclaredType))
+            case tqual: PreTransTree =>
+              val tqualCast = optQualDeclaredType match {
+                case Some(ClassType(qualDeclaredClass, _)) =>
+                  foldCast(tqual, ClassType(qualDeclaredClass, nullable = true))
                 case _ =>
-                  newQual1
+                  tqual
               }
-              cont(PreTransTree(Select(newQual2, field)(expectedType),
-                  RefinedType(expectedType)))
+              val newQual = finishTransformExpr(tqualCast)
+              cont(PreTransTree(Select(newQual, field)(expectedType)))
           }
         }
 
         preTransQual.tpe match {
           // Try to inline an inlineable field body
-          case RefinedType(ClassType(qualClassName), _, _) if !isLhsOfAssign =>
+          case RefinedType(ClassType(qualClassName, _), _) if !isLhsOfAssign =>
             if (myself.exists(m => m.enclosingClassName == qualClassName && m.methodName.isConstructor)) {
               /* Within the constructor of a class, we cannot trust the
                * inlineable field bodies of that class, since they only reflect
@@ -1343,7 +1349,7 @@ private[optimizer] abstract class OptimizerCore(
 
         (trhs.tpe.base, lhsOrigType) match {
           case (LongType, RefinedType(
-              ClassType(LongImpl.RuntimeLongClass), true, false)) =>
+              ClassType(LongImpl.RuntimeLongClass, false), true)) =>
             /* The lhs is a stack-allocated RuntimeLong, but the rhs is
              * a primitive Long. We expand the primitive Long into a
              * new stack-allocated RuntimeLong so that we do not need
@@ -1374,13 +1380,11 @@ private[optimizer] abstract class OptimizerCore(
               ctor, targs, cancelFun)(cont)
         } { () =>
           cont(PreTransTree(
-              New(className, ctor, targs.map(finishTransformExpr)),
-              RefinedType(ClassType(className), isExact = true, isNullable = false)))
+              New(className, ctor, targs.map(finishTransformExpr))))
         }
       case None =>
         cont(PreTransTree(
-            New(className, ctor, targs.map(finishTransformExpr)),
-            RefinedType(ClassType(className), isExact = true, isNullable = false)))
+            New(className, ctor, targs.map(finishTransformExpr))))
     }
   }
 
@@ -1480,12 +1484,6 @@ private[optimizer] abstract class OptimizerCore(
     }
   }
 
-  /** Finishes an expression pretransform to get a normal [[Tree]], recording
-   *  whether the pretransform was known to be not-null.
-   */
-  private def finishTransformExprMaybeAssumeNotNull(preTrans: PreTransform): Tree =
-    maybeAssumeNotNull(finishTransformExpr(preTrans), preTrans.tpe)
-
   /** Finishes an expression pretransform to get a normal [[Tree]].
    *  This method (together with finishTransformStat) must not be called more
    *  than once per pretransform and per translation.
@@ -1516,7 +1514,7 @@ private[optimizer] abstract class OptimizerCore(
        * We do something similar in LocalDef.newReplacement.
        */
       case PreTransRecordTree(tree, tpe, _)
-          if tpe.base == ClassType(LongImpl.RuntimeLongClass) =>
+          if tpe.base == ClassType(LongImpl.RuntimeLongClass, nullable = false) =>
         tree match {
           case RecordValue(_, List(lo, hi)) =>
             createNewLong(lo, hi)
@@ -1724,9 +1722,17 @@ private[optimizer] abstract class OptimizerCore(
     case UnwrapFromThrowable(expr) =>
       checkNotNullStatement(expr)(stat.pos)
 
-    // By definition, a failed cast is always UB, so it cannot have side effects
-    case Transient(Cast(expr, _)) =>
-      keepOnlySideEffects(expr)
+    /* By definition, a failed cast is always UB, so it cannot have side effects.
+     * However, if the target type is `nothing`, we keep the cast not to lose
+     * the information that anything that follows is dead code.
+     */
+    case Transient(Cast(expr, tpe)) =>
+      implicit val pos = stat.pos
+      val exprSideEffects = keepOnlySideEffects(expr)
+      if (tpe != NothingType)
+        exprSideEffects
+      else
+        Block(exprSideEffects, Transient(Cast(Null(), tpe)))
 
     case _ =>
       stat
@@ -1824,6 +1830,8 @@ private[optimizer] abstract class OptimizerCore(
       }
     }
 
+    def isNotNull(tree: Tree): Boolean = !tree.tpe.isNullable
+
     def recs(bodies: List[Tree]): EvalContextInsertion[List[Tree]] = bodies match {
       case Nil =>
         NotFoundPureSoFar
@@ -1959,7 +1967,7 @@ private[optimizer] abstract class OptimizerCore(
           rec(expr).mapOrFailed(AsInstanceOf(_, tpe))
 
         case Transient(Cast(expr, tpe)) =>
-          rec(expr).mapOrKeepGoing(newExpr => Transient(Cast(newExpr, tpe)))
+          rec(expr).mapOrKeepGoing(newExpr => makeCast(newExpr, tpe))
 
         case GetClass(expr) =>
           rec(expr).mapOrKeepGoingIf(GetClass(_))(keepGoingIf = isNotNull(expr))
@@ -2039,24 +2047,15 @@ private[optimizer] abstract class OptimizerCore(
 
     def treeNotInlined = {
       cont(PreTransTree(Apply(flags,
-          finishTransformExprMaybeAssumeNotNull(treceiver), methodIdent,
-          targs.map(finishTransformExpr))(resultType), RefinedType(resultType)))
+          finishTransformExpr(treceiver), methodIdent,
+          targs.map(finishTransformExpr))(resultType)))
     }
 
     treceiver.tpe.base match {
       case NothingType =>
         cont(treceiver) // throws
       case NullType =>
-        val checked = checkNotNull(treceiver)
-        /* When NPEs are Unchecked, checkNotNull directly returns `treceiver`,
-         * whose `tpe` is still `Null`. If the call is used in a context that
-         * expects a non-nullable type (such as a primitive), this causes
-         * ill-typed IR. In that case, we explicitly insert a `throw null`.
-         */
-        val checkedAndWellTyped =
-          if (checked.tpe.isNothingType) checked
-          else PreTransTree(Block(finishTransformStat(checked), Throw(Null())))
-        cont(checkedAndWellTyped)
+        cont(checkNotNull(treceiver))
       case _ =>
         if (methodName.isReflectiveProxy || flags.noinline) {
           // Never inline reflective proxies or explicit noinlines.
@@ -2085,11 +2084,11 @@ private[optimizer] abstract class OptimizerCore(
               if (isWasm) {
                 // Replace by an ApplyStatically to guarantee static dispatch
                 val targetClassName = impls.head.enclosingClassName
-                val castTReceiver = foldCast(treceiver, ClassType(targetClassName))
+                val castTReceiver = foldCast(treceiver, ClassType(targetClassName, nullable = true))
                 cont(PreTransTree(ApplyStatically(flags,
-                    finishTransformExprMaybeAssumeNotNull(castTReceiver),
+                    finishTransformExpr(castTReceiver),
                     targetClassName, methodIdent,
-                    targs.map(finishTransformExpr))(resultType), RefinedType(resultType)))
+                    targs.map(finishTransformExpr))(resultType)))
               } else {
                 /* In case you get tempted to perform the same optimization on
                  * JS, we tried it before (in a much more involved way) and we
@@ -2150,7 +2149,8 @@ private[optimizer] abstract class OptimizerCore(
            * since we need to pass it as the receiver of the `ApplyStatically`,
            * which expects a known type.
            */
-          val treceiverCast = foldCast(checkNotNull(treceiver), ClassType(className))
+          val treceiverCast = foldCast(checkNotNull(treceiver),
+              ClassType(className, nullable = false))
 
           val target = staticCall(className,
               MemberNamespace.forNonStaticCall(flags), methodName)
@@ -2158,7 +2158,7 @@ private[optimizer] abstract class OptimizerCore(
           pretransformSingleDispatch(flags, target, Some(treceiverCast), targs,
               isStat, usePreTransform)(cont) {
             val newTree = ApplyStatically(flags,
-                finishTransformExprMaybeAssumeNotNull(treceiverCast),
+                finishTransformExpr(treceiverCast),
                 className, MethodIdent(methodName),
                 targs.map(finishTransformExpr))(
                 body.tpe)
@@ -2202,10 +2202,12 @@ private[optimizer] abstract class OptimizerCore(
 
             /* Generate a new, fake body that we will inline. For
              * type-preservation, the type of its `This()` node is the type of
-             * our receiver. For stability, the parameter names are normalized
-             * (taking them from `body` would make the result depend on which
-             * method came up first in the list of targets).
+             * our receiver but non-nullable. For stability, the parameter
+             * names are normalized (taking them from `body` would make the
+             * result depend on which method came up first in the list of
+             * targets).
              */
+            val thisType = treceiver.tpe.base.toNonNullable
             val normalizedParams: List[(LocalName, Type)] = {
               referenceMethodDef.args.zipWithIndex.map {
                 case (referenceParam, i) => (LocalName("x" + i), referenceParam.ptpe)
@@ -2213,7 +2215,7 @@ private[optimizer] abstract class OptimizerCore(
             }
             val normalizedBody = Apply(
               flags,
-              This()(treceiver.tpe.base),
+              This()(thisType),
               MethodIdent(methodName),
               normalizedParams.zip(referenceArgs).map {
                 case ((name, ptpe), AsInstanceOf(_, castTpe)) =>
@@ -2225,7 +2227,7 @@ private[optimizer] abstract class OptimizerCore(
 
             // Construct bindings; need to check null for the receiver to preserve evaluation order
             val receiverBinding =
-              Binding(Binding.This, treceiver.tpe.base, mutable = false, checkNotNull(treceiver))
+              Binding(Binding.This, thisType, mutable = false, checkNotNull(treceiver))
             val argsBindings = normalizedParams.zip(targs).map {
               case ((name, ptpe), targ) =>
                 Binding(Binding.Local(name, NoOriginalName), ptpe, mutable = false, targ)
@@ -2249,26 +2251,29 @@ private[optimizer] abstract class OptimizerCore(
   }
 
   private def boxedClassForType(tpe: Type): ClassName = (tpe: @unchecked) match {
-    case ClassType(className) =>
+    case ClassType(className, _) =>
       if (className == BoxedLongClass && useRuntimeLong)
         LongImpl.RuntimeLongClass
       else
         className
 
-    case AnyType      => ObjectClass
-    case UndefType    => BoxedUnitClass
-    case BooleanType  => BoxedBooleanClass
-    case CharType     => BoxedCharacterClass
-    case ByteType     => BoxedByteClass
-    case ShortType    => BoxedShortClass
-    case IntType      => BoxedIntegerClass
-    case LongType     =>
+    case AnyType | AnyNotNullType | _:ArrayType =>
+      ObjectClass
+
+    case UndefType   => BoxedUnitClass
+    case BooleanType => BoxedBooleanClass
+    case CharType    => BoxedCharacterClass
+    case ByteType    => BoxedByteClass
+    case ShortType   => BoxedShortClass
+    case IntType     => BoxedIntegerClass
+
+    case LongType =>
       if (useRuntimeLong) LongImpl.RuntimeLongClass
       else BoxedLongClass
-    case FloatType    => BoxedFloatClass
-    case DoubleType   => BoxedDoubleClass
-    case StringType   => BoxedStringClass
-    case ArrayType(_) => ObjectClass
+
+    case FloatType  => BoxedFloatClass
+    case DoubleType => BoxedDoubleClass
+    case StringType => BoxedStringClass
   }
 
   private def pretransformStaticApply(tree: ApplyStatically, isStat: Boolean,
@@ -2281,7 +2286,7 @@ private[optimizer] abstract class OptimizerCore(
 
     def treeNotInlined0(transformedReceiver: Tree, transformedArgs: List[Tree]) =
       cont(PreTransTree(ApplyStatically(flags, transformedReceiver, className,
-          methodIdent, transformedArgs)(tree.tpe), RefinedType(tree.tpe)))
+          methodIdent, transformedArgs)(tree.tpe)))
 
     if (methodName.isReflectiveProxy) {
       // Never inline reflective proxies
@@ -2291,15 +2296,17 @@ private[optimizer] abstract class OptimizerCore(
           methodName)
       pretransformExprs(receiver, args) { (treceiver, targs) =>
         pretransformSingleDispatch(flags, target, Some(treceiver), targs, isStat, usePreTransform)(cont) {
-          treeNotInlined0(finishTransformExprMaybeAssumeNotNull(treceiver),
+          treeNotInlined0(finishTransformExpr(treceiver),
               targs.map(finishTransformExpr))
         }
       }
     }
   }
 
-  private def receiverTypeFor(target: MethodID): Type =
-    BoxedClassToPrimType.getOrElse(target.enclosingClassName, ClassType(target.enclosingClassName))
+  private def receiverTypeFor(target: MethodID): Type = {
+    BoxedClassToPrimType.getOrElse(target.enclosingClassName,
+        ClassType(target.enclosingClassName, nullable = false))
+  }
 
   private def pretransformApplyStatic(tree: ApplyStatic, isStat: Boolean,
       usePreTransform: Boolean)(
@@ -2315,7 +2322,7 @@ private[optimizer] abstract class OptimizerCore(
       pretransformSingleDispatch(flags, target, None, targs, isStat, usePreTransform)(cont) {
         val newArgs = targs.map(finishTransformExpr)
         cont(PreTransTree(ApplyStatic(flags, className, methodIdent,
-            newArgs)(tree.tpe), RefinedType(tree.tpe)))
+            newArgs)(tree.tpe)))
       }
     }
   }
@@ -2328,8 +2335,7 @@ private[optimizer] abstract class OptimizerCore(
     implicit val pos = tree.pos
 
     def treeNotInlined0(transformedArgs: List[Tree]) =
-      cont(PreTransTree(ApplyDynamicImport(flags, className, method, transformedArgs),
-          RefinedType(AnyType)))
+      cont(PreTransTree(ApplyDynamicImport(flags, className, method, transformedArgs)))
 
     def treeNotInlined = treeNotInlined0(args.map(transformExpr))
 
@@ -2588,7 +2594,7 @@ private[optimizer] abstract class OptimizerCore(
   private def shouldInlineBecauseOfArgs(target: MethodID,
       receiverAndArgs: List[PreTransform]): Boolean = {
     def isTypeLikelyOptimizable(tpe: RefinedType): Boolean = tpe.base match {
-      case ClassType(className) =>
+      case ClassType(className, _) =>
         ClassNamesThatShouldBeInlined.contains(className)
       case _ =>
         false
@@ -2600,8 +2606,8 @@ private[optimizer] abstract class OptimizerCore(
        * method only because we pass it an instance of RuntimeLong.
        */
       tpe.base match {
-        case ClassType(LongImpl.RuntimeLongClass)       => true
-        case _                                          => false
+        case ClassType(LongImpl.RuntimeLongClass, _) => true
+        case _                                       => false
       }
     }
 
@@ -2663,14 +2669,10 @@ private[optimizer] abstract class OptimizerCore(
     body match {
       case Skip() =>
         assert(isStat, "Found Skip() in expression position")
-        cont(PreTransTree(
-            finishTransformArgsAsStat(),
-            RefinedType.NoRefinedType))
+        cont(PreTransTree(finishTransformArgsAsStat()))
 
       case _: Literal =>
-        cont(PreTransTree(
-            Block(finishTransformArgsAsStat(), body),
-            RefinedType(body.tpe)))
+        cont(PreTransTree(Block(finishTransformArgsAsStat(), body)))
 
       case This() if args.isEmpty =>
         assert(optReceiver.isDefined,
@@ -2695,7 +2697,7 @@ private[optimizer] abstract class OptimizerCore(
 
         if (!isFieldRead(field.name)) {
           // Field is never read, discard assign, keep side effects only.
-          cont(PreTransTree(finishTransformArgsAsStat(), RefinedType.NoRefinedType))
+          cont(PreTransTree(finishTransformArgsAsStat()))
         } else {
           pretransformSelectCommon(lhs.tpe, treceiver,
               optQualDeclaredType = Some(optReceiver.get._1),
@@ -2785,7 +2787,7 @@ private[optimizer] abstract class OptimizerCore(
 
     @inline def contTree(result: Tree) = cont(result.toPreTransform)
 
-    @inline def StringClassType = ClassType(BoxedStringClass)
+    @inline def StringClassType = ClassType(BoxedStringClass, nullable = true)
 
     def cursoryArrayElemType(tpe: ArrayType): Type = {
       if (tpe.arrayTypeRef.dimensions != 1) AnyType
@@ -2851,7 +2853,7 @@ private[optimizer] abstract class OptimizerCore(
       case ArrayApply =>
         val List(tarray, tindex) = targs
         tarray.tpe.base match {
-          case arrayTpe @ ArrayType(ArrayTypeRef(base, _)) =>
+          case arrayTpe @ ArrayType(ArrayTypeRef(base, _), _) =>
             /* Rewrite to `tarray[tindex]` as an `ArraySelect` node.
              * If `tarray` is `null`, an `ArraySelect`'s semantics will run
              * into a (UB) NPE *before* evaluating `tindex`, by spec. This is
@@ -2866,7 +2868,7 @@ private[optimizer] abstract class OptimizerCore(
              */
             val elemType = cursoryArrayElemType(arrayTpe)
             if (!tarray.tpe.isNullable) {
-              val array = finishTransformExprMaybeAssumeNotNull(tarray)
+              val array = finishTransformExpr(tarray)
               val index = finishTransformExpr(tindex)
               val select = ArraySelect(array, index)(elemType)
               contTree(select)
@@ -2884,13 +2886,13 @@ private[optimizer] abstract class OptimizerCore(
       case ArrayUpdate =>
         val List(tarray, tindex, tvalue) = targs
         tarray.tpe.base match {
-          case arrayTpe @ ArrayType(ArrayTypeRef(base, depth)) =>
+          case arrayTpe @ ArrayType(ArrayTypeRef(base, depth), _) =>
             /* Rewrite to `tarray[index] = tvalue` as an `Assign(ArraySelect, _)`.
              * See `ArrayApply` above for the handling of a nullable `tarray`.
              */
             val elemType = cursoryArrayElemType(arrayTpe)
             if (!tarray.tpe.isNullable) {
-              val array = finishTransformExprMaybeAssumeNotNull(tarray)
+              val array = finishTransformExpr(tarray)
               val index = finishTransformExpr(tindex)
               val select = ArraySelect(array, index)(elemType)
               val tunboxedValue = foldAsInstanceOf(tvalue, elemType)
@@ -2913,7 +2915,7 @@ private[optimizer] abstract class OptimizerCore(
         val tarray = targs.head
         tarray.tpe.base match {
           case _: ArrayType =>
-            val array = finishTransformExprMaybeAssumeNotNull(tarray)
+            val array = finishTransformExpr(tarray)
             contTree(Trees.ArrayLength(array))
           case _ =>
             default
@@ -3037,7 +3039,8 @@ private[optimizer] abstract class OptimizerCore(
         } else {
           pretransformApply(ApplyFlags.empty, targs.head,
               MethodIdent(LongImpl.divideUnsigned), targs.tail,
-              ClassType(LongImpl.RuntimeLongClass), isStat, usePreTransform)(
+              ClassType(LongImpl.RuntimeLongClass, nullable = true), isStat,
+              usePreTransform)(
               cont)
         }
       case LongRemainderUnsigned =>
@@ -3047,7 +3050,8 @@ private[optimizer] abstract class OptimizerCore(
         } else {
           pretransformApply(ApplyFlags.empty, targs.head,
               MethodIdent(LongImpl.remainderUnsigned), targs.tail,
-              ClassType(LongImpl.RuntimeLongClass), isStat, usePreTransform)(
+              ClassType(LongImpl.RuntimeLongClass, nullable = true), isStat,
+              usePreTransform)(
               cont)
         }
 
@@ -3116,12 +3120,14 @@ private[optimizer] abstract class OptimizerCore(
         // This is a private API: `runtimeClass` is known not to be `null`
         val List(runtimeClass, array) = targs.map(finishTransformExpr(_))
         val (resultType, isExact) = runtimeClass match {
-          case ClassOf(elemTypeRef) => (ArrayType(ArrayTypeRef.of(elemTypeRef)), true)
-          case _                    => (AnyType, false)
+          case ClassOf(elemTypeRef) =>
+            (ArrayType(ArrayTypeRef.of(elemTypeRef), nullable = false), true)
+          case _ =>
+            (AnyNotNullType, false)
         }
         cont(PreTransTree(
             Transient(NativeArrayWrapper(runtimeClass, array)(resultType)),
-            RefinedType(resultType, isExact = isExact, isNullable = false)))
+            RefinedType(resultType, isExact = isExact)))
 
       case ArrayBuilderZeroOf =>
         // This is a private API: `runtimeClass` is known not to be `null`
@@ -3182,7 +3188,8 @@ private[optimizer] abstract class OptimizerCore(
             contTree(finishTransformBindings(
                 bindingsAndStats, StringLiteral(nameString)))
 
-          case PreTransMaybeBlock(bindingsAndStats, PreTransTree(GetClass(expr), _)) =>
+          case PreTransMaybeBlock(bindingsAndStats,
+              PreTransTree(MaybeCast(GetClass(expr)), _)) =>
             contTree(finishTransformBindings(
                 bindingsAndStats, Transient(ObjectClassName(expr))))
 
@@ -3209,19 +3216,19 @@ private[optimizer] abstract class OptimizerCore(
         tprops match {
           case PreTransMaybeBlock(bindingsAndStats,
               PreTransLocalDef(LocalDef(
-                  RefinedType(ClassType(JSWrappedArrayClass), _, _),
+                  RefinedType(ClassType(JSWrappedArrayClass, _), _),
                   false,
                   InlineClassInstanceReplacement(_, wrappedArrayFields, _)))) =>
             assert(wrappedArrayFields.size == 1)
             val jsArray = wrappedArrayFields.head._2
             jsArray.replacement match {
               case InlineJSArrayReplacement(elemLocalDefs, _)
-                  if elemLocalDefs.forall(e => isSubtype(e.tpe.base, ClassType(Tuple2Class))) =>
+                  if elemLocalDefs.forall(e => isSubtype(e.tpe.base, ClassType(Tuple2Class, nullable = true))) =>
                 val fields: List[(Tree, Tree)] = for {
                   (elemLocalDef, idx) <- elemLocalDefs.toList.zipWithIndex
                 } yield {
                   elemLocalDef match {
-                    case LocalDef(RefinedType(ClassType(Tuple2Class), _, _), false,
+                    case LocalDef(RefinedType(ClassType(Tuple2Class, _), _), false,
                         InlineClassInstanceReplacement(structure, tupleFields, _)) =>
                       val List(key, value) = structure.fieldNames.map(tupleFields)
                       (key.newReplacement, value.newReplacement)
@@ -3247,7 +3254,7 @@ private[optimizer] abstract class OptimizerCore(
 
           case _ =>
             tprops.tpe match {
-              case RefinedType(ClassType(NilClass), _, false) =>
+              case RefinedType(ClassType(NilClass, false), _) =>
                 contTree(Block(finishTransformStat(tprops), JSObjectConstr(Nil)))
               case _ =>
                 default
@@ -3257,17 +3264,17 @@ private[optimizer] abstract class OptimizerCore(
       // TypedArray conversions
 
       case ByteArrayToInt8Array =>
-        contTree(Transient(ArrayToTypedArray(finishTransformExprMaybeAssumeNotNull(targs.head), ByteRef)))
+        contTree(Transient(ArrayToTypedArray(finishTransformExpr(targs.head), ByteRef)))
       case ShortArrayToInt16Array =>
-        contTree(Transient(ArrayToTypedArray(finishTransformExprMaybeAssumeNotNull(targs.head), ShortRef)))
+        contTree(Transient(ArrayToTypedArray(finishTransformExpr(targs.head), ShortRef)))
       case CharArrayToUint16Array =>
-        contTree(Transient(ArrayToTypedArray(finishTransformExprMaybeAssumeNotNull(targs.head), CharRef)))
+        contTree(Transient(ArrayToTypedArray(finishTransformExpr(targs.head), CharRef)))
       case IntArrayToInt32Array =>
-        contTree(Transient(ArrayToTypedArray(finishTransformExprMaybeAssumeNotNull(targs.head), IntRef)))
+        contTree(Transient(ArrayToTypedArray(finishTransformExpr(targs.head), IntRef)))
       case FloatArrayToFloat32Array =>
-        contTree(Transient(ArrayToTypedArray(finishTransformExprMaybeAssumeNotNull(targs.head), FloatRef)))
+        contTree(Transient(ArrayToTypedArray(finishTransformExpr(targs.head), FloatRef)))
       case DoubleArrayToFloat64Array =>
-        contTree(Transient(ArrayToTypedArray(finishTransformExprMaybeAssumeNotNull(targs.head), DoubleRef)))
+        contTree(Transient(ArrayToTypedArray(finishTransformExpr(targs.head), DoubleRef)))
 
       case Int8ArrayToByteArray =>
         contTree(Transient(TypedArrayToArray(finishTransformExpr(targs.head), ByteRef)))
@@ -3304,8 +3311,8 @@ private[optimizer] abstract class OptimizerCore(
       inlineClassConstructorBody(allocationSite, structure, initialFieldLocalDefs,
           className, className, ctor, args, cancelFun) { (finalFieldLocalDefs, cont2) =>
         cont2(LocalDef(
-            RefinedType(ClassType(className), isExact = true,
-                isNullable = false, allocationSite = allocationSite),
+            RefinedType(ClassType(className, nullable = false), isExact = true,
+                allocationSite = allocationSite),
             mutable = false,
             InlineClassInstanceReplacement(structure, finalFieldLocalDefs,
                 cancelFun)).toPreTransform)
@@ -3342,7 +3349,7 @@ private[optimizer] abstract class OptimizerCore(
 
     withBindings(argsBindings) { (bodyScope, cont1) =>
       val thisLocalDef = LocalDef(
-          RefinedType(ClassType(className), isExact = true, isNullable = false),
+          RefinedType(ClassType(className, nullable = false), isExact = true),
           false,
           InlineClassBeingConstructedReplacement(structure, inputFieldsLocalDefs, cancelFun))
       val statsScope = bodyScope.inlining(targetID).withEnv(
@@ -3370,7 +3377,7 @@ private[optimizer] abstract class OptimizerCore(
               className, rest, cancelFun)(buildInner)(cont)
         case _ =>
           if (transformedStat.tpe == NothingType)
-            cont(PreTransTree(transformedStat, RefinedType.Nothing))
+            cont(PreTransTree(transformedStat))
           else {
             inlineClassConstructorBodyList(allocationSite, structure,
                 thisLocalDef, inputFieldsLocalDefs,
@@ -3501,7 +3508,7 @@ private[optimizer] abstract class OptimizerCore(
             case (_, _, BooleanLiteral(true)) =>
               foldIf(negCond, BooleanLiteral(true), thenp)(tpe) // canonical || form
 
-            /* if (lhs === null) rhs === null else lhs === rhs
+            /* if (lhs === null) rhs === null else lhs.as![T!] === rhs
              * -> lhs === rhs
              * This is the typical shape of a lhs == rhs test where
              * the equals() method has been inlined as a reference
@@ -3509,9 +3516,9 @@ private[optimizer] abstract class OptimizerCore(
              */
             case (BinaryOp(BinaryOp.===, VarRef(lhsIdent), Null()),
                 BinaryOp(BinaryOp.===, VarRef(rhsIdent), Null()),
-                BinaryOp(BinaryOp.===, VarRef(lhsIdent2), VarRef(rhsIdent2)))
+                BinaryOp(BinaryOp.===, MaybeCast(l @ VarRef(lhsIdent2)), r @ VarRef(rhsIdent2)))
                 if lhsIdent2 == lhsIdent && rhsIdent2 == rhsIdent =>
-              elsep
+              BinaryOp(BinaryOp.===, l, r)(elsep.pos)
 
             // Example: (x > y) || (x == y)  ->  (x >= y)
             case (BinaryOp(op1 @ (Int_== | Int_!= | Int_< | Int_<= | Int_> | Int_>=), l1, r1),
@@ -3594,15 +3601,15 @@ private[optimizer] abstract class OptimizerCore(
     assert(useRuntimeLong)
 
     /* To force the expansion, we first store the `value` in a temporary
-     * variable of type `RuntimeLong` (not `Long`, otherwise we would go into
+     * variable of type `RuntimeLong!` (not `Long`, otherwise we would go into
      * infinite recursion), then we create a `new RuntimeLong` with its lo and
      * hi part. Basically, we're doing:
      *
-     * val t: RuntimeLong = value
+     * val t: RuntimeLong! = value
      * new RuntimeLong(t.lo__I(), t.hi__I())
      */
     val tName = LocalName("t")
-    val rtLongClassType = ClassType(LongImpl.RuntimeLongClass)
+    val rtLongClassType = ClassType(LongImpl.RuntimeLongClass, nullable = false)
     val rtLongBinding = Binding.temp(tName, rtLongClassType, mutable = false,
         value)
     withBinding(rtLongBinding) { (scope1, cont1) =>
@@ -3620,11 +3627,14 @@ private[optimizer] abstract class OptimizerCore(
       implicit scope: Scope): TailRec[Tree] = {
     implicit val pos = pretrans.pos
 
-    def rtLongClassType = ClassType(LongImpl.RuntimeLongClass)
+    // unfortunately nullable for the result types of methods
+    def rtLongClassType = ClassType(LongImpl.RuntimeLongClass, nullable = true)
 
     def expandLongModuleOp(methodName: MethodName,
         arg: PreTransform): TailRec[Tree] = {
-      val receiver = LoadModule(LongImpl.RuntimeLongModuleClass).toPreTransform
+      import LongImpl.{RuntimeLongModuleClass => modCls}
+      val receiver =
+        makeCast(LoadModule(modCls), ClassType(modCls, nullable = false)).toPreTransform
       pretransformApply(ApplyFlags.empty, receiver, MethodIdent(methodName),
           arg :: Nil, rtLongClassType, isStat = false,
           usePreTransform = true)(
@@ -4979,7 +4989,7 @@ private[optimizer] abstract class OptimizerCore(
   private def foldAsInstanceOf(arg: PreTransform, tpe: Type)(
       implicit pos: Position): PreTransform = {
     def mayRequireUnboxing: Boolean =
-      arg.tpe.isNullable && !isNullableType(tpe)
+      arg.tpe.isNullable && tpe.isInstanceOf[PrimType]
 
     if (semantics.asInstanceOfs == CheckedBehavior.Unchecked && !mayRequireUnboxing)
       foldCast(arg, tpe)
@@ -4991,8 +5001,9 @@ private[optimizer] abstract class OptimizerCore(
 
   private def foldCast(arg: PreTransform, tpe: Type)(
       implicit pos: Position): PreTransform = {
+
     def default(arg: PreTransform, newTpe: RefinedType): PreTransform =
-      PreTransTree(Transient(Cast(finishTransformExpr(arg), tpe)), newTpe)
+      PreTransTree(makeCast(finishTransformExpr(arg), newTpe.base), newTpe)
 
     def castLocalDef(arg: PreTransform, newTpe: RefinedType): PreTransform = arg match {
       case PreTransMaybeBlock(bindingsAndStats, PreTransLocalDef(localDef)) =>
@@ -5009,9 +5020,11 @@ private[optimizer] abstract class OptimizerCore(
     if (isSubtype(arg.tpe.base, tpe)) {
       arg
     } else {
-      val castTpe = RefinedType(tpe, isExact = false,
-          isNullable = arg.tpe.isNullable && isNullableType(tpe),
-          arg.tpe.allocationSite)
+      val tpe1 =
+        if (arg.tpe.isNullable) tpe
+        else tpe.toNonNullable
+
+      val castTpe = RefinedType(tpe1, isExact = false, arg.tpe.allocationSite)
 
       val isCastFreeAtRunTime = tpe != CharType
 
@@ -5169,11 +5182,11 @@ private[optimizer] abstract class OptimizerCore(
       val returnedTypes0 = info.returnedTypes.value.map(_._1)
       if (returnedTypes0.isEmpty) {
         // no return to that label, we can eliminate it
-        cont(PreTransTree(newBody, RefinedType(newBody.tpe)))
+        cont(PreTransTree(newBody))
       } else {
         val returnedTypes = newBody.tpe :: returnedTypes0
         val tree = doMakeTree(newBody, returnedTypes)
-        cont(PreTransTree(tree, RefinedType(tree.tpe)))
+        cont(PreTransTree(tree))
       }
     }
   }
@@ -5251,34 +5264,18 @@ private[optimizer] abstract class OptimizerCore(
     if (!texpr.tpe.isNullable) {
       texpr
     } else if (semantics.nullPointers == CheckedBehavior.Unchecked) {
-      // If possible, improve the type of the expression to be non-nullable
-
-      val nonNullType = texpr.tpe.toNonNullable
-
-      def rec(texpr: PreTransform): PreTransform = texpr match {
-        case PreTransBlock(bindingsAndStats, result) =>
-          PreTransBlock(bindingsAndStats, rec(result).asInstanceOf[PreTransResult])
-        case PreTransLocalDef(localDef) =>
-          PreTransLocalDef(localDef.tryWithRefinedType(nonNullType))(texpr.pos)
-        case PreTransTree(tree, tpe) =>
-          PreTransTree(tree, nonNullType)
-        case _:PreTransUnaryOp | _:PreTransBinaryOp | _:PreTransRecordTree =>
-          // We cannot improve the type of those
-          texpr
-      }
-
-      if (nonNullType.isNothingType)
-        texpr // things blow up otherwise
-      else
-        rec(texpr)
+      foldCast(texpr, texpr.tpe.base.toNonNullable)
     } else {
-      PreTransTree(Transient(CheckNotNull(finishTransformExpr(texpr))), texpr.tpe.toNonNullable)
+      PreTransTree(Transient(CheckNotNull(finishTransformExpr(texpr))),
+          texpr.tpe.toNonNullable)
     }
   }
 
   private def checkNotNull(expr: Tree)(implicit pos: Position): Tree = {
-    if (semantics.nullPointers == CheckedBehavior.Unchecked || isNotNull(expr))
+    if (!expr.tpe.isNullable)
       expr
+    else if (semantics.nullPointers == CheckedBehavior.Unchecked)
+      makeCast(expr, expr.tpe.toNonNullable)
     else
       Transient(CheckNotNull(expr))
   }
@@ -5291,53 +5288,12 @@ private[optimizer] abstract class OptimizerCore(
   }
 
   private def checkNotNullStatement(expr: Tree)(implicit pos: Position): Tree = {
-    if (semantics.nullPointers == CheckedBehavior.Unchecked || isNotNull(expr))
+    if (!expr.tpe.isNullable || semantics.nullPointers == CheckedBehavior.Unchecked)
       keepOnlySideEffects(expr)
     else
       Transient(CheckNotNull(expr))
   }
 
-  private def maybeAssumeNotNull(tree: Tree, tpe: RefinedType): Tree = {
-    if (tpe.isNullable || semantics.nullPointers == CheckedBehavior.Unchecked) {
-      tree
-    } else {
-      /* Do not introduce AssumeNotNull for some tree shapes that the function
-       * emitter will trivially recognize as non-null. This is particularly
-       * important not to hide `This` nodes in a way that prevents elimination
-       * of `StoreModule`s.
-       */
-      if (isNotNull(tree))
-        tree
-      else
-        Transient(AssumeNotNull(tree))(tree.pos)
-    }
-  }
-
-  private def isNullableType(tpe: Type): Boolean = tpe match {
-    case NullType    => true
-    case _: PrimType => false
-    case _           => true
-  }
-
-  private def isNotNull(tree: Tree): Boolean = {
-    // !!! Duplicate code with FunctionEmitter.isNotNull
-
-    def isShapeNotNull(tree: Tree): Boolean = tree match {
-      case Transient(CheckNotNull(_) | AssumeNotNull(_)) =>
-        true
-      case Transient(Cast(expr, _)) =>
-        isShapeNotNull(expr)
-      case _: This =>
-        tree.tpe != AnyType
-      case _:New | _:LoadModule | _:NewArray | _:ArrayValue | _:Clone | _:ClassOf =>
-        true
-      case _ =>
-        false
-    }
-
-    !isNullableType(tree.tpe) || isShapeNotNull(tree)
-  }
-
   private def newParamReplacement(paramDef: ParamDef): ((LocalName, LocalDef), ParamDef) = {
     val ParamDef(ident @ LocalIdent(name), originalName, ptpe, mutable) = paramDef
 
@@ -5350,11 +5306,8 @@ private[optimizer] abstract class OptimizerCore(
     (name -> localDef, newParamDef)
   }
 
-  private def newThisLocalDef(thisType: Type): LocalDef = {
-    LocalDef(
-        RefinedType(thisType, isExact = false, isNullable = false),
-        false, ReplaceWithThis())
-  }
+  private def newThisLocalDef(thisType: Type): LocalDef =
+    LocalDef(RefinedType(thisType), false, ReplaceWithThis())
 
   private def withBindings(bindings: List[Binding])(
       buildInner: (Scope, PreTransCont) => TailRec[Tree])(
@@ -5422,9 +5375,9 @@ private[optimizer] abstract class OptimizerCore(
     implicit val pos = value.pos
 
     def withDedicatedVar(tpe: RefinedType): TailRec[Tree] = {
-      val rtLongClassType = ClassType(LongImpl.RuntimeLongClass)
+      val rtLongClassType = ClassType(LongImpl.RuntimeLongClass, nullable = false)
 
-      if (tpe.base == LongType && declaredType != rtLongClassType &&
+      if (tpe.base == LongType && declaredType.toNonNullable != rtLongClassType &&
           useRuntimeLong) {
         /* If the value's type is a primitive Long, and the declared type is
          * not RuntimeLong, we want to force the expansion of the primitive
@@ -5555,10 +5508,7 @@ private[optimizer] abstract class OptimizerCore(
     else if (lhs == rhs) lhs
     else if (lhs.isNothingType) rhs
     else if (rhs.isNothingType) lhs
-    else {
-      RefinedType(constrainedLub(lhs.base, rhs.base, upperBound),
-          false, lhs.isNullable || rhs.isNullable)
-    }
+    else RefinedType(constrainedLub(lhs.base, rhs.base, upperBound))
   }
 
   /** Finds a type as precise as possible which is a supertype of lhs and rhs
@@ -5571,6 +5521,9 @@ private[optimizer] abstract class OptimizerCore(
     else if (lhs == rhs) lhs
     else if (lhs == NothingType) rhs
     else if (rhs == NothingType) lhs
+    else if (lhs.toNonNullable == rhs) lhs
+    else if (rhs.toNonNullable == lhs) rhs
+    else if (!lhs.isNullable && !rhs.isNullable) upperBound.toNonNullable
     else upperBound
   }
 
@@ -5634,8 +5587,8 @@ private[optimizer] object OptimizerCore {
   private val NilClass = ClassName("scala.collection.immutable.Nil$")
   private val Tuple2Class = ClassName("scala.Tuple2")
 
-  private val JavaScriptExceptionClassType = ClassType(JavaScriptExceptionClass)
-  private val ThrowableClassType = ClassType(ThrowableClass)
+  private val JavaScriptExceptionClassType = ClassType(JavaScriptExceptionClass, nullable = true)
+  private val ThrowableClassType = ClassType(ThrowableClass, nullable = true)
 
   private val exceptionFieldName =
     FieldName(JavaScriptExceptionClass, SimpleFieldName("exception"))
@@ -5759,41 +5712,41 @@ private[optimizer] object OptimizerCore {
   private type CancelFun = () => Nothing
   private type PreTransCont = PreTransform => TailRec[Tree]
 
-  private final case class RefinedType private (base: Type, isExact: Boolean,
-      isNullable: Boolean)(val allocationSite: AllocationSite, dummy: Int = 0) {
+  private final case class RefinedType private (base: Type, isExact: Boolean)(
+      val allocationSite: AllocationSite, dummy: Int = 0) {
+
+    def isNullable: Boolean = base.isNullable
 
     def isNothingType: Boolean = base == NothingType
 
     def toNonNullable: RefinedType = {
       if (!isNullable) this
       else if (base == NullType) RefinedType.Nothing
-      else RefinedType(base, isExact, isNullable = false, allocationSite)
+      else RefinedType(base.toNonNullable, isExact, allocationSite)
     }
   }
 
   private object RefinedType {
-    def apply(base: Type, isExact: Boolean, isNullable: Boolean,
+    def apply(base: Type, isExact: Boolean,
         allocationSite: AllocationSite): RefinedType =
-      new RefinedType(base, isExact, isNullable)(allocationSite)
+      new RefinedType(base, isExact)(allocationSite)
 
-    def apply(base: Type, isExact: Boolean, isNullable: Boolean): RefinedType =
-      RefinedType(base, isExact, isNullable, AllocationSite.Anonymous)
+    def apply(base: Type, isExact: Boolean): RefinedType =
+      RefinedType(base, isExact, AllocationSite.Anonymous)
 
-    def apply(tpe: Type): RefinedType = tpe match {
-      case AnyType | ClassType(_) | ArrayType(_) =>
-        RefinedType(tpe, isExact = false, isNullable = true)
-      case NullType =>
-        RefinedType(tpe, isExact = true, isNullable = true)
-      case NothingType | UndefType | BooleanType | CharType | LongType |
-          StringType | NoType =>
-        RefinedType(tpe, isExact = true, isNullable = false)
-      case ByteType | ShortType | IntType | FloatType | DoubleType |
-          RecordType(_) =>
-        /* At run-time, a byte will answer true to `x.isInstanceOf[Int]`,
-         * therefore `byte`s must be non-exact. The same reasoning applies to
-         * other primitive numeric types.
-         */
-        RefinedType(tpe, isExact = false, isNullable = false)
+    def apply(tpe: Type): RefinedType = {
+      val isExact = tpe match {
+        case NullType | NothingType | UndefType | BooleanType | CharType |
+            LongType | StringType | NoType =>
+          true
+        case _ =>
+          /* At run-time, a byte will answer true to `x.isInstanceOf[Int]`,
+           * therefore `byte`s must be non-exact. The same reasoning applies to
+           * other primitive numeric types.
+           */
+          false
+      }
+      RefinedType(tpe, isExact)
     }
 
     val NoRefinedType = RefinedType(NoType)
@@ -5855,7 +5808,7 @@ private[optimizer] object OptimizerCore {
        * safe to do so.
        */
       case ReplaceWithRecordVarRef(name, recordType, used, _)
-          if tpe.base == ClassType(LongImpl.RuntimeLongClass) =>
+          if tpe.base == ClassType(LongImpl.RuntimeLongClass, nullable = false) =>
         used.value = used.value.inc
         createNewLong(VarRef(LocalIdent(name))(recordType))
 
@@ -5881,7 +5834,7 @@ private[optimizer] object OptimizerCore {
         if (underlying.tpe == tpe.base)
           underlying
         else
-          Transient(Cast(underlying, tpe.base))
+          makeCast(underlying, tpe.base)
 
       case ReplaceWithConstant(value) =>
         value
@@ -5897,7 +5850,7 @@ private[optimizer] object OptimizerCore {
        * safe to do so.
        */
       case InlineClassInstanceReplacement(structure, fieldLocalDefs, _)
-          if tpe.base == ClassType(LongImpl.RuntimeLongClass) =>
+          if tpe.base == ClassType(LongImpl.RuntimeLongClass, nullable = false) =>
         val List(loField, hiField) = structure.fieldNames
         val lo = fieldLocalDefs(loField).newReplacement
         val hi = fieldLocalDefs(hiField).newReplacement
@@ -6296,13 +6249,14 @@ private[optimizer] object OptimizerCore {
   private object PreTransTree {
     def apply(tree: Tree): PreTransTree = {
       val refinedTpe: RefinedType = BlockOrAlone.last(tree) match {
-        case _:LoadModule | _:NewArray | _:ArrayValue | _:ClassOf =>
-          RefinedType(tree.tpe, isExact = true, isNullable = false)
-        case GetClass(x) if x.tpe != AnyType && x.tpe != ClassType(ObjectClass) =>
-          /* If x.tpe is neither AnyType nor j.l.Object, it cannot be a JS
-           * object, so its getClass() cannot be null.
+        case _:New | _:NewArray | _:ArrayValue | _:ClassOf =>
+          RefinedType(tree.tpe, isExact = true)
+        case Transient(Cast(LoadModule(_), ClassType(_, false))) =>
+          /* If a LoadModule is cast to be non-nullable, we know it is exact.
+           * If it is nullable, it cannot be exact since it could be `null` or
+           * an actual instance.
            */
-          RefinedType(tree.tpe, isExact = true, isNullable = false)
+          RefinedType(tree.tpe, isExact = true)
         case _ =>
           RefinedType(tree.tpe)
       }
@@ -6412,6 +6366,20 @@ private[optimizer] object OptimizerCore {
     }
   }
 
+  /** Makes a `Transient(Cast(expr, tpe))` but collapses consecutive casts. */
+  private def makeCast(expr: Tree, tpe: Type)(implicit pos: Position): Tree = {
+    val innerExpr = expr match {
+      case Transient(Cast(innerExpr, _)) => innerExpr
+      case _                             => expr
+    }
+
+    /* We could refine the result type to be the intersection of `expr.tpe`
+     * and `tpe`, but we do not have any infrastructure to do so. We always use
+     * `tpe` instead.
+     */
+    Transient(Cast(innerExpr, tpe))
+  }
+
   /** Creates a new instance of `RuntimeLong` from a record of its `lo` and
    *  `hi` parts.
    */
@@ -6821,6 +6789,13 @@ private[optimizer] object OptimizerCore {
     }
   }
 
+  private object MaybeCast {
+    def unapply(tree: Tree): Some[Tree] = tree match {
+      case Transient(Cast(inner, _)) => Some(inner)
+      case _                         => Some(tree)
+    }
+  }
+
   private val TraitInitSimpleMethodName = SimpleMethodName("$init$")
 
   private def isTrivialConstructorStat(stat: Tree): Boolean = stat match {
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/AnalyzerTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/AnalyzerTest.scala
index d1746c9886..f797ad25a1 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/AnalyzerTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/AnalyzerTest.scala
@@ -316,7 +316,7 @@ class AnalyzerTest {
             methods = List(
                 trivialCtor("A"),
                 MethodDef(EMF, barMethodName, NON, Nil, NoType, Some(Block(
-                  Apply(EAF, This()(ClassType("A")), fooMethodName, Nil)(NoType),
+                  Apply(EAF, thisFor("A"), fooMethodName, Nil)(NoType),
                   Apply(EAF, New("B", NoArgConstructorName, Nil), fooMethodName, Nil)(NoType)
                 )))(EOH, UNV)
             )),
@@ -725,9 +725,9 @@ class AnalyzerTest {
         classDef("X", superClass = Some(ObjectClass),
             methods = List(
                 trivialCtor("X"),
-                MethodDef(EMF, fooAMethodName, NON, Nil, ClassType("A"),
+                MethodDef(EMF, fooAMethodName, NON, Nil, ClassType("A", nullable = true),
                     Some(Null()))(EOH, UNV),
-                MethodDef(EMF, fooBMethodName, NON, Nil, ClassType("B"),
+                MethodDef(EMF, fooBMethodName, NON, Nil, ClassType("B", nullable = true),
                     Some(Null()))(EOH, UNV)
             )
         )
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/IRCheckerTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/IRCheckerTest.scala
index d9a2760c69..9b30403634 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/IRCheckerTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/IRCheckerTest.scala
@@ -63,7 +63,7 @@ class IRCheckerTest {
                  * instances of `Bar`. It will therefore not make `Foo` reachable.
                  */
                 MethodDef(EMF, methMethodName, NON,
-                    List(paramDef("foo", ClassType("Foo"))), NoType,
+                    List(paramDef("foo", ClassType("Foo", nullable = true))), NoType,
                     Some(Skip()))(
                     EOH, UNV)
             )
@@ -74,12 +74,12 @@ class IRCheckerTest {
             methods = List(
                 trivialCtor(MainTestClassName),
                 MethodDef(EMF.withNamespace(MemberNamespace.PublicStatic),
-                    nullBarMethodName, NON, Nil, ClassType("Bar"),
+                    nullBarMethodName, NON, Nil, ClassType("Bar", nullable = true),
                     Some(Null()))(
                     EOH, UNV),
                 mainMethodDef(Block(
                     callMethOn(ApplyStatic(EAF, MainTestClassName,
-                        nullBarMethodName, Nil)(ClassType("Bar"))),
+                        nullBarMethodName, Nil)(ClassType("Bar", nullable = true))),
                     callMethOn(Null()),
                     callMethOn(Throw(Null()))
                 ))
@@ -101,7 +101,7 @@ class IRCheckerTest {
 
     val results = for (receiverClassName <- List(A, B, C, D)) yield {
       val receiverClassRef = ClassRef(receiverClassName)
-      val receiverType = ClassType(receiverClassName)
+      val receiverType = ClassType(receiverClassName, nullable = true)
 
       val testMethodName = m("test", List(receiverClassRef, ClassRef(C), ClassRef(D)), V)
 
@@ -114,7 +114,8 @@ class IRCheckerTest {
           interfaces = Nil,
           methods = List(
             MethodDef(EMF, fooMethodName, NON,
-                List(paramDef("x", ClassType(B))), NoType, Some(Skip()))(EOH, UNV)
+                List(paramDef("x", ClassType(B, nullable = true))), NoType, Some(Skip()))(
+                EOH, UNV)
           )
         ),
         classDef("B", kind = ClassKind.Interface, interfaces = List("A")),
@@ -137,11 +138,17 @@ class IRCheckerTest {
               EMF.withNamespace(MemberNamespace.PublicStatic),
               testMethodName,
               NON,
-              List(paramDef("x", receiverType), paramDef("c", ClassType(C)), paramDef("d", ClassType(D))),
+              List(
+                paramDef("x", receiverType),
+                paramDef("c", ClassType(C, nullable = true)),
+                paramDef("d", ClassType(D, nullable = true))
+              ),
               NoType,
               Some(Block(
-                Apply(EAF, VarRef("x")(receiverType), fooMethodName, List(VarRef("c")(ClassType(C))))(NoType),
-                Apply(EAF, VarRef("x")(receiverType), fooMethodName, List(VarRef("d")(ClassType(D))))(NoType)
+                Apply(EAF, VarRef("x")(receiverType), fooMethodName,
+                    List(VarRef("c")(ClassType(C, nullable = true))))(NoType),
+                Apply(EAF, VarRef("x")(receiverType), fooMethodName,
+                    List(VarRef("d")(ClassType(D, nullable = true))))(NoType)
               ))
             )(EOH, UNV)
           )
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/IncrementalTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/IncrementalTest.scala
index 42ea84755a..245d36b326 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/IncrementalTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/IncrementalTest.scala
@@ -137,9 +137,8 @@ class IncrementalTest {
     val Foo1Class = ClassName("Foo1")
     val Foo2Class = ClassName("Foo2")
 
-    val BarType = ClassType(BarInterface)
-    val Foo1Type = ClassType(Foo1Class)
-    val Foo2Type = ClassType(Foo2Class)
+    val BarType = ClassType(BarInterface, nullable = true)
+    val Foo1Type = ClassType(Foo1Class, nullable = true)
 
     val meth = m("meth", List(ClassRef(Foo1Class), I), I)
 
@@ -180,7 +179,7 @@ class IncrementalTest {
             methods = List(
               trivialCtor(Foo1Class),
               MethodDef(EMF, meth, NON, methParamDefs, IntType, Some({
-                ApplyStatically(EAF, if (pre) This()(Foo1Type) else foo1Ref,
+                ApplyStatically(EAF, if (pre) thisFor(Foo1Class) else foo1Ref,
                     BarInterface, meth, List(foo1Ref, xRef))(IntType)
               }))(EOH, UNV)
             )
@@ -190,7 +189,7 @@ class IncrementalTest {
         v0 -> classDef(Foo2Class, superClass = Some(ObjectClass), interfaces = List(BarInterface), methods = List(
             trivialCtor(Foo2Class),
             MethodDef(EMF, meth, NON, methParamDefs, IntType, Some({
-              ApplyStatically(EAF, This()(Foo2Type), BarInterface, meth, List(foo1Ref, xRef))(IntType)
+              ApplyStatically(EAF, thisFor(Foo2Class), BarInterface, meth, List(foo1Ref, xRef))(IntType)
             }))(EOH, UNV)
         ))
     )
@@ -316,7 +315,7 @@ class IncrementalTest {
     def fooCtor(pre: Boolean) = {
       val superCtor = {
         ApplyStatically(EAF.withConstructor(true),
-            This()(ClassType(FooModule)),
+            thisFor(FooModule),
             ObjectClass, MethodIdent(NoArgConstructorName),
             Nil)(NoType)
       }
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/LibraryReachabilityTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/LibraryReachabilityTest.scala
index 29166c621b..0aedcc4906 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/LibraryReachabilityTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/LibraryReachabilityTest.scala
@@ -38,7 +38,7 @@ class LibraryReachabilityTest {
   def juPropertiesNotReachableWhenUsingGetSetClearProperty(): AsyncResult = await {
     val systemMod = LoadModule("java.lang.System$")
     val emptyStr = str("")
-    val StringType = ClassType(BoxedStringClass)
+    val StringType = ClassType(BoxedStringClass, nullable = true)
 
     val classDefs = Seq(
         classDef("A", superClass = Some(ObjectClass), methods = List(
@@ -66,7 +66,7 @@ class LibraryReachabilityTest {
 
   @Test
   def jmBigNumbersNotInstantiatedWhenUsingStringFormat(): AsyncResult = await {
-    val StringType = ClassType(BoxedStringClass)
+    val StringType = ClassType(BoxedStringClass, nullable = true)
     val formatMethod = m("format", List(T, ArrayTypeRef(O, 1)), T)
 
     val classDefs = Seq(
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/LibrarySizeTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/LibrarySizeTest.scala
index c55930f74f..6dd8041406 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/LibrarySizeTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/LibrarySizeTest.scala
@@ -52,12 +52,12 @@ class LibrarySizeTest {
       val compiledPattern = ApplyStatic(EAF, PatternClass,
           m("compile", List(T, I), ClassRef(PatternClass)),
           List(str(pattern), int(flags)))(
-          ClassType(PatternClass))
+          ClassType(PatternClass, nullable = true))
 
       val matcher = Apply(EAF, compiledPattern,
           m("matcher", List(ClassRef("java.lang.CharSequence")), ClassRef(MatcherClass)),
           List(str(input)))(
-          ClassType(MatcherClass))
+          ClassType(MatcherClass, nullable = true))
 
       consoleLog(Apply(EAF, matcher, m("matches", Nil, Z), Nil)(BooleanType))
     }
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/OptimizerTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/OptimizerTest.scala
index 441b146638..d81ce35df5 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/OptimizerTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/OptimizerTest.scala
@@ -58,9 +58,9 @@ class OptimizerTest {
   private def testCloneOnArrayInliningGeneric(inlinedWhenOnObject: Boolean,
       customMethodDefs: List[MethodDef]): Future[Unit] = {
 
-    val thisFoo = This()(ClassType("Foo"))
+    val thisFoo = thisFor("Foo")
     val intArrayTypeRef = ArrayTypeRef(IntRef, 1)
-    val intArrayType = ArrayType(intArrayTypeRef)
+    val intArrayType = ArrayType(intArrayTypeRef, nullable = true)
     val anArrayOfInts = ArrayValue(intArrayTypeRef, List(IntLiteral(1)))
     val newFoo = New("Foo", NoArgConstructorName, Nil)
 
@@ -118,7 +118,10 @@ class OptimizerTest {
         .find(_.className == MainTestClassName).get
       linkedClass.hasNot("any call to Foo.witness()") {
         case Apply(_, receiver, MethodIdent(`witnessMethodName`), _) =>
-          receiver.tpe == ClassType("Foo")
+          receiver.tpe match {
+            case ClassType(cls, _) => cls == ClassName("Foo")
+            case _                 => false
+          }
       }.hasExactly(if (inlinedWhenOnObject) 1 else 0, "IsInstanceOf node") {
         case IsInstanceOf(_, _) => true
       }.hasExactly(if (inlinedWhenOnObject) 1 else 0, "Throw node") {
@@ -139,7 +142,7 @@ class OptimizerTest {
     testCloneOnArrayInliningGeneric(inlinedWhenOnObject = false, List(
         // @inline override def clone(): AnyRef = witness()
         MethodDef(EMF, cloneMethodName, NON, Nil, AnyType, Some {
-          Apply(EAF, This()(ClassType("Foo")), witnessMethodName, Nil)(AnyType)
+          Apply(EAF, thisFor("Foo"), witnessMethodName, Nil)(AnyType)
         })(EOH.withInline(true), UNV)
     ))
   }
@@ -164,8 +167,8 @@ class OptimizerTest {
         // @inline override def clone(): AnyRef = witness()
         MethodDef(EMF, cloneMethodName, NON, Nil, AnyType, Some {
           Block(
-              Apply(EAF, This()(ClassType("Foo")), witnessMethodName, Nil)(AnyType),
-              ApplyStatically(EAF, This()(ClassType("Foo")),
+              Apply(EAF, thisFor("Foo"), witnessMethodName, Nil)(AnyType),
+              ApplyStatically(EAF, thisFor("Foo"),
                   ObjectClass, cloneMethodName, Nil)(AnyType)
           )
         })(EOH.withInline(true), UNV)
@@ -193,7 +196,7 @@ class OptimizerTest {
 
   @Test
   def testOptimizerDoesNotEliminateRequiredStaticField_Issue4021(): AsyncResult = await {
-    val StringType = ClassType(BoxedStringClass)
+    val StringType = ClassType(BoxedStringClass, nullable = true)
     val fooGetter = m("foo", Nil, T)
     val classDefs = Seq(
         classDef(
@@ -243,10 +246,10 @@ class OptimizerTest {
      *   val x1: any = null;
      *   matchAlts1: {
      *     matchAlts2: {
-     *       if (x1.isInstanceOf[java.lang.Integer]) {
+     *       if (x1.isInstanceOf[java.lang.Integer!]) {
      *         return@matchAlts2 (void 0)
      *       };
-     *       if (x1.isInstanceOf[java.lang.String]) {
+     *       if (x1.isInstanceOf[java.lang.String!]) {
      *         return@matchAlts2 (void 0)
      *       };
      *       return@matchAlts1 (void 0)
@@ -275,10 +278,10 @@ class OptimizerTest {
                 VarDef(x1, NON, AnyType, mutable = false, Null()),
                 Labeled(matchAlts1, NoType, Block(
                     Labeled(matchAlts2, NoType, Block(
-                        If(IsInstanceOf(VarRef(x1)(AnyType), ClassType(BoxedIntegerClass)), {
+                        If(IsInstanceOf(VarRef(x1)(AnyType), ClassType(BoxedIntegerClass, nullable = false)), {
                           Return(Undefined(), matchAlts2)
                         }, Skip())(NoType),
-                        If(IsInstanceOf(VarRef(x1)(AnyType), ClassType(BoxedStringClass)), {
+                        If(IsInstanceOf(VarRef(x1)(AnyType), ClassType(BoxedStringClass, nullable = false)), {
                           Return(Undefined(), matchAlts2)
                         }, Skip())(NoType),
                         Return(Undefined(), matchAlts1)
@@ -484,7 +487,7 @@ class OptimizerTest {
       witnessMutable: Boolean): Seq[ClassDef] = {
     val methodName = m("method", Nil, I)
 
-    val witnessType = ClassType("Witness")
+    val witnessType = ClassType("Witness", nullable = true)
 
     Seq(
       classDef("Witness", kind = ClassKind.Interface),
@@ -502,13 +505,13 @@ class OptimizerTest {
             //   this.y = 5
             // }
             MethodDef(EMF.withNamespace(Constructor), NoArgConstructorName, NON, Nil, NoType, Some(Block(
-              Assign(Select(This()(ClassType("Foo")), FieldName("Foo", "x"))(witnessType), Null()),
-              Assign(Select(This()(ClassType("Foo")), FieldName("Foo", "y"))(IntType), int(5))
+              Assign(Select(thisFor("Foo"), FieldName("Foo", "x"))(witnessType), Null()),
+              Assign(Select(thisFor("Foo"), FieldName("Foo", "y"))(IntType), int(5))
             )))(EOH, UNV),
 
             // def method(): Int = this.y
             MethodDef(EMF, methodName, NON, Nil, IntType, Some {
-              Select(This()(ClassType("Foo")), FieldName("Foo", "y"))(IntType)
+              Select(thisFor("Foo"), FieldName("Foo", "y"))(IntType)
             })(EOH, UNV)
           ),
           optimizerHints = EOH.withInline(classInline)
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/SmallModulesForSplittingTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/SmallModulesForSplittingTest.scala
index 1fefebf792..ce6a9b2386 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/SmallModulesForSplittingTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/SmallModulesForSplittingTest.scala
@@ -38,7 +38,7 @@ class SmallModulesForSplittingTest {
     /* Test splitting in the degenerate case, where dependencies traverse the
      * split boundary multiple times.
      */
-    val strClsType = ClassType(BoxedStringClass)
+    val strClsType = ClassType(BoxedStringClass, nullable = true)
 
     val methodName = m("get", Nil, T)
 
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/SmallestModulesSplittingTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/SmallestModulesSplittingTest.scala
index 94b8340753..fd91b55f53 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/SmallestModulesSplittingTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/SmallestModulesSplittingTest.scala
@@ -33,7 +33,7 @@ class SmallestModulesSplittingTest {
   /** Smoke test to ensure modules do not get merged too much. */
   @Test
   def splitsModules(): AsyncResult = await {
-    val strClsType = ClassType(BoxedStringClass)
+    val strClsType = ClassType(BoxedStringClass, nullable = true)
 
     val greetMethodName = m("greet", Nil, T)
 
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/checker/ClassDefCheckerTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/checker/ClassDefCheckerTest.scala
index e9f6ba2306..62fbd15bff 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/checker/ClassDefCheckerTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/checker/ClassDefCheckerTest.scala
@@ -165,6 +165,27 @@ class ClassDefCheckerTest {
         "duplicate field 'A::foobar'")
   }
 
+  @Test
+  def illegalFieldTypes(): Unit = {
+    val badFieldTypes: List[Type] = List(
+      AnyNotNullType,
+      ClassType(BoxedStringClass, nullable = false),
+      ArrayType(ArrayTypeRef(I, 1), nullable = false),
+      RecordType(List(RecordType.Field("I", NON, IntType, mutable = true))),
+      NothingType,
+      NoType
+    )
+
+    for (fieldType <- badFieldTypes) {
+      assertError(
+          classDef("A", superClass = Some(ObjectClass),
+              fields = List(
+                FieldDef(EMF, FieldName("A", "x"), NON, fieldType)
+              )),
+          s"FieldDef cannot have type ${fieldType.show()}")
+    }
+  }
+
   @Test
   def noDuplicateMethods(): Unit = {
     val babarMethodName = MethodName("babar", List(IntRef), IntRef)
@@ -182,14 +203,13 @@ class ClassDefCheckerTest {
 
   @Test
   def noDuplicateConstructors(): Unit = {
-    val BoxedStringType = ClassType(BoxedStringClass)
+    val BoxedStringType = ClassType(BoxedStringClass, nullable = true)
     val stringCtorName = MethodName.constructor(List(T))
 
     val FooClass = ClassName("Foo")
-    val FooType = ClassType(FooClass)
 
     val callPrimaryCtorBody: Tree = {
-      ApplyStatically(EAF.withConstructor(true), This()(FooType),
+      ApplyStatically(EAF.withConstructor(true), thisFor(FooClass),
           FooClass, NoArgConstructorName, Nil)(NoType)
     }
 
@@ -306,20 +326,28 @@ class ClassDefCheckerTest {
         "Cannot find `this` in scope")
 
     testThisTypeError(static = true,
-        This()(ClassType("Foo")),
+        This()(ClassType("Foo", nullable = false)),
         "Cannot find `this` in scope")
 
     testThisTypeError(static = false,
         This()(NoType),
-        "`this` of type Foo typed as <notype>")
+        "`this` of type Foo! typed as <notype>")
 
     testThisTypeError(static = false,
         This()(AnyType),
-        "`this` of type Foo typed as any")
+        "`this` of type Foo! typed as any")
 
     testThisTypeError(static = false,
-        This()(ClassType("Bar")),
-        "`this` of type Foo typed as Bar")
+        This()(AnyNotNullType),
+        "`this` of type Foo! typed as any!")
+
+    testThisTypeError(static = false,
+        This()(ClassType("Bar", nullable = false)),
+        "`this` of type Foo! typed as Bar!")
+
+    testThisTypeError(static = false,
+        This()(ClassType("Foo", nullable = true)),
+        "`this` of type Foo! typed as Foo")
 
     testThisTypeError(static = false,
         Closure(arrow = true, Nil, Nil, None, This()(NoType), Nil),
@@ -334,15 +362,15 @@ class ClassDefCheckerTest {
         "`this` of type any typed as <notype>")
 
     testThisTypeError(static = false,
-        Closure(arrow = false, Nil, Nil, None, This()(ClassType("Foo")), Nil),
-        "`this` of type any typed as Foo")
+        Closure(arrow = false, Nil, Nil, None, This()(ClassType("Foo", nullable = false)), Nil),
+        "`this` of type any typed as Foo!")
   }
 
   @Test
   def storeModule(): Unit = {
     val ctorFlags = EMF.withNamespace(MemberNamespace.Constructor)
 
-    val superCtorCall = ApplyStatically(EAF.withConstructor(true), This()(ClassType("Foo")),
+    val superCtorCall = ApplyStatically(EAF.withConstructor(true), thisFor("Foo"),
         ObjectClass, NoArgConstructorName, Nil)(NoType)
 
     assertError(
@@ -393,6 +421,42 @@ class ClassDefCheckerTest {
       "Cannot find `this` in scope for StoreModule()"
     )
   }
+
+  @Test
+  def isAsInstanceOf(): Unit = {
+    def testIsInstanceOfError(testType: Type): Unit = {
+      assertError(
+          mainTestClassDef(IsInstanceOf(int(5), testType)),
+          s"${testType.show()} is not a valid test type for IsInstanceOf")
+    }
+
+    def testAsInstanceOfError(targetType: Type): Unit = {
+      assertError(
+          mainTestClassDef(AsInstanceOf(int(5), targetType)),
+          s"${targetType.show()} is not a valid target type for AsInstanceOf")
+    }
+
+    def testIsAsInstanceOfError(tpe: Type): Unit = {
+      testIsInstanceOfError(tpe)
+      testAsInstanceOfError(tpe)
+    }
+
+    testIsAsInstanceOfError(NoType)
+    testIsAsInstanceOfError(NullType)
+    testIsAsInstanceOfError(NothingType)
+
+    testIsAsInstanceOfError(
+        RecordType(List(RecordType.Field("f", NON, IntType, mutable = false))))
+
+    testIsInstanceOfError(AnyType)
+    testAsInstanceOfError(AnyNotNullType)
+
+    testIsInstanceOfError(ClassType(BoxedStringClass, nullable = true))
+    testAsInstanceOfError(ClassType(BoxedStringClass, nullable = false))
+
+    testIsInstanceOfError(ArrayType(ArrayTypeRef(IntRef, 1), nullable = true))
+    testAsInstanceOfError(ArrayType(ArrayTypeRef(IntRef, 1), nullable = false))
+  }
 }
 
 private object ClassDefCheckerTest {
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/testutils/TestIRBuilder.scala b/linker/shared/src/test/scala/org/scalajs/linker/testutils/TestIRBuilder.scala
index be6dbb33a9..de55615fcf 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/testutils/TestIRBuilder.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/testutils/TestIRBuilder.scala
@@ -90,7 +90,7 @@ object TestIRBuilder {
     val flags = MemberFlags.empty.withNamespace(MemberNamespace.Constructor)
     MethodDef(flags, MethodIdent(NoArgConstructorName), NON, Nil, NoType,
         Some(ApplyStatically(EAF.withConstructor(true),
-            This()(ClassType(enclosingClassName)),
+            thisFor(enclosingClassName),
             parentClassName, MethodIdent(NoArgConstructorName),
             Nil)(NoType)))(
         EOH, UNV)
@@ -105,7 +105,7 @@ object TestIRBuilder {
   val MainMethodName: MethodName = m("main", List(AT), VoidRef)
 
   def mainMethodDef(body: Tree): MethodDef = {
-    val argsParamDef = paramDef("args", ArrayType(AT))
+    val argsParamDef = paramDef("args", ArrayType(AT, nullable = true))
     MethodDef(MemberFlags.empty.withNamespace(MemberNamespace.PublicStatic),
         MainMethodName, NON, List(argsParamDef), NoType, Some(body))(
         EOH, UNV)
@@ -119,7 +119,8 @@ object TestIRBuilder {
     val outMethodName = m("out", Nil, ClassRef(PrintStreamClass))
     val printlnMethodName = m("println", List(O), VoidRef)
 
-    val out = ApplyStatic(EAF, "java.lang.System", outMethodName, Nil)(ClassType(PrintStreamClass))
+    val out = ApplyStatic(EAF, "java.lang.System", outMethodName, Nil)(
+        ClassType(PrintStreamClass, nullable = true))
     Apply(EAF, out, printlnMethodName, List(expr))(NoType)
   }
 
@@ -151,6 +152,9 @@ object TestIRBuilder {
     else None
   }
 
+  def thisFor(cls: ClassName): This =
+    This()(ClassType(cls, nullable = false))
+
   implicit def string2LocalName(name: String): LocalName =
     LocalName(name)
   implicit def string2LabelName(name: String): LabelName =
diff --git a/project/BinaryIncompatibilities.scala b/project/BinaryIncompatibilities.scala
index 08a3f5b462..3567e90ef1 100644
--- a/project/BinaryIncompatibilities.scala
+++ b/project/BinaryIncompatibilities.scala
@@ -5,6 +5,22 @@ import com.typesafe.tools.mima.core.ProblemFilters._
 
 object BinaryIncompatibilities {
   val IR = Seq(
+    // !!! Breaking, OK in minor release
+
+    ProblemFilters.exclude[IncompatibleResultTypeProblem]("org.scalajs.ir.Trees#*.tpe"),
+
+    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Types#ClassType.this"),
+    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Types#ClassType.apply"),
+    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Types#ClassType.copy"),
+    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Types#ArrayType.this"),
+    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Types#ArrayType.apply"),
+    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Types#ArrayType.copy"),
+
+    ProblemFilters.exclude[MissingTypesProblem]("org.scalajs.ir.Types$ClassType$"),
+    ProblemFilters.exclude[MissingTypesProblem]("org.scalajs.ir.Types$ArrayType$"),
+
+    // New abstract member in sealed hierarchy, not an issue
+    ProblemFilters.exclude[ReversedMissingMethodProblem]("org.scalajs.ir.Types#Type.toNonNullable"),
   )
 
   val Linker = Seq(
diff --git a/project/Build.scala b/project/Build.scala
index d56961696d..5ccf4893b2 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -2064,10 +2064,10 @@ object Build {
               ))
             } else {
               Some(ExpectedSizes(
-                  fastLink = 433000 to 434000,
-                  fullLink = 283000 to 284000,
-                  fastLinkGz = 62000 to 63000,
-                  fullLinkGz = 44000 to 45000,
+                  fastLink = 425000 to 426000,
+                  fullLink = 282000 to 283000,
+                  fastLinkGz = 61000 to 62000,
+                  fullLinkGz = 43000 to 44000,
               ))
             }
 
@@ -2081,9 +2081,9 @@ object Build {
               ))
             } else {
               Some(ExpectedSizes(
-                  fastLink = 309000 to 310000,
-                  fullLink = 263000 to 264000,
-                  fastLinkGz = 49000 to 50000,
+                  fastLink = 306000 to 307000,
+                  fullLink = 262000 to 263000,
+                  fastLinkGz = 48000 to 49000,
                   fullLinkGz = 43000 to 44000,
               ))
             }
diff --git a/project/JavaLangObject.scala b/project/JavaLangObject.scala
index aa2c4d1931..28a076e3bf 100644
--- a/project/JavaLangObject.scala
+++ b/project/JavaLangObject.scala
@@ -26,7 +26,7 @@ object JavaLangObject {
     implicit val DummyPos = NoPosition
 
     // ClassType(Object) is normally invalid, but not in this class def
-    val ThisType = ClassType(ObjectClass)
+    val ThisType = ClassType(ObjectClass, nullable = true) // temp to test deserialization hack
 
     val ObjectClassRef = ClassRef(ObjectClass)
     val ClassClassRef = ClassRef(ClassClass)
@@ -60,7 +60,7 @@ object JavaLangObject {
           MethodIdent(MethodName("getClass", Nil, ClassClassRef)),
           NoOriginalName,
           Nil,
-          ClassType(ClassClass),
+          ClassType(ClassClass, nullable = true),
           Some {
             GetClass(This()(ThisType))
           })(OptimizerHints.empty.withInline(true), Unversioned),
@@ -101,8 +101,9 @@ object JavaLangObject {
           Nil,
           AnyType,
           Some {
-            If(IsInstanceOf(This()(ThisType), ClassType(CloneableClass)), {
-              Clone(AsInstanceOf(This()(ThisType), ClassType(CloneableClass)))
+            // temporarily use nullable in IsInstanceOf to test deserialization hack
+            If(IsInstanceOf(This()(ThisType), ClassType(CloneableClass, nullable = true)), {
+              Clone(AsInstanceOf(This()(ThisType), ClassType(CloneableClass, nullable = true)))
             }, {
               Throw(New(ClassName("java.lang.CloneNotSupportedException"),
                 MethodIdent(NoArgConstructorName), Nil))
@@ -117,15 +118,16 @@ object JavaLangObject {
           MethodIdent(MethodName("toString", Nil, StringClassRef)),
           NoOriginalName,
           Nil,
-          ClassType(BoxedStringClass),
+          ClassType(BoxedStringClass, nullable = true),
           Some {
             BinaryOp(BinaryOp.String_+, BinaryOp(BinaryOp.String_+,
               Apply(
                 EAF,
                 Apply(EAF, This()(ThisType),
                   MethodIdent(MethodName("getClass", Nil, ClassClassRef)), Nil)(
-                  ClassType(ClassClass)),
-                MethodIdent(MethodName("getName", Nil, StringClassRef)), Nil)(ClassType(BoxedStringClass)),
+                  ClassType(ClassClass, nullable = true)),
+                MethodIdent(MethodName("getName", Nil, StringClassRef)), Nil)(
+                ClassType(BoxedStringClass, nullable = true)),
               // +
               StringLiteral("@")),
               // +
@@ -134,7 +136,7 @@ object JavaLangObject {
                 LoadModule(ClassName("java.lang.Integer$")),
                 MethodIdent(MethodName("toHexString", List(IntRef), StringClassRef)),
                 List(Apply(EAF, This()(ThisType), MethodIdent(MethodName("hashCode", Nil, IntRef)), Nil)(IntType)))(
-                ClassType(BoxedStringClass)))
+                ClassType(BoxedStringClass, nullable = true)))
           })(OptimizerHints.empty, Unversioned),
 
         /* Since wait() is not supported in any way, a correct implementation
@@ -178,7 +180,7 @@ object JavaLangObject {
           {
             Apply(EAF, This()(ThisType),
                 MethodIdent(MethodName("toString", Nil, StringClassRef)),
-                Nil)(ClassType(BoxedStringClass))
+                Nil)(ClassType(BoxedStringClass, nullable = true))
           })(OptimizerHints.empty, Unversioned)
       ),
       jsNativeMembers = Nil,
diff --git a/project/JavalibIRCleaner.scala b/project/JavalibIRCleaner.scala
index 305fc74212..4eab2d5a6f 100644
--- a/project/JavalibIRCleaner.scala
+++ b/project/JavalibIRCleaner.scala
@@ -567,16 +567,16 @@ final class JavalibIRCleaner(baseDirectoryURI: URI) {
 
     private def transformType(tpe: Type)(implicit pos: Position): Type = {
       tpe match {
-        case ClassType(ObjectClass) =>
+        case ClassType(ObjectClass, _) =>
           // In java.lang.Object iself, there are ClassType(ObjectClass) that must be preserved as is.
           tpe
-        case ClassType(cls) =>
+        case ClassType(cls, nullable) =>
           transformClassName(cls) match {
-            case ObjectClass => AnyType
-            case newCls      => ClassType(newCls)
+            case ObjectClass => if (nullable) AnyType else AnyNotNullType
+            case newCls      => ClassType(newCls, nullable)
           }
-        case ArrayType(arrayTypeRef) =>
-          ArrayType(transformArrayTypeRef(arrayTypeRef))
+        case ArrayType(arrayTypeRef, nullable) =>
+          ArrayType(transformArrayTypeRef(arrayTypeRef), nullable)
         case _ =>
           tpe
       }
@@ -724,7 +724,7 @@ object JavalibIRCleaner {
   }
 
   private def isFunctionNType(n: Int, tpe: Type): Boolean = tpe match {
-    case ClassType(cls) =>
+    case ClassType(cls, _) =>
       cls == FunctionNClasses(n) || cls == AnonFunctionNClasses(n)
     case _ =>
       false

From dfd7b93d61bdea73779086cf00b0c50570f3b753 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Thu, 22 Aug 2024 16:31:31 +0200
Subject: [PATCH 131/298] Adapt the compiler to generate non-nullable types.

For `This` nodes and `IsInstanceOf` nodes.

We only active the relevant deserialization hacks when reading IR
from before 1.17.
---
 .../org/scalajs/nscplugin/GenJSCode.scala     | 36 ++++++++++++-------
 .../org/scalajs/nscplugin/GenJSExports.scala  |  2 +-
 .../scala/org/scalajs/ir/Serializers.scala    |  4 +--
 project/JavaLangObject.scala                  |  5 ++-
 4 files changed, 29 insertions(+), 18 deletions(-)

diff --git a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
index 42718ce041..788e8dc61b 100644
--- a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
+++ b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
@@ -152,12 +152,19 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
     private val fieldsMutatedInCurrentClass = new ScopedVar[mutable.Set[Name]]
     private val generatedSAMWrapperCount = new ScopedVar[VarBox[Int]]
 
+    def currentThisTypeNullable: jstpe.Type =
+      encodeClassType(currentClassSym)
+
     def currentThisType: jstpe.Type = {
-      encodeClassType(currentClassSym) match {
+      currentThisTypeNullable match {
         case tpe @ jstpe.ClassType(cls, _) =>
-          jstpe.BoxedClassToPrimType.getOrElse(cls, tpe)
-        case tpe =>
+          jstpe.BoxedClassToPrimType.getOrElse(cls, tpe.toNonNullable)
+        case tpe @ jstpe.AnyType =>
+          // We are in a JS class, in which even `this` is nullable
           tpe
+        case tpe =>
+          throw new AssertionError(
+              s"Unexpected IR this type $tpe for class ${currentClassSym.get}")
       }
     }
 
@@ -2124,8 +2131,13 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
           if (thisSym.isMutable)
             mutableLocalVars += thisSym
 
+          /* The `thisLocalIdent` must be nullable. Even though we initially
+           * assign it to `this`, which is non-nullable, tail-recursive calls
+           * may reassign it to a different value, which in general will be
+           * nullable.
+           */
           val thisLocalIdent = encodeLocalSym(thisSym)
-          val thisLocalType = currentThisType
+          val thisLocalType = currentThisTypeNullable
 
           val genRhs = {
             /* #3267 In default methods, scalac will type its _$this
@@ -2222,7 +2234,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
      *  @param tree
      *    The tree to adapt.
      *  @param tpe
-     *    The target type, which must be either `AnyType` or `ClassType(_)`.
+     *    The target type, which must be either `AnyType` or `ClassType`.
      */
     private def forceAdapt(tree: js.Tree, tpe: jstpe.Type): js.Tree = {
       if (tree.tpe == tpe || tpe == jstpe.AnyType) {
@@ -2670,7 +2682,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
         js.This()(currentThisType)
       } { thisLocalIdent =>
         // .copy() to get the correct position
-        js.VarRef(thisLocalIdent.copy())(currentThisType)
+        js.VarRef(thisLocalIdent.copy())(currentThisTypeNullable)
       }
     }
 
@@ -3333,7 +3345,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
           val isTailJumpThisLocalVar = formalArgSym.name == nme.THIS
 
           val tpe =
-            if (isTailJumpThisLocalVar) currentThisType
+            if (isTailJumpThisLocalVar) currentThisTypeNullable
             else toIRType(formalArgSym.tpe)
 
           val fixedActualArg =
@@ -3561,7 +3573,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
         // The Scala type system prevents x.isInstanceOf[Null] and ...[Nothing]
         assert(sym != NullClass && sym != NothingClass,
             s"Found a .isInstanceOf[$sym] at $pos")
-        js.IsInstanceOf(value, toIRType(to))
+        js.IsInstanceOf(value, toIRType(to).toNonNullable)
       }
     }
 
@@ -6334,7 +6346,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
       }
       val className = encodeClassName(currentClassSym).withSuffix(suffix)
 
-      val classType = jstpe.ClassType(className, nullable = true)
+      val thisType = jstpe.ClassType(className, nullable = false)
 
       // val f: Any
       val fFieldIdent = js.FieldIdent(FieldName(className, SimpleFieldName("f")))
@@ -6353,10 +6365,10 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
             jstpe.NoType,
             Some(js.Block(List(
                 js.Assign(
-                    js.Select(js.This()(classType), fFieldIdent)(jstpe.AnyType),
+                    js.Select(js.This()(thisType), fFieldIdent)(jstpe.AnyType),
                     fParamDef.ref),
                 js.ApplyStatically(js.ApplyFlags.empty.withConstructor(true),
-                    js.This()(classType),
+                    js.This()(thisType),
                     ir.Names.ObjectClass,
                     js.MethodIdent(ir.Names.NoArgConstructorName),
                     Nil)(jstpe.NoType)))))(
@@ -6404,7 +6416,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
         }.map((ensureBoxed _).tupled)
 
         val call = js.JSFunctionApply(
-            js.Select(js.This()(classType), fFieldIdent)(jstpe.AnyType),
+            js.Select(js.This()(thisType), fFieldIdent)(jstpe.AnyType),
             actualParams)
 
         val body = fromAny(call, enteringPhase(currentRun.posterasurePhase) {
diff --git a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSExports.scala b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSExports.scala
index e0c32d1d81..beca736586 100644
--- a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSExports.scala
+++ b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSExports.scala
@@ -930,7 +930,7 @@ trait GenJSExports[G <: Global with Singleton] extends SubComponent {
 
   private sealed abstract class RTTypeTest
 
-  private case class PrimitiveTypeTest(tpe: jstpe.Type, rank: Int)
+  private case class PrimitiveTypeTest(tpe: jstpe.PrimType, rank: Int)
       extends RTTypeTest
 
   // scalastyle:off equals.hash.code
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
index 0ba241bbac..bad2b82fa5 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
@@ -1234,7 +1234,7 @@ object Serializers {
         case TagIsInstanceOf =>
           val expr = readTree()
           val testType0 = readType()
-          val testType = if (true /* hacks.use16 */) { // scalastyle:ignore
+          val testType = if (hacks.use16) {
             testType0 match {
               case ClassType(className, true)    => ClassType(className, nullable = false)
               case ArrayType(arrayTypeRef, true) => ArrayType(arrayTypeRef, nullable = false)
@@ -1414,7 +1414,7 @@ object Serializers {
       val originalName = readOriginalName()
       val kind = ClassKind.fromByte(readByte())
 
-      if (true /* hacks.use16 */) { // scalastyle:ignore
+      if (hacks.use16) {
         thisTypeForHack = kind match {
           case ClassKind.Class | ClassKind.ModuleClass | ClassKind.Interface =>
             Some(ClassType(cls, nullable = false))
diff --git a/project/JavaLangObject.scala b/project/JavaLangObject.scala
index 28a076e3bf..c316ecc7a0 100644
--- a/project/JavaLangObject.scala
+++ b/project/JavaLangObject.scala
@@ -26,7 +26,7 @@ object JavaLangObject {
     implicit val DummyPos = NoPosition
 
     // ClassType(Object) is normally invalid, but not in this class def
-    val ThisType = ClassType(ObjectClass, nullable = true) // temp to test deserialization hack
+    val ThisType = ClassType(ObjectClass, nullable = false)
 
     val ObjectClassRef = ClassRef(ObjectClass)
     val ClassClassRef = ClassRef(ClassClass)
@@ -101,8 +101,7 @@ object JavaLangObject {
           Nil,
           AnyType,
           Some {
-            // temporarily use nullable in IsInstanceOf to test deserialization hack
-            If(IsInstanceOf(This()(ThisType), ClassType(CloneableClass, nullable = true)), {
+            If(IsInstanceOf(This()(ThisType), ClassType(CloneableClass, nullable = false)), {
               Clone(AsInstanceOf(This()(ThisType), ClassType(CloneableClass, nullable = true)))
             }, {
               Throw(New(ClassName("java.lang.CloneNotSupportedException"),

From 8cb699d42b49053b1b3b1bed7a51d03497b4c4a3 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Mon, 26 Aug 2024 21:28:56 +0200
Subject: [PATCH 132/298] Enable compliant nullPointers for the partest
 `run/t8925.scala`.

It relies on the fact that `throw null` throws an exception that
can be caught. Under our semantics that is a `NullPointerException`
caused by the fact that the argument to `throw` is `null`. Under
unchecked NPEs, the optimizer can assume this code to be
unreachable and dead-code-eliminate it instead of throwing
anything.
---
 .../resources/scala/tools/partest/scalajs/2.12.19/run/t8925.sem  | 1 +
 .../resources/scala/tools/partest/scalajs/2.13.13/run/t8925.sem  | 1 +
 2 files changed, 2 insertions(+)
 create mode 100644 partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/t8925.sem
 create mode 100644 partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/t8925.sem

diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/t8925.sem b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/t8925.sem
new file mode 100644
index 0000000000..faf2309802
--- /dev/null
+++ b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/t8925.sem
@@ -0,0 +1 @@
+nullPointers
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/t8925.sem b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/t8925.sem
new file mode 100644
index 0000000000..faf2309802
--- /dev/null
+++ b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/t8925.sem
@@ -0,0 +1 @@
+nullPointers

From a8a15312212463998e92e59fe6eb218d3f051cbc Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Mon, 26 Aug 2024 21:36:34 +0200
Subject: [PATCH 133/298] Rearrange a complex pattern match not to crash Scala
 2.12.{2,3}.

---
 .../org/scalajs/linker/frontend/optimizer/OptimizerCore.scala | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
index 06f62a2007..59663392bf 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
@@ -3516,8 +3516,8 @@ private[optimizer] abstract class OptimizerCore(
              */
             case (BinaryOp(BinaryOp.===, VarRef(lhsIdent), Null()),
                 BinaryOp(BinaryOp.===, VarRef(rhsIdent), Null()),
-                BinaryOp(BinaryOp.===, MaybeCast(l @ VarRef(lhsIdent2)), r @ VarRef(rhsIdent2)))
-                if lhsIdent2 == lhsIdent && rhsIdent2 == rhsIdent =>
+                BinaryOp(BinaryOp.===, MaybeCast(l: VarRef), r: VarRef))
+                if l.ident == lhsIdent && r.ident == rhsIdent =>
               BinaryOp(BinaryOp.===, l, r)(elsep.pos)
 
             // Example: (x > y) || (x == y)  ->  (x >= y)

From 0bfdf3e192c61bed9f65965ccf4f34601491970d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Thu, 29 Aug 2024 11:18:33 +0200
Subject: [PATCH 134/298] Wasm: Correctly implement `JSLinkingInfo`.

---
 .../linker/backend/wasmemitter/Emitter.scala  | 21 +++++++++++++++++++
 .../backend/wasmemitter/LoaderContent.scala   | 21 ++++++-------------
 .../testsuite/library/LinkingInfoTest.scala   | 10 ++-------
 3 files changed, 29 insertions(+), 23 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala
index 0a477f6a59..46a06ec1f1 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala
@@ -18,6 +18,7 @@ import org.scalajs.ir.Names._
 import org.scalajs.ir.Types._
 import org.scalajs.ir.OriginalName
 import org.scalajs.ir.Position
+import org.scalajs.ir.ScalaJSVersions
 
 import org.scalajs.linker.interface._
 import org.scalajs.linker.interface.unstable._
@@ -269,6 +270,25 @@ final class Emitter(config: Emitter.Config) {
   private def buildJSFileContent(module: ModuleSet.Module): Array[Byte] = {
     implicit val noPos = Position.NoPosition
 
+    // Linking info
+    val linkingInfo = {
+      // must be in sync with scala.scalajs.runtime.LinkingInfo
+      import config.coreSpec._
+      import js.{BooleanLiteral => bool, IntLiteral => int, StringLiteral => str}
+
+      def objectFreeze(tree: js.Tree): js.Tree =
+        js.Apply(js.DotSelect(js.VarRef(js.Ident("Object")), js.Ident("freeze")), tree :: Nil)
+
+      objectFreeze(js.ObjectConstr(List(
+        str("esVersion") -> int(esFeatures.esVersion.edition),
+        str("assumingES6") -> bool(esFeatures.useECMAScript2015Semantics), // different name for historical reasons
+        str("isWebAssembly") -> bool(true),
+        str("productionMode") -> bool(semantics.productionMode),
+        str("linkerVersion") -> str(ScalaJSVersions.current),
+        str("fileLevelThis") -> js.This()
+      )))
+    }
+
     // Sort for stability
     val importedModules = module.externalDependencies.toList.sorted
 
@@ -310,6 +330,7 @@ final class Emitter(config: Emitter.Config) {
       js.VarRef(loadFunIdent),
       List(
         js.StringLiteral(config.internalWasmFileURIPattern(module.id)),
+        linkingInfo,
         importedModulesDict,
         exportSettersDict
       )
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala
index 01614586c1..77687a15da 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala
@@ -14,8 +14,6 @@ package org.scalajs.linker.backend.wasmemitter
 
 import java.nio.charset.StandardCharsets
 
-import org.scalajs.ir.ScalaJSVersions
-
 import EmbeddedConstants._
 
 /** Contents of the `__loader.js` file that we emit in every output. */
@@ -79,16 +77,6 @@ function installJSField(instance, name, value) {
   });
 }
 
-// FIXME We need to adapt this to the correct values
-const linkingInfo = Object.freeze({
-  "esVersion": 6,
-  "assumingES6": true,
-  "isWebAssembly": true,
-  "productionMode": false,
-  "linkerVersion": "${ScalaJSVersions.current}",
-  "fileLevelThis": this
-});
-
 const scalaJSHelpers = {
   // JSTag
   JSTag: WebAssembly.JSTag,
@@ -203,7 +191,6 @@ const scalaJSHelpers = {
   jsDelete: (o, p) => { delete o[p]; },
   jsForInSimple: (o, f) => { for (var k in o) f(k); },
   jsIsTruthy: (x) => !!x,
-  jsLinkingInfo: linkingInfo,
 
   // Excruciating list of all the JS operators
   jsUnaryPlus: (a) => +a,
@@ -306,8 +293,12 @@ const scalaJSHelpers = {
   },
 }
 
-export async function load(wasmFileURL, importedModules, exportSetters) {
-  const myScalaJSHelpers = { ...scalaJSHelpers, idHashCodeMap: new WeakMap() };
+export async function load(wasmFileURL, linkingInfo, importedModules, exportSetters) {
+  const myScalaJSHelpers = {
+    ...scalaJSHelpers,
+    jsLinkingInfo: linkingInfo,
+    idHashCodeMap: new WeakMap()
+  };
   const importsObj = {
     "__scalaJSHelpers": myScalaJSHelpers,
     "__scalaJSImports": importedModules,
diff --git a/test-suite/js/src/test/scala/org/scalajs/testsuite/library/LinkingInfoTest.scala b/test-suite/js/src/test/scala/org/scalajs/testsuite/library/LinkingInfoTest.scala
index b2b4c89ed8..7dbcd44d22 100644
--- a/test-suite/js/src/test/scala/org/scalajs/testsuite/library/LinkingInfoTest.scala
+++ b/test-suite/js/src/test/scala/org/scalajs/testsuite/library/LinkingInfoTest.scala
@@ -22,17 +22,11 @@ import org.junit.Test
 import org.scalajs.testsuite.utils.Platform
 
 class LinkingInfoTest {
-  @Test def productionMode(): Unit = {
-    assumeFalse("Not implemented yet on WebAssembly", Platform.executingInWebAssembly)
-
+  @Test def productionMode(): Unit =
     assertEquals(Platform.isInProductionMode, LinkingInfo.productionMode)
-  }
-
-  @Test def developmentMode(): Unit = {
-    assumeFalse("Not implemented yet on WebAssembly", Platform.executingInWebAssembly)
 
+  @Test def developmentMode(): Unit =
     assertEquals(!Platform.isInProductionMode, LinkingInfo.developmentMode)
-  }
 
   @Test def esVersion(): Unit =
     assertEquals(Platform.assumedESVersion, LinkingInfo.esVersion)

From 506b976acfd49e693a20f664ca9d3e966eb9ee9a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Mon, 24 Jun 2024 20:04:58 +0200
Subject: [PATCH 135/298] Wasm: Implement checked asInstanceOfs.

---
 Jenkinsfile                                   |  14 +
 .../backend/WebAssemblyLinkerBackend.scala    |   1 -
 .../backend/wasmemitter/ClassEmitter.scala    | 110 ++++-
 .../backend/wasmemitter/CoreWasmLib.scala     | 377 +++++++++++++++++-
 .../linker/backend/wasmemitter/Emitter.scala  |  46 ++-
 .../backend/wasmemitter/FunctionEmitter.scala |  37 +-
 .../backend/wasmemitter/LoaderContent.scala   |   8 +
 .../backend/wasmemitter/Preprocessor.scala    |   8 +-
 .../backend/wasmemitter/SpecialNames.scala    |   7 +
 .../linker/backend/wasmemitter/VarGen.scala   |   7 +
 .../backend/wasmemitter/WasmContext.scala     |   5 +-
 project/Build.scala                           |  28 +-
 12 files changed, 600 insertions(+), 48 deletions(-)

diff --git a/Jenkinsfile b/Jenkinsfile
index a217171026..9e1b827a81 100644
--- a/Jenkinsfile
+++ b/Jenkinsfile
@@ -431,6 +431,20 @@ def Tasks = [
         'set scalaJSLinkerConfig in $testSuite.v$v ~= (_.withOptimizer(false))' \
         'set scalaJSStage in Global := FullOptStage' \
         $testSuite$v/test &&
+    sbtretry ++$scala \
+        'set Global/enableWasmEverywhere := true' \
+        'set scalaJSLinkerConfig in $testSuite.v$v ~= makeCompliant' \
+        $testSuite$v/test &&
+    sbtretry ++$scala \
+        'set Global/enableWasmEverywhere := true' \
+        'set scalaJSLinkerConfig in $testSuite.v$v ~= makeCompliant' \
+        'set scalaJSStage in Global := FullOptStage' \
+        $testSuite$v/test &&
+    sbtretry ++$scala \
+        'set Global/enableWasmEverywhere := true' \
+        'set scalaJSLinkerConfig in $testSuite.v$v ~= makeCompliant' \
+        'set scalaJSLinkerConfig in $testSuite.v$v ~= (_.withOptimizer(false))' \
+        $testSuite$v/test &&
     sbtretry ++$scala \
         'set Global/enableWasmEverywhere := true' \
         testingExample$v/testHtml &&
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/WebAssemblyLinkerBackend.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/WebAssemblyLinkerBackend.scala
index 2e614993f1..eb264753d4 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/WebAssemblyLinkerBackend.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/WebAssemblyLinkerBackend.scala
@@ -37,7 +37,6 @@ final class WebAssemblyLinkerBackend(config: LinkerBackendImpl.Config)
     s"The WebAssembly backend only supports ES modules; was ${coreSpec.moduleKind}."
   )
   require(
-    coreSpec.semantics.asInstanceOfs == CheckedBehavior.Unchecked &&
     coreSpec.semantics.arrayIndexOutOfBounds == CheckedBehavior.Unchecked &&
     coreSpec.semantics.arrayStores == CheckedBehavior.Unchecked &&
     coreSpec.semantics.negativeArraySizes == CheckedBehavior.Unchecked &&
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/ClassEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/ClassEmitter.scala
index f669847fe2..3d6c1d3c45 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/ClassEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/ClassEmitter.scala
@@ -20,6 +20,7 @@ import org.scalajs.ir.OriginalName.NoOriginalName
 import org.scalajs.ir.Trees._
 import org.scalajs.ir.Types._
 
+import org.scalajs.linker.interface.CheckedBehavior
 import org.scalajs.linker.interface.unstable.RuntimeClassNameMapperImpl
 import org.scalajs.linker.standard.{CoreSpec, LinkedClass, LinkedTopLevelExport}
 
@@ -37,6 +38,7 @@ import WasmContext._
 
 class ClassEmitter(coreSpec: CoreSpec) {
   import ClassEmitter._
+  import coreSpec.semantics
 
   def genClassDef(clazz: LinkedClass)(implicit ctx: WasmContext): Unit = {
     val classInfo = ctx.getClassInfo(clazz.className)
@@ -373,6 +375,12 @@ class ClassEmitter(coreSpec: CoreSpec) {
         genCloneFunction(clazz)
     }
 
+    // Generate cast functions
+    if (clazz.hasInstanceTests && semantics.asInstanceOfs != CheckedBehavior.Unchecked) {
+      if (className != ObjectClass)
+        genClassCastFunction(clazz)
+    }
+
     // Generate the module accessor
     if (clazz.kind == ClassKind.ModuleClass && clazz.hasInstances) {
       val heapType = watpe.HeapType(genTypeID.forClass(clazz.className))
@@ -408,7 +416,7 @@ class ClassEmitter(coreSpec: CoreSpec) {
       case None    => genTypeID.typeData
       case Some(s) => genTypeID.forVTable(s.name)
     }
-    val structType = watpe.StructType(CoreWasmLib.typeDataStructFields ::: vtableFields)
+    val structType = watpe.StructType(ctx.coreLib.typeDataStructFields ::: vtableFields)
     val subType = watpe.SubType(
       typeID,
       makeDebugName(ns.VTable, className),
@@ -522,6 +530,50 @@ class ClassEmitter(coreSpec: CoreSpec) {
     fb.buildAndAddToModule()
   }
 
+  /** Generate the cast function for an interface.
+   *
+   *  When `asInstanceOfs` are checked, the expression `asInstanceOf[<interface>]`
+   *  will be compiled to a CALL to the function generated by this method.
+   */
+  private def genInterfaceCastFunction(clazz: LinkedClass)(
+      implicit ctx: WasmContext): Unit = {
+    assert(clazz.kind == ClassKind.Interface)
+
+    val className = clazz.className
+    val resultType = TypeTransformer.transformClassType(className, nullable = true)
+
+    val fb = new FunctionBuilder(
+      ctx.moduleBuilder,
+      genFunctionID.asInstance(ClassType(className, nullable = true)),
+      makeDebugName(ns.AsInstance, className),
+      clazz.pos
+    )
+    val objParam = fb.addParam("obj", watpe.RefType.anyref)
+    fb.setResultType(resultType)
+
+    fb.block() { successLabel =>
+      // Succeed if null
+      fb += wa.LocalGet(objParam)
+      fb += wa.BrOnNull(successLabel)
+
+      // Succeed if the instance test succeeds
+      fb += wa.Call(genFunctionID.instanceTest(className))
+      fb += wa.BrIf(successLabel)
+
+      // If we get here, it's a CCE
+      fb += wa.LocalGet(objParam)
+      fb += wa.GlobalGet(genGlobalID.forVTable(className))
+      fb += wa.Call(genFunctionID.classCastException)
+      fb += wa.Unreachable
+    }
+
+    fb += wa.LocalGet(objParam)
+    if (resultType != watpe.RefType.anyref)
+      fb += wa.RefCast(resultType)
+
+    fb.buildAndAddToModule()
+  }
+
   private def genNewDefaultFunc(clazz: LinkedClass)(implicit ctx: WasmContext): Unit = {
     val className = clazz.name.name
     val classInfo = ctx.getClassInfo(className)
@@ -598,6 +650,56 @@ class ClassEmitter(coreSpec: CoreSpec) {
     fb.buildAndAddToModule()
   }
 
+  /** Generate the cast function for a class.
+   *
+   *  When `asInstanceOfs` are checked, the expression `asInstanceOf[<class>]`
+   *  will be compiled to a CALL to the function generated by this method.
+   */
+  private def genClassCastFunction(clazz: LinkedClass)(implicit ctx: WasmContext): Unit = {
+    val className = clazz.className
+
+    val resultType = TypeTransformer.transformClassType(className, nullable = true)
+
+    val fb = new FunctionBuilder(
+      ctx.moduleBuilder,
+      genFunctionID.asInstance(ClassType(clazz.className, nullable = true)),
+      makeDebugName(ns.AsInstance, className),
+      clazz.pos
+    )
+    val objParam = fb.addParam("obj", watpe.RefType.anyref)
+    fb.setResultType(resultType)
+
+    fb.block(resultType) { successLabel =>
+      fb += wa.LocalGet(objParam)
+
+      if (className == SpecialNames.JLNumberClass) {
+        /* jl.Number is special, because it is the only non-Object *class*
+         * that is an  ancestor of a hijacked class.
+         */
+        fb += wa.BrOnCast(successLabel, watpe.RefType.anyref,
+            watpe.RefType.nullable(genTypeID.forClass(SpecialNames.JLNumberClass)))
+
+        /* The `obj` still on the stack will be used for:
+         * a) the result in the true case
+         * b) consistency with non-Number in the false case
+         */
+
+        fb += wa.LocalGet(objParam)
+        fb += wa.Call(genFunctionID.typeTest(DoubleRef))
+        fb += wa.BrIf(successLabel)
+      } else {
+        fb += wa.BrOnCast(successLabel, watpe.RefType.anyref, resultType)
+      }
+
+      // If we get here, it's a CCE -- `obj` is still on the stack
+      fb += wa.GlobalGet(genGlobalID.forVTable(className))
+      fb += wa.Call(genFunctionID.classCastException)
+      fb += wa.Unreachable
+    }
+
+    fb.buildAndAddToModule()
+  }
+
   private def genModuleAccessor(clazz: LinkedClass)(implicit ctx: WasmContext): Unit = {
     assert(clazz.kind == ClassKind.ModuleClass)
 
@@ -685,8 +787,11 @@ class ClassEmitter(coreSpec: CoreSpec) {
       itableType
     )
 
-    if (clazz.hasInstanceTests)
+    if (clazz.hasInstanceTests) {
       genInterfaceInstanceTest(clazz)
+      if (semantics.asInstanceOfs != CheckedBehavior.Unchecked)
+        genInterfaceCastFunction(clazz)
+    }
   }
 
   private def genJSClass(clazz: LinkedClass)(implicit ctx: WasmContext): Unit = {
@@ -1262,6 +1367,7 @@ object ClassEmitter {
     val JSClassValueCache = UTF8String("b.")
     val TypeData = UTF8String("d.")
     val IsInstance = UTF8String("is.")
+    val AsInstance = UTF8String("as.")
 
     // Shared with JS backend -- string
     val TopLevelExport = UTF8String("e.")
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
index 855c37f888..e9c9f0d3a3 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
@@ -13,9 +13,13 @@
 package org.scalajs.linker.backend.wasmemitter
 
 import org.scalajs.ir.Names._
+import org.scalajs.ir.OriginalName.NoOriginalName
 import org.scalajs.ir.Trees.{JSUnaryOp, JSBinaryOp, MemberNamespace}
 import org.scalajs.ir.Types.{Type => _, ArrayType => _, _}
-import org.scalajs.ir.{OriginalName, Position}
+import org.scalajs.ir.{OriginalName, Position, Types => irtpe}
+
+import org.scalajs.linker.interface.CheckedBehavior
+import org.scalajs.linker.standard.CoreSpec
 
 import org.scalajs.linker.backend.webassembly._
 import org.scalajs.linker.backend.webassembly.Instructions._
@@ -27,8 +31,9 @@ import EmbeddedConstants._
 import VarGen._
 import TypeTransformer._
 
-object CoreWasmLib {
+final class CoreWasmLib(coreSpec: CoreSpec) {
   import RefType.anyref
+  import coreSpec.semantics
 
   private implicit val noPos: Position = Position.NoPosition
 
@@ -363,6 +368,7 @@ object CoreWasmLib {
     addHelperImport(genFunctionID.isString, List(anyref), List(Int32))
 
     addHelperImport(genFunctionID.jsValueType, List(RefType.any), List(Int32))
+    addHelperImport(genFunctionID.jsValueDescription, List(anyref), List(RefType.any))
     addHelperImport(genFunctionID.bigintHashCode, List(RefType.any), List(Int32))
     addHelperImport(
       genFunctionID.symbolDescription,
@@ -590,6 +596,15 @@ object CoreWasmLib {
     genCreateClassOf()
     genGetClassOf()
     genArrayTypeData()
+
+    if (semantics.asInstanceOfs != CheckedBehavior.Unchecked) {
+      genValueDescription()
+      genClassCastException()
+      genPrimitiveAsInstances()
+      genArrayAsInstances()
+    }
+
+    genIsInstanceExternal()
     genIsInstance()
     genIsAssignableFromExternal()
     genIsAssignableFrom()
@@ -908,7 +923,7 @@ object CoreWasmLib {
     fb += Call(genFunctionID.jsObjectPush)
     // "isInstance": closure(isInstance, typeData)
     fb ++= ctx.stringPool.getConstantStringInstr("isInstance")
-    fb += ctx.refFuncWithDeclaration(genFunctionID.isInstance)
+    fb += ctx.refFuncWithDeclaration(genFunctionID.isInstanceExternal)
     fb += LocalGet(typeDataParam)
     fb += Call(genFunctionID.closure)
     fb += Call(genFunctionID.jsObjectPush)
@@ -982,6 +997,273 @@ object CoreWasmLib {
     fb.buildAndAddToModule()
   }
 
+  /** `valueDescription: anyref -> (ref any)` (a string).
+   *
+   *  Returns a safe string description of a value. This helper is never called
+   *  for `value === null`. As implemented, it would return `"object"` if it were.
+   */
+  private def genValueDescription()(implicit ctx: WasmContext): Unit = {
+    val objectType = RefType(genTypeID.ObjectStruct)
+
+    val fb = newFunctionBuilder(genFunctionID.valueDescription)
+    val valueParam = fb.addParam("value", anyref)
+    fb.setResultType(RefType.any)
+
+    fb.block(anyref) { notOurObjectLabel =>
+      fb.block(objectType) { isCharLabel =>
+        fb.block(objectType) { isLongLabel =>
+          // If it not our object, jump out of notOurObject
+          fb += LocalGet(valueParam)
+          fb += BrOnCastFail(notOurObjectLabel, anyref, objectType)
+
+          // If is a long or char box, jump out to the appropriate label
+          fb += BrOnCast(isLongLabel, objectType, RefType(genTypeID.forClass(SpecialNames.LongBoxClass)))
+          fb += BrOnCast(isCharLabel, objectType, RefType(genTypeID.forClass(SpecialNames.CharBoxClass)))
+
+          // Get and return the class name
+          fb += StructGet(genTypeID.ObjectStruct, genFieldID.objStruct.vtable)
+          fb += ReturnCall(genFunctionID.typeDataName)
+        }
+
+        // Return the constant string "long"
+        fb ++= ctx.stringPool.getConstantStringInstr("long")
+        fb += Return
+      }
+
+      // Return the constant string "char"
+      fb ++= ctx.stringPool.getConstantStringInstr("char")
+      fb += Return
+    }
+
+    // When it is not one of our objects, use the JS helper
+    fb += Call(genFunctionID.jsValueDescription)
+
+    fb.buildAndAddToModule()
+  }
+
+  /** `classCastException: [anyref, (ref typeData)] -> void`.
+   *
+   *  This function always throws. It should be followed by an `unreachable`
+   *  statement.
+   */
+  private def genClassCastException()(implicit ctx: WasmContext): Unit = {
+    val typeDataType = RefType(genTypeID.typeData)
+
+    val fb = newFunctionBuilder(genFunctionID.classCastException)
+    val objParam = fb.addParam("obj", anyref)
+    val typeDataParam = fb.addParam("typeData", typeDataType)
+
+    maybeWrapInUBE(fb, semantics.asInstanceOfs) {
+      genNewScalaClass(fb, ClassCastExceptionClass, SpecialNames.StringArgConstructorName) {
+        fb += LocalGet(objParam)
+        fb += Call(genFunctionID.valueDescription)
+
+        fb ++= ctx.stringPool.getConstantStringInstr(" cannot be cast to ")
+        fb += Call(genFunctionID.stringConcat)
+
+        fb += LocalGet(typeDataParam)
+        fb += Call(genFunctionID.typeDataName)
+        fb += Call(genFunctionID.stringConcat)
+      }
+    }
+
+    fb += ExternConvertAny
+    fb += Throw(genTagID.exception)
+
+    fb.buildAndAddToModule()
+  }
+
+  /** Generates the `asInstance` functions for primitive types.
+   */
+  private def genPrimitiveAsInstances()(implicit ctx: WasmContext): Unit = {
+    val primTypesWithAsInstances: List[PrimType] = List(
+      UndefType,
+      BooleanType,
+      CharType,
+      ByteType,
+      ShortType,
+      IntType,
+      LongType,
+      FloatType,
+      DoubleType,
+      StringType
+    )
+
+    for (primType <- primTypesWithAsInstances) {
+      // asInstanceOf[PrimType]
+      genPrimitiveOrBoxedClassAsInstance(primType, targetTpe = primType, isUnbox = true)
+
+      // asInstanceOf[BoxedClass]
+      val boxedClassType = ClassType(PrimTypeToBoxedClass(primType), nullable = true)
+      genPrimitiveOrBoxedClassAsInstance(primType, targetTpe = boxedClassType, isUnbox = false)
+    }
+  }
+
+  /** Common logic for primitives and boxed classes in `genPrimitiveAsInstances`. */
+  private def genPrimitiveOrBoxedClassAsInstance(primType: PrimType,
+      targetTpe: irtpe.Type, isUnbox: Boolean)(
+      implicit ctx: WasmContext): Unit = {
+
+    val origName = OriginalName("as." + targetTpe.show())
+
+    val resultType = TypeTransformer.transformSingleType(targetTpe)
+
+    val fb = newFunctionBuilder(genFunctionID.asInstance(targetTpe), origName)
+    val objParam = fb.addParam("obj", RefType.anyref)
+    fb.setResultType(resultType)
+
+    fb.block() { objIsNullLabel =>
+      primType match {
+        // For char and long, use br_on_cast_fail to test+cast to the box class
+        case CharType | LongType =>
+          val boxClass =
+            if (primType == CharType) SpecialNames.CharBoxClass
+            else SpecialNames.LongBoxClass
+          val structTypeID = genTypeID.forClass(boxClass)
+
+          fb.block(RefType.anyref) { castFailLabel =>
+            fb += LocalGet(objParam)
+            fb += BrOnNull(objIsNullLabel)
+            fb += BrOnCastFail(castFailLabel, RefType.anyref, RefType(structTypeID))
+
+            // Extract the `value` field if unboxing
+            if (isUnbox) {
+              val fieldName = FieldName(boxClass, SpecialNames.valueFieldSimpleName)
+              fb += StructGet(structTypeID, genFieldID.forClassInstanceField(fieldName))
+            }
+
+            fb += Return
+          }
+
+        // For all other types, use type test, and separately unbox if required
+        case _ =>
+          fb += LocalGet(objParam)
+          fb += BrOnNull(objIsNullLabel)
+
+          // if obj.isInstanceOf[primType]
+          primType match {
+            case UndefType =>
+              fb += Call(genFunctionID.isUndef)
+            case StringType =>
+              fb += Call(genFunctionID.isString)
+            case primType: PrimTypeWithRef =>
+              fb += Call(genFunctionID.typeTest(primType.primRef))
+          }
+          fb.ifThen() {
+            // then, unbox if required then return
+            if (isUnbox) {
+              primType match {
+                case UndefType =>
+                  fb += GlobalGet(genGlobalID.undef)
+                case StringType =>
+                  fb += LocalGet(objParam)
+                  fb += RefAsNonNull
+                case primType: PrimTypeWithRef =>
+                  fb += LocalGet(objParam)
+                  fb += Call(genFunctionID.unbox(primType.primRef))
+              }
+            } else {
+              fb += LocalGet(objParam)
+            }
+
+            fb += Return
+          }
+
+          // Fall through for CCE
+          fb += LocalGet(objParam)
+      }
+
+      // If we get here, it is a CCE
+      fb += GlobalGet(genGlobalID.forVTable(PrimTypeToBoxedClass(primType)))
+      fb += Call(genFunctionID.classCastException)
+      fb += Unreachable
+    }
+
+    // obj is null -- load the zero of the target type (which is `null` for boxed classes)
+    fb += SWasmGen.genZeroOf(targetTpe)
+
+    fb.buildAndAddToModule()
+  }
+
+  private def genArrayAsInstances()(implicit ctx: WasmContext): Unit = {
+    for (baseRef <- arrayBaseRefs)
+      genBaseArrayAsInstance(baseRef)
+
+    genAsSpecificRefArray()
+  }
+
+  private def genBaseArrayAsInstance(baseRef: NonArrayTypeRef)(implicit ctx: WasmContext): Unit = {
+    val arrayTypeRef = ArrayTypeRef(baseRef, 1)
+
+    val wasmTypeID = genTypeID.forArrayClass(arrayTypeRef)
+    val resultType = RefType.nullable(wasmTypeID)
+
+    val fb = newFunctionBuilder(
+      genFunctionID.asInstance(irtpe.ArrayType(arrayTypeRef, nullable = true)),
+      OriginalName("asArray." + baseRef.displayName)
+    )
+    val objParam = fb.addParam("obj", anyref)
+    fb.setResultType(resultType)
+
+    fb.block(resultType) { successLabel =>
+      fb += LocalGet(objParam)
+      fb += BrOnCast(successLabel, anyref, resultType)
+
+      // If we get here, it's a CCE -- `obj` is still on the stack
+      fb += GlobalGet(genGlobalID.forVTable(baseRef))
+      fb += I32Const(1)
+      fb += Call(genFunctionID.arrayTypeData)
+      fb += Call(genFunctionID.classCastException)
+      fb += Unreachable
+    }
+
+    fb.buildAndAddToModule()
+  }
+
+  private def genAsSpecificRefArray()(implicit ctx: WasmContext): Unit = {
+    val refArrayStructTypeID = genTypeID.forArrayClass(ArrayTypeRef(ClassRef(ObjectClass), 1))
+    val resultType = RefType.nullable(refArrayStructTypeID)
+
+    val fb = newFunctionBuilder(genFunctionID.asSpecificRefArray)
+    val objParam = fb.addParam("obj", anyref)
+    val arrayTypeDataParam = fb.addParam("arrayTypeData", RefType(genTypeID.typeData))
+    fb.setResultType(resultType)
+
+    val refArrayLocal = fb.addLocal("refArray", RefType(refArrayStructTypeID))
+
+    fb.block(resultType) { successLabel =>
+      fb.block() { isNullLabel =>
+        fb.block(anyref) { failureLabel =>
+          // If obj is null, return null
+          fb += LocalGet(objParam)
+          fb += BrOnNull(isNullLabel)
+
+          // Otherwise, if we cannot cast to ObjectArray, fail
+          fb += BrOnCastFail(failureLabel, RefType.any, RefType(refArrayStructTypeID))
+          fb += LocalTee(refArrayLocal) // leave it on the stack for BrIf or for fall through to CCE
+
+          // Otherwise, test assignability of the array type
+          fb += LocalGet(arrayTypeDataParam)
+          fb += LocalGet(refArrayLocal)
+          fb += StructGet(genTypeID.ObjectStruct, genFieldID.objStruct.vtable)
+          fb += Call(genFunctionID.isAssignableFrom)
+
+          // If true, jump to success
+          fb += BrIf(successLabel)
+        }
+
+        // If we get here, it's a CCE -- `obj` is still on the stack
+        fb += LocalGet(arrayTypeDataParam)
+        fb += Call(genFunctionID.classCastException)
+        fb += Unreachable // for clarity; technically redundant since the stacks align
+      }
+
+      fb += RefNull(HeapType.None)
+    }
+
+    fb.buildAndAddToModule()
+  }
+
   /** `arrayTypeData: (ref typeData), i32 -> (ref vtable.java.lang.Object)`.
    *
    *  Returns the typeData/vtable of an array with `dims` dimensions over the given typeData. `dims`
@@ -1116,13 +1398,34 @@ object CoreWasmLib {
     fb.buildAndAddToModule()
   }
 
-  /** `isInstance: (ref typeData), anyref -> anyref` (a boxed boolean).
+  /** `isInstanceExternal: (ref typeData), anyref -> anyref` (a boxed boolean).
    *
    *  Tests whether the given value is a non-null instance of the given type.
    *
    *  Specified by `"isInstance"` at
    *  [[https://lampwww.epfl.ch/~doeraene/sjsir-semantics/#sec-sjsir-createclassdataof]].
    */
+  private def genIsInstanceExternal()(implicit ctx: WasmContext): Unit = {
+    val fb = newFunctionBuilder(genFunctionID.isInstanceExternal)
+    val typeDataParam = fb.addParam("typeData", RefType(genTypeID.typeData))
+    val valueParam = fb.addParam("value", RefType.anyref)
+    fb.setResultType(anyref)
+
+    fb += LocalGet(typeDataParam)
+    fb += LocalGet(valueParam)
+    fb += Call(genFunctionID.isInstance)
+    fb += Call(genFunctionID.box(BooleanRef))
+
+    fb.buildAndAddToModule()
+  }
+
+  /** `isInstance: (ref typeData), anyref -> i32` (a boolean).
+   *
+   *  Tests whether the given value is a non-null instance of the given type.
+   *
+   *  Internal implementation of `isInstanceExternal`, returning a primitive
+   *  `i32` instead of a boxed boolean.
+   */
   private def genIsInstance()(implicit ctx: WasmContext): Unit = {
     import genFieldID.typeData._
 
@@ -1132,7 +1435,7 @@ object CoreWasmLib {
     val fb = newFunctionBuilder(genFunctionID.isInstance)
     val typeDataParam = fb.addParam("typeData", typeDataType)
     val valueParam = fb.addParam("value", RefType.anyref)
-    fb.setResultType(anyref)
+    fb.setResultType(Int32)
 
     val valueNonNullLocal = fb.addLocal("valueNonNull", RefType.any)
     val specialInstanceTypesLocal = fb.addLocal("specialInstanceTypes", Int32)
@@ -1208,7 +1511,6 @@ object CoreWasmLib {
 
           // Call the function
           fb += CallRef(genTypeID.isJSClassInstanceFuncType)
-          fb += Call(genFunctionID.box(BooleanRef))
           fb += Return
         }
         fb += Drop // drop `value` which was left on the stack
@@ -1232,7 +1534,7 @@ object CoreWasmLib {
       fb.block(RefType.any) { nonNullLabel =>
         fb += LocalGet(valueParam)
         fb += BrOnNonNull(nonNullLabel)
-        fb += GlobalGet(genGlobalID.bFalse)
+        fb += I32Const(0)
         fb += Return
       }
       fb += LocalSet(valueNonNullLocal)
@@ -1278,7 +1580,6 @@ object CoreWasmLib {
         fb.ifThen() {
           // then return true
           fb += I32Const(1)
-          fb += Call(genFunctionID.box(BooleanRef))
           fb += Return
         }
       }
@@ -1295,7 +1596,7 @@ object CoreWasmLib {
         fb += BrOnCast(ourObjectLabel, RefType.any, objectRefType)
 
         // on cast fail, return false
-        fb += GlobalGet(genGlobalID.bFalse)
+        fb += I32Const(0)
         fb += Return
       }
       fb += StructGet(genTypeID.ObjectStruct, genFieldID.objStruct.vtable)
@@ -1304,8 +1605,6 @@ object CoreWasmLib {
       fb += Call(genFunctionID.isAssignableFrom)
     }
 
-    fb += Call(genFunctionID.box(BooleanRef))
-
     fb.buildAndAddToModule()
   }
 
@@ -1461,7 +1760,7 @@ object CoreWasmLib {
     fb.buildAndAddToModule()
   }
 
-  /** `checkCast: (ref typeData), anyref -> anyref`.
+  /** `checkCast: (ref typeData), anyref -> []`.
    *
    *  Casts the given value to the given type; subject to undefined behaviors.
    */
@@ -1471,13 +1770,34 @@ object CoreWasmLib {
     val fb = newFunctionBuilder(genFunctionID.checkCast)
     val typeDataParam = fb.addParam("typeData", typeDataType)
     val valueParam = fb.addParam("value", RefType.anyref)
-    fb.setResultType(RefType.anyref)
 
-    /* Given that we only implement `CheckedBehavior.Unchecked` semantics for
-     * now, this is always the identity.
-     */
+    if (semantics.asInstanceOfs != CheckedBehavior.Unchecked) {
+      fb.block() { successLabel =>
+        // If typeData.kind == KindJSType, succeed
+        fb += LocalGet(typeDataParam)
+        fb += StructGet(genTypeID.typeData, genFieldID.typeData.kind)
+        fb += I32Const(KindJSType)
+        fb += I32Eq
+        fb += BrIf(successLabel)
 
-    fb += LocalGet(valueParam)
+        // If value is null, succeed
+        fb += LocalGet(valueParam)
+        fb += RefIsNull // consumes `value`, unlike `BrOnNull` which would leave it on the stack
+        fb += BrIf(successLabel)
+
+        // If isInstance(typeData, value), succeed
+        fb += LocalGet(typeDataParam)
+        fb += LocalGet(valueParam)
+        fb += Call(genFunctionID.isInstance)
+        fb += BrIf(successLabel)
+
+        // Otherwise, it is a CCE
+        fb += LocalGet(valueParam)
+        fb += LocalGet(typeDataParam)
+        fb += Call(genFunctionID.classCastException)
+        fb += Unreachable // for clarity; technically redundant since the stacks align
+      }
+    }
 
     fb.buildAndAddToModule()
   }
@@ -2324,4 +2644,27 @@ object CoreWasmLib {
     fb.buildAndAddToModule()
   }
 
+  private def maybeWrapInUBE(fb: FunctionBuilder, behavior: CheckedBehavior)(
+      genExceptionInstance: => Unit): Unit = {
+    if (behavior == CheckedBehavior.Fatal) {
+      genNewScalaClass(fb, SpecialNames.UndefinedBehaviorErrorClass,
+          SpecialNames.ThrowableArgConsructorName) {
+        genExceptionInstance
+      }
+    } else {
+      genExceptionInstance
+    }
+  }
+
+  private def genNewScalaClass(fb: FunctionBuilder, cls: ClassName, ctor: MethodName)(
+      genCtorArgs: => Unit): Unit = {
+    val instanceLocal = fb.addLocal(NoOriginalName, RefType(genTypeID.forClass(cls)))
+
+    fb += Call(genFunctionID.newDefault(cls))
+    fb += LocalTee(instanceLocal)
+    genCtorArgs
+    fb += Call(genFunctionID.forMethod(MemberNamespace.Constructor, cls, ctor))
+    fb += LocalGet(instanceLocal)
+  }
+
 }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala
index 0a477f6a59..145739a409 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala
@@ -44,10 +44,13 @@ import org.scalajs.linker.backend.javascript.ByteArrayWriter
 final class Emitter(config: Emitter.Config) {
   import Emitter._
 
-  private val classEmitter = new ClassEmitter(config.coreSpec)
+  private val coreSpec = config.coreSpec
+
+  private val coreLib = new CoreWasmLib(coreSpec)
+  private val classEmitter = new ClassEmitter(coreSpec)
 
   val symbolRequirements: SymbolRequirement =
-    Emitter.symbolRequirements(config.coreSpec)
+    Emitter.symbolRequirements(coreSpec)
 
   val injectedIRFiles: Seq[IRFile] = PrivateLibHolder.files
 
@@ -77,13 +80,13 @@ final class Emitter(config: Emitter.Config) {
     val moduleInitializers = module.initializers.toList
 
     implicit val ctx: WasmContext =
-      Preprocessor.preprocess(sortedClasses, topLevelExports)
+      Preprocessor.preprocess(coreSpec, coreLib, sortedClasses, topLevelExports)
 
-    CoreWasmLib.genPreClasses()
+    coreLib.genPreClasses()
     genExternalModuleImports(module)
     sortedClasses.foreach(classEmitter.genClassDef(_))
     topLevelExports.foreach(classEmitter.genTopLevelExport(_))
-    CoreWasmLib.genPostClasses()
+    coreLib.genPostClasses()
 
     genStartFunction(sortedClasses, moduleInitializers, topLevelExports)
 
@@ -383,16 +386,37 @@ object Emitter {
    *  linker frontend will dead-code eliminate our box classes.
    */
   private def symbolRequirements(coreSpec: CoreSpec): SymbolRequirement = {
-    val factory = SymbolRequirement.factory("wasm")
+    import coreSpec.semantics._
+    import CheckedBehavior._
+    import SpecialNames._
+
+    val factory = SymbolRequirement.factory("emitter")
+    import factory._
+
+    def cond(p: Boolean)(v: => SymbolRequirement): SymbolRequirement =
+      if (p) v else none()
+
+    def isAnyFatal(behaviors: CheckedBehavior*): Boolean =
+      behaviors.contains(Fatal)
+
+    multiple(
+      cond(asInstanceOfs != Unchecked) {
+        instantiateClass(ClassCastExceptionClass, StringArgConstructorName)
+      },
+
+      cond(isAnyFatal(asInstanceOfs, arrayIndexOutOfBounds, arrayStores,
+          negativeArraySizes, nullPointers, stringIndexOutOfBounds)) {
+        instantiateClass(UndefinedBehaviorErrorClass,
+            ThrowableArgConsructorName)
+      },
 
-    factory.multiple(
       // TODO Ideally we should not require these, but rather adapt to their absence
-      factory.instantiateClass(ClassClass, AnyArgConstructorName),
-      factory.instantiateClass(JSExceptionClass, AnyArgConstructorName),
+      instantiateClass(ClassClass, AnyArgConstructorName),
+      instantiateClass(JSExceptionClass, AnyArgConstructorName),
 
       // See genIdentityHashCode in HelperFunctions
-      factory.callMethodStatically(BoxedDoubleClass, hashCodeMethodName),
-      factory.callMethodStatically(BoxedStringClass, hashCodeMethodName)
+      callMethodStatically(BoxedDoubleClass, hashCodeMethodName),
+      callMethodStatically(BoxedStringClass, hashCodeMethodName)
     )
   }
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
index 5fecd5dbd2..8ce4030ea8 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
@@ -22,6 +22,7 @@ import org.scalajs.ir.OriginalName.NoOriginalName
 import org.scalajs.ir.Trees._
 import org.scalajs.ir.Types._
 
+import org.scalajs.linker.interface.CheckedBehavior
 import org.scalajs.linker.backend.emitter.Transients
 
 import org.scalajs.linker.backend.webassembly._
@@ -291,6 +292,9 @@ private class FunctionEmitter private (
 )(implicit ctx: WasmContext) {
   import FunctionEmitter._
 
+  private val coreSpec = ctx.coreSpec
+  import coreSpec.semantics
+
   private var closureIdx: Int = 0
   private var currentEnv: Env = paramsEnv
 
@@ -1786,7 +1790,38 @@ private class FunctionEmitter private (
   private def genAsInstanceOf(tree: AsInstanceOf): Type = {
     val AsInstanceOf(expr, targetTpe) = tree
 
-    genCast(expr, targetTpe, tree.pos)
+    if (semantics.asInstanceOfs == CheckedBehavior.Unchecked)
+      genCast(expr, targetTpe, tree.pos)
+    else
+      genCheckedCast(expr, targetTpe, tree.pos)
+  }
+
+  private def genCheckedCast(expr: Tree, targetTpe: Type, pos: Position): Type = {
+    genTree(expr, AnyType)
+
+    markPosition(pos)
+
+    targetTpe match {
+      case AnyType | ClassType(ObjectClass, true) =>
+        // no-op
+        ()
+
+      case ArrayType(arrayTypeRef, true) =>
+        arrayTypeRef match {
+          case ArrayTypeRef(ClassRef(ObjectClass) | _: PrimRef, 1) =>
+            // For primitive arrays and exactly Array[Object], we have a dedicated function
+            fb += wa.Call(genFunctionID.asInstance(targetTpe))
+          case _ =>
+            // For other array types, we must use the generic function
+            genLoadArrayTypeData(fb, arrayTypeRef)
+            fb += wa.Call(genFunctionID.asSpecificRefArray)
+        }
+
+      case _ =>
+        fb += wa.Call(genFunctionID.asInstance(targetTpe))
+    }
+
+    targetTpe
   }
 
   private def genCast(expr: Tree, targetTpe: Type, pos: Position): Type = {
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala
index 01614586c1..d6b338eca0 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala
@@ -172,6 +172,14 @@ const scalaJSHelpers = {
     return $JSValueTypeOther;
   },
 
+  // JS side of the `valueDescription` helper
+  // TODO: only emit this when required by checked behaviors
+  jsValueDescription: ((x) =>
+    (typeof x === 'number')
+      ? (Object.is(x, -0) ? "number(-0)" : ("number(" + x + ")"))
+      : (typeof x)
+  ),
+
   // Identity hash code
   bigintHashCode,
   symbolDescription: (x) => {
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Preprocessor.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Preprocessor.scala
index 1aa1ea6f2f..2568fcb1fd 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Preprocessor.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Preprocessor.scala
@@ -19,13 +19,14 @@ import org.scalajs.ir.Trees._
 import org.scalajs.ir.Types._
 import org.scalajs.ir.{ClassKind, Traversers}
 
-import org.scalajs.linker.standard.{LinkedClass, LinkedTopLevelExport}
+import org.scalajs.linker.standard.{CoreSpec, LinkedClass, LinkedTopLevelExport}
 
 import EmbeddedConstants._
 import WasmContext._
 
 object Preprocessor {
-  def preprocess(classes: List[LinkedClass], tles: List[LinkedTopLevelExport]): WasmContext = {
+  def preprocess(coreSpec: CoreSpec, coreLib: CoreWasmLib,
+      classes: List[LinkedClass], tles: List[LinkedTopLevelExport]): WasmContext = {
     val staticFieldMirrors = computeStaticFieldMirrors(tles)
 
     val specialInstanceTypes = computeSpecialInstanceTypes(classes)
@@ -62,7 +63,8 @@ object Preprocessor {
     // sort for stability
     val reflectiveProxyIDs = definedReflectiveProxyNames.toList.sorted.zipWithIndex.toMap
 
-    new WasmContext(classInfos, reflectiveProxyIDs, itableBucketCount)
+    new WasmContext(coreSpec, coreLib, classInfos, reflectiveProxyIDs,
+        itableBucketCount)
   }
 
   private def computeStaticFieldMirrors(
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/SpecialNames.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/SpecialNames.scala
index 9a060bc3b4..00b858c39e 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/SpecialNames.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/SpecialNames.scala
@@ -28,9 +28,14 @@ object SpecialNames {
   val CharBoxCtor = MethodName.constructor(List(CharRef))
   val LongBoxCtor = MethodName.constructor(List(LongRef))
 
+  val JLNumberClass = ClassName("java.lang.Number")
+
   // js.JavaScriptException, for WrapAsThrowable and UnwrapFromThrowable
   val JSExceptionClass = ClassName("scala.scalajs.js.JavaScriptException")
 
+  val UndefinedBehaviorErrorClass =
+    ClassName("org.scalajs.linker.runtime.UndefinedBehaviorError")
+
   // Field names
 
   val valueFieldSimpleName = SimpleFieldName("value")
@@ -40,6 +45,8 @@ object SpecialNames {
   // Method names
 
   val AnyArgConstructorName = MethodName.constructor(List(ClassRef(ObjectClass)))
+  val StringArgConstructorName = MethodName.constructor(List(ClassRef(BoxedStringClass)))
+  val ThrowableArgConsructorName = MethodName.constructor(List(ClassRef(ThrowableClass)))
 
   val hashCodeMethodName = MethodName("hashCode", Nil, IntRef)
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
index aafdf2f98b..fc25891dc2 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
@@ -77,6 +77,8 @@ object VarGen {
     final case class clone(className: ClassName) extends FunctionID
     final case class cloneArray(arrayBaseRef: NonArrayTypeRef) extends FunctionID
 
+    final case class asInstance(targetTpe: Type) extends FunctionID
+
     final case class isJSClassInstance(className: ClassName) extends FunctionID
     final case class loadJSClass(className: ClassName) extends FunctionID
     final case class createJSClassOf(className: ClassName) extends FunctionID
@@ -133,6 +135,7 @@ object VarGen {
     case object isString extends JSHelperFunctionID
 
     case object jsValueType extends JSHelperFunctionID
+    case object jsValueDescription extends JSHelperFunctionID
     case object bigintHashCode extends JSHelperFunctionID
     case object symbolDescription extends JSHelperFunctionID
     case object idHashCodeGet extends JSHelperFunctionID
@@ -220,6 +223,10 @@ object VarGen {
     case object createClassOf extends FunctionID
     case object getClassOf extends FunctionID
     case object arrayTypeData extends FunctionID
+    case object valueDescription extends FunctionID
+    case object classCastException extends FunctionID
+    case object asSpecificRefArray extends FunctionID
+    case object isInstanceExternal extends FunctionID
     case object isInstance extends FunctionID
     case object isAssignableFromExternal extends FunctionID
     case object isAssignableFrom extends FunctionID
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/WasmContext.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/WasmContext.scala
index aa230752a3..f5eb6dd89e 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/WasmContext.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/WasmContext.scala
@@ -25,8 +25,7 @@ import org.scalajs.ir.Types._
 
 import org.scalajs.linker.interface.ModuleInitializer
 import org.scalajs.linker.interface.unstable.ModuleInitializerImpl
-import org.scalajs.linker.standard.LinkedTopLevelExport
-import org.scalajs.linker.standard.LinkedClass
+import org.scalajs.linker.standard.{CoreSpec, LinkedClass, LinkedTopLevelExport}
 
 import org.scalajs.linker.backend.webassembly.ModuleBuilder
 import org.scalajs.linker.backend.webassembly.{Instructions => wa}
@@ -38,6 +37,8 @@ import VarGen._
 import org.scalajs.ir.OriginalName
 
 final class WasmContext(
+    val coreSpec: CoreSpec,
+    val coreLib: CoreWasmLib,
     classInfo: Map[ClassName, WasmContext.ClassInfo],
     reflectiveProxies: Map[MethodName, Int],
     val itablesLength: Int
diff --git a/project/Build.scala b/project/Build.scala
index 5ccf4893b2..63990ee237 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -59,16 +59,23 @@ object ExposedValues extends AutoPlugin {
       settingKey("enable the WebAssembly backend everywhere, including additional required linker config")
 
     // set scalaJSLinkerConfig in someProject ~= makeCompliant
-    val makeCompliant: StandardConfig => StandardConfig = {
-      _.withSemantics { semantics =>
-        semantics
-          .withAsInstanceOfs(CheckedBehavior.Compliant)
-          .withArrayIndexOutOfBounds(CheckedBehavior.Compliant)
-          .withArrayStores(CheckedBehavior.Compliant)
-          .withNegativeArraySizes(CheckedBehavior.Compliant)
-          .withNullPointers(CheckedBehavior.Compliant)
-          .withStringIndexOutOfBounds(CheckedBehavior.Compliant)
-          .withModuleInit(CheckedBehavior.Compliant)
+    val makeCompliant: StandardConfig => StandardConfig = { prev =>
+      if (prev.experimentalUseWebAssembly) {
+        prev.withSemantics { semantics =>
+          semantics
+            .withAsInstanceOfs(CheckedBehavior.Compliant)
+        }
+      } else {
+        prev.withSemantics { semantics =>
+          semantics
+            .withAsInstanceOfs(CheckedBehavior.Compliant)
+            .withArrayIndexOutOfBounds(CheckedBehavior.Compliant)
+            .withArrayStores(CheckedBehavior.Compliant)
+            .withNegativeArraySizes(CheckedBehavior.Compliant)
+            .withNullPointers(CheckedBehavior.Compliant)
+            .withStringIndexOutOfBounds(CheckedBehavior.Compliant)
+            .withModuleInit(CheckedBehavior.Compliant)
+        }
       }
     }
 
@@ -166,7 +173,6 @@ object MyScalaJSPlugin extends AutoPlugin {
             .withModuleKind(ModuleKind.ESModule)
             .withSemantics { sems =>
               sems
-                .withAsInstanceOfs(Unchecked)
                 .withArrayIndexOutOfBounds(Unchecked)
                 .withArrayStores(Unchecked)
                 .withNegativeArraySizes(Unchecked)

From 89dddcdf76ad11b7de54179afc0afd49018a008f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Mon, 24 Jun 2024 23:10:34 +0200
Subject: [PATCH 136/298] Wasm: Implement checked stringIndexOutOfBounds.

---
 .../backend/WebAssemblyLinkerBackend.scala    |  1 -
 .../backend/wasmemitter/CoreWasmLib.scala     | 40 +++++++++++++++++++
 .../linker/backend/wasmemitter/Emitter.scala  |  5 +++
 .../backend/wasmemitter/FunctionEmitter.scala |  5 ++-
 .../backend/wasmemitter/SpecialNames.scala    |  1 +
 .../linker/backend/wasmemitter/VarGen.scala   |  1 +
 project/Build.scala                           |  2 +-
 7 files changed, 52 insertions(+), 3 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/WebAssemblyLinkerBackend.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/WebAssemblyLinkerBackend.scala
index eb264753d4..3bac291a05 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/WebAssemblyLinkerBackend.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/WebAssemblyLinkerBackend.scala
@@ -41,7 +41,6 @@ final class WebAssemblyLinkerBackend(config: LinkerBackendImpl.Config)
     coreSpec.semantics.arrayStores == CheckedBehavior.Unchecked &&
     coreSpec.semantics.negativeArraySizes == CheckedBehavior.Unchecked &&
     coreSpec.semantics.nullPointers == CheckedBehavior.Unchecked &&
-    coreSpec.semantics.stringIndexOutOfBounds == CheckedBehavior.Unchecked &&
     coreSpec.semantics.moduleInit == CheckedBehavior.Unchecked,
     "The WebAssembly backend currently only supports CheckedBehavior.Unchecked semantics; " +
     s"was ${coreSpec.semantics}."
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
index e9c9f0d3a3..c542d820dc 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
@@ -604,6 +604,10 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
       genArrayAsInstances()
     }
 
+    if (semantics.stringIndexOutOfBounds != CheckedBehavior.Unchecked) {
+      genCheckedStringCharAt()
+    }
+
     genIsInstanceExternal()
     genIsInstance()
     genIsAssignableFromExternal()
@@ -1398,6 +1402,42 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
     fb.buildAndAddToModule()
   }
 
+  /** `checkedStringCharAt: (ref any), i32 -> i32`.
+   *
+   *  Accesses a char of a string by index. Used when stringIndexOutOfBounds
+   *  are checked.
+   */
+  private def genCheckedStringCharAt()(implicit ctx: WasmContext): Unit = {
+    val fb = newFunctionBuilder(genFunctionID.checkedStringCharAt)
+    val strParam = fb.addParam("str", RefType.any)
+    val indexParam = fb.addParam("index", Int32)
+    fb.setResultType(Int32)
+
+    // if index unsigned_>= str.length
+    fb += LocalGet(indexParam)
+    fb += LocalGet(strParam)
+    fb += Call(genFunctionID.stringLength)
+    fb += I32GeU // unsigned comparison makes negative values of index larger than the length
+    fb.ifThen() {
+      // then, throw a StringIndexOutOfBoundsException
+      maybeWrapInUBE(fb, semantics.stringIndexOutOfBounds) {
+        genNewScalaClass(fb, StringIndexOutOfBoundsExceptionClass,
+            SpecialNames.IntArgConstructorName) {
+          fb += LocalGet(indexParam)
+        }
+      }
+      fb += ExternConvertAny
+      fb += Throw(genTagID.exception)
+    }
+
+    // otherwise, read the char
+    fb += LocalGet(strParam)
+    fb += LocalGet(indexParam)
+    fb += Call(genFunctionID.stringCharAt)
+
+    fb.buildAndAddToModule()
+  }
+
   /** `isInstanceExternal: (ref typeData), anyref -> anyref` (a boxed boolean).
    *
    *  Tests whether the given value is a non-null instance of the given type.
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala
index 145739a409..cbf929e0af 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala
@@ -404,6 +404,11 @@ object Emitter {
         instantiateClass(ClassCastExceptionClass, StringArgConstructorName)
       },
 
+      cond(stringIndexOutOfBounds != Unchecked) {
+        instantiateClass(StringIndexOutOfBoundsExceptionClass,
+            IntArgConstructorName)
+      },
+
       cond(isAnyFatal(asInstanceOfs, arrayIndexOutOfBounds, arrayStores,
           negativeArraySizes, nullPointers, stringIndexOutOfBounds)) {
         instantiateClass(UndefinedBehaviorErrorClass,
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
index 8ce4030ea8..13a288ddbf 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
@@ -1323,7 +1323,10 @@ private class FunctionEmitter private (
         genTree(lhs, StringType)
         genTree(rhs, IntType)
         markPosition(tree)
-        fb += wa.Call(genFunctionID.stringCharAt)
+        if (semantics.stringIndexOutOfBounds == CheckedBehavior.Unchecked)
+          fb += wa.Call(genFunctionID.stringCharAt)
+        else
+          fb += wa.Call(genFunctionID.checkedStringCharAt)
         CharType
 
       case _ =>
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/SpecialNames.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/SpecialNames.scala
index 00b858c39e..946532dfce 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/SpecialNames.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/SpecialNames.scala
@@ -46,6 +46,7 @@ object SpecialNames {
 
   val AnyArgConstructorName = MethodName.constructor(List(ClassRef(ObjectClass)))
   val StringArgConstructorName = MethodName.constructor(List(ClassRef(BoxedStringClass)))
+  val IntArgConstructorName = MethodName.constructor(List(IntRef))
   val ThrowableArgConsructorName = MethodName.constructor(List(ClassRef(ThrowableClass)))
 
   val hashCodeMethodName = MethodName("hashCode", Nil, IntRef)
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
index fc25891dc2..7e4f3f7fd8 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
@@ -226,6 +226,7 @@ object VarGen {
     case object valueDescription extends FunctionID
     case object classCastException extends FunctionID
     case object asSpecificRefArray extends FunctionID
+    case object checkedStringCharAt extends FunctionID
     case object isInstanceExternal extends FunctionID
     case object isInstance extends FunctionID
     case object isAssignableFromExternal extends FunctionID
diff --git a/project/Build.scala b/project/Build.scala
index 63990ee237..39b880a573 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -64,6 +64,7 @@ object ExposedValues extends AutoPlugin {
         prev.withSemantics { semantics =>
           semantics
             .withAsInstanceOfs(CheckedBehavior.Compliant)
+            .withStringIndexOutOfBounds(CheckedBehavior.Compliant)
         }
       } else {
         prev.withSemantics { semantics =>
@@ -177,7 +178,6 @@ object MyScalaJSPlugin extends AutoPlugin {
                 .withArrayStores(Unchecked)
                 .withNegativeArraySizes(Unchecked)
                 .withNullPointers(Unchecked)
-                .withStringIndexOutOfBounds(Unchecked)
                 .withModuleInit(Unchecked)
             }
         } else {

From 833f778f6aa4f48d18be4cfcedc6d12e0a9f6277 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Mon, 24 Jun 2024 23:41:59 +0200
Subject: [PATCH 137/298] Wasm: Implement checked moduleInit.

---
 .../backend/WebAssemblyLinkerBackend.scala    |  3 +-
 .../backend/wasmemitter/ClassEmitter.scala    | 41 ++++++++++++++++++-
 .../backend/wasmemitter/CoreWasmLib.scala     | 28 +++++++++++++
 .../linker/backend/wasmemitter/Emitter.scala  |  5 +++
 .../linker/backend/wasmemitter/VarGen.scala   |  2 +
 project/Build.scala                           |  2 +-
 6 files changed, 77 insertions(+), 4 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/WebAssemblyLinkerBackend.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/WebAssemblyLinkerBackend.scala
index 3bac291a05..da77b1bebc 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/WebAssemblyLinkerBackend.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/WebAssemblyLinkerBackend.scala
@@ -40,8 +40,7 @@ final class WebAssemblyLinkerBackend(config: LinkerBackendImpl.Config)
     coreSpec.semantics.arrayIndexOutOfBounds == CheckedBehavior.Unchecked &&
     coreSpec.semantics.arrayStores == CheckedBehavior.Unchecked &&
     coreSpec.semantics.negativeArraySizes == CheckedBehavior.Unchecked &&
-    coreSpec.semantics.nullPointers == CheckedBehavior.Unchecked &&
-    coreSpec.semantics.moduleInit == CheckedBehavior.Unchecked,
+    coreSpec.semantics.nullPointers == CheckedBehavior.Unchecked,
     "The WebAssembly backend currently only supports CheckedBehavior.Unchecked semantics; " +
     s"was ${coreSpec.semantics}."
   )
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/ClassEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/ClassEmitter.scala
index 3d6c1d3c45..23582e35e4 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/ClassEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/ClassEmitter.scala
@@ -395,6 +395,17 @@ class ClassEmitter(coreSpec: CoreSpec) {
       )
       ctx.addGlobal(global)
 
+      if (semantics.moduleInit != CheckedBehavior.Unchecked) {
+        val initFlagGlobal = wamod.Global(
+          genGlobalID.forModuleInitFlag(className),
+          makeDebugName(ns.ModuleInitFlag, className),
+          isMutable = true,
+          watpe.Int32,
+          wa.Expr(List(wa.I32Const(0)))
+        )
+        ctx.addGlobal(initFlagGlobal)
+      }
+
       genModuleAccessor(clazz)
     }
   }
@@ -715,7 +726,10 @@ class ClassEmitter(coreSpec: CoreSpec) {
       makeDebugName(ns.ModuleAccessor, className),
       clazz.pos
     )
-    fb.setResultType(resultType)
+    if (semantics.moduleInit == CheckedBehavior.Compliant)
+      fb.setResultType(resultType.toNullable)
+    else
+      fb.setResultType(resultType)
 
     val instanceLocal = fb.addLocal("instance", resultType)
 
@@ -724,6 +738,30 @@ class ClassEmitter(coreSpec: CoreSpec) {
       fb += wa.GlobalGet(globalInstanceID)
       fb += wa.BrOnNonNull(nonNullLabel)
 
+      // check ongoing initialization
+      if (semantics.moduleInit != CheckedBehavior.Unchecked) {
+        val initFlagID = genGlobalID.forModuleInitFlag(className)
+
+        // if being initialized
+        fb += wa.GlobalGet(initFlagID)
+        fb.ifThen() {
+          if (semantics.moduleInit == CheckedBehavior.Compliant) {
+            // then, return null
+            fb += wa.RefNull(watpe.HeapType.None)
+            fb += wa.Return
+          } else {
+            // then, throw
+            fb += wa.GlobalGet(genGlobalID.forVTable(className))
+            fb += wa.Call(genFunctionID.throwModuleInitError)
+            fb += wa.Unreachable // for clarity; technically redundant since the stacks align
+          }
+        }
+
+        // mark as being initialized
+        fb += wa.I32Const(1)
+        fb += wa.GlobalSet(initFlagID)
+      }
+
       // create an instance and call its constructor
       fb += wa.Call(genFunctionID.newDefault(className))
       fb += wa.LocalTee(instanceLocal)
@@ -1363,6 +1401,7 @@ object ClassEmitter {
     // Shared with JS backend -- className
     val ModuleAccessor = UTF8String("m.")
     val ModuleInstance = UTF8String("n.")
+    val ModuleInitFlag = UTF8String("ni.")
     val JSClassAccessor = UTF8String("a.")
     val JSClassValueCache = UTF8String("b.")
     val TypeData = UTF8String("d.")
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
index c542d820dc..118ec474a6 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
@@ -608,6 +608,10 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
       genCheckedStringCharAt()
     }
 
+    if (semantics.moduleInit == CheckedBehavior.Fatal) {
+      genThrowModuleInitError()
+    }
+
     genIsInstanceExternal()
     genIsInstance()
     genIsAssignableFromExternal()
@@ -1438,6 +1442,30 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
     fb.buildAndAddToModule()
   }
 
+  /** `throwModuleInitError: [] -> []` (always throws).
+   *
+   *  Throws an `UndefinedBehaviorError` for a module initialization error.
+   */
+  private def genThrowModuleInitError()(implicit ctx: WasmContext): Unit = {
+    val fb = newFunctionBuilder(genFunctionID.throwModuleInitError)
+    val typeDataParam = fb.addParam("typeData", RefType(genTypeID.typeData))
+
+    genNewScalaClass(fb, SpecialNames.UndefinedBehaviorErrorClass,
+        SpecialNames.StringArgConstructorName) {
+      fb ++= ctx.stringPool.getConstantStringInstr("Initializer of ")
+      fb += LocalGet(typeDataParam)
+      fb += Call(genFunctionID.typeDataName)
+      fb += Call(genFunctionID.stringConcat)
+      fb ++= ctx.stringPool.getConstantStringInstr(
+          " called before completion of its super constructor")
+      fb += Call(genFunctionID.stringConcat)
+    }
+    fb += ExternConvertAny
+    fb += Throw(genTagID.exception)
+
+    fb.buildAndAddToModule()
+  }
+
   /** `isInstanceExternal: (ref typeData), anyref -> anyref` (a boxed boolean).
    *
    *  Tests whether the given value is a non-null instance of the given type.
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala
index cbf929e0af..bd484fa73f 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala
@@ -415,6 +415,11 @@ object Emitter {
             ThrowableArgConsructorName)
       },
 
+      cond(moduleInit == Fatal) {
+        instantiateClass(UndefinedBehaviorErrorClass,
+            StringArgConstructorName)
+      },
+
       // TODO Ideally we should not require these, but rather adapt to their absence
       instantiateClass(ClassClass, AnyArgConstructorName),
       instantiateClass(JSExceptionClass, AnyArgConstructorName),
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
index 7e4f3f7fd8..b3bd680d35 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
@@ -27,6 +27,7 @@ object VarGen {
   object genGlobalID {
     final case class forImportedModule(moduleName: String) extends GlobalID
     final case class forModuleInstance(className: ClassName) extends GlobalID
+    final case class forModuleInitFlag(className: ClassName) extends GlobalID
     final case class forJSClassValue(className: ClassName) extends GlobalID
 
     final case class forVTable(typeRef: NonArrayTypeRef) extends GlobalID
@@ -227,6 +228,7 @@ object VarGen {
     case object classCastException extends FunctionID
     case object asSpecificRefArray extends FunctionID
     case object checkedStringCharAt extends FunctionID
+    case object throwModuleInitError extends FunctionID
     case object isInstanceExternal extends FunctionID
     case object isInstance extends FunctionID
     case object isAssignableFromExternal extends FunctionID
diff --git a/project/Build.scala b/project/Build.scala
index 39b880a573..2e83b60638 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -65,6 +65,7 @@ object ExposedValues extends AutoPlugin {
           semantics
             .withAsInstanceOfs(CheckedBehavior.Compliant)
             .withStringIndexOutOfBounds(CheckedBehavior.Compliant)
+            .withModuleInit(CheckedBehavior.Compliant)
         }
       } else {
         prev.withSemantics { semantics =>
@@ -178,7 +179,6 @@ object MyScalaJSPlugin extends AutoPlugin {
                 .withArrayStores(Unchecked)
                 .withNegativeArraySizes(Unchecked)
                 .withNullPointers(Unchecked)
-                .withModuleInit(Unchecked)
             }
         } else {
           baseConfig

From 41b259b1d3f123d71daa5486916b336b68023856 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Tue, 25 Jun 2024 11:01:50 +0200
Subject: [PATCH 138/298] Wasm: Implement checked arrayIndexOutOfBounds.

---
 .../backend/WebAssemblyLinkerBackend.scala    |   1 -
 .../backend/wasmemitter/CoreWasmLib.scala     | 215 ++++++++++++++++++
 .../linker/backend/wasmemitter/Emitter.scala  |   5 +
 .../backend/wasmemitter/FunctionEmitter.scala |  67 +++---
 .../linker/backend/wasmemitter/VarGen.scala   |  16 ++
 project/Build.scala                           |   2 +-
 6 files changed, 277 insertions(+), 29 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/WebAssemblyLinkerBackend.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/WebAssemblyLinkerBackend.scala
index da77b1bebc..184d41089b 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/WebAssemblyLinkerBackend.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/WebAssemblyLinkerBackend.scala
@@ -37,7 +37,6 @@ final class WebAssemblyLinkerBackend(config: LinkerBackendImpl.Config)
     s"The WebAssembly backend only supports ES modules; was ${coreSpec.moduleKind}."
   )
   require(
-    coreSpec.semantics.arrayIndexOutOfBounds == CheckedBehavior.Unchecked &&
     coreSpec.semantics.arrayStores == CheckedBehavior.Unchecked &&
     coreSpec.semantics.negativeArraySizes == CheckedBehavior.Unchecked &&
     coreSpec.semantics.nullPointers == CheckedBehavior.Unchecked,
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
index 118ec474a6..7939bd41df 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
@@ -604,6 +604,12 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
       genArrayAsInstances()
     }
 
+    if (semantics.arrayIndexOutOfBounds != CheckedBehavior.Unchecked) {
+      genThrowArrayIndexOutOfBoundsException()
+      genArrayGets()
+      genArraySets()
+    }
+
     if (semantics.stringIndexOutOfBounds != CheckedBehavior.Unchecked) {
       genCheckedStringCharAt()
     }
@@ -1272,6 +1278,140 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
     fb.buildAndAddToModule()
   }
 
+  /** `throwArrayIndexOutOfBoundsException: i32 -> void`.
+   *
+   *  This function always throws. It should be followed by an `unreachable`
+   *  statement.
+   */
+  private def genThrowArrayIndexOutOfBoundsException()(implicit ctx: WasmContext): Unit = {
+    val typeDataType = RefType(genTypeID.typeData)
+
+    val fb = newFunctionBuilder(genFunctionID.throwArrayIndexOutOfBoundsException)
+    val indexParam = fb.addParam("index", Int32)
+
+    maybeWrapInUBE(fb, semantics.arrayIndexOutOfBounds) {
+      genNewScalaClass(fb, ArrayIndexOutOfBoundsExceptionClass,
+          SpecialNames.StringArgConstructorName) {
+        fb += LocalGet(indexParam)
+        fb += Call(genFunctionID.intToString)
+      }
+    }
+    fb += ExternConvertAny
+    fb += Throw(genTagID.exception)
+
+    fb.buildAndAddToModule()
+  }
+
+  /** Generates the `arrayGet.x` functions. */
+  private def genArrayGets()(implicit ctx: WasmContext): Unit = {
+    for (baseRef <- arrayBaseRefs)
+      genArrayGet(baseRef)
+  }
+
+  /** `arrayGet.x: (ref null xArray), i32 -> x`. */
+  private def genArrayGet(baseRef: NonArrayTypeRef)(implicit ctx: WasmContext): Unit = {
+    val origName = OriginalName("arrayGet." + charCodeForOriginalName(baseRef))
+
+    val arrayTypeRef = ArrayTypeRef(baseRef, 1)
+    val arrayStructTypeID = genTypeID.forArrayClass(arrayTypeRef)
+    val underlyingTypeID = genTypeID.underlyingOf(arrayTypeRef)
+
+    val elemWasmType = baseRef match {
+      case PrimRef(tpe) => transformSingleType(tpe)
+      case ClassRef(_)  => anyref
+    }
+
+    val fb = newFunctionBuilder(genFunctionID.arrayGet(baseRef), origName)
+    val arrayParam = fb.addParam("array", RefType.nullable(arrayStructTypeID))
+    val indexParam = fb.addParam("index", Int32)
+    fb.setResultType(elemWasmType)
+
+    val underlyingLocal = fb.addLocal("underlying", RefType(underlyingTypeID))
+
+    // Get the underlying array
+    fb += LocalGet(arrayParam)
+    fb += StructGet(arrayStructTypeID, genFieldID.objStruct.arrayUnderlying)
+    fb += LocalTee(underlyingLocal)
+
+    // if underlying.length unsigned_<= index
+    fb += ArrayLen
+    fb += LocalGet(indexParam)
+    fb += I32LeU
+    fb.ifThen() {
+      // then throw ArrayIndexOutOfBoundsException
+      fb += LocalGet(indexParam)
+      fb += Call(genFunctionID.throwArrayIndexOutOfBoundsException)
+      fb += Unreachable
+    }
+
+    // Load the underlying and index
+    fb += LocalGet(underlyingLocal)
+    fb += LocalGet(indexParam)
+
+    // Use the appropriate variant of array.get for sign extension
+    baseRef match {
+      case BooleanRef | CharRef =>
+        fb += ArrayGetU(underlyingTypeID)
+      case ByteRef | ShortRef =>
+        fb += ArrayGetS(underlyingTypeID)
+      case _ =>
+        fb += ArrayGet(underlyingTypeID)
+    }
+
+    fb.buildAndAddToModule()
+  }
+
+  /** Generates the `arraySet.x` functions. */
+  private def genArraySets()(implicit ctx: WasmContext): Unit = {
+    for (baseRef <- arrayBaseRefs)
+      genArraySet(baseRef)
+  }
+
+  /** `arraySet.x: (ref null xArray), i32, x -> []`. */
+  private def genArraySet(baseRef: NonArrayTypeRef)(implicit ctx: WasmContext): Unit = {
+    val origName = OriginalName("arraySet." + charCodeForOriginalName(baseRef))
+
+    val arrayTypeRef = ArrayTypeRef(baseRef, 1)
+    val arrayStructTypeID = genTypeID.forArrayClass(arrayTypeRef)
+    val underlyingTypeID = genTypeID.underlyingOf(arrayTypeRef)
+
+    val elemWasmType = baseRef match {
+      case PrimRef(tpe) => transformSingleType(tpe)
+      case ClassRef(_)  => anyref
+    }
+
+    val fb = newFunctionBuilder(genFunctionID.arraySet(baseRef), origName)
+    val arrayParam = fb.addParam("array", RefType.nullable(arrayStructTypeID))
+    val indexParam = fb.addParam("index", Int32)
+    val valueParam = fb.addParam("value", elemWasmType)
+
+    val underlyingLocal = fb.addLocal("underlying", RefType(underlyingTypeID))
+
+    // Get the underlying array
+    fb += LocalGet(arrayParam)
+    fb += StructGet(arrayStructTypeID, genFieldID.objStruct.arrayUnderlying)
+    fb += LocalTee(underlyingLocal)
+
+    // if underlying.length unsigned_<= index
+    fb += ArrayLen
+    fb += LocalGet(indexParam)
+    fb += I32LeU
+    fb.ifThen() {
+      // then throw ArrayIndexOutOfBoundsException
+      fb += LocalGet(indexParam)
+      fb += Call(genFunctionID.throwArrayIndexOutOfBoundsException)
+      fb += Unreachable
+    }
+
+    // Store the value
+    fb += LocalGet(underlyingLocal)
+    fb += LocalGet(indexParam)
+    fb += LocalGet(valueParam)
+    fb += ArraySet(underlyingTypeID)
+
+    fb.buildAndAddToModule()
+  }
+
   /** `arrayTypeData: (ref typeData), i32 -> (ref vtable.java.lang.Object)`.
    *
    *  Returns the typeData/vtable of an array with `dims` dimensions over the given typeData. `dims`
@@ -2639,12 +2779,74 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
   }
 
   private def genArrayCopyFunctions()(implicit ctx: WasmContext): Unit = {
+    if (semantics.arrayIndexOutOfBounds != CheckedBehavior.Unchecked)
+      genArrayCopyCheckBounds()
+
     for (baseRef <- arrayBaseRefs)
       genSpecializedArrayCopy(baseRef)
 
     genGenericArrayCopy()
   }
 
+  /** `arrayCopyCheckBounds: [i32, i32, i32, i32, i32] -> []`.
+   *
+   *  Checks all the bounds for an `arrayCopy`. Arguments correspond to the
+   *  arguments of the `arrayCopy`, where arrays are replaced by their lengths.
+   */
+  private def genArrayCopyCheckBounds()(implicit ctx: WasmContext): Unit = {
+    val fb = newFunctionBuilder(genFunctionID.arrayCopyCheckBounds)
+    val srcLengthParam = fb.addParam("srcLength", Int32)
+    val srcPosParam = fb.addParam("srcPos", Int32)
+    val destLengthParam = fb.addParam("destLength", Int32)
+    val destPosParam = fb.addParam("destPos", Int32)
+    val lengthParam = fb.addParam("length", Int32)
+
+    fb.block() { failureLabel =>
+      /* if (srcPos < 0) || (destPos < 0) || (length < 0), fail
+       * we test all of those with a single branch as follows:
+       * ((srcPos | destPos | length) & 0x80000000) != 0
+       */
+      fb += LocalGet(srcPosParam)
+      fb += LocalGet(destPosParam)
+      fb += I32Or
+      fb += LocalGet(lengthParam)
+      fb += I32Or
+      fb += I32Const(0x80000000)
+      fb += I32And
+      fb += BrIf(failureLabel)
+
+      // if srcPos > (srcLength - length), fail
+      fb += LocalGet(srcPosParam)
+      fb += LocalGet(srcLengthParam)
+      fb += LocalGet(lengthParam)
+      fb += I32Sub
+      fb += I32GtS
+      fb += BrIf(failureLabel)
+
+      // if destPos > (destLength - length), fail
+      fb += LocalGet(destPosParam)
+      fb += LocalGet(destLengthParam)
+      fb += LocalGet(lengthParam)
+      fb += I32Sub
+      fb += I32GtS
+      fb += BrIf(failureLabel)
+
+      // otherwise, succeed
+      fb += Return
+    }
+
+    maybeWrapInUBE(fb, semantics.arrayIndexOutOfBounds) {
+      genNewScalaClass(fb, ArrayIndexOutOfBoundsExceptionClass,
+          SpecialNames.StringArgConstructorName) {
+        fb += RefNull(HeapType.None)
+      }
+    }
+    fb += ExternConvertAny
+    fb += Throw(genTagID.exception)
+
+    fb.buildAndAddToModule()
+  }
+
   /** Generates a specialized arrayCopy for the array class with the given base. */
   private def genSpecializedArrayCopy(baseRef: NonArrayTypeRef)(implicit ctx: WasmContext): Unit = {
     val originalName = OriginalName("arrayCopy." + charCodeForOriginalName(baseRef))
@@ -2661,6 +2863,19 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
     val destPosParam = fb.addParam("destPos", Int32)
     val lengthParam = fb.addParam("length", Int32)
 
+    if (semantics.arrayIndexOutOfBounds != CheckedBehavior.Unchecked) {
+      fb += LocalGet(srcParam)
+      fb += StructGet(arrayStructTypeID, genFieldID.objStruct.arrayUnderlying)
+      fb += ArrayLen
+      fb += LocalGet(srcPosParam)
+      fb += LocalGet(destParam)
+      fb += StructGet(arrayStructTypeID, genFieldID.objStruct.arrayUnderlying)
+      fb += ArrayLen
+      fb += LocalGet(destPosParam)
+      fb += LocalGet(lengthParam)
+      fb += Call(genFunctionID.arrayCopyCheckBounds)
+    }
+
     fb += LocalGet(destParam)
     fb += StructGet(arrayStructTypeID, genFieldID.objStruct.arrayUnderlying)
     fb += LocalGet(destPosParam)
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala
index bd484fa73f..b67679c858 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala
@@ -404,6 +404,11 @@ object Emitter {
         instantiateClass(ClassCastExceptionClass, StringArgConstructorName)
       },
 
+      cond(arrayIndexOutOfBounds != Unchecked) {
+        instantiateClass(ArrayIndexOutOfBoundsExceptionClass,
+            StringArgConstructorName)
+      },
+
       cond(stringIndexOutOfBounds != Unchecked) {
         instantiateClass(StringIndexOutOfBoundsExceptionClass,
             IntArgConstructorName)
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
index 13a288ddbf..324f4c7f8b 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
@@ -548,16 +548,23 @@ private class FunctionEmitter private (
         genTreeAuto(array)
         array.tpe match {
           case ArrayType(arrayTypeRef, _) =>
-            // Get the underlying array; implicit trap on null
-            markPosition(tree)
-            fb += wa.StructGet(
-              genTypeID.forArrayClass(arrayTypeRef),
-              genFieldID.objStruct.arrayUnderlying
-            )
-            genTree(index, IntType)
-            genTree(rhs, lhs.tpe)
-            markPosition(tree)
-            fb += wa.ArraySet(genTypeID.underlyingOf(arrayTypeRef))
+            if (semantics.arrayIndexOutOfBounds == CheckedBehavior.Unchecked) {
+              // Get the underlying array; implicit trap on null
+              markPosition(tree)
+              fb += wa.StructGet(
+                genTypeID.forArrayClass(arrayTypeRef),
+                genFieldID.objStruct.arrayUnderlying
+              )
+              genTree(index, IntType)
+              genTree(rhs, lhs.tpe)
+              markPosition(tree)
+              fb += wa.ArraySet(genTypeID.underlyingOf(arrayTypeRef))
+            } else {
+              genTree(index, IntType)
+              genTree(rhs, lhs.tpe)
+              markPosition(tree)
+              fb += wa.Call(genFunctionID.arraySetFor(arrayTypeRef))
+            }
           case NothingType =>
             // unreachable
             ()
@@ -2631,26 +2638,32 @@ private class FunctionEmitter private (
 
     array.tpe match {
       case ArrayType(arrayTypeRef, _) =>
-        // Get the underlying array; implicit trap on null
-        fb += wa.StructGet(
-          genTypeID.forArrayClass(arrayTypeRef),
-          genFieldID.objStruct.arrayUnderlying
-        )
+        if (semantics.arrayIndexOutOfBounds == CheckedBehavior.Unchecked) {
+          // Get the underlying array; implicit trap on null
+          fb += wa.StructGet(
+            genTypeID.forArrayClass(arrayTypeRef),
+            genFieldID.objStruct.arrayUnderlying
+          )
 
-        // Load the index
-        genTree(index, IntType)
+          // Load the index
+          genTree(index, IntType)
 
-        markPosition(tree)
+          markPosition(tree)
 
-        // Use the appropriate variant of array.get for sign extension
-        val typeIdx = genTypeID.underlyingOf(arrayTypeRef)
-        arrayTypeRef match {
-          case ArrayTypeRef(BooleanRef | CharRef, 1) =>
-            fb += wa.ArrayGetU(typeIdx)
-          case ArrayTypeRef(ByteRef | ShortRef, 1) =>
-            fb += wa.ArrayGetS(typeIdx)
-          case _ =>
-            fb += wa.ArrayGet(typeIdx)
+          // Use the appropriate variant of array.get for sign extension
+          val typeIdx = genTypeID.underlyingOf(arrayTypeRef)
+          arrayTypeRef match {
+            case ArrayTypeRef(BooleanRef | CharRef, 1) =>
+              fb += wa.ArrayGetU(typeIdx)
+            case ArrayTypeRef(ByteRef | ShortRef, 1) =>
+              fb += wa.ArrayGetS(typeIdx)
+            case _ =>
+              fb += wa.ArrayGet(typeIdx)
+          }
+        } else {
+          genTree(index, IntType)
+          markPosition(tree)
+          fb += wa.Call(genFunctionID.arrayGetFor(arrayTypeRef))
         }
 
         /* If it is a reference array type whose element type does not translate
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
index b3bd680d35..43517afab2 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
@@ -80,6 +80,20 @@ object VarGen {
 
     final case class asInstance(targetTpe: Type) extends FunctionID
 
+    final case class arrayGet(baseRef: NonArrayTypeRef) extends FunctionID
+
+    def arrayGetFor(arrayTypeRef: ArrayTypeRef): arrayGet = arrayTypeRef match {
+      case ArrayTypeRef(base: PrimRef, 1) => arrayGet(base)
+      case _                              => arrayGet(ClassRef(ObjectClass))
+    }
+
+    final case class arraySet(baseRef: NonArrayTypeRef) extends FunctionID
+
+    def arraySetFor(arrayTypeRef: ArrayTypeRef): arraySet = arrayTypeRef match {
+      case ArrayTypeRef(base: PrimRef, 1) => arraySet(base)
+      case _                              => arraySet(ClassRef(ObjectClass))
+    }
+
     final case class isJSClassInstance(className: ClassName) extends FunctionID
     final case class loadJSClass(className: ClassName) extends FunctionID
     final case class createJSClassOf(className: ClassName) extends FunctionID
@@ -227,6 +241,7 @@ object VarGen {
     case object valueDescription extends FunctionID
     case object classCastException extends FunctionID
     case object asSpecificRefArray extends FunctionID
+    case object throwArrayIndexOutOfBoundsException extends FunctionID
     case object checkedStringCharAt extends FunctionID
     case object throwModuleInitError extends FunctionID
     case object isInstanceExternal extends FunctionID
@@ -253,6 +268,7 @@ object VarGen {
       SpecializedArrayCopyID(baseRef)
     }
 
+    case object arrayCopyCheckBounds extends FunctionID
     case object genericArrayCopy extends FunctionID
   }
 
diff --git a/project/Build.scala b/project/Build.scala
index 2e83b60638..a56d5aa371 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -64,6 +64,7 @@ object ExposedValues extends AutoPlugin {
         prev.withSemantics { semantics =>
           semantics
             .withAsInstanceOfs(CheckedBehavior.Compliant)
+            .withArrayIndexOutOfBounds(CheckedBehavior.Compliant)
             .withStringIndexOutOfBounds(CheckedBehavior.Compliant)
             .withModuleInit(CheckedBehavior.Compliant)
         }
@@ -175,7 +176,6 @@ object MyScalaJSPlugin extends AutoPlugin {
             .withModuleKind(ModuleKind.ESModule)
             .withSemantics { sems =>
               sems
-                .withArrayIndexOutOfBounds(Unchecked)
                 .withArrayStores(Unchecked)
                 .withNegativeArraySizes(Unchecked)
                 .withNullPointers(Unchecked)

From cff558ff8616a372accf049f3f44e9555a951dc7 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Tue, 25 Jun 2024 13:17:47 +0200
Subject: [PATCH 139/298] Wasm: Implement checked arrayStores.

---
 .../backend/WebAssemblyLinkerBackend.scala    |   1 -
 .../backend/wasmemitter/CoreWasmLib.scala     | 237 ++++++++++++++++--
 .../linker/backend/wasmemitter/Emitter.scala  |   5 +
 .../backend/wasmemitter/FunctionEmitter.scala |   8 +-
 .../linker/backend/wasmemitter/VarGen.scala   |   2 +
 project/Build.scala                           |   2 +-
 6 files changed, 226 insertions(+), 29 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/WebAssemblyLinkerBackend.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/WebAssemblyLinkerBackend.scala
index 184d41089b..c3276f550e 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/WebAssemblyLinkerBackend.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/WebAssemblyLinkerBackend.scala
@@ -37,7 +37,6 @@ final class WebAssemblyLinkerBackend(config: LinkerBackendImpl.Config)
     s"The WebAssembly backend only supports ES modules; was ${coreSpec.moduleKind}."
   )
   require(
-    coreSpec.semantics.arrayStores == CheckedBehavior.Unchecked &&
     coreSpec.semantics.negativeArraySizes == CheckedBehavior.Unchecked &&
     coreSpec.semantics.nullPointers == CheckedBehavior.Unchecked,
     "The WebAssembly backend currently only supports CheckedBehavior.Unchecked semantics; " +
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
index 7939bd41df..f89d1d7e67 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
@@ -597,17 +597,26 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
     genGetClassOf()
     genArrayTypeData()
 
-    if (semantics.asInstanceOfs != CheckedBehavior.Unchecked) {
+    if (semantics.asInstanceOfs != CheckedBehavior.Unchecked ||
+        semantics.arrayStores != CheckedBehavior.Unchecked) {
       genValueDescription()
+    }
+
+    if (semantics.asInstanceOfs != CheckedBehavior.Unchecked) {
       genClassCastException()
       genPrimitiveAsInstances()
       genArrayAsInstances()
     }
 
+    if (semantics.arrayStores != CheckedBehavior.Unchecked)
+      genThrowArrayStoreException()
+
     if (semantics.arrayIndexOutOfBounds != CheckedBehavior.Unchecked) {
       genThrowArrayIndexOutOfBoundsException()
       genArrayGets()
       genArraySets()
+    } else if (semantics.arrayStores != CheckedBehavior.Unchecked) {
+      genArraySet(ClassRef(ObjectClass))
     }
 
     if (semantics.stringIndexOutOfBounds != CheckedBehavior.Unchecked) {
@@ -1278,6 +1287,28 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
     fb.buildAndAddToModule()
   }
 
+  /** `throwArrayStoreException: anyref -> void`.
+   *
+   *  This function always throws. It should be followed by an `unreachable`
+   *  statement.
+   */
+  private def genThrowArrayStoreException()(implicit ctx: WasmContext): Unit = {
+    val fb = newFunctionBuilder(genFunctionID.throwArrayStoreException)
+    val valueParam = fb.addParam("value", anyref)
+
+    maybeWrapInUBE(fb, semantics.arrayStores) {
+      genNewScalaClass(fb, ArrayStoreExceptionClass,
+          SpecialNames.StringArgConstructorName) {
+        fb += LocalGet(valueParam)
+        fb += Call(genFunctionID.valueDescription)
+      }
+    }
+    fb += ExternConvertAny
+    fb += Throw(genTagID.exception)
+
+    fb.buildAndAddToModule()
+  }
+
   /** `throwArrayIndexOutOfBoundsException: i32 -> void`.
    *
    *  This function always throws. It should be followed by an `unreachable`
@@ -1390,17 +1421,66 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
     // Get the underlying array
     fb += LocalGet(arrayParam)
     fb += StructGet(arrayStructTypeID, genFieldID.objStruct.arrayUnderlying)
-    fb += LocalTee(underlyingLocal)
 
-    // if underlying.length unsigned_<= index
-    fb += ArrayLen
-    fb += LocalGet(indexParam)
-    fb += I32LeU
-    fb.ifThen() {
-      // then throw ArrayIndexOutOfBoundsException
+    // Bounds check
+    if (semantics.arrayIndexOutOfBounds != CheckedBehavior.Unchecked) {
+      fb += LocalTee(underlyingLocal)
+
+      // if underlying.length unsigned_<= index
+      fb += ArrayLen
       fb += LocalGet(indexParam)
-      fb += Call(genFunctionID.throwArrayIndexOutOfBoundsException)
-      fb += Unreachable
+      fb += I32LeU
+      fb.ifThen() {
+        // then throw ArrayIndexOutOfBoundsException
+        fb += LocalGet(indexParam)
+        fb += Call(genFunctionID.throwArrayIndexOutOfBoundsException)
+        fb += Unreachable
+      }
+    } else {
+      fb += LocalSet(underlyingLocal)
+    }
+
+    // Store check
+    if (semantics.arrayStores != CheckedBehavior.Unchecked &&
+        baseRef.isInstanceOf[ClassRef]) {
+      val componentTypeDataLocal = fb.addLocal("componentTypeData", RefType(genTypeID.typeData))
+
+      fb.block() { successLabel =>
+        // Get the component type data
+        fb += LocalGet(arrayParam)
+        fb += StructGet(arrayStructTypeID, genFieldID.objStruct.vtable)
+        fb += StructGet(genTypeID.ObjectVTable, genFieldID.typeData.componentType)
+        fb += RefAsNonNull
+        fb += LocalTee(componentTypeDataLocal)
+
+        // Fast path: if componentTypeData eq typeDataOf[jl.Object], succeed
+        fb += GlobalGet(genGlobalID.forVTable(ClassRef(ObjectClass)))
+        fb += RefEq
+        fb += BrIf(successLabel)
+
+        // If componentTypeData.kind == KindJSType, succeed
+        fb += LocalGet(componentTypeDataLocal)
+        fb += StructGet(genTypeID.typeData, genFieldID.typeData.kind)
+        fb += I32Const(KindJSType)
+        fb += I32Eq
+        fb += BrIf(successLabel)
+
+        // If value is null, succeed
+        fb += LocalGet(valueParam)
+        fb += RefIsNull
+        fb += BrIf(successLabel)
+
+        // If isInstance(componentTypeData, value), succeed
+        fb += LocalGet(componentTypeDataLocal)
+        fb += LocalGet(valueParam)
+        fb += Call(genFunctionID.isInstance)
+        fb += BrIf(successLabel)
+
+        // Otherwise, it is a store exception
+        fb += LocalGet(valueParam)
+        fb += Call(genFunctionID.throwArrayStoreException)
+        fb += Unreachable // for clarity; technically redundant since the stacks align
+      }
     }
 
     // Store the value
@@ -2782,6 +2862,9 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
     if (semantics.arrayIndexOutOfBounds != CheckedBehavior.Unchecked)
       genArrayCopyCheckBounds()
 
+    if (semantics.arrayStores != CheckedBehavior.Unchecked)
+      genSlowRefArrayCopy()
+
     for (baseRef <- arrayBaseRefs)
       genSpecializedArrayCopy(baseRef)
 
@@ -2847,6 +2930,72 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
     fb.buildAndAddToModule()
   }
 
+  /** `slowRefArrayCopy: [ArrayObject, i32, ArrayObject, i32, i32] -> []`
+   *
+   *  Used when the type of the dest is not assignable from the type of the source.
+   *  Performs an `arraySet` call for every element in order to detect
+   *  `ArrayStoreException`s.
+   *
+   *  Bounds are already known to be valid.
+   */
+  private def genSlowRefArrayCopy()(implicit ctx: WasmContext): Unit = {
+    val baseRef = ClassRef(ObjectClass)
+    val arrayTypeRef = ArrayTypeRef(baseRef, 1)
+    val arrayStructTypeID = genTypeID.forArrayClass(arrayTypeRef)
+    val arrayClassType = RefType.nullable(arrayStructTypeID)
+    val underlyingArrayTypeID = genTypeID.underlyingOf(arrayTypeRef)
+
+    val fb = newFunctionBuilder(genFunctionID.slowRefArrayCopy)
+    val srcParam = fb.addParam("src", arrayClassType)
+    val srcPosParam = fb.addParam("srcPos", Int32)
+    val destParam = fb.addParam("dest", arrayClassType)
+    val destPosParam = fb.addParam("destPos", Int32)
+    val lengthParam = fb.addParam("length", Int32)
+
+    val srcUnderlyingLocal = fb.addLocal("srcUnderlying", RefType(underlyingArrayTypeID))
+    val iLocal = fb.addLocal("i", Int32)
+
+    // srcUnderlying := src.underlying
+    fb += LocalGet(srcParam)
+    fb += StructGet(arrayStructTypeID, genFieldID.objStruct.arrayUnderlying)
+    fb += LocalSet(srcUnderlyingLocal)
+
+    // i := 0
+    fb += I32Const(0)
+    fb += LocalSet(iLocal)
+
+    // while i != length
+    fb.whileLoop() {
+      fb += LocalGet(iLocal)
+      fb += LocalGet(lengthParam)
+      fb += I32Ne
+    } {
+      // arraySet.O(dest, destPos + i, srcUnderlying(srcPos + i))
+
+      fb += LocalGet(destParam)
+
+      fb += LocalGet(destPosParam)
+      fb += LocalGet(iLocal)
+      fb += I32Add
+
+      fb += LocalGet(srcUnderlyingLocal)
+      fb += LocalGet(srcPosParam)
+      fb += LocalGet(iLocal)
+      fb += I32Add
+      fb += ArrayGet(underlyingArrayTypeID)
+
+      fb += Call(genFunctionID.arraySet(baseRef))
+
+      // i := i + 1
+      fb += LocalGet(iLocal)
+      fb += I32Const(1)
+      fb += I32Add
+      fb += LocalSet(iLocal)
+    }
+
+    fb.buildAndAddToModule()
+  }
+
   /** Generates a specialized arrayCopy for the array class with the given base. */
   private def genSpecializedArrayCopy(baseRef: NonArrayTypeRef)(implicit ctx: WasmContext): Unit = {
     val originalName = OriginalName("arrayCopy." + charCodeForOriginalName(baseRef))
@@ -2876,6 +3025,25 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
       fb += Call(genFunctionID.arrayCopyCheckBounds)
     }
 
+    if (baseRef.isInstanceOf[ClassRef] && semantics.arrayStores != CheckedBehavior.Unchecked) {
+      // if !isAssignableFrom(dest.vtable, src.vtable)
+      fb += LocalGet(destParam)
+      fb += StructGet(arrayStructTypeID, genFieldID.objStruct.vtable)
+      fb += LocalGet(srcParam)
+      fb += StructGet(arrayStructTypeID, genFieldID.objStruct.vtable)
+      fb += Call(genFunctionID.isAssignableFrom) // contains a fast-path for `eq` vtables
+      fb += I32Eqz
+      fb.ifThen() {
+        // then, delegate to the slow copy method
+        fb += LocalGet(srcParam)
+        fb += LocalGet(srcPosParam)
+        fb += LocalGet(destParam)
+        fb += LocalGet(destPosParam)
+        fb += LocalGet(lengthParam)
+        fb += ReturnCall(genFunctionID.slowRefArrayCopy)
+      }
+    }
+
     fb += LocalGet(destParam)
     fb += StructGet(arrayStructTypeID, genFieldID.objStruct.arrayUnderlying)
     fb += LocalGet(destPosParam)
@@ -2900,29 +3068,46 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
     val anyrefToAnyrefBlockType =
       fb.sigToBlockType(FunctionType(List(RefType.anyref), List(RefType.anyref)))
 
-    // Dispatch done based on the type of src
-    fb += LocalGet(srcParam)
+    // note: this block is never used for Unchecked arrayStores, but it does not hurt much
+    fb.block(anyref) { mismatchLabel =>
+      // Dispatch done based on the type of src
+      fb += LocalGet(srcParam)
 
-    for (baseRef <- arrayBaseRefs) {
-      val arrayTypeRef = ArrayTypeRef(baseRef, 1)
-      val arrayStructTypeID = genTypeID.forArrayClass(arrayTypeRef)
-      val nonNullArrayClassType = RefType(arrayStructTypeID)
+      for (baseRef <- arrayBaseRefs) {
+        val arrayTypeRef = ArrayTypeRef(baseRef, 1)
+        val arrayStructTypeID = genTypeID.forArrayClass(arrayTypeRef)
+        val nonNullArrayClassType = RefType(arrayStructTypeID)
 
-      fb.block(anyrefToAnyrefBlockType) { notThisArrayTypeLabel =>
-        fb += BrOnCastFail(notThisArrayTypeLabel, RefType.anyref, nonNullArrayClassType)
+        fb.block(anyrefToAnyrefBlockType) { notThisArrayTypeLabel =>
+          fb += BrOnCastFail(notThisArrayTypeLabel, RefType.anyref, nonNullArrayClassType)
 
-        fb += LocalGet(srcPosParam)
-        fb += LocalGet(destParam)
-        fb += RefCast(nonNullArrayClassType)
-        fb += LocalGet(destPosParam)
-        fb += LocalGet(lengthParam)
+          fb += LocalGet(srcPosParam)
+          fb += LocalGet(destParam)
+          if (semantics.arrayStores == CheckedBehavior.Unchecked)
+            fb += RefCast(nonNullArrayClassType)
+          else
+            fb += BrOnCastFail(mismatchLabel, anyref, nonNullArrayClassType)
+          fb += LocalGet(destPosParam)
+          fb += LocalGet(lengthParam)
 
-        fb += ReturnCall(genFunctionID.specializedArrayCopy(arrayTypeRef))
+          fb += ReturnCall(genFunctionID.specializedArrayCopy(arrayTypeRef))
+        }
       }
     }
 
-    // Trap if `src` was not an instance of any of the array class types
-    fb += Unreachable
+    // Mismatch of array types, or either array was not an array
+    if (semantics.arrayStores == CheckedBehavior.Unchecked) {
+      fb += Unreachable // trap
+    } else {
+      maybeWrapInUBE(fb, semantics.arrayStores) {
+        genNewScalaClass(fb, ArrayStoreExceptionClass,
+            SpecialNames.StringArgConstructorName) {
+          fb += RefNull(HeapType.None)
+        }
+      }
+      fb += ExternConvertAny
+      fb += Throw(genTagID.exception)
+    }
 
     fb.buildAndAddToModule()
   }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala
index b67679c858..91796f5b7e 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala
@@ -409,6 +409,11 @@ object Emitter {
             StringArgConstructorName)
       },
 
+      cond(arrayStores != Unchecked) {
+        instantiateClass(ArrayStoreExceptionClass,
+            StringArgConstructorName)
+      },
+
       cond(stringIndexOutOfBounds != Unchecked) {
         instantiateClass(StringIndexOutOfBoundsExceptionClass,
             IntArgConstructorName)
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
index 324f4c7f8b..b421b8b9b1 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
@@ -548,7 +548,13 @@ private class FunctionEmitter private (
         genTreeAuto(array)
         array.tpe match {
           case ArrayType(arrayTypeRef, _) =>
-            if (semantics.arrayIndexOutOfBounds == CheckedBehavior.Unchecked) {
+            def isPrimArray = arrayTypeRef match {
+              case ArrayTypeRef(_: PrimRef, 1) => true
+              case _                           => false
+            }
+
+            if (semantics.arrayIndexOutOfBounds == CheckedBehavior.Unchecked &&
+                (semantics.arrayStores == CheckedBehavior.Unchecked || isPrimArray)) {
               // Get the underlying array; implicit trap on null
               markPosition(tree)
               fb += wa.StructGet(
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
index 43517afab2..949455faa4 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
@@ -241,6 +241,7 @@ object VarGen {
     case object valueDescription extends FunctionID
     case object classCastException extends FunctionID
     case object asSpecificRefArray extends FunctionID
+    case object throwArrayStoreException extends FunctionID
     case object throwArrayIndexOutOfBoundsException extends FunctionID
     case object checkedStringCharAt extends FunctionID
     case object throwModuleInitError extends FunctionID
@@ -269,6 +270,7 @@ object VarGen {
     }
 
     case object arrayCopyCheckBounds extends FunctionID
+    case object slowRefArrayCopy extends FunctionID
     case object genericArrayCopy extends FunctionID
   }
 
diff --git a/project/Build.scala b/project/Build.scala
index a56d5aa371..d6ad8df80c 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -65,6 +65,7 @@ object ExposedValues extends AutoPlugin {
           semantics
             .withAsInstanceOfs(CheckedBehavior.Compliant)
             .withArrayIndexOutOfBounds(CheckedBehavior.Compliant)
+            .withArrayStores(CheckedBehavior.Compliant)
             .withStringIndexOutOfBounds(CheckedBehavior.Compliant)
             .withModuleInit(CheckedBehavior.Compliant)
         }
@@ -176,7 +177,6 @@ object MyScalaJSPlugin extends AutoPlugin {
             .withModuleKind(ModuleKind.ESModule)
             .withSemantics { sems =>
               sems
-                .withArrayStores(Unchecked)
                 .withNegativeArraySizes(Unchecked)
                 .withNullPointers(Unchecked)
             }

From e22e40e8e5d910e433c627ce5d4c6ff5dce6e333 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Tue, 25 Jun 2024 19:50:45 +0200
Subject: [PATCH 140/298] Wasm: Implement checked negativeArraySizes.

---
 .../backend/WebAssemblyLinkerBackend.scala    |  1 -
 .../backend/wasmemitter/CoreWasmLib.scala     | 42 +++++++++++++++++++
 .../linker/backend/wasmemitter/Emitter.scala  |  5 +++
 .../backend/wasmemitter/FunctionEmitter.scala | 20 +++++++++
 .../linker/backend/wasmemitter/VarGen.scala   |  1 +
 project/Build.scala                           |  2 +-
 6 files changed, 69 insertions(+), 2 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/WebAssemblyLinkerBackend.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/WebAssemblyLinkerBackend.scala
index c3276f550e..b0d5c407f1 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/WebAssemblyLinkerBackend.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/WebAssemblyLinkerBackend.scala
@@ -37,7 +37,6 @@ final class WebAssemblyLinkerBackend(config: LinkerBackendImpl.Config)
     s"The WebAssembly backend only supports ES modules; was ${coreSpec.moduleKind}."
   )
   require(
-    coreSpec.semantics.negativeArraySizes == CheckedBehavior.Unchecked &&
     coreSpec.semantics.nullPointers == CheckedBehavior.Unchecked,
     "The WebAssembly backend currently only supports CheckedBehavior.Unchecked semantics; " +
     s"was ${coreSpec.semantics}."
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
index f89d1d7e67..424444d50c 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
@@ -619,6 +619,10 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
       genArraySet(ClassRef(ObjectClass))
     }
 
+    if (semantics.negativeArraySizes != CheckedBehavior.Unchecked) {
+      genThrowNegativeArraySizeException()
+    }
+
     if (semantics.stringIndexOutOfBounds != CheckedBehavior.Unchecked) {
       genCheckedStringCharAt()
     }
@@ -1333,6 +1337,30 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
     fb.buildAndAddToModule()
   }
 
+  /** `throwNegativeArraySizeException: i32 -> void`.
+   *
+   *  This function always throws. It should be followed by an `unreachable`
+   *  statement.
+   */
+  private def genThrowNegativeArraySizeException()(implicit ctx: WasmContext): Unit = {
+    val typeDataType = RefType(genTypeID.typeData)
+
+    val fb = newFunctionBuilder(genFunctionID.throwNegativeArraySizeException)
+    val sizeParam = fb.addParam("size", Int32)
+
+    maybeWrapInUBE(fb, semantics.negativeArraySizes) {
+      genNewScalaClass(fb, NegativeArraySizeExceptionClass,
+          SpecialNames.StringArgConstructorName) {
+        fb += LocalGet(sizeParam)
+        fb += Call(genFunctionID.intToString)
+      }
+    }
+    fb += ExternConvertAny
+    fb += Throw(genTagID.exception)
+
+    fb.buildAndAddToModule()
+  }
+
   /** Generates the `arrayGet.x` functions. */
   private def genArrayGets()(implicit ctx: WasmContext): Unit = {
     for (baseRef <- arrayBaseRefs)
@@ -2419,6 +2447,7 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
      * def newArrayObject(arrayTypeData, lengths, lengthIndex) {
      *   // create an array of the right primitive type
      *   val len = lengths(lengthIndex)
+     *   // possibly: check negative array size
      *   switch (arrayTypeData.componentType.kind) {
      *     // for primitives, return without recursion
      *     case KindBoolean => new Array[Boolean](len)
@@ -2459,6 +2488,19 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
     fb += LocalGet(lengthIndexParam)
     fb += ArrayGet(genTypeID.i32Array)
 
+    // Check negative array size
+    if (semantics.negativeArraySizes != CheckedBehavior.Unchecked) {
+      fb += LocalTee(lenLocal)
+      fb += I32Const(0)
+      fb += I32LtS
+      fb.ifThen() {
+        fb += LocalGet(lenLocal)
+        fb += Call(genFunctionID.throwNegativeArraySizeException)
+        fb += Unreachable
+      }
+      fb += LocalGet(lenLocal)
+    }
+
     // componentTypeData := ref_as_non_null(arrayTypeData.componentType)
     // switch (componentTypeData.kind)
     val switchClauseSig = FunctionType(
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala
index 91796f5b7e..bd4fa6697a 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala
@@ -414,6 +414,11 @@ object Emitter {
             StringArgConstructorName)
       },
 
+      cond(negativeArraySizes != Unchecked) {
+        instantiateClass(NegativeArraySizeExceptionClass,
+            StringArgConstructorName)
+      },
+
       cond(stringIndexOutOfBounds != Unchecked) {
         instantiateClass(StringIndexOutOfBoundsExceptionClass,
             IntArgConstructorName)
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
index b421b8b9b1..672bf26edd 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
@@ -2605,6 +2605,26 @@ private class FunctionEmitter private (
       genTree(lengths.head, IntType)
       markPosition(tree)
 
+      if (semantics.negativeArraySizes != CheckedBehavior.Unchecked) {
+        lengths.head match {
+          case IntLiteral(lengthValue) if lengthValue >= 0 =>
+            () // always good
+          case _ =>
+            // if length < 0
+            val lengthLocal = addSyntheticLocal(watpe.Int32)
+            fb += wa.LocalTee(lengthLocal)
+            fb += wa.I32Const(0)
+            fb += wa.I32LtS
+            fb.ifThen() {
+              // then throw NegativeArraySizeException
+              fb += wa.LocalGet(lengthLocal)
+              fb += wa.Call(genFunctionID.throwNegativeArraySizeException)
+              fb += wa.Unreachable
+            }
+            fb += wa.LocalGet(lengthLocal)
+        }
+      }
+
       val underlyingArrayType = genTypeID.underlyingOf(arrayTypeRef)
       fb += wa.ArrayNewDefault(underlyingArrayType)
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
index 949455faa4..de6494b653 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
@@ -243,6 +243,7 @@ object VarGen {
     case object asSpecificRefArray extends FunctionID
     case object throwArrayStoreException extends FunctionID
     case object throwArrayIndexOutOfBoundsException extends FunctionID
+    case object throwNegativeArraySizeException extends FunctionID
     case object checkedStringCharAt extends FunctionID
     case object throwModuleInitError extends FunctionID
     case object isInstanceExternal extends FunctionID
diff --git a/project/Build.scala b/project/Build.scala
index d6ad8df80c..a979a5d46e 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -66,6 +66,7 @@ object ExposedValues extends AutoPlugin {
             .withAsInstanceOfs(CheckedBehavior.Compliant)
             .withArrayIndexOutOfBounds(CheckedBehavior.Compliant)
             .withArrayStores(CheckedBehavior.Compliant)
+            .withNegativeArraySizes(CheckedBehavior.Compliant)
             .withStringIndexOutOfBounds(CheckedBehavior.Compliant)
             .withModuleInit(CheckedBehavior.Compliant)
         }
@@ -177,7 +178,6 @@ object MyScalaJSPlugin extends AutoPlugin {
             .withModuleKind(ModuleKind.ESModule)
             .withSemantics { sems =>
               sems
-                .withNegativeArraySizes(Unchecked)
                 .withNullPointers(Unchecked)
             }
         } else {

From 58af468534ea2373d1b85fb9f6e803c40d1e18ad Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Tue, 25 Jun 2024 23:15:45 +0200
Subject: [PATCH 141/298] Wasm: Implement checked nullPointers.

---
 .../backend/WebAssemblyLinkerBackend.scala    |   5 -
 .../backend/wasmemitter/CoreWasmLib.scala     |  43 ++-
 .../linker/backend/wasmemitter/Emitter.scala  |   4 +
 .../backend/wasmemitter/FunctionEmitter.scala | 260 +++++++++++++++---
 .../linker/backend/wasmemitter/VarGen.scala   |   1 +
 .../backend/webassembly/FunctionBuilder.scala |   3 +
 project/Build.scala                           |  35 +--
 7 files changed, 273 insertions(+), 78 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/WebAssemblyLinkerBackend.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/WebAssemblyLinkerBackend.scala
index b0d5c407f1..4ee5222d90 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/WebAssemblyLinkerBackend.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/WebAssemblyLinkerBackend.scala
@@ -36,11 +36,6 @@ final class WebAssemblyLinkerBackend(config: LinkerBackendImpl.Config)
     coreSpec.moduleKind == ModuleKind.ESModule,
     s"The WebAssembly backend only supports ES modules; was ${coreSpec.moduleKind}."
   )
-  require(
-    coreSpec.semantics.nullPointers == CheckedBehavior.Unchecked,
-    "The WebAssembly backend currently only supports CheckedBehavior.Unchecked semantics; " +
-    s"was ${coreSpec.semantics}."
-  )
   require(
     coreSpec.semantics.strictFloats,
     "The WebAssembly backend only supports strict float semantics."
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
index 424444d50c..3bfe0a05cd 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
@@ -627,6 +627,10 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
       genCheckedStringCharAt()
     }
 
+    if (semantics.nullPointers != CheckedBehavior.Unchecked) {
+      genThrowNullPointerException()
+    }
+
     if (semantics.moduleInit == CheckedBehavior.Fatal) {
       genThrowModuleInitError()
     }
@@ -1361,6 +1365,26 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
     fb.buildAndAddToModule()
   }
 
+  /** `throwNullPointerException: void -> void`.
+   *
+   *  This function always throws. It should be followed by an `unreachable`
+   *  statement.
+   */
+  private def genThrowNullPointerException()(implicit ctx: WasmContext): Unit = {
+    val typeDataType = RefType(genTypeID.typeData)
+
+    val fb = newFunctionBuilder(genFunctionID.throwNullPointerException)
+
+    maybeWrapInUBE(fb, semantics.nullPointers) {
+      genNewScalaClass(fb, NullPointerExceptionClass, NoArgConstructorName) {
+      }
+    }
+    fb += ExternConvertAny
+    fb += Throw(genTagID.exception)
+
+    fb.buildAndAddToModule()
+  }
+
   /** Generates the `arrayGet.x` functions. */
   private def genArrayGets()(implicit ctx: WasmContext): Unit = {
     for (baseRef <- arrayBaseRefs)
@@ -2248,10 +2272,21 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
     val valueParam = fb.addParam("value", RefType.any)
     fb.setResultType(RefType.any)
 
-    fb += LocalGet(valueParam)
-    fb += Call(genFunctionID.anyGetTypeData)
-    fb += RefAsNonNull // NPE for null.getName()
-    fb += ReturnCall(genFunctionID.typeDataName)
+    if (semantics.nullPointers == CheckedBehavior.Unchecked) {
+      fb += LocalGet(valueParam)
+      fb += Call(genFunctionID.anyGetTypeData)
+      fb += RefAsNonNull // NPE for null.getName()
+      fb += ReturnCall(genFunctionID.typeDataName)
+    } else {
+      fb.block() { npeLabel =>
+        fb += LocalGet(valueParam)
+        fb += Call(genFunctionID.anyGetTypeData)
+        fb += BrOnNull(npeLabel) // NPE for null.getName()
+        fb += ReturnCall(genFunctionID.typeDataName)
+      }
+      fb += Call(genFunctionID.throwNullPointerException)
+      fb += Unreachable
+    }
 
     fb.buildAndAddToModule()
   }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala
index bd4fa6697a..ab80622a00 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala
@@ -419,6 +419,10 @@ object Emitter {
             StringArgConstructorName)
       },
 
+      cond(nullPointers != Unchecked) {
+        instantiateClass(NullPointerExceptionClass, NoArgConstructorName)
+      },
+
       cond(stringIndexOutOfBounds != Unchecked) {
         instantiateClass(StringIndexOutOfBoundsExceptionClass,
             IntArgConstructorName)
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
index 672bf26edd..d503596e5b 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
@@ -117,15 +117,17 @@ object FunctionEmitter {
         List(preSuperEnvType)
       )
 
-      emitter.genBlockStats(ctorBody.beforeSuper) {
-        // Build and return the preSuperEnv struct
-        for (varDef <- preSuperDecls) {
-          val localID = (emitter.lookupLocal(varDef.name.name): @unchecked) match {
-            case VarStorage.Local(localID) => localID
+      emitter.returnWithNPEScope() {
+        emitter.genBlockStats(ctorBody.beforeSuper) {
+          // Build and return the preSuperEnv struct
+          for (varDef <- preSuperDecls) {
+            val localID = (emitter.lookupLocal(varDef.name.name): @unchecked) match {
+              case VarStorage.Local(localID) => localID
+            }
+            emitter.fb += wa.LocalGet(localID)
           }
-          emitter.fb += wa.LocalGet(localID)
+          emitter.fb += wa.StructNew(preSuperEnvStructTypeID)
         }
-        emitter.fb += wa.StructNew(preSuperEnvStructTypeID)
       }
 
       emitter.fb.buildAndAddToModule()
@@ -295,6 +297,7 @@ private class FunctionEmitter private (
   private val coreSpec = ctx.coreSpec
   import coreSpec.semantics
 
+  private var currentNPELabel: Option[wanme.LabelID] = null
   private var closureIdx: Int = 0
   private var currentEnv: Env = paramsEnv
 
@@ -304,6 +307,155 @@ private class FunctionEmitter private (
   private def receiverStorage: VarStorage.Local =
     _receiverStorage.getOrElse(throw new Error("Cannot access to the receiver in this context."))
 
+  /** Opens a new scope in which NPEs can be thrown by jumping to the NPE label.
+   *
+   *  When NPEs are unchecked this is a no-op (other than calling `body`).
+   *
+   *  Otherwise, this method logically generates the following code:
+   *
+   *  {{{
+   *  block resultType $noNPELabel
+   *    block $npeLabel
+   *      body
+   *      br $noNPELabel
+   *    end
+   *    call $throwNullPointerException
+   *    unreachable
+   *  end
+   *  }}}
+   *
+   *  Inside the `body`, it is therefore possible to throw an NPE by jumping to
+   *  the `npeLabel`. This is typically done through a `br_on_null $npeLabel`
+   *  instruction.
+   *
+   *  If the `npeLabel` is not actually requested while generated `body`, the
+   *  surrounding code is skipped.
+   */
+  private def withNPEScope[A](resultType: List[watpe.Type])(body: => A): A = {
+    if (semantics.nullPointers == CheckedBehavior.Unchecked) {
+      body
+    } else {
+      val savedNPELabel = currentNPELabel
+
+      currentNPELabel = None
+      val startIndex = fb.markCurrentInstructionIndex()
+
+      val result = body
+
+      for (npeLabel <- currentNPELabel) {
+        val noNPELabel = fb.genLabel()
+
+        // Go back and open the two blocks
+        val blockType = fb.sigToBlockType(watpe.FunctionType(Nil, resultType))
+        fb.insertAll(
+          startIndex,
+          List(
+            wa.Block(blockType, Some(noNPELabel)),
+            wa.Block(wa.BlockType.ValueType(), Some(npeLabel))
+          )
+        )
+
+        // Add the code after the body in the normal way
+        fb += wa.Br(noNPELabel)
+        fb += wa.End // npeLabel
+        fb += wa.Call(genFunctionID.throwNullPointerException)
+        fb += wa.Unreachable
+        fb += wa.End // noNPELabel
+      }
+
+      currentNPELabel = savedNPELabel
+      result
+    }
+  }
+
+  /** Like `withNPEScope`, but `return` for the success path.
+   *
+   *  This alternative can be used instead of `withNPEScope` when the `body`
+   *  is what gets returned from the current function. It generates better code
+   *  for that common case, namely:
+   *
+   *  {{{
+   *  block $npeLabel
+   *    body
+   *    return
+   *  end
+   *  call $throwNullPointerException
+   *  unreachable
+   *  }}}
+   */
+  private def returnWithNPEScope[A]()(body: => A): A = {
+    if (semantics.nullPointers == CheckedBehavior.Unchecked) {
+      body
+    } else {
+      val savedNPELabel = currentNPELabel
+
+      currentNPELabel = None
+      val startIndex = fb.markCurrentInstructionIndex()
+
+      val result = body
+
+      for (npeLabel <- currentNPELabel) {
+        // Go back and open the block
+        fb.insert(startIndex, wa.Block(wa.BlockType.ValueType(), Some(npeLabel)))
+
+        // Add the code after the body in the normal way
+        fb += wa.Return
+        fb += wa.End // npeLabel
+        fb += wa.Call(genFunctionID.throwNullPointerException)
+        fb += wa.Unreachable
+      }
+
+      currentNPELabel = savedNPELabel
+      result
+    }
+  }
+
+  private def getNPELabel(): wanme.LabelID = {
+    assert(semantics.nullPointers != CheckedBehavior.Unchecked)
+    currentNPELabel.getOrElse {
+      val label = fb.genLabel()
+      currentNPELabel = Some(label)
+      label
+    }
+  }
+
+  /** Emits a `ref.as_non_null` or an NPE check if required for the given `Tree`.
+   *
+   *  This method does not emit `tree`. It only uses it to determine whether
+   *  a check is required.
+   */
+  private def genAsNonNullOrNPEFor(tree: Tree): Unit = {
+    if (tree.tpe.isNullable) {
+      if (tree.tpe == NullType)
+        genNPE()
+      else if (semantics.nullPointers != CheckedBehavior.Unchecked)
+        fb += wa.BrOnNull(getNPELabel())
+      else
+        fb += wa.RefAsNonNull
+    }
+  }
+
+  /** Emits an NPE check if required for the given `Tree`, otherwise nothing.
+   *
+   *  This method does not emit `tree`. It only uses it to determine whether
+   *  a check is required.
+   *
+   *  Unlike `genAsNonNullOrNPE`, after this codegen the value on the stack is
+   *  still statically typed as nullable at the Wasm level.
+   */
+  private def genCheckNonNullFor(tree: Tree): Unit = {
+    if (tree.tpe.isNullable && semantics.nullPointers != CheckedBehavior.Unchecked)
+      fb += wa.BrOnNull(getNPELabel())
+  }
+
+  /** Emits an unconditional NPE. */
+  private def genNPE(): Unit = {
+    if (semantics.nullPointers == CheckedBehavior.Unchecked)
+      fb += wa.Unreachable
+    else
+      fb += wa.Br(getNPELabel())
+  }
+
   private def withNewLocal[A](name: LocalName, originalName: OriginalName, tpe: watpe.Type)(
       body: wanme.LocalID => A
   ): A = {
@@ -372,12 +524,18 @@ private class FunctionEmitter private (
   private def markPosition(tree: Tree): Unit =
     markPosition(tree.pos)
 
-  def genBody(tree: Tree, expectedType: Type): Unit =
-    genTree(tree, expectedType)
+  def genBody(tree: Tree, expectedType: Type): Unit = {
+    returnWithNPEScope() {
+      genTree(tree, expectedType)
+    }
+  }
 
   def genTreeAuto(tree: Tree): Unit =
     genTree(tree, tree.tpe)
 
+  def genTreeToAny(tree: Tree): Unit =
+    genTree(tree, if (tree.tpe.isNullable) AnyType else AnyNotNullType)
+
   def genTree(tree: Tree, expectedType: Type): Unit = {
     val generatedType: Type = tree match {
       case t: Literal             => genLiteral(t, expectedType)
@@ -518,8 +676,9 @@ private class FunctionEmitter private (
            * point, so we can trap as NPE.
            */
           markPosition(tree)
-          fb += wa.Unreachable
+          genNPE()
         } else {
+          genCheckNonNullFor(qualifier)
           genTree(rhs, lhs.tpe)
           markPosition(tree)
           fb += wa.StructSet(
@@ -553,10 +712,11 @@ private class FunctionEmitter private (
               case _                           => false
             }
 
+            genCheckNonNullFor(array)
+
             if (semantics.arrayIndexOutOfBounds == CheckedBehavior.Unchecked &&
                 (semantics.arrayStores == CheckedBehavior.Unchecked || isPrimArray)) {
-              // Get the underlying array; implicit trap on null
-              markPosition(tree)
+              // Get the underlying array
               fb += wa.StructGet(
                 genTypeID.forArrayClass(arrayTypeRef),
                 genFieldID.objStruct.arrayUnderlying
@@ -576,7 +736,7 @@ private class FunctionEmitter private (
             ()
           case NullType =>
             markPosition(tree)
-            fb += wa.Unreachable
+            genNPE()
           case _ =>
             throw new IllegalArgumentException(
                 s"ArraySelect.array must be an array type, but has type ${array.tpe}")
@@ -649,7 +809,7 @@ private class FunctionEmitter private (
 
       case NullType =>
         genTree(receiver, NullType)
-        fb += wa.Unreachable // trap
+        genNPE()
         NothingType
 
       case _ if method.name.isReflectiveProxy =>
@@ -707,8 +867,8 @@ private class FunctionEmitter private (
      */
 
     // Load receiver and arguments
-    genTree(receiver, AnyType)
-    fb += wa.RefAsNonNull
+    genTreeToAny(receiver)
+    genAsNonNullOrNPEFor(receiver)
     fb += wa.LocalTee(receiverLocalForDispatch)
     genArgs(args, methodName)
 
@@ -770,7 +930,7 @@ private class FunctionEmitter private (
      */
     def genReceiverNotNull(): Unit = {
       genTreeAuto(receiver)
-      fb += wa.RefAsNonNull
+      genAsNonNullOrNPEFor(receiver)
     }
 
     /* Generates a resolved call to a method of a hijacked class.
@@ -792,7 +952,7 @@ private class FunctionEmitter private (
        */
       genTreeAuto(receiver)
       markPosition(tree)
-      fb += wa.Unreachable // NPE
+      genNPE()
     } else if (!receiverClassInfo.isAncestorOfHijackedClass) {
       // Standard dispatch codegen
       genReceiverNotNull()
@@ -1033,7 +1193,7 @@ private class FunctionEmitter private (
       case NullType =>
         genTree(receiver, NullType)
         markPosition(tree)
-        fb += wa.Unreachable // trap
+        genNPE()
         NothingType
 
       case _ =>
@@ -1048,15 +1208,15 @@ private class FunctionEmitter private (
 
         BoxedClassToPrimType.get(targetClassName) match {
           case None =>
-            genTree(receiver, ClassType(targetClassName, nullable = true))
-            fb += wa.RefAsNonNull
+            genTree(receiver, ClassType(targetClassName, nullable = receiver.tpe.isNullable))
+            genAsNonNullOrNPEFor(receiver)
 
           case Some(primReceiverType) =>
             if (receiver.tpe == primReceiverType) {
               genTreeAuto(receiver)
             } else {
-              genTree(receiver, AnyType)
-              fb += wa.RefAsNonNull
+              genTreeToAny(receiver)
+              genAsNonNullOrNPEFor(receiver)
               genUnbox(primReceiverType)
             }
         }
@@ -1152,8 +1312,9 @@ private class FunctionEmitter private (
        * However we necessarily have a `null` receiver if we reach this point,
        * so we can trap as NPE.
        */
-      fb += wa.Unreachable
+      genNPE()
     } else {
+      genCheckNonNullFor(qualifier)
       fb += wa.StructGet(
         genTypeID.forClass(className),
         genFieldID.forClassInstanceField(fieldName)
@@ -1976,12 +2137,13 @@ private class FunctionEmitter private (
 
       genTreeAuto(expr)
       markPosition(tree)
-      fb += wa.StructGet(genTypeID.ObjectStruct, genFieldID.objStruct.vtable) // implicit trap on null
+      genCheckNonNullFor(expr)
+      fb += wa.StructGet(genTypeID.ObjectStruct, genFieldID.objStruct.vtable)
       fb += wa.Call(genFunctionID.getClassOf)
     } else {
-      genTree(expr, AnyType)
+      genTreeToAny(expr)
       markPosition(tree)
-      fb += wa.RefAsNonNull
+      genAsNonNullOrNPEFor(expr)
       fb += wa.Call(genFunctionID.anyGetClass)
     }
 
@@ -2128,7 +2290,9 @@ private class FunctionEmitter private (
     if (UseLegacyExceptionsForTryCatch) {
       markPosition(tree)
       fb += wa.Try(fb.sigToBlockType(Sig(Nil, resultType)))
-      genTree(block, expectedType)
+      withNPEScope(resultType) {
+        genTree(block, expectedType)
+      }
       markPosition(tree)
       fb += wa.Catch(genTagID.exception)
       withNewLocal(errVarName, errVarOrigName, watpe.RefType.anyref) { exceptionLocal =>
@@ -2150,7 +2314,9 @@ private class FunctionEmitter private (
           fb.tryTable(watpe.RefType.externref)(
             List(wa.CatchClause.Catch(genTagID.exception, catchLabel))
           ) {
-            genTree(block, expectedType)
+            withNPEScope(resultType) {
+              genTree(block, expectedType)
+            }
             markPosition(tree)
             fb += wa.Br(doneLabel)
           }
@@ -2325,11 +2491,11 @@ private class FunctionEmitter private (
     val UnwrapFromThrowable(expr) = tree
 
     fb.block(watpe.RefType.anyref) { doneLabel =>
-      genTree(expr, ClassType(ThrowableClass, nullable = true))
+      genTreeAuto(expr)
 
       markPosition(tree)
 
-      fb += wa.RefAsNonNull
+      genAsNonNullOrNPEFor(expr)
 
       // if !expr.isInstanceOf[js.JavaScriptException], then br $done
       fb += wa.BrOnCastFail(
@@ -2567,7 +2733,8 @@ private class FunctionEmitter private (
 
     array.tpe match {
       case ArrayType(arrayTypeRef, _) =>
-        // Get the underlying array; implicit trap on null
+        // Get the underlying array
+        genCheckNonNullFor(array)
         fb += wa.StructGet(
           genTypeID.forArrayClass(arrayTypeRef),
           genFieldID.objStruct.arrayUnderlying
@@ -2580,7 +2747,7 @@ private class FunctionEmitter private (
         // unreachable
         NothingType
       case NullType =>
-        fb += wa.Unreachable
+        genNPE()
         NothingType
       case _ =>
         throw new IllegalArgumentException(
@@ -2660,12 +2827,12 @@ private class FunctionEmitter private (
 
     genTreeAuto(array)
 
-    markPosition(tree)
-
     array.tpe match {
       case ArrayType(arrayTypeRef, _) =>
+        genCheckNonNullFor(array)
+
         if (semantics.arrayIndexOutOfBounds == CheckedBehavior.Unchecked) {
-          // Get the underlying array; implicit trap on null
+          // Get the underlying array
           fb += wa.StructGet(
             genTypeID.forArrayClass(arrayTypeRef),
             genFieldID.objStruct.arrayUnderlying
@@ -2717,7 +2884,7 @@ private class FunctionEmitter private (
         // unreachable
         NothingType
       case NullType =>
-        fb += wa.Unreachable
+        genNPE()
         NothingType
       case _ =>
         throw new IllegalArgumentException(
@@ -2808,17 +2975,17 @@ private class FunctionEmitter private (
 
       case NullType =>
         genTree(expr, NullType)
-        fb += wa.Unreachable // trap for NPE
+        genNPE()
         NothingType
 
       case exprType =>
         val exprLocal = addSyntheticLocal(watpe.RefType(genTypeID.ObjectStruct))
 
-        genTree(expr, ClassType(CloneableClass, nullable = true))
+        genTreeAuto(expr)
 
         markPosition(tree)
 
-        fb += wa.RefAsNonNull
+        genAsNonNullOrNPEFor(expr)
         fb += wa.LocalTee(exprLocal)
 
         fb += wa.LocalGet(exprLocal)
@@ -3024,6 +3191,11 @@ private class FunctionEmitter private (
 
   private def genTransient(tree: Transient): Type = {
     tree.value match {
+      case Transients.CheckNotNull(expr) =>
+        genTreeAuto(expr)
+        genAsNonNullOrNPEFor(expr)
+        tree.tpe
+
       case Transients.Cast(expr, tpe) =>
         genCast(expr, tpe, tree.pos)
 
@@ -3031,9 +3203,9 @@ private class FunctionEmitter private (
         genSystemArrayCopy(tree, value)
 
       case Transients.ObjectClassName(obj) =>
-        genTree(obj, AnyType)
+        genTreeToAny(obj)
         markPosition(tree)
-        fb += wa.RefAsNonNull // trap on NPE
+        genAsNonNullOrNPEFor(obj)
         fb += wa.Call(genFunctionID.anyGetClassName)
         StringType
 
@@ -3485,7 +3657,9 @@ private class FunctionEmitter private (
           fb.tryTable()(List(wa.CatchClause.CatchAllRef(catchLabel))) {
             // try block
             enterTryFinally(entry) {
-              genTree(tryBlock, expectedType)
+              withNPEScope(resultType) {
+                genTree(tryBlock, expectedType)
+              }
             }
 
             markPosition(tree)
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
index de6494b653..f7fed865f8 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
@@ -244,6 +244,7 @@ object VarGen {
     case object throwArrayStoreException extends FunctionID
     case object throwArrayIndexOutOfBoundsException extends FunctionID
     case object throwNegativeArraySizeException extends FunctionID
+    case object throwNullPointerException extends FunctionID
     case object checkedStringCharAt extends FunctionID
     case object throwModuleInitError extends FunctionID
     case object isInstanceExternal extends FunctionID
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/FunctionBuilder.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/FunctionBuilder.scala
index fff0a74acd..25162bc9f9 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/FunctionBuilder.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/FunctionBuilder.scala
@@ -140,6 +140,9 @@ final class FunctionBuilder(
   def insert(index: InstructionIndex, instr: Instr): Unit =
     instrs.insert(index.value, instr)
 
+  def insertAll(index: InstructionIndex, instrs: List[Instr]): Unit =
+    this.instrs.insertAll(index.value, instrs)
+
   // Helpers to build structured control flow
 
   def sigToBlockType(sig: FunctionType): BlockType = sig match {
diff --git a/project/Build.scala b/project/Build.scala
index a979a5d46e..3d9a259fe3 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -60,27 +60,15 @@ object ExposedValues extends AutoPlugin {
 
     // set scalaJSLinkerConfig in someProject ~= makeCompliant
     val makeCompliant: StandardConfig => StandardConfig = { prev =>
-      if (prev.experimentalUseWebAssembly) {
-        prev.withSemantics { semantics =>
-          semantics
-            .withAsInstanceOfs(CheckedBehavior.Compliant)
-            .withArrayIndexOutOfBounds(CheckedBehavior.Compliant)
-            .withArrayStores(CheckedBehavior.Compliant)
-            .withNegativeArraySizes(CheckedBehavior.Compliant)
-            .withStringIndexOutOfBounds(CheckedBehavior.Compliant)
-            .withModuleInit(CheckedBehavior.Compliant)
-        }
-      } else {
-        prev.withSemantics { semantics =>
-          semantics
-            .withAsInstanceOfs(CheckedBehavior.Compliant)
-            .withArrayIndexOutOfBounds(CheckedBehavior.Compliant)
-            .withArrayStores(CheckedBehavior.Compliant)
-            .withNegativeArraySizes(CheckedBehavior.Compliant)
-            .withNullPointers(CheckedBehavior.Compliant)
-            .withStringIndexOutOfBounds(CheckedBehavior.Compliant)
-            .withModuleInit(CheckedBehavior.Compliant)
-        }
+      prev.withSemantics { semantics =>
+        semantics
+          .withAsInstanceOfs(CheckedBehavior.Compliant)
+          .withArrayIndexOutOfBounds(CheckedBehavior.Compliant)
+          .withArrayStores(CheckedBehavior.Compliant)
+          .withNegativeArraySizes(CheckedBehavior.Compliant)
+          .withNullPointers(CheckedBehavior.Compliant)
+          .withStringIndexOutOfBounds(CheckedBehavior.Compliant)
+          .withModuleInit(CheckedBehavior.Compliant)
       }
     }
 
@@ -172,14 +160,9 @@ object MyScalaJSPlugin extends AutoPlugin {
           .withMinify(enableMinifyEverywhere.value)
 
         if (enableWasmEverywhere.value) {
-          import CheckedBehavior.Unchecked
           baseConfig
             .withExperimentalUseWebAssembly(true)
             .withModuleKind(ModuleKind.ESModule)
-            .withSemantics { sems =>
-              sems
-                .withNullPointers(Unchecked)
-            }
         } else {
           baseConfig
         }

From 906276cf772282757fb7c7720e3ec8c421d3cce3 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Thu, 29 Aug 2024 23:37:19 +0200
Subject: [PATCH 142/298] Wasm: Fix unboxing `null` to the primitive type
 `string`.

This is a theoretical issue. We have no source syntax to generate
an `asInstanceOf[string]`.

This was discovered while auditing all the `RefAsNonNull`s in
`FunctionEmitter` to implement checked NPEs.
---
 .../linker/backend/wasmemitter/FunctionEmitter.scala        | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
index d503596e5b..0a9874f32c 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
@@ -2082,7 +2082,11 @@ private class FunctionEmitter private (
         fb += wa.GlobalGet(genGlobalID.undef)
 
       case StringType =>
-        fb += wa.RefAsNonNull
+        val sig = watpe.FunctionType(List(watpe.RefType.anyref), List(watpe.RefType.any))
+        fb.block(sig) { nonNullLabel =>
+          fb += wa.BrOnNonNull(nonNullLabel)
+          fb += wa.GlobalGet(genGlobalID.emptyString)
+        }
 
       case CharType | LongType =>
         // Extract the `value` field (the only field) out of the box class.

From a92d4ae43f0b17fc89690f46433dcacfa42a1d4b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Mon, 12 Aug 2024 10:28:39 +0200
Subject: [PATCH 143/298] Run the partest suites with the Wasm backend.

With the `--wasm` flag.
---
 Jenkinsfile                                   | 15 ++++---
 .../scalajs/2.13.13/BlacklistedTests.txt      | 10 +++++
 .../tools/partest/scalajs/ScalaJSRunner.scala |  1 +
 .../tools/partest/scalajs/ScalaJSRunner.scala |  1 +
 .../scala/tools/nsc/MainGenericRunner.scala   | 41 ++++++++++++++++---
 .../partest/scalajs/PartestInterface.scala    |  6 ++-
 .../scalajs/ScalaJSPartestOptions.scala       |  7 +++-
 project/Build.scala                           |  1 +
 8 files changed, 69 insertions(+), 13 deletions(-)

diff --git a/Jenkinsfile b/Jenkinsfile
index 9e1b827a81..814467aee2 100644
--- a/Jenkinsfile
+++ b/Jenkinsfile
@@ -511,21 +511,21 @@ def Tasks = [
     setJavaVersion $java
     npm install &&
     sbtnoretry ++$scala partestSuite$v/test:compile &&
-    sbtnoretry ++$scala "partestSuite$v/testOnly -- --showDiff"
+    sbtnoretry ++$scala "partestSuite$v/testOnly -- $partestopts --showDiff"
   ''',
 
   "partest-fastopt": '''
     setJavaVersion $java
     npm install &&
     sbtnoretry ++$scala partestSuite$v/test:compile &&
-    sbtnoretry ++$scala "partestSuite$v/testOnly -- --fastOpt --showDiff"
+    sbtnoretry ++$scala "partestSuite$v/testOnly -- $partestopts --fastOpt --showDiff"
   ''',
 
   "partest-fullopt": '''
     setJavaVersion $java
     npm install &&
     sbtnoretry ++$scala partestSuite$v/test:compile &&
-    sbtnoretry ++$scala "partestSuite$v/testOnly -- --fullOpt --showDiff"
+    sbtnoretry ++$scala "partestSuite$v/testOnly -- $partestopts --fullOpt --showDiff"
   ''',
 
   "scala3-compat": '''
@@ -603,7 +603,8 @@ mainScalaVersions.each { scalaVersion ->
   quickMatrix.add([task: "test-suite-custom-esversion", scala: scalaVersion, java: mainJavaVersion, esVersion: "ES5_1", testSuite: "scalaTestSuite"])
   quickMatrix.add([task: "test-suite-webassembly", scala: scalaVersion, java: mainJavaVersion, testMinify: "false", testSuite: "scalaTestSuite"])
   quickMatrix.add([task: "bootstrap", scala: scalaVersion, java: mainJavaVersion])
-  quickMatrix.add([task: "partest-fastopt", scala: scalaVersion, java: mainJavaVersion])
+  quickMatrix.add([task: "partest-fastopt", scala: scalaVersion, java: mainJavaVersion, partestopts: ""])
+  quickMatrix.add([task: "partest-fastopt", scala: scalaVersion, java: mainJavaVersion, partestopts: "--wasm"])
 }
 allESVersions.each { esVersion ->
   quickMatrix.add([task: "test-suite-custom-esversion-force-polyfills", scala: mainScalaVersion, java: mainJavaVersion, esVersion: esVersion, testSuite: "testSuite"])
@@ -623,8 +624,10 @@ mainScalaVersions.each { scalaVersion ->
   otherJavaVersions.each { javaVersion ->
     quickMatrix.add([task: "test-suite-default-esversion", scala: scalaVersion, java: javaVersion, testMinify: "false", testSuite: "testSuite"])
   }
-  fullMatrix.add([task: "partest-noopt", scala: scalaVersion, java: mainJavaVersion])
-  fullMatrix.add([task: "partest-fullopt", scala: scalaVersion, java: mainJavaVersion])
+  fullMatrix.add([task: "partest-noopt", scala: scalaVersion, java: mainJavaVersion, partestopts: ""])
+  fullMatrix.add([task: "partest-noopt", scala: scalaVersion, java: mainJavaVersion, partestopts: "--wasm"])
+  fullMatrix.add([task: "partest-fullopt", scala: scalaVersion, java: mainJavaVersion, partestopts: ""])
+  fullMatrix.add([task: "partest-fullopt", scala: scalaVersion, java: mainJavaVersion, partestopts: "--wasm"])
 }
 otherJavaVersions.each { javaVersion ->
   fullMatrix.add([task: "scala3-compat", scala: scala3Version, java: javaVersion])
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/BlacklistedTests.txt b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/BlacklistedTests.txt
index 72066a2706..49e69dacc8 100644
--- a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/BlacklistedTests.txt
+++ b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/BlacklistedTests.txt
@@ -46,6 +46,16 @@ run/valueclasses-classtag-existential.scala
 # Relies on a particular execution speed
 run/t5857.scala
 
+# Uses too much memory (GC stress test), at least on Wasm
+# TODO Investigate. The test came from
+# https://github.com/scala/scala/commit/505b01c06e12c9ca230a17eba1dd9a58d17e7e0b
+# whose commit message is "Null out local vars created by the inliner".
+# Perhaps there is something similar we could do. However, note that in our case
+# the test fails even without the optimizer, so it is not inlining-related.
+# Reducing the size of the big array allows the test to pass, so this might only
+# be a question of differing size constants.
+run/t9137.scala
+
 # Using parts of the javalib we don't plan to support
 
 run/f-interpolator-unit.scala
diff --git a/partest/src/main/scala-new-partest/scala/tools/partest/scalajs/ScalaJSRunner.scala b/partest/src/main/scala-new-partest/scala/tools/partest/scalajs/ScalaJSRunner.scala
index 344c24dcc8..4284e9bb97 100644
--- a/partest/src/main/scala-new-partest/scala/tools/partest/scalajs/ScalaJSRunner.scala
+++ b/partest/src/main/scala-new-partest/scala/tools/partest/scalajs/ScalaJSRunner.scala
@@ -33,6 +33,7 @@ class ScalaJSRunner(testInfo: ScalaJSTestInfo, suiteRunner: AbstractRunner,
 
   override def extraJavaOptions = {
     super.extraJavaOptions ++ Seq(
+        s"-Dscalajs.partest.useWasm=${options.useWasm}",
         s"-Dscalajs.partest.optMode=${options.optMode.id}",
         s"-Dscalajs.partest.compliantSems=${testInfo.compliantSems.mkString(",")}"
     )
diff --git a/partest/src/main/scala-old-partest/scala/tools/partest/scalajs/ScalaJSRunner.scala b/partest/src/main/scala-old-partest/scala/tools/partest/scalajs/ScalaJSRunner.scala
index 865fdaaef9..8fa429a125 100644
--- a/partest/src/main/scala-old-partest/scala/tools/partest/scalajs/ScalaJSRunner.scala
+++ b/partest/src/main/scala-old-partest/scala/tools/partest/scalajs/ScalaJSRunner.scala
@@ -56,6 +56,7 @@ class ScalaJSRunner(testFile: File, suiteRunner: SuiteRunner,
 
   override def extraJavaOptions = {
     super.extraJavaOptions ++ Seq(
+        s"-Dscalajs.partest.useWasm=${options.useWasm}",
         s"-Dscalajs.partest.optMode=${options.optMode.id}",
         s"-Dscalajs.partest.compliantSems=${compliantSems.mkString(",")}"
     )
diff --git a/partest/src/main/scala/scala/tools/nsc/MainGenericRunner.scala b/partest/src/main/scala/scala/tools/nsc/MainGenericRunner.scala
index 184b0afea9..1ee94d93cb 100644
--- a/partest/src/main/scala/scala/tools/nsc/MainGenericRunner.scala
+++ b/partest/src/main/scala/scala/tools/nsc/MainGenericRunner.scala
@@ -49,6 +49,7 @@ class MainGenericRunner {
     false
   }
 
+  val useWasm = System.getProperty("scalajs.partest.useWasm").toBoolean
   val optMode = OptMode.fromId(System.getProperty("scalajs.partest.optMode"))
 
   def readSemantics() = {
@@ -85,23 +86,38 @@ class MainGenericRunner {
     val semantics0 = readSemantics()
     val semantics = if (optMode == FullOpt) semantics0.optimized else semantics0
 
+    val useESModule = useWasm
+
     val moduleInitializers = Seq(ModuleInitializer.mainMethodWithArgs(
         command.thingToRun, "main", command.arguments))
 
     val linkerConfig = StandardConfig()
       .withCheckIR(true)
       .withSemantics(semantics)
+      .withExperimentalUseWebAssembly(useWasm)
+      .withModuleKind(if (useESModule) ModuleKind.ESModule else ModuleKind.NoModule)
       .withSourceMap(false)
       .withOptimizer(optMode != NoOpt)
       .withClosureCompiler(optMode == FullOpt)
       .withBatchMode(true)
+      .withOutputPatterns(OutputPatterns.fromJSFile(if (useESModule) "%s.mjs" else "%s.js"))
 
     val linker = StandardImpl.linker(linkerConfig)
 
-    val sjsCode = {
-      val dir = Jimfs.newFileSystem().getPath("tmp")
-      Files.createDirectory(dir)
+    val dir: Path = if (!useWasm) {
+      val tempDir = Jimfs.newFileSystem().getPath("tmp")
+      Files.createDirectory(tempDir)
+      tempDir
+    } else {
+      /* The Wasm output needs to read other files in the same directory,
+       * with predictable names. Therefore, we need to use real files.
+       */
+      val tempDir = Files.createTempDirectory("tmp-scalajs-partest")
+      tempDir.toFile().deleteOnExit()
+      tempDir
+    }
 
+    val sjsCode = {
       val cache = StandardImpl.irFileCache().newCache
       val result = PathIRContainer
         .fromClasspath(command.settings.classpathURLs.map(urlToPath _))
@@ -117,10 +133,25 @@ class MainGenericRunner {
       dir.resolve(report.publicModules.head.jsFileName)
     }
 
-    val input = Input.Script(sjsCode) :: Nil
+    val jsEnvConfig: NodeJSEnv.Config = if (!useWasm) {
+      NodeJSEnv.Config()
+    } else {
+      NodeJSEnv.Config().withArgs(List(
+        "--experimental-wasm-exnref",
+        /* Force using the Turboshaft infrastructure for the optimizing compiler.
+         * It appears to be more stable for the Wasm that we throw at it.
+         * See also the use of this flag in Build.scala.
+         */
+        "--turboshaft-wasm"
+      ))
+    }
+
+    val input =
+      if (useESModule) Input.ESModule(sjsCode) :: Nil
+      else Input.Script(sjsCode) :: Nil
     val config = RunConfig().withLogger(logger)
 
-    val run = new NodeJSEnv().start(input, config)
+    val run = new NodeJSEnv(jsEnvConfig).start(input, config)
     try {
       Await.result(run.future, Duration.Inf)
     } finally {
diff --git a/partest/src/main/scala/scala/tools/partest/scalajs/PartestInterface.scala b/partest/src/main/scala/scala/tools/partest/scalajs/PartestInterface.scala
index d5b8dafd84..84ab834e3d 100644
--- a/partest/src/main/scala/scala/tools/partest/scalajs/PartestInterface.scala
+++ b/partest/src/main/scala/scala/tools/partest/scalajs/PartestInterface.scala
@@ -96,10 +96,14 @@ case class PartestTask(taskDef: TaskDef, args: Array[String]) extends Task {
       ScalaJSPartestOptions(args, str => loggers.foreach(_.error(str)))
 
     maybeOptions foreach { options =>
+      val testDirs =
+        if (options.useWasm) Array("run") // no point in testing the others twice
+        else Array("run", "pos", "neg")
+
       val runner = SBTRunner(
           Framework.fingerprint, eventHandler, loggers,
           new File(s"../../partest/fetchedSources/${scalaVersion}"),
-          classLoader, null, null, Array.empty[String], Array("run", "pos", "neg"), options, scalaVersion)
+          classLoader, null, null, Array.empty[String], testDirs, options, scalaVersion)
 
       try runner.run()
       catch {
diff --git a/partest/src/main/scala/scala/tools/partest/scalajs/ScalaJSPartestOptions.scala b/partest/src/main/scala/scala/tools/partest/scalajs/ScalaJSPartestOptions.scala
index 953114e410..397d571454 100644
--- a/partest/src/main/scala/scala/tools/partest/scalajs/ScalaJSPartestOptions.scala
+++ b/partest/src/main/scala/scala/tools/partest/scalajs/ScalaJSPartestOptions.scala
@@ -14,6 +14,7 @@ package scala.tools.partest.scalajs
 
 class ScalaJSPartestOptions private (
   val testFilter: ScalaJSPartestOptions.TestFilter,
+  val useWasm: Boolean,
   val optMode: ScalaJSPartestOptions.OptMode,
   val showDiff: Boolean
 ) {
@@ -23,6 +24,7 @@ class ScalaJSPartestOptions private (
     s"""
     |Scala.js version is: $currentVersion
     |Scala.js options are:
+    |Wasm:                ${useWasm}
     |optimizer:           ${optMode.shortStr}
     |testFilter:          ${testFilter.descr}
     """.stripMargin
@@ -77,6 +79,7 @@ object ScalaJSPartestOptions {
     var failed = false
 
     var filter: Option[TestFilter] = None
+    var useWasm: Boolean = false
     var optMode: OptMode = NoOpt
     var showDiff: Boolean = false
 
@@ -96,6 +99,8 @@ object ScalaJSPartestOptions {
     }
 
     for (arg <- args) arg match {
+      case "--wasm" =>
+        useWasm = true
       case "--fastOpt" =>
         optMode = FastOpt
       case "--noOpt" =>
@@ -115,7 +120,7 @@ object ScalaJSPartestOptions {
     if (failed) None
     else Some {
       new ScalaJSPartestOptions(
-        filter.getOrElse(WhitelistedTests), optMode, showDiff)
+        filter.getOrElse(WhitelistedTests), useWasm, optMode, showDiff)
     }
   }
 
diff --git a/project/Build.scala b/project/Build.scala
index 3d9a259fe3..eeca43d4f5 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -252,6 +252,7 @@ object MyScalaJSPlugin extends AutoPlugin {
             /* Force using the Turboshaft infrastructure for the optimizing compiler.
              * It appears to be more stable for the Wasm that we throw at it.
              * If you remove it, try running `scalaTestSuite2_13/test` with Wasm.
+             * See also the use of this flag in MainGenericRunner.scala.
              */
             "--turboshaft-wasm",
           ))

From c3a2fe973c4cffad03c9f33c3410f0f5caf8c04f Mon Sep 17 00:00:00 2001
From: Rikito Taniguchi <rikiriki1238@gmail.com>
Date: Sat, 31 Aug 2024 11:03:22 +0900
Subject: [PATCH 144/298] Update local publish instructions

It was seemingly `scalalib2_12` (which is dependent to Scala version) was
missing from the local publish instructions.
---
 DEVELOPING.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/DEVELOPING.md b/DEVELOPING.md
index 1664d8a3c4..29dc5d18fa 100644
--- a/DEVELOPING.md
+++ b/DEVELOPING.md
@@ -171,7 +171,7 @@ following incantations.
 `SCALA_VERSION` refers to the Scala version used by the separate project.
 
     > ;ir2_12/publishLocal;linkerInterface2_12/publishLocal;linker2_12/publishLocal;testAdapter2_12/publishLocal;sbtPlugin/publishLocal;javalib/publishLocal;javalibintf/publishLocal
-    > ;library2_12/publishLocal;testInterface2_12/publishLocal;testBridge2_12/publishLocal;jUnitRuntime2_12/publishLocal;jUnitPlugin2_12/publishLocal
+    > ;library2_12/publishLocal;testInterface2_12/publishLocal;testBridge2_12/publishLocal;jUnitRuntime2_12/publishLocal;jUnitPlugin2_12/publishLocal;scalalib2_12/publishLocal
     > ++SCALA_VERSION compiler2_12/publishLocal
 
 If using a non-2.12.x version for the Scala version, the `2_12` suffixes must be adapted in the second and third command (not in the first command).

From 6bc953e3688ebaa2b072b918c1431fba8d68243b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Sat, 31 Aug 2024 12:04:35 +0200
Subject: [PATCH 145/298] Use some more methods on strings from ES 2015.

---
 .../src/main/scala/java/lang/Character.scala  | 26 ++++++++++------
 .../src/main/scala/java/lang/_String.scala    | 31 +++++++++++++++----
 .../testsuite/javalib/lang/StringTest.scala   |  8 ++++-
 3 files changed, 49 insertions(+), 16 deletions(-)

diff --git a/javalib/src/main/scala/java/lang/Character.scala b/javalib/src/main/scala/java/lang/Character.scala
index e5f132fd49..30cd3efcd9 100644
--- a/javalib/src/main/scala/java/lang/Character.scala
+++ b/javalib/src/main/scala/java/lang/Character.scala
@@ -13,7 +13,10 @@
 package java.lang
 
 import scala.annotation.{tailrec, switch}
+
 import scala.scalajs.js
+import scala.scalajs.runtime.linkingInfo
+import scala.scalajs.LinkingInfo.ESVersion
 
 import java.lang.constant.Constable
 import java.util.{ArrayList, Arrays, HashMap}
@@ -121,16 +124,21 @@ object Character {
     "" + c
 
   def toString(codePoint: Int): String = {
-    if (isBmpCodePoint(codePoint)) {
-      js.Dynamic.global.String
-        .fromCharCode(codePoint)
-        .asInstanceOf[String]
-    } else if (isValidCodePoint(codePoint)) {
-      js.Dynamic.global.String
-        .fromCharCode(highSurrogate(codePoint).toInt, lowSurrogate(codePoint).toInt)
-        .asInstanceOf[String]
-    } else {
+    if (!isValidCodePoint(codePoint))
       throw new IllegalArgumentException()
+
+    if (linkingInfo.esVersion >= ESVersion.ES2015) {
+      js.Dynamic.global.String.fromCodePoint(codePoint).asInstanceOf[String]
+    } else {
+      if (codePoint < MIN_SUPPLEMENTARY_CODE_POINT) {
+        js.Dynamic.global.String
+          .fromCharCode(codePoint)
+          .asInstanceOf[String]
+      } else {
+        js.Dynamic.global.String
+          .fromCharCode(highSurrogate(codePoint).toInt, lowSurrogate(codePoint).toInt)
+          .asInstanceOf[String]
+      }
     }
   }
 
diff --git a/javalib/src/main/scala/java/lang/_String.scala b/javalib/src/main/scala/java/lang/_String.scala
index e016d070d4..8ea2a2c70a 100644
--- a/javalib/src/main/scala/java/lang/_String.scala
+++ b/javalib/src/main/scala/java/lang/_String.scala
@@ -213,8 +213,15 @@ final class _String private () // scalastyle:ignore
   def contains(s: CharSequence): scala.Boolean =
     indexOf(s.toString) != -1
 
-  def endsWith(suffix: String): scala.Boolean =
-    thisString.jsSubstring(this.length() - suffix.length()) == suffix
+  @inline
+  def endsWith(suffix: String): scala.Boolean = {
+    if (linkingInfo.esVersion >= ESVersion.ES2015) {
+      suffix.getClass() // null check
+      thisString.asInstanceOf[js.Dynamic].endsWith(suffix).asInstanceOf[scala.Boolean]
+    } else {
+      thisString.jsSubstring(this.length() - suffix.length()) == suffix
+    }
+  }
 
   def getBytes(): Array[scala.Byte] =
     getBytes(Charset.defaultCharset())
@@ -359,13 +366,25 @@ final class _String private () // scalastyle:ignore
     Pattern.compile(regex).split(thisString, limit)
 
   @inline
-  def startsWith(prefix: String): scala.Boolean =
-    startsWith(prefix, 0)
+  def startsWith(prefix: String): scala.Boolean = {
+    if (linkingInfo.esVersion >= ESVersion.ES2015) {
+      prefix.getClass() // null check
+      thisString.asInstanceOf[js.Dynamic].startsWith(prefix).asInstanceOf[scala.Boolean]
+    } else {
+      thisString.jsSubstring(0, prefix.length()) == prefix
+    }
+  }
 
   @inline
   def startsWith(prefix: String, toffset: Int): scala.Boolean = {
-    (toffset <= length() && toffset >= 0 &&
-        thisString.jsSubstring(toffset, toffset + prefix.length()) == prefix)
+    if (linkingInfo.esVersion >= ESVersion.ES2015) {
+      prefix.getClass() // null check
+      (toffset <= length() && toffset >= 0 &&
+          thisString.asInstanceOf[js.Dynamic].startsWith(prefix, toffset).asInstanceOf[scala.Boolean])
+    } else {
+      (toffset <= length() && toffset >= 0 &&
+          thisString.jsSubstring(toffset, toffset + prefix.length()) == prefix)
+    }
   }
 
   @inline
diff --git a/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/lang/StringTest.scala b/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/lang/StringTest.scala
index 49b7786a2e..1637b7e687 100644
--- a/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/lang/StringTest.scala
+++ b/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/lang/StringTest.scala
@@ -18,7 +18,7 @@ import org.junit.Test
 import org.junit.Assert._
 import org.junit.Assume._
 
-import org.scalajs.testsuite.utils.AssertThrows.assertThrows
+import org.scalajs.testsuite.utils.AssertThrows.{assertThrows, assertThrowsNPEIfCompliant}
 import org.scalajs.testsuite.utils.Platform._
 
 class StringTest {
@@ -96,6 +96,8 @@ class StringTest {
     assertTrue("Scala.js".startsWith("Scala.js"))
     assertFalse("Scala.js".startsWith("scala"))
     assertTrue("ananas".startsWith("an"))
+
+    assertThrowsNPEIfCompliant("ananas".startsWith(null))
   }
 
   @Test def endsWith(): Unit = {
@@ -103,6 +105,8 @@ class StringTest {
     assertTrue("Scala.js".endsWith("Scala.js"))
     assertFalse("Scala.js".endsWith("JS"))
     assertTrue("banana".endsWith("na"))
+
+    assertThrowsNPEIfCompliant("banana".endsWith(null))
   }
 
   @Test def indexOfString(): Unit = {
@@ -429,6 +433,8 @@ class StringTest {
     assertFalse("Scala.js".startsWith(".js", 10))
     assertFalse("Scala.js".startsWith("", -1))
     assertFalse("Scala.js".startsWith("", 9))
+
+    assertThrowsNPEIfCompliant("Scala.js".startsWith(null, 2))
   }
 
   @Test def toCharArray(): Unit = {

From ca8ba12781ec0761643dea7e9be9e1edc0351243 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Sun, 25 Aug 2024 20:24:05 +0200
Subject: [PATCH 146/298] Wasm: Use dedicated helpers to support some
 operations of the core lib.

Previously, the core lib itself used the general-purpose JS
interop helpers. That was fine, but required several round-trips
for no good reason. We now use dedicated helpers instead.
---
 .../backend/wasmemitter/CoreWasmLib.scala     | 158 ++++--------------
 .../backend/wasmemitter/LoaderContent.scala   |  18 ++
 .../linker/backend/wasmemitter/VarGen.scala   |   7 +-
 3 files changed, 60 insertions(+), 123 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
index 3bfe0a05cd..cfb85db08a 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
@@ -386,6 +386,26 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
       Nil
     )
 
+    addHelperImport(
+      genFunctionID.genJSTypeMetaData,
+      List(
+        RefType(genTypeID.typeData), // typeData
+        RefType.any, // name
+        Int32, // isPrimitive
+        Int32, // isArrayClass
+        Int32, // isInterface,
+        RefType.func, // isInstanceFun
+        RefType.func, // isAssignableFromFun
+        RefType.func, // checkCastFun
+        RefType.func, // getComponentTypeFun
+        RefType.func // newArrayOfThisClassFun
+      ),
+      List(RefType.any)
+    )
+    addHelperImport(genFunctionID.makeTypeError, List(RefType.any), List(RefType.extern))
+    addHelperImport(genFunctionID.jsArrayLength, List(anyref), List(Int32))
+    addHelperImport(genFunctionID.jsArrayGetInt, List(anyref, Int32), List(Int32))
+
     addHelperImport(genFunctionID.jsGlobalRefGet, List(RefType.any), List(anyref))
     addHelperImport(genFunctionID.jsGlobalRefSet, List(RefType.any, anyref), Nil)
     addHelperImport(genFunctionID.jsGlobalRefTypeof, List(RefType.any), List(RefType.any))
@@ -635,9 +655,7 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
       genThrowModuleInitError()
     }
 
-    genIsInstanceExternal()
     genIsInstance()
-    genIsAssignableFromExternal()
     genIsAssignableFrom()
     genCheckCast()
     genGetComponentType()
@@ -917,71 +935,35 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
      * Specified by https://lampwww.epfl.ch/~doeraene/sjsir-semantics/#sec-sjsir-createclassdataof
      * Leave it on the stack.
      */
-    fb += Call(genFunctionID.jsNewObject)
-    // "__typeData": typeData (TODO hide this better? although nobody will notice anyway)
-    // (this is used by `isAssignableFromExternal`)
-    fb ++= ctx.stringPool.getConstantStringInstr("__typeData")
+
+    // typeData
     fb += LocalGet(typeDataParam)
-    fb += Call(genFunctionID.jsObjectPush)
-    // "name": typeDataName(typeData)
-    fb ++= ctx.stringPool.getConstantStringInstr("name")
+    // name
     fb += LocalGet(typeDataParam)
     fb += Call(genFunctionID.typeDataName)
-    fb += Call(genFunctionID.jsObjectPush)
-    // "isPrimitive": (typeData.kind <= KindLastPrimitive)
-    fb ++= ctx.stringPool.getConstantStringInstr("isPrimitive")
+    // isPrimitive: (typeData.kind <= KindLastPrimitive)
     fb += LocalGet(typeDataParam)
     fb += StructGet(genTypeID.typeData, genFieldID.typeData.kind)
     fb += I32Const(KindLastPrimitive)
     fb += I32LeU
-    fb += Call(genFunctionID.box(BooleanRef))
-    fb += Call(genFunctionID.jsObjectPush)
-    // "isArrayClass": (typeData.kind == KindArray)
-    fb ++= ctx.stringPool.getConstantStringInstr("isArrayClass")
+    // isArrayClass: (typeData.kind == KindArray)
     fb += LocalGet(typeDataParam)
     fb += StructGet(genTypeID.typeData, genFieldID.typeData.kind)
     fb += I32Const(KindArray)
     fb += I32Eq
-    fb += Call(genFunctionID.box(BooleanRef))
-    fb += Call(genFunctionID.jsObjectPush)
-    // "isInterface": (typeData.kind == KindInterface)
-    fb ++= ctx.stringPool.getConstantStringInstr("isInterface")
+    // isInterface: (typeData.kind == KindInterface)
     fb += LocalGet(typeDataParam)
     fb += StructGet(genTypeID.typeData, genFieldID.typeData.kind)
     fb += I32Const(KindInterface)
     fb += I32Eq
-    fb += Call(genFunctionID.box(BooleanRef))
-    fb += Call(genFunctionID.jsObjectPush)
-    // "isInstance": closure(isInstance, typeData)
-    fb ++= ctx.stringPool.getConstantStringInstr("isInstance")
-    fb += ctx.refFuncWithDeclaration(genFunctionID.isInstanceExternal)
-    fb += LocalGet(typeDataParam)
-    fb += Call(genFunctionID.closure)
-    fb += Call(genFunctionID.jsObjectPush)
-    // "isAssignableFrom": closure(isAssignableFrom, typeData)
-    fb ++= ctx.stringPool.getConstantStringInstr("isAssignableFrom")
-    fb += ctx.refFuncWithDeclaration(genFunctionID.isAssignableFromExternal)
-    fb += LocalGet(typeDataParam)
-    fb += Call(genFunctionID.closure)
-    fb += Call(genFunctionID.jsObjectPush)
-    // "checkCast": closure(checkCast, typeData)
-    fb ++= ctx.stringPool.getConstantStringInstr("checkCast")
+    // the various helper functions
+    fb += ctx.refFuncWithDeclaration(genFunctionID.isInstance)
+    fb += ctx.refFuncWithDeclaration(genFunctionID.isAssignableFrom)
     fb += ctx.refFuncWithDeclaration(genFunctionID.checkCast)
-    fb += LocalGet(typeDataParam)
-    fb += Call(genFunctionID.closure)
-    fb += Call(genFunctionID.jsObjectPush)
-    // "getComponentType": closure(getComponentType, typeData)
-    fb ++= ctx.stringPool.getConstantStringInstr("getComponentType")
     fb += ctx.refFuncWithDeclaration(genFunctionID.getComponentType)
-    fb += LocalGet(typeDataParam)
-    fb += Call(genFunctionID.closure)
-    fb += Call(genFunctionID.jsObjectPush)
-    // "newArrayOfThisClass": closure(newArrayOfThisClass, typeData)
-    fb ++= ctx.stringPool.getConstantStringInstr("newArrayOfThisClass")
     fb += ctx.refFuncWithDeclaration(genFunctionID.newArrayOfThisClass)
-    fb += LocalGet(typeDataParam)
-    fb += Call(genFunctionID.closure)
-    fb += Call(genFunctionID.jsObjectPush)
+    // call the helper to build the metadata object
+    fb += Call(genFunctionID.genJSTypeMetaData)
 
     // Call java.lang.Class::<init>(dataObject)
     fb += Call(
@@ -1738,33 +1720,9 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
     fb.buildAndAddToModule()
   }
 
-  /** `isInstanceExternal: (ref typeData), anyref -> anyref` (a boxed boolean).
-   *
-   *  Tests whether the given value is a non-null instance of the given type.
-   *
-   *  Specified by `"isInstance"` at
-   *  [[https://lampwww.epfl.ch/~doeraene/sjsir-semantics/#sec-sjsir-createclassdataof]].
-   */
-  private def genIsInstanceExternal()(implicit ctx: WasmContext): Unit = {
-    val fb = newFunctionBuilder(genFunctionID.isInstanceExternal)
-    val typeDataParam = fb.addParam("typeData", RefType(genTypeID.typeData))
-    val valueParam = fb.addParam("value", RefType.anyref)
-    fb.setResultType(anyref)
-
-    fb += LocalGet(typeDataParam)
-    fb += LocalGet(valueParam)
-    fb += Call(genFunctionID.isInstance)
-    fb += Call(genFunctionID.box(BooleanRef))
-
-    fb.buildAndAddToModule()
-  }
-
   /** `isInstance: (ref typeData), anyref -> i32` (a boolean).
    *
    *  Tests whether the given value is a non-null instance of the given type.
-   *
-   *  Internal implementation of `isInstanceExternal`, returning a primitive
-   *  `i32` instead of a boxed boolean.
    */
   private def genIsInstance()(implicit ctx: WasmContext): Unit = {
     import genFieldID.typeData._
@@ -1856,15 +1814,10 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
         fb += Drop // drop `value` which was left on the stack
 
         // throw new TypeError("...")
-        fb ++= ctx.stringPool.getConstantStringInstr("TypeError")
-        fb += Call(genFunctionID.jsGlobalRefGet)
-        fb += Call(genFunctionID.jsNewArray)
         fb ++= ctx.stringPool.getConstantStringInstr(
           "Cannot call isInstance() on a Class representing a JS trait/object"
         )
-        fb += Call(genFunctionID.jsArrayPush)
-        fb += Call(genFunctionID.jsNew)
-        fb += ExternConvertAny
+        fb += Call(genFunctionID.makeTypeError)
         fb += Throw(genTagID.exception)
       }
     ) { () =>
@@ -1948,34 +1901,6 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
     fb.buildAndAddToModule()
   }
 
-  /** `isAssignableFromExternal: (ref typeData), anyref -> i32` (a boolean).
-   *
-   *  This is the underlying func for the `isAssignableFrom()` closure inside class data objects.
-   */
-  private def genIsAssignableFromExternal()(implicit ctx: WasmContext): Unit = {
-    val typeDataType = RefType(genTypeID.typeData)
-
-    val fb = newFunctionBuilder(genFunctionID.isAssignableFromExternal)
-    val typeDataParam = fb.addParam("typeData", typeDataType)
-    val fromParam = fb.addParam("from", RefType.anyref)
-    fb.setResultType(anyref)
-
-    // load typeData
-    fb += LocalGet(typeDataParam)
-
-    // load ref.cast<typeData> from["__typeData"] (as a JS selection)
-    fb += LocalGet(fromParam)
-    fb ++= ctx.stringPool.getConstantStringInstr("__typeData")
-    fb += Call(genFunctionID.jsSelect)
-    fb += RefCast(RefType(typeDataType.heapType))
-
-    // delegate to isAssignableFrom
-    fb += Call(genFunctionID.isAssignableFrom)
-    fb += Call(genFunctionID.box(BooleanRef))
-
-    fb.buildAndAddToModule()
-  }
-
   /** `isAssignableFrom: (ref typeData), (ref typeData) -> i32` (a boolean).
    *
    *  Specified by `java.lang.Class.isAssignableFrom(Class)`.
@@ -2186,11 +2111,9 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
     val lengthsValuesLocal = fb.addLocal("lengthsValues", i32ArrayType)
     val iLocal = fb.addLocal("i", Int32)
 
-    // lengthsLen := lengths.length // as a JS field access
+    // lengthsLen := lengths.length // as a JS field access, through a helper
     fb += LocalGet(lengthsParam)
-    fb ++= ctx.stringPool.getConstantStringInstr("length")
-    fb += Call(genFunctionID.jsSelect)
-    fb += Call(genFunctionID.unbox(IntRef))
+    fb += Call(genFunctionID.jsArrayLength)
     fb += LocalTee(lengthsLenLocal)
 
     // lengthsValues := array.new<i32Array> lengthsLen
@@ -2207,16 +2130,14 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
       fb += LocalGet(lengthsLenLocal)
       fb += I32Ne
     } {
-      // lengthsValue[i] := lengths[i] (where the rhs is a JS field access)
+      // lengthsValue[i] := lengths[i] (where the rhs is a JS field access, though a helper)
 
       fb += LocalGet(lengthsValuesLocal)
       fb += LocalGet(iLocal)
 
       fb += LocalGet(lengthsParam)
       fb += LocalGet(iLocal)
-      fb += RefI31
-      fb += Call(genFunctionID.jsSelect)
-      fb += Call(genFunctionID.unbox(IntRef))
+      fb += Call(genFunctionID.jsArrayGetInt)
 
       fb += ArraySet(genTypeID.i32Array)
 
@@ -2864,15 +2785,10 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
     }
 
     // throw new TypeError("...")
-    fb ++= ctx.stringPool.getConstantStringInstr("TypeError")
-    fb += Call(genFunctionID.jsGlobalRefGet)
-    fb += Call(genFunctionID.jsNewArray)
     // Originally, exception is thrown from JS saying e.g. "obj2.z1__ is not a function"
     // TODO Improve the error message to include some information about the missing method
     fb ++= ctx.stringPool.getConstantStringInstr("Method not found")
-    fb += Call(genFunctionID.jsArrayPush)
-    fb += Call(genFunctionID.jsNew)
-    fb += ExternConvertAny
+    fb += Call(genFunctionID.makeTypeError)
     fb += Throw(genTagID.exception)
 
     fb.buildAndAddToModule()
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala
index d05d14942a..b658a8b745 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala
@@ -177,6 +177,24 @@ const scalaJSHelpers = {
   idHashCodeGet: (map, obj) => map.get(obj) | 0, // undefined becomes 0
   idHashCodeSet: (map, obj, value) => map.set(obj, value),
 
+  // Some support functions for CoreWasmLib
+  genJSTypeMetaData: (typeData, name, isPrimitive, isArrayClass, isInterface, isInstanceFun,
+      isAssignableFromFun, checkCastFun, getComponentTypeFun, newArrayOfThisClassFun) => ({
+    __typeData: typeData, // (TODO hide this better? although nobody will notice anyway)
+    "name": name,
+    "isPrimitive": isPrimitive !== 0,
+    "isArrayClass": isArrayClass !== 0,
+    "isInterface": isInterface !== 0,
+    "isInstance": (value) => isInstanceFun(typeData, value) !== 0,
+    "isAssignableFrom": (that) => isAssignableFromFun(typeData, that.__typeData) !== 0,
+    "checkCast": (value) => checkCastFun(typeData, value),
+    "getComponentType": () => getComponentTypeFun(typeData),
+    "newArrayOfThisClass": (lengths) => newArrayOfThisClassFun(typeData, lengths),
+  }),
+  makeTypeError: (msg) => new TypeError(msg),
+  jsArrayLength: (array) => array.length,
+  jsArrayGetInt: (array, index) => array[index],
+
   // JS interop
   jsGlobalRefGet: (globalRefName) => (new Function("return " + globalRefName))(),
   jsGlobalRefSet: (globalRefName, v) => {
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
index f7fed865f8..21c0166a08 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
@@ -156,6 +156,11 @@ object VarGen {
     case object idHashCodeGet extends JSHelperFunctionID
     case object idHashCodeSet extends JSHelperFunctionID
 
+    case object genJSTypeMetaData extends JSHelperFunctionID
+    case object makeTypeError extends JSHelperFunctionID
+    case object jsArrayLength extends JSHelperFunctionID
+    case object jsArrayGetInt extends JSHelperFunctionID
+
     case object jsGlobalRefGet extends JSHelperFunctionID
     case object jsGlobalRefSet extends JSHelperFunctionID
     case object jsGlobalRefTypeof extends JSHelperFunctionID
@@ -247,9 +252,7 @@ object VarGen {
     case object throwNullPointerException extends FunctionID
     case object checkedStringCharAt extends FunctionID
     case object throwModuleInitError extends FunctionID
-    case object isInstanceExternal extends FunctionID
     case object isInstance extends FunctionID
-    case object isAssignableFromExternal extends FunctionID
     case object isAssignableFrom extends FunctionID
     case object checkCast extends FunctionID
     case object getComponentType extends FunctionID

From 8d5b08949b289c16ef7fdd220ad48d3e45d68ffe Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Mon, 3 Jun 2024 16:07:46 +0200
Subject: [PATCH 147/298] Wasm: Optimize reference equality as `ref.is_null` or
 `ref.eq`.

Avoiding the round-trip to a JS helper when we can was measured to
provide significant performance improvements.
---
 .../backend/wasmemitter/FunctionEmitter.scala | 74 ++++++++++++++++---
 1 file changed, 64 insertions(+), 10 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
index 0a9874f32c..8e9fed6d9f 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
@@ -1518,19 +1518,73 @@ private class FunctionEmitter private (
     val BinaryOp(op, lhs, rhs) = tree
     assert(op == === || op == !==)
 
-    // TODO Optimize this when the operands have a better type than `any`
-
-    genTree(lhs, AnyType)
-    genTree(rhs, AnyType)
-
-    markPosition(tree)
+    def maybeGenInvert(): Unit = {
+      if (op == BinaryOp.!==)
+        fb += wa.I32Eqz
+    }
 
-    fb += wa.Call(genFunctionID.is)
+    /* Can we use `ref.eq` for the given type?
+     *
+     * This is the case if the Wasm encoding of the given type a subtype of
+     * `eqref`, i.e., `(ref null eq)`.
+     *
+     * This requires that it be a ref type of the form `(ref null? heapType)`
+     * and that the `heapType` be a sub-heap-type of `eq`.
+     *
+     * Note that all the `HeapType.Type(_)`s returned by `transformSingleType`
+     * point to struct types, which are sub-heap-types of `eq`. (In general
+     * this is not true, since they could also point to `func` heap types,
+     * which are not sub-heap-types of `eq`.)
+     *
+     * Therefore, in practice, the only heap type we can observe and that is
+     * *not* a sub-heap-type of `eq` is `any`.
+     */
+    def canUseRefEq(tpe: Type): Boolean = transformSingleType(tpe) match {
+      case watpe.RefType(_, heapType) => heapType != watpe.HeapType.Any
+      case _                          => false
+    }
 
-    if (op == !==)
-      fb += wa.I32Eqz
+    val lhsType = lhs.tpe
+    val rhsType = rhs.tpe
 
-    BooleanType
+    if (lhsType == NothingType) {
+      genTree(lhs, NothingType)
+      NothingType
+    } else if (rhsType == NothingType) {
+      genTree(lhs, NoType)
+      genTree(rhs, NothingType)
+      NothingType
+    } else if (rhsType == NullType) {
+      /* Note that the optimizer normalizes Literals on the right of `===`,
+       * so testing for the `lhsType == NullType` is not as useful.
+       */
+      genTree(lhs, AnyType)
+      genTree(rhs, NoType) // no-op if it is actually a Null() literal
+      markPosition(tree)
+      fb += wa.RefIsNull
+      maybeGenInvert()
+      BooleanType
+    } else if (canUseRefEq(lhsType) && canUseRefEq(rhsType)) {
+      /* When both types translate to Wasm types that are subtypes of `eqref`,
+       * we can use `ref.eq`. Note that for all possible `eqref`s (in all of
+       * Wasm, not just the subset that we use), `Object.is` coincides with
+       * `ref.eq`. So this is a sound optimization over using `Object.is`.
+       */
+      genTree(lhs, lhsType)
+      genTree(rhs, rhsType)
+      markPosition(tree)
+      fb += wa.RefEq
+      maybeGenInvert()
+      BooleanType
+    } else {
+      // Otherwise, fall back on the `Object.is` helper
+      genTree(lhs, AnyType)
+      genTree(rhs, AnyType)
+      markPosition(tree)
+      fb += wa.Call(genFunctionID.is)
+      maybeGenInvert()
+      BooleanType
+    }
   }
 
   private def getElementaryBinaryOpInstr(op: BinaryOp.Code): wa.Instr = {

From 25c3bc9cba7f50ed5f199fc16187646eec32a9c6 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Sun, 9 Jun 2024 12:04:53 +0200
Subject: [PATCH 148/298] Wasm: Optimize boxing and unboxing Ints by using
 ref.i31 when possible.

Profiling showed that going through the JS helpers is sufficiently
expensive that spending more instructions on the Wasm side is better.
---
 .../backend/wasmemitter/CoreWasmLib.scala     | 75 ++++++++++++++++++-
 .../backend/wasmemitter/LoaderContent.scala   |  4 +-
 .../linker/backend/wasmemitter/VarGen.scala   |  3 +
 .../linker/backend/webassembly/Types.scala    |  4 +
 4 files changed, 81 insertions(+), 5 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
index 3bfe0a05cd..c8646aa6bb 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
@@ -310,7 +310,7 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
 
     addHelperImport(genFunctionID.isUndef, List(anyref), List(Int32))
 
-    for (primRef <- List(BooleanRef, ByteRef, ShortRef, IntRef, FloatRef, DoubleRef)) {
+    for (primRef <- List(BooleanRef, ByteRef, ShortRef, FloatRef, DoubleRef)) {
       val wasmType = primRef match {
         case FloatRef  => Float32
         case DoubleRef => Float64
@@ -321,6 +321,10 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
       addHelperImport(genFunctionID.typeTest(primRef), List(anyref), List(Int32))
     }
 
+    addHelperImport(genFunctionID.bIFallback, List(Int32), List(RefType.any))
+    addHelperImport(genFunctionID.uIFallback, List(anyref), List(Int32))
+    addHelperImport(genFunctionID.typeTest(IntRef), List(anyref), List(Int32))
+
     addHelperImport(genFunctionID.fmod, List(Float64, Float64), List(Float64))
 
     addHelperImport(
@@ -590,6 +594,8 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
 
   /** Generates all the helper function definitions of the core Wasm lib. */
   private def genHelperDefinitions()(implicit ctx: WasmContext): Unit = {
+    genBoxInt()
+    genUnboxInt()
     genStringLiteral()
     genCreateStringFromData()
     genTypeDataName()
@@ -662,6 +668,57 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
     newFunctionBuilder(functionID, OriginalName(functionID.toString()))
   }
 
+  private def genBoxInt()(implicit ctx: WasmContext): Unit = {
+    val fb = newFunctionBuilder(genFunctionID.box(IntRef))
+    val xParam = fb.addParam("x", Int32)
+    fb.setResultType(RefType.any)
+
+    /* Test if the two most significant bits are different: (x ^ (x << 1)) & 0x80000000
+     * If they are, we cannot box as i31 since sign extension on unbox will
+     * duplicate the second most significant bit (and JS would see the wrong
+     * number value as well).
+     */
+    fb += LocalGet(xParam)
+    fb += LocalGet(xParam)
+    fb += I32Const(1)
+    fb += I32Shl
+    fb += I32Xor
+    fb += I32Const(0x80000000)
+    fb += I32And
+
+    // If non-zero,
+    fb.ifThenElse(RefType.any) {
+      // then call the fallback JS helper
+      fb += LocalGet(xParam)
+      fb += Call(genFunctionID.bIFallback)
+    } {
+      // else use ref.i31
+      fb += LocalGet(xParam)
+      fb += RefI31
+    }
+
+    fb.buildAndAddToModule()
+  }
+
+  private def genUnboxInt()(implicit ctx: WasmContext): Unit = {
+    val fb = newFunctionBuilder(genFunctionID.unbox(IntRef))
+    val xParam = fb.addParam("x", RefType.anyref)
+    fb.setResultType(Int32)
+
+    // If x is a (ref i31), extract it
+    fb.block(RefType.anyref) { xIsNotI31Label =>
+      fb += LocalGet(xParam)
+      fb += BrOnCastFail(xIsNotI31Label, RefType.anyref, RefType.i31)
+      fb += I31GetS
+      fb += Return
+    }
+
+    // Otherwise, use the fallback helper
+    fb += Call(genFunctionID.uIFallback)
+
+    fb.buildAndAddToModule()
+  }
+
   private def genStringLiteral()(implicit ctx: WasmContext): Unit = {
     val fb = newFunctionBuilder(genFunctionID.stringLiteral)
     val offsetParam = fb.addParam("offset", Int32)
@@ -1168,8 +1225,20 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
 
         // For all other types, use type test, and separately unbox if required
         case _ =>
-          fb += LocalGet(objParam)
-          fb += BrOnNull(objIsNullLabel)
+          // For Int, include a fast path for values that fit in i31
+          if (primType == IntType) {
+            fb.block(RefType.any) { notI31Label =>
+              fb += LocalGet(objParam)
+              fb += BrOnNull(objIsNullLabel)
+              fb += BrOnCastFail(notI31Label, RefType.any, RefType.i31)
+              if (isUnbox)
+                fb += I31GetS
+              fb += Return
+            }
+          } else {
+            fb += LocalGet(objParam)
+            fb += BrOnNull(objIsNullLabel)
+          }
 
           // if obj.isInstanceOf[primType]
           primType match {
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala
index d05d14942a..decbdaf0ac 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala
@@ -96,7 +96,7 @@ const scalaJSHelpers = {
   bZ: (x) => x !== 0,
   bB: (x) => x,
   bS: (x) => x,
-  bI: (x) => x,
+  bIFallback: (x) => x,
   bF: (x) => x,
   bD: (x) => x,
 
@@ -104,7 +104,7 @@ const scalaJSHelpers = {
   uZ: (x) => x, // ToInt32 turns false into 0 and true into 1, so this is also an identity
   uB: (x) => x,
   uS: (x) => x,
-  uI: (x) => x,
+  uIFallback: (x) => x,
   uF: (x) => x,
   uD: (x) => x,
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
index f7fed865f8..46253ed910 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
@@ -127,6 +127,9 @@ object VarGen {
       override def toString(): String = "t" + primRef.charCode
     }
 
+    case object bIFallback extends JSHelperFunctionID
+    case object uIFallback extends JSHelperFunctionID
+
     case object fmod extends JSHelperFunctionID
 
     case object closure extends JSHelperFunctionID
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/Types.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/Types.scala
index 36b4b5cad4..76370187ac 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/Types.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/Types.scala
@@ -83,6 +83,9 @@ object Types {
     /** `(ref null func)`, i.e., `funcref`. */
     val funcref: RefType = nullable(HeapType.Func)
 
+    /** `(ref i31)`. */
+    val i31: RefType = apply(HeapType.I31)
+
     /** `(ref extern)`. */
     val extern: RefType = apply(HeapType.Extern)
 
@@ -119,6 +122,7 @@ object Types {
     case object Extern extends AbsHeapType("extern", "externref", 0x6F)
     case object Any extends AbsHeapType("any", "anyref", 0x6E)
     case object Eq extends AbsHeapType("eq", "eqref", 0x6D)
+    case object I31 extends AbsHeapType("i31", "i31ref", 0x6C)
     case object Struct extends AbsHeapType("struct", "structref", 0x6B)
     case object Array extends AbsHeapType("array", "arrayref", 0x6A)
     case object Exn extends AbsHeapType("exn", "exnref", 0x69)

From ffdeb01b88531db37b95767f1d56ce600eb6bd1f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Sun, 9 Jun 2024 12:26:56 +0200
Subject: [PATCH 149/298] Wasm: Perform all the box/unbox/test operations for
 Byte/Short in Wasm.

Because we can, and previous benchmarks show that the JS helper
calls are expensive.
---
 .../backend/wasmemitter/CoreWasmLib.scala     | 102 ++++++++++++++++--
 .../backend/wasmemitter/FunctionEmitter.scala |   2 +
 .../backend/wasmemitter/LoaderContent.scala   |   6 --
 3 files changed, 98 insertions(+), 12 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
index c8646aa6bb..9b57abef76 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
@@ -310,12 +310,9 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
 
     addHelperImport(genFunctionID.isUndef, List(anyref), List(Int32))
 
-    for (primRef <- List(BooleanRef, ByteRef, ShortRef, FloatRef, DoubleRef)) {
-      val wasmType = primRef match {
-        case FloatRef  => Float32
-        case DoubleRef => Float64
-        case _         => Int32
-      }
+    for (primType <- List(BooleanType, FloatType, DoubleType)) {
+      val primRef = primType.primRef
+      val wasmType = transformPrimType(primType)
       addHelperImport(genFunctionID.box(primRef), List(wasmType), List(RefType.any))
       addHelperImport(genFunctionID.unbox(primRef), List(anyref), List(wasmType))
       addHelperImport(genFunctionID.typeTest(primRef), List(anyref), List(Int32))
@@ -596,6 +593,10 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
   private def genHelperDefinitions()(implicit ctx: WasmContext): Unit = {
     genBoxInt()
     genUnboxInt()
+    genUnboxByteOrShort(ByteRef)
+    genUnboxByteOrShort(ShortRef)
+    genTestByteOrShort(ByteRef, I32Extend8S)
+    genTestByteOrShort(ShortRef, I32Extend16S)
     genStringLiteral()
     genCreateStringFromData()
     genTypeDataName()
@@ -719,6 +720,61 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
     fb.buildAndAddToModule()
   }
 
+  private def genUnboxByteOrShort(typeRef: PrimRef)(implicit ctx: WasmContext): Unit = {
+    /* The unboxing functions for Byte and Short actually do exactly the same thing.
+     * We keep them separate so that the rest of the codebase is clearer.
+     * Note that *checked* unboxing goes through `genFunctionID.asInstance` instead.
+     */
+
+    val fb = newFunctionBuilder(genFunctionID.unbox(typeRef))
+    val xParam = fb.addParam("x", RefType.anyref)
+    fb.setResultType(Int32)
+
+    // If x is a (ref i31), extract it
+    fb.block(RefType.anyref) { xIsNotI31Label =>
+      fb += LocalGet(xParam)
+      fb += BrOnCastFail(xIsNotI31Label, RefType.anyref, RefType.i31)
+      fb += I31GetS
+      fb += Return
+    }
+
+    // Otherwise, it must be null, so return 0
+    // Note that all JS `number`s in the correct range are guaranteed to be i31ref's
+    fb += Drop
+    fb += I32Const(0)
+
+    fb.buildAndAddToModule()
+  }
+
+  private def genTestByteOrShort(typeRef: PrimRef, signExtend: SimpleInstr)(
+        implicit ctx: WasmContext): Unit = {
+
+    val fb = newFunctionBuilder(genFunctionID.typeTest(typeRef))
+    val xParam = fb.addParam("x", RefType.anyref)
+    fb.setResultType(Int32)
+
+    val intValueLocal = fb.addLocal("intValue", Int32)
+
+    // If x is a (ref i31), extract it and test whether it sign-extends to itself
+    fb.block(RefType.anyref) { xIsNotI31Label =>
+      fb += LocalGet(xParam)
+      fb += BrOnCastFail(xIsNotI31Label, RefType.anyref, RefType.i31)
+      fb += I31GetS
+      fb += LocalTee(intValueLocal)
+      fb += LocalGet(intValueLocal)
+      fb += signExtend
+      fb += I32Eq
+      fb += Return
+    }
+
+    // Otherwise, return false
+    // Note that all JS `number`s in the correct range are guaranteed to be i31ref's
+    fb += Drop
+    fb += I32Const(0)
+
+    fb.buildAndAddToModule()
+  }
+
   private def genStringLiteral()(implicit ctx: WasmContext): Unit = {
     val fb = newFunctionBuilder(genFunctionID.stringLiteral)
     val offsetParam = fb.addParam("offset", Int32)
@@ -1202,6 +1258,40 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
 
     fb.block() { objIsNullLabel =>
       primType match {
+        // For byte and short, use br_on_cast_fail with i31 then check the value
+        case ByteType | ShortType =>
+          val intValueLocal = fb.addLocal("intValue", Int32)
+
+          fb.block(RefType.anyref) { castFailLabel =>
+            fb += LocalGet(objParam)
+            fb += BrOnNull(objIsNullLabel)
+            fb += BrOnCastFail(castFailLabel, RefType.any, RefType.i31)
+
+            // Extract the i31 value
+            fb += I31GetS
+            fb += LocalTee(intValueLocal)
+
+            // if it sign-extends to itself
+            fb += LocalGet(intValueLocal)
+            if (primType == ByteType)
+              fb += I32Extend8S
+            else
+              fb += I32Extend16S
+            fb += I32Eq
+            fb.ifThen() {
+              // then success
+              if (isUnbox)
+                fb += LocalGet(intValueLocal)
+              else
+                fb += LocalGet(objParam)
+              fb += Return
+            }
+
+            // Fall through for CCE
+            // Note that all JS `number`s in the correct range are guaranteed to be i31ref's
+            fb += LocalGet(objParam)
+          }
+
         // For char and long, use br_on_cast_fail to test+cast to the box class
         case CharType | LongType =>
           val boxClass =
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
index 8e9fed6d9f..02c981ea4e 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
@@ -634,6 +634,8 @@ private class FunctionEmitter private (
         primType match {
           case NullType =>
             ()
+          case ByteType | ShortType =>
+            fb += wa.RefI31
           case CharType =>
             /* `char` and `long` are opaque to JS in the Scala.js semantics.
              * We implement them with real Wasm classes following the correct
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala
index decbdaf0ac..4b6c7f8d5c 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala
@@ -94,24 +94,18 @@ const scalaJSHelpers = {
 
   // Boxes (upcast) -- most are identity at the JS level but with different types in Wasm
   bZ: (x) => x !== 0,
-  bB: (x) => x,
-  bS: (x) => x,
   bIFallback: (x) => x,
   bF: (x) => x,
   bD: (x) => x,
 
   // Unboxes (downcast, null is converted to the zero of the type as part of ToWebAssemblyValue)
   uZ: (x) => x, // ToInt32 turns false into 0 and true into 1, so this is also an identity
-  uB: (x) => x,
-  uS: (x) => x,
   uIFallback: (x) => x,
   uF: (x) => x,
   uD: (x) => x,
 
   // Type tests
   tZ: (x) => typeof x === 'boolean',
-  tB: (x) => typeof x === 'number' && Object.is((x << 24) >> 24, x),
-  tS: (x) => typeof x === 'number' && Object.is((x << 16) >> 16, x),
   tI: (x) => typeof x === 'number' && Object.is(x | 0, x),
   tF: (x) => typeof x === 'number' && (Math.fround(x) === x || x !== x),
   tD: (x) => typeof x === 'number',

From 9d59839c4084367902fa162bf1c47a2e8c290f57 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Sun, 1 Sep 2024 11:50:51 +0200
Subject: [PATCH 150/298] Wasm: Refine some types in `asInstance` for
 `Char`/`Long`.

---
 .../org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala  | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
index 9b57abef76..0d66585a21 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
@@ -1299,10 +1299,10 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
             else SpecialNames.LongBoxClass
           val structTypeID = genTypeID.forClass(boxClass)
 
-          fb.block(RefType.anyref) { castFailLabel =>
+          fb.block(RefType.any) { castFailLabel =>
             fb += LocalGet(objParam)
             fb += BrOnNull(objIsNullLabel)
-            fb += BrOnCastFail(castFailLabel, RefType.anyref, RefType(structTypeID))
+            fb += BrOnCastFail(castFailLabel, RefType.any, RefType(structTypeID))
 
             // Extract the `value` field if unboxing
             if (isUnbox) {

From b5bd3436775a4e17716d6237da0f7d896c82f04c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Wed, 28 Aug 2024 23:05:46 +0200
Subject: [PATCH 151/298] Wasm: Perform the box operation for Boolean in Wasm.

---
 .../backend/wasmemitter/CoreWasmLib.scala      | 18 +++++++++++++++++-
 .../backend/wasmemitter/LoaderContent.scala    |  4 ++--
 .../linker/backend/wasmemitter/VarGen.scala    |  1 +
 .../backend/webassembly/BinaryWriter.scala     |  3 +++
 .../backend/webassembly/Instructions.scala     |  3 +++
 .../backend/webassembly/TextWriter.scala       |  3 +++
 6 files changed, 29 insertions(+), 3 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
index 0d66585a21..5d322492bd 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
@@ -287,6 +287,7 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
     addGlobalHelperImport(genGlobalID.jsLinkingInfo, RefType.any)
     addGlobalHelperImport(genGlobalID.undef, RefType.any)
     addGlobalHelperImport(genGlobalID.bFalse, RefType.any)
+    addGlobalHelperImport(genGlobalID.bTrue, RefType.any)
     addGlobalHelperImport(genGlobalID.bZero, RefType.any)
     addGlobalHelperImport(genGlobalID.emptyString, RefType.any)
     addGlobalHelperImport(genGlobalID.idHashCodeMap, RefType.extern)
@@ -313,7 +314,8 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
     for (primType <- List(BooleanType, FloatType, DoubleType)) {
       val primRef = primType.primRef
       val wasmType = transformPrimType(primType)
-      addHelperImport(genFunctionID.box(primRef), List(wasmType), List(RefType.any))
+      if (primType != BooleanType)
+        addHelperImport(genFunctionID.box(primRef), List(wasmType), List(RefType.any))
       addHelperImport(genFunctionID.unbox(primRef), List(anyref), List(wasmType))
       addHelperImport(genFunctionID.typeTest(primRef), List(anyref), List(Int32))
     }
@@ -591,6 +593,7 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
 
   /** Generates all the helper function definitions of the core Wasm lib. */
   private def genHelperDefinitions()(implicit ctx: WasmContext): Unit = {
+    genBoxBoolean()
     genBoxInt()
     genUnboxInt()
     genUnboxByteOrShort(ByteRef)
@@ -669,6 +672,19 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
     newFunctionBuilder(functionID, OriginalName(functionID.toString()))
   }
 
+  private def genBoxBoolean()(implicit ctx: WasmContext): Unit = {
+    val fb = newFunctionBuilder(genFunctionID.box(BooleanRef))
+    val xParam = fb.addParam("x", Int32)
+    fb.setResultType(RefType.any)
+
+    fb += GlobalGet(genGlobalID.bTrue)
+    fb += GlobalGet(genGlobalID.bFalse)
+    fb += LocalGet(xParam)
+    fb += Select(List(RefType.any))
+
+    fb.buildAndAddToModule()
+  }
+
   private def genBoxInt()(implicit ctx: WasmContext): Unit = {
     val fb = newFunctionBuilder(genFunctionID.box(IntRef))
     val xParam = fb.addParam("x", Int32)
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala
index 4b6c7f8d5c..4b7f03e7ec 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala
@@ -88,12 +88,12 @@ const scalaJSHelpers = {
   undef: void 0,
   isUndef: (x) => x === (void 0),
 
-  // Zero boxes
+  // Constant boxes
   bFalse: false,
+  bTrue: true,
   bZero: 0,
 
   // Boxes (upcast) -- most are identity at the JS level but with different types in Wasm
-  bZ: (x) => x !== 0,
   bIFallback: (x) => x,
   bF: (x) => x,
   bD: (x) => x,
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
index 46253ed910..dbc37ae79b 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
@@ -56,6 +56,7 @@ object VarGen {
     case object jsLinkingInfo extends JSHelperGlobalID
     case object undef extends JSHelperGlobalID
     case object bFalse extends JSHelperGlobalID
+    case object bTrue extends JSHelperGlobalID
     case object bZero extends JSHelperGlobalID
     case object emptyString extends JSHelperGlobalID
     case object idHashCodeMap extends JSHelperGlobalID
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/BinaryWriter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/BinaryWriter.scala
index 1c79f6daea..b90480a3c2 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/BinaryWriter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/BinaryWriter.scala
@@ -440,6 +440,9 @@ private sealed class BinaryWriter(module: Module, emitDebugInfo: Boolean) {
       case F32Const(v) => buf.f32(v)
       case F64Const(v) => buf.f64(v)
 
+      case Select(resultTypes) =>
+        buf.vec(resultTypes)(writeType(_))
+
       case BrTable(labelIdxVector, defaultLabelIdx) =>
         buf.vec(labelIdxVector)(writeLabelIdx(_))
         writeLabelIdx(defaultLabelIdx)
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/Instructions.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/Instructions.scala
index 8b05288287..45ab60e830 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/Instructions.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/Instructions.scala
@@ -156,6 +156,9 @@ object Instructions {
 
   case object Drop extends SimpleInstr("drop", 0x1A)
 
+  final case class Select(resultTypes: List[Type])
+      extends Instr("select", if (resultTypes.isEmpty) 0x1B else 0x1C)
+
   final case class TryTable(i: BlockType, cs: List[CatchClause], label: Option[LabelID] = None)
       extends Instr("try_table", 0x1F) with StructuredLabeledInstr
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/TextWriter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/TextWriter.scala
index 704524c49b..645bc72e52 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/TextWriter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/TextWriter.scala
@@ -470,6 +470,9 @@ private class TextWriter(module: Module) {
       case F32Const(v) => writeFloatString(v.toDouble)
       case F64Const(v) => writeFloatString(v)
 
+      case Select(resultTypes) =>
+        resultTypes.foreach(writeType(_))
+
       case BrTable(labelIdxVector, defaultLabelIdx) =>
         labelIdxVector.foreach(appendName(_))
         appendName(defaultLabelIdx)

From 30e0e1325b0051e3e2486cfa9ee3e5d1752b156c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Sun, 9 Jun 2024 16:48:29 +0200
Subject: [PATCH 152/298] Optimize ju.Random for Wasm.

On Wasm, the implementation we had written to be optimized on JS is
not only useless, it is actively harmful. That is notably because of
the `rawToInt` calls, which use JS interop.

We now internally use two separate implementations of
`ju.Random.next()` and `setSeed()` for Wasm and for JS.
---
 javalib/src/main/scala/java/util/Random.scala | 36 ++++++++++++++++---
 1 file changed, 31 insertions(+), 5 deletions(-)

diff --git a/javalib/src/main/scala/java/util/Random.scala b/javalib/src/main/scala/java/util/Random.scala
index a2ae2eb3f6..8cd654cd1f 100644
--- a/javalib/src/main/scala/java/util/Random.scala
+++ b/javalib/src/main/scala/java/util/Random.scala
@@ -15,11 +15,19 @@ package java.util
 import scala.annotation.tailrec
 
 import scala.scalajs.js
+import scala.scalajs.runtime.linkingInfo
 
 class Random(seed_in: Long) extends AnyRef with java.io.Serializable {
+  /* This class has two different implementations of seeding and computing
+   * bits, depending on whether we are on Wasm or JS. On Wasm, we use the
+   * implementation specified in the JavaDoc verbatim. On JS, however, that is
+   * too slow, due to the use of `Long`s. Therefore, we decompose the
+   * computations using 2x24 bits. See `nextJS()` for details.
+   */
 
-  private var seedHi: Int = _ // 24 msb of the seed
-  private var seedLo: Int = _ // 24 lsb of the seed
+  private var seed: Long = _ // the full seed on Wasm (dce'ed on JS)
+  private var seedHi: Int = _ // 24 msb of the seed in JS (dce'ed on Wasm)
+  private var seedLo: Int = _ // 24 lsb of the seed in JS (dce'ed on Wasm)
 
   // see nextGaussian()
   private var nextNextGaussian: Double = _
@@ -31,12 +39,30 @@ class Random(seed_in: Long) extends AnyRef with java.io.Serializable {
 
   def setSeed(seed_in: Long): Unit = {
     val seed = ((seed_in ^ 0x5DEECE66DL) & ((1L << 48) - 1)) // as documented
-    seedHi = (seed >>> 24).toInt
-    seedLo = seed.toInt & ((1 << 24) - 1)
+    if (linkingInfo.isWebAssembly) {
+      this.seed = seed
+    } else {
+      seedHi = (seed >>> 24).toInt
+      seedLo = seed.toInt & ((1 << 24) - 1)
+    }
     haveNextNextGaussian = false
   }
 
-  protected def next(bits: Int): Int = {
+  @noinline
+  protected def next(bits: Int): Int =
+    if (linkingInfo.isWebAssembly) nextWasm(bits)
+    else nextJS(bits)
+
+  @inline
+  private def nextWasm(bits: Int): Int = {
+    // as documented
+    val newSeed = (seed * 0x5DEECE66DL + 0xBL) & ((1L << 48) - 1)
+    seed = newSeed
+    (newSeed >>> (48 - bits)).toInt
+  }
+
+  @inline
+  private def nextJS(bits: Int): Int = {
     /* This method is originally supposed to work with a Long seed from which
      * 48 bits are used.
      * Since Longs are too slow, we manually decompose the 48-bit seed in two

From 9be09e2594ca2d27b8dbb175f32da94728245de1 Mon Sep 17 00:00:00 2001
From: Tobias Schlatter <tobias@meisch.ch>
Date: Sun, 8 Sep 2024 15:55:44 +0200
Subject: [PATCH 153/298] Fix #5026: Hash internal module names if they get too
 long

We could improve on this later on by allowing more non-ASCII
characters. However, in any case we need an escape hatch like this.
---
 .../InternalModuleIDGenerator.scala           | 46 ++++++++++++++-----
 .../InternalModuleIDGeneratorTest.scala       | 11 ++++-
 2 files changed, 45 insertions(+), 12 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/modulesplitter/InternalModuleIDGenerator.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/modulesplitter/InternalModuleIDGenerator.scala
index 82adb9b823..bc53504ef0 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/modulesplitter/InternalModuleIDGenerator.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/modulesplitter/InternalModuleIDGenerator.scala
@@ -14,7 +14,10 @@ package org.scalajs.linker.frontend.modulesplitter
 
 import scala.collection.immutable.SortedSet
 
+import java.lang.StringBuilder
+
 import org.scalajs.ir.Names.{ClassName, ObjectClass}
+import org.scalajs.ir.SHA1
 import org.scalajs.linker.standard.ModuleSet.ModuleID
 
 /** Generators for internal module IDs.
@@ -91,12 +94,15 @@ private[modulesplitter] object InternalModuleIDGenerator {
        * - '-' is prefixed with '-'.
        * - Non-ASCII characters are all prefixed by '-u' followed by the 6
        *   hexdigits of their codepoint.
+       * - If the resulting name is longer than 100 characters, the ClassName is
+       *   hashed and the hash is prefixed with `-x`.
+       *   This avoids filenames that are too long (see #5026).
        *
        * The last rule is far from being optimal, but it is safe. Encountering
        * non-ASCII characters in class names should be rare anyway.
        */
 
-      val builder = new java.lang.StringBuilder
+      val builder = new StringBuilder
 
       // First, encode uppercase characters to avoid accidental case-insensitive clashes
       val originalNameString = name.nameString
@@ -111,13 +117,29 @@ private[modulesplitter] object InternalModuleIDGenerator {
           builder.append(cp.toChar)
           i += 1
         } else {
-          // Non-ASCII
+          /* Non-ASCII
+           *
+           * TODO: We could look at unicode case folding data here to keep more
+           * non-ASCII characters around (easier to debug, see #5026).
+           */
           new java.util.Formatter(builder).format("-u%06x", Integer.valueOf(cp))
           builder.appendCodePoint(cp)
           i += Character.charCount(cp)
         }
       }
 
+      /* Revert to hash if the string is too long.
+       * We could early abort above, but that would slow down the fast path.
+       */
+      if (builder.length() > 100) {
+        builder.setLength(0) // reset
+        builder.append("-x")
+
+        val digestBuilder = new SHA1.DigestBuilder
+        digestBuilder.updateUTF8String(name.encoded)
+        appendDigest(builder, digestBuilder.finalizeDigest())
+      }
+
       // Second, avoid colliding with the public module IDs in `avoidSet`
       var candidateID = builder.toString()
       while (avoidSet.contains(candidateID)) {
@@ -134,17 +156,19 @@ private[modulesplitter] object InternalModuleIDGenerator {
       this(freeInternalPrefix(avoid))
 
     def forDigest(digest: Array[Byte]): ModuleID = {
-      @inline def hexDigit(digit: Int): Char =
-        Character.forDigit(digit & 0x0f, 16)
-
-      val id = new java.lang.StringBuilder(internalModuleIDPrefix)
+      val id = new StringBuilder(internalModuleIDPrefix)
+      appendDigest(id, digest)
+      ModuleID(id.toString())
+    }
+  }
 
-      for (b <- digest) {
-        id.append(hexDigit(b >> 4))
-        id.append(hexDigit(b))
-      }
+  private def appendDigest(builder: StringBuilder, digest: Array[Byte]) = {
+    @inline def hexDigit(digit: Int): Char =
+      Character.forDigit(digit & 0x0f, 16)
 
-      ModuleID(id.toString())
+    for (b <- digest) {
+      builder.append(hexDigit(b >> 4))
+      builder.append(hexDigit(b))
     }
   }
 
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/frontend/modulesplitter/InternalModuleIDGeneratorTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/frontend/modulesplitter/InternalModuleIDGeneratorTest.scala
index 1b6dceb216..ab600ccb42 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/frontend/modulesplitter/InternalModuleIDGeneratorTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/frontend/modulesplitter/InternalModuleIDGeneratorTest.scala
@@ -22,7 +22,12 @@ import org.scalajs.linker.standard.ModuleSet.ModuleID
 /** Whitebox tests for `InternalModuleIDGenerator`. */
 class InternalModuleIDGeneratorTest {
   @Test def testForClassName(): Unit = {
-    val testPublicModuleIDs = List(ModuleID("test.-Public"), ModuleID("test.-Other-Public"))
+    val testPublicModuleIDs = List(
+      ModuleID("test.-Public"),
+      ModuleID("test.-Other-Public"),
+      // test collision with hashed name
+      ModuleID("-x4a1f096d13ea514c484d8604fd6984a699983e13")
+    )
     val generator = new InternalModuleIDGenerator.ForClassNames(testPublicModuleIDs)
 
     def test(expected: String, classNameString: String): Unit =
@@ -42,6 +47,10 @@ class InternalModuleIDGeneratorTest {
 
     test("test.-Public.", "test.Public")
     test("test.-Other-Public.", "test.OtherPublic")
+
+    // Too long resulting name (#5026)
+    test("-xb204ce10b523cf072bd79c3142cd349f155632b8", "НазваниеКлассаНаРусскомЯзыке")
+    test("-x4a1f096d13ea514c484d8604fd6984a699983e13.", "日本語でも長い名前になれます")
   }
 
   @Test def testForDigest(): Unit = {

From cea8c7c6993a1069810d665b0bb346da9b83e119 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Thu, 12 Sep 2024 16:01:16 +0200
Subject: [PATCH 154/298] Regenerate the Unicode database with Temurin-21+35.

Fixes #5013, among other things.
---
 .../src/main/scala/java/lang/Character.scala  | 805 ++++++++++++------
 project/Build.scala                           |   2 +-
 .../javalib/lang/CharacterTest.scala          |  17 +-
 3 files changed, 529 insertions(+), 295 deletions(-)

diff --git a/javalib/src/main/scala/java/lang/Character.scala b/javalib/src/main/scala/java/lang/Character.scala
index 30cd3efcd9..f9baf3956f 100644
--- a/javalib/src/main/scala/java/lang/Character.scala
+++ b/javalib/src/main/scala/java/lang/Character.scala
@@ -599,12 +599,13 @@ for (cp <- 0 to Character.MAX_CODE_POINT) {
   val upperCaseCP: Int = Character.toUpperCase(cp)
 
   if (titleCaseCP != upperCaseCP) {
-    println(s"    case ${format(cp)} => ${format(titleCaseCP)}")
+    println(s"      case ${format(cp)} => ${format(titleCaseCP)}")
   }
 }
 */
   def toTitleCase(codePoint: scala.Int): scala.Int = {
     (codePoint: @switch) match {
+      // Begin Generated, last updated with Temurin-21+35 (build 21+35-LTS)
       case 0x01c4 => 0x01c5
       case 0x01c5 => 0x01c5
       case 0x01c6 => 0x01c5
@@ -617,7 +618,55 @@ for (cp <- 0 to Character.MAX_CODE_POINT) {
       case 0x01f1 => 0x01f2
       case 0x01f2 => 0x01f2
       case 0x01f3 => 0x01f2
-      case _      => toUpperCase(codePoint)
+      case 0x10d0 => 0x10d0
+      case 0x10d1 => 0x10d1
+      case 0x10d2 => 0x10d2
+      case 0x10d3 => 0x10d3
+      case 0x10d4 => 0x10d4
+      case 0x10d5 => 0x10d5
+      case 0x10d6 => 0x10d6
+      case 0x10d7 => 0x10d7
+      case 0x10d8 => 0x10d8
+      case 0x10d9 => 0x10d9
+      case 0x10da => 0x10da
+      case 0x10db => 0x10db
+      case 0x10dc => 0x10dc
+      case 0x10dd => 0x10dd
+      case 0x10de => 0x10de
+      case 0x10df => 0x10df
+      case 0x10e0 => 0x10e0
+      case 0x10e1 => 0x10e1
+      case 0x10e2 => 0x10e2
+      case 0x10e3 => 0x10e3
+      case 0x10e4 => 0x10e4
+      case 0x10e5 => 0x10e5
+      case 0x10e6 => 0x10e6
+      case 0x10e7 => 0x10e7
+      case 0x10e8 => 0x10e8
+      case 0x10e9 => 0x10e9
+      case 0x10ea => 0x10ea
+      case 0x10eb => 0x10eb
+      case 0x10ec => 0x10ec
+      case 0x10ed => 0x10ed
+      case 0x10ee => 0x10ee
+      case 0x10ef => 0x10ef
+      case 0x10f0 => 0x10f0
+      case 0x10f1 => 0x10f1
+      case 0x10f2 => 0x10f2
+      case 0x10f3 => 0x10f3
+      case 0x10f4 => 0x10f4
+      case 0x10f5 => 0x10f5
+      case 0x10f6 => 0x10f6
+      case 0x10f7 => 0x10f7
+      case 0x10f8 => 0x10f8
+      case 0x10f9 => 0x10f9
+      case 0x10fa => 0x10fa
+      case 0x10fd => 0x10fd
+      case 0x10fe => 0x10fe
+      case 0x10ff => 0x10ff
+      // End generated
+
+      case _ => toUpperCase(codePoint)
     }
   }
 
@@ -737,18 +786,18 @@ for (cp <- 0 to Character.MAX_CODE_POINT) {
 
       historicalMap.get(b.toString) match {
         case Some((historicalName, properName)) =>
-          println(s"""  val $b = addUnicodeBlock("$properName", "$historicalName", $minCodePoint, $maxCodePoint)""")
+          println(s"""    val $b = addUnicodeBlock("$properName", "$historicalName", $minCodePoint, $maxCodePoint)""")
         case None =>
           val properBlockName = blockNameMap.getOrElse(b.toString, throw new IllegalArgumentException("$b"))
           val jvmBlockName = properBlockName.toUpperCase.replaceAll("[\\s\\-_]", "_")
           assert(jvmBlockName == b.toString)
-          println(s"""  val $jvmBlockName = addUnicodeBlock("$properBlockName", $minCodePoint, $maxCodePoint)""")
+          println(s"""    val $jvmBlockName = addUnicodeBlock("$properBlockName", $minCodePoint, $maxCodePoint)""")
       }
     }
 */
 
     //////////////////////////////////////////////////////////////////////////
-    // Begin Generated, last updated with (AdoptOpenJDK) (build 1.8.0_265-b01)
+    // Begin Generated, last updated with Temurin-21+35 (build 21+35-LTS)
     //////////////////////////////////////////////////////////////////////////
     // scalastyle:off line.size.limit
 
@@ -771,6 +820,8 @@ for (cp <- 0 to Character.MAX_CODE_POINT) {
     val NKO = addUnicodeBlock("NKo", 0x07c0, 0x07ff)
     val SAMARITAN = addUnicodeBlock("Samaritan", 0x0800, 0x083f)
     val MANDAIC = addUnicodeBlock("Mandaic", 0x0840, 0x085f)
+    val SYRIAC_SUPPLEMENT = addUnicodeBlock("Syriac Supplement", 0x0860, 0x086f)
+    val ARABIC_EXTENDED_B = addUnicodeBlock("Arabic Extended-B", 0x0870, 0x089f)
     val ARABIC_EXTENDED_A = addUnicodeBlock("Arabic Extended-A", 0x08a0, 0x08ff)
     val DEVANAGARI = addUnicodeBlock("Devanagari", 0x0900, 0x097f)
     val BENGALI = addUnicodeBlock("Bengali", 0x0980, 0x09ff)
@@ -807,11 +858,14 @@ for (cp <- 0 to Character.MAX_CODE_POINT) {
     val KHMER_SYMBOLS = addUnicodeBlock("Khmer Symbols", 0x19e0, 0x19ff)
     val BUGINESE = addUnicodeBlock("Buginese", 0x1a00, 0x1a1f)
     val TAI_THAM = addUnicodeBlock("Tai Tham", 0x1a20, 0x1aaf)
+    val COMBINING_DIACRITICAL_MARKS_EXTENDED = addUnicodeBlock("Combining Diacritical Marks Extended", 0x1ab0, 0x1aff)
     val BALINESE = addUnicodeBlock("Balinese", 0x1b00, 0x1b7f)
     val SUNDANESE = addUnicodeBlock("Sundanese", 0x1b80, 0x1bbf)
     val BATAK = addUnicodeBlock("Batak", 0x1bc0, 0x1bff)
     val LEPCHA = addUnicodeBlock("Lepcha", 0x1c00, 0x1c4f)
     val OL_CHIKI = addUnicodeBlock("Ol Chiki", 0x1c50, 0x1c7f)
+    val CYRILLIC_EXTENDED_C = addUnicodeBlock("Cyrillic Extended-C", 0x1c80, 0x1c8f)
+    val GEORGIAN_EXTENDED = addUnicodeBlock("Georgian Extended", 0x1c90, 0x1cbf)
     val SUNDANESE_SUPPLEMENT = addUnicodeBlock("Sundanese Supplement", 0x1cc0, 0x1ccf)
     val VEDIC_EXTENSIONS = addUnicodeBlock("Vedic Extensions", 0x1cd0, 0x1cff)
     val PHONETIC_EXTENSIONS = addUnicodeBlock("Phonetic Extensions", 0x1d00, 0x1d7f)
@@ -885,11 +939,14 @@ for (cp <- 0 to Character.MAX_CODE_POINT) {
     val REJANG = addUnicodeBlock("Rejang", 0xa930, 0xa95f)
     val HANGUL_JAMO_EXTENDED_A = addUnicodeBlock("Hangul Jamo Extended-A", 0xa960, 0xa97f)
     val JAVANESE = addUnicodeBlock("Javanese", 0xa980, 0xa9df)
+    val MYANMAR_EXTENDED_B = addUnicodeBlock("Myanmar Extended-B", 0xa9e0, 0xa9ff)
     val CHAM = addUnicodeBlock("Cham", 0xaa00, 0xaa5f)
     val MYANMAR_EXTENDED_A = addUnicodeBlock("Myanmar Extended-A", 0xaa60, 0xaa7f)
     val TAI_VIET = addUnicodeBlock("Tai Viet", 0xaa80, 0xaadf)
     val MEETEI_MAYEK_EXTENSIONS = addUnicodeBlock("Meetei Mayek Extensions", 0xaae0, 0xaaff)
     val ETHIOPIC_EXTENDED_A = addUnicodeBlock("Ethiopic Extended-A", 0xab00, 0xab2f)
+    val LATIN_EXTENDED_E = addUnicodeBlock("Latin Extended-E", 0xab30, 0xab6f)
+    val CHEROKEE_SUPPLEMENT = addUnicodeBlock("Cherokee Supplement", 0xab70, 0xabbf)
     val MEETEI_MAYEK = addUnicodeBlock("Meetei Mayek", 0xabc0, 0xabff)
     val HANGUL_SYLLABLES = addUnicodeBlock("Hangul Syllables", 0xac00, 0xd7af)
     val HANGUL_JAMO_EXTENDED_B = addUnicodeBlock("Hangul Jamo Extended-B", 0xd7b0, 0xd7ff)
@@ -916,44 +973,132 @@ for (cp <- 0 to Character.MAX_CODE_POINT) {
     val PHAISTOS_DISC = addUnicodeBlock("Phaistos Disc", 0x101d0, 0x101ff)
     val LYCIAN = addUnicodeBlock("Lycian", 0x10280, 0x1029f)
     val CARIAN = addUnicodeBlock("Carian", 0x102a0, 0x102df)
+    val COPTIC_EPACT_NUMBERS = addUnicodeBlock("Coptic Epact Numbers", 0x102e0, 0x102ff)
     val OLD_ITALIC = addUnicodeBlock("Old Italic", 0x10300, 0x1032f)
     val GOTHIC = addUnicodeBlock("Gothic", 0x10330, 0x1034f)
+    val OLD_PERMIC = addUnicodeBlock("Old Permic", 0x10350, 0x1037f)
     val UGARITIC = addUnicodeBlock("Ugaritic", 0x10380, 0x1039f)
     val OLD_PERSIAN = addUnicodeBlock("Old Persian", 0x103a0, 0x103df)
     val DESERET = addUnicodeBlock("Deseret", 0x10400, 0x1044f)
     val SHAVIAN = addUnicodeBlock("Shavian", 0x10450, 0x1047f)
     val OSMANYA = addUnicodeBlock("Osmanya", 0x10480, 0x104af)
+    val OSAGE = addUnicodeBlock("Osage", 0x104b0, 0x104ff)
+    val ELBASAN = addUnicodeBlock("Elbasan", 0x10500, 0x1052f)
+    val CAUCASIAN_ALBANIAN = addUnicodeBlock("Caucasian Albanian", 0x10530, 0x1056f)
+    val VITHKUQI = addUnicodeBlock("Vithkuqi", 0x10570, 0x105bf)
+    val LINEAR_A = addUnicodeBlock("Linear A", 0x10600, 0x1077f)
+    val LATIN_EXTENDED_F = addUnicodeBlock("Latin Extended-F", 0x10780, 0x107bf)
     val CYPRIOT_SYLLABARY = addUnicodeBlock("Cypriot Syllabary", 0x10800, 0x1083f)
     val IMPERIAL_ARAMAIC = addUnicodeBlock("Imperial Aramaic", 0x10840, 0x1085f)
+    val PALMYRENE = addUnicodeBlock("Palmyrene", 0x10860, 0x1087f)
+    val NABATAEAN = addUnicodeBlock("Nabataean", 0x10880, 0x108af)
+    val HATRAN = addUnicodeBlock("Hatran", 0x108e0, 0x108ff)
     val PHOENICIAN = addUnicodeBlock("Phoenician", 0x10900, 0x1091f)
     val LYDIAN = addUnicodeBlock("Lydian", 0x10920, 0x1093f)
     val MEROITIC_HIEROGLYPHS = addUnicodeBlock("Meroitic Hieroglyphs", 0x10980, 0x1099f)
     val MEROITIC_CURSIVE = addUnicodeBlock("Meroitic Cursive", 0x109a0, 0x109ff)
     val KHAROSHTHI = addUnicodeBlock("Kharoshthi", 0x10a00, 0x10a5f)
     val OLD_SOUTH_ARABIAN = addUnicodeBlock("Old South Arabian", 0x10a60, 0x10a7f)
+    val OLD_NORTH_ARABIAN = addUnicodeBlock("Old North Arabian", 0x10a80, 0x10a9f)
+    val MANICHAEAN = addUnicodeBlock("Manichaean", 0x10ac0, 0x10aff)
     val AVESTAN = addUnicodeBlock("Avestan", 0x10b00, 0x10b3f)
     val INSCRIPTIONAL_PARTHIAN = addUnicodeBlock("Inscriptional Parthian", 0x10b40, 0x10b5f)
     val INSCRIPTIONAL_PAHLAVI = addUnicodeBlock("Inscriptional Pahlavi", 0x10b60, 0x10b7f)
+    val PSALTER_PAHLAVI = addUnicodeBlock("Psalter Pahlavi", 0x10b80, 0x10baf)
     val OLD_TURKIC = addUnicodeBlock("Old Turkic", 0x10c00, 0x10c4f)
+    val OLD_HUNGARIAN = addUnicodeBlock("Old Hungarian", 0x10c80, 0x10cff)
+    val HANIFI_ROHINGYA = addUnicodeBlock("Hanifi Rohingya", 0x10d00, 0x10d3f)
     val RUMI_NUMERAL_SYMBOLS = addUnicodeBlock("Rumi Numeral Symbols", 0x10e60, 0x10e7f)
+    val YEZIDI = addUnicodeBlock("Yezidi", 0x10e80, 0x10ebf)
+    val ARABIC_EXTENDED_C = addUnicodeBlock("Arabic Extended-C", 0x10ec0, 0x10eff)
+    val OLD_SOGDIAN = addUnicodeBlock("Old Sogdian", 0x10f00, 0x10f2f)
+    val SOGDIAN = addUnicodeBlock("Sogdian", 0x10f30, 0x10f6f)
+    val OLD_UYGHUR = addUnicodeBlock("Old Uyghur", 0x10f70, 0x10faf)
+    val CHORASMIAN = addUnicodeBlock("Chorasmian", 0x10fb0, 0x10fdf)
+    val ELYMAIC = addUnicodeBlock("Elymaic", 0x10fe0, 0x10fff)
     val BRAHMI = addUnicodeBlock("Brahmi", 0x11000, 0x1107f)
     val KAITHI = addUnicodeBlock("Kaithi", 0x11080, 0x110cf)
     val SORA_SOMPENG = addUnicodeBlock("Sora Sompeng", 0x110d0, 0x110ff)
     val CHAKMA = addUnicodeBlock("Chakma", 0x11100, 0x1114f)
+    val MAHAJANI = addUnicodeBlock("Mahajani", 0x11150, 0x1117f)
     val SHARADA = addUnicodeBlock("Sharada", 0x11180, 0x111df)
+    val SINHALA_ARCHAIC_NUMBERS = addUnicodeBlock("Sinhala Archaic Numbers", 0x111e0, 0x111ff)
+    val KHOJKI = addUnicodeBlock("Khojki", 0x11200, 0x1124f)
+    val MULTANI = addUnicodeBlock("Multani", 0x11280, 0x112af)
+    val KHUDAWADI = addUnicodeBlock("Khudawadi", 0x112b0, 0x112ff)
+    val GRANTHA = addUnicodeBlock("Grantha", 0x11300, 0x1137f)
+    val NEWA = addUnicodeBlock("Newa", 0x11400, 0x1147f)
+    val TIRHUTA = addUnicodeBlock("Tirhuta", 0x11480, 0x114df)
+    val SIDDHAM = addUnicodeBlock("Siddham", 0x11580, 0x115ff)
+    val MODI = addUnicodeBlock("Modi", 0x11600, 0x1165f)
+    val MONGOLIAN_SUPPLEMENT = addUnicodeBlock("Mongolian Supplement", 0x11660, 0x1167f)
     val TAKRI = addUnicodeBlock("Takri", 0x11680, 0x116cf)
+    val AHOM = addUnicodeBlock("Ahom", 0x11700, 0x1174f)
+    val DOGRA = addUnicodeBlock("Dogra", 0x11800, 0x1184f)
+    val WARANG_CITI = addUnicodeBlock("Warang Citi", 0x118a0, 0x118ff)
+    val DIVES_AKURU = addUnicodeBlock("Dives Akuru", 0x11900, 0x1195f)
+    val NANDINAGARI = addUnicodeBlock("Nandinagari", 0x119a0, 0x119ff)
+    val ZANABAZAR_SQUARE = addUnicodeBlock("Zanabazar Square", 0x11a00, 0x11a4f)
+    val SOYOMBO = addUnicodeBlock("Soyombo", 0x11a50, 0x11aaf)
+    val UNIFIED_CANADIAN_ABORIGINAL_SYLLABICS_EXTENDED_A = addUnicodeBlock("Unified Canadian Aboriginal Syllabics Extended-A", 0x11ab0, 0x11abf)
+    val PAU_CIN_HAU = addUnicodeBlock("Pau Cin Hau", 0x11ac0, 0x11aff)
+    val DEVANAGARI_EXTENDED_A = addUnicodeBlock("Devanagari Extended-A", 0x11b00, 0x11b5f)
+    val BHAIKSUKI = addUnicodeBlock("Bhaiksuki", 0x11c00, 0x11c6f)
+    val MARCHEN = addUnicodeBlock("Marchen", 0x11c70, 0x11cbf)
+    val MASARAM_GONDI = addUnicodeBlock("Masaram Gondi", 0x11d00, 0x11d5f)
+    val GUNJALA_GONDI = addUnicodeBlock("Gunjala Gondi", 0x11d60, 0x11daf)
+    val MAKASAR = addUnicodeBlock("Makasar", 0x11ee0, 0x11eff)
+    val KAWI = addUnicodeBlock("Kawi", 0x11f00, 0x11f5f)
+    val LISU_SUPPLEMENT = addUnicodeBlock("Lisu Supplement", 0x11fb0, 0x11fbf)
+    val TAMIL_SUPPLEMENT = addUnicodeBlock("Tamil Supplement", 0x11fc0, 0x11fff)
     val CUNEIFORM = addUnicodeBlock("Cuneiform", 0x12000, 0x123ff)
     val CUNEIFORM_NUMBERS_AND_PUNCTUATION = addUnicodeBlock("Cuneiform Numbers and Punctuation", 0x12400, 0x1247f)
+    val EARLY_DYNASTIC_CUNEIFORM = addUnicodeBlock("Early Dynastic Cuneiform", 0x12480, 0x1254f)
+    val CYPRO_MINOAN = addUnicodeBlock("Cypro-Minoan", 0x12f90, 0x12fff)
     val EGYPTIAN_HIEROGLYPHS = addUnicodeBlock("Egyptian Hieroglyphs", 0x13000, 0x1342f)
+    val EGYPTIAN_HIEROGLYPH_FORMAT_CONTROLS = addUnicodeBlock("Egyptian Hieroglyph Format Controls", 0x13430, 0x1345f)
+    val ANATOLIAN_HIEROGLYPHS = addUnicodeBlock("Anatolian Hieroglyphs", 0x14400, 0x1467f)
     val BAMUM_SUPPLEMENT = addUnicodeBlock("Bamum Supplement", 0x16800, 0x16a3f)
+    val MRO = addUnicodeBlock("Mro", 0x16a40, 0x16a6f)
+    val TANGSA = addUnicodeBlock("Tangsa", 0x16a70, 0x16acf)
+    val BASSA_VAH = addUnicodeBlock("Bassa Vah", 0x16ad0, 0x16aff)
+    val PAHAWH_HMONG = addUnicodeBlock("Pahawh Hmong", 0x16b00, 0x16b8f)
+    val MEDEFAIDRIN = addUnicodeBlock("Medefaidrin", 0x16e40, 0x16e9f)
     val MIAO = addUnicodeBlock("Miao", 0x16f00, 0x16f9f)
+    val IDEOGRAPHIC_SYMBOLS_AND_PUNCTUATION = addUnicodeBlock("Ideographic Symbols and Punctuation", 0x16fe0, 0x16fff)
+    val TANGUT = addUnicodeBlock("Tangut", 0x17000, 0x187ff)
+    val TANGUT_COMPONENTS = addUnicodeBlock("Tangut Components", 0x18800, 0x18aff)
+    val KHITAN_SMALL_SCRIPT = addUnicodeBlock("Khitan Small Script", 0x18b00, 0x18cff)
+    val TANGUT_SUPPLEMENT = addUnicodeBlock("Tangut Supplement", 0x18d00, 0x18d7f)
+    val KANA_EXTENDED_B = addUnicodeBlock("Kana Extended-B", 0x1aff0, 0x1afff)
     val KANA_SUPPLEMENT = addUnicodeBlock("Kana Supplement", 0x1b000, 0x1b0ff)
+    val KANA_EXTENDED_A = addUnicodeBlock("Kana Extended-A", 0x1b100, 0x1b12f)
+    val SMALL_KANA_EXTENSION = addUnicodeBlock("Small Kana Extension", 0x1b130, 0x1b16f)
+    val NUSHU = addUnicodeBlock("Nushu", 0x1b170, 0x1b2ff)
+    val DUPLOYAN = addUnicodeBlock("Duployan", 0x1bc00, 0x1bc9f)
+    val SHORTHAND_FORMAT_CONTROLS = addUnicodeBlock("Shorthand Format Controls", 0x1bca0, 0x1bcaf)
+    val ZNAMENNY_MUSICAL_NOTATION = addUnicodeBlock("Znamenny Musical Notation", 0x1cf00, 0x1cfcf)
     val BYZANTINE_MUSICAL_SYMBOLS = addUnicodeBlock("Byzantine Musical Symbols", 0x1d000, 0x1d0ff)
     val MUSICAL_SYMBOLS = addUnicodeBlock("Musical Symbols", 0x1d100, 0x1d1ff)
     val ANCIENT_GREEK_MUSICAL_NOTATION = addUnicodeBlock("Ancient Greek Musical Notation", 0x1d200, 0x1d24f)
+    val KAKTOVIK_NUMERALS = addUnicodeBlock("Kaktovik Numerals", 0x1d2c0, 0x1d2df)
+    val MAYAN_NUMERALS = addUnicodeBlock("Mayan Numerals", 0x1d2e0, 0x1d2ff)
     val TAI_XUAN_JING_SYMBOLS = addUnicodeBlock("Tai Xuan Jing Symbols", 0x1d300, 0x1d35f)
     val COUNTING_ROD_NUMERALS = addUnicodeBlock("Counting Rod Numerals", 0x1d360, 0x1d37f)
     val MATHEMATICAL_ALPHANUMERIC_SYMBOLS = addUnicodeBlock("Mathematical Alphanumeric Symbols", 0x1d400, 0x1d7ff)
+    val SUTTON_SIGNWRITING = addUnicodeBlock("Sutton SignWriting", 0x1d800, 0x1daaf)
+    val LATIN_EXTENDED_G = addUnicodeBlock("Latin Extended-G", 0x1df00, 0x1dfff)
+    val GLAGOLITIC_SUPPLEMENT = addUnicodeBlock("Glagolitic Supplement", 0x1e000, 0x1e02f)
+    val CYRILLIC_EXTENDED_D = addUnicodeBlock("Cyrillic Extended-D", 0x1e030, 0x1e08f)
+    val NYIAKENG_PUACHUE_HMONG = addUnicodeBlock("Nyiakeng Puachue Hmong", 0x1e100, 0x1e14f)
+    val TOTO = addUnicodeBlock("Toto", 0x1e290, 0x1e2bf)
+    val WANCHO = addUnicodeBlock("Wancho", 0x1e2c0, 0x1e2ff)
+    val NAG_MUNDARI = addUnicodeBlock("Nag Mundari", 0x1e4d0, 0x1e4ff)
+    val ETHIOPIC_EXTENDED_B = addUnicodeBlock("Ethiopic Extended-B", 0x1e7e0, 0x1e7ff)
+    val MENDE_KIKAKUI = addUnicodeBlock("Mende Kikakui", 0x1e800, 0x1e8df)
+    val ADLAM = addUnicodeBlock("Adlam", 0x1e900, 0x1e95f)
+    val INDIC_SIYAQ_NUMBERS = addUnicodeBlock("Indic Siyaq Numbers", 0x1ec70, 0x1ecbf)
+    val OTTOMAN_SIYAQ_NUMBERS = addUnicodeBlock("Ottoman Siyaq Numbers", 0x1ed00, 0x1ed4f)
     val ARABIC_MATHEMATICAL_ALPHABETIC_SYMBOLS = addUnicodeBlock("Arabic Mathematical Alphabetic Symbols", 0x1ee00, 0x1eeff)
     val MAHJONG_TILES = addUnicodeBlock("Mahjong Tiles", 0x1f000, 0x1f02f)
     val DOMINO_TILES = addUnicodeBlock("Domino Tiles", 0x1f030, 0x1f09f)
@@ -962,12 +1107,23 @@ for (cp <- 0 to Character.MAX_CODE_POINT) {
     val ENCLOSED_IDEOGRAPHIC_SUPPLEMENT = addUnicodeBlock("Enclosed Ideographic Supplement", 0x1f200, 0x1f2ff)
     val MISCELLANEOUS_SYMBOLS_AND_PICTOGRAPHS = addUnicodeBlock("Miscellaneous Symbols and Pictographs", 0x1f300, 0x1f5ff)
     val EMOTICONS = addUnicodeBlock("Emoticons", 0x1f600, 0x1f64f)
+    val ORNAMENTAL_DINGBATS = addUnicodeBlock("Ornamental Dingbats", 0x1f650, 0x1f67f)
     val TRANSPORT_AND_MAP_SYMBOLS = addUnicodeBlock("Transport and Map Symbols", 0x1f680, 0x1f6ff)
     val ALCHEMICAL_SYMBOLS = addUnicodeBlock("Alchemical Symbols", 0x1f700, 0x1f77f)
+    val GEOMETRIC_SHAPES_EXTENDED = addUnicodeBlock("Geometric Shapes Extended", 0x1f780, 0x1f7ff)
+    val SUPPLEMENTAL_ARROWS_C = addUnicodeBlock("Supplemental Arrows-C", 0x1f800, 0x1f8ff)
+    val SUPPLEMENTAL_SYMBOLS_AND_PICTOGRAPHS = addUnicodeBlock("Supplemental Symbols and Pictographs", 0x1f900, 0x1f9ff)
+    val CHESS_SYMBOLS = addUnicodeBlock("Chess Symbols", 0x1fa00, 0x1fa6f)
+    val SYMBOLS_AND_PICTOGRAPHS_EXTENDED_A = addUnicodeBlock("Symbols and Pictographs Extended-A", 0x1fa70, 0x1faff)
+    val SYMBOLS_FOR_LEGACY_COMPUTING = addUnicodeBlock("Symbols for Legacy Computing", 0x1fb00, 0x1fbff)
     val CJK_UNIFIED_IDEOGRAPHS_EXTENSION_B = addUnicodeBlock("CJK Unified Ideographs Extension B", 0x20000, 0x2a6df)
     val CJK_UNIFIED_IDEOGRAPHS_EXTENSION_C = addUnicodeBlock("CJK Unified Ideographs Extension C", 0x2a700, 0x2b73f)
     val CJK_UNIFIED_IDEOGRAPHS_EXTENSION_D = addUnicodeBlock("CJK Unified Ideographs Extension D", 0x2b740, 0x2b81f)
+    val CJK_UNIFIED_IDEOGRAPHS_EXTENSION_E = addUnicodeBlock("CJK Unified Ideographs Extension E", 0x2b820, 0x2ceaf)
+    val CJK_UNIFIED_IDEOGRAPHS_EXTENSION_F = addUnicodeBlock("CJK Unified Ideographs Extension F", 0x2ceb0, 0x2ebef)
     val CJK_COMPATIBILITY_IDEOGRAPHS_SUPPLEMENT = addUnicodeBlock("CJK Compatibility Ideographs Supplement", 0x2f800, 0x2fa1f)
+    val CJK_UNIFIED_IDEOGRAPHS_EXTENSION_G = addUnicodeBlock("CJK Unified Ideographs Extension G", 0x30000, 0x3134f)
+    val CJK_UNIFIED_IDEOGRAPHS_EXTENSION_H = addUnicodeBlock("CJK Unified Ideographs Extension H", 0x31350, 0x323af)
     val TAGS = addUnicodeBlock("Tags", 0xe0000, 0xe007f)
     val VARIATION_SELECTORS_SUPPLEMENT = addUnicodeBlock("Variation Selectors Supplement", 0xe0100, 0xe01ef)
     val SUPPLEMENTARY_PRIVATE_USE_AREA_A = addUnicodeBlock("Supplementary Private Use Area-A", 0xf0000, 0xfffff)
@@ -1010,8 +1166,8 @@ for (cp <- 0 to Character.MAX_CODE_POINT) {
     }
   }
 
-  // Based on Unicode 6.2.0, extended with chars 00BB, 20BC-20BF and 32FF
-  // Generated with OpenJDK 1.8.0_222
+  // Based on Unicode 15.0
+  // Generated with Temurin-21+35 (build 21+35-LTS)
 
   // Types of characters from 0 to 255
   private[this] lazy val charTypesFirst256: Array[Int] = Array(15, 15, 15, 15,
@@ -1038,7 +1194,7 @@ for (cp <- 0 to Character.MAX_CODE_POINT) {
    * They where generated with the following script, which can be pasted into
    * a Scala REPL.
 
-def formatLargeArray(array: Array[Int], indent: String): String = {
+def formatLargeArrayStr(array: Array[String], indent: String): String = {
   val indentMinus1 = indent.substring(1)
   val builder = new java.lang.StringBuilder
   builder.append(indentMinus1)
@@ -1056,6 +1212,9 @@ def formatLargeArray(array: Array[Int], indent: String): String = {
   builder.toString()
 }
 
+def formatLargeArray(array: Array[Int], indent: String): String =
+  formatLargeArrayStr(array.map(_.toString()), indent)
+
 val indicesAndTypes = (256 to Character.MAX_CODE_POINT)
   .map(i => (i, Character.getType(i)))
   .foldLeft[List[(Int, Int)]](Nil) {
@@ -1093,137 +1252,172 @@ println("  )")
         1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
         1, 1, 1, 1, 1, 1, 1, 1, 7, 2, 1, 2, 2, 1, 1, 4, 1, 1, 1, 1, 1, 1, 1, 1,
         69, 1, 27, 18, 4, 12, 14, 5, 7, 1, 1, 1, 17, 112, 1, 1, 1, 1, 1, 1, 1,
-        1, 2, 1, 3, 1, 5, 2, 1, 1, 3, 1, 1, 1, 2, 1, 17, 1, 9, 35, 1, 2, 3, 3,
-        1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 5,
-        1, 1, 1, 1, 1, 2, 2, 51, 48, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
-        1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 5, 2, 1,
+        1, 2, 1, 3, 1, 1, 4, 2, 1, 1, 3, 1, 1, 1, 2, 1, 17, 1, 9, 35, 1, 2, 3,
+        3, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+        5, 1, 1, 1, 1, 1, 2, 2, 51, 48, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+        1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 5, 2,
         1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
         1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
-        1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1,
+        1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1,
         1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
         1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
         1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
-        1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 9, 38, 2, 1, 6, 1, 39, 1, 1, 1, 4, 1,
-        1, 45, 1, 1, 1, 2, 1, 2, 1, 1, 8, 27, 5, 3, 2, 11, 5, 1, 3, 2, 1, 2, 2,
-        11, 1, 2, 2, 32, 1, 10, 21, 10, 4, 2, 1, 99, 1, 1, 7, 1, 1, 6, 2, 2, 1,
-        4, 2, 10, 3, 2, 1, 14, 1, 1, 1, 1, 30, 27, 2, 89, 11, 1, 14, 10, 33, 9,
-        2, 1, 3, 1, 5, 22, 4, 1, 9, 1, 3, 1, 5, 2, 15, 1, 25, 3, 2, 1, 65, 1,
-        1, 11, 55, 27, 1, 3, 1, 54, 1, 1, 1, 1, 3, 8, 4, 1, 2, 1, 7, 10, 2, 2,
-        10, 1, 1, 6, 1, 7, 1, 1, 2, 1, 8, 2, 2, 2, 22, 1, 7, 1, 1, 3, 4, 2, 1,
-        1, 3, 4, 2, 2, 2, 2, 1, 1, 8, 1, 4, 2, 1, 3, 2, 2, 10, 2, 2, 6, 1, 1,
-        5, 2, 1, 1, 6, 4, 2, 2, 22, 1, 7, 1, 2, 1, 2, 1, 2, 2, 1, 1, 3, 2, 4,
-        2, 2, 3, 3, 1, 7, 4, 1, 1, 7, 10, 2, 3, 1, 11, 2, 1, 1, 9, 1, 3, 1, 22,
-        1, 7, 1, 2, 1, 5, 2, 1, 1, 3, 5, 1, 2, 1, 1, 2, 1, 2, 1, 15, 2, 2, 2,
-        10, 1, 1, 15, 1, 2, 1, 8, 2, 2, 2, 22, 1, 7, 1, 2, 1, 5, 2, 1, 1, 1, 1,
-        1, 4, 2, 2, 2, 2, 1, 8, 1, 1, 4, 2, 1, 3, 2, 2, 10, 1, 1, 6, 10, 1, 1,
-        1, 6, 3, 3, 1, 4, 3, 2, 1, 1, 1, 2, 3, 2, 3, 3, 3, 12, 4, 2, 1, 2, 3,
-        3, 1, 3, 1, 2, 1, 6, 1, 14, 10, 3, 6, 1, 1, 6, 3, 1, 8, 1, 3, 1, 23, 1,
-        10, 1, 5, 3, 1, 3, 4, 1, 3, 1, 4, 7, 2, 1, 2, 6, 2, 2, 2, 10, 8, 7, 1,
-        2, 2, 1, 8, 1, 3, 1, 23, 1, 10, 1, 5, 2, 1, 1, 1, 1, 5, 1, 1, 2, 1, 2,
-        2, 7, 2, 7, 1, 1, 2, 2, 2, 10, 1, 2, 15, 2, 1, 8, 1, 3, 1, 41, 2, 1, 3,
-        4, 1, 3, 1, 3, 1, 1, 8, 1, 8, 2, 2, 2, 10, 6, 3, 1, 6, 2, 2, 1, 18, 3,
-        24, 1, 9, 1, 1, 2, 7, 3, 1, 4, 3, 3, 1, 1, 1, 8, 18, 2, 1, 12, 48, 1,
-        2, 7, 4, 1, 6, 1, 8, 1, 10, 2, 37, 2, 1, 1, 2, 2, 1, 1, 2, 1, 6, 4, 1,
-        7, 1, 3, 1, 1, 1, 1, 2, 2, 1, 4, 1, 2, 6, 1, 2, 1, 2, 5, 1, 1, 1, 6, 2,
-        10, 2, 4, 32, 1, 3, 15, 1, 1, 3, 2, 6, 10, 10, 1, 1, 1, 1, 1, 1, 1, 1,
-        1, 1, 2, 8, 1, 36, 4, 14, 1, 5, 1, 2, 5, 11, 1, 36, 1, 8, 1, 6, 1, 2,
-        5, 4, 2, 37, 43, 2, 4, 1, 6, 1, 2, 2, 2, 1, 10, 6, 6, 2, 2, 4, 3, 1, 3,
-        2, 7, 3, 4, 13, 1, 2, 2, 6, 1, 1, 1, 10, 3, 1, 2, 38, 1, 1, 5, 1, 2,
-        43, 1, 1, 332, 1, 4, 2, 7, 1, 1, 1, 4, 2, 41, 1, 4, 2, 33, 1, 4, 2, 7,
-        1, 1, 1, 4, 2, 15, 1, 57, 1, 4, 2, 67, 2, 3, 9, 20, 3, 16, 10, 6, 85,
-        11, 1, 620, 2, 17, 1, 26, 1, 1, 3, 75, 3, 3, 15, 13, 1, 4, 3, 11, 18,
-        3, 2, 9, 18, 2, 12, 13, 1, 3, 1, 2, 12, 52, 2, 1, 7, 8, 1, 2, 11, 3, 1,
-        3, 1, 1, 1, 2, 10, 6, 10, 6, 6, 1, 4, 3, 1, 1, 10, 6, 35, 1, 52, 8, 41,
-        1, 1, 5, 70, 10, 29, 3, 3, 4, 2, 3, 4, 2, 1, 6, 3, 4, 1, 3, 2, 10, 30,
-        2, 5, 11, 44, 4, 17, 7, 2, 6, 10, 1, 3, 34, 23, 2, 3, 2, 2, 53, 1, 1,
-        1, 7, 1, 1, 1, 1, 2, 8, 6, 10, 2, 1, 10, 6, 10, 6, 7, 1, 6, 82, 4, 1,
-        47, 1, 1, 5, 1, 1, 5, 1, 2, 7, 4, 10, 7, 10, 9, 9, 3, 2, 1, 30, 1, 4,
-        2, 2, 1, 1, 2, 2, 10, 44, 1, 1, 2, 3, 1, 1, 3, 2, 8, 4, 36, 8, 8, 2, 2,
-        3, 5, 10, 3, 3, 10, 30, 6, 2, 64, 8, 8, 3, 1, 13, 1, 7, 4, 1, 4, 2, 1,
-        2, 9, 44, 63, 13, 1, 34, 37, 39, 21, 4, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+        1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 38, 2,
+        1, 6, 41, 1, 1, 2, 2, 1, 1, 45, 1, 1, 1, 2, 1, 2, 1, 1, 8, 27, 4, 4, 2,
+        11, 6, 3, 2, 1, 2, 2, 11, 1, 1, 3, 32, 1, 10, 21, 10, 4, 2, 1, 99, 1,
+        1, 7, 1, 1, 6, 2, 2, 1, 4, 2, 10, 3, 2, 1, 14, 1, 1, 1, 1, 30, 27, 2,
+        89, 11, 1, 14, 10, 33, 9, 2, 1, 3, 1, 2, 1, 2, 22, 4, 1, 9, 1, 3, 1, 5,
+        2, 15, 1, 25, 3, 2, 1, 1, 11, 5, 24, 1, 6, 1, 2, 6, 8, 41, 1, 24, 1,
+        32, 1, 54, 1, 1, 1, 1, 3, 8, 4, 1, 2, 1, 7, 10, 2, 2, 10, 1, 1, 15, 1,
+        2, 1, 8, 2, 2, 2, 22, 1, 7, 1, 1, 3, 4, 2, 1, 1, 3, 4, 2, 2, 2, 2, 1,
+        1, 8, 1, 4, 2, 1, 3, 2, 2, 10, 2, 2, 6, 1, 1, 1, 1, 1, 2, 2, 1, 1, 6,
+        4, 2, 2, 22, 1, 7, 1, 2, 1, 2, 1, 2, 2, 1, 1, 3, 2, 4, 2, 2, 3, 3, 1,
+        7, 4, 1, 1, 7, 10, 2, 3, 1, 1, 10, 2, 1, 1, 9, 1, 3, 1, 22, 1, 7, 1, 2,
+        1, 5, 2, 1, 1, 3, 5, 1, 2, 1, 1, 2, 1, 2, 1, 15, 2, 2, 2, 10, 1, 1, 7,
+        1, 6, 1, 1, 2, 1, 8, 2, 2, 2, 22, 1, 7, 1, 2, 1, 5, 2, 1, 1, 1, 1, 1,
+        4, 2, 2, 2, 2, 1, 7, 2, 1, 4, 2, 1, 3, 2, 2, 10, 1, 1, 6, 10, 1, 1, 1,
+        6, 3, 3, 1, 4, 3, 2, 1, 1, 1, 2, 3, 2, 3, 3, 3, 12, 4, 2, 1, 2, 3, 3,
+        1, 3, 1, 2, 1, 6, 1, 14, 10, 3, 6, 1, 1, 5, 1, 3, 1, 8, 1, 3, 1, 23, 1,
+        16, 2, 1, 1, 3, 4, 1, 3, 1, 4, 7, 2, 1, 3, 2, 1, 2, 2, 2, 2, 10, 7, 1,
+        7, 1, 1, 1, 2, 1, 8, 1, 3, 1, 23, 1, 10, 1, 5, 2, 1, 1, 1, 1, 5, 1, 1,
+        2, 1, 2, 2, 7, 2, 6, 2, 1, 2, 2, 2, 10, 1, 2, 1, 12, 2, 2, 9, 1, 3, 1,
+        41, 2, 1, 3, 4, 1, 3, 1, 3, 1, 1, 1, 4, 3, 1, 7, 3, 2, 2, 10, 9, 1, 6,
+        1, 1, 2, 1, 18, 3, 24, 1, 9, 1, 1, 2, 7, 3, 1, 4, 3, 3, 1, 1, 1, 8, 6,
+        10, 2, 2, 1, 12, 48, 1, 2, 7, 4, 1, 6, 1, 8, 1, 10, 2, 37, 2, 1, 1, 1,
+        5, 1, 24, 1, 1, 1, 10, 1, 2, 9, 1, 2, 5, 1, 1, 1, 7, 1, 10, 2, 4, 32,
+        1, 3, 15, 1, 1, 3, 2, 6, 10, 10, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 8, 1,
+        36, 4, 14, 1, 5, 1, 2, 5, 11, 1, 36, 1, 8, 1, 6, 1, 2, 5, 4, 2, 37, 43,
+        2, 4, 1, 6, 1, 2, 2, 2, 1, 10, 6, 6, 2, 2, 4, 3, 1, 3, 2, 7, 3, 4, 13,
+        1, 2, 2, 6, 1, 1, 1, 10, 3, 1, 2, 38, 1, 1, 5, 1, 2, 43, 1, 1, 3, 329,
+        1, 4, 2, 7, 1, 1, 1, 4, 2, 41, 1, 4, 2, 33, 1, 4, 2, 7, 1, 1, 1, 4, 2,
+        15, 1, 57, 1, 4, 2, 67, 2, 3, 9, 20, 3, 16, 10, 6, 86, 2, 6, 2, 1, 620,
+        1, 1, 17, 1, 26, 1, 1, 3, 75, 3, 3, 8, 7, 18, 3, 1, 9, 19, 2, 1, 2, 9,
+        18, 2, 12, 13, 1, 3, 1, 2, 12, 52, 2, 1, 7, 8, 1, 2, 11, 3, 1, 3, 1, 1,
+        1, 2, 10, 6, 10, 6, 6, 1, 4, 3, 1, 1, 10, 6, 35, 1, 53, 7, 5, 2, 34, 1,
+        1, 5, 70, 10, 31, 1, 3, 4, 2, 3, 4, 2, 1, 6, 3, 4, 1, 3, 2, 10, 30, 2,
+        5, 11, 44, 4, 26, 6, 10, 1, 3, 34, 23, 2, 2, 1, 2, 2, 53, 1, 1, 1, 7,
+        1, 1, 1, 1, 2, 8, 6, 10, 2, 1, 10, 6, 10, 6, 7, 1, 6, 2, 14, 1, 16, 49,
+        4, 1, 47, 1, 1, 5, 1, 1, 5, 1, 2, 8, 3, 10, 7, 10, 9, 9, 2, 1, 2, 1,
+        30, 1, 4, 2, 2, 1, 3, 2, 10, 44, 1, 1, 2, 3, 1, 1, 3, 2, 8, 4, 36, 8,
+        8, 2, 2, 3, 5, 10, 3, 3, 10, 30, 6, 2, 9, 7, 43, 2, 3, 8, 8, 3, 1, 13,
+        1, 7, 4, 1, 6, 1, 2, 1, 2, 1, 5, 44, 63, 13, 1, 34, 37, 64, 1, 1, 1, 1,
         1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
         1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
         1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
         1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
         1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
-        1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 9, 1, 1, 1, 1,
         1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+        1, 9, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
         1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
         1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
-        1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 9, 8, 6,
-        2, 6, 2, 8, 8, 8, 8, 6, 2, 6, 2, 8, 1, 1, 1, 1, 1, 1, 1, 1, 8, 8, 14,
-        2, 8, 8, 8, 8, 8, 8, 5, 1, 2, 4, 1, 1, 1, 3, 3, 1, 2, 4, 1, 3, 4, 2, 2,
-        4, 1, 3, 8, 5, 3, 2, 3, 1, 2, 4, 1, 2, 1, 11, 5, 6, 2, 1, 1, 1, 2, 1,
-        1, 1, 8, 1, 1, 5, 1, 9, 1, 1, 4, 2, 3, 1, 1, 1, 11, 1, 1, 1, 10, 1, 5,
-        5, 6, 1, 1, 2, 6, 3, 1, 1, 1, 10, 3, 1, 1, 1, 13, 3, 32, 16, 13, 4, 1,
-        3, 12, 15, 2, 1, 4, 1, 2, 1, 3, 2, 3, 1, 1, 1, 2, 1, 5, 6, 1, 1, 1, 1,
-        1, 1, 4, 1, 1, 4, 1, 4, 1, 2, 2, 2, 5, 1, 4, 1, 1, 2, 1, 1, 16, 35, 1,
-        1, 4, 1, 6, 5, 5, 2, 4, 1, 2, 1, 2, 1, 7, 1, 31, 2, 2, 1, 1, 1, 31,
-        268, 8, 4, 20, 2, 7, 1, 1, 81, 1, 30, 25, 40, 6, 18, 12, 39, 25, 11,
-        21, 60, 78, 22, 183, 1, 9, 1, 54, 8, 111, 1, 144, 1, 103, 1, 1, 1, 1,
-        1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 30, 44, 5, 1, 1, 31, 1, 1, 1, 1, 1, 1, 1,
-        1, 1, 1, 16, 256, 131, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
-        1, 1, 1, 1, 1, 1, 63, 1, 1, 1, 1, 32, 1, 1, 258, 48, 21, 2, 6, 3, 10,
-        166, 47, 1, 47, 1, 1, 1, 3, 2, 1, 1, 1, 1, 1, 1, 4, 1, 1, 2, 1, 6, 2,
-        3, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
         1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+        1, 1, 1, 9, 8, 6, 2, 6, 2, 8, 8, 8, 8, 6, 2, 6, 2, 8, 1, 1, 1, 1, 1, 1,
+        1, 1, 8, 8, 14, 2, 8, 8, 8, 8, 8, 8, 5, 1, 2, 4, 1, 1, 1, 3, 3, 1, 2,
+        4, 1, 3, 4, 2, 2, 4, 1, 3, 8, 5, 3, 2, 3, 1, 2, 4, 1, 2, 1, 11, 5, 6,
+        2, 1, 1, 1, 2, 1, 1, 1, 8, 1, 1, 5, 1, 9, 1, 1, 4, 2, 3, 1, 1, 1, 11,
+        1, 1, 1, 10, 1, 5, 1, 10, 1, 1, 2, 6, 3, 1, 1, 1, 10, 3, 1, 1, 1, 13,
+        3, 33, 15, 13, 4, 1, 3, 12, 15, 2, 1, 4, 1, 2, 1, 3, 2, 3, 1, 1, 1, 2,
+        1, 5, 6, 1, 1, 1, 1, 1, 1, 4, 1, 1, 4, 1, 4, 1, 2, 2, 2, 5, 1, 4, 1, 1,
+        2, 1, 1, 16, 35, 1, 1, 4, 1, 2, 4, 5, 5, 2, 4, 1, 2, 1, 2, 1, 7, 1, 31,
+        2, 2, 1, 1, 1, 31, 268, 8, 1, 1, 1, 1, 20, 2, 7, 1, 1, 81, 1, 30, 25,
+        40, 6, 69, 25, 11, 21, 60, 78, 22, 183, 1, 9, 1, 54, 8, 111, 1, 248, 1,
+        1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 30, 44, 5, 1, 1, 31, 1, 1, 1, 1,
+        1, 1, 1, 1, 1, 1, 16, 256, 131, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+        1, 1, 1, 1, 1, 1, 1, 1, 1, 63, 1, 1, 1, 1, 32, 1, 1, 258, 48, 21, 2, 6,
+        39, 2, 32, 1, 105, 48, 48, 1, 1, 3, 2, 1, 1, 1, 1, 1, 1, 4, 1, 1, 2, 1,
+        6, 2, 3, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
         1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
         1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
-        1, 1, 1, 2, 6, 1, 1, 1, 1, 3, 1, 1, 5, 4, 1, 2, 38, 1, 1, 5, 1, 2, 56,
-        7, 1, 1, 14, 1, 23, 9, 7, 1, 7, 1, 7, 1, 7, 1, 7, 1, 7, 1, 7, 1, 7, 1,
-        32, 2, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 9, 1, 2, 1, 1, 1, 1, 2, 1, 1, 1,
-        1, 1, 1, 1, 1, 1, 1, 5, 1, 10, 2, 68, 26, 1, 89, 12, 214, 26, 12, 4, 1,
-        3, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1,
-        1, 1, 2, 1, 9, 4, 2, 1, 5, 2, 3, 1, 1, 1, 2, 1, 86, 2, 2, 2, 2, 1, 1,
-        90, 1, 3, 1, 5, 41, 3, 94, 1, 2, 4, 10, 27, 5, 36, 12, 16, 31, 1, 10,
-        30, 8, 1, 15, 32, 10, 39, 15, 320, 6582, 10, 64, 20941, 51, 21, 1,
-        1143, 3, 55, 9, 40, 6, 2, 268, 1, 3, 16, 10, 2, 20, 1, 1, 1, 1, 1, 1,
         1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
-        1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 3, 1, 10, 1, 1,
+        1, 1, 1, 1, 1, 2, 6, 1, 1, 1, 1, 3, 1, 1, 5, 4, 1, 2, 38, 1, 1, 5, 1,
+        2, 56, 7, 1, 1, 14, 1, 23, 9, 7, 1, 7, 1, 7, 1, 7, 1, 7, 1, 7, 1, 7, 1,
+        7, 1, 32, 2, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 9, 1, 2, 1, 1, 1, 1, 2, 1,
+        1, 1, 1, 1, 1, 1, 1, 1, 1, 5, 1, 10, 2, 4, 1, 1, 1, 13, 2, 3, 1, 1, 1,
+        1, 1, 1, 1, 1, 1, 34, 26, 1, 89, 12, 214, 26, 12, 4, 1, 3, 1, 1, 1, 1,
+        1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 9,
+        4, 2, 1, 5, 2, 3, 1, 1, 1, 2, 1, 86, 2, 2, 2, 2, 1, 1, 90, 1, 3, 1, 5,
+        43, 1, 94, 1, 2, 4, 10, 32, 36, 12, 16, 31, 1, 10, 30, 8, 1, 15, 32,
+        10, 39, 15, 320, 6592, 64, 21013, 1, 1143, 3, 55, 9, 40, 6, 2, 268, 1,
+        3, 16, 10, 2, 20, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+        1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+        1, 1, 1, 1, 1, 1, 3, 1, 10, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+        1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 70, 10, 2, 6, 8,
+        23, 9, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 1,
         1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
-        7, 1, 70, 10, 2, 6, 8, 23, 9, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
-        3, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
         1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
-        1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 8, 1, 1, 1, 1, 2, 1, 1,
-        1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 12, 1, 1, 1, 1,
-        1, 1, 1, 1, 1, 1, 1, 77, 2, 1, 7, 1, 3, 1, 4, 1, 23, 2, 2, 1, 4, 4, 6,
-        2, 1, 1, 6, 52, 4, 8, 2, 50, 16, 1, 9, 2, 10, 6, 18, 6, 3, 1, 4, 10,
-        28, 8, 2, 23, 11, 2, 11, 1, 29, 3, 3, 1, 47, 1, 2, 4, 2, 1, 4, 13, 1,
-        1, 10, 4, 2, 32, 41, 6, 2, 2, 2, 2, 9, 3, 1, 8, 1, 1, 2, 10, 2, 4, 16,
-        1, 6, 3, 1, 1, 4, 48, 1, 1, 3, 2, 2, 5, 2, 1, 1, 1, 24, 2, 1, 2, 11, 1,
-        2, 2, 2, 1, 2, 1, 1, 10, 6, 2, 6, 2, 6, 9, 7, 1, 7, 145, 35, 2, 1, 2,
-        1, 2, 1, 1, 1, 2, 10, 6, 11172, 12, 23, 4, 49, 4, 2048, 6400, 366, 2,
-        106, 38, 7, 12, 5, 5, 1, 1, 10, 1, 13, 1, 5, 1, 1, 1, 2, 1, 2, 1, 108,
-        16, 17, 363, 1, 1, 16, 64, 2, 54, 40, 12, 1, 1, 2, 16, 7, 1, 1, 1, 6,
-        7, 9, 1, 2, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1,
-        4, 3, 3, 1, 4, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 3, 1, 1, 1, 2, 4, 5, 1,
-        135, 2, 1, 1, 3, 1, 3, 1, 1, 1, 1, 1, 1, 2, 10, 2, 3, 2, 26, 1, 1, 1,
-        1, 1, 1, 26, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 10, 1, 45, 2, 31, 3, 6, 2,
-        6, 2, 6, 2, 3, 3, 2, 1, 1, 1, 2, 1, 1, 4, 2, 10, 3, 2, 2, 12, 1, 26, 1,
-        19, 1, 2, 1, 15, 2, 14, 34, 123, 5, 3, 4, 45, 3, 9, 53, 4, 17, 1, 5,
-        12, 52, 45, 1, 130, 29, 3, 49, 47, 31, 1, 4, 12, 17, 1, 8, 1, 53, 30,
-        1, 1, 36, 4, 8, 1, 5, 42, 40, 40, 78, 2, 10, 854, 6, 2, 1, 1, 44, 1, 2,
-        3, 1, 2, 23, 1, 1, 8, 160, 22, 6, 3, 1, 26, 5, 1, 64, 56, 6, 2, 64, 1,
-        3, 1, 2, 5, 4, 4, 1, 3, 1, 27, 4, 3, 4, 1, 8, 8, 9, 7, 29, 2, 1, 128,
-        54, 3, 7, 22, 2, 8, 19, 5, 8, 128, 73, 535, 31, 385, 1, 1, 1, 53, 15,
-        7, 4, 20, 10, 16, 2, 1, 45, 3, 4, 2, 2, 2, 1, 4, 14, 25, 7, 10, 6, 3,
-        36, 5, 1, 8, 1, 10, 4, 60, 2, 1, 48, 3, 9, 2, 4, 4, 7, 10, 1190, 43, 1,
-        1, 1, 2, 6, 1, 1, 8, 10, 2358, 879, 145, 99, 13, 4, 2956, 1071, 13265,
-        569, 1223, 69, 11, 1, 46, 16, 4, 13, 16480, 2, 8190, 246, 10, 39, 2,
-        60, 2, 3, 3, 6, 8, 8, 2, 7, 30, 4, 48, 34, 66, 3, 1, 186, 87, 9, 18,
-        142, 26, 26, 26, 7, 1, 18, 26, 26, 1, 1, 2, 2, 1, 2, 2, 2, 4, 1, 8, 4,
-        1, 1, 1, 7, 1, 11, 26, 26, 2, 1, 4, 2, 8, 1, 7, 1, 26, 2, 1, 4, 1, 5,
-        1, 1, 3, 7, 1, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 28, 2,
-        25, 1, 25, 1, 6, 25, 1, 25, 1, 6, 25, 1, 25, 1, 6, 25, 1, 25, 1, 6, 25,
-        1, 25, 1, 6, 1, 1, 2, 50, 5632, 4, 1, 27, 1, 2, 1, 1, 2, 1, 1, 10, 1,
-        4, 1, 1, 1, 1, 6, 1, 4, 1, 1, 1, 1, 1, 1, 3, 1, 2, 1, 1, 2, 1, 1, 1, 1,
-        1, 1, 1, 1, 1, 1, 2, 1, 1, 2, 4, 1, 7, 1, 4, 1, 4, 1, 1, 1, 10, 1, 17,
-        5, 3, 1, 5, 1, 17, 52, 2, 270, 44, 4, 100, 12, 15, 2, 14, 2, 15, 1, 15,
-        32, 11, 5, 31, 1, 60, 4, 43, 75, 29, 13, 43, 5, 9, 7, 2, 174, 33, 15,
-        6, 1, 70, 3, 20, 12, 37, 1, 5, 21, 17, 15, 63, 1, 1, 1, 182, 1, 4, 3,
-        62, 2, 4, 12, 24, 147, 70, 4, 11, 48, 70, 58, 116, 2188, 42711, 41,
-        4149, 11, 222, 16354, 542, 722403, 1, 30, 96, 128, 240, 65040, 65534,
-        2, 65534
+        1, 1, 1, 1, 1, 1, 1, 1, 1, 8, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+        1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+        1, 1, 1, 1, 1, 1, 1, 5, 1, 5, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+        1, 4, 1, 1, 1, 5, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 24, 3, 1, 1, 1, 2, 1,
+        7, 1, 3, 1, 4, 1, 23, 2, 2, 1, 4, 1, 3, 6, 2, 1, 1, 6, 52, 4, 8, 2, 50,
+        16, 2, 8, 2, 10, 6, 18, 6, 3, 1, 1, 2, 1, 10, 28, 8, 2, 23, 11, 2, 11,
+        1, 29, 3, 3, 1, 47, 1, 2, 4, 2, 2, 3, 13, 1, 1, 10, 4, 2, 5, 1, 1, 9,
+        10, 5, 1, 41, 6, 2, 2, 2, 2, 9, 3, 1, 8, 1, 1, 2, 10, 2, 4, 16, 1, 6,
+        3, 1, 1, 1, 1, 50, 1, 1, 3, 2, 2, 5, 2, 1, 1, 1, 24, 2, 1, 2, 11, 1, 2,
+        2, 2, 1, 2, 1, 1, 10, 6, 2, 6, 2, 6, 9, 7, 1, 7, 1, 43, 1, 4, 9, 1, 2,
+        4, 80, 35, 2, 1, 2, 1, 2, 1, 1, 1, 2, 10, 6, 11172, 12, 23, 4, 49, 4,
+        2048, 6400, 366, 2, 106, 38, 7, 12, 5, 5, 1, 1, 10, 1, 13, 1, 5, 1, 1,
+        1, 2, 1, 2, 1, 108, 17, 16, 363, 1, 1, 16, 64, 2, 54, 7, 1, 32, 12, 1,
+        3, 16, 7, 1, 1, 1, 6, 16, 1, 2, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+        1, 1, 1, 1, 2, 1, 1, 4, 3, 3, 1, 4, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 3, 1,
+        1, 1, 2, 4, 5, 1, 135, 2, 1, 1, 3, 1, 3, 1, 1, 1, 1, 1, 1, 2, 10, 2, 3,
+        2, 26, 1, 1, 1, 1, 1, 1, 26, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 10, 1, 45,
+        2, 31, 3, 6, 2, 6, 2, 6, 2, 3, 3, 2, 1, 1, 1, 2, 1, 1, 4, 2, 10, 3, 2,
+        2, 12, 1, 26, 1, 19, 1, 2, 1, 15, 2, 14, 34, 123, 5, 3, 4, 45, 3, 9,
+        53, 4, 17, 2, 3, 1, 13, 3, 1, 47, 45, 1, 130, 29, 3, 49, 15, 1, 27, 4,
+        32, 4, 9, 20, 1, 8, 1, 5, 38, 5, 5, 30, 1, 1, 36, 4, 8, 1, 5, 42, 40,
+        40, 78, 2, 10, 6, 36, 4, 36, 4, 40, 8, 52, 11, 1, 11, 1, 15, 1, 7, 1,
+        2, 1, 11, 1, 15, 1, 7, 1, 2, 67, 311, 9, 22, 10, 8, 24, 6, 1, 42, 1, 9,
+        69, 6, 2, 1, 1, 44, 1, 2, 3, 1, 2, 23, 1, 1, 8, 23, 2, 7, 31, 8, 9, 48,
+        19, 1, 2, 5, 5, 22, 6, 3, 1, 26, 5, 1, 64, 56, 4, 2, 2, 16, 2, 46, 1,
+        3, 1, 2, 5, 4, 4, 1, 3, 1, 29, 2, 3, 4, 1, 9, 7, 9, 7, 29, 2, 1, 29, 3,
+        32, 8, 1, 28, 2, 4, 5, 7, 9, 54, 3, 7, 22, 2, 8, 19, 5, 8, 18, 7, 4,
+        12, 7, 80, 73, 55, 51, 13, 51, 7, 6, 36, 4, 8, 10, 294, 31, 1, 42, 1,
+        2, 1, 2, 2, 75, 3, 29, 10, 1, 8, 22, 11, 4, 5, 22, 18, 4, 4, 38, 21, 7,
+        20, 23, 9, 1, 1, 1, 53, 15, 7, 4, 20, 10, 1, 2, 2, 1, 9, 3, 1, 45, 3,
+        4, 2, 2, 2, 1, 4, 1, 10, 1, 2, 25, 7, 10, 6, 3, 36, 5, 1, 8, 1, 10, 4,
+        1, 2, 1, 8, 35, 1, 2, 1, 9, 2, 1, 48, 3, 9, 2, 4, 4, 4, 1, 1, 1, 10, 1,
+        1, 1, 3, 1, 20, 11, 18, 1, 25, 3, 3, 2, 1, 1, 2, 6, 1, 2, 1, 62, 7, 1,
+        1, 1, 4, 1, 15, 1, 10, 1, 6, 47, 1, 3, 8, 5, 10, 6, 2, 2, 1, 8, 2, 2,
+        2, 22, 1, 7, 1, 2, 1, 5, 1, 2, 1, 2, 1, 4, 2, 2, 2, 3, 2, 1, 6, 1, 5,
+        5, 2, 2, 7, 3, 5, 139, 53, 3, 8, 2, 3, 1, 1, 4, 5, 10, 2, 1, 1, 1, 3,
+        30, 48, 3, 6, 1, 1, 4, 2, 1, 2, 2, 1, 1, 8, 10, 166, 47, 3, 4, 2, 4, 2,
+        1, 2, 23, 4, 2, 34, 48, 3, 8, 2, 1, 1, 2, 3, 1, 11, 10, 6, 13, 19, 43,
+        1, 1, 1, 2, 6, 1, 1, 1, 1, 6, 10, 54, 27, 2, 3, 2, 4, 1, 5, 4, 10, 2,
+        3, 1, 7, 185, 44, 3, 9, 1, 2, 1, 100, 32, 32, 10, 9, 12, 8, 2, 1, 2, 8,
+        1, 2, 1, 24, 6, 1, 2, 2, 2, 1, 1, 1, 1, 1, 1, 1, 3, 9, 10, 70, 8, 2,
+        39, 3, 4, 2, 2, 4, 1, 1, 1, 1, 1, 27, 1, 10, 40, 6, 1, 1, 4, 8, 1, 8,
+        1, 6, 2, 3, 46, 13, 1, 2, 3, 1, 5, 13, 73, 7, 10, 246, 9, 1, 37, 1, 7,
+        1, 6, 1, 1, 1, 5, 10, 10, 19, 3, 2, 30, 2, 22, 1, 1, 7, 1, 2, 1, 2, 73,
+        7, 1, 2, 1, 38, 6, 3, 1, 1, 2, 1, 7, 1, 1, 8, 10, 6, 6, 1, 2, 1, 32, 5,
+        1, 2, 1, 2, 1, 1, 1, 1, 7, 10, 310, 19, 2, 2, 2, 7, 2, 1, 1, 13, 1, 34,
+        2, 5, 3, 2, 1, 1, 1, 13, 10, 86, 1, 15, 21, 8, 4, 17, 13, 1, 922, 102,
+        111, 1, 5, 11, 196, 2636, 97, 2, 13, 1072, 16, 1, 6, 15, 4010, 583,
+        8633, 569, 7, 31, 1, 10, 4, 2, 79, 1, 10, 6, 30, 2, 5, 1, 10, 48, 7, 5,
+        4, 4, 1, 1, 10, 10, 1, 7, 1, 21, 5, 19, 688, 32, 32, 23, 4, 101, 75, 4,
+        1, 1, 55, 7, 4, 13, 64, 2, 1, 1, 1, 11, 2, 14, 6136, 8, 1238, 42, 9,
+        8935, 4, 1, 7, 1, 2, 1, 291, 15, 1, 29, 3, 2, 1, 14, 4, 8, 396, 2308,
+        107, 5, 13, 3, 9, 7, 10, 2, 1, 2, 1, 4, 4700, 46, 2, 23, 9, 116, 60,
+        246, 10, 39, 2, 60, 2, 3, 3, 6, 8, 8, 2, 7, 30, 4, 61, 21, 66, 3, 1,
+        122, 20, 12, 20, 12, 87, 9, 25, 135, 26, 26, 26, 7, 1, 18, 26, 26, 1,
+        1, 2, 2, 1, 2, 2, 2, 4, 1, 8, 4, 1, 1, 1, 7, 1, 11, 26, 26, 2, 1, 4, 2,
+        8, 1, 7, 1, 26, 2, 1, 4, 1, 5, 1, 1, 3, 7, 1, 26, 26, 26, 26, 26, 26,
+        26, 26, 26, 26, 26, 26, 28, 2, 25, 1, 25, 1, 6, 25, 1, 25, 1, 6, 25, 1,
+        25, 1, 6, 25, 1, 25, 1, 6, 25, 1, 25, 1, 6, 1, 1, 2, 50, 512, 55, 4,
+        50, 8, 1, 14, 1, 2, 5, 15, 5, 1, 15, 1104, 10, 1, 20, 6, 6, 213, 7, 1,
+        17, 2, 7, 1, 2, 1, 5, 5, 62, 33, 1, 112, 45, 3, 7, 7, 2, 10, 4, 1, 1,
+        320, 30, 1, 17, 44, 4, 10, 5, 1, 464, 27, 1, 4, 10, 742, 7, 1, 4, 1, 2,
+        1, 15, 1, 197, 2, 9, 7, 41, 34, 34, 7, 1, 4, 10, 4, 2, 785, 59, 1, 3,
+        1, 4, 76, 45, 1, 15, 194, 4, 1, 27, 1, 2, 1, 1, 2, 1, 1, 10, 1, 4, 1,
+        1, 1, 1, 6, 1, 4, 1, 1, 1, 1, 1, 1, 3, 1, 2, 1, 1, 2, 1, 1, 1, 1, 1, 1,
+        1, 1, 1, 1, 2, 1, 1, 2, 4, 1, 7, 1, 4, 1, 4, 1, 1, 1, 10, 1, 17, 5, 3,
+        1, 5, 1, 17, 52, 2, 270, 44, 4, 100, 12, 15, 2, 15, 1, 15, 1, 37, 10,
+        13, 161, 56, 29, 13, 44, 4, 9, 7, 2, 14, 6, 154, 251, 5, 728, 4, 17, 3,
+        13, 3, 119, 4, 95, 6, 12, 4, 1, 15, 12, 4, 56, 8, 10, 6, 40, 8, 30, 2,
+        2, 78, 340, 12, 14, 2, 13, 3, 9, 7, 46, 1, 7, 8, 14, 4, 9, 7, 9, 7,
+        147, 1, 55, 37, 10, 1030, 42720, 32, 4154, 6, 222, 2, 5762, 14, 7473,
+        3103, 542, 1506, 4939, 5, 4192, 711761, 1, 30, 96, 128, 240, 65040,
+        65534, 2, 65534
     )
     uncompressDeltas(deltas)
   }
@@ -1242,134 +1436,167 @@ println("  )")
       1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2,
       1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2,
       5, 2, 4, 27, 4, 27, 4, 27, 4, 27, 4, 27, 6, 1, 2, 1, 2, 4, 27, 1, 2, 0,
-      4, 2, 24, 0, 27, 1, 24, 1, 0, 1, 0, 1, 2, 1, 0, 1, 2, 1, 2, 1, 2, 1, 2,
-      1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2,
-      25, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1,
-      2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 28, 6, 7, 1, 2, 1, 2,
-      1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2,
-      1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2,
-      1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2,
-      1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2,
-      1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2,
-      1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2,
-      1, 2, 1, 2, 1, 2, 1, 2, 0, 1, 0, 4, 24, 0, 2, 0, 24, 20, 0, 26, 0, 6, 20,
-      6, 24, 6, 24, 6, 24, 6, 0, 5, 0, 5, 24, 0, 16, 0, 25, 24, 26, 24, 28, 6,
-      24, 0, 24, 5, 4, 5, 6, 9, 24, 5, 6, 5, 24, 5, 6, 16, 28, 6, 4, 6, 28, 6,
-      5, 9, 5, 28, 5, 24, 0, 16, 5, 6, 5, 6, 0, 5, 6, 5, 0, 9, 5, 6, 4, 28, 24,
-      4, 0, 5, 6, 4, 6, 4, 6, 4, 6, 0, 24, 0, 5, 6, 0, 24, 0, 5, 0, 5, 0, 6, 0,
-      6, 8, 5, 6, 8, 6, 5, 8, 6, 8, 6, 8, 5, 6, 5, 6, 24, 9, 24, 4, 5, 0, 5, 0,
-      6, 8, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 6, 5, 8, 6, 0, 8, 0, 8, 6,
-      5, 0, 8, 0, 5, 0, 5, 6, 0, 9, 5, 26, 11, 28, 26, 0, 6, 8, 0, 5, 0, 5, 0,
-      5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 6, 0, 8, 6, 0, 6, 0, 6, 0, 6, 0, 5, 0, 5,
-      0, 9, 6, 5, 6, 0, 6, 8, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 6, 5, 8,
-      6, 0, 6, 8, 0, 8, 6, 0, 5, 0, 5, 6, 0, 9, 24, 26, 0, 6, 8, 0, 5, 0, 5, 0,
-      5, 0, 5, 0, 5, 0, 5, 0, 6, 5, 8, 6, 8, 6, 0, 8, 0, 8, 6, 0, 6, 8, 0, 5,
-      0, 5, 6, 0, 9, 28, 5, 11, 0, 6, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0,
-      5, 0, 5, 0, 5, 0, 8, 6, 8, 0, 8, 0, 8, 6, 0, 5, 0, 8, 0, 9, 11, 28, 26,
-      28, 0, 8, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 6, 8, 0, 6, 0, 6, 0, 6, 0,
-      5, 0, 5, 6, 0, 9, 0, 11, 28, 0, 8, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 6, 5,
-      8, 6, 8, 0, 6, 8, 0, 8, 6, 0, 8, 0, 5, 0, 5, 6, 0, 9, 0, 5, 0, 8, 0, 5,
-      0, 5, 0, 5, 0, 5, 8, 6, 0, 8, 0, 8, 6, 5, 0, 8, 0, 5, 6, 0, 9, 11, 0, 28,
-      5, 0, 8, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 6, 0, 8, 6, 0, 6, 0, 8, 0, 8,
-      24, 0, 5, 6, 5, 6, 0, 26, 5, 4, 6, 24, 9, 24, 0, 5, 0, 5, 0, 5, 0, 5, 0,
-      5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 6, 5, 6, 0, 6, 5, 0, 5, 0,
-      4, 0, 6, 0, 9, 0, 5, 0, 5, 28, 24, 28, 24, 28, 6, 28, 9, 11, 28, 6, 28,
-      6, 28, 6, 21, 22, 21, 22, 8, 5, 0, 5, 0, 6, 8, 6, 24, 6, 5, 6, 0, 6, 0,
-      28, 6, 28, 0, 28, 24, 28, 24, 0, 5, 8, 6, 8, 6, 8, 6, 8, 6, 5, 9, 24, 5,
-      8, 6, 5, 6, 5, 8, 5, 8, 5, 6, 5, 6, 8, 6, 8, 6, 5, 8, 9, 8, 6, 28, 1, 0,
-      1, 0, 1, 0, 5, 24, 4, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5,
-      0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 6, 24, 11, 0, 5, 28, 0, 5,
-      0, 20, 5, 24, 5, 12, 5, 21, 22, 0, 5, 24, 10, 0, 5, 0, 5, 6, 0, 5, 6, 24,
+      4, 2, 24, 1, 0, 27, 1, 24, 1, 0, 1, 0, 1, 2, 1, 0, 1, 2, 1, 2, 1, 2, 1,
+      2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1,
+      2, 25, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2,
+      1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 28, 6, 7, 1, 2, 1,
+      2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1,
+      2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1,
+      2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1,
+      2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1,
+      2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1,
+      2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1,
+      2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 0, 1, 0, 4, 24, 2, 24,
+      20, 0, 28, 26, 0, 6, 20, 6, 24, 6, 24, 6, 24, 6, 0, 5, 0, 5, 24, 0, 16,
+      25, 24, 26, 24, 28, 6, 24, 16, 24, 5, 4, 5, 6, 9, 24, 5, 6, 5, 24, 5, 6,
+      16, 28, 6, 4, 6, 28, 6, 5, 9, 5, 28, 5, 24, 0, 16, 5, 6, 5, 6, 0, 5, 6,
+      5, 0, 9, 5, 6, 4, 28, 24, 4, 0, 6, 26, 5, 6, 4, 6, 4, 6, 4, 6, 0, 24, 0,
+      5, 6, 0, 24, 0, 5, 0, 5, 27, 5, 0, 16, 0, 6, 5, 4, 6, 16, 6, 8, 5, 6, 8,
+      6, 5, 8, 6, 8, 6, 8, 5, 6, 5, 6, 24, 9, 24, 4, 5, 6, 8, 0, 5, 0, 5, 0, 5,
+      0, 5, 0, 5, 0, 5, 0, 6, 5, 8, 6, 0, 8, 0, 8, 6, 5, 0, 8, 0, 5, 0, 5, 6,
+      0, 9, 5, 26, 11, 28, 26, 5, 24, 6, 0, 6, 8, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5,
+      0, 5, 0, 5, 0, 6, 0, 8, 6, 0, 6, 0, 6, 0, 6, 0, 5, 0, 5, 0, 9, 6, 5, 6,
+      24, 0, 6, 8, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 6, 5, 8, 6, 0, 6, 8,
+      0, 8, 6, 0, 5, 0, 5, 6, 0, 9, 24, 26, 0, 5, 6, 0, 6, 8, 0, 5, 0, 5, 0, 5,
+      0, 5, 0, 5, 0, 5, 0, 6, 5, 8, 6, 8, 6, 0, 8, 0, 8, 6, 0, 6, 8, 0, 5, 0,
+      5, 6, 0, 9, 28, 5, 11, 0, 6, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5,
+      0, 5, 0, 5, 0, 8, 6, 8, 0, 8, 0, 8, 6, 0, 5, 0, 8, 0, 9, 11, 28, 26, 28,
+      0, 6, 8, 6, 5, 0, 5, 0, 5, 0, 5, 0, 6, 5, 6, 8, 0, 6, 0, 6, 0, 6, 0, 5,
+      0, 5, 0, 5, 6, 0, 9, 0, 24, 11, 28, 5, 6, 8, 24, 5, 0, 5, 0, 5, 0, 5, 0,
+      5, 0, 6, 5, 8, 6, 8, 0, 6, 8, 0, 8, 6, 0, 8, 0, 5, 0, 5, 6, 0, 9, 0, 5,
+      8, 0, 6, 8, 5, 0, 5, 0, 5, 6, 5, 8, 6, 0, 8, 0, 8, 6, 5, 28, 0, 5, 8, 11,
+      5, 6, 0, 9, 11, 28, 5, 0, 6, 8, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 6, 0, 8,
+      6, 0, 6, 0, 8, 0, 9, 0, 8, 24, 0, 5, 6, 5, 6, 0, 26, 5, 4, 6, 24, 9, 24,
+      0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 6, 5, 6, 5, 0, 5, 0, 4, 0, 6, 0, 9,
+      0, 5, 0, 5, 28, 24, 28, 24, 28, 6, 28, 9, 11, 28, 6, 28, 6, 28, 6, 21,
+      22, 21, 22, 8, 5, 0, 5, 0, 6, 8, 6, 24, 6, 5, 6, 0, 6, 0, 28, 6, 28, 0,
+      28, 24, 28, 24, 0, 5, 8, 6, 8, 6, 8, 6, 8, 6, 5, 9, 24, 5, 8, 6, 5, 6, 5,
+      8, 5, 8, 5, 6, 5, 6, 8, 6, 8, 6, 5, 8, 9, 8, 6, 28, 1, 0, 1, 0, 1, 0, 2,
+      24, 4, 2, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5,
+      0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 6, 24, 11, 0, 5, 28, 0, 1, 0, 2, 0, 20,
+      5, 28, 24, 5, 12, 5, 21, 22, 0, 5, 24, 10, 5, 0, 5, 6, 8, 0, 5, 6, 8, 24,
       0, 5, 6, 0, 5, 0, 5, 0, 6, 0, 5, 6, 8, 6, 8, 6, 8, 6, 24, 4, 24, 26, 5,
-      6, 0, 9, 0, 11, 0, 24, 20, 24, 6, 12, 0, 9, 0, 5, 4, 5, 0, 5, 6, 5, 0, 5,
-      0, 5, 0, 6, 8, 6, 8, 0, 8, 6, 8, 6, 0, 28, 0, 24, 9, 5, 0, 5, 0, 5, 0, 8,
-      5, 8, 0, 9, 11, 0, 28, 5, 6, 8, 0, 24, 5, 8, 6, 8, 6, 0, 6, 8, 6, 8, 6,
-      8, 6, 0, 6, 9, 0, 9, 0, 24, 4, 24, 0, 6, 8, 5, 6, 8, 6, 8, 6, 8, 6, 8, 5,
-      0, 9, 24, 28, 6, 28, 0, 6, 8, 5, 8, 6, 8, 6, 8, 6, 8, 5, 9, 5, 6, 8, 6,
-      8, 6, 8, 6, 8, 0, 24, 5, 8, 6, 8, 6, 0, 24, 9, 0, 5, 9, 5, 4, 24, 0, 24,
-      0, 6, 24, 6, 8, 6, 5, 6, 5, 8, 6, 5, 0, 2, 4, 2, 4, 2, 4, 6, 0, 6, 1, 2,
-      1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2,
-      1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2,
-      1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2,
-      1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2,
-      1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2,
-      1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2,
-      1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2,
-      1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2,
-      1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2,
-      1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2,
-      1, 2, 1, 2, 1, 2, 1, 2, 0, 1, 0, 2, 1, 2, 1, 2, 0, 1, 0, 2, 0, 1, 0, 1,
-      0, 1, 0, 1, 2, 1, 2, 0, 2, 3, 2, 3, 2, 3, 2, 0, 2, 1, 3, 27, 2, 27, 2, 0,
-      2, 1, 3, 27, 2, 0, 2, 1, 0, 27, 2, 1, 27, 0, 2, 0, 2, 1, 3, 27, 0, 12,
-      16, 20, 24, 29, 30, 21, 29, 30, 21, 29, 24, 13, 14, 16, 12, 24, 29, 30,
-      24, 23, 24, 25, 21, 22, 24, 25, 24, 23, 24, 12, 16, 0, 16, 11, 4, 0, 11,
-      25, 21, 22, 4, 11, 25, 21, 22, 0, 4, 0, 26, 0, 6, 7, 6, 7, 6, 0, 28, 1,
-      28, 1, 28, 2, 1, 2, 1, 2, 28, 1, 28, 25, 1, 28, 1, 28, 1, 28, 1, 28, 1,
-      28, 2, 1, 2, 5, 2, 28, 2, 1, 25, 1, 2, 28, 25, 28, 2, 28, 11, 10, 1, 2,
-      10, 11, 0, 25, 28, 25, 28, 25, 28, 25, 28, 25, 28, 25, 28, 25, 28, 25,
-      28, 25, 28, 25, 28, 25, 28, 25, 28, 21, 22, 28, 25, 28, 25, 28, 25, 28,
-      0, 28, 0, 28, 0, 11, 28, 11, 28, 25, 28, 25, 28, 25, 28, 25, 28, 0, 28,
-      21, 22, 21, 22, 21, 22, 21, 22, 21, 22, 21, 22, 21, 22, 11, 28, 25, 21,
-      22, 25, 21, 22, 21, 22, 21, 22, 21, 22, 21, 22, 25, 28, 25, 21, 22, 21,
-      22, 21, 22, 21, 22, 21, 22, 21, 22, 21, 22, 21, 22, 21, 22, 21, 22, 21,
-      22, 25, 21, 22, 21, 22, 25, 21, 22, 25, 28, 25, 28, 25, 0, 28, 0, 1, 0,
-      2, 0, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 4, 1, 2, 1, 2, 1,
+      6, 0, 9, 0, 11, 0, 24, 20, 24, 6, 16, 6, 9, 0, 5, 4, 5, 0, 5, 6, 5, 6, 5,
+      0, 5, 0, 5, 0, 6, 8, 6, 8, 0, 8, 6, 8, 6, 0, 28, 0, 24, 9, 5, 0, 5, 0, 5,
+      0, 5, 0, 9, 11, 0, 28, 5, 6, 8, 6, 0, 24, 5, 8, 6, 8, 6, 0, 6, 8, 6, 8,
+      6, 8, 6, 0, 6, 9, 0, 9, 0, 24, 4, 24, 0, 6, 7, 6, 0, 6, 8, 5, 6, 8, 6, 8,
+      6, 8, 6, 8, 5, 0, 9, 24, 28, 6, 28, 24, 0, 6, 8, 5, 8, 6, 8, 6, 8, 6, 5,
+      9, 5, 6, 8, 6, 8, 6, 8, 6, 8, 0, 24, 5, 8, 6, 8, 6, 0, 24, 9, 0, 5, 9, 5,
+      4, 24, 2, 0, 1, 0, 1, 24, 0, 6, 24, 6, 8, 6, 5, 6, 5, 6, 5, 8, 6, 5, 0,
+      2, 4, 2, 4, 2, 4, 6, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1,
       2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1,
       2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1,
       2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1,
-      2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 28,
-      1, 2, 1, 2, 6, 1, 2, 0, 24, 11, 24, 2, 0, 2, 0, 2, 0, 5, 0, 4, 24, 0, 6,
-      5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 6, 24, 29, 30, 29,
-      30, 24, 29, 30, 24, 29, 30, 24, 20, 24, 20, 24, 29, 30, 24, 29, 30, 21,
-      22, 21, 22, 21, 22, 21, 22, 24, 4, 24, 20, 0, 28, 0, 28, 0, 28, 0, 28, 0,
-      12, 24, 28, 4, 5, 10, 21, 22, 21, 22, 21, 22, 21, 22, 21, 22, 28, 21, 22,
-      21, 22, 21, 22, 21, 22, 20, 21, 22, 28, 10, 6, 8, 20, 4, 28, 10, 4, 5,
-      24, 28, 0, 5, 0, 6, 27, 4, 5, 20, 5, 24, 4, 5, 0, 5, 0, 5, 0, 28, 11, 28,
-      5, 0, 28, 0, 5, 28, 0, 11, 28, 11, 28, 11, 28, 11, 28, 11, 28, 5, 0, 28,
-      5, 0, 5, 4, 5, 0, 28, 0, 5, 4, 24, 5, 4, 24, 5, 9, 5, 0, 1, 2, 1, 2, 1,
       2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1,
-      2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 5, 6, 7, 24, 6, 24, 4,
-      1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2,
-      0, 6, 5, 10, 6, 24, 0, 27, 4, 27, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1,
       2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1,
       2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1,
-      2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 4, 2, 1, 2, 1, 2, 1, 2, 1,
-      2, 1, 2, 1, 2, 1, 2, 4, 27, 1, 2, 1, 2, 0, 1, 2, 1, 2, 0, 1, 2, 1, 2, 1,
-      2, 1, 2, 1, 2, 1, 0, 4, 2, 5, 6, 5, 6, 5, 6, 5, 8, 6, 8, 28, 0, 11, 28,
-      26, 28, 0, 5, 24, 0, 8, 5, 8, 6, 0, 24, 9, 0, 6, 5, 24, 5, 0, 9, 5, 6,
-      24, 5, 6, 8, 0, 24, 5, 0, 6, 8, 5, 6, 8, 6, 8, 6, 8, 24, 0, 4, 9, 0, 24,
-      0, 5, 6, 8, 6, 8, 6, 0, 5, 6, 5, 6, 8, 0, 9, 0, 24, 5, 4, 5, 28, 5, 8, 0,
-      5, 6, 5, 6, 5, 6, 5, 6, 5, 6, 5, 0, 5, 4, 24, 5, 8, 6, 8, 24, 5, 4, 8, 6,
-      0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 8, 6, 8, 6, 8, 24, 8, 6, 0, 9, 0, 5,
-      0, 5, 0, 5, 0, 19, 18, 5, 0, 5, 0, 2, 0, 2, 0, 5, 6, 5, 25, 5, 0, 5, 0,
-      5, 0, 5, 0, 5, 0, 5, 27, 0, 5, 21, 22, 0, 5, 0, 5, 0, 5, 26, 28, 0, 6,
-      24, 21, 22, 24, 0, 6, 0, 24, 20, 23, 21, 22, 21, 22, 21, 22, 21, 22, 21,
-      22, 21, 22, 21, 22, 21, 22, 24, 21, 22, 24, 23, 24, 0, 24, 20, 21, 22,
-      21, 22, 21, 22, 24, 25, 20, 25, 0, 24, 26, 24, 0, 5, 0, 5, 0, 16, 0, 24,
-      26, 24, 21, 22, 24, 25, 24, 20, 24, 9, 24, 25, 24, 1, 21, 24, 22, 27, 23,
-      27, 2, 21, 25, 22, 25, 21, 22, 24, 21, 22, 24, 5, 4, 5, 4, 5, 0, 5, 0, 5,
-      0, 5, 0, 5, 0, 26, 25, 27, 28, 26, 0, 28, 25, 28, 0, 16, 28, 0, 5, 0, 5,
-      0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 24, 0, 11, 0, 28, 10, 11, 28, 11, 0, 28,
-      0, 28, 6, 0, 5, 0, 5, 0, 5, 0, 11, 0, 5, 10, 5, 10, 0, 5, 0, 24, 5, 0, 5,
-      24, 10, 0, 1, 2, 5, 0, 9, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 24, 11,
-      0, 5, 11, 0, 24, 5, 0, 24, 0, 5, 0, 5, 0, 5, 6, 0, 6, 0, 6, 5, 0, 5, 0,
-      5, 0, 6, 0, 6, 11, 0, 24, 0, 5, 11, 24, 0, 5, 0, 24, 5, 0, 11, 5, 0, 11,
-      0, 5, 0, 11, 0, 8, 6, 8, 5, 6, 24, 0, 11, 9, 0, 6, 8, 5, 8, 6, 8, 6, 24,
-      16, 24, 0, 5, 0, 9, 0, 6, 5, 6, 8, 6, 0, 9, 24, 0, 6, 8, 5, 8, 6, 8, 5,
-      24, 0, 9, 0, 5, 6, 8, 6, 8, 6, 8, 6, 0, 9, 0, 5, 0, 10, 0, 24, 0, 5, 0,
-      5, 0, 5, 0, 5, 8, 0, 6, 4, 0, 5, 0, 28, 0, 28, 0, 28, 8, 6, 28, 8, 16, 6,
-      28, 6, 28, 6, 28, 0, 28, 6, 28, 0, 28, 0, 11, 0, 1, 2, 1, 2, 0, 2, 1, 2,
-      1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 2, 0, 2, 0, 2, 0, 2, 1, 2, 1, 0, 1, 0,
-      1, 0, 1, 0, 2, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 2, 1, 2, 1, 2, 1, 2, 1, 2,
-      1, 2, 1, 2, 0, 1, 25, 2, 25, 2, 1, 25, 2, 25, 2, 1, 25, 2, 25, 2, 1, 25,
-      2, 25, 2, 1, 25, 2, 25, 2, 1, 2, 0, 9, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0,
-      5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0,
-      5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0,
-      5, 0, 5, 0, 5, 0, 5, 0, 25, 0, 28, 0, 28, 0, 28, 0, 28, 0, 28, 0, 28, 0,
-      11, 0, 28, 0, 28, 0, 28, 0, 28, 0, 28, 0, 28, 0, 28, 0, 28, 0, 28, 0, 28,
-      0, 28, 0, 28, 0, 28, 0, 28, 0, 28, 0, 28, 0, 28, 0, 28, 0, 28, 0, 28, 0,
-      28, 0, 28, 0, 28, 0, 28, 0, 28, 0, 5, 0, 5, 0, 5, 0, 5, 0, 16, 0, 16, 0,
-      6, 0, 18, 0, 18, 0
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+      2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1,
+      2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1,
+      2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 0, 1, 0, 2, 1, 2, 1,
+      2, 0, 1, 0, 2, 0, 1, 0, 1, 0, 1, 0, 1, 2, 1, 2, 0, 2, 3, 2, 3, 2, 3, 2,
+      0, 2, 1, 3, 27, 2, 27, 2, 0, 2, 1, 3, 27, 2, 0, 2, 1, 0, 27, 2, 1, 27, 0,
+      2, 0, 2, 1, 3, 27, 0, 12, 16, 20, 24, 29, 30, 21, 29, 30, 21, 29, 24, 13,
+      14, 16, 12, 24, 29, 30, 24, 23, 24, 25, 21, 22, 24, 25, 24, 23, 24, 12,
+      16, 0, 16, 11, 4, 0, 11, 25, 21, 22, 4, 11, 25, 21, 22, 0, 4, 0, 26, 0,
+      6, 7, 6, 7, 6, 0, 28, 1, 28, 1, 28, 2, 1, 2, 1, 2, 28, 1, 28, 25, 1, 28,
+      1, 28, 1, 28, 1, 28, 1, 28, 2, 1, 2, 5, 2, 28, 2, 1, 25, 1, 2, 28, 25,
+      28, 2, 28, 11, 10, 1, 2, 10, 11, 28, 0, 25, 28, 25, 28, 25, 28, 25, 28,
+      25, 28, 25, 28, 25, 28, 25, 28, 25, 28, 25, 28, 21, 22, 21, 22, 28, 25,
+      28, 21, 22, 28, 25, 28, 25, 28, 25, 28, 0, 28, 0, 11, 28, 11, 28, 25, 28,
+      25, 28, 25, 28, 25, 28, 21, 22, 21, 22, 21, 22, 21, 22, 21, 22, 21, 22,
+      21, 22, 11, 28, 25, 21, 22, 25, 21, 22, 21, 22, 21, 22, 21, 22, 21, 22,
+      25, 28, 25, 21, 22, 21, 22, 21, 22, 21, 22, 21, 22, 21, 22, 21, 22, 21,
+      22, 21, 22, 21, 22, 21, 22, 25, 21, 22, 21, 22, 25, 21, 22, 25, 28, 25,
+      28, 25, 28, 0, 28, 0, 28, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2,
+      1, 2, 4, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1,
+      2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1,
+      2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1,
+      2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1,
+      2, 1, 2, 1, 2, 1, 2, 28, 1, 2, 1, 2, 6, 1, 2, 0, 24, 11, 24, 2, 0, 2, 0,
+      2, 0, 5, 0, 4, 24, 0, 6, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0,
+      5, 0, 6, 24, 29, 30, 29, 30, 24, 29, 30, 24, 29, 30, 24, 20, 24, 20, 24,
+      29, 30, 24, 29, 30, 21, 22, 21, 22, 21, 22, 21, 22, 24, 4, 24, 20, 24,
+      20, 24, 21, 24, 28, 24, 21, 22, 21, 22, 21, 22, 21, 22, 20, 0, 28, 0, 28,
+      0, 28, 0, 28, 0, 12, 24, 28, 4, 5, 10, 21, 22, 21, 22, 21, 22, 21, 22,
+      21, 22, 28, 21, 22, 21, 22, 21, 22, 21, 22, 20, 21, 22, 28, 10, 6, 8, 20,
+      4, 28, 10, 4, 5, 24, 28, 0, 5, 0, 6, 27, 4, 5, 20, 5, 24, 4, 5, 0, 5, 0,
+      5, 0, 28, 11, 28, 5, 28, 0, 5, 28, 0, 11, 28, 11, 28, 11, 28, 11, 28, 11,
+      28, 5, 28, 5, 4, 5, 0, 28, 0, 5, 4, 24, 5, 4, 24, 5, 9, 5, 0, 1, 2, 1, 2,
+      1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2,
+      1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 5, 6, 7, 24, 6, 24,
+      4, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1,
+      2, 1, 2, 1, 2, 4, 6, 5, 10, 6, 24, 0, 27, 4, 27, 1, 2, 1, 2, 1, 2, 1, 2,
+      1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2,
+      1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2,
+      1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 4, 2, 1, 2,
+      1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 4, 27, 1, 2, 1, 2, 5, 1, 2, 1, 2, 1,
+      2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1,
+      2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 0, 1, 2, 0, 2, 0, 2,
+      1, 2, 1, 2, 0, 4, 1, 2, 5, 4, 2, 5, 6, 5, 6, 5, 6, 5, 8, 6, 8, 28, 6, 0,
+      11, 28, 26, 28, 0, 5, 24, 0, 8, 5, 8, 6, 0, 24, 9, 0, 6, 5, 24, 5, 24, 5,
+      6, 9, 5, 6, 24, 5, 6, 8, 0, 24, 5, 0, 6, 8, 5, 6, 8, 6, 8, 6, 8, 24, 0,
+      4, 9, 0, 24, 5, 6, 4, 5, 9, 5, 0, 5, 6, 8, 6, 8, 6, 0, 5, 6, 5, 6, 8, 0,
+      9, 0, 24, 5, 4, 5, 28, 5, 8, 6, 8, 5, 6, 5, 6, 5, 6, 5, 6, 5, 6, 5, 0, 5,
+      4, 24, 5, 8, 6, 8, 24, 5, 4, 8, 6, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 2,
+      27, 4, 2, 4, 27, 0, 2, 5, 8, 6, 8, 6, 8, 24, 8, 6, 0, 9, 0, 5, 0, 5, 0,
+      5, 0, 19, 18, 5, 0, 5, 0, 2, 0, 2, 0, 5, 6, 5, 25, 5, 0, 5, 0, 5, 0, 5,
+      0, 5, 0, 5, 27, 0, 5, 22, 21, 28, 5, 0, 5, 0, 28, 0, 5, 26, 28, 6, 24,
+      21, 22, 24, 0, 6, 24, 20, 23, 21, 22, 21, 22, 21, 22, 21, 22, 21, 22, 21,
+      22, 21, 22, 21, 22, 24, 21, 22, 24, 23, 24, 0, 24, 20, 21, 22, 21, 22,
+      21, 22, 24, 25, 20, 25, 0, 24, 26, 24, 0, 5, 0, 5, 0, 16, 0, 24, 26, 24,
+      21, 22, 24, 25, 24, 20, 24, 9, 24, 25, 24, 1, 21, 24, 22, 27, 23, 27, 2,
+      21, 25, 22, 25, 21, 22, 24, 21, 22, 24, 5, 4, 5, 4, 5, 0, 5, 0, 5, 0, 5,
+      0, 5, 0, 26, 25, 27, 28, 26, 0, 28, 25, 28, 0, 16, 28, 0, 5, 0, 5, 0, 5,
+      0, 5, 0, 5, 0, 5, 0, 5, 0, 24, 0, 11, 0, 28, 10, 11, 28, 11, 28, 0, 28,
+      0, 28, 0, 28, 6, 0, 5, 0, 5, 0, 6, 11, 0, 5, 11, 0, 5, 10, 5, 10, 0, 5,
+      6, 0, 5, 0, 24, 5, 0, 5, 24, 10, 0, 1, 2, 5, 0, 9, 0, 1, 0, 2, 0, 5, 0,
+      5, 0, 24, 1, 0, 1, 0, 1, 0, 1, 0, 2, 0, 2, 0, 2, 0, 2, 0, 5, 0, 5, 0, 5,
+      0, 4, 0, 4, 0, 4, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 24, 11, 5, 28,
+      11, 5, 0, 11, 0, 5, 0, 5, 0, 11, 5, 11, 0, 24, 5, 0, 24, 0, 5, 0, 11, 5,
+      11, 0, 11, 5, 6, 0, 6, 0, 6, 5, 0, 5, 0, 5, 0, 6, 0, 6, 11, 0, 24, 0, 5,
+      11, 24, 5, 11, 0, 5, 28, 5, 6, 0, 11, 24, 0, 5, 0, 24, 5, 0, 11, 5, 0,
+      11, 5, 0, 24, 0, 11, 0, 5, 0, 1, 0, 2, 0, 11, 5, 6, 0, 9, 0, 11, 0, 5, 0,
+      6, 20, 0, 5, 0, 6, 5, 11, 5, 0, 5, 6, 11, 24, 0, 5, 6, 24, 0, 5, 11, 0,
+      5, 0, 8, 6, 8, 5, 6, 24, 0, 11, 9, 6, 5, 6, 5, 0, 6, 8, 5, 8, 6, 8, 6,
+      24, 16, 24, 6, 0, 16, 0, 5, 0, 9, 0, 6, 5, 6, 8, 6, 0, 9, 24, 5, 8, 5, 0,
+      5, 6, 24, 5, 0, 6, 8, 5, 8, 6, 8, 5, 24, 6, 24, 8, 6, 9, 5, 24, 5, 24, 0,
+      11, 0, 5, 0, 5, 8, 6, 8, 6, 8, 6, 24, 6, 5, 6, 0, 5, 0, 5, 0, 5, 0, 5, 0,
+      5, 24, 0, 5, 6, 8, 6, 0, 9, 0, 6, 8, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5,
+      0, 6, 5, 8, 6, 8, 0, 8, 0, 8, 0, 5, 0, 8, 0, 5, 8, 0, 6, 0, 6, 0, 5, 8,
+      6, 8, 6, 8, 6, 5, 24, 9, 24, 0, 24, 6, 5, 0, 5, 8, 6, 8, 6, 8, 6, 8, 6,
+      5, 24, 5, 0, 9, 0, 5, 8, 6, 0, 8, 6, 8, 6, 24, 5, 6, 0, 5, 8, 6, 8, 6, 8,
+      6, 24, 5, 0, 9, 0, 24, 0, 5, 6, 8, 6, 8, 6, 8, 6, 5, 24, 0, 9, 0, 5, 0,
+      6, 8, 6, 8, 6, 0, 9, 11, 24, 28, 5, 0, 5, 8, 6, 8, 6, 24, 0, 1, 2, 9, 11,
+      0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 8, 0, 8, 0, 6, 8, 6, 5, 8, 5, 8, 6, 24, 0,
+      9, 0, 5, 0, 5, 8, 6, 0, 6, 8, 6, 5, 24, 5, 8, 0, 5, 6, 5, 6, 8, 5, 6, 24,
+      6, 0, 5, 6, 8, 6, 5, 6, 8, 6, 24, 5, 24, 0, 5, 0, 24, 0, 5, 0, 5, 8, 6,
+      0, 6, 8, 6, 5, 24, 0, 9, 11, 0, 24, 5, 0, 6, 0, 8, 6, 8, 6, 8, 6, 0, 5,
+      0, 5, 0, 5, 6, 0, 6, 0, 6, 0, 6, 5, 6, 0, 9, 0, 5, 0, 5, 0, 5, 8, 0, 6,
+      0, 8, 6, 8, 6, 5, 0, 9, 0, 5, 6, 8, 24, 0, 6, 5, 8, 5, 0, 5, 8, 6, 0, 8,
+      6, 8, 6, 24, 9, 0, 5, 0, 11, 28, 26, 28, 0, 24, 5, 0, 10, 0, 24, 0, 5, 0,
+      5, 24, 0, 5, 16, 6, 5, 6, 0, 5, 0, 5, 0, 5, 0, 9, 0, 24, 5, 0, 9, 0, 5,
+      0, 6, 24, 0, 5, 6, 24, 28, 4, 24, 28, 0, 9, 0, 11, 0, 5, 0, 5, 0, 1, 2,
+      11, 24, 0, 5, 0, 6, 5, 8, 0, 6, 4, 0, 4, 24, 4, 6, 0, 8, 0, 5, 0, 5, 0,
+      5, 0, 4, 0, 4, 0, 4, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0,
+      5, 0, 5, 0, 28, 6, 24, 16, 0, 6, 0, 6, 0, 28, 0, 28, 0, 28, 0, 28, 8, 6,
+      28, 8, 16, 6, 28, 6, 28, 6, 28, 0, 28, 6, 28, 0, 11, 0, 11, 0, 28, 0, 11,
+      0, 1, 2, 1, 2, 0, 2, 1, 2, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 2, 0, 2, 0,
+      2, 0, 2, 1, 2, 1, 0, 1, 0, 1, 0, 1, 0, 2, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0,
+      2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 0, 1, 25, 2, 25, 2, 1, 25, 2, 25,
+      2, 1, 25, 2, 25, 2, 1, 25, 2, 25, 2, 1, 25, 2, 25, 2, 1, 2, 0, 9, 28, 6,
+      28, 6, 28, 6, 28, 6, 28, 24, 0, 6, 0, 6, 0, 2, 5, 2, 0, 2, 0, 6, 0, 6, 0,
+      6, 0, 6, 0, 6, 0, 4, 0, 6, 0, 5, 0, 6, 4, 0, 9, 0, 5, 28, 0, 5, 6, 0, 5,
+      6, 9, 0, 26, 0, 5, 4, 6, 9, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 11, 6, 0, 1,
+      2, 6, 4, 0, 9, 0, 24, 0, 11, 28, 11, 26, 11, 0, 11, 28, 11, 0, 5, 0, 5,
+      0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5,
+      0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5,
+      0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 25, 0, 28, 0, 28, 0, 28, 0,
+      28, 0, 28, 0, 28, 0, 11, 28, 0, 28, 0, 28, 0, 28, 0, 28, 0, 28, 0, 28,
+      27, 28, 0, 28, 0, 28, 0, 28, 0, 28, 0, 28, 0, 28, 0, 28, 0, 28, 0, 28, 0,
+      28, 0, 28, 0, 28, 0, 28, 0, 28, 0, 28, 0, 28, 0, 28, 0, 28, 0, 28, 0, 28,
+      0, 28, 0, 28, 0, 28, 0, 9, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0, 5, 0,
+      5, 0, 16, 0, 16, 0, 6, 0, 18, 0, 18, 0
   )
 
   /* Indices representing the start of ranges of codePoint that have the same
@@ -1401,12 +1628,12 @@ println("    )")
         2, 3, 4, 1, 4, 1, 1, 1, 1, 4, 9, 5, 1, 1, 18, 5, 4, 9, 2, 1, 1, 1, 8,
         2, 31, 2, 4, 5, 1, 9, 2, 2, 19, 5, 2, 9, 5, 2, 2, 4, 24, 2, 16, 8, 4,
         20, 2, 7, 2, 1085, 14, 74, 1, 2, 4, 1, 2, 1, 3, 5, 4, 5, 3, 3, 14, 403,
-        22, 2, 21, 8, 1, 7, 6, 3, 1, 4, 5, 1, 2, 2, 5, 4, 1, 1, 3, 2, 2, 10, 6,
-        2, 2, 12, 19, 1, 4, 2, 1, 1, 1, 2, 1, 1, 4, 5, 2, 6, 3, 24, 2, 11, 2,
-        4, 4, 1, 2, 2, 2, 4, 43, 2, 8, 1, 40, 5, 1, 1, 1, 3, 5, 5, 3, 4, 1, 3,
-        5, 1, 1, 772, 4, 3, 2, 1, 2, 14, 2, 2, 10, 478, 10, 2, 8, 52797, 6, 5,
-        2, 162, 2, 18, 1, 1, 1, 28, 1, 1, 1, 29, 1, 1, 1, 1, 2, 1, 2, 55159, 1,
-        57, 1, 57, 1, 57, 1, 57, 1
+        22, 2, 6, 1, 14, 8, 1, 7, 6, 3, 1, 4, 5, 1, 2, 2, 5, 4, 1, 1, 3, 2, 2,
+        10, 6, 2, 2, 12, 19, 1, 4, 2, 1, 1, 1, 2, 1, 1, 4, 5, 2, 6, 3, 24, 2,
+        11, 2, 4, 4, 1, 2, 2, 2, 4, 43, 2, 8, 1, 40, 5, 1, 1, 1, 3, 5, 5, 3, 4,
+        1, 3, 5, 1, 1, 256, 1, 515, 4, 3, 2, 1, 2, 14, 2, 2, 10, 43, 8, 427,
+        10, 2, 8, 52797, 6, 5, 2, 162, 2, 18, 1, 1, 1, 28, 1, 1, 1, 29, 1, 1,
+        1, 1, 2, 1, 2, 55159, 1, 57, 1, 57, 1, 57, 1, 57, 1
     )
     uncompressDeltas(deltas)
   }
@@ -1479,34 +1706,36 @@ println("    )")
         2, 2, 0, 5, 1, 0, 2, 1, 16, 0, 1, 101, 7, 0, 2, 4, 1, 0, 1, 0, 2, 2, 0,
         1, 0, 1, 0, 2, 1, 35, 0, 1, 30, 1, 1, 0, 2, 1, 0, 2, 3, 0, 1, 2, 0, 1,
         1, 0, 3, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 2, 0, 160, 7, 1, 0, 1, 0, 9,
-        0, 1, 24, 4, 0, 1, 9, 0, 1, 3, 0, 1, 5, 0, 43, 0, 3, 119, 0, 1, 0, 14,
-        0, 1, 0, 1, 0, 2, 1, 0, 2, 1, 0, 3, 6, 0, 3, 1, 0, 2, 2, 0, 5, 0, 60,
-        0, 1, 16, 0, 1, 3, 1, 1, 0, 2, 0, 103, 0, 1, 16, 0, 1, 48, 1, 0, 61, 0,
-        1, 16, 0, 1, 110, 0, 1, 16, 0, 1, 110, 0, 1, 16, 0, 1, 127, 0, 1, 127,
-        0, 1, 7, 0, 2, 101, 0, 1, 16, 0, 1, 109, 0, 2, 16, 0, 1, 124, 0, 1,
-        109, 0, 3, 13, 0, 4, 108, 0, 3, 13, 0, 4, 76, 0, 2, 27, 0, 1, 1, 0, 1,
-        1, 0, 1, 55, 0, 2, 1, 0, 1, 5, 0, 4, 2, 0, 1, 1, 2, 1, 1, 2, 0, 62, 0,
-        1, 112, 0, 1, 1, 0, 2, 82, 0, 1, 719, 3, 0, 948, 0, 1, 31, 0, 1, 157,
-        0, 1, 10, 1, 0, 203, 0, 1, 143, 0, 1, 0, 1, 1, 219, 1, 1, 71, 0, 1, 20,
-        8, 0, 2, 0, 1, 48, 5, 6, 0, 2, 1, 1, 0, 2, 115, 0, 1, 15, 0, 1, 38, 1,
-        1, 0, 7, 0, 54, 0, 2, 58, 0, 1, 11, 0, 2, 67, 0, 1, 152, 3, 0, 1, 0, 6,
-        0, 2, 4, 0, 1, 0, 1, 0, 7, 4, 0, 1, 6, 1, 0, 3, 2, 0, 198, 2, 1, 0, 7,
-        1, 0, 2, 4, 0, 37, 4, 1, 1, 2, 0, 1, 1, 720, 2, 2, 0, 4, 3, 0, 2, 0, 4,
-        1, 0, 3, 0, 2, 0, 1, 1, 0, 1, 6, 0, 1, 0, 3070, 3, 0, 141, 0, 1, 96,
-        32, 0, 554, 0, 6, 105, 0, 2, 30164, 1, 0, 4, 10, 0, 32, 2, 0, 80, 2, 0,
-        276, 0, 1, 37, 0, 1, 151, 0, 1, 27, 18, 0, 57, 0, 3, 37, 0, 1, 95, 0,
-        1, 12, 0, 1, 239, 1, 0, 1, 2, 1, 2, 2, 0, 5, 2, 0, 1, 1, 0, 52, 0, 1,
-        246, 0, 1, 20272, 0, 1, 769, 7, 7, 0, 2, 0, 973, 0, 1, 226, 0, 1, 149,
-        5, 0, 1682, 0, 1, 1, 1, 0, 40, 1, 2, 4, 0, 1, 165, 1, 1, 573, 4, 0,
-        387, 2, 0, 153, 0, 2, 0, 3, 1, 0, 1, 4, 245, 0, 1, 56, 0, 1, 57, 0, 2,
-        69, 3, 0, 48, 0, 2, 62, 0, 1, 76, 0, 1, 9, 0, 1, 106, 0, 2, 178, 0, 2,
-        80, 0, 2, 16, 0, 1, 24, 7, 0, 3, 5, 0, 205, 0, 1, 3, 0, 1, 23, 1, 0,
-        99, 0, 2, 251, 0, 2, 126, 0, 1, 118, 0, 2, 115, 0, 1, 269, 0, 2, 258,
-        0, 2, 4, 0, 1, 156, 0, 1, 83, 0, 1, 18, 0, 1, 81, 0, 1, 421, 0, 1, 258,
-        0, 1, 1, 0, 2, 81, 0, 1, 19800, 0, 5, 59, 7, 0, 1209, 0, 2, 19628, 0,
-        1, 5318, 0, 5, 3, 0, 6, 8, 0, 8, 2, 5, 2, 30, 4, 0, 148, 3, 0, 3515, 7,
-        0, 1, 17, 0, 2, 7, 0, 1, 2, 0, 1, 5, 0, 261, 7, 0, 437, 4, 0, 1504, 0,
-        7, 109, 6, 1
+        0, 1, 24, 4, 0, 1, 9, 0, 1, 3, 0, 1, 5, 0, 43, 0, 3, 59, 2, 3, 0, 4, 0,
+        42, 5, 5, 0, 14, 0, 1, 0, 1, 0, 2, 1, 0, 2, 1, 0, 3, 6, 0, 3, 1, 0, 2,
+        2, 0, 5, 0, 60, 0, 1, 16, 0, 1, 3, 1, 1, 0, 2, 0, 103, 0, 1, 16, 0, 1,
+        48, 1, 0, 61, 0, 1, 16, 0, 1, 110, 0, 1, 16, 0, 1, 110, 0, 1, 16, 0, 1,
+        127, 0, 1, 110, 0, 1, 16, 0, 1, 7, 0, 2, 101, 0, 1, 16, 0, 1, 109, 0,
+        2, 16, 0, 1, 124, 0, 1, 109, 0, 3, 13, 0, 4, 108, 0, 3, 13, 0, 4, 76,
+        0, 2, 27, 0, 1, 1, 0, 1, 1, 0, 1, 55, 0, 2, 1, 0, 1, 5, 0, 4, 2, 0, 1,
+        1, 2, 1, 1, 2, 0, 62, 0, 1, 112, 0, 1, 1, 0, 2, 82, 0, 1, 719, 3, 0,
+        948, 0, 2, 30, 0, 1, 157, 0, 1, 10, 1, 0, 203, 0, 1, 143, 0, 1, 0, 1,
+        1, 219, 1, 1, 71, 0, 1, 20, 8, 0, 2, 0, 1, 48, 5, 6, 0, 2, 1, 1, 0, 2,
+        0, 2, 2, 0, 5, 1, 0, 4, 0, 101, 0, 1, 15, 0, 1, 38, 1, 1, 0, 7, 0, 54,
+        0, 2, 58, 0, 1, 11, 0, 2, 67, 0, 1, 152, 3, 0, 1, 0, 6, 0, 2, 4, 0, 1,
+        0, 1, 0, 7, 4, 0, 1, 6, 1, 0, 3, 2, 0, 198, 2, 1, 0, 7, 1, 0, 2, 4, 0,
+        37, 5, 0, 1, 2, 0, 1, 1, 720, 2, 2, 0, 4, 3, 0, 2, 0, 4, 1, 0, 3, 0, 2,
+        0, 1, 1, 0, 1, 6, 0, 1, 0, 3070, 3, 0, 141, 0, 1, 96, 32, 0, 554, 0, 6,
+        105, 0, 2, 30164, 1, 0, 4, 10, 0, 32, 2, 0, 80, 2, 0, 276, 0, 1, 37, 0,
+        1, 151, 0, 1, 27, 18, 0, 57, 0, 3, 37, 0, 1, 95, 0, 1, 12, 0, 1, 239,
+        1, 0, 1, 2, 1, 2, 2, 0, 5, 2, 0, 1, 1, 0, 52, 0, 1, 246, 0, 1, 20272,
+        0, 1, 769, 7, 7, 0, 2, 0, 973, 0, 1, 226, 0, 1, 149, 5, 0, 1682, 0, 1,
+        1, 1, 0, 40, 1, 2, 4, 0, 1, 165, 1, 1, 573, 4, 0, 65, 5, 0, 317, 2, 0,
+        80, 0, 3, 70, 0, 2, 0, 3, 1, 0, 1, 4, 49, 1, 1, 0, 1, 1, 192, 0, 1, 41,
+        0, 1, 14, 0, 1, 57, 0, 2, 69, 3, 0, 48, 0, 2, 62, 0, 1, 76, 0, 1, 9, 0,
+        1, 106, 0, 2, 178, 0, 2, 80, 0, 2, 16, 0, 1, 24, 7, 0, 3, 5, 0, 89, 0,
+        3, 113, 0, 1, 3, 0, 1, 23, 1, 0, 99, 0, 2, 251, 0, 2, 126, 0, 1, 118,
+        0, 2, 115, 0, 1, 269, 0, 2, 258, 0, 2, 4, 0, 1, 156, 0, 1, 83, 0, 1,
+        18, 0, 1, 81, 0, 1, 421, 0, 1, 258, 0, 1, 1, 0, 2, 81, 0, 1, 425, 0, 2,
+        16876, 0, 1, 2496, 0, 5, 59, 7, 0, 1209, 0, 2, 19628, 0, 1, 5318, 0, 5,
+        3, 0, 6, 8, 0, 8, 2, 5, 2, 30, 4, 0, 148, 3, 0, 3515, 7, 0, 1, 17, 0,
+        2, 7, 0, 1, 2, 0, 1, 5, 0, 100, 1, 0, 160, 7, 0, 375, 1, 0, 61, 4, 0,
+        508, 0, 3, 0, 1, 0, 254, 1, 1, 736, 0, 7, 109, 6, 1
     )
     uncompressDeltas(deltas)
   }
@@ -1568,13 +1797,29 @@ println("    )")
    *  Each of them is directly followed by 9 other code points mapping to the
    *  digits 1 to 9, in order. Conversely, there are no other non-ASCII code
    *  point mapping to digits from 0 to 9.
+
+val zeroCodePointReprs = for {
+  cp <- 0x80 to Character.MAX_CODE_POINT
+  if Character.digit(cp, 10) == 0
+} yield {
+  String.format("0x%x", cp)
+}
+println("nonASCIIZeroDigitCodePoints:")
+println("    Array(")
+println(formatLargeArrayStr(zeroCodePointReprs.toArray, "        "))
+println("    )")
+
    */
   private[this] lazy val nonASCIIZeroDigitCodePoints: Array[Int] = {
-    Array(0x660, 0x6f0, 0x7c0, 0x966, 0x9e6, 0xa66, 0xae6, 0xb66, 0xbe6,
-        0xc66, 0xce6, 0xd66, 0xe50, 0xed0, 0xf20, 0x1040, 0x1090, 0x17e0,
+    Array(
+        0x660, 0x6f0, 0x7c0, 0x966, 0x9e6, 0xa66, 0xae6, 0xb66, 0xbe6, 0xc66,
+        0xce6, 0xd66, 0xde6, 0xe50, 0xed0, 0xf20, 0x1040, 0x1090, 0x17e0,
         0x1810, 0x1946, 0x19d0, 0x1a80, 0x1a90, 0x1b50, 0x1bb0, 0x1c40, 0x1c50,
-        0xa620, 0xa8d0, 0xa900, 0xa9d0, 0xaa50, 0xabf0, 0xff10, 0x104a0,
-        0x11066, 0x110f0, 0x11136, 0x111d0, 0x116c0, 0x1d7ce, 0x1d7d8, 0x1d7e2,
-        0x1d7ec, 0x1d7f6)
+        0xa620, 0xa8d0, 0xa900, 0xa9d0, 0xa9f0, 0xaa50, 0xabf0, 0xff10,
+        0x104a0, 0x10d30, 0x11066, 0x110f0, 0x11136, 0x111d0, 0x112f0, 0x11450,
+        0x114d0, 0x11650, 0x116c0, 0x11730, 0x118e0, 0x11950, 0x11c50, 0x11d50,
+        0x11da0, 0x11f50, 0x16a60, 0x16ac0, 0x16b50, 0x1d7ce, 0x1d7d8, 0x1d7e2,
+        0x1d7ec, 0x1d7f6, 0x1e140, 0x1e2f0, 0x1e4f0, 0x1e950, 0x1fbf0
+    )
   }
 }
diff --git a/project/Build.scala b/project/Build.scala
index eeca43d4f5..d7ef98562f 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -2067,7 +2067,7 @@ object Build {
                   fastLink = 451000 to 452000,
                   fullLink = 95000 to 96000,
                   fastLinkGz = 58000 to 59000,
-                  fullLinkGz = 25000 to 26000,
+                  fullLinkGz = 26000 to 27000,
               ))
             } else {
               Some(ExpectedSizes(
diff --git a/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/lang/CharacterTest.scala b/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/lang/CharacterTest.scala
index c255d53035..ab11503d4d 100644
--- a/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/lang/CharacterTest.scala
+++ b/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/lang/CharacterTest.scala
@@ -1271,7 +1271,9 @@ for (cp <- 0 to Character.MAX_CODE_POINT) {
   }
 
   @Test def isUnicodeIdentifierStart(): Unit = {
-    // 100 randomly generated positives and 100 randomly generated negatives
+    /* 100 randomly generated positives and 100 randomly generated negatives,
+     * minus negative ones that became positive later.
+     */
 
     assertTrue(Character.isUnicodeIdentifierStart('\ud6d5'))
     assertTrue(Character.isUnicodeIdentifierStart('\u3f9c'))
@@ -1402,7 +1404,6 @@ for (cp <- 0 to Character.MAX_CODE_POINT) {
     assertFalse(Character.isUnicodeIdentifierStart('\uf03e'))
     assertFalse(Character.isUnicodeIdentifierStart('\uda27'))
     assertFalse(Character.isUnicodeIdentifierStart('\u28fc'))
-    assertFalse(Character.isUnicodeIdentifierStart('\u9ffe'))
     assertFalse(Character.isUnicodeIdentifierStart('\ude19'))
     assertFalse(Character.isUnicodeIdentifierStart('\u0b70'))
     assertFalse(Character.isUnicodeIdentifierStart('\uddfc'))
@@ -2341,7 +2342,6 @@ for (cp <- 0 to Character.MAX_CODE_POINT) {
     assertFalse(Character.isLetterOrDigit('\u05EB'))
     assertFalse(Character.isLetterOrDigit('\u0618'))
     assertFalse(Character.isLetterOrDigit('\u070B'))
-    assertFalse(Character.isLetterOrDigit('\u088C'))
     assertFalse(Character.isLetterOrDigit('\u08D7'))
     assertFalse(Character.isLetterOrDigit('\u0947'))
     assertFalse(Character.isLetterOrDigit('\u0B56'))
@@ -3259,8 +3259,6 @@ for (cp <- 0 to Character.MAX_CODE_POINT) {
     assertFalse(Character.isDefined('\u0DFB'))
     assertFalse(Character.isDefined('\u1FDC'))
     assertFalse(Character.isDefined('\u243A'))
-    assertFalse(Character.isDefined('\u2E54'))
-    assertFalse(Character.isDefined('\uA7F3'))
     assertFalse(Character.isDefined('\u0EEB'))
     assertFalse(Character.isDefined('\u09D6'))
     assertFalse(Character.isDefined('\u2D7C'))
@@ -3270,7 +3268,6 @@ for (cp <- 0 to Character.MAX_CODE_POINT) {
     assertFalse(Character.isDefined('\u1775'))
     assertFalse(Character.isDefined('\u0A54'))
     assertFalse(Character.isDefined('\u175F'))
-    assertFalse(Character.isDefined('\u0882'))
     assertFalse(Character.isDefined('\uFDC8'))
     assertFalse(Character.isDefined('\u1C3A'))
     assertFalse(Character.isDefined('\u0E00'))
@@ -3289,12 +3286,10 @@ for (cp <- 0 to Character.MAX_CODE_POINT) {
     assertFalse(Character.isDefined('\u0D99'))
     assertFalse(Character.isDefined('\u242D'))
     assertFalse(Character.isDefined('\u3130'))
-    assertFalse(Character.isDefined('\uFD49'))
     assertFalse(Character.isDefined('\u1AF5'))
     assertFalse(Character.isDefined('\u0557'))
     assertFalse(Character.isDefined('\uAA5A'))
     assertFalse(Character.isDefined('\u1AE7'))
-    assertFalse(Character.isDefined('\uFD48'))
     assertFalse(Character.isDefined('\u1AEB'))
     assertFalse(Character.isDefined('\u2D9B'))
     assertFalse(Character.isDefined('\u07BF'))
@@ -3306,21 +3301,16 @@ for (cp <- 0 to Character.MAX_CODE_POINT) {
     assertFalse(Character.isDefined('\u09BA'))
     assertFalse(Character.isDefined('\u171C'))
     assertFalse(Character.isDefined('\uFFD9'))
-    assertFalse(Character.isDefined('\uFD40'))
     assertFalse(Character.isDefined('\u243E'))
     assertFalse(Character.isDefined('\u0FF8'))
     assertFalse(Character.isDefined('\u07FC'))
     assertFalse(Character.isDefined('\u16FF'))
-    assertFalse(Character.isDefined('\u1AC2'))
     assertFalse(Character.isDefined('\u1CFB'))
     assertFalse(Character.isDefined('\u1311'))
-    assertFalse(Character.isDefined('\uA7D8'))
     assertFalse(Character.isDefined('\uA7ED'))
     assertFalse(Character.isDefined('\u0B78'))
-    assertFalse(Character.isDefined('\uA7F2'))
     assertFalse(Character.isDefined('\u13FF'))
     assertFalse(Character.isDefined('\u1AD4'))
-    assertFalse(Character.isDefined('\u088A'))
     assertFalse(Character.isDefined('\uAAF8'))
     assertFalse(Character.isDefined('\u1978'))
     assertFalse(Character.isDefined('\u17EA'))
@@ -3334,7 +3324,6 @@ for (cp <- 0 to Character.MAX_CODE_POINT) {
     assertFalse(Character.isDefined('\u0EEA'))
     assertFalse(Character.isDefined('\uFDD3'))
     assertFalse(Character.isDefined('\u0E3B'))
-    assertFalse(Character.isDefined('\u1B4C'))
     assertFalse(Character.isDefined('\uFB45'))
     assertFalse(Character.isDefined('\u1AEF'))
     assertFalse(Character.isDefined('\uA7E7'))

From e10803cb61c50303d19bbdd20c75ef86acafb0e7 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Tue, 10 Sep 2024 13:52:54 +0200
Subject: [PATCH 155/298] Complete methods of Character about code points in
 char sequences.

Implement all overloads of `java.lang.Character.`:

* `codePointAt`
* `codePointBefore`
* `codePointCount`
* `offsetByCodePoints`

In the process, unify with the implementations of methods of the
same name in `jl.String`.

This completes the set of methods of `jl.Character` that do not
need the Unicode database.

Fixes #5010, among other things.
---
 .../main/scala/java/lang/CharSequence.scala   |  28 ++
 .../src/main/scala/java/lang/Character.scala  | 153 ++++++++-
 .../src/main/scala/java/lang/_String.scala    |  74 +----
 .../javalib/lang/CharacterTest.scala          | 293 ++++++++++++++++++
 .../testsuite/javalib/lang/StringTest.scala   |  10 +-
 5 files changed, 489 insertions(+), 69 deletions(-)

diff --git a/javalib/src/main/scala/java/lang/CharSequence.scala b/javalib/src/main/scala/java/lang/CharSequence.scala
index 051e445c2c..0de3e83e49 100644
--- a/javalib/src/main/scala/java/lang/CharSequence.scala
+++ b/javalib/src/main/scala/java/lang/CharSequence.scala
@@ -18,3 +18,31 @@ trait CharSequence {
   def subSequence(start: scala.Int, end: scala.Int): CharSequence
   def toString(): String
 }
+
+private[lang] object CharSequence {
+  /** Wraps an `Array[Char]` as a `CharSequence` to reuse algorithms.
+   *
+   *  `subSequence` has an inefficient implementation. Avoid using this class
+   *  for algorithms that use that method.
+   */
+  @inline
+  private[lang] def ofArray(array: Array[Char]): OfArray = new OfArray(array)
+
+  /** Wraps an `Array[Char]` as a `CharSequence` to reuse algorithms.
+   *
+   *  `subSequence` has an inefficient implementation. Avoid using this class
+   *  for algorithms that use that method.
+   */
+  @inline
+  private[lang] final class OfArray(array: Array[Char]) extends CharSequence {
+    def length(): Int = array.length
+    def charAt(index: Int): Char = array(index)
+
+    // This is not efficient but we do not actually use it
+    def subSequence(start: Int, end: Int): CharSequence =
+      new OfArray(java.util.Arrays.copyOfRange(array, start, end))
+
+    override def toString(): String =
+      String.valueOf(array)
+  }
+}
diff --git a/javalib/src/main/scala/java/lang/Character.scala b/javalib/src/main/scala/java/lang/Character.scala
index f9baf3956f..cc938fb49a 100644
--- a/javalib/src/main/scala/java/lang/Character.scala
+++ b/javalib/src/main/scala/java/lang/Character.scala
@@ -195,6 +195,74 @@ object Character {
 
   // Code point manipulation in character sequences ---------------------------
 
+  @noinline
+  def codePointAt(seq: CharSequence, index: Int): Int =
+    codePointAtImpl(seq, index)
+
+  @noinline
+  def codePointAt(a: Array[Char], index: Int): Int =
+    codePointAtImpl(CharSequence.ofArray(a), index)
+
+  @noinline
+  def codePointAt(a: Array[Char], index: Int, limit: Int): Int = {
+    // implicit null check and bounds check
+    if (!(limit <= a.length && 0 <= index && index < limit))
+      throw new IndexOutOfBoundsException()
+
+    if (index == limit - 1)
+      a(index).toInt // the only case where `limit` makes a difference
+    else
+      codePointAt(a, index)
+  }
+
+  @inline
+  private[lang] def codePointAtImpl(seq: CharSequence, index: Int): Int = {
+    val high = seq.charAt(index) // implicit null check and bounds check
+    if (isHighSurrogate(high) && (index + 1 < seq.length())) {
+      val low = seq.charAt(index + 1)
+      if (isLowSurrogate(low))
+        toCodePoint(high, low)
+      else
+        high.toInt
+    } else {
+      high.toInt
+    }
+  }
+
+  @noinline
+  def codePointBefore(seq: CharSequence, index: Int): Int =
+    codePointBeforeImpl(seq, index)
+
+  @noinline
+  def codePointBefore(a: Array[Char], index: Int): Int =
+    codePointBeforeImpl(CharSequence.ofArray(a), index)
+
+  @noinline
+  def codePointBefore(a: Array[Char], index: Int, start: Int): Int = {
+    // implicit null check and bounds check
+    if (!(index <= a.length && 0 <= start && start < index))
+      throw new IndexOutOfBoundsException()
+
+    if (index == start + 1)
+      a(start).toInt // the only case where `start` makes a difference
+    else
+      codePointBefore(a, index)
+  }
+
+  @inline
+  private[lang] def codePointBeforeImpl(seq: CharSequence, index: Int): Int = {
+    val low = seq.charAt(index - 1) // implicit null check and bounds check
+    if (isLowSurrogate(low) && index > 1) {
+      val high = seq.charAt(index - 2)
+      if (isHighSurrogate(high))
+        toCodePoint(high, low)
+      else
+        low.toInt
+    } else {
+      low.toInt
+    }
+  }
+
   def toChars(codePoint: Int, dst: Array[Char], dstIndex: Int): Int = {
     if (isBmpCodePoint(codePoint)) {
       dst(dstIndex) = codePoint.toChar
@@ -217,20 +285,99 @@ object Character {
       throw new IllegalArgumentException()
   }
 
-  def codePointCount(seq: CharSequence, beginIndex: Int, endIndex: Int): Int = {
+  @noinline
+  def codePointCount(seq: CharSequence, beginIndex: Int, endIndex: Int): Int =
+    codePointCountImpl(seq, beginIndex, endIndex)
+
+  @noinline
+  def codePointCount(a: Array[Char], offset: Int, count: Int): Int =
+    codePointCountImpl(CharSequence.ofArray(a), offset, offset + count)
+
+  @inline
+  private[lang] def codePointCountImpl(seq: CharSequence, beginIndex: Int, endIndex: Int): Int = {
+    // Bounds check (and implicit null check)
     if (endIndex > seq.length() || beginIndex < 0 || endIndex < beginIndex)
-      throw new IndexOutOfBoundsException
+      throw new IndexOutOfBoundsException()
+
     var res = endIndex - beginIndex
     var i = beginIndex
     val end = endIndex - 1
     while (i < end) {
-      if (isSurrogatePair(seq.charAt(i), seq.charAt(i + 1)))
+      if (isHighSurrogate(seq.charAt(i)) && isLowSurrogate(seq.charAt(i + 1)))
         res -= 1
       i += 1
     }
     res
   }
 
+  @noinline
+  def offsetByCodePoints(seq: CharSequence, index: Int, codePointOffset: Int): Int =
+    offsetByCodePointsImpl(seq, index, codePointOffset)
+
+  @noinline
+  def offsetByCodePoints(a: Array[Char], start: Int, count: Int, index: Int,
+      codePointOffset: Int): Int = {
+
+    val len = a.length // implicit null check
+
+    // Bounds check
+    val limit = start + count
+    if (start < 0 || count < 0 || limit > len || index < start || index > limit)
+      throw new IndexOutOfBoundsException()
+
+    offsetByCodePointsInternal(CharSequence.ofArray(a), start, limit, index, codePointOffset)
+  }
+
+  @inline
+  private[lang] def offsetByCodePointsImpl(seq: CharSequence, index: Int, codePointOffset: Int): Int = {
+    val len = seq.length() // implicit null check
+
+    // Bounds check
+    if (index < 0 || index > len)
+      throw new IndexOutOfBoundsException()
+
+    offsetByCodePointsInternal(seq, start = 0, limit = len, index, codePointOffset)
+  }
+
+  @inline
+  private[lang] def offsetByCodePointsInternal(seq: CharSequence, start: Int,
+      limit: Int, index: Int, codePointOffset: Int): Int = {
+
+    if (codePointOffset >= 0) {
+      var i = 0
+      var result = index
+      while (i != codePointOffset) {
+        if (result >= limit)
+          throw new IndexOutOfBoundsException()
+        if ((result < limit - 1) &&
+            isHighSurrogate(seq.charAt(result)) &&
+            isLowSurrogate(seq.charAt(result + 1))) {
+          result += 2
+        } else {
+          result += 1
+        }
+        i += 1
+      }
+      result
+    } else {
+      var i = 0
+      var result = index
+      while (i != codePointOffset) {
+        if (result <= start)
+          throw new IndexOutOfBoundsException()
+        if ((result > start + 1) &&
+            isLowSurrogate(seq.charAt(result - 1)) &&
+            isHighSurrogate(seq.charAt(result - 2))) {
+          result -= 2
+        } else {
+          result -= 1
+        }
+        i -= 1
+      }
+      result
+    }
+  }
+
   // Unicode Character Database-related functions -----------------------------
 
   def getType(ch: scala.Char): Int = getType(ch.toInt)
diff --git a/javalib/src/main/scala/java/lang/_String.scala b/javalib/src/main/scala/java/lang/_String.scala
index 8ea2a2c70a..5a8e03cc0e 100644
--- a/javalib/src/main/scala/java/lang/_String.scala
+++ b/javalib/src/main/scala/java/lang/_String.scala
@@ -59,73 +59,21 @@ final class _String private () // scalastyle:ignore
       charAt(index) // bounds check
       this.asInstanceOf[js.Dynamic].codePointAt(index).asInstanceOf[Int]
     } else {
-      val high = charAt(index)
-      if (index+1 < length()) {
-        val low = charAt(index+1)
-        if (Character.isSurrogatePair(high, low))
-          Character.toCodePoint(high, low)
-        else
-          high.toInt
-      } else {
-        high.toInt
-      }
+      Character.codePointAtImpl(this, index)
     }
   }
 
-  def codePointBefore(index: Int): Int = {
-    val low = charAt(index - 1)
-    if (index > 1) {
-      val high = charAt(index - 2)
-      if (Character.isSurrogatePair(high, low))
-        Character.toCodePoint(high, low)
-      else
-        low.toInt
-    } else {
-      low.toInt
-    }
-  }
+  @noinline
+  def codePointBefore(index: Int): Int =
+    Character.codePointBeforeImpl(this, index)
 
+  @noinline
   def codePointCount(beginIndex: Int, endIndex: Int): Int =
-    Character.codePointCount(this, beginIndex, endIndex)
+    Character.codePointCountImpl(this, beginIndex, endIndex)
 
-  def offsetByCodePoints(index: Int, codePointOffset: Int): Int = {
-    val len = length()
-    if (index < 0 || index > len)
-      throw new StringIndexOutOfBoundsException(index)
-
-    if (codePointOffset >= 0) {
-      var i = 0
-      var result = index
-      while (i != codePointOffset) {
-        if (result >= len)
-          throw new StringIndexOutOfBoundsException
-        if ((result < len - 1) &&
-            Character.isHighSurrogate(charAt(result)) &&
-            Character.isLowSurrogate(charAt(result + 1))) {
-          result += 2
-        } else {
-          result += 1
-        }
-        i += 1
-      }
-      result
-    } else {
-      var i = 0
-      var result = index
-      while (i != codePointOffset) {
-        if (result <= 0)
-          throw new StringIndexOutOfBoundsException
-        if ((result > 1) && Character.isLowSurrogate(charAt(result - 1)) &&
-            Character.isHighSurrogate(charAt(result - 2))) {
-          result -= 2
-        } else {
-          result -= 1
-        }
-        i -= 1
-      }
-      result
-    }
-  }
+  @noinline
+  def offsetByCodePoints(index: Int, codePointOffset: Int): Int =
+    Character.offsetByCodePointsImpl(this, index, codePointOffset)
 
   override def hashCode(): Int = {
     var res = 0
@@ -720,7 +668,7 @@ for (cp <- 0 to Character.MAX_CODE_POINT) {
     val len = length()
     var j = i
     while (j != len) {
-      val cp = codePointAt(j)
+      val cp = this.codePointAt(j)
       if (combiningClassNoneOrAboveOrOther(cp) != CombiningClassIsOther)
         return j
       j += charCount(cp)
@@ -734,7 +682,7 @@ for (cp <- 0 to Character.MAX_CODE_POINT) {
     import Character._
     var j = i
     while (j > 0) {
-      val cp = codePointBefore(j)
+      val cp = this.codePointBefore(j)
       if (combiningClassNoneOrAboveOrOther(cp) != CombiningClassIsOther)
         return j
       j -= charCount(cp)
diff --git a/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/lang/CharacterTest.scala b/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/lang/CharacterTest.scala
index ab11503d4d..0e5d4f8a80 100644
--- a/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/lang/CharacterTest.scala
+++ b/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/lang/CharacterTest.scala
@@ -14,6 +14,7 @@ package org.scalajs.testsuite.javalib.lang
 
 import org.junit.Test
 import org.junit.Assert._
+import org.junit.Assume._
 
 import org.scalajs.testsuite.utils.AssertThrows.assertThrows
 import org.scalajs.testsuite.utils.Platform._
@@ -297,6 +298,164 @@ class CharacterTest {
     assertEquals('9', Character.forDigit(9, 10))
   }
 
+  @Test def codePointAtCharSequence(): Unit = {
+    assertEquals(0x61, Character.codePointAt("abc\ud834\udf06def", 0))
+    assertEquals(0x1d306, Character.codePointAt("abc\ud834\udf06def", 3))
+    assertEquals(0xdf06, Character.codePointAt("abc\ud834\udf06def", 4))
+    assertEquals(0x64, Character.codePointAt("abc\ud834\udf06def", 5))
+    assertEquals(0x1d306, Character.codePointAt("\ud834\udf06def", 0))
+    assertEquals(0xdf06, Character.codePointAt("\ud834\udf06def", 1))
+    assertEquals(0xd834, Character.codePointAt("\ud834abc", 0))
+    assertEquals(0xdf06, Character.codePointAt("\udf06abc", 0))
+    assertEquals(0xd834, Character.codePointAt("abc\ud834", 3))
+  }
+
+  @Test def codePointAtCharSequenceIndexOutOfBounds(): Unit = {
+    assumeTrue("Assuming compliant StringIndexOutOfBounds",
+        hasCompliantStringIndexOutOfBounds)
+
+    assertThrows(classOf[StringIndexOutOfBoundsException],
+        Character.codePointAt("abc\ud834\udf06def", -1))
+    assertThrows(classOf[StringIndexOutOfBoundsException],
+        Character.codePointAt("abc\ud834\udf06def", 8))
+    assertThrows(classOf[StringIndexOutOfBoundsException],
+        Character.codePointAt("abc\ud834\udf06def", 15))
+  }
+
+  @Test def codePointAtArray(): Unit = {
+    assertEquals(0x61, Character.codePointAt("abc\ud834\udf06def".toCharArray(), 0))
+    assertEquals(0x1d306, Character.codePointAt("abc\ud834\udf06def".toCharArray(), 3))
+    assertEquals(0xdf06, Character.codePointAt("abc\ud834\udf06def".toCharArray(), 4))
+    assertEquals(0x64, Character.codePointAt("abc\ud834\udf06def".toCharArray(), 5))
+    assertEquals(0x1d306, Character.codePointAt("\ud834\udf06def".toCharArray(), 0))
+    assertEquals(0xdf06, Character.codePointAt("\ud834\udf06def".toCharArray(), 1))
+    assertEquals(0xd834, Character.codePointAt("\ud834abc".toCharArray(), 0))
+    assertEquals(0xdf06, Character.codePointAt("\udf06abc".toCharArray(), 0))
+    assertEquals(0xd834, Character.codePointAt("abc\ud834".toCharArray(), 3))
+  }
+
+  @Test def codePointAtArrayIndexOutOfBounds(): Unit = {
+    assumeTrue("Assuming compliant ArrayIndexOutOfBounds",
+        hasCompliantArrayIndexOutOfBounds)
+
+    assertThrows(classOf[ArrayIndexOutOfBoundsException],
+        Character.codePointAt("abc\ud834\udf06def".toCharArray(), -1))
+    assertThrows(classOf[ArrayIndexOutOfBoundsException],
+        Character.codePointAt("abc\ud834\udf06def".toCharArray(), 8))
+    assertThrows(classOf[ArrayIndexOutOfBoundsException],
+        Character.codePointAt("abc\ud834\udf06def".toCharArray(), 15))
+  }
+
+  @Test def codePointAtArrayWithLimit(): Unit = {
+    assertEquals(0x61, Character.codePointAt("abc\ud834\udf06def".toCharArray(), 0, 3))
+    assertEquals(0x1d306, Character.codePointAt("abc\ud834\udf06def".toCharArray(), 3, 5))
+    assertEquals(0xdf06, Character.codePointAt("abc\ud834\udf06def".toCharArray(), 4, 5))
+    assertEquals(0x64, Character.codePointAt("abc\ud834\udf06def".toCharArray(), 5, 8))
+    assertEquals(0x1d306, Character.codePointAt("\ud834\udf06def".toCharArray(), 0, 2))
+    assertEquals(0xdf06, Character.codePointAt("\ud834\udf06def".toCharArray(), 1, 2))
+    assertEquals(0xd834, Character.codePointAt("\ud834\udf06def".toCharArray(), 0, 1))
+    assertEquals(0xdf06, Character.codePointAt("\ud834\udf06def".toCharArray(), 1, 2))
+    assertEquals(0xd834, Character.codePointAt("\ud834abc".toCharArray(), 0, 3))
+    assertEquals(0xdf06, Character.codePointAt("\udf06abc".toCharArray(), 0, 1))
+    assertEquals(0xd834, Character.codePointAt("abc\ud834".toCharArray(), 3, 4))
+  }
+
+  @Test def codePointAtArrayWithLimitIndexOutOfBounds(): Unit = {
+    assertThrows(classOf[IndexOutOfBoundsException],
+        Character.codePointAt("abc\ud834\udf06def".toCharArray(), -1, 3))
+    assertThrows(classOf[IndexOutOfBoundsException],
+        Character.codePointAt("abc\ud834\udf06def".toCharArray(), 8, 8))
+    assertThrows(classOf[IndexOutOfBoundsException],
+        Character.codePointAt("abc\ud834\udf06def".toCharArray(), 15, 5))
+    assertThrows(classOf[IndexOutOfBoundsException],
+        Character.codePointAt("abc\ud834\udf06def".toCharArray(), 3, 1))
+    assertThrows(classOf[IndexOutOfBoundsException],
+        Character.codePointAt("abc\ud834\udf06def".toCharArray(), 3, 3))
+    assertThrows(classOf[IndexOutOfBoundsException],
+        Character.codePointAt("abc\ud834\udf06def".toCharArray(), -1, 0))
+    assertThrows(classOf[IndexOutOfBoundsException],
+        Character.codePointAt("abc\ud834\udf06def".toCharArray(), -5, -2))
+    assertThrows(classOf[IndexOutOfBoundsException],
+        Character.codePointAt("abc\ud834\udf06def".toCharArray(), 5, 10))
+  }
+
+  @Test def codePointBeforeCharSequence(): Unit = {
+    assertEquals(0x61, Character.codePointBefore("abc\ud834\udf06def", 1))
+    assertEquals(0x1d306, Character.codePointBefore("abc\ud834\udf06def", 5))
+    assertEquals(0xd834, Character.codePointBefore("abc\ud834\udf06def", 4))
+    assertEquals(0x64, Character.codePointBefore("abc\ud834\udf06def", 6))
+    assertEquals('f'.toInt, Character.codePointBefore("abc\ud834\udf06def", 8))
+    assertEquals(0x1d306, Character.codePointBefore("\ud834\udf06def", 2))
+    assertEquals(0xd834, Character.codePointBefore("\ud834\udf06def", 1))
+    assertEquals(0xd834, Character.codePointBefore("\ud834abc", 1))
+    assertEquals(0xdf06, Character.codePointBefore("\udf06abc", 1))
+  }
+
+  @Test def codePointBeforeCharSequenceIndexOutOfBounds(): Unit = {
+    assumeTrue("Assuming compliant StringIndexOutOfBounds",
+        hasCompliantStringIndexOutOfBounds)
+
+    assertThrows(classOf[StringIndexOutOfBoundsException],
+        Character.codePointBefore("abc\ud834\udf06def", -5))
+    assertThrows(classOf[StringIndexOutOfBoundsException],
+        Character.codePointBefore("abc\ud834\udf06def", 0))
+    assertThrows(classOf[StringIndexOutOfBoundsException],
+        Character.codePointBefore("abc\ud834\udf06def", 9))
+    assertThrows(classOf[StringIndexOutOfBoundsException],
+        Character.codePointBefore("abc\ud834\udf06def", 15))
+  }
+
+  @Test def codePointBeforeArray(): Unit = {
+    assertEquals(0x61, Character.codePointBefore("abc\ud834\udf06def".toCharArray(), 1))
+    assertEquals(0x1d306, Character.codePointBefore("abc\ud834\udf06def".toCharArray(), 5))
+    assertEquals(0xd834, Character.codePointBefore("abc\ud834\udf06def".toCharArray(), 4))
+    assertEquals(0x64, Character.codePointBefore("abc\ud834\udf06def".toCharArray(), 6))
+    assertEquals('f'.toInt, Character.codePointBefore("abc\ud834\udf06def".toCharArray(), 8))
+    assertEquals(0x1d306, Character.codePointBefore("\ud834\udf06def".toCharArray(), 2))
+    assertEquals(0xd834, Character.codePointBefore("\ud834\udf06def".toCharArray(), 1))
+    assertEquals(0xd834, Character.codePointBefore("\ud834abc".toCharArray(), 1))
+    assertEquals(0xdf06, Character.codePointBefore("\udf06abc".toCharArray(), 1))
+  }
+
+  @Test def codePointBeforeArrayIndexOutOfBounds(): Unit = {
+    assumeTrue("Assuming compliant ArrayIndexOutOfBounds",
+        hasCompliantArrayIndexOutOfBounds)
+
+    assertThrows(classOf[ArrayIndexOutOfBoundsException],
+        Character.codePointBefore("abc\ud834\udf06def".toCharArray(), -5))
+    assertThrows(classOf[ArrayIndexOutOfBoundsException],
+        Character.codePointBefore("abc\ud834\udf06def".toCharArray(), 0))
+    assertThrows(classOf[ArrayIndexOutOfBoundsException],
+        Character.codePointBefore("abc\ud834\udf06def".toCharArray(), 9))
+    assertThrows(classOf[ArrayIndexOutOfBoundsException],
+        Character.codePointBefore("abc\ud834\udf06def".toCharArray(), 15))
+  }
+
+  @Test def codePointBeforeArrayWithStart(): Unit = {
+    assertEquals(0x61, Character.codePointBefore("abc\ud834\udf06def".toCharArray(), 1, 0))
+    assertEquals(0x1d306, Character.codePointBefore("abc\ud834\udf06def".toCharArray(), 5, 0))
+    assertEquals(0x1d306, Character.codePointBefore("abc\ud834\udf06def".toCharArray(), 5, 3))
+    assertEquals(0xdf06, Character.codePointBefore("abc\ud834\udf06def".toCharArray(), 5, 4))
+    assertEquals(0xd834, Character.codePointBefore("abc\ud834\udf06def".toCharArray(), 4, 2))
+    assertEquals(0xd834, Character.codePointBefore("abc\ud834\udf06def".toCharArray(), 4, 3))
+    assertEquals(0xd834, Character.codePointBefore("\ud834\udf06def".toCharArray(), 1, 0))
+    assertEquals(0xd834, Character.codePointBefore("\ud834abc".toCharArray(), 1, 0))
+    assertEquals(0xdf06, Character.codePointBefore("\udf06abc".toCharArray(), 1, 0))
+  }
+
+  @Test def codePointBeforeArrayWithStartIndexOutOfBounds(): Unit = {
+    assertThrows(classOf[IndexOutOfBoundsException],
+        Character.codePointBefore("abc\ud834\udf06def".toCharArray(), -5, 0))
+    assertThrows(classOf[IndexOutOfBoundsException],
+        Character.codePointBefore("abc\ud834\udf06def".toCharArray(), 0, 0))
+    assertThrows(classOf[IndexOutOfBoundsException],
+        Character.codePointBefore("abc\ud834\udf06def".toCharArray(), 2, 2))
+    assertThrows(classOf[IndexOutOfBoundsException],
+        Character.codePointBefore("abc\ud834\udf06def".toCharArray(), 2, 5))
+    assertThrows(classOf[IndexOutOfBoundsException],
+        Character.codePointBefore("abc\ud834\udf06def".toCharArray(), 15, 5))
+  }
+
   @Test def toChars(): Unit = {
     assertTrue(Character.toChars(0x61) sameElements Array('a'))
     assertTrue(Character.toChars(0x10000) sameElements Array('\uD800', '\uDC00'))
@@ -342,6 +501,112 @@ class CharacterTest {
     assertThrows(classOf[IllegalArgumentException], Character.toChars(Integer.MAX_VALUE, new Array(2), 0))
   }
 
+  @Test def offsetByCodePointsCharSequence(): Unit = {
+    val s: CharSequence = "abc\ud834\udf06de\ud834\udf06fgh\ud834ij\udf06\ud834kl\udf06"
+
+    assertEquals(s.length, Character.offsetByCodePoints(s, 0, 18))
+    assertEquals(5, Character.offsetByCodePoints(s, 3, 1))
+    assertEquals(3, Character.offsetByCodePoints(s, 2, 1))
+    assertEquals(5, Character.offsetByCodePoints(s, 2, 2))
+    assertEquals(6, Character.offsetByCodePoints(s, 2, 3))
+    assertEquals(17, Character.offsetByCodePoints(s, 12, 5))
+    assertEquals(10, Character.offsetByCodePoints(s, 8, 2))
+    assertEquals(10, Character.offsetByCodePoints(s, 7, 2))
+    assertEquals(7, Character.offsetByCodePoints(s, 7, 0))
+    assertEquals(s.length, Character.offsetByCodePoints(s, s.length - 1, 1))
+    assertEquals(s.length - 1, Character.offsetByCodePoints(s, s.length - 1, 0))
+    assertEquals(s.length, Character.offsetByCodePoints(s, s.length, 0))
+
+    assertThrows(classOf[IndexOutOfBoundsException], Character.offsetByCodePoints(s, -3, 0))
+    assertThrows(classOf[IndexOutOfBoundsException], Character.offsetByCodePoints(s, -3, 4))
+    assertThrows(classOf[IndexOutOfBoundsException], Character.offsetByCodePoints(s, 6, 18))
+    assertThrows(classOf[IndexOutOfBoundsException], Character.offsetByCodePoints(s, 30, 2))
+    assertThrows(classOf[IndexOutOfBoundsException], Character.offsetByCodePoints(s, 30, 0))
+  }
+
+  @Test def offsetByCodePointsCharSequenceBackwards(): Unit = {
+    val s: CharSequence = "abc\ud834\udf06de\ud834\udf06fgh\ud834ij\udf06\ud834kl\udf06"
+
+    assertEquals(0, Character.offsetByCodePoints(s, s.length, -18))
+    assertEquals(3, Character.offsetByCodePoints(s, 5, -1))
+    assertEquals(2, Character.offsetByCodePoints(s, 3, -1))
+    assertEquals(2, Character.offsetByCodePoints(s, 4, -2))
+    assertEquals(2, Character.offsetByCodePoints(s, 5, -2))
+    assertEquals(2, Character.offsetByCodePoints(s, 6, -3))
+    assertEquals(12, Character.offsetByCodePoints(s, 17, -5))
+    assertEquals(7, Character.offsetByCodePoints(s, 10, -2))
+    assertEquals(7, Character.offsetByCodePoints(s, 7, -0))
+    assertEquals(s.length - 1, Character.offsetByCodePoints(s, s.length, -1))
+    assertEquals(s.length - 1, Character.offsetByCodePoints(s, s.length - 1, -0))
+    assertEquals(s.length, Character.offsetByCodePoints(s, s.length, -0))
+
+    assertThrows(classOf[IndexOutOfBoundsException], Character.offsetByCodePoints(s, -3, -4))
+    assertThrows(classOf[IndexOutOfBoundsException], Character.offsetByCodePoints(s, 6, -18))
+    assertThrows(classOf[IndexOutOfBoundsException], Character.offsetByCodePoints(s, 30, -2))
+  }
+
+  @Test def offsetByCodePointsArray(): Unit = {
+    val a: Array[Char] =
+      "abc\ud834\udf06de\ud834\udf06fgh\ud834ij\udf06\ud834kl\udf06".toCharArray()
+    val len = a.length
+
+    assertEquals(len, Character.offsetByCodePoints(a, 0, len, 0, 18))
+    assertEquals(5, Character.offsetByCodePoints(a, 0, len, 3, 1))
+    assertEquals(3, Character.offsetByCodePoints(a, 0, 5, 2, 1))
+    assertEquals(5, Character.offsetByCodePoints(a, 0, 5, 2, 2))
+    assertEquals(6, Character.offsetByCodePoints(a, 0, len, 2, 3))
+    assertEquals(17, Character.offsetByCodePoints(a, 5, 12, 12, 5))
+
+    assertEquals(10, Character.offsetByCodePoints(a, 5, 8, 8, 2))
+    assertEquals(10, Character.offsetByCodePoints(a, 5, 8, 7, 2))
+
+    assertEquals(9, Character.offsetByCodePoints(a, 4, 5, 6, 2))
+    assertEquals(8, Character.offsetByCodePoints(a, 4, 4, 6, 2))
+
+    assertThrows(classOf[IndexOutOfBoundsException], Character.offsetByCodePoints(a, 0, len, -3, 0))
+    assertThrows(classOf[IndexOutOfBoundsException], Character.offsetByCodePoints(a, 0, len, -3, 4))
+    assertThrows(classOf[IndexOutOfBoundsException], Character.offsetByCodePoints(a, 0, len, 6, 18))
+    assertThrows(classOf[IndexOutOfBoundsException], Character.offsetByCodePoints(a, 0, len, 30, 2))
+    assertThrows(classOf[IndexOutOfBoundsException], Character.offsetByCodePoints(a, 0, len, 30, 0))
+
+    assertThrows(classOf[IndexOutOfBoundsException], Character.offsetByCodePoints(a, 3, 6, 2, 0))
+    assertThrows(classOf[IndexOutOfBoundsException], Character.offsetByCodePoints(a, 3, 6, 2, 2))
+    assertThrows(classOf[IndexOutOfBoundsException], Character.offsetByCodePoints(a, 3, 6, 7, 5))
+    assertThrows(classOf[IndexOutOfBoundsException], Character.offsetByCodePoints(a, 3, 6, 10, 2))
+    assertThrows(classOf[IndexOutOfBoundsException], Character.offsetByCodePoints(a, 3, 6, 10, 0))
+
+    assertThrows(classOf[IndexOutOfBoundsException], Character.offsetByCodePoints(a, -1, 6, 2, 0))
+    assertThrows(classOf[IndexOutOfBoundsException], Character.offsetByCodePoints(a, 0, 30, 2, 0))
+    assertThrows(classOf[IndexOutOfBoundsException], Character.offsetByCodePoints(a, 3, -2, 2, 0))
+  }
+
+  @Test def offsetByCodePointsArrayBackwards(): Unit = {
+    val a: Array[Char] =
+      "abc\ud834\udf06de\ud834\udf06fgh\ud834ij\udf06\ud834kl\udf06".toCharArray()
+    val len = a.length
+
+    assertEquals(0, Character.offsetByCodePoints(a, 0, len, len, -18))
+    assertEquals(3, Character.offsetByCodePoints(a, 0, len, 5, -1))
+    assertEquals(2, Character.offsetByCodePoints(a, 0, 5, 3, -1))
+    assertEquals(2, Character.offsetByCodePoints(a, 0, 5, 5, -2))
+    assertEquals(2, Character.offsetByCodePoints(a, 0, len, 6, -3))
+    assertEquals(12, Character.offsetByCodePoints(a, 5, 12, 17, -5))
+
+    assertEquals(6, Character.offsetByCodePoints(a, 5, 8, 8, -2))
+    assertEquals(6, Character.offsetByCodePoints(a, 5, 8, 9, -2))
+
+    assertEquals(3, Character.offsetByCodePoints(a, 3, 5, 6, -2))
+    assertEquals(4, Character.offsetByCodePoints(a, 4, 4, 6, -2))
+
+    assertThrows(classOf[IndexOutOfBoundsException], Character.offsetByCodePoints(a, 0, len, -3, -4))
+    assertThrows(classOf[IndexOutOfBoundsException], Character.offsetByCodePoints(a, 0, len, 6, -18))
+    assertThrows(classOf[IndexOutOfBoundsException], Character.offsetByCodePoints(a, 0, len, 30, -2))
+
+    assertThrows(classOf[IndexOutOfBoundsException], Character.offsetByCodePoints(a, 3, 6, 2, -2))
+    assertThrows(classOf[IndexOutOfBoundsException], Character.offsetByCodePoints(a, 3, 6, 7, -5))
+    assertThrows(classOf[IndexOutOfBoundsException], Character.offsetByCodePoints(a, 3, 6, 10, -2))
+  }
+
   @Test def isDigit(): Unit = {
     assertFalse(Character.isDigit('a'))
     assertTrue(Character.isDigit('0'))
@@ -1064,6 +1329,34 @@ for (cp <- 0 to Character.MAX_CODE_POINT) {
     assertThrows(classOf[IndexOutOfBoundsException], Character.codePointCount(cs, 10, 30))
   }
 
+  @Test def codePointCountArray(): Unit = {
+    /* Attention! The third argument is a count/length value, not an end/limit value.
+     * To keep consistency with the tests above, we use the same values and
+     * subtract the start offset.
+     */
+
+    val a: Array[Char] =
+      "abc\uD834\uDF06de\uD834\uDF06fgh\uD834ij\uDF06\uD834kl\uDF06".toCharArray()
+
+    assertEquals(18, Character.codePointCount(a, 0, a.length - 0))
+    assertEquals(1, Character.codePointCount(a, 3, 5 - 3))
+    assertEquals(1, Character.codePointCount(a, 2, 3 - 2))
+    assertEquals(2, Character.codePointCount(a, 2, 4 - 2))
+    assertEquals(2, Character.codePointCount(a, 2, 5 - 2))
+    assertEquals(3, Character.codePointCount(a, 2, 6 - 2))
+    assertEquals(5, Character.codePointCount(a, 12, 17 - 12))
+    assertEquals(2, Character.codePointCount(a, 8, 10 - 8))
+    assertEquals(2, Character.codePointCount(a, 7, 10 - 7))
+    assertEquals(0, Character.codePointCount(a, 7, 7 - 7))
+    assertEquals(1, Character.codePointCount(a, a.length - 1, a.length - (a.length - 1)))
+    assertEquals(0, Character.codePointCount(a, a.length - 1, a.length - 1 - (a.length - 1)))
+    assertEquals(0, Character.codePointCount(a, a.length, a.length - a.length))
+
+    assertThrows(classOf[IndexOutOfBoundsException], Character.codePointCount(a, -3, 4 - (-3)))
+    assertThrows(classOf[IndexOutOfBoundsException], Character.codePointCount(a, 6, 2 - 6))
+    assertThrows(classOf[IndexOutOfBoundsException], Character.codePointCount(a, 10, 30 - 10))
+  }
+
   @Test def compare(): Unit = {
     assertTrue(Character.compare('0', '5') < 0)
     assertTrue(Character.compare('o', 'g') > 0)
diff --git a/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/lang/StringTest.scala b/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/lang/StringTest.scala
index 1637b7e687..a0b7f55d8d 100644
--- a/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/lang/StringTest.scala
+++ b/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/lang/StringTest.scala
@@ -234,6 +234,8 @@ class StringTest {
     assumeTrue("Assuming compliant StringIndexOutOfBounds",
         hasCompliantStringIndexOutOfBounds)
 
+    assertThrows(classOf[StringIndexOutOfBoundsException],
+        "abc\ud834\udf06def".codePointBefore(-5))
     assertThrows(classOf[StringIndexOutOfBoundsException],
         "abc\ud834\udf06def".codePointBefore(0))
     assertThrows(classOf[StringIndexOutOfBoundsException],
@@ -258,9 +260,11 @@ class StringTest {
     assertEquals(0, s.codePointCount(s.length - 1, s.length - 1))
     assertEquals(0, s.codePointCount(s.length, s.length))
 
+    assertThrows(classOf[IndexOutOfBoundsException], s.codePointCount(-3, 0))
     assertThrows(classOf[IndexOutOfBoundsException], s.codePointCount(-3, 4))
     assertThrows(classOf[IndexOutOfBoundsException], s.codePointCount(6, 2))
     assertThrows(classOf[IndexOutOfBoundsException], s.codePointCount(10, 30))
+    assertThrows(classOf[IndexOutOfBoundsException], s.codePointCount(10, 0))
   }
 
   @Test def offsetByCodePoints(): Unit = {
@@ -300,9 +304,9 @@ class StringTest {
     assertEquals(s.length - 1, s.offsetByCodePoints(s.length - 1, -0))
     assertEquals(s.length, s.offsetByCodePoints(s.length, -0))
 
-    assertThrows(classOf[IndexOutOfBoundsException], s.offsetByCodePoints(-3, 4))
-    assertThrows(classOf[IndexOutOfBoundsException], s.offsetByCodePoints(6, 18))
-    assertThrows(classOf[IndexOutOfBoundsException], s.offsetByCodePoints(30, 2))
+    assertThrows(classOf[IndexOutOfBoundsException], s.offsetByCodePoints(-3, -4))
+    assertThrows(classOf[IndexOutOfBoundsException], s.offsetByCodePoints(6, -18))
+    assertThrows(classOf[IndexOutOfBoundsException], s.offsetByCodePoints(30, -2))
   }
 
   @Test def substringBegin(): Unit = {

From 614e228f41596300c133ec75814f4144869f95ce Mon Sep 17 00:00:00 2001
From: Rikito Taniguchi <rikiriki1238@gmail.com>
Date: Tue, 17 Sep 2024 15:55:33 +0900
Subject: [PATCH 156/298] Wasm: Make itables immutable struct

Previously, we used mutable array-based interface tables (itables) without a specific reason.
However, accessing mutable arrays can lead to missed optimization opportunities.
For instance, loop-invariant code motion (LICM) won't be able to move certain parts of interface dispatching operations out of loops:
When we invoke a method using interface table dispatching, it requires retrieving an itable from the class's itable array, which is considered non-pure.

In fact, reading from an array is marked as unsafe to move in wasm-opt's LICM implementation:

https://github.com/WebAssembly/binaryen/blob/34ad6a7598e662e9ff357987f2c81fde1e05c522/src/ir/effects.h#L207-L210
https://github.com/WebAssembly/binaryen/blob/34ad6a7598e662e9ff357987f2c81fde1e05c522/src/passes/LoopInvariantCodeMotion.cpp#L125-L128

(Note: We may not run wasm-opt's LICM in favor of the VM's LICM, as discussed in https://github.com/WebAssembly/binaryen/issues/6924)

This commit changes itables to be immutable structs, making itable retrieval a pure operation.
Here's a comparison of benchmark results between commit 4c9494e424e0e8b60b6a198e461320897c6e8806 and this change:

|             | array itables | struct itables |
| ----------- | ------------- | -------------- |
| sha512      | 12128.73213   | 12107.94142    |
| queens      | 3.632068223   | 3.655815179    |
| list        | 84.61223471   | 65.69730564    |
| richards    | 92.12833022   | 91.19028905    |
| cd          | 46267.10318   | 46574.81215    |
| gcbench     | 116540.568    | 112594.324     |
| tracerFloat | 2569.675034   | 2551.227714    |
| tracer      | 1725.591249   | 1697.907466    |
| sudoku      | 14863.33909   | 12066.23882    |
| nbody       | 366388.3292   | 199625.971     |
| permute     | 1006.215249   | 983.9858283    |
| deltaBlue   | 2205.002528   | 2320.038418    |
| kmeans      | 1752457.829   | 1754425.973    |
| brainfuck   | 36983.97583   | 36093.7837     |
| json        | 1205.92764    | 1191.768986    |
| bounce      | 21.14001572   | 20.8851082     |

While most benchmark results remain same, some tests such as `list`, `sudoku`, and `nbody` show improved performance compared to the array-based itables (may be thanks to the VM's optimization capabilities).

**immutable array?**
In this change, we implement itables using immutable structs
However, we can use immutable arrays as an alternative.
We implemented and benchmarked itables using immutable arrays, and the results show nearly same performance as the immutable struct-based implementation.

https://github.com/WebAssembly/gc/issues/250
https://github.com/v8/v8/commit/6e36e3ec8576527de6a8bed2eec034679ef95a10

Let's proceed with the immutable struct-based implementation for now because

- While V8 seems to optimize immutable array-related operations, other VMs may not offer similar optimizations (?)
- Currently, wasm-opt doesn't take into account the mutability of arrays in its optimization process.
---
 .../backend/wasmemitter/ClassEmitter.scala    | 67 ++++++++++++++-----
 .../backend/wasmemitter/CoreWasmLib.scala     | 31 ++++-----
 .../linker/backend/wasmemitter/Emitter.scala  | 35 +---------
 .../backend/wasmemitter/FunctionEmitter.scala |  6 +-
 .../linker/backend/wasmemitter/VarGen.scala   |  4 ++
 5 files changed, 72 insertions(+), 71 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/ClassEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/ClassEmitter.scala
index 23582e35e4..e96fcdc04e 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/ClassEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/ClassEmitter.scala
@@ -135,6 +135,15 @@ class ClassEmitter(coreSpec: CoreSpec) {
     }
   }
 
+  /** Generate common itable global for all array classes. */
+  def genGlobalArrayClassItable()(implicit ctx: WasmContext): Unit = {
+    genGlobalClassItable(
+      genGlobalID.arrayClassITable, ctx.getClassInfo(ObjectClass),
+      List(SerializableClass, CloneableClass),
+      OriginalName(genGlobalID.arrayClassITable.toString())
+    )
+  }
+
   private def genIsJSClassInstanceFunction(clazz: LinkedClass)(
       implicit ctx: WasmContext): Option[wanme.FunctionID] = {
     implicit val noPos: Position = Position.NoPosition
@@ -489,8 +498,10 @@ class ClassEmitter(coreSpec: CoreSpec) {
         fb += wa.BrOnNull(testFail)
 
         fb += wa.LocalGet(itables)
-        fb += wa.I32Const(classInfo.itableIdx)
-        fb += wa.ArrayGet(genTypeID.itables)
+        fb += wa.StructGet(
+          genTypeID.itables,
+          genFieldID.itablesStruct.itableSlot(classInfo.itableIdx)
+        )
         fb += wa.RefTest(watpe.RefType(genTypeID.forITable(className)))
         fb += wa.Return
       } // test fail
@@ -785,24 +796,48 @@ class ClassEmitter(coreSpec: CoreSpec) {
    */
   private def genGlobalClassItable(clazz: LinkedClass)(implicit ctx: WasmContext): Unit = {
     val className = clazz.className
-
-    if (ctx.getClassInfo(className).classImplementsAnyInterface) {
-      val globalID = genGlobalID.forITable(className)
-      val itablesInit = List(
-        wa.I32Const(ctx.itablesLength),
-        wa.ArrayNewDefault(genTypeID.itables)
-      )
-      val global = wamod.Global(
-        globalID,
-        makeDebugName(ns.ITable, className),
-        isMutable = false,
-        watpe.RefType(genTypeID.itables),
-        wa.Expr(itablesInit)
+    val classInfo = ctx.getClassInfo(className)
+    if (classInfo.classImplementsAnyInterface) {
+      genGlobalClassItable(
+        genGlobalID.forITable(className),
+        classInfo,
+        clazz.ancestors,
+        makeDebugName(ns.ITable, classInfo.name)
       )
-      ctx.addGlobal(global)
     }
   }
 
+  private def genGlobalClassItable(classITableGlobalID: wanme.GlobalID,
+      classInfoForResolving: WasmContext.ClassInfo, ancestors: List[ClassName],
+      originalName: OriginalName)(
+      implicit ctx: WasmContext): Unit = {
+    val itablesInit = Array.fill[List[wa.Instr]](ctx.itablesLength) {
+      List(wa.RefNull(watpe.HeapType.Struct))
+    }
+    val resolvedMethodInfos = classInfoForResolving.resolvedMethodInfos
+
+    for {
+      ancestor <- ancestors
+      // Use getClassInfoOption in case the reachability analysis got rid of those interfaces
+      interfaceInfo <- ctx.getClassInfoOption(ancestor)
+      if interfaceInfo.isInterface
+    } {
+      val init = interfaceInfo.tableEntries.map { method =>
+        wa.RefFunc(resolvedMethodInfos(method).tableEntryID)
+      } :+ wa.StructNew(genTypeID.forITable(ancestor))
+      itablesInit(interfaceInfo.itableIdx) = init
+    }
+
+    val global = wamod.Global(
+      classITableGlobalID,
+      originalName,
+      isMutable = false,
+      watpe.RefType(genTypeID.itables),
+      wa.Expr(itablesInit.flatten.toList :+ wa.StructNew(genTypeID.itables))
+    )
+    ctx.addGlobal(global)
+  }
+
   private def genInterface(clazz: LinkedClass)(implicit ctx: WasmContext): Unit = {
     assert(clazz.kind == ClassKind.Interface)
     // gen itable type
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
index 745c551533..8e273591f0 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
@@ -120,7 +120,6 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
     genArrayClassTypes()
 
     genBoxedZeroGlobals()
-    genArrayClassGlobals()
   }
 
   // --- Type definitions ---
@@ -161,10 +160,21 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
       genTypeID.typeDataArray,
       ArrayType(FieldType(RefType(genTypeID.typeData), isMutable = false))
     )
+
     genCoreType(
       genTypeID.itables,
-      ArrayType(FieldType(RefType.nullable(HeapType.Struct), isMutable = true))
+      StructType(
+        (0 until ctx.itablesLength).map { i =>
+          StructField(
+            genFieldID.itablesStruct.itableSlot(i),
+            OriginalName.NoOriginalName,
+            RefType.nullable(HeapType.Struct),
+            isMutable = false
+          )
+        }.toList
+      )
     )
+
     genCoreType(
       genTypeID.reflectiveProxies,
       ArrayType(FieldType(RefType(genTypeID.reflectiveProxy), isMutable = false))
@@ -592,23 +602,6 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
     }
   }
 
-  private def genArrayClassGlobals()(implicit ctx: WasmContext): Unit = {
-    // Common itable global for all array classes
-    val itablesInit = List(
-      I32Const(ctx.itablesLength),
-      ArrayNewDefault(genTypeID.itables)
-    )
-    ctx.addGlobal(
-      Global(
-        genGlobalID.arrayClassITable,
-        OriginalName(genGlobalID.arrayClassITable.toString()),
-        isMutable = false,
-        RefType(genTypeID.itables),
-        init = Expr(itablesInit)
-      )
-    )
-  }
-
   // --- Function definitions ---
 
   /** Generates all the helper function definitions of the core Wasm lib. */
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala
index 656e2a5c2c..23ae3c9b34 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala
@@ -87,6 +87,7 @@ final class Emitter(config: Emitter.Config) {
     genExternalModuleImports(module)
     sortedClasses.foreach(classEmitter.genClassDef(_))
     topLevelExports.foreach(classEmitter.genTopLevelExport(_))
+    classEmitter.genGlobalArrayClassItable()
     coreLib.genPostClasses()
 
     genStartFunction(sortedClasses, moduleInitializers, topLevelExports)
@@ -131,40 +132,6 @@ final class Emitter(config: Emitter.Config) {
     val fb =
       new FunctionBuilder(ctx.moduleBuilder, genFunctionID.start, OriginalName("start"), pos)
 
-    // Initialize itables
-
-    def genInitClassITable(classITableGlobalID: wanme.GlobalID,
-        classInfoForResolving: WasmContext.ClassInfo, ancestors: List[ClassName]): Unit = {
-      val resolvedMethodInfos = classInfoForResolving.resolvedMethodInfos
-
-      for {
-        ancestor <- ancestors
-        // Use getClassInfoOption in case the reachability analysis got rid of those interfaces
-        interfaceInfo <- ctx.getClassInfoOption(ancestor)
-        if interfaceInfo.isInterface
-      } {
-        fb += wa.GlobalGet(classITableGlobalID)
-        fb += wa.I32Const(interfaceInfo.itableIdx)
-
-        for (method <- interfaceInfo.tableEntries)
-          fb += ctx.refFuncWithDeclaration(resolvedMethodInfos(method).tableEntryID)
-        fb += wa.StructNew(genTypeID.forITable(ancestor))
-        fb += wa.ArraySet(genTypeID.itables)
-      }
-    }
-
-    // For all concrete, normal classes
-    for (clazz <- sortedClasses if clazz.kind.isClass && clazz.hasDirectInstances) {
-      val className = clazz.className
-      val classInfo = ctx.getClassInfo(className)
-      if (classInfo.classImplementsAnyInterface)
-        genInitClassITable(genGlobalID.forITable(className), classInfo, clazz.ancestors)
-    }
-
-    // For array classes
-    genInitClassITable(genGlobalID.arrayClassITable, ctx.getClassInfo(ObjectClass),
-        List(SerializableClass, CloneableClass))
-
     // Initialize the JS private field symbols
 
     for (clazz <- sortedClasses if clazz.kind.isJSClass) {
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
index 02c981ea4e..061753f3bc 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
@@ -1151,8 +1151,10 @@ private class FunctionEmitter private (
     def genITableDispatch(): Unit = {
       fb += wa.LocalGet(receiverLocalForDispatch)
       fb += wa.StructGet(genTypeID.ObjectStruct, genFieldID.objStruct.itables)
-      fb += wa.I32Const(receiverClassInfo.itableIdx)
-      fb += wa.ArrayGet(genTypeID.itables)
+      fb += wa.StructGet(
+        genTypeID.itables,
+        genFieldID.itablesStruct.itableSlot(receiverClassInfo.itableIdx)
+      )
       fb += wa.RefCast(watpe.RefType(genTypeID.forITable(receiverClassInfo.name)))
       fb += wa.StructGet(
         genTypeID.forITable(receiverClassInfo.name),
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
index 07c1575552..e03f8ce8f8 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
@@ -294,6 +294,10 @@ object VarGen {
       case object arrayUnderlying extends FieldID
     }
 
+    object itablesStruct {
+      final case class itableSlot(i: Int) extends FieldID
+    }
+
     object reflectiveProxy {
       case object methodID extends FieldID
       case object funcRef extends FieldID

From a707deaabe73b64f99679e891b993d84483b8e09 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Mon, 16 Sep 2024 22:46:32 +0200
Subject: [PATCH 157/298] Introduce `UnaryOp.CheckNotNull` in the IR.

Now that we have non-nullable reference types in the IR, it makes
sense to offer that operation at the IR level. It replaces the
`Transient` of the same name.

We use it in the compiler instead of `GetClass`, as it is more
direct.
---
 .../org/scalajs/nscplugin/GenJSCode.scala     |  6 +-
 .../main/scala/org/scalajs/ir/Printers.scala  | 55 ++++++++++---------
 .../src/main/scala/org/scalajs/ir/Trees.scala | 16 +++++-
 .../scala/org/scalajs/ir/PrintersTest.scala   |  2 +
 .../backend/emitter/FunctionEmitter.scala     | 27 ++++-----
 .../linker/backend/emitter/Transients.scala   | 24 --------
 .../backend/wasmemitter/FunctionEmitter.scala |  9 ++-
 .../scalajs/linker/checker/IRChecker.scala    |  2 +
 .../frontend/optimizer/IncOptimizer.scala     |  5 +-
 .../frontend/optimizer/OptimizerCore.scala    | 35 +++++++-----
 project/BinaryIncompatibilities.scala         |  2 +
 project/Build.scala                           |  2 +-
 12 files changed, 93 insertions(+), 92 deletions(-)

diff --git a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
index 788e8dc61b..277d432ffd 100644
--- a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
+++ b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
@@ -1573,7 +1573,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
              * null check remains before the super call, while the associated
              * assignment is moved after.
              */
-            preSuperStats += js.GetClass(genExpr(outer))(tree.pos)
+            preSuperStats += js.UnaryOp(js.UnaryOp.CheckNotNull, genExpr(outer))(tree.pos)
             postSuperStats += genStat(assign)
 
           case stat =>
@@ -2388,7 +2388,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
             tree match {
               case OuterPointerNullCheck(outer, elsep) =>
                 js.Block(
-                  js.GetClass(genExpr(outer)), // null check
+                  js.UnaryOp(js.UnaryOp.CheckNotNull, genExpr(outer)),
                   genStat(elsep)
                 )
               case _ =>
@@ -4759,7 +4759,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
           newArg
         case _ =>
           js.Block(
-              js.GetClass(newReceiver), // null check
+              js.UnaryOp(js.UnaryOp.CheckNotNull, newReceiver),
               newArg)
       }
     }
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala
index 318d69355f..ec0ff8c5f8 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala
@@ -343,33 +343,38 @@ object Printers {
           print(method)
           printArgs(args)
 
-        case UnaryOp(UnaryOp.String_length, lhs) =>
-          print(lhs)
-          print(".length")
-
         case UnaryOp(op, lhs) =>
           import UnaryOp._
-          print('(')
-          print((op: @switch) match {
-            case Boolean_! =>
-              "!"
-            case IntToChar =>
-              "(char)"
-            case IntToByte =>
-              "(byte)"
-            case IntToShort =>
-              "(short)"
-            case CharToInt | ByteToInt | ShortToInt | LongToInt | DoubleToInt =>
-              "(int)"
-            case IntToLong | DoubleToLong =>
-              "(long)"
-            case DoubleToFloat | LongToFloat =>
-              "(float)"
-            case IntToDouble | LongToDouble | FloatToDouble =>
-              "(double)"
-          })
-          print(lhs)
-          print(')')
+
+          if (op < String_length) {
+            print('(')
+            print((op: @switch) match {
+              case Boolean_! =>
+                "!"
+              case IntToChar =>
+                "(char)"
+              case IntToByte =>
+                "(byte)"
+              case IntToShort =>
+                "(short)"
+              case CharToInt | ByteToInt | ShortToInt | LongToInt | DoubleToInt =>
+                "(int)"
+              case IntToLong | DoubleToLong =>
+                "(long)"
+              case DoubleToFloat | LongToFloat =>
+                "(float)"
+              case IntToDouble | LongToDouble | FloatToDouble =>
+                "(double)"
+            })
+            print(lhs)
+            print(')')
+          } else {
+            print(lhs)
+            print((op: @switch) match {
+              case String_length => ".length"
+              case CheckNotNull  => ".notNull"
+            })
+          }
 
         case BinaryOp(BinaryOp.Int_-, IntLiteral(0), rhs) =>
           print("(-")
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala b/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
index 411f6b9a95..34804cc421 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
@@ -283,11 +283,16 @@ object Trees {
     val tpe = AnyType
   }
 
-  /** Unary operation (always preserves pureness). */
+  /** Unary operation.
+   *
+   *  `CheckNotNull` throws NPEs subject to UB.
+   *
+   *  Otherwise, unary operations preserve pureness.
+   */
   sealed case class UnaryOp(op: UnaryOp.Code, lhs: Tree)(
       implicit val pos: Position) extends Tree {
 
-    val tpe = UnaryOp.resultTypeOf(op)
+    val tpe = UnaryOp.resultTypeOf(op, lhs.tpe)
   }
 
   object UnaryOp {
@@ -322,7 +327,10 @@ object Trees {
     // String.length, introduced in 1.11
     final val String_length = 17
 
-    def resultTypeOf(op: Code): Type = (op: @switch) match {
+    // New in 1.17
+    final val CheckNotNull = 18
+
+    def resultTypeOf(op: Code, argType: Type): Type = (op: @switch) match {
       case Boolean_! =>
         BooleanType
       case IntToChar =>
@@ -339,6 +347,8 @@ object Trees {
         FloatType
       case IntToDouble | LongToDouble | FloatToDouble =>
         DoubleType
+      case CheckNotNull =>
+        argType.toNonNullable
     }
   }
 
diff --git a/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala b/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala
index 590a24c209..f3cef80ffa 100644
--- a/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala
+++ b/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala
@@ -392,6 +392,8 @@ class PrintersTest {
     assertPrintEquals("((float)x)", UnaryOp(LongToFloat, ref("x", LongType)))
 
     assertPrintEquals("x.length", UnaryOp(String_length, ref("x", StringType)))
+
+    assertPrintEquals("x.notNull", UnaryOp(CheckNotNull, ref("x", AnyType)))
   }
 
   @Test def printPseudoUnaryOp(): Unit = {
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
index 953a54241f..4e322050b2 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
@@ -1030,7 +1030,7 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
                 }
                 result
 
-              case UnaryOp(op, lhs) =>
+              case UnaryOp(op, lhs) if op != UnaryOp.CheckNotNull || noExtractYet =>
                 UnaryOp(op, rec(lhs))
               case BinaryOp(op, lhs, rhs) =>
                 val newRhs = rec(rhs)
@@ -1097,8 +1097,6 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
               case Transient(ObjectClassName(obj)) =>
                 Transient(ObjectClassName(rec(obj)))
 
-              case Transient(CheckNotNull(obj)) if noExtractYet =>
-                Transient(CheckNotNull(rec(obj)))
               case Transient(NativeArrayWrapper(elemClass, nativeArray)) if noExtractYet =>
                 val newNativeArray = rec(nativeArray)
                 val newElemClass = rec(elemClass)
@@ -1276,7 +1274,7 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
         case Block(trees)            => trees forall test
         case If(cond, thenp, elsep)  => test(cond) && test(thenp) && test(elsep)
         case BinaryOp(_, lhs, rhs)   => test(lhs) && test(rhs)
-        case UnaryOp(_, lhs)         => test(lhs)
+        case UnaryOp(op, lhs)        => if (op == UnaryOp.CheckNotNull) testNPE(lhs) else test(lhs)
         case ArrayLength(array)      => testNPE(array)
         case RecordSelect(record, _) => test(record)
         case IsInstanceOf(expr, _)   => test(expr)
@@ -1336,8 +1334,6 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
           allowSideEffects && args.forall(test)
 
         // Transients with side effects.
-        case Transient(CheckNotNull(obj)) =>
-          allowSideEffects && test(obj)
         case Transient(TypedArrayToArray(expr, primRef)) =>
           allowSideEffects && test(expr) // may TypeError
 
@@ -1821,11 +1817,6 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
             }
           }
 
-        case Transient(CheckNotNull(obj)) =>
-          unnest(obj) { (newObj, env) =>
-            redo(Transient(CheckNotNull(newObj)))(env)
-          }
-
         case Transient(Cast(expr, tpe)) =>
           unnest(expr) { (newExpr, env) =>
             redo(Transient(Cast(newExpr, tpe)))(env)
@@ -2330,7 +2321,7 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
 
         case UnaryOp(op, lhs) =>
           import UnaryOp._
-          val newLhs = transformExpr(lhs, preserveChar = op == CharToInt)
+          val newLhs = transformExpr(lhs, preserveChar = (op == CharToInt || op == CheckNotNull))
           (op: @switch) match {
             case Boolean_! => js.UnaryOp(JSUnaryOp.!, newLhs)
 
@@ -2387,6 +2378,13 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
             // String.length
             case String_length =>
               genIdentBracketSelect(newLhs, "length")
+
+            // Null check
+            case CheckNotNull =>
+              if (semantics.nullPointers == CheckedBehavior.Unchecked)
+                newLhs
+              else
+                genCallHelper(VarField.n, newLhs)
           }
 
         case BinaryOp(op, lhs, rhs) =>
@@ -2762,9 +2760,6 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
 
         // Transients
 
-        case Transient(CheckNotNull(obj)) =>
-          genCallHelper(VarField.n, transformExpr(obj, preserveChar = true))
-
         case Transient(Cast(expr, tpe)) =>
           val newExpr = transformExpr(expr, preserveChar = true)
           if (tpe == CharType && expr.tpe != CharType)
@@ -3208,7 +3203,7 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
       if (semantics.nullPointers == CheckedBehavior.Unchecked || !tree.tpe.isNullable)
         tree
       else
-        Transient(CheckNotNull(tree))
+        UnaryOp(UnaryOp.CheckNotNull, tree)
     }
 
     private def transformParamDef(paramDef: ParamDef): js.ParamDef =
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Transients.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Transients.scala
index bf0aa319ae..5c199fa0be 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Transients.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Transients.scala
@@ -21,30 +21,6 @@ import org.scalajs.ir.Types._
 
 object Transients {
 
-  /** Checks that `obj ne null`, then returns `obj`.
-   *
-   *  If `obj eq null`, throw a `NullPointerException`, or a corresponding
-   *  `UndefinedBehaviorError`.
-   *
-   *  This node must not be used when NPEs are Unchecked.
-   */
-  final case class CheckNotNull(obj: Tree) extends Transient.Value {
-    val tpe: Type = obj.tpe.toNonNullable
-
-    def traverse(traverser: Traverser): Unit =
-      traverser.traverse(obj)
-
-    def transform(transformer: Transformer, isStat: Boolean)(
-        implicit pos: Position): Tree = {
-      Transient(CheckNotNull(transformer.transformExpr(obj)))
-    }
-
-    def printIR(out: IRTreePrinter): Unit = {
-      out.print("$n")
-      out.printArgs(List(obj))
-    }
-  }
-
   /** Casts `expr` to the given `tpe`, without any check.
    *
    *  This operation is only valid if we know that `expr` is indeed a value of
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
index 02c981ea4e..f0e57a2323 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
@@ -1408,6 +1408,10 @@ private class FunctionEmitter private (
       // String.length
       case String_length =>
         fb += wa.Call(genFunctionID.stringLength)
+
+      // Null check
+      case CheckNotNull =>
+        genAsNonNullOrNPEFor(lhs)
     }
 
     tree.tpe
@@ -3251,11 +3255,6 @@ private class FunctionEmitter private (
 
   private def genTransient(tree: Transient): Type = {
     tree.value match {
-      case Transients.CheckNotNull(expr) =>
-        genTreeAuto(expr)
-        genAsNonNullOrNPEFor(expr)
-        tree.tpe
-
       case Transients.Cast(expr, tpe) =>
         genCast(expr, tpe, tree.pos)
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala b/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
index eb12a06b3a..7efab4d3c4 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
@@ -443,6 +443,8 @@ private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter) {
             DoubleType
           case String_length =>
             StringType
+          case CheckNotNull =>
+            AnyType
         }
         typecheckExpect(lhs, env, expectedArgType)
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
index 74255c7ed7..df0b8d72b2 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
@@ -865,7 +865,10 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
         case Closure(_, _, _, _, _, captureValues) =>
           captureValues.forall(isTriviallySideEffectFree(_))
 
-        case GetClass(expr) =>
+        case UnaryOp(UnaryOp.CheckNotNull, expr) =>
+          config.coreSpec.semantics.nullPointers == CheckedBehavior.Unchecked &&
+          isTriviallySideEffectFree(expr)
+        case GetClass(expr) => // Before 1.17, we used GetClass as CheckNotNull
           config.coreSpec.semantics.nullPointers == CheckedBehavior.Unchecked &&
           isTriviallySideEffectFree(expr)
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
index 59663392bf..5cd5045084 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
@@ -1545,8 +1545,12 @@ private[optimizer] abstract class OptimizerCore(
   private def finishTransformStat(stat: PreTransform): Tree = stat match {
     case PreTransBlock(bindingsAndStats, result) =>
       finishTransformBindings(bindingsAndStats, finishTransformStat(result))
-    case PreTransUnaryOp(_, lhs) =>
-      finishTransformStat(lhs)
+
+    case PreTransUnaryOp(op, lhs) =>
+      if (op == UnaryOp.CheckNotNull)
+        finishTransformExpr(stat)
+      else
+        finishTransformStat(lhs)
 
     case PreTransBinaryOp(op, lhs, rhs) =>
       // Here we need to preserve the side-effects of integer division/modulo and String_charAt
@@ -1669,7 +1673,7 @@ private[optimizer] abstract class OptimizerCore(
       checkNotNullStatement(qualifier)(stat.pos)
     case Closure(_, _, _, _, _, captureValues) =>
       Block(captureValues.map(keepOnlySideEffects))(stat.pos)
-    case UnaryOp(_, arg) =>
+    case UnaryOp(op, arg) if op != UnaryOp.CheckNotNull =>
       keepOnlySideEffects(arg)
     case If(cond, thenp, elsep) =>
       (keepOnlySideEffects(thenp), keepOnlySideEffects(elsep)) match {
@@ -1911,7 +1915,7 @@ private[optimizer] abstract class OptimizerCore(
           recs(args).mapOrFailed(ApplyStatic(flags, className, method, _)(body.tpe))
 
         case UnaryOp(op, arg) =>
-          rec(arg).mapOrKeepGoing(UnaryOp(op, _))
+          rec(arg).mapOrKeepGoingIf(UnaryOp(op, _))(keepGoingIf = op != UnaryOp.CheckNotNull)
 
         case BinaryOp(op, lhs, rhs) =>
           import BinaryOp._
@@ -3923,6 +3927,11 @@ private[optimizer] abstract class OptimizerCore(
             default
         }
 
+      // Null check
+
+      case CheckNotNull =>
+        checkNotNull(arg)
+
       case _ =>
         default
     }
@@ -5261,14 +5270,12 @@ private[optimizer] abstract class OptimizerCore(
   }
 
   private def checkNotNull(texpr: PreTransform)(implicit pos: Position): PreTransform = {
-    if (!texpr.tpe.isNullable) {
+    if (!texpr.tpe.isNullable)
       texpr
-    } else if (semantics.nullPointers == CheckedBehavior.Unchecked) {
+    else if (semantics.nullPointers == CheckedBehavior.Unchecked)
       foldCast(texpr, texpr.tpe.base.toNonNullable)
-    } else {
-      PreTransTree(Transient(CheckNotNull(finishTransformExpr(texpr))),
-          texpr.tpe.toNonNullable)
-    }
+    else
+      PreTransUnaryOp(UnaryOp.CheckNotNull, texpr)
   }
 
   private def checkNotNull(expr: Tree)(implicit pos: Position): Tree = {
@@ -5277,21 +5284,21 @@ private[optimizer] abstract class OptimizerCore(
     else if (semantics.nullPointers == CheckedBehavior.Unchecked)
       makeCast(expr, expr.tpe.toNonNullable)
     else
-      Transient(CheckNotNull(expr))
+      UnaryOp(UnaryOp.CheckNotNull, expr)
   }
 
   private def checkNotNullStatement(texpr: PreTransform)(implicit pos: Position): Tree = {
     if (!texpr.tpe.isNullable || semantics.nullPointers == CheckedBehavior.Unchecked)
       finishTransformStat(texpr)
     else
-      Transient(CheckNotNull(finishTransformExpr(texpr)))
+      UnaryOp(UnaryOp.CheckNotNull, finishTransformExpr(texpr))
   }
 
   private def checkNotNullStatement(expr: Tree)(implicit pos: Position): Tree = {
     if (!expr.tpe.isNullable || semantics.nullPointers == CheckedBehavior.Unchecked)
       keepOnlySideEffects(expr)
     else
-      Transient(CheckNotNull(expr))
+      UnaryOp(UnaryOp.CheckNotNull, expr)
   }
 
   private def newParamReplacement(paramDef: ParamDef): ((LocalName, LocalDef), ParamDef) = {
@@ -6195,7 +6202,7 @@ private[optimizer] object OptimizerCore {
       lhs: PreTransform)(implicit val pos: Position)
       extends PreTransResult {
 
-    val tpe: RefinedType = RefinedType(UnaryOp.resultTypeOf(op))
+    val tpe: RefinedType = RefinedType(UnaryOp.resultTypeOf(op, lhs.tpe.base))
   }
 
   /** A `PreTransform` for a `BinaryOp`. */
diff --git a/project/BinaryIncompatibilities.scala b/project/BinaryIncompatibilities.scala
index 3567e90ef1..3606a501a3 100644
--- a/project/BinaryIncompatibilities.scala
+++ b/project/BinaryIncompatibilities.scala
@@ -9,6 +9,8 @@ object BinaryIncompatibilities {
 
     ProblemFilters.exclude[IncompatibleResultTypeProblem]("org.scalajs.ir.Trees#*.tpe"),
 
+    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Trees#UnaryOp.resultTypeOf"),
+
     ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Types#ClassType.this"),
     ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Types#ClassType.apply"),
     ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Types#ClassType.copy"),
diff --git a/project/Build.scala b/project/Build.scala
index d7ef98562f..8c0837ca92 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -2056,7 +2056,7 @@ object Build {
               Some(ExpectedSizes(
                   fastLink = 425000 to 426000,
                   fullLink = 282000 to 283000,
-                  fastLinkGz = 61000 to 62000,
+                  fastLinkGz = 60000 to 61000,
                   fullLinkGz = 43000 to 44000,
               ))
             }

From 086477a61c0f41777218d69b890d96009c859159 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Tue, 17 Sep 2024 17:49:43 +0200
Subject: [PATCH 158/298] Make the `itables` field of objects non-nullable.

Previously, classes that do not implement any interface had a
`null` value for their `itables` field. Now, they all use a shared
instance of `(ref $itables)` that contains `null`s everywhere.

This removes a code path for interface type tests. More importantly,
it removes one source of null checks along the code paths for
interface method calls.
---
 .../backend/wasmemitter/ClassEmitter.scala    | 24 ++++++-------------
 .../backend/wasmemitter/CoreWasmLib.scala     | 17 +++++++++++--
 .../linker/backend/wasmemitter/VarGen.scala   |  1 +
 3 files changed, 23 insertions(+), 19 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/ClassEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/ClassEmitter.scala
index e96fcdc04e..6f400ed145 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/ClassEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/ClassEmitter.scala
@@ -354,7 +354,7 @@ class ClassEmitter(coreSpec: CoreSpec) {
     val itablesField = watpe.StructField(
       genFieldID.objStruct.itables,
       itablesOriginalName,
-      watpe.RefType.nullable(genTypeID.itables),
+      watpe.RefType(genTypeID.itables),
       isMutable = false
     )
     val fields = classInfo.allFieldDefs.map { field =>
@@ -475,8 +475,6 @@ class ClassEmitter(coreSpec: CoreSpec) {
        */
       fb += wa.I32Const(0) // false
     } else {
-      val itables = fb.addLocal("itables", watpe.RefType.nullable(genTypeID.itables))
-
       fb.block(watpe.RefType.anyref) { testFail =>
         // if expr is not an instance of Object, return false
         fb += wa.LocalGet(exprParam)
@@ -486,18 +484,10 @@ class ClassEmitter(coreSpec: CoreSpec) {
           watpe.RefType(genTypeID.ObjectStruct)
         )
 
-        // get itables and store
+        /* Test whether the itable at the target interface's slot is indeed an
+         * instance of that interface's itable struct type.
+         */
         fb += wa.StructGet(genTypeID.ObjectStruct, genFieldID.objStruct.itables)
-        fb += wa.LocalSet(itables)
-
-        // Dummy return value from the block
-        fb += wa.RefNull(watpe.HeapType.Any)
-
-        // if the itables is null (no interfaces are implemented)
-        fb += wa.LocalGet(itables)
-        fb += wa.BrOnNull(testFail)
-
-        fb += wa.LocalGet(itables)
         fb += wa.StructGet(
           genTypeID.itables,
           genFieldID.itablesStruct.itableSlot(classInfo.itableIdx)
@@ -615,7 +605,7 @@ class ClassEmitter(coreSpec: CoreSpec) {
     if (classInfo.classImplementsAnyInterface)
       fb += wa.GlobalGet(genGlobalID.forITable(className))
     else
-      fb += wa.RefNull(watpe.HeapType(genTypeID.itables))
+      fb += wa.GlobalGet(genGlobalID.emptyITable)
 
     classInfo.allFieldDefs.foreach { f =>
       fb += genZeroOf(f.ftpe)
@@ -791,8 +781,8 @@ class ClassEmitter(coreSpec: CoreSpec) {
 
   /** Generates the global instance of the class itable.
    *
-   *  Their init value will be an array of null refs of size = number of interfaces.
-   *  They will be initialized in start function.
+   *  If the class implements no interface at all, we skip this step. Instead,
+   *  we will use the unique `emptyITable` as itable for this class.
    */
   private def genGlobalClassItable(clazz: LinkedClass)(implicit ctx: WasmContext): Unit = {
     val className = clazz.className
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
index 8e273591f0..fbd2c4290d 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
@@ -106,6 +106,7 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
 
     genImports()
 
+    genEmptyITable()
     genPrimitiveTypeDataGlobals()
 
     genHelperDefinitions()
@@ -223,7 +224,7 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
     val itablesField = StructField(
       genFieldID.objStruct.itables,
       OriginalName(genFieldID.objStruct.itables.toString()),
-      RefType.nullable(genTypeID.itables),
+      RefType(genTypeID.itables),
       isMutable = false
     )
 
@@ -515,6 +516,18 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
 
   // --- Global definitions ---
 
+  private def genEmptyITable()(implicit ctx: WasmContext): Unit = {
+    ctx.addGlobal(
+      Global(
+        genGlobalID.emptyITable,
+        OriginalName(genGlobalID.emptyITable.toString()),
+        isMutable = false,
+        RefType(genTypeID.itables),
+        Expr(List(StructNewDefault(genTypeID.itables)))
+      )
+    )
+  }
+
   private def genPrimitiveTypeDataGlobals()(implicit ctx: WasmContext): Unit = {
     import genFieldID.typeData._
 
@@ -2550,7 +2563,7 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
     val i32ArrayType = RefType(genTypeID.i32Array)
     val objectVTableType = RefType(genTypeID.ObjectVTable)
     val arrayTypeDataType = objectVTableType
-    val itablesType = RefType.nullable(genTypeID.itables)
+    val itablesType = RefType(genTypeID.itables)
     val nonNullObjectType = RefType(genTypeID.ObjectStruct)
     val anyArrayType = RefType(genTypeID.anyArray)
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
index e03f8ce8f8..ad2214a1be 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
@@ -44,6 +44,7 @@ object VarGen {
     case object bZeroChar extends GlobalID
     case object bZeroLong extends GlobalID
     case object stringLiteralCache extends GlobalID
+    case object emptyITable extends GlobalID
     case object arrayClassITable extends GlobalID
     case object lastIDHashCode extends GlobalID
 

From 5188b70af1bdeee7e1b7f5c0981e40a2d8e29358 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Mon, 16 Sep 2024 21:44:31 +0200
Subject: [PATCH 159/298] Avoid a JS helper call for nullable `jl.String`s in
 string concatenation.

We can take care of the `null` case entirely on the Wasm side.
---
 .../backend/wasmemitter/FunctionEmitter.scala      | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
index 83fb110272..d333e1c078 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
@@ -1793,10 +1793,16 @@ private class FunctionEmitter private (
 
       case ClassType(BoxedStringClass, nullable) =>
         // Common case for which we want to avoid the hijacked class dispatch
-        genTreeAuto(tree)
-        markPosition(tree)
-        if (nullable)
-          fb += wa.Call(genFunctionID.jsValueToStringForConcat)
+        if (nullable) {
+          fb.block(watpe.RefType.any) { notNullLabel =>
+            genTreeAuto(tree)
+            markPosition(tree)
+            fb += wa.BrOnNonNull(notNullLabel)
+            fb ++= ctx.stringPool.getConstantStringInstr("null")
+          }
+        } else {
+          genTreeAuto(tree)
+        }
 
       case ClassType(className, _) =>
         genWithDispatch(ctx.getClassInfo(className).isAncestorOfHijackedClass)

From 360ce69a07c80b7958c4d1d98a600b31233dcd82 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Fri, 30 Aug 2024 19:15:08 +0200
Subject: [PATCH 160/298] Wasm: Translate string types to `(ref null? extern)`.

Instead of `(ref null? any)`.

This causes a lot of additional conversions between `extern`s and
`any`s when boxing and unboxing, without any added value. This is
only a stepping stone for the next commit. In the latter, we will
start using JS string builtins, which manipulate `extern`s. We will
want strings to already be typed as `extern`s for all the string
manipulations.
---
 .../backend/wasmemitter/ClassEmitter.scala    |  3 +-
 .../backend/wasmemitter/CoreWasmLib.scala     | 94 ++++++++++---------
 .../linker/backend/wasmemitter/Emitter.scala  |  5 +-
 .../backend/wasmemitter/FunctionEmitter.scala | 67 ++++++++++---
 .../linker/backend/wasmemitter/README.md      | 41 ++++----
 .../linker/backend/wasmemitter/SWasmGen.scala |  4 +
 .../backend/wasmemitter/StringPool.scala      |  4 +-
 .../backend/wasmemitter/TypeTransformer.scala |  6 +-
 .../linker/backend/wasmemitter/VarGen.scala   |  3 +
 9 files changed, 143 insertions(+), 84 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/ClassEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/ClassEmitter.scala
index 6f400ed145..caa266fd10 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/ClassEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/ClassEmitter.scala
@@ -286,7 +286,7 @@ class ClassEmitter(coreSpec: CoreSpec) {
         // componentType - always `null` since this method is not used for array types
         wa.RefNull(watpe.HeapType(genTypeID.typeData)),
         // name - initially `null`; filled in by the `typeDataName` helper
-        wa.RefNull(watpe.HeapType.Any),
+        wa.RefNull(watpe.HeapType.NoExtern),
         // the classOf instance - initially `null`; filled in by the `createClassOf` helper
         wa.RefNull(watpe.HeapType(genTypeID.ClassStruct)),
         // arrayOf, the typeData of an array of this type - initially `null`; filled in by the `arrayTypeData` helper
@@ -968,6 +968,7 @@ class ClassEmitter(coreSpec: CoreSpec) {
           case StringLiteral(value) =>
             // Common shape for all the `nameTree` expressions
             fb ++= ctx.stringPool.getConstantStringInstr(value)
+            fb += wa.AnyConvertExtern
 
           case VarRef(LocalIdent(localName)) if classCaptureParamsOfTypeAny.contains(localName) =>
             /* Common shape for the `jsSuperClass` value
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
index fbd2c4290d..10d75cfe6b 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
@@ -77,7 +77,7 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
       make(specialInstanceTypes, Int32, isMutable = false),
       make(strictAncestors, nullable(genTypeID.typeDataArray), isMutable = false),
       make(componentType, nullable(genTypeID.typeData), isMutable = false),
-      make(name, RefType.anyref, isMutable = true),
+      make(name, RefType.externref, isMutable = true),
       make(classOfValue, nullable(genTypeID.ClassStruct), isMutable = true),
       make(arrayOf, nullable(genTypeID.ObjectVTable), isMutable = true),
       make(cloneFunction, nullable(genTypeID.cloneFunctionType), isMutable = false),
@@ -138,6 +138,8 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
     genUnderlyingArrayType(genTypeID.f32Array, Float32)
     genUnderlyingArrayType(genTypeID.f64Array, Float64)
     genUnderlyingArrayType(genTypeID.anyArray, anyref)
+
+    genUnderlyingArrayType(genTypeID.externrefArray, RefType.externref)
   }
 
   private def genCoreTypesInRecType()(implicit ctx: WasmContext): Unit = {
@@ -300,7 +302,7 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
     addGlobalHelperImport(genGlobalID.bFalse, RefType.any)
     addGlobalHelperImport(genGlobalID.bTrue, RefType.any)
     addGlobalHelperImport(genGlobalID.bZero, RefType.any)
-    addGlobalHelperImport(genGlobalID.emptyString, RefType.any)
+    addGlobalHelperImport(genGlobalID.emptyString, RefType.extern)
     addGlobalHelperImport(genGlobalID.idHashCodeMap, RefType.extern)
   }
 
@@ -365,29 +367,29 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
       List(RefType.any)
     )
 
-    addHelperImport(genFunctionID.stringLength, List(RefType.any), List(Int32))
-    addHelperImport(genFunctionID.stringCharAt, List(RefType.any, Int32), List(Int32))
-    addHelperImport(genFunctionID.jsValueToString, List(RefType.any), List(RefType.any))
-    addHelperImport(genFunctionID.jsValueToStringForConcat, List(anyref), List(RefType.any))
-    addHelperImport(genFunctionID.booleanToString, List(Int32), List(RefType.any))
-    addHelperImport(genFunctionID.charToString, List(Int32), List(RefType.any))
-    addHelperImport(genFunctionID.intToString, List(Int32), List(RefType.any))
-    addHelperImport(genFunctionID.longToString, List(Int64), List(RefType.any))
-    addHelperImport(genFunctionID.doubleToString, List(Float64), List(RefType.any))
+    addHelperImport(genFunctionID.stringLength, List(RefType.extern), List(Int32))
+    addHelperImport(genFunctionID.stringCharAt, List(RefType.extern, Int32), List(Int32))
+    addHelperImport(genFunctionID.jsValueToString, List(RefType.any), List(RefType.extern))
+    addHelperImport(genFunctionID.jsValueToStringForConcat, List(anyref), List(RefType.extern))
+    addHelperImport(genFunctionID.booleanToString, List(Int32), List(RefType.extern))
+    addHelperImport(genFunctionID.charToString, List(Int32), List(RefType.extern))
+    addHelperImport(genFunctionID.intToString, List(Int32), List(RefType.extern))
+    addHelperImport(genFunctionID.longToString, List(Int64), List(RefType.extern))
+    addHelperImport(genFunctionID.doubleToString, List(Float64), List(RefType.extern))
     addHelperImport(
       genFunctionID.stringConcat,
-      List(RefType.any, RefType.any),
-      List(RefType.any)
+      List(RefType.extern, RefType.extern),
+      List(RefType.extern)
     )
     addHelperImport(genFunctionID.isString, List(anyref), List(Int32))
 
     addHelperImport(genFunctionID.jsValueType, List(RefType.any), List(Int32))
-    addHelperImport(genFunctionID.jsValueDescription, List(anyref), List(RefType.any))
+    addHelperImport(genFunctionID.jsValueDescription, List(anyref), List(RefType.extern))
     addHelperImport(genFunctionID.bigintHashCode, List(RefType.any), List(Int32))
     addHelperImport(
       genFunctionID.symbolDescription,
       List(RefType.any),
-      List(RefType.anyref)
+      List(RefType.externref)
     )
     addHelperImport(
       genFunctionID.idHashCodeGet,
@@ -404,7 +406,7 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
       genFunctionID.genJSTypeMetaData,
       List(
         RefType(genTypeID.typeData), // typeData
-        RefType.any, // name
+        RefType.extern, // name
         Int32, // isPrimitive
         Int32, // isArrayClass
         Int32, // isInterface,
@@ -416,13 +418,13 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
       ),
       List(RefType.any)
     )
-    addHelperImport(genFunctionID.makeTypeError, List(RefType.any), List(RefType.extern))
+    addHelperImport(genFunctionID.makeTypeError, List(RefType.extern), List(RefType.extern))
     addHelperImport(genFunctionID.jsArrayLength, List(anyref), List(Int32))
     addHelperImport(genFunctionID.jsArrayGetInt, List(anyref, Int32), List(Int32))
 
-    addHelperImport(genFunctionID.jsGlobalRefGet, List(RefType.any), List(anyref))
-    addHelperImport(genFunctionID.jsGlobalRefSet, List(RefType.any, anyref), Nil)
-    addHelperImport(genFunctionID.jsGlobalRefTypeof, List(RefType.any), List(RefType.any))
+    addHelperImport(genFunctionID.jsGlobalRefGet, List(RefType.extern), List(anyref))
+    addHelperImport(genFunctionID.jsGlobalRefSet, List(RefType.extern, anyref), Nil)
+    addHelperImport(genFunctionID.jsGlobalRefTypeof, List(RefType.extern), List(RefType.any))
     addHelperImport(genFunctionID.jsNewArray, Nil, List(RefType.any))
     addHelperImport(genFunctionID.jsArrayPush, List(RefType.any, anyref), List(RefType.any))
     addHelperImport(
@@ -554,7 +556,7 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
       // componentType
       RefNull(HeapType.None),
       // name - initially `null`; filled in by the `typeDataName` helper
-      RefNull(HeapType.None),
+      RefNull(HeapType.NoExtern),
       // the classOf instance - initially `null`; filled in by the `createClassOf` helper
       RefNull(HeapType.None),
       // arrayOf, the typeData of an array of this type - initially `null`; filled in by the `arrayTypeData` helper
@@ -820,14 +822,14 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
     val offsetParam = fb.addParam("offset", Int32)
     val sizeParam = fb.addParam("size", Int32)
     val stringIndexParam = fb.addParam("stringIndex", Int32)
-    fb.setResultType(RefType.any)
+    fb.setResultType(RefType.extern)
 
-    val str = fb.addLocal("str", RefType.any)
+    val str = fb.addLocal("str", RefType.extern)
 
-    fb.block(RefType.any) { cacheHit =>
+    fb.block(RefType.extern) { cacheHit =>
       fb += GlobalGet(genGlobalID.stringLiteralCache)
       fb += LocalGet(stringIndexParam)
-      fb += ArrayGet(genTypeID.anyArray)
+      fb += ArrayGet(genTypeID.externrefArray)
 
       fb += BrOnNonNull(cacheHit)
 
@@ -840,7 +842,7 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
       fb += ArrayNewData(genTypeID.i16Array, genDataID.string)
       fb += Call(genFunctionID.createStringFromData)
       fb += LocalTee(str)
-      fb += ArraySet(genTypeID.anyArray)
+      fb += ArraySet(genTypeID.externrefArray)
 
       fb += LocalGet(str)
     }
@@ -848,17 +850,17 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
     fb.buildAndAddToModule()
   }
 
-  /** `createStringFromData: (ref array u16) -> (ref any)` (representing a `string`). */
+  /** `createStringFromData: (ref array u16) -> (ref extern)` (representing a `string`). */
   private def genCreateStringFromData()(implicit ctx: WasmContext): Unit = {
     val dataType = RefType(genTypeID.i16Array)
 
     val fb = newFunctionBuilder(genFunctionID.createStringFromData)
     val dataParam = fb.addParam("data", dataType)
-    fb.setResultType(RefType.any)
+    fb.setResultType(RefType.extern)
 
     val lenLocal = fb.addLocal("len", Int32)
     val iLocal = fb.addLocal("i", Int32)
-    val resultLocal = fb.addLocal("result", RefType.any)
+    val resultLocal = fb.addLocal("result", RefType.extern)
 
     // len := data.length
     fb += LocalGet(dataParam)
@@ -907,7 +909,7 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
     fb.buildAndAddToModule()
   }
 
-  /** `typeDataName: (ref typeData) -> (ref any)` (representing a `string`).
+  /** `typeDataName: (ref typeData) -> (ref extern)` (representing a `string`).
    *
    *  Initializes the `name` field of the given `typeData` if that was not done yet, and returns its
    *  value.
@@ -924,14 +926,14 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
 
     val fb = newFunctionBuilder(genFunctionID.typeDataName)
     val typeDataParam = fb.addParam("typeData", typeDataType)
-    fb.setResultType(RefType.any)
+    fb.setResultType(RefType.extern)
 
     val componentTypeDataLocal = fb.addLocal("componentTypeData", typeDataType)
     val componentNameDataLocal = fb.addLocal("componentNameData", nameDataType)
     val firstCharLocal = fb.addLocal("firstChar", Int32)
-    val nameLocal = fb.addLocal("name", RefType.any)
+    val nameLocal = fb.addLocal("name", RefType.extern)
 
-    fb.block(RefType.any) { alreadyInitializedLabel =>
+    fb.block(RefType.extern) { alreadyInitializedLabel =>
       // br_on_non_null $alreadyInitialized typeData.name
       fb += LocalGet(typeDataParam)
       fb += StructGet(genTypeID.typeData, genFieldID.typeData.name)
@@ -945,7 +947,7 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
       fb += StructGet(genTypeID.typeData, genFieldID.typeData.kind)
       fb += I32Const(KindArray)
       fb += I32Eq
-      fb.ifThenElse(RefType.any) {
+      fb.ifThenElse(RefType.extern) {
         // it is an array; compute its name from the component type name
 
         // <top of stack> := "[", for the CALL to stringConcat near the end
@@ -963,7 +965,7 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
 
         // switch (componentTypeData.kind)
         // the result of this switch is the string that must come after "["
-        fb.switch(RefType.any) { () =>
+        fb.switch(RefType.extern) { () =>
           // scrutinee
           fb += LocalGet(componentTypeDataLocal)
           fb += StructGet(genTypeID.typeData, genFieldID.typeData.kind)
@@ -1145,7 +1147,7 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
     fb.buildAndAddToModule()
   }
 
-  /** `valueDescription: anyref -> (ref any)` (a string).
+  /** `valueDescription: anyref -> (ref extern)` (a string).
    *
    *  Returns a safe string description of a value. This helper is never called
    *  for `value === null`. As implemented, it would return `"object"` if it were.
@@ -1155,7 +1157,7 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
 
     val fb = newFunctionBuilder(genFunctionID.valueDescription)
     val valueParam = fb.addParam("value", anyref)
-    fb.setResultType(RefType.any)
+    fb.setResultType(RefType.extern)
 
     fb.block(anyref) { notOurObjectLabel =>
       fb.block(objectType) { isCharLabel =>
@@ -1351,6 +1353,7 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
                   fb += GlobalGet(genGlobalID.undef)
                 case StringType =>
                   fb += LocalGet(objParam)
+                  fb += ExternConvertAny
                   fb += RefAsNonNull
                 case primType: PrimTypeWithRef =>
                   fb += LocalGet(objParam)
@@ -1358,6 +1361,8 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
               }
             } else {
               fb += LocalGet(objParam)
+              if (primType == StringType)
+                fb += ExternConvertAny
             }
 
             fb += Return
@@ -1760,7 +1765,7 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
         )
 
         fb += LocalGet(typeDataParam) // componentType
-        fb += RefNull(HeapType.None) // name
+        fb += RefNull(HeapType.NoExtern) // name
         fb += RefNull(HeapType.None) // classOf
         fb += RefNull(HeapType.None) // arrayOf
 
@@ -1841,14 +1846,14 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
     fb.buildAndAddToModule()
   }
 
-  /** `checkedStringCharAt: (ref any), i32 -> i32`.
+  /** `checkedStringCharAt: (ref extern), i32 -> i32`.
    *
    *  Accesses a char of a string by index. Used when stringIndexOutOfBounds
    *  are checked.
    */
   private def genCheckedStringCharAt()(implicit ctx: WasmContext): Unit = {
     val fb = newFunctionBuilder(genFunctionID.checkedStringCharAt)
-    val strParam = fb.addParam("str", RefType.any)
+    val strParam = fb.addParam("str", RefType.extern)
     val indexParam = fb.addParam("index", Int32)
     fb.setResultType(Int32)
 
@@ -2364,7 +2369,7 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
     fb.buildAndAddToModule()
   }
 
-  /** `anyGetClassName: (ref any) -> (ref any)` (a string).
+  /** `anyGetClassName: (ref any) -> (ref extern)` (a string).
    *
    *  This is the implementation of `value.getClass().getName()`, which comes
    *  to the backend as the `ObjectClassName` intrinsic.
@@ -2372,7 +2377,7 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
   private def genAnyGetClassName()(implicit ctx: WasmContext): Unit = {
     val fb = newFunctionBuilder(genFunctionID.anyGetClassName)
     val valueParam = fb.addParam("value", RefType.any)
-    fb.setResultType(RefType.any)
+    fb.setResultType(RefType.extern)
 
     if (semantics.nullPointers == CheckedBehavior.Unchecked) {
       fb += LocalGet(valueParam)
@@ -2788,6 +2793,7 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
         },
         List(JSValueTypeString) -> { () =>
           fb += LocalGet(objNonNullLocal)
+          fb += ExternConvertAny
           fb += Call(
             genFunctionID.forMethod(Public, BoxedStringClass, hashCodeMethodName)
           )
@@ -3095,7 +3101,7 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
     maybeWrapInUBE(fb, semantics.arrayIndexOutOfBounds) {
       genNewScalaClass(fb, ArrayIndexOutOfBoundsExceptionClass,
           SpecialNames.StringArgConstructorName) {
-        fb += RefNull(HeapType.None)
+        fb += RefNull(HeapType.NoExtern)
       }
     }
     fb += ExternConvertAny
@@ -3276,7 +3282,7 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
       maybeWrapInUBE(fb, semantics.arrayStores) {
         genNewScalaClass(fb, ArrayStoreExceptionClass,
             SpecialNames.StringArgConstructorName) {
-          fb += RefNull(HeapType.None)
+          fb += RefNull(HeapType.NoExtern)
         }
       }
       fb += ExternConvertAny
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala
index 23ae3c9b34..93b00423de 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala
@@ -199,7 +199,10 @@ final class Emitter(config: Emitter.Config) {
         case ModuleInitializerImpl.MainMethodWithArgs(className, encodedMainMethodName, args) =>
           val stringArrayTypeRef = ArrayTypeRef(ClassRef(BoxedStringClass), 1)
           SWasmGen.genArrayValue(fb, stringArrayTypeRef, args.size) {
-            args.foreach(arg => fb ++= ctx.stringPool.getConstantStringInstr(arg))
+            for (arg <- args) {
+              fb ++= ctx.stringPool.getConstantStringInstr(arg)
+              fb += wa.AnyConvertExtern
+            }
           }
           genCallStatic(className, encodedMainMethodName)
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
index d333e1c078..37554f66db 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
@@ -633,7 +633,10 @@ private class FunctionEmitter private (
         // box
         primType match {
           case NullType =>
-            ()
+            expectedType match {
+              case ClassType(BoxedStringClass, true) => fb += wa.ExternConvertAny
+              case _                                 => ()
+            }
           case ByteType | ShortType =>
             fb += wa.RefI31
           case CharType =>
@@ -656,6 +659,11 @@ private class FunctionEmitter private (
              */
             fb += wa.Call(genFunctionID.box(primType.primRef))
         }
+      case (StringType | ClassType(BoxedStringClass, _), _) =>
+        expectedType match {
+          case ClassType(BoxedStringClass, _) => ()
+          case _                              => fb += wa.AnyConvertExtern
+        }
       case _ =>
         ()
     }
@@ -716,6 +724,14 @@ private class FunctionEmitter private (
 
             genCheckNonNullFor(array)
 
+            def genRhs(): Unit = {
+              genTree(rhs, lhs.tpe)
+              lhs.tpe match {
+                case ClassType(BoxedStringClass, _) => fb += wa.AnyConvertExtern
+                case _                              => ()
+              }
+            }
+
             if (semantics.arrayIndexOutOfBounds == CheckedBehavior.Unchecked &&
                 (semantics.arrayStores == CheckedBehavior.Unchecked || isPrimArray)) {
               // Get the underlying array
@@ -724,12 +740,12 @@ private class FunctionEmitter private (
                 genFieldID.objStruct.arrayUnderlying
               )
               genTree(index, IntType)
-              genTree(rhs, lhs.tpe)
+              genRhs()
               markPosition(tree)
               fb += wa.ArraySet(genTypeID.underlyingOf(arrayTypeRef))
             } else {
               genTree(index, IntType)
-              genTree(rhs, lhs.tpe)
+              genRhs()
               markPosition(tree)
               fb += wa.Call(genFunctionID.arraySetFor(arrayTypeRef))
             }
@@ -1065,7 +1081,8 @@ private class FunctionEmitter private (
           pushArgs(argsLocals)
           genHijackedClassCall(BoxedDoubleClass)
         } else if (receiverClassName == CharSequenceClass) {
-          // the value must be a `string`; it already has the right type
+          // the value must be a `string`
+          fb += wa.ExternConvertAny
           pushArgs(argsLocals)
           genHijackedClassCall(BoxedStringClass)
         } else if (methodName == compareToMethodName) {
@@ -1097,7 +1114,7 @@ private class FunctionEmitter private (
             // case JSValueTypeString =>
             List(JSValueTypeString) -> { () =>
               fb += wa.LocalGet(receiverLocal)
-              // no need to unbox for string
+              fb += wa.ExternConvertAny
               pushArgs(argsLocals)
               genHijackedClassCall(BoxedStringClass)
             }
@@ -1270,6 +1287,13 @@ private class FunctionEmitter private (
        * type in the IR but they get a `void` expected type.
        */
       expectedType
+    } else if (tree.isInstanceOf[Null] && expectedType == ClassType(BoxedStringClass, true)) {
+      /* Directly emit a `ref.null noextern` instead of requiring an
+       * `extern.convert_from_any` in `genAdapt`.
+       */
+      markPosition(tree)
+      fb += wa.RefNull(watpe.HeapType.NoExtern)
+      expectedType
     } else {
       markPosition(tree)
 
@@ -1544,12 +1568,14 @@ private class FunctionEmitter private (
      * this is not true, since they could also point to `func` heap types,
      * which are not sub-heap-types of `eq`.)
      *
-     * Therefore, in practice, the only heap type we can observe and that is
-     * *not* a sub-heap-type of `eq` is `any`.
+     * Therefore, in practice, the only heap types we can observe and that are
+     * *not* sub-heap-types of `eq` are `any` and `extern`.
      */
     def canUseRefEq(tpe: Type): Boolean = transformSingleType(tpe) match {
-      case watpe.RefType(_, heapType) => heapType != watpe.HeapType.Any
-      case _                          => false
+      case watpe.RefType(_, heapType) =>
+        heapType != watpe.HeapType.Any && heapType != watpe.HeapType.Extern
+      case _ =>
+        false
     }
 
     val lhsType = lhs.tpe
@@ -1695,7 +1721,7 @@ private class FunctionEmitter private (
          *
          * The overall structure of the generated code is as follows:
          *
-         * block (ref any) $done
+         * block (ref extern) $done
          *   block $isNull
          *     load receiver as (ref null java.lang.Object)
          *     br_on_null $isNull
@@ -1706,7 +1732,7 @@ private class FunctionEmitter private (
          * end $done
          */
 
-        fb.block(watpe.RefType.any) { labelDone =>
+        fb.block(watpe.RefType.extern) { labelDone =>
           fb.block() { labelIsNull =>
             genTreeAuto(tree)
             markPosition(tree)
@@ -1723,7 +1749,7 @@ private class FunctionEmitter private (
          *
          * The overall structure of the generated code is as follows:
          *
-         * block (ref any) $done
+         * block (ref extern) $done
          *   block anyref $notOurObject
          *     load receiver
          *     br_on_cast_fail anyref (ref $java.lang.Object) $notOurObject
@@ -1735,7 +1761,7 @@ private class FunctionEmitter private (
          * end $done
          */
 
-        fb.block(watpe.RefType.any) { labelDone =>
+        fb.block(watpe.RefType.extern) { labelDone =>
           // First try the case where the value is one of our objects
           fb.block(watpe.RefType.anyref) { labelNotOurObject =>
             // Load receiver
@@ -1794,7 +1820,7 @@ private class FunctionEmitter private (
       case ClassType(BoxedStringClass, nullable) =>
         // Common case for which we want to avoid the hijacked class dispatch
         if (nullable) {
-          fb.block(watpe.RefType.any) { notNullLabel =>
+          fb.block(watpe.RefType.extern) { notNullLabel =>
             genTreeAuto(tree)
             markPosition(tree)
             fb += wa.BrOnNonNull(notNullLabel)
@@ -2125,6 +2151,10 @@ private class FunctionEmitter private (
               targetWasmType match {
                 case watpe.RefType(true, watpe.HeapType.Any) =>
                   () // nothing to do
+                case watpe.RefType(targetNullable, watpe.HeapType.Extern) =>
+                  fb += wa.ExternConvertAny
+                  if (!targetNullable)
+                    fb += wa.RefAsNonNull
                 case targetWasmType: watpe.RefType =>
                   fb += wa.RefCast(targetWasmType)
                 case _ =>
@@ -2150,7 +2180,8 @@ private class FunctionEmitter private (
         fb += wa.GlobalGet(genGlobalID.undef)
 
       case StringType =>
-        val sig = watpe.FunctionType(List(watpe.RefType.anyref), List(watpe.RefType.any))
+        fb += wa.ExternConvertAny
+        val sig = watpe.FunctionType(List(watpe.RefType.externref), List(watpe.RefType.extern))
         fb.block(sig) { nonNullLabel =>
           fb += wa.BrOnNonNull(nonNullLabel)
           fb += wa.GlobalGet(genGlobalID.emptyString)
@@ -2943,6 +2974,10 @@ private class FunctionEmitter private (
               case watpe.RefType.anyref =>
                 // nothing to do
                 ()
+              case watpe.RefType(nullable, watpe.HeapType.Extern) =>
+                fb += wa.ExternConvertAny
+                if (!nullable)
+                  fb += wa.RefAsNonNull
               case refType: watpe.RefType =>
                 fb += wa.RefCast(refType)
               case otherType =>
@@ -3111,7 +3146,9 @@ private class FunctionEmitter private (
               fb += wa.I32Eq
               fb += wa.BrIf(label)
             case StringLiteral(value) =>
+              fb += wa.AnyConvertExtern
               fb ++= ctx.stringPool.getConstantStringInstr(value)
+              fb += wa.AnyConvertExtern
               fb += wa.Call(genFunctionID.is)
               fb += wa.BrIf(label)
             case Null() =>
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/README.md b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/README.md
index f03a0452bf..09fb8b2ced 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/README.md
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/README.md
@@ -29,31 +29,34 @@ This is however not true when `S` is a primitive type, or when `T = void`.
 
 ### Primitive types
 
-| IR type         | Wasm type   | Value representation (if non-obvious)   |
-|-----------------|-------------|-----------------------------------------|
-| `void`          | no type     | no value on the stack                   |
-| `boolean`       | `i32`       | `0` for `false`, 1 for `true`           |
-| `byte`, `short` | `i32`       | the `.toInt` value, i.e., sign extended |
-| `char`          | `i32`       | the `.toInt` value, i.e., 0-extended    |
-| `int`           | `i32`       |                                         |
-| `long`          | `i64`       |                                         |
-| `float`         | `f32`       |                                         |
-| `double`        | `f64`       |                                         |
-| `undef`         | `(ref any)` | the global JavaScript value `undefined` |
-| `string`        | `(ref any)` | a JavaScript `string`                   |
+| IR type         | Wasm type      | Value representation (if non-obvious)   |
+|-----------------|----------------|-----------------------------------------|
+| `void`          | no type        | no value on the stack                   |
+| `boolean`       | `i32`          | `0` for `false`, 1 for `true`           |
+| `byte`, `short` | `i32`          | the `.toInt` value, i.e., sign extended |
+| `char`          | `i32`          | the `.toInt` value, i.e., 0-extended    |
+| `int`           | `i32`          |                                         |
+| `long`          | `i64`          |                                         |
+| `float`         | `f32`          |                                         |
+| `double`        | `f64`          |                                         |
+| `undef`         | `(ref any)`    | the global JavaScript value `undefined` |
+| `string`        | `(ref extern)` | a JavaScript `string`                   |
 
 ### Reference types
 
 We will describe more precisely the representation of reference types in the coming sections.
 This table is for reference.
 
-| IR type                           | Wasm type                        |
-|-----------------------------------|----------------------------------|
-| `C`, a Scala class                | `(ref null $c.C)` |              |
-| `I`, a Scala interface            | `(ref null $c.jl.Object)`        |
-| all ancestors of hijacked classes | `(ref null any)` (aka `anyref`)  |
-| `PT[]`, a primitive array         | `(ref null $PTArray)`            |
-| `RT[]`, any reference array type  | `(ref null $ObjectArray)`        |
+| IR type                           | Wasm type                             |
+|-----------------------------------|---------------------------------------|
+| `C`, a Scala class                | `(ref null $c.C)` |                   |
+| `I`, a Scala interface            | `(ref null $c.jl.Object)`             |
+| `jl.String`                       | `(ref null extern)` (aka `externref`) |
+| all ancestors of hijacked classes | `(ref null any)` (aka `anyref`)       |
+| `PT[]`, a primitive array         | `(ref null $PTArray)`                 |
+| `RT[]`, any reference array type  | `(ref null $ObjectArray)`             |
+
+Non-nullable variants of the reference types are translated to non-nullable Wasm `ref` types.
 
 ### Nothing
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/SWasmGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/SWasmGen.scala
index b4b73a1556..65140fbe3c 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/SWasmGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/SWasmGen.scala
@@ -35,6 +35,9 @@ object SWasmGen {
       case StringType => GlobalGet(genGlobalID.emptyString)
       case UndefType  => GlobalGet(genGlobalID.undef)
 
+      case ClassType(BoxedStringClass, true) =>
+        RefNull(Types.HeapType.NoExtern)
+
       case AnyType | ClassType(_, true) | ArrayType(_, true) | NullType =>
         RefNull(Types.HeapType.None)
 
@@ -119,6 +122,7 @@ object SWasmGen {
     def genFollowPath(path: List[String]): Unit = {
       for (prop <- path) {
         fb ++= ctx.stringPool.getConstantStringInstr(prop)
+        fb += AnyConvertExtern
         fb += Call(genFunctionID.jsSelect)
       }
     }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/StringPool.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/StringPool.scala
index 12450488cc..fd4f61189c 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/StringPool.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/StringPool.scala
@@ -90,11 +90,11 @@ private[wasmemitter] final class StringPool {
         genGlobalID.stringLiteralCache,
         OriginalName("stringLiteralCache"),
         isMutable = false,
-        RefType(genTypeID.anyArray),
+        RefType(genTypeID.externrefArray),
         Expr(
           List(
             I32Const(nextIndex), // number of entries in the pool
-            ArrayNewDefault(genTypeID.anyArray)
+            ArrayNewDefault(genTypeID.externrefArray)
           )
         )
       )
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/TypeTransformer.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/TypeTransformer.scala
index 6535f352ab..813dcdcd92 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/TypeTransformer.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/TypeTransformer.scala
@@ -102,7 +102,9 @@ object TypeTransformer {
       implicit ctx: WasmContext): watpe.RefType = {
     val heapType: watpe.HeapType = ctx.getClassInfoOption(className) match {
       case Some(info) =>
-        if (info.isAncestorOfHijackedClass)
+        if (className == BoxedStringClass)
+          watpe.HeapType.Extern // for all the JS string builtin functions
+        else if (info.isAncestorOfHijackedClass)
           watpe.HeapType.Any
         else if (!info.hasInstances)
           watpe.HeapType.None
@@ -129,7 +131,7 @@ object TypeTransformer {
       case LongType    => watpe.Int64
       case FloatType   => watpe.Float32
       case DoubleType  => watpe.Float64
-      case StringType  => watpe.RefType.any
+      case StringType  => watpe.RefType.extern
       case NullType    => watpe.RefType.nullref
 
       case NoType | NothingType =>
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
index ad2214a1be..9d3b7e1469 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
@@ -469,6 +469,9 @@ object VarGen {
     case object f64Array extends TypeID
     case object anyArray extends TypeID
 
+    // for the array of cached string constants
+    case object externrefArray extends TypeID
+
     def underlyingOf(arrayTypeRef: ArrayTypeRef): TypeID = {
       if (arrayTypeRef.dimensions > 1) {
         anyArray

From 46b0fa1cd99f5a1aeb29b986739586fb57d9c5fc Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Fri, 30 Aug 2024 22:23:06 +0200
Subject: [PATCH 161/298] Wasm: Use the JS string builtins, with polyfills.

JS string builtins are not yet at stage 4 of standardization, but
they have been pretty stable recently, except for string literals.

We now use some of the builtins to implement our primitive
operations on strings. We provide polyfills for Wasm engines that
do not yet recognize string builtins.

Benchmarks showed that we get significant performance boosts from
these builtins.
---
 .../backend/wasmemitter/CoreWasmLib.scala     | 84 +++++++++++--------
 .../backend/wasmemitter/FunctionEmitter.scala | 28 +++++--
 .../backend/wasmemitter/LoaderContent.scala   | 22 +++--
 .../linker/backend/wasmemitter/README.md      | 13 ++-
 .../linker/backend/wasmemitter/VarGen.scala   | 16 ++--
 5 files changed, 103 insertions(+), 60 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
index 10d75cfe6b..87d94a0dbb 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
@@ -267,6 +267,7 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
   private def genImports()(implicit ctx: WasmContext): Unit = {
     genTagImports()
     genGlobalImports()
+    genStringBuiltinImports()
     genHelperImports()
   }
 
@@ -306,6 +307,30 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
     addGlobalHelperImport(genGlobalID.idHashCodeMap, RefType.extern)
   }
 
+  private def genStringBuiltinImports()(implicit ctx: WasmContext): Unit = {
+    import RefType.{extern, externref}
+
+    def addHelperImport(id: genFunctionID.JSHelperFunctionID,
+        params: List[Type], results: List[Type]): Unit = {
+      val sig = FunctionType(params, results)
+      val typeID = ctx.moduleBuilder.functionTypeToTypeID(sig)
+      ctx.moduleBuilder.addImport(
+        Import(
+          "wasm:js-string",
+          id.toString(), // import name, guaranteed by JSHelperFunctionID
+          ImportDesc.Func(id, OriginalName(id.toString()), typeID)
+        )
+      )
+    }
+
+    addHelperImport(genFunctionID.stringBuiltins.test, List(externref), List(Int32))
+    addHelperImport(genFunctionID.stringBuiltins.fromCharCode, List(Int32), List(extern))
+    addHelperImport(genFunctionID.stringBuiltins.charCodeAt, List(externref, Int32), List(Int32))
+    addHelperImport(genFunctionID.stringBuiltins.length, List(externref), List(Int32))
+    addHelperImport(genFunctionID.stringBuiltins.concat, List(externref, externref), List(extern))
+    addHelperImport(genFunctionID.stringBuiltins.equals, List(externref, externref), List(Int32))
+  }
+
   private def genHelperImports()(implicit ctx: WasmContext): Unit = {
     def addHelperImport(id: genFunctionID.JSHelperFunctionID,
         params: List[Type], results: List[Type]): Unit = {
@@ -367,21 +392,12 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
       List(RefType.any)
     )
 
-    addHelperImport(genFunctionID.stringLength, List(RefType.extern), List(Int32))
-    addHelperImport(genFunctionID.stringCharAt, List(RefType.extern, Int32), List(Int32))
     addHelperImport(genFunctionID.jsValueToString, List(RefType.any), List(RefType.extern))
     addHelperImport(genFunctionID.jsValueToStringForConcat, List(anyref), List(RefType.extern))
     addHelperImport(genFunctionID.booleanToString, List(Int32), List(RefType.extern))
-    addHelperImport(genFunctionID.charToString, List(Int32), List(RefType.extern))
     addHelperImport(genFunctionID.intToString, List(Int32), List(RefType.extern))
     addHelperImport(genFunctionID.longToString, List(Int64), List(RefType.extern))
     addHelperImport(genFunctionID.doubleToString, List(Float64), List(RefType.extern))
-    addHelperImport(
-      genFunctionID.stringConcat,
-      List(RefType.extern, RefType.extern),
-      List(RefType.extern)
-    )
-    addHelperImport(genFunctionID.isString, List(anyref), List(Int32))
 
     addHelperImport(genFunctionID.jsValueType, List(RefType.any), List(Int32))
     addHelperImport(genFunctionID.jsValueDescription, List(anyref), List(RefType.extern))
@@ -891,8 +907,8 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
       fb += LocalGet(dataParam)
       fb += LocalGet(iLocal)
       fb += ArrayGetU(genTypeID.i16Array)
-      fb += Call(genFunctionID.charToString)
-      fb += Call(genFunctionID.stringConcat)
+      fb += Call(genFunctionID.stringBuiltins.fromCharCode)
+      fb += Call(genFunctionID.stringBuiltins.concat)
       fb += LocalSet(resultLocal)
 
       // i := i + 1
@@ -952,7 +968,7 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
 
         // <top of stack> := "[", for the CALL to stringConcat near the end
         fb += I32Const('['.toInt)
-        fb += Call(genFunctionID.charToString)
+        fb += Call(genFunctionID.stringBuiltins.fromCharCode)
 
         // componentTypeData := ref_as_non_null(typeData.componentType)
         fb += LocalGet(typeDataParam)
@@ -972,35 +988,35 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
         }(
           List(KindBoolean) -> { () =>
             fb += I32Const('Z'.toInt)
-            fb += Call(genFunctionID.charToString)
+            fb += Call(genFunctionID.stringBuiltins.fromCharCode)
           },
           List(KindChar) -> { () =>
             fb += I32Const('C'.toInt)
-            fb += Call(genFunctionID.charToString)
+            fb += Call(genFunctionID.stringBuiltins.fromCharCode)
           },
           List(KindByte) -> { () =>
             fb += I32Const('B'.toInt)
-            fb += Call(genFunctionID.charToString)
+            fb += Call(genFunctionID.stringBuiltins.fromCharCode)
           },
           List(KindShort) -> { () =>
             fb += I32Const('S'.toInt)
-            fb += Call(genFunctionID.charToString)
+            fb += Call(genFunctionID.stringBuiltins.fromCharCode)
           },
           List(KindInt) -> { () =>
             fb += I32Const('I'.toInt)
-            fb += Call(genFunctionID.charToString)
+            fb += Call(genFunctionID.stringBuiltins.fromCharCode)
           },
           List(KindLong) -> { () =>
             fb += I32Const('J'.toInt)
-            fb += Call(genFunctionID.charToString)
+            fb += Call(genFunctionID.stringBuiltins.fromCharCode)
           },
           List(KindFloat) -> { () =>
             fb += I32Const('F'.toInt)
-            fb += Call(genFunctionID.charToString)
+            fb += Call(genFunctionID.stringBuiltins.fromCharCode)
           },
           List(KindDouble) -> { () =>
             fb += I32Const('D'.toInt)
-            fb += Call(genFunctionID.charToString)
+            fb += Call(genFunctionID.stringBuiltins.fromCharCode)
           },
           List(KindArray) -> { () =>
             // the component type is an array; get its own name
@@ -1011,17 +1027,17 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
           // default: the component type is neither a primitive nor an array;
           // concatenate "L" + <its own name> + ";"
           fb += I32Const('L'.toInt)
-          fb += Call(genFunctionID.charToString)
+          fb += Call(genFunctionID.stringBuiltins.fromCharCode)
           fb += LocalGet(componentTypeDataLocal)
           fb += Call(genFunctionID.typeDataName)
-          fb += Call(genFunctionID.stringConcat)
+          fb += Call(genFunctionID.stringBuiltins.concat)
           fb += I32Const(';'.toInt)
-          fb += Call(genFunctionID.charToString)
-          fb += Call(genFunctionID.stringConcat)
+          fb += Call(genFunctionID.stringBuiltins.fromCharCode)
+          fb += Call(genFunctionID.stringBuiltins.concat)
         }
 
         // At this point, the stack contains "[" and the string that must be concatenated with it
-        fb += Call(genFunctionID.stringConcat)
+        fb += Call(genFunctionID.stringBuiltins.concat)
       } {
         // it is not an array; its name is stored in nameData
         for (
@@ -1209,11 +1225,11 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
         fb += Call(genFunctionID.valueDescription)
 
         fb ++= ctx.stringPool.getConstantStringInstr(" cannot be cast to ")
-        fb += Call(genFunctionID.stringConcat)
+        fb += Call(genFunctionID.stringBuiltins.concat)
 
         fb += LocalGet(typeDataParam)
         fb += Call(genFunctionID.typeDataName)
-        fb += Call(genFunctionID.stringConcat)
+        fb += Call(genFunctionID.stringBuiltins.concat)
       }
     }
 
@@ -1341,7 +1357,8 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
             case UndefType =>
               fb += Call(genFunctionID.isUndef)
             case StringType =>
-              fb += Call(genFunctionID.isString)
+              fb += ExternConvertAny
+              fb += Call(genFunctionID.stringBuiltins.test)
             case primType: PrimTypeWithRef =>
               fb += Call(genFunctionID.typeTest(primType.primRef))
           }
@@ -1860,7 +1877,7 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
     // if index unsigned_>= str.length
     fb += LocalGet(indexParam)
     fb += LocalGet(strParam)
-    fb += Call(genFunctionID.stringLength)
+    fb += Call(genFunctionID.stringBuiltins.length)
     fb += I32GeU // unsigned comparison makes negative values of index larger than the length
     fb.ifThen() {
       // then, throw a StringIndexOutOfBoundsException
@@ -1877,7 +1894,7 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
     // otherwise, read the char
     fb += LocalGet(strParam)
     fb += LocalGet(indexParam)
-    fb += Call(genFunctionID.stringCharAt)
+    fb += Call(genFunctionID.stringBuiltins.charCodeAt)
 
     fb.buildAndAddToModule()
   }
@@ -1895,10 +1912,10 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
       fb ++= ctx.stringPool.getConstantStringInstr("Initializer of ")
       fb += LocalGet(typeDataParam)
       fb += Call(genFunctionID.typeDataName)
-      fb += Call(genFunctionID.stringConcat)
+      fb += Call(genFunctionID.stringBuiltins.concat)
       fb ++= ctx.stringPool.getConstantStringInstr(
           " called before completion of its super constructor")
-      fb += Call(genFunctionID.stringConcat)
+      fb += Call(genFunctionID.stringBuiltins.concat)
     }
     fb += ExternConvertAny
     fb += Throw(genTagID.exception)
@@ -1980,7 +1997,8 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
       },
       List(KindBoxedString) -> { () =>
         fb += LocalGet(valueParam)
-        fb += Call(genFunctionID.isString)
+        fb += ExternConvertAny
+        fb += Call(genFunctionID.stringBuiltins.test)
       },
       // case KindJSType => call typeData.isJSClassInstance(value) or throw if it is null
       List(KindJSType) -> { () =>
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
index 37554f66db..0696553252 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
@@ -1433,7 +1433,7 @@ private class FunctionEmitter private (
 
       // String.length
       case String_length =>
-        fb += wa.Call(genFunctionID.stringLength)
+        fb += wa.Call(genFunctionID.stringBuiltins.length)
 
       // Null check
       case CheckNotNull =>
@@ -1530,7 +1530,7 @@ private class FunctionEmitter private (
         genTree(rhs, IntType)
         markPosition(tree)
         if (semantics.stringIndexOutOfBounds == CheckedBehavior.Unchecked)
-          fb += wa.Call(genFunctionID.stringCharAt)
+          fb += wa.Call(genFunctionID.stringBuiltins.charCodeAt)
         else
           fb += wa.Call(genFunctionID.checkedStringCharAt)
         CharType
@@ -1578,6 +1578,12 @@ private class FunctionEmitter private (
         false
     }
 
+    def isStringType(tpe: Type): Boolean = tpe match {
+      case StringType                     => true
+      case ClassType(BoxedStringClass, _) => true
+      case _                              => false
+    }
+
     val lhsType = lhs.tpe
     val rhsType = rhs.tpe
 
@@ -1610,6 +1616,13 @@ private class FunctionEmitter private (
       fb += wa.RefEq
       maybeGenInvert()
       BooleanType
+    } else if (isStringType(lhsType) && isStringType(rhsType)) {
+      genTreeAuto(lhs)
+      genTreeAuto(rhs)
+      markPosition(tree)
+      fb += wa.Call(genFunctionID.stringBuiltins.equals)
+      maybeGenInvert()
+      BooleanType
     } else {
       // Otherwise, fall back on the `Object.is` helper
       genTree(lhs, AnyType)
@@ -1692,7 +1705,7 @@ private class FunctionEmitter private (
         genToStringForConcat(lhs)
         genToStringForConcat(rhs)
         markPosition(tree)
-        fb += wa.Call(genFunctionID.stringConcat)
+        fb += wa.Call(genFunctionID.stringBuiltins.concat)
     }
 
     StringType
@@ -1798,7 +1811,7 @@ private class FunctionEmitter private (
           case BooleanType =>
             fb += wa.Call(genFunctionID.booleanToString)
           case CharType =>
-            fb += wa.Call(genFunctionID.charToString)
+            fb += wa.Call(genFunctionID.stringBuiltins.fromCharCode)
           case ByteType | ShortType | IntType =>
             fb += wa.Call(genFunctionID.intToString)
           case LongType =>
@@ -1959,7 +1972,8 @@ private class FunctionEmitter private (
       case UndefType =>
         fb += wa.Call(genFunctionID.isUndef)
       case StringType =>
-        fb += wa.Call(genFunctionID.isString)
+        fb += wa.ExternConvertAny
+        fb += wa.Call(genFunctionID.stringBuiltins.test)
       case CharType =>
         val structTypeID = genTypeID.forClass(SpecialNames.CharBoxClass)
         fb += wa.RefTest(watpe.RefType(structTypeID))
@@ -3146,10 +3160,8 @@ private class FunctionEmitter private (
               fb += wa.I32Eq
               fb += wa.BrIf(label)
             case StringLiteral(value) =>
-              fb += wa.AnyConvertExtern
               fb ++= ctx.stringPool.getConstantStringInstr(value)
-              fb += wa.AnyConvertExtern
-              fb += wa.Call(genFunctionID.is)
+              fb += wa.Call(genFunctionID.stringBuiltins.equals)
               fb += wa.BrIf(label)
             case Null() =>
               fb += wa.RefIsNull
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala
index 7a066e633b..937674a051 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala
@@ -125,17 +125,12 @@ const scalaJSHelpers = {
 
   // Strings
   emptyString: "",
-  stringLength: (s) => s.length,
-  stringCharAt: (s, i) => s.charCodeAt(i),
   jsValueToString: (x) => (x === void 0) ? "undefined" : x.toString(),
   jsValueToStringForConcat: (x) => "" + x,
   booleanToString: (b) => b ? "true" : "false",
-  charToString: (c) => String.fromCharCode(c),
   intToString: (i) => "" + i,
   longToString: (l) => "" + l, // l must be a bigint here
   doubleToString: (d) => "" + d,
-  stringConcat: (x, y) => ("" + x) + y, // the added "" is for the case where x === y === null
-  isString: (x) => typeof x === 'string',
 
   // Get the type of JS value of `x` in a single JS helper call, for the purpose of dispatch.
   jsValueType: (x) => {
@@ -313,6 +308,15 @@ const scalaJSHelpers = {
   },
 }
 
+const stringBuiltinPolyfills = {
+  test: (x) => typeof x === 'string',
+  fromCharCode: (c) => String.fromCharCode(c),
+  charCodeAt: (s, i) => s.charCodeAt(i),
+  length: (s) => s.length,
+  concat: (a, b) => "" + a + b, // "" tells the JIT that this is *always* a string concat operation
+  equals: (a, b) => a === b,
+};
+
 export async function load(wasmFileURL, linkingInfo, importedModules, exportSetters) {
   const myScalaJSHelpers = {
     ...scalaJSHelpers,
@@ -323,6 +327,10 @@ export async function load(wasmFileURL, linkingInfo, importedModules, exportSett
     "__scalaJSHelpers": myScalaJSHelpers,
     "__scalaJSImports": importedModules,
     "__scalaJSExportSetters": exportSetters,
+    "wasm:js-string": stringBuiltinPolyfills,
+  };
+  const options = {
+    builtins: ["js-string"],
   };
   const resolvedURL = new URL(wasmFileURL, import.meta.url);
   if (resolvedURL.protocol === 'file:') {
@@ -330,9 +338,9 @@ export async function load(wasmFileURL, linkingInfo, importedModules, exportSett
     const { readFile } = await import("node:fs/promises");
     const wasmPath = fileURLToPath(resolvedURL);
     const body = await readFile(wasmPath);
-    return WebAssembly.instantiate(body, importsObj);
+    return WebAssembly.instantiate(body, importsObj, options);
   } else {
-    return await WebAssembly.instantiateStreaming(fetch(resolvedURL), importsObj);
+    return await WebAssembly.instantiateStreaming(fetch(resolvedURL), importsObj, options);
   }
 }
     """
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/README.md b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/README.md
index 09fb8b2ced..b72fe8ab8f 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/README.md
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/README.md
@@ -613,8 +613,11 @@ This is implemented in the function `identityHashCode` in `CoreWasmLib`.
 ### Strings
 
 As mentioned above, strings are represented as JS `string`s.
-All the primitive operations on strings, including string concatenation (which embeds conversion to string) are performed by helper JS functions.
+Primitive operations on strings are implemented using [JS String Builtins](https://github.com/WebAssembly/js-string-builtins).
+Since the latter are not yet fully standardized, we polyfill the functions we use.
+Some conversions to strings, which are part of the semantics of string concatenation, are performed by helper JS functions.
 
+Currently, we still generate string literals entirely from the Wasm side.
 String constants are gathered from the entire program and their raw bytes stored in a data segment.
 We deduplicate strings so that we do not store the same string several times, but otherwise do not attempt further compression (such as reusing prefixes).
 Since creating string values from the data segment is expensive, we cache the constructed strings in a global array.
@@ -628,12 +631,8 @@ i32.const 9   ;; index into the cache array for that string
 call $stringLiteral
 ```
 
-In the future, we may want to use one of the following two Wasm proposals to improve efficiency of strings:
-
-* [JS String Builtins](https://github.com/WebAssembly/js-string-builtins)
-* [Reference-Typed Strings, aka `stringref`](https://github.com/WebAssembly/stringref)
-
-Even before that, an alternative for string literals would be to create them upfront from the JS loader and pass them to Wasm as `import`s.
+In the future, we will probably want to use the magic imports for string literals offered by the JS string builtins proposal.
+We have not done so yet because that part of the proposal was still in flux at the time of this writing.
 
 ## JavaScript interoperability
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
index 9d3b7e1469..72e49f4f06 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
@@ -142,17 +142,12 @@ object VarGen {
     case object makeExportedDef extends JSHelperFunctionID
     case object makeExportedDefRest extends JSHelperFunctionID
 
-    case object stringLength extends JSHelperFunctionID
-    case object stringCharAt extends JSHelperFunctionID
     case object jsValueToString extends JSHelperFunctionID // for actual toString() call
     case object jsValueToStringForConcat extends JSHelperFunctionID
     case object booleanToString extends JSHelperFunctionID
-    case object charToString extends JSHelperFunctionID
     case object intToString extends JSHelperFunctionID
     case object longToString extends JSHelperFunctionID
     case object doubleToString extends JSHelperFunctionID
-    case object stringConcat extends JSHelperFunctionID
-    case object isString extends JSHelperFunctionID
 
     case object jsValueType extends JSHelperFunctionID
     case object jsValueDescription extends JSHelperFunctionID
@@ -282,6 +277,17 @@ object VarGen {
     case object arrayCopyCheckBounds extends FunctionID
     case object slowRefArrayCopy extends FunctionID
     case object genericArrayCopy extends FunctionID
+
+    // String builtins
+
+    object stringBuiltins {
+      case object test extends JSHelperFunctionID
+      case object fromCharCode extends JSHelperFunctionID
+      case object charCodeAt extends JSHelperFunctionID
+      case object length extends JSHelperFunctionID
+      case object concat extends JSHelperFunctionID
+      case object equals extends JSHelperFunctionID
+    }
   }
 
   object genFieldID {

From ca675dd8c93bfb636aef808c1e515eff0d2cd081 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Mon, 2 Sep 2024 20:03:06 +0200
Subject: [PATCH 162/298] Opt/Wasm: Intrinsify jl.String.substring.

Implement it using the JS string builtin `substring`.
---
 .../src/main/scala/java/lang/_String.scala    |  2 +
 .../backend/wasmemitter/CoreWasmLib.scala     | 98 +++++++++++++++++++
 .../backend/wasmemitter/FunctionEmitter.scala | 21 ++++
 .../backend/wasmemitter/LoaderContent.scala   |  1 +
 .../linker/backend/wasmemitter/VarGen.scala   |  3 +
 .../backend/wasmemitter/WasmTransients.scala  | 39 ++++++++
 .../backend/webassembly/BinaryWriter.scala    |  3 +-
 .../frontend/optimizer/OptimizerCore.scala    | 24 ++++-
 8 files changed, 189 insertions(+), 2 deletions(-)

diff --git a/javalib/src/main/scala/java/lang/_String.scala b/javalib/src/main/scala/java/lang/_String.scala
index 5a8e03cc0e..52d7fec5c3 100644
--- a/javalib/src/main/scala/java/lang/_String.scala
+++ b/javalib/src/main/scala/java/lang/_String.scala
@@ -339,6 +339,7 @@ final class _String private () // scalastyle:ignore
   def subSequence(beginIndex: Int, endIndex: Int): CharSequence =
     substring(beginIndex, endIndex)
 
+  // Wasm intrinsic
   @inline
   def substring(beginIndex: Int): String = {
     // Bounds check
@@ -348,6 +349,7 @@ final class _String private () // scalastyle:ignore
     thisString.jsSubstring(beginIndex)
   }
 
+  // Wasm intrinsic
   @inline
   def substring(beginIndex: Int, endIndex: Int): String = {
     // Bounds check
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
index 87d94a0dbb..4d4d2ae03f 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
@@ -328,6 +328,7 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
     addHelperImport(genFunctionID.stringBuiltins.charCodeAt, List(externref, Int32), List(Int32))
     addHelperImport(genFunctionID.stringBuiltins.length, List(externref), List(Int32))
     addHelperImport(genFunctionID.stringBuiltins.concat, List(externref, externref), List(extern))
+    addHelperImport(genFunctionID.stringBuiltins.substring, List(externref, Int32, Int32), List(extern))
     addHelperImport(genFunctionID.stringBuiltins.equals, List(externref, externref), List(Int32))
   }
 
@@ -679,6 +680,8 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
 
     if (semantics.stringIndexOutOfBounds != CheckedBehavior.Unchecked) {
       genCheckedStringCharAt()
+      genCheckedSubstringStart()
+      genCheckedSubstringStartEnd()
     }
 
     if (semantics.nullPointers != CheckedBehavior.Unchecked) {
@@ -1899,6 +1902,101 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
     fb.buildAndAddToModule()
   }
 
+  /** `checkedSubstringStart: (ref extern), i32 -> (ref extern)`.
+   *
+   *  Implementation of jl.String.substring(start). Used when
+   *  stringIndexOutOfBounds are checked.
+   */
+  private def genCheckedSubstringStart()(implicit ctx: WasmContext): Unit = {
+    val fb = newFunctionBuilder(genFunctionID.checkedSubstringStart)
+    val strParam = fb.addParam("str", RefType.extern)
+    val startParam = fb.addParam("start", Int32)
+    fb.setResultType(RefType.extern)
+
+    /* if start unsigned_> str.length
+     * The unsigned comparison makes negative values larger than the length.
+     */
+    fb += LocalGet(startParam)
+    fb += LocalGet(strParam)
+    fb += Call(genFunctionID.stringBuiltins.length)
+    fb += I32GtU
+    fb.ifThen() {
+      // then, throw a StringIndexOutOfBoundsException
+      maybeWrapInUBE(fb, semantics.stringIndexOutOfBounds) {
+        genNewScalaClass(fb, StringIndexOutOfBoundsExceptionClass,
+            SpecialNames.IntArgConstructorName) {
+          fb += LocalGet(startParam)
+        }
+      }
+      fb += ExternConvertAny
+      fb += Throw(genTagID.exception)
+    }
+
+    // otherwise, call the substring builtin
+    fb += LocalGet(strParam)
+    fb += LocalGet(startParam)
+    fb += I32Const(-1) // unsigned max value
+    fb += Call(genFunctionID.stringBuiltins.substring)
+
+    fb.buildAndAddToModule()
+  }
+
+  /** `checkedSubstringStartEnd: (ref extern), i32, i32 -> (ref extern)`.
+   *
+   *  Implementation of jl.String.substring(start, end). Used when
+   *  stringIndexOutOfBounds are checked.
+   */
+  private def genCheckedSubstringStartEnd()(implicit ctx: WasmContext): Unit = {
+    val fb = newFunctionBuilder(genFunctionID.checkedSubstringStartEnd)
+    val strParam = fb.addParam("str", RefType.extern)
+    val startParam = fb.addParam("start", Int32)
+    val endParam = fb.addParam("end", Int32)
+    fb.setResultType(RefType.extern)
+
+    /* if (start unsigned_> end) | (end unsigned_> str.length)
+     * The unsigned comparisons make negative values larger than the length
+     * since the happy path evaluates both conditions anyway, we don't bother
+     * with a short-circuiting || and implement an | instead.
+     */
+    fb += LocalGet(startParam)
+    fb += LocalGet(endParam)
+    fb += I32GtU
+    fb += LocalGet(endParam)
+    fb += LocalGet(strParam)
+    fb += Call(genFunctionID.stringBuiltins.length)
+    fb += I32GtU
+    fb += I32Or
+    fb.ifThen() {
+      // then, throw a StringIndexOutOfBoundsException
+      maybeWrapInUBE(fb, semantics.stringIndexOutOfBounds) {
+        genNewScalaClass(fb, StringIndexOutOfBoundsExceptionClass,
+            SpecialNames.IntArgConstructorName) {
+          // Redo part of the test to determine the argument
+          fb += LocalGet(startParam) // value if true for Select
+          fb += LocalGet(endParam) // value if false for Select
+
+          // start unsigned_> string.length
+          fb += LocalGet(startParam)
+          fb += LocalGet(strParam)
+          fb += Call(genFunctionID.stringBuiltins.length)
+          fb += I32GtU
+
+          fb += Select(Nil) // infer i32
+        }
+      }
+      fb += ExternConvertAny
+      fb += Throw(genTagID.exception)
+    }
+
+    // otherwise, call the substring builtin
+    fb += LocalGet(strParam)
+    fb += LocalGet(startParam)
+    fb += LocalGet(endParam)
+    fb += Call(genFunctionID.stringBuiltins.substring)
+
+    fb.buildAndAddToModule()
+  }
+
   /** `throwModuleInitError: [] -> []` (always throws).
    *
    *  Throws an `UndefinedBehaviorError` for a module initialization error.
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
index 0696553252..04d6c8b979 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
@@ -3338,6 +3338,27 @@ private class FunctionEmitter private (
         fb += value.wasmInstr
         value.tpe
 
+      case value @ WasmTransients.WasmSubstring(string, start, optEnd) =>
+        genTree(string, ClassType(BoxedStringClass, nullable = string.tpe.isNullable))
+        if (semantics.stringIndexOutOfBounds == CheckedBehavior.Unchecked)
+          genCheckNonNullFor(string)
+        else
+          genAsNonNullOrNPEFor(string)
+        genTree(start, IntType)
+        optEnd.foreach(genTree(_, IntType))
+        markPosition(tree)
+        if (semantics.stringIndexOutOfBounds == CheckedBehavior.Unchecked) {
+          if (optEnd.isEmpty)
+            fb += wa.I32Const(-1) // unsigned max value
+          fb += wa.Call(genFunctionID.stringBuiltins.substring)
+        } else {
+          if (optEnd.isEmpty)
+            fb += wa.Call(genFunctionID.checkedSubstringStart)
+          else
+            fb += wa.Call(genFunctionID.checkedSubstringStartEnd)
+        }
+        value.tpe
+
       case other =>
         throw new AssertionError(s"Unknown transient: $other")
     }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala
index 937674a051..df56c1a383 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala
@@ -314,6 +314,7 @@ const stringBuiltinPolyfills = {
   charCodeAt: (s, i) => s.charCodeAt(i),
   length: (s) => s.length,
   concat: (a, b) => "" + a + b, // "" tells the JIT that this is *always* a string concat operation
+  substring: (str, start, end) => str.substring(start >>> 0, end >>> 0),
   equals: (a, b) => a === b,
 };
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
index 72e49f4f06..47a535e590 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
@@ -251,6 +251,8 @@ object VarGen {
     case object throwNegativeArraySizeException extends FunctionID
     case object throwNullPointerException extends FunctionID
     case object checkedStringCharAt extends FunctionID
+    case object checkedSubstringStart extends FunctionID
+    case object checkedSubstringStartEnd extends FunctionID
     case object throwModuleInitError extends FunctionID
     case object isInstance extends FunctionID
     case object isAssignableFrom extends FunctionID
@@ -286,6 +288,7 @@ object VarGen {
       case object charCodeAt extends JSHelperFunctionID
       case object length extends JSHelperFunctionID
       case object concat extends JSHelperFunctionID
+      case object substring extends JSHelperFunctionID
       case object equals extends JSHelperFunctionID
     }
   }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/WasmTransients.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/WasmTransients.scala
index b58c06e025..fdfec90018 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/WasmTransients.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/WasmTransients.scala
@@ -206,4 +206,43 @@ object WasmTransients {
         DoubleType
     }
   }
+
+  /** Wasm intrinsic for `jl.String.substring`.
+   *
+   *  Typing rules: `string` must be a `jl.String`; `start` and `optEnd` must
+   *  be `int`s. The result is a `string`.
+   *
+   *  Evaluation semantics are as follows:
+   *
+   *  1. Let `stringV` be the result of evaluating `string`. If it is `null`,
+   *     throw an NPE (subject to UB).
+   *  2. Let `startV` be the result of evaluating `start`.
+   *  3. If `optEnd` is empty, let `endV` be `stringV.length`. Otherwise, let
+   *     `endV` be the result of evaluating `optEnd`.
+   *  4. If `startV < 0`, `endV < startV` or `endV > stringV.length`, throw a
+   *     `StringIndexOutOfBoundsException` (subject to UB).
+   *  5. Return the substring of `stringV` in the range `[startV, endV)`.
+   */
+  final case class WasmSubstring(string: Tree, start: Tree, optEnd: Option[Tree])
+      extends Transient.Value {
+
+    val tpe: Type = StringType
+
+    def traverse(traverser: Traverser): Unit = {
+      traverser.traverse(string)
+      traverser.traverse(start)
+      optEnd.foreach(traverser.traverse(_))
+    }
+
+    def transform(transformer: Transformer, isStat: Boolean)(
+        implicit pos: Position): Tree = {
+      Transient(WasmSubstring(transformer.transformExpr(string),
+          transformer.transformExpr(start), optEnd.map(transformer.transformExpr(_))))
+    }
+
+    def printIR(out: IRTreePrinter): Unit = {
+      out.print("$substring")
+      out.printArgs(string :: start :: optEnd.toList)
+    }
+  }
 }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/BinaryWriter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/BinaryWriter.scala
index b90480a3c2..75a10d2594 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/BinaryWriter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/BinaryWriter.scala
@@ -441,7 +441,8 @@ private sealed class BinaryWriter(module: Module, emitDebugInfo: Boolean) {
       case F64Const(v) => buf.f64(v)
 
       case Select(resultTypes) =>
-        buf.vec(resultTypes)(writeType(_))
+        if (resultTypes.nonEmpty)
+          buf.vec(resultTypes)(writeType(_))
 
       case BrTable(labelIdxVector, defaultLabelIdx) =>
         buf.vec(labelIdxVector)(writeLabelIdx(_))
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
index 5cd5045084..35be6b844e 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
@@ -3094,6 +3094,21 @@ private[optimizer] abstract class OptimizerCore(
       case LongBitsToDouble =>
         contTree(wasmUnaryOp(WasmUnaryOp.F64ReinterpretI64, targs.head))
 
+      // java.lang.String
+
+      case StringSubstringStart =>
+        contTree(Transient(WasmSubstring(
+          finishTransformExpr(optTReceiver.get),
+          finishTransformExpr(targs.head),
+          None
+        )))
+      case StringSubstringStartEnd =>
+        contTree(Transient(WasmSubstring(
+          finishTransformExpr(optTReceiver.get),
+          finishTransformExpr(targs(0)),
+          Some(finishTransformExpr(targs(1)))
+        )))
+
       // java.lang.Math
 
       case MathAbsFloat =>
@@ -6463,7 +6478,10 @@ private[optimizer] object OptimizerCore {
     final val DoubleToLongBits = IntBitsToFloat + 1
     final val LongBitsToDouble = DoubleToLongBits + 1
 
-    final val MathAbsFloat = LongBitsToDouble + 1
+    final val StringSubstringStart = LongBitsToDouble + 1
+    final val StringSubstringStartEnd = StringSubstringStart + 1
+
+    final val MathAbsFloat = StringSubstringStartEnd + 1
     final val MathAbsDouble = MathAbsFloat + 1
     final val MathCeil = MathAbsDouble + 1
     final val MathFloor = MathCeil + 1
@@ -6603,6 +6621,10 @@ private[optimizer] object OptimizerCore {
             m("doubleToLongBits", List(D), J) -> DoubleToLongBits,
             m("longBitsToDouble", List(J), D) -> LongBitsToDouble
         ),
+        ClassName("java.lang.String") -> List(
+            m("substring", List(I), StringClassRef) -> StringSubstringStart,
+            m("substring", List(I, I), StringClassRef) -> StringSubstringStartEnd
+        ),
         ClassName("java.lang.Math$") -> List(
             m("abs", List(F), F) -> MathAbsFloat,
             m("abs", List(D), D) -> MathAbsDouble,

From 5423ed64725875e1df9bf645e45a94b5c46b875c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Tue, 3 Sep 2024 16:03:31 +0200
Subject: [PATCH 163/298] Opt/Wasm: Intrinsify jl.String.codePointAt.

Implement it using the JS string builtin `codePointAt`.
---
 .../src/main/scala/java/lang/_String.scala    |  1 +
 .../backend/wasmemitter/CoreWasmLib.scala     | 21 +++++++----
 .../backend/wasmemitter/FunctionEmitter.scala | 14 ++++++++
 .../backend/wasmemitter/LoaderContent.scala   |  1 +
 .../linker/backend/wasmemitter/VarGen.scala   |  2 ++
 .../backend/wasmemitter/WasmTransients.scala  | 36 +++++++++++++++++++
 .../frontend/optimizer/OptimizerCore.scala    |  9 ++++-
 7 files changed, 76 insertions(+), 8 deletions(-)

diff --git a/javalib/src/main/scala/java/lang/_String.scala b/javalib/src/main/scala/java/lang/_String.scala
index 52d7fec5c3..d5b3e546fa 100644
--- a/javalib/src/main/scala/java/lang/_String.scala
+++ b/javalib/src/main/scala/java/lang/_String.scala
@@ -54,6 +54,7 @@ final class _String private () // scalastyle:ignore
   def charAt(index: Int): Char =
     throw new Error("stub") // body replaced by the compiler back-end
 
+  // Wasm intrinsic
   def codePointAt(index: Int): Int = {
     if (linkingInfo.esVersion >= ESVersion.ES2015) {
       charAt(index) // bounds check
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
index 4d4d2ae03f..4a1ada3ee0 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
@@ -326,6 +326,7 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
     addHelperImport(genFunctionID.stringBuiltins.test, List(externref), List(Int32))
     addHelperImport(genFunctionID.stringBuiltins.fromCharCode, List(Int32), List(extern))
     addHelperImport(genFunctionID.stringBuiltins.charCodeAt, List(externref, Int32), List(Int32))
+    addHelperImport(genFunctionID.stringBuiltins.codePointAt, List(externref, Int32), List(Int32))
     addHelperImport(genFunctionID.stringBuiltins.length, List(externref), List(Int32))
     addHelperImport(genFunctionID.stringBuiltins.concat, List(externref, externref), List(extern))
     addHelperImport(genFunctionID.stringBuiltins.substring, List(externref, Int32, Int32), List(extern))
@@ -679,7 +680,10 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
     }
 
     if (semantics.stringIndexOutOfBounds != CheckedBehavior.Unchecked) {
-      genCheckedStringCharAt()
+      genCheckedStringCharAtOrCodePointAt(
+          genFunctionID.checkedStringCharAt, genFunctionID.stringBuiltins.charCodeAt)
+      genCheckedStringCharAtOrCodePointAt(
+          genFunctionID.checkedStringCodePointAt, genFunctionID.stringBuiltins.codePointAt)
       genCheckedSubstringStart()
       genCheckedSubstringStartEnd()
     }
@@ -1866,13 +1870,16 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
     fb.buildAndAddToModule()
   }
 
-  /** `checkedStringCharAt: (ref extern), i32 -> i32`.
+  /** `checkedString{CharAt,CodePointAt}`: (ref extern), i32 -> i32`.
    *
-   *  Accesses a char of a string by index. Used when stringIndexOutOfBounds
-   *  are checked.
+   *  Accesses a char/code point of a string by index. Used when
+   *  stringIndexOutOfBounds are checked.
    */
-  private def genCheckedStringCharAt()(implicit ctx: WasmContext): Unit = {
-    val fb = newFunctionBuilder(genFunctionID.checkedStringCharAt)
+  private def genCheckedStringCharAtOrCodePointAt(
+      checkedHelperID: FunctionID, builtinID: FunctionID)(
+      implicit ctx: WasmContext): Unit = {
+
+    val fb = newFunctionBuilder(checkedHelperID)
     val strParam = fb.addParam("str", RefType.extern)
     val indexParam = fb.addParam("index", Int32)
     fb.setResultType(Int32)
@@ -1897,7 +1904,7 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
     // otherwise, read the char
     fb += LocalGet(strParam)
     fb += LocalGet(indexParam)
-    fb += Call(genFunctionID.stringBuiltins.charCodeAt)
+    fb += Call(builtinID)
 
     fb.buildAndAddToModule()
   }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
index 04d6c8b979..3e374880ef 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
@@ -3338,6 +3338,20 @@ private class FunctionEmitter private (
         fb += value.wasmInstr
         value.tpe
 
+      case value @ WasmTransients.WasmCodePointAt(string, index) =>
+        genTree(string, ClassType(BoxedStringClass, nullable = string.tpe.isNullable))
+        if (semantics.stringIndexOutOfBounds == CheckedBehavior.Unchecked)
+          genCheckNonNullFor(string)
+        else
+          genAsNonNullOrNPEFor(string)
+        genTree(index, IntType)
+        markPosition(tree)
+        if (semantics.stringIndexOutOfBounds == CheckedBehavior.Unchecked)
+          fb += wa.Call(genFunctionID.stringBuiltins.codePointAt)
+        else
+          fb += wa.Call(genFunctionID.checkedStringCodePointAt)
+        value.tpe
+
       case value @ WasmTransients.WasmSubstring(string, start, optEnd) =>
         genTree(string, ClassType(BoxedStringClass, nullable = string.tpe.isNullable))
         if (semantics.stringIndexOutOfBounds == CheckedBehavior.Unchecked)
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala
index df56c1a383..6c62917490 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala
@@ -312,6 +312,7 @@ const stringBuiltinPolyfills = {
   test: (x) => typeof x === 'string',
   fromCharCode: (c) => String.fromCharCode(c),
   charCodeAt: (s, i) => s.charCodeAt(i),
+  codePointAt: (s, i) => s.codePointAt(i),
   length: (s) => s.length,
   concat: (a, b) => "" + a + b, // "" tells the JIT that this is *always* a string concat operation
   substring: (str, start, end) => str.substring(start >>> 0, end >>> 0),
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
index 47a535e590..734b7b1a28 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
@@ -251,6 +251,7 @@ object VarGen {
     case object throwNegativeArraySizeException extends FunctionID
     case object throwNullPointerException extends FunctionID
     case object checkedStringCharAt extends FunctionID
+    case object checkedStringCodePointAt extends FunctionID
     case object checkedSubstringStart extends FunctionID
     case object checkedSubstringStartEnd extends FunctionID
     case object throwModuleInitError extends FunctionID
@@ -286,6 +287,7 @@ object VarGen {
       case object test extends JSHelperFunctionID
       case object fromCharCode extends JSHelperFunctionID
       case object charCodeAt extends JSHelperFunctionID
+      case object codePointAt extends JSHelperFunctionID
       case object length extends JSHelperFunctionID
       case object concat extends JSHelperFunctionID
       case object substring extends JSHelperFunctionID
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/WasmTransients.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/WasmTransients.scala
index fdfec90018..1bd47639e8 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/WasmTransients.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/WasmTransients.scala
@@ -207,6 +207,42 @@ object WasmTransients {
     }
   }
 
+  /** Wasm intrinsic for `jl.String.codePointAt`.
+   *
+   *  Typing rules: `string` must be a `jl.String`; `index` must be an `int`.
+   *  The result is an `int`.
+   *
+   *  Evaluation semantics are as follows:
+   *
+   *  1. Let `stringV` be the result of evaluating `string`. If it is `null`,
+   *     throw an NPE (subject to UB).
+   *  2. Let `indexV` be the result of evaluating `index`.
+   *  3. If `indexV < 0` or `indexV >= stringV.length`, throw a
+   *     `StringIndexOutOfBoundsException` (subject to UB).
+   *  4. Return the code point starting at index `indexV` of `stringV`.
+   */
+  final case class WasmCodePointAt(string: Tree, index: Tree)
+      extends Transient.Value {
+
+    val tpe: Type = IntType
+
+    def traverse(traverser: Traverser): Unit = {
+      traverser.traverse(string)
+      traverser.traverse(index)
+    }
+
+    def transform(transformer: Transformer, isStat: Boolean)(
+        implicit pos: Position): Tree = {
+      Transient(WasmCodePointAt(transformer.transformExpr(string),
+          transformer.transformExpr(index)))
+    }
+
+    def printIR(out: IRTreePrinter): Unit = {
+      out.print("$codePointAt")
+      out.printArgs(List(string, index))
+    }
+  }
+
   /** Wasm intrinsic for `jl.String.substring`.
    *
    *  Typing rules: `string` must be a `jl.String`; `start` and `optEnd` must
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
index 35be6b844e..3496ad91f1 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
@@ -3096,6 +3096,11 @@ private[optimizer] abstract class OptimizerCore(
 
       // java.lang.String
 
+      case StringCodePointAt =>
+        contTree(Transient(WasmCodePointAt(
+          finishTransformExpr(optTReceiver.get),
+          finishTransformExpr(targs.head)
+        )))
       case StringSubstringStart =>
         contTree(Transient(WasmSubstring(
           finishTransformExpr(optTReceiver.get),
@@ -6478,7 +6483,8 @@ private[optimizer] object OptimizerCore {
     final val DoubleToLongBits = IntBitsToFloat + 1
     final val LongBitsToDouble = DoubleToLongBits + 1
 
-    final val StringSubstringStart = LongBitsToDouble + 1
+    final val StringCodePointAt = LongBitsToDouble + 1
+    final val StringSubstringStart = StringCodePointAt + 1
     final val StringSubstringStartEnd = StringSubstringStart + 1
 
     final val MathAbsFloat = StringSubstringStartEnd + 1
@@ -6622,6 +6628,7 @@ private[optimizer] object OptimizerCore {
             m("longBitsToDouble", List(J), D) -> LongBitsToDouble
         ),
         ClassName("java.lang.String") -> List(
+            m("codePointAt", List(I), I) -> StringCodePointAt,
             m("substring", List(I), StringClassRef) -> StringSubstringStart,
             m("substring", List(I, I), StringClassRef) -> StringSubstringStartEnd
         ),

From 8d0ae0725cdfda5f780596d722df4f33a3c55549 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Tue, 3 Sep 2024 17:07:34 +0200
Subject: [PATCH 164/298] Opt/Wasm: Intrinsify jl.Character.toString(int).

Implement it using the JS string builtin `fromCodePoint`.
---
 Jenkinsfile                                   |  1 +
 .../src/main/scala/java/lang/Character.scala  |  1 +
 .../backend/wasmemitter/CoreWasmLib.scala     |  1 +
 .../backend/wasmemitter/FunctionEmitter.scala |  6 ++
 .../backend/wasmemitter/LoaderContent.scala   |  1 +
 .../linker/backend/wasmemitter/VarGen.scala   |  1 +
 .../backend/wasmemitter/WasmTransients.scala  | 62 +++++++++++++++----
 .../frontend/optimizer/IncOptimizer.scala     | 16 ++++-
 .../frontend/optimizer/OptimizerCore.scala    | 23 ++++++-
 9 files changed, 98 insertions(+), 14 deletions(-)

diff --git a/Jenkinsfile b/Jenkinsfile
index 814467aee2..141b4c1a1d 100644
--- a/Jenkinsfile
+++ b/Jenkinsfile
@@ -623,6 +623,7 @@ otherScalaVersions.each { scalaVersion ->
 mainScalaVersions.each { scalaVersion ->
   otherJavaVersions.each { javaVersion ->
     quickMatrix.add([task: "test-suite-default-esversion", scala: scalaVersion, java: javaVersion, testMinify: "false", testSuite: "testSuite"])
+    quickMatrix.add([task: "test-suite-webassembly", scala: scalaVersion, java: mainJavaVersion, testMinify: "false", testSuite: "testSuite"])
   }
   fullMatrix.add([task: "partest-noopt", scala: scalaVersion, java: mainJavaVersion, partestopts: ""])
   fullMatrix.add([task: "partest-noopt", scala: scalaVersion, java: mainJavaVersion, partestopts: "--wasm"])
diff --git a/javalib/src/main/scala/java/lang/Character.scala b/javalib/src/main/scala/java/lang/Character.scala
index cc938fb49a..50c38793ac 100644
--- a/javalib/src/main/scala/java/lang/Character.scala
+++ b/javalib/src/main/scala/java/lang/Character.scala
@@ -123,6 +123,7 @@ object Character {
   @inline def toString(c: Char): String =
     "" + c
 
+  // Wasm intrinsic
   def toString(codePoint: Int): String = {
     if (!isValidCodePoint(codePoint))
       throw new IllegalArgumentException()
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
index 4a1ada3ee0..4da2acaff9 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
@@ -325,6 +325,7 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
 
     addHelperImport(genFunctionID.stringBuiltins.test, List(externref), List(Int32))
     addHelperImport(genFunctionID.stringBuiltins.fromCharCode, List(Int32), List(extern))
+    addHelperImport(genFunctionID.stringBuiltins.fromCodePoint, List(Int32), List(extern))
     addHelperImport(genFunctionID.stringBuiltins.charCodeAt, List(externref, Int32), List(Int32))
     addHelperImport(genFunctionID.stringBuiltins.codePointAt, List(externref, Int32), List(Int32))
     addHelperImport(genFunctionID.stringBuiltins.length, List(externref), List(Int32))
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
index 3e374880ef..9626403260 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
@@ -3338,6 +3338,12 @@ private class FunctionEmitter private (
         fb += value.wasmInstr
         value.tpe
 
+      case value @ WasmTransients.WasmStringFromCodePoint(codePoint) =>
+        genTree(codePoint, IntType)
+        markPosition(tree)
+        fb += wa.Call(genFunctionID.stringBuiltins.fromCodePoint)
+        value.tpe
+
       case value @ WasmTransients.WasmCodePointAt(string, index) =>
         genTree(string, ClassType(BoxedStringClass, nullable = string.tpe.isNullable))
         if (semantics.stringIndexOutOfBounds == CheckedBehavior.Unchecked)
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala
index 6c62917490..90ce8400bf 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala
@@ -311,6 +311,7 @@ const scalaJSHelpers = {
 const stringBuiltinPolyfills = {
   test: (x) => typeof x === 'string',
   fromCharCode: (c) => String.fromCharCode(c),
+  fromCodePoint: (cp) => String.fromCodePoint(cp),
   charCodeAt: (s, i) => s.charCodeAt(i),
   codePointAt: (s, i) => s.codePointAt(i),
   length: (s) => s.length,
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
index 734b7b1a28..893438b561 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
@@ -286,6 +286,7 @@ object VarGen {
     object stringBuiltins {
       case object test extends JSHelperFunctionID
       case object fromCharCode extends JSHelperFunctionID
+      case object fromCodePoint extends JSHelperFunctionID
       case object charCodeAt extends JSHelperFunctionID
       case object codePointAt extends JSHelperFunctionID
       case object length extends JSHelperFunctionID
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/WasmTransients.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/WasmTransients.scala
index 1bd47639e8..b1471a3f47 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/WasmTransients.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/WasmTransients.scala
@@ -148,6 +148,8 @@ object WasmTransients {
     }
 
     def wasmInstr: wa.SimpleInstr = (op: @switch) match {
+      case I32GtU => wa.I32GtU
+
       case I32DivU => wa.I32DivU
       case I32RemU => wa.I32RemU
       case I32Rotl => wa.I32Rotl
@@ -176,23 +178,28 @@ object WasmTransients {
     /** Codes are raw Ints to be able to write switch matches on them. */
     type Code = Int
 
-    final val I32DivU = 1
-    final val I32RemU = 2
-    final val I32Rotl = 3
-    final val I32Rotr = 4
+    final val I32GtU = 1
+
+    final val I32DivU = 2
+    final val I32RemU = 3
+    final val I32Rotl = 4
+    final val I32Rotr = 5
 
-    final val I64DivU = 5
-    final val I64RemU = 6
-    final val I64Rotl = 7
-    final val I64Rotr = 8
+    final val I64DivU = 6
+    final val I64RemU = 7
+    final val I64Rotl = 8
+    final val I64Rotr = 9
 
-    final val F32Min = 9
-    final val F32Max = 10
+    final val F32Min = 10
+    final val F32Max = 11
 
-    final val F64Min = 11
-    final val F64Max = 12
+    final val F64Min = 12
+    final val F64Max = 13
 
     def resultTypeOf(op: Code): Type = (op: @switch) match {
+      case I32GtU =>
+        BooleanType
+
       case I32DivU | I32RemU | I32Rotl | I32Rotr =>
         IntType
 
@@ -207,6 +214,37 @@ object WasmTransients {
     }
   }
 
+  /** Wasm intrinsic for `jl.Character.toString(int)`.
+   *
+   *  Typing rules: `codePoint` must be an `int`. The result is a `string`.
+   *
+   *  Evaluation semantics are as follows:
+   *
+   *  1. Let `codePointV` be the result of evaluating `codePoint`.
+   *  2. If `codePointV` is not a valid code point, UB (i.e., this transient
+   *     *assumes* that `codePointV` is a valid code point).
+   *  3. Return a string of 1 or 2 chars that represents the given code point.
+   */
+  final case class WasmStringFromCodePoint(codePoint: Tree)
+      extends Transient.Value {
+
+    val tpe: Type = StringType
+
+    def traverse(traverser: Traverser): Unit = {
+      traverser.traverse(codePoint)
+    }
+
+    def transform(transformer: Transformer, isStat: Boolean)(
+        implicit pos: Position): Tree = {
+      Transient(WasmStringFromCodePoint(transformer.transformExpr(codePoint)))
+    }
+
+    def printIR(out: IRTreePrinter): Unit = {
+      out.print("$stringFromCodePoint")
+      out.printArgs(List(codePoint))
+    }
+  }
+
   /** Wasm intrinsic for `jl.String.codePointAt`.
    *
    *  Typing rules: `string` must be a `jl.String`; `index` must be an `int`.
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
index df0b8d72b2..c56ed9420c 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
@@ -63,10 +63,24 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
   import IncOptimizer._
 
   val symbolRequirements: SymbolRequirement = {
+    import config.coreSpec._
+
     val factory = SymbolRequirement.factory("optimizer")
     import factory._
 
-    callMethods(LongImpl.RuntimeLongClass, LongImpl.AllIntrinsicMethods.toList)
+    def cond(p: Boolean)(v: => SymbolRequirement): SymbolRequirement =
+      if (p) v else none()
+
+    multiple(
+      cond(!targetIsWebAssembly && !esFeatures.allowBigIntsForLongs) {
+        // Required by the intrinsics manipulating Longs
+        callMethods(LongImpl.RuntimeLongClass, LongImpl.AllIntrinsicMethods.toList)
+      },
+      cond(targetIsWebAssembly) {
+        // Required by the intrinsic CharacterCodePointToString
+        instantiateClass(OptimizerCore.IllegalArgumentExceptionClass, NoArgConstructorName)
+      }
+    )
   }
 
   /** Are we in batch mode? I.e., are we running from scratch?
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
index 3496ad91f1..82be00b249 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
@@ -3094,6 +3094,21 @@ private[optimizer] abstract class OptimizerCore(
       case LongBitsToDouble =>
         contTree(wasmUnaryOp(WasmUnaryOp.F64ReinterpretI64, targs.head))
 
+      // java.lang.Character
+
+      case CharacterCodePointToString =>
+        withNewLocalDef(Binding.temp(LocalName("codePoint"), targs.head)) { (cpLocalDef, cont1) =>
+          cont1(PreTransTree(Block(
+            If(
+              Transient(WasmBinaryOp(WasmBinaryOp.I32GtU,
+                  cpLocalDef.newReplacement, IntLiteral(Character.MAX_CODE_POINT))),
+              Throw(New(IllegalArgumentExceptionClass, MethodIdent(NoArgConstructorName), Nil)),
+              Skip()
+            )(NoType),
+            Transient(WasmStringFromCodePoint(cpLocalDef.newReplacement))
+          )))
+        } (cont)
+
       // java.lang.String
 
       case StringCodePointAt =>
@@ -5611,6 +5626,7 @@ private[optimizer] object OptimizerCore {
   private val ClassTagModuleClass = ClassName("scala.reflect.ClassTag$")
   private val JavaScriptExceptionClass = ClassName("scala.scalajs.js.JavaScriptException")
   private val JSWrappedArrayClass = ClassName("scala.scalajs.js.WrappedArray")
+  private[optimizer] val IllegalArgumentExceptionClass = ClassName("java.lang.IllegalArgumentException")
   private val NilClass = ClassName("scala.collection.immutable.Nil$")
   private val Tuple2Class = ClassName("scala.Tuple2")
 
@@ -6483,7 +6499,9 @@ private[optimizer] object OptimizerCore {
     final val DoubleToLongBits = IntBitsToFloat + 1
     final val LongBitsToDouble = DoubleToLongBits + 1
 
-    final val StringCodePointAt = LongBitsToDouble + 1
+    final val CharacterCodePointToString = LongBitsToDouble + 1
+
+    final val StringCodePointAt = CharacterCodePointToString + 1
     final val StringSubstringStart = StringCodePointAt + 1
     final val StringSubstringStartEnd = StringSubstringStart + 1
 
@@ -6627,6 +6645,9 @@ private[optimizer] object OptimizerCore {
             m("doubleToLongBits", List(D), J) -> DoubleToLongBits,
             m("longBitsToDouble", List(J), D) -> LongBitsToDouble
         ),
+        ClassName("java.lang.Character$") -> List(
+            m("toString", List(I), StringClassRef) -> CharacterCodePointToString
+        ),
         ClassName("java.lang.String") -> List(
             m("codePointAt", List(I), I) -> StringCodePointAt,
             m("substring", List(I), StringClassRef) -> StringSubstringStart,

From eaf4a2b3aecc2f5407755a8f11cd43c69d12b412 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Wed, 4 Sep 2024 22:00:48 +0200
Subject: [PATCH 165/298] Wasm: Enable the
 `--experimental-wasm-imported-strings` flag in Node.js.

It enables the JS string builtins.
---
 partest/src/main/scala/scala/tools/nsc/MainGenericRunner.scala | 1 +
 project/Build.scala                                            | 1 +
 2 files changed, 2 insertions(+)

diff --git a/partest/src/main/scala/scala/tools/nsc/MainGenericRunner.scala b/partest/src/main/scala/scala/tools/nsc/MainGenericRunner.scala
index 1ee94d93cb..9158f3aa68 100644
--- a/partest/src/main/scala/scala/tools/nsc/MainGenericRunner.scala
+++ b/partest/src/main/scala/scala/tools/nsc/MainGenericRunner.scala
@@ -138,6 +138,7 @@ class MainGenericRunner {
     } else {
       NodeJSEnv.Config().withArgs(List(
         "--experimental-wasm-exnref",
+        "--experimental-wasm-imported-strings", // for JS string builtins
         /* Force using the Turboshaft infrastructure for the optimizing compiler.
          * It appears to be more stable for the Wasm that we throw at it.
          * See also the use of this flag in Build.scala.
diff --git a/project/Build.scala b/project/Build.scala
index 8c0837ca92..9cda252d2e 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -249,6 +249,7 @@ object MyScalaJSPlugin extends AutoPlugin {
         val config = if (enableWasmEverywhere.value) {
           baseConfig.withArgs(List(
             "--experimental-wasm-exnref",
+            "--experimental-wasm-imported-strings", // for JS string builtins
             /* Force using the Turboshaft infrastructure for the optimizing compiler.
              * It appears to be more stable for the Wasm that we throw at it.
              * If you remove it, try running `scalaTestSuite2_13/test` with Wasm.

From a233bb27861aae7c029f6299a4a379fc62af2129 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Sun, 1 Sep 2024 16:52:31 +0200
Subject: [PATCH 166/298] Refactor: Rename `emitter.ArrayClassProperty` to
 `SyntheticProperty`.

In the next commit, we will add `jl.Class.data` as a synthetic
property, which we will have to handle in the same way as
`ArrayClass` properties. We therefore rename the concept to be more
general and include any synthetic property on Scala classes.
---
 .../linker/backend/emitter/CoreJSLib.scala    | 20 ++++++-------
 .../backend/emitter/FunctionEmitter.scala     | 14 +++++-----
 .../backend/emitter/NameCompressor.scala      | 16 +++++------
 .../linker/backend/emitter/SJSGen.scala       | 16 +++++------
 ...Property.scala => SyntheticProperty.scala} | 28 +++++++++++--------
 5 files changed, 50 insertions(+), 44 deletions(-)
 rename linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/{ArrayClassProperty.scala => SyntheticProperty.scala} (50%)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
index 2c27c125b9..792c1a5677 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
@@ -1126,7 +1126,7 @@ private[emitter] object CoreJSLib {
       ) :::
       condDefs(esVersion >= ESVersion.ES2015 && nullPointers != CheckedBehavior.Unchecked)(
         defineFunction5(VarField.systemArraycopy) { (src, srcPos, dest, destPos, length) =>
-          genArrayClassPropApply(src, ArrayClassProperty.copyTo, srcPos, dest, destPos, length)
+          genSyntheticPropApply(src, SyntheticProperty.copyTo, srcPos, dest, destPos, length)
         }
       ) :::
 
@@ -1150,7 +1150,7 @@ private[emitter] object CoreJSLib {
                     srcPos, dest.u.length, destPos, length)
               },
               For(let(i, 0), i < length, i := ((i + 1) | 0), {
-                genArrayClassPropApply(dest, ArrayClassProperty.set,
+                genSyntheticPropApply(dest, SyntheticProperty.set,
                     (destPos + i) | 0, BracketSelect(srcArray, (srcPos + i) | 0))
               })
             )
@@ -1168,7 +1168,7 @@ private[emitter] object CoreJSLib {
               If(srcData && genIdentBracketSelect(srcData, cpn.isArrayClass), {
                 // Fast path: the values are array of the same type
                 if (esVersion >= ESVersion.ES2015 && nullPointers == CheckedBehavior.Unchecked)
-                  genArrayClassPropApply(src, ArrayClassProperty.copyTo, srcPos, dest, destPos, length)
+                  genSyntheticPropApply(src, SyntheticProperty.copyTo, srcPos, dest, destPos, length)
                 else
                   genCallHelper(VarField.systemArraycopy, src, srcPos, dest, destPos, length)
               }, {
@@ -1440,8 +1440,8 @@ private[emitter] object CoreJSLib {
                 genCallHelper(VarField.throwArrayIndexOutOfBoundsException, i))
           }
 
-          val getName = genArrayClassPropertyForDef(ArrayClassProperty.get)
-          val setName = genArrayClassPropertyForDef(ArrayClassProperty.set)
+          val getName = genSyntheticPropertyForDef(SyntheticProperty.get)
+          val setName = genSyntheticPropertyForDef(SyntheticProperty.set)
 
           List(
               MethodDef(static = false, getName, paramList(i), None, {
@@ -1464,7 +1464,7 @@ private[emitter] object CoreJSLib {
           val i = varRef("i")
           val v = varRef("v")
 
-          val setName = genArrayClassPropertyForDef(ArrayClassProperty.set)
+          val setName = genSyntheticPropertyForDef(SyntheticProperty.set)
 
           List(
             MethodDef(static = false, setName, paramList(i, v), None, {
@@ -1481,7 +1481,7 @@ private[emitter] object CoreJSLib {
           val destPos = varRef("destPos")
           val length = varRef("length")
 
-          val copyToName = genArrayClassPropertyForDef(ArrayClassProperty.copyTo)
+          val copyToName = genSyntheticPropertyForDef(SyntheticProperty.copyTo)
 
           val methodDef = MethodDef(static = false, copyToName,
               paramList(srcPos, dest, destPos, length), None, {
@@ -1789,7 +1789,7 @@ private[emitter] object CoreJSLib {
               val i = varRef("i")
               val v = varRef("v")
 
-              val setName = genArrayClassPropertyForDef(ArrayClassProperty.set)
+              val setName = genSyntheticPropertyForDef(SyntheticProperty.set)
 
               val boundsCheck = condTree(arrayIndexOutOfBounds != CheckedBehavior.Unchecked) {
                 If((i < 0) || (i >= This().u.length),
@@ -1821,7 +1821,7 @@ private[emitter] object CoreJSLib {
               val destPos = varRef("destPos")
               val length = varRef("length")
 
-              val copyToName = genArrayClassPropertyForDef(ArrayClassProperty.copyTo)
+              val copyToName = genSyntheticPropertyForDef(SyntheticProperty.copyTo)
 
               val methodDef = MethodDef(static = false, copyToName,
                   paramList(srcPos, dest, destPos, length), None, {
@@ -2269,7 +2269,7 @@ private[emitter] object CoreJSLib {
 
     // cannot extend AnyVal because this is not a static class
     private implicit class CustomTreeOps(private val self: Tree) {
-      def u: Tree = genArrayClassPropSelect(self, ArrayClassProperty.u)
+      def u: Tree = genSyntheticPropSelect(self, SyntheticProperty.u)
     }
   }
 }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
index 4e322050b2..e1e010eeb2 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
@@ -632,11 +632,11 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
                 }
 
                 if (checked) {
-                  genArrayClassPropApply(genArray, ArrayClassProperty.set, genIndex, genRhs)
+                  genSyntheticPropApply(genArray, SyntheticProperty.set, genIndex, genRhs)
                 } else {
                   js.Assign(
                       js.BracketSelect(
-                          genArrayClassPropSelect(genArray, ArrayClassProperty.u)(lhs.pos),
+                          genSyntheticPropSelect(genArray, SyntheticProperty.u)(lhs.pos),
                           genIndex)(lhs.pos),
                       genRhs)
                 }
@@ -876,7 +876,7 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
 
             def genUnchecked(): js.Tree = {
               if (esFeatures.esVersion >= ESVersion.ES2015 && semantics.nullPointers == CheckedBehavior.Unchecked)
-                genArrayClassPropApply(jsArgs.head, ArrayClassProperty.copyTo, jsArgs.tail)
+                genSyntheticPropApply(jsArgs.head, SyntheticProperty.copyTo, jsArgs.tail)
               else
                 genCallHelper(VarField.systemArraycopy, jsArgs: _*)
             }
@@ -2680,7 +2680,7 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
         case ArrayLength(array) =>
           val newArray = transformExprNoChar(checkNotNull(array))
           genIdentBracketSelect(
-              genArrayClassPropSelect(newArray, ArrayClassProperty.u),
+              genSyntheticPropSelect(newArray, SyntheticProperty.u),
               "length")
 
         case ArraySelect(array, index) =>
@@ -2688,9 +2688,9 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
           val newIndex = transformExprNoChar(index)
           semantics.arrayIndexOutOfBounds match {
             case CheckedBehavior.Compliant | CheckedBehavior.Fatal =>
-              genArrayClassPropApply(newArray, ArrayClassProperty.get, newIndex)
+              genSyntheticPropApply(newArray, SyntheticProperty.get, newIndex)
             case CheckedBehavior.Unchecked =>
-              js.BracketSelect(genArrayClassPropSelect(newArray, ArrayClassProperty.u), newIndex)
+              js.BracketSelect(genSyntheticPropSelect(newArray, SyntheticProperty.u), newIndex)
           }
 
         case tree: RecordSelect =>
@@ -2794,7 +2794,7 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
 
         case Transient(ArrayToTypedArray(expr, primRef)) =>
           val value = transformExprNoChar(checkNotNull(expr))
-          val valueUnderlying = genArrayClassPropSelect(value, ArrayClassProperty.u)
+          val valueUnderlying = genSyntheticPropSelect(value, SyntheticProperty.u)
 
           if (es2015) {
             js.Apply(genIdentBracketSelect(valueUnderlying, "slice"), Nil)
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/NameCompressor.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/NameCompressor.scala
index 0db5ead5bf..e2e8d32d34 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/NameCompressor.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/NameCompressor.scala
@@ -56,8 +56,8 @@ private[emitter] final class NameCompressor(config: Emitter.Config) {
   def genResolverFor(methodName: MethodName): Resolver =
     entries.getOrElseUpdate(methodName, new MethodNameEntry(methodName)).genResolver()
 
-  def genResolverFor(prop: ArrayClassProperty): Resolver =
-    entries.getOrElseUpdate(prop, new ArrayClassPropEntry(prop)).genResolver()
+  def genResolverFor(prop: SyntheticProperty): Resolver =
+    entries.getOrElseUpdate(prop, new SyntheticPropEntry(prop)).genResolver()
 
   def genResolverForAncestor(ancestor: ClassName): Resolver =
     ancestorEntries.getOrElseUpdate(ancestor, new AncestorNameEntry(ancestor)).genResolver()
@@ -168,14 +168,14 @@ private[emitter] object NameCompressor {
       case (x: MethodNameEntry, y: MethodNameEntry) =>
         x.methodName.compareTo(y.methodName)
 
-      case (x: ArrayClassPropEntry, y: ArrayClassPropEntry) =>
+      case (x: SyntheticPropEntry, y: SyntheticPropEntry) =>
         x.property.compareTo(y.property)
 
       case _ =>
         def ordinalFor(x: PropertyNameEntry): Int = x match {
-          case _: FieldNameEntry      => 1
-          case _: MethodNameEntry     => 2
-          case _: ArrayClassPropEntry => 3
+          case _: FieldNameEntry     => 1
+          case _: MethodNameEntry    => 2
+          case _: SyntheticPropEntry => 3
         }
         ordinalFor(this) - ordinalFor(that)
     }
@@ -195,11 +195,11 @@ private[emitter] object NameCompressor {
     override def toString(): String = s"MethodNameEntry(${methodName.nameString})"
   }
 
-  private final class ArrayClassPropEntry(val property: ArrayClassProperty)
+  private final class SyntheticPropEntry(val property: SyntheticProperty)
       extends PropertyNameEntry {
     protected def debugString: String = property.nonMinifiedName
 
-    override def toString(): String = s"ArrayClassPropEntry(${property.nonMinifiedName})"
+    override def toString(): String = s"SyntheticPropEntry(${property.nonMinifiedName})"
   }
 
   private final class AncestorNameEntry(val ancestor: ClassName)
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala
index 2a9b3cf93e..ef7aaf8ea8 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala
@@ -356,29 +356,29 @@ private[emitter] final class SJSGen(
     }
   }
 
-  def genArrayClassPropApply(receiver: Tree, prop: ArrayClassProperty, args: Tree*)(
+  def genSyntheticPropApply(receiver: Tree, prop: SyntheticProperty, args: Tree*)(
       implicit pos: Position): Tree = {
-    genArrayClassPropApply(receiver, prop, args.toList)
+    genSyntheticPropApply(receiver, prop, args.toList)
   }
 
-  def genArrayClassPropApply(receiver: Tree, prop: ArrayClassProperty, args: List[Tree])(
+  def genSyntheticPropApply(receiver: Tree, prop: SyntheticProperty, args: List[Tree])(
       implicit pos: Position): Tree = {
-    Apply(genArrayClassPropSelect(receiver, prop), args)
+    Apply(genSyntheticPropSelect(receiver, prop), args)
   }
 
-  def genArrayClassPropSelect(qualifier: Tree, prop: ArrayClassProperty)(
+  def genSyntheticPropSelect(qualifier: Tree, prop: SyntheticProperty)(
       implicit pos: Position): Tree = {
-    DotSelect(qualifier, genArrayClassProperty(prop))
+    DotSelect(qualifier, genSyntheticProperty(prop))
   }
 
-  def genArrayClassProperty(prop: ArrayClassProperty)(implicit pos: Position): MaybeDelayedIdent = {
+  def genSyntheticProperty(prop: SyntheticProperty)(implicit pos: Position): MaybeDelayedIdent = {
     nameCompressor match {
       case None             => Ident(prop.nonMinifiedName)
       case Some(compressor) => DelayedIdent(compressor.genResolverFor(prop))
     }
   }
 
-  def genArrayClassPropertyForDef(prop: ArrayClassProperty)(implicit pos: Position): MaybeDelayedIdent = {
+  def genSyntheticPropertyForDef(prop: SyntheticProperty)(implicit pos: Position): MaybeDelayedIdent = {
     nameCompressor match {
       case None             => Ident(prop.nonMinifiedName)
       case Some(compressor) => DelayedIdent(compressor.genResolverFor(prop), prop.originalName)
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ArrayClassProperty.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SyntheticProperty.scala
similarity index 50%
rename from linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ArrayClassProperty.scala
rename to linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SyntheticProperty.scala
index c33d0a99e7..84afaceff1 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ArrayClassProperty.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SyntheticProperty.scala
@@ -14,33 +14,39 @@ package org.scalajs.linker.backend.emitter
 
 import org.scalajs.ir.OriginalName
 
-/** Represents a property of one of the special `ArrayClass`es.
+/** Represents a synthetic property of some Scala classes.
+ *
+ *  A synthetic property does not exist as `FieldDef` or `MethodDef` in the IR,
+ *  but is added by the Emitter on some classes that belong to the Scala class
+ *  hierarchy.
+ *
+ *  Currently, these only include properties of the `ArrayClass`es.
  *
  *  These properties live in the same namespace as Scala field and method
  *  names, because the `ArrayClass`es extend `j.l.Object`. Therefore, they
  *  must take part in the global property minification algorithm.
  */
-final class ArrayClassProperty(val nonMinifiedName: String)
-    extends Comparable[ArrayClassProperty] {
+final class SyntheticProperty(val nonMinifiedName: String)
+    extends Comparable[SyntheticProperty] {
 
   val originalName: OriginalName = OriginalName(nonMinifiedName)
 
-  def compareTo(that: ArrayClassProperty): Int =
+  def compareTo(that: SyntheticProperty): Int =
     this.nonMinifiedName.compareTo(that.nonMinifiedName)
 
-  override def toString(): String = s"ArrayClassProperty($nonMinifiedName)"
+  override def toString(): String = s"SyntheticProperty($nonMinifiedName)"
 }
 
-object ArrayClassProperty {
-  /** `ArrayClass.u`: the underlying array of typed array. */
-  val u: ArrayClassProperty = new ArrayClassProperty("u")
+object SyntheticProperty {
+  /** `ArrayClass.u`: the underlying array or typed array. */
+  val u: SyntheticProperty = new SyntheticProperty("u")
 
   /** `ArrayClass.get()`: gets one element. */
-  val get: ArrayClassProperty = new ArrayClassProperty("get")
+  val get: SyntheticProperty = new SyntheticProperty("get")
 
   /** `ArrayClass.set()`: sets one element. */
-  val set: ArrayClassProperty = new ArrayClassProperty("set")
+  val set: SyntheticProperty = new SyntheticProperty("set")
 
   /** `ArrayClass.copyTo()`: copies from that array to another array. */
-  val copyTo: ArrayClassProperty = new ArrayClassProperty("copyTo")
+  val copyTo: SyntheticProperty = new SyntheticProperty("copyTo")
 }

From 75bd236432f018bb9b3ae043a20ba552e2dbe50f Mon Sep 17 00:00:00 2001
From: "dependabot[bot]" <49699333+dependabot[bot]@users.noreply.github.com>
Date: Wed, 18 Sep 2024 19:17:33 +0000
Subject: [PATCH 167/298] Bump serve-static and express

Bumps [serve-static](https://github.com/expressjs/serve-static) to 1.16.2 and updates ancestor dependency [express](https://github.com/expressjs/express). These dependencies need to be updated together.


Updates `serve-static` from 1.15.0 to 1.16.2
- [Release notes](https://github.com/expressjs/serve-static/releases)
- [Changelog](https://github.com/expressjs/serve-static/blob/v1.16.2/HISTORY.md)
- [Commits](https://github.com/expressjs/serve-static/compare/v1.15.0...v1.16.2)

Updates `express` from 4.19.2 to 4.21.0
- [Release notes](https://github.com/expressjs/express/releases)
- [Changelog](https://github.com/expressjs/express/blob/4.21.0/History.md)
- [Commits](https://github.com/expressjs/express/compare/4.19.2...4.21.0)

---
updated-dependencies:
- dependency-name: serve-static
  dependency-type: indirect
- dependency-name: express
  dependency-type: direct:development
...

Signed-off-by: dependabot[bot] <support@github.com>
---
 package-lock.json | 480 ++++++++++++++++++++++++++++++++--------------
 package.json      |   2 +-
 2 files changed, 341 insertions(+), 141 deletions(-)

diff --git a/package-lock.json b/package-lock.json
index b7f175e7dc..6cf3197b4a 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -5,7 +5,7 @@
   "packages": {
     "": {
       "devDependencies": {
-        "express": "4.19.2",
+        "express": "4.21.0",
         "jsdom": "16.7.0",
         "jszip": "3.8.0",
         "source-map-support": "0.5.19"
@@ -130,9 +130,9 @@
       "dev": true
     },
     "node_modules/body-parser": {
-      "version": "1.20.2",
-      "resolved": "https://registry.npmjs.org/body-parser/-/body-parser-1.20.2.tgz",
-      "integrity": "sha512-ml9pReCu3M61kGlqoTm2umSXTlRTuGTx0bfYj+uIUKKYycG5NtSbeetV3faSU6R7ajOPw0g/J1PvK4qNy7s5bA==",
+      "version": "1.20.3",
+      "resolved": "https://registry.npmjs.org/body-parser/-/body-parser-1.20.3.tgz",
+      "integrity": "sha512-7rAxByjUMqQ3/bHJy7D6OGXvx/MMc4IqBn/X0fcM1QUcAItpZrBEYhWGem+tzXH90c+G01ypMcYJBO9Y30203g==",
       "dev": true,
       "dependencies": {
         "bytes": "3.1.2",
@@ -143,7 +143,7 @@
         "http-errors": "2.0.0",
         "iconv-lite": "0.4.24",
         "on-finished": "2.4.1",
-        "qs": "6.11.0",
+        "qs": "6.13.0",
         "raw-body": "2.5.2",
         "type-is": "~1.6.18",
         "unpipe": "1.0.0"
@@ -175,13 +175,19 @@
       }
     },
     "node_modules/call-bind": {
-      "version": "1.0.2",
-      "resolved": "https://registry.npmjs.org/call-bind/-/call-bind-1.0.2.tgz",
-      "integrity": "sha512-7O+FbCihrB5WGbFYesctwmTKae6rOiIzmz1icreWJ+0aA7LJfuqhEso2T9ncpcFtzMQtzXf2QGGueWJGTYsqrA==",
+      "version": "1.0.7",
+      "resolved": "https://registry.npmjs.org/call-bind/-/call-bind-1.0.7.tgz",
+      "integrity": "sha512-GHTSNSYICQ7scH7sZ+M2rFopRoLh8t2bLSW6BbgrtLsahOIB5iyAVJf9GjWK3cYTDaMj4XdBpM1cA6pIS0Kv2w==",
       "dev": true,
       "dependencies": {
-        "function-bind": "^1.1.1",
-        "get-intrinsic": "^1.0.2"
+        "es-define-property": "^1.0.0",
+        "es-errors": "^1.3.0",
+        "function-bind": "^1.1.2",
+        "get-intrinsic": "^1.2.4",
+        "set-function-length": "^1.2.1"
+      },
+      "engines": {
+        "node": ">= 0.4"
       },
       "funding": {
         "url": "https://github.com/sponsors/ljharb"
@@ -320,6 +326,23 @@
       "integrity": "sha512-oIPzksmTg4/MriiaYGO+okXDT7ztn/w3Eptv/+gSIdMdKsJo0u4CfYNFJPy+4SKMuCqGw2wxnA+URMg3t8a/bQ==",
       "dev": true
     },
+    "node_modules/define-data-property": {
+      "version": "1.1.4",
+      "resolved": "https://registry.npmjs.org/define-data-property/-/define-data-property-1.1.4.tgz",
+      "integrity": "sha512-rBMvIzlpA8v6E+SJZoo++HAYqsLrkg7MSfIinMPFhmkorw7X+dOXVJQs+QT69zGkzMyfDnIMN2Wid1+NbL3T+A==",
+      "dev": true,
+      "dependencies": {
+        "es-define-property": "^1.0.0",
+        "es-errors": "^1.3.0",
+        "gopd": "^1.0.1"
+      },
+      "engines": {
+        "node": ">= 0.4"
+      },
+      "funding": {
+        "url": "https://github.com/sponsors/ljharb"
+      }
+    },
     "node_modules/delayed-stream": {
       "version": "1.0.0",
       "resolved": "https://registry.npmjs.org/delayed-stream/-/delayed-stream-1.0.0.tgz",
@@ -376,14 +399,35 @@
       "dev": true
     },
     "node_modules/encodeurl": {
-      "version": "1.0.2",
-      "resolved": "https://registry.npmjs.org/encodeurl/-/encodeurl-1.0.2.tgz",
-      "integrity": "sha512-TPJXq8JqFaVYm2CWmPvnP2Iyo4ZSM7/QKcSmuMLDObfpH5fi7RUGmd/rTDf+rut/saiDiQEeVTNgAmJEdAOx0w==",
+      "version": "2.0.0",
+      "resolved": "https://registry.npmjs.org/encodeurl/-/encodeurl-2.0.0.tgz",
+      "integrity": "sha512-Q0n9HRi4m6JuGIV1eFlmvJB7ZEVxu93IrMyiMsGC0lrMJMWzRgx6WGquyfQgZVb31vhGgXnfmPNNXmxnOkRBrg==",
       "dev": true,
       "engines": {
         "node": ">= 0.8"
       }
     },
+    "node_modules/es-define-property": {
+      "version": "1.0.0",
+      "resolved": "https://registry.npmjs.org/es-define-property/-/es-define-property-1.0.0.tgz",
+      "integrity": "sha512-jxayLKShrEqqzJ0eumQbVhTYQM27CfT1T35+gCgDFoL82JLsXqTJ76zv6A0YLOgEnLUMvLzsDsGIrl8NFpT2gQ==",
+      "dev": true,
+      "dependencies": {
+        "get-intrinsic": "^1.2.4"
+      },
+      "engines": {
+        "node": ">= 0.4"
+      }
+    },
+    "node_modules/es-errors": {
+      "version": "1.3.0",
+      "resolved": "https://registry.npmjs.org/es-errors/-/es-errors-1.3.0.tgz",
+      "integrity": "sha512-Zf5H2Kxt2xjTvbJvP2ZWLEICxA6j+hAmMzIlypy4xcBg1vKVnx89Wy0GbS+kf5cwCVFFzdCFh2XSCFNULS6csw==",
+      "dev": true,
+      "engines": {
+        "node": ">= 0.4"
+      }
+    },
     "node_modules/escape-html": {
       "version": "1.0.3",
       "resolved": "https://registry.npmjs.org/escape-html/-/escape-html-1.0.3.tgz",
@@ -453,37 +497,37 @@
       }
     },
     "node_modules/express": {
-      "version": "4.19.2",
-      "resolved": "https://registry.npmjs.org/express/-/express-4.19.2.tgz",
-      "integrity": "sha512-5T6nhjsT+EOMzuck8JjBHARTHfMht0POzlA60WV2pMD3gyXw2LZnZ+ueGdNxG+0calOJcWKbpFcuzLZ91YWq9Q==",
+      "version": "4.21.0",
+      "resolved": "https://registry.npmjs.org/express/-/express-4.21.0.tgz",
+      "integrity": "sha512-VqcNGcj/Id5ZT1LZ/cfihi3ttTn+NJmkli2eZADigjq29qTlWi/hAQ43t/VLPq8+UX06FCEx3ByOYet6ZFblng==",
       "dev": true,
       "dependencies": {
         "accepts": "~1.3.8",
         "array-flatten": "1.1.1",
-        "body-parser": "1.20.2",
+        "body-parser": "1.20.3",
         "content-disposition": "0.5.4",
         "content-type": "~1.0.4",
         "cookie": "0.6.0",
         "cookie-signature": "1.0.6",
         "debug": "2.6.9",
         "depd": "2.0.0",
-        "encodeurl": "~1.0.2",
+        "encodeurl": "~2.0.0",
         "escape-html": "~1.0.3",
         "etag": "~1.8.1",
-        "finalhandler": "1.2.0",
+        "finalhandler": "1.3.1",
         "fresh": "0.5.2",
         "http-errors": "2.0.0",
-        "merge-descriptors": "1.0.1",
+        "merge-descriptors": "1.0.3",
         "methods": "~1.1.2",
         "on-finished": "2.4.1",
         "parseurl": "~1.3.3",
-        "path-to-regexp": "0.1.7",
+        "path-to-regexp": "0.1.10",
         "proxy-addr": "~2.0.7",
-        "qs": "6.11.0",
+        "qs": "6.13.0",
         "range-parser": "~1.2.1",
         "safe-buffer": "5.2.1",
-        "send": "0.18.0",
-        "serve-static": "1.15.0",
+        "send": "0.19.0",
+        "serve-static": "1.16.2",
         "setprototypeof": "1.2.0",
         "statuses": "2.0.1",
         "type-is": "~1.6.18",
@@ -521,13 +565,13 @@
       "dev": true
     },
     "node_modules/finalhandler": {
-      "version": "1.2.0",
-      "resolved": "https://registry.npmjs.org/finalhandler/-/finalhandler-1.2.0.tgz",
-      "integrity": "sha512-5uXcUVftlQMFnWC9qu/svkWv3GTd2PfUhK/3PLkYNAe7FbqJMt3515HaxE6eRL74GdsriiwujiawdaB1BpEISg==",
+      "version": "1.3.1",
+      "resolved": "https://registry.npmjs.org/finalhandler/-/finalhandler-1.3.1.tgz",
+      "integrity": "sha512-6BN9trH7bp3qvnrRyzsBz+g3lZxTNZTbVO2EV1CS0WIcDbawYVdYvGflME/9QP0h0pYlCDBCTjYa9nZzMDpyxQ==",
       "dev": true,
       "dependencies": {
         "debug": "2.6.9",
-        "encodeurl": "~1.0.2",
+        "encodeurl": "~2.0.0",
         "escape-html": "~1.0.3",
         "on-finished": "2.4.1",
         "parseurl": "~1.3.3",
@@ -571,35 +615,67 @@
       }
     },
     "node_modules/function-bind": {
-      "version": "1.1.1",
-      "resolved": "https://registry.npmjs.org/function-bind/-/function-bind-1.1.1.tgz",
-      "integrity": "sha512-yIovAzMX49sF8Yl58fSCWJ5svSLuaibPxXQJFLmBObTuCr0Mf1KiPopGM9NiFjiYBCbfaa2Fh6breQ6ANVTI0A==",
-      "dev": true
+      "version": "1.1.2",
+      "resolved": "https://registry.npmjs.org/function-bind/-/function-bind-1.1.2.tgz",
+      "integrity": "sha512-7XHNxH7qX9xG5mIwxkhumTox/MIRNcOgDrxWsMt2pAr23WHp6MrRlN7FBSFpCpr+oVO0F744iUgR82nJMfG2SA==",
+      "dev": true,
+      "funding": {
+        "url": "https://github.com/sponsors/ljharb"
+      }
     },
     "node_modules/get-intrinsic": {
-      "version": "1.2.0",
-      "resolved": "https://registry.npmjs.org/get-intrinsic/-/get-intrinsic-1.2.0.tgz",
-      "integrity": "sha512-L049y6nFOuom5wGyRc3/gdTLO94dySVKRACj1RmJZBQXlbTMhtNIgkWkUHq+jYmZvKf14EW1EoJnnjbmoHij0Q==",
+      "version": "1.2.4",
+      "resolved": "https://registry.npmjs.org/get-intrinsic/-/get-intrinsic-1.2.4.tgz",
+      "integrity": "sha512-5uYhsJH8VJBTv7oslg4BznJYhDoRI6waYCxMmCdnTrcCrHA/fCFKoTFz2JKKE0HdDFUF7/oQuhzumXJK7paBRQ==",
       "dev": true,
       "dependencies": {
-        "function-bind": "^1.1.1",
-        "has": "^1.0.3",
-        "has-symbols": "^1.0.3"
+        "es-errors": "^1.3.0",
+        "function-bind": "^1.1.2",
+        "has-proto": "^1.0.1",
+        "has-symbols": "^1.0.3",
+        "hasown": "^2.0.0"
+      },
+      "engines": {
+        "node": ">= 0.4"
       },
       "funding": {
         "url": "https://github.com/sponsors/ljharb"
       }
     },
-    "node_modules/has": {
-      "version": "1.0.3",
-      "resolved": "https://registry.npmjs.org/has/-/has-1.0.3.tgz",
-      "integrity": "sha512-f2dvO0VU6Oej7RkWJGrehjbzMAjFp5/VKPp5tTpWIV4JHHZK1/BxbFRtf/siA2SWTe09caDmVtYYzWEIbBS4zw==",
+    "node_modules/gopd": {
+      "version": "1.0.1",
+      "resolved": "https://registry.npmjs.org/gopd/-/gopd-1.0.1.tgz",
+      "integrity": "sha512-d65bNlIadxvpb/A2abVdlqKqV563juRnZ1Wtk6s1sIR8uNsXR70xqIzVqxVf1eTqDunwT2MkczEeaezCKTZhwA==",
       "dev": true,
       "dependencies": {
-        "function-bind": "^1.1.1"
+        "get-intrinsic": "^1.1.3"
       },
+      "funding": {
+        "url": "https://github.com/sponsors/ljharb"
+      }
+    },
+    "node_modules/has-property-descriptors": {
+      "version": "1.0.2",
+      "resolved": "https://registry.npmjs.org/has-property-descriptors/-/has-property-descriptors-1.0.2.tgz",
+      "integrity": "sha512-55JNKuIW+vq4Ke1BjOTjM2YctQIvCT7GFzHwmfZPGo5wnrgkid0YQtnAleFSqumZm4az3n2BS+erby5ipJdgrg==",
+      "dev": true,
+      "dependencies": {
+        "es-define-property": "^1.0.0"
+      },
+      "funding": {
+        "url": "https://github.com/sponsors/ljharb"
+      }
+    },
+    "node_modules/has-proto": {
+      "version": "1.0.3",
+      "resolved": "https://registry.npmjs.org/has-proto/-/has-proto-1.0.3.tgz",
+      "integrity": "sha512-SJ1amZAJUiZS+PhsVLf5tGydlaVB8EdFpaSO4gmiUKUOxk8qzn5AIy4ZeJUmh22znIdk/uMAUT2pl3FxzVUH+Q==",
+      "dev": true,
       "engines": {
-        "node": ">= 0.4.0"
+        "node": ">= 0.4"
+      },
+      "funding": {
+        "url": "https://github.com/sponsors/ljharb"
       }
     },
     "node_modules/has-symbols": {
@@ -614,6 +690,18 @@
         "url": "https://github.com/sponsors/ljharb"
       }
     },
+    "node_modules/hasown": {
+      "version": "2.0.2",
+      "resolved": "https://registry.npmjs.org/hasown/-/hasown-2.0.2.tgz",
+      "integrity": "sha512-0hJU9SCPvmMzIBdZFqNPXWa6dqh7WdH0cII9y+CyS8rG3nL48Bclra9HmKhVVUHyPWNH5Y7xDwAB7bfgSjkUMQ==",
+      "dev": true,
+      "dependencies": {
+        "function-bind": "^1.1.2"
+      },
+      "engines": {
+        "node": ">= 0.4"
+      }
+    },
     "node_modules/html-encoding-sniffer": {
       "version": "2.0.1",
       "resolved": "https://registry.npmjs.org/html-encoding-sniffer/-/html-encoding-sniffer-2.0.1.tgz",
@@ -856,10 +944,13 @@
       }
     },
     "node_modules/merge-descriptors": {
-      "version": "1.0.1",
-      "resolved": "https://registry.npmjs.org/merge-descriptors/-/merge-descriptors-1.0.1.tgz",
-      "integrity": "sha512-cCi6g3/Zr1iqQi6ySbseM1Xvooa98N0w31jzUYrXPX2xqObmFGHJ0tQ5u74H3mVh7wLouTseZyYIq39g8cNp1w==",
-      "dev": true
+      "version": "1.0.3",
+      "resolved": "https://registry.npmjs.org/merge-descriptors/-/merge-descriptors-1.0.3.tgz",
+      "integrity": "sha512-gaNvAS7TZ897/rVaZ0nMtAyxNyi/pdbjbAwUpFQpN70GqnVfOiXpeUUMKRBmzXaSQ8DdTX4/0ms62r2K+hE6mQ==",
+      "dev": true,
+      "funding": {
+        "url": "https://github.com/sponsors/sindresorhus"
+      }
     },
     "node_modules/methods": {
       "version": "1.1.2",
@@ -925,10 +1016,13 @@
       "dev": true
     },
     "node_modules/object-inspect": {
-      "version": "1.12.3",
-      "resolved": "https://registry.npmjs.org/object-inspect/-/object-inspect-1.12.3.tgz",
-      "integrity": "sha512-geUvdk7c+eizMNUDkRpW1wJwgfOiOeHbxBR/hLXK1aT6zmVSO0jsQcs7fj6MGw89jC/cjGfLcNOrtMYtGqm81g==",
+      "version": "1.13.2",
+      "resolved": "https://registry.npmjs.org/object-inspect/-/object-inspect-1.13.2.tgz",
+      "integrity": "sha512-IRZSRuzJiynemAXPYtPe5BoI/RESNYR7TYm50MC5Mqbd3Jmw5y790sErYw3V6SryFJD64b74qQQs9wn5Bg/k3g==",
       "dev": true,
+      "engines": {
+        "node": ">= 0.4"
+      },
       "funding": {
         "url": "https://github.com/sponsors/ljharb"
       }
@@ -984,9 +1078,9 @@
       }
     },
     "node_modules/path-to-regexp": {
-      "version": "0.1.7",
-      "resolved": "https://registry.npmjs.org/path-to-regexp/-/path-to-regexp-0.1.7.tgz",
-      "integrity": "sha512-5DFkuoqlv1uYQKxy8omFBeJPQcdoE07Kv2sferDCrAq1ohOU+MSDswDIbnx3YAM60qIOnYa53wBhXW0EbMonrQ==",
+      "version": "0.1.10",
+      "resolved": "https://registry.npmjs.org/path-to-regexp/-/path-to-regexp-0.1.10.tgz",
+      "integrity": "sha512-7lf7qcQidTku0Gu3YDPc8DJ1q7OOucfa/BSsIwjuh56VU7katFvuM8hULfkwB3Fns/rsVF7PwPKVw1sl5KQS9w==",
       "dev": true
     },
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-      "integrity": "sha512-MvjoMCJwEarSbUYk5O+nmoSzSutSsTwF85zcHPQ9OrlFoZOYIjaqBAJIqIXjptyD5vThxGq52Xu/MaJzRkIk4Q==",
+      "version": "6.13.0",
+      "resolved": "https://registry.npmjs.org/qs/-/qs-6.13.0.tgz",
+      "integrity": "sha512-+38qI9SOr8tfZ4QmJNplMUxqjbe7LKvvZgWdExBOmd+egZTtjLB67Gu0HRX3u/XOq7UU2Nx6nsjvS16Z9uwfpg==",
       "dev": true,
       "requires": {
-        "side-channel": "^1.0.4"
+        "side-channel": "^1.0.6"
       }
     },
     "querystringify": {
@@ -2320,9 +2499,9 @@
       }
     },
     "send": {
-      "version": "0.18.0",
-      "resolved": "https://registry.npmjs.org/send/-/send-0.18.0.tgz",
-      "integrity": "sha512-qqWzuOjSFOuqPjFe4NOsMLafToQQwBSOEpS+FwEt3A2V3vKubTquT3vmLTQpFgMXp8AlFWFuP1qKaJZOtPpVXg==",
+      "version": "0.19.0",
+      "resolved": "https://registry.npmjs.org/send/-/send-0.19.0.tgz",
+      "integrity": "sha512-dW41u5VfLXu8SJh5bwRmyYUbAoSB3c9uQh6L8h/KtsFREPWpbX1lrljJo186Jc4nmci/sGUZ9a0a0J2zgfq2hw==",
       "dev": true,
       "requires": {
         "debug": "2.6.9",
@@ -2340,6 +2519,12 @@
         "statuses": "2.0.1"
       },
       "dependencies": {
+        "encodeurl": {
+          "version": "1.0.2",
+          "resolved": "https://registry.npmjs.org/encodeurl/-/encodeurl-1.0.2.tgz",
+          "integrity": "sha512-TPJXq8JqFaVYm2CWmPvnP2Iyo4ZSM7/QKcSmuMLDObfpH5fi7RUGmd/rTDf+rut/saiDiQEeVTNgAmJEdAOx0w==",
+          "dev": true
+        },
         "ms": {
           "version": "2.1.3",
           "resolved": "https://registry.npmjs.org/ms/-/ms-2.1.3.tgz",
@@ -2349,15 +2534,29 @@
       }
     },
     "serve-static": {
-      "version": "1.15.0",
-      "resolved": "https://registry.npmjs.org/serve-static/-/serve-static-1.15.0.tgz",
-      "integrity": "sha512-XGuRDNjXUijsUL0vl6nSD7cwURuzEgglbOaFuZM9g3kwDXOWVTck0jLzjPzGD+TazWbboZYu52/9/XPdUgne9g==",
+      "version": "1.16.2",
+      "resolved": "https://registry.npmjs.org/serve-static/-/serve-static-1.16.2.tgz",
+      "integrity": "sha512-VqpjJZKadQB/PEbEwvFdO43Ax5dFBZ2UECszz8bQ7pi7wt//PWe1P6MN7eCnjsatYtBT6EuiClbjSWP2WrIoTw==",
       "dev": true,
       "requires": {
-        "encodeurl": "~1.0.2",
+        "encodeurl": "~2.0.0",
         "escape-html": "~1.0.3",
         "parseurl": "~1.3.3",
-        "send": "0.18.0"
+        "send": "0.19.0"
+      }
+    },
+    "set-function-length": {
+      "version": "1.2.2",
+      "resolved": "https://registry.npmjs.org/set-function-length/-/set-function-length-1.2.2.tgz",
+      "integrity": "sha512-pgRc4hJ4/sNjWCSS9AmnS40x3bNMDTknHgL5UaMBTMyJnU90EgWh1Rz+MC9eFu4BuN/UwZjKQuY/1v3rM7HMfg==",
+      "dev": true,
+      "requires": {
+        "define-data-property": "^1.1.4",
+        "es-errors": "^1.3.0",
+        "function-bind": "^1.1.2",
+        "get-intrinsic": "^1.2.4",
+        "gopd": "^1.0.1",
+        "has-property-descriptors": "^1.0.2"
       }
     },
     "set-immediate-shim": {
@@ -2373,14 +2572,15 @@
       "dev": true
     },
     "side-channel": {
-      "version": "1.0.4",
-      "resolved": "https://registry.npmjs.org/side-channel/-/side-channel-1.0.4.tgz",
-      "integrity": "sha512-q5XPytqFEIKHkGdiMIrY10mvLRvnQh42/+GoBlFW3b2LXLE2xxJpZFdm94we0BaoV3RwJyGqg5wS7epxTv0Zvw==",
+      "version": "1.0.6",
+      "resolved": "https://registry.npmjs.org/side-channel/-/side-channel-1.0.6.tgz",
+      "integrity": "sha512-fDW/EZ6Q9RiO8eFG8Hj+7u/oW+XrPTIChwCOM2+th2A6OblDtYYIpve9m+KvI9Z4C9qSEXlaGR6bTEYHReuglA==",
       "dev": true,
       "requires": {
-        "call-bind": "^1.0.0",
-        "get-intrinsic": "^1.0.2",
-        "object-inspect": "^1.9.0"
+        "call-bind": "^1.0.7",
+        "es-errors": "^1.3.0",
+        "get-intrinsic": "^1.2.4",
+        "object-inspect": "^1.13.1"
       }
     },
     "source-map": {
diff --git a/package.json b/package.json
index d091e07ea6..badeab7cd3 100644
--- a/package.json
+++ b/package.json
@@ -1,7 +1,7 @@
 {
   "private": true,
   "devDependencies": {
-    "express": "4.19.2",
+    "express": "4.21.0",
     "jsdom": "16.7.0",
     "jszip": "3.8.0",
     "source-map-support": "0.5.19"

From cafe73184f90cf959aee5c9347bb463bda7c003a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Thu, 13 Jun 2024 23:17:11 +0200
Subject: [PATCH 168/298] Replace the JS object given to `jl.Class` by
 primitive IR operations.

`java.lang.Class` requires primitive capabilities that only the
linker can provide for most of its core methods. This commit changes
the fundamental way to provide those.

In the process, remove creation of multi-dimensional arrays from
the IR, and move it to user-space instead.

---

Previously, the contract was that the linker provided a JS object
with specified properties and methods to the constructor of
`jl.Class`. For example, it contained a `"name"` property in order
to implement `jl.Class.getName()`. We happened to reuse the
`$TypeData` instance as that object, for convenience, and to avoid
more indirections.

This design grew organically over the years, and was eventually
specified in Scala.js IR 1.0.0. However, it always had some
shortcomings that I was not happy about.

First, the `getSuperclass()` method had to be special-cased in the
Analyzer and Emitter: its very presence requires additional metadata.
When it is not reachable, we do not actually provide the supposedly
specified member `"getSuperclass"()` on the JS object. That assumes
that only `jl.Class.getSuperclass()` actually calls that method.
In turn, that assumes it never gets inlined (!), since doing so
would make it unreachable, but the feature would still be required.

Second, for optimization purposes, the emitter needs direct access
to the `$TypeData` stored inside `jl.Class` (for some of its
Transients). There again, that assumed a field with a particular
name be present in `jl.Class` in which the JS object would be
stored. This implicit requirement was already leaking in the way
`jl.Class` was written, in order to prevent scalac from renaming
the field.

---

In this commit, we completely change the approach, and therefore
the IR spec. We remove the JS object passed to `jl.Class`; its
constructor now takes no arguments. Instead, we add primitives in
the IR, in the form of new `UnaryOp`s and `BinaryOp`s. These new
primitives operate on an argument of type `jl.Class!`, and possibly
a second argument.

For example, `UnaryOp.Class_name` replaces the functionality
previously offered by the `"name"` field. `BinaryOp.Class_superClass`
replaces `"getSuperclass"()`.

It is up to the backend to ensure it can, somehow, implement those
operations given an instance of `jl.Class`. We choose to add a
magic field to `jl.Class` at the Emitter level to store the
corresponding instance of `$TypeData`, and implement the operations
in terms of that.

The approach has several benefits:

* It solves the two fundamental issues of the JS object, mentioned
  above.
* It does not require "public" (unminifiable) property names for
  the features; since there is no JS object spec, we can consistently
  minify those members.
* Several methods that were given an *intrinsic* treatment by the
  optimizer now fall, more naturally, under regular folding of
  operations.

---

Since we are changing the spec anyway, we use the opportunity to
switch what is primitive about `Array.newInstance`. Previously, the
overload with multiple dimensions was primitive, and the one with a
single dimension delegated to it. This was a waste, since usages of
the multi-dimensional overload are basically non-existent otherwise.
Similarly, the `NewArray` node was designed for multiple dimensions,
and the single dimension was a special case.

We now make the one-dimensional operations the only primitives.
We implement the multi-dimensional overload of `newInstance` in
terms of the other one. We also use that overload as a replacement
for multi-dimensional `NewArray` nodes. This simplifies the treatment
in the linker, and produces shorter and more efficient code at the
end of the day.

---

The change of approach comes with a non-negligible cost for backward
compatibility. It is entirely done using deserialization hacks. The
most glaring issue is the synthesization of the multi-dimensional
overload of `Array.newInstance`.

In this commit, we do not change the library/compiler yet, so that
we can exercise the deserialization hacks.
---
 .../main/scala/org/scalajs/ir/Printers.scala  |  23 +-
 .../scala/org/scalajs/ir/Serializers.scala    | 306 +++++++++++-
 .../src/main/scala/org/scalajs/ir/Trees.scala |  68 ++-
 .../scala/org/scalajs/ir/PrintersTest.scala   |  15 +
 .../scalajs/linker/analyzer/Analysis.scala    |   2 +
 .../scalajs/linker/analyzer/Analyzer.scala    |  24 +-
 .../org/scalajs/linker/analyzer/Infos.scala   |  14 +
 .../linker/backend/emitter/ClassEmitter.scala |  17 +-
 .../linker/backend/emitter/CoreJSLib.scala    | 148 +++---
 .../linker/backend/emitter/EmitterNames.scala |   1 -
 .../backend/emitter/FunctionEmitter.scala     |  57 ++-
 .../backend/emitter/KnowledgeGuardian.scala   |  27 +-
 .../linker/backend/emitter/SJSGen.scala       |  67 ++-
 .../backend/emitter/SyntheticProperty.scala   |   6 +-
 .../linker/backend/emitter/VarField.scala     |   7 +-
 .../backend/wasmemitter/ClassEmitter.scala    |  18 +-
 .../backend/wasmemitter/CoreWasmLib.scala     | 437 +++++-------------
 .../linker/backend/wasmemitter/Emitter.scala  |   2 +-
 .../backend/wasmemitter/FunctionEmitter.scala | 147 +++---
 .../backend/wasmemitter/LoaderContent.scala   |  15 -
 .../linker/backend/wasmemitter/VarGen.scala   |  11 +-
 .../linker/checker/ClassDefChecker.scala      |   4 +-
 .../scalajs/linker/checker/IRChecker.scala    |  14 +-
 .../scalajs/linker/frontend/BaseLinker.scala  |   7 +-
 .../scalajs/linker/frontend/LinkingUnit.scala |   3 +-
 .../org/scalajs/linker/frontend/Refiner.scala |   6 +-
 .../modulesplitter/ModuleSplitter.scala       |   4 +-
 .../frontend/optimizer/OptimizerCore.scala    | 192 ++++----
 .../linker/standard/LinkedGlobalInfo.scala    |  18 +
 .../scalajs/linker/standard/ModuleSet.scala   |   4 +-
 .../org/scalajs/linker/LibrarySizeTest.scala  |   6 +-
 project/BinaryIncompatibilities.scala         |   1 +
 project/Build.scala                           |  16 +-
 .../testsuite/javalib/lang/ClassTest.scala    |   6 +-
 34 files changed, 992 insertions(+), 701 deletions(-)
 create mode 100644 linker/shared/src/main/scala/org/scalajs/linker/standard/LinkedGlobalInfo.scala

diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala
index ec0ff8c5f8..eca5c547f2 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala
@@ -371,8 +371,14 @@ object Printers {
           } else {
             print(lhs)
             print((op: @switch) match {
-              case String_length => ".length"
-              case CheckNotNull  => ".notNull"
+              case String_length       => ".length"
+              case CheckNotNull        => ".notNull"
+              case Class_name          => ".name"
+              case Class_isPrimitive   => ".isPrimitive"
+              case Class_isInterface   => ".isInterface"
+              case Class_isArray       => ".isArray"
+              case Class_componentType => ".componentType"
+              case Class_superClass    => ".superClass"
             })
           }
 
@@ -413,6 +419,19 @@ object Printers {
           print(rhs)
           print(']')
 
+        case BinaryOp(op, lhs, rhs) if BinaryOp.isClassOp(op) =>
+          import BinaryOp._
+          print((op: @switch) match {
+            case Class_isInstance       => "isInstance("
+            case Class_isAssignableFrom => "isAssignableFrom("
+            case Class_cast             => "cast("
+            case Class_newArray         => "newArray("
+          })
+          print(lhs)
+          print(", ")
+          print(rhs)
+          print(')')
+
         case BinaryOp(op, lhs, rhs) =>
           import BinaryOp._
           print('(')
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
index bad2b82fa5..45453943c5 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
@@ -22,6 +22,7 @@ import scala.collection.mutable
 import scala.concurrent._
 
 import Names._
+import OriginalName.NoOriginalName
 import Position._
 import Trees._
 import Types._
@@ -1223,13 +1224,45 @@ object Serializers {
           ApplyDynamicImport(readApplyFlags(), readClassName(),
               readMethodIdent(), readTrees())
 
-        case TagUnaryOp          => UnaryOp(readByte(), readTree())
-        case TagBinaryOp         => BinaryOp(readByte(), readTree(), readTree())
-        case TagNewArray         => NewArray(readArrayTypeRef(), readTrees())
-        case TagArrayValue       => ArrayValue(readArrayTypeRef(), readTrees())
-        case TagArrayLength      => ArrayLength(readTree())
-        case TagArraySelect      => ArraySelect(readTree(), readTree())(readType())
-        case TagRecordValue      => RecordValue(readType().asInstanceOf[RecordType], readTrees())
+        case TagUnaryOp  => UnaryOp(readByte(), readTree())
+        case TagBinaryOp => BinaryOp(readByte(), readTree(), readTree())
+
+        case TagNewArray =>
+          val arrayTypeRef = readArrayTypeRef()
+          val lengths = readTrees()
+          lengths match {
+            case length :: Nil =>
+              NewArray(arrayTypeRef, lengths)
+
+            case _ =>
+              if (true /* hacks.use16 */) { // scalastyle:ignore
+                // Rewrite as a call to j.l.r.Array.newInstance
+                val ArrayTypeRef(base, origDims) = arrayTypeRef
+                val newDims = origDims - lengths.size
+                if (newDims < 0) {
+                  throw new IOException(
+                      s"Illegal legacy NewArray node with ${lengths.size} lengths but dimension $origDims at $pos")
+                }
+                val newBase =
+                  if (newDims == 0) base
+                  else ArrayTypeRef(base, newDims)
+
+                ApplyStatic(
+                    ApplyFlags.empty,
+                    HackNames.ReflectArrayClass,
+                    MethodIdent(HackNames.newInstanceMultiName),
+                    List(ClassOf(newBase), ArrayValue(ArrayTypeRef(IntRef, 1), lengths)))(
+                    AnyType)
+              } else {
+                throw new IOException(
+                    s"Illegal NewArray node with multiple lengths for IR version 1.17+ at $pos")
+              }
+          }
+
+        case TagArrayValue  => ArrayValue(readArrayTypeRef(), readTrees())
+        case TagArrayLength => ArrayLength(readTree())
+        case TagArraySelect => ArraySelect(readTree(), readTree())(readType())
+        case TagRecordValue => RecordValue(readType().asInstanceOf[RecordType], readTrees())
 
         case TagIsInstanceOf =>
           val expr = readTree()
@@ -1471,6 +1504,10 @@ object Serializers {
         if (hacks.use4 && kind.isJSClass) {
           // #4409: Filter out abstract methods in non-native JS classes for version < 1.5
           methods0.filter(_.body.isDefined)
+        } else if (true /*hacks.use16*/ && cls == ClassClass) { // scalastyle:ignore
+          jlClassMethodsHack16(methods0)
+        } else if (true /*hacks.use16*/ && cls == HackNames.ReflectArrayModClass) { // scalastyle:ignore
+          jlReflectArrayMethodsHack16(methods0)
         } else {
           methods0
         }
@@ -1493,6 +1530,253 @@ object Serializers {
           optimizerHints)
     }
 
+    private def jlClassMethodsHack16(methods: List[MethodDef]): List[MethodDef] = {
+      for (method <- methods) yield {
+        implicit val pos = method.pos
+
+        val methodName = method.methodName
+        val methodSimpleNameString = methodName.simpleName.nameString
+
+        val thisJLClass = This()(ClassType(ClassClass, nullable = false))
+
+        if (methodName.isConstructor) {
+          val newName = MethodIdent(NoArgConstructorName)(method.name.pos)
+          val newBody = ApplyStatically(ApplyFlags.empty.withConstructor(true),
+              thisJLClass, ObjectClass, newName, Nil)(NoType)
+          MethodDef(method.flags, newName, method.originalName,
+              Nil, NoType, Some(newBody))(
+              method.optimizerHints, method.version)
+        } else {
+          def argRef = method.args.head.ref
+          def argRefNotNull = UnaryOp(UnaryOp.CheckNotNull, argRef)
+
+          var forceInline = true // reset to false in the `case _ =>`
+
+          val newBody: Tree = methodSimpleNameString match {
+            case "getName"          => UnaryOp(UnaryOp.Class_name, thisJLClass)
+            case "isPrimitive"      => UnaryOp(UnaryOp.Class_isPrimitive, thisJLClass)
+            case "isInterface"      => UnaryOp(UnaryOp.Class_isInterface, thisJLClass)
+            case "isArray"          => UnaryOp(UnaryOp.Class_isArray, thisJLClass)
+            case "getComponentType" => UnaryOp(UnaryOp.Class_componentType, thisJLClass)
+            case "getSuperclass"    => UnaryOp(UnaryOp.Class_superClass, thisJLClass)
+
+            case "isInstance"       => BinaryOp(BinaryOp.Class_isInstance, thisJLClass, argRef)
+            case "isAssignableFrom" => BinaryOp(BinaryOp.Class_isAssignableFrom, thisJLClass, argRefNotNull)
+            case "cast"             => BinaryOp(BinaryOp.Class_cast, thisJLClass, argRef)
+
+            case _ =>
+              forceInline = false
+
+              /* Unfortunately, some of the other methods directly referred to
+               * `this.data["name"]`, instead of building on `this.getName()`.
+               * We must replace those occurrences with a `Class_name` as well.
+               */
+              val transformer = new Transformers.Transformer {
+                override def transform(tree: Tree, isStat: Boolean): Tree = tree match {
+                  case JSSelect(_, StringLiteral("name")) =>
+                    implicit val pos = tree.pos
+                    UnaryOp(UnaryOp.Class_name, thisJLClass)
+                  case _ =>
+                    super.transform(tree, isStat)
+                }
+              }
+              transformer.transform(method.body.get, isStat = method.resultType == NoType)
+          }
+
+          val newOptimizerHints =
+            if (forceInline) method.optimizerHints.withInline(true)
+            else method.optimizerHints
+
+          MethodDef(method.flags, method.name, method.originalName,
+              method.args, method.resultType, Some(newBody))(
+              newOptimizerHints, method.version)
+        }
+      }
+    }
+
+    private def jlReflectArrayMethodsHack16(methods: List[MethodDef]): List[MethodDef] = {
+      /* Basically this method hard-codes new implementations for the two
+       * overloads of newInstance.
+       * It is horrible, but better than pollute everything else in the linker.
+       */
+
+      import HackNames._
+
+      def paramDef(name: String, ptpe: Type)(implicit pos: Position): ParamDef =
+        ParamDef(LocalIdent(LocalName(name)), NoOriginalName, ptpe, mutable = false)
+
+      def varDef(name: String, vtpe: Type, rhs: Tree, mutable: Boolean = false)(
+          implicit pos: Position): VarDef = {
+        VarDef(LocalIdent(LocalName(name)), NoOriginalName, vtpe, mutable, rhs)
+      }
+
+      val jlClassRef = ClassRef(ClassClass)
+      val intArrayTypeRef = ArrayTypeRef(IntRef, 1)
+      val objectRef = ClassRef(ObjectClass)
+      val objectArrayTypeRef = ArrayTypeRef(objectRef, 1)
+
+      val jlClassType = ClassType(ClassClass, nullable = true)
+
+      val newInstanceRecName = MethodName("newInstanceRec",
+          List(jlClassRef, intArrayTypeRef, IntRef), objectRef)
+
+      val EAF = ApplyFlags.empty
+
+      val newInstanceRecMethod = {
+        /* def newInstanceRec(componentType: jl.Class, dimensions: int[], offset: int): any = {
+         *   val length: int = dimensions[offset]
+         *   val result: any = newInstance(componentType, length)
+         *   val innerOffset = offset + 1
+         *   if (innerOffset < dimensions.length) {
+         *     val result2: Object[] = result.asInstanceOf[Object[]]
+         *     val innerComponentType: jl.Class = componentType.getComponentType()
+         *     var i: Int = 0
+         *     while (i != length)
+         *       result2[i] = newInstanceRec(innerComponentType, dimensions, innerOffset)
+         *       i = i + 1
+         *     }
+         *   }
+         *   result
+         * }
+         */
+
+        implicit val pos = Position.NoPosition
+
+        val getComponentTypeName = MethodName("getComponentType", Nil, jlClassRef)
+
+        val ths = This()(ClassType(ReflectArrayModClass, nullable = false))
+
+        val componentType = paramDef("componentType", jlClassType)
+        val dimensions = paramDef("dimensions", ArrayType(intArrayTypeRef, nullable = true))
+        val offset = paramDef("offset", IntType)
+
+        val length = varDef("length", IntType, ArraySelect(dimensions.ref, offset.ref)(IntType))
+        val result = varDef("result", AnyType,
+            Apply(EAF, ths, MethodIdent(newInstanceSingleName), List(componentType.ref, length.ref))(AnyType))
+        val innerOffset = varDef("innerOffset", IntType,
+            BinaryOp(BinaryOp.Int_+, offset.ref, IntLiteral(1)))
+
+        val result2 = varDef("result2", ArrayType(objectArrayTypeRef, nullable = true),
+            AsInstanceOf(result.ref, ArrayType(objectArrayTypeRef, nullable = true)))
+        val innerComponentType = varDef("innerComponentType", jlClassType,
+            Apply(EAF, componentType.ref, MethodIdent(getComponentTypeName), Nil)(jlClassType))
+        val i = varDef("i", IntType, IntLiteral(0), mutable = true)
+
+        val body = {
+          Block(
+            length,
+            result,
+            innerOffset,
+            If(BinaryOp(BinaryOp.Int_<, innerOffset.ref, ArrayLength(dimensions.ref)), {
+              Block(
+                result2,
+                innerComponentType,
+                i,
+                While(BinaryOp(BinaryOp.Int_!=, i.ref, length.ref), {
+                  Block(
+                    Assign(
+                      ArraySelect(result2.ref, i.ref)(AnyType),
+                      Apply(EAF, ths, MethodIdent(newInstanceRecName),
+                          List(innerComponentType.ref, dimensions.ref, innerOffset.ref))(AnyType)
+                    ),
+                    Assign(
+                      i.ref,
+                      BinaryOp(BinaryOp.Int_+, i.ref, IntLiteral(1))
+                    )
+                  )
+                })
+              )
+            }, Skip())(NoType),
+            result.ref
+          )
+        }
+
+        MethodDef(MemberFlags.empty, MethodIdent(newInstanceRecName),
+            NoOriginalName, List(componentType, dimensions, offset), AnyType,
+            Some(body))(
+            OptimizerHints.empty, Version.fromInt(1))
+      }
+
+      /* Only for the temporary commit where we always apply the hack, because
+       * the hack is applied in the JavalibIRCleaner and then a second time
+       * for the true deserialization.
+       */
+      val oldMethodsTemp =
+        methods.filterNot(_.methodName == newInstanceRecName)
+
+      val newMethods = for (method <- oldMethodsTemp) yield {
+        method.methodName match {
+          case `newInstanceSingleName` =>
+            // newInstance(jl.Class, int)  -->  newArray(jlClass.notNull, length)
+
+            implicit val pos = method.pos
+
+            val List(jlClassParam, lengthParam) = method.args
+
+            val newBody = BinaryOp(BinaryOp.Class_newArray,
+                UnaryOp(UnaryOp.CheckNotNull, jlClassParam.ref),
+                lengthParam.ref)
+
+            MethodDef(method.flags, method.name, method.originalName,
+                method.args, method.resultType, Some(newBody))(
+                method.optimizerHints.withInline(true), method.version)
+
+          case `newInstanceMultiName` =>
+            /* newInstance(jl.Class, int[])  -->
+             * var outermostComponentType: jl.Class = jlClassParam
+             * var i: int = 1
+             * while (i != lengths.length) {
+             *   outermostComponentType = getClass(this.newInstance(outermostComponentType, 0))
+             *   i = i + 1
+             * }
+             * newInstanceRec(outermostComponentType, lengths, 0)
+             */
+
+            implicit val pos = method.pos
+
+            val List(jlClassParam, lengthsParam) = method.args
+
+            val newBody = {
+              val outermostComponentType = varDef("outermostComponentType",
+                  jlClassType, jlClassParam.ref, mutable = true)
+              val i = varDef("i", IntType, IntLiteral(1), mutable = true)
+
+              Block(
+                outermostComponentType,
+                i,
+                While(BinaryOp(BinaryOp.Int_!=, i.ref, ArrayLength(lengthsParam.ref)), {
+                  Block(
+                    Assign(
+                      outermostComponentType.ref,
+                      GetClass(Apply(EAF, This()(ClassType(ReflectArrayModClass, nullable = false)),
+                          MethodIdent(newInstanceSingleName),
+                          List(outermostComponentType.ref, IntLiteral(0)))(AnyType))
+                    ),
+                    Assign(
+                      i.ref,
+                      BinaryOp(BinaryOp.Int_+, i.ref, IntLiteral(1))
+                    )
+                  )
+                }),
+                Apply(EAF, This()(ClassType(ReflectArrayModClass, nullable = false)),
+                    MethodIdent(newInstanceRecName),
+                    List(outermostComponentType.ref, lengthsParam.ref, IntLiteral(0)))(
+                    AnyType)
+              )
+            }
+
+            MethodDef(method.flags, method.name, method.originalName,
+                method.args, method.resultType, Some(newBody))(
+                method.optimizerHints, method.version)
+
+          case _ =>
+            method
+        }
+      }
+
+      newInstanceRecMethod :: newMethods
+    }
+
     private def jsConstructorHack(
         jsMethodProps: List[JSMethodPropDef]): (Option[JSConstructorDef], List[JSMethodPropDef]) = {
       val jsConstructorBuilder = new OptionBuilder[JSConstructorDef]
@@ -2159,11 +2443,19 @@ object Serializers {
       ClassName("java.lang.CloneNotSupportedException")
     val SystemModule: ClassName =
       ClassName("java.lang.System$")
+    val ReflectArrayClass =
+      ClassName("java.lang.reflect.Array")
+    val ReflectArrayModClass =
+      ClassName("java.lang.reflect.Array$")
 
     val cloneName: MethodName =
       MethodName("clone", Nil, ClassRef(ObjectClass))
     val identityHashCodeName: MethodName =
       MethodName("identityHashCode", List(ClassRef(ObjectClass)), IntRef)
+    val newInstanceSingleName: MethodName =
+      MethodName("newInstance", List(ClassRef(ClassClass), IntRef), ClassRef(ObjectClass))
+    val newInstanceMultiName: MethodName =
+      MethodName("newInstance", List(ClassRef(ClassClass), ArrayTypeRef(IntRef, 1)), ClassRef(ObjectClass))
   }
 
   private class OptionBuilder[T] {
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala b/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
index 34804cc421..3eb43c7f11 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
@@ -284,6 +284,9 @@ object Trees {
   }
 
   /** Unary operation.
+   *
+   *  The `Class_x` operations take a `jl.Class!` argument, i.e., a
+   *  non-nullable `jl.Class`.
    *
    *  `CheckNotNull` throws NPEs subject to UB.
    *
@@ -327,11 +330,22 @@ object Trees {
     // String.length, introduced in 1.11
     final val String_length = 17
 
-    // New in 1.17
+    // Null check, introduced in 1.17
     final val CheckNotNull = 18
 
+    // Class operations, introduced in 1.17
+    final val Class_name = 19
+    final val Class_isPrimitive = 20
+    final val Class_isInterface = 21
+    final val Class_isArray = 22
+    final val Class_componentType = 23
+    final val Class_superClass = 24
+
+    def isClassOp(op: Code): Boolean =
+      op >= Class_name && op <= Class_superClass
+
     def resultTypeOf(op: Code, argType: Type): Type = (op: @switch) match {
-      case Boolean_! =>
+      case Boolean_! | Class_isPrimitive | Class_isInterface | Class_isArray =>
         BooleanType
       case IntToChar =>
         CharType
@@ -349,10 +363,42 @@ object Trees {
         DoubleType
       case CheckNotNull =>
         argType.toNonNullable
+      case Class_name =>
+        StringType
+      case Class_componentType | Class_superClass =>
+        ClassType(ClassClass, nullable = true)
     }
   }
 
-  /** Binary operation (always preserves pureness). */
+  /** Binary operation.
+   *
+   *  All binary operations follow common evaluation steps:
+   *
+   *  1. Let `lhsValue` be the result of evaluating `lhs`.
+   *  2. Let `rhsValue` be the result of evaluating `rhs`.
+   *  3. Perform an operation that depends on `op`, `lhsValue` and `rhsValue`.
+   *
+   *  Unless `lhsValue` throws, `rhsValue` will therefore always be evaluated,
+   *  even if the operation `op` would throw based only on `lhsValue`.
+   *
+   *  The integer dividing operators (`Int_/`, `Int_%`, `Long_/` and `Long_%`)
+   *  throw an `ArithmeticException` when their right-hand-side is 0. That
+   *  exception is not subject to undefined behavior.
+   *
+   *  `String_charAt` throws a `StringIndexOutOfBoundsException`.
+   *
+   *  The `Class_x` operations take a `jl.Class!` as lhs, i.e., a
+   *  non-nullable `jl.Class`. `Class_isAssignableFrom` also takes a
+   *  `jl.Class!` as rhs.
+   *
+   *  - `Class_isInstance` and `Class_isAssignableFrom` are pure.
+   *  - `Class_cast` throws a CCE if its second argument is non-null and
+   *    not an instance of the class represented by its first argument.
+   *  - `Class_newArray` throws a `NegativeArraySizeException` if its second
+   *    argument is negative.
+   *
+   *  Otherwise, binary operations preserve pureness.
+   */
   sealed case class BinaryOp(op: BinaryOp.Code, lhs: Tree, rhs: Tree)(
       implicit val pos: Position) extends Tree {
 
@@ -435,12 +481,22 @@ object Trees {
     // New in 1.11
     final val String_charAt = 58
 
+    // New in 1.17
+    final val Class_isInstance = 59
+    final val Class_isAssignableFrom = 60
+    final val Class_cast = 61
+    final val Class_newArray = 62
+
+    def isClassOp(op: Code): Boolean =
+      op >= Class_isInstance && op <= Class_newArray
+
     def resultTypeOf(op: Code): Type = (op: @switch) match {
       case === | !== |
           Boolean_== | Boolean_!= | Boolean_| | Boolean_& |
           Int_== | Int_!= | Int_< | Int_<= | Int_> | Int_>= |
           Long_== | Long_!= | Long_< | Long_<= | Long_> | Long_>= |
-          Double_== | Double_!= | Double_< | Double_<= | Double_> | Double_>= =>
+          Double_== | Double_!= | Double_< | Double_<= | Double_> | Double_>= |
+          Class_isInstance | Class_isAssignableFrom =>
         BooleanType
       case String_+ =>
         StringType
@@ -456,6 +512,10 @@ object Trees {
         DoubleType
       case String_charAt =>
         CharType
+      case Class_cast =>
+        AnyType
+      case Class_newArray =>
+        AnyNotNullType
     }
   }
 
diff --git a/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala b/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala
index f3cef80ffa..16d5120ea3 100644
--- a/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala
+++ b/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala
@@ -394,6 +394,14 @@ class PrintersTest {
     assertPrintEquals("x.length", UnaryOp(String_length, ref("x", StringType)))
 
     assertPrintEquals("x.notNull", UnaryOp(CheckNotNull, ref("x", AnyType)))
+
+    val classVarRef = ref("x", ClassType(ClassClass, nullable = false))
+    assertPrintEquals("x.name", UnaryOp(Class_name, classVarRef))
+    assertPrintEquals("x.isPrimitive", UnaryOp(Class_isPrimitive, classVarRef))
+    assertPrintEquals("x.isInterface", UnaryOp(Class_isInterface, classVarRef))
+    assertPrintEquals("x.isArray", UnaryOp(Class_isArray, classVarRef))
+    assertPrintEquals("x.componentType", UnaryOp(Class_componentType, classVarRef))
+    assertPrintEquals("x.superClass", UnaryOp(Class_superClass, classVarRef))
   }
 
   @Test def printPseudoUnaryOp(): Unit = {
@@ -539,6 +547,13 @@ class PrintersTest {
 
     assertPrintEquals("x[y]",
         BinaryOp(String_charAt, ref("x", StringType), ref("y", IntType)))
+
+    val classVarRef = ref("x", ClassType(ClassClass, nullable = false))
+    assertPrintEquals("isInstance(x, y)", BinaryOp(Class_isInstance, classVarRef, ref("y", AnyType)))
+    assertPrintEquals("isAssignableFrom(x, y)",
+        BinaryOp(Class_isAssignableFrom, classVarRef, ref("y", ClassType(ClassClass, nullable = false))))
+    assertPrintEquals("cast(x, y)", BinaryOp(Class_cast, classVarRef, ref("y", AnyType)))
+    assertPrintEquals("newArray(x, y)", BinaryOp(Class_newArray, classVarRef, ref("y", IntType)))
   }
 
   @Test def printNewArray(): Unit = {
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analysis.scala b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analysis.scala
index 6d0a02e83c..3c1e6f251b 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analysis.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analysis.scala
@@ -37,6 +37,8 @@ trait Analysis {
   def classInfos: scala.collection.Map[ClassName, ClassInfo]
   def topLevelExportInfos: scala.collection.Map[(ModuleID, String), TopLevelExportInfo]
 
+  def isClassSuperClassUsed: Boolean
+
   def errors: scala.collection.Seq[Error]
 }
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala
index 3931d2ab58..79f1ef432f 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala
@@ -118,6 +118,9 @@ private class AnalyzerRun(config: CommonPhaseConfig, initial: Boolean,
 
   def classInfos: scala.collection.Map[ClassName, Analysis.ClassInfo] = _classInfos
 
+  private val _classSuperClassUsed = new AtomicBoolean(false)
+  def isClassSuperClassUsed: Boolean = _classSuperClassUsed.get()
+
   private[this] val _errors = new GrowingList[Error]
 
   override def errors: List[Error] = _errors.get()
@@ -294,20 +297,11 @@ private class AnalyzerRun(config: CommonPhaseConfig, initial: Boolean,
 
   /** Reach additional class data based on reflection methods being used. */
   private def reachDataThroughReflection(): Unit = {
-
-    val classClassInfo = _classInfos.get(ClassClass)
-
-    /* If Class.getSuperclass() is reachable, we can reach the data of all
+    /* If Class_superClass is used, we can reach the data of all
      * superclasses of classes whose data we can already reach.
      */
-    for {
-      getSuperclassMethodInfo <-
-        classClassInfo.flatMap(_.publicMethodInfos.get(getSuperclassMethodName))
-      if getSuperclassMethodInfo.isReachable
-    } {
-      // calledFrom should always be nonEmpty if isReachable, but let's be robust
-      implicit val from =
-        getSuperclassMethodInfo.calledFrom.headOption.getOrElse(fromAnalyzer)
+    if (isClassSuperClassUsed) {
+      implicit val from = fromAnalyzer
       for (classInfo <- _classInfos.values.filter(_.isDataAccessed).toList) {
         @tailrec
         def loop(classInfo: ClassInfo): Unit = {
@@ -1461,7 +1455,7 @@ private class AnalyzerRun(config: CommonPhaseConfig, initial: Boolean,
         objectClassInfo.addStaticDependency(ClassClass)
         lookupClass(ClassClass) { clazz =>
           clazz.instantiated()
-          clazz.callMethodStatically(MemberNamespace.Constructor, ObjectArgConstructorName)
+          clazz.callMethodStatically(MemberNamespace.Constructor, NoArgConstructorName)
         }
       }
 
@@ -1479,6 +1473,10 @@ private class AnalyzerRun(config: CommonPhaseConfig, initial: Boolean,
           config.coreSpec.esFeatures.esVersion < ESVersion.ES2016) {
         _errors ::= ExponentOperatorWithoutES2016Support(from)
       }
+
+      if ((globalFlags & ReachabilityInfo.FlagUsedClassSuperClass) != 0) {
+        _classSuperClassUsed.set(true)
+      }
     }
   }
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala
index a6ed3f6a6e..8dcb89c784 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala
@@ -112,6 +112,7 @@ object Infos {
     final val FlagAccessedNewTarget = 1 << 1
     final val FlagAccessedImportMeta = 1 << 2
     final val FlagUsedExponentOperator = 1 << 3
+    final val FlagUsedClassSuperClass = 1 << 4
   }
 
   /** Things from a given class that are reached by one method. */
@@ -380,6 +381,9 @@ object Infos {
     def addUsedExponentOperator(): this.type =
       setFlag(ReachabilityInfo.FlagUsedExponentOperator)
 
+    def addUsedClassSuperClass(): this.type =
+      setFlag(ReachabilityInfo.FlagUsedClassSuperClass)
+
     def result(): ReachabilityInfo =
       new ReachabilityInfo(version, byClass.valuesIterator.map(_.result()).toArray, flags)
   }
@@ -650,6 +654,16 @@ object Infos {
 
               builder.maybeAddUsedInstanceTest(tpe)
 
+            case UnaryOp(op, _) =>
+              import UnaryOp._
+
+              op match {
+                case Class_superClass =>
+                  builder.addUsedClassSuperClass()
+                case _ =>
+                  // do nothing
+              }
+
             case BinaryOp(op, _, rhs) =>
               import BinaryOp._
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
index 6351e43614..0243d9f7bc 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
@@ -310,6 +310,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
     }
 
     initToInline.fold {
+      assert(className != ClassClass, s"java.lang.Class did not have an inlineable init")
       WithGlobals(
           js.Function(arrow = false, Nil, None, js.Block(superCtorCallAndFieldDefs)))
     } { initMethodDef =>
@@ -326,8 +327,20 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
 
       for (generatedInitMethodFun <- generatedInitMethodFunWithGlobals) yield {
         val js.Function(arrow, args, restParam, initMethodFunBody) = generatedInitMethodFun
-        js.Function(arrow, args, restParam,
-            js.Block(superCtorCallAndFieldDefs ::: initMethodFunBody :: Nil))
+
+        if (className != ClassClass) {
+          js.Function(arrow, args, restParam,
+              js.Block(superCtorCallAndFieldDefs ::: initMethodFunBody :: Nil))
+        } else {
+          // Inject the magical `data` argument and field
+          assert(args.isEmpty, s"Unexpected constructor arguments $args for java.lang.Class")
+          val dataParam = js.ParamDef(fileLevelVarIdent(VarField.data))
+          val createDataField = js.Assign(
+              js.DotSelect(js.This(), genSyntheticPropertyForDef(SyntheticProperty.data)),
+              dataParam.ref)
+          js.Function(arrow, dataParam :: Nil, restParam,
+              js.Block(superCtorCallAndFieldDefs ::: createDataField :: initMethodFunBody :: Nil))
+        }
       }
     }
   }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
index 792c1a5677..e1ff675469 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
@@ -578,7 +578,7 @@ private[emitter] object CoreJSLib {
                   str("char")
                 }, {
                   If(genIsScalaJSObject(value), {
-                    genIdentBracketSelect(value DOT classData, cpn.name)
+                    value DOT classData DOT cpn.name
                   }, {
                     typeof(value)
                   })
@@ -665,33 +665,6 @@ private[emitter] object CoreJSLib {
             str("Cannot call isInstance() on a Class representing a JS trait/object") :: Nil))
       } :::
 
-      defineFunction2(VarField.newArrayObject) { (arrayClassData, lengths) =>
-        Return(genCallHelper(VarField.newArrayObjectInternal, arrayClassData, lengths, int(0)))
-      } :::
-
-      defineFunction3(VarField.newArrayObjectInternal) { (arrayClassData, lengths, lengthIndex) =>
-        val result = varRef("result")
-        val subArrayClassData = varRef("subArrayClassData")
-        val subLengthIndex = varRef("subLengthIndex")
-        val underlying = varRef("underlying")
-        val i = varRef("i")
-
-        Block(
-          const(result, New(arrayClassData DOT cpn.constr,
-              BracketSelect(lengths, lengthIndex) :: Nil)),
-          If(lengthIndex < (lengths.length - 1), Block(
-            const(subArrayClassData, arrayClassData DOT cpn.componentData),
-            const(subLengthIndex, lengthIndex + 1),
-            const(underlying, result.u),
-            For(let(i, 0), i < underlying.length, i.++, {
-              BracketSelect(underlying, i) :=
-                genCallHelper(VarField.newArrayObjectInternal, subArrayClassData, lengths, subLengthIndex)
-            })
-          )),
-          Return(result)
-        )
-      } :::
-
       defineFunction1(VarField.objectClone) { instance =>
         // return Object.create(Object.getPrototypeOf(instance), $getOwnPropertyDescriptors(instance));
         val callGetOwnPropertyDescriptors = genCallPolyfillableBuiltin(
@@ -703,7 +676,7 @@ private[emitter] object CoreJSLib {
 
       defineFunction1(VarField.objectOrArrayClone) { instance =>
         // return instance.$classData.isArrayClass ? instance.clone__O() : $objectClone(instance);
-        Return(If(genIdentBracketSelect(instance DOT classData, cpn.isArrayClass),
+        Return(If(instance DOT classData DOT cpn.isArrayClass,
             genApply(instance, cloneMethodName, Nil),
             genCallHelper(VarField.objectClone, instance)))
       }
@@ -797,7 +770,7 @@ private[emitter] object CoreJSLib {
             StringLiteral(RuntimeClassNameMapperImpl.map(
                 semantics.runtimeClassNameMapper, className.nameString))
           },
-          instance => genIdentBracketSelect(instance DOT classData, cpn.name),
+          instance => instance DOT classData DOT cpn.name,
           {
             if (nullPointers == CheckedBehavior.Unchecked)
               genApply(Null(), getNameMethodName, Nil)
@@ -1132,7 +1105,7 @@ private[emitter] object CoreJSLib {
 
       condDefs(arrayStores != CheckedBehavior.Unchecked)(
         defineFunction5(VarField.systemArraycopyRefs) { (src, srcPos, dest, destPos, length) =>
-          If(Apply(genIdentBracketSelect(dest DOT classData, cpn.isAssignableFrom), List(src DOT classData)), {
+          If(Apply(dest DOT classData DOT cpn.isAssignableFrom, List(src DOT classData)), {
             /* Fast-path, no need for array store checks. This always applies
              * for arrays of the same type, and a fortiori, when `src eq dest`.
              */
@@ -1165,7 +1138,7 @@ private[emitter] object CoreJSLib {
             const(srcData, src && (src DOT classData)),
             If(srcData === (dest && (dest DOT classData)), {
               // Both values have the same "data" (could also be falsy values)
-              If(srcData && genIdentBracketSelect(srcData, cpn.isArrayClass), {
+              If(srcData && (srcData DOT cpn.isArrayClass), {
                 // Fast path: the values are array of the same type
                 if (esVersion >= ESVersion.ES2015 && nullPointers == CheckedBehavior.Unchecked)
                   genSyntheticPropApply(src, SyntheticProperty.copyTo, srcPos, dest, destPos, length)
@@ -1574,9 +1547,6 @@ private[emitter] object CoreJSLib {
       def privateFieldSet(fieldName: String, value: Tree): Tree =
         This() DOT fieldName := value
 
-      def publicFieldSet(fieldName: String, value: Tree): Tree =
-        genIdentBracketSelect(This(), fieldName) := value
-
       val ctor = {
         MethodDef(static = false, Ident("constructor"), Nil, None, {
           Block(
@@ -1603,11 +1573,11 @@ private[emitter] object CoreJSLib {
               privateFieldSet(cpn.wrapArray, Undefined()),
               privateFieldSet(cpn.isJSType, bool(false)),
 
-              publicFieldSet(cpn.name, str("")),
-              publicFieldSet(cpn.isPrimitive, bool(false)),
-              publicFieldSet(cpn.isInterface, bool(false)),
-              publicFieldSet(cpn.isArrayClass, bool(false)),
-              publicFieldSet(cpn.isInstance, Undefined())
+              privateFieldSet(cpn.name, str("")),
+              privateFieldSet(cpn.isPrimitive, bool(false)),
+              privateFieldSet(cpn.isInterface, bool(false)),
+              privateFieldSet(cpn.isArrayClass, bool(false)),
+              privateFieldSet(cpn.isInstance, Undefined())
           )
         })
       }
@@ -1631,9 +1601,9 @@ private[emitter] object CoreJSLib {
               const(self, This()), // capture `this` for use in arrow fun
               privateFieldSet(cpn.isAssignableFromFun,
                   genArrowFunction(paramList(that), Return(that === self))),
-              publicFieldSet(cpn.name, displayName),
-              publicFieldSet(cpn.isPrimitive, bool(true)),
-              publicFieldSet(cpn.isInstance,
+              privateFieldSet(cpn.name, displayName),
+              privateFieldSet(cpn.isPrimitive, bool(true)),
+              privateFieldSet(cpn.isInstance,
                   genArrowFunction(paramList(obj), Return(bool(false)))),
               If(arrayClass !== Undefined(), { // it is undefined for void
                 privateFieldSet(cpn._arrayOf,
@@ -1685,9 +1655,9 @@ private[emitter] object CoreJSLib {
                 })
               }),
               privateFieldSet(cpn.isJSType, kindOrCtor === 2),
-              publicFieldSet(cpn.name, fullName),
-              publicFieldSet(cpn.isInterface, kindOrCtor === 1),
-              publicFieldSet(cpn.isInstance, isInstance || {
+              privateFieldSet(cpn.name, fullName),
+              privateFieldSet(cpn.isInterface, kindOrCtor === 1),
+              privateFieldSet(cpn.isInstance, isInstance || {
                 genArrowFunction(paramList(obj), {
                   Return(!(!(obj && (obj DOT classData) &&
                       BracketSelect(obj DOT classData DOT cpn.ancestors, internalName))))
@@ -1720,8 +1690,8 @@ private[emitter] object CoreJSLib {
             privateFieldSet(cpn.arrayBase, arrayBase),
             privateFieldSet(cpn.arrayDepth, arrayDepth),
             privateFieldSet(cpn.arrayEncodedName, name),
-            publicFieldSet(cpn.name, name),
-            publicFieldSet(cpn.isArrayClass, bool(true))
+            privateFieldSet(cpn.name, name),
+            privateFieldSet(cpn.isArrayClass, bool(true))
         )
       }
 
@@ -1754,7 +1724,7 @@ private[emitter] object CoreJSLib {
                   })
                 })
               }),
-              publicFieldSet(cpn.isInstance,
+              privateFieldSet(cpn.isInstance,
                   genArrowFunction(paramList(obj), Return(obj instanceof arrayClass))),
               Return(This())
           )
@@ -1798,7 +1768,7 @@ private[emitter] object CoreJSLib {
 
               val storeCheck = {
                 If((v !== Null()) && !(componentData DOT cpn.isJSType) &&
-                    !Apply(genIdentBracketSelect(componentData, cpn.isInstance), v :: Nil),
+                    !Apply(componentData DOT cpn.isInstance, v :: Nil),
                     genCallHelper(VarField.throwArrayStoreException, v))
               }
 
@@ -1882,7 +1852,7 @@ private[emitter] object CoreJSLib {
                 Return(New(ArrayClass, array :: Nil))
               })),
               const(self, This()), // don't rely on the lambda being called with `this` as receiver
-              publicFieldSet(cpn.isInstance, genArrowFunction(paramList(obj), {
+              privateFieldSet(cpn.isInstance, genArrowFunction(paramList(obj), {
                 val data = varRef("data")
                 Block(
                     const(data, obj && (obj DOT classData)),
@@ -1911,9 +1881,13 @@ private[emitter] object CoreJSLib {
 
       def getClassOf = {
         MethodDef(static = false, Ident(cpn.getClassOf), Nil, None, {
+          /* We call the NoArgConstructorName with an argument, because it is
+           * added at the emitter level for java.lang.Class, without being in
+           * the IR.
+           */
           Block(
               If(!(This() DOT cpn._classOf),
-                  This() DOT cpn._classOf := genScalaClassNew(ClassClass, ObjectArgConstructorName, This()),
+                  This() DOT cpn._classOf := genScalaClassNew(ClassClass, NoArgConstructorName, This()),
                   Skip()),
               Return(This() DOT cpn._classOf)
           )
@@ -1921,7 +1895,7 @@ private[emitter] object CoreJSLib {
       }
 
       def isAssignableFrom = {
-        /* This is the public method called by j.l.Class.isAssignableFrom. It
+        /* This is the method called by `Class_isAssignableFrom`. It
          * first performs a fast-path with `this === that`, and otherwise calls
          * the internal `isAssignableFromFun` function.
          * The reason for this decomposition (as opposed to performing the
@@ -1931,7 +1905,7 @@ private[emitter] object CoreJSLib {
          * We only need a polymorphic dispatch in the slow path.
          */
         val that = varRef("that")
-        MethodDef(static = false, StringLiteral(cpn.isAssignableFrom),
+        MethodDef(static = false, Ident(cpn.isAssignableFrom),
             paramList(that), None, {
           Return(
               (This() === that) || // fast path
@@ -1939,22 +1913,22 @@ private[emitter] object CoreJSLib {
         })
       }
 
-      def checkCast = {
+      def cast = {
+        assert(asInstanceOfs != CheckedBehavior.Unchecked)
         val obj = varRef("obj")
-        MethodDef(static = false, StringLiteral(cpn.checkCast), paramList(obj), None,
-          if (asInstanceOfs != CheckedBehavior.Unchecked) {
+        MethodDef(static = false, Ident(cpn.cast), paramList(obj), None, {
+          Block(
             If((obj !== Null()) && !(This() DOT cpn.isJSType) &&
-                !Apply(genIdentBracketSelect(This(), cpn.isInstance), obj :: Nil),
-              genCallHelper(VarField.throwClassCastException, obj, genIdentBracketSelect(This(), cpn.name)),
-              Skip())
-          } else {
-            Skip()
-          }
-        )
+                !Apply(This() DOT cpn.isInstance, obj :: Nil),
+              genCallHelper(VarField.throwClassCastException, obj, This() DOT cpn.name),
+              Skip()),
+            Return(obj)
+          )
+        })
       }
 
       def getSuperclass = {
-        MethodDef(static = false, StringLiteral(cpn.getSuperclass), Nil, None, {
+        MethodDef(static = false, Ident(cpn.getSuperclass), Nil, None, {
           Return(If(This() DOT cpn.parentData,
               Apply(This() DOT cpn.parentData DOT cpn.getClassOf, Nil),
               Null()))
@@ -1962,26 +1936,18 @@ private[emitter] object CoreJSLib {
       }
 
       def getComponentType = {
-        MethodDef(static = false, StringLiteral(cpn.getComponentType), Nil, None, {
+        MethodDef(static = false, Ident(cpn.getComponentType), Nil, None, {
           Return(If(This() DOT cpn.componentData,
               Apply(This() DOT cpn.componentData DOT cpn.getClassOf, Nil),
               Null()))
         })
       }
 
-      def newArrayOfThisClass = {
-        val lengths = varRef("lengths")
-        val arrayClassData = varRef("arrayClassData")
-        val i = varRef("i")
-        MethodDef(static = false, StringLiteral(cpn.newArrayOfThisClass),
-            paramList(lengths), None, {
-          Block(
-              let(arrayClassData, This()),
-              For(let(i, 0), i < lengths.length, i.++, {
-                arrayClassData := Apply(arrayClassData DOT cpn.getArrayOf, Nil)
-              }),
-              Return(genCallHelper(VarField.newArrayObject, arrayClassData, lengths))
-          )
+      def newArray = {
+        val length = varRef("length")
+        MethodDef(static = false, Ident(cpn.newArray),
+            paramList(length), None, {
+          Return(New(Apply(This() DOT cpn.getArrayOf, Nil) DOT cpn.constr, length :: Nil))
         })
       }
 
@@ -1995,11 +1961,16 @@ private[emitter] object CoreJSLib {
           if (globalKnowledge.isClassClassInstantiated) {
             List(
                 getClassOf,
-                isAssignableFrom,
-                checkCast,
+                isAssignableFrom
+            ) ::: (
+              if (asInstanceOfs != CheckedBehavior.Unchecked)
+                List(cast)
+              else
+                Nil
+            ) ::: List(
                 getSuperclass,
                 getComponentType,
-                newArrayOfThisClass
+                newArray
             )
           } else if (arrayStores != CheckedBehavior.Unchecked) {
             List(
@@ -2035,7 +2006,7 @@ private[emitter] object CoreJSLib {
               Block(
                   const(arrayDepth, data DOT cpn.arrayDepth),
                   Return(If(arrayDepth === depth, {
-                    !genIdentBracketSelect(data DOT cpn.arrayBase, cpn.isPrimitive)
+                    !(data DOT cpn.arrayBase DOT cpn.isPrimitive)
                   }, {
                     arrayDepth > depth
                   }))
@@ -2098,9 +2069,6 @@ private[emitter] object CoreJSLib {
         def privateFieldSet(fieldName: String, value: Tree): Tree =
           typeDataVar DOT fieldName := value
 
-        def publicFieldSet(fieldName: String, value: Tree): Tree =
-          genIdentBracketSelect(typeDataVar, fieldName) := value
-
         extractWithGlobals(
             globalVarDef(VarField.d, ObjectClass, New(globalVar(VarField.TypeData, CoreVar), Nil))) :::
         List(
@@ -2108,11 +2076,11 @@ private[emitter] object CoreJSLib {
           privateFieldSet(cpn.arrayEncodedName, str("L" + fullName + ";")),
           privateFieldSet(cpn.isAssignableFromFun, {
             genArrowFunction(paramList(that), {
-              Return(!genIdentBracketSelect(that, cpn.isPrimitive))
+              Return(!(that DOT cpn.isPrimitive))
             })
           }),
-          publicFieldSet(cpn.name, str(fullName)),
-          publicFieldSet(cpn.isInstance,
+          privateFieldSet(cpn.name, str(fullName)),
+          privateFieldSet(cpn.isInstance,
               genArrowFunction(paramList(obj), Return(obj !== Null()))),
           privateFieldSet(cpn._arrayOf, {
             Apply(New(globalVar(VarField.TypeData, CoreVar), Nil) DOT cpn.initSpecializedArray, List(
@@ -2124,7 +2092,7 @@ private[emitter] object CoreJSLib {
                 Block(
                     const(thatDepth, that DOT cpn.arrayDepth),
                     Return(If(thatDepth === 1, {
-                      !genIdentBracketSelect(that DOT cpn.arrayBase, cpn.isPrimitive)
+                      !(that DOT cpn.arrayBase DOT cpn.isPrimitive)
                     }, {
                       (thatDepth > 1)
                     }))
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/EmitterNames.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/EmitterNames.scala
index ba31cd7019..a31366670f 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/EmitterNames.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/EmitterNames.scala
@@ -26,7 +26,6 @@ private[emitter] object EmitterNames {
 
   // Field names
 
-  val dataFieldName = FieldName(ClassClass, SimpleFieldName("data"))
   val exceptionFieldName = FieldName(JavaScriptExceptionClass, SimpleFieldName("exception"))
 
   // Method names
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
index e1e010eeb2..184f46c365 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
@@ -1270,6 +1270,12 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
         case BinaryOp(BinaryOp.String_charAt, lhs, rhs) =>
           allowBehavior(semantics.stringIndexOutOfBounds) && test(lhs) && test(rhs)
 
+        // Binary Class_x operations that can have side effects
+        case BinaryOp(BinaryOp.Class_cast, lhs, rhs) =>
+          allowBehavior(semantics.asInstanceOfs) && test(lhs) && test(rhs)
+        case BinaryOp(BinaryOp.Class_newArray, lhs, rhs) =>
+          allowBehavior(semantics.negativeArraySizes) && allowUnpure && test(lhs) && test(rhs)
+
         // Expressions preserving pureness (modulo NPE)
         case Block(trees)            => trees forall test
         case If(cond, thenp, elsep)  => test(cond) && test(thenp) && test(elsep)
@@ -2385,6 +2391,20 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
                 newLhs
               else
                 genCallHelper(VarField.n, newLhs)
+
+            // Class operations
+            case Class_name =>
+              genGetDataOf(newLhs) DOT cpn.name
+            case Class_isPrimitive =>
+              genGetDataOf(newLhs) DOT cpn.isPrimitive
+            case Class_isInterface =>
+              genGetDataOf(newLhs) DOT cpn.isInterface
+            case Class_isArray =>
+              genGetDataOf(newLhs) DOT cpn.isArrayClass
+            case Class_componentType =>
+              js.Apply(genGetDataOf(newLhs) DOT cpn.getComponentType, Nil)
+            case Class_superClass =>
+              js.Apply(genGetDataOf(newLhs) DOT cpn.getSuperclass, Nil)
           }
 
         case BinaryOp(op, lhs, rhs) =>
@@ -2392,6 +2412,11 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
           val newLhs = transformExpr(lhs, preserveChar = (op == String_+))
           val newRhs = transformExpr(rhs, preserveChar = (op == String_+))
 
+          def extractClassData(origTree: Tree, jsTree: js.Tree): js.Tree = origTree match {
+            case ClassOf(typeRef) => genClassDataOf(typeRef)(implicitly, implicitly, origTree.pos)
+            case _                => genGetDataOf(jsTree)
+          }
+
           (op: @switch) match {
             case === | !== =>
               /* Semantically, this is an `Object.is` test in JS. However, we
@@ -2664,10 +2689,29 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
                 case CheckedBehavior.Unchecked =>
                   js.Apply(genIdentBracketSelect(newLhs, "charCodeAt"), List(newRhs))
               }
+
+            case Class_isInstance =>
+              js.Apply(extractClassData(lhs, newLhs) DOT cpn.isInstance, newRhs :: Nil)
+            case Class_isAssignableFrom =>
+              js.Apply(extractClassData(lhs, newLhs) DOT cpn.isAssignableFrom,
+                  extractClassData(rhs, newRhs) :: Nil)
+            case Class_cast =>
+              if (semantics.asInstanceOfs == CheckedBehavior.Unchecked)
+                js.Block(newLhs, newRhs)
+              else
+                js.Apply(extractClassData(lhs, newLhs) DOT cpn.cast, newRhs :: Nil)
+            case Class_newArray =>
+              js.Apply(extractClassData(lhs, newLhs) DOT cpn.newArray, newRhs :: Nil)
           }
 
         case NewArray(typeRef, lengths) =>
-          genNewArray(typeRef, lengths.map(transformExprNoChar))
+          lengths match {
+            case length :: Nil =>
+              js.New(genArrayConstrOf(typeRef), transformExprNoChar(length) :: Nil)
+            case _ =>
+              throw new AssertionError(
+                  s"Illegal legacy NewArray with lengths $lengths at $pos")
+          }
 
         case ArrayValue(typeRef, elems) =>
           val preserveChar = typeRef match {
@@ -2769,8 +2813,7 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
 
         case Transient(ZeroOf(runtimeClass)) =>
           js.DotSelect(
-              genSelect(transformExprNoChar(checkNotNull(runtimeClass)),
-                  FieldIdent(dataFieldName)),
+              genGetDataOf(transformExprNoChar(checkNotNull(runtimeClass))),
               js.Ident(cpn.zero))
 
         case Transient(NativeArrayWrapper(elemClass, nativeArray)) =>
@@ -2781,9 +2824,8 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
               extractWithGlobals(
                   genNativeArrayWrapper(arrayTypeRef, newNativeArray))
             case _ =>
-              val elemClassData = genSelect(
-                  transformExprNoChar(checkNotNull(elemClass)),
-                  FieldIdent(dataFieldName))
+              val elemClassData =
+                genGetDataOf(transformExprNoChar(checkNotNull(elemClass)))
               val arrayClassData = js.Apply(
                   js.DotSelect(elemClassData, js.Ident(cpn.getArrayOf)), Nil)
               js.Apply(arrayClassData DOT cpn.wrapArray, newNativeArray :: Nil)
@@ -3247,6 +3289,9 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
       js.Apply(globalVar(field, (className, method.name)), args)
     }
 
+    private def genGetDataOf(jlClassValue: js.Tree)(implicit pos: Position): js.Tree =
+      genSyntheticPropSelect(jlClassValue, SyntheticProperty.data)
+
     private def genCallPolyfillableBuiltin(
         builtin: PolyfillableBuiltin, args: js.Tree*)(
         implicit pos: Position): js.Tree = {
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/KnowledgeGuardian.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/KnowledgeGuardian.scala
index 562ad1e519..d5c5d23342 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/KnowledgeGuardian.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/KnowledgeGuardian.scala
@@ -98,11 +98,12 @@ private[emitter] final class KnowledgeGuardian(config: Emitter.Config) {
     val invalidateAll = {
       if (specialInfo == null) {
         specialInfo = new SpecialInfo(objectClass, classClass,
-            arithmeticExceptionClass, hijackedClasses.result())
+            arithmeticExceptionClass, hijackedClasses.result(),
+            moduleSet.globalInfo)
         false
       } else {
         specialInfo.update(objectClass, classClass, arithmeticExceptionClass,
-            hijackedClasses.result())
+            hijackedClasses.result(), moduleSet.globalInfo)
       }
     }
 
@@ -512,7 +513,8 @@ private[emitter] final class KnowledgeGuardian(config: Emitter.Config) {
   private class SpecialInfo(initObjectClass: Option[LinkedClass],
       initClassClass: Option[LinkedClass],
       initArithmeticExceptionClass: Option[LinkedClass],
-      initHijackedClasses: Iterable[LinkedClass]) extends Unregisterable {
+      initHijackedClasses: Iterable[LinkedClass],
+      initGlobalInfo: LinkedGlobalInfo) extends Unregisterable {
 
     import SpecialInfo._
 
@@ -520,7 +522,7 @@ private[emitter] final class KnowledgeGuardian(config: Emitter.Config) {
       computeInstantiatedSpecialClassBitSet(initClassClass, initArithmeticExceptionClass)
 
     private var isParentDataAccessed =
-      computeIsParentDataAccessed(initClassClass)
+      computeIsParentDataAccessed(initGlobalInfo)
 
     private var methodsInRepresentativeClasses =
       computeMethodsInRepresentativeClasses(initObjectClass, initHijackedClasses)
@@ -539,7 +541,8 @@ private[emitter] final class KnowledgeGuardian(config: Emitter.Config) {
 
     def update(objectClass: Option[LinkedClass], classClass: Option[LinkedClass],
         arithmeticExceptionClass: Option[LinkedClass],
-        hijackedClasses: Iterable[LinkedClass]): Boolean = {
+        hijackedClasses: Iterable[LinkedClass],
+        globalInfo: LinkedGlobalInfo): Boolean = {
       var invalidateAll = false
 
       val newInstantiatedSpecialClassBitSet =
@@ -549,7 +552,7 @@ private[emitter] final class KnowledgeGuardian(config: Emitter.Config) {
         invalidateAskers(instantiatedSpecialClassAskers)
       }
 
-      val newIsParentDataAccessed = computeIsParentDataAccessed(classClass)
+      val newIsParentDataAccessed = computeIsParentDataAccessed(globalInfo)
       if (newIsParentDataAccessed != isParentDataAccessed) {
         isParentDataAccessed = newIsParentDataAccessed
         invalidateAll = true
@@ -589,16 +592,8 @@ private[emitter] final class KnowledgeGuardian(config: Emitter.Config) {
       bitSet
     }
 
-    private def computeIsParentDataAccessed(classClass: Option[LinkedClass]): Boolean = {
-      def methodExists(linkedClass: LinkedClass, methodName: MethodName): Boolean = {
-        linkedClass.methods.exists { m =>
-          m.flags.namespace == MemberNamespace.Public &&
-          m.methodName == methodName
-        }
-      }
-
-      classClass.exists(methodExists(_, getSuperclassMethodName))
-    }
+    private def computeIsParentDataAccessed(globalInfo: LinkedGlobalInfo): Boolean =
+      globalInfo.isClassSuperClassUsed
 
     private def computeMethodsInRepresentativeClasses(objectClass: Option[LinkedClass],
         hijackedClasses: Iterable[LinkedClass]): List[(MethodName, Set[ClassName])] = {
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala
index ef7aaf8ea8..44f8708265 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala
@@ -55,7 +55,7 @@ private[emitter] final class SJSGen(
     /** `Char.c`: the int value of the character. */
     val c = "c"
 
-    // --- TypeData private fields ---
+    // --- TypeData fields ---
 
     /** `TypeData.constr`: the run-time constructor of the class. */
     val constr = if (minify) "C" else "constr"
@@ -96,6 +96,18 @@ private[emitter] final class SJSGen(
     /** `TypeData.isJSType`: whether it is a JS type. */
     val isJSType = if (minify) "J" else "isJSType"
 
+    /** `TypeData.name`: the user name of the class (the result of `jl.Class.getName()`). */
+    val name = if (minify) "N" else "name"
+
+    /** `TypeData.isPrimitive`: whether it is a primitive type. */
+    val isPrimitive = if (minify) "X" else "isPrimitive"
+
+    /** `TypeData.isInterface`: whether it is an interface type. */
+    val isInterface = if (minify) "Y" else "isInterface"
+
+    /** `TypeData.isArrayClass`: whether it is an array type. */
+    val isArrayClass = if (minify) "Z" else "isArrayClass"
+
     // --- TypeData constructors ---
 
     val initPrim = if (minify) "p" else "initPrim"
@@ -106,7 +118,7 @@ private[emitter] final class SJSGen(
 
     val initArray = if (minify) "a" else "initArray"
 
-    // --- TypeData private methods ---
+    // --- TypeData methods ---
 
     /** `TypeData.getArrayOf()`: the `Type` instance for that type's array type. */
     val getArrayOf = if (minify) "r" else "getArrayOf"
@@ -114,35 +126,23 @@ private[emitter] final class SJSGen(
     /** `TypeData.getClassOf()`: the `jl.Class` instance for that type. */
     val getClassOf = if (minify) "l" else "getClassOf"
 
-    // --- TypeData public fields --- never minified
-
-    /** `TypeData.name`: public, the user name of the class (the result of `jl.Class.getName()`). */
-    val name = "name"
-
-    /** `TypeData.isPrimitive`: public, whether it is a primitive type. */
-    val isPrimitive = "isPrimitive"
-
-    /** `TypeData.isInterface`: public, whether it is an interface type. */
-    val isInterface = "isInterface"
-
-    /** `TypeData.isArrayClass`: public, whether it is an array type. */
-    val isArrayClass = "isArrayClass"
+    /** `TypeData.getSuperclass()`: implementation of `Class_superClass`. */
+    val getSuperclass = if (minify) "S" else "getSuperclass"
 
-    /** `TypeData.isInstance()`: public, implementation of `jl.Class.isInstance`. */
-    val isInstance = "isInstance"
+    /** `TypeData.getComponentType()`: implementation of `Class_componentType`. */
+    val getComponentType = if (minify) "Q" else "getComponentType"
 
-    /** `TypeData.isAssignableFrom()`: public, implementation of `jl.Class.isAssignableFrom`. */
-    val isAssignableFrom = "isAssignableFrom"
+    /** `TypeData.isInstance()`: implementation of `Class_isInstance`. */
+    val isInstance = if (minify) "I" else "isInstance"
 
-    // --- TypeData public methods --- never minified
+    /** `TypeData.isAssignableFrom()`: implementation of `Class_isAssignableFrom`. */
+    val isAssignableFrom = if (minify) "R" else "isAssignableFrom"
 
-    val checkCast = "checkCast"
+    /** `TypeData.cast()`: implementation of `Class_cast`. */
+    val cast = if (minify) "T" else "cast"
 
-    val getSuperclass = "getSuperclass"
-
-    val getComponentType = "getComponentType"
-
-    val newArrayOfThisClass = "newArrayOfThisClass"
+    /** `TypeData.newArray()`: implementation of `Class_newArray`. */
+    val newArray = if (minify) "U" else "newArray"
   }
 
   /* This is a `val` because it is used at the top of every file, outside of
@@ -714,21 +714,6 @@ private[emitter] final class SJSGen(
     }
   }
 
-  def genNewArray(arrayTypeRef: ArrayTypeRef, lengths: List[Tree])(
-      implicit moduleContext: ModuleContext, globalKnowledge: GlobalKnowledge,
-      pos: Position): Tree = {
-    lengths match {
-      case Nil =>
-        throw new IllegalArgumentException(
-            "Cannot create a new array with 0 dimensions")
-      case length :: Nil =>
-        New(genArrayConstrOf(arrayTypeRef), length :: Nil)
-      case _ =>
-        genCallHelper(VarField.newArrayObject, genClassDataOf(arrayTypeRef),
-            ArrayConstr(lengths))
-    }
-  }
-
   def genArrayValue(arrayTypeRef: ArrayTypeRef, elems: List[Tree])(
       implicit moduleContext: ModuleContext, globalKnowledge: GlobalKnowledge,
       tracking: GlobalRefTracking, pos: Position): WithGlobals[Tree] = {
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SyntheticProperty.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SyntheticProperty.scala
index 84afaceff1..6e697988de 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SyntheticProperty.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SyntheticProperty.scala
@@ -20,7 +20,8 @@ import org.scalajs.ir.OriginalName
  *  but is added by the Emitter on some classes that belong to the Scala class
  *  hierarchy.
  *
- *  Currently, these only include properties of the `ArrayClass`es.
+ *  Currently, these only include properties of the `ArrayClass`es, as well as
+ *  the magic `jl.Class.data` property.
  *
  *  These properties live in the same namespace as Scala field and method
  *  names, because the `ArrayClass`es extend `j.l.Object`. Therefore, they
@@ -49,4 +50,7 @@ object SyntheticProperty {
 
   /** `ArrayClass.copyTo()`: copies from that array to another array. */
   val copyTo: SyntheticProperty = new SyntheticProperty("copyTo")
+
+  /** `jl.Class.data`: the underlying `TypeData` of the class. */
+  val data: SyntheticProperty = new SyntheticProperty("data")
 }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/VarField.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/VarField.scala
index e166c997c5..a43a127f61 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/VarField.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/VarField.scala
@@ -132,6 +132,9 @@ private[emitter] object VarField {
   /** Local field for dynamic imports. */
   final val module = mk("$module")
 
+  /** Local field for the magic `data` argument to the constructor of `jl.Class`. */
+  final val data = mk("$data")
+
   // Core fields: Generated by the CoreJSLib
 
   /** The linking info object. */
@@ -231,10 +234,6 @@ private[emitter] object VarField {
 
   final val systemArraycopyFull = mk("$systemArraycopyFull")
 
-  final val newArrayObject = mk("$newArrayObject")
-
-  final val newArrayObjectInternal = mk("$newArrayObjectInternal")
-
   final val throwArrayCastException = mk("$throwArrayCastException")
 
   final val throwArrayIndexOutOfBoundsException = mk("$throwArrayIndexOutOFBoundsException")
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/ClassEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/ClassEmitter.scala
index caa266fd10..a4ff9ceff4 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/ClassEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/ClassEmitter.scala
@@ -365,9 +365,20 @@ class ClassEmitter(coreSpec: CoreSpec) {
         isMutable = true // initialized by the constructors, so always mutable at the Wasm level
       )
     }
+    val jlClassDataField = if (className == ClassClass) {
+      // Inject the magic `data` field
+      watpe.StructField(
+        genFieldID.classData,
+        OriginalName("data"),
+        watpe.RefType(genTypeID.typeData),
+        isMutable = false
+      ) :: Nil
+    } else {
+      Nil
+    }
     val structTypeID = genTypeID.forClass(className)
     val superType = clazz.superClass.map(s => genTypeID.forClass(s.name))
-    val structType = watpe.StructType(vtableField :: itablesField :: fields)
+    val structType = watpe.StructType(vtableField :: itablesField :: fields ::: jlClassDataField)
     val subType = watpe.SubType(
       structTypeID,
       makeDebugName(ns.ClassInstance, className),
@@ -598,6 +609,9 @@ class ClassEmitter(coreSpec: CoreSpec) {
       makeDebugName(ns.NewDefault, className),
       clazz.pos
     )
+    val dataParamOpt =
+      if (className == ClassClass) Some(fb.addParam("data", watpe.RefType(genTypeID.typeData)))
+      else None
     fb.setResultType(watpe.RefType(structTypeID))
 
     fb += wa.GlobalGet(genGlobalID.forVTable(className))
@@ -610,6 +624,8 @@ class ClassEmitter(coreSpec: CoreSpec) {
     classInfo.allFieldDefs.foreach { f =>
       fb += genZeroOf(f.ftpe)
     }
+    for (dataParam <- dataParamOpt)
+      fb += wa.LocalGet(dataParam)
     fb += wa.StructNew(structTypeID)
 
     fb.buildAndAddToModule()
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
index 4da2acaff9..90dfbb16ad 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
@@ -94,6 +94,17 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
     )
   }
 
+  private val primRefsWithArrayTypes = List(
+    BooleanRef -> KindBoolean,
+    CharRef -> KindChar,
+    ByteRef -> KindByte,
+    ShortRef -> KindShort,
+    IntRef -> KindInt,
+    LongRef -> KindLong,
+    FloatRef -> KindFloat,
+    DoubleRef -> KindDouble
+  )
+
   /** Generates definitions that must come *before* the code generated for regular classes.
    *
    *  This notably includes the `typeData` definitions, since the vtable of `jl.Object` is a subtype
@@ -421,25 +432,7 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
       Nil
     )
 
-    addHelperImport(
-      genFunctionID.genJSTypeMetaData,
-      List(
-        RefType(genTypeID.typeData), // typeData
-        RefType.extern, // name
-        Int32, // isPrimitive
-        Int32, // isArrayClass
-        Int32, // isInterface,
-        RefType.func, // isInstanceFun
-        RefType.func, // isAssignableFromFun
-        RefType.func, // checkCastFun
-        RefType.func, // getComponentTypeFun
-        RefType.func // newArrayOfThisClassFun
-      ),
-      List(RefType.any)
-    )
     addHelperImport(genFunctionID.makeTypeError, List(RefType.extern), List(RefType.extern))
-    addHelperImport(genFunctionID.jsArrayLength, List(anyref), List(Int32))
-    addHelperImport(genFunctionID.jsArrayGetInt, List(anyref, Int32), List(Int32))
 
     addHelperImport(genFunctionID.jsGlobalRefGet, List(RefType.extern), List(anyref))
     addHelperImport(genFunctionID.jsGlobalRefSet, List(RefType.extern, anyref), Nil)
@@ -699,13 +692,13 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
 
     genIsInstance()
     genIsAssignableFrom()
-    genCheckCast()
+    if (semantics.asInstanceOfs != CheckedBehavior.Unchecked)
+      genCast()
     genGetComponentType()
-    genNewArrayOfThisClass()
+    genNewArray()
     genAnyGetClass()
     genAnyGetClassName()
     genAnyGetTypeData()
-    genNewArrayObject()
     genIdentityHashCode()
     genSearchReflectiveProxy()
     genArrayCloneFunctions()
@@ -1087,51 +1080,18 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
 
     val classInstanceLocal = fb.addLocal("classInstance", RefType(genTypeID.ClassStruct))
 
-    // classInstance := newDefault$java.lang.Class()
+    // classInstance := newDefault$java.lang.Class(typeData)
     // leave it on the stack for the constructor call
+    fb += LocalGet(typeDataParam)
     fb += Call(genFunctionID.newDefault(ClassClass))
     fb += LocalTee(classInstanceLocal)
 
-    /* The JS object containing metadata to pass as argument to the `jl.Class` constructor.
-     * Specified by https://lampwww.epfl.ch/~doeraene/sjsir-semantics/#sec-sjsir-createclassdataof
-     * Leave it on the stack.
-     */
-
-    // typeData
-    fb += LocalGet(typeDataParam)
-    // name
-    fb += LocalGet(typeDataParam)
-    fb += Call(genFunctionID.typeDataName)
-    // isPrimitive: (typeData.kind <= KindLastPrimitive)
-    fb += LocalGet(typeDataParam)
-    fb += StructGet(genTypeID.typeData, genFieldID.typeData.kind)
-    fb += I32Const(KindLastPrimitive)
-    fb += I32LeU
-    // isArrayClass: (typeData.kind == KindArray)
-    fb += LocalGet(typeDataParam)
-    fb += StructGet(genTypeID.typeData, genFieldID.typeData.kind)
-    fb += I32Const(KindArray)
-    fb += I32Eq
-    // isInterface: (typeData.kind == KindInterface)
-    fb += LocalGet(typeDataParam)
-    fb += StructGet(genTypeID.typeData, genFieldID.typeData.kind)
-    fb += I32Const(KindInterface)
-    fb += I32Eq
-    // the various helper functions
-    fb += ctx.refFuncWithDeclaration(genFunctionID.isInstance)
-    fb += ctx.refFuncWithDeclaration(genFunctionID.isAssignableFrom)
-    fb += ctx.refFuncWithDeclaration(genFunctionID.checkCast)
-    fb += ctx.refFuncWithDeclaration(genFunctionID.getComponentType)
-    fb += ctx.refFuncWithDeclaration(genFunctionID.newArrayOfThisClass)
-    // call the helper to build the metadata object
-    fb += Call(genFunctionID.genJSTypeMetaData)
-
-    // Call java.lang.Class::<init>(dataObject)
+    // Call java.lang.Class::<init>()
     fb += Call(
       genFunctionID.forMethod(
         MemberNamespace.Constructor,
         ClassClass,
-        SpecialNames.AnyArgConstructorName
+        NoArgConstructorName
       )
     )
 
@@ -2335,64 +2295,70 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
     fb.buildAndAddToModule()
   }
 
-  /** `checkCast: (ref typeData), anyref -> []`.
+  /** `cast: (ref jlClass), anyref -> anyref`.
    *
    *  Casts the given value to the given type; subject to undefined behaviors.
+   *
+   *  This is the underlying func for the `Class_cast` operation.
    */
-  private def genCheckCast()(implicit ctx: WasmContext): Unit = {
-    val typeDataType = RefType(genTypeID.typeData)
+  private def genCast()(implicit ctx: WasmContext): Unit = {
+    assert(semantics.asInstanceOfs != CheckedBehavior.Unchecked)
 
-    val fb = newFunctionBuilder(genFunctionID.checkCast)
-    val typeDataParam = fb.addParam("typeData", typeDataType)
+    val fb = newFunctionBuilder(genFunctionID.cast)
+    val jlClassParam = fb.addParam("jlClass", RefType(genTypeID.ClassStruct))
     val valueParam = fb.addParam("value", RefType.anyref)
+    fb.setResultType(RefType.anyref)
 
-    if (semantics.asInstanceOfs != CheckedBehavior.Unchecked) {
-      fb.block() { successLabel =>
-        // If typeData.kind == KindJSType, succeed
-        fb += LocalGet(typeDataParam)
-        fb += StructGet(genTypeID.typeData, genFieldID.typeData.kind)
-        fb += I32Const(KindJSType)
-        fb += I32Eq
-        fb += BrIf(successLabel)
+    val typeDataLocal = fb.addLocal("typeData", RefType(genTypeID.typeData))
 
-        // If value is null, succeed
-        fb += LocalGet(valueParam)
-        fb += RefIsNull // consumes `value`, unlike `BrOnNull` which would leave it on the stack
-        fb += BrIf(successLabel)
+    fb.block() { successLabel =>
+      // typeData := jlClass.data, leave it on the stack for the kind test
+      fb += LocalGet(jlClassParam)
+      fb += StructGet(genTypeID.ClassStruct, genFieldID.classData)
+      fb += LocalTee(typeDataLocal)
 
-        // If isInstance(typeData, value), succeed
-        fb += LocalGet(typeDataParam)
-        fb += LocalGet(valueParam)
-        fb += Call(genFunctionID.isInstance)
-        fb += BrIf(successLabel)
+      // If typeData.kind == KindJSType, succeed
+      fb += StructGet(genTypeID.typeData, genFieldID.typeData.kind)
+      fb += I32Const(KindJSType)
+      fb += I32Eq
+      fb += BrIf(successLabel)
 
-        // Otherwise, it is a CCE
-        fb += LocalGet(valueParam)
-        fb += LocalGet(typeDataParam)
-        fb += Call(genFunctionID.classCastException)
-        fb += Unreachable // for clarity; technically redundant since the stacks align
-      }
+      // If value is null, succeed
+      fb += LocalGet(valueParam)
+      fb += RefIsNull // consumes `value`, unlike `BrOnNull` which would leave it on the stack
+      fb += BrIf(successLabel)
+
+      // If isInstance(typeData, value), succeed
+      fb += LocalGet(typeDataLocal)
+      fb += LocalGet(valueParam)
+      fb += Call(genFunctionID.isInstance)
+      fb += BrIf(successLabel)
+
+      // Otherwise, it is a CCE
+      fb += LocalGet(valueParam)
+      fb += LocalGet(typeDataLocal)
+      fb += Call(genFunctionID.classCastException)
+      fb += Unreachable // for clarity; technically redundant since the stacks align
     }
 
+    fb += LocalGet(valueParam)
+
     fb.buildAndAddToModule()
   }
 
-  /** `getComponentType: (ref typeData) -> (ref null jlClass)`.
+  /** `getComponentType: (ref jlClass) -> (ref null jlClass)`.
    *
-   *  This is the underlying func for the `getComponentType()` closure inside class data objects.
+   *  This is the underlying func for the `Class_componentType` operation.
    */
   private def genGetComponentType()(implicit ctx: WasmContext): Unit = {
-    val typeDataType = RefType(genTypeID.typeData)
-
     val fb = newFunctionBuilder(genFunctionID.getComponentType)
-    val typeDataParam = fb.addParam("typeData", typeDataType)
+    val jlClassParam = fb.addParam("jlClass", RefType(genTypeID.ClassStruct))
     fb.setResultType(RefType.nullable(genTypeID.ClassStruct))
 
-    val componentTypeDataLocal = fb.addLocal("componentTypeData", typeDataType)
-
     fb.block() { nullResultLabel =>
       // Try and extract non-null component type data
-      fb += LocalGet(typeDataParam)
+      fb += LocalGet(jlClassParam)
+      fb += StructGet(genTypeID.ClassStruct, genFieldID.classData)
       fb += StructGet(genTypeID.typeData, genFieldID.typeData.componentType)
       fb += BrOnNull(nullResultLabel)
       // Get the corresponding classOf
@@ -2404,68 +2370,72 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
     fb.buildAndAddToModule()
   }
 
-  /** `newArrayOfThisClass: (ref typeData), anyref -> (ref jlObject)`.
+  /** `newArray: (ref jlClass), i32 -> (ref jlObject)`.
    *
-   *  This is the underlying func for the `newArrayOfThisClass()` closure inside class data objects.
+   *  This is the underlying func for the `Class_newArray` operation.
    */
-  private def genNewArrayOfThisClass()(implicit ctx: WasmContext): Unit = {
+  private def genNewArray()(implicit ctx: WasmContext): Unit = {
     val typeDataType = RefType(genTypeID.typeData)
-    val i32ArrayType = RefType(genTypeID.i32Array)
+    val arrayTypeDataType = RefType(genTypeID.ObjectVTable)
 
-    val fb = newFunctionBuilder(genFunctionID.newArrayOfThisClass)
-    val typeDataParam = fb.addParam("typeData", typeDataType)
-    val lengthsParam = fb.addParam("lengths", RefType.anyref)
+    val fb = newFunctionBuilder(genFunctionID.newArray)
+    val jlClassParam = fb.addParam("jlClass", RefType(genTypeID.ClassStruct))
+    val lengthParam = fb.addParam("length", Int32)
     fb.setResultType(RefType(genTypeID.ObjectStruct))
 
-    val lengthsLenLocal = fb.addLocal("lengthsLenLocal", Int32)
-    val lengthsValuesLocal = fb.addLocal("lengthsValues", i32ArrayType)
-    val iLocal = fb.addLocal("i", Int32)
-
-    // lengthsLen := lengths.length // as a JS field access, through a helper
-    fb += LocalGet(lengthsParam)
-    fb += Call(genFunctionID.jsArrayLength)
-    fb += LocalTee(lengthsLenLocal)
-
-    // lengthsValues := array.new<i32Array> lengthsLen
-    fb += ArrayNewDefault(genTypeID.i32Array)
-    fb += LocalSet(lengthsValuesLocal)
-
-    // i := 0
-    fb += I32Const(0)
-    fb += LocalSet(iLocal)
+    val componentTypeDataLocal = fb.addLocal("componentTypeData", RefType(genTypeID.typeData))
 
-    // while (i != lengthsLen)
-    fb.whileLoop() {
-      fb += LocalGet(iLocal)
-      fb += LocalGet(lengthsLenLocal)
-      fb += I32Ne
-    } {
-      // lengthsValue[i] := lengths[i] (where the rhs is a JS field access, though a helper)
+    // Check negative array size
+    if (semantics.negativeArraySizes != CheckedBehavior.Unchecked) {
+      fb += LocalGet(lengthParam)
+      fb += I32Const(0)
+      fb += I32LtS
+      fb.ifThen() {
+        fb += LocalGet(lengthParam)
+        fb += Call(genFunctionID.throwNegativeArraySizeException)
+        fb += Unreachable
+      }
+    }
 
-      fb += LocalGet(lengthsValuesLocal)
-      fb += LocalGet(iLocal)
+    // componentTypeData := jlClass.data
+    fb += LocalGet(jlClassParam)
+    fb += StructGet(genTypeID.ClassStruct, genFieldID.classData)
+    fb += LocalTee(componentTypeDataLocal)
 
-      fb += LocalGet(lengthsParam)
-      fb += LocalGet(iLocal)
-      fb += Call(genFunctionID.jsArrayGetInt)
+    // Load the vtable and itables of the ArrayClass instance we will create
+    fb += I32Const(1)
+    fb += Call(genFunctionID.arrayTypeData) // vtable
+    fb += GlobalGet(genGlobalID.arrayClassITable) // itables
 
-      fb += ArraySet(genTypeID.i32Array)
+    // Load the length
+    fb += LocalGet(lengthParam)
 
-      // i += 1
-      fb += LocalGet(iLocal)
-      fb += I32Const(1)
-      fb += I32Add
-      fb += LocalSet(iLocal)
+    // switch (componentTypeData.kind)
+    val switchClauseSig = FunctionType(
+      List(arrayTypeDataType, RefType(genTypeID.itables), Int32),
+      List(RefType(genTypeID.ObjectStruct))
+    )
+    fb.switch(switchClauseSig) { () =>
+      // scrutinee
+      fb += LocalGet(componentTypeDataLocal)
+      fb += StructGet(genTypeID.typeData, genFieldID.typeData.kind)
+    }(
+      // case KindPrim => array.new_default underlyingPrimArray; struct.new PrimArray
+      primRefsWithArrayTypes.map { case (primRef, kind) =>
+        List(kind) -> { () =>
+          val arrayTypeRef = ArrayTypeRef(primRef, 1)
+          fb += ArrayNewDefault(genTypeID.underlyingOf(arrayTypeRef))
+          fb += StructNew(genTypeID.forArrayClass(arrayTypeRef))
+          () // required for correct type inference
+        }
+      }: _*
+    ) { () =>
+      // case _ => array.new_default anyrefArray; struct.new ObjectArray
+      val arrayTypeRef = ArrayTypeRef(ClassRef(ObjectClass), 1)
+      fb += ArrayNewDefault(genTypeID.underlyingOf(arrayTypeRef))
+      fb += StructNew(genTypeID.forArrayClass(arrayTypeRef))
     }
 
-    // return newArrayObject(arrayTypeData(typeData, lengthsLen), lengthsValues, 0)
-    fb += LocalGet(typeDataParam)
-    fb += LocalGet(lengthsLenLocal)
-    fb += Call(genFunctionID.arrayTypeData)
-    fb += LocalGet(lengthsValuesLocal)
-    fb += I32Const(0)
-    fb += Call(genFunctionID.newArrayObject)
-
     fb.buildAndAddToModule()
   }
 
@@ -2676,187 +2646,6 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
     fb.buildAndAddToModule()
   }
 
-  /** `newArrayObject`: `(ref typeData), (ref array i32), i32 -> (ref jl.Object)`.
-   *
-   *  The arguments are `arrayTypeData`, `lengths` and `lengthIndex`.
-   *
-   *  This recursive function creates a multi-dimensional array. The resulting array has type data
-   *  `arrayTypeData` and length `lengths(lengthIndex)`. If `lengthIndex < `lengths.length - 1`, its
-   *  elements are recursively initialized with `newArrayObject(arrayTypeData.componentType,
-   *  lengths, lengthIndex - 1)`.
-   */
-  private def genNewArrayObject()(implicit ctx: WasmContext): Unit = {
-    import genFieldID.typeData._
-
-    val typeDataType = RefType(genTypeID.typeData)
-    val i32ArrayType = RefType(genTypeID.i32Array)
-    val objectVTableType = RefType(genTypeID.ObjectVTable)
-    val arrayTypeDataType = objectVTableType
-    val itablesType = RefType(genTypeID.itables)
-    val nonNullObjectType = RefType(genTypeID.ObjectStruct)
-    val anyArrayType = RefType(genTypeID.anyArray)
-
-    val fb = newFunctionBuilder(genFunctionID.newArrayObject)
-    val arrayTypeDataParam = fb.addParam("arrayTypeData", arrayTypeDataType)
-    val lengthsParam = fb.addParam("lengths", i32ArrayType)
-    val lengthIndexParam = fb.addParam("lengthIndex", Int32)
-    fb.setResultType(nonNullObjectType)
-
-    val lenLocal = fb.addLocal("len", Int32)
-    val underlyingLocal = fb.addLocal("underlying", anyArrayType)
-    val subLengthIndexLocal = fb.addLocal("subLengthIndex", Int32)
-    val arrayComponentTypeDataLocal = fb.addLocal("arrayComponentTypeData", arrayTypeDataType)
-    val iLocal = fb.addLocal("i", Int32)
-
-    /* High-level pseudo code of what this function does:
-     *
-     * def newArrayObject(arrayTypeData, lengths, lengthIndex) {
-     *   // create an array of the right primitive type
-     *   val len = lengths(lengthIndex)
-     *   // possibly: check negative array size
-     *   switch (arrayTypeData.componentType.kind) {
-     *     // for primitives, return without recursion
-     *     case KindBoolean => new Array[Boolean](len)
-     *     ...
-     *     case KindDouble => new Array[Double](len)
-     *
-     *     // for reference array types, maybe recursively initialize
-     *     case _ =>
-     *       val result = new Array[Object](len) // with arrayTypeData as vtable
-     *       val subLengthIndex = lengthIndex + 1
-     *       if (subLengthIndex != lengths.length) {
-     *         val arrayComponentTypeData = arrayTypeData.componentType
-     *         for (i <- 0 until len)
-     *           result(i) = newArrayObject(arrayComponentTypeData, lengths, subLengthIndex)
-     *       }
-     *       result
-     *   }
-     * }
-     */
-
-    val primRefsWithArrayTypes = List(
-      BooleanRef -> KindBoolean,
-      CharRef -> KindChar,
-      ByteRef -> KindByte,
-      ShortRef -> KindShort,
-      IntRef -> KindInt,
-      LongRef -> KindLong,
-      FloatRef -> KindFloat,
-      DoubleRef -> KindDouble
-    )
-
-    // Load the vtable and itable of the resulting array on the stack
-    fb += LocalGet(arrayTypeDataParam) // vtable
-    fb += GlobalGet(genGlobalID.arrayClassITable) // itable
-
-    // Load the first length
-    fb += LocalGet(lengthsParam)
-    fb += LocalGet(lengthIndexParam)
-    fb += ArrayGet(genTypeID.i32Array)
-
-    // Check negative array size
-    if (semantics.negativeArraySizes != CheckedBehavior.Unchecked) {
-      fb += LocalTee(lenLocal)
-      fb += I32Const(0)
-      fb += I32LtS
-      fb.ifThen() {
-        fb += LocalGet(lenLocal)
-        fb += Call(genFunctionID.throwNegativeArraySizeException)
-        fb += Unreachable
-      }
-      fb += LocalGet(lenLocal)
-    }
-
-    // componentTypeData := ref_as_non_null(arrayTypeData.componentType)
-    // switch (componentTypeData.kind)
-    val switchClauseSig = FunctionType(
-      List(arrayTypeDataType, itablesType, Int32),
-      List(nonNullObjectType)
-    )
-    fb.switch(switchClauseSig) { () =>
-      // scrutinee
-      fb += LocalGet(arrayTypeDataParam)
-      fb += StructGet(genTypeID.typeData, genFieldID.typeData.componentType)
-      fb += StructGet(genTypeID.typeData, genFieldID.typeData.kind)
-    }(
-      // For all the primitive types, by construction, this is the bottom dimension
-      // case KindPrim => array.new_default underlyingPrimArray; struct.new PrimArray
-      primRefsWithArrayTypes.map { case (primRef, kind) =>
-        List(kind) -> { () =>
-          val arrayTypeRef = ArrayTypeRef(primRef, 1)
-          fb += ArrayNewDefault(genTypeID.underlyingOf(arrayTypeRef))
-          fb += StructNew(genTypeID.forArrayClass(arrayTypeRef))
-          () // required for correct type inference
-        }
-      }: _*
-    ) { () =>
-      // default -- all non-primitive array types
-
-      // len := <top-of-stack> (which is the first length)
-      fb += LocalTee(lenLocal)
-
-      // underlying := array.new_default anyArray
-      val arrayTypeRef = ArrayTypeRef(ClassRef(ObjectClass), 1)
-      fb += ArrayNewDefault(genTypeID.underlyingOf(arrayTypeRef))
-      fb += LocalSet(underlyingLocal)
-
-      // subLengthIndex := lengthIndex + 1
-      fb += LocalGet(lengthIndexParam)
-      fb += I32Const(1)
-      fb += I32Add
-      fb += LocalTee(subLengthIndexLocal)
-
-      // if subLengthIndex != lengths.length
-      fb += LocalGet(lengthsParam)
-      fb += ArrayLen
-      fb += I32Ne
-      fb.ifThen() {
-        // then, recursively initialize all the elements
-
-        // arrayComponentTypeData := ref_cast<arrayTypeDataType> arrayTypeData.componentTypeData
-        fb += LocalGet(arrayTypeDataParam)
-        fb += StructGet(genTypeID.typeData, genFieldID.typeData.componentType)
-        fb += RefCast(RefType(arrayTypeDataType.heapType))
-        fb += LocalSet(arrayComponentTypeDataLocal)
-
-        // i := 0
-        fb += I32Const(0)
-        fb += LocalSet(iLocal)
-
-        // while (i != len)
-        fb.whileLoop() {
-          fb += LocalGet(iLocal)
-          fb += LocalGet(lenLocal)
-          fb += I32Ne
-        } {
-          // underlying[i] := newArrayObject(arrayComponentType, lengths, subLengthIndex)
-
-          fb += LocalGet(underlyingLocal)
-          fb += LocalGet(iLocal)
-
-          fb += LocalGet(arrayComponentTypeDataLocal)
-          fb += LocalGet(lengthsParam)
-          fb += LocalGet(subLengthIndexLocal)
-          fb += Call(genFunctionID.newArrayObject)
-
-          fb += ArraySet(genTypeID.anyArray)
-
-          // i += 1
-          fb += LocalGet(iLocal)
-          fb += I32Const(1)
-          fb += I32Add
-          fb += LocalSet(iLocal)
-        }
-      }
-
-      // load underlying; struct.new ObjectArray
-      fb += LocalGet(underlyingLocal)
-      fb += StructNew(genTypeID.forArrayClass(arrayTypeRef))
-    }
-
-    fb.buildAndAddToModule()
-  }
-
   /** `identityHashCode`: `anyref -> i32`.
    *
    *  This is the implementation of `IdentityHashCode`. It is also used to compute the `hashCode()`
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala
index 93b00423de..dca083127a 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala
@@ -431,7 +431,7 @@ object Emitter {
       },
 
       // TODO Ideally we should not require these, but rather adapt to their absence
-      instantiateClass(ClassClass, AnyArgConstructorName),
+      instantiateClass(ClassClass, NoArgConstructorName),
       instantiateClass(JSExceptionClass, AnyArgConstructorName),
 
       // See genIdentityHashCode in HelperFunctions
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
index 9626403260..fbe918f44b 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
@@ -1438,6 +1438,32 @@ private class FunctionEmitter private (
       // Null check
       case CheckNotNull =>
         genAsNonNullOrNPEFor(lhs)
+
+      // Class operations
+      case Class_name =>
+        fb += wa.StructGet(genTypeID.ClassStruct, genFieldID.classData)
+        fb += wa.Call(genFunctionID.typeDataName)
+      case Class_isPrimitive =>
+        fb += wa.StructGet(genTypeID.ClassStruct, genFieldID.classData)
+        fb += wa.StructGet(genTypeID.typeData, genFieldID.typeData.kind)
+        fb += wa.I32Const(KindLastPrimitive)
+        fb += wa.I32LeU
+      case Class_isInterface =>
+        fb += wa.StructGet(genTypeID.ClassStruct, genFieldID.classData)
+        fb += wa.StructGet(genTypeID.typeData, genFieldID.typeData.kind)
+        fb += wa.I32Const(KindInterface)
+        fb += wa.I32Eq
+      case Class_isArray =>
+        fb += wa.StructGet(genTypeID.ClassStruct, genFieldID.classData)
+        fb += wa.StructGet(genTypeID.typeData, genFieldID.typeData.kind)
+        fb += wa.I32Const(KindArray)
+        fb += wa.I32Eq
+      case Class_componentType =>
+        fb += wa.Call(genFunctionID.getComponentType)
+      case Class_superClass =>
+        // FIXME Implement this
+        fb += wa.Drop
+        fb += wa.RefNull(watpe.HeapType.None)
     }
 
     tree.tpe
@@ -1457,6 +1483,20 @@ private class FunctionEmitter private (
       LongType
     }
 
+    /* Gen the given tree of type `jl.Class!` then extract its `classData`.
+     * If the arg is a literal `ClassOf`, we directly generate its type data.
+     */
+    def genTreeClassData(arg: Tree): Unit = {
+      arg match {
+        case ClassOf(typeRef) =>
+          markPosition(arg)
+          genLoadTypeData(fb, typeRef)
+        case _ =>
+          genTreeAuto(arg)
+          fb += wa.StructGet(genTypeID.ClassStruct, genFieldID.classData)
+      }
+    }
+
     (op: @switch) match {
       case === | !== =>
         genEq(tree)
@@ -1535,6 +1575,32 @@ private class FunctionEmitter private (
           fb += wa.Call(genFunctionID.checkedStringCharAt)
         CharType
 
+      // Class operations for which genTreeAuto would not do the right thing
+      case Class_isInstance =>
+        genTreeClassData(lhs)
+        genTree(rhs, AnyType)
+        markPosition(tree)
+        fb += wa.Call(genFunctionID.isInstance)
+        BooleanType
+      case Class_isAssignableFrom =>
+        genTreeClassData(lhs)
+        genTreeClassData(rhs)
+        markPosition(tree)
+        fb += wa.Call(genFunctionID.isAssignableFrom)
+        BooleanType
+      case Class_cast =>
+        if (semantics.asInstanceOfs != CheckedBehavior.Unchecked) {
+          genTreeAuto(lhs)
+          genTree(rhs, AnyType)
+          markPosition(tree)
+          fb += wa.Call(genFunctionID.cast)
+          AnyType
+        } else {
+          genTree(lhs, NoType)
+          genTreeAuto(rhs)
+          rhs.tpe
+        }
+
       case _ =>
         genTreeAuto(lhs)
         genTreeAuto(rhs)
@@ -1689,6 +1755,8 @@ private class FunctionEmitter private (
       case Double_<= => wa.F64Le
       case Double_>  => wa.F64Gt
       case Double_>= => wa.F64Ge
+
+      case Class_newArray => wa.Call(genFunctionID.newArray)
     }
   }
 
@@ -2873,68 +2941,41 @@ private class FunctionEmitter private (
   }
 
   private def genNewArray(tree: NewArray): Type = {
-    val NewArray(arrayTypeRef, lengths) = tree
-
-    if (lengths.isEmpty || lengths.size > arrayTypeRef.dimensions) {
-      throw new AssertionError(
-          s"invalid lengths ${tree.lengths} for array type ${arrayTypeRef.displayName}")
-    }
+    val NewArray(arrayTypeRef, length :: Nil) = tree: @unchecked
 
     markPosition(tree)
 
-    if (lengths.size == 1) {
-      genLoadVTableAndITableForArray(fb, arrayTypeRef)
+    genLoadVTableAndITableForArray(fb, arrayTypeRef)
 
-      // Create the underlying array
-      genTree(lengths.head, IntType)
-      markPosition(tree)
+    // Create the underlying array
+    genTree(length, IntType)
+    markPosition(tree)
 
-      if (semantics.negativeArraySizes != CheckedBehavior.Unchecked) {
-        lengths.head match {
-          case IntLiteral(lengthValue) if lengthValue >= 0 =>
-            () // always good
-          case _ =>
-            // if length < 0
-            val lengthLocal = addSyntheticLocal(watpe.Int32)
-            fb += wa.LocalTee(lengthLocal)
-            fb += wa.I32Const(0)
-            fb += wa.I32LtS
-            fb.ifThen() {
-              // then throw NegativeArraySizeException
-              fb += wa.LocalGet(lengthLocal)
-              fb += wa.Call(genFunctionID.throwNegativeArraySizeException)
-              fb += wa.Unreachable
-            }
+    if (semantics.negativeArraySizes != CheckedBehavior.Unchecked) {
+      length match {
+        case IntLiteral(lengthValue) if lengthValue >= 0 =>
+          () // always good
+        case _ =>
+          // if length < 0
+          val lengthLocal = addSyntheticLocal(watpe.Int32)
+          fb += wa.LocalTee(lengthLocal)
+          fb += wa.I32Const(0)
+          fb += wa.I32LtS
+          fb.ifThen() {
+            // then throw NegativeArraySizeException
             fb += wa.LocalGet(lengthLocal)
-        }
+            fb += wa.Call(genFunctionID.throwNegativeArraySizeException)
+            fb += wa.Unreachable
+          }
+          fb += wa.LocalGet(lengthLocal)
       }
+    }
 
-      val underlyingArrayType = genTypeID.underlyingOf(arrayTypeRef)
-      fb += wa.ArrayNewDefault(underlyingArrayType)
-
-      // Create the array object
-      fb += wa.StructNew(genTypeID.forArrayClass(arrayTypeRef))
-    } else {
-      /* There is no Scala source code that produces `NewArray` with more than
-       * one specified dimension, so this branch is not tested.
-       * (The underlying function `newArrayObject` is tested as part of
-       * reflective array instantiations, though.)
-       */
-
-      // First arg to `newArrayObject`: the typeData of the array to create
-      genLoadArrayTypeData(fb, arrayTypeRef)
-
-      // Second arg: an array of the lengths
-      for (length <- lengths)
-        genTree(length, IntType)
-      markPosition(tree)
-      fb += wa.ArrayNewFixed(genTypeID.i32Array, lengths.size)
-
-      // Third arg: constant 0 (start index inside the array of lengths)
-      fb += wa.I32Const(0)
+    val underlyingArrayType = genTypeID.underlyingOf(arrayTypeRef)
+    fb += wa.ArrayNewDefault(underlyingArrayType)
 
-      fb += wa.Call(genFunctionID.newArrayObject)
-    }
+    // Create the array object
+    fb += wa.StructNew(genTypeID.forArrayClass(arrayTypeRef))
 
     tree.tpe
   }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala
index 90ce8400bf..af81fcd54e 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala
@@ -167,22 +167,7 @@ const scalaJSHelpers = {
   idHashCodeSet: (map, obj, value) => map.set(obj, value),
 
   // Some support functions for CoreWasmLib
-  genJSTypeMetaData: (typeData, name, isPrimitive, isArrayClass, isInterface, isInstanceFun,
-      isAssignableFromFun, checkCastFun, getComponentTypeFun, newArrayOfThisClassFun) => ({
-    __typeData: typeData, // (TODO hide this better? although nobody will notice anyway)
-    "name": name,
-    "isPrimitive": isPrimitive !== 0,
-    "isArrayClass": isArrayClass !== 0,
-    "isInterface": isInterface !== 0,
-    "isInstance": (value) => isInstanceFun(typeData, value) !== 0,
-    "isAssignableFrom": (that) => isAssignableFromFun(typeData, that.__typeData) !== 0,
-    "checkCast": (value) => checkCastFun(typeData, value),
-    "getComponentType": () => getComponentTypeFun(typeData),
-    "newArrayOfThisClass": (lengths) => newArrayOfThisClassFun(typeData, lengths),
-  }),
   makeTypeError: (msg) => new TypeError(msg),
-  jsArrayLength: (array) => array.length,
-  jsArrayGetInt: (array, index) => array[index],
 
   // JS interop
   jsGlobalRefGet: (globalRefName) => (new Function("return " + globalRefName))(),
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
index 893438b561..18659da4a7 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
@@ -156,10 +156,7 @@ object VarGen {
     case object idHashCodeGet extends JSHelperFunctionID
     case object idHashCodeSet extends JSHelperFunctionID
 
-    case object genJSTypeMetaData extends JSHelperFunctionID
     case object makeTypeError extends JSHelperFunctionID
-    case object jsArrayLength extends JSHelperFunctionID
-    case object jsArrayGetInt extends JSHelperFunctionID
 
     case object jsGlobalRefGet extends JSHelperFunctionID
     case object jsGlobalRefSet extends JSHelperFunctionID
@@ -257,13 +254,12 @@ object VarGen {
     case object throwModuleInitError extends FunctionID
     case object isInstance extends FunctionID
     case object isAssignableFrom extends FunctionID
-    case object checkCast extends FunctionID
+    case object cast extends FunctionID
     case object getComponentType extends FunctionID
-    case object newArrayOfThisClass extends FunctionID
+    case object newArray extends FunctionID
     case object anyGetClass extends FunctionID
     case object anyGetClassName extends FunctionID
     case object anyGetTypeData extends FunctionID
-    case object newArrayObject extends FunctionID
     case object identityHashCode extends FunctionID
     case object searchReflectiveProxy extends FunctionID
 
@@ -419,6 +415,9 @@ object VarGen {
        */
       case object reflectiveProxies extends FieldID
     }
+
+    /** The magic `data` field of type `(ref typeData)`, injected into `jl.Class`. */
+    case object classData extends FieldID
   }
 
   object genTypeID {
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala b/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
index 5da8ba0a6f..45ab1530ca 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
@@ -666,8 +666,8 @@ private final class ClassDefChecker(classDef: ClassDef,
       case NewArray(typeRef, lengths) =>
         if (lengths.isEmpty)
           reportError("NewArray must have non-0 dimensions")
-        if (lengths.size > typeRef.dimensions)
-          reportError("NewArray dimensions may not exceed its type")
+        if (lengths.size > 1)
+          reportError(i"Illegal legacy NewArray with ${lengths.size} dimensions")
 
         checkArrayTypeRef(typeRef)
         checkTrees(lengths, env)
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala b/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
index 7efab4d3c4..347e56bf34 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
@@ -445,6 +445,9 @@ private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter) {
             StringType
           case CheckNotNull =>
             AnyType
+          case Class_name | Class_isPrimitive | Class_isInterface |
+              Class_isArray | Class_componentType | Class_superClass =>
+            ClassType(ClassClass, nullable = false)
         }
         typecheckExpect(lhs, env, expectedArgType)
 
@@ -471,10 +474,17 @@ private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter) {
             DoubleType
           case String_charAt =>
             StringType
+          case Class_isInstance | Class_isAssignableFrom | Class_cast |
+              Class_newArray =>
+            ClassType(ClassClass, nullable = false)
         }
         val expectedRhsType = (op: @switch) match {
-          case Long_<< | Long_>>> | Long_>> | String_charAt => IntType
-          case _                                            => expectedLhsType
+          case Long_<< | Long_>>> | Long_>> | String_charAt | Class_newArray =>
+            IntType
+          case Class_isInstance | Class_cast =>
+            AnyType
+          case _ =>
+            expectedLhsType
         }
         typecheckExpect(lhs, env, expectedLhsType)
         typecheckExpect(rhs, env, expectedRhsType)
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/BaseLinker.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/BaseLinker.scala
index f120dff28a..e9756e38e1 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/BaseLinker.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/BaseLinker.scala
@@ -91,9 +91,14 @@ final class BaseLinker(config: CommonPhaseConfig, checkIR: Boolean) {
     } yield {
       val (linkedClassDefs, linkedTopLevelExports) = assembled.unzip
 
+      val globalInfo = new LinkedGlobalInfo(
+        analysis.isClassSuperClassUsed
+      )
+
       new LinkingUnit(config.coreSpec, linkedClassDefs.toList,
           linkedTopLevelExports.flatten.toList,
-          moduleInitializers.toList)
+          moduleInitializers.toList,
+          globalInfo)
     }
   }
 }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/LinkingUnit.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/LinkingUnit.scala
index dd6f61e0c7..836147cba5 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/LinkingUnit.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/LinkingUnit.scala
@@ -20,5 +20,6 @@ final class LinkingUnit private[frontend] (
     val coreSpec: CoreSpec,
     val classDefs: List[LinkedClass],
     val topLevelExports: List[LinkedTopLevelExport],
-    val moduleInitializers: List[ModuleInitializer]
+    val moduleInitializers: List[ModuleInitializer],
+    val globalInfo: LinkedGlobalInfo
 )
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/Refiner.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/Refiner.scala
index 985023e7ae..df7b262a00 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/Refiner.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/Refiner.scala
@@ -58,8 +58,12 @@ final class Refiner(config: CommonPhaseConfig, checkIR: Boolean) {
 
         val (linkedClassDefs, linkedTopLevelExports) = assembled.unzip
 
+        val globalInfo = new LinkedGlobalInfo(
+          analysis.isClassSuperClassUsed
+        )
+
         new LinkingUnit(config.coreSpec, linkedClassDefs.toList,
-            linkedTopLevelExports.flatten.toList, moduleInitializers)
+            linkedTopLevelExports.flatten.toList, moduleInitializers, globalInfo)
       }
 
       irLoader.cleanAfterRun()
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/modulesplitter/ModuleSplitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/modulesplitter/ModuleSplitter.scala
index 579d440265..2518679ca1 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/modulesplitter/ModuleSplitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/modulesplitter/ModuleSplitter.scala
@@ -45,7 +45,7 @@ final class ModuleSplitter private (analyzer: ModuleAnalyzer) {
        * We have to do it here, otherwise we break the assumption, that all
        * non-abstract classes are reached through a static path.
        */
-      new ModuleSet(unit.coreSpec, Nil, Nil)
+      new ModuleSet(unit.coreSpec, Nil, Nil, unit.globalInfo)
     } else {
       val analysis = logger.time("Module Splitter: Analyze Modules") {
         analyzer.analyze(dependencyInfo)
@@ -124,7 +124,7 @@ final class ModuleSplitter private (analyzer: ModuleAnalyzer) {
 
     val modules = builders.values.map(_.result()).toList
 
-    new ModuleSet(unit.coreSpec, modules, abstractClasses.result())
+    new ModuleSet(unit.coreSpec, modules, abstractClasses.result(), unit.globalInfo)
   }
 
   private def publicModuleDependencies(
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
index 82be00b249..034cfe8020 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
@@ -1553,13 +1553,17 @@ private[optimizer] abstract class OptimizerCore(
         finishTransformStat(lhs)
 
     case PreTransBinaryOp(op, lhs, rhs) =>
-      // Here we need to preserve the side-effects of integer division/modulo and String_charAt
       import BinaryOp._
 
+      implicit val pos = stat.pos
+
       def newLhs = finishTransformStat(lhs)
 
       def finishNoSideEffects: Tree =
-        Block(newLhs, finishTransformStat(rhs))(stat.pos)
+        Block(newLhs, finishTransformStat(rhs))
+
+      def finishWithSideEffects: Tree =
+        BinaryOp(op, finishTransformExpr(lhs), finishTransformExpr(rhs))
 
       (op: @switch) match {
         case Int_/ | Int_% =>
@@ -1567,19 +1571,21 @@ private[optimizer] abstract class OptimizerCore(
             case PreTransLit(IntLiteral(r)) if r != 0 =>
               finishNoSideEffects
             case _ =>
-              Block(newLhs, BinaryOp(op, IntLiteral(0)(stat.pos),
-                  finishTransformExpr(rhs))(stat.pos))(stat.pos)
+              Block(newLhs, BinaryOp(op, IntLiteral(0), finishTransformExpr(rhs)))
           }
         case Long_/ | Long_% =>
           rhs match {
             case PreTransLit(LongLiteral(r)) if r != 0L =>
               finishNoSideEffects
             case _ =>
-              Block(newLhs, BinaryOp(op, LongLiteral(0L)(stat.pos),
-                  finishTransformExpr(rhs))(stat.pos))(stat.pos)
+              Block(newLhs, BinaryOp(op, LongLiteral(0L), finishTransformExpr(rhs)))
           }
         case String_charAt if semantics.stringIndexOutOfBounds != CheckedBehavior.Unchecked =>
-          finishTransformExpr(stat)
+          finishWithSideEffects
+        case Class_cast if semantics.asInstanceOfs != CheckedBehavior.Unchecked =>
+          finishWithSideEffects
+        case Class_newArray if semantics.negativeArraySizes != CheckedBehavior.Unchecked =>
+          finishWithSideEffects
         case _ =>
           finishNoSideEffects
       }
@@ -1682,36 +1688,11 @@ private[optimizer] abstract class OptimizerCore(
       }
 
     case BinaryOp(op, lhs, rhs) =>
-      // Here we need to preserve the side-effects of integer division/modulo and String_charAt
-      import BinaryOp._
-
-      implicit val pos = stat.pos
-
-      def newLhs = keepOnlySideEffects(lhs)
-
-      def finishNoSideEffects: Tree =
-        Block(newLhs, keepOnlySideEffects(rhs))
-
-      op match {
-        case Int_/ | Int_% =>
-          rhs match {
-            case IntLiteral(r) if r != 0 =>
-              finishNoSideEffects
-            case _ =>
-              Block(newLhs, BinaryOp(op, IntLiteral(0), rhs))
-          }
-        case Long_/ | Long_% =>
-          rhs match {
-            case LongLiteral(r) if r != 0L =>
-              finishNoSideEffects
-            case _ =>
-              Block(newLhs, BinaryOp(op, LongLiteral(0L), rhs))
-          }
-        case String_charAt if semantics.stringIndexOutOfBounds != CheckedBehavior.Unchecked =>
-          stat
-        case _ =>
-          finishNoSideEffects
-      }
+      /* The logic here exceeds the complexity threshold for keeping a copy
+       * compared to `finishTransformStat` at the Tree level. Instead, we
+       * convert to a PreTransBinaryOp and delegate to the other function.
+       */
+      finishTransformStat(PreTransBinaryOp(op, lhs.toPreTransform, rhs.toPreTransform)(stat.pos))
 
     case RecordValue(_, elems) =>
       Block(elems.map(keepOnlySideEffects))(stat.pos)
@@ -1927,7 +1908,8 @@ private[optimizer] abstract class OptimizerCore(
             case NotFoundPureSoFar =>
               rec(rhs).mapOrKeepGoingIf(BinaryOp(op, lhs, _)) {
                 (op: @switch) match {
-                  case Int_/ | Int_% | Long_/ | Long_% | String_+ | String_charAt =>
+                  case Int_/ | Int_% | Long_/ | Long_% | String_+ | String_charAt |
+                      Class_cast | Class_newArray =>
                     false
                   case _ =>
                     true
@@ -3192,41 +3174,8 @@ private[optimizer] abstract class OptimizerCore(
 
       // java.lang.Class
 
-      case ClassGetComponentType =>
-        optTReceiver.get match {
-          case PreTransLit(ClassOf(ArrayTypeRef(base, depth))) =>
-            contTree(ClassOf(
-                if (depth == 1) base
-                else ArrayTypeRef(base, depth - 1)))
-          case PreTransLit(ClassOf(ClassRef(_))) =>
-            contTree(Null())
-          case receiver =>
-            default
-        }
-
       case ClassGetName =>
         optTReceiver.get match {
-          case PreTransMaybeBlock(bindingsAndStats, PreTransLit(ClassOf(typeRef))) =>
-            def mappedClassName(className: ClassName): String = {
-              RuntimeClassNameMapperImpl.map(
-                  config.coreSpec.semantics.runtimeClassNameMapper,
-                  className.nameString)
-            }
-
-            val nameString = typeRef match {
-              case primRef: PrimRef =>
-                primRef.displayName
-              case ClassRef(className) =>
-                mappedClassName(className)
-              case ArrayTypeRef(primRef: PrimRef, dimensions) =>
-                "[" * dimensions + primRef.charCode
-              case ArrayTypeRef(ClassRef(className), dimensions) =>
-                "[" * dimensions + "L" + mappedClassName(className) + ";"
-            }
-
-            contTree(finishTransformBindings(
-                bindingsAndStats, StringLiteral(nameString)))
-
           case PreTransMaybeBlock(bindingsAndStats,
               PreTransTree(MaybeCast(GetClass(expr)), _)) =>
             contTree(finishTransformBindings(
@@ -3236,18 +3185,6 @@ private[optimizer] abstract class OptimizerCore(
             default
         }
 
-      // java.lang.reflect.Array
-
-      case ArrayNewInstance =>
-        val List(tcomponentType, tlength) = targs
-        tcomponentType match {
-          case PreTransTree(ClassOf(elementTypeRef), _) if elementTypeRef != VoidRef =>
-            val arrayTypeRef = ArrayTypeRef.of(elementTypeRef)
-            contTree(NewArray(arrayTypeRef, List(finishTransformExpr(tlength))))
-          case _ =>
-            default
-        }
-
       // js.special
 
       case ObjectLiteral =>
@@ -3967,11 +3904,65 @@ private[optimizer] abstract class OptimizerCore(
       case CheckNotNull =>
         checkNotNull(arg)
 
+      // Class operations
+
+      case Class_name =>
+        arg match {
+          case PreTransLit(ClassOf(typeRef)) =>
+            PreTransLit(StringLiteral(constantClassNameOf(typeRef)))
+          case _ =>
+            default
+        }
+      case Class_isPrimitive =>
+        arg match {
+          case PreTransLit(ClassOf(typeRef)) =>
+            PreTransLit(BooleanLiteral(typeRef.isInstanceOf[PrimRef]))
+          case _ =>
+            default
+        }
+      case Class_isArray =>
+        arg match {
+          case PreTransLit(ClassOf(typeRef)) =>
+            PreTransLit(BooleanLiteral(typeRef.isInstanceOf[ArrayTypeRef]))
+          case _ =>
+            default
+        }
+      case Class_componentType =>
+        arg match {
+          case PreTransLit(ClassOf(ArrayTypeRef(base, depth))) =>
+            PreTransLit(ClassOf(
+                if (depth == 1) base
+                else ArrayTypeRef(base, depth - 1)))
+          case PreTransLit(ClassOf(_)) =>
+            PreTransLit(Null())
+          case _ =>
+            default
+        }
+
       case _ =>
         default
     }
   }
 
+  private def constantClassNameOf(typeRef: TypeRef): String = {
+    def mappedClassName(className: ClassName): String = {
+      RuntimeClassNameMapperImpl.map(
+          config.coreSpec.semantics.runtimeClassNameMapper,
+          className.nameString)
+    }
+
+    typeRef match {
+      case primRef: PrimRef =>
+        primRef.displayName
+      case ClassRef(className) =>
+        mappedClassName(className)
+      case ArrayTypeRef(primRef: PrimRef, dimensions) =>
+        "[" * dimensions + primRef.charCode
+      case ArrayTypeRef(ClassRef(className), dimensions) =>
+        "[" * dimensions + "L" + mappedClassName(className) + ";"
+    }
+  }
+
   /** Performs === for two literals.
    *  The result is always known statically.
    *
@@ -4988,6 +4979,30 @@ private[optimizer] abstract class OptimizerCore(
 
           case _ => default
         }
+
+      case Class_isInstance | Class_isAssignableFrom =>
+        /* We could do something clever here if we added a knowledge query to
+         * turn a TypeRef into a Type. Barring that, we cannot tell whether a
+         * ClassRef must become an `AnyType` or a `ClassType`.
+         */
+        default
+
+      case Class_cast =>
+        if (semantics.asInstanceOfs == CheckedBehavior.Unchecked) {
+          PreTransBlock(finishTransformStat(lhs), rhs)
+        } else {
+          // Same comment as in isInstance and isAssignableFrom
+          default
+        }
+
+      case Class_newArray =>
+        lhs match {
+          case PreTransLit(ClassOf(elementTypeRef)) if elementTypeRef != VoidRef =>
+            val arrayTypeRef = ArrayTypeRef.of(elementTypeRef)
+            NewArray(arrayTypeRef, List(finishTransformExpr(rhs))).toPreTransform
+          case _ =>
+            default
+        }
     }
   }
 
@@ -6519,12 +6534,9 @@ private[optimizer] object OptimizerCore {
     final val ArrayBuilderZeroOf = MathMaxDouble + 1
     final val GenericArrayBuilderResult = ArrayBuilderZeroOf + 1
 
-    final val ClassGetComponentType = GenericArrayBuilderResult + 1
-    final val ClassGetName = ClassGetComponentType + 1
+    final val ClassGetName = GenericArrayBuilderResult + 1
 
-    final val ArrayNewInstance = ClassGetName + 1
-
-    final val ObjectLiteral = ArrayNewInstance + 1
+    final val ObjectLiteral = ClassGetName + 1
 
     final val ByteArrayToInt8Array      = ObjectLiteral            + 1
     final val ShortArrayToInt16Array    = ByteArrayToInt8Array     + 1
@@ -6576,12 +6588,8 @@ private[optimizer] object OptimizerCore {
             m("numberOfLeadingZeros", List(I), I) -> IntegerNLZ
         ),
         ClassName("java.lang.Class") -> List(
-            m("getComponentType", Nil, ClassClassRef) -> ClassGetComponentType,
             m("getName", Nil, StringClassRef) -> ClassGetName
         ),
-        ClassName("java.lang.reflect.Array$") -> List(
-            m("newInstance", List(ClassClassRef, I), O) -> ArrayNewInstance
-        ),
         ClassName("scala.scalajs.js.special.package$") -> List(
             m("objectLiteral", List(SeqClassRef), JSObjectClassRef) -> ObjectLiteral
         )
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/standard/LinkedGlobalInfo.scala b/linker/shared/src/main/scala/org/scalajs/linker/standard/LinkedGlobalInfo.scala
new file mode 100644
index 0000000000..86253041af
--- /dev/null
+++ b/linker/shared/src/main/scala/org/scalajs/linker/standard/LinkedGlobalInfo.scala
@@ -0,0 +1,18 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package org.scalajs.linker.standard
+
+/** Global information about a linked program. */
+final class LinkedGlobalInfo private[linker] (
+  val isClassSuperClassUsed: Boolean
+)
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/standard/ModuleSet.scala b/linker/shared/src/main/scala/org/scalajs/linker/standard/ModuleSet.scala
index 849ed527ed..c03557baa9 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/standard/ModuleSet.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/standard/ModuleSet.scala
@@ -42,7 +42,9 @@ final class ModuleSet private[linker] (
      *
      *  For example, a native JS class that is needed for its load spec.
      */
-    val abstractClasses: List[LinkedClass]
+    val abstractClasses: List[LinkedClass],
+
+    val globalInfo: LinkedGlobalInfo
 ) {
   require(modules.isEmpty || modules.count(_.isRoot) == 1,
       "Must have exactly one root module")
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/LibrarySizeTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/LibrarySizeTest.scala
index 6dd8041406..9ab95541de 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/LibrarySizeTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/LibrarySizeTest.scala
@@ -70,9 +70,9 @@ class LibrarySizeTest {
     )
 
     testLinkedSizes(
-      expectedFastLinkSize = 147707,
-      expectedFullLinkSizeWithoutClosure = 86729,
-      expectedFullLinkSizeWithClosure = 21768,
+      expectedFastLinkSize = 147629,
+      expectedFullLinkSizeWithoutClosure = 85718,
+      expectedFullLinkSizeWithClosure = 21625,
       classDefs,
       moduleInitializers = MainTestModuleInitializers
     )
diff --git a/project/BinaryIncompatibilities.scala b/project/BinaryIncompatibilities.scala
index 3606a501a3..01c38bc201 100644
--- a/project/BinaryIncompatibilities.scala
+++ b/project/BinaryIncompatibilities.scala
@@ -31,6 +31,7 @@ object BinaryIncompatibilities {
 
     // private[linker], not an issue
     ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.linker.standard.CoreSpec.apply"),
+    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.linker.standard.ModuleSet.this"),
   )
 
   val LinkerInterface = Seq(
diff --git a/project/Build.scala b/project/Build.scala
index 9cda252d2e..745900effe 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -2048,15 +2048,15 @@ object Build {
           case `default212Version` =>
             if (!useMinifySizes) {
               Some(ExpectedSizes(
-                  fastLink = 626000 to 627000,
-                  fullLink = 97000 to 98000,
+                  fastLink = 623000 to 624000,
+                  fullLink = 96000 to 97000,
                   fastLinkGz = 75000 to 79000,
                   fullLinkGz = 25000 to 26000,
               ))
             } else {
               Some(ExpectedSizes(
-                  fastLink = 425000 to 426000,
-                  fullLink = 282000 to 283000,
+                  fastLink = 423000 to 424000,
+                  fullLink = 280000 to 281000,
                   fastLinkGz = 60000 to 61000,
                   fullLinkGz = 43000 to 44000,
               ))
@@ -2065,15 +2065,15 @@ object Build {
           case `default213Version` =>
             if (!useMinifySizes) {
               Some(ExpectedSizes(
-                  fastLink = 451000 to 452000,
+                  fastLink = 449000 to 450000,
                   fullLink = 95000 to 96000,
                   fastLinkGz = 58000 to 59000,
-                  fullLinkGz = 26000 to 27000,
+                  fullLinkGz = 25000 to 26000,
               ))
             } else {
               Some(ExpectedSizes(
-                  fastLink = 306000 to 307000,
-                  fullLink = 262000 to 263000,
+                  fastLink = 304000 to 305000,
+                  fullLink = 261000 to 262000,
                   fastLinkGz = 48000 to 49000,
                   fullLinkGz = 43000 to 44000,
               ))
diff --git a/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/lang/ClassTest.scala b/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/lang/ClassTest.scala
index 5ec3a41777..a447e5c48b 100644
--- a/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/lang/ClassTest.scala
+++ b/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/lang/ClassTest.scala
@@ -18,7 +18,7 @@ import org.junit.Assume._
 
 import scala.runtime.BoxedUnit
 
-import org.scalajs.testsuite.utils.AssertThrows.assertThrows
+import org.scalajs.testsuite.utils.AssertThrows.{assertThrows, _}
 import org.scalajs.testsuite.utils.Platform._
 
 class ClassTest {
@@ -267,6 +267,10 @@ class ClassTest {
           s"classOf[Comparable[_]].isAssignableFrom($cls) should be true",
           classOf[Comparable[_]].isAssignableFrom(cls))
     }
+
+    // NPE if the rhs is null
+
+    assertThrowsNPEIfCompliant(classOf[Object].isAssignableFrom(null))
   }
 
   @Test def getComponentType(): Unit = {

From e0fff46089edfc046f0615d8f59b31b27a133706 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Fri, 14 Jun 2024 13:55:44 +0200
Subject: [PATCH 169/298] Emit the new `Class_x` operations into `jl.Class`
 from the compiler.

We use the same technique as for `String_length` and `String_charAt`,
for which we hijack the method body from the compiler and replace
it with the appropriate operation.

Likewise, we actually change the `NewArray` data type to contain a
single length.

We only enable the deserialization hacks of the previous commit when
reading old IR.
---
 .../org/scalajs/nscplugin/GenJSCode.scala     | 73 +++++++++++++++---
 .../org/scalajs/nscplugin/JSDefinitions.scala |  2 +
 .../main/scala/org/scalajs/ir/Hashers.scala   |  4 +-
 .../main/scala/org/scalajs/ir/Printers.scala  | 12 ++-
 .../scala/org/scalajs/ir/Serializers.scala    | 22 ++----
 .../scala/org/scalajs/ir/Transformers.scala   |  4 +-
 .../scala/org/scalajs/ir/Traversers.scala     |  4 +-
 .../src/main/scala/org/scalajs/ir/Trees.scala |  2 +-
 .../scala/org/scalajs/ir/PrintersTest.scala   |  8 +-
 javalib/src/main/scala/java/lang/Class.scala  | 74 +++++--------------
 .../main/scala/java/lang/reflect/Array.scala  | 30 ++++++--
 .../backend/emitter/FunctionEmitter.scala     | 24 +++---
 .../backend/wasmemitter/FunctionEmitter.scala |  2 +-
 .../linker/checker/ClassDefChecker.scala      |  9 +--
 .../scalajs/linker/checker/IRChecker.scala    |  5 +-
 .../frontend/optimizer/OptimizerCore.scala    | 16 ++--
 project/BinaryIncompatibilities.scala         |  6 ++
 17 files changed, 161 insertions(+), 136 deletions(-)

diff --git a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
index 277d432ffd..ef5d20f120 100644
--- a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
+++ b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
@@ -2188,15 +2188,45 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
           isJSFunctionDef(currentClassSym)) {
         val flags = js.MemberFlags.empty.withNamespace(namespace)
         val body = {
+          def genAsUnaryOp(op: js.UnaryOp.Code): js.Tree =
+            js.UnaryOp(op, genThis())
+          def genAsBinaryOp(op: js.BinaryOp.Code): js.Tree =
+            js.BinaryOp(op, genThis(), jsParams.head.ref)
+          def genAsBinaryOpRhsNotNull(op: js.BinaryOp.Code): js.Tree =
+            js.BinaryOp(op, genThis(), js.UnaryOp(js.UnaryOp.CheckNotNull, jsParams.head.ref))
+
           if (currentClassSym.get == HackedStringClass) {
             /* Hijack the bodies of String.length and String.charAt and replace
              * them with String_length and String_charAt operations, respectively.
              */
             methodName.name match {
-              case `lengthMethodName` =>
-                js.UnaryOp(js.UnaryOp.String_length, genThis())
-              case `charAtMethodName` =>
-                js.BinaryOp(js.BinaryOp.String_charAt, genThis(), jsParams.head.ref)
+              case `lengthMethodName` => genAsUnaryOp(js.UnaryOp.String_length)
+              case `charAtMethodName` => genAsBinaryOp(js.BinaryOp.String_charAt)
+              case _                  => genBody()
+            }
+          } else if (currentClassSym.get == ClassClass) {
+            // Similar, for the Class_x operations
+            methodName.name match {
+              case `getNameMethodName`          => genAsUnaryOp(js.UnaryOp.Class_name)
+              case `isPrimitiveMethodName`      => genAsUnaryOp(js.UnaryOp.Class_isPrimitive)
+              case `isInterfaceMethodName`      => genAsUnaryOp(js.UnaryOp.Class_isInterface)
+              case `isArrayMethodName`          => genAsUnaryOp(js.UnaryOp.Class_isArray)
+              case `getComponentTypeMethodName` => genAsUnaryOp(js.UnaryOp.Class_componentType)
+              case `getSuperclassMethodName`    => genAsUnaryOp(js.UnaryOp.Class_superClass)
+
+              case `isInstanceMethodName`       => genAsBinaryOp(js.BinaryOp.Class_isInstance)
+              case `isAssignableFromMethodName` => genAsBinaryOpRhsNotNull(js.BinaryOp.Class_isAssignableFrom)
+              case `castMethodName`             => genAsBinaryOp(js.BinaryOp.Class_cast)
+
+              case _ => genBody()
+            }
+          } else if (currentClassSym.get == JavaLangReflectArrayModClass) {
+            methodName.name match {
+              case `arrayNewInstanceMethodName` =>
+                val List(jlClassParam, lengthParam) = jsParams
+                js.BinaryOp(js.BinaryOp.Class_newArray,
+                    js.UnaryOp(js.UnaryOp.CheckNotNull, jlClassParam.ref),
+                    lengthParam.ref)
               case _ =>
                 genBody()
             }
@@ -3644,12 +3674,11 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
      */
     def genNewArray(arrayTypeRef: jstpe.ArrayTypeRef, arguments: List[js.Tree])(
         implicit pos: Position): js.Tree = {
-      assert(arguments.length <= arrayTypeRef.dimensions,
-          "too many arguments for array constructor: found " + arguments.length +
-          " but array has only " + arrayTypeRef.dimensions +
-          " dimension(s)")
+      assert(arguments.size == 1,
+          "expected exactly 1 argument for array constructor: found " +
+          s"${arguments.length} at $pos")
 
-      js.NewArray(arrayTypeRef, arguments)
+      js.NewArray(arrayTypeRef, arguments.head)
     }
 
     /** Gen JS code for an array literal. */
@@ -7084,6 +7113,32 @@ private object GenJSCode {
   private val charAtMethodName =
     MethodName("charAt", List(jstpe.IntRef), jstpe.CharRef)
 
+  private val getNameMethodName =
+    MethodName("getName", Nil, jstpe.ClassRef(ir.Names.BoxedStringClass))
+  private val isPrimitiveMethodName =
+    MethodName("isPrimitive", Nil, jstpe.BooleanRef)
+  private val isInterfaceMethodName =
+    MethodName("isInterface", Nil, jstpe.BooleanRef)
+  private val isArrayMethodName =
+    MethodName("isArray", Nil, jstpe.BooleanRef)
+  private val getComponentTypeMethodName =
+    MethodName("getComponentType", Nil, jstpe.ClassRef(ir.Names.ClassClass))
+  private val getSuperclassMethodName =
+    MethodName("getSuperclass", Nil, jstpe.ClassRef(ir.Names.ClassClass))
+
+  private val isInstanceMethodName =
+    MethodName("isInstance", List(jstpe.ClassRef(ir.Names.ObjectClass)), jstpe.BooleanRef)
+  private val isAssignableFromMethodName =
+    MethodName("isAssignableFrom", List(jstpe.ClassRef(ir.Names.ClassClass)), jstpe.BooleanRef)
+  private val castMethodName =
+    MethodName("cast", List(jstpe.ClassRef(ir.Names.ObjectClass)), jstpe.ClassRef(ir.Names.ObjectClass))
+
+  private val arrayNewInstanceMethodName = {
+    MethodName("newInstance",
+        List(jstpe.ClassRef(ir.Names.ClassClass), jstpe.IntRef),
+        jstpe.ClassRef(ir.Names.ObjectClass))
+  }
+
   private val thisOriginalName = OriginalName("this")
 
   private object BlockOrAlone {
diff --git a/compiler/src/main/scala/org/scalajs/nscplugin/JSDefinitions.scala b/compiler/src/main/scala/org/scalajs/nscplugin/JSDefinitions.scala
index 43fa33aedd..8214985b6a 100644
--- a/compiler/src/main/scala/org/scalajs/nscplugin/JSDefinitions.scala
+++ b/compiler/src/main/scala/org/scalajs/nscplugin/JSDefinitions.scala
@@ -37,6 +37,8 @@ trait JSDefinitions {
 
     lazy val JavaLangVoidClass = getRequiredClass("java.lang.Void")
 
+    lazy val JavaLangReflectArrayModClass = getModuleIfDefined("java.lang.reflect.Array").moduleClass
+
     lazy val BoxedUnitModClass = BoxedUnitModule.moduleClass
 
     lazy val ScalaJSJSPackageModule = getPackageObject("scala.scalajs.js")
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Hashers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Hashers.scala
index b1f69595a3..d37bf739e7 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Hashers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Hashers.scala
@@ -321,10 +321,10 @@ object Hashers {
           mixTree(lhs)
           mixTree(rhs)
 
-        case NewArray(typeRef, lengths) =>
+        case NewArray(typeRef, length) =>
           mixTag(TagNewArray)
           mixArrayTypeRef(typeRef)
-          mixTrees(lengths)
+          mixTrees(length :: Nil) // mixed as a list for historical reasons
 
         case ArrayValue(typeRef, elems) =>
           mixTag(TagArrayValue)
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala
index eca5c547f2..34f5743e69 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala
@@ -511,15 +511,13 @@ object Printers {
           print(rhs)
           print(')')
 
-        case NewArray(typeRef, lengths) =>
+        case NewArray(typeRef, length) =>
           print("new ")
           print(typeRef.base)
-          for (length <- lengths) {
-            print('[')
-            print(length)
-            print(']')
-          }
-          for (dim <- lengths.size until typeRef.dimensions)
+          print('[')
+          print(length)
+          print(']')
+          for (dim <- 1 until typeRef.dimensions)
             print("[]")
 
         case ArrayValue(typeRef, elems) =>
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
index 45453943c5..ae2eec6b1f 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
@@ -363,9 +363,10 @@ object Serializers {
           writeTagAndPos(TagBinaryOp)
           writeByte(op); writeTree(lhs); writeTree(rhs)
 
-        case NewArray(tpe, lengths) =>
+        case NewArray(tpe, length) =>
           writeTagAndPos(TagNewArray)
-          writeArrayTypeRef(tpe); writeTrees(lengths)
+          writeArrayTypeRef(tpe)
+          writeTrees(length :: Nil) // written as a list of historical reasons
 
         case ArrayValue(tpe, elems) =>
           writeTagAndPos(TagArrayValue)
@@ -1232,10 +1233,10 @@ object Serializers {
           val lengths = readTrees()
           lengths match {
             case length :: Nil =>
-              NewArray(arrayTypeRef, lengths)
+              NewArray(arrayTypeRef, length)
 
             case _ =>
-              if (true /* hacks.use16 */) { // scalastyle:ignore
+              if (hacks.use16) {
                 // Rewrite as a call to j.l.r.Array.newInstance
                 val ArrayTypeRef(base, origDims) = arrayTypeRef
                 val newDims = origDims - lengths.size
@@ -1504,9 +1505,9 @@ object Serializers {
         if (hacks.use4 && kind.isJSClass) {
           // #4409: Filter out abstract methods in non-native JS classes for version < 1.5
           methods0.filter(_.body.isDefined)
-        } else if (true /*hacks.use16*/ && cls == ClassClass) { // scalastyle:ignore
+        } else if (hacks.use16 && cls == ClassClass) {
           jlClassMethodsHack16(methods0)
-        } else if (true /*hacks.use16*/ && cls == HackNames.ReflectArrayModClass) { // scalastyle:ignore
+        } else if (hacks.use16 && cls == HackNames.ReflectArrayModClass) {
           jlReflectArrayMethodsHack16(methods0)
         } else {
           methods0
@@ -1697,14 +1698,7 @@ object Serializers {
             OptimizerHints.empty, Version.fromInt(1))
       }
 
-      /* Only for the temporary commit where we always apply the hack, because
-       * the hack is applied in the JavalibIRCleaner and then a second time
-       * for the true deserialization.
-       */
-      val oldMethodsTemp =
-        methods.filterNot(_.methodName == newInstanceRecName)
-
-      val newMethods = for (method <- oldMethodsTemp) yield {
+      val newMethods = for (method <- methods) yield {
         method.methodName match {
           case `newInstanceSingleName` =>
             // newInstance(jl.Class, int)  -->  newArray(jlClass.notNull, length)
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Transformers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Transformers.scala
index 6d30327786..09b82b1757 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Transformers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Transformers.scala
@@ -114,8 +114,8 @@ object Transformers {
         case BinaryOp(op, lhs, rhs) =>
           BinaryOp(op, transformExpr(lhs), transformExpr(rhs))
 
-        case NewArray(tpe, lengths) =>
-          NewArray(tpe, lengths map transformExpr)
+        case NewArray(tpe, length) =>
+          NewArray(tpe, transformExpr(length))
 
         case ArrayValue(tpe, elems) =>
           ArrayValue(tpe, elems map transformExpr)
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Traversers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Traversers.scala
index 8a8909cdce..2f68fac81f 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Traversers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Traversers.scala
@@ -101,8 +101,8 @@ object Traversers {
         traverse(lhs)
         traverse(rhs)
 
-      case NewArray(tpe, lengths) =>
-        lengths foreach traverse
+      case NewArray(tpe, length) =>
+        traverse(length)
 
       case ArrayValue(tpe, elems) =>
         elems foreach traverse
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala b/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
index 3eb43c7f11..51d08ea2e9 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
@@ -519,7 +519,7 @@ object Trees {
     }
   }
 
-  sealed case class NewArray(typeRef: ArrayTypeRef, lengths: List[Tree])(
+  sealed case class NewArray(typeRef: ArrayTypeRef, length: Tree)(
       implicit val pos: Position) extends Tree {
     val tpe = ArrayType(typeRef, nullable = false)
   }
diff --git a/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala b/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala
index 16d5120ea3..57d80c3373 100644
--- a/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala
+++ b/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala
@@ -557,10 +557,10 @@ class PrintersTest {
   }
 
   @Test def printNewArray(): Unit = {
-    assertPrintEquals("new int[3]", NewArray(ArrayTypeRef(IntRef, 1), List(i(3))))
-    assertPrintEquals("new int[3][]", NewArray(ArrayTypeRef(IntRef, 2), List(i(3))))
-    assertPrintEquals("new java.lang.Object[3][4][][]",
-        NewArray(ArrayTypeRef(ObjectClass, 4), List(i(3), i(4))))
+    assertPrintEquals("new int[3]", NewArray(ArrayTypeRef(IntRef, 1), i(3)))
+    assertPrintEquals("new int[3][]", NewArray(ArrayTypeRef(IntRef, 2), i(3)))
+    assertPrintEquals("new java.lang.Object[3][][][]",
+        NewArray(ArrayTypeRef(ObjectClass, 4), i(3)))
   }
 
   @Test def printArrayValue(): Unit = {
diff --git a/javalib/src/main/scala/java/lang/Class.scala b/javalib/src/main/scala/java/lang/Class.scala
index a39bfd3fa7..b0d80c788b 100644
--- a/javalib/src/main/scala/java/lang/Class.scala
+++ b/javalib/src/main/scala/java/lang/Class.scala
@@ -15,68 +15,39 @@ package java.lang
 import java.lang.constant.Constable
 import java.io.Serializable
 
-import scala.scalajs.js
-
-@js.native
-private trait ScalaJSClassData[A] extends js.Object {
-  val name: String = js.native
-  val isPrimitive: scala.Boolean = js.native
-  val isInterface: scala.Boolean = js.native
-  val isArrayClass: scala.Boolean = js.native
-
-  def isInstance(obj: Any): scala.Boolean = js.native
-  def isAssignableFrom(that: ScalaJSClassData[_]): scala.Boolean = js.native
-  def checkCast(obj: Any): scala.Unit = js.native
-
-  def getSuperclass(): Class[_ >: A] = js.native
-  def getComponentType(): Class[_] = js.native
-
-  def newArrayOfThisClass(dimensions: js.Array[Int]): AnyRef = js.native
-}
-
-final class Class[A] private (data0: Object)
+final class Class[A] private ()
     extends Object with Serializable with Constable {
 
-  private[this] val data: ScalaJSClassData[A] =
-    data0.asInstanceOf[ScalaJSClassData[A]]
-
   private[this] var cachedSimpleName: String = _
 
-  /** Access to `data` for other instances or `@inline` methods.
-   *
-   *  Directly accessing the `data` field from `@inline` methods will cause
-   *  scalac to make the field public and mangle its name. Since the Emitter
-   *  relies on the field being called exactly `data` in some of its
-   *  optimizations, we must avoid that.
-   *
-   *  This non-`@noinline` method can be used to access the field without
-   *  triggering scalac's mangling. Since it is a trivial accessor, the
-   *  Scala.js optimizer will inline it anyway.
-   */
-  private def getData(): ScalaJSClassData[A] = data
-
   override def toString(): String = {
     (if (isInterface()) "interface " else
         if (isPrimitive()) "" else "class ")+getName()
   }
 
+  @inline
   def isInstance(obj: Any): scala.Boolean =
-    data.isInstance(obj)
+    throw new Error("Stub filled in by the compiler")
 
+  @inline
   def isAssignableFrom(that: Class[_]): scala.Boolean =
-    this.data.isAssignableFrom(that.getData())
+    throw new Error("Stub filled in by the compiler")
 
+  @inline
   def isInterface(): scala.Boolean =
-    data.isInterface
+    throw new Error("Stub filled in by the compiler")
 
+  @inline
   def isArray(): scala.Boolean =
-    data.isArrayClass
+    throw new Error("Stub filled in by the compiler")
 
+  @inline
   def isPrimitive(): scala.Boolean =
-    data.isPrimitive
+    throw new Error("Stub filled in by the compiler")
 
+  @inline
   def getName(): String =
-    data.name
+    throw new Error("Stub filled in by the compiler")
 
   def getSimpleName(): String = {
     if (cachedSimpleName == null)
@@ -108,7 +79,7 @@ final class Class[A] private (data0: Object)
     if (isArray()) {
       getComponentType().getSimpleName() + "[]"
     } else {
-      val name = data.name
+      val name = getName()
       var idx = name.length - 1
 
       // Include trailing '$'s for module class names
@@ -139,20 +110,15 @@ final class Class[A] private (data0: Object)
     }
   }
 
+  @inline
   def getSuperclass(): Class[_ >: A] =
-    data.getSuperclass()
+    throw new Error("Stub filled in by the compiler")
 
+  @inline
   def getComponentType(): Class[_] =
-    data.getComponentType()
+    throw new Error("Stub filled in by the compiler")
 
   @inline
-  def cast(obj: Any): A = {
-    getData().checkCast(obj)
-    obj.asInstanceOf[A]
-  }
-
-  // java.lang.reflect.Array support
-
-  private[lang] def newArrayOfThisClass(dimensions: js.Array[Int]): AnyRef =
-    data.newArrayOfThisClass(dimensions)
+  def cast(obj: Any): A =
+    throw new Error("Stub filled in by the compiler")
 }
diff --git a/javalib/src/main/scala/java/lang/reflect/Array.scala b/javalib/src/main/scala/java/lang/reflect/Array.scala
index b2f94b8906..f5f6aaa21f 100644
--- a/javalib/src/main/scala/java/lang/reflect/Array.scala
+++ b/javalib/src/main/scala/java/lang/reflect/Array.scala
@@ -17,18 +17,34 @@ import scala.scalajs.js
 import java.lang.Class
 
 object Array {
+  @inline
   def newInstance(componentType: Class[_], length: Int): AnyRef =
-    componentType.newArrayOfThisClass(js.Array(length))
+    throw new Error("Stub filled in by the compiler")
 
   def newInstance(componentType: Class[_], dimensions: scala.Array[Int]): AnyRef = {
-    val jsDims = js.Array[Int]()
-    val len = dimensions.length
-    var i = 0
-    while (i != len) {
-      jsDims.push(dimensions(i))
+    def rec(componentType: Class[_], offset: Int): AnyRef = {
+      val length = dimensions(offset)
+      val result = newInstance(componentType, length)
+      val innerOffset = offset + 1
+      if (innerOffset < dimensions.length) {
+        val result2 = result.asInstanceOf[Array[AnyRef]]
+        val innerComponentType = componentType.getComponentType()
+        var i = 0
+        while (i != length) {
+          result2(i) = rec(innerComponentType, innerOffset)
+          i += 1
+        }
+      }
+      result
+    }
+
+    var outermostComponentType = componentType
+    var i = 1
+    while (i != dimensions.length) {
+      outermostComponentType = newInstance(outermostComponentType, 0).getClass()
       i += 1
     }
-    componentType.newArrayOfThisClass(jsDims)
+    rec(outermostComponentType, 0)
   }
 
   def getLength(array: AnyRef): Int = array match {
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
index 184f46c365..444cca7fb6 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
@@ -1047,8 +1047,8 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
                   if noExtractYet || semantics.asInstanceOfs == Unchecked =>
                 AsInstanceOf(rec(expr), tpe)
 
-              case NewArray(tpe, lengths) =>
-                NewArray(tpe, recs(lengths))
+              case NewArray(tpe, length) =>
+                NewArray(tpe, rec(length))
               case ArrayValue(tpe, elems) =>
                 ArrayValue(tpe, recs(elems))
               case JSArrayConstr(items) if !needsToTranslateAnySpread(items) =>
@@ -1344,8 +1344,8 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
           allowSideEffects && test(expr) // may TypeError
 
         // Array operations with conditional exceptions
-        case NewArray(tpe, lengths) =>
-          allowBehavior(semantics.negativeArraySizes) && allowUnpure && lengths.forall(test)
+        case NewArray(tpe, length) =>
+          allowBehavior(semantics.negativeArraySizes) && allowUnpure && test(length)
         case ArraySelect(array, index) =>
           allowBehavior(semantics.arrayIndexOutOfBounds) && allowUnpure && testNPE(array) && test(index)
 
@@ -1757,9 +1757,9 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
             redo(BinaryOp(op, newLhs, newRhs))(env)
           }
 
-        case NewArray(tpe, lengths) =>
-          unnest(lengths) { (newLengths, env) =>
-            redo(NewArray(tpe, newLengths))(env)
+        case NewArray(tpe, length) =>
+          unnest(length) { (newLength, env) =>
+            redo(NewArray(tpe, newLength))(env)
           }
 
         case ArrayValue(tpe, elems) =>
@@ -2704,14 +2704,8 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
               js.Apply(extractClassData(lhs, newLhs) DOT cpn.newArray, newRhs :: Nil)
           }
 
-        case NewArray(typeRef, lengths) =>
-          lengths match {
-            case length :: Nil =>
-              js.New(genArrayConstrOf(typeRef), transformExprNoChar(length) :: Nil)
-            case _ =>
-              throw new AssertionError(
-                  s"Illegal legacy NewArray with lengths $lengths at $pos")
-          }
+        case NewArray(typeRef, length) =>
+          js.New(genArrayConstrOf(typeRef), transformExprNoChar(length) :: Nil)
 
         case ArrayValue(typeRef, elems) =>
           val preserveChar = typeRef match {
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
index fbe918f44b..4be4ac40ac 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
@@ -2941,7 +2941,7 @@ private class FunctionEmitter private (
   }
 
   private def genNewArray(tree: NewArray): Type = {
-    val NewArray(arrayTypeRef, length :: Nil) = tree: @unchecked
+    val NewArray(arrayTypeRef, length) = tree
 
     markPosition(tree)
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala b/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
index 45ab1530ca..b569825470 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
@@ -663,14 +663,9 @@ private final class ClassDefChecker(classDef: ClassDef,
         checkTree(lhs, env)
         checkTree(rhs, env)
 
-      case NewArray(typeRef, lengths) =>
-        if (lengths.isEmpty)
-          reportError("NewArray must have non-0 dimensions")
-        if (lengths.size > 1)
-          reportError(i"Illegal legacy NewArray with ${lengths.size} dimensions")
-
+      case NewArray(typeRef, length) =>
         checkArrayTypeRef(typeRef)
-        checkTrees(lengths, env)
+        checkTree(length, env)
 
       case ArrayValue(typeRef, elems) =>
         checkArrayTypeRef(typeRef)
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala b/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
index 347e56bf34..5bf5e259c4 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
@@ -489,9 +489,8 @@ private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter) {
         typecheckExpect(lhs, env, expectedLhsType)
         typecheckExpect(rhs, env, expectedRhsType)
 
-      case NewArray(typeRef, lengths) =>
-        for (length <- lengths)
-          typecheckExpect(length, env, IntType)
+      case NewArray(typeRef, length) =>
+        typecheckExpect(length, env, IntType)
 
       case ArrayValue(typeRef, elems) =>
         val elemType = arrayElemType(typeRef)
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
index 034cfe8020..264d1d8a30 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
@@ -530,8 +530,8 @@ private[optimizer] abstract class OptimizerCore(
           pretransformBinaryOp(tree)(finishTransform(isStat))
         }
 
-      case NewArray(tpe, lengths) =>
-        NewArray(tpe, lengths map transformExpr)
+      case NewArray(tpe, length) =>
+        NewArray(tpe, transformExpr(length))
 
       case ArrayValue(tpe, elems) =>
         ArrayValue(tpe, elems map transformExpr)
@@ -1665,10 +1665,10 @@ private[optimizer] abstract class OptimizerCore(
     case LoadModule(moduleClassName) =>
       if (hasElidableConstructors(moduleClassName)) Skip()(stat.pos)
       else stat
-    case NewArray(_, lengths) if lengths.forall(isNonNegativeIntLiteral(_)) =>
+    case NewArray(_, length) if isNonNegativeIntLiteral(length) =>
       Skip()(stat.pos)
-    case NewArray(_, lengths) if semantics.negativeArraySizes == CheckedBehavior.Unchecked =>
-      Block(lengths.map(keepOnlySideEffects))(stat.pos)
+    case NewArray(_, length) if semantics.negativeArraySizes == CheckedBehavior.Unchecked =>
+      keepOnlySideEffects(length)
     case ArrayValue(_, elems) =>
       Block(elems.map(keepOnlySideEffects(_)))(stat.pos)
     case ArrayLength(array) =>
@@ -1917,8 +1917,8 @@ private[optimizer] abstract class OptimizerCore(
               }
           }
 
-        case NewArray(typeRef, lengths) =>
-          recs(lengths).mapOrKeepGoing(NewArray(typeRef, _))
+        case NewArray(typeRef, length) =>
+          rec(length).mapOrKeepGoing(NewArray(typeRef, _))
 
         case ArrayValue(typeRef, elems) =>
           recs(elems).mapOrKeepGoing(ArrayValue(typeRef, _))
@@ -4999,7 +4999,7 @@ private[optimizer] abstract class OptimizerCore(
         lhs match {
           case PreTransLit(ClassOf(elementTypeRef)) if elementTypeRef != VoidRef =>
             val arrayTypeRef = ArrayTypeRef.of(elementTypeRef)
-            NewArray(arrayTypeRef, List(finishTransformExpr(rhs))).toPreTransform
+            NewArray(arrayTypeRef, finishTransformExpr(rhs)).toPreTransform
           case _ =>
             default
         }
diff --git a/project/BinaryIncompatibilities.scala b/project/BinaryIncompatibilities.scala
index 01c38bc201..8c27dca150 100644
--- a/project/BinaryIncompatibilities.scala
+++ b/project/BinaryIncompatibilities.scala
@@ -9,6 +9,12 @@ object BinaryIncompatibilities {
 
     ProblemFilters.exclude[IncompatibleResultTypeProblem]("org.scalajs.ir.Trees#*.tpe"),
 
+    ProblemFilters.exclude[IncompatibleMethTypeProblem]("org.scalajs.ir.Trees#NewArray.this"),
+    ProblemFilters.exclude[IncompatibleMethTypeProblem]("org.scalajs.ir.Trees#NewArray.apply"),
+    ProblemFilters.exclude[IncompatibleMethTypeProblem]("org.scalajs.ir.Trees#NewArray.copy"),
+    ProblemFilters.exclude[IncompatibleResultTypeProblem]("org.scalajs.ir.Trees#NewArray.copy$default$2"),
+    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Trees#NewArray.lengths"),
+
     ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Trees#UnaryOp.resultTypeOf"),
 
     ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Types#ClassType.this"),

From 624f1aecf53692bcc2955e87c1c561f998bf22ed Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Fri, 20 Sep 2024 17:16:12 +0200
Subject: [PATCH 170/298] Wasm: Implement `Class_superClass`.

Since `strictAncestors` already contains an array of the `typeData`
of the ancestors, we reuse it to mention the `superClass`. We make
sure it appears first when `Class_superClass` is used.

We determine whether a given `jl.Class` has a `superClass` at all
based on its `kind`. For JS types, we introduce an additional kind
`KindJSTypeWithSuperClass`. We only use that kind when
`Class_superClass` is used at all.
---
 .../backend/WebAssemblyLinkerBackend.scala    |   2 +-
 .../backend/wasmemitter/ClassEmitter.scala    |  17 ++-
 .../backend/wasmemitter/CoreWasmLib.scala     | 103 ++++++++++++++++--
 .../wasmemitter/EmbeddedConstants.scala       |   1 +
 .../linker/backend/wasmemitter/Emitter.scala  |   9 +-
 .../backend/wasmemitter/FunctionEmitter.scala |   4 +-
 .../linker/backend/wasmemitter/VarGen.scala   |   7 +-
 .../javalib/lang/ClassJSTestEx.scala          |  64 +++++++++++
 .../testsuite/javalib/lang/ClassTestEx.scala  |   7 +-
 9 files changed, 189 insertions(+), 25 deletions(-)
 create mode 100644 test-suite-ex/js/src/test/scala/org/scalajs/testsuite/javalib/lang/ClassJSTestEx.scala

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/WebAssemblyLinkerBackend.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/WebAssemblyLinkerBackend.scala
index 4ee5222d90..cee769bf14 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/WebAssemblyLinkerBackend.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/WebAssemblyLinkerBackend.scala
@@ -69,7 +69,7 @@ final class WebAssemblyLinkerBackend(config: LinkerBackendImpl.Config)
     }
     val moduleID = onlyModule.id.id
 
-    val emitterResult = emitter.emit(onlyModule, logger)
+    val emitterResult = emitter.emit(onlyModule, moduleSet.globalInfo, logger)
     val wasmModule = emitterResult.wasmModule
 
     val outputImpl = OutputDirectoryImpl.fromOutputDirectory(output)
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/ClassEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/ClassEmitter.scala
index a4ff9ceff4..5775d085a3 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/ClassEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/ClassEmitter.scala
@@ -22,7 +22,7 @@ import org.scalajs.ir.Types._
 
 import org.scalajs.linker.interface.CheckedBehavior
 import org.scalajs.linker.interface.unstable.RuntimeClassNameMapperImpl
-import org.scalajs.linker.standard.{CoreSpec, LinkedClass, LinkedTopLevelExport}
+import org.scalajs.linker.standard.{CoreSpec, LinkedClass, LinkedGlobalInfo, LinkedTopLevelExport}
 
 import org.scalajs.linker.backend.webassembly.FunctionBuilder
 import org.scalajs.linker.backend.webassembly.{Instructions => wa}
@@ -221,7 +221,10 @@ class ClassEmitter(coreSpec: CoreSpec) {
           case Interface =>
             KindInterface
           case JSClass | JSModuleClass | AbstractJSType | NativeJSClass | NativeJSModuleClass =>
-            KindJSType
+            if (clazz.superClass.isDefined)
+              KindJSTypeWithSuperClass
+            else
+              KindJSType
         }
     }
 
@@ -233,7 +236,15 @@ class ClassEmitter(coreSpec: CoreSpec) {
         ancestors.headOption.contains(className),
         s"The ancestors of ${className.nameString} do not start with itself: $ancestors"
       )
-      val strictAncestors = ancestors.tail
+      val strictAncestors0 = ancestors.tail
+
+      // If the class has a super class, move it first for the benefit of Class_superClass
+      val strictAncestors = clazz.superClass match {
+        case Some(ClassIdent(superClass)) =>
+          superClass :: strictAncestors0.filter(_ != superClass)
+        case None =>
+          strictAncestors0
+      }
 
       val elems = for {
         ancestor <- strictAncestors
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
index 90dfbb16ad..94ceac5fae 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
@@ -19,7 +19,7 @@ import org.scalajs.ir.Types.{Type => _, ArrayType => _, _}
 import org.scalajs.ir.{OriginalName, Position, Types => irtpe}
 
 import org.scalajs.linker.interface.CheckedBehavior
-import org.scalajs.linker.standard.CoreSpec
+import org.scalajs.linker.standard.{CoreSpec, LinkedGlobalInfo}
 
 import org.scalajs.linker.backend.webassembly._
 import org.scalajs.linker.backend.webassembly.Instructions._
@@ -31,7 +31,7 @@ import EmbeddedConstants._
 import VarGen._
 import TypeTransformer._
 
-final class CoreWasmLib(coreSpec: CoreSpec) {
+final class CoreWasmLib(coreSpec: CoreSpec, globalInfo: LinkedGlobalInfo) {
   import RefType.anyref
   import coreSpec.semantics
 
@@ -695,6 +695,8 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
     if (semantics.asInstanceOfs != CheckedBehavior.Unchecked)
       genCast()
     genGetComponentType()
+    if (globalInfo.isClassSuperClassUsed)
+      genGetSuperClass()
     genNewArray()
     genAnyGetClass()
     genAnyGetClassName()
@@ -1663,11 +1665,11 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
         fb += RefEq
         fb += BrIf(successLabel)
 
-        // If componentTypeData.kind == KindJSType, succeed
+        // If componentTypeData.kind >= KindJSType, succeed
         fb += LocalGet(componentTypeDataLocal)
         fb += StructGet(genTypeID.typeData, genFieldID.typeData.kind)
         fb += I32Const(KindJSType)
-        fb += I32Eq
+        fb += I32GeU
         fb += BrIf(successLabel)
 
         // If value is null, succeed
@@ -1711,7 +1713,7 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
      * we do for other classes.
      */
     val strictAncestors =
-      List(CloneableClass, SerializableClass, ObjectClass)
+      List(ObjectClass, CloneableClass, SerializableClass)
         .filter(name => ctx.getClassInfoOption(name).exists(_.hasRuntimeTypeInfo))
 
     val fb = newFunctionBuilder(genFunctionID.arrayTypeData)
@@ -2066,8 +2068,8 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
         fb += ExternConvertAny
         fb += Call(genFunctionID.stringBuiltins.test)
       },
-      // case KindJSType => call typeData.isJSClassInstance(value) or throw if it is null
-      List(KindJSType) -> { () =>
+      // case KindJSType | KindJSTypeWithSuperClass => call typeData.isJSClassInstance(value) or throw if it is null
+      List(KindJSType, KindJSTypeWithSuperClass) -> { () =>
         fb.block(RefType.anyref) { isJSClassInstanceIsNull =>
           // Load value as the argument to the function
           fb += LocalGet(valueParam)
@@ -2317,10 +2319,10 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
       fb += StructGet(genTypeID.ClassStruct, genFieldID.classData)
       fb += LocalTee(typeDataLocal)
 
-      // If typeData.kind == KindJSType, succeed
+      // If typeData.kind >= KindJSType, succeed
       fb += StructGet(genTypeID.typeData, genFieldID.typeData.kind)
       fb += I32Const(KindJSType)
-      fb += I32Eq
+      fb += I32GeU
       fb += BrIf(successLabel)
 
       // If value is null, succeed
@@ -2370,6 +2372,89 @@ final class CoreWasmLib(coreSpec: CoreSpec) {
     fb.buildAndAddToModule()
   }
 
+  /** `getSuperClass: (ref jlClass) -> (ref null jlClass)`.
+   *
+   *  This is the underlying func for the `Class_superClass` operation.
+   */
+  private def genGetSuperClass()(implicit ctx: WasmContext): Unit = {
+    val fb = newFunctionBuilder(genFunctionID.getSuperClass)
+    val jlClassParam = fb.addParam("jlClass", RefType(genTypeID.ClassStruct))
+    fb.setResultType(RefType.nullable(genTypeID.ClassStruct))
+
+    val typeDataLocal = fb.addLocal("typeData", RefType(genTypeID.typeData))
+    val kindLocal = fb.addLocal("kind", Int32)
+
+    // typeData := jlClass.data
+    fb += LocalGet(jlClassParam)
+    fb += StructGet(genTypeID.ClassStruct, genFieldID.classData)
+    fb += LocalTee(typeDataLocal)
+
+    // kind := typeData.kind
+    fb += StructGet(genTypeID.typeData, genFieldID.typeData.kind)
+    fb += LocalTee(kindLocal)
+
+    /* There are 3 cases that yield non-null results:
+     *
+     * - Scala classes that are not jl.Object (KindObject < kind <= KindClass)
+     * - JS types with a superClass (kind == KindJSTypeWithSuperClass)
+     * - Array classes (kind == KindArray)
+     *
+     * Note that KindArray < KindObject, and KindJSTypeWithSuperClass > KindObject,
+     * so we dispatch these two kinds in the two branches of an
+     * `if kind > KindObject` first.
+     */
+
+    // if kind > KindObject
+    fb += I32Const(KindObject)
+    fb += I32GtU
+    fb.ifThenElse(RefType(genTypeID.typeData)) {
+      // then, we may have to load the superClass from the strictAncestors array
+      fb.block() { loadSuperClassFromStrictAncestorsLabel =>
+        // if kind <= KindClass, then yes
+        fb += LocalGet(kindLocal)
+        fb += I32Const(KindClass)
+        fb += I32LeU
+        fb += BrIf(loadSuperClassFromStrictAncestorsLabel)
+
+        // if kind == KindJSTypeWithSuperClass, then yes
+        fb += LocalGet(kindLocal)
+        fb += I32Const(KindJSTypeWithSuperClass)
+        fb += I32Eq
+        fb += BrIf(loadSuperClassFromStrictAncestorsLabel)
+
+        // otherwise, there is no superClass
+        fb += RefNull(HeapType(genTypeID.ClassStruct))
+        fb += Return
+      }
+
+      // load the superClass from the strictAncestors array
+      fb += LocalGet(typeDataLocal)
+      fb += StructGet(genTypeID.typeData, genFieldID.typeData.strictAncestors)
+      fb += I32Const(0)
+      fb += ArrayGet(genTypeID.typeDataArray)
+    } {
+      // else, it might be an Array class
+
+      // if kind != KindArray
+      fb += LocalGet(kindLocal)
+      fb += I32Const(KindArray)
+      fb += I32Ne
+      fb.ifThen() {
+        // then return null
+        fb += RefNull(HeapType(genTypeID.ClassStruct))
+        fb += Return
+      }
+
+      // otherwise, load the typeData of jl.Object
+      fb += GlobalGet(genGlobalID.forVTable(ClassRef(ObjectClass)))
+    }
+
+    // Load the jl.Class from the typeData
+    fb += Call(genFunctionID.getClassOf)
+
+    fb.buildAndAddToModule()
+  }
+
   /** `newArray: (ref jlClass), i32 -> (ref jlObject)`.
    *
    *  This is the underlying func for the `Class_newArray` operation.
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/EmbeddedConstants.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/EmbeddedConstants.scala
index 58e5f2c82b..e70ec3efbd 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/EmbeddedConstants.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/EmbeddedConstants.scala
@@ -63,6 +63,7 @@ object EmbeddedConstants {
   final val KindClass = 21
   final val KindInterface = 22
   final val KindJSType = 23
+  final val KindJSTypeWithSuperClass = 24
 
   final val KindLastPrimitive = KindDouble
 }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala
index dca083127a..15ec3e20ed 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala
@@ -47,7 +47,6 @@ final class Emitter(config: Emitter.Config) {
 
   private val coreSpec = config.coreSpec
 
-  private val coreLib = new CoreWasmLib(coreSpec)
   private val classEmitter = new ClassEmitter(coreSpec)
 
   val symbolRequirements: SymbolRequirement =
@@ -55,15 +54,15 @@ final class Emitter(config: Emitter.Config) {
 
   val injectedIRFiles: Seq[IRFile] = PrivateLibHolder.files
 
-  def emit(module: ModuleSet.Module, logger: Logger): Result = {
-    val wasmModule = emitWasmModule(module)
+  def emit(module: ModuleSet.Module, globalInfo: LinkedGlobalInfo, logger: Logger): Result = {
+    val wasmModule = emitWasmModule(module, globalInfo)
     val loaderContent = LoaderContent.bytesContent
     val jsFileContent = buildJSFileContent(module)
 
     new Result(wasmModule, loaderContent, jsFileContent)
   }
 
-  private def emitWasmModule(module: ModuleSet.Module): wamod.Module = {
+  private def emitWasmModule(module: ModuleSet.Module, globalInfo: LinkedGlobalInfo): wamod.Module = {
     // Inject the derived linked classes
     val allClasses =
       DerivedClasses.deriveClasses(module.classDefs) ::: module.classDefs
@@ -80,6 +79,8 @@ final class Emitter(config: Emitter.Config) {
     val topLevelExports = module.topLevelExports
     val moduleInitializers = module.initializers.toList
 
+    val coreLib = new CoreWasmLib(coreSpec, globalInfo)
+
     implicit val ctx: WasmContext =
       Preprocessor.preprocess(coreSpec, coreLib, sortedClasses, topLevelExports)
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
index 4be4ac40ac..d0e7d504dd 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
@@ -1461,9 +1461,7 @@ private class FunctionEmitter private (
       case Class_componentType =>
         fb += wa.Call(genFunctionID.getComponentType)
       case Class_superClass =>
-        // FIXME Implement this
-        fb += wa.Drop
-        fb += wa.RefNull(watpe.HeapType.None)
+        fb += wa.Call(genFunctionID.getSuperClass)
     }
 
     tree.tpe
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
index 18659da4a7..cf93a99deb 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
@@ -256,6 +256,7 @@ object VarGen {
     case object isAssignableFrom extends FunctionID
     case object cast extends FunctionID
     case object getComponentType extends FunctionID
+    case object getSuperClass extends FunctionID
     case object newArray extends FunctionID
     case object anyGetClass extends FunctionID
     case object anyGetClassName extends FunctionID
@@ -343,11 +344,15 @@ object VarGen {
 
       /** Array of the strict ancestor classes of this class.
        *
-       *  This is `null` for primitive and array types. For all other types, including JS types, it
+       *  This is `null` for primitives. For all other types, including JS types, it
        *  contains an array of the typeData of their ancestors that:
        *
        *  - are not themselves (hence the *strict* ancestors),
        *  - have typeData to begin with.
+       *
+       *  If this class has a `superClass`, the first element is guaranteed to
+       *  be the `superClass`. The implementation of `Class_superClass` relies
+       *  on that guarantee.
        */
       case object strictAncestors extends FieldID
 
diff --git a/test-suite-ex/js/src/test/scala/org/scalajs/testsuite/javalib/lang/ClassJSTestEx.scala b/test-suite-ex/js/src/test/scala/org/scalajs/testsuite/javalib/lang/ClassJSTestEx.scala
new file mode 100644
index 0000000000..27e29d9b25
--- /dev/null
+++ b/test-suite-ex/js/src/test/scala/org/scalajs/testsuite/javalib/lang/ClassJSTestEx.scala
@@ -0,0 +1,64 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package org.scalajs.testsuite.javalib.lang
+
+import org.junit.Test
+import org.junit.Assert._
+import org.junit.Assume._
+
+import scala.scalajs.js
+
+import org.scalajs.testsuite.utils.Platform._
+
+class ClassJSTestEx {
+  import ClassJSTestEx._
+
+  /** Tests for `java.lang.Class.getSuperclass()` on JS classes and traits. */
+  @Test def getSuperclass(): Unit = {
+    def test(parent: Class[_], child: Class[_]): Unit =
+      assertSame(parent, child.getSuperclass())
+
+    test(null, classOf[js.Any])
+
+    test(classOf[Object], classOf[js.Object])
+
+    test(classOf[SomeParentClass], classOf[SomeChildClass])
+    test(classOf[AnyRef], classOf[String])
+    test(classOf[Number], classOf[Integer])
+
+    test(null, classOf[SomeParentTrait])
+    test(null, classOf[SomeChildTrait])
+
+    test(classOf[Object], classOf[Array[js.Object]])
+    test(classOf[Object], classOf[Array[SomeChildClass]])
+    test(classOf[Object], classOf[Array[SomeChildTrait]])
+    test(classOf[Object], classOf[Array[Array[SomeChildClass]]])
+  }
+
+  @Test def getSuperclassWhenParentClassDataIsNotDirectlyAccessed_Issue1489(): Unit = {
+    assertEquals(
+        "org.scalajs.testsuite.javalib.lang.ClassJSTestEx$ParentClassWhoseDataIsNotAccessedDirectly",
+        classOf[ChildClassWhoseDataIsAccessedDirectly].getSuperclass().getName())
+  }
+}
+
+object ClassJSTestEx {
+  class SomeParentClass extends js.Object
+  class SomeChildClass extends SomeParentClass
+
+  class ParentClassWhoseDataIsNotAccessedDirectly extends js.Object
+  class ChildClassWhoseDataIsAccessedDirectly extends ParentClassWhoseDataIsNotAccessedDirectly
+
+  trait SomeParentTrait extends js.Object
+  trait SomeChildTrait extends SomeParentTrait
+}
diff --git a/test-suite-ex/shared/src/test/scala/org/scalajs/testsuite/javalib/lang/ClassTestEx.scala b/test-suite-ex/shared/src/test/scala/org/scalajs/testsuite/javalib/lang/ClassTestEx.scala
index 9174f1fee8..208787a5cb 100644
--- a/test-suite-ex/shared/src/test/scala/org/scalajs/testsuite/javalib/lang/ClassTestEx.scala
+++ b/test-suite-ex/shared/src/test/scala/org/scalajs/testsuite/javalib/lang/ClassTestEx.scala
@@ -29,13 +29,14 @@ class ClassTestEx {
    *  pollute the whole test suite with those.
    */
   @Test def getSuperclass(): Unit = {
-    assumeFalse("Not implemented yet on WebAssembly", executingInWebAssembly)
-
     def test(parent: Class[_], child: Class[_]): Unit =
       assertSame(parent, child.getSuperclass())
 
     test(null, classOf[AnyRef])
 
+    test(null, classOf[Unit])
+    test(null, classOf[Int])
+
     test(classOf[SomeParentClass], classOf[SomeChildClass])
     test(classOf[AnyRef], classOf[String])
     test(classOf[Number], classOf[Integer])
@@ -52,8 +53,6 @@ class ClassTestEx {
   }
 
   @Test def getSuperclassWhenParentClassDataIsNotDirectlyAccessed_Issue1489(): Unit = {
-    assumeFalse("Not implemented yet on WebAssembly", executingInWebAssembly)
-
     assertEquals("org.scalajs.testsuite.javalib.lang.ClassTestEx$ParentClassWhoseDataIsNotAccessedDirectly",
         classOf[ChildClassWhoseDataIsAccessedDirectly].getSuperclass.getName)
   }

From cb3ac20946703be0b13a0c3b659dfe0c43baed8b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Mon, 23 Sep 2024 16:50:45 +0200
Subject: [PATCH 171/298] Fix the docs and checks about what config is accepted
 by the Wasm backend.

---
 .../org/scalajs/linker/interface/ESFeatures.scala  |  2 +-
 .../scalajs/linker/interface/StandardConfig.scala  | 14 ++++++--------
 .../linker/backend/WebAssemblyLinkerBackend.scala  |  4 ++++
 3 files changed, 11 insertions(+), 9 deletions(-)

diff --git a/linker-interface/shared/src/main/scala/org/scalajs/linker/interface/ESFeatures.scala b/linker-interface/shared/src/main/scala/org/scalajs/linker/interface/ESFeatures.scala
index 64a9bfbe90..df68b6a501 100644
--- a/linker-interface/shared/src/main/scala/org/scalajs/linker/interface/ESFeatures.scala
+++ b/linker-interface/shared/src/main/scala/org/scalajs/linker/interface/ESFeatures.scala
@@ -90,7 +90,7 @@ final class ESFeatures private (
    *    JavaScript arrow functions (`=>`). Lambdas for `js.ThisFunction`s are
    *    `function` functions.
    *  - Throwable classes are proper JavaScript error classes, recognized as
-   *    such by debuggers.
+   *    such by debuggers (only with the JavaScript backend; not in Wasm).
    *  - In Script (`NoModule`) mode, top-level exports are defined as `let`s.
    *
    *  When `false`, the following behaviors apply instead:
diff --git a/linker-interface/shared/src/main/scala/org/scalajs/linker/interface/StandardConfig.scala b/linker-interface/shared/src/main/scala/org/scalajs/linker/interface/StandardConfig.scala
index 14ac9e6a1c..508728fce5 100644
--- a/linker-interface/shared/src/main/scala/org/scalajs/linker/interface/StandardConfig.scala
+++ b/linker-interface/shared/src/main/scala/org/scalajs/linker/interface/StandardConfig.scala
@@ -188,16 +188,14 @@ final class StandardConfig private (
 
   /** Specifies whether to use the experimental WebAssembly backend.
    *
-   *  When using this setting, the following settings must also be set:
+   *  When using this setting, the following properties must also hold:
    *
-   *  - `withSemantics(sems)` such that the behaviors of `sems` are all set to
-   *    `CheckedBehavior.Unchecked`
-   *  - `withModuleKind(ModuleKind.ESModule)`
-   *  - `withOptimizer(false)`
-   *  - `withStrictFloats(true)` (this is the default)
+   *  - `moduleKind == ModuleKind.ESModule`
+   *  - `esFeatures.useECMAScript2015Semantics == true` (true by default)
+   *  - `semantics.strictFloats == true` (true by default; non-strict floats are deprecated)
    *
-   *  These restrictions will be lifted in the future, except for the
-   *  `ModuleKind`.
+   *  We may lift these restrictions in the future, although we do not expect
+   *  to do so.
    *
    *  If any of these restrictions are not met, linking will eventually throw
    *  an `IllegalArgumentException`.
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/WebAssemblyLinkerBackend.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/WebAssemblyLinkerBackend.scala
index 4ee5222d90..f59b9eb222 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/WebAssemblyLinkerBackend.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/WebAssemblyLinkerBackend.scala
@@ -36,6 +36,10 @@ final class WebAssemblyLinkerBackend(config: LinkerBackendImpl.Config)
     coreSpec.moduleKind == ModuleKind.ESModule,
     s"The WebAssembly backend only supports ES modules; was ${coreSpec.moduleKind}."
   )
+  require(
+    coreSpec.esFeatures.useECMAScript2015Semantics,
+    s"The WebAssembly backend only supports the ECMAScript 2015 semantics."
+  )
   require(
     coreSpec.semantics.strictFloats,
     "The WebAssembly backend only supports strict float semantics."

From 7494224deb5d3b142f3d5b142dcebce0cf2c93fe Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Mon, 23 Sep 2024 17:19:54 +0200
Subject: [PATCH 172/298] Bring the Wasm emitter readme up to date.

---
 .../linker/backend/wasmemitter/README.md      | 72 +++++++++++--------
 1 file changed, 43 insertions(+), 29 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/README.md b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/README.md
index b72fe8ab8f..ecafecc311 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/README.md
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/README.md
@@ -11,6 +11,7 @@ This readme gives an overview of the compilation scheme.
 
 * The [GC extension](https://github.com/WebAssembly/gc)
 * The [exception handling proposal](https://github.com/WebAssembly/exception-handling)
+* The [JS string builtins proposal](https://github.com/WebAssembly/js-string-builtins) (currently with polyfills, so it is not required)
 
 All our heap values are allocated as GC data structures.
 We do not use the linear memory of WebAssembly at all.
@@ -21,11 +22,13 @@ Since WebAssembly is strongly statically typed, we have to convert IR types into
 The full compilation pipeline must be type-preserving: a well-typed IR program compiles into a well-typed Wasm module.
 
 In most cases, we also preserve subtyping: if `S <: T` at the IR level, then `transform(S) <: transform(T)` at the Wasm level.
-This is however not true when `S` is a primitive type, or when `T = void`.
+This is however not true in the following cases:
 
 * When `T = void` and `S ≠ void`, we have to `drop` the value of type `S` from the stack.
 * When `S` is a primitive and `T` is a reference type (which must be an ancestor of a hijacked class), we have to "box" the primitive.
   We will come back to this in the [hijacked classes](#hijacked-classes) section.
+* When `S = null` and `T = jl.String`, we insert an `extern.convert_from_any` operation.
+* When `S ∈ {string, jl.String, jl.String!}` and `T` is none of those, we insert an `any.convert_from_extern` operation.
 
 ### Primitive types
 
@@ -47,14 +50,14 @@ This is however not true when `S` is a primitive type, or when `T = void`.
 We will describe more precisely the representation of reference types in the coming sections.
 This table is for reference.
 
-| IR type                           | Wasm type                             |
-|-----------------------------------|---------------------------------------|
-| `C`, a Scala class                | `(ref null $c.C)` |                   |
-| `I`, a Scala interface            | `(ref null $c.jl.Object)`             |
-| `jl.String`                       | `(ref null extern)` (aka `externref`) |
-| all ancestors of hijacked classes | `(ref null any)` (aka `anyref`)       |
-| `PT[]`, a primitive array         | `(ref null $PTArray)`                 |
-| `RT[]`, any reference array type  | `(ref null $ObjectArray)`             |
+| IR type                                     | Wasm type                             |
+|---------------------------------------------|---------------------------------------|
+| `C`, a Scala class                          | `(ref null $c.C)` |                   |
+| `I`, a Scala interface                      | `(ref null $c.jl.Object)`             |
+| `jl.String`                                 | `(ref null extern)` (aka `externref`) |
+| `any` and all ancestors of hijacked classes | `(ref null any)` (aka `anyref`)       |
+| `PT[]`, a primitive array                   | `(ref null $PTArray)`                 |
+| `RT[]`, any reference array type            | `(ref null $ObjectArray)`             |
 
 Non-nullable variants of the reference types are translated to non-nullable Wasm `ref` types.
 
@@ -97,13 +100,13 @@ We define the following GC structs:
 ```wat
 (type $c.A (sub $c.java.lang.Object (struct
   (field $vtable (ref $v.A))
-  (field $itables (ref null $itables))
+  (field $itables (ref $itables))
   (field $f.A.x (mut i32)))
 ))
 
 (type $c.B (sub $c.A (struct
   (field $vtable (ref $v.B))
-  (field $itables (ref null $itables))
+  (field $itables (ref $itables))
   (field $f.A.x (mut i32))
   (field $f.B.y (mut f64)))
 ))
@@ -182,9 +185,7 @@ We get the following implementing functions, assuming all method calls are stati
 ```
 
 In theory, the call to the getter should have been a virtual call in this case.
-In practice, the backend contains an analysis of virtual calls to methods that are never overridden, and statically resolves them instead.
-In the future, we will probably transfer this optimization to the `Optimizer`, as it already contains all the required logic to efficiently do this.
-In the absence of the optimizer, however, this one optimization was important to get decent code size.
+In practice, the optimizer turns virtual calls (`Apply`) into statically resolved calls (`ApplyStatically`) when possible.
 
 ### typeData
 
@@ -278,14 +279,14 @@ A virtual call to `a.foo(1)` is compiled as you would expect: lookup the functio
 ### itables and interface method calls
 
 The itables field contains the method tables for interface call dispatch.
-It is an instance of the following array type:
+It is an instance of the following struct type:
 
 ```wat
-(type $itables (array (mut structref)))
+(type $itables (struct (field $slot1 structref) ... (field $slotN structref)))
 ```
 
 As a first approximation, we assign a distinct index to every interface in the program.
-It is used to index into the itables array of the instance.
+The index maps to a slot of the itables struct of the instance.
 At the index of a given interface `Intf`, we find a `(ref $it.Intf)` whose fields are the method table entries of `Intf`.
 Like for vtables, we use the "table entry bridges" in the itables, i.e., the functions where the receiver is of type `(ref any)`.
 
@@ -320,20 +321,19 @@ We can use the same slot for a set of interfaces that have no concrete class in
 This slot allocation is implemented in `Preprocessor.assignBuckets`.
 
 Since Wasm structs only support single inheritance in their subtyping relationships, we have to transform every interface type as `(ref null jl.Object)` (the common supertype of all interfaces).
-This does not turn out to be a problem for interface method calls, since they pass through the `itables` array anyway, and use the table entry bridges which take `(ref any)` as argument.
+This does not turn out to be a problem for interface method calls, since they pass through the `itables` struct anyway, and use the table entry bridges which take `(ref any)` as argument.
 
-Given the above structure, an interface method call to `intf.foo(1)` is compiled as expected: lookup the function reference in the appropriate slot of the `itables` array, then call it.
+Given the above structure, an interface method call to `intf.foo(1)` is compiled as expected: lookup the function reference in the appropriate slot of the `itables` struct, then call it.
 
 ### Reflective calls
 
 Calls to reflective proxies use yet another strategy.
-Instead of building arrays or structs where each reflective proxy appears at a compile-time-constant slot, we use a search-based strategy.
+Instead of building structs where each reflective proxy appears at a compile-time-constant slot, we use a search-based strategy.
 
 Each reflective proxy name found in the program is allocated a unique integer ID.
 The reflective proxy table of a class is an array of pairs `(id, funcRef)`, stored in the class' `typeData`.
 In order to call a reflective proxy, we perform the following steps:
 
-
 1. Load the `typeData` of the receiver.
 2. Search the reflective proxy ID in `$reflectiveProxies` (using the `searchReflectiveProxy` helper).
 3. Call it (using `call_ref`).
@@ -448,6 +448,19 @@ Instead, they pass pointer values as is through the boundary.
 Concretely, `ToWebAssemblyValue(v, anyref)` and `ToJSValue(ref.host x)` are no-ops.
 The conversions involving `i32` are not free, but they are as efficient as it gets for the target JS engines.
 
+However, going through the Wasm-to-JS interface has a significant cost in itself.
+For performance, we want to avoid crossing the boundary whenever possible.
+In many cases, we can abuse `i31ref`-related operations to perform the conversions.
+Indeed, the Wasm-JS conversion spec also guarantees that a `ref.i31` is seen by JavaScript as the corresponding `number`.
+
+In order to box an `int`, we first test whether it is safe to drop the most significant bit.
+That is the case if and only if it is equal to the second-most significant bit.
+If it is, we "box" the `int` using an `ref.i31` instruction.
+Otherwise, we fall back on the JS helper (which is actually called `$bIFallback`).
+For unboxing, we first try a `br_on_cast (ref i31)` instruction, and fall back on `$uIFallback` if it does not succeed.
+
+We use similar strategies for the other primitive types.
+
 ### Method dispatch
 
 When the receiver of a method call is a primitive or a hijacked class, the call can always be statically resolved by construction, hence no dispatch is necessary.
@@ -465,7 +478,7 @@ All array "classes" follow the same structure:
 * Their vtable type is the same as `jl.Object`
 * They each have their own vtable value for the differing metadata, although the method table entries are the same as in `jl.Object`
   * This is also true for reference types: the vtables are dynamically created at run-time on first use (they are values and share the same type, so that we can do)
-* Their `itables` field points to a common itables array with entries for `jl.Cloneable` and `j.io.Serializable`
+* Their `itables` field points to a common itables struct with entries for `jl.Cloneable` and `j.io.Serializable`
 * They have a unique "user-land" field `$underlyingArray`, which is a Wasm array of its values:
   * For primitives, they are primitive arrays, such as `(array mut i32)`
   * For references, they are all the same type `(array mut anyref)`
@@ -483,18 +496,18 @@ Concretely, here are the relevant Wasm definitions:
 
 (type $BooleanArray (sub final $c.java.lang.Object (struct
   (field $vtable (ref $v.java.lang.Object))
-  (field $itables (ref null $itables))
+  (field $itables (ref $itables))
   (field $arrayUnderlying (ref $i8Array))
 )))
 (type $CharArray (sub final $c.java.lang.Object (struct
   (field $vtable (ref $v.java.lang.Object))
-  (field $itables (ref null $itables))
+  (field $itables (ref $itables))
   (field $arrayUnderlying (ref $i16Array))
 )))
 ...
 (type $ObjectArray (sub final $c.java.lang.Object (struct
   (field $vtable (ref $v.java.lang.Object))
-  (field $itables (ref null $itables))
+  (field $itables (ref $itables))
   (field $arrayUnderlying (ref $anyArray))
 )))
 ```
@@ -537,8 +550,9 @@ For type definitions, we use the following ordering:
 
 For global definitions, we use the following ordering:
 
-1. The typeData of the primitive types (e.g., `$d.I`)
-2. For each linked class, in the same ancestor count-based order:
+1. A unique "empty" itables global for classes that do not implement any interface (`$emptyITable`)
+2. The typeData of the primitive types (e.g., `$d.I`)
+3. For each linked class, in the same ancestor count-based order:
    1. In no particular order, if applicable:
       * Its typeData/vtable global (e.g., `$d.java.lang.Object`), which may refer to the typeData of ancestors, so the order between classes is important
       * Its itables global (e.g., `$it.java.lang.Class`)
@@ -546,8 +560,8 @@ For global definitions, we use the following ordering:
       * Definitions of `Symbol`s for the "names" of private JS fields
       * The module instance
       * The cached JS class value
-3. Cached values of boxed zero values (such as `$bZeroChar`), which refer to the vtable and itables globals of the box classes
-4. The itables global of array classes (namely, `$arrayClassITable`)
+4. Cached values of boxed zero values (such as `$bZeroChar`), which refer to the vtable and itables globals of the box classes
+5. The itables global of array classes (namely, `$arrayClassITable`)
 
 ## Miscellaneous
 

From 0734e77bbb4032b035571b172b2078b8f46e0167 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Wed, 25 Sep 2024 10:06:42 +0200
Subject: [PATCH 173/298] Be more specific about the int/long div/mod code
 paths.

In addition to testing that `ArithmeticException` is instantiated,
we make sure that the `String`-arg constructor exists. Indeed, we
generate a call to that constructor, which is a top-level function.

We also add a comment similar to the one about
`isClassClassInstantiated`, explaining that it is an
over-approximation of what we really need.

We introduce a dedicated Info builder method to register an
int/long div/mod by maybe-zero. This way we have a clear place to
specify which constructor we are using, which is important as the
backends rely on it.
---
 .../org/scalajs/linker/analyzer/Infos.scala   | 12 ++++------
 .../linker/backend/emitter/CoreJSLib.scala    | 15 ++++++++----
 .../backend/emitter/GlobalKnowledge.scala     | 11 ++++++---
 .../backend/emitter/KnowledgeGuardian.scala   | 23 ++++++++++++-------
 4 files changed, 39 insertions(+), 22 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala
index 8dcb89c784..81ed8a8b35 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala
@@ -381,6 +381,9 @@ object Infos {
     def addUsedExponentOperator(): this.type =
       setFlag(ReachabilityInfo.FlagUsedExponentOperator)
 
+    def addUsedIntLongDivModByMaybeZero(): this.type =
+      addInstantiatedClass(ArithmeticExceptionClass, StringArgConstructorName)
+
     def addUsedClassSuperClass(): this.type =
       setFlag(ReachabilityInfo.FlagUsedClassSuperClass)
 
@@ -667,21 +670,16 @@ object Infos {
             case BinaryOp(op, _, rhs) =>
               import BinaryOp._
 
-              def addArithmeticException(): Unit = {
-                builder.addInstantiatedClass(ArithmeticExceptionClass,
-                    StringArgConstructorName)
-              }
-
               op match {
                 case Int_/ | Int_% =>
                   rhs match {
                     case IntLiteral(r) if r != 0 =>
-                    case _                       => addArithmeticException()
+                    case _                       => builder.addUsedIntLongDivModByMaybeZero()
                   }
                 case Long_/ | Long_% =>
                   rhs match {
                     case LongLiteral(r) if r != 0L =>
-                    case _                         => addArithmeticException()
+                    case _                         => builder.addUsedIntLongDivModByMaybeZero()
                   }
                 case _ =>
                   // do nothing
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
index e1ff675469..cf01e02fd1 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
@@ -883,8 +883,15 @@ private[emitter] object CoreJSLib {
     }
 
     private def defineArithmeticOps(): List[Tree] = {
-      val isArithmeticExceptionClassInstantiated =
-        globalKnowledge.isArithmeticExceptionClassInstantiated
+      /* We test whether `ArithmeticException` is instantiated with the
+       * `<init>(jl.String)` constructor. That is an over-approximation of
+       * whether there is any int/long div/mod with a maybe-zero divisor.
+       * If that constructor is not used, emitting the functions would be
+       * invalid, since the generated code would refer to a top-level class
+       * and function that do not exist.
+       */
+      val shouldDefineIntLongDivModFunctions =
+        globalKnowledge.isArithmeticExceptionClassInstantiatedWithStringArg
 
       def throwDivByZero: Tree = {
         Throw(genScalaClassNew(ArithmeticExceptionClass,
@@ -894,7 +901,7 @@ private[emitter] object CoreJSLib {
       def wrapBigInt64(tree: Tree): Tree =
         Apply(genIdentBracketSelect(BigIntRef, "asIntN"), 64 :: tree :: Nil)
 
-      condDefs(isArithmeticExceptionClassInstantiated)(
+      condDefs(shouldDefineIntLongDivModFunctions)(
         defineFunction2(VarField.intDiv) { (x, y) =>
           If(y === 0, throwDivByZero, {
             Return((x / y) | 0)
@@ -928,7 +935,7 @@ private[emitter] object CoreJSLib {
           )
         }
       ) :::
-      condDefs(allowBigIntsForLongs && isArithmeticExceptionClassInstantiated)(
+      condDefs(allowBigIntsForLongs && shouldDefineIntLongDivModFunctions)(
         defineFunction2(VarField.longDiv) { (x, y) =>
           If(y === bigInt(0), throwDivByZero, {
             Return(wrapBigInt64(x / y))
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/GlobalKnowledge.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/GlobalKnowledge.scala
index b8fec3f3ff..0db955ec61 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/GlobalKnowledge.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/GlobalKnowledge.scala
@@ -19,11 +19,16 @@ import org.scalajs.ir.Types.Type
 import org.scalajs.linker.standard.ModuleSet.ModuleID
 
 private[emitter] trait GlobalKnowledge {
-  /** Tests whether the `java.lang.Class` class is instantiated. */
+  /** Tests whether the `java.lang.Class` class is instantiated.
+   *
+   *  If yes, it is necessarily without argument.
+   */
   def isClassClassInstantiated: Boolean
 
-  /** Tests whether the `java.lang.ArithmeticException` class is instantiated. */
-  def isArithmeticExceptionClassInstantiated: Boolean
+  /** Tests whether the `java.lang.ArithmeticException` class is instantiated
+   *  with a string argument.
+   */
+  def isArithmeticExceptionClassInstantiatedWithStringArg: Boolean
 
   /** Tests whether the parent class data is accessed in the linking unit. */
   def isParentDataAccessed: Boolean
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/KnowledgeGuardian.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/KnowledgeGuardian.scala
index d5c5d23342..89146e0970 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/KnowledgeGuardian.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/KnowledgeGuardian.scala
@@ -182,8 +182,8 @@ private[emitter] final class KnowledgeGuardian(config: Emitter.Config) {
     def isClassClassInstantiated: Boolean =
       specialInfo.askIsClassClassInstantiated(this)
 
-    def isArithmeticExceptionClassInstantiated: Boolean =
-      specialInfo.askIsArithmeticExceptionClassInstantiated(this)
+    def isArithmeticExceptionClassInstantiatedWithStringArg: Boolean =
+      specialInfo.askIsArithmeticExceptionClassInstantiatedWithStringArg(this)
 
     def isInterface(className: ClassName): Boolean =
       classes(className).askIsInterface(this)
@@ -584,11 +584,18 @@ private[emitter] final class KnowledgeGuardian(config: Emitter.Config) {
     private def computeInstantiatedSpecialClassBitSet(
         classClass: Option[LinkedClass],
         arithmeticExceptionClass: Option[LinkedClass]): Int = {
+
+      def isInstantiatedWithCtor(linkedClass: Option[LinkedClass], ctor: MethodName): Boolean = {
+        linkedClass.exists { cls =>
+          cls.hasDirectInstances && cls.methods.exists(_.methodName == ctor)
+        }
+      }
+
       var bitSet: Int = 0
-      if (classClass.exists(_.hasInstances))
+      if (classClass.exists(_.hasDirectInstances))
         bitSet |= SpecialClassClass
-      if (arithmeticExceptionClass.exists(_.hasInstances))
-        bitSet |= SpecialClassArithmeticException
+      if (isInstantiatedWithCtor(arithmeticExceptionClass, StringArgConstructorName))
+        bitSet |= SpecialClassArithmeticExceptionWithStringArg
       bitSet
     }
 
@@ -642,10 +649,10 @@ private[emitter] final class KnowledgeGuardian(config: Emitter.Config) {
       (instantiatedSpecialClassBitSet & SpecialClassClass) != 0
     }
 
-    def askIsArithmeticExceptionClassInstantiated(invalidatable: Invalidatable): Boolean = {
+    def askIsArithmeticExceptionClassInstantiatedWithStringArg(invalidatable: Invalidatable): Boolean = {
       invalidatable.registeredTo(this)
       instantiatedSpecialClassAskers += invalidatable
-      (instantiatedSpecialClassBitSet & SpecialClassArithmeticException) != 0
+      (instantiatedSpecialClassBitSet & SpecialClassArithmeticExceptionWithStringArg) != 0
     }
 
     def askIsParentDataAccessed(invalidatable: Invalidatable): Boolean =
@@ -685,7 +692,7 @@ private[emitter] final class KnowledgeGuardian(config: Emitter.Config) {
 
   private object SpecialInfo {
     private final val SpecialClassClass = 1 << 0
-    private final val SpecialClassArithmeticException = 1 << 1
+    private final val SpecialClassArithmeticExceptionWithStringArg = 1 << 1
   }
 
   private def invalidateAskers(askers: mutable.Set[Invalidatable]): Unit = {

From f7721963286ff4b4e3f87f75057b847ddce6aae1 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Sat, 21 Sep 2024 18:29:38 +0200
Subject: [PATCH 174/298] Fix #5044: Handle the IllegalArgumentExceptions in
 jlr.Array.newInstance.

The case of an empty array of dimensions for the multi-dimensions
overload is handled in user-space. The case of `classOf[Unit]` is
handled in the backends, since not doing so leaves the door open
for user-space IR to break the fundamental invariant that there is
no array of `void`.

In the JS backend, we follow the strategy of int/long div/mod to
emit the target method only if `IllegalArgumentException.<init>()`
is reachable. In the Wasm backend, since we do not have that
infrastructure, for now we add an unconditional dependency on that
constructor, like we do for `jl.Class.<init>()`.
---
 .../src/main/scala/org/scalajs/ir/Names.scala |  4 ++
 .../src/main/scala/org/scalajs/ir/Trees.scala |  3 +-
 .../main/scala/java/lang/reflect/Array.scala  |  5 +-
 .../org/scalajs/linker/analyzer/Infos.scala   |  5 ++
 .../linker/backend/emitter/CoreJSLib.scala    | 34 +++++++-----
 .../backend/emitter/FunctionEmitter.scala     |  2 +-
 .../backend/emitter/GlobalKnowledge.scala     |  5 ++
 .../backend/emitter/KnowledgeGuardian.scala   | 38 ++++++++++---
 .../backend/wasmemitter/CoreWasmLib.scala     | 54 +++++++++----------
 .../linker/backend/wasmemitter/Emitter.scala  |  1 +
 .../frontend/optimizer/IncOptimizer.scala     |  2 +-
 .../frontend/optimizer/OptimizerCore.scala    |  3 +-
 project/Build.scala                           |  4 +-
 .../lang/reflect/ReflectArrayTest.scala       | 26 +++++++++
 14 files changed, 128 insertions(+), 58 deletions(-)

diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Names.scala b/ir/shared/src/main/scala/org/scalajs/ir/Names.scala
index 3e4a429e2a..73ea0c8c7d 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Names.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Names.scala
@@ -612,6 +612,10 @@ object Names {
   val ClassCastExceptionClass: ClassName =
     ClassName("java.lang.ClassCastException")
 
+  /** The exception thrown by a `Class_newArray` if the first argument is `classOf[Unit]`. */
+  val IllegalArgumentExceptionClass: ClassName =
+    ClassName("java.lang.IllegalArgumentException")
+
   /** The set of classes and interfaces that are ancestors of array classes. */
   private[ir] val AncestorsOfPseudoArrayClass: Set[ClassName] = {
     /* This would logically be defined in Types, but that introduces a cyclic
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala b/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
index 51d08ea2e9..6cc39f24a8 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
@@ -395,7 +395,8 @@ object Trees {
    *  - `Class_cast` throws a CCE if its second argument is non-null and
    *    not an instance of the class represented by its first argument.
    *  - `Class_newArray` throws a `NegativeArraySizeException` if its second
-   *    argument is negative.
+   *    argument is negative and an `IllegalArgumentException` if its first
+   *    argument is `classOf[Unit]`.
    *
    *  Otherwise, binary operations preserve pureness.
    */
diff --git a/javalib/src/main/scala/java/lang/reflect/Array.scala b/javalib/src/main/scala/java/lang/reflect/Array.scala
index f5f6aaa21f..ac2f23d2b0 100644
--- a/javalib/src/main/scala/java/lang/reflect/Array.scala
+++ b/javalib/src/main/scala/java/lang/reflect/Array.scala
@@ -38,9 +38,12 @@ object Array {
       result
     }
 
+    val len = dimensions.length
+    if (len == 0)
+      throw new IllegalArgumentException()
     var outermostComponentType = componentType
     var i = 1
-    while (i != dimensions.length) {
+    while (i != len) {
       outermostComponentType = newInstance(outermostComponentType, 0).getClass()
       i += 1
     }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala
index 81ed8a8b35..6b622ae82a 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala
@@ -384,6 +384,9 @@ object Infos {
     def addUsedIntLongDivModByMaybeZero(): this.type =
       addInstantiatedClass(ArithmeticExceptionClass, StringArgConstructorName)
 
+    def addUsedClassNewArray(): this.type =
+      addInstantiatedClass(IllegalArgumentExceptionClass, NoArgConstructorName)
+
     def addUsedClassSuperClass(): this.type =
       setFlag(ReachabilityInfo.FlagUsedClassSuperClass)
 
@@ -681,6 +684,8 @@ object Infos {
                     case LongLiteral(r) if r != 0L =>
                     case _                         => builder.addUsedIntLongDivModByMaybeZero()
                   }
+                case Class_newArray =>
+                  builder.addUsedClassNewArray()
                 case _ =>
                   // do nothing
               }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
index cf01e02fd1..35e480f233 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
@@ -1954,10 +1954,28 @@ private[emitter] object CoreJSLib {
         val length = varRef("length")
         MethodDef(static = false, Ident(cpn.newArray),
             paramList(length), None, {
-          Return(New(Apply(This() DOT cpn.getArrayOf, Nil) DOT cpn.constr, length :: Nil))
+          Block(
+            If(This() === globalVar(VarField.d, VoidRef), {
+              Throw(genScalaClassNew(IllegalArgumentExceptionClass, NoArgConstructorName))
+            }, Skip()),
+            Return(New(Apply(This() DOT cpn.getArrayOf, Nil) DOT cpn.constr, length :: Nil))
+          )
         })
       }
 
+      def allClassReflectionMethods: List[MethodDef] = {
+        val b = List.newBuilder[MethodDef]
+        b += getClassOf
+        b += isAssignableFrom
+        if (asInstanceOfs != CheckedBehavior.Unchecked)
+          b += cast
+        b += getSuperclass
+        b += getComponentType
+        if (globalKnowledge.isIllegalArgumentExceptionClassInstantiatedWithNoArg) // over-approximation
+          b += newArray
+        b.result()
+      }
+
       val members = List(
           initPrim,
           initClass,
@@ -1966,19 +1984,7 @@ private[emitter] object CoreJSLib {
           getArrayOf
       ) ::: (
           if (globalKnowledge.isClassClassInstantiated) {
-            List(
-                getClassOf,
-                isAssignableFrom
-            ) ::: (
-              if (asInstanceOfs != CheckedBehavior.Unchecked)
-                List(cast)
-              else
-                Nil
-            ) ::: List(
-                getSuperclass,
-                getComponentType,
-                newArray
-            )
+            allClassReflectionMethods
           } else if (arrayStores != CheckedBehavior.Unchecked) {
             List(
               isAssignableFrom
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
index 444cca7fb6..dc6089ad3f 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
@@ -1274,7 +1274,7 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
         case BinaryOp(BinaryOp.Class_cast, lhs, rhs) =>
           allowBehavior(semantics.asInstanceOfs) && test(lhs) && test(rhs)
         case BinaryOp(BinaryOp.Class_newArray, lhs, rhs) =>
-          allowBehavior(semantics.negativeArraySizes) && allowUnpure && test(lhs) && test(rhs)
+          allowSideEffects && test(lhs) && test(rhs)
 
         // Expressions preserving pureness (modulo NPE)
         case Block(trees)            => trees forall test
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/GlobalKnowledge.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/GlobalKnowledge.scala
index 0db955ec61..40479597fc 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/GlobalKnowledge.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/GlobalKnowledge.scala
@@ -30,6 +30,11 @@ private[emitter] trait GlobalKnowledge {
    */
   def isArithmeticExceptionClassInstantiatedWithStringArg: Boolean
 
+  /** Tests whether the `java.lang.IllegalArgumentException` class is
+   *  instantiated with no argument.
+   */
+  def isIllegalArgumentExceptionClassInstantiatedWithNoArg: Boolean
+
   /** Tests whether the parent class data is accessed in the linking unit. */
   def isParentDataAccessed: Boolean
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/KnowledgeGuardian.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/KnowledgeGuardian.scala
index 89146e0970..5a02604391 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/KnowledgeGuardian.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/KnowledgeGuardian.scala
@@ -49,6 +49,7 @@ private[emitter] final class KnowledgeGuardian(config: Emitter.Config) {
     var objectClass: Option[LinkedClass] = None
     var classClass: Option[LinkedClass] = None
     var arithmeticExceptionClass: Option[LinkedClass] = None
+    var illegalArgumentExceptionClass: Option[LinkedClass] = None
     val hijackedClasses = Iterable.newBuilder[LinkedClass]
 
     // Update classes
@@ -85,6 +86,9 @@ private[emitter] final class KnowledgeGuardian(config: Emitter.Config) {
         case ArithmeticExceptionClass =>
           arithmeticExceptionClass = Some(linkedClass)
 
+        case IllegalArgumentExceptionClass =>
+          illegalArgumentExceptionClass = Some(linkedClass)
+
         case name if HijackedClasses(name) =>
           hijackedClasses += linkedClass
 
@@ -98,11 +102,12 @@ private[emitter] final class KnowledgeGuardian(config: Emitter.Config) {
     val invalidateAll = {
       if (specialInfo == null) {
         specialInfo = new SpecialInfo(objectClass, classClass,
-            arithmeticExceptionClass, hijackedClasses.result(),
-            moduleSet.globalInfo)
+            arithmeticExceptionClass, illegalArgumentExceptionClass,
+            hijackedClasses.result(), moduleSet.globalInfo)
         false
       } else {
-        specialInfo.update(objectClass, classClass, arithmeticExceptionClass,
+        specialInfo.update(objectClass, classClass,
+            arithmeticExceptionClass, illegalArgumentExceptionClass,
             hijackedClasses.result(), moduleSet.globalInfo)
       }
     }
@@ -185,6 +190,9 @@ private[emitter] final class KnowledgeGuardian(config: Emitter.Config) {
     def isArithmeticExceptionClassInstantiatedWithStringArg: Boolean =
       specialInfo.askIsArithmeticExceptionClassInstantiatedWithStringArg(this)
 
+    def isIllegalArgumentExceptionClassInstantiatedWithNoArg: Boolean =
+      specialInfo.askIsIllegalArgumentExceptionClassInstantiatedWithNoArg(this)
+
     def isInterface(className: ClassName): Boolean =
       classes(className).askIsInterface(this)
 
@@ -513,13 +521,16 @@ private[emitter] final class KnowledgeGuardian(config: Emitter.Config) {
   private class SpecialInfo(initObjectClass: Option[LinkedClass],
       initClassClass: Option[LinkedClass],
       initArithmeticExceptionClass: Option[LinkedClass],
+      initIllegalArgumentExceptionClass: Option[LinkedClass],
       initHijackedClasses: Iterable[LinkedClass],
       initGlobalInfo: LinkedGlobalInfo) extends Unregisterable {
 
     import SpecialInfo._
 
-    private var instantiatedSpecialClassBitSet =
-      computeInstantiatedSpecialClassBitSet(initClassClass, initArithmeticExceptionClass)
+    private var instantiatedSpecialClassBitSet = {
+      computeInstantiatedSpecialClassBitSet(initClassClass,
+          initArithmeticExceptionClass, initIllegalArgumentExceptionClass)
+    }
 
     private var isParentDataAccessed =
       computeIsParentDataAccessed(initGlobalInfo)
@@ -541,12 +552,13 @@ private[emitter] final class KnowledgeGuardian(config: Emitter.Config) {
 
     def update(objectClass: Option[LinkedClass], classClass: Option[LinkedClass],
         arithmeticExceptionClass: Option[LinkedClass],
+        illegalArgumentExceptionClass: Option[LinkedClass],
         hijackedClasses: Iterable[LinkedClass],
         globalInfo: LinkedGlobalInfo): Boolean = {
       var invalidateAll = false
 
-      val newInstantiatedSpecialClassBitSet =
-        computeInstantiatedSpecialClassBitSet(classClass, arithmeticExceptionClass)
+      val newInstantiatedSpecialClassBitSet = computeInstantiatedSpecialClassBitSet(
+          classClass, arithmeticExceptionClass, illegalArgumentExceptionClass)
       if (newInstantiatedSpecialClassBitSet != instantiatedSpecialClassBitSet) {
         instantiatedSpecialClassBitSet = newInstantiatedSpecialClassBitSet
         invalidateAskers(instantiatedSpecialClassAskers)
@@ -583,7 +595,8 @@ private[emitter] final class KnowledgeGuardian(config: Emitter.Config) {
 
     private def computeInstantiatedSpecialClassBitSet(
         classClass: Option[LinkedClass],
-        arithmeticExceptionClass: Option[LinkedClass]): Int = {
+        arithmeticExceptionClass: Option[LinkedClass],
+        illegalArgumentExceptionClass: Option[LinkedClass]): Int = {
 
       def isInstantiatedWithCtor(linkedClass: Option[LinkedClass], ctor: MethodName): Boolean = {
         linkedClass.exists { cls =>
@@ -596,6 +609,8 @@ private[emitter] final class KnowledgeGuardian(config: Emitter.Config) {
         bitSet |= SpecialClassClass
       if (isInstantiatedWithCtor(arithmeticExceptionClass, StringArgConstructorName))
         bitSet |= SpecialClassArithmeticExceptionWithStringArg
+      if (isInstantiatedWithCtor(illegalArgumentExceptionClass, NoArgConstructorName))
+        bitSet |= SpecialClassIllegalArgumentExceptionWithNoArg
       bitSet
     }
 
@@ -655,6 +670,12 @@ private[emitter] final class KnowledgeGuardian(config: Emitter.Config) {
       (instantiatedSpecialClassBitSet & SpecialClassArithmeticExceptionWithStringArg) != 0
     }
 
+    def askIsIllegalArgumentExceptionClassInstantiatedWithNoArg(invalidatable: Invalidatable): Boolean = {
+      invalidatable.registeredTo(this)
+      instantiatedSpecialClassAskers += invalidatable
+      (instantiatedSpecialClassBitSet & SpecialClassIllegalArgumentExceptionWithNoArg) != 0
+    }
+
     def askIsParentDataAccessed(invalidatable: Invalidatable): Boolean =
       isParentDataAccessed
 
@@ -693,6 +714,7 @@ private[emitter] final class KnowledgeGuardian(config: Emitter.Config) {
   private object SpecialInfo {
     private final val SpecialClassClass = 1 << 0
     private final val SpecialClassArithmeticExceptionWithStringArg = 1 << 1
+    private final val SpecialClassIllegalArgumentExceptionWithNoArg = 1 << 2
   }
 
   private def invalidateAskers(askers: mutable.Set[Invalidatable]): Unit = {
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
index 94ceac5fae..b160acba44 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
@@ -37,6 +37,18 @@ final class CoreWasmLib(coreSpec: CoreSpec, globalInfo: LinkedGlobalInfo) {
 
   private implicit val noPos: Position = Position.NoPosition
 
+  private val primRefsWithKinds = List(
+    VoidRef -> KindVoid,
+    BooleanRef -> KindBoolean,
+    CharRef -> KindChar,
+    ByteRef -> KindByte,
+    ShortRef -> KindShort,
+    IntRef -> KindInt,
+    LongRef -> KindLong,
+    FloatRef -> KindFloat,
+    DoubleRef -> KindDouble
+  )
+
   private val arrayBaseRefs: List[NonArrayTypeRef] = List(
     BooleanRef,
     CharRef,
@@ -94,17 +106,6 @@ final class CoreWasmLib(coreSpec: CoreSpec, globalInfo: LinkedGlobalInfo) {
     )
   }
 
-  private val primRefsWithArrayTypes = List(
-    BooleanRef -> KindBoolean,
-    CharRef -> KindChar,
-    ByteRef -> KindByte,
-    ShortRef -> KindShort,
-    IntRef -> KindInt,
-    LongRef -> KindLong,
-    FloatRef -> KindFloat,
-    DoubleRef -> KindDouble
-  )
-
   /** Generates definitions that must come *before* the code generated for regular classes.
    *
    *  This notably includes the `typeData` definitions, since the vtable of `jl.Object` is a subtype
@@ -545,18 +546,6 @@ final class CoreWasmLib(coreSpec: CoreSpec, globalInfo: LinkedGlobalInfo) {
   private def genPrimitiveTypeDataGlobals()(implicit ctx: WasmContext): Unit = {
     import genFieldID.typeData._
 
-    val primRefsWithTypeData = List(
-      VoidRef -> KindVoid,
-      BooleanRef -> KindBoolean,
-      CharRef -> KindChar,
-      ByteRef -> KindByte,
-      ShortRef -> KindShort,
-      IntRef -> KindInt,
-      LongRef -> KindLong,
-      FloatRef -> KindFloat,
-      DoubleRef -> KindDouble
-    )
-
     val typeDataTypeID = genTypeID.typeData
 
     // Other than `name` and `kind`, all the fields have the same value for all primitives
@@ -581,7 +570,7 @@ final class CoreWasmLib(coreSpec: CoreSpec, globalInfo: LinkedGlobalInfo) {
       ArrayNewFixed(genTypeID.reflectiveProxies, 0)
     )
 
-    for ((primRef, kind) <- primRefsWithTypeData) {
+    for ((primRef, kind) <- primRefsWithKinds) {
       val nameDataValue: List[Instr] =
         ctx.stringPool.getConstantStringDataInstr(primRef.displayName)
 
@@ -2506,11 +2495,20 @@ final class CoreWasmLib(coreSpec: CoreSpec, globalInfo: LinkedGlobalInfo) {
       fb += StructGet(genTypeID.typeData, genFieldID.typeData.kind)
     }(
       // case KindPrim => array.new_default underlyingPrimArray; struct.new PrimArray
-      primRefsWithArrayTypes.map { case (primRef, kind) =>
+      primRefsWithKinds.map { case (primRef, kind) =>
         List(kind) -> { () =>
-          val arrayTypeRef = ArrayTypeRef(primRef, 1)
-          fb += ArrayNewDefault(genTypeID.underlyingOf(arrayTypeRef))
-          fb += StructNew(genTypeID.forArrayClass(arrayTypeRef))
+          if (primRef == VoidRef) {
+            // throw IllegalArgumentException for VoidRef
+            genNewScalaClass(fb, IllegalArgumentExceptionClass, NoArgConstructorName) {
+              // no argument
+            }
+            fb += ExternConvertAny
+            fb += Throw(genTagID.exception)
+          } else {
+            val arrayTypeRef = ArrayTypeRef(primRef, 1)
+            fb += ArrayNewDefault(genTypeID.underlyingOf(arrayTypeRef))
+            fb += StructNew(genTypeID.forArrayClass(arrayTypeRef))
+          }
           () // required for correct type inference
         }
       }: _*
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala
index 15ec3e20ed..60fd3178d5 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala
@@ -434,6 +434,7 @@ object Emitter {
       // TODO Ideally we should not require these, but rather adapt to their absence
       instantiateClass(ClassClass, NoArgConstructorName),
       instantiateClass(JSExceptionClass, AnyArgConstructorName),
+      instantiateClass(IllegalArgumentExceptionClass, NoArgConstructorName),
 
       // See genIdentityHashCode in HelperFunctions
       callMethodStatically(BoxedDoubleClass, hashCodeMethodName),
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
index c56ed9420c..ab84765129 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
@@ -78,7 +78,7 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
       },
       cond(targetIsWebAssembly) {
         // Required by the intrinsic CharacterCodePointToString
-        instantiateClass(OptimizerCore.IllegalArgumentExceptionClass, NoArgConstructorName)
+        instantiateClass(IllegalArgumentExceptionClass, NoArgConstructorName)
       }
     )
   }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
index 264d1d8a30..2e49b2d40f 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
@@ -1584,7 +1584,7 @@ private[optimizer] abstract class OptimizerCore(
           finishWithSideEffects
         case Class_cast if semantics.asInstanceOfs != CheckedBehavior.Unchecked =>
           finishWithSideEffects
-        case Class_newArray if semantics.negativeArraySizes != CheckedBehavior.Unchecked =>
+        case Class_newArray =>
           finishWithSideEffects
         case _ =>
           finishNoSideEffects
@@ -5641,7 +5641,6 @@ private[optimizer] object OptimizerCore {
   private val ClassTagModuleClass = ClassName("scala.reflect.ClassTag$")
   private val JavaScriptExceptionClass = ClassName("scala.scalajs.js.JavaScriptException")
   private val JSWrappedArrayClass = ClassName("scala.scalajs.js.WrappedArray")
-  private[optimizer] val IllegalArgumentExceptionClass = ClassName("java.lang.IllegalArgumentException")
   private val NilClass = ClassName("scala.collection.immutable.Nil$")
   private val Tuple2Class = ClassName("scala.Tuple2")
 
diff --git a/project/Build.scala b/project/Build.scala
index 745900effe..8e5f1eba16 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -2056,7 +2056,7 @@ object Build {
             } else {
               Some(ExpectedSizes(
                   fastLink = 423000 to 424000,
-                  fullLink = 280000 to 281000,
+                  fullLink = 281000 to 282000,
                   fastLinkGz = 60000 to 61000,
                   fullLinkGz = 43000 to 44000,
               ))
@@ -2065,7 +2065,7 @@ object Build {
           case `default213Version` =>
             if (!useMinifySizes) {
               Some(ExpectedSizes(
-                  fastLink = 449000 to 450000,
+                  fastLink = 450000 to 451000,
                   fullLink = 95000 to 96000,
                   fastLinkGz = 58000 to 59000,
                   fullLinkGz = 25000 to 26000,
diff --git a/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/lang/reflect/ReflectArrayTest.scala b/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/lang/reflect/ReflectArrayTest.scala
index 981ff8b49d..7a63a99a88 100644
--- a/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/lang/reflect/ReflectArrayTest.scala
+++ b/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/lang/reflect/ReflectArrayTest.scala
@@ -93,4 +93,30 @@ class ReflectArrayTest {
     assertThrows(classOf[NegativeArraySizeException], jlr.Array.newInstance(classOf[String], 5, -5))
     assertThrows(classOf[NegativeArraySizeException], jlr.Array.newInstance(classOf[Array[AnyRef]], 5, -5))
   }
+
+  @Test def newInstanceIllegalArgument(): Unit = {
+    import java.lang.{reflect => jlr}
+
+    assertThrows(classOf[IllegalArgumentException], jlr.Array.newInstance(classOf[Unit], 0))
+    assertThrows(classOf[IllegalArgumentException], jlr.Array.newInstance(classOf[Unit], 5))
+
+    assertThrows(classOf[IllegalArgumentException], jlr.Array.newInstance(classOf[Unit]))
+    assertThrows(classOf[IllegalArgumentException], jlr.Array.newInstance(classOf[Unit], 1, 1))
+
+    assertThrows(classOf[IllegalArgumentException], jlr.Array.newInstance(classOf[Unit]))
+    assertThrows(classOf[IllegalArgumentException], jlr.Array.newInstance(classOf[Int]))
+    assertThrows(classOf[IllegalArgumentException], jlr.Array.newInstance(classOf[AnyRef]))
+    assertThrows(classOf[IllegalArgumentException], jlr.Array.newInstance(classOf[Array[Int]]))
+    assertThrows(classOf[IllegalArgumentException], jlr.Array.newInstance(classOf[Array[String]]))
+  }
+
+  @Test def newInstanceNegativeArraySizeOrIllegalArgument(): Unit = {
+    import java.lang.{reflect => jlr}
+
+    assumeTrue("Assuming compliant negative array sizes", hasCompliantNegativeArraySizes)
+
+    assertThrows(classOf[RuntimeException], jlr.Array.newInstance(classOf[Unit], -3))
+    assertThrows(classOf[RuntimeException], jlr.Array.newInstance(classOf[Unit], -3, 1))
+    assertThrows(classOf[RuntimeException], jlr.Array.newInstance(classOf[Unit], 3, -1))
+  }
 }

From 9bffe2a5eaee372a2ef5f5c46b13fe09ca8d4511 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Wed, 25 Sep 2024 13:46:39 +0200
Subject: [PATCH 175/298] Allow `DelayedIdent`s for non-property JS
 identifiers.

Now all JS identifiers, except labels, can be `DelayedIdent`s.

Since `MaybeDelayedIdent`s are now much more prevalent, we refactor
some parts of the printer to make them more happy path than they
were before. That is also why we turn into an `abstract class`
instead of a `trait`.
---
 .../closure/ClosureAstTransformer.scala       |  8 ++---
 .../linker/backend/emitter/JSGen.scala        |  4 +--
 .../linker/backend/javascript/Printers.scala  | 33 ++++++++-----------
 .../linker/backend/javascript/Trees.scala     | 26 ++++++++-------
 4 files changed, 33 insertions(+), 38 deletions(-)

diff --git a/linker/jvm/src/main/scala/org/scalajs/linker/backend/closure/ClosureAstTransformer.scala b/linker/jvm/src/main/scala/org/scalajs/linker/backend/closure/ClosureAstTransformer.scala
index cad0fd9434..f3caeba0af 100644
--- a/linker/jvm/src/main/scala/org/scalajs/linker/backend/closure/ClosureAstTransformer.scala
+++ b/linker/jvm/src/main/scala/org/scalajs/linker/backend/closure/ClosureAstTransformer.scala
@@ -180,7 +180,7 @@ private class ClosureAstTransformer(featureSet: FeatureSet,
 
       case FunctionDef(name, args, restParam, body) =>
         val node = transformName(name)
-        val rhs = genFunction(name.name, args, restParam, body)
+        val rhs = genFunction(name.resolveName(), args, restParam, body)
         node.addChildToFront(rhs)
         new Node(Token.VAR, node)
 
@@ -390,7 +390,7 @@ private class ClosureAstTransformer(featureSet: FeatureSet,
         node.setIsArrowFunction(arrow)
         node
       case FunctionDef(name, args, restParam, body) =>
-        genFunction(name.name, args, restParam, body)
+        genFunction(name.resolveName(), args, restParam, body)
 
       case classDef: ClassDef =>
         transformClassDef(classDef)
@@ -421,8 +421,8 @@ private class ClosureAstTransformer(featureSet: FeatureSet,
     new Node(Token.FUNCTION, nameNode, paramList, transformBlock(body))
   }
 
-  def transformName(ident: Ident)(implicit parentPos: Position): Node =
-    setNodePosition(Node.newString(Token.NAME, ident.name),
+  def transformName(ident: MaybeDelayedIdent)(implicit parentPos: Position): Node =
+    setNodePosition(Node.newString(Token.NAME, ident.resolveName()),
         ident.pos orElse parentPos)
 
   def transformLabel(ident: Ident)(implicit parentPos: Position): Node =
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/JSGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/JSGen.scala
index 4da09323c5..a706292ed0 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/JSGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/JSGen.scala
@@ -66,10 +66,10 @@ private[emitter] final class JSGen(val config: Emitter.Config) {
    */
   val useLets = esFeatures.esVersion >= ESVersion.ES2015 && !esFeatures.avoidLetsAndConsts
 
-  def genConst(name: Ident, rhs: Tree)(implicit pos: Position): LocalDef =
+  def genConst(name: MaybeDelayedIdent, rhs: Tree)(implicit pos: Position): LocalDef =
     genLet(name, mutable = false, rhs)
 
-  def genLet(name: Ident, mutable: Boolean, rhs: Tree)(
+  def genLet(name: MaybeDelayedIdent, mutable: Boolean, rhs: Tree)(
       implicit pos: Position): LocalDef = {
     if (useLets)
       Let(name, mutable, Some(rhs))
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Printers.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Printers.scala
index aa8045f892..56c8c4aefe 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Printers.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Printers.scala
@@ -751,16 +751,12 @@ object Printers {
     protected def printEscapeJS(s: String): Unit =
       out.writeASCIIEscapedJSString(s)
 
-    protected def print(ident: Ident): Unit =
-      printEscapeJS(ident.name)
-
-    protected def print(ident: DelayedIdent): Unit =
+    protected def print(ident: MaybeDelayedIdent): Unit =
       printEscapeJS(ident.resolveName())
 
     private final def print(propName: PropertyName): Unit = propName match {
-      case lit: StringLiteral  => print(lit: Tree)
-      case ident: Ident        => print(ident)
-      case ident: DelayedIdent => print(ident)
+      case lit: StringLiteral       => print(lit: Tree)
+      case ident: MaybeDelayedIdent => print(ident)
 
       case ComputedName(tree) =>
         print("[")
@@ -802,15 +798,7 @@ object Printers {
     override protected def printEscapeJS(s: String): Unit =
       column += out.writeASCIIEscapedJSString(s)
 
-    override protected def print(ident: Ident): Unit = {
-      if (ident.pos.isDefined)
-        sourceMap.startIdentNode(column, ident.pos, ident.originalName)
-      super.print(ident)
-      if (ident.pos.isDefined)
-        sourceMap.endNode(column)
-    }
-
-    override protected def print(ident: DelayedIdent): Unit = {
+    override protected def print(ident: MaybeDelayedIdent): Unit = {
       if (ident.pos.isDefined)
         sourceMap.startIdentNode(column, ident.pos, ident.originalName)
       printEscapeJS(ident.resolveName())
@@ -863,10 +851,15 @@ object Printers {
     def printTreeForShow(tree: Tree): Unit =
       printTree(tree, isStat = true)
 
-    override protected def print(ident: DelayedIdent): Unit = {
-      print("<delayed:")
-      print(ident.resolver.debugString)
-      print(">")
+    override protected def print(ident: MaybeDelayedIdent): Unit = {
+      ident match {
+        case ident: Ident =>
+          super.print(ident)
+        case ident: DelayedIdent =>
+          print("<delayed:")
+          print(ident.resolver.debugString)
+          print(">")
+      }
     }
   }
 }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Trees.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Trees.scala
index 00405e253e..a7ff95c9a5 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Trees.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Trees.scala
@@ -45,7 +45,9 @@ object Trees {
     def pos: Position
   }
 
-  sealed trait MaybeDelayedIdent extends PropertyName {
+  sealed abstract class MaybeDelayedIdent extends PropertyName {
+    val originalName: OriginalName
+
     def resolveName(): String
   }
 
@@ -135,24 +137,24 @@ object Trees {
   // Definitions
 
   sealed trait LocalDef extends Tree {
-    def name: Ident
+    def name: MaybeDelayedIdent
     def mutable: Boolean
 
     def ref(implicit pos: Position): Tree = VarRef(name)
   }
 
-  sealed case class VarDef(name: Ident, rhs: Option[Tree])(
+  sealed case class VarDef(name: MaybeDelayedIdent, rhs: Option[Tree])(
       implicit val pos: Position)
       extends LocalDef {
     def mutable: Boolean = true
   }
 
   /** ES6 let or const (depending on the mutable flag). */
-  sealed case class Let(name: Ident, mutable: Boolean, rhs: Option[Tree])(
+  sealed case class Let(name: MaybeDelayedIdent, mutable: Boolean, rhs: Option[Tree])(
       implicit val pos: Position)
       extends LocalDef
 
-  sealed case class ParamDef(name: Ident)(implicit val pos: Position)
+  sealed case class ParamDef(name: MaybeDelayedIdent)(implicit val pos: Position)
       extends LocalDef {
     def mutable: Boolean = true
   }
@@ -241,7 +243,7 @@ object Trees {
       implicit val pos: Position)
       extends Tree
 
-  sealed case class TryCatch(block: Tree, errVar: Ident, handler: Tree)(
+  sealed case class TryCatch(block: Tree, errVar: MaybeDelayedIdent, handler: Tree)(
       implicit val pos: Position)
       extends Tree
 
@@ -382,7 +384,7 @@ object Trees {
 
   // Atomic expressions
 
-  sealed case class VarRef(ident: Ident)(implicit val pos: Position)
+  sealed case class VarRef(ident: MaybeDelayedIdent)(implicit val pos: Position)
       extends Tree
 
   sealed case class This()(implicit val pos: Position) extends Tree
@@ -393,13 +395,13 @@ object Trees {
 
   // Named function definition
 
-  sealed case class FunctionDef(name: Ident, args: List[ParamDef],
+  sealed case class FunctionDef(name: MaybeDelayedIdent, args: List[ParamDef],
       restParam: Option[ParamDef], body: Tree)(
       implicit val pos: Position) extends Tree
 
   // ECMAScript 6 classes
 
-  sealed case class ClassDef(className: Option[Ident],
+  sealed case class ClassDef(className: Option[MaybeDelayedIdent],
       parentClass: Option[Tree], members: List[Tree])(
       implicit val pos: Position)
       extends Tree
@@ -499,7 +501,7 @@ object Trees {
    *    `import { binding } from 'from'`.
    *  - When `_1.name == "default"`, it is equivalent to a default import.
    */
-  sealed case class Import(bindings: List[(ExportName, Ident)],
+  sealed case class Import(bindings: List[(ExportName, MaybeDelayedIdent)],
       from: StringLiteral)(
       implicit val pos: Position)
       extends Tree
@@ -511,7 +513,7 @@ object Trees {
    *  import * as <binding> from <from>
    *  }}}
    */
-  sealed case class ImportNamespace(binding: Ident, from: StringLiteral)(
+  sealed case class ImportNamespace(binding: MaybeDelayedIdent, from: StringLiteral)(
       implicit val pos: Position)
       extends Tree
 
@@ -525,7 +527,7 @@ object Trees {
    *  module that are exported. The `_2` parts are the names under which they
    *  are exported to other modules.
    */
-  sealed case class Export(bindings: List[(Ident, ExportName)])(
+  sealed case class Export(bindings: List[(MaybeDelayedIdent, ExportName)])(
       implicit val pos: Position)
       extends Tree
 

From 933c7edfa2a3b4f6143a5c06dd25355262c8bb16 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Wed, 28 Aug 2024 17:09:02 +0200
Subject: [PATCH 176/298] Wasm: Use custom JS helpers for almost all JS
 interop.

Previously, we used a small set of fixed JS helpers to implement
all the Wasm-to-JS interop nodes. For example, there was a unique
`jsMethodApply` helper, used for all `JSMethodApply` nodes. We also
used a single entry point to read all `JSGlobalRef`s, using a JS
`new Function("...")` to read global variables.

This strategy, while having the advantage of doing all the
codebase-dependent work on the Wasm side, was extremely slow.
Imagine that calling `Math.cos(x)` had to:

1. load the constant string `"Math"`,
2. use `jsGlobalRefGet("Math")`, using a `new Function` to read that,
3. load the constant string `"cos"`,
4. use `jsNewArray` and `jsArrayPush` to create a JS array with `x`
   as argument (plus a `bD` call to box `x`!),
5. use `jsMethodApply`, which uses a `...spread` operator to
   re-expand the one-element array of arguments.

A unique call like that in a more-or-less tight loop would destroy
any hope of good performance.

---

We now use a completely different strategy. For every Wasm-to-JS
interop node, `FunctionEmitter` creates a dedicated JS helper. It
is registered in the context and will be inserted in the generated
`main.js` file.

We build on a unified toolkit to generate efficient JS helpers and
managing their inputs: `CustomJSHelperBuilder`. It manages the
evaluatation of Wasm values on one side, then gives them to a
dedicated JS function body. Boxing is fused into the JS function
call through the built-in Wasm-to-JS interop features when
possible. Moreover, literals and JS global refs are
"constant-folded" into the JS function altogether.

For the above example scenario, we end up with a helper of the form
`(x) => Math.cos(x)`, typed in Wasm as a `[f64] -> [anyref]`. We
can call it directly with a `double` value, without explicit call
to `bD`, without JS array, and without string values representing
`"Math"` nor `"cos"`. This is almost as good as it gets. The only
non-optimal aspect is that we still return an `anyref`, which we
have to unbox later with a call to `uD`. Improving that last point
is left for future work.

---

We use the same mechanism to build dedicated helpers for `Closure`s,
top-level exported defs and for non-native JS classes.

---

There are two things that we can still improve in the future
without too much effort:

* Handling of the arguments to the super constructor calls in
  non-native JS classes, for which we could leverage Wasm functions
  with multiple return values.
* Move the management of the `Symbol`s for private JS fields to the
  JS side of things, instead of passing them from Wasm every time.
---
 .../backend/emitter/FunctionEmitter.scala     |  24 +-
 .../linker/backend/emitter/JSGen.scala        |  15 +-
 .../linker/backend/emitter/NameGen.scala      |  84 ++--
 .../linker/backend/emitter/VarGen.scala       |   4 +-
 .../linker/backend/javascript/Trees.scala     |  42 +-
 .../backend/wasmemitter/ClassEmitter.scala    | 374 +++++++++++-------
 .../backend/wasmemitter/CoreWasmLib.scala     | 102 +----
 .../wasmemitter/CustomJSHelperBuilder.scala   | 284 +++++++++++++
 .../linker/backend/wasmemitter/Emitter.scala  | 113 ++++--
 .../backend/wasmemitter/FunctionEmitter.scala | 337 +++++++++++-----
 .../backend/wasmemitter/LoaderContent.scala   | 132 +------
 .../linker/backend/wasmemitter/README.md      | 136 ++++---
 .../linker/backend/wasmemitter/SWasmGen.scala |  57 ---
 .../linker/backend/wasmemitter/VarGen.scala   |  71 +---
 .../backend/wasmemitter/WasmContext.scala     |  34 ++
 15 files changed, 1015 insertions(+), 794 deletions(-)
 create mode 100644 linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CustomJSHelperBuilder.scala

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
index dc6089ad3f..b8b802695f 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
@@ -2885,29 +2885,7 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
               transformExprNoChar(item))
 
         case JSFunctionApply(fun, args) =>
-          /* Protect the fun so that if it is, e.g.,
-           * path.f
-           * we emit
-           * (0, path.f)(args...)
-           * instead of
-           * path.f(args...)
-           * If we emit the latter, then `this` will be bound to `path` in
-           * `f`, which is sometimes extremely harmful (e.g., for builtin
-           * methods of `window`).
-           *
-           * A bare identifier `eval` also need to be protected in the same
-           * way, because calling a bare `eval` executes the code in the
-           * current lexical scope, as opposed to the global scope.
-           */
-          val transformedFun = transformExprNoChar(fun)
-          val protectedFun = transformedFun match {
-            case _:js.DotSelect | _:js.BracketSelect |
-                js.VarRef(js.Ident("eval", _)) =>
-              js.Block(js.IntLiteral(0), transformedFun)
-            case _ =>
-              transformedFun
-          }
-          js.Apply(protectedFun, args.map(transformJSArg))
+          js.Apply.makeProtected(transformExprNoChar(fun), args.map(transformJSArg))
 
         case JSMethodApply(receiver, method, args) =>
           js.Apply(genBracketSelect(transformExprNoChar(receiver),
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/JSGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/JSGen.scala
index a706292ed0..3676a947c8 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/JSGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/JSGen.scala
@@ -92,17 +92,10 @@ private[emitter] final class JSGen(val config: Emitter.Config) {
   }
 
   def genBracketSelect(qual: Tree, item: Tree)(implicit pos: Position): Tree = {
-    item match {
-      case StringLiteral(name) if optimizeBracketSelects &&
-          Ident.isValidJSIdentifierName(name) && name != "eval" =>
-        /* We exclude "eval" because we do not want to rely too much on the
-         * strict mode peculiarities of eval(), so that we can keep running
-         * on VMs that do not support strict mode.
-         */
-        DotSelect(qual, Ident(name))
-      case _ =>
-        BracketSelect(qual, item)
-    }
+    if (optimizeBracketSelects)
+      BracketSelect.makeOptimized(qual, item)
+    else
+      BracketSelect(qual, item)
   }
 
   def genIdentBracketSelect(qual: Tree, item: String)(
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/NameGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/NameGen.scala
index ae8502211d..4e26efd4b7 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/NameGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/NameGen.scala
@@ -24,7 +24,7 @@ import org.scalajs.ir.Types._
  *  - Converts IR names to JavaScript names.
  *  - Converts module names to JavaScript names.
  */
-private[emitter] final class NameGen {
+private[backend] final class NameGen {
   import NameGen._
 
   private val genLocalNameCache = {
@@ -259,49 +259,9 @@ private[emitter] final class NameGen {
     else if (sameName) NoOriginalName
     else OriginalName(name)
   }
-
-  def genModuleName(module: String): String = {
-    /* This is written so that the happy path, when `module` contains only
-     * valid characters, is fast.
-     */
-
-    def isValidChar(c: Char): Boolean =
-      (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') || (c >= '0' && c <= '9')
-
-    def containsOnlyValidChars(): Boolean = {
-      // scalastyle:off return
-      val len = module.length
-      var i = 0
-      while (i != len) {
-        if (!isValidChar(module.charAt(i)))
-          return false
-        i += 1
-      }
-      true
-      // scalastyle:on return
-    }
-
-    def buildValidName(): String = {
-      val result = new java.lang.StringBuilder()
-      val len = module.length
-      var i = 0
-      while (i != len) {
-        val c = module.charAt(i)
-        if (isValidChar(c))
-          result.append(c)
-        else
-          result.append("$%04x".format(c.toInt))
-        i += 1
-      }
-      result.toString()
-    }
-
-    if (containsOnlyValidChars()) module
-    else buildValidName()
-  }
 }
 
-private[emitter] object NameGen {
+private[backend] object NameGen {
 
   private final val FullwidthSpacingUnderscore = '\uff3f'
   private final val GreekSmallLetterDelta = '\u03b4'
@@ -416,4 +376,44 @@ private[emitter] object NameGen {
     // scalastyle:on return
   }
 
+  def genModuleName(module: String): String = {
+    /* This is written so that the happy path, when `module` contains only
+     * valid characters, is fast.
+     */
+
+    def isValidChar(c: Char): Boolean =
+      (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') || (c >= '0' && c <= '9')
+
+    def containsOnlyValidChars(): Boolean = {
+      // scalastyle:off return
+      val len = module.length
+      var i = 0
+      while (i != len) {
+        if (!isValidChar(module.charAt(i)))
+          return false
+        i += 1
+      }
+      true
+      // scalastyle:on return
+    }
+
+    def buildValidName(): String = {
+      val result = new java.lang.StringBuilder()
+      val len = module.length
+      var i = 0
+      while (i != len) {
+        val c = module.charAt(i)
+        if (isValidChar(c))
+          result.append(c)
+        else
+          result.append("$%04x".format(c.toInt))
+        i += 1
+      }
+      result.toString()
+    }
+
+    if (containsOnlyValidChars()) module
+    else buildValidName()
+  }
+
 }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/VarGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/VarGen.scala
index 11d93244d9..d867b347ed 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/VarGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/VarGen.scala
@@ -258,10 +258,10 @@ private[emitter] final class VarGen(jsGen: JSGen, nameGen: NameGen,
   }
 
   def externalModuleFieldIdent(moduleName: String)(implicit pos: Position): Ident =
-    fileLevelVarIdent(VarField.i, genModuleName(moduleName), OriginalName(moduleName))
+    fileLevelVarIdent(VarField.i, NameGen.genModuleName(moduleName), OriginalName(moduleName))
 
   def internalModuleFieldIdent(module: ModuleID)(implicit pos: Position): Ident =
-    fileLevelVarIdent(VarField.j, genModuleName(module.id), OriginalName(module.id))
+    fileLevelVarIdent(VarField.j, NameGen.genModuleName(module.id), OriginalName(module.id))
 
   private def genericIdent(field: VarField, subField: String,
       origName: OriginalName = NoOriginalName)(
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Trees.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Trees.scala
index a7ff95c9a5..2ad5d6658f 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Trees.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Trees.scala
@@ -140,7 +140,7 @@ object Trees {
     def name: MaybeDelayedIdent
     def mutable: Boolean
 
-    def ref(implicit pos: Position): Tree = VarRef(name)
+    def ref(implicit pos: Position): VarRef = VarRef(name)
   }
 
   sealed case class VarDef(name: MaybeDelayedIdent, rhs: Option[Tree])(
@@ -282,6 +282,20 @@ object Trees {
       implicit val pos: Position)
       extends Tree
 
+  object BracketSelect {
+    /* Semantically builds a `BracketSelect`, and optimizes it as `DotSelect` if possible. */
+    def makeOptimized(qualifier: Tree, item: Tree)(implicit pos: Position): Tree = item match {
+      case StringLiteral(name) if Ident.isValidJSIdentifierName(name) && name != "eval" =>
+        /* We exclude "eval" because we do not want to rely too much on the
+         * strict mode peculiarities of eval(), so that we can keep running
+         * on VMs that do not support strict mode.
+         */
+        DotSelect(qualifier, Ident(name))
+      case _ =>
+        BracketSelect(qualifier, item)
+    }
+  }
+
   /** Syntactic apply.
    *  It is a method call if fun is a dot-select or bracket-select. It is a
    *  function call otherwise.
@@ -290,6 +304,32 @@ object Trees {
       implicit val pos: Position)
       extends Tree
 
+  object Apply {
+    /** Builds an `Apply` that is protected against accidental `this` binding and
+     *  lexically-scoped `eval`.
+     *
+     *  By default, if the `fun` is syntactically a `DotSelect` or
+     *  `BracketSelect`, an `Apply` node binds `this` to the qualifier of the
+     *  selection.
+     *
+     *  Likewise, by default, if the `fun` happens to be a bare `eval`
+     *  identifier, the `Apply` node executes the eval'ed code in the current
+     *  lexical scope, as opposed to the global scope.
+     *
+     *  This builder method protects the `fun` against both of those accidental
+     *  semantic quirks.
+     */
+    def makeProtected(fun: Tree, args: List[Tree])(implicit pos: Position): Apply = {
+      val protectedFun = fun match {
+        case _:DotSelect | _:BracketSelect | VarRef(Ident("eval", _)) =>
+          Block(IntLiteral(0), fun)
+        case _ =>
+          fun
+      }
+      Apply(protectedFun, args)
+    }
+  }
+
   /** Dynamic `import(arg)`. */
   sealed case class ImportCall(arg: Tree)(implicit val pos: Position)
       extends Tree
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/ClassEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/ClassEmitter.scala
index 5775d085a3..c4be465718 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/ClassEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/ClassEmitter.scala
@@ -24,6 +24,8 @@ import org.scalajs.linker.interface.CheckedBehavior
 import org.scalajs.linker.interface.unstable.RuntimeClassNameMapperImpl
 import org.scalajs.linker.standard.{CoreSpec, LinkedClass, LinkedGlobalInfo, LinkedTopLevelExport}
 
+import org.scalajs.linker.backend.javascript.{Trees => js}
+
 import org.scalajs.linker.backend.webassembly.FunctionBuilder
 import org.scalajs.linker.backend.webassembly.{Instructions => wa}
 import org.scalajs.linker.backend.webassembly.{Modules => wamod}
@@ -173,10 +175,23 @@ class ClassEmitter(coreSpec: CoreSpec) {
          */
         fb += wa.I32Const(0) // false
       } else {
-        fb += wa.LocalGet(xParam)
-        genLoadJSConstructor(fb, className)
-        fb += wa.Call(genFunctionID.jsBinaryOps(JSBinaryOp.instanceof))
-        fb += wa.Call(genFunctionID.unbox(BooleanRef))
+        val helperBuilder = new CustomJSHelperBuilder()
+        val xRef = helperBuilder.addWasmInput("x", watpe.RefType.anyref) {
+          fb += wa.LocalGet(xParam)
+        }
+        val ctorRef = clazz.jsNativeLoadSpec match {
+          case Some(loadSpec) =>
+            helperBuilder.genJSNativeLoadSpec(loadSpec)
+          case None =>
+            // This is a non-native JS class
+            helperBuilder.addWasmInput("ctor", watpe.RefType.any) {
+              fb += wa.Call(genFunctionID.loadJSClass(className))
+            }
+        }
+        val helperID = helperBuilder.build(BooleanType) {
+          js.Return(js.BinaryOp(JSBinaryOp.instanceof, xRef, ctorRef))
+        }
+        fb += wa.Call(helperID)
       }
 
       val func = fb.buildAndAddToModule()
@@ -917,7 +932,7 @@ class ClassEmitter(coreSpec: CoreSpec) {
   }
 
   private def genCreateJSClassFunction(clazz: LinkedClass)(implicit ctx: WasmContext): Unit = {
-    implicit val noPos: Position = Position.NoPosition
+    implicit val pos: Position = Position.NoPosition
 
     val className = clazz.className
     val jsClassCaptures = clazz.jsClassCaptures.getOrElse(Nil)
@@ -955,31 +970,31 @@ class ClassEmitter(coreSpec: CoreSpec) {
       ctor
     )
 
-    // Build the actual `createJSClass` function
-    val createJSClassFun = {
-      val fb = new FunctionBuilder(
-        ctx.moduleBuilder,
-        genFunctionID.createJSClassOf(className),
-        makeDebugName(ns.CreateJSClass, className),
-        clazz.pos
-      )
-      val classCaptureParams = jsClassCaptures.map { cc =>
-        fb.addParam("cc." + cc.name.name.nameString, transformParamType(cc.ptpe))
-      }
-      fb.setResultType(watpe.RefType.any)
+    val fb = new FunctionBuilder(
+      ctx.moduleBuilder,
+      genFunctionID.createJSClassOf(className),
+      makeDebugName(ns.CreateJSClass, className),
+      clazz.pos
+    )
+    val classCaptureParams = jsClassCaptures.map { cc =>
+      fb.addParam("cc." + cc.name.name.nameString, transformParamType(cc.ptpe))
+    }
+    fb.setResultType(watpe.RefType.any)
 
-      val dataStructTypeID = ctx.getClosureDataStructType(jsClassCaptures.map(_.ptpe))
+    val dataStructTypeID = ctx.getClosureDataStructType(jsClassCaptures.map(_.ptpe))
 
-      val dataStructLocal = fb.addLocal("classCaptures", watpe.RefType(dataStructTypeID))
-      val jsClassLocal = fb.addLocal("jsClass", watpe.RefType.any)
+    val dataStructLocal = fb.addLocal("classCaptures", watpe.RefType(dataStructTypeID))
+    val jsClassLocal = fb.addLocal("jsClass", watpe.RefType.any)
 
+    // Build the actual `createJSClass` helper
+    val createJSClassHelperID: wanme.FunctionID = {
       // --- Actual start of instructions of `createJSClass`
 
-      // Bundle class captures in a capture data struct -- leave it on the stack for createJSClass
+      // Bundle class captures in a capture data struct
       for (classCaptureParam <- classCaptureParams)
         fb += wa.LocalGet(classCaptureParam)
       fb += wa.StructNew(dataStructTypeID)
-      fb += wa.LocalTee(dataStructLocal)
+      fb += wa.LocalSet(dataStructLocal)
 
       val classCaptureParamsOfTypeAny: Map[LocalName, wanme.LocalID] = {
         jsClassCaptures
@@ -990,13 +1005,8 @@ class ClassEmitter(coreSpec: CoreSpec) {
           .toMap
       }
 
-      def genLoadIsolatedTree(tree: Tree): Unit = {
-        tree match {
-          case StringLiteral(value) =>
-            // Common shape for all the `nameTree` expressions
-            fb ++= ctx.stringPool.getConstantStringInstr(value)
-            fb += wa.AnyConvertExtern
-
+      val helperBuilder = new CustomJSHelperBuilder.WithTreeEval() {
+        protected def evalTreeAtCallSite(tree: Tree, expectedType: Type): Unit = tree match {
           case VarRef(LocalIdent(localName)) if classCaptureParamsOfTypeAny.contains(localName) =>
             /* Common shape for the `jsSuperClass` value
              * We can only deal with class captures of type `AnyType` in this way,
@@ -1023,72 +1033,108 @@ class ClassEmitter(coreSpec: CoreSpec) {
         }
       }
 
-      /* Load super constructor; specified by
+      /* Get a Tree for the super constructor; specified by
        * https://lampwww.epfl.ch/~doeraene/sjsir-semantics/#sec-sjsir-classdef-runtime-semantics-evaluation
        * - if `jsSuperClass` is defined, evaluate it;
        * - otherwise load the JS constructor of the declared superClass,
        *   as if by `LoadJSConstructor`.
        */
-      clazz.jsSuperClass match {
-        case None =>
-          genLoadJSConstructor(fb, clazz.superClass.get.name)
-        case Some(jsSuperClassTree) =>
-          genLoadIsolatedTree(jsSuperClassTree)
+      val jsSuperClassTree = clazz.jsSuperClass.getOrElse {
+        LoadJSConstructor(clazz.superClass.get.name)
       }
 
-      // Load the references to the 3 functions that make up the constructor
-      fb += ctx.refFuncWithDeclaration(preSuperStatsFunctionID)
-      fb += ctx.refFuncWithDeclaration(superArgsFunctionID)
-      fb += ctx.refFuncWithDeclaration(postSuperStatsFunctionID)
-
-      // Load the array of field names and initial values
-      fb += wa.Call(genFunctionID.jsNewArray)
-      for (fieldDef <- clazz.fields if !fieldDef.flags.namespace.isStatic) {
-        // Append the name
-        fieldDef match {
-          case FieldDef(_, name, _, _) =>
-            fb += wa.GlobalGet(genGlobalID.forJSPrivateField(name.name))
-          case JSFieldDef(_, nameTree, _) =>
-            genLoadIsolatedTree(nameTree)
-        }
-        fb += wa.Call(genFunctionID.jsArrayPush)
+      val dataRef = helperBuilder.addWasmInput("data", watpe.RefType(dataStructTypeID)) {
+        fb += wa.LocalGet(dataStructLocal)
+      }
+      val preSuperStatsFunctionRef = helperBuilder.addWasmInput("preSuperStats", watpe.RefType.func) {
+        fb += ctx.refFuncWithDeclaration(preSuperStatsFunctionID)
+      }
+      val superArgsFunctionRef = helperBuilder.addWasmInput("superArgs", watpe.RefType.func) {
+        fb += ctx.refFuncWithDeclaration(superArgsFunctionID)
+      }
+      val postSuperStatsFunctionRef = helperBuilder.addWasmInput("postSuperStats", watpe.RefType.func) {
+        fb += ctx.refFuncWithDeclaration(postSuperStatsFunctionID)
+      }
 
-        // Append the boxed representation of the zero of the field
-        fb += genBoxedZeroOf(fieldDef.ftpe)
-        fb += wa.Call(genFunctionID.jsArrayPush)
+      def genDefineProperty(obj: js.Tree, name: js.Tree, value: js.Tree): js.Tree = {
+        js.Apply(
+          js.DotSelect(js.VarRef(js.Ident("Object")), js.Ident("defineProperty")),
+          List(
+            obj,
+            name,
+            js.ObjectConstr(
+              List(
+                js.Ident("configurable") -> js.BooleanLiteral(true),
+                js.Ident("enumerable") -> js.BooleanLiteral(true),
+                js.Ident("writable") -> js.BooleanLiteral(true),
+                js.Ident("value") -> value
+              )
+            )
+          )
+        )
       }
 
-      // Call the createJSClass helper to bundle everything
-      if (ctor.restParam.isDefined) {
-        fb += wa.I32Const(ctor.args.size) // number of fixed params
-        fb += wa.Call(genFunctionID.createJSClassRest)
-      } else {
-        fb += wa.Call(genFunctionID.createJSClass)
+      def toJSPropertyName(tree: js.Tree): js.PropertyName = tree match {
+        case js.StringLiteral("constructor")                                  => js.ComputedName(tree)
+        case js.StringLiteral(name) if js.Ident.isValidJSIdentifierName(name) => js.Ident(name)
+        case tree: js.StringLiteral                                           => tree
+        case _                                                                => js.ComputedName(tree)
       }
 
-      // Store the result, locally in `jsClass` and possibly in the global cache
-      if (clazz.jsClassCaptures.isEmpty) {
-        /* Static JS class with a global cache. We must fill the global cache
-         * before we call the class initializer, later in the current function.
-         */
-        fb += wa.LocalTee(jsClassLocal)
-        fb += wa.GlobalSet(genGlobalID.forJSClassValue(className))
-      } else {
-        // Local or inner JS class, which is new every time
-        fb += wa.LocalSet(jsClassLocal)
+      val jsClassIdent = helperBuilder.newLocalIdent("cls")
+
+      val jsCtorDef: js.MethodDef = {
+        val JSConstructorDef(_, params, restParam, body) = ctor
+        val (paramDefs, restParamDef) = helperBuilder.genJSParamDefs(params, restParam)
+        val allParamRefs = (paramDefs ::: restParamDef.toList).map(_.ref)
+        js.MethodDef(static = false, js.Ident("constructor"), paramDefs, restParamDef, {
+          val preSuperEnv = helperBuilder.newLocalIdent("preSuperEnv")
+          js.Block(
+            // var preSuperEnv = preSuperStats(data, new.target, ...allParamRefs);
+            js.VarDef(preSuperEnv, Some(js.Apply(preSuperStatsFunctionRef,
+                dataRef :: js.NewTarget() :: allParamRefs))),
+            // super(...superArgs(data, preSuperEnv, new.target, ...args));
+            js.Apply(
+              js.Super(),
+              List(
+                js.Spread(
+                  js.Apply(
+                    superArgsFunctionRef,
+                    dataRef :: js.VarRef(preSuperEnv) :: js.NewTarget() :: allParamRefs
+                  )
+                )
+              )
+            ),
+            // Initialize fields to the (boxed) zero of their type
+            js.Block(for (fieldDef <- clazz.fields if !fieldDef.flags.namespace.isStatic) yield {
+              val nameRef = fieldDef match {
+                case FieldDef(_, name, _, _) =>
+                  helperBuilder.addWasmInput("name", watpe.RefType.anyref) {
+                    fb += wa.GlobalGet(genGlobalID.forJSPrivateField(name.name))
+                  }
+                case JSFieldDef(_, nameTree, _) =>
+                  helperBuilder.addInput(nameTree)
+              }
+              val valueRef = helperBuilder.addInput(zeroOf(fieldDef.ftpe))
+              genDefineProperty(js.This(), nameRef, valueRef)
+            }),
+            // postSuperStats(data, preSuperEnv, new.target, this, ...args);
+            js.Apply(postSuperStatsFunctionRef,
+                dataRef :: js.VarRef(preSuperEnv) :: js.NewTarget() :: js.This() :: allParamRefs)
+          )
+        })
       }
 
-      // Install methods and properties
-      for (methodOrProp <- clazz.exportedMembers) {
+      // Methods and properties
+      val jsMethodProps: List[js.Tree] = clazz.exportedMembers.flatMap { methodOrProp =>
         val isStatic = methodOrProp.flags.namespace.isStatic
-        fb += wa.LocalGet(dataStructLocal)
-        fb += wa.LocalGet(jsClassLocal)
+        val jsThisUnlessStatic = if (isStatic) Nil else List(js.This())
 
         val receiverType = if (isStatic) None else Some(watpe.RefType.anyref)
 
         methodOrProp match {
           case JSMethodDef(flags, nameTree, params, restParam, body) =>
-            genLoadIsolatedTree(nameTree)
+            val nameRef = toJSPropertyName(helperBuilder.addInput(nameTree))
 
             val closureFuncID = new JSClassClosureFunctionID(className)
             FunctionEmitter.emitFunction(
@@ -1102,106 +1148,141 @@ class ClassEmitter(coreSpec: CoreSpec) {
               body,
               AnyType
             )
-            fb += ctx.refFuncWithDeclaration(closureFuncID)
+            val fRef = helperBuilder.addWasmInput("f", watpe.RefType.func) {
+              fb += ctx.refFuncWithDeclaration(closureFuncID)
+            }
 
-            fb += wa.I32Const(if (restParam.isDefined) params.size else -1)
-            if (isStatic)
-              fb += wa.Call(genFunctionID.installJSStaticMethod)
-            else
-              fb += wa.Call(genFunctionID.installJSMethod)
+            val (argsParamDefs, restParamDef) = helperBuilder.genJSParamDefs(params, restParam)
+            val jsMethodDef = js.MethodDef(isStatic, nameRef, argsParamDefs, restParamDef, {
+              js.Return(js.Apply(
+                  fRef,
+                  dataRef ::
+                  jsThisUnlessStatic :::
+                  argsParamDefs.map(_.ref) :::
+                  restParamDef.map(_.ref).toList
+              ))
+            })
+
+            List(jsMethodDef)
 
           case JSPropertyDef(flags, nameTree, optGetter, optSetter) =>
-            genLoadIsolatedTree(nameTree)
-
-            optGetter match {
-              case None =>
-                fb += wa.RefNull(watpe.HeapType.Func)
-
-              case Some(getterBody) =>
-                val closureFuncID = new JSClassClosureFunctionID(className)
-                FunctionEmitter.emitFunction(
-                  closureFuncID,
-                  NoOriginalName, // TODO Come up with something here?
-                  Some(className),
-                  Some(jsClassCaptures),
-                  receiverType,
-                  paramDefs = Nil,
-                  restParam = None,
-                  getterBody,
-                  resultType = AnyType
-                )
+            val nameRef = toJSPropertyName(helperBuilder.addInput(nameTree))
+
+            val jsGetter = optGetter.map { getterBody =>
+              val closureFuncID = new JSClassClosureFunctionID(className)
+              FunctionEmitter.emitFunction(
+                closureFuncID,
+                NoOriginalName, // TODO Come up with something here?
+                Some(className),
+                Some(jsClassCaptures),
+                receiverType,
+                paramDefs = Nil,
+                restParam = None,
+                getterBody,
+                resultType = AnyType
+              )
+              val getterRef = helperBuilder.addWasmInput("get", watpe.RefType.func) {
                 fb += ctx.refFuncWithDeclaration(closureFuncID)
+              }
+              js.GetterDef(isStatic, nameRef, {
+                js.Return(js.Apply(getterRef, dataRef :: jsThisUnlessStatic))
+              })
             }
 
-            optSetter match {
-              case None =>
-                fb += wa.RefNull(watpe.HeapType.Func)
-
-              case Some((setterParamDef, setterBody)) =>
-                val closureFuncID = new JSClassClosureFunctionID(className)
-                FunctionEmitter.emitFunction(
-                  closureFuncID,
-                  NoOriginalName, // TODO Come up with something here?
-                  Some(className),
-                  Some(jsClassCaptures),
-                  receiverType,
-                  setterParamDef :: Nil,
-                  restParam = None,
-                  setterBody,
-                  resultType = NoType
-                )
+            val jsSetter = optSetter.map { setter =>
+              val (setterParamDef, setterBody) = setter
+              val closureFuncID = new JSClassClosureFunctionID(className)
+              FunctionEmitter.emitFunction(
+                closureFuncID,
+                NoOriginalName, // TODO Come up with something here?
+                Some(className),
+                Some(jsClassCaptures),
+                receiverType,
+                setterParamDef :: Nil,
+                restParam = None,
+                setterBody,
+                resultType = NoType
+              )
+              val setterRef = helperBuilder.addWasmInput("set", watpe.RefType.func) {
                 fb += ctx.refFuncWithDeclaration(closureFuncID)
+              }
+              val jsSetterParamDef = helperBuilder.genJSParamDef(setterParamDef)
+              js.SetterDef(isStatic, nameRef, jsSetterParamDef, {
+                js.Apply(setterRef, dataRef :: jsThisUnlessStatic ::: jsSetterParamDef.ref :: Nil)
+              })
             }
 
-            if (isStatic)
-              fb += wa.Call(genFunctionID.installJSStaticProperty)
-            else
-              fb += wa.Call(genFunctionID.installJSProperty)
+            jsGetter.toList ::: jsSetter.toList
         }
       }
 
-      // Static fields
-      for (fieldDef <- clazz.fields if fieldDef.flags.namespace.isStatic) {
-        // Load class value
-        fb += wa.LocalGet(jsClassLocal)
+      val jsSuperClass = helperBuilder.addInput(jsSuperClassTree)
+      val jsClassDef = js.ClassDef(Some(jsClassIdent), Some(jsSuperClass),
+          jsCtorDef :: jsMethodProps)
 
-        // Load name
-        fieldDef match {
+      // Static fields
+      val jsInitStaticFields = for {
+        fieldDef <- clazz.fields if fieldDef.flags.namespace.isStatic
+      } yield {
+        // Name
+        val nameRef = fieldDef match {
           case FieldDef(_, name, _, _) =>
             throw new AssertionError(
               s"Unexpected private static field ${name.name.nameString} "
                 + s"in JS class ${className.nameString}"
             )
           case JSFieldDef(_, nameTree, _) =>
-            genLoadIsolatedTree(nameTree)
+            helperBuilder.addInput(nameTree)
         }
 
         // Generate boxed representation of the zero of the field
-        fb += genBoxedZeroOf(fieldDef.ftpe)
+        val valueRef = helperBuilder.addInput(zeroOf(fieldDef.ftpe))
 
-        /* Note: there is no `installJSStaticField` because it would do the
-         * same as `installJSField` anyway.
-         */
-        fb += wa.Call(genFunctionID.installJSField)
+        genDefineProperty(js.VarRef(jsClassIdent), nameRef, valueRef)
       }
 
-      // Class initializer
-      if (clazz.methods.exists(_.methodName.isClassInitializer)) {
-        assert(
-          clazz.jsClassCaptures.isEmpty,
-          s"Illegal class initializer in non-static class ${className.nameString}"
-        )
-        val namespace = MemberNamespace.StaticConstructor
-        fb += wa.Call(
-          genFunctionID.forMethod(namespace, className, ClassInitializerName)
+      // Complete the helper
+      helperBuilder.build(AnyNotNullType) {
+        js.Block(
+          jsClassDef ::
+          jsInitStaticFields :::
+          js.Return(js.VarRef(jsClassIdent)) ::
+          Nil
         )
       }
+    }
 
-      // Final result
-      fb += wa.LocalGet(jsClassLocal)
+    // Call the helper to produce the JS class value
+    fb += wa.Call(createJSClassHelperID)
 
-      fb.buildAndAddToModule()
+    // Store the result, locally in `jsClass` and possibly in the global cache
+    if (clazz.jsClassCaptures.isEmpty) {
+      /* Static JS class with a global cache. We must fill the global cache
+       * before we call the class initializer, later in the current function.
+       */
+      fb += wa.LocalTee(jsClassLocal)
+      fb += wa.GlobalSet(genGlobalID.forJSClassValue(className))
+    } else {
+      // Local or inner JS class, which is new every time
+      fb += wa.LocalSet(jsClassLocal)
     }
+
+    // Class initializer
+    if (clazz.methods.exists(_.methodName.isClassInitializer)) {
+      assert(
+        clazz.jsClassCaptures.isEmpty,
+        s"Illegal class initializer in non-static class ${className.nameString}"
+      )
+      val namespace = MemberNamespace.StaticConstructor
+      fb += wa.Call(
+        genFunctionID.forMethod(namespace, className, ClassInitializerName)
+      )
+    }
+
+    // Final result
+    fb += wa.LocalGet(jsClassLocal)
+
+    fb.buildAndAddToModule()
   }
 
   private def genLoadJSClassFunction(clazz: LinkedClass)(implicit ctx: WasmContext): Unit = {
@@ -1266,8 +1347,7 @@ class ClassEmitter(coreSpec: CoreSpec) {
 
       // Get the JS class and instantiate it
       fb += wa.Call(genFunctionID.loadJSClass(className))
-      fb += wa.Call(genFunctionID.jsNewArray)
-      fb += wa.Call(genFunctionID.jsNew)
+      fb += wa.Call(genFunctionID.jsNewNoArg)
 
       // Store and return the result
       fb += wa.GlobalSet(cacheGlobalID)
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
index b160acba44..d74aa2d810 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
@@ -29,6 +29,7 @@ import org.scalajs.linker.backend.webassembly.Types._
 
 import EmbeddedConstants._
 import VarGen._
+import SWasmGen._
 import TypeTransformer._
 
 final class CoreWasmLib(coreSpec: CoreSpec, globalInfo: LinkedGlobalInfo) {
@@ -314,7 +315,6 @@ final class CoreWasmLib(coreSpec: CoreSpec, globalInfo: LinkedGlobalInfo) {
     addGlobalHelperImport(genGlobalID.undef, RefType.any)
     addGlobalHelperImport(genGlobalID.bFalse, RefType.any)
     addGlobalHelperImport(genGlobalID.bTrue, RefType.any)
-    addGlobalHelperImport(genGlobalID.bZero, RefType.any)
     addGlobalHelperImport(genGlobalID.emptyString, RefType.extern)
     addGlobalHelperImport(genGlobalID.idHashCodeMap, RefType.extern)
   }
@@ -379,34 +379,6 @@ final class CoreWasmLib(coreSpec: CoreSpec, globalInfo: LinkedGlobalInfo) {
 
     addHelperImport(genFunctionID.fmod, List(Float64, Float64), List(Float64))
 
-    addHelperImport(
-      genFunctionID.closure,
-      List(RefType.func, anyref),
-      List(RefType.any)
-    )
-    addHelperImport(
-      genFunctionID.closureThis,
-      List(RefType.func, anyref),
-      List(RefType.any)
-    )
-    addHelperImport(
-      genFunctionID.closureRest,
-      List(RefType.func, anyref, Int32),
-      List(RefType.any)
-    )
-    addHelperImport(
-      genFunctionID.closureThisRest,
-      List(RefType.func, anyref, Int32),
-      List(RefType.any)
-    )
-
-    addHelperImport(genFunctionID.makeExportedDef, List(RefType.func), List(RefType.any))
-    addHelperImport(
-      genFunctionID.makeExportedDefRest,
-      List(RefType.func, Int32),
-      List(RefType.any)
-    )
-
     addHelperImport(genFunctionID.jsValueToString, List(RefType.any), List(RefType.extern))
     addHelperImport(genFunctionID.jsValueToStringForConcat, List(anyref), List(RefType.extern))
     addHelperImport(genFunctionID.booleanToString, List(Int32), List(RefType.extern))
@@ -435,83 +407,18 @@ final class CoreWasmLib(coreSpec: CoreSpec, globalInfo: LinkedGlobalInfo) {
 
     addHelperImport(genFunctionID.makeTypeError, List(RefType.extern), List(RefType.extern))
 
-    addHelperImport(genFunctionID.jsGlobalRefGet, List(RefType.extern), List(anyref))
-    addHelperImport(genFunctionID.jsGlobalRefSet, List(RefType.extern, anyref), Nil)
-    addHelperImport(genFunctionID.jsGlobalRefTypeof, List(RefType.extern), List(RefType.any))
     addHelperImport(genFunctionID.jsNewArray, Nil, List(RefType.any))
-    addHelperImport(genFunctionID.jsArrayPush, List(RefType.any, anyref), List(RefType.any))
-    addHelperImport(
-      genFunctionID.jsArraySpreadPush,
-      List(RefType.any, anyref),
-      List(RefType.any)
-    )
     addHelperImport(genFunctionID.jsNewObject, Nil, List(RefType.any))
-    addHelperImport(
-      genFunctionID.jsObjectPush,
-      List(RefType.any, anyref, anyref),
-      List(RefType.any)
-    )
     addHelperImport(genFunctionID.jsSelect, List(anyref, anyref), List(anyref))
     addHelperImport(genFunctionID.jsSelectSet, List(anyref, anyref, anyref), Nil)
-    addHelperImport(genFunctionID.jsNew, List(anyref, anyref), List(anyref))
-    addHelperImport(genFunctionID.jsFunctionApply, List(anyref, anyref), List(anyref))
-    addHelperImport(
-      genFunctionID.jsMethodApply,
-      List(anyref, anyref, anyref),
-      List(anyref)
-    )
+    addHelperImport(genFunctionID.jsNewNoArg, List(anyref), List(anyref))
     addHelperImport(genFunctionID.jsImportCall, List(anyref), List(anyref))
     addHelperImport(genFunctionID.jsImportMeta, Nil, List(anyref))
     addHelperImport(genFunctionID.jsDelete, List(anyref, anyref), Nil)
     addHelperImport(genFunctionID.jsForInSimple, List(anyref, anyref), Nil)
     addHelperImport(genFunctionID.jsIsTruthy, List(anyref), List(Int32))
 
-    for ((op, funcID) <- genFunctionID.jsUnaryOps)
-      addHelperImport(funcID, List(anyref), List(anyref))
-
-    for ((op, funcID) <- genFunctionID.jsBinaryOps) {
-      val resultType =
-        if (op == JSBinaryOp.=== || op == JSBinaryOp.!==) Int32
-        else anyref
-      addHelperImport(funcID, List(anyref, anyref), List(resultType))
-    }
-
     addHelperImport(genFunctionID.newSymbol, Nil, List(anyref))
-    addHelperImport(
-      genFunctionID.createJSClass,
-      List(anyref, anyref, RefType.func, RefType.func, RefType.func, anyref),
-      List(RefType.any)
-    )
-    addHelperImport(
-      genFunctionID.createJSClassRest,
-      List(anyref, anyref, RefType.func, RefType.func, RefType.func, anyref, Int32),
-      List(RefType.any)
-    )
-    addHelperImport(
-      genFunctionID.installJSField,
-      List(anyref, anyref, anyref),
-      Nil
-    )
-    addHelperImport(
-      genFunctionID.installJSMethod,
-      List(anyref, anyref, anyref, RefType.func, Int32),
-      Nil
-    )
-    addHelperImport(
-      genFunctionID.installJSStaticMethod,
-      List(anyref, anyref, anyref, RefType.func, Int32),
-      Nil
-    )
-    addHelperImport(
-      genFunctionID.installJSProperty,
-      List(anyref, anyref, anyref, RefType.funcref, RefType.funcref),
-      Nil
-    )
-    addHelperImport(
-      genFunctionID.installJSStaticProperty,
-      List(anyref, anyref, anyref, RefType.funcref, RefType.funcref),
-      Nil
-    )
     addHelperImport(
       genFunctionID.jsSuperSelect,
       List(anyref, anyref, anyref),
@@ -522,11 +429,6 @@ final class CoreWasmLib(coreSpec: CoreSpec, globalInfo: LinkedGlobalInfo) {
       List(anyref, anyref, anyref, anyref),
       Nil
     )
-    addHelperImport(
-      genFunctionID.jsSuperCall,
-      List(anyref, anyref, anyref, anyref),
-      List(anyref)
-    )
   }
 
   // --- Global definitions ---
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CustomJSHelperBuilder.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CustomJSHelperBuilder.scala
new file mode 100644
index 0000000000..194dadd076
--- /dev/null
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CustomJSHelperBuilder.scala
@@ -0,0 +1,284 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package org.scalajs.linker.backend.wasmemitter
+
+import scala.collection.mutable
+
+import org.scalajs.ir.{ClassKind, OriginalName, Position, UTF8String}
+import org.scalajs.ir.Names._
+import org.scalajs.ir.OriginalName.NoOriginalName
+import org.scalajs.ir.Trees._
+import org.scalajs.ir.Types._
+
+import org.scalajs.linker.backend.emitter.{NameGen => JSNameGen}
+
+import org.scalajs.linker.backend.javascript.{Trees => js}
+
+import org.scalajs.linker.backend.webassembly.FunctionBuilder
+import org.scalajs.linker.backend.webassembly.{Instructions => wa}
+import org.scalajs.linker.backend.webassembly.{Modules => wamod}
+import org.scalajs.linker.backend.webassembly.{Identitities => wanme}
+import org.scalajs.linker.backend.webassembly.{Types => watpe}
+
+import EmbeddedConstants._
+import SWasmGen._
+import VarGen._
+import TypeTransformer._
+import WasmContext._
+
+/** Toolkit to build custom JS helpers that take Wasm inputs, while trying to
+ *  optimize them directly as JavaScript trees.
+ *
+ *  The usage scenario for this class is as follows:
+ *
+ *  {{{
+ *  val builder = new CustomJSHelperBuilder()
+ *
+ *  // Add inputs that will be evaluated on the Wasm call site, and whose
+ *  // values are then available as `js.Tree`s in the JS helper:
+ *  val xRef = builder.addWasmInput(watpe.Int32) {
+ *    // Wasm code evaluated at call site
+ *    fb += wa.LocalGet(someLocal)
+ *  }
+ *  ...
+ *
+ *  // Build the body of the helper using the above inputs
+ *  val helperID = builder.build(watpe.Int32) {
+ *    js.Return(js.BinaryOp(JSBinaryOp.+, xRef, js.IntLiteral(5)))
+ *  }
+ *
+ *  // Call the helper, which consumes the declared inputs and leaves the result on the stack
+ *  fb += wa.Call(helperID)
+ *  }}}
+ *
+ *  The subclass [[CustomJSHelperBuilder.WithTreeEval]] provides even richer
+ *  capabilities, by allowing to evaluate arbitrary IR `Tree`s as inputs. The
+ *  builder will optimize the evaluation and transfer from Wasm to JS:
+ *
+ *  - Evaluate some trees entirely on the JS side instead of on the Wasm side.
+ *    This is notably the case for string literals, which commonly appear as
+ *    method names, and global refs/external imports, which commonly appear as
+ *    method receivers.
+ *  - For other trees, evaluate them on the Wasm side, but fuse their boxing
+ *    operation with the Wasm-to-JS interoperability layer, by choosing the
+ *    best possible Wasm type for the helper function.
+ *
+ *  When using the `WithTreeEval` subclass, the user must provide a concrete
+ *  method to evaluate `Tree`s at call site with a given expected type. In the
+ *  context of `FunctionEmitter`, that directly translates to the `genTree`
+ *  method.
+ *
+ *  A typical scenario looks like:
+ *
+ *  {{{
+ *  val builder = new CustomJSHelperBuilder.WithTreeEval() {
+ *    protected def evalTreeAtCallSite(tree: Tree, expectedType: Type): Unit = ???
+ *  }
+ *
+ *  // Add inputs that will be evaluated on the JS side if possible, otherwise
+ *  // evaluated on the Wasm call site, and whose values are then available as
+ *  // `js.Tree`s in the JS helper:
+ *  val xRef = builder.addInput(someIRTree)
+ *  ...
+ *  }}}
+ *
+ *  In addition to the input management, `CustomJSHelperBuilder` provides tools
+ *  for local name management, and generation of `js.ParamDef`s for inner
+ *  functions.
+ */
+class CustomJSHelperBuilder()(implicit ctx: WasmContext, pos: Position) {
+  import CustomJSHelperBuilder._
+
+  private val usedGlobalRefs = mutable.Set.empty[String]
+  private val allocatedLocalIdentResolvers = mutable.ListBuffer.empty[LocalResolver]
+
+  private val jsParamDefs = mutable.ListBuffer.empty[js.ParamDef]
+  private val wasmParamTypes = mutable.ListBuffer.empty[watpe.Type]
+
+  def newLocalIdent(origName: String): js.DelayedIdent = {
+    val resolver = new LocalResolver(origName)
+    allocatedLocalIdentResolvers += resolver
+    js.DelayedIdent(resolver)
+  }
+
+  def newLocalIdent(name: LocalName): js.DelayedIdent =
+    newLocalIdent(ctx.jsNameGen.genName(name))
+
+  private def addParamDef(origName: String, wasmType: watpe.Type): js.VarRef = {
+    val jsParamDef = js.ParamDef(newLocalIdent(origName))
+    jsParamDefs += jsParamDef
+    wasmParamTypes += wasmType
+    jsParamDef.ref
+  }
+
+  /** Adds an input of an arbitrary Wasm type, to be evaluated on the Wasm
+   *  stack.
+   *
+   *  The `evalValue` must add code to the call site context to evaluate the
+   *  value on the Wasm site. It is passed as by-name parameter to show
+   *  intent, but is in fact called immediately.
+   *
+   *  @return
+   *    A `js.VarRef` that can be used in the JS helper to read the input.
+   */
+  def addWasmInput(origName: String, wasmType: watpe.Type)(evalValue: => Unit): js.VarRef = {
+    evalValue
+    addParamDef(origName, wasmType)
+  }
+
+  def genGlobalRef(name: String): js.VarRef = {
+    usedGlobalRefs += name
+    js.VarRef(js.Ident(name))
+  }
+
+  def genJSNativeLoadSpec(jsNativeLoadSpec: JSNativeLoadSpec): js.Tree = {
+    def genFollowPath(owner: js.Tree, path: List[String]): js.Tree = {
+      path.foldLeft(owner) { (owner, item) =>
+        js.BracketSelect.makeOptimized(owner, js.StringLiteral(item))
+      }
+    }
+
+    jsNativeLoadSpec match {
+      case JSNativeLoadSpec.Global(globalRef, path) =>
+        genFollowPath(genGlobalRef(globalRef), path)
+      case JSNativeLoadSpec.Import(module, path) =>
+        genFollowPath(js.VarRef(js.Ident("imported" + JSNameGen.genModuleName(module))), path)
+      case JSNativeLoadSpec.ImportWithGlobalFallback(importSpec, _) =>
+        genJSNativeLoadSpec(importSpec)
+    }
+  }
+
+  def genJSParamDef(param: ParamDef): js.ParamDef =
+    js.ParamDef(newLocalIdent(param.name.name))
+
+  def genJSParamDefs(params: List[ParamDef],
+      restParam: Option[ParamDef]): (List[js.ParamDef], Option[js.ParamDef]) = {
+    (params.map(genJSParamDef(_)), restParam.map(genJSParamDef(_)))
+  }
+
+  def build(resultType: Type)(body: js.Tree): wanme.FunctionID = {
+    // Allocate names for the local ident resolvers
+    val usedLocalNames = usedGlobalRefs.clone()
+    for (resolver <- allocatedLocalIdentResolvers) {
+      var allocatedName = resolver.origName
+      var index = 0
+      while (!usedLocalNames.add(allocatedName)) {
+        index += 1
+        allocatedName = resolver.origName + index
+      }
+      resolver.setResolved(allocatedName)
+    }
+
+    val helperFun = js.Function(arrow = true, jsParamDefs.toList, None, body)
+    val wasmFunType = watpe.FunctionType(wasmParamTypes.toList, transformResultType(resultType))
+    ctx.addCustomJSHelper(helperFun, wasmFunType)
+  }
+}
+
+object CustomJSHelperBuilder {
+
+  private final class LocalResolver(val origName: String) extends js.DelayedIdent.Resolver {
+    private var resolved: Option[String] = None
+
+    def debugString: String = origName
+
+    def resolve(): String = {
+      resolved.getOrElse {
+        throw new IllegalStateException(s"Local JS ident '$origName' not resolved")
+      }
+    }
+
+    def setResolved(resolved: String): Unit = {
+      if (this.resolved.isDefined)
+        throw new IllegalStateException(s"Local JS ident '$origName' was already resolved")
+      this.resolved = Some(resolved)
+    }
+  }
+
+  abstract class WithTreeEval()(implicit ctx: WasmContext, pos: Position) extends CustomJSHelperBuilder {
+    /** Evaluates an arbitrary `Tree` with the given expected type and puts it
+     *  on the call site's stack.
+     *
+     *  Concrete subclasses must implement this method to evaluate trees in
+     *  their own call site context.
+     *
+     *  The given `tree` is guaranteed to be none of:
+     *
+     *  - `JSGlobalRef`
+     *  - `LoadJSConstructor` for a native JS class
+     *  - `LoadJSModule` for a native JS module class
+     *  - `SelectJSNativeMember`
+     */
+    protected def evalTreeAtCallSite(tree: Tree, expectedType: Type): Unit
+
+    def addInput(tree: TreeOrJSSpread): js.Tree = {
+      tree match {
+        case JSSpread(items) =>
+          js.Spread(addInput(items))
+
+        // Literals that we can directly constant-fold into the JS code
+        case Undefined()           => js.Undefined()
+        case Null()                => js.Null()
+        case BooleanLiteral(value) => js.BooleanLiteral(value)
+        case ByteLiteral(value)    => js.IntLiteral(value)
+        case ShortLiteral(value)   => js.IntLiteral(value)
+        case IntLiteral(value)     => js.IntLiteral(value)
+        case FloatLiteral(value)   => js.DoubleLiteral(value)
+        case DoubleLiteral(value)  => js.DoubleLiteral(value)
+        case StringLiteral(value)  => js.StringLiteral(value)
+
+        // Global refs and native load specs
+        case JSGlobalRef(name) =>
+          genGlobalRef(name)
+        case LoadJSConstructor(ClassNameWithJSNativeLoadSpec(jsNativeLoadSpec)) =>
+          genJSNativeLoadSpec(jsNativeLoadSpec)
+        case LoadJSModule(ClassNameWithJSNativeLoadSpec(jsNativeLoadSpec)) =>
+          genJSNativeLoadSpec(jsNativeLoadSpec)
+        case SelectJSNativeMember(className, MethodIdent(memberName)) =>
+          genJSNativeLoadSpec(ctx.getClassInfo(className).jsNativeMembers.getOrElse(memberName, {
+            throw new AssertionError(
+                s"Found $tree for non-existing JS native member at ${tree.pos}")
+          }))
+
+        // Other trees, which must be evaluated at the call site
+        case arg: Tree =>
+          def addInputAsType(expectedType: Type): js.Tree = {
+            addWasmInput("x", transformParamType(expectedType)) {
+              evalTreeAtCallSite(arg, expectedType)
+            }
+          }
+
+          arg.tpe match {
+            case BooleanType =>
+              // Pass in an i32; convert to boolean in the JS code
+              val input = addInputAsType(BooleanType)
+              js.BinaryOp(JSBinaryOp.!==, input, js.IntLiteral(0))
+
+            case CharType | LongType =>
+              // Box on the Wasm side; pass in an anyref
+              addInputAsType(AnyType)
+
+            case argTpe =>
+              // For all other types, we can rely on the Wasm-to-JS type conversions
+              addInputAsType(argTpe)
+          }
+      }
+    }
+  }
+
+  private object ClassNameWithJSNativeLoadSpec {
+    def unapply(className: ClassName)(implicit ctx: WasmContext): Option[JSNativeLoadSpec] =
+      ctx.getClassInfo(className).jsNativeLoadSpec
+  }
+
+}
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala
index 60fd3178d5..fcbe987f50 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala
@@ -25,7 +25,7 @@ import org.scalajs.linker.interface.unstable._
 import org.scalajs.linker.standard._
 import org.scalajs.linker.standard.ModuleSet.ModuleID
 
-import org.scalajs.linker.backend.emitter.PrivateLibHolder
+import org.scalajs.linker.backend.emitter.{NameGen => JSNameGen, PrivateLibHolder}
 
 import org.scalajs.linker.backend.javascript.Printers.JSTreePrinter
 import org.scalajs.linker.backend.javascript.{Trees => js}
@@ -55,14 +55,15 @@ final class Emitter(config: Emitter.Config) {
   val injectedIRFiles: Seq[IRFile] = PrivateLibHolder.files
 
   def emit(module: ModuleSet.Module, globalInfo: LinkedGlobalInfo, logger: Logger): Result = {
-    val wasmModule = emitWasmModule(module, globalInfo)
+    val (wasmModule, jsFileContentInfo) = emitWasmModule(module, globalInfo)
     val loaderContent = LoaderContent.bytesContent
-    val jsFileContent = buildJSFileContent(module)
+    val jsFileContent = buildJSFileContent(module, jsFileContentInfo)
 
     new Result(wasmModule, loaderContent, jsFileContent)
   }
 
-  private def emitWasmModule(module: ModuleSet.Module, globalInfo: LinkedGlobalInfo): wamod.Module = {
+  private def emitWasmModule(module: ModuleSet.Module,
+      globalInfo: LinkedGlobalInfo): (wamod.Module, JSFileContentInfo) = {
     // Inject the derived linked classes
     val allClasses =
       DerivedClasses.deriveClasses(module.classDefs) ::: module.classDefs
@@ -85,7 +86,6 @@ final class Emitter(config: Emitter.Config) {
       Preprocessor.preprocess(coreSpec, coreLib, sortedClasses, topLevelExports)
 
     coreLib.genPreClasses()
-    genExternalModuleImports(module)
     sortedClasses.foreach(classEmitter.genClassDef(_))
     topLevelExports.foreach(classEmitter.genTopLevelExport(_))
     classEmitter.genGlobalArrayClassItable()
@@ -99,26 +99,13 @@ final class Emitter(config: Emitter.Config) {
     ctx.stringPool.genPool()
     genDeclarativeElements()
 
-    ctx.moduleBuilder.build()
-  }
+    val wasmModule = ctx.moduleBuilder.build()
 
-  private def genExternalModuleImports(module: ModuleSet.Module)(
-      implicit ctx: WasmContext): Unit = {
-    // Sort for stability
-    val allImportedModules = module.externalDependencies.toList.sorted
-
-    // Gen imports of external modules on the Wasm side
-    for (moduleName <- allImportedModules) {
-      val id = genGlobalID.forImportedModule(moduleName)
-      val origName = OriginalName("import." + moduleName)
-      ctx.moduleBuilder.addImport(
-        wamod.Import(
-          "__scalaJSImports",
-          moduleName,
-          wamod.ImportDesc.Global(id, origName, isMutable = false, watpe.RefType.anyref)
-        )
-      )
-    }
+    val jsFileContentInfo = new JSFileContentInfo(
+      customJSHelpers = ctx.getAllCustomJSHelpers()
+    )
+
+    (wasmModule, jsFileContentInfo)
   }
 
   private def genStartFunction(
@@ -168,13 +155,7 @@ final class Emitter(config: Emitter.Config) {
         case TopLevelModuleExportDef(_, exportName) =>
           fb += wa.Call(genFunctionID.loadModule(tle.owningClass))
         case TopLevelMethodExportDef(_, methodDef) =>
-          fb += ctx.refFuncWithDeclaration(genFunctionID.forExport(tle.exportName))
-          if (methodDef.restParam.isDefined) {
-            fb += wa.I32Const(methodDef.args.size)
-            fb += wa.Call(genFunctionID.makeExportedDefRest)
-          } else {
-            fb += wa.Call(genFunctionID.makeExportedDef)
-          }
+          genTopLevelExportedFun(fb, tle.exportName, methodDef)
         case TopLevelFieldExportDef(_, _, fieldIdent) =>
           /* Usually redundant, but necessary if the static field is never
            * explicitly set and keeps its default (zero) value instead. In that
@@ -218,6 +199,38 @@ final class Emitter(config: Emitter.Config) {
     ctx.moduleBuilder.setStart(genFunctionID.start)
   }
 
+  private def genTopLevelExportedFun(fb: FunctionBuilder, exportName: String,
+      methodDef: org.scalajs.ir.Trees.JSMethodDef)(
+      implicit ctx: WasmContext): Unit = {
+
+    import org.scalajs.ir.Trees._
+
+    val JSMethodDef(_, _, params, restParam, _) = methodDef
+
+    implicit val pos = methodDef.pos
+
+    val builder = new CustomJSHelperBuilder()
+
+    val fRef = builder.addWasmInput("f", watpe.RefType.func) {
+      fb += ctx.refFuncWithDeclaration(genFunctionID.forExport(exportName))
+    }
+
+    val helperID = builder.build(AnyNotNullType) {
+      js.Return {
+        val (argsParamDefs, restParamDef) = builder.genJSParamDefs(params, restParam)
+        // Exported defs must be `function`s although they do not use their `this`
+        js.Function(arrow = false, argsParamDefs, restParamDef, {
+          js.Return(js.Apply(
+              fRef,
+              argsParamDefs.map(_.ref) ::: restParamDef.map(_.ref).toList
+          ))
+        })
+      }
+    }
+
+    fb += wa.Call(helperID)
+  }
+
   private def genDeclarativeElements()(implicit ctx: WasmContext): Unit = {
     // Aggregated Elements
 
@@ -241,7 +254,9 @@ final class Emitter(config: Emitter.Config) {
     }
   }
 
-  private def buildJSFileContent(module: ModuleSet.Module): Array[Byte] = {
+  private def buildJSFileContent(module: ModuleSet.Module,
+      info: JSFileContentInfo): Array[Byte] = {
+
     implicit val noPos = Position.NoPosition
 
     // Linking info
@@ -266,17 +281,15 @@ final class Emitter(config: Emitter.Config) {
     // Sort for stability
     val importedModules = module.externalDependencies.toList.sorted
 
-    val (moduleImports, importedModulesItems) = (for {
-      (moduleName, idx) <- importedModules.zipWithIndex
-    } yield {
-      val importIdent = js.Ident(s"imported$idx")
+    // External imports
+
+    val moduleImports = for (moduleName <- importedModules) yield {
+      val importIdent = js.Ident("imported" + JSNameGen.genModuleName(moduleName))
       val moduleNameStr = js.StringLiteral(moduleName)
-      val moduleImport = js.ImportNamespace(importIdent, moduleNameStr)
-      val item = moduleNameStr -> js.VarRef(importIdent)
-      (moduleImport, item)
-    }).unzip
+      js.ImportNamespace(importIdent, moduleNameStr)
+    }
 
-    val importedModulesDict = js.ObjectConstr(importedModulesItems)
+    // Exports
 
     val (exportDecls, exportSettersItems) = (for {
       exportName <- module.topLevelExports.map(_.exportName)
@@ -294,6 +307,15 @@ final class Emitter(config: Emitter.Config) {
 
     val exportSettersDict = js.ObjectConstr(exportSettersItems)
 
+    // Custom JS helpers
+
+    val customJSHelpersItems = for ((importName, jsFunction) <- info.customJSHelpers) yield {
+      js.StringLiteral(importName) -> jsFunction
+    }
+    val customJSHelpersDict = js.ObjectConstr(customJSHelpersItems)
+
+    // Overall structure of the result
+
     val loadFunIdent = js.Ident("__load")
     val loaderImport = js.Import(
       List(js.ExportName("load") -> loadFunIdent),
@@ -305,8 +327,8 @@ final class Emitter(config: Emitter.Config) {
       List(
         js.StringLiteral(config.internalWasmFileURIPattern(module.id)),
         linkingInfo,
-        importedModulesDict,
-        exportSettersDict
+        exportSettersDict,
+        customJSHelpersDict
       )
     )
 
@@ -364,6 +386,11 @@ object Emitter {
       new Config(coreSpec, loaderModuleName)
   }
 
+  private final class JSFileContentInfo(
+      /** Custom JS helpers to generate: pairs of `(importName, jsFunction)`. */
+      val customJSHelpers: List[(String, js.Function)]
+  )
+
   final class Result(
       val wasmModule: wamod.Module,
       val loaderContent: Array[Byte],
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
index d0e7d504dd..051fd64887 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
@@ -31,6 +31,8 @@ import org.scalajs.linker.backend.webassembly.{Identitities => wanme}
 import org.scalajs.linker.backend.webassembly.{Types => watpe}
 import org.scalajs.linker.backend.webassembly.Types.{FunctionType => Sig}
 
+import org.scalajs.linker.backend.javascript.{Trees => js}
+
 import EmbeddedConstants._
 import SWasmGen._
 import VarGen._
@@ -672,6 +674,8 @@ private class FunctionEmitter private (
   private def genAssign(tree: Assign): Type = {
     val Assign(lhs, rhs) = tree
 
+    implicit val pos = tree.pos
+
     lhs match {
       case Select(qualifier, field) =>
         val className = field.name.className
@@ -768,11 +772,10 @@ private class FunctionEmitter private (
         fb += wa.Call(genFunctionID.jsSelectSet)
 
       case JSSelect(qualifier, item) =>
-        genTree(qualifier, AnyType)
-        genTree(item, AnyType)
-        genTree(rhs, AnyType)
-        markPosition(tree)
-        fb += wa.Call(genFunctionID.jsSelectSet)
+        genThroughCustomJSHelper(List(qualifier, item, rhs), NoType) { allJSArgs =>
+          val List(jsQualifier, jsItem, jsRhs) = allJSArgs
+          js.Assign(js.BracketSelect.makeOptimized(jsQualifier, jsItem), jsRhs)
+        }
 
       case JSSuperSelect(superClass, receiver, item) =>
         genTree(superClass, AnyType)
@@ -782,12 +785,14 @@ private class FunctionEmitter private (
         markPosition(tree)
         fb += wa.Call(genFunctionID.jsSuperSelectSet)
 
-      case JSGlobalRef(name) =>
-        markPosition(tree)
-        fb ++= ctx.stringPool.getConstantStringInstr(name)
-        genTree(rhs, AnyType)
+      case lhs @ JSGlobalRef(name) =>
+        val builder = new CustomJSHelperBuilderWithTreeSupport()
+        val rhsRef = builder.addInput(rhs)
+        val helperID = builder.build(NoType) {
+          js.Assign(builder.genGlobalRef(name), rhsRef)
+        }
         markPosition(tree)
-        fb += wa.Call(genFunctionID.jsGlobalRefSet)
+        fb += wa.Call(helperID)
 
       case VarRef(LocalIdent(name)) =>
         genTree(rhs, lhs.tpe)
@@ -2700,42 +2705,45 @@ private class FunctionEmitter private (
   private def genJSNew(tree: JSNew): Type = {
     val JSNew(ctor, args) = tree
 
-    genTree(ctor, AnyType)
-    genJSArgsArray(args)
-    markPosition(tree)
-    fb += wa.Call(genFunctionID.jsNew)
-    AnyType
+    implicit val pos = tree.pos
+
+    genThroughCustomJSHelper(ctor :: args) { allJSArgs =>
+      val jsCtor :: jsArgs = allJSArgs
+      js.Return(js.New(jsCtor, jsArgs))
+    }
   }
 
   private def genJSSelect(tree: JSSelect): Type = {
     val JSSelect(qualifier, item) = tree
 
-    genTree(qualifier, AnyType)
-    genTree(item, AnyType)
-    markPosition(tree)
-    fb += wa.Call(genFunctionID.jsSelect)
-    AnyType
+    implicit val pos = tree.pos
+
+    genThroughCustomJSHelper(List(qualifier, item)) { allJSArgs =>
+      val List(jsQualifier, jsItem) = allJSArgs
+      js.Return(js.BracketSelect.makeOptimized(jsQualifier, jsItem))
+    }
   }
 
   private def genJSFunctionApply(tree: JSFunctionApply): Type = {
     val JSFunctionApply(fun, args) = tree
 
-    genTree(fun, AnyType)
-    genJSArgsArray(args)
-    markPosition(tree)
-    fb += wa.Call(genFunctionID.jsFunctionApply)
-    AnyType
+    implicit val pos = tree.pos
+
+    genThroughCustomJSHelper(fun :: args) { allJSArgs =>
+      val jsFun :: jsArgs = allJSArgs
+      js.Return(js.Apply.makeProtected(jsFun, jsArgs))
+    }
   }
 
   private def genJSMethodApply(tree: JSMethodApply): Type = {
     val JSMethodApply(receiver, method, args) = tree
 
-    genTree(receiver, AnyType)
-    genTree(method, AnyType)
-    genJSArgsArray(args)
-    markPosition(tree)
-    fb += wa.Call(genFunctionID.jsMethodApply)
-    AnyType
+    implicit val pos = tree.pos
+
+    genThroughCustomJSHelper(receiver :: method :: args) { allJSArgs =>
+      val jsReceiver :: jsMethod :: jsArgs = allJSArgs
+      js.Return(js.Apply(js.BracketSelect.makeOptimized(jsReceiver, jsMethod), jsArgs))
+    }
   }
 
   private def genJSImportCall(tree: JSImportCall): Type = {
@@ -2757,7 +2765,15 @@ private class FunctionEmitter private (
     val LoadJSConstructor(className) = tree
 
     markPosition(tree)
-    SWasmGen.genLoadJSConstructor(fb, className)
+
+    ctx.getClassInfo(className).jsNativeLoadSpec match {
+      case Some(loadSpec) =>
+        genLoadJSFromSpec(loadSpec)(tree.pos)
+      case None =>
+        // This is a non-native JS class
+        fb += wa.Call(genFunctionID.loadJSClass(className))
+    }
+
     AnyType
   }
 
@@ -2768,7 +2784,7 @@ private class FunctionEmitter private (
 
     ctx.getClassInfo(className).jsNativeLoadSpec match {
       case Some(loadSpec) =>
-        genLoadJSFromSpec(fb, loadSpec)
+        genLoadJSFromSpec(loadSpec)(tree.pos)
       case None =>
         // This is a non-native JS module
         fb += wa.Call(genFunctionID.loadModule(className))
@@ -2785,11 +2801,23 @@ private class FunctionEmitter private (
       throw new AssertionError(
           s"Found $tree for non-existing JS native member at ${tree.pos}")
     })
-    markPosition(tree)
-    genLoadJSFromSpec(fb, jsNativeLoadSpec)
+    genLoadJSFromSpec(jsNativeLoadSpec)(tree.pos)
     AnyType
   }
 
+  private def genLoadJSFromSpec(jsNativeLoadSpec: JSNativeLoadSpec)(
+      implicit pos: Position): Unit = {
+
+    val builder = new CustomJSHelperBuilder()
+    val result = builder.genJSNativeLoadSpec(jsNativeLoadSpec)
+    val helperID = builder.build(AnyType) {
+      js.Return(result)
+    }
+
+    markPosition(pos)
+    fb += wa.Call(helperID)
+  }
+
   private def genJSDelete(tree: JSDelete): Type = {
     val JSDelete(qualifier, item) = tree
 
@@ -2803,10 +2831,24 @@ private class FunctionEmitter private (
   private def genJSUnaryOp(tree: JSUnaryOp): Type = {
     val JSUnaryOp(op, lhs) = tree
 
-    genTree(lhs, AnyType)
-    markPosition(tree)
-    fb += wa.Call(genFunctionID.jsUnaryOps(op))
-    AnyType
+    implicit val pos = tree.pos
+
+    genThroughCustomJSHelper(List(lhs), tree.tpe) { allJSArgs =>
+      val List(jsLhs) = allJSArgs
+
+      val protectedLhs = if (op == JSUnaryOp.typeof && lhs.isInstanceOf[JSGlobalRef]) {
+        /* #3822 We protect the argument so that it throws a ReferenceError
+         * if the global variable is not defined at all, as specified.
+         */
+        js.Block(js.IntLiteral(0), jsLhs)
+      } else {
+        jsLhs
+      }
+
+      js.Return(js.UnaryOp(op, protectedLhs))
+    }
+
+    tree.tpe
   }
 
   private def genJSBinaryOp(tree: JSBinaryOp): Type = {
@@ -2839,10 +2881,12 @@ private class FunctionEmitter private (
         }
 
       case _ =>
-        genTree(lhs, AnyType)
-        genTree(rhs, AnyType)
-        markPosition(tree)
-        fb += wa.Call(genFunctionID.jsBinaryOps(op))
+        implicit val pos = tree.pos
+
+        genThroughCustomJSHelper(List(lhs, rhs), tree.tpe) { allJSArgs =>
+          val List(jsLhs, jsRhs) = allJSArgs
+          js.Return(js.BinaryOp(op, jsLhs, jsRhs))
+        }
     }
 
     tree.tpe
@@ -2851,54 +2895,73 @@ private class FunctionEmitter private (
   private def genJSArrayConstr(tree: JSArrayConstr): Type = {
     val JSArrayConstr(items) = tree
 
-    markPosition(tree)
-    genJSArgsArray(items)
-    AnyType
+    implicit val pos = tree.pos
+
+    if (items.isEmpty) {
+      markPosition(tree)
+      fb += wa.Call(genFunctionID.jsNewArray)
+      AnyType
+    } else {
+      genThroughCustomJSHelper(items, AnyNotNullType) { jsItems =>
+        js.Return(js.ArrayConstr(jsItems))
+      }
+    }
   }
 
   private def genJSObjectConstr(tree: JSObjectConstr): Type = {
     val JSObjectConstr(fields) = tree
 
-    markPosition(tree)
-    fb += wa.Call(genFunctionID.jsNewObject)
-    for ((prop, value) <- fields) {
-      genTree(prop, AnyType)
-      genTree(value, AnyType)
-      fb += wa.Call(genFunctionID.jsObjectPush)
+    implicit val pos = tree.pos
+
+    if (fields.isEmpty) {
+      markPosition(tree)
+      fb += wa.Call(genFunctionID.jsNewObject)
+      AnyType
+    } else {
+      val flatPropValues = fields.flatMap(pv => List(pv._1, pv._2))
+
+      genThroughCustomJSHelper(flatPropValues, AnyNotNullType) { jsFlatPropValues =>
+        val jsPropValuesIter = jsFlatPropValues.grouped(2).map { pvList =>
+          val List(jsPropTree, jsValue) = pvList
+          val jsProp: js.PropertyName = jsPropTree match {
+            case jsPropTree: js.StringLiteral => jsPropTree
+            case _                            => js.ComputedName(jsPropTree)
+          }
+          jsProp -> jsValue
+        }
+        js.Return(js.ObjectConstr(jsPropValuesIter.toList))
+      }
     }
-    AnyType
   }
 
   private def genJSGlobalRef(tree: JSGlobalRef): Type = {
     val JSGlobalRef(name) = tree
 
-    markPosition(tree)
-    fb ++= ctx.stringPool.getConstantStringInstr(name)
-    fb += wa.Call(genFunctionID.jsGlobalRefGet)
+    implicit val pos = tree.pos
+
+    val builder = new CustomJSHelperBuilder()
+    val helperID = builder.build(AnyType) {
+      js.Return(builder.genGlobalRef(name))
+    }
+
+    markPosition(pos)
+    fb += wa.Call(helperID)
     AnyType
   }
 
   private def genJSTypeOfGlobalRef(tree: JSTypeOfGlobalRef): Type = {
     val JSTypeOfGlobalRef(JSGlobalRef(name)) = tree
 
-    markPosition(tree)
-    fb ++= ctx.stringPool.getConstantStringInstr(name)
-    fb += wa.Call(genFunctionID.jsGlobalRefTypeof)
-    AnyType
-  }
+    implicit val pos = tree.pos
 
-  private def genJSArgsArray(args: List[TreeOrJSSpread]): Unit = {
-    fb += wa.Call(genFunctionID.jsNewArray)
-    for (arg <- args) {
-      arg match {
-        case arg: Tree =>
-          genTree(arg, AnyType)
-          fb += wa.Call(genFunctionID.jsArrayPush)
-        case JSSpread(items) =>
-          genTree(items, AnyType)
-          fb += wa.Call(genFunctionID.jsArraySpreadPush)
-      }
+    val builder = new CustomJSHelperBuilder()
+    val helperID = builder.build(AnyType) {
+      js.Return(js.UnaryOp(JSUnaryOp.typeof, builder.genGlobalRef(name)))
     }
+
+    markPosition(pos)
+    fb += wa.Call(helperID)
+    AnyType
   }
 
   private def genJSLinkingInfo(tree: JSLinkingInfo): Type = {
@@ -3077,8 +3140,8 @@ private class FunctionEmitter private (
   private def genClosure(tree: Closure): Type = {
     val Closure(arrow, captureParams, params, restParam, body, captureValues) = tree
 
-    val hasThis = !arrow
-    val hasRestParam = restParam.isDefined
+    implicit val pos = tree.pos
+
     val dataStructTypeID = ctx.getClosureDataStructType(captureParams.map(_.ptpe))
 
     // Define the function where captures are reified as a `__captureData` argument.
@@ -3089,40 +3152,45 @@ private class FunctionEmitter private (
       closureFuncOrigName,
       enclosingClassName = None,
       Some(captureParams),
-      receiverType = if (!hasThis) None else Some(watpe.RefType.anyref),
+      receiverType = if (arrow) None else Some(watpe.RefType.anyref),
       params,
       restParam,
       body,
       resultType = AnyType
-    )(ctx, tree.pos)
-
-    markPosition(tree)
-
-    // Put a reference to the function on the stack
-    fb += ctx.refFuncWithDeclaration(closureFuncID)
+    )
 
-    // Evaluate the capture values and instantiate the capture data struct
-    for ((param, value) <- captureParams.zip(captureValues))
-      genTree(value, param.ptpe)
-    markPosition(tree)
-    fb += wa.StructNew(dataStructTypeID)
+    val builder = new CustomJSHelperBuilder()
 
-    /* If there is a ...rest param, the helper requires as third argument the
-     * number of regular arguments.
-     */
-    if (hasRestParam)
-      fb += wa.I32Const(params.size)
+    val fRef = builder.addWasmInput("f", watpe.RefType.func) {
+      markPosition(tree)
+      fb += ctx.refFuncWithDeclaration(closureFuncID)
+    }
+    val dataRef = builder.addWasmInput("d", watpe.RefType(dataStructTypeID)) {
+      for ((param, value) <- captureParams.zip(captureValues))
+        genTree(value, param.ptpe)
+      markPosition(tree)
+      fb += wa.StructNew(dataStructTypeID)
+    }
 
-    // Call the appropriate helper
-    val helper = (hasThis, hasRestParam) match {
-      case (false, false) => genFunctionID.closure
-      case (true, false)  => genFunctionID.closureThis
-      case (false, true)  => genFunctionID.closureRest
-      case (true, true)   => genFunctionID.closureThisRest
+    val helperID = builder.build(AnyNotNullType) {
+      js.Return {
+        val (argsParamDefs, restParamDef) = builder.genJSParamDefs(params, restParam)
+        js.Function(arrow, argsParamDefs, restParamDef, {
+          js.Return(js.Apply(
+              fRef,
+              dataRef ::
+              (if (arrow) Nil else List(js.This())) :::
+              argsParamDefs.map(_.ref) :::
+              restParamDef.map(_.ref).toList
+          ))
+        })
+      }
     }
-    fb += wa.Call(helper)
 
-    AnyType
+    markPosition(tree)
+    fb += wa.Call(helperID)
+
+    AnyNotNullType
   }
 
   private def genClone(tree: Clone): Type = {
@@ -3276,16 +3344,25 @@ private class FunctionEmitter private (
   private def genJSSuperMethodCall(tree: JSSuperMethodCall): Type = {
     val JSSuperMethodCall(superClass, receiver, method, args) = tree
 
-    genTree(superClass, AnyType)
-    genTree(receiver, AnyType)
-    genTree(method, AnyType)
-    genJSArgsArray(args)
-
-    markPosition(tree)
-
-    fb += wa.Call(genFunctionID.jsSuperCall)
-
-    AnyType
+    implicit val pos = tree.pos
+
+    genThroughCustomJSHelper(superClass :: receiver :: method :: args) { allJSArgs =>
+      val jsSuperClass :: jsReceiver :: jsMethod :: jsArgs = allJSArgs
+
+      // return superClass.prototype[method].call(receiver, ...args);
+      js.Return(
+        js.Apply(
+          js.DotSelect(
+            js.BracketSelect.makeOptimized(
+              js.DotSelect(jsSuperClass, js.Ident("prototype")),
+              jsMethod
+            ),
+            js.Ident("call")
+          ),
+          jsReceiver :: jsArgs
+        )
+      )
+    }
   }
 
   private def genJSNewTarget(tree: JSNewTarget): Type = {
@@ -3449,6 +3526,48 @@ private class FunctionEmitter private (
     NoType
   }
 
+  // Helpers to generate code going through custom JS helpers
+
+  /** Generates code with a custom JS helper based on Tree inputs.
+   *
+   *  Logically, the following steps happen:
+   *
+   *  1. Generates Wasm code to evaluate the `args`, in order.
+   *  2. Passes the values, converted for use by JavaScript, to a custom JS
+   *     helper whose body is provided by `makeJSHelperBody`.
+   *     `makeJSHelperBody` receives a list of JS trees corresponding to the JS
+   *     evaluated values of `args`.
+   *  3. Leaves the result of `makeJSHelperBody` on the stack, typed as
+   *     `resultType`.
+   *
+   *  Some `args` may be evaluated on the JS side when possible, notably for
+   *  most literals, JS global refs and imports.
+   *
+   *  @see [[CustomJSHelperBuilder]]
+   */
+  private def genThroughCustomJSHelper(args: List[TreeOrJSSpread],
+      resultType: Type = AnyType)(
+      makeJSHelperBody: List[js.Tree] => js.Tree)(
+      implicit pos: Position): Type = {
+
+    val builder = new CustomJSHelperBuilderWithTreeSupport()
+    val jsArgs = args.map(builder.addInput(_))
+    val helperID = builder.build(resultType) {
+      makeJSHelperBody(jsArgs)
+    }
+
+    markPosition(pos)
+    fb += wa.Call(helperID)
+
+    resultType
+  }
+
+  private final class CustomJSHelperBuilderWithTreeSupport()(implicit pos: Position)
+      extends CustomJSHelperBuilder.WithTreeEval {
+    protected def evalTreeAtCallSite(tree: Tree, expectedType: Type): Unit =
+      genTree(tree, expectedType)
+  }
+
   /*--------------------------------------------------------------------*
    * HERE BE DRAGONS --- Handling of TryFinally, Labeled and Return --- *
    *--------------------------------------------------------------------*/
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala
index af81fcd54e..a94e132626 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala
@@ -68,15 +68,6 @@ function superSelectSet(superClass, self, propName, value) {
   throw new TypeError("super has no setter '" + propName + "'.");
 }
 
-function installJSField(instance, name, value) {
-  Object.defineProperty(instance, name, {
-    value,
-    configurable: true,
-    enumerable: true,
-    writable: true,
-  });
-}
-
 const scalaJSHelpers = {
   // JSTag
   JSTag: WebAssembly.JSTag,
@@ -91,7 +82,6 @@ const scalaJSHelpers = {
   // Constant boxes
   bFalse: false,
   bTrue: true,
-  bZero: 0,
 
   // Boxes (upcast) -- most are identity at the JS level but with different types in Wasm
   bIFallback: (x) => x,
@@ -113,16 +103,6 @@ const scalaJSHelpers = {
   // fmod, to implement Float_% and Double_% (it is apparently quite hard to implement fmod otherwise)
   fmod: (x, y) => x % y,
 
-  // Closure
-  closure: (f, data) => f.bind(void 0, data),
-  closureThis: (f, data) => function(...args) { return f(data, this, ...args); },
-  closureRest: (f, data, n) => ((...args) => f(data, ...args.slice(0, n), args.slice(n))),
-  closureThisRest: (f, data, n) => function(...args) { return f(data, this, ...args.slice(0, n), args.slice(n)); },
-
-  // Top-level exported defs -- they must be `function`s but have no actual `this` nor `data`
-  makeExportedDef: (f) => function(...args) { return f(...args); },
-  makeExportedDefRest: (f, n) => function(...args) { return f(...args.slice(0, n), args.slice(n)); },
-
   // Strings
   emptyString: "",
   jsValueToString: (x) => (x === void 0) ? "undefined" : x.toString(),
@@ -170,127 +150,21 @@ const scalaJSHelpers = {
   makeTypeError: (msg) => new TypeError(msg),
 
   // JS interop
-  jsGlobalRefGet: (globalRefName) => (new Function("return " + globalRefName))(),
-  jsGlobalRefSet: (globalRefName, v) => {
-    var argName = globalRefName === 'v' ? 'w' : 'v';
-    (new Function(argName, globalRefName + " = " + argName))(v);
-  },
-  jsGlobalRefTypeof: (globalRefName) => (new Function("return typeof " + globalRefName))(),
   jsNewArray: () => [],
-  jsArrayPush: (a, v) => (a.push(v), a),
-  jsArraySpreadPush: (a, vs) => (a.push(...vs), a),
   jsNewObject: () => ({}),
-  jsObjectPush: (o, p, v) => (o[p] = v, o),
   jsSelect: (o, p) => o[p],
   jsSelectSet: (o, p, v) => o[p] = v,
-  jsNew: (constr, args) => new constr(...args),
-  jsFunctionApply: (f, args) => f(...args),
-  jsMethodApply: (o, m, args) => o[m](...args),
+  jsNewNoArg: (constr) => new constr(),
   jsImportCall: (s) => import(s),
   jsImportMeta: () => import.meta,
   jsDelete: (o, p) => { delete o[p]; },
   jsForInSimple: (o, f) => { for (var k in o) f(k); },
   jsIsTruthy: (x) => !!x,
 
-  // Excruciating list of all the JS operators
-  jsUnaryPlus: (a) => +a,
-  jsUnaryMinus: (a) => -a,
-  jsUnaryTilde: (a) => ~a,
-  jsUnaryBang: (a) => !a,
-  jsUnaryTypeof: (a) => typeof a,
-  jsStrictEquals: (a, b) => a === b,
-  jsNotStrictEquals: (a, b) => a !== b,
-  jsPlus: (a, b) => a + b,
-  jsMinus: (a, b) => a - b,
-  jsTimes: (a, b) => a * b,
-  jsDivide: (a, b) => a / b,
-  jsModulus: (a, b) => a % b,
-  jsBinaryOr: (a, b) => a | b,
-  jsBinaryAnd: (a, b) => a & b,
-  jsBinaryXor: (a, b) => a ^ b,
-  jsShiftLeft: (a, b) => a << b,
-  jsArithmeticShiftRight: (a, b) => a >> b,
-  jsLogicalShiftRight: (a, b) => a >>> b,
-  jsLessThan: (a, b) => a < b,
-  jsLessEqual: (a, b) => a <= b,
-  jsGreaterThan: (a, b) => a > b,
-  jsGreaterEqual: (a, b) => a >= b,
-  jsIn: (a, b) => a in b,
-  jsInstanceof: (a, b) => a instanceof b,
-  jsExponent: (a, b) => a ** b,
-
   // Non-native JS class support
   newSymbol: Symbol,
-  createJSClass: (data, superClass, preSuperStats, superArgs, postSuperStats, fields) => {
-    // fields is an array where even indices are field names and odd indices are initial values
-    return class extends superClass {
-      constructor(...args) {
-        var preSuperEnv = preSuperStats(data, new.target, ...args);
-        super(...superArgs(data, preSuperEnv, new.target, ...args));
-        for (var i = 0; i != fields.length; i = (i + 2) | 0)
-          installJSField(this, fields[i], fields[(i + 1) | 0]);
-        postSuperStats(data, preSuperEnv, new.target, this, ...args);
-      }
-    };
-  },
-  createJSClassRest: (data, superClass, preSuperStats, superArgs, postSuperStats, fields, n) => {
-    // fields is an array where even indices are field names and odd indices are initial values
-    return class extends superClass {
-      constructor(...args) {
-        var fixedArgs = args.slice(0, n);
-        var restArg = args.slice(n);
-        var preSuperEnv = preSuperStats(data, new.target, ...fixedArgs, restArg);
-        super(...superArgs(data, preSuperEnv, new.target, ...fixedArgs, restArg));
-        for (var i = 0; i != fields.length; i = (i + 2) | 0)
-          installJSField(this, fields[i], fields[(i + 1) | 0]);
-        postSuperStats(data, preSuperEnv, new.target, this, ...fixedArgs, restArg);
-      }
-    };
-  },
-  installJSField,
-  installJSMethod: (data, jsClass, name, func, fixedArgCount) => {
-    var closure = fixedArgCount < 0
-      ? (function(...args) { return func(data, this, ...args); })
-      : (function(...args) { return func(data, this, ...args.slice(0, fixedArgCount), args.slice(fixedArgCount))});
-    jsClass.prototype[name] = closure;
-  },
-  installJSStaticMethod: (data, jsClass, name, func, fixedArgCount) => {
-    var closure = fixedArgCount < 0
-      ? (function(...args) { return func(data, ...args); })
-      : (function(...args) { return func(data, ...args.slice(0, fixedArgCount), args.slice(fixedArgCount))});
-    jsClass[name] = closure;
-  },
-  installJSProperty: (data, jsClass, name, getter, setter) => {
-    var getterClosure = getter
-      ? (function() { return getter(data, this) })
-      : (void 0);
-    var setterClosure = setter
-      ? (function(arg) { setter(data, this, arg) })
-      : (void 0);
-    Object.defineProperty(jsClass.prototype, name, {
-      get: getterClosure,
-      set: setterClosure,
-      configurable: true,
-    });
-  },
-  installJSStaticProperty: (data, jsClass, name, getter, setter) => {
-    var getterClosure = getter
-      ? (function() { return getter(data) })
-      : (void 0);
-    var setterClosure = setter
-      ? (function(arg) { setter(data, arg) })
-      : (void 0);
-    Object.defineProperty(jsClass, name, {
-      get: getterClosure,
-      set: setterClosure,
-      configurable: true,
-    });
-  },
   jsSuperSelect: superSelect,
   jsSuperSelectSet: superSelectSet,
-  jsSuperCall: (superClass, receiver, method, args) => {
-    return superClass.prototype[method].apply(receiver, args);
-  },
 }
 
 const stringBuiltinPolyfills = {
@@ -305,7 +179,7 @@ const stringBuiltinPolyfills = {
   equals: (a, b) => a === b,
 };
 
-export async function load(wasmFileURL, linkingInfo, importedModules, exportSetters) {
+export async function load(wasmFileURL, linkingInfo, exportSetters, customJSHelpers) {
   const myScalaJSHelpers = {
     ...scalaJSHelpers,
     jsLinkingInfo: linkingInfo,
@@ -313,8 +187,8 @@ export async function load(wasmFileURL, linkingInfo, importedModules, exportSett
   };
   const importsObj = {
     "__scalaJSHelpers": myScalaJSHelpers,
-    "__scalaJSImports": importedModules,
     "__scalaJSExportSetters": exportSetters,
+    "__scalaJSCustomHelpers": customJSHelpers,
     "wasm:js-string": stringBuiltinPolyfills,
   };
   const options = {
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/README.md b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/README.md
index ecafecc311..4ccd99bdf2 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/README.md
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/README.md
@@ -659,27 +659,57 @@ Other than that, we have:
 
 ### JS operation IR nodes
 
-We use a series of helper JS functions that directly embed the operation semantics.
-For example, `JSMethodApply` is implemented as a call to the following helper:
+For most IR nodes that implement JS operations, we generate dedicated JS helper functions that we call from Wasm.
+For example, a node `JSMethodApply(receiver, method, List(arg1, arg2))` is implemented as a call to a helper that looks like:
 
 ```js
-__scalaJSHelpers: {
-  jsMethodApply: (o, m, args) => o[m](...args),
+__scalaJSCustomHelpers: {
+  "1": (o, m, arg1, arg2) => o[m](arg1, arg2),
 }
 ```
 
-The `args` are passed a JS array, which is built one element at a time, using the following helpers:
+The `receiver`, `method`, `arg1` and `arg2` are, in general, evaluated on the Wasm side and boxed to `any`.
+
+Often, some of the inputs of these nodes are literals, or other trees that can be evaluated on the JS side.
+For example, the `method` is very often a `StringLiteral`.
+The receiver might be a `JSGlobalRef` or `LoadJSModule` to a native JS module.
+
+For other nodes, we have to evaluate them on the Wasm side, but the boxing operation can still often be fused with the built-in Wasm-to-JS interoperability semantics.
+
+For example, consider the following Scala.js source code:
+
+```scala
+val x: Double = ...
+val y: Double = js.Math.cos(x)
+```
+
+At the IR level, the call to `js.Math.cos` looks as follows:
+
+```scala
+AsInstanceOf(
+  JSMethodApply(
+    LoadJSModule("js.Math"),
+    StringLiteral("cos"),
+    List(VarRef("x")(DoubleType))
+  ),
+  DoubleType
+)
+```
+
+We can evaluate the `LoadJSModule` and the `StringLiteral` entirely on the JS side.
+We have to evaluate `x` on the Wasm side, but we can declare the JS helper as taking an `f64`, which will automatically box the value.
+We therefore produce the following JS helper:
 
 ```js
-__scalaJSHelpers: {
-  jsNewArray: () => [],
-  jsArrayPush: (a, v) => (a.push(v), a),
-  jsArraySpreadPush: (a, vs) => (a.push(...vs), a),
+__scalaJSCustomHelpers: {
+  "2": (x) => Math.cos(x),
 }
 ```
 
-This is of course far from being ideal.
-In the future, we will likely want to generate a JS helper for each call site, so that it can be specialized for the method name and shape of argument list.
+and give it the type `[f64] -> [anyref]` at the Wasm level.
+
+So far, we still have to perform the unboxing operation of the result on the Wasm side, as an additional step.
+In the future, we should try to fuse it as well, so that the type of the helper becomes `[f64] -> [f64]`.
 
 ### Closures
 
@@ -692,61 +722,53 @@ It is a reference to a `struct` with values for all the capture params of the IR
 We allocate that struct when creating the `Closure`, then pass it to a JS helper, along with the function reference.
 The JS helper then creates an actual closure from the JS side and returns it to Wasm.
 
-To accomodate the combination of `function`/`=>` and `...rest`/no-rest, we use the following four helpers:
+We generate a dedicated JS helper for each `Closure` node, in order to cater for the particular amount of parameters and to keep things as monomorphic as possible.
+For example, given a `Closure` node taking 2 non-rest parameters, we generate the following helper:
 
 ```js
-__scalaJSHelpers: {
-  closure: (f, data) => f.bind(void 0, data),
-  closureThis: (f, data) => function(...args) { return f(data, this, ...args); },
-  closureRest: (f, data, n) => ((...args) => f(data, ...args.slice(0, n), args.slice(n))),
-  closureThisRest: (f, data, n) => function(...args) { return f(data, this, ...args.slice(0, n), args.slice(n)); },
+__scalaJSCustomHelpers: {
+  "1": (f, data) => (x1, x2) => f(data, x1, x2),
 }
 ```
 
-The `n` parameter is the number of non-rest parameters to the function.
-
-They are imported into Wasm with the following signatures:
-
-```wat
-(import "__scalaJSHelpers" "closure"
-  (func $closure (param (ref func)) (param anyref) (result (ref any))))
-(import "__scalaJSHelpers" "closureThis"
-  (func $closureThis (param (ref func)) (param anyref) (result (ref any))))
-(import "__scalaJSHelpers" "closureRest"
-  (func $closureRest (param (ref func)) (param anyref) (param i32) (result (ref any))))
-(import "__scalaJSHelpers" "closureThisRest"
-  (func $closureThisRest (param (ref func)) (param anyref) (param i32) (result (ref any))))
-```
+and we import it in Wasm with the signature `[(ref func), anyref] -> [(ref any)]`.
 
 ### Non-native JS classes
 
 For non-native JS classes, we take the above approach to another level.
-We use a unique JS helper function to create arbitrary JavaScript classes.
-It reads as follows:
+We generate a dedicated helper for every non-native JS class in the codebase, to define all the fields and methods.
+Like for JS interop IR nodes, we fuse as many inputs (typically the names of fields and methods, as well as the initial values of fields) into the generated JS helpers.
+
+The bodies of the methods, getters and setters call dedicated `ref.func`s.
+They work similarly to `Closure`s, although the `data` is always the same class captures data struct.
+
+The generated constructor then looks as follows:
 
 ```js
-__scalaJSHelpers: {
-  createJSClass: (data, superClass, preSuperStats, superArgs, postSuperStats, fields) => {
-    // fields is an array where even indices are field names and odd indices are initial values
-    return class extends superClass {
-      constructor(...args) {
-        var preSuperEnv = preSuperStats(data, new.target, ...args);
-        super(...superArgs(data, preSuperEnv, new.target, ...args));
-        for (var i = 0; i != fields.length; i = (i + 2) | 0) {
-          Object.defineProperty(this, fields[i], {
-            value: fields[(i + 1) | 0],
-            configurable: true,
-            enumerable: true,
-            writable: true,
-          });
-        }
-        postSuperStats(data, preSuperEnv, new.target, this, ...args);
+__scalaJSCustomHelpers: {
+  createJSClass: (data, superClass, preSuperStats, superArgs, postSuperStats, ...otherStuff) => {
+    class cls extends superClass {
+      constructor(arg1, arg2, ..., argN) {
+        var preSuperEnv = preSuperStats(data, new.target, arg1, arg2, ..., argN);
+        super(...superArgs(data, preSuperEnv, new.target, arg1, arg2, ..., argN));
+        Object.defineProperty(this, "someField", {
+          value: 0, // zero of the type, as a JS (boxed) value
+          configurable: true,
+          enumerable: true,
+          writable: true,
+        });
+        ... // other fields
+        postSuperStats(data, preSuperEnv, new.target, this, arg1, arg2, ..., argN);
       }
     };
+    return cls;
   },
 }
 ```
 
+Boxed `char`s and `long`s cannot be synthesized on the JS side, and are therefore passed as inputs to the JS helper.
+Likewise for the `superClass` and member names, if they are not constants/globals.
+
 Since the `super()` call must lexically appear in the `constructor` of the class, we have to decompose the body of the constructor into 3 functions:
 
 * `preSuperStats` contains the statements before the super call, and returns an environment of the locally declared variables as a `struct` (much like capture data),
@@ -756,18 +778,12 @@ Since the `super()` call must lexically appear in the `constructor` of the class
 The latter two take the `preSuperEnv` environment computed by `preSuperStats` as parameter.
 All functions also receive the class captures `data` and the value of `new.target`.
 
-The helper also takes the `superClass` as argument, as well as an array describing what `fields` should be created.
-The `fields` array contains an even number of elements:
-
-* even indices are field names,
-* odd indices are the initial value of the corresponding field.
-
-The method `ClassEmitter.genCreateJSClassFunction` is responsible for generating the code that calls `createJSClass`.
-After that call, it uses more straightforward helpers to install the instance methods/properties and static methods/properties.
-Those are created as `function` closures, which mimics the run-time spec behavior of the `class` construct.
+In the future, we may still want to improve a bit on this scheme.
+In particular, we should be able to return multiple values from `superArgs`, one for each argument.
+Wasm functions that return multiple Wasm values are exposed to JS as returning a JS array of the results.
+We can then statically know the number of elements of that array and how to pass them to the super constructor, avoiding the `...spread` operator.
 
-In the future, we may also want to generate a specialized version of `createJSClass` for each declared non-native JS class.
-It could specialize the shape of constructor parameters, the shape of the arguments to the super constructor, and the fields.
+Furthermore, we could fuse `preSuperStats` and `superArgs` in a single Wasm function, returning both the `preSuperEnv` and the arguments to the super constructor call.
 
 ## Exceptions
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/SWasmGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/SWasmGen.scala
index 65140fbe3c..d8566b503a 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/SWasmGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/SWasmGen.scala
@@ -13,7 +13,6 @@
 package org.scalajs.linker.backend.wasmemitter
 
 import org.scalajs.ir.Names._
-import org.scalajs.ir.Trees.JSNativeLoadSpec
 import org.scalajs.ir.Types._
 
 import org.scalajs.linker.backend.webassembly._
@@ -47,25 +46,6 @@ object SWasmGen {
     }
   }
 
-  def genBoxedZeroOf(tpe: Type)(implicit ctx: WasmContext): Instr = {
-    tpe match {
-      case BooleanType =>
-        GlobalGet(genGlobalID.bFalse)
-      case CharType =>
-        GlobalGet(genGlobalID.bZeroChar)
-      case ByteType | ShortType | IntType | FloatType | DoubleType =>
-        GlobalGet(genGlobalID.bZero)
-      case LongType =>
-        GlobalGet(genGlobalID.bZeroLong)
-      case AnyType | ClassType(_, true) | ArrayType(_, true) | StringType | UndefType | NullType =>
-        RefNull(Types.HeapType.None)
-
-      case NothingType | NoType | ClassType(_, false) | ArrayType(_, false) |
-          AnyNotNullType | _:RecordType =>
-        throw new AssertionError(s"Unexpected type for field: ${tpe.show()}")
-    }
-  }
-
   def genLoadTypeData(fb: FunctionBuilder, typeRef: TypeRef): Unit = typeRef match {
     case typeRef: NonArrayTypeRef => genLoadNonArrayTypeData(fb, typeRef)
     case typeRef: ArrayTypeRef    => genLoadArrayTypeData(fb, typeRef)
@@ -103,41 +83,4 @@ object SWasmGen {
     fb += StructNew(genTypeID.forArrayClass(arrayTypeRef))
   }
 
-  def genLoadJSConstructor(fb: FunctionBuilder, className: ClassName)(
-      implicit ctx: WasmContext): Unit = {
-    val info = ctx.getClassInfo(className)
-
-    info.jsNativeLoadSpec match {
-      case None =>
-        // This is a non-native JS class
-        fb += Call(genFunctionID.loadJSClass(className))
-
-      case Some(loadSpec) =>
-        genLoadJSFromSpec(fb, loadSpec)
-    }
-  }
-
-  def genLoadJSFromSpec(fb: FunctionBuilder, loadSpec: JSNativeLoadSpec)(
-      implicit ctx: WasmContext): Unit = {
-    def genFollowPath(path: List[String]): Unit = {
-      for (prop <- path) {
-        fb ++= ctx.stringPool.getConstantStringInstr(prop)
-        fb += AnyConvertExtern
-        fb += Call(genFunctionID.jsSelect)
-      }
-    }
-
-    loadSpec match {
-      case JSNativeLoadSpec.Global(globalRef, path) =>
-        fb ++= ctx.stringPool.getConstantStringInstr(globalRef)
-        fb += Call(genFunctionID.jsGlobalRefGet)
-        genFollowPath(path)
-      case JSNativeLoadSpec.Import(module, path) =>
-        fb += GlobalGet(genGlobalID.forImportedModule(module))
-        genFollowPath(path)
-      case JSNativeLoadSpec.ImportWithGlobalFallback(importSpec, _) =>
-        genLoadJSFromSpec(fb, importSpec)
-    }
-  }
-
 }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
index cf93a99deb..f01d9f49e9 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
@@ -25,7 +25,6 @@ import org.scalajs.linker.backend.webassembly.Identitities._
 object VarGen {
 
   object genGlobalID {
-    final case class forImportedModule(moduleName: String) extends GlobalID
     final case class forModuleInstance(className: ClassName) extends GlobalID
     final case class forModuleInitFlag(className: ClassName) extends GlobalID
     final case class forJSClassValue(className: ClassName) extends GlobalID
@@ -58,7 +57,6 @@ object VarGen {
     case object undef extends JSHelperGlobalID
     case object bFalse extends JSHelperGlobalID
     case object bTrue extends JSHelperGlobalID
-    case object bZero extends JSHelperGlobalID
     case object emptyString extends JSHelperGlobalID
     case object idHashCodeMap extends JSHelperGlobalID
   }
@@ -134,14 +132,6 @@ object VarGen {
 
     case object fmod extends JSHelperFunctionID
 
-    case object closure extends JSHelperFunctionID
-    case object closureThis extends JSHelperFunctionID
-    case object closureRest extends JSHelperFunctionID
-    case object closureThisRest extends JSHelperFunctionID
-
-    case object makeExportedDef extends JSHelperFunctionID
-    case object makeExportedDefRest extends JSHelperFunctionID
-
     case object jsValueToString extends JSHelperFunctionID // for actual toString() call
     case object jsValueToStringForConcat extends JSHelperFunctionID
     case object booleanToString extends JSHelperFunctionID
@@ -158,79 +148,20 @@ object VarGen {
 
     case object makeTypeError extends JSHelperFunctionID
 
-    case object jsGlobalRefGet extends JSHelperFunctionID
-    case object jsGlobalRefSet extends JSHelperFunctionID
-    case object jsGlobalRefTypeof extends JSHelperFunctionID
     case object jsNewArray extends JSHelperFunctionID
-    case object jsArrayPush extends JSHelperFunctionID
-    case object jsArraySpreadPush extends JSHelperFunctionID
     case object jsNewObject extends JSHelperFunctionID
-    case object jsObjectPush extends JSHelperFunctionID
     case object jsSelect extends JSHelperFunctionID
     case object jsSelectSet extends JSHelperFunctionID
-    case object jsNew extends JSHelperFunctionID
-    case object jsFunctionApply extends JSHelperFunctionID
-    case object jsMethodApply extends JSHelperFunctionID
+    case object jsNewNoArg extends JSHelperFunctionID
     case object jsImportCall extends JSHelperFunctionID
     case object jsImportMeta extends JSHelperFunctionID
     case object jsDelete extends JSHelperFunctionID
     case object jsForInSimple extends JSHelperFunctionID
     case object jsIsTruthy extends JSHelperFunctionID
 
-    final case class jsUnaryOp(name: String) extends JSHelperFunctionID {
-      override def toString(): String = name
-    }
-
-    val jsUnaryOps: Map[JSUnaryOp.Code, jsUnaryOp] = {
-      Map(
-        JSUnaryOp.+ -> jsUnaryOp("jsUnaryPlus"),
-        JSUnaryOp.- -> jsUnaryOp("jsUnaryMinus"),
-        JSUnaryOp.~ -> jsUnaryOp("jsUnaryTilde"),
-        JSUnaryOp.! -> jsUnaryOp("jsUnaryBang"),
-        JSUnaryOp.typeof -> jsUnaryOp("jsUnaryTypeof")
-      )
-    }
-
-    final case class jsBinaryOp(name: String) extends JSHelperFunctionID {
-      override def toString(): String = name
-    }
-
-    val jsBinaryOps: Map[JSBinaryOp.Code, jsBinaryOp] = {
-      Map(
-        JSBinaryOp.=== -> jsBinaryOp("jsStrictEquals"),
-        JSBinaryOp.!== -> jsBinaryOp("jsNotStrictEquals"),
-        JSBinaryOp.+ -> jsBinaryOp("jsPlus"),
-        JSBinaryOp.- -> jsBinaryOp("jsMinus"),
-        JSBinaryOp.* -> jsBinaryOp("jsTimes"),
-        JSBinaryOp./ -> jsBinaryOp("jsDivide"),
-        JSBinaryOp.% -> jsBinaryOp("jsModulus"),
-        JSBinaryOp.| -> jsBinaryOp("jsBinaryOr"),
-        JSBinaryOp.& -> jsBinaryOp("jsBinaryAnd"),
-        JSBinaryOp.^ -> jsBinaryOp("jsBinaryXor"),
-        JSBinaryOp.<< -> jsBinaryOp("jsShiftLeft"),
-        JSBinaryOp.>> -> jsBinaryOp("jsArithmeticShiftRight"),
-        JSBinaryOp.>>> -> jsBinaryOp("jsLogicalShiftRight"),
-        JSBinaryOp.< -> jsBinaryOp("jsLessThan"),
-        JSBinaryOp.<= -> jsBinaryOp("jsLessEqual"),
-        JSBinaryOp.> -> jsBinaryOp("jsGreaterThan"),
-        JSBinaryOp.>= -> jsBinaryOp("jsGreaterEqual"),
-        JSBinaryOp.in -> jsBinaryOp("jsIn"),
-        JSBinaryOp.instanceof -> jsBinaryOp("jsInstanceof"),
-        JSBinaryOp.** -> jsBinaryOp("jsExponent")
-      )
-    }
-
     case object newSymbol extends JSHelperFunctionID
-    case object createJSClass extends JSHelperFunctionID
-    case object createJSClassRest extends JSHelperFunctionID
-    case object installJSField extends JSHelperFunctionID
-    case object installJSMethod extends JSHelperFunctionID
-    case object installJSStaticMethod extends JSHelperFunctionID
-    case object installJSProperty extends JSHelperFunctionID
-    case object installJSStaticProperty extends JSHelperFunctionID
     case object jsSuperSelect extends JSHelperFunctionID
     case object jsSuperSelectSet extends JSHelperFunctionID
-    case object jsSuperCall extends JSHelperFunctionID
 
     // Wasm internal helpers
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/WasmContext.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/WasmContext.scala
index f5eb6dd89e..0bc110dbbc 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/WasmContext.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/WasmContext.scala
@@ -27,12 +27,16 @@ import org.scalajs.linker.interface.ModuleInitializer
 import org.scalajs.linker.interface.unstable.ModuleInitializerImpl
 import org.scalajs.linker.standard.{CoreSpec, LinkedClass, LinkedTopLevelExport}
 
+import org.scalajs.linker.backend.emitter.{NameGen => JSNameGen}
+
 import org.scalajs.linker.backend.webassembly.ModuleBuilder
 import org.scalajs.linker.backend.webassembly.{Instructions => wa}
 import org.scalajs.linker.backend.webassembly.{Modules => wamod}
 import org.scalajs.linker.backend.webassembly.{Identitities => wanme}
 import org.scalajs.linker.backend.webassembly.{Types => watpe}
 
+import org.scalajs.linker.backend.javascript.{Trees => js}
+
 import VarGen._
 import org.scalajs.ir.OriginalName
 
@@ -49,6 +53,10 @@ final class WasmContext(
   private val tableFunctionTypes = mutable.HashMap.empty[MethodName, wanme.TypeID]
   private val closureDataTypes = LinkedHashMap.empty[List[Type], wanme.TypeID]
 
+  val jsNameGen = new JSNameGen()
+
+  private val customJSHelpers = mutable.ListBuffer.empty[(String, js.Function)]
+
   val moduleBuilder: ModuleBuilder = {
     new ModuleBuilder(new ModuleBuilder.FunctionTypeProvider {
       def functionTypeToTypeID(sig: watpe.FunctionType): wanme.TypeID = {
@@ -63,6 +71,23 @@ final class WasmContext(
     })
   }
 
+  def addCustomJSHelper(jsFunction: js.Function, wasmType: watpe.FunctionType): wanme.FunctionID = {
+    val id = CustomJSHelperFunctionID(customJSHelpers.size)
+    moduleBuilder.addImport(
+      wamod.Import(
+        "__scalaJSCustomHelpers",
+        id.importName,
+        wamod.ImportDesc.Func(
+          id,
+          OriginalName(id.toString()),
+          moduleBuilder.functionTypeToTypeID(wasmType)
+        )
+      )
+    )
+    customJSHelpers += ((id.importName, jsFunction))
+    id
+  }
+
   private var nextClosureDataTypeIndex: Int = 1
 
   private val _funcDeclarations: mutable.LinkedHashSet[wanme.FunctionID] =
@@ -160,11 +185,20 @@ final class WasmContext(
   def addGlobal(g: wamod.Global): Unit =
     moduleBuilder.addGlobal(g)
 
+  def getAllCustomJSHelpers(): List[(String, js.Function)] =
+    customJSHelpers.toList
+
   def getAllFuncDeclarations(): List[wanme.FunctionID] =
     _funcDeclarations.toList
 }
 
 object WasmContext {
+  private final case class CustomJSHelperFunctionID(index: Int) extends wanme.FunctionID {
+    override def toString(): String = s"customJSHelper.$index"
+
+    val importName: String = index.toString()
+  }
+
   final class ClassInfo(
       val name: ClassName,
       val kind: ClassKind,

From 5990470883527cfd27f61b38fca88645551ebe32 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Fri, 27 Sep 2024 16:12:30 +0200
Subject: [PATCH 177/298] Version 1.17.0.

---
 ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala b/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala
index 7b68d93faa..97162b8bed 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala
@@ -17,8 +17,8 @@ import java.util.concurrent.ConcurrentHashMap
 import scala.util.matching.Regex
 
 object ScalaJSVersions extends VersionChecks(
-    current = "1.17.0-SNAPSHOT",
-    binaryEmitted = "1.17-SNAPSHOT"
+    current = "1.17.0",
+    binaryEmitted = "1.17"
 )
 
 /** Helper class to allow for testing of logic. */

From 7c95972e30c9897440e4404515d05bf663639daa Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Fri, 27 Sep 2024 23:18:22 +0200
Subject: [PATCH 178/298] Towards 1.17.1.

---
 .../org/scalajs/ir/ScalaJSVersions.scala      |  2 +-
 project/BinaryIncompatibilities.scala         | 32 -------------------
 project/Build.scala                           |  2 +-
 3 files changed, 2 insertions(+), 34 deletions(-)

diff --git a/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala b/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala
index 97162b8bed..cd695d6894 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala
@@ -17,7 +17,7 @@ import java.util.concurrent.ConcurrentHashMap
 import scala.util.matching.Regex
 
 object ScalaJSVersions extends VersionChecks(
-    current = "1.17.0",
+    current = "1.17.1-SNAPSHOT",
     binaryEmitted = "1.17"
 )
 
diff --git a/project/BinaryIncompatibilities.scala b/project/BinaryIncompatibilities.scala
index 8c27dca150..4713fe6bf8 100644
--- a/project/BinaryIncompatibilities.scala
+++ b/project/BinaryIncompatibilities.scala
@@ -5,39 +5,9 @@ import com.typesafe.tools.mima.core.ProblemFilters._
 
 object BinaryIncompatibilities {
   val IR = Seq(
-    // !!! Breaking, OK in minor release
-
-    ProblemFilters.exclude[IncompatibleResultTypeProblem]("org.scalajs.ir.Trees#*.tpe"),
-
-    ProblemFilters.exclude[IncompatibleMethTypeProblem]("org.scalajs.ir.Trees#NewArray.this"),
-    ProblemFilters.exclude[IncompatibleMethTypeProblem]("org.scalajs.ir.Trees#NewArray.apply"),
-    ProblemFilters.exclude[IncompatibleMethTypeProblem]("org.scalajs.ir.Trees#NewArray.copy"),
-    ProblemFilters.exclude[IncompatibleResultTypeProblem]("org.scalajs.ir.Trees#NewArray.copy$default$2"),
-    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Trees#NewArray.lengths"),
-
-    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Trees#UnaryOp.resultTypeOf"),
-
-    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Types#ClassType.this"),
-    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Types#ClassType.apply"),
-    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Types#ClassType.copy"),
-    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Types#ArrayType.this"),
-    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Types#ArrayType.apply"),
-    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Types#ArrayType.copy"),
-
-    ProblemFilters.exclude[MissingTypesProblem]("org.scalajs.ir.Types$ClassType$"),
-    ProblemFilters.exclude[MissingTypesProblem]("org.scalajs.ir.Types$ArrayType$"),
-
-    // New abstract member in sealed hierarchy, not an issue
-    ProblemFilters.exclude[ReversedMissingMethodProblem]("org.scalajs.ir.Types#Type.toNonNullable"),
   )
 
   val Linker = Seq(
-    // private, not an issue
-    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.linker.standard.CoreSpec.this"),
-
-    // private[linker], not an issue
-    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.linker.standard.CoreSpec.apply"),
-    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.linker.standard.ModuleSet.this"),
   )
 
   val LinkerInterface = Seq(
@@ -50,8 +20,6 @@ object BinaryIncompatibilities {
   )
 
   val Library = Seq(
-    // New abstract member in JS trait, not an issue
-    ProblemFilters.exclude[ReversedMissingMethodProblem]("scala.scalajs.runtime.LinkingInfo.isWebAssembly"),
   )
 
   val TestInterface = Seq(
diff --git a/project/Build.scala b/project/Build.scala
index 8e5f1eba16..9ba80d3b93 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -394,7 +394,7 @@ object Build {
   val previousVersions = List("1.0.0", "1.0.1", "1.1.0", "1.1.1", "1.2.0",
       "1.3.0", "1.3.1", "1.4.0", "1.5.0", "1.5.1", "1.6.0", "1.7.0", "1.7.1",
       "1.8.0", "1.9.0", "1.10.0", "1.10.1", "1.11.0", "1.12.0", "1.13.0",
-      "1.13.1", "1.13.2", "1.14.0", "1.15.0", "1.16.0")
+      "1.13.1", "1.13.2", "1.14.0", "1.15.0", "1.16.0", "1.17.0")
   val previousVersion = previousVersions.last
 
   val previousBinaryCrossVersion = CrossVersion.binaryWith("sjs1_", "")

From b442f016c7f22cd8a17788641300f77f183fb407 Mon Sep 17 00:00:00 2001
From: Rikito Taniguchi <rikiriki1238@gmail.com>
Date: Sun, 29 Sep 2024 12:20:54 +0900
Subject: [PATCH 179/298] Fix #5048: Wasm: Emit no files when no modules are
 defined.

Remove any existing files if there are.

The previous error message in `WebAssemblyLinkerBackend` is not
clear for users not very familiar with Scala.js when no modules
are defined. It said:

  The WebAssembly backend does not support multiple modules. Found: .

This behavior was not aligned with the JS backend, and it could be
confusing for users.

This commit changes the behavior of the Wasm backend when no
modules are defined: we now delete previous artifacts and emit no
files. This change aligns the behavior with that of the JS backend.
---
 Jenkinsfile                                   |  5 ++++-
 .../backend/WebAssemblyLinkerBackend.scala    | 19 ++++++++++++++++---
 2 files changed, 20 insertions(+), 4 deletions(-)

diff --git a/Jenkinsfile b/Jenkinsfile
index 141b4c1a1d..43009dfd57 100644
--- a/Jenkinsfile
+++ b/Jenkinsfile
@@ -451,7 +451,10 @@ def Tasks = [
     sbtretry ++$scala \
         'set Global/enableWasmEverywhere := true' \
         'set scalaJSStage in Global := FullOptStage' \
-        testingExample$v/testHtml
+        testingExample$v/testHtml &&
+    sbtretry ++$scala \
+        'set Global/enableWasmEverywhere := true' \
+        irJS$v/fastLinkJS
   ''',
 
   /* For the bootstrap tests to be able to call
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/WebAssemblyLinkerBackend.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/WebAssemblyLinkerBackend.scala
index 14f2a6de09..ba12a26b59 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/WebAssemblyLinkerBackend.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/WebAssemblyLinkerBackend.scala
@@ -63,17 +63,30 @@ final class WebAssemblyLinkerBackend(config: LinkerBackendImpl.Config)
 
   def emit(moduleSet: ModuleSet, output: OutputDirectory, logger: Logger)(
       implicit ec: ExecutionContext): Future[Report] = {
-    val onlyModule = moduleSet.modules match {
+    moduleSet.modules match {
+      case Nil =>
+        val outputImpl = OutputDirectoryImpl.fromOutputDirectory(output)
+        for {
+          currentFilesList <- outputImpl.listFiles()
+          _ <- Future.traverse(currentFilesList) { f =>
+            outputImpl.delete(f)
+          }
+        } yield new ReportImpl(Nil)
       case onlyModule :: Nil =>
-        onlyModule
+        emit(onlyModule, moduleSet.globalInfo, output, logger)
       case modules =>
         throw new UnsupportedOperationException(
             "The WebAssembly backend does not support multiple modules. Found: " +
             modules.map(_.id.id).mkString(", "))
     }
+  }
+
+  private def emit(onlyModule: ModuleSet.Module, globalInfo: LinkedGlobalInfo,
+      output: OutputDirectory, logger: Logger)(
+      implicit ec: ExecutionContext): Future[Report] = {
     val moduleID = onlyModule.id.id
 
-    val emitterResult = emitter.emit(onlyModule, moduleSet.globalInfo, logger)
+    val emitterResult = emitter.emit(onlyModule, globalInfo, logger)
     val wasmModule = emitterResult.wasmModule
 
     val outputImpl = OutputDirectoryImpl.fromOutputDirectory(output)

From 9f0d899be37830ca20dc5e2b41a9321c4fcc7fd6 Mon Sep 17 00:00:00 2001
From: Rikito Taniguchi <rikiriki1238@gmail.com>
Date: Tue, 1 Oct 2024 14:49:08 +0900
Subject: [PATCH 180/298] Bump the version to 1.18.0-SNAPSHOT for the upcoming
 changes.

---
 ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala b/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala
index cd695d6894..37521f5065 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala
@@ -17,8 +17,8 @@ import java.util.concurrent.ConcurrentHashMap
 import scala.util.matching.Regex
 
 object ScalaJSVersions extends VersionChecks(
-    current = "1.17.1-SNAPSHOT",
-    binaryEmitted = "1.17"
+    current = "1.18.0-SNAPSHOT",
+    binaryEmitted = "1.18-SNAPSHOT"
 )
 
 /** Helper class to allow for testing of logic. */

From 7bf410dd922662dabfc85f1d76d40431c1fe0910 Mon Sep 17 00:00:00 2001
From: Rikito Taniguchi <rikiriki1238@gmail.com>
Date: Thu, 5 Sep 2024 19:30:43 +0900
Subject: [PATCH 181/298] Introduce `LinkTimeProperty`.

ref: scala-js#5000

Previously, accessing link-time information via `scala.scalajs.runtime.linkingInfo` required interacting with a JavaScript object.
That introduced JS interop in the Wasm backend causing a slowdown, and could hinder the optimization pipeline (In fact, we folded the access to `JSLinkingInfo` into `Literal`s in `OptimizerCore`).

`LinkTimeProperty` is a new IR node that is guaranteed to be transformed into a `Literal` at the optimizer or backend stage.
We plan to introduce a new primitive, such as `linkTimePropertyXXX`, which will be transformed into a `LinkTimeProperty` in a later commit.
Additionally, we will update `scala.scalajs.LinkingInfo` to use `linkTimePropertyXXX` instead of `runtime.linkingInfo`, allowing us to eliminate the JS object when accessing link-time information.

This commit also deprecates the `JSLinkingInfo` IR node.
For backward compatibility, we introduced a deserialization hack that transforms `JSSelect(JSLinkingInfo(), StringLiteral(...))` into the corresponding `LinkTimeProperty`. An isolated `JSLinkingInfo` will be deserialized into a `JSObjectConstr()` containing the corresponding `LinkTimeProperty` values.

Also, this commit introduces validation for `LinkTimeProperty` during reachability analysis.

The Analyzer now verifies that the `LinkTimeProperty` in the IR has a valid name and type pair, ensuring it can be resolved using the provided link-time information.
If an invalid `LinkTimeProperty` is detected, an error will be recorded in the `Analysis`
---
 .../org/scalajs/nscplugin/GenJSCode.scala     |  2 +-
 .../main/scala/org/scalajs/ir/Hashers.scala   |  5 ++
 .../main/scala/org/scalajs/ir/Printers.scala  |  5 ++
 .../scala/org/scalajs/ir/Serializers.scala    | 54 +++++++++++++--
 .../src/main/scala/org/scalajs/ir/Tags.scala  |  3 +
 .../scala/org/scalajs/ir/Transformers.scala   |  2 +-
 .../scala/org/scalajs/ir/Traversers.scala     |  2 +-
 .../src/main/scala/org/scalajs/ir/Trees.scala | 23 ++++++-
 .../scala/org/scalajs/ir/PrintersTest.scala   |  8 +++
 .../scalajs/linker/analyzer/Analysis.scala    |  8 +++
 .../scalajs/linker/analyzer/Analyzer.scala    |  8 +++
 .../org/scalajs/linker/analyzer/Infos.scala   | 33 +++++++--
 .../linker/backend/emitter/ClassEmitter.scala |  1 +
 .../linker/backend/emitter/CoreJSLib.scala    | 21 ++----
 .../linker/backend/emitter/Emitter.scala      | 36 +++-------
 .../backend/emitter/FunctionEmitter.scala     | 23 +++++--
 .../linker/backend/emitter/JSGen.scala        |  1 +
 .../backend/emitter/KnowledgeGuardian.scala   |  2 +-
 .../linker/backend/emitter/SJSGen.scala       |  1 +
 .../linker/backend/emitter/VarField.scala     |  4 +-
 .../linker/backend/emitter/VarGen.scala       | 10 +--
 .../backend/wasmemitter/CoreWasmLib.scala     |  1 -
 .../backend/wasmemitter/FunctionEmitter.scala | 29 +++++---
 .../linker/backend/wasmemitter/VarGen.scala   |  1 -
 .../linker/checker/ClassDefChecker.scala      |  5 ++
 .../scalajs/linker/checker/IRChecker.scala    |  2 +
 .../frontend/optimizer/OptimizerCore.scala    | 32 ++-------
 .../scalajs/linker/standard/CoreSpec.scala    |  3 +
 .../linker/standard/LinkTimeProperties.scala  | 68 +++++++++++++++++++
 .../org/scalajs/linker/AnalyzerTest.scala     | 31 +++++++++
 .../org/scalajs/linker/LibrarySizeTest.scala  |  4 +-
 project/Build.scala                           |  6 +-
 .../testsuite/library/LinkingInfoTest.scala   |  9 +++
 33 files changed, 328 insertions(+), 115 deletions(-)
 create mode 100644 linker/shared/src/main/scala/org/scalajs/linker/standard/LinkTimeProperties.scala

diff --git a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
index ef5d20f120..c3dff7493b 100644
--- a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
+++ b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
@@ -6758,7 +6758,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
         implicit pos: Position): js.JSGlobalRef = {
       propName match {
         case js.StringLiteral(value) =>
-          if (js.JSGlobalRef.isValidJSGlobalRefName(value)) {
+          if (js.JSGlobalRef.isValidJSGlobalRefName(value) && value != js.JSGlobalRef.FileLevelThis) {
             if (value == "await") {
               global.runReporting.warning(pos,
                   s"$actionFull of the global scope with the name '$value' is deprecated.\n" +
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Hashers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Hashers.scala
index d37bf739e7..2ed30d9443 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Hashers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Hashers.scala
@@ -550,6 +550,11 @@ object Hashers {
           mixName(className)
           mixTrees(captureValues)
 
+        case LinkTimeProperty(name) =>
+          mixTag(TagLinkTimeProperty)
+          mixString(name)
+          mixType(tree.tpe)
+
         case Transient(value) =>
           throw new InvalidIRException(tree,
               "Cannot hash a transient IR node (its value is of class " +
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala
index 34f5743e69..16cb79b85d 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala
@@ -901,6 +901,11 @@ object Printers {
           print(className)
           printRow(captureValues, "](", ", ", ")")
 
+        case LinkTimeProperty(name) =>
+          print("<linkTimeProperty>(")
+          print(name)
+          print(")")
+
         // Transient
 
         case Transient(value) =>
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
index ae2eec6b1f..ca58392661 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
@@ -25,6 +25,7 @@ import Names._
 import OriginalName.NoOriginalName
 import Position._
 import Trees._
+import LinkTimeProperty.{ProductionMode, ESVersion, UseECMAScript2015Semantics, IsWebAssembly, LinkerVersion}
 import Types._
 import Tags._
 import Version.Unversioned
@@ -572,6 +573,11 @@ object Serializers {
           writeName(className)
           writeTrees(captureValues)
 
+        case LinkTimeProperty(name) =>
+          writeTagAndPos(TagLinkTimeProperty)
+          writeString(name)
+          writeType(tree.tpe)
+
         case Transient(value) =>
           throw new InvalidIRException(tree,
               "Cannot serialize a transient IR node (its value is of class " +
@@ -1290,9 +1296,32 @@ object Serializers {
         case TagUnwrapFromThrowable =>
           UnwrapFromThrowable(readTree())
 
-        case TagJSNew                => JSNew(readTree(), readTreeOrJSSpreads())
-        case TagJSPrivateSelect      => JSPrivateSelect(readTree(), readFieldIdent())
-        case TagJSSelect             => JSSelect(readTree(), readTree())
+        case TagJSNew           => JSNew(readTree(), readTreeOrJSSpreads())
+        case TagJSPrivateSelect => JSPrivateSelect(readTree(), readFieldIdent())
+
+        case TagJSSelect =>
+          if (/* hacks.use17 */ true && buf.get(buf.position()) == TagJSLinkingInfo) { // scalastyle:ignore
+            val jsLinkingInfo = readTree()
+            readTree() match {
+              case StringLiteral("productionMode") =>
+                LinkTimeProperty(ProductionMode)(BooleanType)
+              case StringLiteral("esVersion") =>
+                LinkTimeProperty(ESVersion)(IntType)
+              case StringLiteral("assumingES6") =>
+                LinkTimeProperty(UseECMAScript2015Semantics)(BooleanType)
+              case StringLiteral("isWebAssembly") =>
+                LinkTimeProperty(IsWebAssembly)(BooleanType)
+              case StringLiteral("linkerVersion") =>
+                LinkTimeProperty(LinkerVersion)(StringType)
+              case StringLiteral("fileLevelThis") =>
+                JSGlobalRef(JSGlobalRef.FileLevelThis)
+              case otherItem =>
+                JSSelect(jsLinkingInfo, otherItem)
+          }
+        } else {
+          JSSelect(readTree(), readTree())
+        }
+
         case TagJSFunctionApply      => JSFunctionApply(readTree(), readTreeOrJSSpreads())
         case TagJSMethodApply        => JSMethodApply(readTree(), readTree(), readTreeOrJSSpreads())
         case TagJSSuperSelect        => JSSuperSelect(readTree(), readTree(), readTree())
@@ -1312,7 +1341,21 @@ object Serializers {
           JSObjectConstr(List.fill(readInt())((readTree(), readTree())))
         case TagJSGlobalRef          => JSGlobalRef(readString())
         case TagJSTypeOfGlobalRef    => JSTypeOfGlobalRef(readTree().asInstanceOf[JSGlobalRef])
-        case TagJSLinkingInfo        => JSLinkingInfo()
+
+        case TagJSLinkingInfo =>
+          if (/* hacks.use17 */ true) { // scalastyle:ignore
+            JSObjectConstr(List(
+              (StringLiteral("productionMode"), LinkTimeProperty(ProductionMode)(BooleanType)),
+              (StringLiteral("esVersion"), LinkTimeProperty(ESVersion)(IntType)),
+              (StringLiteral("assumingES6"), LinkTimeProperty(UseECMAScript2015Semantics)(BooleanType)),
+              (StringLiteral("isWebAssembly"), LinkTimeProperty(IsWebAssembly)(BooleanType)),
+              (StringLiteral("linkerVersion"), LinkTimeProperty(LinkerVersion)(StringType)),
+              (StringLiteral("fileLevelThis"), JSGlobalRef(JSGlobalRef.FileLevelThis))
+            ))
+          } else {
+            throw new IOException(
+                s"Found invalid pre-1.18 JSLinkingInfo def at ${pos}")
+          }
 
         case TagUndefined      => Undefined()
         case TagNull           => Null()
@@ -1355,6 +1398,9 @@ object Serializers {
 
         case TagCreateJSClass =>
           CreateJSClass(readClassName(), readTrees())
+
+        case TagLinkTimeProperty =>
+          LinkTimeProperty(readString())(readType())
       }
     }
 
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Tags.scala b/ir/shared/src/main/scala/org/scalajs/ir/Tags.scala
index 3c3162245b..577a3ceca6 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Tags.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Tags.scala
@@ -127,6 +127,9 @@ private[ir] object Tags {
   final val TagWrapAsThrowable = TagJSNewTarget + 1
   final val TagUnwrapFromThrowable = TagWrapAsThrowable + 1
 
+  // New in 1.18
+  final val TagLinkTimeProperty = TagUnwrapFromThrowable + 1
+
   // Tags for member defs
 
   final val TagFieldDef = 1
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Transformers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Transformers.scala
index 09b82b1757..99f16e8755 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Transformers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Transformers.scala
@@ -223,7 +223,7 @@ object Transformers {
         case _:Skip | _:Debugger | _:LoadModule | _:StoreModule |
             _:SelectStatic | _:SelectJSNativeMember | _:LoadJSConstructor |
             _:LoadJSModule | _:JSNewTarget | _:JSImportMeta | _:JSLinkingInfo |
-            _:Literal | _:VarRef | _:This | _:JSGlobalRef  =>
+            _:Literal | _:VarRef | _:This | _:JSGlobalRef | _:LinkTimeProperty =>
           tree
       }
     }
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Traversers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Traversers.scala
index 2f68fac81f..4c6fd1a355 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Traversers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Traversers.scala
@@ -222,7 +222,7 @@ object Traversers {
       case _:Skip | _:Debugger | _:LoadModule | _:StoreModule |
           _:SelectStatic | _:SelectJSNativeMember | _:LoadJSConstructor |
           _:LoadJSModule | _:JSNewTarget | _:JSImportMeta | _:JSLinkingInfo |
-          _:Literal | _:VarRef | _:This | _:JSGlobalRef =>
+          _:Literal | _:VarRef | _:This | _:JSGlobalRef | _:LinkTimeProperty =>
     }
 
     def traverseClassDef(tree: ClassDef): Unit = {
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala b/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
index 6cc39f24a8..4b36f1808e 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
@@ -966,8 +966,15 @@ object Trees {
      *  [[isJSIdentifierName]]) *and* it is not reserved (see
      *  [[ReservedJSIdentifierNames]]).
      */
-    def isValidJSGlobalRefName(name: String): Boolean =
-      isJSIdentifierName(name) && !ReservedJSIdentifierNames.contains(name)
+    def isValidJSGlobalRefName(name: String): Boolean = {
+      (isJSIdentifierName(name) && !ReservedJSIdentifierNames.contains(name)) ||
+      name == FileLevelThis
+    }
+
+    /** The JavaScript value that is an alias to `this`
+     *  at the top-level of the generated file.
+     */
+    final val FileLevelThis = "this"
   }
 
   sealed case class JSTypeOfGlobalRef(globalRef: JSGlobalRef)(
@@ -1072,6 +1079,18 @@ object Trees {
     val tpe = ClassType(ClassClass, nullable = false)
   }
 
+  sealed case class LinkTimeProperty(name: String)(val tpe: Type)(
+      implicit val pos: Position)
+      extends Tree
+
+  object LinkTimeProperty {
+    final val ProductionMode = "core/productionMode"
+    final val ESVersion = "core/esVersion"
+    final val UseECMAScript2015Semantics = "core/useECMAScript2015Semantics"
+    final val IsWebAssembly = "core/isWebAssembly"
+    final val LinkerVersion = "core/linkerVersion"
+  }
+
   // Atomic expressions
 
   sealed case class VarRef(ident: LocalIdent)(val tpe: Type)(
diff --git a/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala b/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala
index 57d80c3373..013dc6672e 100644
--- a/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala
+++ b/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala
@@ -937,6 +937,14 @@ class PrintersTest {
         CreateJSClass("Foo", List(ref("x", IntType), ref("y", AnyType))))
   }
 
+  @Test def printLinkTimeProperty(): Unit = {
+    assertPrintEquals(
+        """
+          |<linkTimeProperty>(foo)
+        """,
+        LinkTimeProperty("foo")(StringType))
+  }
+
   @Test def printTransient(): Unit = {
     class MyTransient(expr: Tree) extends Transient.Value {
       val tpe: Type = AnyType
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analysis.scala b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analysis.scala
index 3c1e6f251b..0c1b0118e5 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analysis.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analysis.scala
@@ -208,6 +208,12 @@ object Analysis {
 
   final case class ExponentOperatorWithoutES2016Support(from: From) extends Error
 
+  final case class InvalidLinkTimeProperty(
+    linkTimePropertyName: String,
+    linkTimePropertyType: Type,
+    from: From
+  ) extends Error
+
   sealed trait From
   final case class FromMethod(methodInfo: MethodInfo) extends From
   final case class FromDispatch(classInfo: ClassInfo, methodName: MethodName) extends From
@@ -264,6 +270,8 @@ object Analysis {
         "Uses import.meta with a module kind other than ESModule"
       case ExponentOperatorWithoutES2016Support(_) =>
         "Uses the ** operator with an ECMAScript version older than ES 2016"
+      case InvalidLinkTimeProperty(name, tpe, _) =>
+        s"Uses invalid link-time property ${name} of type ${tpe}"
     }
 
     logger.log(level, headMsg)
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala
index 79f1ef432f..daf81ec531 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala
@@ -1478,6 +1478,14 @@ private class AnalyzerRun(config: CommonPhaseConfig, initial: Boolean,
         _classSuperClassUsed.set(true)
       }
     }
+
+    if (data.referencedLinkTimeProperties.nonEmpty) {
+      for ((name, tpe) <- data.referencedLinkTimeProperties) {
+        if (!config.coreSpec.linkTimeProperties.validate(name, tpe)) {
+          _errors ::= InvalidLinkTimeProperty(name, tpe, from)
+        }
+      }
+    }
   }
 
   @tailrec
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala
index 6b622ae82a..3ff5ee059d 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala
@@ -78,13 +78,14 @@ object Infos {
     val isAbstract: Boolean,
     version: Version,
     byClass: Array[ReachabilityInfoInClass],
-    globalFlags: ReachabilityInfo.Flags
-  ) extends ReachabilityInfo(version, byClass, globalFlags)
+    globalFlags: ReachabilityInfo.Flags,
+    referencedLinkTimeProperties: Array[(String, Type)]
+  ) extends ReachabilityInfo(version, byClass, globalFlags, referencedLinkTimeProperties)
 
   object MethodInfo {
     def apply(isAbstract: Boolean, reachabilityInfo: ReachabilityInfo): MethodInfo = {
       import reachabilityInfo._
-      new MethodInfo(isAbstract, version, byClass, globalFlags)
+      new MethodInfo(isAbstract, version, byClass, globalFlags, referencedLinkTimeProperties)
     }
   }
 
@@ -102,7 +103,8 @@ object Infos {
      */
     val version: Version,
     val byClass: Array[ReachabilityInfoInClass],
-    val globalFlags: ReachabilityInfo.Flags
+    val globalFlags: ReachabilityInfo.Flags,
+    val referencedLinkTimeProperties: Array[(String, Type)]
   )
 
   object ReachabilityInfo {
@@ -196,8 +198,10 @@ object Infos {
   }
 
   final class ReachabilityInfoBuilder(version: Version) {
+    import ReachabilityInfoBuilder._
     private val byClass = mutable.Map.empty[ClassName, ReachabilityInfoInClassBuilder]
     private var flags: ReachabilityInfo.Flags = 0
+    private val linkTimeProperties = mutable.ListBuffer.empty[(String, Type)]
 
     private def forClass(cls: ClassName): ReachabilityInfoInClassBuilder =
       byClass.getOrElseUpdate(cls, new ReachabilityInfoInClassBuilder(cls))
@@ -390,8 +394,22 @@ object Infos {
     def addUsedClassSuperClass(): this.type =
       setFlag(ReachabilityInfo.FlagUsedClassSuperClass)
 
-    def result(): ReachabilityInfo =
-      new ReachabilityInfo(version, byClass.valuesIterator.map(_.result()).toArray, flags)
+    def addReferencedLinkTimeProperty(linkTimeProperty: LinkTimeProperty): this.type = {
+      linkTimeProperties.append((linkTimeProperty.name, linkTimeProperty.tpe))
+      this
+    }
+
+    def result(): ReachabilityInfo = {
+      val referencedLinkTimeProperties =
+        if (linkTimeProperties.isEmpty) emptyLinkTimePropertyArray
+        else linkTimeProperties.toArray
+      new ReachabilityInfo(version, byClass.valuesIterator.map(_.result()).toArray, flags,
+          referencedLinkTimeProperties)
+    }
+  }
+
+  object ReachabilityInfoBuilder {
+    private val emptyLinkTimePropertyArray = new Array[(String, Type)](0)
   }
 
   final class ReachabilityInfoInClassBuilder(val className: ClassName) {
@@ -744,6 +762,9 @@ object Infos {
             case VarDef(_, _, vtpe, _, _) =>
               builder.maybeAddReferencedClass(vtpe)
 
+            case linkTimeProperty: LinkTimeProperty =>
+              builder.addReferencedLinkTimeProperty(linkTimeProperty)
+
             case _ =>
           }
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
index 0243d9f7bc..1b1751df60 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
@@ -40,6 +40,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
   import sjsGen._
   import jsGen._
   import config._
+  import coreSpec._
   import nameGen._
   import varGen._
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
index 35e480f233..ffbea0e2f7 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
@@ -63,6 +63,7 @@ private[emitter] object CoreJSLib {
     import sjsGen._
     import jsGen._
     import config._
+    import coreSpec._
     import nameGen._
     import varGen._
     import esFeatures._
@@ -127,7 +128,7 @@ private[emitter] object CoreJSLib {
     }
 
     private def buildPreObjectDefinitions(): List[Tree] = {
-      defineLinkingInfo() :::
+      defineFileLevelThis() :::
       defineJSBuiltinsSnapshotsAndPolyfills() :::
       declareCachedL0() :::
       defineCharClass() :::
@@ -154,22 +155,8 @@ private[emitter] object CoreJSLib {
       assignCachedL0()
     }
 
-    private def defineLinkingInfo(): List[Tree] = {
-      // must be in sync with scala.scalajs.runtime.LinkingInfo
-
-      def objectFreeze(tree: Tree): Tree =
-        Apply(genIdentBracketSelect(ObjectRef, "freeze"), tree :: Nil)
-
-      val linkingInfo = objectFreeze(ObjectConstr(List(
-          str("esVersion") -> int(esVersion.edition),
-          str("assumingES6") -> bool(useECMAScript2015Semantics), // different name for historical reasons
-          str("isWebAssembly") -> bool(false),
-          str("productionMode") -> bool(productionMode),
-          str("linkerVersion") -> str(ScalaJSVersions.current),
-          str("fileLevelThis") -> This()
-      )))
-
-      extractWithGlobals(globalVarDef(VarField.linkingInfo, CoreVar, linkingInfo))
+    private def defineFileLevelThis(): List[Tree] = {
+      extractWithGlobals(globalVarDef(VarField.fileLevelThis, CoreVar, This()))
     }
 
     private def defineJSBuiltinsSnapshotsAndPolyfills(): List[Tree] = {
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala
index 07e4dee5f8..c6576f4f5d 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala
@@ -37,6 +37,7 @@ final class Emitter(config: Emitter.Config, prePrinter: Emitter.PrePrinter) {
 
   import Emitter._
   import config._
+  import coreSpec._
 
   require(!config.minify || prePrinter == PrePrinter.Off,
       "When using the 'minify' option, the prePrinter must be Off.")
@@ -1088,23 +1089,16 @@ object Emitter {
 
   /** Configuration for the Emitter. */
   final class Config private (
-      val semantics: Semantics,
-      val moduleKind: ModuleKind,
-      val esFeatures: ESFeatures,
+      val coreSpec: CoreSpec,
       val jsHeader: String,
       val internalModulePattern: ModuleID => String,
       val optimizeBracketSelects: Boolean,
       val trackAllGlobalRefs: Boolean,
       val minify: Boolean
   ) {
-    private def this(
-        semantics: Semantics,
-        moduleKind: ModuleKind,
-        esFeatures: ESFeatures) = {
+    private def this(coreSpec: CoreSpec) = {
       this(
-          semantics,
-          moduleKind,
-          esFeatures,
+          coreSpec,
           jsHeader = "",
           internalModulePattern = "./" + _.id,
           optimizeBracketSelects = true,
@@ -1117,14 +1111,8 @@ object Emitter {
       if (trackAllGlobalRefs) GlobalRefTracking.All
       else GlobalRefTracking.Dangerous
 
-    def withSemantics(f: Semantics => Semantics): Config =
-      copy(semantics = f(semantics))
-
-    def withModuleKind(moduleKind: ModuleKind): Config =
-      copy(moduleKind = moduleKind)
-
-    def withESFeatures(f: ESFeatures => ESFeatures): Config =
-      copy(esFeatures = f(esFeatures))
+    def withCoreSpec(coreSpec: CoreSpec): Config =
+      copy(coreSpec = coreSpec)
 
     def withJSHeader(jsHeader: String): Config = {
       require(StandardConfig.isValidJSHeader(jsHeader), jsHeader)
@@ -1144,16 +1132,14 @@ object Emitter {
       copy(minify = minify)
 
     private def copy(
-        semantics: Semantics = semantics,
-        moduleKind: ModuleKind = moduleKind,
-        esFeatures: ESFeatures = esFeatures,
+        coreSpec: CoreSpec = coreSpec,
         jsHeader: String = jsHeader,
         internalModulePattern: ModuleID => String = internalModulePattern,
         optimizeBracketSelects: Boolean = optimizeBracketSelects,
         trackAllGlobalRefs: Boolean = trackAllGlobalRefs,
         minify: Boolean = minify
     ): Config = {
-      new Config(semantics, moduleKind, esFeatures, jsHeader,
+      new Config(coreSpec, jsHeader,
           internalModulePattern, optimizeBracketSelects, trackAllGlobalRefs,
           minify)
     }
@@ -1161,7 +1147,7 @@ object Emitter {
 
   object Config {
     def apply(coreSpec: CoreSpec): Config =
-      new Config(coreSpec.semantics, coreSpec.moduleKind, coreSpec.esFeatures)
+      new Config(coreSpec)
   }
 
   sealed trait PrePrinter {
@@ -1257,7 +1243,7 @@ object Emitter {
       ancestors: List[ClassName], moduleContext: ModuleContext)
 
   private def symbolRequirements(config: Config): SymbolRequirement = {
-    import config.semantics._
+    import config.coreSpec.semantics._
     import CheckedBehavior._
 
     val factory = SymbolRequirement.factory("emitter")
@@ -1313,7 +1299,7 @@ object Emitter {
         callMethod(BoxedDoubleClass, hashCodeMethodName),
         callMethod(BoxedStringClass, hashCodeMethodName),
 
-        cond(!config.esFeatures.allowBigIntsForLongs) {
+        cond(!config.coreSpec.esFeatures.allowBigIntsForLongs) {
           multiple(
               instanceTests(LongImpl.RuntimeLongClass),
               instantiateClass(LongImpl.RuntimeLongClass, LongImpl.AllConstructors.toList),
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
index b8b802695f..18d4272cf1 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
@@ -251,6 +251,7 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
   import sjsGen._
   import jsGen._
   import config._
+  import coreSpec._
   import nameGen._
   import varGen._
 
@@ -1243,10 +1244,11 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
 
       def test(tree: Tree): Boolean = tree match {
         // Atomic expressions
-        case _: Literal       => true
-        case _: This          => true
-        case _: JSNewTarget   => true
-        case _: JSLinkingInfo => true
+        case _: Literal          => true
+        case _: This             => true
+        case _: JSNewTarget      => true
+        case _: JSLinkingInfo    => true
+        case _: LinkTimeProperty => true
 
         // Vars (side-effect free, pure if immutable)
         case VarRef(name) =>
@@ -2796,6 +2798,11 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
               genSelect(newExpr, FieldIdent(exceptionFieldName)),
               genCheckNotNull(newExpr))
 
+        case prop: LinkTimeProperty =>
+          transformExpr(
+              config.coreSpec.linkTimeProperties.transformLinkTimeProperty(prop),
+              preserveChar)
+
         // Transients
 
         case Transient(Cast(expr, tpe)) =>
@@ -2947,13 +2954,17 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
           })
 
         case JSGlobalRef(name) =>
-          js.VarRef(transformGlobalVarIdent(name))
+          if (name == JSGlobalRef.FileLevelThis)
+            globalVar(VarField.fileLevelThis, CoreVar)
+          else
+            js.VarRef(transformGlobalVarIdent(name))
 
         case JSTypeOfGlobalRef(globalRef) =>
           js.UnaryOp(JSUnaryOp.typeof, transformExprNoChar(globalRef))
 
         case JSLinkingInfo() =>
-          globalVar(VarField.linkingInfo, CoreVar)
+          throw new IllegalArgumentException(
+              "JSLinkingInfo was removed in 1.18.0.")
 
         // Literals
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/JSGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/JSGen.scala
index 3676a947c8..ea9be90e76 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/JSGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/JSGen.scala
@@ -25,6 +25,7 @@ import org.scalajs.linker.interface.ESVersion
 private[emitter] final class JSGen(val config: Emitter.Config) {
 
   import config._
+  import coreSpec._
 
   /** Should we use ECMAScript classes for JavaScript classes and Throwable
    *  classes?
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/KnowledgeGuardian.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/KnowledgeGuardian.scala
index 5a02604391..c7a94abfb9 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/KnowledgeGuardian.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/KnowledgeGuardian.scala
@@ -152,7 +152,7 @@ private[emitter] final class KnowledgeGuardian(config: Emitter.Config) {
 
   private def computeStaticFieldMirrors(
       moduleSet: ModuleSet): Map[ClassName, Map[FieldName, List[String]]] = {
-    if (config.moduleKind != ModuleKind.NoModule) {
+    if (config.coreSpec.moduleKind != ModuleKind.NoModule) {
       Map.empty
     } else {
       var result = Map.empty[ClassName, Map[FieldName, List[String]]]
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala
index 44f8708265..d16df3126a 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala
@@ -38,6 +38,7 @@ private[emitter] final class SJSGen(
 
   import jsGen._
   import config._
+  import coreSpec._
   import nameGen._
   import varGen._
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/VarField.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/VarField.scala
index a43a127f61..44193542b9 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/VarField.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/VarField.scala
@@ -137,8 +137,8 @@ private[emitter] object VarField {
 
   // Core fields: Generated by the CoreJSLib
 
-  /** The linking info object. */
-  final val linkingInfo = mk("$linkingInfo")
+  /** The alias to file level `this` in the generated JS file. */
+  final val fileLevelThis = mk("$fileLevelThis")
 
   /** The TypeData class. */
   final val TypeData = mk("$TypeData")
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/VarGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/VarGen.scala
index d867b347ed..cdcf20560f 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/VarGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/VarGen.scala
@@ -97,7 +97,7 @@ private[emitter] final class VarGen(jsGen: JSGen, nameGen: NameGen,
     val ident = globalVarIdent(field, scope, origName)
     val varDef = genLet(ident, mutable = true, value)
 
-    if (config.moduleKind == ModuleKind.ESModule && !moduleContext.public) {
+    if (config.coreSpec.moduleKind == ModuleKind.ESModule && !moduleContext.public) {
       val setterIdent = globalVarIdent(setterField, scope)
       val x = Ident("x")
       val setter = FunctionDef(setterIdent, List(ParamDef(x)), None, {
@@ -117,7 +117,7 @@ private[emitter] final class VarGen(jsGen: JSGen, nameGen: NameGen,
   def needToUseGloballyMutableVarSetter[T](scope: T)(
       implicit moduleContext: ModuleContext, globalKnowledge: GlobalKnowledge,
       scopeType: Scope[T]): Boolean = {
-    config.moduleKind == ModuleKind.ESModule &&
+    config.coreSpec.moduleKind == ModuleKind.ESModule &&
     globalKnowledge.getModule(scopeType.reprClass(scope)) != moduleContext.moduleID
   }
 
@@ -125,7 +125,7 @@ private[emitter] final class VarGen(jsGen: JSGen, nameGen: NameGen,
       origName: OriginalName = NoOriginalName)(
       implicit moduleContext: ModuleContext, globalKnowledge: GlobalKnowledge,
       pos: Position): Tree = {
-    assert(config.moduleKind == ModuleKind.ESModule)
+    assert(config.coreSpec.moduleKind == ModuleKind.ESModule)
 
     val ident = globalVarIdent(field, scope, origName)
     foldSameModule[T, Tree](scope) {
@@ -163,7 +163,7 @@ private[emitter] final class VarGen(jsGen: JSGen, nameGen: NameGen,
     } { moduleID =>
       val moduleName = config.internalModulePattern(moduleID)
 
-      val moduleTree = config.moduleKind match {
+      val moduleTree = config.coreSpec.moduleKind match {
         case ModuleKind.NoModule =>
           /* If we get here, it means that what we are trying to import is in a
            * different module than the module we're currently generating
@@ -279,7 +279,7 @@ private[emitter] final class VarGen(jsGen: JSGen, nameGen: NameGen,
     if (moduleContext.public) {
       WithGlobals(tree :: Nil)
     } else {
-      val exportStat = config.moduleKind match {
+      val exportStat = config.coreSpec.moduleKind match {
         case ModuleKind.NoModule =>
           throw new AssertionError("non-public module in NoModule mode")
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
index d74aa2d810..6a00aaab2c 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
@@ -311,7 +311,6 @@ final class CoreWasmLib(coreSpec: CoreSpec, globalInfo: LinkedGlobalInfo) {
       )
     }
 
-    addGlobalHelperImport(genGlobalID.jsLinkingInfo, RefType.any)
     addGlobalHelperImport(genGlobalID.undef, RefType.any)
     addGlobalHelperImport(genGlobalID.bFalse, RefType.any)
     addGlobalHelperImport(genGlobalID.bTrue, RefType.any)
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
index 051fd64887..7babc4ee9c 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
@@ -575,6 +575,7 @@ private class FunctionEmitter private (
       case t: IdentityHashCode    => genIdentityHashCode(t)
       case t: WrapAsThrowable     => genWrapAsThrowable(t)
       case t: UnwrapFromThrowable => genUnwrapFromThrowable(t)
+      case t: LinkTimeProperty    => genLinkTimeProperty(t)
 
       // JavaScript expressions
       case t: JSNew                => genJSNew(t)
@@ -2702,6 +2703,12 @@ private class FunctionEmitter private (
     AnyType
   }
 
+  private def genLinkTimeProperty(tree: LinkTimeProperty): Type = {
+    val lit = ctx.coreSpec.linkTimeProperties.transformLinkTimeProperty(tree)
+    genLiteral(lit, lit.tpe)
+    lit.tpe
+  }
+
   private def genJSNew(tree: JSNew): Type = {
     val JSNew(ctor, args) = tree
 
@@ -2938,14 +2945,19 @@ private class FunctionEmitter private (
     val JSGlobalRef(name) = tree
 
     implicit val pos = tree.pos
+    markPosition(pos)
 
-    val builder = new CustomJSHelperBuilder()
-    val helperID = builder.build(AnyType) {
-      js.Return(builder.genGlobalRef(name))
-    }
+    if (name == JSGlobalRef.FileLevelThis) {
+      // In ES modules global this is undefined, and Wasm backend only supports `ESModule`
+      fb += wa.GlobalGet(genGlobalID.undef)
+    } else {
+      val builder = new CustomJSHelperBuilder()
+      val helperID = builder.build(AnyType) {
+        js.Return(builder.genGlobalRef(name))
+      }
 
-    markPosition(pos)
-    fb += wa.Call(helperID)
+      fb += wa.Call(helperID)
+    }
     AnyType
   }
 
@@ -2965,9 +2977,8 @@ private class FunctionEmitter private (
   }
 
   private def genJSLinkingInfo(tree: JSLinkingInfo): Type = {
-    markPosition(tree)
-    fb += wa.GlobalGet(genGlobalID.jsLinkingInfo)
-    AnyType
+    throw new IllegalArgumentException(
+      "JSLinkingInfo is deprecated as of 1.18.0.")
   }
 
   private def genArrayLength(tree: ArrayLength): Type = {
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
index f01d9f49e9..6a01f55cb6 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
@@ -53,7 +53,6 @@ object VarGen {
      */
     sealed abstract class JSHelperGlobalID extends GlobalID
 
-    case object jsLinkingInfo extends JSHelperGlobalID
     case object undef extends JSHelperGlobalID
     case object bFalse extends JSHelperGlobalID
     case object bTrue extends JSHelperGlobalID
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala b/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
index b569825470..ee5cbcd719 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
@@ -562,6 +562,9 @@ private final class ClassDefChecker(classDef: ClassDef,
             if (env.locals.get(name).exists(!_.mutable))
               reportError(i"Assignment to immutable variable $name.")
 
+          case JSGlobalRef(JSGlobalRef.FileLevelThis) =>
+            reportError(i"Assignment to global this.")
+
           case _:Select | _:JSPrivateSelect | _:SelectStatic |
               _:ArraySelect | _:RecordSelect | _:JSSelect | _:JSSuperSelect |
               _:JSGlobalRef =>
@@ -727,6 +730,8 @@ private final class ClassDefChecker(classDef: ClassDef,
       case UnwrapFromThrowable(expr) =>
         checkTree(expr, env)
 
+      case LinkTimeProperty(name) =>
+
       // JavaScript expressions
 
       case JSNew(ctor, args) =>
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala b/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
index 5bf5e259c4..6f9aa2c12c 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
@@ -536,6 +536,8 @@ private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter) {
       case UnwrapFromThrowable(expr) =>
         typecheckExpect(expr, env, ClassType(ThrowableClass, nullable = true))
 
+      case LinkTimeProperty(name) =>
+
       // JavaScript expressions
 
       case JSNew(ctor, args) =>
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
index 2e49b2d40f..502af60ace 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
@@ -610,6 +610,9 @@ private[optimizer] abstract class OptimizerCore(
           pretransformExpr(tree)(finishTransform(isStat))
         }
 
+      case prop: LinkTimeProperty =>
+        config.coreSpec.linkTimeProperties.transformLinkTimeProperty(prop)
+
       // JavaScript expressions
 
       case JSNew(ctor, args) =>
@@ -2393,7 +2396,7 @@ private[optimizer] abstract class OptimizerCore(
       val titem = optimizeJSBracketSelectItem(titem0)
 
       def default: TailRec[Tree] = {
-        cont(PreTransTree(foldJSSelect(finishTransformExpr(tqual),
+        cont(PreTransTree(JSSelect(finishTransformExpr(tqual),
             finishTransformExpr(titem))))
       }
 
@@ -5096,33 +5099,6 @@ private[optimizer] abstract class OptimizerCore(
     }
   }
 
-  private def foldJSSelect(qualifier: Tree, item: Tree)(
-      implicit pos: Position): Tree = {
-    // !!! Must be in sync with scala.scalajs.runtime.LinkingInfo
-
-    import config.coreSpec.esFeatures
-
-    (qualifier, item) match {
-      case (JSLinkingInfo(), StringLiteral("productionMode")) =>
-        BooleanLiteral(semantics.productionMode)
-
-      case (JSLinkingInfo(), StringLiteral("esVersion")) =>
-        IntLiteral(esFeatures.esVersion.edition)
-
-      case (JSLinkingInfo(), StringLiteral("assumingES6")) =>
-        BooleanLiteral(esFeatures.useECMAScript2015Semantics)
-
-      case (JSLinkingInfo(), StringLiteral("isWebAssembly")) =>
-        BooleanLiteral(isWasm)
-
-      case (JSLinkingInfo(), StringLiteral("version")) =>
-        StringLiteral(ScalaJSVersions.current)
-
-      case _ =>
-        JSSelect(qualifier, item)
-    }
-  }
-
   private def transformMethodDefBody(optTarget: Option[MethodID], thisType: Type,
       params: List[ParamDef], jsClassCaptures: List[ParamDef], resultType: Type,
       body: Tree, isNoArgCtor: Boolean): (List[ParamDef], Tree) = {
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/standard/CoreSpec.scala b/linker/shared/src/main/scala/org/scalajs/linker/standard/CoreSpec.scala
index 3c4c979adc..e5e285268f 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/standard/CoreSpec.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/standard/CoreSpec.scala
@@ -96,6 +96,9 @@ final class CoreSpec private (
       targetIsWebAssembly
     )
   }
+
+  private[linker] lazy val linkTimeProperties = new LinkTimeProperties(
+      semantics, esFeatures, targetIsWebAssembly)
 }
 
 private[linker] object CoreSpec {
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/standard/LinkTimeProperties.scala b/linker/shared/src/main/scala/org/scalajs/linker/standard/LinkTimeProperties.scala
new file mode 100644
index 0000000000..875196c736
--- /dev/null
+++ b/linker/shared/src/main/scala/org/scalajs/linker/standard/LinkTimeProperties.scala
@@ -0,0 +1,68 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package org.scalajs.linker.standard
+
+import org.scalajs.ir.{Types => jstpe, Trees => js}
+import org.scalajs.ir.Trees.LinkTimeProperty._
+import org.scalajs.ir.ScalaJSVersions
+import org.scalajs.ir.Position.NoPosition
+import org.scalajs.linker.interface.{Semantics, ESFeatures}
+
+private[linker] final class LinkTimeProperties (
+  semantics: Semantics,
+  esFeatures: ESFeatures,
+  targetIsWebAssembly: Boolean
+) {
+  import LinkTimeProperties._
+
+  private val linkTimeProperties: Map[String, LinkTimeValue] = Map(
+    ESVersion ->
+      LinkTimeInt(esFeatures.esVersion.edition),
+    UseECMAScript2015Semantics ->
+      LinkTimeBoolean(esFeatures.useECMAScript2015Semantics),
+    IsWebAssembly ->
+      LinkTimeBoolean(targetIsWebAssembly),
+    ProductionMode ->
+      LinkTimeBoolean(semantics.productionMode),
+    LinkerVersion ->
+      LinkTimeString(ScalaJSVersions.current)
+  )
+
+  def validate(name: String, tpe: jstpe.Type): Boolean = {
+    linkTimeProperties.get(name).exists {
+      case _: LinkTimeBoolean => tpe == jstpe.BooleanType
+      case _: LinkTimeInt     => tpe == jstpe.IntType
+      case _: LinkTimeString  => tpe == jstpe.StringType
+    }
+  }
+
+  def transformLinkTimeProperty(prop: js.LinkTimeProperty): js.Literal = {
+    val value = linkTimeProperties.getOrElse(prop.name,
+        throw new IllegalArgumentException(s"link time property not found: '${prop.name}' of type ${prop.tpe}"))
+    value match {
+      case LinkTimeBoolean(value) =>
+        js.BooleanLiteral(value)(prop.pos)
+      case LinkTimeInt(value) =>
+        js.IntLiteral(value)(prop.pos)
+      case LinkTimeString(value) =>
+        js.StringLiteral(value)(prop.pos)
+    }
+  }
+}
+
+private[linker] object LinkTimeProperties {
+  sealed abstract class LinkTimeValue
+  final case class LinkTimeInt(value: Int) extends LinkTimeValue
+  final case class LinkTimeBoolean(value: Boolean) extends LinkTimeValue
+  final case class LinkTimeString(value: String) extends LinkTimeValue
+}
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/AnalyzerTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/AnalyzerTest.scala
index f797ad25a1..1ae0a8d801 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/AnalyzerTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/AnalyzerTest.scala
@@ -806,6 +806,37 @@ class AnalyzerTest {
       assertFalse(I2barMethodInfo.isAbstractReachable)
     }
   }
+
+  @Test
+  def invalidLinkTimeProperty(): AsyncResult = await {
+    def test(invalidLinkTimeProperty: LinkTimeProperty): Future[Unit] = {
+      val classDefs = Seq(
+        classDef("A",
+          kind = ClassKind.ModuleClass, superClass = Some(ObjectClass),
+          methods = List(
+            trivialCtor("A"),
+            mainMethodDef(invalidLinkTimeProperty)
+          )
+        )
+      )
+
+      val moduleInitializer = ModuleInitializer.mainMethodWithArgs("A", "main")
+
+      val analysis = computeAnalysis(classDefs,
+          moduleInitializers = List(moduleInitializer))
+
+      assertContainsError(s"InvalidLinkTimeProperty(${invalidLinkTimeProperty.name})", analysis) {
+        case InvalidLinkTimeProperty(name, tpe, _) =>
+          name == invalidLinkTimeProperty.name && tpe == invalidLinkTimeProperty.tpe
+      }
+    }
+
+    val results = List(
+      test(LinkTimeProperty("not-found")(IntType)),
+      test(LinkTimeProperty(LinkTimeProperty.ESVersion)(BooleanType)) // ESVersion should be IntType
+    )
+    Future.sequence(results)
+  }
 }
 
 object AnalyzerTest {
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/LibrarySizeTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/LibrarySizeTest.scala
index 9ab95541de..a9fbf49876 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/LibrarySizeTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/LibrarySizeTest.scala
@@ -70,9 +70,9 @@ class LibrarySizeTest {
     )
 
     testLinkedSizes(
-      expectedFastLinkSize = 147629,
+      expectedFastLinkSize = 147459,
       expectedFullLinkSizeWithoutClosure = 85718,
-      expectedFullLinkSizeWithClosure = 21625,
+      expectedFullLinkSizeWithClosure = 21495,
       classDefs,
       moduleInitializers = MainTestModuleInitializers
     )
diff --git a/project/Build.scala b/project/Build.scala
index 9ba80d3b93..b4cab25a64 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -2048,7 +2048,7 @@ object Build {
           case `default212Version` =>
             if (!useMinifySizes) {
               Some(ExpectedSizes(
-                  fastLink = 623000 to 624000,
+                  fastLink = 622000 to 623000,
                   fullLink = 96000 to 97000,
                   fastLinkGz = 75000 to 79000,
                   fullLinkGz = 25000 to 26000,
@@ -2056,7 +2056,7 @@ object Build {
             } else {
               Some(ExpectedSizes(
                   fastLink = 423000 to 424000,
-                  fullLink = 281000 to 282000,
+                  fullLink = 280000 to 281000,
                   fastLinkGz = 60000 to 61000,
                   fullLinkGz = 43000 to 44000,
               ))
@@ -2065,7 +2065,7 @@ object Build {
           case `default213Version` =>
             if (!useMinifySizes) {
               Some(ExpectedSizes(
-                  fastLink = 450000 to 451000,
+                  fastLink = 449000 to 450000,
                   fullLink = 95000 to 96000,
                   fastLinkGz = 58000 to 59000,
                   fullLinkGz = 25000 to 26000,
diff --git a/test-suite/js/src/test/scala/org/scalajs/testsuite/library/LinkingInfoTest.scala b/test-suite/js/src/test/scala/org/scalajs/testsuite/library/LinkingInfoTest.scala
index 7dbcd44d22..50fc1fe8af 100644
--- a/test-suite/js/src/test/scala/org/scalajs/testsuite/library/LinkingInfoTest.scala
+++ b/test-suite/js/src/test/scala/org/scalajs/testsuite/library/LinkingInfoTest.scala
@@ -51,4 +51,13 @@ class LinkingInfoTest {
     assertEquals(11, ESVersion.ES2020)
     assertEquals(12, ESVersion.ES2021)
   }
+
+  @Test def isolatedJSLinkingInfo(): Unit = {
+    val linkingInfo = scala.scalajs.runtime.linkingInfo
+    assertEquals(Platform.isInProductionMode, linkingInfo.productionMode)
+    assertEquals(Platform.assumedESVersion, linkingInfo.esVersion)
+    assertEquals(Platform.assumedESVersion >= ESVersion.ES2015, linkingInfo.assumingES6)
+    assertEquals(Platform.executingInWebAssembly, linkingInfo.isWebAssembly)
+    assertEquals(Platform.assumedESVersion, linkingInfo.esVersion)
+  }
 }

From 3763e426d3accfa90dbe9e6a3def7e5b0de80b37 Mon Sep 17 00:00:00 2001
From: Rikito Taniguchi <rikiriki1238@gmail.com>
Date: Fri, 6 Sep 2024 13:27:10 +0900
Subject: [PATCH 182/298] Emit `LinkTimeProperty` via
 `LinkingInfo.linkTimeProperty` APIs

TLDR:
- Add `scala.scalajs.LinkingInfo.linkTimeProperty` APIs that emits
  `LinkTimeProperty` IRs.
- Deprecate `scala.scalajs.runtime.linkingInfo` in favor of
  `scala.scalajs.LinkingInfo` and
  `scala.scalajs.js.special.fileLevelThis`.
- Keeping `scala.scalajs.runtime.linkingInfo` because Scala3 compiler
  looks like depends on the symbol of `runtime.linkingInfo`
  https://github.com/scala/scala3/blob/67cd3ebe3f70bb9045cc966af5b96a623a7da973/compiler/src/dotty/tools/backend/sjs/JSDefinitions.scala#L182-L183

This commit introduces new APIs under `scala.scalajs.LinkingInfo`:
`linkTimeProperty(Int|String|Boolean)`.
These APIs allow us to define link-time properties in a more optimized and JS-independent way, replacing the previous `scala.scalajs.runtime.linkingInfo`.

For instance, `linkTimePropertyInt("core/esVersion")` emits the IR `LinkTimeProperty("core/esVersion")(IntType)`, which will later be transformed into an `IntLiteral` by the optimizer or linker backend.

`scala.scalajs.runtime.linkingInfo` is now deprecated in favor of `scala.scalajs.LinkingInfo`. For cases where `scala.scalajs.runtime.linkingInfo.fileLevelThis` was used, users should migrate to `scala.scalajs.js.special.fileLevelThis`.
---
 .../org/scalajs/nscplugin/GenJSCode.scala     | 44 +++++++++++++++----
 .../org/scalajs/nscplugin/JSDefinitions.scala |  5 +++
 .../org/scalajs/nscplugin/JSPrimitives.scala  | 11 +++--
 .../nscplugin/test/JSGlobalScopeTest.scala    | 32 +++++++++++++-
 .../nscplugin/test/OptimizationTest.scala     |  6 +--
 .../main/scala/org/scalajs/ir/Hashers.scala   |  3 --
 .../main/scala/org/scalajs/ir/Printers.scala  |  3 --
 .../scala/org/scalajs/ir/Serializers.scala    |  9 ++--
 .../scala/org/scalajs/ir/Transformers.scala   |  2 +-
 .../scala/org/scalajs/ir/Traversers.scala     |  2 +-
 .../src/main/scala/org/scalajs/ir/Trees.scala |  4 --
 .../scala/org/scalajs/ir/PrintersTest.scala   |  4 --
 .../src/main/scala/java/lang/Character.scala  |  4 +-
 .../src/main/scala/java/lang/ClassValue.scala |  6 +--
 javalib/src/main/scala/java/lang/Double.scala |  4 +-
 .../scala/java/lang/FloatingPointBits.scala   |  6 +--
 .../src/main/scala/java/lang/Integer.scala    |  4 +-
 javalib/src/main/scala/java/lang/Math.scala   |  4 +-
 javalib/src/main/scala/java/lang/System.scala |  4 +-
 .../src/main/scala/java/lang/_String.scala    | 12 ++---
 javalib/src/main/scala/java/util/Random.scala |  6 +--
 .../java/util/regex/PatternCompiler.scala     | 20 ++++-----
 .../util/regex/PatternSyntaxException.scala   |  1 -
 .../scala/scala/scalajs/LinkingInfo.scala     | 24 +++++++---
 .../scala/scalajs/js/special/package.scala    |  2 +-
 .../scala/scalajs/runtime/LinkingInfo.scala   |  6 ++-
 .../scala/scala/scalajs/runtime/package.scala | 13 +++++-
 .../backend/emitter/FunctionEmitter.scala     |  5 ---
 .../backend/wasmemitter/FunctionEmitter.scala |  6 ---
 .../linker/checker/ClassDefChecker.scala      |  2 -
 .../scalajs/linker/checker/IRChecker.scala    |  2 -
 .../frontend/optimizer/OptimizerCore.scala    |  2 +-
 project/BinaryIncompatibilities.scala         |  3 ++
 project/JavalibIRCleaner.scala                | 17 +++++++
 .../collection/mutable/ArrayBuilder.scala     |  4 +-
 .../collection/mutable/ArrayBuilder.scala     |  4 +-
 .../compiler/InteroperabilityTest.scala       | 24 ++++++++++
 .../testsuite/javalib/lang/SystemJSTest.scala |  4 +-
 .../testsuite/jsinterop/MiscInteropTest.scala | 23 ++++++++++
 39 files changed, 233 insertions(+), 104 deletions(-)

diff --git a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
index c3dff7493b..8dfacc7a37 100644
--- a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
+++ b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
@@ -27,7 +27,15 @@ import scala.reflect.internal.Flags
 
 import org.scalajs.ir
 import org.scalajs.ir.{Trees => js, Types => jstpe, ClassKind, Hashers, OriginalName}
-import org.scalajs.ir.Names.{LocalName, SimpleFieldName, FieldName, SimpleMethodName, MethodName, ClassName}
+import org.scalajs.ir.Names.{
+  LocalName,
+  SimpleFieldName,
+  FieldName,
+  SimpleMethodName,
+  MethodName,
+  ClassName,
+  BoxedStringClass
+}
 import org.scalajs.ir.OriginalName.NoOriginalName
 import org.scalajs.ir.Trees.OptimizerHints
 import org.scalajs.ir.Version.Unversioned
@@ -5202,10 +5210,6 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
             genStatOrExpr(args(1), isStat)
           }
 
-        case LINKING_INFO =>
-          // runtime.linkingInfo
-          js.JSLinkingInfo()
-
         case IDENTITY_HASH_CODE =>
           // runtime.identityHashCode(arg)
           val arg = genArgs1
@@ -5390,6 +5394,22 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
         case UNWRAP_FROM_THROWABLE =>
           // js.special.unwrapFromThrowable(arg)
           js.UnwrapFromThrowable(genArgs1)
+
+        case LINKTIME_PROPERTY =>
+          // LinkingInfo.linkTimePropertyXXX("...")
+          val arg = genArgs1
+          val tpe: jstpe.Type = toIRType(tree.tpe) match {
+            case jstpe.ClassType(BoxedStringClass, _) => jstpe.StringType
+            case irType                               => irType
+          }
+          arg match {
+            case js.StringLiteral(name) =>
+              js.LinkTimeProperty(name)(tpe)
+            case _ =>
+              reporter.error(args.head.pos,
+                  "The argument of linkTimePropertyXXX must be a String literal: \"...\"")
+              js.LinkTimeProperty("erroneous")(tpe)
+          }
       }
     }
 
@@ -5501,8 +5521,16 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
       def genSelectGet(propName: js.Tree): js.Tree =
         genSuperReference(propName)
 
-      def genSelectSet(propName: js.Tree, value: js.Tree): js.Tree =
-        js.Assign(genSuperReference(propName), value)
+      def genSelectSet(propName: js.Tree, value: js.Tree): js.Tree = {
+        val lhs = genSuperReference(propName)
+        lhs match {
+          case js.JSGlobalRef(js.JSGlobalRef.FileLevelThis) =>
+            reporter.error(pos,
+                "Illegal assignment to global this.")
+          case _ =>
+        }
+        js.Assign(lhs, value)
+      }
 
       def genCall(methodName: js.Tree,
           args: List[js.TreeOrJSSpread]): js.Tree = {
@@ -6758,7 +6786,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
         implicit pos: Position): js.JSGlobalRef = {
       propName match {
         case js.StringLiteral(value) =>
-          if (js.JSGlobalRef.isValidJSGlobalRefName(value) && value != js.JSGlobalRef.FileLevelThis) {
+          if (js.JSGlobalRef.isValidJSGlobalRefName(value)) {
             if (value == "await") {
               global.runReporting.warning(pos,
                   s"$actionFull of the global scope with the name '$value' is deprecated.\n" +
diff --git a/compiler/src/main/scala/org/scalajs/nscplugin/JSDefinitions.scala b/compiler/src/main/scala/org/scalajs/nscplugin/JSDefinitions.scala
index 8214985b6a..5a46388543 100644
--- a/compiler/src/main/scala/org/scalajs/nscplugin/JSDefinitions.scala
+++ b/compiler/src/main/scala/org/scalajs/nscplugin/JSDefinitions.scala
@@ -127,6 +127,11 @@ trait JSDefinitions {
       lazy val Runtime_identityHashCode           = getMemberMethod(RuntimePackageModule, newTermName("identityHashCode"))
       lazy val Runtime_dynamicImport              = getMemberMethod(RuntimePackageModule, newTermName("dynamicImport"))
 
+    lazy val LinkingInfoModule = getRequiredModule("scala.scalajs.LinkingInfo")
+      lazy val LinkingInfo_linkTimePropertyBoolean = getMemberMethod(LinkingInfoModule, newTermName("linkTimePropertyBoolean"))
+      lazy val LinkingInfo_linkTimePropertyInt = getMemberMethod(LinkingInfoModule, newTermName("linkTimePropertyInt"))
+      lazy val LinkingInfo_linkTimePropertyString = getMemberMethod(LinkingInfoModule, newTermName("linkTimePropertyString"))
+
     lazy val DynamicImportThunkClass = getRequiredClass("scala.scalajs.runtime.DynamicImportThunk")
       lazy val DynamicImportThunkClass_apply = getMemberMethod(DynamicImportThunkClass, nme.apply)
 
diff --git a/compiler/src/main/scala/org/scalajs/nscplugin/JSPrimitives.scala b/compiler/src/main/scala/org/scalajs/nscplugin/JSPrimitives.scala
index df5ff293db..c93709363b 100644
--- a/compiler/src/main/scala/org/scalajs/nscplugin/JSPrimitives.scala
+++ b/compiler/src/main/scala/org/scalajs/nscplugin/JSPrimitives.scala
@@ -55,8 +55,7 @@ abstract class JSPrimitives {
   final val CREATE_INNER_JS_CLASS = CONSTRUCTOROF + 1                  // runtime.createInnerJSClass
   final val CREATE_LOCAL_JS_CLASS = CREATE_INNER_JS_CLASS + 1          // runtime.createLocalJSClass
   final val WITH_CONTEXTUAL_JS_CLASS_VALUE = CREATE_LOCAL_JS_CLASS + 1 // runtime.withContextualJSClassValue
-  final val LINKING_INFO = WITH_CONTEXTUAL_JS_CLASS_VALUE + 1          // runtime.linkingInfo
-  final val IDENTITY_HASH_CODE = LINKING_INFO + 1                      // runtime.identityHashCode
+  final val IDENTITY_HASH_CODE = WITH_CONTEXTUAL_JS_CLASS_VALUE + 1    // runtime.identityHashCode
   final val DYNAMIC_IMPORT = IDENTITY_HASH_CODE + 1                    // runtime.dynamicImport
 
   final val STRICT_EQ = DYNAMIC_IMPORT + 1                // js.special.strictEquals
@@ -69,8 +68,9 @@ abstract class JSPrimitives {
   final val WRAP_AS_THROWABLE = JS_TRY_CATCH + 1          // js.special.wrapAsThrowable
   final val UNWRAP_FROM_THROWABLE = WRAP_AS_THROWABLE + 1 // js.special.unwrapFromThrowable
   final val DEBUGGER = UNWRAP_FROM_THROWABLE + 1          // js.special.debugger
+  final val LINKTIME_PROPERTY = DEBUGGER + 1              // LinkingInfo.linkTimePropertyXXX
 
-  final val LastJSPrimitiveCode = DEBUGGER
+  final val LastJSPrimitiveCode = LINKTIME_PROPERTY
 
   /** Initialize the map of primitive methods (for GenJSCode) */
   def init(): Unit = initWithPrimitives(addPrimitive)
@@ -109,7 +109,6 @@ abstract class JSPrimitives {
     addPrimitive(Runtime_createLocalJSClass, CREATE_LOCAL_JS_CLASS)
     addPrimitive(Runtime_withContextualJSClassValue,
         WITH_CONTEXTUAL_JS_CLASS_VALUE)
-    addPrimitive(Runtime_linkingInfo, LINKING_INFO)
     addPrimitive(Runtime_identityHashCode, IDENTITY_HASH_CODE)
     addPrimitive(Runtime_dynamicImport, DYNAMIC_IMPORT)
 
@@ -123,6 +122,10 @@ abstract class JSPrimitives {
     addPrimitive(Special_wrapAsThrowable, WRAP_AS_THROWABLE)
     addPrimitive(Special_unwrapFromThrowable, UNWRAP_FROM_THROWABLE)
     addPrimitive(Special_debugger, DEBUGGER)
+
+    addPrimitive(LinkingInfo_linkTimePropertyBoolean, LINKTIME_PROPERTY)
+    addPrimitive(LinkingInfo_linkTimePropertyInt, LINKTIME_PROPERTY)
+    addPrimitive(LinkingInfo_linkTimePropertyString, LINKTIME_PROPERTY)
   }
 
   def isJavaScriptPrimitive(code: Int): Boolean =
diff --git a/compiler/src/test/scala/org/scalajs/nscplugin/test/JSGlobalScopeTest.scala b/compiler/src/test/scala/org/scalajs/nscplugin/test/JSGlobalScopeTest.scala
index 6d5628abf2..19d3f0f8d3 100644
--- a/compiler/src/test/scala/org/scalajs/nscplugin/test/JSGlobalScopeTest.scala
+++ b/compiler/src/test/scala/org/scalajs/nscplugin/test/JSGlobalScopeTest.scala
@@ -342,7 +342,7 @@ class JSGlobalScopeTest extends DirectTest with TestHelpers {
         "extends", "false", "finally", "for", "function", "if", "implements",
         "import", "in", "instanceof", "interface", "let", "new", "null",
         "package", "private", "protected", "public", "return", "static",
-        "super", "switch", "this", "throw", "true", "try", "typeof", "var",
+        "super", "switch", "throw", "true", "try", "typeof", "var",
         "void", "while", "with", "yield")
 
     for (reservedIdentifier <- reservedIdentifiers) {
@@ -497,4 +497,34 @@ class JSGlobalScopeTest extends DirectTest with TestHelpers {
     }
   }
 
+  @Test
+  def rejectAssignmentToGlobalThis(): Unit = {
+    """
+    import scala.scalajs.js
+    import scala.scalajs.js.annotation._
+
+    object Main {
+      def main(): Unit = {
+        js.Dynamic.global.`this` = 0
+        GlobalScope.globalThis = 0
+      }
+    }
+
+    @js.native
+    @JSGlobalScope
+    object GlobalScope extends js.Any {
+      @JSName("this")
+      var globalThis: Any = js.native
+    }
+    """ hasErrors
+    s"""
+      |newSource1.scala:44: error: Illegal assignment to global this.
+      |        js.Dynamic.global.`this` = 0
+      |                   ^
+      |newSource1.scala:45: error: Illegal assignment to global this.
+      |        GlobalScope.globalThis = 0
+      |                               ^
+    """
+  }
+
 }
diff --git a/compiler/src/test/scala/org/scalajs/nscplugin/test/OptimizationTest.scala b/compiler/src/test/scala/org/scalajs/nscplugin/test/OptimizationTest.scala
index 7e140ebd38..47f843c696 100644
--- a/compiler/src/test/scala/org/scalajs/nscplugin/test/OptimizationTest.scala
+++ b/compiler/src/test/scala/org/scalajs/nscplugin/test/OptimizationTest.scala
@@ -170,14 +170,14 @@ class OptimizationTest extends JSASTTest {
     // Verify the optimized emitted code for 'new js.Object' and 'new js.Array'
     """
     import scala.scalajs.js
-
     class A {
       val o = new js.Object
       val a = new js.Array
     }
     """.
-    hasNot("any reference to the global scope") {
-      case js.JSLinkingInfo() =>
+    hasNot("any reference to the global scope nor loading JS constructor") {
+      case js.JSGlobalRef(_) =>
+      case js.LoadJSConstructor(_) =>
     }
   }
 
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Hashers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Hashers.scala
index 2ed30d9443..e866e32fb4 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Hashers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Hashers.scala
@@ -478,9 +478,6 @@ object Hashers {
           mixTag(TagJSTypeOfGlobalRef)
           mixTree(globalRef)
 
-        case JSLinkingInfo() =>
-          mixTag(TagJSLinkingInfo)
-
         case Undefined() =>
           mixTag(TagUndefined)
 
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala
index 16cb79b85d..5895bf9773 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala
@@ -778,9 +778,6 @@ object Printers {
           print(globalRef)
           print(")")
 
-        case JSLinkingInfo() =>
-          print("<linkinginfo>")
-
         // Literals
 
         case Undefined() =>
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
index ca58392661..0b3d7bd6a8 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
@@ -501,9 +501,6 @@ object Serializers {
           writeTagAndPos(TagJSTypeOfGlobalRef)
           writeTree(globalRef)
 
-        case JSLinkingInfo() =>
-          writeTagAndPos(TagJSLinkingInfo)
-
         case Undefined() =>
           writeTagAndPos(TagUndefined)
 
@@ -1300,7 +1297,7 @@ object Serializers {
         case TagJSPrivateSelect => JSPrivateSelect(readTree(), readFieldIdent())
 
         case TagJSSelect =>
-          if (/* hacks.use17 */ true && buf.get(buf.position()) == TagJSLinkingInfo) { // scalastyle:ignore
+          if (hacks.use17 && buf.get(buf.position()) == TagJSLinkingInfo) {
             val jsLinkingInfo = readTree()
             readTree() match {
               case StringLiteral("productionMode") =>
@@ -1343,7 +1340,7 @@ object Serializers {
         case TagJSTypeOfGlobalRef    => JSTypeOfGlobalRef(readTree().asInstanceOf[JSGlobalRef])
 
         case TagJSLinkingInfo =>
-          if (/* hacks.use17 */ true) { // scalastyle:ignore
+          if (hacks.use17) {
             JSObjectConstr(List(
               (StringLiteral("productionMode"), LinkTimeProperty(ProductionMode)(BooleanType)),
               (StringLiteral("esVersion"), LinkTimeProperty(ESVersion)(IntType)),
@@ -2475,6 +2472,8 @@ object Serializers {
     assert(sourceVersion != "1.15", "source version 1.15 does not exist")
 
     val use16: Boolean = use13 || sourceVersion == "1.16"
+
+    val use17: Boolean = use16 || sourceVersion == "1.17"
   }
 
   /** Names needed for hacks. */
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Transformers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Transformers.scala
index 99f16e8755..0b9719da0f 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Transformers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Transformers.scala
@@ -222,7 +222,7 @@ object Transformers {
 
         case _:Skip | _:Debugger | _:LoadModule | _:StoreModule |
             _:SelectStatic | _:SelectJSNativeMember | _:LoadJSConstructor |
-            _:LoadJSModule | _:JSNewTarget | _:JSImportMeta | _:JSLinkingInfo |
+            _:LoadJSModule | _:JSNewTarget | _:JSImportMeta |
             _:Literal | _:VarRef | _:This | _:JSGlobalRef | _:LinkTimeProperty =>
           tree
       }
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Traversers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Traversers.scala
index 4c6fd1a355..ec39bb1086 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Traversers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Traversers.scala
@@ -221,7 +221,7 @@ object Traversers {
 
       case _:Skip | _:Debugger | _:LoadModule | _:StoreModule |
           _:SelectStatic | _:SelectJSNativeMember | _:LoadJSConstructor |
-          _:LoadJSModule | _:JSNewTarget | _:JSImportMeta | _:JSLinkingInfo |
+          _:LoadJSModule | _:JSNewTarget | _:JSImportMeta |
           _:Literal | _:VarRef | _:This | _:JSGlobalRef | _:LinkTimeProperty =>
     }
 
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala b/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
index 4b36f1808e..96145a12f5 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
@@ -982,10 +982,6 @@ object Trees {
     val tpe = AnyType
   }
 
-  sealed case class JSLinkingInfo()(implicit val pos: Position) extends Tree {
-    val tpe = AnyType
-  }
-
   // Literals
 
   /** Marker for literals. Literals are always pure.
diff --git a/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala b/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala
index 013dc6672e..1df89dc5d8 100644
--- a/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala
+++ b/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala
@@ -807,10 +807,6 @@ class PrintersTest {
     assertPrintEquals("(typeof global:Foo)", JSTypeOfGlobalRef(JSGlobalRef("Foo")))
   }
 
-  @Test def printJSLinkingInfo(): Unit = {
-    assertPrintEquals("<linkinginfo>", JSLinkingInfo())
-  }
-
   @Test def printUndefined(): Unit = {
     assertPrintEquals("(void 0)", Undefined())
   }
diff --git a/javalib/src/main/scala/java/lang/Character.scala b/javalib/src/main/scala/java/lang/Character.scala
index 50c38793ac..a085f427d7 100644
--- a/javalib/src/main/scala/java/lang/Character.scala
+++ b/javalib/src/main/scala/java/lang/Character.scala
@@ -15,7 +15,7 @@ package java.lang
 import scala.annotation.{tailrec, switch}
 
 import scala.scalajs.js
-import scala.scalajs.runtime.linkingInfo
+import scala.scalajs.LinkingInfo
 import scala.scalajs.LinkingInfo.ESVersion
 
 import java.lang.constant.Constable
@@ -128,7 +128,7 @@ object Character {
     if (!isValidCodePoint(codePoint))
       throw new IllegalArgumentException()
 
-    if (linkingInfo.esVersion >= ESVersion.ES2015) {
+    if (LinkingInfo.esVersion >= ESVersion.ES2015) {
       js.Dynamic.global.String.fromCodePoint(codePoint).asInstanceOf[String]
     } else {
       if (codePoint < MIN_SUPPLEMENTARY_CODE_POINT) {
diff --git a/javalib/src/main/scala/java/lang/ClassValue.scala b/javalib/src/main/scala/java/lang/ClassValue.scala
index 94f46965e4..74f91999ca 100644
--- a/javalib/src/main/scala/java/lang/ClassValue.scala
+++ b/javalib/src/main/scala/java/lang/ClassValue.scala
@@ -16,14 +16,14 @@ import java.util.HashMap
 
 import scala.scalajs.js
 import scala.scalajs.js.annotation._
-import scala.scalajs.runtime.linkingInfo
+import scala.scalajs.LinkingInfo
 import scala.scalajs.LinkingInfo.ESVersion
 
 import Utils._
 
 abstract class ClassValue[T] protected () {
   private val jsMap: js.Map[Class[_], T] = {
-    if (linkingInfo.esVersion >= ESVersion.ES2015 || js.typeOf(js.Dynamic.global.Map) != "undefined")
+    if (LinkingInfo.esVersion >= ESVersion.ES2015 || js.typeOf(js.Dynamic.global.Map) != "undefined")
       new js.Map()
     else
       null
@@ -35,7 +35,7 @@ abstract class ClassValue[T] protected () {
      * emitting ES 2015 code, which allows to dead-code-eliminate the branches
      * using `HashMap`s, and therefore `HashMap` itself.
      */
-    linkingInfo.esVersion >= ESVersion.ES2015 || jsMap != null
+    LinkingInfo.esVersion >= ESVersion.ES2015 || jsMap != null
   }
 
   /* We use a HashMap instead of an IdentityHashMap because the latter is
diff --git a/javalib/src/main/scala/java/lang/Double.scala b/javalib/src/main/scala/java/lang/Double.scala
index e2768f8aca..aa6e3bc8d9 100644
--- a/javalib/src/main/scala/java/lang/Double.scala
+++ b/javalib/src/main/scala/java/lang/Double.scala
@@ -15,7 +15,7 @@ package java.lang
 import java.lang.constant.{Constable, ConstantDesc}
 
 import scala.scalajs.js
-import scala.scalajs.runtime.linkingInfo
+import scala.scalajs.LinkingInfo
 
 import Utils._
 
@@ -365,7 +365,7 @@ object Double {
     !isNaN(d) && !isInfinite(d)
 
   @inline def hashCode(value: scala.Double): Int = {
-    if (linkingInfo.isWebAssembly)
+    if (LinkingInfo.isWebAssembly)
       hashCodeForWasm(value)
     else
       FloatingPointBits.numberHashCode(value)
diff --git a/javalib/src/main/scala/java/lang/FloatingPointBits.scala b/javalib/src/main/scala/java/lang/FloatingPointBits.scala
index 3b3f972346..fb9b89ff93 100644
--- a/javalib/src/main/scala/java/lang/FloatingPointBits.scala
+++ b/javalib/src/main/scala/java/lang/FloatingPointBits.scala
@@ -20,11 +20,11 @@ import scala.scalajs.LinkingInfo.ESVersion
 /** Manipulating the bits of floating point numbers. */
 private[lang] object FloatingPointBits {
 
-  import scala.scalajs.runtime.linkingInfo
+  import scala.scalajs.LinkingInfo
 
   private[this] val _areTypedArraysSupported = {
     // Here we use the `esVersion` test to dce the 4 subsequent tests
-    linkingInfo.esVersion >= ESVersion.ES2015 || {
+    LinkingInfo.esVersion >= ESVersion.ES2015 || {
       js.typeOf(global.ArrayBuffer) != "undefined" &&
       js.typeOf(global.Int32Array) != "undefined" &&
       js.typeOf(global.Float32Array) != "undefined" &&
@@ -42,7 +42,7 @@ private[lang] object FloatingPointBits {
      * * If we emit ES5, replace `areTypedArraysSupported` by
      *   `_areTypedArraysSupported` so we do not calculate it multiple times.
      */
-    linkingInfo.esVersion >= ESVersion.ES2015 || _areTypedArraysSupported
+    LinkingInfo.esVersion >= ESVersion.ES2015 || _areTypedArraysSupported
   }
 
   private val arrayBuffer =
diff --git a/javalib/src/main/scala/java/lang/Integer.scala b/javalib/src/main/scala/java/lang/Integer.scala
index 78267337da..8ef617e7d0 100644
--- a/javalib/src/main/scala/java/lang/Integer.scala
+++ b/javalib/src/main/scala/java/lang/Integer.scala
@@ -15,7 +15,7 @@ package java.lang
 import java.lang.constant.{Constable, ConstantDesc}
 
 import scala.scalajs.js
-import scala.scalajs.runtime.linkingInfo
+import scala.scalajs.LinkingInfo
 import scala.scalajs.LinkingInfo.ESVersion
 
 /* This is a hijacked class. Its instances are primitive numbers.
@@ -279,7 +279,7 @@ object Integer {
 
   // Intrinsic, fallback on actual code for non-literal in JS
   @inline def numberOfLeadingZeros(i: scala.Int): scala.Int = {
-    if (linkingInfo.esVersion >= ESVersion.ES2015) js.Math.clz32(i)
+    if (LinkingInfo.esVersion >= ESVersion.ES2015) js.Math.clz32(i)
     else clz32Dynamic(i)
   }
 
diff --git a/javalib/src/main/scala/java/lang/Math.scala b/javalib/src/main/scala/java/lang/Math.scala
index 42262255f3..cb965bb56b 100644
--- a/javalib/src/main/scala/java/lang/Math.scala
+++ b/javalib/src/main/scala/java/lang/Math.scala
@@ -16,7 +16,7 @@ package lang
 import scala.scalajs.js
 import js.Dynamic.{ global => g }
 
-import scala.scalajs.runtime.linkingInfo
+import scala.scalajs.LinkingInfo
 import scala.scalajs.LinkingInfo.ESVersion
 
 object Math {
@@ -24,7 +24,7 @@ object Math {
   final val PI = 3.141592653589793
 
   @inline private def assumingES6: scala.Boolean =
-    linkingInfo.esVersion >= ESVersion.ES2015
+    LinkingInfo.esVersion >= ESVersion.ES2015
 
   @inline def abs(a: scala.Int): scala.Int = if (a < 0) -a else a
   @inline def abs(a: scala.Long): scala.Long = if (a < 0) -a else a
diff --git a/javalib/src/main/scala/java/lang/System.scala b/javalib/src/main/scala/java/lang/System.scala
index c7424a218a..8075a6ac70 100644
--- a/javalib/src/main/scala/java/lang/System.scala
+++ b/javalib/src/main/scala/java/lang/System.scala
@@ -16,7 +16,7 @@ import java.io._
 
 import scala.scalajs.js
 import scala.scalajs.js.Dynamic.global
-import scala.scalajs.runtime.linkingInfo
+import scala.scalajs.LinkingInfo
 
 import java.{util => ju}
 
@@ -200,7 +200,7 @@ object System {
       dictSet(result, "java.vm.specification.vendor", "Oracle Corporation")
       dictSet(result, "java.vm.specification.name", "Java Virtual Machine Specification")
       dictSet(result, "java.vm.name", "Scala.js")
-      dictSet(result, "java.vm.version", linkingInfo.linkerVersion)
+      dictSet(result, "java.vm.version", LinkingInfo.linkerVersion)
       dictSet(result, "java.specification.version", "1.8")
       dictSet(result, "java.specification.vendor", "Oracle Corporation")
       dictSet(result, "java.specification.name", "Java Platform API Specification")
diff --git a/javalib/src/main/scala/java/lang/_String.scala b/javalib/src/main/scala/java/lang/_String.scala
index d5b3e546fa..d89ada96dc 100644
--- a/javalib/src/main/scala/java/lang/_String.scala
+++ b/javalib/src/main/scala/java/lang/_String.scala
@@ -19,7 +19,7 @@ import java.util.Comparator
 import scala.scalajs.js
 import scala.scalajs.js.annotation._
 import scala.scalajs.js.JSStringOps.enableJSStringOps
-import scala.scalajs.runtime.linkingInfo
+import scala.scalajs.LinkingInfo
 import scala.scalajs.LinkingInfo.ESVersion
 
 import java.lang.constant.{Constable, ConstantDesc}
@@ -56,7 +56,7 @@ final class _String private () // scalastyle:ignore
 
   // Wasm intrinsic
   def codePointAt(index: Int): Int = {
-    if (linkingInfo.esVersion >= ESVersion.ES2015) {
+    if (LinkingInfo.esVersion >= ESVersion.ES2015) {
       charAt(index) // bounds check
       this.asInstanceOf[js.Dynamic].codePointAt(index).asInstanceOf[Int]
     } else {
@@ -164,7 +164,7 @@ final class _String private () // scalastyle:ignore
 
   @inline
   def endsWith(suffix: String): scala.Boolean = {
-    if (linkingInfo.esVersion >= ESVersion.ES2015) {
+    if (LinkingInfo.esVersion >= ESVersion.ES2015) {
       suffix.getClass() // null check
       thisString.asInstanceOf[js.Dynamic].endsWith(suffix).asInstanceOf[scala.Boolean]
     } else {
@@ -270,7 +270,7 @@ final class _String private () // scalastyle:ignore
   def repeat(count: Int): String = {
     if (count < 0) {
       throw new IllegalArgumentException
-    } else if (linkingInfo.esVersion >= ESVersion.ES2015) {
+    } else if (LinkingInfo.esVersion >= ESVersion.ES2015) {
       /* This will throw a `js.RangeError` if `count` is too large, instead of
        * an `OutOfMemoryError`. That's fine because the behavior of `repeat` is
        * not specified for `count` too large.
@@ -316,7 +316,7 @@ final class _String private () // scalastyle:ignore
 
   @inline
   def startsWith(prefix: String): scala.Boolean = {
-    if (linkingInfo.esVersion >= ESVersion.ES2015) {
+    if (LinkingInfo.esVersion >= ESVersion.ES2015) {
       prefix.getClass() // null check
       thisString.asInstanceOf[js.Dynamic].startsWith(prefix).asInstanceOf[scala.Boolean]
     } else {
@@ -326,7 +326,7 @@ final class _String private () // scalastyle:ignore
 
   @inline
   def startsWith(prefix: String, toffset: Int): scala.Boolean = {
-    if (linkingInfo.esVersion >= ESVersion.ES2015) {
+    if (LinkingInfo.esVersion >= ESVersion.ES2015) {
       prefix.getClass() // null check
       (toffset <= length() && toffset >= 0 &&
           thisString.asInstanceOf[js.Dynamic].startsWith(prefix, toffset).asInstanceOf[scala.Boolean])
diff --git a/javalib/src/main/scala/java/util/Random.scala b/javalib/src/main/scala/java/util/Random.scala
index 8cd654cd1f..f0452ffb0d 100644
--- a/javalib/src/main/scala/java/util/Random.scala
+++ b/javalib/src/main/scala/java/util/Random.scala
@@ -15,7 +15,7 @@ package java.util
 import scala.annotation.tailrec
 
 import scala.scalajs.js
-import scala.scalajs.runtime.linkingInfo
+import scala.scalajs.LinkingInfo
 
 class Random(seed_in: Long) extends AnyRef with java.io.Serializable {
   /* This class has two different implementations of seeding and computing
@@ -39,7 +39,7 @@ class Random(seed_in: Long) extends AnyRef with java.io.Serializable {
 
   def setSeed(seed_in: Long): Unit = {
     val seed = ((seed_in ^ 0x5DEECE66DL) & ((1L << 48) - 1)) // as documented
-    if (linkingInfo.isWebAssembly) {
+    if (LinkingInfo.isWebAssembly) {
       this.seed = seed
     } else {
       seedHi = (seed >>> 24).toInt
@@ -50,7 +50,7 @@ class Random(seed_in: Long) extends AnyRef with java.io.Serializable {
 
   @noinline
   protected def next(bits: Int): Int =
-    if (linkingInfo.isWebAssembly) nextWasm(bits)
+    if (LinkingInfo.isWebAssembly) nextWasm(bits)
     else nextJS(bits)
 
   @inline
diff --git a/javalib/src/main/scala/java/util/regex/PatternCompiler.scala b/javalib/src/main/scala/java/util/regex/PatternCompiler.scala
index b2f001407f..93754f24b7 100644
--- a/javalib/src/main/scala/java/util/regex/PatternCompiler.scala
+++ b/javalib/src/main/scala/java/util/regex/PatternCompiler.scala
@@ -30,7 +30,7 @@ import java.util.ScalaOps._
 
 import scala.scalajs.js
 import scala.scalajs.js.JSStringOps.enableJSStringOps
-import scala.scalajs.runtime.linkingInfo
+import scala.scalajs.LinkingInfo
 import scala.scalajs.LinkingInfo.ESVersion
 
 /** Compiler from Java regular expressions to JavaScript regular expressions.
@@ -83,15 +83,15 @@ private[regex] object PatternCompiler {
 
   /** Cache for `Support.supportsUnicode`. */
   private val _supportsUnicode =
-    (linkingInfo.esVersion >= ESVersion.ES2015) || featureTest("u")
+    (LinkingInfo.esVersion >= ESVersion.ES2015) || featureTest("u")
 
   /** Cache for `Support.supportsSticky`. */
   private val _supportsSticky =
-    (linkingInfo.esVersion >= ESVersion.ES2015) || featureTest("y")
+    (LinkingInfo.esVersion >= ESVersion.ES2015) || featureTest("y")
 
   /** Cache for `Support.supportsDotAll`. */
   private val _supportsDotAll =
-    (linkingInfo.esVersion >= ESVersion.ES2018) || featureTest("us")
+    (LinkingInfo.esVersion >= ESVersion.ES2018) || featureTest("us")
 
   /** Cache for `Support.supportsIndices`. */
   private val _supportsIndices =
@@ -107,17 +107,17 @@ private[regex] object PatternCompiler {
     /** Tests whether the underlying JS RegExp supports the 'u' flag. */
     @inline
     def supportsUnicode: Boolean =
-      (linkingInfo.esVersion >= ESVersion.ES2015) || _supportsUnicode
+      (LinkingInfo.esVersion >= ESVersion.ES2015) || _supportsUnicode
 
     /** Tests whether the underlying JS RegExp supports the 'y' flag. */
     @inline
     def supportsSticky: Boolean =
-      (linkingInfo.esVersion >= ESVersion.ES2015) || _supportsSticky
+      (LinkingInfo.esVersion >= ESVersion.ES2015) || _supportsSticky
 
     /** Tests whether the underlying JS RegExp supports the 's' flag. */
     @inline
     def supportsDotAll: Boolean =
-      (linkingInfo.esVersion >= ESVersion.ES2018) || _supportsDotAll
+      (LinkingInfo.esVersion >= ESVersion.ES2018) || _supportsDotAll
 
     /** Tests whether the underlying JS RegExp supports the 'd' flag. */
     @inline
@@ -131,7 +131,7 @@ private[regex] object PatternCompiler {
      */
     @inline
     def enableUnicodeCaseInsensitive: Boolean =
-      linkingInfo.esVersion >= ESVersion.ES2015
+      LinkingInfo.esVersion >= ESVersion.ES2015
 
     /** Tests whether features requiring \p{} and/or look-behind assertions are enabled.
      *
@@ -140,7 +140,7 @@ private[regex] object PatternCompiler {
      */
     @inline
     def enableUnicodeCharacterClassesAndLookBehinds: Boolean =
-      linkingInfo.esVersion >= ESVersion.ES2018
+      LinkingInfo.esVersion >= ESVersion.ES2018
   }
 
   import Support._
@@ -215,7 +215,7 @@ private[regex] object PatternCompiler {
   import InlinedHelpers._
 
   private def codePointToString(codePoint: Int): String = {
-    if (linkingInfo.esVersion >= ESVersion.ES2015) {
+    if (LinkingInfo.esVersion >= ESVersion.ES2015) {
       js.Dynamic.global.String.fromCodePoint(codePoint).asInstanceOf[String]
     } else {
       if (isBmpCodePoint(codePoint)) {
diff --git a/javalib/src/main/scala/java/util/regex/PatternSyntaxException.scala b/javalib/src/main/scala/java/util/regex/PatternSyntaxException.scala
index 945753d91b..e0bd4e1223 100644
--- a/javalib/src/main/scala/java/util/regex/PatternSyntaxException.scala
+++ b/javalib/src/main/scala/java/util/regex/PatternSyntaxException.scala
@@ -13,7 +13,6 @@
 package java.util.regex
 
 import scala.scalajs.js
-import scala.scalajs.runtime.linkingInfo
 import scala.scalajs.LinkingInfo
 
 class PatternSyntaxException(desc: String, regex: String, index: Int)
diff --git a/library/src/main/scala/scala/scalajs/LinkingInfo.scala b/library/src/main/scala/scala/scalajs/LinkingInfo.scala
index bf1bfa9c00..ea9d6c1a2f 100644
--- a/library/src/main/scala/scala/scalajs/LinkingInfo.scala
+++ b/library/src/main/scala/scala/scalajs/LinkingInfo.scala
@@ -14,8 +14,6 @@ package scala.scalajs
 
 object LinkingInfo {
 
-  import scala.scalajs.runtime.linkingInfo
-
   /** Returns true if we are linking for production, false otherwise.
    *
    *  `productionMode` is always equal to `!developmentMode`.
@@ -46,7 +44,7 @@ object LinkingInfo {
    */
   @inline
   def productionMode: Boolean =
-    linkingInfo.productionMode
+    linkTimePropertyBoolean("core/productionMode")
 
   /** Returns true if we are linking for development, false otherwise.
    *
@@ -124,7 +122,7 @@ object LinkingInfo {
    */
   @inline
   def esVersion: Int =
-    linkingInfo.esVersion
+    linkTimePropertyInt("core/esVersion")
 
   /** Returns true if we are assuming that the target platform supports
    *  ECMAScript 6, false otherwise.
@@ -222,7 +220,7 @@ object LinkingInfo {
    */
   @inline
   def useECMAScript2015Semantics: Boolean =
-    linkingInfo.assumingES6 // name mismatch for historical reasons
+    linkTimePropertyBoolean("core/useECMAScript2015Semantics")
 
   /** Whether we are linking to WebAssembly.
    *
@@ -256,7 +254,12 @@ object LinkingInfo {
    */
   @inline
   def isWebAssembly: Boolean =
-    linkingInfo.isWebAssembly
+    linkTimePropertyBoolean("core/isWebAssembly")
+
+  /** Version of the linker. */
+  @inline
+  def linkerVersion: String =
+    linkTimePropertyString("core/linkerVersion")
 
   /** Constants for the value of `esVersion`. */
   object ESVersion {
@@ -326,4 +329,13 @@ object LinkingInfo {
      */
     final val ES2021 = 12
   }
+
+  private[scalajs] def linkTimePropertyInt(name: String): Int =
+    throw new java.lang.Error("stub")
+
+  private[scalajs] def linkTimePropertyBoolean(name: String): Boolean =
+    throw new java.lang.Error("stub")
+
+  private[scalajs] def linkTimePropertyString(name: String): String =
+    throw new java.lang.Error("stub")
 }
diff --git a/library/src/main/scala/scala/scalajs/js/special/package.scala b/library/src/main/scala/scala/scalajs/js/special/package.scala
index 2ad1da9ece..64f7edd6fb 100644
--- a/library/src/main/scala/scala/scalajs/js/special/package.scala
+++ b/library/src/main/scala/scala/scalajs/js/special/package.scala
@@ -214,7 +214,7 @@ package object special {
    */
   @inline
   def fileLevelThis: scala.Any =
-    scala.scalajs.runtime.linkingInfo.fileLevelThis
+    js.Dynamic.global.`this`
 
   /** Exact equivalent of the `debugger` keyword of JavaScript.
    *
diff --git a/library/src/main/scala/scala/scalajs/runtime/LinkingInfo.scala b/library/src/main/scala/scala/scalajs/runtime/LinkingInfo.scala
index 3dd8395202..0645b93f0f 100644
--- a/library/src/main/scala/scala/scalajs/runtime/LinkingInfo.scala
+++ b/library/src/main/scala/scala/scalajs/runtime/LinkingInfo.scala
@@ -15,7 +15,11 @@ package scala.scalajs.runtime
 import scala.scalajs.js
 
 /** Information about link-time configuration of Scala.js. */
-sealed trait LinkingInfo extends js.Object {
+@deprecated(
+    "Use scala.scalajs.LinkingInfo instead. " +
+    "For fileLevelThis, use scala.scalajs.js.special.fileLevelThis.",
+    since = "1.18.0")
+trait LinkingInfo extends js.Object {
   /** Version (edition) of ECMAScript that is assumed to be supported by the
    *  runtime.
    *
diff --git a/library/src/main/scala/scala/scalajs/runtime/package.scala b/library/src/main/scala/scala/scalajs/runtime/package.scala
index 151769c2b9..d3ba4f766f 100644
--- a/library/src/main/scala/scala/scalajs/runtime/package.scala
+++ b/library/src/main/scala/scala/scalajs/runtime/package.scala
@@ -97,7 +97,18 @@ package object runtime {
    *
    *  See [[LinkingInfo]] for details.
    */
-  def linkingInfo: LinkingInfo = throw new Error("stub")
+  @deprecated(
+      "Use scala.scalajs.LinkingInfo instead. " +
+      "For fileLevelThis, use scala.scalajs.js.special.fileLevelThis.",
+      since = "1.18.0")
+  def linkingInfo: LinkingInfo = new LinkingInfo {
+    override val esVersion: Int = scalajs.LinkingInfo.esVersion
+    override val assumingES6: Boolean = scalajs.LinkingInfo.assumingES6
+    override val isWebAssembly: Boolean = scalajs.LinkingInfo.isWebAssembly
+    override val productionMode: Boolean = scalajs.LinkingInfo.productionMode
+    override val linkerVersion: String = scalajs.LinkingInfo.linkerVersion
+    override val fileLevelThis: Any = js.special.fileLevelThis
+  }
 
   /** Identity hash code of an object. */
   def identityHashCode(x: Object): Int = throw new Error("stub")
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
index 18d4272cf1..dcd45d0533 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
@@ -1247,7 +1247,6 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
         case _: Literal          => true
         case _: This             => true
         case _: JSNewTarget      => true
-        case _: JSLinkingInfo    => true
         case _: LinkTimeProperty => true
 
         // Vars (side-effect free, pure if immutable)
@@ -2962,10 +2961,6 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
         case JSTypeOfGlobalRef(globalRef) =>
           js.UnaryOp(JSUnaryOp.typeof, transformExprNoChar(globalRef))
 
-        case JSLinkingInfo() =>
-          throw new IllegalArgumentException(
-              "JSLinkingInfo was removed in 1.18.0.")
-
         // Literals
 
         case Undefined()            => js.Undefined()
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
index 7babc4ee9c..88d53a47e3 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
@@ -594,7 +594,6 @@ private class FunctionEmitter private (
       case t: JSObjectConstr       => genJSObjectConstr(t)
       case t: JSGlobalRef          => genJSGlobalRef(t)
       case t: JSTypeOfGlobalRef    => genJSTypeOfGlobalRef(t)
-      case t: JSLinkingInfo        => genJSLinkingInfo(t)
       case t: Closure              => genClosure(t)
 
       // array
@@ -2976,11 +2975,6 @@ private class FunctionEmitter private (
     AnyType
   }
 
-  private def genJSLinkingInfo(tree: JSLinkingInfo): Type = {
-    throw new IllegalArgumentException(
-      "JSLinkingInfo is deprecated as of 1.18.0.")
-  }
-
   private def genArrayLength(tree: ArrayLength): Type = {
     val ArrayLength(array) = tree
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala b/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
index ee5cbcd719..6c4c6d5426 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
@@ -806,8 +806,6 @@ private final class ClassDefChecker(classDef: ClassDef,
 
       case JSTypeOfGlobalRef(_) =>
 
-      case JSLinkingInfo() =>
-
       // Literals
 
       case ClassOf(typeRef) =>
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala b/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
index 6f9aa2c12c..4d388be2ea 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
@@ -645,8 +645,6 @@ private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter) {
 
       case JSTypeOfGlobalRef(_) =>
 
-      case JSLinkingInfo() =>
-
       // Literals
 
       case _: Literal =>
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
index 502af60ace..3f80a981fa 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
@@ -698,7 +698,7 @@ private[optimizer] abstract class OptimizerCore(
       // Trees that need not be transformed
 
       case _:Skip | _:Debugger | _:StoreModule |
-          _:SelectStatic | _:JSNewTarget | _:JSImportMeta | _:JSLinkingInfo |
+          _:SelectStatic | _:JSNewTarget | _:JSImportMeta |
           _:JSGlobalRef | _:JSTypeOfGlobalRef | _:Literal =>
         tree
 
diff --git a/project/BinaryIncompatibilities.scala b/project/BinaryIncompatibilities.scala
index 4713fe6bf8..959802dff4 100644
--- a/project/BinaryIncompatibilities.scala
+++ b/project/BinaryIncompatibilities.scala
@@ -5,6 +5,9 @@ import com.typesafe.tools.mima.core.ProblemFilters._
 
 object BinaryIncompatibilities {
   val IR = Seq(
+    // !!! Breaking, OK in minor release
+    ProblemFilters.exclude[MissingClassProblem]("org.scalajs.ir.Trees$JSLinkingInfo"),
+    ProblemFilters.exclude[MissingClassProblem]("org.scalajs.ir.Trees$JSLinkingInfo$")
   )
 
   val Linker = Seq(
diff --git a/project/JavalibIRCleaner.scala b/project/JavalibIRCleaner.scala
index 4eab2d5a6f..035732d7c4 100644
--- a/project/JavalibIRCleaner.scala
+++ b/project/JavalibIRCleaner.scala
@@ -394,6 +394,17 @@ final class JavalibIRCleaner(baseDirectoryURI: URI) {
             result
           }
 
+        // LinkingInfo
+        // Must stay in sync with the definitions in `scala.scalajs.LinkingInfo`
+        case IntrinsicCall(LinkingInfoClass, `esVersionMethodName`, Nil) =>
+          LinkTimeProperty(LinkTimeProperty.ESVersion)(IntType)
+
+        case IntrinsicCall(LinkingInfoClass, `isWebAssemblyMethodName`, Nil) =>
+          LinkTimeProperty(LinkTimeProperty.IsWebAssembly)(BooleanType)
+
+        case IntrinsicCall(LinkingInfoClass, `linkerVersionMethodName`, Nil) =>
+          LinkTimeProperty(LinkTimeProperty.LinkerVersion)(StringType)
+
         case _ =>
           tree
       }
@@ -655,6 +666,7 @@ object JavalibIRCleaner {
   private val UnionType = ClassName("scala.scalajs.js.$bar")
   private val UnionTypeMod = ClassName("scala.scalajs.js.$bar$")
   private val UnionTypeEvidence = ClassName("scala.scalajs.js.$bar$Evidence")
+  private val LinkingInfoClass = ClassName("scala.scalajs.LinkingInfo$")
 
   private val FunctionNClasses: IndexedSeq[ClassName] =
     (0 to MaxFunctionArity).map(n => ClassName(s"scala.Function$n"))
@@ -699,6 +711,11 @@ object JavalibIRCleaner {
   private val writeReplaceMethodName =
     MethodName("writeReplace", Nil, ClassRef(ObjectClass))
 
+  // LinkingInfo
+  private val esVersionMethodName = MethodName("esVersion", Nil, IntRef)
+  private val isWebAssemblyMethodName = MethodName("isWebAssembly", Nil, BooleanRef)
+  private val linkerVersionMethodName = MethodName("linkerVersion", Nil, ClassRef(BoxedStringClass))
+
   private val functionApplyMethodNames: IndexedSeq[MethodName] = {
     (0 to MaxFunctionArity).map { n =>
       MethodName("apply", (1 to n).toList.map(_ => ClassRef(ObjectClass)), ClassRef(ObjectClass))
diff --git a/scalalib/overrides-2.12/scala/collection/mutable/ArrayBuilder.scala b/scalalib/overrides-2.12/scala/collection/mutable/ArrayBuilder.scala
index 0e1c43c45e..fc3e0ee4a6 100644
--- a/scalalib/overrides-2.12/scala/collection/mutable/ArrayBuilder.scala
+++ b/scalalib/overrides-2.12/scala/collection/mutable/ArrayBuilder.scala
@@ -14,7 +14,7 @@ import scala.reflect.ClassTag
 import scala.runtime.BoxedUnit
 
 import scala.scalajs.js
-import scala.scalajs.runtime.linkingInfo
+import scala.scalajs.LinkingInfo
 
 /** A builder class for arrays.
  *
@@ -37,7 +37,7 @@ object ArrayBuilder {
    */
   @inline
   def make[T: ClassTag](): ArrayBuilder[T] =
-    if (linkingInfo.isWebAssembly) makeForWasm()
+    if (LinkingInfo.isWebAssembly) makeForWasm()
     else makeForJS()
 
   /** Implementation of `make` for JS. */
diff --git a/scalalib/overrides-2.13/scala/collection/mutable/ArrayBuilder.scala b/scalalib/overrides-2.13/scala/collection/mutable/ArrayBuilder.scala
index a49ae231c2..531a6438a2 100644
--- a/scalalib/overrides-2.13/scala/collection/mutable/ArrayBuilder.scala
+++ b/scalalib/overrides-2.13/scala/collection/mutable/ArrayBuilder.scala
@@ -17,7 +17,7 @@ import scala.reflect.ClassTag
 import scala.runtime.BoxedUnit
 
 import scala.scalajs.js
-import scala.scalajs.runtime.linkingInfo
+import scala.scalajs.LinkingInfo
 
 /** A builder class for arrays.
  *
@@ -90,7 +90,7 @@ object ArrayBuilder {
    */
   @inline
   def make[T: ClassTag]: ArrayBuilder[T] =
-    if (linkingInfo.isWebAssembly) makeForWasm
+    if (LinkingInfo.isWebAssembly) makeForWasm
     else makeForJS
 
   /** Implementation of `make` for JS. */
diff --git a/test-suite/js/src/test/scala/org/scalajs/testsuite/compiler/InteroperabilityTest.scala b/test-suite/js/src/test/scala/org/scalajs/testsuite/compiler/InteroperabilityTest.scala
index cc8f62fdcc..d69dd148f0 100644
--- a/test-suite/js/src/test/scala/org/scalajs/testsuite/compiler/InteroperabilityTest.scala
+++ b/test-suite/js/src/test/scala/org/scalajs/testsuite/compiler/InteroperabilityTest.scala
@@ -741,6 +741,22 @@ class InteroperabilityTest {
     assertEquals(6, InteroperabilityTestLetConstGlobals_method(5))
   }
 
+  @Test def accessGlobalThis(): Unit = {
+    import InteroperabilityTestScalaObjectContainer._
+    assumeTrue(isNoModule)
+    assertSame(js.Math, GlobalScope.globalThis.asInstanceOf[js.Dynamic].Math)
+    assertSame(js.Math, GlobalScope.`this`.asInstanceOf[js.Dynamic].Math)
+    assertSame(js.Math, js.Dynamic.global.`this`.Math)
+  }
+
+  @Test def accessGlobalThisESModule(): Unit = {
+    import InteroperabilityTestScalaObjectContainer._
+    assumeTrue(isESModule)
+    assertSame(js.undefined, GlobalScope.globalThis)
+    assertSame(js.undefined, GlobalScope.`this`)
+    assertSame(js.undefined, js.Dynamic.global.`this`)
+  }
+
 }
 
 object InteroperabilityTest {
@@ -1154,4 +1170,12 @@ object InteroperabilityTestScalaObjectContainer {
     var InteroperabilityTestLetConstGlobals_variable: String = js.native
     def InteroperabilityTestLetConstGlobals_method(x: Int): Int = js.native
   }
+
+  @js.native
+  @JSGlobalScope
+  object GlobalScope extends js.Any {
+    def `this`: Any = js.native
+    @JSName("this")
+    def globalThis: Any = js.native
+  }
 }
diff --git a/test-suite/js/src/test/scala/org/scalajs/testsuite/javalib/lang/SystemJSTest.scala b/test-suite/js/src/test/scala/org/scalajs/testsuite/javalib/lang/SystemJSTest.scala
index 12dc332f64..b57f6f25ce 100644
--- a/test-suite/js/src/test/scala/org/scalajs/testsuite/javalib/lang/SystemJSTest.scala
+++ b/test-suite/js/src/test/scala/org/scalajs/testsuite/javalib/lang/SystemJSTest.scala
@@ -15,7 +15,7 @@ package org.scalajs.testsuite.javalib.lang
 import org.scalajs.testsuite.utils.Platform
 
 import scala.scalajs.js
-import scala.scalajs.runtime.linkingInfo
+import scala.scalajs.LinkingInfo
 
 import org.junit.Test
 import org.junit.Assert._
@@ -179,6 +179,6 @@ class SystemJSTest {
     assertEquals("/", get("file.separator"))
     assertEquals(":", get("path.separator"))
     assertEquals("\n", get("line.separator"))
-    assertEquals(linkingInfo.linkerVersion, get("java.vm.version"))
+    assertEquals(LinkingInfo.linkerVersion, get("java.vm.version"))
   }
 }
diff --git a/test-suite/js/src/test/scala/org/scalajs/testsuite/jsinterop/MiscInteropTest.scala b/test-suite/js/src/test/scala/org/scalajs/testsuite/jsinterop/MiscInteropTest.scala
index bb422ac84a..6e5c97a7a4 100644
--- a/test-suite/js/src/test/scala/org/scalajs/testsuite/jsinterop/MiscInteropTest.scala
+++ b/test-suite/js/src/test/scala/org/scalajs/testsuite/jsinterop/MiscInteropTest.scala
@@ -194,6 +194,22 @@ class MiscInteropTest {
     assertEquals((), js.Dynamic.global.undefined)
   }
 
+  @Test def typeOfGlobalThis(): Unit = {
+    import MiscInteropTest._
+    assumeTrue(isNoModule)
+    assertSame("object", js.typeOf(GlobalScope.globalThis))
+    assertSame("object", js.typeOf(GlobalScope.`this`))
+    assertSame("object", js.typeOf(js.Dynamic.global.`this`))
+  }
+
+  @Test def accessGlobalThisESModule(): Unit = {
+    import MiscInteropTest._
+    assumeTrue(isESModule)
+    assertSame("undefined", js.typeOf(GlobalScope.globalThis))
+    assertSame("undefined", js.typeOf(GlobalScope.`this`))
+    assertSame("undefined", js.typeOf(js.Dynamic.global.`this`))
+  }
+
   // Emitted classes
 
   @Test def meaningfulNameProperty(): Unit = {
@@ -234,4 +250,11 @@ object MiscInteropTest {
 
   class SomeJSClass extends js.Object
 
+  @js.native
+  @JSGlobalScope
+  object GlobalScope extends js.Any {
+    def `this`: Any = js.native
+    @JSName("this")
+    def globalThis: Any = js.native
+  }
 }

From 9e4905ff87e35951a5aff2d5ed1acee97bd64271 Mon Sep 17 00:00:00 2001
From: Tobias Schlatter <tobias@meisch.ch>
Date: Sat, 14 Sep 2024 16:21:52 +0200
Subject: [PATCH 183/298] Remove unused ReplaceWithVarRef#longOpTree

Discovered while attempting to run the IRChecker post optimizer.
---
 .../frontend/optimizer/OptimizerCore.scala    | 25 +++++++++----------
 1 file changed, 12 insertions(+), 13 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
index 3f80a981fa..944c8ae079 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
@@ -423,7 +423,7 @@ private[optimizer] abstract class OptimizerCore(
         val (newName, newOriginalName) =
           freshLocalName(name, originalName, mutable = false)
         val localDef = LocalDef(RefinedType(AnyType), mutable = false,
-            ReplaceWithVarRef(newName, newSimpleState(UsedAtLeastOnce), None))
+            ReplaceWithVarRef(newName, newSimpleState(UsedAtLeastOnce)))
         val bodyScope = scope.withEnv(scope.env.withLocalDef(name, localDef))
 
         val newBody = if (isWasm) {
@@ -448,7 +448,7 @@ private[optimizer] abstract class OptimizerCore(
         val (newName, newOriginalName) =
           freshLocalName(name, originalName, mutable = false)
         val localDef = LocalDef(RefinedType(AnyType), true,
-            ReplaceWithVarRef(newName, newSimpleState(UsedAtLeastOnce), None))
+            ReplaceWithVarRef(newName, newSimpleState(UsedAtLeastOnce)))
         val newHandler = {
           val handlerScope = scope.withEnv(scope.env.withLocalDef(name, localDef))
           transform(handler, isStat)(handlerScope)
@@ -769,7 +769,7 @@ private[optimizer] abstract class OptimizerCore(
       def addCaptureParam(newName: LocalName): LocalDef = {
         val newOriginalName = originalNameForFresh(paramName, originalName, newName)
 
-        val replacement = ReplaceWithVarRef(newName, newSimpleState(Unused), None)
+        val replacement = ReplaceWithVarRef(newName, newSimpleState(Unused))
         val localDef = LocalDef(tcaptureValue.tpe, mutable, replacement)
         val localIdent = LocalIdent(newName)(ident.pos)
         val newParamDef = ParamDef(localIdent, newOriginalName, tcaptureValue.tpe.base, mutable)(paramDef.pos)
@@ -790,7 +790,7 @@ private[optimizer] abstract class OptimizerCore(
         case PreTransLit(literal) =>
           captureParamLocalDefs += paramName -> LocalDef(tcaptureValue.tpe, false, ReplaceWithConstant(literal))
 
-        case PreTransLocalDef(LocalDef(_, /* mutable = */ false, ReplaceWithVarRef(captureName, _, _))) =>
+        case PreTransLocalDef(LocalDef(_, /* mutable = */ false, ReplaceWithVarRef(captureName, _))) =>
           captureParamLocalDefsForVarRefs.get(captureName).fold[Unit] {
             captureParamLocalDefsForVarRefs += captureName -> addCaptureParam(captureName)
           } { prevLocalDef =>
@@ -1618,7 +1618,7 @@ private[optimizer] abstract class OptimizerCore(
         val LocalDef(tpe, mutable, replacement) = localDef
 
         val (name, used) = (replacement: @unchecked) match {
-          case ReplaceWithVarRef(name, used, _) =>
+          case ReplaceWithVarRef(name, used) =>
             (name, used)
           case ReplaceWithRecordVarRef(name, _, used, _) =>
             (name, used)
@@ -5111,7 +5111,7 @@ private[optimizer] abstract class OptimizerCore(
        */
       localNameAllocator.reserve(name)
 
-      val replacement = ReplaceWithVarRef(name, newSimpleState(Unused), None)
+      val replacement = ReplaceWithVarRef(name, newSimpleState(Unused))
       val localDef = LocalDef(RefinedType(ptpe), mutable, replacement)
       name -> localDef
     }
@@ -5332,7 +5332,7 @@ private[optimizer] abstract class OptimizerCore(
 
     val (newName, newOriginalName) = freshLocalName(name, originalName, mutable)
 
-    val replacement = ReplaceWithVarRef(newName, newSimpleState(Unused), None)
+    val replacement = ReplaceWithVarRef(newName, newSimpleState(Unused))
     val localDef = LocalDef(RefinedType(ptpe), mutable, replacement)
     val localIdent = LocalIdent(newName)(ident.pos)
     val newParamDef = ParamDef(localIdent, newOriginalName, ptpe, mutable)(paramDef.pos)
@@ -5439,7 +5439,7 @@ private[optimizer] abstract class OptimizerCore(
             (ReplaceWithRecordVarRef(newName, recordType, used, cancelFun), value.tpe)
 
           case None =>
-            (ReplaceWithVarRef(newName, used, None), tpe)
+            (ReplaceWithVarRef(newName, used), tpe)
         }
 
         val localDef = LocalDef(refinedType, mutable, replacement)
@@ -5475,7 +5475,7 @@ private[optimizer] abstract class OptimizerCore(
         case PreTransTree(VarRef(LocalIdent(refName)), _)
             if !localIsMutable(refName) =>
           buildInner(LocalDef(value.tpe, false,
-              ReplaceWithVarRef(refName, newSimpleState(UsedAtLeastOnce), None)), cont)
+              ReplaceWithVarRef(refName, newSimpleState(UsedAtLeastOnce))), cont)
 
         case _ =>
           withDedicatedVar(value.tpe)
@@ -5832,7 +5832,7 @@ private[optimizer] object OptimizerCore {
     }
 
     def newReplacement(implicit pos: Position): Tree = this.replacement match {
-      case ReplaceWithVarRef(name, used, _) =>
+      case ReplaceWithVarRef(name, used) =>
         used.value = used.value.inc
         VarRef(LocalIdent(name))(tpe.base)
 
@@ -5936,8 +5936,7 @@ private[optimizer] object OptimizerCore {
   private sealed abstract class LocalDefReplacement
 
   private final case class ReplaceWithVarRef(name: LocalName,
-      used: SimpleState[IsUsed],
-      longOpTree: Option[() => Tree]) extends LocalDefReplacement
+      used: SimpleState[IsUsed]) extends LocalDefReplacement
 
   private final case class ReplaceWithRecordVarRef(name: LocalName,
       recordType: RecordType,
@@ -6121,7 +6120,7 @@ private[optimizer] object OptimizerCore {
         localDef.replacement)
 
     def isAlreadyUsed: Boolean = (localDef.replacement: @unchecked) match {
-      case ReplaceWithVarRef(_, used, _)          => used.value.isUsed
+      case ReplaceWithVarRef(_, used)             => used.value.isUsed
       case ReplaceWithRecordVarRef(_, _, used, _) => used.value.isUsed
     }
   }

From ee1015840400b12972bea6f0582ded654e8ca509 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Sat, 24 Aug 2024 13:36:19 +0200
Subject: [PATCH 184/298] Check that constructor calls follow a chaining
 discipline.

* The constructor of `jl.Object` cannot call any other constructor.
* Every other constructor must call exactly one other constructor,
  on `this`, either from the same class or the direct superclass.

There cannot be any other call to constructors.

These restrictions are also enforced by the JVM. Technically we are
more restrictive because the JVM allows different code paths, each
having a single constructor call, whereas we require exactly one at
the top level. This is fine because both Scala and Java, as
languages, enforce that more restrictive property.

Unfortunately, we used to generate an illegal super constructor
call in the synthetic classes that extend `DynamicImportThunk`. We
patch them with a deserialization hack.

In this commit, we do not yet change the compiler to fix the above.
---
 .../scala/org/scalajs/ir/Serializers.scala    |  33 ++++-
 .../linker/checker/ClassDefChecker.scala      | 124 ++++++++++++++----
 .../org/scalajs/linker/AnalyzerTest.scala     |  10 +-
 .../org/scalajs/linker/BaseLinkerTest.scala   |   2 +-
 .../org/scalajs/linker/IRCheckerTest.scala    |   2 +-
 .../org/scalajs/linker/OptimizerTest.scala    |   4 +-
 .../linker/checker/ClassDefCheckerTest.scala  |  86 +++++++++++-
 .../linker/testutils/TestIRBuilder.scala      |  23 ++--
 8 files changed, 241 insertions(+), 43 deletions(-)

diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
index 0b3d7bd6a8..6d4c315b94 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
@@ -41,6 +41,10 @@ object Serializers {
    */
   final val IRMagicNumber = 0xCAFE4A53
 
+  // For deserialization hack
+  private final val DynamicImportThunkClass =
+    ClassName("scala.scalajs.runtime.DynamicImportThunk")
+
   def serialize(stream: OutputStream, classDef: ClassDef): Unit = {
     new Serializer().serialize(stream, classDef)
   }
@@ -1042,6 +1046,7 @@ object Serializers {
 
     private[this] var enclosingClassName: ClassName = _
     private[this] var thisTypeForHack: Option[Type] = None
+    private[this] var patchDynamicImportThunkSuperCtorCall: Boolean = false
 
     def deserializeEntryPointsInfo(): EntryPointsInfo = {
       hacks = new Hacks(sourceVersion = readHeader())
@@ -1218,9 +1223,24 @@ object Serializers {
         case TagApply =>
           Apply(readApplyFlags(), readTree(), readMethodIdent(), readTrees())(
               readType())
+
         case TagApplyStatically =>
-          ApplyStatically(readApplyFlags(), readTree(), readClassName(),
-              readMethodIdent(), readTrees())(readType())
+          val flags = readApplyFlags()
+          val receiver = readTree()
+          val className0 = readClassName()
+          val method = readMethodIdent()
+          val args = readTrees()
+          val tpe = readType()
+
+          val className = {
+            if (patchDynamicImportThunkSuperCtorCall && method.name.isConstructor)
+              DynamicImportThunkClass
+            else
+              className0
+          }
+
+          ApplyStatically(flags, receiver, className, method, args)(tpe)
+
         case TagApplyStatic =>
           ApplyStatic(readApplyFlags(), readClassName(), readMethodIdent(),
               readTrees())(readType())
@@ -1510,6 +1530,15 @@ object Serializers {
       val superClass = readOptClassIdent()
       val parents = readClassIdents()
 
+      if (/* hacks.use17 &&*/ kind.isClass) { // scalastyle:ignore
+        /* In 1.18, we started enforcing the constructor chaining discipline.
+         * Unfortunately, we used to generate a wrong super constructor call in
+         * synthetic classes extending `DynamicImportThunk`, so we patch them.
+         */
+        patchDynamicImportThunkSuperCtorCall =
+          superClass.exists(_.name == DynamicImportThunkClass)
+      }
+
       /* jsSuperClass is not hacked like in readMemberDef.bodyHack5. The
        * compilers before 1.6 always use a simple VarRef() as jsSuperClass,
        * when there is one, so no hack is required.
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala b/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
index 6c4c6d5426..958845a90d 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
@@ -236,7 +236,7 @@ private final class ClassDefChecker(classDef: ClassDef,
   }
 
   private def checkMethodDef(methodDef: MethodDef): Unit = withPerMethodState {
-    val MethodDef(flags, MethodIdent(name), _, params, _, body) = methodDef
+    val MethodDef(flags, MethodIdent(name), _, params, _, optBody) = methodDef
     implicit val ctx = ErrorContext(methodDef)
 
     val namespace = flags.namespace
@@ -251,7 +251,7 @@ private final class ClassDefChecker(classDef: ClassDef,
     if (!methods(namespace.ordinal).add(name))
       reportError(i"duplicate ${namespace.prefixString}method '$name'")
 
-    if (body.isEmpty && namespace != MemberNamespace.Public)
+    if (optBody.isEmpty && namespace != MemberNamespace.Public)
       reportError("Abstract methods may only be in the public namespace")
 
     // ClassInitializer
@@ -299,11 +299,17 @@ private final class ClassDefChecker(classDef: ClassDef,
     }
 
     // Body
-    val thisType = if (static) NoType else instanceThisType
-    val bodyEnv = Env.fromParams(params)
-      .withThisType(thisType)
-      .withInConstructor(isConstructor)
-    body.foreach(checkTree(_, bodyEnv))
+    for (body <- optBody) {
+      val thisType = if (static) NoType else instanceThisType
+      val bodyEnv = Env.fromParams(params)
+        .withThisType(thisType)
+        .withInConstructor(isConstructor)
+
+      if (isConstructor)
+        checkConstructorBody(body, bodyEnv)
+      else
+        checkTree(body, bodyEnv)
+    }
   }
 
   private def checkJSConstructorDef(ctorDef: JSConstructorDef): Unit = withPerMethodState {
@@ -324,14 +330,10 @@ private final class ClassDefChecker(classDef: ClassDef,
       .withHasNewTarget(true)
       .withInConstructor(true)
 
-    val envJustBeforeSuper = body.beforeSuper.foldLeft(startEnv) { (prevEnv, stat) =>
-      checkTree(stat, prevEnv)
-    }
+    val envJustBeforeSuper = checkBlockStats(body.beforeSuper, startEnv)
     checkTreeOrSpreads(body.superCall.args, envJustBeforeSuper)
     val envJustAfterSuper = envJustBeforeSuper.withThisType(instanceThisType)
-    body.afterSuper.foldLeft(envJustAfterSuper) { (prevEnv, stat) =>
-      checkTree(stat, prevEnv)
-    }
+    checkBlockStats(body.afterSuper, envJustAfterSuper)
   }
 
   private def checkJSMethodDef(methodDef: JSMethodDef): Unit = withPerMethodState {
@@ -510,6 +512,80 @@ private final class ClassDefChecker(classDef: ClassDef,
     }
   }
 
+  private def checkConstructorBody(body: Tree, bodyEnv: Env): Unit = {
+    /* If the enclosing class is `jl.Object`, the `body` cannot contain any
+     * delegate constructor call.
+     *
+     * Otherwise:
+     *
+     * - Let `stats` be the list of flattened statements in `body`.
+     * - There exists a unique `stat` in the `stats` list that is an
+     *   `ApplyStatically(_, This(), cls, someConstructor, args)`, called the
+     *   delegate constructor call.
+     * - There is no such `ApplyStatically` anywhere else in the body.
+     * - `cls` must be the enclosing class or its direct superclass.
+     *
+     * After the optimizer, there may be no delegate constructor call at all.
+     * This frequently happens as the optimizer inlines super constructor
+     * calls. If there is one, `cls` can be any class (it must still be some
+     * class in the superclass chain for the types to align, but this is not
+     * checked here).
+     */
+
+    implicit val ctx = ErrorContext(body)
+
+    val bodyStats = body match {
+      case Block(stats) => stats
+      case Skip()       => Nil
+      case _            => body :: Nil
+    }
+
+    if (isJLObject) {
+      checkBlockStats(bodyStats, bodyEnv)
+    } else {
+      val (beforeDelegateCtor, rest) = bodyStats.span {
+        case ApplyStatically(_, This(), _, MethodIdent(ctor), _) =>
+          !ctor.isConstructor
+        case _ =>
+          true
+      }
+
+      if (rest.isEmpty) {
+        if (!postOptimizer)
+          reportError(i"Constructor must contain a delegate constructor call")
+
+        checkBlockStats(bodyStats, bodyEnv)
+      } else {
+        val (delegateCtorCall: ApplyStatically) :: afterDelegateCtor = rest
+        val ApplyStatically(_, receiver, cls, MethodIdent(ctor), args) = delegateCtorCall
+
+        val envJustBeforeDelegate = checkBlockStats(beforeDelegateCtor, bodyEnv)
+
+        checkApplyArgs(ctor, args, envJustBeforeDelegate)
+
+        checkTree(receiver, envJustBeforeDelegate) // check that the This itself is valid
+
+        if (!postOptimizer) {
+          if (!(cls == classDef.className || classDef.superClass.exists(_.name == cls))) {
+            implicit val ctx = ErrorContext(delegateCtorCall)
+            reportError(
+                i"Invalid target class $cls for delegate constructor call; " +
+                i"expected ${classDef.className}" +
+                classDef.superClass.fold("")(s => i" or ${s.name}"))
+          }
+        }
+
+        checkBlockStats(afterDelegateCtor, envJustBeforeDelegate)
+      }
+    }
+  }
+
+  private def checkBlockStats(stats: List[Tree], env: Env): Env = {
+    stats.foldLeft(env) { (prevEnv, stat) =>
+      checkTree(stat, prevEnv)
+    }
+  }
+
   private def checkTreeOrSpreads(trees: List[TreeOrJSSpread], env: Env): Unit = {
     trees.foreach {
       case JSSpread(items) => checkTree(items, env)
@@ -520,15 +596,19 @@ private final class ClassDefChecker(classDef: ClassDef,
   private def checkTrees(trees: List[Tree], env: Env): Unit =
     trees.foreach(checkTree(_, env))
 
+  private def checkApplyArgs(methodName: MethodName, args: List[Tree], env: Env)(
+      implicit ctx: ErrorContext): Unit = {
+    val paramRefsCount = methodName.paramTypeRefs.size
+    if (args.size != paramRefsCount)
+      reportError(i"Arity mismatch: $paramRefsCount expected but ${args.size} found")
+    checkTrees(args, env)
+  }
+
   private def checkTree(tree: Tree, env: Env): Env = {
     implicit val ctx = ErrorContext(tree)
 
-    def checkApplyGeneric(methodName: MethodName, args: List[Tree]): Unit = {
-      val paramRefsCount = methodName.paramTypeRefs.size
-      if (args.size != paramRefsCount)
-        reportError(i"Arity mismatch: $paramRefsCount expected but ${args.size} found")
-      checkTrees(args, env)
-    }
+    def checkApplyGeneric(methodName: MethodName, args: List[Tree]): Unit =
+      checkApplyArgs(methodName, args, env)
 
     val newEnv = tree match {
       case VarDef(ident, _, vtpe, mutable, _) =>
@@ -545,9 +625,7 @@ private final class ClassDefChecker(classDef: ClassDef,
       case Skip() =>
 
       case Block(stats) =>
-        stats.foldLeft(env) { (prevEnv, stat) =>
-          checkTree(stat, prevEnv)
-        }
+        checkBlockStats(stats, env)
 
       case Labeled(label, _, body) =>
         checkDeclareLabel(label)
@@ -645,6 +723,8 @@ private final class ClassDefChecker(classDef: ClassDef,
         checkApplyGeneric(method, args)
 
       case ApplyStatically(_, receiver, _, MethodIdent(method), args) =>
+        if (method.isConstructor)
+          reportError(i"Illegal constructor call")
         checkTree(receiver, env)
         checkApplyGeneric(method, args)
 
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/AnalyzerTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/AnalyzerTest.scala
index 1ae0a8d801..924cd3cabe 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/AnalyzerTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/AnalyzerTest.scala
@@ -192,7 +192,7 @@ class AnalyzerTest {
         val classDefs = Seq(
             classDef("A", kind = kindSub,
                 superClass = Some("B"),
-                methods = requiredMethods("A", kindSub),
+                methods = requiredMethods("A", kindSub, "B"),
                 jsConstructor = requiredJSConstructor(kindSub)),
             classDef("B", kind = kindBase,
                 superClass = validParentForKind(kindBase),
@@ -321,7 +321,7 @@ class AnalyzerTest {
                 )))(EOH, UNV)
             )),
         classDef("B", superClass = Some("A"),
-            methods = List(trivialCtor("B")))
+            methods = List(trivialCtor("B", "A")))
     )
 
     val analysis = computeAnalysis(classDefs,
@@ -350,7 +350,7 @@ class AnalyzerTest {
             methods = List(trivialCtor("A"))),
         classDef("B", superClass = Some("A"),
             methods = List(
-                trivialCtor("B"),
+                trivialCtor("B", "A"),
                 MethodDef(EMF, fooMethodName, NON, Nil, IntType, Some(int(5)))(EOH, UNV)
             ))
     )
@@ -771,12 +771,12 @@ class AnalyzerTest {
             )),
         classDef("B", superClass = Some("A"), interfaces = List("I2"),
             methods = List(
-                trivialCtor("B"),
+                trivialCtor("B", "A"),
                 MethodDef(EMF, fooMethodName, NON, Nil, IntType, Some(int(5)))(EOH, UNV)
             )),
         classDef("C", superClass = Some("B"),
             methods = List(
-                trivialCtor("C"),
+                trivialCtor("C", "B"),
                 MethodDef(EMF, barMethodName, NON, Nil, IntType, Some(int(5)))(EOH, UNV)
             ))
     )
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/BaseLinkerTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/BaseLinkerTest.scala
index 2f4c74f00a..1997d0f789 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/BaseLinkerTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/BaseLinkerTest.scala
@@ -55,7 +55,7 @@ class BaseLinkerTest {
           "Sub",
           kind = ClassKind.Class,
           superClass = Some("Base"),
-          methods = List(trivialCtor("Sub"))
+          methods = List(trivialCtor("Sub", "Base"))
       ),
       mainTestClassDef(
         consoleLog(Apply(EAF, New("Sub", NoArgConstructorName, Nil), fooName, Nil)(IntType))
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/IRCheckerTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/IRCheckerTest.scala
index 9b30403634..fd2faebe8b 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/IRCheckerTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/IRCheckerTest.scala
@@ -133,7 +133,7 @@ class IRCheckerTest {
           superClass = Some("C"),
           interfaces = List("B"),
           methods = List(
-            trivialCtor("D"),
+            trivialCtor("D", "C"),
             MethodDef(
               EMF.withNamespace(MemberNamespace.PublicStatic),
               testMethodName,
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/OptimizerTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/OptimizerTest.scala
index d81ce35df5..3854cd89ad 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/OptimizerTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/OptimizerTest.scala
@@ -503,10 +503,12 @@ class OptimizerTest {
             // def this() = {
             //   this.x = null
             //   this.y = 5
+            //   this.jl.Object::<init>()
             // }
             MethodDef(EMF.withNamespace(Constructor), NoArgConstructorName, NON, Nil, NoType, Some(Block(
               Assign(Select(thisFor("Foo"), FieldName("Foo", "x"))(witnessType), Null()),
-              Assign(Select(thisFor("Foo"), FieldName("Foo", "y"))(IntType), int(5))
+              Assign(Select(thisFor("Foo"), FieldName("Foo", "y"))(IntType), int(5)),
+              trivialSuperCtorCall("Foo")
             )))(EOH, UNV),
 
             // def method(): Int = this.y
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/checker/ClassDefCheckerTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/checker/ClassDefCheckerTest.scala
index 62fbd15bff..db1d5ef955 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/checker/ClassDefCheckerTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/checker/ClassDefCheckerTest.scala
@@ -109,7 +109,7 @@ class ClassDefCheckerTest {
       val name = if (kind == ClassKind.HijackedClass) BoxedIntegerClass else ClassName("A")
       assertError(
           classDef(name, kind = kind,
-              methods = requiredMethods(name, kind),
+              methods = requiredMethods(name, kind, parentClassName = name),
               jsConstructor = requiredJSConstructor(kind)),
           "missing superClass")
     }
@@ -302,6 +302,87 @@ class ClassDefCheckerTest {
     )
   }
 
+  @Test
+  def missingDelegateCtorCall(): Unit = {
+    val ctorFlags = EMF.withNamespace(MemberNamespace.Constructor)
+
+    assertError(
+        classDef(
+          "Foo", superClass = Some(ObjectClass),
+          methods = List(
+            MethodDef(ctorFlags, NoArgConstructorName, NON, Nil, NoType,
+                Some(int(5)))(EOH, UNV)
+          )
+        ),
+        "Constructor must contain a delegate constructor call")
+  }
+
+  @Test
+  def invalidDelegateCtorCallTarget(): Unit = {
+    val ctorFlags = EMF.withNamespace(MemberNamespace.Constructor)
+
+    assertError(
+        classDef(
+          "Foo", superClass = Some(ObjectClass),
+          methods = List(
+            MethodDef(ctorFlags, NoArgConstructorName, NON, Nil, NoType, Some {
+              ApplyStatically(EAF.withConstructor(true), thisFor("Foo"),
+                  "Bar", NoArgConstructorName, Nil)(NoType)
+            })(EOH, UNV)
+          )
+        ),
+        "Invalid target class Bar for delegate constructor call; " +
+        "expected Foo or java.lang.Object")
+  }
+
+  @Test
+  def illegalCtorCall(): Unit = {
+    val ctorFlags = EMF.withNamespace(MemberNamespace.Constructor)
+
+    def ctorCall(receiver: Tree): ApplyStatically = {
+      ApplyStatically(EAF.withConstructor(true), receiver,
+          ObjectClass, NoArgConstructorName, Nil)(NoType)
+    }
+
+    val thiz = thisFor("Foo")
+
+    assertError(
+        classDef(
+          "Foo", superClass = Some(ObjectClass),
+          methods = List(
+            MethodDef(ctorFlags, NoArgConstructorName, NON, Nil, NoType, Some(Block(
+              ctorCall(thiz),
+              ctorCall(Null())
+            )))(EOH, UNV)
+          )
+        ),
+        "Illegal constructor call")
+
+    assertError(
+        classDef(
+          "Foo", superClass = Some(ObjectClass),
+          methods = List(
+            MethodDef(ctorFlags, NoArgConstructorName, NON, Nil, NoType, Some(Block(
+              ctorCall(thiz),
+              If(BooleanLiteral(true), ctorCall(thiz), Skip())(NoType)
+            )))(EOH, UNV)
+          )
+        ),
+        "Illegal constructor call")
+
+    assertError(
+        classDef(
+          "Foo", superClass = Some(ObjectClass),
+          methods = List(
+            trivialCtor("Foo"),
+            MethodDef(EMF, m("foo", Nil, V), NON, Nil, NoType, Some(Block(
+              ctorCall(thiz)
+            )))(EOH, UNV)
+          )
+        ),
+        "Illegal constructor call")
+  }
+
   @Test
   def thisType(): Unit = {
     def testThisTypeError(static: Boolean, expr: Tree, expectedMsg: String): Unit = {
@@ -370,8 +451,7 @@ class ClassDefCheckerTest {
   def storeModule(): Unit = {
     val ctorFlags = EMF.withNamespace(MemberNamespace.Constructor)
 
-    val superCtorCall = ApplyStatically(EAF.withConstructor(true), thisFor("Foo"),
-        ObjectClass, NoArgConstructorName, Nil)(NoType)
+    val superCtorCall = trivialSuperCtorCall("Foo")
 
     assertError(
       classDef(
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/testutils/TestIRBuilder.scala b/linker/shared/src/test/scala/org/scalajs/linker/testutils/TestIRBuilder.scala
index de55615fcf..42c8736b02 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/testutils/TestIRBuilder.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/testutils/TestIRBuilder.scala
@@ -89,13 +89,18 @@ object TestIRBuilder {
   def trivialCtor(enclosingClassName: ClassName, parentClassName: ClassName = ObjectClass): MethodDef = {
     val flags = MemberFlags.empty.withNamespace(MemberNamespace.Constructor)
     MethodDef(flags, MethodIdent(NoArgConstructorName), NON, Nil, NoType,
-        Some(ApplyStatically(EAF.withConstructor(true),
-            thisFor(enclosingClassName),
-            parentClassName, MethodIdent(NoArgConstructorName),
-            Nil)(NoType)))(
+        Some(trivialSuperCtorCall(enclosingClassName, parentClassName)))(
         EOH, UNV)
   }
 
+  def trivialSuperCtorCall(enclosingClassName: ClassName,
+      parentClassName: ClassName = ObjectClass): ApplyStatically = {
+    ApplyStatically(EAF.withConstructor(true),
+        thisFor(enclosingClassName),
+        parentClassName, MethodIdent(NoArgConstructorName),
+        Nil)(NoType)
+  }
+
   def trivialJSCtor: JSConstructorDef = {
     JSConstructorDef(JSCtorFlags, Nil, None,
         JSConstructorBody(Nil, JSSuperConstructorCall(Nil), Undefined() :: Nil))(
@@ -141,10 +146,12 @@ object TestIRBuilder {
     )
   }
 
-  def requiredMethods(className: ClassName,
-      classKind: ClassKind): List[MethodDef] = {
-    if (classKind == ClassKind.ModuleClass) List(trivialCtor(className))
-    else Nil
+  def requiredMethods(className: ClassName, classKind: ClassKind,
+      parentClassName: ClassName = ObjectClass): List[MethodDef] = {
+    if (classKind == ClassKind.ModuleClass)
+      List(trivialCtor(className, parentClassName))
+    else
+      Nil
   }
 
   def requiredJSConstructor(classKind: ClassKind): Option[JSConstructorDef] = {

From 20e334bfc5843ce64a1e3cdd973b592cd9756369 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Sat, 24 Aug 2024 13:44:51 +0200
Subject: [PATCH 185/298] Fix the super constructor call to
 `DynamicImportThunk`.

And only enable the corresponding deserialization hack for
IR < 1.18.
---
 .../src/main/scala/org/scalajs/nscplugin/PrepJSInterop.scala    | 2 +-
 ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala       | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/compiler/src/main/scala/org/scalajs/nscplugin/PrepJSInterop.scala b/compiler/src/main/scala/org/scalajs/nscplugin/PrepJSInterop.scala
index 2a59a931bc..592b9aa381 100644
--- a/compiler/src/main/scala/org/scalajs/nscplugin/PrepJSInterop.scala
+++ b/compiler/src/main/scala/org/scalajs/nscplugin/PrepJSInterop.scala
@@ -475,7 +475,7 @@ abstract class PrepJSInterop[G <: Global with Singleton](val global: G)
                */
               val superCtorCall = gen.mkMethodCall(
                   Super(clsSym, tpnme.EMPTY),
-                  ObjectClass.primaryConstructor, Nil, Nil)
+                  DynamicImportThunkClass.primaryConstructor, Nil, Nil)
 
               // class $anon extends DynamicImportThunk
               val clsDef = ClassDef(clsSym, List(
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
index 6d4c315b94..15a2e251ec 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
@@ -1530,7 +1530,7 @@ object Serializers {
       val superClass = readOptClassIdent()
       val parents = readClassIdents()
 
-      if (/* hacks.use17 &&*/ kind.isClass) { // scalastyle:ignore
+      if (hacks.use17 && kind.isClass) {
         /* In 1.18, we started enforcing the constructor chaining discipline.
          * Unfortunately, we used to generate a wrong super constructor call in
          * synthetic classes extending `DynamicImportThunk`, so we patch them.

From 3bacf85541389b0f98a8263964770738faf8ca1a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Mon, 7 Oct 2024 15:27:40 +0200
Subject: [PATCH 186/298] Emit lifted methods and lambda methods as static if
 possible.

For all lifted methods and methods that contain the body of
lambdas, we analyze whether they (transitively) refer to `this`.
If not, we emit them as static.

The JVM backend does a similar analysis in the `delambdafy` phase,
which comes after our backend.

As a side effect, this solves an issue with lifted local methods
coming from arguments to a super constructor call. They would
previously result in references to `this` from the super constructor
call arguments, which we will not consider as valid IR anymore.
Since Scala lexical scoping rules ensure that they do not actually
refer to `this`, they will now always be compiled as static.
---
 .../org/scalajs/nscplugin/GenJSCode.scala     | 147 ++++++++++++++++--
 1 file changed, 134 insertions(+), 13 deletions(-)

diff --git a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
index 8dfacc7a37..714fc7bd1b 100644
--- a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
+++ b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
@@ -248,6 +248,133 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
       )(withNewLocalNameScope(body))
     }
 
+    // Global state for tracking methods that reference `this` -----------------
+
+    /* scalac generates private instance methods for
+     * a) local defs and
+     * b) anonymous functions.
+     *
+     * In many cases, these methods do not need access to the enclosing `this`
+     * value. For every other local variable, `lambdalift` only adds them as
+     * arguments when they are needed; but `this` is always implicitly added
+     * because all such methods are instance methods.
+     *
+     * We run a separate analysis to figure out which of those methods actually
+     * need their `this` value. We compile those that do not as static methods,
+     * as if they were `isStaticMember`.
+     *
+     * The `delambdafy` phase of scalac performs a similar analysis, although
+     * as it runs after our backend (for other reasons), we do not benefit from
+     * it. Our analysis is much simpler because it deals with local defs and
+     * anonymous functions in a unified way.
+     *
+     * Performing this analysis is particularly important for lifted methods
+     * that appear within arguments to a super constructor call. The lexical
+     * scope of Scala guarantees that they cannot use `this`, but if they are
+     * compiled as instance methods, they force the constructor to leak the
+     * `this` value before the super constructor call, which is invalid.
+     * While most of the time this analysis is only an optimization, in those
+     * (rare) situations it is required for correctness. See for example
+     * the partest `run/t8733.scala`.
+     */
+
+    private var statifyCandidateMethodsThatReferenceThis: scala.collection.Set[Symbol] = null
+
+    /** Is that given method a statify-candidate?
+     *
+     *  If a method is a statify-candidate, we will analyze whether it actually
+     *  needs its `this` value. If it does not, we will compile it as a static
+     *  method in the IR.
+     *
+     *  A method is a statify-candidate if it is a lifted method (a local def)
+     *  or the target of an anonymous function.
+     *
+     *  TODO Currently we also require that the method owner not be a JS type.
+     *  We should relax that restriction in the future.
+     */
+    private def isStatifyCandidate(sym: Symbol): Boolean =
+      (sym.isLiftedMethod || sym.isDelambdafyTarget) && !isJSType(sym.owner)
+
+    /** Do we compile the given method as a static method in the IR?
+     *
+     *  This is true if one of the following is true:
+     *
+     *  - It is `isStaticMember`, or
+     *  - It is a statify-candidate method and it does not reference `this`.
+     */
+    private def compileAsStaticMethod(sym: Symbol): Boolean = {
+      sym.isStaticMember || {
+        isStatifyCandidate(sym) &&
+        !statifyCandidateMethodsThatReferenceThis.contains(sym)
+      }
+    }
+
+    /** Finds all statify-candidate methods that reference `this`, inspired by Delambdafy. */
+    private final class ThisReferringMethodsTraverser extends Traverser {
+      // the set of statify-candidate methods that directly refer to `this`
+      private val roots = mutable.Set.empty[Symbol]
+
+      // for each statify-candidate method `m`, the set of statify-candidate methods that call `m`
+      private val methodReferences = mutable.Map.empty[Symbol, mutable.Set[Symbol]]
+
+      def methodReferencesThisIn(tree: Tree): collection.Set[Symbol] = {
+        traverse(tree)
+        propagateReferences()
+      }
+
+      private def addRoot(symbol: Symbol): Unit =
+        roots += symbol
+
+      private def addReference(from: Symbol, to: Symbol): Unit =
+        methodReferences.getOrElseUpdate(to, mutable.Set.empty) += from
+
+      private def propagateReferences(): collection.Set[Symbol] = {
+        val result = mutable.Set.empty[Symbol]
+
+        def rec(symbol: Symbol): Unit = {
+          // mark `symbol` as referring to `this`
+          if (result.add(symbol)) {
+            // `symbol` was not yet in the set; propagate further
+            methodReferences.getOrElse(symbol, Nil).foreach(rec(_))
+          }
+        }
+
+        roots.foreach(rec(_))
+
+        result
+      }
+
+      private var currentMethod: Symbol = NoSymbol
+
+      override def traverse(tree: Tree): Unit = tree match {
+        case _: DefDef =>
+          if (isStatifyCandidate(tree.symbol)) {
+            currentMethod = tree.symbol
+            super.traverse(tree)
+            currentMethod = NoSymbol
+          } else {
+            // No need to traverse other methods; we always assume they refer to `this`.
+          }
+        case Function(_, Apply(target, _)) =>
+          /* We don't drill into functions because at this phase they will always refer to `this`.
+           * They will be of the form {(args...) => this.anonfun(args...)}
+           * but we do need to make note of the lifted body method in case it refers to `this`.
+           */
+          if (currentMethod.exists)
+            addReference(from = currentMethod, to = target.symbol)
+        case Apply(sel @ Select(This(_), _), args) if isStatifyCandidate(sel.symbol) =>
+          if (currentMethod.exists)
+            addReference(from = currentMethod, to = sel.symbol)
+          super.traverseTrees(args)
+        case This(_) =>
+          // Note: tree.symbol != enclClass is possible if it is a module loaded with genLoadModule
+          if (currentMethod.exists && tree.symbol == currentMethod.enclClass)
+            addRoot(currentMethod)
+        case _ =>
+          super.traverse(tree)
+      }
+    }
+
     // Global class generation state -------------------------------------------
 
     private val lazilyGeneratedAnonClasses = mutable.Map.empty[Symbol, ClassDef]
@@ -306,6 +433,9 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
      */
     override def apply(cunit: CompilationUnit): Unit = {
       try {
+        statifyCandidateMethodsThatReferenceThis =
+          new ThisReferringMethodsTraverser().methodReferencesThisIn(cunit.body)
+
         def collectClassDefs(tree: Tree): List[ClassDef] = {
           tree match {
             case EmptyTree => Nil
@@ -455,6 +585,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
         lazilyGeneratedAnonClasses.clear()
         generatedStaticForwarderClasses.clear()
         generatedClasses.clear()
+        statifyCandidateMethodsThatReferenceThis = null
         pos2irPosCache.clear()
       }
     }
@@ -1144,16 +1275,6 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
 
       assert(moduleClass.isModuleClass, moduleClass)
 
-      val hasAnyExistingPublicStaticMethod =
-        existingMethods.exists(_.flags.namespace == js.MemberNamespace.PublicStatic)
-      if (hasAnyExistingPublicStaticMethod) {
-        reporter.error(pos,
-            "Unexpected situation: found existing public static methods in " +
-            s"the class ${moduleClass.fullName} while trying to generate " +
-            "static forwarders for its companion object. " +
-            "Please report this as a bug in Scala.js.")
-      }
-
       def listMembersBasedOnFlags = {
         // Copy-pasted from BCodeHelpers.
         val ExcludedForwarderFlags: Long = {
@@ -1964,7 +2085,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
             } else {
               val resultIRType = toIRType(sym.tpe.resultType)
               val namespace = {
-                if (sym.isStaticMember) {
+                if (compileAsStaticMethod(sym)) {
                   if (sym.isPrivate) js.MemberNamespace.PrivateStatic
                   else js.MemberNamespace.PublicStatic
                 } else {
@@ -3453,7 +3574,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
           genApplyJSClassMethod(genExpr(receiver), sym, genActualArgs(sym, args))
       } else if (sym.hasAnnotation(JSNativeAnnotation)) {
         genJSNativeMemberCall(tree, isStat)
-      } else if (sym.isStaticMember) {
+      } else if (compileAsStaticMethod(sym)) {
         if (sym.isMixinConstructor) {
           /* Do not emit a call to the $init$ method of JS traits.
            * This exception is necessary because optional JS fields cause the
@@ -6333,7 +6454,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
 
       val formalArgs = params.map(genParamDef(_))
 
-      val (allFormalCaptures, body, allActualCaptures) = if (!target.isStaticMember) {
+      val (allFormalCaptures, body, allActualCaptures) = if (!compileAsStaticMethod(target)) {
         val thisActualCapture = genExpr(receiver)
         val thisFormalCapture = js.ParamDef(
             freshLocalIdent("this")(receiver.pos), thisOriginalName,

From 274713ecf587e529a632b0890751d28f687bb785 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Fri, 23 Aug 2024 17:16:16 +0200
Subject: [PATCH 187/298] Check restrictions on how `this` values can be used
 in constructors.

Essentially, `this` cannot be used before the super constructor
call, except to assign fields (but not reading).

These restrictions match those enforced by the JVM for bytecode.

While we never intended `this` values to be restricted in this way,
in practice we never produced IR that would violate those
restrictions.

There was one exception before the parent commit: we could have
lifted methods coming from the arguments to a super constructor
call. Since they were lifted as instance methods, they caused the
constructor to refer to `this` before the super constructor call.

This is in theory a backward breaking change in the IR! However,
we audited the entire ecosystem of libraries published on Maven
Central. None of them contained IR that violates the new
restriction.

In the future, we may leverage those restrictions to validate
strict field initialization. If a field *needs* to be initialized
before it is ever read (for example, because it has a non-nullable
reference type), then we can do so: we only have to check that it
is definitely initialized before the super constructor call. The
restrictions implemented in this commit ensure that nobody can
read the field before the super constructor call starts.
---
 .../linker/checker/ClassDefChecker.scala      | 55 +++++++++++++---
 .../linker/checker/ClassDefCheckerTest.scala  | 66 +++++++++++++++++++
 2 files changed, 111 insertions(+), 10 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala b/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
index 958845a90d..f2134214a7 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
@@ -524,6 +524,13 @@ private final class ClassDefChecker(classDef: ClassDef,
      *   delegate constructor call.
      * - There is no such `ApplyStatically` anywhere else in the body.
      * - `cls` must be the enclosing class or its direct superclass.
+     * - In the statements before the delegate constructor call, and within
+     *   `args`:
+     *   - `This()` cannot be used except in `Assign(Select(This(), _), _)`,
+     *     i.e., to assign to a field (but not read from one).
+     *   - `StoreModule()` cannot be used.
+     * - After the delegate constructor call, `This` can be used without
+     *   restriction.
      *
      * After the optimizer, there may be no delegate constructor call at all.
      * This frequently happens as the optimizer inlines super constructor
@@ -559,11 +566,14 @@ private final class ClassDefChecker(classDef: ClassDef,
         val (delegateCtorCall: ApplyStatically) :: afterDelegateCtor = rest
         val ApplyStatically(_, receiver, cls, MethodIdent(ctor), args) = delegateCtorCall
 
-        val envJustBeforeDelegate = checkBlockStats(beforeDelegateCtor, bodyEnv)
+        val initEnv = bodyEnv.withIsThisRestricted(true)
+        val envJustBeforeDelegate = checkBlockStats(beforeDelegateCtor, initEnv)
 
         checkApplyArgs(ctor, args, envJustBeforeDelegate)
 
-        checkTree(receiver, envJustBeforeDelegate) // check that the This itself is valid
+        val unrestrictedEnv = envJustBeforeDelegate.withIsThisRestricted(false)
+
+        checkTree(receiver, unrestrictedEnv) // check that the This itself is valid
 
         if (!postOptimizer) {
           if (!(cls == classDef.className || classDef.superClass.exists(_.name == cls))) {
@@ -575,7 +585,7 @@ private final class ClassDefChecker(classDef: ClassDef,
           }
         }
 
-        checkBlockStats(afterDelegateCtor, envJustBeforeDelegate)
+        checkBlockStats(afterDelegateCtor, unrestrictedEnv)
       }
     }
   }
@@ -632,7 +642,12 @@ private final class ClassDefChecker(classDef: ClassDef,
         checkTree(body, env.withLabel(label.name))
 
       case Assign(lhs, rhs) =>
-        checkTree(lhs, env)
+        lhs match {
+          case Select(This(), _) if env.isThisRestricted =>
+            checkTree(lhs, env.withIsThisRestricted(false))
+          case _ =>
+            checkTree(lhs, env)
+        }
         checkTree(rhs, env)
 
         lhs match {
@@ -708,6 +723,8 @@ private final class ClassDefChecker(classDef: ClassDef,
           reportError(i"Illegal StoreModule outside of constructor")
         if (env.thisType == NoType) // can happen before JSSuperConstructorCall in JSModuleClass
           reportError(i"Cannot find `this` in scope for StoreModule()")
+        if (env.isThisRestricted)
+          reportError(i"Restricted use of `this` for StoreModule() before super constructor call")
 
       case Select(qualifier, _) =>
         checkTree(qualifier, env)
@@ -915,6 +932,8 @@ private final class ClassDefChecker(classDef: ClassDef,
           reportError(i"Cannot find `this` in scope")
         else if (tree.tpe != env.thisType)
           reportError(i"`this` of type ${env.thisType} typed as ${tree.tpe}")
+        if (env.isThisRestricted)
+          reportError(i"Restricted use of `this` before the super constructor call")
 
       case Closure(arrow, captureParams, params, restParam, body, captureValues) =>
         /* Check compliance of captureValues wrt. captureParams in the current
@@ -1045,7 +1064,9 @@ object ClassDefChecker {
       /** Return types by label. */
       val returnLabels: Set[LabelName],
       /** Whether we are in a constructor of the class. */
-      val inConstructor: Boolean
+      val inConstructor: Boolean,
+      /** Whether usages of `this` are restricted in this scope. */
+      val isThisRestricted: Boolean
   ) {
     import Env._
 
@@ -1064,20 +1085,33 @@ object ClassDefChecker {
     def withInConstructor(inConstructor: Boolean): Env =
       copy(inConstructor = inConstructor)
 
+    def withIsThisRestricted(isThisRestricted: Boolean): Env =
+      copy(isThisRestricted = isThisRestricted)
+
     private def copy(
       hasNewTarget: Boolean = hasNewTarget,
       thisType: Type = thisType,
       locals: Map[LocalName, LocalDef] = locals,
       returnLabels: Set[LabelName] = returnLabels,
-      inConstructor: Boolean = inConstructor
+      inConstructor: Boolean = inConstructor,
+      isThisRestricted: Boolean = isThisRestricted
     ): Env = {
-      new Env(hasNewTarget, thisType, locals, returnLabels, inConstructor)
+      new Env(hasNewTarget, thisType, locals, returnLabels, inConstructor,
+          isThisRestricted)
     }
   }
 
   private object Env {
-    val empty: Env =
-      new Env(hasNewTarget = false, thisType = NoType, Map.empty, Set.empty, inConstructor = false)
+    val empty: Env = {
+      new Env(
+        hasNewTarget = false,
+        thisType = NoType,
+        locals = Map.empty,
+        returnLabels = Set.empty,
+        inConstructor = false,
+        isThisRestricted = false
+      )
+    }
 
     def fromParams(params: List[ParamDef]): Env = {
       val paramLocalDefs =
@@ -1089,7 +1123,8 @@ object ClassDefChecker {
         thisType = NoType,
         paramLocalDefs.toMap,
         Set.empty,
-        inConstructor = false
+        inConstructor = false,
+        isThisRestricted = false
       )
     }
   }
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/checker/ClassDefCheckerTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/checker/ClassDefCheckerTest.scala
index db1d5ef955..d48a8f7c45 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/checker/ClassDefCheckerTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/checker/ClassDefCheckerTest.scala
@@ -447,6 +447,55 @@ class ClassDefCheckerTest {
         "`this` of type any typed as Foo!")
   }
 
+  @Test
+  def restrictedThis(): Unit = {
+    val xParamDef = paramDef("x", IntType)
+    val xFieldName = FieldName("Foo", "x")
+
+    def testRestrictedThisError(ctorStats: Tree*): Unit = {
+      val ctorFlags = EMF.withNamespace(MemberNamespace.Constructor)
+
+      assertError(
+          classDef(
+            "Foo", superClass = Some(ObjectClass),
+            methods = List(
+              MethodDef(ctorFlags, MethodName.constructor(List(I)), NON,
+                  List(xParamDef), NoType, Some(Block(ctorStats: _*)))(EOH, UNV)
+            )
+          ),
+          "Restricted use of `this` before the super constructor call")
+    }
+
+    val superCtorCall = trivialSuperCtorCall("Foo")
+    val thiz = thisFor("Foo")
+
+    testRestrictedThisError(
+      thiz,
+      superCtorCall
+    )
+
+    testRestrictedThisError(
+      Select(thiz, xFieldName)(IntType),
+      superCtorCall
+    )
+
+    testRestrictedThisError(
+      Assign(Select(Select(thiz, xFieldName)(IntType), xFieldName)(IntType), int(5)),
+      superCtorCall
+    )
+
+    testRestrictedThisError(
+      Assign(Select(thiz, xFieldName)(IntType), Select(thiz, xFieldName)(IntType)),
+      superCtorCall
+    )
+
+    testRestrictedThisError(
+      ApplyStatically(EAF.withConstructor(true), thiz, ObjectClass,
+          MethodIdent(MethodName.constructor(List(O))),
+          List(thiz))(NoType)
+    )
+  }
+
   @Test
   def storeModule(): Unit = {
     val ctorFlags = EMF.withNamespace(MemberNamespace.Constructor)
@@ -470,6 +519,23 @@ class ClassDefCheckerTest {
       "Illegal StoreModule inside class of kind Class"
     )
 
+    assertError(
+      classDef(
+        "Foo",
+        kind = ClassKind.ModuleClass,
+        superClass = Some(ObjectClass),
+        methods = List(
+          MethodDef(ctorFlags, NoArgConstructorName, NON, Nil, NoType, Some {
+            Block(
+              StoreModule(),
+              superCtorCall
+            )
+          })(EOH, UNV)
+        )
+      ),
+      "Restricted use of `this` for StoreModule() before super constructor call"
+    )
+
     assertError(
       classDef(
         "Foo",

From f3244d8ff23dd82a91566a74c87225c55d2181e4 Mon Sep 17 00:00:00 2001
From: "dependabot[bot]" <49699333+dependabot[bot]@users.noreply.github.com>
Date: Sat, 19 Oct 2024 10:36:02 +0000
Subject: [PATCH 188/298] Bump cookie and express

Bumps [cookie](https://github.com/jshttp/cookie) to 0.7.1 and updates ancestor dependency [express](https://github.com/expressjs/express). These dependencies need to be updated together.


Updates `cookie` from 0.6.0 to 0.7.1
- [Release notes](https://github.com/jshttp/cookie/releases)
- [Commits](https://github.com/jshttp/cookie/compare/v0.6.0...v0.7.1)

Updates `express` from 4.21.0 to 4.21.1
- [Release notes](https://github.com/expressjs/express/releases)
- [Changelog](https://github.com/expressjs/express/blob/4.21.1/History.md)
- [Commits](https://github.com/expressjs/express/compare/4.21.0...4.21.1)

---
updated-dependencies:
- dependency-name: cookie
  dependency-type: indirect
- dependency-name: express
  dependency-type: direct:development
...

Signed-off-by: dependabot[bot] <support@github.com>
---
 package-lock.json | 30 +++++++++++++++---------------
 package.json      |  2 +-
 2 files changed, 16 insertions(+), 16 deletions(-)

diff --git a/package-lock.json b/package-lock.json
index 6cf3197b4a..82d8f5dd50 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -5,7 +5,7 @@
   "packages": {
     "": {
       "devDependencies": {
-        "express": "4.21.0",
+        "express": "4.21.1",
         "jsdom": "16.7.0",
         "jszip": "3.8.0",
         "source-map-support": "0.5.19"
@@ -247,9 +247,9 @@
       }
     },
     "node_modules/cookie": {
-      "version": "0.6.0",
-      "resolved": "https://registry.npmjs.org/cookie/-/cookie-0.6.0.tgz",
-      "integrity": "sha512-U71cyTamuh1CRNCfpGY6to28lxvNwPG4Guz/EVjgf3Jmzv0vlDp1atT9eS5dDjMYHucpHbWns6Lwf3BKz6svdw==",
+      "version": "0.7.1",
+      "resolved": "https://registry.npmjs.org/cookie/-/cookie-0.7.1.tgz",
+      "integrity": "sha512-6DnInpx7SJ2AK3+CTUE/ZM0vWTUboZCegxhC2xiIydHR9jNuTAASBrfEpHhiGOZw/nX51bHt6YQl8jsGo4y/0w==",
       "dev": true,
       "engines": {
         "node": ">= 0.6"
@@ -497,9 +497,9 @@
       }
     },
     "node_modules/express": {
-      "version": "4.21.0",
-      "resolved": "https://registry.npmjs.org/express/-/express-4.21.0.tgz",
-      "integrity": "sha512-VqcNGcj/Id5ZT1LZ/cfihi3ttTn+NJmkli2eZADigjq29qTlWi/hAQ43t/VLPq8+UX06FCEx3ByOYet6ZFblng==",
+      "version": "4.21.1",
+      "resolved": "https://registry.npmjs.org/express/-/express-4.21.1.tgz",
+      "integrity": "sha512-YSFlK1Ee0/GC8QaO91tHcDxJiE/X4FbpAyQWkxAvG6AXCuR65YzK8ua6D9hvi/TzUfZMpc+BwuM1IPw8fmQBiQ==",
       "dev": true,
       "dependencies": {
         "accepts": "~1.3.8",
@@ -507,7 +507,7 @@
         "body-parser": "1.20.3",
         "content-disposition": "0.5.4",
         "content-type": "~1.0.4",
-        "cookie": "0.6.0",
+        "cookie": "0.7.1",
         "cookie-signature": "1.0.6",
         "debug": "2.6.9",
         "depd": "2.0.0",
@@ -1754,9 +1754,9 @@
       "dev": true
     },
     "cookie": {
-      "version": "0.6.0",
-      "resolved": "https://registry.npmjs.org/cookie/-/cookie-0.6.0.tgz",
-      "integrity": "sha512-U71cyTamuh1CRNCfpGY6to28lxvNwPG4Guz/EVjgf3Jmzv0vlDp1atT9eS5dDjMYHucpHbWns6Lwf3BKz6svdw==",
+      "version": "0.7.1",
+      "resolved": "https://registry.npmjs.org/cookie/-/cookie-0.7.1.tgz",
+      "integrity": "sha512-6DnInpx7SJ2AK3+CTUE/ZM0vWTUboZCegxhC2xiIydHR9jNuTAASBrfEpHhiGOZw/nX51bHt6YQl8jsGo4y/0w==",
       "dev": true
     },
     "cookie-signature": {
@@ -1943,9 +1943,9 @@
       "dev": true
     },
     "express": {
-      "version": "4.21.0",
-      "resolved": "https://registry.npmjs.org/express/-/express-4.21.0.tgz",
-      "integrity": "sha512-VqcNGcj/Id5ZT1LZ/cfihi3ttTn+NJmkli2eZADigjq29qTlWi/hAQ43t/VLPq8+UX06FCEx3ByOYet6ZFblng==",
+      "version": "4.21.1",
+      "resolved": "https://registry.npmjs.org/express/-/express-4.21.1.tgz",
+      "integrity": "sha512-YSFlK1Ee0/GC8QaO91tHcDxJiE/X4FbpAyQWkxAvG6AXCuR65YzK8ua6D9hvi/TzUfZMpc+BwuM1IPw8fmQBiQ==",
       "dev": true,
       "requires": {
         "accepts": "~1.3.8",
@@ -1953,7 +1953,7 @@
         "body-parser": "1.20.3",
         "content-disposition": "0.5.4",
         "content-type": "~1.0.4",
-        "cookie": "0.6.0",
+        "cookie": "0.7.1",
         "cookie-signature": "1.0.6",
         "debug": "2.6.9",
         "depd": "2.0.0",
diff --git a/package.json b/package.json
index badeab7cd3..05186d318e 100644
--- a/package.json
+++ b/package.json
@@ -1,7 +1,7 @@
 {
   "private": true,
   "devDependencies": {
-    "express": "4.21.0",
+    "express": "4.21.1",
     "jsdom": "16.7.0",
     "jszip": "3.8.0",
     "source-map-support": "0.5.19"

From a7e023250fa5142512a0c9241d59f01ad8f993eb Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Mon, 21 Oct 2024 11:08:22 +0200
Subject: [PATCH 189/298] Only clean the IR loader after the result is
 completed in Refiner.

Port to `Refiner` the way `BaseLinker` already handled
`irLoader.cleanAfterRun()`. We need to wait for the `result`
future to be completed before cleaning, otherwise we can leave
`NullPointerException`s hanging.
---
 .../main/scala/org/scalajs/linker/frontend/Refiner.scala  | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/Refiner.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/Refiner.scala
index df7b262a00..51da80fd6d 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/Refiner.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/Refiner.scala
@@ -44,10 +44,10 @@ final class Refiner(config: CommonPhaseConfig, checkIR: Boolean) {
       analyzer.computeReachability(moduleInitializers, symbolRequirements, logger)
     }
 
-    for {
+    val result = for {
       analysis <- analysis
     } yield {
-      val result = logger.time("Refiner: Assemble LinkedClasses") {
+      logger.time("Refiner: Assemble LinkedClasses") {
         val assembled = for {
           (classDef, version) <- classDefs
           if analysis.classInfos.contains(classDef.className)
@@ -65,10 +65,10 @@ final class Refiner(config: CommonPhaseConfig, checkIR: Boolean) {
         new LinkingUnit(config.coreSpec, linkedClassDefs.toList,
             linkedTopLevelExports.flatten.toList, moduleInitializers, globalInfo)
       }
+    }
 
+    result.andThen { case _ =>
       irLoader.cleanAfterRun()
-
-      result
     }
   }
 }

From c399f63d9a938580aea73aeac1c1a95fec0db0f8 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Mon, 21 Oct 2024 11:42:24 +0200
Subject: [PATCH 190/298] Avoid self-suppression in `Analyzer.WorkTracker`.

---
 .../main/scala/org/scalajs/linker/analyzer/Analyzer.scala    | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala
index daf81ec531..dc4dab1816 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala
@@ -1581,7 +1581,10 @@ private object AnalyzerRun {
         case Nil =>
           promise.success(())
         case firstFailure :: moreFailures =>
-          for (t <- moreFailures)
+          /* The same `Throwable` can be propagated to several tracked Futures.
+           * Since t.addSuppressed(t) is not allowed, we filter out duplicates.
+           */
+          for (t <- moreFailures if t ne firstFailure)
             firstFailure.addSuppressed(t)
           promise.failure(firstFailure)
       }

From 7840ce17318a22ba8708de4f55b6df89b1091e7f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Mon, 21 Oct 2024 11:25:07 +0200
Subject: [PATCH 191/298] Only allow `StoreModule` at the top-level of
 constructor bodies.

This allows to get rid of `Env.inConstructor` in the
`ClassDefChecker`.

In theory, this is a breaking change. However, we never emitted IR
with `StoreModule`s that would violate the new rule.

In fact, all the IR we emit is even stricter: there is always a
`StoreModule` *immediately after* the super constructor call of
(JS) module class constructors, and never anywhere else.
---
 .../linker/checker/ClassDefChecker.scala      | 52 +++++++++----------
 .../linker/checker/ClassDefCheckerTest.scala  | 40 ++++++++++++--
 2 files changed, 60 insertions(+), 32 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala b/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
index f2134214a7..418a18b05c 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
@@ -303,7 +303,6 @@ private final class ClassDefChecker(classDef: ClassDef,
       val thisType = if (static) NoType else instanceThisType
       val bodyEnv = Env.fromParams(params)
         .withThisType(thisType)
-        .withInConstructor(isConstructor)
 
       if (isConstructor)
         checkConstructorBody(body, bodyEnv)
@@ -328,12 +327,13 @@ private final class ClassDefChecker(classDef: ClassDef,
 
     val startEnv = Env.fromParams(classDef.jsClassCaptures.getOrElse(Nil) ++ params ++ restParam)
       .withHasNewTarget(true)
-      .withInConstructor(true)
 
     val envJustBeforeSuper = checkBlockStats(body.beforeSuper, startEnv)
     checkTreeOrSpreads(body.superCall.args, envJustBeforeSuper)
     val envJustAfterSuper = envJustBeforeSuper.withThisType(instanceThisType)
-    checkBlockStats(body.afterSuper, envJustAfterSuper)
+    val afterSuperStoreModulesHandled =
+      handleStoreModulesAfterSuperCtorCall(body.afterSuper)
+    checkBlockStats(afterSuperStoreModulesHandled, envJustAfterSuper)
   }
 
   private def checkJSMethodDef(methodDef: JSMethodDef): Unit = withPerMethodState {
@@ -525,12 +525,10 @@ private final class ClassDefChecker(classDef: ClassDef,
      * - There is no such `ApplyStatically` anywhere else in the body.
      * - `cls` must be the enclosing class or its direct superclass.
      * - In the statements before the delegate constructor call, and within
-     *   `args`:
-     *   - `This()` cannot be used except in `Assign(Select(This(), _), _)`,
-     *     i.e., to assign to a field (but not read from one).
-     *   - `StoreModule()` cannot be used.
+     *   `args`, `This()` cannot be used except in `Assign(Select(This(), _), _)`,
+     *   i.e., to assign to a field (but not read from one).
      * - After the delegate constructor call, `This` can be used without
-     *   restriction.
+     *   restriction. Moreover, we can have `StoreModule`s at the top-level.
      *
      * After the optimizer, there may be no delegate constructor call at all.
      * This frequently happens as the optimizer inlines super constructor
@@ -561,7 +559,9 @@ private final class ClassDefChecker(classDef: ClassDef,
         if (!postOptimizer)
           reportError(i"Constructor must contain a delegate constructor call")
 
-        checkBlockStats(bodyStats, bodyEnv)
+        val bodyStatsStoreModulesHandled =
+          handleStoreModulesAfterSuperCtorCall(bodyStats)
+        checkBlockStats(bodyStatsStoreModulesHandled, bodyEnv)
       } else {
         val (delegateCtorCall: ApplyStatically) :: afterDelegateCtor = rest
         val ApplyStatically(_, receiver, cls, MethodIdent(ctor), args) = delegateCtorCall
@@ -585,11 +585,23 @@ private final class ClassDefChecker(classDef: ClassDef,
           }
         }
 
-        checkBlockStats(afterDelegateCtor, unrestrictedEnv)
+        val afterDelegateCtorStoreModulesHandled =
+          handleStoreModulesAfterSuperCtorCall(afterDelegateCtor)
+        checkBlockStats(afterDelegateCtorStoreModulesHandled, unrestrictedEnv)
       }
     }
   }
 
+  private def handleStoreModulesAfterSuperCtorCall(trees: List[Tree]): List[Tree] = {
+    /* If StoreModule's are allowed, there is nothing left to check about them,
+     * so we filter them out.
+     */
+    if (classDef.kind.hasModuleAccessor)
+      trees.filter(!_.isInstanceOf[StoreModule])
+    else
+      trees
+  }
+
   private def checkBlockStats(stats: List[Tree], env: Env): Env = {
     stats.foldLeft(env) { (prevEnv, stat) =>
       checkTree(stat, prevEnv)
@@ -717,14 +729,7 @@ private final class ClassDefChecker(classDef: ClassDef,
       case _: LoadModule =>
 
       case StoreModule() =>
-        if (!classDef.kind.hasModuleAccessor)
-          reportError(i"Illegal StoreModule inside class of kind ${classDef.kind}")
-        if (!env.inConstructor)
-          reportError(i"Illegal StoreModule outside of constructor")
-        if (env.thisType == NoType) // can happen before JSSuperConstructorCall in JSModuleClass
-          reportError(i"Cannot find `this` in scope for StoreModule()")
-        if (env.isThisRestricted)
-          reportError(i"Restricted use of `this` for StoreModule() before super constructor call")
+        reportError(i"Illegal StoreModule")
 
       case Select(qualifier, _) =>
         checkTree(qualifier, env)
@@ -1063,8 +1068,6 @@ object ClassDefChecker {
       val locals: Map[LocalName, LocalDef],
       /** Return types by label. */
       val returnLabels: Set[LabelName],
-      /** Whether we are in a constructor of the class. */
-      val inConstructor: Boolean,
       /** Whether usages of `this` are restricted in this scope. */
       val isThisRestricted: Boolean
   ) {
@@ -1082,9 +1085,6 @@ object ClassDefChecker {
     def withLabel(label: LabelName): Env =
       copy(returnLabels = returnLabels + label)
 
-    def withInConstructor(inConstructor: Boolean): Env =
-      copy(inConstructor = inConstructor)
-
     def withIsThisRestricted(isThisRestricted: Boolean): Env =
       copy(isThisRestricted = isThisRestricted)
 
@@ -1093,11 +1093,9 @@ object ClassDefChecker {
       thisType: Type = thisType,
       locals: Map[LocalName, LocalDef] = locals,
       returnLabels: Set[LabelName] = returnLabels,
-      inConstructor: Boolean = inConstructor,
       isThisRestricted: Boolean = isThisRestricted
     ): Env = {
-      new Env(hasNewTarget, thisType, locals, returnLabels, inConstructor,
-          isThisRestricted)
+      new Env(hasNewTarget, thisType, locals, returnLabels, isThisRestricted)
     }
   }
 
@@ -1108,7 +1106,6 @@ object ClassDefChecker {
         thisType = NoType,
         locals = Map.empty,
         returnLabels = Set.empty,
-        inConstructor = false,
         isThisRestricted = false
       )
     }
@@ -1123,7 +1120,6 @@ object ClassDefChecker {
         thisType = NoType,
         paramLocalDefs.toMap,
         Set.empty,
-        inConstructor = false,
         isThisRestricted = false
       )
     }
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/checker/ClassDefCheckerTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/checker/ClassDefCheckerTest.scala
index d48a8f7c45..f1e17cc5f1 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/checker/ClassDefCheckerTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/checker/ClassDefCheckerTest.scala
@@ -516,7 +516,7 @@ class ClassDefCheckerTest {
           })(EOH, UNV)
         )
       ),
-      "Illegal StoreModule inside class of kind Class"
+      "Illegal StoreModule"
     )
 
     assertError(
@@ -533,7 +533,24 @@ class ClassDefCheckerTest {
           })(EOH, UNV)
         )
       ),
-      "Restricted use of `this` for StoreModule() before super constructor call"
+      "Illegal StoreModule"
+    )
+
+    assertError(
+      classDef(
+        "Foo",
+        kind = ClassKind.ModuleClass,
+        superClass = Some(ObjectClass),
+        methods = List(
+          MethodDef(ctorFlags, NoArgConstructorName, NON, Nil, NoType, Some {
+            Block(
+              superCtorCall,
+              If(BooleanLiteral(true), StoreModule(), Skip())(NoType)
+            )
+          })(EOH, UNV)
+        )
+      ),
+      "Illegal StoreModule"
     )
 
     assertError(
@@ -550,7 +567,7 @@ class ClassDefCheckerTest {
           })(EOH, UNV)
         )
       ),
-      "Illegal StoreModule outside of constructor"
+      "Illegal StoreModule"
     )
 
     assertError(
@@ -564,7 +581,22 @@ class ClassDefCheckerTest {
               EOH, UNV)
         )
       ),
-      "Cannot find `this` in scope for StoreModule()"
+      "Illegal StoreModule"
+    )
+
+    assertError(
+      classDef(
+        "Foo",
+        kind = ClassKind.JSModuleClass,
+        superClass = Some("scala.scalajs.js.Object"),
+        jsConstructor = Some(
+          JSConstructorDef(JSCtorFlags, Nil, None,
+              JSConstructorBody(Nil, JSSuperConstructorCall(Nil),
+                  If(BooleanLiteral(true), StoreModule(), Skip())(NoType) :: Undefined() :: Nil))(
+              EOH, UNV)
+        )
+      ),
+      "Illegal StoreModule"
     )
   }
 

From f3c0590cb9b18eeb6ab17d7c0127d8283ec6e72e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Mon, 21 Oct 2024 13:47:38 +0200
Subject: [PATCH 192/298] Under restrictedThis, do not allow assigning fields
 of super classes.

We can only assign fields of `this` that are declared by the
current class. This restriction matches a restriction on the JVM.
---
 .../scala/org/scalajs/linker/checker/ClassDefChecker.scala | 7 +++++--
 .../org/scalajs/linker/checker/ClassDefCheckerTest.scala   | 5 +++++
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala b/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
index f2134214a7..fbe01036dc 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
@@ -643,8 +643,11 @@ private final class ClassDefChecker(classDef: ClassDef,
 
       case Assign(lhs, rhs) =>
         lhs match {
-          case Select(This(), _) if env.isThisRestricted =>
-            checkTree(lhs, env.withIsThisRestricted(false))
+          case Select(This(), field) if env.isThisRestricted =>
+            if (postOptimizer || field.name.className == classDef.className)
+              checkTree(lhs, env.withIsThisRestricted(false))
+            else
+              checkTree(lhs, env)
           case _ =>
             checkTree(lhs, env)
         }
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/checker/ClassDefCheckerTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/checker/ClassDefCheckerTest.scala
index d48a8f7c45..32f394ebb9 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/checker/ClassDefCheckerTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/checker/ClassDefCheckerTest.scala
@@ -479,6 +479,11 @@ class ClassDefCheckerTest {
       superCtorCall
     )
 
+    testRestrictedThisError(
+      Assign(Select(thiz, FieldName("Bar", "y"))(IntType), int(5)),
+      superCtorCall
+    )
+
     testRestrictedThisError(
       Assign(Select(Select(thiz, xFieldName)(IntType), xFieldName)(IntType), int(5)),
       superCtorCall

From f1732b16a19a7c6620904f55e21ecd822cc3a283 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Sat, 26 Oct 2024 12:29:23 +0200
Subject: [PATCH 193/298] Switch to `try_table` to compile `TryCatch`.

And remove the internal support for the legacy `try/catch`
instruction pair.

Now that Node.js 23 is released, we can always use `try_table`. The
main browsers already have full support for `try_table`.
---
 .../backend/wasmemitter/FunctionEmitter.scala | 72 ++++++-------------
 .../backend/webassembly/FunctionBuilder.scala |  2 +-
 .../backend/webassembly/Instructions.scala    | 11 ---
 .../backend/webassembly/TextWriter.scala      |  8 +--
 4 files changed, 25 insertions(+), 68 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
index 88d53a47e3..133dde2cde 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
@@ -40,22 +40,6 @@ import TypeTransformer._
 
 object FunctionEmitter {
 
-  /** Whether to use the legacy `try` instruction to implement `TryCatch`.
-   *
-   *  Support for catching JS exceptions was only added to `try_table` in V8 12.5 from April 2024.
-   *  While waiting for Node.js to catch up with V8, we use `try` to implement our `TryCatch`.
-   *
-   *  We use this "fixed configuration option" to keep the code that implements `TryCatch` using
-   *  `try_table` in the codebase, as code that is actually compiled, so that refactorings apply to
-   *  it as well. It also makes it easier to manually experiment with the new `try_table` encoding,
-   *  which is available in Chrome since v125.
-   *
-   *  Note that we use `try_table` regardless to implement `TryFinally`. Its `catch_all_ref` handler
-   *  is perfectly happy to catch and rethrow JavaScript exception in Node.js 22. Duplicating that
-   *  implementation for `try` would be a nightmare, given how complex it is already.
-   */
-  private final val UseLegacyExceptionsForTryCatch = true
-
   private val dotUTF8String = UTF8String(".")
 
   def emitFunction(
@@ -2475,47 +2459,31 @@ private class FunctionEmitter private (
 
     val resultType = transformResultType(expectedType)
 
-    if (UseLegacyExceptionsForTryCatch) {
-      markPosition(tree)
-      fb += wa.Try(fb.sigToBlockType(Sig(Nil, resultType)))
-      withNPEScope(resultType) {
-        genTree(block, expectedType)
-      }
-      markPosition(tree)
-      fb += wa.Catch(genTagID.exception)
+    markPosition(tree)
+    fb.block(resultType) { doneLabel =>
+      fb.block(watpe.RefType.externref) { catchLabel =>
+        /* We used to have `resultType` as result of the try_table, with the
+         * `wa.BR(doneLabel)` outside of the try_table. Unfortunately it seems
+         * V8 cannot handle try_table with a result type that is `(ref ...)`.
+         * The current encoding with `externref` as result type (to match the
+         * enclosing block) and the `br` *inside* the `try_table` works.
+         */
+        fb.tryTable(watpe.RefType.externref)(
+          List(wa.CatchClause.Catch(genTagID.exception, catchLabel))
+        ) {
+          withNPEScope(resultType) {
+            genTree(block, expectedType)
+          }
+          markPosition(tree)
+          fb += wa.Br(doneLabel)
+        }
+      } // end block $catch
       withNewLocal(errVarName, errVarOrigName, watpe.RefType.anyref) { exceptionLocal =>
         fb += wa.AnyConvertExtern
         fb += wa.LocalSet(exceptionLocal)
         genTree(handler, expectedType)
       }
-      fb += wa.End
-    } else {
-      markPosition(tree)
-      fb.block(resultType) { doneLabel =>
-        fb.block(watpe.RefType.externref) { catchLabel =>
-          /* We used to have `resultType` as result of the try_table, with the
-           * `wa.BR(doneLabel)` outside of the try_table. Unfortunately it seems
-           * V8 cannot handle try_table with a result type that is `(ref ...)`.
-           * The current encoding with `externref` as result type (to match the
-           * enclosing block) and the `br` *inside* the `try_table` works.
-           */
-          fb.tryTable(watpe.RefType.externref)(
-            List(wa.CatchClause.Catch(genTagID.exception, catchLabel))
-          ) {
-            withNPEScope(resultType) {
-              genTree(block, expectedType)
-            }
-            markPosition(tree)
-            fb += wa.Br(doneLabel)
-          }
-        } // end block $catch
-        withNewLocal(errVarName, errVarOrigName, watpe.RefType.anyref) { exceptionLocal =>
-          fb += wa.AnyConvertExtern
-          fb += wa.LocalSet(exceptionLocal)
-          genTree(handler, expectedType)
-        }
-      } // end block $done
-    }
+    } // end block $done
 
     if (expectedType == NothingType)
       fb += wa.Unreachable
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/FunctionBuilder.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/FunctionBuilder.scala
index 25162bc9f9..5c31310cae 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/FunctionBuilder.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/FunctionBuilder.scala
@@ -377,7 +377,7 @@ final class FunctionBuilder(
         while (nestingLevel >= 0 && iter.hasNext) {
           val deadCodeInstr = iter.next()
           deadCodeInstr match {
-            case End | Else | _: Catch if nestingLevel == 0 =>
+            case End | Else if nestingLevel == 0 =>
               /* We have reached the end of the original block of dead code.
                * Actually emit this END or ELSE and then drop `nestingLevel`
                * below 0 to end the dead code processing loop.
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/Instructions.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/Instructions.scala
index 45ab60e830..26b9e02c9b 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/Instructions.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/Instructions.scala
@@ -120,17 +120,6 @@ object Instructions {
 
   case object Else extends SimpleInstr("else", 0x05)
 
-  /** `try` in the legacy exception system.
-   *
-   *  @see
-   *    [[https://webassembly.github.io/exception-handling/legacy/exceptions/core/syntax.html]]
-   */
-  final case class Try(i: BlockType, label: Option[LabelID] = None)
-      extends BlockTypeLabeledInstr("try", 0x06, i)
-
-  /** `catch` in the legacy exception system. */
-  final case class Catch(i: TagID) extends TagInstr("catch", 0x07, i)
-
   final case class Throw(i: TagID) extends TagInstr("throw", 0x08, i) with StackPolymorphicInstr
   case object ThrowRef extends SimpleInstr("throw_ref", 0x0A) with StackPolymorphicInstr
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/TextWriter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/TextWriter.scala
index 645bc72e52..d8adec9b9f 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/TextWriter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/TextWriter.scala
@@ -411,8 +411,8 @@ private class TextWriter(module: Module) {
 
       case _ =>
         instr match {
-          case End | Else | _: Catch => b.deindent()
-          case _                     => // do nothing
+          case End | Else => b.deindent()
+          case _          => // do nothing
         }
         b.newLine()
         b.appendElement(instr.mnemonic)
@@ -429,8 +429,8 @@ private class TextWriter(module: Module) {
         writeInstrImmediates(instr)
 
         instr match {
-          case _: StructuredLabeledInstr | Else | _: Catch => b.indent()
-          case _                                           => // do nothing
+          case _: StructuredLabeledInstr | Else => b.indent()
+          case _                                => // do nothing
         }
     }
   }

From 8998caf50902b09619bd1a4bcafabca820e0d7f0 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Sat, 2 Nov 2024 14:56:53 +0100
Subject: [PATCH 194/298] Make record types *not* subtypes of `any`.

And clarify that `any` is not a universal top type. It is only the
supertype of all values that can be passed to JavaScript.
---
 .../src/main/scala/org/scalajs/ir/Types.scala | 36 +++++++++++++------
 1 file changed, 26 insertions(+), 10 deletions(-)

diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Types.scala b/ir/shared/src/main/scala/org/scalajs/ir/Types.scala
index 000583a135..df0ee5b926 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Types.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Types.scala
@@ -78,13 +78,17 @@ object Types {
     }
   }
 
-  /** Any type (the top type of this type system).
-   *  A variable of this type can contain any value, including `undefined`
-   *  and `null` and any JS value. This type supports a very limited set
-   *  of Scala operations, the ones common to all values. Basically only
-   *  reference equality tests and instance tests. It also supports all
-   *  JavaScript operations, since all Scala objects are also genuine
-   *  JavaScript objects.
+  /** Any type.
+   *
+   *  This is the supertype of all value types that can be passed to JavaScript
+   *  code. Record types are the canonical counter-example: they are not
+   *  subtypes of `any` because their values cannot be given to JavaScript.
+   *
+   *  This type supports a very limited set of Scala operations, the ones
+   *  common to all values. Basically only reference equality tests and
+   *  instance tests. It also supports all JavaScript operations, since all
+   *  Scala objects are also genuine JavaScript values.
+   *
    *  The type java.lang.Object in the back-end maps to [[AnyType]] because it
    *  can hold JS values (not only instances of Scala.js classes).
    */
@@ -179,11 +183,19 @@ object Types {
   }
 
   /** Record type.
+   *
    *  Used by the optimizer to inline classes as records with multiple fields.
    *  They are desugared as several local variables by JSDesugaring.
    *  Record types cannot cross method boundaries, so they cannot appear as
    *  the type of fields or parameters, nor as result types of methods.
    *  The compiler itself never generates record types.
+   *
+   *  Record types currently do not feature any form of subtyping. For R1 to be
+   *  a subtype of R2, it must have the same fields, in the same order, with
+   *  equivalent types.
+   *
+   *  Record types are not subtypes of `any`. As such, they can never be passed
+   *  to JavaScript.
    */
   final case class RecordType(fields: List[RecordType.Field]) extends Type {
     def findField(name: SimpleFieldName): RecordType.Field =
@@ -393,12 +405,16 @@ object Types {
 
     (lhs == rhs) ||
     ((lhs, rhs) match {
+      case (NothingType, _) => true
       case (_, NoType)      => true
       case (NoType, _)      => false
-      case (_, AnyType)     => true
-      case (NothingType, _) => true
 
-      case (NullType, _)       => rhs.isNullable
+      case (NullType, _) => rhs.isNullable
+
+      case (_: RecordType, _) => false
+      case (_, _: RecordType) => false
+
+      case (_, AnyType)        => true
       case (_, AnyNotNullType) => !lhs.isNullable
 
       case (ClassType(lhsClass, lhsNullable), ClassType(rhsClass, rhsNullable)) =>

From ec936732befbd3bef2dc19e843834085029a9b1b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Mon, 21 Oct 2024 16:13:32 +0200
Subject: [PATCH 195/298] Print `Undefined()/UndefType` as `undefined/undef`
 rather than "void".

The concept of "void" will be reserved for "statement types", not
for expressions with the `undefined` value.
---
 ir/shared/src/main/scala/org/scalajs/ir/Printers.scala     | 4 ++--
 ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala | 6 +++---
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala
index 5895bf9773..bd7e615a7f 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala
@@ -781,7 +781,7 @@ object Printers {
         // Literals
 
         case Undefined() =>
-          print("(void 0)")
+          print("undefined")
 
         case Null() =>
           print("null")
@@ -1093,7 +1093,7 @@ object Printers {
       case AnyType        => print("any")
       case AnyNotNullType => print("any!")
       case NothingType    => print("nothing")
-      case UndefType      => print("void")
+      case UndefType      => print("undef")
       case BooleanType    => print("boolean")
       case CharType       => print("char")
       case ByteType       => print("byte")
diff --git a/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala b/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala
index 1df89dc5d8..852535a9be 100644
--- a/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala
+++ b/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala
@@ -52,7 +52,7 @@ class PrintersTest {
     assertPrintEquals("any", AnyType)
     assertPrintEquals("any!", AnyNotNullType)
     assertPrintEquals("nothing", NothingType)
-    assertPrintEquals("void", UndefType)
+    assertPrintEquals("undef", UndefType)
     assertPrintEquals("boolean", BooleanType)
     assertPrintEquals("char", CharType)
     assertPrintEquals("byte", ByteType)
@@ -808,7 +808,7 @@ class PrintersTest {
   }
 
   @Test def printUndefined(): Unit = {
-    assertPrintEquals("(void 0)", Undefined())
+    assertPrintEquals("undefined", Undefined())
   }
 
   @Test def printNull(): Unit = {
@@ -1298,7 +1298,7 @@ class PrintersTest {
           |constructor def constructor(x: any): any = {
           |  5;
           |  super(6);
-          |  (void 0)
+          |  undefined
           |}
         """,
         JSConstructorDef(MemberFlags.empty.withNamespace(Constructor),

From cdcff9973579ed77e87343f3edd9429661b4a786 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Mon, 21 Oct 2024 16:28:43 +0200
Subject: [PATCH 196/298] Rename NoType to VoidType and print it as "void".

Also clarify that it is the real top type of our type system.

We have been using `void` in the "theoretical" type system since
Scala.js 1.0.0, but for historical reasons, `NoType` kept its old
name.

We now officially rename it to `VoidType`, and print it as `void`
instead of `<notype>`, giving it a true `Type` status.
---
 .../org/scalajs/nscplugin/GenJSCode.scala     | 68 +++++++++----------
 .../org/scalajs/nscplugin/GenJSExports.scala  |  4 +-
 .../scalajs/nscplugin/TypeConversions.scala   |  2 +-
 .../main/scala/org/scalajs/ir/Hashers.scala   |  4 +-
 .../src/main/scala/org/scalajs/ir/Names.scala |  2 +-
 .../main/scala/org/scalajs/ir/Printers.scala  |  8 +--
 .../scala/org/scalajs/ir/Serializers.scala    | 30 ++++----
 .../src/main/scala/org/scalajs/ir/Tags.scala  |  7 +-
 .../scala/org/scalajs/ir/Transformers.scala   |  2 +-
 .../src/main/scala/org/scalajs/ir/Trees.scala | 19 +++---
 .../src/main/scala/org/scalajs/ir/Types.scala | 29 ++++----
 .../scala/org/scalajs/ir/PrintersTest.scala   | 20 +++---
 .../scala/org/scalajs/linker/RunTest.scala    |  2 +-
 .../org/scalajs/linker/analyzer/Infos.scala   |  2 +-
 .../linker/backend/emitter/ClassEmitter.scala |  8 +--
 .../linker/backend/emitter/CoreJSLib.scala    |  2 +-
 .../backend/emitter/FunctionEmitter.scala     |  6 +-
 .../linker/backend/emitter/NameGen.scala      |  2 +-
 .../linker/backend/emitter/SJSGen.scala       |  8 +--
 .../linker/backend/emitter/Transients.scala   |  2 +-
 .../linker/backend/emitter/VarGen.scala       |  2 +-
 .../backend/wasmemitter/ClassEmitter.scala    |  2 +-
 .../backend/wasmemitter/DerivedClasses.scala  |  2 +-
 .../backend/wasmemitter/FunctionEmitter.scala | 58 ++++++++--------
 .../linker/backend/wasmemitter/SWasmGen.scala |  2 +-
 .../backend/wasmemitter/TypeTransformer.scala |  4 +-
 .../linker/checker/ClassDefChecker.scala      | 34 +++++-----
 .../scalajs/linker/checker/IRChecker.scala    |  8 +--
 .../frontend/optimizer/IncOptimizer.scala     |  6 +-
 .../frontend/optimizer/OptimizerCore.scala    | 30 ++++----
 .../org/scalajs/linker/AnalyzerTest.scala     | 12 ++--
 .../org/scalajs/linker/IRCheckerTest.scala    | 18 ++---
 .../org/scalajs/linker/IncrementalTest.scala  | 12 ++--
 .../linker/LibraryReachabilityTest.scala      |  4 +-
 .../org/scalajs/linker/OptimizerTest.scala    | 12 ++--
 .../linker/checker/ClassDefCheckerTest.scala  | 58 ++++++++--------
 .../linker/testutils/TestIRBuilder.scala      |  8 +--
 project/BinaryIncompatibilities.scala         |  4 +-
 project/JavaLangObject.scala                  |  8 +--
 39 files changed, 258 insertions(+), 253 deletions(-)

diff --git a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
index 714fc7bd1b..5ac71f2c26 100644
--- a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
+++ b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
@@ -1414,7 +1414,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
           js.MethodIdent(name),
           NoOriginalName,
           Nil,
-          jstpe.NoType,
+          jstpe.VoidType,
           Some(stats))(
           OptimizerHints.empty, Unversioned)
     }
@@ -1842,7 +1842,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
             }
           }
 
-          js.If(cond, body, js.Skip())(jstpe.NoType)
+          js.If(cond, body, js.Skip())(jstpe.VoidType)
       }
 
       /* preStats / postStats use pre/post order traversal respectively to
@@ -2080,7 +2080,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
               val namespace = js.MemberNamespace.Constructor
               js.MethodDef(
                   js.MemberFlags.empty.withNamespace(namespace), methodName,
-                  originalName, jsParams, jstpe.NoType, Some(genStat(dd.rhs)))(
+                  originalName, jsParams, jstpe.VoidType, Some(genStat(dd.rhs)))(
                   optimizerHints, Unversioned)
             } else {
               val resultIRType = toIRType(sym.tpe.resultType)
@@ -2180,7 +2180,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
         }
       }
       val newBody = body.map(
-          b => transformer.transform(b, isStat = resultType == jstpe.NoType))
+          b => transformer.transform(b, isStat = resultType == jstpe.VoidType))
       js.MethodDef(flags, methodName, originalName, newParams, resultType,
           newBody)(methodDef.optimizerHints, Unversioned)(methodDef.pos)
     }
@@ -2216,7 +2216,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
         }
       }
       val newBody = body.map(
-          b => transformer.transform(b, isStat = resultType == jstpe.NoType))
+          b => transformer.transform(b, isStat = resultType == jstpe.VoidType))
       js.MethodDef(flags, methodName, originalName, newParams, resultType,
           newBody)(methodDef.optimizerHints, Unversioned)(methodDef.pos)
     }
@@ -2248,7 +2248,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
         optimizerHints: OptimizerHints): js.MethodDef = {
       implicit val pos = tree.pos
 
-      val bodyIsStat = resultIRType == jstpe.NoType
+      val bodyIsStat = resultIRType == jstpe.VoidType
 
       def genBodyWithinReturnableScope(): js.Tree = tree match {
         case Block(
@@ -2439,8 +2439,8 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
      */
     def genExpr(tree: Tree): js.Tree = {
       val result = genStatOrExpr(tree, isStat = false)
-      assert(result.tpe != jstpe.NoType,
-          s"genExpr($tree) returned a tree with type NoType at pos ${tree.pos}")
+      assert(result.tpe != jstpe.VoidType,
+          s"genExpr($tree) returned a tree with type VoidType at pos ${tree.pos}")
       result
     }
 
@@ -2517,7 +2517,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
         case tree @ If(cond, thenp, elsep) =>
           def default: js.Tree = {
             val tpe =
-              if (isStat) jstpe.NoType
+              if (isStat) jstpe.VoidType
               else toIRType(tree.tpe)
 
             js.If(genExpr(cond), genStatOrExpr(thenp, isStat),
@@ -2559,8 +2559,8 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
 
         case Return(expr) =>
           js.Return(toIRType(expr.tpe) match {
-            case jstpe.NoType => js.Block(genStat(expr), js.Undefined())
-            case _            => genExpr(expr)
+            case jstpe.VoidType => js.Block(genStat(expr), js.Undefined())
+            case _              => genExpr(expr)
           }, getEnclosingReturnLabel())
 
         case t: Try =>
@@ -2916,7 +2916,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
         if (transformedRhs.tpe == jstpe.NothingType) {
           // In this case, we do not need the outer block label
           js.While(js.BooleanLiteral(true), {
-            js.Labeled(labelIdent, jstpe.NoType, {
+            js.Labeled(labelIdent, jstpe.VoidType, {
               transformedRhs match {
                 // Eliminate a trailing return@lab
                 case js.Block(stats :+ ReturnFromThisLabel(exprAsStat)) =>
@@ -2930,11 +2930,11 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
           // When all else has failed, we need the full machinery
           val blockLabelIdent = freshLabelIdent("block")
           val bodyType =
-            if (isStat) jstpe.NoType
+            if (isStat) jstpe.VoidType
             else toIRType(tree.tpe)
           js.Labeled(blockLabelIdent, bodyType, {
             js.While(js.BooleanLiteral(true), {
-              js.Labeled(labelIdent, jstpe.NoType, {
+              js.Labeled(labelIdent, jstpe.VoidType, {
                 if (isStat)
                   js.Block(transformedRhs, js.Return(js.Undefined(), blockLabelIdent))
                 else
@@ -3050,7 +3050,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
       val blockAST = genStatOrExpr(block, isStat)
 
       val resultType =
-        if (isStat) jstpe.NoType
+        if (isStat) jstpe.VoidType
         else toIRType(tree.tpe)
 
       val handled =
@@ -3282,7 +3282,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
       val r = toIRType(to)
 
       def isValueType(tpe: jstpe.Type): Boolean = tpe match {
-        case jstpe.NoType | jstpe.BooleanType | jstpe.CharType |
+        case jstpe.VoidType | jstpe.BooleanType | jstpe.CharType |
             jstpe.ByteType | jstpe.ShortType | jstpe.IntType | jstpe.LongType |
             jstpe.FloatType | jstpe.DoubleType =>
           true
@@ -3625,7 +3625,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
         .withNoinline(noinline)
       val methodIdent = encodeMethodSym(method)
       val resultType =
-        if (method.isClassConstructor) jstpe.NoType
+        if (method.isClassConstructor) jstpe.VoidType
         else toIRType(method.tpe.resultType)
       js.ApplyStatically(flags, receiver, encodeClassName(method.owner),
           methodIdent, arguments)(resultType)
@@ -3891,7 +3891,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
       val genSelector = genExpr(selector)
 
       val resultType =
-        if (isStat) jstpe.NoType
+        if (isStat) jstpe.VoidType
         else toIRType(tree.tpe)
 
       val defaultLabelSym = cases.collectFirst {
@@ -4035,8 +4035,8 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
           (alts, newBody)
         }
         js.Labeled(matchResultLabel, resultType, js.Block(List(
-            js.Labeled(elseClauseLabel, jstpe.NoType, {
-              buildMatch(patchedClauses.reverse, js.Skip(), jstpe.NoType)
+            js.Labeled(elseClauseLabel, jstpe.VoidType, {
+              buildMatch(patchedClauses.reverse, js.Skip(), jstpe.VoidType)
             }),
             elseClause
         )))
@@ -4133,7 +4133,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
             val translatedMatch = genTranslatedMatch(cases, matchEnd)
             val genMore = genBlockWithCaseLabelDefs(more, isStat)
             val label = getEnclosingReturnLabel()
-            if (translatedMatch.tpe == jstpe.NoType) {
+            if (translatedMatch.tpe == jstpe.VoidType) {
               // Could not actually reproduce this, but better be safe than sorry
               translatedMatch :: js.Return(js.Undefined(), label) :: genMore
             } else {
@@ -4217,7 +4217,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
             tree match {
               case If(cond, thenp, elsep) =>
                 js.If(genExpr(cond), genCaseBody(thenp), genCaseBody(elsep))(
-                    jstpe.NoType)
+                    jstpe.VoidType)
 
               case Block(stats, Literal(Constant(()))) =>
                 // Generated a lot by the async transform
@@ -4272,7 +4272,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
 
       def genMatchEndBody(): js.Tree = {
         genStatOrExpr(matchEndBody,
-            isStat = toIRType(matchEndBody.tpe) == jstpe.NoType)
+            isStat = toIRType(matchEndBody.tpe) == jstpe.VoidType)
       }
 
       matchEnd.params match {
@@ -4326,7 +4326,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
           ) {
             genTranslatedCases
           }
-          val optimized = genOptimizedMatchEndLabeled(labelIdent, jstpe.NoType,
+          val optimized = genOptimizedMatchEndLabeled(labelIdent, jstpe.VoidType,
               translatedCases, info.generatedReturns)
           js.Block(varDefs ::: optimized :: genMatchEndBody() :: Nil)
       }
@@ -4379,7 +4379,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
         implicit pos: Position): js.Tree = {
 
       def default: js.Tree =
-        js.Labeled(label, jstpe.NoType, translatedBody)
+        js.Labeled(label, jstpe.VoidType, translatedBody)
 
       if (returnCount == 0) {
         translatedBody
@@ -4403,7 +4403,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
                   case _ =>
                     js.UnaryOp(js.UnaryOp.Boolean_!, cond)
                 }
-                js.Block(stats1 :+ js.If(notCond, js.Block(stats2), js.Skip())(jstpe.NoType))
+                js.Block(stats1 :+ js.If(notCond, js.Block(stats2), js.Skip())(jstpe.VoidType))
 
               case _ :: _ =>
                 throw new AssertionError("unreachable code")
@@ -5219,7 +5219,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
     def makePrimitiveBox(expr: js.Tree, tpe: Type)(
         implicit pos: Position): js.Tree = {
       toIRType(tpe) match {
-        case jstpe.NoType => // for JS interop cases
+        case jstpe.VoidType => // for JS interop cases
           js.Block(expr, js.Undefined())
         case jstpe.BooleanType | jstpe.CharType | jstpe.ByteType |
             jstpe.ShortType | jstpe.IntType | jstpe.LongType | jstpe.FloatType |
@@ -5234,8 +5234,8 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
     def makePrimitiveUnbox(expr: js.Tree, tpe: Type)(
         implicit pos: Position): js.Tree = {
       toIRType(tpe) match {
-        case jstpe.NoType => expr // for JS interop cases
-        case irTpe        => js.AsInstanceOf(expr, irTpe)
+        case jstpe.VoidType => expr // for JS interop cases
+        case irTpe          => js.AsInstanceOf(expr, irTpe)
       }
     }
 
@@ -6135,8 +6135,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
      *
      *  we generate a function:
      *
-     *    lambda<o, c1, ..., cM>[notype](
-     *        outer, capture1, ..., captureM, param1, ..., paramN) {
+     *    arrow-lambda<o = outer, c1 = capture1, ..., cM = captureM>(param1, ..., paramN) {
      *      <body>
      *    }
      *
@@ -6206,8 +6205,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
      *
      *  we generate a function:
      *
-     *    lambda<o, c1, ..., cM>[notype](
-     *        outer, capture1, ..., captureM, param1, ..., paramN) {
+     *    arrow-lambda<o = outer, c1 = capture1, ..., cM = captureM>(param1, ..., paramN) {
      *      outer.lambdaImpl(param1, ..., paramN, capture1, ..., captureM)
      *    }
      */
@@ -6540,7 +6538,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
             js.MethodIdent(ObjectArgConstructorName),
             NoOriginalName,
             List(fParamDef),
-            jstpe.NoType,
+            jstpe.VoidType,
             Some(js.Block(List(
                 js.Assign(
                     js.Select(js.This()(thisType), fFieldIdent)(jstpe.AnyType),
@@ -6549,7 +6547,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
                     js.This()(thisType),
                     ir.Names.ObjectClass,
                     js.MethodIdent(ir.Names.NoArgConstructorName),
-                    Nil)(jstpe.NoType)))))(
+                    Nil)(jstpe.VoidType)))))(
             js.OptimizerHints.empty, Unversioned)
       }
 
diff --git a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSExports.scala b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSExports.scala
index beca736586..bf668424ae 100644
--- a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSExports.scala
+++ b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSExports.scala
@@ -870,7 +870,7 @@ trait GenJSExports[G <: Global with Singleton] extends SubComponent {
       }
 
       // #4684 If the getter returns void, we must "box" it by returning undefined
-      if (callGetter.tpe == jstpe.NoType)
+      if (callGetter.tpe == jstpe.VoidType)
         js.Block(callGetter, js.Undefined())
       else
         callGetter
@@ -975,7 +975,7 @@ trait GenJSExports[G <: Global with Singleton] extends SubComponent {
         (toIRType(tpe): @unchecked) match {
           case jstpe.AnyType | jstpe.AnyNotNullType => NoTypeTest
 
-          case jstpe.NoType      => PrimitiveTypeTest(jstpe.UndefType, 0)
+          case jstpe.VoidType    => PrimitiveTypeTest(jstpe.UndefType, 0)
           case jstpe.BooleanType => PrimitiveTypeTest(jstpe.BooleanType, 1)
           case jstpe.CharType    => PrimitiveTypeTest(jstpe.CharType, 2)
           case jstpe.ByteType    => PrimitiveTypeTest(jstpe.ByteType, 3)
diff --git a/compiler/src/main/scala/org/scalajs/nscplugin/TypeConversions.scala b/compiler/src/main/scala/org/scalajs/nscplugin/TypeConversions.scala
index 97db07f24f..eae31fdb14 100644
--- a/compiler/src/main/scala/org/scalajs/nscplugin/TypeConversions.scala
+++ b/compiler/src/main/scala/org/scalajs/nscplugin/TypeConversions.scala
@@ -25,7 +25,7 @@ trait TypeConversions[G <: Global with Singleton] extends SubComponent {
 
   private lazy val primitiveIRTypeMap: Map[Symbol, Types.Type] = {
     Map(
-        UnitClass    -> Types.NoType,
+        UnitClass    -> Types.VoidType,
         BooleanClass -> Types.BooleanType,
         CharClass    -> Types.CharType,
         ByteClass    -> Types.ByteType,
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Hashers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Hashers.scala
index e866e32fb4..1c159fe9b2 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Hashers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Hashers.scala
@@ -581,7 +581,7 @@ object Hashers {
     def mixTypeRef(typeRef: TypeRef): Unit = typeRef match {
       case PrimRef(tpe) =>
         tpe match {
-          case NoType      => mixTag(TagVoidRef)
+          case VoidType    => mixTag(TagVoidRef)
           case BooleanType => mixTag(TagBooleanRef)
           case CharType    => mixTag(TagCharRef)
           case ByteType    => mixTag(TagByteRef)
@@ -621,7 +621,7 @@ object Hashers {
       case DoubleType     => mixTag(TagDoubleType)
       case StringType     => mixTag(TagStringType)
       case NullType       => mixTag(TagNullType)
-      case NoType         => mixTag(TagNoType)
+      case VoidType       => mixTag(TagVoidType)
 
       case ClassType(className, nullable) =>
         mixTag(if (nullable) TagClassType else TagNonNullClassType)
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Names.scala b/ir/shared/src/main/scala/org/scalajs/ir/Names.scala
index 73ea0c8c7d..8193227be0 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Names.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Names.scala
@@ -393,7 +393,7 @@ object Names {
       def appendTypeRef(typeRef: TypeRef): Unit = typeRef match {
         case PrimRef(tpe) =>
           tpe match {
-            case NoType      => builder.append('V')
+            case VoidType    => builder.append('V')
             case BooleanType => builder.append('Z')
             case CharType    => builder.append('C')
             case ByteType    => builder.append('B')
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala
index bd7e615a7f..e245cffeb4 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala
@@ -106,7 +106,7 @@ object Printers {
 
       print(")")
 
-      if (resultType != NoType) {
+      if (resultType != VoidType) {
         print(": ")
         print(resultType)
         print(" = ")
@@ -173,7 +173,7 @@ object Printers {
 
         case Labeled(label, tpe, body) =>
           print(label)
-          if (tpe != NoType) {
+          if (tpe != VoidType) {
             print('[')
             print(tpe)
             print(']')
@@ -1037,7 +1037,7 @@ object Printers {
             print(flags.namespace.prefixString)
             print("set ")
             printJSMemberName(name)
-            printSig(arg :: Nil, None, NoType)
+            printSig(arg :: Nil, None, VoidType)
             printBlock(body)
           }
 
@@ -1104,7 +1104,7 @@ object Printers {
       case DoubleType     => print("double")
       case StringType     => print("string")
       case NullType       => print("null")
-      case NoType         => print("<notype>")
+      case VoidType       => print("void")
 
       case ClassType(className, nullable) =>
         print(className)
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
index 15a2e251ec..5a69b79b42 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
@@ -199,7 +199,7 @@ object Serializers {
       def writeTypeRef(typeRef: TypeRef): Unit = typeRef match {
         case PrimRef(tpe) =>
           tpe match {
-            case NoType      => s.writeByte(TagVoidRef)
+            case VoidType    => s.writeByte(TagVoidRef)
             case BooleanType => s.writeByte(TagBooleanRef)
             case CharType    => s.writeByte(TagCharRef)
             case ByteType    => s.writeByte(TagByteRef)
@@ -874,7 +874,7 @@ object Serializers {
         case DoubleType     => buffer.write(TagDoubleType)
         case StringType     => buffer.write(TagStringType)
         case NullType       => buffer.write(TagNullType)
-        case NoType         => buffer.write(TagNoType)
+        case VoidType       => buffer.write(TagVoidType)
 
         case ClassType(className, nullable) =>
           buffer.write(if (nullable) TagClassType else TagNonNullClassType)
@@ -899,7 +899,7 @@ object Serializers {
     def writeTypeRef(typeRef: TypeRef): Unit = typeRef match {
       case PrimRef(tpe) =>
         tpe match {
-          case NoType      => buffer.writeByte(TagVoidRef)
+          case VoidType    => buffer.writeByte(TagVoidRef)
           case BooleanType => buffer.writeByte(TagBooleanRef)
           case CharType    => buffer.writeByte(TagCharRef)
           case ByteType    => buffer.writeByte(TagByteRef)
@@ -1615,9 +1615,9 @@ object Serializers {
         if (methodName.isConstructor) {
           val newName = MethodIdent(NoArgConstructorName)(method.name.pos)
           val newBody = ApplyStatically(ApplyFlags.empty.withConstructor(true),
-              thisJLClass, ObjectClass, newName, Nil)(NoType)
+              thisJLClass, ObjectClass, newName, Nil)(VoidType)
           MethodDef(method.flags, newName, method.originalName,
-              Nil, NoType, Some(newBody))(
+              Nil, VoidType, Some(newBody))(
               method.optimizerHints, method.version)
         } else {
           def argRef = method.args.head.ref
@@ -1653,7 +1653,7 @@ object Serializers {
                     super.transform(tree, isStat)
                 }
               }
-              transformer.transform(method.body.get, isStat = method.resultType == NoType)
+              transformer.transform(method.body.get, isStat = method.resultType == VoidType)
           }
 
           val newOptimizerHints =
@@ -1759,7 +1759,7 @@ object Serializers {
                   )
                 })
               )
-            }, Skip())(NoType),
+            }, Skip())(VoidType),
             result.ref
           )
         }
@@ -1980,7 +1980,7 @@ object Serializers {
         MethodDef(flags, name, originalName, args, resultType, patchedBody)(
             patchedOptimizerHints, optHash)
       } else {
-        val patchedBody = body.map(bodyHack5(_, isStat = resultType == NoType))
+        val patchedBody = body.map(bodyHack5(_, isStat = resultType == VoidType))
         MethodDef(flags, name, originalName, args, resultType, patchedBody)(
             optimizerHints, optHash)
       }
@@ -2058,7 +2058,7 @@ object Serializers {
         body
       } else {
         /* #4442 and #4601: Patch Labeled, If, Match and TryCatch nodes in
-         * statement position to have type NoType. These 4 nodes are the
+         * statement position to have type VoidType. These 4 nodes are the
          * control structures whose result type is explicitly specified (and
          * not derived from their children like Block or TryFinally, or
          * constant like While).
@@ -2066,16 +2066,16 @@ object Serializers {
         new Transformers.Transformer {
           override def transform(tree: Tree, isStat: Boolean): Tree = {
             val newTree = super.transform(tree, isStat)
-            if (isStat && newTree.tpe != NoType) {
+            if (isStat && newTree.tpe != VoidType) {
               newTree match {
                 case Labeled(label, _, body) =>
-                  Labeled(label, NoType, body)(newTree.pos)
+                  Labeled(label, VoidType, body)(newTree.pos)
                 case If(cond, thenp, elsep) =>
-                  If(cond, thenp, elsep)(NoType)(newTree.pos)
+                  If(cond, thenp, elsep)(VoidType)(newTree.pos)
                 case Match(selector, cases, default) =>
-                  Match(selector, cases, default)(NoType)(newTree.pos)
+                  Match(selector, cases, default)(VoidType)(newTree.pos)
                 case TryCatch(block, errVar, errVarOriginalName, handler) =>
-                  TryCatch(block, errVar, errVarOriginalName, handler)(NoType)(newTree.pos)
+                  TryCatch(block, errVar, errVarOriginalName, handler)(VoidType)(newTree.pos)
                 case _ =>
                   newTree
               }
@@ -2223,7 +2223,7 @@ object Serializers {
         case TagDoubleType     => DoubleType
         case TagStringType     => StringType
         case TagNullType       => NullType
-        case TagNoType         => NoType
+        case TagVoidType       => VoidType
 
         case TagClassType => ClassType(readClassName(), nullable = true)
         case TagArrayType => ArrayType(readArrayTypeRef(), nullable = true)
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Tags.scala b/ir/shared/src/main/scala/org/scalajs/ir/Tags.scala
index 577a3ceca6..1bc0a52f78 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Tags.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Tags.scala
@@ -171,11 +171,14 @@ private[ir] object Tags {
   final val TagClassType = TagNullType + 1
   final val TagArrayType = TagClassType + 1
   final val TagRecordType = TagArrayType + 1
-  final val TagNoType = TagRecordType + 1
+  final val TagVoidType = TagRecordType + 1
+
+  @deprecated("Use TagVoidType instead", since = "1.18.0")
+  final val TagNoType = TagVoidType
 
   // New in 1.17
 
-  final val TagAnyNotNullType = TagNoType + 1
+  final val TagAnyNotNullType = TagVoidType + 1
   final val TagNonNullClassType = TagAnyNotNullType + 1
   final val TagNonNullArrayType = TagNonNullClassType + 1
 
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Transformers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Transformers.scala
index 0b9719da0f..2fcc5bd1ee 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Transformers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Transformers.scala
@@ -246,7 +246,7 @@ object Transformers {
 
     def transformMethodDef(methodDef: MethodDef): MethodDef = {
       val MethodDef(flags, name, originalName, args, resultType, body) = methodDef
-      val newBody = body.map(transform(_, isStat = resultType == NoType))
+      val newBody = body.map(transform(_, isStat = resultType == VoidType))
       MethodDef(flags, name, originalName, args, resultType, newBody)(
           methodDef.optimizerHints, Unversioned)(methodDef.pos)
     }
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala b/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
index 96145a12f5..bf7eaff25b 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
@@ -102,7 +102,7 @@ object Trees {
   sealed case class VarDef(name: LocalIdent, originalName: OriginalName,
       vtpe: Type, mutable: Boolean, rhs: Tree)(
       implicit val pos: Position) extends Tree {
-    val tpe = NoType // cannot be in expression position
+    val tpe = VoidType
 
     def ref(implicit pos: Position): VarRef = VarRef(name)(vtpe)
   }
@@ -116,7 +116,7 @@ object Trees {
   // Control flow constructs
 
   sealed case class Skip()(implicit val pos: Position) extends Tree {
-    val tpe = NoType // cannot be in expression position
+    val tpe = VoidType
   }
 
   sealed class Block private (val stats: List[Tree])(
@@ -157,7 +157,7 @@ object Trees {
 
   sealed case class Assign(lhs: AssignLhs, rhs: Tree)(
       implicit val pos: Position) extends Tree {
-    val tpe = NoType // cannot be in expression position
+    val tpe = VoidType
   }
 
   sealed case class Return(expr: Tree, label: LabelIdent)(
@@ -170,17 +170,16 @@ object Trees {
 
   sealed case class While(cond: Tree, body: Tree)(
       implicit val pos: Position) extends Tree {
-    // cannot be in expression position, unless it is infinite
     val tpe = cond match {
       case BooleanLiteral(true) => NothingType
-      case _                    => NoType
+      case _                    => VoidType
     }
   }
 
   sealed case class ForIn(obj: Tree, keyVar: LocalIdent,
       keyVarOriginalName: OriginalName, body: Tree)(
       implicit val pos: Position) extends Tree {
-    val tpe = NoType
+    val tpe = VoidType
   }
 
   sealed case class TryCatch(block: Tree, errVar: LocalIdent,
@@ -224,7 +223,7 @@ object Trees {
       default: Tree)(val tpe: Type)(implicit val pos: Position) extends Tree
 
   sealed case class Debugger()(implicit val pos: Position) extends Tree {
-    val tpe = NoType // cannot be in expression position
+    val tpe = VoidType
   }
 
   // Scala expressions
@@ -246,7 +245,7 @@ object Trees {
   }
 
   sealed case class StoreModule()(implicit val pos: Position) extends Tree {
-    val tpe = NoType // cannot be in expression position
+    val tpe = VoidType
   }
 
   sealed case class Select(qualifier: Tree, field: FieldIdent)(val tpe: Type)(
@@ -734,7 +733,7 @@ object Trees {
    */
   sealed case class JSSuperConstructorCall(args: List[TreeOrJSSpread])(
       implicit val pos: Position) extends Tree {
-    val tpe = NoType
+    val tpe = VoidType
   }
 
   /** JavaScript dynamic import of the form `import(arg)`.
@@ -827,7 +826,7 @@ object Trees {
       implicit val pos: Position)
       extends Tree {
 
-    val tpe = NoType // cannot be in expression position
+    val tpe = VoidType
   }
 
   /** Unary operation (always preserves pureness).
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Types.scala b/ir/shared/src/main/scala/org/scalajs/ir/Types.scala
index df0ee5b926..b801857290 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Types.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Types.scala
@@ -46,9 +46,9 @@ object Types {
     }
 
     /** A type that accepts the same values as this type except `null`, unless
-     *  this type is `NoType`.
+     *  this type is `VoidType`.
      *
-     *  If `this` is `NoType`, returns this type.
+     *  If `this` is `VoidType`, returns this type.
      *
      *  For all other types `tpe`, `tpe.toNonNullable.isNullable` is `false`.
      */
@@ -64,7 +64,7 @@ object Types {
 
   sealed abstract class PrimTypeWithRef extends PrimType {
     def primRef: PrimRef = this match {
-      case NoType      => VoidRef
+      case VoidType    => VoidRef
       case BooleanType => BooleanRef
       case CharType    => CharRef
       case ByteType    => ByteRef
@@ -209,8 +209,11 @@ object Types {
         tpe: Type, mutable: Boolean)
   }
 
-  /** No type. */
-  case object NoType extends PrimTypeWithRef
+  /** Void type, the top of type of our type system. */
+  case object VoidType extends PrimTypeWithRef
+
+  @deprecated("Use VoidType instead", since = "1.18.0")
+  lazy val NoType: VoidType.type = VoidType
 
   /** Type reference (allowed for classOf[], is/asInstanceOf[]).
    *
@@ -276,7 +279,7 @@ object Types {
      *  `"nothing"`, respectively.
      */
     val displayName: String = tpe match {
-      case NoType      => "void"
+      case VoidType    => "void"
       case BooleanType => "boolean"
       case CharType    => "char"
       case ByteType    => "byte"
@@ -300,7 +303,7 @@ object Types {
      *  respectively.
      */
     val charCode: Char = tpe match {
-      case NoType      => 'V'
+      case VoidType    => 'V'
       case BooleanType => 'Z'
       case CharType    => 'C'
       case ByteType    => 'B'
@@ -315,15 +318,15 @@ object Types {
   }
 
   /* @unchecked for the initialization checker of Scala 3
-   * When we get here, `NoType` is not yet considered fully initialized because
+   * When we get here, `VoidType` is not yet considered fully initialized because
    * its method `primRef` can access `VoidRef`. Since the constructor of
-   * `PrimRef` pattern-matches on its `tpe`, which is `NoType`, this is flagged
+   * `PrimRef` pattern-matches on its `tpe`, which is `VoidType`, this is flagged
    * by the init checker, although our usage is safe given that we do not call
    * `primRef`. The same reasoning applies to the other primitive types.
    * In the future, we may want to rearrange the initialization sequence of
    * this file to avoid this issue.
    */
-  final val VoidRef = PrimRef(NoType: @unchecked)
+  final val VoidRef = PrimRef(VoidType: @unchecked)
   final val BooleanRef = PrimRef(BooleanType: @unchecked)
   final val CharRef = PrimRef(CharType: @unchecked)
   final val ByteRef = PrimRef(ByteType: @unchecked)
@@ -372,7 +375,7 @@ object Types {
     case tpe: RecordType =>
       RecordValue(tpe, tpe.fields.map(f => zeroOf(f.tpe)))
 
-    case NothingType | NoType | ClassType(_, false) | ArrayType(_, false) |
+    case NothingType | VoidType | ClassType(_, false) | ArrayType(_, false) |
         AnyNotNullType =>
       throw new IllegalArgumentException(s"cannot generate a zero for $tpe")
   }
@@ -406,8 +409,8 @@ object Types {
     (lhs == rhs) ||
     ((lhs, rhs) match {
       case (NothingType, _) => true
-      case (_, NoType)      => true
-      case (NoType, _)      => false
+      case (_, VoidType)    => true
+      case (VoidType, _)    => false
 
       case (NullType, _) => rhs.isNullable
 
diff --git a/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala b/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala
index 852535a9be..a2e7a2d51f 100644
--- a/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala
+++ b/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala
@@ -63,7 +63,7 @@ class PrintersTest {
     assertPrintEquals("double", DoubleType)
     assertPrintEquals("string", StringType)
     assertPrintEquals("null", NullType)
-    assertPrintEquals("<notype>", NoType)
+    assertPrintEquals("void", VoidType)
 
     assertPrintEquals("java.lang.Object", ClassType(ObjectClass, nullable = true))
     assertPrintEquals("java.lang.String!",
@@ -127,7 +127,7 @@ class PrintersTest {
           |  6
           |}
         """,
-        Labeled("lab", NoType, i(6)))
+        Labeled("lab", VoidType, i(6)))
 
     assertPrintEquals(
         """
@@ -144,7 +144,7 @@ class PrintersTest {
           |  6
           |}
         """,
-        Labeled("lab", NoType, Block(i(5), i(6))))
+        Labeled("lab", VoidType, Block(i(5), i(6))))
   }
 
   @Test def printAssign(): Unit = {
@@ -173,7 +173,7 @@ class PrintersTest {
           |  5
           |}
         """,
-        If(b(true), i(5), Skip())(NoType))
+        If(b(true), i(5), Skip())(VoidType))
 
     assertPrintEquals(
         """
@@ -322,7 +322,7 @@ class PrintersTest {
 
   @Test def printApply(): Unit = {
     assertPrintEquals("x.m;V()",
-        Apply(EAF, ref("x", "test.Test"), MethodName("m", Nil, V), Nil)(NoType))
+        Apply(EAF, ref("x", "test.Test"), MethodName("m", Nil, V), Nil)(VoidType))
     assertPrintEquals("x.m;I;I(5)",
         Apply(EAF, ref("x", "test.Test"), MethodName("m", List(I), I),
             List(i(5)))(IntType))
@@ -334,7 +334,7 @@ class PrintersTest {
   @Test def printApplyStatically(): Unit = {
     assertPrintEquals("x.test.Test::m;V()",
         ApplyStatically(EAF, ref("x", "test.Test"), "test.Test",
-            MethodName("m", Nil, V), Nil)(NoType))
+            MethodName("m", Nil, V), Nil)(VoidType))
     assertPrintEquals("x.test.Test::m;I;I(5)",
         ApplyStatically(EAF, ref("x", "test.Test"), "test.Test",
             MethodName("m", List(I), I), List(i(5)))(IntType))
@@ -344,12 +344,12 @@ class PrintersTest {
 
     assertPrintEquals("x.test.Test::private::m;V()",
         ApplyStatically(EAF.withPrivate(true), ref("x", "test.Test"),
-            "test.Test", MethodName("m", Nil, V), Nil)(NoType))
+            "test.Test", MethodName("m", Nil, V), Nil)(VoidType))
   }
 
   @Test def printApplyStatic(): Unit = {
     assertPrintEquals("test.Test::m;V()",
-        ApplyStatic(EAF, "test.Test", MethodName("m", Nil, V), Nil)(NoType))
+        ApplyStatic(EAF, "test.Test", MethodName("m", Nil, V), Nil)(VoidType))
     assertPrintEquals("test.Test::m;I;I(5)",
         ApplyStatic(EAF, "test.Test", MethodName("m", List(I), I),
             List(i(5)))(IntType))
@@ -359,7 +359,7 @@ class PrintersTest {
 
     assertPrintEquals("test.Test::private::m;V()",
         ApplyStatic(EAF.withPrivate(true), "test.Test", MethodName("m", Nil, V),
-            Nil)(NoType))
+            Nil)(VoidType))
   }
 
   @Test def printApplyDynamicImportStatic(): Unit = {
@@ -1251,7 +1251,7 @@ class PrintersTest {
         """,
         MethodDef(MemberFlags.empty, mIVMethodName, NON,
             List(ParamDef("x", NON, IntType, mutable = false)),
-            NoType, Some(i(5)))(NoOptHints, UNV))
+            VoidType, Some(i(5)))(NoOptHints, UNV))
 
     assertPrintEquals(
         """
diff --git a/linker/jvm/src/test/scala/org/scalajs/linker/RunTest.scala b/linker/jvm/src/test/scala/org/scalajs/linker/RunTest.scala
index 9adde311f8..0f7f6a628a 100644
--- a/linker/jvm/src/test/scala/org/scalajs/linker/RunTest.scala
+++ b/linker/jvm/src/test/scala/org/scalajs/linker/RunTest.scala
@@ -89,7 +89,7 @@ class RunTest {
     If(UnaryOp(UnaryOp.Boolean_!, test),
         Throw(JSNew(JSGlobalRef("Error"), List(str("Assertion failed")))),
         Skip())(
-        NoType)
+        VoidType)
   }
 
   private def testLinkAndRun(classDefs: Seq[ClassDef],
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala
index 3ff5ee059d..84a8d8a630 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala
@@ -254,7 +254,7 @@ object Infos {
         case NullType | NothingType =>
           // Nothing to do
 
-        case NoType | RecordType(_) =>
+        case VoidType | RecordType(_) =>
           throw new IllegalArgumentException(
               s"Illegal receiver type: $receiverTpe")
       }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
index 1b1751df60..a27cb2dd1e 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
@@ -320,10 +320,10 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
         val initMethodBody = initMethodDef.body.getOrElse {
           throw new AssertionError("Cannot generate an abstract constructor")
         }
-        assert(initMethodDef.resultType == NoType,
+        assert(initMethodDef.resultType == VoidType,
             s"Found a constructor with type ${initMethodDef.resultType} at $pos")
         desugarToFunction(className, initMethodDef.args, initMethodBody,
-            resultType = NoType)
+            resultType = VoidType)
       }
 
       for (generatedInitMethodFun <- generatedInitMethodFunWithGlobals) yield {
@@ -597,7 +597,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
     // optional setter definition
     val optSetterWithGlobals = property.setterArgAndBody map {
       case (arg, body) =>
-        desugarToFunction(className, arg :: Nil, body, resultType = NoType)
+        desugarToFunction(className, arg :: Nil, body, resultType = VoidType)
     }
 
     for {
@@ -629,7 +629,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
       }
 
       val setterWithGlobals = property.setterArgAndBody.map { case (arg, body) =>
-        for (fun <- desugarToFunction(className, arg :: Nil, body, resultType = NoType))
+        for (fun <- desugarToFunction(className, arg :: Nil, body, resultType = VoidType))
           yield js.SetterDef(static, propName, fun.args.head, fun.body)
       }
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
index ffbea0e2f7..77e47c1fb4 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
@@ -2109,7 +2109,7 @@ private[emitter] object CoreJSLib {
          * `scala.collection.mutable.ArrayBuilder.genericArrayBuilderResult`.
          * This code is Scala-specific, and "unboxes" `null` as the zero of
          * primitive types. For `void`, it is even more special, as it produces
-         * a boxed Unit value, which is `undefined` (although `VoidRef`/`NoType`
+         * a boxed Unit value, which is `undefined` (although `VoidRef`/`VoidType`
          * doesn't have a zero value per se).
          */
         val zero = primRef match {
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
index dcd45d0533..546bbb1e3b 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
@@ -284,7 +284,7 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
       implicit moduleContext: ModuleContext, globalKnowledge: GlobalKnowledge,
       globalRefTracking: GlobalRefTracking, pos: Position): WithGlobals[js.Function] = {
     new JSDesugar(globalRefTracking).desugarToFunction(
-        params, restParam, body, isStat = resultType == NoType,
+        params, restParam, body, isStat = resultType == VoidType,
         Env.empty(resultType).withEnclosingClassName(Some(enclosingClassName)))
   }
 
@@ -296,7 +296,7 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
       implicit moduleContext: ModuleContext, globalKnowledge: GlobalKnowledge,
       globalRefTracking: GlobalRefTracking, pos: Position): WithGlobals[js.Function] = {
     new JSDesugar(globalRefTracking).desugarToFunctionWithExplicitThis(
-        params, body, isStat = resultType == NoType,
+        params, body, isStat = resultType == VoidType,
         Env.empty(resultType).withEnclosingClassName(Some(enclosingClassName)))
   }
 
@@ -307,7 +307,7 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
       implicit moduleContext: ModuleContext, globalKnowledge: GlobalKnowledge,
       globalRefTracking: GlobalRefTracking, pos: Position): WithGlobals[js.Function] = {
     new JSDesugar(globalRefTracking).desugarToFunction(
-        params, restParam, body, isStat = resultType == NoType,
+        params, restParam, body, isStat = resultType == VoidType,
         Env.empty(resultType))
   }
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/NameGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/NameGen.scala
index 4e26efd4b7..a6c6b720a0 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/NameGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/NameGen.scala
@@ -144,7 +144,7 @@ private[backend] final class NameGen {
         typeRef match {
           case PrimRef(tpe) =>
             tpe match {
-              case NoType      => builder.append('V')
+              case VoidType    => builder.append('V')
               case BooleanType => builder.append('Z')
               case CharType    => builder.append('C')
               case ByteType    => builder.append('B')
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala
index d16df3126a..38f73dfd8a 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala
@@ -213,7 +213,7 @@ private[emitter] final class SJSGen(
       case UndefType   => Undefined()
       case NullType    => Null()
 
-      case NoType | NothingType =>
+      case VoidType | NothingType =>
         throw new IllegalArgumentException(s"cannot generate a zero for $tpe")
     }
   }
@@ -443,7 +443,7 @@ private[emitter] final class SJSGen(
 
       case AnyNotNullType => expr !== Null()
 
-      case NoType | NullType | NothingType | AnyType |
+      case VoidType | NullType | NothingType | AnyType |
           ClassType(_, true) | ArrayType(_, true) | _:RecordType =>
         throw new AssertionError(s"Unexpected type $tpe in genIsInstanceOf")
     }
@@ -527,7 +527,7 @@ private[emitter] final class SJSGen(
           if (semantics.strictFloats) genCallPolyfillableBuiltin(FroundBuiltin, expr)
           else wg(UnaryOp(irt.JSUnaryOp.+, expr))
 
-        case NoType | NullType | NothingType | AnyNotNullType |
+        case VoidType | NullType | NothingType | AnyNotNullType |
             ClassType(_, false) | ArrayType(_, false) | _:RecordType =>
           throw new AssertionError(s"Unexpected type $tpe in genAsInstanceOf")
       }
@@ -553,7 +553,7 @@ private[emitter] final class SJSGen(
         case StringType  => genCallHelper(VarField.uT, expr)
         case AnyType     => expr
 
-        case NoType | NullType | NothingType | AnyNotNullType |
+        case VoidType | NullType | NothingType | AnyNotNullType |
             ClassType(_, false) | ArrayType(_, false) | _:RecordType =>
           throw new AssertionError(s"Unexpected type $tpe in genAsInstanceOf")
       }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Transients.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Transients.scala
index 5c199fa0be..dc772cfa1a 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Transients.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Transients.scala
@@ -62,7 +62,7 @@ object Transients {
   final case class SystemArrayCopy(src: Tree, srcPos: Tree, dest: Tree,
       destPos: Tree, length: Tree)
       extends Transient.Value {
-    val tpe: Type = NoType
+    val tpe: Type = VoidType
 
     def traverse(traverser: Traverser): Unit = {
       traverser.traverse(src)
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/VarGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/VarGen.scala
index cdcf20560f..1aab60acd6 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/VarGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/VarGen.scala
@@ -379,7 +379,7 @@ private[emitter] final class VarGen(jsGen: JSGen, nameGen: NameGen,
       def subField(x: PrimRef): String = {
         // The mapping in this function is an implementation detail of the emitter
         x.tpe match {
-          case NoType      => "V"
+          case VoidType    => "V"
           case BooleanType => "Z"
           case CharType    => "C"
           case ByteType    => "B"
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/ClassEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/ClassEmitter.scala
index c4be465718..43409fa133 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/ClassEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/ClassEmitter.scala
@@ -1201,7 +1201,7 @@ class ClassEmitter(coreSpec: CoreSpec) {
                 setterParamDef :: Nil,
                 restParam = None,
                 setterBody,
-                resultType = NoType
+                resultType = VoidType
               )
               val setterRef = helperBuilder.addWasmInput("set", watpe.RefType.func) {
                 fb += ctx.refFuncWithDeclaration(closureFuncID)
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/DerivedClasses.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/DerivedClasses.scala
index 02a3d34bea..1935e130fc 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/DerivedClasses.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/DerivedClasses.scala
@@ -103,7 +103,7 @@ object DerivedClasses {
       MethodIdent(MethodName.constructor(List(primType.primRef))),
       NON,
       List(ctorParamDef),
-      NoType,
+      VoidType,
       Some(Assign(selectField, ctorParamDef.ref))
     )(EOH, NOV)
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
index 133dde2cde..d8f18921b4 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
@@ -553,8 +553,8 @@ private class FunctionEmitter private (
       case t: TryFinally          => unwinding.genTryFinally(t, expectedType)
       case t: Throw               => genThrow(t)
       case t: Match               => genMatch(t, expectedType)
-      case t: Debugger            => NoType // ignore
-      case t: Skip                => NoType
+      case t: Debugger            => VoidType // ignore
+      case t: Skip                => VoidType
       case t: Clone               => genClone(t)
       case t: IdentityHashCode    => genIdentityHashCode(t)
       case t: WrapAsThrowable     => genWrapAsThrowable(t)
@@ -613,7 +613,7 @@ private class FunctionEmitter private (
         ()
       case (NothingType, _) =>
         ()
-      case (_, NoType) =>
+      case (_, VoidType) =>
         fb += wa.Drop
       case (primType: PrimTypeWithRef, _) =>
         // box
@@ -633,7 +633,7 @@ private class FunctionEmitter private (
             genBox(watpe.Int32, SpecialNames.CharBoxClass)
           case LongType =>
             genBox(watpe.Int64, SpecialNames.LongBoxClass)
-          case NoType | NothingType =>
+          case VoidType | NothingType =>
             throw new AssertionError(s"Unexpected adaptation from $primType to $expectedType")
           case _ =>
             /* Calls a `bX` helper. Most of them are of the form
@@ -756,7 +756,7 @@ private class FunctionEmitter private (
         fb += wa.Call(genFunctionID.jsSelectSet)
 
       case JSSelect(qualifier, item) =>
-        genThroughCustomJSHelper(List(qualifier, item, rhs), NoType) { allJSArgs =>
+        genThroughCustomJSHelper(List(qualifier, item, rhs), VoidType) { allJSArgs =>
           val List(jsQualifier, jsItem, jsRhs) = allJSArgs
           js.Assign(js.BracketSelect.makeOptimized(jsQualifier, jsItem), jsRhs)
         }
@@ -772,7 +772,7 @@ private class FunctionEmitter private (
       case lhs @ JSGlobalRef(name) =>
         val builder = new CustomJSHelperBuilderWithTreeSupport()
         val rhsRef = builder.addInput(rhs)
-        val helperID = builder.build(NoType) {
+        val helperID = builder.build(VoidType) {
           js.Assign(builder.genGlobalRef(name), rhsRef)
         }
         markPosition(tree)
@@ -789,7 +789,7 @@ private class FunctionEmitter private (
         genWriteToStorage(lookupRecordSelect(lhs))
     }
 
-    NoType
+    VoidType
   }
 
   private def genWriteToStorage(storage: VarStorage): Unit = {
@@ -1269,7 +1269,7 @@ private class FunctionEmitter private (
   }
 
   private def genLiteral(tree: Literal, expectedType: Type): Type = {
-    if (expectedType == NoType) {
+    if (expectedType == VoidType) {
       /* Since all literals are pure, we can always get rid of them.
        * This is mostly useful for the argument of `Return` nodes that target a
        * `Labeled` in statement position, since they must have a non-`void`
@@ -1358,7 +1358,7 @@ private class FunctionEmitter private (
 
     markPosition(tree)
     fb += wa.GlobalSet(genGlobalID.forModuleInstance(className))
-    NoType
+    VoidType
   }
 
   private def genLoadModule(tree: LoadModule): Type = {
@@ -1583,7 +1583,7 @@ private class FunctionEmitter private (
           fb += wa.Call(genFunctionID.cast)
           AnyType
         } else {
-          genTree(lhs, NoType)
+          genTree(lhs, VoidType)
           genTreeAuto(rhs)
           rhs.tpe
         }
@@ -1644,7 +1644,7 @@ private class FunctionEmitter private (
       genTree(lhs, NothingType)
       NothingType
     } else if (rhsType == NothingType) {
-      genTree(lhs, NoType)
+      genTree(lhs, VoidType)
       genTree(rhs, NothingType)
       NothingType
     } else if (rhsType == NullType) {
@@ -1652,7 +1652,7 @@ private class FunctionEmitter private (
        * so testing for the `lhsType == NullType` is not as useful.
        */
       genTree(lhs, AnyType)
-      genTree(rhs, NoType) // no-op if it is actually a Null() literal
+      genTree(rhs, VoidType) // no-op if it is actually a Null() literal
       markPosition(tree)
       fb += wa.RefIsNull
       maybeGenInvert()
@@ -1880,7 +1880,7 @@ private class FunctionEmitter private (
             fb += wa.Call(genFunctionID.jsValueToStringForConcat)
           case NothingType =>
             () // unreachable
-          case NoType =>
+          case VoidType =>
             throw new AssertionError(
                 s"Found expression of type void in String_+ at ${tree.pos}: $tree")
         }
@@ -2035,7 +2035,7 @@ private class FunctionEmitter private (
       case LongType =>
         val structTypeID = genTypeID.forClass(SpecialNames.LongBoxClass)
         fb += wa.RefTest(watpe.RefType(structTypeID))
-      case NoType | NothingType | NullType =>
+      case VoidType | NothingType | NullType =>
         throw new AssertionError(s"Illegal isInstanceOf[$testType]")
       case testType: PrimTypeWithRef =>
         fb += wa.Call(genFunctionID.typeTest(testType.primRef))
@@ -2175,12 +2175,12 @@ private class FunctionEmitter private (
       genTree(expr, NothingType)
       NothingType
     } else if (targetTpe == NothingType) {
-      genTree(expr, NoType)
+      genTree(expr, VoidType)
       fb += wa.Unreachable
       NothingType
     } else {
       /* At this point, neither sourceTpe nor targetTpe can be NothingType,
-       * NoType or RecordType, so we can use `transformSingleType`.
+       * VoidType or RecordType, so we can use `transformSingleType`.
        */
 
       val sourceWasmType = transformSingleType(sourceTpe)
@@ -2238,7 +2238,7 @@ private class FunctionEmitter private (
 
   /** Unbox the `anyref` on the stack to the target `PrimType`.
    *
-   *  `targetTpe` must not be `NothingType`, `NullType` nor `NoType`.
+   *  `targetTpe` must not be `NothingType`, `NullType` nor `VoidType`.
    *
    *  The type left on the stack is non-nullable.
    */
@@ -2279,7 +2279,7 @@ private class FunctionEmitter private (
           fb += genZeroOf(targetTpe)
         }
 
-      case NothingType | NullType | NoType =>
+      case NothingType | NullType | VoidType =>
         throw new IllegalArgumentException(s"Illegal type in genUnbox: $targetTpe")
 
       case targetTpe: PrimTypeWithRef =>
@@ -2357,8 +2357,8 @@ private class FunctionEmitter private (
      * Its scope is empty by construction, and therefore it need not be stored.
      */
     val VarDef(_, _, _, _, rhs) = tree
-    genTree(rhs, NoType)
-    NoType
+    genTree(rhs, VoidType)
+    VoidType
   }
 
   private def genIf(tree: If, expectedType: Type): Type = {
@@ -2371,7 +2371,7 @@ private class FunctionEmitter private (
 
     elsep match {
       case Skip() =>
-        assert(expectedType == NoType)
+        assert(expectedType == VoidType)
         fb.ifThen() {
           genTree(thenp, expectedType)
         }
@@ -2397,7 +2397,7 @@ private class FunctionEmitter private (
         // infinite loop that must be typed as `nothing`, i.e., unreachable
         markPosition(tree)
         fb.loop() { label =>
-          genTree(body, NoType)
+          genTree(body, VoidType)
           markPosition(tree)
           fb += wa.Br(label)
         }
@@ -2411,12 +2411,12 @@ private class FunctionEmitter private (
           genTree(cond, BooleanType)
           markPosition(tree)
           fb.ifThen() {
-            genTree(body, NoType)
+            genTree(body, VoidType)
             markPosition(tree)
             fb += wa.Br(label)
           }
         }
-        NoType
+        VoidType
     }
   }
 
@@ -2451,7 +2451,7 @@ private class FunctionEmitter private (
         throw new NotImplementedError(s"Unsupported shape of ForIn node at ${tree.pos}: $tree")
     }
 
-    NoType
+    VoidType
   }
 
   private def genTryCatch(tree: TryCatch, expectedType: Type): Type = {
@@ -2540,7 +2540,7 @@ private class FunctionEmitter private (
           genWriteToStorage(storage)
 
         case _ =>
-          genTree(stat, NoType)
+          genTree(stat, VoidType)
       }
     }
 
@@ -2799,7 +2799,7 @@ private class FunctionEmitter private (
     genTree(item, AnyType)
     markPosition(tree)
     fb += wa.Call(genFunctionID.jsDelete)
-    NoType
+    VoidType
   }
 
   private def genJSUnaryOp(tree: JSUnaryOp): Type = {
@@ -3496,7 +3496,7 @@ private class FunctionEmitter private (
         fb += wa.Call(genFunctionID.genericArrayCopy)
     }
 
-    NoType
+    VoidType
   }
 
   // Helpers to generate code going through custom JS helpers
@@ -3993,7 +3993,7 @@ private class FunctionEmitter private (
         } // end block $catch
 
         // finally block (during which we leave the `(ref null exn)` on the stack)
-        genTree(finalizer, NoType)
+        genTree(finalizer, VoidType)
 
         markPosition(tree)
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/SWasmGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/SWasmGen.scala
index d8566b503a..f13320065d 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/SWasmGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/SWasmGen.scala
@@ -40,7 +40,7 @@ object SWasmGen {
       case AnyType | ClassType(_, true) | ArrayType(_, true) | NullType =>
         RefNull(Types.HeapType.None)
 
-      case NothingType | NoType | ClassType(_, false) | ArrayType(_, false) |
+      case NothingType | VoidType | ClassType(_, false) | ArrayType(_, false) |
           AnyNotNullType | _:RecordType =>
         throw new AssertionError(s"Unexpected type for field: ${tpe.show()}")
     }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/TypeTransformer.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/TypeTransformer.scala
index 813dcdcd92..d38694e284 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/TypeTransformer.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/TypeTransformer.scala
@@ -68,7 +68,7 @@ object TypeTransformer {
    */
   def transformResultType(tpe: Type)(implicit ctx: WasmContext): List[watpe.Type] = {
     tpe match {
-      case NoType             => Nil
+      case VoidType           => Nil
       case NothingType        => Nil
       case RecordType(fields) => fields.flatMap(f => transformResultType(f.tpe))
       case _                  => List(transformSingleType(tpe))
@@ -134,7 +134,7 @@ object TypeTransformer {
       case StringType  => watpe.RefType.extern
       case NullType    => watpe.RefType.nullref
 
-      case NoType | NothingType =>
+      case VoidType | NothingType =>
         throw new IllegalArgumentException(
             s"${tpe.show()} does not have a corresponding Wasm type")
     }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala b/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
index 718a710051..b23a83d5fc 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
@@ -152,8 +152,8 @@ private final class ClassDefChecker(classDef: ClassDef,
         val name = ident.name
         if (!alreadyDeclared.add(name))
             reportError(i"Duplicate JS class capture '$name'")
-        if (tpe == NoType)
-          reportError(i"The JS class capture $name cannot have type NoType")
+        if (tpe == VoidType)
+          reportError(i"The JS class capture $name cannot have type VoidType")
         if (mutable)
           reportError(i"The JS class capture $name cannot be mutable")
       }
@@ -227,7 +227,7 @@ private final class ClassDefChecker(classDef: ClassDef,
     }
 
     fieldDef.ftpe match {
-      case NoType | NothingType | AnyNotNullType | ClassType(_, false) |
+      case VoidType | NothingType | AnyNotNullType | ClassType(_, false) |
           ArrayType(_, false) | _:RecordType =>
         reportError(i"FieldDef cannot have type ${fieldDef.ftpe}")
       case _ =>
@@ -294,13 +294,13 @@ private final class ClassDefChecker(classDef: ClassDef,
     // Params
     for (ParamDef(name, _, tpe, _) <- params) {
       checkDeclareLocalVar(name)
-      if (tpe == NoType)
-        reportError(i"Parameter $name has type NoType")
+      if (tpe == VoidType)
+        reportError(i"Parameter $name has type VoidType")
     }
 
     // Body
     for (body <- optBody) {
-      val thisType = if (static) NoType else instanceThisType
+      val thisType = if (static) VoidType else instanceThisType
       val bodyEnv = Env.fromParams(params)
         .withThisType(thisType)
 
@@ -357,7 +357,7 @@ private final class ClassDefChecker(classDef: ClassDef,
     checkExportedPropertyName(pName)
     checkJSParamDefs(params, restParam)
 
-    val thisType = if (static) NoType else instanceThisType
+    val thisType = if (static) VoidType else instanceThisType
     val env =
       Env.fromParams(classDef.jsClassCaptures.getOrElse(Nil) ++ params ++ restParam).withThisType(thisType)
 
@@ -383,7 +383,7 @@ private final class ClassDefChecker(classDef: ClassDef,
     checkExportedPropertyName(pName)
 
     val jsClassCaptures = classDef.jsClassCaptures.getOrElse(Nil)
-    val thisType = if (static) NoType else instanceThisType
+    val thisType = if (static) VoidType else instanceThisType
 
     getterBody.foreach { body =>
       withPerMethodState {
@@ -799,7 +799,7 @@ private final class ClassDefChecker(classDef: ClassDef,
       case IsInstanceOf(expr, testType) =>
         checkTree(expr, env)
         testType match {
-          case NoType | NullType | NothingType | AnyType |
+          case VoidType | NullType | NothingType | AnyType |
               ClassType(_, true) | ArrayType(_, true) | _:RecordType =>
             reportError(i"$testType is not a valid test type for IsInstanceOf")
           case testType: ArrayType =>
@@ -811,7 +811,7 @@ private final class ClassDefChecker(classDef: ClassDef,
       case AsInstanceOf(expr, tpe) =>
         checkTree(expr, env)
         tpe match {
-          case NoType | NullType | NothingType | AnyNotNullType |
+          case VoidType | NullType | NothingType | AnyNotNullType |
               ClassType(_, false) | ArrayType(_, false) | _:RecordType =>
             reportError(i"$tpe is not a valid target type for AsInstanceOf")
           case tpe: ArrayType =>
@@ -936,7 +936,7 @@ private final class ClassDefChecker(classDef: ClassDef,
         }
 
       case This() =>
-        if (env.thisType == NoType)
+        if (env.thisType == VoidType)
           reportError(i"Cannot find `this` in scope")
         else if (tree.tpe != env.thisType)
           reportError(i"`this` of type ${env.thisType} typed as ${tree.tpe}")
@@ -961,8 +961,8 @@ private final class ClassDefChecker(classDef: ClassDef,
             checkDeclareLocalVar(name)
             if (mutable)
               reportError(i"Capture parameter $name cannot be mutable")
-            if (ctpe == NoType)
-              reportError(i"Parameter $name has type NoType")
+            if (ctpe == VoidType)
+              reportError(i"Parameter $name has type VoidType")
           }
 
           checkJSParamDefs(params, restParam)
@@ -970,7 +970,7 @@ private final class ClassDefChecker(classDef: ClassDef,
           val bodyEnv = Env
             .fromParams(captureParams ++ params ++ restParam)
             .withHasNewTarget(!arrow)
-            .withThisType(if (arrow) NoType else AnyType)
+            .withThisType(if (arrow) VoidType else AnyType)
           checkTree(body, bodyEnv)
         }
 
@@ -1065,7 +1065,7 @@ object ClassDefChecker {
   private class Env(
       /** Whether there is a valid `new.target` in scope. */
       val hasNewTarget: Boolean,
-      /** The type of `this` in scope, or `NoType` if there is no `this` in scope. */
+      /** The type of `this` in scope, or `VoidType` if there is no `this` in scope. */
       val thisType: Type,
       /** Local variables in scope (including through closures). */
       val locals: Map[LocalName, LocalDef],
@@ -1106,7 +1106,7 @@ object ClassDefChecker {
     val empty: Env = {
       new Env(
         hasNewTarget = false,
-        thisType = NoType,
+        thisType = VoidType,
         locals = Map.empty,
         returnLabels = Set.empty,
         isThisRestricted = false
@@ -1120,7 +1120,7 @@ object ClassDefChecker {
 
       new Env(
         hasNewTarget = false,
-        thisType = NoType,
+        thisType = VoidType,
         paramLocalDefs.toMap,
         Set.empty,
         isThisRestricted = false
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala b/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
index 4d388be2ea..f6df8de449 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
@@ -139,8 +139,8 @@ private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter) {
     body.superCall.args.foreach(typecheckExprOrSpread(_, bodyEnv))
     body.afterSuper.foreach(typecheck(_, bodyEnv))
 
-    val resultType = body.afterSuper.lastOption.fold[Type](NoType)(_.tpe)
-    if (resultType == NoType)
+    val resultType = body.afterSuper.lastOption.fold[Type](VoidType)(_.tpe)
+    if (resultType == VoidType)
       reportError(i"${AnyType} expected but $resultType found for JS constructor body")
   }
 
@@ -257,7 +257,7 @@ private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter) {
 
       case Return(expr, label) =>
         val returnType = env.returnTypes(label.name)
-        if (returnType == NoType)
+        if (returnType == VoidType)
           typecheckExpr(expr, env)
         else
           typecheckExpect(expr, env, returnType)
@@ -312,7 +312,7 @@ private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter) {
         val clazz = lookupClass(className)
         if (clazz.kind != ClassKind.Class)
           reportError(i"new $className which is not a class")
-        checkApplyGeneric(className, ctor.name, args, NoType, isStatic = false)
+        checkApplyGeneric(className, ctor.name, args, VoidType, isStatic = false)
 
       case LoadModule(className) =>
         val clazz = lookupClass(className)
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
index ab84765129..15818137e4 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
@@ -419,7 +419,7 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
     val className: ClassName = linkedClass.className
 
     def untrackedThisType: Type =
-      if (namespace.isStatic) NoType
+      if (namespace.isStatic) VoidType
       else myInterface.untrackedInstanceThisType
 
     val methods = mutable.Map.empty[MethodName, MethodImpl]
@@ -1162,7 +1162,7 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
     def untrackedJSClassCaptures: List[ParamDef] = _jsClassCaptures
 
     def untrackedThisType(namespace: MemberNamespace): Type =
-      if (namespace.isStatic) NoType
+      if (namespace.isStatic) VoidType
       else myInterface.untrackedInstanceThisType
 
     def updateWith(linkedClass: LinkedClass): Unit = {
@@ -1220,7 +1220,7 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
     private[this] var methods = Map.empty[(String, String), (JSMethodImpl, Position)]
 
     val untrackedJSClassCaptures: List[ParamDef] = Nil
-    def untrackedThisType(namespace: MemberNamespace): Type = NoType
+    def untrackedThisType(namespace: MemberNamespace): Type = VoidType
 
     override def toString(): String = "<top-level>"
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
index 944c8ae079..adaac12ee7 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
@@ -270,8 +270,8 @@ private[optimizer] abstract class OptimizerCore(
   private val isSubclassFun = isSubclass _
 
   private def isSubtype(lhs: Type, rhs: Type): Boolean = {
-    assert(lhs != NoType)
-    assert(rhs != NoType)
+    assert(lhs != VoidType)
+    assert(rhs != VoidType)
 
     Types.isSubtype(lhs, rhs)(isSubclassFun) || {
       (lhs, rhs) match {
@@ -337,7 +337,7 @@ private[optimizer] abstract class OptimizerCore(
 
       case Labeled(ident @ LabelIdent(label), tpe, body) =>
         trampoline {
-          pretransformLabeled(label, if (isStat) NoType else tpe, body, isStat,
+          pretransformLabeled(label, if (isStat) VoidType else tpe, body, isStat,
               usePreTransform = false)(finishTransform(isStat))
         }
 
@@ -1157,13 +1157,13 @@ private[optimizer] abstract class OptimizerCore(
           pretransformExprs(thenp, elsep) { (tthenp, telsep) =>
             if (tthenp.tpe.isNothingType) {
               cont(PreTransBlock(
-                  If(newCond, finishTransformStat(tthenp), Skip())(NoType),
+                  If(newCond, finishTransformStat(tthenp), Skip())(VoidType),
                   telsep))
             } else if (telsep.tpe.isNothingType) {
               val negCond = finishTransformExpr(
                   foldUnaryOp(UnaryOp.Boolean_!, newCond.toPreTransform))
               cont(PreTransBlock(
-                  If(negCond, finishTransformStat(telsep), Skip())(NoType),
+                  If(negCond, finishTransformStat(telsep), Skip())(VoidType),
                   tthenp))
             } else {
               (resolveLocalDef(tthenp), resolveLocalDef(telsep)) match {
@@ -1687,7 +1687,7 @@ private[optimizer] abstract class OptimizerCore(
     case If(cond, thenp, elsep) =>
       (keepOnlySideEffects(thenp), keepOnlySideEffects(elsep)) match {
         case (Skip(), Skip())     => keepOnlySideEffects(cond)
-        case (newThenp, newElsep) => If(cond, newThenp, newElsep)(NoType)(stat.pos)
+        case (newThenp, newElsep) => If(cond, newThenp, newElsep)(VoidType)(stat.pos)
       }
 
     case BinaryOp(op, lhs, rhs) =>
@@ -3089,7 +3089,7 @@ private[optimizer] abstract class OptimizerCore(
                   cpLocalDef.newReplacement, IntLiteral(Character.MAX_CODE_POINT))),
               Throw(New(IllegalArgumentExceptionClass, MethodIdent(NoArgConstructorName), Nil)),
               Skip()
-            )(NoType),
+            )(VoidType),
             Transient(WasmStringFromCodePoint(cpLocalDef.newReplacement))
           )))
         } (cont)
@@ -3166,7 +3166,7 @@ private[optimizer] abstract class OptimizerCore(
              */
             tpe match {
               case CharType => IntLiteral(0)
-              case NoType   => Undefined()
+              case VoidType => Undefined()
               case _        => zeroOf(tpe)
             }
           case ClassOf(_) =>
@@ -5119,7 +5119,7 @@ private[optimizer] abstract class OptimizerCore(
     val (paramLocalDefs, newParamDefs) = params.map(newParamReplacement(_)).unzip
 
     val thisLocalDef =
-      if (thisType == NoType) None
+      if (thisType == VoidType) None
       else Some(newThisLocalDef(thisType))
 
     val env = OptEnv.Empty
@@ -5140,7 +5140,7 @@ private[optimizer] abstract class OptimizerCore(
       }
     }
 
-    val newBody0 = transform(body, resultType == NoType)(scope)
+    val newBody0 = transform(body, resultType == VoidType)(scope)
 
     val newBody =
       if (isNoArgCtor) tryElimStoreModule(newBody0)
@@ -5258,7 +5258,7 @@ private[optimizer] abstract class OptimizerCore(
             def tryDropReturn(body: Tree): Option[Tree] = body match {
               case BlockOrAlone(prep, Return(result, LabelIdent(`newLabelName`))) =>
                 val result1 =
-                  if (refinedType == NoType) keepOnlySideEffects(result)
+                  if (refinedType == VoidType) keepOnlySideEffects(result)
                   else result
                 Some(Block(prep, result1)(body.pos))
 
@@ -5537,7 +5537,7 @@ private[optimizer] abstract class OptimizerCore(
    */
   private def constrainedLub(lhs: RefinedType, rhs: RefinedType,
       upperBound: Type): RefinedType = {
-    if (upperBound == NoType) RefinedType(upperBound)
+    if (upperBound == VoidType) RefinedType(upperBound)
     else if (lhs == rhs) lhs
     else if (lhs.isNothingType) rhs
     else if (rhs.isNothingType) lhs
@@ -5550,7 +5550,7 @@ private[optimizer] abstract class OptimizerCore(
    */
   private def constrainedLub(lhs: Type, rhs: Type, upperBound: Type): Type = {
     // TODO Improve this
-    if (upperBound == NoType) upperBound
+    if (upperBound == VoidType) upperBound
     else if (lhs == rhs) lhs
     else if (lhs == NothingType) rhs
     else if (rhs == NothingType) lhs
@@ -5770,7 +5770,7 @@ private[optimizer] object OptimizerCore {
     def apply(tpe: Type): RefinedType = {
       val isExact = tpe match {
         case NullType | NothingType | UndefType | BooleanType | CharType |
-            LongType | StringType | NoType =>
+            LongType | StringType | VoidType =>
           true
         case _ =>
           /* At run-time, a byte will answer true to `x.isInstanceOf[Int]`,
@@ -5782,7 +5782,7 @@ private[optimizer] object OptimizerCore {
       RefinedType(tpe, isExact)
     }
 
-    val NoRefinedType = RefinedType(NoType)
+    val NoRefinedType = RefinedType(VoidType)
     val Nothing = RefinedType(NothingType)
   }
 
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/AnalyzerTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/AnalyzerTest.scala
index 924cd3cabe..da9e9658c0 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/AnalyzerTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/AnalyzerTest.scala
@@ -315,9 +315,9 @@ class AnalyzerTest {
         classDef("A", superClass = Some(ObjectClass),
             methods = List(
                 trivialCtor("A"),
-                MethodDef(EMF, barMethodName, NON, Nil, NoType, Some(Block(
-                  Apply(EAF, thisFor("A"), fooMethodName, Nil)(NoType),
-                  Apply(EAF, New("B", NoArgConstructorName, Nil), fooMethodName, Nil)(NoType)
+                MethodDef(EMF, barMethodName, NON, Nil, VoidType, Some(Block(
+                  Apply(EAF, thisFor("A"), fooMethodName, Nil)(VoidType),
+                  Apply(EAF, New("B", NoArgConstructorName, Nil), fooMethodName, Nil)(VoidType)
                 )))(EOH, UNV)
             )),
         classDef("B", superClass = Some("A"),
@@ -413,7 +413,7 @@ class AnalyzerTest {
     val testName = m("test", Nil, O)
     val method = MethodDef(
         EMF.withNamespace(MemberNamespace.PublicStatic),
-        mainName, NON, Nil, NoType,
+        mainName, NON, Nil, VoidType,
         Some(SelectJSNativeMember("A", testName)))(EOH, UNV)
 
     val classDefs = Seq(
@@ -433,7 +433,7 @@ class AnalyzerTest {
   @Test
   def conflictingDefaultMethods(): AsyncResult = await {
     val defaultMethodDef = MethodDef(EMF, m("foo", Nil, V), NON, Nil,
-        NoType, Some(Skip()))(EOH, UNV)
+        VoidType, Some(Skip()))(EOH, UNV)
     val classDefs = Seq(
         classDef("I1", kind = ClassKind.Interface,
             methods = List(defaultMethodDef)),
@@ -603,7 +603,7 @@ class AnalyzerTest {
 
     val mainMethod = MethodDef(
         EMF.withNamespace(MemberNamespace.PublicStatic),
-        mainName, NON, Nil, NoType,
+        mainName, NON, Nil, VoidType,
         Some(SelectJSNativeMember("A", testName)))(EOH, UNV)
     val nativeMember = JSNativeMemberDef(
         EMF.withNamespace(MemberNamespace.PublicStatic), testName,
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/IRCheckerTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/IRCheckerTest.scala
index fd2faebe8b..8617ae460d 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/IRCheckerTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/IRCheckerTest.scala
@@ -48,7 +48,7 @@ class IRCheckerTest {
     val nullBarMethodName = m("nullBar", Nil, ClassRef(BarClass))
 
     def callMethOn(receiver: Tree): Tree =
-      Apply(EAF, receiver, methMethodName, List(Null()))(NoType)
+      Apply(EAF, receiver, methMethodName, List(Null()))(VoidType)
 
     val classDefs = Seq(
         // LFoo will be dropped by base linking
@@ -63,7 +63,7 @@ class IRCheckerTest {
                  * instances of `Bar`. It will therefore not make `Foo` reachable.
                  */
                 MethodDef(EMF, methMethodName, NON,
-                    List(paramDef("foo", ClassType("Foo", nullable = true))), NoType,
+                    List(paramDef("foo", ClassType("Foo", nullable = true))), VoidType,
                     Some(Skip()))(
                     EOH, UNV)
             )
@@ -114,7 +114,7 @@ class IRCheckerTest {
           interfaces = Nil,
           methods = List(
             MethodDef(EMF, fooMethodName, NON,
-                List(paramDef("x", ClassType(B, nullable = true))), NoType, Some(Skip()))(
+                List(paramDef("x", ClassType(B, nullable = true))), VoidType, Some(Skip()))(
                 EOH, UNV)
           )
         ),
@@ -143,19 +143,19 @@ class IRCheckerTest {
                 paramDef("c", ClassType(C, nullable = true)),
                 paramDef("d", ClassType(D, nullable = true))
               ),
-              NoType,
+              VoidType,
               Some(Block(
                 Apply(EAF, VarRef("x")(receiverType), fooMethodName,
-                    List(VarRef("c")(ClassType(C, nullable = true))))(NoType),
+                    List(VarRef("c")(ClassType(C, nullable = true))))(VoidType),
                 Apply(EAF, VarRef("x")(receiverType), fooMethodName,
-                    List(VarRef("d")(ClassType(D, nullable = true))))(NoType)
+                    List(VarRef("d")(ClassType(D, nullable = true))))(VoidType)
               ))
             )(EOH, UNV)
           )
         ),
 
         mainTestClassDef(
-          ApplyStatic(EAF, D, testMethodName, List(newD, newD, newD))(NoType)
+          ApplyStatic(EAF, D, testMethodName, List(newD, newD, newD))(VoidType)
         )
       )
 
@@ -220,7 +220,7 @@ class IRCheckerTest {
 
     for (log <- testLinkIRErrors(classDefs, MainTestModuleInitializers)) yield {
       log.assertContainsError(
-          "any expected but <notype> found for JS constructor body")
+          "any expected but void found for JS constructor body")
     }
   }
 
@@ -249,7 +249,7 @@ class IRCheckerTest {
 
     for (log <- testLinkIRErrors(classDefs, MainTestModuleInitializers)) yield {
       log.assertContainsError(
-          "any expected but <notype> found for JS constructor body")
+          "any expected but void found for JS constructor body")
     }
   }
 
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/IncrementalTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/IncrementalTest.scala
index 245d36b326..105ba204d0 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/IncrementalTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/IncrementalTest.scala
@@ -205,10 +205,10 @@ class IncrementalTest {
     val meth2 = m("meth2", Nil, VoidRef)
 
     def methDef(name: MethodName, body: Tree): MethodDef =
-      MethodDef(EMF, name, NON, Nil, NoType, Some(body))(EOH.withNoinline(true), UNV)
+      MethodDef(EMF, name, NON, Nil, VoidType, Some(body))(EOH.withNoinline(true), UNV)
 
     def callMeth(targetMeth: MethodName): Tree =
-      Apply(EAF, LoadModule(FooClass), targetMeth, Nil)(NoType)
+      Apply(EAF, LoadModule(FooClass), targetMeth, Nil)(VoidType)
 
     def classDefs(step: Int) = {
       val stepDependentMembers = step match {
@@ -263,12 +263,12 @@ class IncrementalTest {
 
     def methDef(name: MethodName, body: Tree): MethodDef = {
       MethodDef(EMF.withNamespace(MemberNamespace.PublicStatic), name, NON, Nil,
-          NoType, Some(body))(
+          VoidType, Some(body))(
           EOH.withNoinline(true), UNV)
     }
 
     def callMeth(targetMeth: MethodName): Tree =
-      ApplyStatic(EAF, FooClass, targetMeth, Nil)(NoType)
+      ApplyStatic(EAF, FooClass, targetMeth, Nil)(VoidType)
 
     def classDefs(step: Int) = {
       val stepDependentMembers = step match {
@@ -317,7 +317,7 @@ class IncrementalTest {
         ApplyStatically(EAF.withConstructor(true),
             thisFor(FooModule),
             ObjectClass, MethodIdent(NoArgConstructorName),
-            Nil)(NoType)
+            Nil)(VoidType)
       }
 
       val body =
@@ -325,7 +325,7 @@ class IncrementalTest {
         else Block(superCtor, consoleLog(str("bar")))
 
       MethodDef(MemberFlags.empty.withNamespace(MemberNamespace.Constructor),
-          MethodIdent(NoArgConstructorName), NON, Nil, NoType,
+          MethodIdent(NoArgConstructorName), NON, Nil, VoidType,
           Some(body))(EOH, UNV)
     }
 
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/LibraryReachabilityTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/LibraryReachabilityTest.scala
index 0aedcc4906..8b08bcf860 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/LibraryReachabilityTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/LibraryReachabilityTest.scala
@@ -43,7 +43,7 @@ class LibraryReachabilityTest {
     val classDefs = Seq(
         classDef("A", superClass = Some(ObjectClass), methods = List(
             trivialCtor("A"),
-            MethodDef(EMF, m("test", Nil, V), NON, Nil, NoType, Some(Block(
+            MethodDef(EMF, m("test", Nil, V), NON, Nil, VoidType, Some(Block(
                 Apply(EAF, systemMod, m("getProperty", List(T), T), List(emptyStr))(StringType),
                 Apply(EAF, systemMod, m("getProperty", List(T, T), T), List(emptyStr, emptyStr))(StringType),
                 Apply(EAF, systemMod, m("setProperty", List(T, T), T), List(emptyStr, emptyStr))(StringType),
@@ -72,7 +72,7 @@ class LibraryReachabilityTest {
     val classDefs = Seq(
       classDef("A", superClass = Some(ObjectClass), methods = List(
         trivialCtor("A"),
-        MethodDef(EMF, m("test", Nil, V), NON, Nil, NoType, Some(Block(
+        MethodDef(EMF, m("test", Nil, V), NON, Nil, VoidType, Some(Block(
           ApplyStatic(EAF, BoxedStringClass, formatMethod, List(str("hello %d"), int(42)))(StringType)
         )))(EOH, UNV)
       ))
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/OptimizerTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/OptimizerTest.scala
index 3854cd89ad..0a77c1414c 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/OptimizerTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/OptimizerTest.scala
@@ -274,16 +274,16 @@ class OptimizerTest {
 
     val classDefs = Seq(
         mainTestClassDef(Block(
-            Labeled(matchResult1, NoType, Block(
+            Labeled(matchResult1, VoidType, Block(
                 VarDef(x1, NON, AnyType, mutable = false, Null()),
-                Labeled(matchAlts1, NoType, Block(
-                    Labeled(matchAlts2, NoType, Block(
+                Labeled(matchAlts1, VoidType, Block(
+                    Labeled(matchAlts2, VoidType, Block(
                         If(IsInstanceOf(VarRef(x1)(AnyType), ClassType(BoxedIntegerClass, nullable = false)), {
                           Return(Undefined(), matchAlts2)
-                        }, Skip())(NoType),
+                        }, Skip())(VoidType),
                         If(IsInstanceOf(VarRef(x1)(AnyType), ClassType(BoxedStringClass, nullable = false)), {
                           Return(Undefined(), matchAlts2)
-                        }, Skip())(NoType),
+                        }, Skip())(VoidType),
                         Return(Undefined(), matchAlts1)
                     )),
                     Return(Undefined(), matchResult1)
@@ -505,7 +505,7 @@ class OptimizerTest {
             //   this.y = 5
             //   this.jl.Object::<init>()
             // }
-            MethodDef(EMF.withNamespace(Constructor), NoArgConstructorName, NON, Nil, NoType, Some(Block(
+            MethodDef(EMF.withNamespace(Constructor), NoArgConstructorName, NON, Nil, VoidType, Some(Block(
               Assign(Select(thisFor("Foo"), FieldName("Foo", "x"))(witnessType), Null()),
               Assign(Select(thisFor("Foo"), FieldName("Foo", "y"))(IntType), int(5)),
               trivialSuperCtorCall("Foo")
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/checker/ClassDefCheckerTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/checker/ClassDefCheckerTest.scala
index 899abc9857..df23c6b3f5 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/checker/ClassDefCheckerTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/checker/ClassDefCheckerTest.scala
@@ -173,7 +173,7 @@ class ClassDefCheckerTest {
       ArrayType(ArrayTypeRef(I, 1), nullable = false),
       RecordType(List(RecordType.Field("I", NON, IntType, mutable = true))),
       NothingType,
-      NoType
+      VoidType
     )
 
     for (fieldType <- badFieldTypes) {
@@ -210,7 +210,7 @@ class ClassDefCheckerTest {
 
     val callPrimaryCtorBody: Tree = {
       ApplyStatically(EAF.withConstructor(true), thisFor(FooClass),
-          FooClass, NoArgConstructorName, Nil)(NoType)
+          FooClass, NoArgConstructorName, Nil)(VoidType)
     }
 
     assertError(
@@ -219,11 +219,11 @@ class ClassDefCheckerTest {
               trivialCtor(FooClass),
               MethodDef(EMF.withNamespace(MemberNamespace.Constructor),
                   stringCtorName, NON, List(paramDef("x", BoxedStringType)),
-                  NoType, Some(callPrimaryCtorBody))(
+                  VoidType, Some(callPrimaryCtorBody))(
                   EOH, UNV),
               MethodDef(EMF.withNamespace(MemberNamespace.Constructor),
                   stringCtorName, NON, List(paramDef("y", BoxedStringType)),
-                  NoType, Some(callPrimaryCtorBody))(
+                  VoidType, Some(callPrimaryCtorBody))(
                   EOH, UNV)
           )),
         "duplicate constructor method '<init>(java.lang.String)void'")
@@ -293,7 +293,7 @@ class ClassDefCheckerTest {
   def noDuplicateVarDefTryCatch(): Unit = {
     val body = Block(
       VarDef("x", NoOriginalName, IntType, mutable = false, int(1)),
-      TryCatch(Skip(), "x", NoOriginalName, Skip())(NoType)
+      TryCatch(Skip(), "x", NoOriginalName, Skip())(VoidType)
     )
 
     assertError(
@@ -310,7 +310,7 @@ class ClassDefCheckerTest {
         classDef(
           "Foo", superClass = Some(ObjectClass),
           methods = List(
-            MethodDef(ctorFlags, NoArgConstructorName, NON, Nil, NoType,
+            MethodDef(ctorFlags, NoArgConstructorName, NON, Nil, VoidType,
                 Some(int(5)))(EOH, UNV)
           )
         ),
@@ -325,9 +325,9 @@ class ClassDefCheckerTest {
         classDef(
           "Foo", superClass = Some(ObjectClass),
           methods = List(
-            MethodDef(ctorFlags, NoArgConstructorName, NON, Nil, NoType, Some {
+            MethodDef(ctorFlags, NoArgConstructorName, NON, Nil, VoidType, Some {
               ApplyStatically(EAF.withConstructor(true), thisFor("Foo"),
-                  "Bar", NoArgConstructorName, Nil)(NoType)
+                  "Bar", NoArgConstructorName, Nil)(VoidType)
             })(EOH, UNV)
           )
         ),
@@ -341,7 +341,7 @@ class ClassDefCheckerTest {
 
     def ctorCall(receiver: Tree): ApplyStatically = {
       ApplyStatically(EAF.withConstructor(true), receiver,
-          ObjectClass, NoArgConstructorName, Nil)(NoType)
+          ObjectClass, NoArgConstructorName, Nil)(VoidType)
     }
 
     val thiz = thisFor("Foo")
@@ -350,7 +350,7 @@ class ClassDefCheckerTest {
         classDef(
           "Foo", superClass = Some(ObjectClass),
           methods = List(
-            MethodDef(ctorFlags, NoArgConstructorName, NON, Nil, NoType, Some(Block(
+            MethodDef(ctorFlags, NoArgConstructorName, NON, Nil, VoidType, Some(Block(
               ctorCall(thiz),
               ctorCall(Null())
             )))(EOH, UNV)
@@ -362,9 +362,9 @@ class ClassDefCheckerTest {
         classDef(
           "Foo", superClass = Some(ObjectClass),
           methods = List(
-            MethodDef(ctorFlags, NoArgConstructorName, NON, Nil, NoType, Some(Block(
+            MethodDef(ctorFlags, NoArgConstructorName, NON, Nil, VoidType, Some(Block(
               ctorCall(thiz),
-              If(BooleanLiteral(true), ctorCall(thiz), Skip())(NoType)
+              If(BooleanLiteral(true), ctorCall(thiz), Skip())(VoidType)
             )))(EOH, UNV)
           )
         ),
@@ -375,7 +375,7 @@ class ClassDefCheckerTest {
           "Foo", superClass = Some(ObjectClass),
           methods = List(
             trivialCtor("Foo"),
-            MethodDef(EMF, m("foo", Nil, V), NON, Nil, NoType, Some(Block(
+            MethodDef(EMF, m("foo", Nil, V), NON, Nil, VoidType, Some(Block(
               ctorCall(thiz)
             )))(EOH, UNV)
           )
@@ -394,7 +394,7 @@ class ClassDefCheckerTest {
           classDef(
             "Foo", superClass = Some(ObjectClass),
             methods = List(
-              MethodDef(methodFlags, m("bar", Nil, V), NON, Nil, NoType, Some({
+              MethodDef(methodFlags, m("bar", Nil, V), NON, Nil, VoidType, Some({
                 consoleLog(expr)
               }))(EOH, UNV)
             )
@@ -403,7 +403,7 @@ class ClassDefCheckerTest {
     }
 
     testThisTypeError(static = true,
-        This()(NoType),
+        This()(VoidType),
         "Cannot find `this` in scope")
 
     testThisTypeError(static = true,
@@ -411,8 +411,8 @@ class ClassDefCheckerTest {
         "Cannot find `this` in scope")
 
     testThisTypeError(static = false,
-        This()(NoType),
-        "`this` of type Foo! typed as <notype>")
+        This()(VoidType),
+        "`this` of type Foo! typed as void")
 
     testThisTypeError(static = false,
         This()(AnyType),
@@ -431,7 +431,7 @@ class ClassDefCheckerTest {
         "`this` of type Foo! typed as Foo")
 
     testThisTypeError(static = false,
-        Closure(arrow = true, Nil, Nil, None, This()(NoType), Nil),
+        Closure(arrow = true, Nil, Nil, None, This()(VoidType), Nil),
         "Cannot find `this` in scope")
 
     testThisTypeError(static = false,
@@ -439,8 +439,8 @@ class ClassDefCheckerTest {
         "Cannot find `this` in scope")
 
     testThisTypeError(static = false,
-        Closure(arrow = false, Nil, Nil, None, This()(NoType), Nil),
-        "`this` of type any typed as <notype>")
+        Closure(arrow = false, Nil, Nil, None, This()(VoidType), Nil),
+        "`this` of type any typed as void")
 
     testThisTypeError(static = false,
         Closure(arrow = false, Nil, Nil, None, This()(ClassType("Foo", nullable = false)), Nil),
@@ -460,7 +460,7 @@ class ClassDefCheckerTest {
             "Foo", superClass = Some(ObjectClass),
             methods = List(
               MethodDef(ctorFlags, MethodName.constructor(List(I)), NON,
-                  List(xParamDef), NoType, Some(Block(ctorStats: _*)))(EOH, UNV)
+                  List(xParamDef), VoidType, Some(Block(ctorStats: _*)))(EOH, UNV)
             )
           ),
           "Restricted use of `this` before the super constructor call")
@@ -497,7 +497,7 @@ class ClassDefCheckerTest {
     testRestrictedThisError(
       ApplyStatically(EAF.withConstructor(true), thiz, ObjectClass,
           MethodIdent(MethodName.constructor(List(O))),
-          List(thiz))(NoType)
+          List(thiz))(VoidType)
     )
   }
 
@@ -513,7 +513,7 @@ class ClassDefCheckerTest {
         kind = ClassKind.Class,
         superClass = Some(ObjectClass),
         methods = List(
-          MethodDef(ctorFlags, NoArgConstructorName, NON, Nil, NoType, Some {
+          MethodDef(ctorFlags, NoArgConstructorName, NON, Nil, VoidType, Some {
             Block(
               superCtorCall,
               StoreModule()
@@ -530,7 +530,7 @@ class ClassDefCheckerTest {
         kind = ClassKind.ModuleClass,
         superClass = Some(ObjectClass),
         methods = List(
-          MethodDef(ctorFlags, NoArgConstructorName, NON, Nil, NoType, Some {
+          MethodDef(ctorFlags, NoArgConstructorName, NON, Nil, VoidType, Some {
             Block(
               StoreModule(),
               superCtorCall
@@ -547,10 +547,10 @@ class ClassDefCheckerTest {
         kind = ClassKind.ModuleClass,
         superClass = Some(ObjectClass),
         methods = List(
-          MethodDef(ctorFlags, NoArgConstructorName, NON, Nil, NoType, Some {
+          MethodDef(ctorFlags, NoArgConstructorName, NON, Nil, VoidType, Some {
             Block(
               superCtorCall,
-              If(BooleanLiteral(true), StoreModule(), Skip())(NoType)
+              If(BooleanLiteral(true), StoreModule(), Skip())(VoidType)
             )
           })(EOH, UNV)
         )
@@ -565,7 +565,7 @@ class ClassDefCheckerTest {
         superClass = Some(ObjectClass),
         methods = List(
           trivialCtor("Foo"),
-          MethodDef(EMF, MethodName("foo", Nil, VoidRef), NON, Nil, NoType, Some {
+          MethodDef(EMF, MethodName("foo", Nil, VoidRef), NON, Nil, VoidType, Some {
             Block(
               StoreModule()
             )
@@ -597,7 +597,7 @@ class ClassDefCheckerTest {
         jsConstructor = Some(
           JSConstructorDef(JSCtorFlags, Nil, None,
               JSConstructorBody(Nil, JSSuperConstructorCall(Nil),
-                  If(BooleanLiteral(true), StoreModule(), Skip())(NoType) :: Undefined() :: Nil))(
+                  If(BooleanLiteral(true), StoreModule(), Skip())(VoidType) :: Undefined() :: Nil))(
               EOH, UNV)
         )
       ),
@@ -624,7 +624,7 @@ class ClassDefCheckerTest {
       testAsInstanceOfError(tpe)
     }
 
-    testIsAsInstanceOfError(NoType)
+    testIsAsInstanceOfError(VoidType)
     testIsAsInstanceOfError(NullType)
     testIsAsInstanceOfError(NothingType)
 
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/testutils/TestIRBuilder.scala b/linker/shared/src/test/scala/org/scalajs/linker/testutils/TestIRBuilder.scala
index 42c8736b02..d17d8e21c0 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/testutils/TestIRBuilder.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/testutils/TestIRBuilder.scala
@@ -88,7 +88,7 @@ object TestIRBuilder {
 
   def trivialCtor(enclosingClassName: ClassName, parentClassName: ClassName = ObjectClass): MethodDef = {
     val flags = MemberFlags.empty.withNamespace(MemberNamespace.Constructor)
-    MethodDef(flags, MethodIdent(NoArgConstructorName), NON, Nil, NoType,
+    MethodDef(flags, MethodIdent(NoArgConstructorName), NON, Nil, VoidType,
         Some(trivialSuperCtorCall(enclosingClassName, parentClassName)))(
         EOH, UNV)
   }
@@ -98,7 +98,7 @@ object TestIRBuilder {
     ApplyStatically(EAF.withConstructor(true),
         thisFor(enclosingClassName),
         parentClassName, MethodIdent(NoArgConstructorName),
-        Nil)(NoType)
+        Nil)(VoidType)
   }
 
   def trivialJSCtor: JSConstructorDef = {
@@ -112,7 +112,7 @@ object TestIRBuilder {
   def mainMethodDef(body: Tree): MethodDef = {
     val argsParamDef = paramDef("args", ArrayType(AT, nullable = true))
     MethodDef(MemberFlags.empty.withNamespace(MemberNamespace.PublicStatic),
-        MainMethodName, NON, List(argsParamDef), NoType, Some(body))(
+        MainMethodName, NON, List(argsParamDef), VoidType, Some(body))(
         EOH, UNV)
   }
 
@@ -126,7 +126,7 @@ object TestIRBuilder {
 
     val out = ApplyStatic(EAF, "java.lang.System", outMethodName, Nil)(
         ClassType(PrintStreamClass, nullable = true))
-    Apply(EAF, out, printlnMethodName, List(expr))(NoType)
+    Apply(EAF, out, printlnMethodName, List(expr))(VoidType)
   }
 
   def paramDef(name: LocalName, ptpe: Type): ParamDef =
diff --git a/project/BinaryIncompatibilities.scala b/project/BinaryIncompatibilities.scala
index 959802dff4..75c5dbb18a 100644
--- a/project/BinaryIncompatibilities.scala
+++ b/project/BinaryIncompatibilities.scala
@@ -7,7 +7,9 @@ object BinaryIncompatibilities {
   val IR = Seq(
     // !!! Breaking, OK in minor release
     ProblemFilters.exclude[MissingClassProblem]("org.scalajs.ir.Trees$JSLinkingInfo"),
-    ProblemFilters.exclude[MissingClassProblem]("org.scalajs.ir.Trees$JSLinkingInfo$")
+    ProblemFilters.exclude[MissingClassProblem]("org.scalajs.ir.Trees$JSLinkingInfo$"),
+    ProblemFilters.exclude[IncompatibleResultTypeProblem]("org.scalajs.ir.Trees#*.tpe"),
+    ProblemFilters.exclude[MissingClassProblem]("org.scalajs.ir.Types$NoType$"),
   )
 
   val Linker = Seq(
diff --git a/project/JavaLangObject.scala b/project/JavaLangObject.scala
index c316ecc7a0..789d57df73 100644
--- a/project/JavaLangObject.scala
+++ b/project/JavaLangObject.scala
@@ -51,7 +51,7 @@ object JavaLangObject {
           MethodIdent(NoArgConstructorName),
           NoOriginalName,
           Nil,
-          NoType,
+          VoidType,
           Some(Skip()))(OptimizerHints.empty, Unversioned),
 
         /* def getClass(): java.lang.Class[_] = <getclass>(this) */
@@ -148,7 +148,7 @@ object JavaLangObject {
           MethodIdent(MethodName("notify", Nil, VoidRef)),
           NoOriginalName,
           Nil,
-          NoType,
+          VoidType,
           Some(Skip()))(OptimizerHints.empty, Unversioned),
 
         /* def notifyAll(): Unit = () */
@@ -157,7 +157,7 @@ object JavaLangObject {
           MethodIdent(MethodName("notifyAll", Nil, VoidRef)),
           NoOriginalName,
           Nil,
-          NoType,
+          VoidType,
           Some(Skip()))(OptimizerHints.empty, Unversioned),
 
         /* def finalize(): Unit = () */
@@ -166,7 +166,7 @@ object JavaLangObject {
           MethodIdent(MethodName("finalize", Nil, VoidRef)),
           NoOriginalName,
           Nil,
-          NoType,
+          VoidType,
           Some(Skip()))(OptimizerHints.empty, Unversioned),
       ),
       jsConstructor = None,

From ff197d81228e94b6d86cb890dbb412bb27340748 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Mon, 21 Oct 2024 13:26:23 +0200
Subject: [PATCH 197/298] Restrict usages of `StoreModule` even further.

* Must appear exactly once, right after the super constructor call,
  in module classes.
* Cannot appear anywhere else.

This was not actually the case for JS module classes. We never
emitted `StoreModule`s in JS constructors. We use a deserialization
hack to introduce them, and add tests for the corner case that
`StoreModule` is meant to solve.

In this commit, we always enable the deserialization hack, and do
not change the compiler yet.
---
 .../scala/org/scalajs/ir/Serializers.scala    | 18 ++++-
 .../linker/checker/ClassDefChecker.scala      | 30 +++++--
 .../org/scalajs/linker/AnalyzerTest.scala     | 19 ++---
 .../org/scalajs/linker/IRCheckerTest.scala    |  2 +-
 .../org/scalajs/linker/IncrementalTest.scala  | 19 ++---
 .../linker/checker/ClassDefCheckerTest.scala  | 79 +++++++++++++++++--
 .../linker/testutils/TestIRBuilder.scala      | 24 ++++--
 .../compiler/StoreModuleJSTest.scala          | 42 ++++++++++
 .../testsuite/compiler/StoreModuleTest.scala  | 40 ++++++++++
 9 files changed, 229 insertions(+), 44 deletions(-)
 create mode 100644 test-suite/js/src/test/scala/org/scalajs/testsuite/compiler/StoreModuleJSTest.scala
 create mode 100644 test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/StoreModuleTest.scala

diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
index 5a69b79b42..de1c74d161 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
@@ -1560,7 +1560,7 @@ object Serializers {
           case TagFieldDef          => fieldsBuilder += readFieldDef()
           case TagJSFieldDef        => fieldsBuilder += readJSFieldDef()
           case TagMethodDef         => methodsBuilder += readMethodDef(cls, kind)
-          case TagJSConstructorDef  => jsConstructorBuilder += readJSConstructorDef()
+          case TagJSConstructorDef  => jsConstructorBuilder += readJSConstructorDef(kind)
           case TagJSMethodDef       => jsMethodPropsBuilder += readJSMethodDef()
           case TagJSPropertyDef     => jsMethodPropsBuilder += readJSPropertyDef()
           case TagJSNativeMemberDef => jsNativeMembersBuilder += readJSNativeMemberDef()
@@ -1986,7 +1986,9 @@ object Serializers {
       }
     }
 
-    private def readJSConstructorDef()(implicit pos: Position): JSConstructorDef = {
+    private def readJSConstructorDef(ownerKind: ClassKind)(
+        implicit pos: Position): JSConstructorDef = {
+
       val optHash = readOptHash()
       // read and discard the length
       val len = readInt()
@@ -2001,7 +2003,17 @@ object Serializers {
       val bodyPos = readPosition()
       val beforeSuper = readTrees()
       val superCall = readTree().asInstanceOf[JSSuperConstructorCall]
-      val afterSuper = readTrees()
+      val afterSuper0 = readTrees()
+
+      val afterSuper = if (true /*hacks.use17*/ && ownerKind == ClassKind.JSModuleClass) { // scalastyle:ignore
+        afterSuper0 match {
+          case StoreModule() :: _ => afterSuper0
+          case _                  => StoreModule()(superCall.pos) :: afterSuper0
+        }
+      } else {
+        afterSuper0
+      }
+
       val body = JSConstructorBody(beforeSuper, superCall, afterSuper)(bodyPos)
       JSConstructorDef(flags, params, restParam, body)(
           OptimizerHints.fromBits(readInt()), optHash)
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala b/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
index b23a83d5fc..baf49343e3 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
@@ -592,14 +592,30 @@ private final class ClassDefChecker(classDef: ClassDef,
     }
   }
 
-  private def handleStoreModulesAfterSuperCtorCall(trees: List[Tree]): List[Tree] = {
-    /* If StoreModule's are allowed, there is nothing left to check about them,
-     * so we filter them out.
-     */
-    if (classDef.kind.hasModuleAccessor)
-      trees.filter(!_.isInstanceOf[StoreModule])
-    else
+  private def handleStoreModulesAfterSuperCtorCall(trees: List[Tree])(
+      implicit ctx: ErrorContext): List[Tree] = {
+
+    if (classDef.kind.hasModuleAccessor) {
+      if (postOptimizer) {
+        /* If the super constructor call was inlined, the StoreModule can be anywhere.
+         * Moreover, the optimizer can remove StoreModules altogether in many cases.
+         */
+        trees.filter(!_.isInstanceOf[StoreModule])
+      } else {
+        /* Before the optimizer, there must be a StoreModule and it must come
+         * right after the super constructor call.
+         */
+        trees match {
+          case StoreModule() :: rest =>
+            rest
+          case _ =>
+            reportError(i"Missing StoreModule right after the super constructor call")
+            trees
+        }
+      }
+    } else {
       trees
+    }
   }
 
   private def checkBlockStats(stats: List[Tree], env: Env): Env = {
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/AnalyzerTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/AnalyzerTest.scala
index da9e9658c0..ad0aeb6655 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/AnalyzerTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/AnalyzerTest.scala
@@ -467,7 +467,7 @@ class AnalyzerTest {
             "A",
             kind = ClassKind.ModuleClass,
             superClass = Some(ObjectClass),
-            methods = List(trivialCtor("A")),
+            methods = List(trivialCtor("A", forModuleClass = true)),
             topLevelExportDefs = List(
                 TopLevelMethodExportDef("main", JSMethodDef(
                     EMF.withNamespace(MemberNamespace.PublicStatic),
@@ -492,7 +492,7 @@ class AnalyzerTest {
     def singleDef(name: String) = {
       classDef(name,
           kind = ClassKind.ModuleClass, superClass = Some(ObjectClass),
-          methods = List(trivialCtor(name)),
+          methods = List(trivialCtor(name, forModuleClass = true)),
           topLevelExportDefs = List(TopLevelModuleExportDef(name, "foo")))
     }
 
@@ -515,7 +515,7 @@ class AnalyzerTest {
     def singleDef(name: String) = {
       classDef(name,
           kind = ClassKind.ModuleClass, superClass = Some(ObjectClass),
-          methods = List(trivialCtor(name)),
+          methods = List(trivialCtor(name, forModuleClass = true)),
           topLevelExportDefs = List(TopLevelModuleExportDef("main", "foo")))
     }
 
@@ -536,7 +536,7 @@ class AnalyzerTest {
   def degenerateConflictingTopLevelExports(): AsyncResult = await {
     val classDefs = Seq(classDef("A",
         kind = ClassKind.ModuleClass, superClass = Some(ObjectClass),
-        methods = List(trivialCtor("A")),
+        methods = List(trivialCtor("A", forModuleClass = true)),
         topLevelExportDefs = List(
             TopLevelModuleExportDef("main", "foo"),
             TopLevelModuleExportDef("main", "foo"))))
@@ -552,7 +552,7 @@ class AnalyzerTest {
     val classDefs = Seq(classDef("A",
         kind = ClassKind.ModuleClass, superClass = Some(ObjectClass),
         methods = List(
-            trivialCtor("A"),
+            trivialCtor("A", forModuleClass = true),
             mainMethodDef(Skip())
         ),
         topLevelExportDefs = List(TopLevelModuleExportDef("A", "foo"))))
@@ -630,9 +630,8 @@ class AnalyzerTest {
 
     val classDefs = Seq(
         classDef("A",
-            kind = ClassKind.ModuleClass, superClass = Some(ObjectClass),
+            kind = ClassKind.Class, superClass = Some(ObjectClass),
             methods = List(
-                trivialCtor("A"),
                 mainMethodDef(ApplyDynamicImport(EAF, "B", dynName, Nil)))
         ),
         classDef("B",
@@ -688,9 +687,8 @@ class AnalyzerTest {
   def importMetaWithoutESModule(): AsyncResult = await {
     val classDefs = Seq(
       classDef("A",
-        kind = ClassKind.ModuleClass, superClass = Some(ObjectClass),
+        kind = ClassKind.Class, superClass = Some(ObjectClass),
         methods = List(
-          trivialCtor("A"),
           mainMethodDef(JSImportMeta())
         )
       )
@@ -812,9 +810,8 @@ class AnalyzerTest {
     def test(invalidLinkTimeProperty: LinkTimeProperty): Future[Unit] = {
       val classDefs = Seq(
         classDef("A",
-          kind = ClassKind.ModuleClass, superClass = Some(ObjectClass),
+          kind = ClassKind.Class, superClass = Some(ObjectClass),
           methods = List(
-            trivialCtor("A"),
             mainMethodDef(invalidLinkTimeProperty)
           )
         )
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/IRCheckerTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/IRCheckerTest.scala
index 8617ae460d..66455360d1 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/IRCheckerTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/IRCheckerTest.scala
@@ -176,7 +176,7 @@ class IRCheckerTest {
       classDef("B", kind = ClassKind.NativeJSClass, superClass = Some(ObjectClass)),
       classDef("C", kind = ClassKind.NativeJSModuleClass, superClass = Some(ObjectClass)),
 
-      classDef("D", kind = ClassKind.JSClass, superClass = Some("A"), jsConstructor = Some(trivialJSCtor)),
+      classDef("D", kind = ClassKind.JSClass, superClass = Some("A"), jsConstructor = Some(trivialJSCtor())),
 
       mainTestClassDef(Block(
         LoadJSConstructor("B"),
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/IncrementalTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/IncrementalTest.scala
index 105ba204d0..7129402959 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/IncrementalTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/IncrementalTest.scala
@@ -57,7 +57,7 @@ class IncrementalTest {
             kind = ClassKind.ModuleClass,
             superClass = Some(ObjectClass),
             methods = List(
-              trivialCtor(FooClass),
+              trivialCtor(FooClass, forModuleClass = true),
               MethodDef(EMF.withNamespace(MemberNamespace.PublicStatic),
                   staticMethodName, NON, Nil, IntType, Some(int(6)))(EOH, UNV)
             ),
@@ -238,7 +238,7 @@ class IncrementalTest {
 
       List(
         v -> classDef(FooClass, kind = ClassKind.ModuleClass, superClass = Some(ObjectClass),
-            methods = trivialCtor(FooClass) :: stepDependentMembers),
+            methods = trivialCtor(FooClass, forModuleClass = true) :: stepDependentMembers),
 
         v -> mainTestClassDef(Block(stepDependentMainStats))
       )
@@ -313,12 +313,13 @@ class IncrementalTest {
     val FooModule = ClassName("Foo")
 
     def fooCtor(pre: Boolean) = {
-      val superCtor = {
+      val superCtor = Block(
         ApplyStatically(EAF.withConstructor(true),
             thisFor(FooModule),
             ObjectClass, MethodIdent(NoArgConstructorName),
-            Nil)(VoidType)
-      }
+            Nil)(VoidType),
+        StoreModule()
+      )
 
       val body =
         if (pre) superCtor
@@ -362,7 +363,7 @@ class IncrementalTest {
           kind = ClassKind.ModuleClass,
           superClass = Some(ObjectClass),
           methods = List(
-            trivialCtor(AModule)
+            trivialCtor(AModule, forModuleClass = true)
           ),
           jsMethodProps = List(
             JSMethodDef(EMF, str("foo"), Nil, None,
@@ -374,7 +375,7 @@ class IncrementalTest {
           kind = ClassKind.ModuleClass,
           superClass = Some(ObjectClass),
           methods = List(
-              trivialCtor(BModule),
+              trivialCtor(BModule, forModuleClass = true),
               MethodDef(EMF, targetMethodName, NON, Nil, IntType,
                   Some(int(if (pre) 1 else 2)))(EOH.withInline(true), UNV)
           )
@@ -419,7 +420,7 @@ class IncrementalTest {
           kind = ClassKind.ModuleClass,
           superClass = Some(ObjectClass),
           methods = List(
-              trivialCtor(BModule),
+              trivialCtor(BModule, forModuleClass = true),
               MethodDef(EMF, targetMethodName, NON, Nil, IntType,
                   Some(int(if (pre) 1 else 2)))(EOH.withInline(true), UNV)
           )
@@ -451,7 +452,7 @@ class IncrementalTest {
           kind = ClassKind.ModuleClass,
           superClass = Some(ObjectClass),
           methods = List(
-              trivialCtor(BModule),
+              trivialCtor(BModule, forModuleClass = true),
               MethodDef(EMF, targetMethodName, NON, Nil, IntType,
                   Some(int(if (pre) 1 else 2)))(EOH.withInline(true), UNV)
           )
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/checker/ClassDefCheckerTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/checker/ClassDefCheckerTest.scala
index df23c6b3f5..1d338034d8 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/checker/ClassDefCheckerTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/checker/ClassDefCheckerTest.scala
@@ -145,7 +145,7 @@ class ClassDefCheckerTest {
         fields = List(
           FieldDef(EMF.withNamespace(MemberNamespace.PublicStatic), FieldName("A", "foo"), NON, IntType)
         ),
-        methods = List(trivialCtor("A")),
+        methods = List(trivialCtor("A", forModuleClass = true)),
         topLevelExportDefs = List(
           TopLevelFieldExportDef("main", "foo", FieldName("B", "foo"))
         )
@@ -533,7 +533,8 @@ class ClassDefCheckerTest {
           MethodDef(ctorFlags, NoArgConstructorName, NON, Nil, VoidType, Some {
             Block(
               StoreModule(),
-              superCtorCall
+              superCtorCall,
+              StoreModule()
             )
           })(EOH, UNV)
         )
@@ -541,6 +542,39 @@ class ClassDefCheckerTest {
       "Illegal StoreModule"
     )
 
+    assertError(
+      classDef(
+        "Foo",
+        kind = ClassKind.ModuleClass,
+        superClass = Some(ObjectClass),
+        methods = List(
+          MethodDef(ctorFlags, NoArgConstructorName, NON, Nil, VoidType, Some {
+            Block(
+              superCtorCall
+            )
+          })(EOH, UNV)
+        )
+      ),
+      "Missing StoreModule right after the super constructor call"
+    )
+
+    assertError(
+      classDef(
+        "Foo",
+        kind = ClassKind.ModuleClass,
+        superClass = Some(ObjectClass),
+        methods = List(
+          MethodDef(ctorFlags, NoArgConstructorName, NON, Nil, VoidType, Some {
+            Block(
+              superCtorCall,
+              IntLiteral(1)
+            )
+          })(EOH, UNV)
+        )
+      ),
+      "Missing StoreModule right after the super constructor call"
+    )
+
     assertError(
       classDef(
         "Foo",
@@ -550,6 +584,7 @@ class ClassDefCheckerTest {
           MethodDef(ctorFlags, NoArgConstructorName, NON, Nil, VoidType, Some {
             Block(
               superCtorCall,
+              StoreModule(),
               If(BooleanLiteral(true), StoreModule(), Skip())(VoidType)
             )
           })(EOH, UNV)
@@ -564,7 +599,25 @@ class ClassDefCheckerTest {
         kind = ClassKind.ModuleClass,
         superClass = Some(ObjectClass),
         methods = List(
-          trivialCtor("Foo"),
+          MethodDef(ctorFlags, NoArgConstructorName, NON, Nil, VoidType, Some {
+            Block(
+              superCtorCall,
+              StoreModule(),
+              StoreModule()
+            )
+          })(EOH, UNV)
+        )
+      ),
+      "Illegal StoreModule"
+    )
+
+    assertError(
+      classDef(
+        "Foo",
+        kind = ClassKind.ModuleClass,
+        superClass = Some(ObjectClass),
+        methods = List(
+          trivialCtor("Foo", forModuleClass = true),
           MethodDef(EMF, MethodName("foo", Nil, VoidRef), NON, Nil, VoidType, Some {
             Block(
               StoreModule()
@@ -582,7 +635,8 @@ class ClassDefCheckerTest {
         superClass = Some("scala.scalajs.js.Object"),
         jsConstructor = Some(
           JSConstructorDef(JSCtorFlags, Nil, None,
-              JSConstructorBody(StoreModule() :: Nil, JSSuperConstructorCall(Nil), Undefined() :: Nil))(
+              JSConstructorBody(StoreModule() :: Nil, JSSuperConstructorCall(Nil),
+                  StoreModule() :: Undefined() :: Nil))(
               EOH, UNV)
         )
       ),
@@ -597,7 +651,22 @@ class ClassDefCheckerTest {
         jsConstructor = Some(
           JSConstructorDef(JSCtorFlags, Nil, None,
               JSConstructorBody(Nil, JSSuperConstructorCall(Nil),
-                  If(BooleanLiteral(true), StoreModule(), Skip())(VoidType) :: Undefined() :: Nil))(
+                  Undefined() :: Nil))(
+              EOH, UNV)
+        )
+      ),
+      "Missing StoreModule right after the super constructor call"
+    )
+
+    assertError(
+      classDef(
+        "Foo",
+        kind = ClassKind.JSModuleClass,
+        superClass = Some("scala.scalajs.js.Object"),
+        jsConstructor = Some(
+          JSConstructorDef(JSCtorFlags, Nil, None,
+              JSConstructorBody(Nil, JSSuperConstructorCall(Nil),
+                  StoreModule() :: StoreModule() :: Undefined() :: Nil))(
               EOH, UNV)
         )
       ),
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/testutils/TestIRBuilder.scala b/linker/shared/src/test/scala/org/scalajs/linker/testutils/TestIRBuilder.scala
index d17d8e21c0..295d78fd29 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/testutils/TestIRBuilder.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/testutils/TestIRBuilder.scala
@@ -77,7 +77,7 @@ object TestIRBuilder {
   def mainTestClassDef(mainBody: Tree): ClassDef = {
     classDef(
         MainTestClassName,
-        kind = ClassKind.ModuleClass,
+        kind = ClassKind.Class,
         superClass = Some(ObjectClass),
         methods = List(
             trivialCtor(MainTestClassName),
@@ -86,10 +86,15 @@ object TestIRBuilder {
     )
   }
 
-  def trivialCtor(enclosingClassName: ClassName, parentClassName: ClassName = ObjectClass): MethodDef = {
+  def trivialCtor(enclosingClassName: ClassName,
+      parentClassName: ClassName = ObjectClass,
+      forModuleClass: Boolean = false): MethodDef = {
     val flags = MemberFlags.empty.withNamespace(MemberNamespace.Constructor)
-    MethodDef(flags, MethodIdent(NoArgConstructorName), NON, Nil, VoidType,
-        Some(trivialSuperCtorCall(enclosingClassName, parentClassName)))(
+    val superCtorCall = trivialSuperCtorCall(enclosingClassName, parentClassName)
+    val body =
+      if (forModuleClass) Block(superCtorCall, StoreModule())
+      else superCtorCall
+    MethodDef(flags, MethodIdent(NoArgConstructorName), NON, Nil, VoidType, Some(body))(
         EOH, UNV)
   }
 
@@ -101,9 +106,12 @@ object TestIRBuilder {
         Nil)(VoidType)
   }
 
-  def trivialJSCtor: JSConstructorDef = {
+  def trivialJSCtor(forModuleClass: Boolean = false): JSConstructorDef = {
+    val afterSuper =
+      if (forModuleClass) StoreModule() :: Undefined() :: Nil
+      else Undefined() :: Nil
     JSConstructorDef(JSCtorFlags, Nil, None,
-        JSConstructorBody(Nil, JSSuperConstructorCall(Nil), Undefined() :: Nil))(
+        JSConstructorBody(Nil, JSSuperConstructorCall(Nil), afterSuper))(
         EOH, UNV)
   }
 
@@ -149,13 +157,13 @@ object TestIRBuilder {
   def requiredMethods(className: ClassName, classKind: ClassKind,
       parentClassName: ClassName = ObjectClass): List[MethodDef] = {
     if (classKind == ClassKind.ModuleClass)
-      List(trivialCtor(className, parentClassName))
+      List(trivialCtor(className, parentClassName, forModuleClass = true))
     else
       Nil
   }
 
   def requiredJSConstructor(classKind: ClassKind): Option[JSConstructorDef] = {
-    if (classKind.isJSClass) Some(trivialJSCtor)
+    if (classKind.isJSClass) Some(trivialJSCtor(forModuleClass = classKind.hasModuleAccessor))
     else None
   }
 
diff --git a/test-suite/js/src/test/scala/org/scalajs/testsuite/compiler/StoreModuleJSTest.scala b/test-suite/js/src/test/scala/org/scalajs/testsuite/compiler/StoreModuleJSTest.scala
new file mode 100644
index 0000000000..677b81161b
--- /dev/null
+++ b/test-suite/js/src/test/scala/org/scalajs/testsuite/compiler/StoreModuleJSTest.scala
@@ -0,0 +1,42 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package org.scalajs.testsuite.compiler
+
+import scala.scalajs.js
+
+import org.junit.Test
+import org.junit.Assert._
+
+class StoreModuleJSTest {
+  import StoreModuleJSTest._
+
+  @Test def jsModuleClass(): Unit = {
+    val a = JSObjA
+    val b = JSObjB
+
+    assertNotNull(a)
+    assertNotNull(b)
+    assertSame(a, b.a)
+    assertSame(b, a.b)
+  }
+}
+
+object StoreModuleJSTest {
+  object JSObjA extends js.Object {
+    val b = JSObjB
+  }
+
+  object JSObjB extends js.Object {
+    val a = JSObjA
+  }
+}
diff --git a/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/StoreModuleTest.scala b/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/StoreModuleTest.scala
new file mode 100644
index 0000000000..e47906845f
--- /dev/null
+++ b/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/StoreModuleTest.scala
@@ -0,0 +1,40 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package org.scalajs.testsuite.compiler
+
+import org.junit.Test
+import org.junit.Assert._
+
+class StoreModuleTest {
+  import StoreModuleTest._
+
+  @Test def scalaModuleClass(): Unit = {
+    val a = ScalaObjA
+    val b = ScalaObjB
+
+    assertNotNull(a)
+    assertNotNull(b)
+    assertSame(a, b.a)
+    assertSame(b, a.b)
+  }
+}
+
+object StoreModuleTest {
+  object ScalaObjA {
+    val b = ScalaObjB
+  }
+
+  object ScalaObjB {
+    val a = ScalaObjA
+  }
+}

From d36cba3eaf7482e8e4b66cd0ad2adb24533e6b16 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Sat, 2 Nov 2024 19:24:38 +0100
Subject: [PATCH 198/298] Insert `StoreModule`s for JS module classes in the
 compiler.

And only enable the deserialization when reading IR < 1.18.
---
 .../src/main/scala/org/scalajs/nscplugin/GenJSCode.scala | 9 ++++++++-
 .../src/main/scala/org/scalajs/ir/Serializers.scala      | 2 +-
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
index 5ac71f2c26..81cfa6df15 100644
--- a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
+++ b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
@@ -1610,7 +1610,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
 
       var preSuperStats = List.newBuilder[js.Tree]
       var jsSuperCall: Option[js.JSSuperConstructorCall] = None
-      val postSuperStats = List.newBuilder[js.Tree]
+      val postSuperStats = mutable.ListBuffer.empty[js.Tree]
 
       /* Move param accessor initializers and early initializers after the
        * super constructor call since JS cannot access `this` before the super
@@ -1714,6 +1714,13 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
       assert(jsSuperCall.isDefined, "Did not find Super call in primary JS " +
           s"construtor at ${dd.pos}")
 
+      /* Insert a StoreModule if required.
+       * Do this now so we have the pos of the super ctor call.
+       * +=: prepends to the ListBuffer in O(1) -- yes, it's a cryptic name.
+       */
+      if (isStaticModule(currentClassSym))
+        js.StoreModule()(jsSuperCall.get.pos) +=: postSuperStats
+
       new PrimaryJSCtor(sym, genParamsAndInfo(sym, vparamss),
           js.JSConstructorBody(preSuperStats.result(), jsSuperCall.get, postSuperStats.result())(dd.pos))
     }
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
index de1c74d161..0a366a12b5 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
@@ -2005,7 +2005,7 @@ object Serializers {
       val superCall = readTree().asInstanceOf[JSSuperConstructorCall]
       val afterSuper0 = readTrees()
 
-      val afterSuper = if (true /*hacks.use17*/ && ownerKind == ClassKind.JSModuleClass) { // scalastyle:ignore
+      val afterSuper = if (hacks.use17 && ownerKind == ClassKind.JSModuleClass) {
         afterSuper0 match {
           case StoreModule() :: _ => afterSuper0
           case _                  => StoreModule()(superCall.pos) :: afterSuper0

From ab0f29b4cc68864ad192ddef76491e3b4cd5c6d9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Thu, 7 Nov 2024 13:47:37 +0100
Subject: [PATCH 199/298] Wasm: Implement full support of `ForIn` using a JS
 generator function.

We can abuse a JS generator function (`function*`) to turn the
"push-based" `for..in` loop of JavaScript into a "pull-based"
generator. This way we can call it from Wasm and keep the loop
body inline, without needing to pass a callback function to JS.

This allows to implement any shape of `ForIn` loop. We can
therefore remove the optimizer limitation for those loops in Wasm.
---
 .../backend/wasmemitter/CoreWasmLib.scala     |  3 +-
 .../backend/wasmemitter/FunctionEmitter.scala | 50 +++++++++----------
 .../backend/wasmemitter/LoaderContent.scala   |  3 +-
 .../linker/backend/wasmemitter/VarGen.scala   |  3 +-
 .../frontend/optimizer/OptimizerCore.scala    | 16 +-----
 5 files changed, 32 insertions(+), 43 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
index 6a00aaab2c..73bf05e3d6 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
@@ -414,7 +414,8 @@ final class CoreWasmLib(coreSpec: CoreSpec, globalInfo: LinkedGlobalInfo) {
     addHelperImport(genFunctionID.jsImportCall, List(anyref), List(anyref))
     addHelperImport(genFunctionID.jsImportMeta, Nil, List(anyref))
     addHelperImport(genFunctionID.jsDelete, List(anyref, anyref), Nil)
-    addHelperImport(genFunctionID.jsForInSimple, List(anyref, anyref), Nil)
+    addHelperImport(genFunctionID.jsForInStart, List(anyref), List(anyref))
+    addHelperImport(genFunctionID.jsForInNext, List(anyref), List(anyref, Int32))
     addHelperImport(genFunctionID.jsIsTruthy, List(anyref), List(Int32))
 
     addHelperImport(genFunctionID.newSymbol, Nil, List(anyref))
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
index d8f18921b4..83a6854719 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
@@ -2421,34 +2421,34 @@ private class FunctionEmitter private (
   }
 
   private def genForIn(tree: ForIn): Type = {
-    /* This is tricky. In general, the body of a ForIn can be an arbitrary
-     * statement, which can refer to the enclosing scope and its locals,
-     * including for mutations. Unfortunately, there is no way to implement a
-     * ForIn other than actually doing a JS `for (var key in obj) { body }`
-     * loop. That means we need to pass the `body` as a JS closure.
-     *
-     * That is problematic for our backend because we basically need to perform
-     * lambda lifting: identifying captures ourselves, and turn references to
-     * local variables into accessing the captured environment.
-     *
-     * We side-step this issue for now by exploiting the known shape of `ForIn`
-     * generated by the Scala.js compiler. This is fine as long as we do not
-     * support the Scala.js optimizer. We will have to revisit this code when
-     * we add that support.
-     */
+    val ForIn(obj, LocalIdent(keyVarName), keyVarOrigName, body) = tree
 
-    val ForIn(obj, LocalIdent(keyVarName), _, body) = tree
+    val generatorLocal = addSyntheticLocal(watpe.RefType.anyref)
 
-    body match {
-      case JSFunctionApply(fVarRef: VarRef, List(VarRef(argIdent)))
-          if fVarRef.ident.name != keyVarName && argIdent.name == keyVarName =>
-        genTree(obj, AnyType)
-        genTree(fVarRef, AnyType)
-        markPosition(tree)
-        fb += wa.Call(genFunctionID.jsForInSimple)
+    // Evaluate the obj and create the for..in generator
+    genTree(obj, AnyType)
+    markPosition(tree)
+    fb += wa.Call(genFunctionID.jsForInStart)
+    fb += wa.LocalSet(generatorLocal)
 
-      case _ =>
-        throw new NotImplementedError(s"Unsupported shape of ForIn node at ${tree.pos}: $tree")
+    // Loop over the keys returned by the generator
+    fb.block() { doneLabel =>
+      fb.loop() { loopLabel =>
+        fb += wa.LocalGet(generatorLocal)
+        fb += wa.Call(genFunctionID.jsForInNext) // returns [value, done]
+
+        // if done, jump to done
+        fb += wa.BrIf(doneLabel)
+
+        // otherwise, store the value and execute the body
+        withNewLocal(keyVarName, keyVarOrigName, watpe.RefType.anyref) { keyLocal =>
+          fb += wa.LocalSet(keyLocal)
+          genTree(body, VoidType)
+        }
+
+        // and loop back
+        fb += wa.Br(loopLabel)
+      }
     }
 
     VoidType
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala
index a94e132626..a096a66c5d 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala
@@ -158,7 +158,8 @@ const scalaJSHelpers = {
   jsImportCall: (s) => import(s),
   jsImportMeta: () => import.meta,
   jsDelete: (o, p) => { delete o[p]; },
-  jsForInSimple: (o, f) => { for (var k in o) f(k); },
+  jsForInStart: function*(o) { for (var k in o) yield k; },
+  jsForInNext: (g) => { var r = g.next(); return [r.value, r.done]; },
   jsIsTruthy: (x) => !!x,
 
   // Non-native JS class support
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
index 6a01f55cb6..c71230948d 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
@@ -155,7 +155,8 @@ object VarGen {
     case object jsImportCall extends JSHelperFunctionID
     case object jsImportMeta extends JSHelperFunctionID
     case object jsDelete extends JSHelperFunctionID
-    case object jsForInSimple extends JSHelperFunctionID
+    case object jsForInStart extends JSHelperFunctionID
+    case object jsForInNext extends JSHelperFunctionID
     case object jsIsTruthy extends JSHelperFunctionID
 
     case object newSymbol extends JSHelperFunctionID
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
index adaac12ee7..d69da3d2e4 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
@@ -425,21 +425,7 @@ private[optimizer] abstract class OptimizerCore(
         val localDef = LocalDef(RefinedType(AnyType), mutable = false,
             ReplaceWithVarRef(newName, newSimpleState(UsedAtLeastOnce)))
         val bodyScope = scope.withEnv(scope.env.withLocalDef(name, localDef))
-
-        val newBody = if (isWasm) {
-          // Avoid destroying the only shape of ForIn that the Wasm backend can handle
-          body match {
-            case JSFunctionApply(f: VarRef, List(arg: VarRef)) =>
-              JSFunctionApply(transformExpr(f)(bodyScope),
-                  List(transformExpr(arg)(bodyScope)))(body.pos)
-            case _ =>
-              // Wasm will not be able to deal with anything else, but we cannot do anything about it
-              transformStat(body)(bodyScope)
-          }
-        } else {
-          transformStat(body)(bodyScope)
-        }
-
+        val newBody = transformStat(body)(bodyScope)
         ForIn(newObj, LocalIdent(newName)(keyVar.pos), newOriginalName, newBody)
 
       case TryCatch(block, errVar @ LocalIdent(name), originalName, handler) =>

From 41e9e118d8ccb29ca1b98320992c2a93e883ff85 Mon Sep 17 00:00:00 2001
From: Tobias Schlatter <tobias@meisch.ch>
Date: Sun, 13 Oct 2024 09:19:07 +0200
Subject: [PATCH 200/298] IRChecker: Allow subtypes of ArrayType in array
 position

---
 .../org/scalajs/linker/checker/IRChecker.scala   |  6 +++++-
 .../scala/org/scalajs/linker/IRCheckerTest.scala | 16 ++++++++++++++++
 2 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala b/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
index f6df8de449..3ab776070b 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
@@ -499,13 +499,17 @@ private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter) {
 
       case ArrayLength(array) =>
         typecheckExpr(array, env)
-        if (!array.tpe.isInstanceOf[ArrayType])
+        if (array.tpe != NullType &&
+            array.tpe != NothingType &&
+            !array.tpe.isInstanceOf[ArrayType])
           reportError(i"Array type expected but ${array.tpe} found")
 
       case ArraySelect(array, index) =>
         typecheckExpect(index, env, IntType)
         typecheckExpr(array, env)
         array.tpe match {
+          case NothingType => // ok
+          case NullType => // will NPE, but allowed.
           case arrayType: ArrayType =>
             if (tree.tpe != arrayElemType(arrayType))
               reportError(i"Array select of array type $arrayType typed as ${tree.tpe}")
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/IRCheckerTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/IRCheckerTest.scala
index 66455360d1..cc4847d684 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/IRCheckerTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/IRCheckerTest.scala
@@ -253,6 +253,22 @@ class IRCheckerTest {
     }
   }
 
+  @Test
+  def arrayOpsNullOrNothing(): AsyncResult = await {
+    val classDefs = Seq(
+      mainTestClassDef(
+        Block(
+          ArraySelect(Null(), int(1))(NothingType),
+          ArrayLength(Null()),
+          ArraySelect(Throw(Null()), int(1))(NothingType),
+          ArrayLength(Throw(Null()))
+        )
+      )
+    )
+
+    testLinkNoIRError(classDefs, MainTestModuleInitializers)
+  }
+
 }
 
 object IRCheckerTest {

From d5a3baf0b4741179986edd11ad4a07acb6f988a7 Mon Sep 17 00:00:00 2001
From: Tobias Schlatter <tobias@meisch.ch>
Date: Sun, 10 Nov 2024 10:25:09 +0100
Subject: [PATCH 201/298] Optimizer: Add `fieldsReadAskers` to
 `unregisterDependee`

Forgotten in #4681 / d50b69fc52f8559aea33f9c4dd2de74eac91ea74.
---
 .../org/scalajs/linker/frontend/optimizer/IncOptimizer.scala     | 1 +
 1 file changed, 1 insertion(+)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
index 15818137e4..16c576a6ac 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
@@ -1479,6 +1479,7 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
       dynamicCallers.forEachValue(Long.MaxValue, _.remove(dependee))
       staticCallers.foreach(_.forEachValue(Long.MaxValue, _.remove(dependee)))
       jsNativeImportsAskers.remove(dependee)
+      fieldsReadAskers.remove(dependee)
     }
 
     private def computeJSNativeImports(linkedClass: LinkedClass): JSNativeImports = {

From f0aa3dff02aa34032525e40024f67ec9f7b64572 Mon Sep 17 00:00:00 2001
From: Tobias Schlatter <tobias@meisch.ch>
Date: Sun, 10 Nov 2024 10:59:28 +0100
Subject: [PATCH 202/298] Optimizer: Use constrainedLub to re-type `Match`

This is cleaner in general, but we specifically do this to profit from
the `isStat` fix in the next commit.
---
 .../linker/frontend/optimizer/OptimizerCore.scala      | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
index adaac12ee7..591ded9e55 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
@@ -475,9 +475,13 @@ private[optimizer] abstract class OptimizerCore(
             }.getOrElse(default)
             transform(body, isStat)
           case _ =>
-            Match(newSelector,
-                cases map (c => (c._1, transform(c._2, isStat))),
-                transform(default, isStat))(tree.tpe)
+            val newCases = cases.map(c => (c._1, transform(c._2, isStat)))
+            val newDefault = transform(default, isStat)
+
+            val refinedType = (newDefault.tpe :: newCases.map(_._2.tpe))
+              .reduce(constrainedLub(_, _, tree.tpe))
+
+            Match(newSelector, newCases, newDefault)(refinedType)
         }
 
       // Scala expressions

From b46a0942ab24e3a72503700616fc1fb19be94d10 Mon Sep 17 00:00:00 2001
From: Tobias Schlatter <tobias@meisch.ch>
Date: Sun, 10 Nov 2024 10:52:36 +0100
Subject: [PATCH 203/298] Optimizer: Add isStat flag to constrainedLub

Split out from #5066.

This is to ensure that we correctly raise the overall tree type in
case we are in statement position.

Before this commit, the inner trees were typed as `VoidType` (due to
the `isStat` flag on `transform`), but the outer (aggregate) tree kept
its original (expression) type. This lead to ill-typed IR.
---
 .../frontend/optimizer/OptimizerCore.scala    | 23 +++++++++++--------
 1 file changed, 13 insertions(+), 10 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
index 591ded9e55..58f245d4a6 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
@@ -407,7 +407,7 @@ private[optimizer] abstract class OptimizerCore(
             val newThenp = transform(thenp, isStat)
             val newElsep = transform(elsep, isStat)
             val refinedType =
-              constrainedLub(newThenp.tpe, newElsep.tpe, tree.tpe)
+              constrainedLub(newThenp.tpe, newElsep.tpe, tree.tpe, isStat)
             foldIf(newCond, newThenp, newElsep)(refinedType)
         }
 
@@ -454,7 +454,7 @@ private[optimizer] abstract class OptimizerCore(
           transform(handler, isStat)(handlerScope)
         }
 
-        val refinedType = constrainedLub(newBlock.tpe, newHandler.tpe, tree.tpe)
+        val refinedType = constrainedLub(newBlock.tpe, newHandler.tpe, tree.tpe, isStat)
         TryCatch(newBlock, LocalIdent(newName)(errVar.pos), newOriginalName,
             newHandler)(refinedType)
 
@@ -479,7 +479,7 @@ private[optimizer] abstract class OptimizerCore(
             val newDefault = transform(default, isStat)
 
             val refinedType = (newDefault.tpe :: newCases.map(_._2.tpe))
-              .reduce(constrainedLub(_, _, tree.tpe))
+              .reduce(constrainedLub(_, _, tree.tpe, isStat))
 
             Match(newSelector, newCases, newDefault)(refinedType)
         }
@@ -1190,7 +1190,7 @@ private[optimizer] abstract class OptimizerCore(
                   val newThenp = finishTransformExpr(tthenpNoLocalDef)
                   val newElsep = finishTransformExpr(telsepNoLocalDef)
                   val refinedType =
-                    constrainedLub(newThenp.tpe, newElsep.tpe, tree.tpe)
+                    constrainedLub(newThenp.tpe, newElsep.tpe, tree.tpe, isStat = false)
                   cont(foldIf(newCond, newThenp, newElsep)(
                       refinedType).toPreTransform)
               }
@@ -1200,7 +1200,7 @@ private[optimizer] abstract class OptimizerCore(
           val newThenp = transformExpr(thenp)
           val newElsep = transformExpr(elsep)
           val refinedType =
-            constrainedLub(newThenp.tpe, newElsep.tpe, tree.tpe)
+            constrainedLub(newThenp.tpe, newElsep.tpe, tree.tpe, isStat = false)
           cont(foldIf(newCond, newThenp, newElsep)(
               refinedType).toPreTransform)
         }
@@ -5161,7 +5161,7 @@ private[optimizer] abstract class OptimizerCore(
 
     def doMakeTree(newBody: Tree, returnedTypes: List[Type]): Tree = {
       val refinedType =
-        returnedTypes.reduce(constrainedLub(_, _, resultType))
+        returnedTypes.reduce(constrainedLub(_, _, resultType, isStat))
       val returnCount = returnedTypes.size - 1
 
       tryOptimizePatternMatch(oldLabelName, newLabel, refinedType,
@@ -5538,23 +5538,26 @@ private[optimizer] abstract class OptimizerCore(
   /** Finds a type as precise as possible which is a supertype of lhs and rhs
    *  but still a subtype of upperBound.
    *  Requires that lhs and rhs be subtypes of upperBound, obviously.
+   *
+   *  The RefinedType version does not have an `isStat` flag, since RefinedTypes
+   *  only exist in a PreTransform context, which is always an expression context.
    */
   private def constrainedLub(lhs: RefinedType, rhs: RefinedType,
       upperBound: Type): RefinedType = {
-    if (upperBound == VoidType) RefinedType(upperBound)
+    if (upperBound == VoidType) RefinedType(VoidType)
     else if (lhs == rhs) lhs
     else if (lhs.isNothingType) rhs
     else if (rhs.isNothingType) lhs
-    else RefinedType(constrainedLub(lhs.base, rhs.base, upperBound))
+    else RefinedType(constrainedLub(lhs.base, rhs.base, upperBound, isStat = false))
   }
 
   /** Finds a type as precise as possible which is a supertype of lhs and rhs
    *  but still a subtype of upperBound.
    *  Requires that lhs and rhs be subtypes of upperBound, obviously.
    */
-  private def constrainedLub(lhs: Type, rhs: Type, upperBound: Type): Type = {
+  private def constrainedLub(lhs: Type, rhs: Type, upperBound: Type, isStat: Boolean): Type = {
     // TODO Improve this
-    if (upperBound == VoidType) upperBound
+    if (isStat || upperBound == VoidType) VoidType
     else if (lhs == rhs) lhs
     else if (lhs == NothingType) rhs
     else if (rhs == NothingType) lhs

From 30098dd790a9af38e675fd78ad067e6c9c2b5a8c Mon Sep 17 00:00:00 2001
From: Tobias Schlatter <tobias@meisch.ch>
Date: Sat, 2 Nov 2024 19:31:47 +0100
Subject: [PATCH 204/298] Optimizer: Fix types of ArraySelect trees

To do this, we need to introduce a isJSType knowledge query to convert
from type refs to types.
---
 .../frontend/optimizer/IncOptimizer.scala     | 19 +++++++
 .../frontend/optimizer/OptimizerCore.scala    | 57 ++++++++++++++-----
 project/Build.scala                           |  2 +-
 3 files changed, 64 insertions(+), 14 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
index 16c576a6ac..38a02b54ad 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
@@ -1275,6 +1275,7 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
 
     private val jsNativeImportsAskers = new ConcurrentHashMap[Processable, Unit]
     private val fieldsReadAskers = new ConcurrentHashMap[Processable, Unit]
+    private val isJSTypeAskers = new ConcurrentHashMap[Processable, Unit]
 
     private var _ancestors: List[ClassName] = linkedClass.ancestors
 
@@ -1305,6 +1306,7 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
 
     private var fieldsRead: Set[FieldName] = linkedClass.fieldsRead
     private var staticFieldsRead: Set[FieldName] = linkedClass.staticFieldsRead
+    private var isJSType = linkedClass.kind.isJSType
 
     /** The type of instances of this interface.
      *
@@ -1399,6 +1401,12 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
       staticFieldsRead.contains(name)
     }
 
+    def askIsJSType(asker: Processable): Boolean = {
+      isJSTypeAskers.put(asker, ())
+      asker.registerTo(this)
+      isJSType
+    }
+
     @inline
     def staticLike(namespace: MemberNamespace): StaticLikeNamespace =
       staticLikes(namespace.ordinal)
@@ -1435,6 +1443,13 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
         fieldsReadAskers.clear()
       }
 
+      // Update isJSType
+      if (isJSType != linkedClass.kind.isJSType) {
+        isJSType = linkedClass.kind.isJSType
+        isJSTypeAskers.forEachKey(Long.MaxValue, _.tag())
+        isJSTypeAskers.clear()
+      }
+
       // Update static likes
       for (staticLike <- staticLikes) {
         val (_, changed, _) = staticLike.updateWith(linkedClass)
@@ -1480,6 +1495,7 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
       staticCallers.foreach(_.forEachValue(Long.MaxValue, _.remove(dependee)))
       jsNativeImportsAskers.remove(dependee)
       fieldsReadAskers.remove(dependee)
+      isJSTypeAskers.remove(dependee)
     }
 
     private def computeJSNativeImports(linkedClass: LinkedClass): JSNativeImports = {
@@ -1798,6 +1814,9 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
       else clazz.askInlineableFieldBodies(asker)
     }
 
+    protected def isJSType(className: ClassName): Boolean =
+      getInterface(className).askIsJSType(asker)
+
     protected def tryNewInlineableClass(
         className: ClassName): Option[OptimizerCore.InlineableClassStructure] = {
       classes.get(className).tryNewInlineable
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
index adaac12ee7..ba87c3c38d 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
@@ -105,6 +105,9 @@ private[optimizer] abstract class OptimizerCore(
   /** Returns true if the given static field is ever read. */
   protected def isStaticFieldRead(fieldName: FieldName): Boolean
 
+  /** Whether the given class is a JS type */
+  protected def isJSType(className: ClassName): Boolean
+
   private val localNameAllocator = new FreshNameAllocator.Local
 
   /** An allocated local variable name is mutable iff it belongs to this set. */
@@ -540,7 +543,26 @@ private[optimizer] abstract class OptimizerCore(
         ArrayLength(transformExpr(array))
 
       case ArraySelect(array, index) =>
-        ArraySelect(transformExpr(array), transformExpr(index))(tree.tpe)
+        val newArray = transformExpr(array)
+
+        val newElemType = newArray.tpe match {
+          case NothingType | NullType =>
+            /* Will throw / NPE / UB.
+             *
+             * Note that we cannot easily replace the ArraySelect with, say a
+             * checkNotNullStatement, because it might be used as lhs of an Assign node.
+             */
+            NothingType
+
+          case tpe: ArrayType =>
+            arrayElemType(tpe)
+
+          case _ =>
+            throw new AssertionError(
+                s"got non-array type after transforming ArraySelect at ${tree.pos}")
+        }
+
+        ArraySelect(newArray, transformExpr(index))(newElemType)
 
       case RecordValue(tpe, elems) =>
         RecordValue(tpe, elems map transformExpr)
@@ -2778,14 +2800,6 @@ private[optimizer] abstract class OptimizerCore(
 
     @inline def StringClassType = ClassType(BoxedStringClass, nullable = true)
 
-    def cursoryArrayElemType(tpe: ArrayType): Type = {
-      if (tpe.arrayTypeRef.dimensions != 1) AnyType
-      else (tpe.arrayTypeRef.base match {
-        case PrimRef(elemType) => elemType
-        case ClassRef(_)       => AnyType
-      })
-    }
-
     def longToInt(longExpr: Tree): Tree =
       UnaryOp(UnaryOp.LongToInt, longExpr)
     def wasmUnaryOp(op: WasmUnaryOp.Code, lhs: PreTransform): Tree =
@@ -2855,7 +2869,7 @@ private[optimizer] abstract class OptimizerCore(
              * code path, the semantics of `ArraySelect` are equivalent to the
              * intrinsic.
              */
-            val elemType = cursoryArrayElemType(arrayTpe)
+            val elemType = arrayElemType(arrayTpe)
             if (!tarray.tpe.isNullable) {
               val array = finishTransformExpr(tarray)
               val index = finishTransformExpr(tindex)
@@ -2879,7 +2893,7 @@ private[optimizer] abstract class OptimizerCore(
             /* Rewrite to `tarray[index] = tvalue` as an `Assign(ArraySelect, _)`.
              * See `ArrayApply` above for the handling of a nullable `tarray`.
              */
-            val elemType = cursoryArrayElemType(arrayTpe)
+            val elemType = arrayElemType(arrayTpe)
             if (!tarray.tpe.isNullable) {
               val array = finishTransformExpr(tarray)
               val index = finishTransformExpr(tindex)
@@ -4984,8 +4998,8 @@ private[optimizer] abstract class OptimizerCore(
         }
 
       case Class_isInstance | Class_isAssignableFrom =>
-        /* We could do something clever here if we added a knowledge query to
-         * turn a TypeRef into a Type. Barring that, we cannot tell whether a
+        /* TODO: Improve this, now that we have a knowledge query to
+         * turn a TypeRef into a Type. Before that, we couldn't tell whether a
          * ClassRef must become an `AnyType` or a `ClassType`.
          */
         default
@@ -5295,6 +5309,23 @@ private[optimizer] abstract class OptimizerCore(
     }
   }
 
+  private def arrayElemType(tpe: ArrayType): Type = {
+    val ArrayTypeRef(base, dimensions) = tpe.arrayTypeRef
+
+    if (dimensions == 1) {
+      base match {
+        case PrimRef(elemType)     => elemType
+        case ClassRef(ObjectClass) => AnyType
+
+        case ClassRef(className) =>
+          if (isJSType(className)) AnyType
+          else ClassType(className, nullable = true)
+      }
+    } else {
+      ArrayType(ArrayTypeRef(base, dimensions - 1), nullable = true)
+    }
+  }
+
   private def checkNotNull(texpr: PreTransform)(implicit pos: Position): PreTransform = {
     if (!texpr.tpe.isNullable)
       texpr
diff --git a/project/Build.scala b/project/Build.scala
index b4cab25a64..ba0669e9bc 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -2055,7 +2055,7 @@ object Build {
               ))
             } else {
               Some(ExpectedSizes(
-                  fastLink = 423000 to 424000,
+                  fastLink = 422000 to 423000,
                   fullLink = 280000 to 281000,
                   fastLinkGz = 60000 to 61000,
                   fullLinkGz = 43000 to 44000,

From 40f7ff5771211a7fb9aa917f330852fb4f409204 Mon Sep 17 00:00:00 2001
From: Tobias Schlatter <tobias@meisch.ch>
Date: Sun, 13 Oct 2024 09:21:14 +0200
Subject: [PATCH 205/298] IRChecker: Allow unsound assignments to arrays

I have inspected the backends to make sure they handle this.

For both backends, non-primitive arrays are not typed (beyond Object
for WASM). So unchecked assignments are trivial:

https://github.com/scala-js/scala-js/blob/0bc8c065a1db144f6bfcfbe72f2ad2a246284b2c/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala#L638-L642

https://github.com/scala-js/scala-js/blob/0bc8c065a1db144f6bfcfbe72f2ad2a246284b2c/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala#L741-L749
https://github.com/scala-js/scala-js/blob/0bc8c065a1db144f6bfcfbe72f2ad2a246284b2c/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala#L387-L403
---
 .../scalajs/linker/checker/IRChecker.scala    | 32 +++++++++++++++-
 .../org/scalajs/linker/IRCheckerTest.scala    | 37 +++++++++++++++++++
 2 files changed, 68 insertions(+), 1 deletion(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala b/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
index 3ab776070b..92f27dc03b 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
@@ -253,7 +253,37 @@ private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter) {
               _:JSSuperSelect | _:JSGlobalRef =>
         }
         typecheckExpr(lhs, env)
-        typecheckExpect(rhs, env, lhs.tpe)
+
+        val expectedRhsTpe = lhs match {
+          case ArraySelect(array, _) =>
+            /* Array assignments are unsound due to covariance of arrays
+             * To maintain the subtyping relationship in the IR, we have to
+             * allow assignments of any type to
+             * - Array[Object] (that's expected)
+             * - and its subtypes (that's not expected)
+             */
+
+            array.tpe match {
+              case ArrayType(ArrayTypeRef(PrimRef(tpe), 1), _) =>
+                // for primitive arrays, only allow assignment of that primitive.
+                tpe
+
+              case _ =>
+                /* All other types are either
+                 * - Subtypes of Array[Object] (including null / nothing)
+                 *   Recall: `Array[Array[A]] <: Array[Object]` even for primitive `A`.
+                 * - Ill typed IR
+                 *   (in which case typechecking the lhs above will emit an error).
+                 *
+                 * Allow any rhs.
+                 */
+                AnyType
+            }
+
+          case _ => lhs.tpe
+        }
+
+        typecheckExpect(rhs, env, expectedRhsTpe)
 
       case Return(expr, label) =>
         val returnType = env.returnTypes(label.name)
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/IRCheckerTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/IRCheckerTest.scala
index cc4847d684..50ba841937 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/IRCheckerTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/IRCheckerTest.scala
@@ -269,6 +269,43 @@ class IRCheckerTest {
     testLinkNoIRError(classDefs, MainTestModuleInitializers)
   }
 
+  @Test
+  def arrayAssignCovariant(): AsyncResult = await {
+    val classDefs = Seq(
+      classDef("Foo", superClass = Some(ObjectClass)),
+      mainTestClassDef(
+        Assign(
+          ArraySelect(
+            ArrayValue(ArrayTypeRef.of(ClassRef("Foo")), Nil),
+            int(1)
+          )(ClassType("Foo", true)),
+          int(1) // not a Foo, but OK.
+        )
+      )
+    )
+
+    testLinkNoIRError(classDefs, MainTestModuleInitializers)
+  }
+
+  @Test
+  def arrayNoAssignCovariantPrimitive(): AsyncResult = await {
+    val classDefs = Seq(
+      mainTestClassDef(
+        Assign(
+          ArraySelect(
+            ArrayValue(ArrayTypeRef.of(IntRef), Nil),
+            int(1)
+          )(IntType),
+          str("foo")
+        )
+      )
+    )
+
+    for (log <- testLinkIRErrors(classDefs, MainTestModuleInitializers)) yield {
+      log.assertContainsError("int expected but string found for tree of type")
+    }
+  }
+
 }
 
 object IRCheckerTest {

From fb3f7c0123315d17e44ec5fa5eaaea7ed563fd74 Mon Sep 17 00:00:00 2001
From: Tobias Schlatter <tobias@meisch.ch>
Date: Tue, 12 Nov 2024 12:55:24 +0100
Subject: [PATCH 206/298] IRChecker: Distinguish any from expressions

Follow-up to #5065 (8998caf50902b09619bd1a4bcafabca820e0d7f0).

Most notably:
- Records are expressions
- Distinguish which places require `any` vs just an expression.
---
 .../scalajs/linker/checker/IRChecker.scala    | 105 ++++++++++--------
 1 file changed, 58 insertions(+), 47 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala b/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
index 92f27dc03b..91e48c2732 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
@@ -50,7 +50,7 @@ private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter) {
 
       classDef.fields.foreach {
         case _: FieldDef            => // no further checks
-        case JSFieldDef(_, name, _) => typecheckExpr(name, Env.empty)
+        case JSFieldDef(_, name, _) => typecheckAny(name, Env.empty)
       }
 
       classDef.methods.foreach(checkMethodDef(_, classDef))
@@ -69,7 +69,7 @@ private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter) {
       topLevelExport.tree match {
         case TopLevelMethodExportDef(_, methodDef) =>
           implicit val ctx = ErrorContext(methodDef)
-          typecheckExpect(methodDef.body, Env.empty, AnyType)
+          typecheckAny(methodDef.body, Env.empty)
 
         case _:TopLevelJSClassExportDef | _:TopLevelModuleExportDef |
             _:TopLevelFieldExportDef =>
@@ -89,7 +89,7 @@ private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter) {
         else if (superClass.kind == ClassKind.NativeJSClass && superClass.jsNativeLoadSpec.isEmpty)
           reportError(i"Native super class ${superClass.name} must have a native load spec")
       } { tree =>
-        typecheckExpect(tree, Env.empty, AnyType)
+        typecheckAny(tree, Env.empty)
       }
     } else {
       assert(classDef.jsSuperClass.isEmpty) // checked by ClassDefChecker
@@ -136,7 +136,7 @@ private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter) {
 
     val bodyEnv = Env.forConstructorOf(clazz.name.name)
     body.beforeSuper.foreach(typecheck(_, bodyEnv))
-    body.superCall.args.foreach(typecheckExprOrSpread(_, bodyEnv))
+    body.superCall.args.foreach(typecheckAnyOrSpread(_, bodyEnv))
     body.afterSuper.foreach(typecheck(_, bodyEnv))
 
     val resultType = body.afterSuper.lastOption.fold[Type](VoidType)(_.tpe)
@@ -151,9 +151,9 @@ private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter) {
 
     val static = flags.namespace.isStatic
 
-    typecheckExpr(pName, Env.empty)
+    typecheckAny(pName, Env.empty)
 
-    typecheckExpect(body, Env.empty, AnyType)
+    typecheckAny(body, Env.empty)
   }
 
   private def checkJSPropertyDef(propDef: JSPropertyDef,
@@ -161,15 +161,26 @@ private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter) {
     val JSPropertyDef(flags, pName, getterBody, setterArgAndBody) = propDef
     implicit val ctx = ErrorContext(propDef)
 
-    typecheckExpr(pName, Env.empty)
+    typecheckAny(pName, Env.empty)
 
-    getterBody.foreach(typecheckExpr(_, Env.empty))
+    getterBody.foreach(typecheckAny(_, Env.empty))
 
     setterArgAndBody.foreach { case (_, body) =>
       typecheck(body, Env.empty)
     }
   }
 
+  private def typecheckExpr(tree: Tree, env: Env)(
+      implicit ctx: ErrorContext): Unit = {
+    typecheck(tree, env)
+
+    if (tree.tpe == VoidType) {
+      reportError(
+          i"expression expected but type ${tree.tpe} " +
+          i" found for tree of type ${tree.getClass().getName()}")
+    }
+  }
+
   private def typecheckExpect(tree: Tree, env: Env, expectedType: Type)(
       implicit ctx: ErrorContext): Unit = {
     typecheck(tree, env)
@@ -180,18 +191,18 @@ private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter) {
     }
   }
 
-  private def typecheckExpr(tree: Tree, env: Env)(
+  private def typecheckAny(tree: Tree, env: Env)(
       implicit ctx: ErrorContext): Unit = {
     typecheckExpect(tree, env, AnyType)
   }
 
-  private def typecheckExprOrSpread(tree: TreeOrJSSpread, env: Env)(
+  private def typecheckAnyOrSpread(tree: TreeOrJSSpread, env: Env)(
       implicit ctx: ErrorContext): Unit = {
     tree match {
       case JSSpread(items) =>
-        typecheckExpr(items, env)
+        typecheckAny(items, env)
       case tree: Tree =>
-        typecheckExpr(tree, env)
+        typecheckAny(tree, env)
     }
   }
 
@@ -303,7 +314,7 @@ private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter) {
         typecheck(body, env)
 
       case ForIn(obj, keyVar, _, body) =>
-        typecheckExpr(obj, env)
+        typecheckAny(obj, env)
         typecheck(body, env)
 
       case TryCatch(block, errVar, _, handler) =>
@@ -317,7 +328,7 @@ private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter) {
         typecheck(finalizer, env)
 
       case Throw(expr) =>
-        typecheckExpr(expr, env)
+        typecheckAny(expr, env)
 
       case Match(selector, cases, default) =>
         // Typecheck the selector as an int or a java.lang.String
@@ -408,7 +419,7 @@ private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter) {
       case Apply(flags, receiver, MethodIdent(method), args) =>
         if (flags.isPrivate)
           reportError("Illegal flag for Apply: Private")
-        typecheckExpr(receiver, env)
+        typecheckAny(receiver, env)
         val fullCheck = receiver.tpe match {
           case ClassType(className, _) =>
             /* For class types, we only perform full checks if the class has
@@ -548,24 +559,24 @@ private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter) {
         }
 
       case IsInstanceOf(expr, testType) =>
-        typecheckExpr(expr, env)
+        typecheckAny(expr, env)
         checkIsAsInstanceTargetType(testType)
 
       case AsInstanceOf(expr, tpe) =>
-        typecheckExpr(expr, env)
+        typecheckAny(expr, env)
         checkIsAsInstanceTargetType(tpe)
 
       case GetClass(expr) =>
-        typecheckExpr(expr, env)
+        typecheckAny(expr, env)
 
       case Clone(expr) =>
         typecheckExpect(expr, env, ClassType(CloneableClass, nullable = true))
 
       case IdentityHashCode(expr) =>
-        typecheckExpr(expr, env)
+        typecheckAny(expr, env)
 
       case WrapAsThrowable(expr) =>
-        typecheckExpr(expr, env)
+        typecheckAny(expr, env)
 
       case UnwrapFromThrowable(expr) =>
         typecheckExpect(expr, env, ClassType(ThrowableClass, nullable = true))
@@ -575,12 +586,12 @@ private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter) {
       // JavaScript expressions
 
       case JSNew(ctor, args) =>
-        typecheckExpr(ctor, env)
+        typecheckAny(ctor, env)
         for (arg <- args)
-          typecheckExprOrSpread(arg, env)
+          typecheckAnyOrSpread(arg, env)
 
       case JSPrivateSelect(qualifier, field) =>
-        typecheckExpr(qualifier, env)
+        typecheckAny(qualifier, env)
         val className = field.name.className
         val checkedClass = lookupClass(className)
         if (!checkedClass.kind.isJSClass && checkedClass.kind != ClassKind.AbstractJSType) {
@@ -595,34 +606,34 @@ private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter) {
         }
 
       case JSSelect(qualifier, item) =>
-        typecheckExpr(qualifier, env)
-        typecheckExpr(item, env)
+        typecheckAny(qualifier, env)
+        typecheckAny(item, env)
 
       case JSFunctionApply(fun, args) =>
-        typecheckExpr(fun, env)
+        typecheckAny(fun, env)
         for (arg <- args)
-          typecheckExprOrSpread(arg, env)
+          typecheckAnyOrSpread(arg, env)
 
       case JSMethodApply(receiver, method, args) =>
-        typecheckExpr(receiver, env)
-        typecheckExpr(method, env)
+        typecheckAny(receiver, env)
+        typecheckAny(method, env)
         for (arg <- args)
-          typecheckExprOrSpread(arg, env)
+          typecheckAnyOrSpread(arg, env)
 
       case JSSuperSelect(superClass, qualifier, item) =>
-        typecheckExpr(superClass, env)
-        typecheckExpr(qualifier, env)
-        typecheckExpr(item, env)
+        typecheckAny(superClass, env)
+        typecheckAny(qualifier, env)
+        typecheckAny(item, env)
 
       case JSSuperMethodCall(superClass, receiver, method, args) =>
-        typecheckExpr(superClass, env)
-        typecheckExpr(receiver, env)
-        typecheckExpr(method, env)
+        typecheckAny(superClass, env)
+        typecheckAny(receiver, env)
+        typecheckAny(method, env)
         for (arg <- args)
-          typecheckExprOrSpread(arg, env)
+          typecheckAnyOrSpread(arg, env)
 
       case JSImportCall(arg) =>
-        typecheckExpr(arg, env)
+        typecheckAny(arg, env)
 
       case JSNewTarget() =>
 
@@ -655,24 +666,24 @@ private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter) {
           reportError(i"Cannot load JS module of native JS module class $className without native load spec")
 
       case JSDelete(qualifier, item) =>
-        typecheckExpr(qualifier, env)
-        typecheckExpr(item, env)
+        typecheckAny(qualifier, env)
+        typecheckAny(item, env)
 
       case JSUnaryOp(op, lhs) =>
-        typecheckExpr(lhs, env)
+        typecheckAny(lhs, env)
 
       case JSBinaryOp(op, lhs, rhs) =>
-        typecheckExpr(lhs, env)
-        typecheckExpr(rhs, env)
+        typecheckAny(lhs, env)
+        typecheckAny(rhs, env)
 
       case JSArrayConstr(items) =>
         for (item <- items)
-          typecheckExprOrSpread(item, env)
+          typecheckAnyOrSpread(item, env)
 
       case JSObjectConstr(fields) =>
         for ((key, value) <- fields) {
-          typecheckExpr(key, env)
-          typecheckExpr(value, env)
+          typecheckAny(key, env)
+          typecheckAny(value, env)
         }
 
       case JSGlobalRef(_) =>
@@ -698,7 +709,7 @@ private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter) {
         }
 
         // Then check the closure params and body in its own env
-        typecheckExpect(body, Env.empty, AnyType)
+        typecheckAny(body, Env.empty)
 
       case CreateJSClass(className, captureValues) =>
         val clazz = lookupClass(className)

From d15567de7f82f19391be829d90eb03dfacf06632 Mon Sep 17 00:00:00 2001
From: Tobias Schlatter <tobias@meisch.ch>
Date: Sat, 2 Nov 2024 19:38:18 +0100
Subject: [PATCH 207/298] Run IRChecker after optimizer if RuntimeLongs aren't
 in use

---
 .../scalajs/linker/checker/IRChecker.scala    | 28 ++++--
 .../org/scalajs/linker/frontend/Refiner.scala | 25 +++++-
 .../org/scalajs/linker/IRCheckerTest.scala    | 89 ++++++++++++++++---
 3 files changed, 125 insertions(+), 17 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala b/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
index 91e48c2732..fac0022dc3 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
@@ -28,7 +28,8 @@ import org.scalajs.linker.standard.LinkedClass
 import org.scalajs.linker.checker.ErrorReporter._
 
 /** Checker for the validity of the IR. */
-private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter) {
+private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter,
+    postOptimizer: Boolean) {
 
   import IRChecker._
   import reporter.reportError
@@ -238,8 +239,14 @@ private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter) {
       case Assign(lhs, rhs) =>
         def checkNonStaticField(receiver: Tree, name: FieldName): Unit = {
           receiver match {
-            case This() if env.inConstructorOf == Some(name.className) =>
-              // ok
+            case This() if (postOptimizer && env.inConstructorOf.isDefined) ||
+                env.inConstructorOf == Some(name.className) =>
+              /* ctors can write immutable fields of the class they are constructing.
+               * postOptimizer, due to ctor inlining, we may write immutable parent class fields as well.
+               * IR checking of the lhs makes sure this field is actually in the parent class chain
+               * (otherwise `This` would be ill-typed).
+               */
+
             case _ =>
               if (lookupClass(name.className).lookupField(name).exists(!_.flags.isMutable))
                 reportError(i"Assignment to immutable field $name.")
@@ -725,6 +732,17 @@ private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter) {
             typecheckExpect(value, env, ctpe)
         }
 
+      case Transient(transient) if postOptimizer =>
+        transient.traverse(new Traversers.Traverser {
+          override def traverse(tree: Tree): Unit = typecheck(tree, env)
+        })
+
+      case _: RecordSelect if postOptimizer =>
+        // TODO
+
+      case _: RecordValue if postOptimizer =>
+        // TODO
+
       case _:RecordSelect | _:RecordValue | _:Transient | _:JSSuperConstructorCall =>
         reportError("invalid tree")
     }
@@ -893,9 +911,9 @@ object IRChecker {
    *
    *  @return Count of IR checking errors (0 in case of success)
    */
-  def check(unit: LinkingUnit, logger: Logger): Int = {
+  def check(unit: LinkingUnit, logger: Logger, postOptimizer: Boolean = false): Int = {
     val reporter = new LoggerErrorReporter(logger)
-    new IRChecker(unit, reporter).check()
+    new IRChecker(unit, reporter, postOptimizer).check()
     reporter.errorCount
   }
 }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/Refiner.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/Refiner.scala
index 51da80fd6d..51c4cbd590 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/Refiner.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/Refiner.scala
@@ -20,6 +20,7 @@ import org.scalajs.ir.Trees.ClassDef
 
 import org.scalajs.logging._
 
+import org.scalajs.linker.checker.IRChecker
 import org.scalajs.linker.interface.ModuleInitializer
 import org.scalajs.linker.standard._
 import org.scalajs.linker.standard.ModuleSet.ModuleID
@@ -33,6 +34,16 @@ final class Refiner(config: CommonPhaseConfig, checkIR: Boolean) {
   private val analyzer =
     new Analyzer(config, initial = false, checkIR = checkIR, failOnError = true, irLoader)
 
+  /* TODO: Remove this and replace with `checkIR` once the optimizer generates
+   * well-typed IR with runtime longs.
+   */
+  private val shouldRunIRChecker = {
+    val optimizerUsesRuntimeLong =
+      !config.coreSpec.esFeatures.allowBigIntsForLongs &&
+      !config.coreSpec.targetIsWebAssembly
+    checkIR && !optimizerUsesRuntimeLong
+  }
+
   def refine(classDefs: Seq[(ClassDef, Version)],
       moduleInitializers: List[ModuleInitializer],
       symbolRequirements: SymbolRequirement, logger: Logger)(
@@ -47,7 +58,7 @@ final class Refiner(config: CommonPhaseConfig, checkIR: Boolean) {
     val result = for {
       analysis <- analysis
     } yield {
-      logger.time("Refiner: Assemble LinkedClasses") {
+      val result = logger.time("Refiner: Assemble LinkedClasses") {
         val assembled = for {
           (classDef, version) <- classDefs
           if analysis.classInfos.contains(classDef.className)
@@ -65,6 +76,18 @@ final class Refiner(config: CommonPhaseConfig, checkIR: Boolean) {
         new LinkingUnit(config.coreSpec, linkedClassDefs.toList,
             linkedTopLevelExports.flatten.toList, moduleInitializers, globalInfo)
       }
+
+      if (shouldRunIRChecker) {
+        logger.time("Refiner: Check IR") {
+          val errorCount = IRChecker.check(result, logger, postOptimizer = true)
+          if (errorCount != 0) {
+            throw new AssertionError(
+                s"There were $errorCount IR checking errors after optimization (this is a Scala.js bug)")
+          }
+        }
+      }
+
+      result
     }
 
     result.andThen { case _ =>
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/IRCheckerTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/IRCheckerTest.scala
index 50ba841937..bc7d7e1da1 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/IRCheckerTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/IRCheckerTest.scala
@@ -28,7 +28,9 @@ import org.scalajs.logging._
 import org.scalajs.junit.async._
 
 import org.scalajs.linker.interface._
+import org.scalajs.linker.interface.unstable.IRFileImpl
 import org.scalajs.linker.standard._
+import org.scalajs.linker.frontend.Refiner
 
 import org.scalajs.linker.testutils._
 import org.scalajs.linker.testutils.TestIRBuilder._
@@ -306,22 +308,65 @@ class IRCheckerTest {
     }
   }
 
+  def immutableFieldAssignTestClassDefs(parent: Boolean): Seq[ClassDef] = {
+    val ctorBodyUnderTest =
+      Assign(Select(thisFor("Bar"), FieldName("Foo", "fooFld"))(IntType), int(1))
+
+    Seq(
+      classDef(
+        "Foo",
+        superClass = Some(ObjectClass),
+        fields = List(FieldDef(EMF, FieldName("Foo", "fooFld"), NON, IntType))
+      ),
+      classDef(
+        "Bar",
+        superClass = Some(if (parent) "Foo" else ObjectClass),
+        methods = List(
+          MethodDef(
+              EMF.withNamespace(MemberNamespace.Constructor),
+              NoArgConstructorName, NON, Nil, VoidType,
+              Some(ctorBodyUnderTest))(EOH, UNV)
+        )
+      ),
+      mainTestClassDef(New("Bar", NoArgConstructorName, Nil))
+    )
+  }
+
+  @Test
+  def noImmutableAssignNonParent(): AsyncResult = await {
+    val classDefs = immutableFieldAssignTestClassDefs(parent = false)
+
+    for {
+      log <- testLinkIRErrors(classDefs, MainTestModuleInitializers, postOptimizer = true)
+    } yield {
+      log.assertContainsError("Foo expected but Bar! found for tree of type org.scalajs.ir.Trees$This")
+    }
+  }
+
+  @Test
+  def allowImmutableAssignParent(): AsyncResult = await {
+    val classDefs = immutableFieldAssignTestClassDefs(parent = true)
+    testLinkNoIRError(classDefs, MainTestModuleInitializers, postOptimizer = true)
+  }
+
 }
 
 object IRCheckerTest {
   def testLinkNoIRError(classDefs: Seq[ClassDef],
-      moduleInitializers: List[ModuleInitializer])(
+      moduleInitializers: List[ModuleInitializer],
+      postOptimizer: Boolean = false)(
       implicit ec: ExecutionContext): Future[Unit] = {
-    link(classDefs, moduleInitializers, new ScalaConsoleLogger(Level.Error))
+    link(classDefs, moduleInitializers, new ScalaConsoleLogger(Level.Error), postOptimizer)
   }
 
   def testLinkIRErrors(classDefs: Seq[ClassDef],
-      moduleInitializers: List[ModuleInitializer])(
+      moduleInitializers: List[ModuleInitializer],
+      postOptimizer: Boolean = false)(
       implicit ec: ExecutionContext): Future[LogLines] = {
 
     val logger = new CapturingLogger
 
-    link(classDefs, moduleInitializers, logger).transform {
+    link(classDefs, moduleInitializers, logger, postOptimizer).transform {
       case Success(_) => Failure(new AssertionError("IR checking did not fail"))
       case Failure(_) => Success(logger.allLogLines)
     }
@@ -329,23 +374,45 @@ object IRCheckerTest {
 
   private def link(classDefs: Seq[ClassDef],
       moduleInitializers: List[ModuleInitializer],
-      logger: Logger)(implicit ec: ExecutionContext): Future[Unit] = {
-    val config = StandardConfig()
+      logger: Logger, postOptimizer: Boolean)(
+      implicit ec: ExecutionContext): Future[Unit] = {
+    val baseConfig = StandardConfig()
       .withCheckIR(true)
       .withOptimizer(false)
-    val linkerFrontend = StandardLinkerFrontend(config)
+
+    val config = {
+      /* Disable RuntimeLongs to workaround the Refiner disabling IRChecks in this case.
+       * TODO: Remove once we run IRChecks post optimizer all the time.
+       */
+      if (postOptimizer) baseConfig.withESFeatures(_.withAllowBigIntsForLongs(true))
+      else baseConfig
+    }
 
     val noSymbolRequirements = SymbolRequirement
       .factory("IRCheckerTest")
       .none()
 
     TestIRRepo.minilib.flatMap { stdLibFiles =>
-      val irFiles = (
+      if (postOptimizer) {
+        val refiner = new Refiner(CommonPhaseConfig.fromStandardConfig(config), checkIR = true)
+
+        Future.traverse(stdLibFiles)(f => IRFileImpl.fromIRFile(f).tree).flatMap { stdLibClassDefs =>
+          val allClassDefs = (
+            stdLibClassDefs ++
+            classDefs
+          )
+
+          refiner.refine(allClassDefs.map(c => (c, UNV)), moduleInitializers,
+              noSymbolRequirements, logger)
+        }
+      } else {
+        val linkerFrontend = StandardLinkerFrontend(config)
+        val irFiles = (
           stdLibFiles ++
           classDefs.map(MemClassDefIRFile(_))
-      )
-
-      linkerFrontend.link(irFiles, moduleInitializers, noSymbolRequirements, logger)
+        )
+        linkerFrontend.link(irFiles, moduleInitializers, noSymbolRequirements, logger)
+      }
     }.map(_ => ())
   }
 }

From 1d6214e9be9502e85887a0880362784645026907 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Tue, 12 Nov 2024 16:33:32 +0100
Subject: [PATCH 208/298] Add JDK 17 and 21 to the CI; remove 16.

Now we test the four active LTS versions: 1.8, 11, 17 and 21.

We upgrade our Scala 3 references to 3.3.4 which is the latest LTS.
Scala 3.3.1+ is required for JDK 21.

We also remove the `MaxPermSize` option from the CI script. It has
been useless since JDK 1.8, and actually causes an error starting
with JDK 17.
---
 Jenkinsfile                                   | 11 +++++---
 .../src/sbt-test/scala3/basic/build.sbt       |  2 +-
 .../src/sbt-test/scala3/junit/build.sbt       |  2 +-
 .../sbt-test/scala3/tasty-reader/build.sbt    |  2 +-
 .../scalajs/testing/adapter/TestAdapter.scala | 26 ++++++++++++++++-
 .../scalajs/testsuite/utils/Platform.scala    |  2 ++
 .../scalajs/testsuite/utils/Platform.scala    |  2 ++
 .../concurrent/ThreadLocalRandomTest.scala    |  8 +++++-
 .../testsuite/niocharset/CharsetTest.scala    | 28 ++++++++++++++-----
 9 files changed, 67 insertions(+), 16 deletions(-)

diff --git a/Jenkinsfile b/Jenkinsfile
index 43009dfd57..921ac4915f 100644
--- a/Jenkinsfile
+++ b/Jenkinsfile
@@ -64,7 +64,7 @@ rm -rf $TEST_LOCAL_IVY_HOME
 mkdir $TEST_LOCAL_IVY_HOME
 ln -s "$LOC_IVY_HOME/cache" "$TEST_LOCAL_IVY_HOME/cache"
 
-export SBT_OPTS="-J-Xmx5G -J-XX:MaxPermSize=512M -Dsbt.boot.directory=$LOC_SBT_BOOT -Dsbt.ivy.home=$TEST_LOCAL_IVY_HOME -Divy.home=$TEST_LOCAL_IVY_HOME -Dsbt.global.base=$LOC_SBT_BASE"
+export SBT_OPTS="-J-Xmx5G -Dsbt.boot.directory=$LOC_SBT_BOOT -Dsbt.ivy.home=$TEST_LOCAL_IVY_HOME -Divy.home=$TEST_LOCAL_IVY_HOME -Dsbt.global.base=$LOC_SBT_BASE"
 export COURSIER_CACHE="$LOC_CS_CACHE"
 
 export NODE_PATH="$HOME/node_modules/"
@@ -539,7 +539,7 @@ def Tasks = [
 ]
 
 def mainJavaVersion = "1.8"
-def otherJavaVersions = ["11", "16"]
+def otherJavaVersions = ["11", "17", "21"]
 def allJavaVersions = otherJavaVersions.clone()
 allJavaVersions << mainJavaVersion
 
@@ -577,7 +577,7 @@ def otherScalaVersions = [
   "2.13.12"
 ]
 
-def scala3Version = "3.2.1"
+def scala3Version = "3.3.4"
 
 def allESVersions = [
   "ES5_1",
@@ -614,7 +614,10 @@ allESVersions.each { esVersion ->
 }
 allJavaVersions.each { javaVersion ->
   // the `scala` version is irrelevant here
-  quickMatrix.add([task: "sbt-plugin-and-scalastyle", scala: mainScalaVersion, java: javaVersion])
+  // We exclude JDK 21 because our sbt scripted tests use old sbt versions (on purpose), which do not support JDK 21
+  if (javaVersion != '21') {
+    quickMatrix.add([task: "sbt-plugin-and-scalastyle", scala: mainScalaVersion, java: javaVersion])
+  }
 }
 quickMatrix.add([task: "scala3-compat", scala: scala3Version, java: mainJavaVersion])
 
diff --git a/sbt-plugin/src/sbt-test/scala3/basic/build.sbt b/sbt-plugin/src/sbt-test/scala3/basic/build.sbt
index 47788c2ad9..6a461c06fc 100644
--- a/sbt-plugin/src/sbt-test/scala3/basic/build.sbt
+++ b/sbt-plugin/src/sbt-test/scala3/basic/build.sbt
@@ -1,6 +1,6 @@
 enablePlugins(ScalaJSPlugin)
 
-scalaVersion := "3.0.0"
+scalaVersion := "3.3.4"
 
 // Test CrossVersion.for3Use2_13 for %%% dependencies
 libraryDependencies +=
diff --git a/sbt-plugin/src/sbt-test/scala3/junit/build.sbt b/sbt-plugin/src/sbt-test/scala3/junit/build.sbt
index 809933c9ef..d1d33900ab 100644
--- a/sbt-plugin/src/sbt-test/scala3/junit/build.sbt
+++ b/sbt-plugin/src/sbt-test/scala3/junit/build.sbt
@@ -1,3 +1,3 @@
 enablePlugins(ScalaJSPlugin, ScalaJSJUnitPlugin)
 
-scalaVersion := "3.0.0"
+scalaVersion := "3.3.4"
diff --git a/sbt-plugin/src/sbt-test/scala3/tasty-reader/build.sbt b/sbt-plugin/src/sbt-test/scala3/tasty-reader/build.sbt
index a0af60a58e..683c749c5a 100644
--- a/sbt-plugin/src/sbt-test/scala3/tasty-reader/build.sbt
+++ b/sbt-plugin/src/sbt-test/scala3/tasty-reader/build.sbt
@@ -3,7 +3,7 @@ lazy val root = project.in(file("."))
 lazy val testlib = project.in(file("testlib"))
   .enablePlugins(ScalaJSPlugin)
   .settings(
-    scalaVersion := "3.1.3"
+    scalaVersion := "3.3.4"
   )
 
 lazy val app = project.in(file("app"))
diff --git a/test-adapter/src/main/scala/org/scalajs/testing/adapter/TestAdapter.scala b/test-adapter/src/main/scala/org/scalajs/testing/adapter/TestAdapter.scala
index 0172b89964..7c3bd880a3 100644
--- a/test-adapter/src/main/scala/org/scalajs/testing/adapter/TestAdapter.scala
+++ b/test-adapter/src/main/scala/org/scalajs/testing/adapter/TestAdapter.scala
@@ -47,6 +47,26 @@ final class TestAdapter(jsEnv: JSEnv, input: Seq[Input], config: TestAdapter.Con
   private implicit val executionContext: ExecutionContext =
     ExecutionContext.fromExecutor(ExecutionContext.global, reportFailure)
 
+  /** Accessor to the deprecated method `jl.Thread.getId()`.
+   *
+   *  Since JDK 19, Thread.getId() is deprecated in favor of Thread.threadId().
+   *  The only reason is that getId() was not marked `final`, and hence there
+   *  was no guarantee that subclasses wouldn't override it with something that
+   *  is not the thread's ID.
+   *
+   *  We cannot directly use Thread.threadId() since it was only added in JDK 19.
+   *  Since we probably don't need to care about the potential "threat", we do
+   *  the override-with-deprecated dance to silence the warning.
+   *
+   *  Reminder: we cannot use `@nowarn` since it was only introduced in
+   *  Scala 2.12.13/2.13.2.
+   */
+  private val threadIDAccessor: ThreadIDAccessor = new ThreadIDAccessor {
+    @deprecated("warning silencer", since = "forever")
+    def getCurrentThreadId(): Long =
+      Thread.currentThread().getId()
+  }
+
   /** Creates an `sbt.testing.Framework` for each framework that can be found.
    *
    *  The returned Frameworks bind to this TestAdapter and are only valid until
@@ -113,7 +133,7 @@ final class TestAdapter(jsEnv: JSEnv, input: Seq[Input], config: TestAdapter.Con
   }
 
   private[adapter] def getRunnerForThread(): ManagedRunner = {
-    val threadId = Thread.currentThread().getId()
+    val threadId = threadIDAccessor.getCurrentThreadId()
 
     // Note that this is thread safe, since each thread can only operate on
     // the value associated to its thread id.
@@ -167,4 +187,8 @@ object TestAdapter {
       val com: RPCCore,
       val mux: RunMuxRPC
   )
+
+  private abstract class ThreadIDAccessor {
+    def getCurrentThreadId(): Long
+  }
 }
diff --git a/test-suite/js/src/main/scala/org/scalajs/testsuite/utils/Platform.scala b/test-suite/js/src/main/scala/org/scalajs/testsuite/utils/Platform.scala
index 97ad78c948..7712e426a6 100644
--- a/test-suite/js/src/main/scala/org/scalajs/testsuite/utils/Platform.scala
+++ b/test-suite/js/src/main/scala/org/scalajs/testsuite/utils/Platform.scala
@@ -36,6 +36,8 @@ object Platform {
 
   final val executingInJVMOnLowerThanJDK17 = false
 
+  def executingInJVMOnLowerThanJDK(version: Int): Boolean = false
+
   def executingInWebAssembly: Boolean = BuildInfo.isWebAssembly
 
   def executingInNodeJS: Boolean = {
diff --git a/test-suite/jvm/src/main/scala/org/scalajs/testsuite/utils/Platform.scala b/test-suite/jvm/src/main/scala/org/scalajs/testsuite/utils/Platform.scala
index ba855134c9..e66c2faa24 100644
--- a/test-suite/jvm/src/main/scala/org/scalajs/testsuite/utils/Platform.scala
+++ b/test-suite/jvm/src/main/scala/org/scalajs/testsuite/utils/Platform.scala
@@ -34,6 +34,8 @@ object Platform {
 
   def executingInJVMOnLowerThanJDK17: Boolean = jdkVersion < 17
 
+  def executingInJVMOnLowerThanJDK(version: Int): Boolean = jdkVersion < version
+
   private lazy val jdkVersion = {
     val v = System.getProperty("java.version")
     if (v.startsWith("1.")) Integer.parseInt(v.drop(2).takeWhile(_.isDigit))
diff --git a/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/util/concurrent/ThreadLocalRandomTest.scala b/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/util/concurrent/ThreadLocalRandomTest.scala
index 084effeb1d..d8c193d171 100644
--- a/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/util/concurrent/ThreadLocalRandomTest.scala
+++ b/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/util/concurrent/ThreadLocalRandomTest.scala
@@ -508,7 +508,13 @@ class ThreadLocalRandomTest {
   @Test def nextDoubleDoubleDouble(): Unit = {
     implicit val tlr = ThreadLocalRandom.current()
 
-    checkDoubleBounds(Double.MinValue, Double.MaxValue)
+    if (!executingInJVMOnLowerThanJDK(19) || executingInJVMOnLowerThanJDK(17)) {
+      /* For some reason, JDK 17-18 throw an IllegalArgumentException for this one.
+       * Older and more recent versions of the JDK succeed.
+       */
+      checkDoubleBounds(Double.MinValue, Double.MaxValue)
+    }
+
     checkDoubleBounds(Double.MinValue, 0L)
     checkDoubleBounds(Double.MaxValue, 0L)
     checkDoubleBounds(0.14303466203185822, 0.7471945354839639)
diff --git a/test-suite/shared/src/test/scala/org/scalajs/testsuite/niocharset/CharsetTest.scala b/test-suite/shared/src/test/scala/org/scalajs/testsuite/niocharset/CharsetTest.scala
index 78df50ee1e..c6453c6cf7 100644
--- a/test-suite/shared/src/test/scala/org/scalajs/testsuite/niocharset/CharsetTest.scala
+++ b/test-suite/shared/src/test/scala/org/scalajs/testsuite/niocharset/CharsetTest.scala
@@ -22,12 +22,19 @@ import org.junit.Assert._
 
 import org.scalajs.testsuite.javalib.util.TrivialImmutableCollection
 import org.scalajs.testsuite.utils.AssertThrows.assertThrows
-import org.scalajs.testsuite.utils.Platform.executingInJVM
+import org.scalajs.testsuite.utils.Platform._
 
 class CharsetTest {
   def javaSet[A](elems: A*): java.util.Set[A] =
     new java.util.HashSet(TrivialImmutableCollection(elems: _*))
 
+  /* "default" was removed as alias of US_ASCII in JDK 18 through JEP 400.
+   * See https://openjdk.org/jeps/400#The-legacy-default-charset
+   * TODO Maybe we should remove it as well in our implementation.
+   */
+  lazy val isDefaultSupported: Boolean =
+    !executingInJVM || executingInJVMOnLowerThanJDK(18)
+
   @Test def defaultCharset(): Unit = {
     assertSame(UTF_8, Charset.defaultCharset())
   }
@@ -40,7 +47,9 @@ class CharsetTest {
     assertSame(ISO_8859_1, Charset.forName("l1"))
 
     assertSame(US_ASCII, Charset.forName("US-ASCII"))
-    assertSame(US_ASCII, Charset.forName("Default"))
+
+    if (isDefaultSupported)
+      assertSame(US_ASCII, Charset.forName("Default"))
 
     assertSame(UTF_8, Charset.forName("UTF-8"))
     assertSame(UTF_8, Charset.forName("utf-8"))
@@ -70,13 +79,14 @@ class CharsetTest {
   @Test def isSupported(): Unit = {
     assertTrue(Charset.isSupported("ISO-8859-1"))
     assertTrue(Charset.isSupported("US-ASCII"))
-    assertTrue(Charset.isSupported("Default"))
     assertTrue(Charset.isSupported("utf-8"))
     assertTrue(Charset.isSupported("UnicodeBigUnmarked"))
     assertTrue(Charset.isSupported("Utf_16le"))
     assertTrue(Charset.isSupported("UTF-16"))
     assertTrue(Charset.isSupported("unicode"))
 
+    assertEquals(isDefaultSupported, Charset.isSupported("Default"))
+
     assertFalse(Charset.isSupported("this-charset-does-not-exist"))
   }
 
@@ -90,10 +100,14 @@ class CharsetTest {
             "UnicodeBigUnmarked"))
     assertEquals(Charset.forName("UTF-16LE").aliases(),
         javaSet("UnicodeLittleUnmarked", "UTF_16LE", "X-UTF-16LE"))
-    assertEquals(Charset.forName("US-ASCII").aliases(),
-        javaSet("ANSI_X3.4-1968", "cp367", "csASCII", "iso-ir-6", "ASCII",
-            "iso_646.irv:1983", "ANSI_X3.4-1986", "ascii7", "default",
-            "ISO_646.irv:1991", "ISO646-US", "IBM367", "646", "us"))
+
+    val expectedUSAsciiAliases = javaSet("ANSI_X3.4-1968", "cp367", "csASCII",
+        "iso-ir-6", "ASCII", "iso_646.irv:1983", "ANSI_X3.4-1986", "ascii7",
+        "ISO_646.irv:1991", "ISO646-US", "IBM367", "646", "us")
+    if (isDefaultSupported)
+      expectedUSAsciiAliases.add("default")
+    assertEquals(Charset.forName("US-ASCII").aliases(), expectedUSAsciiAliases)
+
     assertEquals(Charset.forName("ISO-8859-1").aliases(),
         javaSet("819", "ISO8859-1", "l1", "ISO_8859-1:1987", "ISO_8859-1", "8859_1",
             "iso-ir-100", "latin1", "cp819", "ISO8859_1", "IBM819", "ISO_8859_1",

From 8f98b8fc9fd5f2e9aeb891d7d8cc773d4d9291ce Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Wed, 13 Nov 2024 17:58:47 +0100
Subject: [PATCH 209/298] Add trait definitions for
 ju.Sequenced{Collection,Map,Set}.

We only add the trait definitions and the relevant inheritance
relationships. This is enough to fix linking issues arising only
from type inference when compiling on JDK 21+.

We do not any of the methods of those new traits in this commit.
They all rely on new `reversed()` methods, which are supposed to
provide reverse *views* of the collections. Implementing all those
views correctly turns out to be a bottomless well, which is left
for future work.
---
 javalib/src/main/scala/java/util/Deque.scala  |  2 +-
 .../main/scala/java/util/LinkedHashMap.scala  |  2 +-
 .../main/scala/java/util/LinkedHashSet.scala  |  2 +-
 javalib/src/main/scala/java/util/List.scala   |  2 +-
 .../scala/java/util/SequencedCollection.scala | 15 ++++++
 .../main/scala/java/util/SequencedMap.scala   | 17 +++++++
 .../main/scala/java/util/SequencedSet.scala   | 15 ++++++
 .../src/main/scala/java/util/SortedMap.scala  |  2 +-
 .../src/main/scala/java/util/SortedSet.scala  |  2 +-
 project/Build.scala                           |  1 +
 .../util/SequencedCollectionTest.scala        | 46 ++++++++++++++++++
 .../javalib/util/SequencedMapTest.scala       | 47 +++++++++++++++++++
 .../javalib/util/SequencedSetTest.scala       | 47 +++++++++++++++++++
 13 files changed, 194 insertions(+), 6 deletions(-)
 create mode 100644 javalib/src/main/scala/java/util/SequencedCollection.scala
 create mode 100644 javalib/src/main/scala/java/util/SequencedMap.scala
 create mode 100644 javalib/src/main/scala/java/util/SequencedSet.scala
 create mode 100644 test-suite/shared/src/test/require-jdk21/org/scalajs/testsuite/javalib/util/SequencedCollectionTest.scala
 create mode 100644 test-suite/shared/src/test/require-jdk21/org/scalajs/testsuite/javalib/util/SequencedMapTest.scala
 create mode 100644 test-suite/shared/src/test/require-jdk21/org/scalajs/testsuite/javalib/util/SequencedSetTest.scala

diff --git a/javalib/src/main/scala/java/util/Deque.scala b/javalib/src/main/scala/java/util/Deque.scala
index 89b70bc615..d4a4e0918c 100644
--- a/javalib/src/main/scala/java/util/Deque.scala
+++ b/javalib/src/main/scala/java/util/Deque.scala
@@ -12,7 +12,7 @@
 
 package java.util
 
-trait Deque[E] extends Queue[E] {
+trait Deque[E] extends Queue[E] with SequencedCollection[E] {
   def addFirst(e: E): Unit
   def addLast(e: E): Unit
   def offerFirst(e: E): Boolean
diff --git a/javalib/src/main/scala/java/util/LinkedHashMap.scala b/javalib/src/main/scala/java/util/LinkedHashMap.scala
index ba46ffc844..958aeff409 100644
--- a/javalib/src/main/scala/java/util/LinkedHashMap.scala
+++ b/javalib/src/main/scala/java/util/LinkedHashMap.scala
@@ -17,7 +17,7 @@ import java.util.function.BiConsumer
 
 class LinkedHashMap[K, V](initialCapacity: Int, loadFactor: Float,
     accessOrder: Boolean)
-    extends HashMap[K, V](initialCapacity, loadFactor) {
+    extends HashMap[K, V](initialCapacity, loadFactor) with SequencedMap[K, V] {
   self =>
 
   import LinkedHashMap._
diff --git a/javalib/src/main/scala/java/util/LinkedHashSet.scala b/javalib/src/main/scala/java/util/LinkedHashSet.scala
index 6133d013d9..f24d3f5bd4 100644
--- a/javalib/src/main/scala/java/util/LinkedHashSet.scala
+++ b/javalib/src/main/scala/java/util/LinkedHashSet.scala
@@ -15,7 +15,7 @@ package java.util
 import java.lang.Cloneable
 
 class LinkedHashSet[E] private[util] (inner: LinkedHashMap[E, Any])
-    extends HashSet[E](inner) with Set[E] with Cloneable with Serializable {
+    extends HashSet[E](inner) with SequencedSet[E] with Cloneable with Serializable {
 
   def this(initialCapacity: Int, loadFactor: Float) =
     this(new LinkedHashMap[E, Any](initialCapacity, loadFactor))
diff --git a/javalib/src/main/scala/java/util/List.scala b/javalib/src/main/scala/java/util/List.scala
index 66465dde50..982e373b01 100644
--- a/javalib/src/main/scala/java/util/List.scala
+++ b/javalib/src/main/scala/java/util/List.scala
@@ -14,7 +14,7 @@ package java.util
 
 import java.util.function.UnaryOperator
 
-trait List[E] extends Collection[E] {
+trait List[E] extends SequencedCollection[E] {
   def replaceAll(operator: UnaryOperator[E]): Unit = {
     val iter = listIterator()
     while (iter.hasNext())
diff --git a/javalib/src/main/scala/java/util/SequencedCollection.scala b/javalib/src/main/scala/java/util/SequencedCollection.scala
new file mode 100644
index 0000000000..9f49537f33
--- /dev/null
+++ b/javalib/src/main/scala/java/util/SequencedCollection.scala
@@ -0,0 +1,15 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package java.util
+
+trait SequencedCollection[E] extends Collection[E]
diff --git a/javalib/src/main/scala/java/util/SequencedMap.scala b/javalib/src/main/scala/java/util/SequencedMap.scala
new file mode 100644
index 0000000000..a1eb13cd23
--- /dev/null
+++ b/javalib/src/main/scala/java/util/SequencedMap.scala
@@ -0,0 +1,17 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package java.util
+
+import java.util.Map.Entry
+
+trait SequencedMap[K, V] extends Map[K, V]
diff --git a/javalib/src/main/scala/java/util/SequencedSet.scala b/javalib/src/main/scala/java/util/SequencedSet.scala
new file mode 100644
index 0000000000..8bf692997a
--- /dev/null
+++ b/javalib/src/main/scala/java/util/SequencedSet.scala
@@ -0,0 +1,15 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package java.util
+
+trait SequencedSet[E] extends SequencedCollection[E] with Set[E]
diff --git a/javalib/src/main/scala/java/util/SortedMap.scala b/javalib/src/main/scala/java/util/SortedMap.scala
index e2ac54cfef..c5076c0019 100644
--- a/javalib/src/main/scala/java/util/SortedMap.scala
+++ b/javalib/src/main/scala/java/util/SortedMap.scala
@@ -12,7 +12,7 @@
 
 package java.util
 
-trait SortedMap[K, V] extends Map[K, V] {
+trait SortedMap[K, V] extends SequencedMap[K, V] {
   def firstKey(): K
   def comparator(): Comparator[_ >: K]
   def lastKey(): K
diff --git a/javalib/src/main/scala/java/util/SortedSet.scala b/javalib/src/main/scala/java/util/SortedSet.scala
index b4f6fcc83d..95694ab938 100644
--- a/javalib/src/main/scala/java/util/SortedSet.scala
+++ b/javalib/src/main/scala/java/util/SortedSet.scala
@@ -12,7 +12,7 @@
 
 package java.util
 
-trait SortedSet[E] extends Set[E] {
+trait SortedSet[E] extends SequencedSet[E] {
   def comparator(): Comparator[_ >: E]
   def subSet(fromElement: E, toElement: E): SortedSet[E]
   def headSet(toElement: E): SortedSet[E]
diff --git a/project/Build.scala b/project/Build.scala
index ba0669e9bc..487e8482e7 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -2134,6 +2134,7 @@ object Build {
         collectionsEraDependentDirectory(scalaV, sharedTestDir) ::
         includeIf(sharedTestDir / "require-jdk11", javaV >= 11) :::
         includeIf(sharedTestDir / "require-jdk15", javaV >= 15) :::
+        includeIf(sharedTestDir / "require-jdk21", javaV >= 21) :::
         includeIf(testDir / "require-scala2", isJSTest)
       },
 
diff --git a/test-suite/shared/src/test/require-jdk21/org/scalajs/testsuite/javalib/util/SequencedCollectionTest.scala b/test-suite/shared/src/test/require-jdk21/org/scalajs/testsuite/javalib/util/SequencedCollectionTest.scala
new file mode 100644
index 0000000000..02686c4e35
--- /dev/null
+++ b/test-suite/shared/src/test/require-jdk21/org/scalajs/testsuite/javalib/util/SequencedCollectionTest.scala
@@ -0,0 +1,46 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package org.scalajs.testsuite.javalib.util
+
+import org.junit.Test
+import org.junit.Assert._
+
+import java.{util => ju}
+
+class SequencedCollectionTest {
+
+  @Test def knownSequencedCollections(): Unit = {
+    def test(expected: Boolean, testClass: Class[_]): Unit = {
+      assertEquals(expected, classOf[ju.SequencedCollection[_]].isAssignableFrom(testClass))
+    }
+
+    test(true, classOf[ju.List[String]])
+    test(true, classOf[ju.LinkedList[String]])
+    test(true, classOf[ju.ArrayList[String]])
+    test(true, classOf[ju.LinkedHashSet[String]])
+    test(true, classOf[ju.TreeSet[String]])
+    test(true, classOf[ju.NavigableSet[String]])
+    test(true, classOf[ju.Deque[String]])
+    test(true, classOf[ju.ArrayDeque[String]])
+    test(true, classOf[ju.SequencedSet[String]])
+
+    test(false, classOf[ju.SequencedMap[String, String]])
+    test(false, classOf[ju.HashSet[String]])
+    test(false, classOf[ju.HashMap[String, String]])
+    test(false, classOf[ju.LinkedHashMap[String, String]])
+    test(false, classOf[ju.TreeMap[String, String]])
+    test(false, classOf[ju.NavigableMap[String, String]])
+    test(false, classOf[ju.Queue[String]])
+  }
+
+}
diff --git a/test-suite/shared/src/test/require-jdk21/org/scalajs/testsuite/javalib/util/SequencedMapTest.scala b/test-suite/shared/src/test/require-jdk21/org/scalajs/testsuite/javalib/util/SequencedMapTest.scala
new file mode 100644
index 0000000000..5acf97f99a
--- /dev/null
+++ b/test-suite/shared/src/test/require-jdk21/org/scalajs/testsuite/javalib/util/SequencedMapTest.scala
@@ -0,0 +1,47 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package org.scalajs.testsuite.javalib.util
+
+import org.junit.Test
+import org.junit.Assert._
+
+import java.{util => ju}
+
+class SequencedMapTest {
+
+  @Test def knownSequencedMaps(): Unit = {
+    def test(expected: Boolean, testClass: Class[_]): Unit = {
+      assertEquals(expected, classOf[ju.SequencedMap[_, _]].isAssignableFrom(testClass))
+    }
+
+    test(true, classOf[ju.SortedMap[String, String]])
+    test(true, classOf[ju.LinkedHashMap[String, String]])
+    test(true, classOf[ju.TreeMap[String, String]])
+    test(true, classOf[ju.NavigableMap[String, String]])
+
+    test(false, classOf[ju.HashMap[String, String]])
+    test(false, classOf[ju.LinkedHashSet[String]])
+    test(false, classOf[ju.LinkedHashSet[String]])
+    test(false, classOf[ju.TreeSet[String]])
+    test(false, classOf[ju.NavigableSet[String]])
+    test(false, classOf[ju.List[String]])
+    test(false, classOf[ju.LinkedList[String]])
+    test(false, classOf[ju.ArrayList[String]])
+    test(false, classOf[ju.Deque[String]])
+    test(false, classOf[ju.ArrayDeque[String]])
+    test(false, classOf[ju.HashSet[String]])
+    test(false, classOf[ju.SequencedCollection[String]])
+    test(false, classOf[ju.SequencedSet[String]])
+  }
+
+}
diff --git a/test-suite/shared/src/test/require-jdk21/org/scalajs/testsuite/javalib/util/SequencedSetTest.scala b/test-suite/shared/src/test/require-jdk21/org/scalajs/testsuite/javalib/util/SequencedSetTest.scala
new file mode 100644
index 0000000000..1bcf4be735
--- /dev/null
+++ b/test-suite/shared/src/test/require-jdk21/org/scalajs/testsuite/javalib/util/SequencedSetTest.scala
@@ -0,0 +1,47 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package org.scalajs.testsuite.javalib.util
+
+import org.junit.Test
+import org.junit.Assert._
+
+import java.{util => ju}
+
+class SequencedSetTest {
+
+  @Test def knownSequencedSets(): Unit = {
+    def test(expected: Boolean, testClass: Class[_]): Unit = {
+      assertEquals(expected, classOf[ju.SequencedSet[_]].isAssignableFrom(testClass))
+    }
+
+    test(true, classOf[ju.LinkedHashSet[String]])
+    test(true, classOf[ju.LinkedHashSet[String]])
+    test(true, classOf[ju.TreeSet[String]])
+    test(true, classOf[ju.NavigableSet[String]])
+    test(true, classOf[ju.SortedSet[String]])
+
+    test(false, classOf[ju.List[String]])
+    test(false, classOf[ju.LinkedList[String]])
+    test(false, classOf[ju.ArrayList[String]])
+    test(false, classOf[ju.Deque[String]])
+    test(false, classOf[ju.ArrayDeque[String]])
+    test(false, classOf[ju.HashSet[String]])
+    test(false, classOf[ju.HashMap[String, String]])
+    test(false, classOf[ju.LinkedHashMap[String, String]])
+    test(false, classOf[ju.TreeMap[String, String]])
+    test(false, classOf[ju.NavigableMap[String, String]])
+    test(false, classOf[ju.SequencedCollection[String]])
+    test(false, classOf[ju.SequencedMap[String, String]])
+  }
+
+}

From 7ae4a051e7111808b473d48fa9e5a27577cde483 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Sat, 16 Nov 2024 10:45:17 +0100
Subject: [PATCH 210/298] Simplify the test API we use to identify specific
 JDKs.

---
 .../testsuite/javalib/util/FormatterTestEx.scala   |  4 ++--
 .../org/scalajs/testsuite/utils/Platform.scala     | 14 ++------------
 .../org/scalajs/testsuite/utils/Platform.scala     | 14 ++------------
 .../scalajs/testsuite/javalib/net/URITest.scala    |  4 ++--
 .../testsuite/javalib/net/URLDecoderTest.scala     |  2 +-
 .../testsuite/javalib/util/FormatterTest.scala     |  4 ++--
 .../scalajs/testsuite/javalib/util/MapTest.scala   |  2 +-
 .../util/concurrent/ThreadLocalRandomTest.scala    |  2 +-
 .../javalib/util/regex/RegexEngineTest.scala       | 12 ++++++------
 .../testsuite/niobuffer/BaseBufferTest.scala       |  2 +-
 10 files changed, 20 insertions(+), 40 deletions(-)

diff --git a/test-suite-ex/shared/src/test/scala/org/scalajs/testsuite/javalib/util/FormatterTestEx.scala b/test-suite-ex/shared/src/test/scala/org/scalajs/testsuite/javalib/util/FormatterTestEx.scala
index 27dc5ecb60..1f0186c747 100644
--- a/test-suite-ex/shared/src/test/scala/org/scalajs/testsuite/javalib/util/FormatterTestEx.scala
+++ b/test-suite-ex/shared/src/test/scala/org/scalajs/testsuite/javalib/util/FormatterTestEx.scala
@@ -76,7 +76,7 @@ class FormatterTestEx {
      * locale uses U+202F NARROW NO-BREAK SPACE as grouping
      * separator, instead of U+00A0 NO-BREAK SPACE.
      */
-    if (!executingInJVMOnLowerThanJDK13) {
+    if (!executingInJVMOnLowerThanJDK(13)) {
       // U+202F NARROW NO-BREAK SPACE
       assertF(French, "1\u202F234\u202F567", "%,d", 1234567)
       assertF(French, "1\u202F234\u202F567,89", "%,.2f", 1234567.89)
@@ -119,7 +119,7 @@ class FormatterTestEx {
 
   @Test def testFormatTurkish(): Unit = {
     assumeFalse("Affected by https://bugs.openjdk.java.net/browse/JDK-8060094",
-        executingInJVMOnJDK8OrLower)
+        executingInJVMOnLowerThanJDK(9))
 
     // U+0130 LATIN CAPITAL LETTER I WITH DOT ABOVE
     assertF(Turkish, "TİTLE", "%S", "title")
diff --git a/test-suite/js/src/main/scala/org/scalajs/testsuite/utils/Platform.scala b/test-suite/js/src/main/scala/org/scalajs/testsuite/utils/Platform.scala
index 7712e426a6..6251f85b88 100644
--- a/test-suite/js/src/main/scala/org/scalajs/testsuite/utils/Platform.scala
+++ b/test-suite/js/src/main/scala/org/scalajs/testsuite/utils/Platform.scala
@@ -24,20 +24,10 @@ object Platform {
    */
   final val executingInJVM = false
 
-  final val executingInJVMOnJDK8OrLower = false
-
-  final val executingInJVMOnLowerThanJDK10 = false
-
-  final val executingInJVMOnLowerThanJDK13 = false
-
-  final val executingInJVMOnLowerThanJDK15 = false
-
-  final val executingInJVMOnLowerThanJDK16 = false
-
-  final val executingInJVMOnLowerThanJDK17 = false
-
   def executingInJVMOnLowerThanJDK(version: Int): Boolean = false
 
+  def executingInJVMWithJDKIn(range: Range): Boolean = false
+
   def executingInWebAssembly: Boolean = BuildInfo.isWebAssembly
 
   def executingInNodeJS: Boolean = {
diff --git a/test-suite/jvm/src/main/scala/org/scalajs/testsuite/utils/Platform.scala b/test-suite/jvm/src/main/scala/org/scalajs/testsuite/utils/Platform.scala
index e66c2faa24..6b480fd9b6 100644
--- a/test-suite/jvm/src/main/scala/org/scalajs/testsuite/utils/Platform.scala
+++ b/test-suite/jvm/src/main/scala/org/scalajs/testsuite/utils/Platform.scala
@@ -22,20 +22,10 @@ object Platform {
    */
   final val executingInJVM = true
 
-  def executingInJVMOnJDK8OrLower: Boolean = jdkVersion <= 8
-
-  def executingInJVMOnLowerThanJDK10: Boolean = jdkVersion < 10
-
-  def executingInJVMOnLowerThanJDK13: Boolean = jdkVersion < 13
-
-  def executingInJVMOnLowerThanJDK15: Boolean = jdkVersion < 15
-
-  def executingInJVMOnLowerThanJDK16: Boolean = jdkVersion < 16
-
-  def executingInJVMOnLowerThanJDK17: Boolean = jdkVersion < 17
-
   def executingInJVMOnLowerThanJDK(version: Int): Boolean = jdkVersion < version
 
+  def executingInJVMWithJDKIn(range: Range): Boolean = range.contains(jdkVersion)
+
   private lazy val jdkVersion = {
     val v = System.getProperty("java.version")
     if (v.startsWith("1.")) Integer.parseInt(v.drop(2).takeWhile(_.isDigit))
diff --git a/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/net/URITest.scala b/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/net/URITest.scala
index 9d74d833db..464b79af10 100644
--- a/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/net/URITest.scala
+++ b/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/net/URITest.scala
@@ -18,7 +18,7 @@ import org.junit.Assert._
 import org.junit.Test
 
 import org.scalajs.testsuite.utils.AssertThrows.assertThrows
-import org.scalajs.testsuite.utils.Platform.executingInJVMOnLowerThanJDK15
+import org.scalajs.testsuite.utils.Platform._
 
 class URITest {
 
@@ -170,7 +170,7 @@ class URITest {
     val rel3 = new URI("/foo/ccc")
 
     // https://bugs.openjdk.java.net/browse/JDK-5064980
-    if (!executingInJVMOnLowerThanJDK15)
+    if (!executingInJVMOnLowerThanJDK(15))
       assertTrue(x.compareTo(y) == 0)
 
     assertTrue(x.compareTo(z) < 0)
diff --git a/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/net/URLDecoderTest.scala b/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/net/URLDecoderTest.scala
index de8e9dcc66..20f588b02c 100644
--- a/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/net/URLDecoderTest.scala
+++ b/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/net/URLDecoderTest.scala
@@ -99,7 +99,7 @@ class URLDecoderTest {
      * the implementation. So in all likelihood, it will not be coming back.
      * It is still throwing as of JDK 17.
      */
-    if (!executingInJVMOnLowerThanJDK10) {
+    if (!executingInJVMOnLowerThanJDK(10)) {
       unsupportedEncoding("abc", enc = "dummy")
       unsupportedEncoding("a+b+c", enc = "dummy")
     }
diff --git a/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/util/FormatterTest.scala b/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/util/FormatterTest.scala
index f22659c320..06f3fb1fe9 100644
--- a/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/util/FormatterTest.scala
+++ b/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/util/FormatterTest.scala
@@ -1694,7 +1694,7 @@ class FormatterTest {
 
   @Test def indexNotInRangeThrows(): Unit = {
     assumeFalse("https://bugs.openjdk.java.net/browse/JDK-8253875",
-        executingInJVMOnLowerThanJDK16)
+        executingInJVMOnLowerThanJDK(16))
 
     /* The public JavaDoc says that these situations throw an
      * IllegalFormatException, without being more specific. However, the bug
@@ -1716,7 +1716,7 @@ class FormatterTest {
 
   @Test def widthOrPrecisionTooLargeThrows(): Unit = {
     assumeFalse("https://bugs.openjdk.java.net/browse/JDK-8253875",
-        executingInJVMOnLowerThanJDK16)
+        executingInJVMOnLowerThanJDK(16))
 
     expectFormatterThrows(classOf[IllegalFormatWidthException], "%d %9876543210d", 56, 78)
     expectFormatterThrows(classOf[IllegalFormatPrecisionException], "%d %.9876543210f", 56, 78.5)
diff --git a/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/util/MapTest.scala b/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/util/MapTest.scala
index 6a401ad58c..5bacd9f8ed 100644
--- a/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/util/MapTest.scala
+++ b/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/util/MapTest.scala
@@ -1391,7 +1391,7 @@ trait MapTest {
        * https://bugs.openjdk.org/browse/JDK-8259622
        */
       assumeFalse("affected by JDK-8259622",
-          executingInJVMOnLowerThanJDK17 && !executingInJVMOnLowerThanJDK15 &&
+          executingInJVMWithJDKIn(15 to 16) &&
           mp.isInstanceOf[ju.TreeMap[_, _]])
 
       mp.put("nullable", null)
diff --git a/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/util/concurrent/ThreadLocalRandomTest.scala b/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/util/concurrent/ThreadLocalRandomTest.scala
index d8c193d171..7bd09eeb1b 100644
--- a/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/util/concurrent/ThreadLocalRandomTest.scala
+++ b/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/util/concurrent/ThreadLocalRandomTest.scala
@@ -508,7 +508,7 @@ class ThreadLocalRandomTest {
   @Test def nextDoubleDoubleDouble(): Unit = {
     implicit val tlr = ThreadLocalRandom.current()
 
-    if (!executingInJVMOnLowerThanJDK(19) || executingInJVMOnLowerThanJDK(17)) {
+    if (!executingInJVMWithJDKIn(17 to 18)) {
       /* For some reason, JDK 17-18 throw an IllegalArgumentException for this one.
        * Older and more recent versions of the JDK succeed.
        */
diff --git a/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/util/regex/RegexEngineTest.scala b/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/util/regex/RegexEngineTest.scala
index 99beb524fe..4cc2a720b4 100644
--- a/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/util/regex/RegexEngineTest.scala
+++ b/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/util/regex/RegexEngineTest.scala
@@ -1034,7 +1034,7 @@ class RegexEngineTest  {
     assertNotMatches(lower, "É")
 
     // https://bugs.openjdk.java.net/browse/JDK-8214245
-    if (!executingInJVMOnLowerThanJDK15) {
+    if (!executingInJVMOnLowerThanJDK(15)) {
       val lowerCI = compile("\\p{Lower}", CaseInsensitive)
       assertMatches(lowerCI, "a")
       assertMatches(lowerCI, "f")
@@ -1223,7 +1223,7 @@ class RegexEngineTest  {
     assertNotMatches(lower, "É")
 
     // https://bugs.openjdk.java.net/browse/JDK-8214245
-    if (!executingInJVMOnLowerThanJDK15) {
+    if (!executingInJVMOnLowerThanJDK(15)) {
       val lowerCI = compile("\\p{Lower}", CaseInsensitive | UnicodeCharacterClass)
       assertMatches(lowerCI, "a")
       assertMatches(lowerCI, "f")
@@ -1389,7 +1389,7 @@ class RegexEngineTest  {
     checkConsistency("javaIdentifierIgnorable", "[\u0000-\u0008\u000E-\u001B\u007F-\u009F\\p{Cf}]")
     checkConsistency("javaIdeographic", "\\p{IsIdeographic}")
     checkConsistency("javaISOControl", "[\u0000-\u001F\u007F-\u009F]")
-    if (!executingInJVMOnJDK8OrLower) {
+    if (!executingInJVMOnLowerThanJDK(9)) {
       checkConsistency("javaJavaIdentifierPart",
           "[\\p{L}\\p{Sc}\\p{Pc}\\p{Nd}\\p{Nl}\\p{Mn}\\p{Mc}\u0000-\u0008\u000E-\u001B\u007F-\u009F\\p{Cf}]")
       checkConsistency("javaJavaIdentifierStart", "[\\p{L}\\p{Sc}\\p{Pc}\\p{Nl}]")
@@ -1459,7 +1459,7 @@ class RegexEngineTest  {
     /* SignWriting is special because of its canonical name, which is not Sign_Writing.
      * It's from Unicode 8.0.0, so it requires JDK 9+.
      */
-    if (!executingInJVMOnJDK8OrLower) {
+    if (!executingInJVMOnLowerThanJDK(9)) {
       val signWriting = compile("\\p{script=signwrItIng}")
       assertMatches(signWriting, "\uD836\uDC36") // U+1D836 SIGNWRITING HAND-FIST MIDDLE THUMB CUPPED INDEX UP
       assertNotMatches(signWriting, "A")
@@ -1846,7 +1846,7 @@ class RegexEngineTest  {
     assertNotMatches(complexUnionsAndIntersections, "z")
 
     // https://bugs.openjdk.java.net/browse/JDK-8216391
-    if (!executingInJVMOnJDK8OrLower) {
+    if (!executingInJVMOnLowerThanJDK(9)) {
       val not_ad_or_mp = compile("[^a-d[m-p]]")
       assertNotMatches(not_ad_or_mp, "a")
       assertNotMatches(not_ad_or_mp, "c")
@@ -2572,7 +2572,7 @@ class RegexEngineTest  {
     }
 
     // JDK 9+ features
-    if (!executingInJVMOnJDK8OrLower) {
+    if (!executingInJVMOnLowerThanJDK(9)) {
       assertSyntaxErrorInJS("\\N{DIGIT TWO}", "\\N is not supported", 1)
       assertSyntaxErrorInJS("foo\\b{g}.", "\\b{g} is not supported", 4)
       assertSyntaxErrorInJS("foo\\X", "\\X is not supported", 4)
diff --git a/test-suite/shared/src/test/scala/org/scalajs/testsuite/niobuffer/BaseBufferTest.scala b/test-suite/shared/src/test/scala/org/scalajs/testsuite/niobuffer/BaseBufferTest.scala
index fc6822f31a..606732f87e 100644
--- a/test-suite/shared/src/test/scala/org/scalajs/testsuite/niobuffer/BaseBufferTest.scala
+++ b/test-suite/shared/src/test/scala/org/scalajs/testsuite/niobuffer/BaseBufferTest.scala
@@ -313,7 +313,7 @@ abstract class BaseBufferTest {
 
   @Test def compact(): Unit = {
     assumeFalse("Affected by a bug in the JDK.",
-        executingInJVMOnJDK8OrLower &&
+        executingInJVMOnLowerThanJDK(9) &&
         factory.isInstanceOf[BufferFactory.ByteBufferViewFactory])
 
     if (!createsReadOnly) {

From 8c05d338c6b324f61d688d6bddd37738040a1fe2 Mon Sep 17 00:00:00 2001
From: Tobias Schlatter <tobias@meisch.ch>
Date: Sat, 16 Nov 2024 15:25:33 +0100
Subject: [PATCH 211/298] ClassDef check RecordSelect assignments

---
 .../linker/checker/ClassDefChecker.scala      | 25 +++++++++++++++++--
 .../linker/checker/ClassDefCheckerTest.scala  |  8 ++++++
 2 files changed, 31 insertions(+), 2 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala b/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
index baf49343e3..1c4bd11d74 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
@@ -12,7 +12,7 @@
 
 package org.scalajs.linker.checker
 
-import scala.annotation.switch
+import scala.annotation.{switch, tailrec}
 
 import scala.collection.mutable
 
@@ -689,8 +689,29 @@ private final class ClassDefChecker(classDef: ClassDef,
           case JSGlobalRef(JSGlobalRef.FileLevelThis) =>
             reportError(i"Assignment to global this.")
 
+          case RecordSelect(record, SimpleFieldIdent(fieldName)) =>
+            record.tpe match {
+              case RecordType(fields) =>
+                if (fields.find(_.name == fieldName).exists(!_.mutable))
+                  reportError(i"assignment to immutable record field $fieldName")
+
+              case _ =>
+                // ok (NothingType) or IRChecker will complain.
+            }
+
+            @tailrec
+            def check(lhs: Tree): Unit = lhs match {
+              case RecordSelect(inner, _) => check(inner)
+              case _: VarRef              => // ok
+
+              case lhs =>
+                reportError(i"Assignment to RecordSelect of illegal tree: ${lhs.getClass.getName}")
+            }
+
+            check(record)
+
           case _:Select | _:JSPrivateSelect | _:SelectStatic |
-              _:ArraySelect | _:RecordSelect | _:JSSelect | _:JSSuperSelect |
+              _:ArraySelect | _:JSSelect | _:JSSuperSelect |
               _:JSGlobalRef =>
         }
 
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/checker/ClassDefCheckerTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/checker/ClassDefCheckerTest.scala
index 1d338034d8..78e4e1dd2c 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/checker/ClassDefCheckerTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/checker/ClassDefCheckerTest.scala
@@ -709,6 +709,14 @@ class ClassDefCheckerTest {
     testIsInstanceOfError(ArrayType(ArrayTypeRef(IntRef, 1), nullable = true))
     testAsInstanceOfError(ArrayType(ArrayTypeRef(IntRef, 1), nullable = false))
   }
+
+  @Test
+  def assignRecordSelect(): Unit = {
+    assertError(
+        mainTestClassDef(Assign(RecordSelect(int(5), "i")(IntType), int(6))),
+        "Assignment to RecordSelect of illegal tree: org.scalajs.ir.Trees$IntLiteral",
+        allowTransients = true)
+  }
 }
 
 private object ClassDefCheckerTest {

From ad69956d977c08c0bde215aac7e5493a5baeec5f Mon Sep 17 00:00:00 2001
From: Tobias Schlatter <tobias@meisch.ch>
Date: Sat, 16 Nov 2024 15:27:34 +0100
Subject: [PATCH 212/298] IRCheck Records

---
 .../scalajs/linker/checker/IRChecker.scala    | 35 +++++++++++++--
 .../org/scalajs/linker/IRCheckerTest.scala    | 44 +++++++++++++++++++
 .../linker/testutils/TestIRBuilder.scala      |  4 ++
 3 files changed, 79 insertions(+), 4 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala b/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
index fac0022dc3..125462cef3 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
@@ -737,11 +737,38 @@ private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter,
           override def traverse(tree: Tree): Unit = typecheck(tree, env)
         })
 
-      case _: RecordSelect if postOptimizer =>
-        // TODO
+      case RecordSelect(record, SimpleFieldIdent(fieldName)) if postOptimizer =>
+        record.tpe match {
+          case NothingType => // ok
+
+          case RecordType(fields) =>
+            fields.find(_.name == fieldName) match {
+              case Some(field) =>
+                if (tree.tpe != field.tpe)
+                  reportError(i"Record select of field type ${field.tpe} typed as ${tree.tpe}")
+
+              case None =>
+                reportError(i"Record select of non-existent field: $fieldName")
+            }
+
+          case tpe =>
+            reportError(i"Record type expected but $tpe found")
+        }
 
-      case _: RecordValue if postOptimizer =>
-        // TODO
+        typecheck(record, env)
+
+      case RecordValue(RecordType(fields), elems) if postOptimizer =>
+        if (fields.size == elems.size) {
+          for ((field, elem) <- fields.zip(elems))
+            typecheckExpect(elem, env, field.tpe)
+        } else {
+          reportError(
+              "Mismatched size for record fields / elements: " +
+              i"${fields.size} fields vs ${elems.size} elements")
+
+          for (elem <- elems)
+            typecheck(elem, env)
+        }
 
       case _:RecordSelect | _:RecordValue | _:Transient | _:JSSuperConstructorCall =>
         reportError("invalid tree")
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/IRCheckerTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/IRCheckerTest.scala
index bc7d7e1da1..a0333eccf1 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/IRCheckerTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/IRCheckerTest.scala
@@ -349,6 +349,50 @@ class IRCheckerTest {
     testLinkNoIRError(classDefs, MainTestModuleInitializers, postOptimizer = true)
   }
 
+  @Test
+  def badRecordSelect(): AsyncResult = await {
+    val recordValue = RecordValue(
+      RecordType(List(
+        RecordType.Field("i", NON, IntType, false),
+        RecordType.Field("s", NON, StringType, false)
+      )),
+      List(int(1), str("foo")))
+
+    val classDefs = Seq(
+      mainTestClassDef(Block(
+        RecordSelect(recordValue, "i")(StringType),
+        RecordSelect(recordValue, "x")(StringType)
+      ))
+    )
+
+    for {
+      log <- testLinkIRErrors(classDefs, MainTestModuleInitializers, postOptimizer = true)
+    } yield {
+      log.assertContainsError("Record select of field type int typed as string")
+      log.assertContainsError("Record select of non-existent field: x")
+    }
+  }
+
+  @Test
+  def badRecordValue(): AsyncResult = await {
+    val classDefs = Seq(
+      mainTestClassDef(Block(
+        RecordValue(RecordType(Nil), List(int(1))),
+        RecordValue(
+            RecordType(List(RecordType.Field("i", NON, IntType, false))),
+            List(str("foo"))
+        )
+      ))
+    )
+
+    for {
+      log <- testLinkIRErrors(classDefs, MainTestModuleInitializers, postOptimizer = true)
+    } yield {
+      log.assertContainsError("Mismatched size for record fields / elements: 0 fields vs 1 elements")
+      log.assertContainsError("int expected but string found")
+    }
+  }
+
 }
 
 object IRCheckerTest {
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/testutils/TestIRBuilder.scala b/linker/shared/src/test/scala/org/scalajs/linker/testutils/TestIRBuilder.scala
index 295d78fd29..528dfb2fcc 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/testutils/TestIRBuilder.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/testutils/TestIRBuilder.scala
@@ -183,11 +183,15 @@ object TestIRBuilder {
     LocalIdent(LocalName(name))
   implicit def string2LabelIdent(name: String): LabelIdent =
     LabelIdent(LabelName(name))
+  implicit def string2SimpleFieldIdent(name: String): SimpleFieldIdent =
+   SimpleFieldIdent(SimpleFieldName(name))
   implicit def string2ClassIdent(name: String): ClassIdent =
     ClassIdent(ClassName(name))
 
   implicit def localName2LocalIdent(name: LocalName): LocalIdent =
     LocalIdent(name)
+  implicit def simpleFieldName2SimpleFieldIdent(name: SimpleFieldName): SimpleFieldIdent =
+    SimpleFieldIdent(name)
   implicit def fieldName2FieldIdent(name: FieldName): FieldIdent =
     FieldIdent(name)
   implicit def methodName2MethodIdent(name: MethodName): MethodIdent =

From bb4f6da3628913639a82ad371c22731d9b2347f5 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Wed, 13 Nov 2024 13:52:01 +0100
Subject: [PATCH 213/298] Allow `Return` arg to be a `void` if the target
 `Labeled` is a `void`.

Previously, even if the target label of a `Return` declared a
`void` result type, the argument to the `Return` had to be an
expression, with a non-`void` type. Because of that rule, we
generated fake `Undefined()` arguments to the `Return`s.

In this commit, we remove that restriction. This simplifies the IR
specification and removes some ad hoc code paths to generate the
fake `Undefined()`. We do have to add some handling in the JS
function emitter. The Wasm function emitter requires no change.

The changes in `doReturnToLabel()` are necessary to maintain the
status quo in terms of the emitted JS. My understanding is that
before, we would get a lot of `Block(stats, Return(Undefined))`
which are now `Return(Block(stats))`. If the `stats` contain `If`s
and other branches, the new `Return` can be pushed down a lot more.
When it wasn't pushed down, we would have regular fall-through
behavior without `js.Break`s. Now with the `Return`s pushed down,
we get a lot of `js.Break`s that are not actually necessary. The
new optimization in `doReturnToLabel()` removes them.
---
 .../org/scalajs/nscplugin/GenJSCode.scala     | 32 +++----
 .../main/scala/org/scalajs/ir/Printers.scala  |  6 +-
 .../scala/org/scalajs/ir/Transformers.scala   |  2 +-
 .../scala/org/scalajs/ir/PrintersTest.scala   |  1 +
 .../backend/emitter/FunctionEmitter.scala     | 93 ++++++++++++-------
 .../scalajs/linker/checker/IRChecker.scala    |  6 +-
 .../frontend/optimizer/OptimizerCore.scala    |  9 +-
 .../org/scalajs/linker/OptimizerTest.scala    | 46 ++++-----
 8 files changed, 109 insertions(+), 86 deletions(-)

diff --git a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
index 81cfa6df15..d1b75dab51 100644
--- a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
+++ b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
@@ -2565,10 +2565,9 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
           }
 
         case Return(expr) =>
-          js.Return(toIRType(expr.tpe) match {
-            case jstpe.VoidType => js.Block(genStat(expr), js.Undefined())
-            case _              => genExpr(expr)
-          }, getEnclosingReturnLabel())
+          js.Return(
+              genStatOrExpr(expr, isStat = toIRType(expr.tpe) == jstpe.VoidType),
+              getEnclosingReturnLabel())
 
         case t: Try =>
           genTry(t, isStat)
@@ -2882,7 +2881,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
      *  are transformed into
      *  {{{
      *  ...labelParams = ...args;
-     *  return@labelName (void 0)
+     *  return@labelName;
      *  }}}
      *
      *  This is always correct, so it can handle arbitrary labels and jumps
@@ -2943,7 +2942,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
             js.While(js.BooleanLiteral(true), {
               js.Labeled(labelIdent, jstpe.VoidType, {
                 if (isStat)
-                  js.Block(transformedRhs, js.Return(js.Undefined(), blockLabelIdent))
+                  js.Block(transformedRhs, js.Return(js.Skip(), blockLabelIdent))
                 else
                   js.Return(transformedRhs, blockLabelIdent)
               })
@@ -3454,7 +3453,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
           val paramSyms = info.paramSyms
           assertArgCountMatches(paramSyms.size)
 
-          val jump = js.Return(js.Undefined(), labelIdent)
+          val jump = js.Return(js.Skip(), labelIdent)
 
           if (args.isEmpty) {
             // fast path, applicable notably to loops and case labels
@@ -3914,7 +3913,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
       def genJumpToElseClause(implicit pos: ir.Position): js.Tree = {
         if (optElseClauseLabel.isEmpty)
           optElseClauseLabel = Some(freshLabelIdent("default"))
-        js.Return(js.Undefined(), optElseClauseLabel.get)
+        js.Return(js.Skip(), optElseClauseLabel.get)
       }
 
       for (caze @ CaseDef(pat, guard, body) <- cases) {
@@ -4036,9 +4035,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
         val matchResultLabel = freshLabelIdent("matchResult")
         val patchedClauses = for ((alts, body) <- clauses) yield {
           implicit val pos = body.pos
-          val newBody =
-            if (isStat) js.Block(body, js.Return(js.Undefined(), matchResultLabel))
-            else js.Return(body, matchResultLabel)
+          val newBody = js.Return(body, matchResultLabel)
           (alts, newBody)
         }
         js.Labeled(matchResultLabel, resultType, js.Block(List(
@@ -4140,12 +4137,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
             val translatedMatch = genTranslatedMatch(cases, matchEnd)
             val genMore = genBlockWithCaseLabelDefs(more, isStat)
             val label = getEnclosingReturnLabel()
-            if (translatedMatch.tpe == jstpe.VoidType) {
-              // Could not actually reproduce this, but better be safe than sorry
-              translatedMatch :: js.Return(js.Undefined(), label) :: genMore
-            } else {
-              js.Return(translatedMatch, label) :: genMore
-            }
+            js.Return(translatedMatch, label) :: genMore
 
           // Otherwise, there is no matchEnd, only consecutive cases
           case Nil =>
@@ -4396,21 +4388,21 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
         translatedBody match {
           case js.Block(stats) =>
             val (stats1, testAndStats2) = stats.span {
-              case js.If(_, js.Return(js.Undefined(), `label`), js.Skip()) =>
+              case js.If(_, js.Return(_, `label`), js.Skip()) =>
                 false
               case _ =>
                 true
             }
 
             testAndStats2 match {
-              case js.If(cond, _, _) :: stats2 =>
+              case js.If(cond, js.Return(returnedValue, _), _) :: stats2 =>
                 val notCond = cond match {
                   case js.UnaryOp(js.UnaryOp.Boolean_!, notCond) =>
                     notCond
                   case _ =>
                     js.UnaryOp(js.UnaryOp.Boolean_!, cond)
                 }
-                js.Block(stats1 :+ js.If(notCond, js.Block(stats2), js.Skip())(jstpe.VoidType))
+                js.Block(stats1 :+ js.If(notCond, js.Block(stats2), returnedValue)(jstpe.VoidType))
 
               case _ :: _ =>
                 throw new AssertionError("unreachable code")
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala
index e245cffeb4..b5bfccc64e 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala
@@ -189,8 +189,10 @@ object Printers {
         case Return(expr, label) =>
           print("return@")
           print(label)
-          print(" ")
-          print(expr)
+          if (!expr.isInstanceOf[Skip]) {
+            print(" ")
+            print(expr)
+          }
 
         case If(cond, BooleanLiteral(true), elsep) =>
           print(cond)
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Transformers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Transformers.scala
index 2fcc5bd1ee..10f490225b 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Transformers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Transformers.scala
@@ -58,7 +58,7 @@ object Transformers {
           Assign(transformExpr(lhs).asInstanceOf[AssignLhs], transformExpr(rhs))
 
         case Return(expr, label) =>
-          Return(transformExpr(expr), label)
+          Return(transformExpr(expr), label) // pessimistic; maybe `expr` is actually a statement
 
         case If(cond, thenp, elsep) =>
           If(transformExpr(cond), transform(thenp, isStat),
diff --git a/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala b/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala
index a2e7a2d51f..980b7c9bc3 100644
--- a/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala
+++ b/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala
@@ -154,6 +154,7 @@ class PrintersTest {
 
   @Test def printReturn(): Unit = {
     assertPrintEquals("return@lab 5", Return(i(5), "lab"))
+    assertPrintEquals("return@lab", Return(Skip(), "lab"))
   }
 
   @Test def printIf(): Unit = {
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
index 546bbb1e3b..834ec7a554 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
@@ -1538,25 +1538,30 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
 
       def doReturnToLabel(l: LabelIdent): js.Tree = {
         val newLhs = env.lhsForLabeledExpr(l)
-        val body = pushLhsInto(newLhs, rhs, Set.empty)
         if (newLhs.hasNothingType) {
           /* A touch of peephole dead code elimination.
            * This is actually necessary to avoid dangling breaks to eliminated
            * labels, as in issue #2307.
            */
-          body
+          pushLhsInto(newLhs, rhs, tailPosLabels)
         } else if (tailPosLabels.contains(l.name)) {
-          body
-        } else if (env.isDefaultBreakTarget(l.name)) {
-          js.Block(body, js.Break(None))
-        } else if (env.isDefaultContinueTarget(l.name)) {
-          js.Block(body, js.Continue(None))
+          pushLhsInto(newLhs, rhs, tailPosLabels)
         } else {
-          usedLabels += l.name
-          val transformedLabel = Some(transformLabelIdent(l))
-          val jump =
-            if (env.isLabelTurnedIntoContinue(l.name)) js.Continue(transformedLabel)
-            else js.Break(transformedLabel)
+          val body = pushLhsInto(newLhs, rhs, Set.empty)
+
+          val jump = if (env.isDefaultBreakTarget(l.name)) {
+            js.Break(None)
+          } else if (env.isDefaultContinueTarget(l.name)) {
+            js.Continue(None)
+          } else {
+            usedLabels += l.name
+            val transformedLabel = Some(transformLabelIdent(l))
+            if (env.isLabelTurnedIntoContinue(l.name))
+              js.Continue(transformedLabel)
+            else
+              js.Break(transformedLabel)
+          }
+
           js.Block(body, jump)
         }
       }
@@ -1597,7 +1602,10 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
             case Lhs.Assign(lhs) =>
               doAssign(lhs, rhs)
             case Lhs.ReturnFromFunction =>
-              js.Return(transformExpr(rhs, env.expectedReturnType))
+              if (env.expectedReturnType == VoidType)
+                js.Block(transformStat(rhs, tailPosLabels = Set.empty), js.Return(js.Undefined()))
+              else
+                js.Return(transformExpr(rhs, env.expectedReturnType))
             case Lhs.Return(l) =>
               doReturnToLabel(l)
             case Lhs.Throw =>
@@ -2016,29 +2024,44 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
             redo(CreateJSClass(className, newCaptureValues))(env)
           }
 
-        case _ =>
-          if (lhs == Lhs.Discard) {
-            /* Go "back" to transformStat() after having dived into
-             * expression statements. Remember that Lhs.Discard is a trick that
-             * we use to "add" all the code of pushLhsInto() to transformStat().
-             */
-            rhs match {
-              case _:Skip | _:VarDef | _:Assign | _:While |
-                  _:Debugger | _:JSSuperConstructorCall | _:JSDelete |
-                  _:StoreModule | Transient(_:SystemArrayCopy) =>
-                transformStat(rhs, tailPosLabels)
-              case _ =>
-                throw new IllegalArgumentException(
-                    "Illegal tree in JSDesugar.pushLhsInto():\n" +
-                    "lhs = " + lhs + "\n" +
-                    "rhs = " + rhs + " of class " + rhs.getClass)
-            }
-          } else {
-            throw new IllegalArgumentException(
-                "Illegal tree in JSDesugar.pushLhsInto():\n" +
-                "lhs = " + lhs + "\n" +
-                "rhs = " + rhs + " of class " + rhs.getClass)
+        // Statement-only trees
+
+        case _:Skip | _:VarDef | _:Assign | _:While | _:Debugger |
+            _:JSSuperConstructorCall | _:JSDelete | _:StoreModule |
+            Transient(_:SystemArrayCopy) =>
+          /* Go "back" to transformStat() after having dived into
+           * expression statements. This can only happen for Lhs.Discard and
+           * for Lhs.Return's whose target is a statement.
+           */
+          lhs match {
+            case Lhs.Discard =>
+              transformStat(rhs, tailPosLabels)
+            case Lhs.ReturnFromFunction =>
+              /* If we get here, it is because desugarToFunctionInternal()
+               * found a top-level Labeled and eliminated it. Therefore, unless
+               * we're mistaken, by construction we cannot be in tail position
+               * of the whole function (otherwise doReturnToLabel would have
+               * eliminated the lhs). That means there is no point trying to
+               * avoid the `js.Return(js.Undefined())`.
+               */
+              js.Block(
+                  transformStat(rhs, tailPosLabels = Set.empty),
+                  js.Return(js.Undefined()))
+            case Lhs.Return(l) =>
+              doReturnToLabel(l)
+
+            case _:Lhs.VarDef | _:Lhs.Assign | Lhs.Throw =>
+              throw new IllegalArgumentException(
+                  "Illegal tree in FunctionEmitter.pushLhsInto():\n" +
+                  "lhs = " + lhs + "\n" +
+                  "rhs = " + rhs + " of class " + rhs.getClass)
           }
+
+        case _ =>
+          throw new IllegalArgumentException(
+              "Illegal tree in FunctionEmitter.pushLhsInto():\n" +
+              "lhs = " + lhs + "\n" +
+              "rhs = " + rhs + " of class " + rhs.getClass)
       })
     }
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala b/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
index fac0022dc3..51575cd744 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
@@ -304,11 +304,7 @@ private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter,
         typecheckExpect(rhs, env, expectedRhsTpe)
 
       case Return(expr, label) =>
-        val returnType = env.returnTypes(label.name)
-        if (returnType == VoidType)
-          typecheckExpr(expr, env)
-        else
-          typecheckExpect(expr, env, returnType)
+        typecheckExpect(expr, env, env.returnTypes(label.name))
 
       case If(cond, thenp, elsep) =>
         val tpe = tree.tpe
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
index fe7d8c03a8..0f519afdb2 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
@@ -383,7 +383,11 @@ private[optimizer] abstract class OptimizerCore(
       case Return(expr, label) =>
         val info = scope.env.labelInfos(label.name)
         val newLabel = LabelIdent(info.newName)
-        if (!info.acceptRecords) {
+        if (info.isStat) {
+          val newExpr = transformStat(expr)
+          info.returnedTypes.value ::= (VoidType, RefinedType.NoRefinedType)
+          Return(newExpr, newLabel)
+        } else if (!info.acceptRecords) {
           val newExpr = transformExpr(expr)
           info.returnedTypes.value ::= (newExpr.tpe, RefinedType(newExpr.tpe))
           Return(newExpr, newLabel)
@@ -5170,7 +5174,7 @@ private[optimizer] abstract class OptimizerCore(
       }
     }
 
-    val info = new LabelInfo(newLabel, acceptRecords = usePreTransform,
+    val info = new LabelInfo(newLabel, isStat, acceptRecords = usePreTransform,
         returnedTypes = newSimpleState(Nil))
     val bodyScope = scope.withEnv(scope.env.withLabelInfo(oldLabelName, info))
 
@@ -6011,6 +6015,7 @@ private[optimizer] object OptimizerCore {
 
   private final class LabelInfo(
       val newName: LabelName,
+      val isStat: Boolean,
       val acceptRecords: Boolean,
       /** (actualType, originalType), actualType can be a RecordType. */
       val returnedTypes: SimpleState[List[(Type, RefinedType)]])
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/OptimizerTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/OptimizerTest.scala
index 0a77c1414c..08838c0627 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/OptimizerTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/OptimizerTest.scala
@@ -272,28 +272,32 @@ class OptimizerTest {
     val matchAlts1 = LabelIdent("matchAlts1")
     val matchAlts2 = LabelIdent("matchAlts2")
 
-    val classDefs = Seq(
-        mainTestClassDef(Block(
-            Labeled(matchResult1, VoidType, Block(
-                VarDef(x1, NON, AnyType, mutable = false, Null()),
-                Labeled(matchAlts1, VoidType, Block(
-                    Labeled(matchAlts2, VoidType, Block(
-                        If(IsInstanceOf(VarRef(x1)(AnyType), ClassType(BoxedIntegerClass, nullable = false)), {
-                          Return(Undefined(), matchAlts2)
-                        }, Skip())(VoidType),
-                        If(IsInstanceOf(VarRef(x1)(AnyType), ClassType(BoxedStringClass, nullable = false)), {
-                          Return(Undefined(), matchAlts2)
-                        }, Skip())(VoidType),
-                        Return(Undefined(), matchAlts1)
-                    )),
-                    Return(Undefined(), matchResult1)
-                )),
-                Throw(New("java.lang.Exception", NoArgConstructorName, Nil))
-            ))
-        ))
-    )
+    val results = for (voidReturnArgument <- List(Undefined(), Skip())) yield {
+      val classDefs = Seq(
+          mainTestClassDef(Block(
+              Labeled(matchResult1, VoidType, Block(
+                  VarDef(x1, NON, AnyType, mutable = false, Null()),
+                  Labeled(matchAlts1, VoidType, Block(
+                      Labeled(matchAlts2, VoidType, Block(
+                          If(IsInstanceOf(VarRef(x1)(AnyType), ClassType(BoxedIntegerClass, nullable = false)), {
+                            Return(voidReturnArgument, matchAlts2)
+                          }, Skip())(VoidType),
+                          If(IsInstanceOf(VarRef(x1)(AnyType), ClassType(BoxedStringClass, nullable = false)), {
+                            Return(voidReturnArgument, matchAlts2)
+                          }, Skip())(VoidType),
+                          Return(voidReturnArgument, matchAlts1)
+                      )),
+                      Return(voidReturnArgument, matchResult1)
+                  )),
+                  Throw(New("java.lang.Exception", NoArgConstructorName, Nil))
+              ))
+          ))
+      )
+
+      testLink(classDefs, MainTestModuleInitializers)
+    }
 
-    testLink(classDefs, MainTestModuleInitializers)
+    Future.sequence(results)
   }
 
   @Test

From 0e9dfa69312ef0edbfdb3927d0154284956ff5ac Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Mon, 18 Nov 2024 17:52:02 +0100
Subject: [PATCH 214/298] Recognize more methods as anonfun's that should have
 the `inline` hint.

When a `$anonfun` method gets an expanded name---typically because
it must be made non-private---, its name receives a new *prefix*.
That prevented the previous `startsWith` test to recognize them as
the methods behind anonymous functions. We now use a `containsName`
test to recognize them, so that we can give them the `inline` hint.
---
 .../src/main/scala/org/scalajs/nscplugin/GenJSCode.scala    | 2 +-
 .../src/test/scala/org/scalajs/linker/LibrarySizeTest.scala | 6 +++---
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
index d1b75dab51..9839b71954 100644
--- a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
+++ b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
@@ -2068,7 +2068,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
         } else {
           val shouldMarkInline = {
             sym.hasAnnotation(InlineAnnotationClass) ||
-            sym.name.startsWith(nme.ANON_FUN_NAME) ||
+            sym.name.containsName(nme.ANON_FUN_NAME) ||
             adHocInlineMethods.contains(sym.fullName)
           }
 
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/LibrarySizeTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/LibrarySizeTest.scala
index a9fbf49876..137d8e7400 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/LibrarySizeTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/LibrarySizeTest.scala
@@ -70,9 +70,9 @@ class LibrarySizeTest {
     )
 
     testLinkedSizes(
-      expectedFastLinkSize = 147459,
-      expectedFullLinkSizeWithoutClosure = 85718,
-      expectedFullLinkSizeWithClosure = 21495,
+      expectedFastLinkSize = 147046,
+      expectedFullLinkSizeWithoutClosure = 85355,
+      expectedFullLinkSizeWithClosure = 21492,
       classDefs,
       moduleInitializers = MainTestModuleInitializers
     )

From 5e9956bfd93fa2567e6207a5d34cb6118fc11eaa Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Mon, 18 Nov 2024 13:23:21 +0100
Subject: [PATCH 215/298] Use explicit 0-arg functions instead of by-name
 params in javalib.

---
 .../src/main/scala/java/io/PrintStream.scala  | 20 ++++++++---------
 .../src/main/scala/java/io/PrintWriter.scala  | 20 ++++++++---------
 .../src/main/scala/java/lang/ClassValue.scala |  2 +-
 javalib/src/main/scala/java/lang/Float.scala  | 10 ++++-----
 .../src/main/scala/java/lang/StackTrace.scala |  8 +++----
 javalib/src/main/scala/java/lang/System.scala |  4 ++--
 javalib/src/main/scala/java/lang/Utils.scala  | 22 +++++++++----------
 .../src/main/scala/java/math/BigInteger.scala | 11 ++++------
 .../main/scala/java/nio/charset/Charset.scala |  2 +-
 .../scala/java/nio/charset/CoderResult.scala  |  4 ++--
 .../main/scala/java/util/AbstractMap.scala    |  2 +-
 .../src/main/scala/java/util/Formatter.scala  | 14 ++++++------
 .../src/main/scala/java/util/ScalaOps.scala   |  6 ++---
 javalib/src/main/scala/java/util/Timer.scala  | 10 ++++-----
 .../src/main/scala/java/util/TimerTask.scala  |  4 ++--
 .../java/util/regex/IndicesBuilder.scala      |  4 ++--
 .../main/scala/java/util/regex/Matcher.scala  |  8 +++----
 .../main/scala/java/util/regex/Pattern.scala  |  2 +-
 .../java/util/regex/PatternCompiler.scala     |  6 ++---
 19 files changed, 78 insertions(+), 81 deletions(-)

diff --git a/javalib/src/main/scala/java/io/PrintStream.scala b/javalib/src/main/scala/java/io/PrintStream.scala
index d6141609c3..9b61270d43 100644
--- a/javalib/src/main/scala/java/io/PrintStream.scala
+++ b/javalib/src/main/scala/java/io/PrintStream.scala
@@ -79,9 +79,9 @@ class PrintStream private (_out: OutputStream, autoFlush: Boolean,
   private var errorFlag: Boolean = false
 
   override def flush(): Unit =
-    ensureOpenAndTrapIOExceptions(out.flush())
+    ensureOpenAndTrapIOExceptions(() => out.flush())
 
-  override def close(): Unit = trapIOExceptions {
+  override def close(): Unit = trapIOExceptions { () =>
     if (!closing) {
       closing = true
       encoder.close()
@@ -133,7 +133,7 @@ class PrintStream private (_out: OutputStream, autoFlush: Boolean,
    */
 
   override def write(b: Int): Unit = {
-    ensureOpenAndTrapIOExceptions {
+    ensureOpenAndTrapIOExceptions { () =>
       out.write(b)
       if (autoFlush && b == '\n')
         flush()
@@ -141,7 +141,7 @@ class PrintStream private (_out: OutputStream, autoFlush: Boolean,
   }
 
   override def write(buf: Array[Byte], off: Int, len: Int): Unit = {
-    ensureOpenAndTrapIOExceptions {
+    ensureOpenAndTrapIOExceptions { () =>
       out.write(buf, off, len)
       if (autoFlush)
         flush()
@@ -157,17 +157,17 @@ class PrintStream private (_out: OutputStream, autoFlush: Boolean,
   def print(s: String): Unit   = printString(if (s == null) "null" else s)
   def print(obj: AnyRef): Unit = printString(String.valueOf(obj))
 
-  private def printString(s: String): Unit = ensureOpenAndTrapIOExceptions {
+  private def printString(s: String): Unit = ensureOpenAndTrapIOExceptions { () =>
     encoder.write(s)
     encoder.flushBuffer()
   }
 
-  def print(s: Array[Char]): Unit = ensureOpenAndTrapIOExceptions {
+  def print(s: Array[Char]): Unit = ensureOpenAndTrapIOExceptions { () =>
     encoder.write(s)
     encoder.flushBuffer()
   }
 
-  def println(): Unit = ensureOpenAndTrapIOExceptions {
+  def println(): Unit = ensureOpenAndTrapIOExceptions { () =>
     encoder.write('\n') // In Scala.js the line separator is always LF
     encoder.flushBuffer()
     if (autoFlush)
@@ -214,15 +214,15 @@ class PrintStream private (_out: OutputStream, autoFlush: Boolean,
     this
   }
 
-  @inline private[this] def trapIOExceptions(body: => Unit): Unit = {
+  @inline private[this] def trapIOExceptions(body: () => Unit): Unit = {
     try {
-      body
+      body()
     } catch {
       case _: IOException => setError()
     }
   }
 
-  @inline private[this] def ensureOpenAndTrapIOExceptions(body: => Unit): Unit = {
+  @inline private[this] def ensureOpenAndTrapIOExceptions(body: () => Unit): Unit = {
     if (closed) setError()
     else trapIOExceptions(body)
   }
diff --git a/javalib/src/main/scala/java/io/PrintWriter.scala b/javalib/src/main/scala/java/io/PrintWriter.scala
index 5e3facf333..e03ddb7d2c 100644
--- a/javalib/src/main/scala/java/io/PrintWriter.scala
+++ b/javalib/src/main/scala/java/io/PrintWriter.scala
@@ -41,9 +41,9 @@ class PrintWriter(protected[io] var out: Writer,
   private var errorFlag: Boolean = false
 
   def flush(): Unit =
-    ensureOpenAndTrapIOExceptions(out.flush())
+    ensureOpenAndTrapIOExceptions(() => out.flush())
 
-  def close(): Unit = trapIOExceptions {
+  def close(): Unit = trapIOExceptions { () =>
     if (!closed) {
       flush()
       closed = true
@@ -76,19 +76,19 @@ class PrintWriter(protected[io] var out: Writer,
   protected[io] def clearError(): Unit = errorFlag = false
 
   override def write(c: Int): Unit =
-    ensureOpenAndTrapIOExceptions(out.write(c))
+    ensureOpenAndTrapIOExceptions(() => out.write(c))
 
   override def write(buf: Array[Char], off: Int, len: Int): Unit =
-    ensureOpenAndTrapIOExceptions(out.write(buf, off, len))
+    ensureOpenAndTrapIOExceptions(() => out.write(buf, off, len))
 
   override def write(buf: Array[Char]): Unit =
-    ensureOpenAndTrapIOExceptions(out.write(buf))
+    ensureOpenAndTrapIOExceptions(() => out.write(buf))
 
   override def write(s: String, off: Int, len: Int): Unit =
-    ensureOpenAndTrapIOExceptions(out.write(s, off, len))
+    ensureOpenAndTrapIOExceptions(() => out.write(s, off, len))
 
   override def write(s: String): Unit =
-    ensureOpenAndTrapIOExceptions(out.write(s))
+    ensureOpenAndTrapIOExceptions(() => out.write(s))
 
   def print(b: Boolean): Unit     = write(String.valueOf(b))
   def print(c: Char): Unit        = write(c)
@@ -147,15 +147,15 @@ class PrintWriter(protected[io] var out: Writer,
     this
   }
 
-  @inline private[this] def trapIOExceptions(body: => Unit): Unit = {
+  @inline private[this] def trapIOExceptions(body: () => Unit): Unit = {
     try {
-      body
+      body()
     } catch {
       case _: IOException => setError()
     }
   }
 
-  @inline private[this] def ensureOpenAndTrapIOExceptions(body: => Unit): Unit = {
+  @inline private[this] def ensureOpenAndTrapIOExceptions(body: () => Unit): Unit = {
     if (closed) setError()
     else trapIOExceptions(body)
   }
diff --git a/javalib/src/main/scala/java/lang/ClassValue.scala b/javalib/src/main/scala/java/lang/ClassValue.scala
index 74f91999ca..0ab92d37cb 100644
--- a/javalib/src/main/scala/java/lang/ClassValue.scala
+++ b/javalib/src/main/scala/java/lang/ClassValue.scala
@@ -50,7 +50,7 @@ abstract class ClassValue[T] protected () {
 
   def get(`type`: Class[_]): T = {
     if (useJSMap) {
-      mapGetOrElseUpdate(jsMap, `type`)(computeValue(`type`))
+      mapGetOrElseUpdate(jsMap, `type`)(() => computeValue(`type`))
     } else {
       /* We first perform `get`, and if the result is null, we use
        * `containsKey` to disambiguate a present null from an absent key.
diff --git a/javalib/src/main/scala/java/lang/Float.scala b/javalib/src/main/scala/java/lang/Float.scala
index 6bb6bb4565..c9c6ea2e84 100644
--- a/javalib/src/main/scala/java/lang/Float.scala
+++ b/javalib/src/main/scala/java/lang/Float.scala
@@ -122,14 +122,14 @@ object Float {
     } else if (undefOrIsDefined(groups(4))) {
       // Decimal notation
       val fullNumberStr = undefOrForceGet(groups(4))
-      val integralPartStr = undefOrGetOrElse(groups(5))("")
-      val fractionalPartStr = undefOrGetOrElse(groups(6))("") + undefOrGetOrElse(groups(7))("")
-      val exponentStr = undefOrGetOrElse(groups(8))("0")
+      val integralPartStr = undefOrGetOrElse(groups(5))(() => "")
+      val fractionalPartStr = undefOrGetOrElse(groups(6))(() => "") + undefOrGetOrElse(groups(7))(() => "")
+      val exponentStr = undefOrGetOrElse(groups(8))(() => "0")
       parseFloatDecimal(fullNumberStr, integralPartStr, fractionalPartStr, exponentStr)
     } else {
       // Hexadecimal notation
-      val integralPartStr = undefOrGetOrElse(groups(10))("")
-      val fractionalPartStr = undefOrGetOrElse(groups(11))("") + undefOrGetOrElse(groups(12))("")
+      val integralPartStr = undefOrGetOrElse(groups(10))(() => "")
+      val fractionalPartStr = undefOrGetOrElse(groups(11))(() => "") + undefOrGetOrElse(groups(12))(() => "")
       val binaryExpStr = undefOrForceGet(groups(13))
       parseFloatHexadecimal(integralPartStr, fractionalPartStr, binaryExpStr)
     }
diff --git a/javalib/src/main/scala/java/lang/StackTrace.scala b/javalib/src/main/scala/java/lang/StackTrace.scala
index 76b3d067e7..31960903b9 100644
--- a/javalib/src/main/scala/java/lang/StackTrace.scala
+++ b/javalib/src/main/scala/java/lang/StackTrace.scala
@@ -126,7 +126,7 @@ private[lang] object StackTrace {
           trace.push(new StackTraceElement(classAndMethodName(0),
               classAndMethodName(1), undefOrForceGet(mtch(2)),
               parseInt(undefOrForceGet(mtch(3))),
-              undefOrFold(mtch(4))(-1)(parseInt(_))))
+              undefOrFold(mtch(4))(() => -1)(parseInt(_))))
         } else {
           // just in case
           // (explicitly use the constructor with column number so that STE has an inlineable init)
@@ -413,7 +413,7 @@ private[lang] object StackTrace {
     while (i < len) {
       val mtch = lineRE.exec(lines(i))
       if (mtch ne null) {
-        val fnName = undefOrGetOrElse(mtch(3))("{anonymous}")
+        val fnName = undefOrGetOrElse(mtch(3))(() => "{anonymous}")
         result.push(
             fnName + "()@" + undefOrForceGet(mtch(2)) + ":" +
             undefOrForceGet(mtch(1))
@@ -438,7 +438,7 @@ private[lang] object StackTrace {
     while (i < len) {
       val mtch = lineRE.exec(lines(i))
       if (mtch ne null) {
-        val fnName = undefOrFold(mtch(1))("global code")(_ + "()")
+        val fnName = undefOrFold(mtch(1))(() => "global code")(_ + "()")
         result.push(fnName + "@" + undefOrForceGet(mtch(2)) + ":" + undefOrForceGet(mtch(3)))
       }
       i += 1
@@ -458,7 +458,7 @@ private[lang] object StackTrace {
       val mtch = lineRE.exec(lines(i))
       if (mtch ne null) {
         val location = undefOrForceGet(mtch(4)) + ":" + undefOrForceGet(mtch(1)) + ":" + undefOrForceGet(mtch(2))
-        val fnName0 = undefOrGetOrElse(mtch(2))("global code")
+        val fnName0 = undefOrGetOrElse(mtch(2))(() => "global code")
         val fnName = fnName0
           .jsReplace("""<anonymous function: (\S+)>""".re, "$1")
           .jsReplace("""<anonymous function>""".re, "{anonymous}")
diff --git a/javalib/src/main/scala/java/lang/System.scala b/javalib/src/main/scala/java/lang/System.scala
index 8075a6ac70..4938d237ca 100644
--- a/javalib/src/main/scala/java/lang/System.scala
+++ b/javalib/src/main/scala/java/lang/System.scala
@@ -233,11 +233,11 @@ object System {
     }
 
     def getProperty(key: String): String =
-      if (dict ne null) dictGetOrElse(dict, key)(null)
+      if (dict ne null) dictGetOrElse(dict, key)(() => null)
       else properties.getProperty(key)
 
     def getProperty(key: String, default: String): String =
-      if (dict ne null) dictGetOrElse(dict, key)(default)
+      if (dict ne null) dictGetOrElse(dict, key)(() => default)
       else properties.getProperty(key, default)
 
     def clearProperty(key: String): String =
diff --git a/javalib/src/main/scala/java/lang/Utils.scala b/javalib/src/main/scala/java/lang/Utils.scala
index b57bc2a520..6e0a535831 100644
--- a/javalib/src/main/scala/java/lang/Utils.scala
+++ b/javalib/src/main/scala/java/lang/Utils.scala
@@ -34,9 +34,9 @@ private[java] object Utils {
     x.asInstanceOf[A]
 
   @inline
-  def undefOrGetOrElse[A](x: js.UndefOr[A])(default: => A): A =
+  def undefOrGetOrElse[A](x: js.UndefOr[A])(default: () => A): A =
     if (undefOrIsDefined(x)) undefOrForceGet(x)
-    else default
+    else default()
 
   @inline
   def undefOrGetOrNull[A >: Null](x: js.UndefOr[A]): A =
@@ -50,9 +50,9 @@ private[java] object Utils {
   }
 
   @inline
-  def undefOrFold[A, B](x: js.UndefOr[A])(default: => B)(f: A => B): B =
+  def undefOrFold[A, B](x: js.UndefOr[A])(default: () => B)(f: A => B): B =
     if (undefOrIsDefined(x)) f(undefOrForceGet(x))
-    else default
+    else default()
 
   private object Cache {
     val safeHasOwnProperty =
@@ -84,11 +84,11 @@ private[java] object Utils {
 
   @inline
   def dictGetOrElse[A](dict: js.Dictionary[_ <: A], key: String)(
-      default: => A): A = {
+      default: () => A): A = {
     if (dictContains(dict, key))
       dictRawApply(dict, key)
     else
-      default
+      default()
   }
 
   def dictGetOrElseAndRemove[A](dict: js.Dictionary[_ <: A], key: String,
@@ -139,16 +139,16 @@ private[java] object Utils {
     map.asInstanceOf[MapRaw[K, V]].set(key, value)
 
   @inline
-  def mapGetOrElse[K, V](map: js.Map[K, V], key: K)(default: => V): V = {
+  def mapGetOrElse[K, V](map: js.Map[K, V], key: K)(default: () => V): V = {
     val value = map.asInstanceOf[MapRaw[K, V]].getOrUndefined(key)
     if (!isUndefined(value) || mapHas(map, key)) value.asInstanceOf[V]
-    else default
+    else default()
   }
 
   @inline
-  def mapGetOrElseUpdate[K, V](map: js.Map[K, V], key: K)(default: => V): V = {
-    mapGetOrElse(map, key) {
-      val value = default
+  def mapGetOrElseUpdate[K, V](map: js.Map[K, V], key: K)(default: () => V): V = {
+    mapGetOrElse(map, key) { () =>
+      val value = default()
       mapSet(map, key, value)
       value
     }
diff --git a/javalib/src/main/scala/java/math/BigInteger.scala b/javalib/src/main/scala/java/math/BigInteger.scala
index dcae03d0f9..bab8c44301 100644
--- a/javalib/src/main/scala/java/math/BigInteger.scala
+++ b/javalib/src/main/scala/java/math/BigInteger.scala
@@ -124,12 +124,6 @@ object BigInteger {
       reference
   }
 
-  @inline
-  private def checkCriticalArgument(expression: Boolean, errorMessage: => String): Unit = {
-    if (!expression)
-      throw new IllegalArgumentException(errorMessage)
-  }
-
   private[math] def checkRangeBasedOnIntArrayLength(byteLength: Int): Unit = {
     if (byteLength < 0 || byteLength >= ((Int.MaxValue + 1) >>> 5))
       throw new ArithmeticException("BigInteger would overflow supported range")
@@ -221,7 +215,10 @@ class BigInteger extends Number with Comparable[BigInteger] {
 
   def this(numBits: Int, rnd: Random) = {
     this()
-    checkCriticalArgument(numBits >= 0, "numBits must be non-negative")
+
+    if (numBits < 0)
+      throw new IllegalArgumentException("numBits must be non-negative")
+
     if (numBits == 0) {
       sign = 0
       numberLength = 1
diff --git a/javalib/src/main/scala/java/nio/charset/Charset.scala b/javalib/src/main/scala/java/nio/charset/Charset.scala
index 752600eb8c..981bb16c07 100644
--- a/javalib/src/main/scala/java/nio/charset/Charset.scala
+++ b/javalib/src/main/scala/java/nio/charset/Charset.scala
@@ -80,7 +80,7 @@ object Charset {
     UTF_8
 
   def forName(charsetName: String): Charset = {
-    dictGetOrElse(CharsetMap, charsetName.toLowerCase()) {
+    dictGetOrElse(CharsetMap, charsetName.toLowerCase()) { () =>
       throw new UnsupportedCharsetException(charsetName)
     }
   }
diff --git a/javalib/src/main/scala/java/nio/charset/CoderResult.scala b/javalib/src/main/scala/java/nio/charset/CoderResult.scala
index 4cbb5a9fd0..1a4213f192 100644
--- a/javalib/src/main/scala/java/nio/charset/CoderResult.scala
+++ b/javalib/src/main/scala/java/nio/charset/CoderResult.scala
@@ -78,7 +78,7 @@ object CoderResult {
   }
 
   private def malformedForLengthImpl(length: Int): CoderResult = {
-    undefOrFold(uniqueMalformed(length)) {
+    undefOrFold(uniqueMalformed(length)) { () =>
       val result = new CoderResult(Malformed, length)
       uniqueMalformed(length) = result
       result
@@ -96,7 +96,7 @@ object CoderResult {
   }
 
   private def unmappableForLengthImpl(length: Int): CoderResult = {
-    undefOrFold(uniqueUnmappable(length)) {
+    undefOrFold(uniqueUnmappable(length)) { () =>
       val result = new CoderResult(Unmappable, length)
       uniqueUnmappable(length) = result
       result
diff --git a/javalib/src/main/scala/java/util/AbstractMap.scala b/javalib/src/main/scala/java/util/AbstractMap.scala
index df75f5ba67..00249d5911 100644
--- a/javalib/src/main/scala/java/util/AbstractMap.scala
+++ b/javalib/src/main/scala/java/util/AbstractMap.scala
@@ -94,7 +94,7 @@ abstract class AbstractMap[K, V] protected () extends java.util.Map[K, V] {
     entrySet().scalaOps.exists(entry => Objects.equals(key, entry.getKey()))
 
   def get(key: Any): V = {
-    entrySet().scalaOps.findFold(entry => Objects.equals(key, entry.getKey())) {
+    entrySet().scalaOps.findFold(entry => Objects.equals(key, entry.getKey())) { () =>
       null.asInstanceOf[V]
     } { entry =>
       entry.getValue()
diff --git a/javalib/src/main/scala/java/util/Formatter.scala b/javalib/src/main/scala/java/util/Formatter.scala
index 750bebf4c4..c8c3af05ef 100644
--- a/javalib/src/main/scala/java/util/Formatter.scala
+++ b/javalib/src/main/scala/java/util/Formatter.scala
@@ -51,9 +51,9 @@ final class Formatter private (private[this] var dest: Appendable,
   def this(a: Appendable, l: Locale) = this(a, new Formatter.LocaleLocaleInfo(l))
 
   @inline
-  private def trapIOExceptions(body: => Unit): Unit = {
+  private def trapIOExceptions(body: () => Unit): Unit = {
     try {
-      body
+      body()
     } catch {
       case th: IOException =>
         lastIOException = th
@@ -83,7 +83,7 @@ final class Formatter private (private[this] var dest: Appendable,
 
   @noinline
   private def sendToDestSlowPath(ss: js.Array[String]): Unit = {
-    trapIOExceptions {
+    trapIOExceptions { () =>
       forArrayElems(ss)(dest.append(_))
     }
   }
@@ -92,7 +92,7 @@ final class Formatter private (private[this] var dest: Appendable,
     if (!closed && (dest ne null)) {
       dest match {
         case cl: Closeable =>
-          trapIOExceptions {
+          trapIOExceptions { () =>
             cl.close()
           }
         case _ =>
@@ -106,7 +106,7 @@ final class Formatter private (private[this] var dest: Appendable,
     if (dest ne null) {
       dest match {
         case fl: Flushable =>
-          trapIOExceptions {
+          trapIOExceptions { () =>
             fl.flush()
           }
         case _ =>
@@ -335,7 +335,7 @@ final class Formatter private (private[this] var dest: Appendable,
    *  Int range.
    */
   private def parsePositiveInt(capture: js.UndefOr[String]): Int = {
-    undefOrFold(capture) {
+    undefOrFold(capture) { () =>
       -1
     } { s =>
       val x = js.Dynamic.global.parseInt(s, 10).asInstanceOf[Double]
@@ -993,7 +993,7 @@ object Formatter {
   }
 
   @inline
-  private def assert(condition: Boolean, msg: => String): Unit = {
+  private def assert(condition: Boolean, msg: String): Unit = {
     if (!condition)
       throw new AssertionError(msg)
   }
diff --git a/javalib/src/main/scala/java/util/ScalaOps.scala b/javalib/src/main/scala/java/util/ScalaOps.scala
index 32023f2ab7..6f5cb57cff 100644
--- a/javalib/src/main/scala/java/util/ScalaOps.scala
+++ b/javalib/src/main/scala/java/util/ScalaOps.scala
@@ -72,7 +72,7 @@ private[java] object ScalaOps {
     @inline def indexWhere(f: A => Boolean): Int =
       __self.iterator().scalaOps.indexWhere(f)
 
-    @inline def findFold[B](f: A => Boolean)(default: => B)(g: A => B): B =
+    @inline def findFold[B](f: A => Boolean)(default: () => B)(g: A => B): B =
       __self.iterator().scalaOps.findFold(f)(default)(g)
 
     @inline def foldLeft[B](z: B)(f: (B, A) => B): B =
@@ -127,14 +127,14 @@ private[java] object ScalaOps {
       // scalastyle:on return
     }
 
-    @inline def findFold[B](f: A => Boolean)(default: => B)(g: A => B): B = {
+    @inline def findFold[B](f: A => Boolean)(default: () => B)(g: A => B): B = {
       // scalastyle:off return
       while (__self.hasNext()) {
         val x = __self.next()
         if (f(x))
           return g(x)
       }
-      default
+      default()
       // scalastyle:on return
     }
 
diff --git a/javalib/src/main/scala/java/util/Timer.scala b/javalib/src/main/scala/java/util/Timer.scala
index b377b5a33f..e802db4a31 100644
--- a/javalib/src/main/scala/java/util/Timer.scala
+++ b/javalib/src/main/scala/java/util/Timer.scala
@@ -47,7 +47,7 @@ class Timer() {
 
   private def scheduleOnce(task: TimerTask, delay: Long): Unit = {
     acquire(task)
-    task.timeout(delay) {
+    task.timeout(delay) { () =>
       task.scheduledOnceAndStarted = true
       task.doRun()
     }
@@ -76,12 +76,12 @@ class Timer() {
       task.doRun()
       val endTime = System.nanoTime()
       val duration = (endTime - startTime) / 1000000
-      task.timeout(period - duration) {
+      task.timeout(period - duration) { () =>
         loop()
       }
     }
 
-    task.timeout(delay) {
+    task.timeout(delay) { () =>
       loop()
     }
   }
@@ -112,13 +112,13 @@ class Timer() {
         loop(nextScheduledTime)
       } else {
         // Re-run after a timeout.
-        task.timeout(nextScheduledTime - nowTime) {
+        task.timeout(nextScheduledTime - nowTime) { () =>
           loop(nextScheduledTime)
         }
       }
     }
 
-    task.timeout(delay) {
+    task.timeout(delay) { () =>
       loop(System.nanoTime() / 1000000L + period)
     }
   }
diff --git a/javalib/src/main/scala/java/util/TimerTask.scala b/javalib/src/main/scala/java/util/TimerTask.scala
index 4299157e89..063e9dd47d 100644
--- a/javalib/src/main/scala/java/util/TimerTask.scala
+++ b/javalib/src/main/scala/java/util/TimerTask.scala
@@ -41,9 +41,9 @@ abstract class TimerTask {
 
   def scheduledExecutionTime(): Long = lastScheduled
 
-  private[util] def timeout(delay: Long)(body: => Unit): Unit = {
+  private[util] def timeout(delay: Long)(body: () => Unit): Unit = {
     if (!canceled) {
-      handle = setTimeout(() => body, delay.toDouble)
+      handle = setTimeout(() => body(), delay.toDouble)
     }
   }
 
diff --git a/javalib/src/main/scala/java/util/regex/IndicesBuilder.scala b/javalib/src/main/scala/java/util/regex/IndicesBuilder.scala
index 85216af945..3d2b480a94 100644
--- a/javalib/src/main/scala/java/util/regex/IndicesBuilder.scala
+++ b/javalib/src/main/scala/java/util/regex/IndicesBuilder.scala
@@ -182,7 +182,7 @@ private[regex] object IndicesBuilder {
     final def propagateFromEnd(matchResult: js.RegExp.ExecResult,
         indices: IndicesArray, end: Int): Unit = {
 
-      val start = undefOrFold(matchResult(newGroup))(-1)(matched => end - matched.length)
+      val start = undefOrFold(matchResult(newGroup))(() => -1)(matched => end - matched.length)
       propagate(matchResult, indices, start, end)
     }
 
@@ -194,7 +194,7 @@ private[regex] object IndicesBuilder {
     final def propagateFromStart(matchResult: js.RegExp.ExecResult,
         indices: IndicesArray, start: Int): Int = {
 
-      val end = undefOrFold(matchResult(newGroup))(-1)(matched => start + matched.length)
+      val end = undefOrFold(matchResult(newGroup))(() => -1)(matched => start + matched.length)
       propagate(matchResult, indices, start, end)
       end
     }
diff --git a/javalib/src/main/scala/java/util/regex/Matcher.scala b/javalib/src/main/scala/java/util/regex/Matcher.scala
index 07f94a8076..5acda2c9bb 100644
--- a/javalib/src/main/scala/java/util/regex/Matcher.scala
+++ b/javalib/src/main/scala/java/util/regex/Matcher.scala
@@ -190,7 +190,7 @@ final class Matcher private[regex] (
     pattern().getIndices(ensureLastMatch, lastMatchIsForMatches)
 
   private def startInternal(compiledGroup: Int): Int =
-    undefOrFold(indices(compiledGroup))(-1)(_._1 + regionStart())
+    undefOrFold(indices(compiledGroup))(() => -1)(_._1 + regionStart())
 
   def start(group: Int): Int =
     startInternal(pattern().numberedGroup(group))
@@ -199,7 +199,7 @@ final class Matcher private[regex] (
     startInternal(pattern().namedGroup(name))
 
   private def endInternal(compiledGroup: Int): Int =
-    undefOrFold(indices(compiledGroup))(-1)(_._2 + regionStart())
+    undefOrFold(indices(compiledGroup))(() => -1)(_._2 + regionStart())
 
   def end(group: Int): Int =
     endInternal(pattern().numberedGroup(group))
@@ -278,10 +278,10 @@ object Matcher {
      */
 
     def start(group: Int): Int =
-      undefOrFold(indices(pattern.numberedGroup(group)))(-1)(_._1 + regionStart)
+      undefOrFold(indices(pattern.numberedGroup(group)))(() => -1)(_._1 + regionStart)
 
     def end(group: Int): Int =
-      undefOrFold(indices(pattern.numberedGroup(group)))(-1)(_._2 + regionStart)
+      undefOrFold(indices(pattern.numberedGroup(group)))(() => -1)(_._2 + regionStart)
 
     def group(group: Int): String =
       undefOrGetOrNull(ensureLastMatch(pattern.numberedGroup(group)))
diff --git a/javalib/src/main/scala/java/util/regex/Pattern.scala b/javalib/src/main/scala/java/util/regex/Pattern.scala
index 05ee30db58..52dcc3e8f0 100644
--- a/javalib/src/main/scala/java/util/regex/Pattern.scala
+++ b/javalib/src/main/scala/java/util/regex/Pattern.scala
@@ -133,7 +133,7 @@ final class Pattern private[regex] (
   }
 
   private[regex] def namedGroup(name: String): Int = {
-    groupNumberMap(dictGetOrElse(namedGroups, name) {
+    groupNumberMap(dictGetOrElse(namedGroups, name) { () =>
       throw new IllegalArgumentException(s"No group with name <$name>")
     })
   }
diff --git a/javalib/src/main/scala/java/util/regex/PatternCompiler.scala b/javalib/src/main/scala/java/util/regex/PatternCompiler.scala
index 93754f24b7..751f2e8f78 100644
--- a/javalib/src/main/scala/java/util/regex/PatternCompiler.scala
+++ b/javalib/src/main/scala/java/util/regex/PatternCompiler.scala
@@ -1385,7 +1385,7 @@ private final class PatternCompiler(private val pattern: String, private var fla
           parseError("\\k is not followed by '<' for named capturing group")
         pIndex += 1
         val groupName = parseGroupName()
-        val groupNumber = dictGetOrElse(namedGroups, groupName) {
+        val groupNumber = dictGetOrElse(namedGroups, groupName) { () =>
           parseError(s"named capturing group <$groupName> does not exit")
         }
         val compiledGroupNumber = groupNumberMap(groupNumber)
@@ -1639,7 +1639,7 @@ private final class PatternCompiler(private val pattern: String, private var fla
       // For anything else, we need built-in support for \p
       requireES2018Features("Unicode character family")
 
-      mapGetOrElse(predefinedPCharacterClasses, property) {
+      mapGetOrElse(predefinedPCharacterClasses, property) { () =>
         val scriptPrefixLen = if (property.startsWith("Is")) {
           2
         } else if (property.startsWith("sc=")) {
@@ -1674,7 +1674,7 @@ private final class PatternCompiler(private val pattern: String, private var fla
 
     val lowercase = scriptName.toLowerCase()
 
-    mapGetOrElseUpdate(canonicalizedScriptNameCache, lowercase) {
+    mapGetOrElseUpdate(canonicalizedScriptNameCache, lowercase) { () =>
       val canonical = lowercase.jsReplace(scriptCanonicalizeRegExp,
           ((s: String) => s.toUpperCase()): js.Function1[String, String])
 

From 52f32a58a8160a66013a99ab194fa16d90842b3a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Mon, 18 Nov 2024 18:15:48 +0100
Subject: [PATCH 216/298] Directly use ju.function.* instead of Scala functions
 in the javalib.

This way, we can simplify the `JavalibIRCleaner`. It does not need
to deal with the function rewrites anymore.

Code readability is only affected at the definition sites of the
higher-order methods. The use sites leverage SAM conversion. Some
use sites need a bit more help for the type inference, because
Java function types are invariant in all their type parameters.

Since virtually all the higher-order functions are always inlined
anyway, this commit does not make a difference to the generated
code. The only exceptions were `ju.TimerTask.timeout` and
`jl.System.NanoTime.getPrecisionTime`. For those, we explicitly
declare that we want a `js.Function0`. This won't make performance
worse on Wasm because the relevant code uses JS interop anyway.

The changes in this commit will also make the transition to
`TypedClosure`s easier. Indeed, it would be tricky for the
`JavalibIRCleaner` to deal with Scala functions without the
possibility to use JS `Closure`s and without the full liberty of
sending bare `TypedClosure`s across methods.
---
 .../src/main/scala/java/io/PrintStream.scala  |  6 +-
 .../src/main/scala/java/io/PrintWriter.scala  |  6 +-
 .../src/main/scala/java/lang/Integer.scala    |  3 +-
 javalib/src/main/scala/java/lang/System.scala | 15 ++---
 .../src/main/scala/java/lang/Throwables.scala | 18 +++---
 javalib/src/main/scala/java/lang/Utils.scala  | 34 ++++++-----
 .../src/main/scala/java/lang/_String.scala    |  5 +-
 .../src/main/scala/java/math/BigInteger.scala |  5 +-
 .../src/main/scala/java/nio/GenBuffer.scala   |  3 +-
 .../scala/java/util/AbstractCollection.scala  |  6 +-
 .../main/scala/java/util/Collections.scala    | 13 ++--
 javalib/src/main/scala/java/util/Date.scala   |  5 +-
 .../src/main/scala/java/util/Formatter.scala  |  4 +-
 .../src/main/scala/java/util/Properties.scala |  5 +-
 .../main/scala/java/util/RedBlackTree.scala   |  4 +-
 .../src/main/scala/java/util/ScalaOps.scala   | 60 ++++++++++---------
 .../src/main/scala/java/util/TimerTask.scala  |  4 +-
 project/JavalibIRCleaner.scala                | 58 +-----------------
 18 files changed, 108 insertions(+), 146 deletions(-)

diff --git a/javalib/src/main/scala/java/io/PrintStream.scala b/javalib/src/main/scala/java/io/PrintStream.scala
index 9b61270d43..7868abd03c 100644
--- a/javalib/src/main/scala/java/io/PrintStream.scala
+++ b/javalib/src/main/scala/java/io/PrintStream.scala
@@ -214,15 +214,15 @@ class PrintStream private (_out: OutputStream, autoFlush: Boolean,
     this
   }
 
-  @inline private[this] def trapIOExceptions(body: () => Unit): Unit = {
+  @inline private[this] def trapIOExceptions(body: Runnable): Unit = {
     try {
-      body()
+      body.run()
     } catch {
       case _: IOException => setError()
     }
   }
 
-  @inline private[this] def ensureOpenAndTrapIOExceptions(body: () => Unit): Unit = {
+  @inline private[this] def ensureOpenAndTrapIOExceptions(body: Runnable): Unit = {
     if (closed) setError()
     else trapIOExceptions(body)
   }
diff --git a/javalib/src/main/scala/java/io/PrintWriter.scala b/javalib/src/main/scala/java/io/PrintWriter.scala
index e03ddb7d2c..57833e56f5 100644
--- a/javalib/src/main/scala/java/io/PrintWriter.scala
+++ b/javalib/src/main/scala/java/io/PrintWriter.scala
@@ -147,15 +147,15 @@ class PrintWriter(protected[io] var out: Writer,
     this
   }
 
-  @inline private[this] def trapIOExceptions(body: () => Unit): Unit = {
+  @inline private[this] def trapIOExceptions(body: Runnable): Unit = {
     try {
-      body()
+      body.run()
     } catch {
       case _: IOException => setError()
     }
   }
 
-  @inline private[this] def ensureOpenAndTrapIOExceptions(body: () => Unit): Unit = {
+  @inline private[this] def ensureOpenAndTrapIOExceptions(body: Runnable): Unit = {
     if (closed) setError()
     else trapIOExceptions(body)
   }
diff --git a/javalib/src/main/scala/java/lang/Integer.scala b/javalib/src/main/scala/java/lang/Integer.scala
index 8ef617e7d0..a4c2694365 100644
--- a/javalib/src/main/scala/java/lang/Integer.scala
+++ b/javalib/src/main/scala/java/lang/Integer.scala
@@ -13,6 +13,7 @@
 package java.lang
 
 import java.lang.constant.{Constable, ConstantDesc}
+import java.util.function._
 
 import scala.scalajs.js
 import scala.scalajs.LinkingInfo
@@ -132,7 +133,7 @@ object Integer {
     decodeGeneric(nm, valueOf(_, _))
 
   @inline private[lang] def decodeGeneric[A](nm: String,
-      parse: (String, Int) => A): A = {
+      parse: BiFunction[String, Int, A]): A = {
 
     val len = nm.length()
     var i = 0
diff --git a/javalib/src/main/scala/java/lang/System.scala b/javalib/src/main/scala/java/lang/System.scala
index 4938d237ca..976ea7ff15 100644
--- a/javalib/src/main/scala/java/lang/System.scala
+++ b/javalib/src/main/scala/java/lang/System.scala
@@ -19,6 +19,7 @@ import scala.scalajs.js.Dynamic.global
 import scala.scalajs.LinkingInfo
 
 import java.{util => ju}
+import java.util.function._
 
 object System {
   /* System contains a bag of unrelated features. If we naively implement
@@ -70,7 +71,7 @@ object System {
     (new js.Date).getTime().toLong
 
   private object NanoTime {
-    val getHighPrecisionTime: () => scala.Double = {
+    val getHighPrecisionTime: js.Function0[scala.Double] = {
       import js.DynamicImplicits.truthValue
 
       if (js.typeOf(global.performance) != "undefined") {
@@ -102,27 +103,27 @@ object System {
     def mismatch(): Nothing =
       throw new ArrayStoreException("Incompatible array types")
 
-    def impl(srcLen: Int, destLen: Int, f: (Int, Int) => Any): Unit = {
+    def impl(srcLen: Int, destLen: Int, f: BiConsumer[Int, Int]): Unit = {
       /* Perform dummy swaps to trigger an ArrayIndexOutOfBoundsException or
        * UBE if the positions / lengths are bad.
        */
       if (srcPos < 0 || destPos < 0)
-        f(destPos, srcPos)
+        f.accept(destPos, srcPos)
       if (length < 0)
-        f(length, length)
+        f.accept(length, length)
       if (srcPos > srcLen - length || destPos > destLen - length)
-        f(destPos + length, srcPos + length)
+        f.accept(destPos + length, srcPos + length)
 
       if ((src ne dest) || destPos < srcPos || srcPos + length < destPos) {
         var i = 0
         while (i < length) {
-          f(i + destPos, i + srcPos)
+          f.accept(i + destPos, i + srcPos)
           i += 1
         }
       } else {
         var i = length - 1
         while (i >= 0) {
-          f(i + destPos, i + srcPos)
+          f.accept(i + destPos, i + srcPos)
           i -= 1
         }
       }
diff --git a/javalib/src/main/scala/java/lang/Throwables.scala b/javalib/src/main/scala/java/lang/Throwables.scala
index 38b17384b9..af7701641f 100644
--- a/javalib/src/main/scala/java/lang/Throwables.scala
+++ b/javalib/src/main/scala/java/lang/Throwables.scala
@@ -12,6 +12,8 @@
 
 package java.lang
 
+import java.util.function._
+
 import scala.scalajs.js
 import scala.scalajs.js.annotation.JSExport
 
@@ -80,21 +82,21 @@ class Throwable protected (s: String, private var e: Throwable,
   def printStackTrace(s: java.io.PrintWriter): Unit =
     printStackTraceImpl(s.println(_))
 
-  private[this] def printStackTraceImpl(sprintln: String => Unit): Unit = {
+  private[this] def printStackTraceImpl(sprintln: Consumer[String]): Unit = {
     getStackTrace() // will init it if still null
 
     // Message
-    sprintln(toString)
+    sprintln.accept(toString)
 
     // Trace
     if (stackTrace.length != 0) {
       var i = 0
       while (i < stackTrace.length) {
-        sprintln(s"  at ${stackTrace(i)}")
+        sprintln.accept(s"  at ${stackTrace(i)}")
         i += 1
       }
     } else {
-      sprintln("  <no stack trace available>")
+      sprintln.accept("  <no stack trace available>")
     }
 
     // Causes
@@ -107,7 +109,7 @@ class Throwable protected (s: String, private var e: Throwable,
       val thisLength = thisTrace.length
       val parentLength = parentTrace.length
 
-      sprintln(s"Caused by: $wCause")
+      sprintln.accept(s"Caused by: $wCause")
 
       if (thisLength != 0) {
         /* Count how many frames are shared between this stack trace and the
@@ -129,14 +131,14 @@ class Throwable protected (s: String, private var e: Throwable,
         val lengthToPrint = thisLength - sameFrameCount
         var i = 0
         while (i < lengthToPrint) {
-          sprintln(s"  at ${thisTrace(i)}")
+          sprintln.accept(s"  at ${thisTrace(i)}")
           i += 1
         }
 
         if (sameFrameCount > 0)
-          sprintln(s"  ... $sameFrameCount more")
+          sprintln.accept(s"  ... $sameFrameCount more")
       } else {
-        sprintln("  <no stack trace available>")
+        sprintln.accept("  <no stack trace available>")
       }
     }
   }
diff --git a/javalib/src/main/scala/java/lang/Utils.scala b/javalib/src/main/scala/java/lang/Utils.scala
index 6e0a535831..94d323e026 100644
--- a/javalib/src/main/scala/java/lang/Utils.scala
+++ b/javalib/src/main/scala/java/lang/Utils.scala
@@ -14,6 +14,8 @@ package java.lang
 
 import scala.language.implicitConversions
 
+import java.util.function._
+
 import scala.scalajs.js
 import scala.scalajs.js.annotation._
 
@@ -34,9 +36,9 @@ private[java] object Utils {
     x.asInstanceOf[A]
 
   @inline
-  def undefOrGetOrElse[A](x: js.UndefOr[A])(default: () => A): A =
+  def undefOrGetOrElse[A](x: js.UndefOr[A])(default: Supplier[A]): A =
     if (undefOrIsDefined(x)) undefOrForceGet(x)
-    else default()
+    else default.get()
 
   @inline
   def undefOrGetOrNull[A >: Null](x: js.UndefOr[A]): A =
@@ -44,15 +46,15 @@ private[java] object Utils {
     else null
 
   @inline
-  def undefOrForeach[A](x: js.UndefOr[A])(f: A => Any): Unit = {
+  def undefOrForeach[A](x: js.UndefOr[A])(f: Consumer[A]): Unit = {
     if (undefOrIsDefined(x))
-      f(undefOrForceGet(x))
+      f.accept(undefOrForceGet(x))
   }
 
   @inline
-  def undefOrFold[A, B](x: js.UndefOr[A])(default: () => B)(f: A => B): B =
+  def undefOrFold[A, B](x: js.UndefOr[A])(default: Supplier[B])(f: Function[A, B]): B =
     if (undefOrIsDefined(x)) f(undefOrForceGet(x))
-    else default()
+    else default.get()
 
   private object Cache {
     val safeHasOwnProperty =
@@ -84,11 +86,11 @@ private[java] object Utils {
 
   @inline
   def dictGetOrElse[A](dict: js.Dictionary[_ <: A], key: String)(
-      default: () => A): A = {
+      default: Supplier[A]): A = {
     if (dictContains(dict, key))
       dictRawApply(dict, key)
     else
-      default()
+      default.get()
   }
 
   def dictGetOrElseAndRemove[A](dict: js.Dictionary[_ <: A], key: String,
@@ -139,27 +141,27 @@ private[java] object Utils {
     map.asInstanceOf[MapRaw[K, V]].set(key, value)
 
   @inline
-  def mapGetOrElse[K, V](map: js.Map[K, V], key: K)(default: () => V): V = {
+  def mapGetOrElse[K, V](map: js.Map[K, V], key: K)(default: Supplier[V]): V = {
     val value = map.asInstanceOf[MapRaw[K, V]].getOrUndefined(key)
     if (!isUndefined(value) || mapHas(map, key)) value.asInstanceOf[V]
-    else default()
+    else default.get()
   }
 
   @inline
-  def mapGetOrElseUpdate[K, V](map: js.Map[K, V], key: K)(default: () => V): V = {
+  def mapGetOrElseUpdate[K, V](map: js.Map[K, V], key: K)(default: Supplier[V]): V = {
     mapGetOrElse(map, key) { () =>
-      val value = default()
+      val value = default.get()
       mapSet(map, key, value)
       value
     }
   }
 
   @inline
-  def forArrayElems[A](array: js.Array[A])(f: A => Any): Unit = {
+  def forArrayElems[A](array: js.Array[A])(f: Consumer[A]): Unit = {
     val len = array.length
     var i = 0
     while (i != len) {
-      f(array(i))
+      f.accept(array(i))
       i += 1
     }
   }
@@ -173,12 +175,12 @@ private[java] object Utils {
     array.splice(index, 1)(0)
 
   @inline
-  def arrayExists[A](array: js.Array[A])(f: A => scala.Boolean): scala.Boolean = {
+  def arrayExists[A](array: js.Array[A])(f: Predicate[A]): scala.Boolean = {
     // scalastyle:off return
     val len = array.length
     var i = 0
     while (i != len) {
-      if (f(array(i)))
+      if (f.test(array(i)))
         return true
       i += 1
     }
diff --git a/javalib/src/main/scala/java/lang/_String.scala b/javalib/src/main/scala/java/lang/_String.scala
index d89ada96dc..ea29540e37 100644
--- a/javalib/src/main/scala/java/lang/_String.scala
+++ b/javalib/src/main/scala/java/lang/_String.scala
@@ -26,6 +26,7 @@ import java.lang.constant.{Constable, ConstantDesc}
 import java.nio.ByteBuffer
 import java.nio.charset.Charset
 import java.util.Locale
+import java.util.function._
 import java.util.regex._
 
 /* This is the implementation of java.lang.String, which is a hijacked class.
@@ -643,7 +644,7 @@ for (cp <- 0 to Character.MAX_CODE_POINT) {
    *    the character at the given index is not special.
    */
   @inline
-  private def replaceCharsAtIndex(replacementAtIndex: Int => String): String = {
+  private def replaceCharsAtIndex(replacementAtIndex: IntFunction[String]): String = {
     var prep = ""
     val len = this.length()
     var i = 0
@@ -776,7 +777,7 @@ for (cp <- 0 to Character.MAX_CODE_POINT) {
 
   def indent(n: Int): String = {
 
-    def forEachLn(f: String => String): String = {
+    def forEachLn(f: Function[String, String]): String = {
       var out = ""
       var i = 0
       val xs = splitLines()
diff --git a/javalib/src/main/scala/java/math/BigInteger.scala b/javalib/src/main/scala/java/math/BigInteger.scala
index bab8c44301..9864183573 100644
--- a/javalib/src/main/scala/java/math/BigInteger.scala
+++ b/javalib/src/main/scala/java/math/BigInteger.scala
@@ -45,6 +45,7 @@ import scala.annotation.tailrec
 
 import java.util.Random
 import java.util.ScalaOps._
+import java.util.function._
 
 object BigInteger {
 
@@ -736,9 +737,9 @@ class BigInteger extends Number with Comparable[BigInteger] {
 
     @inline
     @tailrec
-    def loopBytes(tempDigit: Int => Unit): Unit = {
+    def loopBytes(tempDigit: IntConsumer): Unit = {
       if (bytesLen > firstByteNumber) {
-        tempDigit(digitIndex)
+        tempDigit.accept(digitIndex)
         loopBytes(tempDigit)
       }
     }
diff --git a/javalib/src/main/scala/java/nio/GenBuffer.scala b/javalib/src/main/scala/java/nio/GenBuffer.scala
index 9aa57e92d8..2fc5f52d3f 100644
--- a/javalib/src/main/scala/java/nio/GenBuffer.scala
+++ b/javalib/src/main/scala/java/nio/GenBuffer.scala
@@ -12,6 +12,7 @@
 
 package java.nio
 
+import java.util.function._
 import java.util.internal.GenericArrayOps._
 
 private[nio] object GenBuffer {
@@ -137,7 +138,7 @@ private[nio] final class GenBuffer[B <: Buffer] private (val self: B)
 
   @inline
   def generic_compareTo(that: BufferType)(
-      compare: (ElementType, ElementType) => Int): Int = {
+      compare: BiFunction[ElementType, ElementType, Int]): Int = {
     // scalastyle:off return
     if (self eq that) {
       0
diff --git a/javalib/src/main/scala/java/util/AbstractCollection.scala b/javalib/src/main/scala/java/util/AbstractCollection.scala
index 8385d981da..34920f1bdb 100644
--- a/javalib/src/main/scala/java/util/AbstractCollection.scala
+++ b/javalib/src/main/scala/java/util/AbstractCollection.scala
@@ -18,6 +18,8 @@ import ScalaOps._
 
 import java.lang.{reflect => jlr}
 
+import java.util.function.Predicate
+
 abstract class AbstractCollection[E] protected () extends Collection[E] {
   def iterator(): Iterator[E]
   def size(): Int
@@ -78,11 +80,11 @@ abstract class AbstractCollection[E] protected () extends Collection[E] {
   def clear(): Unit =
     removeWhere(_ => true)
 
-  private def removeWhere(p: Any => Boolean): Boolean = {
+  private def removeWhere(p: Predicate[Any]): Boolean = {
     val iter = iterator()
     var changed = false
     while (iter.hasNext()) {
-      if (p(iter.next())) {
+      if (p.test(iter.next())) {
         iter.remove()
         changed = true
       }
diff --git a/javalib/src/main/scala/java/util/Collections.scala b/javalib/src/main/scala/java/util/Collections.scala
index 687ba74b5e..8f9a630de5 100644
--- a/javalib/src/main/scala/java/util/Collections.scala
+++ b/javalib/src/main/scala/java/util/Collections.scala
@@ -14,6 +14,7 @@ package java.util
 
 import java.{lang => jl}
 import java.io.Serializable
+import java.util.function._
 
 import scala.language.implicitConversions
 
@@ -79,16 +80,16 @@ object Collections {
     binarySearchImpl(list, (elem: T) => c.compare(elem, key))
 
   @inline
-  private def binarySearchImpl[E](list: List[E], compareToKey: E => Int): Int = {
+  private def binarySearchImpl[E](list: List[_ <: E], compareToKey: ToIntFunction[E]): Int = {
     def notFound(insertionPoint: Int): Int = {
       -insertionPoint - 1
     }
 
     @tailrec
-    def binarySearch(lo: Int, hi: Int, get: Int => E): Int = {
+    def binarySearch(lo: Int, hi: Int, get: IntFunction[E]): Int = {
       if (lo < hi) {
         val mid = lo + (hi - lo) / 2
-        val cmp = compareToKey(get(mid))
+        val cmp = compareToKey.applyAsInt(get(mid))
         if (cmp == 0) mid
         else if (cmp > 0) binarySearch(lo, mid, get)
         else binarySearch(mid + 1, hi, get)
@@ -102,7 +103,7 @@ object Collections {
         binarySearch(0, list.size(), list.get(_))
 
       case _ =>
-        def getFrom(iter: ListIterator[E])(index: Int): E = {
+        def getFrom(iter: ListIterator[_ <: E])(index: Int): E = {
           val shift = index - iter.nextIndex()
           if (shift > 0)
             (0 until shift).foreach(_ => iter.next())
@@ -263,14 +264,14 @@ object Collections {
     min(coll, Comparator.naturalOrder[T])
 
   def min[T](coll: Collection[_ <: T], comp: Comparator[_ >: T]): T =
-    coll.scalaOps.reduceLeft((a, b) => if (comp.compare(a, b) <= 0) a else b)
+    coll.scalaOps.reduceLeft[T]((a, b) => if (comp.compare(a, b) <= 0) a else b)
 
   // Differs from original type definition, original: [T <: jl.Comparable[_ >: T]], returning T
   def max[T <: AnyRef with jl.Comparable[T]](coll: Collection[_ <: T]): AnyRef =
     max(coll, Comparator.naturalOrder[T])
 
   def max[T](coll: Collection[_ <: T], comp: Comparator[_ >: T]): T =
-    coll.scalaOps.reduceLeft((a, b) => if (comp.compare(a, b) >= 0) a else b)
+    coll.scalaOps.reduceLeft[T]((a, b) => if (comp.compare(a, b) >= 0) a else b)
 
   def rotate(list: List[_], distance: Int): Unit =
     rotateImpl(list, distance)
diff --git a/javalib/src/main/scala/java/util/Date.scala b/javalib/src/main/scala/java/util/Date.scala
index 170d5829d2..68fe483627 100644
--- a/javalib/src/main/scala/java/util/Date.scala
+++ b/javalib/src/main/scala/java/util/Date.scala
@@ -14,6 +14,7 @@ package java.util
 
 import java.lang.Cloneable
 import java.time.Instant
+import java.util.function._
 
 import scalajs.js
 
@@ -69,9 +70,9 @@ class Date(private var millis: Long) extends Object
   }
 
   @inline
-  private def mutDate(mutator: js.Date => Unit): Unit = {
+  private def mutDate(mutator: Consumer[js.Date]): Unit = {
     val date = asDate()
-    mutator(date)
+    mutator.accept(date)
     millis = safeGetTime(date)
   }
 
diff --git a/javalib/src/main/scala/java/util/Formatter.scala b/javalib/src/main/scala/java/util/Formatter.scala
index c8c3af05ef..909fab1929 100644
--- a/javalib/src/main/scala/java/util/Formatter.scala
+++ b/javalib/src/main/scala/java/util/Formatter.scala
@@ -51,9 +51,9 @@ final class Formatter private (private[this] var dest: Appendable,
   def this(a: Appendable, l: Locale) = this(a, new Formatter.LocaleLocaleInfo(l))
 
   @inline
-  private def trapIOExceptions(body: () => Unit): Unit = {
+  private def trapIOExceptions(body: Runnable): Unit = {
     try {
-      body()
+      body.run()
     } catch {
       case th: IOException =>
         lastIOException = th
diff --git a/javalib/src/main/scala/java/util/Properties.scala b/javalib/src/main/scala/java/util/Properties.scala
index d75d89e601..d70e639fa4 100644
--- a/javalib/src/main/scala/java/util/Properties.scala
+++ b/javalib/src/main/scala/java/util/Properties.scala
@@ -19,6 +19,7 @@ import java.{lang => jl}
 import java.{util => ju}
 import java.io._
 import java.nio.charset.StandardCharsets
+import java.util.function._
 
 import scala.scalajs.js
 
@@ -114,8 +115,8 @@ class Properties(protected val defaults: Properties)
   }
 
   @inline @tailrec
-  private final def foreachAncestor(f: Properties => Unit): Unit = {
-    f(this)
+  private final def foreachAncestor(f: Consumer[Properties]): Unit = {
+    f.accept(this)
     if (defaults ne null)
       defaults.foreachAncestor(f)
   }
diff --git a/javalib/src/main/scala/java/util/RedBlackTree.scala b/javalib/src/main/scala/java/util/RedBlackTree.scala
index 3e91b22e66..a1554e264d 100644
--- a/javalib/src/main/scala/java/util/RedBlackTree.scala
+++ b/javalib/src/main/scala/java/util/RedBlackTree.scala
@@ -14,6 +14,8 @@ package java.util
 
 import scala.annotation.tailrec
 
+import java.util.function._
+
 import scala.scalajs.js
 
 /** The red-black tree implementation used by `TreeSet`s and `TreeMap`s.
@@ -609,7 +611,7 @@ private[util] object RedBlackTree {
 
   /** Returns `null.asInstanceOf[C]` if `node eq null`, otherwise `f(node)`. */
   @inline
-  private def nullableNodeFlatMap[A, B, C](node: Node[A, B])(f: Node[A, B] => C): C =
+  private def nullableNodeFlatMap[A, B, C](node: Node[A, B])(f: Function[Node[A, B], C]): C =
     if (node eq null) null.asInstanceOf[C]
     else f(node)
 
diff --git a/javalib/src/main/scala/java/util/ScalaOps.scala b/javalib/src/main/scala/java/util/ScalaOps.scala
index 6f5cb57cff..a00c7d379f 100644
--- a/javalib/src/main/scala/java/util/ScalaOps.scala
+++ b/javalib/src/main/scala/java/util/ScalaOps.scala
@@ -12,6 +12,8 @@
 
 package java.util
 
+import java.util.function._
+
 /** Make some Scala collection APIs available on Java collections. */
 private[java] object ScalaOps {
 
@@ -26,10 +28,10 @@ private[java] object ScalaOps {
   @inline
   final class SimpleRange(start: Int, end: Int) {
     @inline
-    def foreach[U](f: Int => U): Unit = {
+    def foreach[U](f: IntConsumer): Unit = {
       var i = start
       while (i < end) {
-        f(i)
+        f.accept(i)
         i += 1
       }
     }
@@ -38,10 +40,10 @@ private[java] object ScalaOps {
   @inline
   final class SimpleInclusiveRange(start: Int, end: Int) {
     @inline
-    def foreach[U](f: Int => U): Unit = {
+    def foreach[U](f: IntConsumer): Unit = {
       var i = start
       while (i <= end) {
-        f(i)
+        f.accept(i)
         i += 1
       }
     }
@@ -57,28 +59,28 @@ private[java] object ScalaOps {
       val __self: java.lang.Iterable[A])
       extends AnyVal {
 
-    @inline def foreach[U](f: A => U): Unit =
+    @inline def foreach(f: Consumer[A]): Unit =
       __self.iterator().scalaOps.foreach(f)
 
-    @inline def count(f: A => Boolean): Int =
+    @inline def count(f: Predicate[A]): Int =
       __self.iterator().scalaOps.count(f)
 
-    @inline def exists(f: A => Boolean): Boolean =
+    @inline def exists(f: Predicate[A]): Boolean =
       __self.iterator().scalaOps.exists(f)
 
-    @inline def forall(f: A => Boolean): Boolean =
+    @inline def forall(f: Predicate[A]): Boolean =
       __self.iterator().scalaOps.forall(f)
 
-    @inline def indexWhere(f: A => Boolean): Int =
+    @inline def indexWhere(f: Predicate[A]): Int =
       __self.iterator().scalaOps.indexWhere(f)
 
-    @inline def findFold[B](f: A => Boolean)(default: () => B)(g: A => B): B =
+    @inline def findFold[B](f: Predicate[A])(default: Supplier[B])(g: Function[A, B]): B =
       __self.iterator().scalaOps.findFold(f)(default)(g)
 
-    @inline def foldLeft[B](z: B)(f: (B, A) => B): B =
+    @inline def foldLeft[B](z: B)(f: BiFunction[B, A, B]): B =
       __self.iterator().scalaOps.foldLeft(z)(f)
 
-    @inline def reduceLeft[B >: A](f: (B, A) => B): B =
+    @inline def reduceLeft[B >: A](f: BiFunction[B, A, B]): B =
       __self.iterator().scalaOps.reduceLeft(f)
 
     @inline def mkString(start: String, sep: String, end: String): String =
@@ -94,32 +96,32 @@ private[java] object ScalaOps {
   class JavaIteratorOps[A] private[ScalaOps] (val __self: Iterator[A])
       extends AnyVal {
 
-    @inline def foreach[U](f: A => U): Unit = {
+    @inline def foreach(f: Consumer[A]): Unit = {
       while (__self.hasNext())
-        f(__self.next())
+        f.accept(__self.next())
     }
 
-    @inline def count(f: A => Boolean): Int =
-      foldLeft(0)((prev, x) => if (f(x)) prev + 1 else prev)
+    @inline def count(f: Predicate[A]): Int =
+      foldLeft(0)((prev, x) => if (f.test(x)) prev + 1 else prev)
 
-    @inline def exists(f: A => Boolean): Boolean = {
+    @inline def exists(f: Predicate[A]): Boolean = {
       // scalastyle:off return
       while (__self.hasNext()) {
-        if (f(__self.next()))
+        if (f.test(__self.next()))
           return true
       }
       false
       // scalastyle:on return
     }
 
-    @inline def forall(f: A => Boolean): Boolean =
-      !exists(x => !f(x))
+    @inline def forall(f: Predicate[A]): Boolean =
+      !exists(x => !f.test(x))
 
-    @inline def indexWhere(f: A => Boolean): Int = {
+    @inline def indexWhere(f: Predicate[A]): Int = {
       // scalastyle:off return
       var i = 0
       while (__self.hasNext()) {
-        if (f(__self.next()))
+        if (f.test(__self.next()))
           return i
         i += 1
       }
@@ -127,25 +129,25 @@ private[java] object ScalaOps {
       // scalastyle:on return
     }
 
-    @inline def findFold[B](f: A => Boolean)(default: () => B)(g: A => B): B = {
+    @inline def findFold[B](f: Predicate[A])(default: Supplier[B])(g: Function[A, B]): B = {
       // scalastyle:off return
       while (__self.hasNext()) {
         val x = __self.next()
-        if (f(x))
+        if (f.test(x))
           return g(x)
       }
-      default()
+      default.get()
       // scalastyle:on return
     }
 
-    @inline def foldLeft[B](z: B)(f: (B, A) => B): B = {
+    @inline def foldLeft[B](z: B)(f: BiFunction[B, A, B]): B = {
       var result: B = z
       while (__self.hasNext())
         result = f(result, __self.next())
       result
     }
 
-    @inline def reduceLeft[B >: A](f: (B, A) => B): B = {
+    @inline def reduceLeft[B >: A](f: BiFunction[B, A, B]): B = {
       if (!__self.hasNext())
         throw new NoSuchElementException("collection is empty")
       foldLeft[B](__self.next())(f)
@@ -174,9 +176,9 @@ private[java] object ScalaOps {
   class JavaEnumerationOps[A] private[ScalaOps] (val __self: Enumeration[A])
       extends AnyVal {
 
-    @inline def foreach[U](f: A => U): Unit = {
+    @inline def foreach(f: Consumer[A]): Unit = {
       while (__self.hasMoreElements())
-        f(__self.nextElement())
+        f.accept(__self.nextElement())
     }
   }
 
diff --git a/javalib/src/main/scala/java/util/TimerTask.scala b/javalib/src/main/scala/java/util/TimerTask.scala
index 063e9dd47d..439add8f55 100644
--- a/javalib/src/main/scala/java/util/TimerTask.scala
+++ b/javalib/src/main/scala/java/util/TimerTask.scala
@@ -41,9 +41,9 @@ abstract class TimerTask {
 
   def scheduledExecutionTime(): Long = lastScheduled
 
-  private[util] def timeout(delay: Long)(body: () => Unit): Unit = {
+  private[util] def timeout(delay: Long)(body: js.Function0[Any]): Unit = {
     if (!canceled) {
-      handle = setTimeout(() => body(), delay.toDouble)
+      handle = setTimeout(body, delay.toDouble)
     }
   }
 
diff --git a/project/JavalibIRCleaner.scala b/project/JavalibIRCleaner.scala
index 035732d7c4..61ed4ea743 100644
--- a/project/JavalibIRCleaner.scala
+++ b/project/JavalibIRCleaner.scala
@@ -33,8 +33,6 @@ import sbt.{Logger, MessageOnlyException}
  *    the JS load spec of the mentioned class ref.
  *  - Replace calls to "intrinsic" methods of the Scala.js library by their
  *    meaning at call site.
- *  - Erase Scala FunctionN's to JavaScript closures (hence, of type `any`),
- *    including `new AnonFunctionN` and `someFunctionN.apply` calls.
  *
  *  Afterwards, we check that the IR does not contain any reference to classes
  *  under the `scala.*` package.
@@ -321,15 +319,6 @@ final class JavalibIRCleaner(baseDirectoryURI: URI) {
       implicit val pos = tree.pos
 
       tree match {
-        // new AnonFunctionN(closure)  -->  closure
-        case New(AnonFunctionNClass(n), _, List(closure)) =>
-          closure
-
-        // someFunctionN.apply(args)  -->  someFunctionN(args)
-        case Apply(ApplyFlags.empty, fun, MethodIdent(FunctionApplyMethodName(n)), args)
-            if isFunctionNType(n, fun.tpe) =>
-          JSFunctionApply(fun, args)
-
         // <= 2.12 : toJSVarArgs(jsArrayOps(jsArray).toSeq) -> jsArray
         case IntrinsicCall(ScalaJSRuntimeMod, `toJSVarArgsReadOnlyMethodName`,
             List(Apply(
@@ -637,8 +626,6 @@ final class JavalibIRCleaner(baseDirectoryURI: URI) {
 }
 
 object JavalibIRCleaner {
-  private final val MaxFunctionArity = 4
-
   // Within js.JavaScriptException, which is part of the linker private lib, we can refer to itself
   private val JavaScriptExceptionClass = ClassName("scala.scalajs.js.JavaScriptException")
 
@@ -668,12 +655,6 @@ object JavalibIRCleaner {
   private val UnionTypeEvidence = ClassName("scala.scalajs.js.$bar$Evidence")
   private val LinkingInfoClass = ClassName("scala.scalajs.LinkingInfo$")
 
-  private val FunctionNClasses: IndexedSeq[ClassName] =
-    (0 to MaxFunctionArity).map(n => ClassName(s"scala.Function$n"))
-
-  private val AnonFunctionNClasses: IndexedSeq[ClassName] =
-    (0 to MaxFunctionArity).map(n => ClassName(s"scala.scalajs.runtime.AnonFunction$n"))
-
   private val enableJSNumberOpsDoubleMethodName =
     MethodName("enableJSNumberOps", List(DoubleRef), ClassRef(JSNumberOps))
   private val enableJSNumberOpsIntMethodName =
@@ -716,44 +697,7 @@ object JavalibIRCleaner {
   private val isWebAssemblyMethodName = MethodName("isWebAssembly", Nil, BooleanRef)
   private val linkerVersionMethodName = MethodName("linkerVersion", Nil, ClassRef(BoxedStringClass))
 
-  private val functionApplyMethodNames: IndexedSeq[MethodName] = {
-    (0 to MaxFunctionArity).map { n =>
-      MethodName("apply", (1 to n).toList.map(_ => ClassRef(ObjectClass)), ClassRef(ObjectClass))
-    }
-  }
-
-  private object AnonFunctionNClass {
-    private val AnonFunctionNClassToN: Map[ClassName, Int] =
-      AnonFunctionNClasses.zipWithIndex.toMap
-
-    def apply(n: Int): ClassName = AnonFunctionNClasses(n)
-
-    def unapply(cls: ClassName): Option[Int] = AnonFunctionNClassToN.get(cls)
-  }
-
-  private object FunctionApplyMethodName {
-    private val FunctionApplyMethodNameToN: Map[MethodName, Int] =
-      functionApplyMethodNames.zipWithIndex.toMap
-
-    def apply(n: Int): MethodName = functionApplyMethodNames(n)
-
-    def unapply(name: MethodName): Option[Int] = FunctionApplyMethodNameToN.get(name)
-  }
-
-  private def isFunctionNType(n: Int, tpe: Type): Boolean = tpe match {
-    case ClassType(cls, _) =>
-      cls == FunctionNClasses(n) || cls == AnonFunctionNClasses(n)
-    case _ =>
-      false
-  }
-
   private val ClassNameSubstitutions: Map[ClassName, ClassName] = {
-    val functionTypePairs = for {
-      funClass <- FunctionNClasses ++ AnonFunctionNClasses
-    } yield {
-      funClass -> ObjectClass
-    }
-
     val refBaseNames =
       List("Boolean", "Char", "Byte", "Short", "Int", "Long", "Float", "Double", "Object")
     val refPairs = for {
@@ -777,7 +721,7 @@ object JavalibIRCleaner {
       ClassName("scala.MatchError") -> ClassName("java.lang.AssertionError"),
     )
 
-    val allPairs = functionTypePairs ++ refPairs ++ tuplePairs ++ otherPairs
+    val allPairs = refPairs ++ tuplePairs ++ otherPairs
     allPairs.toMap
   }
 }

From 0d16b42e54d823dbd79a06fb6247730a01206831 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Mon, 25 Nov 2024 23:40:28 +0100
Subject: [PATCH 217/298] Codegen: Inline the target of `Function` nodes in
 their `js.Closure`s.

The body of `Function` nodes always has a simple shape that calls a
helper method. We previously generated that call in the body of the
`js.Closure`, and marked the target method `@inline` so that the
optimizer would always inline it.

Instead, we now directly "inline" it from the codegen, by
generating the `js.MethodDef` right inside the `js.Closure` scope.

As is, this does not change the generated code. However, it may
speed up (cold) linker runs, since it will have less work to do.
Notably, it performs two fewer knowledge queries to find and inline
the target method. It also reduces the total amount of methods to
manipulate in the incremental analysis.

More importantly, this will be necessary later if we want to add
support for `async/await` or `function*/yield`. Indeed, for those,
we will need `await`/`yield` expressions to be lexically scoped
in the body of their enclosing closure. That won't work if they are
in the body of a separate helper method.
---
 .../org/scalajs/nscplugin/GenJSCode.scala     | 263 +++++++++++-------
 .../nscplugin/test/JSNewTargetTest.scala      |  20 +-
 2 files changed, 165 insertions(+), 118 deletions(-)

diff --git a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
index 9839b71954..267b85d20f 100644
--- a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
+++ b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
@@ -159,6 +159,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
     val currentClassSym = new ScopedVar[Symbol]
     private val fieldsMutatedInCurrentClass = new ScopedVar[mutable.Set[Name]]
     private val generatedSAMWrapperCount = new ScopedVar[VarBox[Int]]
+    private val delambdafyTargetDefDefs = new ScopedVar[mutable.Map[Symbol, DefDef]]
 
     def currentThisTypeNullable: jstpe.Type =
       encodeClassType(currentClassSym)
@@ -185,10 +186,12 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
     private val mutableLocalVars = new ScopedVar[mutable.Set[Symbol]]
     private val mutatedLocalVars = new ScopedVar[mutable.Set[Symbol]]
 
-    private def withPerMethodBodyState[A](methodSym: Symbol)(body: => A): A = {
+    private def withPerMethodBodyState[A](methodSym: Symbol,
+        initThisLocalVarIdent: Option[js.LocalIdent] = None)(body: => A): A = {
+
       withScopedVars(
           currentMethodSym := methodSym,
-          thisLocalVarIdent := None,
+          thisLocalVarIdent := initThisLocalVarIdent,
           enclosingLabelDefInfos := Map.empty,
           isModuleInitialized := new VarBox(false),
           undefinedDefaultParams := mutable.Set.empty,
@@ -236,6 +239,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
           currentClassSym := clsSym,
           fieldsMutatedInCurrentClass := mutable.Set.empty,
           generatedSAMWrapperCount := new VarBox(0),
+          delambdafyTargetDefDefs := mutable.Map.empty,
           currentMethodSym := null,
           thisLocalVarIdent := null,
           enclosingLabelDefInfos := null,
@@ -481,7 +485,8 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
             withScopedVars(
                 currentClassSym := sym,
                 fieldsMutatedInCurrentClass := mutable.Set.empty,
-                generatedSAMWrapperCount := new VarBox(0)
+                generatedSAMWrapperCount := new VarBox(0),
+                delambdafyTargetDefDefs := mutable.Map.empty
             ) {
               val tree = if (isJSType(sym)) {
                 if (!sym.isTraitOrInterface && isNonNativeJSClass(sym) &&
@@ -590,6 +595,34 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
       }
     }
 
+    private def collectDefDefs(impl: Template): List[DefDef] = {
+      val b = List.newBuilder[DefDef]
+
+      for (stat <- impl.body) {
+        stat match {
+          case stat: DefDef =>
+            if (stat.symbol.isDelambdafyTarget)
+              delambdafyTargetDefDefs += stat.symbol -> stat
+            else
+              b += stat
+
+          case EmptyTree | _:ValDef =>
+            ()
+
+          case _ =>
+            abort(s"Unexpected tree in template: $stat at ${stat.pos}")
+        }
+      }
+
+      b.result()
+    }
+
+    private def consumeDelambdafyTarget(sym: Symbol): DefDef = {
+      delambdafyTargetDefDefs.remove(sym).getOrElse {
+        abort(s"Cannot resolve delambdafy target $sym at ${sym.pos}")
+      }
+    }
+
     // Generate a class --------------------------------------------------------
 
     /** Gen the IR ClassDef for a class definition (maybe a module class).
@@ -640,26 +673,13 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
       val methodsBuilder = List.newBuilder[js.MethodDef]
       val jsNativeMembersBuilder = List.newBuilder[js.JSNativeMemberDef]
 
-      def gen(tree: Tree): Unit = {
-        tree match {
-          case EmptyTree => ()
-          case Template(_, _, body) => body foreach gen
-
-          case ValDef(mods, name, tpt, rhs) =>
-            () // fields are added via genClassFields()
-
-          case dd: DefDef =>
-            if (dd.symbol.hasAnnotation(JSNativeAnnotation))
-              jsNativeMembersBuilder += genJSNativeMemberDef(dd)
-            else
-              methodsBuilder ++= genMethod(dd)
-
-          case _ => abort("Illegal tree in gen of genClass(): " + tree)
-        }
+      for (dd <- collectDefDefs(impl)) {
+        if (dd.symbol.hasAnnotation(JSNativeAnnotation))
+          jsNativeMembersBuilder += genJSNativeMemberDef(dd)
+        else
+          methodsBuilder ++= genMethod(dd)
       }
 
-      gen(impl)
-
       val fields = if (!isHijacked) genClassFields(cd) else Nil
 
       val jsNativeMembers = jsNativeMembersBuilder.result()
@@ -797,44 +817,31 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
       val generatedMethods = new ListBuffer[js.MethodDef]
       val dispatchMethodNames = new ListBuffer[JSName]
 
-      def gen(tree: Tree): Unit = {
-        tree match {
-          case EmptyTree => ()
-          case Template(_, _, body) => body foreach gen
-
-          case ValDef(mods, name, tpt, rhs) =>
-            () // fields are added via genClassFields()
-
-          case dd: DefDef =>
-            val sym = dd.symbol
-            val exposed = isExposed(sym)
-
-            if (sym.isClassConstructor) {
-              constructorTrees += dd
-            } else if (exposed && sym.isAccessor && !sym.isLazy) {
-              /* Exposed accessors must not be emitted, since the field they
-               * access is enough.
-               */
-            } else if (sym.hasAnnotation(JSOptionalAnnotation)) {
-              // Optional methods must not be emitted
-            } else {
-              generatedMethods ++= genMethod(dd)
+      for (dd <- collectDefDefs(cd.impl)) {
+        val sym = dd.symbol
+        val exposed = isExposed(sym)
 
-              // Collect the names of the dispatchers we have to create
-              if (exposed && !sym.isDeferred) {
-                /* We add symbols that we have to expose here. This way we also
-                 * get inherited stuff that is implemented in this class.
-                 */
-                dispatchMethodNames += jsNameOf(sym)
-              }
-            }
+        if (sym.isClassConstructor) {
+          constructorTrees += dd
+        } else if (exposed && sym.isAccessor && !sym.isLazy) {
+          /* Exposed accessors must not be emitted, since the field they
+           * access is enough.
+           */
+        } else if (sym.hasAnnotation(JSOptionalAnnotation)) {
+          // Optional methods must not be emitted
+        } else {
+          generatedMethods ++= genMethod(dd)
 
-          case _ => abort("Illegal tree in gen of genClass(): " + tree)
+          // Collect the names of the dispatchers we have to create
+          if (exposed && !sym.isDeferred) {
+            /* We add symbols that we have to expose here. This way we also
+             * get inherited stuff that is implemented in this class.
+             */
+            dispatchMethodNames += jsNameOf(sym)
+          }
         }
       }
 
-      gen(cd.impl)
-
       // Static members (exported from the companion object)
       val (staticFields, staticExports) = {
         /* Phase travel is necessary for non-top-level classes, because flatten
@@ -1158,20 +1165,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
 
       val classIdent = encodeClassNameIdent(sym)
 
-      // fill in class info builder
-      def gen(tree: Tree): List[js.MethodDef] = {
-        tree match {
-          case EmptyTree            => Nil
-          case Template(_, _, body) => body.flatMap(gen)
-
-          case dd: DefDef =>
-            genMethod(dd).toList
-
-          case _ =>
-            abort("Illegal tree in gen of genInterface(): " + tree)
-        }
-      }
-      val generatedMethods = gen(cd.impl)
+      val generatedMethods = collectDefDefs(cd.impl).flatMap(genMethod(_))
       val interfaces = genClassInterfaces(sym, forJSClass = false)
 
       val allMemberDefs =
@@ -2045,11 +2039,13 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
      *
      *  Other (normal) methods are emitted with `genMethodDef()`.
      */
-    def genMethodWithCurrentLocalNameScope(dd: DefDef): js.MethodDef = {
+    def genMethodWithCurrentLocalNameScope(dd: DefDef,
+        initThisLocalVarIdent: Option[js.LocalIdent] = None): js.MethodDef = {
+
       implicit val pos = dd.pos
       val sym = dd.symbol
 
-      withPerMethodBodyState(sym) {
+      withPerMethodBodyState(sym, initThisLocalVarIdent) {
         val methodName = encodeMethodSym(sym)
         val originalName = originalNameOfMethod(sym)
 
@@ -6409,13 +6405,16 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
      *
      *  To translate them, we first construct a JS closure for the body:
      *  {{{
-     *  lambda<this, capture1, ..., captureM>(
-     *      _this, capture1, ..., captureM, arg1, ..., argN) {
-     *    _this.someMethod(arg1, ..., argN, capture1, ..., captureM)
+     *  arrow-lambda<_this = this, capture1: U1 = capture1, ..., captureM: UM = captureM>(
+     *      arg1: any, ..., argN: any): any = {
+     *    val arg1Unboxed: T1 = arg1.asInstanceOf[T1];
+     *    ...
+     *    val argNUnboxed: TN = argN.asInstanceOf[TN];
+     *    // inlined body of `someMethod`, boxed
      *  }
      *  }}}
      *  In the closure, input params are unboxed before use, and the result of
-     *  `someMethod()` is boxed back.
+     *  the body of `someMethod` is boxed back.
      *
      *  Then, we wrap that closure in a class satisfying the expected type.
      *  For Scala function types, we use the existing
@@ -6440,53 +6439,101 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
           targetTree @ Select(receiver, _), allArgs0)) = originalFunction
 
       val captureSyms =
-        global.delambdafy.FreeVarTraverser.freeVarsOf(originalFunction)
+        global.delambdafy.FreeVarTraverser.freeVarsOf(originalFunction).toList
       val target = targetTree.symbol
-      val params = paramTrees.map(_.symbol)
 
-      val allArgs = allArgs0 map genExpr
+      val isTargetStatic = compileAsStaticMethod(target)
 
-      val formalCaptures = captureSyms.toList.map(genParamDef(_, pos))
-      val actualCaptures = formalCaptures.map(_.ref)
-
-      val formalArgs = params.map(genParamDef(_))
-
-      val (allFormalCaptures, body, allActualCaptures) = if (!compileAsStaticMethod(target)) {
-        val thisActualCapture = genExpr(receiver)
-        val thisFormalCapture = js.ParamDef(
-            freshLocalIdent("this")(receiver.pos), thisOriginalName,
-            thisActualCapture.tpe, mutable = false)(receiver.pos)
-        val thisCaptureArg = thisFormalCapture.ref
+      // Gen actual captures in the local name scope of the enclosing method
+      val actualCaptures: List[js.Tree] = {
+        val base = captureSyms.map(genVarRef(_))
+        if (isTargetStatic)
+          base
+        else
+          genExpr(receiver) :: base
+      }
 
-        val body = if (isJSType(receiver.tpe) && target.owner != ObjectClass) {
-          assert(isNonNativeJSClass(target.owner) && !isExposed(target),
-              s"A Function lambda is trying to call an exposed JS method ${target.fullName}")
-          genApplyJSClassMethod(thisCaptureArg, target, allArgs)
+      val closure: js.Closure = withNewLocalNameScope {
+        // Gen the formal capture params for the closure
+        val thisFormalCapture: Option[js.ParamDef] = if (isTargetStatic) {
+          None
         } else {
-          genApplyMethodMaybeStatically(thisCaptureArg, target, allArgs)
+          Some(js.ParamDef(
+              freshLocalIdent("this")(receiver.pos), thisOriginalName,
+              toIRType(receiver.tpe), mutable = false)(receiver.pos))
         }
+        val formalCaptures: List[js.ParamDef] =
+          thisFormalCapture.toList ::: captureSyms.map(genParamDef(_, pos))
 
-        (thisFormalCapture :: formalCaptures,
-            body, thisActualCapture :: actualCaptures)
-      } else {
-        val body = genApplyStatic(target, allArgs)
+        // Gen the inlined target method body
+        val genMethodDef = {
+          genMethodWithCurrentLocalNameScope(consumeDelambdafyTarget(target),
+              initThisLocalVarIdent = thisFormalCapture.map(_.name))
+        }
+        val js.MethodDef(methodFlags, _, _, methodParams, _, methodBody) = genMethodDef
 
-        (formalCaptures, body, actualCaptures)
-      }
+        /* If the target method was not supposed to be static, but genMethodDef
+         * turns out to be static, it means it is a non-exposed method of a JS
+         * class. The `this` param was turned into a regular param, for which
+         * we need a `js.VarDef`.
+         */
+        val (maybeThisParamAsVarDef, remainingMethodParams) = {
+          if (methodFlags.namespace.isStatic && !isTargetStatic) {
+            val thisParamDef :: remainingMethodParams = methodParams: @unchecked
+            val thisParamAsVarDef = js.VarDef(thisParamDef.name, thisParamDef.originalName,
+                thisParamDef.ptpe, thisParamDef.mutable, thisFormalCapture.get.ref)
+            (thisParamAsVarDef :: Nil, remainingMethodParams)
+          } else {
+            (Nil, methodParams)
+          }
+        }
 
-      val (patchedFormalArgs, paramsLocals) =
-        patchFunParamsWithBoxes(target, formalArgs, useParamsBeforeLambdaLift = true)
+        // After that, the args found in the `Function` node had better match the remaining method params
+        assert(remainingMethodParams.size == allArgs0.size,
+            s"Arity mismatch: $remainingMethodParams <-> $allArgs0 at $pos")
 
-      val patchedBody =
-        js.Block(paramsLocals :+ ensureResultBoxed(body, target))
+        /* Declare each method param as a VarDef, initialized to the corresponding arg.
+         * In practice, all the args are `This` nodes or `VarRef` nodes, so the
+         * optimizer will alias those VarDefs away.
+         * We do this because we have different Symbols, hence different
+         * encoded LocalIdents.
+         */
+        val methodParamsAsVarDefs = for ((methodParam, arg) <- remainingMethodParams.zip(allArgs0)) yield {
+          js.VarDef(methodParam.name, methodParam.originalName, methodParam.ptpe,
+              methodParam.mutable, genExpr(arg))
+        }
 
-      val closure = js.Closure(
+        /* Adapt the params and result so that they are boxed from the outside.
+         * We need this because a `js.Closure` is always from `any`s to `any`.
+         *
+         * TODO In total we generate *3* locals for each original param: the
+         * patched ParamDef, the VarDef for the unboxed value, and a VarDef for
+         * the original parameter of the delambdafy target. In theory we only
+         * need 2: can we make it so?
+         */
+        val formalArgs = paramTrees.map(p => genParamDef(p.symbol))
+        val (patchedFormalArgs, paramsLocals) =
+          patchFunParamsWithBoxes(target, formalArgs, useParamsBeforeLambdaLift = true)
+        val patchedBodyWithBox =
+          ensureResultBoxed(methodBody.get, target)
+
+        // Finally, assemble all the pieces
+        val fullClosureBody = js.Block(
+          paramsLocals :::
+          maybeThisParamAsVarDef :::
+          methodParamsAsVarDefs :::
+          patchedBodyWithBox ::
+          Nil
+        )
+        js.Closure(
           arrow = true,
-          allFormalCaptures,
+          formalCaptures,
           patchedFormalArgs,
           restParam = None,
-          patchedBody,
-          allActualCaptures)
+          fullClosureBody,
+          actualCaptures
+        )
+      }
 
       // Wrap the closure in the appropriate box for the SAM type
       val funSym = originalFunction.tpe.typeSymbolDirect
@@ -6494,7 +6541,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
         /* This is a scala.FunctionN. We use the existing AnonFunctionN
          * wrapper.
          */
-        genJSFunctionToScala(closure, params.size)
+        genJSFunctionToScala(closure, paramTrees.size)
       } else {
         /* This is an arbitrary SAM type (can only happen in 2.12).
          * We have to synthesize a class like LambdaMetaFactory would do on
diff --git a/compiler/src/test/scala/org/scalajs/nscplugin/test/JSNewTargetTest.scala b/compiler/src/test/scala/org/scalajs/nscplugin/test/JSNewTargetTest.scala
index edfa1afd01..2e2c1664f2 100644
--- a/compiler/src/test/scala/org/scalajs/nscplugin/test/JSNewTargetTest.scala
+++ b/compiler/src/test/scala/org/scalajs/nscplugin/test/JSNewTargetTest.scala
@@ -122,16 +122,6 @@ class JSNewTargetTest extends DirectTest with TestHelpers {
     }
     """ hasErrors
     """
-      |newSource1.scala:4: error: Illegal use of js.`new`.target.
-      |It can only be used in the constructor of a JS class, as a statement or in the rhs of a val or var.
-      |It cannot be used inside a lambda or by-name parameter, nor in any other location.
-      |      val x = () => js.`new`.target
-      |                             ^
-      |newSource1.scala:5: error: Illegal use of js.`new`.target.
-      |It can only be used in the constructor of a JS class, as a statement or in the rhs of a val or var.
-      |It cannot be used inside a lambda or by-name parameter, nor in any other location.
-      |      val y = Option(null).getOrElse(js.`new`.target)
-      |                                              ^
       |newSource1.scala:6: error: Illegal use of js.`new`.target.
       |It can only be used in the constructor of a JS class, as a statement or in the rhs of a val or var.
       |It cannot be used inside a lambda or by-name parameter, nor in any other location.
@@ -142,6 +132,16 @@ class JSNewTargetTest extends DirectTest with TestHelpers {
       |It cannot be used inside a lambda or by-name parameter, nor in any other location.
       |      val w: js.ThisFunction0[Any, Any] = (x: Any) => js.`new`.target
       |                                                               ^
+      |newSource1.scala:4: error: Illegal use of js.`new`.target.
+      |It can only be used in the constructor of a JS class, as a statement or in the rhs of a val or var.
+      |It cannot be used inside a lambda or by-name parameter, nor in any other location.
+      |      val x = () => js.`new`.target
+      |                             ^
+      |newSource1.scala:5: error: Illegal use of js.`new`.target.
+      |It can only be used in the constructor of a JS class, as a statement or in the rhs of a val or var.
+      |It cannot be used inside a lambda or by-name parameter, nor in any other location.
+      |      val y = Option(null).getOrElse(js.`new`.target)
+      |                                              ^
     """
 
   }

From a235da719cf0755ac17c0a67f6add4f94635d524 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Thu, 5 Dec 2024 16:15:08 +0100
Subject: [PATCH 218/298] Update the CLA check after the rename of Lightbend to
 Akka.

The URLs did contain a redirect, but `curl` does not follow
redirects by default.

We should always have the canonical URLs anyway, so I update them
instead of making `curl` follow redirects.
---
 ci/check-cla.sh | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/ci/check-cla.sh b/ci/check-cla.sh
index 05fc9ad6b0..fd3e487c95 100755
--- a/ci/check-cla.sh
+++ b/ci/check-cla.sh
@@ -4,13 +4,13 @@ set -eux
 AUTHOR="$1"
 echo "Pull request submitted by $AUTHOR";
 URL_AUTHOR=$(jq -rn --arg x "$AUTHOR" '$x|@uri')
-signed=$(curl -s "https://www.lightbend.com/contribute/cla/scala/check/$URL_AUTHOR" | jq -r ".signed");
+signed=$(curl -s "https://contribute.akka.io/contribute/cla/scala/check/$URL_AUTHOR" | jq -r ".signed");
 if [ "$signed" = "true" ] ; then
   echo "CLA check for $AUTHOR successful";
 else
   echo "CLA check for $AUTHOR failed";
   echo "Please sign the Scala CLA to contribute to Scala.js.";
-  echo "Go to https://www.lightbend.com/contribute/cla/scala and then";
+  echo "Go to https://contribute.akka.io/contribute/cla/scala and then";
   echo "comment on the pull request to ask for a new check.";
   exit 1;
 fi;

From 6ff7c8e7a349d07ddb5883c341e72bd7834cc97d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Sat, 14 Dec 2024 11:03:19 +0100
Subject: [PATCH 219/298] Use the new dedicated GitHub action to check the CLA.

See https://github.com/scala/cla-checker
---
 .github/workflows/cla.yml |  6 ++++--
 ci/check-cla.sh           | 16 ----------------
 2 files changed, 4 insertions(+), 18 deletions(-)
 delete mode 100755 ci/check-cla.sh

diff --git a/.github/workflows/cla.yml b/.github/workflows/cla.yml
index e3a39bd5aa..718146327c 100644
--- a/.github/workflows/cla.yml
+++ b/.github/workflows/cla.yml
@@ -4,5 +4,7 @@ jobs:
   check:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v1
-    - run: ./ci/check-cla.sh "${{ github.event.pull_request.user.login }}"
+      - name: Verify CLA
+        uses: scala/cla-checker@v1
+        with:
+          author: ${{ github.event.pull_request.user.login }}
diff --git a/ci/check-cla.sh b/ci/check-cla.sh
deleted file mode 100755
index fd3e487c95..0000000000
--- a/ci/check-cla.sh
+++ /dev/null
@@ -1,16 +0,0 @@
-#!/usr/bin/env bash
-set -eux
-
-AUTHOR="$1"
-echo "Pull request submitted by $AUTHOR";
-URL_AUTHOR=$(jq -rn --arg x "$AUTHOR" '$x|@uri')
-signed=$(curl -s "https://contribute.akka.io/contribute/cla/scala/check/$URL_AUTHOR" | jq -r ".signed");
-if [ "$signed" = "true" ] ; then
-  echo "CLA check for $AUTHOR successful";
-else
-  echo "CLA check for $AUTHOR failed";
-  echo "Please sign the Scala CLA to contribute to Scala.js.";
-  echo "Go to https://contribute.akka.io/contribute/cla/scala and then";
-  echo "comment on the pull request to ask for a new check.";
-  exit 1;
-fi;

From 2f0eed8fe960ec0a5ee6ad06e2858796f94537af Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Sat, 14 Dec 2024 12:56:09 +0100
Subject: [PATCH 220/298] Remove the stat/expr distinction from
 `Transformers.Transformer`.

Recent changes have all but removed the distinction between
statements and expressions in the IR. Notably:

* bb4f6da3628913639a82ad371c22731d9b2347f5
  Allow Return arg to be a void if the target Labeled is a void.
* cdcff9973579ed77e87343f3edd9429661b4a786
  Rename NoType to VoidType and print it as "void".

Therefore, it made no sense anymore that `Transformer.transform`
had an `isStat` argument. In fact, the first of the two commits
mentionned above semi-broke the semantics of that argument anyway.
Moreover, `isStat` was never *used* in our codebase (only forwarded
everywhere for no reason).

The only exception was a deserialization hack for IR <= 1.5. This
one was already hacking around the fact the IR produced back then
was not well-typed. See #4442 for context.

We now remove that parameter everywhere. It makes the
deserialization hack a bit more verbose, but everything else
becomes simpler.
---
 .../org/scalajs/nscplugin/GenJSCode.scala     |  31 ++--
 .../scala/org/scalajs/ir/Serializers.scala    |  97 ++++++----
 .../scala/org/scalajs/ir/Transformers.scala   | 166 ++++++++----------
 .../src/main/scala/org/scalajs/ir/Trees.scala |   2 +-
 .../scala/org/scalajs/ir/PrintersTest.scala   |   2 +-
 .../backend/emitter/FunctionEmitter.scala     |  11 +-
 .../linker/backend/emitter/Transients.scala   |  35 ++--
 .../backend/wasmemitter/WasmTransients.scala  |  33 ++--
 project/BinaryIncompatibilities.scala         |   9 +
 project/JavalibIRCleaner.scala                |  12 +-
 10 files changed, 205 insertions(+), 193 deletions(-)

diff --git a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
index 267b85d20f..41b035fde2 100644
--- a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
+++ b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
@@ -1107,19 +1107,19 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
 
         // After the super call, substitute `selfRef` for `This()`
         val afterSuper = new ir.Transformers.Transformer {
-          override def transform(tree: js.Tree, isStat: Boolean): js.Tree = tree match {
+          override def transform(tree: js.Tree): js.Tree = tree match {
             case js.This() =>
               selfRef(tree.pos)
 
             // Don't traverse closure boundaries
             case closure: js.Closure =>
-              val newCaptureValues = closure.captureValues.map(transformExpr)
+              val newCaptureValues = transformTrees(closure.captureValues)
               closure.copy(captureValues = newCaptureValues)(closure.pos)
 
             case tree =>
-              super.transform(tree, isStat)
+              super.transform(tree)
           }
-        }.transformStats(ctorBody.afterSuper)
+        }.transformTrees(ctorBody.afterSuper)
 
         beforeSuper ::: superCall ::: afterSuper
       }
@@ -2170,20 +2170,18 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
         js.ParamDef(name, originalName, ptpe, newMutable(name.name, mutable))(p.pos)
       }
       val transformer = new ir.Transformers.Transformer {
-        override def transform(tree: js.Tree, isStat: Boolean): js.Tree = tree match {
+        override def transform(tree: js.Tree): js.Tree = tree match {
           case js.VarDef(name, originalName, vtpe, mutable, rhs) =>
-            assert(isStat, s"found a VarDef in expression position at ${tree.pos}")
             super.transform(js.VarDef(name, originalName, vtpe,
-                newMutable(name.name, mutable), rhs)(tree.pos), isStat)
+                newMutable(name.name, mutable), rhs)(tree.pos))
           case js.Closure(arrow, captureParams, params, restParam, body, captureValues) =>
             js.Closure(arrow, captureParams, params, restParam, body,
-                captureValues.map(transformExpr))(tree.pos)
+                transformTrees(captureValues))(tree.pos)
           case _ =>
-            super.transform(tree, isStat)
+            super.transform(tree)
         }
       }
-      val newBody = body.map(
-          b => transformer.transform(b, isStat = resultType == jstpe.VoidType))
+      val newBody = transformer.transformTreeOpt(body)
       js.MethodDef(flags, methodName, originalName, newParams, resultType,
           newBody)(methodDef.optimizerHints, Unversioned)(methodDef.pos)
     }
@@ -2208,18 +2206,17 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
         js.ParamDef(name, originalName, newType(name, ptpe), mutable)(p.pos)
       }
       val transformer = new ir.Transformers.Transformer {
-        override def transform(tree: js.Tree, isStat: Boolean): js.Tree = tree match {
+        override def transform(tree: js.Tree): js.Tree = tree match {
           case tree @ js.VarRef(name) =>
             js.VarRef(name)(newType(name, tree.tpe))(tree.pos)
           case js.Closure(arrow, captureParams, params, restParam, body, captureValues) =>
             js.Closure(arrow, captureParams, params, restParam, body,
-                captureValues.map(transformExpr))(tree.pos)
+                transformTrees(captureValues))(tree.pos)
           case _ =>
-            super.transform(tree, isStat)
+            super.transform(tree)
         }
       }
-      val newBody = body.map(
-          b => transformer.transform(b, isStat = resultType == jstpe.VoidType))
+      val newBody = transformer.transformTreeOpt(body)
       js.MethodDef(flags, methodName, originalName, newParams, resultType,
           newBody)(methodDef.optimizerHints, Unversioned)(methodDef.pos)
     }
@@ -7282,7 +7279,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
 
     def traverse(traverser: ir.Traversers.Traverser): Unit = ()
 
-    def transform(transformer: ir.Transformers.Transformer, isStat: Boolean)(
+    def transform(transformer: ir.Transformers.Transformer)(
         implicit pos: ir.Position): js.Tree = {
       js.Transient(this)
     }
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
index 0a366a12b5..11bafee148 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
@@ -1645,15 +1645,15 @@ object Serializers {
                * We must replace those occurrences with a `Class_name` as well.
                */
               val transformer = new Transformers.Transformer {
-                override def transform(tree: Tree, isStat: Boolean): Tree = tree match {
+                override def transform(tree: Tree): Tree = tree match {
                   case JSSelect(_, StringLiteral("name")) =>
                     implicit val pos = tree.pos
                     UnaryOp(UnaryOp.Class_name, thisJLClass)
                   case _ =>
-                    super.transform(tree, isStat)
+                    super.transform(tree)
                 }
               }
-              transformer.transform(method.body.get, isStat = method.resultType == VoidType)
+              transformer.transform(method.body.get)
           }
 
           val newOptimizerHints =
@@ -2065,40 +2065,69 @@ object Serializers {
       JSNativeMemberDef(flags, name, jsNativeLoadSpec)
     }
 
-    private def bodyHack5(body: Tree, isStat: Boolean): Tree = {
-      if (!hacks.use5) {
-        body
-      } else {
-        /* #4442 and #4601: Patch Labeled, If, Match and TryCatch nodes in
-         * statement position to have type VoidType. These 4 nodes are the
-         * control structures whose result type is explicitly specified (and
-         * not derived from their children like Block or TryFinally, or
-         * constant like While).
-         */
-        new Transformers.Transformer {
-          override def transform(tree: Tree, isStat: Boolean): Tree = {
-            val newTree = super.transform(tree, isStat)
-            if (isStat && newTree.tpe != VoidType) {
-              newTree match {
-                case Labeled(label, _, body) =>
-                  Labeled(label, VoidType, body)(newTree.pos)
-                case If(cond, thenp, elsep) =>
-                  If(cond, thenp, elsep)(VoidType)(newTree.pos)
-                case Match(selector, cases, default) =>
-                  Match(selector, cases, default)(VoidType)(newTree.pos)
-                case TryCatch(block, errVar, errVarOriginalName, handler) =>
-                  TryCatch(block, errVar, errVarOriginalName, handler)(VoidType)(newTree.pos)
-                case _ =>
-                  newTree
-              }
-            } else {
-              newTree
-            }
-          }
-        }.transform(body, isStat)
+    /* #4442 and #4601: Patch Labeled, If, Match and TryCatch nodes in
+     * statement position to have type VoidType. These 4 nodes are the
+     * control structures whose result type is explicitly specified (and
+     * not derived from their children like Block or TryFinally, or
+     * constant like While).
+     */
+    private object BodyHack5Transformer extends Transformers.Transformer {
+      def transformStat(tree: Tree): Tree = {
+        implicit val pos = tree.pos
+
+        tree match {
+          // Nodes that we actually need to alter
+          case Labeled(label, _, body) =>
+            Labeled(label, VoidType, transformStat(body))
+          case If(cond, thenp, elsep) =>
+            If(transform(cond), transformStat(thenp), transformStat(elsep))(VoidType)
+          case Match(selector, cases, default) =>
+            Match(transform(selector), cases.map(c => (c._1, transformStat(c._2))),
+                transformStat(default))(VoidType)
+          case TryCatch(block, errVar, errVarOriginalName, handler) =>
+            TryCatch(transformStat(block), errVar, errVarOriginalName,
+                transformStat(handler))(VoidType)
+
+          // Nodes for which we need to forward the statement position
+          case Block(stats) =>
+            Block(stats.map(transformStat(_)))
+          case TryFinally(block, finalizer) =>
+            Block(transformStat(block), transformStat(finalizer))
+
+          // For everything else, delegate to transform
+          case _ =>
+            transform(tree)
+        }
       }
+
+      override def transform(tree: Tree): Tree = {
+        implicit val pos = tree.pos
+
+        tree match {
+          // Nodes that force a statement position for some of their parts
+          case Block(stats) =>
+            Block(stats.init.map(transformStat(_)), transform(stats.last))
+          case While(cond, body) =>
+            While(transform(cond), transformStat(body))
+          case ForIn(obj, keyVar, keyVarOriginalName, body) =>
+            ForIn(transform(obj), keyVar, keyVarOriginalName, transformStat(body))
+          case TryFinally(block, finalizer) =>
+            TryFinally(transform(block), transformStat(finalizer))
+
+          case _ =>
+            super.transform(tree)
+        }
+      }
+
+      def transform(tree: Tree, isStat: Boolean): Tree =
+        if (isStat) transformStat(tree)
+        else transform(tree)
     }
 
+    private def bodyHack5(body: Tree, isStat: Boolean): Tree =
+      if (!hacks.use5) body
+      else BodyHack5Transformer.transform(body, isStat)
+
     private def bodyHack5Expr(body: Tree): Tree = bodyHack5(body, isStat = false)
 
     def readTopLevelExportDef(): TopLevelExportDef = {
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Transformers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Transformers.scala
index 10f490225b..5aa07f32ff 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Transformers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Transformers.scala
@@ -19,204 +19,197 @@ import Version.Unversioned
 object Transformers {
 
   abstract class Transformer {
-    final def transformStats(trees: List[Tree]): List[Tree] =
-      trees.map(transformStat(_))
-
-    final def transformStat(tree: Tree): Tree =
-      transform(tree, isStat = true)
-
-    final def transformExpr(tree: Tree): Tree =
-      transform(tree, isStat = false)
-
-    def transformExprOrJSSpread(tree: TreeOrJSSpread): TreeOrJSSpread = {
+    final def transformTreeOrJSSpread(tree: TreeOrJSSpread): TreeOrJSSpread = {
       implicit val pos = tree.pos
 
       tree match {
-        case JSSpread(items) => JSSpread(transformExpr(items))
-        case tree: Tree      => transformExpr(tree)
+        case JSSpread(items) => JSSpread(transform(items))
+        case tree: Tree      => transform(tree)
       }
     }
 
-    def transform(tree: Tree, isStat: Boolean): Tree = {
+    final def transformTrees(trees: List[Tree]): List[Tree] =
+      trees.map(transform(_))
+
+    final def transformTreeOpt(treeOpt: Option[Tree]): Option[Tree] =
+      treeOpt.map(transform(_))
+
+    def transform(tree: Tree): Tree = {
       implicit val pos = tree.pos
 
       tree match {
         // Definitions
 
         case VarDef(ident, originalName, vtpe, mutable, rhs) =>
-          VarDef(ident, originalName, vtpe, mutable, transformExpr(rhs))
+          VarDef(ident, originalName, vtpe, mutable, transform(rhs))
 
         // Control flow constructs
 
         case Block(stats) =>
-          Block(stats.init.map(transformStat) :+ transform(stats.last, isStat))
+          Block(transformTrees(stats))
 
         case Labeled(label, tpe, body) =>
-          Labeled(label, tpe, transform(body, isStat))
+          Labeled(label, tpe, transform(body))
 
         case Assign(lhs, rhs) =>
-          Assign(transformExpr(lhs).asInstanceOf[AssignLhs], transformExpr(rhs))
+          Assign(transform(lhs).asInstanceOf[AssignLhs], transform(rhs))
 
         case Return(expr, label) =>
-          Return(transformExpr(expr), label) // pessimistic; maybe `expr` is actually a statement
+          Return(transform(expr), label)
 
         case If(cond, thenp, elsep) =>
-          If(transformExpr(cond), transform(thenp, isStat),
-              transform(elsep, isStat))(tree.tpe)
+          If(transform(cond), transform(thenp), transform(elsep))(tree.tpe)
 
         case While(cond, body) =>
-          While(transformExpr(cond), transformStat(body))
+          While(transform(cond), transform(body))
 
         case ForIn(obj, keyVar, keyVarOriginalName, body) =>
-          ForIn(transformExpr(obj), keyVar, keyVarOriginalName,
-              transformStat(body))
+          ForIn(transform(obj), keyVar, keyVarOriginalName, transform(body))
 
         case TryCatch(block, errVar, errVarOriginalName, handler) =>
-          TryCatch(transform(block, isStat), errVar, errVarOriginalName,
-              transform(handler, isStat))(tree.tpe)
+          TryCatch(transform(block), errVar, errVarOriginalName,
+              transform(handler))(tree.tpe)
 
         case TryFinally(block, finalizer) =>
-          TryFinally(transform(block, isStat), transformStat(finalizer))
+          TryFinally(transform(block), transform(finalizer))
 
         case Throw(expr) =>
-          Throw(transformExpr(expr))
+          Throw(transform(expr))
 
         case Match(selector, cases, default) =>
-          Match(transformExpr(selector),
-              cases map (c => (c._1, transform(c._2, isStat))),
-              transform(default, isStat))(tree.tpe)
+          Match(transform(selector), cases.map(c => (c._1, transform(c._2))),
+              transform(default))(tree.tpe)
 
         // Scala expressions
 
         case New(className, ctor, args) =>
-          New(className, ctor, args map transformExpr)
+          New(className, ctor, transformTrees(args))
 
         case Select(qualifier, field) =>
-          Select(transformExpr(qualifier), field)(tree.tpe)
+          Select(transform(qualifier), field)(tree.tpe)
 
         case Apply(flags, receiver, method, args) =>
-          Apply(flags, transformExpr(receiver), method,
-              args map transformExpr)(tree.tpe)
+          Apply(flags, transform(receiver), method,
+              transformTrees(args))(tree.tpe)
 
         case ApplyStatically(flags, receiver, className, method, args) =>
-          ApplyStatically(flags, transformExpr(receiver), className, method,
-              args map transformExpr)(tree.tpe)
+          ApplyStatically(flags, transform(receiver), className, method,
+              transformTrees(args))(tree.tpe)
 
         case ApplyStatic(flags, className, method, args) =>
-          ApplyStatic(flags, className, method, args map transformExpr)(tree.tpe)
+          ApplyStatic(flags, className, method, transformTrees(args))(tree.tpe)
 
         case ApplyDynamicImport(flags, className, method, args) =>
-          ApplyDynamicImport(flags, className, method, args.map(transformExpr))
+          ApplyDynamicImport(flags, className, method, transformTrees(args))
 
         case UnaryOp(op, lhs) =>
-          UnaryOp(op, transformExpr(lhs))
+          UnaryOp(op, transform(lhs))
 
         case BinaryOp(op, lhs, rhs) =>
-          BinaryOp(op, transformExpr(lhs), transformExpr(rhs))
+          BinaryOp(op, transform(lhs), transform(rhs))
 
         case NewArray(tpe, length) =>
-          NewArray(tpe, transformExpr(length))
+          NewArray(tpe, transform(length))
 
         case ArrayValue(tpe, elems) =>
-          ArrayValue(tpe, elems map transformExpr)
+          ArrayValue(tpe, transformTrees(elems))
 
         case ArrayLength(array) =>
-          ArrayLength(transformExpr(array))
+          ArrayLength(transform(array))
 
         case ArraySelect(array, index) =>
-          ArraySelect(transformExpr(array), transformExpr(index))(tree.tpe)
+          ArraySelect(transform(array), transform(index))(tree.tpe)
 
         case RecordValue(tpe, elems) =>
-          RecordValue(tpe, elems map transformExpr)
+          RecordValue(tpe, transformTrees(elems))
 
         case RecordSelect(record, field) =>
-          RecordSelect(transformExpr(record), field)(tree.tpe)
+          RecordSelect(transform(record), field)(tree.tpe)
 
         case IsInstanceOf(expr, testType) =>
-          IsInstanceOf(transformExpr(expr), testType)
+          IsInstanceOf(transform(expr), testType)
 
         case AsInstanceOf(expr, tpe) =>
-          AsInstanceOf(transformExpr(expr), tpe)
+          AsInstanceOf(transform(expr), tpe)
 
         case GetClass(expr) =>
-          GetClass(transformExpr(expr))
+          GetClass(transform(expr))
 
         case Clone(expr) =>
-          Clone(transformExpr(expr))
+          Clone(transform(expr))
 
         case IdentityHashCode(expr) =>
-          IdentityHashCode(transformExpr(expr))
+          IdentityHashCode(transform(expr))
 
         case WrapAsThrowable(expr) =>
-          WrapAsThrowable(transformExpr(expr))
+          WrapAsThrowable(transform(expr))
 
         case UnwrapFromThrowable(expr) =>
-          UnwrapFromThrowable(transformExpr(expr))
+          UnwrapFromThrowable(transform(expr))
 
         // JavaScript expressions
 
         case JSNew(ctor, args) =>
-          JSNew(transformExpr(ctor), args.map(transformExprOrJSSpread))
+          JSNew(transform(ctor), args.map(transformTreeOrJSSpread))
 
         case JSPrivateSelect(qualifier, field) =>
-          JSPrivateSelect(transformExpr(qualifier), field)
+          JSPrivateSelect(transform(qualifier), field)
 
         case JSSelect(qualifier, item) =>
-          JSSelect(transformExpr(qualifier), transformExpr(item))
+          JSSelect(transform(qualifier), transform(item))
 
         case JSFunctionApply(fun, args) =>
-          JSFunctionApply(transformExpr(fun), args.map(transformExprOrJSSpread))
+          JSFunctionApply(transform(fun), args.map(transformTreeOrJSSpread))
 
         case JSMethodApply(receiver, method, args) =>
-          JSMethodApply(transformExpr(receiver), transformExpr(method),
-              args.map(transformExprOrJSSpread))
+          JSMethodApply(transform(receiver), transform(method),
+              args.map(transformTreeOrJSSpread))
 
         case JSSuperSelect(superClass, qualifier, item) =>
-          JSSuperSelect(superClass, transformExpr(qualifier),
-              transformExpr(item))
+          JSSuperSelect(superClass, transform(qualifier), transform(item))
 
         case JSSuperMethodCall(superClass, receiver, method, args) =>
-          JSSuperMethodCall(superClass, transformExpr(receiver),
-              transformExpr(method), args.map(transformExprOrJSSpread))
+          JSSuperMethodCall(superClass, transform(receiver),
+              transform(method), args.map(transformTreeOrJSSpread))
 
         case JSSuperConstructorCall(args) =>
-          JSSuperConstructorCall(args.map(transformExprOrJSSpread))
+          JSSuperConstructorCall(args.map(transformTreeOrJSSpread))
 
         case JSImportCall(arg) =>
-          JSImportCall(transformExpr(arg))
+          JSImportCall(transform(arg))
 
         case JSDelete(qualifier, item) =>
-          JSDelete(transformExpr(qualifier), transformExpr(item))
+          JSDelete(transform(qualifier), transform(item))
 
         case JSUnaryOp(op, lhs) =>
-          JSUnaryOp(op, transformExpr(lhs))
+          JSUnaryOp(op, transform(lhs))
 
         case JSBinaryOp(op, lhs, rhs) =>
-          JSBinaryOp(op, transformExpr(lhs), transformExpr(rhs))
+          JSBinaryOp(op, transform(lhs), transform(rhs))
 
         case JSArrayConstr(items) =>
-          JSArrayConstr(items.map(transformExprOrJSSpread))
+          JSArrayConstr(items.map(transformTreeOrJSSpread))
 
         case JSObjectConstr(fields) =>
           JSObjectConstr(fields.map { field =>
-            (transformExpr(field._1), transformExpr(field._2))
+            (transform(field._1), transform(field._2))
           })
 
         case JSTypeOfGlobalRef(globalRef) =>
-          JSTypeOfGlobalRef(transformExpr(globalRef).asInstanceOf[JSGlobalRef])
+          JSTypeOfGlobalRef(transform(globalRef).asInstanceOf[JSGlobalRef])
 
         // Atomic expressions
 
         case Closure(arrow, captureParams, params, restParam, body, captureValues) =>
-          Closure(arrow, captureParams, params, restParam, transformExpr(body),
-              captureValues.map(transformExpr))
+          Closure(arrow, captureParams, params, restParam, transform(body),
+              transformTrees(captureValues))
 
         case CreateJSClass(className, captureValues) =>
-          CreateJSClass(className, captureValues.map(transformExpr))
+          CreateJSClass(className, transformTrees(captureValues))
 
         // Transients
         case Transient(value) =>
-          value.transform(this, isStat)
+          value.transform(this)
 
         // Trees that need not be transformed
 
@@ -233,7 +226,7 @@ object Transformers {
     def transformClassDef(tree: ClassDef): ClassDef = {
       import tree._
       ClassDef(name, originalName, kind, jsClassCaptures, superClass,
-          interfaces, jsSuperClass.map(transformExpr), jsNativeLoadSpec,
+          interfaces, transformTreeOpt(jsSuperClass), jsNativeLoadSpec,
           fields.map(transformAnyFieldDef(_)),
           methods.map(transformMethodDef), jsConstructor.map(transformJSConstructorDef),
           jsMethodProps.map(transformJSMethodPropDef), jsNativeMembers,
@@ -246,7 +239,7 @@ object Transformers {
 
     def transformMethodDef(methodDef: MethodDef): MethodDef = {
       val MethodDef(flags, name, originalName, args, resultType, body) = methodDef
-      val newBody = body.map(transform(_, isStat = resultType == VoidType))
+      val newBody = transformTreeOpt(body)
       MethodDef(flags, name, originalName, args, resultType, newBody)(
           methodDef.optimizerHints, Unversioned)(methodDef.pos)
     }
@@ -265,29 +258,26 @@ object Transformers {
         case JSPropertyDef(flags, name, getterBody, setterArgAndBody) =>
           JSPropertyDef(
               flags,
-              transformExpr(name),
-              getterBody.map(transformStat),
-              setterArgAndBody map { case (arg, body) =>
-                (arg, transformStat(body))
+              transform(name),
+              transformTreeOpt(getterBody),
+              setterArgAndBody.map { case (arg, body) =>
+                (arg, transform(body))
               })(Unversioned)(jsMethodPropDef.pos)
       }
     }
 
     def transformJSMethodDef(jsMethodDef: JSMethodDef): JSMethodDef = {
       val JSMethodDef(flags, name, args, restParam, body) = jsMethodDef
-      JSMethodDef(flags, transformExpr(name), args, restParam, transformExpr(body))(
+      JSMethodDef(flags, transform(name), args, restParam, transform(body))(
           jsMethodDef.optimizerHints, Unversioned)(jsMethodDef.pos)
     }
 
     def transformJSConstructorBody(body: JSConstructorBody): JSConstructorBody = {
       implicit val pos = body.pos
 
-      val newBeforeSuper = body.beforeSuper.map(transformStat(_))
-      val newSuperCall = transformStat(body.superCall).asInstanceOf[JSSuperConstructorCall]
-      val newAfterSuper = body.afterSuper match {
-        case stats :+ expr => stats.map(transformStat(_)) :+ transformExpr(expr)
-        case empty         => empty // cannot use Nil here because the compiler does not know that it is exhaustive
-      }
+      val newBeforeSuper = transformTrees(body.beforeSuper)
+      val newSuperCall = transform(body.superCall).asInstanceOf[JSSuperConstructorCall]
+      val newAfterSuper = transformTrees(body.afterSuper)
 
       JSConstructorBody(newBeforeSuper, newSuperCall, newAfterSuper)
     }
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala b/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
index bf7eaff25b..4b1e58ce12 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
@@ -1158,7 +1158,7 @@ object Trees {
        *
        *  Implementations should transform contained trees and potentially adjust the result.
        */
-      def transform(transformer: Transformers.Transformer, isStat: Boolean)(
+      def transform(transformer: Transformers.Transformer)(
           implicit pos: Position): Tree
 
       /** Prints the IR representation of this transient node.
diff --git a/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala b/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala
index 980b7c9bc3..052db4b9da 100644
--- a/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala
+++ b/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala
@@ -948,7 +948,7 @@ class PrintersTest {
 
       def traverse(traverser: Traversers.Traverser): Unit = ???
 
-      def transform(transformer: Transformers.Transformer, isStat: Boolean)(
+      def transform(transformer: Transformers.Transformer)(
           implicit pos: Position): Tree = ???
 
       def printIR(out: Printers.IRTreePrinter): Unit = {
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
index 834ec7a554..f2847be772 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
@@ -3355,10 +3355,8 @@ private object FunctionEmitter {
 
     def traverse(traverser: Traverser): Unit = ()
 
-    def transform(transformer: Transformer, isStat: Boolean)(
-        implicit pos: Position): Tree = {
+    def transform(transformer: Transformer)(implicit pos: Position): Tree =
       Transient(this)
-    }
 
     def printIR(out: org.scalajs.ir.Printers.IRTreePrinter): Unit =
       out.print(ident.name)
@@ -3373,10 +3371,9 @@ private object FunctionEmitter {
       traverser.traverse(argArray)
     }
 
-    def transform(transformer: Transformer, isStat: Boolean)(
-        implicit pos: Position): Tree = {
-      Transient(JSNewVararg(transformer.transformExpr(ctor),
-          transformer.transformExpr(argArray)))
+    def transform(transformer: Transformer)(implicit pos: Position): Tree = {
+      Transient(JSNewVararg(transformer.transform(ctor),
+          transformer.transform(argArray)))
     }
 
     def printIR(out: IRTreePrinter): Unit = {
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Transients.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Transients.scala
index dc772cfa1a..61f9ece247 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Transients.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Transients.scala
@@ -40,9 +40,9 @@ object Transients {
     def traverse(traverser: Traverser): Unit =
       traverser.traverse(expr)
 
-    def transform(transformer: Transformer, isStat: Boolean)(
+    def transform(transformer: Transformer)(
         implicit pos: Position): Tree = {
-      Transient(Cast(transformer.transformExpr(expr), tpe))
+      Transient(Cast(transformer.transform(expr), tpe))
     }
 
     def printIR(out: IRTreePrinter): Unit = {
@@ -72,12 +72,9 @@ object Transients {
       traverser.traverse(length)
     }
 
-    def transform(transformer: Transformer, isStat: Boolean)(
-        implicit pos: Position): Tree = {
-      import transformer.transformExpr
-
-      Transient(SystemArrayCopy(transformExpr(src), transformExpr(srcPos),
-          transformExpr(dest), transformExpr(destPos), transformExpr(length)))
+    def transform(t: Transformer)(implicit pos: Position): Tree = {
+      Transient(SystemArrayCopy(t.transform(src), t.transform(srcPos),
+          t.transform(dest), t.transform(destPos), t.transform(length)))
     }
 
     def printIR(out: IRTreePrinter): Unit = {
@@ -101,9 +98,9 @@ object Transients {
     def traverse(traverser: Traverser): Unit =
       traverser.traverse(runtimeClass)
 
-    def transform(transformer: Transformer, isStat: Boolean)(
+    def transform(transformer: Transformer)(
         implicit pos: Position): Tree = {
-      Transient(ZeroOf(transformer.transformExpr(runtimeClass)))
+      Transient(ZeroOf(transformer.transform(runtimeClass)))
     }
 
     def printIR(out: IRTreePrinter): Unit = {
@@ -126,10 +123,10 @@ object Transients {
       traverser.traverse(nativeArray)
     }
 
-    def transform(transformer: Transformer, isStat: Boolean)(
+    def transform(transformer: Transformer)(
         implicit pos: Position): Tree = {
-      Transient(NativeArrayWrapper(transformer.transformExpr(elemClass),
-          transformer.transformExpr(nativeArray))(tpe))
+      Transient(NativeArrayWrapper(transformer.transform(elemClass),
+          transformer.transform(nativeArray))(tpe))
     }
 
     def printIR(out: IRTreePrinter): Unit = {
@@ -150,9 +147,9 @@ object Transients {
     def traverse(traverser: Traverser): Unit =
       traverser.traverse(obj)
 
-    def transform(transformer: Transformer, isStat: Boolean)(
+    def transform(transformer: Transformer)(
         implicit pos: Position): Tree = {
-      Transient(ObjectClassName(transformer.transformExpr(obj)))
+      Transient(ObjectClassName(transformer.transform(obj)))
     }
 
     def printIR(out: IRTreePrinter): Unit = {
@@ -172,9 +169,9 @@ object Transients {
     def traverse(traverser: Traverser): Unit =
       traverser.traverse(expr)
 
-    def transform(transformer: Transformer, isStat: Boolean)(
+    def transform(transformer: Transformer)(
         implicit pos: Position): Tree = {
-      Transient(ArrayToTypedArray(transformer.transformExpr(expr), primRef))
+      Transient(ArrayToTypedArray(transformer.transform(expr), primRef))
     }
 
     def printIR(out: IRTreePrinter): Unit = {
@@ -198,9 +195,9 @@ object Transients {
     def traverse(traverser: Traverser): Unit =
       traverser.traverse(expr)
 
-    def transform(transformer: Transformer, isStat: Boolean)(
+    def transform(transformer: Transformer)(
         implicit pos: Position): Tree = {
-      Transient(TypedArrayToArray(transformer.transformExpr(expr), primRef))
+      Transient(TypedArrayToArray(transformer.transform(expr), primRef))
     }
 
     def printIR(out: IRTreePrinter): Unit = {
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/WasmTransients.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/WasmTransients.scala
index b1471a3f47..bf41838a98 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/WasmTransients.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/WasmTransients.scala
@@ -43,10 +43,8 @@ object WasmTransients {
     def traverse(traverser: Traverser): Unit =
       traverser.traverse(lhs)
 
-    def transform(transformer: Transformer, isStat: Boolean)(
-        implicit pos: Position): Tree = {
-      Transient(WasmUnaryOp(op, transformer.transformExpr(lhs)))
-    }
+    def transform(transformer: Transformer)(implicit pos: Position): Tree =
+      Transient(WasmUnaryOp(op, transformer.transform(lhs)))
 
     def wasmInstr: wa.SimpleInstr = (op: @switch) match {
       case I32Clz    => wa.I32Clz
@@ -141,10 +139,9 @@ object WasmTransients {
       traverser.traverse(rhs)
     }
 
-    def transform(transformer: Transformer, isStat: Boolean)(
-        implicit pos: Position): Tree = {
-      Transient(WasmBinaryOp(op, transformer.transformExpr(lhs),
-          transformer.transformExpr(rhs)))
+    def transform(transformer: Transformer)(implicit pos: Position): Tree = {
+      Transient(WasmBinaryOp(op, transformer.transform(lhs),
+          transformer.transform(rhs)))
     }
 
     def wasmInstr: wa.SimpleInstr = (op: @switch) match {
@@ -234,10 +231,8 @@ object WasmTransients {
       traverser.traverse(codePoint)
     }
 
-    def transform(transformer: Transformer, isStat: Boolean)(
-        implicit pos: Position): Tree = {
-      Transient(WasmStringFromCodePoint(transformer.transformExpr(codePoint)))
-    }
+    def transform(transformer: Transformer)(implicit pos: Position): Tree =
+      Transient(WasmStringFromCodePoint(transformer.transform(codePoint)))
 
     def printIR(out: IRTreePrinter): Unit = {
       out.print("$stringFromCodePoint")
@@ -269,10 +264,9 @@ object WasmTransients {
       traverser.traverse(index)
     }
 
-    def transform(transformer: Transformer, isStat: Boolean)(
-        implicit pos: Position): Tree = {
-      Transient(WasmCodePointAt(transformer.transformExpr(string),
-          transformer.transformExpr(index)))
+    def transform(transformer: Transformer)(implicit pos: Position): Tree = {
+      Transient(WasmCodePointAt(transformer.transform(string),
+          transformer.transform(index)))
     }
 
     def printIR(out: IRTreePrinter): Unit = {
@@ -308,10 +302,9 @@ object WasmTransients {
       optEnd.foreach(traverser.traverse(_))
     }
 
-    def transform(transformer: Transformer, isStat: Boolean)(
-        implicit pos: Position): Tree = {
-      Transient(WasmSubstring(transformer.transformExpr(string),
-          transformer.transformExpr(start), optEnd.map(transformer.transformExpr(_))))
+    def transform(transformer: Transformer)(implicit pos: Position): Tree = {
+      Transient(WasmSubstring(transformer.transform(string),
+          transformer.transform(start), transformer.transformTreeOpt(optEnd)))
     }
 
     def printIR(out: IRTreePrinter): Unit = {
diff --git a/project/BinaryIncompatibilities.scala b/project/BinaryIncompatibilities.scala
index 75c5dbb18a..133cf0906a 100644
--- a/project/BinaryIncompatibilities.scala
+++ b/project/BinaryIncompatibilities.scala
@@ -10,6 +10,15 @@ object BinaryIncompatibilities {
     ProblemFilters.exclude[MissingClassProblem]("org.scalajs.ir.Trees$JSLinkingInfo$"),
     ProblemFilters.exclude[IncompatibleResultTypeProblem]("org.scalajs.ir.Trees#*.tpe"),
     ProblemFilters.exclude[MissingClassProblem]("org.scalajs.ir.Types$NoType$"),
+
+    // !!! Breaking, OK in minor release
+    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Transformers#Transformer.transform"),
+    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Transformers#Transformer.transformExpr"),
+    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Transformers#Transformer.transformExprOrJSSpread"),
+    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Transformers#Transformer.transformStat"),
+    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Transformers#Transformer.transformStats"),
+    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Trees#Transient#Value.transform"),
+    ProblemFilters.exclude[ReversedMissingMethodProblem]("org.scalajs.ir.Trees#Transient#Value.transform"),
   )
 
   val Linker = Seq(
diff --git a/project/JavalibIRCleaner.scala b/project/JavalibIRCleaner.scala
index 61ed4ea743..dc0d38d249 100644
--- a/project/JavalibIRCleaner.scala
+++ b/project/JavalibIRCleaner.scala
@@ -302,12 +302,12 @@ final class JavalibIRCleaner(baseDirectoryURI: URI) {
       }
     }
 
-    override def transform(tree: Tree, isStat: Boolean): Tree = {
+    override def transform(tree: Tree): Tree = {
       implicit val pos = tree.pos
 
-      val tree1 = preTransform(tree, isStat)
-      val tree2 = if (tree1 eq tree) super.transform(tree, isStat) else transform(tree1, isStat)
-      val result = postTransform(tree2, isStat)
+      val tree1 = preTransform(tree)
+      val tree2 = if (tree1 eq tree) super.transform(tree) else transform(tree1)
+      val result = postTransform(tree2)
 
       if (transformType(result.tpe) != result.tpe)
         reportError(s"the result type of a ${result.getClass().getSimpleName()} was not transformed")
@@ -315,7 +315,7 @@ final class JavalibIRCleaner(baseDirectoryURI: URI) {
       result
     }
 
-    private def preTransform(tree: Tree, isStat: Boolean): Tree = {
+    private def preTransform(tree: Tree): Tree = {
       implicit val pos = tree.pos
 
       tree match {
@@ -421,7 +421,7 @@ final class JavalibIRCleaner(baseDirectoryURI: URI) {
       }
     }
 
-    private def postTransform(tree: Tree, isStat: Boolean): Tree = {
+    private def postTransform(tree: Tree): Tree = {
       implicit val pos = tree.pos
 
       tree match {

From 6041bad6963a8017c26889d7191edc4182e98ca7 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Mon, 16 Dec 2024 16:47:12 +0100
Subject: [PATCH 221/298] Fix #5085: Zero.stripTrailingZeros() returns
 BigDecimal.ZERO.

As directly specified by its JavaDoc.
---
 javalib/src/main/scala/java/math/BigDecimal.scala            | 5 ++---
 .../javalib/math/BigDecimalScaleOperationsTest.scala         | 4 ++++
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/javalib/src/main/scala/java/math/BigDecimal.scala b/javalib/src/main/scala/java/math/BigDecimal.scala
index 98baffe296..d045ffc57e 100644
--- a/javalib/src/main/scala/java/math/BigDecimal.scala
+++ b/javalib/src/main/scala/java/math/BigDecimal.scala
@@ -1226,9 +1226,8 @@ class BigDecimal() extends Number with Comparable[BigDecimal] {
 
   def stripTrailingZeros(): BigDecimal = {
     if (isZero) {
-      // Preserve RI compatibility, so BigDecimal.equals (which checks
-      // value *and* scale) continues to work.
-      this
+      // As specified by the JavaDoc, we must return BigDecimal.ZERO, which has a scale of 0
+      BigDecimal.ZERO
     } else {
       val lastPow = BigTenPows.length - 1
 
diff --git a/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/math/BigDecimalScaleOperationsTest.scala b/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/math/BigDecimalScaleOperationsTest.scala
index 5589f3bb60..0faca1f058 100644
--- a/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/math/BigDecimalScaleOperationsTest.scala
+++ b/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/math/BigDecimalScaleOperationsTest.scala
@@ -287,4 +287,8 @@ class  BigDecimalScaleOperationsTest {
     val prec = aNumber.precision()
     assertEquals(prec, 68)
   }
+
+  @Test def testStripTrailingZeros(): Unit = {
+    assertEquals(0, java.math.BigDecimal.valueOf(0, 9).stripTrailingZeros().scale())
+  }
 }

From 3d65f79a9bb7f9c2d864db5208bd41b30be5cda7 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Sat, 21 Dec 2024 10:45:06 +0100
Subject: [PATCH 222/298] Improve test suite error messages when `HashersTest`
 fails.

---
 ir/shared/src/test/scala/org/scalajs/ir/HashersTest.scala | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/ir/shared/src/test/scala/org/scalajs/ir/HashersTest.scala b/ir/shared/src/test/scala/org/scalajs/ir/HashersTest.scala
index 4115c19c81..c92f911f11 100644
--- a/ir/shared/src/test/scala/org/scalajs/ir/HashersTest.scala
+++ b/ir/shared/src/test/scala/org/scalajs/ir/HashersTest.scala
@@ -38,11 +38,9 @@ class HashersTest {
       out.close()
       out.toByteArray()
     }
+    val actualString = actualBytes.map(b => "%02x".format(b & 0xff)).mkString
 
-    val expectedBytes = expected.grouped(2)
-      .map(Integer.parseInt(_, 16).toByte).toArray
-
-    assertArrayEquals(expectedBytes, actualBytes)
+    assertEquals(expected, actualString)
   }
 
   private val bodyWithInterestingStuff = Block(

From 5dc41278c02a03e2f6312f177236122f48c84efe Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Sat, 21 Dec 2024 11:17:44 +0100
Subject: [PATCH 223/298] Directly store a LocalName inside VarRef, instead of
 a LocalIdent.

The only point of a `LocalIdent` is to keep track of a position in
addition to the local name. However, in a `VarRef`, the position
should always be the same as the `VarRef` itself. Storing a
separate instance of `LocalIdent` is therefore wasteful.
---
 .../org/scalajs/nscplugin/GenJSCode.scala     | 64 +++++++++----------
 .../org/scalajs/nscplugin/GenJSExports.scala  | 10 +--
 .../org/scalajs/nscplugin/JSEncoding.scala    |  7 +-
 .../main/scala/org/scalajs/ir/Hashers.scala   |  4 +-
 .../main/scala/org/scalajs/ir/Printers.scala  |  4 +-
 .../scala/org/scalajs/ir/Serializers.scala    |  9 ++-
 .../src/main/scala/org/scalajs/ir/Trees.scala |  6 +-
 .../scala/org/scalajs/ir/HashersTest.scala    |  4 +-
 .../scala/org/scalajs/ir/TestIRBuilder.scala  |  4 +-
 .../backend/emitter/FunctionEmitter.scala     | 29 +++++----
 .../backend/wasmemitter/ClassEmitter.scala    |  2 +-
 .../backend/wasmemitter/FunctionEmitter.scala |  6 +-
 .../linker/checker/ClassDefChecker.scala      |  4 +-
 .../frontend/optimizer/IncOptimizer.scala     |  2 +-
 .../frontend/optimizer/OptimizerCore.scala    | 41 ++++++------
 .../org/scalajs/linker/OptimizerTest.scala    |  4 +-
 project/BinaryIncompatibilities.scala         |  1 +
 project/JavaLangObject.scala                  |  2 +-
 project/JavalibIRCleaner.scala                |  2 +-
 19 files changed, 108 insertions(+), 97 deletions(-)

diff --git a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
index 41b035fde2..23981dcaba 100644
--- a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
+++ b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
@@ -179,7 +179,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
 
     // Per method body
     private val currentMethodSym = new ScopedVar[Symbol]
-    private val thisLocalVarIdent = new ScopedVar[Option[js.LocalIdent]]
+    private val thisLocalVarName = new ScopedVar[Option[LocalName]]
     private val enclosingLabelDefInfos = new ScopedVar[Map[Symbol, EnclosingLabelDefInfo]]
     private val isModuleInitialized = new ScopedVar[VarBox[Boolean]]
     private val undefinedDefaultParams = new ScopedVar[mutable.Set[Symbol]]
@@ -187,11 +187,11 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
     private val mutatedLocalVars = new ScopedVar[mutable.Set[Symbol]]
 
     private def withPerMethodBodyState[A](methodSym: Symbol,
-        initThisLocalVarIdent: Option[js.LocalIdent] = None)(body: => A): A = {
+        initThisLocalVarName: Option[LocalName] = None)(body: => A): A = {
 
       withScopedVars(
           currentMethodSym := methodSym,
-          thisLocalVarIdent := initThisLocalVarIdent,
+          thisLocalVarName := initThisLocalVarName,
           enclosingLabelDefInfos := Map.empty,
           isModuleInitialized := new VarBox(false),
           undefinedDefaultParams := mutable.Set.empty,
@@ -241,7 +241,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
           generatedSAMWrapperCount := new VarBox(0),
           delambdafyTargetDefDefs := mutable.Map.empty,
           currentMethodSym := null,
-          thisLocalVarIdent := null,
+          thisLocalVarName := null,
           enclosingLabelDefInfos := null,
           isModuleInitialized := null,
           undefinedDefaultParams := null,
@@ -999,9 +999,9 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
        * FIXME This could clash with a local variable of the constructor or a JS
        * class capture. How do we avoid this?
        */
-      val selfName = freshLocalIdent("this")(pos)
+      val selfIdent = freshLocalIdent("this")(pos)
       def selfRef(implicit pos: ir.Position) =
-        js.VarRef(selfName)(jstpe.AnyType)
+        js.VarRef(selfIdent.name)(jstpe.AnyType)
 
       def memberLambda(params: List[js.ParamDef], restParam: Option[js.ParamDef],
           body: js.Tree)(implicit pos: ir.Position) = {
@@ -1101,7 +1101,8 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
               js.JSNew(jsSuperClassRef, args)
           }
 
-          val selfVarDef = js.VarDef(selfName, thisOriginalName, jstpe.AnyType, mutable = false, newTree)
+          val selfVarDef = js.VarDef(selfIdent.copy(), // copy for the correct `pos`
+              thisOriginalName, jstpe.AnyType, mutable = false, newTree)
           selfVarDef :: memberDefinitions
         }
 
@@ -2040,12 +2041,12 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
      *  Other (normal) methods are emitted with `genMethodDef()`.
      */
     def genMethodWithCurrentLocalNameScope(dd: DefDef,
-        initThisLocalVarIdent: Option[js.LocalIdent] = None): js.MethodDef = {
+        initThisLocalVarName: Option[LocalName] = None): js.MethodDef = {
 
       implicit val pos = dd.pos
       val sym = dd.symbol
 
-      withPerMethodBodyState(sym, initThisLocalVarIdent) {
+      withPerMethodBodyState(sym, initThisLocalVarName) {
         val methodName = encodeMethodSym(sym)
         val originalName = originalNameOfMethod(sym)
 
@@ -2112,8 +2113,8 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
               methodDef
             } else {
               val patches = (
-                  unmutatedMutableLocalVars.map(encodeLocalSym(_).name -> false) :::
-                  mutatedImmutableLocalVals.map(encodeLocalSym(_).name -> true)
+                  unmutatedMutableLocalVars.map(encodeLocalSymName(_) -> false) :::
+                  mutatedImmutableLocalVals.map(encodeLocalSymName(_) -> true)
               ).toMap
               patchMutableFlagOfLocals(methodDef, patches)
             }
@@ -2195,15 +2196,15 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
     private def patchTypeOfParamDefs(methodDef: js.MethodDef,
         patches: Map[LocalName, jstpe.Type]): js.MethodDef = {
 
-      def newType(name: js.LocalIdent, oldType: jstpe.Type): jstpe.Type =
-        patches.getOrElse(name.name, oldType)
+      def newType(name: LocalName, oldType: jstpe.Type): jstpe.Type =
+        patches.getOrElse(name, oldType)
 
       val js.MethodDef(flags, methodName, originalName, params, resultType, body) =
         methodDef
       val newParams = for {
         p @ js.ParamDef(name, originalName, ptpe, mutable) <- params
       } yield {
-        js.ParamDef(name, originalName, newType(name, ptpe), mutable)(p.pos)
+        js.ParamDef(name, originalName, newType(name.name, ptpe), mutable)(p.pos)
       }
       val transformer = new ir.Transformers.Transformer {
         override def transform(tree: js.Tree): js.Tree = tree match {
@@ -2292,7 +2293,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
 
           val innerBody = {
             withScopedVars(
-              thisLocalVarIdent := Some(thisLocalIdent)
+              thisLocalVarName := Some(thisLocalIdent.name)
             ) {
               js.Block(otherStats.map(genStat) :+ (
                 if (bodyIsStat) genStat(rhs)
@@ -2371,7 +2372,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
 
         val thisLocalIdent = freshLocalIdent("this")
         withScopedVars(
-          thisLocalVarIdent := Some(thisLocalIdent)
+          thisLocalVarName := Some(thisLocalIdent.name)
         ) {
           val staticNamespace =
             if (namespace.isPrivate) js.MemberNamespace.PrivateStatic
@@ -2782,7 +2783,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
             case _ =>
               mutatedLocalVars += sym
               js.Assign(
-                  js.VarRef(encodeLocalSym(sym))(toIRType(sym.tpe)),
+                  js.VarRef(encodeLocalSymName(sym))(toIRType(sym.tpe)),
                   genRhs)
           }
 
@@ -2832,15 +2833,14 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
      *  is one.
      */
     private def genThis()(implicit pos: Position): js.Tree = {
-      thisLocalVarIdent.fold[js.Tree] {
+      thisLocalVarName.fold[js.Tree] {
         if (tryingToGenMethodAsJSFunction) {
           throw new CancelGenMethodAsJSFunction(
               "Trying to generate `this` inside the body")
         }
         js.This()(currentThisType)
-      } { thisLocalIdent =>
-        // .copy() to get the correct position
-        js.VarRef(thisLocalIdent.copy())(currentThisTypeNullable)
+      } { thisLocalName =>
+        js.VarRef(thisLocalName)(currentThisTypeNullable)
       }
     }
 
@@ -3093,7 +3093,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
         implicit pos: Position): js.Tree = {
 
       val exceptIdent = freshLocalIdent("e")
-      val origExceptVar = js.VarRef(exceptIdent)(jstpe.AnyType)
+      val origExceptVar = js.VarRef(exceptIdent.name)(jstpe.AnyType)
 
       val mightCatchJavaScriptException = catches.exists { caseDef =>
         caseDef.pat match {
@@ -3486,7 +3486,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
           List.newBuilder[(js.VarRef, jstpe.Type, js.LocalIdent, js.Tree)]
 
         for ((formalArgSym, arg) <- targetSyms.zip(values)) {
-          val formalArg = encodeLocalSym(formalArgSym)
+          val formalArgName = encodeLocalSymName(formalArgSym)
           val actualArg = genExpr(arg)
 
           /* #3267 The formal argument representing the special `this` of a
@@ -3511,13 +3511,13 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
             else actualArg
 
           actualArg match {
-            case js.VarRef(`formalArg`) =>
+            case js.VarRef(`formalArgName`) =>
               // This is trivial assignment, we don't need it
 
             case _ =>
               mutatedLocalVars += formalArgSym
-              quadruplets += ((js.VarRef(formalArg)(tpe), tpe,
-                  freshLocalIdent(formalArg.name.withPrefix("temp$")),
+              quadruplets += ((js.VarRef(formalArgName)(tpe), tpe,
+                  freshLocalIdent(formalArgName.withPrefix("temp$")),
                   fixedActualArg))
           }
         }
@@ -3538,7 +3538,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
               yield js.VarDef(tempArg, NoOriginalName, argType, mutable = false, actualArg)
           val trueAssignments =
             for ((formalArg, argType, tempArg, _) <- quadruplets)
-              yield js.Assign(formalArg, js.VarRef(tempArg)(argType))
+              yield js.Assign(formalArg, js.VarRef(tempArg.name)(argType))
           tempAssignments ::: trueAssignments
       }
     }
@@ -5002,7 +5002,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
       val callTrgIdent = freshLocalIdent()
       val callTrgVarDef = js.VarDef(callTrgIdent, NoOriginalName, receiverType,
           mutable = false, genExpr(receiver))
-      val callTrg = js.VarRef(callTrgIdent)(receiverType)
+      val callTrg = js.VarRef(callTrgIdent.name)(receiverType)
 
       val arguments = args zip sym.tpe.params map { case (arg, param) =>
         /* No need for enteringPosterasure, because value classes are not
@@ -5453,7 +5453,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
           val fVarDef = js.VarDef(freshLocalIdent("f"), NoOriginalName,
               jstpe.AnyType, mutable = false, arg2)
           val keyVarIdent = freshLocalIdent("key")
-          val keyVarRef = js.VarRef(keyVarIdent)(jstpe.AnyType)
+          val keyVarRef = js.VarRef(keyVarIdent.name)(jstpe.AnyType)
           js.Block(
               objVarDef,
               fVarDef,
@@ -5488,7 +5488,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
           val handlerVarDef = js.VarDef(freshLocalIdent("handler"), NoOriginalName,
               jstpe.AnyType, mutable = false, arg2)
           val exceptionVarIdent = freshLocalIdent("e")
-          val exceptionVarRef = js.VarRef(exceptionVarIdent)(jstpe.AnyType)
+          val exceptionVarRef = js.VarRef(exceptionVarIdent.name)(jstpe.AnyType)
           js.Block(
             bodyVarDef,
             handlerVarDef,
@@ -6465,7 +6465,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
         // Gen the inlined target method body
         val genMethodDef = {
           genMethodWithCurrentLocalNameScope(consumeDelambdafyTarget(target),
-              initThisLocalVarIdent = thisFormalCapture.map(_.name))
+              initThisLocalVarName = thisFormalCapture.map(_.name.name))
         }
         val js.MethodDef(methodFlags, _, _, methodParams, _, methodBody) = genMethodDef
 
@@ -6777,7 +6777,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
     // Utilities ---------------------------------------------------------------
 
     def genVarRef(sym: Symbol)(implicit pos: Position): js.VarRef =
-      js.VarRef(encodeLocalSym(sym))(toIRType(sym.tpe))
+      js.VarRef(encodeLocalSymName(sym))(toIRType(sym.tpe))
 
     def genParamDef(sym: Symbol): js.ParamDef =
       genParamDef(sym, toIRType(sym.tpe))
diff --git a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSExports.scala b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSExports.scala
index bf668424ae..603a6286d3 100644
--- a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSExports.scala
+++ b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSExports.scala
@@ -684,7 +684,7 @@ trait GenJSExports[G <: Global with Singleton] extends SubComponent {
       val superClass = {
         val superClassSym = currentClassSym.superClass
         if (isNestedJSClass(superClassSym)) {
-          js.VarRef(js.LocalIdent(JSSuperClassParamName))(jstpe.AnyType)
+          js.VarRef(JSSuperClassParamName)(jstpe.AnyType)
         } else {
           js.LoadJSConstructor(encodeClassName(superClassSym))
         }
@@ -1053,7 +1053,7 @@ trait GenJSExports[G <: Global with Singleton] extends SubComponent {
 
     def genArgRef(index: Int)(implicit pos: Position): js.Tree = {
       if (index < minArgc)
-        js.VarRef(js.LocalIdent(fixedParamNames(index)))(jstpe.AnyType)
+        js.VarRef(fixedParamNames(index))(jstpe.AnyType)
       else
         js.JSSelect(genRestArgRef(), js.IntLiteral(index - minArgc))
     }
@@ -1073,16 +1073,16 @@ trait GenJSExports[G <: Global with Singleton] extends SubComponent {
     def genRestArgRef()(implicit pos: Position): js.Tree = {
       assert(needsRestParam,
           s"trying to generate a reference to non-existent rest param at $pos")
-      js.VarRef(js.LocalIdent(restParamName))(jstpe.AnyType)
+      js.VarRef(restParamName)(jstpe.AnyType)
     }
 
     def genAllArgsRefsForForwarder()(implicit pos: Position): List[js.TreeOrJSSpread] = {
       val fixedArgRefs = fixedParamNames.toList.map { paramName =>
-        js.VarRef(js.LocalIdent(paramName))(jstpe.AnyType)
+        js.VarRef(paramName)(jstpe.AnyType)
       }
 
       if (needsRestParam) {
-        val restArgRef = js.VarRef(js.LocalIdent(restParamName))(jstpe.AnyType)
+        val restArgRef = js.VarRef(restParamName)(jstpe.AnyType)
         fixedArgRefs :+ js.JSSpread(restArgRef)
       } else {
         fixedArgRefs
diff --git a/compiler/src/main/scala/org/scalajs/nscplugin/JSEncoding.scala b/compiler/src/main/scala/org/scalajs/nscplugin/JSEncoding.scala
index 51ec7de709..c4d8188c44 100644
--- a/compiler/src/main/scala/org/scalajs/nscplugin/JSEncoding.scala
+++ b/compiler/src/main/scala/org/scalajs/nscplugin/JSEncoding.scala
@@ -256,7 +256,10 @@ trait JSEncoding[G <: Global with Singleton] extends SubComponent {
     }
   }
 
-  def encodeLocalSym(sym: Symbol)(implicit pos: Position): js.LocalIdent = {
+  def encodeLocalSym(sym: Symbol)(implicit pos: Position): js.LocalIdent =
+    js.LocalIdent(encodeLocalSymName(sym))
+
+  def encodeLocalSymName(sym: Symbol): LocalName = {
     /* The isValueParameter case is necessary to work around an internal bug
      * of scalac: for some @varargs methods, the owner of some parameters is
      * the enclosing class rather the method, so !sym.owner.isClass fails.
@@ -266,7 +269,7 @@ trait JSEncoding[G <: Global with Singleton] extends SubComponent {
     require(sym.isValueParameter ||
         (!sym.owner.isClass && sym.isTerm && !sym.isMethod && !sym.isModule),
         "encodeLocalSym called with non-local symbol: " + sym)
-    js.LocalIdent(localSymbolName(sym))
+    localSymbolName(sym)
   }
 
   def encodeClassType(sym: Symbol): jstpe.Type = {
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Hashers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Hashers.scala
index 1c159fe9b2..10847a8ba3 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Hashers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Hashers.scala
@@ -524,9 +524,9 @@ object Hashers {
           mixTag(TagClassOf)
           mixTypeRef(typeRef)
 
-        case VarRef(ident) =>
+        case VarRef(name) =>
           mixTag(TagVarRef)
-          mixLocalIdent(ident)
+          mixName(name)
           mixType(tree.tpe)
 
         case This() =>
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala
index b5bfccc64e..af6ed1023c 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala
@@ -869,8 +869,8 @@ object Printers {
 
         // Atomic expressions
 
-        case VarRef(ident) =>
-          print(ident)
+        case VarRef(name) =>
+          print(name)
 
         case This() =>
           print("this")
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
index 11bafee148..b8fd8790b2 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
@@ -551,9 +551,9 @@ object Serializers {
           writeTagAndPos(TagClassOf)
           writeTypeRef(typeRef)
 
-        case VarRef(ident) =>
+        case VarRef(name) =>
           writeTagAndPos(TagVarRef)
-          writeLocalIdent(ident)
+          writeName(name)
           writeType(tree.tpe)
 
         case This() =>
@@ -1388,7 +1388,10 @@ object Serializers {
         case TagClassOf        => ClassOf(readTypeRef())
 
         case TagVarRef =>
-          VarRef(readLocalIdent())(readType())
+          val name =
+            if (hacks.use17) readLocalIdent().name
+            else readLocalName()
+          VarRef(name)(readType())
 
         case TagThis =>
           val tpe = readType()
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala b/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
index 4b1e58ce12..dfb4671d26 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
@@ -104,13 +104,13 @@ object Trees {
       implicit val pos: Position) extends Tree {
     val tpe = VoidType
 
-    def ref(implicit pos: Position): VarRef = VarRef(name)(vtpe)
+    def ref(implicit pos: Position): VarRef = VarRef(name.name)(vtpe)
   }
 
   sealed case class ParamDef(name: LocalIdent, originalName: OriginalName,
       ptpe: Type, mutable: Boolean)(
       implicit val pos: Position) extends IRNode {
-    def ref(implicit pos: Position): VarRef = VarRef(name)(ptpe)
+    def ref(implicit pos: Position): VarRef = VarRef(name.name)(ptpe)
   }
 
   // Control flow constructs
@@ -1088,7 +1088,7 @@ object Trees {
 
   // Atomic expressions
 
-  sealed case class VarRef(ident: LocalIdent)(val tpe: Type)(
+  sealed case class VarRef(name: LocalName)(val tpe: Type)(
       implicit val pos: Position) extends AssignLhs
 
   sealed case class This()(val tpe: Type)(implicit val pos: Position)
diff --git a/ir/shared/src/test/scala/org/scalajs/ir/HashersTest.scala b/ir/shared/src/test/scala/org/scalajs/ir/HashersTest.scala
index c92f911f11..612174ffff 100644
--- a/ir/shared/src/test/scala/org/scalajs/ir/HashersTest.scala
+++ b/ir/shared/src/test/scala/org/scalajs/ir/HashersTest.scala
@@ -91,7 +91,7 @@ class HashersTest {
     )
 
     test(
-        "309805e5680ffa1804811ff5c9ebc77e91846957",
+        "82df9d6beb7df0ee9f501380323bdb2038cc50cb",
         MethodDef(MemberFlags.empty, mIIMethodName, NON,
             List(ParamDef("x", NON, IntType, mutable = false)),
             IntType, Some(bodyWithInterestingStuff))(
@@ -106,7 +106,7 @@ class HashersTest {
     }
 
     test(
-        "c0f1ef1b22fd1cfdc9bba78bf3e0f433e9f82fc1",
+        "d0fa6c753502e3d1df34e53ca6f6afb5cbdcd9d4",
         JSMethodDef(MemberFlags.empty, s("m"),
             List(ParamDef("x", NON, AnyType, mutable = false)), None,
             bodyWithInterestingStuff)(
diff --git a/ir/shared/src/test/scala/org/scalajs/ir/TestIRBuilder.scala b/ir/shared/src/test/scala/org/scalajs/ir/TestIRBuilder.scala
index d89d8050a7..8c578c296e 100644
--- a/ir/shared/src/test/scala/org/scalajs/ir/TestIRBuilder.scala
+++ b/ir/shared/src/test/scala/org/scalajs/ir/TestIRBuilder.scala
@@ -37,6 +37,8 @@ object TestIRBuilder {
   val NoOptHints = OptimizerHints.empty
 
   // String -> Name conversions
+  implicit def string2localName(name: String): LocalName =
+    LocalName(name)
   implicit def string2simpleFieldName(name: String): SimpleFieldName =
     SimpleFieldName(name)
   implicit def string2className(name: String): ClassName =
@@ -79,7 +81,7 @@ object TestIRBuilder {
   def d(value: Double): DoubleLiteral = DoubleLiteral(value)
   def s(value: String): StringLiteral = StringLiteral(value)
 
-  def ref(ident: LocalIdent, tpe: Type): VarRef = VarRef(ident)(tpe)
+  def ref(name: LocalName, tpe: Type): VarRef = VarRef(name)(tpe)
 
   def arrayType(base: NonArrayTypeRef, dimensions: Int): ArrayType =
     ArrayType(ArrayTypeRef(base, dimensions), nullable = true)
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
index f2847be772..6abeb4dd36 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
@@ -450,7 +450,7 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
         implicit pos: Position): js.Ident = {
 
       val recIdent = (tree.record: @unchecked) match {
-        case VarRef(ident)                 => transformLocalVarIdent(ident)
+        case record: VarRef                => transformLocalVarRefIdent(record)
         case Transient(JSVarRef(ident, _)) => ident
         case record: RecordSelect          => makeRecordFieldIdentForVarRef(record)
       }
@@ -1456,7 +1456,7 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
       lhs.tpe match {
         case RecordType(fields) =>
           val ident = (lhs: @unchecked) match {
-            case VarRef(ident)                 => transformLocalVarIdent(ident)
+            case lhs: VarRef                   => transformLocalVarRefIdent(lhs)
             case Transient(JSVarRef(ident, _)) => ident
           }
           val elems = extractRecordElems(rhs)
@@ -1495,9 +1495,9 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
         case RecordValue(_, elems) =>
           elems
 
-        case VarRef(ident) =>
-          val jsIdent = transformLocalVarIdent(ident)
-          val mutable = env.isLocalMutable(ident)
+        case recordTree @ VarRef(name) =>
+          val jsIdent = transformLocalVarRefIdent(recordTree)
+          val mutable = env.isLocalMutable(name)
           for (RecordType.Field(fName, fOrigName, fTpe, _) <- recordType.fields)
             yield Transient(JSVarRef(makeRecordFieldIdent(jsIdent, fName, fOrigName), mutable)(fTpe))
 
@@ -3014,10 +3014,10 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
 
         // Atomic expressions
 
-        case VarRef(name) =>
+        case tree @ VarRef(name) =>
           env.varKind(name) match {
             case VarKind.Mutable | VarKind.Immutable =>
-              js.VarRef(transformLocalVarIdent(name))
+              js.VarRef(transformLocalVarRefIdent(tree))
 
             case VarKind.ThisAlias =>
               js.This()
@@ -3026,7 +3026,7 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
               fileLevelVar(VarField.thiz)
 
             case VarKind.ClassCapture =>
-              fileLevelVar(VarField.cc, genName(name.name))
+              fileLevelVar(VarField.cc, genName(name))
           }
 
         case Transient(JSVarRef(name, _)) =>
@@ -3165,7 +3165,7 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
            * For other usages (notably ApplyDynamicImport), we generate the
            * body, so it's easy to ensure no collision.
            */
-          def permitImplicitNameCapture = forceName.forall(_ == name.name)
+          def permitImplicitNameCapture = forceName.forall(_ == name)
 
           env.varKind(name) match {
             case VarKind.Immutable if !env.inLoopForVarCapture && permitImplicitNameCapture =>
@@ -3255,6 +3255,9 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
     private def transformLabelIdent(ident: LabelIdent): js.Ident =
       js.Ident(genName(ident.name))(ident.pos)
 
+    private def transformLocalVarRefIdent(varRef: VarRef): js.Ident =
+      js.Ident(transformLocalName(varRef.name))(varRef.pos)
+
     private def transformLocalVarIdent(ident: LocalIdent): js.Ident =
       js.Ident(transformLocalName(ident.name))(ident.pos)
 
@@ -3433,13 +3436,13 @@ private object FunctionEmitter {
       defaultContinueTargets: Set[LabelName],
       val inLoopForVarCapture: Boolean
   ) {
-    def varKind(ident: LocalIdent): VarKind = {
+    def varKind(name: LocalName): VarKind = {
       // If we do not know the var, it must be a JS class capture.
-      vars.getOrElse(ident.name, VarKind.ClassCapture)
+      vars.getOrElse(name, VarKind.ClassCapture)
     }
 
-    def isLocalMutable(ident: LocalIdent): Boolean =
-      VarKind.Mutable == varKind(ident)
+    def isLocalMutable(name: LocalName): Boolean =
+      VarKind.Mutable == varKind(name)
 
     def lhsForLabeledExpr(label: LabelIdent): Lhs = labeledExprLHSes(label.name)
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/ClassEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/ClassEmitter.scala
index 43409fa133..44d18110fb 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/ClassEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/ClassEmitter.scala
@@ -1007,7 +1007,7 @@ class ClassEmitter(coreSpec: CoreSpec) {
 
       val helperBuilder = new CustomJSHelperBuilder.WithTreeEval() {
         protected def evalTreeAtCallSite(tree: Tree, expectedType: Type): Unit = tree match {
-          case VarRef(LocalIdent(localName)) if classCaptureParamsOfTypeAny.contains(localName) =>
+          case VarRef(localName) if classCaptureParamsOfTypeAny.contains(localName) =>
             /* Common shape for the `jsSuperClass` value
              * We can only deal with class captures of type `AnyType` in this way,
              * since otherwise we might need `adapt` to box the values.
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
index 83a6854719..85cc991c39 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
@@ -464,7 +464,7 @@ private class FunctionEmitter private (
     val RecordSelect(record, field) = tree
 
     val recordStorage = record match {
-      case VarRef(LocalIdent(name)) =>
+      case VarRef(name) =>
         lookupLocal(name)
       case record: RecordSelect =>
         lookupRecordSelect(record)
@@ -778,7 +778,7 @@ private class FunctionEmitter private (
         markPosition(tree)
         fb += wa.Call(helperID)
 
-      case VarRef(LocalIdent(name)) =>
+      case VarRef(name) =>
         genTree(rhs, lhs.tpe)
         markPosition(tree)
         genWriteToStorage(lookupLocal(name))
@@ -2336,7 +2336,7 @@ private class FunctionEmitter private (
   }
 
   private def genVarRef(tree: VarRef): Type = {
-    val VarRef(LocalIdent(name)) = tree
+    val VarRef(name) = tree
 
     markPosition(tree)
     if (tree.tpe == NothingType)
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala b/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
index 1c4bd11d74..919e2262c6 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
@@ -682,7 +682,7 @@ private final class ClassDefChecker(classDef: ClassDef,
         checkTree(rhs, env)
 
         lhs match {
-          case VarRef(LocalIdent(name)) =>
+          case VarRef(name) =>
             if (env.locals.get(name).exists(!_.mutable))
               reportError(i"Assignment to immutable variable $name.")
 
@@ -964,7 +964,7 @@ private final class ClassDefChecker(classDef: ClassDef,
 
       // Atomic expressions
 
-      case VarRef(LocalIdent(name)) =>
+      case VarRef(name) =>
         env.locals.get(name).fold[Unit] {
           reportError(i"Cannot find variable $name in scope")
         } { localDef =>
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
index 38a02b54ad..5b2cf7ad5e 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
@@ -1009,7 +1009,7 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
           case lit: Literal =>
             Some(FieldBody.Literal(lit))
 
-          case VarRef(LocalIdent(valName)) =>
+          case VarRef(valName) =>
             paramBodies.get(valName)
 
           case LoadModule(moduleClassName) =>
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
index 0f519afdb2..b280a7776a 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
@@ -923,7 +923,7 @@ private[optimizer] abstract class OptimizerCore(
       case tree: Block =>
         pretransformBlock(tree)(cont)
 
-      case VarRef(LocalIdent(name)) =>
+      case VarRef(name) =>
         val localDef = scope.env.localDefs.getOrElse(name, {
           throw new AssertionError(
               s"Cannot find local def '$name' at $pos\n" +
@@ -1427,8 +1427,7 @@ private[optimizer] abstract class OptimizerCore(
         replacement match {
           case ReplaceWithRecordVarRef(name, recordType, used, cancelFun) =>
             used.value = used.value.inc
-            PreTransRecordTree(
-                VarRef(LocalIdent(name))(recordType), tpe, cancelFun)
+            PreTransRecordTree(VarRef(name)(recordType), tpe, cancelFun)
 
           case InlineClassInstanceReplacement(structure, fieldLocalDefs, cancelFun) =>
             val recordType = structure.recordType
@@ -1828,8 +1827,8 @@ private[optimizer] abstract class OptimizerCore(
       override def traverse(tree: Tree): Unit = {
         super.traverse(tree)
         tree match {
-          case Assign(VarRef(ident), _) => mutatedLocalVars += ident.name
-          case _                        => ()
+          case Assign(VarRef(name), _) => mutatedLocalVars += name
+          case _                       => ()
         }
       }
     }
@@ -1851,10 +1850,10 @@ private[optimizer] abstract class OptimizerCore(
       implicit val pos = body.pos
 
       body match {
-        case VarRef(ident) =>
-          if (ident.name == valName)
+        case VarRef(name) =>
+          if (name == valName)
             Success(valTree)
-          else if (valTreeInfo.mutatedLocalVars.contains(ident.name))
+          else if (valTreeInfo.mutatedLocalVars.contains(name))
             Failed
           else
             NotFoundPureSoFar
@@ -2224,9 +2223,9 @@ private[optimizer] abstract class OptimizerCore(
               MethodIdent(methodName),
               normalizedParams.zip(referenceArgs).map {
                 case ((name, ptpe), AsInstanceOf(_, castTpe)) =>
-                  AsInstanceOf(VarRef(LocalIdent(name))(ptpe), castTpe)
+                  AsInstanceOf(VarRef(name)(ptpe), castTpe)
                 case ((name, ptpe), _) =>
-                  VarRef(LocalIdent(name))(ptpe)
+                  VarRef(name)(ptpe)
               }
             )(body.tpe)
 
@@ -2477,7 +2476,7 @@ private[optimizer] abstract class OptimizerCore(
           cancelFun()
 
         used.value = used.value.inc
-        val module = VarRef(LocalIdent(moduleVarName))(AnyType)
+        val module = VarRef(moduleVarName)(AnyType)
         path.foldLeft[Tree](module) { (inner, pathElem) =>
           JSSelect(inner, StringLiteral(pathElem))
         }
@@ -2691,7 +2690,7 @@ private[optimizer] abstract class OptimizerCore(
             optQualDeclaredType = Some(optReceiver.get._1),
             field, isLhsOfAssign = false)(cont)
 
-      case Assign(lhs @ Select(This(), field), VarRef(LocalIdent(rhsName)))
+      case Assign(lhs @ Select(This(), field), VarRef(rhsName))
           if formals.size == 1 && formals.head.name.name == rhsName =>
         assert(isStat, "Found Assign in expression position")
         assert(optReceiver.isDefined,
@@ -3501,10 +3500,10 @@ private[optimizer] abstract class OptimizerCore(
              * the equals() method has been inlined as a reference
              * equality test.
              */
-            case (BinaryOp(BinaryOp.===, VarRef(lhsIdent), Null()),
-                BinaryOp(BinaryOp.===, VarRef(rhsIdent), Null()),
+            case (BinaryOp(BinaryOp.===, VarRef(lhsName), Null()),
+                BinaryOp(BinaryOp.===, VarRef(rhsName), Null()),
                 BinaryOp(BinaryOp.===, MaybeCast(l: VarRef), r: VarRef))
-                if l.ident == lhsIdent && r.ident == rhsIdent =>
+                if l.name == lhsName && r.name == rhsName =>
               BinaryOp(BinaryOp.===, l, r)(elsep.pos)
 
             // Example: (x > y) || (x == y)  ->  (x >= y)
@@ -3601,7 +3600,7 @@ private[optimizer] abstract class OptimizerCore(
         value)
     withBinding(rtLongBinding) { (scope1, cont1) =>
       implicit val scope = scope1
-      val tRef = VarRef(LocalIdent(tName))(rtLongClassType)
+      val tRef = VarRef(tName)(rtLongClassType)
       val newTree = New(LongImpl.RuntimeLongClass,
           MethodIdent(LongImpl.initFromParts),
           List(Apply(ApplyFlags.empty, tRef, MethodIdent(LongImpl.lo), Nil)(IntType),
@@ -5497,7 +5496,7 @@ private[optimizer] abstract class OptimizerCore(
           buildInner(LocalDef(value.tpe, false,
               ReplaceWithConstant(literal)), cont)
 
-        case PreTransTree(VarRef(LocalIdent(refName)), _)
+        case PreTransTree(VarRef(refName), _)
             if !localIsMutable(refName) =>
           buildInner(LocalDef(value.tpe, false,
               ReplaceWithVarRef(refName, newSimpleState(UsedAtLeastOnce))), cont)
@@ -5862,7 +5861,7 @@ private[optimizer] object OptimizerCore {
     def newReplacement(implicit pos: Position): Tree = this.replacement match {
       case ReplaceWithVarRef(name, used) =>
         used.value = used.value.inc
-        VarRef(LocalIdent(name))(tpe.base)
+        VarRef(name)(tpe.base)
 
       /* Allocate an instance of RuntimeLong on the fly.
        * See the comment in finishTransformExpr about why it is desirable and
@@ -5871,7 +5870,7 @@ private[optimizer] object OptimizerCore {
       case ReplaceWithRecordVarRef(name, recordType, used, _)
           if tpe.base == ClassType(LongImpl.RuntimeLongClass, nullable = false) =>
         used.value = used.value.inc
-        createNewLong(VarRef(LocalIdent(name))(recordType))
+        createNewLong(VarRef(name)(recordType))
 
       case ReplaceWithRecordVarRef(_, _, _, cancelFun) =>
         cancelFun()
@@ -6755,7 +6754,7 @@ private[optimizer] object OptimizerCore {
         case ApplyStatically(_, This(), className, method, args) =>
           args.size == params.size &&
           args.zip(params).forall {
-            case (VarRef(LocalIdent(aname)), ParamDef(LocalIdent(pname), _, _, _)) =>
+            case (VarRef(aname), ParamDef(LocalIdent(pname), _, _, _)) =>
               aname == pname
             case _ =>
               false
@@ -6766,7 +6765,7 @@ private[optimizer] object OptimizerCore {
           !method.name.isReflectiveProxy &&
           (args.size == params.size) &&
           args.zip(params).forall {
-            case (MaybeUnbox(VarRef(LocalIdent(aname)), _),
+            case (MaybeUnbox(VarRef(aname), _),
                 ParamDef(LocalIdent(pname), _, _, _)) => aname == pname
             case _ => false
           }
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/OptimizerTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/OptimizerTest.scala
index 08838c0627..e80affe3bc 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/OptimizerTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/OptimizerTest.scala
@@ -268,7 +268,7 @@ class OptimizerTest {
      */
 
     val matchResult1 = LabelIdent("matchResult1")
-    val x1 = LocalIdent("x1")
+    val x1 = LocalName("x1")
     val matchAlts1 = LabelIdent("matchAlts1")
     val matchAlts2 = LabelIdent("matchAlts2")
 
@@ -475,7 +475,7 @@ class OptimizerTest {
       traverseMainMethod(moduleSet) {
         case c: Closure =>
           c.captureValues match {
-            case List(VarRef(LocalIdent(name))) =>
+            case List(VarRef(name)) =>
               assertEquals(s"unexpected capture name: $c", c.captureParams.head.name.name, name)
 
             case _ =>
diff --git a/project/BinaryIncompatibilities.scala b/project/BinaryIncompatibilities.scala
index 133cf0906a..7c373ae05f 100644
--- a/project/BinaryIncompatibilities.scala
+++ b/project/BinaryIncompatibilities.scala
@@ -8,6 +8,7 @@ object BinaryIncompatibilities {
     // !!! Breaking, OK in minor release
     ProblemFilters.exclude[MissingClassProblem]("org.scalajs.ir.Trees$JSLinkingInfo"),
     ProblemFilters.exclude[MissingClassProblem]("org.scalajs.ir.Trees$JSLinkingInfo$"),
+    ProblemFilters.exclude[Problem]("org.scalajs.ir.Trees#VarRef.*"),
     ProblemFilters.exclude[IncompatibleResultTypeProblem]("org.scalajs.ir.Trees#*.tpe"),
     ProblemFilters.exclude[MissingClassProblem]("org.scalajs.ir.Types$NoType$"),
 
diff --git a/project/JavaLangObject.scala b/project/JavaLangObject.scala
index 789d57df73..eb3eedabef 100644
--- a/project/JavaLangObject.scala
+++ b/project/JavaLangObject.scala
@@ -87,7 +87,7 @@ object JavaLangObject {
           Some {
             BinaryOp(BinaryOp.===,
               This()(ThisType),
-              VarRef(LocalIdent(LocalName("that")))(AnyType))
+              VarRef(LocalName("that"))(AnyType))
           })(OptimizerHints.empty.withInline(true), Unversioned),
 
         /* protected def clone(): Object =
diff --git a/project/JavalibIRCleaner.scala b/project/JavalibIRCleaner.scala
index dc0d38d249..6f014a4e93 100644
--- a/project/JavalibIRCleaner.scala
+++ b/project/JavalibIRCleaner.scala
@@ -215,7 +215,7 @@ final class JavalibIRCleaner(baseDirectoryURI: URI) {
 
       def argsCorrespond(args: List[Tree], paramDefs: List[ParamDef]): Boolean = {
         (args.size == paramDefs.size) && args.zip(paramDefs).forall {
-          case (VarRef(LocalIdent(argName)), ParamDef(LocalIdent(paramName), _, _, _)) =>
+          case (VarRef(argName), ParamDef(LocalIdent(paramName), _, _, _)) =>
             argName == paramName
           case _ =>
             false

From 2ba9ea710e86b1aa1b62c2e35656faabc3a55754 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Sat, 21 Dec 2024 11:55:12 +0100
Subject: [PATCH 224/298] Remove `LabelIdent`. Directly store `LabelName`
 instead.

The position of labels is always irrelevant, as they are synthetic.
Therefore, storing them through `LabelIdent`s is wasteful.
---
 .../org/scalajs/nscplugin/GenJSCode.scala     | 28 ++++++-------
 .../org/scalajs/nscplugin/JSEncoding.scala    | 15 +++----
 .../nscplugin/test/OptimizationTest.scala     |  4 +-
 .../main/scala/org/scalajs/ir/Hashers.scala   |  9 +----
 .../main/scala/org/scalajs/ir/Printers.scala  |  4 --
 .../scala/org/scalajs/ir/Serializers.scala    | 24 +++++------
 .../src/main/scala/org/scalajs/ir/Trees.scala |  7 +---
 .../scala/org/scalajs/ir/TestIRBuilder.scala  |  4 +-
 .../backend/emitter/FunctionEmitter.scala     | 40 +++++++++----------
 .../backend/wasmemitter/FunctionEmitter.scala |  4 +-
 .../linker/checker/ClassDefChecker.scala      | 10 ++---
 .../scalajs/linker/checker/IRChecker.scala    |  4 +-
 .../frontend/optimizer/OptimizerCore.scala    | 12 +++---
 .../org/scalajs/linker/OptimizerTest.scala    |  6 +--
 .../linker/testutils/TestIRBuilder.scala      |  2 -
 project/BinaryIncompatibilities.scala         | 10 +++++
 16 files changed, 86 insertions(+), 97 deletions(-)

diff --git a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
index 23981dcaba..674ffc3ba6 100644
--- a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
+++ b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
@@ -29,6 +29,7 @@ import org.scalajs.ir
 import org.scalajs.ir.{Trees => js, Types => jstpe, ClassKind, Hashers, OriginalName}
 import org.scalajs.ir.Names.{
   LocalName,
+  LabelName,
   SimpleFieldName,
   FieldName,
   SimpleMethodName,
@@ -2890,8 +2891,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
       val labelParamSyms = tree.params.map(_.symbol)
       val info = new EnclosingLabelDefInfoWithResultAsAssigns(labelParamSyms)
 
-      val labelIdent = encodeLabelSym(sym)
-      val labelName = labelIdent.name
+      val labelName = encodeLabelSym(sym)
 
       val transformedRhs = withScopedVars(
         enclosingLabelDefInfos := enclosingLabelDefInfos.get + (sym -> info)
@@ -2906,7 +2906,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
        */
       object ReturnFromThisLabel {
         def unapply(tree: js.Return): Option[js.Tree] = {
-          if (tree.label.name == labelName) Some(exprToStat(tree.expr))
+          if (tree.label == labelName) Some(exprToStat(tree.expr))
           else None
         }
       }
@@ -2915,7 +2915,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
         if (transformedRhs.tpe == jstpe.NothingType) {
           // In this case, we do not need the outer block label
           js.While(js.BooleanLiteral(true), {
-            js.Labeled(labelIdent, jstpe.VoidType, {
+            js.Labeled(labelName, jstpe.VoidType, {
               transformedRhs match {
                 // Eliminate a trailing return@lab
                 case js.Block(stats :+ ReturnFromThisLabel(exprAsStat)) =>
@@ -2927,17 +2927,17 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
           })
         } else {
           // When all else has failed, we need the full machinery
-          val blockLabelIdent = freshLabelIdent("block")
+          val blockLabelName = freshLabelName("block")
           val bodyType =
             if (isStat) jstpe.VoidType
             else toIRType(tree.tpe)
-          js.Labeled(blockLabelIdent, bodyType, {
+          js.Labeled(blockLabelName, bodyType, {
             js.While(js.BooleanLiteral(true), {
-              js.Labeled(labelIdent, jstpe.VoidType, {
+              js.Labeled(labelName, jstpe.VoidType, {
                 if (isStat)
-                  js.Block(transformedRhs, js.Return(js.Skip(), blockLabelIdent))
+                  js.Block(transformedRhs, js.Return(js.Skip(), blockLabelName))
                 else
-                  js.Return(transformedRhs, blockLabelIdent)
+                  js.Return(transformedRhs, blockLabelName)
               })
             })
           })
@@ -3901,11 +3901,11 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
 
       var clauses: List[(List[js.MatchableLiteral], js.Tree)] = Nil
       var optElseClause: Option[js.Tree] = None
-      var optElseClauseLabel: Option[js.LabelIdent] = None
+      var optElseClauseLabel: Option[LabelName] = None
 
       def genJumpToElseClause(implicit pos: ir.Position): js.Tree = {
         if (optElseClauseLabel.isEmpty)
-          optElseClauseLabel = Some(freshLabelIdent("default"))
+          optElseClauseLabel = Some(freshLabelName("default"))
         js.Return(js.Skip(), optElseClauseLabel.get)
       }
 
@@ -4025,7 +4025,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
       optElseClauseLabel.fold[js.Tree] {
         buildMatch(clauses.reverse, elseClause, resultType)
       } { elseClauseLabel =>
-        val matchResultLabel = freshLabelIdent("matchResult")
+        val matchResultLabel = freshLabelName("matchResult")
         val patchedClauses = for ((alts, body) <- clauses) yield {
           implicit val pos = body.pos
           val newBody = js.Return(body, matchResultLabel)
@@ -4366,7 +4366,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
      *  all jumps to case labels are already caught upstream by `genCaseBody()`
      *  inside `genTranslatedMatch()`.
      */
-    private def genOptimizedCaseLabeled(label: js.LabelIdent,
+    private def genOptimizedCaseLabeled(label: LabelName,
         translatedBody: js.Tree, returnCount: Int)(
         implicit pos: Position): js.Tree = {
 
@@ -4423,7 +4423,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
      *  !!! There is quite of bit of code duplication with
      *      OptimizerCore.tryOptimizePatternMatch.
      */
-    def genOptimizedMatchEndLabeled(label: js.LabelIdent, tpe: jstpe.Type,
+    def genOptimizedMatchEndLabeled(label: LabelName, tpe: jstpe.Type,
         translatedCases: List[js.Tree], returnCount: Int)(
         implicit pos: Position): js.Tree = {
       def default: js.Tree =
diff --git a/compiler/src/main/scala/org/scalajs/nscplugin/JSEncoding.scala b/compiler/src/main/scala/org/scalajs/nscplugin/JSEncoding.scala
index c4d8188c44..b1b4c888f5 100644
--- a/compiler/src/main/scala/org/scalajs/nscplugin/JSEncoding.scala
+++ b/compiler/src/main/scala/org/scalajs/nscplugin/JSEncoding.scala
@@ -91,7 +91,7 @@ trait JSEncoding[G <: Global with Singleton] extends SubComponent {
         case None =>
           inner
         case Some(labelName) =>
-          js.Labeled(js.LabelIdent(labelName), tpe, inner)
+          js.Labeled(labelName, tpe, inner)
       }
     }
   }
@@ -151,29 +151,26 @@ trait JSEncoding[G <: Global with Singleton] extends SubComponent {
   private def freshLabelName(base: LabelName): LabelName =
     freshNameGeneric(base, usedLabelNames)(_.withSuffix(_))
 
-  private def freshLabelName(base: String): LabelName =
+  def freshLabelName(base: String): LabelName =
     freshLabelName(LabelName(base))
 
-  def freshLabelIdent(base: String)(implicit pos: ir.Position): js.LabelIdent =
-    js.LabelIdent(freshLabelName(base))
-
   private def labelSymbolName(sym: Symbol): LabelName =
     labelSymbolNames.getOrElseUpdate(sym, freshLabelName(sym.name.toString))
 
-  def getEnclosingReturnLabel()(implicit pos: ir.Position): js.LabelIdent = {
+  def getEnclosingReturnLabel()(implicit pos: Position): LabelName = {
     val box = returnLabelName.get
     if (box == null)
       throw new IllegalStateException(s"No enclosing returnable scope at $pos")
     if (box.value.isEmpty)
       box.value = Some(freshLabelName("_return"))
-    js.LabelIdent(box.value.get)
+    box.value.get
   }
 
   // Encoding methods ----------------------------------------------------------
 
-  def encodeLabelSym(sym: Symbol)(implicit pos: Position): js.LabelIdent = {
+  def encodeLabelSym(sym: Symbol): LabelName = {
     require(sym.isLabel, "encodeLabelSym called with non-label symbol: " + sym)
-    js.LabelIdent(labelSymbolName(sym))
+    labelSymbolName(sym)
   }
 
   def encodeFieldSym(sym: Symbol)(implicit pos: Position): js.FieldIdent = {
diff --git a/compiler/src/test/scala/org/scalajs/nscplugin/test/OptimizationTest.scala b/compiler/src/test/scala/org/scalajs/nscplugin/test/OptimizationTest.scala
index 47f843c696..24914ca07b 100644
--- a/compiler/src/test/scala/org/scalajs/nscplugin/test/OptimizationTest.scala
+++ b/compiler/src/test/scala/org/scalajs/nscplugin/test/OptimizationTest.scala
@@ -250,7 +250,7 @@ class OptimizationTest extends JSASTTest {
       }
     }
     """.hasNot("non-return labeled block") {
-      case js.Labeled(name, _, _) if !name.name.nameString.startsWith("_return") =>
+      case js.Labeled(name, _, _) if !name.nameString.startsWith("_return") =>
     }
   }
 
@@ -323,7 +323,7 @@ class OptimizationTest extends JSASTTest {
       }
     }
     """.hasNot("non-return labeled block") {
-      case js.Labeled(name, _, _) if !name.name.nameString.startsWith("_return") =>
+      case js.Labeled(name, _, _) if !name.nameString.startsWith("_return") =>
     }
   }
 
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Hashers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Hashers.scala
index 10847a8ba3..a653c15fce 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Hashers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Hashers.scala
@@ -185,7 +185,7 @@ object Hashers {
 
         case Labeled(label, tpe, body) =>
           mixTag(TagLabeled)
-          mixLabelIdent(label)
+          mixName(label)
           mixType(tpe)
           mixTree(body)
 
@@ -197,7 +197,7 @@ object Hashers {
         case Return(expr, label) =>
           mixTag(TagReturn)
           mixTree(expr)
-          mixLabelIdent(label)
+          mixName(label)
 
         case If(cond, thenp, elsep) =>
           mixTag(TagIf)
@@ -646,11 +646,6 @@ object Hashers {
       mixName(ident.name)
     }
 
-    def mixLabelIdent(ident: LabelIdent): Unit = {
-      mixPos(ident.pos)
-      mixName(ident.name)
-    }
-
     def mixSimpleFieldIdent(ident: SimpleFieldIdent): Unit = {
       mixPos(ident.pos)
       mixName(ident.name)
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala
index af6ed1023c..4c4401a406 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala
@@ -122,7 +122,6 @@ object Printers {
     def printAnyNode(node: IRNode): Unit = {
       node match {
         case node: LocalIdent        => print(node)
-        case node: LabelIdent        => print(node)
         case node: SimpleFieldIdent  => print(node)
         case node: FieldIdent        => print(node)
         case node: MethodIdent       => print(node)
@@ -1138,9 +1137,6 @@ object Printers {
     def print(ident: LocalIdent): Unit =
       print(ident.name)
 
-    def print(ident: LabelIdent): Unit =
-      print(ident.name)
-
     def print(ident: SimpleFieldIdent): Unit =
       print(ident.name)
 
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
index b8fd8790b2..da0dc4d01e 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
@@ -265,7 +265,7 @@ object Serializers {
 
         case Labeled(label, tpe, body) =>
           writeTagAndPos(TagLabeled)
-          writeLabelIdent(label); writeType(tpe); writeTree(body)
+          writeName(label); writeType(tpe); writeTree(body)
 
         case Assign(lhs, rhs) =>
           writeTagAndPos(TagAssign)
@@ -273,7 +273,7 @@ object Serializers {
 
         case Return(expr, label) =>
           writeTagAndPos(TagReturn)
-          writeTree(expr); writeLabelIdent(label)
+          writeTree(expr); writeName(label)
 
         case If(cond, thenp, elsep) =>
           writeTagAndPos(TagIf)
@@ -786,11 +786,6 @@ object Serializers {
       writeName(ident.name)
     }
 
-    def writeLabelIdent(ident: LabelIdent): Unit = {
-      writePosition(ident.pos)
-      writeName(ident.name)
-    }
-
     def writeSimpleFieldIdent(ident: SimpleFieldIdent): Unit = {
       writePosition(ident.pos)
       writeName(ident.name)
@@ -1135,7 +1130,7 @@ object Serializers {
         case TagVarDef  => VarDef(readLocalIdent(), readOriginalName(), readType(), readBoolean(), readTree())
         case TagSkip    => Skip()
         case TagBlock   => Block(readTrees())
-        case TagLabeled => Labeled(readLabelIdent(), readType(), readTree())
+        case TagLabeled => Labeled(readLabelName(), readType(), readTree())
 
         case TagAssign =>
           val lhs0 = readTree()
@@ -1155,7 +1150,7 @@ object Serializers {
 
           Assign(lhs.asInstanceOf[AssignLhs], rhs)
 
-        case TagReturn  => Return(readTree(), readLabelIdent())
+        case TagReturn  => Return(readTree(), readLabelName())
         case TagIf      => If(readTree(), readTree(), readTree())(readType())
         case TagWhile   => While(readTree(), readTree())
 
@@ -2166,11 +2161,6 @@ object Serializers {
       LocalIdent(readLocalName())
     }
 
-    def readLabelIdent(): LabelIdent = {
-      implicit val pos = readPosition()
-      LabelIdent(readLabelName())
-    }
-
     def readFieldIdent(): FieldIdent = {
       // For historical reasons, the className comes *before* the position
       val className = readClassName()
@@ -2399,6 +2389,12 @@ object Serializers {
     }
 
     private def readLabelName(): LabelName = {
+      /* Before 1.18, `LabelName`s were always wrapped in `LabelIdent`s, whose
+       * encoding was a `Position` followed by the actual `LabelName`.
+       */
+      if (hacks.use17)
+        readPosition() // intentional discard
+
       val i = readInt()
       val existing = labelNames(i)
       if (existing ne null) {
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala b/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
index dfb4671d26..917df781ed 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
@@ -56,9 +56,6 @@ object Trees {
   sealed case class LocalIdent(name: LocalName)(implicit val pos: Position)
       extends IRNode
 
-  sealed case class LabelIdent(name: LabelName)(implicit val pos: Position)
-      extends IRNode
-
   sealed case class SimpleFieldIdent(name: SimpleFieldName)(implicit val pos: Position)
       extends IRNode
 
@@ -150,7 +147,7 @@ object Trees {
     def unapply(block: Block): Some[List[Tree]] = Some(block.stats)
   }
 
-  sealed case class Labeled(label: LabelIdent, tpe: Type, body: Tree)(
+  sealed case class Labeled(label: LabelName, tpe: Type, body: Tree)(
       implicit val pos: Position) extends Tree
 
   sealed trait AssignLhs extends Tree
@@ -160,7 +157,7 @@ object Trees {
     val tpe = VoidType
   }
 
-  sealed case class Return(expr: Tree, label: LabelIdent)(
+  sealed case class Return(expr: Tree, label: LabelName)(
       implicit val pos: Position) extends Tree {
     val tpe = NothingType
   }
diff --git a/ir/shared/src/test/scala/org/scalajs/ir/TestIRBuilder.scala b/ir/shared/src/test/scala/org/scalajs/ir/TestIRBuilder.scala
index 8c578c296e..44aed0ef4f 100644
--- a/ir/shared/src/test/scala/org/scalajs/ir/TestIRBuilder.scala
+++ b/ir/shared/src/test/scala/org/scalajs/ir/TestIRBuilder.scala
@@ -39,6 +39,8 @@ object TestIRBuilder {
   // String -> Name conversions
   implicit def string2localName(name: String): LocalName =
     LocalName(name)
+  implicit def string2labelName(name: String): LabelName =
+    LabelName(name)
   implicit def string2simpleFieldName(name: String): SimpleFieldName =
     SimpleFieldName(name)
   implicit def string2className(name: String): ClassName =
@@ -47,8 +49,6 @@ object TestIRBuilder {
   // String -> Ident conversions
   implicit def string2localIdent(name: String): LocalIdent =
     LocalIdent(LocalName(name))
-  implicit def string2labelIdent(name: String): LabelIdent =
-    LabelIdent(LabelName(name))
   implicit def string2simpleFieldIdent(name: String): SimpleFieldIdent =
     SimpleFieldIdent(SimpleFieldName(name))
   implicit def string2classIdent(name: String): ClassIdent =
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
index 6abeb4dd36..89516298bb 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
@@ -710,12 +710,12 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
               case Labeled(label, _, innerBody) =>
                 val innerBodyEnv = loopEnv
                   .withLabeledExprLHS(label, Lhs.Discard)
-                  .withTurnLabelIntoContinue(label.name)
+                  .withTurnLabelIntoContinue(label)
                   .withDefaultBreakTargets(tailPosLabels)
-                  .withDefaultContinueTargets(Set(label.name))
+                  .withDefaultContinueTargets(Set(label))
                 val newBody =
-                  pushLhsInto(Lhs.Discard, innerBody, Set(label.name))(innerBodyEnv)
-                val optLabel = if (usedLabels.contains(label.name))
+                  pushLhsInto(Lhs.Discard, innerBody, Set(label))(innerBodyEnv)
+                val optLabel = if (usedLabels.contains(label))
                   Some(transformLabelIdent(label))
                 else
                   None
@@ -1536,27 +1536,27 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
         }
       }
 
-      def doReturnToLabel(l: LabelIdent): js.Tree = {
-        val newLhs = env.lhsForLabeledExpr(l)
+      def doReturnToLabel(label: LabelName): js.Tree = {
+        val newLhs = env.lhsForLabeledExpr(label)
         if (newLhs.hasNothingType) {
           /* A touch of peephole dead code elimination.
            * This is actually necessary to avoid dangling breaks to eliminated
            * labels, as in issue #2307.
            */
           pushLhsInto(newLhs, rhs, tailPosLabels)
-        } else if (tailPosLabels.contains(l.name)) {
+        } else if (tailPosLabels.contains(label)) {
           pushLhsInto(newLhs, rhs, tailPosLabels)
         } else {
           val body = pushLhsInto(newLhs, rhs, Set.empty)
 
-          val jump = if (env.isDefaultBreakTarget(l.name)) {
+          val jump = if (env.isDefaultBreakTarget(label)) {
             js.Break(None)
-          } else if (env.isDefaultContinueTarget(l.name)) {
+          } else if (env.isDefaultContinueTarget(label)) {
             js.Continue(None)
           } else {
-            usedLabels += l.name
-            val transformedLabel = Some(transformLabelIdent(l))
-            if (env.isLabelTurnedIntoContinue(l.name))
+            usedLabels += label
+            val transformedLabel = Some(transformLabelIdent(label))
+            if (env.isLabelTurnedIntoContinue(label))
               js.Continue(transformedLabel)
             else
               js.Break(transformedLabel)
@@ -1649,8 +1649,8 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
           extractLet { newLhs =>
             val bodyEnv = env.withLabeledExprLHS(label, newLhs)
             val newBody =
-              pushLhsInto(newLhs, body, tailPosLabels + label.name)(bodyEnv)
-            if (usedLabels.contains(label.name))
+              pushLhsInto(newLhs, body, tailPosLabels + label)(bodyEnv)
+            if (usedLabels.contains(label))
               js.Labeled(transformLabelIdent(label), newBody)
             else
               newBody
@@ -3252,8 +3252,8 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
     private def transformParamDef(paramDef: ParamDef): js.ParamDef =
       js.ParamDef(transformLocalVarIdent(paramDef.name, paramDef.originalName))(paramDef.pos)
 
-    private def transformLabelIdent(ident: LabelIdent): js.Ident =
-      js.Ident(genName(ident.name))(ident.pos)
+    private def transformLabelIdent(label: LabelName)(implicit pos: Position): js.Ident =
+      js.Ident(genName(label))
 
     private def transformLocalVarRefIdent(varRef: VarRef): js.Ident =
       js.Ident(transformLocalName(varRef.name))(varRef.pos)
@@ -3401,7 +3401,7 @@ private object FunctionEmitter {
       override def hasNothingType: Boolean = true
     }
 
-    final case class Return(label: LabelIdent) extends Lhs {
+    final case class Return(label: LabelName) extends Lhs {
       override def hasNothingType: Boolean = true
     }
 
@@ -3444,7 +3444,7 @@ private object FunctionEmitter {
     def isLocalMutable(name: LocalName): Boolean =
       VarKind.Mutable == varKind(name)
 
-    def lhsForLabeledExpr(label: LabelIdent): Lhs = labeledExprLHSes(label.name)
+    def lhsForLabeledExpr(label: LabelName): Lhs = labeledExprLHSes(label)
 
     def isLabelTurnedIntoContinue(label: LabelName): Boolean =
       labelsTurnedIntoContinue.contains(label)
@@ -3478,8 +3478,8 @@ private object FunctionEmitter {
       copy(vars = vars + (ident.name -> kind))
     }
 
-    def withLabeledExprLHS(label: LabelIdent, lhs: Lhs): Env =
-      copy(labeledExprLHSes = labeledExprLHSes + (label.name -> lhs))
+    def withLabeledExprLHS(label: LabelName, lhs: Lhs): Env =
+      copy(labeledExprLHSes = labeledExprLHSes + (label -> lhs))
 
     def withTurnLabelIntoContinue(label: LabelName): Env =
       copy(labelsTurnedIntoContinue = labelsTurnedIntoContinue + label)
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
index 85cc991c39..22332110ac 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
@@ -3853,7 +3853,7 @@ private class FunctionEmitter private (
     }
 
     def genLabeled(tree: Labeled, expectedType: Type): Type = {
-      val Labeled(LabelIdent(labelName), tpe, body) = tree
+      val Labeled(labelName, tpe, body) = tree
 
       val entry = new LabeledEntry(currentUnwindingStackDepth, labelName, expectedType)
 
@@ -4082,7 +4082,7 @@ private class FunctionEmitter private (
     }
 
     def genReturn(tree: Return): Type = {
-      val Return(expr, LabelIdent(labelName)) = tree
+      val Return(expr, labelName) = tree
 
       val targetEntry = enclosingLabeledBlocks(labelName)
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala b/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
index 919e2262c6..763255f2c1 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
@@ -667,7 +667,7 @@ private final class ClassDefChecker(classDef: ClassDef,
 
       case Labeled(label, _, body) =>
         checkDeclareLabel(label)
-        checkTree(body, env.withLabel(label.name))
+        checkTree(body, env.withLabel(label))
 
       case Assign(lhs, rhs) =>
         lhs match {
@@ -716,7 +716,7 @@ private final class ClassDefChecker(classDef: ClassDef,
         }
 
       case Return(expr, label) =>
-        if (!env.returnLabels.contains(label.name))
+        if (!env.returnLabels.contains(label))
           reportError(i"unknown label $label.")
 
         checkTree(expr, env)
@@ -1057,10 +1057,10 @@ private final class ClassDefChecker(classDef: ClassDef,
       reportError(i"Duplicate local variable name ${ident.name}.")
   }
 
-  private def checkDeclareLabel(label: LabelIdent)(
+  private def checkDeclareLabel(label: LabelName)(
       implicit ctx: ErrorContext): Unit = {
-    if (!declaredLabelNamesPerMethod.add(label.name))
-      reportError(i"Duplicate label named ${label.name}.")
+    if (!declaredLabelNamesPerMethod.add(label))
+      reportError(i"Duplicate label named $label.")
   }
 }
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala b/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
index b4b743ee63..dcd87e7c5a 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
@@ -234,7 +234,7 @@ private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter,
         trees.foreach(typecheck(_, env))
 
       case Labeled(label, tpe, body) =>
-        typecheckExpect(body, env.withLabeledReturnType(label.name, tpe), tpe)
+        typecheckExpect(body, env.withLabeledReturnType(label, tpe), tpe)
 
       case Assign(lhs, rhs) =>
         def checkNonStaticField(receiver: Tree, name: FieldName): Unit = {
@@ -304,7 +304,7 @@ private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter,
         typecheckExpect(rhs, env, expectedRhsTpe)
 
       case Return(expr, label) =>
-        typecheckExpect(expr, env, env.returnTypes(label.name))
+        typecheckExpect(expr, env, env.returnTypes(label))
 
       case If(cond, thenp, elsep) =>
         val tpe = tree.tpe
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
index b280a7776a..94a294a4cc 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
@@ -338,7 +338,7 @@ private[optimizer] abstract class OptimizerCore(
       case tree: Block =>
         transformBlock(tree, isStat)
 
-      case Labeled(ident @ LabelIdent(label), tpe, body) =>
+      case Labeled(label, tpe, body) =>
         trampoline {
           pretransformLabeled(label, if (isStat) VoidType else tpe, body, isStat,
               usePreTransform = false)(finishTransform(isStat))
@@ -381,8 +381,8 @@ private[optimizer] abstract class OptimizerCore(
         }
 
       case Return(expr, label) =>
-        val info = scope.env.labelInfos(label.name)
-        val newLabel = LabelIdent(info.newName)
+        val info = scope.env.labelInfos(label)
+        val newLabel = info.newName
         if (info.isStat) {
           val newExpr = transformStat(expr)
           info.returnedTypes.value ::= (VoidType, RefinedType.NoRefinedType)
@@ -960,7 +960,7 @@ private[optimizer] abstract class OptimizerCore(
                 transformExpr(default))(tree.tpe).toPreTransform)
         }
 
-      case Labeled(ident @ LabelIdent(label), tpe, body) =>
+      case Labeled(label, tpe, body) =>
         pretransformLabeled(label, tpe, body, isStat = false,
             usePreTransform = true)(cont)
 
@@ -5169,7 +5169,7 @@ private[optimizer] abstract class OptimizerCore(
 
       tryOptimizePatternMatch(oldLabelName, newLabel, refinedType,
           returnCount, newBody) getOrElse {
-        Labeled(LabelIdent(newLabel), refinedType, newBody)
+        Labeled(newLabel, refinedType, newBody)
       }
     }
 
@@ -5263,7 +5263,7 @@ private[optimizer] abstract class OptimizerCore(
 
           if (revAlts.size == returnCount - 1) {
             def tryDropReturn(body: Tree): Option[Tree] = body match {
-              case BlockOrAlone(prep, Return(result, LabelIdent(`newLabelName`))) =>
+              case BlockOrAlone(prep, Return(result, `newLabelName`)) =>
                 val result1 =
                   if (refinedType == VoidType) keepOnlySideEffects(result)
                   else result
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/OptimizerTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/OptimizerTest.scala
index e80affe3bc..7b37ab5648 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/OptimizerTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/OptimizerTest.scala
@@ -267,10 +267,10 @@ class OptimizerTest {
      * optimized code can be linked all the way to the Emitter.
      */
 
-    val matchResult1 = LabelIdent("matchResult1")
+    val matchResult1 = LabelName("matchResult1")
     val x1 = LocalName("x1")
-    val matchAlts1 = LabelIdent("matchAlts1")
-    val matchAlts2 = LabelIdent("matchAlts2")
+    val matchAlts1 = LabelName("matchAlts1")
+    val matchAlts2 = LabelName("matchAlts2")
 
     val results = for (voidReturnArgument <- List(Undefined(), Skip())) yield {
       val classDefs = Seq(
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/testutils/TestIRBuilder.scala b/linker/shared/src/test/scala/org/scalajs/linker/testutils/TestIRBuilder.scala
index 528dfb2fcc..d48649c245 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/testutils/TestIRBuilder.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/testutils/TestIRBuilder.scala
@@ -181,8 +181,6 @@ object TestIRBuilder {
 
   implicit def string2LocalIdent(name: String): LocalIdent =
     LocalIdent(LocalName(name))
-  implicit def string2LabelIdent(name: String): LabelIdent =
-    LabelIdent(LabelName(name))
   implicit def string2SimpleFieldIdent(name: String): SimpleFieldIdent =
    SimpleFieldIdent(SimpleFieldName(name))
   implicit def string2ClassIdent(name: String): ClassIdent =
diff --git a/project/BinaryIncompatibilities.scala b/project/BinaryIncompatibilities.scala
index 7c373ae05f..ec5063ac59 100644
--- a/project/BinaryIncompatibilities.scala
+++ b/project/BinaryIncompatibilities.scala
@@ -6,8 +6,13 @@ import com.typesafe.tools.mima.core.ProblemFilters._
 object BinaryIncompatibilities {
   val IR = Seq(
     // !!! Breaking, OK in minor release
+    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Printers#IRTreePrinter.print"),
     ProblemFilters.exclude[MissingClassProblem]("org.scalajs.ir.Trees$JSLinkingInfo"),
     ProblemFilters.exclude[MissingClassProblem]("org.scalajs.ir.Trees$JSLinkingInfo$"),
+    ProblemFilters.exclude[MissingClassProblem]("org.scalajs.ir.Trees$LabelIdent"),
+    ProblemFilters.exclude[MissingClassProblem]("org.scalajs.ir.Trees$LabelIdent$"),
+    ProblemFilters.exclude[Problem]("org.scalajs.ir.Trees#Labeled.*"),
+    ProblemFilters.exclude[Problem]("org.scalajs.ir.Trees#Return.*"),
     ProblemFilters.exclude[Problem]("org.scalajs.ir.Trees#VarRef.*"),
     ProblemFilters.exclude[IncompatibleResultTypeProblem]("org.scalajs.ir.Trees#*.tpe"),
     ProblemFilters.exclude[MissingClassProblem]("org.scalajs.ir.Types$NoType$"),
@@ -20,6 +25,11 @@ object BinaryIncompatibilities {
     ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Transformers#Transformer.transformStats"),
     ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Trees#Transient#Value.transform"),
     ProblemFilters.exclude[ReversedMissingMethodProblem]("org.scalajs.ir.Trees#Transient#Value.transform"),
+
+    // private, not an issue
+    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Serializers#Deserializer.readLabelIdent"),
+    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Serializers#Serializer.writeLabelIdent"),
+    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Hashers#TreeHasher.mixLabelIdent"),
   )
 
   val Linker = Seq(

From c1646d14fb01e915766215a7ab5450c08e7153e0 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Sun, 15 Dec 2024 13:44:52 +0100
Subject: [PATCH 225/298] Merge several IR nodes into `UnaryOp`.

`ArrayLength`, `GetClass`, `Clone`, `IdentityHashCode`,
`WrapAsThrowable`, `UnwrapFromThrowable` and `Throw` are now ops
of `UnaryOp`, rather than having their own IR nodes.

They all follow the general contract of how a `UnaryOp` must behave:
first evaluate the argument, then perform an operation that only
depends on the value of the argument (and not, for example, on the
scope).

It makes the JS `FunctionEmitter` a bit messier. However,
everything else gets simpler, as we get rid of dedicated paths for
those 7 IR nodes.

In order to better fit with the other `UnaryOp`s, notably the ones
for `jl.Class` operations, we demand non-nullable arguments. An
explicit `CheckNotNull` must be used for arguments that are
nullable.

---

In this commit, we do not update the compiler yet. It still emits
the old IR nodes, so that we can test the deserialiation hacks.
That also means the case classes still exist for now.
---
 .../main/scala/org/scalajs/ir/Printers.scala  |  73 ++--
 .../scala/org/scalajs/ir/Serializers.scala    |  87 +++--
 .../src/main/scala/org/scalajs/ir/Trees.scala |  54 ++-
 .../scala/org/scalajs/ir/PrintersTest.scala   |   8 +
 .../scala/org/scalajs/linker/RunTest.scala    |   4 +-
 .../org/scalajs/linker/analyzer/Infos.scala   |  17 +-
 .../linker/backend/emitter/CoreJSLib.scala    |  21 +-
 .../backend/emitter/FunctionEmitter.scala     | 223 ++++++------
 .../linker/backend/emitter/Transients.scala   |   4 +-
 .../backend/wasmemitter/FunctionEmitter.scala | 329 +++++++-----------
 .../linker/checker/ClassDefChecker.scala      |  34 +-
 .../scalajs/linker/checker/IRChecker.scala    |  47 ++-
 .../frontend/optimizer/IncOptimizer.scala     |   4 +-
 .../frontend/optimizer/OptimizerCore.scala    | 184 ++++------
 .../org/scalajs/linker/IRCheckerTest.scala    |  42 ++-
 .../org/scalajs/linker/OptimizerTest.scala    |  10 +-
 project/Build.scala                           |   2 +-
 17 files changed, 533 insertions(+), 610 deletions(-)

diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala
index 4c4401a406..3008148c71 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala
@@ -347,40 +347,47 @@ object Printers {
         case UnaryOp(op, lhs) =>
           import UnaryOp._
 
-          if (op < String_length) {
-            print('(')
-            print((op: @switch) match {
-              case Boolean_! =>
-                "!"
-              case IntToChar =>
-                "(char)"
-              case IntToByte =>
-                "(byte)"
-              case IntToShort =>
-                "(short)"
-              case CharToInt | ByteToInt | ShortToInt | LongToInt | DoubleToInt =>
-                "(int)"
-              case IntToLong | DoubleToLong =>
-                "(long)"
-              case DoubleToFloat | LongToFloat =>
-                "(float)"
-              case IntToDouble | LongToDouble | FloatToDouble =>
-                "(double)"
-            })
-            print(lhs)
-            print(')')
-          } else {
+          def p(prefix: String, suffix: String): Unit = {
+            print(prefix)
             print(lhs)
-            print((op: @switch) match {
-              case String_length       => ".length"
-              case CheckNotNull        => ".notNull"
-              case Class_name          => ".name"
-              case Class_isPrimitive   => ".isPrimitive"
-              case Class_isInterface   => ".isInterface"
-              case Class_isArray       => ".isArray"
-              case Class_componentType => ".componentType"
-              case Class_superClass    => ".superClass"
-            })
+            print(suffix)
+          }
+
+          (op: @switch) match {
+            case Boolean_! =>
+              p("(!", ")")
+            case IntToChar =>
+              p("((char)", ")")
+            case IntToByte =>
+              p("((byte)", ")")
+            case IntToShort =>
+              p("((short)", ")")
+            case CharToInt | ByteToInt | ShortToInt | LongToInt | DoubleToInt =>
+              p("((int)", ")")
+            case IntToLong | DoubleToLong =>
+              p("((long)", ")")
+            case DoubleToFloat | LongToFloat =>
+              p("((float)", ")")
+            case IntToDouble | LongToDouble | FloatToDouble =>
+              p("((double)", ")")
+
+            case String_length       => p("", ".length")
+            case CheckNotNull        => p("", ".notNull")
+            case Class_name          => p("", ".name")
+            case Class_isPrimitive   => p("", ".isPrimitive")
+            case Class_isInterface   => p("", ".isInterface")
+            case Class_isArray       => p("", ".isArray")
+            case Class_componentType => p("", ".componentType")
+            case Class_superClass    => p("", ".superClass")
+            case Array_length        => p("", ".length")
+            case GetClass            => p("", ".getClass()")
+
+            case Clone               => p("<clone>(", ")")
+            case IdentityHashCode    => p("<identityHashCode>(", ")")
+            case WrapAsThrowable     => p("<wrapAsThrowable>(", ")")
+            case UnwrapFromThrowable => p("<unwrapFromThrowable>(", ")")
+
+            case Throw => p("throw ", "")
           }
 
         case BinaryOp(BinaryOp.Int_-, IntLiteral(0), rhs) =>
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
index da0dc4d01e..369cb5990c 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
@@ -1139,8 +1139,8 @@ object Serializers {
              * (throw qual.field[null]) = rhs  -->  qual.field[null] = rhs
              */
             lhs0 match {
-              case Throw(sel: Select) if sel.tpe == NullType => sel
-              case _                                         => lhs0
+              case UnaryOp(UnaryOp.Throw, sel: Select) if sel.tpe == NullType => sel
+              case _                                                          => lhs0
             }
           } else {
             lhs0
@@ -1170,13 +1170,6 @@ object Serializers {
         case TagTryFinally =>
           TryFinally(readTree(), readTree())
 
-        case TagThrow =>
-          val expr = readTree()
-          val patchedExpr =
-            if (hacks.use8) throwArgumentHack8(expr)
-            else expr
-          Throw(patchedExpr)
-
         case TagMatch =>
           Match(readTree(), List.fill(readInt()) {
             (readTrees().map(_.asInstanceOf[MatchableLiteral]), readTree())
@@ -1207,7 +1200,7 @@ object Serializers {
             /* Note [Nothing FieldDef rewrite]
              * qual.field[nothing]  -->  throw qual.field[null]
              */
-            Throw(Select(qualifier, field)(NullType))
+            UnaryOp(UnaryOp.Throw, Select(qualifier, field)(NullType))
           } else {
             Select(qualifier, field)(tpe)
           }
@@ -1246,6 +1239,36 @@ object Serializers {
         case TagUnaryOp  => UnaryOp(readByte(), readTree())
         case TagBinaryOp => BinaryOp(readByte(), readTree(), readTree())
 
+        case TagArrayLength | TagGetClass | TagClone | TagIdentityHashCode |
+            TagWrapAsThrowable | TagUnwrapFromThrowable | TagThrow =>
+          if (false /*!hacks.use17*/) { // scalastyle:ignore
+            throw new IOException(
+                s"Illegal legacy node $tag found in class ${enclosingClassName.nameString}")
+          }
+
+          val lhs = readTree()
+          def checkNotNullLhs: Tree = UnaryOp(UnaryOp.CheckNotNull, lhs)
+
+          (tag: @switch) match {
+            case TagArrayLength =>
+              UnaryOp(UnaryOp.Array_length, checkNotNullLhs)
+            case TagGetClass =>
+              UnaryOp(UnaryOp.GetClass, checkNotNullLhs)
+            case TagClone =>
+              UnaryOp(UnaryOp.Clone, checkNotNullLhs)
+            case TagIdentityHashCode =>
+              UnaryOp(UnaryOp.IdentityHashCode, lhs)
+            case TagWrapAsThrowable =>
+              UnaryOp(UnaryOp.WrapAsThrowable, lhs)
+            case TagUnwrapFromThrowable =>
+              UnaryOp(UnaryOp.UnwrapFromThrowable, checkNotNullLhs)
+            case TagThrow =>
+              val patchedLhs =
+                if (hacks.use8) throwArgumentHack8(lhs)
+                else lhs
+              UnaryOp(UnaryOp.Throw, patchedLhs)
+          }
+
         case TagNewArray =>
           val arrayTypeRef = readArrayTypeRef()
           val lengths = readTrees()
@@ -1279,7 +1302,6 @@ object Serializers {
           }
 
         case TagArrayValue  => ArrayValue(readArrayTypeRef(), readTrees())
-        case TagArrayLength => ArrayLength(readTree())
         case TagArraySelect => ArraySelect(readTree(), readTree())(readType())
         case TagRecordValue => RecordValue(readType().asInstanceOf[RecordType], readTrees())
 
@@ -1299,14 +1321,6 @@ object Serializers {
           IsInstanceOf(expr, testType)
 
         case TagAsInstanceOf     => AsInstanceOf(readTree(), readType())
-        case TagGetClass         => GetClass(readTree())
-        case TagClone            => Clone(readTree())
-        case TagIdentityHashCode => IdentityHashCode(readTree())
-
-        case TagWrapAsThrowable =>
-          WrapAsThrowable(readTree())
-        case TagUnwrapFromThrowable =>
-          UnwrapFromThrowable(readTree())
 
         case TagJSNew           => JSNew(readTree(), readTreeOrJSSpreads())
         case TagJSPrivateSelect => JSPrivateSelect(readTree(), readFieldIdent())
@@ -1462,10 +1476,13 @@ object Serializers {
      *    `runtime.package$.unwrapJavaScriptException(x)`.
      */
     private def throwArgumentHack8(expr: Tree)(implicit pos: Position): Tree = {
+      def unwrapFromThrowable(t: Tree): Tree =
+        UnaryOp(UnaryOp.UnwrapFromThrowable, t)
+
       expr.tpe match {
         case NullType =>
           // Evaluate the expression then definitely run into an NPE UB
-          UnwrapFromThrowable(expr)
+          unwrapFromThrowable(expr)
 
         case ClassType(_, _) =>
           expr match {
@@ -1476,7 +1493,7 @@ object Serializers {
               /* Common case (explicit re-throw of the form `throw th`) where we don't need the IIFE.
                * if (expr === null) unwrapFromThrowable(null) else expr
                */
-              If(BinaryOp(BinaryOp.===, expr, Null()), UnwrapFromThrowable(Null()), expr)(AnyType)
+              If(BinaryOp(BinaryOp.===, expr, Null()), unwrapFromThrowable(Null()), expr)(AnyType)
             case _ =>
               /* General case where we need to avoid evaluating `expr` twice.
                * ((x) => if (x === null) unwrapFromThrowable(null) else x)(expr)
@@ -1485,7 +1502,7 @@ object Serializers {
               val xParamDef = ParamDef(x, OriginalName.NoOriginalName, AnyType, mutable = false)
               val xRef = xParamDef.ref
               val closure = Closure(arrow = true, Nil, List(xParamDef), None, {
-                If(BinaryOp(BinaryOp.===, xRef, Null()), UnwrapFromThrowable(Null()), xRef)(AnyType)
+                If(BinaryOp(BinaryOp.===, xRef, Null()), unwrapFromThrowable(Null()), xRef)(AnyType)
               }, Nil)
               JSFunctionApply(closure, List(expr))
           }
@@ -1681,6 +1698,12 @@ object Serializers {
         VarDef(LocalIdent(LocalName(name)), NoOriginalName, vtpe, mutable, rhs)
       }
 
+      def arrayLength(t: Tree)(implicit pos: Position): Tree =
+        UnaryOp(UnaryOp.Array_length, t)
+
+      def getClass(t: Tree)(implicit pos: Position): Tree =
+        UnaryOp(UnaryOp.GetClass, t)
+
       val jlClassRef = ClassRef(ClassClass)
       val intArrayTypeRef = ArrayTypeRef(IntRef, 1)
       val objectRef = ClassRef(ObjectClass)
@@ -1738,7 +1761,7 @@ object Serializers {
             length,
             result,
             innerOffset,
-            If(BinaryOp(BinaryOp.Int_<, innerOffset.ref, ArrayLength(dimensions.ref)), {
+            If(BinaryOp(BinaryOp.Int_<, innerOffset.ref, arrayLength(dimensions.ref)), {
               Block(
                 result2,
                 innerComponentType,
@@ -1808,11 +1831,11 @@ object Serializers {
               Block(
                 outermostComponentType,
                 i,
-                While(BinaryOp(BinaryOp.Int_!=, i.ref, ArrayLength(lengthsParam.ref)), {
+                While(BinaryOp(BinaryOp.Int_!=, i.ref, arrayLength(lengthsParam.ref)), {
                   Block(
                     Assign(
                       outermostComponentType.ref,
-                      GetClass(Apply(EAF, This()(ClassType(ReflectArrayModClass, nullable = false)),
+                      getClass(Apply(EAF, This()(ClassType(ReflectArrayModClass, nullable = false)),
                           MethodIdent(newInstanceSingleName),
                           List(outermostComponentType.ref, IntLiteral(0)))(AnyType))
                     ),
@@ -1942,7 +1965,7 @@ object Serializers {
          */
         assert(args.size == 1)
 
-        val patchedBody = Some(IdentityHashCode(args(0).ref))
+        val patchedBody = Some(UnaryOp(UnaryOp.IdentityHashCode, args(0).ref))
         val patchedOptimizerHints = OptimizerHints.empty.withInline(true)
 
         MethodDef(flags, name, originalName, args, resultType, patchedBody)(
@@ -1967,11 +1990,13 @@ object Serializers {
 
         val patchedBody = Some {
           If(IsInstanceOf(thisValue, cloneableClassType.toNonNullable),
-              Clone(AsInstanceOf(thisValue, cloneableClassType)),
-              Throw(New(
-                  HackNames.CloneNotSupportedExceptionClass,
-                  MethodIdent(NoArgConstructorName),
-                  Nil)))(cloneableClassType)
+              UnaryOp(UnaryOp.Clone,
+                  UnaryOp(UnaryOp.CheckNotNull, AsInstanceOf(thisValue, cloneableClassType))),
+              UnaryOp(UnaryOp.Throw,
+                  New(
+                    HackNames.CloneNotSupportedExceptionClass,
+                    MethodIdent(NoArgConstructorName),
+                    Nil)))(cloneableClassType)
         }
         val patchedOptimizerHints = OptimizerHints.empty.withInline(true)
 
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala b/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
index 917df781ed..031970c895 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
@@ -280,12 +280,24 @@ object Trees {
   }
 
   /** Unary operation.
+   *
+   *  All unary operations follow common evaluation steps:
+   *
+   *  1. Let `lhsValue` be the result of evaluating `lhs`.
+   *  2. Perform an operation that depends on `op` and `lhsValue`.
    *
    *  The `Class_x` operations take a `jl.Class!` argument, i.e., a
    *  non-nullable `jl.Class`.
    *
+   *  Likewise, `Array_length`, `GetClass`, `Clone` and `UnwrapFromThrowable`
+   *  take arguments of non-nullable types.
+   *
    *  `CheckNotNull` throws NPEs subject to UB.
    *
+   *  `Throw` always throws, obviously.
+   *
+   *  `Clone` and `WrapAsThrowable` are side-effect-free but not pure.
+   *
    *  Otherwise, unary operations preserve pureness.
    */
   sealed case class UnaryOp(op: UnaryOp.Code, lhs: Tree)(
@@ -337,9 +349,26 @@ object Trees {
     final val Class_componentType = 23
     final val Class_superClass = 24
 
+    // Misc ops introduced in 1.18, which used to have dedicated IR nodes
+    final val Array_length = 25
+    final val GetClass = 26
+    final val Clone = 27
+    final val IdentityHashCode = 28
+    final val WrapAsThrowable = 29
+    final val UnwrapFromThrowable = 30
+    final val Throw = 31
+
     def isClassOp(op: Code): Boolean =
       op >= Class_name && op <= Class_superClass
 
+    def isPureOp(op: Code): Boolean = (op: @switch) match {
+      case CheckNotNull | Clone | WrapAsThrowable | Throw => false
+      case _                                              => true
+    }
+
+    def isSideEffectFreeOp(op: Code): Boolean =
+      op != CheckNotNull && op != Throw
+
     def resultTypeOf(op: Code, argType: Type): Type = (op: @switch) match {
       case Boolean_! | Class_isPrimitive | Class_isInterface | Class_isArray =>
         BooleanType
@@ -349,7 +378,8 @@ object Trees {
         ByteType
       case IntToShort =>
         ShortType
-      case CharToInt | ByteToInt | ShortToInt | LongToInt | DoubleToInt | String_length =>
+      case CharToInt | ByteToInt | ShortToInt | LongToInt | DoubleToInt |
+          String_length | Array_length | IdentityHashCode =>
         IntType
       case IntToLong | DoubleToLong =>
         LongType
@@ -357,12 +387,18 @@ object Trees {
         FloatType
       case IntToDouble | LongToDouble | FloatToDouble =>
         DoubleType
-      case CheckNotNull =>
+      case CheckNotNull | Clone =>
         argType.toNonNullable
       case Class_name =>
         StringType
-      case Class_componentType | Class_superClass =>
+      case Class_componentType | Class_superClass | GetClass =>
         ClassType(ClassClass, nullable = true)
+      case WrapAsThrowable =>
+        ClassType(ThrowableClass, nullable = false)
+      case UnwrapFromThrowable =>
+        AnyType
+      case Throw =>
+        NothingType
     }
   }
 
@@ -826,11 +862,7 @@ object Trees {
     val tpe = VoidType
   }
 
-  /** Unary operation (always preserves pureness).
-   *
-   *  Operations which do not preserve pureness are not allowed in this tree.
-   *  These are notably ++ and --
-   */
+  /** JavaScript unary operation. */
   sealed case class JSUnaryOp(op: JSUnaryOp.Code, lhs: Tree)(
       implicit val pos: Position) extends Tree {
     val tpe = JSUnaryOp.resultTypeOf(op)
@@ -851,11 +883,7 @@ object Trees {
       AnyType
   }
 
-  /** Binary operation (always preserves pureness).
-   *
-   *  Operations which do not preserve pureness are not allowed in this tree.
-   *  These are notably +=, -=, *=, /= and %=
-   */
+  /** JavaScript binary operation. */
   sealed case class JSBinaryOp(op: JSBinaryOp.Code, lhs: Tree, rhs: Tree)(
       implicit val pos: Position) extends Tree {
     val tpe = JSBinaryOp.resultTypeOf(op)
diff --git a/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala b/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala
index 052db4b9da..06c2d0de56 100644
--- a/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala
+++ b/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala
@@ -403,6 +403,14 @@ class PrintersTest {
     assertPrintEquals("x.isArray", UnaryOp(Class_isArray, classVarRef))
     assertPrintEquals("x.componentType", UnaryOp(Class_componentType, classVarRef))
     assertPrintEquals("x.superClass", UnaryOp(Class_superClass, classVarRef))
+
+    assertPrintEquals("x.length", UnaryOp(Array_length, ref("x", arrayType(IntRef, 1))))
+    assertPrintEquals("x.getClass()", UnaryOp(GetClass, ref("x", AnyType)))
+    assertPrintEquals("<clone>(x)", UnaryOp(Clone, ref("x", arrayType(ObjectClass, 1))))
+    assertPrintEquals("<identityHashCode>(x)", UnaryOp(IdentityHashCode, ref("x", AnyType)))
+    assertPrintEquals("<wrapAsThrowable>(e)", UnaryOp(WrapAsThrowable, ref("e", AnyType)))
+    assertPrintEquals("<unwrapFromThrowable>(e)",
+        UnaryOp(UnwrapFromThrowable, ref("e", ClassType(ThrowableClass, nullable = true))))
   }
 
   @Test def printPseudoUnaryOp(): Unit = {
diff --git a/linker/jvm/src/test/scala/org/scalajs/linker/RunTest.scala b/linker/jvm/src/test/scala/org/scalajs/linker/RunTest.scala
index 0f7f6a628a..5c49da7dee 100644
--- a/linker/jvm/src/test/scala/org/scalajs/linker/RunTest.scala
+++ b/linker/jvm/src/test/scala/org/scalajs/linker/RunTest.scala
@@ -71,7 +71,7 @@ class RunTest {
     val classDefs = Seq(
       mainTestClassDef(Block(
         VarDef("e", NON, ClassType(ThrowableClass, nullable = true), mutable = false,
-            WrapAsThrowable(JSNew(JSGlobalRef("RangeError"), List(str("boom"))))),
+            UnaryOp(UnaryOp.WrapAsThrowable, JSNew(JSGlobalRef("RangeError"), List(str("boom"))))),
         genAssert(IsInstanceOf(e, ClassType("java.lang.Exception", nullable = false))),
         genAssertEquals(str("RangeError: boom"),
             Apply(EAF, e, getMessage, Nil)(ClassType(BoxedStringClass, nullable = true)))
@@ -87,7 +87,7 @@ class RunTest {
 
   private def genAssert(test: Tree): Tree = {
     If(UnaryOp(UnaryOp.Boolean_!, test),
-        Throw(JSNew(JSGlobalRef("Error"), List(str("Assertion failed")))),
+        UnaryOp(UnaryOp.Throw, JSNew(JSGlobalRef("Error"), List(str("Assertion failed")))),
         Skip())(
         VoidType)
   }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala
index 84a8d8a630..1458e107f4 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala
@@ -684,6 +684,13 @@ object Infos {
               op match {
                 case Class_superClass =>
                   builder.addUsedClassSuperClass()
+                case GetClass =>
+                  builder.addAccessedClassClass()
+                case WrapAsThrowable =>
+                  builder.addUsedInstanceTest(ThrowableClass)
+                  builder.addInstantiatedClass(JavaScriptExceptionClass, AnyArgConstructorName)
+                case UnwrapFromThrowable =>
+                  builder.addUsedInstanceTest(JavaScriptExceptionClass)
                 case _ =>
                   // do nothing
               }
@@ -727,16 +734,6 @@ object Infos {
               builder.maybeAddAccessedClassData(cls)
               builder.addAccessedClassClass()
 
-            case GetClass(_) =>
-              builder.addAccessedClassClass()
-
-            case WrapAsThrowable(_) =>
-              builder.addUsedInstanceTest(ThrowableClass)
-              builder.addInstantiatedClass(JavaScriptExceptionClass, AnyArgConstructorName)
-
-            case UnwrapFromThrowable(_) =>
-              builder.addUsedInstanceTest(JavaScriptExceptionClass)
-
             case JSPrivateSelect(_, field) =>
               builder.addStaticallyReferencedClass(field.name.className) // for the private name of the field
               builder.addFieldRead(field.name)
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
index 77e47c1fb4..467e73d68b 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
@@ -712,23 +712,16 @@ private[emitter] object CoreJSLib {
                 Return(constantClassResult(BoxedUnitClass))
               }
           ), {
-            If(instance === Null(), {
-              if (nullPointers == CheckedBehavior.Unchecked)
-                Return(genApply(instance, getClassMethodName, Nil))
-              else
-                genCallHelper(VarField.throwNullPointerException)
+            If(genIsInstanceOfHijackedClass(instance, BoxedLongClass), {
+              Return(constantClassResult(BoxedLongClass))
             }, {
-              If(genIsInstanceOfHijackedClass(instance, BoxedLongClass), {
-                Return(constantClassResult(BoxedLongClass))
+              If(genIsInstanceOfHijackedClass(instance, BoxedCharacterClass), {
+                Return(constantClassResult(BoxedCharacterClass))
               }, {
-                If(genIsInstanceOfHijackedClass(instance, BoxedCharacterClass), {
-                  Return(constantClassResult(BoxedCharacterClass))
+                If(genIsScalaJSObject(instance), {
+                  Return(scalaObjectResult(instance))
                 }, {
-                  If(genIsScalaJSObject(instance), {
-                    Return(scalaObjectResult(instance))
-                  }, {
-                    Return(jsObjectResult)
-                  })
+                  Return(jsObjectResult)
                 })
               })
             })
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
index 89516298bb..12af2ad9ab 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
@@ -1031,8 +1031,10 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
                 }
                 result
 
-              case UnaryOp(op, lhs) if op != UnaryOp.CheckNotNull || noExtractYet =>
+              case arg @ UnaryOp(op, lhs)
+                  if canUnaryOpBeExpression(arg) && (UnaryOp.isPureOp(op) || noExtractYet) =>
                 UnaryOp(op, rec(lhs))
+
               case BinaryOp(op, lhs, rhs) =>
                 val newRhs = rec(rhs)
                 BinaryOp(op, rec(lhs), newRhs)
@@ -1083,8 +1085,6 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
                 ApplyStatic(flags, className, method, recs(args))(arg.tpe)
               case ApplyDynamicImport(flags, className, method, args) if noExtractYet =>
                 ApplyDynamicImport(flags, className, method, recs(args))
-              case ArrayLength(array) if noExtractYet =>
-                ArrayLength(rec(array))
               case ArraySelect(array, index) if noExtractYet =>
                 val newIndex = rec(index)
                 ArraySelect(rec(array), newIndex)(arg.tpe)
@@ -1219,6 +1219,22 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
       }
     }
 
+    private def canUnaryOpBeExpression(tree: UnaryOp): Boolean = {
+      import UnaryOp._
+
+      tree.op match {
+        case Throw =>
+          false
+        case WrapAsThrowable | UnwrapFromThrowable =>
+          tree.lhs match {
+            case VarRef(_) | Transient(JSVarRef(_, _)) => true
+            case _                                     => false
+          }
+        case _ =>
+          true
+      }
+    }
+
     /** Common implementation for the functions below.
      *  A pure expression can be moved around or executed twice, because it
      *  will always produce the same result and never have side-effects.
@@ -1255,6 +1271,16 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
         case Transient(JSVarRef(_, mutable)) =>
           allowUnpure || !mutable
 
+        case tree @ UnaryOp(op, lhs) if canUnaryOpBeExpression(tree) =>
+          if (op == UnaryOp.CheckNotNull)
+            testNPE(lhs)
+          else if (UnaryOp.isPureOp(op))
+            test(lhs)
+          else if (UnaryOp.isSideEffectFreeOp(op))
+            allowUnpure && test(lhs)
+          else
+            allowSideEffects && test(lhs)
+
         // Division and modulo, preserve pureness unless they can divide by 0
         case BinaryOp(BinaryOp.Int_/ | BinaryOp.Int_%, lhs, rhs) if !allowSideEffects =>
           rhs match {
@@ -1281,16 +1307,8 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
         case Block(trees)            => trees forall test
         case If(cond, thenp, elsep)  => test(cond) && test(thenp) && test(elsep)
         case BinaryOp(_, lhs, rhs)   => test(lhs) && test(rhs)
-        case UnaryOp(op, lhs)        => if (op == UnaryOp.CheckNotNull) testNPE(lhs) else test(lhs)
-        case ArrayLength(array)      => testNPE(array)
         case RecordSelect(record, _) => test(record)
         case IsInstanceOf(expr, _)   => test(expr)
-        case IdentityHashCode(expr)  => test(expr)
-        case GetClass(arg)           => testNPE(arg)
-
-        // Expressions preserving pureness (modulo NPE) but requiring that expr be a var
-        case WrapAsThrowable(expr @ (VarRef(_) | Transient(JSVarRef(_, _))))     => test(expr)
-        case UnwrapFromThrowable(expr @ (VarRef(_) | Transient(JSVarRef(_, _)))) => testNPE(expr)
 
         // Transients preserving pureness (modulo NPE)
         case Transient(Cast(expr, _)) =>
@@ -1298,7 +1316,7 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
         case Transient(ZeroOf(runtimeClass)) =>
           test(runtimeClass) // ZeroOf *assumes* that `runtimeClass ne null`
         case Transient(ObjectClassName(obj)) =>
-          testNPE(obj)
+          test(obj)
 
         // Expressions preserving side-effect freedom (modulo NPE)
         case Select(qualifier, _) =>
@@ -1307,8 +1325,6 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
           allowUnpure
         case ArrayValue(tpe, elems) =>
           allowUnpure && (elems forall test)
-        case Clone(arg) =>
-          allowUnpure && testNPE(arg)
         case JSArrayConstr(items) =>
           allowUnpure && (items.forall(testJSArg))
         case tree @ JSObjectConstr(items) =>
@@ -1685,9 +1701,6 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
             js.TryFinally(newBlock, newFinalizer)
           }
 
-        case Throw(expr) =>
-          pushLhsInto(Lhs.Throw, expr, tailPosLabels)
-
         /** Matches are desugared into switches
          *
          *  A match is different from a switch in two respects, both linked
@@ -1757,8 +1770,22 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
           }
 
         case UnaryOp(op, lhs) =>
-          unnest(lhs) { (newLhs, env) =>
-            redo(UnaryOp(op, newLhs))(env)
+          op match {
+            case UnaryOp.Throw =>
+              pushLhsInto(Lhs.Throw, lhs, tailPosLabels)
+
+            case UnaryOp.WrapAsThrowable | UnaryOp.UnwrapFromThrowable =>
+              unnest(lhs) { (newLhs, newEnv) =>
+                implicit val env = newEnv
+                withTempJSVar(newLhs) { varRef =>
+                  redo(UnaryOp(op, varRef))
+                }
+              }
+
+            case _ =>
+              unnest(lhs) { (newLhs, env) =>
+                redo(UnaryOp(op, newLhs))(env)
+              }
           }
 
         case BinaryOp(op, lhs, rhs) =>
@@ -1776,11 +1803,6 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
             redo(ArrayValue(tpe, newElems))(env)
           }
 
-        case ArrayLength(array) =>
-          unnest(array) { (newArray, env) =>
-            redo(ArrayLength(newArray))(env)
-          }
-
         case ArraySelect(array, index) =>
           unnest(checkNotNull(array), index) { (newArray, newIndex, env) =>
             redo(ArraySelect(newArray, newIndex)(rhs.tpe))(env)
@@ -1801,37 +1823,6 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
             redo(AsInstanceOf(newExpr, tpe))(env)
           }
 
-        case GetClass(expr) =>
-          unnest(expr) { (newExpr, env) =>
-            redo(GetClass(newExpr))(env)
-          }
-
-        case Clone(expr) =>
-          unnest(expr) { (newExpr, env) =>
-            redo(Clone(newExpr))(env)
-          }
-
-        case IdentityHashCode(expr) =>
-          unnest(expr) { (newExpr, env) =>
-            redo(IdentityHashCode(newExpr))(env)
-          }
-
-        case WrapAsThrowable(expr) =>
-          unnest(expr) { (newExpr, newEnv) =>
-            implicit val env = newEnv
-            withTempJSVar(newExpr) { varRef =>
-              redo(WrapAsThrowable(varRef))
-            }
-          }
-
-        case UnwrapFromThrowable(expr) =>
-          unnest(expr) { (newExpr, newEnv) =>
-            implicit val env = newEnv
-            withTempJSVar(newExpr) { varRef =>
-              redo(UnwrapFromThrowable(varRef))
-            }
-          }
-
         case Transient(Cast(expr, tpe)) =>
           unnest(expr) { (newExpr, env) =>
             redo(Transient(Cast(newExpr, tpe)))(env)
@@ -2429,6 +2420,66 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
               js.Apply(genGetDataOf(newLhs) DOT cpn.getComponentType, Nil)
             case Class_superClass =>
               js.Apply(genGetDataOf(newLhs) DOT cpn.getSuperclass, Nil)
+
+            case Array_length =>
+              genIdentBracketSelect(
+                  genSyntheticPropSelect(newLhs, SyntheticProperty.u),
+                  "length")
+
+            case GetClass =>
+              genCallHelper(VarField.objectGetClass, newLhs)
+
+            case Clone =>
+              lhs.tpe match {
+                /* If the argument is known to be an array, directly call its
+                 * `clone__O` method.
+                 * This happens all the time when calling `clone()` on an array,
+                 * since the optimizer will inline `java.lang.Object.clone()` in
+                 * those cases, leaving a `Clone()` node an array.
+                 */
+                case _: ArrayType =>
+                  genApply(newLhs, cloneMethodName, Nil)
+
+                /* Otherwise, if it might be an array, use the full dispatcher.
+                 * In theory, only the `CloneableClass` case is required, since
+                 * `Clone` only accepts values of type `Cloneable`. However, since
+                 * the inliner does not always refine the type of receivers, we
+                 * also account for other supertypes of array types. There is a
+                 * similar issue for CharSequenceClass in `Apply` nodes.
+                 *
+                 * TODO Is the above comment still relevant now that the optimizer
+                 * is type-preserving?
+                 *
+                 * In practice, this only happens in the (non-inlined) definition
+                 * of `java.lang.Object.clone()` itself, since everywhere else it
+                 * is inlined in contexts where the receiver has a more precise
+                 * type.
+                 */
+                case ClassType(CloneableClass, _) | ClassType(SerializableClass, _) |
+                    ClassType(ObjectClass, _) | AnyType | AnyNotNullType =>
+                  genCallHelper(VarField.objectOrArrayClone, newLhs)
+
+                // Otherwise, it is known not to be an array.
+                case _ =>
+                  genCallHelper(VarField.objectClone, newLhs)
+              }
+
+            case IdentityHashCode =>
+              genCallHelper(VarField.systemIdentityHashCode, newLhs)
+
+            case WrapAsThrowable =>
+              val newLhsVar = newLhs.asInstanceOf[js.VarRef]
+              js.If(
+                  genIsInstanceOfClass(newLhsVar, ThrowableClass),
+                  newLhsVar,
+                  genScalaClassNew(JavaScriptExceptionClass, AnyArgConstructorName, newLhsVar))
+
+            case UnwrapFromThrowable =>
+              val newLhsVar = newLhs.asInstanceOf[js.VarRef]
+              js.If(
+                  genIsInstanceOfClass(newLhsVar, JavaScriptExceptionClass),
+                  genSelect(newLhsVar, FieldIdent(exceptionFieldName)),
+                  newLhsVar)
           }
 
         case BinaryOp(op, lhs, rhs) =>
@@ -2739,12 +2790,6 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
           extractWithGlobals(
               genArrayValue(typeRef, elems.map(transformExpr(_, preserveChar))))
 
-        case ArrayLength(array) =>
-          val newArray = transformExprNoChar(checkNotNull(array))
-          genIdentBracketSelect(
-              genSyntheticPropSelect(newArray, SyntheticProperty.u),
-              "length")
-
         case ArraySelect(array, index) =>
           val newArray = transformExprNoChar(checkNotNull(array))
           val newIndex = transformExprNoChar(index)
@@ -2764,62 +2809,6 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
         case AsInstanceOf(expr, tpe) =>
           extractWithGlobals(genAsInstanceOf(transformExprNoChar(expr), tpe))
 
-        case GetClass(expr) =>
-          genCallHelper(VarField.objectGetClass, transformExprNoChar(expr))
-
-        case Clone(expr) =>
-          val newExpr = transformExprNoChar(checkNotNull(expr))
-          expr.tpe match {
-            /* If the argument is known to be an array, directly call its
-             * `clone__O` method.
-             * This happens all the time when calling `clone()` on an array,
-             * since the optimizer will inline `java.lang.Object.clone()` in
-             * those cases, leaving a `Clone()` node an array.
-             */
-            case _: ArrayType =>
-              genApply(newExpr, cloneMethodName, Nil)
-
-            /* Otherwise, if it might be an array, use the full dispatcher.
-             * In theory, only the `CloneableClass` case is required, since
-             * `Clone` only accepts values of type `Cloneable`. However, since
-             * the inliner does not always refine the type of receivers, we
-             * also account for other supertypes of array types. There is a
-             * similar issue for CharSequenceClass in `Apply` nodes.
-             *
-             * TODO Is the above comment still relevant now that the optimizer
-             * is type-preserving?
-             *
-             * In practice, this only happens in the (non-inlined) definition
-             * of `java.lang.Object.clone()` itself, since everywhere else it
-             * is inlined in contexts where the receiver has a more precise
-             * type.
-             */
-            case ClassType(CloneableClass, _) | ClassType(SerializableClass, _) |
-                ClassType(ObjectClass, _) | AnyType | AnyNotNullType =>
-              genCallHelper(VarField.objectOrArrayClone, newExpr)
-
-            // Otherwise, it is known not to be an array.
-            case _ =>
-              genCallHelper(VarField.objectClone, newExpr)
-          }
-
-        case IdentityHashCode(expr) =>
-          genCallHelper(VarField.systemIdentityHashCode, transformExprNoChar(expr))
-
-        case WrapAsThrowable(expr) =>
-          val newExpr = transformExprNoChar(expr).asInstanceOf[js.VarRef]
-          js.If(
-              genIsInstanceOfClass(newExpr, ThrowableClass),
-              newExpr,
-              genScalaClassNew(JavaScriptExceptionClass, AnyArgConstructorName, newExpr))
-
-        case UnwrapFromThrowable(expr) =>
-          val newExpr = transformExprNoChar(expr).asInstanceOf[js.VarRef]
-          js.If(
-              genIsInstanceOfClass(newExpr, JavaScriptExceptionClass),
-              genSelect(newExpr, FieldIdent(exceptionFieldName)),
-              genCheckNotNull(newExpr))
-
         case prop: LinkTimeProperty =>
           transformExpr(
               config.coreSpec.linkTimeProperties.transformLinkTimeProperty(prop),
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Transients.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Transients.scala
index 61f9ece247..00301771cc 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Transients.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Transients.scala
@@ -137,9 +137,7 @@ object Transients {
 
   /** Intrinsic for `obj.getClass().getName()`.
    *
-   *  This node accepts any value for `obj`, including `null`. Its
-   *  implementation takes care of throwing `NullPointerException`s as
-   *  required.
+   *  The argument's type must conform to `AnyNotNullType`.
    */
   final case class ObjectClassName(obj: Tree) extends Transient.Value {
     val tpe: Type = StringType
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
index 22332110ac..78f0b2ec39 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
@@ -537,7 +537,6 @@ private class FunctionEmitter private (
       case t: ApplyDynamicImport  => genApplyDynamicImport(t)
       case t: IsInstanceOf        => genIsInstanceOf(t)
       case t: AsInstanceOf        => genAsInstanceOf(t)
-      case t: GetClass            => genGetClass(t)
       case t: Block               => genBlock(t, expectedType)
       case t: Labeled             => unwinding.genLabeled(t, expectedType)
       case t: Return              => unwinding.genReturn(t)
@@ -551,14 +550,9 @@ private class FunctionEmitter private (
       case t: ForIn               => genForIn(t)
       case t: TryCatch            => genTryCatch(t, expectedType)
       case t: TryFinally          => unwinding.genTryFinally(t, expectedType)
-      case t: Throw               => genThrow(t)
       case t: Match               => genMatch(t, expectedType)
       case t: Debugger            => VoidType // ignore
       case t: Skip                => VoidType
-      case t: Clone               => genClone(t)
-      case t: IdentityHashCode    => genIdentityHashCode(t)
-      case t: WrapAsThrowable     => genWrapAsThrowable(t)
-      case t: UnwrapFromThrowable => genUnwrapFromThrowable(t)
       case t: LinkTimeProperty    => genLinkTimeProperty(t)
 
       // JavaScript expressions
@@ -581,7 +575,6 @@ private class FunctionEmitter private (
       case t: Closure              => genClosure(t)
 
       // array
-      case t: ArrayLength => genArrayLength(t)
       case t: NewArray    => genNewArray(t)
       case t: ArraySelect => genArraySelect(t)
       case t: ArrayValue  => genArrayValue(t)
@@ -602,6 +595,11 @@ private class FunctionEmitter private (
 
       case _: JSSuperConstructorCall =>
         throw new AssertionError(s"Invalid tree: $tree")
+
+      case _:Throw | _:ArrayLength | _:GetClass | _:Clone | _:IdentityHashCode |
+          _:WrapAsThrowable | _:UnwrapFromThrowable =>
+        throw new AssertionError(
+            s"illegal legacy node of class ${tree.getClass().getSimpleName()}")
     }
 
     genAdapt(generatedType, expectedType)
@@ -1370,11 +1368,27 @@ private class FunctionEmitter private (
   }
 
   private def genUnaryOp(tree: UnaryOp): Type = {
+    // scalastyle:off return
+
     import UnaryOp._
 
     val UnaryOp(op, lhs) = tree
 
-    genTreeAuto(lhs)
+    /* Touch of peephole optimization; useful so that the various operators can
+     * assume the NothingType case away (e.g., `Array_length`, `Clone`).
+     */
+    if (lhs.tpe == NothingType) {
+      genTreeAuto(lhs)
+      return NothingType
+    }
+
+    // scalastyle:on return
+
+    genTree(lhs, op match {
+      case IdentityHashCode        => AnyNotNullType
+      case WrapAsThrowable | Throw => AnyType
+      case _                       => lhs.tpe
+    })
 
     markPosition(tree)
 
@@ -1451,6 +1465,107 @@ private class FunctionEmitter private (
         fb += wa.Call(genFunctionID.getComponentType)
       case Class_superClass =>
         fb += wa.Call(genFunctionID.getSuperClass)
+
+      case Array_length =>
+        val ArrayType(arrayTypeRef, _) = lhs.tpe: @unchecked
+        fb += wa.StructGet(
+          genTypeID.forArrayClass(arrayTypeRef),
+          genFieldID.objStruct.arrayUnderlying
+        )
+        fb += wa.ArrayLen
+
+      case GetClass =>
+        val needHijackedClassDispatch = lhs.tpe match {
+          case ClassType(className, _) =>
+            ctx.getClassInfo(className).isAncestorOfHijackedClass
+          case ArrayType(_, _) =>
+            false
+          case _ =>
+            true
+        }
+
+        if (!needHijackedClassDispatch) {
+          fb += wa.StructGet(genTypeID.ObjectStruct, genFieldID.objStruct.vtable)
+          fb += wa.Call(genFunctionID.getClassOf)
+        } else {
+          genAdapt(lhs.tpe, AnyNotNullType) // no-op when the optimizer is enabled
+          fb += wa.Call(genFunctionID.anyGetClass)
+        }
+
+      case Clone =>
+        val lhsLocal = addSyntheticLocal(watpe.RefType(genTypeID.ObjectStruct))
+        fb += wa.LocalTee(lhsLocal)
+        fb += wa.LocalGet(lhsLocal)
+        fb += wa.StructGet(genTypeID.ObjectStruct, genFieldID.objStruct.vtable)
+        fb += wa.StructGet(genTypeID.typeData, genFieldID.typeData.cloneFunction)
+        // cloneFunction: (ref jl.Object) -> (ref jl.Object)
+        fb += wa.CallRef(genTypeID.cloneFunctionType)
+
+        // cast the (ref jl.Object) back down to the result type
+        transformSingleType(lhs.tpe) match {
+          case watpe.RefType(_, watpe.HeapType.Type(genTypeID.ObjectStruct)) =>
+            // no need to cast to (ref null? jl.Object)
+          case wasmType: watpe.RefType =>
+            fb += wa.RefCast(wasmType.toNonNullable)
+          case wasmType =>
+            // Since no hijacked class extends jl.Cloneable, this case cannot happen
+            throw new AssertionError(
+                s"Unexpected type for Clone: ${lhs.tpe} (Wasm: $wasmType)")
+        }
+
+      case IdentityHashCode =>
+        // TODO Avoid dispatch when we know a more precise type than any
+        fb += wa.Call(genFunctionID.identityHashCode)
+
+      case WrapAsThrowable =>
+        val nonNullThrowableType = watpe.RefType(genTypeID.ThrowableStruct)
+        val jsExceptionType = watpe.RefType(genTypeID.JSExceptionStruct)
+
+        val anyRefToNonNullThrowable =
+          Sig(List(watpe.RefType.anyref), List(nonNullThrowableType))
+        fb.block(anyRefToNonNullThrowable) { doneLabel =>
+          // if expr.isInstanceOf[Throwable], then br $done
+          fb += wa.BrOnCast(doneLabel, watpe.RefType.anyref, nonNullThrowableType)
+
+          // otherwise, wrap in a new JavaScriptException
+
+          val lhsLocal = addSyntheticLocal(watpe.RefType.anyref)
+          val instanceLocal = addSyntheticLocal(jsExceptionType)
+
+          fb += wa.LocalSet(lhsLocal)
+          fb += wa.Call(genFunctionID.newDefault(SpecialNames.JSExceptionClass))
+          fb += wa.LocalTee(instanceLocal)
+          fb += wa.LocalGet(lhsLocal)
+          fb += wa.Call(
+            genFunctionID.forMethod(
+              MemberNamespace.Constructor,
+              SpecialNames.JSExceptionClass,
+              SpecialNames.AnyArgConstructorName
+            )
+          )
+          fb += wa.LocalGet(instanceLocal)
+        }
+
+      case UnwrapFromThrowable =>
+        val nonNullThrowableToAnyRef =
+          Sig(List(watpe.RefType(genTypeID.ThrowableStruct)), List(watpe.RefType.anyref))
+        fb.block(nonNullThrowableToAnyRef) { doneLabel =>
+          // if !expr.isInstanceOf[js.JavaScriptException], then br $done
+          fb += wa.BrOnCastFail(
+            doneLabel,
+            watpe.RefType(genTypeID.ThrowableStruct),
+            watpe.RefType(genTypeID.JSExceptionStruct)
+          )
+          // otherwise, unwrap the JavaScriptException by reading its field
+          fb += wa.StructGet(
+            genTypeID.JSExceptionStruct,
+            genFieldID.forClassInstanceField(SpecialNames.exceptionFieldName)
+          )
+        }
+
+      case Throw =>
+        fb += wa.ExternConvertAny
+        fb += wa.Throw(genTagID.exception)
     }
 
     tree.tpe
@@ -2287,41 +2402,6 @@ private class FunctionEmitter private (
     }
   }
 
-  private def genGetClass(tree: GetClass): Type = {
-    /* Unlike in `genApply` or `genStringConcat`, here we make no effort to
-     * optimize known-primitive receivers. In practice, such cases would be
-     * useless.
-     */
-
-    val GetClass(expr) = tree
-
-    val needHijackedClassDispatch = expr.tpe match {
-      case ClassType(className, _) =>
-        ctx.getClassInfo(className).isAncestorOfHijackedClass
-      case ArrayType(_, _) | NothingType | NullType =>
-        false
-      case _ =>
-        true
-    }
-
-    if (!needHijackedClassDispatch) {
-      val typeDataLocal = addSyntheticLocal(watpe.RefType(genTypeID.typeData))
-
-      genTreeAuto(expr)
-      markPosition(tree)
-      genCheckNonNullFor(expr)
-      fb += wa.StructGet(genTypeID.ObjectStruct, genFieldID.objStruct.vtable)
-      fb += wa.Call(genFunctionID.getClassOf)
-    } else {
-      genTreeToAny(expr)
-      markPosition(tree)
-      genAsNonNullOrNPEFor(expr)
-      fb += wa.Call(genFunctionID.anyGetClass)
-    }
-
-    tree.tpe
-  }
-
   private def genReadStorage(storage: VarStorage): Unit = {
     storage match {
       case VarStorage.Local(localID) =>
@@ -2491,17 +2571,6 @@ private class FunctionEmitter private (
     expectedType
   }
 
-  private def genThrow(tree: Throw): Type = {
-    val Throw(expr) = tree
-
-    genTree(expr, AnyType)
-    markPosition(tree)
-    fb += wa.ExternConvertAny
-    fb += wa.Throw(genTagID.exception)
-
-    NothingType
-  }
-
   private def genBlock(tree: Block, expectedType: Type): Type = {
     val Block(stats) = tree
 
@@ -2595,81 +2664,6 @@ private class FunctionEmitter private (
     ClassType(boxClassName, nullable = false)
   }
 
-  private def genIdentityHashCode(tree: IdentityHashCode): Type = {
-    val IdentityHashCode(expr) = tree
-
-    // TODO Avoid dispatch when we know a more precise type than any
-    genTree(expr, AnyType)
-
-    markPosition(tree)
-    fb += wa.Call(genFunctionID.identityHashCode)
-
-    IntType
-  }
-
-  private def genWrapAsThrowable(tree: WrapAsThrowable): Type = {
-    val WrapAsThrowable(expr) = tree
-
-    val nonNullThrowableType = watpe.RefType(genTypeID.ThrowableStruct)
-    val jsExceptionType = watpe.RefType(genTypeID.JSExceptionStruct)
-
-    fb.block(nonNullThrowableType) { doneLabel =>
-      genTree(expr, AnyType)
-
-      markPosition(tree)
-
-      // if expr.isInstanceOf[Throwable], then br $done
-      fb += wa.BrOnCast(doneLabel, watpe.RefType.anyref, nonNullThrowableType)
-
-      // otherwise, wrap in a new JavaScriptException
-
-      val exprLocal = addSyntheticLocal(watpe.RefType.anyref)
-      val instanceLocal = addSyntheticLocal(jsExceptionType)
-
-      fb += wa.LocalSet(exprLocal)
-      fb += wa.Call(genFunctionID.newDefault(SpecialNames.JSExceptionClass))
-      fb += wa.LocalTee(instanceLocal)
-      fb += wa.LocalGet(exprLocal)
-      fb += wa.Call(
-        genFunctionID.forMethod(
-          MemberNamespace.Constructor,
-          SpecialNames.JSExceptionClass,
-          SpecialNames.AnyArgConstructorName
-        )
-      )
-      fb += wa.LocalGet(instanceLocal)
-    }
-
-    tree.tpe
-  }
-
-  private def genUnwrapFromThrowable(tree: UnwrapFromThrowable): Type = {
-    val UnwrapFromThrowable(expr) = tree
-
-    fb.block(watpe.RefType.anyref) { doneLabel =>
-      genTreeAuto(expr)
-
-      markPosition(tree)
-
-      genAsNonNullOrNPEFor(expr)
-
-      // if !expr.isInstanceOf[js.JavaScriptException], then br $done
-      fb += wa.BrOnCastFail(
-        doneLabel,
-        watpe.RefType(genTypeID.ThrowableStruct),
-        watpe.RefType(genTypeID.JSExceptionStruct)
-      )
-
-      // otherwise, unwrap the JavaScriptException by reading its field
-      fb += wa.StructGet(
-        genTypeID.JSExceptionStruct,
-        genFieldID.forClassInstanceField(SpecialNames.exceptionFieldName)
-      )
-    }
-
-    AnyType
-  }
-
   private def genLinkTimeProperty(tree: LinkTimeProperty): Type = {
     val lit = ctx.coreSpec.linkTimeProperties.transformLinkTimeProperty(tree)
     genLiteral(lit, lit.tpe)
@@ -2943,37 +2937,6 @@ private class FunctionEmitter private (
     AnyType
   }
 
-  private def genArrayLength(tree: ArrayLength): Type = {
-    val ArrayLength(array) = tree
-
-    genTreeAuto(array)
-
-    markPosition(tree)
-
-    array.tpe match {
-      case ArrayType(arrayTypeRef, _) =>
-        // Get the underlying array
-        genCheckNonNullFor(array)
-        fb += wa.StructGet(
-          genTypeID.forArrayClass(arrayTypeRef),
-          genFieldID.objStruct.arrayUnderlying
-        )
-        // Get the length
-        fb += wa.ArrayLen
-        IntType
-
-      case NothingType =>
-        // unreachable
-        NothingType
-      case NullType =>
-        genNPE()
-        NothingType
-      case _ =>
-        throw new IllegalArgumentException(
-            s"ArraySelect.array must be an array type, but has type ${tree.array.tpe}")
-    }
-  }
-
   private def genNewArray(tree: NewArray): Type = {
     val NewArray(arrayTypeRef, length) = tree
 
@@ -3166,51 +3129,6 @@ private class FunctionEmitter private (
     AnyNotNullType
   }
 
-  private def genClone(tree: Clone): Type = {
-    val Clone(expr) = tree
-
-    expr.tpe match {
-      case NothingType =>
-        genTree(expr, NothingType)
-        NothingType
-
-      case NullType =>
-        genTree(expr, NullType)
-        genNPE()
-        NothingType
-
-      case exprType =>
-        val exprLocal = addSyntheticLocal(watpe.RefType(genTypeID.ObjectStruct))
-
-        genTreeAuto(expr)
-
-        markPosition(tree)
-
-        genAsNonNullOrNPEFor(expr)
-        fb += wa.LocalTee(exprLocal)
-
-        fb += wa.LocalGet(exprLocal)
-        fb += wa.StructGet(genTypeID.ObjectStruct, genFieldID.objStruct.vtable)
-        fb += wa.StructGet(genTypeID.typeData, genFieldID.typeData.cloneFunction)
-        // cloneFunction: (ref jl.Object) -> (ref jl.Object)
-        fb += wa.CallRef(genTypeID.cloneFunctionType)
-
-        // cast the (ref jl.Object) back down to the result type
-        transformSingleType(exprType) match {
-          case watpe.RefType(_, watpe.HeapType.Type(genTypeID.ObjectStruct)) =>
-            // no need to cast to (ref null? jl.Object)
-          case wasmType: watpe.RefType =>
-            fb += wa.RefCast(wasmType.toNonNullable)
-          case wasmType =>
-            // Since no hijacked class extends jl.Cloneable, this case cannot happen
-            throw new AssertionError(
-                s"Unexpected type for Clone: $exprType (Wasm: $wasmType)")
-        }
-
-        exprType
-    }
-  }
-
   private def genMatch(tree: Match, expectedType: Type): Type = {
     val Match(selector, cases, defaultBody) = tree
 
@@ -3410,7 +3328,6 @@ private class FunctionEmitter private (
       case Transients.ObjectClassName(obj) =>
         genTreeToAny(obj)
         markPosition(tree)
-        genAsNonNullOrNPEFor(obj)
         fb += wa.Call(genFunctionID.anyGetClassName)
         StringType
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala b/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
index 763255f2c1..c6dd5e7fd8 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
@@ -747,9 +747,6 @@ private final class ClassDefChecker(classDef: ClassDef,
         checkTree(block, env)
         checkTree(finalizer, env)
 
-      case Throw(expr) =>
-        checkTree(expr, env)
-
       case Match(selector, cases, default) =>
         checkTree(selector, env)
         for ((alts, body) <- cases) {
@@ -816,12 +813,7 @@ private final class ClassDefChecker(classDef: ClassDef,
         checkArrayTypeRef(typeRef)
         checkTrees(elems, env)
 
-      case ArrayLength(array) =>
-        checkArrayReceiverType(array.tpe)
-        checkTree(array, env)
-
       case ArraySelect(array, index) =>
-        checkArrayReceiverType(array.tpe)
         checkTree(array, env)
         checkTree(index, env)
 
@@ -857,21 +849,6 @@ private final class ClassDefChecker(classDef: ClassDef,
             // ok
         }
 
-      case GetClass(expr) =>
-        checkTree(expr, env)
-
-      case Clone(expr) =>
-        checkTree(expr, env)
-
-      case IdentityHashCode(expr) =>
-        checkTree(expr, env)
-
-      case WrapAsThrowable(expr) =>
-        checkTree(expr, env)
-
-      case UnwrapFromThrowable(expr) =>
-        checkTree(expr, env)
-
       case LinkTimeProperty(name) =>
 
       // JavaScript expressions
@@ -1019,6 +996,10 @@ private final class ClassDefChecker(classDef: ClassDef,
         transient.traverse(new Traversers.Traverser {
           override def traverse(tree: Tree): Unit = checkTree(tree, env)
         })
+
+      case _:Throw | _:ArrayLength | _:GetClass | _:Clone | _:IdentityHashCode |
+          _:WrapAsThrowable | _:UnwrapFromThrowable =>
+        reportError(i"illegal legacy node of class ${tree.getClass().getSimpleName()}")
     }
 
     newEnv
@@ -1029,13 +1010,6 @@ private final class ClassDefChecker(classDef: ClassDef,
       reportError("invalid transient tree")
   }
 
-  private def checkArrayReceiverType(tpe: Type)(
-      implicit ctx: ErrorContext): Unit = tpe match {
-    case tpe: ArrayType         => checkArrayType(tpe)
-    case NullType | NothingType => // ok
-    case _                      => reportError(i"Array type expected but $tpe found")
-  }
-
   private def checkArrayType(tpe: ArrayType)(
       implicit ctx: ErrorContext): Unit = {
     checkArrayTypeRef(tpe.arrayTypeRef)
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala b/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
index dcd87e7c5a..fd17c06147 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
@@ -330,9 +330,6 @@ private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter,
         typecheckExpect(block, env, tpe)
         typecheck(finalizer, env)
 
-      case Throw(expr) =>
-        typecheckAny(expr, env)
-
       case Match(selector, cases, default) =>
         // Typecheck the selector as an int or a java.lang.String
         typecheck(selector, env)
@@ -466,6 +463,16 @@ private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter,
               i"with non-object result type: $resultType")
         }
 
+      case UnaryOp(UnaryOp.Array_length, lhs) =>
+        // Array_length is a bit special because it allows any non-nullable array type
+        typecheck(lhs, env)
+        lhs.tpe match {
+          case NothingType | ArrayType(_, false) =>
+            // ok
+          case other =>
+            reportError(i"Array type expected but $other found")
+        }
+
       case UnaryOp(op, lhs) =>
         import UnaryOp._
         val expectedArgType = (op: @switch) match {
@@ -487,11 +494,17 @@ private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter,
             DoubleType
           case String_length =>
             StringType
-          case CheckNotNull =>
+          case CheckNotNull | IdentityHashCode | WrapAsThrowable | Throw =>
             AnyType
           case Class_name | Class_isPrimitive | Class_isInterface |
               Class_isArray | Class_componentType | Class_superClass =>
             ClassType(ClassClass, nullable = false)
+          case GetClass =>
+            AnyNotNullType
+          case Clone =>
+            ClassType(CloneableClass, nullable = false)
+          case UnwrapFromThrowable =>
+            ClassType(ThrowableClass, nullable = false)
         }
         typecheckExpect(lhs, env, expectedArgType)
 
@@ -541,13 +554,6 @@ private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter,
         for (elem <- elems)
           typecheckExpect(elem, env, elemType)
 
-      case ArrayLength(array) =>
-        typecheckExpr(array, env)
-        if (array.tpe != NullType &&
-            array.tpe != NothingType &&
-            !array.tpe.isInstanceOf[ArrayType])
-          reportError(i"Array type expected but ${array.tpe} found")
-
       case ArraySelect(array, index) =>
         typecheckExpect(index, env, IntType)
         typecheckExpr(array, env)
@@ -569,21 +575,6 @@ private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter,
         typecheckAny(expr, env)
         checkIsAsInstanceTargetType(tpe)
 
-      case GetClass(expr) =>
-        typecheckAny(expr, env)
-
-      case Clone(expr) =>
-        typecheckExpect(expr, env, ClassType(CloneableClass, nullable = true))
-
-      case IdentityHashCode(expr) =>
-        typecheckAny(expr, env)
-
-      case WrapAsThrowable(expr) =>
-        typecheckAny(expr, env)
-
-      case UnwrapFromThrowable(expr) =>
-        typecheckExpect(expr, env, ClassType(ThrowableClass, nullable = true))
-
       case LinkTimeProperty(name) =>
 
       // JavaScript expressions
@@ -768,6 +759,10 @@ private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter,
 
       case _:RecordSelect | _:RecordValue | _:Transient | _:JSSuperConstructorCall =>
         reportError("invalid tree")
+
+      case _:Throw | _:ArrayLength | _:GetClass | _:Clone | _:IdentityHashCode |
+          _:WrapAsThrowable | _:UnwrapFromThrowable =>
+        reportError(i"illegal legacy node of class ${tree.getClass().getSimpleName()}")
     }
   }
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
index 5b2cf7ad5e..589220ef0f 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
@@ -882,8 +882,8 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
         case UnaryOp(UnaryOp.CheckNotNull, expr) =>
           config.coreSpec.semantics.nullPointers == CheckedBehavior.Unchecked &&
           isTriviallySideEffectFree(expr)
-        case GetClass(expr) => // Before 1.17, we used GetClass as CheckNotNull
-          config.coreSpec.semantics.nullPointers == CheckedBehavior.Unchecked &&
+        case UnaryOp(op, expr) => // Before 1.17, we used GetClass as CheckNotNull
+          UnaryOp.isSideEffectFreeOp(op) &&
           isTriviallySideEffectFree(expr)
 
         case New(className, _, args) =>
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
index 94a294a4cc..61612d9783 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
@@ -456,9 +456,6 @@ private[optimizer] abstract class OptimizerCore(
         val newFinalizer = transformStat(finalizer)
         TryFinally(newBlock, newFinalizer)
 
-      case Throw(expr) =>
-        Throw(transformExpr(expr))
-
       case Match(selector, cases, default) =>
         val newSelector = transformExpr(selector)
         newSelector match {
@@ -533,9 +530,6 @@ private[optimizer] abstract class OptimizerCore(
       case ArrayValue(tpe, elems) =>
         ArrayValue(tpe, elems map transformExpr)
 
-      case ArrayLength(array) =>
-        ArrayLength(transformExpr(array))
-
       case ArraySelect(array, index) =>
         val newArray = transformExpr(array)
 
@@ -588,44 +582,6 @@ private[optimizer] abstract class OptimizerCore(
           }
         }
 
-      case GetClass(expr) =>
-        trampoline {
-          pretransformExpr(expr) { texpr =>
-            def constant(typeRef: TypeRef): TailRec[Tree] =
-              TailCalls.done(Block(checkNotNullStatement(texpr), ClassOf(typeRef)))
-
-            texpr.tpe match {
-              case RefinedType(ClassType(LongImpl.RuntimeLongClass, false), true) =>
-                constant(ClassRef(BoxedLongClass))
-              case RefinedType(ClassType(className, false), true) =>
-                constant(ClassRef(className))
-              case RefinedType(ArrayType(arrayTypeRef, false), true) =>
-                constant(arrayTypeRef)
-              case RefinedType(AnyType | AnyNotNullType | ClassType(ObjectClass, _), _) =>
-                // The result can be anything, including null
-                TailCalls.done(GetClass(finishTransformExpr(texpr)))
-              case _ =>
-                /* If texpr.tpe is neither AnyType nor j.l.Object, it cannot be
-                 * a JS object, so its getClass() cannot be null. Cast away
-                 * nullability to help downstream optimizations.
-                 */
-                val newGetClass = GetClass(finishTransformExpr(texpr))
-                TailCalls.done(makeCast(newGetClass, newGetClass.tpe.toNonNullable))
-            }
-          }
-        }
-
-      case Clone(expr) =>
-        Clone(transformExpr(expr))
-
-      case IdentityHashCode(expr) =>
-        IdentityHashCode(transformExpr(expr))
-
-      case _:WrapAsThrowable | _:UnwrapFromThrowable =>
-        trampoline {
-          pretransformExpr(tree)(finishTransform(isStat))
-        }
-
       case prop: LinkTimeProperty =>
         config.coreSpec.linkTimeProperties.transformLinkTimeProperty(prop)
 
@@ -993,42 +949,6 @@ private[optimizer] abstract class OptimizerCore(
       case tree: BinaryOp =>
         pretransformBinaryOp(tree)(cont)
 
-      case WrapAsThrowable(expr) =>
-        pretransformExpr(expr) { texpr =>
-          if (isSubtype(texpr.tpe.base, ThrowableClassType.toNonNullable)) {
-            cont(texpr)
-          } else {
-            if (texpr.tpe.isExact) {
-              pretransformNew(AllocationSite.Tree(tree), JavaScriptExceptionClass,
-                  MethodIdent(AnyArgConstructorName), texpr :: Nil)(cont)
-            } else {
-              cont(PreTransTree(WrapAsThrowable(finishTransformExpr(texpr))))
-            }
-          }
-        }
-
-      case UnwrapFromThrowable(expr) =>
-        pretransformExpr(expr) { texpr =>
-          def default =
-            cont(PreTransTree(UnwrapFromThrowable(finishTransformExpr(texpr))))
-
-          val baseTpe = texpr.tpe.base
-
-          if (baseTpe == NothingType) {
-            cont(texpr)
-          } else if (baseTpe == NullType) {
-            cont(checkNotNull(texpr))
-          } else if (isSubtype(baseTpe, JavaScriptExceptionClassType)) {
-            pretransformSelectCommon(AnyType, texpr, optQualDeclaredType = None,
-                FieldIdent(exceptionFieldName), isLhsOfAssign = false)(cont)
-          } else {
-            if (texpr.tpe.isExact || !isSubtype(JavaScriptExceptionClassType.toNonNullable, baseTpe))
-              cont(checkNotNull(texpr))
-            else
-              default
-          }
-        }
-
       case tree: JSSelect =>
         pretransformJSSelect(tree, isLhsOfAssign = false)(cont)
 
@@ -1565,7 +1485,7 @@ private[optimizer] abstract class OptimizerCore(
       finishTransformBindings(bindingsAndStats, finishTransformStat(result))
 
     case PreTransUnaryOp(op, lhs) =>
-      if (op == UnaryOp.CheckNotNull)
+      if (!UnaryOp.isSideEffectFreeOp(op))
         finishTransformExpr(stat)
       else
         finishTransformStat(lhs)
@@ -1689,15 +1609,13 @@ private[optimizer] abstract class OptimizerCore(
       keepOnlySideEffects(length)
     case ArrayValue(_, elems) =>
       Block(elems.map(keepOnlySideEffects(_)))(stat.pos)
-    case ArrayLength(array) =>
-      checkNotNullStatement(array)(stat.pos)
     case ArraySelect(array, index) if semantics.arrayIndexOutOfBounds == CheckedBehavior.Unchecked =>
       Block(checkNotNullStatement(array)(stat.pos), keepOnlySideEffects(index))(stat.pos)
     case Select(qualifier, _) =>
       checkNotNullStatement(qualifier)(stat.pos)
     case Closure(_, _, _, _, _, captureValues) =>
       Block(captureValues.map(keepOnlySideEffects))(stat.pos)
-    case UnaryOp(op, arg) if op != UnaryOp.CheckNotNull =>
+    case UnaryOp(op, arg) if UnaryOp.isSideEffectFreeOp(op) =>
       keepOnlySideEffects(arg)
     case If(cond, thenp, elsep) =>
       (keepOnlySideEffects(thenp), keepOnlySideEffects(elsep)) match {
@@ -1716,14 +1634,6 @@ private[optimizer] abstract class OptimizerCore(
       Block(elems.map(keepOnlySideEffects))(stat.pos)
     case RecordSelect(record, _) =>
       keepOnlySideEffects(record)
-    case GetClass(expr) =>
-      checkNotNullStatement(expr)(stat.pos)
-    case Clone(expr) =>
-      checkNotNullStatement(expr)(stat.pos)
-    case WrapAsThrowable(expr) =>
-      keepOnlySideEffects(expr)
-    case UnwrapFromThrowable(expr) =>
-      checkNotNullStatement(expr)(stat.pos)
 
     /* By definition, a failed cast is always UB, so it cannot have side effects.
      * However, if the target type is `nothing`, we keep the cast not to lose
@@ -1873,9 +1783,6 @@ private[optimizer] abstract class OptimizerCore(
         case If(cond, thenp, elsep) =>
           rec(cond).mapOrFailed(If(_, thenp, elsep)(body.tpe))
 
-        case Throw(expr) =>
-          rec(expr).mapOrFailed(Throw(_))
-
         case Match(selector, cases, default) =>
           rec(selector).mapOrFailed(Match(_, cases, default)(body.tpe))
 
@@ -1914,7 +1821,7 @@ private[optimizer] abstract class OptimizerCore(
           recs(args).mapOrFailed(ApplyStatic(flags, className, method, _)(body.tpe))
 
         case UnaryOp(op, arg) =>
-          rec(arg).mapOrKeepGoingIf(UnaryOp(op, _))(keepGoingIf = op != UnaryOp.CheckNotNull)
+          rec(arg).mapOrKeepGoingIf(UnaryOp(op, _))(keepGoingIf = UnaryOp.isPureOp(op))
 
         case BinaryOp(op, lhs, rhs) =>
           import BinaryOp._
@@ -1941,9 +1848,6 @@ private[optimizer] abstract class OptimizerCore(
         case ArrayValue(typeRef, elems) =>
           recs(elems).mapOrKeepGoing(ArrayValue(typeRef, _))
 
-        case ArrayLength(array) =>
-          rec(array).mapOrKeepGoingIf(ArrayLength(_))(keepGoingIf = isNotNull(array))
-
         case ArraySelect(array, index) =>
           rec(array) match {
             case Success(newArray) =>
@@ -1973,12 +1877,6 @@ private[optimizer] abstract class OptimizerCore(
         case Transient(Cast(expr, tpe)) =>
           rec(expr).mapOrKeepGoing(newExpr => makeCast(newExpr, tpe))
 
-        case GetClass(expr) =>
-          rec(expr).mapOrKeepGoingIf(GetClass(_))(keepGoingIf = isNotNull(expr))
-
-        case Clone(expr) =>
-          rec(expr).mapOrFailed(Clone(_))
-
         case JSUnaryOp(op, arg) =>
           rec(arg).mapOrFailed(JSUnaryOp(op, _))
 
@@ -2911,8 +2809,7 @@ private[optimizer] abstract class OptimizerCore(
         val tarray = targs.head
         tarray.tpe.base match {
           case _: ArrayType =>
-            val array = finishTransformExpr(tarray)
-            contTree(Trees.ArrayLength(array))
+            cont(foldUnaryOp(UnaryOp.Array_length, checkNotNull(tarray)))
           case _ =>
             default
         }
@@ -3094,7 +2991,8 @@ private[optimizer] abstract class OptimizerCore(
             If(
               Transient(WasmBinaryOp(WasmBinaryOp.I32GtU,
                   cpLocalDef.newReplacement, IntLiteral(Character.MAX_CODE_POINT))),
-              Throw(New(IllegalArgumentExceptionClass, MethodIdent(NoArgConstructorName), Nil)),
+              UnaryOp(UnaryOp.Throw,
+                  New(IllegalArgumentExceptionClass, MethodIdent(NoArgConstructorName), Nil)),
               Skip()
             )(VoidType),
             Transient(WasmStringFromCodePoint(cpLocalDef.newReplacement))
@@ -3187,10 +3085,16 @@ private[optimizer] abstract class OptimizerCore(
       case ClassGetName =>
         optTReceiver.get match {
           case PreTransMaybeBlock(bindingsAndStats,
-              PreTransTree(MaybeCast(GetClass(expr)), _)) =>
+              PreTransTree(MaybeCast(UnaryOp(UnaryOp.GetClass, expr)), _)) =>
             contTree(finishTransformBindings(
                 bindingsAndStats, Transient(ObjectClassName(expr))))
 
+          // Same thing, but the argument stayed as a PreTransUnaryOp
+          case PreTransMaybeBlock(bindingsAndStats,
+              PreTransUnaryOp(UnaryOp.GetClass, texpr)) =>
+            contTree(finishTransformBindings(
+                bindingsAndStats, Transient(ObjectClassName(finishTransformExpr(texpr)))))
+
           case _ =>
             default
         }
@@ -3425,7 +3329,7 @@ private[optimizer] abstract class OptimizerCore(
        * coming from Scala.js < 1.15.1 (since 1.15.1, we intercept that shape
        * already in the compiler back-end).
        */
-      case If(cond, th: Throw, Assign(Select(This(), _), value)) :: rest =>
+      case If(cond, th @ UnaryOp(UnaryOp.Throw, _), Assign(Select(This(), _), value)) :: rest =>
         // work around a bug of the compiler (these should be @-bindings)
         val stat = stats.head.asInstanceOf[If]
         val ass = stat.elsep.asInstanceOf[Assign]
@@ -3567,7 +3471,42 @@ private[optimizer] abstract class OptimizerCore(
     val UnaryOp(op, arg) = tree
 
     pretransformExpr(arg) { tlhs =>
-      expandLongOps(foldUnaryOp(op, tlhs))(cont)
+      def folded: PreTransform =
+        foldUnaryOp(op, tlhs)
+
+      op match {
+        case UnaryOp.WrapAsThrowable =>
+          if (isSubtype(tlhs.tpe.base, ThrowableClassType.toNonNullable)) {
+            cont(tlhs)
+          } else {
+            if (tlhs.tpe.isExact) {
+              pretransformNew(AllocationSite.Tree(tree), JavaScriptExceptionClass,
+                  MethodIdent(AnyArgConstructorName), tlhs :: Nil)(cont)
+            } else {
+              cont(folded)
+            }
+          }
+
+        case UnaryOp.UnwrapFromThrowable =>
+          val baseTpe = tlhs.tpe.base
+
+          if (baseTpe == NothingType) {
+            cont(tlhs)
+          } else if (baseTpe == NullType) {
+            cont(checkNotNull(tlhs))
+          } else if (isSubtype(baseTpe, JavaScriptExceptionClassType)) {
+            pretransformSelectCommon(AnyType, tlhs, optQualDeclaredType = None,
+                FieldIdent(exceptionFieldName), isLhsOfAssign = false)(cont)
+          } else {
+            if (tlhs.tpe.isExact || !isSubtype(JavaScriptExceptionClassType.toNonNullable, baseTpe))
+              cont(checkNotNull(tlhs))
+            else
+              cont(folded)
+          }
+
+        case _ =>
+          expandLongOps(folded)(cont)
+      }
     }
   }
 
@@ -3949,6 +3888,28 @@ private[optimizer] abstract class OptimizerCore(
             default
         }
 
+      case GetClass =>
+        def constant(typeRef: TypeRef): PreTransform =
+          PreTransTree(Block(finishTransformStat(arg), ClassOf(typeRef)))
+
+        arg.tpe match {
+          case RefinedType(ClassType(LongImpl.RuntimeLongClass, false), true) =>
+            constant(ClassRef(BoxedLongClass))
+          case RefinedType(ClassType(className, false), true) =>
+            constant(ClassRef(className))
+          case RefinedType(ArrayType(arrayTypeRef, false), true) =>
+            constant(arrayTypeRef)
+          case RefinedType(AnyType | AnyNotNullType | ClassType(ObjectClass, _), _) =>
+            // The result can be anything, including null
+            default
+          case _ =>
+            /* If texpr.tpe is neither AnyType nor j.l.Object, it cannot be
+             * a JS object, so its getClass() cannot be null. Cast away
+             * nullability to help downstream optimizations.
+             */
+            foldCast(default, ClassType(ClassClass, nullable = false))
+        }
+
       case _ =>
         default
     }
@@ -6919,7 +6880,6 @@ private[optimizer] object OptimizerCore {
       case ApplyStatically(_, receiver, _, _, Nil) => isTrivialArg(receiver)
       case ApplyStatic(_, _, _, Nil)               => true
 
-      case ArrayLength(array)        => isTrivialArg(array)
       case ArraySelect(array, index) => isTrivialArg(array) && isTrivialArg(index)
 
       case AsInstanceOf(inner, _) => isSimpleArg(inner)
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/IRCheckerTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/IRCheckerTest.scala
index a0333eccf1..0fe3988e97 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/IRCheckerTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/IRCheckerTest.scala
@@ -31,6 +31,7 @@ import org.scalajs.linker.interface._
 import org.scalajs.linker.interface.unstable.IRFileImpl
 import org.scalajs.linker.standard._
 import org.scalajs.linker.frontend.Refiner
+import org.scalajs.linker.backend.emitter.PrivateLibHolder
 
 import org.scalajs.linker.testutils._
 import org.scalajs.linker.testutils.TestIRBuilder._
@@ -83,7 +84,7 @@ class IRCheckerTest {
                     callMethOn(ApplyStatic(EAF, MainTestClassName,
                         nullBarMethodName, Nil)(ClassType("Bar", nullable = true))),
                     callMethOn(Null()),
-                    callMethOn(Throw(Null()))
+                    callMethOn(UnaryOp(UnaryOp.Throw, Null()))
                 ))
             )
         )
@@ -255,15 +256,45 @@ class IRCheckerTest {
     }
   }
 
+  @Test
+  def unaryOpNonNullableArguments(): AsyncResult = await {
+    import UnaryOp._
+
+    // List of ops that take non-nullable reference types as argument
+    val ops = List(
+      Class_name,
+      Class_isPrimitive,
+      Class_isInterface,
+      Class_isArray,
+      Class_componentType,
+      Class_superClass,
+      Array_length,
+      GetClass,
+      Clone,
+      UnwrapFromThrowable
+    )
+
+    val results = for (op <- ops) yield {
+      val classDefs = Seq(
+        mainTestClassDef(UnaryOp(op, Null()))
+      )
+
+      for (log <- testLinkIRErrors(classDefs, MainTestModuleInitializers)) yield {
+        log.assertContainsError("expected but null found")
+      }
+    }
+
+    Future.sequence(results)
+  }
+
   @Test
   def arrayOpsNullOrNothing(): AsyncResult = await {
     val classDefs = Seq(
       mainTestClassDef(
         Block(
           ArraySelect(Null(), int(1))(NothingType),
-          ArrayLength(Null()),
-          ArraySelect(Throw(Null()), int(1))(NothingType),
-          ArrayLength(Throw(Null()))
+          ArraySelect(UnaryOp(UnaryOp.Throw, Null()), int(1))(NothingType),
+          UnaryOp(UnaryOp.Array_length, UnaryOp(UnaryOp.Throw, Null()))
         )
       )
     )
@@ -453,7 +484,8 @@ object IRCheckerTest {
         val linkerFrontend = StandardLinkerFrontend(config)
         val irFiles = (
           stdLibFiles ++
-          classDefs.map(MemClassDefIRFile(_))
+          classDefs.map(MemClassDefIRFile(_)) ++
+          PrivateLibHolder.files
         )
         linkerFrontend.link(irFiles, moduleInitializers, noSymbolRequirements, logger)
       }
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/OptimizerTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/OptimizerTest.scala
index 7b37ab5648..3954dfe278 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/OptimizerTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/OptimizerTest.scala
@@ -76,7 +76,7 @@ class OptimizerTest {
 
         // @noinline def witness(): AnyRef = throw null
         MethodDef(EMF, witnessMethodName, NON, Nil, AnyType, Some {
-          Throw(Null())
+          UnaryOp(UnaryOp.Throw, Null())
         })(EOH.withNoinline(true), UNV),
 
         // @noinline def reachClone(): Object = clone()
@@ -124,10 +124,10 @@ class OptimizerTest {
           }
       }.hasExactly(if (inlinedWhenOnObject) 1 else 0, "IsInstanceOf node") {
         case IsInstanceOf(_, _) => true
-      }.hasExactly(if (inlinedWhenOnObject) 1 else 0, "Throw node") {
-        case Throw(_) => true
+      }.hasExactly(if (inlinedWhenOnObject) 1 else 0, "throw operation") {
+        case UnaryOp(UnaryOp.Throw, _) => true
       }.hasExactly(if (inlinedWhenOnObject) 3 else 2, "built-in <clone>() operations") {
-        case Clone(_) => true
+        case UnaryOp(UnaryOp.Clone, _) => true
       }.hasExactly(if (inlinedWhenOnObject) 0 else 1, "call to clone() (not inlined)") {
         case Apply(_, _, MethodIdent(`cloneMethodName`), _) => true
       }
@@ -289,7 +289,7 @@ class OptimizerTest {
                       )),
                       Return(voidReturnArgument, matchResult1)
                   )),
-                  Throw(New("java.lang.Exception", NoArgConstructorName, Nil))
+                  UnaryOp(UnaryOp.Throw, New("java.lang.Exception", NoArgConstructorName, Nil))
               ))
           ))
       )
diff --git a/project/Build.scala b/project/Build.scala
index 487e8482e7..2fc1510e58 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -2066,7 +2066,7 @@ object Build {
             if (!useMinifySizes) {
               Some(ExpectedSizes(
                   fastLink = 449000 to 450000,
-                  fullLink = 95000 to 96000,
+                  fullLink = 94000 to 95000,
                   fastLinkGz = 58000 to 59000,
                   fullLinkGz = 25000 to 26000,
               ))

From e4bdf168d46637db211d87bf9312a79740f8ec04 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Sun, 15 Dec 2024 15:19:05 +0100
Subject: [PATCH 226/298] Remove the IR nodes that were merged in `UnaryOp`.

And update the compiler to directly generate the new `UnaryOp`s.

We only enable the deserialization hack when reading IR <= 1.17.
---
 .../org/scalajs/nscplugin/GenJSCode.scala     | 24 +++++++------
 .../org/scalajs/nscplugin/GenJSExports.scala  |  2 +-
 .../nscplugin/test/OptimizationTest.scala     |  4 +--
 .../main/scala/org/scalajs/ir/Hashers.scala   | 28 ---------------
 .../main/scala/org/scalajs/ir/Printers.scala  | 32 -----------------
 .../scala/org/scalajs/ir/Serializers.scala    | 30 +---------------
 .../scala/org/scalajs/ir/Transformers.scala   | 21 -----------
 .../scala/org/scalajs/ir/Traversers.scala     | 21 -----------
 .../src/main/scala/org/scalajs/ir/Trees.scala | 35 -------------------
 .../scala/org/scalajs/ir/PrintersTest.scala   | 29 ---------------
 .../backend/wasmemitter/FunctionEmitter.scala |  5 ---
 .../linker/checker/ClassDefChecker.scala      |  4 ---
 .../scalajs/linker/checker/IRChecker.scala    |  4 ---
 project/BinaryIncompatibilities.scala         | 14 ++++++++
 project/JavaLangObject.scala                  |  9 ++---
 15 files changed, 37 insertions(+), 225 deletions(-)

diff --git a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
index 674ffc3ba6..a64d6a8656 100644
--- a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
+++ b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
@@ -2572,9 +2572,10 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
           ex match {
             case js.New(cls, _, _) if cls != JavaScriptExceptionClassName =>
               // Common case where ex is neither null nor a js.JavaScriptException
-              js.Throw(ex)
+              js.UnaryOp(js.UnaryOp.Throw, ex)
             case _ =>
-              js.Throw(js.UnwrapFromThrowable(ex))
+              js.UnaryOp(js.UnaryOp.Throw,
+                  js.UnaryOp(js.UnaryOp.UnwrapFromThrowable, js.UnaryOp(js.UnaryOp.CheckNotNull, ex)))
           }
 
         /* !!! Copy-pasted from `CleanUp.scala` upstream and simplified with
@@ -3108,13 +3109,14 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
 
       val (exceptValDef, exceptVar) = if (mightCatchJavaScriptException) {
         val valDef = js.VarDef(freshLocalIdent("e"), NoOriginalName,
-            encodeClassType(ThrowableClass), mutable = false, js.WrapAsThrowable(origExceptVar))
+            encodeClassType(ThrowableClass), mutable = false,
+            js.UnaryOp(js.UnaryOp.WrapAsThrowable, origExceptVar))
         (valDef, valDef.ref)
       } else {
         (js.Skip(), origExceptVar)
       }
 
-      val elseHandler: js.Tree = js.Throw(origExceptVar)
+      val elseHandler: js.Tree = js.UnaryOp(js.UnaryOp.Throw, origExceptVar)
 
       val handler = catches.foldRight(elseHandler) { (caseDef, elsep) =>
         implicit val pos = caseDef.pos
@@ -3323,7 +3325,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
     private def genThrowClassCastException()(implicit pos: Position): js.Tree = {
       val ctor = ClassCastExceptionClass.info.member(
           nme.CONSTRUCTOR).suchThat(_.tpe.params.isEmpty)
-      js.Throw(genNew(ClassCastExceptionClass, ctor, Nil))
+      js.UnaryOp(js.UnaryOp.Throw, genNew(ClassCastExceptionClass, ctor, Nil))
     }
 
     /** Gen JS code for a super call, of the form Class.super[mix].fun(args).
@@ -4891,7 +4893,8 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
         js.Assign(genSelect(fun.tpe.paramTypes(1)), arguments(1))
       } else {
         // length of the array
-        js.ArrayLength(arrayValue)
+        js.UnaryOp(js.UnaryOp.Array_length,
+            js.UnaryOp(js.UnaryOp.CheckNotNull, arrayValue))
       }
     }
 
@@ -5326,7 +5329,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
         case IDENTITY_HASH_CODE =>
           // runtime.identityHashCode(arg)
           val arg = genArgs1
-          js.IdentityHashCode(arg)
+          js.UnaryOp(js.UnaryOp.IdentityHashCode, arg)
 
         case DEBUGGER =>
           // js.special.debugger()
@@ -5463,7 +5466,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
 
         case JS_THROW =>
           // js.special.throw(arg)
-          js.Throw(genArgs1)
+          js.UnaryOp(js.UnaryOp.Throw, genArgs1)
 
         case JS_TRY_CATCH =>
           /* js.special.tryCatch(arg1, arg2)
@@ -5502,11 +5505,12 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
 
         case WRAP_AS_THROWABLE =>
           // js.special.wrapAsThrowable(arg)
-          js.WrapAsThrowable(genArgs1)
+          js.UnaryOp(js.UnaryOp.WrapAsThrowable, genArgs1)
 
         case UNWRAP_FROM_THROWABLE =>
           // js.special.unwrapFromThrowable(arg)
-          js.UnwrapFromThrowable(genArgs1)
+          js.UnaryOp(js.UnaryOp.UnwrapFromThrowable,
+              js.UnaryOp(js.UnaryOp.CheckNotNull, genArgs1))
 
         case LINKTIME_PROPERTY =>
           // LinkingInfo.linkTimePropertyXXX("...")
diff --git a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSExports.scala b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSExports.scala
index 603a6286d3..4cdc4369c3 100644
--- a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSExports.scala
+++ b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSExports.scala
@@ -1022,7 +1022,7 @@ trait GenJSExports[G <: Global with Singleton] extends SubComponent {
 
   private def genThrowTypeError(msg: String = "No matching overload")(
       implicit pos: Position): js.Tree = {
-    js.Throw(js.StringLiteral(msg))
+    js.UnaryOp(js.UnaryOp.Throw, js.StringLiteral(msg))
   }
 
   class FormalArgsRegistry(minArgc: Int, needsRestParam: Boolean) {
diff --git a/compiler/src/test/scala/org/scalajs/nscplugin/test/OptimizationTest.scala b/compiler/src/test/scala/org/scalajs/nscplugin/test/OptimizationTest.scala
index 24914ca07b..b10bef4b95 100644
--- a/compiler/src/test/scala/org/scalajs/nscplugin/test/OptimizationTest.scala
+++ b/compiler/src/test/scala/org/scalajs/nscplugin/test/OptimizationTest.scala
@@ -519,7 +519,7 @@ class OptimizationTest extends JSASTTest {
       }
     }
     """.hasNot("WrapAsThrowable") {
-      case js.WrapAsThrowable(_) =>
+      case js.UnaryOp(js.UnaryOp.WrapAsThrowable, _) =>
     }
 
     // Confidence check
@@ -536,7 +536,7 @@ class OptimizationTest extends JSASTTest {
       }
     }
     """.hasExactly(1, "WrapAsThrowable") {
-      case js.WrapAsThrowable(_) =>
+      case js.UnaryOp(js.UnaryOp.WrapAsThrowable, _) =>
     }
   }
 
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Hashers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Hashers.scala
index a653c15fce..770d83a7c7 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Hashers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Hashers.scala
@@ -232,10 +232,6 @@ object Hashers {
           mixTree(finalizer)
           mixType(tree.tpe)
 
-        case Throw(expr) =>
-          mixTag(TagThrow)
-          mixTree(expr)
-
         case Match(selector, cases, default) =>
           mixTag(TagMatch)
           mixTree(selector)
@@ -331,10 +327,6 @@ object Hashers {
           mixArrayTypeRef(typeRef)
           mixTrees(elems)
 
-        case ArrayLength(array) =>
-          mixTag(TagArrayLength)
-          mixTree(array)
-
         case ArraySelect(array, index) =>
           mixTag(TagArraySelect)
           mixTree(array)
@@ -362,26 +354,6 @@ object Hashers {
           mixTree(expr)
           mixType(tpe)
 
-        case GetClass(expr) =>
-          mixTag(TagGetClass)
-          mixTree(expr)
-
-        case Clone(expr) =>
-          mixTag(TagClone)
-          mixTree(expr)
-
-        case IdentityHashCode(expr) =>
-          mixTag(TagIdentityHashCode)
-          mixTree(expr)
-
-        case WrapAsThrowable(expr) =>
-          mixTag(TagWrapAsThrowable)
-          mixTree(expr)
-
-        case UnwrapFromThrowable(expr) =>
-          mixTag(TagUnwrapFromThrowable)
-          mixTree(expr)
-
         case JSNew(ctor, args) =>
           mixTag(TagJSNew)
           mixTree(ctor)
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala
index 3008148c71..d6a490b634 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala
@@ -260,10 +260,6 @@ object Printers {
           print(" finally ")
           printBlock(finalizer)
 
-        case Throw(expr) =>
-          print("throw ")
-          print(expr)
-
         case Match(selector, cases, default) =>
           print("match (")
           print(selector)
@@ -532,10 +528,6 @@ object Printers {
           print(typeRef)
           printArgs(elems)
 
-        case ArrayLength(array) =>
-          print(array)
-          print(".length")
-
         case ArraySelect(array, index) =>
           print(array)
           print('[')
@@ -571,30 +563,6 @@ object Printers {
           print(tpe)
           print(']')
 
-        case GetClass(expr) =>
-          print(expr)
-          print(".getClass()")
-
-        case Clone(expr) =>
-          print("<clone>(")
-          print(expr)
-          print(')')
-
-        case IdentityHashCode(expr) =>
-          print("<identityHashCode>(")
-          print(expr)
-          print(')')
-
-        case WrapAsThrowable(expr) =>
-          print("<wrapAsThrowable>(")
-          print(expr)
-          print(")")
-
-        case UnwrapFromThrowable(expr) =>
-          print("<unwrapFromThrowable>(")
-          print(expr)
-          print(")")
-
         // JavaScript expressions
 
         case JSNew(ctor, args) =>
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
index 369cb5990c..66c3249f9e 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
@@ -299,10 +299,6 @@ object Serializers {
           writeTagAndPos(TagTryFinally)
           writeTree(block); writeTree(finalizer)
 
-        case Throw(expr) =>
-          writeTagAndPos(TagThrow)
-          writeTree(expr)
-
         case Match(selector, cases, default) =>
           writeTagAndPos(TagMatch)
           writeTree(selector)
@@ -377,10 +373,6 @@ object Serializers {
           writeTagAndPos(TagArrayValue)
           writeArrayTypeRef(tpe); writeTrees(elems)
 
-        case ArrayLength(array) =>
-          writeTagAndPos(TagArrayLength)
-          writeTree(array)
-
         case ArraySelect(array, index) =>
           writeTagAndPos(TagArraySelect)
           writeTree(array); writeTree(index)
@@ -403,26 +395,6 @@ object Serializers {
           writeTagAndPos(TagAsInstanceOf)
           writeTree(expr); writeType(tpe)
 
-        case GetClass(expr) =>
-          writeTagAndPos(TagGetClass)
-          writeTree(expr)
-
-        case Clone(expr) =>
-          writeTagAndPos(TagClone)
-          writeTree(expr)
-
-        case IdentityHashCode(expr) =>
-          writeTagAndPos(TagIdentityHashCode)
-          writeTree(expr)
-
-        case WrapAsThrowable(expr) =>
-          writeTagAndPos(TagWrapAsThrowable)
-          writeTree(expr)
-
-        case UnwrapFromThrowable(expr) =>
-          writeTagAndPos(TagUnwrapFromThrowable)
-          writeTree(expr)
-
         case JSNew(ctor, args) =>
           writeTagAndPos(TagJSNew)
           writeTree(ctor); writeTreeOrJSSpreads(args)
@@ -1241,7 +1213,7 @@ object Serializers {
 
         case TagArrayLength | TagGetClass | TagClone | TagIdentityHashCode |
             TagWrapAsThrowable | TagUnwrapFromThrowable | TagThrow =>
-          if (false /*!hacks.use17*/) { // scalastyle:ignore
+          if (!hacks.use17) {
             throw new IOException(
                 s"Illegal legacy node $tag found in class ${enclosingClassName.nameString}")
           }
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Transformers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Transformers.scala
index 5aa07f32ff..7be426e058 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Transformers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Transformers.scala
@@ -73,9 +73,6 @@ object Transformers {
         case TryFinally(block, finalizer) =>
           TryFinally(transform(block), transform(finalizer))
 
-        case Throw(expr) =>
-          Throw(transform(expr))
-
         case Match(selector, cases, default) =>
           Match(transform(selector), cases.map(c => (c._1, transform(c._2))),
               transform(default))(tree.tpe)
@@ -114,9 +111,6 @@ object Transformers {
         case ArrayValue(tpe, elems) =>
           ArrayValue(tpe, transformTrees(elems))
 
-        case ArrayLength(array) =>
-          ArrayLength(transform(array))
-
         case ArraySelect(array, index) =>
           ArraySelect(transform(array), transform(index))(tree.tpe)
 
@@ -132,21 +126,6 @@ object Transformers {
         case AsInstanceOf(expr, tpe) =>
           AsInstanceOf(transform(expr), tpe)
 
-        case GetClass(expr) =>
-          GetClass(transform(expr))
-
-        case Clone(expr) =>
-          Clone(transform(expr))
-
-        case IdentityHashCode(expr) =>
-          IdentityHashCode(transform(expr))
-
-        case WrapAsThrowable(expr) =>
-          WrapAsThrowable(transform(expr))
-
-        case UnwrapFromThrowable(expr) =>
-          UnwrapFromThrowable(transform(expr))
-
         // JavaScript expressions
 
         case JSNew(ctor, args) =>
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Traversers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Traversers.scala
index ec39bb1086..d242bbfce7 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Traversers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Traversers.scala
@@ -64,9 +64,6 @@ object Traversers {
         traverse(block)
         traverse(finalizer)
 
-      case Throw(expr) =>
-        traverse(expr)
-
       case Match(selector, cases, default) =>
         traverse(selector)
         cases foreach (c => (c._1 map traverse, traverse(c._2)))
@@ -107,9 +104,6 @@ object Traversers {
       case ArrayValue(tpe, elems) =>
         elems foreach traverse
 
-      case ArrayLength(array) =>
-        traverse(array)
-
       case ArraySelect(array, index) =>
         traverse(array)
         traverse(index)
@@ -126,21 +120,6 @@ object Traversers {
       case AsInstanceOf(expr, _) =>
         traverse(expr)
 
-      case GetClass(expr) =>
-        traverse(expr)
-
-      case Clone(expr) =>
-        traverse(expr)
-
-      case IdentityHashCode(expr) =>
-        traverse(expr)
-
-      case WrapAsThrowable(expr) =>
-        traverse(expr)
-
-      case UnwrapFromThrowable(expr) =>
-        traverse(expr)
-
       // JavaScript expressions
 
       case JSNew(ctor, args) =>
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala b/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
index 031970c895..6cd4db23c7 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
@@ -188,10 +188,6 @@ object Trees {
     val tpe = block.tpe
   }
 
-  sealed case class Throw(expr: Tree)(implicit val pos: Position) extends Tree {
-    val tpe = NothingType
-  }
-
   /** A break-free switch (without fallthrough behavior).
    *
    *  Unlike a JavaScript switch, it can be used in expression position.
@@ -562,11 +558,6 @@ object Trees {
     val tpe = ArrayType(typeRef, nullable = false)
   }
 
-  sealed case class ArrayLength(array: Tree)(implicit val pos: Position)
-      extends Tree {
-    val tpe = IntType
-  }
-
   sealed case class ArraySelect(array: Tree, index: Tree)(val tpe: Type)(
       implicit val pos: Position) extends AssignLhs
 
@@ -588,32 +579,6 @@ object Trees {
       implicit val pos: Position)
       extends Tree
 
-  sealed case class GetClass(expr: Tree)(implicit val pos: Position)
-      extends Tree {
-    val tpe = ClassType(ClassClass, nullable = true)
-  }
-
-  sealed case class Clone(expr: Tree)(implicit val pos: Position)
-      extends Tree {
-    // this is OK because our type system does not have singleton types
-    val tpe: Type = expr.tpe.toNonNullable
-  }
-
-  sealed case class IdentityHashCode(expr: Tree)(implicit val pos: Position)
-      extends Tree {
-    val tpe = IntType
-  }
-
-  sealed case class WrapAsThrowable(expr: Tree)(implicit val pos: Position)
-      extends Tree {
-    val tpe = ClassType(ThrowableClass, nullable = false)
-  }
-
-  sealed case class UnwrapFromThrowable(expr: Tree)(implicit val pos: Position)
-      extends Tree {
-    val tpe = AnyType
-  }
-
   // JavaScript expressions
 
   sealed case class JSNew(ctor: Tree, args: List[TreeOrJSSpread])(
diff --git a/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala b/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala
index 06c2d0de56..0b2cb5a9b6 100644
--- a/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala
+++ b/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala
@@ -267,10 +267,6 @@ class PrintersTest {
         TryFinally(TryCatch(i(5), "e", NON, i(6))(IntType), i(7)))
   }
 
-  @Test def printThrow(): Unit = {
-    assertPrintEquals("throw null", Throw(Null()))
-  }
-
   @Test def printMatch(): Unit = {
     assertPrintEquals(
         """
@@ -582,10 +578,6 @@ class PrintersTest {
         ArrayValue(ArrayTypeRef(IntRef, 2), List(Null())))
   }
 
-  @Test def printArrayLength(): Unit = {
-    assertPrintEquals("x.length", ArrayLength(ref("x", arrayType(IntRef, 1))))
-  }
-
   @Test def printArraySelect(): Unit = {
     assertPrintEquals("x[3]",
         ArraySelect(ref("x", arrayType(IntRef, 1)), i(3))(IntType))
@@ -614,27 +606,6 @@ class PrintersTest {
         AsInstanceOf(ref("x", AnyType), IntType))
   }
 
-  @Test def printGetClass(): Unit = {
-    assertPrintEquals("x.getClass()", GetClass(ref("x", AnyType)))
-  }
-
-  @Test def printClone(): Unit = {
-    assertPrintEquals("<clone>(x)", Clone(ref("x", arrayType(ObjectClass, 1))))
-  }
-
-  @Test def printIdentityHashCode(): Unit = {
-    assertPrintEquals("<identityHashCode>(x)", IdentityHashCode(ref("x", AnyType)))
-  }
-
-  @Test def printWrapAsThrowable(): Unit = {
-    assertPrintEquals("<wrapAsThrowable>(e)", WrapAsThrowable(ref("e", AnyType)))
-  }
-
-  @Test def printUnwrapFromThrowable(): Unit = {
-    assertPrintEquals("<unwrapFromThrowable>(e)",
-        UnwrapFromThrowable(ref("e", ClassType(ThrowableClass, nullable = true))))
-  }
-
   @Test def printJSNew(): Unit = {
     assertPrintEquals("new C()", JSNew(ref("C", AnyType), Nil))
     assertPrintEquals("new C(4, 5)", JSNew(ref("C", AnyType), List(i(4), i(5))))
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
index 78f0b2ec39..bf0e54adc5 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
@@ -595,11 +595,6 @@ private class FunctionEmitter private (
 
       case _: JSSuperConstructorCall =>
         throw new AssertionError(s"Invalid tree: $tree")
-
-      case _:Throw | _:ArrayLength | _:GetClass | _:Clone | _:IdentityHashCode |
-          _:WrapAsThrowable | _:UnwrapFromThrowable =>
-        throw new AssertionError(
-            s"illegal legacy node of class ${tree.getClass().getSimpleName()}")
     }
 
     genAdapt(generatedType, expectedType)
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala b/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
index c6dd5e7fd8..1e75d4db31 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
@@ -996,10 +996,6 @@ private final class ClassDefChecker(classDef: ClassDef,
         transient.traverse(new Traversers.Traverser {
           override def traverse(tree: Tree): Unit = checkTree(tree, env)
         })
-
-      case _:Throw | _:ArrayLength | _:GetClass | _:Clone | _:IdentityHashCode |
-          _:WrapAsThrowable | _:UnwrapFromThrowable =>
-        reportError(i"illegal legacy node of class ${tree.getClass().getSimpleName()}")
     }
 
     newEnv
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala b/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
index fd17c06147..4c2c4f8464 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
@@ -759,10 +759,6 @@ private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter,
 
       case _:RecordSelect | _:RecordValue | _:Transient | _:JSSuperConstructorCall =>
         reportError("invalid tree")
-
-      case _:Throw | _:ArrayLength | _:GetClass | _:Clone | _:IdentityHashCode |
-          _:WrapAsThrowable | _:UnwrapFromThrowable =>
-        reportError(i"illegal legacy node of class ${tree.getClass().getSimpleName()}")
     }
   }
 
diff --git a/project/BinaryIncompatibilities.scala b/project/BinaryIncompatibilities.scala
index ec5063ac59..305e97d428 100644
--- a/project/BinaryIncompatibilities.scala
+++ b/project/BinaryIncompatibilities.scala
@@ -7,13 +7,27 @@ object BinaryIncompatibilities {
   val IR = Seq(
     // !!! Breaking, OK in minor release
     ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Printers#IRTreePrinter.print"),
+    ProblemFilters.exclude[MissingClassProblem]("org.scalajs.ir.Trees$ArrayLength"),
+    ProblemFilters.exclude[MissingClassProblem]("org.scalajs.ir.Trees$ArrayLength$"),
+    ProblemFilters.exclude[MissingClassProblem]("org.scalajs.ir.Trees$Clone"),
+    ProblemFilters.exclude[MissingClassProblem]("org.scalajs.ir.Trees$Clone$"),
+    ProblemFilters.exclude[MissingClassProblem]("org.scalajs.ir.Trees$GetClass"),
+    ProblemFilters.exclude[MissingClassProblem]("org.scalajs.ir.Trees$GetClass$"),
+    ProblemFilters.exclude[MissingClassProblem]("org.scalajs.ir.Trees$IdentityHashCode"),
+    ProblemFilters.exclude[MissingClassProblem]("org.scalajs.ir.Trees$IdentityHashCode$"),
     ProblemFilters.exclude[MissingClassProblem]("org.scalajs.ir.Trees$JSLinkingInfo"),
     ProblemFilters.exclude[MissingClassProblem]("org.scalajs.ir.Trees$JSLinkingInfo$"),
     ProblemFilters.exclude[MissingClassProblem]("org.scalajs.ir.Trees$LabelIdent"),
     ProblemFilters.exclude[MissingClassProblem]("org.scalajs.ir.Trees$LabelIdent$"),
     ProblemFilters.exclude[Problem]("org.scalajs.ir.Trees#Labeled.*"),
     ProblemFilters.exclude[Problem]("org.scalajs.ir.Trees#Return.*"),
+    ProblemFilters.exclude[MissingClassProblem]("org.scalajs.ir.Trees$Throw"),
+    ProblemFilters.exclude[MissingClassProblem]("org.scalajs.ir.Trees$Throw$"),
+    ProblemFilters.exclude[MissingClassProblem]("org.scalajs.ir.Trees$UnwrapFromThrowable"),
+    ProblemFilters.exclude[MissingClassProblem]("org.scalajs.ir.Trees$UnwrapFromThrowable$"),
     ProblemFilters.exclude[Problem]("org.scalajs.ir.Trees#VarRef.*"),
+    ProblemFilters.exclude[MissingClassProblem]("org.scalajs.ir.Trees$WrapAsThrowable"),
+    ProblemFilters.exclude[MissingClassProblem]("org.scalajs.ir.Trees$WrapAsThrowable$"),
     ProblemFilters.exclude[IncompatibleResultTypeProblem]("org.scalajs.ir.Trees#*.tpe"),
     ProblemFilters.exclude[MissingClassProblem]("org.scalajs.ir.Types$NoType$"),
 
diff --git a/project/JavaLangObject.scala b/project/JavaLangObject.scala
index eb3eedabef..1b32bac8ff 100644
--- a/project/JavaLangObject.scala
+++ b/project/JavaLangObject.scala
@@ -62,7 +62,7 @@ object JavaLangObject {
           Nil,
           ClassType(ClassClass, nullable = true),
           Some {
-            GetClass(This()(ThisType))
+            UnaryOp(UnaryOp.GetClass, This()(ThisType))
           })(OptimizerHints.empty.withInline(true), Unversioned),
 
         /* def hashCode(): Int = <identityHashCode>(this) */
@@ -73,7 +73,7 @@ object JavaLangObject {
           Nil,
           IntType,
           Some {
-            IdentityHashCode(This()(ThisType))
+            UnaryOp(UnaryOp.IdentityHashCode, This()(ThisType))
           })(OptimizerHints.empty.withInline(true), Unversioned),
 
         /* def equals(that: Object): Boolean = this eq that */
@@ -102,9 +102,10 @@ object JavaLangObject {
           AnyType,
           Some {
             If(IsInstanceOf(This()(ThisType), ClassType(CloneableClass, nullable = false)), {
-              Clone(AsInstanceOf(This()(ThisType), ClassType(CloneableClass, nullable = true)))
+              UnaryOp(UnaryOp.Clone, UnaryOp(UnaryOp.CheckNotNull,
+                  AsInstanceOf(This()(ThisType), ClassType(CloneableClass, nullable = true))))
             }, {
-              Throw(New(ClassName("java.lang.CloneNotSupportedException"),
+              UnaryOp(UnaryOp.Throw, New(ClassName("java.lang.CloneNotSupportedException"),
                 MethodIdent(NoArgConstructorName), Nil))
             })(AnyType)
           })(OptimizerHints.empty.withInline(true), Unversioned),

From 24c79c26e938f6bc398a4637c690cb18cf8bf11a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Wed, 18 Dec 2024 11:13:21 +0100
Subject: [PATCH 227/298] Fix #4947: Retain the `structure` of
 `PreTransRecordTree`.

Instead of only retaining the `RecordType`.

The `structure` contains the complete information required to map
`FieldName`s to the record's `SimpleFieldName`s.
---
 .../frontend/optimizer/IncOptimizer.scala     |   7 +-
 .../frontend/optimizer/OptimizerCore.scala    | 291 ++++++++++--------
 .../testsuite/compiler/RegressionTest.scala   |  29 ++
 3 files changed, 192 insertions(+), 135 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
index 5b2cf7ad5e..c7c2f3d1ef 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
@@ -804,10 +804,13 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
         None
       } else {
         val allFields = computeAllInstanceFieldDefs()
-        Some(new OptimizerCore.InlineableClassStructure(allFields))
+        Some(new OptimizerCore.InlineableClassStructure(className, allFields))
       }
 
-      tryNewInlineable != oldTryNewInlineable
+      (tryNewInlineable, oldTryNewInlineable) match {
+        case (Some(n), Some(o)) => !n.sameStructureAs(o)
+        case _                  => tryNewInlineable != oldTryNewInlineable
+      }
     }
 
     /** UPDATE PASS ONLY, used by `computeInlineableFieldBodies` and `updateTryNewInlineable`. */
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
index 94a294a4cc..bfaff0c8d8 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
@@ -383,24 +383,41 @@ private[optimizer] abstract class OptimizerCore(
       case Return(expr, label) =>
         val info = scope.env.labelInfos(label)
         val newLabel = info.newName
+
+        // Recall that `info.returnedTypes` does not want to contain NothingType
         if (info.isStat) {
           val newExpr = transformStat(expr)
-          info.returnedTypes.value ::= (VoidType, RefinedType.NoRefinedType)
-          Return(newExpr, newLabel)
+          if (newExpr.tpe == NothingType) {
+            newExpr
+          } else {
+            /* We need to track even the `VoidType`s. We need to know how many
+             * `Return`s we produce in order to decide whether we can remove
+             * the `Labeled`.
+             */
+            info.returnedTreeTypes.value ::= RefinedType.NoRefinedType
+            Return(newExpr, newLabel)
+          }
         } else if (!info.acceptRecords) {
           val newExpr = transformExpr(expr)
-          info.returnedTypes.value ::= (newExpr.tpe, RefinedType(newExpr.tpe))
-          Return(newExpr, newLabel)
+          if (newExpr.tpe == NothingType) {
+            newExpr
+          } else {
+            info.returnedTreeTypes.value ::= RefinedType(newExpr.tpe)
+            Return(newExpr, newLabel)
+          }
         } else trampoline {
           pretransformNoLocalDef(expr) { texpr =>
-            texpr match {
-              case PreTransRecordTree(newExpr, origType, cancelFun) =>
-                info.returnedTypes.value ::= (newExpr.tpe, origType)
-                TailCalls.done(Return(newExpr, newLabel))
+            val resultTree: Tree = texpr match {
+              case _ if texpr.tpe.isNothingType =>
+                finishTransformExpr(texpr)
+              case PreTransRecordTree(newExpr, structure, cancelFun) =>
+                info.returnedStructures.value ::= structure
+                Return(newExpr, newLabel)
               case PreTransTree(newExpr, tpe) =>
-                info.returnedTypes.value ::= (newExpr.tpe, tpe)
-                TailCalls.done(Return(newExpr, newLabel))
+                info.returnedTreeTypes.value ::= tpe
+                Return(newExpr, newLabel)
             }
+            TailCalls.done(resultTree)
           }
         }
 
@@ -1183,19 +1200,14 @@ private[optimizer] abstract class OptimizerCore(
                   tthenp))
             } else {
               (resolveLocalDef(tthenp), resolveLocalDef(telsep)) match {
-                case (PreTransRecordTree(thenTree, thenOrigType, thenCancelFun),
-                    PreTransRecordTree(elseTree, elseOrigType, elseCancelFun)) =>
-                  val commonType = {
-                    if (thenTree.tpe == elseTree.tpe && thenOrigType == elseOrigType)
-                      thenTree.tpe
-                    else
-                      cancelFun()
-                  }
-                  val refinedOrigType =
-                    constrainedLub(thenOrigType, elseOrigType, tree.tpe)
+                case (PreTransRecordTree(thenTree, thenStructure, thenCancelFun),
+                    PreTransRecordTree(elseTree, elseStructure, elseCancelFun)) =>
+                  if (!thenStructure.sameClassAs(elseStructure))
+                    cancelFun()
+                  assert(thenTree.tpe == elseTree.tpe)
                   cont(PreTransRecordTree(
-                      If(newCond, thenTree, elseTree)(commonType),
-                      refinedOrigType,
+                      If(newCond, thenTree, elseTree)(thenTree.tpe),
+                      thenStructure,
                       cancelFun))
 
                 case (tthenpNoLocalDef, telsepNoLocalDef) =>
@@ -1274,18 +1286,16 @@ private[optimizer] abstract class OptimizerCore(
       case _ =>
         def default: TailRec[Tree] = {
           resolveLocalDef(preTransQual) match {
-            case PreTransRecordTree(newQual, origType, cancelFun) =>
-              val recordType = newQual.tpe.asInstanceOf[RecordType]
-              /* FIXME How come this lookup requires only the `simpleName`?
-               * The `recordType` is created at `InlineableClassStructure.recordType`,
-               * where it uses an allocator. Something fishy is going on here.
-               * (And no, this is not dead code.)
-               */
-              val recordField = recordType.findField(field.name.simpleName)
+            case PreTransRecordTree(newQual, structure, cancelFun) =>
+              val recordField = structure.findField(field.name)
               val sel = RecordSelect(newQual, SimpleFieldIdent(recordField.name))(recordField.tpe)
               sel.tpe match {
                 case _: RecordType =>
-                  cont(PreTransRecordTree(sel, RefinedType(expectedType), cancelFun))
+                  /* We're trying to select a reified subrecord. We lost its
+                   * structure so cannot build an accurate `PreTransRecordTree`.
+                   * This did not happen in our test suite at the time of writing.
+                   */
+                  cancelFun()
                 case _ =>
                   cont(PreTransTree(sel))
               }
@@ -1352,34 +1362,29 @@ private[optimizer] abstract class OptimizerCore(
       cont(PreTransTree(Assign(lhs.asInstanceOf[AssignLhs], rhs)))
 
     resolveLocalDef(tlhs) match {
-      case PreTransRecordTree(lhsTree, lhsOrigType, lhsCancelFun) =>
-        val recordType = lhsTree.tpe.asInstanceOf[RecordType]
-
+      case PreTransRecordTree(lhsTree, lhsStructure, lhsCancelFun) =>
         def buildInner(trhs: PreTransform): TailRec[Tree] = {
           resolveLocalDef(trhs) match {
-            case PreTransRecordTree(rhsTree, rhsOrigType, rhsCancelFun) =>
-              if (rhsTree.tpe != recordType || rhsOrigType != lhsOrigType)
+            case PreTransRecordTree(rhsTree, rhsStructure, rhsCancelFun) =>
+              if (!lhsStructure.sameClassAs(rhsStructure))
                 lhsCancelFun()
+              assert(rhsTree.tpe == lhsTree.tpe)
               contAssign(lhsTree, rhsTree)
             case _ =>
               lhsCancelFun()
           }
         }
 
-        (trhs.tpe.base, lhsOrigType) match {
-          case (LongType, RefinedType(
-              ClassType(LongImpl.RuntimeLongClass, false), true)) =>
-            /* The lhs is a stack-allocated RuntimeLong, but the rhs is
-             * a primitive Long. We expand the primitive Long into a
-             * new stack-allocated RuntimeLong so that we do not need
-             * to cancel.
-             */
-            expandLongValue(trhs) { expandedRhs =>
-              buildInner(expandedRhs)
-            }
-
-          case _ =>
-            buildInner(trhs)
+        if (lhsStructure.className == LongImpl.RuntimeLongClass && trhs.tpe.base == LongType) {
+          /* The lhs is a stack-allocated RuntimeLong, but the rhs is a
+           * primitive Long. We expand the primitive Long into a new
+           * stack-allocated RuntimeLong so that we do not need to cancel.
+           */
+          expandLongValue(trhs) { expandedRhs =>
+            buildInner(expandedRhs)
+          }
+        } else {
+          buildInner(trhs)
         }
 
       case PreTransTree(lhsTree, _) =>
@@ -1413,9 +1418,9 @@ private[optimizer] abstract class OptimizerCore(
     preTrans match {
       case PreTransBlock(bindingsAndStats, result) =>
         resolveLocalDef(result) match {
-          case PreTransRecordTree(tree, tpe, cancelFun) =>
+          case PreTransRecordTree(tree, structure, cancelFun) =>
             PreTransRecordTree(finishTransformBindings(bindingsAndStats, tree),
-                tpe, cancelFun)
+                structure, cancelFun)
           case PreTransTree(tree, tpe) =>
             PreTransTree(finishTransformBindings(bindingsAndStats, tree), tpe)
         }
@@ -1423,11 +1428,11 @@ private[optimizer] abstract class OptimizerCore(
       case _:PreTransUnaryOp | _:PreTransBinaryOp =>
         PreTransTree(finishTransformExpr(preTrans), preTrans.tpe)
 
-      case PreTransLocalDef(localDef @ LocalDef(tpe, _, replacement)) =>
-        replacement match {
-          case ReplaceWithRecordVarRef(name, recordType, used, cancelFun) =>
+      case PreTransLocalDef(localDef) =>
+        localDef.replacement match {
+          case ReplaceWithRecordVarRef(name, structure, used, cancelFun) =>
             used.value = used.value.inc
-            PreTransRecordTree(VarRef(name)(recordType), tpe, cancelFun)
+            PreTransRecordTree(VarRef(name)(structure.recordType), structure, cancelFun)
 
           case InlineClassInstanceReplacement(structure, fieldLocalDefs, cancelFun) =>
             val recordType = structure.recordType
@@ -1436,7 +1441,7 @@ private[optimizer] abstract class OptimizerCore(
             PreTransRecordTree(
                 RecordValue(recordType, structure.fieldNames.map(
                     id => fieldLocalDefs(id).newReplacement)),
-                tpe, cancelFun)
+                structure, cancelFun)
 
           case _ =>
             PreTransTree(localDef.newReplacement, localDef.tpe)
@@ -1447,38 +1452,35 @@ private[optimizer] abstract class OptimizerCore(
     }
   }
 
-  /** Resolves any [[RecordType]] in a [[PreTransform]].
+  /** Resolves the [[InlineableClassStructure]] of a [[PreTransform]], if any.
    *
    *  If `preTrans` would resolve to a `PreTransRecordTree`, returns a `Some`
-   *  of its (lowered) [[RecordType]] and its `cancelFun`. Otherwise, returns
-   *  `None`.
-   *
-   *  Note that the record type is not the same as `preTrans.tpe.base`, which
-   *  is the *original* type of the tree (not lowered to a record type).
+   *  of its [[InlineableClassStructure]] and its `cancelFun`. Otherwise,
+   *  returns `None`.
    */
-  private def resolveRecordType(
-      preTrans: PreTransform): Option[(RecordType, CancelFun)] = {
+  private def resolveRecordStructure(
+      preTrans: PreTransform): Option[(InlineableClassStructure, CancelFun)] = {
     preTrans match {
       case PreTransBlock(_, result) =>
-        resolveRecordType(result)
+        resolveRecordStructure(result)
 
       case _:PreTransUnaryOp | _:PreTransBinaryOp =>
         None
 
       case PreTransLocalDef(localDef @ LocalDef(tpe, _, replacement)) =>
         replacement match {
-          case ReplaceWithRecordVarRef(name, recordType, used, cancelFun) =>
-            Some((recordType, cancelFun))
+          case ReplaceWithRecordVarRef(name, structure, used, cancelFun) =>
+            Some((structure, cancelFun))
 
           case InlineClassInstanceReplacement(structure, fieldLocalDefs, cancelFun) =>
-            Some((structure.recordType, cancelFun))
+            Some((structure, cancelFun))
 
           case _ =>
             None
         }
 
-      case PreTransRecordTree(tree, _, cancelFun) =>
-        Some((tree.tpe.asInstanceOf[RecordType], cancelFun))
+      case PreTransRecordTree(tree, structure, cancelFun) =>
+        Some((structure, cancelFun))
 
       case PreTransTree(_, _) =>
         None
@@ -1531,8 +1533,8 @@ private[optimizer] abstract class OptimizerCore(
        *
        * We do something similar in LocalDef.newReplacement.
        */
-      case PreTransRecordTree(tree, tpe, _)
-          if tpe.base == ClassType(LongImpl.RuntimeLongClass, nullable = false) =>
+      case PreTransRecordTree(tree, structure, _)
+          if structure.className == LongImpl.RuntimeLongClass =>
         tree match {
           case RecordValue(_, List(lo, hi)) =>
             createNewLong(lo, hi)
@@ -1642,8 +1644,9 @@ private[optimizer] abstract class OptimizerCore(
         if (used.value.isUsed) {
           val ident = LocalIdent(name)
           resolveLocalDef(value) match {
-            case PreTransRecordTree(valueTree, valueTpe, cancelFun) =>
-              val recordType = valueTree.tpe.asInstanceOf[RecordType]
+            case PreTransRecordTree(valueTree, valueStructure, cancelFun) =>
+              val recordType = valueStructure.recordType
+              assert(valueTree.tpe == recordType)
               if (!isImmutableType(recordType))
                 cancelFun()
               Block(VarDef(ident, originalName, recordType, mutable, valueTree), innerBody)
@@ -5162,56 +5165,63 @@ private[optimizer] abstract class OptimizerCore(
       implicit scope: Scope, pos: Position): TailRec[Tree] = tailcall {
     val newLabel = freshLabelName(oldLabelName)
 
-    def doMakeTree(newBody: Tree, returnedTypes: List[Type]): Tree = {
-      val refinedType =
-        returnedTypes.reduce(constrainedLub(_, _, resultType, isStat))
-      val returnCount = returnedTypes.size - 1
-
-      tryOptimizePatternMatch(oldLabelName, newLabel, refinedType,
+    def doMakeTree(newBody: Tree, newResultType: Type, returnCount: Int): Tree = {
+      tryOptimizePatternMatch(oldLabelName, newLabel, newResultType,
           returnCount, newBody) getOrElse {
-        Labeled(newLabel, refinedType, newBody)
+        Labeled(newLabel, newResultType, newBody)
       }
     }
 
     val info = new LabelInfo(newLabel, isStat, acceptRecords = usePreTransform,
-        returnedTypes = newSimpleState(Nil))
+        returnedTreeTypes = newSimpleState(Nil), returnedStructures = newSimpleState(Nil))
     val bodyScope = scope.withEnv(scope.env.withLabelInfo(oldLabelName, info))
 
     if (usePreTransform) {
       assert(!isStat, "Cannot use pretransform in statement position")
       tryOrRollback { cancelFun =>
         pretransformExpr(body) { tbody0 =>
-          val returnedTypes0 = info.returnedTypes.value
-          if (returnedTypes0.isEmpty) {
+          val returnedTypes = info.returnedTreeTypes.value
+          val returnedStructures = info.returnedStructures.value
+
+          if (returnedTypes.isEmpty && returnedStructures.isEmpty) {
             // no return to that label, we can eliminate it
             cont(tbody0)
           } else {
+            // Extract the body, and take its result into account as well
             val tbody = resolveLocalDef(tbody0)
-            val (newBody, returnedTypes) = tbody match {
-              case PreTransRecordTree(bodyTree, origType, _) =>
-                (bodyTree, (bodyTree.tpe, origType) :: returnedTypes0)
+            val (newBody, resultTypes, resultStructures) = tbody match {
+              case PreTransRecordTree(bodyTree, structure, _) =>
+                (bodyTree, returnedTypes, structure :: returnedStructures)
               case PreTransTree(bodyTree, tpe) =>
-                (bodyTree, (bodyTree.tpe, tpe) :: returnedTypes0)
+                if (tpe.isNothingType)
+                  (bodyTree, returnedTypes, returnedStructures)
+                else
+                  (bodyTree, tpe :: returnedTypes, returnedStructures)
             }
-            val (actualTypes, origTypes) = returnedTypes.unzip
-            val refinedOrigType =
-              origTypes.reduce(constrainedLub(_, _, resultType))
-            actualTypes.collectFirst {
-              case actualType: RecordType => actualType
-            }.fold[TailRec[Tree]] {
-              // None of the returned types are records
+
+            if (resultStructures.isEmpty) {
+              // implies returnedStructures.isEmpty, which implies !returnedTypes.isEmpty, which implies:
+              assert(!resultTypes.isEmpty)
+
+              // No records; compute constrained lub of refined types
+              val refinedType = resultTypes.reduce(constrainedLub(_, _, resultType))
               cont(PreTransTree(
-                  doMakeTree(newBody, actualTypes), refinedOrigType))
-            } { recordType =>
-              if (actualTypes.exists(t => t != recordType && t != NothingType))
-                cancelFun()
+                  doMakeTree(newBody, refinedType.base, returnedTypes.size),
+                  refinedType))
+            } else {
+              // At least one record -- they must all agree on being records of the same class
 
-              val resultTree = doMakeTree(newBody, actualTypes)
+              if (resultTypes.nonEmpty)
+                cancelFun()
 
-              if (origTypes.exists(t => t != refinedOrigType && !t.isNothingType))
+              val structure = resultStructures.head
+              if (resultStructures.tail.exists(!_.sameClassAs(structure)))
                 cancelFun()
 
-              cont(PreTransRecordTree(resultTree, refinedOrigType, cancelFun))
+              cont(PreTransRecordTree(
+                  doMakeTree(newBody, structure.recordType, returnedStructures.size),
+                  structure,
+                  cancelFun))
             }
           }
         } (bodyScope)
@@ -5220,15 +5230,19 @@ private[optimizer] abstract class OptimizerCore(
             usePreTransform = false)(cont)
       }
     } else {
+      assert(info.returnedStructures.value.isEmpty)
+
       val newBody = transform(body, isStat)(bodyScope)
-      val returnedTypes0 = info.returnedTypes.value.map(_._1)
-      if (returnedTypes0.isEmpty) {
+      val returnedTypes = info.returnedTreeTypes.value
+      if (returnedTypes.isEmpty) {
         // no return to that label, we can eliminate it
         cont(PreTransTree(newBody))
       } else {
-        val returnedTypes = newBody.tpe :: returnedTypes0
-        val tree = doMakeTree(newBody, returnedTypes)
-        cont(PreTransTree(tree))
+        val refinedType =
+          returnedTypes.fold(RefinedType(newBody.tpe))(constrainedLub(_, _, resultType))
+        cont(PreTransTree(
+            doMakeTree(newBody, refinedType.base, returnedTypes.size),
+            refinedType))
       }
     }
   }
@@ -5458,9 +5472,9 @@ private[optimizer] abstract class OptimizerCore(
 
         val used = newSimpleState[IsUsed](Unused)
 
-        val (replacement, refinedType) = resolveRecordType(value) match {
-          case Some((recordType, cancelFun)) =>
-            (ReplaceWithRecordVarRef(newName, recordType, used, cancelFun), value.tpe)
+        val (replacement, refinedType) = resolveRecordStructure(value) match {
+          case Some((structure, cancelFun)) =>
+            (ReplaceWithRecordVarRef(newName, structure, used, cancelFun), value.tpe)
 
           case None =>
             (ReplaceWithVarRef(newName, used), tpe)
@@ -5544,10 +5558,10 @@ private[optimizer] abstract class OptimizerCore(
         PreTransBlock(bindingsAndStats, result)
       case result: PreTransResult =>
         PreTransBlock(bindingsAndStats, result)
-      case PreTransRecordTree(tree, tpe, cancelFun) =>
+      case PreTransRecordTree(tree, structure, cancelFun) =>
         PreTransRecordTree(
             finishTransformBindings(bindingsAndStats, tree),
-            tpe, cancelFun)
+            structure, cancelFun)
       case PreTransTree(tree, tpe) =>
         PreTransTree(
             finishTransformBindings(bindingsAndStats, tree),
@@ -5660,7 +5674,10 @@ private[optimizer] object OptimizerCore {
   private val ClassTagApplyMethodName =
     MethodName("apply", List(ClassRef(ClassClass)), ClassRef(ClassName("scala.reflect.ClassTag")))
 
-  final class InlineableClassStructure(private val allFields: List[FieldDef]) {
+  final class InlineableClassStructure(val className: ClassName, private val allFields: List[FieldDef]) {
+    private[OptimizerCore] val refinedType: RefinedType =
+      RefinedType(ClassType(className, nullable = false), isExact = true)
+
     private[OptimizerCore] val fieldNames: List[FieldName] =
       allFields.map(_.name.name)
 
@@ -5677,28 +5694,30 @@ private[optimizer] object OptimizerCore {
       RecordType(recordFields)
     }
 
-    private val recordFieldNames: Map[FieldName, RecordType.Field] = {
+    private val recordFields: Map[FieldName, RecordType.Field] = {
       val elems = for ((fieldDef, recordField) <- allFields.zip(recordType.fields))
         yield fieldDef.name.name -> recordField
       elems.toMap
     }
 
+    private[OptimizerCore] def findField(fieldName: FieldName): RecordType.Field =
+      recordFields(fieldName)
+
     private[OptimizerCore] def fieldOriginalName(fieldName: FieldName): OriginalName =
-      recordFieldNames(fieldName).originalName
+      recordFields(fieldName).originalName
 
-    override def equals(that: Any): Boolean = that match {
-      case that: InlineableClassStructure =>
-        this.allFields == that.allFields
-      case _ =>
-        false
+    def sameStructureAs(that: InlineableClassStructure): Boolean = {
+      assert(this.sameClassAs(that))
+      this.allFields == that.allFields
     }
 
-    override def hashCode(): Int = allFields.##
+    def sameClassAs(that: InlineableClassStructure): Boolean =
+      this.className == that.className
 
     override def toString(): String = {
       allFields
         .map(f => s"${f.name.name.nameString}: ${f.ftpe}")
-        .mkString("InlineableClassStructure(", ", ", ")")
+        .mkString(s"InlineableClassStructure(${className.nameString}, ", ", ", ")")
     }
   }
 
@@ -5867,10 +5886,10 @@ private[optimizer] object OptimizerCore {
        * See the comment in finishTransformExpr about why it is desirable and
        * safe to do so.
        */
-      case ReplaceWithRecordVarRef(name, recordType, used, _)
+      case ReplaceWithRecordVarRef(name, structure, used, _)
           if tpe.base == ClassType(LongImpl.RuntimeLongClass, nullable = false) =>
         used.value = used.value.inc
-        createNewLong(VarRef(name)(recordType))
+        createNewLong(VarRef(name)(structure.recordType))
 
       case ReplaceWithRecordVarRef(_, _, _, cancelFun) =>
         cancelFun()
@@ -5966,7 +5985,7 @@ private[optimizer] object OptimizerCore {
       used: SimpleState[IsUsed]) extends LocalDefReplacement
 
   private final case class ReplaceWithRecordVarRef(name: LocalName,
-      recordType: RecordType,
+      structure: InlineableClassStructure,
       used: SimpleState[IsUsed],
       cancelFun: CancelFun) extends LocalDefReplacement
 
@@ -6016,8 +6035,10 @@ private[optimizer] object OptimizerCore {
       val newName: LabelName,
       val isStat: Boolean,
       val acceptRecords: Boolean,
-      /** (actualType, originalType), actualType can be a RecordType. */
-      val returnedTypes: SimpleState[List[(Type, RefinedType)]])
+      /** Types of normal trees that are returned; cannot contain `RecordType` nor `NothingType`. */
+      val returnedTreeTypes: SimpleState[List[RefinedType]],
+      /** Record structures that are returned. */
+      val returnedStructures: SimpleState[List[InlineableClassStructure]])
 
   private class OptEnv(
       val thisLocalDef: Option[LocalDef],
@@ -6198,8 +6219,8 @@ private[optimizer] object OptimizerCore {
         "Prefer directly creating the relevant PreTransRecordTree",
         "forever")
     def apply(stat: Tree, result: PreTransRecordTree): PreTransRecordTree = {
-      PreTransRecordTree(Block(stat, result.tree)(result.pos), result.tpe,
-          result.cancelFun)
+      PreTransRecordTree(Block(stat, result.tree)(result.pos),
+          result.structure, result.cancelFun)
     }
 
     @deprecated(
@@ -6218,8 +6239,8 @@ private[optimizer] object OptimizerCore {
             new PreTransBlock(Right(stat) :: innerBindingsAndStats, innerResult)
           case result: PreTransResult =>
             new PreTransBlock(Right(stat) :: Nil, result)
-          case PreTransRecordTree(tree, tpe, cancelFun) =>
-            PreTransRecordTree(Block(stat, tree)(tree.pos), tpe, cancelFun)
+          case PreTransRecordTree(tree, structure, cancelFun) =>
+            PreTransRecordTree(Block(stat, tree)(tree.pos), structure, cancelFun)
           case PreTransTree(tree, tpe) =>
             PreTransTree(Block(stat, tree)(tree.pos), tpe)
         }
@@ -6286,9 +6307,13 @@ private[optimizer] object OptimizerCore {
    *  whereas `tree.tpe` is always the lowered `RecordType`.
    */
   private final case class PreTransRecordTree(tree: Tree,
-      tpe: RefinedType, cancelFun: CancelFun) extends PreTransGenTree {
+      structure: InlineableClassStructure, cancelFun: CancelFun)
+      extends PreTransGenTree {
+
     def pos: Position = tree.pos
 
+    val tpe: RefinedType = structure.refinedType
+
     assert(tree.tpe.isInstanceOf[RecordType],
         s"Cannot create a PreTransRecordTree with non-record type ${tree.tpe}")
   }
diff --git a/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/RegressionTest.scala b/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/RegressionTest.scala
index 72319844a9..5ad32e6f30 100644
--- a/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/RegressionTest.scala
+++ b/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/RegressionTest.scala
@@ -964,6 +964,22 @@ class RegressionTest {
     }
   }
 
+  @Test
+  def inlineClassWithMultipleFieldsOfSameSimpleName_Issue4947(): Unit = {
+    @noinline
+    def hide(x: Any): Any = x
+
+    @noinline
+    def test: Boolean = false
+
+    val b =
+      if (test) new Bug4947.B("f")
+      else new Bug4947.B("g")
+
+    assertEquals(1, hide(b.foo))
+    assertEquals("g", hide(b.bar))
+  }
+
 }
 
 object RegressionTest {
@@ -1036,6 +1052,19 @@ object RegressionTest {
     def bar(x: String): String = x
   }
 
+  object Bug4947 {
+    class A {
+      private val x: Int = 1
+      def foo: Int = x
+    }
+
+    @inline
+    class B(init: String) extends A {
+      private val x: String = init
+      def bar: String = x
+    }
+  }
+
   /* The objects and classes here intentionally have names that differ only in
    * case, and are intentionally defined in a specific order. This is required
    * to properly test the fix for #4148 (static forwarders can overwrite

From eac8bf71214c77e031a272171e5ecf54b4d3c969 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Tue, 17 Dec 2024 11:28:14 +0100
Subject: [PATCH 228/298] Merge the IR node `This` into `VarRef`, with a magic
 `LocalName`.

Everywhere we handle `VarRef`s, we applied the same treatment to
`This` nodes. In some places, like in the optimizer's `Binding`s,
we also had an additional abstraction to represent either an actual
`VarRef` or a `this` value.

We now merge `This` as a particular case of `VarRef`. We use a
magic `LocalName` that is otherwise invalid, namely `.this`.

A variable of that name cannot be declared, either in a `ParamDef`
or in a `VarDef`. It is only introduced for receivers, and is
always immutable.

Several areas of the code get simpler with the merge. The
optimizer's `Binding`s is the most obvious example. The
`FunctionEmitter`s also benefit from the changes. Other areas get
nothing but a reduction of alternatives in pattern matches.

`this` values still hold particular meaning in many situations.
Therefore, we keep a source compatible constructor/extractor object
for `This()`.
---
 .../org/scalajs/nscplugin/GenJSCode.scala     |   8 +-
 .../main/scala/org/scalajs/ir/Hashers.scala   |  13 +-
 .../src/main/scala/org/scalajs/ir/Names.scala |  30 +++-
 .../main/scala/org/scalajs/ir/Printers.scala  |   9 +-
 .../scala/org/scalajs/ir/Serializers.scala    |  24 +--
 .../scala/org/scalajs/ir/Transformers.scala   |   2 +-
 .../scala/org/scalajs/ir/Traversers.scala     |   2 +-
 .../src/main/scala/org/scalajs/ir/Trees.scala |  10 +-
 .../scala/org/scalajs/ir/PrintersTest.scala   |   3 -
 .../backend/emitter/FunctionEmitter.scala     |  45 ++---
 .../backend/wasmemitter/FunctionEmitter.scala |  26 +--
 .../linker/checker/ClassDefChecker.scala      |  44 +++--
 .../linker/checker/ErrorReporter.scala        |   2 +
 .../scalajs/linker/checker/IRChecker.scala    |   2 -
 .../frontend/optimizer/IncOptimizer.scala     |   2 +-
 .../frontend/optimizer/OptimizerCore.scala    | 164 +++++++-----------
 .../org/scalajs/linker/IRCheckerTest.scala    |   2 +-
 .../linker/checker/ClassDefCheckerTest.scala  | 124 +++++++++++--
 .../linker/testutils/TestIRBuilder.scala      |   2 +-
 project/BinaryIncompatibilities.scala         |   4 +
 20 files changed, 298 insertions(+), 220 deletions(-)

diff --git a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
index a64d6a8656..5d393dfa47 100644
--- a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
+++ b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
@@ -1107,7 +1107,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
           selfVarDef :: memberDefinitions
         }
 
-        // After the super call, substitute `selfRef` for `This()`
+        // After the super call, substitute `selfRef` for `this`
         val afterSuper = new ir.Transformers.Transformer {
           override def transform(tree: js.Tree): js.Tree = tree match {
             case js.This() =>
@@ -2430,7 +2430,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
       tree match {
         case js.Block(stats :+ expr) =>
           js.Block(stats :+ exprToStat(expr))
-        case _:js.Literal | _:js.This | _:js.VarRef =>
+        case _:js.Literal | _:js.VarRef =>
           js.Skip()
         case _ =>
           tree
@@ -4907,8 +4907,8 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
       val newReceiver = genExpr(receiver)
       val newArg = genStatOrExpr(arg, isStat)
       newReceiver match {
-        case js.This() =>
-          // common case for which there is no side-effect nor NPE
+        case newReceiver: js.VarRef if !newReceiver.tpe.isNullable =>
+          // common case (notably for `this`) for which there is no side-effect nor NPE
           newArg
         case _ =>
           js.Block(
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Hashers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Hashers.scala
index 770d83a7c7..4f6c3eeb72 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Hashers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Hashers.scala
@@ -497,12 +497,13 @@ object Hashers {
           mixTypeRef(typeRef)
 
         case VarRef(name) =>
-          mixTag(TagVarRef)
-          mixName(name)
-          mixType(tree.tpe)
-
-        case This() =>
-          mixTag(TagThis)
+          if (name.isThis) {
+            // "Optimized" representation, like in Serializers
+            mixTag(TagThis)
+          } else {
+            mixTag(TagVarRef)
+            mixName(name)
+          }
           mixType(tree.tpe)
 
         case Closure(arrow, captureParams, params, restParam, body, captureValues) =>
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Names.scala b/ir/shared/src/main/scala/org/scalajs/ir/Names.scala
index 8193227be0..d9bee3518b 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Names.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Names.scala
@@ -64,6 +64,10 @@ object Names {
    *
    *  Local names must be non-empty, and can contain any Unicode code point
    *  except `/ . ; [`.
+   *
+   *  As an exception, the local name `".this"` represents the `this` binding.
+   *  It cannot be used to declare variables (in `VarDef`s or `ParamDef`s) but
+   *  can be referred to with a `VarRef`.
    */
   final class LocalName private (encoded: UTF8String)
       extends Name(encoded) with Comparable[LocalName] {
@@ -79,22 +83,40 @@ object Names {
 
     protected def stringPrefix: String = "LocalName"
 
-    final def withPrefix(prefix: LocalName): LocalName =
+    final def isThis: Boolean =
+      this eq LocalName.This
+
+    final def withPrefix(prefix: LocalName): LocalName = {
+      require(!isThis && !prefix.isThis, "cannot concatenate LocalName.This")
       new LocalName(prefix.encoded ++ this.encoded)
+    }
 
     final def withPrefix(prefix: String): LocalName =
       LocalName(UTF8String(prefix) ++ this.encoded)
 
-    final def withSuffix(suffix: LocalName): LocalName =
+    final def withSuffix(suffix: LocalName): LocalName = {
+      require(!isThis && !suffix.isThis, "cannot concatenate LocalName.This")
       new LocalName(this.encoded ++ suffix.encoded)
+    }
 
     final def withSuffix(suffix: String): LocalName =
       LocalName(this.encoded ++ UTF8String(suffix))
   }
 
   object LocalName {
-    def apply(name: UTF8String): LocalName =
-      new LocalName(validateSimpleEncodedName(name))
+    private final val ThisEncodedName: UTF8String =
+      UTF8String(".this")
+
+    /** The unique `LocalName` with encoded name `.this`. */
+    val This: LocalName =
+      new LocalName(ThisEncodedName)
+
+    def apply(name: UTF8String): LocalName = {
+      if (UTF8String.equals(name, ThisEncodedName))
+        This
+      else
+        new LocalName(validateSimpleEncodedName(name))
+    }
 
     def apply(name: String): LocalName =
       LocalName(UTF8String(name))
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala
index d6a490b634..5c606e81ee 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala
@@ -570,7 +570,6 @@ object Printers {
             case JSPrivateSelect(qual, _) => containsOnlySelectsFromAtom(qual)
             case JSSelect(qual, _)        => containsOnlySelectsFromAtom(qual)
             case VarRef(_)                => true
-            case This()                   => true
             case _                        => false // in particular, Apply
           }
           if (containsOnlySelectsFromAtom(ctor)) {
@@ -844,10 +843,10 @@ object Printers {
         // Atomic expressions
 
         case VarRef(name) =>
-          print(name)
-
-        case This() =>
-          print("this")
+          if (name.isThis)
+            print("this")
+          else
+            print(name)
 
         case Closure(arrow, captureParams, params, restParam, body, captureValues) =>
           if (arrow)
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
index 66c3249f9e..74e7d2c1aa 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
@@ -524,12 +524,13 @@ object Serializers {
           writeTypeRef(typeRef)
 
         case VarRef(name) =>
-          writeTagAndPos(TagVarRef)
-          writeName(name)
-          writeType(tree.tpe)
-
-        case This() =>
-          writeTagAndPos(TagThis)
+          if (name.isThis) {
+            // "Optimized" representation that is compatible with IR < 1.18
+            writeTagAndPos(TagThis)
+          } else {
+            writeTagAndPos(TagVarRef)
+            writeName(name)
+          }
           writeType(tree.tpe)
 
         case Closure(arrow, captureParams, params, restParam, body, captureValues) =>
@@ -1155,10 +1156,13 @@ object Serializers {
           if (hacks.use13) {
             val cls = readClassName()
             val rhs = readTree()
-            if (cls != enclosingClassName || !rhs.isInstanceOf[This]) {
-              throw new IOException(
-                  s"Illegal legacy StoreModule(${cls.nameString}, $rhs) " +
-                  s"found in class ${enclosingClassName.nameString}")
+            rhs match {
+              case This() if cls == enclosingClassName =>
+                // ok
+              case _ =>
+                throw new IOException(
+                    s"Illegal legacy StoreModule(${cls.nameString}, $rhs) " +
+                    s"found in class ${enclosingClassName.nameString}")
             }
           }
           StoreModule()
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Transformers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Transformers.scala
index 7be426e058..82617dfd01 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Transformers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Transformers.scala
@@ -195,7 +195,7 @@ object Transformers {
         case _:Skip | _:Debugger | _:LoadModule | _:StoreModule |
             _:SelectStatic | _:SelectJSNativeMember | _:LoadJSConstructor |
             _:LoadJSModule | _:JSNewTarget | _:JSImportMeta |
-            _:Literal | _:VarRef | _:This | _:JSGlobalRef | _:LinkTimeProperty =>
+            _:Literal | _:VarRef | _:JSGlobalRef | _:LinkTimeProperty =>
           tree
       }
     }
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Traversers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Traversers.scala
index d242bbfce7..3edb2ac178 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Traversers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Traversers.scala
@@ -201,7 +201,7 @@ object Traversers {
       case _:Skip | _:Debugger | _:LoadModule | _:StoreModule |
           _:SelectStatic | _:SelectJSNativeMember | _:LoadJSConstructor |
           _:LoadJSModule | _:JSNewTarget | _:JSImportMeta |
-          _:Literal | _:VarRef | _:This | _:JSGlobalRef | _:LinkTimeProperty =>
+          _:Literal | _:VarRef | _:JSGlobalRef | _:LinkTimeProperty =>
     }
 
     def traverseClassDef(tree: ClassDef): Unit = {
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala b/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
index 6cd4db23c7..7fc574d991 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
@@ -1081,8 +1081,14 @@ object Trees {
   sealed case class VarRef(name: LocalName)(val tpe: Type)(
       implicit val pos: Position) extends AssignLhs
 
-  sealed case class This()(val tpe: Type)(implicit val pos: Position)
-      extends Tree
+  /** Convenience constructor and extractor for `VarRef`s representing `this` bindings. */
+  object This {
+    def apply()(tpe: Type)(implicit pos: Position): VarRef =
+      VarRef(LocalName.This)(tpe)
+
+    def unapply(tree: VarRef): Boolean =
+      tree.name.isThis
+  }
 
   /** Closure with explicit captures.
    *
diff --git a/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala b/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala
index 0b2cb5a9b6..6f68760422 100644
--- a/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala
+++ b/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala
@@ -863,9 +863,6 @@ class PrintersTest {
 
   @Test def printVarRef(): Unit = {
     assertPrintEquals("x", VarRef("x")(IntType))
-  }
-
-  @Test def printThis(): Unit = {
     assertPrintEquals("this", This()(AnyType))
   }
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
index 12af2ad9ab..df5ed07b70 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
@@ -1261,7 +1261,6 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
       def test(tree: Tree): Boolean = tree match {
         // Atomic expressions
         case _: Literal          => true
-        case _: This             => true
         case _: JSNewTarget      => true
         case _: LinkTimeProperty => true
 
@@ -2468,18 +2467,18 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
               genCallHelper(VarField.systemIdentityHashCode, newLhs)
 
             case WrapAsThrowable =>
-              val newLhsVar = newLhs.asInstanceOf[js.VarRef]
+              assert(newLhs.isInstanceOf[js.VarRef] || newLhs.isInstanceOf[js.This], newLhs)
               js.If(
-                  genIsInstanceOfClass(newLhsVar, ThrowableClass),
-                  newLhsVar,
-                  genScalaClassNew(JavaScriptExceptionClass, AnyArgConstructorName, newLhsVar))
+                  genIsInstanceOfClass(newLhs, ThrowableClass),
+                  newLhs,
+                  genScalaClassNew(JavaScriptExceptionClass, AnyArgConstructorName, newLhs))
 
             case UnwrapFromThrowable =>
-              val newLhsVar = newLhs.asInstanceOf[js.VarRef]
+              assert(newLhs.isInstanceOf[js.VarRef] || newLhs.isInstanceOf[js.This], newLhs)
               js.If(
-                  genIsInstanceOfClass(newLhsVar, JavaScriptExceptionClass),
-                  genSelect(newLhsVar, FieldIdent(exceptionFieldName)),
-                  newLhsVar)
+                  genIsInstanceOfClass(newLhs, JavaScriptExceptionClass),
+                  genSelect(newLhs, FieldIdent(exceptionFieldName)),
+                  newLhs)
           }
 
         case BinaryOp(op, lhs, rhs) =>
@@ -2519,7 +2518,10 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
                    * that the body of `Object.equals__O__Z` can be compiled as
                    * `this === that` instead of `Object.is(this, that)`.
                    */
-                  !tree.isInstanceOf[This]
+                  tree match {
+                    case This() => false
+                    case _      => true
+                  }
                 case ClassType(BoxedByteClass | BoxedShortClass |
                     BoxedIntegerClass | BoxedFloatClass | BoxedDoubleClass, _) =>
                   true
@@ -3021,12 +3023,6 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
         case Transient(JSVarRef(name, _)) =>
           js.VarRef(name)
 
-        case This() =>
-          if (env.hasExplicitThis)
-            fileLevelVar(VarField.thiz)
-          else
-            js.This()
-
         case tree: Closure =>
           transformClosure(tree)
 
@@ -3180,12 +3176,6 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
               VarKind.Immutable
           }
 
-        case This() if env.hasExplicitThis =>
-          VarKind.ExplicitThisAlias
-
-        case This() if permitImplicitJSThisCapture =>
-          VarKind.ThisAlias
-
         case _ =>
           explicitCapture()
           VarKind.Immutable
@@ -3415,7 +3405,6 @@ private object FunctionEmitter {
   // Environment
 
   final class Env private (
-      val hasExplicitThis: Boolean,
       val expectedReturnType: Type,
       val enclosingClassName: Option[ClassName],
       vars: Map[LocalName, VarKind],
@@ -3448,7 +3437,7 @@ private object FunctionEmitter {
       copy(enclosingClassName = enclosingClassName)
 
     def withExplicitThis(): Env =
-      copy(hasExplicitThis = true)
+      copy(vars = vars + (LocalName.This -> VarKind.ExplicitThisAlias))
 
     def withVars(newVars: Map[LocalName, VarKind]): Env =
       copy(vars = vars ++ newVars)
@@ -3483,7 +3472,6 @@ private object FunctionEmitter {
       copy(inLoopForVarCapture = inLoopForVarCapture)
 
     private def copy(
-        hasExplicitThis: Boolean = this.hasExplicitThis,
         expectedReturnType: Type = this.expectedReturnType,
         enclosingClassName: Option[ClassName] = this.enclosingClassName,
         vars: Map[LocalName, VarKind] = this.vars,
@@ -3492,15 +3480,18 @@ private object FunctionEmitter {
         defaultBreakTargets: Set[LabelName] = this.defaultBreakTargets,
         defaultContinueTargets: Set[LabelName] = this.defaultContinueTargets,
         inLoopForVarCapture: Boolean = this.inLoopForVarCapture): Env = {
-      new Env(hasExplicitThis, expectedReturnType, enclosingClassName, vars,
+      new Env(expectedReturnType, enclosingClassName, vars,
           labeledExprLHSes, labelsTurnedIntoContinue, defaultBreakTargets,
           defaultContinueTargets, inLoopForVarCapture)
     }
   }
 
   object Env {
+    private val InitVars: Map[LocalName, VarKind] =
+      Map(LocalName.This -> VarKind.ThisAlias)
+
     def empty(expectedReturnType: Type): Env = {
-      new Env(false, expectedReturnType, None, Map.empty, Map.empty, Set.empty,
+      new Env(expectedReturnType, None, InitVars, Map.empty, Set.empty,
           Set.empty, Set.empty, false)
     }
   }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
index bf0e54adc5..7ef7a87ac3 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
@@ -209,9 +209,12 @@ object FunctionEmitter {
       Some(VarStorage.Local(newTargetParam))
     }
 
-    val receiverStorage = receiverType.map { tpe =>
-      val receiverParam = fb.addParam(receiverOriginalName, tpe)
-      VarStorage.Local(receiverParam)
+    val receiverEnv: Env = receiverType match {
+      case None =>
+        Map.empty
+      case Some(tpe) =>
+        val receiverParam = fb.addParam(receiverOriginalName, tpe)
+        Map(LocalName.This -> VarStorage.Local(receiverParam))
     }
 
     val normalParamsEnv: Env = paramDefs.map { paramDef =>
@@ -222,7 +225,7 @@ object FunctionEmitter {
       paramDef.name.name -> VarStorage.Local(param)
     }.toMap
 
-    val fullEnv: Env = captureParamsEnv ++ preSuperEnvEnv ++ normalParamsEnv
+    val fullEnv: Env = captureParamsEnv ++ preSuperEnvEnv ++ receiverEnv ++ normalParamsEnv
 
     fb.setResultTypes(resultTypes)
 
@@ -230,7 +233,6 @@ object FunctionEmitter {
       fb,
       enclosingClassName,
       newTargetStorage,
-      receiverStorage,
       fullEnv
     )
   }
@@ -275,7 +277,6 @@ private class FunctionEmitter private (
     val fb: FunctionBuilder,
     enclosingClassName: Option[ClassName],
     _newTargetStorage: Option[FunctionEmitter.VarStorage.Local],
-    _receiverStorage: Option[FunctionEmitter.VarStorage.Local],
     paramsEnv: FunctionEmitter.Env
 )(implicit ctx: WasmContext) {
   import FunctionEmitter._
@@ -290,9 +291,6 @@ private class FunctionEmitter private (
   private def newTargetStorage: VarStorage.Local =
     _newTargetStorage.getOrElse(throw new Error("Cannot access new.target in this context."))
 
-  private def receiverStorage: VarStorage.Local =
-    _receiverStorage.getOrElse(throw new Error("Cannot access to the receiver in this context."))
-
   /** Opens a new scope in which NPEs can be thrown by jumping to the NPE label.
    *
    *  When NPEs are unchecked this is a no-op (other than calling `body`).
@@ -530,7 +528,6 @@ private class FunctionEmitter private (
       case t: VarRef              => genVarRef(t)
       case t: LoadModule          => genLoadModule(t)
       case t: StoreModule         => genStoreModule(t)
-      case t: This                => genThis(t)
       case t: ApplyStatically     => genApplyStatically(t)
       case t: Apply               => genApply(t)
       case t: ApplyStatic         => genApplyStatic(t)
@@ -1347,9 +1344,8 @@ private class FunctionEmitter private (
       throw new AssertionError(s"Cannot emit $tree at ${tree.pos} without enclosing class name")
     }
 
-    genTreeAuto(This()(ClassType(className, nullable = false))(tree.pos))
-
     markPosition(tree)
+    genReadStorage(lookupLocal(LocalName.This))
     fb += wa.GlobalSet(genGlobalID.forModuleInstance(className))
     VoidType
   }
@@ -2421,12 +2417,6 @@ private class FunctionEmitter private (
     tree.tpe
   }
 
-  private def genThis(tree: This): Type = {
-    markPosition(tree)
-    genReadStorage(receiverStorage)
-    tree.tpe
-  }
-
   private def genVarDef(tree: VarDef): Type = {
     /* This is an isolated VarDef that is not in a Block.
      * Its scope is empty by construction, and therefore it need not be stored.
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala b/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
index 1e75d4db31..103d19f963 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
@@ -150,8 +150,10 @@ private final class ClassDefChecker(classDef: ClassDef,
       } {
         implicit val ctx = ErrorContext(p)
         val name = ident.name
+        if (name.isThis)
+          reportError(i"Illegal JS class capture with name '$name'")
         if (!alreadyDeclared.add(name))
-            reportError(i"Duplicate JS class capture '$name'")
+          reportError(i"Duplicate JS class capture '$name'")
         if (tpe == VoidType)
           reportError(i"The JS class capture $name cannot have type VoidType")
         if (mutable)
@@ -300,9 +302,8 @@ private final class ClassDefChecker(classDef: ClassDef,
 
     // Body
     for (body <- optBody) {
-      val thisType = if (static) VoidType else instanceThisType
       val bodyEnv = Env.fromParams(params)
-        .withThisType(thisType)
+        .withMaybeThisType(!static, instanceThisType)
 
       if (isConstructor)
         checkConstructorBody(body, bodyEnv)
@@ -357,9 +358,8 @@ private final class ClassDefChecker(classDef: ClassDef,
     checkExportedPropertyName(pName)
     checkJSParamDefs(params, restParam)
 
-    val thisType = if (static) VoidType else instanceThisType
-    val env =
-      Env.fromParams(classDef.jsClassCaptures.getOrElse(Nil) ++ params ++ restParam).withThisType(thisType)
+    val env = Env.fromParams(classDef.jsClassCaptures.getOrElse(Nil) ++ params ++ restParam)
+      .withMaybeThisType(!static, instanceThisType)
 
     checkTree(body, env)
   }
@@ -383,11 +383,11 @@ private final class ClassDefChecker(classDef: ClassDef,
     checkExportedPropertyName(pName)
 
     val jsClassCaptures = classDef.jsClassCaptures.getOrElse(Nil)
-    val thisType = if (static) VoidType else instanceThisType
 
     getterBody.foreach { body =>
       withPerMethodState {
-        val bodyEnv = Env.fromParams(jsClassCaptures).withThisType(thisType)
+        val bodyEnv = Env.fromParams(jsClassCaptures)
+          .withMaybeThisType(!static, instanceThisType)
         checkTree(body, bodyEnv)
       }
     }
@@ -395,7 +395,8 @@ private final class ClassDefChecker(classDef: ClassDef,
     setterArgAndBody.foreach { case (setterArg, body) =>
       withPerMethodState {
         checkJSParamDefs(setterArg :: Nil, None)
-        val bodyEnv = Env.fromParams(jsClassCaptures :+ setterArg).withThisType(thisType)
+        val bodyEnv = Env.fromParams(jsClassCaptures :+ setterArg)
+          .withMaybeThisType(!static, instanceThisType)
         checkTree(body, bodyEnv)
       }
     }
@@ -948,13 +949,7 @@ private final class ClassDefChecker(classDef: ClassDef,
           if (tree.tpe != localDef.tpe)
             reportError(i"Variable $name of type ${localDef.tpe} typed as ${tree.tpe}")
         }
-
-      case This() =>
-        if (env.thisType == VoidType)
-          reportError(i"Cannot find `this` in scope")
-        else if (tree.tpe != env.thisType)
-          reportError(i"`this` of type ${env.thisType} typed as ${tree.tpe}")
-        if (env.isThisRestricted)
+        if (env.isThisRestricted && name.isThis)
           reportError(i"Restricted use of `this` before the super constructor call")
 
       case Closure(arrow, captureParams, params, restParam, body, captureValues) =>
@@ -984,7 +979,7 @@ private final class ClassDefChecker(classDef: ClassDef,
           val bodyEnv = Env
             .fromParams(captureParams ++ params ++ restParam)
             .withHasNewTarget(!arrow)
-            .withThisType(if (arrow) VoidType else AnyType)
+            .withMaybeThisType(!arrow, AnyType)
           checkTree(body, bodyEnv)
         }
 
@@ -1023,6 +1018,8 @@ private final class ClassDefChecker(classDef: ClassDef,
 
   private def checkDeclareLocalVar(ident: LocalIdent)(
       implicit ctx: ErrorContext): Unit = {
+    if (ident.name.isThis)
+      reportError(i"Illegal definition of a variable with name ${ident.name}")
     if (!declaredLocalVarNamesPerMethod.add(ident.name))
       reportError(i"Duplicate local variable name ${ident.name}.")
   }
@@ -1072,8 +1069,6 @@ object ClassDefChecker {
   private class Env(
       /** Whether there is a valid `new.target` in scope. */
       val hasNewTarget: Boolean,
-      /** The type of `this` in scope, or `VoidType` if there is no `this` in scope. */
-      val thisType: Type,
       /** Local variables in scope (including through closures). */
       val locals: Map[LocalName, LocalDef],
       /** Return types by label. */
@@ -1087,7 +1082,11 @@ object ClassDefChecker {
       copy(hasNewTarget = hasNewTarget)
 
     def withThisType(thisType: Type): Env =
-      copy(thisType = thisType)
+      withLocal(LocalDef(LocalName.This, thisType, mutable = false))
+
+    def withMaybeThisType(hasThis: Boolean, thisType: Type): Env =
+      if (hasThis) withThisType(thisType)
+      else this
 
     def withLocal(localDef: LocalDef): Env =
       copy(locals = locals + (localDef.name -> localDef))
@@ -1100,12 +1099,11 @@ object ClassDefChecker {
 
     private def copy(
       hasNewTarget: Boolean = hasNewTarget,
-      thisType: Type = thisType,
       locals: Map[LocalName, LocalDef] = locals,
       returnLabels: Set[LabelName] = returnLabels,
       isThisRestricted: Boolean = isThisRestricted
     ): Env = {
-      new Env(hasNewTarget, thisType, locals, returnLabels, isThisRestricted)
+      new Env(hasNewTarget, locals, returnLabels, isThisRestricted)
     }
   }
 
@@ -1113,7 +1111,6 @@ object ClassDefChecker {
     val empty: Env = {
       new Env(
         hasNewTarget = false,
-        thisType = VoidType,
         locals = Map.empty,
         returnLabels = Set.empty,
         isThisRestricted = false
@@ -1127,7 +1124,6 @@ object ClassDefChecker {
 
       new Env(
         hasNewTarget = false,
-        thisType = VoidType,
         paramLocalDefs.toMap,
         Set.empty,
         isThisRestricted = false
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/checker/ErrorReporter.scala b/linker/shared/src/main/scala/org/scalajs/linker/checker/ErrorReporter.scala
index 18c6527d13..ab45bd4316 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/checker/ErrorReporter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/checker/ErrorReporter.scala
@@ -35,6 +35,8 @@ private[checker] object ErrorReporter {
 
     private def format(arg: Any): String = {
       arg match {
+        case arg: LocalName if arg.isThis => "`this`"
+
         case arg: Name       => arg.nameString
         case arg: FieldName  => arg.nameString
         case arg: MethodName => arg.displayName
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala b/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
index 4c2c4f8464..a749e4807e 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
@@ -692,8 +692,6 @@ private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter,
 
       case _: VarRef =>
 
-      case This() =>
-
       case Closure(arrow, captureParams, params, restParam, body, captureValues) =>
         assert(captureParams.size == captureValues.size) // checked by ClassDefChecker
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
index a3fb5319c3..6d4aa83022 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
@@ -876,7 +876,7 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
       val getterDependenciesBuilder = Set.newBuilder[(ClassName, MethodName)]
 
       def isTriviallySideEffectFree(tree: Tree): Boolean = tree match {
-        case _:VarRef | _:Literal | _:This | _:Skip =>
+        case _:VarRef | _:Literal | _:Skip =>
           true
 
         case Closure(_, _, _, _, _, captureValues) =>
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
index d55b70744d..5f275ea841 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
@@ -232,16 +232,6 @@ private[optimizer] abstract class OptimizerCore(
     (newName, newOriginalName)
   }
 
-  private def freshLocalName(base: Binding.Name,
-      mutable: Boolean): (LocalName, OriginalName) = {
-    base match {
-      case Binding.This =>
-        freshLocalName(LocalThisNameForFresh, thisOriginalName, mutable)
-      case Binding.Local(name, originalName) =>
-        freshLocalName(name, originalName, mutable)
-    }
-  }
-
   private def freshLabelName(base: LabelName): LabelName =
     labelNameAllocator.freshName(base)
 
@@ -659,7 +649,7 @@ private[optimizer] abstract class OptimizerCore(
 
       // Atomic expressions
 
-      case _:VarRef | _:This =>
+      case _:VarRef =>
         trampoline {
           pretransformExpr(tree)(finishTransform(isStat))
         }
@@ -779,7 +769,8 @@ private[optimizer] abstract class OptimizerCore(
         case PreTransLit(literal) =>
           captureParamLocalDefs += paramName -> LocalDef(tcaptureValue.tpe, false, ReplaceWithConstant(literal))
 
-        case PreTransLocalDef(LocalDef(_, /* mutable = */ false, ReplaceWithVarRef(captureName, _))) =>
+        case PreTransLocalDef(LocalDef(_, /* mutable = */ false, ReplaceWithVarRef(captureName, _)))
+            if !captureName.isThis =>
           captureParamLocalDefsForVarRefs.get(captureName).fold[Unit] {
             captureParamLocalDefsForVarRefs += captureName -> addCaptureParam(captureName)
           } { prevLocalDef =>
@@ -906,16 +897,6 @@ private[optimizer] abstract class OptimizerCore(
         })
         cont(localDef.toPreTransform)
 
-      case This() =>
-        val localDef = scope.env.thisLocalDef.getOrElse {
-          throw new AssertionError(
-              s"Found invalid 'this' at $pos\n" +
-              s"While optimizing $debugID\n" +
-              s"Env is ${scope.env}\n" +
-              s"Inlining ${scope.implsBeingInlined}")
-        }
-        cont(localDef.toPreTransform)
-
       case tree: If =>
         pretransformIf(tree)(cont)
 
@@ -1591,7 +1572,7 @@ private[optimizer] abstract class OptimizerCore(
 
   /** Keeps only the side effects of a Tree (overapproximation). */
   private def keepOnlySideEffects(stat: Tree): Tree = stat match {
-    case _:VarRef | _:This | _:Literal | _:SelectStatic =>
+    case _:VarRef | _:Literal | _:SelectStatic =>
       Skip()(stat.pos)
     case VarDef(_, _, _, _, rhs) =>
       keepOnlySideEffects(rhs)
@@ -1903,9 +1884,6 @@ private[optimizer] abstract class OptimizerCore(
         case _: Literal =>
           NotFoundPureSoFar
 
-        case This() =>
-          NotFoundPureSoFar
-
         case Closure(arrow, captureParams, params, restParam, body, captureValues) =>
           recs(captureValues).mapOrKeepGoing(Closure(arrow, captureParams, params, restParam, body, _))
 
@@ -2105,12 +2083,11 @@ private[optimizer] abstract class OptimizerCore(
              * the unboxes in the correct evaluation order.
              */
 
-            /* Generate a new, fake body that we will inline. For
-             * type-preservation, the type of its `This()` node is the type of
-             * our receiver but non-nullable. For stability, the parameter
-             * names are normalized (taking them from `body` would make the
-             * result depend on which method came up first in the list of
-             * targets).
+            /* Generate a new, fake body that we will inline. For type
+             * preservation, the type of its `this` var ref is the type of our
+             * receiver but non-nullable. For stability, the parameter names
+             * are normalized (taking them from `body` would make the result
+             * depend on which method came up first in the list of targets).
              */
             val thisType = treceiver.tpe.base.toNonNullable
             val normalizedParams: List[(LocalName, Type)] = {
@@ -2132,10 +2109,10 @@ private[optimizer] abstract class OptimizerCore(
 
             // Construct bindings; need to check null for the receiver to preserve evaluation order
             val receiverBinding =
-              Binding(Binding.This, thisType, mutable = false, checkNotNull(treceiver))
+              Binding.forReceiver(thisType, checkNotNull(treceiver))
             val argsBindings = normalizedParams.zip(targs).map {
               case ((name, ptpe), targ) =>
-                Binding(Binding.Local(name, NoOriginalName), ptpe, mutable = false, targ)
+                Binding(name, NoOriginalName, ptpe, mutable = false, targ)
             }
 
             withBindings(receiverBinding :: argsBindings) { (bodyScope, cont1) =>
@@ -2581,12 +2558,12 @@ private[optimizer] abstract class OptimizerCore(
 
       case This() if args.isEmpty =>
         assert(optReceiver.isDefined,
-            "There was a This(), there should be a receiver")
+            "There was a `this`, there should be a receiver")
         cont(foldCast(checkNotNull(optReceiver.get._2), optReceiver.get._1))
 
       case Select(This(), field) if formals.isEmpty =>
         assert(optReceiver.isDefined,
-            "There was a This(), there should be a receiver")
+            "There was a `this`, there should be a receiver")
         pretransformSelectCommon(body.tpe, optReceiver.get._2,
             optQualDeclaredType = Some(optReceiver.get._1),
             field, isLhsOfAssign = false)(cont)
@@ -2595,7 +2572,7 @@ private[optimizer] abstract class OptimizerCore(
           if formals.size == 1 && formals.head.name.name == rhsName =>
         assert(isStat, "Found Assign in expression position")
         assert(optReceiver.isDefined,
-            "There was a This(), there should be a receiver")
+            "There was a `this`, there should be a receiver")
 
         val treceiver = optReceiver.get._2
         val trhs = args.head
@@ -2634,7 +2611,7 @@ private[optimizer] abstract class OptimizerCore(
        */
       val (declaredType, value0) = receiver
       val value = foldCast(checkNotNull(value0), declaredType)
-      Binding(Binding.This, declaredType, false, value)
+      Binding.forReceiver(declaredType, value)
     }
 
     assert(formals.size == args.size,
@@ -3193,8 +3170,7 @@ private[optimizer] abstract class OptimizerCore(
     val initialFieldBindings = for {
       RecordType.Field(name, originalName, tpe, mutable) <- structure.recordType.fields
     } yield {
-      Binding(Binding.Local(name.toLocalName, originalName), tpe, mutable,
-          PreTransTree(zeroOf(tpe)))
+      Binding(name.toLocalName, originalName, tpe, mutable, PreTransTree(zeroOf(tpe)))
     }
 
     withNewLocalDefs(initialFieldBindings) { (initialFieldLocalDefList, cont1) =>
@@ -3282,22 +3258,22 @@ private[optimizer] abstract class OptimizerCore(
     }
 
     stats match {
-      case This() :: rest =>
+      case VarRef(_) :: rest =>
+        // mostly for `this`
         inlineClassConstructorBodyList(allocationSite, structure, thisLocalDef,
             inputFieldsLocalDefs, className, rest, cancelFun)(buildInner)(cont)
 
-      case Assign(s @ Select(ths: This, field), value) :: rest
+      case Assign(s @ Select(This(), field), value) :: rest
           if !inputFieldsLocalDefs.contains(field.name) =>
         // Field is being optimized away. Only keep side effects of the write.
         withStat(value, rest)
 
-      case Assign(s @ Select(ths: This, field), value) :: rest
+      case Assign(s @ Select(This(), field), value) :: rest
           if !inputFieldsLocalDefs(field.name).mutable =>
         pretransformExpr(value) { tvalue =>
           val originalName = structure.fieldOriginalName(field.name)
-          val binding = Binding(
-              Binding.Local(field.name.simpleName.toLocalName, originalName),
-              s.tpe, false, tvalue)
+          val binding = Binding(field.name.simpleName.toLocalName,
+              originalName, s.tpe, mutable = false, tvalue)
           withNewLocalDef(binding) { (localDef, cont1) =>
             if (localDef.contains(thisLocalDef)) {
               /* Uh oh, there is a `val x = ...this...`. We can't keep it,
@@ -3342,7 +3318,7 @@ private[optimizer] abstract class OptimizerCore(
             Assign(lhs, If(cond, th, value)(lhs.tpe)(stat.pos))(ass.pos) :: rest,
             cancelFun)(buildInner)(cont)
 
-      case ApplyStatically(flags, ths: This, superClass, superCtor, args) :: rest
+      case ApplyStatically(flags, This(), superClass, superCtor, args) :: rest
           if flags.isConstructor =>
         pretransformExprs(args) { targs =>
           inlineClassConstructorBody(allocationSite, structure,
@@ -5338,8 +5314,10 @@ private[optimizer] abstract class OptimizerCore(
     (name -> localDef, newParamDef)
   }
 
-  private def newThisLocalDef(thisType: Type): LocalDef =
-    LocalDef(RefinedType(thisType), false, ReplaceWithThis())
+  private def newThisLocalDef(thisType: Type): LocalDef = {
+    LocalDef(RefinedType(thisType), false,
+        ReplaceWithVarRef(LocalName.This, new SimpleState(this, UsedAtLeastOnce)))
+  }
 
   private def withBindings(bindings: List[Binding])(
       buildInner: (Scope, PreTransCont) => TailRec[Tree])(
@@ -5403,7 +5381,7 @@ private[optimizer] abstract class OptimizerCore(
       buildInner: (LocalDef, PreTransCont) => TailRec[Tree])(
       cont: PreTransCont)(
       implicit scope: Scope): TailRec[Tree] = tailcall {
-    val Binding(bindingName, declaredType, mutable, value) = binding
+    val Binding(bindingName, originalName, declaredType, mutable, value) = binding
     implicit val pos = value.pos
 
     def withDedicatedVar(tpe: RefinedType): TailRec[Tree] = {
@@ -5423,13 +5401,13 @@ private[optimizer] abstract class OptimizerCore(
          * RuntimeLong.
          */
         expandLongValue(value) { expandedValue =>
-          val expandedBinding = Binding(bindingName, rtLongClassType,
-              mutable, expandedValue)
+          val expandedBinding = Binding(bindingName, originalName,
+              rtLongClassType, mutable, expandedValue)
           withNewLocalDef(expandedBinding)(buildInner)(cont)
         }
       } else {
         // Otherwise, we effectively declare a new binding
-        val (newName, newOriginalName) = freshLocalName(bindingName, mutable)
+        val (newName, newOriginalName) = freshLocalName(bindingName, originalName, mutable)
 
         val used = newSimpleState[IsUsed](Unused)
 
@@ -5609,7 +5587,7 @@ private[optimizer] abstract class OptimizerCore(
 
 private[optimizer] object OptimizerCore {
 
-  /** When creating a `freshName` based on a `Binding.This`, use this name as
+  /** When creating a `freshName` based on a `LocalName.This`, use this name as
    *  base.
    */
   private val LocalThisNameForFresh = LocalName("this")
@@ -5855,15 +5833,11 @@ private[optimizer] object OptimizerCore {
       case ReplaceWithRecordVarRef(_, _, _, cancelFun) =>
         cancelFun()
 
-      case ReplaceWithThis() =>
-        This()(tpe.base)
-
       case ReplaceWithOtherLocalDef(localDef) =>
         /* A previous version would push down the `tpe` of this `LocalDef` to
          * use for the replacement. While that creates trees with narrower types,
-         * it also creates inconsistent trees:
-         * - This() not typed as the enclosing class.
-         * - VarRef not typed as the corresponding VarDef / ParamDef.
+         * it also creates inconsistent trees, with `VarRef`s that are not typed
+         * as the corresponding VarDef / ParamDef / receiver type.
          *
          * Type based optimizations happen (mainly) in the optimizer so
          * consistent downstream types are more important than narrower types;
@@ -5917,20 +5891,19 @@ private[optimizer] object OptimizerCore {
           elemLocalDefs.exists(_.contains(that))
 
         case _:ReplaceWithVarRef | _:ReplaceWithRecordVarRef |
-             _:ReplaceWithThis | _:ReplaceWithConstant =>
+             _:ReplaceWithConstant =>
           false
       })
     }
 
     def tryWithRefinedType(refinedType: RefinedType): LocalDef = {
-      /* Only adjust if the replacement if ReplaceWithThis or
-       * ReplaceWithVarRef, because other types have nothing to gain
-       * (e.g., ReplaceWithConstant) or we want to keep them unwrapped
-       * because they are examined in optimizations (notably all the
-       * types with virtualized objects).
+      /* Only adjust if the replacement if ReplaceWithVarRef, because other
+       * types have nothing to gain (e.g., ReplaceWithConstant) or we want to
+       * keep them unwrapped because they are examined in optimizations
+       * (notably all the types with virtualized objects).
        */
       replacement match {
-        case _:ReplaceWithThis | _:ReplaceWithVarRef =>
+        case _:ReplaceWithVarRef =>
           LocalDef(refinedType, mutable, ReplaceWithOtherLocalDef(this))
         case replacement: ReplaceWithOtherLocalDef =>
           LocalDef(refinedType, mutable, replacement)
@@ -5950,8 +5923,6 @@ private[optimizer] object OptimizerCore {
       used: SimpleState[IsUsed],
       cancelFun: CancelFun) extends LocalDefReplacement
 
-  private final case class ReplaceWithThis() extends LocalDefReplacement
-
   /** An alias to another `LocalDef`, used only to refine the type of that
    *  `LocalDef` in a specific scope.
    *
@@ -6002,41 +5973,37 @@ private[optimizer] object OptimizerCore {
       val returnedStructures: SimpleState[List[InlineableClassStructure]])
 
   private class OptEnv(
-      val thisLocalDef: Option[LocalDef],
       val localDefs: Map[LocalName, LocalDef],
       val labelInfos: Map[LabelName, LabelInfo]) {
 
     def withThisLocalDef(rep: LocalDef): OptEnv =
-      withThisLocalDef(Some(rep))
+      withLocalDef(LocalName.This, rep)
 
+    /** Optionally adds a binding for `this`.
+     *
+     *  If `rep.isEmpty`, returns this environment unchanged.
+     */
     def withThisLocalDef(rep: Option[LocalDef]): OptEnv =
-      new OptEnv(rep, localDefs, labelInfos)
+      if (rep.isEmpty) this
+      else withThisLocalDef(rep.get)
 
     def withLocalDef(oldName: LocalName, rep: LocalDef): OptEnv =
-      new OptEnv(thisLocalDef, localDefs + (oldName -> rep), labelInfos)
-
-    def withLocalDef(oldName: Binding.Name, rep: LocalDef): OptEnv = {
-      oldName match {
-        case Binding.This           => withThisLocalDef(rep)
-        case Binding.Local(name, _) => withLocalDef(name, rep)
-      }
-    }
+      new OptEnv(localDefs + (oldName -> rep), labelInfos)
 
     def withLocalDefs(reps: List[(LocalName, LocalDef)]): OptEnv =
-      new OptEnv(thisLocalDef, localDefs ++ reps, labelInfos)
+      new OptEnv(localDefs ++ reps, labelInfos)
 
     def withLabelInfo(oldName: LabelName, info: LabelInfo): OptEnv =
-      new OptEnv(thisLocalDef, localDefs, labelInfos + (oldName -> info))
+      new OptEnv(localDefs, labelInfos + (oldName -> info))
 
     override def toString(): String = {
-      "thisLocalDef:\n  " + thisLocalDef.fold("<none>")(_.toString()) + "\n" +
       "localDefs:" + localDefs.mkString("\n  ", "\n  ", "\n") +
       "labelInfos:" + labelInfos.mkString("\n  ", "\n  ", "")
     }
   }
 
   private object OptEnv {
-    val Empty: OptEnv = new OptEnv(None, Map.empty, Map.empty)
+    val Empty: OptEnv = new OptEnv(Map.empty, Map.empty)
   }
 
   private class Scope private (
@@ -6337,26 +6304,21 @@ private[optimizer] object OptimizerCore {
     }
   }
 
-  private final case class Binding(name: Binding.Name, declaredType: Type,
-      mutable: Boolean, value: PreTransform)
+  private final case class Binding(name: LocalName, originalName: OriginalName,
+      declaredType: Type, mutable: Boolean, value: PreTransform)
 
   private object Binding {
-    sealed abstract class Name
-
-    case object This extends Name
-
-    final case class Local(name: LocalName, originalName: OriginalName)
-        extends Name
-
     def apply(localIdent: LocalIdent, originalName: OriginalName,
         declaredType: Type, mutable: Boolean, value: PreTransform): Binding = {
-      apply(Local(localIdent.name, originalName), declaredType,
-          mutable, value)
+      apply(localIdent.name, originalName, declaredType, mutable, value)
     }
 
+    def forReceiver(declaredType: Type, value: PreTransform): Binding =
+      apply(LocalName.This, NoOriginalName, declaredType, mutable = false, value)
+
     def temp(baseName: LocalName, declaredType: Type, mutable: Boolean,
         value: PreTransform): Binding = {
-      apply(Local(baseName, NoOriginalName), declaredType, mutable, value)
+      apply(baseName, NoOriginalName, declaredType, mutable, value)
     }
 
     def temp(baseName: LocalName, value: PreTransform): Binding =
@@ -6764,7 +6726,7 @@ private[optimizer] object OptimizerCore {
       val shouldInline = inlineable && {
         optimizerHints.inline || isForwarder || {
           body match {
-            case _:Skip | _:This | _:Literal =>
+            case _:Skip | _:VarRef | _:Literal =>
               true
 
             // Shape of accessors
@@ -6852,7 +6814,7 @@ private[optimizer] object OptimizerCore {
   private val TraitInitSimpleMethodName = SimpleMethodName("$init$")
 
   private def isTrivialConstructorStat(stat: Tree): Boolean = stat match {
-    case This() =>
+    case _: VarRef =>
       true
     case ApplyStatically(_, This(), _, _, Nil) =>
       true
@@ -6915,7 +6877,7 @@ private[optimizer] object OptimizerCore {
     }
 
     private def isTrivialArg(arg: Tree): Boolean = arg match {
-      case _:VarRef | _:This | _:Literal | _:LoadModule =>
+      case _:VarRef | _:Literal | _:LoadModule =>
         true
       case _ =>
         false
@@ -7025,6 +6987,9 @@ private[optimizer] object OptimizerCore {
       EmitterReservedJSIdentifiers.map(i => LocalName(i) -> 1).toMap
 
     final class Local extends FreshNameAllocator[LocalName](InitialLocalMap) {
+      override def freshName(base: LocalName): LocalName =
+        super.freshName(if (base.isThis) LocalThisNameForFresh else base)
+
       protected def nameWithSuffix(name: LocalName, suffix: String): LocalName =
         name.withSuffix(suffix)
     }
@@ -7052,6 +7017,7 @@ private[optimizer] object OptimizerCore {
   def originalNameForFresh(base: Name, originalName: OriginalName,
       freshName: Name): OriginalName = {
     if (originalName.isDefined || (freshName eq base)) originalName
+    else if (base eq LocalName.This) thisOriginalName
     else OriginalName(base)
   }
 
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/IRCheckerTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/IRCheckerTest.scala
index 0fe3988e97..d283ae189e 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/IRCheckerTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/IRCheckerTest.scala
@@ -370,7 +370,7 @@ class IRCheckerTest {
     for {
       log <- testLinkIRErrors(classDefs, MainTestModuleInitializers, postOptimizer = true)
     } yield {
-      log.assertContainsError("Foo expected but Bar! found for tree of type org.scalajs.ir.Trees$This")
+      log.assertContainsError("Foo expected but Bar! found for tree of type org.scalajs.ir.Trees$VarRef")
     }
   }
 
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/checker/ClassDefCheckerTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/checker/ClassDefCheckerTest.scala
index 78e4e1dd2c..2d22331cc0 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/checker/ClassDefCheckerTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/checker/ClassDefCheckerTest.scala
@@ -383,6 +383,108 @@ class ClassDefCheckerTest {
         "Illegal constructor call")
   }
 
+  @Test
+  def illegalThisDeclarations(): Unit = {
+    val thisParamDef = paramDef(LocalName.This, AnyType)
+
+    // Local var
+    assertError(
+      mainTestClassDef(Block(
+        VarDef(LocalName.This, NON, IntType, mutable = false, int(5))
+      )),
+      "Illegal definition of a variable with name `this`"
+    )
+
+    // Method param
+    assertError(
+      classDef(
+        "Foo", superClass = Some(ObjectClass),
+        methods = List(
+          trivialCtor("Foo"),
+          MethodDef(EMF, m("foo", List(I), V), NON, List(thisParamDef), VoidType, Some(Skip()))(EOH, UNV)
+        )
+      ),
+      "Illegal definition of a variable with name `this`"
+    )
+
+    // Capture param of a Closure
+    assertError(
+      mainTestClassDef(Block(
+        Closure(arrow = true, List(thisParamDef), Nil, None, int(5), List(int(6)))
+      )),
+      "Illegal definition of a variable with name `this`"
+    )
+
+    // Param of a closure
+    assertError(
+      mainTestClassDef(Block(
+        Closure(arrow = true, Nil, List(thisParamDef), None, int(5), Nil)
+      )),
+      "Illegal definition of a variable with name `this`"
+    )
+
+    // Rest param of a closure
+    assertError(
+      mainTestClassDef(Block(
+        Closure(arrow = true, Nil, Nil, Some(thisParamDef), int(5), Nil)
+      )),
+      "Illegal definition of a variable with name `this`"
+    )
+
+    // JS method param
+    assertError(
+      classDef(
+        "Foo", superClass = Some(ObjectClass),
+        kind = ClassKind.JSClass,
+        jsConstructor = Some(trivialJSCtor()),
+        jsMethodProps = List(
+          JSMethodDef(EMF, str("foo"), List(thisParamDef), None, Skip())(EOH, UNV)
+        )
+      ),
+      "Illegal definition of a variable with name `this`"
+    )
+
+    // JS class capture
+    assertError(
+      classDef(
+        "Foo", superClass = Some(ObjectClass),
+        kind = ClassKind.JSClass,
+        jsClassCaptures = Some(List(thisParamDef)),
+        jsConstructor = Some(trivialJSCtor())
+      ),
+      "Illegal JS class capture with name '`this`'"
+    )
+  }
+
+  @Test
+  def assignmentToImmutable(): Unit = {
+    assertError(
+      mainTestClassDef(Block(
+        VarDef("x", NON, IntType, mutable = false, int(5)),
+        Assign(VarRef("x")(IntType), int(6))
+      )),
+      "Assignment to immutable variable x."
+    )
+
+    assertError(
+      classDef(
+        "Foo", superClass = Some(ObjectClass),
+        methods = List(
+          trivialCtor("Foo"),
+          MethodDef(EMF, m("foo", Nil, V), NON, Nil, VoidType, Some(Block(
+            Assign(thisFor("Foo"), thisFor("Foo"))
+          )))(EOH, UNV)
+        )
+      ),
+      "Assignment to immutable variable `this`."
+    )
+
+    assertError(
+      mainTestClassDef(Assign(JSGlobalRef(JSGlobalRef.FileLevelThis), int(5))),
+      "Assignment to global this."
+    )
+  }
+
   @Test
   def thisType(): Unit = {
     def testThisTypeError(static: Boolean, expr: Tree, expectedMsg: String): Unit = {
@@ -404,47 +506,47 @@ class ClassDefCheckerTest {
 
     testThisTypeError(static = true,
         This()(VoidType),
-        "Cannot find `this` in scope")
+        "Cannot find variable `this` in scope")
 
     testThisTypeError(static = true,
         This()(ClassType("Foo", nullable = false)),
-        "Cannot find `this` in scope")
+        "Cannot find variable `this` in scope")
 
     testThisTypeError(static = false,
         This()(VoidType),
-        "`this` of type Foo! typed as void")
+        "Variable `this` of type Foo! typed as void")
 
     testThisTypeError(static = false,
         This()(AnyType),
-        "`this` of type Foo! typed as any")
+        "Variable `this` of type Foo! typed as any")
 
     testThisTypeError(static = false,
         This()(AnyNotNullType),
-        "`this` of type Foo! typed as any!")
+        "Variable `this` of type Foo! typed as any!")
 
     testThisTypeError(static = false,
         This()(ClassType("Bar", nullable = false)),
-        "`this` of type Foo! typed as Bar!")
+        "Variable `this` of type Foo! typed as Bar!")
 
     testThisTypeError(static = false,
         This()(ClassType("Foo", nullable = true)),
-        "`this` of type Foo! typed as Foo")
+        "Variable `this` of type Foo! typed as Foo")
 
     testThisTypeError(static = false,
         Closure(arrow = true, Nil, Nil, None, This()(VoidType), Nil),
-        "Cannot find `this` in scope")
+        "Cannot find variable `this` in scope")
 
     testThisTypeError(static = false,
         Closure(arrow = true, Nil, Nil, None, This()(AnyType), Nil),
-        "Cannot find `this` in scope")
+        "Cannot find variable `this` in scope")
 
     testThisTypeError(static = false,
         Closure(arrow = false, Nil, Nil, None, This()(VoidType), Nil),
-        "`this` of type any typed as void")
+        "Variable `this` of type any typed as void")
 
     testThisTypeError(static = false,
         Closure(arrow = false, Nil, Nil, None, This()(ClassType("Foo", nullable = false)), Nil),
-        "`this` of type any typed as Foo!")
+        "Variable `this` of type any typed as Foo!")
   }
 
   @Test
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/testutils/TestIRBuilder.scala b/linker/shared/src/test/scala/org/scalajs/linker/testutils/TestIRBuilder.scala
index d48649c245..e6b045c286 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/testutils/TestIRBuilder.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/testutils/TestIRBuilder.scala
@@ -167,7 +167,7 @@ object TestIRBuilder {
     else None
   }
 
-  def thisFor(cls: ClassName): This =
+  def thisFor(cls: ClassName): VarRef =
     This()(ClassType(cls, nullable = false))
 
   implicit def string2LocalName(name: String): LocalName =
diff --git a/project/BinaryIncompatibilities.scala b/project/BinaryIncompatibilities.scala
index 305e97d428..5df88fa444 100644
--- a/project/BinaryIncompatibilities.scala
+++ b/project/BinaryIncompatibilities.scala
@@ -21,6 +21,10 @@ object BinaryIncompatibilities {
     ProblemFilters.exclude[MissingClassProblem]("org.scalajs.ir.Trees$LabelIdent$"),
     ProblemFilters.exclude[Problem]("org.scalajs.ir.Trees#Labeled.*"),
     ProblemFilters.exclude[Problem]("org.scalajs.ir.Trees#Return.*"),
+    ProblemFilters.exclude[MissingClassProblem]("org.scalajs.ir.Trees$This"),
+    ProblemFilters.exclude[MissingTypesProblem]("org.scalajs.ir.Trees$This$"),
+    ProblemFilters.exclude[IncompatibleResultTypeProblem]("org.scalajs.ir.Trees#This.apply"),
+    ProblemFilters.exclude[IncompatibleMethTypeProblem]("org.scalajs.ir.Trees#This.unapply"),
     ProblemFilters.exclude[MissingClassProblem]("org.scalajs.ir.Trees$Throw"),
     ProblemFilters.exclude[MissingClassProblem]("org.scalajs.ir.Trees$Throw$"),
     ProblemFilters.exclude[MissingClassProblem]("org.scalajs.ir.Trees$UnwrapFromThrowable"),

From cebcd0a36d29d97c65b32446ea8d5f43953c0b0f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Fri, 27 Dec 2024 18:12:59 +0100
Subject: [PATCH 229/298] Ignore the deprecation of mutable.AnyRefMap in Scala
 2.13.16+.

It was deprecated because mutable.HashMap is just as fast,
starting from 2.13.0. However we still use it for performance in
Scala 2.12.x, which is important because that's the version of the
linker used by the sbt plugin.
---
 project/Build.scala | 34 +++++++++++++++++++++++-----------
 1 file changed, 23 insertions(+), 11 deletions(-)

diff --git a/project/Build.scala b/project/Build.scala
index 2fc1510e58..d7f7f5e234 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -482,6 +482,20 @@ object Build {
     },
   )
 
+  def addWconfSettingIf2_13(conf: String): Def.Setting[_] = {
+    scalacOptions ++= {
+      /* We exclude 2.13.0 and 2.13.1 because they did not support -Wconf yet.
+       * Fortunately, our use cases for -Wconf are only triggered with later
+       * versions.
+       */
+      val v = scalaVersion.value
+      if (v.startsWith("2.13.") && v != "2.13.0" && v != "2.13.1")
+        List("-Wconf:" + conf)
+      else
+        Nil
+    }
+  }
+
   val commonSettings = Seq(
       organization := "org.scala-js",
       version := scalaJSVersion,
@@ -517,6 +531,14 @@ object Build {
           "-encoding", "utf8"
       ),
 
+      /* Ignore the deprecation of mutable.AnyRefMap in Scala 2.13.16+.
+       * It was deprecated because mutable.HashMap is just as fast, starting
+       * from 2.13.0. However we still use it for performance in Scala 2.12.x,
+       * which is important because that's the version of the linker used by
+       * the sbt plugin.
+       */
+      addWconfSettingIf2_13("cat=deprecation&origin=scala\\.collection\\.mutable\\.AnyRefMap.*:s"),
+
       scalastyleCheck := Def.task {
         val _ = (scalastyle in Compile).toTask("").value
         (scalastyle in Test).toTask("").value
@@ -1816,17 +1838,7 @@ object Build {
       /* Silence a Scala 2.13.13+ warning that we cannot address without breaking our API.
        * See `js.WrappedDictionary.keys` and `js.WrappedMap.keys`.
        */
-      scalacOptions ++= {
-        /* We only need the option in 2.13.13+, but listing all previous 2.13.x
-         * versions is cumberson. We only exclude 2.13.0 and 2.13.1 because
-         * they did not support -Wconf at all.
-         */
-        val v = scalaVersion.value
-        if (v.startsWith("2.13.") && v != "2.13.0" && v != "2.13.1")
-          List("-Wconf:msg=overriding method keys in trait MapOps is deprecated:s")
-        else
-          Nil
-      },
+      addWconfSettingIf2_13("msg=overriding method keys in trait MapOps is deprecated:s"),
 
       test in Test := {
         streams.value.log.warn("Skipping library/test. Run testSuite/test to test library.")

From 23032648f150b572bb5d45c2cb7628957a15acdf Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Sun, 29 Dec 2024 13:00:33 +0100
Subject: [PATCH 230/298] Refactoring: Introduce
 LocalScope{Transfomer,Traverser}.

In several places, we transform or traverse (part of) a method body
in a way that is dependent on the local scope. In those situations,
we must stop at `Closure` boundaries.

We now introduce dedicated subclasses that handle this particular
behavior. This factors out the correct handling of `Closure`s, and
at the same time makes the intent clearer.

One use of `Traverser` in `OptimizerCore` did not handle `Closure`s
in a special way, but it should also be about the local scope.
---
 .../org/scalajs/nscplugin/GenJSCode.scala      | 18 +++---------------
 .../scala/org/scalajs/ir/Transformers.scala    | 15 +++++++++++++++
 .../main/scala/org/scalajs/ir/Traversers.scala | 14 ++++++++++++++
 .../frontend/optimizer/OptimizerCore.scala     |  2 +-
 4 files changed, 33 insertions(+), 16 deletions(-)

diff --git a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
index 5d393dfa47..cccd431460 100644
--- a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
+++ b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
@@ -1108,16 +1108,10 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
         }
 
         // After the super call, substitute `selfRef` for `this`
-        val afterSuper = new ir.Transformers.Transformer {
+        val afterSuper = new ir.Transformers.LocalScopeTransformer {
           override def transform(tree: js.Tree): js.Tree = tree match {
             case js.This() =>
               selfRef(tree.pos)
-
-            // Don't traverse closure boundaries
-            case closure: js.Closure =>
-              val newCaptureValues = transformTrees(closure.captureValues)
-              closure.copy(captureValues = newCaptureValues)(closure.pos)
-
             case tree =>
               super.transform(tree)
           }
@@ -2171,14 +2165,11 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
       } yield {
         js.ParamDef(name, originalName, ptpe, newMutable(name.name, mutable))(p.pos)
       }
-      val transformer = new ir.Transformers.Transformer {
+      val transformer = new ir.Transformers.LocalScopeTransformer {
         override def transform(tree: js.Tree): js.Tree = tree match {
           case js.VarDef(name, originalName, vtpe, mutable, rhs) =>
             super.transform(js.VarDef(name, originalName, vtpe,
                 newMutable(name.name, mutable), rhs)(tree.pos))
-          case js.Closure(arrow, captureParams, params, restParam, body, captureValues) =>
-            js.Closure(arrow, captureParams, params, restParam, body,
-                transformTrees(captureValues))(tree.pos)
           case _ =>
             super.transform(tree)
         }
@@ -2207,13 +2198,10 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
       } yield {
         js.ParamDef(name, originalName, newType(name.name, ptpe), mutable)(p.pos)
       }
-      val transformer = new ir.Transformers.Transformer {
+      val transformer = new ir.Transformers.LocalScopeTransformer {
         override def transform(tree: js.Tree): js.Tree = tree match {
           case tree @ js.VarRef(name) =>
             js.VarRef(name)(newType(name, tree.tpe))(tree.pos)
-          case js.Closure(arrow, captureParams, params, restParam, body, captureValues) =>
-            js.Closure(arrow, captureParams, params, restParam, body,
-                transformTrees(captureValues))(tree.pos)
           case _ =>
             super.transform(tree)
         }
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Transformers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Transformers.scala
index 82617dfd01..bbc0c3350b 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Transformers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Transformers.scala
@@ -277,4 +277,19 @@ object Transformers {
     }
   }
 
+  /** Transformer that only transforms in the local scope.
+   *
+   *  In practice, this means stopping at `Closure` boundaries: their
+   *  `captureValues` are transformed, but not their other members.
+   */
+  abstract class LocalScopeTransformer extends Transformer {
+    override def transform(tree: Tree): Tree = tree match {
+      case Closure(arrow, captureParams, params, restParam, body, captureValues) =>
+        Closure(arrow, captureParams, params, restParam, body,
+            transformTrees(captureValues))(tree.pos)
+      case _ =>
+        super.transform(tree)
+    }
+  }
+
 }
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Traversers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Traversers.scala
index 3edb2ac178..232014750e 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Traversers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Traversers.scala
@@ -245,4 +245,18 @@ object Traversers {
     }
   }
 
+  /** Traverser that only traverses the local scope.
+   *
+   *  In practice, this means stopping at `Closure` boundaries: their
+   *  `captureValues` are traversed, but not their other members.
+   */
+  abstract class LocalScopeTraverser extends Traverser {
+    override def traverse(tree: Tree): Unit = tree match {
+      case Closure(_, _, _, _, _, captureValues) =>
+        captureValues.foreach(traverse(_))
+      case _ =>
+        super.traverse(tree)
+    }
+  }
+
 }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
index 5f275ea841..584e269323 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
@@ -1713,7 +1713,7 @@ private[optimizer] abstract class OptimizerCore(
   private def tryInsertAtFirstEvalContext(valName: LocalName, valTree: Tree, body: Tree): Option[Tree] = {
     import EvalContextInsertion._
 
-    object valTreeInfo extends Traversers.Traverser {
+    object valTreeInfo extends Traversers.LocalScopeTraverser {
       val mutatedLocalVars = mutable.Set.empty[LocalName]
 
       traverse(valTree)

From edc13a8f02c10e36eb151549aa790ad17a3c0804 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Sun, 29 Dec 2024 14:42:55 +0100
Subject: [PATCH 231/298] Drop support for Scala 2.12.{2-5}.

These were the 2.12.x versions for which we still had some custom
code paths, workarounds or exceptions lying around.

Scala 2.12.2 and 2.12.3 exhibited compiler crashes on recent
changes in the linker, which triggered this decision.
---
 Jenkinsfile                                   |   3 -
 .../scalajs/nscplugin/CompatComponent.scala   |   5 -
 .../org/scalajs/nscplugin/GenJSCode.scala     |  10 +-
 .../nscplugin/test/JSInteropTest.scala        |   4 -
 ...icForwardersWarningsTopLevelOnlyTest.scala |  22 +--
 .../src/main/scala/org/scalajs/ir/Trees.scala |   8 +-
 .../linker/backend/javascript/Trees.scala     |   8 +-
 project/Build.scala                           |  16 --
 project/JavalibIRCleaner.scala                |  32 ----
 .../resources/2.12.1/BlacklistedTests.txt     | 117 ---------------
 .../resources/2.12.2/BlacklistedTests.txt     | 124 ----------------
 .../resources/2.12.3/BlacklistedTests.txt     | 130 ----------------
 .../resources/2.12.4/BlacklistedTests.txt     | 132 -----------------
 .../resources/2.12.5/BlacklistedTests.txt     | 139 ------------------
 .../testsuite/compiler/RegressionTest.scala   |  13 --
 15 files changed, 17 insertions(+), 746 deletions(-)
 delete mode 100644 scala-test-suite/src/test/resources/2.12.1/BlacklistedTests.txt
 delete mode 100644 scala-test-suite/src/test/resources/2.12.2/BlacklistedTests.txt
 delete mode 100644 scala-test-suite/src/test/resources/2.12.3/BlacklistedTests.txt
 delete mode 100644 scala-test-suite/src/test/resources/2.12.4/BlacklistedTests.txt
 delete mode 100644 scala-test-suite/src/test/resources/2.12.5/BlacklistedTests.txt

diff --git a/Jenkinsfile b/Jenkinsfile
index 921ac4915f..aaa2897fbc 100644
--- a/Jenkinsfile
+++ b/Jenkinsfile
@@ -546,9 +546,6 @@ allJavaVersions << mainJavaVersion
 def mainScalaVersion = "2.12.19"
 def mainScalaVersions = ["2.12.19", "2.13.13"]
 def otherScalaVersions = [
-  "2.12.2",
-  "2.12.3",
-  "2.12.5",
   "2.12.6",
   "2.12.7",
   "2.12.8",
diff --git a/compiler/src/main/scala/org/scalajs/nscplugin/CompatComponent.scala b/compiler/src/main/scala/org/scalajs/nscplugin/CompatComponent.scala
index af59c2b4d0..2c8951a67f 100644
--- a/compiler/src/main/scala/org/scalajs/nscplugin/CompatComponent.scala
+++ b/compiler/src/main/scala/org/scalajs/nscplugin/CompatComponent.scala
@@ -71,11 +71,6 @@ trait CompatComponent {
 
   lazy val DottyEnumSingletonCompat = AttachmentsCompat.Inner.DottyEnumSingletonAlias
 
-  implicit final class SAMFunctionCompatOps(self: SAMFunction) {
-    // Introduced in 2.12.5 to synthesize bridges in LMF classes
-    def synthCls: Symbol = NoSymbol
-  }
-
   /* global.genBCode.bTypes.initializeCoreBTypes()
    * Early 2.12.x versions require that this method be called from
    * GenJSCode.run(), but it disappeared later in the 2.12.x series.
diff --git a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
index 5d393dfa47..fc31a97bb7 100644
--- a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
+++ b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
@@ -6605,16 +6605,10 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
 
         /* scala/bug#10512: any methods which `samInfo.sam` overrides need
          * bridges made for them.
-         * On Scala < 2.12.5, `synthCls` is polyfilled to `NoSymbol` and hence
-         * `samBridges` will always be empty. This causes our compiler to be
-         * bug-compatible on these versions.
          */
-        val synthCls = samInfo.synthCls
-        val samBridges = if (synthCls == NoSymbol) {
-          Nil
-        } else {
+        val samBridges = {
           import scala.reflect.internal.Flags.BRIDGE
-          synthCls.info.findMembers(excludedFlags = 0L, requiredFlags = BRIDGE).toList
+          samInfo.synthCls.info.findMembers(excludedFlags = 0L, requiredFlags = BRIDGE).toList
         }
 
         for (sam <- samInfo.sam :: samBridges) {
diff --git a/compiler/src/test/scala/org/scalajs/nscplugin/test/JSInteropTest.scala b/compiler/src/test/scala/org/scalajs/nscplugin/test/JSInteropTest.scala
index 582aba2f40..907bf0c83e 100644
--- a/compiler/src/test/scala/org/scalajs/nscplugin/test/JSInteropTest.scala
+++ b/compiler/src/test/scala/org/scalajs/nscplugin/test/JSInteropTest.scala
@@ -4419,10 +4419,6 @@ class JSInteropTest extends DirectTest with TestHelpers {
 
     val postUnarySpace = {
       val hasNoSpace = {
-        version == "2.12.2" ||
-        version == "2.12.3" ||
-        version == "2.12.4" ||
-        version == "2.12.5" ||
         version == "2.12.6" ||
         version == "2.12.7" ||
         version == "2.12.8" ||
diff --git a/compiler/src/test/scala/org/scalajs/nscplugin/test/StaticForwardersWarningsTopLevelOnlyTest.scala b/compiler/src/test/scala/org/scalajs/nscplugin/test/StaticForwardersWarningsTopLevelOnlyTest.scala
index e0781dcf1b..1b2438655e 100644
--- a/compiler/src/test/scala/org/scalajs/nscplugin/test/StaticForwardersWarningsTopLevelOnlyTest.scala
+++ b/compiler/src/test/scala/org/scalajs/nscplugin/test/StaticForwardersWarningsTopLevelOnlyTest.scala
@@ -24,22 +24,6 @@ class StaticForwardersWarningsTopLevelOnlyTest extends DirectTest with TestHelpe
 
   @Test
   def warnWhenAvoidingStaticForwardersForTopLevelObject: Unit = {
-    val jvmBackendIssuesWarningOfItsOwn = {
-      scalaVersion != "2.12.2" &&
-      scalaVersion != "2.12.3" &&
-      scalaVersion != "2.12.4"
-    }
-    val jvmBackendMessage = if (!jvmBackendIssuesWarningOfItsOwn) {
-      ""
-    } else {
-      """
-        |newSource1.scala:4: warning: Generated class a differs only in case from A.
-        |  Such classes will overwrite one another on case-insensitive filesystems.
-        |    object a {
-        |           ^
-      """
-    }
-
     """
     class A
 
@@ -50,7 +34,11 @@ class StaticForwardersWarningsTopLevelOnlyTest extends DirectTest with TestHelpe
     s"""
       |newSource1.scala:4: warning: Not generating the static forwarders of a because its name differs only in case from the name of another class or trait in this compilation unit.
       |    object a {
-      |           ^$jvmBackendMessage
+      |           ^
+      |newSource1.scala:4: warning: Generated class a differs only in case from A.
+      |  Such classes will overwrite one another on case-insensitive filesystems.
+      |    object a {
+      |           ^
     """
   }
 
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala b/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
index 7fc574d991..e75ab17925 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
@@ -20,9 +20,11 @@ import Position.NoPosition
 import Types._
 
 object Trees {
-  /* The case classes for IR Nodes are sealed instead of final because making
-   * them final triggers bugs with Scala 2.12.{1-4}, in combination
-   * with their `implicit val pos`.
+  /* The case classes for IR Nodes are sealed instead of final for historical
+   * reasons. Making them final used to trigger bugs with Scala 2.12.{1-4}, in
+   * combination with their `implicit val pos`.
+   * TODO Now that we dropped support for Scala 2.12.5 and below, we should
+   * revisit this.
    */
 
   /** Base class for all nodes in the IR.
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Trees.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Trees.scala
index 2ad5d6658f..d0117dede1 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Trees.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Trees.scala
@@ -22,9 +22,11 @@ import org.scalajs.ir.OriginalName.NoOriginalName
 import org.scalajs.ir.Position.NoPosition
 
 object Trees {
-  /* The case classes for JS Trees are sealed instead of final because making
-   * them final triggers bugs with 2.12.{1-4}, in combination
-   * with their `implicit val pos`.
+  /* The case classes for JS Trees are sealed instead of final for historical
+   * reasons. Making them final used to trigger bugs with Scala 2.12.{1-4}, in
+   * combination with their `implicit val pos`.
+   * TODO Now that we dropped support for Scala 2.12.5 and below, we should
+   * revisit this.
    */
 
   /** AST node of JavaScript. */
diff --git a/project/Build.scala b/project/Build.scala
index d7f7f5e234..5c1c69e528 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -950,9 +950,6 @@ object Build {
 
   val thisBuildSettings = Def.settings(
       cross212ScalaVersions := Seq(
-        "2.12.2",
-        "2.12.3",
-        "2.12.5",
         "2.12.6",
         "2.12.7",
         "2.12.8",
@@ -2149,19 +2146,6 @@ object Build {
         includeIf(sharedTestDir / "require-jdk21", javaV >= 21) :::
         includeIf(testDir / "require-scala2", isJSTest)
       },
-
-      sources in Test := {
-        val allSources = (sources in Test).value
-        val scalaV = scalaVersion.value
-
-        val hasBugWithOverriddenMethods =
-          Set("2.12.2", "2.12.3", "2.12.4").contains(scalaV)
-
-        if (hasBugWithOverriddenMethods)
-          allSources.filter(_.getName != "SAMWithOverridingBridgesTest.scala")
-        else
-          allSources
-      }
   )
 
   def testSuiteBootstrapSetting(testSuiteLinker: Project) = Def.settings(
diff --git a/project/JavalibIRCleaner.scala b/project/JavalibIRCleaner.scala
index 6f014a4e93..d2f4be2881 100644
--- a/project/JavalibIRCleaner.scala
+++ b/project/JavalibIRCleaner.scala
@@ -356,33 +356,6 @@ final class JavalibIRCleaner(baseDirectoryURI: URI) {
               JSUnaryOp(JSUnaryOp.!, JSUnaryOp(JSUnaryOp.!, arg)),
               BooleanType)
 
-        // s"..." interpolator in 2.12.2 up to 2.12.4
-        case Apply(
-            ApplyFlags.empty,
-            New(StringContextClass, MethodIdent(`stringContextCtorMethodName`),
-                List(ScalaVarArgsReadOnlyLiteral(stringElems))),
-            MethodIdent(`sMethodName`),
-            List(ScalaVarArgsReadOnlyLiteral(valueElems))) =>
-          if (stringElems.size != valueElems.size + 1) {
-            reportError("Found s\"...\" interpolator but the sizes do not match")
-            tree
-          } else {
-            val processedEscapesStringElems = stringElems.map { s =>
-              (s: @unchecked) match {
-                case StringLiteral(value) =>
-                  StringLiteral(StringContext.processEscapes(value))
-              }
-            }
-            val stringsIter = processedEscapesStringElems.iterator
-            val valuesIter = valueElems.iterator
-            var result: Tree = stringsIter.next()
-            while (valuesIter.hasNext) {
-              result = BinaryOp(BinaryOp.String_+, result, valuesIter.next())
-              result = BinaryOp(BinaryOp.String_+, result, stringsIter.next())
-            }
-            result
-          }
-
         // LinkingInfo
         // Must stay in sync with the definitions in `scala.scalajs.LinkingInfo`
         case IntrinsicCall(LinkingInfoClass, `esVersionMethodName`, Nil) =>
@@ -649,7 +622,6 @@ object JavalibIRCleaner {
   private val ReadOnlySeq = ClassName("scala.collection.Seq")
   private val ScalaSerializable = ClassName("scala.Serializable")
   private val ScalaJSRuntimeMod = ClassName("scala.scalajs.runtime.package$")
-  private val StringContextClass = ClassName("scala.StringContext")
   private val UnionType = ClassName("scala.scalajs.js.$bar")
   private val UnionTypeMod = ClassName("scala.scalajs.js.$bar$")
   private val UnionTypeEvidence = ClassName("scala.scalajs.js.$bar$Evidence")
@@ -671,10 +643,6 @@ object JavalibIRCleaner {
     MethodName("jsArrayOps", List(ClassRef(JSArray)), ClassRef(JSArrayOps))
   private val number2dynamicMethodName =
     MethodName("number2dynamic", List(DoubleRef), ClassRef(JSDynamic))
-  private val sMethodName =
-    MethodName("s", List(ClassRef(ReadOnlySeq)), ClassRef(BoxedStringClass))
-  private val stringContextCtorMethodName =
-    MethodName.constructor(List(ClassRef(ReadOnlySeq)))
   private val toImmutableSeqExtensionMethodName =
     MethodName("toSeq$extension", List(ClassRef(JSArray)), ClassRef(ImmutableSeq))
   private val toJSVarArgsImmutableMethodName =
diff --git a/scala-test-suite/src/test/resources/2.12.1/BlacklistedTests.txt b/scala-test-suite/src/test/resources/2.12.1/BlacklistedTests.txt
deleted file mode 100644
index 94059d76c2..0000000000
--- a/scala-test-suite/src/test/resources/2.12.1/BlacklistedTests.txt
+++ /dev/null
@@ -1,117 +0,0 @@
-## Do not compile
-scala/lang/annotations/BytecodeTest.scala
-scala/lang/annotations/RunTest.scala
-scala/lang/traits/BytecodeTest.scala
-scala/lang/traits/RunTest.scala
-scala/lang/primitives/NaNTest.scala
-scala/lang/primitives/BoxUnboxTest.scala
-scala/reflect/ClassOfTest.scala
-scala/reflect/QTest.scala
-scala/reflect/io/ZipArchiveTest.scala
-scala/reflect/internal/util/AbstractFileClassLoaderTest.scala
-scala/reflect/internal/util/SourceFileTest.scala
-scala/reflect/internal/util/StringOpsTest.scala
-scala/reflect/internal/PrintersTest.scala
-scala/reflect/internal/ScopeTest.scala
-scala/reflect/internal/TreeGenTest.scala
-scala/reflect/internal/TypesTest.scala
-scala/reflect/internal/util/WeakHashSetTest.scala
-scala/reflect/internal/MirrorsTest.scala
-scala/reflect/internal/NamesTest.scala
-scala/tools/nsc/backend/jvm/BTypesTest.scala
-scala/tools/nsc/backend/jvm/BytecodeTest.scala
-scala/tools/nsc/backend/jvm/DefaultMethodTest.scala
-scala/tools/nsc/backend/jvm/DirectCompileTest.scala
-scala/tools/nsc/backend/jvm/IndyLambdaTest.scala
-scala/tools/nsc/backend/jvm/IndySammyTest.scala
-scala/tools/nsc/backend/jvm/OptimizedBytecodeTest.scala
-scala/tools/nsc/backend/jvm/StringConcatTest.scala
-scala/tools/nsc/backend/jvm/analysis/NullnessAnalyzerTest.scala
-scala/tools/nsc/backend/jvm/analysis/ProdConsAnalyzerTest.scala
-scala/tools/nsc/backend/jvm/opt/AnalyzerTest.scala
-scala/tools/nsc/backend/jvm/opt/BTypesFromClassfileTest.scala
-scala/tools/nsc/backend/jvm/opt/CallGraphTest.scala
-scala/tools/nsc/backend/jvm/opt/ClosureOptimizerTest.scala
-scala/tools/nsc/backend/jvm/opt/CompactLocalVariablesTest.scala
-scala/tools/nsc/backend/jvm/opt/EmptyExceptionHandlersTest.scala
-scala/tools/nsc/backend/jvm/opt/EmptyLabelsAndLineNumbersTest.scala
-scala/tools/nsc/backend/jvm/opt/InlineInfoTest.scala
-scala/tools/nsc/backend/jvm/opt/InlinerIllegalAccessTest.scala
-scala/tools/nsc/backend/jvm/opt/InlinerSeparateCompilationTest.scala
-scala/tools/nsc/backend/jvm/opt/InlinerTest.scala
-scala/tools/nsc/backend/jvm/opt/InlineWarningTest.scala
-scala/tools/nsc/backend/jvm/opt/MethodLevelOptsTest.scala
-scala/tools/nsc/backend/jvm/opt/ScalaInlineInfoTest.scala
-scala/tools/nsc/backend/jvm/opt/SimplifyJumpsTest.scala
-scala/tools/nsc/backend/jvm/opt/UnreachableCodeTest.scala
-scala/tools/nsc/backend/jvm/opt/UnusedLocalVariablesTest.scala
-scala/tools/nsc/ScriptRunnerTest.scala
-scala/tools/nsc/classpath/AggregateClassPathTest.scala
-scala/tools/nsc/classpath/PathResolverBaseTest.scala
-scala/tools/nsc/classpath/VirtualDirectoryClassPathTest.scala
-scala/tools/nsc/doc/html/HtmlDocletTest.scala
-scala/tools/nsc/interpreter/CompletionTest.scala
-scala/tools/nsc/interpreter/ScriptedTest.scala
-scala/tools/nsc/interpreter/TabulatorTest.scala
-scala/tools/nsc/settings/ScalaVersionTest.scala
-scala/tools/nsc/settings/SettingsTest.scala
-scala/tools/nsc/symtab/CannotHaveAttrsTest.scala
-scala/tools/nsc/symtab/FlagsTest.scala
-scala/tools/nsc/symtab/FreshNameExtractorTest.scala
-scala/tools/nsc/symtab/StdNamesTest.scala
-scala/tools/nsc/symtab/SymbolTableForUnitTesting.scala
-scala/tools/nsc/symtab/SymbolTableTest.scala
-scala/tools/nsc/transform/delambdafy/DelambdafyTest.scala
-scala/tools/nsc/transform/patmat/SolvingTest.scala
-scala/tools/nsc/transform/patmat/PatmatBytecodeTest.scala
-scala/tools/nsc/util/StackTraceTest.scala
-scala/tools/testing/BytecodeTesting.scala
-scala/tools/testing/RunTesting.scala
-scala/util/matching/RegexTest.scala
-
-## Do not link
-scala/PartialFunctionSerializationTest.scala
-scala/lang/stringinterpol/StringContextTest.scala
-scala/collection/IteratorTest.scala
-scala/collection/NewBuilderTest.scala
-scala/collection/ParallelConsistencyTest.scala
-scala/collection/SeqViewTest.scala
-scala/collection/SetMapConsistencyTest.scala
-scala/collection/convert/WrapperSerializationTest.scala
-scala/collection/immutable/ListTest.scala
-scala/collection/immutable/StreamTest.scala
-scala/collection/immutable/StringLikeTest.scala
-scala/collection/mutable/ArrayBufferTest.scala
-scala/collection/mutable/MutableListTest.scala
-scala/collection/mutable/OpenHashMapTest.scala
-scala/collection/mutable/PriorityQueueTest.scala
-scala/collection/parallel/immutable/ParRangeTest.scala
-scala/concurrent/duration/SerializationTest.scala
-scala/concurrent/impl/DefaultPromiseTest.scala
-scala/io/SourceTest.scala
-scala/runtime/ScalaRunTimeTest.scala
-scala/sys/process/PipedProcessTest.scala
-scala/sys/process/ProcessTest.scala
-scala/tools/testing/AssertUtilTest.scala
-scala/tools/testing/AssertThrowsTest.scala
-scala/util/SpecVersionTest.scala
-scala/util/SystemPropertiesTest.scala
-
-## Tests fail
-
-# Reflection
-scala/reflect/ClassTagTest.scala
-
-# Require strict-floats
-scala/math/BigDecimalTest.scala
-
-# Test fails only some times with
-#   'set scalaJSLinkerConfig in scalaTestSuite ~= (_.withOptimizer(false))'
-scala/collection/immutable/PagedSeqTest.scala
-
-# Bugs
-scala/collection/convert/MapWrapperTest.scala
-
-# Tests passed but are too slow (timeouts)
-scala/collection/immutable/ListSetTest.scala
-scala/util/SortingTest.scala
diff --git a/scala-test-suite/src/test/resources/2.12.2/BlacklistedTests.txt b/scala-test-suite/src/test/resources/2.12.2/BlacklistedTests.txt
deleted file mode 100644
index 7ab77797a7..0000000000
--- a/scala-test-suite/src/test/resources/2.12.2/BlacklistedTests.txt
+++ /dev/null
@@ -1,124 +0,0 @@
-## Do not compile
-scala/lang/annotations/BytecodeTest.scala
-scala/lang/annotations/RunTest.scala
-scala/lang/traits/BytecodeTest.scala
-scala/lang/traits/RunTest.scala
-scala/lang/primitives/NaNTest.scala
-scala/lang/primitives/BoxUnboxTest.scala
-scala/reflect/ClassOfTest.scala
-scala/reflect/QTest.scala
-scala/reflect/io/ZipArchiveTest.scala
-scala/reflect/internal/util/AbstractFileClassLoaderTest.scala
-scala/reflect/internal/util/SourceFileTest.scala
-scala/reflect/internal/util/StringOpsTest.scala
-scala/reflect/internal/PrintersTest.scala
-scala/reflect/internal/ScopeTest.scala
-scala/reflect/internal/TreeGenTest.scala
-scala/reflect/internal/TypesTest.scala
-scala/reflect/internal/util/WeakHashSetTest.scala
-scala/reflect/internal/MirrorsTest.scala
-scala/reflect/internal/NamesTest.scala
-scala/tools/nsc/backend/jvm/BTypesTest.scala
-scala/tools/nsc/backend/jvm/BytecodeTest.scala
-scala/tools/nsc/backend/jvm/DefaultMethodTest.scala
-scala/tools/nsc/backend/jvm/DirectCompileTest.scala
-scala/tools/nsc/backend/jvm/IndyLambdaTest.scala
-scala/tools/nsc/backend/jvm/IndySammyTest.scala
-scala/tools/nsc/backend/jvm/OptimizedBytecodeTest.scala
-scala/tools/nsc/backend/jvm/StringConcatTest.scala
-scala/tools/nsc/backend/jvm/analysis/NullnessAnalyzerTest.scala
-scala/tools/nsc/backend/jvm/analysis/ProdConsAnalyzerTest.scala
-scala/tools/nsc/backend/jvm/opt/AnalyzerTest.scala
-scala/tools/nsc/backend/jvm/opt/BTypesFromClassfileTest.scala
-scala/tools/nsc/backend/jvm/opt/CallGraphTest.scala
-scala/tools/nsc/backend/jvm/opt/ClosureOptimizerTest.scala
-scala/tools/nsc/backend/jvm/opt/CompactLocalVariablesTest.scala
-scala/tools/nsc/backend/jvm/opt/EmptyExceptionHandlersTest.scala
-scala/tools/nsc/backend/jvm/opt/EmptyLabelsAndLineNumbersTest.scala
-scala/tools/nsc/backend/jvm/opt/InlineInfoTest.scala
-scala/tools/nsc/backend/jvm/opt/InlinerIllegalAccessTest.scala
-scala/tools/nsc/backend/jvm/opt/InlinerSeparateCompilationTest.scala
-scala/tools/nsc/backend/jvm/opt/InlinerTest.scala
-scala/tools/nsc/backend/jvm/opt/InlineWarningTest.scala
-scala/tools/nsc/backend/jvm/opt/MethodLevelOptsTest.scala
-scala/tools/nsc/backend/jvm/opt/ScalaInlineInfoTest.scala
-scala/tools/nsc/backend/jvm/opt/SimplifyJumpsTest.scala
-scala/tools/nsc/backend/jvm/opt/UnreachableCodeTest.scala
-scala/tools/nsc/backend/jvm/opt/UnusedLocalVariablesTest.scala
-scala/tools/nsc/ScriptRunnerTest.scala
-scala/tools/nsc/classpath/AggregateClassPathTest.scala
-scala/tools/nsc/classpath/JrtClassPathTest.scala
-scala/tools/nsc/classpath/PathResolverBaseTest.scala
-scala/tools/nsc/classpath/VirtualDirectoryClassPathTest.scala
-scala/tools/nsc/doc/html/HtmlDocletTest.scala
-scala/tools/nsc/interpreter/CompletionTest.scala
-scala/tools/nsc/interpreter/ScriptedTest.scala
-scala/tools/nsc/interpreter/TabulatorTest.scala
-scala/tools/nsc/reporters/ConsoleReporterTest.scala
-scala/tools/nsc/settings/ScalaVersionTest.scala
-scala/tools/nsc/settings/SettingsTest.scala
-scala/tools/nsc/symtab/CannotHaveAttrsTest.scala
-scala/tools/nsc/symtab/FlagsTest.scala
-scala/tools/nsc/symtab/FreshNameExtractorTest.scala
-scala/tools/nsc/symtab/StdNamesTest.scala
-scala/tools/nsc/symtab/SymbolTableForUnitTesting.scala
-scala/tools/nsc/symtab/SymbolTableTest.scala
-scala/tools/nsc/transform/delambdafy/DelambdafyTest.scala
-scala/tools/nsc/transform/patmat/SolvingTest.scala
-scala/tools/nsc/transform/patmat/PatmatBytecodeTest.scala
-scala/tools/nsc/typechecker/Implicits.scala
-scala/tools/nsc/util/StackTraceTest.scala
-scala/tools/testing/BytecodeTesting.scala
-scala/tools/testing/RunTesting.scala
-scala/util/matching/RegexTest.scala
-
-## Do not link
-scala/PartialFunctionSerializationTest.scala
-scala/lang/stringinterpol/StringContextTest.scala
-scala/collection/IteratorTest.scala
-scala/collection/NewBuilderTest.scala
-scala/collection/ParallelConsistencyTest.scala
-scala/collection/SeqViewTest.scala
-scala/collection/SetMapConsistencyTest.scala
-scala/collection/concurrent/TrieMapTest.scala
-scala/collection/convert/WrapperSerializationTest.scala
-scala/collection/immutable/ListTest.scala
-scala/collection/immutable/StreamTest.scala
-scala/collection/immutable/StringLikeTest.scala
-scala/collection/mutable/ArrayBufferTest.scala
-scala/collection/mutable/MutableListTest.scala
-scala/collection/mutable/OpenHashMapTest.scala
-scala/collection/mutable/PriorityQueueTest.scala
-scala/collection/parallel/immutable/ParRangeTest.scala
-scala/concurrent/duration/SerializationTest.scala
-scala/concurrent/impl/DefaultPromiseTest.scala
-scala/io/SourceTest.scala
-scala/runtime/ScalaRunTimeTest.scala
-scala/sys/process/PipedProcessTest.scala
-scala/sys/process/ProcessTest.scala
-scala/tools/testing/AssertUtilTest.scala
-scala/tools/testing/AssertThrowsTest.scala
-scala/util/SpecVersionTest.scala
-scala/util/SystemPropertiesTest.scala
-
-## Tests fail
-
-# Reflection
-scala/reflect/ClassTagTest.scala
-
-# Require strict-floats
-scala/math/BigDecimalTest.scala
-
-# Difference of getClass() on primitive values
-scala/collection/immutable/RangeTest.scala
-
-# Test fails only some times with
-#   'set scalaJSLinkerConfig in scalaTestSuite ~= (_.withOptimizer(false))'
-scala/collection/immutable/PagedSeqTest.scala
-
-# Bugs
-scala/collection/convert/MapWrapperTest.scala
-
-# Tests passed but are too slow (timeouts)
-scala/collection/immutable/ListSetTest.scala
-scala/util/SortingTest.scala
diff --git a/scala-test-suite/src/test/resources/2.12.3/BlacklistedTests.txt b/scala-test-suite/src/test/resources/2.12.3/BlacklistedTests.txt
deleted file mode 100644
index 3f06cda42a..0000000000
--- a/scala-test-suite/src/test/resources/2.12.3/BlacklistedTests.txt
+++ /dev/null
@@ -1,130 +0,0 @@
-## Do not compile
-scala/lang/annotations/BytecodeTest.scala
-scala/lang/annotations/RunTest.scala
-scala/lang/traits/BytecodeTest.scala
-scala/lang/traits/RunTest.scala
-scala/lang/primitives/NaNTest.scala
-scala/lang/primitives/BoxUnboxTest.scala
-scala/reflect/ClassOfTest.scala
-scala/reflect/QTest.scala
-scala/reflect/io/ZipArchiveTest.scala
-scala/reflect/internal/util/AbstractFileClassLoaderTest.scala
-scala/reflect/internal/util/SourceFileTest.scala
-scala/reflect/internal/util/StringOpsTest.scala
-scala/reflect/internal/PrintersTest.scala
-scala/reflect/internal/ScopeTest.scala
-scala/reflect/internal/TreeGenTest.scala
-scala/reflect/internal/TypesTest.scala
-scala/reflect/internal/util/WeakHashSetTest.scala
-scala/reflect/internal/MirrorsTest.scala
-scala/reflect/internal/NamesTest.scala
-scala/tools/nsc/backend/jvm/BTypesTest.scala
-scala/tools/nsc/backend/jvm/BytecodeTest.scala
-scala/tools/nsc/backend/jvm/DefaultMethodTest.scala
-scala/tools/nsc/backend/jvm/DirectCompileTest.scala
-scala/tools/nsc/backend/jvm/GenericSignaturesTest.scala
-scala/tools/nsc/backend/jvm/IndyLambdaTest.scala
-scala/tools/nsc/backend/jvm/IndySammyTest.scala
-scala/tools/nsc/backend/jvm/InnerClassAttributeTest.scala
-scala/tools/nsc/backend/jvm/NestedClassesCollectorTest.scala
-scala/tools/nsc/backend/jvm/OptimizedBytecodeTest.scala
-scala/tools/nsc/backend/jvm/StringConcatTest.scala
-scala/tools/nsc/backend/jvm/analysis/NullnessAnalyzerTest.scala
-scala/tools/nsc/backend/jvm/analysis/ProdConsAnalyzerTest.scala
-scala/tools/nsc/backend/jvm/opt/AnalyzerTest.scala
-scala/tools/nsc/backend/jvm/opt/BTypesFromClassfileTest.scala
-scala/tools/nsc/backend/jvm/opt/CallGraphTest.scala
-scala/tools/nsc/backend/jvm/opt/ClosureOptimizerTest.scala
-scala/tools/nsc/backend/jvm/opt/CompactLocalVariablesTest.scala
-scala/tools/nsc/backend/jvm/opt/EmptyExceptionHandlersTest.scala
-scala/tools/nsc/backend/jvm/opt/EmptyLabelsAndLineNumbersTest.scala
-scala/tools/nsc/backend/jvm/opt/InlineInfoTest.scala
-scala/tools/nsc/backend/jvm/opt/InlinerIllegalAccessTest.scala
-scala/tools/nsc/backend/jvm/opt/InlinerSeparateCompilationTest.scala
-scala/tools/nsc/backend/jvm/opt/InlinerTest.scala
-scala/tools/nsc/backend/jvm/opt/InlineSourceMatcherTest.scala
-scala/tools/nsc/backend/jvm/opt/InlineWarningTest.scala
-scala/tools/nsc/backend/jvm/opt/MethodLevelOptsTest.scala
-scala/tools/nsc/backend/jvm/opt/ScalaInlineInfoTest.scala
-scala/tools/nsc/backend/jvm/opt/SimplifyJumpsTest.scala
-scala/tools/nsc/backend/jvm/opt/UnreachableCodeTest.scala
-scala/tools/nsc/backend/jvm/opt/UnusedLocalVariablesTest.scala
-scala/tools/nsc/ScriptRunnerTest.scala
-scala/tools/nsc/classpath/AggregateClassPathTest.scala
-scala/tools/nsc/classpath/JrtClassPathTest.scala
-scala/tools/nsc/classpath/PathResolverBaseTest.scala
-scala/tools/nsc/classpath/VirtualDirectoryClassPathTest.scala
-scala/tools/nsc/doc/html/HtmlDocletTest.scala
-scala/tools/nsc/interpreter/CompletionTest.scala
-scala/tools/nsc/interpreter/ScriptedTest.scala
-scala/tools/nsc/interpreter/TabulatorTest.scala
-scala/tools/nsc/reporters/ConsoleReporterTest.scala
-scala/tools/nsc/settings/ScalaVersionTest.scala
-scala/tools/nsc/settings/SettingsTest.scala
-scala/tools/nsc/symtab/CannotHaveAttrsTest.scala
-scala/tools/nsc/symtab/FlagsTest.scala
-scala/tools/nsc/symtab/FreshNameExtractorTest.scala
-scala/tools/nsc/symtab/StdNamesTest.scala
-scala/tools/nsc/symtab/SymbolTableForUnitTesting.scala
-scala/tools/nsc/symtab/SymbolTableTest.scala
-scala/tools/nsc/transform/delambdafy/DelambdafyTest.scala
-scala/tools/nsc/transform/patmat/SolvingTest.scala
-scala/tools/nsc/transform/patmat/PatmatBytecodeTest.scala
-scala/tools/nsc/typechecker/Implicits.scala
-scala/tools/nsc/util/StackTraceTest.scala
-scala/tools/testing/BytecodeTesting.scala
-scala/tools/testing/RunTesting.scala
-scala/util/matching/RegexTest.scala
-
-## Do not link
-scala/MatchErrorSerializationTest.scala
-scala/PartialFunctionSerializationTest.scala
-scala/lang/stringinterpol/StringContextTest.scala
-scala/collection/IteratorTest.scala
-scala/collection/NewBuilderTest.scala
-scala/collection/ParallelConsistencyTest.scala
-scala/collection/SeqViewTest.scala
-scala/collection/SetMapConsistencyTest.scala
-scala/collection/concurrent/TrieMapTest.scala
-scala/collection/convert/WrapperSerializationTest.scala
-scala/collection/immutable/ListTest.scala
-scala/collection/immutable/StreamTest.scala
-scala/collection/immutable/StringLikeTest.scala
-scala/collection/mutable/ArrayBufferTest.scala
-scala/collection/mutable/MutableListTest.scala
-scala/collection/mutable/OpenHashMapTest.scala
-scala/collection/mutable/PriorityQueueTest.scala
-scala/collection/parallel/immutable/ParRangeTest.scala
-scala/concurrent/duration/SerializationTest.scala
-scala/concurrent/impl/DefaultPromiseTest.scala
-scala/io/SourceTest.scala
-scala/runtime/ScalaRunTimeTest.scala
-scala/sys/process/PipedProcessTest.scala
-scala/sys/process/ProcessTest.scala
-scala/tools/testing/AssertUtilTest.scala
-scala/tools/testing/AssertThrowsTest.scala
-scala/util/SpecVersionTest.scala
-scala/util/SystemPropertiesTest.scala
-
-## Tests fail
-
-# Reflection
-scala/reflect/ClassTagTest.scala
-
-# Require strict-floats
-scala/math/BigDecimalTest.scala
-
-# Difference of getClass() on primitive values
-scala/collection/immutable/RangeTest.scala
-
-# Test fails only some times with
-#   'set scalaJSOptimizerOptions in scalaTestSuite ~= (_.withDisableOptimizer(true))'
-#   and' 'set scalaJSUseRhino in Global := false'
-scala/collection/immutable/PagedSeqTest.scala
-
-# Bugs
-scala/collection/convert/MapWrapperTest.scala
-
-# Tests passed but are too slow (timeouts)
-scala/collection/immutable/ListSetTest.scala
-scala/util/SortingTest.scala
diff --git a/scala-test-suite/src/test/resources/2.12.4/BlacklistedTests.txt b/scala-test-suite/src/test/resources/2.12.4/BlacklistedTests.txt
deleted file mode 100644
index 0ecca4009f..0000000000
--- a/scala-test-suite/src/test/resources/2.12.4/BlacklistedTests.txt
+++ /dev/null
@@ -1,132 +0,0 @@
-## Do not compile
-scala/lang/annotations/BytecodeTest.scala
-scala/lang/annotations/RunTest.scala
-scala/lang/traits/BytecodeTest.scala
-scala/lang/traits/RunTest.scala
-scala/lang/primitives/NaNTest.scala
-scala/lang/primitives/BoxUnboxTest.scala
-scala/reflect/ClassOfTest.scala
-scala/reflect/QTest.scala
-scala/reflect/io/ZipArchiveTest.scala
-scala/reflect/internal/util/AbstractFileClassLoaderTest.scala
-scala/reflect/internal/util/SourceFileTest.scala
-scala/reflect/internal/util/StringOpsTest.scala
-scala/reflect/internal/PrintersTest.scala
-scala/reflect/internal/ScopeTest.scala
-scala/reflect/internal/TreeGenTest.scala
-scala/reflect/internal/TypesTest.scala
-scala/reflect/internal/util/WeakHashSetTest.scala
-scala/reflect/internal/MirrorsTest.scala
-scala/reflect/internal/NamesTest.scala
-scala/tools/nsc/backend/jvm/BTypesTest.scala
-scala/tools/nsc/backend/jvm/BytecodeTest.scala
-scala/tools/nsc/backend/jvm/DefaultMethodTest.scala
-scala/tools/nsc/backend/jvm/DirectCompileTest.scala
-scala/tools/nsc/backend/jvm/GenericSignaturesTest.scala
-scala/tools/nsc/backend/jvm/IndyLambdaTest.scala
-scala/tools/nsc/backend/jvm/IndySammyTest.scala
-scala/tools/nsc/backend/jvm/InnerClassAttributeTest.scala
-scala/tools/nsc/backend/jvm/NestedClassesCollectorTest.scala
-scala/tools/nsc/backend/jvm/OptimizedBytecodeTest.scala
-scala/tools/nsc/backend/jvm/StringConcatTest.scala
-scala/tools/nsc/backend/jvm/analysis/NullnessAnalyzerTest.scala
-scala/tools/nsc/backend/jvm/analysis/ProdConsAnalyzerTest.scala
-scala/tools/nsc/backend/jvm/opt/AnalyzerTest.scala
-scala/tools/nsc/backend/jvm/opt/BoxUnboxTest.scala
-scala/tools/nsc/backend/jvm/opt/BTypesFromClassfileTest.scala
-scala/tools/nsc/backend/jvm/opt/CallGraphTest.scala
-scala/tools/nsc/backend/jvm/opt/ClosureOptimizerTest.scala
-scala/tools/nsc/backend/jvm/opt/CompactLocalVariablesTest.scala
-scala/tools/nsc/backend/jvm/opt/EmptyExceptionHandlersTest.scala
-scala/tools/nsc/backend/jvm/opt/EmptyLabelsAndLineNumbersTest.scala
-scala/tools/nsc/backend/jvm/opt/InlineInfoTest.scala
-scala/tools/nsc/backend/jvm/opt/InlinerIllegalAccessTest.scala
-scala/tools/nsc/backend/jvm/opt/InlinerSeparateCompilationTest.scala
-scala/tools/nsc/backend/jvm/opt/InlinerTest.scala
-scala/tools/nsc/backend/jvm/opt/InlineSourceMatcherTest.scala
-scala/tools/nsc/backend/jvm/opt/InlineWarningTest.scala
-scala/tools/nsc/backend/jvm/opt/MethodLevelOptsTest.scala
-scala/tools/nsc/backend/jvm/opt/ScalaInlineInfoTest.scala
-scala/tools/nsc/backend/jvm/opt/SimplifyJumpsTest.scala
-scala/tools/nsc/backend/jvm/opt/UnreachableCodeTest.scala
-scala/tools/nsc/backend/jvm/opt/UnusedLocalVariablesTest.scala
-scala/tools/nsc/ScriptRunnerTest.scala
-scala/tools/nsc/classpath/AggregateClassPathTest.scala
-scala/tools/nsc/classpath/JrtClassPathTest.scala
-scala/tools/nsc/classpath/PathResolverBaseTest.scala
-scala/tools/nsc/classpath/VirtualDirectoryClassPathTest.scala
-scala/tools/nsc/classpath/ZipAndJarFileLookupFactoryTest.scala
-scala/tools/nsc/doc/html/HtmlDocletTest.scala
-scala/tools/nsc/interpreter/CompletionTest.scala
-scala/tools/nsc/interpreter/ScriptedTest.scala
-scala/tools/nsc/interpreter/TabulatorTest.scala
-scala/tools/nsc/reporters/ConsoleReporterTest.scala
-scala/tools/nsc/settings/ScalaVersionTest.scala
-scala/tools/nsc/settings/SettingsTest.scala
-scala/tools/nsc/symtab/CannotHaveAttrsTest.scala
-scala/tools/nsc/symtab/FlagsTest.scala
-scala/tools/nsc/symtab/FreshNameExtractorTest.scala
-scala/tools/nsc/symtab/StdNamesTest.scala
-scala/tools/nsc/symtab/SymbolTableForUnitTesting.scala
-scala/tools/nsc/symtab/SymbolTableTest.scala
-scala/tools/nsc/transform/delambdafy/DelambdafyTest.scala
-scala/tools/nsc/transform/patmat/SolvingTest.scala
-scala/tools/nsc/transform/patmat/PatmatBytecodeTest.scala
-scala/tools/nsc/typechecker/Implicits.scala
-scala/tools/nsc/util/StackTraceTest.scala
-scala/tools/testing/BytecodeTesting.scala
-scala/tools/testing/RunTesting.scala
-scala/util/matching/RegexTest.scala
-
-## Do not link
-scala/MatchErrorSerializationTest.scala
-scala/PartialFunctionSerializationTest.scala
-scala/lang/stringinterpol/StringContextTest.scala
-scala/collection/IteratorTest.scala
-scala/collection/NewBuilderTest.scala
-scala/collection/ParallelConsistencyTest.scala
-scala/collection/SeqViewTest.scala
-scala/collection/SetMapConsistencyTest.scala
-scala/collection/concurrent/TrieMapTest.scala
-scala/collection/convert/WrapperSerializationTest.scala
-scala/collection/immutable/ListTest.scala
-scala/collection/immutable/StreamTest.scala
-scala/collection/immutable/StringLikeTest.scala
-scala/collection/mutable/ArrayBufferTest.scala
-scala/collection/mutable/MutableListTest.scala
-scala/collection/mutable/OpenHashMapTest.scala
-scala/collection/mutable/PriorityQueueTest.scala
-scala/collection/parallel/immutable/ParRangeTest.scala
-scala/concurrent/duration/SerializationTest.scala
-scala/concurrent/impl/DefaultPromiseTest.scala
-scala/io/SourceTest.scala
-scala/runtime/ScalaRunTimeTest.scala
-scala/sys/process/PipedProcessTest.scala
-scala/sys/process/ProcessTest.scala
-scala/tools/testing/AssertUtilTest.scala
-scala/tools/testing/AssertThrowsTest.scala
-scala/util/SpecVersionTest.scala
-scala/util/SystemPropertiesTest.scala
-
-## Tests fail
-
-# Reflection
-scala/reflect/ClassTagTest.scala
-
-# Require strict-floats
-scala/math/BigDecimalTest.scala
-
-# Difference of getClass() on primitive values
-scala/collection/immutable/RangeTest.scala
-
-# Test fails only some times with
-#   'set scalaJSOptimizerOptions in scalaTestSuite ~= (_.withDisableOptimizer(true))'
-#   and' 'set scalaJSUseRhino in Global := false'
-scala/collection/immutable/PagedSeqTest.scala
-
-# Bugs
-scala/collection/convert/MapWrapperTest.scala
-
-# Tests passed but are too slow (timeouts)
-scala/collection/immutable/ListSetTest.scala
-scala/util/SortingTest.scala
diff --git a/scala-test-suite/src/test/resources/2.12.5/BlacklistedTests.txt b/scala-test-suite/src/test/resources/2.12.5/BlacklistedTests.txt
deleted file mode 100644
index 6cef01dfa3..0000000000
--- a/scala-test-suite/src/test/resources/2.12.5/BlacklistedTests.txt
+++ /dev/null
@@ -1,139 +0,0 @@
-## Do not compile
-scala/lang/annotations/BytecodeTest.scala
-scala/lang/annotations/RunTest.scala
-scala/lang/traits/BytecodeTest.scala
-scala/lang/traits/RunTest.scala
-scala/lang/primitives/NaNTest.scala
-scala/lang/primitives/BoxUnboxTest.scala
-scala/reflect/ClassOfTest.scala
-scala/reflect/QTest.scala
-scala/reflect/io/AbstractFileTest.scala
-scala/reflect/io/ZipArchiveTest.scala
-scala/reflect/internal/util/AbstractFileClassLoaderTest.scala
-scala/reflect/internal/util/SourceFileTest.scala
-scala/reflect/internal/util/StringOpsTest.scala
-scala/reflect/internal/PrintersTest.scala
-scala/reflect/internal/ScopeTest.scala
-scala/reflect/internal/TreeGenTest.scala
-scala/reflect/internal/TypesTest.scala
-scala/reflect/internal/util/WeakHashSetTest.scala
-scala/reflect/internal/MirrorsTest.scala
-scala/reflect/internal/NamesTest.scala
-scala/tools/nsc/backend/jvm/BTypesTest.scala
-scala/tools/nsc/backend/jvm/BytecodeTest.scala
-scala/tools/nsc/backend/jvm/DefaultMethodTest.scala
-scala/tools/nsc/backend/jvm/DirectCompileTest.scala
-scala/tools/nsc/backend/jvm/GenericSignaturesTest.scala
-scala/tools/nsc/backend/jvm/IndyLambdaTest.scala
-scala/tools/nsc/backend/jvm/IndySammyTest.scala
-scala/tools/nsc/backend/jvm/InnerClassAttributeTest.scala
-scala/tools/nsc/backend/jvm/NestedClassesCollectorTest.scala
-scala/tools/nsc/backend/jvm/OptimizedBytecodeTest.scala
-scala/tools/nsc/backend/jvm/PerRunInitTest.scala
-scala/tools/nsc/backend/jvm/StringConcatTest.scala
-scala/tools/nsc/backend/jvm/analysis/NullnessAnalyzerTest.scala
-scala/tools/nsc/backend/jvm/analysis/ProdConsAnalyzerTest.scala
-scala/tools/nsc/backend/jvm/opt/AnalyzerTest.scala
-scala/tools/nsc/backend/jvm/opt/BoxUnboxTest.scala
-scala/tools/nsc/backend/jvm/opt/BTypesFromClassfileTest.scala
-scala/tools/nsc/backend/jvm/opt/CallGraphTest.scala
-scala/tools/nsc/backend/jvm/opt/ClosureOptimizerTest.scala
-scala/tools/nsc/backend/jvm/opt/CompactLocalVariablesTest.scala
-scala/tools/nsc/backend/jvm/opt/EmptyExceptionHandlersTest.scala
-scala/tools/nsc/backend/jvm/opt/EmptyLabelsAndLineNumbersTest.scala
-scala/tools/nsc/backend/jvm/opt/InlineInfoTest.scala
-scala/tools/nsc/backend/jvm/opt/InlinerIllegalAccessTest.scala
-scala/tools/nsc/backend/jvm/opt/InlinerSeparateCompilationTest.scala
-scala/tools/nsc/backend/jvm/opt/InlinerTest.scala
-scala/tools/nsc/backend/jvm/opt/InlineSourceMatcherTest.scala
-scala/tools/nsc/backend/jvm/opt/InlineWarningTest.scala
-scala/tools/nsc/backend/jvm/opt/MethodLevelOptsTest.scala
-scala/tools/nsc/backend/jvm/opt/ScalaInlineInfoTest.scala
-scala/tools/nsc/backend/jvm/opt/SimplifyJumpsTest.scala
-scala/tools/nsc/backend/jvm/opt/UnreachableCodeTest.scala
-scala/tools/nsc/backend/jvm/opt/UnusedLocalVariablesTest.scala
-scala/tools/nsc/ScriptRunnerTest.scala
-scala/tools/nsc/classpath/AggregateClassPathTest.scala
-scala/tools/nsc/classpath/JrtClassPathTest.scala
-scala/tools/nsc/classpath/MultiReleaseJarTest.scala
-scala/tools/nsc/classpath/PathResolverBaseTest.scala
-scala/tools/nsc/classpath/VirtualDirectoryClassPathTest.scala
-scala/tools/nsc/classpath/ZipAndJarFileLookupFactoryTest.scala
-scala/tools/nsc/doc/html/HtmlDocletTest.scala
-scala/tools/nsc/interpreter/CompletionTest.scala
-scala/tools/nsc/interpreter/ScriptedTest.scala
-scala/tools/nsc/interpreter/TabulatorTest.scala
-scala/tools/nsc/reporters/ConsoleReporterTest.scala
-scala/tools/nsc/settings/ScalaVersionTest.scala
-scala/tools/nsc/settings/SettingsTest.scala
-scala/tools/nsc/symtab/CannotHaveAttrsTest.scala
-scala/tools/nsc/symtab/FlagsTest.scala
-scala/tools/nsc/symtab/FreshNameExtractorTest.scala
-scala/tools/nsc/symtab/StdNamesTest.scala
-scala/tools/nsc/symtab/SymbolTableForUnitTesting.scala
-scala/tools/nsc/symtab/SymbolTableTest.scala
-scala/tools/nsc/transform/MixinTest.scala
-scala/tools/nsc/transform/delambdafy/DelambdafyTest.scala
-scala/tools/nsc/transform/patmat/SolvingTest.scala
-scala/tools/nsc/transform/patmat/PatmatBytecodeTest.scala
-scala/tools/nsc/typechecker/Implicits.scala
-scala/tools/nsc/typechecker/TypedTreeTest.scala
-scala/tools/nsc/util/StackTraceTest.scala
-scala/tools/testing/BytecodeTesting.scala
-scala/tools/testing/RunTesting.scala
-scala/util/matching/RegexTest.scala
-
-## Do not link
-scala/MatchErrorSerializationTest.scala
-scala/PartialFunctionSerializationTest.scala
-scala/lang/stringinterpol/StringContextTest.scala
-scala/collection/IteratorTest.scala
-scala/collection/NewBuilderTest.scala
-scala/collection/ParallelConsistencyTest.scala
-scala/collection/SeqViewTest.scala
-scala/collection/SetMapConsistencyTest.scala
-scala/collection/concurrent/TrieMapTest.scala
-scala/collection/convert/WrapperSerializationTest.scala
-scala/collection/immutable/ListTest.scala
-scala/collection/immutable/StreamTest.scala
-scala/collection/immutable/StringLikeTest.scala
-scala/collection/mutable/ArrayBufferTest.scala
-scala/collection/mutable/MutableListTest.scala
-scala/collection/mutable/OpenHashMapTest.scala
-scala/collection/mutable/PriorityQueueTest.scala
-scala/collection/parallel/TaskTest.scala
-scala/collection/parallel/immutable/ParRangeTest.scala
-scala/concurrent/FutureTest.scala
-scala/concurrent/duration/SerializationTest.scala
-scala/concurrent/impl/DefaultPromiseTest.scala
-scala/io/SourceTest.scala
-scala/runtime/ScalaRunTimeTest.scala
-scala/sys/process/PipedProcessTest.scala
-scala/sys/process/ProcessTest.scala
-scala/tools/testing/AssertUtilTest.scala
-scala/tools/testing/AssertThrowsTest.scala
-scala/util/SpecVersionTest.scala
-scala/util/SystemPropertiesTest.scala
-
-## Tests fail
-
-# Reflection
-scala/reflect/ClassTagTest.scala
-
-# Require strict-floats
-scala/math/BigDecimalTest.scala
-
-# Difference of getClass() on primitive values
-scala/collection/immutable/RangeTest.scala
-
-# Test fails only some times with
-#   'set scalaJSOptimizerOptions in scalaTestSuite ~= (_.withDisableOptimizer(true))'
-#   and' 'set scalaJSUseRhino in Global := false'
-scala/collection/immutable/PagedSeqTest.scala
-
-# Bugs
-scala/collection/convert/MapWrapperTest.scala
-
-# Tests passed but are too slow (timeouts)
-scala/collection/immutable/ListSetTest.scala
-scala/util/SortingTest.scala
diff --git a/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/RegressionTest.scala b/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/RegressionTest.scala
index 5ad32e6f30..6642451b5d 100644
--- a/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/RegressionTest.scala
+++ b/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/RegressionTest.scala
@@ -20,7 +20,6 @@ import org.junit.Assume._
 
 import org.scalajs.testsuite.utils.AssertThrows.{assertThrows, _}
 
-import org.scalajs.testsuite.utils.Platform
 import org.scalajs.testsuite.utils.Platform._
 
 class RegressionTest {
@@ -102,14 +101,6 @@ class RegressionTest {
   }
 
   @Test def classLiteralsForExistentialValueTypes_Issue218(): Unit = {
-    import Platform.scalaVersion
-
-    assumeFalse("Affected by https://github.com/scala/bug/issues/10551",
-        Platform.executingInJVM && {
-          scalaVersion == "2.12.2" || scalaVersion == "2.12.3" ||
-          scalaVersion == "2.12.4"
-        })
-
     assertEquals("org.scalajs.testsuite.compiler.RegressionTest$Bug218Foo",
         scala.reflect.classTag[Bug218Foo[_]].toString)
   }
@@ -717,10 +708,6 @@ class RegressionTest {
   }
 
   @Test def superMixinCallIn212_Issue3013(): Unit = {
-    assumeTrue(
-        "Super mixin calls are broken in Scala/JVM 2.12.{0-2}",
-        !Platform.executingInJVM || Platform.scalaVersion != "2.12.2")
-
     import Bug3013._
 
     val b = new B

From de3a015ba31e651dda6cf4d347ceb5c91cfa04fe Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Sun, 5 Jan 2025 11:51:22 +0100
Subject: [PATCH 232/298] Remove dead code in `OptimizerCore`.

---
 .../frontend/optimizer/OptimizerCore.scala    | 19 -------------------
 1 file changed, 19 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
index 584e269323..4aa187b975 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
@@ -5725,8 +5725,6 @@ private[optimizer] object OptimizerCore {
   private final class TooManyRollbacksException
       extends scala.util.control.ControlThrowable
 
-  private val AnonFunctionClassPrefix = "sjsr_AnonFunction"
-
   private type CancelFun = () => Nothing
   private type PreTransCont = PreTransform => TailRec[Tree]
 
@@ -5736,12 +5734,6 @@ private[optimizer] object OptimizerCore {
     def isNullable: Boolean = base.isNullable
 
     def isNothingType: Boolean = base == NothingType
-
-    def toNonNullable: RefinedType = {
-      if (!isNullable) this
-      else if (base == NullType) RefinedType.Nothing
-      else RefinedType(base.toNonNullable, isExact, allocationSite)
-    }
   }
 
   private object RefinedType {
@@ -5768,7 +5760,6 @@ private[optimizer] object OptimizerCore {
     }
 
     val NoRefinedType = RefinedType(VoidType)
-    val Nothing = RefinedType(NothingType)
   }
 
   /**
@@ -6018,12 +6009,6 @@ private[optimizer] object OptimizerCore {
       copy(implsBeingInlined = implsBeingInlined + impl)
     }
 
-    def inlining(impls: Set[Scope.InliningID]): Scope = {
-      val intersection = implsBeingInlined.intersect(impls)
-      assert(intersection.isEmpty, s"Circular inlining of $intersection")
-      copy(implsBeingInlined = implsBeingInlined ++ impls)
-    }
-
     def withImportReplacement(importReplacement: ImportReplacement): Scope = {
       assert(this.importReplacement.isEmpty, "Alreadying replacing " +
           s"$this.importReplacement while trying to replace $importReplacement")
@@ -6418,10 +6403,6 @@ private[optimizer] object OptimizerCore {
     if (y >= 0) x-y <= x
     else        x-y >  x
 
-  /** Tests whether `-x` is valid without falling out of range. */
-  private def canNegateLong(x: Long): Boolean =
-    x != Long.MinValue
-
   private final class Intrinsics(intrinsicsMap: Map[(ClassName, MethodName), Int]) {
     def apply(flags: ApplyFlags, target: AbstractMethodID): Int = {
       if (flags.isPrivate || flags.isConstructor) {

From 67fac71cc04aea45e045aef11f90b7f68f6a6499 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Sun, 5 Jan 2025 12:26:38 +0100
Subject: [PATCH 233/298] Inline `RefinedType.NoRefinedType` at its unique use
 site.

The other code paths in the method have to allocate a `RefinedType`
anyway, so there was no strong reason to avoid the allocation there.
---
 .../org/scalajs/linker/frontend/optimizer/OptimizerCore.scala | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
index 4aa187b975..53b8a11ee5 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
@@ -384,7 +384,7 @@ private[optimizer] abstract class OptimizerCore(
              * `Return`s we produce in order to decide whether we can remove
              * the `Labeled`.
              */
-            info.returnedTreeTypes.value ::= RefinedType.NoRefinedType
+            info.returnedTreeTypes.value ::= RefinedType(VoidType)
             Return(newExpr, newLabel)
           }
         } else if (!info.acceptRecords) {
@@ -5758,8 +5758,6 @@ private[optimizer] object OptimizerCore {
       }
       RefinedType(tpe, isExact)
     }
-
-    val NoRefinedType = RefinedType(VoidType)
   }
 
   /**

From e86b32da589744369e4955cf0e1de03399e206dd Mon Sep 17 00:00:00 2001
From: Tobias Schlatter <tobias@meisch.ch>
Date: Sun, 5 Jan 2025 14:28:04 +0100
Subject: [PATCH 234/298] Remove coreSpec from ModuleSet / LinkingUnit and
 verifyModuleSet

The core spec is configuration, not a part of the linking unit.

One could argue that `verifyModuleSet` adds a little bit of safety,
but IMO, it does not warrant the cost / boilerplate of copying
coreSpec around everywhere.
---
 .../backend/closure/ClosureLinkerBackend.scala    |  2 --
 .../linker/backend/BasicLinkerBackend.scala       |  2 --
 .../org/scalajs/linker/frontend/BaseLinker.scala  |  2 +-
 .../org/scalajs/linker/frontend/LinkingUnit.scala |  1 -
 .../org/scalajs/linker/frontend/Refiner.scala     |  2 +-
 .../frontend/modulesplitter/ModuleSplitter.scala  |  4 ++--
 .../scalajs/linker/standard/LinkerBackend.scala   | 15 ---------------
 .../org/scalajs/linker/standard/ModuleSet.scala   |  1 -
 project/BinaryIncompatibilities.scala             |  4 ++++
 9 files changed, 8 insertions(+), 25 deletions(-)

diff --git a/linker/jvm/src/main/scala/org/scalajs/linker/backend/closure/ClosureLinkerBackend.scala b/linker/jvm/src/main/scala/org/scalajs/linker/backend/closure/ClosureLinkerBackend.scala
index a013049de8..de9fdefa68 100644
--- a/linker/jvm/src/main/scala/org/scalajs/linker/backend/closure/ClosureLinkerBackend.scala
+++ b/linker/jvm/src/main/scala/org/scalajs/linker/backend/closure/ClosureLinkerBackend.scala
@@ -99,8 +99,6 @@ final class ClosureLinkerBackend(config: LinkerBackendImpl.Config)
    */
   def emit(moduleSet: ModuleSet, output: OutputDirectory, logger: Logger)(
       implicit ec: ExecutionContext): Future[Report] = {
-    verifyModuleSet(moduleSet)
-
     require(moduleSet.modules.size <= 1,
         "Cannot use multiple modules with the Closure Compiler")
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/BasicLinkerBackend.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/BasicLinkerBackend.scala
index 84b01582b9..622daf283f 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/BasicLinkerBackend.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/BasicLinkerBackend.scala
@@ -76,8 +76,6 @@ final class BasicLinkerBackend(config: LinkerBackendImpl.Config)
    */
   def emit(moduleSet: ModuleSet, output: OutputDirectory, logger: Logger)(
       implicit ec: ExecutionContext): Future[Report] = {
-    verifyModuleSet(moduleSet)
-
     // Reset stats.
 
     totalModules = moduleSet.modules.size
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/BaseLinker.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/BaseLinker.scala
index e9756e38e1..98b3fdf0de 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/BaseLinker.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/BaseLinker.scala
@@ -95,7 +95,7 @@ final class BaseLinker(config: CommonPhaseConfig, checkIR: Boolean) {
         analysis.isClassSuperClassUsed
       )
 
-      new LinkingUnit(config.coreSpec, linkedClassDefs.toList,
+      new LinkingUnit(linkedClassDefs.toList,
           linkedTopLevelExports.flatten.toList,
           moduleInitializers.toList,
           globalInfo)
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/LinkingUnit.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/LinkingUnit.scala
index 836147cba5..a512aa6ec2 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/LinkingUnit.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/LinkingUnit.scala
@@ -17,7 +17,6 @@ import org.scalajs.linker.interface.ModuleInitializer
 import org.scalajs.linker.standard._
 
 final class LinkingUnit private[frontend] (
-    val coreSpec: CoreSpec,
     val classDefs: List[LinkedClass],
     val topLevelExports: List[LinkedTopLevelExport],
     val moduleInitializers: List[ModuleInitializer],
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/Refiner.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/Refiner.scala
index 51c4cbd590..a263a7b388 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/Refiner.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/Refiner.scala
@@ -73,7 +73,7 @@ final class Refiner(config: CommonPhaseConfig, checkIR: Boolean) {
           analysis.isClassSuperClassUsed
         )
 
-        new LinkingUnit(config.coreSpec, linkedClassDefs.toList,
+        new LinkingUnit(linkedClassDefs.toList,
             linkedTopLevelExports.flatten.toList, moduleInitializers, globalInfo)
       }
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/modulesplitter/ModuleSplitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/modulesplitter/ModuleSplitter.scala
index 2518679ca1..93f9d12a8e 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/modulesplitter/ModuleSplitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/modulesplitter/ModuleSplitter.scala
@@ -45,7 +45,7 @@ final class ModuleSplitter private (analyzer: ModuleAnalyzer) {
        * We have to do it here, otherwise we break the assumption, that all
        * non-abstract classes are reached through a static path.
        */
-      new ModuleSet(unit.coreSpec, Nil, Nil, unit.globalInfo)
+      new ModuleSet(Nil, Nil, unit.globalInfo)
     } else {
       val analysis = logger.time("Module Splitter: Analyze Modules") {
         analyzer.analyze(dependencyInfo)
@@ -124,7 +124,7 @@ final class ModuleSplitter private (analyzer: ModuleAnalyzer) {
 
     val modules = builders.values.map(_.result()).toList
 
-    new ModuleSet(unit.coreSpec, modules, abstractClasses.result(), unit.globalInfo)
+    new ModuleSet(modules, abstractClasses.result(), unit.globalInfo)
   }
 
   private def publicModuleDependencies(
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/standard/LinkerBackend.scala b/linker/shared/src/main/scala/org/scalajs/linker/standard/LinkerBackend.scala
index b1d35ebba4..7b1a9f201b 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/standard/LinkerBackend.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/standard/LinkerBackend.scala
@@ -54,19 +54,4 @@ abstract class LinkerBackend {
   def emit(moduleSet: ModuleSet, output: OutputDirectory, logger: Logger)(
       implicit ec: ExecutionContext): Future[Report]
 
-  /** Verify that a `ModuleSet` can be processed by this `LinkerBackend`.
-   *
-   *  Currently, this only tests that the module set core specification
-   *  matches [[coreSpec]].
-   *
-   *  In the future, this test could be extended to test [[symbolRequirements]]
-   *  too.
-   *
-   *  @throws java.lang.IllegalArgumentException if there is a mismatch
-   */
-  protected def verifyModuleSet(moduleSet: ModuleSet): Unit = {
-    require(moduleSet.coreSpec == coreSpec,
-        "ModuleSet and LinkerBackend must agree on their core specification")
-  }
-
 }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/standard/ModuleSet.scala b/linker/shared/src/main/scala/org/scalajs/linker/standard/ModuleSet.scala
index c03557baa9..639032bdfe 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/standard/ModuleSet.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/standard/ModuleSet.scala
@@ -34,7 +34,6 @@ import org.scalajs.linker.interface.ModuleInitializer
  *  are no public modules.
  */
 final class ModuleSet private[linker] (
-    val coreSpec: CoreSpec,
     val modules: List[ModuleSet.Module],
 
     /** Abstract classes may not have any definitions, but are still required
diff --git a/project/BinaryIncompatibilities.scala b/project/BinaryIncompatibilities.scala
index 5df88fa444..c4530e7467 100644
--- a/project/BinaryIncompatibilities.scala
+++ b/project/BinaryIncompatibilities.scala
@@ -51,6 +51,10 @@ object BinaryIncompatibilities {
   )
 
   val Linker = Seq(
+    // !!! Breaking, OK in minor release
+    exclude[DirectMissingMethodProblem]("org.scalajs.linker.standard.ModuleSet.coreSpec"),
+    exclude[DirectMissingMethodProblem]("org.scalajs.linker.standard.ModuleSet.this"),
+    exclude[DirectMissingMethodProblem]("org.scalajs.linker.standard.LinkerBackend.verifyModuleSet"),
   )
 
   val LinkerInterface = Seq(

From 68b1c71867656081db1529dbb6523e4ea4e78343 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Sun, 5 Jan 2025 11:35:06 +0100
Subject: [PATCH 235/298] Drop support for Scala 2.13.{0-2}.

These were the 2.13.x versions for which we still had some custom
code paths, workarounds or exceptions lying around.

This commit is a followup to edc13a8f02c10e36eb151549aa790ad17a3c0804.
---
 CODINGSTYLE.md                                |   2 +-
 Jenkinsfile                                   |   3 -
 .../org/scalajs/nscplugin/GenJSCode.scala     |   2 +-
 .../nscplugin/test/DiverseErrorsTest.scala    |   9 +-
 .../nscplugin/test/JSInteropTest.scala        |   4 +-
 .../test/util/VersionDependentUtils.scala     |  19 +-
 project/Build.scala                           |  17 +-
 .../resources/2.13.0/BlacklistedTests.txt     | 180 -----------------
 .../resources/2.13.1/BlacklistedTests.txt     | 181 -----------------
 .../resources/2.13.2/BlacklistedTests.txt     | 190 ------------------
 scalalib/overrides-2.13.0/scala/Symbol.scala  | 113 -----------
 scalalib/overrides-2.13.1/scala/Symbol.scala  | 113 -----------
 scalalib/overrides-2.13.2/scala/Symbol.scala  | 113 -----------
 .../testsuite/scalalib/SymbolTest.scala       |   9 +-
 14 files changed, 12 insertions(+), 943 deletions(-)
 delete mode 100644 scala-test-suite/src/test/resources/2.13.0/BlacklistedTests.txt
 delete mode 100644 scala-test-suite/src/test/resources/2.13.1/BlacklistedTests.txt
 delete mode 100644 scala-test-suite/src/test/resources/2.13.2/BlacklistedTests.txt
 delete mode 100644 scalalib/overrides-2.13.0/scala/Symbol.scala
 delete mode 100644 scalalib/overrides-2.13.1/scala/Symbol.scala
 delete mode 100644 scalalib/overrides-2.13.2/scala/Symbol.scala

diff --git a/CODINGSTYLE.md b/CODINGSTYLE.md
index 47cb6a448a..eb79ec4986 100644
--- a/CODINGSTYLE.md
+++ b/CODINGSTYLE.md
@@ -227,7 +227,7 @@ value :: list
 ```
 
 When calling a method declared with an empty pair of parentheses, always use `()`.
-Not doing so causes (fatal) warnings when calling Scala-declared methods in Scala 2.13.3+.
+Not doing so causes (fatal) warnings when calling Scala-declared methods in Scala 2.13.x.
 For consistency, we also apply this rule to all Java-defined methods, including `toString()`.
 
 ### Method definition
diff --git a/Jenkinsfile b/Jenkinsfile
index aaa2897fbc..63e464571d 100644
--- a/Jenkinsfile
+++ b/Jenkinsfile
@@ -559,9 +559,6 @@ def otherScalaVersions = [
   "2.12.16",
   "2.12.17",
   "2.12.18",
-  "2.13.0",
-  "2.13.1",
-  "2.13.2",
   "2.13.3",
   "2.13.4",
   "2.13.5",
diff --git a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
index acf2d096ad..7c4548e67f 100644
--- a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
+++ b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
@@ -3875,7 +3875,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
        * true `int`s can reach the back-end, as asserted by the String-switch
        * transformation in `cleanup`. Therefore, we do not adapt, preserving
        * the `string`s and `null`s that come out of the pattern matching in
-       * Scala 2.13.2+.
+       * Scala 2.13.x.
        */
       val genSelector = genExpr(selector)
 
diff --git a/compiler/src/test/scala/org/scalajs/nscplugin/test/DiverseErrorsTest.scala b/compiler/src/test/scala/org/scalajs/nscplugin/test/DiverseErrorsTest.scala
index da1360b581..9ed869cbcc 100644
--- a/compiler/src/test/scala/org/scalajs/nscplugin/test/DiverseErrorsTest.scala
+++ b/compiler/src/test/scala/org/scalajs/nscplugin/test/DiverseErrorsTest.scala
@@ -26,13 +26,8 @@ class DiverseErrorsTest extends DirectTest with TestHelpers  {
 
   private def version = scala.util.Properties.versionNumberString
 
-  private val allowsSingletonClassOf = (
-      !version.startsWith("2.12.") &&
-      version != "2.13.0" &&
-      version != "2.13.1" &&
-      version != "2.13.2" &&
-      version != "2.13.3"
-  )
+  private val allowsSingletonClassOf =
+    !version.startsWith("2.12.") && version != "2.13.3"
 
   @Test
   def noIsInstanceOnJS(): Unit = {
diff --git a/compiler/src/test/scala/org/scalajs/nscplugin/test/JSInteropTest.scala b/compiler/src/test/scala/org/scalajs/nscplugin/test/JSInteropTest.scala
index 907bf0c83e..8d79f251a3 100644
--- a/compiler/src/test/scala/org/scalajs/nscplugin/test/JSInteropTest.scala
+++ b/compiler/src/test/scala/org/scalajs/nscplugin/test/JSInteropTest.scala
@@ -4423,9 +4423,7 @@ class JSInteropTest extends DirectTest with TestHelpers {
         version == "2.12.7" ||
         version == "2.12.8" ||
         version == "2.12.9" ||
-        version == "2.12.10" ||
-        version == "2.13.0" ||
-        version == "2.13.1"
+        version == "2.12.10"
       }
       if (hasNoSpace) ""
       else " "
diff --git a/compiler/src/test/scala/org/scalajs/nscplugin/test/util/VersionDependentUtils.scala b/compiler/src/test/scala/org/scalajs/nscplugin/test/util/VersionDependentUtils.scala
index 5b54f73a1b..7e52a1edf8 100644
--- a/compiler/src/test/scala/org/scalajs/nscplugin/test/util/VersionDependentUtils.scala
+++ b/compiler/src/test/scala/org/scalajs/nscplugin/test/util/VersionDependentUtils.scala
@@ -15,23 +15,12 @@ package org.scalajs.nscplugin.test.util
 object VersionDependentUtils {
   val scalaVersion = scala.util.Properties.versionNumberString
 
-  /** Does the current Scala version support the `@nowarn` annotation? */
-  val scalaSupportsNoWarn = {
-    !scalaVersion.startsWith("2.12.") &&
-    scalaVersion != "2.13.0" &&
-    scalaVersion != "2.13.1"
-  }
+  private val isScala212 = scalaVersion.startsWith("2.12.")
 
-  private val usesColonInMethodSig = {
-    /* Yes, this is the same test as in scalaSupportsNoWarn, but that's
-     * completely coincidental, so we have a copy.
-     */
-    !scalaVersion.startsWith("2.12.") &&
-    scalaVersion != "2.13.0" &&
-    scalaVersion != "2.13.1"
-  }
+  /** Does the current Scala version support the `@nowarn` annotation? */
+  val scalaSupportsNoWarn = !isScala212
 
   def methodSig(params: String, resultType: String): String =
-    if (usesColonInMethodSig) params + ": " + resultType
+    if (!isScala212) params + ": " + resultType
     else params + resultType
 }
diff --git a/project/Build.scala b/project/Build.scala
index 5c1c69e528..9eb18bbd1e 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -484,12 +484,7 @@ object Build {
 
   def addWconfSettingIf2_13(conf: String): Def.Setting[_] = {
     scalacOptions ++= {
-      /* We exclude 2.13.0 and 2.13.1 because they did not support -Wconf yet.
-       * Fortunately, our use cases for -Wconf are only triggered with later
-       * versions.
-       */
-      val v = scalaVersion.value
-      if (v.startsWith("2.13.") && v != "2.13.0" && v != "2.13.1")
+      if (scalaVersion.value.startsWith("2.13."))
         List("-Wconf:" + conf)
       else
         Nil
@@ -739,12 +734,7 @@ object Build {
 
       scalacOptions in (Compile, doc) := {
         val prev = (scalacOptions in (Compile, doc)).value
-        val scalaV = scalaVersion.value
-        def scaladocFullySupportsJDKgreaterThan8 = {
-          !scalaV.startsWith("2.12.") &&
-          scalaV != "2.13.0" && scalaV != "2.13.1" && scalaV != "2.13.2"
-        }
-        if (javaVersion.value > 8 && !scaladocFullySupportsJDKgreaterThan8)
+        if (javaVersion.value > 8 && scalaVersion.value.startsWith("2.12."))
           prev.filter(_ != "-Xfatal-warnings")
         else
           prev
@@ -966,9 +956,6 @@ object Build {
         "2.12.19",
       ),
       cross213ScalaVersions := Seq(
-        "2.13.0",
-        "2.13.1",
-        "2.13.2",
         "2.13.3",
         "2.13.4",
         "2.13.5",
diff --git a/scala-test-suite/src/test/resources/2.13.0/BlacklistedTests.txt b/scala-test-suite/src/test/resources/2.13.0/BlacklistedTests.txt
deleted file mode 100644
index 67798232ba..0000000000
--- a/scala-test-suite/src/test/resources/2.13.0/BlacklistedTests.txt
+++ /dev/null
@@ -1,180 +0,0 @@
-## Do not compile
-scala/ExtractorTest.scala
-scala/OptionTest.scala
-scala/SerializationStabilityTest.scala
-scala/StringTest.scala
-scala/collection/FactoriesTest.scala
-scala/collection/LazyZipOpsTest.scala
-scala/collection/immutable/IndexedSeqTest.scala
-scala/collection/immutable/RangeTest.scala
-scala/lang/annotations/BytecodeTest.scala
-scala/lang/annotations/RunTest.scala
-scala/lang/traits/BytecodeTest.scala
-scala/lang/traits/RunTest.scala
-scala/lang/primitives/NaNTest.scala
-scala/reflect/ClassOfTest.scala
-scala/reflect/FieldAccessTest.scala
-scala/reflect/QTest.scala
-scala/reflect/io/ZipArchiveTest.scala
-scala/reflect/internal/Infer.scala
-scala/reflect/internal/LongNamesTest.scala
-scala/reflect/internal/MirrorsTest.scala
-scala/reflect/internal/NamesTest.scala
-scala/reflect/internal/PositionsTest.scala
-scala/reflect/internal/PrintersTest.scala
-scala/reflect/internal/ScopeTest.scala
-scala/reflect/internal/TreeGenTest.scala
-scala/reflect/internal/TypesTest.scala
-scala/reflect/internal/util/AbstractFileClassLoaderTest.scala
-scala/reflect/internal/util/FileUtilsTest.scala
-scala/reflect/internal/util/SourceFileTest.scala
-scala/reflect/internal/util/StringOpsTest.scala
-scala/reflect/internal/util/WeakHashSetTest.scala
-scala/reflect/io/AbstractFileTest.scala
-scala/tools/cmd/CommandLineParserTest.scala
-scala/tools/nsc/DeterminismTest.scala
-scala/tools/nsc/GlobalCustomizeClassloaderTest.scala
-scala/tools/nsc/ScriptRunnerTest.scala
-scala/tools/nsc/backend/jvm/BTypesTest.scala
-scala/tools/nsc/backend/jvm/BytecodeTest.scala
-scala/tools/nsc/backend/jvm/DefaultMethodTest.scala
-scala/tools/nsc/backend/jvm/DirectCompileTest.scala
-scala/tools/nsc/backend/jvm/GenericSignaturesTest.scala
-scala/tools/nsc/backend/jvm/IndyLambdaTest.scala
-scala/tools/nsc/backend/jvm/IndySammyTest.scala
-scala/tools/nsc/backend/jvm/InnerClassAttributeTest.scala
-scala/tools/nsc/backend/jvm/NestedClassesCollectorTest.scala
-scala/tools/nsc/backend/jvm/OptimizedBytecodeTest.scala
-scala/tools/nsc/backend/jvm/PerRunInitTest.scala
-scala/tools/nsc/backend/jvm/StringConcatTest.scala
-scala/tools/nsc/backend/jvm/analysis/NullnessAnalyzerTest.scala
-scala/tools/nsc/backend/jvm/analysis/ProdConsAnalyzerTest.scala
-scala/tools/nsc/backend/jvm/analysis/TypeFlowAnalyzerTest.scala
-scala/tools/nsc/backend/jvm/opt/AnalyzerTest.scala
-scala/tools/nsc/backend/jvm/opt/BTypesFromClassfileTest.scala
-scala/tools/nsc/backend/jvm/opt/BoxUnboxTest.scala
-scala/tools/nsc/backend/jvm/opt/CallGraphTest.scala
-scala/tools/nsc/backend/jvm/opt/ClosureOptimizerTest.scala
-scala/tools/nsc/backend/jvm/opt/CompactLocalVariablesTest.scala
-scala/tools/nsc/backend/jvm/opt/EmptyExceptionHandlersTest.scala
-scala/tools/nsc/backend/jvm/opt/EmptyLabelsAndLineNumbersTest.scala
-scala/tools/nsc/backend/jvm/opt/InlineInfoTest.scala
-scala/tools/nsc/backend/jvm/opt/InlinerIllegalAccessTest.scala
-scala/tools/nsc/backend/jvm/opt/InlinerSeparateCompilationTest.scala
-scala/tools/nsc/backend/jvm/opt/InlinerTest.scala
-scala/tools/nsc/backend/jvm/opt/InlineSourceMatcherTest.scala
-scala/tools/nsc/backend/jvm/opt/InlineWarningTest.scala
-scala/tools/nsc/backend/jvm/opt/MethodLevelOptsTest.scala
-scala/tools/nsc/backend/jvm/opt/ScalaInlineInfoTest.scala
-scala/tools/nsc/backend/jvm/opt/SimplifyJumpsTest.scala
-scala/tools/nsc/backend/jvm/opt/UnreachableCodeTest.scala
-scala/tools/nsc/backend/jvm/opt/UnusedLocalVariablesTest.scala
-scala/tools/nsc/classpath/AggregateClassPathTest.scala
-scala/tools/nsc/classpath/JrtClassPathTest.scala
-scala/tools/nsc/classpath/MultiReleaseJarTest.scala
-scala/tools/nsc/classpath/PathResolverBaseTest.scala
-scala/tools/nsc/classpath/VirtualDirectoryClassPathTest.scala
-scala/tools/nsc/classpath/ZipAndJarFileLookupFactoryTest.scala
-scala/tools/nsc/doc/html/HtmlDocletTest.scala
-scala/tools/nsc/doc/html/StringLiteralTest.scala
-scala/tools/nsc/interpreter/CompletionTest.scala
-scala/tools/nsc/interpreter/ScriptedTest.scala
-scala/tools/nsc/interpreter/TabulatorTest.scala
-scala/tools/nsc/parser/ParserTest.scala
-scala/tools/nsc/reporters/ConsoleReporterTest.scala
-scala/tools/nsc/reporters/PositionFilterTest.scala
-scala/tools/nsc/settings/ScalaVersionTest.scala
-scala/tools/nsc/settings/SettingsTest.scala
-scala/tools/nsc/symtab/CannotHaveAttrsTest.scala
-scala/tools/nsc/symtab/FlagsTest.scala
-scala/tools/nsc/symtab/FreshNameExtractorTest.scala
-scala/tools/nsc/symtab/StdNamesTest.scala
-scala/tools/nsc/symtab/SymbolTableForUnitTesting.scala
-scala/tools/nsc/symtab/SymbolTableTest.scala
-scala/tools/nsc/symtab/classfile/PicklerTest.scala
-scala/tools/nsc/transform/ErasureTest.scala
-scala/tools/nsc/transform/MixinTest.scala
-scala/tools/nsc/transform/ReleaseFenceTest.scala
-scala/tools/nsc/transform/SpecializationTest.scala
-scala/tools/nsc/transform/delambdafy/DelambdafyTest.scala
-scala/tools/nsc/transform/patmat/SolvingTest.scala
-scala/tools/nsc/transform/patmat/PatmatBytecodeTest.scala
-scala/tools/nsc/typechecker/Implicits.scala
-scala/tools/nsc/typechecker/Infer.scala
-scala/tools/nsc/typechecker/NamerTest.scala
-scala/tools/nsc/typechecker/OverridingPairsTest.scala
-scala/tools/nsc/typechecker/ParamAliasTest.scala
-scala/tools/nsc/typechecker/TypedTreeTest.scala
-scala/tools/nsc/util/StackTraceTest.scala
-scala/tools/testing/BytecodeTesting.scala
-scala/tools/testing/RunTesting.scala
-scala/tools/testing/VirtualCompilerTesting.scala
-scala/util/ChainingOpsTest.scala
-scala/util/matching/RegexTest.scala
-
-## Do not link
-scala/CollectTest.scala
-scala/MatchErrorSerializationTest.scala
-scala/PartialFunctionSerializationTest.scala
-scala/lang/stringinterpol/StringContextTest.scala
-scala/collection/IterableTest.scala
-scala/collection/IteratorTest.scala
-scala/collection/NewBuilderTest.scala
-scala/collection/SeqViewTest.scala
-scala/collection/SetMapConsistencyTest.scala
-scala/collection/SetMapRulesTest.scala
-scala/collection/concurrent/TrieMapTest.scala
-scala/collection/convert/WrapperSerializationTest.scala
-scala/collection/immutable/ChampMapSmokeTest.scala
-scala/collection/immutable/ChampSetSmokeTest.scala
-scala/collection/immutable/LazyListGCTest.scala
-scala/collection/immutable/LazyListLazinessTest.scala
-scala/collection/immutable/ListTest.scala
-scala/collection/immutable/SerializationTest.scala
-scala/collection/immutable/StreamTest.scala
-scala/collection/immutable/StringLikeTest.scala
-scala/collection/immutable/VectorTest.scala
-scala/collection/mutable/ArrayBufferTest.scala
-scala/collection/mutable/OpenHashMapTest.scala
-scala/collection/mutable/PriorityQueueTest.scala
-scala/collection/mutable/SerializationTest.scala
-scala/concurrent/FutureTest.scala
-scala/concurrent/duration/SerializationTest.scala
-scala/concurrent/impl/DefaultPromiseTest.scala
-scala/io/SourceTest.scala
-scala/jdk/AccumulatorTest.scala
-scala/jdk/DurationConvertersTest.scala
-scala/jdk/FunctionConvertersTest.scala
-scala/jdk/OptionConvertersTest.scala
-scala/jdk/StepperConversionTest.scala
-scala/jdk/StepperTest.scala
-scala/jdk/StreamConvertersTest.scala
-scala/jdk/StreamConvertersTypingTest.scala
-scala/math/OrderingTest.scala
-scala/runtime/ScalaRunTimeTest.scala
-scala/sys/process/ParserTest.scala
-scala/sys/process/PipedProcessTest.scala
-scala/sys/process/ProcessBuilderTest.scala
-scala/sys/process/ProcessTest.scala
-scala/tools/testing/AssertUtilTest.scala
-scala/tools/testing/AssertThrowsTest.scala
-scala/util/PropertiesTest.scala
-scala/util/SpecVersionTest.scala
-scala/util/SystemPropertiesTest.scala
-
-## Tests fail
-
-# Reflection
-scala/reflect/ClassTagTest.scala
-
-# Require strict-floats
-scala/math/BigDecimalTest.scala
-
-# Tests passed but are too slow (timeouts)
-scala/collection/immutable/ListSetTest.scala
-scala/util/SortingTest.scala
-
-# Relies on undefined behavior
-scala/collection/StringOpsTest.scala
-scala/collection/StringParsersTest.scala
-scala/collection/convert/MapWrapperTest.scala
diff --git a/scala-test-suite/src/test/resources/2.13.1/BlacklistedTests.txt b/scala-test-suite/src/test/resources/2.13.1/BlacklistedTests.txt
deleted file mode 100644
index 70b0dce1a0..0000000000
--- a/scala-test-suite/src/test/resources/2.13.1/BlacklistedTests.txt
+++ /dev/null
@@ -1,181 +0,0 @@
-## Do not compile
-scala/ExtractorTest.scala
-scala/OptionTest.scala
-scala/SerializationStabilityTest.scala
-scala/StringTest.scala
-scala/collection/FactoriesTest.scala
-scala/collection/LazyZipOpsTest.scala
-scala/collection/immutable/IndexedSeqTest.scala
-scala/collection/immutable/RangeTest.scala
-scala/lang/annotations/BytecodeTest.scala
-scala/lang/annotations/RunTest.scala
-scala/lang/traits/BytecodeTest.scala
-scala/lang/traits/RunTest.scala
-scala/lang/primitives/NaNTest.scala
-scala/reflect/ClassOfTest.scala
-scala/reflect/FieldAccessTest.scala
-scala/reflect/QTest.scala
-scala/reflect/io/ZipArchiveTest.scala
-scala/reflect/internal/Infer.scala
-scala/reflect/internal/LongNamesTest.scala
-scala/reflect/internal/MirrorsTest.scala
-scala/reflect/internal/NamesTest.scala
-scala/reflect/internal/PositionsTest.scala
-scala/reflect/internal/PrintersTest.scala
-scala/reflect/internal/ScopeTest.scala
-scala/reflect/internal/TreeGenTest.scala
-scala/reflect/internal/TypesTest.scala
-scala/reflect/internal/util/AbstractFileClassLoaderTest.scala
-scala/reflect/internal/util/FileUtilsTest.scala
-scala/reflect/internal/util/SourceFileTest.scala
-scala/reflect/internal/util/StringOpsTest.scala
-scala/reflect/internal/util/WeakHashSetTest.scala
-scala/reflect/io/AbstractFileTest.scala
-scala/reflect/runtime/ThreadSafetyTest.scala
-scala/tools/cmd/CommandLineParserTest.scala
-scala/tools/nsc/DeterminismTest.scala
-scala/tools/nsc/FileUtils.scala
-scala/tools/nsc/GlobalCustomizeClassloaderTest.scala
-scala/tools/nsc/PhaseAssemblyTest.scala
-scala/tools/nsc/PipelineMainTest.scala
-scala/tools/nsc/ScriptRunnerTest.scala
-scala/tools/nsc/backend/jvm/BTypesTest.scala
-scala/tools/nsc/backend/jvm/BytecodeTest.scala
-scala/tools/nsc/backend/jvm/DefaultMethodTest.scala
-scala/tools/nsc/backend/jvm/DirectCompileTest.scala
-scala/tools/nsc/backend/jvm/GenericSignaturesTest.scala
-scala/tools/nsc/backend/jvm/IndyLambdaTest.scala
-scala/tools/nsc/backend/jvm/IndySammyTest.scala
-scala/tools/nsc/backend/jvm/InnerClassAttributeTest.scala
-scala/tools/nsc/backend/jvm/NestedClassesCollectorTest.scala
-scala/tools/nsc/backend/jvm/OptimizedBytecodeTest.scala
-scala/tools/nsc/backend/jvm/PerRunInitTest.scala
-scala/tools/nsc/backend/jvm/StringConcatTest.scala
-scala/tools/nsc/backend/jvm/analysis/NullnessAnalyzerTest.scala
-scala/tools/nsc/backend/jvm/analysis/ProdConsAnalyzerTest.scala
-scala/tools/nsc/backend/jvm/analysis/TypeFlowAnalyzerTest.scala
-scala/tools/nsc/backend/jvm/opt/AnalyzerTest.scala
-scala/tools/nsc/backend/jvm/opt/BTypesFromClassfileTest.scala
-scala/tools/nsc/backend/jvm/opt/BoxUnboxTest.scala
-scala/tools/nsc/backend/jvm/opt/CallGraphTest.scala
-scala/tools/nsc/backend/jvm/opt/ClosureOptimizerTest.scala
-scala/tools/nsc/backend/jvm/opt/CompactLocalVariablesTest.scala
-scala/tools/nsc/backend/jvm/opt/EmptyExceptionHandlersTest.scala
-scala/tools/nsc/backend/jvm/opt/EmptyLabelsAndLineNumbersTest.scala
-scala/tools/nsc/backend/jvm/opt/InlineInfoTest.scala
-scala/tools/nsc/backend/jvm/opt/InlinerIllegalAccessTest.scala
-scala/tools/nsc/backend/jvm/opt/InlinerSeparateCompilationTest.scala
-scala/tools/nsc/backend/jvm/opt/InlinerTest.scala
-scala/tools/nsc/backend/jvm/opt/InlineSourceMatcherTest.scala
-scala/tools/nsc/backend/jvm/opt/InlineWarningTest.scala
-scala/tools/nsc/backend/jvm/opt/MethodLevelOptsTest.scala
-scala/tools/nsc/backend/jvm/opt/ScalaInlineInfoTest.scala
-scala/tools/nsc/backend/jvm/opt/SimplifyJumpsTest.scala
-scala/tools/nsc/backend/jvm/opt/UnreachableCodeTest.scala
-scala/tools/nsc/backend/jvm/opt/UnusedLocalVariablesTest.scala
-scala/tools/nsc/classpath/AggregateClassPathTest.scala
-scala/tools/nsc/classpath/JrtClassPathTest.scala
-scala/tools/nsc/classpath/MultiReleaseJarTest.scala
-scala/tools/nsc/classpath/PathResolverBaseTest.scala
-scala/tools/nsc/classpath/VirtualDirectoryClassPathTest.scala
-scala/tools/nsc/classpath/ZipAndJarFileLookupFactoryTest.scala
-scala/tools/nsc/doc/html/HtmlDocletTest.scala
-scala/tools/nsc/doc/html/StringLiteralTest.scala
-scala/tools/nsc/interpreter/CompletionTest.scala
-scala/tools/nsc/interpreter/ScriptedTest.scala
-scala/tools/nsc/interpreter/TabulatorTest.scala
-scala/tools/nsc/parser/ParserTest.scala
-scala/tools/nsc/reporters/ConsoleReporterTest.scala
-scala/tools/nsc/reporters/PositionFilterTest.scala
-scala/tools/nsc/settings/ScalaVersionTest.scala
-scala/tools/nsc/settings/SettingsTest.scala
-scala/tools/nsc/settings/TargetTest.scala
-scala/tools/nsc/symtab/CannotHaveAttrsTest.scala
-scala/tools/nsc/symtab/FlagsTest.scala
-scala/tools/nsc/symtab/FreshNameExtractorTest.scala
-scala/tools/nsc/symtab/StdNamesTest.scala
-scala/tools/nsc/symtab/SymbolTableForUnitTesting.scala
-scala/tools/nsc/symtab/SymbolTableTest.scala
-scala/tools/nsc/symtab/classfile/PicklerTest.scala
-scala/tools/nsc/transform/ErasureTest.scala
-scala/tools/nsc/transform/MixinTest.scala
-scala/tools/nsc/transform/ReleaseFenceTest.scala
-scala/tools/nsc/transform/SpecializationTest.scala
-scala/tools/nsc/transform/delambdafy/DelambdafyTest.scala
-scala/tools/nsc/transform/patmat/SolvingTest.scala
-scala/tools/nsc/transform/patmat/PatmatBytecodeTest.scala
-scala/tools/nsc/typechecker/Implicits.scala
-scala/tools/nsc/typechecker/Infer.scala
-scala/tools/nsc/typechecker/NamerTest.scala
-scala/tools/nsc/typechecker/OverridingPairsTest.scala
-scala/tools/nsc/typechecker/ParamAliasTest.scala
-scala/tools/nsc/typechecker/TypedTreeTest.scala
-scala/tools/nsc/util/StackTraceTest.scala
-scala/util/ChainingOpsTest.scala
-scala/util/matching/RegexTest.scala
-
-## Do not link
-scala/CollectTest.scala
-scala/MatchErrorSerializationTest.scala
-scala/PartialFunctionSerializationTest.scala
-scala/lang/stringinterpol/StringContextTest.scala
-scala/collection/IterableTest.scala
-scala/collection/IteratorTest.scala
-scala/collection/NewBuilderTest.scala
-scala/collection/SeqViewTest.scala
-scala/collection/SetMapConsistencyTest.scala
-scala/collection/SetMapRulesTest.scala
-scala/collection/concurrent/TrieMapTest.scala
-scala/collection/convert/WrapperSerializationTest.scala
-scala/collection/immutable/ChampMapSmokeTest.scala
-scala/collection/immutable/ChampSetSmokeTest.scala
-scala/collection/immutable/LazyListGCTest.scala
-scala/collection/immutable/LazyListLazinessTest.scala
-scala/collection/immutable/ListTest.scala
-scala/collection/immutable/SerializationTest.scala
-scala/collection/immutable/StreamTest.scala
-scala/collection/immutable/StringLikeTest.scala
-scala/collection/immutable/VectorTest.scala
-scala/collection/mutable/ArrayBufferTest.scala
-scala/collection/mutable/OpenHashMapTest.scala
-scala/collection/mutable/PriorityQueueTest.scala
-scala/collection/mutable/SerializationTest.scala
-scala/concurrent/FutureTest.scala
-scala/concurrent/duration/SerializationTest.scala
-scala/concurrent/impl/DefaultPromiseTest.scala
-scala/io/SourceTest.scala
-scala/jdk/AccumulatorTest.scala
-scala/jdk/DurationConvertersTest.scala
-scala/jdk/FunctionConvertersTest.scala
-scala/jdk/OptionConvertersTest.scala
-scala/jdk/StepperConversionTest.scala
-scala/jdk/StepperTest.scala
-scala/jdk/StreamConvertersTest.scala
-scala/jdk/StreamConvertersTypingTest.scala
-scala/math/OrderingTest.scala
-scala/runtime/ScalaRunTimeTest.scala
-scala/sys/process/ParserTest.scala
-scala/sys/process/PipedProcessTest.scala
-scala/sys/process/ProcessBuilderTest.scala
-scala/sys/process/ProcessTest.scala
-scala/tools/testkit/AssertUtilTest.scala
-scala/util/PropertiesTest.scala
-scala/util/SpecVersionTest.scala
-scala/util/SystemPropertiesTest.scala
-
-## Tests fail
-
-# Reflection
-scala/reflect/ClassTagTest.scala
-
-# Require strict-floats
-scala/math/BigDecimalTest.scala
-
-# Tests passed but are too slow (timeouts)
-scala/collection/immutable/ListSetTest.scala
-scala/util/SortingTest.scala
-
-# Relies on undefined behavior
-scala/collection/StringOpsTest.scala
-scala/collection/StringParsersTest.scala
-scala/collection/convert/MapWrapperTest.scala
diff --git a/scala-test-suite/src/test/resources/2.13.2/BlacklistedTests.txt b/scala-test-suite/src/test/resources/2.13.2/BlacklistedTests.txt
deleted file mode 100644
index 7ad0c9c4c5..0000000000
--- a/scala-test-suite/src/test/resources/2.13.2/BlacklistedTests.txt
+++ /dev/null
@@ -1,190 +0,0 @@
-## Do not compile
-scala/ExtractorTest.scala
-scala/OptionTest.scala
-scala/SerializationStabilityTest.scala
-scala/StringTest.scala
-scala/collection/FactoriesTest.scala
-scala/collection/LazyZipOpsTest.scala
-scala/collection/immutable/IndexedSeqTest.scala
-scala/collection/immutable/MapHashcodeTest.scala
-scala/collection/immutable/RangeTest.scala
-scala/collection/mutable/BitSetTest.scala
-scala/lang/annotations/BytecodeTest.scala
-scala/lang/annotations/RunTest.scala
-scala/lang/traits/BytecodeTest.scala
-scala/lang/traits/RunTest.scala
-scala/lang/primitives/NaNTest.scala
-scala/reflect/ClassOfTest.scala
-scala/reflect/FieldAccessTest.scala
-scala/reflect/QTest.scala
-scala/reflect/io/ZipArchiveTest.scala
-scala/reflect/internal/Infer.scala
-scala/reflect/internal/LongNamesTest.scala
-scala/reflect/internal/MirrorsTest.scala
-scala/reflect/internal/NamesTest.scala
-scala/reflect/internal/PositionsTest.scala
-scala/reflect/internal/PrintersTest.scala
-scala/reflect/internal/ScopeTest.scala
-scala/reflect/internal/TreeGenTest.scala
-scala/reflect/internal/TypesTest.scala
-scala/reflect/internal/util/AbstractFileClassLoaderTest.scala
-scala/reflect/internal/util/FileUtilsTest.scala
-scala/reflect/internal/util/SourceFileTest.scala
-scala/reflect/internal/util/StringOpsTest.scala
-scala/reflect/internal/util/WeakHashSetTest.scala
-scala/reflect/io/AbstractFileTest.scala
-scala/reflect/runtime/ThreadSafetyTest.scala
-scala/tools/cmd/CommandLineParserTest.scala
-scala/tools/nsc/Build.scala
-scala/tools/nsc/DeterminismTest.scala
-scala/tools/nsc/FileUtils.scala
-scala/tools/nsc/GlobalCustomizeClassloaderTest.scala
-scala/tools/nsc/PhaseAssemblyTest.scala
-scala/tools/nsc/PickleWriteTest.scala
-scala/tools/nsc/PipelineMainTest.scala
-scala/tools/nsc/ScriptRunnerTest.scala
-scala/tools/nsc/backend/jvm/BTypesTest.scala
-scala/tools/nsc/backend/jvm/BytecodeTest.scala
-scala/tools/nsc/backend/jvm/DefaultMethodTest.scala
-scala/tools/nsc/backend/jvm/DirectCompileTest.scala
-scala/tools/nsc/backend/jvm/GenericSignaturesTest.scala
-scala/tools/nsc/backend/jvm/IndyLambdaTest.scala
-scala/tools/nsc/backend/jvm/IndySammyTest.scala
-scala/tools/nsc/backend/jvm/InnerClassAttributeTest.scala
-scala/tools/nsc/backend/jvm/NestedClassesCollectorTest.scala
-scala/tools/nsc/backend/jvm/OptimizedBytecodeTest.scala
-scala/tools/nsc/backend/jvm/PerRunInitTest.scala
-scala/tools/nsc/backend/jvm/StringConcatTest.scala
-scala/tools/nsc/backend/jvm/analysis/NullnessAnalyzerTest.scala
-scala/tools/nsc/backend/jvm/analysis/ProdConsAnalyzerTest.scala
-scala/tools/nsc/backend/jvm/analysis/TypeFlowAnalyzerTest.scala
-scala/tools/nsc/backend/jvm/opt/AnalyzerTest.scala
-scala/tools/nsc/backend/jvm/opt/BTypesFromClassfileTest.scala
-scala/tools/nsc/backend/jvm/opt/BoxUnboxTest.scala
-scala/tools/nsc/backend/jvm/opt/CallGraphTest.scala
-scala/tools/nsc/backend/jvm/opt/ClosureOptimizerTest.scala
-scala/tools/nsc/backend/jvm/opt/CompactLocalVariablesTest.scala
-scala/tools/nsc/backend/jvm/opt/EmptyExceptionHandlersTest.scala
-scala/tools/nsc/backend/jvm/opt/EmptyLabelsAndLineNumbersTest.scala
-scala/tools/nsc/backend/jvm/opt/InlineInfoTest.scala
-scala/tools/nsc/backend/jvm/opt/InlinerIllegalAccessTest.scala
-scala/tools/nsc/backend/jvm/opt/InlinerSeparateCompilationTest.scala
-scala/tools/nsc/backend/jvm/opt/InlinerTest.scala
-scala/tools/nsc/backend/jvm/opt/InlineSourceMatcherTest.scala
-scala/tools/nsc/backend/jvm/opt/InlineWarningTest.scala
-scala/tools/nsc/backend/jvm/opt/MethodLevelOptsTest.scala
-scala/tools/nsc/backend/jvm/opt/ScalaInlineInfoTest.scala
-scala/tools/nsc/backend/jvm/opt/SimplifyJumpsTest.scala
-scala/tools/nsc/backend/jvm/opt/UnreachableCodeTest.scala
-scala/tools/nsc/backend/jvm/opt/UnusedLocalVariablesTest.scala
-scala/tools/nsc/classpath/AggregateClassPathTest.scala
-scala/tools/nsc/classpath/JrtClassPathTest.scala
-scala/tools/nsc/classpath/MultiReleaseJarTest.scala
-scala/tools/nsc/classpath/PathResolverBaseTest.scala
-scala/tools/nsc/classpath/VirtualDirectoryClassPathTest.scala
-scala/tools/nsc/classpath/ZipAndJarFileLookupFactoryTest.scala
-scala/tools/nsc/doc/html/HtmlDocletTest.scala
-scala/tools/nsc/doc/html/StringLiteralTest.scala
-scala/tools/nsc/interpreter/CompletionTest.scala
-scala/tools/nsc/interpreter/ScriptedTest.scala
-scala/tools/nsc/interpreter/TabulatorTest.scala
-scala/tools/nsc/parser/ParserTest.scala
-scala/tools/nsc/reporters/ConsoleReporterTest.scala
-scala/tools/nsc/reporters/PositionFilterTest.scala
-scala/tools/nsc/reporters/WConfTest.scala
-scala/tools/nsc/settings/ScalaVersionTest.scala
-scala/tools/nsc/settings/SettingsTest.scala
-scala/tools/nsc/settings/TargetTest.scala
-scala/tools/nsc/symtab/CannotHaveAttrsTest.scala
-scala/tools/nsc/symtab/FlagsTest.scala
-scala/tools/nsc/symtab/FreshNameExtractorTest.scala
-scala/tools/nsc/symtab/StdNamesTest.scala
-scala/tools/nsc/symtab/SymbolTableForUnitTesting.scala
-scala/tools/nsc/symtab/SymbolTableTest.scala
-scala/tools/nsc/symtab/classfile/PicklerTest.scala
-scala/tools/nsc/transform/ErasureTest.scala
-scala/tools/nsc/transform/MixinTest.scala
-scala/tools/nsc/transform/ReleaseFenceTest.scala
-scala/tools/nsc/transform/SpecializationTest.scala
-scala/tools/nsc/transform/UncurryTest.scala
-scala/tools/nsc/transform/delambdafy/DelambdafyTest.scala
-scala/tools/nsc/transform/patmat/SolvingTest.scala
-scala/tools/nsc/transform/patmat/PatmatBytecodeTest.scala
-scala/tools/nsc/typechecker/Implicits.scala
-scala/tools/nsc/typechecker/Infer.scala
-scala/tools/nsc/typechecker/NamerTest.scala
-scala/tools/nsc/typechecker/OverridingPairsTest.scala
-scala/tools/nsc/typechecker/ParamAliasTest.scala
-scala/tools/nsc/typechecker/TypedTreeTest.scala
-scala/tools/nsc/util/StackTraceTest.scala
-scala/util/ChainingOpsTest.scala
-scala/util/TryTest.scala
-scala/util/matching/RegexTest.scala
-
-## Do not link
-scala/CollectTest.scala
-scala/MatchErrorSerializationTest.scala
-scala/PartialFunctionSerializationTest.scala
-scala/lang/stringinterpol/StringContextTest.scala
-scala/collection/IterableTest.scala
-scala/collection/IteratorTest.scala
-scala/collection/NewBuilderTest.scala
-scala/collection/SeqViewTest.scala
-scala/collection/SetMapConsistencyTest.scala
-scala/collection/SetMapRulesTest.scala
-scala/collection/concurrent/TrieMapTest.scala
-scala/collection/convert/WrapperSerializationTest.scala
-scala/collection/immutable/ChampMapSmokeTest.scala
-scala/collection/immutable/ChampSetSmokeTest.scala
-scala/collection/immutable/LazyListGCTest.scala
-scala/collection/immutable/LazyListLazinessTest.scala
-scala/collection/immutable/ListTest.scala
-scala/collection/immutable/SerializationTest.scala
-scala/collection/immutable/StreamTest.scala
-scala/collection/immutable/StringLikeTest.scala
-scala/collection/immutable/VectorTest.scala
-scala/collection/mutable/AnyRefMapTest.scala
-scala/collection/mutable/ArrayBufferTest.scala
-scala/collection/mutable/OpenHashMapTest.scala
-scala/collection/mutable/PriorityQueueTest.scala
-scala/collection/mutable/SerializationTest.scala
-scala/concurrent/FutureTest.scala
-scala/concurrent/duration/SerializationTest.scala
-scala/concurrent/impl/DefaultPromiseTest.scala
-scala/io/SourceTest.scala
-scala/jdk/AccumulatorTest.scala
-scala/jdk/DurationConvertersTest.scala
-scala/jdk/FunctionConvertersTest.scala
-scala/jdk/OptionConvertersTest.scala
-scala/jdk/StepperConversionTest.scala
-scala/jdk/StepperTest.scala
-scala/jdk/StreamConvertersTest.scala
-scala/jdk/StreamConvertersTypingTest.scala
-scala/math/OrderingTest.scala
-scala/runtime/ScalaRunTimeTest.scala
-scala/sys/env.scala
-scala/sys/process/ParserTest.scala
-scala/sys/process/PipedProcessTest.scala
-scala/sys/process/ProcessBuilderTest.scala
-scala/sys/process/ProcessTest.scala
-scala/tools/testkit/AssertUtilTest.scala
-scala/util/PropertiesTest.scala
-scala/util/SpecVersionTest.scala
-scala/util/SystemPropertiesTest.scala
-
-## Tests fail
-
-# Reflection
-scala/reflect/ClassTagTest.scala
-
-# Require strict-floats
-scala/math/BigDecimalTest.scala
-
-# Tests passed but are too slow (timeouts)
-scala/collection/immutable/ListSetTest.scala
-scala/util/SortingTest.scala
-
-# Relies on undefined behavior
-scala/collection/StringOpsTest.scala
-scala/collection/StringParsersTest.scala
-scala/collection/convert/MapWrapperTest.scala
diff --git a/scalalib/overrides-2.13.0/scala/Symbol.scala b/scalalib/overrides-2.13.0/scala/Symbol.scala
deleted file mode 100644
index 0000b5fe6f..0000000000
--- a/scalalib/overrides-2.13.0/scala/Symbol.scala
+++ /dev/null
@@ -1,113 +0,0 @@
-/*
- * Scala (https://www.scala-lang.org)
- *
- * Copyright EPFL and Lightbend, Inc.
- *
- * Licensed under Apache License 2.0
- * (http://www.apache.org/licenses/LICENSE-2.0).
- *
- * See the NOTICE file distributed with this work for
- * additional information regarding copyright ownership.
- */
-
-package scala
-
-import scala.scalajs.js
-
-/** This class provides a simple way to get unique objects for equal strings.
- *  Since symbols are interned, they can be compared using reference equality.
- *  Instances of `Symbol` can be created easily with Scala's built-in quote
- *  mechanism.
- *
- *  For instance, the Scala term `'mysym` will
- *  invoke the constructor of the `Symbol` class in the following way:
- *  `Symbol("mysym")`.
- *
- *  @author  Martin Odersky, Iulian Dragos
- *  @since   1.7
- */
-final class Symbol private (val name: String) extends Serializable {
-  /** Converts this symbol to a string.
-   */
-  override def toString(): String = "'" + name
-
-  @throws(classOf[java.io.ObjectStreamException])
-  private def readResolve(): Any = Symbol.apply(name)
-  override def hashCode = name.hashCode()
-  override def equals(other: Any) = this eq other.asInstanceOf[AnyRef]
-}
-
-// Modified to use Scala.js specific cache
-object Symbol extends JSUniquenessCache[Symbol] {
-  override def apply(name: String): Symbol = super.apply(name)
-  protected def valueFromKey(name: String): Symbol = new Symbol(name)
-  protected def keyFromValue(sym: Symbol): Option[String] = Some(sym.name)
-}
-
-private[scala] abstract class JSUniquenessCache[V]
-{
-  private val cache = js.Dictionary.empty[V]
-
-  protected def valueFromKey(k: String): V
-  protected def keyFromValue(v: V): Option[String]
-
-  def apply(name: String): V =
-    cache.getOrElseUpdate(name, valueFromKey(name))
-
-  def unapply(other: V): Option[String] = keyFromValue(other)
-}
-
-/** This is private so it won't appear in the library API, but
-  * abstracted to offer some hope of reusability.  */
-/* DELETED for Scala.js
-private[scala] abstract class UniquenessCache[K >: js.String, V >: Null]
-{
-
-  import java.lang.ref.WeakReference
-  import java.util.WeakHashMap
-  import java.util.concurrent.locks.ReentrantReadWriteLock
-
-  private[this] val rwl = new ReentrantReadWriteLock()
-  private[this] val rlock = rwl.readLock
-  private[this] val wlock = rwl.writeLock
-  private[this] val map = new WeakHashMap[K, WeakReference[V]]
-
-  protected def valueFromKey(k: K): V
-  protected def keyFromValue(v: V): Option[K]
-
-  def apply(name: K): V = {
-    def cached(): V = {
-      rlock.lock
-      try {
-        val reference = map get name
-        if (reference == null) null
-        else reference.get  // will be null if we were gc-ed
-      }
-      finally rlock.unlock
-    }
-    def updateCache(): V = {
-      wlock.lock
-      try {
-        val res = cached()
-        if (res != null) res
-        else {
-          // If we don't remove the old String key from the map, we can
-          // wind up with one String as the key and a different String as
-          // the name field in the Symbol, which can lead to surprising GC
-          // behavior and duplicate Symbols. See scala/bug#6706.
-          map remove name
-          val sym = valueFromKey(name)
-          map.put(name, new WeakReference(sym))
-          sym
-        }
-      }
-      finally wlock.unlock
-    }
-
-    val res = cached()
-    if (res == null) updateCache()
-    else res
-  }
-  def unapply(other: V): Option[K] = keyFromValue(other)
-}
-*/
diff --git a/scalalib/overrides-2.13.1/scala/Symbol.scala b/scalalib/overrides-2.13.1/scala/Symbol.scala
deleted file mode 100644
index 0000b5fe6f..0000000000
--- a/scalalib/overrides-2.13.1/scala/Symbol.scala
+++ /dev/null
@@ -1,113 +0,0 @@
-/*
- * Scala (https://www.scala-lang.org)
- *
- * Copyright EPFL and Lightbend, Inc.
- *
- * Licensed under Apache License 2.0
- * (http://www.apache.org/licenses/LICENSE-2.0).
- *
- * See the NOTICE file distributed with this work for
- * additional information regarding copyright ownership.
- */
-
-package scala
-
-import scala.scalajs.js
-
-/** This class provides a simple way to get unique objects for equal strings.
- *  Since symbols are interned, they can be compared using reference equality.
- *  Instances of `Symbol` can be created easily with Scala's built-in quote
- *  mechanism.
- *
- *  For instance, the Scala term `'mysym` will
- *  invoke the constructor of the `Symbol` class in the following way:
- *  `Symbol("mysym")`.
- *
- *  @author  Martin Odersky, Iulian Dragos
- *  @since   1.7
- */
-final class Symbol private (val name: String) extends Serializable {
-  /** Converts this symbol to a string.
-   */
-  override def toString(): String = "'" + name
-
-  @throws(classOf[java.io.ObjectStreamException])
-  private def readResolve(): Any = Symbol.apply(name)
-  override def hashCode = name.hashCode()
-  override def equals(other: Any) = this eq other.asInstanceOf[AnyRef]
-}
-
-// Modified to use Scala.js specific cache
-object Symbol extends JSUniquenessCache[Symbol] {
-  override def apply(name: String): Symbol = super.apply(name)
-  protected def valueFromKey(name: String): Symbol = new Symbol(name)
-  protected def keyFromValue(sym: Symbol): Option[String] = Some(sym.name)
-}
-
-private[scala] abstract class JSUniquenessCache[V]
-{
-  private val cache = js.Dictionary.empty[V]
-
-  protected def valueFromKey(k: String): V
-  protected def keyFromValue(v: V): Option[String]
-
-  def apply(name: String): V =
-    cache.getOrElseUpdate(name, valueFromKey(name))
-
-  def unapply(other: V): Option[String] = keyFromValue(other)
-}
-
-/** This is private so it won't appear in the library API, but
-  * abstracted to offer some hope of reusability.  */
-/* DELETED for Scala.js
-private[scala] abstract class UniquenessCache[K >: js.String, V >: Null]
-{
-
-  import java.lang.ref.WeakReference
-  import java.util.WeakHashMap
-  import java.util.concurrent.locks.ReentrantReadWriteLock
-
-  private[this] val rwl = new ReentrantReadWriteLock()
-  private[this] val rlock = rwl.readLock
-  private[this] val wlock = rwl.writeLock
-  private[this] val map = new WeakHashMap[K, WeakReference[V]]
-
-  protected def valueFromKey(k: K): V
-  protected def keyFromValue(v: V): Option[K]
-
-  def apply(name: K): V = {
-    def cached(): V = {
-      rlock.lock
-      try {
-        val reference = map get name
-        if (reference == null) null
-        else reference.get  // will be null if we were gc-ed
-      }
-      finally rlock.unlock
-    }
-    def updateCache(): V = {
-      wlock.lock
-      try {
-        val res = cached()
-        if (res != null) res
-        else {
-          // If we don't remove the old String key from the map, we can
-          // wind up with one String as the key and a different String as
-          // the name field in the Symbol, which can lead to surprising GC
-          // behavior and duplicate Symbols. See scala/bug#6706.
-          map remove name
-          val sym = valueFromKey(name)
-          map.put(name, new WeakReference(sym))
-          sym
-        }
-      }
-      finally wlock.unlock
-    }
-
-    val res = cached()
-    if (res == null) updateCache()
-    else res
-  }
-  def unapply(other: V): Option[K] = keyFromValue(other)
-}
-*/
diff --git a/scalalib/overrides-2.13.2/scala/Symbol.scala b/scalalib/overrides-2.13.2/scala/Symbol.scala
deleted file mode 100644
index 0000b5fe6f..0000000000
--- a/scalalib/overrides-2.13.2/scala/Symbol.scala
+++ /dev/null
@@ -1,113 +0,0 @@
-/*
- * Scala (https://www.scala-lang.org)
- *
- * Copyright EPFL and Lightbend, Inc.
- *
- * Licensed under Apache License 2.0
- * (http://www.apache.org/licenses/LICENSE-2.0).
- *
- * See the NOTICE file distributed with this work for
- * additional information regarding copyright ownership.
- */
-
-package scala
-
-import scala.scalajs.js
-
-/** This class provides a simple way to get unique objects for equal strings.
- *  Since symbols are interned, they can be compared using reference equality.
- *  Instances of `Symbol` can be created easily with Scala's built-in quote
- *  mechanism.
- *
- *  For instance, the Scala term `'mysym` will
- *  invoke the constructor of the `Symbol` class in the following way:
- *  `Symbol("mysym")`.
- *
- *  @author  Martin Odersky, Iulian Dragos
- *  @since   1.7
- */
-final class Symbol private (val name: String) extends Serializable {
-  /** Converts this symbol to a string.
-   */
-  override def toString(): String = "'" + name
-
-  @throws(classOf[java.io.ObjectStreamException])
-  private def readResolve(): Any = Symbol.apply(name)
-  override def hashCode = name.hashCode()
-  override def equals(other: Any) = this eq other.asInstanceOf[AnyRef]
-}
-
-// Modified to use Scala.js specific cache
-object Symbol extends JSUniquenessCache[Symbol] {
-  override def apply(name: String): Symbol = super.apply(name)
-  protected def valueFromKey(name: String): Symbol = new Symbol(name)
-  protected def keyFromValue(sym: Symbol): Option[String] = Some(sym.name)
-}
-
-private[scala] abstract class JSUniquenessCache[V]
-{
-  private val cache = js.Dictionary.empty[V]
-
-  protected def valueFromKey(k: String): V
-  protected def keyFromValue(v: V): Option[String]
-
-  def apply(name: String): V =
-    cache.getOrElseUpdate(name, valueFromKey(name))
-
-  def unapply(other: V): Option[String] = keyFromValue(other)
-}
-
-/** This is private so it won't appear in the library API, but
-  * abstracted to offer some hope of reusability.  */
-/* DELETED for Scala.js
-private[scala] abstract class UniquenessCache[K >: js.String, V >: Null]
-{
-
-  import java.lang.ref.WeakReference
-  import java.util.WeakHashMap
-  import java.util.concurrent.locks.ReentrantReadWriteLock
-
-  private[this] val rwl = new ReentrantReadWriteLock()
-  private[this] val rlock = rwl.readLock
-  private[this] val wlock = rwl.writeLock
-  private[this] val map = new WeakHashMap[K, WeakReference[V]]
-
-  protected def valueFromKey(k: K): V
-  protected def keyFromValue(v: V): Option[K]
-
-  def apply(name: K): V = {
-    def cached(): V = {
-      rlock.lock
-      try {
-        val reference = map get name
-        if (reference == null) null
-        else reference.get  // will be null if we were gc-ed
-      }
-      finally rlock.unlock
-    }
-    def updateCache(): V = {
-      wlock.lock
-      try {
-        val res = cached()
-        if (res != null) res
-        else {
-          // If we don't remove the old String key from the map, we can
-          // wind up with one String as the key and a different String as
-          // the name field in the Symbol, which can lead to surprising GC
-          // behavior and duplicate Symbols. See scala/bug#6706.
-          map remove name
-          val sym = valueFromKey(name)
-          map.put(name, new WeakReference(sym))
-          sym
-        }
-      }
-      finally wlock.unlock
-    }
-
-    val res = cached()
-    if (res == null) updateCache()
-    else res
-  }
-  def unapply(other: V): Option[K] = keyFromValue(other)
-}
-*/
diff --git a/test-suite/shared/src/test/scala/org/scalajs/testsuite/scalalib/SymbolTest.scala b/test-suite/shared/src/test/scala/org/scalajs/testsuite/scalalib/SymbolTest.scala
index 15ecdef4b0..bc6ad8f53a 100644
--- a/test-suite/shared/src/test/scala/org/scalajs/testsuite/scalalib/SymbolTest.scala
+++ b/test-suite/shared/src/test/scala/org/scalajs/testsuite/scalalib/SymbolTest.scala
@@ -56,14 +56,7 @@ class SymbolTest {
   @Test def testToString(): Unit = {
     val scalajs = Symbol("ScalaJS")
 
-    val toStringUsesQuoteSyntax = {
-      scalaVersion.startsWith("2.12.") ||
-      scalaVersion == "2.13.0" ||
-      scalaVersion == "2.13.1" ||
-      scalaVersion == "2.13.2"
-    }
-
-    if (toStringUsesQuoteSyntax) {
+    if (scalaVersion.startsWith("2.12.")) {
       assertEquals("'ScalaJS", scalajs.toString)
       assertEquals("'$", Symbol("$").toString)
       assertEquals("'$$", Symbol("$$").toString)

From 40d68469bb85a0133beaf16ef7d836cbc03b0945 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Sun, 5 Jan 2025 22:24:14 +0100
Subject: [PATCH 236/298] Version 1.18.0.

---
 ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala b/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala
index 37521f5065..5d96f087bb 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala
@@ -17,8 +17,8 @@ import java.util.concurrent.ConcurrentHashMap
 import scala.util.matching.Regex
 
 object ScalaJSVersions extends VersionChecks(
-    current = "1.18.0-SNAPSHOT",
-    binaryEmitted = "1.18-SNAPSHOT"
+    current = "1.18.0",
+    binaryEmitted = "1.18"
 )
 
 /** Helper class to allow for testing of logic. */

From 5eb1546d574301094f23deb24538687c182c888c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Mon, 6 Jan 2025 15:49:14 +0100
Subject: [PATCH 237/298] Towards 1.18.1.

---
 .../org/scalajs/ir/ScalaJSVersions.scala      |  2 +-
 project/BinaryIncompatibilities.scala         | 47 -------------------
 project/Build.scala                           |  2 +-
 3 files changed, 2 insertions(+), 49 deletions(-)

diff --git a/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala b/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala
index 5d96f087bb..b30026fb8f 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala
@@ -17,7 +17,7 @@ import java.util.concurrent.ConcurrentHashMap
 import scala.util.matching.Regex
 
 object ScalaJSVersions extends VersionChecks(
-    current = "1.18.0",
+    current = "1.18.1-SNAPSHOT",
     binaryEmitted = "1.18"
 )
 
diff --git a/project/BinaryIncompatibilities.scala b/project/BinaryIncompatibilities.scala
index c4530e7467..4713fe6bf8 100644
--- a/project/BinaryIncompatibilities.scala
+++ b/project/BinaryIncompatibilities.scala
@@ -5,56 +5,9 @@ import com.typesafe.tools.mima.core.ProblemFilters._
 
 object BinaryIncompatibilities {
   val IR = Seq(
-    // !!! Breaking, OK in minor release
-    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Printers#IRTreePrinter.print"),
-    ProblemFilters.exclude[MissingClassProblem]("org.scalajs.ir.Trees$ArrayLength"),
-    ProblemFilters.exclude[MissingClassProblem]("org.scalajs.ir.Trees$ArrayLength$"),
-    ProblemFilters.exclude[MissingClassProblem]("org.scalajs.ir.Trees$Clone"),
-    ProblemFilters.exclude[MissingClassProblem]("org.scalajs.ir.Trees$Clone$"),
-    ProblemFilters.exclude[MissingClassProblem]("org.scalajs.ir.Trees$GetClass"),
-    ProblemFilters.exclude[MissingClassProblem]("org.scalajs.ir.Trees$GetClass$"),
-    ProblemFilters.exclude[MissingClassProblem]("org.scalajs.ir.Trees$IdentityHashCode"),
-    ProblemFilters.exclude[MissingClassProblem]("org.scalajs.ir.Trees$IdentityHashCode$"),
-    ProblemFilters.exclude[MissingClassProblem]("org.scalajs.ir.Trees$JSLinkingInfo"),
-    ProblemFilters.exclude[MissingClassProblem]("org.scalajs.ir.Trees$JSLinkingInfo$"),
-    ProblemFilters.exclude[MissingClassProblem]("org.scalajs.ir.Trees$LabelIdent"),
-    ProblemFilters.exclude[MissingClassProblem]("org.scalajs.ir.Trees$LabelIdent$"),
-    ProblemFilters.exclude[Problem]("org.scalajs.ir.Trees#Labeled.*"),
-    ProblemFilters.exclude[Problem]("org.scalajs.ir.Trees#Return.*"),
-    ProblemFilters.exclude[MissingClassProblem]("org.scalajs.ir.Trees$This"),
-    ProblemFilters.exclude[MissingTypesProblem]("org.scalajs.ir.Trees$This$"),
-    ProblemFilters.exclude[IncompatibleResultTypeProblem]("org.scalajs.ir.Trees#This.apply"),
-    ProblemFilters.exclude[IncompatibleMethTypeProblem]("org.scalajs.ir.Trees#This.unapply"),
-    ProblemFilters.exclude[MissingClassProblem]("org.scalajs.ir.Trees$Throw"),
-    ProblemFilters.exclude[MissingClassProblem]("org.scalajs.ir.Trees$Throw$"),
-    ProblemFilters.exclude[MissingClassProblem]("org.scalajs.ir.Trees$UnwrapFromThrowable"),
-    ProblemFilters.exclude[MissingClassProblem]("org.scalajs.ir.Trees$UnwrapFromThrowable$"),
-    ProblemFilters.exclude[Problem]("org.scalajs.ir.Trees#VarRef.*"),
-    ProblemFilters.exclude[MissingClassProblem]("org.scalajs.ir.Trees$WrapAsThrowable"),
-    ProblemFilters.exclude[MissingClassProblem]("org.scalajs.ir.Trees$WrapAsThrowable$"),
-    ProblemFilters.exclude[IncompatibleResultTypeProblem]("org.scalajs.ir.Trees#*.tpe"),
-    ProblemFilters.exclude[MissingClassProblem]("org.scalajs.ir.Types$NoType$"),
-
-    // !!! Breaking, OK in minor release
-    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Transformers#Transformer.transform"),
-    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Transformers#Transformer.transformExpr"),
-    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Transformers#Transformer.transformExprOrJSSpread"),
-    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Transformers#Transformer.transformStat"),
-    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Transformers#Transformer.transformStats"),
-    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Trees#Transient#Value.transform"),
-    ProblemFilters.exclude[ReversedMissingMethodProblem]("org.scalajs.ir.Trees#Transient#Value.transform"),
-
-    // private, not an issue
-    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Serializers#Deserializer.readLabelIdent"),
-    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Serializers#Serializer.writeLabelIdent"),
-    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Hashers#TreeHasher.mixLabelIdent"),
   )
 
   val Linker = Seq(
-    // !!! Breaking, OK in minor release
-    exclude[DirectMissingMethodProblem]("org.scalajs.linker.standard.ModuleSet.coreSpec"),
-    exclude[DirectMissingMethodProblem]("org.scalajs.linker.standard.ModuleSet.this"),
-    exclude[DirectMissingMethodProblem]("org.scalajs.linker.standard.LinkerBackend.verifyModuleSet"),
   )
 
   val LinkerInterface = Seq(
diff --git a/project/Build.scala b/project/Build.scala
index 9eb18bbd1e..e453908f9f 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -394,7 +394,7 @@ object Build {
   val previousVersions = List("1.0.0", "1.0.1", "1.1.0", "1.1.1", "1.2.0",
       "1.3.0", "1.3.1", "1.4.0", "1.5.0", "1.5.1", "1.6.0", "1.7.0", "1.7.1",
       "1.8.0", "1.9.0", "1.10.0", "1.10.1", "1.11.0", "1.12.0", "1.13.0",
-      "1.13.1", "1.13.2", "1.14.0", "1.15.0", "1.16.0", "1.17.0")
+      "1.13.1", "1.13.2", "1.14.0", "1.15.0", "1.16.0", "1.17.0", "1.18.0")
   val previousVersion = previousVersions.last
 
   val previousBinaryCrossVersion = CrossVersion.binaryWith("sjs1_", "")

From f0c74cb450df190a1b3a0ef41dc489cae35cd3fa Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Tue, 7 Jan 2025 11:26:46 +0100
Subject: [PATCH 238/298] Use `CheckNotNull` in the `Throw` deserialization
 hack.

Back in Scala.js 1.11, we did not have `CheckNotNull` as a separate
node. The deserialization hack was therefore pretty complicated,
but all it wanted to do was check for null values.

Unfortunately we broke that deserialization hack in Scala.js 1.18.0
because `UnwrapFromThrowable` now demands a non-nullable argument.
So we have to insert an explicit `CheckNotNull`.

It turns out we can dramatically simplify the whole hack with
nothing but `CheckNotNull`.
---
 .../scala/org/scalajs/ir/Serializers.scala    | 71 +++++--------------
 .../scalajs/linker/BackwardsCompatTest.scala  | 34 +++++++++
 2 files changed, 51 insertions(+), 54 deletions(-)

diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
index 74e7d2c1aa..c1d082c9f5 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
@@ -1424,69 +1424,32 @@ object Serializers {
      *  so that `Throw(e)` only ever throws the value of `e`, while the NPE UB
      *  is specified by `UnwrapFromThrowable`. Among other things, this allows
      *  the user-space code `js.special.throw(e)` to indiscriminately throw `e`
-     *  even if it is `null`.
+     *  even if it is `null`. Later, in Scala.js 1.18, we further separated the
+     *  null check of `UnwrapFromThrowable` to be an explicit `CheckNotNull`.
      *
-     *  With this hack, we patch `Throw(e)` where `e` is a nullable `Throwable`
-     *  by inserting an appropriate `UnwrapFromThrowable`.
+     *  With this hack, we patch `Throw(e)` by inserting an appropriate
+     *  `CheckNotNull`.
      *
-     *  Naively, we would just return `UnwrapFromThrowable(e)`. Unfortunately,
-     *  we cannot prove that this is type-correct when the type of `e` is a
-     *  `ClassType(cls)`, as we cannot test whether `cls` is a subclass of
-     *  `java.lang.Throwable`. So we have to produce the following instead:
-     *
-     *  {{{
-     *    if (expr === null) unwrapFromThrowable(null) else expr
-     *  }}}
-     *
-     *  except that evaluates `expr` twice. If it is a `VarRef`, which is a
-     *  common case, that is fine. Otherwise, we have to wrap this pattern in
-     *  an IIFE.
-     *
-     *  We also have to avoid the transformation altogether when the `expr` is
-     *  an `AnyType`. This happens when the previous Scala.js compiler already
-     *  provides the unwrapped exception, which is either
+     *  However, we must not do that when the previous Scala.js compiler
+     *  already provides the *unwrapped* exception. This happened in two
+     *  situations:
      *
      *  - when automatically re-throwing an unhandled exception at the end of a
      *    `try..catch`, or
      *  - when throwing a maybe-JavaScriptException, with an explicit call to
      *    `runtime.package$.unwrapJavaScriptException(x)`.
+     *
+     *  Fortunately, in both situations, the type of the `expr` is always
+     *  `AnyType`. We can accurately use that test to know whether we need to
+     *  apply the patch.
      */
     private def throwArgumentHack8(expr: Tree)(implicit pos: Position): Tree = {
-      def unwrapFromThrowable(t: Tree): Tree =
-        UnaryOp(UnaryOp.UnwrapFromThrowable, t)
-
-      expr.tpe match {
-        case NullType =>
-          // Evaluate the expression then definitely run into an NPE UB
-          unwrapFromThrowable(expr)
-
-        case ClassType(_, _) =>
-          expr match {
-            case New(_, _, _) =>
-              // Common case (`throw new SomeException(...)`) that is known not to be `null`
-              expr
-            case VarRef(_) =>
-              /* Common case (explicit re-throw of the form `throw th`) where we don't need the IIFE.
-               * if (expr === null) unwrapFromThrowable(null) else expr
-               */
-              If(BinaryOp(BinaryOp.===, expr, Null()), unwrapFromThrowable(Null()), expr)(AnyType)
-            case _ =>
-              /* General case where we need to avoid evaluating `expr` twice.
-               * ((x) => if (x === null) unwrapFromThrowable(null) else x)(expr)
-               */
-              val x = LocalIdent(LocalName("x"))
-              val xParamDef = ParamDef(x, OriginalName.NoOriginalName, AnyType, mutable = false)
-              val xRef = xParamDef.ref
-              val closure = Closure(arrow = true, Nil, List(xParamDef), None, {
-                If(BinaryOp(BinaryOp.===, xRef, Null()), unwrapFromThrowable(Null()), xRef)(AnyType)
-              }, Nil)
-              JSFunctionApply(closure, List(expr))
-          }
-
-        case _ =>
-          // Do not transform expressions of other types, in particular `AnyType`
-          expr
-      }
+      if (expr.tpe == AnyType)
+        expr
+      else if (!expr.tpe.isNullable)
+        expr // no CheckNotNull needed; common case because of `throw new ...`
+      else
+        UnaryOp(UnaryOp.CheckNotNull, expr)
     }
 
     def readTrees(): List[Tree] =
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/BackwardsCompatTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/BackwardsCompatTest.scala
index 54a1a0f105..c1e33411d9 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/BackwardsCompatTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/BackwardsCompatTest.scala
@@ -75,6 +75,40 @@ class BackwardsCompatTest {
     test(classDefs, MainTestModuleInitializers)
   }
 
+  @Test
+  def testThrowHackWithVariable_Issue5107(): AsyncResult = await {
+    val Base64Class = ClassName("java.util.Base64")
+    val DecoderClass = ClassName("java.util.Base64$Decoder")
+    val ByteBufferClass = ClassName("java.nio.ByteBuffer")
+
+    val DecoderTypeRef = ClassRef(DecoderClass)
+    val ByteBufferTypeRef = ClassRef(ByteBufferClass)
+    val AB = ArrayTypeRef(ByteRef, 1)
+
+    val DecoderType = ClassType(DecoderClass, nullable = true)
+    val ByteBufferType = ClassType(ByteBufferClass, nullable = true)
+
+    /* java.util.Base64.getDecoder().decode(java.nio.ByteBuffer.wrap(Array(65, 81, 73, 61)))
+     * That is the only method I found in our javalib that contains a `throw e`,
+     * as opposed to a `throw new ...`.
+     */
+    val classDefs = Seq(
+      mainTestClassDef(systemOutPrintln {
+        Apply(
+          EAF,
+          ApplyStatic(EAF, Base64Class, m("getDecoder", Nil, DecoderTypeRef), Nil)(DecoderType),
+          m("decode", List(ByteBufferTypeRef), ByteBufferTypeRef),
+          List(
+            ApplyStatic(EAF, ByteBufferClass, m("wrap", List(AB), ByteBufferTypeRef),
+                List(ArrayValue(AB, List[Byte](65, 81, 73, 61).map(ByteLiteral(_)))))(ByteBufferType)
+          )
+        )(ByteBufferType)
+      })
+    )
+
+    test(classDefs, MainTestModuleInitializers)
+  }
+
   private def test(classDefs: Seq[ClassDef],
       moduleInitializers: Seq[ModuleInitializer]): Future[_] = {
     val classDefFiles = classDefs.map(MemClassDefIRFile(_))

From 0b94e0386d8d5dfb2086a39155ebd175739ed673 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Tue, 7 Jan 2025 12:36:18 +0100
Subject: [PATCH 239/298] Fix missing `CheckNotNull`s in the deserialization
 hacks of `newInstance`.

---
 .../scala/org/scalajs/ir/Serializers.scala    |  4 +--
 .../scalajs/linker/BackwardsCompatTest.scala  | 27 +++++++++++++++++++
 2 files changed, 29 insertions(+), 2 deletions(-)

diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
index c1d082c9f5..bf50ef07fc 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
@@ -1638,10 +1638,10 @@ object Serializers {
       }
 
       def arrayLength(t: Tree)(implicit pos: Position): Tree =
-        UnaryOp(UnaryOp.Array_length, t)
+        UnaryOp(UnaryOp.Array_length, UnaryOp(UnaryOp.CheckNotNull, t))
 
       def getClass(t: Tree)(implicit pos: Position): Tree =
-        UnaryOp(UnaryOp.GetClass, t)
+        UnaryOp(UnaryOp.GetClass, UnaryOp(UnaryOp.CheckNotNull, t))
 
       val jlClassRef = ClassRef(ClassClass)
       val intArrayTypeRef = ArrayTypeRef(IntRef, 1)
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/BackwardsCompatTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/BackwardsCompatTest.scala
index c1e33411d9..3439a80251 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/BackwardsCompatTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/BackwardsCompatTest.scala
@@ -109,6 +109,33 @@ class BackwardsCompatTest {
     test(classDefs, MainTestModuleInitializers)
   }
 
+  @Test
+  def testArrayNewInstanceHacks_Issue5107(): AsyncResult = await {
+    val ReflectArrayClass = ClassName("java.lang.reflect.Array")
+
+    val ClassClassRef = ClassRef(ClassClass)
+
+    val AI = ArrayTypeRef(IntRef, 1)
+
+    /* jlr.Array.newInstance(classOf[String], 5)
+     * jlr.Array.newInstance(classOf[String], Array(5, 4))
+     */
+    val classDefs = Seq(
+      mainTestClassDef(Block(
+        systemOutPrintln(
+          ApplyStatic(EAF, ReflectArrayClass, m("newInstance", List(ClassClassRef, I), O),
+              List(ClassOf(T), int(5)))(AnyType)
+        ),
+        systemOutPrintln(
+          ApplyStatic(EAF, ReflectArrayClass, m("newInstance", List(ClassClassRef, AI), O),
+              List(ClassOf(T), ArrayValue(AI, List(int(5), int(4)))))(AnyType)
+        )
+      ))
+    )
+
+    test(classDefs, MainTestModuleInitializers)
+  }
+
   private def test(classDefs: Seq[ClassDef],
       moduleInitializers: Seq[ModuleInitializer]): Future[_] = {
     val classDefFiles = classDefs.map(MemClassDefIRFile(_))

From 0fdaff514b09eca6ea559fb1ed62668c76fbfd5f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Wed, 8 Jan 2025 09:13:53 +0100
Subject: [PATCH 240/298] Version 1.18.1.

---
 ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala b/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala
index b30026fb8f..dc545b120f 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala
@@ -17,7 +17,7 @@ import java.util.concurrent.ConcurrentHashMap
 import scala.util.matching.Regex
 
 object ScalaJSVersions extends VersionChecks(
-    current = "1.18.1-SNAPSHOT",
+    current = "1.18.1",
     binaryEmitted = "1.18"
 )
 

From 2cdb10b08a123e8f0097b89915d318e5d80aa84e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Wed, 8 Jan 2025 17:47:01 +0100
Subject: [PATCH 241/298] Towards 1.18.2.

---
 ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala | 2 +-
 project/Build.scala                                           | 3 ++-
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala b/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala
index dc545b120f..581ed885cd 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala
@@ -17,7 +17,7 @@ import java.util.concurrent.ConcurrentHashMap
 import scala.util.matching.Regex
 
 object ScalaJSVersions extends VersionChecks(
-    current = "1.18.1",
+    current = "1.18.2-SNAPSHOT",
     binaryEmitted = "1.18"
 )
 
diff --git a/project/Build.scala b/project/Build.scala
index e453908f9f..8e02322bfe 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -394,7 +394,8 @@ object Build {
   val previousVersions = List("1.0.0", "1.0.1", "1.1.0", "1.1.1", "1.2.0",
       "1.3.0", "1.3.1", "1.4.0", "1.5.0", "1.5.1", "1.6.0", "1.7.0", "1.7.1",
       "1.8.0", "1.9.0", "1.10.0", "1.10.1", "1.11.0", "1.12.0", "1.13.0",
-      "1.13.1", "1.13.2", "1.14.0", "1.15.0", "1.16.0", "1.17.0", "1.18.0")
+      "1.13.1", "1.13.2", "1.14.0", "1.15.0", "1.16.0", "1.17.0", "1.18.0",
+      "1.18.1")
   val previousVersion = previousVersions.last
 
   val previousBinaryCrossVersion = CrossVersion.binaryWith("sjs1_", "")

From 4f96d2c336609834f7dc057197cc5b5ae12e375b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Sun, 12 Jan 2025 13:03:02 +0100
Subject: [PATCH 242/298] Upgrade to Scala 2.12.20.

---
 Jenkinsfile                                   |   5 +-
 .../{2.12.19 => 2.12.20}/BlacklistedTests.txt |   1 +
 .../{2.12.19 => 2.12.20}/neg/choices.check    |   0
 .../neg/partestInvalidFlag.check              |   0
 .../{2.12.19 => 2.12.20}/neg/t11952b.check    |   0
 .../neg/t6446-additional.check                |   0
 .../{2.12.19 => 2.12.20}/neg/t6446-list.check |   0
 .../neg/t6446-missing.check                   |   0
 .../neg/t6446-show-phases.check               |   0
 .../neg/t7494-no-options.check                |   0
 .../run/Course-2002-01.check                  |   0
 .../run/Course-2002-02.check                  |   0
 .../run/Course-2002-04.check                  |   0
 .../run/Course-2002-08.check                  |   0
 .../run/Course-2002-09.check                  |   0
 .../run/Course-2002-10.check                  |   0
 .../{2.12.19 => 2.12.20}/run/Meter.check      |   0
 .../run/MeterCaseClass.check                  |   0
 .../run/anyval-box-types.check                |   0
 .../scalajs/{2.12.19 => 2.12.20}/run/bugs.sem |   0
 .../run/caseClassHash.check                   |   0
 .../{2.12.19 => 2.12.20}/run/classof.check    |   0
 .../{2.12.19 => 2.12.20}/run/deeps.check      |   0
 .../run/dynamic-anyval.check                  |   0
 .../{2.12.19 => 2.12.20}/run/exceptions-2.sem |   0
 .../run/exceptions-nest.check                 |   0
 .../run/exceptions-nest.sem                   |   0
 .../run/impconvtimes.check                    |   0
 .../{2.12.19 => 2.12.20}/run/imports.check    |   0
 .../run/inlineHandlers.sem                    |   0
 .../run/interpolation.check                   |   0
 .../run/interpolationMultiline1.check         |   0
 .../run/macro-bundle-static.check             |   0
 .../run/macro-bundle-toplevel.check           |   0
 .../run/macro-bundle-whitebox-decl.check      |   0
 .../{2.12.19 => 2.12.20}/run/misc.check       |   0
 .../run/optimizer-array-load.sem              |   0
 .../{2.12.19 => 2.12.20}/run/pf-catch.sem     |   0
 .../{2.12.19 => 2.12.20}/run/promotion.check  |   0
 .../{2.12.19 => 2.12.20}/run/runtime.check    |   0
 .../{2.12.19 => 2.12.20}/run/spec-self.check  |   0
 .../{2.12.19 => 2.12.20}/run/structural.check |   0
 .../{2.12.19 => 2.12.20}/run/t0421-new.check  |   0
 .../{2.12.19 => 2.12.20}/run/t0421-old.check  |   0
 .../{2.12.19 => 2.12.20}/run/t1503.sem        |   0
 .../{2.12.19 => 2.12.20}/run/t3702.check      |   0
 .../{2.12.19 => 2.12.20}/run/t4148.sem        |   0
 .../{2.12.19 => 2.12.20}/run/t4617.check      |   0
 .../{2.12.19 => 2.12.20}/run/t5356.check      |   0
 .../{2.12.19 => 2.12.20}/run/t5552.check      |   0
 .../{2.12.19 => 2.12.20}/run/t5568.check      |   0
 .../{2.12.19 => 2.12.20}/run/t5629b.check     |   0
 .../{2.12.19 => 2.12.20}/run/t5680.check      |   0
 .../{2.12.19 => 2.12.20}/run/t5866.check      |   0
 .../run/t6318_primitives.check                |   0
 .../{2.12.19 => 2.12.20}/run/t6662.check      |   0
 .../{2.12.19 => 2.12.20}/run/t6827.sem        |   0
 .../{2.12.19 => 2.12.20}/run/t7657.check      |   0
 .../{2.12.19 => 2.12.20}/run/t7763.sem        |   0
 .../{2.12.19 => 2.12.20}/run/t8570a.check     |   0
 .../{2.12.19 => 2.12.20}/run/t8601b.sem       |   0
 .../{2.12.19 => 2.12.20}/run/t8601c.sem       |   0
 .../{2.12.19 => 2.12.20}/run/t8601d.sem       |   0
 .../{2.12.19 => 2.12.20}/run/t8764.check      |   0
 .../{2.12.19 => 2.12.20}/run/t8925.sem        |   0
 .../{2.12.19 => 2.12.20}/run/t9387b.check     |   0
 .../{2.12.19 => 2.12.20}/run/t9656.check      |   0
 .../run/try-catch-unify.check                 |   0
 .../run/virtpatmat_switch.check               |   0
 .../run/virtpatmat_typetag.check              |   0
 project/Build.scala                           |   1 +
 .../change-config-and-source/build.sbt        |   2 +-
 .../incremental/change-config/build.sbt       |   2 +-
 .../incremental/fix-compile-error/build.sbt   |   2 +-
 .../linker/concurrent-linker-use/build.sbt    |   2 +-
 .../sbt-test/linker/custom-linker/build.sbt   |   4 +-
 .../no-root-dependency-resolution/build.sbt   |   2 +-
 .../linker/non-existent-classpath/build.sbt   |   2 +-
 .../sbt-test/settings/cross-version/build.sbt |   2 +-
 .../src/sbt-test/settings/env-vars/build.sbt  |   2 +-
 .../settings/legacy-link-empty/build.sbt      |   2 +-
 .../settings/legacy-link-tasks/build.sbt      |   2 +-
 .../sbt-test/settings/module-init/build.sbt   |   2 +-
 .../sbt-test/settings/source-map/build.sbt    |   2 +-
 .../testing/multi-framework/build.sbt         |   2 +-
 .../resources/2.12.20/BlacklistedTests.txt    | 197 ++++++++++++++++++
 86 files changed, 217 insertions(+), 17 deletions(-)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.19 => 2.12.20}/BlacklistedTests.txt (99%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.19 => 2.12.20}/neg/choices.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.19 => 2.12.20}/neg/partestInvalidFlag.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.19 => 2.12.20}/neg/t11952b.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.19 => 2.12.20}/neg/t6446-additional.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.19 => 2.12.20}/neg/t6446-list.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.19 => 2.12.20}/neg/t6446-missing.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.19 => 2.12.20}/neg/t6446-show-phases.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.19 => 2.12.20}/neg/t7494-no-options.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.19 => 2.12.20}/run/Course-2002-01.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.19 => 2.12.20}/run/Course-2002-02.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.19 => 2.12.20}/run/Course-2002-04.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.19 => 2.12.20}/run/Course-2002-08.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.19 => 2.12.20}/run/Course-2002-09.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.19 => 2.12.20}/run/Course-2002-10.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.19 => 2.12.20}/run/Meter.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.19 => 2.12.20}/run/MeterCaseClass.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.19 => 2.12.20}/run/anyval-box-types.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.19 => 2.12.20}/run/bugs.sem (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.19 => 2.12.20}/run/caseClassHash.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.19 => 2.12.20}/run/classof.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.19 => 2.12.20}/run/deeps.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.19 => 2.12.20}/run/dynamic-anyval.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.19 => 2.12.20}/run/exceptions-2.sem (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.19 => 2.12.20}/run/exceptions-nest.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.19 => 2.12.20}/run/exceptions-nest.sem (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.19 => 2.12.20}/run/impconvtimes.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.19 => 2.12.20}/run/imports.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.19 => 2.12.20}/run/inlineHandlers.sem (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.19 => 2.12.20}/run/interpolation.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.19 => 2.12.20}/run/interpolationMultiline1.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.19 => 2.12.20}/run/macro-bundle-static.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.19 => 2.12.20}/run/macro-bundle-toplevel.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.19 => 2.12.20}/run/macro-bundle-whitebox-decl.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.19 => 2.12.20}/run/misc.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.19 => 2.12.20}/run/optimizer-array-load.sem (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.19 => 2.12.20}/run/pf-catch.sem (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.19 => 2.12.20}/run/promotion.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.19 => 2.12.20}/run/runtime.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.19 => 2.12.20}/run/spec-self.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.19 => 2.12.20}/run/structural.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.19 => 2.12.20}/run/t0421-new.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.19 => 2.12.20}/run/t0421-old.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.19 => 2.12.20}/run/t1503.sem (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.19 => 2.12.20}/run/t3702.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.19 => 2.12.20}/run/t4148.sem (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.19 => 2.12.20}/run/t4617.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.19 => 2.12.20}/run/t5356.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.19 => 2.12.20}/run/t5552.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.19 => 2.12.20}/run/t5568.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.19 => 2.12.20}/run/t5629b.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.19 => 2.12.20}/run/t5680.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.19 => 2.12.20}/run/t5866.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.19 => 2.12.20}/run/t6318_primitives.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.19 => 2.12.20}/run/t6662.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.19 => 2.12.20}/run/t6827.sem (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.19 => 2.12.20}/run/t7657.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.19 => 2.12.20}/run/t7763.sem (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.19 => 2.12.20}/run/t8570a.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.19 => 2.12.20}/run/t8601b.sem (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.19 => 2.12.20}/run/t8601c.sem (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.19 => 2.12.20}/run/t8601d.sem (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.19 => 2.12.20}/run/t8764.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.19 => 2.12.20}/run/t8925.sem (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.19 => 2.12.20}/run/t9387b.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.19 => 2.12.20}/run/t9656.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.19 => 2.12.20}/run/try-catch-unify.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.19 => 2.12.20}/run/virtpatmat_switch.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.12.19 => 2.12.20}/run/virtpatmat_typetag.check (100%)
 create mode 100644 scala-test-suite/src/test/resources/2.12.20/BlacklistedTests.txt

diff --git a/Jenkinsfile b/Jenkinsfile
index 63e464571d..e9e1630b8b 100644
--- a/Jenkinsfile
+++ b/Jenkinsfile
@@ -543,8 +543,8 @@ def otherJavaVersions = ["11", "17", "21"]
 def allJavaVersions = otherJavaVersions.clone()
 allJavaVersions << mainJavaVersion
 
-def mainScalaVersion = "2.12.19"
-def mainScalaVersions = ["2.12.19", "2.13.13"]
+def mainScalaVersion = "2.12.20"
+def mainScalaVersions = ["2.12.20", "2.13.13"]
 def otherScalaVersions = [
   "2.12.6",
   "2.12.7",
@@ -559,6 +559,7 @@ def otherScalaVersions = [
   "2.12.16",
   "2.12.17",
   "2.12.18",
+  "2.12.19",
   "2.13.3",
   "2.13.4",
   "2.13.5",
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/BlacklistedTests.txt b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.20/BlacklistedTests.txt
similarity index 99%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/BlacklistedTests.txt
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.20/BlacklistedTests.txt
index 1bb8c9a08d..82db4eb5b7 100644
--- a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/BlacklistedTests.txt
+++ b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.20/BlacklistedTests.txt
@@ -145,6 +145,7 @@ run/t10233.scala
 run/t10244.scala
 run/t10522.scala
 run/t11255
+run/t12774.scala
 run/transient-object.scala
 
 # Using System.getProperties
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/neg/choices.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.20/neg/choices.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/neg/choices.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.20/neg/choices.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/neg/partestInvalidFlag.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.20/neg/partestInvalidFlag.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/neg/partestInvalidFlag.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.20/neg/partestInvalidFlag.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/neg/t11952b.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.20/neg/t11952b.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/neg/t11952b.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.20/neg/t11952b.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/neg/t6446-additional.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.20/neg/t6446-additional.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/neg/t6446-additional.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.20/neg/t6446-additional.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/neg/t6446-list.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.20/neg/t6446-list.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/neg/t6446-list.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.20/neg/t6446-list.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/neg/t6446-missing.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.20/neg/t6446-missing.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/neg/t6446-missing.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.20/neg/t6446-missing.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/neg/t6446-show-phases.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.20/neg/t6446-show-phases.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/neg/t6446-show-phases.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.20/neg/t6446-show-phases.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/neg/t7494-no-options.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.20/neg/t7494-no-options.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/neg/t7494-no-options.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.20/neg/t7494-no-options.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/Course-2002-01.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.20/run/Course-2002-01.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/Course-2002-01.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.20/run/Course-2002-01.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/Course-2002-02.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.20/run/Course-2002-02.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/Course-2002-02.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.20/run/Course-2002-02.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/Course-2002-04.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.20/run/Course-2002-04.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/Course-2002-04.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.20/run/Course-2002-04.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/Course-2002-08.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.20/run/Course-2002-08.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/Course-2002-08.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.20/run/Course-2002-08.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/Course-2002-09.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.20/run/Course-2002-09.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/Course-2002-09.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.20/run/Course-2002-09.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/Course-2002-10.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.20/run/Course-2002-10.check
similarity index 100%
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diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/t8764.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.20/run/t8764.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/t8764.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.20/run/t8764.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/t8925.sem b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.20/run/t8925.sem
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/t8925.sem
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.20/run/t8925.sem
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/t9387b.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.20/run/t9387b.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/t9387b.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.20/run/t9387b.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/t9656.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.20/run/t9656.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/t9656.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.20/run/t9656.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/try-catch-unify.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.20/run/try-catch-unify.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/try-catch-unify.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.20/run/try-catch-unify.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/virtpatmat_switch.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.20/run/virtpatmat_switch.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/virtpatmat_switch.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.20/run/virtpatmat_switch.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/virtpatmat_typetag.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.20/run/virtpatmat_typetag.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.19/run/virtpatmat_typetag.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.12.20/run/virtpatmat_typetag.check
diff --git a/project/Build.scala b/project/Build.scala
index 8e02322bfe..561214147f 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -955,6 +955,7 @@ object Build {
         "2.12.17",
         "2.12.18",
         "2.12.19",
+        "2.12.20",
       ),
       cross213ScalaVersions := Seq(
         "2.13.3",
diff --git a/sbt-plugin/src/sbt-test/incremental/change-config-and-source/build.sbt b/sbt-plugin/src/sbt-test/incremental/change-config-and-source/build.sbt
index d0f231b6de..7f5bb2e802 100644
--- a/sbt-plugin/src/sbt-test/incremental/change-config-and-source/build.sbt
+++ b/sbt-plugin/src/sbt-test/incremental/change-config-and-source/build.sbt
@@ -1,4 +1,4 @@
-scalaVersion := "2.12.19"
+scalaVersion := "2.12.20"
 
 enablePlugins(ScalaJSPlugin)
 
diff --git a/sbt-plugin/src/sbt-test/incremental/change-config/build.sbt b/sbt-plugin/src/sbt-test/incremental/change-config/build.sbt
index d0f231b6de..7f5bb2e802 100644
--- a/sbt-plugin/src/sbt-test/incremental/change-config/build.sbt
+++ b/sbt-plugin/src/sbt-test/incremental/change-config/build.sbt
@@ -1,4 +1,4 @@
-scalaVersion := "2.12.19"
+scalaVersion := "2.12.20"
 
 enablePlugins(ScalaJSPlugin)
 
diff --git a/sbt-plugin/src/sbt-test/incremental/fix-compile-error/build.sbt b/sbt-plugin/src/sbt-test/incremental/fix-compile-error/build.sbt
index d0f231b6de..7f5bb2e802 100644
--- a/sbt-plugin/src/sbt-test/incremental/fix-compile-error/build.sbt
+++ b/sbt-plugin/src/sbt-test/incremental/fix-compile-error/build.sbt
@@ -1,4 +1,4 @@
-scalaVersion := "2.12.19"
+scalaVersion := "2.12.20"
 
 enablePlugins(ScalaJSPlugin)
 
diff --git a/sbt-plugin/src/sbt-test/linker/concurrent-linker-use/build.sbt b/sbt-plugin/src/sbt-test/linker/concurrent-linker-use/build.sbt
index 0c84905ef6..dfa800157b 100644
--- a/sbt-plugin/src/sbt-test/linker/concurrent-linker-use/build.sbt
+++ b/sbt-plugin/src/sbt-test/linker/concurrent-linker-use/build.sbt
@@ -11,7 +11,7 @@ lazy val concurrentUseOfLinkerTest = taskKey[Any]("")
 name := "Scala.js sbt test"
 
 version := scalaJSVersion
-scalaVersion := "2.12.19"
+scalaVersion := "2.12.20"
 
 enablePlugins(ScalaJSPlugin)
 
diff --git a/sbt-plugin/src/sbt-test/linker/custom-linker/build.sbt b/sbt-plugin/src/sbt-test/linker/custom-linker/build.sbt
index 1d4b83961d..cff4d0dc5c 100644
--- a/sbt-plugin/src/sbt-test/linker/custom-linker/build.sbt
+++ b/sbt-plugin/src/sbt-test/linker/custom-linker/build.sbt
@@ -13,14 +13,14 @@
 
 inThisBuild(Def.settings(
   version := scalaJSVersion,
-  scalaVersion := "2.12.19",
+  scalaVersion := "2.12.20",
 ))
 
 lazy val check = taskKey[Any]("")
 
 lazy val customLinker = project.in(file("custom-linker"))
   .settings(
-    scalaVersion := "2.12.19", // needs to match the minor version of Scala used by sbt
+    scalaVersion := "2.12.20", // needs to match the minor version of Scala used by sbt
     libraryDependencies += "org.scala-js" %% "scalajs-linker" % scalaJSVersion,
   )
 
diff --git a/sbt-plugin/src/sbt-test/linker/no-root-dependency-resolution/build.sbt b/sbt-plugin/src/sbt-test/linker/no-root-dependency-resolution/build.sbt
index 2359461fa6..31a6169d0b 100644
--- a/sbt-plugin/src/sbt-test/linker/no-root-dependency-resolution/build.sbt
+++ b/sbt-plugin/src/sbt-test/linker/no-root-dependency-resolution/build.sbt
@@ -1,7 +1,7 @@
 name := "Scala.js sbt test"
 
 version in ThisBuild := scalaJSVersion
-scalaVersion in ThisBuild := "2.12.19"
+scalaVersion in ThisBuild := "2.12.20"
 
 // Disable the IvyPlugin on the root project
 disablePlugins(sbt.plugins.IvyPlugin)
diff --git a/sbt-plugin/src/sbt-test/linker/non-existent-classpath/build.sbt b/sbt-plugin/src/sbt-test/linker/non-existent-classpath/build.sbt
index a3d81f1d03..3e470558f8 100644
--- a/sbt-plugin/src/sbt-test/linker/non-existent-classpath/build.sbt
+++ b/sbt-plugin/src/sbt-test/linker/non-existent-classpath/build.sbt
@@ -1,5 +1,5 @@
 version := scalaJSVersion
-scalaVersion := "2.12.19"
+scalaVersion := "2.12.20"
 
 enablePlugins(ScalaJSPlugin)
 
diff --git a/sbt-plugin/src/sbt-test/settings/cross-version/build.sbt b/sbt-plugin/src/sbt-test/settings/cross-version/build.sbt
index bab1e57ecf..774305e752 100644
--- a/sbt-plugin/src/sbt-test/settings/cross-version/build.sbt
+++ b/sbt-plugin/src/sbt-test/settings/cross-version/build.sbt
@@ -3,7 +3,7 @@ import org.scalajs.sbtplugin.ScalaJSCrossVersion
 val check = taskKey[Unit]("Run checks of this test")
 
 version := scalaJSVersion
-scalaVersion := "2.12.19"
+scalaVersion := "2.12.20"
 
 lazy val js = project.enablePlugins(ScalaJSPlugin).settings(
     check := {
diff --git a/sbt-plugin/src/sbt-test/settings/env-vars/build.sbt b/sbt-plugin/src/sbt-test/settings/env-vars/build.sbt
index 83878dc189..c975c2ba68 100644
--- a/sbt-plugin/src/sbt-test/settings/env-vars/build.sbt
+++ b/sbt-plugin/src/sbt-test/settings/env-vars/build.sbt
@@ -1,5 +1,5 @@
 inThisBuild(Def.settings(
-  scalaVersion := "2.12.19",
+  scalaVersion := "2.12.20",
 ))
 
 lazy val sharedSettings = Def.settings(
diff --git a/sbt-plugin/src/sbt-test/settings/legacy-link-empty/build.sbt b/sbt-plugin/src/sbt-test/settings/legacy-link-empty/build.sbt
index 4044def10a..dcd8e9e22b 100644
--- a/sbt-plugin/src/sbt-test/settings/legacy-link-empty/build.sbt
+++ b/sbt-plugin/src/sbt-test/settings/legacy-link-empty/build.sbt
@@ -1,4 +1,4 @@
 version := scalaJSVersion
-scalaVersion := "2.12.19"
+scalaVersion := "2.12.20"
 
 enablePlugins(ScalaJSPlugin)
diff --git a/sbt-plugin/src/sbt-test/settings/legacy-link-tasks/build.sbt b/sbt-plugin/src/sbt-test/settings/legacy-link-tasks/build.sbt
index 001fe4b7ca..8058a8682e 100644
--- a/sbt-plugin/src/sbt-test/settings/legacy-link-tasks/build.sbt
+++ b/sbt-plugin/src/sbt-test/settings/legacy-link-tasks/build.sbt
@@ -1,7 +1,7 @@
 val checkNoClosure = taskKey[Unit]("Check that fullOptJS wasn't run with closure")
 
 version := scalaJSVersion
-scalaVersion := "2.12.19"
+scalaVersion := "2.12.20"
 
 enablePlugins(ScalaJSPlugin)
 
diff --git a/sbt-plugin/src/sbt-test/settings/module-init/build.sbt b/sbt-plugin/src/sbt-test/settings/module-init/build.sbt
index b3cb9bef50..2835a2690f 100644
--- a/sbt-plugin/src/sbt-test/settings/module-init/build.sbt
+++ b/sbt-plugin/src/sbt-test/settings/module-init/build.sbt
@@ -3,7 +3,7 @@ import org.scalajs.linker.interface.ModuleInitializer
 val check = taskKey[Unit]("Run checks of this test")
 
 version := scalaJSVersion
-scalaVersion := "2.12.19"
+scalaVersion := "2.12.20"
 
 enablePlugins(ScalaJSPlugin)
 
diff --git a/sbt-plugin/src/sbt-test/settings/source-map/build.sbt b/sbt-plugin/src/sbt-test/settings/source-map/build.sbt
index fa3901cdcc..2fe6ae5b00 100644
--- a/sbt-plugin/src/sbt-test/settings/source-map/build.sbt
+++ b/sbt-plugin/src/sbt-test/settings/source-map/build.sbt
@@ -3,7 +3,7 @@ import org.scalajs.linker.interface.ModuleInitializer
 val check = taskKey[Unit]("Run checks of this test")
 
 version := scalaJSVersion
-scalaVersion := "2.12.19"
+scalaVersion := "2.12.20"
 
 enablePlugins(ScalaJSPlugin)
 
diff --git a/sbt-plugin/src/sbt-test/testing/multi-framework/build.sbt b/sbt-plugin/src/sbt-test/testing/multi-framework/build.sbt
index 5a8b4240c9..054279d188 100644
--- a/sbt-plugin/src/sbt-test/testing/multi-framework/build.sbt
+++ b/sbt-plugin/src/sbt-test/testing/multi-framework/build.sbt
@@ -1,5 +1,5 @@
 inThisBuild(version := scalaJSVersion)
-inThisBuild(scalaVersion := "2.12.19")
+inThisBuild(scalaVersion := "2.12.20")
 
 lazy val root = project.in(file(".")).
   aggregate(multiTestJS, multiTestJVM)
diff --git a/scala-test-suite/src/test/resources/2.12.20/BlacklistedTests.txt b/scala-test-suite/src/test/resources/2.12.20/BlacklistedTests.txt
new file mode 100644
index 0000000000..6c78101e5b
--- /dev/null
+++ b/scala-test-suite/src/test/resources/2.12.20/BlacklistedTests.txt
@@ -0,0 +1,197 @@
+## Do not compile
+scala/lang/annotations/BytecodeTest.scala
+scala/lang/annotations/RunTest.scala
+scala/lang/traits/BytecodeTest.scala
+scala/lang/traits/RunTest.scala
+scala/lang/primitives/NaNTest.scala
+scala/lang/primitives/BoxUnboxTest.scala
+scala/collection/SeqTest.scala
+scala/collection/Sizes.scala
+scala/collection/immutable/HashMapTest.scala
+scala/collection/immutable/HashSetTest.scala
+scala/collection/immutable/ListMapTest.scala
+scala/collection/immutable/MapHashcodeTest.scala
+scala/collection/immutable/SetTest.scala
+scala/collection/immutable/SeqTest.scala
+scala/collection/immutable/SmallMapTest.scala
+scala/collection/immutable/SortedMapTest.scala
+scala/collection/immutable/SortedSetTest.scala
+scala/collection/immutable/TreeMapTest.scala
+scala/collection/immutable/TreeSetTest.scala
+scala/reflect/ClassOfTest.scala
+scala/reflect/QTest.scala
+scala/reflect/io/AbstractFileTest.scala
+scala/reflect/io/ZipArchiveTest.scala
+scala/reflect/internal/util/AbstractFileClassLoaderTest.scala
+scala/reflect/internal/util/FileUtilsTest.scala
+scala/reflect/internal/util/SourceFileTest.scala
+scala/reflect/internal/util/StringOpsTest.scala
+scala/reflect/internal/util/WeakHashSetTest.scala
+scala/reflect/internal/LongNamesTest.scala
+scala/reflect/internal/MirrorsTest.scala
+scala/reflect/internal/NamesTest.scala
+scala/reflect/internal/PositionsTest.scala
+scala/reflect/internal/PrintersTest.scala
+scala/reflect/internal/ScopeTest.scala
+scala/reflect/internal/TreeGenTest.scala
+scala/reflect/internal/TypesTest.scala
+scala/reflect/macros/AttachmentsTest.scala
+scala/reflect/runtime/ReflectionUtilsShowTest.scala
+scala/reflect/runtime/ThreadSafetyTest.scala
+scala/runtime/BooleanBoxingTest.scala
+scala/runtime/ByteBoxingTest.scala
+scala/runtime/CharBoxingTest.scala
+scala/runtime/DoubleBoxingTest.scala
+scala/runtime/IntBoxingTest.scala
+scala/runtime/FloatBoxingTest.scala
+scala/runtime/LongBoxingTest.scala
+scala/runtime/ShortBoxingTest.scala
+scala/tools/cmd/CommandLineParserTest.scala
+scala/tools/nsc/Build.scala
+scala/tools/nsc/DeterminismTest.scala
+scala/tools/nsc/DeterminismTester.scala
+scala/tools/nsc/FileUtils.scala
+scala/tools/nsc/GlobalCustomizeClassloaderTest.scala
+scala/tools/nsc/PickleWriteTest.scala
+scala/tools/nsc/PipelineMainTest.scala
+scala/tools/nsc/async/AnnotationDrivenAsync.scala
+scala/tools/nsc/async/CustomFuture.scala
+scala/tools/nsc/backend/jvm/BTypesTest.scala
+scala/tools/nsc/backend/jvm/BytecodeTest.scala
+scala/tools/nsc/backend/jvm/ClassfileParserTest.scala
+scala/tools/nsc/backend/jvm/DefaultMethodTest.scala
+scala/tools/nsc/backend/jvm/DirectCompileTest.scala
+scala/tools/nsc/backend/jvm/GenericSignaturesTest.scala
+scala/tools/nsc/backend/jvm/IndyLambdaDirectTest.scala
+scala/tools/nsc/backend/jvm/IndyLambdaTest.scala
+scala/tools/nsc/backend/jvm/IndySammyTest.scala
+scala/tools/nsc/backend/jvm/InnerClassAttributeTest.scala
+scala/tools/nsc/backend/jvm/LineNumberTest.scala
+scala/tools/nsc/backend/jvm/NestedClassesCollectorTest.scala
+scala/tools/nsc/backend/jvm/OptimizedBytecodeTest.scala
+scala/tools/nsc/backend/jvm/PerRunInitTest.scala
+scala/tools/nsc/backend/jvm/StringConcatTest.scala
+scala/tools/nsc/backend/jvm/analysis/NullnessAnalyzerTest.scala
+scala/tools/nsc/backend/jvm/analysis/ProdConsAnalyzerTest.scala
+scala/tools/nsc/backend/jvm/opt/AnalyzerTest.scala
+scala/tools/nsc/backend/jvm/opt/BoxUnboxAndInlineTest.scala
+scala/tools/nsc/backend/jvm/opt/BoxUnboxTest.scala
+scala/tools/nsc/backend/jvm/opt/BTypesFromClassfileTest.scala
+scala/tools/nsc/backend/jvm/opt/CallGraphTest.scala
+scala/tools/nsc/backend/jvm/opt/ClosureOptimizerTest.scala
+scala/tools/nsc/backend/jvm/opt/CompactLocalVariablesTest.scala
+scala/tools/nsc/backend/jvm/opt/EmptyExceptionHandlersTest.scala
+scala/tools/nsc/backend/jvm/opt/EmptyLabelsAndLineNumbersTest.scala
+scala/tools/nsc/backend/jvm/opt/InlineInfoTest.scala
+scala/tools/nsc/backend/jvm/opt/InlinerIllegalAccessTest.scala
+scala/tools/nsc/backend/jvm/opt/InlinerSeparateCompilationTest.scala
+scala/tools/nsc/backend/jvm/opt/InlinerTest.scala
+scala/tools/nsc/backend/jvm/opt/InlineSourceMatcherTest.scala
+scala/tools/nsc/backend/jvm/opt/InlineWarningTest.scala
+scala/tools/nsc/backend/jvm/opt/MethodLevelOptsTest.scala
+scala/tools/nsc/backend/jvm/opt/ScalaInlineInfoTest.scala
+scala/tools/nsc/backend/jvm/opt/SimplifyJumpsTest.scala
+scala/tools/nsc/backend/jvm/opt/UnreachableCodeTest.scala
+scala/tools/nsc/backend/jvm/opt/UnusedLocalVariablesTest.scala
+scala/tools/nsc/ScriptRunnerTest.scala
+scala/tools/nsc/classpath/AggregateClassPathTest.scala
+scala/tools/nsc/classpath/JrtClassPathTest.scala
+scala/tools/nsc/classpath/MultiReleaseJarTest.scala
+scala/tools/nsc/classpath/PathResolverBaseTest.scala
+scala/tools/nsc/classpath/VirtualDirectoryClassPathTest.scala
+scala/tools/nsc/classpath/ZipAndJarFileLookupFactoryTest.scala
+scala/tools/nsc/doc/html/HtmlDocletTest.scala
+scala/tools/nsc/interpreter/CompletionTest.scala
+scala/tools/nsc/interpreter/ScriptedTest.scala
+scala/tools/nsc/interpreter/TabulatorTest.scala
+scala/tools/nsc/parser/ParserTest.scala
+scala/tools/nsc/reporters/ConsoleReporterTest.scala
+scala/tools/nsc/reporters/WConfTest.scala
+scala/tools/nsc/settings/ScalaVersionTest.scala
+scala/tools/nsc/settings/SettingsTest.scala
+scala/tools/nsc/settings/TargetTest.scala
+scala/tools/nsc/symtab/CannotHaveAttrsTest.scala
+scala/tools/nsc/symtab/FlagsTest.scala
+scala/tools/nsc/symtab/FreshNameExtractorTest.scala
+scala/tools/nsc/symtab/StdNamesTest.scala
+scala/tools/nsc/symtab/SymbolLoadersAssociatedFileTest.scala
+scala/tools/nsc/symtab/SymbolTableForUnitTesting.scala
+scala/tools/nsc/symtab/SymbolTableTest.scala
+scala/tools/nsc/symtab/classfile/PicklerTest.scala
+scala/tools/nsc/transform/MixinTest.scala
+scala/tools/nsc/transform/SpecializationTest.scala
+scala/tools/nsc/transform/ThicketTransformerTest.scala
+scala/tools/nsc/transform/delambdafy/DelambdafyTest.scala
+scala/tools/nsc/transform/patmat/SolvingTest.scala
+scala/tools/nsc/transform/patmat/PatmatBytecodeTest.scala
+scala/tools/nsc/typechecker/Implicits.scala
+scala/tools/nsc/typechecker/NamerTest.scala
+scala/tools/nsc/typechecker/ParamAliasTest.scala
+scala/tools/nsc/typechecker/TreeAttachmentTest.scala
+scala/tools/nsc/typechecker/TypedTreeTest.scala
+scala/tools/nsc/util/StackTraceTest.scala
+scala/tools/testing/AllocationTest.scala
+scala/tools/testing/BytecodeTesting.scala
+scala/tools/testing/JOL.scala
+scala/tools/testing/RunTesting.scala
+scala/tools/testing/VirtualCompilerTesting.scala
+scala/util/matching/RegexTest.scala
+
+## Do not link
+scala/MatchErrorSerializationTest.scala
+scala/PartialFunctionSerializationTest.scala
+scala/lang/stringinterpol/StringContextTest.scala
+scala/collection/IteratorTest.scala
+scala/collection/NewBuilderTest.scala
+scala/collection/ParallelConsistencyTest.scala
+scala/collection/SetMapRulesTest.scala
+scala/collection/SeqViewTest.scala
+scala/collection/SetMapConsistencyTest.scala
+scala/collection/concurrent/TrieMapTest.scala
+scala/collection/convert/WrapperSerializationTest.scala
+scala/collection/immutable/ListTest.scala
+scala/collection/immutable/RedBlackTreeSerialFormat.scala
+scala/collection/immutable/StreamTest.scala
+scala/collection/immutable/StringLikeTest.scala
+scala/collection/immutable/VectorTest.scala
+scala/collection/mutable/AnyRefMapTest.scala
+scala/collection/mutable/ArrayBufferTest.scala
+scala/collection/mutable/MutableListTest.scala
+scala/collection/mutable/OpenHashMapTest.scala
+scala/collection/mutable/PriorityQueueTest.scala
+scala/collection/parallel/TaskTest.scala
+scala/collection/parallel/immutable/ParRangeTest.scala
+scala/concurrent/FutureTest.scala
+scala/concurrent/duration/SerializationTest.scala
+scala/concurrent/impl/DefaultPromiseTest.scala
+scala/io/SourceTest.scala
+scala/runtime/ScalaRunTimeTest.scala
+scala/sys/process/PipedProcessTest.scala
+scala/sys/process/ProcessTest.scala
+scala/tools/testing/AssertUtilTest.scala
+scala/tools/testing/AssertThrowsTest.scala
+scala/util/SpecVersionTest.scala
+scala/util/SystemPropertiesTest.scala
+
+## Tests fail
+
+# Reflection
+scala/reflect/ClassTagTest.scala
+
+# Require strict-floats
+scala/math/BigDecimalTest.scala
+
+# Difference of getClass() on primitive values
+scala/collection/immutable/RangeTest.scala
+
+# Test fails only some times with
+#   'set scalaJSOptimizerOptions in scalaTestSuite ~= (_.withDisableOptimizer(true))'
+#   and' 'set scalaJSUseRhino in Global := false'
+scala/collection/immutable/PagedSeqTest.scala
+
+# Bugs
+scala/collection/convert/MapWrapperTest.scala
+
+# Tests passed but are too slow (timeouts)
+scala/collection/immutable/ListSetTest.scala
+scala/util/SortingTest.scala

From ff72b7f24a1aa2fd4cc1b8aa36af73b0606e5e01 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Sun, 12 Jan 2025 13:55:06 +0100
Subject: [PATCH 243/298] Upgrade to Scala 2.13.16, and add 2.13.14, 2.13.15 to
 the CI.

---
 Jenkinsfile                                   |   7 +-
 .../{2.13.13 => 2.13.16}/BlacklistedTests.txt |  16 +-
 .../{2.13.13 => 2.13.16}/neg/choices.check    |   0
 .../neg/partestInvalidFlag.check              |   0
 .../{2.13.13 => 2.13.16}/neg/t11952b.check    |   0
 .../{2.13.13 => 2.13.16}/neg/t12494.check     |   0
 .../neg/t6446-additional.check                |   0
 .../{2.13.13 => 2.13.16}/neg/t6446-list.check |   0
 .../neg/t6446-missing.check                   |   0
 .../neg/t6446-show-phases.check               |   0
 .../neg/t7494-no-options.check                |   0
 .../scalajs/2.13.16/neg/t8755-regress-a.check |  33 +++
 .../partest/scalajs/2.13.16/neg/t8755.check   |  34 +++
 .../partest/scalajs/2.13.16/neg/t8755b.check  |  32 +++
 .../partest/scalajs/2.13.16/neg/t8755c.check  |  33 +++
 .../run/Course-2002-01.check                  |   0
 .../run/Course-2002-02.check                  |   0
 .../run/Course-2002-04.check                  |   0
 .../run/Course-2002-08.check                  |   0
 .../run/Course-2002-09.check                  |   0
 .../run/Course-2002-10.check                  |   0
 .../{2.13.13 => 2.13.16}/run/Meter.check      |   0
 .../run/MeterCaseClass.check                  |   0
 .../run/anyval-box-types.check                |   0
 .../scalajs/{2.13.13 => 2.13.16}/run/bugs.sem |   0
 .../run/caseClassHash.check                   |   0
 .../{2.13.13 => 2.13.16}/run/classof.check    |   0
 .../{2.13.13 => 2.13.16}/run/deeps.check      |   0
 .../run/dynamic-anyval.check                  |   0
 .../{2.13.13 => 2.13.16}/run/exceptions-2.sem |   0
 .../run/exceptions-nest.check                 |   0
 .../run/exceptions-nest.sem                   |   0
 .../run/impconvtimes.check                    |   0
 .../{2.13.13 => 2.13.16}/run/imports.check    |   0
 .../run/inlineHandlers.sem                    |   0
 .../run/interpolation.check                   |   0
 .../run/interpolationMultiline1.check         |   0
 .../run/macro-bundle-static.check             |   0
 .../run/macro-bundle-toplevel.check           |   0
 .../run/macro-bundle-whitebox-decl.check      |   0
 ...expand-varargs-implicit-over-varargs.check |   0
 .../{2.13.13 => 2.13.16}/run/misc.check       |   0
 .../run/optimizer-array-load.sem              |   0
 .../{2.13.13 => 2.13.16}/run/pf-catch.sem     |   0
 .../{2.13.13 => 2.13.16}/run/promotion.check  |   0
 .../{2.13.13 => 2.13.16}/run/runtime.check    |   0
 .../run/sammy_vararg_cbn.check                |   0
 .../{2.13.13 => 2.13.16}/run/spec-self.check  |   0
 .../run/string-switch.check                   |   0
 .../{2.13.13 => 2.13.16}/run/structural.check |   0
 .../{2.13.13 => 2.13.16}/run/t0421-new.check  |   0
 .../{2.13.13 => 2.13.16}/run/t0421-old.check  |   0
 .../{2.13.13 => 2.13.16}/run/t12221.check     |   0
 .../{2.13.13 => 2.13.16}/run/t1503.sem        |   0
 .../{2.13.13 => 2.13.16}/run/t3702.check      |   0
 .../{2.13.13 => 2.13.16}/run/t4148.sem        |   0
 .../{2.13.13 => 2.13.16}/run/t4617.check      |   0
 .../{2.13.13 => 2.13.16}/run/t5356.check      |   0
 .../{2.13.13 => 2.13.16}/run/t5552.check      |   0
 .../{2.13.13 => 2.13.16}/run/t5568.check      |   0
 .../{2.13.13 => 2.13.16}/run/t5629b.check     |   0
 .../{2.13.13 => 2.13.16}/run/t5680.check      |   0
 .../{2.13.13 => 2.13.16}/run/t5866.check      |   0
 .../{2.13.13 => 2.13.16}/run/t5966.check      |   0
 .../{2.13.13 => 2.13.16}/run/t6265.check      |   0
 .../run/t6318_primitives.check                |   0
 .../{2.13.13 => 2.13.16}/run/t6662.check      |   0
 .../{2.13.13 => 2.13.16}/run/t6827.sem        |   0
 .../{2.13.13 => 2.13.16}/run/t7657.check      |   0
 .../{2.13.13 => 2.13.16}/run/t7763.sem        |   0
 .../{2.13.13 => 2.13.16}/run/t8570a.check     |   0
 .../{2.13.13 => 2.13.16}/run/t8601b.sem       |   0
 .../{2.13.13 => 2.13.16}/run/t8601c.sem       |   0
 .../{2.13.13 => 2.13.16}/run/t8601d.sem       |   0
 .../{2.13.13 => 2.13.16}/run/t8764.check      |   0
 .../{2.13.13 => 2.13.16}/run/t8925.sem        |   0
 .../{2.13.13 => 2.13.16}/run/t9387b.check     |   0
 .../run/try-catch-unify.check                 |   0
 .../run/virtpatmat_switch.check               |   0
 .../run/virtpatmat_typetag.check              |   0
 project/Build.scala                           |   5 +-
 .../src/sbt-test/cross-version/2.13/build.sbt |   2 +-
 .../sbt-test/scala3/tasty-reader/build.sbt    |   2 +-
 .../resources/2.13.14/BlacklistedTests.txt    | 247 +++++++++++++++++
 .../resources/2.13.15/BlacklistedTests.txt    | 249 +++++++++++++++++
 .../resources/2.13.16/BlacklistedTests.txt    | 250 ++++++++++++++++++
 86 files changed, 903 insertions(+), 7 deletions(-)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/BlacklistedTests.txt (99%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/neg/choices.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/neg/partestInvalidFlag.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/neg/t11952b.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/neg/t12494.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/neg/t6446-additional.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/neg/t6446-list.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/neg/t6446-missing.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/neg/t6446-show-phases.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/neg/t7494-no-options.check (100%)
 create mode 100644 partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/neg/t8755-regress-a.check
 create mode 100644 partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/neg/t8755.check
 create mode 100644 partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/neg/t8755b.check
 create mode 100644 partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/neg/t8755c.check
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/run/Course-2002-01.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/run/Course-2002-02.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/run/Course-2002-04.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/run/Course-2002-08.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/run/Course-2002-09.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/run/Course-2002-10.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/run/Meter.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/run/MeterCaseClass.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/run/anyval-box-types.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/run/bugs.sem (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/run/caseClassHash.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/run/classof.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/run/deeps.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/run/dynamic-anyval.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/run/exceptions-2.sem (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/run/exceptions-nest.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/run/exceptions-nest.sem (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/run/impconvtimes.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/run/imports.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/run/inlineHandlers.sem (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/run/interpolation.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/run/interpolationMultiline1.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/run/macro-bundle-static.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/run/macro-bundle-toplevel.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/run/macro-bundle-whitebox-decl.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/run/macro-expand-varargs-implicit-over-varargs.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/run/misc.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/run/optimizer-array-load.sem (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/run/pf-catch.sem (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/run/promotion.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/run/runtime.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/run/sammy_vararg_cbn.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/run/spec-self.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/run/string-switch.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/run/structural.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/run/t0421-new.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/run/t0421-old.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/run/t12221.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/run/t1503.sem (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/run/t3702.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/run/t4148.sem (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/run/t4617.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/run/t5356.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/run/t5552.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/run/t5568.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/run/t5629b.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/run/t5680.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/run/t5866.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/run/t5966.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/run/t6265.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/run/t6318_primitives.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/run/t6662.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/run/t6827.sem (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/run/t7657.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/run/t7763.sem (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/run/t8570a.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/run/t8601b.sem (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/run/t8601c.sem (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/run/t8601d.sem (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/run/t8764.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/run/t8925.sem (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/run/t9387b.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/run/try-catch-unify.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/run/virtpatmat_switch.check (100%)
 rename partest-suite/src/test/resources/scala/tools/partest/scalajs/{2.13.13 => 2.13.16}/run/virtpatmat_typetag.check (100%)
 create mode 100644 scala-test-suite/src/test/resources/2.13.14/BlacklistedTests.txt
 create mode 100644 scala-test-suite/src/test/resources/2.13.15/BlacklistedTests.txt
 create mode 100644 scala-test-suite/src/test/resources/2.13.16/BlacklistedTests.txt

diff --git a/Jenkinsfile b/Jenkinsfile
index e9e1630b8b..aa8a89111d 100644
--- a/Jenkinsfile
+++ b/Jenkinsfile
@@ -544,7 +544,7 @@ def allJavaVersions = otherJavaVersions.clone()
 allJavaVersions << mainJavaVersion
 
 def mainScalaVersion = "2.12.20"
-def mainScalaVersions = ["2.12.20", "2.13.13"]
+def mainScalaVersions = ["2.12.20", "2.13.16"]
 def otherScalaVersions = [
   "2.12.6",
   "2.12.7",
@@ -569,7 +569,10 @@ def otherScalaVersions = [
   "2.13.9",
   "2.13.10",
   "2.13.11",
-  "2.13.12"
+  "2.13.12",
+  "2.12.13",
+  "2.12.14",
+  "2.12.15"
 ]
 
 def scala3Version = "3.3.4"
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/BlacklistedTests.txt b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/BlacklistedTests.txt
similarity index 99%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/BlacklistedTests.txt
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/BlacklistedTests.txt
index 49e69dacc8..a468ddcaa1 100644
--- a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/BlacklistedTests.txt
+++ b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/BlacklistedTests.txt
@@ -94,6 +94,7 @@ run/predef-cycle.scala
 run/synchronized.scala
 run/sd409.scala
 run/t12572.scala
+run/deadlock.scala
 
 # Uses java.security
 run/t2318.scala
@@ -783,7 +784,6 @@ run/t7319.scala
 run/t7482a.scala
 run/t7634.scala
 run/t7747-repl.scala
-run/t7805-repl-i.scala
 run/tpeCache-tyconCache.scala
 run/repl-empty-package
 run/repl-javap-def.scala
@@ -843,6 +843,9 @@ run/repl-release.scala
 run/eta-dependent.scala
 run/t10655.scala
 run/repl-suspended-warnings.scala
+run/annot-infix-tostr.scala
+run/substSymRefinementOwner.scala
+run/t13050.scala
 
 # Using Scala Script (partest.ScriptTest)
 
@@ -935,7 +938,6 @@ run/t9097.scala
 run/macroPlugins-enterStats.scala
 run/sbt-icode-interface.scala
 run/t8502b.scala
-run/repl-paste-parse.scala
 run/t5463.scala
 run/t8433.scala
 run/sd275.scala
@@ -975,6 +977,8 @@ run/debug-type-error.scala
 run/t12757.scala
 run/t12757b.scala
 run/t12757c.scala
+run/huge-string.scala
+run/t12720.scala
 
 # Using partest.StoreReporterDirectTest
 run/package-object-stale-decl.scala
@@ -984,6 +988,9 @@ run/package-object-with-inner-class-in-ancestor-simpler.scala
 run/package-object-with-inner-class-in-ancestor-simpler-still.scala
 run/t7324.scala
 run/t10171
+run/t12289.scala
+run/t12289b.scala
+run/t12289c.scala
 
 # partest.StubErrorMessageTest
 run/StubErrorBInheritsFromA.scala
@@ -1013,6 +1020,7 @@ run/t7974
 run/t8601-closure-elim.scala
 run/t4788
 run/t4788-separate-compilation
+run/staticQualifier
 
 # partest.SessionTest
 run/t8843-repl-xlat.scala
@@ -1022,6 +1030,8 @@ run/t8918-unary-ids.scala
 run/t1931.scala
 run/t8935-class.scala
 run/t8935-object.scala
+run/t7722.scala
+run/t7879.scala
 
 # partest.JavapTest
 run/t8608-no-format.scala
@@ -1132,6 +1142,8 @@ run/t12380
 run/t12523
 run/t12290
 run/t9714
+run/t13007
+run/t13307b
 
 # Using scala-script
 run/t7791-script-linenums.scala
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/neg/choices.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/neg/choices.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/neg/choices.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/neg/choices.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/neg/partestInvalidFlag.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/neg/partestInvalidFlag.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/neg/partestInvalidFlag.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/neg/partestInvalidFlag.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/neg/t11952b.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/neg/t11952b.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/neg/t11952b.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/neg/t11952b.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/neg/t12494.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/neg/t12494.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/neg/t12494.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/neg/t12494.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/neg/t6446-additional.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/neg/t6446-additional.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/neg/t6446-additional.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/neg/t6446-additional.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/neg/t6446-list.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/neg/t6446-list.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/neg/t6446-list.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/neg/t6446-list.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/neg/t6446-missing.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/neg/t6446-missing.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/neg/t6446-missing.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/neg/t6446-missing.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/neg/t6446-show-phases.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/neg/t6446-show-phases.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/neg/t6446-show-phases.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/neg/t6446-show-phases.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/neg/t7494-no-options.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/neg/t7494-no-options.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/neg/t7494-no-options.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/neg/t7494-no-options.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/neg/t8755-regress-a.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/neg/t8755-regress-a.check
new file mode 100644
index 0000000000..4adf98bdd3
--- /dev/null
+++ b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/neg/t8755-regress-a.check
@@ -0,0 +1,33 @@
+    phase name  id  description
+    ----------  --  -----------
+        parser   1  parse source into ASTs, perform simple desugaring
+    jspretyper   2  capture pre-typer only tree info (for Scala.js)
+         namer   3  resolve names, attach symbols to named trees
+packageobjects   4  load package objects
+         typer   5  the meat and potatoes: type the trees
+            C8   0  C8 makes C7 reachable
+     jsinterop   7  prepare ASTs for JavaScript interop
+superaccessors   8  add super accessors in traits and nested classes
+            C7   0  C7 has only a before constraint
+    extmethods  10  add extension methods for inline classes
+       pickler  11  serialize symbol tables
+     refchecks  12  reference/override checking, translate nested objects
+        patmat  13  translate match expressions
+xplicitinnerjs  14  make references to inner JS classes explicit
+       uncurry  15  uncurry, translate function values to anonymous classes
+        fields  16  synthesize accessors and fields, add bitmaps for lazy vals
+     tailcalls  17  replace tail calls by jumps
+    specialize  18  @specialized-driven class and method specialization
+xplicitlocaljs  19  make references to local JS classes explicit
+ explicitouter  20  this refs to outer pointers
+       erasure  21  erase types, add interfaces for traits
+   posterasure  22  clean up erased inline classes
+    lambdalift  23  move nested functions to top level
+  constructors  24  move field definitions into constructors
+       flatten  25  eliminate inner classes
+         mixin  26  mixin composition
+        jscode  27  generate JavaScript code from ASTs
+       cleanup  28  platform-specific cleanups, generate reflective calls
+    delambdafy  29  remove lambdas
+           jvm  30  generate JVM bytecode
+      terminal  31  the last phase during a compilation run
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/neg/t8755.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/neg/t8755.check
new file mode 100644
index 0000000000..ed7312e737
--- /dev/null
+++ b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/neg/t8755.check
@@ -0,0 +1,34 @@
+warning: No phase `refchicks` for ploogin.runsAfter - did you mean refchecks?
+warning: No phase `java` for ploogin.runsBefore - did you mean jvm?
+warning: Dropping phase ploogin, it is not reachable from parser
+    phase name  id  description
+    ----------  --  -----------
+        parser   1  parse source into ASTs, perform simple desugaring
+    jspretyper   2  capture pre-typer only tree info (for Scala.js)
+         namer   3  resolve names, attach symbols to named trees
+packageobjects   4  load package objects
+         typer   5  the meat and potatoes: type the trees
+     jsinterop   6  prepare ASTs for JavaScript interop
+superaccessors   7  add super accessors in traits and nested classes
+    extmethods   8  add extension methods for inline classes
+       pickler   9  serialize symbol tables
+     refchecks  10  reference/override checking, translate nested objects
+        patmat  11  translate match expressions
+xplicitinnerjs  12  make references to inner JS classes explicit
+       uncurry  13  uncurry, translate function values to anonymous classes
+        fields  14  synthesize accessors and fields, add bitmaps for lazy vals
+     tailcalls  15  replace tail calls by jumps
+    specialize  16  @specialized-driven class and method specialization
+xplicitlocaljs  17  make references to local JS classes explicit
+ explicitouter  18  this refs to outer pointers
+       erasure  19  erase types, add interfaces for traits
+   posterasure  20  clean up erased inline classes
+    lambdalift  21  move nested functions to top level
+  constructors  22  move field definitions into constructors
+       flatten  23  eliminate inner classes
+         mixin  24  mixin composition
+        jscode  25  generate JavaScript code from ASTs
+       cleanup  26  platform-specific cleanups, generate reflective calls
+    delambdafy  27  remove lambdas
+           jvm  28  generate JVM bytecode
+      terminal  29  the last phase during a compilation run
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/neg/t8755b.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/neg/t8755b.check
new file mode 100644
index 0000000000..61518a437a
--- /dev/null
+++ b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/neg/t8755b.check
@@ -0,0 +1,32 @@
+warning: Dropping phase ploogin, it is not reachable from parser
+    phase name  id  description
+    ----------  --  -----------
+        parser   1  parse source into ASTs, perform simple desugaring
+    jspretyper   2  capture pre-typer only tree info (for Scala.js)
+         namer   3  resolve names, attach symbols to named trees
+packageobjects   4  load package objects
+         typer   5  the meat and potatoes: type the trees
+     jsinterop   6  prepare ASTs for JavaScript interop
+superaccessors   7  add super accessors in traits and nested classes
+    extmethods   8  add extension methods for inline classes
+       pickler   9  serialize symbol tables
+     refchecks  10  reference/override checking, translate nested objects
+        patmat  11  translate match expressions
+xplicitinnerjs  12  make references to inner JS classes explicit
+       uncurry  13  uncurry, translate function values to anonymous classes
+        fields  14  synthesize accessors and fields, add bitmaps for lazy vals
+     tailcalls  15  replace tail calls by jumps
+    specialize  16  @specialized-driven class and method specialization
+xplicitlocaljs  17  make references to local JS classes explicit
+ explicitouter  18  this refs to outer pointers
+       erasure  19  erase types, add interfaces for traits
+   posterasure  20  clean up erased inline classes
+    lambdalift  21  move nested functions to top level
+  constructors  22  move field definitions into constructors
+       flatten  23  eliminate inner classes
+         mixin  24  mixin composition
+        jscode  25  generate JavaScript code from ASTs
+       cleanup  26  platform-specific cleanups, generate reflective calls
+    delambdafy  27  remove lambdas
+           jvm  28  generate JVM bytecode
+      terminal  29  the last phase during a compilation run
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/neg/t8755c.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/neg/t8755c.check
new file mode 100644
index 0000000000..aedf56a035
--- /dev/null
+++ b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/neg/t8755c.check
@@ -0,0 +1,33 @@
+    phase name  id  description
+    ----------  --  -----------
+        parser   1  parse source into ASTs, perform simple desugaring
+    jspretyper   2  capture pre-typer only tree info (for Scala.js)
+         namer   3  resolve names, attach symbols to named trees
+packageobjects   4  load package objects
+         typer   5  the meat and potatoes: type the trees
+            C1   0  C1 tests phase assembly
+     jsinterop   7  prepare ASTs for JavaScript interop
+superaccessors   8  add super accessors in traits and nested classes
+    extmethods   9  add extension methods for inline classes
+       pickler  10  serialize symbol tables
+     refchecks  11  reference/override checking, translate nested objects
+        patmat  12  translate match expressions
+xplicitinnerjs  13  make references to inner JS classes explicit
+            C6   0  C6 tests phase assembly after a phase missing in Scaladoc
+       uncurry  15  uncurry, translate function values to anonymous classes
+        fields  16  synthesize accessors and fields, add bitmaps for lazy vals
+     tailcalls  17  replace tail calls by jumps
+    specialize  18  @specialized-driven class and method specialization
+xplicitlocaljs  19  make references to local JS classes explicit
+ explicitouter  20  this refs to outer pointers
+       erasure  21  erase types, add interfaces for traits
+   posterasure  22  clean up erased inline classes
+    lambdalift  23  move nested functions to top level
+  constructors  24  move field definitions into constructors
+       flatten  25  eliminate inner classes
+         mixin  26  mixin composition
+        jscode  27  generate JavaScript code from ASTs
+       cleanup  28  platform-specific cleanups, generate reflective calls
+    delambdafy  29  remove lambdas
+           jvm  30  generate JVM bytecode
+      terminal  31  the last phase during a compilation run
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/Course-2002-01.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/Course-2002-01.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/Course-2002-01.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/Course-2002-01.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/Course-2002-02.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/Course-2002-02.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/Course-2002-02.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/Course-2002-02.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/Course-2002-04.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/Course-2002-04.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/Course-2002-04.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/Course-2002-04.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/Course-2002-08.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/Course-2002-08.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/Course-2002-08.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/Course-2002-08.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/Course-2002-09.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/Course-2002-09.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/Course-2002-09.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/Course-2002-09.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/Course-2002-10.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/Course-2002-10.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/Course-2002-10.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/Course-2002-10.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/Meter.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/Meter.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/Meter.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/Meter.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/MeterCaseClass.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/MeterCaseClass.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/MeterCaseClass.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/MeterCaseClass.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/anyval-box-types.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/anyval-box-types.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/anyval-box-types.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/anyval-box-types.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/bugs.sem b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/bugs.sem
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/bugs.sem
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/bugs.sem
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/caseClassHash.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/caseClassHash.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/caseClassHash.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/caseClassHash.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/classof.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/classof.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/classof.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/classof.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/deeps.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/deeps.check
similarity index 100%
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rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/deeps.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/dynamic-anyval.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/dynamic-anyval.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/dynamic-anyval.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/dynamic-anyval.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/exceptions-2.sem b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/exceptions-2.sem
similarity index 100%
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diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/exceptions-nest.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/exceptions-nest.check
similarity index 100%
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diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/exceptions-nest.sem b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/exceptions-nest.sem
similarity index 100%
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rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/exceptions-nest.sem
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/impconvtimes.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/impconvtimes.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/impconvtimes.check
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diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/imports.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/imports.check
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diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/inlineHandlers.sem b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/inlineHandlers.sem
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diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/interpolation.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/interpolation.check
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diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/interpolationMultiline1.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/interpolationMultiline1.check
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diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/macro-bundle-static.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/macro-bundle-static.check
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diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/macro-bundle-toplevel.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/macro-bundle-toplevel.check
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diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/macro-bundle-whitebox-decl.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/macro-bundle-whitebox-decl.check
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diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/macro-expand-varargs-implicit-over-varargs.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/macro-expand-varargs-implicit-over-varargs.check
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diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/misc.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/misc.check
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diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/optimizer-array-load.sem b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/optimizer-array-load.sem
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diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/pf-catch.sem b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/pf-catch.sem
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/pf-catch.sem
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/pf-catch.sem
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/promotion.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/promotion.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/promotion.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/promotion.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/runtime.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/runtime.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/runtime.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/runtime.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/sammy_vararg_cbn.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/sammy_vararg_cbn.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/sammy_vararg_cbn.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/sammy_vararg_cbn.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/spec-self.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/spec-self.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/spec-self.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/spec-self.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/string-switch.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/string-switch.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/string-switch.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/string-switch.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/structural.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/structural.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/structural.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/structural.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/t0421-new.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/t0421-new.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/t0421-new.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/t0421-new.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/t0421-old.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/t0421-old.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/t0421-old.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/t0421-old.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/t12221.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/t12221.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/t12221.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/t12221.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/t1503.sem b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/t1503.sem
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/t1503.sem
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/t1503.sem
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/t3702.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/t3702.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/t3702.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/t3702.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/t4148.sem b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/t4148.sem
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/t4148.sem
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/t4148.sem
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/t4617.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/t4617.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/t4617.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/t4617.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/t5356.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/t5356.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/t5356.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/t5356.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/t5552.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/t5552.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/t5552.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/t5552.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/t5568.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/t5568.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/t5568.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/t5568.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/t5629b.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/t5629b.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/t5629b.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/t5629b.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/t5680.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/t5680.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/t5680.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/t5680.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/t5866.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/t5866.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/t5866.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/t5866.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/t5966.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/t5966.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/t5966.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/t5966.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/t6265.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/t6265.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/t6265.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/t6265.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/t6318_primitives.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/t6318_primitives.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/t6318_primitives.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/t6318_primitives.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/t6662.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/t6662.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/t6662.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/t6662.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/t6827.sem b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/t6827.sem
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/t6827.sem
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/t6827.sem
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/t7657.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/t7657.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/t7657.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/t7657.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/t7763.sem b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/t7763.sem
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/t7763.sem
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/t7763.sem
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/t8570a.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/t8570a.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/t8570a.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/t8570a.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/t8601b.sem b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/t8601b.sem
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/t8601b.sem
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/t8601b.sem
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/t8601c.sem b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/t8601c.sem
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/t8601c.sem
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/t8601c.sem
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/t8601d.sem b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/t8601d.sem
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/t8601d.sem
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/t8601d.sem
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/t8764.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/t8764.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/t8764.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/t8764.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/t8925.sem b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/t8925.sem
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/t8925.sem
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/t8925.sem
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/t9387b.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/t9387b.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/t9387b.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/t9387b.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/try-catch-unify.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/try-catch-unify.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/try-catch-unify.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/try-catch-unify.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/virtpatmat_switch.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/virtpatmat_switch.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/virtpatmat_switch.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/virtpatmat_switch.check
diff --git a/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/virtpatmat_typetag.check b/partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/virtpatmat_typetag.check
similarity index 100%
rename from partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.13/run/virtpatmat_typetag.check
rename to partest-suite/src/test/resources/scala/tools/partest/scalajs/2.13.16/run/virtpatmat_typetag.check
diff --git a/project/Build.scala b/project/Build.scala
index 561214147f..8dd80196c4 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -969,6 +969,9 @@ object Build {
         "2.13.11",
         "2.13.12",
         "2.13.13",
+        "2.13.14",
+        "2.13.15",
+        "2.13.16",
       ),
 
       default212ScalaVersion := cross212ScalaVersions.value.last,
@@ -2064,7 +2067,7 @@ object Build {
             if (!useMinifySizes) {
               Some(ExpectedSizes(
                   fastLink = 449000 to 450000,
-                  fullLink = 94000 to 95000,
+                  fullLink = 95000 to 96000,
                   fastLinkGz = 58000 to 59000,
                   fullLinkGz = 25000 to 26000,
               ))
diff --git a/sbt-plugin/src/sbt-test/cross-version/2.13/build.sbt b/sbt-plugin/src/sbt-test/cross-version/2.13/build.sbt
index 9eaf7236fc..82c5d1a728 100644
--- a/sbt-plugin/src/sbt-test/cross-version/2.13/build.sbt
+++ b/sbt-plugin/src/sbt-test/cross-version/2.13/build.sbt
@@ -2,6 +2,6 @@ enablePlugins(ScalaJSPlugin)
 enablePlugins(ScalaJSJUnitPlugin)
 
 version := scalaJSVersion
-scalaVersion := "2.13.13"
+scalaVersion := "2.13.16"
 
 scalaJSUseMainModuleInitializer := true
diff --git a/sbt-plugin/src/sbt-test/scala3/tasty-reader/build.sbt b/sbt-plugin/src/sbt-test/scala3/tasty-reader/build.sbt
index 683c749c5a..479044430c 100644
--- a/sbt-plugin/src/sbt-test/scala3/tasty-reader/build.sbt
+++ b/sbt-plugin/src/sbt-test/scala3/tasty-reader/build.sbt
@@ -10,7 +10,7 @@ lazy val app = project.in(file("app"))
   .enablePlugins(ScalaJSPlugin)
   .dependsOn(testlib)
   .settings(
-    scalaVersion := "2.13.13",
+    scalaVersion := "2.13.16",
     scalacOptions += "-Ytasty-reader",
     scalaJSUseMainModuleInitializer := true
   )
diff --git a/scala-test-suite/src/test/resources/2.13.14/BlacklistedTests.txt b/scala-test-suite/src/test/resources/2.13.14/BlacklistedTests.txt
new file mode 100644
index 0000000000..c813883a16
--- /dev/null
+++ b/scala-test-suite/src/test/resources/2.13.14/BlacklistedTests.txt
@@ -0,0 +1,247 @@
+## Do not compile
+scala/ExtractorTest.scala
+scala/OptionTest.scala
+scala/SerializationStabilityTest.scala
+scala/StringTest.scala
+scala/collection/FactoriesTest.scala
+scala/collection/LazyZipOpsTest.scala
+scala/collection/SeqTest.scala
+scala/collection/immutable/HashMapTest.scala
+scala/collection/immutable/HashSetTest.scala
+scala/collection/immutable/IndexedSeqTest.scala
+scala/collection/immutable/IntMapTest.scala
+scala/collection/immutable/LazyListTest.scala
+scala/collection/immutable/ListMapTest.scala
+scala/collection/immutable/LongMapTest.scala
+scala/collection/immutable/MapHashcodeTest.scala
+scala/collection/immutable/SeqTest.scala
+scala/collection/immutable/SmallMapTest.scala
+scala/collection/immutable/SortedMapTest.scala
+scala/collection/immutable/SortedSetTest.scala
+scala/collection/immutable/TreeMapTest.scala
+scala/collection/immutable/TreeSetTest.scala
+scala/lang/annotations/BytecodeTest.scala
+scala/lang/annotations/RunTest.scala
+scala/lang/traits/BytecodeTest.scala
+scala/lang/traits/RunTest.scala
+scala/lang/primitives/NaNTest.scala
+scala/reflect/ClassOfTest.scala
+scala/reflect/FieldAccessTest.scala
+scala/reflect/QTest.scala
+scala/reflect/macros/AttachmentsTest.scala
+scala/reflect/io/ZipArchiveTest.scala
+scala/reflect/internal/InferTest.scala
+scala/reflect/internal/LongNamesTest.scala
+scala/reflect/internal/MirrorsTest.scala
+scala/reflect/internal/NamesTest.scala
+scala/reflect/internal/PositionsTest.scala
+scala/reflect/internal/PrintersTest.scala
+scala/reflect/internal/ScopeTest.scala
+scala/reflect/internal/SubstMapTest.scala
+scala/reflect/internal/TreeGenTest.scala
+scala/reflect/internal/TypesTest.scala
+scala/reflect/internal/util/AbstractFileClassLoaderTest.scala
+scala/reflect/internal/util/FileUtilsTest.scala
+scala/reflect/internal/util/SourceFileTest.scala
+scala/reflect/internal/util/StringOpsTest.scala
+scala/reflect/internal/util/WeakHashSetTest.scala
+scala/reflect/io/AbstractFileTest.scala
+scala/reflect/runtime/ReflectionUtilsShowTest.scala
+scala/reflect/runtime/ThreadSafetyTest.scala
+scala/runtime/BooleanBoxingTest.scala
+scala/runtime/ByteBoxingTest.scala
+scala/runtime/CharBoxingTest.scala
+scala/runtime/DoubleBoxingTest.scala
+scala/runtime/IntBoxingTest.scala
+scala/runtime/FloatBoxingTest.scala
+scala/runtime/LongBoxingTest.scala
+scala/runtime/ShortBoxingTest.scala
+scala/tools/nsc/Build.scala
+scala/tools/nsc/DeterminismTest.scala
+scala/tools/nsc/DeterminismTester.scala
+scala/tools/nsc/FileUtils.scala
+scala/tools/nsc/GlobalCustomizeClassloaderTest.scala
+scala/tools/nsc/MainRunnerTest.scala
+scala/tools/nsc/PhaseAssemblyTest.scala
+scala/tools/nsc/PickleWriteTest.scala
+scala/tools/nsc/PipelineMainTest.scala
+scala/tools/nsc/ScriptRunnerTest.scala
+scala/tools/nsc/async/AnnotationDrivenAsyncTest.scala
+scala/tools/nsc/async/CustomFuture.scala
+scala/tools/nsc/backend/jvm/BTypesTest.scala
+scala/tools/nsc/backend/jvm/BytecodeTest.scala
+scala/tools/nsc/backend/jvm/ClassfileParserTest.scala
+scala/tools/nsc/backend/jvm/DefaultMethodTest.scala
+scala/tools/nsc/backend/jvm/DirectCompileTest.scala
+scala/tools/nsc/backend/jvm/GenericSignaturesTest.scala
+scala/tools/nsc/backend/jvm/IndyLambdaTest.scala
+scala/tools/nsc/backend/jvm/IndySammyTest.scala
+scala/tools/nsc/backend/jvm/InnerClassAttributeTest.scala
+scala/tools/nsc/backend/jvm/LineNumberTest.scala
+scala/tools/nsc/backend/jvm/NestedClassesCollectorTest.scala
+scala/tools/nsc/backend/jvm/OptimizedBytecodeTest.scala
+scala/tools/nsc/backend/jvm/PerRunInitTest.scala
+scala/tools/nsc/backend/jvm/StringConcatTest.scala
+scala/tools/nsc/backend/jvm/analysis/NullnessAnalyzerTest.scala
+scala/tools/nsc/backend/jvm/analysis/ProdConsAnalyzerTest.scala
+scala/tools/nsc/backend/jvm/analysis/TypeFlowAnalyzerTest.scala
+scala/tools/nsc/backend/jvm/opt/AnalyzerTest.scala
+scala/tools/nsc/backend/jvm/opt/BTypesFromClassfileTest.scala
+scala/tools/nsc/backend/jvm/opt/BoxUnboxAndInlineTest.scala
+scala/tools/nsc/backend/jvm/opt/BoxUnboxTest.scala
+scala/tools/nsc/backend/jvm/opt/CallGraphTest.scala
+scala/tools/nsc/backend/jvm/opt/ClosureOptimizerTest.scala
+scala/tools/nsc/backend/jvm/opt/CompactLocalVariablesTest.scala
+scala/tools/nsc/backend/jvm/opt/EmptyExceptionHandlersTest.scala
+scala/tools/nsc/backend/jvm/opt/EmptyLabelsAndLineNumbersTest.scala
+scala/tools/nsc/backend/jvm/opt/InlineInfoTest.scala
+scala/tools/nsc/backend/jvm/opt/InlinerIllegalAccessTest.scala
+scala/tools/nsc/backend/jvm/opt/InlinerSeparateCompilationTest.scala
+scala/tools/nsc/backend/jvm/opt/InlinerTest.scala
+scala/tools/nsc/backend/jvm/opt/InlineSourceMatcherTest.scala
+scala/tools/nsc/backend/jvm/opt/InlineWarningTest.scala
+scala/tools/nsc/backend/jvm/opt/MethodLevelOptsTest.scala
+scala/tools/nsc/backend/jvm/opt/ScalaInlineInfoTest.scala
+scala/tools/nsc/backend/jvm/opt/SimplifyJumpsTest.scala
+scala/tools/nsc/backend/jvm/opt/UnreachableCodeTest.scala
+scala/tools/nsc/backend/jvm/opt/UnusedLocalVariablesTest.scala
+scala/tools/nsc/classpath/AggregateClassPathTest.scala
+scala/tools/nsc/classpath/JrtClassPathTest.scala
+scala/tools/nsc/classpath/MultiReleaseJarTest.scala
+scala/tools/nsc/classpath/PathResolverBaseTest.scala
+scala/tools/nsc/classpath/VirtualDirectoryClassPathTest.scala
+scala/tools/nsc/classpath/ZipAndJarFileLookupFactoryTest.scala
+scala/tools/nsc/doc/html/HtmlDocletTest.scala
+scala/tools/nsc/doc/html/ModelFactoryTest.scala
+scala/tools/nsc/doc/html/StringLiteralTest.scala
+scala/tools/nsc/interpreter/CompletionTest.scala
+scala/tools/nsc/interpreter/ScriptedTest.scala
+scala/tools/nsc/interpreter/TabulatorTest.scala
+scala/tools/nsc/parser/ParserTest.scala
+scala/tools/nsc/reporters/ConsoleReporterTest.scala
+scala/tools/nsc/reporters/PositionFilterTest.scala
+scala/tools/nsc/reporters/WConfTest.scala
+scala/tools/nsc/reporters/AbstractCodeActionTest.scala
+scala/tools/nsc/reporters/CodeActionXsource3Test.scala
+scala/tools/nsc/reporters/CodeActionTest.scala
+scala/tools/nsc/settings/ScalaVersionTest.scala
+scala/tools/nsc/settings/SettingsTest.scala
+scala/tools/nsc/settings/TargetTest.scala
+scala/tools/nsc/symtab/CannotHaveAttrsTest.scala
+scala/tools/nsc/symtab/FlagsTest.scala
+scala/tools/nsc/symtab/FreshNameExtractorTest.scala
+scala/tools/nsc/symtab/StdNamesTest.scala
+scala/tools/nsc/symtab/SymbolTableForUnitTesting.scala
+scala/tools/nsc/symtab/SymbolTableTest.scala
+scala/tools/nsc/symtab/classfile/PicklerTest.scala
+scala/tools/nsc/transform/ErasureTest.scala
+scala/tools/nsc/transform/MixinTest.scala
+scala/tools/nsc/transform/ReleaseFenceTest.scala
+scala/tools/nsc/transform/SpecializationTest.scala
+scala/tools/nsc/transform/ThicketTransformerTest.scala
+scala/tools/nsc/transform/UncurryTest.scala
+scala/tools/nsc/transform/delambdafy/DelambdafyTest.scala
+scala/tools/nsc/transform/patmat/SolvingTest.scala
+scala/tools/nsc/transform/patmat/PatmatBytecodeTest.scala
+scala/tools/nsc/typechecker/ConstantFolderTest.scala
+scala/tools/nsc/typechecker/ImplicitsTest.scala
+scala/tools/nsc/typechecker/InferencerTest.scala
+scala/tools/nsc/typechecker/NamerTest.scala
+scala/tools/nsc/typechecker/OverridingPairsTest.scala
+scala/tools/nsc/typechecker/ParamAliasTest.scala
+scala/tools/nsc/typechecker/TreeAttachmentTest.scala
+scala/tools/nsc/typechecker/TypedTreeTest.scala
+scala/tools/nsc/QuickfixTest.scala
+scala/tools/nsc/util/StackTraceTest.scala
+scala/tools/testkit/ReflectUtilTest.scala
+scala/tools/xsbt/BridgeTesting.scala
+scala/tools/xsbt/BasicBridgeTest.scala
+scala/tools/xsbt/ClassNameTest.scala
+scala/tools/xsbt/CodeActionTest.scala
+scala/tools/xsbt/DependencyTest.scala
+scala/tools/xsbt/ExtractAPITest.scala
+scala/tools/xsbt/ExtractUsedNamesTest.scala
+scala/tools/xsbt/InteractiveConsoleInterfaceTest.scala
+scala/tools/xsbt/SameAPI.scala
+scala/tools/xsbt/TestCallback.scala
+scala/util/ChainingOpsTest.scala
+
+## Do not link
+scala/CollectTest.scala
+scala/MatchErrorSerializationTest.scala
+scala/PartialFunctionSerializationTest.scala
+scala/lang/stringinterpol/StringContextTest.scala
+scala/collection/IterableTest.scala
+scala/collection/IteratorTest.scala
+scala/collection/NewBuilderTest.scala
+scala/collection/SeqViewTest.scala
+scala/collection/SetMapConsistencyTest.scala
+scala/collection/SetMapRulesTest.scala
+scala/collection/Sizes.scala
+scala/collection/ViewTest.scala
+scala/collection/concurrent/TrieMapTest.scala
+scala/collection/convert/EqualsTest.scala
+scala/collection/convert/JConcurrentMapWrapperTest.scala
+scala/collection/convert/WrapperSerializationTest.scala
+scala/collection/immutable/ChampMapSmokeTest.scala
+scala/collection/immutable/ChampSetSmokeTest.scala
+scala/collection/immutable/LazyListGCTest.scala
+scala/collection/immutable/LazyListLazinessTest.scala
+scala/collection/immutable/ListTest.scala
+scala/collection/immutable/SerializationTest.scala
+scala/collection/immutable/StreamTest.scala
+scala/collection/immutable/StringLikeTest.scala
+scala/collection/immutable/VectorTest.scala
+scala/collection/mutable/AnyRefMapTest.scala
+scala/collection/mutable/ArrayBufferTest.scala
+scala/collection/mutable/ListBufferTest.scala
+scala/collection/mutable/OpenHashMapTest.scala
+scala/collection/mutable/PriorityQueueTest.scala
+scala/collection/mutable/SerializationTest.scala
+scala/concurrent/FutureTest.scala
+scala/concurrent/duration/SerializationTest.scala
+scala/concurrent/impl/DefaultPromiseTest.scala
+scala/io/SourceTest.scala
+scala/jdk/AccumulatorTest.scala
+scala/jdk/DurationConvertersTest.scala
+scala/jdk/FunctionConvertersTest.scala
+scala/jdk/OptionConvertersTest.scala
+scala/jdk/StepperConversionTest.scala
+scala/jdk/StepperTest.scala
+scala/jdk/StreamConvertersTest.scala
+scala/jdk/StreamConvertersTypingTest.scala
+scala/math/OrderingTest.scala
+scala/runtime/ScalaRunTimeTest.scala
+scala/sys/env.scala
+scala/sys/process/ParserTest.scala
+scala/sys/process/PipedProcessTest.scala
+scala/sys/process/ProcessBuilderTest.scala
+scala/sys/process/ProcessTest.scala
+scala/tools/testkit/AssertUtilTest.scala
+scala/util/PropertiesTest.scala
+scala/util/SpecVersionTest.scala
+scala/util/SystemPropertiesTest.scala
+
+## Tests fail
+
+# Reflection
+scala/reflect/ClassTagTest.scala
+
+# Require strict-floats
+scala/math/BigDecimalTest.scala
+
+# Tests passed but are too slow (timeouts)
+scala/collection/immutable/ListSetTest.scala
+scala/util/SortingTest.scala
+
+# Whitebox testing of ArrayBuilder.ofUnit
+scala/collection/mutable/ArrayBuilderTest.scala
+
+# Relies on undefined behavior
+scala/collection/MapTest.scala
+scala/collection/StringOpsTest.scala
+scala/collection/StringParsersTest.scala
+scala/collection/convert/CollectionConvertersTest.scala
+scala/collection/convert/MapWrapperTest.scala
+scala/collection/immutable/NumericRangeTest.scala
+scala/math/BigIntTest.scala
diff --git a/scala-test-suite/src/test/resources/2.13.15/BlacklistedTests.txt b/scala-test-suite/src/test/resources/2.13.15/BlacklistedTests.txt
new file mode 100644
index 0000000000..00808d0865
--- /dev/null
+++ b/scala-test-suite/src/test/resources/2.13.15/BlacklistedTests.txt
@@ -0,0 +1,249 @@
+## Do not compile
+scala/ExtractorTest.scala
+scala/OptionTest.scala
+scala/SerializationStabilityTest.scala
+scala/StringTest.scala
+scala/collection/FactoriesTest.scala
+scala/collection/LazyZipOpsTest.scala
+scala/collection/SeqTest.scala
+scala/collection/immutable/HashMapTest.scala
+scala/collection/immutable/HashSetTest.scala
+scala/collection/immutable/IndexedSeqTest.scala
+scala/collection/immutable/IntMapTest.scala
+scala/collection/immutable/LazyListTest.scala
+scala/collection/immutable/ListMapTest.scala
+scala/collection/immutable/LongMapTest.scala
+scala/collection/immutable/MapHashcodeTest.scala
+scala/collection/immutable/SeqTest.scala
+scala/collection/immutable/SmallMapTest.scala
+scala/collection/immutable/SortedMapTest.scala
+scala/collection/immutable/SortedSetTest.scala
+scala/collection/immutable/TreeMapTest.scala
+scala/collection/immutable/TreeSetTest.scala
+scala/collection/mutable/LongMapTest.scala
+scala/lang/annotations/BytecodeTest.scala
+scala/lang/annotations/RunTest.scala
+scala/lang/traits/BytecodeTest.scala
+scala/lang/traits/RunTest.scala
+scala/lang/primitives/NaNTest.scala
+scala/reflect/ClassOfTest.scala
+scala/reflect/FieldAccessTest.scala
+scala/reflect/QTest.scala
+scala/reflect/macros/AttachmentsTest.scala
+scala/reflect/io/ZipArchiveTest.scala
+scala/reflect/internal/InferTest.scala
+scala/reflect/internal/LongNamesTest.scala
+scala/reflect/internal/MirrorsTest.scala
+scala/reflect/internal/NamesTest.scala
+scala/reflect/internal/PositionsTest.scala
+scala/reflect/internal/PrintersTest.scala
+scala/reflect/internal/ScopeTest.scala
+scala/reflect/internal/SubstMapTest.scala
+scala/reflect/internal/TreeGenTest.scala
+scala/reflect/internal/TypesTest.scala
+scala/reflect/internal/util/AbstractFileClassLoaderTest.scala
+scala/reflect/internal/util/FileUtilsTest.scala
+scala/reflect/internal/util/SourceFileTest.scala
+scala/reflect/internal/util/StringOpsTest.scala
+scala/reflect/internal/util/WeakHashSetTest.scala
+scala/reflect/io/AbstractFileTest.scala
+scala/reflect/runtime/ReflectionUtilsShowTest.scala
+scala/reflect/runtime/ThreadSafetyTest.scala
+scala/runtime/BooleanBoxingTest.scala
+scala/runtime/ByteBoxingTest.scala
+scala/runtime/CharBoxingTest.scala
+scala/runtime/DoubleBoxingTest.scala
+scala/runtime/IntBoxingTest.scala
+scala/runtime/FloatBoxingTest.scala
+scala/runtime/LongBoxingTest.scala
+scala/runtime/ShortBoxingTest.scala
+scala/tools/nsc/Build.scala
+scala/tools/nsc/DeterminismTest.scala
+scala/tools/nsc/DeterminismTester.scala
+scala/tools/nsc/FileUtils.scala
+scala/tools/nsc/GlobalCustomizeClassloaderTest.scala
+scala/tools/nsc/MainRunnerTest.scala
+scala/tools/nsc/PhaseAssemblyTest.scala
+scala/tools/nsc/PickleWriteTest.scala
+scala/tools/nsc/PipelineMainTest.scala
+scala/tools/nsc/ScriptRunnerTest.scala
+scala/tools/nsc/async/AnnotationDrivenAsyncTest.scala
+scala/tools/nsc/async/CustomFuture.scala
+scala/tools/nsc/backend/jvm/BTypesTest.scala
+scala/tools/nsc/backend/jvm/BytecodeTest.scala
+scala/tools/nsc/backend/jvm/ClassfileParserTest.scala
+scala/tools/nsc/backend/jvm/DefaultMethodTest.scala
+scala/tools/nsc/backend/jvm/DirectCompileTest.scala
+scala/tools/nsc/backend/jvm/GenericSignaturesTest.scala
+scala/tools/nsc/backend/jvm/IndyLambdaTest.scala
+scala/tools/nsc/backend/jvm/IndySammyTest.scala
+scala/tools/nsc/backend/jvm/InnerClassAttributeTest.scala
+scala/tools/nsc/backend/jvm/LineNumberTest.scala
+scala/tools/nsc/backend/jvm/NestedClassesCollectorTest.scala
+scala/tools/nsc/backend/jvm/OptimizedBytecodeTest.scala
+scala/tools/nsc/backend/jvm/PerRunInitTest.scala
+scala/tools/nsc/backend/jvm/StringConcatTest.scala
+scala/tools/nsc/backend/jvm/analysis/NullnessAnalyzerTest.scala
+scala/tools/nsc/backend/jvm/analysis/ProdConsAnalyzerTest.scala
+scala/tools/nsc/backend/jvm/analysis/TypeFlowAnalyzerTest.scala
+scala/tools/nsc/backend/jvm/opt/AnalyzerTest.scala
+scala/tools/nsc/backend/jvm/opt/BTypesFromClassfileTest.scala
+scala/tools/nsc/backend/jvm/opt/BoxUnboxAndInlineTest.scala
+scala/tools/nsc/backend/jvm/opt/BoxUnboxTest.scala
+scala/tools/nsc/backend/jvm/opt/CallGraphTest.scala
+scala/tools/nsc/backend/jvm/opt/ClosureOptimizerTest.scala
+scala/tools/nsc/backend/jvm/opt/CompactLocalVariablesTest.scala
+scala/tools/nsc/backend/jvm/opt/EmptyExceptionHandlersTest.scala
+scala/tools/nsc/backend/jvm/opt/EmptyLabelsAndLineNumbersTest.scala
+scala/tools/nsc/backend/jvm/opt/InlineInfoTest.scala
+scala/tools/nsc/backend/jvm/opt/InlinerIllegalAccessTest.scala
+scala/tools/nsc/backend/jvm/opt/InlinerSeparateCompilationTest.scala
+scala/tools/nsc/backend/jvm/opt/InlinerTest.scala
+scala/tools/nsc/backend/jvm/opt/InlineSourceMatcherTest.scala
+scala/tools/nsc/backend/jvm/opt/InlineWarningTest.scala
+scala/tools/nsc/backend/jvm/opt/MethodLevelOptsTest.scala
+scala/tools/nsc/backend/jvm/opt/ScalaInlineInfoTest.scala
+scala/tools/nsc/backend/jvm/opt/SimplifyJumpsTest.scala
+scala/tools/nsc/backend/jvm/opt/UnreachableCodeTest.scala
+scala/tools/nsc/backend/jvm/opt/UnusedLocalVariablesTest.scala
+scala/tools/nsc/classpath/AggregateClassPathTest.scala
+scala/tools/nsc/classpath/JrtClassPathTest.scala
+scala/tools/nsc/classpath/MultiReleaseJarTest.scala
+scala/tools/nsc/classpath/PathResolverBaseTest.scala
+scala/tools/nsc/classpath/VirtualDirectoryClassPathTest.scala
+scala/tools/nsc/classpath/ZipAndJarFileLookupFactoryTest.scala
+scala/tools/nsc/doc/html/HtmlDocletTest.scala
+scala/tools/nsc/doc/html/ModelFactoryTest.scala
+scala/tools/nsc/doc/html/StringLiteralTest.scala
+scala/tools/nsc/interpreter/CompletionTest.scala
+scala/tools/nsc/interpreter/ScriptedTest.scala
+scala/tools/nsc/interpreter/TabulatorTest.scala
+scala/tools/nsc/parser/ParserTest.scala
+scala/tools/nsc/reporters/ConsoleReporterTest.scala
+scala/tools/nsc/reporters/PositionFilterTest.scala
+scala/tools/nsc/reporters/WConfTest.scala
+scala/tools/nsc/reporters/AbstractCodeActionTest.scala
+scala/tools/nsc/reporters/CodeActionXsource3Test.scala
+scala/tools/nsc/reporters/CodeActionTest.scala
+scala/tools/nsc/settings/ScalaVersionTest.scala
+scala/tools/nsc/settings/SettingsTest.scala
+scala/tools/nsc/settings/TargetTest.scala
+scala/tools/nsc/symtab/CannotHaveAttrsTest.scala
+scala/tools/nsc/symtab/FlagsTest.scala
+scala/tools/nsc/symtab/FreshNameExtractorTest.scala
+scala/tools/nsc/symtab/StdNamesTest.scala
+scala/tools/nsc/symtab/SymbolTableForUnitTesting.scala
+scala/tools/nsc/symtab/SymbolTableTest.scala
+scala/tools/nsc/symtab/classfile/PicklerTest.scala
+scala/tools/nsc/transform/ErasureTest.scala
+scala/tools/nsc/transform/MixinTest.scala
+scala/tools/nsc/transform/ReleaseFenceTest.scala
+scala/tools/nsc/transform/SpecializationTest.scala
+scala/tools/nsc/transform/ThicketTransformerTest.scala
+scala/tools/nsc/transform/UncurryTest.scala
+scala/tools/nsc/transform/delambdafy/DelambdafyTest.scala
+scala/tools/nsc/transform/patmat/SolvingTest.scala
+scala/tools/nsc/transform/patmat/PatmatBytecodeTest.scala
+scala/tools/nsc/typechecker/ConstantFolderTest.scala
+scala/tools/nsc/typechecker/ImplicitsTest.scala
+scala/tools/nsc/typechecker/InferencerTest.scala
+scala/tools/nsc/typechecker/NamerTest.scala
+scala/tools/nsc/typechecker/OverridingPairsTest.scala
+scala/tools/nsc/typechecker/ParamAliasTest.scala
+scala/tools/nsc/typechecker/TreeAttachmentTest.scala
+scala/tools/nsc/typechecker/TypedTreeTest.scala
+scala/tools/nsc/QuickfixTest.scala
+scala/tools/nsc/util/StackTraceTest.scala
+scala/tools/testkit/ReflectUtilTest.scala
+scala/tools/xsbt/BridgeTesting.scala
+scala/tools/xsbt/BasicBridgeTest.scala
+scala/tools/xsbt/ClassNameTest.scala
+scala/tools/xsbt/CodeActionTest.scala
+scala/tools/xsbt/DependencyTest.scala
+scala/tools/xsbt/ExtractAPITest.scala
+scala/tools/xsbt/ExtractUsedNamesTest.scala
+scala/tools/xsbt/InteractiveConsoleInterfaceTest.scala
+scala/tools/xsbt/SameAPI.scala
+scala/tools/xsbt/TestCallback.scala
+scala/util/ChainingOpsTest.scala
+
+## Do not link
+scala/CollectTest.scala
+scala/MatchErrorSerializationTest.scala
+scala/PartialFunctionSerializationTest.scala
+scala/lang/stringinterpol/StringContextTest.scala
+scala/collection/IterableTest.scala
+scala/collection/IteratorTest.scala
+scala/collection/NewBuilderTest.scala
+scala/collection/SeqViewTest.scala
+scala/collection/SetMapConsistencyTest.scala
+scala/collection/SetMapRulesTest.scala
+scala/collection/Sizes.scala
+scala/collection/ViewTest.scala
+scala/collection/concurrent/TrieMapTest.scala
+scala/collection/convert/EqualsTest.scala
+scala/collection/convert/JConcurrentMapWrapperTest.scala
+scala/collection/convert/WrapperSerializationTest.scala
+scala/collection/immutable/ChampMapSmokeTest.scala
+scala/collection/immutable/ChampSetSmokeTest.scala
+scala/collection/immutable/LazyListGCTest.scala
+scala/collection/immutable/LazyListLazinessTest.scala
+scala/collection/immutable/ListTest.scala
+scala/collection/immutable/SerializationTest.scala
+scala/collection/immutable/StreamTest.scala
+scala/collection/immutable/StringLikeTest.scala
+scala/collection/immutable/VectorTest.scala
+scala/collection/mutable/AnyRefMapTest.scala
+scala/collection/mutable/ArrayBufferTest.scala
+scala/collection/mutable/ListBufferTest.scala
+scala/collection/mutable/OpenHashMapTest.scala
+scala/collection/mutable/PriorityQueueTest.scala
+scala/collection/mutable/SerializationTest.scala
+scala/concurrent/FutureTest.scala
+scala/concurrent/duration/SerializationTest.scala
+scala/concurrent/impl/DefaultPromiseTest.scala
+scala/collection/generic/DecoratorsTest.scala
+scala/io/SourceTest.scala
+scala/jdk/AccumulatorTest.scala
+scala/jdk/DurationConvertersTest.scala
+scala/jdk/FunctionConvertersTest.scala
+scala/jdk/OptionConvertersTest.scala
+scala/jdk/StepperConversionTest.scala
+scala/jdk/StepperTest.scala
+scala/jdk/StreamConvertersTest.scala
+scala/jdk/StreamConvertersTypingTest.scala
+scala/math/OrderingTest.scala
+scala/runtime/ScalaRunTimeTest.scala
+scala/sys/env.scala
+scala/sys/process/ParserTest.scala
+scala/sys/process/PipedProcessTest.scala
+scala/sys/process/ProcessBuilderTest.scala
+scala/sys/process/ProcessTest.scala
+scala/tools/testkit/AssertUtilTest.scala
+scala/util/PropertiesTest.scala
+scala/util/SpecVersionTest.scala
+scala/util/SystemPropertiesTest.scala
+
+## Tests fail
+
+# Reflection
+scala/reflect/ClassTagTest.scala
+
+# Require strict-floats
+scala/math/BigDecimalTest.scala
+
+# Tests passed but are too slow (timeouts)
+scala/collection/immutable/ListSetTest.scala
+scala/util/SortingTest.scala
+
+# Whitebox testing of ArrayBuilder.ofUnit
+scala/collection/mutable/ArrayBuilderTest.scala
+
+# Relies on undefined behavior
+scala/collection/MapTest.scala
+scala/collection/StringOpsTest.scala
+scala/collection/StringParsersTest.scala
+scala/collection/convert/CollectionConvertersTest.scala
+scala/collection/convert/MapWrapperTest.scala
+scala/collection/immutable/NumericRangeTest.scala
+scala/math/BigIntTest.scala
diff --git a/scala-test-suite/src/test/resources/2.13.16/BlacklistedTests.txt b/scala-test-suite/src/test/resources/2.13.16/BlacklistedTests.txt
new file mode 100644
index 0000000000..0bbff2e24d
--- /dev/null
+++ b/scala-test-suite/src/test/resources/2.13.16/BlacklistedTests.txt
@@ -0,0 +1,250 @@
+## Do not compile
+scala/ExtractorTest.scala
+scala/OptionTest.scala
+scala/SerializationStabilityTest.scala
+scala/StringTest.scala
+scala/collection/FactoriesTest.scala
+scala/collection/LazyZipOpsTest.scala
+scala/collection/SeqTest.scala
+scala/collection/immutable/HashMapTest.scala
+scala/collection/immutable/HashSetTest.scala
+scala/collection/immutable/IndexedSeqTest.scala
+scala/collection/immutable/IntMapTest.scala
+scala/collection/immutable/LazyListTest.scala
+scala/collection/immutable/ListMapTest.scala
+scala/collection/immutable/LongMapTest.scala
+scala/collection/immutable/MapHashcodeTest.scala
+scala/collection/immutable/SeqTest.scala
+scala/collection/immutable/SmallMapTest.scala
+scala/collection/immutable/SortedMapTest.scala
+scala/collection/immutable/SortedSetTest.scala
+scala/collection/immutable/TreeMapTest.scala
+scala/collection/immutable/TreeSetTest.scala
+scala/collection/mutable/LongMapTest.scala
+scala/lang/annotations/BytecodeTest.scala
+scala/lang/annotations/RunTest.scala
+scala/lang/traits/BytecodeTest.scala
+scala/lang/traits/RunTest.scala
+scala/lang/primitives/NaNTest.scala
+scala/reflect/ClassOfTest.scala
+scala/reflect/FieldAccessTest.scala
+scala/reflect/QTest.scala
+scala/reflect/macros/AttachmentsTest.scala
+scala/reflect/io/ZipArchiveTest.scala
+scala/reflect/internal/InferTest.scala
+scala/reflect/internal/LongNamesTest.scala
+scala/reflect/internal/MirrorsTest.scala
+scala/reflect/internal/NamesTest.scala
+scala/reflect/internal/PositionsTest.scala
+scala/reflect/internal/PrintersTest.scala
+scala/reflect/internal/ScopeTest.scala
+scala/reflect/internal/SubstMapTest.scala
+scala/reflect/internal/TreeGenTest.scala
+scala/reflect/internal/TypesTest.scala
+scala/reflect/internal/util/AbstractFileClassLoaderTest.scala
+scala/reflect/internal/util/FileUtilsTest.scala
+scala/reflect/internal/util/SourceFileTest.scala
+scala/reflect/internal/util/StringOpsTest.scala
+scala/reflect/internal/util/WeakHashSetTest.scala
+scala/reflect/io/AbstractFileTest.scala
+scala/reflect/runtime/ReflectionUtilsShowTest.scala
+scala/reflect/runtime/ThreadSafetyTest.scala
+scala/runtime/BooleanBoxingTest.scala
+scala/runtime/ByteBoxingTest.scala
+scala/runtime/CharBoxingTest.scala
+scala/runtime/DoubleBoxingTest.scala
+scala/runtime/IntBoxingTest.scala
+scala/runtime/FloatBoxingTest.scala
+scala/runtime/LongBoxingTest.scala
+scala/runtime/ShortBoxingTest.scala
+scala/tools/nsc/Build.scala
+scala/tools/nsc/DeterminismTest.scala
+scala/tools/nsc/DeterminismTester.scala
+scala/tools/nsc/FileUtils.scala
+scala/tools/nsc/GlobalCustomizeClassloaderTest.scala
+scala/tools/nsc/MainRunnerTest.scala
+scala/tools/nsc/PhaseAssemblyTest.scala
+scala/tools/nsc/PickleWriteTest.scala
+scala/tools/nsc/PipelineMainTest.scala
+scala/tools/nsc/ScriptRunnerTest.scala
+scala/tools/nsc/async/AnnotationDrivenAsyncTest.scala
+scala/tools/nsc/async/CustomFuture.scala
+scala/tools/nsc/backend/jvm/BTypesTest.scala
+scala/tools/nsc/backend/jvm/BytecodeTest.scala
+scala/tools/nsc/backend/jvm/ClassfileParserTest.scala
+scala/tools/nsc/backend/jvm/DefaultMethodTest.scala
+scala/tools/nsc/backend/jvm/DirectCompileTest.scala
+scala/tools/nsc/backend/jvm/GenericSignaturesTest.scala
+scala/tools/nsc/backend/jvm/IndyLambdaTest.scala
+scala/tools/nsc/backend/jvm/IndySammyTest.scala
+scala/tools/nsc/backend/jvm/InnerClassAttributeTest.scala
+scala/tools/nsc/backend/jvm/LineNumberTest.scala
+scala/tools/nsc/backend/jvm/NestedClassesCollectorTest.scala
+scala/tools/nsc/backend/jvm/OptimizedBytecodeTest.scala
+scala/tools/nsc/backend/jvm/PerRunInitTest.scala
+scala/tools/nsc/backend/jvm/StringConcatTest.scala
+scala/tools/nsc/backend/jvm/analysis/NullnessAnalyzerTest.scala
+scala/tools/nsc/backend/jvm/analysis/ProdConsAnalyzerTest.scala
+scala/tools/nsc/backend/jvm/analysis/TypeFlowAnalyzerTest.scala
+scala/tools/nsc/backend/jvm/opt/AnalyzerTest.scala
+scala/tools/nsc/backend/jvm/opt/BTypesFromClassfileTest.scala
+scala/tools/nsc/backend/jvm/opt/BoxUnboxAndInlineTest.scala
+scala/tools/nsc/backend/jvm/opt/BoxUnboxTest.scala
+scala/tools/nsc/backend/jvm/opt/CallGraphTest.scala
+scala/tools/nsc/backend/jvm/opt/ClosureOptimizerTest.scala
+scala/tools/nsc/backend/jvm/opt/CompactLocalVariablesTest.scala
+scala/tools/nsc/backend/jvm/opt/EmptyExceptionHandlersTest.scala
+scala/tools/nsc/backend/jvm/opt/EmptyLabelsAndLineNumbersTest.scala
+scala/tools/nsc/backend/jvm/opt/InlineInfoTest.scala
+scala/tools/nsc/backend/jvm/opt/InlinerIllegalAccessTest.scala
+scala/tools/nsc/backend/jvm/opt/InlinerSeparateCompilationTest.scala
+scala/tools/nsc/backend/jvm/opt/InlinerTest.scala
+scala/tools/nsc/backend/jvm/opt/InlineSourceMatcherTest.scala
+scala/tools/nsc/backend/jvm/opt/InlineWarningTest.scala
+scala/tools/nsc/backend/jvm/opt/MethodLevelOptsTest.scala
+scala/tools/nsc/backend/jvm/opt/ScalaInlineInfoTest.scala
+scala/tools/nsc/backend/jvm/opt/SimplifyJumpsTest.scala
+scala/tools/nsc/backend/jvm/opt/UnreachableCodeTest.scala
+scala/tools/nsc/backend/jvm/opt/UnusedLocalVariablesTest.scala
+scala/tools/nsc/classpath/AggregateClassPathTest.scala
+scala/tools/nsc/classpath/JrtClassPathTest.scala
+scala/tools/nsc/classpath/MultiReleaseJarTest.scala
+scala/tools/nsc/classpath/PathResolverBaseTest.scala
+scala/tools/nsc/classpath/VirtualDirectoryClassPathTest.scala
+scala/tools/nsc/classpath/ZipAndJarFileLookupFactoryTest.scala
+scala/tools/nsc/doc/html/HtmlDocletTest.scala
+scala/tools/nsc/doc/html/ModelFactoryTest.scala
+scala/tools/nsc/doc/html/StringLiteralTest.scala
+scala/tools/nsc/interpreter/CompletionTest.scala
+scala/tools/nsc/interpreter/ScriptedTest.scala
+scala/tools/nsc/interpreter/TabulatorTest.scala
+scala/tools/nsc/parser/ParserTest.scala
+scala/tools/nsc/reporters/ConsoleReporterTest.scala
+scala/tools/nsc/reporters/PositionFilterTest.scala
+scala/tools/nsc/reporters/WConfTest.scala
+scala/tools/nsc/reporters/AbstractCodeActionTest.scala
+scala/tools/nsc/reporters/CodeActionXsource3Test.scala
+scala/tools/nsc/reporters/CodeActionTest.scala
+scala/tools/nsc/settings/ScalaVersionTest.scala
+scala/tools/nsc/settings/SettingsTest.scala
+scala/tools/nsc/settings/TargetTest.scala
+scala/tools/nsc/symtab/CannotHaveAttrsTest.scala
+scala/tools/nsc/symtab/FlagsTest.scala
+scala/tools/nsc/symtab/FreshNameExtractorTest.scala
+scala/tools/nsc/symtab/StdNamesTest.scala
+scala/tools/nsc/symtab/SymbolTableForUnitTesting.scala
+scala/tools/nsc/symtab/SymbolTableTest.scala
+scala/tools/nsc/symtab/classfile/PicklerTest.scala
+scala/tools/nsc/transform/ErasureTest.scala
+scala/tools/nsc/transform/MixinTest.scala
+scala/tools/nsc/transform/ReleaseFenceTest.scala
+scala/tools/nsc/transform/SpecializationTest.scala
+scala/tools/nsc/transform/ThicketTransformerTest.scala
+scala/tools/nsc/transform/UncurryTest.scala
+scala/tools/nsc/transform/delambdafy/DelambdafyTest.scala
+scala/tools/nsc/transform/patmat/SolvingTest.scala
+scala/tools/nsc/transform/patmat/PatmatBytecodeTest.scala
+scala/tools/nsc/typechecker/ConstantFolderTest.scala
+scala/tools/nsc/typechecker/ImplicitsTest.scala
+scala/tools/nsc/typechecker/InferencerTest.scala
+scala/tools/nsc/typechecker/NamerTest.scala
+scala/tools/nsc/typechecker/OverridingPairsTest.scala
+scala/tools/nsc/typechecker/ParamAliasTest.scala
+scala/tools/nsc/typechecker/TreeAttachmentTest.scala
+scala/tools/nsc/typechecker/TypedTreeTest.scala
+scala/tools/nsc/typechecker/XMLTest.scala
+scala/tools/nsc/QuickfixTest.scala
+scala/tools/nsc/util/StackTraceTest.scala
+scala/tools/testkit/ReflectUtilTest.scala
+scala/tools/xsbt/BridgeTesting.scala
+scala/tools/xsbt/BasicBridgeTest.scala
+scala/tools/xsbt/ClassNameTest.scala
+scala/tools/xsbt/CodeActionTest.scala
+scala/tools/xsbt/DependencyTest.scala
+scala/tools/xsbt/ExtractAPITest.scala
+scala/tools/xsbt/ExtractUsedNamesTest.scala
+scala/tools/xsbt/InteractiveConsoleInterfaceTest.scala
+scala/tools/xsbt/SameAPI.scala
+scala/tools/xsbt/TestCallback.scala
+scala/util/ChainingOpsTest.scala
+
+## Do not link
+scala/CollectTest.scala
+scala/MatchErrorSerializationTest.scala
+scala/PartialFunctionSerializationTest.scala
+scala/lang/stringinterpol/StringContextTest.scala
+scala/collection/IterableTest.scala
+scala/collection/IteratorTest.scala
+scala/collection/NewBuilderTest.scala
+scala/collection/SeqViewTest.scala
+scala/collection/SetMapConsistencyTest.scala
+scala/collection/SetMapRulesTest.scala
+scala/collection/Sizes.scala
+scala/collection/ViewTest.scala
+scala/collection/concurrent/TrieMapTest.scala
+scala/collection/convert/EqualsTest.scala
+scala/collection/convert/JConcurrentMapWrapperTest.scala
+scala/collection/convert/WrapperSerializationTest.scala
+scala/collection/immutable/ChampMapSmokeTest.scala
+scala/collection/immutable/ChampSetSmokeTest.scala
+scala/collection/immutable/LazyListGCTest.scala
+scala/collection/immutable/LazyListLazinessTest.scala
+scala/collection/immutable/ListTest.scala
+scala/collection/immutable/SerializationTest.scala
+scala/collection/immutable/StreamTest.scala
+scala/collection/immutable/StringLikeTest.scala
+scala/collection/immutable/VectorTest.scala
+scala/collection/mutable/AnyRefMapTest.scala
+scala/collection/mutable/ArrayBufferTest.scala
+scala/collection/mutable/ListBufferTest.scala
+scala/collection/mutable/OpenHashMapTest.scala
+scala/collection/mutable/PriorityQueueTest.scala
+scala/collection/mutable/SerializationTest.scala
+scala/concurrent/FutureTest.scala
+scala/concurrent/duration/SerializationTest.scala
+scala/concurrent/impl/DefaultPromiseTest.scala
+scala/collection/generic/DecoratorsTest.scala
+scala/io/SourceTest.scala
+scala/jdk/AccumulatorTest.scala
+scala/jdk/DurationConvertersTest.scala
+scala/jdk/FunctionConvertersTest.scala
+scala/jdk/OptionConvertersTest.scala
+scala/jdk/StepperConversionTest.scala
+scala/jdk/StepperTest.scala
+scala/jdk/StreamConvertersTest.scala
+scala/jdk/StreamConvertersTypingTest.scala
+scala/math/OrderingTest.scala
+scala/runtime/ScalaRunTimeTest.scala
+scala/sys/env.scala
+scala/sys/process/ParserTest.scala
+scala/sys/process/PipedProcessTest.scala
+scala/sys/process/ProcessBuilderTest.scala
+scala/sys/process/ProcessTest.scala
+scala/tools/testkit/AssertUtilTest.scala
+scala/util/PropertiesTest.scala
+scala/util/SpecVersionTest.scala
+scala/util/SystemPropertiesTest.scala
+
+## Tests fail
+
+# Reflection
+scala/reflect/ClassTagTest.scala
+
+# Require strict-floats
+scala/math/BigDecimalTest.scala
+
+# Tests passed but are too slow (timeouts)
+scala/collection/immutable/ListSetTest.scala
+scala/util/SortingTest.scala
+
+# Whitebox testing of ArrayBuilder.ofUnit
+scala/collection/mutable/ArrayBuilderTest.scala
+
+# Relies on undefined behavior
+scala/collection/MapTest.scala
+scala/collection/StringOpsTest.scala
+scala/collection/StringParsersTest.scala
+scala/collection/convert/CollectionConvertersTest.scala
+scala/collection/convert/MapWrapperTest.scala
+scala/collection/immutable/NumericRangeTest.scala
+scala/math/BigIntTest.scala

From 78ce1c81052fb15e64efb5af798d7bb43b119ab7 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Wed, 15 Jan 2025 17:46:39 +0100
Subject: [PATCH 244/298] Fix #5115: Apply the StoreModule hack to
 JSConstructorDef from 1.8.

Before 1.11, the body of `JSConstructorDef`s was a straight list of
trees. We have a hack that extracts the three parts of a structured
`JSConstructorBody`: `beforeSuper`, `superCall` and `afterSuper`.

In 1.18, we introduced a separate hack to ensure that `afterSuper`
starts with a `StoreModule` instruction.

Unfortunately, we did not apply the latter hack on the result of
the former. This means our deserializer incorrectly reads JS module
classes from before 1.11.

This commit makes sure to also apply the hack in that situation.

Unfortunately, this does not come with automated tests. We do not
have any non-native JS module class in our standard library, which
is currently our only source of old IR for backward compatibility
tests.
---
 .../scala/org/scalajs/ir/Serializers.scala    | 22 +++++++++++--------
 1 file changed, 13 insertions(+), 9 deletions(-)

diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
index bf50ef07fc..707dfc61d7 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
@@ -1543,7 +1543,7 @@ object Serializers {
       val (jsConstructor, jsMethodProps) = {
         if (hacks.use8 && kind.isJSClass) {
           assert(jsConstructorBuilder.result().isEmpty, "found JSConstructorDef in pre 1.8 IR")
-          jsConstructorHack(jsMethodPropsBuilder.result())
+          jsConstructorHack(kind, jsMethodPropsBuilder.result())
         } else {
           (jsConstructorBuilder.result(), jsMethodPropsBuilder.result())
         }
@@ -1803,7 +1803,7 @@ object Serializers {
       newInstanceRecMethod :: newMethods
     }
 
-    private def jsConstructorHack(
+    private def jsConstructorHack(ownerKind: ClassKind,
         jsMethodProps: List[JSMethodPropDef]): (Option[JSConstructorDef], List[JSMethodPropDef]) = {
       val jsConstructorBuilder = new OptionBuilder[JSConstructorDef]
       val jsMethodPropsBuilder = List.newBuilder[JSMethodPropDef]
@@ -1817,8 +1817,9 @@ object Serializers {
           }
 
           bodyStats.span(!_.isInstanceOf[JSSuperConstructorCall]) match {
-            case (beforeSuper, (superCall: JSSuperConstructorCall) :: afterSuper) =>
+            case (beforeSuper, (superCall: JSSuperConstructorCall) :: afterSuper0) =>
               val newFlags = flags.withNamespace(MemberNamespace.Constructor)
+              val afterSuper = maybeHackJSConstructorDefAfterSuper(ownerKind, afterSuper0, superCall.pos)
               val newBody = JSConstructorBody(beforeSuper, superCall, afterSuper)(body.pos)
               val ctorDef = JSConstructorDef(newFlags, args, restParam, newBody)(
                   methodDef.optimizerHints, Unversioned)(methodDef.pos)
@@ -1966,19 +1967,22 @@ object Serializers {
       val beforeSuper = readTrees()
       val superCall = readTree().asInstanceOf[JSSuperConstructorCall]
       val afterSuper0 = readTrees()
+      val afterSuper = maybeHackJSConstructorDefAfterSuper(ownerKind, afterSuper0, superCall.pos)
+      val body = JSConstructorBody(beforeSuper, superCall, afterSuper)(bodyPos)
+      JSConstructorDef(flags, params, restParam, body)(
+          OptimizerHints.fromBits(readInt()), optHash)
+    }
 
-      val afterSuper = if (hacks.use17 && ownerKind == ClassKind.JSModuleClass) {
+    private def maybeHackJSConstructorDefAfterSuper(ownerKind: ClassKind,
+        afterSuper0: List[Tree], superCallPos: Position): List[Tree] = {
+      if (hacks.use17 && ownerKind == ClassKind.JSModuleClass) {
         afterSuper0 match {
           case StoreModule() :: _ => afterSuper0
-          case _                  => StoreModule()(superCall.pos) :: afterSuper0
+          case _                  => StoreModule()(superCallPos) :: afterSuper0
         }
       } else {
         afterSuper0
       }
-
-      val body = JSConstructorBody(beforeSuper, superCall, afterSuper)(bodyPos)
-      JSConstructorDef(flags, params, restParam, body)(
-          OptimizerHints.fromBits(readInt()), optHash)
     }
 
     private def readJSMethodDef()(implicit pos: Position): JSMethodDef = {

From 7b5528e8aa425b56a0f1b329b146007dd7cdfe4f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Mon, 13 Jan 2025 10:30:25 +0100
Subject: [PATCH 245/298] Ensure the switch of Bug1955 is always a switch by
 adding more cases.

Under 4 cases, some versions of the compiler do not emit a switch
match. That defeats the purpose of that test.
---
 .../testsuite/compiler/RegressionTest.scala      | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/RegressionTest.scala b/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/RegressionTest.scala
index 6642451b5d..301045cf74 100644
--- a/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/RegressionTest.scala
+++ b/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/RegressionTest.scala
@@ -418,10 +418,13 @@ class RegressionTest {
   @Test def switchMatchWithGuardAndResultTypeOfBoxedUnit_Issue1955(): Unit = {
     val bug = new Bug1955
     bug.bug(2, true)
-    assertEquals(0, bug.result)
+    assertEquals(22, bug.result)
+    bug.bug(2, false)
+    assertEquals(-1, bug.result)
     bug.bug(1, true)
     assertEquals(579, bug.result)
-    assertThrows(classOf[MatchError], bug.bug(2, false))
+    bug.bug(6, true)
+    assertEquals(-1, bug.result)
   }
 
   @Test def switchMatchWithGuardInStatementPosButWithNonUnitBranches_Issue4105(): Unit = {
@@ -987,9 +990,12 @@ object RegressionTest {
     }
 
     def bug(x: Int, e: Boolean): Unit = {
-      x match {
-        case 1 => doSomething(123, 456, ())
-        case 2 if e =>
+      (x: @switch) match {
+        case 1      => doSomething(123, 456, ())
+        case 2 if e => result = 22
+        case 3      => result = 33
+        case 4      => result = 44
+        case _      => result = -1
       }
 
       if (false) ()

From 498e56b0d0fb0484dbbf4eafe74f87a94ab03181 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Mon, 13 Jan 2025 13:29:28 +0100
Subject: [PATCH 246/298] Fix #5112: Recognize asInstanceOf around jump to
 default label.

That shape gets produced by Scala 2.13.16+ in some cases.
---
 .../org/scalajs/nscplugin/GenJSCode.scala     |  2 +-
 .../testsuite/compiler/RegressionTest.scala   | 33 +++++++++++++++++++
 2 files changed, 34 insertions(+), 1 deletion(-)

diff --git a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
index 7c4548e67f..d707905ba7 100644
--- a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
+++ b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
@@ -3903,7 +3903,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
         assert(guard == EmptyTree, s"found a case guard at ${caze.pos}")
 
         def genBody(body: Tree): js.Tree = body match {
-          case app @ Apply(_, Nil) if app.symbol == defaultLabelSym =>
+          case MaybeAsInstanceOf(app @ Apply(_, Nil)) if app.symbol == defaultLabelSym =>
             genJumpToElseClause
           case Block(List(app @ Apply(_, Nil)), _) if app.symbol == defaultLabelSym =>
             genJumpToElseClause
diff --git a/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/RegressionTest.scala b/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/RegressionTest.scala
index 301045cf74..f3d762645b 100644
--- a/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/RegressionTest.scala
+++ b/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/RegressionTest.scala
@@ -427,6 +427,20 @@ class RegressionTest {
     assertEquals(-1, bug.result)
   }
 
+  @Test def switchMatchWithGuardAndResultTypeOfBoxedUnitWithTailrec_Issue5112(): Unit = {
+    val bug = new Bug5112
+    bug.bug('d', true)
+    assertEquals(44, bug.result)
+    bug.bug('a', true)
+    assertEquals(11, bug.result)
+    bug.bug('E', true)
+    assertEquals(22, bug.result)
+    bug.bug('e', false)
+    assertEquals(44, bug.result)
+    bug.bug('G', false)
+    assertEquals(33, bug.result)
+  }
+
   @Test def switchMatchWithGuardInStatementPosButWithNonUnitBranches_Issue4105(): Unit = {
     def encodeString(string: String, isKey: Boolean): String = {
       val buffer = new java.lang.StringBuilder()
@@ -1002,6 +1016,25 @@ object RegressionTest {
     }
   }
 
+  class Bug5112 {
+    var result: Int = 0
+
+    // The tail-recursive transformation is required to trigger the bug
+    @tailrec
+    final def bug(ch: Char, guard: Boolean): Unit = {
+      if (ch >= 'A' && ch <= 'Z') {
+        bug((ch + 'a' - 'A').toChar, guard)
+      } else {
+        (ch: @switch) match {
+          case 'a'                => result = 11
+          case 'c' | 'e' if guard => result = 22
+          case 'g'                => result = 33
+          case _                  => result = 44
+        }
+      }
+    }
+  }
+
   object Bug3013 {
     trait A1 {
       private val s = "A1"

From ee3e9a026cc6a0d5919b1f2a9036021b01d5eaa0 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Mon, 13 Jan 2025 14:06:35 +0100
Subject: [PATCH 247/298] Codegen: Make the handling of default clause jumps
 more generic.

Previously, we had to recognize specific shapes of case bodies in
order to extract jumps to default labels. This was fragile, as
changes in nsc's codegen could invalidate our assumptions.

We now take a more general approach. We register the default label
in the `enclosingLabelDefInfos`. Jumps to that label can therefore
be handled wherever they appear inside the case bodies.

We still require a specific shape to extract the *definition* of
the default label in the wildcard case. This can't be helped, as
far as I can tell.

Ultimately, the JS code generated for the test suites is unchanged,
both in 2.12 and 2.13.
---
 .../org/scalajs/nscplugin/GenJSCode.scala     | 138 +++++++-----------
 1 file changed, 51 insertions(+), 87 deletions(-)

diff --git a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
index d707905ba7..0ad5ed423e 100644
--- a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
+++ b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
@@ -3883,93 +3883,55 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
         if (isStat) jstpe.VoidType
         else toIRType(tree.tpe)
 
-      val defaultLabelSym = cases.collectFirst {
+      val optDefaultLabelSymAndInfo = cases.collectFirst {
         case CaseDef(Ident(nme.WILDCARD), EmptyTree,
             body @ LabelDef(_, Nil, rhs)) if hasSynthCaseSymbol(body) =>
-          body.symbol
-      }.getOrElse(NoSymbol)
+          body.symbol -> new EnclosingLabelDefInfoWithResultAsAssigns(Nil)
+      }
 
       var clauses: List[(List[js.MatchableLiteral], js.Tree)] = Nil
       var optElseClause: Option[js.Tree] = None
-      var optElseClauseLabel: Option[LabelName] = None
-
-      def genJumpToElseClause(implicit pos: ir.Position): js.Tree = {
-        if (optElseClauseLabel.isEmpty)
-          optElseClauseLabel = Some(freshLabelName("default"))
-        js.Return(js.Skip(), optElseClauseLabel.get)
-      }
-
-      for (caze @ CaseDef(pat, guard, body) <- cases) {
-        assert(guard == EmptyTree, s"found a case guard at ${caze.pos}")
-
-        def genBody(body: Tree): js.Tree = body match {
-          case MaybeAsInstanceOf(app @ Apply(_, Nil)) if app.symbol == defaultLabelSym =>
-            genJumpToElseClause
-          case Block(List(app @ Apply(_, Nil)), _) if app.symbol == defaultLabelSym =>
-            genJumpToElseClause
-
-          case If(cond, thenp, elsep) =>
-            js.If(genExpr(cond), genBody(thenp), genBody(elsep))(
-                resultType)(body.pos)
-
-          /* For #1955. If we receive a tree with the shape
-           *   if (cond) {
-           *     thenp
-           *   } else {
-           *     elsep
-           *   }
-           *   scala.runtime.BoxedUnit.UNIT
-           * we rewrite it as
-           *   if (cond) {
-           *     thenp
-           *     scala.runtime.BoxedUnit.UNIT
-           *   } else {
-           *     elsep
-           *     scala.runtime.BoxedUnit.UNIT
-           *   }
-           * so that it fits the shape of if/elses we can deal with.
-           */
-          case Block(List(If(cond, thenp, elsep)), s: Select)
-              if s.symbol == definitions.BoxedUnit_UNIT =>
-            val newThenp = Block(thenp, s).setType(s.tpe).setPos(thenp.pos)
-            val newElsep = Block(elsep, s).setType(s.tpe).setPos(elsep.pos)
-            js.If(genExpr(cond), genBody(newThenp), genBody(newElsep))(
-                resultType)(body.pos)
 
-          case _ =>
+      withScopedVars(
+        enclosingLabelDefInfos := enclosingLabelDefInfos.get ++ optDefaultLabelSymAndInfo.toList
+      ) {
+        for (caze @ CaseDef(pat, guard, body) <- cases) {
+          assert(guard == EmptyTree, s"found a case guard at ${caze.pos}")
+
+          def genBody(body: Tree): js.Tree =
             genStatOrExpr(body, isStat)
-        }
 
-        def invalidCase(tree: Tree): Nothing =
-          abort(s"Invalid case in alternative in switch-like pattern match: $tree at: ${tree.pos}")
+          def invalidCase(tree: Tree): Nothing =
+            abort(s"Invalid case in alternative in switch-like pattern match: $tree at: ${tree.pos}")
 
-        def genMatchableLiteral(tree: Literal): js.MatchableLiteral = {
-          genExpr(tree) match {
-            case matchableLiteral: js.MatchableLiteral => matchableLiteral
-            case otherExpr                             => invalidCase(tree)
+          def genMatchableLiteral(tree: Literal): js.MatchableLiteral = {
+            genExpr(tree) match {
+              case matchableLiteral: js.MatchableLiteral => matchableLiteral
+              case otherExpr                             => invalidCase(tree)
+            }
           }
-        }
 
-        pat match {
-          case lit: Literal =>
-            clauses = (List(genMatchableLiteral(lit)), genBody(body)) :: clauses
-          case Ident(nme.WILDCARD) =>
-            optElseClause = Some(body match {
-              case LabelDef(_, Nil, rhs) if hasSynthCaseSymbol(body) =>
-                genBody(rhs)
-              case _ =>
-                genBody(body)
-            })
-          case Alternative(alts) =>
-            val genAlts = {
-              alts map {
-                case lit: Literal => genMatchableLiteral(lit)
-                case _            => invalidCase(tree)
+          pat match {
+            case lit: Literal =>
+              clauses = (List(genMatchableLiteral(lit)), genBody(body)) :: clauses
+            case Ident(nme.WILDCARD) =>
+              optElseClause = Some(body match {
+                case LabelDef(_, Nil, rhs) if hasSynthCaseSymbol(body) =>
+                  genBody(rhs)
+                case _ =>
+                  genBody(body)
+              })
+            case Alternative(alts) =>
+              val genAlts = {
+                alts map {
+                  case lit: Literal => genMatchableLiteral(lit)
+                  case _            => invalidCase(tree)
+                }
               }
-            }
-            clauses = (genAlts, genBody(body)) :: clauses
-          case _ =>
-            invalidCase(tree)
+              clauses = (genAlts, genBody(body)) :: clauses
+            case _ =>
+              invalidCase(tree)
+          }
         }
       }
 
@@ -4012,21 +3974,23 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
         }
       }
 
-      optElseClauseLabel.fold[js.Tree] {
-        buildMatch(clauses.reverse, elseClause, resultType)
-      } { elseClauseLabel =>
-        val matchResultLabel = freshLabelName("matchResult")
-        val patchedClauses = for ((alts, body) <- clauses) yield {
-          implicit val pos = body.pos
-          val newBody = js.Return(body, matchResultLabel)
-          (alts, newBody)
-        }
-        js.Labeled(matchResultLabel, resultType, js.Block(List(
-            js.Labeled(elseClauseLabel, jstpe.VoidType, {
+      optDefaultLabelSymAndInfo match {
+        case Some((defaultLabelSym, defaultLabelInfo)) if defaultLabelInfo.generatedReturns > 0 =>
+          val matchResultLabel = freshLabelName("matchResult")
+          val patchedClauses = for ((alts, body) <- clauses) yield {
+            implicit val pos = body.pos
+            val newBody = js.Return(body, matchResultLabel)
+            (alts, newBody)
+          }
+          js.Labeled(matchResultLabel, resultType, js.Block(List(
+            js.Labeled(encodeLabelSym(defaultLabelSym), jstpe.VoidType, {
               buildMatch(patchedClauses.reverse, js.Skip(), jstpe.VoidType)
             }),
             elseClause
-        )))
+          )))
+
+        case _ =>
+          buildMatch(clauses.reverse, elseClause, resultType)
       }
     }
 

From dac9aa7ff54c6c793eb915329aaa83539f088af0 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Tue, 14 Jan 2025 17:49:16 +0100
Subject: [PATCH 248/298] Optimize the shapes of `js.Dynamic.literal()` in
 Scala 2.13.

Somehow it had always escaped us that we did not correctly perform
that optimization in Scala 2.13.
---
 .../linker/frontend/optimizer/OptimizerCore.scala  |  7 +++++--
 project/Build.scala                                | 14 +++++++-------
 2 files changed, 12 insertions(+), 9 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
index 53b8a11ee5..dae5f87e43 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
@@ -3086,7 +3086,7 @@ private[optimizer] abstract class OptimizerCore(
         tprops match {
           case PreTransMaybeBlock(bindingsAndStats,
               PreTransLocalDef(LocalDef(
-                  RefinedType(ClassType(JSWrappedArrayClass, _), _),
+                  RefinedType(ClassType(JSWrappedArrayClass | WrappedVarArgsClass, _), _),
                   false,
                   InlineClassInstanceReplacement(_, wrappedArrayFields, _)))) =>
             assert(wrappedArrayFields.size == 1)
@@ -5597,6 +5597,7 @@ private[optimizer] object OptimizerCore {
   private val ClassTagModuleClass = ClassName("scala.reflect.ClassTag$")
   private val JavaScriptExceptionClass = ClassName("scala.scalajs.js.JavaScriptException")
   private val JSWrappedArrayClass = ClassName("scala.scalajs.js.WrappedArray")
+  private val WrappedVarArgsClass = ClassName("scala.scalajs.runtime.WrappedVarArgs")
   private val NilClass = ClassName("scala.collection.immutable.Nil$")
   private val Tuple2Class = ClassName("scala.Tuple2")
 
@@ -6495,6 +6496,7 @@ private[optimizer] object OptimizerCore {
     private val ClassClassRef = ClassRef(ClassClass)
     private val StringClassRef = ClassRef(BoxedStringClass)
     private val SeqClassRef = ClassRef(ClassName("scala.collection.Seq"))
+    private val ImmutableSeqClassRef = ClassRef(ClassName("scala.collection.immutable.Seq"))
     private val JSObjectClassRef = ClassRef(ClassName("scala.scalajs.js.Object"))
     private val JSArrayClassRef = ClassRef(ClassName("scala.scalajs.js.Array"))
 
@@ -6520,7 +6522,8 @@ private[optimizer] object OptimizerCore {
             m("getName", Nil, StringClassRef) -> ClassGetName
         ),
         ClassName("scala.scalajs.js.special.package$") -> List(
-            m("objectLiteral", List(SeqClassRef), JSObjectClassRef) -> ObjectLiteral
+            m("objectLiteral", List(SeqClassRef), JSObjectClassRef) -> ObjectLiteral, // 2.12
+            m("objectLiteral", List(ImmutableSeqClassRef), JSObjectClassRef) -> ObjectLiteral // 2.13
         )
     )
 
diff --git a/project/Build.scala b/project/Build.scala
index 8dd80196c4..3e2f1c72f4 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -2066,17 +2066,17 @@ object Build {
           case `default213Version` =>
             if (!useMinifySizes) {
               Some(ExpectedSizes(
-                  fastLink = 449000 to 450000,
-                  fullLink = 95000 to 96000,
-                  fastLinkGz = 58000 to 59000,
+                  fastLink = 439000 to 440000,
+                  fullLink = 92000 to 93000,
+                  fastLinkGz = 57000 to 58000,
                   fullLinkGz = 25000 to 26000,
               ))
             } else {
               Some(ExpectedSizes(
-                  fastLink = 304000 to 305000,
-                  fullLink = 261000 to 262000,
-                  fastLinkGz = 48000 to 49000,
-                  fullLinkGz = 43000 to 44000,
+                  fastLink = 298000 to 299000,
+                  fullLink = 256000 to 257000,
+                  fastLinkGz = 47000 to 48000,
+                  fullLinkGz = 42000 to 43000,
               ))
             }
 

From c7cbc7ada4e88cf8dc3181c6963c4c30ef8be461 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Tue, 21 Jan 2025 21:08:00 +0100
Subject: [PATCH 249/298] Version 1.18.2.

---
 ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala b/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala
index 581ed885cd..ca9c29094f 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala
@@ -17,7 +17,7 @@ import java.util.concurrent.ConcurrentHashMap
 import scala.util.matching.Regex
 
 object ScalaJSVersions extends VersionChecks(
-    current = "1.18.2-SNAPSHOT",
+    current = "1.18.2",
     binaryEmitted = "1.18"
 )
 

From 797953158c3f7ec6130832c71086c2722b2bbc70 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Wed, 22 Jan 2025 11:16:06 +0100
Subject: [PATCH 250/298] Towards 1.18.3.

---
 ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala | 2 +-
 project/Build.scala                                           | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala b/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala
index ca9c29094f..0f03e6a638 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala
@@ -17,7 +17,7 @@ import java.util.concurrent.ConcurrentHashMap
 import scala.util.matching.Regex
 
 object ScalaJSVersions extends VersionChecks(
-    current = "1.18.2",
+    current = "1.18.3-SNAPSHOT",
     binaryEmitted = "1.18"
 )
 
diff --git a/project/Build.scala b/project/Build.scala
index 3e2f1c72f4..8749ef5c74 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -395,7 +395,7 @@ object Build {
       "1.3.0", "1.3.1", "1.4.0", "1.5.0", "1.5.1", "1.6.0", "1.7.0", "1.7.1",
       "1.8.0", "1.9.0", "1.10.0", "1.10.1", "1.11.0", "1.12.0", "1.13.0",
       "1.13.1", "1.13.2", "1.14.0", "1.15.0", "1.16.0", "1.17.0", "1.18.0",
-      "1.18.1")
+      "1.18.1", "1.18.2")
   val previousVersion = previousVersions.last
 
   val previousBinaryCrossVersion = CrossVersion.binaryWith("sjs1_", "")

From 795d3e062de91e341b072e5b25e61e4faa1e07aa Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Fri, 31 Jan 2025 11:06:31 +0100
Subject: [PATCH 251/298] Bump the Scala 3 version used for source compat of
 `ir/` to 3.6.3.

`private[this]` is deprecated in favor of `private`. This should
not have a real impact on post-JIT performance.

`var x = _` is deprecated in favor `= scala.compiletime.unitialized`.
The latter does not exist in Scala 2, so we use `= null`. We only
used that during the construction of a `Deserializer` instance. It
could theoretically affect performance, but not in any measurable
way compared to everything else that happens in a `Deserializer`.
---
 Jenkinsfile                                   |  2 +-
 .../main/scala/org/scalajs/ir/Hashers.scala   |  4 +-
 .../scala/org/scalajs/ir/Serializers.scala    | 54 +++++++++----------
 project/Build.scala                           |  2 +-
 4 files changed, 31 insertions(+), 31 deletions(-)

diff --git a/Jenkinsfile b/Jenkinsfile
index aa8a89111d..8f6ecc3c8e 100644
--- a/Jenkinsfile
+++ b/Jenkinsfile
@@ -575,7 +575,7 @@ def otherScalaVersions = [
   "2.12.15"
 ]
 
-def scala3Version = "3.3.4"
+def scala3Version = "3.6.3"
 
 def allESVersions = [
   "ES5_1",
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Hashers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Hashers.scala
index 4f6c3eeb72..d37b6ffdfc 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Hashers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Hashers.scala
@@ -136,9 +136,9 @@ object Hashers {
   }
 
   private final class TreeHasher {
-    private[this] val digestBuilder = new SHA1.DigestBuilder
+    private val digestBuilder = new SHA1.DigestBuilder
 
-    private[this] val digestStream = {
+    private val digestStream = {
       new DataOutputStream(new OutputStream {
         def write(b: Int): Unit =
           digestBuilder.update(b.toByte)
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
index 707dfc61d7..4866e36457 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
@@ -121,24 +121,24 @@ object Serializers {
   }
 
   private final class Serializer {
-    private[this] val bufferUnderlying = new JumpBackByteArrayOutputStream
-    private[this] val buffer = new DataOutputStream(bufferUnderlying)
+    private val bufferUnderlying = new JumpBackByteArrayOutputStream
+    private val buffer = new DataOutputStream(bufferUnderlying)
 
-    private[this] val files = mutable.ListBuffer.empty[URI]
-    private[this] val fileIndexMap = mutable.Map.empty[URI, Int]
+    private val files = mutable.ListBuffer.empty[URI]
+    private val fileIndexMap = mutable.Map.empty[URI, Int]
     private def fileToIndex(file: URI): Int =
       fileIndexMap.getOrElseUpdate(file, (files += file).size - 1)
 
-    private[this] val encodedNames = mutable.ListBuffer.empty[UTF8String]
-    private[this] val encodedNameIndexMap = mutable.Map.empty[EncodedNameKey, Int]
+    private val encodedNames = mutable.ListBuffer.empty[UTF8String]
+    private val encodedNameIndexMap = mutable.Map.empty[EncodedNameKey, Int]
     private def encodedNameToIndex(encoded: UTF8String): Int = {
       val byteString = new EncodedNameKey(encoded)
       encodedNameIndexMap.getOrElseUpdate(byteString,
           (encodedNames += encoded).size - 1)
     }
 
-    private[this] val methodNames = mutable.ListBuffer.empty[MethodName]
-    private[this] val methodNameIndexMap = mutable.Map.empty[MethodName, Int]
+    private val methodNames = mutable.ListBuffer.empty[MethodName]
+    private val methodNameIndexMap = mutable.Map.empty[MethodName, Int]
     private def methodNameToIndex(methodName: MethodName): Int = {
       methodNameIndexMap.getOrElseUpdate(methodName, {
         // need to reserve the internal simple names
@@ -159,12 +159,12 @@ object Serializers {
       })
     }
 
-    private[this] val strings = mutable.ListBuffer.empty[String]
-    private[this] val stringIndexMap = mutable.Map.empty[String, Int]
+    private val strings = mutable.ListBuffer.empty[String]
+    private val stringIndexMap = mutable.Map.empty[String, Int]
     private def stringToIndex(str: String): Int =
       stringIndexMap.getOrElseUpdate(str, (strings += str).size - 1)
 
-    private[this] var lastPosition: Position = Position.NoPosition
+    private var lastPosition: Position = Position.NoPosition
 
     def serialize(stream: OutputStream, classDef: ClassDef): Unit = {
       // Write tree to buffer and record files, names and strings
@@ -988,16 +988,16 @@ object Serializers {
   private final class Deserializer(buf: ByteBuffer) {
     require(buf.order() == ByteOrder.BIG_ENDIAN)
 
-    private[this] var hacks: Hacks = _
-    private[this] var files: Array[URI] = _
-    private[this] var encodedNames: Array[UTF8String] = _
-    private[this] var localNames: Array[LocalName] = _
-    private[this] var labelNames: Array[LabelName] = _
-    private[this] var simpleFieldNames: Array[SimpleFieldName] = _
-    private[this] var simpleMethodNames: Array[SimpleMethodName] = _
-    private[this] var classNames: Array[ClassName] = _
-    private[this] var methodNames: Array[MethodName] = _
-    private[this] var strings: Array[String] = _
+    private var hacks: Hacks = null
+    private var files: Array[URI] = null
+    private var encodedNames: Array[UTF8String] = null
+    private var localNames: Array[LocalName] = null
+    private var labelNames: Array[LabelName] = null
+    private var simpleFieldNames: Array[SimpleFieldName] = null
+    private var simpleMethodNames: Array[SimpleMethodName] = null
+    private var classNames: Array[ClassName] = null
+    private var methodNames: Array[MethodName] = null
+    private var strings: Array[String] = null
 
     /** Uniqueness cache for FieldName's.
      *
@@ -1008,13 +1008,13 @@ object Serializers {
      *  to make them all `eq`, consuming less memory and speeding up equality
      *  tests.
      */
-    private[this] val uniqueFieldNames = mutable.AnyRefMap.empty[FieldName, FieldName]
+    private val uniqueFieldNames = mutable.AnyRefMap.empty[FieldName, FieldName]
 
-    private[this] var lastPosition: Position = Position.NoPosition
+    private var lastPosition: Position = Position.NoPosition
 
-    private[this] var enclosingClassName: ClassName = _
-    private[this] var thisTypeForHack: Option[Type] = None
-    private[this] var patchDynamicImportThunkSuperCtorCall: Boolean = false
+    private var enclosingClassName: ClassName = null
+    private var thisTypeForHack: Option[Type] = None
+    private var patchDynamicImportThunkSuperCtorCall: Boolean = false
 
     def deserializeEntryPointsInfo(): EntryPointsInfo = {
       hacks = new Hacks(sourceVersion = readHeader())
@@ -2535,7 +2535,7 @@ object Serializers {
   }
 
   private class OptionBuilder[T] {
-    private[this] var value: Option[T] = None
+    private var value: Option[T] = None
 
     def +=(x: T): Unit = {
       require(value.isEmpty)
diff --git a/project/Build.scala b/project/Build.scala
index 8749ef5c74..446aeebfab 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -1061,7 +1061,7 @@ object Build {
        */
       scalacOptions ++= {
         if (scalaVersion.value.startsWith("3."))
-          List("-Ysafe-init")
+          List("-Wsafe-init")
         else
           Nil
       },

From 2a77c9cea28dfa4086802f230035366e55c20fdd Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Wed, 22 Jan 2025 12:11:22 +0100
Subject: [PATCH 252/298] Refactoring: Generic notion of CheckingPhase for the
 IR checkers.

We previously had two boolean options for deciding what IR is
allowed or not between phases. Of the four possible combinations
of values, one was actually invalid.

With the introduction of the desugarer, there would have been
*three* such boolean options. Only 4 out of their 8 combinations
would have been valid.

We now introduce a generic concept of `CheckingPhase`. Some IR
features are allowed as output of each `CheckingPhase`. Since the
`ClassDefChecker` and `IRChecker` must agree on what features are
valid when, we factor that logic into `FeatureSet`. It represents
a set of logical features, and can compute which set is valid for
each phase.
---
 .../scalajs/linker/analyzer/Analyzer.scala    | 14 ++--
 .../scalajs/linker/analyzer/InfoLoader.scala  | 36 +++------
 .../linker/checker/CheckingPhase.scala        | 28 +++++++
 .../linker/checker/ClassDefChecker.scala      | 39 +++++-----
 .../scalajs/linker/checker/FeatureSet.scala   | 76 +++++++++++++++++++
 .../scalajs/linker/checker/IRChecker.scala    | 19 +++--
 .../scalajs/linker/frontend/BaseLinker.scala  |  8 +-
 .../org/scalajs/linker/frontend/Refiner.scala | 10 ++-
 .../org/scalajs/linker/BaseLinkerTest.scala   |  5 +-
 .../linker/checker/ClassDefCheckerTest.scala  |  8 +-
 .../linker/testutils/LinkingUtils.scala       |  4 +-
 11 files changed, 173 insertions(+), 74 deletions(-)
 create mode 100644 linker/shared/src/main/scala/org/scalajs/linker/checker/CheckingPhase.scala
 create mode 100644 linker/shared/src/main/scala/org/scalajs/linker/checker/FeatureSet.scala

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala
index dc4dab1816..9dc14c1574 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala
@@ -29,6 +29,7 @@ import org.scalajs.ir.Trees.{MemberNamespace, JSNativeLoadSpec}
 import org.scalajs.ir.Types.ClassRef
 
 import org.scalajs.linker._
+import org.scalajs.linker.checker.CheckingPhase
 import org.scalajs.linker.frontend.IRLoader
 import org.scalajs.linker.interface._
 import org.scalajs.linker.interface.unstable.ModuleInitializerImpl
@@ -43,15 +44,10 @@ import Analysis._
 import Infos.{NamespacedMethodName, ReachabilityInfo, ReachabilityInfoInClass}
 
 final class Analyzer(config: CommonPhaseConfig, initial: Boolean,
-    checkIR: Boolean, failOnError: Boolean, irLoader: IRLoader) {
-
-  private val infoLoader: InfoLoader = {
-    new InfoLoader(irLoader,
-        if (!checkIR) InfoLoader.NoIRCheck
-        else if (initial) InfoLoader.InitialIRCheck
-        else InfoLoader.InternalIRCheck
-    )
-  }
+    checkIRFor: Option[CheckingPhase], failOnError: Boolean, irLoader: IRLoader) {
+
+  private val infoLoader: InfoLoader =
+    new InfoLoader(irLoader, checkIRFor)
 
   def computeReachability(moduleInitializers: Seq[ModuleInitializer],
       symbolRequirements: SymbolRequirement, logger: Logger)(implicit ec: ExecutionContext): Future[Analysis] = {
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/InfoLoader.scala b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/InfoLoader.scala
index 7eeb5d197b..83003e6be5 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/InfoLoader.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/InfoLoader.scala
@@ -22,14 +22,14 @@ import org.scalajs.ir.Trees._
 
 import org.scalajs.logging._
 
-import org.scalajs.linker.checker.ClassDefChecker
+import org.scalajs.linker.checker._
 import org.scalajs.linker.frontend.IRLoader
 import org.scalajs.linker.interface.LinkingException
 import org.scalajs.linker.CollectionsCompat.MutableMapCompatOps
 
 import Platform.emptyThreadSafeMap
 
-private[analyzer] final class InfoLoader(irLoader: IRLoader, irCheckMode: InfoLoader.IRCheckMode) {
+private[analyzer] final class InfoLoader(irLoader: IRLoader, checkIRFor: Option[CheckingPhase]) {
   private var logger: Logger = _
   private val cache = emptyThreadSafeMap[ClassName, InfoLoader.ClassInfoCache]
 
@@ -44,7 +44,7 @@ private[analyzer] final class InfoLoader(irLoader: IRLoader, irCheckMode: InfoLo
       implicit ec: ExecutionContext): Option[Future[Infos.ClassInfo]] = {
     if (irLoader.classExists(className)) {
       val infoCache = cache.getOrElseUpdate(className,
-          new InfoLoader.ClassInfoCache(className, irLoader, irCheckMode))
+          new InfoLoader.ClassInfoCache(className, irLoader, checkIRFor))
       Some(infoCache.loadInfo(logger))
     } else {
       None
@@ -58,15 +58,9 @@ private[analyzer] final class InfoLoader(irLoader: IRLoader, irCheckMode: InfoLo
 }
 
 private[analyzer] object InfoLoader {
-  sealed trait IRCheckMode
-
-  case object NoIRCheck extends IRCheckMode
-  case object InitialIRCheck extends IRCheckMode
-  case object InternalIRCheck extends IRCheckMode
-
   private type MethodInfos = Array[Map[MethodName, Infos.MethodInfo]]
 
-  private class ClassInfoCache(className: ClassName, irLoader: IRLoader, irCheckMode: InfoLoader.IRCheckMode) {
+  private class ClassInfoCache(className: ClassName, irLoader: IRLoader, checkIRFor: Option[CheckingPhase]) {
     private var cacheUsed: Boolean = false
     private var version: Version = Version.Unversioned
     private var info: Future[Infos.ClassInfo] = _
@@ -86,26 +80,18 @@ private[analyzer] object InfoLoader {
         if (!version.sameVersion(newVersion)) {
           version = newVersion
           info = irLoader.loadClassDef(className).map { tree =>
-            irCheckMode match {
-              case InfoLoader.NoIRCheck =>
-                // no check
-
-              case InfoLoader.InitialIRCheck =>
-                val errorCount = ClassDefChecker.check(tree,
-                    postBaseLinker = false, postOptimizer = false, logger)
-                if (errorCount != 0) {
+            for (previousPhase <- checkIRFor) {
+              val errorCount = ClassDefChecker.check(tree, previousPhase, logger)
+              if (errorCount != 0) {
+                if (previousPhase == CheckingPhase.Compiler) {
                   throw new LinkingException(
                       s"There were $errorCount ClassDef checking errors.")
-                }
-
-              case InfoLoader.InternalIRCheck =>
-                val errorCount = ClassDefChecker.check(tree,
-                    postBaseLinker = true, postOptimizer = true, logger)
-                if (errorCount != 0) {
+                } else {
                   throw new LinkingException(
-                      s"There were $errorCount ClassDef checking errors after optimizing. " +
+                      s"There were $errorCount ClassDef checking errors after transformations. " +
                       "Please report this as a bug.")
                 }
+              }
             }
 
             generateInfos(tree)
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/checker/CheckingPhase.scala b/linker/shared/src/main/scala/org/scalajs/linker/checker/CheckingPhase.scala
new file mode 100644
index 0000000000..ff198744de
--- /dev/null
+++ b/linker/shared/src/main/scala/org/scalajs/linker/checker/CheckingPhase.scala
@@ -0,0 +1,28 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package org.scalajs.linker.checker
+
+/** A phase *after which* we are checking IR.
+ *
+ *  When checking IR (with `ClassDefChecker` or `IRChecker`), different nodes
+ *  and transients are allowed between different phases. The `CheckingPhase`
+ *  records the *previous* phase to run before the check. We are therefore
+ *  checking that the IR is a valid *output* of the target phase.
+ */
+sealed abstract class CheckingPhase
+
+object CheckingPhase {
+  case object Compiler extends CheckingPhase
+  case object BaseLinker extends CheckingPhase
+  case object Optimizer extends CheckingPhase
+}
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala b/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
index 103d19f963..b3dd10acb8 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
@@ -28,11 +28,13 @@ import org.scalajs.linker.standard.LinkedClass
 
 /** Checker for the validity of the IR. */
 private final class ClassDefChecker(classDef: ClassDef,
-    postBaseLinker: Boolean, postOptimizer: Boolean, reporter: ErrorReporter) {
+    previousPhase: CheckingPhase, reporter: ErrorReporter) {
   import ClassDefChecker._
 
   import reporter.reportError
 
+  private val featureSet = FeatureSet.allowedAfter(previousPhase)
+
   private[this] val isJLObject = classDef.name.name == ObjectClass
 
   private[this] val instanceThisType: Type = {
@@ -107,7 +109,7 @@ private final class ClassDefChecker(classDef: ClassDef,
      * module classes and JS classes that are never instantiated. The classes
      * may still exist because their class data are accessed.
      */
-    if (!postBaseLinker) {
+    if (!featureSet.supports(FeatureSet.OptionalConstructors)) {
       /* Check that we have exactly 1 constructor in a module class. This goes
        * together with `checkMethodDef`, which checks that a constructor in a
        * module class must be 0-arg.
@@ -489,7 +491,7 @@ private final class ClassDefChecker(classDef: ClassDef,
   private def checkMethodNameNamespace(name: MethodName, namespace: MemberNamespace)(
       implicit ctx: ErrorContext): Unit = {
     if (name.isReflectiveProxy) {
-      if (postBaseLinker) {
+      if (featureSet.supports(FeatureSet.ReflectiveProxies)) {
         if (namespace != MemberNamespace.Public)
           reportError("reflective profixes are only allowed in the public namespace")
       } else {
@@ -557,7 +559,7 @@ private final class ClassDefChecker(classDef: ClassDef,
       }
 
       if (rest.isEmpty) {
-        if (!postOptimizer)
+        if (!featureSet.supports(FeatureSet.RelaxedCtorBodies))
           reportError(i"Constructor must contain a delegate constructor call")
 
         val bodyStatsStoreModulesHandled =
@@ -576,7 +578,7 @@ private final class ClassDefChecker(classDef: ClassDef,
 
         checkTree(receiver, unrestrictedEnv) // check that the This itself is valid
 
-        if (!postOptimizer) {
+        if (!featureSet.supports(FeatureSet.RelaxedCtorBodies)) {
           if (!(cls == classDef.className || classDef.superClass.exists(_.name == cls))) {
             implicit val ctx = ErrorContext(delegateCtorCall)
             reportError(
@@ -597,7 +599,7 @@ private final class ClassDefChecker(classDef: ClassDef,
       implicit ctx: ErrorContext): List[Tree] = {
 
     if (classDef.kind.hasModuleAccessor) {
-      if (postOptimizer) {
+      if (featureSet.supports(FeatureSet.RelaxedCtorBodies)) {
         /* If the super constructor call was inlined, the StoreModule can be anywhere.
          * Moreover, the optimizer can remove StoreModules altogether in many cases.
          */
@@ -673,7 +675,7 @@ private final class ClassDefChecker(classDef: ClassDef,
       case Assign(lhs, rhs) =>
         lhs match {
           case Select(This(), field) if env.isThisRestricted =>
-            if (postOptimizer || field.name.className == classDef.className)
+            if (featureSet.supports(FeatureSet.RelaxedCtorBodies) || field.name.className == classDef.className)
               checkTree(lhs, env.withIsThisRestricted(false))
             else
               checkTree(lhs, env)
@@ -819,11 +821,13 @@ private final class ClassDefChecker(classDef: ClassDef,
         checkTree(index, env)
 
       case RecordSelect(record, _) =>
-        checkAllowTransients()
+        if (!featureSet.supports(FeatureSet.Records))
+          reportError("invalid use of records")
         checkTree(record, env)
 
       case RecordValue(_, elems) =>
-        checkAllowTransients()
+        if (!featureSet.supports(FeatureSet.Records))
+          reportError("invalid use of records")
         checkTrees(elems, env)
 
       case IsInstanceOf(expr, testType) =>
@@ -987,7 +991,9 @@ private final class ClassDefChecker(classDef: ClassDef,
         checkTrees(captureValues, env)
 
       case Transient(transient) =>
-        checkAllowTransients()
+        if (!featureSet.supports(FeatureSet.OptimizedTransients))
+          reportError(i"invalid transient tree of class ${transient.getClass().getName()}")
+
         transient.traverse(new Traversers.Traverser {
           override def traverse(tree: Tree): Unit = checkTree(tree, env)
         })
@@ -996,11 +1002,6 @@ private final class ClassDefChecker(classDef: ClassDef,
     newEnv
   }
 
-  private def checkAllowTransients()(implicit ctx: ErrorContext): Unit = {
-    if (!postOptimizer)
-      reportError("invalid transient tree")
-  }
-
   private def checkArrayType(tpe: ArrayType)(
       implicit ctx: ErrorContext): Unit = {
     checkArrayTypeRef(tpe.arrayTypeRef)
@@ -1036,13 +1037,13 @@ object ClassDefChecker {
    *
    *  @return Count of IR checking errors (0 in case of success)
    */
-  def check(classDef: ClassDef, postBaseLinker: Boolean, postOptimizer: Boolean, logger: Logger): Int = {
+  def check(classDef: ClassDef, previousPhase: CheckingPhase, logger: Logger): Int = {
     val reporter = new LoggerErrorReporter(logger)
-    new ClassDefChecker(classDef, postBaseLinker, postOptimizer, reporter).checkClassDef()
+    new ClassDefChecker(classDef, previousPhase, reporter).checkClassDef()
     reporter.errorCount
   }
 
-  def check(linkedClass: LinkedClass, postOptimizer: Boolean, logger: Logger): Int = {
+  def check(linkedClass: LinkedClass, previousPhase: CheckingPhase, logger: Logger): Int = {
     // Rebuild a ClassDef out of the LinkedClass
     import linkedClass._
     implicit val pos = linkedClass.pos
@@ -1063,7 +1064,7 @@ object ClassDefChecker {
       topLevelExportDefs = Nil
     )(optimizerHints)
 
-    check(classDef, postBaseLinker = true, postOptimizer, logger)
+    check(classDef, previousPhase, logger)
   }
 
   private class Env(
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/checker/FeatureSet.scala b/linker/shared/src/main/scala/org/scalajs/linker/checker/FeatureSet.scala
new file mode 100644
index 0000000000..73f89b0d8b
--- /dev/null
+++ b/linker/shared/src/main/scala/org/scalajs/linker/checker/FeatureSet.scala
@@ -0,0 +1,76 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package org.scalajs.linker.checker
+
+import org.scalajs.linker.checker.CheckingPhase._
+
+/** A set of conditional IR features that the checkers can accept.
+ *
+ *  At any given phase, the `ClassDefChecker` and the `IRChecker` must agree on
+ *  the set of IR features that are valid. A `FeatureSet` factors out the
+ *  knowledge of what feature is acceptable when.
+ */
+private[checker] final class FeatureSet private (private val flags: Int) extends AnyVal {
+  /** Does this feature set support (all of) the given feature set. */
+  def supports(features: FeatureSet): Boolean =
+    (features.flags & flags) == features.flags
+
+  /** The union of this feature set and `that` feature set. */
+  def |(that: FeatureSet): FeatureSet =
+    new FeatureSet(this.flags | that.flags)
+}
+
+private[checker] object FeatureSet {
+  /** Empty feature set. */
+  val Empty = new FeatureSet(0)
+
+  // Individual features
+
+  /** Optional constructors in module classes and JS classes. */
+  val OptionalConstructors = new FeatureSet(1 << 0)
+
+  /** Explicit reflective proxy definitions. */
+  val ReflectiveProxies = new FeatureSet(1 << 1)
+
+  /** Transients that are the result of optimizations. */
+  val OptimizedTransients = new FeatureSet(1 << 2)
+
+  /** Records and record types. */
+  val Records = new FeatureSet(1 << 3)
+
+  /** Relaxed constructor discipline.
+   *
+   *  - Optional super/delegate constructor call.
+   *  - Delegate constructor calls can target any super class.
+   *  - `this.x = ...` assignments before the delegate call can assign super class fields.
+   *  - `StoreModule` can be anywhere, or not be there at all.
+   */
+  val RelaxedCtorBodies = new FeatureSet(1 << 4)
+
+  // Common sets
+
+  /** Features introduced by the base linker. */
+  private val Linked =
+    OptionalConstructors | ReflectiveProxies
+
+  /** IR that is only the result of optimizations. */
+  private val Optimized =
+    OptimizedTransients | Records | RelaxedCtorBodies
+
+  /** The set of features allowed as output of the given phase. */
+  def allowedAfter(phase: CheckingPhase): FeatureSet = phase match {
+    case Compiler   => Empty
+    case BaseLinker => Linked
+    case Optimizer  => Linked | Optimized
+  }
+}
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala b/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
index a749e4807e..de827f396a 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
@@ -29,11 +29,13 @@ import org.scalajs.linker.checker.ErrorReporter._
 
 /** Checker for the validity of the IR. */
 private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter,
-    postOptimizer: Boolean) {
+    previousPhase: CheckingPhase) {
 
   import IRChecker._
   import reporter.reportError
 
+  private val featureSet = FeatureSet.allowedAfter(previousPhase)
+
   private val classes: mutable.Map[ClassName, CheckedClass] = {
     val tups = for (classDef <- unit.classDefs) yield {
       implicit val ctx = ErrorContext(classDef)
@@ -239,7 +241,7 @@ private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter,
       case Assign(lhs, rhs) =>
         def checkNonStaticField(receiver: Tree, name: FieldName): Unit = {
           receiver match {
-            case This() if (postOptimizer && env.inConstructorOf.isDefined) ||
+            case This() if (featureSet.supports(FeatureSet.RelaxedCtorBodies) && env.inConstructorOf.isDefined) ||
                 env.inConstructorOf == Some(name.className) =>
               /* ctors can write immutable fields of the class they are constructing.
                * postOptimizer, due to ctor inlining, we may write immutable parent class fields as well.
@@ -717,12 +719,14 @@ private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter,
             typecheckExpect(value, env, ctpe)
         }
 
-      case Transient(transient) if postOptimizer =>
+      case Transient(transient) if featureSet.supports(FeatureSet.OptimizedTransients) =>
+        // No precise rules, but at least check that its children type-check on their own
         transient.traverse(new Traversers.Traverser {
           override def traverse(tree: Tree): Unit = typecheck(tree, env)
         })
 
-      case RecordSelect(record, SimpleFieldIdent(fieldName)) if postOptimizer =>
+      case RecordSelect(record, SimpleFieldIdent(fieldName))
+          if featureSet.supports(FeatureSet.Records) =>
         record.tpe match {
           case NothingType => // ok
 
@@ -742,7 +746,8 @@ private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter,
 
         typecheck(record, env)
 
-      case RecordValue(RecordType(fields), elems) if postOptimizer =>
+      case RecordValue(RecordType(fields), elems)
+          if featureSet.supports(FeatureSet.Records) =>
         if (fields.size == elems.size) {
           for ((field, elem) <- fields.zip(elems))
             typecheckExpect(elem, env, field.tpe)
@@ -923,9 +928,9 @@ object IRChecker {
    *
    *  @return Count of IR checking errors (0 in case of success)
    */
-  def check(unit: LinkingUnit, logger: Logger, postOptimizer: Boolean = false): Int = {
+  def check(unit: LinkingUnit, logger: Logger, previousPhase: CheckingPhase): Int = {
     val reporter = new LoggerErrorReporter(logger)
-    new IRChecker(unit, reporter, postOptimizer).check()
+    new IRChecker(unit, reporter, previousPhase).check()
     reporter.errorCount
   }
 }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/BaseLinker.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/BaseLinker.scala
index 98b3fdf0de..ddf5b71f14 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/BaseLinker.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/BaseLinker.scala
@@ -36,8 +36,10 @@ final class BaseLinker(config: CommonPhaseConfig, checkIR: Boolean) {
   import BaseLinker._
 
   private val irLoader = new FileIRLoader
-  private val analyzer =
-    new Analyzer(config, initial = true, checkIR = checkIR, failOnError = true, irLoader)
+  private val analyzer = {
+    val checkIRFor = if (checkIR) Some(CheckingPhase.Compiler) else None
+    new Analyzer(config, initial = true, checkIRFor, failOnError = true, irLoader)
+  }
   private val methodSynthesizer = new MethodSynthesizer(irLoader)
 
   def link(irInput: Seq[IRFile],
@@ -56,7 +58,7 @@ final class BaseLinker(config: CommonPhaseConfig, checkIR: Boolean) {
     } yield {
       if (checkIR) {
         logger.time("Linker: Check IR") {
-          val errorCount = IRChecker.check(linkResult, logger)
+          val errorCount = IRChecker.check(linkResult, logger, CheckingPhase.BaseLinker)
           if (errorCount != 0) {
             throw new LinkingException(
                 s"There were $errorCount IR checking errors.")
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/Refiner.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/Refiner.scala
index a263a7b388..0f074adf55 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/Refiner.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/Refiner.scala
@@ -20,7 +20,7 @@ import org.scalajs.ir.Trees.ClassDef
 
 import org.scalajs.logging._
 
-import org.scalajs.linker.checker.IRChecker
+import org.scalajs.linker.checker._
 import org.scalajs.linker.interface.ModuleInitializer
 import org.scalajs.linker.standard._
 import org.scalajs.linker.standard.ModuleSet.ModuleID
@@ -31,8 +31,10 @@ final class Refiner(config: CommonPhaseConfig, checkIR: Boolean) {
   import Refiner._
 
   private val irLoader = new ClassDefIRLoader
-  private val analyzer =
-    new Analyzer(config, initial = false, checkIR = checkIR, failOnError = true, irLoader)
+  private val analyzer = {
+    val checkIRFor = if (checkIR) Some(CheckingPhase.Optimizer) else None
+    new Analyzer(config, initial = false, checkIRFor, failOnError = true, irLoader)
+  }
 
   /* TODO: Remove this and replace with `checkIR` once the optimizer generates
    * well-typed IR with runtime longs.
@@ -79,7 +81,7 @@ final class Refiner(config: CommonPhaseConfig, checkIR: Boolean) {
 
       if (shouldRunIRChecker) {
         logger.time("Refiner: Check IR") {
-          val errorCount = IRChecker.check(result, logger, postOptimizer = true)
+          val errorCount = IRChecker.check(result, logger, CheckingPhase.Optimizer)
           if (errorCount != 0) {
             throw new AssertionError(
                 s"There were $errorCount IR checking errors after optimization (this is a Scala.js bug)")
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/BaseLinkerTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/BaseLinkerTest.scala
index 1997d0f789..22033b7d3c 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/BaseLinkerTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/BaseLinkerTest.scala
@@ -24,7 +24,7 @@ import org.scalajs.junit.async._
 
 import org.scalajs.logging._
 
-import org.scalajs.linker.checker.ClassDefChecker
+import org.scalajs.linker.checker._
 import org.scalajs.linker.interface.StandardConfig
 import org.scalajs.linker.standard._
 
@@ -86,7 +86,8 @@ class BaseLinkerTest {
 
     for (moduleSet <- linkToModuleSet(classDefs, MainTestModuleInitializers, config = config)) yield {
       val clazz = findClass(moduleSet, BoxedIntegerClass).get
-      val errorCount = ClassDefChecker.check(clazz, postOptimizer = false,
+      val previousPhase = CheckingPhase.BaseLinker
+      val errorCount = ClassDefChecker.check(clazz, previousPhase,
           new ScalaConsoleLogger(Level.Error))
       assertEquals(0, errorCount)
     }
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/checker/ClassDefCheckerTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/checker/ClassDefCheckerTest.scala
index 2d22331cc0..8bbf5ff00a 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/checker/ClassDefCheckerTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/checker/ClassDefCheckerTest.scala
@@ -257,7 +257,7 @@ class ClassDefCheckerTest {
           )
         ),
         "reflective profixes are only allowed in the public namespace",
-        allowReflectiveProxies = true
+        previousPhase = CheckingPhase.BaseLinker
     )
   }
 
@@ -817,13 +817,13 @@ class ClassDefCheckerTest {
     assertError(
         mainTestClassDef(Assign(RecordSelect(int(5), "i")(IntType), int(6))),
         "Assignment to RecordSelect of illegal tree: org.scalajs.ir.Trees$IntLiteral",
-        allowTransients = true)
+        previousPhase = CheckingPhase.Optimizer)
   }
 }
 
 private object ClassDefCheckerTest {
   private def assertError(clazz: ClassDef, expectMsg: String,
-      allowReflectiveProxies: Boolean = false, allowTransients: Boolean = false) = {
+      previousPhase: CheckingPhase = CheckingPhase.Compiler): Unit = {
     var seen = false
     val reporter = new ErrorReporter {
       def reportError(msg: String)(implicit ctx: ErrorReporter.ErrorContext) = {
@@ -833,7 +833,7 @@ private object ClassDefCheckerTest {
       }
     }
 
-    new ClassDefChecker(clazz, allowReflectiveProxies, allowTransients, reporter).checkClassDef()
+    new ClassDefChecker(clazz, previousPhase, reporter).checkClassDef()
     assertTrue("no errors reported", seen)
   }
 }
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/testutils/LinkingUtils.scala b/linker/shared/src/test/scala/org/scalajs/linker/testutils/LinkingUtils.scala
index f3854a7a76..68a59755ba 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/testutils/LinkingUtils.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/testutils/LinkingUtils.scala
@@ -20,6 +20,7 @@ import org.scalajs.logging._
 
 import org.scalajs.linker._
 import org.scalajs.linker.analyzer._
+import org.scalajs.linker.checker.CheckingPhase
 import org.scalajs.linker.frontend.FileIRLoader
 import org.scalajs.linker.interface._
 import org.scalajs.linker.standard._
@@ -101,8 +102,9 @@ object LinkingUtils {
     val injectedIRFiles = StandardLinkerBackend(config).injectedIRFiles
 
     val irLoader = new FileIRLoader
+    val checkIRFor = Some(CheckingPhase.Compiler)
     val analyzer = new Analyzer(CommonPhaseConfig.fromStandardConfig(config),
-        initial = true, checkIR = true, failOnError = false, irLoader)
+        initial = true, checkIRFor, failOnError = false, irLoader)
     val logger = new ScalaConsoleLogger(Level.Error)
 
     for {

From ca39c30dd73285545293d285835df3054b778479 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Fri, 31 Jan 2025 17:13:52 +0100
Subject: [PATCH 253/298] Remove ancient codegen opt for expanded Scala anon
 function classes.

Since the very early days of Scala.js, we have had a code size
optimization for lambdas expanded as anonymous classes. We tried
very hard to recover the captures from fields, and the body of the
`apply` method, in order to reconstruct a `js.Closure`.

That made sense as long as we supported Scala 2.11 (and before
that, 2.10). However, since Scala 2.12.x, scalac almost never
expands lambdas of `scala.FunctionN`. Instead, they reach the
backend as `Function` node.

The only situations where scalac still expands lambdas as anonymous
classes is if it used in an argument to a super constructor (or
delegate `this()` constructor).

The code paths for that code size optimization are therefore almost
dead code, and do not pull their weight anymore. It was, AFAICT,
the only place where we still *tried* to emit something a certain
way, with a fallback.

This commit removes the optimization and all the related
infrastructure.
---
 .../org/scalajs/nscplugin/GenJSCode.scala     | 187 ++++--------------
 .../scalajs/nscplugin/test/JSSAMTest.scala    |   4 +-
 2 files changed, 39 insertions(+), 152 deletions(-)

diff --git a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
index 0ad5ed423e..60cea646b0 100644
--- a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
+++ b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
@@ -204,8 +204,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
     }
 
     // For anonymous methods
-    // These have a default, since we always read them.
-    private val tryingToGenMethodAsJSFunction = new ScopedVar[Boolean](false)
+    // It has a default, since we always read it.
     private val paramAccessorLocals = new ScopedVar(Map.empty[Symbol, js.ParamDef])
 
     /* Contextual JS class value for some operations of nested JS classes that
@@ -223,11 +222,6 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
       }
     }
 
-    private class CancelGenMethodAsJSFunction(message: String)
-        extends scala.util.control.ControlThrowable {
-      override def getMessage(): String = message
-    }
-
     // Rewriting of anonymous function classes ---------------------------------
 
     /** Start nested generation of a class.
@@ -248,7 +242,6 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
           undefinedDefaultParams := null,
           mutableLocalVars := null,
           mutatedLocalVars := null,
-          tryingToGenMethodAsJSFunction := false,
           paramAccessorLocals := Map.empty
       )(withNewLocalNameScope(body))
     }
@@ -387,21 +380,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
     private val generatedStaticForwarderClasses = ListBuffer.empty[(Symbol, js.ClassDef)]
 
     private def consumeLazilyGeneratedAnonClass(sym: Symbol): ClassDef = {
-      /* If we are trying to generate an method as JSFunction, we cannot
-       * actually consume the symbol, since we might fail trying and retry.
-       * We will then see the same tree again and not find the symbol anymore.
-       *
-       * If we are sure this is the only generation, we remove the symbol to
-       * make sure we don't generate the same class twice.
-       */
-      val optDef = {
-        if (tryingToGenMethodAsJSFunction)
-          lazilyGeneratedAnonClasses.get(sym)
-        else
-          lazilyGeneratedAnonClasses.remove(sym)
-      }
-
-      optDef.getOrElse {
+      lazilyGeneratedAnonClasses.remove(sym).getOrElse {
         abort("Couldn't find tree for lazily generated anonymous class " +
             s"${sym.fullName} at ${sym.pos}")
       }
@@ -450,25 +429,22 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
         }
         val allClassDefs = collectClassDefs(cunit.body)
 
-        /* There are three types of anonymous classes we want to generate
-         * only once we need them so we can inline them at construction site:
+        /* There are two types of anonymous classes we want to generate only
+         * once we need them, so we can inline them at construction site:
          *
-         * - anonymous class that are JS types, which includes:
-         *   - lambdas for js.FunctionN and js.ThisFunctionN (SAMs). (We may
-         *     not generate actual Scala classes for these).
-         *   - anonymous (non-lambda) JS classes. These classes may not have
-         *     their own prototype. Therefore, their constructor *must* be
-         *     inlined.
-         * - lambdas for scala.FunctionN. This is only an optimization and may
-         *   fail. In the case of failure, we fall back to generating a
-         *   fully-fledged Scala class.
+         * - Lambdas for `js.Function` SAMs, including `js.FunctionN`,
+         *   `js.ThisFunctionN` and custom JS function SAMs. We must generate
+         *   JS functions for these, instead of actual classes.
+         * - Anonymous (non-lambda) JS classes. These classes may not have
+         *   their own prototype. Therefore, their constructor *must* be
+         *   inlined.
          *
          * Since for all these, we don't know how they inter-depend, we just
          * store them in a map at this point.
          */
         val (lazyAnons, fullClassDefs) = allClassDefs.partition { cd =>
           val sym = cd.symbol
-          isAnonymousJSClass(sym) || isJSFunctionDef(sym) || sym.isAnonymousFunction
+          isAnonymousJSClass(sym) || isJSFunctionDef(sym)
         }
 
         lazilyGeneratedAnonClasses ++= lazyAnons.map(cd => cd.symbol -> cd)
@@ -2824,9 +2800,10 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
      */
     private def genThis()(implicit pos: Position): js.Tree = {
       thisLocalVarName.fold[js.Tree] {
-        if (tryingToGenMethodAsJSFunction) {
-          throw new CancelGenMethodAsJSFunction(
-              "Trying to generate `this` inside the body")
+        if (isJSFunctionDef(currentClassSym)) {
+          abort(
+              "Unexpected `this` reference inside the body of a JS function class: " +
+              currentClassSym.fullName)
         }
         js.This()(currentThisType)
       } { thisLocalName =>
@@ -3359,10 +3336,10 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
     }
 
     /** Gen JS code for a constructor call (new).
+     *
      *  Further refined into:
-     *  * new String(...)
      *  * new of a hijacked boxed class
-     *  * new of an anonymous function class that was recorded as JS function
+     *  * new of a JS function class
      *  * new of a JS class
      *  * new Array
      *  * regular new
@@ -3382,13 +3359,6 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
       } else if (isJSFunctionDef(clsSym)) {
         val classDef = consumeLazilyGeneratedAnonClass(clsSym)
         genJSFunction(classDef, args.map(genExpr))
-      } else if (clsSym.isAnonymousFunction) {
-        val classDef = consumeLazilyGeneratedAnonClass(clsSym)
-        tryGenAnonFunctionClass(classDef, args.map(genExpr)).getOrElse {
-          // Cannot optimize anonymous function class. Generate full class.
-          generatedClasses += nestedGenerateClass(clsSym)(genClass(classDef)) -> clsSym.pos
-          genNew(clsSym, ctor, genActualArgs(ctor, args))
-        }
       } else if (isJSType(clsSym)) {
         genPrimitiveJSNew(tree)
       } else {
@@ -6057,69 +6027,6 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
 
     // Synthesizers for JS functions -------------------------------------------
 
-    /** Try and generate JS code for an anonymous function class.
-     *
-     *  Returns Some(<js code>) if the class could be rewritten that way, None
-     *  otherwise.
-     *
-     *  We make the following assumptions on the form of such classes:
-     *  - It is an anonymous function
-     *    - Includes being anonymous, final, and having exactly one constructor
-     *  - It is not a PartialFunction
-     *  - It has no field other than param accessors
-     *  - It has exactly one constructor
-     *  - It has exactly one non-bridge method apply if it is not specialized,
-     *    or a method apply$...$sp and a forwarder apply if it is specialized.
-     *  - As a precaution: it is synthetic
-     *
-     *  From a class looking like this:
-     *
-     *    final class <anon>(outer, capture1, ..., captureM) extends AbstractionFunctionN[...] {
-     *      def apply(param1, ..., paramN) = {
-     *        <body>
-     *      }
-     *    }
-     *    new <anon>(o, c1, ..., cM)
-     *
-     *  we generate a function:
-     *
-     *    arrow-lambda<o = outer, c1 = capture1, ..., cM = captureM>(param1, ..., paramN) {
-     *      <body>
-     *    }
-     *
-     *  so that, at instantiation point, we can write:
-     *
-     *    new AnonFunctionN(function)
-     *
-     *  the latter tree is returned in case of success.
-     *
-     *  Trickier things apply when the function is specialized.
-     */
-    private def tryGenAnonFunctionClass(cd: ClassDef,
-        capturedArgs: List[js.Tree]): Option[js.Tree] = {
-      // scalastyle:off return
-      implicit val pos = cd.pos
-      val sym = cd.symbol
-      assert(sym.isAnonymousFunction,
-          s"tryGenAndRecordAnonFunctionClass called with non-anonymous function $cd")
-
-      if (!sym.superClass.fullName.startsWith("scala.runtime.AbstractFunction")) {
-        /* This is an anonymous class for a non-LMF capable SAM in 2.12.
-         * We must not rewrite it, as it would then not inherit from the
-         * appropriate parent class and/or interface.
-         */
-        None
-      } else {
-        nestedGenerateClass(sym) {
-          val (functionBase, arity) =
-            tryGenAnonFunctionClassGeneric(cd, capturedArgs)(_ => return None)
-
-          Some(genJSFunctionToScala(functionBase, arity))
-        }
-      }
-      // scalastyle:on return
-    }
-
     /** Gen a conversion from a JavaScript function into a Scala function. */
     private def genJSFunctionToScala(jsFunction: js.Tree, arity: Int)(
         implicit pos: Position): js.Tree = {
@@ -6136,11 +6043,9 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
      *  functions are not classes, we deconstruct the ClassDef, then
      *  reconstruct it to be a genuine Closure.
      *
-     *  Compared to `tryGenAnonFunctionClass()`, this function must
-     *  always succeed, because we really cannot afford keeping them as
-     *  anonymous classes. The good news is that it can do so, because the
-     *  body of SAM lambdas is hoisted in the enclosing class. Hence, the
-     *  apply() method is just a forwarder to calling that hoisted method.
+     *  We can always do so, because the body of SAM lambdas is hoisted in the
+     *  enclosing class. Hence, the apply() method is just a forwarder to
+     *  calling that hoisted method.
      *
      *  From a class looking like this:
      *
@@ -6163,26 +6068,18 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
           s"genAndRecordJSFunctionClass called with non-JS function $cd")
 
       nestedGenerateClass(sym) {
-        val (function, _) = tryGenAnonFunctionClassGeneric(cd, captures)(msg =>
-            abort(s"Could not generate function for JS function: $msg"))
-
-        function
+        genJSFunctionInner(cd, captures)
       }
     }
 
-    /** Code common to tryGenAndRecordAnonFunctionClass and
-     *  genAndRecordJSFunctionClass.
-     */
-    private def tryGenAnonFunctionClassGeneric(cd: ClassDef,
-        initialCapturedArgs: List[js.Tree])(
-        fail: (=> String) => Nothing): (js.Tree, Int) = {
+    /** The code of `genJSFunction` that is inside the `nestedGenerateClass` wrapper. */
+    private def genJSFunctionInner(cd: ClassDef,
+        initialCapturedArgs: List[js.Tree]): js.Closure = {
       implicit val pos = cd.pos
       val sym = cd.symbol
 
-      // First checks
-
-      if (sym.isSubClass(PartialFunctionClass))
-        fail(s"Cannot rewrite PartialFunction $cd")
+      def fail(reason: String): Nothing =
+        abort(s"Could not generate function for JS function: $reason")
 
       // First step: find the apply method def, and collect param accessors
 
@@ -6210,10 +6107,12 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
               if (!ddsym.isPrimaryConstructor)
                 fail(s"Non-primary constructor $ddsym in anon function $cd")
             } else {
-              val name = dd.name.toString
-              if (name == "apply" || (ddsym.isSpecialized && name.startsWith("apply$"))) {
-                if ((applyDef eq null) || ddsym.isSpecialized)
+              if (dd.name == nme.apply) {
+                if (!ddsym.isBridge) {
+                  if (applyDef ne null)
+                    fail(s"Found duplicate apply method $ddsym in $cd")
                   applyDef = dd
+                }
               } else if (ddsym.hasAnnotation(JSOptionalAnnotation)) {
                 // Ignore (this is useful for default parameters in custom JS function types)
               } else {
@@ -6253,24 +6152,15 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
         // Third step: emit the body of the apply method def
 
         val applyMethod = withScopedVars(
-            paramAccessorLocals := (paramAccessors zip ctorParamDefs).toMap,
-            tryingToGenMethodAsJSFunction := true
+            paramAccessorLocals := (paramAccessors zip ctorParamDefs).toMap
         ) {
-          try {
-            genMethodWithCurrentLocalNameScope(applyDef)
-          } catch {
-            case e: CancelGenMethodAsJSFunction =>
-              fail(e.getMessage)
-          }
+          genMethodWithCurrentLocalNameScope(applyDef)
         }
 
         // Fourth step: patch the body to unbox parameters and box result
 
-        val hasRepeatedParam = {
-          sym.superClass == JSFunctionClass && // Scala functions are known not to have repeated params
-          enteringUncurry {
-            applyDef.symbol.paramss.flatten.lastOption.exists(isRepeated(_))
-          }
+        val hasRepeatedParam = enteringUncurry {
+          applyDef.symbol.paramss.flatten.lastOption.exists(isRepeated(_))
         }
 
         val js.MethodDef(_, _, _, params, _, body) = applyMethod
@@ -6303,8 +6193,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
           val ok = patchedParams.nonEmpty
           if (!ok) {
             reporter.error(pos,
-                "The SAM or apply method for a js.ThisFunction must have a " +
-                "leading non-varargs parameter")
+                "The apply method for a js.ThisFunction must have a leading non-varargs parameter")
           }
           ok
         }
@@ -6335,9 +6224,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
           }
         }
 
-        val arity = params.size
-
-        (closure, arity)
+        closure
       }
     }
 
diff --git a/compiler/src/test/scala/org/scalajs/nscplugin/test/JSSAMTest.scala b/compiler/src/test/scala/org/scalajs/nscplugin/test/JSSAMTest.scala
index 3513fff2e3..4eedcb3447 100644
--- a/compiler/src/test/scala/org/scalajs/nscplugin/test/JSSAMTest.scala
+++ b/compiler/src/test/scala/org/scalajs/nscplugin/test/JSSAMTest.scala
@@ -126,10 +126,10 @@ class JSSAMTest extends DirectTest with TestHelpers {
     }
     """ hasErrors
     """
-      |newSource1.scala:14: error: The SAM or apply method for a js.ThisFunction must have a leading non-varargs parameter
+      |newSource1.scala:14: error: The apply method for a js.ThisFunction must have a leading non-varargs parameter
       |      val badThisFunction1: BadThisFunction1 = () => 42
       |                                                  ^
-      |newSource1.scala:15: error: The SAM or apply method for a js.ThisFunction must have a leading non-varargs parameter
+      |newSource1.scala:15: error: The apply method for a js.ThisFunction must have a leading non-varargs parameter
       |      val badThisFunction2: BadThisFunction2 = args => args.size
       |                                                    ^
     """

From 0181706748268e4e33cfc3b3c5e3438702732e7d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Tue, 4 Feb 2025 09:51:36 +0100
Subject: [PATCH 254/298] Wasm: Remove dead code jsLinkingInfo object.

This was forgotten in 7bf410dd922662dabfc85f1d76d40431c1fe0910.
---
 .../linker/backend/wasmemitter/Emitter.scala  | 20 -------------------
 .../backend/wasmemitter/LoaderContent.scala   |  3 +--
 2 files changed, 1 insertion(+), 22 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala
index fcbe987f50..51d1c99fd0 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala
@@ -259,25 +259,6 @@ final class Emitter(config: Emitter.Config) {
 
     implicit val noPos = Position.NoPosition
 
-    // Linking info
-    val linkingInfo = {
-      // must be in sync with scala.scalajs.runtime.LinkingInfo
-      import config.coreSpec._
-      import js.{BooleanLiteral => bool, IntLiteral => int, StringLiteral => str}
-
-      def objectFreeze(tree: js.Tree): js.Tree =
-        js.Apply(js.DotSelect(js.VarRef(js.Ident("Object")), js.Ident("freeze")), tree :: Nil)
-
-      objectFreeze(js.ObjectConstr(List(
-        str("esVersion") -> int(esFeatures.esVersion.edition),
-        str("assumingES6") -> bool(esFeatures.useECMAScript2015Semantics), // different name for historical reasons
-        str("isWebAssembly") -> bool(true),
-        str("productionMode") -> bool(semantics.productionMode),
-        str("linkerVersion") -> str(ScalaJSVersions.current),
-        str("fileLevelThis") -> js.This()
-      )))
-    }
-
     // Sort for stability
     val importedModules = module.externalDependencies.toList.sorted
 
@@ -326,7 +307,6 @@ final class Emitter(config: Emitter.Config) {
       js.VarRef(loadFunIdent),
       List(
         js.StringLiteral(config.internalWasmFileURIPattern(module.id)),
-        linkingInfo,
         exportSettersDict,
         customJSHelpersDict
       )
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala
index a096a66c5d..271894e7f5 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala
@@ -180,10 +180,9 @@ const stringBuiltinPolyfills = {
   equals: (a, b) => a === b,
 };
 
-export async function load(wasmFileURL, linkingInfo, exportSetters, customJSHelpers) {
+export async function load(wasmFileURL, exportSetters, customJSHelpers) {
   const myScalaJSHelpers = {
     ...scalaJSHelpers,
-    jsLinkingInfo: linkingInfo,
     idHashCodeMap: new WeakMap()
   };
   const importsObj = {

From bdd73fb9ea90c9cf0d15773d64bb42fb3a18312d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Fri, 31 Jan 2025 14:16:57 +0100
Subject: [PATCH 255/298] Make the guards for deserialization hacks clearer.

Previously, deserialization hacks were guarded by the last IR
version to which they applied. This was confusing when IR versions
skipped one or more minor number, for example from 1.8 to 1.11.
The version that introduces the hack was 1.11, but the guards were
`hacks.use8`.

Comments and error messages were typically disagreeing with that
convention. For example, in that situation, they would refer to
"prior to 1.11" or "1.11 introduced". That was another mismatch
between the programmatic guards and the text in the comments.

Overall this was very confusing.

Now, we refer to the *first* IR version to which a hack must *not*
be applied. This corresponds to the comments, and in general to
the IR version that introduced the hack.

---

In addition, we take the opportunity to use a unique `useBelow(V)`
instead of individual `useV` methods. The fixed list of `useV`
methods with their corresponding string versions had become too
long.
---
 .../scala/org/scalajs/ir/Serializers.scala    | 156 ++++++++----------
 .../org/scalajs/ir/SerializersTest.scala      |  61 +++++++
 project/BinaryIncompatibilities.scala         |   3 +
 3 files changed, 135 insertions(+), 85 deletions(-)
 create mode 100644 ir/shared/src/test/scala/org/scalajs/ir/SerializersTest.scala

diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
index 4866e36457..dbd8a03f83 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
@@ -41,6 +41,14 @@ object Serializers {
    */
   final val IRMagicNumber = 0xCAFE4A53
 
+  /** A regex for a compatible stable binary IR version from which we may need
+   *  to migrate things with hacks.
+   */
+  private val CompatibleStableIRVersionRegex = {
+    val prefix = java.util.regex.Pattern.quote(ScalaJSVersions.binaryCross + ".")
+    new scala.util.matching.Regex(prefix + "(\\d+)")
+  }
+
   // For deserialization hack
   private final val DynamicImportThunkClass =
     ClassName("scala.scalajs.runtime.DynamicImportThunk")
@@ -1107,7 +1115,7 @@ object Serializers {
 
         case TagAssign =>
           val lhs0 = readTree()
-          val lhs = if (hacks.use4 && lhs0.tpe == NothingType) {
+          val lhs = if (hacks.useBelow(5) && lhs0.tpe == NothingType) {
             /* Note [Nothing FieldDef rewrite]
              * (throw qual.field[null]) = rhs  -->  qual.field[null] = rhs
              */
@@ -1128,7 +1136,7 @@ object Serializers {
         case TagWhile   => While(readTree(), readTree())
 
         case TagDoWhile =>
-          if (!hacks.use12)
+          if (!hacks.useBelow(13))
             throw new IOException(s"Found invalid pre-1.13 DoWhile loop at $pos")
           // Rewrite `do { body } while (cond)` to `while ({ body; cond }) {}`
           val body = readTree()
@@ -1153,7 +1161,7 @@ object Serializers {
         case TagLoadModule   => LoadModule(readClassName())
 
         case TagStoreModule =>
-          if (hacks.use13) {
+          if (hacks.useBelow(16)) {
             val cls = readClassName()
             val rhs = readTree()
             rhs match {
@@ -1172,7 +1180,7 @@ object Serializers {
           val field = readFieldIdent()
           val tpe = readType()
 
-          if (hacks.use4 && tpe == NothingType) {
+          if (hacks.useBelow(5) && tpe == NothingType) {
             /* Note [Nothing FieldDef rewrite]
              * qual.field[nothing]  -->  throw qual.field[null]
              */
@@ -1217,7 +1225,7 @@ object Serializers {
 
         case TagArrayLength | TagGetClass | TagClone | TagIdentityHashCode |
             TagWrapAsThrowable | TagUnwrapFromThrowable | TagThrow =>
-          if (!hacks.use17) {
+          if (!hacks.useBelow(18)) {
             throw new IOException(
                 s"Illegal legacy node $tag found in class ${enclosingClassName.nameString}")
           }
@@ -1240,7 +1248,7 @@ object Serializers {
               UnaryOp(UnaryOp.UnwrapFromThrowable, checkNotNullLhs)
             case TagThrow =>
               val patchedLhs =
-                if (hacks.use8) throwArgumentHack8(lhs)
+                if (hacks.useBelow(11)) throwArgumentHackBelow11(lhs)
                 else lhs
               UnaryOp(UnaryOp.Throw, patchedLhs)
           }
@@ -1253,7 +1261,7 @@ object Serializers {
               NewArray(arrayTypeRef, length)
 
             case _ =>
-              if (hacks.use16) {
+              if (hacks.useBelow(17)) {
                 // Rewrite as a call to j.l.r.Array.newInstance
                 val ArrayTypeRef(base, origDims) = arrayTypeRef
                 val newDims = origDims - lengths.size
@@ -1284,7 +1292,7 @@ object Serializers {
         case TagIsInstanceOf =>
           val expr = readTree()
           val testType0 = readType()
-          val testType = if (hacks.use16) {
+          val testType = if (hacks.useBelow(17)) {
             testType0 match {
               case ClassType(className, true)    => ClassType(className, nullable = false)
               case ArrayType(arrayTypeRef, true) => ArrayType(arrayTypeRef, nullable = false)
@@ -1302,7 +1310,7 @@ object Serializers {
         case TagJSPrivateSelect => JSPrivateSelect(readTree(), readFieldIdent())
 
         case TagJSSelect =>
-          if (hacks.use17 && buf.get(buf.position()) == TagJSLinkingInfo) {
+          if (hacks.useBelow(18) && buf.get(buf.position()) == TagJSLinkingInfo) {
             val jsLinkingInfo = readTree()
             readTree() match {
               case StringLiteral("productionMode") =>
@@ -1345,7 +1353,7 @@ object Serializers {
         case TagJSTypeOfGlobalRef    => JSTypeOfGlobalRef(readTree().asInstanceOf[JSGlobalRef])
 
         case TagJSLinkingInfo =>
-          if (hacks.use17) {
+          if (hacks.useBelow(18)) {
             JSObjectConstr(List(
               (StringLiteral("productionMode"), LinkTimeProperty(ProductionMode)(BooleanType)),
               (StringLiteral("esVersion"), LinkTimeProperty(ESVersion)(IntType)),
@@ -1374,7 +1382,7 @@ object Serializers {
 
         case TagVarRef =>
           val name =
-            if (hacks.use17) readLocalIdent().name
+            if (hacks.useBelow(18)) readLocalIdent().name
             else readLocalName()
           VarRef(name)(readType())
 
@@ -1409,7 +1417,7 @@ object Serializers {
       }
     }
 
-    /** Patches the argument of a `Throw` for IR version until 1.8.
+    /** Patches the argument of a `Throw` for IR version below 1.11.
      *
      *  Prior to Scala.js 1.11, `Throw(e)` was emitted by the compiler with
      *  the somewhat implied assumption that it would "throw an NPE" (but
@@ -1443,7 +1451,7 @@ object Serializers {
      *  `AnyType`. We can accurately use that test to know whether we need to
      *  apply the patch.
      */
-    private def throwArgumentHack8(expr: Tree)(implicit pos: Position): Tree = {
+    private def throwArgumentHackBelow11(expr: Tree)(implicit pos: Position): Tree = {
       if (expr.tpe == AnyType)
         expr
       else if (!expr.tpe.isNullable)
@@ -1465,11 +1473,11 @@ object Serializers {
       val originalName = readOriginalName()
       val kind = ClassKind.fromByte(readByte())
 
-      if (hacks.use16) {
+      if (hacks.useBelow(17)) {
         thisTypeForHack = kind match {
           case ClassKind.Class | ClassKind.ModuleClass | ClassKind.Interface =>
             Some(ClassType(cls, nullable = false))
-          case ClassKind.HijackedClass if hacks.use8 =>
+          case ClassKind.HijackedClass if hacks.useBelow(11) =>
             // Use getOrElse as safety guard for otherwise invalid inputs
             Some(BoxedClassToPrimType.getOrElse(cls, ClassType(cls, nullable = false)))
           case _ =>
@@ -1484,7 +1492,7 @@ object Serializers {
       val superClass = readOptClassIdent()
       val parents = readClassIdents()
 
-      if (hacks.use17 && kind.isClass) {
+      if (hacks.useBelow(18) && kind.isClass) {
         /* In 1.18, we started enforcing the constructor chaining discipline.
          * Unfortunately, we used to generate a wrong super constructor call in
          * synthetic classes extending `DynamicImportThunk`, so we patch them.
@@ -1493,7 +1501,7 @@ object Serializers {
           superClass.exists(_.name == DynamicImportThunkClass)
       }
 
-      /* jsSuperClass is not hacked like in readMemberDef.bodyHack5. The
+      /* jsSuperClass is not hacked like in readMemberDef.bodyHackBelow6. The
        * compilers before 1.6 always use a simple VarRef() as jsSuperClass,
        * when there is one, so no hack is required.
        */
@@ -1528,22 +1536,22 @@ object Serializers {
 
       val methods = {
         val methods0 = methodsBuilder.result()
-        if (hacks.use4 && kind.isJSClass) {
+        if (hacks.useBelow(5) && kind.isJSClass) {
           // #4409: Filter out abstract methods in non-native JS classes for version < 1.5
           methods0.filter(_.body.isDefined)
-        } else if (hacks.use16 && cls == ClassClass) {
-          jlClassMethodsHack16(methods0)
-        } else if (hacks.use16 && cls == HackNames.ReflectArrayModClass) {
-          jlReflectArrayMethodsHack16(methods0)
+        } else if (hacks.useBelow(17) && cls == ClassClass) {
+          jlClassMethodsHackBelow17(methods0)
+        } else if (hacks.useBelow(17) && cls == HackNames.ReflectArrayModClass) {
+          jlReflectArrayMethodsHackBelow17(methods0)
         } else {
           methods0
         }
       }
 
       val (jsConstructor, jsMethodProps) = {
-        if (hacks.use8 && kind.isJSClass) {
-          assert(jsConstructorBuilder.result().isEmpty, "found JSConstructorDef in pre 1.8 IR")
-          jsConstructorHack(kind, jsMethodPropsBuilder.result())
+        if (hacks.useBelow(11) && kind.isJSClass) {
+          assert(jsConstructorBuilder.result().isEmpty, "found JSConstructorDef in pre 1.11 IR")
+          jsConstructorHackBelow11(kind, jsMethodPropsBuilder.result())
         } else {
           (jsConstructorBuilder.result(), jsMethodPropsBuilder.result())
         }
@@ -1557,7 +1565,7 @@ object Serializers {
           optimizerHints)
     }
 
-    private def jlClassMethodsHack16(methods: List[MethodDef]): List[MethodDef] = {
+    private def jlClassMethodsHackBelow17(methods: List[MethodDef]): List[MethodDef] = {
       for (method <- methods) yield {
         implicit val pos = method.pos
 
@@ -1621,7 +1629,7 @@ object Serializers {
       }
     }
 
-    private def jlReflectArrayMethodsHack16(methods: List[MethodDef]): List[MethodDef] = {
+    private def jlReflectArrayMethodsHackBelow17(methods: List[MethodDef]): List[MethodDef] = {
       /* Basically this method hard-codes new implementations for the two
        * overloads of newInstance.
        * It is horrible, but better than pollute everything else in the linker.
@@ -1803,7 +1811,7 @@ object Serializers {
       newInstanceRecMethod :: newMethods
     }
 
-    private def jsConstructorHack(ownerKind: ClassKind,
+    private def jsConstructorHackBelow11(ownerKind: ClassKind,
         jsMethodProps: List[JSMethodPropDef]): (Option[JSConstructorDef], List[JSMethodPropDef]) = {
       val jsConstructorBuilder = new OptionBuilder[JSConstructorDef]
       val jsMethodPropsBuilder = List.newBuilder[JSMethodPropDef]
@@ -1847,7 +1855,7 @@ object Serializers {
       val originalName = readOriginalName()
 
       val ftpe0 = readType()
-      val ftpe = if (hacks.use4 && ftpe0 == NothingType) {
+      val ftpe = if (hacks.useBelow(5) && ftpe0 == NothingType) {
         /* Note [Nothing FieldDef rewrite]
          * val field: nothing  -->  val field: null
          */
@@ -1881,7 +1889,7 @@ object Serializers {
          * rewrite it as a static initializers instead (`<stinit>`).
          */
         val name0 = readMethodIdent()
-        if (hacks.use1 &&
+        if (hacks.useBelow(2) &&
             name0.name == ClassInitializerName &&
             !ownerKind.isJSType) {
           MethodIdent(StaticInitializerName)(name0.pos)
@@ -1896,11 +1904,11 @@ object Serializers {
       val body = readOptTree()
       val optimizerHints = OptimizerHints.fromBits(readInt())
 
-      if (hacks.use0 &&
+      if (hacks.useBelow(1) &&
           flags.namespace == MemberNamespace.Public &&
           owner == HackNames.SystemModule &&
           name.name == HackNames.identityHashCodeName) {
-        /* #3976: 1.0 javalib relied on wrong linker dispatch.
+        /* #3976: Before 1.1, the javalib relied on wrong linker dispatch.
          * We simply replace it with a correct implementation.
          */
         assert(args.size == 1)
@@ -1910,7 +1918,7 @@ object Serializers {
 
         MethodDef(flags, name, originalName, args, resultType, patchedBody)(
             patchedOptimizerHints, optHash)
-      } else if (hacks.use4 &&
+      } else if (hacks.useBelow(5) &&
           flags.namespace == MemberNamespace.Public &&
           owner == ObjectClass &&
           name.name == HackNames.cloneName) {
@@ -1943,7 +1951,7 @@ object Serializers {
         MethodDef(flags, name, originalName, args, resultType, patchedBody)(
             patchedOptimizerHints, optHash)
       } else {
-        val patchedBody = body.map(bodyHack5(_, isStat = resultType == VoidType))
+        val patchedBody = body.map(bodyHackBelow6(_, isStat = resultType == VoidType))
         MethodDef(flags, name, originalName, args, resultType, patchedBody)(
             optimizerHints, optHash)
       }
@@ -1958,7 +1966,7 @@ object Serializers {
       assert(len >= 0)
 
       /* JSConstructorDef was introduced in 1.11. Therefore, by
-       * construction, they never need the body hack of 1.5.
+       * construction, they never need the body hack below 1.6.
        */
 
       val flags = MemberFlags.fromBits(readInt())
@@ -1975,7 +1983,7 @@ object Serializers {
 
     private def maybeHackJSConstructorDefAfterSuper(ownerKind: ClassKind,
         afterSuper0: List[Tree], superCallPos: Position): List[Tree] = {
-      if (hacks.use17 && ownerKind == ClassKind.JSModuleClass) {
+      if (hacks.useBelow(18) && ownerKind == ClassKind.JSModuleClass) {
         afterSuper0 match {
           case StoreModule() :: _ => afterSuper0
           case _                  => StoreModule()(superCallPos) :: afterSuper0
@@ -1992,16 +2000,16 @@ object Serializers {
       assert(len >= 0)
 
       val flags = MemberFlags.fromBits(readInt())
-      val name = bodyHack5Expr(readTree())
+      val name = bodyHackBelow6Expr(readTree())
       val (params, restParam) = readParamDefsWithRest()
-      val body = bodyHack5Expr(readTree())
+      val body = bodyHackBelow6Expr(readTree())
       JSMethodDef(flags, name, params, restParam, body)(
           OptimizerHints.fromBits(readInt()), optHash)
     }
 
     private def readJSPropertyDef()(implicit pos: Position): JSPropertyDef = {
       val optHash: Version = {
-        if (hacks.use12) {
+        if (hacks.useBelow(13)) {
           Unversioned
         } else {
           val optHash = readOptHash()
@@ -2013,11 +2021,11 @@ object Serializers {
       }
 
       val flags = MemberFlags.fromBits(readInt())
-      val name = bodyHack5Expr(readTree())
-      val getterBody = readOptTree().map(bodyHack5Expr(_))
+      val name = bodyHackBelow6Expr(readTree())
+      val getterBody = readOptTree().map(bodyHackBelow6Expr(_))
       val setterArgAndBody = {
         if (readBoolean())
-          Some((readParamDef(), bodyHack5Expr(readTree())))
+          Some((readParamDef(), bodyHackBelow6Expr(readTree())))
         else
           None
       }
@@ -2037,7 +2045,7 @@ object Serializers {
      * not derived from their children like Block or TryFinally, or
      * constant like While).
      */
-    private object BodyHack5Transformer extends Transformers.Transformer {
+    private object BodyHackBelow6Transformer extends Transformers.Transformer {
       def transformStat(tree: Tree): Tree = {
         implicit val pos = tree.pos
 
@@ -2090,11 +2098,11 @@ object Serializers {
         else transform(tree)
     }
 
-    private def bodyHack5(body: Tree, isStat: Boolean): Tree =
-      if (!hacks.use5) body
-      else BodyHack5Transformer.transform(body, isStat)
+    private def bodyHackBelow6(body: Tree, isStat: Boolean): Tree =
+      if (!hacks.useBelow(6)) body
+      else BodyHackBelow6Transformer.transform(body, isStat)
 
-    private def bodyHack5Expr(body: Tree): Tree = bodyHack5(body, isStat = false)
+    private def bodyHackBelow6Expr(body: Tree): Tree = bodyHackBelow6(body, isStat = false)
 
     def readTopLevelExportDef(): TopLevelExportDef = {
       implicit val pos = readPosition()
@@ -2108,7 +2116,7 @@ object Serializers {
       }
 
       def readModuleID(): String =
-        if (hacks.use2) DefaultModuleID
+        if (hacks.useBelow(3)) DefaultModuleID
         else readString()
 
       (tag: @switch) match {
@@ -2173,7 +2181,7 @@ object Serializers {
       val ptpe = readType()
       val mutable = readBoolean()
 
-      if (hacks.use4) {
+      if (hacks.useBelow(5)) {
         val rest = readBoolean()
         assert(!rest, "Illegal rest parameter")
       }
@@ -2185,7 +2193,7 @@ object Serializers {
       List.fill(readInt())(readParamDef())
 
     def readParamDefsWithRest(): (List[ParamDef], Option[ParamDef]) = {
-      if (hacks.use4) {
+      if (hacks.useBelow(5)) {
         val (params, isRest) = List.fill(readInt()) {
           implicit val pos = readPosition()
           (ParamDef(readLocalIdent(), readOriginalName(), readType(), readBoolean()), readBoolean())
@@ -2360,7 +2368,7 @@ object Serializers {
       /* Before 1.18, `LabelName`s were always wrapped in `LabelIdent`s, whose
        * encoding was a `Position` followed by the actual `LabelName`.
        */
-      if (hacks.use17)
+      if (hacks.useBelow(18))
         readPosition() // intentional discard
 
       val i = readInt()
@@ -2476,41 +2484,19 @@ object Serializers {
     }
   }
 
-  /** Hacks for backwards compatible deserializing. */
-  private final class Hacks(sourceVersion: String) {
-    val use0: Boolean = sourceVersion == "1.0"
-
-    val use1: Boolean = use0 || sourceVersion == "1.1"
-
-    val use2: Boolean = use1 || sourceVersion == "1.2"
-
-    private val use3: Boolean = use2 || sourceVersion == "1.3"
-
-    val use4: Boolean = use3 || sourceVersion == "1.4"
-
-    val use5: Boolean = use4 || sourceVersion == "1.5"
-
-    private val use6: Boolean = use5 || sourceVersion == "1.6"
-
-    private val use7: Boolean = use6 || sourceVersion == "1.7"
-
-    val use8: Boolean = use7 || sourceVersion == "1.8"
-
-    assert(sourceVersion != "1.9", "source version 1.9 does not exist")
-    assert(sourceVersion != "1.10", "source version 1.10 does not exist")
-
-    private val use11: Boolean = use8 || sourceVersion == "1.11"
-
-    val use12: Boolean = use11 || sourceVersion == "1.12"
-
-    val use13: Boolean = use12 || sourceVersion == "1.13"
-
-    assert(sourceVersion != "1.14", "source version 1.14 does not exist")
-    assert(sourceVersion != "1.15", "source version 1.15 does not exist")
-
-    val use16: Boolean = use13 || sourceVersion == "1.16"
+  /** Hacks for backwards compatible deserializing.
+   *
+   *  `private[ir]` for testing purposes only.
+   */
+  private[ir] final class Hacks(sourceVersion: String) {
+    private val fromVersion = sourceVersion match {
+      case CompatibleStableIRVersionRegex(minorDigits) => minorDigits.toInt
+      case _                                           => Int.MaxValue // never use any hack
+    }
 
-    val use17: Boolean = use16 || sourceVersion == "1.17"
+    /** Should we use the hacks to migrate from an IR version below `targetVersion`? */
+    def useBelow(targetVersion: Int): Boolean =
+      fromVersion < targetVersion
   }
 
   /** Names needed for hacks. */
diff --git a/ir/shared/src/test/scala/org/scalajs/ir/SerializersTest.scala b/ir/shared/src/test/scala/org/scalajs/ir/SerializersTest.scala
new file mode 100644
index 0000000000..a8c18507d9
--- /dev/null
+++ b/ir/shared/src/test/scala/org/scalajs/ir/SerializersTest.scala
@@ -0,0 +1,61 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package org.scalajs.ir
+
+import org.junit.Test
+import org.junit.Assert._
+
+class SerializersTest {
+  @Test def testHacksUseBelow(): Unit = {
+    import Serializers.Hacks
+
+    val hacks1_0 = new Hacks("1.0")
+    assertFalse(hacks1_0.useBelow(0))
+    assertTrue(hacks1_0.useBelow(1))
+    assertTrue(hacks1_0.useBelow(5))
+    assertTrue(hacks1_0.useBelow(15))
+    assertTrue(hacks1_0.useBelow(1000))
+
+    val hacks1_7 = new Hacks("1.7")
+    assertFalse(hacks1_7.useBelow(0))
+    assertFalse(hacks1_7.useBelow(1))
+    assertFalse(hacks1_7.useBelow(5))
+    assertFalse(hacks1_7.useBelow(7))
+    assertTrue(hacks1_7.useBelow(8))
+    assertTrue(hacks1_7.useBelow(15))
+    assertTrue(hacks1_7.useBelow(1000))
+
+    val hacks1_50 = new Hacks("1.50")
+    assertFalse(hacks1_50.useBelow(0))
+    assertFalse(hacks1_50.useBelow(1))
+    assertFalse(hacks1_50.useBelow(5))
+    assertFalse(hacks1_50.useBelow(15))
+    assertTrue(hacks1_50.useBelow(1000))
+
+    // Non-stable versions never get any hacks
+    val hacks1_9_snapshot = new Hacks("1.9-SNAPSHOT")
+    assertFalse(hacks1_9_snapshot.useBelow(0))
+    assertFalse(hacks1_9_snapshot.useBelow(1))
+    assertFalse(hacks1_9_snapshot.useBelow(5))
+    assertFalse(hacks1_9_snapshot.useBelow(15))
+    assertFalse(hacks1_9_snapshot.useBelow(1000))
+
+    // Incompatible versions never get any hacks
+    val hacks2_5 = new Hacks("2.5")
+    assertFalse(hacks2_5.useBelow(0))
+    assertFalse(hacks2_5.useBelow(1))
+    assertFalse(hacks2_5.useBelow(5))
+    assertFalse(hacks2_5.useBelow(15))
+    assertFalse(hacks2_5.useBelow(1000))
+  }
+}
diff --git a/project/BinaryIncompatibilities.scala b/project/BinaryIncompatibilities.scala
index 4713fe6bf8..af6f47f735 100644
--- a/project/BinaryIncompatibilities.scala
+++ b/project/BinaryIncompatibilities.scala
@@ -5,6 +5,9 @@ import com.typesafe.tools.mima.core.ProblemFilters._
 
 object BinaryIncompatibilities {
   val IR = Seq(
+    // private, not an issue
+    ProblemFilters.exclude[MissingClassProblem]("org.scalajs.ir.Serializers$Deserializer$BodyHack5Transformer$"),
+    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Serializers#Hacks.use*"),
   )
 
   val Linker = Seq(

From 38636cf028b0506835c5c0dea5b1ab31cefa7d00 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Sat, 25 Jan 2025 14:06:32 +0100
Subject: [PATCH 256/298] Bump the version to 1.19.0-SNAPSHOT for the upcoming
 changes.

---
 ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala b/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala
index 0f03e6a638..3f7c4d501e 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala
@@ -17,7 +17,7 @@ import java.util.concurrent.ConcurrentHashMap
 import scala.util.matching.Regex
 
 object ScalaJSVersions extends VersionChecks(
-    current = "1.18.3-SNAPSHOT",
+    current = "1.19.0-SNAPSHOT",
     binaryEmitted = "1.18"
 )
 

From 1987d8726b40405147bad5b4f3ee5bf06452afd3 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Sun, 29 Dec 2024 20:49:17 +0100
Subject: [PATCH 257/298] Add a desugaring pass between the base linker and the
 optimizer.

Previously, the emitters and the optimizer all had to perform the
same desugaring for `LinkTimeProperty` nodes. Instead, we now
perform the desugaring in a dedicated phase, after the base
linker.

The reachability analysis records whether each method needs
desugaring or not. We mark those that do so that the desugaring
pass knows what to process. Methods that do not require
desugaring are not processed, and so incur no additional cost.

No caching is performed in `Desugarer`. It processes so few
methods that caching makes it (slightly) *slower*.

The machinery is heavy. It definitely outweighs the benefits in
terms of duplication for `LinkTimeProperty` alone. However, the
same machinery will be used to desugar `NewLambda` nodes. This
commit serves as a stepping stone in that direction.
---
 .../scala/org/scalajs/ir/Transformers.scala   |  22 ++-
 .../scalajs/linker/analyzer/Analysis.scala    |   4 +
 .../scalajs/linker/analyzer/Analyzer.scala    |  11 +-
 .../org/scalajs/linker/analyzer/Infos.scala   |   2 +
 .../backend/emitter/FunctionEmitter.scala     |  10 +-
 .../backend/wasmemitter/DerivedClasses.scala  |   1 +
 .../backend/wasmemitter/FunctionEmitter.scala |   9 +-
 .../linker/checker/CheckingPhase.scala        |   1 +
 .../linker/checker/ClassDefChecker.scala      |   2 +
 .../scalajs/linker/checker/FeatureSet.scala   |  28 ++-
 .../scalajs/linker/checker/IRChecker.scala    |   5 +-
 .../scalajs/linker/frontend/BaseLinker.scala  |  32 ++--
 .../scalajs/linker/frontend/Desugarer.scala   | 159 ++++++++++++++++++
 .../linker/frontend/LinkerFrontendImpl.scala  |  13 +-
 .../frontend/optimizer/OptimizerCore.scala    |   3 -
 .../scalajs/linker/standard/LinkedClass.scala |  44 ++++-
 .../standard/LinkedTopLevelExport.scala       |   3 +-
 .../org/scalajs/linker/IRCheckerTest.scala    |  50 +++++-
 project/BinaryIncompatibilities.scala         |   3 +
 19 files changed, 342 insertions(+), 60 deletions(-)
 create mode 100644 linker/shared/src/main/scala/org/scalajs/linker/frontend/Desugarer.scala

diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Transformers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Transformers.scala
index bbc0c3350b..a2edeaf797 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Transformers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Transformers.scala
@@ -234,14 +234,8 @@ object Transformers {
         case jsMethodDef: JSMethodDef =>
           transformJSMethodDef(jsMethodDef)
 
-        case JSPropertyDef(flags, name, getterBody, setterArgAndBody) =>
-          JSPropertyDef(
-              flags,
-              transform(name),
-              transformTreeOpt(getterBody),
-              setterArgAndBody.map { case (arg, body) =>
-                (arg, transform(body))
-              })(Unversioned)(jsMethodPropDef.pos)
+        case jsPropertyDef: JSPropertyDef =>
+          transformJSPropertyDef(jsPropertyDef)
       }
     }
 
@@ -251,6 +245,18 @@ object Transformers {
           jsMethodDef.optimizerHints, Unversioned)(jsMethodDef.pos)
     }
 
+    def transformJSPropertyDef(jsPropertyDef: JSPropertyDef): JSPropertyDef = {
+      val JSPropertyDef(flags, name, getterBody, setterArgAndBody) = jsPropertyDef
+      JSPropertyDef(
+        flags,
+        transform(name),
+        transformTreeOpt(getterBody),
+        setterArgAndBody.map { case (arg, body) =>
+          (arg, transform(body))
+        }
+      )(Unversioned)(jsPropertyDef.pos)
+    }
+
     def transformJSConstructorBody(body: JSConstructorBody): JSConstructorBody = {
       implicit val pos = body.pos
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analysis.scala b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analysis.scala
index 0c1b0118e5..781fc30c48 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analysis.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analysis.scala
@@ -84,6 +84,8 @@ object Analysis {
     def methodInfos(
         namespace: MemberNamespace): scala.collection.Map[MethodName, MethodInfo]
 
+    def anyJSMemberNeedsDesugaring: Boolean
+
     def displayName: String = className.nameString
   }
 
@@ -103,6 +105,7 @@ object Analysis {
     def instantiatedSubclasses: scala.collection.Seq[ClassInfo]
     def nonExistent: Boolean
     def syntheticKind: MethodSyntheticKind
+    def needsDesugaring: Boolean
 
     def displayName: String = methodName.displayName
 
@@ -161,6 +164,7 @@ object Analysis {
     def owningClass: ClassName
     def staticDependencies: scala.collection.Set[ClassName]
     def externalDependencies: scala.collection.Set[String]
+    def needsDesugaring: Boolean
   }
 
   sealed trait Error {
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala
index 9dc14c1574..e1faf2fa1a 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala
@@ -686,6 +686,9 @@ private class AnalyzerRun(config: CommonPhaseConfig, initial: Boolean,
     val publicMethodInfos: mutable.Map[MethodName, MethodInfo] =
       methodInfos(MemberNamespace.Public)
 
+    def anyJSMemberNeedsDesugaring: Boolean =
+      data.jsMethodProps.exists(info => (info.globalFlags & ReachabilityInfo.FlagNeedsDesugaring) != 0)
+
     def lookupAbstractMethod(methodName: MethodName): MethodInfo = {
       val candidatesIterator = for {
         ancestor <- ancestors.iterator
@@ -1285,6 +1288,9 @@ private class AnalyzerRun(config: CommonPhaseConfig, initial: Boolean,
     def isDefaultBridge: Boolean =
       syntheticKind.isInstanceOf[MethodSyntheticKind.DefaultBridge]
 
+    def needsDesugaring: Boolean =
+      (data.globalFlags & ReachabilityInfo.FlagNeedsDesugaring) != 0
+
     /** Throws MatchError if `!isDefaultBridge`. */
     def defaultBridgeTarget: ClassName = (syntheticKind: @unchecked) match {
       case MethodSyntheticKind.DefaultBridge(target) => target
@@ -1367,6 +1373,9 @@ private class AnalyzerRun(config: CommonPhaseConfig, initial: Boolean,
     def staticDependencies: scala.collection.Set[ClassName] = _staticDependencies.keySet
     def externalDependencies: scala.collection.Set[String] = _externalDependencies.keySet
 
+    def needsDesugaring: Boolean =
+      (data.reachability.globalFlags & ReachabilityInfo.FlagNeedsDesugaring) != 0
+
     def reach(): Unit = followReachabilityInfo(data.reachability, this)(FromExports)
   }
 
@@ -1441,7 +1450,7 @@ private class AnalyzerRun(config: CommonPhaseConfig, initial: Boolean,
       }
     }
 
-    val globalFlags = data.globalFlags
+    val globalFlags = data.globalFlags & ~ReachabilityInfo.FlagNeedsDesugaring
 
     if (globalFlags != 0) {
       if ((globalFlags & ReachabilityInfo.FlagAccessedClassClass) != 0) {
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala
index 1458e107f4..c713d5799e 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala
@@ -115,6 +115,7 @@ object Infos {
     final val FlagAccessedImportMeta = 1 << 2
     final val FlagUsedExponentOperator = 1 << 3
     final val FlagUsedClassSuperClass = 1 << 4
+    final val FlagNeedsDesugaring = 1 << 5
   }
 
   /** Things from a given class that are reached by one method. */
@@ -395,6 +396,7 @@ object Infos {
       setFlag(ReachabilityInfo.FlagUsedClassSuperClass)
 
     def addReferencedLinkTimeProperty(linkTimeProperty: LinkTimeProperty): this.type = {
+      setFlag(ReachabilityInfo.FlagNeedsDesugaring)
       linkTimeProperties.append((linkTimeProperty.name, linkTimeProperty.tpe))
       this
     }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
index df5ed07b70..2252d71cd4 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
@@ -1260,9 +1260,8 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
 
       def test(tree: Tree): Boolean = tree match {
         // Atomic expressions
-        case _: Literal          => true
-        case _: JSNewTarget      => true
-        case _: LinkTimeProperty => true
+        case _: Literal     => true
+        case _: JSNewTarget => true
 
         // Vars (side-effect free, pure if immutable)
         case VarRef(name) =>
@@ -2811,11 +2810,6 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
         case AsInstanceOf(expr, tpe) =>
           extractWithGlobals(genAsInstanceOf(transformExprNoChar(expr), tpe))
 
-        case prop: LinkTimeProperty =>
-          transformExpr(
-              config.coreSpec.linkTimeProperties.transformLinkTimeProperty(prop),
-              preserveChar)
-
         // Transients
 
         case Transient(Cast(expr, tpe)) =>
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/DerivedClasses.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/DerivedClasses.scala
index 1935e130fc..c65065dab5 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/DerivedClasses.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/DerivedClasses.scala
@@ -146,6 +146,7 @@ object DerivedClasses {
       staticDependencies = Set.empty,
       externalDependencies = Set.empty,
       dynamicDependencies = Set.empty,
+      desugaringRequirements = LinkedClass.DesugaringRequirements.Empty,
       clazz.version
     )
   }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
index 7ef7a87ac3..68e1ab881d 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
@@ -550,7 +550,6 @@ private class FunctionEmitter private (
       case t: Match               => genMatch(t, expectedType)
       case t: Debugger            => VoidType // ignore
       case t: Skip                => VoidType
-      case t: LinkTimeProperty    => genLinkTimeProperty(t)
 
       // JavaScript expressions
       case t: JSNew                => genJSNew(t)
@@ -590,7 +589,7 @@ private class FunctionEmitter private (
       // Transients (only generated by the optimizer)
       case t: Transient => genTransient(t)
 
-      case _: JSSuperConstructorCall =>
+      case _:JSSuperConstructorCall | _:LinkTimeProperty =>
         throw new AssertionError(s"Invalid tree: $tree")
     }
 
@@ -2649,12 +2648,6 @@ private class FunctionEmitter private (
     ClassType(boxClassName, nullable = false)
   }
 
-  private def genLinkTimeProperty(tree: LinkTimeProperty): Type = {
-    val lit = ctx.coreSpec.linkTimeProperties.transformLinkTimeProperty(tree)
-    genLiteral(lit, lit.tpe)
-    lit.tpe
-  }
-
   private def genJSNew(tree: JSNew): Type = {
     val JSNew(ctor, args) = tree
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/checker/CheckingPhase.scala b/linker/shared/src/main/scala/org/scalajs/linker/checker/CheckingPhase.scala
index ff198744de..ac62d4d25e 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/checker/CheckingPhase.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/checker/CheckingPhase.scala
@@ -24,5 +24,6 @@ sealed abstract class CheckingPhase
 object CheckingPhase {
   case object Compiler extends CheckingPhase
   case object BaseLinker extends CheckingPhase
+  case object Desugarer extends CheckingPhase
   case object Optimizer extends CheckingPhase
 }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala b/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
index b3dd10acb8..671a320632 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
@@ -855,6 +855,8 @@ private final class ClassDefChecker(classDef: ClassDef,
         }
 
       case LinkTimeProperty(name) =>
+        if (!featureSet.supports(FeatureSet.LinkTimeProperty))
+          reportError(i"Illegal link-time property '$name' after desugaring")
 
       // JavaScript expressions
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/checker/FeatureSet.scala b/linker/shared/src/main/scala/org/scalajs/linker/checker/FeatureSet.scala
index 73f89b0d8b..59f1d89c54 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/checker/FeatureSet.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/checker/FeatureSet.scala
@@ -36,17 +36,20 @@ private[checker] object FeatureSet {
 
   // Individual features
 
+  /** The `LinkTimeProperty` IR node. */
+  val LinkTimeProperty = new FeatureSet(1 << 0)
+
   /** Optional constructors in module classes and JS classes. */
-  val OptionalConstructors = new FeatureSet(1 << 0)
+  val OptionalConstructors = new FeatureSet(1 << 1)
 
   /** Explicit reflective proxy definitions. */
-  val ReflectiveProxies = new FeatureSet(1 << 1)
+  val ReflectiveProxies = new FeatureSet(1 << 2)
 
   /** Transients that are the result of optimizations. */
-  val OptimizedTransients = new FeatureSet(1 << 2)
+  val OptimizedTransients = new FeatureSet(1 << 3)
 
   /** Records and record types. */
-  val Records = new FeatureSet(1 << 3)
+  val Records = new FeatureSet(1 << 4)
 
   /** Relaxed constructor discipline.
    *
@@ -55,7 +58,7 @@ private[checker] object FeatureSet {
    *  - `this.x = ...` assignments before the delegate call can assign super class fields.
    *  - `StoreModule` can be anywhere, or not be there at all.
    */
-  val RelaxedCtorBodies = new FeatureSet(1 << 4)
+  val RelaxedCtorBodies = new FeatureSet(1 << 5)
 
   // Common sets
 
@@ -63,14 +66,23 @@ private[checker] object FeatureSet {
   private val Linked =
     OptionalConstructors | ReflectiveProxies
 
+  /** Features that must be desugared away. */
+  private val NeedsDesugaring =
+    LinkTimeProperty
+
+  /** IR that is only the result of desugaring (currently empty). */
+  private val Desugared =
+    Empty
+
   /** IR that is only the result of optimizations. */
   private val Optimized =
     OptimizedTransients | Records | RelaxedCtorBodies
 
   /** The set of features allowed as output of the given phase. */
   def allowedAfter(phase: CheckingPhase): FeatureSet = phase match {
-    case Compiler   => Empty
-    case BaseLinker => Linked
-    case Optimizer  => Linked | Optimized
+    case Compiler   => NeedsDesugaring
+    case BaseLinker => Linked | NeedsDesugaring
+    case Desugarer  => Linked | Desugared
+    case Optimizer  => Linked | Desugared | Optimized
   }
 }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala b/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
index de827f396a..a6c786fb01 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
@@ -577,7 +577,7 @@ private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter,
         typecheckAny(expr, env)
         checkIsAsInstanceTargetType(tpe)
 
-      case LinkTimeProperty(name) =>
+      case LinkTimeProperty(name) if featureSet.supports(FeatureSet.LinkTimeProperty) =>
 
       // JavaScript expressions
 
@@ -760,7 +760,8 @@ private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter,
             typecheck(elem, env)
         }
 
-      case _:RecordSelect | _:RecordValue | _:Transient | _:JSSuperConstructorCall =>
+      case _:RecordSelect | _:RecordValue | _:Transient |
+          _:JSSuperConstructorCall | _:LinkTimeProperty =>
         reportError("invalid tree")
     }
   }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/BaseLinker.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/BaseLinker.scala
index ddf5b71f14..07eb08b294 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/BaseLinker.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/BaseLinker.scala
@@ -129,17 +129,20 @@ private[frontend] object BaseLinker {
         classInfo.isAnySubclassInstantiated
     }
 
-    val methods = classDef.methods.filter { m =>
-      val methodInfo =
-        classInfo.methodInfos(m.flags.namespace)(m.methodName)
-
-      val reachable = methodInfo.isReachable
-      assert(m.body.isDefined || !reachable,
-          s"The abstract method ${classDef.name.name}.${m.methodName} " +
-          "is reachable.")
-
-      reachable
-    }
+    // Will stay empty for most classes
+    var desugaringRequirements = LinkedClass.DesugaringRequirements.Empty
+
+    val methods: List[MethodDef] = classDef.methods.iterator
+      .map(m => m -> classInfo.methodInfos(m.flags.namespace)(m.methodName))
+      .filter(_._2.isReachable)
+      .map { case (m, info) =>
+        assert(m.body.isDefined,
+            s"The abstract method ${classDef.name.name}.${m.methodName} is reachable.")
+        if (info.needsDesugaring)
+          desugaringRequirements = desugaringRequirements.addMethod(m.flags.namespace, m.methodName)
+        m
+      }
+      .toList
 
     val jsConstructor =
       if (classInfo.isAnySubclassInstantiated) classDef.jsConstructor
@@ -149,6 +152,9 @@ private[frontend] object BaseLinker {
       if (classInfo.isAnySubclassInstantiated) classDef.jsMethodProps
       else Nil
 
+    if (classInfo.anyJSMemberNeedsDesugaring)
+      desugaringRequirements = desugaringRequirements.addAnyExportedMember()
+
     val jsNativeMembers = classDef.jsNativeMembers
       .filter(m => classInfo.jsNativeMembersUsed.contains(m.name.name))
 
@@ -181,6 +187,7 @@ private[frontend] object BaseLinker {
         staticDependencies = classInfo.staticDependencies.toSet,
         externalDependencies = classInfo.externalDependencies.toSet,
         dynamicDependencies = classInfo.dynamicDependencies.toSet,
+        desugaringRequirements,
         version)
 
     val linkedTopLevelExports = for {
@@ -189,7 +196,8 @@ private[frontend] object BaseLinker {
       val infos = analysis.topLevelExportInfos(
         (ModuleID(topLevelExport.moduleID), topLevelExport.topLevelExportName))
       new LinkedTopLevelExport(classDef.className, topLevelExport,
-          infos.staticDependencies.toSet, infos.externalDependencies.toSet)
+          infos.staticDependencies.toSet, infos.externalDependencies.toSet,
+          needsDesugaring = infos.needsDesugaring)
     }
 
     (linkedClass, linkedTopLevelExports)
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/Desugarer.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/Desugarer.scala
new file mode 100644
index 0000000000..65323bfd69
--- /dev/null
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/Desugarer.scala
@@ -0,0 +1,159 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package org.scalajs.linker.frontend
+
+import org.scalajs.logging._
+
+import org.scalajs.linker.standard._
+import org.scalajs.linker.checker._
+
+import org.scalajs.ir.Names._
+import org.scalajs.ir.Transformers._
+import org.scalajs.ir.Trees._
+import org.scalajs.ir.{Position, Version}
+
+/** Desugars a linking unit. */
+final class Desugarer(config: CommonPhaseConfig, checkIR: Boolean) {
+  import Desugarer._
+
+  private val desugarTransformer = new DesugarTransformer(config.coreSpec)
+
+  def desugar(unit: LinkingUnit, logger: Logger): LinkingUnit = {
+    val result = logger.time("Desugarer: Desugar") {
+      val desugaredClasses = unit.classDefs.map(desugarClass(_))
+      val desugaredTopLevelExports = unit.topLevelExports.map(desugarTopLevelExport(_))
+
+      new LinkingUnit(desugaredClasses, desugaredTopLevelExports,
+          unit.moduleInitializers, unit.globalInfo)
+    }
+
+    if (checkIR) {
+      logger.time("Desugarer: Check IR") {
+        val errorCount = IRChecker.check(result, logger, CheckingPhase.Desugarer)
+        if (errorCount != 0) {
+          throw new AssertionError(
+              s"There were $errorCount IR checking errors after desugaring (this is a Scala.js bug)")
+        }
+      }
+    }
+
+    result
+  }
+
+  private def desugarClass(linkedClass: LinkedClass): LinkedClass = {
+    import linkedClass._
+
+    if (desugaringRequirements.isEmpty) {
+      linkedClass
+    } else {
+      val newMethods = methods.map { method =>
+        if (!desugaringRequirements.containsMethod(method.flags.namespace, method.methodName))
+          method
+        else
+          desugarTransformer.transformMethodDef(method)
+      }
+
+      val newJSConstructorDef =
+        if (!desugaringRequirements.exportedMembers) jsConstructorDef
+        else jsConstructorDef.map(desugarTransformer.transformJSConstructorDef(_))
+
+      val newExportedMembers =
+        if (!desugaringRequirements.exportedMembers) exportedMembers
+        else exportedMembers.map(desugarTransformer.transformJSMethodPropDef(_))
+
+      new LinkedClass(
+        name,
+        kind,
+        jsClassCaptures,
+        superClass,
+        interfaces,
+        jsSuperClass,
+        jsNativeLoadSpec,
+        fields,
+        methods = newMethods,
+        jsConstructorDef = newJSConstructorDef,
+        exportedMembers = newExportedMembers,
+        jsNativeMembers,
+        optimizerHints,
+        pos,
+        ancestors,
+        hasInstances,
+        hasDirectInstances,
+        hasInstanceTests,
+        hasRuntimeTypeInfo,
+        fieldsRead,
+        staticFieldsRead,
+        staticDependencies,
+        externalDependencies,
+        dynamicDependencies,
+        LinkedClass.DesugaringRequirements.Empty,
+        version
+      )
+    }
+  }
+
+  private def desugarTopLevelExport(tle: LinkedTopLevelExport): LinkedTopLevelExport = {
+    import tle._
+    if (!tle.needsDesugaring) {
+      tle
+    } else {
+      val newTree = desugarTransformer.transformTopLevelExportDef(tree)
+      new LinkedTopLevelExport(owningClass, newTree, staticDependencies,
+          externalDependencies, needsDesugaring = false)
+    }
+  }
+}
+
+private[linker] object Desugarer {
+
+  private final class DesugarTransformer(coreSpec: CoreSpec)
+      extends ClassTransformer {
+
+    override def transform(tree: Tree): Tree = {
+      tree match {
+        case prop: LinkTimeProperty =>
+          coreSpec.linkTimeProperties.transformLinkTimeProperty(prop)
+
+        case _ =>
+          super.transform(tree)
+      }
+    }
+
+    /* Transfer Version from old members to transformed members.
+     * We can do this because the transformation only depends on the
+     * `coreSpec`, which is immutable.
+     */
+
+    override def transformMethodDef(methodDef: MethodDef): MethodDef = {
+      val newMethodDef = super.transformMethodDef(methodDef)
+      newMethodDef.copy()(newMethodDef.optimizerHints, methodDef.version)(newMethodDef.pos)
+    }
+
+    override def transformJSConstructorDef(jsConstructor: JSConstructorDef): JSConstructorDef = {
+      val newJSConstructor = super.transformJSConstructorDef(jsConstructor)
+      newJSConstructor.copy()(newJSConstructor.optimizerHints, jsConstructor.version)(
+          newJSConstructor.pos)
+    }
+
+    override def transformJSMethodDef(jsMethodDef: JSMethodDef): JSMethodDef = {
+      val newJSMethodDef = super.transformJSMethodDef(jsMethodDef)
+      newJSMethodDef.copy()(newJSMethodDef.optimizerHints, jsMethodDef.version)(
+          newJSMethodDef.pos)
+    }
+
+    override def transformJSPropertyDef(jsPropertyDef: JSPropertyDef): JSPropertyDef = {
+      val newJSPropertyDef = super.transformJSPropertyDef(jsPropertyDef)
+      newJSPropertyDef.copy()(jsPropertyDef.version)(newJSPropertyDef.pos)
+    }
+  }
+}
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/LinkerFrontendImpl.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/LinkerFrontendImpl.scala
index 11d10064a9..d75fd57eab 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/LinkerFrontendImpl.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/LinkerFrontendImpl.scala
@@ -40,6 +40,9 @@ final class LinkerFrontendImpl private (config: LinkerFrontendImpl.Config)
   private[this] val linker: BaseLinker =
     new BaseLinker(config.commonConfig, config.checkIR)
 
+  private[this] val desugarer: Desugarer =
+    new Desugarer(config.commonConfig, config.checkIR)
+
   private[this] val optOptimizer: Option[IncOptimizer] =
     LinkerFrontendImplPlatform.createOptimizer(config)
 
@@ -69,8 +72,14 @@ final class LinkerFrontendImpl private (config: LinkerFrontendImpl.Config)
           preOptimizerRequirements)
     }
 
-    val optimizedResult = optOptimizer.fold(linkResult) { optimizer =>
-      linkResult.flatMap(optimize(_, symbolRequirements, optimizer, logger))
+    val desugaredResult = linkResult.map { unit =>
+      logger.time("Desugarer") {
+        desugarer.desugar(unit, logger)
+      }
+    }
+
+    val optimizedResult = optOptimizer.fold(desugaredResult) { optimizer =>
+      desugaredResult.flatMap(optimize(_, symbolRequirements, optimizer, logger))
     }
 
     optimizedResult.map { unit =>
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
index dae5f87e43..9c026ac032 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
@@ -589,9 +589,6 @@ private[optimizer] abstract class OptimizerCore(
           }
         }
 
-      case prop: LinkTimeProperty =>
-        config.coreSpec.linkTimeProperties.transformLinkTimeProperty(prop)
-
       // JavaScript expressions
 
       case JSNew(ctor, args) =>
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/standard/LinkedClass.scala b/linker/shared/src/main/scala/org/scalajs/linker/standard/LinkedClass.scala
index afa257b289..010214777a 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/standard/LinkedClass.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/standard/LinkedClass.scala
@@ -14,7 +14,7 @@ package org.scalajs.linker.standard
 
 import org.scalajs.ir.Trees._
 import org.scalajs.ir.{ClassKind, Position, Version}
-import org.scalajs.ir.Names.{ClassName, FieldName}
+import org.scalajs.ir.Names.{ClassName, FieldName, MethodName}
 
 /** A ClassDef after linking.
  *
@@ -65,6 +65,9 @@ final class LinkedClass(
     val externalDependencies: Set[String],
     val dynamicDependencies: Set[ClassName],
 
+    // Desugaring requirements
+    val desugaringRequirements: LinkedClass.DesugaringRequirements,
+
     val version: Version) {
 
   require(ancestors.headOption.contains(name.name),
@@ -89,3 +92,42 @@ final class LinkedClass(
 
   def fullName: String = className.nameString
 }
+
+object LinkedClass {
+  /** Desugaring requirements of a `LinkedClass`.
+   *
+   *  These requirements are a set of members that need desugaring.
+   */
+  final class DesugaringRequirements private (
+    methods: Vector[Set[MethodName]], // indexed by MemberNamespace ordinal
+    val exportedMembers: Boolean
+  ) {
+    private def this() = {
+      this(
+        methods = Vector.fill(MemberNamespace.Count)(Set.empty),
+        exportedMembers = false
+      )
+    }
+
+    /** Are these requirements empty, i.e., does the corresponding require no desugaring at all? */
+    def isEmpty: Boolean =
+      this eq DesugaringRequirements.Empty // by construction, only that specific instance is empty
+
+    /** Do the requirements contain the given method, i.e., does that method need desugaring? */
+    def containsMethod(namespace: MemberNamespace, methodName: MethodName): Boolean =
+      methods(namespace.ordinal).contains(methodName)
+
+    def addMethod(namespace: MemberNamespace, methodName: MethodName): DesugaringRequirements = {
+      val newMethods =
+        methods.updated(namespace.ordinal, methods(namespace.ordinal) + methodName)
+      new DesugaringRequirements(newMethods, exportedMembers)
+    }
+
+    def addAnyExportedMember(): DesugaringRequirements =
+      new DesugaringRequirements(methods, exportedMembers = true)
+  }
+
+  object DesugaringRequirements {
+    val Empty: DesugaringRequirements = new DesugaringRequirements()
+  }
+}
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/standard/LinkedTopLevelExport.scala b/linker/shared/src/main/scala/org/scalajs/linker/standard/LinkedTopLevelExport.scala
index 1702ecd02e..339280f150 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/standard/LinkedTopLevelExport.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/standard/LinkedTopLevelExport.scala
@@ -19,7 +19,8 @@ final class LinkedTopLevelExport(
     val owningClass: ClassName,
     val tree: TopLevelExportDef,
     val staticDependencies: Set[ClassName],
-    val externalDependencies: Set[String]
+    val externalDependencies: Set[String],
+    val needsDesugaring: Boolean
 ) {
   def exportName: String = tree.topLevelExportName
 }
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/IRCheckerTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/IRCheckerTest.scala
index d283ae189e..1d6dd4759f 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/IRCheckerTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/IRCheckerTest.scala
@@ -18,8 +18,9 @@ import scala.util.{Failure, Success}
 import org.junit.Test
 import org.junit.Assert._
 
-import org.scalajs.ir.ClassKind
+import org.scalajs.ir.{ClassKind, EntryPointsInfo}
 import org.scalajs.ir.Names._
+import org.scalajs.ir.Transformers._
 import org.scalajs.ir.Trees._
 import org.scalajs.ir.Types._
 
@@ -427,6 +428,41 @@ class IRCheckerTest {
 }
 
 object IRCheckerTest {
+  /** Version of the minilib where we have replaced every node requiring
+   *  desugaring by a placeholder.
+   *
+   *  We need this to directly feed to the IR checker post-optimizer, since
+   *  nodes requiring desugaring are rejected at that point.
+   */
+  private lazy val minilibRequiringNoDesugaring: Future[Seq[IRFile]] = {
+    import scala.concurrent.ExecutionContext.Implicits.global
+
+    TestIRRepo.minilib.map { stdLibFiles =>
+      for (irFile <- stdLibFiles) yield {
+        val irFileImpl = IRFileImpl.fromIRFile(irFile)
+
+        val patchedTreeFuture = irFileImpl.tree.map { tree =>
+          new ClassTransformer {
+            override def transform(tree: Tree): Tree = tree match {
+              case tree: LinkTimeProperty => zeroOf(tree.tpe)
+              case _                      => super.transform(tree)
+            }
+          }.transformClassDef(tree)
+        }
+
+        new IRFileImpl(irFileImpl.path, irFileImpl.version) {
+          /** Entry points information for this file. */
+          def entryPointsInfo(implicit ec: ExecutionContext): Future[EntryPointsInfo] =
+            irFileImpl.entryPointsInfo(ec)
+
+          /** IR Tree of this file. */
+          def tree(implicit ec: ExecutionContext): Future[ClassDef] =
+            patchedTreeFuture
+        }
+      }
+    }
+  }
+
   def testLinkNoIRError(classDefs: Seq[ClassDef],
       moduleInitializers: List[ModuleInitializer],
       postOptimizer: Boolean = false)(
@@ -467,8 +503,8 @@ object IRCheckerTest {
       .factory("IRCheckerTest")
       .none()
 
-    TestIRRepo.minilib.flatMap { stdLibFiles =>
-      if (postOptimizer) {
+    if (postOptimizer) {
+      minilibRequiringNoDesugaring.flatMap { stdLibFiles =>
         val refiner = new Refiner(CommonPhaseConfig.fromStandardConfig(config), checkIR = true)
 
         Future.traverse(stdLibFiles)(f => IRFileImpl.fromIRFile(f).tree).flatMap { stdLibClassDefs =>
@@ -480,7 +516,9 @@ object IRCheckerTest {
           refiner.refine(allClassDefs.map(c => (c, UNV)), moduleInitializers,
               noSymbolRequirements, logger)
         }
-      } else {
+      }.map(_ => ())
+    } else {
+      TestIRRepo.minilib.flatMap { stdLibFiles =>
         val linkerFrontend = StandardLinkerFrontend(config)
         val irFiles = (
           stdLibFiles ++
@@ -488,7 +526,7 @@ object IRCheckerTest {
           PrivateLibHolder.files
         )
         linkerFrontend.link(irFiles, moduleInitializers, noSymbolRequirements, logger)
-      }
-    }.map(_ => ())
+      }.map(_ => ())
+    }
   }
 }
diff --git a/project/BinaryIncompatibilities.scala b/project/BinaryIncompatibilities.scala
index af6f47f735..8ac39f199d 100644
--- a/project/BinaryIncompatibilities.scala
+++ b/project/BinaryIncompatibilities.scala
@@ -11,6 +11,9 @@ object BinaryIncompatibilities {
   )
 
   val Linker = Seq(
+    // !!! Breaking, OK in minor release
+    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.linker.standard.LinkedClass.this"),
+    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.linker.standard.LinkedTopLevelExport.this"),
   )
 
   val LinkerInterface = Seq(

From b38201c0cf6f99fc146d0ee90de989b23d6e9c68 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Thu, 16 Jan 2025 23:35:37 +0100
Subject: [PATCH 258/298] Drop support for non-strict floats.

Non-strict floats were deprecated 3 years ago in Scala.js 1.9.0.
I don't recall seeing any comment about them ever since.
---
 Jenkinsfile                                   |  36 --
 javalib/src/main/scala/java/lang/Float.scala  |   9 +-
 .../scala/java/lang/FloatingPointBits.scala   |  46 +--
 .../scalajs/linker/interface/Semantics.scala  |  25 +-
 .../linker/interface/StandardConfig.scala     |   1 -
 .../backend/WebAssemblyLinkerBackend.scala    |   4 -
 .../linker/backend/emitter/CoreJSLib.scala    | 312 +++++++++---------
 .../linker/backend/emitter/SJSGen.scala       |  16 +-
 project/BinaryIncompatibilities.scala         |   2 +
 project/Build.scala                           |   1 -
 .../scalajs/testsuite/utils/BuildInfo.scala   |   1 -
 .../scalajs/testsuite/utils/Platform.scala    |  34 --
 .../testsuite/compiler/FloatJSTest.scala      |   2 -
 .../scalajs/testsuite/utils/Requires.scala    |   5 -
 .../scalajs/testsuite/utils/Platform.scala    |   2 -
 .../testsuite/compiler/DoubleTest.scala       |   4 -
 .../testsuite/compiler/FloatTest.scala        |  28 +-
 .../scalajs/testsuite/compiler/LongTest.scala |   2 -
 .../compiler/RuntimeTypeTestsTest.scala       |   2 +-
 .../testsuite/javalib/lang/ClassTest.scala    |   2 +-
 .../testsuite/javalib/lang/FloatTest.scala    |  15 +-
 .../testsuite/javalib/lang/ObjectTest.scala   |   2 +-
 .../javalib/math/BigDecimalConvertTest.scala  |  14 +-
 .../javalib/math/BigIntegerConvertTest.scala  |  12 -
 24 files changed, 196 insertions(+), 381 deletions(-)

diff --git a/Jenkinsfile b/Jenkinsfile
index 8f6ecc3c8e..5cbf59ce7f 100644
--- a/Jenkinsfile
+++ b/Jenkinsfile
@@ -232,17 +232,6 @@ def Tasks = [
         'set scalaJSLinkerConfig in $testSuite.v$v ~= makeCompliant' \
         'set scalaJSLinkerConfig in $testSuite.v$v ~= (_.withOptimizer(false))' \
         $testSuite$v/test &&
-    sbtretry ++$scala 'set Global/enableMinifyEverywhere := $testMinify' \
-        'set scalaJSLinkerConfig in $testSuite.v$v ~= { _.withSemantics(_.withStrictFloats(false)) }' \
-        $testSuite$v/test &&
-    sbtretry ++$scala 'set Global/enableMinifyEverywhere := $testMinify' \
-        'set scalaJSLinkerConfig in $testSuite.v$v ~= { _.withSemantics(_.withStrictFloats(false)) }' \
-        'set scalaJSStage in Global := FullOptStage' \
-        $testSuite$v/test &&
-    sbtretry ++$scala 'set Global/enableMinifyEverywhere := $testMinify' \
-        'set scalaJSLinkerConfig in $testSuite.v$v ~= { _.withSemantics(_.withStrictFloats(false)) }' \
-        'set scalaJSLinkerConfig in $testSuite.v$v ~= (_.withOptimizer(false))' \
-        $testSuite$v/test &&
     sbtretry ++$scala 'set Global/enableMinifyEverywhere := $testMinify' \
         'set scalaJSLinkerConfig in $testSuite.v$v ~= (_.withESFeatures(_.withAllowBigIntsForLongs(true)))' \
         $testSuite$v/test &&
@@ -312,20 +301,6 @@ def Tasks = [
         'set Seq(jsEnv in $testSuite.v$v := new NodeJSEnvForcePolyfills(ESVersion.$esVersion), MyScalaJSPlugin.wantSourceMaps in $testSuite.v$v := ("$esVersion" != "ES5_1"))' \
         'set scalaJSLinkerConfig in $testSuite.v$v ~= makeCompliant' \
         'set scalaJSLinkerConfig in $testSuite.v$v ~= (_.withOptimizer(false))' \
-        ++$scala $testSuite$v/test &&
-    sbtretry 'set scalaJSLinkerConfig in $testSuite.v$v ~= (_.withESFeatures(_.withESVersion(ESVersion.$esVersion)))' \
-        'set Seq(jsEnv in $testSuite.v$v := new NodeJSEnvForcePolyfills(ESVersion.$esVersion), MyScalaJSPlugin.wantSourceMaps in $testSuite.v$v := ("$esVersion" != "ES5_1"))' \
-        'set scalaJSLinkerConfig in $testSuite.v$v ~= { _.withSemantics(_.withStrictFloats(false)) }' \
-        ++$scala $testSuite$v/test &&
-    sbtretry 'set scalaJSLinkerConfig in $testSuite.v$v ~= (_.withESFeatures(_.withESVersion(ESVersion.$esVersion)))' \
-        'set Seq(jsEnv in $testSuite.v$v := new NodeJSEnvForcePolyfills(ESVersion.$esVersion), MyScalaJSPlugin.wantSourceMaps in $testSuite.v$v := ("$esVersion" != "ES5_1"))' \
-        'set scalaJSLinkerConfig in $testSuite.v$v ~= { _.withSemantics(_.withStrictFloats(false)) }' \
-        'set scalaJSStage in Global := FullOptStage' \
-        ++$scala $testSuite$v/test &&
-    sbtretry 'set scalaJSLinkerConfig in $testSuite.v$v ~= (_.withESFeatures(_.withESVersion(ESVersion.$esVersion)))' \
-        'set Seq(jsEnv in $testSuite.v$v := new NodeJSEnvForcePolyfills(ESVersion.$esVersion), MyScalaJSPlugin.wantSourceMaps in $testSuite.v$v := ("$esVersion" != "ES5_1"))' \
-        'set scalaJSLinkerConfig in $testSuite.v$v ~= { _.withSemantics(_.withStrictFloats(false)) }' \
-        'set scalaJSLinkerConfig in $testSuite.v$v ~= (_.withOptimizer(false))' \
         ++$scala $testSuite$v/test
   ''',
 
@@ -355,17 +330,6 @@ def Tasks = [
         'set scalaJSLinkerConfig in $testSuite.v$v ~= makeCompliant' \
         'set scalaJSLinkerConfig in $testSuite.v$v ~= (_.withOptimizer(false))' \
         ++$scala $testSuite$v/test &&
-    sbtretry 'set scalaJSLinkerConfig in $testSuite.v$v ~= (_.withESFeatures(_.withESVersion(ESVersion.$esVersion)))' \
-        'set scalaJSLinkerConfig in $testSuite.v$v ~= { _.withSemantics(_.withStrictFloats(false)) }' \
-        ++$scala $testSuite$v/test &&
-    sbtretry 'set scalaJSLinkerConfig in $testSuite.v$v ~= (_.withESFeatures(_.withESVersion(ESVersion.$esVersion)))' \
-        'set scalaJSLinkerConfig in $testSuite.v$v ~= { _.withSemantics(_.withStrictFloats(false)) }' \
-        'set scalaJSStage in Global := FullOptStage' \
-        ++$scala $testSuite$v/test &&
-    sbtretry 'set scalaJSLinkerConfig in $testSuite.v$v ~= (_.withESFeatures(_.withESVersion(ESVersion.$esVersion)))' \
-        'set scalaJSLinkerConfig in $testSuite.v$v ~= { _.withSemantics(_.withStrictFloats(false)) }' \
-        'set scalaJSLinkerConfig in $testSuite.v$v ~= (_.withOptimizer(false))' \
-        ++$scala $testSuite$v/test &&
     sbtretry 'set scalaJSLinkerConfig in $testSuite.v$v ~= (_.withESFeatures(_.withESVersion(ESVersion.$esVersion).withAllowBigIntsForLongs(true)))' \
         ++$scala $testSuite$v/test &&
     sbtretry 'set scalaJSLinkerConfig in $testSuite.v$v ~= (_.withESFeatures(_.withESVersion(ESVersion.$esVersion).withAllowBigIntsForLongs(true)).withOptimizer(false))' \
diff --git a/javalib/src/main/scala/java/lang/Float.scala b/javalib/src/main/scala/java/lang/Float.scala
index c9c6ea2e84..8fa4ce3070 100644
--- a/javalib/src/main/scala/java/lang/Float.scala
+++ b/javalib/src/main/scala/java/lang/Float.scala
@@ -150,14 +150,7 @@ object Float {
     val zDouble = z.toDouble
 
     if (zDouble == z0) {
-      /* This branch is always taken when strictFloats are disabled, and there
-       * is no Math.fround support. In that case, Floats are basically
-       * equivalent to Doubles, and we make no specific guarantee about the
-       * result, so we can quickly return `z`.
-       * More importantly, the computations in the `else` branch assume that
-       * Float operations are exact, so we must return early.
-       *
-       * This branch is also always taken when z0 is 0.0 or Infinity, which the
+      /* This branch is always taken when z0 is 0.0 or Infinity, which the
        * `else` branch assumes does not happen.
        */
       z
diff --git a/javalib/src/main/scala/java/lang/FloatingPointBits.scala b/javalib/src/main/scala/java/lang/FloatingPointBits.scala
index fb9b89ff93..96e1c8f64c 100644
--- a/javalib/src/main/scala/java/lang/FloatingPointBits.scala
+++ b/javalib/src/main/scala/java/lang/FloatingPointBits.scala
@@ -149,7 +149,7 @@ private[lang] object FloatingPointBits {
       float32Array(0) = value
       int32Array(0)
     } else {
-      floatToIntBitsPolyfill(value.toDouble)
+      floatToIntBitsPolyfill(value)
     }
   }
 
@@ -181,8 +181,7 @@ private[lang] object FloatingPointBits {
    * Note that if typed arrays are not supported, it is almost certain that
    * fround is not supported natively, so Float operations are extremely slow.
    *
-   * We therefore do all computations in Doubles here, which is also more
-   * predictable, since the results do not depend on strict floats semantics.
+   * We therefore do all computations in Doubles here.
    */
 
   private def intBitsToFloatPolyfill(bits: Int): scala.Double = {
@@ -194,21 +193,23 @@ private[lang] object FloatingPointBits {
     decodeIEEE754(ebits, fbits, floatPowsOf2, scala.Float.MinPositiveValue, sign, e, f)
   }
 
-  private def floatToIntBitsPolyfill(value: scala.Double): Int = {
+  private def floatToIntBitsPolyfill(floatValue: scala.Float): Int = {
     // Some constants
     val ebits = 8
     val fbits = 23
 
+    // Force computations to be on Doubles
+    val value = floatValue.toDouble
+
     // Determine sign bit and compute the absolute value av
     val sign = if (value < 0.0 || (value == 0.0 && 1.0 / value < 0.0)) -1 else 1
     val s = sign & scala.Int.MinValue
     val av = sign * value
 
     // Compute e and f
-    val avr = forceFround(av)
     val powsOf2 = this.floatPowsOf2 // local cache
-    val e = encodeIEEE754Exponent(ebits, powsOf2, avr)
-    val f = encodeIEEE754MantissaBits(ebits, fbits, powsOf2, scala.Float.MinPositiveValue.toDouble, avr, e)
+    val e = encodeIEEE754Exponent(ebits, powsOf2, av)
+    val f = encodeIEEE754MantissaBits(ebits, fbits, powsOf2, scala.Float.MinPositiveValue.toDouble, av, e)
 
     // Encode
     s | (e << fbits) | rawToInt(f)
@@ -277,37 +278,6 @@ private[lang] object FloatingPointBits {
     }
   }
 
-  /** Force rounding of `av` to fit in 32 bits (this is a manual `fround`).
-   *
-   *  `av` must not be negative, i.e., `av < 0.0` must be false (it can be
-   *  `NaN` or `Infinity`).
-   *
-   *  When we use strict-float semantics, this is redundant, because the input
-   *  came from a `Float` and is therefore guaranteed to be rounded already.
-   *  However, here we don't know whether we use strict floats semantics or
-   *  not, so we must always do it. This is not a big deal because, if this
-   *  code is called, then any operation on `Float`s is calling the same code
-   *  from the `CoreJSLib`, so doing one more such operation for
-   *  `floatToIntBits` is negligible.
-   *
-   *  TODO Remove this when we get rid of non-strict float semantics altogether.
-   */
-  @inline
-  private def forceFround(av: scala.Double): scala.Double = {
-    // See the `fround` polyfill in CoreJSLib
-    val overflowThreshold = 3.4028235677973366e38
-    val normalThreshold = 1.1754943508222875e-38
-    if (av >= overflowThreshold) {
-      scala.Double.PositiveInfinity
-    } else if (av >= normalThreshold) {
-      val p = av * 536870913.0 // pow(2, 29) + 1
-      p + (av - p)
-    } else {
-      val roundingFactor = scala.Double.MinPositiveValue / scala.Float.MinPositiveValue.toDouble
-      (av * roundingFactor) / roundingFactor
-    }
-  }
-
   private def encodeIEEE754Exponent(ebits: Int,
       powsOf2: js.Array[scala.Double], av: scala.Double): Int = {
 
diff --git a/linker-interface/shared/src/main/scala/org/scalajs/linker/interface/Semantics.scala b/linker-interface/shared/src/main/scala/org/scalajs/linker/interface/Semantics.scala
index 5795b1c5db..d8608016c1 100644
--- a/linker-interface/shared/src/main/scala/org/scalajs/linker/interface/Semantics.scala
+++ b/linker-interface/shared/src/main/scala/org/scalajs/linker/interface/Semantics.scala
@@ -12,6 +12,8 @@
 
 package org.scalajs.linker.interface
 
+import scala.annotation.compileTimeOnly
+
 import CheckedBehavior._
 import Fingerprint.FingerprintBuilder
 
@@ -23,12 +25,16 @@ final class Semantics private (
     val nullPointers: CheckedBehavior,
     val stringIndexOutOfBounds: CheckedBehavior,
     val moduleInit: CheckedBehavior,
-    val strictFloats: Boolean,
     val productionMode: Boolean,
     val runtimeClassNameMapper: Semantics.RuntimeClassNameMapper) {
 
   import Semantics._
 
+  @deprecated(
+      "non-strict floats are not supported anymore; strictFloats is always true",
+      since = "1.19.0")
+  val strictFloats: Boolean = true
+
   def withAsInstanceOfs(behavior: CheckedBehavior): Semantics =
     copy(asInstanceOfs = behavior)
 
@@ -50,13 +56,11 @@ final class Semantics private (
   def withModuleInit(moduleInit: CheckedBehavior): Semantics =
     copy(moduleInit = moduleInit)
 
-  @deprecated(
-      "Scala.js now uses strict floats by default. " +
-      "Non-strict float semantics are deprecated and will eventually be " +
-      "removed.",
-      "1.9.0")
+  @compileTimeOnly(
+      "Non-strict floats are not supported anymore. " +
+      "The default is `true` and cannot be turned to `false`.")
   def withStrictFloats(strictFloats: Boolean): Semantics =
-    copy(strictFloats = strictFloats)
+    this
 
   def withProductionMode(productionMode: Boolean): Semantics =
     copy(productionMode = productionMode)
@@ -86,7 +90,6 @@ final class Semantics private (
       this.nullPointers == that.nullPointers &&
       this.stringIndexOutOfBounds == that.stringIndexOutOfBounds &&
       this.moduleInit == that.moduleInit &&
-      this.strictFloats == that.strictFloats &&
       this.productionMode == that.productionMode &&
       this.runtimeClassNameMapper == that.runtimeClassNameMapper
     case _ =>
@@ -103,7 +106,6 @@ final class Semantics private (
     acc = mix(acc, nullPointers.##)
     acc = mix(acc, stringIndexOutOfBounds.##)
     acc = mix(acc, moduleInit.##)
-    acc = mix(acc, strictFloats.##)
     acc = mix(acc, productionMode.##)
     acc = mixLast(acc, runtimeClassNameMapper.##)
     finalizeHash(acc, 10)
@@ -118,7 +120,6 @@ final class Semantics private (
        |  nullPointers           = $nullPointers,
        |  stringIndexOutOfBounds = $stringIndexOutOfBounds,
        |  moduleInit             = $moduleInit,
-       |  strictFloats           = $strictFloats,
        |  productionMode         = $productionMode
        |)""".stripMargin
   }
@@ -131,7 +132,6 @@ final class Semantics private (
       nullPointers: CheckedBehavior = this.nullPointers,
       stringIndexOutOfBounds: CheckedBehavior = this.stringIndexOutOfBounds,
       moduleInit: CheckedBehavior = this.moduleInit,
-      strictFloats: Boolean = this.strictFloats,
       productionMode: Boolean = this.productionMode,
       runtimeClassNameMapper: RuntimeClassNameMapper =
         this.runtimeClassNameMapper): Semantics = {
@@ -143,7 +143,6 @@ final class Semantics private (
         nullPointers = nullPointers,
         stringIndexOutOfBounds = stringIndexOutOfBounds,
         moduleInit = moduleInit,
-        strictFloats = strictFloats,
         productionMode = productionMode,
         runtimeClassNameMapper = runtimeClassNameMapper)
   }
@@ -262,7 +261,6 @@ object Semantics {
         .addField("nullPointers", semantics.nullPointers)
         .addField("stringIndexOutOfBounds", semantics.stringIndexOutOfBounds)
         .addField("moduleInit", semantics.moduleInit)
-        .addField("strictFloats", semantics.strictFloats)
         .addField("productionMode", semantics.productionMode)
         .addField("runtimeClassNameMapper", semantics.runtimeClassNameMapper)
         .build()
@@ -277,7 +275,6 @@ object Semantics {
       nullPointers = Fatal,
       stringIndexOutOfBounds = Fatal,
       moduleInit = Unchecked,
-      strictFloats = true,
       productionMode = false,
       runtimeClassNameMapper = RuntimeClassNameMapper.keepAll())
 }
diff --git a/linker-interface/shared/src/main/scala/org/scalajs/linker/interface/StandardConfig.scala b/linker-interface/shared/src/main/scala/org/scalajs/linker/interface/StandardConfig.scala
index 508728fce5..2f3a2afe7b 100644
--- a/linker-interface/shared/src/main/scala/org/scalajs/linker/interface/StandardConfig.scala
+++ b/linker-interface/shared/src/main/scala/org/scalajs/linker/interface/StandardConfig.scala
@@ -192,7 +192,6 @@ final class StandardConfig private (
    *
    *  - `moduleKind == ModuleKind.ESModule`
    *  - `esFeatures.useECMAScript2015Semantics == true` (true by default)
-   *  - `semantics.strictFloats == true` (true by default; non-strict floats are deprecated)
    *
    *  We may lift these restrictions in the future, although we do not expect
    *  to do so.
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/WebAssemblyLinkerBackend.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/WebAssemblyLinkerBackend.scala
index ba12a26b59..a167a7bf9f 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/WebAssemblyLinkerBackend.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/WebAssemblyLinkerBackend.scala
@@ -40,10 +40,6 @@ final class WebAssemblyLinkerBackend(config: LinkerBackendImpl.Config)
     coreSpec.esFeatures.useECMAScript2015Semantics,
     s"The WebAssembly backend only supports the ECMAScript 2015 semantics."
   )
-  require(
-    coreSpec.semantics.strictFloats,
-    "The WebAssembly backend only supports strict float semantics."
-  )
 
   require(coreSpec.targetIsWebAssembly,
       s"A WebAssembly backend cannot be used with CoreSpec targeting JavaScript")
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
index 467e73d68b..8b30a408f5 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
@@ -191,154 +191,150 @@ private[emitter] object CoreJSLib {
 
         case FroundBuiltin =>
           val v = varRef("v")
-          if (!strictFloats) {
-            genArrowFunction(paramList(v), Return(+v))
-          } else {
-            val Float32ArrayRef = globalRef("Float32Array")
-
-            /* (function(array) {
-             *   return function(v) {
-             *     array[0] = v;
-             *     return array[0];
-             *   }
-             * })(new Float32Array(1))
-             *
-             * Allocating the Float32Array once and for all, and capturing it
-             * in an IIFE, is *much* faster than recreating it in every call of
-             * the polyfill (about an order of magnitude).
-             */
-            val array = varRef("array")
-            val typedArrayPolyfillInner = genArrowFunction(paramList(v), {
-              Block(
-                  BracketSelect(array, 0) := v,
-                  Return(BracketSelect(array, 0))
-              )
-            })
-            val typedArrayPolyfill = Apply(
-                genArrowFunction(paramList(array), Return(typedArrayPolyfillInner)),
-                New(Float32ArrayRef, 1 :: Nil) :: Nil)
-
-            // scalastyle:off line.size.limit
-            /* Originally inspired by the Typed Array polyfills written by
-             * Joshua Bell:
-             * https://github.com/inexorabletash/polyfill/blob/a682f42c1092280bb01907c245979fb07219513d/typedarray.js#L150-L255
-             * Then simplified quite a lot because
-             * 1) we do not need to produce the actual bit string that serves
-             *    as storage of the floats, and
-             * 2) we are only interested in the float32 case.
-             *
-             * Eventually, the last bits of the above were replaced by an
-             * application of Veltkamp's splitting (see below). The inspiration
-             * for that use case came from core-js' implementation at
-             * https://github.com/zloirock/core-js/blob/a3f591658e063a6e2c2594ec3c80eff16340a98d/packages/core-js/internals/math-fround.js
-             * The code does not mention Veltkamp's splitting, but the PR
-             * discussion that led to it does, although with a question mark,
-             * and without any explanation of how/why it works:
-             * https://github.com/paulmillr/es6-shim/pull/140#issuecomment-91787165
-             * We tracked down the descriptions and proofs relative to
-             * Veltkamp's splitting and re-derived an implementation from there.
-             *
-             * The direct tests for this polyfill are the tests for `toFloat`
-             * in org.scalajs.testsuite.compiler.DoubleTest.
-             */
-            // scalastyle:on line.size.limit
-            val sign = varRef("sign")
-            val av = varRef("av")
-            val p = varRef("p")
-
-            val Inf = double(Double.PositiveInfinity)
-            val overflowThreshold = double(3.4028235677973366e38)
-            val normalThreshold = double(1.1754943508222875e-38)
-
-            val noTypedArrayPolyfill = genArrowFunction(paramList(v), Block(
-              v := +v, // turns `null` into +0, making sure not to deoptimize what follows
-              const(sign, If(v < 0, -1, 1)), // 1 for NaN, +0 and -0
-              const(av, sign * v), // abs(v), or -0 if v is -0
-              If(av >= overflowThreshold, { // also handles the case av === Infinity
-                Return(sign * Inf)
-              }, If(av >= normalThreshold, Block(
-                /* Here, we know that both the input and output are expressed
-                 * in a Double normal form, so standard floating point
-                 * algorithms from papers can be used.
-                 *
-                 * We use Veltkamp's splitting, as described and studied in
-                 *   Sylvie Boldo.
-                 *   Pitfalls of a Full Floating-Point Proof: Example on the
-                 *   Formal Proof of the Veltkamp/Dekker Algorithms
-                 *   https://dx.doi.org/10.1007/11814771_6
-                 * Section 3, with β = 2, t = 53, s = 53 - 24 = 29, x = av.
-                 * 53 is the number of effective mantissa bits in a Double;
-                 * 24 in a Float.
-                 *
-                 * ◦ is the round-to-nearest operation with a tie-breaking
-                 * rule (in our case, break-to-even).
-                 *
-                 *   Let C = βˢ + 1 = 536870913
-                 *   p = ◦(x × C)
-                 *   q = ◦(x − p)
-                 *   x₁ = ◦(p + q)
-                 *
-                 * Boldo proves that x₁ is the (t-s)-bit float closest to x,
-                 * using the same tie-breaking rule as ◦. Since (t-s) = 24,
-                 * this is the closest float32 (with 24 mantissa bits), and
-                 * therefore the correct result of `fround`.
-                 *
-                 * Boldo also proves that if the computation of x × C does not
-                 * cause overflow, then none of the following operations will
-                 * cause overflow. We know that x (av) is less than the
-                 * overflowThreshold, and overflowThreshold × C does not
-                 * overflow, so that computation can never cause an overflow.
-                 *
-                 * If the reader does not have access to Boldo's paper, they
-                 * may refer instead to
-                 *   Claude-Pierre Jeannerod, Jean-Michel Muller, Paul Zimmermann.
-                 *   On various ways to split a floating-point number.
-                 *   ARITH 2018 - 25th IEEE Symposium on Computer Arithmetic,
-                 *   Jun 2018, Amherst (MA), United States.
-                 *   pp.53-60, 10.1109/ARITH.2018.8464793. hal-01774587v2
-                 * available at
-                 *   https://hal.inria.fr/hal-01774587v2/document
-                 * Section III, although that paper defers some theorems and
-                 * proofs to Boldo's.
-                 */
-                const(p, av * 536870913),
-                Return(sign * (p + (av - p)))
-              ), {
-                /* Here, the result is represented as a subnormal form in a
-                 * float32 representation.
-                 *
-                 * We round `av` to the nearest multiple of the smallest
-                 * positive Float value (i.e., `Float.MinPositiveValue`),
-                 * breaking ties to an even multiple.
-                 *
-                 * We do this by leveraging the inherent loss of precision near
-                 * the minimum positive *double* value: conceptually, we divide
-                 * the value by
-                 *   Float.MinPositiveValue / Double.MinPositiveValue
-                 * which will drop the excess precision, applying exactly the
-                 * rounding strategy that we want. Then we multiply the value
-                 * back by the same constant.
-                 *
-                 * However, `Float.MinPositiveValue / Double.MinPositiveValue`
-                 * is not representable as a finite Double. Therefore, we
-                 * instead use the *inverse* constant
-                 *   Double.MinPositiveValue / Float.MinPositiveValue
-                 * and we first multiply by that constant, then divide by it.
-                 *
-                 * ---
-                 *
-                 * As an additional "hack", the input values NaN, +0 and -0
-                 * also fall in this code path. For them, this computation
-                 * happens to be an identity, and is therefore correct as well.
-                 */
-                val roundingFactor = double(Double.MinPositiveValue / Float.MinPositiveValue.toDouble)
-                Return(sign * ((av * roundingFactor) / roundingFactor))
-              }))
-            ))
+          val Float32ArrayRef = globalRef("Float32Array")
 
-            If(typeof(Float32ArrayRef) !== str("undefined"),
-                typedArrayPolyfill, noTypedArrayPolyfill)
-          }
+          /* (function(array) {
+           *   return function(v) {
+           *     array[0] = v;
+           *     return array[0];
+           *   }
+           * })(new Float32Array(1))
+           *
+           * Allocating the Float32Array once and for all, and capturing it
+           * in an IIFE, is *much* faster than recreating it in every call of
+           * the polyfill (about an order of magnitude).
+           */
+          val array = varRef("array")
+          val typedArrayPolyfillInner = genArrowFunction(paramList(v), {
+            Block(
+                BracketSelect(array, 0) := v,
+                Return(BracketSelect(array, 0))
+            )
+          })
+          val typedArrayPolyfill = Apply(
+              genArrowFunction(paramList(array), Return(typedArrayPolyfillInner)),
+              New(Float32ArrayRef, 1 :: Nil) :: Nil)
+
+          // scalastyle:off line.size.limit
+          /* Originally inspired by the Typed Array polyfills written by
+           * Joshua Bell:
+           * https://github.com/inexorabletash/polyfill/blob/a682f42c1092280bb01907c245979fb07219513d/typedarray.js#L150-L255
+           * Then simplified quite a lot because
+           * 1) we do not need to produce the actual bit string that serves
+           *    as storage of the floats, and
+           * 2) we are only interested in the float32 case.
+           *
+           * Eventually, the last bits of the above were replaced by an
+           * application of Veltkamp's splitting (see below). The inspiration
+           * for that use case came from core-js' implementation at
+           * https://github.com/zloirock/core-js/blob/a3f591658e063a6e2c2594ec3c80eff16340a98d/packages/core-js/internals/math-fround.js
+           * The code does not mention Veltkamp's splitting, but the PR
+           * discussion that led to it does, although with a question mark,
+           * and without any explanation of how/why it works:
+           * https://github.com/paulmillr/es6-shim/pull/140#issuecomment-91787165
+           * We tracked down the descriptions and proofs relative to
+           * Veltkamp's splitting and re-derived an implementation from there.
+           *
+           * The direct tests for this polyfill are the tests for `toFloat`
+           * in org.scalajs.testsuite.compiler.DoubleTest.
+           */
+          // scalastyle:on line.size.limit
+          val sign = varRef("sign")
+          val av = varRef("av")
+          val p = varRef("p")
+
+          val Inf = double(Double.PositiveInfinity)
+          val overflowThreshold = double(3.4028235677973366e38)
+          val normalThreshold = double(1.1754943508222875e-38)
+
+          val noTypedArrayPolyfill = genArrowFunction(paramList(v), Block(
+            v := +v, // turns `null` into +0, making sure not to deoptimize what follows
+            const(sign, If(v < 0, -1, 1)), // 1 for NaN, +0 and -0
+            const(av, sign * v), // abs(v), or -0 if v is -0
+            If(av >= overflowThreshold, { // also handles the case av === Infinity
+              Return(sign * Inf)
+            }, If(av >= normalThreshold, Block(
+              /* Here, we know that both the input and output are expressed
+               * in a Double normal form, so standard floating point
+               * algorithms from papers can be used.
+               *
+               * We use Veltkamp's splitting, as described and studied in
+               *   Sylvie Boldo.
+               *   Pitfalls of a Full Floating-Point Proof: Example on the
+               *   Formal Proof of the Veltkamp/Dekker Algorithms
+               *   https://dx.doi.org/10.1007/11814771_6
+               * Section 3, with β = 2, t = 53, s = 53 - 24 = 29, x = av.
+               * 53 is the number of effective mantissa bits in a Double;
+               * 24 in a Float.
+               *
+               * ◦ is the round-to-nearest operation with a tie-breaking
+               * rule (in our case, break-to-even).
+               *
+               *   Let C = βˢ + 1 = 536870913
+               *   p = ◦(x × C)
+               *   q = ◦(x − p)
+               *   x₁ = ◦(p + q)
+               *
+               * Boldo proves that x₁ is the (t-s)-bit float closest to x,
+               * using the same tie-breaking rule as ◦. Since (t-s) = 24,
+               * this is the closest float32 (with 24 mantissa bits), and
+               * therefore the correct result of `fround`.
+               *
+               * Boldo also proves that if the computation of x × C does not
+               * cause overflow, then none of the following operations will
+               * cause overflow. We know that x (av) is less than the
+               * overflowThreshold, and overflowThreshold × C does not
+               * overflow, so that computation can never cause an overflow.
+               *
+               * If the reader does not have access to Boldo's paper, they
+               * may refer instead to
+               *   Claude-Pierre Jeannerod, Jean-Michel Muller, Paul Zimmermann.
+               *   On various ways to split a floating-point number.
+               *   ARITH 2018 - 25th IEEE Symposium on Computer Arithmetic,
+               *   Jun 2018, Amherst (MA), United States.
+               *   pp.53-60, 10.1109/ARITH.2018.8464793. hal-01774587v2
+               * available at
+               *   https://hal.inria.fr/hal-01774587v2/document
+               * Section III, although that paper defers some theorems and
+               * proofs to Boldo's.
+               */
+              const(p, av * 536870913),
+              Return(sign * (p + (av - p)))
+            ), {
+              /* Here, the result is represented as a subnormal form in a
+               * float32 representation.
+               *
+               * We round `av` to the nearest multiple of the smallest
+               * positive Float value (i.e., `Float.MinPositiveValue`),
+               * breaking ties to an even multiple.
+               *
+               * We do this by leveraging the inherent loss of precision near
+               * the minimum positive *double* value: conceptually, we divide
+               * the value by
+               *   Float.MinPositiveValue / Double.MinPositiveValue
+               * which will drop the excess precision, applying exactly the
+               * rounding strategy that we want. Then we multiply the value
+               * back by the same constant.
+               *
+               * However, `Float.MinPositiveValue / Double.MinPositiveValue`
+               * is not representable as a finite Double. Therefore, we
+               * instead use the *inverse* constant
+               *   Double.MinPositiveValue / Float.MinPositiveValue
+               * and we first multiply by that constant, then divide by it.
+               *
+               * ---
+               *
+               * As an additional "hack", the input values NaN, +0 and -0
+               * also fall in this code path. For them, this computation
+               * happens to be an identity, and is therefore correct as well.
+               */
+              val roundingFactor = double(Double.MinPositiveValue / Float.MinPositiveValue.toDouble)
+              Return(sign * ((av * roundingFactor) / roundingFactor))
+            }))
+          ))
+
+          If(typeof(Float32ArrayRef) !== str("undefined"),
+              typedArrayPolyfill, noTypedArrayPolyfill)
 
         case PrivateSymbolBuiltin =>
           /* function privateJSFieldSymbol(description) {
@@ -693,15 +689,11 @@ private[emitter] object CoreJSLib {
                         })
                       })
                     }, {
-                      if (strictFloats) {
-                        If(genCallHelper(VarField.isFloat, instance), {
-                          Return(constantClassResult(BoxedFloatClass))
-                        }, {
-                          Return(constantClassResult(BoxedDoubleClass))
-                        })
-                      } else {
+                      If(genCallHelper(VarField.isFloat, instance), {
                         Return(constantClassResult(BoxedFloatClass))
-                      }
+                      }, {
+                        Return(constantClassResult(BoxedDoubleClass))
+                      })
                     })
                 )
               },
@@ -1313,12 +1305,10 @@ private[emitter] object CoreJSLib {
               (Apply(genIdentBracketSelect(BigIntRef, "asIntN"), int(64) :: v :: Nil) === v))
         }
       ) :::
-      condDefs(strictFloats)(
-        defineFunction1(VarField.isFloat) { v =>
-          Return((typeof(v) === str("number")) &&
-              ((v !== v) || (genCallPolyfillableBuiltin(FroundBuiltin, v) === v)))
-        }
-      )
+      defineFunction1(VarField.isFloat) { v =>
+        Return((typeof(v) === str("number")) &&
+            ((v !== v) || (genCallPolyfillableBuiltin(FroundBuiltin, v) === v)))
+      }
     }
 
     private def defineBoxFunctions(): List[Tree] = (
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala
index 38f73dfd8a..2ff301a7bf 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala
@@ -437,7 +437,7 @@ private[emitter] final class SJSGen(
       case ShortType   => genCallHelper(VarField.isShort, expr)
       case IntType     => genCallHelper(VarField.isInt, expr)
       case LongType    => genIsLong(expr)
-      case FloatType   => genIsFloat(expr)
+      case FloatType   => genCallHelper(VarField.isFloat, expr)
       case DoubleType  => typeof(expr) === "number"
       case StringType  => typeof(expr) === "string"
 
@@ -478,7 +478,7 @@ private[emitter] final class SJSGen(
       case BoxedShortClass     => genCallHelper(VarField.isShort, expr)
       case BoxedIntegerClass   => genCallHelper(VarField.isInt, expr)
       case BoxedLongClass      => genIsLong(expr)
-      case BoxedFloatClass     => genIsFloat(expr)
+      case BoxedFloatClass     => genCallHelper(VarField.isFloat, expr)
       case BoxedDoubleClass    => typeof(expr) === "number"
       case BoxedStringClass    => typeof(expr) === "string"
     }
@@ -493,15 +493,6 @@ private[emitter] final class SJSGen(
     else expr instanceof globalVar(VarField.c, LongImpl.RuntimeLongClass)
   }
 
-  private def genIsFloat(expr: Tree)(
-      implicit moduleContext: ModuleContext, globalKnowledge: GlobalKnowledge,
-      pos: Position): Tree = {
-    import TreeDSL._
-
-    if (semantics.strictFloats) genCallHelper(VarField.isFloat, expr)
-    else typeof(expr) === "number"
-  }
-
   def genAsInstanceOf(expr: Tree, tpe: Type)(
       implicit moduleContext: ModuleContext, globalKnowledge: GlobalKnowledge,
       tracking: GlobalRefTracking, pos: Position): WithGlobals[Tree] = {
@@ -524,8 +515,7 @@ private[emitter] final class SJSGen(
         case StringType                    => wg(expr || StringLiteral(""))
 
         case FloatType =>
-          if (semantics.strictFloats) genCallPolyfillableBuiltin(FroundBuiltin, expr)
-          else wg(UnaryOp(irt.JSUnaryOp.+, expr))
+          genCallPolyfillableBuiltin(FroundBuiltin, expr)
 
         case VoidType | NullType | NothingType | AnyNotNullType |
             ClassType(_, false) | ArrayType(_, false) | _:RecordType =>
diff --git a/project/BinaryIncompatibilities.scala b/project/BinaryIncompatibilities.scala
index 8ac39f199d..032ec1440e 100644
--- a/project/BinaryIncompatibilities.scala
+++ b/project/BinaryIncompatibilities.scala
@@ -17,6 +17,8 @@ object BinaryIncompatibilities {
   )
 
   val LinkerInterface = Seq(
+    // private, not an issue
+    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.linker.interface.Semantics.this"),
   )
 
   val SbtPlugin = Seq(
diff --git a/project/Build.scala b/project/Build.scala
index 446aeebfab..d08f6224c9 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -2326,7 +2326,6 @@ object Build {
           "compliantNullPointers" -> (sems.nullPointers == CheckedBehavior.Compliant),
           "compliantStringIndexOutOfBounds" -> (sems.stringIndexOutOfBounds == CheckedBehavior.Compliant),
           "compliantModuleInit" -> (sems.moduleInit == CheckedBehavior.Compliant),
-          "strictFloats" -> sems.strictFloats,
           "productionMode" -> sems.productionMode,
           "esVersion" -> linkerConfig.esFeatures.esVersion.edition,
           "useECMAScript2015Semantics" -> linkerConfig.esFeatures.useECMAScript2015Semantics,
diff --git a/test-suite/js/src/main/scala-ide-stubs/org/scalajs/testsuite/utils/BuildInfo.scala b/test-suite/js/src/main/scala-ide-stubs/org/scalajs/testsuite/utils/BuildInfo.scala
index d577790522..8356a0da7c 100644
--- a/test-suite/js/src/main/scala-ide-stubs/org/scalajs/testsuite/utils/BuildInfo.scala
+++ b/test-suite/js/src/main/scala-ide-stubs/org/scalajs/testsuite/utils/BuildInfo.scala
@@ -31,7 +31,6 @@ private[utils] object BuildInfo {
   final val compliantNullPointers = false
   final val compliantStringIndexOutOfBounds = false
   final val compliantModuleInit = false
-  final val strictFloats = false
   final val productionMode = false
   final val esVersion = 0
   final val useECMAScript2015Semantics = false
diff --git a/test-suite/js/src/main/scala/org/scalajs/testsuite/utils/Platform.scala b/test-suite/js/src/main/scala/org/scalajs/testsuite/utils/Platform.scala
index 6251f85b88..65ab362539 100644
--- a/test-suite/js/src/main/scala/org/scalajs/testsuite/utils/Platform.scala
+++ b/test-suite/js/src/main/scala/org/scalajs/testsuite/utils/Platform.scala
@@ -88,40 +88,6 @@ object Platform {
 
   def hasDirectBuffers: Boolean = typedArrays
 
-  /** Do we use strict-floats semantics?
-   *
-   *  If yes, `number` values that cannot be exactly represented as `Float`
-   *  values respond `false` to an `isInstanceOf[Float]` test. If not, they
-   *  respond `true`.
-   *
-   *  In addition, if we use strict-float semantics, all arithmetic operations
-   *  on `Float` are accurate wrt. 32-bit floating point semantics. In other
-   *  words, `hasStrictFloats` implies `hasAccurateFloats`.
-   */
-  def hasStrictFloats: Boolean = BuildInfo.strictFloats
-
-  /** Are `Float` arithmetics accurate?
-   *
-   *  If yes, the result of arithmetic operations on `Float`s, as well as
-   *  `number.toFloat` operations, will be accurate wrt. IEEE-754 32-bit
-   *  floating point operations. In other words, they behave exactly as
-   *  specified on the JVM.
-   *
-   *  This is true if either or both of the following are true:
-   *
-   *  - We use strict-float semantics (see `hasStrictFloats`), or
-   *  - The JavaScript runtime supports `Math.fround`.
-   *
-   *  If neither is true, then the result of `Float` arithmetics can behave as
-   *  if they were `Double` arithmetics instead.
-   *
-   *  When the runtime does not support `Math.fround` but we strict-float
-   *  semantics, Scala.js uses a semantically correct polyfill for it, which
-   *  guarantees accurate float arithmetics.
-   */
-  def hasAccurateFloats: Boolean =
-    hasStrictFloats || js.typeOf(js.Dynamic.global.Math.fround) != "undefined"
-
   def regexSupportsUnicodeCase: Boolean =
     assumedESVersion >= ESVersion.ES2015
 
diff --git a/test-suite/js/src/test/scala/org/scalajs/testsuite/compiler/FloatJSTest.scala b/test-suite/js/src/test/scala/org/scalajs/testsuite/compiler/FloatJSTest.scala
index 612ea03d74..054f2bac59 100644
--- a/test-suite/js/src/test/scala/org/scalajs/testsuite/compiler/FloatJSTest.scala
+++ b/test-suite/js/src/test/scala/org/scalajs/testsuite/compiler/FloatJSTest.scala
@@ -17,8 +17,6 @@ import org.junit.Assert._
 
 import org.scalajs.testsuite.utils.Requires
 
-object FloatJSTest extends Requires.StrictFloats
-
 class FloatJSTest {
 
   @noinline def froundNotInlined(x: Double): Float =
diff --git a/test-suite/js/src/test/scala/org/scalajs/testsuite/utils/Requires.scala b/test-suite/js/src/test/scala/org/scalajs/testsuite/utils/Requires.scala
index c72fed474d..90e539e020 100644
--- a/test-suite/js/src/test/scala/org/scalajs/testsuite/utils/Requires.scala
+++ b/test-suite/js/src/test/scala/org/scalajs/testsuite/utils/Requires.scala
@@ -23,9 +23,4 @@ object Requires {
       assumeTrue("Assumed typed arrays are supported", typedArrays)
   }
 
-  trait StrictFloats {
-    @BeforeClass def needsTypedArrays(): Unit =
-      assumeTrue("Assumed strict floats", hasStrictFloats)
-  }
-
 }
diff --git a/test-suite/jvm/src/main/scala/org/scalajs/testsuite/utils/Platform.scala b/test-suite/jvm/src/main/scala/org/scalajs/testsuite/utils/Platform.scala
index 6b480fd9b6..38e5007356 100644
--- a/test-suite/jvm/src/main/scala/org/scalajs/testsuite/utils/Platform.scala
+++ b/test-suite/jvm/src/main/scala/org/scalajs/testsuite/utils/Platform.scala
@@ -46,8 +46,6 @@ object Platform {
   def hasCompliantStringIndexOutOfBounds: Boolean = true
   def hasCompliantModule: Boolean = true
   def hasDirectBuffers: Boolean = true
-  def hasStrictFloats: Boolean = true
-  def hasAccurateFloats: Boolean = true
 
   def regexSupportsUnicodeCase: Boolean = true
   def regexSupportsUnicodeCharacterClasses: Boolean = true
diff --git a/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/DoubleTest.scala b/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/DoubleTest.scala
index 6f158aa23e..f7b7d2005d 100644
--- a/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/DoubleTest.scala
+++ b/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/DoubleTest.scala
@@ -16,8 +16,6 @@ import org.junit.Test
 import org.junit.Assert._
 import org.junit.Assume._
 
-import org.scalajs.testsuite.utils.Platform.hasAccurateFloats
-
 class DoubleTest {
   final def assertExactEquals(expected: Double, actual: Double): Unit =
     assertTrue(s"expected: $expected; actual: $actual", expected.equals(actual))
@@ -62,8 +60,6 @@ class DoubleTest {
   def toFloat(): Unit = {
     // This is the closest we get to directly testing our `Math.fround` polyfill
 
-    assumeTrue("requires accurate floats", hasAccurateFloats)
-
     @noinline
     def test(expected: Float, value: Double): Unit =
       assertExactEquals(s"for value $value", expected, value.toFloat)
diff --git a/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/FloatTest.scala b/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/FloatTest.scala
index d4dbdee940..60a4e40060 100644
--- a/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/FloatTest.scala
+++ b/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/FloatTest.scala
@@ -15,8 +15,6 @@ package org.scalajs.testsuite.compiler
 import org.junit.Test
 import org.junit.Assert._
 
-import org.scalajs.testsuite.utils.Platform.hasStrictFloats
-
 class FloatTest {
   final def assertExactEquals(expected: Float, actual: Float): Unit =
     assertTrue(s"expected: $expected; actual: $actual", expected.equals(actual))
@@ -144,17 +142,15 @@ class FloatTest {
 
     // Non-special values
     // { val l = List(2.1f, 5.5f, -151.189f); for (n <- l; d <- l) println(s"      test(${n % d}f, ${n}f, ${d}f)") }
-    if (hasStrictFloats) {
-      test(0.0f, 2.1f, 2.1f)
-      test(2.1f, 2.1f, 5.5f)
-      test(2.1f, 2.1f, -151.189f)
-      test(1.3000002f, 5.5f, 2.1f)
-      test(0.0f, 5.5f, 5.5f)
-      test(5.5f, 5.5f, -151.189f)
-      test(-2.0890021f, -151.189f, 2.1f)
-      test(-2.6889954f, -151.189f, 5.5f)
-      test(-0.0f, -151.189f, -151.189f)
-    }
+    test(0.0f, 2.1f, 2.1f)
+    test(2.1f, 2.1f, 5.5f)
+    test(2.1f, 2.1f, -151.189f)
+    test(1.3000002f, 5.5f, 2.1f)
+    test(0.0f, 5.5f, 5.5f)
+    test(5.5f, 5.5f, -151.189f)
+    test(-2.0890021f, -151.189f, 2.1f)
+    test(-2.6889954f, -151.189f, 5.5f)
+    test(-0.0f, -151.189f, -151.189f)
   }
 
   @Test
@@ -244,10 +240,8 @@ class FloatTest {
     @inline
     def negate(x: Float): Float = -x
 
-    if (hasStrictFloats) {
-      assertExactEquals(0.8f, (hide(0.1f) + 0.3f) + 0.4f)
-      assertExactEquals(0.8000001f, 0.1f + (0.3f + hide(0.4f)))
-    }
+    assertExactEquals(0.8f, (hide(0.1f) + 0.3f) + 0.4f)
+    assertExactEquals(0.8000001f, 0.1f + (0.3f + hide(0.4f)))
 
     assertExactEquals(0.0f, 0.0f + hide(-0.0f))
     assertExactEquals(0.0f, 0.0f - hide(0.0f))
diff --git a/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/LongTest.scala b/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/LongTest.scala
index dd9ed7a5a6..108dc817de 100644
--- a/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/LongTest.scala
+++ b/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/LongTest.scala
@@ -609,8 +609,6 @@ class LongTest {
   }
 
   @Test def toFloat(): Unit = {
-    assumeTrue("Assumed accurate floats", hasAccurateFloats)
-
     @inline def test(expected: Float, x: Long, epsilon: Float = 0.0f): Unit = {
       assertEquals(expected, x.toFloat, epsilon)
       assertEquals(expected, hideFromOptimizer(x).toFloat, epsilon)
diff --git a/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/RuntimeTypeTestsTest.scala b/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/RuntimeTypeTestsTest.scala
index 5916c9a301..1b73998241 100644
--- a/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/RuntimeTypeTestsTest.scala
+++ b/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/RuntimeTypeTestsTest.scala
@@ -198,7 +198,7 @@ class RuntimeTypeTestsTest {
     testFloat(false, 'e')
     testDouble(false, 'f')
 
-    testFloat(!hasStrictFloats, 1.2)
+    testFloat(false, 1.2)
 
     // Special cases for negative 0, NaN and Infinity
 
diff --git a/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/lang/ClassTest.scala b/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/lang/ClassTest.scala
index a447e5c48b..4994137cf8 100644
--- a/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/lang/ClassTest.scala
+++ b/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/lang/ClassTest.scala
@@ -108,7 +108,7 @@ class ClassTest {
     test("java.lang.Float", -0.0f)
     test("java.lang.Float", 1.5f)
     test("java.lang.Float", Float.NaN)
-    test(if (hasStrictFloats) "java.lang.Double" else "java.lang.Float", 1.4)
+    test("java.lang.Double", 1.4)
     test("java.lang.String", "hello")
     test("java.lang.Object", new Object)
     test("scala.Some", Some(5))
diff --git a/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/lang/FloatTest.scala b/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/lang/FloatTest.scala
index e16c2703d2..37bcc4838a 100644
--- a/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/lang/FloatTest.scala
+++ b/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/lang/FloatTest.scala
@@ -21,7 +21,7 @@ import java.lang.{Float => JFloat}
 import scala.util.Try
 
 import org.scalajs.testsuite.utils.AssertThrows.assertThrows
-import org.scalajs.testsuite.utils.Platform.{executingInJVM, hasAccurateFloats}
+import org.scalajs.testsuite.utils.Platform.executingInJVM
 
 class FloatTest {
 
@@ -109,16 +109,9 @@ class FloatTest {
 
   @Test def parseStringMethods(): Unit = {
     def test(expected: Float, s: String): Unit = {
-      if (hasAccurateFloats) {
-        assertEquals(s, expected: Any, JFloat.parseFloat(s))
-        assertEquals(s, expected: Any, JFloat.valueOf(s).floatValue())
-        assertEquals(s, expected: Any, new JFloat(s).floatValue())
-      } else {
-        val epsilon = Math.ulp(expected)
-        assertEquals(s, expected, JFloat.parseFloat(s), epsilon)
-        assertEquals(s, expected, JFloat.valueOf(s).floatValue(), epsilon)
-        assertEquals(s, expected, new JFloat(s).floatValue(), epsilon)
-      }
+      assertEquals(s, expected: Any, JFloat.parseFloat(s))
+      assertEquals(s, expected: Any, JFloat.valueOf(s).floatValue())
+      assertEquals(s, expected: Any, new JFloat(s).floatValue())
     }
 
     // Specials
diff --git a/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/lang/ObjectTest.scala b/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/lang/ObjectTest.scala
index 2868849763..cd86d36945 100644
--- a/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/lang/ObjectTest.scala
+++ b/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/lang/ObjectTest.scala
@@ -43,7 +43,7 @@ class ObjectTest {
     test(classOf[java.lang.Float], -0.0f)
     test(classOf[java.lang.Float], 1.5f)
     test(classOf[java.lang.Float], Float.NaN)
-    test(if (hasStrictFloats) classOf[java.lang.Double] else classOf[java.lang.Float], 1.4)
+    test(classOf[java.lang.Double], 1.4)
     test(classOf[java.lang.String], "hello")
     test(classOf[java.lang.Object], new Object)
     test(classOf[Some[_]], Some(5))
diff --git a/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/math/BigDecimalConvertTest.scala b/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/math/BigDecimalConvertTest.scala
index 57533ab042..89c611735c 100644
--- a/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/math/BigDecimalConvertTest.scala
+++ b/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/math/BigDecimalConvertTest.scala
@@ -73,8 +73,6 @@ class BigDecimalConvertTest {
   }
 
   @Test def testFloatValueNegInfinity(): Unit = {
-    assumeTrue("requires accurate floats", hasAccurateFloats)
-
     val a = "-123809648392384755735.63567887678287E+200"
     val aNumber = new BigDecimal(a)
     val result =  Float.NegativeInfinity
@@ -89,8 +87,6 @@ class BigDecimalConvertTest {
   }
 
   @Test def testFloatValuePosInfinity(): Unit = {
-    assumeTrue("requires accurate floats", hasAccurateFloats)
-
     val a = "123809648373567356745735.6356789787678287E+200"
     val aNumber = new BigDecimal(a)
     val result =  Float.PositiveInfinity
@@ -99,14 +95,8 @@ class BigDecimalConvertTest {
 
   /** Test cases for `Float.parseFloat`, with an indirection through `BigDecimal`. */
   @Test def testFloatValueLikeParseFloat_Issue4726(): Unit = {
-    def test(expected: Float, s: String): Unit = {
-      if (hasAccurateFloats) {
-        assertEquals(s, expected: Any, new BigDecimal(s).floatValue())
-      } else {
-        val epsilon = Math.ulp(expected)
-        assertEquals(s, expected, new BigDecimal(s).floatValue(), epsilon)
-      }
-    }
+    def test(expected: Float, s: String): Unit =
+      assertEquals(s, expected: Any, new BigDecimal(s).floatValue())
 
     // Zeros (BigDecimal has no negative 0, so they all parse to +0.0f)
 
diff --git a/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/math/BigIntegerConvertTest.scala b/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/math/BigIntegerConvertTest.scala
index c383d455f4..cc2e5cd3e6 100644
--- a/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/math/BigIntegerConvertTest.scala
+++ b/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/math/BigIntegerConvertTest.scala
@@ -255,8 +255,6 @@ class BigIntegerConvertTest {
   }
 
   @Test def testFloatValueNegativeInfinity2(): Unit = {
-    assumeTrue("requires accurate floats", hasAccurateFloats)
-
     val a = Array[Byte](0, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1)
     val aSign = -1
     val aNumber = new BigInteger(aSign, a).floatValue()
@@ -264,8 +262,6 @@ class BigIntegerConvertTest {
   }
 
   @Test def testFloatValueNegMantissaIsZero(): Unit = {
-    assumeTrue("requires accurate floats", hasAccurateFloats)
-
     val a = Array[Byte](1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0)
     val aSign = -1
     val aNumber = new BigInteger(aSign, a).floatValue()
@@ -300,8 +296,6 @@ class BigIntegerConvertTest {
   }
 
   @Test def testFloatValuePastNegMaxValue(): Unit = {
-    assumeTrue("requires accurate floats", hasAccurateFloats)
-
     val a = Array[Byte](0, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1)
     val aSign = -1
     val aNumber = new BigInteger(aSign, a).floatValue()
@@ -309,8 +303,6 @@ class BigIntegerConvertTest {
   }
 
   @Test def testFloatValuePastPosMaxValue(): Unit = {
-    assumeTrue("requires accurate floats", hasAccurateFloats)
-
     val a = Array[Byte](0, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1)
     val aSign = 1
     val aNumber = new BigInteger(aSign, a).floatValue()
@@ -333,8 +325,6 @@ class BigIntegerConvertTest {
   }
 
   @Test def testFloatValuePositiveInfinity1(): Unit = {
-    assumeTrue("requires accurate floats", hasAccurateFloats)
-
     val a = Array[Byte](0, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1)
     val aSign = 1
     val aNumber: Float = new BigInteger(aSign, a).floatValue()
@@ -648,8 +638,6 @@ class BigIntegerConvertTest {
   }
 
   @Test def testFloatValueBug2482(): Unit = {
-    assumeTrue("Assumed strict floats", hasStrictFloats)
-
     val a = "2147483649"
     val result = 2.14748365E9f
     val aNumber = new BigInteger(a).floatValue()

From dbce9db8527d81b9324f1daae1d347f945438a5e Mon Sep 17 00:00:00 2001
From: Leonid Dubinsky <dub@podval.org>
Date: Thu, 20 Feb 2025 15:01:06 -0500
Subject: [PATCH 259/298] JUnit: populate sbt.testing.Event.throwable on test
 failure

If a Throwable associated with the test event is available, bubble it up through the SBT's test interface using the slot dedicated to just such information: `sbt.testing.Event.throwable`.

In addition to it being a shame to throw away information about the test failure that is literally in our hands, this simplifies integration with runners that assume that test failure is always accompanied by a `Throwable` (e.g., Gradle).
---
 .../scala/org/scalajs/junit/Reporter.scala    | 12 ++++---
 .../junit/AssertEquals2TestAssertions_.txt    |  2 +-
 .../junit/AssertEquals2TestAssertions_a.txt   |  2 +-
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 .../junit/AssertEquals2TestAssertions_nv.txt  |  2 +-
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 .../AssertEqualsDoubleTestAssertions_.txt     | 12 +++----
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 .../ExceptionInAfterTestAssertions_a.txt      |  2 +-
 .../ExceptionInAfterTestAssertions_n.txt      |  2 +-
 .../ExceptionInAfterTestAssertions_na.txt     |  2 +-
 .../ExceptionInAfterTestAssertions_nv.txt     |  2 +-
 .../ExceptionInAfterTestAssertions_nva.txt    |  2 +-
 .../ExceptionInAfterTestAssertions_nvc.txt    |  2 +-
 .../ExceptionInAfterTestAssertions_nvca.txt   |  2 +-
 .../ExceptionInAfterTestAssertions_v.txt      |  2 +-
 .../ExceptionInAfterTestAssertions_va.txt     |  2 +-
 .../ExceptionInAfterTestAssertions_vc.txt     |  2 +-
 .../ExceptionInAfterTestAssertions_vs.txt     |  2 +-
 .../ExceptionInAfterTestAssertions_vsn.txt    |  2 +-
 .../ExceptionInBeforeTestAssertions_.txt      |  2 +-
 .../ExceptionInBeforeTestAssertions_a.txt     |  2 +-
 .../ExceptionInBeforeTestAssertions_n.txt     |  2 +-
 .../ExceptionInBeforeTestAssertions_na.txt    |  2 +-
 .../ExceptionInBeforeTestAssertions_nv.txt    |  2 +-
 .../ExceptionInBeforeTestAssertions_nva.txt   |  2 +-
 .../ExceptionInBeforeTestAssertions_nvc.txt   |  2 +-
 .../ExceptionInBeforeTestAssertions_nvca.txt  |  2 +-
 .../ExceptionInBeforeTestAssertions_v.txt     |  2 +-
 .../ExceptionInBeforeTestAssertions_va.txt    |  2 +-
 .../ExceptionInBeforeTestAssertions_vc.txt    |  2 +-
 .../ExceptionInBeforeTestAssertions_vs.txt    |  2 +-
 .../ExceptionInBeforeTestAssertions_vsn.txt   |  2 +-
 .../ExceptionInConstructorTestAssertions_.txt |  2 +-
 ...ExceptionInConstructorTestAssertions_a.txt |  2 +-
 ...ExceptionInConstructorTestAssertions_n.txt |  2 +-
 ...xceptionInConstructorTestAssertions_na.txt |  2 +-
 ...xceptionInConstructorTestAssertions_nv.txt |  2 +-
 ...ceptionInConstructorTestAssertions_nva.txt |  2 +-
 ...ceptionInConstructorTestAssertions_nvc.txt |  2 +-
 ...eptionInConstructorTestAssertions_nvca.txt |  2 +-
 ...ExceptionInConstructorTestAssertions_v.txt |  2 +-
 ...xceptionInConstructorTestAssertions_va.txt |  2 +-
 ...xceptionInConstructorTestAssertions_vc.txt |  2 +-
 ...xceptionInConstructorTestAssertions_vs.txt |  2 +-
 ...ceptionInConstructorTestAssertions_vsn.txt |  2 +-
 .../junit/ExceptionTestAssertions_.txt        |  2 +-
 .../junit/ExceptionTestAssertions_a.txt       |  2 +-
 .../junit/ExceptionTestAssertions_n.txt       |  2 +-
 .../junit/ExceptionTestAssertions_na.txt      |  2 +-
 .../junit/ExceptionTestAssertions_nv.txt      |  2 +-
 .../junit/ExceptionTestAssertions_nva.txt     |  2 +-
 .../junit/ExceptionTestAssertions_nvc.txt     |  2 +-
 .../junit/ExceptionTestAssertions_nvca.txt    |  2 +-
 .../junit/ExceptionTestAssertions_v.txt       |  2 +-
 .../junit/ExceptionTestAssertions_va.txt      |  2 +-
 .../junit/ExceptionTestAssertions_vc.txt      |  2 +-
 .../junit/ExceptionTestAssertions_vs.txt      |  2 +-
 .../junit/ExceptionTestAssertions_vsn.txt     |  2 +-
 .../scalajs/junit/ExpectTestAssertions_.txt   | 10 +++---
 .../scalajs/junit/ExpectTestAssertions_a.txt  | 10 +++---
 .../scalajs/junit/ExpectTestAssertions_n.txt  | 10 +++---
 .../scalajs/junit/ExpectTestAssertions_na.txt | 10 +++---
 .../scalajs/junit/ExpectTestAssertions_nv.txt | 10 +++---
 .../junit/ExpectTestAssertions_nva.txt        | 10 +++---
 .../junit/ExpectTestAssertions_nvc.txt        | 10 +++---
 .../junit/ExpectTestAssertions_nvca.txt       | 10 +++---
 .../scalajs/junit/ExpectTestAssertions_v.txt  | 10 +++---
 .../scalajs/junit/ExpectTestAssertions_va.txt | 10 +++---
 .../scalajs/junit/ExpectTestAssertions_vc.txt | 10 +++---
 .../scalajs/junit/ExpectTestAssertions_vs.txt | 10 +++---
 .../junit/ExpectTestAssertions_vsn.txt        | 10 +++---
 .../scalajs/junit/IgnoreTestAssertions_.txt   |  2 +-
 .../scalajs/junit/IgnoreTestAssertions_a.txt  |  2 +-
 .../scalajs/junit/IgnoreTestAssertions_n.txt  |  2 +-
 .../scalajs/junit/IgnoreTestAssertions_na.txt |  2 +-
 .../scalajs/junit/IgnoreTestAssertions_nv.txt |  2 +-
 .../junit/IgnoreTestAssertions_nva.txt        |  2 +-
 .../junit/IgnoreTestAssertions_nvc.txt        |  2 +-
 .../junit/IgnoreTestAssertions_nvca.txt       |  2 +-
 .../scalajs/junit/IgnoreTestAssertions_v.txt  |  2 +-
 .../scalajs/junit/IgnoreTestAssertions_va.txt |  2 +-
 .../scalajs/junit/IgnoreTestAssertions_vc.txt |  2 +-
 .../scalajs/junit/IgnoreTestAssertions_vs.txt |  2 +-
 .../junit/IgnoreTestAssertions_vsn.txt        |  2 +-
 .../junit/MethodNameDecodeTestAssertions_.txt |  2 +-
 .../MethodNameDecodeTestAssertions_a.txt      |  2 +-
 .../MethodNameDecodeTestAssertions_n.txt      |  2 +-
 .../MethodNameDecodeTestAssertions_na.txt     |  2 +-
 .../MethodNameDecodeTestAssertions_nv.txt     |  2 +-
 .../MethodNameDecodeTestAssertions_nva.txt    |  2 +-
 .../MethodNameDecodeTestAssertions_nvc.txt    |  2 +-
 .../MethodNameDecodeTestAssertions_nvca.txt   |  2 +-
 .../MethodNameDecodeTestAssertions_v.txt      |  2 +-
 .../MethodNameDecodeTestAssertions_va.txt     |  2 +-
 .../MethodNameDecodeTestAssertions_vc.txt     |  2 +-
 .../MethodNameDecodeTestAssertions_vs.txt     |  2 +-
 .../MethodNameDecodeTestAssertions_vsn.txt    |  2 +-
 .../scalajs/junit/Multi1TestAssertions_.txt   |  4 +--
 .../scalajs/junit/Multi1TestAssertions_a.txt  |  4 +--
 .../scalajs/junit/Multi1TestAssertions_n.txt  |  4 +--
 .../scalajs/junit/Multi1TestAssertions_na.txt |  4 +--
 .../scalajs/junit/Multi1TestAssertions_nv.txt |  4 +--
 .../junit/Multi1TestAssertions_nva.txt        |  4 +--
 .../junit/Multi1TestAssertions_nvc.txt        |  4 +--
 .../junit/Multi1TestAssertions_nvca.txt       |  4 +--
 .../scalajs/junit/Multi1TestAssertions_v.txt  |  4 +--
 .../scalajs/junit/Multi1TestAssertions_va.txt |  4 +--
 .../scalajs/junit/Multi1TestAssertions_vc.txt |  4 +--
 .../scalajs/junit/Multi1TestAssertions_vs.txt |  4 +--
 .../junit/Multi1TestAssertions_vsn.txt        |  4 +--
 .../scalajs/junit/Multi2TestAssertions_.txt   | 10 +++---
 .../scalajs/junit/Multi2TestAssertions_a.txt  | 10 +++---
 .../scalajs/junit/Multi2TestAssertions_n.txt  | 10 +++---
 .../scalajs/junit/Multi2TestAssertions_na.txt | 10 +++---
 .../scalajs/junit/Multi2TestAssertions_nv.txt | 10 +++---
 .../junit/Multi2TestAssertions_nva.txt        | 10 +++---
 .../junit/Multi2TestAssertions_nvc.txt        | 10 +++---
 .../junit/Multi2TestAssertions_nvca.txt       | 10 +++---
 .../scalajs/junit/Multi2TestAssertions_v.txt  | 10 +++---
 .../scalajs/junit/Multi2TestAssertions_va.txt | 10 +++---
 .../scalajs/junit/Multi2TestAssertions_vc.txt | 10 +++---
 .../scalajs/junit/Multi2TestAssertions_vs.txt | 10 +++---
 .../junit/Multi2TestAssertions_vsn.txt        | 10 +++---
 .../junit/MultiAssumeFail1TestAssertions_.txt | 10 +++---
 .../MultiAssumeFail1TestAssertions_a.txt      | 10 +++---
 .../MultiAssumeFail1TestAssertions_n.txt      | 10 +++---
 .../MultiAssumeFail1TestAssertions_na.txt     | 10 +++---
 .../MultiAssumeFail1TestAssertions_nv.txt     | 10 +++---
 .../MultiAssumeFail1TestAssertions_nva.txt    | 10 +++---
 .../MultiAssumeFail1TestAssertions_nvc.txt    | 10 +++---
 .../MultiAssumeFail1TestAssertions_nvca.txt   | 10 +++---
 .../MultiAssumeFail1TestAssertions_v.txt      | 10 +++---
 .../MultiAssumeFail1TestAssertions_va.txt     | 10 +++---
 .../MultiAssumeFail1TestAssertions_vc.txt     | 10 +++---
 .../MultiAssumeFail1TestAssertions_vs.txt     | 10 +++---
 .../MultiAssumeFail1TestAssertions_vsn.txt    | 10 +++---
 .../junit/MultiAssumeFail2TestAssertions_.txt | 10 +++---
 .../MultiAssumeFail2TestAssertions_a.txt      | 10 +++---
 .../MultiAssumeFail2TestAssertions_n.txt      | 10 +++---
 .../MultiAssumeFail2TestAssertions_na.txt     | 10 +++---
 .../MultiAssumeFail2TestAssertions_nv.txt     | 10 +++---
 .../MultiAssumeFail2TestAssertions_nva.txt    | 10 +++---
 .../MultiAssumeFail2TestAssertions_nvc.txt    | 10 +++---
 .../MultiAssumeFail2TestAssertions_nvca.txt   | 10 +++---
 .../MultiAssumeFail2TestAssertions_v.txt      | 10 +++---
 .../MultiAssumeFail2TestAssertions_va.txt     | 10 +++---
 .../MultiAssumeFail2TestAssertions_vc.txt     | 10 +++---
 .../MultiAssumeFail2TestAssertions_vs.txt     | 10 +++---
 .../MultiAssumeFail2TestAssertions_vsn.txt    | 10 +++---
 .../MultiBeforeAssumeFailTestAssertions_.txt  |  2 +-
 .../MultiBeforeAssumeFailTestAssertions_a.txt |  2 +-
 .../MultiBeforeAssumeFailTestAssertions_n.txt |  2 +-
 ...MultiBeforeAssumeFailTestAssertions_na.txt |  2 +-
 ...MultiBeforeAssumeFailTestAssertions_nv.txt |  2 +-
 ...ultiBeforeAssumeFailTestAssertions_nva.txt |  2 +-
 ...ultiBeforeAssumeFailTestAssertions_nvc.txt |  2 +-
 ...ltiBeforeAssumeFailTestAssertions_nvca.txt |  2 +-
 .../MultiBeforeAssumeFailTestAssertions_v.txt |  2 +-
 ...MultiBeforeAssumeFailTestAssertions_va.txt |  2 +-
 ...MultiBeforeAssumeFailTestAssertions_vc.txt |  2 +-
 ...MultiBeforeAssumeFailTestAssertions_vs.txt |  2 +-
 ...ultiBeforeAssumeFailTestAssertions_vsn.txt |  2 +-
 .../junit/MultiIgnore1TestAssertions_.txt     | 10 +++---
 .../junit/MultiIgnore1TestAssertions_a.txt    | 10 +++---
 .../junit/MultiIgnore1TestAssertions_n.txt    | 10 +++---
 .../junit/MultiIgnore1TestAssertions_na.txt   | 10 +++---
 .../junit/MultiIgnore1TestAssertions_nv.txt   | 10 +++---
 .../junit/MultiIgnore1TestAssertions_nva.txt  | 10 +++---
 .../junit/MultiIgnore1TestAssertions_nvc.txt  | 10 +++---
 .../junit/MultiIgnore1TestAssertions_nvca.txt | 10 +++---
 .../junit/MultiIgnore1TestAssertions_v.txt    | 10 +++---
 .../junit/MultiIgnore1TestAssertions_va.txt   | 10 +++---
 .../junit/MultiIgnore1TestAssertions_vc.txt   | 10 +++---
 .../junit/MultiIgnore1TestAssertions_vs.txt   | 10 +++---
 .../junit/MultiIgnore1TestAssertions_vsn.txt  | 10 +++---
 .../junit/MultiIgnore2TestAssertions_.txt     | 10 +++---
 .../junit/MultiIgnore2TestAssertions_a.txt    | 10 +++---
 .../junit/MultiIgnore2TestAssertions_n.txt    | 10 +++---
 .../junit/MultiIgnore2TestAssertions_na.txt   | 10 +++---
 .../junit/MultiIgnore2TestAssertions_nv.txt   | 10 +++---
 .../junit/MultiIgnore2TestAssertions_nva.txt  | 10 +++---
 .../junit/MultiIgnore2TestAssertions_nvc.txt  | 10 +++---
 .../junit/MultiIgnore2TestAssertions_nvca.txt | 10 +++---
 .../junit/MultiIgnore2TestAssertions_v.txt    | 10 +++---
 .../junit/MultiIgnore2TestAssertions_va.txt   | 10 +++---
 .../junit/MultiIgnore2TestAssertions_vc.txt   | 10 +++---
 .../junit/MultiIgnore2TestAssertions_vs.txt   | 10 +++---
 .../junit/MultiIgnore2TestAssertions_vsn.txt  | 10 +++---
 .../junit/MultiIgnoreAllTestAssertions_.txt   | 10 +++---
 .../junit/MultiIgnoreAllTestAssertions_a.txt  | 10 +++---
 .../junit/MultiIgnoreAllTestAssertions_n.txt  | 10 +++---
 .../junit/MultiIgnoreAllTestAssertions_na.txt | 10 +++---
 .../junit/MultiIgnoreAllTestAssertions_nv.txt | 10 +++---
 .../MultiIgnoreAllTestAssertions_nva.txt      | 10 +++---
 .../MultiIgnoreAllTestAssertions_nvc.txt      | 10 +++---
 .../MultiIgnoreAllTestAssertions_nvca.txt     | 10 +++---
 .../junit/MultiIgnoreAllTestAssertions_v.txt  | 10 +++---
 .../junit/MultiIgnoreAllTestAssertions_va.txt | 10 +++---
 .../junit/MultiIgnoreAllTestAssertions_vc.txt | 10 +++---
 .../junit/MultiIgnoreAllTestAssertions_vs.txt | 10 +++---
 .../MultiIgnoreAllTestAssertions_vsn.txt      | 10 +++---
 .../org/scalajs/junit/utils/JUnitTest.scala   | 31 ++++++++++++++-----
 457 files changed, 1006 insertions(+), 987 deletions(-)

diff --git a/junit-runtime/src/main/scala/org/scalajs/junit/Reporter.scala b/junit-runtime/src/main/scala/org/scalajs/junit/Reporter.scala
index 4673a4cf9e..4cdbfbeb9f 100644
--- a/junit-runtime/src/main/scala/org/scalajs/junit/Reporter.scala
+++ b/junit-runtime/src/main/scala/org/scalajs/junit/Reporter.scala
@@ -59,7 +59,7 @@ private[junit] final class Reporter(eventHandler: EventHandler,
 
     if (errors.nonEmpty) {
       emit(errors.head)
-      emitEvent(method, Status.Failure)
+      emitEvent(method, Status.Failure, new OptionalThrowable(errors.head))
       errors.tail.foreach(emit)
     }
   }
@@ -67,7 +67,7 @@ private[junit] final class Reporter(eventHandler: EventHandler,
   def reportAssumptionViolation(method: Option[String], timeInSeconds: Double, e: Throwable): Unit = {
     logTestException(_.warn, "Test assumption in test ", method, e,
         timeInSeconds)
-    emitEvent(method, Status.Skipped)
+    emitEvent(method, Status.Skipped, new OptionalThrowable(e))
   }
 
   private def logTestInfo(level: Reporter.Level, method: Option[String], msg: String): Unit =
@@ -114,11 +114,15 @@ private[junit] final class Reporter(eventHandler: EventHandler,
     prefix + Ansi.c(name, color)
   }
 
-  private def emitEvent(method: Option[String], status: Status): Unit = {
+  private def emitEvent(
+    method: Option[String],
+    status: Status,
+    throwable: OptionalThrowable = new OptionalThrowable
+  ): Unit = {
     val testName = method.fold(taskDef.fullyQualifiedName())(method =>
         taskDef.fullyQualifiedName() + "." + settings.decodeName(method))
     val selector = new TestSelector(testName)
-    eventHandler.handle(new JUnitEvent(taskDef, status, selector))
+    eventHandler.handle(new JUnitEvent(taskDef, status, selector, throwable))
   }
 
   def log(level: Reporter.Level, s: String): Unit = {
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_.txt b/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_.txt
index 2a161db9ae..2072559893 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.AssertEquals2Test.test started
 leTest org.scalajs.junit.AssertEquals2Test.test failed: This is the message expected:<false> but was:<true>, took <TIME>
-e2org.scalajs.junit.AssertEquals2Test.test
+e2org.scalajs.junit.AssertEquals2Test.test::java.lang.AssertionError: This is the message expected:<false> but was:<true>
 ldTest org.scalajs.junit.AssertEquals2Test.test finished, took <TIME>
 ldTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_a.txt b/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_a.txt
index 83e124a286..f2e6a0564d 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_a.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_a.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.AssertEquals2Test.test started
 leTest org.scalajs.junit.AssertEquals2Test.test failed: java.lang.AssertionError: This is the message expected:<false> but was:<true>, took <TIME>
-e2org.scalajs.junit.AssertEquals2Test.test
+e2org.scalajs.junit.AssertEquals2Test.test::java.lang.AssertionError: This is the message expected:<false> but was:<true>
 ldTest org.scalajs.junit.AssertEquals2Test.test finished, took <TIME>
 ldTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_n.txt b/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_n.txt
index f8ebbb3159..7ac05cdcbe 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_n.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_n.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.AssertEquals2Test.test started
 leTest org.scalajs.junit.AssertEquals2Test.test failed: This is the message expected:<false> but was:<true>, took <TIME>
-e2org.scalajs.junit.AssertEquals2Test.test
+e2org.scalajs.junit.AssertEquals2Test.test::java.lang.AssertionError: This is the message expected:<false> but was:<true>
 ldTest org.scalajs.junit.AssertEquals2Test.test finished, took <TIME>
 ldTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_na.txt b/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_na.txt
index f41b098d34..5c4ebe5b37 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_na.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_na.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.AssertEquals2Test.test started
 leTest org.scalajs.junit.AssertEquals2Test.test failed: java.lang.AssertionError: This is the message expected:<false> but was:<true>, took <TIME>
-e2org.scalajs.junit.AssertEquals2Test.test
+e2org.scalajs.junit.AssertEquals2Test.test::java.lang.AssertionError: This is the message expected:<false> but was:<true>
 ldTest org.scalajs.junit.AssertEquals2Test.test finished, took <TIME>
 ldTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_nv.txt b/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_nv.txt
index 461bcb4fc1..479365ca78 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_nv.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_nv.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertEquals2Test.test started
 leTest org.scalajs.junit.AssertEquals2Test.test failed: This is the message expected:<false> but was:<true>, took <TIME>
-e2org.scalajs.junit.AssertEquals2Test.test
+e2org.scalajs.junit.AssertEquals2Test.test::java.lang.AssertionError: This is the message expected:<false> but was:<true>
 ldTest org.scalajs.junit.AssertEquals2Test.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_nva.txt b/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_nva.txt
index 44a8d5c7da..180503930f 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_nva.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_nva.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertEquals2Test.test started
 leTest org.scalajs.junit.AssertEquals2Test.test failed: java.lang.AssertionError: This is the message expected:<false> but was:<true>, took <TIME>
-e2org.scalajs.junit.AssertEquals2Test.test
+e2org.scalajs.junit.AssertEquals2Test.test::java.lang.AssertionError: This is the message expected:<false> but was:<true>
 ldTest org.scalajs.junit.AssertEquals2Test.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_nvc.txt b/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_nvc.txt
index 461bcb4fc1..479365ca78 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_nvc.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_nvc.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertEquals2Test.test started
 leTest org.scalajs.junit.AssertEquals2Test.test failed: This is the message expected:<false> but was:<true>, took <TIME>
-e2org.scalajs.junit.AssertEquals2Test.test
+e2org.scalajs.junit.AssertEquals2Test.test::java.lang.AssertionError: This is the message expected:<false> but was:<true>
 ldTest org.scalajs.junit.AssertEquals2Test.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_nvca.txt b/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_nvca.txt
index 461bcb4fc1..479365ca78 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_nvca.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_nvca.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertEquals2Test.test started
 leTest org.scalajs.junit.AssertEquals2Test.test failed: This is the message expected:<false> but was:<true>, took <TIME>
-e2org.scalajs.junit.AssertEquals2Test.test
+e2org.scalajs.junit.AssertEquals2Test.test::java.lang.AssertionError: This is the message expected:<false> but was:<true>
 ldTest org.scalajs.junit.AssertEquals2Test.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_v.txt b/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_v.txt
index 510e5a8220..a1063772e6 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_v.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_v.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertEquals2Test.test started
 leTest org.scalajs.junit.AssertEquals2Test.test failed: This is the message expected:<false> but was:<true>, took <TIME>
-e2org.scalajs.junit.AssertEquals2Test.test
+e2org.scalajs.junit.AssertEquals2Test.test::java.lang.AssertionError: This is the message expected:<false> but was:<true>
 ldTest org.scalajs.junit.AssertEquals2Test.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_va.txt b/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_va.txt
index 0f5d1a0be3..80f4b8d43c 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_va.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_va.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertEquals2Test.test started
 leTest org.scalajs.junit.AssertEquals2Test.test failed: java.lang.AssertionError: This is the message expected:<false> but was:<true>, took <TIME>
-e2org.scalajs.junit.AssertEquals2Test.test
+e2org.scalajs.junit.AssertEquals2Test.test::java.lang.AssertionError: This is the message expected:<false> but was:<true>
 ldTest org.scalajs.junit.AssertEquals2Test.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_vc.txt b/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_vc.txt
index 510e5a8220..a1063772e6 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_vc.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_vc.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertEquals2Test.test started
 leTest org.scalajs.junit.AssertEquals2Test.test failed: This is the message expected:<false> but was:<true>, took <TIME>
-e2org.scalajs.junit.AssertEquals2Test.test
+e2org.scalajs.junit.AssertEquals2Test.test::java.lang.AssertionError: This is the message expected:<false> but was:<true>
 ldTest org.scalajs.junit.AssertEquals2Test.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_vs.txt b/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_vs.txt
index 510e5a8220..a1063772e6 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_vs.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_vs.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertEquals2Test.test started
 leTest org.scalajs.junit.AssertEquals2Test.test failed: This is the message expected:<false> but was:<true>, took <TIME>
-e2org.scalajs.junit.AssertEquals2Test.test
+e2org.scalajs.junit.AssertEquals2Test.test::java.lang.AssertionError: This is the message expected:<false> but was:<true>
 ldTest org.scalajs.junit.AssertEquals2Test.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_vsn.txt b/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_vsn.txt
index 461bcb4fc1..479365ca78 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_vsn.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_vsn.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertEquals2Test.test started
 leTest org.scalajs.junit.AssertEquals2Test.test failed: This is the message expected:<false> but was:<true>, took <TIME>
-e2org.scalajs.junit.AssertEquals2Test.test
+e2org.scalajs.junit.AssertEquals2Test.test::java.lang.AssertionError: This is the message expected:<false> but was:<true>
 ldTest org.scalajs.junit.AssertEquals2Test.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_.txt b/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_.txt
index 7b19acc576..71e6ad67fa 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_.txt
@@ -1,23 +1,23 @@
 ldTest run started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble started
 leTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble failed: Use assertEquals(expected, actual, delta) to compare floating-point numbers, took <TIME>
-e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble
+e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble finished, took <TIME>
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage started
 leTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage failed: Use assertEquals(expected, actual, delta) to compare floating-point numbers, took <TIME>
-e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage
+e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage finished, took <TIME>
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte::
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon::
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt::
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort::
 ldTest run finished: 2 failed, 0 ignored, 6 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_a.txt b/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_a.txt
index a044c7e414..b182d3ca38 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_a.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_a.txt
@@ -1,23 +1,23 @@
 ldTest run started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble started
 leTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble failed: java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers, took <TIME>
-e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble
+e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble finished, took <TIME>
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage started
 leTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage failed: java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers, took <TIME>
-e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage
+e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage finished, took <TIME>
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte::
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon::
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt::
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort::
 ldTest run finished: 2 failed, 0 ignored, 6 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_n.txt b/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_n.txt
index 0f80a01d43..13c5d835e9 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_n.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_n.txt
@@ -1,23 +1,23 @@
 ldTest run started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble started
 leTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble failed: Use assertEquals(expected, actual, delta) to compare floating-point numbers, took <TIME>
-e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble
+e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble finished, took <TIME>
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage started
 leTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage failed: Use assertEquals(expected, actual, delta) to compare floating-point numbers, took <TIME>
-e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage
+e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage finished, took <TIME>
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte::
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon::
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt::
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort::
 ldTest run finished: 2 failed, 0 ignored, 6 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_na.txt b/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_na.txt
index 5be56a1b56..c9a35784af 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_na.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_na.txt
@@ -1,23 +1,23 @@
 ldTest run started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble started
 leTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble failed: java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers, took <TIME>
-e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble
+e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble finished, took <TIME>
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage started
 leTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage failed: java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers, took <TIME>
-e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage
+e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage finished, took <TIME>
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte::
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon::
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt::
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort::
 ldTest run finished: 2 failed, 0 ignored, 6 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_nv.txt b/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_nv.txt
index c4ef1ca43e..8bd6462aac 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_nv.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_nv.txt
@@ -1,23 +1,23 @@
 liTest run started
 liTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble started
 leTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble failed: Use assertEquals(expected, actual, delta) to compare floating-point numbers, took <TIME>
-e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble
+e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble finished, took <TIME>
 liTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage started
 leTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage failed: Use assertEquals(expected, actual, delta) to compare floating-point numbers, took <TIME>
-e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage
+e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage finished, took <TIME>
 liTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte::
 liTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon::
 liTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt::
 liTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort::
 liTest run finished: 2 failed, 0 ignored, 6 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_nva.txt b/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_nva.txt
index c5899284c9..6161aeaf80 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_nva.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_nva.txt
@@ -1,23 +1,23 @@
 liTest run started
 liTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble started
 leTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble failed: java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers, took <TIME>
-e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble
+e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble finished, took <TIME>
 liTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage started
 leTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage failed: java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers, took <TIME>
-e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage
+e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage finished, took <TIME>
 liTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte::
 liTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon::
 liTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt::
 liTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort::
 liTest run finished: 2 failed, 0 ignored, 6 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_nvc.txt b/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_nvc.txt
index c4ef1ca43e..8bd6462aac 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_nvc.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_nvc.txt
@@ -1,23 +1,23 @@
 liTest run started
 liTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble started
 leTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble failed: Use assertEquals(expected, actual, delta) to compare floating-point numbers, took <TIME>
-e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble
+e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble finished, took <TIME>
 liTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage started
 leTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage failed: Use assertEquals(expected, actual, delta) to compare floating-point numbers, took <TIME>
-e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage
+e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage finished, took <TIME>
 liTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte::
 liTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon::
 liTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt::
 liTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort::
 liTest run finished: 2 failed, 0 ignored, 6 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_nvca.txt b/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_nvca.txt
index c4ef1ca43e..8bd6462aac 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_nvca.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_nvca.txt
@@ -1,23 +1,23 @@
 liTest run started
 liTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble started
 leTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble failed: Use assertEquals(expected, actual, delta) to compare floating-point numbers, took <TIME>
-e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble
+e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble finished, took <TIME>
 liTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage started
 leTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage failed: Use assertEquals(expected, actual, delta) to compare floating-point numbers, took <TIME>
-e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage
+e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage finished, took <TIME>
 liTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte::
 liTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon::
 liTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt::
 liTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort::
 liTest run finished: 2 failed, 0 ignored, 6 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_v.txt b/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_v.txt
index 2ffcfd2f26..9e1779dd8c 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_v.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_v.txt
@@ -1,23 +1,23 @@
 liTest run started
 liTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble started
 leTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble failed: Use assertEquals(expected, actual, delta) to compare floating-point numbers, took <TIME>
-e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble
+e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble finished, took <TIME>
 liTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage started
 leTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage failed: Use assertEquals(expected, actual, delta) to compare floating-point numbers, took <TIME>
-e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage
+e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage finished, took <TIME>
 liTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte::
 liTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon::
 liTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt::
 liTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort::
 liTest run finished: 2 failed, 0 ignored, 6 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_va.txt b/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_va.txt
index 210bf95a4c..dd92158837 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_va.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_va.txt
@@ -1,23 +1,23 @@
 liTest run started
 liTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble started
 leTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble failed: java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers, took <TIME>
-e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble
+e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble finished, took <TIME>
 liTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage started
 leTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage failed: java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers, took <TIME>
-e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage
+e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage finished, took <TIME>
 liTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte::
 liTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon::
 liTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt::
 liTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort::
 liTest run finished: 2 failed, 0 ignored, 6 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_vc.txt b/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_vc.txt
index 2ffcfd2f26..9e1779dd8c 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_vc.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_vc.txt
@@ -1,23 +1,23 @@
 liTest run started
 liTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble started
 leTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble failed: Use assertEquals(expected, actual, delta) to compare floating-point numbers, took <TIME>
-e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble
+e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble finished, took <TIME>
 liTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage started
 leTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage failed: Use assertEquals(expected, actual, delta) to compare floating-point numbers, took <TIME>
-e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage
+e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage finished, took <TIME>
 liTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte::
 liTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon::
 liTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt::
 liTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort::
 liTest run finished: 2 failed, 0 ignored, 6 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_vs.txt b/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_vs.txt
index 2ffcfd2f26..9e1779dd8c 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_vs.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_vs.txt
@@ -1,23 +1,23 @@
 liTest run started
 liTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble started
 leTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble failed: Use assertEquals(expected, actual, delta) to compare floating-point numbers, took <TIME>
-e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble
+e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble finished, took <TIME>
 liTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage started
 leTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage failed: Use assertEquals(expected, actual, delta) to compare floating-point numbers, took <TIME>
-e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage
+e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage finished, took <TIME>
 liTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte::
 liTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon::
 liTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt::
 liTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort::
 liTest run finished: 2 failed, 0 ignored, 6 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_vsn.txt b/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_vsn.txt
index c4ef1ca43e..8bd6462aac 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_vsn.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_vsn.txt
@@ -1,23 +1,23 @@
 liTest run started
 liTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble started
 leTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble failed: Use assertEquals(expected, actual, delta) to compare floating-point numbers, took <TIME>
-e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble
+e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble finished, took <TIME>
 liTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage started
 leTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage failed: Use assertEquals(expected, actual, delta) to compare floating-point numbers, took <TIME>
-e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage
+e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage finished, took <TIME>
 liTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte::
 liTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon::
 liTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt::
 liTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort::
 liTest run finished: 2 failed, 0 ignored, 6 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_.txt b/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_.txt
index d7e8982aca..93ad3cc5bb 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.AssertEqualsTest.test started
 leTest org.scalajs.junit.AssertEqualsTest.test failed: expected:<false> but was:<true>, took <TIME>
-e2org.scalajs.junit.AssertEqualsTest.test
+e2org.scalajs.junit.AssertEqualsTest.test::java.lang.AssertionError: expected:<false> but was:<true>
 ldTest org.scalajs.junit.AssertEqualsTest.test finished, took <TIME>
 ldTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_a.txt b/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_a.txt
index aca166f8fe..56685b67f4 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_a.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_a.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.AssertEqualsTest.test started
 leTest org.scalajs.junit.AssertEqualsTest.test failed: java.lang.AssertionError: expected:<false> but was:<true>, took <TIME>
-e2org.scalajs.junit.AssertEqualsTest.test
+e2org.scalajs.junit.AssertEqualsTest.test::java.lang.AssertionError: expected:<false> but was:<true>
 ldTest org.scalajs.junit.AssertEqualsTest.test finished, took <TIME>
 ldTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_n.txt b/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_n.txt
index 228aaf3465..fca48a0747 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_n.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_n.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.AssertEqualsTest.test started
 leTest org.scalajs.junit.AssertEqualsTest.test failed: expected:<false> but was:<true>, took <TIME>
-e2org.scalajs.junit.AssertEqualsTest.test
+e2org.scalajs.junit.AssertEqualsTest.test::java.lang.AssertionError: expected:<false> but was:<true>
 ldTest org.scalajs.junit.AssertEqualsTest.test finished, took <TIME>
 ldTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_na.txt b/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_na.txt
index d58fad3254..bfbfca6c86 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_na.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_na.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.AssertEqualsTest.test started
 leTest org.scalajs.junit.AssertEqualsTest.test failed: java.lang.AssertionError: expected:<false> but was:<true>, took <TIME>
-e2org.scalajs.junit.AssertEqualsTest.test
+e2org.scalajs.junit.AssertEqualsTest.test::java.lang.AssertionError: expected:<false> but was:<true>
 ldTest org.scalajs.junit.AssertEqualsTest.test finished, took <TIME>
 ldTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_nv.txt b/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_nv.txt
index ba1257ffe7..fa53033016 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_nv.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_nv.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertEqualsTest.test started
 leTest org.scalajs.junit.AssertEqualsTest.test failed: expected:<false> but was:<true>, took <TIME>
-e2org.scalajs.junit.AssertEqualsTest.test
+e2org.scalajs.junit.AssertEqualsTest.test::java.lang.AssertionError: expected:<false> but was:<true>
 ldTest org.scalajs.junit.AssertEqualsTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_nva.txt b/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_nva.txt
index a1de6d513c..4dc0a43c99 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_nva.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_nva.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertEqualsTest.test started
 leTest org.scalajs.junit.AssertEqualsTest.test failed: java.lang.AssertionError: expected:<false> but was:<true>, took <TIME>
-e2org.scalajs.junit.AssertEqualsTest.test
+e2org.scalajs.junit.AssertEqualsTest.test::java.lang.AssertionError: expected:<false> but was:<true>
 ldTest org.scalajs.junit.AssertEqualsTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_nvc.txt b/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_nvc.txt
index ba1257ffe7..fa53033016 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_nvc.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_nvc.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertEqualsTest.test started
 leTest org.scalajs.junit.AssertEqualsTest.test failed: expected:<false> but was:<true>, took <TIME>
-e2org.scalajs.junit.AssertEqualsTest.test
+e2org.scalajs.junit.AssertEqualsTest.test::java.lang.AssertionError: expected:<false> but was:<true>
 ldTest org.scalajs.junit.AssertEqualsTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_nvca.txt b/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_nvca.txt
index ba1257ffe7..fa53033016 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_nvca.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_nvca.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertEqualsTest.test started
 leTest org.scalajs.junit.AssertEqualsTest.test failed: expected:<false> but was:<true>, took <TIME>
-e2org.scalajs.junit.AssertEqualsTest.test
+e2org.scalajs.junit.AssertEqualsTest.test::java.lang.AssertionError: expected:<false> but was:<true>
 ldTest org.scalajs.junit.AssertEqualsTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_v.txt b/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_v.txt
index 2146f0f7d8..c0aa908a22 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_v.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_v.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertEqualsTest.test started
 leTest org.scalajs.junit.AssertEqualsTest.test failed: expected:<false> but was:<true>, took <TIME>
-e2org.scalajs.junit.AssertEqualsTest.test
+e2org.scalajs.junit.AssertEqualsTest.test::java.lang.AssertionError: expected:<false> but was:<true>
 ldTest org.scalajs.junit.AssertEqualsTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_va.txt b/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_va.txt
index 5556bead10..84eb6768c0 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_va.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_va.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertEqualsTest.test started
 leTest org.scalajs.junit.AssertEqualsTest.test failed: java.lang.AssertionError: expected:<false> but was:<true>, took <TIME>
-e2org.scalajs.junit.AssertEqualsTest.test
+e2org.scalajs.junit.AssertEqualsTest.test::java.lang.AssertionError: expected:<false> but was:<true>
 ldTest org.scalajs.junit.AssertEqualsTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_vc.txt b/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_vc.txt
index 2146f0f7d8..c0aa908a22 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_vc.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_vc.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertEqualsTest.test started
 leTest org.scalajs.junit.AssertEqualsTest.test failed: expected:<false> but was:<true>, took <TIME>
-e2org.scalajs.junit.AssertEqualsTest.test
+e2org.scalajs.junit.AssertEqualsTest.test::java.lang.AssertionError: expected:<false> but was:<true>
 ldTest org.scalajs.junit.AssertEqualsTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_vs.txt b/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_vs.txt
index 2146f0f7d8..c0aa908a22 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_vs.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_vs.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertEqualsTest.test started
 leTest org.scalajs.junit.AssertEqualsTest.test failed: expected:<false> but was:<true>, took <TIME>
-e2org.scalajs.junit.AssertEqualsTest.test
+e2org.scalajs.junit.AssertEqualsTest.test::java.lang.AssertionError: expected:<false> but was:<true>
 ldTest org.scalajs.junit.AssertEqualsTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_vsn.txt b/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_vsn.txt
index ba1257ffe7..fa53033016 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_vsn.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_vsn.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertEqualsTest.test started
 leTest org.scalajs.junit.AssertEqualsTest.test failed: expected:<false> but was:<true>, took <TIME>
-e2org.scalajs.junit.AssertEqualsTest.test
+e2org.scalajs.junit.AssertEqualsTest.test::java.lang.AssertionError: expected:<false> but was:<true>
 ldTest org.scalajs.junit.AssertEqualsTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_.txt b/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_.txt
index 66556bc61c..6113781da0 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.AssertFalse2Test.test started
 leTest org.scalajs.junit.AssertFalse2Test.test failed: This is the message, took <TIME>
-e2org.scalajs.junit.AssertFalse2Test.test
+e2org.scalajs.junit.AssertFalse2Test.test::java.lang.AssertionError: This is the message
 ldTest org.scalajs.junit.AssertFalse2Test.test finished, took <TIME>
 ldTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_a.txt b/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_a.txt
index eb9044a7bd..399521dee2 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_a.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_a.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.AssertFalse2Test.test started
 leTest org.scalajs.junit.AssertFalse2Test.test failed: java.lang.AssertionError: This is the message, took <TIME>
-e2org.scalajs.junit.AssertFalse2Test.test
+e2org.scalajs.junit.AssertFalse2Test.test::java.lang.AssertionError: This is the message
 ldTest org.scalajs.junit.AssertFalse2Test.test finished, took <TIME>
 ldTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_n.txt b/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_n.txt
index f10e3b2084..82eb36b848 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_n.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_n.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.AssertFalse2Test.test started
 leTest org.scalajs.junit.AssertFalse2Test.test failed: This is the message, took <TIME>
-e2org.scalajs.junit.AssertFalse2Test.test
+e2org.scalajs.junit.AssertFalse2Test.test::java.lang.AssertionError: This is the message
 ldTest org.scalajs.junit.AssertFalse2Test.test finished, took <TIME>
 ldTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_na.txt b/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_na.txt
index 27d1306dc2..03bacc3f6d 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_na.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_na.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.AssertFalse2Test.test started
 leTest org.scalajs.junit.AssertFalse2Test.test failed: java.lang.AssertionError: This is the message, took <TIME>
-e2org.scalajs.junit.AssertFalse2Test.test
+e2org.scalajs.junit.AssertFalse2Test.test::java.lang.AssertionError: This is the message
 ldTest org.scalajs.junit.AssertFalse2Test.test finished, took <TIME>
 ldTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_nv.txt b/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_nv.txt
index 1d203390d5..ab934867b7 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_nv.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_nv.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertFalse2Test.test started
 leTest org.scalajs.junit.AssertFalse2Test.test failed: This is the message, took <TIME>
-e2org.scalajs.junit.AssertFalse2Test.test
+e2org.scalajs.junit.AssertFalse2Test.test::java.lang.AssertionError: This is the message
 ldTest org.scalajs.junit.AssertFalse2Test.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_nva.txt b/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_nva.txt
index 42341f97e9..477dcedd2e 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_nva.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_nva.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertFalse2Test.test started
 leTest org.scalajs.junit.AssertFalse2Test.test failed: java.lang.AssertionError: This is the message, took <TIME>
-e2org.scalajs.junit.AssertFalse2Test.test
+e2org.scalajs.junit.AssertFalse2Test.test::java.lang.AssertionError: This is the message
 ldTest org.scalajs.junit.AssertFalse2Test.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_nvc.txt b/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_nvc.txt
index 1d203390d5..ab934867b7 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_nvc.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_nvc.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertFalse2Test.test started
 leTest org.scalajs.junit.AssertFalse2Test.test failed: This is the message, took <TIME>
-e2org.scalajs.junit.AssertFalse2Test.test
+e2org.scalajs.junit.AssertFalse2Test.test::java.lang.AssertionError: This is the message
 ldTest org.scalajs.junit.AssertFalse2Test.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_nvca.txt b/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_nvca.txt
index 1d203390d5..ab934867b7 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_nvca.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_nvca.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertFalse2Test.test started
 leTest org.scalajs.junit.AssertFalse2Test.test failed: This is the message, took <TIME>
-e2org.scalajs.junit.AssertFalse2Test.test
+e2org.scalajs.junit.AssertFalse2Test.test::java.lang.AssertionError: This is the message
 ldTest org.scalajs.junit.AssertFalse2Test.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_v.txt b/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_v.txt
index a31c3567cb..e00e69eeac 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_v.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_v.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertFalse2Test.test started
 leTest org.scalajs.junit.AssertFalse2Test.test failed: This is the message, took <TIME>
-e2org.scalajs.junit.AssertFalse2Test.test
+e2org.scalajs.junit.AssertFalse2Test.test::java.lang.AssertionError: This is the message
 ldTest org.scalajs.junit.AssertFalse2Test.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_va.txt b/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_va.txt
index aef0d8bb4e..43673ec0c1 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_va.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_va.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertFalse2Test.test started
 leTest org.scalajs.junit.AssertFalse2Test.test failed: java.lang.AssertionError: This is the message, took <TIME>
-e2org.scalajs.junit.AssertFalse2Test.test
+e2org.scalajs.junit.AssertFalse2Test.test::java.lang.AssertionError: This is the message
 ldTest org.scalajs.junit.AssertFalse2Test.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_vc.txt b/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_vc.txt
index a31c3567cb..e00e69eeac 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_vc.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_vc.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertFalse2Test.test started
 leTest org.scalajs.junit.AssertFalse2Test.test failed: This is the message, took <TIME>
-e2org.scalajs.junit.AssertFalse2Test.test
+e2org.scalajs.junit.AssertFalse2Test.test::java.lang.AssertionError: This is the message
 ldTest org.scalajs.junit.AssertFalse2Test.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_vs.txt b/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_vs.txt
index a31c3567cb..e00e69eeac 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_vs.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_vs.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertFalse2Test.test started
 leTest org.scalajs.junit.AssertFalse2Test.test failed: This is the message, took <TIME>
-e2org.scalajs.junit.AssertFalse2Test.test
+e2org.scalajs.junit.AssertFalse2Test.test::java.lang.AssertionError: This is the message
 ldTest org.scalajs.junit.AssertFalse2Test.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_vsn.txt b/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_vsn.txt
index 1d203390d5..ab934867b7 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_vsn.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_vsn.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertFalse2Test.test started
 leTest org.scalajs.junit.AssertFalse2Test.test failed: This is the message, took <TIME>
-e2org.scalajs.junit.AssertFalse2Test.test
+e2org.scalajs.junit.AssertFalse2Test.test::java.lang.AssertionError: This is the message
 ldTest org.scalajs.junit.AssertFalse2Test.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_.txt b/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_.txt
index 9394b0a07b..d6b56eaf42 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.AssertFalseTest.test started
 leTest org.scalajs.junit.AssertFalseTest.test failed: null, took <TIME>
-e2org.scalajs.junit.AssertFalseTest.test
+e2org.scalajs.junit.AssertFalseTest.test::java.lang.AssertionError
 ldTest org.scalajs.junit.AssertFalseTest.test finished, took <TIME>
 ldTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_a.txt b/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_a.txt
index b44a464dfa..ab058bdd2e 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_a.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_a.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.AssertFalseTest.test started
 leTest org.scalajs.junit.AssertFalseTest.test failed: java.lang.AssertionError: null, took <TIME>
-e2org.scalajs.junit.AssertFalseTest.test
+e2org.scalajs.junit.AssertFalseTest.test::java.lang.AssertionError
 ldTest org.scalajs.junit.AssertFalseTest.test finished, took <TIME>
 ldTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_n.txt b/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_n.txt
index 62fa7252d0..032e6c350c 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_n.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_n.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.AssertFalseTest.test started
 leTest org.scalajs.junit.AssertFalseTest.test failed: null, took <TIME>
-e2org.scalajs.junit.AssertFalseTest.test
+e2org.scalajs.junit.AssertFalseTest.test::java.lang.AssertionError
 ldTest org.scalajs.junit.AssertFalseTest.test finished, took <TIME>
 ldTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_na.txt b/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_na.txt
index 067e0ad74b..245f1406a0 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_na.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_na.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.AssertFalseTest.test started
 leTest org.scalajs.junit.AssertFalseTest.test failed: java.lang.AssertionError: null, took <TIME>
-e2org.scalajs.junit.AssertFalseTest.test
+e2org.scalajs.junit.AssertFalseTest.test::java.lang.AssertionError
 ldTest org.scalajs.junit.AssertFalseTest.test finished, took <TIME>
 ldTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_nv.txt b/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_nv.txt
index 629ab0c6a0..936f21a783 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_nv.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_nv.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertFalseTest.test started
 leTest org.scalajs.junit.AssertFalseTest.test failed: null, took <TIME>
-e2org.scalajs.junit.AssertFalseTest.test
+e2org.scalajs.junit.AssertFalseTest.test::java.lang.AssertionError
 ldTest org.scalajs.junit.AssertFalseTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_nva.txt b/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_nva.txt
index 71cc975621..5541a0d8cc 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_nva.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_nva.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertFalseTest.test started
 leTest org.scalajs.junit.AssertFalseTest.test failed: java.lang.AssertionError: null, took <TIME>
-e2org.scalajs.junit.AssertFalseTest.test
+e2org.scalajs.junit.AssertFalseTest.test::java.lang.AssertionError
 ldTest org.scalajs.junit.AssertFalseTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_nvc.txt b/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_nvc.txt
index 629ab0c6a0..936f21a783 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_nvc.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_nvc.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertFalseTest.test started
 leTest org.scalajs.junit.AssertFalseTest.test failed: null, took <TIME>
-e2org.scalajs.junit.AssertFalseTest.test
+e2org.scalajs.junit.AssertFalseTest.test::java.lang.AssertionError
 ldTest org.scalajs.junit.AssertFalseTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_nvca.txt b/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_nvca.txt
index 629ab0c6a0..936f21a783 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_nvca.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_nvca.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertFalseTest.test started
 leTest org.scalajs.junit.AssertFalseTest.test failed: null, took <TIME>
-e2org.scalajs.junit.AssertFalseTest.test
+e2org.scalajs.junit.AssertFalseTest.test::java.lang.AssertionError
 ldTest org.scalajs.junit.AssertFalseTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_v.txt b/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_v.txt
index 62110fcff0..f2b97e6fba 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_v.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_v.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertFalseTest.test started
 leTest org.scalajs.junit.AssertFalseTest.test failed: null, took <TIME>
-e2org.scalajs.junit.AssertFalseTest.test
+e2org.scalajs.junit.AssertFalseTest.test::java.lang.AssertionError
 ldTest org.scalajs.junit.AssertFalseTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_va.txt b/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_va.txt
index b68453b46b..142f954105 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_va.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_va.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertFalseTest.test started
 leTest org.scalajs.junit.AssertFalseTest.test failed: java.lang.AssertionError: null, took <TIME>
-e2org.scalajs.junit.AssertFalseTest.test
+e2org.scalajs.junit.AssertFalseTest.test::java.lang.AssertionError
 ldTest org.scalajs.junit.AssertFalseTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_vc.txt b/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_vc.txt
index 62110fcff0..f2b97e6fba 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_vc.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_vc.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertFalseTest.test started
 leTest org.scalajs.junit.AssertFalseTest.test failed: null, took <TIME>
-e2org.scalajs.junit.AssertFalseTest.test
+e2org.scalajs.junit.AssertFalseTest.test::java.lang.AssertionError
 ldTest org.scalajs.junit.AssertFalseTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_vs.txt b/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_vs.txt
index 62110fcff0..f2b97e6fba 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_vs.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_vs.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertFalseTest.test started
 leTest org.scalajs.junit.AssertFalseTest.test failed: null, took <TIME>
-e2org.scalajs.junit.AssertFalseTest.test
+e2org.scalajs.junit.AssertFalseTest.test::java.lang.AssertionError
 ldTest org.scalajs.junit.AssertFalseTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_vsn.txt b/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_vsn.txt
index 629ab0c6a0..936f21a783 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_vsn.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_vsn.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertFalseTest.test started
 leTest org.scalajs.junit.AssertFalseTest.test failed: null, took <TIME>
-e2org.scalajs.junit.AssertFalseTest.test
+e2org.scalajs.junit.AssertFalseTest.test::java.lang.AssertionError
 ldTest org.scalajs.junit.AssertFalseTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_.txt b/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_.txt
index 47f67193e2..4831b5344d 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.AssertStringEqualsTest.test started
 leTest org.scalajs.junit.AssertStringEqualsTest.test failed: expected:<foob[a]r> but was:<foob[bb]r>, took <TIME>
-e2org.scalajs.junit.AssertStringEqualsTest.test
+e2org.scalajs.junit.AssertStringEqualsTest.test::org.junit.ComparisonFailure: expected:<foob[a]r> but was:<foob[bb]r>
 ldTest org.scalajs.junit.AssertStringEqualsTest.test finished, took <TIME>
 ldTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_a.txt b/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_a.txt
index 8ff782c6c1..f214868851 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_a.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_a.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.AssertStringEqualsTest.test started
 leTest org.scalajs.junit.AssertStringEqualsTest.test failed: org.junit.ComparisonFailure: expected:<foob[a]r> but was:<foob[bb]r>, took <TIME>
-e2org.scalajs.junit.AssertStringEqualsTest.test
+e2org.scalajs.junit.AssertStringEqualsTest.test::org.junit.ComparisonFailure: expected:<foob[a]r> but was:<foob[bb]r>
 ldTest org.scalajs.junit.AssertStringEqualsTest.test finished, took <TIME>
 ldTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_n.txt b/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_n.txt
index bf4caa9571..8314d809ae 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_n.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_n.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.AssertStringEqualsTest.test started
 leTest org.scalajs.junit.AssertStringEqualsTest.test failed: expected:<foob[a]r> but was:<foob[bb]r>, took <TIME>
-e2org.scalajs.junit.AssertStringEqualsTest.test
+e2org.scalajs.junit.AssertStringEqualsTest.test::org.junit.ComparisonFailure: expected:<foob[a]r> but was:<foob[bb]r>
 ldTest org.scalajs.junit.AssertStringEqualsTest.test finished, took <TIME>
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diff --git a/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_na.txt b/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_na.txt
index 6a6af909aa..7044a087eb 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_na.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_na.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.AssertStringEqualsTest.test started
 leTest org.scalajs.junit.AssertStringEqualsTest.test failed: org.junit.ComparisonFailure: expected:<foob[a]r> but was:<foob[bb]r>, took <TIME>
-e2org.scalajs.junit.AssertStringEqualsTest.test
+e2org.scalajs.junit.AssertStringEqualsTest.test::org.junit.ComparisonFailure: expected:<foob[a]r> but was:<foob[bb]r>
 ldTest org.scalajs.junit.AssertStringEqualsTest.test finished, took <TIME>
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diff --git a/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_nv.txt b/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_nv.txt
index b649abd563..050a280abb 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_nv.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_nv.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertStringEqualsTest.test started
 leTest org.scalajs.junit.AssertStringEqualsTest.test failed: expected:<foob[a]r> but was:<foob[bb]r>, took <TIME>
-e2org.scalajs.junit.AssertStringEqualsTest.test
+e2org.scalajs.junit.AssertStringEqualsTest.test::org.junit.ComparisonFailure: expected:<foob[a]r> but was:<foob[bb]r>
 ldTest org.scalajs.junit.AssertStringEqualsTest.test finished, took <TIME>
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diff --git a/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_nva.txt b/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_nva.txt
index d579562475..fa7faaf21c 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_nva.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_nva.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertStringEqualsTest.test started
 leTest org.scalajs.junit.AssertStringEqualsTest.test failed: org.junit.ComparisonFailure: expected:<foob[a]r> but was:<foob[bb]r>, took <TIME>
-e2org.scalajs.junit.AssertStringEqualsTest.test
+e2org.scalajs.junit.AssertStringEqualsTest.test::org.junit.ComparisonFailure: expected:<foob[a]r> but was:<foob[bb]r>
 ldTest org.scalajs.junit.AssertStringEqualsTest.test finished, took <TIME>
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diff --git a/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_nvc.txt b/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_nvc.txt
index b649abd563..050a280abb 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_nvc.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_nvc.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertStringEqualsTest.test started
 leTest org.scalajs.junit.AssertStringEqualsTest.test failed: expected:<foob[a]r> but was:<foob[bb]r>, took <TIME>
-e2org.scalajs.junit.AssertStringEqualsTest.test
+e2org.scalajs.junit.AssertStringEqualsTest.test::org.junit.ComparisonFailure: expected:<foob[a]r> but was:<foob[bb]r>
 ldTest org.scalajs.junit.AssertStringEqualsTest.test finished, took <TIME>
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diff --git a/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_nvca.txt b/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_nvca.txt
index b649abd563..050a280abb 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_nvca.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_nvca.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertStringEqualsTest.test started
 leTest org.scalajs.junit.AssertStringEqualsTest.test failed: expected:<foob[a]r> but was:<foob[bb]r>, took <TIME>
-e2org.scalajs.junit.AssertStringEqualsTest.test
+e2org.scalajs.junit.AssertStringEqualsTest.test::org.junit.ComparisonFailure: expected:<foob[a]r> but was:<foob[bb]r>
 ldTest org.scalajs.junit.AssertStringEqualsTest.test finished, took <TIME>
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diff --git a/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_v.txt b/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_v.txt
index 6caa85d132..4ada7cf6df 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_v.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_v.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertStringEqualsTest.test started
 leTest org.scalajs.junit.AssertStringEqualsTest.test failed: expected:<foob[a]r> but was:<foob[bb]r>, took <TIME>
-e2org.scalajs.junit.AssertStringEqualsTest.test
+e2org.scalajs.junit.AssertStringEqualsTest.test::org.junit.ComparisonFailure: expected:<foob[a]r> but was:<foob[bb]r>
 ldTest org.scalajs.junit.AssertStringEqualsTest.test finished, took <TIME>
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diff --git a/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_va.txt b/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_va.txt
index 004e3273f5..c2c9792f56 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_va.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_va.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertStringEqualsTest.test started
 leTest org.scalajs.junit.AssertStringEqualsTest.test failed: org.junit.ComparisonFailure: expected:<foob[a]r> but was:<foob[bb]r>, took <TIME>
-e2org.scalajs.junit.AssertStringEqualsTest.test
+e2org.scalajs.junit.AssertStringEqualsTest.test::org.junit.ComparisonFailure: expected:<foob[a]r> but was:<foob[bb]r>
 ldTest org.scalajs.junit.AssertStringEqualsTest.test finished, took <TIME>
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diff --git a/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_vc.txt b/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_vc.txt
index 6caa85d132..4ada7cf6df 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_vc.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_vc.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertStringEqualsTest.test started
 leTest org.scalajs.junit.AssertStringEqualsTest.test failed: expected:<foob[a]r> but was:<foob[bb]r>, took <TIME>
-e2org.scalajs.junit.AssertStringEqualsTest.test
+e2org.scalajs.junit.AssertStringEqualsTest.test::org.junit.ComparisonFailure: expected:<foob[a]r> but was:<foob[bb]r>
 ldTest org.scalajs.junit.AssertStringEqualsTest.test finished, took <TIME>
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diff --git a/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_vs.txt b/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_vs.txt
index 6caa85d132..4ada7cf6df 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_vs.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_vs.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertStringEqualsTest.test started
 leTest org.scalajs.junit.AssertStringEqualsTest.test failed: expected:<foob[a]r> but was:<foob[bb]r>, took <TIME>
-e2org.scalajs.junit.AssertStringEqualsTest.test
+e2org.scalajs.junit.AssertStringEqualsTest.test::org.junit.ComparisonFailure: expected:<foob[a]r> but was:<foob[bb]r>
 ldTest org.scalajs.junit.AssertStringEqualsTest.test finished, took <TIME>
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diff --git a/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_vsn.txt b/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_vsn.txt
index b649abd563..050a280abb 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_vsn.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_vsn.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertStringEqualsTest.test started
 leTest org.scalajs.junit.AssertStringEqualsTest.test failed: expected:<foob[a]r> but was:<foob[bb]r>, took <TIME>
-e2org.scalajs.junit.AssertStringEqualsTest.test
+e2org.scalajs.junit.AssertStringEqualsTest.test::org.junit.ComparisonFailure: expected:<foob[a]r> but was:<foob[bb]r>
 ldTest org.scalajs.junit.AssertStringEqualsTest.test finished, took <TIME>
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diff --git a/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_.txt b/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_.txt
index a46cb27938..e49cdd3f01 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_.txt
@@ -1,10 +1,10 @@
 ldTest run started
 ldTest org.scalajs.junit.AssertTrueTest.failTest started
 leTest org.scalajs.junit.AssertTrueTest.failTest failed: null, took <TIME>
-e2org.scalajs.junit.AssertTrueTest.failTest
+e2org.scalajs.junit.AssertTrueTest.failTest::java.lang.AssertionError
 ldTest org.scalajs.junit.AssertTrueTest.failTest finished, took <TIME>
 ldTest org.scalajs.junit.AssertTrueTest.successTest started
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 ldTest run finished: 1 failed, 0 ignored, 2 total, <TIME>
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diff --git a/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_a.txt b/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_a.txt
index eb9edaa2f4..cc95f5c7a7 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_a.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_a.txt
@@ -1,10 +1,10 @@
 ldTest run started
 ldTest org.scalajs.junit.AssertTrueTest.failTest started
 leTest org.scalajs.junit.AssertTrueTest.failTest failed: java.lang.AssertionError: null, took <TIME>
-e2org.scalajs.junit.AssertTrueTest.failTest
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 ldTest org.scalajs.junit.AssertTrueTest.failTest finished, took <TIME>
 ldTest org.scalajs.junit.AssertTrueTest.successTest started
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diff --git a/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_n.txt b/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_n.txt
index 58bbb1372c..706781bd5b 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_n.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_n.txt
@@ -1,10 +1,10 @@
 ldTest run started
 ldTest org.scalajs.junit.AssertTrueTest.failTest started
 leTest org.scalajs.junit.AssertTrueTest.failTest failed: null, took <TIME>
-e2org.scalajs.junit.AssertTrueTest.failTest
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 ldTest org.scalajs.junit.AssertTrueTest.failTest finished, took <TIME>
 ldTest org.scalajs.junit.AssertTrueTest.successTest started
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 ldTest run finished: 1 failed, 0 ignored, 2 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_na.txt b/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_na.txt
index e89ed0ed75..6aabf28c21 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_na.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_na.txt
@@ -1,10 +1,10 @@
 ldTest run started
 ldTest org.scalajs.junit.AssertTrueTest.failTest started
 leTest org.scalajs.junit.AssertTrueTest.failTest failed: java.lang.AssertionError: null, took <TIME>
-e2org.scalajs.junit.AssertTrueTest.failTest
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 ldTest org.scalajs.junit.AssertTrueTest.failTest finished, took <TIME>
 ldTest org.scalajs.junit.AssertTrueTest.successTest started
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diff --git a/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_nv.txt b/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_nv.txt
index 4bd207b4b1..04cdb29958 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_nv.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_nv.txt
@@ -1,10 +1,10 @@
 liTest run started
 liTest org.scalajs.junit.AssertTrueTest.failTest started
 leTest org.scalajs.junit.AssertTrueTest.failTest failed: null, took <TIME>
-e2org.scalajs.junit.AssertTrueTest.failTest
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 ldTest org.scalajs.junit.AssertTrueTest.failTest finished, took <TIME>
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diff --git a/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_nva.txt b/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_nva.txt
index 6bc3e72736..2f5d0b3100 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_nva.txt
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@@ -1,10 +1,10 @@
 liTest run started
 liTest org.scalajs.junit.AssertTrueTest.failTest started
 leTest org.scalajs.junit.AssertTrueTest.failTest failed: java.lang.AssertionError: null, took <TIME>
-e2org.scalajs.junit.AssertTrueTest.failTest
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 ldTest org.scalajs.junit.AssertTrueTest.failTest finished, took <TIME>
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diff --git a/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_nvc.txt b/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_nvc.txt
index 4bd207b4b1..04cdb29958 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_nvc.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_nvc.txt
@@ -1,10 +1,10 @@
 liTest run started
 liTest org.scalajs.junit.AssertTrueTest.failTest started
 leTest org.scalajs.junit.AssertTrueTest.failTest failed: null, took <TIME>
-e2org.scalajs.junit.AssertTrueTest.failTest
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 ldTest org.scalajs.junit.AssertTrueTest.failTest finished, took <TIME>
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diff --git a/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_nvca.txt b/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_nvca.txt
index 4bd207b4b1..04cdb29958 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_nvca.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_nvca.txt
@@ -1,10 +1,10 @@
 liTest run started
 liTest org.scalajs.junit.AssertTrueTest.failTest started
 leTest org.scalajs.junit.AssertTrueTest.failTest failed: null, took <TIME>
-e2org.scalajs.junit.AssertTrueTest.failTest
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 ldTest org.scalajs.junit.AssertTrueTest.failTest finished, took <TIME>
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diff --git a/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_v.txt b/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_v.txt
index 9f4a334562..29300050df 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_v.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_v.txt
@@ -1,10 +1,10 @@
 liTest run started
 liTest org.scalajs.junit.AssertTrueTest.failTest started
 leTest org.scalajs.junit.AssertTrueTest.failTest failed: null, took <TIME>
-e2org.scalajs.junit.AssertTrueTest.failTest
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 ldTest org.scalajs.junit.AssertTrueTest.failTest finished, took <TIME>
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diff --git a/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_va.txt b/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_va.txt
index 6760f10ace..7a01eb25ac 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_va.txt
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@@ -1,10 +1,10 @@
 liTest run started
 liTest org.scalajs.junit.AssertTrueTest.failTest started
 leTest org.scalajs.junit.AssertTrueTest.failTest failed: java.lang.AssertionError: null, took <TIME>
-e2org.scalajs.junit.AssertTrueTest.failTest
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 ldTest org.scalajs.junit.AssertTrueTest.failTest finished, took <TIME>
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diff --git a/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_vc.txt b/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_vc.txt
index 9f4a334562..29300050df 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_vc.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_vc.txt
@@ -1,10 +1,10 @@
 liTest run started
 liTest org.scalajs.junit.AssertTrueTest.failTest started
 leTest org.scalajs.junit.AssertTrueTest.failTest failed: null, took <TIME>
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 ldTest org.scalajs.junit.AssertTrueTest.failTest finished, took <TIME>
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diff --git a/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_vs.txt b/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_vs.txt
index 9f4a334562..29300050df 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_vs.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_vs.txt
@@ -1,10 +1,10 @@
 liTest run started
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 ldTest org.scalajs.junit.AssertTrueTest.failTest finished, took <TIME>
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diff --git a/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_vsn.txt b/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_vsn.txt
index 4bd207b4b1..04cdb29958 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_vsn.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_vsn.txt
@@ -1,10 +1,10 @@
 liTest run started
 liTest org.scalajs.junit.AssertTrueTest.failTest started
 leTest org.scalajs.junit.AssertTrueTest.failTest failed: null, took <TIME>
-e2org.scalajs.junit.AssertTrueTest.failTest
+e2org.scalajs.junit.AssertTrueTest.failTest::java.lang.AssertionError
 ldTest org.scalajs.junit.AssertTrueTest.failTest finished, took <TIME>
 liTest org.scalajs.junit.AssertTrueTest.successTest started
 ldTest org.scalajs.junit.AssertTrueTest.successTest finished, took <TIME>
-e0org.scalajs.junit.AssertTrueTest.successTest
+e0org.scalajs.junit.AssertTrueTest.successTest::
 liTest run finished: 1 failed, 0 ignored, 2 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_.txt
index 5f2f425518..b38d469dcd 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_.txt
@@ -2,7 +2,7 @@ ldTest run started
 ldTest org.scalajs.junit.AssumeAfterAssume.assumeFail started
 leTest org.scalajs.junit.AssumeAfterAssume.assumeFail failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
-e2org.scalajs.junit.AssumeAfterAssume.assumeFail
+e2org.scalajs.junit.AssumeAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures
 leTest org.scalajs.junit.AssumeAfterAssume.assumeFail failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeAfterAssume.assumeFail finished, took <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_a.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_a.txt
index 5f2f425518..b38d469dcd 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_a.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_a.txt
@@ -2,7 +2,7 @@ ldTest run started
 ldTest org.scalajs.junit.AssumeAfterAssume.assumeFail started
 leTest org.scalajs.junit.AssumeAfterAssume.assumeFail failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
-e2org.scalajs.junit.AssumeAfterAssume.assumeFail
+e2org.scalajs.junit.AssumeAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures
 leTest org.scalajs.junit.AssumeAfterAssume.assumeFail failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeAfterAssume.assumeFail finished, took <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_n.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_n.txt
index 73a32555fa..4eabc3c5a5 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_n.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_n.txt
@@ -2,7 +2,7 @@ ldTest run started
 ldTest org.scalajs.junit.AssumeAfterAssume.assumeFail started
 leTest org.scalajs.junit.AssumeAfterAssume.assumeFail failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
-e2org.scalajs.junit.AssumeAfterAssume.assumeFail
+e2org.scalajs.junit.AssumeAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures
 leTest org.scalajs.junit.AssumeAfterAssume.assumeFail failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeAfterAssume.assumeFail finished, took <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_na.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_na.txt
index 73a32555fa..4eabc3c5a5 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_na.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_na.txt
@@ -2,7 +2,7 @@ ldTest run started
 ldTest org.scalajs.junit.AssumeAfterAssume.assumeFail started
 leTest org.scalajs.junit.AssumeAfterAssume.assumeFail failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
-e2org.scalajs.junit.AssumeAfterAssume.assumeFail
+e2org.scalajs.junit.AssumeAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures
 leTest org.scalajs.junit.AssumeAfterAssume.assumeFail failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeAfterAssume.assumeFail finished, took <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_nv.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_nv.txt
index a9eff193fd..144099360a 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_nv.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_nv.txt
@@ -2,7 +2,7 @@ liTest run started
 liTest org.scalajs.junit.AssumeAfterAssume.assumeFail started
 leTest org.scalajs.junit.AssumeAfterAssume.assumeFail failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
-e2org.scalajs.junit.AssumeAfterAssume.assumeFail
+e2org.scalajs.junit.AssumeAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures
 leTest org.scalajs.junit.AssumeAfterAssume.assumeFail failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeAfterAssume.assumeFail finished, took <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_nva.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_nva.txt
index a9eff193fd..144099360a 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_nva.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_nva.txt
@@ -2,7 +2,7 @@ liTest run started
 liTest org.scalajs.junit.AssumeAfterAssume.assumeFail started
 leTest org.scalajs.junit.AssumeAfterAssume.assumeFail failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
-e2org.scalajs.junit.AssumeAfterAssume.assumeFail
+e2org.scalajs.junit.AssumeAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures
 leTest org.scalajs.junit.AssumeAfterAssume.assumeFail failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeAfterAssume.assumeFail finished, took <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_nvc.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_nvc.txt
index 4ee673f87c..1b894cf4dc 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_nvc.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_nvc.txt
@@ -2,7 +2,7 @@ liTest run started
 liTest org.scalajs.junit.AssumeAfterAssume.assumeFail started
 leTest org.scalajs.junit.AssumeAfterAssume.assumeFail failed: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
-e2org.scalajs.junit.AssumeAfterAssume.assumeFail
+e2org.scalajs.junit.AssumeAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures
 leTest org.scalajs.junit.AssumeAfterAssume.assumeFail failed: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeAfterAssume.assumeFail finished, took <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_nvca.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_nvca.txt
index 4ee673f87c..1b894cf4dc 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_nvca.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_nvca.txt
@@ -2,7 +2,7 @@ liTest run started
 liTest org.scalajs.junit.AssumeAfterAssume.assumeFail started
 leTest org.scalajs.junit.AssumeAfterAssume.assumeFail failed: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
-e2org.scalajs.junit.AssumeAfterAssume.assumeFail
+e2org.scalajs.junit.AssumeAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures
 leTest org.scalajs.junit.AssumeAfterAssume.assumeFail failed: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeAfterAssume.assumeFail finished, took <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_v.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_v.txt
index 994ab1df26..55e72df4b1 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_v.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_v.txt
@@ -2,7 +2,7 @@ liTest run started
 liTest org.scalajs.junit.AssumeAfterAssume.assumeFail started
 leTest org.scalajs.junit.AssumeAfterAssume.assumeFail failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
-e2org.scalajs.junit.AssumeAfterAssume.assumeFail
+e2org.scalajs.junit.AssumeAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures
 leTest org.scalajs.junit.AssumeAfterAssume.assumeFail failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeAfterAssume.assumeFail finished, took <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_va.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_va.txt
index 994ab1df26..55e72df4b1 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_va.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_va.txt
@@ -2,7 +2,7 @@ liTest run started
 liTest org.scalajs.junit.AssumeAfterAssume.assumeFail started
 leTest org.scalajs.junit.AssumeAfterAssume.assumeFail failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
-e2org.scalajs.junit.AssumeAfterAssume.assumeFail
+e2org.scalajs.junit.AssumeAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures
 leTest org.scalajs.junit.AssumeAfterAssume.assumeFail failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeAfterAssume.assumeFail finished, took <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_vc.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_vc.txt
index 6d6af2f31e..37c9099ed3 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_vc.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_vc.txt
@@ -2,7 +2,7 @@ liTest run started
 liTest org.scalajs.junit.AssumeAfterAssume.assumeFail started
 leTest org.scalajs.junit.AssumeAfterAssume.assumeFail failed: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
-e2org.scalajs.junit.AssumeAfterAssume.assumeFail
+e2org.scalajs.junit.AssumeAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures
 leTest org.scalajs.junit.AssumeAfterAssume.assumeFail failed: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeAfterAssume.assumeFail finished, took <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_vs.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_vs.txt
index 994ab1df26..55e72df4b1 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_vs.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_vs.txt
@@ -2,7 +2,7 @@ liTest run started
 liTest org.scalajs.junit.AssumeAfterAssume.assumeFail started
 leTest org.scalajs.junit.AssumeAfterAssume.assumeFail failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
-e2org.scalajs.junit.AssumeAfterAssume.assumeFail
+e2org.scalajs.junit.AssumeAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures
 leTest org.scalajs.junit.AssumeAfterAssume.assumeFail failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeAfterAssume.assumeFail finished, took <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_vsn.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_vsn.txt
index a9eff193fd..144099360a 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_vsn.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_vsn.txt
@@ -2,7 +2,7 @@ liTest run started
 liTest org.scalajs.junit.AssumeAfterAssume.assumeFail started
 leTest org.scalajs.junit.AssumeAfterAssume.assumeFail failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
-e2org.scalajs.junit.AssumeAfterAssume.assumeFail
+e2org.scalajs.junit.AssumeAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures
 leTest org.scalajs.junit.AssumeAfterAssume.assumeFail failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeAfterAssume.assumeFail finished, took <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_.txt
index 7c2c3d6eb5..c64383011f 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_.txt
@@ -1,8 +1,8 @@
 ldTest run started
 ldTest org.scalajs.junit.AssumeAfterClassTest.test started
 ldTest org.scalajs.junit.AssumeAfterClassTest.test finished, took <TIME>
-e0org.scalajs.junit.AssumeAfterClassTest.test
+e0org.scalajs.junit.AssumeAfterClassTest.test::
 lwTest assumption in test org.scalajs.junit.AssumeAfterClassTest failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeAfterClassTest
+e3org.scalajs.junit.AssumeAfterClassTest::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_a.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_a.txt
index 7c2c3d6eb5..c64383011f 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_a.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_a.txt
@@ -1,8 +1,8 @@
 ldTest run started
 ldTest org.scalajs.junit.AssumeAfterClassTest.test started
 ldTest org.scalajs.junit.AssumeAfterClassTest.test finished, took <TIME>
-e0org.scalajs.junit.AssumeAfterClassTest.test
+e0org.scalajs.junit.AssumeAfterClassTest.test::
 lwTest assumption in test org.scalajs.junit.AssumeAfterClassTest failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeAfterClassTest
+e3org.scalajs.junit.AssumeAfterClassTest::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_n.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_n.txt
index 7110131503..cf859e586e 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_n.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_n.txt
@@ -1,8 +1,8 @@
 ldTest run started
 ldTest org.scalajs.junit.AssumeAfterClassTest.test started
 ldTest org.scalajs.junit.AssumeAfterClassTest.test finished, took <TIME>
-e0org.scalajs.junit.AssumeAfterClassTest.test
+e0org.scalajs.junit.AssumeAfterClassTest.test::
 lwTest assumption in test org.scalajs.junit.AssumeAfterClassTest failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeAfterClassTest
+e3org.scalajs.junit.AssumeAfterClassTest::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_na.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_na.txt
index 7110131503..cf859e586e 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_na.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_na.txt
@@ -1,8 +1,8 @@
 ldTest run started
 ldTest org.scalajs.junit.AssumeAfterClassTest.test started
 ldTest org.scalajs.junit.AssumeAfterClassTest.test finished, took <TIME>
-e0org.scalajs.junit.AssumeAfterClassTest.test
+e0org.scalajs.junit.AssumeAfterClassTest.test::
 lwTest assumption in test org.scalajs.junit.AssumeAfterClassTest failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeAfterClassTest
+e3org.scalajs.junit.AssumeAfterClassTest::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_nv.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_nv.txt
index c261cc405f..7fb2119057 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_nv.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_nv.txt
@@ -1,8 +1,8 @@
 liTest run started
 liTest org.scalajs.junit.AssumeAfterClassTest.test started
 ldTest org.scalajs.junit.AssumeAfterClassTest.test finished, took <TIME>
-e0org.scalajs.junit.AssumeAfterClassTest.test
+e0org.scalajs.junit.AssumeAfterClassTest.test::
 lwTest assumption in test org.scalajs.junit.AssumeAfterClassTest failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeAfterClassTest
+e3org.scalajs.junit.AssumeAfterClassTest::org.junit.AssumptionViolatedException: This assume should not pass
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_nva.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_nva.txt
index c261cc405f..7fb2119057 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_nva.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_nva.txt
@@ -1,8 +1,8 @@
 liTest run started
 liTest org.scalajs.junit.AssumeAfterClassTest.test started
 ldTest org.scalajs.junit.AssumeAfterClassTest.test finished, took <TIME>
-e0org.scalajs.junit.AssumeAfterClassTest.test
+e0org.scalajs.junit.AssumeAfterClassTest.test::
 lwTest assumption in test org.scalajs.junit.AssumeAfterClassTest failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeAfterClassTest
+e3org.scalajs.junit.AssumeAfterClassTest::org.junit.AssumptionViolatedException: This assume should not pass
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_nvc.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_nvc.txt
index 80e07ba572..cf5ed08fab 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_nvc.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_nvc.txt
@@ -1,8 +1,8 @@
 liTest run started
 liTest org.scalajs.junit.AssumeAfterClassTest.test started
 ldTest org.scalajs.junit.AssumeAfterClassTest.test finished, took <TIME>
-e0org.scalajs.junit.AssumeAfterClassTest.test
+e0org.scalajs.junit.AssumeAfterClassTest.test::
 lwTest assumption in test org.scalajs.junit.AssumeAfterClassTest failed: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeAfterClassTest
+e3org.scalajs.junit.AssumeAfterClassTest::org.junit.AssumptionViolatedException: This assume should not pass
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_nvca.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_nvca.txt
index 80e07ba572..cf5ed08fab 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_nvca.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_nvca.txt
@@ -1,8 +1,8 @@
 liTest run started
 liTest org.scalajs.junit.AssumeAfterClassTest.test started
 ldTest org.scalajs.junit.AssumeAfterClassTest.test finished, took <TIME>
-e0org.scalajs.junit.AssumeAfterClassTest.test
+e0org.scalajs.junit.AssumeAfterClassTest.test::
 lwTest assumption in test org.scalajs.junit.AssumeAfterClassTest failed: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeAfterClassTest
+e3org.scalajs.junit.AssumeAfterClassTest::org.junit.AssumptionViolatedException: This assume should not pass
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_v.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_v.txt
index 56be74b74f..3ac52e8745 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_v.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_v.txt
@@ -1,8 +1,8 @@
 liTest run started
 liTest org.scalajs.junit.AssumeAfterClassTest.test started
 ldTest org.scalajs.junit.AssumeAfterClassTest.test finished, took <TIME>
-e0org.scalajs.junit.AssumeAfterClassTest.test
+e0org.scalajs.junit.AssumeAfterClassTest.test::
 lwTest assumption in test org.scalajs.junit.AssumeAfterClassTest failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeAfterClassTest
+e3org.scalajs.junit.AssumeAfterClassTest::org.junit.AssumptionViolatedException: This assume should not pass
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_va.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_va.txt
index 56be74b74f..3ac52e8745 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_va.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_va.txt
@@ -1,8 +1,8 @@
 liTest run started
 liTest org.scalajs.junit.AssumeAfterClassTest.test started
 ldTest org.scalajs.junit.AssumeAfterClassTest.test finished, took <TIME>
-e0org.scalajs.junit.AssumeAfterClassTest.test
+e0org.scalajs.junit.AssumeAfterClassTest.test::
 lwTest assumption in test org.scalajs.junit.AssumeAfterClassTest failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeAfterClassTest
+e3org.scalajs.junit.AssumeAfterClassTest::org.junit.AssumptionViolatedException: This assume should not pass
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_vc.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_vc.txt
index fff88c8f91..a730ea7a71 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_vc.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_vc.txt
@@ -1,8 +1,8 @@
 liTest run started
 liTest org.scalajs.junit.AssumeAfterClassTest.test started
 ldTest org.scalajs.junit.AssumeAfterClassTest.test finished, took <TIME>
-e0org.scalajs.junit.AssumeAfterClassTest.test
+e0org.scalajs.junit.AssumeAfterClassTest.test::
 lwTest assumption in test org.scalajs.junit.AssumeAfterClassTest failed: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeAfterClassTest
+e3org.scalajs.junit.AssumeAfterClassTest::org.junit.AssumptionViolatedException: This assume should not pass
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_vs.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_vs.txt
index 56be74b74f..3ac52e8745 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_vs.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_vs.txt
@@ -1,8 +1,8 @@
 liTest run started
 liTest org.scalajs.junit.AssumeAfterClassTest.test started
 ldTest org.scalajs.junit.AssumeAfterClassTest.test finished, took <TIME>
-e0org.scalajs.junit.AssumeAfterClassTest.test
+e0org.scalajs.junit.AssumeAfterClassTest.test::
 lwTest assumption in test org.scalajs.junit.AssumeAfterClassTest failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeAfterClassTest
+e3org.scalajs.junit.AssumeAfterClassTest::org.junit.AssumptionViolatedException: This assume should not pass
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_vsn.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_vsn.txt
index c261cc405f..7fb2119057 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_vsn.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_vsn.txt
@@ -1,8 +1,8 @@
 liTest run started
 liTest org.scalajs.junit.AssumeAfterClassTest.test started
 ldTest org.scalajs.junit.AssumeAfterClassTest.test finished, took <TIME>
-e0org.scalajs.junit.AssumeAfterClassTest.test
+e0org.scalajs.junit.AssumeAfterClassTest.test::
 lwTest assumption in test org.scalajs.junit.AssumeAfterClassTest failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeAfterClassTest
+e3org.scalajs.junit.AssumeAfterClassTest::org.junit.AssumptionViolatedException: This assume should not pass
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_.txt
index 6823e1c531..24985459cf 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.AssumeAfterException.test started
 leTest org.scalajs.junit.AssumeAfterException.test failed: java.lang.IllegalArgumentException: test throws, took <TIME>
-e2org.scalajs.junit.AssumeAfterException.test
+e2org.scalajs.junit.AssumeAfterException.test::java.lang.IllegalArgumentException: test throws
 leTest org.scalajs.junit.AssumeAfterException.test failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeAfterException.test finished, took <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_a.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_a.txt
index 6823e1c531..24985459cf 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_a.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_a.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.AssumeAfterException.test started
 leTest org.scalajs.junit.AssumeAfterException.test failed: java.lang.IllegalArgumentException: test throws, took <TIME>
-e2org.scalajs.junit.AssumeAfterException.test
+e2org.scalajs.junit.AssumeAfterException.test::java.lang.IllegalArgumentException: test throws
 leTest org.scalajs.junit.AssumeAfterException.test failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeAfterException.test finished, took <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_n.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_n.txt
index f78cb141bb..a6a4599a17 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_n.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_n.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.AssumeAfterException.test started
 leTest org.scalajs.junit.AssumeAfterException.test failed: java.lang.IllegalArgumentException: test throws, took <TIME>
-e2org.scalajs.junit.AssumeAfterException.test
+e2org.scalajs.junit.AssumeAfterException.test::java.lang.IllegalArgumentException: test throws
 leTest org.scalajs.junit.AssumeAfterException.test failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeAfterException.test finished, took <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_na.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_na.txt
index f78cb141bb..a6a4599a17 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_na.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_na.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.AssumeAfterException.test started
 leTest org.scalajs.junit.AssumeAfterException.test failed: java.lang.IllegalArgumentException: test throws, took <TIME>
-e2org.scalajs.junit.AssumeAfterException.test
+e2org.scalajs.junit.AssumeAfterException.test::java.lang.IllegalArgumentException: test throws
 leTest org.scalajs.junit.AssumeAfterException.test failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeAfterException.test finished, took <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_nv.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_nv.txt
index c8c9fefdd3..bff68c6a01 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_nv.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_nv.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssumeAfterException.test started
 leTest org.scalajs.junit.AssumeAfterException.test failed: java.lang.IllegalArgumentException: test throws, took <TIME>
-e2org.scalajs.junit.AssumeAfterException.test
+e2org.scalajs.junit.AssumeAfterException.test::java.lang.IllegalArgumentException: test throws
 leTest org.scalajs.junit.AssumeAfterException.test failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeAfterException.test finished, took <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_nva.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_nva.txt
index c8c9fefdd3..bff68c6a01 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_nva.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_nva.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssumeAfterException.test started
 leTest org.scalajs.junit.AssumeAfterException.test failed: java.lang.IllegalArgumentException: test throws, took <TIME>
-e2org.scalajs.junit.AssumeAfterException.test
+e2org.scalajs.junit.AssumeAfterException.test::java.lang.IllegalArgumentException: test throws
 leTest org.scalajs.junit.AssumeAfterException.test failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeAfterException.test finished, took <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_nvc.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_nvc.txt
index 8e27d74be0..65b2345b1b 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_nvc.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_nvc.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssumeAfterException.test started
 leTest org.scalajs.junit.AssumeAfterException.test failed: test throws, took <TIME>
-e2org.scalajs.junit.AssumeAfterException.test
+e2org.scalajs.junit.AssumeAfterException.test::java.lang.IllegalArgumentException: test throws
 leTest org.scalajs.junit.AssumeAfterException.test failed: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeAfterException.test finished, took <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_nvca.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_nvca.txt
index 8e27d74be0..65b2345b1b 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_nvca.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_nvca.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssumeAfterException.test started
 leTest org.scalajs.junit.AssumeAfterException.test failed: test throws, took <TIME>
-e2org.scalajs.junit.AssumeAfterException.test
+e2org.scalajs.junit.AssumeAfterException.test::java.lang.IllegalArgumentException: test throws
 leTest org.scalajs.junit.AssumeAfterException.test failed: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeAfterException.test finished, took <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_v.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_v.txt
index ce7d615a2f..e35b1d0554 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_v.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_v.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssumeAfterException.test started
 leTest org.scalajs.junit.AssumeAfterException.test failed: java.lang.IllegalArgumentException: test throws, took <TIME>
-e2org.scalajs.junit.AssumeAfterException.test
+e2org.scalajs.junit.AssumeAfterException.test::java.lang.IllegalArgumentException: test throws
 leTest org.scalajs.junit.AssumeAfterException.test failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeAfterException.test finished, took <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_va.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_va.txt
index ce7d615a2f..e35b1d0554 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_va.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_va.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssumeAfterException.test started
 leTest org.scalajs.junit.AssumeAfterException.test failed: java.lang.IllegalArgumentException: test throws, took <TIME>
-e2org.scalajs.junit.AssumeAfterException.test
+e2org.scalajs.junit.AssumeAfterException.test::java.lang.IllegalArgumentException: test throws
 leTest org.scalajs.junit.AssumeAfterException.test failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeAfterException.test finished, took <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_vc.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_vc.txt
index b157c5c83b..c55ba232de 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_vc.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_vc.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssumeAfterException.test started
 leTest org.scalajs.junit.AssumeAfterException.test failed: test throws, took <TIME>
-e2org.scalajs.junit.AssumeAfterException.test
+e2org.scalajs.junit.AssumeAfterException.test::java.lang.IllegalArgumentException: test throws
 leTest org.scalajs.junit.AssumeAfterException.test failed: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeAfterException.test finished, took <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_vs.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_vs.txt
index ce7d615a2f..e35b1d0554 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_vs.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_vs.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssumeAfterException.test started
 leTest org.scalajs.junit.AssumeAfterException.test failed: java.lang.IllegalArgumentException: test throws, took <TIME>
-e2org.scalajs.junit.AssumeAfterException.test
+e2org.scalajs.junit.AssumeAfterException.test::java.lang.IllegalArgumentException: test throws
 leTest org.scalajs.junit.AssumeAfterException.test failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeAfterException.test finished, took <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_vsn.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_vsn.txt
index c8c9fefdd3..bff68c6a01 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_vsn.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_vsn.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssumeAfterException.test started
 leTest org.scalajs.junit.AssumeAfterException.test failed: java.lang.IllegalArgumentException: test throws, took <TIME>
-e2org.scalajs.junit.AssumeAfterException.test
+e2org.scalajs.junit.AssumeAfterException.test::java.lang.IllegalArgumentException: test throws
 leTest org.scalajs.junit.AssumeAfterException.test failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeAfterException.test finished, took <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_.txt b/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_.txt
index 0b0b908777..04e96edf37 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.AssumeInAfter.test started
 lwTest assumption in test org.scalajs.junit.AssumeInAfter.test failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeInAfter.test
+e3org.scalajs.junit.AssumeInAfter.test::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeInAfter.test finished, took <TIME>
 ldTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_a.txt b/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_a.txt
index 0b0b908777..04e96edf37 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_a.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_a.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.AssumeInAfter.test started
 lwTest assumption in test org.scalajs.junit.AssumeInAfter.test failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeInAfter.test
+e3org.scalajs.junit.AssumeInAfter.test::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeInAfter.test finished, took <TIME>
 ldTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_n.txt b/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_n.txt
index d2272af649..8aeee7ad9f 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_n.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_n.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.AssumeInAfter.test started
 lwTest assumption in test org.scalajs.junit.AssumeInAfter.test failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeInAfter.test
+e3org.scalajs.junit.AssumeInAfter.test::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeInAfter.test finished, took <TIME>
 ldTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_na.txt b/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_na.txt
index d2272af649..8aeee7ad9f 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_na.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_na.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.AssumeInAfter.test started
 lwTest assumption in test org.scalajs.junit.AssumeInAfter.test failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeInAfter.test
+e3org.scalajs.junit.AssumeInAfter.test::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeInAfter.test finished, took <TIME>
 ldTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_nv.txt b/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_nv.txt
index 69580c614b..d4b040d5cb 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_nv.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_nv.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssumeInAfter.test started
 lwTest assumption in test org.scalajs.junit.AssumeInAfter.test failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeInAfter.test
+e3org.scalajs.junit.AssumeInAfter.test::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeInAfter.test finished, took <TIME>
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_nva.txt b/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_nva.txt
index 69580c614b..d4b040d5cb 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_nva.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_nva.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssumeInAfter.test started
 lwTest assumption in test org.scalajs.junit.AssumeInAfter.test failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeInAfter.test
+e3org.scalajs.junit.AssumeInAfter.test::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeInAfter.test finished, took <TIME>
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_nvc.txt b/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_nvc.txt
index 267833682d..4a85b7acc8 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_nvc.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_nvc.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssumeInAfter.test started
 lwTest assumption in test org.scalajs.junit.AssumeInAfter.test failed: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeInAfter.test
+e3org.scalajs.junit.AssumeInAfter.test::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeInAfter.test finished, took <TIME>
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_nvca.txt b/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_nvca.txt
index 267833682d..4a85b7acc8 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_nvca.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_nvca.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssumeInAfter.test started
 lwTest assumption in test org.scalajs.junit.AssumeInAfter.test failed: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeInAfter.test
+e3org.scalajs.junit.AssumeInAfter.test::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeInAfter.test finished, took <TIME>
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_v.txt b/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_v.txt
index 83b71fa2fe..1c61788745 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_v.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_v.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssumeInAfter.test started
 lwTest assumption in test org.scalajs.junit.AssumeInAfter.test failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeInAfter.test
+e3org.scalajs.junit.AssumeInAfter.test::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeInAfter.test finished, took <TIME>
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_va.txt b/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_va.txt
index 83b71fa2fe..1c61788745 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_va.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_va.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssumeInAfter.test started
 lwTest assumption in test org.scalajs.junit.AssumeInAfter.test failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeInAfter.test
+e3org.scalajs.junit.AssumeInAfter.test::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeInAfter.test finished, took <TIME>
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_vc.txt b/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_vc.txt
index 286e8a127b..6a9b739565 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_vc.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_vc.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssumeInAfter.test started
 lwTest assumption in test org.scalajs.junit.AssumeInAfter.test failed: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeInAfter.test
+e3org.scalajs.junit.AssumeInAfter.test::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeInAfter.test finished, took <TIME>
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_vs.txt b/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_vs.txt
index 83b71fa2fe..1c61788745 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_vs.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_vs.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssumeInAfter.test started
 lwTest assumption in test org.scalajs.junit.AssumeInAfter.test failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeInAfter.test
+e3org.scalajs.junit.AssumeInAfter.test::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeInAfter.test finished, took <TIME>
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_vsn.txt b/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_vsn.txt
index 69580c614b..d4b040d5cb 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_vsn.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_vsn.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssumeInAfter.test started
 lwTest assumption in test org.scalajs.junit.AssumeInAfter.test failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeInAfter.test
+e3org.scalajs.junit.AssumeInAfter.test::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeInAfter.test finished, took <TIME>
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_.txt b/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_.txt
index 56b731993a..4c3706abdb 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.AssumeTest.assumeFail started
 lwTest assumption in test org.scalajs.junit.AssumeTest.assumeFail failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeTest.assumeFail
+e3org.scalajs.junit.AssumeTest.assumeFail::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeTest.assumeFail finished, took <TIME>
 ldTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_a.txt b/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_a.txt
index 56b731993a..4c3706abdb 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_a.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_a.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.AssumeTest.assumeFail started
 lwTest assumption in test org.scalajs.junit.AssumeTest.assumeFail failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeTest.assumeFail
+e3org.scalajs.junit.AssumeTest.assumeFail::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeTest.assumeFail finished, took <TIME>
 ldTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_n.txt b/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_n.txt
index df8b0f8196..cc72fbc62e 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_n.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_n.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.AssumeTest.assumeFail started
 lwTest assumption in test org.scalajs.junit.AssumeTest.assumeFail failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeTest.assumeFail
+e3org.scalajs.junit.AssumeTest.assumeFail::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeTest.assumeFail finished, took <TIME>
 ldTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_na.txt b/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_na.txt
index df8b0f8196..cc72fbc62e 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_na.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_na.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.AssumeTest.assumeFail started
 lwTest assumption in test org.scalajs.junit.AssumeTest.assumeFail failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeTest.assumeFail
+e3org.scalajs.junit.AssumeTest.assumeFail::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeTest.assumeFail finished, took <TIME>
 ldTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_nv.txt b/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_nv.txt
index 30f0ab96bc..313778536f 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_nv.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_nv.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssumeTest.assumeFail started
 lwTest assumption in test org.scalajs.junit.AssumeTest.assumeFail failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeTest.assumeFail
+e3org.scalajs.junit.AssumeTest.assumeFail::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeTest.assumeFail finished, took <TIME>
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_nva.txt b/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_nva.txt
index 30f0ab96bc..313778536f 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_nva.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_nva.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssumeTest.assumeFail started
 lwTest assumption in test org.scalajs.junit.AssumeTest.assumeFail failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeTest.assumeFail
+e3org.scalajs.junit.AssumeTest.assumeFail::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeTest.assumeFail finished, took <TIME>
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_nvc.txt b/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_nvc.txt
index d3963e90bf..b5bdfb9968 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_nvc.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_nvc.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssumeTest.assumeFail started
 lwTest assumption in test org.scalajs.junit.AssumeTest.assumeFail failed: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeTest.assumeFail
+e3org.scalajs.junit.AssumeTest.assumeFail::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeTest.assumeFail finished, took <TIME>
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_nvca.txt b/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_nvca.txt
index d3963e90bf..b5bdfb9968 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_nvca.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_nvca.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssumeTest.assumeFail started
 lwTest assumption in test org.scalajs.junit.AssumeTest.assumeFail failed: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeTest.assumeFail
+e3org.scalajs.junit.AssumeTest.assumeFail::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeTest.assumeFail finished, took <TIME>
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_v.txt b/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_v.txt
index bf4e6a3bc8..e6e79ca64f 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_v.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_v.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssumeTest.assumeFail started
 lwTest assumption in test org.scalajs.junit.AssumeTest.assumeFail failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeTest.assumeFail
+e3org.scalajs.junit.AssumeTest.assumeFail::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeTest.assumeFail finished, took <TIME>
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_va.txt b/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_va.txt
index bf4e6a3bc8..e6e79ca64f 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_va.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_va.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssumeTest.assumeFail started
 lwTest assumption in test org.scalajs.junit.AssumeTest.assumeFail failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeTest.assumeFail
+e3org.scalajs.junit.AssumeTest.assumeFail::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeTest.assumeFail finished, took <TIME>
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_vc.txt b/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_vc.txt
index cd7c488782..12cef272b2 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_vc.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_vc.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssumeTest.assumeFail started
 lwTest assumption in test org.scalajs.junit.AssumeTest.assumeFail failed: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeTest.assumeFail
+e3org.scalajs.junit.AssumeTest.assumeFail::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeTest.assumeFail finished, took <TIME>
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_vs.txt b/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_vs.txt
index bf4e6a3bc8..e6e79ca64f 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_vs.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_vs.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssumeTest.assumeFail started
 lwTest assumption in test org.scalajs.junit.AssumeTest.assumeFail failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeTest.assumeFail
+e3org.scalajs.junit.AssumeTest.assumeFail::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeTest.assumeFail finished, took <TIME>
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_vsn.txt b/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_vsn.txt
index 30f0ab96bc..313778536f 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_vsn.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_vsn.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssumeTest.assumeFail started
 lwTest assumption in test org.scalajs.junit.AssumeTest.assumeFail failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeTest.assumeFail
+e3org.scalajs.junit.AssumeTest.assumeFail::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeTest.assumeFail finished, took <TIME>
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_.txt b/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_.txt
index f28ef62864..9f9feb10a4 100644
--- a/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_.txt
+++ b/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_.txt
@@ -1,13 +1,13 @@
 ldTest run started
 ldTest org.scalajs.junit.AsyncTest.asyncFailure started
 leTest org.scalajs.junit.AsyncTest.asyncFailure failed: java.lang.IllegalArgumentException: null, took <TIME>
-e2org.scalajs.junit.AsyncTest.asyncFailure
+e2org.scalajs.junit.AsyncTest.asyncFailure::java.lang.IllegalArgumentException
 ldTest org.scalajs.junit.AsyncTest.asyncFailure finished, took <TIME>
 ldTest org.scalajs.junit.AsyncTest.expectedException started
 ldTest org.scalajs.junit.AsyncTest.expectedException finished, took <TIME>
-e0org.scalajs.junit.AsyncTest.expectedException
+e0org.scalajs.junit.AsyncTest.expectedException::
 ldTest org.scalajs.junit.AsyncTest.success started
 ldTest org.scalajs.junit.AsyncTest.success finished, took <TIME>
-e0org.scalajs.junit.AsyncTest.success
+e0org.scalajs.junit.AsyncTest.success::
 ldTest run finished: 1 failed, 0 ignored, 3 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_a.txt b/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_a.txt
index f28ef62864..9f9feb10a4 100644
--- a/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_a.txt
+++ b/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_a.txt
@@ -1,13 +1,13 @@
 ldTest run started
 ldTest org.scalajs.junit.AsyncTest.asyncFailure started
 leTest org.scalajs.junit.AsyncTest.asyncFailure failed: java.lang.IllegalArgumentException: null, took <TIME>
-e2org.scalajs.junit.AsyncTest.asyncFailure
+e2org.scalajs.junit.AsyncTest.asyncFailure::java.lang.IllegalArgumentException
 ldTest org.scalajs.junit.AsyncTest.asyncFailure finished, took <TIME>
 ldTest org.scalajs.junit.AsyncTest.expectedException started
 ldTest org.scalajs.junit.AsyncTest.expectedException finished, took <TIME>
-e0org.scalajs.junit.AsyncTest.expectedException
+e0org.scalajs.junit.AsyncTest.expectedException::
 ldTest org.scalajs.junit.AsyncTest.success started
 ldTest org.scalajs.junit.AsyncTest.success finished, took <TIME>
-e0org.scalajs.junit.AsyncTest.success
+e0org.scalajs.junit.AsyncTest.success::
 ldTest run finished: 1 failed, 0 ignored, 3 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_n.txt b/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_n.txt
index f1b941ca3f..a4e8bbbf30 100644
--- a/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_n.txt
+++ b/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_n.txt
@@ -1,13 +1,13 @@
 ldTest run started
 ldTest org.scalajs.junit.AsyncTest.asyncFailure started
 leTest org.scalajs.junit.AsyncTest.asyncFailure failed: java.lang.IllegalArgumentException: null, took <TIME>
-e2org.scalajs.junit.AsyncTest.asyncFailure
+e2org.scalajs.junit.AsyncTest.asyncFailure::java.lang.IllegalArgumentException
 ldTest org.scalajs.junit.AsyncTest.asyncFailure finished, took <TIME>
 ldTest org.scalajs.junit.AsyncTest.expectedException started
 ldTest org.scalajs.junit.AsyncTest.expectedException finished, took <TIME>
-e0org.scalajs.junit.AsyncTest.expectedException
+e0org.scalajs.junit.AsyncTest.expectedException::
 ldTest org.scalajs.junit.AsyncTest.success started
 ldTest org.scalajs.junit.AsyncTest.success finished, took <TIME>
-e0org.scalajs.junit.AsyncTest.success
+e0org.scalajs.junit.AsyncTest.success::
 ldTest run finished: 1 failed, 0 ignored, 3 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_na.txt b/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_na.txt
index f1b941ca3f..a4e8bbbf30 100644
--- a/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_na.txt
+++ b/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_na.txt
@@ -1,13 +1,13 @@
 ldTest run started
 ldTest org.scalajs.junit.AsyncTest.asyncFailure started
 leTest org.scalajs.junit.AsyncTest.asyncFailure failed: java.lang.IllegalArgumentException: null, took <TIME>
-e2org.scalajs.junit.AsyncTest.asyncFailure
+e2org.scalajs.junit.AsyncTest.asyncFailure::java.lang.IllegalArgumentException
 ldTest org.scalajs.junit.AsyncTest.asyncFailure finished, took <TIME>
 ldTest org.scalajs.junit.AsyncTest.expectedException started
 ldTest org.scalajs.junit.AsyncTest.expectedException finished, took <TIME>
-e0org.scalajs.junit.AsyncTest.expectedException
+e0org.scalajs.junit.AsyncTest.expectedException::
 ldTest org.scalajs.junit.AsyncTest.success started
 ldTest org.scalajs.junit.AsyncTest.success finished, took <TIME>
-e0org.scalajs.junit.AsyncTest.success
+e0org.scalajs.junit.AsyncTest.success::
 ldTest run finished: 1 failed, 0 ignored, 3 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_nv.txt b/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_nv.txt
index 622f617605..6583d223dc 100644
--- a/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_nv.txt
+++ b/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_nv.txt
@@ -1,13 +1,13 @@
 liTest run started
 liTest org.scalajs.junit.AsyncTest.asyncFailure started
 leTest org.scalajs.junit.AsyncTest.asyncFailure failed: java.lang.IllegalArgumentException: null, took <TIME>
-e2org.scalajs.junit.AsyncTest.asyncFailure
+e2org.scalajs.junit.AsyncTest.asyncFailure::java.lang.IllegalArgumentException
 ldTest org.scalajs.junit.AsyncTest.asyncFailure finished, took <TIME>
 liTest org.scalajs.junit.AsyncTest.expectedException started
 ldTest org.scalajs.junit.AsyncTest.expectedException finished, took <TIME>
-e0org.scalajs.junit.AsyncTest.expectedException
+e0org.scalajs.junit.AsyncTest.expectedException::
 liTest org.scalajs.junit.AsyncTest.success started
 ldTest org.scalajs.junit.AsyncTest.success finished, took <TIME>
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 liTest run finished: 1 failed, 0 ignored, 3 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_nva.txt b/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_nva.txt
index 622f617605..6583d223dc 100644
--- a/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_nva.txt
+++ b/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_nva.txt
@@ -1,13 +1,13 @@
 liTest run started
 liTest org.scalajs.junit.AsyncTest.asyncFailure started
 leTest org.scalajs.junit.AsyncTest.asyncFailure failed: java.lang.IllegalArgumentException: null, took <TIME>
-e2org.scalajs.junit.AsyncTest.asyncFailure
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 ldTest org.scalajs.junit.AsyncTest.asyncFailure finished, took <TIME>
 liTest org.scalajs.junit.AsyncTest.expectedException started
 ldTest org.scalajs.junit.AsyncTest.expectedException finished, took <TIME>
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 ldTest org.scalajs.junit.AsyncTest.success finished, took <TIME>
-e0org.scalajs.junit.AsyncTest.success
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 liTest run finished: 1 failed, 0 ignored, 3 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_nvc.txt b/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_nvc.txt
index f83351d073..ea55b9d9a4 100644
--- a/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_nvc.txt
+++ b/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_nvc.txt
@@ -1,13 +1,13 @@
 liTest run started
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 leTest org.scalajs.junit.AsyncTest.asyncFailure failed: null, took <TIME>
-e2org.scalajs.junit.AsyncTest.asyncFailure
+e2org.scalajs.junit.AsyncTest.asyncFailure::java.lang.IllegalArgumentException
 ldTest org.scalajs.junit.AsyncTest.asyncFailure finished, took <TIME>
 liTest org.scalajs.junit.AsyncTest.expectedException started
 ldTest org.scalajs.junit.AsyncTest.expectedException finished, took <TIME>
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 ldTest org.scalajs.junit.AsyncTest.success finished, took <TIME>
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 liTest run finished: 1 failed, 0 ignored, 3 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_nvca.txt b/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_nvca.txt
index f83351d073..ea55b9d9a4 100644
--- a/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_nvca.txt
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@@ -1,13 +1,13 @@
 liTest run started
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 leTest org.scalajs.junit.AsyncTest.asyncFailure failed: null, took <TIME>
-e2org.scalajs.junit.AsyncTest.asyncFailure
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 ldTest org.scalajs.junit.AsyncTest.asyncFailure finished, took <TIME>
 liTest org.scalajs.junit.AsyncTest.expectedException started
 ldTest org.scalajs.junit.AsyncTest.expectedException finished, took <TIME>
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 liTest org.scalajs.junit.AsyncTest.success started
 ldTest org.scalajs.junit.AsyncTest.success finished, took <TIME>
-e0org.scalajs.junit.AsyncTest.success
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 liTest run finished: 1 failed, 0 ignored, 3 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_v.txt b/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_v.txt
index 3ed7f28ec6..4196d95050 100644
--- a/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_v.txt
+++ b/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_v.txt
@@ -1,13 +1,13 @@
 liTest run started
 liTest org.scalajs.junit.AsyncTest.asyncFailure started
 leTest org.scalajs.junit.AsyncTest.asyncFailure failed: java.lang.IllegalArgumentException: null, took <TIME>
-e2org.scalajs.junit.AsyncTest.asyncFailure
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 ldTest org.scalajs.junit.AsyncTest.asyncFailure finished, took <TIME>
 liTest org.scalajs.junit.AsyncTest.expectedException started
 ldTest org.scalajs.junit.AsyncTest.expectedException finished, took <TIME>
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 liTest org.scalajs.junit.AsyncTest.success started
 ldTest org.scalajs.junit.AsyncTest.success finished, took <TIME>
-e0org.scalajs.junit.AsyncTest.success
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 liTest run finished: 1 failed, 0 ignored, 3 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_va.txt b/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_va.txt
index 3ed7f28ec6..4196d95050 100644
--- a/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_va.txt
+++ b/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_va.txt
@@ -1,13 +1,13 @@
 liTest run started
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 leTest org.scalajs.junit.AsyncTest.asyncFailure failed: java.lang.IllegalArgumentException: null, took <TIME>
-e2org.scalajs.junit.AsyncTest.asyncFailure
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 ldTest org.scalajs.junit.AsyncTest.asyncFailure finished, took <TIME>
 liTest org.scalajs.junit.AsyncTest.expectedException started
 ldTest org.scalajs.junit.AsyncTest.expectedException finished, took <TIME>
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 liTest org.scalajs.junit.AsyncTest.success started
 ldTest org.scalajs.junit.AsyncTest.success finished, took <TIME>
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 liTest run finished: 1 failed, 0 ignored, 3 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_vc.txt b/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_vc.txt
index 7a89203ee1..a87fc04a85 100644
--- a/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_vc.txt
+++ b/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_vc.txt
@@ -1,13 +1,13 @@
 liTest run started
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 leTest org.scalajs.junit.AsyncTest.asyncFailure failed: null, took <TIME>
-e2org.scalajs.junit.AsyncTest.asyncFailure
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 ldTest org.scalajs.junit.AsyncTest.asyncFailure finished, took <TIME>
 liTest org.scalajs.junit.AsyncTest.expectedException started
 ldTest org.scalajs.junit.AsyncTest.expectedException finished, took <TIME>
-e0org.scalajs.junit.AsyncTest.expectedException
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 liTest org.scalajs.junit.AsyncTest.success started
 ldTest org.scalajs.junit.AsyncTest.success finished, took <TIME>
-e0org.scalajs.junit.AsyncTest.success
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 liTest run finished: 1 failed, 0 ignored, 3 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_vs.txt b/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_vs.txt
index 3ed7f28ec6..4196d95050 100644
--- a/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_vs.txt
+++ b/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_vs.txt
@@ -1,13 +1,13 @@
 liTest run started
 liTest org.scalajs.junit.AsyncTest.asyncFailure started
 leTest org.scalajs.junit.AsyncTest.asyncFailure failed: java.lang.IllegalArgumentException: null, took <TIME>
-e2org.scalajs.junit.AsyncTest.asyncFailure
+e2org.scalajs.junit.AsyncTest.asyncFailure::java.lang.IllegalArgumentException
 ldTest org.scalajs.junit.AsyncTest.asyncFailure finished, took <TIME>
 liTest org.scalajs.junit.AsyncTest.expectedException started
 ldTest org.scalajs.junit.AsyncTest.expectedException finished, took <TIME>
-e0org.scalajs.junit.AsyncTest.expectedException
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 liTest org.scalajs.junit.AsyncTest.success started
 ldTest org.scalajs.junit.AsyncTest.success finished, took <TIME>
-e0org.scalajs.junit.AsyncTest.success
+e0org.scalajs.junit.AsyncTest.success::
 liTest run finished: 1 failed, 0 ignored, 3 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_vsn.txt b/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_vsn.txt
index 622f617605..6583d223dc 100644
--- a/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_vsn.txt
+++ b/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_vsn.txt
@@ -1,13 +1,13 @@
 liTest run started
 liTest org.scalajs.junit.AsyncTest.asyncFailure started
 leTest org.scalajs.junit.AsyncTest.asyncFailure failed: java.lang.IllegalArgumentException: null, took <TIME>
-e2org.scalajs.junit.AsyncTest.asyncFailure
+e2org.scalajs.junit.AsyncTest.asyncFailure::java.lang.IllegalArgumentException
 ldTest org.scalajs.junit.AsyncTest.asyncFailure finished, took <TIME>
 liTest org.scalajs.junit.AsyncTest.expectedException started
 ldTest org.scalajs.junit.AsyncTest.expectedException finished, took <TIME>
-e0org.scalajs.junit.AsyncTest.expectedException
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 liTest org.scalajs.junit.AsyncTest.success started
 ldTest org.scalajs.junit.AsyncTest.success finished, took <TIME>
-e0org.scalajs.junit.AsyncTest.success
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 liTest run finished: 1 failed, 0 ignored, 3 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_.txt b/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_.txt
index fbe95e78c0..9b12c6c05e 100644
--- a/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_.txt
+++ b/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_.txt
@@ -1,6 +1,6 @@
 ldTest run started
 ldTest org.scalajs.junit.BeforeAndAfterTest.test started
 ldTest org.scalajs.junit.BeforeAndAfterTest.test finished, took <TIME>
-e0org.scalajs.junit.BeforeAndAfterTest.test
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 ldTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_a.txt b/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_a.txt
index fbe95e78c0..9b12c6c05e 100644
--- a/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_a.txt
+++ b/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_a.txt
@@ -1,6 +1,6 @@
 ldTest run started
 ldTest org.scalajs.junit.BeforeAndAfterTest.test started
 ldTest org.scalajs.junit.BeforeAndAfterTest.test finished, took <TIME>
-e0org.scalajs.junit.BeforeAndAfterTest.test
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 ldTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_n.txt b/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_n.txt
index f8f4caeceb..137e029bcb 100644
--- a/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_n.txt
+++ b/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_n.txt
@@ -1,6 +1,6 @@
 ldTest run started
 ldTest org.scalajs.junit.BeforeAndAfterTest.test started
 ldTest org.scalajs.junit.BeforeAndAfterTest.test finished, took <TIME>
-e0org.scalajs.junit.BeforeAndAfterTest.test
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 ldTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_na.txt b/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_na.txt
index f8f4caeceb..137e029bcb 100644
--- a/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_na.txt
+++ b/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_na.txt
@@ -1,6 +1,6 @@
 ldTest run started
 ldTest org.scalajs.junit.BeforeAndAfterTest.test started
 ldTest org.scalajs.junit.BeforeAndAfterTest.test finished, took <TIME>
-e0org.scalajs.junit.BeforeAndAfterTest.test
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 ldTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_nv.txt b/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_nv.txt
index ac74accf38..d018185503 100644
--- a/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_nv.txt
+++ b/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_nv.txt
@@ -1,6 +1,6 @@
 liTest run started
 liTest org.scalajs.junit.BeforeAndAfterTest.test started
 ldTest org.scalajs.junit.BeforeAndAfterTest.test finished, took <TIME>
-e0org.scalajs.junit.BeforeAndAfterTest.test
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 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_nva.txt b/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_nva.txt
index ac74accf38..d018185503 100644
--- a/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_nva.txt
+++ b/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_nva.txt
@@ -1,6 +1,6 @@
 liTest run started
 liTest org.scalajs.junit.BeforeAndAfterTest.test started
 ldTest org.scalajs.junit.BeforeAndAfterTest.test finished, took <TIME>
-e0org.scalajs.junit.BeforeAndAfterTest.test
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 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_nvc.txt b/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_nvc.txt
index ac74accf38..d018185503 100644
--- a/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_nvc.txt
+++ b/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_nvc.txt
@@ -1,6 +1,6 @@
 liTest run started
 liTest org.scalajs.junit.BeforeAndAfterTest.test started
 ldTest org.scalajs.junit.BeforeAndAfterTest.test finished, took <TIME>
-e0org.scalajs.junit.BeforeAndAfterTest.test
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 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_nvca.txt b/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_nvca.txt
index ac74accf38..d018185503 100644
--- a/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_nvca.txt
+++ b/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_nvca.txt
@@ -1,6 +1,6 @@
 liTest run started
 liTest org.scalajs.junit.BeforeAndAfterTest.test started
 ldTest org.scalajs.junit.BeforeAndAfterTest.test finished, took <TIME>
-e0org.scalajs.junit.BeforeAndAfterTest.test
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 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_v.txt b/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_v.txt
index ef2a1696a9..e1003375a5 100644
--- a/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_v.txt
+++ b/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_v.txt
@@ -1,6 +1,6 @@
 liTest run started
 liTest org.scalajs.junit.BeforeAndAfterTest.test started
 ldTest org.scalajs.junit.BeforeAndAfterTest.test finished, took <TIME>
-e0org.scalajs.junit.BeforeAndAfterTest.test
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 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_va.txt b/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_va.txt
index ef2a1696a9..e1003375a5 100644
--- a/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_va.txt
+++ b/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_va.txt
@@ -1,6 +1,6 @@
 liTest run started
 liTest org.scalajs.junit.BeforeAndAfterTest.test started
 ldTest org.scalajs.junit.BeforeAndAfterTest.test finished, took <TIME>
-e0org.scalajs.junit.BeforeAndAfterTest.test
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 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_vc.txt b/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_vc.txt
index ef2a1696a9..e1003375a5 100644
--- a/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_vc.txt
+++ b/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_vc.txt
@@ -1,6 +1,6 @@
 liTest run started
 liTest org.scalajs.junit.BeforeAndAfterTest.test started
 ldTest org.scalajs.junit.BeforeAndAfterTest.test finished, took <TIME>
-e0org.scalajs.junit.BeforeAndAfterTest.test
+e0org.scalajs.junit.BeforeAndAfterTest.test::
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_vs.txt b/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_vs.txt
index ef2a1696a9..e1003375a5 100644
--- a/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_vs.txt
+++ b/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_vs.txt
@@ -1,6 +1,6 @@
 liTest run started
 liTest org.scalajs.junit.BeforeAndAfterTest.test started
 ldTest org.scalajs.junit.BeforeAndAfterTest.test finished, took <TIME>
-e0org.scalajs.junit.BeforeAndAfterTest.test
+e0org.scalajs.junit.BeforeAndAfterTest.test::
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_vsn.txt b/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_vsn.txt
index ac74accf38..d018185503 100644
--- a/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_vsn.txt
+++ b/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_vsn.txt
@@ -1,6 +1,6 @@
 liTest run started
 liTest org.scalajs.junit.BeforeAndAfterTest.test started
 ldTest org.scalajs.junit.BeforeAndAfterTest.test finished, took <TIME>
-e0org.scalajs.junit.BeforeAndAfterTest.test
+e0org.scalajs.junit.BeforeAndAfterTest.test::
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_.txt b/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_.txt
index 6f8890e545..3e25af9a55 100644
--- a/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_.txt
+++ b/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_.txt
@@ -1,5 +1,5 @@
 ldTest run started
 lwTest assumption in test org.scalajs.junit.BeforeAssumeFailTest failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.BeforeAssumeFailTest
+e3org.scalajs.junit.BeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest run finished: 0 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_a.txt b/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_a.txt
index 6f8890e545..3e25af9a55 100644
--- a/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_a.txt
+++ b/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_a.txt
@@ -1,5 +1,5 @@
 ldTest run started
 lwTest assumption in test org.scalajs.junit.BeforeAssumeFailTest failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.BeforeAssumeFailTest
+e3org.scalajs.junit.BeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest run finished: 0 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_n.txt b/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_n.txt
index 5e5f0cfa5f..6cff2ae7b5 100644
--- a/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_n.txt
+++ b/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_n.txt
@@ -1,5 +1,5 @@
 ldTest run started
 lwTest assumption in test org.scalajs.junit.BeforeAssumeFailTest failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.BeforeAssumeFailTest
+e3org.scalajs.junit.BeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest run finished: 0 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_na.txt b/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_na.txt
index 5e5f0cfa5f..6cff2ae7b5 100644
--- a/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_na.txt
+++ b/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_na.txt
@@ -1,5 +1,5 @@
 ldTest run started
 lwTest assumption in test org.scalajs.junit.BeforeAssumeFailTest failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.BeforeAssumeFailTest
+e3org.scalajs.junit.BeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest run finished: 0 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_nv.txt b/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_nv.txt
index c4339d408b..e2195fcc62 100644
--- a/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_nv.txt
+++ b/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_nv.txt
@@ -1,5 +1,5 @@
 liTest run started
 lwTest assumption in test org.scalajs.junit.BeforeAssumeFailTest failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.BeforeAssumeFailTest
+e3org.scalajs.junit.BeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass
 liTest run finished: 0 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_nva.txt b/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_nva.txt
index c4339d408b..e2195fcc62 100644
--- a/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_nva.txt
+++ b/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_nva.txt
@@ -1,5 +1,5 @@
 liTest run started
 lwTest assumption in test org.scalajs.junit.BeforeAssumeFailTest failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.BeforeAssumeFailTest
+e3org.scalajs.junit.BeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass
 liTest run finished: 0 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_nvc.txt b/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_nvc.txt
index fe8aa92ca9..02bee59865 100644
--- a/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_nvc.txt
+++ b/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_nvc.txt
@@ -1,5 +1,5 @@
 liTest run started
 lwTest assumption in test org.scalajs.junit.BeforeAssumeFailTest failed: This assume should not pass, took <TIME>
-e3org.scalajs.junit.BeforeAssumeFailTest
+e3org.scalajs.junit.BeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass
 liTest run finished: 0 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_nvca.txt b/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_nvca.txt
index fe8aa92ca9..02bee59865 100644
--- a/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_nvca.txt
+++ b/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_nvca.txt
@@ -1,5 +1,5 @@
 liTest run started
 lwTest assumption in test org.scalajs.junit.BeforeAssumeFailTest failed: This assume should not pass, took <TIME>
-e3org.scalajs.junit.BeforeAssumeFailTest
+e3org.scalajs.junit.BeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass
 liTest run finished: 0 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_v.txt b/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_v.txt
index 22da50f9c8..c3b0f4cbd0 100644
--- a/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_v.txt
+++ b/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_v.txt
@@ -1,5 +1,5 @@
 liTest run started
 lwTest assumption in test org.scalajs.junit.BeforeAssumeFailTest failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.BeforeAssumeFailTest
+e3org.scalajs.junit.BeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass
 liTest run finished: 0 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_va.txt b/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_va.txt
index 22da50f9c8..c3b0f4cbd0 100644
--- a/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_va.txt
+++ b/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_va.txt
@@ -1,5 +1,5 @@
 liTest run started
 lwTest assumption in test org.scalajs.junit.BeforeAssumeFailTest failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.BeforeAssumeFailTest
+e3org.scalajs.junit.BeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass
 liTest run finished: 0 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_vc.txt b/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_vc.txt
index 5af600271f..fa4723fe92 100644
--- a/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_vc.txt
+++ b/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_vc.txt
@@ -1,5 +1,5 @@
 liTest run started
 lwTest assumption in test org.scalajs.junit.BeforeAssumeFailTest failed: This assume should not pass, took <TIME>
-e3org.scalajs.junit.BeforeAssumeFailTest
+e3org.scalajs.junit.BeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass
 liTest run finished: 0 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_vs.txt b/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_vs.txt
index 22da50f9c8..c3b0f4cbd0 100644
--- a/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_vs.txt
+++ b/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_vs.txt
@@ -1,5 +1,5 @@
 liTest run started
 lwTest assumption in test org.scalajs.junit.BeforeAssumeFailTest failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.BeforeAssumeFailTest
+e3org.scalajs.junit.BeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass
 liTest run finished: 0 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_vsn.txt b/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_vsn.txt
index c4339d408b..e2195fcc62 100644
--- a/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_vsn.txt
+++ b/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_vsn.txt
@@ -1,5 +1,5 @@
 liTest run started
 lwTest assumption in test org.scalajs.junit.BeforeAssumeFailTest failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.BeforeAssumeFailTest
+e3org.scalajs.junit.BeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass
 liTest run finished: 0 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_.txt b/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_.txt
index eb667a9c42..60eff1daad 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_.txt
@@ -2,7 +2,7 @@ ldTest run started
 ldTest org.scalajs.junit.ExceptionAfterAssume.assumeFail started
 leTest org.scalajs.junit.ExceptionAfterAssume.assumeFail failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
-e2org.scalajs.junit.ExceptionAfterAssume.assumeFail
+e2org.scalajs.junit.ExceptionAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures
 leTest org.scalajs.junit.ExceptionAfterAssume.assumeFail failed: java.lang.IllegalArgumentException: after() must be called, took <TIME>
 ldTest org.scalajs.junit.ExceptionAfterAssume.assumeFail finished, took <TIME>
 ldTest run finished: 2 failed, 0 ignored, 1 total, <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_a.txt b/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_a.txt
index eb667a9c42..60eff1daad 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_a.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_a.txt
@@ -2,7 +2,7 @@ ldTest run started
 ldTest org.scalajs.junit.ExceptionAfterAssume.assumeFail started
 leTest org.scalajs.junit.ExceptionAfterAssume.assumeFail failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
-e2org.scalajs.junit.ExceptionAfterAssume.assumeFail
+e2org.scalajs.junit.ExceptionAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures
 leTest org.scalajs.junit.ExceptionAfterAssume.assumeFail failed: java.lang.IllegalArgumentException: after() must be called, took <TIME>
 ldTest org.scalajs.junit.ExceptionAfterAssume.assumeFail finished, took <TIME>
 ldTest run finished: 2 failed, 0 ignored, 1 total, <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_n.txt b/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_n.txt
index 838646d72d..326ed5462d 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_n.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_n.txt
@@ -2,7 +2,7 @@ ldTest run started
 ldTest org.scalajs.junit.ExceptionAfterAssume.assumeFail started
 leTest org.scalajs.junit.ExceptionAfterAssume.assumeFail failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
-e2org.scalajs.junit.ExceptionAfterAssume.assumeFail
+e2org.scalajs.junit.ExceptionAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures
 leTest org.scalajs.junit.ExceptionAfterAssume.assumeFail failed: java.lang.IllegalArgumentException: after() must be called, took <TIME>
 ldTest org.scalajs.junit.ExceptionAfterAssume.assumeFail finished, took <TIME>
 ldTest run finished: 2 failed, 0 ignored, 1 total, <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_na.txt b/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_na.txt
index 838646d72d..326ed5462d 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_na.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_na.txt
@@ -2,7 +2,7 @@ ldTest run started
 ldTest org.scalajs.junit.ExceptionAfterAssume.assumeFail started
 leTest org.scalajs.junit.ExceptionAfterAssume.assumeFail failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
-e2org.scalajs.junit.ExceptionAfterAssume.assumeFail
+e2org.scalajs.junit.ExceptionAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures
 leTest org.scalajs.junit.ExceptionAfterAssume.assumeFail failed: java.lang.IllegalArgumentException: after() must be called, took <TIME>
 ldTest org.scalajs.junit.ExceptionAfterAssume.assumeFail finished, took <TIME>
 ldTest run finished: 2 failed, 0 ignored, 1 total, <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_nv.txt b/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_nv.txt
index beed89fe3e..2299664b94 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_nv.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_nv.txt
@@ -2,7 +2,7 @@ liTest run started
 liTest org.scalajs.junit.ExceptionAfterAssume.assumeFail started
 leTest org.scalajs.junit.ExceptionAfterAssume.assumeFail failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
-e2org.scalajs.junit.ExceptionAfterAssume.assumeFail
+e2org.scalajs.junit.ExceptionAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures
 leTest org.scalajs.junit.ExceptionAfterAssume.assumeFail failed: java.lang.IllegalArgumentException: after() must be called, took <TIME>
 ldTest org.scalajs.junit.ExceptionAfterAssume.assumeFail finished, took <TIME>
 liTest run finished: 2 failed, 0 ignored, 1 total, <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_nva.txt b/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_nva.txt
index beed89fe3e..2299664b94 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_nva.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_nva.txt
@@ -2,7 +2,7 @@ liTest run started
 liTest org.scalajs.junit.ExceptionAfterAssume.assumeFail started
 leTest org.scalajs.junit.ExceptionAfterAssume.assumeFail failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
-e2org.scalajs.junit.ExceptionAfterAssume.assumeFail
+e2org.scalajs.junit.ExceptionAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures
 leTest org.scalajs.junit.ExceptionAfterAssume.assumeFail failed: java.lang.IllegalArgumentException: after() must be called, took <TIME>
 ldTest org.scalajs.junit.ExceptionAfterAssume.assumeFail finished, took <TIME>
 liTest run finished: 2 failed, 0 ignored, 1 total, <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_nvc.txt b/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_nvc.txt
index 111a0ec574..89f146aa5b 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_nvc.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_nvc.txt
@@ -2,7 +2,7 @@ liTest run started
 liTest org.scalajs.junit.ExceptionAfterAssume.assumeFail started
 leTest org.scalajs.junit.ExceptionAfterAssume.assumeFail failed: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
-e2org.scalajs.junit.ExceptionAfterAssume.assumeFail
+e2org.scalajs.junit.ExceptionAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures
 leTest org.scalajs.junit.ExceptionAfterAssume.assumeFail failed: after() must be called, took <TIME>
 ldTest org.scalajs.junit.ExceptionAfterAssume.assumeFail finished, took <TIME>
 liTest run finished: 2 failed, 0 ignored, 1 total, <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_nvca.txt b/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_nvca.txt
index 111a0ec574..89f146aa5b 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_nvca.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_nvca.txt
@@ -2,7 +2,7 @@ liTest run started
 liTest org.scalajs.junit.ExceptionAfterAssume.assumeFail started
 leTest org.scalajs.junit.ExceptionAfterAssume.assumeFail failed: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
-e2org.scalajs.junit.ExceptionAfterAssume.assumeFail
+e2org.scalajs.junit.ExceptionAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures
 leTest org.scalajs.junit.ExceptionAfterAssume.assumeFail failed: after() must be called, took <TIME>
 ldTest org.scalajs.junit.ExceptionAfterAssume.assumeFail finished, took <TIME>
 liTest run finished: 2 failed, 0 ignored, 1 total, <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_v.txt b/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_v.txt
index 8d547454f4..9565096712 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_v.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_v.txt
@@ -2,7 +2,7 @@ liTest run started
 liTest org.scalajs.junit.ExceptionAfterAssume.assumeFail started
 leTest org.scalajs.junit.ExceptionAfterAssume.assumeFail failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
-e2org.scalajs.junit.ExceptionAfterAssume.assumeFail
+e2org.scalajs.junit.ExceptionAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures
 leTest org.scalajs.junit.ExceptionAfterAssume.assumeFail failed: java.lang.IllegalArgumentException: after() must be called, took <TIME>
 ldTest org.scalajs.junit.ExceptionAfterAssume.assumeFail finished, took <TIME>
 liTest run finished: 2 failed, 0 ignored, 1 total, <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_va.txt b/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_va.txt
index 8d547454f4..9565096712 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_va.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_va.txt
@@ -2,7 +2,7 @@ liTest run started
 liTest org.scalajs.junit.ExceptionAfterAssume.assumeFail started
 leTest org.scalajs.junit.ExceptionAfterAssume.assumeFail failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
-e2org.scalajs.junit.ExceptionAfterAssume.assumeFail
+e2org.scalajs.junit.ExceptionAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures
 leTest org.scalajs.junit.ExceptionAfterAssume.assumeFail failed: java.lang.IllegalArgumentException: after() must be called, took <TIME>
 ldTest org.scalajs.junit.ExceptionAfterAssume.assumeFail finished, took <TIME>
 liTest run finished: 2 failed, 0 ignored, 1 total, <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_vc.txt b/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_vc.txt
index 3a045cfbc2..83d810b8c7 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_vc.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_vc.txt
@@ -2,7 +2,7 @@ liTest run started
 liTest org.scalajs.junit.ExceptionAfterAssume.assumeFail started
 leTest org.scalajs.junit.ExceptionAfterAssume.assumeFail failed: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
-e2org.scalajs.junit.ExceptionAfterAssume.assumeFail
+e2org.scalajs.junit.ExceptionAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures
 leTest org.scalajs.junit.ExceptionAfterAssume.assumeFail failed: after() must be called, took <TIME>
 ldTest org.scalajs.junit.ExceptionAfterAssume.assumeFail finished, took <TIME>
 liTest run finished: 2 failed, 0 ignored, 1 total, <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_vs.txt b/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_vs.txt
index 8d547454f4..9565096712 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_vs.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_vs.txt
@@ -2,7 +2,7 @@ liTest run started
 liTest org.scalajs.junit.ExceptionAfterAssume.assumeFail started
 leTest org.scalajs.junit.ExceptionAfterAssume.assumeFail failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
-e2org.scalajs.junit.ExceptionAfterAssume.assumeFail
+e2org.scalajs.junit.ExceptionAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures
 leTest org.scalajs.junit.ExceptionAfterAssume.assumeFail failed: java.lang.IllegalArgumentException: after() must be called, took <TIME>
 ldTest org.scalajs.junit.ExceptionAfterAssume.assumeFail finished, took <TIME>
 liTest run finished: 2 failed, 0 ignored, 1 total, <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_vsn.txt b/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_vsn.txt
index beed89fe3e..2299664b94 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_vsn.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_vsn.txt
@@ -2,7 +2,7 @@ liTest run started
 liTest org.scalajs.junit.ExceptionAfterAssume.assumeFail started
 leTest org.scalajs.junit.ExceptionAfterAssume.assumeFail failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
-e2org.scalajs.junit.ExceptionAfterAssume.assumeFail
+e2org.scalajs.junit.ExceptionAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures
 leTest org.scalajs.junit.ExceptionAfterAssume.assumeFail failed: java.lang.IllegalArgumentException: after() must be called, took <TIME>
 ldTest org.scalajs.junit.ExceptionAfterAssume.assumeFail finished, took <TIME>
 liTest run finished: 2 failed, 0 ignored, 1 total, <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_.txt b/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_.txt
index 125a33b00d..9297a9663c 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_.txt
@@ -1,11 +1,11 @@
 ldTest run started
 ldTest org.scalajs.junit.ExceptionAfterClass.test1 started
 ldTest org.scalajs.junit.ExceptionAfterClass.test1 finished, took <TIME>
-e0org.scalajs.junit.ExceptionAfterClass.test1
+e0org.scalajs.junit.ExceptionAfterClass.test1::
 ldTest org.scalajs.junit.ExceptionAfterClass.test2 started
 ldTest org.scalajs.junit.ExceptionAfterClass.test2 finished, took <TIME>
-e0org.scalajs.junit.ExceptionAfterClass.test2
+e0org.scalajs.junit.ExceptionAfterClass.test2::
 leTest org.scalajs.junit.ExceptionAfterClass failed: java.lang.IllegalArgumentException: foo, took <TIME>
-e2org.scalajs.junit.ExceptionAfterClass
+e2org.scalajs.junit.ExceptionAfterClass::java.lang.IllegalArgumentException: foo
 ldTest run finished: 1 failed, 0 ignored, 2 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_a.txt b/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_a.txt
index 125a33b00d..9297a9663c 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_a.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_a.txt
@@ -1,11 +1,11 @@
 ldTest run started
 ldTest org.scalajs.junit.ExceptionAfterClass.test1 started
 ldTest org.scalajs.junit.ExceptionAfterClass.test1 finished, took <TIME>
-e0org.scalajs.junit.ExceptionAfterClass.test1
+e0org.scalajs.junit.ExceptionAfterClass.test1::
 ldTest org.scalajs.junit.ExceptionAfterClass.test2 started
 ldTest org.scalajs.junit.ExceptionAfterClass.test2 finished, took <TIME>
-e0org.scalajs.junit.ExceptionAfterClass.test2
+e0org.scalajs.junit.ExceptionAfterClass.test2::
 leTest org.scalajs.junit.ExceptionAfterClass failed: java.lang.IllegalArgumentException: foo, took <TIME>
-e2org.scalajs.junit.ExceptionAfterClass
+e2org.scalajs.junit.ExceptionAfterClass::java.lang.IllegalArgumentException: foo
 ldTest run finished: 1 failed, 0 ignored, 2 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_n.txt b/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_n.txt
index 89f0a45d7d..49d2ed086c 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_n.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_n.txt
@@ -1,11 +1,11 @@
 ldTest run started
 ldTest org.scalajs.junit.ExceptionAfterClass.test1 started
 ldTest org.scalajs.junit.ExceptionAfterClass.test1 finished, took <TIME>
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-e0org.scalajs.junit.ExceptionAfterClass.test2
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 leTest org.scalajs.junit.ExceptionAfterClass failed: java.lang.IllegalArgumentException: foo, took <TIME>
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 ldTest run finished: 1 failed, 0 ignored, 2 total, <TIME>
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diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_na.txt b/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_na.txt
index 89f0a45d7d..49d2ed086c 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_na.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_na.txt
@@ -1,11 +1,11 @@
 ldTest run started
 ldTest org.scalajs.junit.ExceptionAfterClass.test1 started
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-e0org.scalajs.junit.ExceptionAfterClass.test2
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 leTest org.scalajs.junit.ExceptionAfterClass failed: java.lang.IllegalArgumentException: foo, took <TIME>
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 ldTest run finished: 1 failed, 0 ignored, 2 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_nv.txt b/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_nv.txt
index 87c112e080..cc8d30ef2c 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_nv.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_nv.txt
@@ -1,11 +1,11 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionAfterClass.test1 started
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 leTest org.scalajs.junit.ExceptionAfterClass failed: java.lang.IllegalArgumentException: foo, took <TIME>
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 liTest run finished: 1 failed, 0 ignored, 2 total, <TIME>
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diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_nva.txt b/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_nva.txt
index 87c112e080..cc8d30ef2c 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_nva.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_nva.txt
@@ -1,11 +1,11 @@
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 liTest run finished: 1 failed, 0 ignored, 2 total, <TIME>
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diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_nvc.txt b/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_nvc.txt
index ff759de2ba..03ccfa39d6 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_nvc.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_nvc.txt
@@ -1,11 +1,11 @@
 liTest run started
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diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_nvca.txt b/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_nvca.txt
index ff759de2ba..03ccfa39d6 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_nvca.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_nvca.txt
@@ -1,11 +1,11 @@
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diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_v.txt b/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_v.txt
index a717a4fae5..c27ec46ef9 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_v.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_v.txt
@@ -1,11 +1,11 @@
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 liTest run finished: 1 failed, 0 ignored, 2 total, <TIME>
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diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_va.txt b/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_va.txt
index a717a4fae5..c27ec46ef9 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_va.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_va.txt
@@ -1,11 +1,11 @@
 liTest run started
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diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_vc.txt b/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_vc.txt
index cba43ae5b4..b3bc1ef216 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_vc.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_vc.txt
@@ -1,11 +1,11 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionAfterClass.test1 started
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diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_vs.txt b/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_vs.txt
index a717a4fae5..c27ec46ef9 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_vs.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_vs.txt
@@ -1,11 +1,11 @@
 liTest run started
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 liTest run finished: 1 failed, 0 ignored, 2 total, <TIME>
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diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_vsn.txt b/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_vsn.txt
index 87c112e080..cc8d30ef2c 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_vsn.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_vsn.txt
@@ -1,11 +1,11 @@
 liTest run started
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 liTest run finished: 1 failed, 0 ignored, 2 total, <TIME>
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diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_.txt b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_.txt
index 9a4be9f39f..21020ec657 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_.txt
@@ -1,6 +1,6 @@
 ldTest run started
 leTest org.scalajs.junit.ExceptionBeforeAndAfterClass failed: before, took <TIME>
-e2org.scalajs.junit.ExceptionBeforeAndAfterClass
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diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_a.txt b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_a.txt
index f7bf74e3f1..842ee1e9d3 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_a.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_a.txt
@@ -1,6 +1,6 @@
 ldTest run started
 leTest org.scalajs.junit.ExceptionBeforeAndAfterClass failed: java.lang.AssertionError: before, took <TIME>
-e2org.scalajs.junit.ExceptionBeforeAndAfterClass
+e2org.scalajs.junit.ExceptionBeforeAndAfterClass::java.lang.AssertionError: before
 leTest org.scalajs.junit.ExceptionBeforeAndAfterClass failed: java.lang.IllegalArgumentException: after, took <TIME>
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diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_n.txt b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_n.txt
index c7506cc969..67272652bd 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_n.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_n.txt
@@ -1,6 +1,6 @@
 ldTest run started
 leTest org.scalajs.junit.ExceptionBeforeAndAfterClass failed: before, took <TIME>
-e2org.scalajs.junit.ExceptionBeforeAndAfterClass
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 leTest org.scalajs.junit.ExceptionBeforeAndAfterClass failed: java.lang.IllegalArgumentException: after, took <TIME>
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diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_na.txt b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_na.txt
index 1a306375eb..e31ffe9d36 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_na.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_na.txt
@@ -1,6 +1,6 @@
 ldTest run started
 leTest org.scalajs.junit.ExceptionBeforeAndAfterClass failed: java.lang.AssertionError: before, took <TIME>
-e2org.scalajs.junit.ExceptionBeforeAndAfterClass
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diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_nv.txt b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_nv.txt
index 775e5448ea..64f96715ed 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_nv.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_nv.txt
@@ -1,6 +1,6 @@
 liTest run started
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diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_nva.txt b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_nva.txt
index 8647dbaf1d..2c12da8d97 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_nva.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_nva.txt
@@ -1,6 +1,6 @@
 liTest run started
 leTest org.scalajs.junit.ExceptionBeforeAndAfterClass failed: java.lang.AssertionError: before, took <TIME>
-e2org.scalajs.junit.ExceptionBeforeAndAfterClass
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diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_nvc.txt b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_nvc.txt
index e975be6178..39ba700989 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_nvc.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_nvc.txt
@@ -1,6 +1,6 @@
 liTest run started
 leTest org.scalajs.junit.ExceptionBeforeAndAfterClass failed: before, took <TIME>
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diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_nvca.txt b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_nvca.txt
index e975be6178..39ba700989 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_nvca.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_nvca.txt
@@ -1,6 +1,6 @@
 liTest run started
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-e2org.scalajs.junit.ExceptionBeforeAndAfterClass
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diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_v.txt b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_v.txt
index 14b89cc88a..dcea945692 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_v.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_v.txt
@@ -1,6 +1,6 @@
 liTest run started
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diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_va.txt b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_va.txt
index 6b906a04eb..f37328933a 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_va.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_va.txt
@@ -1,6 +1,6 @@
 liTest run started
 leTest org.scalajs.junit.ExceptionBeforeAndAfterClass failed: java.lang.AssertionError: before, took <TIME>
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diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_vc.txt b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_vc.txt
index a12d881bdc..36cdde8136 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_vc.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_vc.txt
@@ -1,6 +1,6 @@
 liTest run started
 leTest org.scalajs.junit.ExceptionBeforeAndAfterClass failed: before, took <TIME>
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diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_vs.txt b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_vs.txt
index 14b89cc88a..dcea945692 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_vs.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_vs.txt
@@ -1,6 +1,6 @@
 liTest run started
 leTest org.scalajs.junit.ExceptionBeforeAndAfterClass failed: before, took <TIME>
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 leTest org.scalajs.junit.ExceptionBeforeAndAfterClass failed: java.lang.IllegalArgumentException: after, took <TIME>
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diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_vsn.txt b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_vsn.txt
index 775e5448ea..64f96715ed 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_vsn.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_vsn.txt
@@ -1,6 +1,6 @@
 liTest run started
 leTest org.scalajs.junit.ExceptionBeforeAndAfterClass failed: before, took <TIME>
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diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_.txt b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_.txt
index 62acb72068..6f86d87d17 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_.txt
@@ -1,5 +1,5 @@
 ldTest run started
 leTest org.scalajs.junit.ExceptionBeforeClass failed: java.lang.IllegalArgumentException: foo, took <TIME>
-e2org.scalajs.junit.ExceptionBeforeClass
+e2org.scalajs.junit.ExceptionBeforeClass::java.lang.IllegalArgumentException: foo
 ldTest run finished: 1 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_a.txt b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_a.txt
index 62acb72068..6f86d87d17 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_a.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_a.txt
@@ -1,5 +1,5 @@
 ldTest run started
 leTest org.scalajs.junit.ExceptionBeforeClass failed: java.lang.IllegalArgumentException: foo, took <TIME>
-e2org.scalajs.junit.ExceptionBeforeClass
+e2org.scalajs.junit.ExceptionBeforeClass::java.lang.IllegalArgumentException: foo
 ldTest run finished: 1 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_n.txt b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_n.txt
index f0581e1e07..e49141f66a 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_n.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_n.txt
@@ -1,5 +1,5 @@
 ldTest run started
 leTest org.scalajs.junit.ExceptionBeforeClass failed: java.lang.IllegalArgumentException: foo, took <TIME>
-e2org.scalajs.junit.ExceptionBeforeClass
+e2org.scalajs.junit.ExceptionBeforeClass::java.lang.IllegalArgumentException: foo
 ldTest run finished: 1 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_na.txt b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_na.txt
index f0581e1e07..e49141f66a 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_na.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_na.txt
@@ -1,5 +1,5 @@
 ldTest run started
 leTest org.scalajs.junit.ExceptionBeforeClass failed: java.lang.IllegalArgumentException: foo, took <TIME>
-e2org.scalajs.junit.ExceptionBeforeClass
+e2org.scalajs.junit.ExceptionBeforeClass::java.lang.IllegalArgumentException: foo
 ldTest run finished: 1 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_nv.txt b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_nv.txt
index bec46ad160..f57776bd63 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_nv.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_nv.txt
@@ -1,5 +1,5 @@
 liTest run started
 leTest org.scalajs.junit.ExceptionBeforeClass failed: java.lang.IllegalArgumentException: foo, took <TIME>
-e2org.scalajs.junit.ExceptionBeforeClass
+e2org.scalajs.junit.ExceptionBeforeClass::java.lang.IllegalArgumentException: foo
 liTest run finished: 1 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_nva.txt b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_nva.txt
index bec46ad160..f57776bd63 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_nva.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_nva.txt
@@ -1,5 +1,5 @@
 liTest run started
 leTest org.scalajs.junit.ExceptionBeforeClass failed: java.lang.IllegalArgumentException: foo, took <TIME>
-e2org.scalajs.junit.ExceptionBeforeClass
+e2org.scalajs.junit.ExceptionBeforeClass::java.lang.IllegalArgumentException: foo
 liTest run finished: 1 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_nvc.txt b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_nvc.txt
index 86a7077113..d5cdbe1efd 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_nvc.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_nvc.txt
@@ -1,5 +1,5 @@
 liTest run started
 leTest org.scalajs.junit.ExceptionBeforeClass failed: foo, took <TIME>
-e2org.scalajs.junit.ExceptionBeforeClass
+e2org.scalajs.junit.ExceptionBeforeClass::java.lang.IllegalArgumentException: foo
 liTest run finished: 1 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_nvca.txt b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_nvca.txt
index 86a7077113..d5cdbe1efd 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_nvca.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_nvca.txt
@@ -1,5 +1,5 @@
 liTest run started
 leTest org.scalajs.junit.ExceptionBeforeClass failed: foo, took <TIME>
-e2org.scalajs.junit.ExceptionBeforeClass
+e2org.scalajs.junit.ExceptionBeforeClass::java.lang.IllegalArgumentException: foo
 liTest run finished: 1 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_v.txt b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_v.txt
index 568c70b998..ce2f836a74 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_v.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_v.txt
@@ -1,5 +1,5 @@
 liTest run started
 leTest org.scalajs.junit.ExceptionBeforeClass failed: java.lang.IllegalArgumentException: foo, took <TIME>
-e2org.scalajs.junit.ExceptionBeforeClass
+e2org.scalajs.junit.ExceptionBeforeClass::java.lang.IllegalArgumentException: foo
 liTest run finished: 1 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_va.txt b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_va.txt
index 568c70b998..ce2f836a74 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_va.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_va.txt
@@ -1,5 +1,5 @@
 liTest run started
 leTest org.scalajs.junit.ExceptionBeforeClass failed: java.lang.IllegalArgumentException: foo, took <TIME>
-e2org.scalajs.junit.ExceptionBeforeClass
+e2org.scalajs.junit.ExceptionBeforeClass::java.lang.IllegalArgumentException: foo
 liTest run finished: 1 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_vc.txt b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_vc.txt
index 41c8033527..4a6907891f 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_vc.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_vc.txt
@@ -1,5 +1,5 @@
 liTest run started
 leTest org.scalajs.junit.ExceptionBeforeClass failed: foo, took <TIME>
-e2org.scalajs.junit.ExceptionBeforeClass
+e2org.scalajs.junit.ExceptionBeforeClass::java.lang.IllegalArgumentException: foo
 liTest run finished: 1 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_vs.txt b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_vs.txt
index 568c70b998..ce2f836a74 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_vs.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_vs.txt
@@ -1,5 +1,5 @@
 liTest run started
 leTest org.scalajs.junit.ExceptionBeforeClass failed: java.lang.IllegalArgumentException: foo, took <TIME>
-e2org.scalajs.junit.ExceptionBeforeClass
+e2org.scalajs.junit.ExceptionBeforeClass::java.lang.IllegalArgumentException: foo
 liTest run finished: 1 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_vsn.txt b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_vsn.txt
index bec46ad160..f57776bd63 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_vsn.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_vsn.txt
@@ -1,5 +1,5 @@
 liTest run started
 leTest org.scalajs.junit.ExceptionBeforeClass failed: java.lang.IllegalArgumentException: foo, took <TIME>
-e2org.scalajs.junit.ExceptionBeforeClass
+e2org.scalajs.junit.ExceptionBeforeClass::java.lang.IllegalArgumentException: foo
 liTest run finished: 1 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_.txt b/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_.txt
index b7b30f6d21..a6f2913c4e 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_.txt
@@ -1,6 +1,6 @@
 ldTest run started
 leTest org.scalajs.junit.ExceptionEverywhere failed: before class, took <TIME>
-e2org.scalajs.junit.ExceptionEverywhere
+e2org.scalajs.junit.ExceptionEverywhere::java.lang.AssertionError: before class
 leTest org.scalajs.junit.ExceptionEverywhere failed: after class, took <TIME>
 ldTest run finished: 2 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_a.txt b/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_a.txt
index ab245780e8..79417183a5 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_a.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_a.txt
@@ -1,6 +1,6 @@
 ldTest run started
 leTest org.scalajs.junit.ExceptionEverywhere failed: java.lang.AssertionError: before class, took <TIME>
-e2org.scalajs.junit.ExceptionEverywhere
+e2org.scalajs.junit.ExceptionEverywhere::java.lang.AssertionError: before class
 leTest org.scalajs.junit.ExceptionEverywhere failed: java.lang.AssertionError: after class, took <TIME>
 ldTest run finished: 2 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_n.txt b/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_n.txt
index 78a322df3f..30b992edb7 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_n.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_n.txt
@@ -1,6 +1,6 @@
 ldTest run started
 leTest org.scalajs.junit.ExceptionEverywhere failed: before class, took <TIME>
-e2org.scalajs.junit.ExceptionEverywhere
+e2org.scalajs.junit.ExceptionEverywhere::java.lang.AssertionError: before class
 leTest org.scalajs.junit.ExceptionEverywhere failed: after class, took <TIME>
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 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_na.txt b/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_na.txt
index d5b7a4ca53..5905a59da4 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_na.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_na.txt
@@ -1,6 +1,6 @@
 ldTest run started
 leTest org.scalajs.junit.ExceptionEverywhere failed: java.lang.AssertionError: before class, took <TIME>
-e2org.scalajs.junit.ExceptionEverywhere
+e2org.scalajs.junit.ExceptionEverywhere::java.lang.AssertionError: before class
 leTest org.scalajs.junit.ExceptionEverywhere failed: java.lang.AssertionError: after class, took <TIME>
 ldTest run finished: 2 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_nv.txt b/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_nv.txt
index 28b1436944..ee5afc2ca2 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_nv.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_nv.txt
@@ -1,6 +1,6 @@
 liTest run started
 leTest org.scalajs.junit.ExceptionEverywhere failed: before class, took <TIME>
-e2org.scalajs.junit.ExceptionEverywhere
+e2org.scalajs.junit.ExceptionEverywhere::java.lang.AssertionError: before class
 leTest org.scalajs.junit.ExceptionEverywhere failed: after class, took <TIME>
 liTest run finished: 2 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_nva.txt b/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_nva.txt
index e28fa6c56d..92d17d724e 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_nva.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_nva.txt
@@ -1,6 +1,6 @@
 liTest run started
 leTest org.scalajs.junit.ExceptionEverywhere failed: java.lang.AssertionError: before class, took <TIME>
-e2org.scalajs.junit.ExceptionEverywhere
+e2org.scalajs.junit.ExceptionEverywhere::java.lang.AssertionError: before class
 leTest org.scalajs.junit.ExceptionEverywhere failed: java.lang.AssertionError: after class, took <TIME>
 liTest run finished: 2 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_nvc.txt b/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_nvc.txt
index 28b1436944..ee5afc2ca2 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_nvc.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_nvc.txt
@@ -1,6 +1,6 @@
 liTest run started
 leTest org.scalajs.junit.ExceptionEverywhere failed: before class, took <TIME>
-e2org.scalajs.junit.ExceptionEverywhere
+e2org.scalajs.junit.ExceptionEverywhere::java.lang.AssertionError: before class
 leTest org.scalajs.junit.ExceptionEverywhere failed: after class, took <TIME>
 liTest run finished: 2 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_nvca.txt b/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_nvca.txt
index 28b1436944..ee5afc2ca2 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_nvca.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_nvca.txt
@@ -1,6 +1,6 @@
 liTest run started
 leTest org.scalajs.junit.ExceptionEverywhere failed: before class, took <TIME>
-e2org.scalajs.junit.ExceptionEverywhere
+e2org.scalajs.junit.ExceptionEverywhere::java.lang.AssertionError: before class
 leTest org.scalajs.junit.ExceptionEverywhere failed: after class, took <TIME>
 liTest run finished: 2 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_v.txt b/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_v.txt
index 7c7edcfa5c..26f23b9718 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_v.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_v.txt
@@ -1,6 +1,6 @@
 liTest run started
 leTest org.scalajs.junit.ExceptionEverywhere failed: before class, took <TIME>
-e2org.scalajs.junit.ExceptionEverywhere
+e2org.scalajs.junit.ExceptionEverywhere::java.lang.AssertionError: before class
 leTest org.scalajs.junit.ExceptionEverywhere failed: after class, took <TIME>
 liTest run finished: 2 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_va.txt b/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_va.txt
index bd50da7a8f..2cb1cfd773 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_va.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_va.txt
@@ -1,6 +1,6 @@
 liTest run started
 leTest org.scalajs.junit.ExceptionEverywhere failed: java.lang.AssertionError: before class, took <TIME>
-e2org.scalajs.junit.ExceptionEverywhere
+e2org.scalajs.junit.ExceptionEverywhere::java.lang.AssertionError: before class
 leTest org.scalajs.junit.ExceptionEverywhere failed: java.lang.AssertionError: after class, took <TIME>
 liTest run finished: 2 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_vc.txt b/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_vc.txt
index 7c7edcfa5c..26f23b9718 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_vc.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_vc.txt
@@ -1,6 +1,6 @@
 liTest run started
 leTest org.scalajs.junit.ExceptionEverywhere failed: before class, took <TIME>
-e2org.scalajs.junit.ExceptionEverywhere
+e2org.scalajs.junit.ExceptionEverywhere::java.lang.AssertionError: before class
 leTest org.scalajs.junit.ExceptionEverywhere failed: after class, took <TIME>
 liTest run finished: 2 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_vs.txt b/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_vs.txt
index 7c7edcfa5c..26f23b9718 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_vs.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_vs.txt
@@ -1,6 +1,6 @@
 liTest run started
 leTest org.scalajs.junit.ExceptionEverywhere failed: before class, took <TIME>
-e2org.scalajs.junit.ExceptionEverywhere
+e2org.scalajs.junit.ExceptionEverywhere::java.lang.AssertionError: before class
 leTest org.scalajs.junit.ExceptionEverywhere failed: after class, took <TIME>
 liTest run finished: 2 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_vsn.txt b/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_vsn.txt
index 28b1436944..ee5afc2ca2 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_vsn.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_vsn.txt
@@ -1,6 +1,6 @@
 liTest run started
 leTest org.scalajs.junit.ExceptionEverywhere failed: before class, took <TIME>
-e2org.scalajs.junit.ExceptionEverywhere
+e2org.scalajs.junit.ExceptionEverywhere::java.lang.AssertionError: before class
 leTest org.scalajs.junit.ExceptionEverywhere failed: after class, took <TIME>
 liTest run finished: 2 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_.txt
index 5c37897f58..14d3235518 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.ExceptionInAfterTest.test started
 leTest org.scalajs.junit.ExceptionInAfterTest.test failed: java.lang.UnsupportedOperationException: Exception in after(), took <TIME>
-e2org.scalajs.junit.ExceptionInAfterTest.test
+e2org.scalajs.junit.ExceptionInAfterTest.test::java.lang.UnsupportedOperationException: Exception in after()
 ldTest org.scalajs.junit.ExceptionInAfterTest.test finished, took <TIME>
 ldTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_a.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_a.txt
index 5c37897f58..14d3235518 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_a.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_a.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.ExceptionInAfterTest.test started
 leTest org.scalajs.junit.ExceptionInAfterTest.test failed: java.lang.UnsupportedOperationException: Exception in after(), took <TIME>
-e2org.scalajs.junit.ExceptionInAfterTest.test
+e2org.scalajs.junit.ExceptionInAfterTest.test::java.lang.UnsupportedOperationException: Exception in after()
 ldTest org.scalajs.junit.ExceptionInAfterTest.test finished, took <TIME>
 ldTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_n.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_n.txt
index 331ef8fb05..03b803addb 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_n.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_n.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.ExceptionInAfterTest.test started
 leTest org.scalajs.junit.ExceptionInAfterTest.test failed: java.lang.UnsupportedOperationException: Exception in after(), took <TIME>
-e2org.scalajs.junit.ExceptionInAfterTest.test
+e2org.scalajs.junit.ExceptionInAfterTest.test::java.lang.UnsupportedOperationException: Exception in after()
 ldTest org.scalajs.junit.ExceptionInAfterTest.test finished, took <TIME>
 ldTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_na.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_na.txt
index 331ef8fb05..03b803addb 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_na.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_na.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.ExceptionInAfterTest.test started
 leTest org.scalajs.junit.ExceptionInAfterTest.test failed: java.lang.UnsupportedOperationException: Exception in after(), took <TIME>
-e2org.scalajs.junit.ExceptionInAfterTest.test
+e2org.scalajs.junit.ExceptionInAfterTest.test::java.lang.UnsupportedOperationException: Exception in after()
 ldTest org.scalajs.junit.ExceptionInAfterTest.test finished, took <TIME>
 ldTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_nv.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_nv.txt
index 7339fe41c9..ff0c035392 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_nv.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_nv.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionInAfterTest.test started
 leTest org.scalajs.junit.ExceptionInAfterTest.test failed: java.lang.UnsupportedOperationException: Exception in after(), took <TIME>
-e2org.scalajs.junit.ExceptionInAfterTest.test
+e2org.scalajs.junit.ExceptionInAfterTest.test::java.lang.UnsupportedOperationException: Exception in after()
 ldTest org.scalajs.junit.ExceptionInAfterTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_nva.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_nva.txt
index 7339fe41c9..ff0c035392 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_nva.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_nva.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionInAfterTest.test started
 leTest org.scalajs.junit.ExceptionInAfterTest.test failed: java.lang.UnsupportedOperationException: Exception in after(), took <TIME>
-e2org.scalajs.junit.ExceptionInAfterTest.test
+e2org.scalajs.junit.ExceptionInAfterTest.test::java.lang.UnsupportedOperationException: Exception in after()
 ldTest org.scalajs.junit.ExceptionInAfterTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_nvc.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_nvc.txt
index 4f8ca2985b..ac5b174a3a 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_nvc.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_nvc.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionInAfterTest.test started
 leTest org.scalajs.junit.ExceptionInAfterTest.test failed: Exception in after(), took <TIME>
-e2org.scalajs.junit.ExceptionInAfterTest.test
+e2org.scalajs.junit.ExceptionInAfterTest.test::java.lang.UnsupportedOperationException: Exception in after()
 ldTest org.scalajs.junit.ExceptionInAfterTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_nvca.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_nvca.txt
index 4f8ca2985b..ac5b174a3a 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_nvca.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_nvca.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionInAfterTest.test started
 leTest org.scalajs.junit.ExceptionInAfterTest.test failed: Exception in after(), took <TIME>
-e2org.scalajs.junit.ExceptionInAfterTest.test
+e2org.scalajs.junit.ExceptionInAfterTest.test::java.lang.UnsupportedOperationException: Exception in after()
 ldTest org.scalajs.junit.ExceptionInAfterTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_v.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_v.txt
index 80fc346adb..ca2f0122e9 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_v.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_v.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionInAfterTest.test started
 leTest org.scalajs.junit.ExceptionInAfterTest.test failed: java.lang.UnsupportedOperationException: Exception in after(), took <TIME>
-e2org.scalajs.junit.ExceptionInAfterTest.test
+e2org.scalajs.junit.ExceptionInAfterTest.test::java.lang.UnsupportedOperationException: Exception in after()
 ldTest org.scalajs.junit.ExceptionInAfterTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_va.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_va.txt
index 80fc346adb..ca2f0122e9 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_va.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_va.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionInAfterTest.test started
 leTest org.scalajs.junit.ExceptionInAfterTest.test failed: java.lang.UnsupportedOperationException: Exception in after(), took <TIME>
-e2org.scalajs.junit.ExceptionInAfterTest.test
+e2org.scalajs.junit.ExceptionInAfterTest.test::java.lang.UnsupportedOperationException: Exception in after()
 ldTest org.scalajs.junit.ExceptionInAfterTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_vc.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_vc.txt
index f736e5aa34..3d1aebb353 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_vc.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_vc.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionInAfterTest.test started
 leTest org.scalajs.junit.ExceptionInAfterTest.test failed: Exception in after(), took <TIME>
-e2org.scalajs.junit.ExceptionInAfterTest.test
+e2org.scalajs.junit.ExceptionInAfterTest.test::java.lang.UnsupportedOperationException: Exception in after()
 ldTest org.scalajs.junit.ExceptionInAfterTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_vs.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_vs.txt
index 80fc346adb..ca2f0122e9 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_vs.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_vs.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionInAfterTest.test started
 leTest org.scalajs.junit.ExceptionInAfterTest.test failed: java.lang.UnsupportedOperationException: Exception in after(), took <TIME>
-e2org.scalajs.junit.ExceptionInAfterTest.test
+e2org.scalajs.junit.ExceptionInAfterTest.test::java.lang.UnsupportedOperationException: Exception in after()
 ldTest org.scalajs.junit.ExceptionInAfterTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_vsn.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_vsn.txt
index 7339fe41c9..ff0c035392 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_vsn.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_vsn.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionInAfterTest.test started
 leTest org.scalajs.junit.ExceptionInAfterTest.test failed: java.lang.UnsupportedOperationException: Exception in after(), took <TIME>
-e2org.scalajs.junit.ExceptionInAfterTest.test
+e2org.scalajs.junit.ExceptionInAfterTest.test::java.lang.UnsupportedOperationException: Exception in after()
 ldTest org.scalajs.junit.ExceptionInAfterTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_.txt
index 58fc6f9f9d..d6ba6e71fd 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.ExceptionInBeforeTest.test started
 leTest org.scalajs.junit.ExceptionInBeforeTest.test failed: java.lang.UnsupportedOperationException: Exception in before(), took <TIME>
-e2org.scalajs.junit.ExceptionInBeforeTest.test
+e2org.scalajs.junit.ExceptionInBeforeTest.test::java.lang.UnsupportedOperationException: Exception in before()
 leTest org.scalajs.junit.ExceptionInBeforeTest.test failed: java.lang.IllegalArgumentException: after() must actually be called, took <TIME>
 ldTest org.scalajs.junit.ExceptionInBeforeTest.test finished, took <TIME>
 ldTest run finished: 2 failed, 0 ignored, 1 total, <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_a.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_a.txt
index 58fc6f9f9d..d6ba6e71fd 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_a.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_a.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.ExceptionInBeforeTest.test started
 leTest org.scalajs.junit.ExceptionInBeforeTest.test failed: java.lang.UnsupportedOperationException: Exception in before(), took <TIME>
-e2org.scalajs.junit.ExceptionInBeforeTest.test
+e2org.scalajs.junit.ExceptionInBeforeTest.test::java.lang.UnsupportedOperationException: Exception in before()
 leTest org.scalajs.junit.ExceptionInBeforeTest.test failed: java.lang.IllegalArgumentException: after() must actually be called, took <TIME>
 ldTest org.scalajs.junit.ExceptionInBeforeTest.test finished, took <TIME>
 ldTest run finished: 2 failed, 0 ignored, 1 total, <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_n.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_n.txt
index cfbcc88b0a..b1cea044df 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_n.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_n.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.ExceptionInBeforeTest.test started
 leTest org.scalajs.junit.ExceptionInBeforeTest.test failed: java.lang.UnsupportedOperationException: Exception in before(), took <TIME>
-e2org.scalajs.junit.ExceptionInBeforeTest.test
+e2org.scalajs.junit.ExceptionInBeforeTest.test::java.lang.UnsupportedOperationException: Exception in before()
 leTest org.scalajs.junit.ExceptionInBeforeTest.test failed: java.lang.IllegalArgumentException: after() must actually be called, took <TIME>
 ldTest org.scalajs.junit.ExceptionInBeforeTest.test finished, took <TIME>
 ldTest run finished: 2 failed, 0 ignored, 1 total, <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_na.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_na.txt
index cfbcc88b0a..b1cea044df 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_na.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_na.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.ExceptionInBeforeTest.test started
 leTest org.scalajs.junit.ExceptionInBeforeTest.test failed: java.lang.UnsupportedOperationException: Exception in before(), took <TIME>
-e2org.scalajs.junit.ExceptionInBeforeTest.test
+e2org.scalajs.junit.ExceptionInBeforeTest.test::java.lang.UnsupportedOperationException: Exception in before()
 leTest org.scalajs.junit.ExceptionInBeforeTest.test failed: java.lang.IllegalArgumentException: after() must actually be called, took <TIME>
 ldTest org.scalajs.junit.ExceptionInBeforeTest.test finished, took <TIME>
 ldTest run finished: 2 failed, 0 ignored, 1 total, <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_nv.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_nv.txt
index 1bbbbaedb5..f82dfea4e4 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_nv.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_nv.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionInBeforeTest.test started
 leTest org.scalajs.junit.ExceptionInBeforeTest.test failed: java.lang.UnsupportedOperationException: Exception in before(), took <TIME>
-e2org.scalajs.junit.ExceptionInBeforeTest.test
+e2org.scalajs.junit.ExceptionInBeforeTest.test::java.lang.UnsupportedOperationException: Exception in before()
 leTest org.scalajs.junit.ExceptionInBeforeTest.test failed: java.lang.IllegalArgumentException: after() must actually be called, took <TIME>
 ldTest org.scalajs.junit.ExceptionInBeforeTest.test finished, took <TIME>
 liTest run finished: 2 failed, 0 ignored, 1 total, <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_nva.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_nva.txt
index 1bbbbaedb5..f82dfea4e4 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_nva.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_nva.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionInBeforeTest.test started
 leTest org.scalajs.junit.ExceptionInBeforeTest.test failed: java.lang.UnsupportedOperationException: Exception in before(), took <TIME>
-e2org.scalajs.junit.ExceptionInBeforeTest.test
+e2org.scalajs.junit.ExceptionInBeforeTest.test::java.lang.UnsupportedOperationException: Exception in before()
 leTest org.scalajs.junit.ExceptionInBeforeTest.test failed: java.lang.IllegalArgumentException: after() must actually be called, took <TIME>
 ldTest org.scalajs.junit.ExceptionInBeforeTest.test finished, took <TIME>
 liTest run finished: 2 failed, 0 ignored, 1 total, <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_nvc.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_nvc.txt
index 7ed0e0a590..dd02f92e2e 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_nvc.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_nvc.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionInBeforeTest.test started
 leTest org.scalajs.junit.ExceptionInBeforeTest.test failed: Exception in before(), took <TIME>
-e2org.scalajs.junit.ExceptionInBeforeTest.test
+e2org.scalajs.junit.ExceptionInBeforeTest.test::java.lang.UnsupportedOperationException: Exception in before()
 leTest org.scalajs.junit.ExceptionInBeforeTest.test failed: after() must actually be called, took <TIME>
 ldTest org.scalajs.junit.ExceptionInBeforeTest.test finished, took <TIME>
 liTest run finished: 2 failed, 0 ignored, 1 total, <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_nvca.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_nvca.txt
index 7ed0e0a590..dd02f92e2e 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_nvca.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_nvca.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionInBeforeTest.test started
 leTest org.scalajs.junit.ExceptionInBeforeTest.test failed: Exception in before(), took <TIME>
-e2org.scalajs.junit.ExceptionInBeforeTest.test
+e2org.scalajs.junit.ExceptionInBeforeTest.test::java.lang.UnsupportedOperationException: Exception in before()
 leTest org.scalajs.junit.ExceptionInBeforeTest.test failed: after() must actually be called, took <TIME>
 ldTest org.scalajs.junit.ExceptionInBeforeTest.test finished, took <TIME>
 liTest run finished: 2 failed, 0 ignored, 1 total, <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_v.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_v.txt
index 66abe4c7c4..0b91d80a97 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_v.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_v.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionInBeforeTest.test started
 leTest org.scalajs.junit.ExceptionInBeforeTest.test failed: java.lang.UnsupportedOperationException: Exception in before(), took <TIME>
-e2org.scalajs.junit.ExceptionInBeforeTest.test
+e2org.scalajs.junit.ExceptionInBeforeTest.test::java.lang.UnsupportedOperationException: Exception in before()
 leTest org.scalajs.junit.ExceptionInBeforeTest.test failed: java.lang.IllegalArgumentException: after() must actually be called, took <TIME>
 ldTest org.scalajs.junit.ExceptionInBeforeTest.test finished, took <TIME>
 liTest run finished: 2 failed, 0 ignored, 1 total, <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_va.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_va.txt
index 66abe4c7c4..0b91d80a97 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_va.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_va.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionInBeforeTest.test started
 leTest org.scalajs.junit.ExceptionInBeforeTest.test failed: java.lang.UnsupportedOperationException: Exception in before(), took <TIME>
-e2org.scalajs.junit.ExceptionInBeforeTest.test
+e2org.scalajs.junit.ExceptionInBeforeTest.test::java.lang.UnsupportedOperationException: Exception in before()
 leTest org.scalajs.junit.ExceptionInBeforeTest.test failed: java.lang.IllegalArgumentException: after() must actually be called, took <TIME>
 ldTest org.scalajs.junit.ExceptionInBeforeTest.test finished, took <TIME>
 liTest run finished: 2 failed, 0 ignored, 1 total, <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_vc.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_vc.txt
index b55874172b..3acd966c6f 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_vc.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_vc.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionInBeforeTest.test started
 leTest org.scalajs.junit.ExceptionInBeforeTest.test failed: Exception in before(), took <TIME>
-e2org.scalajs.junit.ExceptionInBeforeTest.test
+e2org.scalajs.junit.ExceptionInBeforeTest.test::java.lang.UnsupportedOperationException: Exception in before()
 leTest org.scalajs.junit.ExceptionInBeforeTest.test failed: after() must actually be called, took <TIME>
 ldTest org.scalajs.junit.ExceptionInBeforeTest.test finished, took <TIME>
 liTest run finished: 2 failed, 0 ignored, 1 total, <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_vs.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_vs.txt
index 66abe4c7c4..0b91d80a97 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_vs.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_vs.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionInBeforeTest.test started
 leTest org.scalajs.junit.ExceptionInBeforeTest.test failed: java.lang.UnsupportedOperationException: Exception in before(), took <TIME>
-e2org.scalajs.junit.ExceptionInBeforeTest.test
+e2org.scalajs.junit.ExceptionInBeforeTest.test::java.lang.UnsupportedOperationException: Exception in before()
 leTest org.scalajs.junit.ExceptionInBeforeTest.test failed: java.lang.IllegalArgumentException: after() must actually be called, took <TIME>
 ldTest org.scalajs.junit.ExceptionInBeforeTest.test finished, took <TIME>
 liTest run finished: 2 failed, 0 ignored, 1 total, <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_vsn.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_vsn.txt
index 1bbbbaedb5..f82dfea4e4 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_vsn.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_vsn.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionInBeforeTest.test started
 leTest org.scalajs.junit.ExceptionInBeforeTest.test failed: java.lang.UnsupportedOperationException: Exception in before(), took <TIME>
-e2org.scalajs.junit.ExceptionInBeforeTest.test
+e2org.scalajs.junit.ExceptionInBeforeTest.test::java.lang.UnsupportedOperationException: Exception in before()
 leTest org.scalajs.junit.ExceptionInBeforeTest.test failed: java.lang.IllegalArgumentException: after() must actually be called, took <TIME>
 ldTest org.scalajs.junit.ExceptionInBeforeTest.test finished, took <TIME>
 liTest run finished: 2 failed, 0 ignored, 1 total, <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_.txt
index b139903ea2..c1cad1d384 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.ExceptionInConstructorTest.test started
 leTest org.scalajs.junit.ExceptionInConstructorTest.test failed: java.lang.UnsupportedOperationException: Exception while constructing the test class, took <TIME>
-e2org.scalajs.junit.ExceptionInConstructorTest.test
+e2org.scalajs.junit.ExceptionInConstructorTest.test::java.lang.UnsupportedOperationException: Exception while constructing the test class
 ldTest org.scalajs.junit.ExceptionInConstructorTest.test finished, took <TIME>
 ldTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_a.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_a.txt
index b139903ea2..c1cad1d384 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_a.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_a.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.ExceptionInConstructorTest.test started
 leTest org.scalajs.junit.ExceptionInConstructorTest.test failed: java.lang.UnsupportedOperationException: Exception while constructing the test class, took <TIME>
-e2org.scalajs.junit.ExceptionInConstructorTest.test
+e2org.scalajs.junit.ExceptionInConstructorTest.test::java.lang.UnsupportedOperationException: Exception while constructing the test class
 ldTest org.scalajs.junit.ExceptionInConstructorTest.test finished, took <TIME>
 ldTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_n.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_n.txt
index 7c0a854717..12fe8b5772 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_n.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_n.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.ExceptionInConstructorTest.test started
 leTest org.scalajs.junit.ExceptionInConstructorTest.test failed: java.lang.UnsupportedOperationException: Exception while constructing the test class, took <TIME>
-e2org.scalajs.junit.ExceptionInConstructorTest.test
+e2org.scalajs.junit.ExceptionInConstructorTest.test::java.lang.UnsupportedOperationException: Exception while constructing the test class
 ldTest org.scalajs.junit.ExceptionInConstructorTest.test finished, took <TIME>
 ldTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_na.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_na.txt
index 7c0a854717..12fe8b5772 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_na.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_na.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.ExceptionInConstructorTest.test started
 leTest org.scalajs.junit.ExceptionInConstructorTest.test failed: java.lang.UnsupportedOperationException: Exception while constructing the test class, took <TIME>
-e2org.scalajs.junit.ExceptionInConstructorTest.test
+e2org.scalajs.junit.ExceptionInConstructorTest.test::java.lang.UnsupportedOperationException: Exception while constructing the test class
 ldTest org.scalajs.junit.ExceptionInConstructorTest.test finished, took <TIME>
 ldTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_nv.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_nv.txt
index 6afd5b4d21..730e13987a 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_nv.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_nv.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionInConstructorTest.test started
 leTest org.scalajs.junit.ExceptionInConstructorTest.test failed: java.lang.UnsupportedOperationException: Exception while constructing the test class, took <TIME>
-e2org.scalajs.junit.ExceptionInConstructorTest.test
+e2org.scalajs.junit.ExceptionInConstructorTest.test::java.lang.UnsupportedOperationException: Exception while constructing the test class
 ldTest org.scalajs.junit.ExceptionInConstructorTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_nva.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_nva.txt
index 6afd5b4d21..730e13987a 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_nva.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_nva.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionInConstructorTest.test started
 leTest org.scalajs.junit.ExceptionInConstructorTest.test failed: java.lang.UnsupportedOperationException: Exception while constructing the test class, took <TIME>
-e2org.scalajs.junit.ExceptionInConstructorTest.test
+e2org.scalajs.junit.ExceptionInConstructorTest.test::java.lang.UnsupportedOperationException: Exception while constructing the test class
 ldTest org.scalajs.junit.ExceptionInConstructorTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_nvc.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_nvc.txt
index 86a73246b1..d3219559e5 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_nvc.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_nvc.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionInConstructorTest.test started
 leTest org.scalajs.junit.ExceptionInConstructorTest.test failed: Exception while constructing the test class, took <TIME>
-e2org.scalajs.junit.ExceptionInConstructorTest.test
+e2org.scalajs.junit.ExceptionInConstructorTest.test::java.lang.UnsupportedOperationException: Exception while constructing the test class
 ldTest org.scalajs.junit.ExceptionInConstructorTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_nvca.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_nvca.txt
index 86a73246b1..d3219559e5 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_nvca.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_nvca.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionInConstructorTest.test started
 leTest org.scalajs.junit.ExceptionInConstructorTest.test failed: Exception while constructing the test class, took <TIME>
-e2org.scalajs.junit.ExceptionInConstructorTest.test
+e2org.scalajs.junit.ExceptionInConstructorTest.test::java.lang.UnsupportedOperationException: Exception while constructing the test class
 ldTest org.scalajs.junit.ExceptionInConstructorTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_v.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_v.txt
index 08cb51dd63..ef647db57d 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_v.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_v.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionInConstructorTest.test started
 leTest org.scalajs.junit.ExceptionInConstructorTest.test failed: java.lang.UnsupportedOperationException: Exception while constructing the test class, took <TIME>
-e2org.scalajs.junit.ExceptionInConstructorTest.test
+e2org.scalajs.junit.ExceptionInConstructorTest.test::java.lang.UnsupportedOperationException: Exception while constructing the test class
 ldTest org.scalajs.junit.ExceptionInConstructorTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_va.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_va.txt
index 08cb51dd63..ef647db57d 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_va.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_va.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionInConstructorTest.test started
 leTest org.scalajs.junit.ExceptionInConstructorTest.test failed: java.lang.UnsupportedOperationException: Exception while constructing the test class, took <TIME>
-e2org.scalajs.junit.ExceptionInConstructorTest.test
+e2org.scalajs.junit.ExceptionInConstructorTest.test::java.lang.UnsupportedOperationException: Exception while constructing the test class
 ldTest org.scalajs.junit.ExceptionInConstructorTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_vc.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_vc.txt
index 890e5bcd49..1336060086 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_vc.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_vc.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionInConstructorTest.test started
 leTest org.scalajs.junit.ExceptionInConstructorTest.test failed: Exception while constructing the test class, took <TIME>
-e2org.scalajs.junit.ExceptionInConstructorTest.test
+e2org.scalajs.junit.ExceptionInConstructorTest.test::java.lang.UnsupportedOperationException: Exception while constructing the test class
 ldTest org.scalajs.junit.ExceptionInConstructorTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_vs.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_vs.txt
index 08cb51dd63..ef647db57d 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_vs.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_vs.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionInConstructorTest.test started
 leTest org.scalajs.junit.ExceptionInConstructorTest.test failed: java.lang.UnsupportedOperationException: Exception while constructing the test class, took <TIME>
-e2org.scalajs.junit.ExceptionInConstructorTest.test
+e2org.scalajs.junit.ExceptionInConstructorTest.test::java.lang.UnsupportedOperationException: Exception while constructing the test class
 ldTest org.scalajs.junit.ExceptionInConstructorTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_vsn.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_vsn.txt
index 6afd5b4d21..730e13987a 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_vsn.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_vsn.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionInConstructorTest.test started
 leTest org.scalajs.junit.ExceptionInConstructorTest.test failed: java.lang.UnsupportedOperationException: Exception while constructing the test class, took <TIME>
-e2org.scalajs.junit.ExceptionInConstructorTest.test
+e2org.scalajs.junit.ExceptionInConstructorTest.test::java.lang.UnsupportedOperationException: Exception while constructing the test class
 ldTest org.scalajs.junit.ExceptionInConstructorTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_.txt b/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_.txt
index df5ed598f3..a2cb636eb6 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.ExceptionTest.test started
 leTest org.scalajs.junit.ExceptionTest.test failed: java.lang.IndexOutOfBoundsException: Exception message, took <TIME>
-e2org.scalajs.junit.ExceptionTest.test
+e2org.scalajs.junit.ExceptionTest.test::java.lang.IndexOutOfBoundsException: Exception message
 ldTest org.scalajs.junit.ExceptionTest.test finished, took <TIME>
 ldTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_a.txt b/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_a.txt
index df5ed598f3..a2cb636eb6 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_a.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_a.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.ExceptionTest.test started
 leTest org.scalajs.junit.ExceptionTest.test failed: java.lang.IndexOutOfBoundsException: Exception message, took <TIME>
-e2org.scalajs.junit.ExceptionTest.test
+e2org.scalajs.junit.ExceptionTest.test::java.lang.IndexOutOfBoundsException: Exception message
 ldTest org.scalajs.junit.ExceptionTest.test finished, took <TIME>
 ldTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_n.txt b/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_n.txt
index e3901fb329..baf7da3727 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_n.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_n.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.ExceptionTest.test started
 leTest org.scalajs.junit.ExceptionTest.test failed: java.lang.IndexOutOfBoundsException: Exception message, took <TIME>
-e2org.scalajs.junit.ExceptionTest.test
+e2org.scalajs.junit.ExceptionTest.test::java.lang.IndexOutOfBoundsException: Exception message
 ldTest org.scalajs.junit.ExceptionTest.test finished, took <TIME>
 ldTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_na.txt b/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_na.txt
index e3901fb329..baf7da3727 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_na.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_na.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.ExceptionTest.test started
 leTest org.scalajs.junit.ExceptionTest.test failed: java.lang.IndexOutOfBoundsException: Exception message, took <TIME>
-e2org.scalajs.junit.ExceptionTest.test
+e2org.scalajs.junit.ExceptionTest.test::java.lang.IndexOutOfBoundsException: Exception message
 ldTest org.scalajs.junit.ExceptionTest.test finished, took <TIME>
 ldTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_nv.txt b/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_nv.txt
index 258447cab4..fe2fdd138f 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_nv.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_nv.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionTest.test started
 leTest org.scalajs.junit.ExceptionTest.test failed: java.lang.IndexOutOfBoundsException: Exception message, took <TIME>
-e2org.scalajs.junit.ExceptionTest.test
+e2org.scalajs.junit.ExceptionTest.test::java.lang.IndexOutOfBoundsException: Exception message
 ldTest org.scalajs.junit.ExceptionTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_nva.txt b/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_nva.txt
index 258447cab4..fe2fdd138f 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_nva.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_nva.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionTest.test started
 leTest org.scalajs.junit.ExceptionTest.test failed: java.lang.IndexOutOfBoundsException: Exception message, took <TIME>
-e2org.scalajs.junit.ExceptionTest.test
+e2org.scalajs.junit.ExceptionTest.test::java.lang.IndexOutOfBoundsException: Exception message
 ldTest org.scalajs.junit.ExceptionTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_nvc.txt b/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_nvc.txt
index 9c1479e3c6..ebc2be30ea 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_nvc.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_nvc.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionTest.test started
 leTest org.scalajs.junit.ExceptionTest.test failed: Exception message, took <TIME>
-e2org.scalajs.junit.ExceptionTest.test
+e2org.scalajs.junit.ExceptionTest.test::java.lang.IndexOutOfBoundsException: Exception message
 ldTest org.scalajs.junit.ExceptionTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_nvca.txt b/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_nvca.txt
index 9c1479e3c6..ebc2be30ea 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_nvca.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_nvca.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionTest.test started
 leTest org.scalajs.junit.ExceptionTest.test failed: Exception message, took <TIME>
-e2org.scalajs.junit.ExceptionTest.test
+e2org.scalajs.junit.ExceptionTest.test::java.lang.IndexOutOfBoundsException: Exception message
 ldTest org.scalajs.junit.ExceptionTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_v.txt b/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_v.txt
index a385dca76a..5b096e3aa3 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_v.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_v.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionTest.test started
 leTest org.scalajs.junit.ExceptionTest.test failed: java.lang.IndexOutOfBoundsException: Exception message, took <TIME>
-e2org.scalajs.junit.ExceptionTest.test
+e2org.scalajs.junit.ExceptionTest.test::java.lang.IndexOutOfBoundsException: Exception message
 ldTest org.scalajs.junit.ExceptionTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_va.txt b/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_va.txt
index a385dca76a..5b096e3aa3 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_va.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_va.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionTest.test started
 leTest org.scalajs.junit.ExceptionTest.test failed: java.lang.IndexOutOfBoundsException: Exception message, took <TIME>
-e2org.scalajs.junit.ExceptionTest.test
+e2org.scalajs.junit.ExceptionTest.test::java.lang.IndexOutOfBoundsException: Exception message
 ldTest org.scalajs.junit.ExceptionTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_vc.txt b/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_vc.txt
index 9866f9d948..e6b60ba892 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_vc.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_vc.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionTest.test started
 leTest org.scalajs.junit.ExceptionTest.test failed: Exception message, took <TIME>
-e2org.scalajs.junit.ExceptionTest.test
+e2org.scalajs.junit.ExceptionTest.test::java.lang.IndexOutOfBoundsException: Exception message
 ldTest org.scalajs.junit.ExceptionTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_vs.txt b/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_vs.txt
index a385dca76a..5b096e3aa3 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_vs.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_vs.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionTest.test started
 leTest org.scalajs.junit.ExceptionTest.test failed: java.lang.IndexOutOfBoundsException: Exception message, took <TIME>
-e2org.scalajs.junit.ExceptionTest.test
+e2org.scalajs.junit.ExceptionTest.test::java.lang.IndexOutOfBoundsException: Exception message
 ldTest org.scalajs.junit.ExceptionTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_vsn.txt b/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_vsn.txt
index 258447cab4..fe2fdd138f 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_vsn.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_vsn.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionTest.test started
 leTest org.scalajs.junit.ExceptionTest.test failed: java.lang.IndexOutOfBoundsException: Exception message, took <TIME>
-e2org.scalajs.junit.ExceptionTest.test
+e2org.scalajs.junit.ExceptionTest.test::java.lang.IndexOutOfBoundsException: Exception message
 ldTest org.scalajs.junit.ExceptionTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_.txt b/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_.txt
index a56596488d..72e5ff3b5a 100644
--- a/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_.txt
@@ -1,22 +1,22 @@
 ldTest run started
 ldTest org.scalajs.junit.ExpectTest.expectAssert started
 ldTest org.scalajs.junit.ExpectTest.expectAssert finished, took <TIME>
-e0org.scalajs.junit.ExpectTest.expectAssert
+e0org.scalajs.junit.ExpectTest.expectAssert::
 ldTest org.scalajs.junit.ExpectTest.expectNormal started
 ldTest org.scalajs.junit.ExpectTest.expectNormal finished, took <TIME>
-e0org.scalajs.junit.ExpectTest.expectNormal
+e0org.scalajs.junit.ExpectTest.expectNormal::
 ldTest org.scalajs.junit.ExpectTest.failExpectAssert started
 leTest org.scalajs.junit.ExpectTest.failExpectAssert failed: Expected exception: java.lang.AssertionError, took <TIME>
-e2org.scalajs.junit.ExpectTest.failExpectAssert
+e2org.scalajs.junit.ExpectTest.failExpectAssert::java.lang.AssertionError: Expected exception: java.lang.AssertionError
 ldTest org.scalajs.junit.ExpectTest.failExpectAssert finished, took <TIME>
 ldTest org.scalajs.junit.ExpectTest.failExpectDifferent started
 leTest org.scalajs.junit.ExpectTest.failExpectDifferent failed: java.lang.Exception: Unexpected exception, expected<java.io.IOException> but was<java.lang.IllegalArgumentException>, took <TIME>
 leCaused by: java.lang.IllegalArgumentException
-e2org.scalajs.junit.ExpectTest.failExpectDifferent
+e2org.scalajs.junit.ExpectTest.failExpectDifferent::java.lang.Exception: Unexpected exception, expected<java.io.IOException> but was<java.lang.IllegalArgumentException>
 ldTest org.scalajs.junit.ExpectTest.failExpectDifferent finished, took <TIME>
 ldTest org.scalajs.junit.ExpectTest.failExpectNoThrow started
 leTest org.scalajs.junit.ExpectTest.failExpectNoThrow failed: Expected exception: java.io.IOException, took <TIME>
-e2org.scalajs.junit.ExpectTest.failExpectNoThrow
+e2org.scalajs.junit.ExpectTest.failExpectNoThrow::java.lang.AssertionError: Expected exception: java.io.IOException
 ldTest org.scalajs.junit.ExpectTest.failExpectNoThrow finished, took <TIME>
 ldTest run finished: 3 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_a.txt b/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_a.txt
index 1f77672df8..4f2ff68a1a 100644
--- a/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_a.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_a.txt
@@ -1,22 +1,22 @@
 ldTest run started
 ldTest org.scalajs.junit.ExpectTest.expectAssert started
 ldTest org.scalajs.junit.ExpectTest.expectAssert finished, took <TIME>
-e0org.scalajs.junit.ExpectTest.expectAssert
+e0org.scalajs.junit.ExpectTest.expectAssert::
 ldTest org.scalajs.junit.ExpectTest.expectNormal started
 ldTest org.scalajs.junit.ExpectTest.expectNormal finished, took <TIME>
-e0org.scalajs.junit.ExpectTest.expectNormal
+e0org.scalajs.junit.ExpectTest.expectNormal::
 ldTest org.scalajs.junit.ExpectTest.failExpectAssert started
 leTest org.scalajs.junit.ExpectTest.failExpectAssert failed: java.lang.AssertionError: Expected exception: java.lang.AssertionError, took <TIME>
-e2org.scalajs.junit.ExpectTest.failExpectAssert
+e2org.scalajs.junit.ExpectTest.failExpectAssert::java.lang.AssertionError: Expected exception: java.lang.AssertionError
 ldTest org.scalajs.junit.ExpectTest.failExpectAssert finished, took <TIME>
 ldTest org.scalajs.junit.ExpectTest.failExpectDifferent started
 leTest org.scalajs.junit.ExpectTest.failExpectDifferent failed: java.lang.Exception: Unexpected exception, expected<java.io.IOException> but was<java.lang.IllegalArgumentException>, took <TIME>
 leCaused by: java.lang.IllegalArgumentException
-e2org.scalajs.junit.ExpectTest.failExpectDifferent
+e2org.scalajs.junit.ExpectTest.failExpectDifferent::java.lang.Exception: Unexpected exception, expected<java.io.IOException> but was<java.lang.IllegalArgumentException>
 ldTest org.scalajs.junit.ExpectTest.failExpectDifferent finished, took <TIME>
 ldTest org.scalajs.junit.ExpectTest.failExpectNoThrow started
 leTest org.scalajs.junit.ExpectTest.failExpectNoThrow failed: java.lang.AssertionError: Expected exception: java.io.IOException, took <TIME>
-e2org.scalajs.junit.ExpectTest.failExpectNoThrow
+e2org.scalajs.junit.ExpectTest.failExpectNoThrow::java.lang.AssertionError: Expected exception: java.io.IOException
 ldTest org.scalajs.junit.ExpectTest.failExpectNoThrow finished, took <TIME>
 ldTest run finished: 3 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_n.txt b/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_n.txt
index 465409f0c3..37fe0cbb05 100644
--- a/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_n.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_n.txt
@@ -1,22 +1,22 @@
 ldTest run started
 ldTest org.scalajs.junit.ExpectTest.expectAssert started
 ldTest org.scalajs.junit.ExpectTest.expectAssert finished, took <TIME>
-e0org.scalajs.junit.ExpectTest.expectAssert
+e0org.scalajs.junit.ExpectTest.expectAssert::
 ldTest org.scalajs.junit.ExpectTest.expectNormal started
 ldTest org.scalajs.junit.ExpectTest.expectNormal finished, took <TIME>
-e0org.scalajs.junit.ExpectTest.expectNormal
+e0org.scalajs.junit.ExpectTest.expectNormal::
 ldTest org.scalajs.junit.ExpectTest.failExpectAssert started
 leTest org.scalajs.junit.ExpectTest.failExpectAssert failed: Expected exception: java.lang.AssertionError, took <TIME>
-e2org.scalajs.junit.ExpectTest.failExpectAssert
+e2org.scalajs.junit.ExpectTest.failExpectAssert::java.lang.AssertionError: Expected exception: java.lang.AssertionError
 ldTest org.scalajs.junit.ExpectTest.failExpectAssert finished, took <TIME>
 ldTest org.scalajs.junit.ExpectTest.failExpectDifferent started
 leTest org.scalajs.junit.ExpectTest.failExpectDifferent failed: java.lang.Exception: Unexpected exception, expected<java.io.IOException> but was<java.lang.IllegalArgumentException>, took <TIME>
 leCaused by: java.lang.IllegalArgumentException
-e2org.scalajs.junit.ExpectTest.failExpectDifferent
+e2org.scalajs.junit.ExpectTest.failExpectDifferent::java.lang.Exception: Unexpected exception, expected<java.io.IOException> but was<java.lang.IllegalArgumentException>
 ldTest org.scalajs.junit.ExpectTest.failExpectDifferent finished, took <TIME>
 ldTest org.scalajs.junit.ExpectTest.failExpectNoThrow started
 leTest org.scalajs.junit.ExpectTest.failExpectNoThrow failed: Expected exception: java.io.IOException, took <TIME>
-e2org.scalajs.junit.ExpectTest.failExpectNoThrow
+e2org.scalajs.junit.ExpectTest.failExpectNoThrow::java.lang.AssertionError: Expected exception: java.io.IOException
 ldTest org.scalajs.junit.ExpectTest.failExpectNoThrow finished, took <TIME>
 ldTest run finished: 3 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_na.txt b/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_na.txt
index e55df72b34..6150ebebfd 100644
--- a/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_na.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_na.txt
@@ -1,22 +1,22 @@
 ldTest run started
 ldTest org.scalajs.junit.ExpectTest.expectAssert started
 ldTest org.scalajs.junit.ExpectTest.expectAssert finished, took <TIME>
-e0org.scalajs.junit.ExpectTest.expectAssert
+e0org.scalajs.junit.ExpectTest.expectAssert::
 ldTest org.scalajs.junit.ExpectTest.expectNormal started
 ldTest org.scalajs.junit.ExpectTest.expectNormal finished, took <TIME>
-e0org.scalajs.junit.ExpectTest.expectNormal
+e0org.scalajs.junit.ExpectTest.expectNormal::
 ldTest org.scalajs.junit.ExpectTest.failExpectAssert started
 leTest org.scalajs.junit.ExpectTest.failExpectAssert failed: java.lang.AssertionError: Expected exception: java.lang.AssertionError, took <TIME>
-e2org.scalajs.junit.ExpectTest.failExpectAssert
+e2org.scalajs.junit.ExpectTest.failExpectAssert::java.lang.AssertionError: Expected exception: java.lang.AssertionError
 ldTest org.scalajs.junit.ExpectTest.failExpectAssert finished, took <TIME>
 ldTest org.scalajs.junit.ExpectTest.failExpectDifferent started
 leTest org.scalajs.junit.ExpectTest.failExpectDifferent failed: java.lang.Exception: Unexpected exception, expected<java.io.IOException> but was<java.lang.IllegalArgumentException>, took <TIME>
 leCaused by: java.lang.IllegalArgumentException
-e2org.scalajs.junit.ExpectTest.failExpectDifferent
+e2org.scalajs.junit.ExpectTest.failExpectDifferent::java.lang.Exception: Unexpected exception, expected<java.io.IOException> but was<java.lang.IllegalArgumentException>
 ldTest org.scalajs.junit.ExpectTest.failExpectDifferent finished, took <TIME>
 ldTest org.scalajs.junit.ExpectTest.failExpectNoThrow started
 leTest org.scalajs.junit.ExpectTest.failExpectNoThrow failed: java.lang.AssertionError: Expected exception: java.io.IOException, took <TIME>
-e2org.scalajs.junit.ExpectTest.failExpectNoThrow
+e2org.scalajs.junit.ExpectTest.failExpectNoThrow::java.lang.AssertionError: Expected exception: java.io.IOException
 ldTest org.scalajs.junit.ExpectTest.failExpectNoThrow finished, took <TIME>
 ldTest run finished: 3 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_nv.txt b/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_nv.txt
index 7553260b48..f497cc9554 100644
--- a/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_nv.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_nv.txt
@@ -1,22 +1,22 @@
 liTest run started
 liTest org.scalajs.junit.ExpectTest.expectAssert started
 ldTest org.scalajs.junit.ExpectTest.expectAssert finished, took <TIME>
-e0org.scalajs.junit.ExpectTest.expectAssert
+e0org.scalajs.junit.ExpectTest.expectAssert::
 liTest org.scalajs.junit.ExpectTest.expectNormal started
 ldTest org.scalajs.junit.ExpectTest.expectNormal finished, took <TIME>
-e0org.scalajs.junit.ExpectTest.expectNormal
+e0org.scalajs.junit.ExpectTest.expectNormal::
 liTest org.scalajs.junit.ExpectTest.failExpectAssert started
 leTest org.scalajs.junit.ExpectTest.failExpectAssert failed: Expected exception: java.lang.AssertionError, took <TIME>
-e2org.scalajs.junit.ExpectTest.failExpectAssert
+e2org.scalajs.junit.ExpectTest.failExpectAssert::java.lang.AssertionError: Expected exception: java.lang.AssertionError
 ldTest org.scalajs.junit.ExpectTest.failExpectAssert finished, took <TIME>
 liTest org.scalajs.junit.ExpectTest.failExpectDifferent started
 leTest org.scalajs.junit.ExpectTest.failExpectDifferent failed: java.lang.Exception: Unexpected exception, expected<java.io.IOException> but was<java.lang.IllegalArgumentException>, took <TIME>
 leCaused by: java.lang.IllegalArgumentException
-e2org.scalajs.junit.ExpectTest.failExpectDifferent
+e2org.scalajs.junit.ExpectTest.failExpectDifferent::java.lang.Exception: Unexpected exception, expected<java.io.IOException> but was<java.lang.IllegalArgumentException>
 ldTest org.scalajs.junit.ExpectTest.failExpectDifferent finished, took <TIME>
 liTest org.scalajs.junit.ExpectTest.failExpectNoThrow started
 leTest org.scalajs.junit.ExpectTest.failExpectNoThrow failed: Expected exception: java.io.IOException, took <TIME>
-e2org.scalajs.junit.ExpectTest.failExpectNoThrow
+e2org.scalajs.junit.ExpectTest.failExpectNoThrow::java.lang.AssertionError: Expected exception: java.io.IOException
 ldTest org.scalajs.junit.ExpectTest.failExpectNoThrow finished, took <TIME>
 liTest run finished: 3 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_nva.txt b/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_nva.txt
index 9971339280..4da5dd77e6 100644
--- a/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_nva.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_nva.txt
@@ -1,22 +1,22 @@
 liTest run started
 liTest org.scalajs.junit.ExpectTest.expectAssert started
 ldTest org.scalajs.junit.ExpectTest.expectAssert finished, took <TIME>
-e0org.scalajs.junit.ExpectTest.expectAssert
+e0org.scalajs.junit.ExpectTest.expectAssert::
 liTest org.scalajs.junit.ExpectTest.expectNormal started
 ldTest org.scalajs.junit.ExpectTest.expectNormal finished, took <TIME>
-e0org.scalajs.junit.ExpectTest.expectNormal
+e0org.scalajs.junit.ExpectTest.expectNormal::
 liTest org.scalajs.junit.ExpectTest.failExpectAssert started
 leTest org.scalajs.junit.ExpectTest.failExpectAssert failed: java.lang.AssertionError: Expected exception: java.lang.AssertionError, took <TIME>
-e2org.scalajs.junit.ExpectTest.failExpectAssert
+e2org.scalajs.junit.ExpectTest.failExpectAssert::java.lang.AssertionError: Expected exception: java.lang.AssertionError
 ldTest org.scalajs.junit.ExpectTest.failExpectAssert finished, took <TIME>
 liTest org.scalajs.junit.ExpectTest.failExpectDifferent started
 leTest org.scalajs.junit.ExpectTest.failExpectDifferent failed: java.lang.Exception: Unexpected exception, expected<java.io.IOException> but was<java.lang.IllegalArgumentException>, took <TIME>
 leCaused by: java.lang.IllegalArgumentException
-e2org.scalajs.junit.ExpectTest.failExpectDifferent
+e2org.scalajs.junit.ExpectTest.failExpectDifferent::java.lang.Exception: Unexpected exception, expected<java.io.IOException> but was<java.lang.IllegalArgumentException>
 ldTest org.scalajs.junit.ExpectTest.failExpectDifferent finished, took <TIME>
 liTest org.scalajs.junit.ExpectTest.failExpectNoThrow started
 leTest org.scalajs.junit.ExpectTest.failExpectNoThrow failed: java.lang.AssertionError: Expected exception: java.io.IOException, took <TIME>
-e2org.scalajs.junit.ExpectTest.failExpectNoThrow
+e2org.scalajs.junit.ExpectTest.failExpectNoThrow::java.lang.AssertionError: Expected exception: java.io.IOException
 ldTest org.scalajs.junit.ExpectTest.failExpectNoThrow finished, took <TIME>
 liTest run finished: 3 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_nvc.txt b/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_nvc.txt
index 58febb5940..413630af26 100644
--- a/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_nvc.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_nvc.txt
@@ -1,22 +1,22 @@
 liTest run started
 liTest org.scalajs.junit.ExpectTest.expectAssert started
 ldTest org.scalajs.junit.ExpectTest.expectAssert finished, took <TIME>
-e0org.scalajs.junit.ExpectTest.expectAssert
+e0org.scalajs.junit.ExpectTest.expectAssert::
 liTest org.scalajs.junit.ExpectTest.expectNormal started
 ldTest org.scalajs.junit.ExpectTest.expectNormal finished, took <TIME>
-e0org.scalajs.junit.ExpectTest.expectNormal
+e0org.scalajs.junit.ExpectTest.expectNormal::
 liTest org.scalajs.junit.ExpectTest.failExpectAssert started
 leTest org.scalajs.junit.ExpectTest.failExpectAssert failed: Expected exception: java.lang.AssertionError, took <TIME>
-e2org.scalajs.junit.ExpectTest.failExpectAssert
+e2org.scalajs.junit.ExpectTest.failExpectAssert::java.lang.AssertionError: Expected exception: java.lang.AssertionError
 ldTest org.scalajs.junit.ExpectTest.failExpectAssert finished, took <TIME>
 liTest org.scalajs.junit.ExpectTest.failExpectDifferent started
 leTest org.scalajs.junit.ExpectTest.failExpectDifferent failed: Unexpected exception, expected<java.io.IOException> but was<java.lang.IllegalArgumentException>, took <TIME>
 leCaused by: java.lang.IllegalArgumentException
-e2org.scalajs.junit.ExpectTest.failExpectDifferent
+e2org.scalajs.junit.ExpectTest.failExpectDifferent::java.lang.Exception: Unexpected exception, expected<java.io.IOException> but was<java.lang.IllegalArgumentException>
 ldTest org.scalajs.junit.ExpectTest.failExpectDifferent finished, took <TIME>
 liTest org.scalajs.junit.ExpectTest.failExpectNoThrow started
 leTest org.scalajs.junit.ExpectTest.failExpectNoThrow failed: Expected exception: java.io.IOException, took <TIME>
-e2org.scalajs.junit.ExpectTest.failExpectNoThrow
+e2org.scalajs.junit.ExpectTest.failExpectNoThrow::java.lang.AssertionError: Expected exception: java.io.IOException
 ldTest org.scalajs.junit.ExpectTest.failExpectNoThrow finished, took <TIME>
 liTest run finished: 3 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_nvca.txt b/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_nvca.txt
index 58febb5940..413630af26 100644
--- a/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_nvca.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_nvca.txt
@@ -1,22 +1,22 @@
 liTest run started
 liTest org.scalajs.junit.ExpectTest.expectAssert started
 ldTest org.scalajs.junit.ExpectTest.expectAssert finished, took <TIME>
-e0org.scalajs.junit.ExpectTest.expectAssert
+e0org.scalajs.junit.ExpectTest.expectAssert::
 liTest org.scalajs.junit.ExpectTest.expectNormal started
 ldTest org.scalajs.junit.ExpectTest.expectNormal finished, took <TIME>
-e0org.scalajs.junit.ExpectTest.expectNormal
+e0org.scalajs.junit.ExpectTest.expectNormal::
 liTest org.scalajs.junit.ExpectTest.failExpectAssert started
 leTest org.scalajs.junit.ExpectTest.failExpectAssert failed: Expected exception: java.lang.AssertionError, took <TIME>
-e2org.scalajs.junit.ExpectTest.failExpectAssert
+e2org.scalajs.junit.ExpectTest.failExpectAssert::java.lang.AssertionError: Expected exception: java.lang.AssertionError
 ldTest org.scalajs.junit.ExpectTest.failExpectAssert finished, took <TIME>
 liTest org.scalajs.junit.ExpectTest.failExpectDifferent started
 leTest org.scalajs.junit.ExpectTest.failExpectDifferent failed: Unexpected exception, expected<java.io.IOException> but was<java.lang.IllegalArgumentException>, took <TIME>
 leCaused by: java.lang.IllegalArgumentException
-e2org.scalajs.junit.ExpectTest.failExpectDifferent
+e2org.scalajs.junit.ExpectTest.failExpectDifferent::java.lang.Exception: Unexpected exception, expected<java.io.IOException> but was<java.lang.IllegalArgumentException>
 ldTest org.scalajs.junit.ExpectTest.failExpectDifferent finished, took <TIME>
 liTest org.scalajs.junit.ExpectTest.failExpectNoThrow started
 leTest org.scalajs.junit.ExpectTest.failExpectNoThrow failed: Expected exception: java.io.IOException, took <TIME>
-e2org.scalajs.junit.ExpectTest.failExpectNoThrow
+e2org.scalajs.junit.ExpectTest.failExpectNoThrow::java.lang.AssertionError: Expected exception: java.io.IOException
 ldTest org.scalajs.junit.ExpectTest.failExpectNoThrow finished, took <TIME>
 liTest run finished: 3 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_v.txt b/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_v.txt
index bfad7b2077..8c8f6c7eab 100644
--- a/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_v.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_v.txt
@@ -1,22 +1,22 @@
 liTest run started
 liTest org.scalajs.junit.ExpectTest.expectAssert started
 ldTest org.scalajs.junit.ExpectTest.expectAssert finished, took <TIME>
-e0org.scalajs.junit.ExpectTest.expectAssert
+e0org.scalajs.junit.ExpectTest.expectAssert::
 liTest org.scalajs.junit.ExpectTest.expectNormal started
 ldTest org.scalajs.junit.ExpectTest.expectNormal finished, took <TIME>
-e0org.scalajs.junit.ExpectTest.expectNormal
+e0org.scalajs.junit.ExpectTest.expectNormal::
 liTest org.scalajs.junit.ExpectTest.failExpectAssert started
 leTest org.scalajs.junit.ExpectTest.failExpectAssert failed: Expected exception: java.lang.AssertionError, took <TIME>
-e2org.scalajs.junit.ExpectTest.failExpectAssert
+e2org.scalajs.junit.ExpectTest.failExpectAssert::java.lang.AssertionError: Expected exception: java.lang.AssertionError
 ldTest org.scalajs.junit.ExpectTest.failExpectAssert finished, took <TIME>
 liTest org.scalajs.junit.ExpectTest.failExpectDifferent started
 leTest org.scalajs.junit.ExpectTest.failExpectDifferent failed: java.lang.Exception: Unexpected exception, expected<java.io.IOException> but was<java.lang.IllegalArgumentException>, took <TIME>
 leCaused by: java.lang.IllegalArgumentException
-e2org.scalajs.junit.ExpectTest.failExpectDifferent
+e2org.scalajs.junit.ExpectTest.failExpectDifferent::java.lang.Exception: Unexpected exception, expected<java.io.IOException> but was<java.lang.IllegalArgumentException>
 ldTest org.scalajs.junit.ExpectTest.failExpectDifferent finished, took <TIME>
 liTest org.scalajs.junit.ExpectTest.failExpectNoThrow started
 leTest org.scalajs.junit.ExpectTest.failExpectNoThrow failed: Expected exception: java.io.IOException, took <TIME>
-e2org.scalajs.junit.ExpectTest.failExpectNoThrow
+e2org.scalajs.junit.ExpectTest.failExpectNoThrow::java.lang.AssertionError: Expected exception: java.io.IOException
 ldTest org.scalajs.junit.ExpectTest.failExpectNoThrow finished, took <TIME>
 liTest run finished: 3 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_va.txt b/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_va.txt
index 74c70c0c99..0d1b8efa4a 100644
--- a/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_va.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_va.txt
@@ -1,22 +1,22 @@
 liTest run started
 liTest org.scalajs.junit.ExpectTest.expectAssert started
 ldTest org.scalajs.junit.ExpectTest.expectAssert finished, took <TIME>
-e0org.scalajs.junit.ExpectTest.expectAssert
+e0org.scalajs.junit.ExpectTest.expectAssert::
 liTest org.scalajs.junit.ExpectTest.expectNormal started
 ldTest org.scalajs.junit.ExpectTest.expectNormal finished, took <TIME>
-e0org.scalajs.junit.ExpectTest.expectNormal
+e0org.scalajs.junit.ExpectTest.expectNormal::
 liTest org.scalajs.junit.ExpectTest.failExpectAssert started
 leTest org.scalajs.junit.ExpectTest.failExpectAssert failed: java.lang.AssertionError: Expected exception: java.lang.AssertionError, took <TIME>
-e2org.scalajs.junit.ExpectTest.failExpectAssert
+e2org.scalajs.junit.ExpectTest.failExpectAssert::java.lang.AssertionError: Expected exception: java.lang.AssertionError
 ldTest org.scalajs.junit.ExpectTest.failExpectAssert finished, took <TIME>
 liTest org.scalajs.junit.ExpectTest.failExpectDifferent started
 leTest org.scalajs.junit.ExpectTest.failExpectDifferent failed: java.lang.Exception: Unexpected exception, expected<java.io.IOException> but was<java.lang.IllegalArgumentException>, took <TIME>
 leCaused by: java.lang.IllegalArgumentException
-e2org.scalajs.junit.ExpectTest.failExpectDifferent
+e2org.scalajs.junit.ExpectTest.failExpectDifferent::java.lang.Exception: Unexpected exception, expected<java.io.IOException> but was<java.lang.IllegalArgumentException>
 ldTest org.scalajs.junit.ExpectTest.failExpectDifferent finished, took <TIME>
 liTest org.scalajs.junit.ExpectTest.failExpectNoThrow started
 leTest org.scalajs.junit.ExpectTest.failExpectNoThrow failed: java.lang.AssertionError: Expected exception: java.io.IOException, took <TIME>
-e2org.scalajs.junit.ExpectTest.failExpectNoThrow
+e2org.scalajs.junit.ExpectTest.failExpectNoThrow::java.lang.AssertionError: Expected exception: java.io.IOException
 ldTest org.scalajs.junit.ExpectTest.failExpectNoThrow finished, took <TIME>
 liTest run finished: 3 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_vc.txt b/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_vc.txt
index cb5a7dd548..cccda11d1a 100644
--- a/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_vc.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_vc.txt
@@ -1,22 +1,22 @@
 liTest run started
 liTest org.scalajs.junit.ExpectTest.expectAssert started
 ldTest org.scalajs.junit.ExpectTest.expectAssert finished, took <TIME>
-e0org.scalajs.junit.ExpectTest.expectAssert
+e0org.scalajs.junit.ExpectTest.expectAssert::
 liTest org.scalajs.junit.ExpectTest.expectNormal started
 ldTest org.scalajs.junit.ExpectTest.expectNormal finished, took <TIME>
-e0org.scalajs.junit.ExpectTest.expectNormal
+e0org.scalajs.junit.ExpectTest.expectNormal::
 liTest org.scalajs.junit.ExpectTest.failExpectAssert started
 leTest org.scalajs.junit.ExpectTest.failExpectAssert failed: Expected exception: java.lang.AssertionError, took <TIME>
-e2org.scalajs.junit.ExpectTest.failExpectAssert
+e2org.scalajs.junit.ExpectTest.failExpectAssert::java.lang.AssertionError: Expected exception: java.lang.AssertionError
 ldTest org.scalajs.junit.ExpectTest.failExpectAssert finished, took <TIME>
 liTest org.scalajs.junit.ExpectTest.failExpectDifferent started
 leTest org.scalajs.junit.ExpectTest.failExpectDifferent failed: Unexpected exception, expected<java.io.IOException> but was<java.lang.IllegalArgumentException>, took <TIME>
 leCaused by: java.lang.IllegalArgumentException
-e2org.scalajs.junit.ExpectTest.failExpectDifferent
+e2org.scalajs.junit.ExpectTest.failExpectDifferent::java.lang.Exception: Unexpected exception, expected<java.io.IOException> but was<java.lang.IllegalArgumentException>
 ldTest org.scalajs.junit.ExpectTest.failExpectDifferent finished, took <TIME>
 liTest org.scalajs.junit.ExpectTest.failExpectNoThrow started
 leTest org.scalajs.junit.ExpectTest.failExpectNoThrow failed: Expected exception: java.io.IOException, took <TIME>
-e2org.scalajs.junit.ExpectTest.failExpectNoThrow
+e2org.scalajs.junit.ExpectTest.failExpectNoThrow::java.lang.AssertionError: Expected exception: java.io.IOException
 ldTest org.scalajs.junit.ExpectTest.failExpectNoThrow finished, took <TIME>
 liTest run finished: 3 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_vs.txt b/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_vs.txt
index bfad7b2077..8c8f6c7eab 100644
--- a/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_vs.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_vs.txt
@@ -1,22 +1,22 @@
 liTest run started
 liTest org.scalajs.junit.ExpectTest.expectAssert started
 ldTest org.scalajs.junit.ExpectTest.expectAssert finished, took <TIME>
-e0org.scalajs.junit.ExpectTest.expectAssert
+e0org.scalajs.junit.ExpectTest.expectAssert::
 liTest org.scalajs.junit.ExpectTest.expectNormal started
 ldTest org.scalajs.junit.ExpectTest.expectNormal finished, took <TIME>
-e0org.scalajs.junit.ExpectTest.expectNormal
+e0org.scalajs.junit.ExpectTest.expectNormal::
 liTest org.scalajs.junit.ExpectTest.failExpectAssert started
 leTest org.scalajs.junit.ExpectTest.failExpectAssert failed: Expected exception: java.lang.AssertionError, took <TIME>
-e2org.scalajs.junit.ExpectTest.failExpectAssert
+e2org.scalajs.junit.ExpectTest.failExpectAssert::java.lang.AssertionError: Expected exception: java.lang.AssertionError
 ldTest org.scalajs.junit.ExpectTest.failExpectAssert finished, took <TIME>
 liTest org.scalajs.junit.ExpectTest.failExpectDifferent started
 leTest org.scalajs.junit.ExpectTest.failExpectDifferent failed: java.lang.Exception: Unexpected exception, expected<java.io.IOException> but was<java.lang.IllegalArgumentException>, took <TIME>
 leCaused by: java.lang.IllegalArgumentException
-e2org.scalajs.junit.ExpectTest.failExpectDifferent
+e2org.scalajs.junit.ExpectTest.failExpectDifferent::java.lang.Exception: Unexpected exception, expected<java.io.IOException> but was<java.lang.IllegalArgumentException>
 ldTest org.scalajs.junit.ExpectTest.failExpectDifferent finished, took <TIME>
 liTest org.scalajs.junit.ExpectTest.failExpectNoThrow started
 leTest org.scalajs.junit.ExpectTest.failExpectNoThrow failed: Expected exception: java.io.IOException, took <TIME>
-e2org.scalajs.junit.ExpectTest.failExpectNoThrow
+e2org.scalajs.junit.ExpectTest.failExpectNoThrow::java.lang.AssertionError: Expected exception: java.io.IOException
 ldTest org.scalajs.junit.ExpectTest.failExpectNoThrow finished, took <TIME>
 liTest run finished: 3 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_vsn.txt b/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_vsn.txt
index 7553260b48..f497cc9554 100644
--- a/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_vsn.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_vsn.txt
@@ -1,22 +1,22 @@
 liTest run started
 liTest org.scalajs.junit.ExpectTest.expectAssert started
 ldTest org.scalajs.junit.ExpectTest.expectAssert finished, took <TIME>
-e0org.scalajs.junit.ExpectTest.expectAssert
+e0org.scalajs.junit.ExpectTest.expectAssert::
 liTest org.scalajs.junit.ExpectTest.expectNormal started
 ldTest org.scalajs.junit.ExpectTest.expectNormal finished, took <TIME>
-e0org.scalajs.junit.ExpectTest.expectNormal
+e0org.scalajs.junit.ExpectTest.expectNormal::
 liTest org.scalajs.junit.ExpectTest.failExpectAssert started
 leTest org.scalajs.junit.ExpectTest.failExpectAssert failed: Expected exception: java.lang.AssertionError, took <TIME>
-e2org.scalajs.junit.ExpectTest.failExpectAssert
+e2org.scalajs.junit.ExpectTest.failExpectAssert::java.lang.AssertionError: Expected exception: java.lang.AssertionError
 ldTest org.scalajs.junit.ExpectTest.failExpectAssert finished, took <TIME>
 liTest org.scalajs.junit.ExpectTest.failExpectDifferent started
 leTest org.scalajs.junit.ExpectTest.failExpectDifferent failed: java.lang.Exception: Unexpected exception, expected<java.io.IOException> but was<java.lang.IllegalArgumentException>, took <TIME>
 leCaused by: java.lang.IllegalArgumentException
-e2org.scalajs.junit.ExpectTest.failExpectDifferent
+e2org.scalajs.junit.ExpectTest.failExpectDifferent::java.lang.Exception: Unexpected exception, expected<java.io.IOException> but was<java.lang.IllegalArgumentException>
 ldTest org.scalajs.junit.ExpectTest.failExpectDifferent finished, took <TIME>
 liTest org.scalajs.junit.ExpectTest.failExpectNoThrow started
 leTest org.scalajs.junit.ExpectTest.failExpectNoThrow failed: Expected exception: java.io.IOException, took <TIME>
-e2org.scalajs.junit.ExpectTest.failExpectNoThrow
+e2org.scalajs.junit.ExpectTest.failExpectNoThrow::java.lang.AssertionError: Expected exception: java.io.IOException
 ldTest org.scalajs.junit.ExpectTest.failExpectNoThrow finished, took <TIME>
 liTest run finished: 3 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_.txt b/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_.txt
index 5652de8097..50d9c8e58b 100644
--- a/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_.txt
+++ b/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_.txt
@@ -1,5 +1,5 @@
 ldTest run started
 liTest org.scalajs.junit.IgnoreTest.onlyTest ignored
-e3org.scalajs.junit.IgnoreTest.onlyTest
+e3org.scalajs.junit.IgnoreTest.onlyTest::
 ldTest run finished: 0 failed, 1 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_a.txt b/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_a.txt
index 5652de8097..50d9c8e58b 100644
--- a/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_a.txt
+++ b/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_a.txt
@@ -1,5 +1,5 @@
 ldTest run started
 liTest org.scalajs.junit.IgnoreTest.onlyTest ignored
-e3org.scalajs.junit.IgnoreTest.onlyTest
+e3org.scalajs.junit.IgnoreTest.onlyTest::
 ldTest run finished: 0 failed, 1 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_n.txt b/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_n.txt
index 862404ffe0..bcdf276d8c 100644
--- a/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_n.txt
+++ b/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_n.txt
@@ -1,5 +1,5 @@
 ldTest run started
 liTest org.scalajs.junit.IgnoreTest.onlyTest ignored
-e3org.scalajs.junit.IgnoreTest.onlyTest
+e3org.scalajs.junit.IgnoreTest.onlyTest::
 ldTest run finished: 0 failed, 1 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_na.txt b/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_na.txt
index 862404ffe0..bcdf276d8c 100644
--- a/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_na.txt
+++ b/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_na.txt
@@ -1,5 +1,5 @@
 ldTest run started
 liTest org.scalajs.junit.IgnoreTest.onlyTest ignored
-e3org.scalajs.junit.IgnoreTest.onlyTest
+e3org.scalajs.junit.IgnoreTest.onlyTest::
 ldTest run finished: 0 failed, 1 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_nv.txt b/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_nv.txt
index b86f34ed38..8e4c0cfe5a 100644
--- a/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_nv.txt
+++ b/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_nv.txt
@@ -1,5 +1,5 @@
 liTest run started
 liTest org.scalajs.junit.IgnoreTest.onlyTest ignored
-e3org.scalajs.junit.IgnoreTest.onlyTest
+e3org.scalajs.junit.IgnoreTest.onlyTest::
 liTest run finished: 0 failed, 1 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_nva.txt b/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_nva.txt
index b86f34ed38..8e4c0cfe5a 100644
--- a/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_nva.txt
+++ b/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_nva.txt
@@ -1,5 +1,5 @@
 liTest run started
 liTest org.scalajs.junit.IgnoreTest.onlyTest ignored
-e3org.scalajs.junit.IgnoreTest.onlyTest
+e3org.scalajs.junit.IgnoreTest.onlyTest::
 liTest run finished: 0 failed, 1 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_nvc.txt b/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_nvc.txt
index b86f34ed38..8e4c0cfe5a 100644
--- a/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_nvc.txt
+++ b/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_nvc.txt
@@ -1,5 +1,5 @@
 liTest run started
 liTest org.scalajs.junit.IgnoreTest.onlyTest ignored
-e3org.scalajs.junit.IgnoreTest.onlyTest
+e3org.scalajs.junit.IgnoreTest.onlyTest::
 liTest run finished: 0 failed, 1 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_nvca.txt b/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_nvca.txt
index b86f34ed38..8e4c0cfe5a 100644
--- a/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_nvca.txt
+++ b/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_nvca.txt
@@ -1,5 +1,5 @@
 liTest run started
 liTest org.scalajs.junit.IgnoreTest.onlyTest ignored
-e3org.scalajs.junit.IgnoreTest.onlyTest
+e3org.scalajs.junit.IgnoreTest.onlyTest::
 liTest run finished: 0 failed, 1 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_v.txt b/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_v.txt
index 68728fc116..4f4956b499 100644
--- a/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_v.txt
+++ b/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_v.txt
@@ -1,5 +1,5 @@
 liTest run started
 liTest org.scalajs.junit.IgnoreTest.onlyTest ignored
-e3org.scalajs.junit.IgnoreTest.onlyTest
+e3org.scalajs.junit.IgnoreTest.onlyTest::
 liTest run finished: 0 failed, 1 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_va.txt b/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_va.txt
index 68728fc116..4f4956b499 100644
--- a/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_va.txt
+++ b/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_va.txt
@@ -1,5 +1,5 @@
 liTest run started
 liTest org.scalajs.junit.IgnoreTest.onlyTest ignored
-e3org.scalajs.junit.IgnoreTest.onlyTest
+e3org.scalajs.junit.IgnoreTest.onlyTest::
 liTest run finished: 0 failed, 1 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_vc.txt b/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_vc.txt
index 68728fc116..4f4956b499 100644
--- a/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_vc.txt
+++ b/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_vc.txt
@@ -1,5 +1,5 @@
 liTest run started
 liTest org.scalajs.junit.IgnoreTest.onlyTest ignored
-e3org.scalajs.junit.IgnoreTest.onlyTest
+e3org.scalajs.junit.IgnoreTest.onlyTest::
 liTest run finished: 0 failed, 1 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_vs.txt b/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_vs.txt
index 68728fc116..4f4956b499 100644
--- a/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_vs.txt
+++ b/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_vs.txt
@@ -1,5 +1,5 @@
 liTest run started
 liTest org.scalajs.junit.IgnoreTest.onlyTest ignored
-e3org.scalajs.junit.IgnoreTest.onlyTest
+e3org.scalajs.junit.IgnoreTest.onlyTest::
 liTest run finished: 0 failed, 1 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_vsn.txt b/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_vsn.txt
index b86f34ed38..8e4c0cfe5a 100644
--- a/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_vsn.txt
+++ b/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_vsn.txt
@@ -1,5 +1,5 @@
 liTest run started
 liTest org.scalajs.junit.IgnoreTest.onlyTest ignored
-e3org.scalajs.junit.IgnoreTest.onlyTest
+e3org.scalajs.junit.IgnoreTest.onlyTest::
 liTest run finished: 0 failed, 1 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_.txt b/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_.txt
index 3c1a5cacb2..fd6b462615 100644
--- a/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_.txt
+++ b/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_.txt
@@ -1,6 +1,6 @@
 ldTest run started
 ldTest org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$ started
 ldTest org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$ finished, took <TIME>
-e0org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$
+e0org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$::
 ldTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_a.txt b/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_a.txt
index 3c1a5cacb2..fd6b462615 100644
--- a/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_a.txt
+++ b/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_a.txt
@@ -1,6 +1,6 @@
 ldTest run started
 ldTest org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$ started
 ldTest org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$ finished, took <TIME>
-e0org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$
+e0org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$::
 ldTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_n.txt b/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_n.txt
index 6041e671fd..90cf573f4c 100644
--- a/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_n.txt
+++ b/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_n.txt
@@ -1,6 +1,6 @@
 ldTest run started
 ldTest org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$ started
 ldTest org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$ finished, took <TIME>
-e0org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$
+e0org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$::
 ldTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_na.txt b/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_na.txt
index 6041e671fd..90cf573f4c 100644
--- a/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_na.txt
+++ b/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_na.txt
@@ -1,6 +1,6 @@
 ldTest run started
 ldTest org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$ started
 ldTest org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$ finished, took <TIME>
-e0org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$
+e0org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$::
 ldTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_nv.txt b/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_nv.txt
index 74e87e34fc..272ac60261 100644
--- a/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_nv.txt
+++ b/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_nv.txt
@@ -1,6 +1,6 @@
 liTest run started
 liTest org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$ started
 ldTest org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$ finished, took <TIME>
-e0org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$
+e0org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$::
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_nva.txt b/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_nva.txt
index 74e87e34fc..272ac60261 100644
--- a/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_nva.txt
+++ b/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_nva.txt
@@ -1,6 +1,6 @@
 liTest run started
 liTest org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$ started
 ldTest org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$ finished, took <TIME>
-e0org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$
+e0org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$::
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_nvc.txt b/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_nvc.txt
index 74e87e34fc..272ac60261 100644
--- a/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_nvc.txt
+++ b/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_nvc.txt
@@ -1,6 +1,6 @@
 liTest run started
 liTest org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$ started
 ldTest org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$ finished, took <TIME>
-e0org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$
+e0org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$::
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_nvca.txt b/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_nvca.txt
index 74e87e34fc..272ac60261 100644
--- a/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_nvca.txt
+++ b/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_nvca.txt
@@ -1,6 +1,6 @@
 liTest run started
 liTest org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$ started
 ldTest org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$ finished, took <TIME>
-e0org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$
+e0org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$::
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_v.txt b/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_v.txt
index 88a65289a4..962ab08aa7 100644
--- a/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_v.txt
+++ b/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_v.txt
@@ -1,6 +1,6 @@
 liTest run started
 liTest org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$ started
 ldTest org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$ finished, took <TIME>
-e0org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$
+e0org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$::
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_va.txt b/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_va.txt
index 88a65289a4..962ab08aa7 100644
--- a/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_va.txt
+++ b/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_va.txt
@@ -1,6 +1,6 @@
 liTest run started
 liTest org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$ started
 ldTest org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$ finished, took <TIME>
-e0org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$
+e0org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$::
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_vc.txt b/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_vc.txt
index 88a65289a4..962ab08aa7 100644
--- a/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_vc.txt
+++ b/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_vc.txt
@@ -1,6 +1,6 @@
 liTest run started
 liTest org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$ started
 ldTest org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$ finished, took <TIME>
-e0org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$
+e0org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$::
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_vs.txt b/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_vs.txt
index 29dd7e4090..5921633584 100644
--- a/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_vs.txt
+++ b/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_vs.txt
@@ -1,6 +1,6 @@
 liTest run started
 liTest org.scalajs.junit.MethodNameDecodeTest.abcd ∆ƒ 😀 * #&$ started
 ldTest org.scalajs.junit.MethodNameDecodeTest.abcd ∆ƒ 😀 * #&$ finished, took <TIME>
-e0org.scalajs.junit.MethodNameDecodeTest.abcd ∆ƒ 😀 * #&$
+e0org.scalajs.junit.MethodNameDecodeTest.abcd ∆ƒ 😀 * #&$::
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_vsn.txt b/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_vsn.txt
index ff144237dc..a5fccd7f30 100644
--- a/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_vsn.txt
+++ b/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_vsn.txt
@@ -1,6 +1,6 @@
 liTest run started
 liTest org.scalajs.junit.MethodNameDecodeTest.abcd ∆ƒ 😀 * #&$ started
 ldTest org.scalajs.junit.MethodNameDecodeTest.abcd ∆ƒ 😀 * #&$ finished, took <TIME>
-e0org.scalajs.junit.MethodNameDecodeTest.abcd ∆ƒ 😀 * #&$
+e0org.scalajs.junit.MethodNameDecodeTest.abcd ∆ƒ 😀 * #&$::
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_.txt b/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_.txt
index 027bbf23e0..8922fa63dc 100644
--- a/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_.txt
+++ b/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_.txt
@@ -1,9 +1,9 @@
 ldTest run started
 ldTest org.scalajs.junit.Multi1Test.multiTest1 started
 ldTest org.scalajs.junit.Multi1Test.multiTest1 finished, took <TIME>
-e0org.scalajs.junit.Multi1Test.multiTest1
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 ldTest org.scalajs.junit.Multi1Test.multiTest2 started
 ldTest org.scalajs.junit.Multi1Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.Multi1Test.multiTest2
+e0org.scalajs.junit.Multi1Test.multiTest2::
 ldTest run finished: 0 failed, 0 ignored, 2 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_a.txt b/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_a.txt
index 027bbf23e0..8922fa63dc 100644
--- a/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_a.txt
+++ b/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_a.txt
@@ -1,9 +1,9 @@
 ldTest run started
 ldTest org.scalajs.junit.Multi1Test.multiTest1 started
 ldTest org.scalajs.junit.Multi1Test.multiTest1 finished, took <TIME>
-e0org.scalajs.junit.Multi1Test.multiTest1
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 ldTest org.scalajs.junit.Multi1Test.multiTest2 started
 ldTest org.scalajs.junit.Multi1Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.Multi1Test.multiTest2
+e0org.scalajs.junit.Multi1Test.multiTest2::
 ldTest run finished: 0 failed, 0 ignored, 2 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_n.txt b/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_n.txt
index 266a3ec7e7..51394ffdc9 100644
--- a/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_n.txt
+++ b/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_n.txt
@@ -1,9 +1,9 @@
 ldTest run started
 ldTest org.scalajs.junit.Multi1Test.multiTest1 started
 ldTest org.scalajs.junit.Multi1Test.multiTest1 finished, took <TIME>
-e0org.scalajs.junit.Multi1Test.multiTest1
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 ldTest org.scalajs.junit.Multi1Test.multiTest2 started
 ldTest org.scalajs.junit.Multi1Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.Multi1Test.multiTest2
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 ldTest run finished: 0 failed, 0 ignored, 2 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_na.txt b/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_na.txt
index 266a3ec7e7..51394ffdc9 100644
--- a/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_na.txt
+++ b/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_na.txt
@@ -1,9 +1,9 @@
 ldTest run started
 ldTest org.scalajs.junit.Multi1Test.multiTest1 started
 ldTest org.scalajs.junit.Multi1Test.multiTest1 finished, took <TIME>
-e0org.scalajs.junit.Multi1Test.multiTest1
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 ldTest org.scalajs.junit.Multi1Test.multiTest2 started
 ldTest org.scalajs.junit.Multi1Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.Multi1Test.multiTest2
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 ldTest run finished: 0 failed, 0 ignored, 2 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_nv.txt b/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_nv.txt
index 5c672dbfa2..9c026ac573 100644
--- a/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_nv.txt
+++ b/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_nv.txt
@@ -1,9 +1,9 @@
 liTest run started
 liTest org.scalajs.junit.Multi1Test.multiTest1 started
 ldTest org.scalajs.junit.Multi1Test.multiTest1 finished, took <TIME>
-e0org.scalajs.junit.Multi1Test.multiTest1
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 liTest org.scalajs.junit.Multi1Test.multiTest2 started
 ldTest org.scalajs.junit.Multi1Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.Multi1Test.multiTest2
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 liTest run finished: 0 failed, 0 ignored, 2 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_nva.txt b/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_nva.txt
index 5c672dbfa2..9c026ac573 100644
--- a/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_nva.txt
+++ b/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_nva.txt
@@ -1,9 +1,9 @@
 liTest run started
 liTest org.scalajs.junit.Multi1Test.multiTest1 started
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-e0org.scalajs.junit.Multi1Test.multiTest1
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 liTest org.scalajs.junit.Multi1Test.multiTest2 started
 ldTest org.scalajs.junit.Multi1Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.Multi1Test.multiTest2
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 liTest run finished: 0 failed, 0 ignored, 2 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_nvc.txt b/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_nvc.txt
index 5c672dbfa2..9c026ac573 100644
--- a/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_nvc.txt
+++ b/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_nvc.txt
@@ -1,9 +1,9 @@
 liTest run started
 liTest org.scalajs.junit.Multi1Test.multiTest1 started
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-e0org.scalajs.junit.Multi1Test.multiTest1
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 liTest org.scalajs.junit.Multi1Test.multiTest2 started
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-e0org.scalajs.junit.Multi1Test.multiTest2
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 liTest run finished: 0 failed, 0 ignored, 2 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_nvca.txt b/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_nvca.txt
index 5c672dbfa2..9c026ac573 100644
--- a/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_nvca.txt
+++ b/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_nvca.txt
@@ -1,9 +1,9 @@
 liTest run started
 liTest org.scalajs.junit.Multi1Test.multiTest1 started
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-e0org.scalajs.junit.Multi1Test.multiTest1
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 liTest org.scalajs.junit.Multi1Test.multiTest2 started
 ldTest org.scalajs.junit.Multi1Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.Multi1Test.multiTest2
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 liTest run finished: 0 failed, 0 ignored, 2 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_v.txt b/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_v.txt
index 13f8ff375a..4569389a5e 100644
--- a/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_v.txt
+++ b/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_v.txt
@@ -1,9 +1,9 @@
 liTest run started
 liTest org.scalajs.junit.Multi1Test.multiTest1 started
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-e0org.scalajs.junit.Multi1Test.multiTest1
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 liTest org.scalajs.junit.Multi1Test.multiTest2 started
 ldTest org.scalajs.junit.Multi1Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.Multi1Test.multiTest2
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 liTest run finished: 0 failed, 0 ignored, 2 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_va.txt b/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_va.txt
index 13f8ff375a..4569389a5e 100644
--- a/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_va.txt
+++ b/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_va.txt
@@ -1,9 +1,9 @@
 liTest run started
 liTest org.scalajs.junit.Multi1Test.multiTest1 started
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-e0org.scalajs.junit.Multi1Test.multiTest1
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 liTest org.scalajs.junit.Multi1Test.multiTest2 started
 ldTest org.scalajs.junit.Multi1Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.Multi1Test.multiTest2
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 liTest run finished: 0 failed, 0 ignored, 2 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_vc.txt b/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_vc.txt
index 13f8ff375a..4569389a5e 100644
--- a/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_vc.txt
+++ b/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_vc.txt
@@ -1,9 +1,9 @@
 liTest run started
 liTest org.scalajs.junit.Multi1Test.multiTest1 started
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-e0org.scalajs.junit.Multi1Test.multiTest1
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 liTest org.scalajs.junit.Multi1Test.multiTest2 started
 ldTest org.scalajs.junit.Multi1Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.Multi1Test.multiTest2
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 liTest run finished: 0 failed, 0 ignored, 2 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_vs.txt b/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_vs.txt
index 13f8ff375a..4569389a5e 100644
--- a/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_vs.txt
+++ b/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_vs.txt
@@ -1,9 +1,9 @@
 liTest run started
 liTest org.scalajs.junit.Multi1Test.multiTest1 started
 ldTest org.scalajs.junit.Multi1Test.multiTest1 finished, took <TIME>
-e0org.scalajs.junit.Multi1Test.multiTest1
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 liTest org.scalajs.junit.Multi1Test.multiTest2 started
 ldTest org.scalajs.junit.Multi1Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.Multi1Test.multiTest2
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 liTest run finished: 0 failed, 0 ignored, 2 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_vsn.txt b/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_vsn.txt
index 5c672dbfa2..9c026ac573 100644
--- a/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_vsn.txt
+++ b/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_vsn.txt
@@ -1,9 +1,9 @@
 liTest run started
 liTest org.scalajs.junit.Multi1Test.multiTest1 started
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-e0org.scalajs.junit.Multi1Test.multiTest1
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 liTest org.scalajs.junit.Multi1Test.multiTest2 started
 ldTest org.scalajs.junit.Multi1Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.Multi1Test.multiTest2
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 liTest run finished: 0 failed, 0 ignored, 2 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_.txt b/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_.txt
index f81dc55f9d..7361b034e9 100644
--- a/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_.txt
+++ b/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_.txt
@@ -1,18 +1,18 @@
 ldTest run started
 ldTest org.scalajs.junit.Multi2Test.multiTest1 started
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-e0org.scalajs.junit.Multi2Test.multiTest1
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 ldTest org.scalajs.junit.Multi2Test.multiTest2 started
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-e0org.scalajs.junit.Multi2Test.multiTest2
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 ldTest org.scalajs.junit.Multi2Test.multiTest3 started
 ldTest org.scalajs.junit.Multi2Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest3
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 ldTest org.scalajs.junit.Multi2Test.multiTest4 started
 ldTest org.scalajs.junit.Multi2Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest4
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 ldTest org.scalajs.junit.Multi2Test.multiTest5 started
 ldTest org.scalajs.junit.Multi2Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest5
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 ldTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_a.txt b/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_a.txt
index f81dc55f9d..7361b034e9 100644
--- a/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_a.txt
+++ b/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_a.txt
@@ -1,18 +1,18 @@
 ldTest run started
 ldTest org.scalajs.junit.Multi2Test.multiTest1 started
 ldTest org.scalajs.junit.Multi2Test.multiTest1 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest1
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 ldTest org.scalajs.junit.Multi2Test.multiTest2 started
 ldTest org.scalajs.junit.Multi2Test.multiTest2 finished, took <TIME>
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 ldTest org.scalajs.junit.Multi2Test.multiTest3 started
 ldTest org.scalajs.junit.Multi2Test.multiTest3 finished, took <TIME>
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 ldTest org.scalajs.junit.Multi2Test.multiTest4 started
 ldTest org.scalajs.junit.Multi2Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest4
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 ldTest org.scalajs.junit.Multi2Test.multiTest5 started
 ldTest org.scalajs.junit.Multi2Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest5
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 ldTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_n.txt b/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_n.txt
index d30e331d65..633d2f6adf 100644
--- a/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_n.txt
+++ b/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_n.txt
@@ -1,18 +1,18 @@
 ldTest run started
 ldTest org.scalajs.junit.Multi2Test.multiTest1 started
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 ldTest org.scalajs.junit.Multi2Test.multiTest2 started
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 ldTest org.scalajs.junit.Multi2Test.multiTest3 started
 ldTest org.scalajs.junit.Multi2Test.multiTest3 finished, took <TIME>
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 ldTest org.scalajs.junit.Multi2Test.multiTest4 started
 ldTest org.scalajs.junit.Multi2Test.multiTest4 finished, took <TIME>
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 ldTest org.scalajs.junit.Multi2Test.multiTest5 started
 ldTest org.scalajs.junit.Multi2Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest5
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 ldTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_na.txt b/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_na.txt
index d30e331d65..633d2f6adf 100644
--- a/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_na.txt
+++ b/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_na.txt
@@ -1,18 +1,18 @@
 ldTest run started
 ldTest org.scalajs.junit.Multi2Test.multiTest1 started
 ldTest org.scalajs.junit.Multi2Test.multiTest1 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest1
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 ldTest org.scalajs.junit.Multi2Test.multiTest2 started
 ldTest org.scalajs.junit.Multi2Test.multiTest2 finished, took <TIME>
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 ldTest org.scalajs.junit.Multi2Test.multiTest3 started
 ldTest org.scalajs.junit.Multi2Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest3
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 ldTest org.scalajs.junit.Multi2Test.multiTest4 started
 ldTest org.scalajs.junit.Multi2Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest4
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 ldTest org.scalajs.junit.Multi2Test.multiTest5 started
 ldTest org.scalajs.junit.Multi2Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest5
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 ldTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_nv.txt b/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_nv.txt
index 9e51a0d6d2..ef9160fa43 100644
--- a/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_nv.txt
+++ b/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_nv.txt
@@ -1,18 +1,18 @@
 liTest run started
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 liTest org.scalajs.junit.Multi2Test.multiTest2 started
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-e0org.scalajs.junit.Multi2Test.multiTest2
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 liTest org.scalajs.junit.Multi2Test.multiTest3 started
 ldTest org.scalajs.junit.Multi2Test.multiTest3 finished, took <TIME>
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 liTest org.scalajs.junit.Multi2Test.multiTest4 started
 ldTest org.scalajs.junit.Multi2Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest4
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 liTest org.scalajs.junit.Multi2Test.multiTest5 started
 ldTest org.scalajs.junit.Multi2Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest5
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 liTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_nva.txt b/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_nva.txt
index 9e51a0d6d2..ef9160fa43 100644
--- a/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_nva.txt
+++ b/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_nva.txt
@@ -1,18 +1,18 @@
 liTest run started
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-e0org.scalajs.junit.Multi2Test.multiTest1
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 liTest org.scalajs.junit.Multi2Test.multiTest3 started
 ldTest org.scalajs.junit.Multi2Test.multiTest3 finished, took <TIME>
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 liTest org.scalajs.junit.Multi2Test.multiTest4 started
 ldTest org.scalajs.junit.Multi2Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest4
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 liTest org.scalajs.junit.Multi2Test.multiTest5 started
 ldTest org.scalajs.junit.Multi2Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest5
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 liTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_nvc.txt b/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_nvc.txt
index 9e51a0d6d2..ef9160fa43 100644
--- a/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_nvc.txt
+++ b/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_nvc.txt
@@ -1,18 +1,18 @@
 liTest run started
 liTest org.scalajs.junit.Multi2Test.multiTest1 started
 ldTest org.scalajs.junit.Multi2Test.multiTest1 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest1
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 liTest org.scalajs.junit.Multi2Test.multiTest2 started
 ldTest org.scalajs.junit.Multi2Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest2
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 liTest org.scalajs.junit.Multi2Test.multiTest3 started
 ldTest org.scalajs.junit.Multi2Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest3
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 liTest org.scalajs.junit.Multi2Test.multiTest4 started
 ldTest org.scalajs.junit.Multi2Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest4
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 liTest org.scalajs.junit.Multi2Test.multiTest5 started
 ldTest org.scalajs.junit.Multi2Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest5
+e0org.scalajs.junit.Multi2Test.multiTest5::
 liTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_nvca.txt b/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_nvca.txt
index 9e51a0d6d2..ef9160fa43 100644
--- a/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_nvca.txt
+++ b/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_nvca.txt
@@ -1,18 +1,18 @@
 liTest run started
 liTest org.scalajs.junit.Multi2Test.multiTest1 started
 ldTest org.scalajs.junit.Multi2Test.multiTest1 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest1
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 liTest org.scalajs.junit.Multi2Test.multiTest2 started
 ldTest org.scalajs.junit.Multi2Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest2
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 liTest org.scalajs.junit.Multi2Test.multiTest3 started
 ldTest org.scalajs.junit.Multi2Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest3
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 liTest org.scalajs.junit.Multi2Test.multiTest4 started
 ldTest org.scalajs.junit.Multi2Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest4
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 liTest org.scalajs.junit.Multi2Test.multiTest5 started
 ldTest org.scalajs.junit.Multi2Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest5
+e0org.scalajs.junit.Multi2Test.multiTest5::
 liTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_v.txt b/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_v.txt
index 0034d865be..de892dea4a 100644
--- a/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_v.txt
+++ b/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_v.txt
@@ -1,18 +1,18 @@
 liTest run started
 liTest org.scalajs.junit.Multi2Test.multiTest1 started
 ldTest org.scalajs.junit.Multi2Test.multiTest1 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest1
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 liTest org.scalajs.junit.Multi2Test.multiTest2 started
 ldTest org.scalajs.junit.Multi2Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest2
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 liTest org.scalajs.junit.Multi2Test.multiTest3 started
 ldTest org.scalajs.junit.Multi2Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest3
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 liTest org.scalajs.junit.Multi2Test.multiTest4 started
 ldTest org.scalajs.junit.Multi2Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest4
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 liTest org.scalajs.junit.Multi2Test.multiTest5 started
 ldTest org.scalajs.junit.Multi2Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest5
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 liTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_va.txt b/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_va.txt
index 0034d865be..de892dea4a 100644
--- a/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_va.txt
+++ b/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_va.txt
@@ -1,18 +1,18 @@
 liTest run started
 liTest org.scalajs.junit.Multi2Test.multiTest1 started
 ldTest org.scalajs.junit.Multi2Test.multiTest1 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest1
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 liTest org.scalajs.junit.Multi2Test.multiTest2 started
 ldTest org.scalajs.junit.Multi2Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest2
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 liTest org.scalajs.junit.Multi2Test.multiTest3 started
 ldTest org.scalajs.junit.Multi2Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest3
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 liTest org.scalajs.junit.Multi2Test.multiTest4 started
 ldTest org.scalajs.junit.Multi2Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest4
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 liTest org.scalajs.junit.Multi2Test.multiTest5 started
 ldTest org.scalajs.junit.Multi2Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest5
+e0org.scalajs.junit.Multi2Test.multiTest5::
 liTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_vc.txt b/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_vc.txt
index 0034d865be..de892dea4a 100644
--- a/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_vc.txt
+++ b/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_vc.txt
@@ -1,18 +1,18 @@
 liTest run started
 liTest org.scalajs.junit.Multi2Test.multiTest1 started
 ldTest org.scalajs.junit.Multi2Test.multiTest1 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest1
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 liTest org.scalajs.junit.Multi2Test.multiTest2 started
 ldTest org.scalajs.junit.Multi2Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest2
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 liTest org.scalajs.junit.Multi2Test.multiTest3 started
 ldTest org.scalajs.junit.Multi2Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest3
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 liTest org.scalajs.junit.Multi2Test.multiTest4 started
 ldTest org.scalajs.junit.Multi2Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest4
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 liTest org.scalajs.junit.Multi2Test.multiTest5 started
 ldTest org.scalajs.junit.Multi2Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest5
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 liTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_vs.txt b/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_vs.txt
index 0034d865be..de892dea4a 100644
--- a/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_vs.txt
+++ b/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_vs.txt
@@ -1,18 +1,18 @@
 liTest run started
 liTest org.scalajs.junit.Multi2Test.multiTest1 started
 ldTest org.scalajs.junit.Multi2Test.multiTest1 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest1
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 liTest org.scalajs.junit.Multi2Test.multiTest2 started
 ldTest org.scalajs.junit.Multi2Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest2
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 liTest org.scalajs.junit.Multi2Test.multiTest3 started
 ldTest org.scalajs.junit.Multi2Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest3
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 liTest org.scalajs.junit.Multi2Test.multiTest4 started
 ldTest org.scalajs.junit.Multi2Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest4
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 liTest org.scalajs.junit.Multi2Test.multiTest5 started
 ldTest org.scalajs.junit.Multi2Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest5
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 liTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_vsn.txt b/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_vsn.txt
index 9e51a0d6d2..ef9160fa43 100644
--- a/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_vsn.txt
+++ b/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_vsn.txt
@@ -1,18 +1,18 @@
 liTest run started
 liTest org.scalajs.junit.Multi2Test.multiTest1 started
 ldTest org.scalajs.junit.Multi2Test.multiTest1 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest1
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 liTest org.scalajs.junit.Multi2Test.multiTest2 started
 ldTest org.scalajs.junit.Multi2Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest2
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 liTest org.scalajs.junit.Multi2Test.multiTest3 started
 ldTest org.scalajs.junit.Multi2Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest3
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 liTest org.scalajs.junit.Multi2Test.multiTest4 started
 ldTest org.scalajs.junit.Multi2Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest4
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 liTest org.scalajs.junit.Multi2Test.multiTest5 started
 ldTest org.scalajs.junit.Multi2Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest5
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 liTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_.txt b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_.txt
index aa21df4ef0..2b1028c5a0 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_.txt
@@ -1,19 +1,19 @@
 ldTest run started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest1 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail1Test.multiTest1 failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail1Test.multiTest1
+e3org.scalajs.junit.MultiAssumeFail1Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest1 finished, took <TIME>
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest2 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest2
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 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest3 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest3
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 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest4 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest4
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 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest5 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest5
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest5::
 ldTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_a.txt b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_a.txt
index aa21df4ef0..2b1028c5a0 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_a.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_a.txt
@@ -1,19 +1,19 @@
 ldTest run started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest1 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail1Test.multiTest1 failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail1Test.multiTest1
+e3org.scalajs.junit.MultiAssumeFail1Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest1 finished, took <TIME>
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest2 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest2
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 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest3 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest3
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 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest4 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest4
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 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest5 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest5
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest5::
 ldTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_n.txt b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_n.txt
index 36a220d7f8..7bcb8dc9b1 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_n.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_n.txt
@@ -1,19 +1,19 @@
 ldTest run started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest1 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail1Test.multiTest1 failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail1Test.multiTest1
+e3org.scalajs.junit.MultiAssumeFail1Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest1 finished, took <TIME>
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest2 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest2
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 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest3 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest3
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 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest4 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest4
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest4::
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest5 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest5
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest5::
 ldTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_na.txt b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_na.txt
index 36a220d7f8..7bcb8dc9b1 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_na.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_na.txt
@@ -1,19 +1,19 @@
 ldTest run started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest1 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail1Test.multiTest1 failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail1Test.multiTest1
+e3org.scalajs.junit.MultiAssumeFail1Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest1 finished, took <TIME>
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest2 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest2
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest2::
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest3 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest3
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 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest4 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest4
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 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest5 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest5
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest5::
 ldTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_nv.txt b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_nv.txt
index f13130d224..c1ef53f411 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_nv.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_nv.txt
@@ -1,19 +1,19 @@
 liTest run started
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest1 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail1Test.multiTest1 failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail1Test.multiTest1
+e3org.scalajs.junit.MultiAssumeFail1Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest1 finished, took <TIME>
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest2 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest2
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest2::
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest3 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest3
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 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest4 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest4
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest4::
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest5 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest5
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest5::
 liTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_nva.txt b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_nva.txt
index f13130d224..c1ef53f411 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_nva.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_nva.txt
@@ -1,19 +1,19 @@
 liTest run started
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest1 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail1Test.multiTest1 failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail1Test.multiTest1
+e3org.scalajs.junit.MultiAssumeFail1Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest1 finished, took <TIME>
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest2 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest2
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest2::
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest3 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest3
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest3::
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest4 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest4
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest4::
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest5 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest5
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest5::
 liTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_nvc.txt b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_nvc.txt
index cfca6dffd3..2081bb74eb 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_nvc.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_nvc.txt
@@ -1,19 +1,19 @@
 liTest run started
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest1 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail1Test.multiTest1 failed: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail1Test.multiTest1
+e3org.scalajs.junit.MultiAssumeFail1Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest1 finished, took <TIME>
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest2 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest2
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest2::
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest3 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest3
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest3::
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest4 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest4
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest4::
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest5 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest5
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest5::
 liTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_nvca.txt b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_nvca.txt
index cfca6dffd3..2081bb74eb 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_nvca.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_nvca.txt
@@ -1,19 +1,19 @@
 liTest run started
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest1 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail1Test.multiTest1 failed: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail1Test.multiTest1
+e3org.scalajs.junit.MultiAssumeFail1Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest1 finished, took <TIME>
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest2 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest2
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest2::
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest3 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest3
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest3::
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest4 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest4
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest4::
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest5 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest5
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest5::
 liTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_v.txt b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_v.txt
index abc464c5b8..f722c33262 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_v.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_v.txt
@@ -1,19 +1,19 @@
 liTest run started
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest1 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail1Test.multiTest1 failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail1Test.multiTest1
+e3org.scalajs.junit.MultiAssumeFail1Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest1 finished, took <TIME>
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest2 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest2
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest2::
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest3 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest3
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest3::
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest4 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest4
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest4::
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest5 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest5
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest5::
 liTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_va.txt b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_va.txt
index abc464c5b8..f722c33262 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_va.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_va.txt
@@ -1,19 +1,19 @@
 liTest run started
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest1 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail1Test.multiTest1 failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail1Test.multiTest1
+e3org.scalajs.junit.MultiAssumeFail1Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest1 finished, took <TIME>
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest2 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest2
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest2::
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest3 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest3
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest3::
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest4 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest4
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest4::
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest5 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest5
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest5::
 liTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_vc.txt b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_vc.txt
index 843915c659..55bbc61efa 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_vc.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_vc.txt
@@ -1,19 +1,19 @@
 liTest run started
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest1 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail1Test.multiTest1 failed: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail1Test.multiTest1
+e3org.scalajs.junit.MultiAssumeFail1Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest1 finished, took <TIME>
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest2 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest2
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest2::
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest3 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest3
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest3::
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest4 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest4
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest4::
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest5 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest5
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest5::
 liTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_vs.txt b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_vs.txt
index abc464c5b8..f722c33262 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_vs.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_vs.txt
@@ -1,19 +1,19 @@
 liTest run started
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest1 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail1Test.multiTest1 failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail1Test.multiTest1
+e3org.scalajs.junit.MultiAssumeFail1Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest1 finished, took <TIME>
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest2 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest2
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest2::
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest3 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest3
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest3::
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest4 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest4
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest4::
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest5 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest5
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest5::
 liTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_vsn.txt b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_vsn.txt
index f13130d224..c1ef53f411 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_vsn.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_vsn.txt
@@ -1,19 +1,19 @@
 liTest run started
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest1 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail1Test.multiTest1 failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail1Test.multiTest1
+e3org.scalajs.junit.MultiAssumeFail1Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest1 finished, took <TIME>
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest2 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest2
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest2::
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest3 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest3
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest3::
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest4 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest4
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest4::
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest5 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest5
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest5::
 liTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_.txt b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_.txt
index d5815e75a3..f9047db04c 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_.txt
@@ -1,20 +1,20 @@
 ldTest run started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest1 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail2Test.multiTest1 failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail2Test.multiTest1
+e3org.scalajs.junit.MultiAssumeFail2Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest1 finished, took <TIME>
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest2 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest2
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest2::
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest3 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest3
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest3::
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest4 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail2Test.multiTest4 failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail2Test.multiTest4
+e3org.scalajs.junit.MultiAssumeFail2Test.multiTest4::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest4 finished, took <TIME>
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest5 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest5
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest5::
 ldTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_a.txt b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_a.txt
index d5815e75a3..f9047db04c 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_a.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_a.txt
@@ -1,20 +1,20 @@
 ldTest run started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest1 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail2Test.multiTest1 failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail2Test.multiTest1
+e3org.scalajs.junit.MultiAssumeFail2Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest1 finished, took <TIME>
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest2 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest2
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest2::
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest3 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest3
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest3::
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest4 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail2Test.multiTest4 failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail2Test.multiTest4
+e3org.scalajs.junit.MultiAssumeFail2Test.multiTest4::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest4 finished, took <TIME>
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest5 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest5
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest5::
 ldTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_n.txt b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_n.txt
index f718eb2300..f27cd9e937 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_n.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_n.txt
@@ -1,20 +1,20 @@
 ldTest run started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest1 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail2Test.multiTest1 failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail2Test.multiTest1
+e3org.scalajs.junit.MultiAssumeFail2Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest1 finished, took <TIME>
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest2 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest2
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest2::
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest3 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest3
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest3::
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest4 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail2Test.multiTest4 failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail2Test.multiTest4
+e3org.scalajs.junit.MultiAssumeFail2Test.multiTest4::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest4 finished, took <TIME>
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest5 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest5
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest5::
 ldTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_na.txt b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_na.txt
index f718eb2300..f27cd9e937 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_na.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_na.txt
@@ -1,20 +1,20 @@
 ldTest run started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest1 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail2Test.multiTest1 failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail2Test.multiTest1
+e3org.scalajs.junit.MultiAssumeFail2Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest1 finished, took <TIME>
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest2 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest2
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest2::
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest3 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest3
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest3::
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest4 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail2Test.multiTest4 failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail2Test.multiTest4
+e3org.scalajs.junit.MultiAssumeFail2Test.multiTest4::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest4 finished, took <TIME>
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest5 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest5
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest5::
 ldTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_nv.txt b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_nv.txt
index 5495960543..99d229d87f 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_nv.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_nv.txt
@@ -1,20 +1,20 @@
 liTest run started
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest1 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail2Test.multiTest1 failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail2Test.multiTest1
+e3org.scalajs.junit.MultiAssumeFail2Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest1 finished, took <TIME>
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest2 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest2
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest2::
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest3 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest3
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest3::
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest4 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail2Test.multiTest4 failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail2Test.multiTest4
+e3org.scalajs.junit.MultiAssumeFail2Test.multiTest4::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest4 finished, took <TIME>
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest5 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest5
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest5::
 liTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_nva.txt b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_nva.txt
index 5495960543..99d229d87f 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_nva.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_nva.txt
@@ -1,20 +1,20 @@
 liTest run started
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest1 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail2Test.multiTest1 failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail2Test.multiTest1
+e3org.scalajs.junit.MultiAssumeFail2Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest1 finished, took <TIME>
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest2 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest2
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest2::
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest3 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest3
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest3::
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest4 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail2Test.multiTest4 failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail2Test.multiTest4
+e3org.scalajs.junit.MultiAssumeFail2Test.multiTest4::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest4 finished, took <TIME>
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest5 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest5
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest5::
 liTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_nvc.txt b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_nvc.txt
index d52ebd703f..116f3267e6 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_nvc.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_nvc.txt
@@ -1,20 +1,20 @@
 liTest run started
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest1 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail2Test.multiTest1 failed: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail2Test.multiTest1
+e3org.scalajs.junit.MultiAssumeFail2Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest1 finished, took <TIME>
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest2 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest2
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest2::
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest3 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest3
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest3::
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest4 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail2Test.multiTest4 failed: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail2Test.multiTest4
+e3org.scalajs.junit.MultiAssumeFail2Test.multiTest4::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest4 finished, took <TIME>
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest5 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest5
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest5::
 liTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_nvca.txt b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_nvca.txt
index d52ebd703f..116f3267e6 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_nvca.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_nvca.txt
@@ -1,20 +1,20 @@
 liTest run started
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest1 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail2Test.multiTest1 failed: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail2Test.multiTest1
+e3org.scalajs.junit.MultiAssumeFail2Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest1 finished, took <TIME>
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest2 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest2
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest2::
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest3 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest3
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest3::
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest4 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail2Test.multiTest4 failed: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail2Test.multiTest4
+e3org.scalajs.junit.MultiAssumeFail2Test.multiTest4::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest4 finished, took <TIME>
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest5 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest5
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest5::
 liTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_v.txt b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_v.txt
index 1b0481ead2..44ed8d6500 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_v.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_v.txt
@@ -1,20 +1,20 @@
 liTest run started
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest1 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail2Test.multiTest1 failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail2Test.multiTest1
+e3org.scalajs.junit.MultiAssumeFail2Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest1 finished, took <TIME>
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest2 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest2
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest2::
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest3 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest3
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest3::
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest4 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail2Test.multiTest4 failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail2Test.multiTest4
+e3org.scalajs.junit.MultiAssumeFail2Test.multiTest4::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest4 finished, took <TIME>
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest5 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest5
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest5::
 liTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_va.txt b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_va.txt
index 1b0481ead2..44ed8d6500 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_va.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_va.txt
@@ -1,20 +1,20 @@
 liTest run started
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest1 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail2Test.multiTest1 failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail2Test.multiTest1
+e3org.scalajs.junit.MultiAssumeFail2Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest1 finished, took <TIME>
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest2 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest2
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest2::
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest3 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest3
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest3::
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest4 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail2Test.multiTest4 failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail2Test.multiTest4
+e3org.scalajs.junit.MultiAssumeFail2Test.multiTest4::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest4 finished, took <TIME>
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest5 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest5
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest5::
 liTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_vc.txt b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_vc.txt
index 0bf16e43a7..e209c65918 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_vc.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_vc.txt
@@ -1,20 +1,20 @@
 liTest run started
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest1 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail2Test.multiTest1 failed: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail2Test.multiTest1
+e3org.scalajs.junit.MultiAssumeFail2Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest1 finished, took <TIME>
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest2 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest2
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest2::
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest3 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest3
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest3::
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest4 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail2Test.multiTest4 failed: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail2Test.multiTest4
+e3org.scalajs.junit.MultiAssumeFail2Test.multiTest4::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest4 finished, took <TIME>
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest5 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest5
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest5::
 liTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_vs.txt b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_vs.txt
index 1b0481ead2..44ed8d6500 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_vs.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_vs.txt
@@ -1,20 +1,20 @@
 liTest run started
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest1 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail2Test.multiTest1 failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail2Test.multiTest1
+e3org.scalajs.junit.MultiAssumeFail2Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest1 finished, took <TIME>
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest2 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest2
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest2::
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest3 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest3
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest3::
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest4 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail2Test.multiTest4 failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail2Test.multiTest4
+e3org.scalajs.junit.MultiAssumeFail2Test.multiTest4::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest4 finished, took <TIME>
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest5 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest5
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest5::
 liTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_vsn.txt b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_vsn.txt
index 5495960543..99d229d87f 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_vsn.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_vsn.txt
@@ -1,20 +1,20 @@
 liTest run started
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest1 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail2Test.multiTest1 failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail2Test.multiTest1
+e3org.scalajs.junit.MultiAssumeFail2Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest1 finished, took <TIME>
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest2 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest2
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest2::
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest3 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest3
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest3::
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest4 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail2Test.multiTest4 failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail2Test.multiTest4
+e3org.scalajs.junit.MultiAssumeFail2Test.multiTest4::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest4 finished, took <TIME>
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest5 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest5
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest5::
 liTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_.txt b/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_.txt
index 18364b3163..e86d2bf4bb 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_.txt
@@ -1,5 +1,5 @@
 ldTest run started
 lwTest assumption in test org.scalajs.junit.MultiBeforeAssumeFailTest failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiBeforeAssumeFailTest
+e3org.scalajs.junit.MultiBeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest run finished: 0 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_a.txt b/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_a.txt
index 18364b3163..e86d2bf4bb 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_a.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_a.txt
@@ -1,5 +1,5 @@
 ldTest run started
 lwTest assumption in test org.scalajs.junit.MultiBeforeAssumeFailTest failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiBeforeAssumeFailTest
+e3org.scalajs.junit.MultiBeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest run finished: 0 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_n.txt b/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_n.txt
index 9b15280cf6..36cb87022e 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_n.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_n.txt
@@ -1,5 +1,5 @@
 ldTest run started
 lwTest assumption in test org.scalajs.junit.MultiBeforeAssumeFailTest failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiBeforeAssumeFailTest
+e3org.scalajs.junit.MultiBeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest run finished: 0 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_na.txt b/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_na.txt
index 9b15280cf6..36cb87022e 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_na.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_na.txt
@@ -1,5 +1,5 @@
 ldTest run started
 lwTest assumption in test org.scalajs.junit.MultiBeforeAssumeFailTest failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiBeforeAssumeFailTest
+e3org.scalajs.junit.MultiBeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass
 ldTest run finished: 0 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_nv.txt b/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_nv.txt
index 0b18e943d7..be6b889225 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_nv.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_nv.txt
@@ -1,5 +1,5 @@
 liTest run started
 lwTest assumption in test org.scalajs.junit.MultiBeforeAssumeFailTest failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiBeforeAssumeFailTest
+e3org.scalajs.junit.MultiBeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass
 liTest run finished: 0 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_nva.txt b/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_nva.txt
index 0b18e943d7..be6b889225 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_nva.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_nva.txt
@@ -1,5 +1,5 @@
 liTest run started
 lwTest assumption in test org.scalajs.junit.MultiBeforeAssumeFailTest failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiBeforeAssumeFailTest
+e3org.scalajs.junit.MultiBeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass
 liTest run finished: 0 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_nvc.txt b/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_nvc.txt
index 19ccf761bf..bf5abd3192 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_nvc.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_nvc.txt
@@ -1,5 +1,5 @@
 liTest run started
 lwTest assumption in test org.scalajs.junit.MultiBeforeAssumeFailTest failed: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiBeforeAssumeFailTest
+e3org.scalajs.junit.MultiBeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass
 liTest run finished: 0 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_nvca.txt b/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_nvca.txt
index 19ccf761bf..bf5abd3192 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_nvca.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_nvca.txt
@@ -1,5 +1,5 @@
 liTest run started
 lwTest assumption in test org.scalajs.junit.MultiBeforeAssumeFailTest failed: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiBeforeAssumeFailTest
+e3org.scalajs.junit.MultiBeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass
 liTest run finished: 0 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_v.txt b/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_v.txt
index a5808ff296..ab67afd984 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_v.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_v.txt
@@ -1,5 +1,5 @@
 liTest run started
 lwTest assumption in test org.scalajs.junit.MultiBeforeAssumeFailTest failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiBeforeAssumeFailTest
+e3org.scalajs.junit.MultiBeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass
 liTest run finished: 0 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_va.txt b/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_va.txt
index a5808ff296..ab67afd984 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_va.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_va.txt
@@ -1,5 +1,5 @@
 liTest run started
 lwTest assumption in test org.scalajs.junit.MultiBeforeAssumeFailTest failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiBeforeAssumeFailTest
+e3org.scalajs.junit.MultiBeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass
 liTest run finished: 0 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_vc.txt b/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_vc.txt
index 2d77c818bb..4ff91826dc 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_vc.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_vc.txt
@@ -1,5 +1,5 @@
 liTest run started
 lwTest assumption in test org.scalajs.junit.MultiBeforeAssumeFailTest failed: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiBeforeAssumeFailTest
+e3org.scalajs.junit.MultiBeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass
 liTest run finished: 0 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_vs.txt b/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_vs.txt
index a5808ff296..ab67afd984 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_vs.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_vs.txt
@@ -1,5 +1,5 @@
 liTest run started
 lwTest assumption in test org.scalajs.junit.MultiBeforeAssumeFailTest failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiBeforeAssumeFailTest
+e3org.scalajs.junit.MultiBeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass
 liTest run finished: 0 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_vsn.txt b/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_vsn.txt
index 0b18e943d7..be6b889225 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_vsn.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_vsn.txt
@@ -1,5 +1,5 @@
 liTest run started
 lwTest assumption in test org.scalajs.junit.MultiBeforeAssumeFailTest failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiBeforeAssumeFailTest
+e3org.scalajs.junit.MultiBeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass
 liTest run finished: 0 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_.txt
index 7a84a7033a..0d0de86bec 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_.txt
@@ -1,17 +1,17 @@
 ldTest run started
 liTest org.scalajs.junit.MultiIgnore1Test.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnore1Test.multiTest1
+e3org.scalajs.junit.MultiIgnore1Test.multiTest1::
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest2 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest2
+e0org.scalajs.junit.MultiIgnore1Test.multiTest2::
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest3 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest3
+e0org.scalajs.junit.MultiIgnore1Test.multiTest3::
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest4 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest4
+e0org.scalajs.junit.MultiIgnore1Test.multiTest4::
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest5 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest5
+e0org.scalajs.junit.MultiIgnore1Test.multiTest5::
 ldTest run finished: 0 failed, 1 ignored, 4 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_a.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_a.txt
index 7a84a7033a..0d0de86bec 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_a.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_a.txt
@@ -1,17 +1,17 @@
 ldTest run started
 liTest org.scalajs.junit.MultiIgnore1Test.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnore1Test.multiTest1
+e3org.scalajs.junit.MultiIgnore1Test.multiTest1::
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest2 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest2
+e0org.scalajs.junit.MultiIgnore1Test.multiTest2::
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest3 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest3
+e0org.scalajs.junit.MultiIgnore1Test.multiTest3::
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest4 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest4
+e0org.scalajs.junit.MultiIgnore1Test.multiTest4::
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest5 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest5
+e0org.scalajs.junit.MultiIgnore1Test.multiTest5::
 ldTest run finished: 0 failed, 1 ignored, 4 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_n.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_n.txt
index 62fe8b86ca..a4a934491d 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_n.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_n.txt
@@ -1,17 +1,17 @@
 ldTest run started
 liTest org.scalajs.junit.MultiIgnore1Test.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnore1Test.multiTest1
+e3org.scalajs.junit.MultiIgnore1Test.multiTest1::
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest2 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest2
+e0org.scalajs.junit.MultiIgnore1Test.multiTest2::
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest3 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest3
+e0org.scalajs.junit.MultiIgnore1Test.multiTest3::
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest4 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest4
+e0org.scalajs.junit.MultiIgnore1Test.multiTest4::
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest5 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest5
+e0org.scalajs.junit.MultiIgnore1Test.multiTest5::
 ldTest run finished: 0 failed, 1 ignored, 4 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_na.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_na.txt
index 62fe8b86ca..a4a934491d 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_na.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_na.txt
@@ -1,17 +1,17 @@
 ldTest run started
 liTest org.scalajs.junit.MultiIgnore1Test.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnore1Test.multiTest1
+e3org.scalajs.junit.MultiIgnore1Test.multiTest1::
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest2 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest2
+e0org.scalajs.junit.MultiIgnore1Test.multiTest2::
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest3 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest3
+e0org.scalajs.junit.MultiIgnore1Test.multiTest3::
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest4 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest4
+e0org.scalajs.junit.MultiIgnore1Test.multiTest4::
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest5 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest5
+e0org.scalajs.junit.MultiIgnore1Test.multiTest5::
 ldTest run finished: 0 failed, 1 ignored, 4 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_nv.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_nv.txt
index fa07a3e3de..66b9cf269d 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_nv.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_nv.txt
@@ -1,17 +1,17 @@
 liTest run started
 liTest org.scalajs.junit.MultiIgnore1Test.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnore1Test.multiTest1
+e3org.scalajs.junit.MultiIgnore1Test.multiTest1::
 liTest org.scalajs.junit.MultiIgnore1Test.multiTest2 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest2
+e0org.scalajs.junit.MultiIgnore1Test.multiTest2::
 liTest org.scalajs.junit.MultiIgnore1Test.multiTest3 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest3
+e0org.scalajs.junit.MultiIgnore1Test.multiTest3::
 liTest org.scalajs.junit.MultiIgnore1Test.multiTest4 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest4
+e0org.scalajs.junit.MultiIgnore1Test.multiTest4::
 liTest org.scalajs.junit.MultiIgnore1Test.multiTest5 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest5
+e0org.scalajs.junit.MultiIgnore1Test.multiTest5::
 liTest run finished: 0 failed, 1 ignored, 4 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_nva.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_nva.txt
index fa07a3e3de..66b9cf269d 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_nva.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_nva.txt
@@ -1,17 +1,17 @@
 liTest run started
 liTest org.scalajs.junit.MultiIgnore1Test.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnore1Test.multiTest1
+e3org.scalajs.junit.MultiIgnore1Test.multiTest1::
 liTest org.scalajs.junit.MultiIgnore1Test.multiTest2 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest2
+e0org.scalajs.junit.MultiIgnore1Test.multiTest2::
 liTest org.scalajs.junit.MultiIgnore1Test.multiTest3 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest3
+e0org.scalajs.junit.MultiIgnore1Test.multiTest3::
 liTest org.scalajs.junit.MultiIgnore1Test.multiTest4 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest4
+e0org.scalajs.junit.MultiIgnore1Test.multiTest4::
 liTest org.scalajs.junit.MultiIgnore1Test.multiTest5 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest5
+e0org.scalajs.junit.MultiIgnore1Test.multiTest5::
 liTest run finished: 0 failed, 1 ignored, 4 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_nvc.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_nvc.txt
index fa07a3e3de..66b9cf269d 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_nvc.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_nvc.txt
@@ -1,17 +1,17 @@
 liTest run started
 liTest org.scalajs.junit.MultiIgnore1Test.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnore1Test.multiTest1
+e3org.scalajs.junit.MultiIgnore1Test.multiTest1::
 liTest org.scalajs.junit.MultiIgnore1Test.multiTest2 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest2
+e0org.scalajs.junit.MultiIgnore1Test.multiTest2::
 liTest org.scalajs.junit.MultiIgnore1Test.multiTest3 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest3
+e0org.scalajs.junit.MultiIgnore1Test.multiTest3::
 liTest org.scalajs.junit.MultiIgnore1Test.multiTest4 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest4
+e0org.scalajs.junit.MultiIgnore1Test.multiTest4::
 liTest org.scalajs.junit.MultiIgnore1Test.multiTest5 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest5
+e0org.scalajs.junit.MultiIgnore1Test.multiTest5::
 liTest run finished: 0 failed, 1 ignored, 4 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_nvca.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_nvca.txt
index fa07a3e3de..66b9cf269d 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_nvca.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_nvca.txt
@@ -1,17 +1,17 @@
 liTest run started
 liTest org.scalajs.junit.MultiIgnore1Test.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnore1Test.multiTest1
+e3org.scalajs.junit.MultiIgnore1Test.multiTest1::
 liTest org.scalajs.junit.MultiIgnore1Test.multiTest2 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest2
+e0org.scalajs.junit.MultiIgnore1Test.multiTest2::
 liTest org.scalajs.junit.MultiIgnore1Test.multiTest3 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest3
+e0org.scalajs.junit.MultiIgnore1Test.multiTest3::
 liTest org.scalajs.junit.MultiIgnore1Test.multiTest4 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest4
+e0org.scalajs.junit.MultiIgnore1Test.multiTest4::
 liTest org.scalajs.junit.MultiIgnore1Test.multiTest5 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest5 finished, took <TIME>
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 liTest run finished: 0 failed, 1 ignored, 4 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_v.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_v.txt
index 12abaa11c0..015e238a7b 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_v.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_v.txt
@@ -1,17 +1,17 @@
 liTest run started
 liTest org.scalajs.junit.MultiIgnore1Test.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnore1Test.multiTest1
+e3org.scalajs.junit.MultiIgnore1Test.multiTest1::
 liTest org.scalajs.junit.MultiIgnore1Test.multiTest2 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest2
+e0org.scalajs.junit.MultiIgnore1Test.multiTest2::
 liTest org.scalajs.junit.MultiIgnore1Test.multiTest3 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest3
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 liTest org.scalajs.junit.MultiIgnore1Test.multiTest4 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest4
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 liTest org.scalajs.junit.MultiIgnore1Test.multiTest5 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest5 finished, took <TIME>
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 liTest run finished: 0 failed, 1 ignored, 4 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_va.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_va.txt
index 12abaa11c0..015e238a7b 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_va.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_va.txt
@@ -1,17 +1,17 @@
 liTest run started
 liTest org.scalajs.junit.MultiIgnore1Test.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnore1Test.multiTest1
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 liTest org.scalajs.junit.MultiIgnore1Test.multiTest2 started
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-e0org.scalajs.junit.MultiIgnore1Test.multiTest3
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 liTest org.scalajs.junit.MultiIgnore1Test.multiTest4 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest4
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 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest5
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 liTest run finished: 0 failed, 1 ignored, 4 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_vc.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_vc.txt
index 12abaa11c0..015e238a7b 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_vc.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_vc.txt
@@ -1,17 +1,17 @@
 liTest run started
 liTest org.scalajs.junit.MultiIgnore1Test.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnore1Test.multiTest1
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 liTest org.scalajs.junit.MultiIgnore1Test.multiTest2 started
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 liTest org.scalajs.junit.MultiIgnore1Test.multiTest3 started
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 liTest org.scalajs.junit.MultiIgnore1Test.multiTest4 started
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-e0org.scalajs.junit.MultiIgnore1Test.multiTest4
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 liTest org.scalajs.junit.MultiIgnore1Test.multiTest5 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest5
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 liTest run finished: 0 failed, 1 ignored, 4 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_vs.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_vs.txt
index 12abaa11c0..015e238a7b 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_vs.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_vs.txt
@@ -1,17 +1,17 @@
 liTest run started
 liTest org.scalajs.junit.MultiIgnore1Test.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnore1Test.multiTest1
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 liTest org.scalajs.junit.MultiIgnore1Test.multiTest2 started
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 liTest org.scalajs.junit.MultiIgnore1Test.multiTest3 started
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-e0org.scalajs.junit.MultiIgnore1Test.multiTest3
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 liTest org.scalajs.junit.MultiIgnore1Test.multiTest4 started
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-e0org.scalajs.junit.MultiIgnore1Test.multiTest4
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 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest5
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 liTest run finished: 0 failed, 1 ignored, 4 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_vsn.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_vsn.txt
index fa07a3e3de..66b9cf269d 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_vsn.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_vsn.txt
@@ -1,17 +1,17 @@
 liTest run started
 liTest org.scalajs.junit.MultiIgnore1Test.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnore1Test.multiTest1
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 liTest org.scalajs.junit.MultiIgnore1Test.multiTest4 started
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 liTest run finished: 0 failed, 1 ignored, 4 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_.txt
index d167546c92..84425fd6b6 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_.txt
@@ -1,16 +1,16 @@
 ldTest run started
 liTest org.scalajs.junit.MultiIgnore2Test.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnore2Test.multiTest1
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 ldTest org.scalajs.junit.MultiIgnore2Test.multiTest2 started
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-e0org.scalajs.junit.MultiIgnore2Test.multiTest3
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 liTest org.scalajs.junit.MultiIgnore2Test.multiTest4 ignored
-e3org.scalajs.junit.MultiIgnore2Test.multiTest4
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 ldTest org.scalajs.junit.MultiIgnore2Test.multiTest5 started
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-e0org.scalajs.junit.MultiIgnore2Test.multiTest5
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 ldTest run finished: 0 failed, 2 ignored, 3 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_a.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_a.txt
index d167546c92..84425fd6b6 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_a.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_a.txt
@@ -1,16 +1,16 @@
 ldTest run started
 liTest org.scalajs.junit.MultiIgnore2Test.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnore2Test.multiTest1
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-e0org.scalajs.junit.MultiIgnore2Test.multiTest3
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 liTest org.scalajs.junit.MultiIgnore2Test.multiTest4 ignored
-e3org.scalajs.junit.MultiIgnore2Test.multiTest4
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 ldTest org.scalajs.junit.MultiIgnore2Test.multiTest5 started
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-e0org.scalajs.junit.MultiIgnore2Test.multiTest5
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 ldTest run finished: 0 failed, 2 ignored, 3 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_n.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_n.txt
index 960f5b1149..a3bb9a46dd 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_n.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_n.txt
@@ -1,16 +1,16 @@
 ldTest run started
 liTest org.scalajs.junit.MultiIgnore2Test.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnore2Test.multiTest1
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 ldTest org.scalajs.junit.MultiIgnore2Test.multiTest2 started
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-e3org.scalajs.junit.MultiIgnore2Test.multiTest4
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 ldTest org.scalajs.junit.MultiIgnore2Test.multiTest5 started
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 ldTest run finished: 0 failed, 2 ignored, 3 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_na.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_na.txt
index 960f5b1149..a3bb9a46dd 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_na.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_na.txt
@@ -1,16 +1,16 @@
 ldTest run started
 liTest org.scalajs.junit.MultiIgnore2Test.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnore2Test.multiTest1
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 liTest org.scalajs.junit.MultiIgnore2Test.multiTest4 ignored
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 ldTest org.scalajs.junit.MultiIgnore2Test.multiTest5 started
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-e0org.scalajs.junit.MultiIgnore2Test.multiTest5
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 ldTest run finished: 0 failed, 2 ignored, 3 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_nv.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_nv.txt
index b5b6f8efda..941ed7a212 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_nv.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_nv.txt
@@ -1,16 +1,16 @@
 liTest run started
 liTest org.scalajs.junit.MultiIgnore2Test.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnore2Test.multiTest1
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 liTest org.scalajs.junit.MultiIgnore2Test.multiTest4 ignored
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 liTest org.scalajs.junit.MultiIgnore2Test.multiTest5 started
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 liTest run finished: 0 failed, 2 ignored, 3 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_nva.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_nva.txt
index b5b6f8efda..941ed7a212 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_nva.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_nva.txt
@@ -1,16 +1,16 @@
 liTest run started
 liTest org.scalajs.junit.MultiIgnore2Test.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnore2Test.multiTest1
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 liTest org.scalajs.junit.MultiIgnore2Test.multiTest4 ignored
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 liTest org.scalajs.junit.MultiIgnore2Test.multiTest5 started
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 liTest run finished: 0 failed, 2 ignored, 3 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_nvc.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_nvc.txt
index b5b6f8efda..941ed7a212 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_nvc.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_nvc.txt
@@ -1,16 +1,16 @@
 liTest run started
 liTest org.scalajs.junit.MultiIgnore2Test.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnore2Test.multiTest1
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 liTest org.scalajs.junit.MultiIgnore2Test.multiTest4 ignored
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 liTest org.scalajs.junit.MultiIgnore2Test.multiTest5 started
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 liTest run finished: 0 failed, 2 ignored, 3 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_nvca.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_nvca.txt
index b5b6f8efda..941ed7a212 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_nvca.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_nvca.txt
@@ -1,16 +1,16 @@
 liTest run started
 liTest org.scalajs.junit.MultiIgnore2Test.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnore2Test.multiTest1
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 liTest org.scalajs.junit.MultiIgnore2Test.multiTest2 started
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 liTest org.scalajs.junit.MultiIgnore2Test.multiTest4 ignored
-e3org.scalajs.junit.MultiIgnore2Test.multiTest4
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 liTest org.scalajs.junit.MultiIgnore2Test.multiTest5 started
 ldTest org.scalajs.junit.MultiIgnore2Test.multiTest5 finished, took <TIME>
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 liTest run finished: 0 failed, 2 ignored, 3 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_v.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_v.txt
index 4bff1124bf..cce69a4cc8 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_v.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_v.txt
@@ -1,16 +1,16 @@
 liTest run started
 liTest org.scalajs.junit.MultiIgnore2Test.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnore2Test.multiTest1
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 liTest org.scalajs.junit.MultiIgnore2Test.multiTest4 ignored
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 liTest org.scalajs.junit.MultiIgnore2Test.multiTest5 started
 ldTest org.scalajs.junit.MultiIgnore2Test.multiTest5 finished, took <TIME>
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diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_va.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_va.txt
index 4bff1124bf..cce69a4cc8 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_va.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_va.txt
@@ -1,16 +1,16 @@
 liTest run started
 liTest org.scalajs.junit.MultiIgnore2Test.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnore2Test.multiTest1
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 liTest org.scalajs.junit.MultiIgnore2Test.multiTest4 ignored
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 ldTest org.scalajs.junit.MultiIgnore2Test.multiTest5 finished, took <TIME>
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diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_vc.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_vc.txt
index 4bff1124bf..cce69a4cc8 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_vc.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_vc.txt
@@ -1,16 +1,16 @@
 liTest run started
 liTest org.scalajs.junit.MultiIgnore2Test.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnore2Test.multiTest1
+e3org.scalajs.junit.MultiIgnore2Test.multiTest1::
 liTest org.scalajs.junit.MultiIgnore2Test.multiTest2 started
 ldTest org.scalajs.junit.MultiIgnore2Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore2Test.multiTest2
+e0org.scalajs.junit.MultiIgnore2Test.multiTest2::
 liTest org.scalajs.junit.MultiIgnore2Test.multiTest3 started
 ldTest org.scalajs.junit.MultiIgnore2Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore2Test.multiTest3
+e0org.scalajs.junit.MultiIgnore2Test.multiTest3::
 liTest org.scalajs.junit.MultiIgnore2Test.multiTest4 ignored
-e3org.scalajs.junit.MultiIgnore2Test.multiTest4
+e3org.scalajs.junit.MultiIgnore2Test.multiTest4::
 liTest org.scalajs.junit.MultiIgnore2Test.multiTest5 started
 ldTest org.scalajs.junit.MultiIgnore2Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore2Test.multiTest5
+e0org.scalajs.junit.MultiIgnore2Test.multiTest5::
 liTest run finished: 0 failed, 2 ignored, 3 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_vs.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_vs.txt
index 4bff1124bf..cce69a4cc8 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_vs.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_vs.txt
@@ -1,16 +1,16 @@
 liTest run started
 liTest org.scalajs.junit.MultiIgnore2Test.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnore2Test.multiTest1
+e3org.scalajs.junit.MultiIgnore2Test.multiTest1::
 liTest org.scalajs.junit.MultiIgnore2Test.multiTest2 started
 ldTest org.scalajs.junit.MultiIgnore2Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore2Test.multiTest2
+e0org.scalajs.junit.MultiIgnore2Test.multiTest2::
 liTest org.scalajs.junit.MultiIgnore2Test.multiTest3 started
 ldTest org.scalajs.junit.MultiIgnore2Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore2Test.multiTest3
+e0org.scalajs.junit.MultiIgnore2Test.multiTest3::
 liTest org.scalajs.junit.MultiIgnore2Test.multiTest4 ignored
-e3org.scalajs.junit.MultiIgnore2Test.multiTest4
+e3org.scalajs.junit.MultiIgnore2Test.multiTest4::
 liTest org.scalajs.junit.MultiIgnore2Test.multiTest5 started
 ldTest org.scalajs.junit.MultiIgnore2Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore2Test.multiTest5
+e0org.scalajs.junit.MultiIgnore2Test.multiTest5::
 liTest run finished: 0 failed, 2 ignored, 3 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_vsn.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_vsn.txt
index b5b6f8efda..941ed7a212 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_vsn.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_vsn.txt
@@ -1,16 +1,16 @@
 liTest run started
 liTest org.scalajs.junit.MultiIgnore2Test.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnore2Test.multiTest1
+e3org.scalajs.junit.MultiIgnore2Test.multiTest1::
 liTest org.scalajs.junit.MultiIgnore2Test.multiTest2 started
 ldTest org.scalajs.junit.MultiIgnore2Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore2Test.multiTest2
+e0org.scalajs.junit.MultiIgnore2Test.multiTest2::
 liTest org.scalajs.junit.MultiIgnore2Test.multiTest3 started
 ldTest org.scalajs.junit.MultiIgnore2Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore2Test.multiTest3
+e0org.scalajs.junit.MultiIgnore2Test.multiTest3::
 liTest org.scalajs.junit.MultiIgnore2Test.multiTest4 ignored
-e3org.scalajs.junit.MultiIgnore2Test.multiTest4
+e3org.scalajs.junit.MultiIgnore2Test.multiTest4::
 liTest org.scalajs.junit.MultiIgnore2Test.multiTest5 started
 ldTest org.scalajs.junit.MultiIgnore2Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore2Test.multiTest5
+e0org.scalajs.junit.MultiIgnore2Test.multiTest5::
 liTest run finished: 0 failed, 2 ignored, 3 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_.txt
index c2bd9eee34..cb142ec998 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_.txt
@@ -1,13 +1,13 @@
 ldTest run started
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest1
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest1::
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest2 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest2
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest2::
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest3 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest3
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest3::
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest4 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest4
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest4::
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest5 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest5
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest5::
 ldTest run finished: 0 failed, 5 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_a.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_a.txt
index c2bd9eee34..cb142ec998 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_a.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_a.txt
@@ -1,13 +1,13 @@
 ldTest run started
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest1
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest1::
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest2 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest2
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest2::
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest3 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest3
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest3::
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest4 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest4
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest4::
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest5 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest5
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest5::
 ldTest run finished: 0 failed, 5 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_n.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_n.txt
index 9f0ae0a3d8..3fe19eea5c 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_n.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_n.txt
@@ -1,13 +1,13 @@
 ldTest run started
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest1
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest1::
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest2 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest2
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest2::
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest3 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest3
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest3::
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest4 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest4
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest4::
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest5 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest5
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest5::
 ldTest run finished: 0 failed, 5 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_na.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_na.txt
index 9f0ae0a3d8..3fe19eea5c 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_na.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_na.txt
@@ -1,13 +1,13 @@
 ldTest run started
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest1
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest1::
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest2 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest2
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest2::
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest3 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest3
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest3::
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest4 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest4
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest4::
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest5 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest5
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest5::
 ldTest run finished: 0 failed, 5 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_nv.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_nv.txt
index 01b08a81ca..c7d123ab0b 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_nv.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_nv.txt
@@ -1,13 +1,13 @@
 liTest run started
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest1
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest1::
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest2 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest2
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest2::
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest3 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest3
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest3::
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest4 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest4
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest4::
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest5 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest5
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest5::
 liTest run finished: 0 failed, 5 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_nva.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_nva.txt
index 01b08a81ca..c7d123ab0b 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_nva.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_nva.txt
@@ -1,13 +1,13 @@
 liTest run started
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest1
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest1::
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest2 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest2
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest2::
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest3 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest3
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest3::
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest4 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest4
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest4::
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest5 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest5
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest5::
 liTest run finished: 0 failed, 5 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_nvc.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_nvc.txt
index 01b08a81ca..c7d123ab0b 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_nvc.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_nvc.txt
@@ -1,13 +1,13 @@
 liTest run started
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest1
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest1::
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest2 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest2
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest2::
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest3 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest3
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest3::
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest4 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest4
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest4::
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest5 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest5
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest5::
 liTest run finished: 0 failed, 5 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_nvca.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_nvca.txt
index 01b08a81ca..c7d123ab0b 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_nvca.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_nvca.txt
@@ -1,13 +1,13 @@
 liTest run started
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest1
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest1::
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest2 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest2
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest2::
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest3 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest3
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest3::
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest4 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest4
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest4::
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest5 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest5
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest5::
 liTest run finished: 0 failed, 5 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_v.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_v.txt
index a2f98a2075..e2040b03b5 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_v.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_v.txt
@@ -1,13 +1,13 @@
 liTest run started
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest1
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest1::
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest2 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest2
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest2::
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest3 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest3
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest3::
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest4 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest4
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest4::
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest5 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest5
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest5::
 liTest run finished: 0 failed, 5 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_va.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_va.txt
index a2f98a2075..e2040b03b5 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_va.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_va.txt
@@ -1,13 +1,13 @@
 liTest run started
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest1
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest1::
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest2 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest2
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest2::
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest3 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest3
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest3::
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest4 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest4
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest4::
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest5 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest5
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest5::
 liTest run finished: 0 failed, 5 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_vc.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_vc.txt
index a2f98a2075..e2040b03b5 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_vc.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_vc.txt
@@ -1,13 +1,13 @@
 liTest run started
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest1
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest1::
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest2 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest2
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest2::
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest3 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest3
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest3::
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest4 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest4
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest4::
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest5 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest5
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest5::
 liTest run finished: 0 failed, 5 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_vs.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_vs.txt
index a2f98a2075..e2040b03b5 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_vs.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_vs.txt
@@ -1,13 +1,13 @@
 liTest run started
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest1
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest1::
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest2 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest2
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest2::
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest3 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest3
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest3::
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest4 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest4
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest4::
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest5 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest5
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest5::
 liTest run finished: 0 failed, 5 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_vsn.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_vsn.txt
index 01b08a81ca..c7d123ab0b 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_vsn.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_vsn.txt
@@ -1,13 +1,13 @@
 liTest run started
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest1
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest1::
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest2 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest2
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest2::
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest3 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest3
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest3::
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest4 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest4
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest4::
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest5 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest5
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest5::
 liTest run finished: 0 failed, 5 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/shared/src/test/scala/org/scalajs/junit/utils/JUnitTest.scala b/junit-test/shared/src/test/scala/org/scalajs/junit/utils/JUnitTest.scala
index 76474fe4d9..84d94af22f 100644
--- a/junit-test/shared/src/test/scala/org/scalajs/junit/utils/JUnitTest.scala
+++ b/junit-test/shared/src/test/scala/org/scalajs/junit/utils/JUnitTest.scala
@@ -179,7 +179,7 @@ abstract class JUnitTest {
         Some(msg.substring(s + testNamePrefix.length, e))
       }
 
-    case Event(_, name) =>
+    case Event(_, name, _) =>
       if (name == suiteUnderTestName) None
       else if (name.startsWith(testNamePrefix)) Some(name.stripPrefix(testNamePrefix))
       else throw new AssertionError(s"Unknown test name: $name")
@@ -216,7 +216,7 @@ abstract class JUnitTest {
       throw new UnsupportedOperationException("trace is not supported")
 
     def handle(event: sbt.testing.Event): Unit = {
-      val testName = event.selector() match {
+      val testName: String = event.selector() match {
         case s: TestSelector =>
           s.testName()
 
@@ -224,7 +224,11 @@ abstract class JUnitTest {
           throw new AssertionError("unexpected selector")
       }
 
-      buf += Event(event.status(), testName)
+      buf += Event(
+        event.status(),
+        testName,
+        if (event.throwable.isEmpty) None else Some(event.throwable.get.toString)
+      )
     }
 
     def recordDone(msg: String): Unit = buf += Done(msg)
@@ -236,21 +240,32 @@ abstract class JUnitTest {
 object JUnitTest {
   sealed trait Output
   final case class Log(level: Char, msg: String) extends Output
-  final case class Event(status: Status, testName: String) extends Output
+  final case class Event(status: Status, testName: String, throwableToString: Option[String]) extends Output
   final case class Done(msg: String) extends Output
 
   object Output {
+    // We need something that does not occur in test names nor in Throwable.toString.
+    final val separator = "::"
+
     def deserialize(line: String): Output = line.toList match {
       case 'l' :: level :: msg  => Log(level, msg.mkString(""))
-      case 'e' :: s :: testName => Event(Status.values()(s - '0'), testName.mkString(""))
       case 'd' :: msg           => Done(msg.mkString(""))
+
+      case 'e' :: s :: tail =>
+        val rest: Array[String] = tail.mkString("").split(separator, -1)
+        val testName: String = rest(0)
+        val throwableToString: String = rest(1)
+        Event(
+          status = Status.values()(s - '0'),
+          testName,
+          throwableToString = if (throwableToString.isEmpty) None else Some(throwableToString)
+        )
     }
 
     def serialize(o: Output): String = o match {
       case Log(level, msg) => "l" + level + msg
-      case Event(s, n)   => "e" + s.ordinal + n
-      case Done(msg)     => "d" + msg
+      case Done(msg)       => "d" + msg
+      case Event(s, n, t)  => "e" + s.ordinal + n + separator + t.getOrElse("")
     }
   }
 }
-

From 82910a086fe6133e20242b74938a61c0b0084643 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Mon, 3 Mar 2025 13:46:25 +0100
Subject: [PATCH 260/298] Fix #5135: Move well-known names to a new object
 `WellKnownNames`.

This breaks the circular dependency between the initialization of
`object Types` and `object Names`.
---
 .../org/scalajs/nscplugin/GenJSCode.scala     |  50 +++---
 .../org/scalajs/nscplugin/GenJSExports.scala  |   8 +-
 .../org/scalajs/nscplugin/JSEncoding.scala    |   8 +-
 .../org/scalajs/nscplugin/PrepJSExports.scala |   2 +-
 .../src/main/scala/org/scalajs/ir/Names.scala | 139 ++-------------
 .../scala/org/scalajs/ir/Serializers.scala    |   1 +
 .../src/main/scala/org/scalajs/ir/Trees.scala |   1 +
 .../src/main/scala/org/scalajs/ir/Types.scala |  22 +--
 .../scala/org/scalajs/ir/WellKnownNames.scala | 158 ++++++++++++++++++
 .../scala/org/scalajs/ir/PrintersTest.scala   |   1 +
 .../scala/org/scalajs/ir/TestIRBuilder.scala  |   1 +
 .../linker/interface/ModuleInitializer.scala  |   1 +
 .../scala/org/scalajs/linker/RunTest.scala    |   1 +
 .../scalajs/linker/analyzer/Analyzer.scala    |   1 +
 .../org/scalajs/linker/analyzer/Infos.scala   |   1 +
 .../linker/backend/emitter/ClassEmitter.scala |   1 +
 .../linker/backend/emitter/CoreJSLib.scala    |   1 +
 .../linker/backend/emitter/Emitter.scala      |   1 +
 .../linker/backend/emitter/EmitterNames.scala |   1 +
 .../backend/emitter/FunctionEmitter.scala     |   1 +
 .../backend/emitter/KnowledgeGuardian.scala   |   1 +
 .../linker/backend/emitter/LongImpl.scala     |   1 +
 .../linker/backend/emitter/NameGen.scala      |   1 +
 .../linker/backend/emitter/SJSGen.scala       |   1 +
 .../linker/backend/emitter/VarGen.scala       |   1 +
 .../backend/wasmemitter/ClassEmitter.scala    |   1 +
 .../backend/wasmemitter/CoreWasmLib.scala     |   1 +
 .../backend/wasmemitter/DerivedClasses.scala  |   1 +
 .../linker/backend/wasmemitter/Emitter.scala  |   1 +
 .../backend/wasmemitter/FunctionEmitter.scala |   1 +
 .../backend/wasmemitter/Preprocessor.scala    |   1 +
 .../linker/backend/wasmemitter/SWasmGen.scala |   2 +-
 .../backend/wasmemitter/SpecialNames.scala    |   1 +
 .../backend/wasmemitter/TypeTransformer.scala |   1 +
 .../linker/backend/wasmemitter/VarGen.scala   |   1 +
 .../backend/wasmemitter/WasmContext.scala     |   1 +
 .../linker/checker/ClassDefChecker.scala      |   1 +
 .../scalajs/linker/checker/IRChecker.scala    |   1 +
 .../linker/frontend/MethodSynthesizer.scala   |   1 +
 .../InternalModuleIDGenerator.scala           |   4 +-
 .../modulesplitter/ModuleSplitter.scala       |   1 +
 .../frontend/optimizer/IncOptimizer.scala     |   1 +
 .../frontend/optimizer/OptimizerCore.scala    |   1 +
 .../org/scalajs/linker/AnalyzerTest.scala     |   1 +
 .../scalajs/linker/BackwardsCompatTest.scala  |   1 +
 .../org/scalajs/linker/BaseLinkerTest.scala   |   1 +
 .../linker/FewestModulesSplittingTest.scala   |   2 +-
 .../org/scalajs/linker/IRCheckerTest.scala    |   1 +
 .../org/scalajs/linker/IncrementalTest.scala  |   1 +
 .../linker/LibraryReachabilityTest.scala      |   2 +-
 .../org/scalajs/linker/OptimizerTest.scala    |   1 +
 .../linker/SmallModulesForSplittingTest.scala |   1 +
 .../linker/SmallestModulesSplittingTest.scala |   2 +-
 .../linker/checker/ClassDefCheckerTest.scala  |   1 +
 .../standard/StandardIRFileCacheTest.scala    |   3 +-
 .../linker/testutils/TestIRBuilder.scala      |   1 +
 project/BinaryIncompatibilities.scala         |  11 ++
 project/JavaLangObject.scala                  |   1 +
 project/JavalibIRCleaner.scala                |   1 +
 59 files changed, 281 insertions(+), 177 deletions(-)
 create mode 100644 ir/shared/src/main/scala/org/scalajs/ir/WellKnownNames.scala

diff --git a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
index 60cea646b0..8070b19f50 100644
--- a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
+++ b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
@@ -26,7 +26,14 @@ import scala.annotation.tailrec
 import scala.reflect.internal.Flags
 
 import org.scalajs.ir
-import org.scalajs.ir.{Trees => js, Types => jstpe, ClassKind, Hashers, OriginalName}
+import org.scalajs.ir.{
+  Trees => js,
+  Types => jstpe,
+  WellKnownNames => jswkn,
+  ClassKind,
+  Hashers,
+  OriginalName
+}
 import org.scalajs.ir.Names.{
   LocalName,
   LabelName,
@@ -34,8 +41,7 @@ import org.scalajs.ir.Names.{
   FieldName,
   SimpleMethodName,
   MethodName,
-  ClassName,
-  BoxedStringClass
+  ClassName
 }
 import org.scalajs.ir.OriginalName.NoOriginalName
 import org.scalajs.ir.Trees.OptimizerHints
@@ -168,7 +174,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
     def currentThisType: jstpe.Type = {
       currentThisTypeNullable match {
         case tpe @ jstpe.ClassType(cls, _) =>
-          jstpe.BoxedClassToPrimType.getOrElse(cls, tpe.toNonNullable)
+          jswkn.BoxedClassToPrimType.getOrElse(cls, tpe.toNonNullable)
         case tpe @ jstpe.AnyType =>
           // We are in a JS class, in which even `this` is nullable
           tpe
@@ -692,7 +698,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
           reflectInit.toList ::: staticModuleInit.toList
         if (staticInitializerStats.nonEmpty) {
           List(genStaticConstructorWithStats(
-              ir.Names.StaticInitializerName,
+              jswkn.StaticInitializerName,
               js.Block(staticInitializerStats)))
         } else {
           Nil
@@ -723,7 +729,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
                   originalName,
                   ClassKind.Class,
                   None,
-                  Some(js.ClassIdent(ir.Names.ObjectClass)),
+                  Some(js.ClassIdent(jswkn.ObjectClass)),
                   Nil,
                   None,
                   None,
@@ -838,7 +844,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
 
           if (staticFields.nonEmpty) {
             generatedMethods += genStaticConstructorWithStats(
-                ir.Names.ClassInitializerName, genLoadModule(companionModuleClass))
+                jswkn.ClassInitializerName, genLoadModule(companionModuleClass))
           }
 
           (staticFields, staticExports)
@@ -943,7 +949,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
       // Make new class def with static members
       val newClassDef = {
         implicit val pos = origJsClass.pos
-        val parent = js.ClassIdent(ir.Names.ObjectClass)
+        val parent = js.ClassIdent(jswkn.ObjectClass)
         js.ClassDef(origJsClass.name, origJsClass.originalName,
             ClassKind.AbstractJSType, None, Some(parent), interfaces = Nil,
             jsSuperClass = None, jsNativeLoadSpec = None, fields = Nil,
@@ -5438,8 +5444,8 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
           // LinkingInfo.linkTimePropertyXXX("...")
           val arg = genArgs1
           val tpe: jstpe.Type = toIRType(tree.tpe) match {
-            case jstpe.ClassType(BoxedStringClass, _) => jstpe.StringType
-            case irType                               => irType
+            case jstpe.ClassType(jswkn.BoxedStringClass, _) => jstpe.StringType
+            case irType                                     => irType
           }
           arg match {
             case js.StringLiteral(name) =>
@@ -6431,8 +6437,8 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
                     fParamDef.ref),
                 js.ApplyStatically(js.ApplyFlags.empty.withConstructor(true),
                     js.This()(thisType),
-                    ir.Names.ObjectClass,
-                    js.MethodIdent(ir.Names.NoArgConstructorName),
+                    jswkn.ObjectClass,
+                    js.MethodIdent(jswkn.NoArgConstructorName),
                     Nil)(jstpe.VoidType)))))(
             js.OptimizerHints.empty, Unversioned)
       }
@@ -6491,7 +6497,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
           NoOriginalName,
           ClassKind.Class,
           None,
-          Some(js.ClassIdent(ir.Names.ObjectClass)),
+          Some(js.ClassIdent(jswkn.ObjectClass)),
           List(js.ClassIdent(intfName)),
           None,
           None,
@@ -7133,7 +7139,7 @@ private object GenJSCode {
   private val newSimpleMethodName = SimpleMethodName("new")
 
   private val ObjectArgConstructorName =
-    MethodName.constructor(List(jstpe.ClassRef(ir.Names.ObjectClass)))
+    MethodName.constructor(List(jswkn.ObjectRef))
 
   private val lengthMethodName =
     MethodName("length", Nil, jstpe.IntRef)
@@ -7141,7 +7147,7 @@ private object GenJSCode {
     MethodName("charAt", List(jstpe.IntRef), jstpe.CharRef)
 
   private val getNameMethodName =
-    MethodName("getName", Nil, jstpe.ClassRef(ir.Names.BoxedStringClass))
+    MethodName("getName", Nil, jstpe.ClassRef(jswkn.BoxedStringClass))
   private val isPrimitiveMethodName =
     MethodName("isPrimitive", Nil, jstpe.BooleanRef)
   private val isInterfaceMethodName =
@@ -7149,21 +7155,21 @@ private object GenJSCode {
   private val isArrayMethodName =
     MethodName("isArray", Nil, jstpe.BooleanRef)
   private val getComponentTypeMethodName =
-    MethodName("getComponentType", Nil, jstpe.ClassRef(ir.Names.ClassClass))
+    MethodName("getComponentType", Nil, jstpe.ClassRef(jswkn.ClassClass))
   private val getSuperclassMethodName =
-    MethodName("getSuperclass", Nil, jstpe.ClassRef(ir.Names.ClassClass))
+    MethodName("getSuperclass", Nil, jstpe.ClassRef(jswkn.ClassClass))
 
   private val isInstanceMethodName =
-    MethodName("isInstance", List(jstpe.ClassRef(ir.Names.ObjectClass)), jstpe.BooleanRef)
+    MethodName("isInstance", List(jstpe.ClassRef(jswkn.ObjectClass)), jstpe.BooleanRef)
   private val isAssignableFromMethodName =
-    MethodName("isAssignableFrom", List(jstpe.ClassRef(ir.Names.ClassClass)), jstpe.BooleanRef)
+    MethodName("isAssignableFrom", List(jstpe.ClassRef(jswkn.ClassClass)), jstpe.BooleanRef)
   private val castMethodName =
-    MethodName("cast", List(jstpe.ClassRef(ir.Names.ObjectClass)), jstpe.ClassRef(ir.Names.ObjectClass))
+    MethodName("cast", List(jstpe.ClassRef(jswkn.ObjectClass)), jstpe.ClassRef(jswkn.ObjectClass))
 
   private val arrayNewInstanceMethodName = {
     MethodName("newInstance",
-        List(jstpe.ClassRef(ir.Names.ClassClass), jstpe.IntRef),
-        jstpe.ClassRef(ir.Names.ObjectClass))
+        List(jstpe.ClassRef(jswkn.ClassClass), jstpe.IntRef),
+        jstpe.ClassRef(jswkn.ObjectClass))
   }
 
   private val thisOriginalName = OriginalName("this")
diff --git a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSExports.scala b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSExports.scala
index 4cdc4369c3..bcac2098ea 100644
--- a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSExports.scala
+++ b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSExports.scala
@@ -20,7 +20,7 @@ import scala.reflect.{ClassTag, classTag}
 import scala.reflect.internal.Flags
 
 import org.scalajs.ir
-import org.scalajs.ir.{Trees => js, Types => jstpe}
+import org.scalajs.ir.{Trees => js, Types => jstpe, WellKnownNames => jswkn}
 import org.scalajs.ir.Names.LocalName
 import org.scalajs.ir.OriginalName.NoOriginalName
 import org.scalajs.ir.Trees.OptimizerHints
@@ -970,8 +970,6 @@ trait GenJSExports[G <: Global with Singleton] extends SubComponent {
         InstanceOfTypeTest(tpe.valueClazz.typeConstructor)
 
       case _ =>
-        import org.scalajs.ir.Names
-
         (toIRType(tpe): @unchecked) match {
           case jstpe.AnyType | jstpe.AnyNotNullType => NoTypeTest
 
@@ -985,8 +983,8 @@ trait GenJSExports[G <: Global with Singleton] extends SubComponent {
           case jstpe.FloatType   => PrimitiveTypeTest(jstpe.FloatType, 7)
           case jstpe.DoubleType  => PrimitiveTypeTest(jstpe.DoubleType, 8)
 
-          case jstpe.ClassType(Names.BoxedUnitClass, _)   => PrimitiveTypeTest(jstpe.UndefType, 0)
-          case jstpe.ClassType(Names.BoxedStringClass, _) => PrimitiveTypeTest(jstpe.StringType, 9)
+          case jstpe.ClassType(jswkn.BoxedUnitClass, _)   => PrimitiveTypeTest(jstpe.UndefType, 0)
+          case jstpe.ClassType(jswkn.BoxedStringClass, _) => PrimitiveTypeTest(jstpe.StringType, 9)
           case jstpe.ClassType(_, _)                      => InstanceOfTypeTest(tpe)
 
           case jstpe.ArrayType(_, _) => InstanceOfTypeTest(tpe)
diff --git a/compiler/src/main/scala/org/scalajs/nscplugin/JSEncoding.scala b/compiler/src/main/scala/org/scalajs/nscplugin/JSEncoding.scala
index b1b4c888f5..263f1def30 100644
--- a/compiler/src/main/scala/org/scalajs/nscplugin/JSEncoding.scala
+++ b/compiler/src/main/scala/org/scalajs/nscplugin/JSEncoding.scala
@@ -17,7 +17,7 @@ import scala.collection.mutable
 import scala.tools.nsc._
 
 import org.scalajs.ir
-import org.scalajs.ir.{Trees => js, Types => jstpe}
+import org.scalajs.ir.{Trees => js, Types => jstpe, WellKnownNames => jswkn}
 import org.scalajs.ir.Names.{LocalName, LabelName, SimpleFieldName, FieldName, SimpleMethodName, MethodName, ClassName}
 import org.scalajs.ir.OriginalName
 import org.scalajs.ir.OriginalName.NoOriginalName
@@ -237,7 +237,7 @@ trait JSEncoding[G <: Global with Singleton] extends SubComponent {
   def encodeDynamicImportForwarderIdent(params: List[Symbol])(
       implicit pos: Position): js.MethodIdent = {
     val paramTypeRefs = params.map(sym => paramOrResultTypeRef(sym.tpe))
-    val resultTypeRef = jstpe.ClassRef(ir.Names.ObjectClass)
+    val resultTypeRef = jstpe.ClassRef(jswkn.ObjectClass)
     val methodName =
       MethodName(dynamicImportForwarderSimpleName, paramTypeRefs, resultTypeRef)
 
@@ -288,13 +288,13 @@ trait JSEncoding[G <: Global with Singleton] extends SubComponent {
     assert(!sym.isPrimitiveValueClass,
         s"Illegal encodeClassName(${sym.fullName}")
     if (sym == jsDefinitions.HackedStringClass) {
-      ir.Names.BoxedStringClass
+      jswkn.BoxedStringClass
     } else if (sym == jsDefinitions.HackedStringModClass) {
       BoxedStringModuleClassName
     } else if (sym == definitions.BoxedUnitClass || sym == jsDefinitions.BoxedUnitModClass) {
       // Rewire scala.runtime.BoxedUnit to java.lang.Void, as the IR expects
       // BoxedUnit$ is a JVM artifact
-      ir.Names.BoxedUnitClass
+      jswkn.BoxedUnitClass
     } else {
       ClassName(sym.fullName + (if (needsModuleClassSuffix(sym)) "$" else ""))
     }
diff --git a/compiler/src/main/scala/org/scalajs/nscplugin/PrepJSExports.scala b/compiler/src/main/scala/org/scalajs/nscplugin/PrepJSExports.scala
index 9c2b0b5c62..e9217c04a7 100644
--- a/compiler/src/main/scala/org/scalajs/nscplugin/PrepJSExports.scala
+++ b/compiler/src/main/scala/org/scalajs/nscplugin/PrepJSExports.scala
@@ -16,8 +16,8 @@ import scala.collection.mutable
 
 import scala.tools.nsc.Global
 
-import org.scalajs.ir.Names.DefaultModuleID
 import org.scalajs.ir.Trees.TopLevelExportDef.isValidTopLevelExportName
+import org.scalajs.ir.WellKnownNames.DefaultModuleID
 
 /**
  *  Prepare export generation
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Names.scala b/ir/shared/src/main/scala/org/scalajs/ir/Names.scala
index d9bee3518b..ecceef2dfa 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Names.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Names.scala
@@ -471,9 +471,6 @@ object Names {
   }
 
   object MethodName {
-    private val ReflectiveProxyResultTypeRef = ClassRef(ObjectClass)
-    private final val ReflectiveProxyResultTypeName = "java.lang.Object"
-
     def apply(simpleName: SimpleMethodName, paramTypeRefs: List[TypeRef],
         resultTypeRef: TypeRef, isReflectiveProxy: Boolean): MethodName = {
       if ((simpleName.isConstructor || simpleName.isStaticInitializer ||
@@ -481,11 +478,18 @@ object Names {
         throw new IllegalArgumentException(
             "A constructor or static initializer must have a void result type")
       }
-      if (isReflectiveProxy && resultTypeRef != ReflectiveProxyResultTypeRef) {
-        throw new IllegalArgumentException(
-            "A reflective proxy must have a result type of " +
-            ReflectiveProxyResultTypeName)
+
+      if (isReflectiveProxy) {
+        /* It is fine to use WellKnownNames here because nothing in `Names`
+         * nor `Types` ever creates a reflective proxy name. So this code path
+         * is not reached during their initialization.
+         */
+        if (resultTypeRef != WellKnownNames.ObjectRef) {
+          throw new IllegalArgumentException(
+              "A reflective proxy must have a result type of java.lang.Object")
+        }
       }
+
       new MethodName(simpleName, paramTypeRefs, resultTypeRef,
           isReflectiveProxy)
     }
@@ -509,7 +513,11 @@ object Names {
 
     def reflectiveProxy(simpleName: SimpleMethodName,
         paramTypeRefs: List[TypeRef]): MethodName = {
-      apply(simpleName, paramTypeRefs, ReflectiveProxyResultTypeRef,
+      /* It is fine to use WellKnownNames here because nothing in `Names`
+       * nor `Types` ever creates a reflective proxy name. So this code path
+       * is not reached during their initialization.
+       */
+      apply(simpleName, paramTypeRefs, WellKnownNames.ObjectRef,
           isReflectiveProxy = true)
     }
 
@@ -553,121 +561,6 @@ object Names {
 
   // scalastyle:on equals.hash.code
 
-  /** `java.lang.Object`, the root of the class hierarchy. */
-  val ObjectClass: ClassName = ClassName("java.lang.Object")
-
-  // Hijacked classes
-  val BoxedUnitClass: ClassName = ClassName("java.lang.Void")
-  val BoxedBooleanClass: ClassName = ClassName("java.lang.Boolean")
-  val BoxedCharacterClass: ClassName = ClassName("java.lang.Character")
-  val BoxedByteClass: ClassName = ClassName("java.lang.Byte")
-  val BoxedShortClass: ClassName = ClassName("java.lang.Short")
-  val BoxedIntegerClass: ClassName = ClassName("java.lang.Integer")
-  val BoxedLongClass: ClassName = ClassName("java.lang.Long")
-  val BoxedFloatClass: ClassName = ClassName("java.lang.Float")
-  val BoxedDoubleClass: ClassName = ClassName("java.lang.Double")
-  val BoxedStringClass: ClassName = ClassName("java.lang.String")
-
-  /** The set of all hijacked classes. */
-  val HijackedClasses: Set[ClassName] = Set(
-      BoxedUnitClass,
-      BoxedBooleanClass,
-      BoxedCharacterClass,
-      BoxedByteClass,
-      BoxedShortClass,
-      BoxedIntegerClass,
-      BoxedLongClass,
-      BoxedFloatClass,
-      BoxedDoubleClass,
-      BoxedStringClass
-  )
-
-  /** The class of things returned by `ClassOf` and `GetClass`. */
-  val ClassClass: ClassName = ClassName("java.lang.Class")
-
-  /** `java.lang.Cloneable`, which is an ancestor of array classes and is used
-   *  by `Clone`.
-   */
-  val CloneableClass: ClassName = ClassName("java.lang.Cloneable")
-
-  /** `java.io.Serializable`, which is an ancestor of array classes. */
-  val SerializableClass: ClassName = ClassName("java.io.Serializable")
-
-  /** The superclass of all throwables.
-   *
-   *  This is the result type of `WrapAsThrowable` nodes, as well as the input
-   *  type of `UnwrapFromThrowable`.
-   */
-  val ThrowableClass = ClassName("java.lang.Throwable")
-
-  /** The exception thrown by a division by 0. */
-  val ArithmeticExceptionClass: ClassName =
-    ClassName("java.lang.ArithmeticException")
-
-  /** The exception thrown by an `ArraySelect` that is out of bounds. */
-  val ArrayIndexOutOfBoundsExceptionClass: ClassName =
-    ClassName("java.lang.ArrayIndexOutOfBoundsException")
-
-  /** The exception thrown by an `Assign(ArraySelect, ...)` where the value cannot be stored. */
-  val ArrayStoreExceptionClass: ClassName =
-    ClassName("java.lang.ArrayStoreException")
-
-  /** The exception thrown by a `NewArray(...)` with a negative size. */
-  val NegativeArraySizeExceptionClass: ClassName =
-    ClassName("java.lang.NegativeArraySizeException")
-
-  /** The exception thrown by a variety of nodes for `null` arguments.
-   *
-   *  - `Apply` and `ApplyStatically` for the receiver,
-   *  - `Select` for the qualifier,
-   *  - `ArrayLength` and `ArraySelect` for the array,
-   *  - `GetClass`, `Clone` and `UnwrapFromException` for their respective only arguments.
-   */
-  val NullPointerExceptionClass: ClassName =
-    ClassName("java.lang.NullPointerException")
-
-  /** The exception thrown by a `BinaryOp.String_charAt` that is out of bounds. */
-  val StringIndexOutOfBoundsExceptionClass: ClassName =
-    ClassName("java.lang.StringIndexOutOfBoundsException")
-
-  /** The exception thrown by an `AsInstanceOf` that fails. */
-  val ClassCastExceptionClass: ClassName =
-    ClassName("java.lang.ClassCastException")
-
-  /** The exception thrown by a `Class_newArray` if the first argument is `classOf[Unit]`. */
-  val IllegalArgumentExceptionClass: ClassName =
-    ClassName("java.lang.IllegalArgumentException")
-
-  /** The set of classes and interfaces that are ancestors of array classes. */
-  private[ir] val AncestorsOfPseudoArrayClass: Set[ClassName] = {
-    /* This would logically be defined in Types, but that introduces a cyclic
-     * dependency between the initialization of Names and Types.
-     */
-    Set(ObjectClass, CloneableClass, SerializableClass)
-  }
-
-  /** Name of a constructor without argument.
-   *
-   *  This is notably the signature of constructors of module classes.
-   */
-  final val NoArgConstructorName: MethodName =
-    MethodName.constructor(Nil)
-
-  /** This is used to construct a java.lang.Class. */
-  final val ObjectArgConstructorName: MethodName =
-    MethodName.constructor(List(ClassRef(ObjectClass)))
-
-  /** Name of the static initializer method. */
-  final val StaticInitializerName: MethodName =
-    MethodName(SimpleMethodName.StaticInitializer, Nil, VoidRef)
-
-  /** Name of the class initializer method. */
-  final val ClassInitializerName: MethodName =
-    MethodName(SimpleMethodName.ClassInitializer, Nil, VoidRef)
-
-  /** ModuleID of the default module */
-  final val DefaultModuleID: String = "main"
-
   // ---------------------------------------------------
   // ----- Private helpers for validation of names -----
   // ---------------------------------------------------
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
index dbd8a03f83..d690110e0f 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
@@ -29,6 +29,7 @@ import LinkTimeProperty.{ProductionMode, ESVersion, UseECMAScript2015Semantics,
 import Types._
 import Tags._
 import Version.Unversioned
+import WellKnownNames._
 
 import Utils.JumpBackByteArrayOutputStream
 
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala b/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
index e75ab17925..51751c49e0 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
@@ -18,6 +18,7 @@ import Names._
 import OriginalName.NoOriginalName
 import Position.NoPosition
 import Types._
+import WellKnownNames._
 
 object Trees {
   /* The case classes for IR Nodes are sealed instead of final for historical
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Types.scala b/ir/shared/src/main/scala/org/scalajs/ir/Types.scala
index b801857290..debd69ab56 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Types.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Types.scala
@@ -380,22 +380,6 @@ object Types {
       throw new IllegalArgumentException(s"cannot generate a zero for $tpe")
   }
 
-  val BoxedClassToPrimType: Map[ClassName, PrimType] = Map(
-    BoxedUnitClass -> UndefType,
-    BoxedBooleanClass -> BooleanType,
-    BoxedCharacterClass -> CharType,
-    BoxedByteClass -> ByteType,
-    BoxedShortClass -> ShortType,
-    BoxedIntegerClass -> IntType,
-    BoxedLongClass -> LongType,
-    BoxedFloatClass -> FloatType,
-    BoxedDoubleClass -> DoubleType,
-    BoxedStringClass -> StringType
-  )
-
-  val PrimTypeToBoxedClass: Map[PrimType, ClassName] =
-    BoxedClassToPrimType.map(_.swap)
-
   /** Tests whether a type `lhs` is a subtype of `rhs` (or equal).
    *  @param isSubclass A function testing whether a class/interface is a
    *                    subclass of another class/interface.
@@ -403,6 +387,12 @@ object Types {
   def isSubtype(lhs: Type, rhs: Type)(
       isSubclass: (ClassName, ClassName) => Boolean): Boolean = {
 
+    /* It is fine to use WellKnownNames here because nothing in `Names` nor
+     * `Types` calls `isSubtype`. So this code path is not reached during their
+     * initialization.
+     */
+    import WellKnownNames.{AncestorsOfPseudoArrayClass, ObjectClass, PrimTypeToBoxedClass}
+
     def isSubnullable(lhs: Boolean, rhs: Boolean): Boolean =
       rhs || !lhs
 
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/WellKnownNames.scala b/ir/shared/src/main/scala/org/scalajs/ir/WellKnownNames.scala
new file mode 100644
index 0000000000..cc85cd47da
--- /dev/null
+++ b/ir/shared/src/main/scala/org/scalajs/ir/WellKnownNames.scala
@@ -0,0 +1,158 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package org.scalajs.ir
+
+import Names._
+import Types._
+
+/** Names for "well-known" classes and methods.
+ *
+ *  Well-known classes and methods have a dedicated meaning in the semantics of
+ *  the IR. For example, `java.lang.Class` is well-known because it is the type
+ *  of `ClassOf` nodes.
+ */
+object WellKnownNames {
+
+  /** `java.lang.Object`, the root of the class hierarchy. */
+  val ObjectClass: ClassName = ClassName("java.lang.Object")
+
+  /** `ClassRef(ObjectClass)`. */
+  val ObjectRef: ClassRef = ClassRef(ObjectClass)
+
+  // Hijacked classes
+  val BoxedUnitClass: ClassName = ClassName("java.lang.Void")
+  val BoxedBooleanClass: ClassName = ClassName("java.lang.Boolean")
+  val BoxedCharacterClass: ClassName = ClassName("java.lang.Character")
+  val BoxedByteClass: ClassName = ClassName("java.lang.Byte")
+  val BoxedShortClass: ClassName = ClassName("java.lang.Short")
+  val BoxedIntegerClass: ClassName = ClassName("java.lang.Integer")
+  val BoxedLongClass: ClassName = ClassName("java.lang.Long")
+  val BoxedFloatClass: ClassName = ClassName("java.lang.Float")
+  val BoxedDoubleClass: ClassName = ClassName("java.lang.Double")
+  val BoxedStringClass: ClassName = ClassName("java.lang.String")
+
+  /** The set of all hijacked classes. */
+  val HijackedClasses: Set[ClassName] = Set(
+      BoxedUnitClass,
+      BoxedBooleanClass,
+      BoxedCharacterClass,
+      BoxedByteClass,
+      BoxedShortClass,
+      BoxedIntegerClass,
+      BoxedLongClass,
+      BoxedFloatClass,
+      BoxedDoubleClass,
+      BoxedStringClass
+  )
+
+  /** Map from hijacked classes to their respective primitive types. */
+  val BoxedClassToPrimType: Map[ClassName, PrimType] = Map(
+    BoxedUnitClass -> UndefType,
+    BoxedBooleanClass -> BooleanType,
+    BoxedCharacterClass -> CharType,
+    BoxedByteClass -> ByteType,
+    BoxedShortClass -> ShortType,
+    BoxedIntegerClass -> IntType,
+    BoxedLongClass -> LongType,
+    BoxedFloatClass -> FloatType,
+    BoxedDoubleClass -> DoubleType,
+    BoxedStringClass -> StringType
+  )
+
+  /** Map from primitive types to their respective boxed (hijacked) classes. */
+  val PrimTypeToBoxedClass: Map[PrimType, ClassName] =
+    BoxedClassToPrimType.map(_.swap)
+
+  /** The class of things returned by `ClassOf` and `GetClass`. */
+  val ClassClass: ClassName = ClassName("java.lang.Class")
+
+  /** `java.lang.Cloneable`, which is an ancestor of array classes and is used
+   *  by `Clone`.
+   */
+  val CloneableClass: ClassName = ClassName("java.lang.Cloneable")
+
+  /** `java.io.Serializable`, which is an ancestor of array classes. */
+  val SerializableClass: ClassName = ClassName("java.io.Serializable")
+
+  /** The superclass of all throwables.
+   *
+   *  This is the result type of `WrapAsThrowable` nodes, as well as the input
+   *  type of `UnwrapFromThrowable`.
+   */
+  val ThrowableClass = ClassName("java.lang.Throwable")
+
+  /** The exception thrown by a division by 0. */
+  val ArithmeticExceptionClass: ClassName =
+    ClassName("java.lang.ArithmeticException")
+
+  /** The exception thrown by an `ArraySelect` that is out of bounds. */
+  val ArrayIndexOutOfBoundsExceptionClass: ClassName =
+    ClassName("java.lang.ArrayIndexOutOfBoundsException")
+
+  /** The exception thrown by an `Assign(ArraySelect, ...)` where the value cannot be stored. */
+  val ArrayStoreExceptionClass: ClassName =
+    ClassName("java.lang.ArrayStoreException")
+
+  /** The exception thrown by a `NewArray(...)` with a negative size. */
+  val NegativeArraySizeExceptionClass: ClassName =
+    ClassName("java.lang.NegativeArraySizeException")
+
+  /** The exception thrown by a variety of nodes for `null` arguments.
+   *
+   *  - `Apply` and `ApplyStatically` for the receiver,
+   *  - `Select` for the qualifier,
+   *  - `ArrayLength` and `ArraySelect` for the array,
+   *  - `GetClass`, `Clone` and `UnwrapFromException` for their respective only arguments.
+   */
+  val NullPointerExceptionClass: ClassName =
+    ClassName("java.lang.NullPointerException")
+
+  /** The exception thrown by a `BinaryOp.String_charAt` that is out of bounds. */
+  val StringIndexOutOfBoundsExceptionClass: ClassName =
+    ClassName("java.lang.StringIndexOutOfBoundsException")
+
+  /** The exception thrown by an `AsInstanceOf` that fails. */
+  val ClassCastExceptionClass: ClassName =
+    ClassName("java.lang.ClassCastException")
+
+  /** The exception thrown by a `Class_newArray` if the first argument is `classOf[Unit]`. */
+  val IllegalArgumentExceptionClass: ClassName =
+    ClassName("java.lang.IllegalArgumentException")
+
+  /** The set of classes and interfaces that are ancestors of array classes. */
+  private[ir] val AncestorsOfPseudoArrayClass: Set[ClassName] = {
+    /* This would logically be defined in Types, but that introduces a cyclic
+     * dependency between the initialization of Names and Types.
+     */
+    Set(ObjectClass, CloneableClass, SerializableClass)
+  }
+
+  /** Name of a constructor without argument.
+   *
+   *  This is notably the signature of constructors of module classes.
+   */
+  final val NoArgConstructorName: MethodName =
+    MethodName.constructor(Nil)
+
+  /** Name of the static initializer method. */
+  final val StaticInitializerName: MethodName =
+    MethodName(SimpleMethodName.StaticInitializer, Nil, VoidRef)
+
+  /** Name of the class initializer method. */
+  final val ClassInitializerName: MethodName =
+    MethodName(SimpleMethodName.ClassInitializer, Nil, VoidRef)
+
+  /** ModuleID of the default module */
+  final val DefaultModuleID: String = "main"
+
+}
diff --git a/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala b/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala
index 6f68760422..f3d88274a5 100644
--- a/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala
+++ b/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala
@@ -22,6 +22,7 @@ import OriginalName.NoOriginalName
 import Printers._
 import Trees._
 import Types._
+import WellKnownNames._
 
 import TestIRBuilder._
 
diff --git a/ir/shared/src/test/scala/org/scalajs/ir/TestIRBuilder.scala b/ir/shared/src/test/scala/org/scalajs/ir/TestIRBuilder.scala
index 44aed0ef4f..ac2e9cecd0 100644
--- a/ir/shared/src/test/scala/org/scalajs/ir/TestIRBuilder.scala
+++ b/ir/shared/src/test/scala/org/scalajs/ir/TestIRBuilder.scala
@@ -19,6 +19,7 @@ import OriginalName.NoOriginalName
 import Printers._
 import Trees._
 import Types._
+import WellKnownNames._
 
 object TestIRBuilder {
 
diff --git a/linker-interface/shared/src/main/scala/org/scalajs/linker/interface/ModuleInitializer.scala b/linker-interface/shared/src/main/scala/org/scalajs/linker/interface/ModuleInitializer.scala
index 5ecb12ed9f..4141480f60 100644
--- a/linker-interface/shared/src/main/scala/org/scalajs/linker/interface/ModuleInitializer.scala
+++ b/linker-interface/shared/src/main/scala/org/scalajs/linker/interface/ModuleInitializer.scala
@@ -14,6 +14,7 @@ package org.scalajs.linker.interface
 
 import org.scalajs.ir.Names._
 import org.scalajs.ir.Types._
+import org.scalajs.ir.WellKnownNames._
 
 import org.scalajs.linker.interface.unstable.ModuleInitializerImpl
 
diff --git a/linker/jvm/src/test/scala/org/scalajs/linker/RunTest.scala b/linker/jvm/src/test/scala/org/scalajs/linker/RunTest.scala
index 5c49da7dee..15d64d8400 100644
--- a/linker/jvm/src/test/scala/org/scalajs/linker/RunTest.scala
+++ b/linker/jvm/src/test/scala/org/scalajs/linker/RunTest.scala
@@ -24,6 +24,7 @@ import org.junit.rules.TemporaryFolder
 import org.scalajs.ir.Names._
 import org.scalajs.ir.Trees._
 import org.scalajs.ir.Types._
+import org.scalajs.ir.WellKnownNames._
 
 import org.scalajs.junit.async._
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala
index e1faf2fa1a..7b773c7633 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala
@@ -27,6 +27,7 @@ import org.scalajs.ir.ClassKind
 import org.scalajs.ir.Names._
 import org.scalajs.ir.Trees.{MemberNamespace, JSNativeLoadSpec}
 import org.scalajs.ir.Types.ClassRef
+import org.scalajs.ir.WellKnownNames._
 
 import org.scalajs.linker._
 import org.scalajs.linker.checker.CheckingPhase
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala
index c713d5799e..40510666b6 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala
@@ -20,6 +20,7 @@ import org.scalajs.ir.Traversers._
 import org.scalajs.ir.Trees._
 import org.scalajs.ir.Types._
 import org.scalajs.ir.Version
+import org.scalajs.ir.WellKnownNames._
 
 import org.scalajs.linker.backend.emitter.Transients._
 import org.scalajs.linker.standard.LinkedTopLevelExport
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
index a27cb2dd1e..ea962ee95a 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
@@ -19,6 +19,7 @@ import org.scalajs.ir.Position._
 import org.scalajs.ir.Transformers._
 import org.scalajs.ir.Trees._
 import org.scalajs.ir.Types._
+import org.scalajs.ir.WellKnownNames._
 
 import org.scalajs.linker._
 import org.scalajs.linker.interface._
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
index 8b30a408f5..74f8f2449c 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
@@ -22,6 +22,7 @@ import org.scalajs.ir.Names._
 import org.scalajs.ir.OriginalName.NoOriginalName
 import org.scalajs.ir.Trees.{JSUnaryOp, JSBinaryOp}
 import org.scalajs.ir.Types._
+import org.scalajs.ir.WellKnownNames._
 
 import org.scalajs.linker.interface.{CheckedBehavior, ESVersion, ModuleKind}
 import org.scalajs.linker.interface.unstable.RuntimeClassNameMapperImpl
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala
index c6576f4f5d..fa7d02153a 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala
@@ -20,6 +20,7 @@ import org.scalajs.ir.{ClassKind, Position, Version}
 import org.scalajs.ir.Names._
 import org.scalajs.ir.OriginalName.NoOriginalName
 import org.scalajs.ir.Trees.{JSNativeLoadSpec, MemberNamespace}
+import org.scalajs.ir.WellKnownNames._
 
 import org.scalajs.logging._
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/EmitterNames.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/EmitterNames.scala
index a31366670f..02e46fd548 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/EmitterNames.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/EmitterNames.scala
@@ -14,6 +14,7 @@ package org.scalajs.linker.backend.emitter
 
 import org.scalajs.ir.Names._
 import org.scalajs.ir.Types._
+import org.scalajs.ir.WellKnownNames._
 
 private[emitter] object EmitterNames {
   // Class names
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
index 2252d71cd4..8fa5e60d4a 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
@@ -25,6 +25,7 @@ import org.scalajs.ir.Transformers._
 import org.scalajs.ir.Traversers._
 import org.scalajs.ir.Trees._
 import org.scalajs.ir.Types._
+import org.scalajs.ir.WellKnownNames._
 
 import org.scalajs.linker.interface._
 import org.scalajs.linker.interface.CheckedBehavior._
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/KnowledgeGuardian.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/KnowledgeGuardian.scala
index c7a94abfb9..349dc2b9af 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/KnowledgeGuardian.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/KnowledgeGuardian.scala
@@ -19,6 +19,7 @@ import org.scalajs.ir.Names._
 import org.scalajs.ir.Trees._
 import org.scalajs.ir.Types.Type
 import org.scalajs.ir.Version
+import org.scalajs.ir.WellKnownNames._
 
 import org.scalajs.linker.interface.ModuleKind
 import org.scalajs.linker.standard._
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/LongImpl.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/LongImpl.scala
index e741aacebb..e4059324e0 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/LongImpl.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/LongImpl.scala
@@ -14,6 +14,7 @@ package org.scalajs.linker.backend.emitter
 
 import org.scalajs.ir.Names._
 import org.scalajs.ir.Types._
+import org.scalajs.ir.WellKnownNames._
 
 private[linker] object LongImpl {
   final val RuntimeLongClass = ClassName("org.scalajs.linker.runtime.RuntimeLong")
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/NameGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/NameGen.scala
index a6c6b720a0..1c2c56f8f3 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/NameGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/NameGen.scala
@@ -18,6 +18,7 @@ import org.scalajs.ir.{OriginalName, UTF8String}
 import org.scalajs.ir.Names._
 import org.scalajs.ir.OriginalName.NoOriginalName
 import org.scalajs.ir.Types._
+import org.scalajs.ir.WellKnownNames._
 
 /** Performs state independent name mangling.
  *
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala
index 2ff301a7bf..c4e228eae1 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala
@@ -16,6 +16,7 @@ import org.scalajs.ir._
 import org.scalajs.ir.Names._
 import org.scalajs.ir.Types._
 import org.scalajs.ir.{Trees => irt}
+import org.scalajs.ir.WellKnownNames._
 
 import org.scalajs.linker.backend.javascript.Trees._
 import org.scalajs.linker.interface._
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/VarGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/VarGen.scala
index 1aab60acd6..34bc1ae6f2 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/VarGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/VarGen.scala
@@ -18,6 +18,7 @@ import org.scalajs.ir._
 import org.scalajs.ir.Names._
 import org.scalajs.ir.OriginalName.NoOriginalName
 import org.scalajs.ir.Types._
+import org.scalajs.ir.WellKnownNames._
 
 import org.scalajs.linker.backend.javascript.Trees._
 import org.scalajs.linker.interface.ModuleKind
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/ClassEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/ClassEmitter.scala
index 44d18110fb..67cfa32b52 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/ClassEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/ClassEmitter.scala
@@ -19,6 +19,7 @@ import org.scalajs.ir.Names._
 import org.scalajs.ir.OriginalName.NoOriginalName
 import org.scalajs.ir.Trees._
 import org.scalajs.ir.Types._
+import org.scalajs.ir.WellKnownNames._
 
 import org.scalajs.linker.interface.CheckedBehavior
 import org.scalajs.linker.interface.unstable.RuntimeClassNameMapperImpl
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
index 73bf05e3d6..68b14c51c2 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
@@ -17,6 +17,7 @@ import org.scalajs.ir.OriginalName.NoOriginalName
 import org.scalajs.ir.Trees.{JSUnaryOp, JSBinaryOp, MemberNamespace}
 import org.scalajs.ir.Types.{Type => _, ArrayType => _, _}
 import org.scalajs.ir.{OriginalName, Position, Types => irtpe}
+import org.scalajs.ir.WellKnownNames._
 
 import org.scalajs.linker.interface.CheckedBehavior
 import org.scalajs.linker.standard.{CoreSpec, LinkedGlobalInfo}
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/DerivedClasses.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/DerivedClasses.scala
index c65065dab5..2cdcd787c2 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/DerivedClasses.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/DerivedClasses.scala
@@ -21,6 +21,7 @@ import org.scalajs.ir.OriginalName.NoOriginalName
 import org.scalajs.ir.Position
 import org.scalajs.ir.Trees._
 import org.scalajs.ir.Types._
+import org.scalajs.ir.WellKnownNames._
 import org.scalajs.ir.{EntryPointsInfo, Version}
 
 import org.scalajs.linker.interface.IRFile
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala
index 51d1c99fd0..6c78b14fa3 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala
@@ -19,6 +19,7 @@ import org.scalajs.ir.Types._
 import org.scalajs.ir.OriginalName
 import org.scalajs.ir.Position
 import org.scalajs.ir.ScalaJSVersions
+import org.scalajs.ir.WellKnownNames._
 
 import org.scalajs.linker.interface._
 import org.scalajs.linker.interface.unstable._
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
index 68e1ab881d..a37ce49768 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
@@ -21,6 +21,7 @@ import org.scalajs.ir.Names._
 import org.scalajs.ir.OriginalName.NoOriginalName
 import org.scalajs.ir.Trees._
 import org.scalajs.ir.Types._
+import org.scalajs.ir.WellKnownNames._
 
 import org.scalajs.linker.interface.CheckedBehavior
 import org.scalajs.linker.backend.emitter.Transients
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Preprocessor.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Preprocessor.scala
index 2568fcb1fd..7221cab491 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Preprocessor.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Preprocessor.scala
@@ -17,6 +17,7 @@ import scala.collection.mutable
 import org.scalajs.ir.Names._
 import org.scalajs.ir.Trees._
 import org.scalajs.ir.Types._
+import org.scalajs.ir.WellKnownNames._
 import org.scalajs.ir.{ClassKind, Traversers}
 
 import org.scalajs.linker.standard.{CoreSpec, LinkedClass, LinkedTopLevelExport}
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/SWasmGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/SWasmGen.scala
index f13320065d..f8d4bcd55e 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/SWasmGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/SWasmGen.scala
@@ -12,8 +12,8 @@
 
 package org.scalajs.linker.backend.wasmemitter
 
-import org.scalajs.ir.Names._
 import org.scalajs.ir.Types._
+import org.scalajs.ir.WellKnownNames._
 
 import org.scalajs.linker.backend.webassembly._
 import org.scalajs.linker.backend.webassembly.Instructions._
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/SpecialNames.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/SpecialNames.scala
index 946532dfce..6e5887ddda 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/SpecialNames.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/SpecialNames.scala
@@ -14,6 +14,7 @@ package org.scalajs.linker.backend.wasmemitter
 
 import org.scalajs.ir.Names._
 import org.scalajs.ir.Types._
+import org.scalajs.ir.WellKnownNames._
 
 object SpecialNames {
   // Class names
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/TypeTransformer.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/TypeTransformer.scala
index d38694e284..cfc1eeb81c 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/TypeTransformer.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/TypeTransformer.scala
@@ -14,6 +14,7 @@ package org.scalajs.linker.backend.wasmemitter
 
 import org.scalajs.ir.Names._
 import org.scalajs.ir.Types._
+import org.scalajs.ir.WellKnownNames._
 
 import org.scalajs.linker.backend.webassembly.{Types => watpe}
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
index c71230948d..4173b0ff52 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
@@ -15,6 +15,7 @@ package org.scalajs.linker.backend.wasmemitter
 import org.scalajs.ir.Names._
 import org.scalajs.ir.Trees.{JSUnaryOp, JSBinaryOp, MemberNamespace}
 import org.scalajs.ir.Types._
+import org.scalajs.ir.WellKnownNames._
 
 import org.scalajs.linker.backend.webassembly.Identitities._
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/WasmContext.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/WasmContext.scala
index 0bc110dbbc..acab6a3b0f 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/WasmContext.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/WasmContext.scala
@@ -22,6 +22,7 @@ import org.scalajs.ir.Names._
 import org.scalajs.ir.OriginalName.NoOriginalName
 import org.scalajs.ir.Trees.{FieldDef, ParamDef, JSNativeLoadSpec}
 import org.scalajs.ir.Types._
+import org.scalajs.ir.WellKnownNames._
 
 import org.scalajs.linker.interface.ModuleInitializer
 import org.scalajs.linker.interface.unstable.ModuleInitializerImpl
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala b/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
index 671a320632..4fcf593d70 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
@@ -20,6 +20,7 @@ import org.scalajs.ir._
 import org.scalajs.ir.Names._
 import org.scalajs.ir.Trees._
 import org.scalajs.ir.Types._
+import org.scalajs.ir.WellKnownNames._
 
 import org.scalajs.logging._
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala b/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
index a6c786fb01..49dc20096e 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
@@ -20,6 +20,7 @@ import org.scalajs.ir._
 import org.scalajs.ir.Names._
 import org.scalajs.ir.Trees._
 import org.scalajs.ir.Types._
+import org.scalajs.ir.WellKnownNames._
 
 import org.scalajs.logging._
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/MethodSynthesizer.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/MethodSynthesizer.scala
index 79d31dc8ab..56d3502771 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/MethodSynthesizer.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/MethodSynthesizer.scala
@@ -22,6 +22,7 @@ import org.scalajs.ir
 import org.scalajs.ir.Names._
 import org.scalajs.ir.Trees._
 import org.scalajs.ir.Types._
+import org.scalajs.ir.WellKnownNames._
 
 import Analysis._
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/modulesplitter/InternalModuleIDGenerator.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/modulesplitter/InternalModuleIDGenerator.scala
index bc53504ef0..c59faf5e52 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/modulesplitter/InternalModuleIDGenerator.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/modulesplitter/InternalModuleIDGenerator.scala
@@ -16,8 +16,10 @@ import scala.collection.immutable.SortedSet
 
 import java.lang.StringBuilder
 
-import org.scalajs.ir.Names.{ClassName, ObjectClass}
+import org.scalajs.ir.Names.ClassName
 import org.scalajs.ir.SHA1
+import org.scalajs.ir.WellKnownNames.ObjectClass
+
 import org.scalajs.linker.standard.ModuleSet.ModuleID
 
 /** Generators for internal module IDs.
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/modulesplitter/ModuleSplitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/modulesplitter/ModuleSplitter.scala
index 93f9d12a8e..b814af97e3 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/modulesplitter/ModuleSplitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/modulesplitter/ModuleSplitter.scala
@@ -18,6 +18,7 @@ import scala.collection.mutable.Builder
 import org.scalajs.logging.Logger
 
 import org.scalajs.ir.Names._
+import org.scalajs.ir.WellKnownNames._
 
 import org.scalajs.linker.frontend.LinkingUnit
 import org.scalajs.linker.interface.ModuleInitializer
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
index 6d4aa83022..53320ad923 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
@@ -23,6 +23,7 @@ import org.scalajs.ir._
 import org.scalajs.ir.Names._
 import org.scalajs.ir.Trees._
 import org.scalajs.ir.Types._
+import org.scalajs.ir.WellKnownNames._
 import org.scalajs.ir.Position.NoPosition
 
 import org.scalajs.logging._
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
index 9c026ac032..fb07015f30 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
@@ -26,6 +26,7 @@ import org.scalajs.ir.Names._
 import org.scalajs.ir.OriginalName.NoOriginalName
 import org.scalajs.ir.Trees._
 import org.scalajs.ir.Types._
+import org.scalajs.ir.WellKnownNames._
 
 import org.scalajs.logging._
 import org.scalajs.linker.interface._
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/AnalyzerTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/AnalyzerTest.scala
index ad0aeb6655..8469d41420 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/AnalyzerTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/AnalyzerTest.scala
@@ -22,6 +22,7 @@ import org.scalajs.ir.EntryPointsInfo
 import org.scalajs.ir.Names._
 import org.scalajs.ir.Trees._
 import org.scalajs.ir.Types._
+import org.scalajs.ir.WellKnownNames._
 
 import org.scalajs.junit.async._
 
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/BackwardsCompatTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/BackwardsCompatTest.scala
index 3439a80251..d0eb7b9c70 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/BackwardsCompatTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/BackwardsCompatTest.scala
@@ -19,6 +19,7 @@ import org.junit.Test
 import org.scalajs.ir.Names._
 import org.scalajs.ir.Trees._
 import org.scalajs.ir.Types._
+import org.scalajs.ir.WellKnownNames._
 
 import org.scalajs.logging._
 
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/BaseLinkerTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/BaseLinkerTest.scala
index 22033b7d3c..d45cad0134 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/BaseLinkerTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/BaseLinkerTest.scala
@@ -19,6 +19,7 @@ import org.scalajs.ir.ClassKind
 import org.scalajs.ir.Names._
 import org.scalajs.ir.Trees._
 import org.scalajs.ir.Types._
+import org.scalajs.ir.WellKnownNames._
 
 import org.scalajs.junit.async._
 
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/FewestModulesSplittingTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/FewestModulesSplittingTest.scala
index 74770e1505..2112d02710 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/FewestModulesSplittingTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/FewestModulesSplittingTest.scala
@@ -18,9 +18,9 @@ import org.junit.Test
 import org.junit.Assert._
 
 import org.scalajs.ir.ClassKind
-import org.scalajs.ir.Names._
 import org.scalajs.ir.Trees._
 import org.scalajs.ir.Types._
+import org.scalajs.ir.WellKnownNames._
 
 import org.scalajs.junit.async._
 
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/IRCheckerTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/IRCheckerTest.scala
index 1d6dd4759f..25b641d900 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/IRCheckerTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/IRCheckerTest.scala
@@ -23,6 +23,7 @@ import org.scalajs.ir.Names._
 import org.scalajs.ir.Transformers._
 import org.scalajs.ir.Trees._
 import org.scalajs.ir.Types._
+import org.scalajs.ir.WellKnownNames._
 
 import org.scalajs.logging._
 
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/IncrementalTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/IncrementalTest.scala
index 7129402959..6c24d25619 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/IncrementalTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/IncrementalTest.scala
@@ -24,6 +24,7 @@ import org.scalajs.ir.Names._
 import org.scalajs.ir.Trees._
 import org.scalajs.ir.Types._
 import org.scalajs.ir.Version
+import org.scalajs.ir.WellKnownNames._
 
 import org.scalajs.logging._
 
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/LibraryReachabilityTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/LibraryReachabilityTest.scala
index 8b08bcf860..0dca816d43 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/LibraryReachabilityTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/LibraryReachabilityTest.scala
@@ -17,9 +17,9 @@ import scala.concurrent._
 import org.junit.Test
 import org.junit.Assert._
 
-import org.scalajs.ir.Names._
 import org.scalajs.ir.Trees._
 import org.scalajs.ir.Types._
+import org.scalajs.ir.WellKnownNames._
 
 import org.scalajs.junit.async._
 
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/OptimizerTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/OptimizerTest.scala
index 3954dfe278..c7bc282ff2 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/OptimizerTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/OptimizerTest.scala
@@ -24,6 +24,7 @@ import org.scalajs.ir.Traversers.Traverser
 import org.scalajs.ir.Trees._
 import org.scalajs.ir.Trees.MemberNamespace._
 import org.scalajs.ir.Types._
+import org.scalajs.ir.WellKnownNames._
 
 import org.scalajs.logging._
 
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/SmallModulesForSplittingTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/SmallModulesForSplittingTest.scala
index ce6a9b2386..654e328ab1 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/SmallModulesForSplittingTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/SmallModulesForSplittingTest.scala
@@ -22,6 +22,7 @@ import org.scalajs.ir.ClassKind
 import org.scalajs.ir.Names._
 import org.scalajs.ir.Trees._
 import org.scalajs.ir.Types._
+import org.scalajs.ir.WellKnownNames._
 
 import org.scalajs.junit.async._
 
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/SmallestModulesSplittingTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/SmallestModulesSplittingTest.scala
index fd91b55f53..ea8259b2d5 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/SmallestModulesSplittingTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/SmallestModulesSplittingTest.scala
@@ -17,9 +17,9 @@ import scala.concurrent._
 import org.junit.Test
 import org.junit.Assert._
 
-import org.scalajs.ir.Names._
 import org.scalajs.ir.Trees._
 import org.scalajs.ir.Types._
+import org.scalajs.ir.WellKnownNames._
 
 import org.scalajs.junit.async._
 
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/checker/ClassDefCheckerTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/checker/ClassDefCheckerTest.scala
index 8bbf5ff00a..c29c3443c4 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/checker/ClassDefCheckerTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/checker/ClassDefCheckerTest.scala
@@ -20,6 +20,7 @@ import org.scalajs.ir.Names._
 import org.scalajs.ir.OriginalName.NoOriginalName
 import org.scalajs.ir.Trees._
 import org.scalajs.ir.Types._
+import org.scalajs.ir.WellKnownNames._
 
 import org.scalajs.logging.NullLogger
 
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/standard/StandardIRFileCacheTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/standard/StandardIRFileCacheTest.scala
index fa4b3adbf2..e4e949c1ca 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/standard/StandardIRFileCacheTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/standard/StandardIRFileCacheTest.scala
@@ -21,8 +21,9 @@ import org.scalajs.junit.async._
 
 import org.scalajs.ir.EntryPointsInfo
 import org.scalajs.ir.Trees.ClassDef
-import org.scalajs.ir.Names.{ClassName, ObjectClass}
+import org.scalajs.ir.Names.ClassName
 import org.scalajs.ir.Version.Unversioned
+import org.scalajs.ir.WellKnownNames.ObjectClass
 
 import org.scalajs.linker.interface._
 import org.scalajs.linker.interface.unstable._
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/testutils/TestIRBuilder.scala b/linker/shared/src/test/scala/org/scalajs/linker/testutils/TestIRBuilder.scala
index e6b045c286..7d022a5123 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/testutils/TestIRBuilder.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/testutils/TestIRBuilder.scala
@@ -22,6 +22,7 @@ import org.scalajs.ir.OriginalName
 import org.scalajs.ir.OriginalName.NoOriginalName
 import org.scalajs.ir.Trees._
 import org.scalajs.ir.Types._
+import org.scalajs.ir.WellKnownNames._
 
 import org.scalajs.linker.interface.ModuleInitializer
 
diff --git a/project/BinaryIncompatibilities.scala b/project/BinaryIncompatibilities.scala
index 032ec1440e..edc3b894b3 100644
--- a/project/BinaryIncompatibilities.scala
+++ b/project/BinaryIncompatibilities.scala
@@ -5,6 +5,17 @@ import com.typesafe.tools.mima.core.ProblemFilters._
 
 object BinaryIncompatibilities {
   val IR = Seq(
+    // !!! Breaking, OK in minor release
+    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Names.*Class"),
+    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Names.ClassInitializerName"),
+    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Names.DefaultModuleID"),
+    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Names.HijackedClasses"),
+    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Names.NoArgConstructorName"),
+    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Names.ObjectArgConstructorName"),
+    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Names.StaticInitializerName"),
+    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Types.BoxedClassToPrimType"),
+    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Types.PrimTypeToBoxedClass"),
+
     // private, not an issue
     ProblemFilters.exclude[MissingClassProblem]("org.scalajs.ir.Serializers$Deserializer$BodyHack5Transformer$"),
     ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Serializers#Hacks.use*"),
diff --git a/project/JavaLangObject.scala b/project/JavaLangObject.scala
index 1b32bac8ff..9312578ae4 100644
--- a/project/JavaLangObject.scala
+++ b/project/JavaLangObject.scala
@@ -14,6 +14,7 @@ import org.scalajs.ir.Trees._
 import org.scalajs.ir.Types._
 import org.scalajs.ir.Position.NoPosition
 import org.scalajs.ir.Version.Unversioned
+import org.scalajs.ir.WellKnownNames._
 
 /** Hard-coded IR for java.lang.Object.
  *  We cannot so much as begin to fake a compilation of java.lang.Object,
diff --git a/project/JavalibIRCleaner.scala b/project/JavalibIRCleaner.scala
index d2f4be2881..87095c1265 100644
--- a/project/JavalibIRCleaner.scala
+++ b/project/JavalibIRCleaner.scala
@@ -6,6 +6,7 @@ import org.scalajs.ir.Names._
 import org.scalajs.ir.Trees._
 import org.scalajs.ir.Types._
 import org.scalajs.ir.Version.Unversioned
+import org.scalajs.ir.WellKnownNames._
 
 import java.io._
 import java.net.URI

From 53ecbe341a09b073085afff969e998b4fd2f762b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Mon, 3 Mar 2025 10:33:22 +0100
Subject: [PATCH 261/298] Add tests for the `nameString` method of names.

This also serves as a test that there is no deadlock between
`Names` and `Types` anymore. Without that fix, the addtion of
`NamesTest` triggered a deadlock in virtually every run of
`ir2_12/test`.
---
 .../test/scala/org/scalajs/ir/NamesTest.scala | 76 +++++++++++++++++++
 1 file changed, 76 insertions(+)
 create mode 100644 ir/shared/src/test/scala/org/scalajs/ir/NamesTest.scala

diff --git a/ir/shared/src/test/scala/org/scalajs/ir/NamesTest.scala b/ir/shared/src/test/scala/org/scalajs/ir/NamesTest.scala
new file mode 100644
index 0000000000..412c223f77
--- /dev/null
+++ b/ir/shared/src/test/scala/org/scalajs/ir/NamesTest.scala
@@ -0,0 +1,76 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package org.scalajs.ir
+
+import org.junit.Test
+import org.junit.Assert._
+
+import Names._
+import Types._
+import WellKnownNames._
+
+class NamesTest {
+  @Test def nameStringLocalName(): Unit = {
+    assertEquals("foo", LocalName("foo").nameString)
+    assertEquals(".this", LocalName.This.nameString)
+  }
+
+  @Test def nameStringLabelName(): Unit = {
+    assertEquals("foo", LabelName("foo").nameString)
+  }
+
+  @Test def nameStringSimpleFieldName(): Unit = {
+    assertEquals("foo", SimpleFieldName("foo").nameString)
+  }
+
+  @Test def nameStringFieldName(): Unit = {
+    assertEquals("a.B::foo",
+        FieldName(ClassName("a.B"), SimpleFieldName("foo")).nameString)
+  }
+
+  @Test def nameStringSimpleMethodName(): Unit = {
+    assertEquals("foo", SimpleMethodName("foo").nameString)
+    assertEquals("<init>", SimpleMethodName.Constructor.nameString)
+    assertEquals("<stinit>", SimpleMethodName.StaticInitializer.nameString)
+    assertEquals("<clinit>", SimpleMethodName.ClassInitializer.nameString)
+  }
+
+  @Test def nameStringMethodName(): Unit = {
+    assertEquals("foo;I", MethodName("foo", Nil, IntRef).nameString)
+    assertEquals("foo;Z;I", MethodName("foo", List(BooleanRef), IntRef).nameString)
+    assertEquals("foo;Z;V", MethodName("foo", List(BooleanRef), VoidRef).nameString)
+
+    assertEquals("foo;S;Ljava.io.Serializable;V",
+        MethodName("foo", List(ShortRef, ClassRef(SerializableClass)), VoidRef).nameString)
+
+    assertEquals("<init>;I;V", MethodName.constructor(List(IntRef)).nameString)
+
+    assertEquals("foo;Z;R", MethodName.reflectiveProxy("foo", List(BooleanRef)).nameString)
+
+    val refAndNameStrings: List[(TypeRef, String)] = List(
+      ClassRef(ObjectClass) -> "Ljava.lang.Object",
+      ClassRef(SerializableClass) -> "Ljava.io.Serializable",
+      ClassRef(BoxedStringClass) -> "Ljava.lang.String",
+      ArrayTypeRef(ClassRef(ObjectClass), 2) -> "[[Ljava.lang.Object",
+      ArrayTypeRef(ShortRef, 1) -> "[S"
+    )
+    for ((ref, nameString) <- refAndNameStrings) {
+      assertEquals(s"foo;$nameString;V",
+          MethodName("foo", List(ref), VoidRef).nameString)
+    }
+  }
+
+  @Test def nameStringClassName(): Unit = {
+    assertEquals("a.B", ClassName("a.B").nameString)
+  }
+}

From a4cdc6f2d45a7590df3be76ee96fc0e560042eae Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Mon, 3 Feb 2025 13:03:31 +0100
Subject: [PATCH 262/298] Deprecate support for ECMAScript 5.1.

That support is the biggest source of alternative code paths and
polyfills in our codebase.

The polyfills and other alternative implementations we need to
support ES 5.1 include:

* `Math.fround` to support `Float` operations (in `CoreJSLib`).
* Other bit manipulation magic for floating-point numbers
  (in `FloatingPointBits`).
* Using dynamic JS `Array`s instead of typed arrays for Scala
  `Array`s of primitive types.
* Using custom Java `Map`s instead of `js.Map`.
* Various implementations of math methods in `jl.Math` (although
  these may come back for a Wasm-only target, along with more of
  them).
* Using run-time generated random property names instead of
  `Symbol`s.
* Very complex code to handle surrogate pairs in `ju.regex.*`.
* (Imperfect) desugaring of `...rest` parameters and `...spread`
  operators.

Moreover, the ES 5.1 output does not even have exactly the same
semantics as later versions:

* JS classes are not true `class`es. Notably, that means they
  cannot extend native ES classes, and they do not inherit static
  members.
* Top-level exports are declared as `var`s instead of `let`s.

10 years after the instruction of ECMAScript 2015, I believe it
is time to deprecate the support for Es 5.1, so that we can
eventually remove it.
---
 .../main/scala/org/scalajs/linker/interface/ESVersion.scala | 6 +++++-
 .../linker/interface/StandardConfigFingerprintTest.scala    | 2 +-
 .../linker/backend/closure/ClosureLinkerBackend.scala       | 5 ++++-
 .../src/test/scala/org/scalajs/linker/AnalyzerTest.scala    | 1 +
 4 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/linker-interface/shared/src/main/scala/org/scalajs/linker/interface/ESVersion.scala b/linker-interface/shared/src/main/scala/org/scalajs/linker/interface/ESVersion.scala
index 6c55b76b8f..2634139655 100644
--- a/linker-interface/shared/src/main/scala/org/scalajs/linker/interface/ESVersion.scala
+++ b/linker-interface/shared/src/main/scala/org/scalajs/linker/interface/ESVersion.scala
@@ -30,7 +30,11 @@ final class ESVersion private (val edition: Int, val name: String)
 }
 
 object ESVersion {
-  /** ECMAScrîpt 5.1. */
+  // !!! When we actually remove this, remove the code mentioning it in ClosureLinkerBackend.scala
+  /** ECMAScript 5.1. */
+  @deprecated(
+      "Support for ECMAScript 5.1 is deprecated and will eventually be removed.",
+      since = "1.19.0")
   val ES5_1: ESVersion = new ESVersion(5, "ECMAScript 5.1")
 
   /** ECMAScript 2015 (6th edition). */
diff --git a/linker-interface/shared/src/test/scala/org/scalajs/linker/interface/StandardConfigFingerprintTest.scala b/linker-interface/shared/src/test/scala/org/scalajs/linker/interface/StandardConfigFingerprintTest.scala
index 193015cc07..0b495a5d3c 100644
--- a/linker-interface/shared/src/test/scala/org/scalajs/linker/interface/StandardConfigFingerprintTest.scala
+++ b/linker-interface/shared/src/test/scala/org/scalajs/linker/interface/StandardConfigFingerprintTest.scala
@@ -42,7 +42,7 @@ class StandardConfigFingerprintTest {
   @Test
   def noFingerprintCollisionESFeatures(): Unit = {
     val sc1 = StandardConfig().withESFeatures(_.withESVersion(ESVersion.ES2015))
-    val sc2 = StandardConfig().withESFeatures(_.withESVersion(ESVersion.ES5_1))
+    val sc2 = StandardConfig().withESFeatures(_.withESVersion(ESVersion.ES2016))
     assertFingerprintsNotEquals(sc1, sc2)
   }
 
diff --git a/linker/jvm/src/main/scala/org/scalajs/linker/backend/closure/ClosureLinkerBackend.scala b/linker/jvm/src/main/scala/org/scalajs/linker/backend/closure/ClosureLinkerBackend.scala
index de9fdefa68..44944f1d64 100644
--- a/linker/jvm/src/main/scala/org/scalajs/linker/backend/closure/ClosureLinkerBackend.scala
+++ b/linker/jvm/src/main/scala/org/scalajs/linker/backend/closure/ClosureLinkerBackend.scala
@@ -78,7 +78,6 @@ final class ClosureLinkerBackend(config: LinkerBackendImpl.Config)
     import ClosureOptions.LanguageMode._
 
     esFeatures.esVersion match {
-      case ESVersion.ES5_1  => ECMASCRIPT5_STRICT
       case ESVersion.ES2015 => ECMASCRIPT_2015
       case ESVersion.ES2016 => ECMASCRIPT_2016
       case ESVersion.ES2017 => ECMASCRIPT_2017
@@ -87,6 +86,10 @@ final class ClosureLinkerBackend(config: LinkerBackendImpl.Config)
       case ESVersion.ES2020 => ECMASCRIPT_2020
       case ESVersion.ES2021 => ECMASCRIPT_2021
 
+      // Test for ESVersion.ES5_1 without triggering the deprecation warning
+      case esVersion if esVersion.edition == 5 =>
+        ECMASCRIPT5_STRICT
+
       case _ =>
         throw new AssertionError(s"Unknown ES version ${esFeatures.esVersion}")
     }
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/AnalyzerTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/AnalyzerTest.scala
index ad0aeb6655..572998563a 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/AnalyzerTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/AnalyzerTest.scala
@@ -654,6 +654,7 @@ class AnalyzerTest {
     }
   }
 
+  @deprecated("test deprecated features", "forever")
   @Test
   def newTargetWithoutES2015(): AsyncResult = await {
     val classDefs = Seq(

From 822095147c31f37f804564cbc310baedffe3d6b3 Mon Sep 17 00:00:00 2001
From: Leonid Dubinsky <dub@podval.org>
Date: Mon, 24 Feb 2025 13:49:09 -0500
Subject: [PATCH 263/298] JUnit: populate sbt.testing.Event.duration.

If duration associated with the test event is available, bubble it up through the SBT's test interface using the slot dedicated to just such information: sbt.testing.Event.duration.

In addition to it being a shame to throw away information about the duration that is literally in our hands, this avoids weird-looking negative duration values in test reports.
---
 .../scala/org/scalajs/junit/Reporter.scala    | 15 +++++++-----
 .../junit/AssertEquals2TestAssertions_.txt    |  2 +-
 .../junit/AssertEquals2TestAssertions_a.txt   |  2 +-
 .../junit/AssertEquals2TestAssertions_n.txt   |  2 +-
 .../junit/AssertEquals2TestAssertions_na.txt  |  2 +-
 .../junit/AssertEquals2TestAssertions_nv.txt  |  2 +-
 .../junit/AssertEquals2TestAssertions_nva.txt |  2 +-
 .../junit/AssertEquals2TestAssertions_nvc.txt |  2 +-
 .../AssertEquals2TestAssertions_nvca.txt      |  2 +-
 .../junit/AssertEquals2TestAssertions_v.txt   |  2 +-
 .../junit/AssertEquals2TestAssertions_va.txt  |  2 +-
 .../junit/AssertEquals2TestAssertions_vc.txt  |  2 +-
 .../junit/AssertEquals2TestAssertions_vs.txt  |  2 +-
 .../junit/AssertEquals2TestAssertions_vsn.txt |  2 +-
 .../AssertEqualsDoubleTestAssertions_.txt     | 12 +++++-----
 .../AssertEqualsDoubleTestAssertions_a.txt    | 12 +++++-----
 .../AssertEqualsDoubleTestAssertions_n.txt    | 12 +++++-----
 .../AssertEqualsDoubleTestAssertions_na.txt   | 12 +++++-----
 .../AssertEqualsDoubleTestAssertions_nv.txt   | 12 +++++-----
 .../AssertEqualsDoubleTestAssertions_nva.txt  | 12 +++++-----
 .../AssertEqualsDoubleTestAssertions_nvc.txt  | 12 +++++-----
 .../AssertEqualsDoubleTestAssertions_nvca.txt | 12 +++++-----
 .../AssertEqualsDoubleTestAssertions_v.txt    | 12 +++++-----
 .../AssertEqualsDoubleTestAssertions_va.txt   | 12 +++++-----
 .../AssertEqualsDoubleTestAssertions_vc.txt   | 12 +++++-----
 .../AssertEqualsDoubleTestAssertions_vs.txt   | 12 +++++-----
 .../AssertEqualsDoubleTestAssertions_vsn.txt  | 12 +++++-----
 .../junit/AssertEqualsTestAssertions_.txt     |  2 +-
 .../junit/AssertEqualsTestAssertions_a.txt    |  2 +-
 .../junit/AssertEqualsTestAssertions_n.txt    |  2 +-
 .../junit/AssertEqualsTestAssertions_na.txt   |  2 +-
 .../junit/AssertEqualsTestAssertions_nv.txt   |  2 +-
 .../junit/AssertEqualsTestAssertions_nva.txt  |  2 +-
 .../junit/AssertEqualsTestAssertions_nvc.txt  |  2 +-
 .../junit/AssertEqualsTestAssertions_nvca.txt |  2 +-
 .../junit/AssertEqualsTestAssertions_v.txt    |  2 +-
 .../junit/AssertEqualsTestAssertions_va.txt   |  2 +-
 .../junit/AssertEqualsTestAssertions_vc.txt   |  2 +-
 .../junit/AssertEqualsTestAssertions_vs.txt   |  2 +-
 .../junit/AssertEqualsTestAssertions_vsn.txt  |  2 +-
 .../junit/AssertFalse2TestAssertions_.txt     |  2 +-
 .../junit/AssertFalse2TestAssertions_a.txt    |  2 +-
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 .../junit/AssertFalseTestAssertions_.txt      |  2 +-
 .../junit/AssertFalseTestAssertions_a.txt     |  2 +-
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 .../junit/AssertFalseTestAssertions_v.txt     |  2 +-
 .../junit/AssertFalseTestAssertions_va.txt    |  2 +-
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 .../junit/AssertFalseTestAssertions_vs.txt    |  2 +-
 .../junit/AssertFalseTestAssertions_vsn.txt   |  2 +-
 .../AssertStringEqualsTestAssertions_.txt     |  2 +-
 .../AssertStringEqualsTestAssertions_a.txt    |  2 +-
 .../AssertStringEqualsTestAssertions_n.txt    |  2 +-
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 .../AssertStringEqualsTestAssertions_vsn.txt  |  2 +-
 .../junit/AssertTrueTestAssertions_.txt       |  4 ++--
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 .../scalajs/junit/AssumeTestAssertions_a.txt  |  2 +-
 .../scalajs/junit/AssumeTestAssertions_n.txt  |  2 +-
 .../scalajs/junit/AssumeTestAssertions_na.txt |  2 +-
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 .../ExceptionAfterClassAssertions_vsn.txt     |  6 ++---
 ...xceptionBeforeAndAfterClassAssertions_.txt |  2 +-
 ...ceptionBeforeAndAfterClassAssertions_a.txt |  2 +-
 ...ceptionBeforeAndAfterClassAssertions_n.txt |  2 +-
 ...eptionBeforeAndAfterClassAssertions_na.txt |  2 +-
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 ...ptionBeforeAndAfterClassAssertions_nva.txt |  2 +-
 ...ptionBeforeAndAfterClassAssertions_nvc.txt |  2 +-
 ...tionBeforeAndAfterClassAssertions_nvca.txt |  2 +-
 ...ceptionBeforeAndAfterClassAssertions_v.txt |  2 +-
 ...eptionBeforeAndAfterClassAssertions_va.txt |  2 +-
 ...eptionBeforeAndAfterClassAssertions_vc.txt |  2 +-
 ...eptionBeforeAndAfterClassAssertions_vs.txt |  2 +-
 ...ptionBeforeAndAfterClassAssertions_vsn.txt |  2 +-
 .../junit/ExceptionBeforeClassAssertions_.txt |  2 +-
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 .../ExceptionBeforeClassAssertions_na.txt     |  2 +-
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 .../ExceptionBeforeClassAssertions_nva.txt    |  2 +-
 .../ExceptionBeforeClassAssertions_nvc.txt    |  2 +-
 .../ExceptionBeforeClassAssertions_nvca.txt   |  2 +-
 .../ExceptionBeforeClassAssertions_v.txt      |  2 +-
 .../ExceptionBeforeClassAssertions_va.txt     |  2 +-
 .../ExceptionBeforeClassAssertions_vc.txt     |  2 +-
 .../ExceptionBeforeClassAssertions_vs.txt     |  2 +-
 .../ExceptionBeforeClassAssertions_vsn.txt    |  2 +-
 .../junit/ExceptionEverywhereAssertions_.txt  |  2 +-
 .../junit/ExceptionEverywhereAssertions_a.txt |  2 +-
 .../junit/ExceptionEverywhereAssertions_n.txt |  2 +-
 .../ExceptionEverywhereAssertions_na.txt      |  2 +-
 .../ExceptionEverywhereAssertions_nv.txt      |  2 +-
 .../ExceptionEverywhereAssertions_nva.txt     |  2 +-
 .../ExceptionEverywhereAssertions_nvc.txt     |  2 +-
 .../ExceptionEverywhereAssertions_nvca.txt    |  2 +-
 .../junit/ExceptionEverywhereAssertions_v.txt |  2 +-
 .../ExceptionEverywhereAssertions_va.txt      |  2 +-
 .../ExceptionEverywhereAssertions_vc.txt      |  2 +-
 .../ExceptionEverywhereAssertions_vs.txt      |  2 +-
 .../ExceptionEverywhereAssertions_vsn.txt     |  2 +-
 .../junit/ExceptionInAfterTestAssertions_.txt |  2 +-
 .../ExceptionInAfterTestAssertions_a.txt      |  2 +-
 .../ExceptionInAfterTestAssertions_n.txt      |  2 +-
 .../ExceptionInAfterTestAssertions_na.txt     |  2 +-
 .../ExceptionInAfterTestAssertions_nv.txt     |  2 +-
 .../ExceptionInAfterTestAssertions_nva.txt    |  2 +-
 .../ExceptionInAfterTestAssertions_nvc.txt    |  2 +-
 .../ExceptionInAfterTestAssertions_nvca.txt   |  2 +-
 .../ExceptionInAfterTestAssertions_v.txt      |  2 +-
 .../ExceptionInAfterTestAssertions_va.txt     |  2 +-
 .../ExceptionInAfterTestAssertions_vc.txt     |  2 +-
 .../ExceptionInAfterTestAssertions_vs.txt     |  2 +-
 .../ExceptionInAfterTestAssertions_vsn.txt    |  2 +-
 .../ExceptionInBeforeTestAssertions_.txt      |  2 +-
 .../ExceptionInBeforeTestAssertions_a.txt     |  2 +-
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 .../ExceptionInBeforeTestAssertions_na.txt    |  2 +-
 .../ExceptionInBeforeTestAssertions_nv.txt    |  2 +-
 .../ExceptionInBeforeTestAssertions_nva.txt   |  2 +-
 .../ExceptionInBeforeTestAssertions_nvc.txt   |  2 +-
 .../ExceptionInBeforeTestAssertions_nvca.txt  |  2 +-
 .../ExceptionInBeforeTestAssertions_v.txt     |  2 +-
 .../ExceptionInBeforeTestAssertions_va.txt    |  2 +-
 .../ExceptionInBeforeTestAssertions_vc.txt    |  2 +-
 .../ExceptionInBeforeTestAssertions_vs.txt    |  2 +-
 .../ExceptionInBeforeTestAssertions_vsn.txt   |  2 +-
 .../ExceptionInConstructorTestAssertions_.txt |  2 +-
 ...ExceptionInConstructorTestAssertions_a.txt |  2 +-
 ...ExceptionInConstructorTestAssertions_n.txt |  2 +-
 ...xceptionInConstructorTestAssertions_na.txt |  2 +-
 ...xceptionInConstructorTestAssertions_nv.txt |  2 +-
 ...ceptionInConstructorTestAssertions_nva.txt |  2 +-
 ...ceptionInConstructorTestAssertions_nvc.txt |  2 +-
 ...eptionInConstructorTestAssertions_nvca.txt |  2 +-
 ...ExceptionInConstructorTestAssertions_v.txt |  2 +-
 ...xceptionInConstructorTestAssertions_va.txt |  2 +-
 ...xceptionInConstructorTestAssertions_vc.txt |  2 +-
 ...xceptionInConstructorTestAssertions_vs.txt |  2 +-
 ...ceptionInConstructorTestAssertions_vsn.txt |  2 +-
 .../junit/ExceptionTestAssertions_.txt        |  2 +-
 .../junit/ExceptionTestAssertions_a.txt       |  2 +-
 .../junit/ExceptionTestAssertions_n.txt       |  2 +-
 .../junit/ExceptionTestAssertions_na.txt      |  2 +-
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 .../junit/ExceptionTestAssertions_nva.txt     |  2 +-
 .../junit/ExceptionTestAssertions_nvc.txt     |  2 +-
 .../junit/ExceptionTestAssertions_nvca.txt    |  2 +-
 .../junit/ExceptionTestAssertions_v.txt       |  2 +-
 .../junit/ExceptionTestAssertions_va.txt      |  2 +-
 .../junit/ExceptionTestAssertions_vc.txt      |  2 +-
 .../junit/ExceptionTestAssertions_vs.txt      |  2 +-
 .../junit/ExceptionTestAssertions_vsn.txt     |  2 +-
 .../scalajs/junit/ExpectTestAssertions_.txt   | 10 ++++----
 .../scalajs/junit/ExpectTestAssertions_a.txt  | 10 ++++----
 .../scalajs/junit/ExpectTestAssertions_n.txt  | 10 ++++----
 .../scalajs/junit/ExpectTestAssertions_na.txt | 10 ++++----
 .../scalajs/junit/ExpectTestAssertions_nv.txt | 10 ++++----
 .../junit/ExpectTestAssertions_nva.txt        | 10 ++++----
 .../junit/ExpectTestAssertions_nvc.txt        | 10 ++++----
 .../junit/ExpectTestAssertions_nvca.txt       | 10 ++++----
 .../scalajs/junit/ExpectTestAssertions_v.txt  | 10 ++++----
 .../scalajs/junit/ExpectTestAssertions_va.txt | 10 ++++----
 .../scalajs/junit/ExpectTestAssertions_vc.txt | 10 ++++----
 .../scalajs/junit/ExpectTestAssertions_vs.txt | 10 ++++----
 .../junit/ExpectTestAssertions_vsn.txt        | 10 ++++----
 .../scalajs/junit/IgnoreTestAssertions_.txt   |  2 +-
 .../scalajs/junit/IgnoreTestAssertions_a.txt  |  2 +-
 .../scalajs/junit/IgnoreTestAssertions_n.txt  |  2 +-
 .../scalajs/junit/IgnoreTestAssertions_na.txt |  2 +-
 .../scalajs/junit/IgnoreTestAssertions_nv.txt |  2 +-
 .../junit/IgnoreTestAssertions_nva.txt        |  2 +-
 .../junit/IgnoreTestAssertions_nvc.txt        |  2 +-
 .../junit/IgnoreTestAssertions_nvca.txt       |  2 +-
 .../scalajs/junit/IgnoreTestAssertions_v.txt  |  2 +-
 .../scalajs/junit/IgnoreTestAssertions_va.txt |  2 +-
 .../scalajs/junit/IgnoreTestAssertions_vc.txt |  2 +-
 .../scalajs/junit/IgnoreTestAssertions_vs.txt |  2 +-
 .../junit/IgnoreTestAssertions_vsn.txt        |  2 +-
 .../junit/MethodNameDecodeTestAssertions_.txt |  2 +-
 .../MethodNameDecodeTestAssertions_a.txt      |  2 +-
 .../MethodNameDecodeTestAssertions_n.txt      |  2 +-
 .../MethodNameDecodeTestAssertions_na.txt     |  2 +-
 .../MethodNameDecodeTestAssertions_nv.txt     |  2 +-
 .../MethodNameDecodeTestAssertions_nva.txt    |  2 +-
 .../MethodNameDecodeTestAssertions_nvc.txt    |  2 +-
 .../MethodNameDecodeTestAssertions_nvca.txt   |  2 +-
 .../MethodNameDecodeTestAssertions_v.txt      |  2 +-
 .../MethodNameDecodeTestAssertions_va.txt     |  2 +-
 .../MethodNameDecodeTestAssertions_vc.txt     |  2 +-
 .../MethodNameDecodeTestAssertions_vs.txt     |  2 +-
 .../MethodNameDecodeTestAssertions_vsn.txt    |  2 +-
 .../scalajs/junit/Multi1TestAssertions_.txt   |  4 ++--
 .../scalajs/junit/Multi1TestAssertions_a.txt  |  4 ++--
 .../scalajs/junit/Multi1TestAssertions_n.txt  |  4 ++--
 .../scalajs/junit/Multi1TestAssertions_na.txt |  4 ++--
 .../scalajs/junit/Multi1TestAssertions_nv.txt |  4 ++--
 .../junit/Multi1TestAssertions_nva.txt        |  4 ++--
 .../junit/Multi1TestAssertions_nvc.txt        |  4 ++--
 .../junit/Multi1TestAssertions_nvca.txt       |  4 ++--
 .../scalajs/junit/Multi1TestAssertions_v.txt  |  4 ++--
 .../scalajs/junit/Multi1TestAssertions_va.txt |  4 ++--
 .../scalajs/junit/Multi1TestAssertions_vc.txt |  4 ++--
 .../scalajs/junit/Multi1TestAssertions_vs.txt |  4 ++--
 .../junit/Multi1TestAssertions_vsn.txt        |  4 ++--
 .../scalajs/junit/Multi2TestAssertions_.txt   | 10 ++++----
 .../scalajs/junit/Multi2TestAssertions_a.txt  | 10 ++++----
 .../scalajs/junit/Multi2TestAssertions_n.txt  | 10 ++++----
 .../scalajs/junit/Multi2TestAssertions_na.txt | 10 ++++----
 .../scalajs/junit/Multi2TestAssertions_nv.txt | 10 ++++----
 .../junit/Multi2TestAssertions_nva.txt        | 10 ++++----
 .../junit/Multi2TestAssertions_nvc.txt        | 10 ++++----
 .../junit/Multi2TestAssertions_nvca.txt       | 10 ++++----
 .../scalajs/junit/Multi2TestAssertions_v.txt  | 10 ++++----
 .../scalajs/junit/Multi2TestAssertions_va.txt | 10 ++++----
 .../scalajs/junit/Multi2TestAssertions_vc.txt | 10 ++++----
 .../scalajs/junit/Multi2TestAssertions_vs.txt | 10 ++++----
 .../junit/Multi2TestAssertions_vsn.txt        | 10 ++++----
 .../junit/MultiAssumeFail1TestAssertions_.txt | 10 ++++----
 .../MultiAssumeFail1TestAssertions_a.txt      | 10 ++++----
 .../MultiAssumeFail1TestAssertions_n.txt      | 10 ++++----
 .../MultiAssumeFail1TestAssertions_na.txt     | 10 ++++----
 .../MultiAssumeFail1TestAssertions_nv.txt     | 10 ++++----
 .../MultiAssumeFail1TestAssertions_nva.txt    | 10 ++++----
 .../MultiAssumeFail1TestAssertions_nvc.txt    | 10 ++++----
 .../MultiAssumeFail1TestAssertions_nvca.txt   | 10 ++++----
 .../MultiAssumeFail1TestAssertions_v.txt      | 10 ++++----
 .../MultiAssumeFail1TestAssertions_va.txt     | 10 ++++----
 .../MultiAssumeFail1TestAssertions_vc.txt     | 10 ++++----
 .../MultiAssumeFail1TestAssertions_vs.txt     | 10 ++++----
 .../MultiAssumeFail1TestAssertions_vsn.txt    | 10 ++++----
 .../junit/MultiAssumeFail2TestAssertions_.txt | 10 ++++----
 .../MultiAssumeFail2TestAssertions_a.txt      | 10 ++++----
 .../MultiAssumeFail2TestAssertions_n.txt      | 10 ++++----
 .../MultiAssumeFail2TestAssertions_na.txt     | 10 ++++----
 .../MultiAssumeFail2TestAssertions_nv.txt     | 10 ++++----
 .../MultiAssumeFail2TestAssertions_nva.txt    | 10 ++++----
 .../MultiAssumeFail2TestAssertions_nvc.txt    | 10 ++++----
 .../MultiAssumeFail2TestAssertions_nvca.txt   | 10 ++++----
 .../MultiAssumeFail2TestAssertions_v.txt      | 10 ++++----
 .../MultiAssumeFail2TestAssertions_va.txt     | 10 ++++----
 .../MultiAssumeFail2TestAssertions_vc.txt     | 10 ++++----
 .../MultiAssumeFail2TestAssertions_vs.txt     | 10 ++++----
 .../MultiAssumeFail2TestAssertions_vsn.txt    | 10 ++++----
 .../MultiBeforeAssumeFailTestAssertions_.txt  |  2 +-
 .../MultiBeforeAssumeFailTestAssertions_a.txt |  2 +-
 .../MultiBeforeAssumeFailTestAssertions_n.txt |  2 +-
 ...MultiBeforeAssumeFailTestAssertions_na.txt |  2 +-
 ...MultiBeforeAssumeFailTestAssertions_nv.txt |  2 +-
 ...ultiBeforeAssumeFailTestAssertions_nva.txt |  2 +-
 ...ultiBeforeAssumeFailTestAssertions_nvc.txt |  2 +-
 ...ltiBeforeAssumeFailTestAssertions_nvca.txt |  2 +-
 .../MultiBeforeAssumeFailTestAssertions_v.txt |  2 +-
 ...MultiBeforeAssumeFailTestAssertions_va.txt |  2 +-
 ...MultiBeforeAssumeFailTestAssertions_vc.txt |  2 +-
 ...MultiBeforeAssumeFailTestAssertions_vs.txt |  2 +-
 ...ultiBeforeAssumeFailTestAssertions_vsn.txt |  2 +-
 .../junit/MultiIgnore1TestAssertions_.txt     | 10 ++++----
 .../junit/MultiIgnore1TestAssertions_a.txt    | 10 ++++----
 .../junit/MultiIgnore1TestAssertions_n.txt    | 10 ++++----
 .../junit/MultiIgnore1TestAssertions_na.txt   | 10 ++++----
 .../junit/MultiIgnore1TestAssertions_nv.txt   | 10 ++++----
 .../junit/MultiIgnore1TestAssertions_nva.txt  | 10 ++++----
 .../junit/MultiIgnore1TestAssertions_nvc.txt  | 10 ++++----
 .../junit/MultiIgnore1TestAssertions_nvca.txt | 10 ++++----
 .../junit/MultiIgnore1TestAssertions_v.txt    | 10 ++++----
 .../junit/MultiIgnore1TestAssertions_va.txt   | 10 ++++----
 .../junit/MultiIgnore1TestAssertions_vc.txt   | 10 ++++----
 .../junit/MultiIgnore1TestAssertions_vs.txt   | 10 ++++----
 .../junit/MultiIgnore1TestAssertions_vsn.txt  | 10 ++++----
 .../junit/MultiIgnore2TestAssertions_.txt     | 10 ++++----
 .../junit/MultiIgnore2TestAssertions_a.txt    | 10 ++++----
 .../junit/MultiIgnore2TestAssertions_n.txt    | 10 ++++----
 .../junit/MultiIgnore2TestAssertions_na.txt   | 10 ++++----
 .../junit/MultiIgnore2TestAssertions_nv.txt   | 10 ++++----
 .../junit/MultiIgnore2TestAssertions_nva.txt  | 10 ++++----
 .../junit/MultiIgnore2TestAssertions_nvc.txt  | 10 ++++----
 .../junit/MultiIgnore2TestAssertions_nvca.txt | 10 ++++----
 .../junit/MultiIgnore2TestAssertions_v.txt    | 10 ++++----
 .../junit/MultiIgnore2TestAssertions_va.txt   | 10 ++++----
 .../junit/MultiIgnore2TestAssertions_vc.txt   | 10 ++++----
 .../junit/MultiIgnore2TestAssertions_vs.txt   | 10 ++++----
 .../junit/MultiIgnore2TestAssertions_vsn.txt  | 10 ++++----
 .../junit/MultiIgnoreAllTestAssertions_.txt   | 10 ++++----
 .../junit/MultiIgnoreAllTestAssertions_a.txt  | 10 ++++----
 .../junit/MultiIgnoreAllTestAssertions_n.txt  | 10 ++++----
 .../junit/MultiIgnoreAllTestAssertions_na.txt | 10 ++++----
 .../junit/MultiIgnoreAllTestAssertions_nv.txt | 10 ++++----
 .../MultiIgnoreAllTestAssertions_nva.txt      | 10 ++++----
 .../MultiIgnoreAllTestAssertions_nvc.txt      | 10 ++++----
 .../MultiIgnoreAllTestAssertions_nvca.txt     | 10 ++++----
 .../junit/MultiIgnoreAllTestAssertions_v.txt  | 10 ++++----
 .../junit/MultiIgnoreAllTestAssertions_va.txt | 10 ++++----
 .../junit/MultiIgnoreAllTestAssertions_vc.txt | 10 ++++----
 .../junit/MultiIgnoreAllTestAssertions_vs.txt | 10 ++++----
 .../MultiIgnoreAllTestAssertions_vsn.txt      | 10 ++++----
 .../org/scalajs/junit/utils/JUnitTest.scala   | 23 +++++++++++++------
 457 files changed, 1000 insertions(+), 988 deletions(-)

diff --git a/junit-runtime/src/main/scala/org/scalajs/junit/Reporter.scala b/junit-runtime/src/main/scala/org/scalajs/junit/Reporter.scala
index 4cdbfbeb9f..015c328818 100644
--- a/junit-runtime/src/main/scala/org/scalajs/junit/Reporter.scala
+++ b/junit-runtime/src/main/scala/org/scalajs/junit/Reporter.scala
@@ -37,7 +37,7 @@ private[junit] final class Reporter(eventHandler: EventHandler,
 
   def reportIgnored(method: Option[String]): Unit = {
     logTestInfo(_.info, method, "ignored")
-    emitEvent(method, Status.Skipped)
+    emitEvent(method, Status.Skipped, 0, None)
   }
 
   def reportTestStarted(method: String): Unit =
@@ -47,7 +47,7 @@ private[junit] final class Reporter(eventHandler: EventHandler,
     logTestInfo(_.debug, Some(method), s"finished, took $timeInSeconds sec")
 
     if (succeeded)
-      emitEvent(Some(method), Status.Success)
+      emitEvent(Some(method), Status.Success, timeInSeconds, None)
   }
 
   def reportErrors(prefix: String, method: Option[String],
@@ -59,7 +59,7 @@ private[junit] final class Reporter(eventHandler: EventHandler,
 
     if (errors.nonEmpty) {
       emit(errors.head)
-      emitEvent(method, Status.Failure, new OptionalThrowable(errors.head))
+      emitEvent(method, Status.Failure, timeInSeconds, Some(errors.head))
       errors.tail.foreach(emit)
     }
   }
@@ -67,7 +67,7 @@ private[junit] final class Reporter(eventHandler: EventHandler,
   def reportAssumptionViolation(method: Option[String], timeInSeconds: Double, e: Throwable): Unit = {
     logTestException(_.warn, "Test assumption in test ", method, e,
         timeInSeconds)
-    emitEvent(method, Status.Skipped, new OptionalThrowable(e))
+    emitEvent(method, Status.Skipped, timeInSeconds, Some(e))
   }
 
   private def logTestInfo(level: Reporter.Level, method: Option[String], msg: String): Unit =
@@ -117,12 +117,15 @@ private[junit] final class Reporter(eventHandler: EventHandler,
   private def emitEvent(
     method: Option[String],
     status: Status,
-    throwable: OptionalThrowable = new OptionalThrowable
+    timeInSeconds: Double,
+    throwable: Option[Throwable]
   ): Unit = {
     val testName = method.fold(taskDef.fullyQualifiedName())(method =>
         taskDef.fullyQualifiedName() + "." + settings.decodeName(method))
     val selector = new TestSelector(testName)
-    eventHandler.handle(new JUnitEvent(taskDef, status, selector, throwable))
+    val optionalThrowable: OptionalThrowable = new OptionalThrowable(throwable.orNull)
+    val duration: Long = (timeInSeconds*1000).toLong
+    eventHandler.handle(new JUnitEvent(taskDef, status, selector, optionalThrowable, duration))
   }
 
   def log(level: Reporter.Level, s: String): Unit = {
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_.txt b/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_.txt
index 2072559893..1890d11297 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.AssertEquals2Test.test started
 leTest org.scalajs.junit.AssertEquals2Test.test failed: This is the message expected:<false> but was:<true>, took <TIME>
-e2org.scalajs.junit.AssertEquals2Test.test::java.lang.AssertionError: This is the message expected:<false> but was:<true>
+e2org.scalajs.junit.AssertEquals2Test.test::java.lang.AssertionError: This is the message expected:<false> but was:<true>::true
 ldTest org.scalajs.junit.AssertEquals2Test.test finished, took <TIME>
 ldTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_a.txt b/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_a.txt
index f2e6a0564d..fb9d2d8d70 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_a.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_a.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.AssertEquals2Test.test started
 leTest org.scalajs.junit.AssertEquals2Test.test failed: java.lang.AssertionError: This is the message expected:<false> but was:<true>, took <TIME>
-e2org.scalajs.junit.AssertEquals2Test.test::java.lang.AssertionError: This is the message expected:<false> but was:<true>
+e2org.scalajs.junit.AssertEquals2Test.test::java.lang.AssertionError: This is the message expected:<false> but was:<true>::true
 ldTest org.scalajs.junit.AssertEquals2Test.test finished, took <TIME>
 ldTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_n.txt b/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_n.txt
index 7ac05cdcbe..b0d3f76a44 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_n.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_n.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.AssertEquals2Test.test started
 leTest org.scalajs.junit.AssertEquals2Test.test failed: This is the message expected:<false> but was:<true>, took <TIME>
-e2org.scalajs.junit.AssertEquals2Test.test::java.lang.AssertionError: This is the message expected:<false> but was:<true>
+e2org.scalajs.junit.AssertEquals2Test.test::java.lang.AssertionError: This is the message expected:<false> but was:<true>::true
 ldTest org.scalajs.junit.AssertEquals2Test.test finished, took <TIME>
 ldTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_na.txt b/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_na.txt
index 5c4ebe5b37..dcd3479936 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_na.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_na.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.AssertEquals2Test.test started
 leTest org.scalajs.junit.AssertEquals2Test.test failed: java.lang.AssertionError: This is the message expected:<false> but was:<true>, took <TIME>
-e2org.scalajs.junit.AssertEquals2Test.test::java.lang.AssertionError: This is the message expected:<false> but was:<true>
+e2org.scalajs.junit.AssertEquals2Test.test::java.lang.AssertionError: This is the message expected:<false> but was:<true>::true
 ldTest org.scalajs.junit.AssertEquals2Test.test finished, took <TIME>
 ldTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_nv.txt b/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_nv.txt
index 479365ca78..a33ccb2633 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_nv.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_nv.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertEquals2Test.test started
 leTest org.scalajs.junit.AssertEquals2Test.test failed: This is the message expected:<false> but was:<true>, took <TIME>
-e2org.scalajs.junit.AssertEquals2Test.test::java.lang.AssertionError: This is the message expected:<false> but was:<true>
+e2org.scalajs.junit.AssertEquals2Test.test::java.lang.AssertionError: This is the message expected:<false> but was:<true>::true
 ldTest org.scalajs.junit.AssertEquals2Test.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_nva.txt b/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_nva.txt
index 180503930f..32ec567fb0 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_nva.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_nva.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertEquals2Test.test started
 leTest org.scalajs.junit.AssertEquals2Test.test failed: java.lang.AssertionError: This is the message expected:<false> but was:<true>, took <TIME>
-e2org.scalajs.junit.AssertEquals2Test.test::java.lang.AssertionError: This is the message expected:<false> but was:<true>
+e2org.scalajs.junit.AssertEquals2Test.test::java.lang.AssertionError: This is the message expected:<false> but was:<true>::true
 ldTest org.scalajs.junit.AssertEquals2Test.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_nvc.txt b/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_nvc.txt
index 479365ca78..a33ccb2633 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_nvc.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_nvc.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertEquals2Test.test started
 leTest org.scalajs.junit.AssertEquals2Test.test failed: This is the message expected:<false> but was:<true>, took <TIME>
-e2org.scalajs.junit.AssertEquals2Test.test::java.lang.AssertionError: This is the message expected:<false> but was:<true>
+e2org.scalajs.junit.AssertEquals2Test.test::java.lang.AssertionError: This is the message expected:<false> but was:<true>::true
 ldTest org.scalajs.junit.AssertEquals2Test.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_nvca.txt b/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_nvca.txt
index 479365ca78..a33ccb2633 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_nvca.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_nvca.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertEquals2Test.test started
 leTest org.scalajs.junit.AssertEquals2Test.test failed: This is the message expected:<false> but was:<true>, took <TIME>
-e2org.scalajs.junit.AssertEquals2Test.test::java.lang.AssertionError: This is the message expected:<false> but was:<true>
+e2org.scalajs.junit.AssertEquals2Test.test::java.lang.AssertionError: This is the message expected:<false> but was:<true>::true
 ldTest org.scalajs.junit.AssertEquals2Test.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_v.txt b/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_v.txt
index a1063772e6..5085e4ab04 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_v.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_v.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertEquals2Test.test started
 leTest org.scalajs.junit.AssertEquals2Test.test failed: This is the message expected:<false> but was:<true>, took <TIME>
-e2org.scalajs.junit.AssertEquals2Test.test::java.lang.AssertionError: This is the message expected:<false> but was:<true>
+e2org.scalajs.junit.AssertEquals2Test.test::java.lang.AssertionError: This is the message expected:<false> but was:<true>::true
 ldTest org.scalajs.junit.AssertEquals2Test.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_va.txt b/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_va.txt
index 80f4b8d43c..0bda28643e 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_va.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_va.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertEquals2Test.test started
 leTest org.scalajs.junit.AssertEquals2Test.test failed: java.lang.AssertionError: This is the message expected:<false> but was:<true>, took <TIME>
-e2org.scalajs.junit.AssertEquals2Test.test::java.lang.AssertionError: This is the message expected:<false> but was:<true>
+e2org.scalajs.junit.AssertEquals2Test.test::java.lang.AssertionError: This is the message expected:<false> but was:<true>::true
 ldTest org.scalajs.junit.AssertEquals2Test.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_vc.txt b/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_vc.txt
index a1063772e6..5085e4ab04 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_vc.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_vc.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertEquals2Test.test started
 leTest org.scalajs.junit.AssertEquals2Test.test failed: This is the message expected:<false> but was:<true>, took <TIME>
-e2org.scalajs.junit.AssertEquals2Test.test::java.lang.AssertionError: This is the message expected:<false> but was:<true>
+e2org.scalajs.junit.AssertEquals2Test.test::java.lang.AssertionError: This is the message expected:<false> but was:<true>::true
 ldTest org.scalajs.junit.AssertEquals2Test.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_vs.txt b/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_vs.txt
index a1063772e6..5085e4ab04 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_vs.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_vs.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertEquals2Test.test started
 leTest org.scalajs.junit.AssertEquals2Test.test failed: This is the message expected:<false> but was:<true>, took <TIME>
-e2org.scalajs.junit.AssertEquals2Test.test::java.lang.AssertionError: This is the message expected:<false> but was:<true>
+e2org.scalajs.junit.AssertEquals2Test.test::java.lang.AssertionError: This is the message expected:<false> but was:<true>::true
 ldTest org.scalajs.junit.AssertEquals2Test.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_vsn.txt b/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_vsn.txt
index 479365ca78..a33ccb2633 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_vsn.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEquals2TestAssertions_vsn.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertEquals2Test.test started
 leTest org.scalajs.junit.AssertEquals2Test.test failed: This is the message expected:<false> but was:<true>, took <TIME>
-e2org.scalajs.junit.AssertEquals2Test.test::java.lang.AssertionError: This is the message expected:<false> but was:<true>
+e2org.scalajs.junit.AssertEquals2Test.test::java.lang.AssertionError: This is the message expected:<false> but was:<true>::true
 ldTest org.scalajs.junit.AssertEquals2Test.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_.txt b/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_.txt
index 71e6ad67fa..e52483f439 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_.txt
@@ -1,23 +1,23 @@
 ldTest run started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble started
 leTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble failed: Use assertEquals(expected, actual, delta) to compare floating-point numbers, took <TIME>
-e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers
+e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers::true
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble finished, took <TIME>
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage started
 leTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage failed: Use assertEquals(expected, actual, delta) to compare floating-point numbers, took <TIME>
-e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers
+e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers::true
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage finished, took <TIME>
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte::
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte::::true
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon::
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon::::true
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt::
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt::::true
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort::
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort::::true
 ldTest run finished: 2 failed, 0 ignored, 6 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_a.txt b/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_a.txt
index b182d3ca38..7694e449c0 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_a.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_a.txt
@@ -1,23 +1,23 @@
 ldTest run started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble started
 leTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble failed: java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers, took <TIME>
-e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers
+e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers::true
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble finished, took <TIME>
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage started
 leTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage failed: java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers, took <TIME>
-e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers
+e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers::true
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage finished, took <TIME>
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte::
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte::::true
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon::
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon::::true
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt::
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt::::true
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort::
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort::::true
 ldTest run finished: 2 failed, 0 ignored, 6 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_n.txt b/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_n.txt
index 13c5d835e9..1fead85900 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_n.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_n.txt
@@ -1,23 +1,23 @@
 ldTest run started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble started
 leTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble failed: Use assertEquals(expected, actual, delta) to compare floating-point numbers, took <TIME>
-e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers
+e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers::true
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble finished, took <TIME>
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage started
 leTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage failed: Use assertEquals(expected, actual, delta) to compare floating-point numbers, took <TIME>
-e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers
+e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers::true
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage finished, took <TIME>
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte::
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte::::true
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon::
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon::::true
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt::
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt::::true
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort::
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort::::true
 ldTest run finished: 2 failed, 0 ignored, 6 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_na.txt b/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_na.txt
index c9a35784af..b317fd4b12 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_na.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_na.txt
@@ -1,23 +1,23 @@
 ldTest run started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble started
 leTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble failed: java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers, took <TIME>
-e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers
+e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers::true
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble finished, took <TIME>
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage started
 leTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage failed: java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers, took <TIME>
-e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers
+e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers::true
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage finished, took <TIME>
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte::
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte::::true
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon::
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon::::true
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt::
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt::::true
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort::
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort::::true
 ldTest run finished: 2 failed, 0 ignored, 6 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_nv.txt b/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_nv.txt
index 8bd6462aac..b242e8cc3f 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_nv.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_nv.txt
@@ -1,23 +1,23 @@
 liTest run started
 liTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble started
 leTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble failed: Use assertEquals(expected, actual, delta) to compare floating-point numbers, took <TIME>
-e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers
+e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers::true
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble finished, took <TIME>
 liTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage started
 leTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage failed: Use assertEquals(expected, actual, delta) to compare floating-point numbers, took <TIME>
-e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers
+e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers::true
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage finished, took <TIME>
 liTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte::
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte::::true
 liTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon::
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon::::true
 liTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt::
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt::::true
 liTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort::
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort::::true
 liTest run finished: 2 failed, 0 ignored, 6 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_nva.txt b/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_nva.txt
index 6161aeaf80..35b4dc7d8f 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_nva.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_nva.txt
@@ -1,23 +1,23 @@
 liTest run started
 liTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble started
 leTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble failed: java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers, took <TIME>
-e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers
+e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers::true
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble finished, took <TIME>
 liTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage started
 leTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage failed: java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers, took <TIME>
-e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers
+e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers::true
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage finished, took <TIME>
 liTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte::
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte::::true
 liTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon::
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon::::true
 liTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt::
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt::::true
 liTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort::
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort::::true
 liTest run finished: 2 failed, 0 ignored, 6 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_nvc.txt b/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_nvc.txt
index 8bd6462aac..b242e8cc3f 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_nvc.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_nvc.txt
@@ -1,23 +1,23 @@
 liTest run started
 liTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble started
 leTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble failed: Use assertEquals(expected, actual, delta) to compare floating-point numbers, took <TIME>
-e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers
+e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers::true
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble finished, took <TIME>
 liTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage started
 leTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage failed: Use assertEquals(expected, actual, delta) to compare floating-point numbers, took <TIME>
-e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers
+e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers::true
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage finished, took <TIME>
 liTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte::
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte::::true
 liTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon::
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon::::true
 liTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt::
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt::::true
 liTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort::
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort::::true
 liTest run finished: 2 failed, 0 ignored, 6 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_nvca.txt b/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_nvca.txt
index 8bd6462aac..b242e8cc3f 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_nvca.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_nvca.txt
@@ -1,23 +1,23 @@
 liTest run started
 liTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble started
 leTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble failed: Use assertEquals(expected, actual, delta) to compare floating-point numbers, took <TIME>
-e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers
+e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers::true
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble finished, took <TIME>
 liTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage started
 leTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage failed: Use assertEquals(expected, actual, delta) to compare floating-point numbers, took <TIME>
-e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers
+e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers::true
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage finished, took <TIME>
 liTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte::
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte::::true
 liTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon::
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon::::true
 liTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt::
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt::::true
 liTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort::
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort::::true
 liTest run finished: 2 failed, 0 ignored, 6 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_v.txt b/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_v.txt
index 9e1779dd8c..57bb4bd9b2 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_v.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_v.txt
@@ -1,23 +1,23 @@
 liTest run started
 liTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble started
 leTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble failed: Use assertEquals(expected, actual, delta) to compare floating-point numbers, took <TIME>
-e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers
+e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers::true
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble finished, took <TIME>
 liTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage started
 leTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage failed: Use assertEquals(expected, actual, delta) to compare floating-point numbers, took <TIME>
-e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers
+e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers::true
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage finished, took <TIME>
 liTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte::
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte::::true
 liTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon::
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon::::true
 liTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt::
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt::::true
 liTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort::
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort::::true
 liTest run finished: 2 failed, 0 ignored, 6 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_va.txt b/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_va.txt
index dd92158837..6c9e7f43bc 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_va.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_va.txt
@@ -1,23 +1,23 @@
 liTest run started
 liTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble started
 leTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble failed: java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers, took <TIME>
-e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers
+e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers::true
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble finished, took <TIME>
 liTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage started
 leTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage failed: java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers, took <TIME>
-e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers
+e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers::true
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage finished, took <TIME>
 liTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte::
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte::::true
 liTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon::
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon::::true
 liTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt::
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt::::true
 liTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort::
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort::::true
 liTest run finished: 2 failed, 0 ignored, 6 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_vc.txt b/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_vc.txt
index 9e1779dd8c..57bb4bd9b2 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_vc.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_vc.txt
@@ -1,23 +1,23 @@
 liTest run started
 liTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble started
 leTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble failed: Use assertEquals(expected, actual, delta) to compare floating-point numbers, took <TIME>
-e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers
+e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers::true
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble finished, took <TIME>
 liTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage started
 leTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage failed: Use assertEquals(expected, actual, delta) to compare floating-point numbers, took <TIME>
-e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers
+e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers::true
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage finished, took <TIME>
 liTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte::
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte::::true
 liTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon::
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon::::true
 liTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt::
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt::::true
 liTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort::
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort::::true
 liTest run finished: 2 failed, 0 ignored, 6 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_vs.txt b/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_vs.txt
index 9e1779dd8c..57bb4bd9b2 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_vs.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_vs.txt
@@ -1,23 +1,23 @@
 liTest run started
 liTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble started
 leTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble failed: Use assertEquals(expected, actual, delta) to compare floating-point numbers, took <TIME>
-e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers
+e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers::true
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble finished, took <TIME>
 liTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage started
 leTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage failed: Use assertEquals(expected, actual, delta) to compare floating-point numbers, took <TIME>
-e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers
+e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers::true
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage finished, took <TIME>
 liTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte::
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte::::true
 liTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon::
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon::::true
 liTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt::
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt::::true
 liTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort::
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort::::true
 liTest run finished: 2 failed, 0 ignored, 6 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_vsn.txt b/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_vsn.txt
index 8bd6462aac..b242e8cc3f 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_vsn.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEqualsDoubleTestAssertions_vsn.txt
@@ -1,23 +1,23 @@
 liTest run started
 liTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble started
 leTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble failed: Use assertEquals(expected, actual, delta) to compare floating-point numbers, took <TIME>
-e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers
+e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers::true
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDouble finished, took <TIME>
 liTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage started
 leTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage failed: Use assertEquals(expected, actual, delta) to compare floating-point numbers, took <TIME>
-e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers
+e2org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage::java.lang.AssertionError: Use assertEquals(expected, actual, delta) to compare floating-point numbers::true
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.failsWithDoubleMessage finished, took <TIME>
 liTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte::
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithByte::::true
 liTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon::
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithEpsilon::::true
 liTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt::
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithInt::::true
 liTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort started
 ldTest org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort finished, took <TIME>
-e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort::
+e0org.scalajs.junit.AssertEqualsDoubleTest.worksWithShort::::true
 liTest run finished: 2 failed, 0 ignored, 6 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_.txt b/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_.txt
index 93ad3cc5bb..724b2ae15c 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.AssertEqualsTest.test started
 leTest org.scalajs.junit.AssertEqualsTest.test failed: expected:<false> but was:<true>, took <TIME>
-e2org.scalajs.junit.AssertEqualsTest.test::java.lang.AssertionError: expected:<false> but was:<true>
+e2org.scalajs.junit.AssertEqualsTest.test::java.lang.AssertionError: expected:<false> but was:<true>::true
 ldTest org.scalajs.junit.AssertEqualsTest.test finished, took <TIME>
 ldTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_a.txt b/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_a.txt
index 56685b67f4..d9bc116e45 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_a.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_a.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.AssertEqualsTest.test started
 leTest org.scalajs.junit.AssertEqualsTest.test failed: java.lang.AssertionError: expected:<false> but was:<true>, took <TIME>
-e2org.scalajs.junit.AssertEqualsTest.test::java.lang.AssertionError: expected:<false> but was:<true>
+e2org.scalajs.junit.AssertEqualsTest.test::java.lang.AssertionError: expected:<false> but was:<true>::true
 ldTest org.scalajs.junit.AssertEqualsTest.test finished, took <TIME>
 ldTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_n.txt b/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_n.txt
index fca48a0747..f2ad17ddf1 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_n.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_n.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.AssertEqualsTest.test started
 leTest org.scalajs.junit.AssertEqualsTest.test failed: expected:<false> but was:<true>, took <TIME>
-e2org.scalajs.junit.AssertEqualsTest.test::java.lang.AssertionError: expected:<false> but was:<true>
+e2org.scalajs.junit.AssertEqualsTest.test::java.lang.AssertionError: expected:<false> but was:<true>::true
 ldTest org.scalajs.junit.AssertEqualsTest.test finished, took <TIME>
 ldTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_na.txt b/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_na.txt
index bfbfca6c86..97c7373b1a 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_na.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_na.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.AssertEqualsTest.test started
 leTest org.scalajs.junit.AssertEqualsTest.test failed: java.lang.AssertionError: expected:<false> but was:<true>, took <TIME>
-e2org.scalajs.junit.AssertEqualsTest.test::java.lang.AssertionError: expected:<false> but was:<true>
+e2org.scalajs.junit.AssertEqualsTest.test::java.lang.AssertionError: expected:<false> but was:<true>::true
 ldTest org.scalajs.junit.AssertEqualsTest.test finished, took <TIME>
 ldTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_nv.txt b/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_nv.txt
index fa53033016..d9e1c5e459 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_nv.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_nv.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertEqualsTest.test started
 leTest org.scalajs.junit.AssertEqualsTest.test failed: expected:<false> but was:<true>, took <TIME>
-e2org.scalajs.junit.AssertEqualsTest.test::java.lang.AssertionError: expected:<false> but was:<true>
+e2org.scalajs.junit.AssertEqualsTest.test::java.lang.AssertionError: expected:<false> but was:<true>::true
 ldTest org.scalajs.junit.AssertEqualsTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_nva.txt b/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_nva.txt
index 4dc0a43c99..271044f200 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_nva.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_nva.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertEqualsTest.test started
 leTest org.scalajs.junit.AssertEqualsTest.test failed: java.lang.AssertionError: expected:<false> but was:<true>, took <TIME>
-e2org.scalajs.junit.AssertEqualsTest.test::java.lang.AssertionError: expected:<false> but was:<true>
+e2org.scalajs.junit.AssertEqualsTest.test::java.lang.AssertionError: expected:<false> but was:<true>::true
 ldTest org.scalajs.junit.AssertEqualsTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_nvc.txt b/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_nvc.txt
index fa53033016..d9e1c5e459 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_nvc.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_nvc.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertEqualsTest.test started
 leTest org.scalajs.junit.AssertEqualsTest.test failed: expected:<false> but was:<true>, took <TIME>
-e2org.scalajs.junit.AssertEqualsTest.test::java.lang.AssertionError: expected:<false> but was:<true>
+e2org.scalajs.junit.AssertEqualsTest.test::java.lang.AssertionError: expected:<false> but was:<true>::true
 ldTest org.scalajs.junit.AssertEqualsTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
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diff --git a/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_nvca.txt b/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_nvca.txt
index fa53033016..d9e1c5e459 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_nvca.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_nvca.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertEqualsTest.test started
 leTest org.scalajs.junit.AssertEqualsTest.test failed: expected:<false> but was:<true>, took <TIME>
-e2org.scalajs.junit.AssertEqualsTest.test::java.lang.AssertionError: expected:<false> but was:<true>
+e2org.scalajs.junit.AssertEqualsTest.test::java.lang.AssertionError: expected:<false> but was:<true>::true
 ldTest org.scalajs.junit.AssertEqualsTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_v.txt b/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_v.txt
index c0aa908a22..f9d49184cf 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_v.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_v.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertEqualsTest.test started
 leTest org.scalajs.junit.AssertEqualsTest.test failed: expected:<false> but was:<true>, took <TIME>
-e2org.scalajs.junit.AssertEqualsTest.test::java.lang.AssertionError: expected:<false> but was:<true>
+e2org.scalajs.junit.AssertEqualsTest.test::java.lang.AssertionError: expected:<false> but was:<true>::true
 ldTest org.scalajs.junit.AssertEqualsTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_va.txt b/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_va.txt
index 84eb6768c0..4030c564cd 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_va.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_va.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertEqualsTest.test started
 leTest org.scalajs.junit.AssertEqualsTest.test failed: java.lang.AssertionError: expected:<false> but was:<true>, took <TIME>
-e2org.scalajs.junit.AssertEqualsTest.test::java.lang.AssertionError: expected:<false> but was:<true>
+e2org.scalajs.junit.AssertEqualsTest.test::java.lang.AssertionError: expected:<false> but was:<true>::true
 ldTest org.scalajs.junit.AssertEqualsTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_vc.txt b/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_vc.txt
index c0aa908a22..f9d49184cf 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_vc.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_vc.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertEqualsTest.test started
 leTest org.scalajs.junit.AssertEqualsTest.test failed: expected:<false> but was:<true>, took <TIME>
-e2org.scalajs.junit.AssertEqualsTest.test::java.lang.AssertionError: expected:<false> but was:<true>
+e2org.scalajs.junit.AssertEqualsTest.test::java.lang.AssertionError: expected:<false> but was:<true>::true
 ldTest org.scalajs.junit.AssertEqualsTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
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diff --git a/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_vs.txt b/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_vs.txt
index c0aa908a22..f9d49184cf 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_vs.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_vs.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertEqualsTest.test started
 leTest org.scalajs.junit.AssertEqualsTest.test failed: expected:<false> but was:<true>, took <TIME>
-e2org.scalajs.junit.AssertEqualsTest.test::java.lang.AssertionError: expected:<false> but was:<true>
+e2org.scalajs.junit.AssertEqualsTest.test::java.lang.AssertionError: expected:<false> but was:<true>::true
 ldTest org.scalajs.junit.AssertEqualsTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
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diff --git a/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_vsn.txt b/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_vsn.txt
index fa53033016..d9e1c5e459 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_vsn.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertEqualsTestAssertions_vsn.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertEqualsTest.test started
 leTest org.scalajs.junit.AssertEqualsTest.test failed: expected:<false> but was:<true>, took <TIME>
-e2org.scalajs.junit.AssertEqualsTest.test::java.lang.AssertionError: expected:<false> but was:<true>
+e2org.scalajs.junit.AssertEqualsTest.test::java.lang.AssertionError: expected:<false> but was:<true>::true
 ldTest org.scalajs.junit.AssertEqualsTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
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diff --git a/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_.txt b/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_.txt
index 6113781da0..661bcea21f 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.AssertFalse2Test.test started
 leTest org.scalajs.junit.AssertFalse2Test.test failed: This is the message, took <TIME>
-e2org.scalajs.junit.AssertFalse2Test.test::java.lang.AssertionError: This is the message
+e2org.scalajs.junit.AssertFalse2Test.test::java.lang.AssertionError: This is the message::true
 ldTest org.scalajs.junit.AssertFalse2Test.test finished, took <TIME>
 ldTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
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diff --git a/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_a.txt b/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_a.txt
index 399521dee2..d37d99f8a3 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_a.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_a.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.AssertFalse2Test.test started
 leTest org.scalajs.junit.AssertFalse2Test.test failed: java.lang.AssertionError: This is the message, took <TIME>
-e2org.scalajs.junit.AssertFalse2Test.test::java.lang.AssertionError: This is the message
+e2org.scalajs.junit.AssertFalse2Test.test::java.lang.AssertionError: This is the message::true
 ldTest org.scalajs.junit.AssertFalse2Test.test finished, took <TIME>
 ldTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
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diff --git a/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_n.txt b/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_n.txt
index 82eb36b848..fa21717922 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_n.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_n.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.AssertFalse2Test.test started
 leTest org.scalajs.junit.AssertFalse2Test.test failed: This is the message, took <TIME>
-e2org.scalajs.junit.AssertFalse2Test.test::java.lang.AssertionError: This is the message
+e2org.scalajs.junit.AssertFalse2Test.test::java.lang.AssertionError: This is the message::true
 ldTest org.scalajs.junit.AssertFalse2Test.test finished, took <TIME>
 ldTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
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diff --git a/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_na.txt b/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_na.txt
index 03bacc3f6d..eed9dd4f83 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_na.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_na.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.AssertFalse2Test.test started
 leTest org.scalajs.junit.AssertFalse2Test.test failed: java.lang.AssertionError: This is the message, took <TIME>
-e2org.scalajs.junit.AssertFalse2Test.test::java.lang.AssertionError: This is the message
+e2org.scalajs.junit.AssertFalse2Test.test::java.lang.AssertionError: This is the message::true
 ldTest org.scalajs.junit.AssertFalse2Test.test finished, took <TIME>
 ldTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
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diff --git a/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_nv.txt b/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_nv.txt
index ab934867b7..40f7f5ed07 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_nv.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_nv.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertFalse2Test.test started
 leTest org.scalajs.junit.AssertFalse2Test.test failed: This is the message, took <TIME>
-e2org.scalajs.junit.AssertFalse2Test.test::java.lang.AssertionError: This is the message
+e2org.scalajs.junit.AssertFalse2Test.test::java.lang.AssertionError: This is the message::true
 ldTest org.scalajs.junit.AssertFalse2Test.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
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diff --git a/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_nva.txt b/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_nva.txt
index 477dcedd2e..7f691de7b9 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_nva.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_nva.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertFalse2Test.test started
 leTest org.scalajs.junit.AssertFalse2Test.test failed: java.lang.AssertionError: This is the message, took <TIME>
-e2org.scalajs.junit.AssertFalse2Test.test::java.lang.AssertionError: This is the message
+e2org.scalajs.junit.AssertFalse2Test.test::java.lang.AssertionError: This is the message::true
 ldTest org.scalajs.junit.AssertFalse2Test.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
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diff --git a/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_nvc.txt b/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_nvc.txt
index ab934867b7..40f7f5ed07 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_nvc.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_nvc.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertFalse2Test.test started
 leTest org.scalajs.junit.AssertFalse2Test.test failed: This is the message, took <TIME>
-e2org.scalajs.junit.AssertFalse2Test.test::java.lang.AssertionError: This is the message
+e2org.scalajs.junit.AssertFalse2Test.test::java.lang.AssertionError: This is the message::true
 ldTest org.scalajs.junit.AssertFalse2Test.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
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diff --git a/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_nvca.txt b/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_nvca.txt
index ab934867b7..40f7f5ed07 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_nvca.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_nvca.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertFalse2Test.test started
 leTest org.scalajs.junit.AssertFalse2Test.test failed: This is the message, took <TIME>
-e2org.scalajs.junit.AssertFalse2Test.test::java.lang.AssertionError: This is the message
+e2org.scalajs.junit.AssertFalse2Test.test::java.lang.AssertionError: This is the message::true
 ldTest org.scalajs.junit.AssertFalse2Test.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
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diff --git a/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_v.txt b/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_v.txt
index e00e69eeac..4857bb5fec 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_v.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_v.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertFalse2Test.test started
 leTest org.scalajs.junit.AssertFalse2Test.test failed: This is the message, took <TIME>
-e2org.scalajs.junit.AssertFalse2Test.test::java.lang.AssertionError: This is the message
+e2org.scalajs.junit.AssertFalse2Test.test::java.lang.AssertionError: This is the message::true
 ldTest org.scalajs.junit.AssertFalse2Test.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
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diff --git a/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_va.txt b/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_va.txt
index 43673ec0c1..761be25271 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_va.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_va.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertFalse2Test.test started
 leTest org.scalajs.junit.AssertFalse2Test.test failed: java.lang.AssertionError: This is the message, took <TIME>
-e2org.scalajs.junit.AssertFalse2Test.test::java.lang.AssertionError: This is the message
+e2org.scalajs.junit.AssertFalse2Test.test::java.lang.AssertionError: This is the message::true
 ldTest org.scalajs.junit.AssertFalse2Test.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
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diff --git a/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_vc.txt b/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_vc.txt
index e00e69eeac..4857bb5fec 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_vc.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_vc.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertFalse2Test.test started
 leTest org.scalajs.junit.AssertFalse2Test.test failed: This is the message, took <TIME>
-e2org.scalajs.junit.AssertFalse2Test.test::java.lang.AssertionError: This is the message
+e2org.scalajs.junit.AssertFalse2Test.test::java.lang.AssertionError: This is the message::true
 ldTest org.scalajs.junit.AssertFalse2Test.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_vs.txt b/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_vs.txt
index e00e69eeac..4857bb5fec 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_vs.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_vs.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertFalse2Test.test started
 leTest org.scalajs.junit.AssertFalse2Test.test failed: This is the message, took <TIME>
-e2org.scalajs.junit.AssertFalse2Test.test::java.lang.AssertionError: This is the message
+e2org.scalajs.junit.AssertFalse2Test.test::java.lang.AssertionError: This is the message::true
 ldTest org.scalajs.junit.AssertFalse2Test.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_vsn.txt b/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_vsn.txt
index ab934867b7..40f7f5ed07 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_vsn.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertFalse2TestAssertions_vsn.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertFalse2Test.test started
 leTest org.scalajs.junit.AssertFalse2Test.test failed: This is the message, took <TIME>
-e2org.scalajs.junit.AssertFalse2Test.test::java.lang.AssertionError: This is the message
+e2org.scalajs.junit.AssertFalse2Test.test::java.lang.AssertionError: This is the message::true
 ldTest org.scalajs.junit.AssertFalse2Test.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_.txt b/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_.txt
index d6b56eaf42..586866f719 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.AssertFalseTest.test started
 leTest org.scalajs.junit.AssertFalseTest.test failed: null, took <TIME>
-e2org.scalajs.junit.AssertFalseTest.test::java.lang.AssertionError
+e2org.scalajs.junit.AssertFalseTest.test::java.lang.AssertionError::true
 ldTest org.scalajs.junit.AssertFalseTest.test finished, took <TIME>
 ldTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_a.txt b/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_a.txt
index ab058bdd2e..a4f4b592e4 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_a.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_a.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.AssertFalseTest.test started
 leTest org.scalajs.junit.AssertFalseTest.test failed: java.lang.AssertionError: null, took <TIME>
-e2org.scalajs.junit.AssertFalseTest.test::java.lang.AssertionError
+e2org.scalajs.junit.AssertFalseTest.test::java.lang.AssertionError::true
 ldTest org.scalajs.junit.AssertFalseTest.test finished, took <TIME>
 ldTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_n.txt b/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_n.txt
index 032e6c350c..18ac7a01f1 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_n.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_n.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.AssertFalseTest.test started
 leTest org.scalajs.junit.AssertFalseTest.test failed: null, took <TIME>
-e2org.scalajs.junit.AssertFalseTest.test::java.lang.AssertionError
+e2org.scalajs.junit.AssertFalseTest.test::java.lang.AssertionError::true
 ldTest org.scalajs.junit.AssertFalseTest.test finished, took <TIME>
 ldTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_na.txt b/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_na.txt
index 245f1406a0..62bc21bec3 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_na.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_na.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.AssertFalseTest.test started
 leTest org.scalajs.junit.AssertFalseTest.test failed: java.lang.AssertionError: null, took <TIME>
-e2org.scalajs.junit.AssertFalseTest.test::java.lang.AssertionError
+e2org.scalajs.junit.AssertFalseTest.test::java.lang.AssertionError::true
 ldTest org.scalajs.junit.AssertFalseTest.test finished, took <TIME>
 ldTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_nv.txt b/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_nv.txt
index 936f21a783..1b86d5e6f8 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_nv.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_nv.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertFalseTest.test started
 leTest org.scalajs.junit.AssertFalseTest.test failed: null, took <TIME>
-e2org.scalajs.junit.AssertFalseTest.test::java.lang.AssertionError
+e2org.scalajs.junit.AssertFalseTest.test::java.lang.AssertionError::true
 ldTest org.scalajs.junit.AssertFalseTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_nva.txt b/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_nva.txt
index 5541a0d8cc..12b71d5f12 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_nva.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_nva.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertFalseTest.test started
 leTest org.scalajs.junit.AssertFalseTest.test failed: java.lang.AssertionError: null, took <TIME>
-e2org.scalajs.junit.AssertFalseTest.test::java.lang.AssertionError
+e2org.scalajs.junit.AssertFalseTest.test::java.lang.AssertionError::true
 ldTest org.scalajs.junit.AssertFalseTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_nvc.txt b/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_nvc.txt
index 936f21a783..1b86d5e6f8 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_nvc.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_nvc.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertFalseTest.test started
 leTest org.scalajs.junit.AssertFalseTest.test failed: null, took <TIME>
-e2org.scalajs.junit.AssertFalseTest.test::java.lang.AssertionError
+e2org.scalajs.junit.AssertFalseTest.test::java.lang.AssertionError::true
 ldTest org.scalajs.junit.AssertFalseTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_nvca.txt b/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_nvca.txt
index 936f21a783..1b86d5e6f8 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_nvca.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_nvca.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertFalseTest.test started
 leTest org.scalajs.junit.AssertFalseTest.test failed: null, took <TIME>
-e2org.scalajs.junit.AssertFalseTest.test::java.lang.AssertionError
+e2org.scalajs.junit.AssertFalseTest.test::java.lang.AssertionError::true
 ldTest org.scalajs.junit.AssertFalseTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_v.txt b/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_v.txt
index f2b97e6fba..28c5a161cd 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_v.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_v.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertFalseTest.test started
 leTest org.scalajs.junit.AssertFalseTest.test failed: null, took <TIME>
-e2org.scalajs.junit.AssertFalseTest.test::java.lang.AssertionError
+e2org.scalajs.junit.AssertFalseTest.test::java.lang.AssertionError::true
 ldTest org.scalajs.junit.AssertFalseTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_va.txt b/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_va.txt
index 142f954105..329e202166 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_va.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_va.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertFalseTest.test started
 leTest org.scalajs.junit.AssertFalseTest.test failed: java.lang.AssertionError: null, took <TIME>
-e2org.scalajs.junit.AssertFalseTest.test::java.lang.AssertionError
+e2org.scalajs.junit.AssertFalseTest.test::java.lang.AssertionError::true
 ldTest org.scalajs.junit.AssertFalseTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_vc.txt b/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_vc.txt
index f2b97e6fba..28c5a161cd 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_vc.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_vc.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertFalseTest.test started
 leTest org.scalajs.junit.AssertFalseTest.test failed: null, took <TIME>
-e2org.scalajs.junit.AssertFalseTest.test::java.lang.AssertionError
+e2org.scalajs.junit.AssertFalseTest.test::java.lang.AssertionError::true
 ldTest org.scalajs.junit.AssertFalseTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_vs.txt b/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_vs.txt
index f2b97e6fba..28c5a161cd 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_vs.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_vs.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertFalseTest.test started
 leTest org.scalajs.junit.AssertFalseTest.test failed: null, took <TIME>
-e2org.scalajs.junit.AssertFalseTest.test::java.lang.AssertionError
+e2org.scalajs.junit.AssertFalseTest.test::java.lang.AssertionError::true
 ldTest org.scalajs.junit.AssertFalseTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_vsn.txt b/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_vsn.txt
index 936f21a783..1b86d5e6f8 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_vsn.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertFalseTestAssertions_vsn.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertFalseTest.test started
 leTest org.scalajs.junit.AssertFalseTest.test failed: null, took <TIME>
-e2org.scalajs.junit.AssertFalseTest.test::java.lang.AssertionError
+e2org.scalajs.junit.AssertFalseTest.test::java.lang.AssertionError::true
 ldTest org.scalajs.junit.AssertFalseTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_.txt b/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_.txt
index 4831b5344d..43bf8bbeec 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.AssertStringEqualsTest.test started
 leTest org.scalajs.junit.AssertStringEqualsTest.test failed: expected:<foob[a]r> but was:<foob[bb]r>, took <TIME>
-e2org.scalajs.junit.AssertStringEqualsTest.test::org.junit.ComparisonFailure: expected:<foob[a]r> but was:<foob[bb]r>
+e2org.scalajs.junit.AssertStringEqualsTest.test::org.junit.ComparisonFailure: expected:<foob[a]r> but was:<foob[bb]r>::true
 ldTest org.scalajs.junit.AssertStringEqualsTest.test finished, took <TIME>
 ldTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_a.txt b/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_a.txt
index f214868851..6f6e82fcdb 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_a.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_a.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.AssertStringEqualsTest.test started
 leTest org.scalajs.junit.AssertStringEqualsTest.test failed: org.junit.ComparisonFailure: expected:<foob[a]r> but was:<foob[bb]r>, took <TIME>
-e2org.scalajs.junit.AssertStringEqualsTest.test::org.junit.ComparisonFailure: expected:<foob[a]r> but was:<foob[bb]r>
+e2org.scalajs.junit.AssertStringEqualsTest.test::org.junit.ComparisonFailure: expected:<foob[a]r> but was:<foob[bb]r>::true
 ldTest org.scalajs.junit.AssertStringEqualsTest.test finished, took <TIME>
 ldTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_n.txt b/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_n.txt
index 8314d809ae..4d9c2e293b 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_n.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_n.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.AssertStringEqualsTest.test started
 leTest org.scalajs.junit.AssertStringEqualsTest.test failed: expected:<foob[a]r> but was:<foob[bb]r>, took <TIME>
-e2org.scalajs.junit.AssertStringEqualsTest.test::org.junit.ComparisonFailure: expected:<foob[a]r> but was:<foob[bb]r>
+e2org.scalajs.junit.AssertStringEqualsTest.test::org.junit.ComparisonFailure: expected:<foob[a]r> but was:<foob[bb]r>::true
 ldTest org.scalajs.junit.AssertStringEqualsTest.test finished, took <TIME>
 ldTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_na.txt b/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_na.txt
index 7044a087eb..c3d3a7f42d 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_na.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_na.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.AssertStringEqualsTest.test started
 leTest org.scalajs.junit.AssertStringEqualsTest.test failed: org.junit.ComparisonFailure: expected:<foob[a]r> but was:<foob[bb]r>, took <TIME>
-e2org.scalajs.junit.AssertStringEqualsTest.test::org.junit.ComparisonFailure: expected:<foob[a]r> but was:<foob[bb]r>
+e2org.scalajs.junit.AssertStringEqualsTest.test::org.junit.ComparisonFailure: expected:<foob[a]r> but was:<foob[bb]r>::true
 ldTest org.scalajs.junit.AssertStringEqualsTest.test finished, took <TIME>
 ldTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_nv.txt b/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_nv.txt
index 050a280abb..6fb57996d9 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_nv.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_nv.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertStringEqualsTest.test started
 leTest org.scalajs.junit.AssertStringEqualsTest.test failed: expected:<foob[a]r> but was:<foob[bb]r>, took <TIME>
-e2org.scalajs.junit.AssertStringEqualsTest.test::org.junit.ComparisonFailure: expected:<foob[a]r> but was:<foob[bb]r>
+e2org.scalajs.junit.AssertStringEqualsTest.test::org.junit.ComparisonFailure: expected:<foob[a]r> but was:<foob[bb]r>::true
 ldTest org.scalajs.junit.AssertStringEqualsTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_nva.txt b/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_nva.txt
index fa7faaf21c..4665783540 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_nva.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_nva.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertStringEqualsTest.test started
 leTest org.scalajs.junit.AssertStringEqualsTest.test failed: org.junit.ComparisonFailure: expected:<foob[a]r> but was:<foob[bb]r>, took <TIME>
-e2org.scalajs.junit.AssertStringEqualsTest.test::org.junit.ComparisonFailure: expected:<foob[a]r> but was:<foob[bb]r>
+e2org.scalajs.junit.AssertStringEqualsTest.test::org.junit.ComparisonFailure: expected:<foob[a]r> but was:<foob[bb]r>::true
 ldTest org.scalajs.junit.AssertStringEqualsTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_nvc.txt b/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_nvc.txt
index 050a280abb..6fb57996d9 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_nvc.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_nvc.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertStringEqualsTest.test started
 leTest org.scalajs.junit.AssertStringEqualsTest.test failed: expected:<foob[a]r> but was:<foob[bb]r>, took <TIME>
-e2org.scalajs.junit.AssertStringEqualsTest.test::org.junit.ComparisonFailure: expected:<foob[a]r> but was:<foob[bb]r>
+e2org.scalajs.junit.AssertStringEqualsTest.test::org.junit.ComparisonFailure: expected:<foob[a]r> but was:<foob[bb]r>::true
 ldTest org.scalajs.junit.AssertStringEqualsTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_nvca.txt b/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_nvca.txt
index 050a280abb..6fb57996d9 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_nvca.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_nvca.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertStringEqualsTest.test started
 leTest org.scalajs.junit.AssertStringEqualsTest.test failed: expected:<foob[a]r> but was:<foob[bb]r>, took <TIME>
-e2org.scalajs.junit.AssertStringEqualsTest.test::org.junit.ComparisonFailure: expected:<foob[a]r> but was:<foob[bb]r>
+e2org.scalajs.junit.AssertStringEqualsTest.test::org.junit.ComparisonFailure: expected:<foob[a]r> but was:<foob[bb]r>::true
 ldTest org.scalajs.junit.AssertStringEqualsTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_v.txt b/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_v.txt
index 4ada7cf6df..08ab2fd093 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_v.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_v.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertStringEqualsTest.test started
 leTest org.scalajs.junit.AssertStringEqualsTest.test failed: expected:<foob[a]r> but was:<foob[bb]r>, took <TIME>
-e2org.scalajs.junit.AssertStringEqualsTest.test::org.junit.ComparisonFailure: expected:<foob[a]r> but was:<foob[bb]r>
+e2org.scalajs.junit.AssertStringEqualsTest.test::org.junit.ComparisonFailure: expected:<foob[a]r> but was:<foob[bb]r>::true
 ldTest org.scalajs.junit.AssertStringEqualsTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_va.txt b/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_va.txt
index c2c9792f56..b67d6f654a 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_va.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_va.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertStringEqualsTest.test started
 leTest org.scalajs.junit.AssertStringEqualsTest.test failed: org.junit.ComparisonFailure: expected:<foob[a]r> but was:<foob[bb]r>, took <TIME>
-e2org.scalajs.junit.AssertStringEqualsTest.test::org.junit.ComparisonFailure: expected:<foob[a]r> but was:<foob[bb]r>
+e2org.scalajs.junit.AssertStringEqualsTest.test::org.junit.ComparisonFailure: expected:<foob[a]r> but was:<foob[bb]r>::true
 ldTest org.scalajs.junit.AssertStringEqualsTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_vc.txt b/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_vc.txt
index 4ada7cf6df..08ab2fd093 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_vc.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_vc.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertStringEqualsTest.test started
 leTest org.scalajs.junit.AssertStringEqualsTest.test failed: expected:<foob[a]r> but was:<foob[bb]r>, took <TIME>
-e2org.scalajs.junit.AssertStringEqualsTest.test::org.junit.ComparisonFailure: expected:<foob[a]r> but was:<foob[bb]r>
+e2org.scalajs.junit.AssertStringEqualsTest.test::org.junit.ComparisonFailure: expected:<foob[a]r> but was:<foob[bb]r>::true
 ldTest org.scalajs.junit.AssertStringEqualsTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_vs.txt b/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_vs.txt
index 4ada7cf6df..08ab2fd093 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_vs.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_vs.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertStringEqualsTest.test started
 leTest org.scalajs.junit.AssertStringEqualsTest.test failed: expected:<foob[a]r> but was:<foob[bb]r>, took <TIME>
-e2org.scalajs.junit.AssertStringEqualsTest.test::org.junit.ComparisonFailure: expected:<foob[a]r> but was:<foob[bb]r>
+e2org.scalajs.junit.AssertStringEqualsTest.test::org.junit.ComparisonFailure: expected:<foob[a]r> but was:<foob[bb]r>::true
 ldTest org.scalajs.junit.AssertStringEqualsTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_vsn.txt b/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_vsn.txt
index 050a280abb..6fb57996d9 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_vsn.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertStringEqualsTestAssertions_vsn.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssertStringEqualsTest.test started
 leTest org.scalajs.junit.AssertStringEqualsTest.test failed: expected:<foob[a]r> but was:<foob[bb]r>, took <TIME>
-e2org.scalajs.junit.AssertStringEqualsTest.test::org.junit.ComparisonFailure: expected:<foob[a]r> but was:<foob[bb]r>
+e2org.scalajs.junit.AssertStringEqualsTest.test::org.junit.ComparisonFailure: expected:<foob[a]r> but was:<foob[bb]r>::true
 ldTest org.scalajs.junit.AssertStringEqualsTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_.txt b/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_.txt
index e49cdd3f01..53a6bd050d 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_.txt
@@ -1,10 +1,10 @@
 ldTest run started
 ldTest org.scalajs.junit.AssertTrueTest.failTest started
 leTest org.scalajs.junit.AssertTrueTest.failTest failed: null, took <TIME>
-e2org.scalajs.junit.AssertTrueTest.failTest::java.lang.AssertionError
+e2org.scalajs.junit.AssertTrueTest.failTest::java.lang.AssertionError::true
 ldTest org.scalajs.junit.AssertTrueTest.failTest finished, took <TIME>
 ldTest org.scalajs.junit.AssertTrueTest.successTest started
 ldTest org.scalajs.junit.AssertTrueTest.successTest finished, took <TIME>
-e0org.scalajs.junit.AssertTrueTest.successTest::
+e0org.scalajs.junit.AssertTrueTest.successTest::::true
 ldTest run finished: 1 failed, 0 ignored, 2 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_a.txt b/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_a.txt
index cc95f5c7a7..d2e3600825 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_a.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_a.txt
@@ -1,10 +1,10 @@
 ldTest run started
 ldTest org.scalajs.junit.AssertTrueTest.failTest started
 leTest org.scalajs.junit.AssertTrueTest.failTest failed: java.lang.AssertionError: null, took <TIME>
-e2org.scalajs.junit.AssertTrueTest.failTest::java.lang.AssertionError
+e2org.scalajs.junit.AssertTrueTest.failTest::java.lang.AssertionError::true
 ldTest org.scalajs.junit.AssertTrueTest.failTest finished, took <TIME>
 ldTest org.scalajs.junit.AssertTrueTest.successTest started
 ldTest org.scalajs.junit.AssertTrueTest.successTest finished, took <TIME>
-e0org.scalajs.junit.AssertTrueTest.successTest::
+e0org.scalajs.junit.AssertTrueTest.successTest::::true
 ldTest run finished: 1 failed, 0 ignored, 2 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_n.txt b/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_n.txt
index 706781bd5b..334609fa16 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_n.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_n.txt
@@ -1,10 +1,10 @@
 ldTest run started
 ldTest org.scalajs.junit.AssertTrueTest.failTest started
 leTest org.scalajs.junit.AssertTrueTest.failTest failed: null, took <TIME>
-e2org.scalajs.junit.AssertTrueTest.failTest::java.lang.AssertionError
+e2org.scalajs.junit.AssertTrueTest.failTest::java.lang.AssertionError::true
 ldTest org.scalajs.junit.AssertTrueTest.failTest finished, took <TIME>
 ldTest org.scalajs.junit.AssertTrueTest.successTest started
 ldTest org.scalajs.junit.AssertTrueTest.successTest finished, took <TIME>
-e0org.scalajs.junit.AssertTrueTest.successTest::
+e0org.scalajs.junit.AssertTrueTest.successTest::::true
 ldTest run finished: 1 failed, 0 ignored, 2 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_na.txt b/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_na.txt
index 6aabf28c21..a2f0515d10 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_na.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_na.txt
@@ -1,10 +1,10 @@
 ldTest run started
 ldTest org.scalajs.junit.AssertTrueTest.failTest started
 leTest org.scalajs.junit.AssertTrueTest.failTest failed: java.lang.AssertionError: null, took <TIME>
-e2org.scalajs.junit.AssertTrueTest.failTest::java.lang.AssertionError
+e2org.scalajs.junit.AssertTrueTest.failTest::java.lang.AssertionError::true
 ldTest org.scalajs.junit.AssertTrueTest.failTest finished, took <TIME>
 ldTest org.scalajs.junit.AssertTrueTest.successTest started
 ldTest org.scalajs.junit.AssertTrueTest.successTest finished, took <TIME>
-e0org.scalajs.junit.AssertTrueTest.successTest::
+e0org.scalajs.junit.AssertTrueTest.successTest::::true
 ldTest run finished: 1 failed, 0 ignored, 2 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_nv.txt b/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_nv.txt
index 04cdb29958..10cf085297 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_nv.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_nv.txt
@@ -1,10 +1,10 @@
 liTest run started
 liTest org.scalajs.junit.AssertTrueTest.failTest started
 leTest org.scalajs.junit.AssertTrueTest.failTest failed: null, took <TIME>
-e2org.scalajs.junit.AssertTrueTest.failTest::java.lang.AssertionError
+e2org.scalajs.junit.AssertTrueTest.failTest::java.lang.AssertionError::true
 ldTest org.scalajs.junit.AssertTrueTest.failTest finished, took <TIME>
 liTest org.scalajs.junit.AssertTrueTest.successTest started
 ldTest org.scalajs.junit.AssertTrueTest.successTest finished, took <TIME>
-e0org.scalajs.junit.AssertTrueTest.successTest::
+e0org.scalajs.junit.AssertTrueTest.successTest::::true
 liTest run finished: 1 failed, 0 ignored, 2 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_nva.txt b/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_nva.txt
index 2f5d0b3100..9f9195a405 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_nva.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_nva.txt
@@ -1,10 +1,10 @@
 liTest run started
 liTest org.scalajs.junit.AssertTrueTest.failTest started
 leTest org.scalajs.junit.AssertTrueTest.failTest failed: java.lang.AssertionError: null, took <TIME>
-e2org.scalajs.junit.AssertTrueTest.failTest::java.lang.AssertionError
+e2org.scalajs.junit.AssertTrueTest.failTest::java.lang.AssertionError::true
 ldTest org.scalajs.junit.AssertTrueTest.failTest finished, took <TIME>
 liTest org.scalajs.junit.AssertTrueTest.successTest started
 ldTest org.scalajs.junit.AssertTrueTest.successTest finished, took <TIME>
-e0org.scalajs.junit.AssertTrueTest.successTest::
+e0org.scalajs.junit.AssertTrueTest.successTest::::true
 liTest run finished: 1 failed, 0 ignored, 2 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_nvc.txt b/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_nvc.txt
index 04cdb29958..10cf085297 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_nvc.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_nvc.txt
@@ -1,10 +1,10 @@
 liTest run started
 liTest org.scalajs.junit.AssertTrueTest.failTest started
 leTest org.scalajs.junit.AssertTrueTest.failTest failed: null, took <TIME>
-e2org.scalajs.junit.AssertTrueTest.failTest::java.lang.AssertionError
+e2org.scalajs.junit.AssertTrueTest.failTest::java.lang.AssertionError::true
 ldTest org.scalajs.junit.AssertTrueTest.failTest finished, took <TIME>
 liTest org.scalajs.junit.AssertTrueTest.successTest started
 ldTest org.scalajs.junit.AssertTrueTest.successTest finished, took <TIME>
-e0org.scalajs.junit.AssertTrueTest.successTest::
+e0org.scalajs.junit.AssertTrueTest.successTest::::true
 liTest run finished: 1 failed, 0 ignored, 2 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_nvca.txt b/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_nvca.txt
index 04cdb29958..10cf085297 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_nvca.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_nvca.txt
@@ -1,10 +1,10 @@
 liTest run started
 liTest org.scalajs.junit.AssertTrueTest.failTest started
 leTest org.scalajs.junit.AssertTrueTest.failTest failed: null, took <TIME>
-e2org.scalajs.junit.AssertTrueTest.failTest::java.lang.AssertionError
+e2org.scalajs.junit.AssertTrueTest.failTest::java.lang.AssertionError::true
 ldTest org.scalajs.junit.AssertTrueTest.failTest finished, took <TIME>
 liTest org.scalajs.junit.AssertTrueTest.successTest started
 ldTest org.scalajs.junit.AssertTrueTest.successTest finished, took <TIME>
-e0org.scalajs.junit.AssertTrueTest.successTest::
+e0org.scalajs.junit.AssertTrueTest.successTest::::true
 liTest run finished: 1 failed, 0 ignored, 2 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_v.txt b/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_v.txt
index 29300050df..8f2564272c 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_v.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_v.txt
@@ -1,10 +1,10 @@
 liTest run started
 liTest org.scalajs.junit.AssertTrueTest.failTest started
 leTest org.scalajs.junit.AssertTrueTest.failTest failed: null, took <TIME>
-e2org.scalajs.junit.AssertTrueTest.failTest::java.lang.AssertionError
+e2org.scalajs.junit.AssertTrueTest.failTest::java.lang.AssertionError::true
 ldTest org.scalajs.junit.AssertTrueTest.failTest finished, took <TIME>
 liTest org.scalajs.junit.AssertTrueTest.successTest started
 ldTest org.scalajs.junit.AssertTrueTest.successTest finished, took <TIME>
-e0org.scalajs.junit.AssertTrueTest.successTest::
+e0org.scalajs.junit.AssertTrueTest.successTest::::true
 liTest run finished: 1 failed, 0 ignored, 2 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_va.txt b/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_va.txt
index 7a01eb25ac..81b107dd9e 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_va.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_va.txt
@@ -1,10 +1,10 @@
 liTest run started
 liTest org.scalajs.junit.AssertTrueTest.failTest started
 leTest org.scalajs.junit.AssertTrueTest.failTest failed: java.lang.AssertionError: null, took <TIME>
-e2org.scalajs.junit.AssertTrueTest.failTest::java.lang.AssertionError
+e2org.scalajs.junit.AssertTrueTest.failTest::java.lang.AssertionError::true
 ldTest org.scalajs.junit.AssertTrueTest.failTest finished, took <TIME>
 liTest org.scalajs.junit.AssertTrueTest.successTest started
 ldTest org.scalajs.junit.AssertTrueTest.successTest finished, took <TIME>
-e0org.scalajs.junit.AssertTrueTest.successTest::
+e0org.scalajs.junit.AssertTrueTest.successTest::::true
 liTest run finished: 1 failed, 0 ignored, 2 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_vc.txt b/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_vc.txt
index 29300050df..8f2564272c 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_vc.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_vc.txt
@@ -1,10 +1,10 @@
 liTest run started
 liTest org.scalajs.junit.AssertTrueTest.failTest started
 leTest org.scalajs.junit.AssertTrueTest.failTest failed: null, took <TIME>
-e2org.scalajs.junit.AssertTrueTest.failTest::java.lang.AssertionError
+e2org.scalajs.junit.AssertTrueTest.failTest::java.lang.AssertionError::true
 ldTest org.scalajs.junit.AssertTrueTest.failTest finished, took <TIME>
 liTest org.scalajs.junit.AssertTrueTest.successTest started
 ldTest org.scalajs.junit.AssertTrueTest.successTest finished, took <TIME>
-e0org.scalajs.junit.AssertTrueTest.successTest::
+e0org.scalajs.junit.AssertTrueTest.successTest::::true
 liTest run finished: 1 failed, 0 ignored, 2 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_vs.txt b/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_vs.txt
index 29300050df..8f2564272c 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_vs.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_vs.txt
@@ -1,10 +1,10 @@
 liTest run started
 liTest org.scalajs.junit.AssertTrueTest.failTest started
 leTest org.scalajs.junit.AssertTrueTest.failTest failed: null, took <TIME>
-e2org.scalajs.junit.AssertTrueTest.failTest::java.lang.AssertionError
+e2org.scalajs.junit.AssertTrueTest.failTest::java.lang.AssertionError::true
 ldTest org.scalajs.junit.AssertTrueTest.failTest finished, took <TIME>
 liTest org.scalajs.junit.AssertTrueTest.successTest started
 ldTest org.scalajs.junit.AssertTrueTest.successTest finished, took <TIME>
-e0org.scalajs.junit.AssertTrueTest.successTest::
+e0org.scalajs.junit.AssertTrueTest.successTest::::true
 liTest run finished: 1 failed, 0 ignored, 2 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_vsn.txt b/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_vsn.txt
index 04cdb29958..10cf085297 100644
--- a/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_vsn.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssertTrueTestAssertions_vsn.txt
@@ -1,10 +1,10 @@
 liTest run started
 liTest org.scalajs.junit.AssertTrueTest.failTest started
 leTest org.scalajs.junit.AssertTrueTest.failTest failed: null, took <TIME>
-e2org.scalajs.junit.AssertTrueTest.failTest::java.lang.AssertionError
+e2org.scalajs.junit.AssertTrueTest.failTest::java.lang.AssertionError::true
 ldTest org.scalajs.junit.AssertTrueTest.failTest finished, took <TIME>
 liTest org.scalajs.junit.AssertTrueTest.successTest started
 ldTest org.scalajs.junit.AssertTrueTest.successTest finished, took <TIME>
-e0org.scalajs.junit.AssertTrueTest.successTest::
+e0org.scalajs.junit.AssertTrueTest.successTest::::true
 liTest run finished: 1 failed, 0 ignored, 2 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_.txt
index b38d469dcd..20044d553b 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_.txt
@@ -2,7 +2,7 @@ ldTest run started
 ldTest org.scalajs.junit.AssumeAfterAssume.assumeFail started
 leTest org.scalajs.junit.AssumeAfterAssume.assumeFail failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
-e2org.scalajs.junit.AssumeAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures
+e2org.scalajs.junit.AssumeAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures::true
 leTest org.scalajs.junit.AssumeAfterAssume.assumeFail failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeAfterAssume.assumeFail finished, took <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_a.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_a.txt
index b38d469dcd..20044d553b 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_a.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_a.txt
@@ -2,7 +2,7 @@ ldTest run started
 ldTest org.scalajs.junit.AssumeAfterAssume.assumeFail started
 leTest org.scalajs.junit.AssumeAfterAssume.assumeFail failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
-e2org.scalajs.junit.AssumeAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures
+e2org.scalajs.junit.AssumeAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures::true
 leTest org.scalajs.junit.AssumeAfterAssume.assumeFail failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeAfterAssume.assumeFail finished, took <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_n.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_n.txt
index 4eabc3c5a5..834b8c69f1 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_n.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_n.txt
@@ -2,7 +2,7 @@ ldTest run started
 ldTest org.scalajs.junit.AssumeAfterAssume.assumeFail started
 leTest org.scalajs.junit.AssumeAfterAssume.assumeFail failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
-e2org.scalajs.junit.AssumeAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures
+e2org.scalajs.junit.AssumeAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures::true
 leTest org.scalajs.junit.AssumeAfterAssume.assumeFail failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeAfterAssume.assumeFail finished, took <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_na.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_na.txt
index 4eabc3c5a5..834b8c69f1 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_na.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_na.txt
@@ -2,7 +2,7 @@ ldTest run started
 ldTest org.scalajs.junit.AssumeAfterAssume.assumeFail started
 leTest org.scalajs.junit.AssumeAfterAssume.assumeFail failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
-e2org.scalajs.junit.AssumeAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures
+e2org.scalajs.junit.AssumeAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures::true
 leTest org.scalajs.junit.AssumeAfterAssume.assumeFail failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeAfterAssume.assumeFail finished, took <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_nv.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_nv.txt
index 144099360a..099059f44f 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_nv.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_nv.txt
@@ -2,7 +2,7 @@ liTest run started
 liTest org.scalajs.junit.AssumeAfterAssume.assumeFail started
 leTest org.scalajs.junit.AssumeAfterAssume.assumeFail failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
-e2org.scalajs.junit.AssumeAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures
+e2org.scalajs.junit.AssumeAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures::true
 leTest org.scalajs.junit.AssumeAfterAssume.assumeFail failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeAfterAssume.assumeFail finished, took <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_nva.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_nva.txt
index 144099360a..099059f44f 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_nva.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_nva.txt
@@ -2,7 +2,7 @@ liTest run started
 liTest org.scalajs.junit.AssumeAfterAssume.assumeFail started
 leTest org.scalajs.junit.AssumeAfterAssume.assumeFail failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
-e2org.scalajs.junit.AssumeAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures
+e2org.scalajs.junit.AssumeAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures::true
 leTest org.scalajs.junit.AssumeAfterAssume.assumeFail failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeAfterAssume.assumeFail finished, took <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_nvc.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_nvc.txt
index 1b894cf4dc..97d5bf8835 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_nvc.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_nvc.txt
@@ -2,7 +2,7 @@ liTest run started
 liTest org.scalajs.junit.AssumeAfterAssume.assumeFail started
 leTest org.scalajs.junit.AssumeAfterAssume.assumeFail failed: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
-e2org.scalajs.junit.AssumeAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures
+e2org.scalajs.junit.AssumeAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures::true
 leTest org.scalajs.junit.AssumeAfterAssume.assumeFail failed: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeAfterAssume.assumeFail finished, took <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_nvca.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_nvca.txt
index 1b894cf4dc..97d5bf8835 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_nvca.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_nvca.txt
@@ -2,7 +2,7 @@ liTest run started
 liTest org.scalajs.junit.AssumeAfterAssume.assumeFail started
 leTest org.scalajs.junit.AssumeAfterAssume.assumeFail failed: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
-e2org.scalajs.junit.AssumeAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures
+e2org.scalajs.junit.AssumeAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures::true
 leTest org.scalajs.junit.AssumeAfterAssume.assumeFail failed: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeAfterAssume.assumeFail finished, took <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_v.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_v.txt
index 55e72df4b1..6502f87a27 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_v.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_v.txt
@@ -2,7 +2,7 @@ liTest run started
 liTest org.scalajs.junit.AssumeAfterAssume.assumeFail started
 leTest org.scalajs.junit.AssumeAfterAssume.assumeFail failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
-e2org.scalajs.junit.AssumeAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures
+e2org.scalajs.junit.AssumeAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures::true
 leTest org.scalajs.junit.AssumeAfterAssume.assumeFail failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeAfterAssume.assumeFail finished, took <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_va.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_va.txt
index 55e72df4b1..6502f87a27 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_va.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_va.txt
@@ -2,7 +2,7 @@ liTest run started
 liTest org.scalajs.junit.AssumeAfterAssume.assumeFail started
 leTest org.scalajs.junit.AssumeAfterAssume.assumeFail failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
-e2org.scalajs.junit.AssumeAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures
+e2org.scalajs.junit.AssumeAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures::true
 leTest org.scalajs.junit.AssumeAfterAssume.assumeFail failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeAfterAssume.assumeFail finished, took <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_vc.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_vc.txt
index 37c9099ed3..f5d92b9a7b 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_vc.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_vc.txt
@@ -2,7 +2,7 @@ liTest run started
 liTest org.scalajs.junit.AssumeAfterAssume.assumeFail started
 leTest org.scalajs.junit.AssumeAfterAssume.assumeFail failed: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
-e2org.scalajs.junit.AssumeAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures
+e2org.scalajs.junit.AssumeAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures::true
 leTest org.scalajs.junit.AssumeAfterAssume.assumeFail failed: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeAfterAssume.assumeFail finished, took <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_vs.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_vs.txt
index 55e72df4b1..6502f87a27 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_vs.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_vs.txt
@@ -2,7 +2,7 @@ liTest run started
 liTest org.scalajs.junit.AssumeAfterAssume.assumeFail started
 leTest org.scalajs.junit.AssumeAfterAssume.assumeFail failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
-e2org.scalajs.junit.AssumeAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures
+e2org.scalajs.junit.AssumeAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures::true
 leTest org.scalajs.junit.AssumeAfterAssume.assumeFail failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeAfterAssume.assumeFail finished, took <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_vsn.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_vsn.txt
index 144099360a..099059f44f 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_vsn.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterAssumeAssertions_vsn.txt
@@ -2,7 +2,7 @@ liTest run started
 liTest org.scalajs.junit.AssumeAfterAssume.assumeFail started
 leTest org.scalajs.junit.AssumeAfterAssume.assumeFail failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
-e2org.scalajs.junit.AssumeAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures
+e2org.scalajs.junit.AssumeAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures::true
 leTest org.scalajs.junit.AssumeAfterAssume.assumeFail failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeAfterAssume.assumeFail finished, took <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_.txt
index c64383011f..fc60f67f9b 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_.txt
@@ -1,8 +1,8 @@
 ldTest run started
 ldTest org.scalajs.junit.AssumeAfterClassTest.test started
 ldTest org.scalajs.junit.AssumeAfterClassTest.test finished, took <TIME>
-e0org.scalajs.junit.AssumeAfterClassTest.test::
+e0org.scalajs.junit.AssumeAfterClassTest.test::::true
 lwTest assumption in test org.scalajs.junit.AssumeAfterClassTest failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeAfterClassTest::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.AssumeAfterClassTest::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_a.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_a.txt
index c64383011f..fc60f67f9b 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_a.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_a.txt
@@ -1,8 +1,8 @@
 ldTest run started
 ldTest org.scalajs.junit.AssumeAfterClassTest.test started
 ldTest org.scalajs.junit.AssumeAfterClassTest.test finished, took <TIME>
-e0org.scalajs.junit.AssumeAfterClassTest.test::
+e0org.scalajs.junit.AssumeAfterClassTest.test::::true
 lwTest assumption in test org.scalajs.junit.AssumeAfterClassTest failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeAfterClassTest::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.AssumeAfterClassTest::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_n.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_n.txt
index cf859e586e..eb770d6b0b 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_n.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_n.txt
@@ -1,8 +1,8 @@
 ldTest run started
 ldTest org.scalajs.junit.AssumeAfterClassTest.test started
 ldTest org.scalajs.junit.AssumeAfterClassTest.test finished, took <TIME>
-e0org.scalajs.junit.AssumeAfterClassTest.test::
+e0org.scalajs.junit.AssumeAfterClassTest.test::::true
 lwTest assumption in test org.scalajs.junit.AssumeAfterClassTest failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeAfterClassTest::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.AssumeAfterClassTest::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_na.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_na.txt
index cf859e586e..eb770d6b0b 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_na.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_na.txt
@@ -1,8 +1,8 @@
 ldTest run started
 ldTest org.scalajs.junit.AssumeAfterClassTest.test started
 ldTest org.scalajs.junit.AssumeAfterClassTest.test finished, took <TIME>
-e0org.scalajs.junit.AssumeAfterClassTest.test::
+e0org.scalajs.junit.AssumeAfterClassTest.test::::true
 lwTest assumption in test org.scalajs.junit.AssumeAfterClassTest failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeAfterClassTest::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.AssumeAfterClassTest::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_nv.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_nv.txt
index 7fb2119057..7d23bb0c15 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_nv.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_nv.txt
@@ -1,8 +1,8 @@
 liTest run started
 liTest org.scalajs.junit.AssumeAfterClassTest.test started
 ldTest org.scalajs.junit.AssumeAfterClassTest.test finished, took <TIME>
-e0org.scalajs.junit.AssumeAfterClassTest.test::
+e0org.scalajs.junit.AssumeAfterClassTest.test::::true
 lwTest assumption in test org.scalajs.junit.AssumeAfterClassTest failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeAfterClassTest::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.AssumeAfterClassTest::org.junit.AssumptionViolatedException: This assume should not pass::true
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_nva.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_nva.txt
index 7fb2119057..7d23bb0c15 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_nva.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_nva.txt
@@ -1,8 +1,8 @@
 liTest run started
 liTest org.scalajs.junit.AssumeAfterClassTest.test started
 ldTest org.scalajs.junit.AssumeAfterClassTest.test finished, took <TIME>
-e0org.scalajs.junit.AssumeAfterClassTest.test::
+e0org.scalajs.junit.AssumeAfterClassTest.test::::true
 lwTest assumption in test org.scalajs.junit.AssumeAfterClassTest failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeAfterClassTest::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.AssumeAfterClassTest::org.junit.AssumptionViolatedException: This assume should not pass::true
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_nvc.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_nvc.txt
index cf5ed08fab..827810d922 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_nvc.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_nvc.txt
@@ -1,8 +1,8 @@
 liTest run started
 liTest org.scalajs.junit.AssumeAfterClassTest.test started
 ldTest org.scalajs.junit.AssumeAfterClassTest.test finished, took <TIME>
-e0org.scalajs.junit.AssumeAfterClassTest.test::
+e0org.scalajs.junit.AssumeAfterClassTest.test::::true
 lwTest assumption in test org.scalajs.junit.AssumeAfterClassTest failed: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeAfterClassTest::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.AssumeAfterClassTest::org.junit.AssumptionViolatedException: This assume should not pass::true
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_nvca.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_nvca.txt
index cf5ed08fab..827810d922 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_nvca.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_nvca.txt
@@ -1,8 +1,8 @@
 liTest run started
 liTest org.scalajs.junit.AssumeAfterClassTest.test started
 ldTest org.scalajs.junit.AssumeAfterClassTest.test finished, took <TIME>
-e0org.scalajs.junit.AssumeAfterClassTest.test::
+e0org.scalajs.junit.AssumeAfterClassTest.test::::true
 lwTest assumption in test org.scalajs.junit.AssumeAfterClassTest failed: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeAfterClassTest::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.AssumeAfterClassTest::org.junit.AssumptionViolatedException: This assume should not pass::true
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_v.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_v.txt
index 3ac52e8745..552c971779 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_v.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_v.txt
@@ -1,8 +1,8 @@
 liTest run started
 liTest org.scalajs.junit.AssumeAfterClassTest.test started
 ldTest org.scalajs.junit.AssumeAfterClassTest.test finished, took <TIME>
-e0org.scalajs.junit.AssumeAfterClassTest.test::
+e0org.scalajs.junit.AssumeAfterClassTest.test::::true
 lwTest assumption in test org.scalajs.junit.AssumeAfterClassTest failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeAfterClassTest::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.AssumeAfterClassTest::org.junit.AssumptionViolatedException: This assume should not pass::true
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_va.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_va.txt
index 3ac52e8745..552c971779 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_va.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_va.txt
@@ -1,8 +1,8 @@
 liTest run started
 liTest org.scalajs.junit.AssumeAfterClassTest.test started
 ldTest org.scalajs.junit.AssumeAfterClassTest.test finished, took <TIME>
-e0org.scalajs.junit.AssumeAfterClassTest.test::
+e0org.scalajs.junit.AssumeAfterClassTest.test::::true
 lwTest assumption in test org.scalajs.junit.AssumeAfterClassTest failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeAfterClassTest::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.AssumeAfterClassTest::org.junit.AssumptionViolatedException: This assume should not pass::true
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_vc.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_vc.txt
index a730ea7a71..8defa8f183 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_vc.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_vc.txt
@@ -1,8 +1,8 @@
 liTest run started
 liTest org.scalajs.junit.AssumeAfterClassTest.test started
 ldTest org.scalajs.junit.AssumeAfterClassTest.test finished, took <TIME>
-e0org.scalajs.junit.AssumeAfterClassTest.test::
+e0org.scalajs.junit.AssumeAfterClassTest.test::::true
 lwTest assumption in test org.scalajs.junit.AssumeAfterClassTest failed: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeAfterClassTest::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.AssumeAfterClassTest::org.junit.AssumptionViolatedException: This assume should not pass::true
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_vs.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_vs.txt
index 3ac52e8745..552c971779 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_vs.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_vs.txt
@@ -1,8 +1,8 @@
 liTest run started
 liTest org.scalajs.junit.AssumeAfterClassTest.test started
 ldTest org.scalajs.junit.AssumeAfterClassTest.test finished, took <TIME>
-e0org.scalajs.junit.AssumeAfterClassTest.test::
+e0org.scalajs.junit.AssumeAfterClassTest.test::::true
 lwTest assumption in test org.scalajs.junit.AssumeAfterClassTest failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeAfterClassTest::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.AssumeAfterClassTest::org.junit.AssumptionViolatedException: This assume should not pass::true
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_vsn.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_vsn.txt
index 7fb2119057..7d23bb0c15 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_vsn.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterClassTestAssertions_vsn.txt
@@ -1,8 +1,8 @@
 liTest run started
 liTest org.scalajs.junit.AssumeAfterClassTest.test started
 ldTest org.scalajs.junit.AssumeAfterClassTest.test finished, took <TIME>
-e0org.scalajs.junit.AssumeAfterClassTest.test::
+e0org.scalajs.junit.AssumeAfterClassTest.test::::true
 lwTest assumption in test org.scalajs.junit.AssumeAfterClassTest failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeAfterClassTest::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.AssumeAfterClassTest::org.junit.AssumptionViolatedException: This assume should not pass::true
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_.txt
index 24985459cf..c2d75e6b9c 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.AssumeAfterException.test started
 leTest org.scalajs.junit.AssumeAfterException.test failed: java.lang.IllegalArgumentException: test throws, took <TIME>
-e2org.scalajs.junit.AssumeAfterException.test::java.lang.IllegalArgumentException: test throws
+e2org.scalajs.junit.AssumeAfterException.test::java.lang.IllegalArgumentException: test throws::true
 leTest org.scalajs.junit.AssumeAfterException.test failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeAfterException.test finished, took <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_a.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_a.txt
index 24985459cf..c2d75e6b9c 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_a.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_a.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.AssumeAfterException.test started
 leTest org.scalajs.junit.AssumeAfterException.test failed: java.lang.IllegalArgumentException: test throws, took <TIME>
-e2org.scalajs.junit.AssumeAfterException.test::java.lang.IllegalArgumentException: test throws
+e2org.scalajs.junit.AssumeAfterException.test::java.lang.IllegalArgumentException: test throws::true
 leTest org.scalajs.junit.AssumeAfterException.test failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeAfterException.test finished, took <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_n.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_n.txt
index a6a4599a17..8263984eac 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_n.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_n.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.AssumeAfterException.test started
 leTest org.scalajs.junit.AssumeAfterException.test failed: java.lang.IllegalArgumentException: test throws, took <TIME>
-e2org.scalajs.junit.AssumeAfterException.test::java.lang.IllegalArgumentException: test throws
+e2org.scalajs.junit.AssumeAfterException.test::java.lang.IllegalArgumentException: test throws::true
 leTest org.scalajs.junit.AssumeAfterException.test failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeAfterException.test finished, took <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_na.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_na.txt
index a6a4599a17..8263984eac 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_na.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_na.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.AssumeAfterException.test started
 leTest org.scalajs.junit.AssumeAfterException.test failed: java.lang.IllegalArgumentException: test throws, took <TIME>
-e2org.scalajs.junit.AssumeAfterException.test::java.lang.IllegalArgumentException: test throws
+e2org.scalajs.junit.AssumeAfterException.test::java.lang.IllegalArgumentException: test throws::true
 leTest org.scalajs.junit.AssumeAfterException.test failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeAfterException.test finished, took <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_nv.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_nv.txt
index bff68c6a01..b0048c5d83 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_nv.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_nv.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssumeAfterException.test started
 leTest org.scalajs.junit.AssumeAfterException.test failed: java.lang.IllegalArgumentException: test throws, took <TIME>
-e2org.scalajs.junit.AssumeAfterException.test::java.lang.IllegalArgumentException: test throws
+e2org.scalajs.junit.AssumeAfterException.test::java.lang.IllegalArgumentException: test throws::true
 leTest org.scalajs.junit.AssumeAfterException.test failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeAfterException.test finished, took <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_nva.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_nva.txt
index bff68c6a01..b0048c5d83 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_nva.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_nva.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssumeAfterException.test started
 leTest org.scalajs.junit.AssumeAfterException.test failed: java.lang.IllegalArgumentException: test throws, took <TIME>
-e2org.scalajs.junit.AssumeAfterException.test::java.lang.IllegalArgumentException: test throws
+e2org.scalajs.junit.AssumeAfterException.test::java.lang.IllegalArgumentException: test throws::true
 leTest org.scalajs.junit.AssumeAfterException.test failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeAfterException.test finished, took <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_nvc.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_nvc.txt
index 65b2345b1b..df4b64e3e3 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_nvc.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_nvc.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssumeAfterException.test started
 leTest org.scalajs.junit.AssumeAfterException.test failed: test throws, took <TIME>
-e2org.scalajs.junit.AssumeAfterException.test::java.lang.IllegalArgumentException: test throws
+e2org.scalajs.junit.AssumeAfterException.test::java.lang.IllegalArgumentException: test throws::true
 leTest org.scalajs.junit.AssumeAfterException.test failed: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeAfterException.test finished, took <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_nvca.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_nvca.txt
index 65b2345b1b..df4b64e3e3 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_nvca.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_nvca.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssumeAfterException.test started
 leTest org.scalajs.junit.AssumeAfterException.test failed: test throws, took <TIME>
-e2org.scalajs.junit.AssumeAfterException.test::java.lang.IllegalArgumentException: test throws
+e2org.scalajs.junit.AssumeAfterException.test::java.lang.IllegalArgumentException: test throws::true
 leTest org.scalajs.junit.AssumeAfterException.test failed: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeAfterException.test finished, took <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_v.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_v.txt
index e35b1d0554..61115c2fd0 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_v.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_v.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssumeAfterException.test started
 leTest org.scalajs.junit.AssumeAfterException.test failed: java.lang.IllegalArgumentException: test throws, took <TIME>
-e2org.scalajs.junit.AssumeAfterException.test::java.lang.IllegalArgumentException: test throws
+e2org.scalajs.junit.AssumeAfterException.test::java.lang.IllegalArgumentException: test throws::true
 leTest org.scalajs.junit.AssumeAfterException.test failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeAfterException.test finished, took <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_va.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_va.txt
index e35b1d0554..61115c2fd0 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_va.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_va.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssumeAfterException.test started
 leTest org.scalajs.junit.AssumeAfterException.test failed: java.lang.IllegalArgumentException: test throws, took <TIME>
-e2org.scalajs.junit.AssumeAfterException.test::java.lang.IllegalArgumentException: test throws
+e2org.scalajs.junit.AssumeAfterException.test::java.lang.IllegalArgumentException: test throws::true
 leTest org.scalajs.junit.AssumeAfterException.test failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeAfterException.test finished, took <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_vc.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_vc.txt
index c55ba232de..1ed0c928ee 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_vc.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_vc.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssumeAfterException.test started
 leTest org.scalajs.junit.AssumeAfterException.test failed: test throws, took <TIME>
-e2org.scalajs.junit.AssumeAfterException.test::java.lang.IllegalArgumentException: test throws
+e2org.scalajs.junit.AssumeAfterException.test::java.lang.IllegalArgumentException: test throws::true
 leTest org.scalajs.junit.AssumeAfterException.test failed: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeAfterException.test finished, took <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_vs.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_vs.txt
index e35b1d0554..61115c2fd0 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_vs.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_vs.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssumeAfterException.test started
 leTest org.scalajs.junit.AssumeAfterException.test failed: java.lang.IllegalArgumentException: test throws, took <TIME>
-e2org.scalajs.junit.AssumeAfterException.test::java.lang.IllegalArgumentException: test throws
+e2org.scalajs.junit.AssumeAfterException.test::java.lang.IllegalArgumentException: test throws::true
 leTest org.scalajs.junit.AssumeAfterException.test failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeAfterException.test finished, took <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_vsn.txt b/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_vsn.txt
index bff68c6a01..b0048c5d83 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_vsn.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeAfterExceptionAssertions_vsn.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssumeAfterException.test started
 leTest org.scalajs.junit.AssumeAfterException.test failed: java.lang.IllegalArgumentException: test throws, took <TIME>
-e2org.scalajs.junit.AssumeAfterException.test::java.lang.IllegalArgumentException: test throws
+e2org.scalajs.junit.AssumeAfterException.test::java.lang.IllegalArgumentException: test throws::true
 leTest org.scalajs.junit.AssumeAfterException.test failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
 ldTest org.scalajs.junit.AssumeAfterException.test finished, took <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_.txt b/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_.txt
index 04e96edf37..67c51af4ee 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.AssumeInAfter.test started
 lwTest assumption in test org.scalajs.junit.AssumeInAfter.test failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeInAfter.test::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.AssumeInAfter.test::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest org.scalajs.junit.AssumeInAfter.test finished, took <TIME>
 ldTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_a.txt b/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_a.txt
index 04e96edf37..67c51af4ee 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_a.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_a.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.AssumeInAfter.test started
 lwTest assumption in test org.scalajs.junit.AssumeInAfter.test failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeInAfter.test::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.AssumeInAfter.test::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest org.scalajs.junit.AssumeInAfter.test finished, took <TIME>
 ldTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_n.txt b/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_n.txt
index 8aeee7ad9f..714e0aef74 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_n.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_n.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.AssumeInAfter.test started
 lwTest assumption in test org.scalajs.junit.AssumeInAfter.test failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeInAfter.test::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.AssumeInAfter.test::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest org.scalajs.junit.AssumeInAfter.test finished, took <TIME>
 ldTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_na.txt b/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_na.txt
index 8aeee7ad9f..714e0aef74 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_na.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_na.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.AssumeInAfter.test started
 lwTest assumption in test org.scalajs.junit.AssumeInAfter.test failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeInAfter.test::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.AssumeInAfter.test::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest org.scalajs.junit.AssumeInAfter.test finished, took <TIME>
 ldTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_nv.txt b/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_nv.txt
index d4b040d5cb..613137504f 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_nv.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_nv.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssumeInAfter.test started
 lwTest assumption in test org.scalajs.junit.AssumeInAfter.test failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeInAfter.test::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.AssumeInAfter.test::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest org.scalajs.junit.AssumeInAfter.test finished, took <TIME>
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_nva.txt b/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_nva.txt
index d4b040d5cb..613137504f 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_nva.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_nva.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssumeInAfter.test started
 lwTest assumption in test org.scalajs.junit.AssumeInAfter.test failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeInAfter.test::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.AssumeInAfter.test::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest org.scalajs.junit.AssumeInAfter.test finished, took <TIME>
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_nvc.txt b/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_nvc.txt
index 4a85b7acc8..98a3ab79cd 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_nvc.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_nvc.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssumeInAfter.test started
 lwTest assumption in test org.scalajs.junit.AssumeInAfter.test failed: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeInAfter.test::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.AssumeInAfter.test::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest org.scalajs.junit.AssumeInAfter.test finished, took <TIME>
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_nvca.txt b/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_nvca.txt
index 4a85b7acc8..98a3ab79cd 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_nvca.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_nvca.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssumeInAfter.test started
 lwTest assumption in test org.scalajs.junit.AssumeInAfter.test failed: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeInAfter.test::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.AssumeInAfter.test::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest org.scalajs.junit.AssumeInAfter.test finished, took <TIME>
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_v.txt b/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_v.txt
index 1c61788745..67cb1bc33b 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_v.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_v.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssumeInAfter.test started
 lwTest assumption in test org.scalajs.junit.AssumeInAfter.test failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeInAfter.test::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.AssumeInAfter.test::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest org.scalajs.junit.AssumeInAfter.test finished, took <TIME>
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_va.txt b/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_va.txt
index 1c61788745..67cb1bc33b 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_va.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_va.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssumeInAfter.test started
 lwTest assumption in test org.scalajs.junit.AssumeInAfter.test failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeInAfter.test::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.AssumeInAfter.test::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest org.scalajs.junit.AssumeInAfter.test finished, took <TIME>
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_vc.txt b/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_vc.txt
index 6a9b739565..1fd1c35aad 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_vc.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_vc.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssumeInAfter.test started
 lwTest assumption in test org.scalajs.junit.AssumeInAfter.test failed: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeInAfter.test::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.AssumeInAfter.test::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest org.scalajs.junit.AssumeInAfter.test finished, took <TIME>
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_vs.txt b/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_vs.txt
index 1c61788745..67cb1bc33b 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_vs.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_vs.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssumeInAfter.test started
 lwTest assumption in test org.scalajs.junit.AssumeInAfter.test failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeInAfter.test::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.AssumeInAfter.test::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest org.scalajs.junit.AssumeInAfter.test finished, took <TIME>
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_vsn.txt b/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_vsn.txt
index d4b040d5cb..613137504f 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_vsn.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeInAfterAssertions_vsn.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssumeInAfter.test started
 lwTest assumption in test org.scalajs.junit.AssumeInAfter.test failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeInAfter.test::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.AssumeInAfter.test::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest org.scalajs.junit.AssumeInAfter.test finished, took <TIME>
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_.txt b/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_.txt
index 4c3706abdb..9c8cb0a41c 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.AssumeTest.assumeFail started
 lwTest assumption in test org.scalajs.junit.AssumeTest.assumeFail failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeTest.assumeFail::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.AssumeTest.assumeFail::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest org.scalajs.junit.AssumeTest.assumeFail finished, took <TIME>
 ldTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_a.txt b/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_a.txt
index 4c3706abdb..9c8cb0a41c 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_a.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_a.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.AssumeTest.assumeFail started
 lwTest assumption in test org.scalajs.junit.AssumeTest.assumeFail failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeTest.assumeFail::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.AssumeTest.assumeFail::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest org.scalajs.junit.AssumeTest.assumeFail finished, took <TIME>
 ldTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_n.txt b/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_n.txt
index cc72fbc62e..bfd68c5f97 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_n.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_n.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.AssumeTest.assumeFail started
 lwTest assumption in test org.scalajs.junit.AssumeTest.assumeFail failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeTest.assumeFail::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.AssumeTest.assumeFail::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest org.scalajs.junit.AssumeTest.assumeFail finished, took <TIME>
 ldTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_na.txt b/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_na.txt
index cc72fbc62e..bfd68c5f97 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_na.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_na.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.AssumeTest.assumeFail started
 lwTest assumption in test org.scalajs.junit.AssumeTest.assumeFail failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeTest.assumeFail::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.AssumeTest.assumeFail::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest org.scalajs.junit.AssumeTest.assumeFail finished, took <TIME>
 ldTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_nv.txt b/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_nv.txt
index 313778536f..1f8d28f146 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_nv.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_nv.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssumeTest.assumeFail started
 lwTest assumption in test org.scalajs.junit.AssumeTest.assumeFail failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeTest.assumeFail::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.AssumeTest.assumeFail::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest org.scalajs.junit.AssumeTest.assumeFail finished, took <TIME>
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_nva.txt b/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_nva.txt
index 313778536f..1f8d28f146 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_nva.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_nva.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssumeTest.assumeFail started
 lwTest assumption in test org.scalajs.junit.AssumeTest.assumeFail failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeTest.assumeFail::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.AssumeTest.assumeFail::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest org.scalajs.junit.AssumeTest.assumeFail finished, took <TIME>
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_nvc.txt b/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_nvc.txt
index b5bdfb9968..d3a9400ad1 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_nvc.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_nvc.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssumeTest.assumeFail started
 lwTest assumption in test org.scalajs.junit.AssumeTest.assumeFail failed: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeTest.assumeFail::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.AssumeTest.assumeFail::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest org.scalajs.junit.AssumeTest.assumeFail finished, took <TIME>
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_nvca.txt b/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_nvca.txt
index b5bdfb9968..d3a9400ad1 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_nvca.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_nvca.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssumeTest.assumeFail started
 lwTest assumption in test org.scalajs.junit.AssumeTest.assumeFail failed: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeTest.assumeFail::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.AssumeTest.assumeFail::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest org.scalajs.junit.AssumeTest.assumeFail finished, took <TIME>
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_v.txt b/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_v.txt
index e6e79ca64f..0c7af733e1 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_v.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_v.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssumeTest.assumeFail started
 lwTest assumption in test org.scalajs.junit.AssumeTest.assumeFail failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeTest.assumeFail::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.AssumeTest.assumeFail::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest org.scalajs.junit.AssumeTest.assumeFail finished, took <TIME>
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_va.txt b/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_va.txt
index e6e79ca64f..0c7af733e1 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_va.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_va.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssumeTest.assumeFail started
 lwTest assumption in test org.scalajs.junit.AssumeTest.assumeFail failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeTest.assumeFail::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.AssumeTest.assumeFail::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest org.scalajs.junit.AssumeTest.assumeFail finished, took <TIME>
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_vc.txt b/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_vc.txt
index 12cef272b2..cda8dfff33 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_vc.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_vc.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssumeTest.assumeFail started
 lwTest assumption in test org.scalajs.junit.AssumeTest.assumeFail failed: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeTest.assumeFail::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.AssumeTest.assumeFail::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest org.scalajs.junit.AssumeTest.assumeFail finished, took <TIME>
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_vs.txt b/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_vs.txt
index e6e79ca64f..0c7af733e1 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_vs.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_vs.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssumeTest.assumeFail started
 lwTest assumption in test org.scalajs.junit.AssumeTest.assumeFail failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeTest.assumeFail::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.AssumeTest.assumeFail::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest org.scalajs.junit.AssumeTest.assumeFail finished, took <TIME>
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_vsn.txt b/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_vsn.txt
index 313778536f..1f8d28f146 100644
--- a/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_vsn.txt
+++ b/junit-test/outputs/org/scalajs/junit/AssumeTestAssertions_vsn.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.AssumeTest.assumeFail started
 lwTest assumption in test org.scalajs.junit.AssumeTest.assumeFail failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.AssumeTest.assumeFail::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.AssumeTest.assumeFail::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest org.scalajs.junit.AssumeTest.assumeFail finished, took <TIME>
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_.txt b/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_.txt
index 9f9feb10a4..3b4d3b211e 100644
--- a/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_.txt
+++ b/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_.txt
@@ -1,13 +1,13 @@
 ldTest run started
 ldTest org.scalajs.junit.AsyncTest.asyncFailure started
 leTest org.scalajs.junit.AsyncTest.asyncFailure failed: java.lang.IllegalArgumentException: null, took <TIME>
-e2org.scalajs.junit.AsyncTest.asyncFailure::java.lang.IllegalArgumentException
+e2org.scalajs.junit.AsyncTest.asyncFailure::java.lang.IllegalArgumentException::true
 ldTest org.scalajs.junit.AsyncTest.asyncFailure finished, took <TIME>
 ldTest org.scalajs.junit.AsyncTest.expectedException started
 ldTest org.scalajs.junit.AsyncTest.expectedException finished, took <TIME>
-e0org.scalajs.junit.AsyncTest.expectedException::
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 ldTest org.scalajs.junit.AsyncTest.success started
 ldTest org.scalajs.junit.AsyncTest.success finished, took <TIME>
-e0org.scalajs.junit.AsyncTest.success::
+e0org.scalajs.junit.AsyncTest.success::::true
 ldTest run finished: 1 failed, 0 ignored, 3 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_a.txt b/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_a.txt
index 9f9feb10a4..3b4d3b211e 100644
--- a/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_a.txt
+++ b/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_a.txt
@@ -1,13 +1,13 @@
 ldTest run started
 ldTest org.scalajs.junit.AsyncTest.asyncFailure started
 leTest org.scalajs.junit.AsyncTest.asyncFailure failed: java.lang.IllegalArgumentException: null, took <TIME>
-e2org.scalajs.junit.AsyncTest.asyncFailure::java.lang.IllegalArgumentException
+e2org.scalajs.junit.AsyncTest.asyncFailure::java.lang.IllegalArgumentException::true
 ldTest org.scalajs.junit.AsyncTest.asyncFailure finished, took <TIME>
 ldTest org.scalajs.junit.AsyncTest.expectedException started
 ldTest org.scalajs.junit.AsyncTest.expectedException finished, took <TIME>
-e0org.scalajs.junit.AsyncTest.expectedException::
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 ldTest org.scalajs.junit.AsyncTest.success started
 ldTest org.scalajs.junit.AsyncTest.success finished, took <TIME>
-e0org.scalajs.junit.AsyncTest.success::
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 ldTest run finished: 1 failed, 0 ignored, 3 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_n.txt b/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_n.txt
index a4e8bbbf30..caa0e4bf71 100644
--- a/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_n.txt
+++ b/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_n.txt
@@ -1,13 +1,13 @@
 ldTest run started
 ldTest org.scalajs.junit.AsyncTest.asyncFailure started
 leTest org.scalajs.junit.AsyncTest.asyncFailure failed: java.lang.IllegalArgumentException: null, took <TIME>
-e2org.scalajs.junit.AsyncTest.asyncFailure::java.lang.IllegalArgumentException
+e2org.scalajs.junit.AsyncTest.asyncFailure::java.lang.IllegalArgumentException::true
 ldTest org.scalajs.junit.AsyncTest.asyncFailure finished, took <TIME>
 ldTest org.scalajs.junit.AsyncTest.expectedException started
 ldTest org.scalajs.junit.AsyncTest.expectedException finished, took <TIME>
-e0org.scalajs.junit.AsyncTest.expectedException::
+e0org.scalajs.junit.AsyncTest.expectedException::::true
 ldTest org.scalajs.junit.AsyncTest.success started
 ldTest org.scalajs.junit.AsyncTest.success finished, took <TIME>
-e0org.scalajs.junit.AsyncTest.success::
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 ldTest run finished: 1 failed, 0 ignored, 3 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_na.txt b/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_na.txt
index a4e8bbbf30..caa0e4bf71 100644
--- a/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_na.txt
+++ b/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_na.txt
@@ -1,13 +1,13 @@
 ldTest run started
 ldTest org.scalajs.junit.AsyncTest.asyncFailure started
 leTest org.scalajs.junit.AsyncTest.asyncFailure failed: java.lang.IllegalArgumentException: null, took <TIME>
-e2org.scalajs.junit.AsyncTest.asyncFailure::java.lang.IllegalArgumentException
+e2org.scalajs.junit.AsyncTest.asyncFailure::java.lang.IllegalArgumentException::true
 ldTest org.scalajs.junit.AsyncTest.asyncFailure finished, took <TIME>
 ldTest org.scalajs.junit.AsyncTest.expectedException started
 ldTest org.scalajs.junit.AsyncTest.expectedException finished, took <TIME>
-e0org.scalajs.junit.AsyncTest.expectedException::
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 ldTest org.scalajs.junit.AsyncTest.success started
 ldTest org.scalajs.junit.AsyncTest.success finished, took <TIME>
-e0org.scalajs.junit.AsyncTest.success::
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 ldTest run finished: 1 failed, 0 ignored, 3 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_nv.txt b/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_nv.txt
index 6583d223dc..c96ea87db5 100644
--- a/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_nv.txt
+++ b/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_nv.txt
@@ -1,13 +1,13 @@
 liTest run started
 liTest org.scalajs.junit.AsyncTest.asyncFailure started
 leTest org.scalajs.junit.AsyncTest.asyncFailure failed: java.lang.IllegalArgumentException: null, took <TIME>
-e2org.scalajs.junit.AsyncTest.asyncFailure::java.lang.IllegalArgumentException
+e2org.scalajs.junit.AsyncTest.asyncFailure::java.lang.IllegalArgumentException::true
 ldTest org.scalajs.junit.AsyncTest.asyncFailure finished, took <TIME>
 liTest org.scalajs.junit.AsyncTest.expectedException started
 ldTest org.scalajs.junit.AsyncTest.expectedException finished, took <TIME>
-e0org.scalajs.junit.AsyncTest.expectedException::
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 liTest org.scalajs.junit.AsyncTest.success started
 ldTest org.scalajs.junit.AsyncTest.success finished, took <TIME>
-e0org.scalajs.junit.AsyncTest.success::
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 liTest run finished: 1 failed, 0 ignored, 3 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_nva.txt b/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_nva.txt
index 6583d223dc..c96ea87db5 100644
--- a/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_nva.txt
+++ b/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_nva.txt
@@ -1,13 +1,13 @@
 liTest run started
 liTest org.scalajs.junit.AsyncTest.asyncFailure started
 leTest org.scalajs.junit.AsyncTest.asyncFailure failed: java.lang.IllegalArgumentException: null, took <TIME>
-e2org.scalajs.junit.AsyncTest.asyncFailure::java.lang.IllegalArgumentException
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 ldTest org.scalajs.junit.AsyncTest.asyncFailure finished, took <TIME>
 liTest org.scalajs.junit.AsyncTest.expectedException started
 ldTest org.scalajs.junit.AsyncTest.expectedException finished, took <TIME>
-e0org.scalajs.junit.AsyncTest.expectedException::
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 liTest org.scalajs.junit.AsyncTest.success started
 ldTest org.scalajs.junit.AsyncTest.success finished, took <TIME>
-e0org.scalajs.junit.AsyncTest.success::
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 liTest run finished: 1 failed, 0 ignored, 3 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_nvc.txt b/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_nvc.txt
index ea55b9d9a4..5a59cef480 100644
--- a/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_nvc.txt
+++ b/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_nvc.txt
@@ -1,13 +1,13 @@
 liTest run started
 liTest org.scalajs.junit.AsyncTest.asyncFailure started
 leTest org.scalajs.junit.AsyncTest.asyncFailure failed: null, took <TIME>
-e2org.scalajs.junit.AsyncTest.asyncFailure::java.lang.IllegalArgumentException
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 ldTest org.scalajs.junit.AsyncTest.asyncFailure finished, took <TIME>
 liTest org.scalajs.junit.AsyncTest.expectedException started
 ldTest org.scalajs.junit.AsyncTest.expectedException finished, took <TIME>
-e0org.scalajs.junit.AsyncTest.expectedException::
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 liTest org.scalajs.junit.AsyncTest.success started
 ldTest org.scalajs.junit.AsyncTest.success finished, took <TIME>
-e0org.scalajs.junit.AsyncTest.success::
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 liTest run finished: 1 failed, 0 ignored, 3 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_nvca.txt b/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_nvca.txt
index ea55b9d9a4..5a59cef480 100644
--- a/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_nvca.txt
+++ b/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_nvca.txt
@@ -1,13 +1,13 @@
 liTest run started
 liTest org.scalajs.junit.AsyncTest.asyncFailure started
 leTest org.scalajs.junit.AsyncTest.asyncFailure failed: null, took <TIME>
-e2org.scalajs.junit.AsyncTest.asyncFailure::java.lang.IllegalArgumentException
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 ldTest org.scalajs.junit.AsyncTest.asyncFailure finished, took <TIME>
 liTest org.scalajs.junit.AsyncTest.expectedException started
 ldTest org.scalajs.junit.AsyncTest.expectedException finished, took <TIME>
-e0org.scalajs.junit.AsyncTest.expectedException::
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 liTest org.scalajs.junit.AsyncTest.success started
 ldTest org.scalajs.junit.AsyncTest.success finished, took <TIME>
-e0org.scalajs.junit.AsyncTest.success::
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 liTest run finished: 1 failed, 0 ignored, 3 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_v.txt b/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_v.txt
index 4196d95050..45efc12355 100644
--- a/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_v.txt
+++ b/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_v.txt
@@ -1,13 +1,13 @@
 liTest run started
 liTest org.scalajs.junit.AsyncTest.asyncFailure started
 leTest org.scalajs.junit.AsyncTest.asyncFailure failed: java.lang.IllegalArgumentException: null, took <TIME>
-e2org.scalajs.junit.AsyncTest.asyncFailure::java.lang.IllegalArgumentException
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 ldTest org.scalajs.junit.AsyncTest.asyncFailure finished, took <TIME>
 liTest org.scalajs.junit.AsyncTest.expectedException started
 ldTest org.scalajs.junit.AsyncTest.expectedException finished, took <TIME>
-e0org.scalajs.junit.AsyncTest.expectedException::
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 liTest org.scalajs.junit.AsyncTest.success started
 ldTest org.scalajs.junit.AsyncTest.success finished, took <TIME>
-e0org.scalajs.junit.AsyncTest.success::
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 liTest run finished: 1 failed, 0 ignored, 3 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_va.txt b/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_va.txt
index 4196d95050..45efc12355 100644
--- a/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_va.txt
+++ b/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_va.txt
@@ -1,13 +1,13 @@
 liTest run started
 liTest org.scalajs.junit.AsyncTest.asyncFailure started
 leTest org.scalajs.junit.AsyncTest.asyncFailure failed: java.lang.IllegalArgumentException: null, took <TIME>
-e2org.scalajs.junit.AsyncTest.asyncFailure::java.lang.IllegalArgumentException
+e2org.scalajs.junit.AsyncTest.asyncFailure::java.lang.IllegalArgumentException::true
 ldTest org.scalajs.junit.AsyncTest.asyncFailure finished, took <TIME>
 liTest org.scalajs.junit.AsyncTest.expectedException started
 ldTest org.scalajs.junit.AsyncTest.expectedException finished, took <TIME>
-e0org.scalajs.junit.AsyncTest.expectedException::
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 liTest org.scalajs.junit.AsyncTest.success started
 ldTest org.scalajs.junit.AsyncTest.success finished, took <TIME>
-e0org.scalajs.junit.AsyncTest.success::
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 liTest run finished: 1 failed, 0 ignored, 3 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_vc.txt b/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_vc.txt
index a87fc04a85..a1081f5071 100644
--- a/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_vc.txt
+++ b/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_vc.txt
@@ -1,13 +1,13 @@
 liTest run started
 liTest org.scalajs.junit.AsyncTest.asyncFailure started
 leTest org.scalajs.junit.AsyncTest.asyncFailure failed: null, took <TIME>
-e2org.scalajs.junit.AsyncTest.asyncFailure::java.lang.IllegalArgumentException
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 ldTest org.scalajs.junit.AsyncTest.asyncFailure finished, took <TIME>
 liTest org.scalajs.junit.AsyncTest.expectedException started
 ldTest org.scalajs.junit.AsyncTest.expectedException finished, took <TIME>
-e0org.scalajs.junit.AsyncTest.expectedException::
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 liTest org.scalajs.junit.AsyncTest.success started
 ldTest org.scalajs.junit.AsyncTest.success finished, took <TIME>
-e0org.scalajs.junit.AsyncTest.success::
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 liTest run finished: 1 failed, 0 ignored, 3 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_vs.txt b/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_vs.txt
index 4196d95050..45efc12355 100644
--- a/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_vs.txt
+++ b/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_vs.txt
@@ -1,13 +1,13 @@
 liTest run started
 liTest org.scalajs.junit.AsyncTest.asyncFailure started
 leTest org.scalajs.junit.AsyncTest.asyncFailure failed: java.lang.IllegalArgumentException: null, took <TIME>
-e2org.scalajs.junit.AsyncTest.asyncFailure::java.lang.IllegalArgumentException
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 ldTest org.scalajs.junit.AsyncTest.asyncFailure finished, took <TIME>
 liTest org.scalajs.junit.AsyncTest.expectedException started
 ldTest org.scalajs.junit.AsyncTest.expectedException finished, took <TIME>
-e0org.scalajs.junit.AsyncTest.expectedException::
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 liTest org.scalajs.junit.AsyncTest.success started
 ldTest org.scalajs.junit.AsyncTest.success finished, took <TIME>
-e0org.scalajs.junit.AsyncTest.success::
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 liTest run finished: 1 failed, 0 ignored, 3 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_vsn.txt b/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_vsn.txt
index 6583d223dc..c96ea87db5 100644
--- a/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_vsn.txt
+++ b/junit-test/outputs/org/scalajs/junit/AsyncTestAssertions_vsn.txt
@@ -1,13 +1,13 @@
 liTest run started
 liTest org.scalajs.junit.AsyncTest.asyncFailure started
 leTest org.scalajs.junit.AsyncTest.asyncFailure failed: java.lang.IllegalArgumentException: null, took <TIME>
-e2org.scalajs.junit.AsyncTest.asyncFailure::java.lang.IllegalArgumentException
+e2org.scalajs.junit.AsyncTest.asyncFailure::java.lang.IllegalArgumentException::true
 ldTest org.scalajs.junit.AsyncTest.asyncFailure finished, took <TIME>
 liTest org.scalajs.junit.AsyncTest.expectedException started
 ldTest org.scalajs.junit.AsyncTest.expectedException finished, took <TIME>
-e0org.scalajs.junit.AsyncTest.expectedException::
+e0org.scalajs.junit.AsyncTest.expectedException::::true
 liTest org.scalajs.junit.AsyncTest.success started
 ldTest org.scalajs.junit.AsyncTest.success finished, took <TIME>
-e0org.scalajs.junit.AsyncTest.success::
+e0org.scalajs.junit.AsyncTest.success::::true
 liTest run finished: 1 failed, 0 ignored, 3 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_.txt b/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_.txt
index 9b12c6c05e..27f1658a67 100644
--- a/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_.txt
+++ b/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_.txt
@@ -1,6 +1,6 @@
 ldTest run started
 ldTest org.scalajs.junit.BeforeAndAfterTest.test started
 ldTest org.scalajs.junit.BeforeAndAfterTest.test finished, took <TIME>
-e0org.scalajs.junit.BeforeAndAfterTest.test::
+e0org.scalajs.junit.BeforeAndAfterTest.test::::true
 ldTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_a.txt b/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_a.txt
index 9b12c6c05e..27f1658a67 100644
--- a/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_a.txt
+++ b/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_a.txt
@@ -1,6 +1,6 @@
 ldTest run started
 ldTest org.scalajs.junit.BeforeAndAfterTest.test started
 ldTest org.scalajs.junit.BeforeAndAfterTest.test finished, took <TIME>
-e0org.scalajs.junit.BeforeAndAfterTest.test::
+e0org.scalajs.junit.BeforeAndAfterTest.test::::true
 ldTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_n.txt b/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_n.txt
index 137e029bcb..244fc3af9e 100644
--- a/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_n.txt
+++ b/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_n.txt
@@ -1,6 +1,6 @@
 ldTest run started
 ldTest org.scalajs.junit.BeforeAndAfterTest.test started
 ldTest org.scalajs.junit.BeforeAndAfterTest.test finished, took <TIME>
-e0org.scalajs.junit.BeforeAndAfterTest.test::
+e0org.scalajs.junit.BeforeAndAfterTest.test::::true
 ldTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_na.txt b/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_na.txt
index 137e029bcb..244fc3af9e 100644
--- a/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_na.txt
+++ b/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_na.txt
@@ -1,6 +1,6 @@
 ldTest run started
 ldTest org.scalajs.junit.BeforeAndAfterTest.test started
 ldTest org.scalajs.junit.BeforeAndAfterTest.test finished, took <TIME>
-e0org.scalajs.junit.BeforeAndAfterTest.test::
+e0org.scalajs.junit.BeforeAndAfterTest.test::::true
 ldTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_nv.txt b/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_nv.txt
index d018185503..2942f51832 100644
--- a/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_nv.txt
+++ b/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_nv.txt
@@ -1,6 +1,6 @@
 liTest run started
 liTest org.scalajs.junit.BeforeAndAfterTest.test started
 ldTest org.scalajs.junit.BeforeAndAfterTest.test finished, took <TIME>
-e0org.scalajs.junit.BeforeAndAfterTest.test::
+e0org.scalajs.junit.BeforeAndAfterTest.test::::true
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_nva.txt b/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_nva.txt
index d018185503..2942f51832 100644
--- a/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_nva.txt
+++ b/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_nva.txt
@@ -1,6 +1,6 @@
 liTest run started
 liTest org.scalajs.junit.BeforeAndAfterTest.test started
 ldTest org.scalajs.junit.BeforeAndAfterTest.test finished, took <TIME>
-e0org.scalajs.junit.BeforeAndAfterTest.test::
+e0org.scalajs.junit.BeforeAndAfterTest.test::::true
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_nvc.txt b/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_nvc.txt
index d018185503..2942f51832 100644
--- a/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_nvc.txt
+++ b/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_nvc.txt
@@ -1,6 +1,6 @@
 liTest run started
 liTest org.scalajs.junit.BeforeAndAfterTest.test started
 ldTest org.scalajs.junit.BeforeAndAfterTest.test finished, took <TIME>
-e0org.scalajs.junit.BeforeAndAfterTest.test::
+e0org.scalajs.junit.BeforeAndAfterTest.test::::true
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_nvca.txt b/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_nvca.txt
index d018185503..2942f51832 100644
--- a/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_nvca.txt
+++ b/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_nvca.txt
@@ -1,6 +1,6 @@
 liTest run started
 liTest org.scalajs.junit.BeforeAndAfterTest.test started
 ldTest org.scalajs.junit.BeforeAndAfterTest.test finished, took <TIME>
-e0org.scalajs.junit.BeforeAndAfterTest.test::
+e0org.scalajs.junit.BeforeAndAfterTest.test::::true
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_v.txt b/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_v.txt
index e1003375a5..7ac8e76320 100644
--- a/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_v.txt
+++ b/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_v.txt
@@ -1,6 +1,6 @@
 liTest run started
 liTest org.scalajs.junit.BeforeAndAfterTest.test started
 ldTest org.scalajs.junit.BeforeAndAfterTest.test finished, took <TIME>
-e0org.scalajs.junit.BeforeAndAfterTest.test::
+e0org.scalajs.junit.BeforeAndAfterTest.test::::true
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_va.txt b/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_va.txt
index e1003375a5..7ac8e76320 100644
--- a/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_va.txt
+++ b/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_va.txt
@@ -1,6 +1,6 @@
 liTest run started
 liTest org.scalajs.junit.BeforeAndAfterTest.test started
 ldTest org.scalajs.junit.BeforeAndAfterTest.test finished, took <TIME>
-e0org.scalajs.junit.BeforeAndAfterTest.test::
+e0org.scalajs.junit.BeforeAndAfterTest.test::::true
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_vc.txt b/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_vc.txt
index e1003375a5..7ac8e76320 100644
--- a/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_vc.txt
+++ b/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_vc.txt
@@ -1,6 +1,6 @@
 liTest run started
 liTest org.scalajs.junit.BeforeAndAfterTest.test started
 ldTest org.scalajs.junit.BeforeAndAfterTest.test finished, took <TIME>
-e0org.scalajs.junit.BeforeAndAfterTest.test::
+e0org.scalajs.junit.BeforeAndAfterTest.test::::true
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_vs.txt b/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_vs.txt
index e1003375a5..7ac8e76320 100644
--- a/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_vs.txt
+++ b/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_vs.txt
@@ -1,6 +1,6 @@
 liTest run started
 liTest org.scalajs.junit.BeforeAndAfterTest.test started
 ldTest org.scalajs.junit.BeforeAndAfterTest.test finished, took <TIME>
-e0org.scalajs.junit.BeforeAndAfterTest.test::
+e0org.scalajs.junit.BeforeAndAfterTest.test::::true
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_vsn.txt b/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_vsn.txt
index d018185503..2942f51832 100644
--- a/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_vsn.txt
+++ b/junit-test/outputs/org/scalajs/junit/BeforeAndAfterTestAssertions_vsn.txt
@@ -1,6 +1,6 @@
 liTest run started
 liTest org.scalajs.junit.BeforeAndAfterTest.test started
 ldTest org.scalajs.junit.BeforeAndAfterTest.test finished, took <TIME>
-e0org.scalajs.junit.BeforeAndAfterTest.test::
+e0org.scalajs.junit.BeforeAndAfterTest.test::::true
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_.txt b/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_.txt
index 3e25af9a55..8756727159 100644
--- a/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_.txt
+++ b/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_.txt
@@ -1,5 +1,5 @@
 ldTest run started
 lwTest assumption in test org.scalajs.junit.BeforeAssumeFailTest failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.BeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.BeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest run finished: 0 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_a.txt b/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_a.txt
index 3e25af9a55..8756727159 100644
--- a/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_a.txt
+++ b/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_a.txt
@@ -1,5 +1,5 @@
 ldTest run started
 lwTest assumption in test org.scalajs.junit.BeforeAssumeFailTest failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.BeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.BeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest run finished: 0 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_n.txt b/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_n.txt
index 6cff2ae7b5..ab1bd9276e 100644
--- a/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_n.txt
+++ b/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_n.txt
@@ -1,5 +1,5 @@
 ldTest run started
 lwTest assumption in test org.scalajs.junit.BeforeAssumeFailTest failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.BeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.BeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest run finished: 0 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_na.txt b/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_na.txt
index 6cff2ae7b5..ab1bd9276e 100644
--- a/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_na.txt
+++ b/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_na.txt
@@ -1,5 +1,5 @@
 ldTest run started
 lwTest assumption in test org.scalajs.junit.BeforeAssumeFailTest failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.BeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.BeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest run finished: 0 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_nv.txt b/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_nv.txt
index e2195fcc62..b480f73ca5 100644
--- a/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_nv.txt
+++ b/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_nv.txt
@@ -1,5 +1,5 @@
 liTest run started
 lwTest assumption in test org.scalajs.junit.BeforeAssumeFailTest failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.BeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.BeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass::true
 liTest run finished: 0 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_nva.txt b/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_nva.txt
index e2195fcc62..b480f73ca5 100644
--- a/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_nva.txt
+++ b/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_nva.txt
@@ -1,5 +1,5 @@
 liTest run started
 lwTest assumption in test org.scalajs.junit.BeforeAssumeFailTest failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.BeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.BeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass::true
 liTest run finished: 0 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_nvc.txt b/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_nvc.txt
index 02bee59865..da1919c99e 100644
--- a/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_nvc.txt
+++ b/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_nvc.txt
@@ -1,5 +1,5 @@
 liTest run started
 lwTest assumption in test org.scalajs.junit.BeforeAssumeFailTest failed: This assume should not pass, took <TIME>
-e3org.scalajs.junit.BeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.BeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass::true
 liTest run finished: 0 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_nvca.txt b/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_nvca.txt
index 02bee59865..da1919c99e 100644
--- a/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_nvca.txt
+++ b/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_nvca.txt
@@ -1,5 +1,5 @@
 liTest run started
 lwTest assumption in test org.scalajs.junit.BeforeAssumeFailTest failed: This assume should not pass, took <TIME>
-e3org.scalajs.junit.BeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.BeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass::true
 liTest run finished: 0 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_v.txt b/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_v.txt
index c3b0f4cbd0..ab3871d7fb 100644
--- a/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_v.txt
+++ b/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_v.txt
@@ -1,5 +1,5 @@
 liTest run started
 lwTest assumption in test org.scalajs.junit.BeforeAssumeFailTest failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.BeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.BeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass::true
 liTest run finished: 0 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_va.txt b/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_va.txt
index c3b0f4cbd0..ab3871d7fb 100644
--- a/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_va.txt
+++ b/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_va.txt
@@ -1,5 +1,5 @@
 liTest run started
 lwTest assumption in test org.scalajs.junit.BeforeAssumeFailTest failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.BeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.BeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass::true
 liTest run finished: 0 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_vc.txt b/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_vc.txt
index fa4723fe92..17ba45a732 100644
--- a/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_vc.txt
+++ b/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_vc.txt
@@ -1,5 +1,5 @@
 liTest run started
 lwTest assumption in test org.scalajs.junit.BeforeAssumeFailTest failed: This assume should not pass, took <TIME>
-e3org.scalajs.junit.BeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.BeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass::true
 liTest run finished: 0 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_vs.txt b/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_vs.txt
index c3b0f4cbd0..ab3871d7fb 100644
--- a/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_vs.txt
+++ b/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_vs.txt
@@ -1,5 +1,5 @@
 liTest run started
 lwTest assumption in test org.scalajs.junit.BeforeAssumeFailTest failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.BeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.BeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass::true
 liTest run finished: 0 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_vsn.txt b/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_vsn.txt
index e2195fcc62..b480f73ca5 100644
--- a/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_vsn.txt
+++ b/junit-test/outputs/org/scalajs/junit/BeforeAssumeFailTestAssertions_vsn.txt
@@ -1,5 +1,5 @@
 liTest run started
 lwTest assumption in test org.scalajs.junit.BeforeAssumeFailTest failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.BeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.BeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass::true
 liTest run finished: 0 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_.txt b/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_.txt
index 60eff1daad..0fc0bf88bc 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_.txt
@@ -2,7 +2,7 @@ ldTest run started
 ldTest org.scalajs.junit.ExceptionAfterAssume.assumeFail started
 leTest org.scalajs.junit.ExceptionAfterAssume.assumeFail failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
-e2org.scalajs.junit.ExceptionAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures
+e2org.scalajs.junit.ExceptionAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures::true
 leTest org.scalajs.junit.ExceptionAfterAssume.assumeFail failed: java.lang.IllegalArgumentException: after() must be called, took <TIME>
 ldTest org.scalajs.junit.ExceptionAfterAssume.assumeFail finished, took <TIME>
 ldTest run finished: 2 failed, 0 ignored, 1 total, <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_a.txt b/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_a.txt
index 60eff1daad..0fc0bf88bc 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_a.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_a.txt
@@ -2,7 +2,7 @@ ldTest run started
 ldTest org.scalajs.junit.ExceptionAfterAssume.assumeFail started
 leTest org.scalajs.junit.ExceptionAfterAssume.assumeFail failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
-e2org.scalajs.junit.ExceptionAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures
+e2org.scalajs.junit.ExceptionAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures::true
 leTest org.scalajs.junit.ExceptionAfterAssume.assumeFail failed: java.lang.IllegalArgumentException: after() must be called, took <TIME>
 ldTest org.scalajs.junit.ExceptionAfterAssume.assumeFail finished, took <TIME>
 ldTest run finished: 2 failed, 0 ignored, 1 total, <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_n.txt b/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_n.txt
index 326ed5462d..826ff3fd1e 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_n.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_n.txt
@@ -2,7 +2,7 @@ ldTest run started
 ldTest org.scalajs.junit.ExceptionAfterAssume.assumeFail started
 leTest org.scalajs.junit.ExceptionAfterAssume.assumeFail failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
-e2org.scalajs.junit.ExceptionAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures
+e2org.scalajs.junit.ExceptionAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures::true
 leTest org.scalajs.junit.ExceptionAfterAssume.assumeFail failed: java.lang.IllegalArgumentException: after() must be called, took <TIME>
 ldTest org.scalajs.junit.ExceptionAfterAssume.assumeFail finished, took <TIME>
 ldTest run finished: 2 failed, 0 ignored, 1 total, <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_na.txt b/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_na.txt
index 326ed5462d..826ff3fd1e 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_na.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_na.txt
@@ -2,7 +2,7 @@ ldTest run started
 ldTest org.scalajs.junit.ExceptionAfterAssume.assumeFail started
 leTest org.scalajs.junit.ExceptionAfterAssume.assumeFail failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
-e2org.scalajs.junit.ExceptionAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures
+e2org.scalajs.junit.ExceptionAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures::true
 leTest org.scalajs.junit.ExceptionAfterAssume.assumeFail failed: java.lang.IllegalArgumentException: after() must be called, took <TIME>
 ldTest org.scalajs.junit.ExceptionAfterAssume.assumeFail finished, took <TIME>
 ldTest run finished: 2 failed, 0 ignored, 1 total, <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_nv.txt b/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_nv.txt
index 2299664b94..5e134537af 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_nv.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_nv.txt
@@ -2,7 +2,7 @@ liTest run started
 liTest org.scalajs.junit.ExceptionAfterAssume.assumeFail started
 leTest org.scalajs.junit.ExceptionAfterAssume.assumeFail failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
-e2org.scalajs.junit.ExceptionAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures
+e2org.scalajs.junit.ExceptionAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures::true
 leTest org.scalajs.junit.ExceptionAfterAssume.assumeFail failed: java.lang.IllegalArgumentException: after() must be called, took <TIME>
 ldTest org.scalajs.junit.ExceptionAfterAssume.assumeFail finished, took <TIME>
 liTest run finished: 2 failed, 0 ignored, 1 total, <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_nva.txt b/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_nva.txt
index 2299664b94..5e134537af 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_nva.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_nva.txt
@@ -2,7 +2,7 @@ liTest run started
 liTest org.scalajs.junit.ExceptionAfterAssume.assumeFail started
 leTest org.scalajs.junit.ExceptionAfterAssume.assumeFail failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
-e2org.scalajs.junit.ExceptionAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures
+e2org.scalajs.junit.ExceptionAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures::true
 leTest org.scalajs.junit.ExceptionAfterAssume.assumeFail failed: java.lang.IllegalArgumentException: after() must be called, took <TIME>
 ldTest org.scalajs.junit.ExceptionAfterAssume.assumeFail finished, took <TIME>
 liTest run finished: 2 failed, 0 ignored, 1 total, <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_nvc.txt b/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_nvc.txt
index 89f146aa5b..1e4ba0385e 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_nvc.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_nvc.txt
@@ -2,7 +2,7 @@ liTest run started
 liTest org.scalajs.junit.ExceptionAfterAssume.assumeFail started
 leTest org.scalajs.junit.ExceptionAfterAssume.assumeFail failed: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
-e2org.scalajs.junit.ExceptionAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures
+e2org.scalajs.junit.ExceptionAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures::true
 leTest org.scalajs.junit.ExceptionAfterAssume.assumeFail failed: after() must be called, took <TIME>
 ldTest org.scalajs.junit.ExceptionAfterAssume.assumeFail finished, took <TIME>
 liTest run finished: 2 failed, 0 ignored, 1 total, <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_nvca.txt b/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_nvca.txt
index 89f146aa5b..1e4ba0385e 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_nvca.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_nvca.txt
@@ -2,7 +2,7 @@ liTest run started
 liTest org.scalajs.junit.ExceptionAfterAssume.assumeFail started
 leTest org.scalajs.junit.ExceptionAfterAssume.assumeFail failed: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
-e2org.scalajs.junit.ExceptionAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures
+e2org.scalajs.junit.ExceptionAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures::true
 leTest org.scalajs.junit.ExceptionAfterAssume.assumeFail failed: after() must be called, took <TIME>
 ldTest org.scalajs.junit.ExceptionAfterAssume.assumeFail finished, took <TIME>
 liTest run finished: 2 failed, 0 ignored, 1 total, <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_v.txt b/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_v.txt
index 9565096712..0db509fa0b 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_v.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_v.txt
@@ -2,7 +2,7 @@ liTest run started
 liTest org.scalajs.junit.ExceptionAfterAssume.assumeFail started
 leTest org.scalajs.junit.ExceptionAfterAssume.assumeFail failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
-e2org.scalajs.junit.ExceptionAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures
+e2org.scalajs.junit.ExceptionAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures::true
 leTest org.scalajs.junit.ExceptionAfterAssume.assumeFail failed: java.lang.IllegalArgumentException: after() must be called, took <TIME>
 ldTest org.scalajs.junit.ExceptionAfterAssume.assumeFail finished, took <TIME>
 liTest run finished: 2 failed, 0 ignored, 1 total, <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_va.txt b/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_va.txt
index 9565096712..0db509fa0b 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_va.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_va.txt
@@ -2,7 +2,7 @@ liTest run started
 liTest org.scalajs.junit.ExceptionAfterAssume.assumeFail started
 leTest org.scalajs.junit.ExceptionAfterAssume.assumeFail failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
-e2org.scalajs.junit.ExceptionAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures
+e2org.scalajs.junit.ExceptionAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures::true
 leTest org.scalajs.junit.ExceptionAfterAssume.assumeFail failed: java.lang.IllegalArgumentException: after() must be called, took <TIME>
 ldTest org.scalajs.junit.ExceptionAfterAssume.assumeFail finished, took <TIME>
 liTest run finished: 2 failed, 0 ignored, 1 total, <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_vc.txt b/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_vc.txt
index 83d810b8c7..111f6ec673 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_vc.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_vc.txt
@@ -2,7 +2,7 @@ liTest run started
 liTest org.scalajs.junit.ExceptionAfterAssume.assumeFail started
 leTest org.scalajs.junit.ExceptionAfterAssume.assumeFail failed: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
-e2org.scalajs.junit.ExceptionAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures
+e2org.scalajs.junit.ExceptionAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures::true
 leTest org.scalajs.junit.ExceptionAfterAssume.assumeFail failed: after() must be called, took <TIME>
 ldTest org.scalajs.junit.ExceptionAfterAssume.assumeFail finished, took <TIME>
 liTest run finished: 2 failed, 0 ignored, 1 total, <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_vs.txt b/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_vs.txt
index 9565096712..0db509fa0b 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_vs.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_vs.txt
@@ -2,7 +2,7 @@ liTest run started
 liTest org.scalajs.junit.ExceptionAfterAssume.assumeFail started
 leTest org.scalajs.junit.ExceptionAfterAssume.assumeFail failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
-e2org.scalajs.junit.ExceptionAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures
+e2org.scalajs.junit.ExceptionAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures::true
 leTest org.scalajs.junit.ExceptionAfterAssume.assumeFail failed: java.lang.IllegalArgumentException: after() must be called, took <TIME>
 ldTest org.scalajs.junit.ExceptionAfterAssume.assumeFail finished, took <TIME>
 liTest run finished: 2 failed, 0 ignored, 1 total, <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_vsn.txt b/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_vsn.txt
index 2299664b94..5e134537af 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_vsn.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionAfterAssumeAssertions_vsn.txt
@@ -2,7 +2,7 @@ liTest run started
 liTest org.scalajs.junit.ExceptionAfterAssume.assumeFail started
 leTest org.scalajs.junit.ExceptionAfterAssume.assumeFail failed: org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures, took <TIME>
 leCaused by: org.junit.AssumptionViolatedException: This assume should not pass
-e2org.scalajs.junit.ExceptionAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures
+e2org.scalajs.junit.ExceptionAfterAssume.assumeFail::org.junit.TestCouldNotBeSkippedException: Test could not be skipped due to other failures::true
 leTest org.scalajs.junit.ExceptionAfterAssume.assumeFail failed: java.lang.IllegalArgumentException: after() must be called, took <TIME>
 ldTest org.scalajs.junit.ExceptionAfterAssume.assumeFail finished, took <TIME>
 liTest run finished: 2 failed, 0 ignored, 1 total, <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_.txt b/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_.txt
index 9297a9663c..36fe5cf33c 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_.txt
@@ -1,11 +1,11 @@
 ldTest run started
 ldTest org.scalajs.junit.ExceptionAfterClass.test1 started
 ldTest org.scalajs.junit.ExceptionAfterClass.test1 finished, took <TIME>
-e0org.scalajs.junit.ExceptionAfterClass.test1::
+e0org.scalajs.junit.ExceptionAfterClass.test1::::true
 ldTest org.scalajs.junit.ExceptionAfterClass.test2 started
 ldTest org.scalajs.junit.ExceptionAfterClass.test2 finished, took <TIME>
-e0org.scalajs.junit.ExceptionAfterClass.test2::
+e0org.scalajs.junit.ExceptionAfterClass.test2::::true
 leTest org.scalajs.junit.ExceptionAfterClass failed: java.lang.IllegalArgumentException: foo, took <TIME>
-e2org.scalajs.junit.ExceptionAfterClass::java.lang.IllegalArgumentException: foo
+e2org.scalajs.junit.ExceptionAfterClass::java.lang.IllegalArgumentException: foo::true
 ldTest run finished: 1 failed, 0 ignored, 2 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_a.txt b/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_a.txt
index 9297a9663c..36fe5cf33c 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_a.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_a.txt
@@ -1,11 +1,11 @@
 ldTest run started
 ldTest org.scalajs.junit.ExceptionAfterClass.test1 started
 ldTest org.scalajs.junit.ExceptionAfterClass.test1 finished, took <TIME>
-e0org.scalajs.junit.ExceptionAfterClass.test1::
+e0org.scalajs.junit.ExceptionAfterClass.test1::::true
 ldTest org.scalajs.junit.ExceptionAfterClass.test2 started
 ldTest org.scalajs.junit.ExceptionAfterClass.test2 finished, took <TIME>
-e0org.scalajs.junit.ExceptionAfterClass.test2::
+e0org.scalajs.junit.ExceptionAfterClass.test2::::true
 leTest org.scalajs.junit.ExceptionAfterClass failed: java.lang.IllegalArgumentException: foo, took <TIME>
-e2org.scalajs.junit.ExceptionAfterClass::java.lang.IllegalArgumentException: foo
+e2org.scalajs.junit.ExceptionAfterClass::java.lang.IllegalArgumentException: foo::true
 ldTest run finished: 1 failed, 0 ignored, 2 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_n.txt b/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_n.txt
index 49d2ed086c..05aeb01868 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_n.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_n.txt
@@ -1,11 +1,11 @@
 ldTest run started
 ldTest org.scalajs.junit.ExceptionAfterClass.test1 started
 ldTest org.scalajs.junit.ExceptionAfterClass.test1 finished, took <TIME>
-e0org.scalajs.junit.ExceptionAfterClass.test1::
+e0org.scalajs.junit.ExceptionAfterClass.test1::::true
 ldTest org.scalajs.junit.ExceptionAfterClass.test2 started
 ldTest org.scalajs.junit.ExceptionAfterClass.test2 finished, took <TIME>
-e0org.scalajs.junit.ExceptionAfterClass.test2::
+e0org.scalajs.junit.ExceptionAfterClass.test2::::true
 leTest org.scalajs.junit.ExceptionAfterClass failed: java.lang.IllegalArgumentException: foo, took <TIME>
-e2org.scalajs.junit.ExceptionAfterClass::java.lang.IllegalArgumentException: foo
+e2org.scalajs.junit.ExceptionAfterClass::java.lang.IllegalArgumentException: foo::true
 ldTest run finished: 1 failed, 0 ignored, 2 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_na.txt b/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_na.txt
index 49d2ed086c..05aeb01868 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_na.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_na.txt
@@ -1,11 +1,11 @@
 ldTest run started
 ldTest org.scalajs.junit.ExceptionAfterClass.test1 started
 ldTest org.scalajs.junit.ExceptionAfterClass.test1 finished, took <TIME>
-e0org.scalajs.junit.ExceptionAfterClass.test1::
+e0org.scalajs.junit.ExceptionAfterClass.test1::::true
 ldTest org.scalajs.junit.ExceptionAfterClass.test2 started
 ldTest org.scalajs.junit.ExceptionAfterClass.test2 finished, took <TIME>
-e0org.scalajs.junit.ExceptionAfterClass.test2::
+e0org.scalajs.junit.ExceptionAfterClass.test2::::true
 leTest org.scalajs.junit.ExceptionAfterClass failed: java.lang.IllegalArgumentException: foo, took <TIME>
-e2org.scalajs.junit.ExceptionAfterClass::java.lang.IllegalArgumentException: foo
+e2org.scalajs.junit.ExceptionAfterClass::java.lang.IllegalArgumentException: foo::true
 ldTest run finished: 1 failed, 0 ignored, 2 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_nv.txt b/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_nv.txt
index cc8d30ef2c..2a6e8ff48c 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_nv.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_nv.txt
@@ -1,11 +1,11 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionAfterClass.test1 started
 ldTest org.scalajs.junit.ExceptionAfterClass.test1 finished, took <TIME>
-e0org.scalajs.junit.ExceptionAfterClass.test1::
+e0org.scalajs.junit.ExceptionAfterClass.test1::::true
 liTest org.scalajs.junit.ExceptionAfterClass.test2 started
 ldTest org.scalajs.junit.ExceptionAfterClass.test2 finished, took <TIME>
-e0org.scalajs.junit.ExceptionAfterClass.test2::
+e0org.scalajs.junit.ExceptionAfterClass.test2::::true
 leTest org.scalajs.junit.ExceptionAfterClass failed: java.lang.IllegalArgumentException: foo, took <TIME>
-e2org.scalajs.junit.ExceptionAfterClass::java.lang.IllegalArgumentException: foo
+e2org.scalajs.junit.ExceptionAfterClass::java.lang.IllegalArgumentException: foo::true
 liTest run finished: 1 failed, 0 ignored, 2 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_nva.txt b/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_nva.txt
index cc8d30ef2c..2a6e8ff48c 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_nva.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_nva.txt
@@ -1,11 +1,11 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionAfterClass.test1 started
 ldTest org.scalajs.junit.ExceptionAfterClass.test1 finished, took <TIME>
-e0org.scalajs.junit.ExceptionAfterClass.test1::
+e0org.scalajs.junit.ExceptionAfterClass.test1::::true
 liTest org.scalajs.junit.ExceptionAfterClass.test2 started
 ldTest org.scalajs.junit.ExceptionAfterClass.test2 finished, took <TIME>
-e0org.scalajs.junit.ExceptionAfterClass.test2::
+e0org.scalajs.junit.ExceptionAfterClass.test2::::true
 leTest org.scalajs.junit.ExceptionAfterClass failed: java.lang.IllegalArgumentException: foo, took <TIME>
-e2org.scalajs.junit.ExceptionAfterClass::java.lang.IllegalArgumentException: foo
+e2org.scalajs.junit.ExceptionAfterClass::java.lang.IllegalArgumentException: foo::true
 liTest run finished: 1 failed, 0 ignored, 2 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_nvc.txt b/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_nvc.txt
index 03ccfa39d6..87e9bd0959 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_nvc.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_nvc.txt
@@ -1,11 +1,11 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionAfterClass.test1 started
 ldTest org.scalajs.junit.ExceptionAfterClass.test1 finished, took <TIME>
-e0org.scalajs.junit.ExceptionAfterClass.test1::
+e0org.scalajs.junit.ExceptionAfterClass.test1::::true
 liTest org.scalajs.junit.ExceptionAfterClass.test2 started
 ldTest org.scalajs.junit.ExceptionAfterClass.test2 finished, took <TIME>
-e0org.scalajs.junit.ExceptionAfterClass.test2::
+e0org.scalajs.junit.ExceptionAfterClass.test2::::true
 leTest org.scalajs.junit.ExceptionAfterClass failed: foo, took <TIME>
-e2org.scalajs.junit.ExceptionAfterClass::java.lang.IllegalArgumentException: foo
+e2org.scalajs.junit.ExceptionAfterClass::java.lang.IllegalArgumentException: foo::true
 liTest run finished: 1 failed, 0 ignored, 2 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_nvca.txt b/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_nvca.txt
index 03ccfa39d6..87e9bd0959 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_nvca.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_nvca.txt
@@ -1,11 +1,11 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionAfterClass.test1 started
 ldTest org.scalajs.junit.ExceptionAfterClass.test1 finished, took <TIME>
-e0org.scalajs.junit.ExceptionAfterClass.test1::
+e0org.scalajs.junit.ExceptionAfterClass.test1::::true
 liTest org.scalajs.junit.ExceptionAfterClass.test2 started
 ldTest org.scalajs.junit.ExceptionAfterClass.test2 finished, took <TIME>
-e0org.scalajs.junit.ExceptionAfterClass.test2::
+e0org.scalajs.junit.ExceptionAfterClass.test2::::true
 leTest org.scalajs.junit.ExceptionAfterClass failed: foo, took <TIME>
-e2org.scalajs.junit.ExceptionAfterClass::java.lang.IllegalArgumentException: foo
+e2org.scalajs.junit.ExceptionAfterClass::java.lang.IllegalArgumentException: foo::true
 liTest run finished: 1 failed, 0 ignored, 2 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_v.txt b/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_v.txt
index c27ec46ef9..f4791fbdc5 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_v.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_v.txt
@@ -1,11 +1,11 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionAfterClass.test1 started
 ldTest org.scalajs.junit.ExceptionAfterClass.test1 finished, took <TIME>
-e0org.scalajs.junit.ExceptionAfterClass.test1::
+e0org.scalajs.junit.ExceptionAfterClass.test1::::true
 liTest org.scalajs.junit.ExceptionAfterClass.test2 started
 ldTest org.scalajs.junit.ExceptionAfterClass.test2 finished, took <TIME>
-e0org.scalajs.junit.ExceptionAfterClass.test2::
+e0org.scalajs.junit.ExceptionAfterClass.test2::::true
 leTest org.scalajs.junit.ExceptionAfterClass failed: java.lang.IllegalArgumentException: foo, took <TIME>
-e2org.scalajs.junit.ExceptionAfterClass::java.lang.IllegalArgumentException: foo
+e2org.scalajs.junit.ExceptionAfterClass::java.lang.IllegalArgumentException: foo::true
 liTest run finished: 1 failed, 0 ignored, 2 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_va.txt b/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_va.txt
index c27ec46ef9..f4791fbdc5 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_va.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_va.txt
@@ -1,11 +1,11 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionAfterClass.test1 started
 ldTest org.scalajs.junit.ExceptionAfterClass.test1 finished, took <TIME>
-e0org.scalajs.junit.ExceptionAfterClass.test1::
+e0org.scalajs.junit.ExceptionAfterClass.test1::::true
 liTest org.scalajs.junit.ExceptionAfterClass.test2 started
 ldTest org.scalajs.junit.ExceptionAfterClass.test2 finished, took <TIME>
-e0org.scalajs.junit.ExceptionAfterClass.test2::
+e0org.scalajs.junit.ExceptionAfterClass.test2::::true
 leTest org.scalajs.junit.ExceptionAfterClass failed: java.lang.IllegalArgumentException: foo, took <TIME>
-e2org.scalajs.junit.ExceptionAfterClass::java.lang.IllegalArgumentException: foo
+e2org.scalajs.junit.ExceptionAfterClass::java.lang.IllegalArgumentException: foo::true
 liTest run finished: 1 failed, 0 ignored, 2 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_vc.txt b/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_vc.txt
index b3bc1ef216..7b764a560a 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_vc.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_vc.txt
@@ -1,11 +1,11 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionAfterClass.test1 started
 ldTest org.scalajs.junit.ExceptionAfterClass.test1 finished, took <TIME>
-e0org.scalajs.junit.ExceptionAfterClass.test1::
+e0org.scalajs.junit.ExceptionAfterClass.test1::::true
 liTest org.scalajs.junit.ExceptionAfterClass.test2 started
 ldTest org.scalajs.junit.ExceptionAfterClass.test2 finished, took <TIME>
-e0org.scalajs.junit.ExceptionAfterClass.test2::
+e0org.scalajs.junit.ExceptionAfterClass.test2::::true
 leTest org.scalajs.junit.ExceptionAfterClass failed: foo, took <TIME>
-e2org.scalajs.junit.ExceptionAfterClass::java.lang.IllegalArgumentException: foo
+e2org.scalajs.junit.ExceptionAfterClass::java.lang.IllegalArgumentException: foo::true
 liTest run finished: 1 failed, 0 ignored, 2 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_vs.txt b/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_vs.txt
index c27ec46ef9..f4791fbdc5 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_vs.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_vs.txt
@@ -1,11 +1,11 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionAfterClass.test1 started
 ldTest org.scalajs.junit.ExceptionAfterClass.test1 finished, took <TIME>
-e0org.scalajs.junit.ExceptionAfterClass.test1::
+e0org.scalajs.junit.ExceptionAfterClass.test1::::true
 liTest org.scalajs.junit.ExceptionAfterClass.test2 started
 ldTest org.scalajs.junit.ExceptionAfterClass.test2 finished, took <TIME>
-e0org.scalajs.junit.ExceptionAfterClass.test2::
+e0org.scalajs.junit.ExceptionAfterClass.test2::::true
 leTest org.scalajs.junit.ExceptionAfterClass failed: java.lang.IllegalArgumentException: foo, took <TIME>
-e2org.scalajs.junit.ExceptionAfterClass::java.lang.IllegalArgumentException: foo
+e2org.scalajs.junit.ExceptionAfterClass::java.lang.IllegalArgumentException: foo::true
 liTest run finished: 1 failed, 0 ignored, 2 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_vsn.txt b/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_vsn.txt
index cc8d30ef2c..2a6e8ff48c 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_vsn.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionAfterClassAssertions_vsn.txt
@@ -1,11 +1,11 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionAfterClass.test1 started
 ldTest org.scalajs.junit.ExceptionAfterClass.test1 finished, took <TIME>
-e0org.scalajs.junit.ExceptionAfterClass.test1::
+e0org.scalajs.junit.ExceptionAfterClass.test1::::true
 liTest org.scalajs.junit.ExceptionAfterClass.test2 started
 ldTest org.scalajs.junit.ExceptionAfterClass.test2 finished, took <TIME>
-e0org.scalajs.junit.ExceptionAfterClass.test2::
+e0org.scalajs.junit.ExceptionAfterClass.test2::::true
 leTest org.scalajs.junit.ExceptionAfterClass failed: java.lang.IllegalArgumentException: foo, took <TIME>
-e2org.scalajs.junit.ExceptionAfterClass::java.lang.IllegalArgumentException: foo
+e2org.scalajs.junit.ExceptionAfterClass::java.lang.IllegalArgumentException: foo::true
 liTest run finished: 1 failed, 0 ignored, 2 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_.txt b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_.txt
index 21020ec657..2a8c2a7886 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_.txt
@@ -1,6 +1,6 @@
 ldTest run started
 leTest org.scalajs.junit.ExceptionBeforeAndAfterClass failed: before, took <TIME>
-e2org.scalajs.junit.ExceptionBeforeAndAfterClass::java.lang.AssertionError: before
+e2org.scalajs.junit.ExceptionBeforeAndAfterClass::java.lang.AssertionError: before::true
 leTest org.scalajs.junit.ExceptionBeforeAndAfterClass failed: java.lang.IllegalArgumentException: after, took <TIME>
 ldTest run finished: 2 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_a.txt b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_a.txt
index 842ee1e9d3..25690bfe21 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_a.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_a.txt
@@ -1,6 +1,6 @@
 ldTest run started
 leTest org.scalajs.junit.ExceptionBeforeAndAfterClass failed: java.lang.AssertionError: before, took <TIME>
-e2org.scalajs.junit.ExceptionBeforeAndAfterClass::java.lang.AssertionError: before
+e2org.scalajs.junit.ExceptionBeforeAndAfterClass::java.lang.AssertionError: before::true
 leTest org.scalajs.junit.ExceptionBeforeAndAfterClass failed: java.lang.IllegalArgumentException: after, took <TIME>
 ldTest run finished: 2 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_n.txt b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_n.txt
index 67272652bd..2b5c63b0bc 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_n.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_n.txt
@@ -1,6 +1,6 @@
 ldTest run started
 leTest org.scalajs.junit.ExceptionBeforeAndAfterClass failed: before, took <TIME>
-e2org.scalajs.junit.ExceptionBeforeAndAfterClass::java.lang.AssertionError: before
+e2org.scalajs.junit.ExceptionBeforeAndAfterClass::java.lang.AssertionError: before::true
 leTest org.scalajs.junit.ExceptionBeforeAndAfterClass failed: java.lang.IllegalArgumentException: after, took <TIME>
 ldTest run finished: 2 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_na.txt b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_na.txt
index e31ffe9d36..458ce4c404 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_na.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_na.txt
@@ -1,6 +1,6 @@
 ldTest run started
 leTest org.scalajs.junit.ExceptionBeforeAndAfterClass failed: java.lang.AssertionError: before, took <TIME>
-e2org.scalajs.junit.ExceptionBeforeAndAfterClass::java.lang.AssertionError: before
+e2org.scalajs.junit.ExceptionBeforeAndAfterClass::java.lang.AssertionError: before::true
 leTest org.scalajs.junit.ExceptionBeforeAndAfterClass failed: java.lang.IllegalArgumentException: after, took <TIME>
 ldTest run finished: 2 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_nv.txt b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_nv.txt
index 64f96715ed..4e4090a49e 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_nv.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_nv.txt
@@ -1,6 +1,6 @@
 liTest run started
 leTest org.scalajs.junit.ExceptionBeforeAndAfterClass failed: before, took <TIME>
-e2org.scalajs.junit.ExceptionBeforeAndAfterClass::java.lang.AssertionError: before
+e2org.scalajs.junit.ExceptionBeforeAndAfterClass::java.lang.AssertionError: before::true
 leTest org.scalajs.junit.ExceptionBeforeAndAfterClass failed: java.lang.IllegalArgumentException: after, took <TIME>
 liTest run finished: 2 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_nva.txt b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_nva.txt
index 2c12da8d97..4d42d2dbfc 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_nva.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_nva.txt
@@ -1,6 +1,6 @@
 liTest run started
 leTest org.scalajs.junit.ExceptionBeforeAndAfterClass failed: java.lang.AssertionError: before, took <TIME>
-e2org.scalajs.junit.ExceptionBeforeAndAfterClass::java.lang.AssertionError: before
+e2org.scalajs.junit.ExceptionBeforeAndAfterClass::java.lang.AssertionError: before::true
 leTest org.scalajs.junit.ExceptionBeforeAndAfterClass failed: java.lang.IllegalArgumentException: after, took <TIME>
 liTest run finished: 2 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_nvc.txt b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_nvc.txt
index 39ba700989..dc7a5ba01f 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_nvc.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_nvc.txt
@@ -1,6 +1,6 @@
 liTest run started
 leTest org.scalajs.junit.ExceptionBeforeAndAfterClass failed: before, took <TIME>
-e2org.scalajs.junit.ExceptionBeforeAndAfterClass::java.lang.AssertionError: before
+e2org.scalajs.junit.ExceptionBeforeAndAfterClass::java.lang.AssertionError: before::true
 leTest org.scalajs.junit.ExceptionBeforeAndAfterClass failed: after, took <TIME>
 liTest run finished: 2 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_nvca.txt b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_nvca.txt
index 39ba700989..dc7a5ba01f 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_nvca.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_nvca.txt
@@ -1,6 +1,6 @@
 liTest run started
 leTest org.scalajs.junit.ExceptionBeforeAndAfterClass failed: before, took <TIME>
-e2org.scalajs.junit.ExceptionBeforeAndAfterClass::java.lang.AssertionError: before
+e2org.scalajs.junit.ExceptionBeforeAndAfterClass::java.lang.AssertionError: before::true
 leTest org.scalajs.junit.ExceptionBeforeAndAfterClass failed: after, took <TIME>
 liTest run finished: 2 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_v.txt b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_v.txt
index dcea945692..dbc23a355f 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_v.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_v.txt
@@ -1,6 +1,6 @@
 liTest run started
 leTest org.scalajs.junit.ExceptionBeforeAndAfterClass failed: before, took <TIME>
-e2org.scalajs.junit.ExceptionBeforeAndAfterClass::java.lang.AssertionError: before
+e2org.scalajs.junit.ExceptionBeforeAndAfterClass::java.lang.AssertionError: before::true
 leTest org.scalajs.junit.ExceptionBeforeAndAfterClass failed: java.lang.IllegalArgumentException: after, took <TIME>
 liTest run finished: 2 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_va.txt b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_va.txt
index f37328933a..0381d8ef25 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_va.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_va.txt
@@ -1,6 +1,6 @@
 liTest run started
 leTest org.scalajs.junit.ExceptionBeforeAndAfterClass failed: java.lang.AssertionError: before, took <TIME>
-e2org.scalajs.junit.ExceptionBeforeAndAfterClass::java.lang.AssertionError: before
+e2org.scalajs.junit.ExceptionBeforeAndAfterClass::java.lang.AssertionError: before::true
 leTest org.scalajs.junit.ExceptionBeforeAndAfterClass failed: java.lang.IllegalArgumentException: after, took <TIME>
 liTest run finished: 2 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_vc.txt b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_vc.txt
index 36cdde8136..6093c365f7 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_vc.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_vc.txt
@@ -1,6 +1,6 @@
 liTest run started
 leTest org.scalajs.junit.ExceptionBeforeAndAfterClass failed: before, took <TIME>
-e2org.scalajs.junit.ExceptionBeforeAndAfterClass::java.lang.AssertionError: before
+e2org.scalajs.junit.ExceptionBeforeAndAfterClass::java.lang.AssertionError: before::true
 leTest org.scalajs.junit.ExceptionBeforeAndAfterClass failed: after, took <TIME>
 liTest run finished: 2 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_vs.txt b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_vs.txt
index dcea945692..dbc23a355f 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_vs.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_vs.txt
@@ -1,6 +1,6 @@
 liTest run started
 leTest org.scalajs.junit.ExceptionBeforeAndAfterClass failed: before, took <TIME>
-e2org.scalajs.junit.ExceptionBeforeAndAfterClass::java.lang.AssertionError: before
+e2org.scalajs.junit.ExceptionBeforeAndAfterClass::java.lang.AssertionError: before::true
 leTest org.scalajs.junit.ExceptionBeforeAndAfterClass failed: java.lang.IllegalArgumentException: after, took <TIME>
 liTest run finished: 2 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_vsn.txt b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_vsn.txt
index 64f96715ed..4e4090a49e 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_vsn.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeAndAfterClassAssertions_vsn.txt
@@ -1,6 +1,6 @@
 liTest run started
 leTest org.scalajs.junit.ExceptionBeforeAndAfterClass failed: before, took <TIME>
-e2org.scalajs.junit.ExceptionBeforeAndAfterClass::java.lang.AssertionError: before
+e2org.scalajs.junit.ExceptionBeforeAndAfterClass::java.lang.AssertionError: before::true
 leTest org.scalajs.junit.ExceptionBeforeAndAfterClass failed: java.lang.IllegalArgumentException: after, took <TIME>
 liTest run finished: 2 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_.txt b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_.txt
index 6f86d87d17..c8cc8554e8 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_.txt
@@ -1,5 +1,5 @@
 ldTest run started
 leTest org.scalajs.junit.ExceptionBeforeClass failed: java.lang.IllegalArgumentException: foo, took <TIME>
-e2org.scalajs.junit.ExceptionBeforeClass::java.lang.IllegalArgumentException: foo
+e2org.scalajs.junit.ExceptionBeforeClass::java.lang.IllegalArgumentException: foo::true
 ldTest run finished: 1 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_a.txt b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_a.txt
index 6f86d87d17..c8cc8554e8 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_a.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_a.txt
@@ -1,5 +1,5 @@
 ldTest run started
 leTest org.scalajs.junit.ExceptionBeforeClass failed: java.lang.IllegalArgumentException: foo, took <TIME>
-e2org.scalajs.junit.ExceptionBeforeClass::java.lang.IllegalArgumentException: foo
+e2org.scalajs.junit.ExceptionBeforeClass::java.lang.IllegalArgumentException: foo::true
 ldTest run finished: 1 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_n.txt b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_n.txt
index e49141f66a..edf8637780 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_n.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_n.txt
@@ -1,5 +1,5 @@
 ldTest run started
 leTest org.scalajs.junit.ExceptionBeforeClass failed: java.lang.IllegalArgumentException: foo, took <TIME>
-e2org.scalajs.junit.ExceptionBeforeClass::java.lang.IllegalArgumentException: foo
+e2org.scalajs.junit.ExceptionBeforeClass::java.lang.IllegalArgumentException: foo::true
 ldTest run finished: 1 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_na.txt b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_na.txt
index e49141f66a..edf8637780 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_na.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_na.txt
@@ -1,5 +1,5 @@
 ldTest run started
 leTest org.scalajs.junit.ExceptionBeforeClass failed: java.lang.IllegalArgumentException: foo, took <TIME>
-e2org.scalajs.junit.ExceptionBeforeClass::java.lang.IllegalArgumentException: foo
+e2org.scalajs.junit.ExceptionBeforeClass::java.lang.IllegalArgumentException: foo::true
 ldTest run finished: 1 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_nv.txt b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_nv.txt
index f57776bd63..8d93347753 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_nv.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_nv.txt
@@ -1,5 +1,5 @@
 liTest run started
 leTest org.scalajs.junit.ExceptionBeforeClass failed: java.lang.IllegalArgumentException: foo, took <TIME>
-e2org.scalajs.junit.ExceptionBeforeClass::java.lang.IllegalArgumentException: foo
+e2org.scalajs.junit.ExceptionBeforeClass::java.lang.IllegalArgumentException: foo::true
 liTest run finished: 1 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_nva.txt b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_nva.txt
index f57776bd63..8d93347753 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_nva.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_nva.txt
@@ -1,5 +1,5 @@
 liTest run started
 leTest org.scalajs.junit.ExceptionBeforeClass failed: java.lang.IllegalArgumentException: foo, took <TIME>
-e2org.scalajs.junit.ExceptionBeforeClass::java.lang.IllegalArgumentException: foo
+e2org.scalajs.junit.ExceptionBeforeClass::java.lang.IllegalArgumentException: foo::true
 liTest run finished: 1 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_nvc.txt b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_nvc.txt
index d5cdbe1efd..bfd00e70f6 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_nvc.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_nvc.txt
@@ -1,5 +1,5 @@
 liTest run started
 leTest org.scalajs.junit.ExceptionBeforeClass failed: foo, took <TIME>
-e2org.scalajs.junit.ExceptionBeforeClass::java.lang.IllegalArgumentException: foo
+e2org.scalajs.junit.ExceptionBeforeClass::java.lang.IllegalArgumentException: foo::true
 liTest run finished: 1 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_nvca.txt b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_nvca.txt
index d5cdbe1efd..bfd00e70f6 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_nvca.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_nvca.txt
@@ -1,5 +1,5 @@
 liTest run started
 leTest org.scalajs.junit.ExceptionBeforeClass failed: foo, took <TIME>
-e2org.scalajs.junit.ExceptionBeforeClass::java.lang.IllegalArgumentException: foo
+e2org.scalajs.junit.ExceptionBeforeClass::java.lang.IllegalArgumentException: foo::true
 liTest run finished: 1 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_v.txt b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_v.txt
index ce2f836a74..ba14e92d2e 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_v.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_v.txt
@@ -1,5 +1,5 @@
 liTest run started
 leTest org.scalajs.junit.ExceptionBeforeClass failed: java.lang.IllegalArgumentException: foo, took <TIME>
-e2org.scalajs.junit.ExceptionBeforeClass::java.lang.IllegalArgumentException: foo
+e2org.scalajs.junit.ExceptionBeforeClass::java.lang.IllegalArgumentException: foo::true
 liTest run finished: 1 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_va.txt b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_va.txt
index ce2f836a74..ba14e92d2e 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_va.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_va.txt
@@ -1,5 +1,5 @@
 liTest run started
 leTest org.scalajs.junit.ExceptionBeforeClass failed: java.lang.IllegalArgumentException: foo, took <TIME>
-e2org.scalajs.junit.ExceptionBeforeClass::java.lang.IllegalArgumentException: foo
+e2org.scalajs.junit.ExceptionBeforeClass::java.lang.IllegalArgumentException: foo::true
 liTest run finished: 1 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_vc.txt b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_vc.txt
index 4a6907891f..1283012627 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_vc.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_vc.txt
@@ -1,5 +1,5 @@
 liTest run started
 leTest org.scalajs.junit.ExceptionBeforeClass failed: foo, took <TIME>
-e2org.scalajs.junit.ExceptionBeforeClass::java.lang.IllegalArgumentException: foo
+e2org.scalajs.junit.ExceptionBeforeClass::java.lang.IllegalArgumentException: foo::true
 liTest run finished: 1 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_vs.txt b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_vs.txt
index ce2f836a74..ba14e92d2e 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_vs.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_vs.txt
@@ -1,5 +1,5 @@
 liTest run started
 leTest org.scalajs.junit.ExceptionBeforeClass failed: java.lang.IllegalArgumentException: foo, took <TIME>
-e2org.scalajs.junit.ExceptionBeforeClass::java.lang.IllegalArgumentException: foo
+e2org.scalajs.junit.ExceptionBeforeClass::java.lang.IllegalArgumentException: foo::true
 liTest run finished: 1 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_vsn.txt b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_vsn.txt
index f57776bd63..8d93347753 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_vsn.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionBeforeClassAssertions_vsn.txt
@@ -1,5 +1,5 @@
 liTest run started
 leTest org.scalajs.junit.ExceptionBeforeClass failed: java.lang.IllegalArgumentException: foo, took <TIME>
-e2org.scalajs.junit.ExceptionBeforeClass::java.lang.IllegalArgumentException: foo
+e2org.scalajs.junit.ExceptionBeforeClass::java.lang.IllegalArgumentException: foo::true
 liTest run finished: 1 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_.txt b/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_.txt
index a6f2913c4e..85fed6c7aa 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_.txt
@@ -1,6 +1,6 @@
 ldTest run started
 leTest org.scalajs.junit.ExceptionEverywhere failed: before class, took <TIME>
-e2org.scalajs.junit.ExceptionEverywhere::java.lang.AssertionError: before class
+e2org.scalajs.junit.ExceptionEverywhere::java.lang.AssertionError: before class::true
 leTest org.scalajs.junit.ExceptionEverywhere failed: after class, took <TIME>
 ldTest run finished: 2 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_a.txt b/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_a.txt
index 79417183a5..02f05e689f 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_a.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_a.txt
@@ -1,6 +1,6 @@
 ldTest run started
 leTest org.scalajs.junit.ExceptionEverywhere failed: java.lang.AssertionError: before class, took <TIME>
-e2org.scalajs.junit.ExceptionEverywhere::java.lang.AssertionError: before class
+e2org.scalajs.junit.ExceptionEverywhere::java.lang.AssertionError: before class::true
 leTest org.scalajs.junit.ExceptionEverywhere failed: java.lang.AssertionError: after class, took <TIME>
 ldTest run finished: 2 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_n.txt b/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_n.txt
index 30b992edb7..42d563eeac 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_n.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_n.txt
@@ -1,6 +1,6 @@
 ldTest run started
 leTest org.scalajs.junit.ExceptionEverywhere failed: before class, took <TIME>
-e2org.scalajs.junit.ExceptionEverywhere::java.lang.AssertionError: before class
+e2org.scalajs.junit.ExceptionEverywhere::java.lang.AssertionError: before class::true
 leTest org.scalajs.junit.ExceptionEverywhere failed: after class, took <TIME>
 ldTest run finished: 2 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_na.txt b/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_na.txt
index 5905a59da4..1d8d9dadf7 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_na.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_na.txt
@@ -1,6 +1,6 @@
 ldTest run started
 leTest org.scalajs.junit.ExceptionEverywhere failed: java.lang.AssertionError: before class, took <TIME>
-e2org.scalajs.junit.ExceptionEverywhere::java.lang.AssertionError: before class
+e2org.scalajs.junit.ExceptionEverywhere::java.lang.AssertionError: before class::true
 leTest org.scalajs.junit.ExceptionEverywhere failed: java.lang.AssertionError: after class, took <TIME>
 ldTest run finished: 2 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_nv.txt b/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_nv.txt
index ee5afc2ca2..0d0d0f5735 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_nv.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_nv.txt
@@ -1,6 +1,6 @@
 liTest run started
 leTest org.scalajs.junit.ExceptionEverywhere failed: before class, took <TIME>
-e2org.scalajs.junit.ExceptionEverywhere::java.lang.AssertionError: before class
+e2org.scalajs.junit.ExceptionEverywhere::java.lang.AssertionError: before class::true
 leTest org.scalajs.junit.ExceptionEverywhere failed: after class, took <TIME>
 liTest run finished: 2 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_nva.txt b/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_nva.txt
index 92d17d724e..716ef4aa37 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_nva.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_nva.txt
@@ -1,6 +1,6 @@
 liTest run started
 leTest org.scalajs.junit.ExceptionEverywhere failed: java.lang.AssertionError: before class, took <TIME>
-e2org.scalajs.junit.ExceptionEverywhere::java.lang.AssertionError: before class
+e2org.scalajs.junit.ExceptionEverywhere::java.lang.AssertionError: before class::true
 leTest org.scalajs.junit.ExceptionEverywhere failed: java.lang.AssertionError: after class, took <TIME>
 liTest run finished: 2 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_nvc.txt b/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_nvc.txt
index ee5afc2ca2..0d0d0f5735 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_nvc.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_nvc.txt
@@ -1,6 +1,6 @@
 liTest run started
 leTest org.scalajs.junit.ExceptionEverywhere failed: before class, took <TIME>
-e2org.scalajs.junit.ExceptionEverywhere::java.lang.AssertionError: before class
+e2org.scalajs.junit.ExceptionEverywhere::java.lang.AssertionError: before class::true
 leTest org.scalajs.junit.ExceptionEverywhere failed: after class, took <TIME>
 liTest run finished: 2 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_nvca.txt b/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_nvca.txt
index ee5afc2ca2..0d0d0f5735 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_nvca.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_nvca.txt
@@ -1,6 +1,6 @@
 liTest run started
 leTest org.scalajs.junit.ExceptionEverywhere failed: before class, took <TIME>
-e2org.scalajs.junit.ExceptionEverywhere::java.lang.AssertionError: before class
+e2org.scalajs.junit.ExceptionEverywhere::java.lang.AssertionError: before class::true
 leTest org.scalajs.junit.ExceptionEverywhere failed: after class, took <TIME>
 liTest run finished: 2 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_v.txt b/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_v.txt
index 26f23b9718..61bb741aa3 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_v.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_v.txt
@@ -1,6 +1,6 @@
 liTest run started
 leTest org.scalajs.junit.ExceptionEverywhere failed: before class, took <TIME>
-e2org.scalajs.junit.ExceptionEverywhere::java.lang.AssertionError: before class
+e2org.scalajs.junit.ExceptionEverywhere::java.lang.AssertionError: before class::true
 leTest org.scalajs.junit.ExceptionEverywhere failed: after class, took <TIME>
 liTest run finished: 2 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_va.txt b/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_va.txt
index 2cb1cfd773..3f968ef907 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_va.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_va.txt
@@ -1,6 +1,6 @@
 liTest run started
 leTest org.scalajs.junit.ExceptionEverywhere failed: java.lang.AssertionError: before class, took <TIME>
-e2org.scalajs.junit.ExceptionEverywhere::java.lang.AssertionError: before class
+e2org.scalajs.junit.ExceptionEverywhere::java.lang.AssertionError: before class::true
 leTest org.scalajs.junit.ExceptionEverywhere failed: java.lang.AssertionError: after class, took <TIME>
 liTest run finished: 2 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_vc.txt b/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_vc.txt
index 26f23b9718..61bb741aa3 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_vc.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_vc.txt
@@ -1,6 +1,6 @@
 liTest run started
 leTest org.scalajs.junit.ExceptionEverywhere failed: before class, took <TIME>
-e2org.scalajs.junit.ExceptionEverywhere::java.lang.AssertionError: before class
+e2org.scalajs.junit.ExceptionEverywhere::java.lang.AssertionError: before class::true
 leTest org.scalajs.junit.ExceptionEverywhere failed: after class, took <TIME>
 liTest run finished: 2 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_vs.txt b/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_vs.txt
index 26f23b9718..61bb741aa3 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_vs.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_vs.txt
@@ -1,6 +1,6 @@
 liTest run started
 leTest org.scalajs.junit.ExceptionEverywhere failed: before class, took <TIME>
-e2org.scalajs.junit.ExceptionEverywhere::java.lang.AssertionError: before class
+e2org.scalajs.junit.ExceptionEverywhere::java.lang.AssertionError: before class::true
 leTest org.scalajs.junit.ExceptionEverywhere failed: after class, took <TIME>
 liTest run finished: 2 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_vsn.txt b/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_vsn.txt
index ee5afc2ca2..0d0d0f5735 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_vsn.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionEverywhereAssertions_vsn.txt
@@ -1,6 +1,6 @@
 liTest run started
 leTest org.scalajs.junit.ExceptionEverywhere failed: before class, took <TIME>
-e2org.scalajs.junit.ExceptionEverywhere::java.lang.AssertionError: before class
+e2org.scalajs.junit.ExceptionEverywhere::java.lang.AssertionError: before class::true
 leTest org.scalajs.junit.ExceptionEverywhere failed: after class, took <TIME>
 liTest run finished: 2 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_.txt
index 14d3235518..7d3932eb7a 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.ExceptionInAfterTest.test started
 leTest org.scalajs.junit.ExceptionInAfterTest.test failed: java.lang.UnsupportedOperationException: Exception in after(), took <TIME>
-e2org.scalajs.junit.ExceptionInAfterTest.test::java.lang.UnsupportedOperationException: Exception in after()
+e2org.scalajs.junit.ExceptionInAfterTest.test::java.lang.UnsupportedOperationException: Exception in after()::true
 ldTest org.scalajs.junit.ExceptionInAfterTest.test finished, took <TIME>
 ldTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_a.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_a.txt
index 14d3235518..7d3932eb7a 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_a.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_a.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.ExceptionInAfterTest.test started
 leTest org.scalajs.junit.ExceptionInAfterTest.test failed: java.lang.UnsupportedOperationException: Exception in after(), took <TIME>
-e2org.scalajs.junit.ExceptionInAfterTest.test::java.lang.UnsupportedOperationException: Exception in after()
+e2org.scalajs.junit.ExceptionInAfterTest.test::java.lang.UnsupportedOperationException: Exception in after()::true
 ldTest org.scalajs.junit.ExceptionInAfterTest.test finished, took <TIME>
 ldTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_n.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_n.txt
index 03b803addb..30fcb37e20 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_n.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_n.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.ExceptionInAfterTest.test started
 leTest org.scalajs.junit.ExceptionInAfterTest.test failed: java.lang.UnsupportedOperationException: Exception in after(), took <TIME>
-e2org.scalajs.junit.ExceptionInAfterTest.test::java.lang.UnsupportedOperationException: Exception in after()
+e2org.scalajs.junit.ExceptionInAfterTest.test::java.lang.UnsupportedOperationException: Exception in after()::true
 ldTest org.scalajs.junit.ExceptionInAfterTest.test finished, took <TIME>
 ldTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_na.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_na.txt
index 03b803addb..30fcb37e20 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_na.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_na.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.ExceptionInAfterTest.test started
 leTest org.scalajs.junit.ExceptionInAfterTest.test failed: java.lang.UnsupportedOperationException: Exception in after(), took <TIME>
-e2org.scalajs.junit.ExceptionInAfterTest.test::java.lang.UnsupportedOperationException: Exception in after()
+e2org.scalajs.junit.ExceptionInAfterTest.test::java.lang.UnsupportedOperationException: Exception in after()::true
 ldTest org.scalajs.junit.ExceptionInAfterTest.test finished, took <TIME>
 ldTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_nv.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_nv.txt
index ff0c035392..becc00a0e8 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_nv.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_nv.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionInAfterTest.test started
 leTest org.scalajs.junit.ExceptionInAfterTest.test failed: java.lang.UnsupportedOperationException: Exception in after(), took <TIME>
-e2org.scalajs.junit.ExceptionInAfterTest.test::java.lang.UnsupportedOperationException: Exception in after()
+e2org.scalajs.junit.ExceptionInAfterTest.test::java.lang.UnsupportedOperationException: Exception in after()::true
 ldTest org.scalajs.junit.ExceptionInAfterTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_nva.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_nva.txt
index ff0c035392..becc00a0e8 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_nva.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_nva.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionInAfterTest.test started
 leTest org.scalajs.junit.ExceptionInAfterTest.test failed: java.lang.UnsupportedOperationException: Exception in after(), took <TIME>
-e2org.scalajs.junit.ExceptionInAfterTest.test::java.lang.UnsupportedOperationException: Exception in after()
+e2org.scalajs.junit.ExceptionInAfterTest.test::java.lang.UnsupportedOperationException: Exception in after()::true
 ldTest org.scalajs.junit.ExceptionInAfterTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_nvc.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_nvc.txt
index ac5b174a3a..bf0c438bd2 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_nvc.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_nvc.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionInAfterTest.test started
 leTest org.scalajs.junit.ExceptionInAfterTest.test failed: Exception in after(), took <TIME>
-e2org.scalajs.junit.ExceptionInAfterTest.test::java.lang.UnsupportedOperationException: Exception in after()
+e2org.scalajs.junit.ExceptionInAfterTest.test::java.lang.UnsupportedOperationException: Exception in after()::true
 ldTest org.scalajs.junit.ExceptionInAfterTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_nvca.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_nvca.txt
index ac5b174a3a..bf0c438bd2 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_nvca.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_nvca.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionInAfterTest.test started
 leTest org.scalajs.junit.ExceptionInAfterTest.test failed: Exception in after(), took <TIME>
-e2org.scalajs.junit.ExceptionInAfterTest.test::java.lang.UnsupportedOperationException: Exception in after()
+e2org.scalajs.junit.ExceptionInAfterTest.test::java.lang.UnsupportedOperationException: Exception in after()::true
 ldTest org.scalajs.junit.ExceptionInAfterTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_v.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_v.txt
index ca2f0122e9..9cd5a01a5e 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_v.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_v.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionInAfterTest.test started
 leTest org.scalajs.junit.ExceptionInAfterTest.test failed: java.lang.UnsupportedOperationException: Exception in after(), took <TIME>
-e2org.scalajs.junit.ExceptionInAfterTest.test::java.lang.UnsupportedOperationException: Exception in after()
+e2org.scalajs.junit.ExceptionInAfterTest.test::java.lang.UnsupportedOperationException: Exception in after()::true
 ldTest org.scalajs.junit.ExceptionInAfterTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_va.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_va.txt
index ca2f0122e9..9cd5a01a5e 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_va.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_va.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionInAfterTest.test started
 leTest org.scalajs.junit.ExceptionInAfterTest.test failed: java.lang.UnsupportedOperationException: Exception in after(), took <TIME>
-e2org.scalajs.junit.ExceptionInAfterTest.test::java.lang.UnsupportedOperationException: Exception in after()
+e2org.scalajs.junit.ExceptionInAfterTest.test::java.lang.UnsupportedOperationException: Exception in after()::true
 ldTest org.scalajs.junit.ExceptionInAfterTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_vc.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_vc.txt
index 3d1aebb353..12bad3fc5e 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_vc.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_vc.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionInAfterTest.test started
 leTest org.scalajs.junit.ExceptionInAfterTest.test failed: Exception in after(), took <TIME>
-e2org.scalajs.junit.ExceptionInAfterTest.test::java.lang.UnsupportedOperationException: Exception in after()
+e2org.scalajs.junit.ExceptionInAfterTest.test::java.lang.UnsupportedOperationException: Exception in after()::true
 ldTest org.scalajs.junit.ExceptionInAfterTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_vs.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_vs.txt
index ca2f0122e9..9cd5a01a5e 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_vs.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_vs.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionInAfterTest.test started
 leTest org.scalajs.junit.ExceptionInAfterTest.test failed: java.lang.UnsupportedOperationException: Exception in after(), took <TIME>
-e2org.scalajs.junit.ExceptionInAfterTest.test::java.lang.UnsupportedOperationException: Exception in after()
+e2org.scalajs.junit.ExceptionInAfterTest.test::java.lang.UnsupportedOperationException: Exception in after()::true
 ldTest org.scalajs.junit.ExceptionInAfterTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_vsn.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_vsn.txt
index ff0c035392..becc00a0e8 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_vsn.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInAfterTestAssertions_vsn.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionInAfterTest.test started
 leTest org.scalajs.junit.ExceptionInAfterTest.test failed: java.lang.UnsupportedOperationException: Exception in after(), took <TIME>
-e2org.scalajs.junit.ExceptionInAfterTest.test::java.lang.UnsupportedOperationException: Exception in after()
+e2org.scalajs.junit.ExceptionInAfterTest.test::java.lang.UnsupportedOperationException: Exception in after()::true
 ldTest org.scalajs.junit.ExceptionInAfterTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_.txt
index d6ba6e71fd..de0b17bb20 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.ExceptionInBeforeTest.test started
 leTest org.scalajs.junit.ExceptionInBeforeTest.test failed: java.lang.UnsupportedOperationException: Exception in before(), took <TIME>
-e2org.scalajs.junit.ExceptionInBeforeTest.test::java.lang.UnsupportedOperationException: Exception in before()
+e2org.scalajs.junit.ExceptionInBeforeTest.test::java.lang.UnsupportedOperationException: Exception in before()::true
 leTest org.scalajs.junit.ExceptionInBeforeTest.test failed: java.lang.IllegalArgumentException: after() must actually be called, took <TIME>
 ldTest org.scalajs.junit.ExceptionInBeforeTest.test finished, took <TIME>
 ldTest run finished: 2 failed, 0 ignored, 1 total, <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_a.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_a.txt
index d6ba6e71fd..de0b17bb20 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_a.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_a.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.ExceptionInBeforeTest.test started
 leTest org.scalajs.junit.ExceptionInBeforeTest.test failed: java.lang.UnsupportedOperationException: Exception in before(), took <TIME>
-e2org.scalajs.junit.ExceptionInBeforeTest.test::java.lang.UnsupportedOperationException: Exception in before()
+e2org.scalajs.junit.ExceptionInBeforeTest.test::java.lang.UnsupportedOperationException: Exception in before()::true
 leTest org.scalajs.junit.ExceptionInBeforeTest.test failed: java.lang.IllegalArgumentException: after() must actually be called, took <TIME>
 ldTest org.scalajs.junit.ExceptionInBeforeTest.test finished, took <TIME>
 ldTest run finished: 2 failed, 0 ignored, 1 total, <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_n.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_n.txt
index b1cea044df..5599252f07 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_n.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_n.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.ExceptionInBeforeTest.test started
 leTest org.scalajs.junit.ExceptionInBeforeTest.test failed: java.lang.UnsupportedOperationException: Exception in before(), took <TIME>
-e2org.scalajs.junit.ExceptionInBeforeTest.test::java.lang.UnsupportedOperationException: Exception in before()
+e2org.scalajs.junit.ExceptionInBeforeTest.test::java.lang.UnsupportedOperationException: Exception in before()::true
 leTest org.scalajs.junit.ExceptionInBeforeTest.test failed: java.lang.IllegalArgumentException: after() must actually be called, took <TIME>
 ldTest org.scalajs.junit.ExceptionInBeforeTest.test finished, took <TIME>
 ldTest run finished: 2 failed, 0 ignored, 1 total, <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_na.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_na.txt
index b1cea044df..5599252f07 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_na.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_na.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.ExceptionInBeforeTest.test started
 leTest org.scalajs.junit.ExceptionInBeforeTest.test failed: java.lang.UnsupportedOperationException: Exception in before(), took <TIME>
-e2org.scalajs.junit.ExceptionInBeforeTest.test::java.lang.UnsupportedOperationException: Exception in before()
+e2org.scalajs.junit.ExceptionInBeforeTest.test::java.lang.UnsupportedOperationException: Exception in before()::true
 leTest org.scalajs.junit.ExceptionInBeforeTest.test failed: java.lang.IllegalArgumentException: after() must actually be called, took <TIME>
 ldTest org.scalajs.junit.ExceptionInBeforeTest.test finished, took <TIME>
 ldTest run finished: 2 failed, 0 ignored, 1 total, <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_nv.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_nv.txt
index f82dfea4e4..a1734b1c8c 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_nv.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_nv.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionInBeforeTest.test started
 leTest org.scalajs.junit.ExceptionInBeforeTest.test failed: java.lang.UnsupportedOperationException: Exception in before(), took <TIME>
-e2org.scalajs.junit.ExceptionInBeforeTest.test::java.lang.UnsupportedOperationException: Exception in before()
+e2org.scalajs.junit.ExceptionInBeforeTest.test::java.lang.UnsupportedOperationException: Exception in before()::true
 leTest org.scalajs.junit.ExceptionInBeforeTest.test failed: java.lang.IllegalArgumentException: after() must actually be called, took <TIME>
 ldTest org.scalajs.junit.ExceptionInBeforeTest.test finished, took <TIME>
 liTest run finished: 2 failed, 0 ignored, 1 total, <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_nva.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_nva.txt
index f82dfea4e4..a1734b1c8c 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_nva.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_nva.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionInBeforeTest.test started
 leTest org.scalajs.junit.ExceptionInBeforeTest.test failed: java.lang.UnsupportedOperationException: Exception in before(), took <TIME>
-e2org.scalajs.junit.ExceptionInBeforeTest.test::java.lang.UnsupportedOperationException: Exception in before()
+e2org.scalajs.junit.ExceptionInBeforeTest.test::java.lang.UnsupportedOperationException: Exception in before()::true
 leTest org.scalajs.junit.ExceptionInBeforeTest.test failed: java.lang.IllegalArgumentException: after() must actually be called, took <TIME>
 ldTest org.scalajs.junit.ExceptionInBeforeTest.test finished, took <TIME>
 liTest run finished: 2 failed, 0 ignored, 1 total, <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_nvc.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_nvc.txt
index dd02f92e2e..07a54c6c31 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_nvc.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_nvc.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionInBeforeTest.test started
 leTest org.scalajs.junit.ExceptionInBeforeTest.test failed: Exception in before(), took <TIME>
-e2org.scalajs.junit.ExceptionInBeforeTest.test::java.lang.UnsupportedOperationException: Exception in before()
+e2org.scalajs.junit.ExceptionInBeforeTest.test::java.lang.UnsupportedOperationException: Exception in before()::true
 leTest org.scalajs.junit.ExceptionInBeforeTest.test failed: after() must actually be called, took <TIME>
 ldTest org.scalajs.junit.ExceptionInBeforeTest.test finished, took <TIME>
 liTest run finished: 2 failed, 0 ignored, 1 total, <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_nvca.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_nvca.txt
index dd02f92e2e..07a54c6c31 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_nvca.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_nvca.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionInBeforeTest.test started
 leTest org.scalajs.junit.ExceptionInBeforeTest.test failed: Exception in before(), took <TIME>
-e2org.scalajs.junit.ExceptionInBeforeTest.test::java.lang.UnsupportedOperationException: Exception in before()
+e2org.scalajs.junit.ExceptionInBeforeTest.test::java.lang.UnsupportedOperationException: Exception in before()::true
 leTest org.scalajs.junit.ExceptionInBeforeTest.test failed: after() must actually be called, took <TIME>
 ldTest org.scalajs.junit.ExceptionInBeforeTest.test finished, took <TIME>
 liTest run finished: 2 failed, 0 ignored, 1 total, <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_v.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_v.txt
index 0b91d80a97..b23177560d 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_v.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_v.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionInBeforeTest.test started
 leTest org.scalajs.junit.ExceptionInBeforeTest.test failed: java.lang.UnsupportedOperationException: Exception in before(), took <TIME>
-e2org.scalajs.junit.ExceptionInBeforeTest.test::java.lang.UnsupportedOperationException: Exception in before()
+e2org.scalajs.junit.ExceptionInBeforeTest.test::java.lang.UnsupportedOperationException: Exception in before()::true
 leTest org.scalajs.junit.ExceptionInBeforeTest.test failed: java.lang.IllegalArgumentException: after() must actually be called, took <TIME>
 ldTest org.scalajs.junit.ExceptionInBeforeTest.test finished, took <TIME>
 liTest run finished: 2 failed, 0 ignored, 1 total, <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_va.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_va.txt
index 0b91d80a97..b23177560d 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_va.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_va.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionInBeforeTest.test started
 leTest org.scalajs.junit.ExceptionInBeforeTest.test failed: java.lang.UnsupportedOperationException: Exception in before(), took <TIME>
-e2org.scalajs.junit.ExceptionInBeforeTest.test::java.lang.UnsupportedOperationException: Exception in before()
+e2org.scalajs.junit.ExceptionInBeforeTest.test::java.lang.UnsupportedOperationException: Exception in before()::true
 leTest org.scalajs.junit.ExceptionInBeforeTest.test failed: java.lang.IllegalArgumentException: after() must actually be called, took <TIME>
 ldTest org.scalajs.junit.ExceptionInBeforeTest.test finished, took <TIME>
 liTest run finished: 2 failed, 0 ignored, 1 total, <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_vc.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_vc.txt
index 3acd966c6f..d78072db6d 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_vc.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_vc.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionInBeforeTest.test started
 leTest org.scalajs.junit.ExceptionInBeforeTest.test failed: Exception in before(), took <TIME>
-e2org.scalajs.junit.ExceptionInBeforeTest.test::java.lang.UnsupportedOperationException: Exception in before()
+e2org.scalajs.junit.ExceptionInBeforeTest.test::java.lang.UnsupportedOperationException: Exception in before()::true
 leTest org.scalajs.junit.ExceptionInBeforeTest.test failed: after() must actually be called, took <TIME>
 ldTest org.scalajs.junit.ExceptionInBeforeTest.test finished, took <TIME>
 liTest run finished: 2 failed, 0 ignored, 1 total, <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_vs.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_vs.txt
index 0b91d80a97..b23177560d 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_vs.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_vs.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionInBeforeTest.test started
 leTest org.scalajs.junit.ExceptionInBeforeTest.test failed: java.lang.UnsupportedOperationException: Exception in before(), took <TIME>
-e2org.scalajs.junit.ExceptionInBeforeTest.test::java.lang.UnsupportedOperationException: Exception in before()
+e2org.scalajs.junit.ExceptionInBeforeTest.test::java.lang.UnsupportedOperationException: Exception in before()::true
 leTest org.scalajs.junit.ExceptionInBeforeTest.test failed: java.lang.IllegalArgumentException: after() must actually be called, took <TIME>
 ldTest org.scalajs.junit.ExceptionInBeforeTest.test finished, took <TIME>
 liTest run finished: 2 failed, 0 ignored, 1 total, <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_vsn.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_vsn.txt
index f82dfea4e4..a1734b1c8c 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_vsn.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInBeforeTestAssertions_vsn.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionInBeforeTest.test started
 leTest org.scalajs.junit.ExceptionInBeforeTest.test failed: java.lang.UnsupportedOperationException: Exception in before(), took <TIME>
-e2org.scalajs.junit.ExceptionInBeforeTest.test::java.lang.UnsupportedOperationException: Exception in before()
+e2org.scalajs.junit.ExceptionInBeforeTest.test::java.lang.UnsupportedOperationException: Exception in before()::true
 leTest org.scalajs.junit.ExceptionInBeforeTest.test failed: java.lang.IllegalArgumentException: after() must actually be called, took <TIME>
 ldTest org.scalajs.junit.ExceptionInBeforeTest.test finished, took <TIME>
 liTest run finished: 2 failed, 0 ignored, 1 total, <TIME>
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_.txt
index c1cad1d384..8fe72a1387 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.ExceptionInConstructorTest.test started
 leTest org.scalajs.junit.ExceptionInConstructorTest.test failed: java.lang.UnsupportedOperationException: Exception while constructing the test class, took <TIME>
-e2org.scalajs.junit.ExceptionInConstructorTest.test::java.lang.UnsupportedOperationException: Exception while constructing the test class
+e2org.scalajs.junit.ExceptionInConstructorTest.test::java.lang.UnsupportedOperationException: Exception while constructing the test class::true
 ldTest org.scalajs.junit.ExceptionInConstructorTest.test finished, took <TIME>
 ldTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_a.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_a.txt
index c1cad1d384..8fe72a1387 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_a.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_a.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.ExceptionInConstructorTest.test started
 leTest org.scalajs.junit.ExceptionInConstructorTest.test failed: java.lang.UnsupportedOperationException: Exception while constructing the test class, took <TIME>
-e2org.scalajs.junit.ExceptionInConstructorTest.test::java.lang.UnsupportedOperationException: Exception while constructing the test class
+e2org.scalajs.junit.ExceptionInConstructorTest.test::java.lang.UnsupportedOperationException: Exception while constructing the test class::true
 ldTest org.scalajs.junit.ExceptionInConstructorTest.test finished, took <TIME>
 ldTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_n.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_n.txt
index 12fe8b5772..7a23eeb432 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_n.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_n.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.ExceptionInConstructorTest.test started
 leTest org.scalajs.junit.ExceptionInConstructorTest.test failed: java.lang.UnsupportedOperationException: Exception while constructing the test class, took <TIME>
-e2org.scalajs.junit.ExceptionInConstructorTest.test::java.lang.UnsupportedOperationException: Exception while constructing the test class
+e2org.scalajs.junit.ExceptionInConstructorTest.test::java.lang.UnsupportedOperationException: Exception while constructing the test class::true
 ldTest org.scalajs.junit.ExceptionInConstructorTest.test finished, took <TIME>
 ldTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_na.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_na.txt
index 12fe8b5772..7a23eeb432 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_na.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_na.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.ExceptionInConstructorTest.test started
 leTest org.scalajs.junit.ExceptionInConstructorTest.test failed: java.lang.UnsupportedOperationException: Exception while constructing the test class, took <TIME>
-e2org.scalajs.junit.ExceptionInConstructorTest.test::java.lang.UnsupportedOperationException: Exception while constructing the test class
+e2org.scalajs.junit.ExceptionInConstructorTest.test::java.lang.UnsupportedOperationException: Exception while constructing the test class::true
 ldTest org.scalajs.junit.ExceptionInConstructorTest.test finished, took <TIME>
 ldTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_nv.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_nv.txt
index 730e13987a..97c92555ae 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_nv.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_nv.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionInConstructorTest.test started
 leTest org.scalajs.junit.ExceptionInConstructorTest.test failed: java.lang.UnsupportedOperationException: Exception while constructing the test class, took <TIME>
-e2org.scalajs.junit.ExceptionInConstructorTest.test::java.lang.UnsupportedOperationException: Exception while constructing the test class
+e2org.scalajs.junit.ExceptionInConstructorTest.test::java.lang.UnsupportedOperationException: Exception while constructing the test class::true
 ldTest org.scalajs.junit.ExceptionInConstructorTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_nva.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_nva.txt
index 730e13987a..97c92555ae 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_nva.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_nva.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionInConstructorTest.test started
 leTest org.scalajs.junit.ExceptionInConstructorTest.test failed: java.lang.UnsupportedOperationException: Exception while constructing the test class, took <TIME>
-e2org.scalajs.junit.ExceptionInConstructorTest.test::java.lang.UnsupportedOperationException: Exception while constructing the test class
+e2org.scalajs.junit.ExceptionInConstructorTest.test::java.lang.UnsupportedOperationException: Exception while constructing the test class::true
 ldTest org.scalajs.junit.ExceptionInConstructorTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_nvc.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_nvc.txt
index d3219559e5..b6bb9fe306 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_nvc.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_nvc.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionInConstructorTest.test started
 leTest org.scalajs.junit.ExceptionInConstructorTest.test failed: Exception while constructing the test class, took <TIME>
-e2org.scalajs.junit.ExceptionInConstructorTest.test::java.lang.UnsupportedOperationException: Exception while constructing the test class
+e2org.scalajs.junit.ExceptionInConstructorTest.test::java.lang.UnsupportedOperationException: Exception while constructing the test class::true
 ldTest org.scalajs.junit.ExceptionInConstructorTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_nvca.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_nvca.txt
index d3219559e5..b6bb9fe306 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_nvca.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_nvca.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionInConstructorTest.test started
 leTest org.scalajs.junit.ExceptionInConstructorTest.test failed: Exception while constructing the test class, took <TIME>
-e2org.scalajs.junit.ExceptionInConstructorTest.test::java.lang.UnsupportedOperationException: Exception while constructing the test class
+e2org.scalajs.junit.ExceptionInConstructorTest.test::java.lang.UnsupportedOperationException: Exception while constructing the test class::true
 ldTest org.scalajs.junit.ExceptionInConstructorTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_v.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_v.txt
index ef647db57d..c7efa1c33b 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_v.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_v.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionInConstructorTest.test started
 leTest org.scalajs.junit.ExceptionInConstructorTest.test failed: java.lang.UnsupportedOperationException: Exception while constructing the test class, took <TIME>
-e2org.scalajs.junit.ExceptionInConstructorTest.test::java.lang.UnsupportedOperationException: Exception while constructing the test class
+e2org.scalajs.junit.ExceptionInConstructorTest.test::java.lang.UnsupportedOperationException: Exception while constructing the test class::true
 ldTest org.scalajs.junit.ExceptionInConstructorTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_va.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_va.txt
index ef647db57d..c7efa1c33b 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_va.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_va.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionInConstructorTest.test started
 leTest org.scalajs.junit.ExceptionInConstructorTest.test failed: java.lang.UnsupportedOperationException: Exception while constructing the test class, took <TIME>
-e2org.scalajs.junit.ExceptionInConstructorTest.test::java.lang.UnsupportedOperationException: Exception while constructing the test class
+e2org.scalajs.junit.ExceptionInConstructorTest.test::java.lang.UnsupportedOperationException: Exception while constructing the test class::true
 ldTest org.scalajs.junit.ExceptionInConstructorTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_vc.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_vc.txt
index 1336060086..a79bfc4804 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_vc.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_vc.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionInConstructorTest.test started
 leTest org.scalajs.junit.ExceptionInConstructorTest.test failed: Exception while constructing the test class, took <TIME>
-e2org.scalajs.junit.ExceptionInConstructorTest.test::java.lang.UnsupportedOperationException: Exception while constructing the test class
+e2org.scalajs.junit.ExceptionInConstructorTest.test::java.lang.UnsupportedOperationException: Exception while constructing the test class::true
 ldTest org.scalajs.junit.ExceptionInConstructorTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_vs.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_vs.txt
index ef647db57d..c7efa1c33b 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_vs.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_vs.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionInConstructorTest.test started
 leTest org.scalajs.junit.ExceptionInConstructorTest.test failed: java.lang.UnsupportedOperationException: Exception while constructing the test class, took <TIME>
-e2org.scalajs.junit.ExceptionInConstructorTest.test::java.lang.UnsupportedOperationException: Exception while constructing the test class
+e2org.scalajs.junit.ExceptionInConstructorTest.test::java.lang.UnsupportedOperationException: Exception while constructing the test class::true
 ldTest org.scalajs.junit.ExceptionInConstructorTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_vsn.txt b/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_vsn.txt
index 730e13987a..97c92555ae 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_vsn.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionInConstructorTestAssertions_vsn.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionInConstructorTest.test started
 leTest org.scalajs.junit.ExceptionInConstructorTest.test failed: java.lang.UnsupportedOperationException: Exception while constructing the test class, took <TIME>
-e2org.scalajs.junit.ExceptionInConstructorTest.test::java.lang.UnsupportedOperationException: Exception while constructing the test class
+e2org.scalajs.junit.ExceptionInConstructorTest.test::java.lang.UnsupportedOperationException: Exception while constructing the test class::true
 ldTest org.scalajs.junit.ExceptionInConstructorTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_.txt b/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_.txt
index a2cb636eb6..ff7eb8a451 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.ExceptionTest.test started
 leTest org.scalajs.junit.ExceptionTest.test failed: java.lang.IndexOutOfBoundsException: Exception message, took <TIME>
-e2org.scalajs.junit.ExceptionTest.test::java.lang.IndexOutOfBoundsException: Exception message
+e2org.scalajs.junit.ExceptionTest.test::java.lang.IndexOutOfBoundsException: Exception message::true
 ldTest org.scalajs.junit.ExceptionTest.test finished, took <TIME>
 ldTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_a.txt b/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_a.txt
index a2cb636eb6..ff7eb8a451 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_a.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_a.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.ExceptionTest.test started
 leTest org.scalajs.junit.ExceptionTest.test failed: java.lang.IndexOutOfBoundsException: Exception message, took <TIME>
-e2org.scalajs.junit.ExceptionTest.test::java.lang.IndexOutOfBoundsException: Exception message
+e2org.scalajs.junit.ExceptionTest.test::java.lang.IndexOutOfBoundsException: Exception message::true
 ldTest org.scalajs.junit.ExceptionTest.test finished, took <TIME>
 ldTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_n.txt b/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_n.txt
index baf7da3727..4bd30e9fd7 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_n.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_n.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.ExceptionTest.test started
 leTest org.scalajs.junit.ExceptionTest.test failed: java.lang.IndexOutOfBoundsException: Exception message, took <TIME>
-e2org.scalajs.junit.ExceptionTest.test::java.lang.IndexOutOfBoundsException: Exception message
+e2org.scalajs.junit.ExceptionTest.test::java.lang.IndexOutOfBoundsException: Exception message::true
 ldTest org.scalajs.junit.ExceptionTest.test finished, took <TIME>
 ldTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_na.txt b/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_na.txt
index baf7da3727..4bd30e9fd7 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_na.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_na.txt
@@ -1,7 +1,7 @@
 ldTest run started
 ldTest org.scalajs.junit.ExceptionTest.test started
 leTest org.scalajs.junit.ExceptionTest.test failed: java.lang.IndexOutOfBoundsException: Exception message, took <TIME>
-e2org.scalajs.junit.ExceptionTest.test::java.lang.IndexOutOfBoundsException: Exception message
+e2org.scalajs.junit.ExceptionTest.test::java.lang.IndexOutOfBoundsException: Exception message::true
 ldTest org.scalajs.junit.ExceptionTest.test finished, took <TIME>
 ldTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_nv.txt b/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_nv.txt
index fe2fdd138f..eb2ea5bab0 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_nv.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_nv.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionTest.test started
 leTest org.scalajs.junit.ExceptionTest.test failed: java.lang.IndexOutOfBoundsException: Exception message, took <TIME>
-e2org.scalajs.junit.ExceptionTest.test::java.lang.IndexOutOfBoundsException: Exception message
+e2org.scalajs.junit.ExceptionTest.test::java.lang.IndexOutOfBoundsException: Exception message::true
 ldTest org.scalajs.junit.ExceptionTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_nva.txt b/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_nva.txt
index fe2fdd138f..eb2ea5bab0 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_nva.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_nva.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionTest.test started
 leTest org.scalajs.junit.ExceptionTest.test failed: java.lang.IndexOutOfBoundsException: Exception message, took <TIME>
-e2org.scalajs.junit.ExceptionTest.test::java.lang.IndexOutOfBoundsException: Exception message
+e2org.scalajs.junit.ExceptionTest.test::java.lang.IndexOutOfBoundsException: Exception message::true
 ldTest org.scalajs.junit.ExceptionTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_nvc.txt b/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_nvc.txt
index ebc2be30ea..8445e5a39e 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_nvc.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_nvc.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionTest.test started
 leTest org.scalajs.junit.ExceptionTest.test failed: Exception message, took <TIME>
-e2org.scalajs.junit.ExceptionTest.test::java.lang.IndexOutOfBoundsException: Exception message
+e2org.scalajs.junit.ExceptionTest.test::java.lang.IndexOutOfBoundsException: Exception message::true
 ldTest org.scalajs.junit.ExceptionTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_nvca.txt b/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_nvca.txt
index ebc2be30ea..8445e5a39e 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_nvca.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_nvca.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionTest.test started
 leTest org.scalajs.junit.ExceptionTest.test failed: Exception message, took <TIME>
-e2org.scalajs.junit.ExceptionTest.test::java.lang.IndexOutOfBoundsException: Exception message
+e2org.scalajs.junit.ExceptionTest.test::java.lang.IndexOutOfBoundsException: Exception message::true
 ldTest org.scalajs.junit.ExceptionTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_v.txt b/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_v.txt
index 5b096e3aa3..5fea8c9e3f 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_v.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_v.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionTest.test started
 leTest org.scalajs.junit.ExceptionTest.test failed: java.lang.IndexOutOfBoundsException: Exception message, took <TIME>
-e2org.scalajs.junit.ExceptionTest.test::java.lang.IndexOutOfBoundsException: Exception message
+e2org.scalajs.junit.ExceptionTest.test::java.lang.IndexOutOfBoundsException: Exception message::true
 ldTest org.scalajs.junit.ExceptionTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_va.txt b/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_va.txt
index 5b096e3aa3..5fea8c9e3f 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_va.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_va.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionTest.test started
 leTest org.scalajs.junit.ExceptionTest.test failed: java.lang.IndexOutOfBoundsException: Exception message, took <TIME>
-e2org.scalajs.junit.ExceptionTest.test::java.lang.IndexOutOfBoundsException: Exception message
+e2org.scalajs.junit.ExceptionTest.test::java.lang.IndexOutOfBoundsException: Exception message::true
 ldTest org.scalajs.junit.ExceptionTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_vc.txt b/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_vc.txt
index e6b60ba892..e0e0a77c8d 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_vc.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_vc.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionTest.test started
 leTest org.scalajs.junit.ExceptionTest.test failed: Exception message, took <TIME>
-e2org.scalajs.junit.ExceptionTest.test::java.lang.IndexOutOfBoundsException: Exception message
+e2org.scalajs.junit.ExceptionTest.test::java.lang.IndexOutOfBoundsException: Exception message::true
 ldTest org.scalajs.junit.ExceptionTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_vs.txt b/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_vs.txt
index 5b096e3aa3..5fea8c9e3f 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_vs.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_vs.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionTest.test started
 leTest org.scalajs.junit.ExceptionTest.test failed: java.lang.IndexOutOfBoundsException: Exception message, took <TIME>
-e2org.scalajs.junit.ExceptionTest.test::java.lang.IndexOutOfBoundsException: Exception message
+e2org.scalajs.junit.ExceptionTest.test::java.lang.IndexOutOfBoundsException: Exception message::true
 ldTest org.scalajs.junit.ExceptionTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_vsn.txt b/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_vsn.txt
index fe2fdd138f..eb2ea5bab0 100644
--- a/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_vsn.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExceptionTestAssertions_vsn.txt
@@ -1,7 +1,7 @@
 liTest run started
 liTest org.scalajs.junit.ExceptionTest.test started
 leTest org.scalajs.junit.ExceptionTest.test failed: java.lang.IndexOutOfBoundsException: Exception message, took <TIME>
-e2org.scalajs.junit.ExceptionTest.test::java.lang.IndexOutOfBoundsException: Exception message
+e2org.scalajs.junit.ExceptionTest.test::java.lang.IndexOutOfBoundsException: Exception message::true
 ldTest org.scalajs.junit.ExceptionTest.test finished, took <TIME>
 liTest run finished: 1 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_.txt b/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_.txt
index 72e5ff3b5a..464af5da50 100644
--- a/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_.txt
@@ -1,22 +1,22 @@
 ldTest run started
 ldTest org.scalajs.junit.ExpectTest.expectAssert started
 ldTest org.scalajs.junit.ExpectTest.expectAssert finished, took <TIME>
-e0org.scalajs.junit.ExpectTest.expectAssert::
+e0org.scalajs.junit.ExpectTest.expectAssert::::true
 ldTest org.scalajs.junit.ExpectTest.expectNormal started
 ldTest org.scalajs.junit.ExpectTest.expectNormal finished, took <TIME>
-e0org.scalajs.junit.ExpectTest.expectNormal::
+e0org.scalajs.junit.ExpectTest.expectNormal::::true
 ldTest org.scalajs.junit.ExpectTest.failExpectAssert started
 leTest org.scalajs.junit.ExpectTest.failExpectAssert failed: Expected exception: java.lang.AssertionError, took <TIME>
-e2org.scalajs.junit.ExpectTest.failExpectAssert::java.lang.AssertionError: Expected exception: java.lang.AssertionError
+e2org.scalajs.junit.ExpectTest.failExpectAssert::java.lang.AssertionError: Expected exception: java.lang.AssertionError::true
 ldTest org.scalajs.junit.ExpectTest.failExpectAssert finished, took <TIME>
 ldTest org.scalajs.junit.ExpectTest.failExpectDifferent started
 leTest org.scalajs.junit.ExpectTest.failExpectDifferent failed: java.lang.Exception: Unexpected exception, expected<java.io.IOException> but was<java.lang.IllegalArgumentException>, took <TIME>
 leCaused by: java.lang.IllegalArgumentException
-e2org.scalajs.junit.ExpectTest.failExpectDifferent::java.lang.Exception: Unexpected exception, expected<java.io.IOException> but was<java.lang.IllegalArgumentException>
+e2org.scalajs.junit.ExpectTest.failExpectDifferent::java.lang.Exception: Unexpected exception, expected<java.io.IOException> but was<java.lang.IllegalArgumentException>::true
 ldTest org.scalajs.junit.ExpectTest.failExpectDifferent finished, took <TIME>
 ldTest org.scalajs.junit.ExpectTest.failExpectNoThrow started
 leTest org.scalajs.junit.ExpectTest.failExpectNoThrow failed: Expected exception: java.io.IOException, took <TIME>
-e2org.scalajs.junit.ExpectTest.failExpectNoThrow::java.lang.AssertionError: Expected exception: java.io.IOException
+e2org.scalajs.junit.ExpectTest.failExpectNoThrow::java.lang.AssertionError: Expected exception: java.io.IOException::true
 ldTest org.scalajs.junit.ExpectTest.failExpectNoThrow finished, took <TIME>
 ldTest run finished: 3 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_a.txt b/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_a.txt
index 4f2ff68a1a..297d99c89d 100644
--- a/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_a.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_a.txt
@@ -1,22 +1,22 @@
 ldTest run started
 ldTest org.scalajs.junit.ExpectTest.expectAssert started
 ldTest org.scalajs.junit.ExpectTest.expectAssert finished, took <TIME>
-e0org.scalajs.junit.ExpectTest.expectAssert::
+e0org.scalajs.junit.ExpectTest.expectAssert::::true
 ldTest org.scalajs.junit.ExpectTest.expectNormal started
 ldTest org.scalajs.junit.ExpectTest.expectNormal finished, took <TIME>
-e0org.scalajs.junit.ExpectTest.expectNormal::
+e0org.scalajs.junit.ExpectTest.expectNormal::::true
 ldTest org.scalajs.junit.ExpectTest.failExpectAssert started
 leTest org.scalajs.junit.ExpectTest.failExpectAssert failed: java.lang.AssertionError: Expected exception: java.lang.AssertionError, took <TIME>
-e2org.scalajs.junit.ExpectTest.failExpectAssert::java.lang.AssertionError: Expected exception: java.lang.AssertionError
+e2org.scalajs.junit.ExpectTest.failExpectAssert::java.lang.AssertionError: Expected exception: java.lang.AssertionError::true
 ldTest org.scalajs.junit.ExpectTest.failExpectAssert finished, took <TIME>
 ldTest org.scalajs.junit.ExpectTest.failExpectDifferent started
 leTest org.scalajs.junit.ExpectTest.failExpectDifferent failed: java.lang.Exception: Unexpected exception, expected<java.io.IOException> but was<java.lang.IllegalArgumentException>, took <TIME>
 leCaused by: java.lang.IllegalArgumentException
-e2org.scalajs.junit.ExpectTest.failExpectDifferent::java.lang.Exception: Unexpected exception, expected<java.io.IOException> but was<java.lang.IllegalArgumentException>
+e2org.scalajs.junit.ExpectTest.failExpectDifferent::java.lang.Exception: Unexpected exception, expected<java.io.IOException> but was<java.lang.IllegalArgumentException>::true
 ldTest org.scalajs.junit.ExpectTest.failExpectDifferent finished, took <TIME>
 ldTest org.scalajs.junit.ExpectTest.failExpectNoThrow started
 leTest org.scalajs.junit.ExpectTest.failExpectNoThrow failed: java.lang.AssertionError: Expected exception: java.io.IOException, took <TIME>
-e2org.scalajs.junit.ExpectTest.failExpectNoThrow::java.lang.AssertionError: Expected exception: java.io.IOException
+e2org.scalajs.junit.ExpectTest.failExpectNoThrow::java.lang.AssertionError: Expected exception: java.io.IOException::true
 ldTest org.scalajs.junit.ExpectTest.failExpectNoThrow finished, took <TIME>
 ldTest run finished: 3 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_n.txt b/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_n.txt
index 37fe0cbb05..992f7c4117 100644
--- a/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_n.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_n.txt
@@ -1,22 +1,22 @@
 ldTest run started
 ldTest org.scalajs.junit.ExpectTest.expectAssert started
 ldTest org.scalajs.junit.ExpectTest.expectAssert finished, took <TIME>
-e0org.scalajs.junit.ExpectTest.expectAssert::
+e0org.scalajs.junit.ExpectTest.expectAssert::::true
 ldTest org.scalajs.junit.ExpectTest.expectNormal started
 ldTest org.scalajs.junit.ExpectTest.expectNormal finished, took <TIME>
-e0org.scalajs.junit.ExpectTest.expectNormal::
+e0org.scalajs.junit.ExpectTest.expectNormal::::true
 ldTest org.scalajs.junit.ExpectTest.failExpectAssert started
 leTest org.scalajs.junit.ExpectTest.failExpectAssert failed: Expected exception: java.lang.AssertionError, took <TIME>
-e2org.scalajs.junit.ExpectTest.failExpectAssert::java.lang.AssertionError: Expected exception: java.lang.AssertionError
+e2org.scalajs.junit.ExpectTest.failExpectAssert::java.lang.AssertionError: Expected exception: java.lang.AssertionError::true
 ldTest org.scalajs.junit.ExpectTest.failExpectAssert finished, took <TIME>
 ldTest org.scalajs.junit.ExpectTest.failExpectDifferent started
 leTest org.scalajs.junit.ExpectTest.failExpectDifferent failed: java.lang.Exception: Unexpected exception, expected<java.io.IOException> but was<java.lang.IllegalArgumentException>, took <TIME>
 leCaused by: java.lang.IllegalArgumentException
-e2org.scalajs.junit.ExpectTest.failExpectDifferent::java.lang.Exception: Unexpected exception, expected<java.io.IOException> but was<java.lang.IllegalArgumentException>
+e2org.scalajs.junit.ExpectTest.failExpectDifferent::java.lang.Exception: Unexpected exception, expected<java.io.IOException> but was<java.lang.IllegalArgumentException>::true
 ldTest org.scalajs.junit.ExpectTest.failExpectDifferent finished, took <TIME>
 ldTest org.scalajs.junit.ExpectTest.failExpectNoThrow started
 leTest org.scalajs.junit.ExpectTest.failExpectNoThrow failed: Expected exception: java.io.IOException, took <TIME>
-e2org.scalajs.junit.ExpectTest.failExpectNoThrow::java.lang.AssertionError: Expected exception: java.io.IOException
+e2org.scalajs.junit.ExpectTest.failExpectNoThrow::java.lang.AssertionError: Expected exception: java.io.IOException::true
 ldTest org.scalajs.junit.ExpectTest.failExpectNoThrow finished, took <TIME>
 ldTest run finished: 3 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_na.txt b/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_na.txt
index 6150ebebfd..013c9ebd5f 100644
--- a/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_na.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_na.txt
@@ -1,22 +1,22 @@
 ldTest run started
 ldTest org.scalajs.junit.ExpectTest.expectAssert started
 ldTest org.scalajs.junit.ExpectTest.expectAssert finished, took <TIME>
-e0org.scalajs.junit.ExpectTest.expectAssert::
+e0org.scalajs.junit.ExpectTest.expectAssert::::true
 ldTest org.scalajs.junit.ExpectTest.expectNormal started
 ldTest org.scalajs.junit.ExpectTest.expectNormal finished, took <TIME>
-e0org.scalajs.junit.ExpectTest.expectNormal::
+e0org.scalajs.junit.ExpectTest.expectNormal::::true
 ldTest org.scalajs.junit.ExpectTest.failExpectAssert started
 leTest org.scalajs.junit.ExpectTest.failExpectAssert failed: java.lang.AssertionError: Expected exception: java.lang.AssertionError, took <TIME>
-e2org.scalajs.junit.ExpectTest.failExpectAssert::java.lang.AssertionError: Expected exception: java.lang.AssertionError
+e2org.scalajs.junit.ExpectTest.failExpectAssert::java.lang.AssertionError: Expected exception: java.lang.AssertionError::true
 ldTest org.scalajs.junit.ExpectTest.failExpectAssert finished, took <TIME>
 ldTest org.scalajs.junit.ExpectTest.failExpectDifferent started
 leTest org.scalajs.junit.ExpectTest.failExpectDifferent failed: java.lang.Exception: Unexpected exception, expected<java.io.IOException> but was<java.lang.IllegalArgumentException>, took <TIME>
 leCaused by: java.lang.IllegalArgumentException
-e2org.scalajs.junit.ExpectTest.failExpectDifferent::java.lang.Exception: Unexpected exception, expected<java.io.IOException> but was<java.lang.IllegalArgumentException>
+e2org.scalajs.junit.ExpectTest.failExpectDifferent::java.lang.Exception: Unexpected exception, expected<java.io.IOException> but was<java.lang.IllegalArgumentException>::true
 ldTest org.scalajs.junit.ExpectTest.failExpectDifferent finished, took <TIME>
 ldTest org.scalajs.junit.ExpectTest.failExpectNoThrow started
 leTest org.scalajs.junit.ExpectTest.failExpectNoThrow failed: java.lang.AssertionError: Expected exception: java.io.IOException, took <TIME>
-e2org.scalajs.junit.ExpectTest.failExpectNoThrow::java.lang.AssertionError: Expected exception: java.io.IOException
+e2org.scalajs.junit.ExpectTest.failExpectNoThrow::java.lang.AssertionError: Expected exception: java.io.IOException::true
 ldTest org.scalajs.junit.ExpectTest.failExpectNoThrow finished, took <TIME>
 ldTest run finished: 3 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_nv.txt b/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_nv.txt
index f497cc9554..4b693fa242 100644
--- a/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_nv.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_nv.txt
@@ -1,22 +1,22 @@
 liTest run started
 liTest org.scalajs.junit.ExpectTest.expectAssert started
 ldTest org.scalajs.junit.ExpectTest.expectAssert finished, took <TIME>
-e0org.scalajs.junit.ExpectTest.expectAssert::
+e0org.scalajs.junit.ExpectTest.expectAssert::::true
 liTest org.scalajs.junit.ExpectTest.expectNormal started
 ldTest org.scalajs.junit.ExpectTest.expectNormal finished, took <TIME>
-e0org.scalajs.junit.ExpectTest.expectNormal::
+e0org.scalajs.junit.ExpectTest.expectNormal::::true
 liTest org.scalajs.junit.ExpectTest.failExpectAssert started
 leTest org.scalajs.junit.ExpectTest.failExpectAssert failed: Expected exception: java.lang.AssertionError, took <TIME>
-e2org.scalajs.junit.ExpectTest.failExpectAssert::java.lang.AssertionError: Expected exception: java.lang.AssertionError
+e2org.scalajs.junit.ExpectTest.failExpectAssert::java.lang.AssertionError: Expected exception: java.lang.AssertionError::true
 ldTest org.scalajs.junit.ExpectTest.failExpectAssert finished, took <TIME>
 liTest org.scalajs.junit.ExpectTest.failExpectDifferent started
 leTest org.scalajs.junit.ExpectTest.failExpectDifferent failed: java.lang.Exception: Unexpected exception, expected<java.io.IOException> but was<java.lang.IllegalArgumentException>, took <TIME>
 leCaused by: java.lang.IllegalArgumentException
-e2org.scalajs.junit.ExpectTest.failExpectDifferent::java.lang.Exception: Unexpected exception, expected<java.io.IOException> but was<java.lang.IllegalArgumentException>
+e2org.scalajs.junit.ExpectTest.failExpectDifferent::java.lang.Exception: Unexpected exception, expected<java.io.IOException> but was<java.lang.IllegalArgumentException>::true
 ldTest org.scalajs.junit.ExpectTest.failExpectDifferent finished, took <TIME>
 liTest org.scalajs.junit.ExpectTest.failExpectNoThrow started
 leTest org.scalajs.junit.ExpectTest.failExpectNoThrow failed: Expected exception: java.io.IOException, took <TIME>
-e2org.scalajs.junit.ExpectTest.failExpectNoThrow::java.lang.AssertionError: Expected exception: java.io.IOException
+e2org.scalajs.junit.ExpectTest.failExpectNoThrow::java.lang.AssertionError: Expected exception: java.io.IOException::true
 ldTest org.scalajs.junit.ExpectTest.failExpectNoThrow finished, took <TIME>
 liTest run finished: 3 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_nva.txt b/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_nva.txt
index 4da5dd77e6..024a540893 100644
--- a/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_nva.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_nva.txt
@@ -1,22 +1,22 @@
 liTest run started
 liTest org.scalajs.junit.ExpectTest.expectAssert started
 ldTest org.scalajs.junit.ExpectTest.expectAssert finished, took <TIME>
-e0org.scalajs.junit.ExpectTest.expectAssert::
+e0org.scalajs.junit.ExpectTest.expectAssert::::true
 liTest org.scalajs.junit.ExpectTest.expectNormal started
 ldTest org.scalajs.junit.ExpectTest.expectNormal finished, took <TIME>
-e0org.scalajs.junit.ExpectTest.expectNormal::
+e0org.scalajs.junit.ExpectTest.expectNormal::::true
 liTest org.scalajs.junit.ExpectTest.failExpectAssert started
 leTest org.scalajs.junit.ExpectTest.failExpectAssert failed: java.lang.AssertionError: Expected exception: java.lang.AssertionError, took <TIME>
-e2org.scalajs.junit.ExpectTest.failExpectAssert::java.lang.AssertionError: Expected exception: java.lang.AssertionError
+e2org.scalajs.junit.ExpectTest.failExpectAssert::java.lang.AssertionError: Expected exception: java.lang.AssertionError::true
 ldTest org.scalajs.junit.ExpectTest.failExpectAssert finished, took <TIME>
 liTest org.scalajs.junit.ExpectTest.failExpectDifferent started
 leTest org.scalajs.junit.ExpectTest.failExpectDifferent failed: java.lang.Exception: Unexpected exception, expected<java.io.IOException> but was<java.lang.IllegalArgumentException>, took <TIME>
 leCaused by: java.lang.IllegalArgumentException
-e2org.scalajs.junit.ExpectTest.failExpectDifferent::java.lang.Exception: Unexpected exception, expected<java.io.IOException> but was<java.lang.IllegalArgumentException>
+e2org.scalajs.junit.ExpectTest.failExpectDifferent::java.lang.Exception: Unexpected exception, expected<java.io.IOException> but was<java.lang.IllegalArgumentException>::true
 ldTest org.scalajs.junit.ExpectTest.failExpectDifferent finished, took <TIME>
 liTest org.scalajs.junit.ExpectTest.failExpectNoThrow started
 leTest org.scalajs.junit.ExpectTest.failExpectNoThrow failed: java.lang.AssertionError: Expected exception: java.io.IOException, took <TIME>
-e2org.scalajs.junit.ExpectTest.failExpectNoThrow::java.lang.AssertionError: Expected exception: java.io.IOException
+e2org.scalajs.junit.ExpectTest.failExpectNoThrow::java.lang.AssertionError: Expected exception: java.io.IOException::true
 ldTest org.scalajs.junit.ExpectTest.failExpectNoThrow finished, took <TIME>
 liTest run finished: 3 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_nvc.txt b/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_nvc.txt
index 413630af26..68776c893f 100644
--- a/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_nvc.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_nvc.txt
@@ -1,22 +1,22 @@
 liTest run started
 liTest org.scalajs.junit.ExpectTest.expectAssert started
 ldTest org.scalajs.junit.ExpectTest.expectAssert finished, took <TIME>
-e0org.scalajs.junit.ExpectTest.expectAssert::
+e0org.scalajs.junit.ExpectTest.expectAssert::::true
 liTest org.scalajs.junit.ExpectTest.expectNormal started
 ldTest org.scalajs.junit.ExpectTest.expectNormal finished, took <TIME>
-e0org.scalajs.junit.ExpectTest.expectNormal::
+e0org.scalajs.junit.ExpectTest.expectNormal::::true
 liTest org.scalajs.junit.ExpectTest.failExpectAssert started
 leTest org.scalajs.junit.ExpectTest.failExpectAssert failed: Expected exception: java.lang.AssertionError, took <TIME>
-e2org.scalajs.junit.ExpectTest.failExpectAssert::java.lang.AssertionError: Expected exception: java.lang.AssertionError
+e2org.scalajs.junit.ExpectTest.failExpectAssert::java.lang.AssertionError: Expected exception: java.lang.AssertionError::true
 ldTest org.scalajs.junit.ExpectTest.failExpectAssert finished, took <TIME>
 liTest org.scalajs.junit.ExpectTest.failExpectDifferent started
 leTest org.scalajs.junit.ExpectTest.failExpectDifferent failed: Unexpected exception, expected<java.io.IOException> but was<java.lang.IllegalArgumentException>, took <TIME>
 leCaused by: java.lang.IllegalArgumentException
-e2org.scalajs.junit.ExpectTest.failExpectDifferent::java.lang.Exception: Unexpected exception, expected<java.io.IOException> but was<java.lang.IllegalArgumentException>
+e2org.scalajs.junit.ExpectTest.failExpectDifferent::java.lang.Exception: Unexpected exception, expected<java.io.IOException> but was<java.lang.IllegalArgumentException>::true
 ldTest org.scalajs.junit.ExpectTest.failExpectDifferent finished, took <TIME>
 liTest org.scalajs.junit.ExpectTest.failExpectNoThrow started
 leTest org.scalajs.junit.ExpectTest.failExpectNoThrow failed: Expected exception: java.io.IOException, took <TIME>
-e2org.scalajs.junit.ExpectTest.failExpectNoThrow::java.lang.AssertionError: Expected exception: java.io.IOException
+e2org.scalajs.junit.ExpectTest.failExpectNoThrow::java.lang.AssertionError: Expected exception: java.io.IOException::true
 ldTest org.scalajs.junit.ExpectTest.failExpectNoThrow finished, took <TIME>
 liTest run finished: 3 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_nvca.txt b/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_nvca.txt
index 413630af26..68776c893f 100644
--- a/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_nvca.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_nvca.txt
@@ -1,22 +1,22 @@
 liTest run started
 liTest org.scalajs.junit.ExpectTest.expectAssert started
 ldTest org.scalajs.junit.ExpectTest.expectAssert finished, took <TIME>
-e0org.scalajs.junit.ExpectTest.expectAssert::
+e0org.scalajs.junit.ExpectTest.expectAssert::::true
 liTest org.scalajs.junit.ExpectTest.expectNormal started
 ldTest org.scalajs.junit.ExpectTest.expectNormal finished, took <TIME>
-e0org.scalajs.junit.ExpectTest.expectNormal::
+e0org.scalajs.junit.ExpectTest.expectNormal::::true
 liTest org.scalajs.junit.ExpectTest.failExpectAssert started
 leTest org.scalajs.junit.ExpectTest.failExpectAssert failed: Expected exception: java.lang.AssertionError, took <TIME>
-e2org.scalajs.junit.ExpectTest.failExpectAssert::java.lang.AssertionError: Expected exception: java.lang.AssertionError
+e2org.scalajs.junit.ExpectTest.failExpectAssert::java.lang.AssertionError: Expected exception: java.lang.AssertionError::true
 ldTest org.scalajs.junit.ExpectTest.failExpectAssert finished, took <TIME>
 liTest org.scalajs.junit.ExpectTest.failExpectDifferent started
 leTest org.scalajs.junit.ExpectTest.failExpectDifferent failed: Unexpected exception, expected<java.io.IOException> but was<java.lang.IllegalArgumentException>, took <TIME>
 leCaused by: java.lang.IllegalArgumentException
-e2org.scalajs.junit.ExpectTest.failExpectDifferent::java.lang.Exception: Unexpected exception, expected<java.io.IOException> but was<java.lang.IllegalArgumentException>
+e2org.scalajs.junit.ExpectTest.failExpectDifferent::java.lang.Exception: Unexpected exception, expected<java.io.IOException> but was<java.lang.IllegalArgumentException>::true
 ldTest org.scalajs.junit.ExpectTest.failExpectDifferent finished, took <TIME>
 liTest org.scalajs.junit.ExpectTest.failExpectNoThrow started
 leTest org.scalajs.junit.ExpectTest.failExpectNoThrow failed: Expected exception: java.io.IOException, took <TIME>
-e2org.scalajs.junit.ExpectTest.failExpectNoThrow::java.lang.AssertionError: Expected exception: java.io.IOException
+e2org.scalajs.junit.ExpectTest.failExpectNoThrow::java.lang.AssertionError: Expected exception: java.io.IOException::true
 ldTest org.scalajs.junit.ExpectTest.failExpectNoThrow finished, took <TIME>
 liTest run finished: 3 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_v.txt b/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_v.txt
index 8c8f6c7eab..77c158379a 100644
--- a/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_v.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_v.txt
@@ -1,22 +1,22 @@
 liTest run started
 liTest org.scalajs.junit.ExpectTest.expectAssert started
 ldTest org.scalajs.junit.ExpectTest.expectAssert finished, took <TIME>
-e0org.scalajs.junit.ExpectTest.expectAssert::
+e0org.scalajs.junit.ExpectTest.expectAssert::::true
 liTest org.scalajs.junit.ExpectTest.expectNormal started
 ldTest org.scalajs.junit.ExpectTest.expectNormal finished, took <TIME>
-e0org.scalajs.junit.ExpectTest.expectNormal::
+e0org.scalajs.junit.ExpectTest.expectNormal::::true
 liTest org.scalajs.junit.ExpectTest.failExpectAssert started
 leTest org.scalajs.junit.ExpectTest.failExpectAssert failed: Expected exception: java.lang.AssertionError, took <TIME>
-e2org.scalajs.junit.ExpectTest.failExpectAssert::java.lang.AssertionError: Expected exception: java.lang.AssertionError
+e2org.scalajs.junit.ExpectTest.failExpectAssert::java.lang.AssertionError: Expected exception: java.lang.AssertionError::true
 ldTest org.scalajs.junit.ExpectTest.failExpectAssert finished, took <TIME>
 liTest org.scalajs.junit.ExpectTest.failExpectDifferent started
 leTest org.scalajs.junit.ExpectTest.failExpectDifferent failed: java.lang.Exception: Unexpected exception, expected<java.io.IOException> but was<java.lang.IllegalArgumentException>, took <TIME>
 leCaused by: java.lang.IllegalArgumentException
-e2org.scalajs.junit.ExpectTest.failExpectDifferent::java.lang.Exception: Unexpected exception, expected<java.io.IOException> but was<java.lang.IllegalArgumentException>
+e2org.scalajs.junit.ExpectTest.failExpectDifferent::java.lang.Exception: Unexpected exception, expected<java.io.IOException> but was<java.lang.IllegalArgumentException>::true
 ldTest org.scalajs.junit.ExpectTest.failExpectDifferent finished, took <TIME>
 liTest org.scalajs.junit.ExpectTest.failExpectNoThrow started
 leTest org.scalajs.junit.ExpectTest.failExpectNoThrow failed: Expected exception: java.io.IOException, took <TIME>
-e2org.scalajs.junit.ExpectTest.failExpectNoThrow::java.lang.AssertionError: Expected exception: java.io.IOException
+e2org.scalajs.junit.ExpectTest.failExpectNoThrow::java.lang.AssertionError: Expected exception: java.io.IOException::true
 ldTest org.scalajs.junit.ExpectTest.failExpectNoThrow finished, took <TIME>
 liTest run finished: 3 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_va.txt b/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_va.txt
index 0d1b8efa4a..99ca2163cf 100644
--- a/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_va.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_va.txt
@@ -1,22 +1,22 @@
 liTest run started
 liTest org.scalajs.junit.ExpectTest.expectAssert started
 ldTest org.scalajs.junit.ExpectTest.expectAssert finished, took <TIME>
-e0org.scalajs.junit.ExpectTest.expectAssert::
+e0org.scalajs.junit.ExpectTest.expectAssert::::true
 liTest org.scalajs.junit.ExpectTest.expectNormal started
 ldTest org.scalajs.junit.ExpectTest.expectNormal finished, took <TIME>
-e0org.scalajs.junit.ExpectTest.expectNormal::
+e0org.scalajs.junit.ExpectTest.expectNormal::::true
 liTest org.scalajs.junit.ExpectTest.failExpectAssert started
 leTest org.scalajs.junit.ExpectTest.failExpectAssert failed: java.lang.AssertionError: Expected exception: java.lang.AssertionError, took <TIME>
-e2org.scalajs.junit.ExpectTest.failExpectAssert::java.lang.AssertionError: Expected exception: java.lang.AssertionError
+e2org.scalajs.junit.ExpectTest.failExpectAssert::java.lang.AssertionError: Expected exception: java.lang.AssertionError::true
 ldTest org.scalajs.junit.ExpectTest.failExpectAssert finished, took <TIME>
 liTest org.scalajs.junit.ExpectTest.failExpectDifferent started
 leTest org.scalajs.junit.ExpectTest.failExpectDifferent failed: java.lang.Exception: Unexpected exception, expected<java.io.IOException> but was<java.lang.IllegalArgumentException>, took <TIME>
 leCaused by: java.lang.IllegalArgumentException
-e2org.scalajs.junit.ExpectTest.failExpectDifferent::java.lang.Exception: Unexpected exception, expected<java.io.IOException> but was<java.lang.IllegalArgumentException>
+e2org.scalajs.junit.ExpectTest.failExpectDifferent::java.lang.Exception: Unexpected exception, expected<java.io.IOException> but was<java.lang.IllegalArgumentException>::true
 ldTest org.scalajs.junit.ExpectTest.failExpectDifferent finished, took <TIME>
 liTest org.scalajs.junit.ExpectTest.failExpectNoThrow started
 leTest org.scalajs.junit.ExpectTest.failExpectNoThrow failed: java.lang.AssertionError: Expected exception: java.io.IOException, took <TIME>
-e2org.scalajs.junit.ExpectTest.failExpectNoThrow::java.lang.AssertionError: Expected exception: java.io.IOException
+e2org.scalajs.junit.ExpectTest.failExpectNoThrow::java.lang.AssertionError: Expected exception: java.io.IOException::true
 ldTest org.scalajs.junit.ExpectTest.failExpectNoThrow finished, took <TIME>
 liTest run finished: 3 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_vc.txt b/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_vc.txt
index cccda11d1a..d1ef916212 100644
--- a/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_vc.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_vc.txt
@@ -1,22 +1,22 @@
 liTest run started
 liTest org.scalajs.junit.ExpectTest.expectAssert started
 ldTest org.scalajs.junit.ExpectTest.expectAssert finished, took <TIME>
-e0org.scalajs.junit.ExpectTest.expectAssert::
+e0org.scalajs.junit.ExpectTest.expectAssert::::true
 liTest org.scalajs.junit.ExpectTest.expectNormal started
 ldTest org.scalajs.junit.ExpectTest.expectNormal finished, took <TIME>
-e0org.scalajs.junit.ExpectTest.expectNormal::
+e0org.scalajs.junit.ExpectTest.expectNormal::::true
 liTest org.scalajs.junit.ExpectTest.failExpectAssert started
 leTest org.scalajs.junit.ExpectTest.failExpectAssert failed: Expected exception: java.lang.AssertionError, took <TIME>
-e2org.scalajs.junit.ExpectTest.failExpectAssert::java.lang.AssertionError: Expected exception: java.lang.AssertionError
+e2org.scalajs.junit.ExpectTest.failExpectAssert::java.lang.AssertionError: Expected exception: java.lang.AssertionError::true
 ldTest org.scalajs.junit.ExpectTest.failExpectAssert finished, took <TIME>
 liTest org.scalajs.junit.ExpectTest.failExpectDifferent started
 leTest org.scalajs.junit.ExpectTest.failExpectDifferent failed: Unexpected exception, expected<java.io.IOException> but was<java.lang.IllegalArgumentException>, took <TIME>
 leCaused by: java.lang.IllegalArgumentException
-e2org.scalajs.junit.ExpectTest.failExpectDifferent::java.lang.Exception: Unexpected exception, expected<java.io.IOException> but was<java.lang.IllegalArgumentException>
+e2org.scalajs.junit.ExpectTest.failExpectDifferent::java.lang.Exception: Unexpected exception, expected<java.io.IOException> but was<java.lang.IllegalArgumentException>::true
 ldTest org.scalajs.junit.ExpectTest.failExpectDifferent finished, took <TIME>
 liTest org.scalajs.junit.ExpectTest.failExpectNoThrow started
 leTest org.scalajs.junit.ExpectTest.failExpectNoThrow failed: Expected exception: java.io.IOException, took <TIME>
-e2org.scalajs.junit.ExpectTest.failExpectNoThrow::java.lang.AssertionError: Expected exception: java.io.IOException
+e2org.scalajs.junit.ExpectTest.failExpectNoThrow::java.lang.AssertionError: Expected exception: java.io.IOException::true
 ldTest org.scalajs.junit.ExpectTest.failExpectNoThrow finished, took <TIME>
 liTest run finished: 3 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_vs.txt b/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_vs.txt
index 8c8f6c7eab..77c158379a 100644
--- a/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_vs.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_vs.txt
@@ -1,22 +1,22 @@
 liTest run started
 liTest org.scalajs.junit.ExpectTest.expectAssert started
 ldTest org.scalajs.junit.ExpectTest.expectAssert finished, took <TIME>
-e0org.scalajs.junit.ExpectTest.expectAssert::
+e0org.scalajs.junit.ExpectTest.expectAssert::::true
 liTest org.scalajs.junit.ExpectTest.expectNormal started
 ldTest org.scalajs.junit.ExpectTest.expectNormal finished, took <TIME>
-e0org.scalajs.junit.ExpectTest.expectNormal::
+e0org.scalajs.junit.ExpectTest.expectNormal::::true
 liTest org.scalajs.junit.ExpectTest.failExpectAssert started
 leTest org.scalajs.junit.ExpectTest.failExpectAssert failed: Expected exception: java.lang.AssertionError, took <TIME>
-e2org.scalajs.junit.ExpectTest.failExpectAssert::java.lang.AssertionError: Expected exception: java.lang.AssertionError
+e2org.scalajs.junit.ExpectTest.failExpectAssert::java.lang.AssertionError: Expected exception: java.lang.AssertionError::true
 ldTest org.scalajs.junit.ExpectTest.failExpectAssert finished, took <TIME>
 liTest org.scalajs.junit.ExpectTest.failExpectDifferent started
 leTest org.scalajs.junit.ExpectTest.failExpectDifferent failed: java.lang.Exception: Unexpected exception, expected<java.io.IOException> but was<java.lang.IllegalArgumentException>, took <TIME>
 leCaused by: java.lang.IllegalArgumentException
-e2org.scalajs.junit.ExpectTest.failExpectDifferent::java.lang.Exception: Unexpected exception, expected<java.io.IOException> but was<java.lang.IllegalArgumentException>
+e2org.scalajs.junit.ExpectTest.failExpectDifferent::java.lang.Exception: Unexpected exception, expected<java.io.IOException> but was<java.lang.IllegalArgumentException>::true
 ldTest org.scalajs.junit.ExpectTest.failExpectDifferent finished, took <TIME>
 liTest org.scalajs.junit.ExpectTest.failExpectNoThrow started
 leTest org.scalajs.junit.ExpectTest.failExpectNoThrow failed: Expected exception: java.io.IOException, took <TIME>
-e2org.scalajs.junit.ExpectTest.failExpectNoThrow::java.lang.AssertionError: Expected exception: java.io.IOException
+e2org.scalajs.junit.ExpectTest.failExpectNoThrow::java.lang.AssertionError: Expected exception: java.io.IOException::true
 ldTest org.scalajs.junit.ExpectTest.failExpectNoThrow finished, took <TIME>
 liTest run finished: 3 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_vsn.txt b/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_vsn.txt
index f497cc9554..4b693fa242 100644
--- a/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_vsn.txt
+++ b/junit-test/outputs/org/scalajs/junit/ExpectTestAssertions_vsn.txt
@@ -1,22 +1,22 @@
 liTest run started
 liTest org.scalajs.junit.ExpectTest.expectAssert started
 ldTest org.scalajs.junit.ExpectTest.expectAssert finished, took <TIME>
-e0org.scalajs.junit.ExpectTest.expectAssert::
+e0org.scalajs.junit.ExpectTest.expectAssert::::true
 liTest org.scalajs.junit.ExpectTest.expectNormal started
 ldTest org.scalajs.junit.ExpectTest.expectNormal finished, took <TIME>
-e0org.scalajs.junit.ExpectTest.expectNormal::
+e0org.scalajs.junit.ExpectTest.expectNormal::::true
 liTest org.scalajs.junit.ExpectTest.failExpectAssert started
 leTest org.scalajs.junit.ExpectTest.failExpectAssert failed: Expected exception: java.lang.AssertionError, took <TIME>
-e2org.scalajs.junit.ExpectTest.failExpectAssert::java.lang.AssertionError: Expected exception: java.lang.AssertionError
+e2org.scalajs.junit.ExpectTest.failExpectAssert::java.lang.AssertionError: Expected exception: java.lang.AssertionError::true
 ldTest org.scalajs.junit.ExpectTest.failExpectAssert finished, took <TIME>
 liTest org.scalajs.junit.ExpectTest.failExpectDifferent started
 leTest org.scalajs.junit.ExpectTest.failExpectDifferent failed: java.lang.Exception: Unexpected exception, expected<java.io.IOException> but was<java.lang.IllegalArgumentException>, took <TIME>
 leCaused by: java.lang.IllegalArgumentException
-e2org.scalajs.junit.ExpectTest.failExpectDifferent::java.lang.Exception: Unexpected exception, expected<java.io.IOException> but was<java.lang.IllegalArgumentException>
+e2org.scalajs.junit.ExpectTest.failExpectDifferent::java.lang.Exception: Unexpected exception, expected<java.io.IOException> but was<java.lang.IllegalArgumentException>::true
 ldTest org.scalajs.junit.ExpectTest.failExpectDifferent finished, took <TIME>
 liTest org.scalajs.junit.ExpectTest.failExpectNoThrow started
 leTest org.scalajs.junit.ExpectTest.failExpectNoThrow failed: Expected exception: java.io.IOException, took <TIME>
-e2org.scalajs.junit.ExpectTest.failExpectNoThrow::java.lang.AssertionError: Expected exception: java.io.IOException
+e2org.scalajs.junit.ExpectTest.failExpectNoThrow::java.lang.AssertionError: Expected exception: java.io.IOException::true
 ldTest org.scalajs.junit.ExpectTest.failExpectNoThrow finished, took <TIME>
 liTest run finished: 3 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_.txt b/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_.txt
index 50d9c8e58b..920df02368 100644
--- a/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_.txt
+++ b/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_.txt
@@ -1,5 +1,5 @@
 ldTest run started
 liTest org.scalajs.junit.IgnoreTest.onlyTest ignored
-e3org.scalajs.junit.IgnoreTest.onlyTest::
+e3org.scalajs.junit.IgnoreTest.onlyTest::::true
 ldTest run finished: 0 failed, 1 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_a.txt b/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_a.txt
index 50d9c8e58b..920df02368 100644
--- a/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_a.txt
+++ b/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_a.txt
@@ -1,5 +1,5 @@
 ldTest run started
 liTest org.scalajs.junit.IgnoreTest.onlyTest ignored
-e3org.scalajs.junit.IgnoreTest.onlyTest::
+e3org.scalajs.junit.IgnoreTest.onlyTest::::true
 ldTest run finished: 0 failed, 1 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_n.txt b/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_n.txt
index bcdf276d8c..e86ad0c6a4 100644
--- a/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_n.txt
+++ b/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_n.txt
@@ -1,5 +1,5 @@
 ldTest run started
 liTest org.scalajs.junit.IgnoreTest.onlyTest ignored
-e3org.scalajs.junit.IgnoreTest.onlyTest::
+e3org.scalajs.junit.IgnoreTest.onlyTest::::true
 ldTest run finished: 0 failed, 1 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_na.txt b/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_na.txt
index bcdf276d8c..e86ad0c6a4 100644
--- a/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_na.txt
+++ b/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_na.txt
@@ -1,5 +1,5 @@
 ldTest run started
 liTest org.scalajs.junit.IgnoreTest.onlyTest ignored
-e3org.scalajs.junit.IgnoreTest.onlyTest::
+e3org.scalajs.junit.IgnoreTest.onlyTest::::true
 ldTest run finished: 0 failed, 1 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_nv.txt b/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_nv.txt
index 8e4c0cfe5a..7416486af1 100644
--- a/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_nv.txt
+++ b/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_nv.txt
@@ -1,5 +1,5 @@
 liTest run started
 liTest org.scalajs.junit.IgnoreTest.onlyTest ignored
-e3org.scalajs.junit.IgnoreTest.onlyTest::
+e3org.scalajs.junit.IgnoreTest.onlyTest::::true
 liTest run finished: 0 failed, 1 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_nva.txt b/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_nva.txt
index 8e4c0cfe5a..7416486af1 100644
--- a/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_nva.txt
+++ b/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_nva.txt
@@ -1,5 +1,5 @@
 liTest run started
 liTest org.scalajs.junit.IgnoreTest.onlyTest ignored
-e3org.scalajs.junit.IgnoreTest.onlyTest::
+e3org.scalajs.junit.IgnoreTest.onlyTest::::true
 liTest run finished: 0 failed, 1 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_nvc.txt b/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_nvc.txt
index 8e4c0cfe5a..7416486af1 100644
--- a/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_nvc.txt
+++ b/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_nvc.txt
@@ -1,5 +1,5 @@
 liTest run started
 liTest org.scalajs.junit.IgnoreTest.onlyTest ignored
-e3org.scalajs.junit.IgnoreTest.onlyTest::
+e3org.scalajs.junit.IgnoreTest.onlyTest::::true
 liTest run finished: 0 failed, 1 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_nvca.txt b/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_nvca.txt
index 8e4c0cfe5a..7416486af1 100644
--- a/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_nvca.txt
+++ b/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_nvca.txt
@@ -1,5 +1,5 @@
 liTest run started
 liTest org.scalajs.junit.IgnoreTest.onlyTest ignored
-e3org.scalajs.junit.IgnoreTest.onlyTest::
+e3org.scalajs.junit.IgnoreTest.onlyTest::::true
 liTest run finished: 0 failed, 1 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_v.txt b/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_v.txt
index 4f4956b499..29eec54f04 100644
--- a/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_v.txt
+++ b/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_v.txt
@@ -1,5 +1,5 @@
 liTest run started
 liTest org.scalajs.junit.IgnoreTest.onlyTest ignored
-e3org.scalajs.junit.IgnoreTest.onlyTest::
+e3org.scalajs.junit.IgnoreTest.onlyTest::::true
 liTest run finished: 0 failed, 1 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_va.txt b/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_va.txt
index 4f4956b499..29eec54f04 100644
--- a/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_va.txt
+++ b/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_va.txt
@@ -1,5 +1,5 @@
 liTest run started
 liTest org.scalajs.junit.IgnoreTest.onlyTest ignored
-e3org.scalajs.junit.IgnoreTest.onlyTest::
+e3org.scalajs.junit.IgnoreTest.onlyTest::::true
 liTest run finished: 0 failed, 1 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_vc.txt b/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_vc.txt
index 4f4956b499..29eec54f04 100644
--- a/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_vc.txt
+++ b/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_vc.txt
@@ -1,5 +1,5 @@
 liTest run started
 liTest org.scalajs.junit.IgnoreTest.onlyTest ignored
-e3org.scalajs.junit.IgnoreTest.onlyTest::
+e3org.scalajs.junit.IgnoreTest.onlyTest::::true
 liTest run finished: 0 failed, 1 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_vs.txt b/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_vs.txt
index 4f4956b499..29eec54f04 100644
--- a/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_vs.txt
+++ b/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_vs.txt
@@ -1,5 +1,5 @@
 liTest run started
 liTest org.scalajs.junit.IgnoreTest.onlyTest ignored
-e3org.scalajs.junit.IgnoreTest.onlyTest::
+e3org.scalajs.junit.IgnoreTest.onlyTest::::true
 liTest run finished: 0 failed, 1 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_vsn.txt b/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_vsn.txt
index 8e4c0cfe5a..7416486af1 100644
--- a/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_vsn.txt
+++ b/junit-test/outputs/org/scalajs/junit/IgnoreTestAssertions_vsn.txt
@@ -1,5 +1,5 @@
 liTest run started
 liTest org.scalajs.junit.IgnoreTest.onlyTest ignored
-e3org.scalajs.junit.IgnoreTest.onlyTest::
+e3org.scalajs.junit.IgnoreTest.onlyTest::::true
 liTest run finished: 0 failed, 1 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_.txt b/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_.txt
index fd6b462615..77a78f75f5 100644
--- a/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_.txt
+++ b/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_.txt
@@ -1,6 +1,6 @@
 ldTest run started
 ldTest org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$ started
 ldTest org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$ finished, took <TIME>
-e0org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$::
+e0org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$::::true
 ldTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_a.txt b/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_a.txt
index fd6b462615..77a78f75f5 100644
--- a/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_a.txt
+++ b/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_a.txt
@@ -1,6 +1,6 @@
 ldTest run started
 ldTest org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$ started
 ldTest org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$ finished, took <TIME>
-e0org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$::
+e0org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$::::true
 ldTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_n.txt b/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_n.txt
index 90cf573f4c..c78751be5f 100644
--- a/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_n.txt
+++ b/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_n.txt
@@ -1,6 +1,6 @@
 ldTest run started
 ldTest org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$ started
 ldTest org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$ finished, took <TIME>
-e0org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$::
+e0org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$::::true
 ldTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_na.txt b/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_na.txt
index 90cf573f4c..c78751be5f 100644
--- a/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_na.txt
+++ b/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_na.txt
@@ -1,6 +1,6 @@
 ldTest run started
 ldTest org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$ started
 ldTest org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$ finished, took <TIME>
-e0org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$::
+e0org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$::::true
 ldTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_nv.txt b/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_nv.txt
index 272ac60261..7c8ab85b5d 100644
--- a/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_nv.txt
+++ b/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_nv.txt
@@ -1,6 +1,6 @@
 liTest run started
 liTest org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$ started
 ldTest org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$ finished, took <TIME>
-e0org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$::
+e0org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$::::true
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_nva.txt b/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_nva.txt
index 272ac60261..7c8ab85b5d 100644
--- a/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_nva.txt
+++ b/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_nva.txt
@@ -1,6 +1,6 @@
 liTest run started
 liTest org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$ started
 ldTest org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$ finished, took <TIME>
-e0org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$::
+e0org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$::::true
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_nvc.txt b/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_nvc.txt
index 272ac60261..7c8ab85b5d 100644
--- a/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_nvc.txt
+++ b/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_nvc.txt
@@ -1,6 +1,6 @@
 liTest run started
 liTest org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$ started
 ldTest org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$ finished, took <TIME>
-e0org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$::
+e0org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$::::true
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_nvca.txt b/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_nvca.txt
index 272ac60261..7c8ab85b5d 100644
--- a/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_nvca.txt
+++ b/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_nvca.txt
@@ -1,6 +1,6 @@
 liTest run started
 liTest org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$ started
 ldTest org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$ finished, took <TIME>
-e0org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$::
+e0org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$::::true
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_v.txt b/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_v.txt
index 962ab08aa7..b46d14d5fe 100644
--- a/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_v.txt
+++ b/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_v.txt
@@ -1,6 +1,6 @@
 liTest run started
 liTest org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$ started
 ldTest org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$ finished, took <TIME>
-e0org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$::
+e0org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$::::true
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_va.txt b/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_va.txt
index 962ab08aa7..b46d14d5fe 100644
--- a/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_va.txt
+++ b/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_va.txt
@@ -1,6 +1,6 @@
 liTest run started
 liTest org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$ started
 ldTest org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$ finished, took <TIME>
-e0org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$::
+e0org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$::::true
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_vc.txt b/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_vc.txt
index 962ab08aa7..b46d14d5fe 100644
--- a/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_vc.txt
+++ b/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_vc.txt
@@ -1,6 +1,6 @@
 liTest run started
 liTest org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$ started
 ldTest org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$ finished, took <TIME>
-e0org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$::
+e0org.scalajs.junit.MethodNameDecodeTest.abcd$u0020$u2206ƒ$u0020$uD83D$uDE00$u0020$times$u0020$hash$amp$::::true
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_vs.txt b/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_vs.txt
index 5921633584..1b6ab36dad 100644
--- a/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_vs.txt
+++ b/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_vs.txt
@@ -1,6 +1,6 @@
 liTest run started
 liTest org.scalajs.junit.MethodNameDecodeTest.abcd ∆ƒ 😀 * #&$ started
 ldTest org.scalajs.junit.MethodNameDecodeTest.abcd ∆ƒ 😀 * #&$ finished, took <TIME>
-e0org.scalajs.junit.MethodNameDecodeTest.abcd ∆ƒ 😀 * #&$::
+e0org.scalajs.junit.MethodNameDecodeTest.abcd ∆ƒ 😀 * #&$::::true
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_vsn.txt b/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_vsn.txt
index a5fccd7f30..7d09d90b6d 100644
--- a/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_vsn.txt
+++ b/junit-test/outputs/org/scalajs/junit/MethodNameDecodeTestAssertions_vsn.txt
@@ -1,6 +1,6 @@
 liTest run started
 liTest org.scalajs.junit.MethodNameDecodeTest.abcd ∆ƒ 😀 * #&$ started
 ldTest org.scalajs.junit.MethodNameDecodeTest.abcd ∆ƒ 😀 * #&$ finished, took <TIME>
-e0org.scalajs.junit.MethodNameDecodeTest.abcd ∆ƒ 😀 * #&$::
+e0org.scalajs.junit.MethodNameDecodeTest.abcd ∆ƒ 😀 * #&$::::true
 liTest run finished: 0 failed, 0 ignored, 1 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_.txt b/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_.txt
index 8922fa63dc..fde7a4564f 100644
--- a/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_.txt
+++ b/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_.txt
@@ -1,9 +1,9 @@
 ldTest run started
 ldTest org.scalajs.junit.Multi1Test.multiTest1 started
 ldTest org.scalajs.junit.Multi1Test.multiTest1 finished, took <TIME>
-e0org.scalajs.junit.Multi1Test.multiTest1::
+e0org.scalajs.junit.Multi1Test.multiTest1::::true
 ldTest org.scalajs.junit.Multi1Test.multiTest2 started
 ldTest org.scalajs.junit.Multi1Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.Multi1Test.multiTest2::
+e0org.scalajs.junit.Multi1Test.multiTest2::::true
 ldTest run finished: 0 failed, 0 ignored, 2 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_a.txt b/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_a.txt
index 8922fa63dc..fde7a4564f 100644
--- a/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_a.txt
+++ b/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_a.txt
@@ -1,9 +1,9 @@
 ldTest run started
 ldTest org.scalajs.junit.Multi1Test.multiTest1 started
 ldTest org.scalajs.junit.Multi1Test.multiTest1 finished, took <TIME>
-e0org.scalajs.junit.Multi1Test.multiTest1::
+e0org.scalajs.junit.Multi1Test.multiTest1::::true
 ldTest org.scalajs.junit.Multi1Test.multiTest2 started
 ldTest org.scalajs.junit.Multi1Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.Multi1Test.multiTest2::
+e0org.scalajs.junit.Multi1Test.multiTest2::::true
 ldTest run finished: 0 failed, 0 ignored, 2 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_n.txt b/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_n.txt
index 51394ffdc9..7054b4aed3 100644
--- a/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_n.txt
+++ b/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_n.txt
@@ -1,9 +1,9 @@
 ldTest run started
 ldTest org.scalajs.junit.Multi1Test.multiTest1 started
 ldTest org.scalajs.junit.Multi1Test.multiTest1 finished, took <TIME>
-e0org.scalajs.junit.Multi1Test.multiTest1::
+e0org.scalajs.junit.Multi1Test.multiTest1::::true
 ldTest org.scalajs.junit.Multi1Test.multiTest2 started
 ldTest org.scalajs.junit.Multi1Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.Multi1Test.multiTest2::
+e0org.scalajs.junit.Multi1Test.multiTest2::::true
 ldTest run finished: 0 failed, 0 ignored, 2 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_na.txt b/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_na.txt
index 51394ffdc9..7054b4aed3 100644
--- a/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_na.txt
+++ b/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_na.txt
@@ -1,9 +1,9 @@
 ldTest run started
 ldTest org.scalajs.junit.Multi1Test.multiTest1 started
 ldTest org.scalajs.junit.Multi1Test.multiTest1 finished, took <TIME>
-e0org.scalajs.junit.Multi1Test.multiTest1::
+e0org.scalajs.junit.Multi1Test.multiTest1::::true
 ldTest org.scalajs.junit.Multi1Test.multiTest2 started
 ldTest org.scalajs.junit.Multi1Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.Multi1Test.multiTest2::
+e0org.scalajs.junit.Multi1Test.multiTest2::::true
 ldTest run finished: 0 failed, 0 ignored, 2 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_nv.txt b/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_nv.txt
index 9c026ac573..1b9d02154b 100644
--- a/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_nv.txt
+++ b/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_nv.txt
@@ -1,9 +1,9 @@
 liTest run started
 liTest org.scalajs.junit.Multi1Test.multiTest1 started
 ldTest org.scalajs.junit.Multi1Test.multiTest1 finished, took <TIME>
-e0org.scalajs.junit.Multi1Test.multiTest1::
+e0org.scalajs.junit.Multi1Test.multiTest1::::true
 liTest org.scalajs.junit.Multi1Test.multiTest2 started
 ldTest org.scalajs.junit.Multi1Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.Multi1Test.multiTest2::
+e0org.scalajs.junit.Multi1Test.multiTest2::::true
 liTest run finished: 0 failed, 0 ignored, 2 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_nva.txt b/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_nva.txt
index 9c026ac573..1b9d02154b 100644
--- a/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_nva.txt
+++ b/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_nva.txt
@@ -1,9 +1,9 @@
 liTest run started
 liTest org.scalajs.junit.Multi1Test.multiTest1 started
 ldTest org.scalajs.junit.Multi1Test.multiTest1 finished, took <TIME>
-e0org.scalajs.junit.Multi1Test.multiTest1::
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 liTest org.scalajs.junit.Multi1Test.multiTest2 started
 ldTest org.scalajs.junit.Multi1Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.Multi1Test.multiTest2::
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 liTest run finished: 0 failed, 0 ignored, 2 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_nvc.txt b/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_nvc.txt
index 9c026ac573..1b9d02154b 100644
--- a/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_nvc.txt
+++ b/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_nvc.txt
@@ -1,9 +1,9 @@
 liTest run started
 liTest org.scalajs.junit.Multi1Test.multiTest1 started
 ldTest org.scalajs.junit.Multi1Test.multiTest1 finished, took <TIME>
-e0org.scalajs.junit.Multi1Test.multiTest1::
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 liTest org.scalajs.junit.Multi1Test.multiTest2 started
 ldTest org.scalajs.junit.Multi1Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.Multi1Test.multiTest2::
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 liTest run finished: 0 failed, 0 ignored, 2 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_nvca.txt b/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_nvca.txt
index 9c026ac573..1b9d02154b 100644
--- a/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_nvca.txt
+++ b/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_nvca.txt
@@ -1,9 +1,9 @@
 liTest run started
 liTest org.scalajs.junit.Multi1Test.multiTest1 started
 ldTest org.scalajs.junit.Multi1Test.multiTest1 finished, took <TIME>
-e0org.scalajs.junit.Multi1Test.multiTest1::
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 liTest org.scalajs.junit.Multi1Test.multiTest2 started
 ldTest org.scalajs.junit.Multi1Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.Multi1Test.multiTest2::
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 liTest run finished: 0 failed, 0 ignored, 2 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_v.txt b/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_v.txt
index 4569389a5e..f66182ed04 100644
--- a/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_v.txt
+++ b/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_v.txt
@@ -1,9 +1,9 @@
 liTest run started
 liTest org.scalajs.junit.Multi1Test.multiTest1 started
 ldTest org.scalajs.junit.Multi1Test.multiTest1 finished, took <TIME>
-e0org.scalajs.junit.Multi1Test.multiTest1::
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 liTest org.scalajs.junit.Multi1Test.multiTest2 started
 ldTest org.scalajs.junit.Multi1Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.Multi1Test.multiTest2::
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 liTest run finished: 0 failed, 0 ignored, 2 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_va.txt b/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_va.txt
index 4569389a5e..f66182ed04 100644
--- a/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_va.txt
+++ b/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_va.txt
@@ -1,9 +1,9 @@
 liTest run started
 liTest org.scalajs.junit.Multi1Test.multiTest1 started
 ldTest org.scalajs.junit.Multi1Test.multiTest1 finished, took <TIME>
-e0org.scalajs.junit.Multi1Test.multiTest1::
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 liTest org.scalajs.junit.Multi1Test.multiTest2 started
 ldTest org.scalajs.junit.Multi1Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.Multi1Test.multiTest2::
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 liTest run finished: 0 failed, 0 ignored, 2 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_vc.txt b/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_vc.txt
index 4569389a5e..f66182ed04 100644
--- a/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_vc.txt
+++ b/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_vc.txt
@@ -1,9 +1,9 @@
 liTest run started
 liTest org.scalajs.junit.Multi1Test.multiTest1 started
 ldTest org.scalajs.junit.Multi1Test.multiTest1 finished, took <TIME>
-e0org.scalajs.junit.Multi1Test.multiTest1::
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 liTest org.scalajs.junit.Multi1Test.multiTest2 started
 ldTest org.scalajs.junit.Multi1Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.Multi1Test.multiTest2::
+e0org.scalajs.junit.Multi1Test.multiTest2::::true
 liTest run finished: 0 failed, 0 ignored, 2 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_vs.txt b/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_vs.txt
index 4569389a5e..f66182ed04 100644
--- a/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_vs.txt
+++ b/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_vs.txt
@@ -1,9 +1,9 @@
 liTest run started
 liTest org.scalajs.junit.Multi1Test.multiTest1 started
 ldTest org.scalajs.junit.Multi1Test.multiTest1 finished, took <TIME>
-e0org.scalajs.junit.Multi1Test.multiTest1::
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 liTest org.scalajs.junit.Multi1Test.multiTest2 started
 ldTest org.scalajs.junit.Multi1Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.Multi1Test.multiTest2::
+e0org.scalajs.junit.Multi1Test.multiTest2::::true
 liTest run finished: 0 failed, 0 ignored, 2 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_vsn.txt b/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_vsn.txt
index 9c026ac573..1b9d02154b 100644
--- a/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_vsn.txt
+++ b/junit-test/outputs/org/scalajs/junit/Multi1TestAssertions_vsn.txt
@@ -1,9 +1,9 @@
 liTest run started
 liTest org.scalajs.junit.Multi1Test.multiTest1 started
 ldTest org.scalajs.junit.Multi1Test.multiTest1 finished, took <TIME>
-e0org.scalajs.junit.Multi1Test.multiTest1::
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 liTest org.scalajs.junit.Multi1Test.multiTest2 started
 ldTest org.scalajs.junit.Multi1Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.Multi1Test.multiTest2::
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 liTest run finished: 0 failed, 0 ignored, 2 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_.txt b/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_.txt
index 7361b034e9..f6f3c4ed14 100644
--- a/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_.txt
+++ b/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_.txt
@@ -1,18 +1,18 @@
 ldTest run started
 ldTest org.scalajs.junit.Multi2Test.multiTest1 started
 ldTest org.scalajs.junit.Multi2Test.multiTest1 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest1::
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 ldTest org.scalajs.junit.Multi2Test.multiTest2 started
 ldTest org.scalajs.junit.Multi2Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest2::
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 ldTest org.scalajs.junit.Multi2Test.multiTest3 started
 ldTest org.scalajs.junit.Multi2Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest3::
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 ldTest org.scalajs.junit.Multi2Test.multiTest4 started
 ldTest org.scalajs.junit.Multi2Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest4::
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 ldTest org.scalajs.junit.Multi2Test.multiTest5 started
 ldTest org.scalajs.junit.Multi2Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest5::
+e0org.scalajs.junit.Multi2Test.multiTest5::::true
 ldTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_a.txt b/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_a.txt
index 7361b034e9..f6f3c4ed14 100644
--- a/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_a.txt
+++ b/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_a.txt
@@ -1,18 +1,18 @@
 ldTest run started
 ldTest org.scalajs.junit.Multi2Test.multiTest1 started
 ldTest org.scalajs.junit.Multi2Test.multiTest1 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest1::
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 ldTest org.scalajs.junit.Multi2Test.multiTest2 started
 ldTest org.scalajs.junit.Multi2Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest2::
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 ldTest org.scalajs.junit.Multi2Test.multiTest3 started
 ldTest org.scalajs.junit.Multi2Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest3::
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 ldTest org.scalajs.junit.Multi2Test.multiTest4 started
 ldTest org.scalajs.junit.Multi2Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest4::
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 ldTest org.scalajs.junit.Multi2Test.multiTest5 started
 ldTest org.scalajs.junit.Multi2Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest5::
+e0org.scalajs.junit.Multi2Test.multiTest5::::true
 ldTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_n.txt b/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_n.txt
index 633d2f6adf..9ba03c57f7 100644
--- a/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_n.txt
+++ b/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_n.txt
@@ -1,18 +1,18 @@
 ldTest run started
 ldTest org.scalajs.junit.Multi2Test.multiTest1 started
 ldTest org.scalajs.junit.Multi2Test.multiTest1 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest1::
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 ldTest org.scalajs.junit.Multi2Test.multiTest2 started
 ldTest org.scalajs.junit.Multi2Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest2::
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 ldTest org.scalajs.junit.Multi2Test.multiTest3 started
 ldTest org.scalajs.junit.Multi2Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest3::
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 ldTest org.scalajs.junit.Multi2Test.multiTest4 started
 ldTest org.scalajs.junit.Multi2Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest4::
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 ldTest org.scalajs.junit.Multi2Test.multiTest5 started
 ldTest org.scalajs.junit.Multi2Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest5::
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 ldTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_na.txt b/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_na.txt
index 633d2f6adf..9ba03c57f7 100644
--- a/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_na.txt
+++ b/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_na.txt
@@ -1,18 +1,18 @@
 ldTest run started
 ldTest org.scalajs.junit.Multi2Test.multiTest1 started
 ldTest org.scalajs.junit.Multi2Test.multiTest1 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest1::
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 ldTest org.scalajs.junit.Multi2Test.multiTest2 started
 ldTest org.scalajs.junit.Multi2Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest2::
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 ldTest org.scalajs.junit.Multi2Test.multiTest3 started
 ldTest org.scalajs.junit.Multi2Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest3::
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 ldTest org.scalajs.junit.Multi2Test.multiTest4 started
 ldTest org.scalajs.junit.Multi2Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest4::
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 ldTest org.scalajs.junit.Multi2Test.multiTest5 started
 ldTest org.scalajs.junit.Multi2Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest5::
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 ldTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_nv.txt b/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_nv.txt
index ef9160fa43..59108236cb 100644
--- a/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_nv.txt
+++ b/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_nv.txt
@@ -1,18 +1,18 @@
 liTest run started
 liTest org.scalajs.junit.Multi2Test.multiTest1 started
 ldTest org.scalajs.junit.Multi2Test.multiTest1 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest1::
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 liTest org.scalajs.junit.Multi2Test.multiTest2 started
 ldTest org.scalajs.junit.Multi2Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest2::
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 liTest org.scalajs.junit.Multi2Test.multiTest3 started
 ldTest org.scalajs.junit.Multi2Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest3::
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 liTest org.scalajs.junit.Multi2Test.multiTest4 started
 ldTest org.scalajs.junit.Multi2Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest4::
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 liTest org.scalajs.junit.Multi2Test.multiTest5 started
 ldTest org.scalajs.junit.Multi2Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest5::
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 liTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_nva.txt b/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_nva.txt
index ef9160fa43..59108236cb 100644
--- a/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_nva.txt
+++ b/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_nva.txt
@@ -1,18 +1,18 @@
 liTest run started
 liTest org.scalajs.junit.Multi2Test.multiTest1 started
 ldTest org.scalajs.junit.Multi2Test.multiTest1 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest1::
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 liTest org.scalajs.junit.Multi2Test.multiTest2 started
 ldTest org.scalajs.junit.Multi2Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest2::
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 liTest org.scalajs.junit.Multi2Test.multiTest3 started
 ldTest org.scalajs.junit.Multi2Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest3::
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 liTest org.scalajs.junit.Multi2Test.multiTest4 started
 ldTest org.scalajs.junit.Multi2Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest4::
+e0org.scalajs.junit.Multi2Test.multiTest4::::true
 liTest org.scalajs.junit.Multi2Test.multiTest5 started
 ldTest org.scalajs.junit.Multi2Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest5::
+e0org.scalajs.junit.Multi2Test.multiTest5::::true
 liTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_nvc.txt b/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_nvc.txt
index ef9160fa43..59108236cb 100644
--- a/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_nvc.txt
+++ b/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_nvc.txt
@@ -1,18 +1,18 @@
 liTest run started
 liTest org.scalajs.junit.Multi2Test.multiTest1 started
 ldTest org.scalajs.junit.Multi2Test.multiTest1 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest1::
+e0org.scalajs.junit.Multi2Test.multiTest1::::true
 liTest org.scalajs.junit.Multi2Test.multiTest2 started
 ldTest org.scalajs.junit.Multi2Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest2::
+e0org.scalajs.junit.Multi2Test.multiTest2::::true
 liTest org.scalajs.junit.Multi2Test.multiTest3 started
 ldTest org.scalajs.junit.Multi2Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest3::
+e0org.scalajs.junit.Multi2Test.multiTest3::::true
 liTest org.scalajs.junit.Multi2Test.multiTest4 started
 ldTest org.scalajs.junit.Multi2Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest4::
+e0org.scalajs.junit.Multi2Test.multiTest4::::true
 liTest org.scalajs.junit.Multi2Test.multiTest5 started
 ldTest org.scalajs.junit.Multi2Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest5::
+e0org.scalajs.junit.Multi2Test.multiTest5::::true
 liTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_nvca.txt b/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_nvca.txt
index ef9160fa43..59108236cb 100644
--- a/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_nvca.txt
+++ b/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_nvca.txt
@@ -1,18 +1,18 @@
 liTest run started
 liTest org.scalajs.junit.Multi2Test.multiTest1 started
 ldTest org.scalajs.junit.Multi2Test.multiTest1 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest1::
+e0org.scalajs.junit.Multi2Test.multiTest1::::true
 liTest org.scalajs.junit.Multi2Test.multiTest2 started
 ldTest org.scalajs.junit.Multi2Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest2::
+e0org.scalajs.junit.Multi2Test.multiTest2::::true
 liTest org.scalajs.junit.Multi2Test.multiTest3 started
 ldTest org.scalajs.junit.Multi2Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest3::
+e0org.scalajs.junit.Multi2Test.multiTest3::::true
 liTest org.scalajs.junit.Multi2Test.multiTest4 started
 ldTest org.scalajs.junit.Multi2Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest4::
+e0org.scalajs.junit.Multi2Test.multiTest4::::true
 liTest org.scalajs.junit.Multi2Test.multiTest5 started
 ldTest org.scalajs.junit.Multi2Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest5::
+e0org.scalajs.junit.Multi2Test.multiTest5::::true
 liTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_v.txt b/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_v.txt
index de892dea4a..0909c97495 100644
--- a/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_v.txt
+++ b/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_v.txt
@@ -1,18 +1,18 @@
 liTest run started
 liTest org.scalajs.junit.Multi2Test.multiTest1 started
 ldTest org.scalajs.junit.Multi2Test.multiTest1 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest1::
+e0org.scalajs.junit.Multi2Test.multiTest1::::true
 liTest org.scalajs.junit.Multi2Test.multiTest2 started
 ldTest org.scalajs.junit.Multi2Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest2::
+e0org.scalajs.junit.Multi2Test.multiTest2::::true
 liTest org.scalajs.junit.Multi2Test.multiTest3 started
 ldTest org.scalajs.junit.Multi2Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest3::
+e0org.scalajs.junit.Multi2Test.multiTest3::::true
 liTest org.scalajs.junit.Multi2Test.multiTest4 started
 ldTest org.scalajs.junit.Multi2Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest4::
+e0org.scalajs.junit.Multi2Test.multiTest4::::true
 liTest org.scalajs.junit.Multi2Test.multiTest5 started
 ldTest org.scalajs.junit.Multi2Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest5::
+e0org.scalajs.junit.Multi2Test.multiTest5::::true
 liTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_va.txt b/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_va.txt
index de892dea4a..0909c97495 100644
--- a/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_va.txt
+++ b/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_va.txt
@@ -1,18 +1,18 @@
 liTest run started
 liTest org.scalajs.junit.Multi2Test.multiTest1 started
 ldTest org.scalajs.junit.Multi2Test.multiTest1 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest1::
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 liTest org.scalajs.junit.Multi2Test.multiTest2 started
 ldTest org.scalajs.junit.Multi2Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest2::
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 liTest org.scalajs.junit.Multi2Test.multiTest3 started
 ldTest org.scalajs.junit.Multi2Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest3::
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 liTest org.scalajs.junit.Multi2Test.multiTest4 started
 ldTest org.scalajs.junit.Multi2Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest4::
+e0org.scalajs.junit.Multi2Test.multiTest4::::true
 liTest org.scalajs.junit.Multi2Test.multiTest5 started
 ldTest org.scalajs.junit.Multi2Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest5::
+e0org.scalajs.junit.Multi2Test.multiTest5::::true
 liTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_vc.txt b/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_vc.txt
index de892dea4a..0909c97495 100644
--- a/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_vc.txt
+++ b/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_vc.txt
@@ -1,18 +1,18 @@
 liTest run started
 liTest org.scalajs.junit.Multi2Test.multiTest1 started
 ldTest org.scalajs.junit.Multi2Test.multiTest1 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest1::
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 liTest org.scalajs.junit.Multi2Test.multiTest2 started
 ldTest org.scalajs.junit.Multi2Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest2::
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 liTest org.scalajs.junit.Multi2Test.multiTest3 started
 ldTest org.scalajs.junit.Multi2Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest3::
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 liTest org.scalajs.junit.Multi2Test.multiTest4 started
 ldTest org.scalajs.junit.Multi2Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest4::
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 liTest org.scalajs.junit.Multi2Test.multiTest5 started
 ldTest org.scalajs.junit.Multi2Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest5::
+e0org.scalajs.junit.Multi2Test.multiTest5::::true
 liTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_vs.txt b/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_vs.txt
index de892dea4a..0909c97495 100644
--- a/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_vs.txt
+++ b/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_vs.txt
@@ -1,18 +1,18 @@
 liTest run started
 liTest org.scalajs.junit.Multi2Test.multiTest1 started
 ldTest org.scalajs.junit.Multi2Test.multiTest1 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest1::
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 liTest org.scalajs.junit.Multi2Test.multiTest2 started
 ldTest org.scalajs.junit.Multi2Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest2::
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 liTest org.scalajs.junit.Multi2Test.multiTest3 started
 ldTest org.scalajs.junit.Multi2Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest3::
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 liTest org.scalajs.junit.Multi2Test.multiTest4 started
 ldTest org.scalajs.junit.Multi2Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest4::
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 liTest org.scalajs.junit.Multi2Test.multiTest5 started
 ldTest org.scalajs.junit.Multi2Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest5::
+e0org.scalajs.junit.Multi2Test.multiTest5::::true
 liTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_vsn.txt b/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_vsn.txt
index ef9160fa43..59108236cb 100644
--- a/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_vsn.txt
+++ b/junit-test/outputs/org/scalajs/junit/Multi2TestAssertions_vsn.txt
@@ -1,18 +1,18 @@
 liTest run started
 liTest org.scalajs.junit.Multi2Test.multiTest1 started
 ldTest org.scalajs.junit.Multi2Test.multiTest1 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest1::
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 liTest org.scalajs.junit.Multi2Test.multiTest2 started
 ldTest org.scalajs.junit.Multi2Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest2::
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 liTest org.scalajs.junit.Multi2Test.multiTest3 started
 ldTest org.scalajs.junit.Multi2Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest3::
+e0org.scalajs.junit.Multi2Test.multiTest3::::true
 liTest org.scalajs.junit.Multi2Test.multiTest4 started
 ldTest org.scalajs.junit.Multi2Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest4::
+e0org.scalajs.junit.Multi2Test.multiTest4::::true
 liTest org.scalajs.junit.Multi2Test.multiTest5 started
 ldTest org.scalajs.junit.Multi2Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.Multi2Test.multiTest5::
+e0org.scalajs.junit.Multi2Test.multiTest5::::true
 liTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_.txt b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_.txt
index 2b1028c5a0..c59501bf62 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_.txt
@@ -1,19 +1,19 @@
 ldTest run started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest1 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail1Test.multiTest1 failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail1Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.MultiAssumeFail1Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest1 finished, took <TIME>
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest2 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest2::
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 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest3 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest3::
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest3::::true
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest4 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest4::
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest4::::true
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest5 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest5::
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest5::::true
 ldTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_a.txt b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_a.txt
index 2b1028c5a0..c59501bf62 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_a.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_a.txt
@@ -1,19 +1,19 @@
 ldTest run started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest1 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail1Test.multiTest1 failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail1Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.MultiAssumeFail1Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest1 finished, took <TIME>
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest2 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest2::
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 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest3 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest3::
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest3::::true
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest4 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest4::
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest4::::true
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest5 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest5::
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest5::::true
 ldTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_n.txt b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_n.txt
index 7bcb8dc9b1..9f75b2f3b5 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_n.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_n.txt
@@ -1,19 +1,19 @@
 ldTest run started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest1 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail1Test.multiTest1 failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail1Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.MultiAssumeFail1Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest1 finished, took <TIME>
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest2 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest2::
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 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest3 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest3::
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest3::::true
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest4 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest4::
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest4::::true
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest5 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest5::
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest5::::true
 ldTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_na.txt b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_na.txt
index 7bcb8dc9b1..9f75b2f3b5 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_na.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_na.txt
@@ -1,19 +1,19 @@
 ldTest run started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest1 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail1Test.multiTest1 failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail1Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.MultiAssumeFail1Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest1 finished, took <TIME>
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest2 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest2::
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest2::::true
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest3 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest3::
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest3::::true
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest4 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest4::
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest4::::true
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest5 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest5::
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest5::::true
 ldTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_nv.txt b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_nv.txt
index c1ef53f411..30760db514 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_nv.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_nv.txt
@@ -1,19 +1,19 @@
 liTest run started
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest1 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail1Test.multiTest1 failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail1Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.MultiAssumeFail1Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest1 finished, took <TIME>
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest2 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest2::
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 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest3 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest3::
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest3::::true
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest4 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest4::
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest4::::true
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest5 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest5::
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest5::::true
 liTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_nva.txt b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_nva.txt
index c1ef53f411..30760db514 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_nva.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_nva.txt
@@ -1,19 +1,19 @@
 liTest run started
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest1 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail1Test.multiTest1 failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail1Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.MultiAssumeFail1Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest1 finished, took <TIME>
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest2 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest2::
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest2::::true
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest3 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest3::
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest3::::true
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest4 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest4::
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest4::::true
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest5 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest5::
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest5::::true
 liTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_nvc.txt b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_nvc.txt
index 2081bb74eb..1a1fbf6456 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_nvc.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_nvc.txt
@@ -1,19 +1,19 @@
 liTest run started
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest1 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail1Test.multiTest1 failed: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail1Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.MultiAssumeFail1Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest1 finished, took <TIME>
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest2 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest2::
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest2::::true
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest3 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest3::
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest3::::true
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest4 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest4::
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest4::::true
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest5 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest5::
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest5::::true
 liTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_nvca.txt b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_nvca.txt
index 2081bb74eb..1a1fbf6456 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_nvca.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_nvca.txt
@@ -1,19 +1,19 @@
 liTest run started
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest1 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail1Test.multiTest1 failed: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail1Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.MultiAssumeFail1Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest1 finished, took <TIME>
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest2 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest2::
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest2::::true
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest3 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest3::
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest3::::true
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest4 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest4::
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest4::::true
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest5 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest5::
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest5::::true
 liTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_v.txt b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_v.txt
index f722c33262..badec2cfae 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_v.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_v.txt
@@ -1,19 +1,19 @@
 liTest run started
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest1 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail1Test.multiTest1 failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail1Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.MultiAssumeFail1Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest1 finished, took <TIME>
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest2 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest2::
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest2::::true
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest3 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest3::
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest3::::true
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest4 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest4::
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest4::::true
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest5 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest5::
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest5::::true
 liTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_va.txt b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_va.txt
index f722c33262..badec2cfae 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_va.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_va.txt
@@ -1,19 +1,19 @@
 liTest run started
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest1 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail1Test.multiTest1 failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail1Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.MultiAssumeFail1Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest1 finished, took <TIME>
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest2 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest2::
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest2::::true
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest3 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest3::
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest3::::true
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest4 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest4::
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest4::::true
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest5 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest5::
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest5::::true
 liTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_vc.txt b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_vc.txt
index 55bbc61efa..ffcca48722 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_vc.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_vc.txt
@@ -1,19 +1,19 @@
 liTest run started
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest1 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail1Test.multiTest1 failed: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail1Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.MultiAssumeFail1Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest1 finished, took <TIME>
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest2 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest2::
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest2::::true
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest3 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest3::
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest3::::true
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest4 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest4::
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest4::::true
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest5 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest5::
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest5::::true
 liTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_vs.txt b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_vs.txt
index f722c33262..badec2cfae 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_vs.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_vs.txt
@@ -1,19 +1,19 @@
 liTest run started
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest1 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail1Test.multiTest1 failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail1Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.MultiAssumeFail1Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest1 finished, took <TIME>
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest2 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest2::
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest2::::true
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest3 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest3::
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest3::::true
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest4 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest4::
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest4::::true
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest5 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest5::
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest5::::true
 liTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_vsn.txt b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_vsn.txt
index c1ef53f411..30760db514 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_vsn.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail1TestAssertions_vsn.txt
@@ -1,19 +1,19 @@
 liTest run started
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest1 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail1Test.multiTest1 failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail1Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.MultiAssumeFail1Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest1 finished, took <TIME>
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest2 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest2::
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest2::::true
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest3 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest3::
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest3::::true
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest4 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest4::
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest4::::true
 liTest org.scalajs.junit.MultiAssumeFail1Test.multiTest5 started
 ldTest org.scalajs.junit.MultiAssumeFail1Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail1Test.multiTest5::
+e0org.scalajs.junit.MultiAssumeFail1Test.multiTest5::::true
 liTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_.txt b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_.txt
index f9047db04c..4a93d475f9 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_.txt
@@ -1,20 +1,20 @@
 ldTest run started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest1 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail2Test.multiTest1 failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail2Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.MultiAssumeFail2Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest1 finished, took <TIME>
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest2 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest2::
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest2::::true
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest3 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest3::
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest3::::true
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest4 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail2Test.multiTest4 failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail2Test.multiTest4::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.MultiAssumeFail2Test.multiTest4::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest4 finished, took <TIME>
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest5 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest5::
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest5::::true
 ldTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_a.txt b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_a.txt
index f9047db04c..4a93d475f9 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_a.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_a.txt
@@ -1,20 +1,20 @@
 ldTest run started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest1 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail2Test.multiTest1 failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail2Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.MultiAssumeFail2Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest1 finished, took <TIME>
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest2 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest2::
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest2::::true
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest3 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest3::
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest3::::true
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest4 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail2Test.multiTest4 failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail2Test.multiTest4::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.MultiAssumeFail2Test.multiTest4::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest4 finished, took <TIME>
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest5 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest5::
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest5::::true
 ldTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_n.txt b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_n.txt
index f27cd9e937..0433808f1f 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_n.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_n.txt
@@ -1,20 +1,20 @@
 ldTest run started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest1 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail2Test.multiTest1 failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail2Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.MultiAssumeFail2Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest1 finished, took <TIME>
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest2 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest2::
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest2::::true
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest3 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest3::
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest3::::true
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest4 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail2Test.multiTest4 failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail2Test.multiTest4::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.MultiAssumeFail2Test.multiTest4::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest4 finished, took <TIME>
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest5 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest5::
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest5::::true
 ldTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_na.txt b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_na.txt
index f27cd9e937..0433808f1f 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_na.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_na.txt
@@ -1,20 +1,20 @@
 ldTest run started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest1 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail2Test.multiTest1 failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail2Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.MultiAssumeFail2Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest1 finished, took <TIME>
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest2 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest2::
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest2::::true
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest3 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest3::
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest3::::true
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest4 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail2Test.multiTest4 failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail2Test.multiTest4::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.MultiAssumeFail2Test.multiTest4::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest4 finished, took <TIME>
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest5 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest5::
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest5::::true
 ldTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_nv.txt b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_nv.txt
index 99d229d87f..e9b3a2ac2d 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_nv.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_nv.txt
@@ -1,20 +1,20 @@
 liTest run started
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest1 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail2Test.multiTest1 failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail2Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.MultiAssumeFail2Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest1 finished, took <TIME>
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest2 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest2::
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest2::::true
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest3 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest3::
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest3::::true
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest4 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail2Test.multiTest4 failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail2Test.multiTest4::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.MultiAssumeFail2Test.multiTest4::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest4 finished, took <TIME>
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest5 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest5::
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest5::::true
 liTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_nva.txt b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_nva.txt
index 99d229d87f..e9b3a2ac2d 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_nva.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_nva.txt
@@ -1,20 +1,20 @@
 liTest run started
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest1 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail2Test.multiTest1 failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail2Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.MultiAssumeFail2Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest1 finished, took <TIME>
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest2 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest2::
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest2::::true
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest3 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest3::
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest3::::true
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest4 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail2Test.multiTest4 failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail2Test.multiTest4::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.MultiAssumeFail2Test.multiTest4::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest4 finished, took <TIME>
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest5 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest5::
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest5::::true
 liTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_nvc.txt b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_nvc.txt
index 116f3267e6..d8a6fe168d 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_nvc.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_nvc.txt
@@ -1,20 +1,20 @@
 liTest run started
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest1 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail2Test.multiTest1 failed: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail2Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.MultiAssumeFail2Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest1 finished, took <TIME>
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest2 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest2::
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest2::::true
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest3 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest3::
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest3::::true
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest4 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail2Test.multiTest4 failed: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail2Test.multiTest4::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.MultiAssumeFail2Test.multiTest4::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest4 finished, took <TIME>
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest5 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest5::
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest5::::true
 liTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_nvca.txt b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_nvca.txt
index 116f3267e6..d8a6fe168d 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_nvca.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_nvca.txt
@@ -1,20 +1,20 @@
 liTest run started
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest1 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail2Test.multiTest1 failed: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail2Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.MultiAssumeFail2Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest1 finished, took <TIME>
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest2 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest2::
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest2::::true
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest3 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest3::
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest3::::true
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest4 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail2Test.multiTest4 failed: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail2Test.multiTest4::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.MultiAssumeFail2Test.multiTest4::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest4 finished, took <TIME>
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest5 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest5::
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest5::::true
 liTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_v.txt b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_v.txt
index 44ed8d6500..a3e750f14b 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_v.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_v.txt
@@ -1,20 +1,20 @@
 liTest run started
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest1 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail2Test.multiTest1 failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail2Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.MultiAssumeFail2Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest1 finished, took <TIME>
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest2 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest2::
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest2::::true
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest3 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest3::
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest3::::true
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest4 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail2Test.multiTest4 failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail2Test.multiTest4::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.MultiAssumeFail2Test.multiTest4::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest4 finished, took <TIME>
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest5 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest5::
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest5::::true
 liTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_va.txt b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_va.txt
index 44ed8d6500..a3e750f14b 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_va.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_va.txt
@@ -1,20 +1,20 @@
 liTest run started
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest1 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail2Test.multiTest1 failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail2Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.MultiAssumeFail2Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest1 finished, took <TIME>
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest2 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest2::
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest2::::true
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest3 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest3::
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest3::::true
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest4 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail2Test.multiTest4 failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail2Test.multiTest4::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.MultiAssumeFail2Test.multiTest4::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest4 finished, took <TIME>
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest5 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest5::
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest5::::true
 liTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_vc.txt b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_vc.txt
index e209c65918..8f73db8c60 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_vc.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_vc.txt
@@ -1,20 +1,20 @@
 liTest run started
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest1 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail2Test.multiTest1 failed: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail2Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.MultiAssumeFail2Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest1 finished, took <TIME>
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest2 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest2::
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest2::::true
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest3 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest3::
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest3::::true
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest4 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail2Test.multiTest4 failed: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail2Test.multiTest4::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.MultiAssumeFail2Test.multiTest4::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest4 finished, took <TIME>
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest5 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest5::
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest5::::true
 liTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_vs.txt b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_vs.txt
index 44ed8d6500..a3e750f14b 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_vs.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_vs.txt
@@ -1,20 +1,20 @@
 liTest run started
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest1 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail2Test.multiTest1 failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail2Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.MultiAssumeFail2Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest1 finished, took <TIME>
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest2 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest2::
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest2::::true
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest3 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest3::
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest3::::true
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest4 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail2Test.multiTest4 failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail2Test.multiTest4::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.MultiAssumeFail2Test.multiTest4::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest4 finished, took <TIME>
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest5 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest5::
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest5::::true
 liTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_vsn.txt b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_vsn.txt
index 99d229d87f..e9b3a2ac2d 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_vsn.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiAssumeFail2TestAssertions_vsn.txt
@@ -1,20 +1,20 @@
 liTest run started
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest1 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail2Test.multiTest1 failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail2Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.MultiAssumeFail2Test.multiTest1::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest1 finished, took <TIME>
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest2 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest2::
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest2::::true
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest3 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest3::
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest3::::true
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest4 started
 lwTest assumption in test org.scalajs.junit.MultiAssumeFail2Test.multiTest4 failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiAssumeFail2Test.multiTest4::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.MultiAssumeFail2Test.multiTest4::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest4 finished, took <TIME>
 liTest org.scalajs.junit.MultiAssumeFail2Test.multiTest5 started
 ldTest org.scalajs.junit.MultiAssumeFail2Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiAssumeFail2Test.multiTest5::
+e0org.scalajs.junit.MultiAssumeFail2Test.multiTest5::::true
 liTest run finished: 0 failed, 0 ignored, 5 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_.txt b/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_.txt
index e86d2bf4bb..8a89ce0e05 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_.txt
@@ -1,5 +1,5 @@
 ldTest run started
 lwTest assumption in test org.scalajs.junit.MultiBeforeAssumeFailTest failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiBeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.MultiBeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest run finished: 0 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_a.txt b/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_a.txt
index e86d2bf4bb..8a89ce0e05 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_a.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_a.txt
@@ -1,5 +1,5 @@
 ldTest run started
 lwTest assumption in test org.scalajs.junit.MultiBeforeAssumeFailTest failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiBeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.MultiBeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest run finished: 0 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_n.txt b/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_n.txt
index 36cb87022e..75a51dc26a 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_n.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_n.txt
@@ -1,5 +1,5 @@
 ldTest run started
 lwTest assumption in test org.scalajs.junit.MultiBeforeAssumeFailTest failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiBeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.MultiBeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest run finished: 0 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_na.txt b/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_na.txt
index 36cb87022e..75a51dc26a 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_na.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_na.txt
@@ -1,5 +1,5 @@
 ldTest run started
 lwTest assumption in test org.scalajs.junit.MultiBeforeAssumeFailTest failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiBeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.MultiBeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass::true
 ldTest run finished: 0 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_nv.txt b/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_nv.txt
index be6b889225..98b0c24735 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_nv.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_nv.txt
@@ -1,5 +1,5 @@
 liTest run started
 lwTest assumption in test org.scalajs.junit.MultiBeforeAssumeFailTest failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiBeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.MultiBeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass::true
 liTest run finished: 0 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_nva.txt b/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_nva.txt
index be6b889225..98b0c24735 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_nva.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_nva.txt
@@ -1,5 +1,5 @@
 liTest run started
 lwTest assumption in test org.scalajs.junit.MultiBeforeAssumeFailTest failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiBeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.MultiBeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass::true
 liTest run finished: 0 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_nvc.txt b/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_nvc.txt
index bf5abd3192..191ec4edd8 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_nvc.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_nvc.txt
@@ -1,5 +1,5 @@
 liTest run started
 lwTest assumption in test org.scalajs.junit.MultiBeforeAssumeFailTest failed: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiBeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.MultiBeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass::true
 liTest run finished: 0 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_nvca.txt b/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_nvca.txt
index bf5abd3192..191ec4edd8 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_nvca.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_nvca.txt
@@ -1,5 +1,5 @@
 liTest run started
 lwTest assumption in test org.scalajs.junit.MultiBeforeAssumeFailTest failed: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiBeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.MultiBeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass::true
 liTest run finished: 0 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_v.txt b/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_v.txt
index ab67afd984..602c39f54c 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_v.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_v.txt
@@ -1,5 +1,5 @@
 liTest run started
 lwTest assumption in test org.scalajs.junit.MultiBeforeAssumeFailTest failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiBeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.MultiBeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass::true
 liTest run finished: 0 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_va.txt b/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_va.txt
index ab67afd984..602c39f54c 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_va.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_va.txt
@@ -1,5 +1,5 @@
 liTest run started
 lwTest assumption in test org.scalajs.junit.MultiBeforeAssumeFailTest failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiBeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.MultiBeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass::true
 liTest run finished: 0 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_vc.txt b/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_vc.txt
index 4ff91826dc..85e0d9852a 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_vc.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_vc.txt
@@ -1,5 +1,5 @@
 liTest run started
 lwTest assumption in test org.scalajs.junit.MultiBeforeAssumeFailTest failed: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiBeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.MultiBeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass::true
 liTest run finished: 0 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_vs.txt b/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_vs.txt
index ab67afd984..602c39f54c 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_vs.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_vs.txt
@@ -1,5 +1,5 @@
 liTest run started
 lwTest assumption in test org.scalajs.junit.MultiBeforeAssumeFailTest failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiBeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.MultiBeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass::true
 liTest run finished: 0 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_vsn.txt b/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_vsn.txt
index be6b889225..98b0c24735 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_vsn.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiBeforeAssumeFailTestAssertions_vsn.txt
@@ -1,5 +1,5 @@
 liTest run started
 lwTest assumption in test org.scalajs.junit.MultiBeforeAssumeFailTest failed: org.junit.AssumptionViolatedException: This assume should not pass, took <TIME>
-e3org.scalajs.junit.MultiBeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass
+e3org.scalajs.junit.MultiBeforeAssumeFailTest::org.junit.AssumptionViolatedException: This assume should not pass::true
 liTest run finished: 0 failed, 0 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_.txt
index 0d0de86bec..19ef73a38c 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_.txt
@@ -1,17 +1,17 @@
 ldTest run started
 liTest org.scalajs.junit.MultiIgnore1Test.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnore1Test.multiTest1::
+e3org.scalajs.junit.MultiIgnore1Test.multiTest1::::true
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest2 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest2::
+e0org.scalajs.junit.MultiIgnore1Test.multiTest2::::true
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest3 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest3::
+e0org.scalajs.junit.MultiIgnore1Test.multiTest3::::true
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest4 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest4::
+e0org.scalajs.junit.MultiIgnore1Test.multiTest4::::true
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest5 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest5::
+e0org.scalajs.junit.MultiIgnore1Test.multiTest5::::true
 ldTest run finished: 0 failed, 1 ignored, 4 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_a.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_a.txt
index 0d0de86bec..19ef73a38c 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_a.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_a.txt
@@ -1,17 +1,17 @@
 ldTest run started
 liTest org.scalajs.junit.MultiIgnore1Test.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnore1Test.multiTest1::
+e3org.scalajs.junit.MultiIgnore1Test.multiTest1::::true
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest2 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest2::
+e0org.scalajs.junit.MultiIgnore1Test.multiTest2::::true
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest3 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest3::
+e0org.scalajs.junit.MultiIgnore1Test.multiTest3::::true
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest4 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest4::
+e0org.scalajs.junit.MultiIgnore1Test.multiTest4::::true
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest5 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest5::
+e0org.scalajs.junit.MultiIgnore1Test.multiTest5::::true
 ldTest run finished: 0 failed, 1 ignored, 4 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_n.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_n.txt
index a4a934491d..552be55bff 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_n.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_n.txt
@@ -1,17 +1,17 @@
 ldTest run started
 liTest org.scalajs.junit.MultiIgnore1Test.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnore1Test.multiTest1::
+e3org.scalajs.junit.MultiIgnore1Test.multiTest1::::true
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest2 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest2::
+e0org.scalajs.junit.MultiIgnore1Test.multiTest2::::true
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest3 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest3::
+e0org.scalajs.junit.MultiIgnore1Test.multiTest3::::true
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest4 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest4::
+e0org.scalajs.junit.MultiIgnore1Test.multiTest4::::true
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest5 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest5::
+e0org.scalajs.junit.MultiIgnore1Test.multiTest5::::true
 ldTest run finished: 0 failed, 1 ignored, 4 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_na.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_na.txt
index a4a934491d..552be55bff 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_na.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_na.txt
@@ -1,17 +1,17 @@
 ldTest run started
 liTest org.scalajs.junit.MultiIgnore1Test.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnore1Test.multiTest1::
+e3org.scalajs.junit.MultiIgnore1Test.multiTest1::::true
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest2 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest2::
+e0org.scalajs.junit.MultiIgnore1Test.multiTest2::::true
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest3 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest3::
+e0org.scalajs.junit.MultiIgnore1Test.multiTest3::::true
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest4 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest4::
+e0org.scalajs.junit.MultiIgnore1Test.multiTest4::::true
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest5 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest5::
+e0org.scalajs.junit.MultiIgnore1Test.multiTest5::::true
 ldTest run finished: 0 failed, 1 ignored, 4 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_nv.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_nv.txt
index 66b9cf269d..3481200a14 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_nv.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_nv.txt
@@ -1,17 +1,17 @@
 liTest run started
 liTest org.scalajs.junit.MultiIgnore1Test.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnore1Test.multiTest1::
+e3org.scalajs.junit.MultiIgnore1Test.multiTest1::::true
 liTest org.scalajs.junit.MultiIgnore1Test.multiTest2 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest2::
+e0org.scalajs.junit.MultiIgnore1Test.multiTest2::::true
 liTest org.scalajs.junit.MultiIgnore1Test.multiTest3 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest3::
+e0org.scalajs.junit.MultiIgnore1Test.multiTest3::::true
 liTest org.scalajs.junit.MultiIgnore1Test.multiTest4 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest4::
+e0org.scalajs.junit.MultiIgnore1Test.multiTest4::::true
 liTest org.scalajs.junit.MultiIgnore1Test.multiTest5 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest5::
+e0org.scalajs.junit.MultiIgnore1Test.multiTest5::::true
 liTest run finished: 0 failed, 1 ignored, 4 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_nva.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_nva.txt
index 66b9cf269d..3481200a14 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_nva.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_nva.txt
@@ -1,17 +1,17 @@
 liTest run started
 liTest org.scalajs.junit.MultiIgnore1Test.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnore1Test.multiTest1::
+e3org.scalajs.junit.MultiIgnore1Test.multiTest1::::true
 liTest org.scalajs.junit.MultiIgnore1Test.multiTest2 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest2::
+e0org.scalajs.junit.MultiIgnore1Test.multiTest2::::true
 liTest org.scalajs.junit.MultiIgnore1Test.multiTest3 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest3::
+e0org.scalajs.junit.MultiIgnore1Test.multiTest3::::true
 liTest org.scalajs.junit.MultiIgnore1Test.multiTest4 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest4::
+e0org.scalajs.junit.MultiIgnore1Test.multiTest4::::true
 liTest org.scalajs.junit.MultiIgnore1Test.multiTest5 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest5::
+e0org.scalajs.junit.MultiIgnore1Test.multiTest5::::true
 liTest run finished: 0 failed, 1 ignored, 4 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_nvc.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_nvc.txt
index 66b9cf269d..3481200a14 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_nvc.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_nvc.txt
@@ -1,17 +1,17 @@
 liTest run started
 liTest org.scalajs.junit.MultiIgnore1Test.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnore1Test.multiTest1::
+e3org.scalajs.junit.MultiIgnore1Test.multiTest1::::true
 liTest org.scalajs.junit.MultiIgnore1Test.multiTest2 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest2::
+e0org.scalajs.junit.MultiIgnore1Test.multiTest2::::true
 liTest org.scalajs.junit.MultiIgnore1Test.multiTest3 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest3::
+e0org.scalajs.junit.MultiIgnore1Test.multiTest3::::true
 liTest org.scalajs.junit.MultiIgnore1Test.multiTest4 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest4::
+e0org.scalajs.junit.MultiIgnore1Test.multiTest4::::true
 liTest org.scalajs.junit.MultiIgnore1Test.multiTest5 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest5::
+e0org.scalajs.junit.MultiIgnore1Test.multiTest5::::true
 liTest run finished: 0 failed, 1 ignored, 4 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_nvca.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_nvca.txt
index 66b9cf269d..3481200a14 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_nvca.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_nvca.txt
@@ -1,17 +1,17 @@
 liTest run started
 liTest org.scalajs.junit.MultiIgnore1Test.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnore1Test.multiTest1::
+e3org.scalajs.junit.MultiIgnore1Test.multiTest1::::true
 liTest org.scalajs.junit.MultiIgnore1Test.multiTest2 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest2::
+e0org.scalajs.junit.MultiIgnore1Test.multiTest2::::true
 liTest org.scalajs.junit.MultiIgnore1Test.multiTest3 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest3::
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 liTest org.scalajs.junit.MultiIgnore1Test.multiTest4 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest4::
+e0org.scalajs.junit.MultiIgnore1Test.multiTest4::::true
 liTest org.scalajs.junit.MultiIgnore1Test.multiTest5 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest5::
+e0org.scalajs.junit.MultiIgnore1Test.multiTest5::::true
 liTest run finished: 0 failed, 1 ignored, 4 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_v.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_v.txt
index 015e238a7b..111b8f9193 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_v.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_v.txt
@@ -1,17 +1,17 @@
 liTest run started
 liTest org.scalajs.junit.MultiIgnore1Test.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnore1Test.multiTest1::
+e3org.scalajs.junit.MultiIgnore1Test.multiTest1::::true
 liTest org.scalajs.junit.MultiIgnore1Test.multiTest2 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest2::
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 liTest org.scalajs.junit.MultiIgnore1Test.multiTest3 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest3::
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 liTest org.scalajs.junit.MultiIgnore1Test.multiTest4 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest4::
+e0org.scalajs.junit.MultiIgnore1Test.multiTest4::::true
 liTest org.scalajs.junit.MultiIgnore1Test.multiTest5 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest5::
+e0org.scalajs.junit.MultiIgnore1Test.multiTest5::::true
 liTest run finished: 0 failed, 1 ignored, 4 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_va.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_va.txt
index 015e238a7b..111b8f9193 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_va.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_va.txt
@@ -1,17 +1,17 @@
 liTest run started
 liTest org.scalajs.junit.MultiIgnore1Test.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnore1Test.multiTest1::
+e3org.scalajs.junit.MultiIgnore1Test.multiTest1::::true
 liTest org.scalajs.junit.MultiIgnore1Test.multiTest2 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest2::
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 liTest org.scalajs.junit.MultiIgnore1Test.multiTest3 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest3::
+e0org.scalajs.junit.MultiIgnore1Test.multiTest3::::true
 liTest org.scalajs.junit.MultiIgnore1Test.multiTest4 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest4::
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 liTest org.scalajs.junit.MultiIgnore1Test.multiTest5 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest5::
+e0org.scalajs.junit.MultiIgnore1Test.multiTest5::::true
 liTest run finished: 0 failed, 1 ignored, 4 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_vc.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_vc.txt
index 015e238a7b..111b8f9193 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_vc.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_vc.txt
@@ -1,17 +1,17 @@
 liTest run started
 liTest org.scalajs.junit.MultiIgnore1Test.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnore1Test.multiTest1::
+e3org.scalajs.junit.MultiIgnore1Test.multiTest1::::true
 liTest org.scalajs.junit.MultiIgnore1Test.multiTest2 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest2::
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 liTest org.scalajs.junit.MultiIgnore1Test.multiTest3 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest3::
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 liTest org.scalajs.junit.MultiIgnore1Test.multiTest4 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest4::
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 liTest org.scalajs.junit.MultiIgnore1Test.multiTest5 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest5::
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 liTest run finished: 0 failed, 1 ignored, 4 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_vs.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_vs.txt
index 015e238a7b..111b8f9193 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_vs.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_vs.txt
@@ -1,17 +1,17 @@
 liTest run started
 liTest org.scalajs.junit.MultiIgnore1Test.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnore1Test.multiTest1::
+e3org.scalajs.junit.MultiIgnore1Test.multiTest1::::true
 liTest org.scalajs.junit.MultiIgnore1Test.multiTest2 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest2::
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 liTest org.scalajs.junit.MultiIgnore1Test.multiTest3 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest3::
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 liTest org.scalajs.junit.MultiIgnore1Test.multiTest4 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest4::
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 liTest org.scalajs.junit.MultiIgnore1Test.multiTest5 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest5::
+e0org.scalajs.junit.MultiIgnore1Test.multiTest5::::true
 liTest run finished: 0 failed, 1 ignored, 4 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_vsn.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_vsn.txt
index 66b9cf269d..3481200a14 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_vsn.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnore1TestAssertions_vsn.txt
@@ -1,17 +1,17 @@
 liTest run started
 liTest org.scalajs.junit.MultiIgnore1Test.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnore1Test.multiTest1::
+e3org.scalajs.junit.MultiIgnore1Test.multiTest1::::true
 liTest org.scalajs.junit.MultiIgnore1Test.multiTest2 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest2::
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 liTest org.scalajs.junit.MultiIgnore1Test.multiTest3 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest3::
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 liTest org.scalajs.junit.MultiIgnore1Test.multiTest4 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest4 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest4::
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 liTest org.scalajs.junit.MultiIgnore1Test.multiTest5 started
 ldTest org.scalajs.junit.MultiIgnore1Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore1Test.multiTest5::
+e0org.scalajs.junit.MultiIgnore1Test.multiTest5::::true
 liTest run finished: 0 failed, 1 ignored, 4 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_.txt
index 84425fd6b6..c32eac55ad 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_.txt
@@ -1,16 +1,16 @@
 ldTest run started
 liTest org.scalajs.junit.MultiIgnore2Test.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnore2Test.multiTest1::
+e3org.scalajs.junit.MultiIgnore2Test.multiTest1::::true
 ldTest org.scalajs.junit.MultiIgnore2Test.multiTest2 started
 ldTest org.scalajs.junit.MultiIgnore2Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore2Test.multiTest2::
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 ldTest org.scalajs.junit.MultiIgnore2Test.multiTest3 started
 ldTest org.scalajs.junit.MultiIgnore2Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore2Test.multiTest3::
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 liTest org.scalajs.junit.MultiIgnore2Test.multiTest4 ignored
-e3org.scalajs.junit.MultiIgnore2Test.multiTest4::
+e3org.scalajs.junit.MultiIgnore2Test.multiTest4::::true
 ldTest org.scalajs.junit.MultiIgnore2Test.multiTest5 started
 ldTest org.scalajs.junit.MultiIgnore2Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore2Test.multiTest5::
+e0org.scalajs.junit.MultiIgnore2Test.multiTest5::::true
 ldTest run finished: 0 failed, 2 ignored, 3 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_a.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_a.txt
index 84425fd6b6..c32eac55ad 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_a.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_a.txt
@@ -1,16 +1,16 @@
 ldTest run started
 liTest org.scalajs.junit.MultiIgnore2Test.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnore2Test.multiTest1::
+e3org.scalajs.junit.MultiIgnore2Test.multiTest1::::true
 ldTest org.scalajs.junit.MultiIgnore2Test.multiTest2 started
 ldTest org.scalajs.junit.MultiIgnore2Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore2Test.multiTest2::
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 ldTest org.scalajs.junit.MultiIgnore2Test.multiTest3 started
 ldTest org.scalajs.junit.MultiIgnore2Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore2Test.multiTest3::
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 liTest org.scalajs.junit.MultiIgnore2Test.multiTest4 ignored
-e3org.scalajs.junit.MultiIgnore2Test.multiTest4::
+e3org.scalajs.junit.MultiIgnore2Test.multiTest4::::true
 ldTest org.scalajs.junit.MultiIgnore2Test.multiTest5 started
 ldTest org.scalajs.junit.MultiIgnore2Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore2Test.multiTest5::
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 ldTest run finished: 0 failed, 2 ignored, 3 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_n.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_n.txt
index a3bb9a46dd..1d7edf76ba 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_n.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_n.txt
@@ -1,16 +1,16 @@
 ldTest run started
 liTest org.scalajs.junit.MultiIgnore2Test.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnore2Test.multiTest1::
+e3org.scalajs.junit.MultiIgnore2Test.multiTest1::::true
 ldTest org.scalajs.junit.MultiIgnore2Test.multiTest2 started
 ldTest org.scalajs.junit.MultiIgnore2Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore2Test.multiTest2::
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 ldTest org.scalajs.junit.MultiIgnore2Test.multiTest3 started
 ldTest org.scalajs.junit.MultiIgnore2Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore2Test.multiTest3::
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 liTest org.scalajs.junit.MultiIgnore2Test.multiTest4 ignored
-e3org.scalajs.junit.MultiIgnore2Test.multiTest4::
+e3org.scalajs.junit.MultiIgnore2Test.multiTest4::::true
 ldTest org.scalajs.junit.MultiIgnore2Test.multiTest5 started
 ldTest org.scalajs.junit.MultiIgnore2Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore2Test.multiTest5::
+e0org.scalajs.junit.MultiIgnore2Test.multiTest5::::true
 ldTest run finished: 0 failed, 2 ignored, 3 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_na.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_na.txt
index a3bb9a46dd..1d7edf76ba 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_na.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_na.txt
@@ -1,16 +1,16 @@
 ldTest run started
 liTest org.scalajs.junit.MultiIgnore2Test.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnore2Test.multiTest1::
+e3org.scalajs.junit.MultiIgnore2Test.multiTest1::::true
 ldTest org.scalajs.junit.MultiIgnore2Test.multiTest2 started
 ldTest org.scalajs.junit.MultiIgnore2Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore2Test.multiTest2::
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 ldTest org.scalajs.junit.MultiIgnore2Test.multiTest3 started
 ldTest org.scalajs.junit.MultiIgnore2Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore2Test.multiTest3::
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 liTest org.scalajs.junit.MultiIgnore2Test.multiTest4 ignored
-e3org.scalajs.junit.MultiIgnore2Test.multiTest4::
+e3org.scalajs.junit.MultiIgnore2Test.multiTest4::::true
 ldTest org.scalajs.junit.MultiIgnore2Test.multiTest5 started
 ldTest org.scalajs.junit.MultiIgnore2Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore2Test.multiTest5::
+e0org.scalajs.junit.MultiIgnore2Test.multiTest5::::true
 ldTest run finished: 0 failed, 2 ignored, 3 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_nv.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_nv.txt
index 941ed7a212..003b857a4a 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_nv.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_nv.txt
@@ -1,16 +1,16 @@
 liTest run started
 liTest org.scalajs.junit.MultiIgnore2Test.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnore2Test.multiTest1::
+e3org.scalajs.junit.MultiIgnore2Test.multiTest1::::true
 liTest org.scalajs.junit.MultiIgnore2Test.multiTest2 started
 ldTest org.scalajs.junit.MultiIgnore2Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore2Test.multiTest2::
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 liTest org.scalajs.junit.MultiIgnore2Test.multiTest3 started
 ldTest org.scalajs.junit.MultiIgnore2Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore2Test.multiTest3::
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 liTest org.scalajs.junit.MultiIgnore2Test.multiTest4 ignored
-e3org.scalajs.junit.MultiIgnore2Test.multiTest4::
+e3org.scalajs.junit.MultiIgnore2Test.multiTest4::::true
 liTest org.scalajs.junit.MultiIgnore2Test.multiTest5 started
 ldTest org.scalajs.junit.MultiIgnore2Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore2Test.multiTest5::
+e0org.scalajs.junit.MultiIgnore2Test.multiTest5::::true
 liTest run finished: 0 failed, 2 ignored, 3 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_nva.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_nva.txt
index 941ed7a212..003b857a4a 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_nva.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_nva.txt
@@ -1,16 +1,16 @@
 liTest run started
 liTest org.scalajs.junit.MultiIgnore2Test.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnore2Test.multiTest1::
+e3org.scalajs.junit.MultiIgnore2Test.multiTest1::::true
 liTest org.scalajs.junit.MultiIgnore2Test.multiTest2 started
 ldTest org.scalajs.junit.MultiIgnore2Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore2Test.multiTest2::
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 liTest org.scalajs.junit.MultiIgnore2Test.multiTest3 started
 ldTest org.scalajs.junit.MultiIgnore2Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore2Test.multiTest3::
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 liTest org.scalajs.junit.MultiIgnore2Test.multiTest4 ignored
-e3org.scalajs.junit.MultiIgnore2Test.multiTest4::
+e3org.scalajs.junit.MultiIgnore2Test.multiTest4::::true
 liTest org.scalajs.junit.MultiIgnore2Test.multiTest5 started
 ldTest org.scalajs.junit.MultiIgnore2Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore2Test.multiTest5::
+e0org.scalajs.junit.MultiIgnore2Test.multiTest5::::true
 liTest run finished: 0 failed, 2 ignored, 3 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_nvc.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_nvc.txt
index 941ed7a212..003b857a4a 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_nvc.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_nvc.txt
@@ -1,16 +1,16 @@
 liTest run started
 liTest org.scalajs.junit.MultiIgnore2Test.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnore2Test.multiTest1::
+e3org.scalajs.junit.MultiIgnore2Test.multiTest1::::true
 liTest org.scalajs.junit.MultiIgnore2Test.multiTest2 started
 ldTest org.scalajs.junit.MultiIgnore2Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore2Test.multiTest2::
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 liTest org.scalajs.junit.MultiIgnore2Test.multiTest3 started
 ldTest org.scalajs.junit.MultiIgnore2Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore2Test.multiTest3::
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 liTest org.scalajs.junit.MultiIgnore2Test.multiTest4 ignored
-e3org.scalajs.junit.MultiIgnore2Test.multiTest4::
+e3org.scalajs.junit.MultiIgnore2Test.multiTest4::::true
 liTest org.scalajs.junit.MultiIgnore2Test.multiTest5 started
 ldTest org.scalajs.junit.MultiIgnore2Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore2Test.multiTest5::
+e0org.scalajs.junit.MultiIgnore2Test.multiTest5::::true
 liTest run finished: 0 failed, 2 ignored, 3 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_nvca.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_nvca.txt
index 941ed7a212..003b857a4a 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_nvca.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_nvca.txt
@@ -1,16 +1,16 @@
 liTest run started
 liTest org.scalajs.junit.MultiIgnore2Test.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnore2Test.multiTest1::
+e3org.scalajs.junit.MultiIgnore2Test.multiTest1::::true
 liTest org.scalajs.junit.MultiIgnore2Test.multiTest2 started
 ldTest org.scalajs.junit.MultiIgnore2Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore2Test.multiTest2::
+e0org.scalajs.junit.MultiIgnore2Test.multiTest2::::true
 liTest org.scalajs.junit.MultiIgnore2Test.multiTest3 started
 ldTest org.scalajs.junit.MultiIgnore2Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore2Test.multiTest3::
+e0org.scalajs.junit.MultiIgnore2Test.multiTest3::::true
 liTest org.scalajs.junit.MultiIgnore2Test.multiTest4 ignored
-e3org.scalajs.junit.MultiIgnore2Test.multiTest4::
+e3org.scalajs.junit.MultiIgnore2Test.multiTest4::::true
 liTest org.scalajs.junit.MultiIgnore2Test.multiTest5 started
 ldTest org.scalajs.junit.MultiIgnore2Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore2Test.multiTest5::
+e0org.scalajs.junit.MultiIgnore2Test.multiTest5::::true
 liTest run finished: 0 failed, 2 ignored, 3 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_v.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_v.txt
index cce69a4cc8..5e2f35549b 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_v.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_v.txt
@@ -1,16 +1,16 @@
 liTest run started
 liTest org.scalajs.junit.MultiIgnore2Test.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnore2Test.multiTest1::
+e3org.scalajs.junit.MultiIgnore2Test.multiTest1::::true
 liTest org.scalajs.junit.MultiIgnore2Test.multiTest2 started
 ldTest org.scalajs.junit.MultiIgnore2Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore2Test.multiTest2::
+e0org.scalajs.junit.MultiIgnore2Test.multiTest2::::true
 liTest org.scalajs.junit.MultiIgnore2Test.multiTest3 started
 ldTest org.scalajs.junit.MultiIgnore2Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore2Test.multiTest3::
+e0org.scalajs.junit.MultiIgnore2Test.multiTest3::::true
 liTest org.scalajs.junit.MultiIgnore2Test.multiTest4 ignored
-e3org.scalajs.junit.MultiIgnore2Test.multiTest4::
+e3org.scalajs.junit.MultiIgnore2Test.multiTest4::::true
 liTest org.scalajs.junit.MultiIgnore2Test.multiTest5 started
 ldTest org.scalajs.junit.MultiIgnore2Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore2Test.multiTest5::
+e0org.scalajs.junit.MultiIgnore2Test.multiTest5::::true
 liTest run finished: 0 failed, 2 ignored, 3 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_va.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_va.txt
index cce69a4cc8..5e2f35549b 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_va.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_va.txt
@@ -1,16 +1,16 @@
 liTest run started
 liTest org.scalajs.junit.MultiIgnore2Test.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnore2Test.multiTest1::
+e3org.scalajs.junit.MultiIgnore2Test.multiTest1::::true
 liTest org.scalajs.junit.MultiIgnore2Test.multiTest2 started
 ldTest org.scalajs.junit.MultiIgnore2Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore2Test.multiTest2::
+e0org.scalajs.junit.MultiIgnore2Test.multiTest2::::true
 liTest org.scalajs.junit.MultiIgnore2Test.multiTest3 started
 ldTest org.scalajs.junit.MultiIgnore2Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore2Test.multiTest3::
+e0org.scalajs.junit.MultiIgnore2Test.multiTest3::::true
 liTest org.scalajs.junit.MultiIgnore2Test.multiTest4 ignored
-e3org.scalajs.junit.MultiIgnore2Test.multiTest4::
+e3org.scalajs.junit.MultiIgnore2Test.multiTest4::::true
 liTest org.scalajs.junit.MultiIgnore2Test.multiTest5 started
 ldTest org.scalajs.junit.MultiIgnore2Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore2Test.multiTest5::
+e0org.scalajs.junit.MultiIgnore2Test.multiTest5::::true
 liTest run finished: 0 failed, 2 ignored, 3 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_vc.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_vc.txt
index cce69a4cc8..5e2f35549b 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_vc.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_vc.txt
@@ -1,16 +1,16 @@
 liTest run started
 liTest org.scalajs.junit.MultiIgnore2Test.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnore2Test.multiTest1::
+e3org.scalajs.junit.MultiIgnore2Test.multiTest1::::true
 liTest org.scalajs.junit.MultiIgnore2Test.multiTest2 started
 ldTest org.scalajs.junit.MultiIgnore2Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore2Test.multiTest2::
+e0org.scalajs.junit.MultiIgnore2Test.multiTest2::::true
 liTest org.scalajs.junit.MultiIgnore2Test.multiTest3 started
 ldTest org.scalajs.junit.MultiIgnore2Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore2Test.multiTest3::
+e0org.scalajs.junit.MultiIgnore2Test.multiTest3::::true
 liTest org.scalajs.junit.MultiIgnore2Test.multiTest4 ignored
-e3org.scalajs.junit.MultiIgnore2Test.multiTest4::
+e3org.scalajs.junit.MultiIgnore2Test.multiTest4::::true
 liTest org.scalajs.junit.MultiIgnore2Test.multiTest5 started
 ldTest org.scalajs.junit.MultiIgnore2Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore2Test.multiTest5::
+e0org.scalajs.junit.MultiIgnore2Test.multiTest5::::true
 liTest run finished: 0 failed, 2 ignored, 3 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_vs.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_vs.txt
index cce69a4cc8..5e2f35549b 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_vs.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_vs.txt
@@ -1,16 +1,16 @@
 liTest run started
 liTest org.scalajs.junit.MultiIgnore2Test.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnore2Test.multiTest1::
+e3org.scalajs.junit.MultiIgnore2Test.multiTest1::::true
 liTest org.scalajs.junit.MultiIgnore2Test.multiTest2 started
 ldTest org.scalajs.junit.MultiIgnore2Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore2Test.multiTest2::
+e0org.scalajs.junit.MultiIgnore2Test.multiTest2::::true
 liTest org.scalajs.junit.MultiIgnore2Test.multiTest3 started
 ldTest org.scalajs.junit.MultiIgnore2Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore2Test.multiTest3::
+e0org.scalajs.junit.MultiIgnore2Test.multiTest3::::true
 liTest org.scalajs.junit.MultiIgnore2Test.multiTest4 ignored
-e3org.scalajs.junit.MultiIgnore2Test.multiTest4::
+e3org.scalajs.junit.MultiIgnore2Test.multiTest4::::true
 liTest org.scalajs.junit.MultiIgnore2Test.multiTest5 started
 ldTest org.scalajs.junit.MultiIgnore2Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore2Test.multiTest5::
+e0org.scalajs.junit.MultiIgnore2Test.multiTest5::::true
 liTest run finished: 0 failed, 2 ignored, 3 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_vsn.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_vsn.txt
index 941ed7a212..003b857a4a 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_vsn.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnore2TestAssertions_vsn.txt
@@ -1,16 +1,16 @@
 liTest run started
 liTest org.scalajs.junit.MultiIgnore2Test.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnore2Test.multiTest1::
+e3org.scalajs.junit.MultiIgnore2Test.multiTest1::::true
 liTest org.scalajs.junit.MultiIgnore2Test.multiTest2 started
 ldTest org.scalajs.junit.MultiIgnore2Test.multiTest2 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore2Test.multiTest2::
+e0org.scalajs.junit.MultiIgnore2Test.multiTest2::::true
 liTest org.scalajs.junit.MultiIgnore2Test.multiTest3 started
 ldTest org.scalajs.junit.MultiIgnore2Test.multiTest3 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore2Test.multiTest3::
+e0org.scalajs.junit.MultiIgnore2Test.multiTest3::::true
 liTest org.scalajs.junit.MultiIgnore2Test.multiTest4 ignored
-e3org.scalajs.junit.MultiIgnore2Test.multiTest4::
+e3org.scalajs.junit.MultiIgnore2Test.multiTest4::::true
 liTest org.scalajs.junit.MultiIgnore2Test.multiTest5 started
 ldTest org.scalajs.junit.MultiIgnore2Test.multiTest5 finished, took <TIME>
-e0org.scalajs.junit.MultiIgnore2Test.multiTest5::
+e0org.scalajs.junit.MultiIgnore2Test.multiTest5::::true
 liTest run finished: 0 failed, 2 ignored, 3 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_.txt
index cb142ec998..0ece061a27 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_.txt
@@ -1,13 +1,13 @@
 ldTest run started
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest1::
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest1::::true
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest2 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest2::
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest2::::true
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest3 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest3::
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest3::::true
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest4 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest4::
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest4::::true
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest5 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest5::
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest5::::true
 ldTest run finished: 0 failed, 5 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_a.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_a.txt
index cb142ec998..0ece061a27 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_a.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_a.txt
@@ -1,13 +1,13 @@
 ldTest run started
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest1::
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest1::::true
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest2 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest2::
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest2::::true
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest3 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest3::
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest3::::true
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest4 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest4::
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest4::::true
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest5 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest5::
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest5::::true
 ldTest run finished: 0 failed, 5 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_n.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_n.txt
index 3fe19eea5c..9c598f3bfa 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_n.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_n.txt
@@ -1,13 +1,13 @@
 ldTest run started
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest1::
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest1::::true
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest2 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest2::
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest2::::true
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest3 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest3::
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest3::::true
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest4 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest4::
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest4::::true
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest5 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest5::
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest5::::true
 ldTest run finished: 0 failed, 5 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_na.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_na.txt
index 3fe19eea5c..9c598f3bfa 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_na.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_na.txt
@@ -1,13 +1,13 @@
 ldTest run started
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest1::
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest1::::true
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest2 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest2::
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest2::::true
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest3 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest3::
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest3::::true
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest4 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest4::
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest4::::true
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest5 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest5::
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest5::::true
 ldTest run finished: 0 failed, 5 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_nv.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_nv.txt
index c7d123ab0b..73f543a502 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_nv.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_nv.txt
@@ -1,13 +1,13 @@
 liTest run started
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest1::
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest1::::true
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest2 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest2::
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest2::::true
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest3 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest3::
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest3::::true
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest4 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest4::
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest4::::true
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest5 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest5::
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest5::::true
 liTest run finished: 0 failed, 5 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_nva.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_nva.txt
index c7d123ab0b..73f543a502 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_nva.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_nva.txt
@@ -1,13 +1,13 @@
 liTest run started
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest1::
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest1::::true
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest2 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest2::
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest2::::true
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest3 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest3::
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest3::::true
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest4 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest4::
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest4::::true
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest5 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest5::
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest5::::true
 liTest run finished: 0 failed, 5 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_nvc.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_nvc.txt
index c7d123ab0b..73f543a502 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_nvc.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_nvc.txt
@@ -1,13 +1,13 @@
 liTest run started
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest1::
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest1::::true
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest2 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest2::
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest2::::true
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest3 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest3::
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest3::::true
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest4 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest4::
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest4::::true
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest5 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest5::
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest5::::true
 liTest run finished: 0 failed, 5 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_nvca.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_nvca.txt
index c7d123ab0b..73f543a502 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_nvca.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_nvca.txt
@@ -1,13 +1,13 @@
 liTest run started
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest1::
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest1::::true
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest2 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest2::
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest2::::true
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest3 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest3::
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest3::::true
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest4 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest4::
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest4::::true
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest5 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest5::
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest5::::true
 liTest run finished: 0 failed, 5 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_v.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_v.txt
index e2040b03b5..31b8dc7069 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_v.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_v.txt
@@ -1,13 +1,13 @@
 liTest run started
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest1::
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest1::::true
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest2 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest2::
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest2::::true
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest3 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest3::
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest3::::true
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest4 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest4::
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest4::::true
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest5 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest5::
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest5::::true
 liTest run finished: 0 failed, 5 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_va.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_va.txt
index e2040b03b5..31b8dc7069 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_va.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_va.txt
@@ -1,13 +1,13 @@
 liTest run started
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest1::
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest1::::true
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest2 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest2::
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest2::::true
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest3 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest3::
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest3::::true
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest4 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest4::
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest4::::true
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest5 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest5::
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest5::::true
 liTest run finished: 0 failed, 5 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_vc.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_vc.txt
index e2040b03b5..31b8dc7069 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_vc.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_vc.txt
@@ -1,13 +1,13 @@
 liTest run started
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest1::
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest1::::true
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest2 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest2::
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest2::::true
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest3 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest3::
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest3::::true
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest4 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest4::
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest4::::true
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest5 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest5::
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest5::::true
 liTest run finished: 0 failed, 5 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_vs.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_vs.txt
index e2040b03b5..31b8dc7069 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_vs.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_vs.txt
@@ -1,13 +1,13 @@
 liTest run started
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest1::
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest1::::true
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest2 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest2::
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest2::::true
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest3 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest3::
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest3::::true
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest4 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest4::
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest4::::true
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest5 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest5::
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest5::::true
 liTest run finished: 0 failed, 5 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_vsn.txt b/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_vsn.txt
index c7d123ab0b..73f543a502 100644
--- a/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_vsn.txt
+++ b/junit-test/outputs/org/scalajs/junit/MultiIgnoreAllTestAssertions_vsn.txt
@@ -1,13 +1,13 @@
 liTest run started
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest1 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest1::
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest1::::true
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest2 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest2::
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest2::::true
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest3 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest3::
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest3::::true
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest4 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest4::
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest4::::true
 liTest org.scalajs.junit.MultiIgnoreAllTest.multiTest5 ignored
-e3org.scalajs.junit.MultiIgnoreAllTest.multiTest5::
+e3org.scalajs.junit.MultiIgnoreAllTest.multiTest5::::true
 liTest run finished: 0 failed, 5 ignored, 0 total, <TIME>
 d
diff --git a/junit-test/shared/src/test/scala/org/scalajs/junit/utils/JUnitTest.scala b/junit-test/shared/src/test/scala/org/scalajs/junit/utils/JUnitTest.scala
index 84d94af22f..af53ce644c 100644
--- a/junit-test/shared/src/test/scala/org/scalajs/junit/utils/JUnitTest.scala
+++ b/junit-test/shared/src/test/scala/org/scalajs/junit/utils/JUnitTest.scala
@@ -179,7 +179,7 @@ abstract class JUnitTest {
         Some(msg.substring(s + testNamePrefix.length, e))
       }
 
-    case Event(_, name, _) =>
+    case Event(_, name, _, _) =>
       if (name == suiteUnderTestName) None
       else if (name.startsWith(testNamePrefix)) Some(name.stripPrefix(testNamePrefix))
       else throw new AssertionError(s"Unknown test name: $name")
@@ -227,7 +227,8 @@ abstract class JUnitTest {
       buf += Event(
         event.status(),
         testName,
-        if (event.throwable.isEmpty) None else Some(event.throwable.get.toString)
+        if (event.throwable.isEmpty) None else Some(event.throwable.get.toString),
+        event.duration >= 0
       )
     }
 
@@ -240,9 +241,15 @@ abstract class JUnitTest {
 object JUnitTest {
   sealed trait Output
   final case class Log(level: Char, msg: String) extends Output
-  final case class Event(status: Status, testName: String, throwableToString: Option[String]) extends Output
   final case class Done(msg: String) extends Output
 
+  final case class Event(
+    status: Status,
+    testName: String,
+    throwableToString: Option[String],
+    durationPopulated: Boolean
+  ) extends Output
+
   object Output {
     // We need something that does not occur in test names nor in Throwable.toString.
     final val separator = "::"
@@ -255,17 +262,19 @@ object JUnitTest {
         val rest: Array[String] = tail.mkString("").split(separator, -1)
         val testName: String = rest(0)
         val throwableToString: String = rest(1)
+        val durationPopulated: Boolean = rest(2).toBoolean
         Event(
           status = Status.values()(s - '0'),
           testName,
-          throwableToString = if (throwableToString.isEmpty) None else Some(throwableToString)
+          throwableToString = if (throwableToString.isEmpty) None else Some(throwableToString),
+          durationPopulated
         )
     }
 
     def serialize(o: Output): String = o match {
-      case Log(level, msg) => "l" + level + msg
-      case Done(msg)       => "d" + msg
-      case Event(s, n, t)  => "e" + s.ordinal + n + separator + t.getOrElse("")
+      case Log(level, msg)   => "l" + level + msg
+      case Done(msg)         => "d" + msg
+      case Event(s, n, t, d) => "e" + s.ordinal + n + separator + t.getOrElse("") + separator + d
     }
   }
 }

From b1eabac0a3f043cd30b0d062d2712f399f190460 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Mon, 3 Mar 2025 13:59:12 +0100
Subject: [PATCH 264/298] Rearrange the init sequence of `PrimRef`s and
 `PrimTypeWithRef`s.

So that it is more obvious that it is not circular.

`PrimRef` is not a case class anymore.
---
 .../src/main/scala/org/scalajs/ir/Types.scala | 121 +++++++-----------
 project/BinaryIncompatibilities.scala         |  21 +++
 2 files changed, 68 insertions(+), 74 deletions(-)

diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Types.scala b/ir/shared/src/main/scala/org/scalajs/ir/Types.scala
index debd69ab56..5cc8bee808 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Types.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Types.scala
@@ -12,8 +12,6 @@
 
 package org.scalajs.ir
 
-import scala.annotation.tailrec
-
 import Names._
 import Trees._
 
@@ -62,20 +60,14 @@ object Types {
     }
   }
 
-  sealed abstract class PrimTypeWithRef extends PrimType {
-    def primRef: PrimRef = this match {
-      case VoidType    => VoidRef
-      case BooleanType => BooleanRef
-      case CharType    => CharRef
-      case ByteType    => ByteRef
-      case ShortType   => ShortRef
-      case IntType     => IntRef
-      case LongType    => LongRef
-      case FloatType   => FloatRef
-      case DoubleType  => DoubleRef
-      case NullType    => NullRef
-      case NothingType => NothingRef
-    }
+  /* Each PrimTypeWithRef creates its corresponding `PrimRef`. Therefore, it
+   * takes the parameters that need to be passed to the `PrimRef` constructor.
+   * This little dance ensures proper initialization safety between
+   * `PrimTypeWithRef`s and `PrimRef`s.
+   */
+  sealed abstract class PrimTypeWithRef(primRefCharCode: Char, primRefDisplayName: String)
+      extends PrimType {
+    val primRef: PrimRef = new PrimRef(this, primRefCharCode, primRefDisplayName)
   }
 
   /** Any type.
@@ -106,7 +98,7 @@ object Types {
    *  Expressions from which one can never come back are typed as `Nothing`.
    *  For example, `throw` and `return`.
    */
-  case object NothingType extends PrimTypeWithRef
+  case object NothingType extends PrimTypeWithRef('E', "nothing")
 
   /** The type of `undefined`. */
   case object UndefType extends PrimType
@@ -114,42 +106,42 @@ object Types {
   /** Boolean type.
    *  It does not accept `null` nor `undefined`.
    */
-  case object BooleanType extends PrimTypeWithRef
+  case object BooleanType extends PrimTypeWithRef('Z', "boolean")
 
   /** `Char` type, a 16-bit UTF-16 code unit.
    *  It does not accept `null` nor `undefined`.
    */
-  case object CharType extends PrimTypeWithRef
+  case object CharType extends PrimTypeWithRef('C', "char")
 
   /** 8-bit signed integer type.
    *  It does not accept `null` nor `undefined`.
    */
-  case object ByteType extends PrimTypeWithRef
+  case object ByteType extends PrimTypeWithRef('B', "byte")
 
   /** 16-bit signed integer type.
    *  It does not accept `null` nor `undefined`.
    */
-  case object ShortType extends PrimTypeWithRef
+  case object ShortType extends PrimTypeWithRef('S', "short")
 
   /** 32-bit signed integer type.
    *  It does not accept `null` nor `undefined`.
    */
-  case object IntType extends PrimTypeWithRef
+  case object IntType extends PrimTypeWithRef('I', "int")
 
   /** 64-bit signed integer type.
    *  It does not accept `null` nor `undefined`.
    */
-  case object LongType extends PrimTypeWithRef
+  case object LongType extends PrimTypeWithRef('J', "long")
 
   /** Float type (32-bit).
    *  It does not accept `null` nor `undefined`.
    */
-  case object FloatType extends PrimTypeWithRef
+  case object FloatType extends PrimTypeWithRef('F', "float")
 
   /** Double type (64-bit).
    *  It does not accept `null` nor `undefined`.
    */
-  case object DoubleType extends PrimTypeWithRef
+  case object DoubleType extends PrimTypeWithRef('D', "double")
 
   /** String type.
    *  It does not accept `null` nor `undefined`.
@@ -160,7 +152,7 @@ object Types {
    *  It does not accept `undefined`.
    *  The null type is a subtype of all class types and array types.
    */
-  case object NullType extends PrimTypeWithRef
+  case object NullType extends PrimTypeWithRef('N', "null")
 
   /** Class (or interface) type. */
   final case class ClassType(className: ClassName, nullable: Boolean) extends Type {
@@ -210,7 +202,7 @@ object Types {
   }
 
   /** Void type, the top of type of our type system. */
-  case object VoidType extends PrimTypeWithRef
+  case object VoidType extends PrimTypeWithRef('V', "void")
 
   @deprecated("Use VoidType instead", since = "1.18.0")
   lazy val NoType: VoidType.type = VoidType
@@ -265,8 +257,12 @@ object Types {
 
   sealed abstract class NonArrayTypeRef extends TypeRef
 
+  // scalastyle:off equals.hash.code
+  // PrimRef uses reference equality, but has a stable hashCode() method
+
   /** Primitive type reference. */
-  final case class PrimRef private[ir] (tpe: PrimTypeWithRef)
+  final class PrimRef private[Types] (val tpe: PrimTypeWithRef,
+      charCodeInit: Char, displayNameInit: String) // "Init" variants so we can have good Scaladoc on the val's
       extends NonArrayTypeRef {
 
     /** The display name of this primitive type.
@@ -278,19 +274,7 @@ object Types {
      *  For `NullType` and `NothingType`, the names are `"null"` and
      *  `"nothing"`, respectively.
      */
-    val displayName: String = tpe match {
-      case VoidType    => "void"
-      case BooleanType => "boolean"
-      case CharType    => "char"
-      case ByteType    => "byte"
-      case ShortType   => "short"
-      case IntType     => "int"
-      case LongType    => "long"
-      case FloatType   => "float"
-      case DoubleType  => "double"
-      case NullType    => "null"
-      case NothingType => "nothing"
-    }
+    val displayName: String = displayNameInit
 
     /** The char code of this primitive type.
      *
@@ -302,41 +286,30 @@ object Types {
      *  For `NullType` and `NothingType`, the char codes are `'N'` and `'E'`,
      *  respectively.
      */
-    val charCode: Char = tpe match {
-      case VoidType    => 'V'
-      case BooleanType => 'Z'
-      case CharType    => 'C'
-      case ByteType    => 'B'
-      case ShortType   => 'S'
-      case IntType     => 'I'
-      case LongType    => 'J'
-      case FloatType   => 'F'
-      case DoubleType  => 'D'
-      case NullType    => 'N'
-      case NothingType => 'E'
-    }
+    val charCode: Char = charCodeInit
+
+    // Stable hash code, corresponding to reference equality
+    override def hashCode(): Int = charCode.##
   }
 
-  /* @unchecked for the initialization checker of Scala 3
-   * When we get here, `VoidType` is not yet considered fully initialized because
-   * its method `primRef` can access `VoidRef`. Since the constructor of
-   * `PrimRef` pattern-matches on its `tpe`, which is `VoidType`, this is flagged
-   * by the init checker, although our usage is safe given that we do not call
-   * `primRef`. The same reasoning applies to the other primitive types.
-   * In the future, we may want to rearrange the initialization sequence of
-   * this file to avoid this issue.
-   */
-  final val VoidRef = PrimRef(VoidType: @unchecked)
-  final val BooleanRef = PrimRef(BooleanType: @unchecked)
-  final val CharRef = PrimRef(CharType: @unchecked)
-  final val ByteRef = PrimRef(ByteType: @unchecked)
-  final val ShortRef = PrimRef(ShortType: @unchecked)
-  final val IntRef = PrimRef(IntType: @unchecked)
-  final val LongRef = PrimRef(LongType: @unchecked)
-  final val FloatRef = PrimRef(FloatType: @unchecked)
-  final val DoubleRef = PrimRef(DoubleType: @unchecked)
-  final val NullRef = PrimRef(NullType: @unchecked)
-  final val NothingRef = PrimRef(NothingType: @unchecked)
+  // scalastyle:on equals.hash.code
+
+  object PrimRef {
+    def unapply(typeRef: PrimRef): Some[PrimTypeWithRef] =
+      Some(typeRef.tpe)
+  }
+
+  final val VoidRef = VoidType.primRef
+  final val BooleanRef = BooleanType.primRef
+  final val CharRef = CharType.primRef
+  final val ByteRef = ByteType.primRef
+  final val ShortRef = ShortType.primRef
+  final val IntRef = IntType.primRef
+  final val LongRef = LongType.primRef
+  final val FloatRef = FloatType.primRef
+  final val DoubleRef = DoubleType.primRef
+  final val NullRef = NullType.primRef
+  final val NothingRef = NothingType.primRef
 
   /** Class (or interface) type. */
   final case class ClassRef(className: ClassName) extends NonArrayTypeRef {
diff --git a/project/BinaryIncompatibilities.scala b/project/BinaryIncompatibilities.scala
index edc3b894b3..a156e6737b 100644
--- a/project/BinaryIncompatibilities.scala
+++ b/project/BinaryIncompatibilities.scala
@@ -16,6 +16,27 @@ object BinaryIncompatibilities {
     ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Types.BoxedClassToPrimType"),
     ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Types.PrimTypeToBoxedClass"),
 
+    // !!! Breaking, PrimRef is not a case class anymore
+    ProblemFilters.exclude[MissingTypesProblem]("org.scalajs.ir.Types$PrimRef"),
+    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Types#PrimRef.canEqual"),
+    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Types#PrimRef.productArity"),
+    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Types#PrimRef.productElement"),
+    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Types#PrimRef.productElementName"),
+    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Types#PrimRef.productElementNames"),
+    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Types#PrimRef.productIterator"),
+    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Types#PrimRef.productPrefix"),
+    ProblemFilters.exclude[IncompatibleResultTypeProblem]("org.scalajs.ir.Types#PrimRef.unapply"),
+
+    // !!! Breaking I guess ... we used to leak public things out of a `case class` with a private[ir] constructor
+    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Types#PrimRef.this"),
+    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Types#PrimRef.apply"),
+    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Types#PrimRef.copy"),
+    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Types#PrimRef.copy$default$1"),
+    ProblemFilters.exclude[MissingTypesProblem]("org.scalajs.ir.Types$PrimRef$"),
+
+    // constructor of a sealed abstract class, not an issue
+    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Types#PrimTypeWithRef.this"),
+
     // private, not an issue
     ProblemFilters.exclude[MissingClassProblem]("org.scalajs.ir.Serializers$Deserializer$BodyHack5Transformer$"),
     ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Serializers#Hacks.use*"),

From 7a05348096103cc1bfecfbd941508316f974d91e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Fri, 10 Jan 2025 10:45:08 +0100
Subject: [PATCH 265/298] Bump the IR version to 1.19-SNAPSHOT for the upcoming
 changes.

---
 ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala b/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala
index 3f7c4d501e..03bf83efcd 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala
@@ -18,7 +18,7 @@ import scala.util.matching.Regex
 
 object ScalaJSVersions extends VersionChecks(
     current = "1.19.0-SNAPSHOT",
-    binaryEmitted = "1.18"
+    binaryEmitted = "1.19-SNAPSHOT"
 )
 
 /** Helper class to allow for testing of logic. */

From 53dc4fe54568acfeb1fd31e89030e98a538bd9c6 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Mon, 1 Jul 2024 20:45:24 +0200
Subject: [PATCH 266/298] Introduce NewLambda to synthesize instances of SAM
 types.

The `NewLambda` node creates an instance of an anonymous class from
a `Descriptor` and a closure `fun`. The `Descriptor` specifies the
shape of the anonymous class: a super class, a list of interfaces to
implement, and the name of a single non-constructor method to provide.
The body of the method calls the `fun` closure.

At link time, the Analyzer and BaseLinker synthesize a unique such
anonymous class per `Descriptor`. In practice, all the lambdas for
a given target type share a common `Descriptor`. This is notably the
case for all the Scala functions of arity N.

`NewLambda` replaces the need for special `AnonFunctionN` classes in
the library. Instead, classes of the right shape are synthesized at
link-time.

The scheme can also be used for most LambdaMetaFactory-style
lambdas, although our `NewLambda` does not support bridge
generation. In the common case where no bridges are necessary, we
now also generate a `NewLambda`. This generalizes the code size
optimization of having only one class per `Descriptor` to non-Scala
functions.

In order to truly support LMF-style lambdas, the closure `fun` must
take parameters that match the (erased) type in their superinterface.
Previously, for Scala `FunctionN`, we knew by construction that the
parameters and result types were always `any`, and so JS `Closure`s
were good enough. Now, we need closures that can accept different
types. This is where typed closures come into play (see below).

---

When bridges are required, we still generate a custom class from
the compiler backend. In that case, we statically inline the closure
body in the produced SAM implementation.

We have to do this not to expose typed closures across method calls.
Moreover, we need the better static types for the parameters to be
able to inline the closures without too much hassle. So this change
*has* to be done in lockstep with the rest of this commit.

---

A typed closure is a `Closure` that does not have any semantics for
JS interop. This is stronger than `Char`, which is "merely" opaque
to JS. A `Char` can still be passed to JS and has a meaningful
`toString()`. A typed closure *cannot* be passed to JS in any way.
That is enforced by making their type *not* a subtype of `any`
(like record types).

Since a typed closure has no JS interop semantics, it is free to
strongly, statically type its parameters and result type.

Additionally, we can freely choose its representation in the best
possible way for the given target. On JS, that remains an arrow
function. On Wasm, however, we represent it as a pair of
`(capture data pointer, function pointer)`. This allows to compile
them in an efficient way that does not require going through a JS
bridge closure. The latter has been shown to have a devastating
impact on performance when a Scala function is used in a tight
loop.

The type of a typed closure is a `ClosureType`. It records its
parameter types and its result type. Closure types are non-variant:
they are only subtypes of themselves. As mentioned, they are not
subtypes of `any`. They are however subtypes of `void` and
supertypes of `nothing`. Unfortunately, they must also be nullable
to have a default value, so they have nullable and non-nullable
alternatives.

To call a typed closure, we introduce a dedicated application node
`ApplyTypedClosure`. IR checking ensures that actual arguments
match the expected parameter types. The result type is directly
used as the type of the application.

There are no changes to the source language. In particular, there
is no way to express typed closures or their types at the user
level. They are only used for `NewLambda` nodes.

In fact, typed closures and `ApplyTypedClosure`s are not
first-class at the IR level. Before desugaring, typed closures are
only allowed as direct children of `NewLambda` nodes. Desugaring
transforms `NewLambda` nodes into `New`s of the synthesized
anonymous classes. At that point, the two typed closure nodes
become first-class expression trees.

---

For Scala functions, these changes have no real impact on the JS
output (only marginal naming differences). On Wasm, however, they
make Scala functions much, much faster. Before, a Scala function in
a tight loop would cause a Wasm implementation to be, in the worst
measured case, 20x slower than on JS. After these changes, similar
benchmarks become significantly faster on Wasm than on JS.
---
 .../org/scalajs/nscplugin/GenJSCode.scala     | 338 ++++++++++++------
 .../main/scala/org/scalajs/ir/Hashers.scala   |  49 ++-
 .../org/scalajs/ir/InvalidIRException.scala   |  11 +-
 .../src/main/scala/org/scalajs/ir/Names.scala |   2 +
 .../main/scala/org/scalajs/ir/Printers.scala  |  64 +++-
 .../scala/org/scalajs/ir/Serializers.scala    | 108 +++++-
 .../src/main/scala/org/scalajs/ir/Tags.scala  |  13 +
 .../scala/org/scalajs/ir/Transformers.scala   |  16 +-
 .../scala/org/scalajs/ir/Traversers.scala     |  11 +-
 .../src/main/scala/org/scalajs/ir/Trees.scala | 179 +++++++++-
 .../src/main/scala/org/scalajs/ir/Types.scala |  90 ++++-
 .../test/scala/org/scalajs/ir/NamesTest.scala |   3 +-
 .../scala/org/scalajs/ir/PrintersTest.scala   |  81 ++++-
 .../scala/scalajs/runtime/AnonFunctions.scala |  23 ++
 .../scalajs/linker/analyzer/Analysis.scala    |   3 +
 .../scalajs/linker/analyzer/Analyzer.scala    |  69 +++-
 .../org/scalajs/linker/analyzer/Infos.scala   |  30 +-
 .../backend/emitter/FunctionEmitter.scala     |  47 ++-
 .../linker/backend/emitter/NameGen.scala      |   2 +
 .../linker/backend/emitter/SJSGen.scala       |   9 +-
 .../backend/wasmemitter/FunctionEmitter.scala | 141 +++++++-
 .../linker/backend/wasmemitter/SWasmGen.scala |   9 +-
 .../backend/wasmemitter/TypeTransformer.scala |   4 +
 .../linker/backend/wasmemitter/VarGen.scala   |  10 +
 .../backend/wasmemitter/WasmContext.scala     |  50 +++
 .../linker/backend/webassembly/Types.scala    |   3 +
 .../linker/checker/ClassDefChecker.scala      | 163 +++++++--
 .../scalajs/linker/checker/FeatureSet.scala   |  32 +-
 .../scalajs/linker/checker/IRChecker.scala    |  38 +-
 .../scalajs/linker/frontend/BaseLinker.scala  |  15 +-
 .../scalajs/linker/frontend/Desugarer.scala   |  19 +
 .../linker/frontend/LambdaSynthesizer.scala   | 178 +++++++++
 .../linker/frontend/MethodSynthesizer.scala   |  22 +-
 .../linker/frontend/SyntheticClassKind.scala  |  21 ++
 .../frontend/optimizer/IncOptimizer.scala     |   2 +-
 .../frontend/optimizer/OptimizerCore.scala    | 116 ++++--
 .../org/scalajs/linker/IRCheckerTest.scala    |   1 +
 .../org/scalajs/linker/OptimizerTest.scala    |   9 +-
 .../linker/checker/ClassDefCheckerTest.scala  |  14 +-
 project/BinaryIncompatibilities.scala         |   4 +
 project/Build.scala                           |  14 +-
 project/JavalibIRCleaner.scala                |  17 +-
 .../SAMWithOverridingBridgesTest.scala        |   4 +-
 43 files changed, 1718 insertions(+), 316 deletions(-)
 create mode 100644 linker/shared/src/main/scala/org/scalajs/linker/frontend/LambdaSynthesizer.scala
 create mode 100644 linker/shared/src/main/scala/org/scalajs/linker/frontend/SyntheticClassKind.scala

diff --git a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
index 8070b19f50..4f8387fe57 100644
--- a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
+++ b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
@@ -544,20 +544,26 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
             genIRFile(cunit, hashedClassDef)
           } catch {
             case e: ir.InvalidIRException =>
-              e.tree match {
-                case ir.Trees.Transient(UndefinedParam) =>
+              e.optTree match {
+                case Some(tree @ ir.Trees.Transient(UndefinedParam)) =>
                   reporter.error(pos,
                       "Found a dangling UndefinedParam at " +
-                      s"${e.tree.pos}. This is likely due to a bad " +
+                      s"${tree.pos}. This is likely due to a bad " +
                       "interaction between a macro or a compiler plugin " +
                       "and the Scala.js compiler plugin. If you hit " +
                       "this, please let us know.")
 
-                case _ =>
+                case Some(tree) =>
                   reporter.error(pos,
                       "The Scala.js compiler generated invalid IR for " +
                       "this class. Please report this as a bug. IR: " +
-                      e.tree)
+                      tree)
+
+                case None =>
+                  reporter.error(pos,
+                      "The Scala.js compiler generated invalid IR for this class. " +
+                      "Please report this as a bug. " +
+                      e.getMessage())
               }
           }
         }
@@ -988,8 +994,8 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
 
       def memberLambda(params: List[js.ParamDef], restParam: Option[js.ParamDef],
           body: js.Tree)(implicit pos: ir.Position) = {
-        js.Closure(arrow = false, captureParams = Nil, params, restParam, body,
-            captureValues = Nil)
+        js.Closure(js.ClosureFlags.function, captureParams = Nil, params,
+            restParam, jstpe.AnyType, body, captureValues = Nil)
       }
 
       val fieldDefinitions = jsFieldDefs.toList.map { fdef =>
@@ -1102,7 +1108,8 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
         beforeSuper ::: superCall ::: afterSuper
       }
 
-      val closure = js.Closure(arrow = true, jsClassCaptures, Nil, None,
+      // Wrap everything in a lambda, for namespacing
+      val closure = js.Closure(js.ClosureFlags.arrow, jsClassCaptures, Nil, None, jstpe.AnyType,
           js.Block(inlinedCtorStats, selfRef), jsSuperClassValue :: args)
       js.JSFunctionApply(closure, Nil)
     }
@@ -1408,7 +1415,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
       val fqcnArg = js.StringLiteral(sym.fullName + "$")
       val runtimeClassArg = js.ClassOf(toTypeRef(sym.info))
       val loadModuleFunArg =
-        js.Closure(arrow = true, Nil, Nil, None, genLoadModule(sym), Nil)
+        js.Closure(js.ClosureFlags.arrow, Nil, Nil, None, jstpe.AnyType, genLoadModule(sym), Nil)
 
       val stat = genApplyMethod(
           genLoadModule(ReflectModule),
@@ -1458,9 +1465,8 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
 
             val paramTypesArray = js.JSArrayConstr(parameterTypes)
 
-            val newInstanceFun = js.Closure(arrow = true, Nil, formalParams, None, {
-              genNew(sym, ctor, actualParams)
-            }, Nil)
+            val newInstanceFun = js.Closure(js.ClosureFlags.arrow, Nil,
+              formalParams, None, jstpe.AnyType, genNew(sym, ctor, actualParams), Nil)
 
             js.JSArrayConstr(List(paramTypesArray, newInstanceFun))
           }
@@ -3375,6 +3381,8 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
             genNewArray(arr, args.map(genExpr))
           case prim: jstpe.PrimRef =>
             abort(s"unexpected primitive type $prim in New at $pos")
+          case typeRef: jstpe.TransientTypeRef =>
+            abort(s"unexpected special type ref $typeRef in New at $pos")
         }
       }
     }
@@ -5138,6 +5146,28 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
       }
     }
 
+    /** Adapt boxes on a tree from and to the given types after posterasure.
+     *
+     *  @param expr
+     *    Tree to be adapted.
+     *  @param fromTpeEnteringPosterasure
+     *    The type of `expr` as it was entering the posterasure phase.
+     *  @param toTpeEnteringPosterausre
+     *    The type of the adapted tree as it would be entering the posterasure phase.
+     */
+    def adaptBoxes(expr: js.Tree, fromTpeEnteringPosterasure: Type,
+        toTpeEnteringPosterasure: Type)(
+        implicit pos: Position): js.Tree = {
+      if (fromTpeEnteringPosterasure =:= toTpeEnteringPosterasure) {
+        expr
+      } else {
+        /* Upcast to `Any` then downcast to `toTpe`. This is not very smart.
+         * We rely on the optimizer to get rid of unnecessary casts.
+         */
+        fromAny(ensureBoxed(expr, fromTpeEnteringPosterasure), toTpeEnteringPosterasure)
+      }
+    }
+
     /** Gen a boxing operation (tpe is the primitive type) */
     def makePrimitiveBox(expr: js.Tree, tpe: Type)(
         implicit pos: Position): js.Tree = {
@@ -6033,14 +6063,6 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
 
     // Synthesizers for JS functions -------------------------------------------
 
-    /** Gen a conversion from a JavaScript function into a Scala function. */
-    private def genJSFunctionToScala(jsFunction: js.Tree, arity: Int)(
-        implicit pos: Position): js.Tree = {
-      val clsSym = getRequiredClass("scala.scalajs.runtime.AnonFunction" + arity)
-      val ctor = clsSym.primaryConstructor
-      genNew(clsSym, ctor, List(jsFunction))
-    }
-
     /** Gen JS code for a JS function class.
      *
      *  This is called when emitting a ClassDef that represents an anonymous
@@ -6175,7 +6197,8 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
             if (hasRepeatedParam) params.init
             else params
           patchFunParamsWithBoxes(applyDef.symbol, nonRepeatedParams,
-              useParamsBeforeLambdaLift = false)
+              useParamsBeforeLambdaLift = false,
+              fromParamTypes = nonRepeatedParams.map(_ => ObjectTpe))
         }
 
         val (patchedRepeatedParam, repeatedParamLocal) = {
@@ -6183,7 +6206,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
            * But that lowers the type to iterable.
            */
           if (hasRepeatedParam) {
-            val (p, l) = genPatchedParam(params.last, genJSArrayToVarArgs(_))
+            val (p, l) = genPatchedParam(params.last, genJSArrayToVarArgs(_), jstpe.AnyType)
             (Some(p), Some(l))
           } else {
             (None, None)
@@ -6214,10 +6237,11 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
           if (isThisFunction) {
             val thisParam :: actualParams = patchedParams
             js.Closure(
-                arrow = false,
+                js.ClosureFlags.function,
                 ctorParamDefs,
                 actualParams,
                 patchedRepeatedParam,
+                jstpe.AnyType,
                 js.Block(
                     js.VarDef(thisParam.name, thisParam.originalName,
                         thisParam.ptpe, mutable = false,
@@ -6225,8 +6249,8 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
                     patchedBody),
                 capturedArgs)
           } else {
-            js.Closure(arrow = true, ctorParamDefs, patchedParams,
-                patchedRepeatedParam, patchedBody, capturedArgs)
+            js.Closure(js.ClosureFlags.arrow, ctorParamDefs, patchedParams,
+                patchedRepeatedParam, jstpe.AnyType, patchedBody, capturedArgs)
           }
         }
 
@@ -6249,33 +6273,48 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
      *  We identify the captures using the same method as the `delambdafy`
      *  phase. We have an additional hack for `this`.
      *
-     *  To translate them, we first construct a JS closure for the body:
+     *  To translate them, we first construct a typed closure for the body:
      *  {{{
-     *  arrow-lambda<_this = this, capture1: U1 = capture1, ..., captureM: UM = captureM>(
-     *      arg1: any, ..., argN: any): any = {
-     *    val arg1Unboxed: T1 = arg1.asInstanceOf[T1];
+     *  typed-lambda<_this = this, capture1: U1 = capture1, ..., captureM: UM = captureM>(
+     *      arg1: T1, ..., argN: TN): TR = {
+     *    val arg1Unboxed: S1 = arg1.asInstanceOf[S1];
      *    ...
-     *    val argNUnboxed: TN = argN.asInstanceOf[TN];
+     *    val argNUnboxed: SN = argN.asInstanceOf[SN];
      *    // inlined body of `someMethod`, boxed
      *  }
      *  }}}
      *  In the closure, input params are unboxed before use, and the result of
-     *  the body of `someMethod` is boxed back.
+     *  the body of `someMethod` is boxed back. The Si and SR are the types
+     *  found in the target `someMethod`; the Ti and TR are the types found in
+     *  the SAM method to be implemented. It is common for `Si` to be different
+     *  from `Ti`. For example, in a Scala function `(x: Int) => x`,
+     *  `S1 = SR = int`, but `T1 = TR = any`, because `scala.Function1` defines
+     *  an `apply` method that erases to using `any`'s.
      *
      *  Then, we wrap that closure in a class satisfying the expected type.
-     *  For Scala function types, we use the existing
-     *  `scala.scalajs.runtime.AnonFunctionN` from the library. For other
-     *  LMF-capable types, we generate a class on the fly, which looks like
-     *  this:
+     *  For SAM types that do not need any bridges (including all Scala
+     *  function types), we use a `NewLambda` node.
+     *
+     *  When bridges are required (which is rare), we generate a class on the
+     *  fly. In that case, we "inline" the captures of the typed closure as
+     *  fields of the class, and its body as the body of the main SAM method
+     *  implementation. Overall, it looks like this:
      *  {{{
      *  class AnonFun extends Object with FunctionalInterface {
-     *    val f: any
-     *    def <init>(f: any) {
+     *    val ...captureI: UI
+     *    def <init>(...captureI: UI) {
      *      super();
-     *      this.f = f
+     *      ...this.captureI = captureI;
+     *    }
+     *    // main SAM method implementation
+     *    def theSAMMethod(params: Ti...): TR = {
+     *      val ...captureI = this.captureI;
+     *      // inline body of the typed-lambda
+     *    }
+     *    // a bridge
+     *    def theSAMMethod(params: Vi...): VR = {
+     *      this.theSAMMethod(...params.asInstanceOf[Ti]).asInstanceOf[VR]
      *    }
-     *    def theSAMMethod(params: Types...): Type =
-     *      unbox((this.f)(boxParams...))
      *  }
      *  }}}
      */
@@ -6284,6 +6323,22 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
       val Function(paramTrees, Apply(
           targetTree @ Select(receiver, _), allArgs0)) = originalFunction
 
+      // Extract information about the SAM type we are implementing
+      val samClassSym = originalFunction.tpe.typeSymbolDirect
+      val (superClass, interfaces, sam, samBridges) = if (isFunctionSymbol(samClassSym)) {
+        // This is a scala.FunctionN SAM; extend the corresponding AbstractFunctionN class
+        val arity = paramTrees.size
+        val superClass = AbstractFunctionClass(arity)
+        val sam = superClass.info.member(nme.apply)
+        (superClass, Nil, sam, Nil)
+      } else {
+        // This is an arbitrary SAM interface
+        val samInfo = originalFunction.attachments.get[SAMFunction].getOrElse {
+          abort(s"Cannot find the SAMFunction attachment on $originalFunction at $pos")
+        }
+        (ObjectClass, samClassSym :: Nil, samInfo.sam, samBridgesFor(samInfo))
+      }
+
       val captureSyms =
         global.delambdafy.FreeVarTraverser.freeVarsOf(originalFunction).toList
       val target = targetTree.symbol
@@ -6349,8 +6404,12 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
               methodParam.mutable, genExpr(arg))
         }
 
+        val (samParamTypes, samResultType, targetResultType) = enteringPhase(currentRun.posterasurePhase) {
+          val methodType = sam.tpe.asInstanceOf[MethodType]
+          (methodType.params.map(_.info), methodType.resultType, target.tpe.finalResultType)
+        }
+
         /* Adapt the params and result so that they are boxed from the outside.
-         * We need this because a `js.Closure` is always from `any`s to `any`.
          *
          * TODO In total we generate *3* locals for each original param: the
          * patched ParamDef, the VarDef for the unboxed value, and a VarDef for
@@ -6359,9 +6418,9 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
          */
         val formalArgs = paramTrees.map(p => genParamDef(p.symbol))
         val (patchedFormalArgs, paramsLocals) =
-          patchFunParamsWithBoxes(target, formalArgs, useParamsBeforeLambdaLift = true)
+          patchFunParamsWithBoxes(target, formalArgs, useParamsBeforeLambdaLift = true, fromParamTypes = samParamTypes)
         val patchedBodyWithBox =
-          ensureResultBoxed(methodBody.get, target)
+          adaptBoxes(methodBody.get, targetResultType, samResultType)
 
         // Finally, assemble all the pieces
         val fullClosureBody = js.Block(
@@ -6372,40 +6431,79 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
           Nil
         )
         js.Closure(
-          arrow = true,
+          js.ClosureFlags.typed,
           formalCaptures,
           patchedFormalArgs,
           restParam = None,
+          resultType = toIRType(underlyingOfEVT(samResultType)),
           fullClosureBody,
           actualCaptures
         )
       }
 
-      // Wrap the closure in the appropriate box for the SAM type
-      val funSym = originalFunction.tpe.typeSymbolDirect
-      if (isFunctionSymbol(funSym)) {
-        /* This is a scala.FunctionN. We use the existing AnonFunctionN
-         * wrapper.
+      // Build the descriptor
+      val closureType = closure.tpe.asInstanceOf[jstpe.ClosureType]
+      val descriptor = js.NewLambda.Descriptor(
+          encodeClassName(superClass), interfaces.map(encodeClassName(_)),
+          encodeMethodSym(sam).name, closureType.paramTypes,
+          closureType.resultType)
+
+      /* Wrap the closure in the appropriate box for the SAM type.
+       * Use a `NewLambda` if we do not need any bridges; otherwise synthesize
+       * a SAM wrapper class.
+       */
+      if (samBridges.isEmpty) {
+        // No bridges are needed; we can directly use a NewLambda
+        js.NewLambda(descriptor, closure)(encodeClassType(samClassSym).toNonNullable)
+      } else {
+        /* We need bridges; expand the `NewLambda` into a synthesized class.
+         * Captures of the closure are turned into fields of the wrapper class.
          */
-        genJSFunctionToScala(closure, paramTrees.size)
+        val formalCaptureTypeRefs = captureSyms.map(sym => toTypeRef(sym.info))
+        val allFormalCaptureTypeRefs =
+          if (isTargetStatic) formalCaptureTypeRefs
+          else toTypeRef(receiver.tpe) :: formalCaptureTypeRefs
+
+        val ctorName = ir.Names.MethodName.constructor(allFormalCaptureTypeRefs)
+        val samWrapperClassName = synthesizeSAMWrapper(descriptor, sam, samBridges, closure, ctorName)
+        js.New(samWrapperClassName, js.MethodIdent(ctorName), closure.captureValues)
+      }
+    }
+
+    private def samBridgesFor(samInfo: SAMFunction)(implicit pos: Position): List[Symbol] = {
+      /* scala/bug#10512: any methods which `samInfo.sam` overrides need
+       * bridges made for them.
+       */
+      val samBridges = {
+        import scala.reflect.internal.Flags.BRIDGE
+        samInfo.synthCls.info.findMembers(excludedFlags = 0L, requiredFlags = BRIDGE).toList
+      }
+
+      if (samBridges.isEmpty) {
+        // fast path
+        Nil
       } else {
-        /* This is an arbitrary SAM type (can only happen in 2.12).
-         * We have to synthesize a class like LambdaMetaFactory would do on
-         * the JVM.
+        /* Remove duplicates, e.g., if we override the same method declared
+         * in two super traits.
          */
-        val sam = originalFunction.attachments.get[SAMFunction].getOrElse {
-          abort(s"Cannot find the SAMFunction attachment on $originalFunction at $pos")
+        val builder = List.newBuilder[Symbol]
+        val seenMethodNames = mutable.Set.empty[MethodName]
+
+        seenMethodNames.add(encodeMethodSym(samInfo.sam).name)
+
+        for (samBridge <- samBridges) {
+          if (seenMethodNames.add(encodeMethodSym(samBridge).name))
+            builder += samBridge
         }
 
-        val samWrapperClassName = synthesizeSAMWrapper(funSym, sam)
-        js.New(samWrapperClassName, js.MethodIdent(ObjectArgConstructorName),
-            List(closure))
+        builder.result()
       }
     }
 
-    private def synthesizeSAMWrapper(funSym: Symbol, samInfo: SAMFunction)(
+    private def synthesizeSAMWrapper(descriptor: js.NewLambda.Descriptor,
+        sam: Symbol, samBridges: List[Symbol], closure: js.Closure,
+        ctorName: ir.Names.MethodName)(
         implicit pos: Position): ClassName = {
-      val intfName = encodeClassName(funSym)
 
       val suffix = {
         generatedSAMWrapperCount.value += 1
@@ -6416,25 +6514,30 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
 
       val thisType = jstpe.ClassType(className, nullable = false)
 
-      // val f: Any
-      val fFieldIdent = js.FieldIdent(FieldName(className, SimpleFieldName("f")))
-      val fFieldDef = js.FieldDef(js.MemberFlags.empty, fFieldIdent,
-          NoOriginalName, jstpe.AnyType)
+      // val captureI: CaptureTypeI
+      val captureFieldDefs = for (captureParam <- closure.captureParams) yield {
+        val simpleFieldName = SimpleFieldName(captureParam.name.name.encoded)
+        val ident = js.FieldIdent(FieldName(className, simpleFieldName))
+        js.FieldDef(js.MemberFlags.empty, ident, captureParam.originalName, captureParam.ptpe)
+      }
 
-      // def this(f: Any) = { this.f = f; super() }
+      // def this(f: Any) = { ...this.captureI = captureI; super() }
       val ctorDef = {
-        val fParamDef = js.ParamDef(js.LocalIdent(LocalName("f")),
-            NoOriginalName, jstpe.AnyType, mutable = false)
+        val captureFieldAssignments = for {
+          (captureFieldDef, captureParam) <- captureFieldDefs.zip(closure.captureParams)
+        } yield {
+          js.Assign(
+              js.Select(js.This()(thisType), captureFieldDef.name)(captureFieldDef.ftpe),
+              captureParam.ref)
+        }
         js.MethodDef(
             js.MemberFlags.empty.withNamespace(js.MemberNamespace.Constructor),
-            js.MethodIdent(ObjectArgConstructorName),
+            js.MethodIdent(ctorName),
             NoOriginalName,
-            List(fParamDef),
+            closure.captureParams,
             jstpe.VoidType,
             Some(js.Block(List(
-                js.Assign(
-                    js.Select(js.This()(thisType), fFieldIdent)(jstpe.AnyType),
-                    fParamDef.ref),
+                js.Block(captureFieldAssignments),
                 js.ApplyStatically(js.ApplyFlags.empty.withConstructor(true),
                     js.This()(thisType),
                     jswkn.ObjectClass,
@@ -6443,50 +6546,49 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
             js.OptimizerHints.empty, Unversioned)
       }
 
-      // Compute the set of method symbols that we need to implement
-      val sams = {
-        val samsBuilder = List.newBuilder[Symbol]
-        val seenMethodNames = mutable.Set.empty[MethodName]
-
-        /* scala/bug#10512: any methods which `samInfo.sam` overrides need
-         * bridges made for them.
-         */
-        val samBridges = {
-          import scala.reflect.internal.Flags.BRIDGE
-          samInfo.synthCls.info.findMembers(excludedFlags = 0L, requiredFlags = BRIDGE).toList
+      /* def samMethod(...closure.params): closure.resultType = {
+       *   val captureI: CaptureTypeI = this.captureI;
+       *   ...
+       *   closure.body
+       * }
+       */
+      val samMethodDef: js.MethodDef = {
+        val localCaptureVarDefs = for {
+          (captureParam, captureFieldDef) <- closure.captureParams.zip(captureFieldDefs)
+        } yield {
+          js.VarDef(captureParam.name, captureParam.originalName, captureParam.ptpe, mutable = false,
+              js.Select(js.This()(thisType), captureFieldDef.name)(captureFieldDef.ftpe))
         }
 
-        for (sam <- samInfo.sam :: samBridges) {
-          /* Remove duplicates, e.g., if we override the same method declared
-           * in two super traits.
-           */
-          if (seenMethodNames.add(encodeMethodSym(sam).name))
-            samsBuilder += sam
-        }
+        val body = js.Block(localCaptureVarDefs, closure.body)
 
-        samsBuilder.result()
+        js.MethodDef(js.MemberFlags.empty, encodeMethodSym(sam),
+            originalNameOfMethod(sam), closure.params, closure.resultType,
+            Some(body))(
+            js.OptimizerHints.empty, Unversioned)
       }
 
-      // def samMethod(...params): resultType = this.f(...params)
-      val samMethodDefs = for (sam <- sams) yield {
-        val jsParams = sam.tpe.params.map(genParamDef(_, pos))
-        val resultType = toIRType(sam.tpe.finalResultType)
+      val adaptBoxesTupled = (adaptBoxes(_, _, _)).tupled
+
+      // def samBridgeMethod(...params): resultType = this.samMethod(...params) // (with adaptBoxes)
+      val samBridgeMethodDefs = for (samBridge <- samBridges) yield {
+        val jsParams = samBridge.tpe.params.map(genParamDef(_, pos))
+        val resultType = toIRType(samBridge.tpe.finalResultType)
 
         val actualParams = enteringPhase(currentRun.posterasurePhase) {
-          for ((formal, param) <- jsParams.zip(sam.tpe.params))
-            yield (formal.ref, param.tpe)
-        }.map((ensureBoxed _).tupled)
+          for (((formal, bridgeParam), samParam) <- jsParams.zip(samBridge.tpe.params).zip(sam.tpe.params))
+            yield (formal.ref, bridgeParam.tpe, samParam.tpe)
+        }.map(adaptBoxesTupled)
 
-        val call = js.JSFunctionApply(
-            js.Select(js.This()(thisType), fFieldIdent)(jstpe.AnyType),
-            actualParams)
+        val call = js.Apply(js.ApplyFlags.empty, js.This()(thisType),
+            samMethodDef.name, actualParams)(samMethodDef.resultType)
 
-        val body = fromAny(call, enteringPhase(currentRun.posterasurePhase) {
-          sam.tpe.finalResultType
+        val body = adaptBoxesTupled(enteringPhase(currentRun.posterasurePhase) {
+          (call, sam.tpe.finalResultType, samBridge.tpe.finalResultType)
         })
 
-        js.MethodDef(js.MemberFlags.empty, encodeMethodSym(sam),
-            originalNameOfMethod(sam), jsParams, resultType,
+        js.MethodDef(js.MemberFlags.empty, encodeMethodSym(samBridge),
+            originalNameOfMethod(samBridge), jsParams, resultType,
             Some(body))(
             js.OptimizerHints.empty, Unversioned)
       }
@@ -6497,12 +6599,12 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
           NoOriginalName,
           ClassKind.Class,
           None,
-          Some(js.ClassIdent(jswkn.ObjectClass)),
-          List(js.ClassIdent(intfName)),
+          Some(js.ClassIdent(descriptor.superClass)),
+          descriptor.interfaces.map(js.ClassIdent(_)),
           None,
           None,
-          fields = fFieldDef :: Nil,
-          methods = ctorDef :: samMethodDefs,
+          fields = captureFieldDefs,
+          methods = ctorDef :: samMethodDef :: samBridgeMethodDefs,
           jsConstructor = None,
           Nil,
           Nil,
@@ -6515,7 +6617,8 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
     }
 
     private def patchFunParamsWithBoxes(methodSym: Symbol,
-        params: List[js.ParamDef], useParamsBeforeLambdaLift: Boolean)(
+        params: List[js.ParamDef], useParamsBeforeLambdaLift: Boolean,
+        fromParamTypes: List[Type])(
         implicit pos: Position): (List[js.ParamDef], List[js.VarDef]) = {
       // See the comment in genPrimitiveJSArgs for a rationale about this
       val paramTpes = enteringPhase(currentRun.posterasurePhase) {
@@ -6540,26 +6643,33 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
       }
 
       (for {
-        (param, paramSym) <- params zip paramSyms
+        ((param, paramSym), fromParamType) <- params.zip(paramSyms).zip(fromParamTypes)
       } yield {
         val paramTpe = paramTpes.getOrElse(paramSym.name, paramSym.tpe)
-        genPatchedParam(param, fromAny(_, paramTpe))
+        genPatchedParam(param, adaptBoxes(_, fromParamType, paramTpe),
+            toIRType(underlyingOfEVT(fromParamType)))
       }).unzip
     }
 
-    private def genPatchedParam(param: js.ParamDef, rhs: js.VarRef => js.Tree)(
+    private def genPatchedParam(param: js.ParamDef, rhs: js.VarRef => js.Tree,
+        fromParamType: jstpe.Type)(
         implicit pos: Position): (js.ParamDef, js.VarDef) = {
       val paramNameIdent = param.name
       val origName = param.originalName
       val newNameIdent = freshLocalIdent(paramNameIdent.name)(paramNameIdent.pos)
       val newOrigName = origName.orElse(paramNameIdent.name)
-      val patchedParam = js.ParamDef(newNameIdent, newOrigName, jstpe.AnyType,
+      val patchedParam = js.ParamDef(newNameIdent, newOrigName, fromParamType,
           mutable = false)(param.pos)
       val paramLocal = js.VarDef(paramNameIdent, origName, param.ptpe,
           mutable = false, rhs(patchedParam.ref))
       (patchedParam, paramLocal)
     }
 
+    private def underlyingOfEVT(tpe: Type): Type = tpe match {
+      case tpe: ErasedValueType => tpe.erasedUnderlying
+      case _                    => tpe
+    }
+
     /** Generates a static method instantiating and calling this
      *  DynamicImportThunk's `apply`:
      *
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Hashers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Hashers.scala
index d37b6ffdfc..a2b0636bf1 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Hashers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Hashers.scala
@@ -306,6 +306,24 @@ object Hashers {
           mixMethodIdent(method)
           mixTrees(args)
 
+        case ApplyTypedClosure(flags, fun, args) =>
+          mixTag(TagApplyTypedClosure)
+          mixInt(ApplyFlags.toBits(flags))
+          mixTree(fun)
+          mixTrees(args)
+
+        case NewLambda(descriptor, fun) =>
+          val NewLambda.Descriptor(superClass, interfaces, methodName, paramTypes, resultType) =
+            descriptor
+          mixTag(TagNewLambda)
+          mixName(superClass)
+          mixNames(interfaces)
+          mixMethodName(methodName)
+          mixTypes(paramTypes)
+          mixType(resultType)
+          mixTree(fun)
+          mixType(tree.tpe)
+
         case UnaryOp(op, lhs) =>
           mixTag(TagUnaryOp)
           mixInt(op)
@@ -506,12 +524,20 @@ object Hashers {
           }
           mixType(tree.tpe)
 
-        case Closure(arrow, captureParams, params, restParam, body, captureValues) =>
+        case Closure(flags, captureParams, params, restParam, resultType, body, captureValues) =>
           mixTag(TagClosure)
-          mixBoolean(arrow)
+          mixByte(ClosureFlags.toBits(flags).toByte)
           mixParamDefs(captureParams)
           mixParamDefs(params)
-          restParam.foreach(mixParamDef(_))
+          if (flags.typed) {
+            if (restParam.isDefined)
+              throw new InvalidIRException(tree, "Cannot hash a typed closure with a rest param")
+            mixType(resultType)
+          } else {
+            if (resultType != AnyType)
+              throw new InvalidIRException(tree, "Cannot hash a JS closure with a result type != AnyType")
+            restParam.foreach(mixParamDef(_))
+          }
           mixTree(body)
           mixTrees(captureValues)
 
@@ -572,6 +598,10 @@ object Hashers {
       case typeRef: ArrayTypeRef =>
         mixTag(TagArrayTypeRef)
         mixArrayTypeRef(typeRef)
+      case TransientTypeRef(name) =>
+        mixTag(TagTransientTypeRefHashingOnly)
+        mixName(name)
+        // The `tpe` is intentionally ignored here; see doc of `TransientTypeRef`.
     }
 
     def mixArrayTypeRef(arrayTypeRef: ArrayTypeRef): Unit = {
@@ -604,6 +634,11 @@ object Hashers {
         mixTag(if (nullable) TagArrayType else TagNonNullArrayType)
         mixArrayTypeRef(arrayTypeRef)
 
+      case ClosureType(paramTypes, resultType, nullable) =>
+        mixTag(if (nullable) TagClosureType else TagNonNullClosureType)
+        mixTypes(paramTypes)
+        mixType(resultType)
+
       case RecordType(fields) =>
         mixTag(TagRecordType)
         for (RecordType.Field(name, originalName, tpe, mutable) <- fields) {
@@ -614,6 +649,9 @@ object Hashers {
         }
     }
 
+    def mixTypes(tpes: List[Type]): Unit =
+      tpes.foreach(mixType)
+
     def mixLocalIdent(ident: LocalIdent): Unit = {
       mixPos(ident.pos)
       mixName(ident.name)
@@ -644,6 +682,11 @@ object Hashers {
     def mixName(name: Name): Unit =
       mixBytes(name.encoded.bytes)
 
+    def mixNames(names: List[Name]): Unit = {
+      mixInt(names.size)
+      names.foreach(mixName(_))
+    }
+
     def mixMethodName(name: MethodName): Unit = {
       mixName(name.simpleName)
       mixInt(name.paramTypeRefs.size)
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/InvalidIRException.scala b/ir/shared/src/main/scala/org/scalajs/ir/InvalidIRException.scala
index f481798458..2e8a272388 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/InvalidIRException.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/InvalidIRException.scala
@@ -12,5 +12,12 @@
 
 package org.scalajs.ir
 
-class InvalidIRException(val tree: Trees.IRNode, message: String)
-    extends Exception(message)
+class InvalidIRException(val optTree: Option[Trees.IRNode], message: String)
+    extends Exception(message) {
+
+  def this(tree: Trees.IRNode, message: String) =
+    this(Some(tree), message)
+
+  def this(message: String) =
+    this(None, message)
+}
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Names.scala b/ir/shared/src/main/scala/org/scalajs/ir/Names.scala
index ecceef2dfa..685949052f 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Names.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Names.scala
@@ -436,6 +436,8 @@ object Names {
             i += 1
           }
           appendTypeRef(base)
+        case TransientTypeRef(name) =>
+          builder.append('t').append(name.nameString)
       }
 
       builder.append(simpleName.nameString)
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala
index 5c606e81ee..e4836fdcc0 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala
@@ -77,6 +77,19 @@ object Printers {
       print(end)
     }
 
+    protected final def printRow(ts: List[Type], start: String, sep: String,
+        end: String)(implicit dummy: DummyImplicit): Unit = {
+      print(start)
+      var rest = ts
+      while (rest.nonEmpty) {
+        print(rest.head)
+        rest = rest.tail
+        if (rest.nonEmpty)
+          print(sep)
+      }
+      print(end)
+    }
+
     protected def printBlock(tree: Tree): Unit = {
       val trees = tree match {
         case Block(trees) => trees
@@ -340,6 +353,40 @@ object Printers {
           print(method)
           printArgs(args)
 
+        case ApplyTypedClosure(flags, fun, args) =>
+          print(fun)
+          printArgs(args)
+
+        case NewLambda(descriptor, fun) =>
+          val NewLambda.Descriptor(superClass, interfaces, methodName, paramTypes, resultType) =
+            descriptor
+
+          print("<newLambda>("); indent(); println()
+
+          print("extends ")
+          print(superClass)
+          if (interfaces.nonEmpty) {
+            print(" implements ")
+            print(interfaces.head)
+            for (intf <- interfaces.tail) {
+              print(", ")
+              print(intf)
+            }
+          }
+          print(',')
+          println()
+
+          print("def ")
+          print(methodName)
+          printRow(paramTypes, "(", ", ", "): ")
+          print(resultType)
+          print(',')
+          println()
+
+          print(fun)
+
+          undent(); println(); print(')')
+
         case UnaryOp(op, lhs) =>
           import UnaryOp._
 
@@ -848,8 +895,10 @@ object Printers {
           else
             print(name)
 
-        case Closure(arrow, captureParams, params, restParam, body, captureValues) =>
-          if (arrow)
+        case Closure(flags, captureParams, params, restParam, resultType, body, captureValues) =>
+          if (flags.typed)
+            print("(typed-lambda<")
+          else if (flags.arrow)
             print("(arrow-lambda<")
           else
             print("(lambda<")
@@ -864,7 +913,7 @@ object Printers {
             print(value)
           }
           print(">")
-          printSig(params, restParam, AnyType)
+          printSig(params, restParam, resultType)
           printBlock(body)
           print(')')
 
@@ -1062,6 +1111,8 @@ object Printers {
         print(base)
         for (i <- 1 to dims)
           print("[]")
+      case TransientTypeRef(name) =>
+        print(name)
     }
 
     def print(tpe: Type): Unit = tpe match {
@@ -1091,6 +1142,13 @@ object Printers {
         if (!nullable)
           print("!")
 
+      case ClosureType(paramTypes, resultType, nullable) =>
+        printRow(paramTypes, "((", ", ", ") => ")
+        print(resultType)
+        print(')')
+        if (!nullable)
+          print('!')
+
       case RecordType(fields) =>
         print('(')
         var first = true
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
index d690110e0f..c6c0c9060c 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
@@ -159,6 +159,8 @@ object Serializers {
             encodedNameToIndex(className.encoded)
           case ArrayTypeRef(base, _) =>
             reserveTypeRef(base)
+          case typeRef: TransientTypeRef =>
+            throw new InvalidIRException(s"Cannot serialize a transient type ref: $typeRef")
         }
 
         encodedNameToIndex(methodName.simpleName.encoded)
@@ -227,6 +229,13 @@ object Serializers {
           s.writeByte(TagArrayTypeRef)
           writeTypeRef(base)
           s.writeInt(dimensions)
+        case typeRef: TransientTypeRef =>
+          throw new InvalidIRException(s"Cannot serialize a transient type ref: $typeRef")
+      }
+
+      def writeTypeRefs(typeRefs: List[TypeRef]): Unit = {
+        s.writeInt(typeRefs.size)
+        typeRefs.foreach(writeTypeRef(_))
       }
 
       // Emit the method names
@@ -234,8 +243,7 @@ object Serializers {
       methodNames.foreach { methodName =>
         s.writeInt(encodedNameIndexMap(
             new EncodedNameKey(methodName.simpleName.encoded)))
-        s.writeInt(methodName.paramTypeRefs.size)
-        methodName.paramTypeRefs.foreach(writeTypeRef(_))
+        writeTypeRefs(methodName.paramTypeRefs)
         writeTypeRef(methodName.resultTypeRef)
         s.writeBoolean(methodName.isReflectiveProxy)
         writeName(methodName.simpleName)
@@ -365,6 +373,22 @@ object Serializers {
           writeTagAndPos(TagApplyDynamicImport)
           writeApplyFlags(flags); writeName(className); writeMethodIdent(method); writeTrees(args)
 
+        case ApplyTypedClosure(flags, fun, args) =>
+          writeTagAndPos(TagApplyTypedClosure)
+          writeApplyFlags(flags); writeTree(fun); writeTrees(args)
+
+        case NewLambda(descriptor, fun) =>
+          val NewLambda.Descriptor(superClass, interfaces, methodName, paramTypes, resultType) =
+            descriptor
+          writeTagAndPos(TagNewLambda)
+          writeName(superClass)
+          writeNames(interfaces)
+          writeMethodName(methodName)
+          writeTypes(paramTypes)
+          writeType(resultType)
+          writeTree(fun)
+          writeType(tree.tpe)
+
         case UnaryOp(op, lhs) =>
           writeTagAndPos(TagUnaryOp)
           writeByte(op); writeTree(lhs)
@@ -542,12 +566,23 @@ object Serializers {
           }
           writeType(tree.tpe)
 
-        case Closure(arrow, captureParams, params, restParam, body, captureValues) =>
+        case Closure(flags, captureParams, params, restParam, resultType, body, captureValues) =>
           writeTagAndPos(TagClosure)
-          writeBoolean(arrow)
+          writeClosureFlags(flags)
           writeParamDefs(captureParams)
           writeParamDefs(params)
-          writeOptParamDef(restParam)
+
+          // Compatible with IR < v1.19, which had no `resultType`
+          if (flags.typed) {
+            if (restParam.isDefined)
+              throw new InvalidIRException(tree, "Cannot serialize a typed closure with a rest param")
+            writeType(resultType)
+          } else {
+            if (resultType != AnyType)
+              throw new InvalidIRException(tree, "Cannot serialize a JS closure with a result type != AnyType")
+            writeOptParamDef(restParam)
+          }
+
           writeTree(body)
           writeTrees(captureValues)
 
@@ -808,6 +843,11 @@ object Serializers {
     def writeName(name: Name): Unit =
       buffer.writeInt(encodedNameToIndex(name.encoded))
 
+    def writeNames(names: List[Name]): Unit = {
+      buffer.writeInt(names.size)
+      names.foreach(writeName(_))
+    }
+
     def writeMethodName(name: MethodName): Unit =
       buffer.writeInt(methodNameToIndex(name))
 
@@ -861,6 +901,11 @@ object Serializers {
           buffer.write(if (nullable) TagArrayType else TagNonNullArrayType)
           writeArrayTypeRef(arrayTypeRef)
 
+        case ClosureType(paramTypes, resultType, nullable) =>
+          buffer.write(if (nullable) TagClosureType else TagNonNullClosureType)
+          writeTypes(paramTypes)
+          writeType(resultType)
+
         case RecordType(fields) =>
           buffer.write(TagRecordType)
           buffer.writeInt(fields.size)
@@ -873,6 +918,11 @@ object Serializers {
       }
     }
 
+    def writeTypes(tpes: List[Type]): Unit = {
+      buffer.writeInt(tpes.size)
+      tpes.foreach(writeType)
+    }
+
     def writeTypeRef(typeRef: TypeRef): Unit = typeRef match {
       case PrimRef(tpe) =>
         tpe match {
@@ -894,6 +944,8 @@ object Serializers {
       case typeRef: ArrayTypeRef =>
         buffer.writeByte(TagArrayTypeRef)
         writeArrayTypeRef(typeRef)
+      case typeRef: TransientTypeRef =>
+        throw new InvalidIRException(s"Cannot serialize a transient type ref: $typeRef")
     }
 
     def writeArrayTypeRef(typeRef: ArrayTypeRef): Unit = {
@@ -901,9 +953,17 @@ object Serializers {
       buffer.writeInt(typeRef.dimensions)
     }
 
+    def writeTypeRefs(typeRefs: List[TypeRef]): Unit = {
+      buffer.writeInt(typeRefs.size)
+      typeRefs.foreach(writeTypeRef(_))
+    }
+
     def writeApplyFlags(flags: ApplyFlags): Unit =
       buffer.writeInt(ApplyFlags.toBits(flags))
 
+    def writeClosureFlags(flags: ClosureFlags): Unit =
+      buffer.writeByte(ClosureFlags.toBits(flags))
+
     def writePosition(pos: Position): Unit = {
       import buffer._
       import PositionFormat._
@@ -1220,6 +1280,12 @@ object Serializers {
         case TagApplyDynamicImport =>
           ApplyDynamicImport(readApplyFlags(), readClassName(),
               readMethodIdent(), readTrees())
+        case TagApplyTypedClosure =>
+          ApplyTypedClosure(readApplyFlags(), readTree(), readTrees())
+        case TagNewLambda =>
+          val descriptor = NewLambda.Descriptor(readClassName(),
+              readClassNames(), readMethodName(), readTypes(), readType())
+          NewLambda(descriptor, readTree())(readType())
 
         case TagUnaryOp  => UnaryOp(readByte(), readTree())
         case TagBinaryOp => BinaryOp(readByte(), readTree(), readTree())
@@ -1392,9 +1458,16 @@ object Serializers {
           This()(thisTypeForHack.getOrElse(tpe))
 
         case TagClosure =>
-          val arrow = readBoolean()
+          val flags = readClosureFlags()
           val captureParams = readParamDefs()
-          val (params, restParam) = readParamDefsWithRest()
+
+          val (params, restParam, resultType) = if (flags.typed) {
+            (readParamDefs(), None, readType())
+          } else {
+            val (params, restParam) = readParamDefsWithRest()
+            (params, restParam, AnyType)
+          }
+
           val body = if (thisTypeForHack.isEmpty) {
             // Fast path; always taken for IR >= 1.17
             readTree()
@@ -1408,7 +1481,7 @@ object Serializers {
             }
           }
           val captureValues = readTrees()
-          Closure(arrow, captureParams, params, restParam, body, captureValues)
+          Closure(flags, captureParams, params, restParam, resultType, body, captureValues)
 
         case TagCreateJSClass =>
           CreateJSClass(readClassName(), readTrees())
@@ -2242,6 +2315,11 @@ object Serializers {
         case TagNonNullClassType => ClassType(readClassName(), nullable = false)
         case TagNonNullArrayType => ArrayType(readArrayTypeRef(), nullable = false)
 
+        case TagClosureType | TagNonNullClosureType =>
+          val paramTypes = readTypes()
+          val resultType = readType()
+          ClosureType(paramTypes, resultType, nullable = tag == TagClosureType)
+
         case TagRecordType =>
           RecordType(List.fill(readInt()) {
             val name = readSimpleFieldName()
@@ -2253,6 +2331,9 @@ object Serializers {
       }
     }
 
+    def readTypes(): List[Type] =
+      List.fill(readInt())(readType())
+
     def readTypeRef(): TypeRef = {
       readByte() match {
         case TagVoidRef      => VoidRef
@@ -2277,6 +2358,14 @@ object Serializers {
     def readApplyFlags(): ApplyFlags =
       ApplyFlags.fromBits(readInt())
 
+    def readClosureFlags(): ClosureFlags = {
+      /* Before 1.19, the `flags` were a single `Boolean` for the `arrow` flag.
+       * The bit pattern of `flags` was crafted so that it matches the old
+       * boolean encoding for common values.
+       */
+      ClosureFlags.fromBits(readByte())
+    }
+
     def readPosition(): Position = {
       import PositionFormat._
 
@@ -2419,6 +2508,9 @@ object Serializers {
       }
     }
 
+    private def readClassNames(): List[ClassName] =
+      List.fill(readInt())(readClassName())
+
     private def readMethodName(): MethodName =
       methodNames(readInt())
 
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Tags.scala b/ir/shared/src/main/scala/org/scalajs/ir/Tags.scala
index 1bc0a52f78..517817b036 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Tags.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Tags.scala
@@ -130,6 +130,10 @@ private[ir] object Tags {
   // New in 1.18
   final val TagLinkTimeProperty = TagUnwrapFromThrowable + 1
 
+  // New in 1.19
+  final val TagApplyTypedClosure = TagLinkTimeProperty + 1
+  final val TagNewLambda = TagApplyTypedClosure + 1
+
   // Tags for member defs
 
   final val TagFieldDef = 1
@@ -182,6 +186,11 @@ private[ir] object Tags {
   final val TagNonNullClassType = TagAnyNotNullType + 1
   final val TagNonNullArrayType = TagNonNullClassType + 1
 
+  // New in 1.19
+
+  final val TagClosureType = TagNonNullArrayType + 1
+  final val TagNonNullClosureType = TagClosureType + 1
+
   // Tags for TypeRefs
 
   final val TagVoidRef = 1
@@ -198,6 +207,10 @@ private[ir] object Tags {
   final val TagClassRef = TagNothingRef + 1
   final val TagArrayTypeRef = TagClassRef + 1
 
+  // New in 1.19
+
+  final val TagTransientTypeRefHashingOnly = TagArrayTypeRef + 1
+
   // Tags for JS native loading specs
 
   final val TagJSNativeLoadSpecNone = 0
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Transformers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Transformers.scala
index a2edeaf797..9a55fbd304 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Transformers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Transformers.scala
@@ -99,6 +99,12 @@ object Transformers {
         case ApplyDynamicImport(flags, className, method, args) =>
           ApplyDynamicImport(flags, className, method, transformTrees(args))
 
+        case ApplyTypedClosure(flags, fun, args) =>
+          ApplyTypedClosure(flags, transform(fun), transformTrees(args))
+
+        case NewLambda(descriptor, fun) =>
+          NewLambda(descriptor, transform(fun))(tree.tpe)
+
         case UnaryOp(op, lhs) =>
           UnaryOp(op, transform(lhs))
 
@@ -179,9 +185,9 @@ object Transformers {
 
         // Atomic expressions
 
-        case Closure(arrow, captureParams, params, restParam, body, captureValues) =>
-          Closure(arrow, captureParams, params, restParam, transform(body),
-              transformTrees(captureValues))
+        case Closure(flags, captureParams, params, restParam, resultType, body, captureValues) =>
+          Closure(flags, captureParams, params, restParam, resultType,
+              transform(body), transformTrees(captureValues))
 
         case CreateJSClass(className, captureValues) =>
           CreateJSClass(className, transformTrees(captureValues))
@@ -290,8 +296,8 @@ object Transformers {
    */
   abstract class LocalScopeTransformer extends Transformer {
     override def transform(tree: Tree): Tree = tree match {
-      case Closure(arrow, captureParams, params, restParam, body, captureValues) =>
-        Closure(arrow, captureParams, params, restParam, body,
+      case Closure(flags, captureParams, params, restParam, resultType, body, captureValues) =>
+        Closure(flags, captureParams, params, restParam, resultType, body,
             transformTrees(captureValues))(tree.pos)
       case _ =>
         super.transform(tree)
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Traversers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Traversers.scala
index 232014750e..9270d4ad3f 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Traversers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Traversers.scala
@@ -91,6 +91,13 @@ object Traversers {
       case ApplyDynamicImport(_, _, _, args) =>
         args.foreach(traverse)
 
+      case ApplyTypedClosure(_, fun, args) =>
+        traverse(fun)
+        args.foreach(traverse)
+
+      case NewLambda(_, fun) =>
+        traverse(fun)
+
       case UnaryOp(op, lhs) =>
         traverse(lhs)
 
@@ -184,7 +191,7 @@ object Traversers {
 
       // Atomic expressions
 
-      case Closure(arrow, captureParams, params, restParam, body, captureValues) =>
+      case Closure(flags, captureParams, params, restParam, resultType, body, captureValues) =>
         traverse(body)
         captureValues.foreach(traverse)
 
@@ -252,7 +259,7 @@ object Traversers {
    */
   abstract class LocalScopeTraverser extends Traverser {
     override def traverse(tree: Tree): Unit = tree match {
-      case Closure(_, _, _, _, _, captureValues) =>
+      case Closure(_, _, _, _, _, _, captureValues) =>
         captureValues.foreach(traverse(_))
       case _ =>
         super.traverse(tree)
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala b/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
index 51751c49e0..e90ecdd3e5 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
@@ -278,6 +278,110 @@ object Trees {
     val tpe = AnyType
   }
 
+  /** Apply a typed closure
+   *
+   *  The given `fun` must have a closure type.
+   *
+   *  The arguments' types must match (be subtypes of) the parameter types of
+   *  the closure type.
+   *
+   *  The `tpe` of this node is the result type of the closure type, or
+   *  `nothing` if the latter is `nothing`.
+   *
+   *  Evaluation steps are as follows:
+   *
+   *  1. Let `funV` be the result of evaluating `fun`.
+   *  2. If `funV` is `nullClosure`, trigger an NPE undefined behavior.
+   *  3. Let `argsV` be the result of evaluating `args`, in order.
+   *  4. Invoke `funV` with arguments `argsV`, and return the result.
+   */
+  sealed case class ApplyTypedClosure(flags: ApplyFlags, fun: Tree, args: List[Tree])(
+      implicit val pos: Position)
+      extends Tree {
+
+    val tpe: Type = fun.tpe match {
+      case ClosureType(_, resultType, _) => resultType
+      case NothingType                   => NothingType
+      case _                             => NothingType // never a valid tree
+    }
+  }
+
+  /** New lambda instance of a SAM class.
+   *
+   *  Functionally, a `NewLambda` is equivalent to an instance of an anonymous
+   *  class with the following shape:
+   *
+   *  {{{
+   *  val funV: ((...Ts) => R)! = fun;
+   *  (new superClass with interfaces {
+   *    def <this>() = this.superClass::<init>()
+   *    def methodName(...args: Ts): R = funV(...args)
+   *  }): tpe
+   *  }}}
+   *
+   *  where `superClass`, `interfaces`, `methodName`, `Ts` and `R` are taken
+   *  from the `descriptor`. `Ts` and `R` are the `paramTypes` and `resultType`
+   *  of the descriptor. They are required because there is no one-to-one
+   *  mapping between `TypeRef`s and `Type`s, and we want the shape of the
+   *  class to be a deterministic function of the `descriptor`.
+   *
+   *  The `fun` must have type `((...Ts) => R)!`.
+   *
+   *  Intuitively, `tpe` must be a supertype of `superClass! & ...interfaces!`.
+   *  Since our type system does not have intersection types, in practice this
+   *  means that there must exist `C ∈ { superClass } ∪ interfaces` such that
+   *  `tpe` is a supertype of `C!`.
+   *
+   *  The uniqueness of the anonymous class and its run-time class name are
+   *  not guaranteed.
+   */
+  sealed case class NewLambda(descriptor: NewLambda.Descriptor, fun: Tree)(
+      val tpe: Type)(
+      implicit val pos: Position)
+      extends Tree
+
+  object NewLambda {
+    final case class Descriptor(superClass: ClassName,
+        interfaces: List[ClassName], methodName: MethodName,
+        paramTypes: List[Type], resultType: Type) {
+
+      require(paramTypes.size == methodName.paramTypeRefs.size)
+
+      private val _hashCode: Int = {
+        import scala.util.hashing.MurmurHash3._
+        var acc = 1546348150 // "NewLambda.Descriptor".hashCode()
+        acc = mix(acc, superClass.##)
+        acc = mix(acc, interfaces.##)
+        acc = mix(acc, methodName.##)
+        acc = mix(acc, paramTypes.##)
+        acc = mixLast(acc, resultType.##)
+        finalizeHash(acc, 5)
+      }
+
+      // Overridden despite the 'case class' because we want the fail fast on different hash codes
+      override def equals(that: Any): Boolean = {
+        (this eq that.asInstanceOf[AnyRef]) || (that match {
+          case that: Descriptor =>
+            this._hashCode == that._hashCode && // fail fast on different hash codes
+            this.superClass == that.superClass &&
+            this.interfaces == that.interfaces &&
+            this.methodName == that.methodName &&
+            this.paramTypes == that.paramTypes &&
+            this.resultType == that.resultType
+          case _ =>
+            false
+        })
+      }
+
+      // Overridden despite the 'case class' because we want to store it
+      override def hashCode(): Int = _hashCode
+
+      // Overridden despite the 'case class' because we want the better prefix string
+      override def toString(): String =
+        s"NewLambda.Descriptor($superClass, $interfaces, $methodName, $paramTypes, $resultType)"
+    }
+  }
+
   /** Unary operation.
    *
    *  All unary operations follow common evaluation steps:
@@ -1095,16 +1199,30 @@ object Trees {
 
   /** Closure with explicit captures.
    *
-   *  @param arrow
-   *    If `true`, the closure is an Arrow Function (`=>`), which does not have
-   *    an `this` parameter, and cannot be constructed (called with `new`).
-   *    If `false`, it is a regular Function (`function`).
+   *  If `flags.typed` is `true`, this is a typed closure with a `ClosureType`.
+   *  In that case, `flags.arrow` must be `true`, and `restParam` must be
+   *  `None`. Typed closures cannot be passed to JavaScript code. This is
+   *  enforced at the type system level, since `ClosureType`s are not subtypes
+   *  of `AnyType`. The only meaningful operation one can perform on a typed
+   *  closure is to call it using `ApplyTypedClosure`.
+   *
+   *  If `flags.typed` is `false`, this is a JavaScript closure with type
+   *  `AnyNotNullType`. In that case, the `ptpe` or all `params` and
+   *  `resultType` must all be `AnyType`.
+   *
+   *  If `flags.arrow` is `true`, the closure is an Arrow Function (`=>`),
+   *  which does not have a `this` parameter, and cannot be constructed (called
+   *  with `new`). If `false`, it is a regular Function (`function`), which
+   *  does have a `this` parameter of type `AnyType`. Typed closures are always
+   *  Arrow functions, since they do not have a `this` parameter.
    */
-  sealed case class Closure(arrow: Boolean, captureParams: List[ParamDef],
-      params: List[ParamDef], restParam: Option[ParamDef], body: Tree,
-      captureValues: List[Tree])(
+  sealed case class Closure(flags: ClosureFlags, captureParams: List[ParamDef],
+      params: List[ParamDef], restParam: Option[ParamDef], resultType: Type,
+      body: Tree, captureValues: List[Tree])(
       implicit val pos: Position) extends Tree {
-    val tpe = AnyNotNullType
+    val tpe: Type =
+      if (flags.typed) ClosureType(params.map(_.ptpe), resultType, nullable = false)
+      else AnyNotNullType
   }
 
   /** Creates a JavaScript class value.
@@ -1449,6 +1567,51 @@ object Trees {
       flags.bits
   }
 
+  final class ClosureFlags private (private val bits: Int) extends AnyVal {
+    import ClosureFlags._
+
+    def arrow: Boolean = (bits & ArrowBit) != 0
+
+    def typed: Boolean = (bits & TypedBit) != 0
+
+    def withArrow(arrow: Boolean): ClosureFlags =
+      if (arrow) new ClosureFlags(bits | ArrowBit)
+      else new ClosureFlags(bits & ~ArrowBit)
+
+    def withTyped(typed: Boolean): ClosureFlags =
+      if (typed) new ClosureFlags(bits | TypedBit)
+      else new ClosureFlags(bits & ~TypedBit)
+  }
+
+  object ClosureFlags {
+    /* The Arrow flag is assigned bit 0 for the serialized encoding to be
+     * directly compatible with the `arrow` parameter from IR < v1.19.
+     */
+    private final val ArrowShift = 0
+    private final val ArrowBit = 1 << ArrowShift
+
+    private final val TypedShift = 1
+    private final val TypedBit = 1 << TypedShift
+
+    /** `function` closure base flags. */
+    final val function: ClosureFlags =
+      new ClosureFlags(0)
+
+    /** Arrow `=>` closure base flags. */
+    final val arrow: ClosureFlags =
+      new ClosureFlags(ArrowBit)
+
+    /** Base flags for a typed closure. */
+    final val typed: ClosureFlags =
+      new ClosureFlags(ArrowBit | TypedBit)
+
+    private[ir] def fromBits(bits: Byte): ClosureFlags =
+      new ClosureFlags(bits & 0xff)
+
+    private[ir] def toBits(flags: ClosureFlags): Byte =
+      flags.bits.toByte
+  }
+
   final class MemberNamespace private (
       val ordinal: Int) // intentionally public
       extends AnyVal {
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Types.scala b/ir/shared/src/main/scala/org/scalajs/ir/Types.scala
index 5cc8bee808..0fde4f7e37 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Types.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Types.scala
@@ -37,10 +37,11 @@ object Types {
 
     /** Is `null` an admissible value of this type? */
     def isNullable: Boolean = this match {
-      case AnyType | NullType     => true
-      case ClassType(_, nullable) => nullable
-      case ArrayType(_, nullable) => nullable
-      case _                      => false
+      case AnyType | NullType          => true
+      case ClassType(_, nullable)      => nullable
+      case ArrayType(_, nullable)      => nullable
+      case ClosureType(_, _, nullable) => nullable
+      case _                           => false
     }
 
     /** A type that accepts the same values as this type except `null`, unless
@@ -174,6 +175,38 @@ object Types {
     def toNonNullable: ArrayType = ArrayType(arrayTypeRef, nullable = false)
   }
 
+  /** Closure type.
+   *
+   *  This is the type of a typed closure. Parameters and result are
+   *  statically typed according to the `closureTypeRef` components.
+   *
+   *  Closure types may be nullable. `Null()` is a valid value of a nullable
+   *  closure type. This is unfortunately required to have default values of
+   *  closure types, which in turn is required to be used as the type of a
+   *  field.
+   *
+   *  Closure types are non-variant in both parameter and result types.
+   *
+   *  Closure types are *not* subtypes of `AnyType`. That statically prevents
+   *  them from going into JavaScript code or in any other universal context.
+   *  They do not support type tests nor casts.
+   *
+   *  The following subtyping relationships hold for any closure type `CT`:
+   *  {{{
+   *  nothing <: CT <: void
+   *  }}}
+   *  For a nullable closure type `CT`, additionally the following subtyping
+   *  relationship holds:
+   *  {{{
+   *  null <: CT
+   *  }}}
+   */
+  final case class ClosureType(paramTypes: List[Type], resultType: Type,
+      nullable: Boolean) extends Type {
+    def toNonNullable: ClosureType =
+      ClosureType(paramTypes, resultType, nullable = false)
+  }
+
   /** Record type.
    *
    *  Used by the optimizer to inline classes as records with multiple fields.
@@ -231,18 +264,25 @@ object Types {
         }
       case thiz: ClassRef =>
         that match {
-          case that: ClassRef     => thiz.className.compareTo(that.className)
-          case that: PrimRef      => 1
-          case that: ArrayTypeRef => -1
+          case that: ClassRef => thiz.className.compareTo(that.className)
+          case _: PrimRef     => 1
+          case _              => -1
         }
       case thiz: ArrayTypeRef =>
         that match {
           case that: ArrayTypeRef =>
             if (thiz.dimensions != that.dimensions) thiz.dimensions - that.dimensions
             else thiz.base.compareTo(that.base)
+          case _: TransientTypeRef =>
+            -1
           case _ =>
             1
         }
+      case thiz: TransientTypeRef =>
+        that match {
+          case that: TransientTypeRef => thiz.name.compareTo(that.name)
+          case _                      => 1
+        }
     }
 
     def show(): String = {
@@ -325,11 +365,28 @@ object Types {
 
   object ArrayTypeRef {
     def of(innerType: TypeRef): ArrayTypeRef = innerType match {
-      case innerType: NonArrayTypeRef => ArrayTypeRef(innerType, 1)
-      case ArrayTypeRef(base, dim)    => ArrayTypeRef(base, dim + 1)
+      case innerType: NonArrayTypeRef  => ArrayTypeRef(innerType, 1)
+      case ArrayTypeRef(base, dim)     => ArrayTypeRef(base, dim + 1)
+      case innerType: TransientTypeRef => throw new IllegalArgumentException(innerType.toString())
     }
   }
 
+  /** Transient TypeRef to store any type as a method parameter or result type.
+   *
+   *  `TransientTypeRef` cannot be serialized. It is only used in the linker to
+   *  support some of its desugarings and/or optimizations.
+   *
+   *  `TransientTypeRef`s cannot be used for methods in the `Public` namespace.
+   *
+   *  The `name` is used for equality, hashing, and sorting. It is assumed that
+   *  all occurrences of a `TransientTypeRef` with the same `name` associated
+   *  to an enclosing method namespace (enclosing class, member namespace and
+   *  simple method name) have the same `tpe`.
+   */
+  final case class TransientTypeRef(name: LabelName)(val tpe: Type) extends TypeRef {
+    def displayName: String = name.nameString
+  }
+
   /** Generates a literal zero of the given type. */
   def zeroOf(tpe: Type)(implicit pos: Position): Tree = tpe match {
     case BooleanType => BooleanLiteral(false)
@@ -343,13 +400,15 @@ object Types {
     case StringType  => StringLiteral("")
     case UndefType   => Undefined()
 
-    case NullType | AnyType | ClassType(_, true) | ArrayType(_, true) => Null()
+    case NullType | AnyType | ClassType(_, true) | ArrayType(_, true) |
+        ClosureType(_, _, true) =>
+      Null()
 
     case tpe: RecordType =>
       RecordValue(tpe, tpe.fields.map(f => zeroOf(f.tpe)))
 
     case NothingType | VoidType | ClassType(_, false) | ArrayType(_, false) |
-        AnyNotNullType =>
+        ClosureType(_, _, false) | AnyNotNullType =>
       throw new IllegalArgumentException(s"cannot generate a zero for $tpe")
   }
 
@@ -377,6 +436,15 @@ object Types {
 
       case (NullType, _) => rhs.isNullable
 
+      case (ClosureType(lhsParamTypes, lhsResultType, lhsNullable),
+          ClosureType(rhsParamTypes, rhsResultType, rhsNullable)) =>
+        isSubnullable(lhsNullable, rhsNullable) &&
+        lhsParamTypes == rhsParamTypes &&
+        lhsResultType == rhsResultType
+
+      case (_: ClosureType, _) => false
+      case (_, _: ClosureType) => false
+
       case (_: RecordType, _) => false
       case (_, _: RecordType) => false
 
diff --git a/ir/shared/src/test/scala/org/scalajs/ir/NamesTest.scala b/ir/shared/src/test/scala/org/scalajs/ir/NamesTest.scala
index 412c223f77..c0667c3b93 100644
--- a/ir/shared/src/test/scala/org/scalajs/ir/NamesTest.scala
+++ b/ir/shared/src/test/scala/org/scalajs/ir/NamesTest.scala
@@ -62,7 +62,8 @@ class NamesTest {
       ClassRef(SerializableClass) -> "Ljava.io.Serializable",
       ClassRef(BoxedStringClass) -> "Ljava.lang.String",
       ArrayTypeRef(ClassRef(ObjectClass), 2) -> "[[Ljava.lang.Object",
-      ArrayTypeRef(ShortRef, 1) -> "[S"
+      ArrayTypeRef(ShortRef, 1) -> "[S",
+      TransientTypeRef(LabelName("bar"))(CharType) -> "tbar"
     )
     for ((ref, nameString) <- refAndNameStrings) {
       assertEquals(s"foo;$nameString;V",
diff --git a/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala b/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala
index f3d88274a5..6d8eb165fd 100644
--- a/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala
+++ b/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala
@@ -75,6 +75,10 @@ class PrintersTest {
     assertPrintEquals("java.lang.String[]!",
         ArrayType(ArrayTypeRef(BoxedStringClass, 1), nullable = false))
 
+    assertPrintEquals("(() => int)", ClosureType(Nil, IntType, nullable = true))
+    assertPrintEquals("((any, java.lang.String!) => boolean)!",
+        ClosureType(List(AnyType, ClassType(BoxedStringClass, nullable = false)), BooleanType, nullable = false))
+
     assertPrintEquals("(x: int, var y: any)",
         RecordType(List(
             RecordType.Field("x", NON, IntType, mutable = false),
@@ -86,6 +90,8 @@ class PrintersTest {
 
     assertPrintEquals("java.lang.Object[]", ArrayTypeRef(ObjectClass, 1))
     assertPrintEquals("int[][]", ArrayTypeRef(IntRef, 2))
+
+    assertPrintEquals("foo", TransientTypeRef(LabelName("foo"))(IntType))
   }
 
   @Test def printVarDef(): Unit = {
@@ -365,6 +371,47 @@ class PrintersTest {
         ApplyDynamicImport(EAF, "test.Test", MethodName("m", Nil, O), Nil))
   }
 
+  @Test def printApplyTypedClosure(): Unit = {
+    assertPrintEquals("f()",
+        ApplyTypedClosure(EAF, ref("f", NothingType), Nil))
+    assertPrintEquals("f(1)",
+        ApplyTypedClosure(EAF, ref("f", NothingType), List(i(1))))
+    assertPrintEquals("f(1, 2)",
+        ApplyTypedClosure(EAF, ref("f", NothingType), List(i(1), i(2))))
+  }
+
+  @Test def printNewLambda(): Unit = {
+    assertPrintEquals(
+        s"""
+        |<newLambda>(
+        |  extends java.lang.Object implements java.lang.Comparable,
+        |  def compareTo;Ljava.lang.Object;Z(any): boolean,
+        |  (typed-lambda<>(that: any): boolean = {
+        |    true
+        |  })
+        |)
+        """,
+        NewLambda(
+          NewLambda.Descriptor(
+            ObjectClass,
+            List("java.lang.Comparable"),
+            MethodName(SimpleMethodName("compareTo"), List(ClassRef(ObjectClass)), BooleanRef),
+            List(AnyType),
+            BooleanType
+          ),
+          Closure(
+            ClosureFlags.typed,
+            Nil,
+            List(ParamDef("that", NON, AnyType, mutable = false)),
+            None,
+            BooleanType,
+            BooleanLiteral(true),
+            Nil
+          )
+        )(ClassType("java.lang.Comparable", nullable = false))
+    )
+  }
+
   @Test def printUnaryOp(): Unit = {
     import UnaryOp._
 
@@ -874,7 +921,7 @@ class PrintersTest {
           |  5
           |})
         """,
-        Closure(false, Nil, Nil, None, i(5), Nil))
+        Closure(ClosureFlags.function, Nil, Nil, None, AnyType, i(5), Nil))
 
     assertPrintEquals(
         """
@@ -883,12 +930,13 @@ class PrintersTest {
           |})
         """,
         Closure(
-            true,
+            ClosureFlags.arrow,
             List(
                 ParamDef("x", NON, AnyType, mutable = false),
                 ParamDef("y", TestON, IntType, mutable = false)),
             List(ParamDef("z", NON, AnyType, mutable = false)),
             None,
+            AnyType,
             ref("z", AnyType),
             List(ref("a", IntType), i(6))))
 
@@ -898,9 +946,34 @@ class PrintersTest {
           |  z
           |})
         """,
-        Closure(false, Nil, Nil,
+        Closure(ClosureFlags.function, Nil, Nil,
             Some(ParamDef("z", NON, AnyType, mutable = false)),
-            ref("z", AnyType), Nil))
+            AnyType, ref("z", AnyType), Nil))
+
+    assertPrintEquals(
+        """
+          |(typed-lambda<>() {
+          |  5
+          |})
+        """,
+        Closure(ClosureFlags.typed, Nil, Nil, None, VoidType, i(5), Nil))
+
+    assertPrintEquals(
+        """
+          |(typed-lambda<x: any = a, y{orig name}: int = 6>(z: int): int = {
+          |  z
+          |})
+        """,
+        Closure(
+            ClosureFlags.typed,
+            List(
+                ParamDef("x", NON, AnyType, mutable = false),
+                ParamDef("y", TestON, IntType, mutable = false)),
+            List(ParamDef("z", NON, IntType, mutable = false)),
+            None,
+            IntType,
+            ref("z", IntType),
+            List(ref("a", IntType), i(6))))
   }
 
   @Test def printCreateJSClass(): Unit = {
diff --git a/library/src/main/scala/scala/scalajs/runtime/AnonFunctions.scala b/library/src/main/scala/scala/scalajs/runtime/AnonFunctions.scala
index 36ebb2c5ff..6441a5ee23 100644
--- a/library/src/main/scala/scala/scalajs/runtime/AnonFunctions.scala
+++ b/library/src/main/scala/scala/scalajs/runtime/AnonFunctions.scala
@@ -17,116 +17,139 @@ import scala.runtime._
 
 // scalastyle:off line.size.limit
 
+@deprecated("used by the codegen before 1.19", since = "1.19.0")
 @inline
 final class AnonFunction0[+R](f: js.Function0[R]) extends AbstractFunction0[R] {
   override def apply(): R = f()
 }
 
+@deprecated("used by the codegen before 1.19", since = "1.19.0")
 @inline
 final class AnonFunction1[-T1, +R](f: js.Function1[T1, R]) extends AbstractFunction1[T1, R] {
   override def apply(arg1: T1): R = f(arg1)
 }
 
+@deprecated("used by the codegen before 1.19", since = "1.19.0")
 @inline
 final class AnonFunction2[-T1, -T2, +R](f: js.Function2[T1, T2, R]) extends AbstractFunction2[T1, T2, R] {
   override def apply(arg1: T1, arg2: T2): R = f(arg1, arg2)
 }
 
+@deprecated("used by the codegen before 1.19", since = "1.19.0")
 @inline
 final class AnonFunction3[-T1, -T2, -T3, +R](f: js.Function3[T1, T2, T3, R]) extends AbstractFunction3[T1, T2, T3, R] {
   override def apply(arg1: T1, arg2: T2, arg3: T3): R = f(arg1, arg2, arg3)
 }
 
+@deprecated("used by the codegen before 1.19", since = "1.19.0")
 @inline
 final class AnonFunction4[-T1, -T2, -T3, -T4, +R](f: js.Function4[T1, T2, T3, T4, R]) extends AbstractFunction4[T1, T2, T3, T4, R] {
   override def apply(arg1: T1, arg2: T2, arg3: T3, arg4: T4): R = f(arg1, arg2, arg3, arg4)
 }
 
+@deprecated("used by the codegen before 1.19", since = "1.19.0")
 @inline
 final class AnonFunction5[-T1, -T2, -T3, -T4, -T5, +R](f: js.Function5[T1, T2, T3, T4, T5, R]) extends AbstractFunction5[T1, T2, T3, T4, T5, R] {
   override def apply(arg1: T1, arg2: T2, arg3: T3, arg4: T4, arg5: T5): R = f(arg1, arg2, arg3, arg4, arg5)
 }
 
+@deprecated("used by the codegen before 1.19", since = "1.19.0")
 @inline
 final class AnonFunction6[-T1, -T2, -T3, -T4, -T5, -T6, +R](f: js.Function6[T1, T2, T3, T4, T5, T6, R]) extends AbstractFunction6[T1, T2, T3, T4, T5, T6, R] {
   override def apply(arg1: T1, arg2: T2, arg3: T3, arg4: T4, arg5: T5, arg6: T6): R = f(arg1, arg2, arg3, arg4, arg5, arg6)
 }
 
+@deprecated("used by the codegen before 1.19", since = "1.19.0")
 @inline
 final class AnonFunction7[-T1, -T2, -T3, -T4, -T5, -T6, -T7, +R](f: js.Function7[T1, T2, T3, T4, T5, T6, T7, R]) extends AbstractFunction7[T1, T2, T3, T4, T5, T6, T7, R] {
   override def apply(arg1: T1, arg2: T2, arg3: T3, arg4: T4, arg5: T5, arg6: T6, arg7: T7): R = f(arg1, arg2, arg3, arg4, arg5, arg6, arg7)
 }
 
+@deprecated("used by the codegen before 1.19", since = "1.19.0")
 @inline
 final class AnonFunction8[-T1, -T2, -T3, -T4, -T5, -T6, -T7, -T8, +R](f: js.Function8[T1, T2, T3, T4, T5, T6, T7, T8, R]) extends AbstractFunction8[T1, T2, T3, T4, T5, T6, T7, T8, R] {
   override def apply(arg1: T1, arg2: T2, arg3: T3, arg4: T4, arg5: T5, arg6: T6, arg7: T7, arg8: T8): R = f(arg1, arg2, arg3, arg4, arg5, arg6, arg7, arg8)
 }
 
+@deprecated("used by the codegen before 1.19", since = "1.19.0")
 @inline
 final class AnonFunction9[-T1, -T2, -T3, -T4, -T5, -T6, -T7, -T8, -T9, +R](f: js.Function9[T1, T2, T3, T4, T5, T6, T7, T8, T9, R]) extends AbstractFunction9[T1, T2, T3, T4, T5, T6, T7, T8, T9, R] {
   override def apply(arg1: T1, arg2: T2, arg3: T3, arg4: T4, arg5: T5, arg6: T6, arg7: T7, arg8: T8, arg9: T9): R = f(arg1, arg2, arg3, arg4, arg5, arg6, arg7, arg8, arg9)
 }
 
+@deprecated("used by the codegen before 1.19", since = "1.19.0")
 @inline
 final class AnonFunction10[-T1, -T2, -T3, -T4, -T5, -T6, -T7, -T8, -T9, -T10, +R](f: js.Function10[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, R]) extends AbstractFunction10[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, R] {
   override def apply(arg1: T1, arg2: T2, arg3: T3, arg4: T4, arg5: T5, arg6: T6, arg7: T7, arg8: T8, arg9: T9, arg10: T10): R = f(arg1, arg2, arg3, arg4, arg5, arg6, arg7, arg8, arg9, arg10)
 }
 
+@deprecated("used by the codegen before 1.19", since = "1.19.0")
 @inline
 final class AnonFunction11[-T1, -T2, -T3, -T4, -T5, -T6, -T7, -T8, -T9, -T10, -T11, +R](f: js.Function11[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, R]) extends AbstractFunction11[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, R] {
   override def apply(arg1: T1, arg2: T2, arg3: T3, arg4: T4, arg5: T5, arg6: T6, arg7: T7, arg8: T8, arg9: T9, arg10: T10, arg11: T11): R = f(arg1, arg2, arg3, arg4, arg5, arg6, arg7, arg8, arg9, arg10, arg11)
 }
 
+@deprecated("used by the codegen before 1.19", since = "1.19.0")
 @inline
 final class AnonFunction12[-T1, -T2, -T3, -T4, -T5, -T6, -T7, -T8, -T9, -T10, -T11, -T12, +R](f: js.Function12[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, R]) extends AbstractFunction12[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, R] {
   override def apply(arg1: T1, arg2: T2, arg3: T3, arg4: T4, arg5: T5, arg6: T6, arg7: T7, arg8: T8, arg9: T9, arg10: T10, arg11: T11, arg12: T12): R = f(arg1, arg2, arg3, arg4, arg5, arg6, arg7, arg8, arg9, arg10, arg11, arg12)
 }
 
+@deprecated("used by the codegen before 1.19", since = "1.19.0")
 @inline
 final class AnonFunction13[-T1, -T2, -T3, -T4, -T5, -T6, -T7, -T8, -T9, -T10, -T11, -T12, -T13, +R](f: js.Function13[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, R]) extends AbstractFunction13[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, R] {
   override def apply(arg1: T1, arg2: T2, arg3: T3, arg4: T4, arg5: T5, arg6: T6, arg7: T7, arg8: T8, arg9: T9, arg10: T10, arg11: T11, arg12: T12, arg13: T13): R = f(arg1, arg2, arg3, arg4, arg5, arg6, arg7, arg8, arg9, arg10, arg11, arg12, arg13)
 }
 
+@deprecated("used by the codegen before 1.19", since = "1.19.0")
 @inline
 final class AnonFunction14[-T1, -T2, -T3, -T4, -T5, -T6, -T7, -T8, -T9, -T10, -T11, -T12, -T13, -T14, +R](f: js.Function14[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, R]) extends AbstractFunction14[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, R] {
   override def apply(arg1: T1, arg2: T2, arg3: T3, arg4: T4, arg5: T5, arg6: T6, arg7: T7, arg8: T8, arg9: T9, arg10: T10, arg11: T11, arg12: T12, arg13: T13, arg14: T14): R = f(arg1, arg2, arg3, arg4, arg5, arg6, arg7, arg8, arg9, arg10, arg11, arg12, arg13, arg14)
 }
 
+@deprecated("used by the codegen before 1.19", since = "1.19.0")
 @inline
 final class AnonFunction15[-T1, -T2, -T3, -T4, -T5, -T6, -T7, -T8, -T9, -T10, -T11, -T12, -T13, -T14, -T15, +R](f: js.Function15[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, R]) extends AbstractFunction15[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, R] {
   override def apply(arg1: T1, arg2: T2, arg3: T3, arg4: T4, arg5: T5, arg6: T6, arg7: T7, arg8: T8, arg9: T9, arg10: T10, arg11: T11, arg12: T12, arg13: T13, arg14: T14, arg15: T15): R = f(arg1, arg2, arg3, arg4, arg5, arg6, arg7, arg8, arg9, arg10, arg11, arg12, arg13, arg14, arg15)
 }
 
+@deprecated("used by the codegen before 1.19", since = "1.19.0")
 @inline
 final class AnonFunction16[-T1, -T2, -T3, -T4, -T5, -T6, -T7, -T8, -T9, -T10, -T11, -T12, -T13, -T14, -T15, -T16, +R](f: js.Function16[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, R]) extends AbstractFunction16[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, R] {
   override def apply(arg1: T1, arg2: T2, arg3: T3, arg4: T4, arg5: T5, arg6: T6, arg7: T7, arg8: T8, arg9: T9, arg10: T10, arg11: T11, arg12: T12, arg13: T13, arg14: T14, arg15: T15, arg16: T16): R = f(arg1, arg2, arg3, arg4, arg5, arg6, arg7, arg8, arg9, arg10, arg11, arg12, arg13, arg14, arg15, arg16)
 }
 
+@deprecated("used by the codegen before 1.19", since = "1.19.0")
 @inline
 final class AnonFunction17[-T1, -T2, -T3, -T4, -T5, -T6, -T7, -T8, -T9, -T10, -T11, -T12, -T13, -T14, -T15, -T16, -T17, +R](f: js.Function17[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, R]) extends AbstractFunction17[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, R] {
   override def apply(arg1: T1, arg2: T2, arg3: T3, arg4: T4, arg5: T5, arg6: T6, arg7: T7, arg8: T8, arg9: T9, arg10: T10, arg11: T11, arg12: T12, arg13: T13, arg14: T14, arg15: T15, arg16: T16, arg17: T17): R = f(arg1, arg2, arg3, arg4, arg5, arg6, arg7, arg8, arg9, arg10, arg11, arg12, arg13, arg14, arg15, arg16, arg17)
 }
 
+@deprecated("used by the codegen before 1.19", since = "1.19.0")
 @inline
 final class AnonFunction18[-T1, -T2, -T3, -T4, -T5, -T6, -T7, -T8, -T9, -T10, -T11, -T12, -T13, -T14, -T15, -T16, -T17, -T18, +R](f: js.Function18[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, T18, R]) extends AbstractFunction18[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, T18, R] {
   override def apply(arg1: T1, arg2: T2, arg3: T3, arg4: T4, arg5: T5, arg6: T6, arg7: T7, arg8: T8, arg9: T9, arg10: T10, arg11: T11, arg12: T12, arg13: T13, arg14: T14, arg15: T15, arg16: T16, arg17: T17, arg18: T18): R = f(arg1, arg2, arg3, arg4, arg5, arg6, arg7, arg8, arg9, arg10, arg11, arg12, arg13, arg14, arg15, arg16, arg17, arg18)
 }
 
+@deprecated("used by the codegen before 1.19", since = "1.19.0")
 @inline
 final class AnonFunction19[-T1, -T2, -T3, -T4, -T5, -T6, -T7, -T8, -T9, -T10, -T11, -T12, -T13, -T14, -T15, -T16, -T17, -T18, -T19, +R](f: js.Function19[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, T18, T19, R]) extends AbstractFunction19[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, T18, T19, R] {
   override def apply(arg1: T1, arg2: T2, arg3: T3, arg4: T4, arg5: T5, arg6: T6, arg7: T7, arg8: T8, arg9: T9, arg10: T10, arg11: T11, arg12: T12, arg13: T13, arg14: T14, arg15: T15, arg16: T16, arg17: T17, arg18: T18, arg19: T19): R = f(arg1, arg2, arg3, arg4, arg5, arg6, arg7, arg8, arg9, arg10, arg11, arg12, arg13, arg14, arg15, arg16, arg17, arg18, arg19)
 }
 
+@deprecated("used by the codegen before 1.19", since = "1.19.0")
 @inline
 final class AnonFunction20[-T1, -T2, -T3, -T4, -T5, -T6, -T7, -T8, -T9, -T10, -T11, -T12, -T13, -T14, -T15, -T16, -T17, -T18, -T19, -T20, +R](f: js.Function20[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, T18, T19, T20, R]) extends AbstractFunction20[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, T18, T19, T20, R] {
   override def apply(arg1: T1, arg2: T2, arg3: T3, arg4: T4, arg5: T5, arg6: T6, arg7: T7, arg8: T8, arg9: T9, arg10: T10, arg11: T11, arg12: T12, arg13: T13, arg14: T14, arg15: T15, arg16: T16, arg17: T17, arg18: T18, arg19: T19, arg20: T20): R = f(arg1, arg2, arg3, arg4, arg5, arg6, arg7, arg8, arg9, arg10, arg11, arg12, arg13, arg14, arg15, arg16, arg17, arg18, arg19, arg20)
 }
 
+@deprecated("used by the codegen before 1.19", since = "1.19.0")
 @inline
 final class AnonFunction21[-T1, -T2, -T3, -T4, -T5, -T6, -T7, -T8, -T9, -T10, -T11, -T12, -T13, -T14, -T15, -T16, -T17, -T18, -T19, -T20, -T21, +R](f: js.Function21[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, T18, T19, T20, T21, R]) extends AbstractFunction21[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, T18, T19, T20, T21, R] {
   override def apply(arg1: T1, arg2: T2, arg3: T3, arg4: T4, arg5: T5, arg6: T6, arg7: T7, arg8: T8, arg9: T9, arg10: T10, arg11: T11, arg12: T12, arg13: T13, arg14: T14, arg15: T15, arg16: T16, arg17: T17, arg18: T18, arg19: T19, arg20: T20, arg21: T21): R = f(arg1, arg2, arg3, arg4, arg5, arg6, arg7, arg8, arg9, arg10, arg11, arg12, arg13, arg14, arg15, arg16, arg17, arg18, arg19, arg20, arg21)
 }
 
+@deprecated("used by the codegen before 1.19", since = "1.19.0")
 @inline
 final class AnonFunction22[-T1, -T2, -T3, -T4, -T5, -T6, -T7, -T8, -T9, -T10, -T11, -T12, -T13, -T14, -T15, -T16, -T17, -T18, -T19, -T20, -T21, -T22, +R](f: js.Function22[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, T18, T19, T20, T21, T22, R]) extends AbstractFunction22[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, T18, T19, T20, T21, T22, R] {
   override def apply(arg1: T1, arg2: T2, arg3: T3, arg4: T4, arg5: T5, arg6: T6, arg7: T7, arg8: T8, arg9: T9, arg10: T10, arg11: T11, arg12: T12, arg13: T13, arg14: T14, arg15: T15, arg16: T16, arg17: T17, arg18: T18, arg19: T19, arg20: T20, arg21: T21, arg22: T22): R = f(arg1, arg2, arg3, arg4, arg5, arg6, arg7, arg8, arg9, arg10, arg11, arg12, arg13, arg14, arg15, arg16, arg17, arg18, arg19, arg20, arg21, arg22)
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analysis.scala b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analysis.scala
index 781fc30c48..3c65ac27ba 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analysis.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analysis.scala
@@ -25,6 +25,8 @@ import org.scalajs.ir.Names._
 import org.scalajs.ir.Trees.MemberNamespace
 import org.scalajs.ir.Types._
 
+import org.scalajs.linker.frontend.SyntheticClassKind
+
 /** Reachability graph produced by the [[Analyzer]].
  *
  *  Warning: this trait is not meant to be extended by third-party libraries
@@ -56,6 +58,7 @@ object Analysis {
     def superClass: Option[ClassInfo]
     def interfaces: scala.collection.Seq[ClassInfo]
     def ancestors: scala.collection.Seq[ClassInfo]
+    def syntheticKind: Option[SyntheticClassKind]
     def nonExistent: Boolean
     /** For a Scala class, it is instantiated with a `New`; for a JS class,
      *  its constructor is accessed with a `JSLoadConstructor` or because it
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala
index 7b773c7633..44d34c5e3a 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala
@@ -25,13 +25,13 @@ import java.util.concurrent.atomic._
 import org.scalajs.ir
 import org.scalajs.ir.ClassKind
 import org.scalajs.ir.Names._
-import org.scalajs.ir.Trees.{MemberNamespace, JSNativeLoadSpec}
+import org.scalajs.ir.Trees.{MemberNamespace, NewLambda, JSNativeLoadSpec}
 import org.scalajs.ir.Types.ClassRef
 import org.scalajs.ir.WellKnownNames._
 
 import org.scalajs.linker._
 import org.scalajs.linker.checker.CheckingPhase
-import org.scalajs.linker.frontend.IRLoader
+import org.scalajs.linker.frontend.{IRLoader, LambdaSynthesizer, SyntheticClassKind}
 import org.scalajs.linker.interface._
 import org.scalajs.linker.interface.unstable.ModuleInitializerImpl
 import org.scalajs.linker.standard._
@@ -115,6 +115,13 @@ private class AnalyzerRun(config: CommonPhaseConfig, initial: Boolean,
 
   def classInfos: scala.collection.Map[ClassName, Analysis.ClassInfo] = _classInfos
 
+  /* Cache the names generated for lambda classes because computing their
+   * `ClassName` is a bit expensive. The constructor names are not expensive,
+   * but we might as well cache them together.
+   */
+  private val syntheticLambdaNamesCache: mutable.Map[NewLambda.Descriptor, (ClassName, MethodName)] =
+    emptyThreadSafeMap
+
   private val _classSuperClassUsed = new AtomicBoolean(false)
   def isClassSuperClassUsed: Boolean = _classSuperClassUsed.get()
 
@@ -318,8 +325,19 @@ private class AnalyzerRun(config: CommonPhaseConfig, initial: Boolean,
 
   private def lookupClass(className: ClassName)(
       onSuccess: ClassInfo => Unit)(implicit from: From): Unit = {
+    lookupOrSynthesizeClassCommon(className, None)(onSuccess)
+  }
+
+  private def lookupOrSynthesizeClass(className: ClassName, syntheticKind: SyntheticClassKind)(
+      onSuccess: ClassInfo => Unit)(implicit from: From): Unit = {
+    lookupOrSynthesizeClassCommon(className, Some(syntheticKind))(onSuccess)
+  }
+
+  private def lookupOrSynthesizeClassCommon(className: ClassName,
+      syntheticKind: Option[SyntheticClassKind])(
+      onSuccess: ClassInfo => Unit)(implicit from: From): Unit = {
     workTracker.track {
-      classLoader.lookupClass(className).map {
+      classLoader.lookupClass(className, syntheticKind).map {
         case info: ClassInfo =>
           info.link()
           onSuccess(info)
@@ -334,8 +352,9 @@ private class AnalyzerRun(config: CommonPhaseConfig, initial: Boolean,
   private final class ClassLoader(implicit ec: ExecutionContext) {
     private[this] val _classInfos = emptyThreadSafeMap[ClassName, ClassLoadingState]
 
-    def lookupClass(className: ClassName): Future[LoadingResult] = {
-      ensureLoading(className) match {
+    def lookupClass(className: ClassName,
+        syntheticKind: Option[SyntheticClassKind]): Future[LoadingResult] = {
+      ensureLoading(className, syntheticKind) match {
         case loading: LoadingClass => loading.result
         case info: ClassInfo       => Future.successful(info)
       }
@@ -353,13 +372,14 @@ private class AnalyzerRun(config: CommonPhaseConfig, initial: Boolean,
 
     private def lookupClassForLinking(className: ClassName,
         origin: LoadingClass): Future[LoadingResult] = {
-      ensureLoading(className) match {
+      ensureLoading(className, syntheticKind = None) match {
         case loading: LoadingClass => loading.requestLink(origin)
         case info: ClassInfo       => Future.successful(info)
       }
     }
 
-    private def ensureLoading(className: ClassName): ClassLoadingState = {
+    private def ensureLoading(className: ClassName,
+        syntheticKind: Option[SyntheticClassKind]): ClassLoadingState = {
       var loading: LoadingClass = null
       val state = _classInfos.getOrElseUpdate(className, {
         loading = new LoadingClass(className)
@@ -368,13 +388,19 @@ private class AnalyzerRun(config: CommonPhaseConfig, initial: Boolean,
 
       if (state eq loading) {
         // We just added `loading`, actually load.
-        val maybeInfo = infoLoader.loadInfo(className)
-        val info = maybeInfo.getOrElse {
-          Future.successful(createMissingClassInfo(className))
-        }
+        val result: Future[LoadingResult] = syntheticKind match {
+          case None =>
+            val maybeInfo = infoLoader.loadInfo(className)
+            val info = maybeInfo.getOrElse {
+              Future.successful(createMissingClassInfo(className))
+            }
+            info.flatMap { data =>
+              doLoad(data, loading, syntheticKind, nonExistent = maybeInfo.isEmpty)
+            }
 
-        val result = info.flatMap { data =>
-          doLoad(data, loading, nonExistent = maybeInfo.isEmpty)
+          case Some(SyntheticClassKind.Lambda(descriptor)) =>
+            val data = LambdaSynthesizer.makeClassInfo(descriptor, className)
+            doLoad(data, loading, syntheticKind, nonExistent = false)
         }
 
         loading.completeWith(result)
@@ -384,6 +410,7 @@ private class AnalyzerRun(config: CommonPhaseConfig, initial: Boolean,
     }
 
     private def doLoad(data: Infos.ClassInfo, origin: LoadingClass,
+        syntheticKind: Option[SyntheticClassKind],
         nonExistent: Boolean): Future[LoadingResult] = {
       val className = data.className
 
@@ -408,7 +435,7 @@ private class AnalyzerRun(config: CommonPhaseConfig, initial: Boolean,
             if (data.superClass.isEmpty) (None, ancestors)
             else (Some(ancestors.head), ancestors.tail)
 
-          val info = new ClassInfo(data, superClass, interfaces, nonExistent)
+          val info = new ClassInfo(data, superClass, interfaces, syntheticKind, nonExistent)
 
           _classInfos.put(className, info)
 
@@ -461,6 +488,7 @@ private class AnalyzerRun(config: CommonPhaseConfig, initial: Boolean,
       val data: Infos.ClassInfo,
       unvalidatedSuperClass: Option[ClassInfo],
       unvalidatedInterfaces: List[ClassInfo],
+      val syntheticKind: Option[SyntheticClassKind],
       val nonExistent: Boolean)
       extends Analysis.ClassInfo with ClassLoadingState with LoadingResult with ModuleUnit {
 
@@ -1451,6 +1479,19 @@ private class AnalyzerRun(config: CommonPhaseConfig, initial: Boolean,
       }
     }
 
+    if (data.lambdaDescriptorsUsed.nonEmpty) {
+      for (descriptor <- data.lambdaDescriptorsUsed) {
+        val (className, ctorName) = syntheticLambdaNamesCache.getOrElseUpdate(descriptor, {
+          (LambdaSynthesizer.makeClassName(descriptor), LambdaSynthesizer.makeConstructorName(descriptor))
+        })
+
+        lookupOrSynthesizeClass(className, SyntheticClassKind.Lambda(descriptor)) { lambdaClassInfo =>
+          lambdaClassInfo.instantiated()
+          lambdaClassInfo.callMethodStatically(MemberNamespace.Constructor, ctorName)
+        }
+      }
+    }
+
     val globalFlags = data.globalFlags & ~ReachabilityInfo.FlagNeedsDesugaring
 
     if (globalFlags != 0) {
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala
index 40510666b6..27bb807a74 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala
@@ -79,14 +79,17 @@ object Infos {
     val isAbstract: Boolean,
     version: Version,
     byClass: Array[ReachabilityInfoInClass],
+    lambdaDescriptorsUsed: Array[NewLambda.Descriptor],
     globalFlags: ReachabilityInfo.Flags,
     referencedLinkTimeProperties: Array[(String, Type)]
-  ) extends ReachabilityInfo(version, byClass, globalFlags, referencedLinkTimeProperties)
+  ) extends ReachabilityInfo(version, byClass, lambdaDescriptorsUsed,
+      globalFlags, referencedLinkTimeProperties)
 
   object MethodInfo {
     def apply(isAbstract: Boolean, reachabilityInfo: ReachabilityInfo): MethodInfo = {
       import reachabilityInfo._
-      new MethodInfo(isAbstract, version, byClass, globalFlags, referencedLinkTimeProperties)
+      new MethodInfo(isAbstract, version, byClass, lambdaDescriptorsUsed,
+          globalFlags, referencedLinkTimeProperties)
     }
   }
 
@@ -104,6 +107,7 @@ object Infos {
      */
     val version: Version,
     val byClass: Array[ReachabilityInfoInClass],
+    val lambdaDescriptorsUsed: Array[NewLambda.Descriptor],
     val globalFlags: ReachabilityInfo.Flags,
     val referencedLinkTimeProperties: Array[(String, Type)]
   )
@@ -202,6 +206,7 @@ object Infos {
   final class ReachabilityInfoBuilder(version: Version) {
     import ReachabilityInfoBuilder._
     private val byClass = mutable.Map.empty[ClassName, ReachabilityInfoInClassBuilder]
+    private val lambdaDescriptorsUsed = mutable.Set.empty[NewLambda.Descriptor]
     private var flags: ReachabilityInfo.Flags = 0
     private val linkTimeProperties = mutable.ListBuffer.empty[(String, Type)]
 
@@ -256,7 +261,7 @@ object Infos {
         case NullType | NothingType =>
           // Nothing to do
 
-        case VoidType | RecordType(_) =>
+        case VoidType | ClosureType(_, _, _) | RecordType(_) =>
           throw new IllegalArgumentException(
               s"Illegal receiver type: $receiverTpe")
       }
@@ -281,6 +286,12 @@ object Infos {
       this
     }
 
+    def addLambdaDescriptorUsed(descriptor: NewLambda.Descriptor): this.type = {
+      setFlag(ReachabilityInfo.FlagNeedsDesugaring)
+      lambdaDescriptorsUsed += descriptor
+      this
+    }
+
     def addJSNativeMemberUsed(cls: ClassName, member: MethodName): this.type = {
       forClass(cls).addJSNativeMemberUsed(member)
       this
@@ -403,16 +414,22 @@ object Infos {
     }
 
     def result(): ReachabilityInfo = {
+      val lambdaDescriptorsUsedArray =
+        if (lambdaDescriptorsUsed.isEmpty) emptyLambdaDescriptorArray
+        else lambdaDescriptorsUsed.toArray
+
       val referencedLinkTimeProperties =
         if (linkTimeProperties.isEmpty) emptyLinkTimePropertyArray
         else linkTimeProperties.toArray
-      new ReachabilityInfo(version, byClass.valuesIterator.map(_.result()).toArray, flags,
-          referencedLinkTimeProperties)
+
+      new ReachabilityInfo(version, byClass.valuesIterator.map(_.result()).toArray,
+          lambdaDescriptorsUsedArray, flags, referencedLinkTimeProperties)
     }
   }
 
   object ReachabilityInfoBuilder {
     private val emptyLinkTimePropertyArray = new Array[(String, Type)](0)
+    private val emptyLambdaDescriptorArray = new Array[NewLambda.Descriptor](0)
   }
 
   final class ReachabilityInfoInClassBuilder(val className: ClassName) {
@@ -664,6 +681,9 @@ object Infos {
               builder.addMethodCalledDynamicImport(className,
                   NamespacedMethodName(namespace, method.name))
 
+            case NewLambda(descriptor, _) =>
+              builder.addLambdaDescriptorUsed(descriptor)
+
             case LoadModule(className) =>
               builder.addAccessedModule(className)
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
index 8fa5e60d4a..b5616527fd 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
@@ -1069,8 +1069,8 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
                 }
                 JSObjectConstr(newItems)
 
-              case Closure(arrow, captureParams, params, restParam, body, captureValues) =>
-                Closure(arrow, captureParams, params, restParam, body, recs(captureValues))
+              case Closure(flags, captureParams, params, restParam, resultType, body, captureValues) =>
+                Closure(flags, captureParams, params, restParam, resultType, body, recs(captureValues))
 
               case New(className, constr, args) if noExtractYet =>
                 New(className, constr, recs(args))
@@ -1086,6 +1086,9 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
                 ApplyStatic(flags, className, method, recs(args))(arg.tpe)
               case ApplyDynamicImport(flags, className, method, args) if noExtractYet =>
                 ApplyDynamicImport(flags, className, method, recs(args))
+              case ApplyTypedClosure(flags, fun, args) if noExtractYet =>
+                val newArgs = recs(args)
+                ApplyTypedClosure(flags, rec(fun), newArgs)
               case ArraySelect(array, index) if noExtractYet =>
                 val newIndex = rec(index)
                 ArraySelect(rec(array), newIndex)(arg.tpe)
@@ -1332,8 +1335,8 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
           items.forall { item =>
             test(item._1) && test(item._2)
           }
-        case Closure(arrow, captureParams, params, restParam, body, captureValues) =>
-          allowUnpure && (captureValues forall test)
+        case Closure(flags, captureParams, params, restParam, resultType, body, captureValues) =>
+          allowUnpure && captureValues.forall(test(_))
 
         // Transients preserving side-effect freedom (modulo NPE)
         case Transient(NativeArrayWrapper(elemClass, nativeArray)) =>
@@ -1354,6 +1357,8 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
           allowSideEffects && (args forall test)
         case ApplyDynamicImport(_, _, _, args) =>
           allowSideEffects && args.forall(test)
+        case ApplyTypedClosure(_, fun, args) =>
+          allowSideEffects && test(fun) && args.forall(test)
 
         // Transients with side effects.
         case Transient(TypedArrayToArray(expr, primRef)) =>
@@ -1768,6 +1773,11 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
             redo(ApplyDynamicImport(flags, className, method, newArgs))(env)
           }
 
+        case ApplyTypedClosure(flags, fun, args) =>
+          unnest(checkNotNull(fun), args) { (newFun, newArgs, env) =>
+            redo(ApplyTypedClosure(flags, newFun, newArgs))(env)
+          }
+
         case UnaryOp(op, lhs) =>
           op match {
             case UnaryOp.Throw =>
@@ -2003,10 +2013,10 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
 
         // Closures
 
-        case Closure(arrow, captureParams, params, restParam, body, captureValues) =>
+        case Closure(flags, captureParams, params, restParam, resultType, body, captureValues) =>
           unnest(captureValues) { (newCaptureValues, env) =>
-            redo(Closure(arrow, captureParams, params, restParam, body, newCaptureValues))(
-                env)
+            redo(Closure(flags, captureParams, params, restParam, resultType,
+                body, newCaptureValues))(env)
           }
 
         case CreateJSClass(className, captureValues) =>
@@ -2339,6 +2349,20 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
         case tree: ApplyDynamicImport =>
           transformApplyDynamicImport(tree)
 
+        case ApplyTypedClosure(_, fun, args) =>
+          val newFun = transformExprNoChar(checkNotNull(fun))
+          val newArgs = fun.tpe match {
+            case ClosureType(paramTypes, _, _) =>
+              for ((arg, paramType) <- args.zip(paramTypes)) yield
+                transformExpr(arg, paramType)
+            case NothingType | NullType =>
+              args.map(transformExpr(_, preserveChar = true))
+            case _ =>
+              throw new AssertionError(
+                  s"Unexpected type for the fun of ApplyTypedClosure: ${fun.tpe}")
+          }
+          js.Apply.makeProtected(newFun, newArgs)
+
         case UnaryOp(op, lhs) =>
           import UnaryOp._
           val newLhs = transformExpr(lhs, preserveChar = (op == CharToInt || op == CheckNotNull))
@@ -3086,7 +3110,7 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
     }
 
     private def transformClosure(tree: Closure)(implicit env: Env): js.Tree = {
-      val Closure(arrow, captureParams, params, restParam, body, captureValues) = tree
+      val Closure(flags, captureParams, params, restParam, resultType, body, captureValues) = tree
 
       implicit val pos = tree.pos
 
@@ -3099,7 +3123,7 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
 
         val captureName = param.name.name
 
-        val varKind = prepareCapture(value, Some(captureName), arrow) { () =>
+        val varKind = prepareCapture(value, Some(captureName), flags.arrow) { () =>
           capturesBuilder += transformParamDef(param) -> transformExpr(value, param.ptpe)
         }
 
@@ -3107,11 +3131,12 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
       }).toMap
 
       val innerFunction = {
-        val bodyEnv = Env.empty(AnyType)
+        val bodyEnv = Env.empty(resultType)
           .withParams(params ++ restParam)
           .withVars(envVarsForCaptures)
 
-        desugarToFunctionInternal(arrow, params, restParam, body, isStat = false, bodyEnv)
+        desugarToFunctionInternal(flags.arrow, params, restParam, body,
+            isStat = resultType == VoidType, bodyEnv)
       }
 
       val captures = capturesBuilder.result()
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/NameGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/NameGen.scala
index 1c2c56f8f3..ffb1d57bbe 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/NameGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/NameGen.scala
@@ -166,6 +166,8 @@ private[backend] final class NameGen {
               i += 1
             }
             appendTypeRef(base)
+          case TransientTypeRef(name) =>
+            builder.append('t').append(genName(name))
         }
       }
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala
index c4e228eae1..73ac6c96c9 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala
@@ -445,7 +445,7 @@ private[emitter] final class SJSGen(
       case AnyNotNullType => expr !== Null()
 
       case VoidType | NullType | NothingType | AnyType |
-          ClassType(_, true) | ArrayType(_, true) | _:RecordType =>
+          ClassType(_, true) | ArrayType(_, true) | _:ClosureType | _:RecordType =>
         throw new AssertionError(s"Unexpected type $tpe in genIsInstanceOf")
     }
   }
@@ -519,7 +519,7 @@ private[emitter] final class SJSGen(
           genCallPolyfillableBuiltin(FroundBuiltin, expr)
 
         case VoidType | NullType | NothingType | AnyNotNullType |
-            ClassType(_, false) | ArrayType(_, false) | _:RecordType =>
+            ClassType(_, false) | ArrayType(_, false) | _:ClosureType | _:RecordType =>
           throw new AssertionError(s"Unexpected type $tpe in genAsInstanceOf")
       }
     } else {
@@ -545,7 +545,7 @@ private[emitter] final class SJSGen(
         case AnyType     => expr
 
         case VoidType | NullType | NothingType | AnyNotNullType |
-            ClassType(_, false) | ArrayType(_, false) | _:RecordType =>
+            ClassType(_, false) | ArrayType(_, false) | _:ClosureType | _:RecordType =>
           throw new AssertionError(s"Unexpected type $tpe in genAsInstanceOf")
       }
 
@@ -771,6 +771,9 @@ private[emitter] final class SJSGen(
         (1 to dims).foldLeft[Tree](baseData) { (prev, _) =>
           Apply(DotSelect(prev, Ident(cpn.getArrayOf)), Nil)
         }
+
+      case typeRef: TransientTypeRef =>
+        throw new IllegalArgumentException(s"Illegal classOf[$typeRef]")
     }
   }
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
index a37ce49768..94fa164d81 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
@@ -59,6 +59,7 @@ object FunctionEmitter {
       originalName,
       enclosingClassName,
       captureParamDefs,
+      captureDataAsRefStruct = false,
       preSuperVarDefs = None,
       hasNewTarget = false,
       receiverType,
@@ -69,6 +70,32 @@ object FunctionEmitter {
     emitter.fb.buildAndAddToModule()
   }
 
+  def emitTypedClosureFunction(
+      functionID: wanme.FunctionID,
+      originalName: OriginalName,
+      funTypeID: wanme.TypeID,
+      captureParamDefs: List[ParamDef],
+      paramDefs: List[ParamDef],
+      body: Tree,
+      resultType: Type
+  )(implicit ctx: WasmContext, pos: Position): Unit = {
+    val emitter = prepareEmitter(
+      functionID,
+      originalName,
+      enclosingClassName = None,
+      Some(captureParamDefs),
+      captureDataAsRefStruct = true,
+      preSuperVarDefs = None,
+      hasNewTarget = false,
+      receiverType = None,
+      paramDefs,
+      transformResultType(resultType)
+    )
+    emitter.fb.setFunctionType(funTypeID)
+    emitter.genBody(body, resultType)
+    emitter.fb.buildAndAddToModule()
+  }
+
   def emitJSConstructorFunctions(
       preSuperStatsFunctionID: wanme.FunctionID,
       superArgsFunctionID: wanme.FunctionID,
@@ -97,6 +124,7 @@ object FunctionEmitter {
         OriginalName(UTF8String("preSuperStats.") ++ enclosingClassName.encoded),
         Some(enclosingClassName),
         Some(jsClassCaptures),
+        captureDataAsRefStruct = false,
         preSuperVarDefs = None,
         hasNewTarget = true,
         receiverType = None,
@@ -127,6 +155,7 @@ object FunctionEmitter {
         OriginalName(UTF8String("superArgs.") ++ enclosingClassName.encoded),
         Some(enclosingClassName),
         Some(jsClassCaptures),
+        captureDataAsRefStruct = false,
         Some(preSuperDecls),
         hasNewTarget = true,
         receiverType = None,
@@ -144,6 +173,7 @@ object FunctionEmitter {
         OriginalName(UTF8String("postSuperStats.") ++ enclosingClassName.encoded),
         Some(enclosingClassName),
         Some(jsClassCaptures),
+        captureDataAsRefStruct = false,
         Some(preSuperDecls),
         hasNewTarget = true,
         receiverType = Some(watpe.RefType.anyref),
@@ -160,6 +190,7 @@ object FunctionEmitter {
       originalName: OriginalName,
       enclosingClassName: Option[ClassName],
       captureParamDefs: Option[List[ParamDef]],
+      captureDataAsRefStruct: Boolean,
       preSuperVarDefs: Option[List[VarDef]],
       hasNewTarget: Boolean,
       receiverType: Option[watpe.Type],
@@ -173,12 +204,23 @@ object FunctionEmitter {
         captureLikes: List[(LocalName, Type)]
     ): Env = {
       val dataStructTypeID = ctx.getClosureDataStructType(captureLikes.map(_._2))
-      val param = fb.addParam(captureParamName, watpe.RefType(dataStructTypeID))
+
+      val dataStructLocal = if (captureDataAsRefStruct) {
+        val param = fb.addParam(captureParamName + "0", watpe.RefType.struct)
+        val local = fb.addLocal(captureParamName, watpe.RefType(dataStructTypeID))
+        fb += wa.LocalGet(param)
+        fb += wa.RefCast(watpe.RefType(dataStructTypeID))
+        fb += wa.LocalSet(local)
+        local
+      } else {
+        fb.addParam(captureParamName, watpe.RefType(dataStructTypeID))
+      }
+
       val env: List[(LocalName, VarStorage)] = for {
         ((name, _), idx) <- captureLikes.zipWithIndex
       } yield {
         val storage = VarStorage.StructField(
-          param,
+          dataStructLocal,
           dataStructTypeID,
           genFieldID.captureParam(idx)
         )
@@ -533,6 +575,7 @@ private class FunctionEmitter private (
       case t: Apply               => genApply(t)
       case t: ApplyStatic         => genApplyStatic(t)
       case t: ApplyDynamicImport  => genApplyDynamicImport(t)
+      case t: ApplyTypedClosure   => genApplyTypedClosure(t)
       case t: IsInstanceOf        => genIsInstanceOf(t)
       case t: AsInstanceOf        => genAsInstanceOf(t)
       case t: Block               => genBlock(t, expectedType)
@@ -590,7 +633,7 @@ private class FunctionEmitter private (
       // Transients (only generated by the optimizer)
       case t: Transient => genTransient(t)
 
-      case _:JSSuperConstructorCall | _:LinkTimeProperty =>
+      case _:JSSuperConstructorCall | _:LinkTimeProperty | _:NewLambda =>
         throw new AssertionError(s"Invalid tree: $tree")
     }
 
@@ -820,7 +863,7 @@ private class FunctionEmitter private (
             cls
           case AnyType | AnyNotNullType | ArrayType(_, _) =>
             ObjectClass
-          case tpe: RecordType =>
+          case tpe @ (_:ClosureType | _:RecordType) =>
             throw new AssertionError(s"Invalid receiver type $tpe")
         }
         val receiverClassInfo = ctx.getClassInfo(receiverClassName)
@@ -1251,6 +1294,42 @@ private class FunctionEmitter private (
         s"Unexpected $tree at ${tree.pos}; multiple modules are not supported yet")
   }
 
+  private def genApplyTypedClosure(tree: ApplyTypedClosure): Type = {
+    tree.fun.tpe match {
+      case NothingType =>
+        genTree(tree.fun, NothingType)
+        NothingType
+
+      case NullType =>
+        genTree(tree.fun, NullType)
+        genNPE()
+        NothingType
+
+      case closureType @ ClosureType(paramTypes, resultType, _) =>
+        val (funTypeID, typedClosureTypeID) = ctx.genTypedClosureStructType(closureType)
+        val funLocal = addSyntheticLocal(watpe.RefType(typedClosureTypeID))
+
+        genTreeAuto(tree.fun)
+        genAsNonNullOrNPEFor(tree.fun)
+        fb += wa.LocalTee(funLocal)
+        fb += wa.StructGet(typedClosureTypeID, genFieldID.typedClosure.data)
+
+        for ((arg, paramType) <- tree.args.zip(paramTypes))
+          genTree(arg, paramType)
+
+        markPosition(tree)
+
+        fb += wa.LocalGet(funLocal)
+        fb += wa.StructGet(typedClosureTypeID, genFieldID.typedClosure.fun)
+        fb += wa.CallRef(funTypeID)
+
+        resultType
+
+      case tpe =>
+        throw new AssertionError(s"Unexpected type for closure: ${tpe.show()} at ${tree.pos}")
+    }
+  }
+
   private def genArgs(args: List[Tree], methodName: MethodName): Unit = {
     for ((arg, paramTypeRef) <- args.zip(methodName.paramTypeRefs)) {
       val paramType = ctx.inferTypeFromTypeRef(paramTypeRef)
@@ -2013,7 +2092,7 @@ private class FunctionEmitter private (
       case ArrayType(_, _) =>
         genWithDispatch(isAncestorOfHijackedClass = false)
 
-      case tpe: RecordType =>
+      case tpe @ (_:ClosureType | _:RecordType) =>
         throw new AssertionError(
             s"Invalid type $tpe for String_+ at ${tree.pos}: $tree")
     }
@@ -2226,7 +2305,7 @@ private class FunctionEmitter private (
             }
         }
 
-      case AnyType | ClassType(_, true) | ArrayType(_, true) | _:RecordType =>
+      case AnyType | ClassType(_, true) | ArrayType(_, true) | _:ClosureType | _:RecordType =>
         throw new AssertionError(s"Illegal type in IsInstanceOf: $testType")
     }
 
@@ -3053,7 +3132,49 @@ private class FunctionEmitter private (
   }
 
   private def genClosure(tree: Closure): Type = {
-    val Closure(arrow, captureParams, params, restParam, body, captureValues) = tree
+    if (tree.flags.typed)
+      genTypedClosure(tree)
+    else
+      genJSClosure(tree)
+  }
+
+  private def genTypedClosure(tree: Closure): Type = {
+    implicit val pos = tree.pos
+
+    val (funTypeID, typedClosureTypeID) =
+      ctx.genTypedClosureStructType(tree.tpe.asInstanceOf[ClosureType])
+    val dataStructTypeID = ctx.getClosureDataStructType(tree.captureParams.map(_.ptpe))
+
+    // Define the function where captures are reified as a `__captureData` argument.
+    val closureFuncOrigName = genClosureFuncOriginalName()
+    val closureFuncID = new ClosureFunctionID(closureFuncOrigName)
+    emitTypedClosureFunction(
+      closureFuncID,
+      closureFuncOrigName,
+      funTypeID,
+      tree.captureParams,
+      tree.params,
+      tree.body,
+      tree.resultType
+    )
+
+    // Evaluate the capture values and instantiate the capture data struct
+    for ((param, value) <- tree.captureParams.zip(tree.captureValues))
+      genTree(value, param.ptpe)
+    markPosition(tree)
+    fb += wa.StructNew(dataStructTypeID)
+
+    // Put a reference to the function on the stack
+    fb += ctx.refFuncWithDeclaration(closureFuncID)
+
+    // Build the typed closure struct
+    fb += wa.StructNew(typedClosureTypeID)
+
+    tree.tpe
+  }
+
+  private def genJSClosure(tree: Closure): Type = {
+    val Closure(flags, captureParams, params, restParam, resultType, body, captureValues) = tree
 
     implicit val pos = tree.pos
 
@@ -3067,7 +3188,7 @@ private class FunctionEmitter private (
       closureFuncOrigName,
       enclosingClassName = None,
       Some(captureParams),
-      receiverType = if (arrow) None else Some(watpe.RefType.anyref),
+      receiverType = if (flags.arrow) None else Some(watpe.RefType.anyref),
       params,
       restParam,
       body,
@@ -3090,11 +3211,11 @@ private class FunctionEmitter private (
     val helperID = builder.build(AnyNotNullType) {
       js.Return {
         val (argsParamDefs, restParamDef) = builder.genJSParamDefs(params, restParam)
-        js.Function(arrow, argsParamDefs, restParamDef, {
+        js.Function(flags.arrow, argsParamDefs, restParamDef, {
           js.Return(js.Apply(
               fRef,
               dataRef ::
-              (if (arrow) Nil else List(js.This())) :::
+              (if (flags.arrow) Nil else List(js.This())) :::
               argsParamDefs.map(_.ref) :::
               restParamDef.map(_.ref).toList
           ))
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/SWasmGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/SWasmGen.scala
index f8d4bcd55e..6764522f17 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/SWasmGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/SWasmGen.scala
@@ -37,18 +37,19 @@ object SWasmGen {
       case ClassType(BoxedStringClass, true) =>
         RefNull(Types.HeapType.NoExtern)
 
-      case AnyType | ClassType(_, true) | ArrayType(_, true) | NullType =>
+      case AnyType | ClassType(_, true) | ArrayType(_, true) | ClosureType(_, _, true) | NullType =>
         RefNull(Types.HeapType.None)
 
       case NothingType | VoidType | ClassType(_, false) | ArrayType(_, false) |
-          AnyNotNullType | _:RecordType =>
+          ClosureType(_, _, false) | AnyNotNullType | _:RecordType =>
         throw new AssertionError(s"Unexpected type for field: ${tpe.show()}")
     }
   }
 
   def genLoadTypeData(fb: FunctionBuilder, typeRef: TypeRef): Unit = typeRef match {
-    case typeRef: NonArrayTypeRef => genLoadNonArrayTypeData(fb, typeRef)
-    case typeRef: ArrayTypeRef    => genLoadArrayTypeData(fb, typeRef)
+    case typeRef: NonArrayTypeRef  => genLoadNonArrayTypeData(fb, typeRef)
+    case typeRef: ArrayTypeRef     => genLoadArrayTypeData(fb, typeRef)
+    case typeRef: TransientTypeRef => throw new IllegalArgumentException(typeRef.toString())
   }
 
   def genLoadNonArrayTypeData(fb: FunctionBuilder, typeRef: NonArrayTypeRef): Unit = {
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/TypeTransformer.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/TypeTransformer.scala
index cfc1eeb81c..505136aea8 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/TypeTransformer.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/TypeTransformer.scala
@@ -94,6 +94,10 @@ object TypeTransformer {
       case ArrayType(arrayTypeRef, nullable) =>
         watpe.RefType(nullable, genTypeID.forArrayClass(arrayTypeRef))
 
+      case tpe @ ClosureType(_, _, nullable) =>
+        val (_, typedClosureTypeID) = ctx.genTypedClosureStructType(tpe)
+        watpe.RefType(nullable, typedClosureTypeID)
+
       case RecordType(fields) =>
         throw new AssertionError(s"Unexpected record type $tpe")
     }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
index 4173b0ff52..c007314c9d 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
@@ -355,6 +355,14 @@ object VarGen {
 
     /** The magic `data` field of type `(ref typeData)`, injected into `jl.Class`. */
     case object classData extends FieldID
+
+    object typedClosure {
+      /** The `data` field of a typed closure struct. */
+      case object data extends FieldID
+
+      /** The `fun` field of a typed closure struct. */
+      case object fun extends FieldID
+    }
   }
 
   object genTypeID {
@@ -364,6 +372,8 @@ object VarGen {
     final case class forITable(className: ClassName) extends TypeID
     final case class forFunction(index: Int) extends TypeID
     final case class forTableFunctionType(methodName: MethodName) extends TypeID
+    final case class forClosureFunType(closureType: ClosureType) extends TypeID
+    final case class forClosureType(closureType: ClosureType) extends TypeID
 
     val ObjectStruct = forClass(ObjectClass)
     val ClassStruct = forClass(ClassClass)
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/WasmContext.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/WasmContext.scala
index acab6a3b0f..5bf34ae492 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/WasmContext.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/WasmContext.scala
@@ -53,6 +53,7 @@ final class WasmContext(
   private val functionTypes = LinkedHashMap.empty[watpe.FunctionType, wanme.TypeID]
   private val tableFunctionTypes = mutable.HashMap.empty[MethodName, wanme.TypeID]
   private val closureDataTypes = LinkedHashMap.empty[List[Type], wanme.TypeID]
+  private val typedClosureTypes = LinkedHashMap.empty[ClosureType, (wanme.TypeID, wanme.TypeID)]
 
   val jsNameGen = new JSNameGen()
 
@@ -115,6 +116,8 @@ final class WasmContext(
         ClassType(className, nullable = true)
     case typeRef: ArrayTypeRef =>
       ArrayType(typeRef, nullable = true)
+    case typeRef: TransientTypeRef =>
+      typeRef.tpe
   }
 
   /** Retrieves a unique identifier for a reflective proxy with the given name.
@@ -178,6 +181,53 @@ final class WasmContext(
     )
   }
 
+  /** Generates the struct type for a `ClosureType`.
+   *
+   *  @return
+   *    `(funTypeID, structTypeID)`, where `funTypeID` is the function type of
+   *    the `ref.func`s, and `structTypeID` is the struct type that contains
+   *    the capture data and the `ref.func` (i.e., the actual Wasm type of
+   *    values of the given `ClosureType`).
+   */
+  def genTypedClosureStructType(tpe0: ClosureType): (wanme.TypeID, wanme.TypeID) = {
+    // Normalize to the non-nullable variant
+    val tpe = tpe0.toNonNullable
+
+    typedClosureTypes.getOrElseUpdate(tpe, {
+      implicit val ctx = this
+
+      val tpeNameString = tpe.show()
+
+      val funType = watpe.FunctionType(
+        watpe.RefType.struct :: tpe.paramTypes.map(TypeTransformer.transformParamType(_)),
+        TypeTransformer.transformResultType(tpe.resultType)
+      )
+      val funTypeID = genTypeID.forClosureFunType(tpe)
+      mainRecType.addSubType(funTypeID, OriginalName("fun" + tpeNameString), funType)
+
+      val fields: List[watpe.StructField] = List(
+        watpe.StructField(
+          genFieldID.typedClosure.data,
+          OriginalName("data"),
+          watpe.RefType.struct,
+          isMutable = false
+        ),
+        watpe.StructField(
+          genFieldID.typedClosure.fun,
+          OriginalName("fun"),
+          watpe.RefType(funTypeID),
+          isMutable = false
+        )
+      )
+
+      val structTypeID = genTypeID.forClosureType(tpe)
+      val structType = watpe.StructType(fields)
+      mainRecType.addSubType(structTypeID, OriginalName(tpeNameString), structType)
+
+      (funTypeID, structTypeID)
+    })
+  }
+
   def refFuncWithDeclaration(funcID: wanme.FunctionID): wa.RefFunc = {
     _funcDeclarations += funcID
     wa.RefFunc(funcID)
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/Types.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/Types.scala
index 76370187ac..58f07eba99 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/Types.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/Types.scala
@@ -86,6 +86,9 @@ object Types {
     /** `(ref i31)`. */
     val i31: RefType = apply(HeapType.I31)
 
+    /** `(ref struct)`. */
+    val struct: RefType = apply(HeapType.Struct)
+
     /** `(ref extern)`. */
     val extern: RefType = apply(HeapType.Extern)
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala b/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
index 4fcf593d70..bd3f6d612e 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
@@ -505,6 +505,26 @@ private final class ClassDefChecker(classDef: ClassDef,
 
     if ((name.isStaticInitializer || name.isClassInitializer) != (namespace == MemberNamespace.StaticConstructor))
       reportError("a member can have a static constructor name iff it is in the static constructor namespace")
+
+    if ((name.resultTypeRef :: name.paramTypeRefs).exists(_.isInstanceOf[TransientTypeRef])) {
+      if (featureSet.supports(FeatureSet.TransientTypeRefs)) {
+        if (namespace == MemberNamespace.Public)
+          reportError(i"Illegal transient type ref in public method $name")
+      } else {
+        reportError(i"Illegal transient type ref in method name $name")
+      }
+    }
+  }
+
+  private def checkCaptureParamDefs(params: List[ParamDef])(
+      implicit ctx: ErrorContext): Unit = {
+    for (ParamDef(name, _, ctpe, mutable) <- params) {
+      checkDeclareLocalVar(name)
+      if (mutable)
+        reportError(i"Capture parameter $name cannot be mutable")
+      if (ctpe == VoidType)
+        reportError(i"Parameter $name has type VoidType")
+    }
   }
 
   private def checkJSParamDefs(params: List[ParamDef], restParam: Option[ParamDef])(
@@ -516,6 +536,15 @@ private final class ClassDefChecker(classDef: ClassDef,
     }
   }
 
+  private def checkTypedParamDefs(params: List[ParamDef])(
+      implicit ctx: ErrorContext): Unit = {
+    for (ParamDef(name, _, ctpe, _) <- params) {
+      checkDeclareLocalVar(name)
+      if (ctpe == VoidType)
+        reportError(i"Parameter $name has type VoidType")
+    }
+  }
+
   private def checkConstructorBody(body: Tree, bodyEnv: Env): Unit = {
     /* If the enclosing class is `jl.Object`, the `body` cannot contain any
      * delegate constructor call.
@@ -802,6 +831,39 @@ private final class ClassDefChecker(classDef: ClassDef,
 
         checkApplyGeneric(method, args)
 
+      case ApplyTypedClosure(flags, fun, args) =>
+        if (!featureSet.supports(FeatureSet.TypedClosures))
+          reportError(i"Illegal node ApplyTypedClosure")
+
+        if (flags.isPrivate)
+          reportError("invalid flag Private for ApplyTypedClosure")
+        if (flags.isConstructor)
+          reportError("invalid flag Constructor for ApplyTypedClosure")
+
+        checkTree(fun, env)
+        checkAppliedClosureType(fun.tpe)
+        checkTrees(args, env)
+
+        fun.tpe match {
+          case ClosureType(paramTypes, resultType, _) =>
+            if (args.size != paramTypes.size)
+              reportError(i"Arity mismatch: ${paramTypes.size} expected but ${args.size} found")
+          case _ =>
+            () // OK, notably for NothingType
+        }
+
+      case NewLambda(descriptor, fun) =>
+        if (!featureSet.supports(FeatureSet.NewLambda))
+          reportError(i"Illegal NewLambda after desugaring")
+
+        fun match {
+          case fun: Closure if fun.flags.typed =>
+            checkClosure(fun, env)
+          case _ =>
+            reportError(i"The argument to a NewLambda must be a typed closure")
+            checkTree(fun, env)
+        }
+
       case UnaryOp(_, lhs) =>
         checkTree(lhs, env)
 
@@ -835,7 +897,7 @@ private final class ClassDefChecker(classDef: ClassDef,
         checkTree(expr, env)
         testType match {
           case VoidType | NullType | NothingType | AnyType |
-              ClassType(_, true) | ArrayType(_, true) | _:RecordType =>
+              ClassType(_, true) | ArrayType(_, true) | _:ClosureType | _:RecordType =>
             reportError(i"$testType is not a valid test type for IsInstanceOf")
           case testType: ArrayType =>
             checkArrayType(testType)
@@ -847,7 +909,7 @@ private final class ClassDefChecker(classDef: ClassDef,
         checkTree(expr, env)
         tpe match {
           case VoidType | NullType | NothingType | AnyNotNullType |
-              ClassType(_, false) | ArrayType(_, false) | _:RecordType =>
+              ClassType(_, false) | ArrayType(_, false) | _:ClosureType | _:RecordType =>
             reportError(i"$tpe is not a valid target type for AsInstanceOf")
           case tpe: ArrayType =>
             checkArrayType(tpe)
@@ -941,6 +1003,8 @@ private final class ClassDefChecker(classDef: ClassDef,
             reportError(i"Invalid classOf[$typeRef]")
           case typeRef: ArrayTypeRef =>
             checkArrayTypeRef(typeRef)
+          case typeRef: TransientTypeRef =>
+            reportError(i"Illegal special type ref in classOf[$typeRef]")
           case _ =>
             // ok
         }
@@ -959,36 +1023,10 @@ private final class ClassDefChecker(classDef: ClassDef,
         if (env.isThisRestricted && name.isThis)
           reportError(i"Restricted use of `this` before the super constructor call")
 
-      case Closure(arrow, captureParams, params, restParam, body, captureValues) =>
-        /* Check compliance of captureValues wrt. captureParams in the current
-         * method state, i.e., outside `withPerMethodState`.
-         */
-        if (captureParams.size != captureValues.size) {
-          reportError(
-              "Mismatched size for captures: "+
-              i"${captureParams.size} params vs ${captureValues.size} values")
-        }
-
-        checkTrees(captureValues, env)
-
-        // Then check the closure params and body in its own per-method state
-        withPerMethodState {
-          for (ParamDef(name, _, ctpe, mutable) <- captureParams) {
-            checkDeclareLocalVar(name)
-            if (mutable)
-              reportError(i"Capture parameter $name cannot be mutable")
-            if (ctpe == VoidType)
-              reportError(i"Parameter $name has type VoidType")
-          }
-
-          checkJSParamDefs(params, restParam)
-
-          val bodyEnv = Env
-            .fromParams(captureParams ++ params ++ restParam)
-            .withHasNewTarget(!arrow)
-            .withMaybeThisType(!arrow, AnyType)
-          checkTree(body, bodyEnv)
-        }
+      case tree: Closure =>
+        if (tree.flags.typed && !featureSet.supports(FeatureSet.TypedClosures))
+          reportError(i"Illegal typed closure outside of a NewLambda")
+        checkClosure(tree, env)
 
       case CreateJSClass(className, captureValues) =>
         checkTrees(captureValues, env)
@@ -1005,6 +1043,48 @@ private final class ClassDefChecker(classDef: ClassDef,
     newEnv
   }
 
+  private def checkClosure(tree: Closure, env: Env): Unit = {
+    implicit val ctx = ErrorContext(tree)
+
+    val Closure(flags, captureParams, params, restParam, resultType, body, captureValues) = tree
+
+    if (flags.typed && !flags.arrow) {
+      reportError(i"A typed closure must have the 'arrow' flag")
+    }
+
+    /* Check compliance of captureValues wrt. captureParams in the current
+     * method state, i.e., outside `withPerMethodState`.
+     */
+    if (captureParams.size != captureValues.size) {
+      reportError(
+          "Mismatched size for captures: "+
+          i"${captureParams.size} params vs ${captureValues.size} values")
+    }
+
+    checkTrees(captureValues, env)
+
+    // Then check the closure params and body in its own per-method state
+    withPerMethodState {
+      checkCaptureParamDefs(captureParams)
+
+      if (flags.typed) {
+        checkTypedParamDefs(params)
+        if (restParam.isDefined)
+          reportError(i"A typed closure may not have a rest param")
+      } else {
+        checkJSParamDefs(params, restParam)
+        if (resultType != AnyType)
+          reportError(i"A JS closure must have result type 'any' but found '$resultType'")
+      }
+
+      val bodyEnv = Env
+        .fromParams(captureParams ++ params ++ restParam)
+        .withHasNewTarget(!flags.arrow)
+        .withMaybeThisType(!flags.arrow, AnyType)
+      checkTree(body, bodyEnv)
+    }
+  }
+
   private def checkArrayType(tpe: ArrayType)(
       implicit ctx: ErrorContext): Unit = {
     checkArrayTypeRef(tpe.arrayTypeRef)
@@ -1020,6 +1100,25 @@ private final class ClassDefChecker(classDef: ClassDef,
     }
   }
 
+  private def checkAppliedClosureType(tpe: Type)(
+      implicit ctx: ErrorContext): Unit = tpe match {
+    case tpe: ClosureType       => checkClosureType(tpe)
+    case NothingType | NullType => // ok
+    case _                      => reportError(s"Closure type expected but $tpe found")
+  }
+
+  private def checkClosureType(tpe: ClosureType)(
+      implicit ctx: ErrorContext): Unit = {
+    for (paramType <- tpe.paramTypes) {
+      paramType match {
+        case paramType: ArrayType   => checkArrayType(paramType)
+        case paramType: ClosureType => checkClosureType(paramType)
+        case VoidType               => reportError(i"Illegal parameter type $paramType")
+        case _                      => () // ok
+      }
+    }
+  }
+
   private def checkDeclareLocalVar(ident: LocalIdent)(
       implicit ctx: ErrorContext): Unit = {
     if (ident.name.isThis)
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/checker/FeatureSet.scala b/linker/shared/src/main/scala/org/scalajs/linker/checker/FeatureSet.scala
index 59f1d89c54..33cbeaa135 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/checker/FeatureSet.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/checker/FeatureSet.scala
@@ -39,17 +39,26 @@ private[checker] object FeatureSet {
   /** The `LinkTimeProperty` IR node. */
   val LinkTimeProperty = new FeatureSet(1 << 0)
 
+  /** The `NewLambda` IR node. */
+  val NewLambda = new FeatureSet(1 << 1)
+
   /** Optional constructors in module classes and JS classes. */
-  val OptionalConstructors = new FeatureSet(1 << 1)
+  val OptionalConstructors = new FeatureSet(1 << 2)
 
   /** Explicit reflective proxy definitions. */
-  val ReflectiveProxies = new FeatureSet(1 << 2)
+  val ReflectiveProxies = new FeatureSet(1 << 3)
+
+  /** `TransientTypeRef`s. */
+  val TransientTypeRefs = new FeatureSet(1 << 4)
+
+  /** General typed closures (not only in `NewLambda` nodes). */
+  val TypedClosures = new FeatureSet(1 << 5)
 
   /** Transients that are the result of optimizations. */
-  val OptimizedTransients = new FeatureSet(1 << 3)
+  val OptimizedTransients = new FeatureSet(1 << 6)
 
   /** Records and record types. */
-  val Records = new FeatureSet(1 << 4)
+  val Records = new FeatureSet(1 << 7)
 
   /** Relaxed constructor discipline.
    *
@@ -58,17 +67,24 @@ private[checker] object FeatureSet {
    *  - `this.x = ...` assignments before the delegate call can assign super class fields.
    *  - `StoreModule` can be anywhere, or not be there at all.
    */
-  val RelaxedCtorBodies = new FeatureSet(1 << 5)
+  val RelaxedCtorBodies = new FeatureSet(1 << 8)
 
   // Common sets
 
-  /** Features introduced by the base linker. */
+  /** Features introduced by the base linker.
+   *
+   *  Although `NewLambda` nodes themselves are desugared in the `Desugarer`,
+   *  the corresponding synthetic *classes* already have an existence after the
+   *  `BaseLinker`. They must, since they must participate in the CHA
+   *  performed by the `Analyzer`. So `TransientTypeRef`s and `TypedClosure`s
+   *  can already appear after the `BaseLinker`.
+   */
   private val Linked =
-    OptionalConstructors | ReflectiveProxies
+    OptionalConstructors | ReflectiveProxies | TransientTypeRefs | TypedClosures
 
   /** Features that must be desugared away. */
   private val NeedsDesugaring =
-    LinkTimeProperty
+    LinkTimeProperty | NewLambda
 
   /** IR that is only the result of desugaring (currently empty). */
   private val Desugared =
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala b/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
index 49dc20096e..0156b596e1 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
@@ -466,6 +466,34 @@ private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter,
               i"with non-object result type: $resultType")
         }
 
+      case ApplyTypedClosure(_, fun, args) if featureSet.supports(FeatureSet.TypedClosures) =>
+        typecheck(fun, env)
+        fun.tpe match {
+          case ClosureType(paramTypes, resultType, _) =>
+            for ((paramType, arg) <- paramTypes.zip(args))
+              typecheckExpect(arg, env, paramType)
+          case NothingType | NullType =>
+            for (arg <- args)
+              typecheckExpr(arg, env)
+          case funTpe =>
+            reportError(i"illegal function type for typed closure application: $funTpe")
+            for (arg <- args)
+              typecheckExpr(arg, env)
+        }
+
+      case NewLambda(descriptor, fun) if featureSet.supports(FeatureSet.NewLambda) =>
+        val closureType = ClosureType(descriptor.paramTypes, descriptor.resultType, nullable = false)
+        typecheckExpect(fun, env, closureType)
+
+      case UnaryOp(UnaryOp.CheckNotNull, lhs) =>
+        // CheckNotNull accepts any closure type in addition to `AnyType`
+        lhs.tpe match {
+          case _: ClosureType =>
+            typecheck(lhs, env)
+          case _ =>
+            typecheckAny(lhs, env)
+        }
+
       case UnaryOp(UnaryOp.Array_length, lhs) =>
         // Array_length is a bit special because it allows any non-nullable array type
         typecheck(lhs, env)
@@ -497,7 +525,7 @@ private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter,
             DoubleType
           case String_length =>
             StringType
-          case CheckNotNull | IdentityHashCode | WrapAsThrowable | Throw =>
+          case IdentityHashCode | WrapAsThrowable | Throw =>
             AnyType
           case Class_name | Class_isPrimitive | Class_isInterface |
               Class_isArray | Class_componentType | Class_superClass =>
@@ -695,7 +723,7 @@ private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter,
 
       case _: VarRef =>
 
-      case Closure(arrow, captureParams, params, restParam, body, captureValues) =>
+      case Closure(flags, captureParams, params, restParam, resultType, body, captureValues) =>
         assert(captureParams.size == captureValues.size) // checked by ClassDefChecker
 
         // Check compliance of captureValues wrt. captureParams in the current env
@@ -704,7 +732,7 @@ private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter,
         }
 
         // Then check the closure params and body in its own env
-        typecheckAny(body, Env.empty)
+        typecheckExpect(body, Env.empty, resultType)
 
       case CreateJSClass(className, captureValues) =>
         val clazz = lookupClass(className)
@@ -762,7 +790,8 @@ private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter,
         }
 
       case _:RecordSelect | _:RecordValue | _:Transient |
-          _:JSSuperConstructorCall | _:LinkTimeProperty =>
+          _:JSSuperConstructorCall | _:LinkTimeProperty |
+          _:ApplyTypedClosure | _:NewLambda =>
         reportError("invalid tree")
     }
   }
@@ -797,6 +826,7 @@ private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter,
       case PrimRef(tpe)               => tpe
       case ClassRef(className)        => classNameToType(className)
       case arrayTypeRef: ArrayTypeRef => ArrayType(arrayTypeRef, nullable = true)
+      case typeRef: TransientTypeRef  => typeRef.tpe
     }
   }
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/BaseLinker.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/BaseLinker.scala
index 07eb08b294..62d05ff87e 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/BaseLinker.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/BaseLinker.scala
@@ -77,12 +77,19 @@ final class BaseLinker(config: CommonPhaseConfig, checkIR: Boolean) {
   private def assemble(moduleInitializers: Seq[ModuleInitializer],
       analysis: Analysis)(implicit ec: ExecutionContext): Future[LinkingUnit] = {
     def assembleClass(info: ClassInfo) = {
-      val version = irLoader.irFileVersion(info.className)
-      val syntheticMethods = methodSynthesizer.synthesizeMembers(info, analysis)
+      val (version, classDefFuture) = info.syntheticKind match {
+        case None =>
+          (irLoader.irFileVersion(info.className), irLoader.loadClassDef(info.className))
+        case Some(SyntheticClassKind.Lambda(descriptor)) =>
+          // Not cached; measurements suggest it takes only a few ms for all synthesized classes combined
+          val classDef = LambdaSynthesizer.makeClassDef(descriptor, info.className)
+          (LambdaSynthesizer.constantVersion, Future.successful(classDef))
+      }
+      val syntheticMethodsFuture = methodSynthesizer.synthesizeMembers(info, analysis)
 
       for {
-        classDef <- irLoader.loadClassDef(info.className)
-        syntheticMethods <- syntheticMethods
+        classDef <- classDefFuture
+        syntheticMethods <- syntheticMethodsFuture
       } yield {
         BaseLinker.linkClassDef(classDef, version, syntheticMethods, analysis)
       }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/Desugarer.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/Desugarer.scala
index 65323bfd69..44e2f66d09 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/Desugarer.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/Desugarer.scala
@@ -12,6 +12,8 @@
 
 package org.scalajs.linker.frontend
 
+import scala.collection.mutable
+
 import org.scalajs.logging._
 
 import org.scalajs.linker.standard._
@@ -119,11 +121,28 @@ private[linker] object Desugarer {
   private final class DesugarTransformer(coreSpec: CoreSpec)
       extends ClassTransformer {
 
+    /* Cache the names generated for lambda classes because computing their
+     * `ClassName` is a bit expensive. The constructor names are not expensive,
+     * but we might as well cache them together.
+     */
+    private val syntheticLambdaNamesCache =
+      mutable.Map.empty[NewLambda.Descriptor, (ClassName, MethodName)]
+
+    private def syntheticLambdaNamesFor(descriptor: NewLambda.Descriptor): (ClassName, MethodName) =
+      syntheticLambdaNamesCache.getOrElseUpdate(descriptor, {
+        (LambdaSynthesizer.makeClassName(descriptor), LambdaSynthesizer.makeConstructorName(descriptor))
+      })
+
     override def transform(tree: Tree): Tree = {
       tree match {
         case prop: LinkTimeProperty =>
           coreSpec.linkTimeProperties.transformLinkTimeProperty(prop)
 
+        case NewLambda(descriptor, fun) =>
+          implicit val pos = tree.pos
+          val (className, ctorName) = syntheticLambdaNamesFor(descriptor)
+          New(className, MethodIdent(ctorName), List(transform(fun)))
+
         case _ =>
           super.transform(tree)
       }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/LambdaSynthesizer.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/LambdaSynthesizer.scala
new file mode 100644
index 0000000000..479a149f16
--- /dev/null
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/LambdaSynthesizer.scala
@@ -0,0 +1,178 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package org.scalajs.linker.frontend
+
+import org.scalajs.ir.{ClassKind, Position, SHA1, UTF8String, Version}
+import org.scalajs.ir.Names._
+import org.scalajs.ir.OriginalName.NoOriginalName
+import org.scalajs.ir.Trees._
+import org.scalajs.ir.Types._
+import org.scalajs.ir.WellKnownNames._
+
+import org.scalajs.linker.analyzer.Infos._
+
+private[linker] object LambdaSynthesizer {
+  /* Everything we create has a constant version because the names are derived
+   * from the descriptors themselves.
+   */
+  val constantVersion = Version.fromByte(0)
+
+  private val ClosureTypeRefName = LabelName("c")
+  private val fFieldSimpleName = SimpleFieldName("f")
+
+  /** Deterministically makes a class name for the lambda class given its descriptor.
+   *
+   *  This computation is mildly expensive. Callers should cache it if possible.
+   */
+  def makeClassName(descriptor: NewLambda.Descriptor): ClassName = {
+    // Choose a base class name that will "makes sense" for debugging purposes
+    val baseClassName = {
+      if (descriptor.superClass == ObjectClass && descriptor.interfaces.nonEmpty)
+        descriptor.interfaces.head
+      else
+        descriptor.superClass
+    }
+
+    val digestBuilder = new SHA1.DigestBuilder()
+    digestBuilder.updateUTF8String(descriptor.superClass.encoded)
+    for (intf <- descriptor.interfaces)
+      digestBuilder.updateUTF8String(intf.encoded)
+
+    // FIXME This is not efficient
+    digestBuilder.updateUTF8String(UTF8String(descriptor.methodName.nameString))
+
+    // No need the hash the paramTypes and resultType because they derive from the method name
+
+    val digest = digestBuilder.finalizeDigest()
+
+    /* The "$$Lambda" segment is meant to match the way LambdaMetaFactory
+     * names generated classes. This is mostly for test compatibility
+     * purposes (like partests that test the class name to tell whether a
+     * lambda was indeed encoded as an LMF).
+     */
+    val suffixBuilder = new java.lang.StringBuilder(".$$Lambda$")
+    for (b <- digest) {
+      val i = b & 0xff
+      suffixBuilder.append(Character.forDigit(i >> 4, 16)).append(Character.forDigit(i & 0x0f, 16))
+    }
+
+    ClassName(baseClassName.encoded ++ UTF8String(suffixBuilder.toString()))
+  }
+
+  /** Computes the constructor name for the lambda class of a descriptor. */
+  def makeConstructorName(descriptor: NewLambda.Descriptor): MethodName = {
+    val closureTypeNonNull =
+      ClosureType(descriptor.paramTypes, descriptor.resultType, nullable = false)
+    MethodName.constructor(TransientTypeRef(ClosureTypeRefName)(closureTypeNonNull) :: Nil)
+  }
+
+  /** Computes the `ClassInfo` of a lambda class, for use by the `Analyzer`.
+   *
+   *  The `className` must be the result of `makeClassName(descriptor)`.
+   */
+  def makeClassInfo(descriptor: NewLambda.Descriptor, className: ClassName): ClassInfo = {
+    val methodInfos = Array.fill(MemberNamespace.Count)(Map.empty[MethodName, MethodInfo])
+
+    val fFieldName = FieldName(className, fFieldSimpleName)
+    val ctorName = makeConstructorName(descriptor)
+
+    val ctorInfo: MethodInfo = {
+      val b = new ReachabilityInfoBuilder(constantVersion)
+      b.addFieldWritten(fFieldName)
+      b.addMethodCalledStatically(descriptor.superClass,
+          NamespacedMethodName(MemberNamespace.Constructor, NoArgConstructorName))
+      MethodInfo(isAbstract = false, b.result())
+    }
+    methodInfos(MemberNamespace.Constructor.ordinal) =
+      Map(ctorName -> ctorInfo)
+
+    val implMethodInfo: MethodInfo = {
+      val b = new ReachabilityInfoBuilder(constantVersion)
+      b.addFieldRead(fFieldName)
+      MethodInfo(isAbstract = false, b.result())
+    }
+    methodInfos(MemberNamespace.Public.ordinal) =
+      Map(descriptor.methodName -> implMethodInfo)
+
+    new ClassInfo(className, ClassKind.Class,
+        Some(descriptor.superClass), descriptor.interfaces,
+        jsNativeLoadSpec = None, referencedFieldClasses = Map.empty, methodInfos,
+        jsNativeMembers = Map.empty, jsMethodProps = Nil, topLevelExports = Nil)
+  }
+
+  /** Synthesizes the `ClassDef` for a lambda class, for use by the `BaseLinker`.
+   *
+   *  The `className` must be the result of `makeClassName(descriptor)`.
+   */
+  def makeClassDef(descriptor: NewLambda.Descriptor, className: ClassName): ClassDef = {
+    implicit val pos = Position.NoPosition
+
+    import descriptor._
+
+    val closureType = ClosureType(paramTypes, resultType, nullable = true)
+
+    val thiz = This()(ClassType(className, nullable = false))
+
+    val fFieldIdent = FieldIdent(FieldName(className, fFieldSimpleName))
+    val fFieldDef = FieldDef(MemberFlags.empty, fFieldIdent, NoOriginalName, closureType)
+    val fFieldSelect = Select(thiz, fFieldIdent)(closureType)
+
+    val ctorParamDef = ParamDef(LocalIdent(LocalName("f")), NoOriginalName,
+        closureType.toNonNullable, mutable = false)
+    val ctorDef = MethodDef(
+      MemberFlags.empty.withNamespace(MemberNamespace.Constructor),
+      MethodIdent(makeConstructorName(descriptor)),
+      NoOriginalName,
+      ctorParamDef :: Nil,
+      VoidType,
+      Some(
+        Block(
+          Assign(fFieldSelect, ctorParamDef.ref),
+          ApplyStatically(ApplyFlags.empty.withConstructor(true), thiz,
+              superClass, MethodIdent(NoArgConstructorName), Nil)(VoidType)
+        )
+      )
+    )(OptimizerHints.empty, constantVersion)
+
+    val methodParamDefs = paramTypes.zipWithIndex.map { case (paramType, index) =>
+      ParamDef(LocalIdent(LocalName("x" + index)), NoOriginalName, paramType, mutable = false)
+    }
+    val methodDef = MethodDef(
+      MemberFlags.empty,
+      MethodIdent(methodName),
+      NoOriginalName,
+      methodParamDefs,
+      resultType,
+      Some(
+        ApplyTypedClosure(ApplyFlags.empty, fFieldSelect, methodParamDefs.map(_.ref))
+      )
+    )(OptimizerHints.empty, constantVersion)
+
+    ClassDef(
+      ClassIdent(className),
+      NoOriginalName,
+      ClassKind.Class,
+      jsClassCaptures = None,
+      superClass = Some(ClassIdent(superClass)),
+      interfaces = interfaces.map(ClassIdent(_)),
+      jsSuperClass = None,
+      jsNativeLoadSpec = None,
+      fields = List(fFieldDef),
+      methods = List(ctorDef, methodDef),
+      jsConstructor = None,
+      jsMethodProps = Nil,
+      jsNativeMembers = Nil,
+      topLevelExportDefs = Nil
+    )(OptimizerHints.empty.withInline(true))
+  }
+}
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/MethodSynthesizer.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/MethodSynthesizer.scala
index 56d3502771..d352a1d4ac 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/MethodSynthesizer.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/MethodSynthesizer.scala
@@ -151,8 +151,28 @@ private[frontend] final class MethodSynthesizer(
 
   private def findMethodDef(classInfo: ClassInfo, methodName: MethodName)(
       implicit ec: ExecutionContext): Future[MethodDef] = {
+    val classDefFuture = classInfo.syntheticKind match {
+      case None =>
+        inputProvider.loadClassDef(classInfo.className)
+
+      case Some(SyntheticClassKind.Lambda(descriptor)) =>
+        /* We are *re*-generating the full ClassDef, in addition to the
+         * generation done in `BaseLinker`.
+         *
+         * This happens at most once per lambda class (hopefully never for
+         * most of them), because:
+         *
+         * - lambda classes are never interfaces, so we must be generating a
+         *   reflective proxy, not a default bridge;
+         * - lambda classes are never extended, so we don't get here through
+         *   an inheritance chain, only when synthesizing methods in the same class;
+         * - lambda classes have a single non-constructor method.
+         */
+        Future.successful(LambdaSynthesizer.makeClassDef(descriptor, classInfo.className))
+    }
+
     for {
-      classDef <- inputProvider.loadClassDef(classInfo.className)
+      classDef <- classDefFuture
     } yield {
       classDef.methods.find { mDef =>
         mDef.flags.namespace == MemberNamespace.Public && mDef.methodName == methodName
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/SyntheticClassKind.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/SyntheticClassKind.scala
new file mode 100644
index 0000000000..98dfd1506d
--- /dev/null
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/SyntheticClassKind.scala
@@ -0,0 +1,21 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package org.scalajs.linker.frontend
+
+import org.scalajs.ir.Trees.NewLambda
+
+sealed abstract class SyntheticClassKind
+
+object SyntheticClassKind {
+  final case class Lambda(descriptor: NewLambda.Descriptor) extends SyntheticClassKind
+}
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
index 53320ad923..38bdb804c3 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
@@ -880,7 +880,7 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
         case _:VarRef | _:Literal | _:Skip =>
           true
 
-        case Closure(_, _, _, _, _, captureValues) =>
+        case Closure(_, _, _, _, _, _, captureValues) =>
           captureValues.forall(isTriviallySideEffectFree(_))
 
         case UnaryOp(UnaryOp.CheckNotNull, expr) =>
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
index fb07015f30..6471b07ff7 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
@@ -522,6 +522,12 @@ private[optimizer] abstract class OptimizerCore(
           pretransformApplyDynamicImport(tree, isStat)(finishTransform(isStat))
         }
 
+      case tree: ApplyTypedClosure =>
+        trampoline {
+          pretransformApplyTypedClosure(tree, isStat, usePreTransform = false)(
+              finishTransform(isStat))
+        }
+
       case tree: UnaryOp =>
         trampoline {
           pretransformUnaryOp(tree)(finishTransform(isStat))
@@ -652,11 +658,12 @@ private[optimizer] abstract class OptimizerCore(
           pretransformExpr(tree)(finishTransform(isStat))
         }
 
-      case Closure(arrow, captureParams, params, restParam, body, captureValues) =>
+      case Closure(flags, captureParams, params, restParam, resultType, body, captureValues) =>
         trampoline {
           pretransformExprs(captureValues) { tcaptureValues =>
-            transformClosureCommon(arrow, captureParams, params, restParam, body,
-                tcaptureValues)(finishTransform(isStat))
+            transformClosureCommon(flags, captureParams, params, restParam,
+                resultType, body, tcaptureValues)(
+                finishTransform(isStat))
           }
         }
 
@@ -679,7 +686,7 @@ private[optimizer] abstract class OptimizerCore(
           _:JSGlobalRef | _:JSTypeOfGlobalRef | _:Literal =>
         tree
 
-      case _ =>
+      case _:LinkTimeProperty | _:NewLambda | _:RecordSelect | _:Transient =>
         throw new IllegalArgumentException(
             s"Invalid tree in transform of class ${tree.getClass.getName}: $tree")
     }
@@ -688,9 +695,9 @@ private[optimizer] abstract class OptimizerCore(
     else result
   }
 
-  private def transformClosureCommon(arrow: Boolean,
+  private def transformClosureCommon(flags: ClosureFlags,
       captureParams: List[ParamDef], params: List[ParamDef],
-      restParam: Option[ParamDef], body: Tree,
+      restParam: Option[ParamDef], resultType: Type, body: Tree,
       tcaptureValues: List[PreTransform])(cont: PreTransCont)(
       implicit scope: Scope, pos: Position): TailRec[Tree] = {
 
@@ -704,7 +711,7 @@ private[optimizer] abstract class OptimizerCore(
     }
 
     val thisLocalDef =
-      if (arrow) None
+      if (flags.arrow) None
       else Some(newThisLocalDef(AnyType))
 
     val innerEnv = OptEnv.Empty
@@ -714,8 +721,11 @@ private[optimizer] abstract class OptimizerCore(
 
     transformCapturingBody(captureParams, tcaptureValues, body, innerEnv) {
       (newCaptureParams, newCaptureValues, newBody) =>
-        PreTransTree(Closure(arrow, newCaptureParams, newParams, newRestParam,
-            newBody, newCaptureValues))
+        val newClosure = {
+          Closure(flags, newCaptureParams, newParams, newRestParam, resultType,
+              newBody, newCaptureValues)
+        }
+        PreTransTree(newClosure, RefinedType(newClosure.tpe, isExact = flags.typed))
     } (cont)
   }
 
@@ -939,6 +949,10 @@ private[optimizer] abstract class OptimizerCore(
       case tree: ApplyDynamicImport =>
         pretransformApplyDynamicImport(tree, isStat = false)(cont)
 
+      case tree: ApplyTypedClosure =>
+        pretransformApplyTypedClosure(tree, isStat = false,
+            usePreTransform = true)(cont)
+
       case tree: UnaryOp =>
         pretransformUnaryOp(tree)(cont)
 
@@ -988,13 +1002,14 @@ private[optimizer] abstract class OptimizerCore(
           cont(foldAsInstanceOf(texpr, tpe))
         }
 
-      case Closure(arrow, captureParams, params, restParam, body, captureValues) =>
+      case Closure(flags, captureParams, params, restParam, resultType, body, captureValues) =>
         pretransformExprs(captureValues) { tcaptureValues =>
           def default(): TailRec[Tree] = {
-            transformClosureCommon(arrow, captureParams, params, restParam, body, tcaptureValues)(cont)
+            transformClosureCommon(flags, captureParams, params, restParam,
+                resultType, body, tcaptureValues)(cont)
           }
 
-          if (!arrow || restParam.isDefined) {
+          if (!flags.arrow || restParam.isDefined) {
             /* TentativeClosureReplacement assumes there are no rest
              * parameters, because that would not be inlineable anyway.
              * Likewise, it assumes that there is no binding for `this` nor for
@@ -1013,10 +1028,10 @@ private[optimizer] abstract class OptimizerCore(
               }
               withNewLocalDefs(captureBindings) { (captureLocalDefs, cont1) =>
                 val replacement = TentativeClosureReplacement(
-                    captureParams, params, body, captureLocalDefs,
+                    flags, captureParams, params, resultType, body, captureLocalDefs,
                     alreadyUsed = newSimpleState(Unused), cancelFun)
                 val localDef = LocalDef(
-                    RefinedType(AnyNotNullType),
+                    RefinedType(tree.tpe, isExact = flags.typed),
                     mutable = false,
                     replacement)
                 cont1(localDef.toPreTransform)
@@ -1595,7 +1610,7 @@ private[optimizer] abstract class OptimizerCore(
       Block(checkNotNullStatement(array)(stat.pos), keepOnlySideEffects(index))(stat.pos)
     case Select(qualifier, _) =>
       checkNotNullStatement(qualifier)(stat.pos)
-    case Closure(_, _, _, _, _, captureValues) =>
+    case Closure(_, _, _, _, _, _, captureValues) =>
       Block(captureValues.map(keepOnlySideEffects))(stat.pos)
     case UnaryOp(op, arg) if UnaryOp.isSideEffectFreeOp(op) =>
       keepOnlySideEffects(arg)
@@ -1882,8 +1897,10 @@ private[optimizer] abstract class OptimizerCore(
         case _: Literal =>
           NotFoundPureSoFar
 
-        case Closure(arrow, captureParams, params, restParam, body, captureValues) =>
-          recs(captureValues).mapOrKeepGoing(Closure(arrow, captureParams, params, restParam, body, _))
+        case Closure(flags, captureParams, params, restParam, resultType, body, captureValues) =>
+          recs(captureValues).mapOrKeepGoing { newCaptureValues =>
+            Closure(flags, captureParams, params, restParam, resultType, body, newCaptureValues)
+          }
 
         case _ =>
           Failed
@@ -2259,8 +2276,9 @@ private[optimizer] abstract class OptimizerCore(
                 if (!importReplacement.used.value.isUsed)
                   cancelFun()
 
-                val closure = Closure(arrow = true, newCaptureParams, List(moduleParam),
-                    restParam = None, newBody, newCaptureValues)
+                val closure = Closure(ClosureFlags.arrow, newCaptureParams,
+                    List(moduleParam), restParam = None, resultType = AnyType,
+                    newBody, newCaptureValues)
 
                 val newTree = JSImport(config.coreSpec.moduleKind, jsNativeLoadSpec.module, closure)
 
@@ -2379,9 +2397,9 @@ private[optimizer] abstract class OptimizerCore(
         tfun match {
           case PreTransLocalDef(LocalDef(_, false,
               closure @ TentativeClosureReplacement(
-                  captureParams, params, body, captureLocalDefs,
-                  alreadyUsed, cancelFun)))
-              if !alreadyUsed.value.isUsed && argsNoSpread.size <= params.size =>
+                  flags, captureParams, params, resultType, body,
+                  captureLocalDefs, alreadyUsed, cancelFun)))
+              if !flags.typed && !alreadyUsed.value.isUsed && argsNoSpread.size <= params.size =>
             alreadyUsed.value = alreadyUsed.value.inc
             val missingArgCount = params.size - argsNoSpread.size
             val expandedArgs =
@@ -2408,6 +2426,36 @@ private[optimizer] abstract class OptimizerCore(
     }
   }
 
+  private def pretransformApplyTypedClosure(tree: ApplyTypedClosure,
+      isStat: Boolean, usePreTransform: Boolean)(
+      cont: PreTransCont)(
+      implicit scope: Scope): TailRec[Tree] = {
+    val ApplyTypedClosure(flags, fun, args) = tree
+    implicit val pos = tree.pos
+
+    pretransformExpr(fun) { tfun =>
+      tfun match {
+        case PreTransLocalDef(LocalDef(_, false,
+            closure @ TentativeClosureReplacement(
+                flags, captureParams, params, resultType, body,
+                captureLocalDefs, alreadyUsed, cancelFun)))
+            if flags.typed && !alreadyUsed.value.isUsed =>
+          alreadyUsed.value = alreadyUsed.value.inc
+          pretransformExprs(args) { targs =>
+            inlineBody(
+                optReceiver = None,
+                captureParams ++ params, resultType, body,
+                captureLocalDefs.map(_.toPreTransform) ++ targs, isStat,
+                usePreTransform)(cont)
+          }
+
+        case _ =>
+          cont(ApplyTypedClosure(flags, finishTransformExpr(tfun),
+              args.map(transformExpr)).toPreTransform)
+      }
+    }
+  }
+
   private def transformExprsOrSpreads(trees: List[TreeOrJSSpread])(
       implicit scope: Scope): List[TreeOrJSSpread] = {
 
@@ -2497,10 +2545,10 @@ private[optimizer] abstract class OptimizerCore(
 
       case PreTransLocalDef(localDef) =>
         (localDef.replacement match {
-          case TentativeClosureReplacement(_, _, _, _, _, _)    => true
-          case ReplaceWithRecordVarRef(_, _, _, _)              => true
-          case InlineClassBeingConstructedReplacement(_, _, _)  => true
-          case InlineClassInstanceReplacement(_, _, _)          => true
+          case _: TentativeClosureReplacement            => true
+          case _: ReplaceWithRecordVarRef                => true
+          case _: InlineClassBeingConstructedReplacement => true
+          case _: InlineClassInstanceReplacement         => true
           case _ =>
             isTypeLikelyOptimizable(localDef.tpe)
         }) && !isLocalOnlyInlineType(localDef.tpe)
@@ -3908,6 +3956,8 @@ private[optimizer] abstract class OptimizerCore(
         "[" * dimensions + primRef.charCode
       case ArrayTypeRef(ClassRef(className), dimensions) =>
         "[" * dimensions + "L" + mappedClassName(className) + ";"
+      case typeRef: TransientTypeRef =>
+        throw new IllegalArgumentException(typeRef.toString())
     }
   }
 
@@ -5841,7 +5891,7 @@ private[optimizer] object OptimizerCore {
       case ReplaceWithConstant(value) =>
         value
 
-      case TentativeClosureReplacement(_, _, _, _, _, cancelFun) =>
+      case TentativeClosureReplacement(_, _, _, _, _, _, _, cancelFun) =>
         cancelFun()
 
       case InlineClassBeingConstructedReplacement(_, _, cancelFun) =>
@@ -5869,7 +5919,7 @@ private[optimizer] object OptimizerCore {
       (this eq that) || (replacement match {
         case ReplaceWithOtherLocalDef(localDef) =>
           localDef.contains(that)
-        case TentativeClosureReplacement(_, _, _, captureLocalDefs, _, _) =>
+        case TentativeClosureReplacement(_, _, _, _, _, captureLocalDefs, _, _) =>
           captureLocalDefs.exists(_.contains(that))
         case InlineClassBeingConstructedReplacement(_, fieldLocalDefs, _) =>
           fieldLocalDefs.valuesIterator.exists(_.contains(that))
@@ -5924,9 +5974,9 @@ private[optimizer] object OptimizerCore {
       value: Tree) extends LocalDefReplacement
 
   private final case class TentativeClosureReplacement(
-      captureParams: List[ParamDef], params: List[ParamDef], body: Tree,
-      captureValues: List[LocalDef],
-      alreadyUsed: SimpleState[IsUsed],
+      flags: ClosureFlags, captureParams: List[ParamDef],
+      params: List[ParamDef], resultType: Type, body: Tree,
+      captureValues: List[LocalDef], alreadyUsed: SimpleState[IsUsed],
       cancelFun: CancelFun) extends LocalDefReplacement
 
   private final case class InlineClassBeingConstructedReplacement(
@@ -6349,7 +6399,8 @@ private[optimizer] object OptimizerCore {
 
           val unitPromise = JSMethodApply(
               JSGlobalRef("Promise"), StringLiteral("resolve"), List(Undefined()))
-          genThen(unitPromise, Closure(arrow = true, Nil, Nil, None, require, Nil))
+          genThen(unitPromise,
+              Closure(ClosureFlags.arrow, Nil, Nil, None, AnyType, require, Nil))
       }
 
       genThen(importTree, callback)
@@ -6826,6 +6877,7 @@ private[optimizer] object OptimizerCore {
       case Apply(_, receiver, _, args)              => areSimpleArgs(receiver :: args)
       case ApplyStatically(_, receiver, _, _, args) => areSimpleArgs(receiver :: args)
       case ApplyStatic(_, _, _, args)               => areSimpleArgs(args)
+      case ApplyTypedClosure(_, fun, args)          => areSimpleArgs(fun :: args)
       case Select(qual, _)                          => isSimpleArg(qual)
       case IsInstanceOf(inner, _)                   => isSimpleArg(inner)
 
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/IRCheckerTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/IRCheckerTest.scala
index 25b641d900..73dce25631 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/IRCheckerTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/IRCheckerTest.scala
@@ -446,6 +446,7 @@ object IRCheckerTest {
           new ClassTransformer {
             override def transform(tree: Tree): Tree = tree match {
               case tree: LinkTimeProperty => zeroOf(tree.tpe)
+              case tree: NewLambda        => UnaryOp(UnaryOp.Throw, Null())
               case _                      => super.transform(tree)
             }
           }.transformClassDef(tree)
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/OptimizerTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/OptimizerTest.scala
index c7bc282ff2..61fb3992c2 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/OptimizerTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/OptimizerTest.scala
@@ -334,10 +334,11 @@ class OptimizerTest {
                  */
                 mainMethodDef({
                   val closure = Closure(
-                    arrow = true,
+                    ClosureFlags.arrow,
                     (1 to 5).toList.map(i => paramDef(LocalName("x" + i), IntType)),
                     Nil,
                     None,
+                    AnyType,
                     Block(
                       consoleLog(VarRef(x4)(IntType)),
                       consoleLog(VarRef(x2)(IntType))
@@ -429,7 +430,7 @@ class OptimizerTest {
   def testFoldLiteralClosureCaptures(): AsyncResult = await {
     val classDefs = Seq(
       mainTestClassDef({
-        consoleLog(Closure(true, List(paramDef("x", IntType)), Nil, None, {
+        consoleLog(Closure(ClosureFlags.arrow, List(paramDef("x", IntType)), Nil, None, AnyType, {
           BinaryOp(BinaryOp.Int_+, VarRef("x")(IntType), int(2))
         }, List(int(3))))
       })
@@ -463,8 +464,8 @@ class OptimizerTest {
               mainMethodDef(Block(
                 VarDef("x", NON, IntType, mutable = false,
                     ApplyStatic(EAF, MainTestClassName, calc, Nil)(IntType)),
-                consoleLog(Closure(true, List(paramDef("y", IntType)), Nil, None,
-                    VarRef("y")(IntType), List(VarRef("x")(IntType))))
+                consoleLog(Closure(ClosureFlags.arrow, List(paramDef("y", IntType)), Nil, None,
+                    AnyType, VarRef("y")(IntType), List(VarRef("x")(IntType))))
               ))
           )
       )
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/checker/ClassDefCheckerTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/checker/ClassDefCheckerTest.scala
index c29c3443c4..25aaa353da 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/checker/ClassDefCheckerTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/checker/ClassDefCheckerTest.scala
@@ -411,7 +411,7 @@ class ClassDefCheckerTest {
     // Capture param of a Closure
     assertError(
       mainTestClassDef(Block(
-        Closure(arrow = true, List(thisParamDef), Nil, None, int(5), List(int(6)))
+        Closure(ClosureFlags.arrow, List(thisParamDef), Nil, None, AnyType, int(5), List(int(6)))
       )),
       "Illegal definition of a variable with name `this`"
     )
@@ -419,7 +419,7 @@ class ClassDefCheckerTest {
     // Param of a closure
     assertError(
       mainTestClassDef(Block(
-        Closure(arrow = true, Nil, List(thisParamDef), None, int(5), Nil)
+        Closure(ClosureFlags.arrow, Nil, List(thisParamDef), None, AnyType, int(5), Nil)
       )),
       "Illegal definition of a variable with name `this`"
     )
@@ -427,7 +427,7 @@ class ClassDefCheckerTest {
     // Rest param of a closure
     assertError(
       mainTestClassDef(Block(
-        Closure(arrow = true, Nil, Nil, Some(thisParamDef), int(5), Nil)
+        Closure(ClosureFlags.arrow, Nil, Nil, Some(thisParamDef), AnyType, int(5), Nil)
       )),
       "Illegal definition of a variable with name `this`"
     )
@@ -534,19 +534,19 @@ class ClassDefCheckerTest {
         "Variable `this` of type Foo! typed as Foo")
 
     testThisTypeError(static = false,
-        Closure(arrow = true, Nil, Nil, None, This()(VoidType), Nil),
+        Closure(ClosureFlags.arrow, Nil, Nil, None, AnyType, This()(VoidType), Nil),
         "Cannot find variable `this` in scope")
 
     testThisTypeError(static = false,
-        Closure(arrow = true, Nil, Nil, None, This()(AnyType), Nil),
+        Closure(ClosureFlags.arrow, Nil, Nil, None, AnyType, This()(AnyType), Nil),
         "Cannot find variable `this` in scope")
 
     testThisTypeError(static = false,
-        Closure(arrow = false, Nil, Nil, None, This()(VoidType), Nil),
+        Closure(ClosureFlags.function, Nil, Nil, None, AnyType, This()(VoidType), Nil),
         "Variable `this` of type any typed as void")
 
     testThisTypeError(static = false,
-        Closure(arrow = false, Nil, Nil, None, This()(ClassType("Foo", nullable = false)), Nil),
+        Closure(ClosureFlags.function, Nil, Nil, None, AnyType, This()(ClassType("Foo", nullable = false)), Nil),
         "Variable `this` of type any typed as Foo!")
   }
 
diff --git a/project/BinaryIncompatibilities.scala b/project/BinaryIncompatibilities.scala
index a156e6737b..b361c1701b 100644
--- a/project/BinaryIncompatibilities.scala
+++ b/project/BinaryIncompatibilities.scala
@@ -16,6 +16,10 @@ object BinaryIncompatibilities {
     ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Types.BoxedClassToPrimType"),
     ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Types.PrimTypeToBoxedClass"),
 
+    // !!! Breaking, OK in minor release
+    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.InvalidIRException.tree"),
+    ProblemFilters.exclude[Problem]("org.scalajs.ir.Trees#Closure.*"),
+
     // !!! Breaking, PrimRef is not a case class anymore
     ProblemFilters.exclude[MissingTypesProblem]("org.scalajs.ir.Types$PrimRef"),
     ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Types#PrimRef.canEqual"),
diff --git a/project/Build.scala b/project/Build.scala
index d08f6224c9..bc2f0376d4 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -2049,15 +2049,15 @@ object Build {
           case `default212Version` =>
             if (!useMinifySizes) {
               Some(ExpectedSizes(
-                  fastLink = 622000 to 623000,
+                  fastLink = 624000 to 625000,
                   fullLink = 96000 to 97000,
                   fastLinkGz = 75000 to 79000,
                   fullLinkGz = 25000 to 26000,
               ))
             } else {
               Some(ExpectedSizes(
-                  fastLink = 422000 to 423000,
-                  fullLink = 280000 to 281000,
+                  fastLink = 424000 to 425000,
+                  fullLink = 281000 to 282000,
                   fastLinkGz = 60000 to 61000,
                   fullLinkGz = 43000 to 44000,
               ))
@@ -2066,15 +2066,15 @@ object Build {
           case `default213Version` =>
             if (!useMinifySizes) {
               Some(ExpectedSizes(
-                  fastLink = 439000 to 440000,
-                  fullLink = 92000 to 93000,
+                  fastLink = 442000 to 443000,
+                  fullLink = 93000 to 94000,
                   fastLinkGz = 57000 to 58000,
                   fullLinkGz = 25000 to 26000,
               ))
             } else {
               Some(ExpectedSizes(
-                  fastLink = 298000 to 299000,
-                  fullLink = 256000 to 257000,
+                  fastLink = 299000 to 300000,
+                  fullLink = 257000 to 258000,
                   fastLinkGz = 47000 to 48000,
                   fullLinkGz = 42000 to 43000,
               ))
diff --git a/project/JavalibIRCleaner.scala b/project/JavalibIRCleaner.scala
index 87095c1265..be6103d72c 100644
--- a/project/JavalibIRCleaner.scala
+++ b/project/JavalibIRCleaner.scala
@@ -453,9 +453,9 @@ final class JavalibIRCleaner(baseDirectoryURI: URI) {
         case t @ VarRef(ident) =>
           VarRef(ident)(transformType(t.tpe))
 
-        case Closure(arrow, captureParams, params, restParam, body, captureValues) =>
-          Closure(arrow, transformParamDefs(captureParams), transformParamDefs(params),
-              restParam, body, captureValues)
+        case Closure(flags, captureParams, params, restParam, resultType, body, captureValues) =>
+          Closure(flags, transformParamDefs(captureParams), transformParamDefs(params),
+              restParam, resultType, body, captureValues)
 
         case _ =>
           tree
@@ -522,9 +522,10 @@ final class JavalibIRCleaner(baseDirectoryURI: URI) {
 
     private def transformTypeRef(typeRef: TypeRef)(
         implicit pos: Position): TypeRef = typeRef match {
-      case typeRef: PrimRef      => typeRef
-      case typeRef: ClassRef     => transformClassRef(typeRef)
-      case typeRef: ArrayTypeRef => transformArrayTypeRef(typeRef)
+      case typeRef: PrimRef          => typeRef
+      case typeRef: ClassRef         => transformClassRef(typeRef)
+      case typeRef: ArrayTypeRef     => transformArrayTypeRef(typeRef)
+      case typeRef: TransientTypeRef => TransientTypeRef(typeRef.name)(transformType(typeRef.tpe))
     }
 
     private def postTransformChecks(classDef: ClassDef): Unit = {
@@ -551,7 +552,9 @@ final class JavalibIRCleaner(baseDirectoryURI: URI) {
           }
         case ArrayType(arrayTypeRef, nullable) =>
           ArrayType(transformArrayTypeRef(arrayTypeRef), nullable)
-        case _ =>
+        case ClosureType(paramTypes, resultType, nullable) =>
+          ClosureType(paramTypes.map(transformType(_)), transformType(resultType), nullable)
+        case AnyType | AnyNotNullType | _:PrimType | _:RecordType =>
           tpe
       }
     }
diff --git a/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/SAMWithOverridingBridgesTest.scala b/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/SAMWithOverridingBridgesTest.scala
index 53bda11da3..b5daaff5c3 100644
--- a/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/SAMWithOverridingBridgesTest.scala
+++ b/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/SAMWithOverridingBridgesTest.scala
@@ -31,6 +31,8 @@ class SAMWithOverridingBridgesTest {
   @Test def testVariantB(): Unit = {
     import VariantB._
 
+    val it = new It
+
     val s1: SAM_A = () => it
     val s2: SAM_A1 = () => it
     val s3: SAM_B = () => it
@@ -103,7 +105,7 @@ object SAMWithOverridingBridgesTest {
     trait A
     trait B extends A
     trait C extends B
-    object it extends C
+    class It extends C
 
     /* try as many weird diamondy things as I can think of */
 

From 9cb865f8aac8fac399a0ebe48259aed9eabc47df Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Fri, 14 Mar 2025 15:25:09 +0100
Subject: [PATCH 267/298] Fix #5097: Implement most of
 `ju.random.RandomGenerator`.

It is bit-for-bit compatible with what the JDK produces.

We did not implement the sub-interfaces of `RandomGenerator`.

We also did not implement the methods `nextGaussian` and
`nextExponential`.
---
 javalib/src/main/scala/java/util/Random.scala |  18 +-
 .../scala/java/util/SplittableRandom.scala    |  32 +-
 .../util/concurrent/ThreadLocalRandom.scala   |  93 ----
 .../java/util/random/RandomGenerator.scala    | 335 ++++++++++++++
 project/Build.scala                           |   1 +
 .../util/random/RandomGeneratorTest.scala     | 433 ++++++++++++++++++
 6 files changed, 790 insertions(+), 122 deletions(-)
 create mode 100644 javalib/src/main/scala/java/util/random/RandomGenerator.scala
 create mode 100644 test-suite/shared/src/test/require-jdk17/org/scalajs/testsuite/javalib/util/random/RandomGeneratorTest.scala

diff --git a/javalib/src/main/scala/java/util/Random.scala b/javalib/src/main/scala/java/util/Random.scala
index f0452ffb0d..7840b8c3c1 100644
--- a/javalib/src/main/scala/java/util/Random.scala
+++ b/javalib/src/main/scala/java/util/Random.scala
@@ -17,7 +17,11 @@ import scala.annotation.tailrec
 import scala.scalajs.js
 import scala.scalajs.LinkingInfo
 
-class Random(seed_in: Long) extends AnyRef with java.io.Serializable {
+import java.util.random.RandomGenerator
+
+class Random(seed_in: Long)
+    extends AnyRef with RandomGenerator with java.io.Serializable {
+
   /* This class has two different implementations of seeding and computing
    * bits, depending on whether we are on Wasm or JS. On Wasm, we use the
    * implementation specified in the JavaDoc verbatim. On JS, however, that is
@@ -108,16 +112,16 @@ class Random(seed_in: Long) extends AnyRef with java.io.Serializable {
     result32 >>> (32 - bits)
   }
 
-  def nextDouble(): Double = {
+  override def nextDouble(): Double = {
     // ((next(26).toLong << 27) + next(27)) / (1L << 53).toDouble
     ((next(26).toDouble * (1L << 27).toDouble) + next(27).toDouble) / (1L << 53).toDouble
   }
 
-  def nextBoolean(): Boolean = next(1) != 0
+  override def nextBoolean(): Boolean = next(1) != 0
 
-  def nextInt(): Int = next(32)
+  override def nextInt(): Int = next(32)
 
-  def nextInt(n: Int): Int = {
+  override def nextInt(n: Int): Int = {
     if (n <= 0) {
       throw new IllegalArgumentException("n must be positive")
     } else if ((n & -n) == n) { // i.e., n is a power of 2
@@ -148,12 +152,12 @@ class Random(seed_in: Long) extends AnyRef with java.io.Serializable {
 
   def nextLong(): Long = (next(32).toLong << 32) + next(32)
 
-  def nextFloat(): Float = {
+  override def nextFloat(): Float = {
     // next(24).toFloat / (1 << 24).toFloat
     (next(24).toDouble / (1 << 24).toDouble).toFloat
   }
 
-  def nextBytes(bytes: Array[Byte]): Unit = {
+  override def nextBytes(bytes: Array[Byte]): Unit = {
     var i = 0
     while (i < bytes.length) {
       var rnd = nextInt()
diff --git a/javalib/src/main/scala/java/util/SplittableRandom.scala b/javalib/src/main/scala/java/util/SplittableRandom.scala
index 9d394b909c..8fced3e262 100644
--- a/javalib/src/main/scala/java/util/SplittableRandom.scala
+++ b/javalib/src/main/scala/java/util/SplittableRandom.scala
@@ -12,6 +12,8 @@
 
 package java.util
 
+import java.util.random.RandomGenerator
+
 /*
  * This is a clean room implementation derived from the original paper
  * and Java implementation mentioned there:
@@ -23,7 +25,6 @@ package java.util
  */
 private object SplittableRandom {
 
-  private final val DoubleULP = 1.0 / (1L << 53)
   private final val GoldenGamma = 0x9e3779b97f4a7c15L
 
   private var defaultGen: Long = new Random().nextLong()
@@ -80,7 +81,8 @@ private object SplittableRandom {
 
 }
 
-final class SplittableRandom private (private var seed: Long, gamma: Long) {
+final class SplittableRandom private (private var seed: Long, gamma: Long)
+    extends RandomGenerator {
   import SplittableRandom._
 
   def this(seed: Long) = {
@@ -106,27 +108,13 @@ final class SplittableRandom private (private var seed: Long, gamma: Long) {
     seed
   }
 
-  def nextInt(): Int = mix32(nextSeed())
-
-  //def nextInt(bound: Int): Int
-
-  //def nextInt(origin: Int, bound: Int): Int
+  /* According to the JavaDoc, this method is not overridden anymore.
+   * However, if we remove our override, we break tests in
+   * `SplittableRandomTest`. I don't know how the JDK produces the values it
+   * produces without that override. So we keep it on our side.
+   */
+  override def nextInt(): Int = mix32(nextSeed())
 
   def nextLong(): Long = mix64(nextSeed())
 
-  //def nextLong(bound: Long): Long
-
-  //def nextLong(origin: Long, bound: Long): Long
-
-  def nextDouble(): Double =
-    (nextLong() >>> 11).toDouble * DoubleULP
-
-  //def nextDouble(bound: Double): Double
-
-  //def nextDouble(origin: Double, bound: Double): Double
-
-  // this should be properly tested
-  // looks to work but just by chance maybe
-  def nextBoolean(): Boolean = nextInt() < 0
-
 }
diff --git a/javalib/src/main/scala/java/util/concurrent/ThreadLocalRandom.scala b/javalib/src/main/scala/java/util/concurrent/ThreadLocalRandom.scala
index ce6ab96c6e..ed5ce571a1 100644
--- a/javalib/src/main/scala/java/util/concurrent/ThreadLocalRandom.scala
+++ b/javalib/src/main/scala/java/util/concurrent/ThreadLocalRandom.scala
@@ -9,7 +9,6 @@
 package java.util.concurrent
 
 import java.util.Random
-import scala.annotation.tailrec
 
 class ThreadLocalRandom extends Random {
 
@@ -22,98 +21,6 @@ class ThreadLocalRandom extends Random {
 
     super.setSeed(seed)
   }
-
-  def nextInt(least: Int, bound: Int): Int = {
-    if (least >= bound)
-      throw new IllegalArgumentException()
-
-    val difference = bound - least
-    if (difference > 0) {
-      nextInt(difference) + least
-    } else {
-      /* The interval size here is greater than Int.MaxValue,
-       * so the loop will exit with a probability of at least 1/2.
-       */
-      @tailrec
-      def loop(): Int = {
-        val n = nextInt()
-        if (n >= least && n < bound) n
-        else loop()
-      }
-
-      loop()
-    }
-  }
-
-  def nextLong(_n: Long): Long = {
-    if (_n <= 0)
-      throw new IllegalArgumentException("n must be positive")
-
-    /*
-     * Divide n by two until small enough for nextInt. On each
-     * iteration (at most 31 of them but usually much less),
-     * randomly choose both whether to include high bit in result
-     * (offset) and whether to continue with the lower vs upper
-     * half (which makes a difference only if odd).
-     */
-
-    var offset = 0L
-    var n = _n
-
-    while (n >= Integer.MAX_VALUE) {
-      val bits = next(2)
-      val halfn = n >>> 1
-      val nextn =
-        if ((bits & 2) == 0) halfn
-        else n - halfn
-      if ((bits & 1) == 0)
-        offset += n - nextn
-      n = nextn
-    }
-    offset + nextInt(n.toInt)
-  }
-
-  def nextLong(least: Long, bound: Long): Long = {
-    if (least >= bound)
-      throw new IllegalArgumentException()
-
-    val difference = bound - least
-    if (difference > 0) {
-      nextLong(difference) + least
-    } else {
-      /* The interval size here is greater than Long.MaxValue,
-       * so the loop will exit with a probability of at least 1/2.
-       */
-      @tailrec
-      def loop(): Long = {
-        val n = nextLong()
-        if (n >= least && n < bound) n
-        else loop()
-      }
-
-      loop()
-    }
-  }
-
-  def nextDouble(n: Double): Double = {
-    if (n <= 0)
-      throw new IllegalArgumentException("n must be positive")
-
-    nextDouble() * n
-  }
-
-  def nextDouble(least: Double, bound: Double): Double = {
-    if (least >= bound)
-      throw new IllegalArgumentException()
-
-    /* Based on documentation for Random.doubles to avoid issue #2144 and other
-     * possible rounding up issues:
-     * https://docs.oracle.com/javase/8/docs/api/java/util/Random.html#doubles-double-double-
-     */
-    val next = nextDouble() * (bound - least) + least
-    if (next < bound) next
-    else Math.nextAfter(bound, Double.NegativeInfinity)
-  }
 }
 
 object ThreadLocalRandom {
diff --git a/javalib/src/main/scala/java/util/random/RandomGenerator.scala b/javalib/src/main/scala/java/util/random/RandomGenerator.scala
new file mode 100644
index 0000000000..ddb38b0469
--- /dev/null
+++ b/javalib/src/main/scala/java/util/random/RandomGenerator.scala
@@ -0,0 +1,335 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package java.util.random
+
+import scala.annotation.tailrec
+
+import java.util.ScalaOps._
+
+trait RandomGenerator {
+  // Comments starting with `// >` are cited from the JavaDoc.
+
+  // Not implemented: all the methods using Streams
+
+  // Not implemented, because
+  // > The default implementation checks for the @Deprecated annotation.
+  // def isDeprecated(): Boolean = ???
+
+  def nextBoolean(): Boolean =
+    nextInt() < 0 // is the sign bit 1?
+
+  def nextBytes(bytes: Array[Byte]): Unit = {
+    val len = bytes.length // implicit NPE
+    var i = 0
+
+    for (_ <- 0 until (len >> 3)) {
+      var rnd = nextLong()
+      for (_ <- 0 until 8) {
+        bytes(i) = rnd.toByte
+        rnd >>>= 8
+        i += 1
+      }
+    }
+
+    if (i != len) {
+      var rnd = nextLong()
+      while (i != len) {
+        bytes(i) = rnd.toByte
+        rnd >>>= 8
+        i += 1
+      }
+    }
+  }
+
+  def nextFloat(): Float = {
+    // > Uses the 24 high-order bits from a call to nextInt()
+    val bits = nextInt() >>> (32 - 24)
+    bits.toFloat * (1.0f / (1 << 24)) // lossless multiplication
+  }
+
+  def nextFloat(bound: Float): Float = {
+    // false for NaN
+    if (bound > 0 && bound != Float.PositiveInfinity)
+      ensureBelowBound(nextFloatBoundedInternal(bound), bound)
+    else
+      throw new IllegalArgumentException(s"Illegal bound: $bound")
+  }
+
+  def nextFloat(origin: Float, bound: Float): Float = {
+    // `origin < bound` is false if either input is NaN
+    if (origin != Float.NegativeInfinity && origin < bound && bound != Float.PositiveInfinity) {
+      val difference = bound - origin
+      val result = if (difference != Float.PositiveInfinity) {
+        // Easy case
+        origin + nextFloatBoundedInternal(difference)
+      } else {
+        // Overflow: scale everything down by 0.5 then scale it back up by 2.0
+        val halfOrigin = origin * 0.5f
+        val halfBound = bound * 0.5f
+        (halfOrigin + nextFloatBoundedInternal(halfBound - halfOrigin)) * 2.0f
+      }
+
+      ensureBelowBound(result, bound)
+    } else {
+      throw new IllegalArgumentException(s"Illegal bounds: [$origin, $bound)")
+    }
+  }
+
+  @inline
+  private def nextFloatBoundedInternal(bound: Float): Float =
+    nextFloat() * bound
+
+  @inline
+  private def ensureBelowBound(value: Float, bound: Float): Float = {
+    /* Based on documentation for Random.doubles to avoid issue #2144 and other
+     * possible rounding up issues:
+     * https://docs.oracle.com/javase/8/docs/api/java/util/Random.html#doubles-double-double-
+     */
+    if (value < bound) value
+    else Math.nextDown(value)
+  }
+
+  def nextDouble(): Double = {
+    // > Uses the 53 high-order bits from a call to nextLong()
+    val bits = nextLong() >>> (64 - 53)
+    bits.toDouble * (1.0 / (1L << 53)) // lossless multiplication
+  }
+
+  def nextDouble(bound: Double): Double = {
+    // false for NaN
+    if (bound > 0 && bound != Double.PositiveInfinity)
+      ensureBelowBound(nextDoubleBoundedInternal(bound), bound)
+    else
+      throw new IllegalArgumentException(s"Illegal bound: $bound")
+  }
+
+  def nextDouble(origin: Double, bound: Double): Double = {
+    // `origin < bound` is false if either input is NaN
+    if (origin != Double.NegativeInfinity && origin < bound && bound != Double.PositiveInfinity) {
+      val difference = bound - origin
+      val result = if (difference != Double.PositiveInfinity) {
+        // Easy case
+        origin + nextDoubleBoundedInternal(difference)
+      } else {
+        // Overflow: scale everything down by 0.5 then scale it back up by 2.0
+        val halfOrigin = origin * 0.5
+        val halfBound = bound * 0.5
+        (halfOrigin + nextDoubleBoundedInternal(halfBound - halfOrigin)) * 2.0
+      }
+
+      ensureBelowBound(result, bound)
+    } else {
+      throw new IllegalArgumentException(s"Illegal bounds: [$origin, $bound)")
+    }
+  }
+
+  @inline
+  private def nextDoubleBoundedInternal(bound: Double): Double =
+    nextDouble() * bound
+
+  @inline
+  private def ensureBelowBound(value: Double, bound: Double): Double = {
+    /* Based on documentation for Random.doubles to avoid issue #2144 and other
+     * possible rounding up issues:
+     * https://docs.oracle.com/javase/8/docs/api/java/util/Random.html#doubles-double-double-
+     */
+    if (value < bound) value
+    else Math.nextDown(value)
+  }
+
+  def nextInt(): Int = {
+    // > Uses the 32 high-order bits from a call to nextLong()
+    (nextLong() >>> 32).toInt
+  }
+
+  /* The algorithms used in nextInt() with bounds were initially part of
+   * ThreadLocalRandom. That implementation had been written by Doug Lea with
+   * assistance from members of JCP JSR-166 Expert Group and released to the
+   * public domain, as explained at
+   * http://creativecommons.org/publicdomain/zero/1.0/
+   */
+
+  def nextInt(bound: Int): Int = {
+    if (bound <= 0)
+      throw new IllegalArgumentException(s"Illegal bound: $bound")
+
+    nextIntBoundedInternal(bound)
+  }
+
+  def nextInt(origin: Int, bound: Int): Int = {
+    if (bound <= origin)
+      throw new IllegalArgumentException(s"Illegal bounds: [$origin, $bound)")
+
+    val difference = bound - origin
+    if (difference > 0 || difference == Int.MinValue) {
+      /* Either the difference did not overflow, or it is the only power of 2
+       * that overflows. In both cases, use the straightforward algorithm.
+       * It works for `MinValue` because the code path for powers of 2
+       * basically interprets the bound as unsigned.
+       */
+      origin + nextIntBoundedInternal(difference)
+    } else {
+      /* The interval size here is greater than Int.MaxValue,
+       * so the loop will exit with a probability of at least 1/2.
+       */
+      @tailrec
+      def loop(): Int = {
+        val rnd = nextInt()
+        if (rnd >= origin && rnd < bound)
+          rnd
+        else
+          loop()
+      }
+
+      loop()
+    }
+  }
+
+  private def nextIntBoundedInternal(bound: Int): Int = {
+    // bound > 0 || bound == Int.MinValue
+
+    if ((bound & -bound) == bound) { // i.e., bound is a power of 2
+      // > If bound is a power of two then limiting is a simple masking operation.
+      nextInt() & (bound - 1)
+    } else {
+      /* > Otherwise, the result is re-calculated by invoking nextInt() until
+       * > the result is greater than or equal zero and less than bound.
+       */
+
+      /* Taken literally, that spec would lead to huge rejection rates for
+       * small bounds.
+       * Instead, we start from a random 31-bit (non-negative) int `rnd`, and
+       * we compute `rnd % bound`.
+       * In order to get a uniform distribution, we must reject and retry if
+       * we get an `rnd` that is >= the largest int multiple of `bound`.
+       */
+
+      @tailrec
+      def loop(): Int = {
+        val rnd = nextInt() >>> 1
+        val value = rnd % bound // candidate result
+
+        // largest multiple of bound that is <= rnd
+        val multiple = rnd - value
+
+        // if multiple + bound overflows
+        if (multiple + bound < 0) {
+          /* then `multiple` is the largest multiple of bound, and
+           * `rnd >= multiple`, so we must retry.
+           */
+          loop()
+        } else {
+          value
+        }
+      }
+
+      loop()
+    }
+  }
+
+  // The only abstract method of RandomGenerator
+  def nextLong(): Long
+
+  /* The algorithms for nextLong() with bounds are copy-pasted from the ones
+   * for nextInt(), mutatis mutandis.
+   */
+
+  def nextLong(bound: Long): Long = {
+    if (bound <= 0)
+      throw new IllegalArgumentException(s"Illegal bound: $bound")
+
+    nextLongBoundedInternal(bound)
+  }
+
+  def nextLong(origin: Long, bound: Long): Long = {
+    if (bound <= origin)
+      throw new IllegalArgumentException(s"Illegal bounds: [$origin, $bound)")
+
+    val difference = bound - origin
+    if (difference > 0 || difference == Long.MinValue) {
+      /* Either the difference did not overflow, or it is the only power of 2
+       * that overflows. In both cases, use the straightforward algorithm.
+       * It works for `MinValue` because the code path for powers of 2
+       * basically interprets the bound as unsigned.
+       */
+      origin + nextLongBoundedInternal(difference)
+    } else {
+      /* The interval size here is greater than Long.MaxValue,
+       * so the loop will exit with a probability of at least 1/2.
+       */
+      @tailrec
+      def loop(): Long = {
+        val rnd = nextLong()
+        if (rnd >= origin && rnd < bound)
+          rnd
+        else
+          loop()
+      }
+
+      loop()
+    }
+  }
+
+  private def nextLongBoundedInternal(bound: Long): Long = {
+    // bound > 0 || bound == Long.MinValue
+
+    if ((bound & -bound) == bound) { // i.e., bound is a power of 2
+      // > If bound is a power of two then limiting is a simple masking operation.
+      nextLong() & (bound - 1L)
+    } else {
+      /* > Otherwise, the result is re-calculated by invoking nextLong() until
+       * > the result is greater than or equal zero and less than bound.
+       */
+
+      /* Taken literally, that spec would lead to huge rejection rates for
+       * small bounds.
+       * Instead, we start from a random 63-bit (non-negative) int `rnd`, and
+       * we compute `rnd % bound`.
+       * In order to get a uniform distribution, we must reject and retry if
+       * we get an `rnd` that is >= the largest int multiple of `bound`.
+       */
+
+      @tailrec
+      def loop(): Long = {
+        val rnd = nextLong() >>> 1
+        val value = rnd % bound // candidate result
+
+        // largest multiple of bound that is <= rnd
+        val multiple = rnd - value
+
+        // if multiple + bound overflows
+        if (multiple + bound < 0L) {
+          /* then `multiple` is the largest multiple of bound, and
+           * `rnd >= multiple`, so we must retry.
+           */
+          loop()
+        } else {
+          value
+        }
+      }
+
+      loop()
+    }
+  }
+
+  // Not implemented
+  // def nextGaussian(): Double = ???
+  // def nextGaussian(mean: Double, stddev: Double): Double = ???
+  // def nextExponential(): Double = ???
+}
+
+object RandomGenerator { // scalastyle:ignore
+  // Not implemented
+  // def of(name: String): RandomGenerator = ???
+  // def getDefault(): RandomGenerator = ???
+}
diff --git a/project/Build.scala b/project/Build.scala
index bc2f0376d4..3ab4587c79 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -2135,6 +2135,7 @@ object Build {
         collectionsEraDependentDirectory(scalaV, sharedTestDir) ::
         includeIf(sharedTestDir / "require-jdk11", javaV >= 11) :::
         includeIf(sharedTestDir / "require-jdk15", javaV >= 15) :::
+        includeIf(sharedTestDir / "require-jdk17", javaV >= 17) :::
         includeIf(sharedTestDir / "require-jdk21", javaV >= 21) :::
         includeIf(testDir / "require-scala2", isJSTest)
       },
diff --git a/test-suite/shared/src/test/require-jdk17/org/scalajs/testsuite/javalib/util/random/RandomGeneratorTest.scala b/test-suite/shared/src/test/require-jdk17/org/scalajs/testsuite/javalib/util/random/RandomGeneratorTest.scala
new file mode 100644
index 0000000000..33696d7213
--- /dev/null
+++ b/test-suite/shared/src/test/require-jdk17/org/scalajs/testsuite/javalib/util/random/RandomGeneratorTest.scala
@@ -0,0 +1,433 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package org.scalajs.testsuite.javalib.util.random
+
+import org.junit.Assert._
+import org.junit.Test
+
+import org.scalajs.testsuite.utils.AssertThrows.assertThrows
+import org.scalajs.testsuite.utils.Platform._
+
+import java.util.random.RandomGenerator
+
+class RandomGeneratorTest {
+  /** Returns a RandomGenerator whose calls to `nextLong()` will return
+   *  the elements of `nextLongs`.
+   *
+   *  It does not loop. Requesting more elements will throw an AssertionError.
+   */
+  private def make(nextLongs: Long*): RandomGenerator = {
+    val iter = nextLongs.iterator
+    new RandomGenerator {
+      def nextLong(): Long = {
+        if (!iter.hasNext)
+          throw new AssertionError("Generator has run out")
+        iter.next()
+      }
+    }
+  }
+
+  /* 20 random Long values that we use as `nextLong` values in our tests
+   * 0xcdff356ba8f073c7L
+   * 0x4dd3ce2b9e4f98d3L
+   * 0xb85927b9d6e3249bL
+   * 0x0bf3df8c2f645e7dL
+   * 0x857f63be5f2f9ca0L
+   * 0xa12351957679f21fL
+   * 0xe01389542264f955L
+   * 0x1348eac1e0b1d30dL
+   * 0x496620384f075af6L
+   * 0xc7a71275b30dde50L
+   * 0xff5c1abdc835a88dL
+   * 0x7cd709fed6fc0e33L
+   * 0x457edabdccfc99b3L
+   * 0x867f0bae045cc0b5L
+   * 0xd9110b1c6a647a80L
+   * 0x27f8c35e876aa500L
+   * 0x700455bf2802ddacL
+   * 0x06b54104f821ddfeL
+   * 0xbf3b87070bbc6313L
+   * 0x74fa600cd5741c70L
+   */
+
+  @Test def testNextBoolean(): Unit = {
+    assertEquals(true, make(0xcdff356ba8f073c7L).nextBoolean())
+    assertEquals(false, make(0x4dd3ce2b9e4f98d3L).nextBoolean())
+    assertEquals(true, make(0xb85927b9d6e3249bL).nextBoolean())
+    assertEquals(false, make(0x0bf3df8c2f645e7dL).nextBoolean())
+    assertEquals(true, make(0x857f63be5f2f9ca0L).nextBoolean())
+    assertEquals(true, make(0xa12351957679f21fL).nextBoolean())
+    assertEquals(true, make(0xe01389542264f955L).nextBoolean())
+    assertEquals(false, make(0x1348eac1e0b1d30dL).nextBoolean())
+    assertEquals(false, make(0x496620384f075af6L).nextBoolean())
+    assertEquals(true, make(0xc7a71275b30dde50L).nextBoolean())
+    assertEquals(true, make(0xff5c1abdc835a88dL).nextBoolean())
+    assertEquals(false, make(0x7cd709fed6fc0e33L).nextBoolean())
+    assertEquals(false, make(0x457edabdccfc99b3L).nextBoolean())
+    assertEquals(true, make(0x867f0bae045cc0b5L).nextBoolean())
+    assertEquals(true, make(0xd9110b1c6a647a80L).nextBoolean())
+    assertEquals(false, make(0x27f8c35e876aa500L).nextBoolean())
+    assertEquals(false, make(0x700455bf2802ddacL).nextBoolean())
+    assertEquals(false, make(0x06b54104f821ddfeL).nextBoolean())
+    assertEquals(true, make(0xbf3b87070bbc6313L).nextBoolean())
+    assertEquals(false, make(0x74fa600cd5741c70L).nextBoolean())
+  }
+
+  @Test def testNextBytes(): Unit = {
+    val a16 = new Array[Byte](16)
+    make(0xcdff356ba8f073c7L, 0x4dd3ce2b9e4f98d3L).nextBytes(a16)
+    assertArrayEquals(
+        Array[Byte](-57, 115, -16, -88, 107, 53, -1, -51, -45, -104, 79, -98, 43, -50, -45, 77),
+        a16)
+
+    val a27 = new Array[Byte](27)
+    make(0xb85927b9d6e3249bL, 0x0bf3df8c2f645e7dL, 0x857f63be5f2f9ca0L, 0xa12351957679f21fL).nextBytes(a27)
+    assertArrayEquals(
+        Array[Byte](-101, 36, -29, -42, -71, 39, 89, -72, 125, 94, 100, 47, -116,
+            -33, -13, 11, -96, -100, 47, 95, -66, 99, 127, -123, 31, -14, 121),
+        a27)
+  }
+
+  @noinline
+  private def assertExactEquals(expected: Float, actual: Float): Unit =
+    assertTrue(s"expected $expected but got $actual", expected.equals(actual))
+
+  @Test def testNextFloat(): Unit = {
+    assertExactEquals(0.8046754f, make(0xcdff356ba8f073c7L).nextFloat())
+    assertExactEquals(0.30401313f, make(0x4dd3ce2b9e4f98d3L).nextFloat())
+    assertExactEquals(0.72011036f, make(0xb85927b9d6e3249bL).nextFloat())
+    assertExactEquals(0.046689928f, make(0x0bf3df8c2f645e7dL).nextFloat())
+    assertExactEquals(0.521475f, make(0x857f63be5f2f9ca0L).nextFloat())
+    assertExactEquals(0.62944514f, make(0xa12351957679f21fL).nextFloat())
+    assertExactEquals(0.8752981f, make(0xe01389542264f955L).nextFloat())
+    assertExactEquals(0.07533133f, make(0x1348eac1e0b1d30dL).nextFloat())
+    assertExactEquals(0.28671455f, make(0x496620384f075af6L).nextFloat())
+    assertExactEquals(0.77989304f, make(0xc7a71275b30dde50L).nextFloat())
+    assertExactEquals(0.9974991f, make(0xff5c1abdc835a88dL).nextFloat())
+    assertExactEquals(0.48765618f, make(0x7cd709fed6fc0e33L).nextFloat())
+    assertExactEquals(0.27146685f, make(0x457edabdccfc99b3L).nextFloat())
+    assertExactEquals(0.525376f, make(0x867f0bae045cc0b5L).nextFloat())
+    assertExactEquals(0.8479163f, make(0xd9110b1c6a647a80L).nextFloat())
+    assertExactEquals(0.15613955f, make(0x27f8c35e876aa500L).nextFloat())
+    assertExactEquals(0.4375661f, make(0x700455bf2802ddacL).nextFloat())
+    assertExactEquals(0.026203215f, make(0x06b54104f821ddfeL).nextFloat())
+    assertExactEquals(0.74700207f, make(0xbf3b87070bbc6313L).nextFloat())
+    assertExactEquals(0.45694542f, make(0x74fa600cd5741c70L).nextFloat())
+  }
+
+  @Test def testNextFloatWithBound(): Unit = {
+    assertExactEquals(0.8046754f, make(0xcdff356ba8f073c7L).nextFloat(1.0f))
+    assertExactEquals(0.15200657f, make(0x4dd3ce2b9e4f98d3L).nextFloat(0.5f))
+    assertExactEquals(88902.516f, make(0xb85927b9d6e3249bL).nextFloat(123456.789f))
+    assertExactEquals(7.0590034f, make(0x0bf3df8c2f645e7dL).nextFloat(151.189f))
+    assertExactEquals(0.0f, make(0x857f63be5f2f9ca0L).nextFloat(Float.MinPositiveValue))
+    assertExactEquals(2.1418906e38f, make(0xa12351957679f21fL).nextFloat(Float.MaxValue))
+
+    assertThrows(classOf[IllegalArgumentException], make().nextFloat(-10.0f))
+    assertThrows(classOf[IllegalArgumentException], make().nextFloat(0.0f))
+    assertThrows(classOf[IllegalArgumentException], make().nextFloat(-0.0f))
+    assertThrows(classOf[IllegalArgumentException], make().nextFloat(Float.MinValue))
+    assertThrows(classOf[IllegalArgumentException], make().nextFloat(Float.PositiveInfinity))
+    assertThrows(classOf[IllegalArgumentException], make().nextFloat(Float.NegativeInfinity))
+    assertThrows(classOf[IllegalArgumentException], make().nextFloat(Float.NaN))
+  }
+
+  @Test def testNextFloatWithOriginAndBound(): Unit = {
+    assertExactEquals(0.9023377f, make(0xcdff356ba8f073c7L).nextFloat(0.5f, 1.0f))
+    assertExactEquals(-10.63579f, make(0x4dd3ce2b9e4f98d3L).nextFloat(-15.5f, 0.5f))
+    assertExactEquals(745774.4f, make(0xb85927b9d6e3249bL).nextFloat(123456.789f, 987654.321f))
+    assertExactEquals(-561941.4f, make(0x0bf3df8c2f645e7dL).nextFloat(-589456.0f, -151.189f))
+    assertExactEquals(123.456f, make(0x857f63be5f2f9ca0L).nextFloat(123.456f, 123.45601f)) // 1 ulp of difference
+
+    if (!executingInJVMOnLowerThanJDK(19)) {
+      // Before JDK 19, these threw IllegalArgumentException's.
+
+      import Float.{MinValue, MaxValue}
+
+      assertExactEquals(-5.4696933e37f, make(0xa12351957679f21fL).nextFloat(MinValue, MaxValue/3.0f))
+      assertExactEquals(8.809577e37f, make(0xa12351957679f21fL).nextFloat(MinValue, MaxValue))
+      assertExactEquals(1.7215796e38f, make(0xa12351957679f21fL).nextFloat(MinValue/3.0f, MaxValue))
+
+      assertExactEquals(5.684898e37f, make(0xe01389542264f955L).nextFloat(MinValue, MaxValue/3.0f))
+      assertExactEquals(2.5541462e38f, make(0xe01389542264f955L).nextFloat(MinValue, MaxValue))
+      assertExactEquals(2.8370388e38f, make(0xe01389542264f955L).nextFloat(MinValue/3.0f, MaxValue))
+
+      assertExactEquals(-3.0610379e38f, make(0x1348eac1e0b1d30dL).nextFloat(MinValue, MaxValue/3.0f))
+      assertExactEquals(-2.890145e38f, make(0x1348eac1e0b1d30dL).nextFloat(MinValue, MaxValue))
+      assertExactEquals(-7.9248886e37f, make(0x1348eac1e0b1d30dL).nextFloat(MinValue/3.0f, MaxValue))
+    }
+
+    // Make sure we do not underflow MinPositiveValue to 0.0
+    assertExactEquals(Float.MinPositiveValue,
+        make(0L).nextFloat(Float.MinPositiveValue, 1024 * Float.MinPositiveValue))
+
+    assertThrows(classOf[IllegalArgumentException], make().nextFloat(-10.0f, -10.0f))
+    assertThrows(classOf[IllegalArgumentException], make().nextFloat(-0.0f, 0.0f))
+    assertThrows(classOf[IllegalArgumentException], make().nextFloat(5.0f, 4.0f))
+    assertThrows(classOf[IllegalArgumentException], make().nextFloat(Float.MinValue, Float.MinValue))
+    assertThrows(classOf[IllegalArgumentException], make().nextFloat(Float.NegativeInfinity, -1.0f))
+    assertThrows(classOf[IllegalArgumentException], make().nextFloat(1.0f, Float.NegativeInfinity))
+    assertThrows(classOf[IllegalArgumentException], make().nextFloat(Float.NaN, 0.0f))
+    assertThrows(classOf[IllegalArgumentException], make().nextFloat(0.0f, Float.NaN))
+  }
+
+  @noinline
+  private def assertExactEquals(expected: Double, actual: Double): Unit =
+    assertTrue(s"expected $expected but got $actual", expected.equals(actual))
+
+  @Test def testNextDouble(): Unit = {
+    assertExactEquals(0.8046754253236388, make(0xcdff356ba8f073c7L).nextDouble())
+    assertExactEquals(0.30401314320471184, make(0x4dd3ce2b9e4f98d3L).nextDouble())
+    assertExactEquals(0.7201104000768166, make(0xb85927b9d6e3249bL).nextDouble())
+    assertExactEquals(0.04668996021736527, make(0x0bf3df8c2f645e7dL).nextDouble())
+    assertExactEquals(0.5214750613951636, make(0x857f63be5f2f9ca0L).nextDouble())
+    assertExactEquals(0.6294451703929338, make(0xa12351957679f21fL).nextDouble())
+    assertExactEquals(0.8752981024175773, make(0xe01389542264f955L).nextDouble())
+    assertExactEquals(0.0753313754400502, make(0x1348eac1e0b1d30dL).nextDouble())
+    assertExactEquals(0.28671456694340003, make(0x496620384f075af6L).nextDouble())
+    assertExactEquals(0.7798930680610775, make(0xc7a71275b30dde50L).nextDouble())
+    assertExactEquals(0.9974991525015954, make(0xff5c1abdc835a88dL).nextDouble())
+    assertExactEquals(0.4876562354247512, make(0x7cd709fed6fc0e33L).nextDouble())
+    assertExactEquals(0.271466895425862, make(0x457edabdccfc99b3L).nextDouble())
+    assertExactEquals(0.5253760623785295, make(0x867f0bae045cc0b5L).nextDouble())
+    assertExactEquals(0.8479163116811764, make(0xd9110b1c6a647a80L).nextDouble())
+    assertExactEquals(0.1561395746024723, make(0x27f8c35e876aa500L).nextDouble())
+    assertExactEquals(0.43756614605809874, make(0x700455bf2802ddacL).nextDouble())
+    assertExactEquals(0.026203216279220398, make(0x06b54104f821ddfeL).nextDouble())
+    assertExactEquals(0.7470020668222204, make(0xbf3b87070bbc6313L).nextDouble())
+    assertExactEquals(0.456945422299626, make(0x74fa600cd5741c70L).nextDouble())
+  }
+
+  @Test def testNextDoubleWithBound(): Unit = {
+    assertExactEquals(0.8046754253236388, make(0xcdff356ba8f073c7L).nextDouble(1.0))
+    assertExactEquals(0.15200657160235592, make(0x4dd3ce2b9e4f98d3L).nextDouble(0.5))
+    assertExactEquals(88902.51771898914, make(0xb85927b9d6e3249bL).nextDouble(123456.789))
+    assertExactEquals(7.059008395303237, make(0x0bf3df8c2f645e7dL).nextDouble(151.189))
+    assertExactEquals(0.0, make(0x857f63be5f2f9ca0L).nextDouble(Double.MinPositiveValue))
+    assertExactEquals(1.1315492615876175E308, make(0xa12351957679f21fL).nextDouble(Double.MaxValue))
+
+    assertThrows(classOf[IllegalArgumentException], make().nextDouble(-10.0))
+    assertThrows(classOf[IllegalArgumentException], make().nextDouble(0.0))
+    assertThrows(classOf[IllegalArgumentException], make().nextDouble(-0.0))
+    assertThrows(classOf[IllegalArgumentException], make().nextDouble(Double.MinValue))
+    assertThrows(classOf[IllegalArgumentException], make().nextDouble(Double.PositiveInfinity))
+    assertThrows(classOf[IllegalArgumentException], make().nextDouble(Double.NegativeInfinity))
+    assertThrows(classOf[IllegalArgumentException], make().nextDouble(Double.NaN))
+  }
+
+  @Test def testNextDoubleWithOriginAndBound(): Unit = {
+    assertExactEquals(0.9023377126618194, make(0xcdff356ba8f073c7L).nextDouble(0.5, 1.0))
+    assertExactEquals(-10.63578970872461, make(0x4dd3ce2b9e4f98d3L).nextDouble(-15.5, 0.5))
+    assertExactEquals(745774.4195139175, make(0xb85927b9d6e3249bL).nextDouble(123456.789, 987654.321))
+    assertExactEquals(-561941.381818508, make(0x0bf3df8c2f645e7dL).nextDouble(-589456.0, -151.189))
+    assertExactEquals(123.456, make(0x857f63be5f2f9ca0L).nextDouble(123.456, 123.45600000000002)) // 1 ulp of diff
+
+    if (!executingInJVMOnLowerThanJDK(19)) {
+      // Before JDK 19, these threw IllegalArgumentException's.
+
+      import Double.{MinValue, MaxValue}
+
+      assertExactEquals(-2.8896078607882544e307, make(0xa12351957679f21fL).nextDouble(MinValue, MaxValue/3.0))
+      assertExactEquals(4.654053883129194e307, make(0xa12351957679f21fL).nextDouble(MinValue, MaxValue))
+      assertExactEquals(9.095013038293849e307, make(0xa12351957679f21fL).nextDouble(MinValue/3.0, MaxValue))
+
+      assertExactEquals(3.003300513698057e307, make(0xe01389542264f955L).nextDouble(MinValue, MaxValue/3.0))
+      assertExactEquals(1.349341644485866e308, make(0xe01389542264f955L).nextDouble(MinValue, MaxValue))
+      assertExactEquals(1.4987921412780162e308, make(0xe01389542264f955L).nextDouble(MinValue/3.0, MaxValue))
+
+      assertExactEquals(-1.6171295395712306e308, make(0x1348eac1e0b1d30dL).nextDouble(MinValue, MaxValue/3.0))
+      assertExactEquals(-1.5268477419256879e308, make(0x1348eac1e0b1d30dL).nextDouble(MinValue, MaxValue))
+      assertExactEquals(-4.1866744966302007e307, make(0x1348eac1e0b1d30dL).nextDouble(MinValue/3.0, MaxValue))
+    }
+
+    // Make sure we do not underflow MinPositiveValue to 0.0
+    assertExactEquals(Double.MinPositiveValue,
+        make(0L).nextDouble(Double.MinPositiveValue, 1024 * Double.MinPositiveValue))
+
+    assertThrows(classOf[IllegalArgumentException], make().nextDouble(-10.0, -10.0))
+    assertThrows(classOf[IllegalArgumentException], make().nextDouble(-0.0, 0.0))
+    assertThrows(classOf[IllegalArgumentException], make().nextDouble(5.0, 4.0))
+    assertThrows(classOf[IllegalArgumentException], make().nextDouble(Double.MinValue, Double.MinValue))
+    assertThrows(classOf[IllegalArgumentException], make().nextDouble(Double.NegativeInfinity, -1.0))
+    assertThrows(classOf[IllegalArgumentException], make().nextDouble(1.0, Double.NegativeInfinity))
+    assertThrows(classOf[IllegalArgumentException], make().nextDouble(Double.NaN, 0.0))
+    assertThrows(classOf[IllegalArgumentException], make().nextDouble(0.0, Double.NaN))
+  }
+
+  @Test def testNextInt(): Unit = {
+    assertEquals(-838912661, make(0xcdff356ba8f073c7L).nextInt())
+    assertEquals(1305726507, make(0x4dd3ce2b9e4f98d3L).nextInt())
+    assertEquals(-1202116679, make(0xb85927b9d6e3249bL).nextInt())
+    assertEquals(200531852, make(0x0bf3df8c2f645e7dL).nextInt())
+    assertEquals(-2055248962, make(0x857f63be5f2f9ca0L).nextInt())
+    assertEquals(-1591520875, make(0xa12351957679f21fL).nextInt())
+    assertEquals(-535590572, make(0xe01389542264f955L).nextInt())
+    assertEquals(323545793, make(0x1348eac1e0b1d30dL).nextInt())
+    assertEquals(1231429688, make(0x496620384f075af6L).nextInt())
+    assertEquals(-945352075, make(0xc7a71275b30dde50L).nextInt())
+    assertEquals(-10741059, make(0xff5c1abdc835a88dL).nextInt())
+    assertEquals(2094467582, make(0x7cd709fed6fc0e33L).nextInt())
+    assertEquals(1165941437, make(0x457edabdccfc99b3L).nextInt())
+    assertEquals(-2038494290, make(0x867f0bae045cc0b5L).nextInt())
+    assertEquals(-653194468, make(0xd9110b1c6a647a80L).nextInt())
+    assertEquals(670614366, make(0x27f8c35e876aa500L).nextInt())
+    assertEquals(1879332287, make(0x700455bf2802ddacL).nextInt())
+    assertEquals(112541956, make(0x06b54104f821ddfeL).nextInt())
+    assertEquals(-1086617849, make(0xbf3b87070bbc6313L).nextInt())
+    assertEquals(1962565644, make(0x74fa600cd5741c70L).nextInt())
+  }
+
+  @Test def testNextIntWithBound(): Unit = {
+    assertEquals(353, make(0xcdff356ba8f073c7L).nextInt(1234))
+    assertEquals(652863253, make(0x4dd3ce2b9e4f98d3L).nextInt(987654321))
+    assertEquals(1546425308, make(0xb85927b9d6e3249bL).nextInt(2000000000))
+    assertEquals(6, make(0x0bf3df8c2f645e7dL).nextInt(10))
+    assertEquals(0, make(0x857f63be5f2f9ca0L).nextInt(1))
+    assertEquals(1351723210, make(0xa12351957679f21fL).nextInt(Int.MaxValue))
+
+    // Rejects one sample
+    assertEquals(1047233791, make(0xff5c1abdc835a88dL, 0x7cd709fed6fc0e33L).nextInt(2000000000))
+
+    // Powers of 2 have a dedicated path
+    assertEquals(5, make(0x457edabdccfc99b3L).nextInt(8))
+    assertEquals(942, make(0x867f0bae045cc0b5L).nextInt(1024))
+    assertEquals(420547356, make(0xd9110b1c6a647a80L).nextInt(1 << 30))
+
+    assertThrows(classOf[IllegalArgumentException], make().nextInt(0))
+    assertThrows(classOf[IllegalArgumentException], make().nextInt(-10))
+    assertThrows(classOf[IllegalArgumentException], make().nextInt(Int.MinValue))
+  }
+
+  @Test def testNextIntWithOriginAndBound(): Unit = {
+    assertEquals(3353, make(0xcdff356ba8f073c7L).nextInt(3000, 4234))
+    assertEquals(529406464, make(0x4dd3ce2b9e4f98d3L).nextInt(-123456789, 987654321))
+    assertEquals(-453574692, make(0xb85927b9d6e3249bL).nextInt(-2000000000, -123456789))
+    assertEquals(-4, make(0x0bf3df8c2f645e7dL).nextInt(-10, 0))
+
+    assertEquals(56, make(0x857f63be5f2f9ca0L).nextInt(56, 57)) // no choice
+
+    // Close to min or max
+    assertEquals(-2147483647, make(0xa12351957679f21fL).nextInt(Int.MinValue, Int.MinValue + 3))
+    assertEquals(2147483645, make(0xe01389542264f955L).nextInt(Int.MaxValue - 3, Int.MaxValue))
+    assertEquals(161772897, make(0x1348eac1e0b1d30dL).nextInt(1, Int.MaxValue))
+
+    // Rejects one sample
+    assertEquals(47233791, make(0xff5c1abdc835a88dL, 0x7cd709fed6fc0e33L).nextInt(-1000000000, 1000000000))
+
+    // bound - origin overflows
+    assertEquals(1165941437, make(0x457edabdccfc99b3L).nextInt(-1000000000, 2000000000))
+
+    // bound - origin overflows and rejects one sample
+    assertEquals(112541956, make(0x77fa600cd5741c70L, 0x06b54104f821ddfeL).nextInt(-1000000000, 2000000000))
+
+    // Powers of 2 have a dedicated path
+    assertEquals(45, make(0x457edabdccfc99b3L).nextInt(40, 40 + 8))
+    assertEquals(-999999058, make(0x867f0bae045cc0b5L).nextInt(-1000000000, -1000000000 + 1024))
+    assertEquals(420090567, make(0xd9110b1c6a647a80L).nextInt(-456789, -456789 + (1 << 30)))
+
+    // The power of 2 that also overflows
+    assertEquals(670157577, make(0x27f8c35e876aa500L).nextInt(-456789, -456789 + (1 << 31)))
+
+    assertThrows(classOf[IllegalArgumentException], make().nextInt(56, 56))
+    assertThrows(classOf[IllegalArgumentException], make().nextInt(-10, -30))
+    assertThrows(classOf[IllegalArgumentException], make().nextInt(Int.MaxValue, Int.MinValue))
+  }
+
+  @Test def testNextLong(): Unit = {
+    assertEquals(-3603102440361004089L, make(0xcdff356ba8f073c7L).nextLong())
+    assertEquals(5608052647741331667L, make(0x4dd3ce2b9e4f98d3L).nextLong())
+    assertEquals(-5163051818675919717L, make(0xb85927b9d6e3249bL).nextLong())
+    assertEquals(861277746941419133L, make(0x0bf3df8c2f645e7dL).nextLong())
+    assertEquals(-8827227075330990944L, make(0x857f63be5f2f9ca0L).nextLong())
+    assertEquals(-6835530107038600673L, make(0xa12351957679f21fL).nextLong())
+    assertEquals(-2300343990208890539L, make(0xe01389542264f955L).nextLong())
+    assertEquals(1389618603463136013L, make(0x1348eac1e0b1d30dL).nextLong())
+    assertEquals(5288950238609365750L, make(0x496620384f075af6L).nextLong())
+    assertEquals(-4060256242326708656L, make(0xc7a71275b30dde50L).nextLong())
+    assertEquals(-46132493770446707L, make(0xff5c1abdc835a88dL).nextLong())
+    assertEquals(8995669770829041203L, make(0x7cd709fed6fc0e33L).nextLong())
+    assertEquals(5007680344405350835L, make(0x457edabdccfc99b3L).nextLong())
+    assertEquals(-8755266308559552331L, make(0x867f0bae045cc0b5L).nextLong())
+    assertEquals(-2805448876203148672L, make(0xd9110b1c6a647a80L).nextLong())
+    assertEquals(2880266772469687552L, make(0x27f8c35e876aa500L).nextLong())
+    assertEquals(8071670711653162412L, make(0x700455bf2802ddacL).nextLong())
+    assertEquals(483364024610840062L, make(0x06b54104f821ddfeL).nextLong())
+    assertEquals(-4666988124507970797L, make(0xbf3b87070bbc6313L).nextLong())
+    assertEquals(8429155260814335088L, make(0x74fa600cd5741c70L).nextLong())
+  }
+
+  @Test def testNextLongWithBound(): Unit = {
+    assertEquals(1179L, make(0xcdff356ba8f073c7L).nextLong(1234L))
+    assertEquals(6567945330301L, make(0x4dd3ce2b9e4f98d3L).nextLong(9876543219876L))
+    assertEquals(2641846127516815949L, make(0xb85927b9d6e3249bL).nextLong(4000000000000000000L))
+    assertEquals(6, make(0x0bf3df8c2f645e7dL).nextLong(10L))
+    assertEquals(0, make(0x857f63be5f2f9ca0L).nextLong(1L))
+    assertEquals(5805606983335475471L, make(0xa12351957679f21fL).nextLong(Long.MaxValue))
+
+    // Rejects one sample
+    assertEquals(497834885414520601L, make(0xff5c1abdc835a88dL, 0x7cd709fed6fc0e33L).nextLong(4000000000000000000L))
+
+    // Powers of 2 have a dedicated path
+    assertEquals(3L, make(0x457edabdccfc99b3L).nextLong(8L))
+    assertEquals(181L, make(0x867f0bae045cc0b5L).nextLong(1024L))
+    assertEquals(711228032L, make(0xd9110b1c6a647a80L).nextLong(1L << 30))
+    assertEquals(214810766255360L, make(0x27f8c35e876aa500L).nextLong(1L << 50))
+    assertEquals(3459984693225774508L, make(0x700455bf2802ddacL).nextLong(1L << 62))
+
+    assertThrows(classOf[IllegalArgumentException], make().nextLong(0L))
+    assertThrows(classOf[IllegalArgumentException], make().nextLong(-10L))
+    assertThrows(classOf[IllegalArgumentException], make().nextLong(Long.MinValue))
+  }
+
+  @Test def testNextLongWithOriginAndBound(): Unit = {
+    assertEquals(4179L, make(0xcdff356ba8f073c7L).nextLong(3000L, 4234L))
+    assertEquals(2867080832779L, make(0x4dd3ce2b9e4f98d3L).nextLong(-1234567891234L, 9876543219876L))
+    assertEquals(-1358152637915292817L, make(0xb85927b9d6e3249bL).nextLong(-4000000000000000000L, -1234567891234L))
+    assertEquals(-4L, make(0x0bf3df8c2f645e7dL).nextLong(-10L, 0L))
+
+    assertEquals(56L, make(0x857f63be5f2f9ca0L).nextLong(56L, 57L)) // no choice
+
+    // Close to min or max
+    assertEquals(-9223372036854775806L, make(0xa12351957679f21fL).nextLong(Long.MinValue, Long.MinValue + 3L))
+    assertEquals(9223372036854775806L, make(0xe01389542264f955L).nextLong(Long.MaxValue - 3L, Long.MaxValue))
+    assertEquals(694809301731568007L, make(0x1348eac1e0b1d30dL).nextLong(1, Long.MaxValue))
+
+    // Rejects one sample
+    assertEquals(-1502165114585479399L,
+        make(0xff5c1abdc835a88dL, 0x7cd709fed6fc0e33L).nextLong(-2000000000000000000L, 2000000000000000000L))
+
+    // bound - origin overflows
+    assertEquals(861277746941419133L, make(0x0bf3df8c2f645e7dL).nextLong(-6000000000000000000L, 4000000000000000000L))
+
+    // bound - origin overflows and rejects one sample
+    assertEquals(483364024610840062L,
+        make(0x457edabdccfc99b3L, 0x06b54104f821ddfeL).nextLong(-6000000000000000000L, 4000000000000000000L))
+
+    // Powers of 2 have a dedicated path
+    assertEquals(43L, make(0x457edabdccfc99b3L).nextLong(40L, 40L + 8L))
+    assertEquals(-999999819L, make(0x867f0bae045cc0b5L).nextLong(-1000000000L, -1000000000 + 1024L))
+    assertEquals(710771243L, make(0xd9110b1c6a647a80L).nextLong(-456789L, -456789L + (1L << 30)))
+    assertEquals(2000214810766255360L,
+        make(0x27f8c35e876aa500L).nextLong(2000000000000000000L, 2000000000000000000L + (1L << 50)))
+    assertEquals(3459983458657883274L,
+        make(0x700455bf2802ddacL).nextLong(-1234567891234L, -1234567891234L + (1L << 62)))
+
+    // The power of 2 that also overflows
+    assertEquals(4556382677778913777L,
+        make(0xbf3b87070bbc6313L).nextLong(-1234567891234L, -1234567891234L + (1L << 63)))
+
+    assertThrows(classOf[IllegalArgumentException], make().nextLong(56L, 56L))
+    assertThrows(classOf[IllegalArgumentException], make().nextLong(-10L, -30L))
+    assertThrows(classOf[IllegalArgumentException], make().nextLong(Long.MaxValue, Long.MinValue))
+  }
+}

From ad8f83049b6f1e7a001118605688bc851b4098ad Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Mon, 10 Feb 2025 15:28:42 +0100
Subject: [PATCH 268/298] Add `js.async { ... js.await(p) ... }` blocks.

We introduce a new pair of primitive methods, `js.async` and
`js.await`. They correspond to JavaScript `async` functions and
`await` expressions.

`js.await(p)` awaits a `Promise`, but it must be directly scoped
within a `js.async { ... }` block.

---

At the IR level, `js.await(p)` directly translates to a dedicated
IR node `JSAwait(arg)`. `js.async` blocks don't have a direct
representation. Instead, the IR models `async function`s and
`async =>`functions, as `Closure`s with an additionnal `async`
flag. This corresponds to the JavaScript model for `async/await`.

A `js.async { body }` block therefore corresponds to an
immediately-applied `async Closure`, which in JavaScript would be
written as `(async () => body)()`.

---

On the JavaScript platform, async `Closure`s and `JSAwait` are
directly compiled as their JavaScript equivalent.

On WebAssembly, we leverage the JavaScript Promise Integration
feature (JSPI). We turn async `Closure`s into
WebAssembly.promising` functions. `js.await(p)` is compiled as
a call to a unique `jsAwait` helper, which is declared as
an "identity" `new WebAssembly.Suspending((x) => x)`. The static
scoping rule of `js.await` guarantees that the suspending call
is always performed in a valid context (one that will not throw
a `WebAssembly.SuspendError`).
---
 Jenkinsfile                                   |  31 +++-
 .../org/scalajs/nscplugin/GenJSCode.scala     |  34 +++-
 .../org/scalajs/nscplugin/JSDefinitions.scala |   2 +
 .../org/scalajs/nscplugin/JSPrimitives.scala  |   7 +-
 .../nscplugin/test/JSAsyncAwaitTest.scala     |  74 +++++++++
 .../main/scala/org/scalajs/ir/Hashers.scala   |   4 +
 .../main/scala/org/scalajs/ir/Printers.scala  |  15 +-
 .../scala/org/scalajs/ir/Serializers.scala    |   8 +
 .../src/main/scala/org/scalajs/ir/Tags.scala  |   1 +
 .../scala/org/scalajs/ir/Transformers.scala   |   3 +
 .../scala/org/scalajs/ir/Traversers.scala     |   3 +
 .../src/main/scala/org/scalajs/ir/Trees.scala |  26 +++
 .../scala/org/scalajs/ir/PrintersTest.scala   |  24 +++
 .../main/scala/scala/scalajs/js/package.scala |  47 ++++++
 .../closure/ClosureAstTransformer.scala       |   7 +-
 .../scalajs/linker/analyzer/Analysis.scala    |   4 +
 .../scalajs/linker/analyzer/Analyzer.scala    |   5 +
 .../org/scalajs/linker/analyzer/Infos.scala   |  12 +-
 .../linker/backend/emitter/ClassEmitter.scala |   9 +-
 .../linker/backend/emitter/CoreJSLib.scala    |   4 +-
 .../backend/emitter/FunctionEmitter.scala     |  30 ++--
 .../linker/backend/emitter/JSGen.scala        |   5 +-
 .../linker/backend/emitter/VarGen.scala       |   5 +-
 .../linker/backend/javascript/Printers.scala  |  11 +-
 .../linker/backend/javascript/Trees.scala     |  11 +-
 .../backend/wasmemitter/CoreWasmLib.scala     |   1 +
 .../wasmemitter/CustomJSHelperBuilder.scala   |   2 +-
 .../linker/backend/wasmemitter/Emitter.scala  |   5 +-
 .../backend/wasmemitter/FunctionEmitter.scala |  30 +++-
 .../backend/wasmemitter/LoaderContent.scala   |   8 +
 .../linker/backend/wasmemitter/VarGen.scala   |   1 +
 .../linker/checker/ClassDefChecker.scala      |  29 +++-
 .../scalajs/linker/checker/IRChecker.scala    |   3 +
 .../frontend/optimizer/OptimizerCore.scala    |  10 +-
 .../org/scalajs/linker/AnalyzerTest.scala     |  19 +++
 .../backend/javascript/PrintersTest.scala     |   3 +-
 project/Build.scala                           |   3 +
 .../jsinterop/JSAsyncAwaitTest.scala          | 148 ++++++++++++++++++
 38 files changed, 589 insertions(+), 55 deletions(-)
 create mode 100644 compiler/src/test/scala/org/scalajs/nscplugin/test/JSAsyncAwaitTest.scala
 create mode 100644 test-suite/js/src/test/require-async-await/org/scalajs/testsuite/jsinterop/JSAsyncAwaitTest.scala

diff --git a/Jenkinsfile b/Jenkinsfile
index 5cbf59ce7f..165dec8254 100644
--- a/Jenkinsfile
+++ b/Jenkinsfile
@@ -365,59 +365,75 @@ def Tasks = [
     npm install &&
     sbtretry ++$scala \
         'set Global/enableWasmEverywhere := true' \
+        'set scalaJSLinkerConfig in helloworld.v$v ~= (_.withESFeatures(_.withESVersion(ESVersion.$esVersion)))' \
         helloworld$v/run &&
     sbtretry ++$scala \
         'set Global/enableWasmEverywhere := true' \
+        'set scalaJSLinkerConfig in helloworld.v$v ~= (_.withESFeatures(_.withESVersion(ESVersion.$esVersion)))' \
         'set scalaJSStage in Global := FullOptStage' \
         'set scalaJSLinkerConfig in helloworld.v$v ~= (_.withPrettyPrint(true))' \
         helloworld$v/run &&
     sbtretry ++$scala \
         'set Global/enableWasmEverywhere := true' \
+        'set scalaJSLinkerConfig in reversi.v$v ~= (_.withESFeatures(_.withESVersion(ESVersion.$esVersion)))' \
         reversi$v/fastLinkJS \
         reversi$v/fullLinkJS &&
     sbtretry ++$scala \
         'set Global/enableWasmEverywhere := true' \
-        jUnitTestOutputsJVM$v/test jUnitTestOutputsJS$v/test testBridge$v/test \
-        'set scalaJSStage in Global := FullOptStage' jUnitTestOutputsJS$v/test testBridge$v/test &&
+        'set scalaJSLinkerConfig in jUnitTestOutputsJS.v$v ~= (_.withESFeatures(_.withESVersion(ESVersion.$esVersion)))' \
+        'set scalaJSLinkerConfig in testBridge.v$v ~= (_.withESFeatures(_.withESVersion(ESVersion.$esVersion)))' \
+        jUnitTestOutputsJS$v/test testBridge$v/test \
+        'set scalaJSStage in Global := FullOptStage' \
+        jUnitTestOutputsJS$v/test testBridge$v/test &&
     sbtretry ++$scala \
         'set Global/enableWasmEverywhere := true' \
+        'set scalaJSLinkerConfig in $testSuite.v$v ~= (_.withESFeatures(_.withESVersion(ESVersion.$esVersion)))' \
         $testSuite$v/test &&
     sbtretry ++$scala \
         'set Global/enableWasmEverywhere := true' \
+        'set scalaJSLinkerConfig in $testSuite.v$v ~= (_.withESFeatures(_.withESVersion(ESVersion.$esVersion)))' \
         'set scalaJSStage in Global := FullOptStage' \
         $testSuite$v/test &&
     sbtretry ++$scala \
         'set Global/enableWasmEverywhere := true' \
+        'set scalaJSLinkerConfig in $testSuite.v$v ~= (_.withESFeatures(_.withESVersion(ESVersion.$esVersion)))' \
         'set scalaJSLinkerConfig in $testSuite.v$v ~= (_.withOptimizer(false))' \
         $testSuite$v/test &&
     sbtretry ++$scala \
         'set Global/enableWasmEverywhere := true' \
+        'set scalaJSLinkerConfig in $testSuite.v$v ~= (_.withESFeatures(_.withESVersion(ESVersion.$esVersion)))' \
         'set scalaJSLinkerConfig in $testSuite.v$v ~= (_.withOptimizer(false))' \
         'set scalaJSStage in Global := FullOptStage' \
         $testSuite$v/test &&
     sbtretry ++$scala \
         'set Global/enableWasmEverywhere := true' \
+        'set scalaJSLinkerConfig in $testSuite.v$v ~= (_.withESFeatures(_.withESVersion(ESVersion.$esVersion)))' \
         'set scalaJSLinkerConfig in $testSuite.v$v ~= makeCompliant' \
         $testSuite$v/test &&
     sbtretry ++$scala \
         'set Global/enableWasmEverywhere := true' \
+        'set scalaJSLinkerConfig in $testSuite.v$v ~= (_.withESFeatures(_.withESVersion(ESVersion.$esVersion)))' \
         'set scalaJSLinkerConfig in $testSuite.v$v ~= makeCompliant' \
         'set scalaJSStage in Global := FullOptStage' \
         $testSuite$v/test &&
     sbtretry ++$scala \
         'set Global/enableWasmEverywhere := true' \
+        'set scalaJSLinkerConfig in $testSuite.v$v ~= (_.withESFeatures(_.withESVersion(ESVersion.$esVersion)))' \
         'set scalaJSLinkerConfig in $testSuite.v$v ~= makeCompliant' \
         'set scalaJSLinkerConfig in $testSuite.v$v ~= (_.withOptimizer(false))' \
         $testSuite$v/test &&
     sbtretry ++$scala \
         'set Global/enableWasmEverywhere := true' \
+        'set scalaJSLinkerConfig in $testSuite.v$v ~= (_.withESFeatures(_.withESVersion(ESVersion.$esVersion)))' \
         testingExample$v/testHtml &&
     sbtretry ++$scala \
         'set Global/enableWasmEverywhere := true' \
+        'set scalaJSLinkerConfig in $testSuite.v$v ~= (_.withESFeatures(_.withESVersion(ESVersion.$esVersion)))' \
         'set scalaJSStage in Global := FullOptStage' \
         testingExample$v/testHtml &&
     sbtretry ++$scala \
         'set Global/enableWasmEverywhere := true' \
+        'set scalaJSLinkerConfig in $testSuite.v$v ~= (_.withESFeatures(_.withESVersion(ESVersion.$esVersion)))' \
         irJS$v/fastLinkJS
   ''',
 
@@ -551,6 +567,8 @@ def allESVersions = [
   "ES2020",
   "ES2021" // We do not use anything specifically from ES2021, but always test the latest to avoid #4675
 ]
+def defaultESVersion = "ES2015"
+def latestESVersion = "ES2021"
 
 // The 'quick' matrix
 def quickMatrix = []
@@ -562,11 +580,12 @@ mainScalaVersions.each { scalaVersion ->
   quickMatrix.add([task: "test-suite-default-esversion", scala: scalaVersion, java: mainJavaVersion, testMinify: "false", testSuite: "testSuite"])
   quickMatrix.add([task: "test-suite-default-esversion", scala: scalaVersion, java: mainJavaVersion, testMinify: "true", testSuite: "testSuite"])
   quickMatrix.add([task: "test-suite-custom-esversion", scala: scalaVersion, java: mainJavaVersion, esVersion: "ES5_1", testSuite: "testSuite"])
-  quickMatrix.add([task: "test-suite-webassembly", scala: scalaVersion, java: mainJavaVersion, testMinify: "false", testSuite: "testSuite"])
-  quickMatrix.add([task: "test-suite-webassembly", scala: scalaVersion, java: mainJavaVersion, testMinify: "false", testSuite: "testSuiteEx"])
+  quickMatrix.add([task: "test-suite-webassembly", scala: scalaVersion, java: mainJavaVersion, esVersion: defaultESVersion, testMinify: "false", testSuite: "testSuite"])
+  quickMatrix.add([task: "test-suite-webassembly", scala: scalaVersion, java: mainJavaVersion, esVersion: latestESVersion, testMinify: "false", testSuite: "testSuite"])
+  quickMatrix.add([task: "test-suite-webassembly", scala: scalaVersion, java: mainJavaVersion, esVersion: defaultESVersion, testMinify: "false", testSuite: "testSuiteEx"])
   quickMatrix.add([task: "test-suite-default-esversion", scala: scalaVersion, java: mainJavaVersion, testMinify: "false", testSuite: "scalaTestSuite"])
   quickMatrix.add([task: "test-suite-custom-esversion", scala: scalaVersion, java: mainJavaVersion, esVersion: "ES5_1", testSuite: "scalaTestSuite"])
-  quickMatrix.add([task: "test-suite-webassembly", scala: scalaVersion, java: mainJavaVersion, testMinify: "false", testSuite: "scalaTestSuite"])
+  quickMatrix.add([task: "test-suite-webassembly", scala: scalaVersion, java: mainJavaVersion, esVersion: defaultESVersion, testMinify: "false", testSuite: "scalaTestSuite"])
   quickMatrix.add([task: "bootstrap", scala: scalaVersion, java: mainJavaVersion])
   quickMatrix.add([task: "partest-fastopt", scala: scalaVersion, java: mainJavaVersion, partestopts: ""])
   quickMatrix.add([task: "partest-fastopt", scala: scalaVersion, java: mainJavaVersion, partestopts: "--wasm"])
@@ -591,7 +610,7 @@ otherScalaVersions.each { scalaVersion ->
 mainScalaVersions.each { scalaVersion ->
   otherJavaVersions.each { javaVersion ->
     quickMatrix.add([task: "test-suite-default-esversion", scala: scalaVersion, java: javaVersion, testMinify: "false", testSuite: "testSuite"])
-    quickMatrix.add([task: "test-suite-webassembly", scala: scalaVersion, java: mainJavaVersion, testMinify: "false", testSuite: "testSuite"])
+    quickMatrix.add([task: "test-suite-webassembly", scala: scalaVersion, java: mainJavaVersion, esVersion: defaultESVersion, testMinify: "false", testSuite: "testSuite"])
   }
   fullMatrix.add([task: "partest-noopt", scala: scalaVersion, java: mainJavaVersion, partestopts: ""])
   fullMatrix.add([task: "partest-noopt", scala: scalaVersion, java: mainJavaVersion, partestopts: "--wasm"])
diff --git a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
index 4f8387fe57..0733ef00e7 100644
--- a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
+++ b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
@@ -167,6 +167,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
     private val fieldsMutatedInCurrentClass = new ScopedVar[mutable.Set[Name]]
     private val generatedSAMWrapperCount = new ScopedVar[VarBox[Int]]
     private val delambdafyTargetDefDefs = new ScopedVar[mutable.Map[Symbol, DefDef]]
+    private val methodsAllowingJSAwait = new ScopedVar[mutable.Set[Symbol]]
 
     def currentThisTypeNullable: jstpe.Type =
       encodeClassType(currentClassSym)
@@ -241,6 +242,7 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
           fieldsMutatedInCurrentClass := mutable.Set.empty,
           generatedSAMWrapperCount := new VarBox(0),
           delambdafyTargetDefDefs := mutable.Map.empty,
+          methodsAllowingJSAwait := mutable.Set.empty,
           currentMethodSym := null,
           thisLocalVarName := null,
           enclosingLabelDefInfos := null,
@@ -469,7 +471,8 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
                 currentClassSym := sym,
                 fieldsMutatedInCurrentClass := mutable.Set.empty,
                 generatedSAMWrapperCount := new VarBox(0),
-                delambdafyTargetDefDefs := mutable.Map.empty
+                delambdafyTargetDefDefs := mutable.Map.empty,
+                methodsAllowingJSAwait := mutable.Set.empty
             ) {
               val tree = if (isJSType(sym)) {
                 if (!sym.isTraitOrInterface && isNonNativeJSClass(sym) &&
@@ -5333,6 +5336,35 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
           // js.import.meta
           js.JSImportMeta()
 
+        case JS_ASYNC =>
+          // js.async(arg)
+          assert(args.size == 1,
+              s"Expected exactly 1 argument for JS primitive $code but got " +
+              s"${args.size} at $pos")
+          val Block(stats, fun @ Function(_, Apply(target, _))) = args.head
+          methodsAllowingJSAwait += target.symbol
+          val genStats = stats.map(genStat(_))
+          val asyncExpr = genAnonFunction(fun) match {
+            case js.NewLambda(_, closure: js.Closure)
+                if closure.params.isEmpty && closure.resultType == jstpe.AnyType =>
+              val newFlags = closure.flags.withTyped(false).withAsync(true)
+              js.JSFunctionApply(closure.copy(flags = newFlags), Nil)
+            case other =>
+              abort(s"Unexpected tree generated for the Function0 argument to js.async at $pos: $other")
+          }
+          js.Block(genStats, asyncExpr)
+
+        case JS_AWAIT =>
+          // js.await(arg)
+          if (!methodsAllowingJSAwait.contains(currentMethodSym)) {
+            reporter.error(pos,
+                "Illegal use of js.await().\n" +
+                "It can only be used inside a js.async {...} block, without any lambda,\n" +
+                "by-name argument or nested method in-between.")
+          }
+          val arg = genArgs1
+          js.JSAwait(arg)
+
         case DYNAMIC_IMPORT =>
           assert(args.size == 1,
               s"Expected exactly 1 argument for JS primitive $code but got " +
diff --git a/compiler/src/main/scala/org/scalajs/nscplugin/JSDefinitions.scala b/compiler/src/main/scala/org/scalajs/nscplugin/JSDefinitions.scala
index 5a46388543..7d9983e974 100644
--- a/compiler/src/main/scala/org/scalajs/nscplugin/JSDefinitions.scala
+++ b/compiler/src/main/scala/org/scalajs/nscplugin/JSDefinitions.scala
@@ -47,6 +47,8 @@ trait JSDefinitions {
       lazy val JSPackage_native        = getMemberMethod(ScalaJSJSPackageModule, newTermName("native"))
       lazy val JSPackage_undefined     = getMemberMethod(ScalaJSJSPackageModule, newTermName("undefined"))
       lazy val JSPackage_dynamicImport = getMemberMethod(ScalaJSJSPackageModule, newTermName("dynamicImport"))
+      lazy val JSPackage_async         = getMemberMethod(ScalaJSJSPackageModule, newTermName("async"))
+      lazy val JSPackage_await         = getMemberMethod(ScalaJSJSPackageModule, newTermName("await"))
 
     lazy val JSNativeAnnotation = getRequiredClass("scala.scalajs.js.native")
 
diff --git a/compiler/src/main/scala/org/scalajs/nscplugin/JSPrimitives.scala b/compiler/src/main/scala/org/scalajs/nscplugin/JSPrimitives.scala
index c93709363b..90aa1b1513 100644
--- a/compiler/src/main/scala/org/scalajs/nscplugin/JSPrimitives.scala
+++ b/compiler/src/main/scala/org/scalajs/nscplugin/JSPrimitives.scala
@@ -51,7 +51,10 @@ abstract class JSPrimitives {
   final val JS_IMPORT = JS_NEW_TARGET + 1  // js.import.apply(specifier)
   final val JS_IMPORT_META = JS_IMPORT + 1 // js.import.meta
 
-  final val CONSTRUCTOROF = JS_IMPORT_META + 1                         // runtime.constructorOf(clazz)
+  final val JS_ASYNC = JS_IMPORT_META + 1 // js.async
+  final val JS_AWAIT = JS_ASYNC + 1       // js.await
+
+  final val CONSTRUCTOROF = JS_AWAIT + 1                               // runtime.constructorOf(clazz)
   final val CREATE_INNER_JS_CLASS = CONSTRUCTOROF + 1                  // runtime.createInnerJSClass
   final val CREATE_LOCAL_JS_CLASS = CREATE_INNER_JS_CLASS + 1          // runtime.createLocalJSClass
   final val WITH_CONTEXTUAL_JS_CLASS_VALUE = CREATE_LOCAL_JS_CLASS + 1 // runtime.withContextualJSClassValue
@@ -96,6 +99,8 @@ abstract class JSPrimitives {
 
     addPrimitive(JSPackage_typeOf, TYPEOF)
     addPrimitive(JSPackage_native, JS_NATIVE)
+    addPrimitive(JSPackage_async, JS_ASYNC)
+    addPrimitive(JSPackage_await, JS_AWAIT)
 
     addPrimitive(BoxedUnit_UNIT, UNITVAL)
 
diff --git a/compiler/src/test/scala/org/scalajs/nscplugin/test/JSAsyncAwaitTest.scala b/compiler/src/test/scala/org/scalajs/nscplugin/test/JSAsyncAwaitTest.scala
new file mode 100644
index 0000000000..2f3060b932
--- /dev/null
+++ b/compiler/src/test/scala/org/scalajs/nscplugin/test/JSAsyncAwaitTest.scala
@@ -0,0 +1,74 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package org.scalajs.nscplugin.test
+
+import org.scalajs.nscplugin.test.util._
+import org.junit.Test
+
+// scalastyle:off line.size.limit
+
+class JSAsyncAwaitTest extends DirectTest with TestHelpers {
+
+  override def preamble: String =
+    """import scala.scalajs.js
+    """
+
+  @Test
+  def orphanAwait(): Unit = {
+    """
+    class A {
+      def foo(x: js.Promise[Int]): Int =
+        js.await(x)
+    }
+    """ hasErrors
+    """
+      |newSource1.scala:5: error: Illegal use of js.await().
+      |It can only be used inside a js.async {...} block, without any lambda,
+      |by-name argument or nested method in-between.
+      |        js.await(x)
+      |                ^
+    """
+
+    """
+    class A {
+      def foo(x: js.Promise[Int]): js.Promise[Int] = js.async {
+        val f: () => Int = () => js.await(x)
+        f()
+      }
+    }
+    """ hasErrors
+    """
+      |newSource1.scala:5: error: Illegal use of js.await().
+      |It can only be used inside a js.async {...} block, without any lambda,
+      |by-name argument or nested method in-between.
+      |        val f: () => Int = () => js.await(x)
+      |                                         ^
+    """
+
+    """
+    class A {
+      def foo(x: js.Promise[Int]): js.Promise[Int] = js.async {
+        def f(): Int = js.await(x)
+        f()
+      }
+    }
+    """ hasErrors
+    """
+      |newSource1.scala:5: error: Illegal use of js.await().
+      |It can only be used inside a js.async {...} block, without any lambda,
+      |by-name argument or nested method in-between.
+      |        def f(): Int = js.await(x)
+      |                               ^
+    """
+  }
+}
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Hashers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Hashers.scala
index a2b0636bf1..ad94d65549 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Hashers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Hashers.scala
@@ -242,6 +242,10 @@ object Hashers {
           mixTree(default)
           mixType(tree.tpe)
 
+        case JSAwait(arg) =>
+          mixTag(TagJSAwait)
+          mixTree(arg)
+
         case Debugger() =>
           mixTag(TagDebugger)
 
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala
index e4836fdcc0..c69ad1447c 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala
@@ -291,6 +291,11 @@ object Printers {
           undent()
           undent(); println(); print('}')
 
+        case JSAwait(arg) =>
+          print("await(")
+          print(arg)
+          print(")")
+
         case Debugger() =>
           print("debugger")
 
@@ -896,12 +901,16 @@ object Printers {
             print(name)
 
         case Closure(flags, captureParams, params, restParam, resultType, body, captureValues) =>
+          print("(")
+          if (flags.async)
+            print("async ")
           if (flags.typed)
-            print("(typed-lambda<")
+            print("typed-lambda")
           else if (flags.arrow)
-            print("(arrow-lambda<")
+            print("arrow-lambda")
           else
-            print("(lambda<")
+            print("lambda")
+          print("<")
           var first = true
           for ((param, value) <- captureParams.zip(captureValues)) {
             if (first)
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
index c6c0c9060c..43abb124ae 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
@@ -326,6 +326,10 @@ object Serializers {
           writeTree(default)
           writeType(tree.tpe)
 
+        case JSAwait(arg) =>
+          writeTagAndPos(TagJSAwait)
+          writeTree(arg)
+
         case Debugger() =>
           writeTagAndPos(TagDebugger)
 
@@ -1216,6 +1220,10 @@ object Serializers {
           Match(readTree(), List.fill(readInt()) {
             (readTrees().map(_.asInstanceOf[MatchableLiteral]), readTree())
           }, readTree())(readType())
+
+        case TagJSAwait =>
+          JSAwait(readTree())
+
         case TagDebugger => Debugger()
 
         case TagNew          => New(readClassName(), readMethodIdent(), readTrees())
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Tags.scala b/ir/shared/src/main/scala/org/scalajs/ir/Tags.scala
index 517817b036..bc7d2982b0 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Tags.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Tags.scala
@@ -133,6 +133,7 @@ private[ir] object Tags {
   // New in 1.19
   final val TagApplyTypedClosure = TagLinkTimeProperty + 1
   final val TagNewLambda = TagApplyTypedClosure + 1
+  final val TagJSAwait = TagNewLambda + 1
 
   // Tags for member defs
 
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Transformers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Transformers.scala
index 9a55fbd304..27d9086435 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Transformers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Transformers.scala
@@ -77,6 +77,9 @@ object Transformers {
           Match(transform(selector), cases.map(c => (c._1, transform(c._2))),
               transform(default))(tree.tpe)
 
+        case JSAwait(arg) =>
+          JSAwait(transform(arg))
+
         // Scala expressions
 
         case New(className, ctor, args) =>
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Traversers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Traversers.scala
index 9270d4ad3f..d5782da074 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Traversers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Traversers.scala
@@ -69,6 +69,9 @@ object Traversers {
         cases foreach (c => (c._1 map traverse, traverse(c._2)))
         traverse(default)
 
+      case JSAwait(arg) =>
+        traverse(arg)
+
       // Scala expressions
 
       case New(_, _, args) =>
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala b/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
index e90ecdd3e5..b62630e212 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
@@ -218,6 +218,19 @@ object Trees {
   sealed case class Match(selector: Tree, cases: List[(List[MatchableLiteral], Tree)],
       default: Tree)(val tpe: Type)(implicit val pos: Position) extends Tree
 
+  /** `await arg`.
+   *
+   *  This is directly equivalent to a JavaScript `await` expression. This node
+   *  is only valid within a [[Closure]] node with the `async` flag.
+   *
+   *  This is not a `UnaryOp` because of the above strict scoping rule. For
+   *  example, it is not safe to pull this node out of or into an intervening
+   *  closure, contrary to `UnaryOp`s.
+   */
+  sealed case class JSAwait(arg: Tree)(implicit val pos: Position) extends Tree {
+    val tpe = AnyType
+  }
+
   sealed case class Debugger()(implicit val pos: Position) extends Tree {
     val tpe = VoidType
   }
@@ -1215,6 +1228,10 @@ object Trees {
    *  with `new`). If `false`, it is a regular Function (`function`), which
    *  does have a `this` parameter of type `AnyType`. Typed closures are always
    *  Arrow functions, since they do not have a `this` parameter.
+   *
+   *  If `flags.async` is `true`, it is an `async` closure. Async closures
+   *  return a `Promise` of their body, and can contain [[JSAwait]] nodes.
+   *  `flags.typed` and `flags.async` cannot both be `true`.
    */
   sealed case class Closure(flags: ClosureFlags, captureParams: List[ParamDef],
       params: List[ParamDef], restParam: Option[ParamDef], resultType: Type,
@@ -1574,6 +1591,8 @@ object Trees {
 
     def typed: Boolean = (bits & TypedBit) != 0
 
+    def async: Boolean = (bits & AsyncBit) != 0
+
     def withArrow(arrow: Boolean): ClosureFlags =
       if (arrow) new ClosureFlags(bits | ArrowBit)
       else new ClosureFlags(bits & ~ArrowBit)
@@ -1581,6 +1600,10 @@ object Trees {
     def withTyped(typed: Boolean): ClosureFlags =
       if (typed) new ClosureFlags(bits | TypedBit)
       else new ClosureFlags(bits & ~TypedBit)
+
+    def withAsync(async: Boolean): ClosureFlags =
+      if (async) new ClosureFlags(bits | AsyncBit)
+      else new ClosureFlags(bits & ~AsyncBit)
   }
 
   object ClosureFlags {
@@ -1593,6 +1616,9 @@ object Trees {
     private final val TypedShift = 1
     private final val TypedBit = 1 << TypedShift
 
+    private final val AsyncShift = 2
+    private final val AsyncBit = 1 << AsyncShift
+
     /** `function` closure base flags. */
     final val function: ClosureFlags =
       new ClosureFlags(0)
diff --git a/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala b/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala
index 6d8eb165fd..060bf4fdb8 100644
--- a/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala
+++ b/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala
@@ -295,6 +295,10 @@ class PrintersTest {
             i(11))(IntType))
   }
 
+  @Test def printJSAwait(): Unit = {
+    assertPrintEquals("await(p)", JSAwait(ref("p", AnyType)))
+  }
+
   @Test def printDebugger(): Unit = {
     assertPrintEquals("debugger", Debugger())
   }
@@ -950,6 +954,26 @@ class PrintersTest {
             Some(ParamDef("z", NON, AnyType, mutable = false)),
             AnyType, ref("z", AnyType), Nil))
 
+    assertPrintEquals(
+        """
+          |(async lambda<>(...z: any): any = {
+          |  z
+          |})
+        """,
+        Closure(ClosureFlags.function.withAsync(true), Nil, Nil,
+            Some(ParamDef("z", NON, AnyType, mutable = false)),
+            AnyType, ref("z", AnyType), Nil))
+
+    assertPrintEquals(
+        """
+          |(async arrow-lambda<>(...z: any): any = {
+          |  z
+          |})
+        """,
+        Closure(ClosureFlags.arrow.withAsync(true), Nil, Nil,
+            Some(ParamDef("z", NON, AnyType, mutable = false)),
+            AnyType, ref("z", AnyType), Nil))
+
     assertPrintEquals(
         """
           |(typed-lambda<>() {
diff --git a/library/src/main/scala/scala/scalajs/js/package.scala b/library/src/main/scala/scala/scalajs/js/package.scala
index 5e3b548db4..919455831b 100644
--- a/library/src/main/scala/scala/scalajs/js/package.scala
+++ b/library/src/main/scala/scala/scalajs/js/package.scala
@@ -158,4 +158,51 @@ package object js {
    */
   def dynamicImport[A](body: => A): js.Promise[A] =
     throw new java.lang.Error("stub")
+
+  /** <span class="badge badge-ecma2017" style="float: right;">ECMAScript 2017</span>
+   *  Executes a block of code under a JavaScript `async` context.
+   *
+   *  The block of code can await [[Promise js.Promise]]s using [[await js.await]].
+   *  Doing so will continue after the call to `js.await` when the given
+   *  `Promise` is resolved. If the `Promise` is rejected, the exception gets
+   *  rethrown at the call site.
+   *
+   *  A block such as `js.async { body }` is equivalent to an
+   *  immediately-applied JavaScript `async` function:
+   *
+   *  {{{
+   *  (async () => body)()
+   *  }}}
+   *
+   *  Example usage:
+   *
+   *  {{{
+   *  val p: js.Promise[String] = downloadSomething()
+   *  val result: js.Promise[Int] = js.async {
+   *    val text: String = js.await(p)
+   *    text.toInt
+   *  }
+   *  }}}
+   *
+   *  This method returns a [[Promise js.Promise]] that will be resolved with
+   *  the result of the code block. If the block throws an exception, the
+   *  `Promise` will be rejected.
+   *
+   *  Calls to `js.await` can only appear within a `js.async` block. They must
+   *  not be nested in any local method, class, by-name argument or closure.
+   *  The latter includes `for` comprehensions. They may appear within
+   *  conditional branches, `while` loops and `try/catch/finally` blocks.
+   */
+  def async[A](body: => A): js.Promise[A] =
+    throw new java.lang.Error("stub")
+
+  /** <span class="badge badge-ecma2017" style="float: right;">ECMAScript 2017</span>
+   *  Awaits a [[Promise js.Promise]] within the context of an [[async js.async]] block.
+   *
+   *  This method corresponds to the JavaScript `await` keyword.
+   *
+   *  See the documentation of [[async js.async]].
+   */
+  def await[A](promise: js.Promise[A]): A =
+    throw new java.lang.Error("stub")
 }
diff --git a/linker/jvm/src/main/scala/org/scalajs/linker/backend/closure/ClosureAstTransformer.scala b/linker/jvm/src/main/scala/org/scalajs/linker/backend/closure/ClosureAstTransformer.scala
index f3caeba0af..2397ff94af 100644
--- a/linker/jvm/src/main/scala/org/scalajs/linker/backend/closure/ClosureAstTransformer.scala
+++ b/linker/jvm/src/main/scala/org/scalajs/linker/backend/closure/ClosureAstTransformer.scala
@@ -348,6 +348,8 @@ private class ClosureAstTransformer(featureSet: FeatureSet,
         new Node(Token.DELPROP, transformExpr(prop))
       case UnaryOp(op, lhs) =>
         mkUnaryOp(op, transformExpr(lhs))
+      case Await(arg) =>
+        new Node(Token.AWAIT, transformExpr(arg))
       case IncDec(prefix, inc, arg) =>
         val token = if (inc) Token.INC else Token.DEC
         val node = new Node(token, transformExpr(arg))
@@ -385,9 +387,10 @@ private class ClosureAstTransformer(featureSet: FeatureSet,
       case Super() =>
         new Node(Token.SUPER)
 
-      case Function(arrow, args, restParam, body) =>
+      case Function(flags, args, restParam, body) =>
         val node = genFunction("", args, restParam, body)
-        node.setIsArrowFunction(arrow)
+        node.setIsArrowFunction(flags.arrow)
+        node.setIsAsyncFunction(flags.async)
         node
       case FunctionDef(name, args, restParam, body) =>
         genFunction(name.resolveName(), args, restParam, body)
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analysis.scala b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analysis.scala
index 3c65ac27ba..83fd01f327 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analysis.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analysis.scala
@@ -215,6 +215,8 @@ object Analysis {
 
   final case class ExponentOperatorWithoutES2016Support(from: From) extends Error
 
+  final case class AsyncWithoutES2017Support(from: From) extends Error
+
   final case class InvalidLinkTimeProperty(
     linkTimePropertyName: String,
     linkTimePropertyType: Type,
@@ -277,6 +279,8 @@ object Analysis {
         "Uses import.meta with a module kind other than ESModule"
       case ExponentOperatorWithoutES2016Support(_) =>
         "Uses the ** operator with an ECMAScript version older than ES 2016"
+      case AsyncWithoutES2017Support(_) =>
+        "Uses an async block with an ECMAScript version older than ES 2017"
       case InvalidLinkTimeProperty(name, tpe, _) =>
         s"Uses invalid link-time property ${name} of type ${tpe}"
     }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala
index 44d34c5e3a..e5705bef67 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala
@@ -1521,6 +1521,11 @@ private class AnalyzerRun(config: CommonPhaseConfig, initial: Boolean,
         _errors ::= ExponentOperatorWithoutES2016Support(from)
       }
 
+      if ((globalFlags & ReachabilityInfo.FlagUsedAsync) != 0 &&
+          config.coreSpec.esFeatures.esVersion < ESVersion.ES2017) {
+        _errors ::= AsyncWithoutES2017Support(from)
+      }
+
       if ((globalFlags & ReachabilityInfo.FlagUsedClassSuperClass) != 0) {
         _classSuperClassUsed.set(true)
       }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala
index 27bb807a74..7d57c965bf 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala
@@ -119,8 +119,9 @@ object Infos {
     final val FlagAccessedNewTarget = 1 << 1
     final val FlagAccessedImportMeta = 1 << 2
     final val FlagUsedExponentOperator = 1 << 3
-    final val FlagUsedClassSuperClass = 1 << 4
-    final val FlagNeedsDesugaring = 1 << 5
+    final val FlagUsedAsync = 1 << 4
+    final val FlagUsedClassSuperClass = 1 << 5
+    final val FlagNeedsDesugaring = 1 << 6
   }
 
   /** Things from a given class that are reached by one method. */
@@ -398,6 +399,9 @@ object Infos {
     def addUsedExponentOperator(): this.type =
       setFlag(ReachabilityInfo.FlagUsedExponentOperator)
 
+    def addUsedAsync(): this.type =
+      setFlag(ReachabilityInfo.FlagUsedAsync)
+
     def addUsedIntLongDivModByMaybeZero(): this.type =
       addInstantiatedClass(ArithmeticExceptionClass, StringArgConstructorName)
 
@@ -770,6 +774,10 @@ object Infos {
             case JSBinaryOp(JSBinaryOp.**, _, _) =>
               builder.addUsedExponentOperator()
 
+            case Closure(flags, _, _, _, _, _, _) =>
+              if (flags.async)
+                builder.addUsedAsync()
+
             case LoadJSConstructor(className) =>
               builder.addInstantiatedClass(className)
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
index ea962ee95a..bd86907769 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
@@ -314,7 +314,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
     initToInline.fold {
       assert(className != ClassClass, s"java.lang.Class did not have an inlineable init")
       WithGlobals(
-          js.Function(arrow = false, Nil, None, js.Block(superCtorCallAndFieldDefs)))
+          js.Function(ClosureFlags.function, Nil, None, js.Block(superCtorCallAndFieldDefs)))
     } { initMethodDef =>
       val generatedInitMethodFunWithGlobals = {
         implicit val pos = initMethodDef.pos
@@ -354,7 +354,8 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
     val dummyCtor = fileLevelVar(VarField.hh, genName(className))
 
     List(
-        js.JSDocConstructor(genConst(dummyCtor.ident, js.Function(false, Nil, None, js.Skip()))),
+        js.JSDocConstructor(
+            genConst(dummyCtor.ident, js.Function(ClosureFlags.function, Nil, None, js.Skip()))),
         dummyCtor.prototype := superCtor.prototype,
         genAssignPrototype(ctorVar, js.New(dummyCtor, Nil), localDeclPrototypeVar)
     )
@@ -523,7 +524,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
     methodFun0WithGlobals.flatMap { methodFun0 =>
       val methodFun = if (namespace == MemberNamespace.Constructor) {
         // init methods have to return `this` so that we can chain them to `new`
-        js.Function(arrow = false, methodFun0.args, methodFun0.restParam, {
+        js.Function(ClosureFlags.function, methodFun0.args, methodFun0.restParam, {
           implicit val pos = methodFun0.body.pos
           js.Block(
               methodFun0.body,
@@ -1107,7 +1108,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
               exportsVarRef,
               js.StringLiteral(exportName),
               List(
-                  "get" -> js.Function(arrow = false, Nil, None, {
+                  "get" -> js.Function(ClosureFlags.function, Nil, None, {
                     js.Return(globalVar(VarField.t, field.name))
                   }),
                   "configurable" -> js.BooleanLiteral(true)
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
index 74f8f2449c..6fb37ce343 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
@@ -20,7 +20,7 @@ import org.scalajs.ir.ScalaJSVersions
 import org.scalajs.ir.Position
 import org.scalajs.ir.Names._
 import org.scalajs.ir.OriginalName.NoOriginalName
-import org.scalajs.ir.Trees.{JSUnaryOp, JSBinaryOp}
+import org.scalajs.ir.Trees.{ClosureFlags, JSUnaryOp, JSBinaryOp}
 import org.scalajs.ir.Types._
 import org.scalajs.ir.WellKnownNames._
 
@@ -2127,7 +2127,7 @@ private[emitter] object CoreJSLib {
         MethodDef(static, name, args, restParam, body) <- members
       } yield {
         val target = if (static) classRef else prototypeFor(classRef)
-        genPropSelect(target, name) := Function(arrow = false, args, restParam, body)
+        genPropSelect(target, name) := Function(ClosureFlags.function, args, restParam, body)
       }
     }
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
index b5616527fd..e5c444e342 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
@@ -490,9 +490,9 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
       performOptimisticThenPessimisticRuns {
         val thisIdent = fileLevelVarIdent(VarField.thiz, thisOriginalName)
         val env = env0.withExplicitThis()
-        val js.Function(jsArrow, jsParams, restParam, jsBody) =
-          desugarToFunctionInternal(arrow = false, params, None, body, isStat, env)
-        js.Function(jsArrow, js.ParamDef(thisIdent) :: jsParams, restParam, jsBody)
+        val js.Function(jsFlags, jsParams, restParam, jsBody) =
+          desugarToFunctionInternal(ClosureFlags.function, params, None, body, isStat, env)
+        js.Function(jsFlags, js.ParamDef(thisIdent) :: jsParams, restParam, jsBody)
       }
     }
 
@@ -502,13 +502,13 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
         body: Tree, isStat: Boolean, env0: Env)(
         implicit pos: Position): WithGlobals[js.Function] = {
       performOptimisticThenPessimisticRuns {
-        desugarToFunctionInternal(arrow = false, params, restParam, body, isStat, env0)
+        desugarToFunctionInternal(ClosureFlags.function, params, restParam, body, isStat, env0)
       }
     }
 
     /** Desugars parameters and body to a JS function.
      */
-    private def desugarToFunctionInternal(arrow: Boolean,
+    private def desugarToFunctionInternal(flags: ClosureFlags,
         params: List[ParamDef], restParam: Option[ParamDef], body: Tree,
         isStat: Boolean, env0: Env)(
         implicit pos: Position): js.Function = {
@@ -533,12 +533,14 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
         case other                                        => other
       }
 
-      val actualArrowFun = arrow && esFeatures.useECMAScript2015Semantics
+      val jsFlags =
+        if (esFeatures.useECMAScript2015Semantics) flags
+        else flags.withArrow(false)
       val jsParams = params.map(transformParamDef(_))
 
       if (es2015) {
         val jsRestParam = restParam.map(transformParamDef(_))
-        js.Function(actualArrowFun, jsParams, jsRestParam, cleanedNewBody)
+        js.Function(jsFlags, jsParams, jsRestParam, cleanedNewBody)
       } else {
         val patchedBody = restParam.fold {
           cleanedNewBody
@@ -546,7 +548,7 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
           js.Block(makeExtractRestParam(restParam, jsParams.size), cleanedNewBody)
         }
 
-        js.Function(actualArrowFun, jsParams, None, patchedBody)
+        js.Function(jsFlags, jsParams, None, patchedBody)
       }
     }
 
@@ -1375,6 +1377,8 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
           allowBehavior(semantics.asInstanceOfs) && test(expr)
 
         // JavaScript expressions that can always have side-effects
+        case JSAwait(arg) =>
+          allowSideEffects && test(arg)
         case SelectJSNativeMember(_, _) =>
           allowSideEffects
         case JSNew(fun, args) =>
@@ -1740,6 +1744,11 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
             }
           }
 
+        case JSAwait(arg) =>
+          unnest(arg) { (newArg, env) =>
+            redo(JSAwait(newArg))(env)
+          }
+
         // Scala expressions (if we reach here their arguments are not expressions)
 
         case New(className, ctor, args) =>
@@ -2225,6 +2234,9 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
           js.If(transformExprNoChar(cond), transformExpr(thenp, tree.tpe),
               transformExpr(elsep, tree.tpe))
 
+        case JSAwait(arg) =>
+          js.Await(transformExprNoChar(arg))
+
         // Scala expressions
 
         case New(className, ctor, args) =>
@@ -3135,7 +3147,7 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
           .withParams(params ++ restParam)
           .withVars(envVarsForCaptures)
 
-        desugarToFunctionInternal(flags.arrow, params, restParam, body,
+        desugarToFunctionInternal(flags, params, restParam, body,
             isStat = resultType == VoidType, bodyEnv)
       }
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/JSGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/JSGen.scala
index ea9be90e76..f32e0619e0 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/JSGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/JSGen.scala
@@ -13,6 +13,7 @@
 package org.scalajs.linker.backend.emitter
 
 import org.scalajs.ir.Position
+import org.scalajs.ir.Trees.ClosureFlags
 
 import org.scalajs.linker.backend.javascript.Trees._
 import org.scalajs.linker.interface.ESVersion
@@ -117,7 +118,9 @@ private[emitter] final class JSGen(val config: Emitter.Config) {
    */
   def genArrowFunction(args: List[ParamDef], restParam: Option[ParamDef], body: Tree)(
       implicit pos: Position): Function = {
-    Function(esFeatures.esVersion >= ESVersion.ES2015, args, restParam, body)
+    val closureFlags =
+      ClosureFlags.function.withArrow(esFeatures.esVersion >= ESVersion.ES2015)
+    Function(closureFlags, args, restParam, body)
   }
 
   def genDefineProperty(obj: Tree, prop: Tree, descriptor: List[(String, Tree)])(
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/VarGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/VarGen.scala
index 34bc1ae6f2..199985d183 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/VarGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/VarGen.scala
@@ -17,6 +17,7 @@ import scala.annotation.tailrec
 import org.scalajs.ir._
 import org.scalajs.ir.Names._
 import org.scalajs.ir.OriginalName.NoOriginalName
+import org.scalajs.ir.Trees.ClosureFlags
 import org.scalajs.ir.Types._
 import org.scalajs.ir.WellKnownNames._
 
@@ -294,8 +295,8 @@ private[emitter] final class VarGen(jsGen: JSGen, nameGen: NameGen,
             if (mutable) {
               val x = Ident("x")
               genDefineProperty(exportsVarRef, name, List(
-                  "get" -> Function(arrow = false, Nil, None, Return(VarRef(ident))),
-                  "set" -> Function(arrow = false, List(ParamDef(x)), None, {
+                  "get" -> Function(ClosureFlags.function, Nil, None, Return(VarRef(ident))),
+                  "set" -> Function(ClosureFlags.function, List(ParamDef(x)), None, {
                       Assign(VarRef(ident), VarRef(x))
                   }),
                   "configurable" -> BooleanLiteral(true)
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Printers.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Printers.scala
index 56c8c4aefe..d4fb5f2284 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Printers.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Printers.scala
@@ -591,9 +591,11 @@ object Printers {
           print("this")
           printSeparatorIfStat()
 
-        case Function(arrow, args, restParam, body) =>
-          if (arrow) {
+        case Function(flags, args, restParam, body) =>
+          if (flags.arrow) {
             print('(')
+            if (flags.async)
+              print("async ")
             printSig(args, restParam)
             print("=> ")
             body match {
@@ -611,7 +613,10 @@ object Printers {
             }
             print(')')
           } else {
-            print("(function")
+            if (flags.async)
+              print("(async function")
+            else
+              print("(function")
             printSig(args, restParam)
             printBlock(body)
             print(')')
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Trees.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Trees.scala
index d0117dede1..0ed4501d8f 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Trees.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Trees.scala
@@ -20,6 +20,7 @@ import org.scalajs.ir
 import org.scalajs.ir.{OriginalName, Position}
 import org.scalajs.ir.OriginalName.NoOriginalName
 import org.scalajs.ir.Position.NoPosition
+import org.scalajs.ir.Trees.ClosureFlags
 
 object Trees {
   /* The case classes for JS Trees are sealed instead of final for historical
@@ -431,7 +432,15 @@ object Trees {
 
   sealed case class This()(implicit val pos: Position) extends Tree
 
-  sealed case class Function(arrow: Boolean, args: List[ParamDef],
+  /** Anonymous function.
+   *
+   *  For convenience to producers, `flags.typed` may or may not be true, and
+   *  is always ignored.
+   *
+   *  The other flags: `arrow` and `async`, are meaningful. They have the same
+   *  meaning as in `ir.Trees.Closure`.
+   */
+  sealed case class Function(flags: ClosureFlags, args: List[ParamDef],
       restParam: Option[ParamDef], body: Tree)(
       implicit val pos: Position) extends Tree
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
index 68b14c51c2..ac8ec3a872 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
@@ -414,6 +414,7 @@ final class CoreWasmLib(coreSpec: CoreSpec, globalInfo: LinkedGlobalInfo) {
     addHelperImport(genFunctionID.jsNewNoArg, List(anyref), List(anyref))
     addHelperImport(genFunctionID.jsImportCall, List(anyref), List(anyref))
     addHelperImport(genFunctionID.jsImportMeta, Nil, List(anyref))
+    addHelperImport(genFunctionID.jsAwait, List(anyref), List(anyref))
     addHelperImport(genFunctionID.jsDelete, List(anyref, anyref), Nil)
     addHelperImport(genFunctionID.jsForInStart, List(anyref), List(anyref))
     addHelperImport(genFunctionID.jsForInNext, List(anyref), List(anyref, Int32))
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CustomJSHelperBuilder.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CustomJSHelperBuilder.scala
index 194dadd076..07096f3ae2 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CustomJSHelperBuilder.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CustomJSHelperBuilder.scala
@@ -179,7 +179,7 @@ class CustomJSHelperBuilder()(implicit ctx: WasmContext, pos: Position) {
       resolver.setResolved(allocatedName)
     }
 
-    val helperFun = js.Function(arrow = true, jsParamDefs.toList, None, body)
+    val helperFun = js.Function(ClosureFlags.arrow, jsParamDefs.toList, None, body)
     val wasmFunType = watpe.FunctionType(wasmParamTypes.toList, transformResultType(resultType))
     ctx.addCustomJSHelper(helperFun, wasmFunType)
   }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala
index 6c78b14fa3..b926450b46 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala
@@ -15,6 +15,7 @@ package org.scalajs.linker.backend.wasmemitter
 import scala.concurrent.{ExecutionContext, Future}
 
 import org.scalajs.ir.Names._
+import org.scalajs.ir.Trees.ClosureFlags
 import org.scalajs.ir.Types._
 import org.scalajs.ir.OriginalName
 import org.scalajs.ir.Position
@@ -220,7 +221,7 @@ final class Emitter(config: Emitter.Config) {
       js.Return {
         val (argsParamDefs, restParamDef) = builder.genJSParamDefs(params, restParam)
         // Exported defs must be `function`s although they do not use their `this`
-        js.Function(arrow = false, argsParamDefs, restParamDef, {
+        js.Function(ClosureFlags.function, argsParamDefs, restParamDef, {
           js.Return(js.Apply(
               fRef,
               argsParamDefs.map(_.ref) ::: restParamDef.map(_.ref).toList
@@ -280,7 +281,7 @@ final class Emitter(config: Emitter.Config) {
       val decl = js.Let(ident, mutable = true, None)
       val exportStat = js.Export(List(ident -> js.ExportName(exportName)))
       val xParam = js.ParamDef(js.Ident("x"))
-      val setterFun = js.Function(arrow = true, List(xParam), None, {
+      val setterFun = js.Function(ClosureFlags.arrow, List(xParam), None, {
         js.Assign(js.VarRef(ident), xParam.ref)
       })
       val setterItem = js.StringLiteral(exportName) -> setterFun
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
index 94fa164d81..b355c1ad1c 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
@@ -592,6 +592,7 @@ private class FunctionEmitter private (
       case t: TryCatch            => genTryCatch(t, expectedType)
       case t: TryFinally          => unwinding.genTryFinally(t, expectedType)
       case t: Match               => genMatch(t, expectedType)
+      case t: JSAwait             => genJSAwait(t)
       case t: Debugger            => VoidType // ignore
       case t: Skip                => VoidType
 
@@ -3209,11 +3210,20 @@ private class FunctionEmitter private (
     }
 
     val helperID = builder.build(AnyNotNullType) {
-      js.Return {
-        val (argsParamDefs, restParamDef) = builder.genJSParamDefs(params, restParam)
-        js.Function(flags.arrow, argsParamDefs, restParamDef, {
+      val (argsParamDefs, restParamDef) = builder.genJSParamDefs(params, restParam)
+
+      val promisingFVarDef = if (flags.async) {
+        Some(js.VarDef(builder.newLocalIdent("pf"), Some({
+          js.Apply(js.DotSelect(builder.genGlobalRef("WebAssembly"), js.Ident("promising")), List(fRef))
+        })))
+      } else {
+        None
+      }
+
+      val ret = js.Return {
+        js.Function(flags.withAsync(false), argsParamDefs, restParamDef, {
           js.Return(js.Apply(
-              fRef,
+              promisingFVarDef.fold(fRef)(_.ref),
               dataRef ::
               (if (flags.arrow) Nil else List(js.This())) :::
               argsParamDefs.map(_.ref) :::
@@ -3221,6 +3231,8 @@ private class FunctionEmitter private (
           ))
         })
       }
+
+      promisingFVarDef.fold[js.Tree](ret)(vd => js.Block(vd, ret))
     }
 
     markPosition(tree)
@@ -3286,6 +3298,16 @@ private class FunctionEmitter private (
     expectedType
   }
 
+  private def genJSAwait(tree: JSAwait): Type = {
+    val JSAwait(arg) = tree
+
+    genTree(arg, AnyType)
+    markPosition(tree)
+    fb += wa.Call(genFunctionID.jsAwait)
+
+    AnyType
+  }
+
   private def genCreateJSClass(tree: CreateJSClass): Type = {
     val CreateJSClass(className, captureValues) = tree
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala
index 271894e7f5..0edc9fe20c 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala
@@ -157,6 +157,14 @@ const scalaJSHelpers = {
   jsNewNoArg: (constr) => new constr(),
   jsImportCall: (s) => import(s),
   jsImportMeta: () => import.meta,
+  jsAwait: (WebAssembly.Suspending ? new WebAssembly.Suspending((x) => x) : ((x) => {
+    /* This should not happen. We cannot get here without going through a
+     * `WebAssembly.promising()` function. If that one succeeded,
+     * `WebAssembly.Suspending` should also exist.
+     * TODO Remove this fallback when JSPI support is widespread.
+     */
+    throw new Error("Unexpected js.await() without JSPI support.");
+  })),
   jsDelete: (o, p) => { delete o[p]; },
   jsForInStart: function*(o) { for (var k in o) yield k; },
   jsForInNext: (g) => { var r = g.next(); return [r.value, r.done]; },
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
index c007314c9d..589c722ad8 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
@@ -155,6 +155,7 @@ object VarGen {
     case object jsNewNoArg extends JSHelperFunctionID
     case object jsImportCall extends JSHelperFunctionID
     case object jsImportMeta extends JSHelperFunctionID
+    case object jsAwait extends JSHelperFunctionID
     case object jsDelete extends JSHelperFunctionID
     case object jsForInStart extends JSHelperFunctionID
     case object jsForInNext extends JSHelperFunctionID
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala b/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
index bd3f6d612e..bfe9177ef6 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
@@ -789,6 +789,11 @@ private final class ClassDefChecker(classDef: ClassDef,
 
         checkTree(default, env)
 
+      case JSAwait(arg) =>
+        if (!env.inAsync)
+          reportError(i"Illegal `await` outside of `async` closure")
+        checkTree(arg, env)
+
       case Debugger() =>
 
       // Scala expressions
@@ -1048,9 +1053,10 @@ private final class ClassDefChecker(classDef: ClassDef,
 
     val Closure(flags, captureParams, params, restParam, resultType, body, captureValues) = tree
 
-    if (flags.typed && !flags.arrow) {
+    if (flags.typed && !flags.arrow)
       reportError(i"A typed closure must have the 'arrow' flag")
-    }
+    if (flags.typed && flags.async)
+      reportError(i"A typed closure cannot have the 'async' flag")
 
     /* Check compliance of captureValues wrt. captureParams in the current
      * method state, i.e., outside `withPerMethodState`.
@@ -1081,6 +1087,7 @@ private final class ClassDefChecker(classDef: ClassDef,
         .fromParams(captureParams ++ params ++ restParam)
         .withHasNewTarget(!flags.arrow)
         .withMaybeThisType(!flags.arrow, AnyType)
+        .withInAsync(flags.async)
       checkTree(body, bodyEnv)
     }
   }
@@ -1177,7 +1184,9 @@ object ClassDefChecker {
       /** Return types by label. */
       val returnLabels: Set[LabelName],
       /** Whether usages of `this` are restricted in this scope. */
-      val isThisRestricted: Boolean
+      val isThisRestricted: Boolean,
+      /** Whether we are in an `async` closure, where `await` expressions are valid. */
+      val inAsync: Boolean
   ) {
     import Env._
 
@@ -1200,13 +1209,17 @@ object ClassDefChecker {
     def withIsThisRestricted(isThisRestricted: Boolean): Env =
       copy(isThisRestricted = isThisRestricted)
 
+    def withInAsync(inAsync: Boolean): Env =
+      copy(inAsync = inAsync)
+
     private def copy(
       hasNewTarget: Boolean = hasNewTarget,
       locals: Map[LocalName, LocalDef] = locals,
       returnLabels: Set[LabelName] = returnLabels,
-      isThisRestricted: Boolean = isThisRestricted
+      isThisRestricted: Boolean = isThisRestricted,
+      inAsync: Boolean = inAsync
     ): Env = {
-      new Env(hasNewTarget, locals, returnLabels, isThisRestricted)
+      new Env(hasNewTarget, locals, returnLabels, isThisRestricted, inAsync)
     }
   }
 
@@ -1216,7 +1229,8 @@ object ClassDefChecker {
         hasNewTarget = false,
         locals = Map.empty,
         returnLabels = Set.empty,
-        isThisRestricted = false
+        isThisRestricted = false,
+        inAsync = false
       )
     }
 
@@ -1229,7 +1243,8 @@ object ClassDefChecker {
         hasNewTarget = false,
         paramLocalDefs.toMap,
         Set.empty,
-        isThisRestricted = false
+        isThisRestricted = false,
+        inAsync = false
       )
     }
   }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala b/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
index 0156b596e1..b66dfeea1f 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
@@ -348,6 +348,9 @@ private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter,
           typecheckExpect(body, env, tpe)
         typecheckExpect(default, env, tpe)
 
+      case JSAwait(arg) =>
+        typecheckAny(arg, env)
+
       case Debugger() =>
 
       // Scala expressions
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
index 6471b07ff7..51cebcdcca 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
@@ -482,6 +482,9 @@ private[optimizer] abstract class OptimizerCore(
             Match(newSelector, newCases, newDefault)(refinedType)
         }
 
+      case JSAwait(arg) =>
+        JSAwait(transformExpr(arg))
+
       // Scala expressions
 
       case New(className, ctor, args) =>
@@ -1009,13 +1012,14 @@ private[optimizer] abstract class OptimizerCore(
                 resultType, body, tcaptureValues)(cont)
           }
 
-          if (!flags.arrow || restParam.isDefined) {
+          if (!flags.arrow || flags.async || restParam.isDefined) {
             /* TentativeClosureReplacement assumes there are no rest
              * parameters, because that would not be inlineable anyway.
              * Likewise, it assumes that there is no binding for `this` nor for
              * `new.target`, which is only true for arrow functions.
-             * So we never try to inline non-arrow Closures, nor Closures with
-             * a rest parameter. There are few use cases for either anyway.
+             * Async closures cannot be inlined, due to their semantics.
+             * So we only ever try to inline non-async arrow Closures without
+             * rest parameters.
              */
             default()
           } else {
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/AnalyzerTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/AnalyzerTest.scala
index 4e77a3d2fb..a8714332f1 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/AnalyzerTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/AnalyzerTest.scala
@@ -685,6 +685,25 @@ class AnalyzerTest {
     }
   }
 
+  @Test
+  def asyncWithoutES2017(): AsyncResult = await {
+    val classDefs = Seq(
+      mainTestClassDef {
+        Closure(ClosureFlags.arrow.withAsync(true), Nil, Nil, None, AnyType, int(5), Nil)
+      }
+    )
+
+    val moduleInitializer = MainTestModuleInitializers
+
+    val analysis = computeAnalysis(classDefs,
+        moduleInitializers = MainTestModuleInitializers,
+        config = StandardConfig().withESFeatures(_.withESVersion(ESVersion.ES2016)))
+
+    assertContainsError("AsyncWithoutES2017Support", analysis) {
+      case AsyncWithoutES2017Support(_) => true
+    }
+  }
+
   @Test
   def importMetaWithoutESModule(): AsyncResult = await {
     val classDefs = Seq(
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/backend/javascript/PrintersTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/backend/javascript/PrintersTest.scala
index 2c5de62dd1..9d13a76444 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/backend/javascript/PrintersTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/backend/javascript/PrintersTest.scala
@@ -20,6 +20,7 @@ import org.junit.Test
 import org.junit.Assert._
 
 import org.scalajs.ir
+import org.scalajs.ir.Trees.ClosureFlags
 
 import Trees._
 
@@ -100,7 +101,7 @@ class PrintersTest {
         |ctor = (function() {
         |});
       """,
-      JSDocConstructor(Assign(VarRef("ctor"), Function(false, Nil, None, Skip())))
+      JSDocConstructor(Assign(VarRef("ctor"), Function(ClosureFlags.function, Nil, None, Skip())))
     )
   }
 
diff --git a/project/Build.scala b/project/Build.scala
index 3ab4587c79..c723cee653 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -250,6 +250,7 @@ object MyScalaJSPlugin extends AutoPlugin {
           baseConfig.withArgs(List(
             "--experimental-wasm-exnref",
             "--experimental-wasm-imported-strings", // for JS string builtins
+            "--experimental-wasm-jspi", // for JSPI, used by async/await
             /* Force using the Turboshaft infrastructure for the optimizing compiler.
              * It appears to be more stable for the Wasm that we throw at it.
              * If you remove it, try running `scalaTestSuite2_13/test` with Wasm.
@@ -2257,6 +2258,8 @@ object Build {
             esVersion >= ESVersion.ES2015) :::
         includeIf(testDir / "require-exponent-op",
             esVersion >= ESVersion.ES2016) :::
+        includeIf(testDir / "require-async-await",
+            esVersion >= ESVersion.ES2017) :::
         includeIf(testDir / "require-modules",
             hasModules) :::
         includeIf(testDir / "require-no-modules",
diff --git a/test-suite/js/src/test/require-async-await/org/scalajs/testsuite/jsinterop/JSAsyncAwaitTest.scala b/test-suite/js/src/test/require-async-await/org/scalajs/testsuite/jsinterop/JSAsyncAwaitTest.scala
new file mode 100644
index 0000000000..3c786702d8
--- /dev/null
+++ b/test-suite/js/src/test/require-async-await/org/scalajs/testsuite/jsinterop/JSAsyncAwaitTest.scala
@@ -0,0 +1,148 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package org.scalajs.testsuite.jsinterop
+
+import scala.scalajs.js
+import scala.scalajs.js.JSConverters._
+import scala.scalajs.js.|
+
+import scala.concurrent.{Future, ExecutionContext}
+import scala.concurrent.ExecutionContext.Implicits.global
+
+import scala.collection.mutable.ArrayBuffer
+
+import org.junit.Assert._
+import org.junit.Assume._
+import org.junit.Test
+
+import org.scalajs.junit.async._
+
+class JSAsyncAwaitTest {
+  @Test
+  def basic(): AsyncResult = await {
+    val buf = new ArrayBuffer[String]()
+
+    val px = js.Promise.resolve[Int](5)
+
+    buf += "before"
+    val p = js.async {
+      buf += "start async"
+      val x = js.await(px)
+      buf += s"got x: $x"
+      x + 13
+    }
+    buf += "after"
+
+    assertArrayEquals(
+        Array[AnyRef]("before", "start async", "after"),
+        buf.toArray[AnyRef])
+
+    p.toFuture.map { (result: Int) =>
+      assertEquals(18, result)
+
+      assertArrayEquals(
+          Array[AnyRef]("before", "start async", "after", "got x: 5"),
+          buf.toArray[AnyRef])
+    }
+  }
+
+  @Test
+  def loop(): AsyncResult = await {
+    val buf = new ArrayBuffer[String]()
+
+    val inputs = (1 to 5).toList
+    val inputPromises = inputs.map(i => js.Promise.resolve[Int](i))
+
+    buf += "before"
+    val p = js.async {
+      buf += "start async"
+      var rest = inputPromises
+      while (!rest.isEmpty) {
+        val x = js.await(rest.head)
+        buf += x.toString()
+        rest = rest.tail
+      }
+      buf += "done"
+    }
+    buf += "after"
+
+    assertArrayEquals(
+        Array[AnyRef]("before", "start async", "after"),
+        buf.toArray[AnyRef])
+
+    p.toFuture.map { _ =>
+      assertArrayEquals(
+          ("before" :: "start async" :: "after" :: inputs.map(_.toString()) ::: "done" :: Nil).toArray[AnyRef],
+          buf.toArray[AnyRef])
+    }
+  }
+
+  @Test
+  def tryCatch(): AsyncResult = await {
+    val successfulInput = js.Promise.resolve[Int](42)
+    val failedInput: js.Promise[Int] = js.Promise.reject(new IllegalArgumentException("nope"))
+
+    val p = js.async {
+      val result1 = try {
+        js.await(successfulInput)
+      } catch {
+        case e: IllegalArgumentException =>
+          throw new AssertionError(e)
+      }
+      val result2 = try {
+        js.await(failedInput)
+        throw new AssertionError("awaiting a failed Promise did not throw")
+      } catch {
+        case e: IllegalArgumentException =>
+          56
+      }
+      (result1, result2)
+    }
+
+    p.toFuture.map { case (result1, result2) =>
+      assertEquals(42, result1)
+      assertEquals(56, result2)
+    }
+  }
+
+  @Test
+  def tryFinally(): AsyncResult = await {
+    val successfulInput = js.Promise.resolve[Int](42)
+    val failedInput: js.Promise[Int] = js.Promise.reject(new IllegalArgumentException("nope"))
+
+    val buf = new ArrayBuffer[String]()
+
+    val p: js.Promise[Int] = js.async {
+      val result1 = try {
+        js.await(successfulInput)
+      } finally {
+        buf += "first"
+      }
+      assertEquals(42, result1)
+      val result2 = try {
+        js.await(failedInput)
+        throw new AssertionError("awaiting a failed Promise did not throw")
+      } finally {
+        buf += "second"
+      }
+      throw new AssertionError("did not rethrow after the finally")
+    }
+
+    p.toFuture.failed.map { e =>
+      assertTrue(e.toString(), e.isInstanceOf[IllegalArgumentException])
+      assertArrayEquals(
+          Array[AnyRef]("first", "second"),
+          buf.toArray[AnyRef])
+    }
+  }
+}

From 5bb0d0905cb964285e20d365d7882aab5521235e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Mon, 17 Mar 2025 13:38:04 +0100
Subject: [PATCH 269/298] Enforce that jl.Throwable must a class extending
 jl.Object.

The emitter relies on that to rewire `jl.Throwable` to extend JS
`Error`, and bridge methods to those of `jl.Object`.

It previously had a side condition that `jl.Throwable` actually
extends `jl.Object` to perform that rewrite. If that were false,
though, some of the guarantees we give about `Throwable`s would
be broken, so I'm pretty sure something would break somewhere.

It is safer to directly enforce that universal fact in the
`ClassDefChecker` in the first place.
---
 .../linker/backend/emitter/ClassEmitter.scala      |  8 ++++----
 .../scalajs/linker/backend/emitter/Emitter.scala   |  2 +-
 .../scalajs/linker/checker/ClassDefChecker.scala   |  6 ++++--
 .../linker/checker/ClassDefCheckerTest.scala       | 14 ++++++++++++++
 4 files changed, 23 insertions(+), 7 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
index ea962ee95a..6e6d6f64e5 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/ClassEmitter.scala
@@ -61,7 +61,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
       if (useESClass) {
         val parentVarWithGlobals = for (parentIdent <- superClass) yield {
           implicit val pos = parentIdent.pos
-          if (shouldExtendJSError(className, superClass)) globalRef("Error")
+          if (shouldExtendJSError(className)) globalRef("Error")
           else WithGlobals(globalVar(VarField.c, parentIdent.name))
         }
 
@@ -190,7 +190,7 @@ private[emitter] final class ClassEmitter(sjsGen: SJSGen) {
         case None =>
           WithGlobals(setPrototypeVar(ctorVar))
 
-        case Some(_) if shouldExtendJSError(className, superClass) =>
+        case Some(_) if shouldExtendJSError(className) =>
           globalRef("Error").map(chainPrototypeWithLocalCtor(className, ctorVar, _, localDeclPrototypeVar = false))
 
         case Some(parentIdent) =>
@@ -1148,6 +1148,6 @@ private[emitter] object ClassEmitter {
   private val ClassInitializerOriginalName: OriginalName =
     OriginalName("<clinit>")
 
-  def shouldExtendJSError(className: ClassName, superClass: Option[ClassIdent]): Boolean =
-    className == ThrowableClass && superClass.exists(_.name == ObjectClass)
+  def shouldExtendJSError(className: ClassName): Boolean =
+    className == ThrowableClass
 }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala
index fa7d02153a..fe8531a191 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala
@@ -576,7 +576,7 @@ final class Emitter(config: Emitter.Config, prePrinter: Emitter.PrePrinter) {
        * because Throwable is rewired to extend JavaScript's Error instead of
        * j.l.Object.
        */
-      val linkedMethodsAndBridges = if (ClassEmitter.shouldExtendJSError(className, linkedClass.superClass)) {
+      val linkedMethodsAndBridges = if (ClassEmitter.shouldExtendJSError(className)) {
         val existingMethods = linkedMethods
           .withFilter(_.flags.namespace == MemberNamespace.Public)
           .map(_.methodName)
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala b/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
index bd3f6d612e..87a33e06cf 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
@@ -128,8 +128,8 @@ private final class ClassDefChecker(classDef: ClassDef,
   private def checkKind()(implicit ctx: ErrorContext): Unit = {
     val className = classDef.name.name
 
-    if (isJLObject && classDef.kind != ClassKind.Class) {
-      reportError("java.lang.Object must be a Class")
+    if ((isJLObject || className == ThrowableClass) && classDef.kind != ClassKind.Class) {
+      reportError(i"$className must be a Class")
     } else {
       val isHijacked = HijackedClasses.contains(className)
       if (isHijacked && classDef.kind != ClassKind.HijackedClass)
@@ -176,6 +176,8 @@ private final class ClassDefChecker(classDef: ClassDef,
           ClassKind.NativeJSClass | ClassKind.NativeJSModuleClass =>
         if (classDef.superClass.isEmpty)
           reportError("missing superClass")
+        else if (classDef.className == ThrowableClass && classDef.superClass.get.name != ObjectClass)
+          reportError("the superClass of java.lang.Throwable must be java.lang.Object")
 
       case ClassKind.Interface =>
         if (classDef.superClass.isDefined)
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/checker/ClassDefCheckerTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/checker/ClassDefCheckerTest.scala
index 25aaa353da..6441fd0c48 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/checker/ClassDefCheckerTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/checker/ClassDefCheckerTest.scala
@@ -83,6 +83,20 @@ class ClassDefCheckerTest {
         "java.lang.Object may not implement any interfaces")
   }
 
+  @Test
+  def javaLangThrowableKind(): Unit = {
+    assertError(
+        classDef(ThrowableClass, kind = ClassKind.Interface),
+        "java.lang.Throwable must be a Class")
+  }
+
+  @Test
+  def javaLangThrowableSuperClass(): Unit = {
+    assertError(
+        classDef(ThrowableClass, superClass = Some("Parent")),
+        "the superClass of java.lang.Throwable must be java.lang.Object")
+  }
+
   @Test
   def hijackedClassesKinds(): Unit = {
     assertError(

From 01ee94a925f86fba511cf3b83f6559be21a4c7d2 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Wed, 26 Mar 2025 11:15:36 +0100
Subject: [PATCH 270/298] Wasm: Better codegen for Long shifts with constant
 right-hand-side.

In our IR, the rhs of Long shifts is an Int, but in Wasm it must be
a Long as well. In the common-case where the rhs is a constant, we
now constant-fold the extension to 64 bits.
---
 .../backend/wasmemitter/FunctionEmitter.scala     | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
index 94fa164d81..d0275d97fc 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
@@ -1648,9 +1648,18 @@ private class FunctionEmitter private (
 
     def genLongShiftOp(shiftInstr: wa.Instr): Type = {
       genTree(lhs, LongType)
-      genTree(rhs, IntType)
-      markPosition(tree)
-      fb += wa.I64ExtendI32S
+      rhs match {
+        case IntLiteral(r) =>
+          // common case: fold the extension to 64 bits into the literal
+          markPosition(rhs)
+          fb += wa.I64Const(r.toLong)
+          markPosition(tree)
+        case _ =>
+          // otherwise, extend at run-time
+          genTree(rhs, IntType)
+          markPosition(tree)
+          fb += wa.I64ExtendI32S
+      }
       fb += shiftInstr
       LongType
     }

From 31666da460131bc7645de604308c52da13b0be7c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Wed, 26 Mar 2025 15:18:58 +0100
Subject: [PATCH 271/298] Reimplement `Math.rint` without floating-point
 remainder.

Now that I know what a `%` on floating-point numbers really looks
like inside, it's worth avoiding it in other low-level operations.

A cursory `git grep` highlighted `rint` as the only method in the
javalib that used that operation, so we rewrite it in a different
way.
---
 javalib/src/main/scala/java/lang/Math.scala   |  75 ++++++++--
 .../testsuite/javalib/lang/MathTest.scala     | 129 +++++++++++++-----
 2 files changed, 162 insertions(+), 42 deletions(-)

diff --git a/javalib/src/main/scala/java/lang/Math.scala b/javalib/src/main/scala/java/lang/Math.scala
index cb965bb56b..7d77391990 100644
--- a/javalib/src/main/scala/java/lang/Math.scala
+++ b/javalib/src/main/scala/java/lang/Math.scala
@@ -53,16 +53,71 @@ object Math {
 
   // Wasm intrinsic
   def rint(a: scala.Double): scala.Double = {
-    val rounded = js.Math.round(a)
-    val mod = a % 1.0
-    // The following test is also false for specials (0's, Infinities and NaN)
-    if (mod == 0.5 || mod == -0.5) {
-      // js.Math.round(a) rounds up but we have to round to even
-      if (rounded % 2.0 == 0.0) rounded
-      else rounded - 1.0
-    } else {
-      rounded
-    }
+    /* Is the integer-valued `x` odd? Fused by hand of `(x.toLong & 1L) != 0L`.
+     * Corner cases: returns false for Infinities and NaN.
+     */
+    @inline def isOdd(x: scala.Double): scala.Boolean =
+      (x.asInstanceOf[js.Dynamic] & 1.asInstanceOf[js.Dynamic]).asInstanceOf[Int] != 0
+
+    /* js.Math.round(a) does *almost* what we want. It rounds to nearest,
+     * breaking ties *up*. We need to break ties to *even*. So we need to
+     * detect ties, and for them, detect if we rounded to odd instead of even.
+     *
+     * The reasons why the apparently simple algorithm below works are subtle,
+     * and vary a lot depending on the range of `a`:
+     *
+     * - a is NaN
+     *   r is NaN, then the == is false
+     *   -> return r
+     *
+     * - a is +-Infinity
+     *   r == a, then == is true! but isOdd(r) is false
+     *   -> return r
+     *
+     * - 2**53 <= abs(a) < Infinity
+     *   r == a, r - 0.5 rounds back to a so == is true!
+     *   fortunately, isOdd(r) is false because all a >= 2**53 are even
+     *   -> return r
+     *
+     * - 2**52 <= abs(a) < 2**53
+     *   r == a (because all a's are integers in that range)
+     *   - a is odd
+     *     r - 0.5 rounds down (towards even) to r - 1.0
+     *     so a == r - 0.5 is false
+     *     -> return r
+     *   - a is even
+     *     r - 0.5 rounds back up! (towards even) to r
+     *     so a == r - 0.5 is true!
+     *     but, isOdd(r) is false
+     *     -> return r
+     *
+     * - 0.5 < abs(a) < 2**52
+     *   then -2**52 + 0.5 <= a <= 2**52 - 0.5 (because values in-between are not representable)
+     *   since Math.round rounds *up* on ties, r is an integer in the range (-2**52, 2**52]
+     *   r - 0.5 is therefore lossless
+     *   so a == r - 0.5 accurately detects ties, and isOdd(r) breaks ties
+     *   -> return `r`` or `r - 1.0`
+     *
+     * - a == +0.5
+     *   r == 1.0
+     *   a == r - 0.5 is true and isOdd(r) is true
+     *   -> return `r - 1.0`, which is +0.0
+     *
+     * - a == -0.5
+     *   r == -0.0
+     *   a == r - 0.5 is true and isOdd(r) is false
+     *   -> return `r`, which is -0.0
+     *
+     * - 0.0 <= abs(a) < 0.5
+     *   r == 0.0 with the same sign as a
+     *   a == r - 0.5 is false
+     *   -> return r
+     */
+    val r = js.Math.round(a)
+    if ((a == r - 0.5) && isOdd(r))
+      r - 1.0
+    else
+      r
   }
 
   @inline def round(a: scala.Float): scala.Int = js.Math.round(a).toInt
diff --git a/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/lang/MathTest.scala b/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/lang/MathTest.scala
index 850d8921ef..86b26e4dfb 100644
--- a/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/lang/MathTest.scala
+++ b/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/lang/MathTest.scala
@@ -415,44 +415,109 @@ class MathTest {
   @Test def rintForDouble(): Unit = {
     import Math.rint
 
-    def isPosZero(x: Double): Boolean =
-      x == 0.0 && (1.0 / x) == Double.PositiveInfinity
-
-    def isNegZero(x: Double): Boolean =
-      x == 0.0 && (1.0 / x) == Double.NegativeInfinity
+    val intLimit = (1L << 52).toDouble
+    val halfIntLimit = (1L << 51).toDouble
+    val doubleIntLimit = (1L << 53).toDouble
 
     // Specials
-    assertTrue(isPosZero(rint(+0.0)))
-    assertTrue(isNegZero(rint(-0.0)))
-    assertEquals(Double.PositiveInfinity, rint(Double.PositiveInfinity), 0.0)
-    assertEquals(Double.NegativeInfinity, rint(Double.NegativeInfinity), 0.0)
-    assertTrue(rint(Double.NaN).isNaN)
+    assertSameDouble(+0.0, rint(+0.0))
+    assertSameDouble(-0.0, rint(-0.0))
+    assertSameDouble(Double.PositiveInfinity, rint(Double.PositiveInfinity))
+    assertSameDouble(Double.NegativeInfinity, rint(Double.NegativeInfinity))
+    assertSameDouble(Double.NaN, rint(Double.NaN))
 
     // Positive values
-    assertTrue(isPosZero(rint(0.1)))
-    assertTrue(isPosZero(rint(0.5)))
-    assertEquals(1.0, rint(0.5000000000000001), 0.0)
-    assertEquals(1.0, rint(0.999), 0.0)
-    assertEquals(1.0, rint(1.4999999999999998), 0.0)
-    assertEquals(2.0, rint(1.5), 0.0)
-    assertEquals(2.0, rint(2.0), 0.0)
-    assertEquals(2.0, rint(2.1), 0.0)
-    assertEquals(2.0, rint(2.5), 0.0)
-    assertEquals(Double.MaxValue, rint(Double.MaxValue), 0.0)
-    assertEquals(4503599627370496.0, rint(4503599627370495.5), 0.0) // MaxSafeInt / 2
+    assertSameDouble(+0.0, rint(Double.MinPositiveValue))
+    assertSameDouble(+0.0, rint(java.lang.Double.MIN_NORMAL))
+    assertSameDouble(+0.0, rint(0.1))
+    assertSameDouble(+0.0, rint(0.5))
+    assertSameDouble(1.0, rint(0.5000000000000001))
+    assertSameDouble(1.0, rint(0.999))
+    assertSameDouble(1.0, rint(1.4999999999999998))
+    assertSameDouble(2.0, rint(1.5))
+    assertSameDouble(2.0, rint(2.0))
+    assertSameDouble(2.0, rint(2.1))
+    assertSameDouble(2.0, rint(2.5))
+    assertSameDouble(3.0, rint(2.75))
+    assertSameDouble(3.0, rint(3.25))
+    assertSameDouble(4.0, rint(3.5))
+    assertSameDouble(4.0, rint(3.75))
+    assertSameDouble(halfIntLimit - 2.0, rint(halfIntLimit - 1.5))
+    assertSameDouble(halfIntLimit - 1.0, rint(halfIntLimit - 1.25))
+    assertSameDouble(halfIntLimit - 1.0, rint(halfIntLimit - 1.0))
+    assertSameDouble(halfIntLimit - 1.0, rint(halfIntLimit - 0.75))
+    assertSameDouble(halfIntLimit, rint(halfIntLimit - 0.5))
+    assertSameDouble(halfIntLimit, rint(halfIntLimit - 0.25))
+    assertSameDouble(halfIntLimit, rint(halfIntLimit))
+    assertSameDouble(halfIntLimit, rint(halfIntLimit + 0.25))
+    assertSameDouble(halfIntLimit, rint(halfIntLimit + 0.5))
+    assertSameDouble(halfIntLimit + 1.0, rint(halfIntLimit + 0.75))
+    assertSameDouble(halfIntLimit + 1.0, rint(halfIntLimit + 1.0))
+    assertSameDouble(halfIntLimit + 1.0, rint(halfIntLimit + 1.25))
+    assertSameDouble(halfIntLimit + 2.0, rint(halfIntLimit + 1.5))
+    assertSameDouble(intLimit - 2.0, rint(intLimit - 1.5))
+    assertSameDouble(intLimit - 1.0, rint(intLimit - 1.0))
+    assertSameDouble(intLimit, rint(intLimit - 0.5))
+    assertSameDouble(intLimit, rint(intLimit))
+
+    val largeIntegers = List(
+      // corner cases just above intLimit
+      intLimit + 1.0,
+      intLimit + 2.0,
+      intLimit + 3.0,
+      intLimit + 4.0,
+      // corner cases around doubleIntLimit
+      doubleIntLimit - 4.0,
+      doubleIntLimit - 3.0,
+      doubleIntLimit - 2.0,
+      doubleIntLimit - 1.0,
+      doubleIntLimit,
+      doubleIntLimit + 2.0,
+      doubleIntLimit + 4.0,
+      doubleIntLimit + 6.0,
+      doubleIntLimit + 8.0,
+      doubleIntLimit + 16.0,
+      Double.MaxValue
+    )
+    for (x <- largeIntegers)
+      assertSameDouble(x, rint(x))
 
     // Negative values
-    assertTrue(isNegZero(rint(-0.1)))
-    assertTrue(isNegZero(rint(-0.5)))
-    assertEquals(-1.0, rint(-0.5000000000000001), 0.0)
-    assertEquals(-1.0, rint(-0.999), 0.0)
-    assertEquals(-1.0, rint(-1.4999999999999998), 0.0)
-    assertEquals(-2.0, rint(-1.5), 0.0)
-    assertEquals(-2.0, rint(-2.0), 0.0)
-    assertEquals(-2.0, rint(-2.1), 0.0)
-    assertEquals(-2.0, rint(-2.5), 0.0)
-    assertEquals(Double.MinValue, rint(Double.MinValue), 0.0)
-    assertEquals(-4503599627370496.0, rint(-4503599627370495.5), 0.0) // -MaxSafeInt / 2
+    assertSameDouble(-0.0, rint(-Double.MinPositiveValue))
+    assertSameDouble(-0.0, rint(-java.lang.Double.MIN_NORMAL))
+    assertSameDouble(-0.0, rint(-0.1))
+    assertSameDouble(-0.0, rint(-0.5))
+    assertSameDouble(-1.0, rint(-0.5000000000000001))
+    assertSameDouble(-1.0, rint(-0.999))
+    assertSameDouble(-1.0, rint(-1.4999999999999998))
+    assertSameDouble(-2.0, rint(-1.5))
+    assertSameDouble(-2.0, rint(-2.0))
+    assertSameDouble(-2.0, rint(-2.1))
+    assertSameDouble(-2.0, rint(-2.5))
+    assertSameDouble(-3.0, rint(-2.75))
+    assertSameDouble(-3.0, rint(-3.25))
+    assertSameDouble(-4.0, rint(-3.5))
+    assertSameDouble(-4.0, rint(-3.75))
+    assertSameDouble(-(halfIntLimit - 2.0), rint(-(halfIntLimit - 1.5)))
+    assertSameDouble(-(halfIntLimit - 1.0), rint(-(halfIntLimit - 1.25)))
+    assertSameDouble(-(halfIntLimit - 1.0), rint(-(halfIntLimit - 1.0)))
+    assertSameDouble(-(halfIntLimit - 1.0), rint(-(halfIntLimit - 0.75)))
+    assertSameDouble(-halfIntLimit, rint(-(halfIntLimit - 0.5)))
+    assertSameDouble(-halfIntLimit, rint(-(halfIntLimit - 0.25)))
+    assertSameDouble(-halfIntLimit, rint(-halfIntLimit))
+    assertSameDouble(-halfIntLimit, rint(-(halfIntLimit + 0.25)))
+    assertSameDouble(-halfIntLimit, rint(-(halfIntLimit + 0.5)))
+    assertSameDouble(-(halfIntLimit + 1.0), rint(-(halfIntLimit + 0.75)))
+    assertSameDouble(-(halfIntLimit + 1.0), rint(-(halfIntLimit + 1.0)))
+    assertSameDouble(-(halfIntLimit + 1.0), rint(-(halfIntLimit + 1.25)))
+    assertSameDouble(-(halfIntLimit + 2.0), rint(-(halfIntLimit + 1.5)))
+    assertSameDouble(-(intLimit - 2.0), rint(-(intLimit - 1.5)))
+    assertSameDouble(-(intLimit - 1.0), rint(-(intLimit - 1.0)))
+    assertSameDouble(-intLimit, rint(-(intLimit - 0.5)))
+    assertSameDouble(-intLimit, rint(-intLimit))
+
+    for (x <- largeIntegers)
+      assertSameDouble(-x, rint(-x))
   }
 
   @Test def addExact(): Unit = {

From 67fa195e2a836dbe8f0be534ca6ca14b3a61645d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Tue, 1 Apr 2025 16:40:02 +0200
Subject: [PATCH 272/298] Actually delete temp files created by partest for
 Wasm.

It turns out `deleteOnExit()` does not do anything for non-empty
directories. So we must recursively delete our temporary output
directory ourselves.
---
 .../scala/tools/nsc/MainGenericRunner.scala   | 95 +++++++++++--------
 1 file changed, 58 insertions(+), 37 deletions(-)

diff --git a/partest/src/main/scala/scala/tools/nsc/MainGenericRunner.scala b/partest/src/main/scala/scala/tools/nsc/MainGenericRunner.scala
index 9158f3aa68..7c9f41153d 100644
--- a/partest/src/main/scala/scala/tools/nsc/MainGenericRunner.scala
+++ b/partest/src/main/scala/scala/tools/nsc/MainGenericRunner.scala
@@ -28,8 +28,10 @@ import com.google.common.jimfs.Jimfs
 
 import scala.tools.partest.scalajs.ScalaJSPartestOptions._
 
+import java.io.IOException
 import java.net.URL
 import java.nio.file._
+import java.nio.file.attribute.BasicFileAttributes
 
 import scala.io.Source
 import scala.concurrent.Await
@@ -112,51 +114,56 @@ class MainGenericRunner {
       /* The Wasm output needs to read other files in the same directory,
        * with predictable names. Therefore, we need to use real files.
        */
-      val tempDir = Files.createTempDirectory("tmp-scalajs-partest")
-      tempDir.toFile().deleteOnExit()
-      tempDir
+      Files.createTempDirectory("tmp-scalajs-partest")
     }
+    try {
+      val sjsCode = {
+        val cache = StandardImpl.irFileCache().newCache
+        val result = PathIRContainer
+          .fromClasspath(command.settings.classpathURLs.map(urlToPath _))
+          .map(_._1)
+          .flatMap(cache.cached _)
+          .flatMap(linker.link(_, moduleInitializers, PathOutputDirectory(dir), logger))
 
-    val sjsCode = {
-      val cache = StandardImpl.irFileCache().newCache
-      val result = PathIRContainer
-        .fromClasspath(command.settings.classpathURLs.map(urlToPath _))
-        .map(_._1)
-        .flatMap(cache.cached _)
-        .flatMap(linker.link(_, moduleInitializers, PathOutputDirectory(dir), logger))
-
-      val report = Await.result(result, Duration.Inf)
+        val report = Await.result(result, Duration.Inf)
 
-      if (report.publicModules.size != 1)
-        throw new AssertionError(s"got other than 1 module: $report")
+        if (report.publicModules.size != 1)
+          throw new AssertionError(s"got other than 1 module: $report")
 
-      dir.resolve(report.publicModules.head.jsFileName)
-    }
+        dir.resolve(report.publicModules.head.jsFileName)
+      }
 
-    val jsEnvConfig: NodeJSEnv.Config = if (!useWasm) {
-      NodeJSEnv.Config()
-    } else {
-      NodeJSEnv.Config().withArgs(List(
-        "--experimental-wasm-exnref",
-        "--experimental-wasm-imported-strings", // for JS string builtins
-        /* Force using the Turboshaft infrastructure for the optimizing compiler.
-         * It appears to be more stable for the Wasm that we throw at it.
-         * See also the use of this flag in Build.scala.
-         */
-        "--turboshaft-wasm"
-      ))
-    }
+      val jsEnvConfig: NodeJSEnv.Config = if (!useWasm) {
+        NodeJSEnv.Config()
+      } else {
+        NodeJSEnv.Config().withArgs(List(
+          "--experimental-wasm-exnref",
+          "--experimental-wasm-imported-strings", // for JS string builtins
+          /* Force using the Turboshaft infrastructure for the optimizing compiler.
+           * It appears to be more stable for the Wasm that we throw at it.
+           * See also the use of this flag in Build.scala.
+           */
+          "--turboshaft-wasm"
+        ))
+      }
 
-    val input =
-      if (useESModule) Input.ESModule(sjsCode) :: Nil
-      else Input.Script(sjsCode) :: Nil
-    val config = RunConfig().withLogger(logger)
+      val input =
+        if (useESModule) Input.ESModule(sjsCode) :: Nil
+        else Input.Script(sjsCode) :: Nil
+      val config = RunConfig().withLogger(logger)
 
-    val run = new NodeJSEnv(jsEnvConfig).start(input, config)
-    try {
-      Await.result(run.future, Duration.Inf)
+      val run = new NodeJSEnv(jsEnvConfig).start(input, config)
+      try {
+        Await.result(run.future, Duration.Inf)
+      } finally {
+        run.close()
+      }
     } finally {
-      run.close()
+      /* If using Wasm, we created actual files that we must delete.
+       * For JS, we use an in-memory file system, so there is no point.
+       */
+      if (useWasm)
+        recursivelyDeleteDir(dir)
     }
 
     true
@@ -169,6 +176,20 @@ class MainGenericRunner {
       case e: java.net.URISyntaxException => Paths.get(url.getPath())
     }
   }
+
+  private def recursivelyDeleteDir(directory: Path): Unit = {
+    Files.walkFileTree(directory, new SimpleFileVisitor[Path] {
+      override def visitFile(file: Path, attrs: BasicFileAttributes): FileVisitResult = {
+        Files.delete(file)
+        FileVisitResult.CONTINUE
+      }
+
+      override def postVisitDirectory(dir: Path, exc: IOException): FileVisitResult = {
+        Files.delete(dir)
+        FileVisitResult.CONTINUE
+      }
+    })
+  }
 }
 
 object MainGenericRunner extends MainGenericRunner {

From 2ff3bc6d923887e8bfb4d49746ddde364e541bd2 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Mon, 10 Feb 2025 23:05:38 +0100
Subject: [PATCH 273/298] Fix #5064: Optionally allow orphan `js.await(p)` on
 WebAssembly.

With the JavaScript Promise Integration (JSPI), there can be as
many frames as we want between a `WebAssembly.promising` function
and the corresponding `WebAssembly.Suspending` calls. The former
is introduced by our `js.async` blocks, and the latter by calls to
`js.await`.

Normally, `js.await` must be directly enclosed within a `js.async`
block. This ensures that it can be compiled to a JavaScript `async`
function and `await` expression.

We introduce a sort of "language import" to allow "orphan awaits".
This way, we can decouple the `js.await` calls from their
`js.async` blocks. The generated IR will then only link when
targeting WebAssembly. Technically, `js.await` requires an
implicit `js.AwaitPermit`. The default one only allows `js.await`
directly inside `js.async`, and we can import a stronger one that
allows orphan awaits.

There must still be a `js.async` block *dynamically* enclosing any
`js.await` call (on the call stack), without intervening JS frame.
If that dynamic property is not satisfied, a
`WebAssembly.SuspendError` gets thrown. This last point is not yet
implemented in Node.js at the time of this commit; instead such a
situation traps. The corresponding test is therefore currently
ignored.
---
 .../org/scalajs/nscplugin/GenJSCode.scala     | 21 +++--
 .../org/scalajs/nscplugin/JSDefinitions.scala |  5 ++
 .../nscplugin/test/JSAsyncAwaitTest.scala     |  9 ++
 .../src/main/scala/org/scalajs/ir/Trees.scala | 11 ++-
 .../scala/scala/scalajs/js/AwaitPermit.scala  | 29 ++++++
 .../main/scala/scala/scalajs/js/package.scala | 18 +++-
 .../scala/scala/scalajs/js/wasm/JSPI.scala    | 28 ++++++
 .../scalajs/linker/analyzer/Analysis.scala    |  4 +
 .../scalajs/linker/analyzer/Analyzer.scala    |  5 ++
 .../org/scalajs/linker/analyzer/Infos.scala   | 37 ++++++--
 .../linker/checker/ClassDefChecker.scala      | 21 ++---
 .../org/scalajs/linker/AnalyzerTest.scala     | 19 ++++
 project/Build.scala                           |  2 +
 .../jsinterop/JSOrphanAwaitTest.scala         | 89 +++++++++++++++++++
 14 files changed, 266 insertions(+), 32 deletions(-)
 create mode 100644 library/src/main/scala/scala/scalajs/js/AwaitPermit.scala
 create mode 100644 library/src/main/scala/scala/scalajs/js/wasm/JSPI.scala
 create mode 100644 test-suite/js/src/test/require-orphan-await/org/scalajs/testsuite/jsinterop/JSOrphanAwaitTest.scala

diff --git a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
index 0733ef00e7..e46b1dc14f 100644
--- a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
+++ b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
@@ -5355,14 +5355,23 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
           js.Block(genStats, asyncExpr)
 
         case JS_AWAIT =>
-          // js.await(arg)
+          // js.await(arg)(permit)
+          val (arg, permitValue) = genArgs2
           if (!methodsAllowingJSAwait.contains(currentMethodSym)) {
-            reporter.error(pos,
-                "Illegal use of js.await().\n" +
-                "It can only be used inside a js.async {...} block, without any lambda,\n" +
-                "by-name argument or nested method in-between.")
+            // This is an orphan await
+            if (!(args(1).tpe <:< WasmJSPI_allowOrphanJSAwaitModuleClass.toTypeConstructor)) {
+              reporter.error(pos,
+                  "Illegal use of js.await().\n" +
+                  "It can only be used inside a js.async {...} block, without any lambda,\n" +
+                  "by-name argument or nested method in-between.\n" +
+                  "If you compile for WebAssembly, you can allow arbitrary js.await()\n" +
+                  "calls by adding the following import:\n" +
+                  "import scala.scalajs.js.wasm.JSPI.allowOrphanJSAwait")
+            }
           }
-          val arg = genArgs1
+          /* In theory we should evaluate `permit` after `arg` but before the `JSAwait`.
+           * It *should* always be side-effect-free, though, so we just discard it.
+           */
           js.JSAwait(arg)
 
         case DYNAMIC_IMPORT =>
diff --git a/compiler/src/main/scala/org/scalajs/nscplugin/JSDefinitions.scala b/compiler/src/main/scala/org/scalajs/nscplugin/JSDefinitions.scala
index 7d9983e974..2b0c5590d9 100644
--- a/compiler/src/main/scala/org/scalajs/nscplugin/JSDefinitions.scala
+++ b/compiler/src/main/scala/org/scalajs/nscplugin/JSDefinitions.scala
@@ -116,6 +116,11 @@ trait JSDefinitions {
       lazy val Special_unwrapFromThrowable = getMemberMethod(SpecialPackageModule, newTermName("unwrapFromThrowable"))
       lazy val Special_debugger = getMemberMethod(SpecialPackageModule, newTermName("debugger"))
 
+    lazy val WasmJSPIModule = getRequiredModule("scala.scalajs.js.wasm.JSPI")
+    lazy val WasmJSPIModuleClass = WasmJSPIModule.moduleClass
+      lazy val WasmJSPI_allowOrphanJSAwaitModule = getMemberModule(WasmJSPIModuleClass, newTermName("allowOrphanJSAwait"))
+      lazy val WasmJSPI_allowOrphanJSAwaitModuleClass = WasmJSPI_allowOrphanJSAwaitModule.moduleClass
+
     lazy val RuntimePackageModule = getPackageObject("scala.scalajs.runtime")
       lazy val Runtime_toScalaVarArgs             = getMemberMethod(RuntimePackageModule, newTermName("toScalaVarArgs"))
       lazy val Runtime_toJSVarArgs                = getMemberMethod(RuntimePackageModule, newTermName("toJSVarArgs"))
diff --git a/compiler/src/test/scala/org/scalajs/nscplugin/test/JSAsyncAwaitTest.scala b/compiler/src/test/scala/org/scalajs/nscplugin/test/JSAsyncAwaitTest.scala
index 2f3060b932..d8147fad0a 100644
--- a/compiler/src/test/scala/org/scalajs/nscplugin/test/JSAsyncAwaitTest.scala
+++ b/compiler/src/test/scala/org/scalajs/nscplugin/test/JSAsyncAwaitTest.scala
@@ -35,6 +35,9 @@ class JSAsyncAwaitTest extends DirectTest with TestHelpers {
       |newSource1.scala:5: error: Illegal use of js.await().
       |It can only be used inside a js.async {...} block, without any lambda,
       |by-name argument or nested method in-between.
+      |If you compile for WebAssembly, you can allow arbitrary js.await()
+      |calls by adding the following import:
+      |import scala.scalajs.js.wasm.JSPI.allowOrphanJSAwait
       |        js.await(x)
       |                ^
     """
@@ -51,6 +54,9 @@ class JSAsyncAwaitTest extends DirectTest with TestHelpers {
       |newSource1.scala:5: error: Illegal use of js.await().
       |It can only be used inside a js.async {...} block, without any lambda,
       |by-name argument or nested method in-between.
+      |If you compile for WebAssembly, you can allow arbitrary js.await()
+      |calls by adding the following import:
+      |import scala.scalajs.js.wasm.JSPI.allowOrphanJSAwait
       |        val f: () => Int = () => js.await(x)
       |                                         ^
     """
@@ -67,6 +73,9 @@ class JSAsyncAwaitTest extends DirectTest with TestHelpers {
       |newSource1.scala:5: error: Illegal use of js.await().
       |It can only be used inside a js.async {...} block, without any lambda,
       |by-name argument or nested method in-between.
+      |If you compile for WebAssembly, you can allow arbitrary js.await()
+      |calls by adding the following import:
+      |import scala.scalajs.js.wasm.JSPI.allowOrphanJSAwait
       |        def f(): Int = js.await(x)
       |                               ^
     """
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala b/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
index b62630e212..ccc3b56196 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
@@ -220,12 +220,15 @@ object Trees {
 
   /** `await arg`.
    *
-   *  This is directly equivalent to a JavaScript `await` expression. This node
-   *  is only valid within a [[Closure]] node with the `async` flag.
+   *  This is directly equivalent to a JavaScript `await` expression.
+   *
+   *  If used directly within a [[Closure]] node with the `async` flag, this
+   *  node is always valid. However, when used anywhere else, it is an "orphan"
+   *  await. Orphan awaits only link when targeting WebAssembly.
    *
    *  This is not a `UnaryOp` because of the above strict scoping rule. For
-   *  example, it is not safe to pull this node out of or into an intervening
-   *  closure, contrary to `UnaryOp`s.
+   *  example, unless it is orphan to begin with, it is not safe to pull this
+   *  node out of or into an intervening closure, contrary to `UnaryOp`s.
    */
   sealed case class JSAwait(arg: Tree)(implicit val pos: Position) extends Tree {
     val tpe = AnyType
diff --git a/library/src/main/scala/scala/scalajs/js/AwaitPermit.scala b/library/src/main/scala/scala/scalajs/js/AwaitPermit.scala
new file mode 100644
index 0000000000..a420d88815
--- /dev/null
+++ b/library/src/main/scala/scala/scalajs/js/AwaitPermit.scala
@@ -0,0 +1,29 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package scala.scalajs.js
+
+/** Kind of permit for calling `js.await()`.
+ *
+ *  A default permit is always available. It allows to call `js.await()` when
+ *  directly enclosed by a `js.async { ... }` block.
+ *
+ *  @see [[scala.scalajs.js.async]]
+ */
+abstract class AwaitPermit private[js] ()
+
+object AwaitPermit {
+  /** Default permit for `js.await()` calls directly enclosed within a
+   *  `js.async` block.
+   */
+  implicit object directlyWithinAsync extends AwaitPermit
+}
diff --git a/library/src/main/scala/scala/scalajs/js/package.scala b/library/src/main/scala/scala/scalajs/js/package.scala
index 919455831b..0c20791538 100644
--- a/library/src/main/scala/scala/scalajs/js/package.scala
+++ b/library/src/main/scala/scala/scalajs/js/package.scala
@@ -192,6 +192,22 @@ package object js {
    *  not be nested in any local method, class, by-name argument or closure.
    *  The latter includes `for` comprehensions. They may appear within
    *  conditional branches, `while` loops and `try/catch/finally` blocks.
+   *
+   *  <h2>Orphan `await`s in WebAssembly</h2>
+   *
+   *  When compiling for Scala.js-on-Wasm only, you can allow calls to
+   *  `js.await` anywhere, by adding the following import:
+   *
+   *  {{{
+   *  import scala.scalajs.js.wasm.JSPI.allowOrphanJSAwait
+   *  }}}
+   *
+   *  Calls to orphan `js.await`s are validated at run-time. There must exist
+   *  a dynamically enclosing `js.async { ... }` block on the call stack.
+   *  Moreover, there cannot be any JavaScript frame (JavaScript function
+   *  invocation) in the call stack between the `js.async { ... }` block and
+   *  the call to `js.await`. If those conditions are not met, a JavaScript
+   *  exception of type `WebAssembly.SuspendError` gets thrown.
    */
   def async[A](body: => A): js.Promise[A] =
     throw new java.lang.Error("stub")
@@ -203,6 +219,6 @@ package object js {
    *
    *  See the documentation of [[async js.async]].
    */
-  def await[A](promise: js.Promise[A]): A =
+  def await[A](promise: js.Promise[A])(implicit permit: AwaitPermit): A =
     throw new java.lang.Error("stub")
 }
diff --git a/library/src/main/scala/scala/scalajs/js/wasm/JSPI.scala b/library/src/main/scala/scala/scalajs/js/wasm/JSPI.scala
new file mode 100644
index 0000000000..3f7926b9be
--- /dev/null
+++ b/library/src/main/scala/scala/scalajs/js/wasm/JSPI.scala
@@ -0,0 +1,28 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package scala.scalajs.js.wasm
+
+import scala.scalajs.js
+
+/** Features related to the WebAssembly JavaScript Promise Integration (JSPI). */
+object JSPI {
+  /** Allow arbitrary calls to `js.await()`.
+   *
+   *  Import this object to allow arbitrary calls to `js.await()`, even when
+   *  they are not directly nested within a `js.async { ... }` block.
+   *  The resulting code will then only link when targeting WebAssembly.
+   *
+   *  @see [[scala.scalajs.js.async]]
+   */
+  implicit object allowOrphanJSAwait extends js.AwaitPermit
+}
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analysis.scala b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analysis.scala
index 83fd01f327..6a9da3b268 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analysis.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analysis.scala
@@ -217,6 +217,8 @@ object Analysis {
 
   final case class AsyncWithoutES2017Support(from: From) extends Error
 
+  final case class OrphanAwaitWithoutWebAssembly(from: From) extends Error
+
   final case class InvalidLinkTimeProperty(
     linkTimePropertyName: String,
     linkTimePropertyType: Type,
@@ -281,6 +283,8 @@ object Analysis {
         "Uses the ** operator with an ECMAScript version older than ES 2016"
       case AsyncWithoutES2017Support(_) =>
         "Uses an async block with an ECMAScript version older than ES 2017"
+      case OrphanAwaitWithoutWebAssembly(_) =>
+        "Uses an orphan await (outside of an async block) without targeting WebAssembly"
       case InvalidLinkTimeProperty(name, tpe, _) =>
         s"Uses invalid link-time property ${name} of type ${tpe}"
     }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala
index e5705bef67..9a80ac96a2 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala
@@ -1526,6 +1526,11 @@ private class AnalyzerRun(config: CommonPhaseConfig, initial: Boolean,
         _errors ::= AsyncWithoutES2017Support(from)
       }
 
+      if ((globalFlags & ReachabilityInfo.FlagUsedOrphanAwait) != 0 &&
+          !config.coreSpec.targetIsWebAssembly) {
+        _errors ::= OrphanAwaitWithoutWebAssembly(from)
+      }
+
       if ((globalFlags & ReachabilityInfo.FlagUsedClassSuperClass) != 0) {
         _classSuperClassUsed.set(true)
       }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala
index 7d57c965bf..fe957ca837 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala
@@ -120,8 +120,9 @@ object Infos {
     final val FlagAccessedImportMeta = 1 << 2
     final val FlagUsedExponentOperator = 1 << 3
     final val FlagUsedAsync = 1 << 4
-    final val FlagUsedClassSuperClass = 1 << 5
-    final val FlagNeedsDesugaring = 1 << 6
+    final val FlagUsedOrphanAwait = 1 << 5
+    final val FlagUsedClassSuperClass = 1 << 6
+    final val FlagNeedsDesugaring = 1 << 7
   }
 
   /** Things from a given class that are reached by one method. */
@@ -402,6 +403,9 @@ object Infos {
     def addUsedAsync(): this.type =
       setFlag(ReachabilityInfo.FlagUsedAsync)
 
+    def addUsedOrphanAwait(): this.type =
+      setFlag(ReachabilityInfo.FlagUsedOrphanAwait)
+
     def addUsedIntLongDivModByMaybeZero(): this.type =
       addInstantiatedClass(ArithmeticExceptionClass, StringArgConstructorName)
 
@@ -577,6 +581,13 @@ object Infos {
   private final class GenInfoTraverser(version: Version) extends Traverser {
     private val builder = new ReachabilityInfoBuilder(version)
 
+    /** Whether we are currently in the body of an `async` closure.
+     *
+     *  If we encounter a `JSAwait` node while this is `false`, it is an
+     *  orphan await.
+     */
+    private var inAsync: Boolean = false
+
     def generateMethodInfo(methodDef: MethodDef): MethodInfo = {
       val methodName = methodDef.methodName
       methodName.paramTypeRefs.foreach(builder.maybeAddReferencedClass)
@@ -657,6 +668,22 @@ object Infos {
           }
           traverse(rhs)
 
+        /* Closure may have to adjust the inAsync flag before and after
+         * traversing its body.
+         */
+        case Closure(flags, _, _, _, _, body, captureValues) =>
+          if (flags.async)
+            builder.addUsedAsync()
+
+          // No point in using a try..finally. Instances of this class are single-use.
+          val savedInAsync = inAsync
+          inAsync = flags.async
+          traverse(body)
+          inAsync = savedInAsync
+
+          // Capture values are in the enclosing scope; not the scope of the closure
+          captureValues.foreach(traverse(_))
+
         // In all other cases, we'll have to call super.traverse()
         case _ =>
           tree match {
@@ -774,9 +801,9 @@ object Infos {
             case JSBinaryOp(JSBinaryOp.**, _, _) =>
               builder.addUsedExponentOperator()
 
-            case Closure(flags, _, _, _, _, _, _) =>
-              if (flags.async)
-                builder.addUsedAsync()
+            case JSAwait(_) =>
+              if (!inAsync)
+                builder.addUsedOrphanAwait()
 
             case LoadJSConstructor(className) =>
               builder.addInstantiatedClass(className)
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala b/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
index bfe9177ef6..e361f2b7ba 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
@@ -790,8 +790,6 @@ private final class ClassDefChecker(classDef: ClassDef,
         checkTree(default, env)
 
       case JSAwait(arg) =>
-        if (!env.inAsync)
-          reportError(i"Illegal `await` outside of `async` closure")
         checkTree(arg, env)
 
       case Debugger() =>
@@ -1087,7 +1085,6 @@ private final class ClassDefChecker(classDef: ClassDef,
         .fromParams(captureParams ++ params ++ restParam)
         .withHasNewTarget(!flags.arrow)
         .withMaybeThisType(!flags.arrow, AnyType)
-        .withInAsync(flags.async)
       checkTree(body, bodyEnv)
     }
   }
@@ -1184,9 +1181,7 @@ object ClassDefChecker {
       /** Return types by label. */
       val returnLabels: Set[LabelName],
       /** Whether usages of `this` are restricted in this scope. */
-      val isThisRestricted: Boolean,
-      /** Whether we are in an `async` closure, where `await` expressions are valid. */
-      val inAsync: Boolean
+      val isThisRestricted: Boolean
   ) {
     import Env._
 
@@ -1209,17 +1204,13 @@ object ClassDefChecker {
     def withIsThisRestricted(isThisRestricted: Boolean): Env =
       copy(isThisRestricted = isThisRestricted)
 
-    def withInAsync(inAsync: Boolean): Env =
-      copy(inAsync = inAsync)
-
     private def copy(
       hasNewTarget: Boolean = hasNewTarget,
       locals: Map[LocalName, LocalDef] = locals,
       returnLabels: Set[LabelName] = returnLabels,
-      isThisRestricted: Boolean = isThisRestricted,
-      inAsync: Boolean = inAsync
+      isThisRestricted: Boolean = isThisRestricted
     ): Env = {
-      new Env(hasNewTarget, locals, returnLabels, isThisRestricted, inAsync)
+      new Env(hasNewTarget, locals, returnLabels, isThisRestricted)
     }
   }
 
@@ -1229,8 +1220,7 @@ object ClassDefChecker {
         hasNewTarget = false,
         locals = Map.empty,
         returnLabels = Set.empty,
-        isThisRestricted = false,
-        inAsync = false
+        isThisRestricted = false
       )
     }
 
@@ -1243,8 +1233,7 @@ object ClassDefChecker {
         hasNewTarget = false,
         paramLocalDefs.toMap,
         Set.empty,
-        isThisRestricted = false,
-        inAsync = false
+        isThisRestricted = false
       )
     }
   }
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/AnalyzerTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/AnalyzerTest.scala
index a8714332f1..4eb535144d 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/AnalyzerTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/AnalyzerTest.scala
@@ -704,6 +704,25 @@ class AnalyzerTest {
     }
   }
 
+  @Test
+  def orphanAwaitWithoutWebAssembly(): AsyncResult = await {
+    val classDefs = Seq(
+      mainTestClassDef {
+        JSAwait(int(5))
+      }
+    )
+
+    val moduleInitializer = MainTestModuleInitializers
+
+    val analysis = computeAnalysis(classDefs,
+        moduleInitializers = MainTestModuleInitializers,
+        config = StandardConfig().withESFeatures(_.withESVersion(ESVersion.ES2017)))
+
+    assertContainsError("OrphanAwaitWithoutWebAssembly", analysis) {
+      case OrphanAwaitWithoutWebAssembly(_) => true
+    }
+  }
+
   @Test
   def importMetaWithoutESModule(): AsyncResult = await {
     val classDefs = Seq(
diff --git a/project/Build.scala b/project/Build.scala
index c723cee653..eb8b6b9f2f 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -2260,6 +2260,8 @@ object Build {
             esVersion >= ESVersion.ES2016) :::
         includeIf(testDir / "require-async-await",
             esVersion >= ESVersion.ES2017) :::
+        includeIf(testDir / "require-orphan-await",
+            esVersion >= ESVersion.ES2017 && isWebAssembly) :::
         includeIf(testDir / "require-modules",
             hasModules) :::
         includeIf(testDir / "require-no-modules",
diff --git a/test-suite/js/src/test/require-orphan-await/org/scalajs/testsuite/jsinterop/JSOrphanAwaitTest.scala b/test-suite/js/src/test/require-orphan-await/org/scalajs/testsuite/jsinterop/JSOrphanAwaitTest.scala
new file mode 100644
index 0000000000..808b36e424
--- /dev/null
+++ b/test-suite/js/src/test/require-orphan-await/org/scalajs/testsuite/jsinterop/JSOrphanAwaitTest.scala
@@ -0,0 +1,89 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package org.scalajs.testsuite.jsinterop
+
+import scala.scalajs.js
+import scala.scalajs.js.JSConverters._
+import scala.scalajs.js.|
+
+import scala.scalajs.js.wasm.JSPI.allowOrphanJSAwait
+
+import scala.concurrent.{Future, ExecutionContext}
+import scala.concurrent.ExecutionContext.Implicits.global
+
+import scala.collection.mutable.ArrayBuffer
+
+import org.junit.Assert._
+import org.junit.Assume._
+import org.junit.Test
+
+import org.scalajs.junit.async._
+
+class JSOrphanAwaitTest {
+  @Test
+  def basic(): AsyncResult = await {
+    @noinline
+    def foo(p: js.Promise[Int]): Int =
+      js.await(p) * 3
+
+    val p = js.Promise.resolve[Int](13).`then`(
+        (i => i + 1): js.Function1[Int, Int | js.Thenable[Int]])
+
+    val result = js.async {
+      foo(p) - 1
+    }
+
+    result.toFuture.map { (result: Int) =>
+      assertEquals(((13 + 1) * 3) - 1, result)
+    }
+  }
+
+  @Test
+  def throughClosure(): AsyncResult = await {
+    @noinline
+    def foo(p: js.Promise[Int])(op: js.Promise[Int] => Int): Int =
+      op(p)
+
+    val p = js.Promise.resolve[Int](13).`then`(
+        (i => i + 1): js.Function1[Int, Int | js.Thenable[Int]])
+
+    val result = js.async {
+      foo(p)(p2 => js.await(p2) * 3) - 1
+    }
+
+    result.toFuture.map { (result: Int) =>
+      assertEquals(((13 + 1) * 3) - 1, result)
+    }
+  }
+
+  /* TODO Enable this test when browsers and Node.js implement the latest spec,
+   * with SuspendError. At the time of writing, it passed in Chrome Canary.
+   */
+  @Test
+  @org.junit.Ignore
+  def suspendError(): AsyncResult = await {
+    val p = js.Promise.resolve[Int](13)
+
+    Future {
+      try {
+        js.await(p)
+        throw new AssertionError(
+            "js.await without an enclosing js.async should throw SuspendError")
+      } catch {
+        case js.JavaScriptException(e: js.Error) =>
+          assertEquals("SuspendError", e.name)
+          assertTrue(js.special.instanceof(e, js.Dynamic.global.WebAssembly.SuspendError))
+      }
+    }
+  }
+}

From a7a613b6a4bc62dc8896095ff866302c679bddad Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Tue, 11 Mar 2025 16:37:00 +0100
Subject: [PATCH 274/298] Fix #5131: Overhaul justifications for caching in
 Emitter.genClass.

Previously, we were missing a number of cases where we should
have set the `changed` flag to true.

That flag is used to decide if a module needs to be rewritten.
Previously, we failed to notice cases where *only* one of the
`Analysis` flags changed (`hasInstances`, `hasRuntimeTypeInfo`
and `hasInstanceTests`). In those cases, all the *cached trees*
are kept. The only thing that changes is the subset thereof that
is actullay included. That does not require invalidation of the
caches, but it does require rewriting the module.

Likewise, we failed to invalidate the module if only the *set*
of static-like methods retained by the analysis changed.

Overall, it had become quite tricky to follow what we are
allowed to use where. This commit overhauls how we track
everything.

First, we include the `kind` of the class in its cache identity,
because too many things depend on it. If it changes, it is
likely that everything will be invalidated anyway.

Other than that, dangerous variables, whose uses must be
justified, are clearly marked with `foo_!` names.

Boolean decisions whose outcome is never cached are tracked
separately; if any of them changes, we marked `changed` to `true`.
This particular change is what fixes #5131.

Finally, we add dedicated tracking of the set of generated
static-like methods, like we do for instance methods.
---
 .../linker/backend/emitter/Emitter.scala      | 375 ++++++++++++------
 .../org/scalajs/linker/IncrementalTest.scala  | 151 ++++++-
 2 files changed, 399 insertions(+), 127 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala
index fe8531a191..b625c51c12 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala
@@ -411,12 +411,23 @@ final class Emitter(config: Emitter.Config, prePrinter: Emitter.PrePrinter) {
     else lhs.className.compareTo(rhs.className) < 0
   }
 
-  private def genClass(linkedClass: LinkedClass,
+  private def genClass(
+      linkedClass_! : LinkedClass, // scalastyle:ignore
       moduleContext: ModuleContext): GeneratedClass = {
-    val className = linkedClass.className
+
+    /* !!! In this method, *every* time you use linkedClass_!, you must justify
+     * why you have the right to access the fields you are reading.
+     * That's why we give it that dangerous-looking name.
+     */
+
+    // Cache identity; always safe to access
+    val kind = linkedClass_!.kind
+    val isJSClass = kind.isJSClass // we use this one a lot
+    val className = linkedClass_!.className
+    val ancestors = linkedClass_!.ancestors
 
     val classCache = classCaches.getOrElseUpdate(
-        new ClassID(linkedClass.ancestors, moduleContext), new ClassCache)
+        new ClassID(kind, ancestors, moduleContext), new ClassCache)
 
     var changed = false
     def extractChanged[T](x: (T, Boolean)): T = {
@@ -424,10 +435,31 @@ final class Emitter(config: Emitter.Config, prePrinter: Emitter.PrePrinter) {
       x._1
     }
 
-    val classTreeCache =
-      extractChanged(classCache.getCache(linkedClass.version))
-
-    val kind = linkedClass.kind
+    /* The class version itself; it's OK to get that one as long as we don't
+     * use it to *produce* trees, which we should never do anyway.
+     */
+    val classVersion = linkedClass_!.version
+
+    val classTreeCache = extractChanged(classCache.getCache(classVersion))
+
+    /* Information that we can use for uncached decision-making.
+     * We call "decision-making" any if/else branch not covered by an explicit
+     * cache.
+     *
+     * Note that it is *not* safe to use uncachedDecisions in *cached*
+     * decision-making!
+     */
+    val uncachedDecisions = extractChanged(classCache.getUncachedDecisions(linkedClass_!))
+
+    /* Delegate justifications for those two to their use sites.
+     *
+     * - Uses of linkedInlineableInit_! must be protected by the classVersion
+     *   and its own version (see `ctorVersion`).
+     * - The sets of things generated by linkedMethods_! must be independently
+     *   tracked (see `trackStaticLikeMethodChanges` and `fullClassChangeTracker`).
+     */
+    val (linkedInlineableInit_!, linkedMethods_!) =
+      classEmitter.extractInlineableInit(linkedClass_!)(classCache)
 
     // Global ref management
 
@@ -445,11 +477,8 @@ final class Emitter(config: Emitter.Config, prePrinter: Emitter.PrePrinter) {
 
     val main = List.newBuilder[js.Tree]
 
-    val (linkedInlineableInit, linkedMethods) =
-      classEmitter.extractInlineableInit(linkedClass)(classCache)
-
     // Symbols for private JS fields
-    if (kind.isJSClass) {
+    if (isJSClass) {
       val fieldDefs = classTreeCache.privateJSFields.getOrElseUpdate {
         classEmitter.genCreatePrivateJSFieldDefsOfJSClass(className)(
             moduleContext, classCache).map(prePrint(_, 0))
@@ -458,37 +487,70 @@ final class Emitter(config: Emitter.Config, prePrinter: Emitter.PrePrinter) {
     }
 
     // Static-like methods
-    for (methodDef <- linkedMethods) {
-      val namespace = methodDef.flags.namespace
-
-      val emitAsStaticLike = {
-        namespace != MemberNamespace.Public ||
-        kind == ClassKind.Interface ||
-        kind == ClassKind.HijackedClass
-      }
-
-      if (emitAsStaticLike) {
+    locally {
+      val emitAllAsStaticLike =
+        kind == ClassKind.Interface || kind == ClassKind.HijackedClass
+
+      // The set is tracked explicitly just after
+      val staticLikeMethods = for {
+        methodDef <- linkedMethods_! // versioning per member inside
+        if emitAllAsStaticLike || methodDef.flags.namespace != MemberNamespace.Public
+      } yield {
         val methodCache =
-          classCache.getStaticLikeMethodCache(namespace, methodDef.methodName)
+          classCache.getStaticLikeMethodCache(methodDef.flags.namespace, methodDef.methodName)
 
-        main ++= extractWithGlobalsAndChanged(methodCache.getOrElseUpdate(methodDef.version, {
+        extractWithGlobalsAndChanged(methodCache.getOrElseUpdate(methodDef.version, {
           classEmitter.genStaticLikeMethod(className, methodDef)(moduleContext, methodCache)
             .map(prePrint(_, 0))
         }))
       }
-    }
 
-    val isJSClass = kind.isJSClass
+      // *Non* short-circuiting boolean or; always evaluate the right-hand-side
+      changed |= classCache.trackStaticLikeMethodChanges(staticLikeMethods)
+
+      for (staticLikeMethod <- staticLikeMethods)
+        main ++= staticLikeMethod
+    }
 
     // Class definition
-    if (linkedClass.hasInstances && kind.isAnyNonNativeClass) {
-      val isJSClassVersion = Version.fromByte(if (isJSClass) 1 else 0)
+    if (uncachedDecisions.hasInstances && kind.isAnyNonNativeClass) {
+      /* Decision-making in this scope is governed by the `fullClassChangeTracker`
+       * below *instead* of the uncachedDecisions. That means we are not allowed
+       * to use `uncachedDecisions` in this scope.
+       *
+       * The `fullClassChangeTracker` is actually called at the end of the
+       * block, because it needs to track *produced* js.Trees in addition to
+       * *inputs* in the LinkedClass. This way, it essentially tracks the *set*
+       * of methods that are emitted (i.e., that were not dce'ed away before
+       * getting here).
+       *
+       * Nevertheless, since it tracks the class version, we are allowed to
+       * use the following facts for uncached decision-making.
+       */
+
+      val hasJSSuperClass = linkedClass_!.jsSuperClass.isDefined
+
+      /* Whether or not there is a class initializer is a constant across the
+       * pipeline. By construction, if there is one in the original `ClassDef`,
+       * it must still be here now. The `classVersion` covers the *entire*
+       * original `ClassDef` (though it does not cover the entire
+       * `LinkedClass`es after transformations). So the `classVersion` covers
+       * whether or not there is a class initializer.
+       */
+      val hasClassInitializer: Boolean = {
+        linkedClass_!.methods.exists { m =>
+          m.flags.namespace == MemberNamespace.StaticConstructor &&
+          m.methodName.isClassInitializer
+        }
+      }
 
       /* Is this class compiled as an ECMAScript `class`?
        *
        * See JSGen.useClassesForRegularClasses for the rationale here.
-       * Accessing `ancestors` without cache invalidation is fine because it
-       * is part of the identity of a class for its cache in the first place.
+       *
+       * This value is a "constant-per-cache", because it only depends on
+       * - the global linker config, and
+       * - isJSClass/ancestors, which are always safe (part of the cache identity).
        *
        * Note that `useClassesForRegularClasses` implies
        * `useClassesForJSClassesAndThrowables`, so the short-cut is valid.
@@ -500,30 +562,26 @@ final class Emitter(config: Emitter.Config, prePrinter: Emitter.PrePrinter) {
        * observable change; whereas rewiring Throwable to extend `Error` when
        * it does not actually directly extend `Object` would break everything,
        * so we need to be more careful there.
-       *
-       * For caching, isJSClassVersion can be used to guard use of `useESClass`:
-       * it is the only "dynamic" value it depends on. The rest is configuration
-       * or part of the cache key (ancestors).
        */
       val useESClass = if (jsGen.useClassesForRegularClasses) {
         assert(jsGen.useClassesForJSClassesAndThrowables)
         true
       } else {
         jsGen.useClassesForJSClassesAndThrowables &&
-        (isJSClass || linkedClass.ancestors.contains(ThrowableClass))
+        (isJSClass || ancestors.contains(ThrowableClass))
       }
 
+      // Therefore, this is also constant-per-cache
       val memberIndent = {
         (if (isJSClass) 1 else 0) + // accessor function
         (if (useESClass) 1 else 0) // nesting from class
       }
 
-      val hasJSSuperClass = linkedClass.jsSuperClass.isDefined
-
       val storeJSSuperClass = if (hasJSSuperClass) {
         extractWithGlobals(classTreeCache.storeJSSuperClass.getOrElseUpdate({
-          val jsSuperClass = linkedClass.jsSuperClass.get
-          classEmitter.genStoreJSSuperClass(jsSuperClass)(moduleContext, classCache, linkedClass.pos)
+          // jsSuperClass and pos invalidated by class version
+          val jsSuperClass = linkedClass_!.jsSuperClass.get
+          classEmitter.genStoreJSSuperClass(jsSuperClass)(moduleContext, classCache, linkedClass_!.pos)
             .map(prePrint(_, 1))
         }))
       } else {
@@ -540,51 +598,58 @@ final class Emitter(config: Emitter.Config, prePrinter: Emitter.PrePrinter) {
         val ctorCache = classCache.getConstructorCache()
 
         if (isJSClass) {
-          assert(linkedInlineableInit.isEmpty)
+          assert(linkedInlineableInit_!.isEmpty) // just an assertion, it's fine
 
-          val jsConstructorDef = linkedClass.jsConstructorDef.getOrElse {
+          // Explicitly versioned just below
+          val jsConstructorDef = linkedClass_!.jsConstructorDef.getOrElse {
             throw new IllegalArgumentException(s"$className does not have an exported constructor")
           }
 
-          val ctorVersion = Version.combine(linkedClass.version, jsConstructorDef.version)
+          val ctorVersion = Version.combine(classVersion, jsConstructorDef.version)
           ctorCache.getOrElseUpdate(ctorVersion,
               classEmitter.genJSConstructor(
-                className, // invalidated by overall class cache (part of ancestors)
-                linkedClass.superClass, // invalidated by class version
-                hasJSSuperClass, // invalidated by class version
-                useESClass, // invalidated by class version
+                className, // always safe
+                linkedClass_!.superClass, // invalidated by class version
+                linkedClass_!.jsSuperClass.isDefined, // invalidated by class version (*not* local decision-making)
+                useESClass, // always safe
                 jsConstructorDef // part of ctor version
-              )(moduleContext, ctorCache, linkedClass.pos).map(prePrint(_, memberIndent)))
+              )(moduleContext, ctorCache, linkedClass_!.pos) // pos invalidated by class version
+                .map(prePrint(_, memberIndent))
+          )
         } else {
-          val ctorVersion = linkedInlineableInit.fold {
-            Version.combine(linkedClass.version)
+          val ctorVersion = linkedInlineableInit_!.fold { // versioning
+            Version.combine(classVersion)
           } { linkedInit =>
-            Version.combine(linkedClass.version, linkedInit.version)
+            Version.combine(classVersion, linkedInit.version)
           }
 
           ctorCache.getOrElseUpdate(ctorVersion,
               classEmitter.genScalaClassConstructor(
-                className, // invalidated by overall class cache (part of ancestors)
-                linkedClass.superClass, // invalidated by class version
+                className, // always safe
+                linkedClass_!.superClass, // invalidated by class version
                 useESClass, // invalidated by class version,
-                linkedInlineableInit // part of ctor version
-              )(moduleContext, ctorCache, linkedClass.pos).map(prePrint(_, memberIndent)))
+                linkedInlineableInit_! // part of ctor version
+              )(moduleContext, ctorCache, linkedClass_!.pos) // pos invalidated by class version
+                .map(prePrint(_, memberIndent))
+          )
         }
       }
 
       /* Bridges from Throwable to methods of Object, which are necessary
        * because Throwable is rewired to extend JavaScript's Error instead of
        * j.l.Object.
+       *
+       * Completely uncached; delegate justifications to use sites.
        */
-      val linkedMethodsAndBridges = if (ClassEmitter.shouldExtendJSError(className)) {
-        val existingMethods = linkedMethods
+      val linkedMethodsAndBridges_! = if (ClassEmitter.shouldExtendJSError(className)) {
+        val existingMethods_! = linkedMethods_!
           .withFilter(_.flags.namespace == MemberNamespace.Public)
           .map(_.methodName)
           .toSet
 
-        val bridges = for {
+        val bridges_! = for {
           methodDef <- uncachedKnowledge.methodsInObject()
-          if !existingMethods.contains(methodDef.methodName)
+          if !existingMethods_!.contains(methodDef.methodName)
         } yield {
           import org.scalajs.ir.Trees._
           import org.scalajs.ir.Types._
@@ -602,76 +667,66 @@ final class Emitter(config: Emitter.Config, prePrinter: Emitter.PrePrinter) {
               OptimizerHints.empty, methodDef.version)
         }
 
-        linkedMethods ++ bridges
+        linkedMethods_! ++ bridges_!
       } else {
-        linkedMethods
+        linkedMethods_!
       }
 
-      // Normal methods
+      // Normal methods -- the set itself is tracked by the fullClassChangeTracker
       val memberMethodsWithGlobals = for {
-        method <- linkedMethodsAndBridges
+        method <- linkedMethodsAndBridges_! // explicitly versioned below, by member
         if method.flags.namespace == MemberNamespace.Public
       } yield {
         val methodCache =
           classCache.getMemberMethodCache(method.methodName)
 
-        val version = Version.combine(isJSClassVersion, method.version)
-        extractChanged(methodCache.getOrElseUpdate(version,
+        extractChanged(methodCache.getOrElseUpdate(method.version,
             classEmitter.genMemberMethod(
-                className, // invalidated by overall class cache
-                isJSClass, // invalidated by isJSClassVersion
-                useESClass, // invalidated by isJSClassVersion
+                className, // always safe
+                isJSClass, // always safe
+                useESClass, // always safe
                 method // invalidated by method.version
             )(moduleContext, methodCache).map(prePrint(_, memberIndent))))
       }
 
-      // Exported Members
+      // Exported Members -- the set itself is tracked by the fullClassChangeTracker
       val exportedMembersWithGlobals = for {
-        (member, idx) <- linkedClass.exportedMembers.zipWithIndex
+        (member, idx) <- linkedClass_!.exportedMembers.zipWithIndex // explicitly versioned below, by member
       } yield {
         val memberCache = classCache.getExportedMemberCache(idx)
-        val version = Version.combine(isJSClassVersion, member.version)
-        extractChanged(memberCache.getOrElseUpdate(version,
+        extractChanged(memberCache.getOrElseUpdate(member.version,
             classEmitter.genExportedMember(
-                className, // invalidated by overall class cache
-                isJSClass, // invalidated by isJSClassVersion
-                useESClass, // invalidated by isJSClassVersion
-                member // invalidated by version
+                className, // always safe
+                isJSClass, // always safe
+                useESClass, // always safe
+                member // invalidated by member.version
             )(moduleContext, memberCache).map(prePrint(_, memberIndent))))
       }
 
-      val hasClassInitializer: Boolean = {
-        linkedClass.methods.exists { m =>
-          m.flags.namespace == MemberNamespace.StaticConstructor &&
-          m.methodName.isClassInitializer
-        }
-      }
+      // Now that we have everything, track changes.
+      val fullClassChangeTracker = classCache.getFullClassChangeTracker()
+      // Put changed state into a val to avoid short circuiting behavior of ||.
+      val classChanged = fullClassChangeTracker.trackChanged(
+          classVersion, ctorWithGlobals,
+          memberMethodsWithGlobals, exportedMembersWithGlobals)
+      changed ||= classChanged
 
       val fullClass = {
-        val fullClassChangeTracker = classCache.getFullClassChangeTracker()
-
-        // Put changed state into a val to avoid short circuiting behavior of ||.
-        val classChanged = fullClassChangeTracker.trackChanged(
-            linkedClass.version, ctorWithGlobals,
-            memberMethodsWithGlobals, exportedMembersWithGlobals)
-
-        changed ||= classChanged
-
         for {
           ctor <- ctorWithGlobals
           memberMethods <- WithGlobals.flatten(memberMethodsWithGlobals)
           exportedMembers <- WithGlobals.flatten(exportedMembersWithGlobals)
           allMembers = ctor ::: memberMethods ::: exportedMembers
           clazz <- classEmitter.buildClass(
-            className, // invalidated by overall class cache (part of ancestors)
-            isJSClass, // invalidated by class version
-            linkedClass.jsClassCaptures, // invalidated by class version
-            hasClassInitializer, // invalidated by class version (optimizer cannot remove it)
-            linkedClass.superClass, // invalidated by class version
+            className, // always safe
+            isJSClass, // always safe
+            linkedClass_!.jsClassCaptures, // invalidated by class version
+            hasClassInitializer, // scope-local decision-making
+            linkedClass_!.superClass, // invalidated by class version
             storeJSSuperClass, // invalidated by class version
-            useESClass, // invalidated by class version (depends on kind, config and ancestry only)
+            useESClass, // always safe
             allMembers // invalidated directly
-          )(moduleContext, fullClassChangeTracker, linkedClass.pos) // pos invalidated by class version
+          )(moduleContext, fullClassChangeTracker, linkedClass_!.pos) // pos invalidated by class version
         } yield {
           clazz
         }
@@ -694,37 +749,39 @@ final class Emitter(config: Emitter.Config, prePrinter: Emitter.PrePrinter) {
        * class `j.l.Object`.
        */
 
-      if (classEmitter.needInstanceTests(linkedClass)(classCache)) {
+      if (uncachedDecisions.needInstanceTests) {
         main ++= extractWithGlobals(classTreeCache.instanceTests.getOrElseUpdate({
-          classEmitter.genInstanceTests(className, kind)(moduleContext, classCache, linkedClass.pos)
+          // pos invalidated by class version
+          classEmitter.genInstanceTests(className, kind)(moduleContext, classCache, linkedClass_!.pos)
             .map(prePrint(_, 0))
         }))
       }
 
-      if (linkedClass.hasRuntimeTypeInfo) {
+      if (uncachedDecisions.hasRuntimeTypeInfo) {
         main ++= extractWithGlobals(classTreeCache.typeData.getOrElseUpdate(
-            linkedClass.hasDirectInstances,
+            linkedClass_!.hasDirectInstances, // versioning
             classEmitter.genTypeData(
-              className, // invalidated by overall class cache (part of ancestors)
-              kind, // invalidated by class version
-              linkedClass.superClass, // invalidated by class version
-              linkedClass.ancestors, // invalidated by overall class cache (identity)
-              linkedClass.jsNativeLoadSpec, // invalidated by class version
-              linkedClass.hasDirectInstances // invalidated directly (it is the input to `getOrElseUpdate`)
-            )(moduleContext, classCache, linkedClass.pos).map(prePrint(_, 0))))
+              className, // always safe
+              kind, // always safe
+              linkedClass_!.superClass, // invalidated by class version
+              ancestors, // always safe
+              linkedClass_!.jsNativeLoadSpec, // invalidated by class version
+              linkedClass_!.hasDirectInstances // invalidated directly (it is the input to `getOrElseUpdate`)
+            )(moduleContext, classCache, linkedClass_!.pos).map(prePrint(_, 0)))) // pos invalidated by class version
       }
     }
 
-    if (linkedClass.kind.hasModuleAccessor && linkedClass.hasInstances) {
+    if (kind.hasModuleAccessor && uncachedDecisions.hasInstances) {
       main ++= extractWithGlobals(classTreeCache.moduleAccessor.getOrElseUpdate({
-        classEmitter.genModuleAccessor(className, isJSClass)(moduleContext, classCache, linkedClass.pos)
+        // pos invalidated by class version
+        classEmitter.genModuleAccessor(className, isJSClass)(moduleContext, classCache, linkedClass_!.pos)
           .map(prePrint(_, 0))
       }))
     }
 
     // Static fields
 
-    val staticFields = if (linkedClass.kind.isJSType) {
+    val staticFields = if (kind.isJSType) {
       Nil
     } else {
       extractWithGlobals(classTreeCache.staticFields.getOrElseUpdate({
@@ -735,9 +792,10 @@ final class Emitter(config: Emitter.Config, prePrinter: Emitter.PrePrinter) {
 
     // Static initialization
 
-    val staticInitialization = if (classEmitter.needStaticInitialization(linkedClass)) {
+    val staticInitialization = if (uncachedDecisions.needStaticInitialization) {
       classTreeCache.staticInitialization.getOrElseUpdate({
-        val tree = classEmitter.genStaticInitialization(className)(moduleContext, classCache, linkedClass.pos)
+        // pos invalidated by class version
+        val tree = classEmitter.genStaticInitialization(className)(moduleContext, classCache, linkedClass_!.pos)
         prePrint(tree, 0)
       })
     } else {
@@ -871,6 +929,8 @@ final class Emitter(config: Emitter.Config, prePrinter: Emitter.PrePrinter) {
     private[this] var _lastVersion: Version = Version.Unversioned
     private[this] var _cacheUsed = false
 
+    private[this] var _uncachedDecisions: UncachedDecisions = UncachedDecisions.Invalid
+
     private[this] val _methodCaches =
       Array.fill(MemberNamespace.Count)(mutable.Map.empty[MethodName, MethodCache[List[js.Tree]]])
 
@@ -882,6 +942,7 @@ final class Emitter(config: Emitter.Config, prePrinter: Emitter.PrePrinter) {
     private[this] val _exportedMembersCache =
       mutable.Map.empty[Int, MethodCache[List[js.Tree]]]
 
+    private[this] var _staticLikeMethodsTracker: Option[List[List[js.Tree]]] = None
     private[this] var _fullClassChangeTracker: Option[FullClassChangeTracker] = None
 
     override def invalidate(): Unit = {
@@ -891,6 +952,7 @@ final class Emitter(config: Emitter.Config, prePrinter: Emitter.PrePrinter) {
       super.invalidate()
       _cache = null
       _lastVersion = Version.Unversioned
+      _uncachedDecisions = UncachedDecisions.Invalid
     }
 
     def startRun(): Unit = {
@@ -915,6 +977,22 @@ final class Emitter(config: Emitter.Config, prePrinter: Emitter.PrePrinter) {
       }
     }
 
+    def getUncachedDecisions(linkedClass: LinkedClass): (UncachedDecisions, Boolean) = {
+      val needInstanceTests = classEmitter.needInstanceTests(linkedClass)(this)
+      val needStaticInitialization = classEmitter.needStaticInitialization(linkedClass)
+      val result = UncachedDecisions(
+        hasInstances = linkedClass.hasInstances,
+        hasRuntimeTypeInfo = linkedClass.hasRuntimeTypeInfo,
+        hasInstanceTests = linkedClass.hasInstanceTests,
+        needInstanceTests = needInstanceTests,
+        needStaticInitialization = needStaticInitialization
+      )
+      val changed = result != _uncachedDecisions
+      if (changed)
+        _uncachedDecisions = result
+      (result, changed)
+    }
+
     def getMemberMethodCache(
         methodName: MethodName): MethodCache[List[js.Tree]] = {
       _memberMethodCache.getOrElseUpdate(methodName, new MethodCache)
@@ -937,6 +1015,19 @@ final class Emitter(config: Emitter.Config, prePrinter: Emitter.PrePrinter) {
     def getExportedMemberCache(idx: Int): MethodCache[List[js.Tree]] =
       _exportedMembersCache.getOrElseUpdate(idx, new MethodCache)
 
+    /** Track changes to the generated list of static-like methods.
+     *
+     *  Returns `true` iff there were changes since the last run.
+     */
+    def trackStaticLikeMethodChanges(staticLikeMethods: List[List[js.Tree]]): Boolean = {
+      if (_staticLikeMethodsTracker.exists(allSame(_, staticLikeMethods))) {
+        false
+      } else {
+        _staticLikeMethodsTracker = Some(staticLikeMethods)
+        true
+      }
+    }
+
     def getFullClassChangeTracker(): FullClassChangeTracker = {
       _fullClassChangeTracker.getOrElse {
         val cache = new FullClassChangeTracker
@@ -1021,14 +1112,6 @@ final class Emitter(config: Emitter.Config, prePrinter: Emitter.PrePrinter) {
         memberMethods: List[WithGlobals[List[js.Tree]]],
         exportedMembers: List[WithGlobals[List[js.Tree]]]): Boolean = {
 
-      @tailrec
-      def allSame[A <: AnyRef](xs: List[A], ys: List[A]): Boolean = {
-        xs.isEmpty == ys.isEmpty && {
-          xs.isEmpty ||
-          ((xs.head eq ys.head) && allSame(xs.tail, ys.tail))
-        }
-      }
-
       _trackerUsed = true
 
       val changed = {
@@ -1193,6 +1276,56 @@ object Emitter {
     }
   }
 
+  @tailrec
+  private def allSame(xs: List[AnyRef], ys: List[AnyRef]): Boolean = {
+    xs.isEmpty == ys.isEmpty && {
+      xs.isEmpty ||
+      ((xs.head eq ys.head) && allSame(xs.tail, ys.tail))
+    }
+  }
+
+  private final class UncachedDecisions(private val flags: Int) extends AnyVal {
+    import UncachedDecisions._
+
+    def hasInstances: Boolean = hasFlag(HasInstances)
+    def hasRuntimeTypeInfo: Boolean = hasFlag(HasRuntimeTypeInfo)
+    def hasInstanceTests: Boolean = hasFlag(HasInstanceTests)
+    def needInstanceTests: Boolean = hasFlag(NeedInstanceTests)
+    def needStaticInitialization: Boolean = hasFlag(NeedStaticInitialization)
+
+    @inline private def hasFlag(flag: Int): Boolean =
+      (flags & flag) != 0
+  }
+
+  private object UncachedDecisions {
+    private final val HasInstances = 1 << 0
+    private final val HasRuntimeTypeInfo = 1 << 1
+    private final val HasInstanceTests = 1 << 2
+    private final val NeedInstanceTests = 1 << 3
+    private final val NeedStaticInitialization = 1 << 4
+
+    final val Invalid: UncachedDecisions = new UncachedDecisions(-1)
+
+    def apply(
+      hasInstances: Boolean,
+      hasRuntimeTypeInfo: Boolean,
+      hasInstanceTests: Boolean,
+      needInstanceTests: Boolean,
+      needStaticInitialization: Boolean
+    ): UncachedDecisions = {
+      def flagIf(cond: Boolean, flag: Int): Int =
+        if (cond) flag else 0
+
+      new UncachedDecisions(
+        flagIf(hasInstances, HasInstances) |
+        flagIf(hasRuntimeTypeInfo, HasRuntimeTypeInfo) |
+        flagIf(hasInstanceTests, HasInstanceTests) |
+        flagIf(needInstanceTests, NeedInstanceTests) |
+        flagIf(needStaticInitialization, NeedStaticInitialization)
+      )
+    }
+  }
+
   private final class DesugaredClassCache {
     val privateJSFields = new OneTimeCache[WithGlobals[List[js.Tree]]]
     val storeJSSuperClass = new OneTimeCache[WithGlobals[List[js.Tree]]]
@@ -1241,7 +1374,7 @@ object Emitter {
   }
 
   private case class ClassID(
-      ancestors: List[ClassName], moduleContext: ModuleContext)
+      kind: ClassKind, ancestors: List[ClassName], moduleContext: ModuleContext)
 
   private def symbolRequirements(config: Config): SymbolRequirement = {
     import config.coreSpec.semantics._
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/IncrementalTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/IncrementalTest.scala
index 6c24d25619..a606e3f067 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/IncrementalTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/IncrementalTest.scala
@@ -462,13 +462,150 @@ class IncrementalTest {
 
     testIncrementalBidirectional(classDefs(_), _ => Nil)
   }
+
+  @Test
+  def testInvalidateInstanceTestsNeededWithModules_Issue5131(): AsyncResult = await {
+    val AClass = ClassName("pack.A")
+    val BClass = ClassName("pack.B")
+    val CClass = ClassName("pack.C")
+
+    val TestClass = ClassName("pack.Test")
+
+    val testMethodName = m("test", List(ClassRef(AClass)), BooleanRef)
+
+    val xParam = paramDef("x", ClassType(AClass, nullable = true))
+
+    def classDefs(pre: Boolean): Seq[(Version, ClassDef)] = Seq(
+      v0 -> classDef(
+        AClass,
+        kind = ClassKind.Interface
+      ),
+      v0 -> classDef(
+        BClass,
+        superClass = Some(ObjectClass),
+        interfaces = List(AClass),
+        methods = List(trivialCtor(BClass))
+      ),
+      v0 -> classDef(
+        CClass,
+        superClass = Some(ObjectClass),
+        interfaces = List(AClass),
+        methods = List(trivialCtor(CClass))
+      ),
+      v(pre) -> classDef(
+          TestClass,
+          superClass = Some(ObjectClass),
+          methods = List(
+            trivialCtor(TestClass),
+            mainMethodDef(Block(
+              consoleLog(ApplyStatic(EAF, TestClass, testMethodName,
+                  List(New(BClass, NoArgConstructorName, Nil)))(BooleanType)),
+              consoleLog(ApplyStatic(EAF, TestClass, testMethodName,
+                  List(New(CClass, NoArgConstructorName, Nil)))(BooleanType))
+            )),
+            MethodDef(
+              EMF.withNamespace(MemberNamespace.PublicStatic),
+              testMethodName,
+              NON,
+              List(xParam),
+              BooleanType,
+              Some({
+                IsInstanceOf(xParam.ref, ClassType(if (pre) BClass else CClass, nullable = false))
+              })
+            )(EOH.withNoinline(true), UNV)
+          )
+      )
+    )
+
+    val moduleInits = mainModuleInitializers(TestClass.nameString)
+
+    val config = StandardConfig()
+      .withModuleKind(ModuleKind.ESModule)
+      .withModuleSplitStyle(ModuleSplitStyle.SmallModulesFor(List("pack")))
+
+    testIncrementalBidirectional(classDefs(_), _ => moduleInits, config)
+  }
+
+  @Test
+  def testInvalidateStaticLikeMethodSetWithModules_Issue5131(): AsyncResult = await {
+    val AClass = ClassName("pack.A") // with instances
+    val BClass = ClassName("pack.B") // static-like only
+
+    val TestClass = ClassName("pack.Test")
+
+    val fooMethodName = m("foo", List(IntRef), IntRef)
+    val barMethodName = m("bar", List(IntRef), IntRef)
+
+    val xParam = paramDef("x", IntType)
+
+    def makeOneMethodDef(name: MethodName): MethodDef = {
+      MethodDef(EMF.withNamespace(MemberNamespace.PublicStatic), name, NON,
+          List(xParam), IntType, Some(xParam.ref))(
+          EOH.withNoinline(true), UNV)
+    }
+
+    def classDefs(pre: Boolean): Seq[(Version, ClassDef)] = Seq(
+      v0 -> classDef(
+        AClass,
+        superClass = Some(ObjectClass),
+        methods = List(
+          trivialCtor(AClass),
+          makeOneMethodDef(fooMethodName),
+          makeOneMethodDef(barMethodName)
+        )
+      ),
+      v0 -> classDef(
+        BClass,
+        superClass = Some(ObjectClass),
+        methods = List(
+          trivialCtor(BClass),
+          makeOneMethodDef(fooMethodName),
+          makeOneMethodDef(barMethodName)
+        )
+      ),
+      v(pre) -> classDef(
+          TestClass,
+          superClass = Some(ObjectClass),
+          methods = List(
+            trivialCtor(TestClass),
+            mainMethodDef(Block(
+              // make an instance of A, but not of B
+              consoleLog(New(AClass, NoArgConstructorName, Nil)),
+
+              // call both foo methods
+              consoleLog(ApplyStatic(EAF, AClass, fooMethodName, List(int(1)))(IntType)),
+              consoleLog(ApplyStatic(EAF, BClass, fooMethodName, List(int(2)))(IntType)),
+
+              // call both bar methods only in v0
+              if (pre) {
+                Block(
+                  consoleLog(ApplyStatic(EAF, AClass, barMethodName, List(int(3)))(IntType)),
+                  consoleLog(ApplyStatic(EAF, BClass, barMethodName, List(int(4)))(IntType))
+                )
+              } else {
+                Skip()
+              }
+            ))
+          )
+      )
+    )
+
+    val moduleInits = mainModuleInitializers(TestClass.nameString)
+
+    val config = StandardConfig()
+      .withModuleKind(ModuleKind.ESModule)
+      .withModuleSplitStyle(ModuleSplitStyle.SmallModulesFor(List("pack")))
+
+    testIncrementalBidirectional(classDefs(_), _ => moduleInits, config)
+  }
 }
 
 object IncrementalTest {
 
   def testIncrementalBidirectional(
       classDefs: Boolean => Seq[(Version, ClassDef)],
-      moduleInitializers: Boolean => List[ModuleInitializer])(
+      moduleInitializers: Boolean => List[ModuleInitializer],
+      config: StandardConfig = StandardConfig())(
       implicit ec: ExecutionContext): Future[Unit] = {
 
     def testOneDirection(contextMessage: String, forward: Boolean): Future[Unit] = {
@@ -476,7 +613,8 @@ object IncrementalTest {
         if (forward) step == 0
         else step == 1
       testIncrementalSteps(contextMessage, steps = 2,
-          step => classDefs(pre(step)), step => moduleInitializers(pre(step)))
+          step => classDefs(pre(step)), step => moduleInitializers(pre(step)),
+          config)
     }
 
     for {
@@ -489,14 +627,15 @@ object IncrementalTest {
       contextMessage: String,
       steps: Int,
       stepToClassDefs: Int => Seq[(Version, ClassDef)],
-      stepToModuleInitializers: Int => List[ModuleInitializer])(
+      stepToModuleInitializers: Int => List[ModuleInitializer],
+      config: StandardConfig = StandardConfig())(
       implicit ec: ExecutionContext): Future[Unit] = {
 
     require(steps >= 2, s"require at least 2 steps but got $steps")
 
     val outputInc = MemOutputDirectory()
-    val config = StandardConfig().withCheckIR(true)
-    val linkerInc = StandardImpl.linker(config)
+    val configWithCheckIR = config.withCheckIR(true)
+    val linkerInc = StandardImpl.linker(configWithCheckIR)
 
     val logger = new ScalaConsoleLogger(Level.Error)
 
@@ -506,7 +645,7 @@ object IncrementalTest {
           Future.successful(())
         } else {
           val outputBatch = MemOutputDirectory()
-          val linkerBatch = StandardImpl.linker(config)
+          val linkerBatch = StandardImpl.linker(configWithCheckIR)
 
           val irFiles = minilib ++ stepToClassDefs(step).map(x => MemClassDefIRFile(x._2, x._1))
           val moduleInitializers = stepToModuleInitializers(step)

From 64edcce73c8ee96f8767ed18783f6e50edabb2f1 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Tue, 1 Apr 2025 13:58:27 +0200
Subject: [PATCH 275/298] Wasm: Use builtin string constants from JS string
 builtins.

In addition to builtin functions, the JS string builtins proposal
provides a way to import (valid UTF-8) string literals from a
dedicated module.

Instead of using a custom data segment, we now import all the
strings we can from that builtin module.

For the rare cases where we need a string literal that is not a
valid UTF-16 string (and therefore cannot be encoded into valid
UTF-8), we use custom imports that we fill in from the JS side.

This alternate encoding is a lot more economical in terms of code
size. It shaves off 5% of the fastLink output, and 8.5% of the
fullLink output. Moreover, it means our string literals are
constant expression globals, which we can directly use in the
initialization of `typeData` constant structs.
---
 .../backend/wasmemitter/ClassEmitter.scala    |  12 +-
 .../backend/wasmemitter/CoreWasmLib.scala     | 290 +++++-------------
 .../wasmemitter/EmbeddedConstants.scala       |  27 ++
 .../linker/backend/wasmemitter/Emitter.scala  |  21 +-
 .../backend/wasmemitter/FunctionEmitter.scala |  12 +-
 .../backend/wasmemitter/LoaderContent.scala   |  20 +-
 .../linker/backend/wasmemitter/README.md      |  22 +-
 .../linker/backend/wasmemitter/SWasmGen.scala |   2 +-
 .../backend/wasmemitter/StringPool.scala      | 111 +++----
 .../linker/backend/wasmemitter/VarGen.scala   |  59 ++--
 .../backend/wasmemitter/WasmContext.scala     |   5 +-
 .../backend/webassembly/TextWriter.scala      |   2 +-
 12 files changed, 237 insertions(+), 346 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/ClassEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/ClassEmitter.scala
index 67cfa32b52..88cdbdbae8 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/ClassEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/ClassEmitter.scala
@@ -212,8 +212,7 @@ class ClassEmitter(coreSpec: CoreSpec) {
       coreSpec.semantics.runtimeClassNameMapper,
       className.nameString
     )
-    val nameDataValue: List[wa.Instr] =
-      ctx.stringPool.getConstantStringDataInstr(nameStr)
+    val nameValue = ctx.stringPool.getConstantStringInstr(nameStr)
 
     val kind = className match {
       case ObjectClass         => KindObject
@@ -299,8 +298,10 @@ class ClassEmitter(coreSpec: CoreSpec) {
       elemsInstrs :+ wa.ArrayNewFixed(genTypeID.reflectiveProxies, reflectiveProxies.size)
     }
 
-    nameDataValue :::
+    (
       List(
+        // name
+        nameValue,
         // kind
         wa.I32Const(kind),
         // specialInstanceTypes
@@ -312,8 +313,6 @@ class ClassEmitter(coreSpec: CoreSpec) {
       List(
         // componentType - always `null` since this method is not used for array types
         wa.RefNull(watpe.HeapType(genTypeID.typeData)),
-        // name - initially `null`; filled in by the `typeDataName` helper
-        wa.RefNull(watpe.HeapType.NoExtern),
         // the classOf instance - initially `null`; filled in by the `createClassOf` helper
         wa.RefNull(watpe.HeapType(genTypeID.ClassStruct)),
         // arrayOf, the typeData of an array of this type - initially `null`; filled in by the `arrayTypeData` helper
@@ -327,6 +326,7 @@ class ClassEmitter(coreSpec: CoreSpec) {
       // Generated instructions create an array of reflective proxy structs, where each struct
       // contains the ID of the reflective proxy and a reference to the actual method implementation.
       reflectiveProxiesInstrs
+    )
   }
 
   private def genTypeDataGlobal(className: ClassName, typeDataTypeID: wanme.TypeID,
@@ -1366,7 +1366,7 @@ class ClassEmitter(coreSpec: CoreSpec) {
 
     ctx.moduleBuilder.addImport(
       wamod.Import(
-        "__scalaJSExportSetters",
+        ExportSettersModule,
         exportedName,
         wamod.ImportDesc.Func(
           functionID,
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
index 68b14c51c2..6369b161e2 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
@@ -84,14 +84,11 @@ final class CoreWasmLib(coreSpec: CoreSpec, globalInfo: LinkedGlobalInfo) {
       StructField(id, OriginalName(id.toString()), tpe, isMutable)
 
     List(
-      make(nameOffset, Int32, isMutable = false),
-      make(nameSize, Int32, isMutable = false),
-      make(nameStringIndex, Int32, isMutable = false),
+      make(name, RefType.externref, isMutable = true),
       make(kind, Int32, isMutable = false),
       make(specialInstanceTypes, Int32, isMutable = false),
       make(strictAncestors, nullable(genTypeID.typeDataArray), isMutable = false),
       make(componentType, nullable(genTypeID.typeData), isMutable = false),
-      make(name, RefType.externref, isMutable = true),
       make(classOfValue, nullable(genTypeID.ClassStruct), isMutable = true),
       make(arrayOf, nullable(genTypeID.ObjectVTable), isMutable = true),
       make(cloneFunction, nullable(genTypeID.cloneFunctionType), isMutable = false),
@@ -290,7 +287,7 @@ final class CoreWasmLib(coreSpec: CoreSpec, globalInfo: LinkedGlobalInfo) {
     val typeID = ctx.moduleBuilder.functionTypeToTypeID(exceptionSig)
     ctx.moduleBuilder.addImport(
       Import(
-        "__scalaJSHelpers",
+        CoreHelpersModule,
         "JSTag",
         ImportDesc.Tag(
           genTagID.exception,
@@ -305,7 +302,7 @@ final class CoreWasmLib(coreSpec: CoreSpec, globalInfo: LinkedGlobalInfo) {
     def addGlobalHelperImport(id: genGlobalID.JSHelperGlobalID, tpe: Type): Unit = {
       ctx.moduleBuilder.addImport(
         Import(
-          "__scalaJSHelpers",
+          CoreHelpersModule,
           id.toString(), // import name, guaranteed by JSHelperGlobalID
           ImportDesc.Global(id, OriginalName(id.toString()), isMutable = false, tpe)
         )
@@ -315,7 +312,6 @@ final class CoreWasmLib(coreSpec: CoreSpec, globalInfo: LinkedGlobalInfo) {
     addGlobalHelperImport(genGlobalID.undef, RefType.any)
     addGlobalHelperImport(genGlobalID.bFalse, RefType.any)
     addGlobalHelperImport(genGlobalID.bTrue, RefType.any)
-    addGlobalHelperImport(genGlobalID.emptyString, RefType.extern)
     addGlobalHelperImport(genGlobalID.idHashCodeMap, RefType.extern)
   }
 
@@ -328,7 +324,7 @@ final class CoreWasmLib(coreSpec: CoreSpec, globalInfo: LinkedGlobalInfo) {
       val typeID = ctx.moduleBuilder.functionTypeToTypeID(sig)
       ctx.moduleBuilder.addImport(
         Import(
-          "wasm:js-string",
+          JSStringBuiltinsModule,
           id.toString(), // import name, guaranteed by JSHelperFunctionID
           ImportDesc.Func(id, OriginalName(id.toString()), typeID)
         )
@@ -353,7 +349,7 @@ final class CoreWasmLib(coreSpec: CoreSpec, globalInfo: LinkedGlobalInfo) {
       val typeID = ctx.moduleBuilder.functionTypeToTypeID(sig)
       ctx.moduleBuilder.addImport(
         Import(
-          "__scalaJSHelpers",
+          CoreHelpersModule,
           id.toString(), // import name, guaranteed by JSHelperFunctionID
           ImportDesc.Func(id, OriginalName(id.toString()), typeID)
         )
@@ -459,8 +455,6 @@ final class CoreWasmLib(coreSpec: CoreSpec, globalInfo: LinkedGlobalInfo) {
       RefNull(HeapType.None),
       // componentType
       RefNull(HeapType.None),
-      // name - initially `null`; filled in by the `typeDataName` helper
-      RefNull(HeapType.NoExtern),
       // the classOf instance - initially `null`; filled in by the `createClassOf` helper
       RefNull(HeapType.None),
       // arrayOf, the typeData of an array of this type - initially `null`; filled in by the `arrayTypeData` helper
@@ -474,11 +468,10 @@ final class CoreWasmLib(coreSpec: CoreSpec, globalInfo: LinkedGlobalInfo) {
     )
 
     for ((primRef, kind) <- primRefsWithKinds) {
-      val nameDataValue: List[Instr] =
-        ctx.stringPool.getConstantStringDataInstr(primRef.displayName)
+      val nameValue = ctx.stringPool.getConstantStringInstr(primRef.displayName)
 
       val instrs: List[Instr] = {
-        nameDataValue ::: I32Const(kind) :: commonFieldValues :::
+        nameValue :: I32Const(kind) :: commonFieldValues :::
           StructNew(genTypeID.typeData) :: Nil
       }
 
@@ -532,8 +525,6 @@ final class CoreWasmLib(coreSpec: CoreSpec, globalInfo: LinkedGlobalInfo) {
     genUnboxByteOrShort(ShortRef)
     genTestByteOrShort(ByteRef, I32Extend8S)
     genTestByteOrShort(ShortRef, I32Extend16S)
-    genStringLiteral()
-    genCreateStringFromData()
     genTypeDataName()
     genCreateClassOf()
     genGetClassOf()
@@ -728,98 +719,6 @@ final class CoreWasmLib(coreSpec: CoreSpec, globalInfo: LinkedGlobalInfo) {
     fb.buildAndAddToModule()
   }
 
-  private def genStringLiteral()(implicit ctx: WasmContext): Unit = {
-    val fb = newFunctionBuilder(genFunctionID.stringLiteral)
-    val offsetParam = fb.addParam("offset", Int32)
-    val sizeParam = fb.addParam("size", Int32)
-    val stringIndexParam = fb.addParam("stringIndex", Int32)
-    fb.setResultType(RefType.extern)
-
-    val str = fb.addLocal("str", RefType.extern)
-
-    fb.block(RefType.extern) { cacheHit =>
-      fb += GlobalGet(genGlobalID.stringLiteralCache)
-      fb += LocalGet(stringIndexParam)
-      fb += ArrayGet(genTypeID.externrefArray)
-
-      fb += BrOnNonNull(cacheHit)
-
-      // cache miss, create a new string and cache it
-      fb += GlobalGet(genGlobalID.stringLiteralCache)
-      fb += LocalGet(stringIndexParam)
-
-      fb += LocalGet(offsetParam)
-      fb += LocalGet(sizeParam)
-      fb += ArrayNewData(genTypeID.i16Array, genDataID.string)
-      fb += Call(genFunctionID.createStringFromData)
-      fb += LocalTee(str)
-      fb += ArraySet(genTypeID.externrefArray)
-
-      fb += LocalGet(str)
-    }
-
-    fb.buildAndAddToModule()
-  }
-
-  /** `createStringFromData: (ref array u16) -> (ref extern)` (representing a `string`). */
-  private def genCreateStringFromData()(implicit ctx: WasmContext): Unit = {
-    val dataType = RefType(genTypeID.i16Array)
-
-    val fb = newFunctionBuilder(genFunctionID.createStringFromData)
-    val dataParam = fb.addParam("data", dataType)
-    fb.setResultType(RefType.extern)
-
-    val lenLocal = fb.addLocal("len", Int32)
-    val iLocal = fb.addLocal("i", Int32)
-    val resultLocal = fb.addLocal("result", RefType.extern)
-
-    // len := data.length
-    fb += LocalGet(dataParam)
-    fb += ArrayLen
-    fb += LocalSet(lenLocal)
-
-    // i := 0
-    fb += I32Const(0)
-    fb += LocalSet(iLocal)
-
-    // result := ""
-    fb += GlobalGet(genGlobalID.emptyString)
-    fb += LocalSet(resultLocal)
-
-    fb.loop() { labelLoop =>
-      // if i == len
-      fb += LocalGet(iLocal)
-      fb += LocalGet(lenLocal)
-      fb += I32Eq
-      fb.ifThen() {
-        // then return result
-        fb += LocalGet(resultLocal)
-        fb += Return
-      }
-
-      // result := concat(result, charToString(data(i)))
-      fb += LocalGet(resultLocal)
-      fb += LocalGet(dataParam)
-      fb += LocalGet(iLocal)
-      fb += ArrayGetU(genTypeID.i16Array)
-      fb += Call(genFunctionID.stringBuiltins.fromCharCode)
-      fb += Call(genFunctionID.stringBuiltins.concat)
-      fb += LocalSet(resultLocal)
-
-      // i := i + 1
-      fb += LocalGet(iLocal)
-      fb += I32Const(1)
-      fb += I32Add
-      fb += LocalSet(iLocal)
-
-      // loop back to the beginning
-      fb += Br(labelLoop)
-    } // end loop $loop
-    fb += Unreachable
-
-    fb.buildAndAddToModule()
-  }
-
   /** `typeDataName: (ref typeData) -> (ref extern)` (representing a `string`).
    *
    *  Initializes the `name` field of the given `typeData` if that was not done yet, and returns its
@@ -840,8 +739,6 @@ final class CoreWasmLib(coreSpec: CoreSpec, globalInfo: LinkedGlobalInfo) {
     fb.setResultType(RefType.extern)
 
     val componentTypeDataLocal = fb.addLocal("componentTypeData", typeDataType)
-    val componentNameDataLocal = fb.addLocal("componentNameData", nameDataType)
-    val firstCharLocal = fb.addLocal("firstChar", Int32)
     val nameLocal = fb.addLocal("name", RefType.extern)
 
     fb.block(RefType.extern) { alreadyInitializedLabel =>
@@ -850,104 +747,86 @@ final class CoreWasmLib(coreSpec: CoreSpec, globalInfo: LinkedGlobalInfo) {
       fb += StructGet(genTypeID.typeData, genFieldID.typeData.name)
       fb += BrOnNonNull(alreadyInitializedLabel)
 
+      /* if it was null, the typeData must represent an array type;
+       * compute its name from the component type name
+       */
+
       // for the STRUCT_SET typeData.name near the end
       fb += LocalGet(typeDataParam)
 
-      // if typeData.kind == KindArray
-      fb += LocalGet(typeDataParam)
-      fb += StructGet(genTypeID.typeData, genFieldID.typeData.kind)
-      fb += I32Const(KindArray)
-      fb += I32Eq
-      fb.ifThenElse(RefType.extern) {
-        // it is an array; compute its name from the component type name
-
-        // <top of stack> := "[", for the CALL to stringConcat near the end
-        fb += I32Const('['.toInt)
-        fb += Call(genFunctionID.stringBuiltins.fromCharCode)
+      // <top of stack> := "[", for the CALL to stringConcat near the end
+      fb += I32Const('['.toInt)
+      fb += Call(genFunctionID.stringBuiltins.fromCharCode)
 
-        // componentTypeData := ref_as_non_null(typeData.componentType)
-        fb += LocalGet(typeDataParam)
-        fb += StructGet(
-          genTypeID.typeData,
-          genFieldID.typeData.componentType
-        )
-        fb += RefAsNonNull
-        fb += LocalSet(componentTypeDataLocal)
+      // componentTypeData := ref_as_non_null(typeData.componentType)
+      fb += LocalGet(typeDataParam)
+      fb += StructGet(
+        genTypeID.typeData,
+        genFieldID.typeData.componentType
+      )
+      fb += RefAsNonNull
+      fb += LocalSet(componentTypeDataLocal)
 
-        // switch (componentTypeData.kind)
-        // the result of this switch is the string that must come after "["
-        fb.switch(RefType.extern) { () =>
-          // scrutinee
-          fb += LocalGet(componentTypeDataLocal)
-          fb += StructGet(genTypeID.typeData, genFieldID.typeData.kind)
-        }(
-          List(KindBoolean) -> { () =>
-            fb += I32Const('Z'.toInt)
-            fb += Call(genFunctionID.stringBuiltins.fromCharCode)
-          },
-          List(KindChar) -> { () =>
-            fb += I32Const('C'.toInt)
-            fb += Call(genFunctionID.stringBuiltins.fromCharCode)
-          },
-          List(KindByte) -> { () =>
-            fb += I32Const('B'.toInt)
-            fb += Call(genFunctionID.stringBuiltins.fromCharCode)
-          },
-          List(KindShort) -> { () =>
-            fb += I32Const('S'.toInt)
-            fb += Call(genFunctionID.stringBuiltins.fromCharCode)
-          },
-          List(KindInt) -> { () =>
-            fb += I32Const('I'.toInt)
-            fb += Call(genFunctionID.stringBuiltins.fromCharCode)
-          },
-          List(KindLong) -> { () =>
-            fb += I32Const('J'.toInt)
-            fb += Call(genFunctionID.stringBuiltins.fromCharCode)
-          },
-          List(KindFloat) -> { () =>
-            fb += I32Const('F'.toInt)
-            fb += Call(genFunctionID.stringBuiltins.fromCharCode)
-          },
-          List(KindDouble) -> { () =>
-            fb += I32Const('D'.toInt)
-            fb += Call(genFunctionID.stringBuiltins.fromCharCode)
-          },
-          List(KindArray) -> { () =>
-            // the component type is an array; get its own name
-            fb += LocalGet(componentTypeDataLocal)
-            fb += Call(genFunctionID.typeDataName)
-          }
-        ) { () =>
-          // default: the component type is neither a primitive nor an array;
-          // concatenate "L" + <its own name> + ";"
-          fb += I32Const('L'.toInt)
+      // switch (componentTypeData.kind)
+      // the result of this switch is the string that must come after "["
+      fb.switch(RefType.extern) { () =>
+        // scrutinee
+        fb += LocalGet(componentTypeDataLocal)
+        fb += StructGet(genTypeID.typeData, genFieldID.typeData.kind)
+      }(
+        List(KindBoolean) -> { () =>
+          fb += I32Const('Z'.toInt)
           fb += Call(genFunctionID.stringBuiltins.fromCharCode)
+        },
+        List(KindChar) -> { () =>
+          fb += I32Const('C'.toInt)
+          fb += Call(genFunctionID.stringBuiltins.fromCharCode)
+        },
+        List(KindByte) -> { () =>
+          fb += I32Const('B'.toInt)
+          fb += Call(genFunctionID.stringBuiltins.fromCharCode)
+        },
+        List(KindShort) -> { () =>
+          fb += I32Const('S'.toInt)
+          fb += Call(genFunctionID.stringBuiltins.fromCharCode)
+        },
+        List(KindInt) -> { () =>
+          fb += I32Const('I'.toInt)
+          fb += Call(genFunctionID.stringBuiltins.fromCharCode)
+        },
+        List(KindLong) -> { () =>
+          fb += I32Const('J'.toInt)
+          fb += Call(genFunctionID.stringBuiltins.fromCharCode)
+        },
+        List(KindFloat) -> { () =>
+          fb += I32Const('F'.toInt)
+          fb += Call(genFunctionID.stringBuiltins.fromCharCode)
+        },
+        List(KindDouble) -> { () =>
+          fb += I32Const('D'.toInt)
+          fb += Call(genFunctionID.stringBuiltins.fromCharCode)
+        },
+        List(KindArray) -> { () =>
+          // the component type is an array; get its own name
           fb += LocalGet(componentTypeDataLocal)
           fb += Call(genFunctionID.typeDataName)
-          fb += Call(genFunctionID.stringBuiltins.concat)
-          fb += I32Const(';'.toInt)
-          fb += Call(genFunctionID.stringBuiltins.fromCharCode)
-          fb += Call(genFunctionID.stringBuiltins.concat)
         }
-
-        // At this point, the stack contains "[" and the string that must be concatenated with it
+      ) { () =>
+        // default: the component type is neither a primitive nor an array;
+        // concatenate "L" + <its own name> + ";"
+        fb += I32Const('L'.toInt)
+        fb += Call(genFunctionID.stringBuiltins.fromCharCode)
+        fb += LocalGet(componentTypeDataLocal)
+        fb += Call(genFunctionID.typeDataName)
+        fb += Call(genFunctionID.stringBuiltins.concat)
+        fb += I32Const(';'.toInt)
+        fb += Call(genFunctionID.stringBuiltins.fromCharCode)
         fb += Call(genFunctionID.stringBuiltins.concat)
-      } {
-        // it is not an array; its name is stored in nameData
-        for (
-          idx <- List(
-            genFieldID.typeData.nameOffset,
-            genFieldID.typeData.nameSize,
-            genFieldID.typeData.nameStringIndex
-          )
-        ) {
-          fb += LocalGet(typeDataParam)
-          fb += StructGet(genTypeID.typeData, idx)
-        }
-        fb += Call(genFunctionID.stringLiteral)
       }
 
+      // At this point, the stack contains "[" and the string that must be concatenated with it
+      fb += Call(genFunctionID.stringBuiltins.concat)
+
       // typeData.name := <top of stack> ; leave it on the stack
       fb += LocalTee(nameLocal)
       fb += StructSet(genTypeID.typeData, genFieldID.typeData.name)
@@ -1054,12 +933,12 @@ final class CoreWasmLib(coreSpec: CoreSpec, globalInfo: LinkedGlobalInfo) {
         }
 
         // Return the constant string "long"
-        fb ++= ctx.stringPool.getConstantStringInstr("long")
+        fb += ctx.stringPool.getConstantStringInstr("long")
         fb += Return
       }
 
       // Return the constant string "char"
-      fb ++= ctx.stringPool.getConstantStringInstr("char")
+      fb += ctx.stringPool.getConstantStringInstr("char")
       fb += Return
     }
 
@@ -1086,7 +965,7 @@ final class CoreWasmLib(coreSpec: CoreSpec, globalInfo: LinkedGlobalInfo) {
         fb += LocalGet(objParam)
         fb += Call(genFunctionID.valueDescription)
 
-        fb ++= ctx.stringPool.getConstantStringInstr(" cannot be cast to ")
+        fb += ctx.stringPool.getConstantStringInstr(" cannot be cast to ")
         fb += Call(genFunctionID.stringBuiltins.concat)
 
         fb += LocalGet(typeDataParam)
@@ -1629,9 +1508,7 @@ final class CoreWasmLib(coreSpec: CoreSpec, globalInfo: LinkedGlobalInfo) {
         fb += LocalGet(typeDataParam)
 
         // typeData := new typeData(...)
-        fb += I32Const(0) // nameOffset
-        fb += I32Const(0) // nameSize
-        fb += I32Const(0) // nameStringIndex
+        fb += RefNull(HeapType.NoExtern) // name (initialized lazily by typeDataName)
         fb += I32Const(KindArray) // kind = KindArray
         fb += I32Const(0) // specialInstanceTypes = 0
 
@@ -1644,7 +1521,6 @@ final class CoreWasmLib(coreSpec: CoreSpec, globalInfo: LinkedGlobalInfo) {
         )
 
         fb += LocalGet(typeDataParam) // componentType
-        fb += RefNull(HeapType.NoExtern) // name
         fb += RefNull(HeapType.None) // classOf
         fb += RefNull(HeapType.None) // arrayOf
 
@@ -1869,11 +1745,11 @@ final class CoreWasmLib(coreSpec: CoreSpec, globalInfo: LinkedGlobalInfo) {
 
     genNewScalaClass(fb, SpecialNames.UndefinedBehaviorErrorClass,
         SpecialNames.StringArgConstructorName) {
-      fb ++= ctx.stringPool.getConstantStringInstr("Initializer of ")
+      fb += ctx.stringPool.getConstantStringInstr("Initializer of ")
       fb += LocalGet(typeDataParam)
       fb += Call(genFunctionID.typeDataName)
       fb += Call(genFunctionID.stringBuiltins.concat)
-      fb ++= ctx.stringPool.getConstantStringInstr(
+      fb += ctx.stringPool.getConstantStringInstr(
           " called before completion of its super constructor")
       fb += Call(genFunctionID.stringBuiltins.concat)
     }
@@ -1978,7 +1854,7 @@ final class CoreWasmLib(coreSpec: CoreSpec, globalInfo: LinkedGlobalInfo) {
         fb += Drop // drop `value` which was left on the stack
 
         // throw new TypeError("...")
-        fb ++= ctx.stringPool.getConstantStringInstr(
+        fb += ctx.stringPool.getConstantStringInstr(
           "Cannot call isInstance() on a Class representing a JS trait/object"
         )
         fb += Call(genFunctionID.makeTypeError)
@@ -2873,7 +2749,7 @@ final class CoreWasmLib(coreSpec: CoreSpec, globalInfo: LinkedGlobalInfo) {
     // throw new TypeError("...")
     // Originally, exception is thrown from JS saying e.g. "obj2.z1__ is not a function"
     // TODO Improve the error message to include some information about the missing method
-    fb ++= ctx.stringPool.getConstantStringInstr("Method not found")
+    fb += ctx.stringPool.getConstantStringInstr("Method not found")
     fb += Call(genFunctionID.makeTypeError)
     fb += Throw(genTagID.exception)
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/EmbeddedConstants.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/EmbeddedConstants.scala
index e70ec3efbd..512765e60d 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/EmbeddedConstants.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/EmbeddedConstants.scala
@@ -13,6 +13,33 @@
 package org.scalajs.linker.backend.wasmemitter
 
 object EmbeddedConstants {
+  /** Module name of the JS string builtins.
+   *
+   *  Unlike the other module names below, this one is spec'ed by the JS string
+   *  builtins proposal. It is not configurable.
+   */
+  final val JSStringBuiltinsModule = "wasm:js-string"
+
+  /** Module for our core helpers, defined by hand in `LoaderContent`. */
+  final val CoreHelpersModule = "__scalaJSHelpers"
+
+  /** Module containing the export setters, generated by the `Emitter`. */
+  final val ExportSettersModule = "__scalaJSExportSetters"
+
+  /** Module containing the custom JS helpers (see CustomJSHelperBuilder). */
+  final val CustomHelpersModule = "__scalaJSCustomHelpers"
+
+  /** Wasm module for builtin string constants using the JS string builtins proposal.
+   *
+   *  We use the recommended trick of using the empty string here, to minimize
+   *  code size bloat. This string gets duplicated for every string literal in
+   *  the codebase.
+   */
+  final val UTF8StringConstantsModule = ""
+
+  /** Imported modules for WTF-16 strings, which cannot use the JS string builtins. */
+  final val WTF16StringConstantsModule = "wtf16Strings"
+
   /* Values returned by the `jsValueType` helper.
    *
    * 0: false
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala
index 6c78b14fa3..54f39c43e9 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala
@@ -97,13 +97,14 @@ final class Emitter(config: Emitter.Config) {
     /* Gen the string pool and the declarative elements at the very end, since
      * they depend on what instructions where produced by all the preceding codegen.
      */
-    ctx.stringPool.genPool()
+    val wtf16Strings = ctx.stringPool.genPool()
     genDeclarativeElements()
 
     val wasmModule = ctx.moduleBuilder.build()
 
     val jsFileContentInfo = new JSFileContentInfo(
-      customJSHelpers = ctx.getAllCustomJSHelpers()
+      customJSHelpers = ctx.getAllCustomJSHelpers(),
+      wtf16Strings = wtf16Strings
     )
 
     (wasmModule, jsFileContentInfo)
@@ -183,7 +184,7 @@ final class Emitter(config: Emitter.Config) {
           val stringArrayTypeRef = ArrayTypeRef(ClassRef(BoxedStringClass), 1)
           SWasmGen.genArrayValue(fb, stringArrayTypeRef, args.size) {
             for (arg <- args) {
-              fb ++= ctx.stringPool.getConstantStringInstr(arg)
+              fb += ctx.stringPool.getConstantStringInstr(arg)
               fb += wa.AnyConvertExtern
             }
           }
@@ -296,6 +297,13 @@ final class Emitter(config: Emitter.Config) {
     }
     val customJSHelpersDict = js.ObjectConstr(customJSHelpersItems)
 
+    // WTF-16 string constants
+
+    val wtf16StringsItems = for ((importName, str) <- info.wtf16Strings) yield {
+      js.StringLiteral(importName) -> js.StringLiteral(str)
+    }
+    val wtf16StringsDict = js.ObjectConstr(wtf16StringsItems)
+
     // Overall structure of the result
 
     val loadFunIdent = js.Ident("__load")
@@ -309,7 +317,8 @@ final class Emitter(config: Emitter.Config) {
       List(
         js.StringLiteral(config.internalWasmFileURIPattern(module.id)),
         exportSettersDict,
-        customJSHelpersDict
+        customJSHelpersDict,
+        wtf16StringsDict
       )
     )
 
@@ -369,7 +378,9 @@ object Emitter {
 
   private final class JSFileContentInfo(
       /** Custom JS helpers to generate: pairs of `(importName, jsFunction)`. */
-      val customJSHelpers: List[(String, js.Function)]
+      val customJSHelpers: List[(String, js.Function)],
+      /** WTF-16 string constants: pairs of `(importName, stringValue)`. */
+      val wtf16Strings: List[(String, String)]
   )
 
   final class Result(
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
index 94fa164d81..d244582c84 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
@@ -1371,7 +1371,7 @@ private class FunctionEmitter private (
           fb += wa.RefNull(watpe.HeapType.None)
 
         case StringLiteral(v) =>
-          fb ++= ctx.stringPool.getConstantStringInstr(v)
+          fb += ctx.stringPool.getConstantStringInstr(v)
 
         case ClassOf(typeRef) =>
           genLoadTypeData(fb, typeRef)
@@ -1995,7 +1995,7 @@ private class FunctionEmitter private (
             fb += wa.BrOnNonNull(labelDone)
           }
 
-          fb ++= ctx.stringPool.getConstantStringInstr("null")
+          fb += ctx.stringPool.getConstantStringInstr("null")
         }
       } else {
         /* Dispatch where the receiver can be a JS value.
@@ -2077,7 +2077,7 @@ private class FunctionEmitter private (
             genTreeAuto(tree)
             markPosition(tree)
             fb += wa.BrOnNonNull(notNullLabel)
-            fb ++= ctx.stringPool.getConstantStringInstr("null")
+            fb += ctx.stringPool.getConstantStringInstr("null")
           }
         } else {
           genTreeAuto(tree)
@@ -2195,7 +2195,7 @@ private class FunctionEmitter private (
   private def genThrowArithmeticException()(implicit pos: Position): Unit = {
     val ctorName = MethodName.constructor(List(ClassRef(BoxedStringClass)))
     genNewScalaClass(ArithmeticExceptionClass, ctorName) {
-      fb ++= ctx.stringPool.getConstantStringInstr("/ by zero")
+      fb += ctx.stringPool.getConstantStringInstr("/ by zero")
     }
     fb += wa.ExternConvertAny
     fb += wa.Throw(genTagID.exception)
@@ -2438,7 +2438,7 @@ private class FunctionEmitter private (
         val sig = watpe.FunctionType(List(watpe.RefType.externref), List(watpe.RefType.extern))
         fb.block(sig) { nonNullLabel =>
           fb += wa.BrOnNonNull(nonNullLabel)
-          fb += wa.GlobalGet(genGlobalID.emptyString)
+          fb += ctx.stringPool.getConstantStringInstr("")
         }
 
       case CharType | LongType =>
@@ -3258,7 +3258,7 @@ private class FunctionEmitter private (
               fb += wa.I32Eq
               fb += wa.BrIf(label)
             case StringLiteral(value) =>
-              fb ++= ctx.stringPool.getConstantStringInstr(value)
+              fb += ctx.stringPool.getConstantStringInstr(value)
               fb += wa.Call(genFunctionID.stringBuiltins.equals)
               fb += wa.BrIf(label)
             case Null() =>
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala
index 271894e7f5..ddca4dc892 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala
@@ -104,7 +104,6 @@ const scalaJSHelpers = {
   fmod: (x, y) => x % y,
 
   // Strings
-  emptyString: "",
   jsValueToString: (x) => (x === void 0) ? "undefined" : x.toString(),
   jsValueToStringForConcat: (x) => "" + x,
   booleanToString: (b) => b ? "true" : "false",
@@ -180,19 +179,28 @@ const stringBuiltinPolyfills = {
   equals: (a, b) => a === b,
 };
 
-export async function load(wasmFileURL, exportSetters, customJSHelpers) {
+const stringConstantsPolyfills = new Proxy({}, {
+  get(target, property, receiver) {
+    return property;
+  },
+});
+
+export async function load(wasmFileURL, exportSetters, customJSHelpers, wtf16Strings) {
   const myScalaJSHelpers = {
     ...scalaJSHelpers,
     idHashCodeMap: new WeakMap()
   };
   const importsObj = {
-    "__scalaJSHelpers": myScalaJSHelpers,
-    "__scalaJSExportSetters": exportSetters,
-    "__scalaJSCustomHelpers": customJSHelpers,
-    "wasm:js-string": stringBuiltinPolyfills,
+    "$CoreHelpersModule": myScalaJSHelpers,
+    "$ExportSettersModule": exportSetters,
+    "$CustomHelpersModule": customJSHelpers,
+    "$WTF16StringConstantsModule": wtf16Strings,
+    "$JSStringBuiltinsModule": stringBuiltinPolyfills,
+    "$UTF8StringConstantsModule": stringConstantsPolyfills,
   };
   const options = {
     builtins: ["js-string"],
+    importedStringConstants: "$UTF8StringConstantsModule",
   };
   const resolvedURL = new URL(wasmFileURL, import.meta.url);
   if (resolvedURL.protocol === 'file:') {
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/README.md b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/README.md
index 4ccd99bdf2..a565099a88 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/README.md
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/README.md
@@ -628,25 +628,17 @@ This is implemented in the function `identityHashCode` in `CoreWasmLib`.
 
 As mentioned above, strings are represented as JS `string`s.
 Primitive operations on strings are implemented using [JS String Builtins](https://github.com/WebAssembly/js-string-builtins).
-Since the latter are not yet fully standardized, we polyfill the functions we use.
+Since the latter are not yet fully supported, notably by Safari, we polyfill the functions we use.
 Some conversions to strings, which are part of the semantics of string concatenation, are performed by helper JS functions.
 
-Currently, we still generate string literals entirely from the Wasm side.
-String constants are gathered from the entire program and their raw bytes stored in a data segment.
-We deduplicate strings so that we do not store the same string several times, but otherwise do not attempt further compression (such as reusing prefixes).
-Since creating string values from the data segment is expensive, we cache the constructed strings in a global array.
+For string constants, we use the builtin imports for string literals offered by the JS string builtins proposal.
+This works by configuring a special module name from which strings can be imported.
+The import name is the string value.
 
-At call site, we emit the following instruction sequence:
+That means that only valid Unicode strings can be imported that way (import names must be valid UTF-8).
+For string constants that are not valid Unicode strings, we generate a dedicated dictionary from our JavaScript loader, in yet another (regular) imported module.
 
-```wat
-i32.const 84  ;; start of the string content in the data segment, in bytes
-i32.const 10  ;; string length, in chars
-i32.const 9   ;; index into the cache array for that string
-call $stringLiteral
-```
-
-In the future, we will probably want to use the magic imports for string literals offered by the JS string builtins proposal.
-We have not done so yet because that part of the proposal was still in flux at the time of this writing.
+We polyfill the string constants module with a JavaScript `Proxy`.
 
 ## JavaScript interoperability
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/SWasmGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/SWasmGen.scala
index 6764522f17..7ac01cf64d 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/SWasmGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/SWasmGen.scala
@@ -31,7 +31,7 @@ object SWasmGen {
       case LongType   => I64Const(0L)
       case FloatType  => F32Const(0.0f)
       case DoubleType => F64Const(0.0)
-      case StringType => GlobalGet(genGlobalID.emptyString)
+      case StringType => ctx.stringPool.getConstantStringInstr("")
       case UndefType  => GlobalGet(genGlobalID.undef)
 
       case ClassType(BoxedStringClass, true) =>
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/StringPool.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/StringPool.scala
index fd4f61189c..ff56938e87 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/StringPool.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/StringPool.scala
@@ -20,85 +20,76 @@ import org.scalajs.linker.backend.webassembly.Instructions._
 import org.scalajs.linker.backend.webassembly.Modules._
 import org.scalajs.linker.backend.webassembly.Types._
 
+import EmbeddedConstants._
 import VarGen._
 
 private[wasmemitter] final class StringPool {
   import StringPool._
 
-  private val registeredStrings = new mutable.AnyRefMap[String, StringData]
-  private val rawData = new mutable.ArrayBuffer[Byte]()
-  private var nextIndex: Int = 0
+  private val registeredStrings = new mutable.HashSet[String]
 
   // Set to true by `genPool()`. When true, registering strings is illegal.
   private var poolWasGenerated: Boolean = false
 
-  /** Registers the given constant string and returns its allocated data. */
-  private def register(str: String): StringData = {
+  /** Returns an instruction that loads the given constant string. */
+  def getConstantStringInstr(str: String): GlobalGet = {
     if (poolWasGenerated)
       throw new IllegalStateException("The string pool was already generated")
 
-    registeredStrings.getOrElseUpdate(str, {
-      // Compute the new entry before changing the state
-      val data = StringData(nextIndex, offset = rawData.size)
-
-      // Write the actual raw data and update the next index
-      rawData ++= str.toCharArray.flatMap { char =>
-        Array((char & 0xFF).toByte, (char >> 8).toByte)
-      }
-      nextIndex += 1
-
-      data
-    })
+    registeredStrings += str
+    GlobalGet(genGlobalID.forStringLiteral(str))
   }
 
-  /** Returns the list of instructions that load the given constant string.
-   *
-   *  The resulting list is *not* a Wasm constant expression, since it includes
-   *  a `call` to the helper function `stringLiteral`.
+  /** Generates the string pool, and returns the list of WTF-16 strings that
+   *  must be provided by the JS embedding.
    */
-  def getConstantStringInstr(str: String): List[Instr] =
-    getConstantStringDataInstr(str) :+ Call(genFunctionID.stringLiteral)
-
-  /** Returns the list of 3 constant integers that must be passed to `stringLiteral`.
-   *
-   *  The resulting list is a Wasm constant expression, and hence can be used
-   *  in the initializer of globals.
-   */
-  def getConstantStringDataInstr(str: String): List[I32Const] = {
-    val data = register(str)
-    List(
-      I32Const(data.offset),
-      I32Const(str.length()),
-      I32Const(data.constantStringIndex)
-    )
-  }
-
-  def genPool()(implicit ctx: WasmContext): Unit = {
+  def genPool()(implicit ctx: WasmContext): List[(String, String)] = {
     poolWasGenerated = true
 
-    ctx.moduleBuilder.addData(
-      Data(
-        genDataID.string,
-        OriginalName("stringPool"),
-        rawData.toArray,
-        Data.Mode.Passive
-      )
-    )
-
-    ctx.addGlobal(
-      Global(
-        genGlobalID.stringLiteralCache,
-        OriginalName("stringLiteralCache"),
-        isMutable = false,
-        RefType(genTypeID.externrefArray),
-        Expr(
-          List(
-            I32Const(nextIndex), // number of entries in the pool
-            ArrayNewDefault(genTypeID.externrefArray)
+    val wtf16Strings = new mutable.ListBuffer[(String, String)]
+
+    for (str <- registeredStrings.toSeq.sorted) {
+      if (isValidUTF16String(str)) {
+        // Builtin import from the JS string builtins proposal
+        ctx.moduleBuilder.addImport(
+          Import(
+            UTF8StringConstantsModule,
+            str, // by definition, the imported member name is the string itself
+            ImportDesc.Global(genGlobalID.forStringLiteral(str),
+                OriginalName("'" + str), isMutable = false, RefType.extern)
           )
         )
-      )
-    )
+      } else {
+        // WTF-16 strings, which we import from a generated JS object
+        val indexStr = wtf16Strings.size.toString()
+        wtf16Strings += indexStr -> str
+        ctx.moduleBuilder.addImport(
+          Import(
+            WTF16StringConstantsModule,
+            indexStr,
+            ImportDesc.Global(genGlobalID.forStringLiteral(str),
+                OriginalName("wtf16." + indexStr), isMutable = false, RefType.extern)
+          )
+        )
+      }
+    }
+
+    wtf16Strings.toList
+  }
+
+  private def isValidUTF16String(str: String): Boolean = {
+    // scalastyle:off return
+    val len = str.length()
+    var i = 0
+    while (i != len) {
+      val cp = str.codePointAt(i)
+      // isSurrogate(cp), but Character.isSurrogate only accepts Char's
+      if (cp >= Character.MIN_SURROGATE && cp <= Character.MAX_SURROGATE)
+        return false
+      i += Character.charCount(cp)
+    }
+    true
+    // scalastyle:on return
   }
 }
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
index c007314c9d..a542dffa23 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
@@ -41,9 +41,10 @@ object VarGen {
     final case class forStaticField(fieldName: FieldName) extends GlobalID
     final case class forJSPrivateField(fieldName: FieldName) extends GlobalID
 
+    final case class forStringLiteral(str: String) extends GlobalID
+
     case object bZeroChar extends GlobalID
     case object bZeroLong extends GlobalID
-    case object stringLiteralCache extends GlobalID
     case object emptyITable extends GlobalID
     case object arrayClassITable extends GlobalID
     case object lastIDHashCode extends GlobalID
@@ -57,7 +58,6 @@ object VarGen {
     case object undef extends JSHelperGlobalID
     case object bFalse extends JSHelperGlobalID
     case object bTrue extends JSHelperGlobalID
-    case object emptyString extends JSHelperGlobalID
     case object idHashCodeMap extends JSHelperGlobalID
   }
 
@@ -166,8 +166,6 @@ object VarGen {
 
     // Wasm internal helpers
 
-    case object createStringFromData extends FunctionID
-    case object stringLiteral extends FunctionID
     case object typeDataName extends FunctionID
     case object createClassOf extends FunctionID
     case object getClassOf extends FunctionID
@@ -248,18 +246,28 @@ object VarGen {
     /** Fields of the typeData structs. */
     object typeData {
 
-      /** The name data as the 3 arguments to `stringLiteral`.
+      /** The name as nullable string (`externref`).
+       *
+       *  For primitives and classes, it is initialized with a string constant
+       *  when creating the `typeData` struct.
+       *
+       *  For arrays, it is left `null`, and later computed from the `name` of
+       *  their component type by the `typeDataName` helper.
+       *
+       *  The contents of this value is specified by `java.lang.Class.getName()`. In particular, for
+       *  array types, it obeys the following rules:
        *
-       *  It is only meaningful for primitives and for classes. For array types, they are all 0, as
-       *  array types compute their `name` from the `name` of their component type.
+       *  - `Array[prim]` where `prim` is a one of the primitive types with `charCode` `X` is
+       *    `"[X"`, for example, `"[I"` for `Array[Int]`.
+       *  - `Array[pack.Cls]` where `Cls` is a class is `"[Lpack.Cls;"`.
+       *  - `Array[nestedArray]` where `nestedArray` is an array type with name `nested` is
+       *    `"[nested"`, for example `"⟦I"` for `Array[Array[Int]]` and `"⟦Ljava.lang.String;"`
+       *    for `Array[Array[String]]`.¹
+       *
+       *  ¹ We use the Unicode character `⟦` to represent two consecutive `[` characters in order
+       *  not to confuse Scaladoc.
        */
-      case object nameOffset extends FieldID
-
-      /** See `nameOffset`. */
-      case object nameSize extends FieldID
-
-      /** See `nameOffset`. */
-      case object nameStringIndex extends FieldID
+      case object name extends FieldID
 
       /** The kind of type data, an `i32`.
        *
@@ -297,25 +305,6 @@ object VarGen {
        */
       case object componentType extends FieldID
 
-      /** The name as nullable string (`anyref`), lazily initialized from the nameData.
-       *
-       *  This field is initialized by the `typeDataName` helper.
-       *
-       *  The contents of this value is specified by `java.lang.Class.getName()`. In particular, for
-       *  array types, it obeys the following rules:
-       *
-       *  - `Array[prim]` where `prim` is a one of the primitive types with `charCode` `X` is
-       *    `"[X"`, for example, `"[I"` for `Array[Int]`.
-       *  - `Array[pack.Cls]` where `Cls` is a class is `"[Lpack.Cls;"`.
-       *  - `Array[nestedArray]` where `nestedArray` is an array type with name `nested` is
-       *    `"[nested"`, for example `"⟦I"` for `Array[Array[Int]]` and `"⟦Ljava.lang.String;"`
-       *    for `Array[Array[String]]`.¹
-       *
-       *  ¹ We use the Unicode character `⟦` to represent two consecutive `[` characters in order
-       *  not to confuse Scaladoc.
-       */
-      case object name extends FieldID
-
       /** The `classOf` value, a nullable `java.lang.Class`, lazily initialized from this typeData.
        *
        *  This field is initialized by the `createClassOf` helper.
@@ -456,8 +445,4 @@ object VarGen {
     case object exception extends TagID
   }
 
-  object genDataID {
-    case object string extends DataID
-  }
-
 }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/WasmContext.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/WasmContext.scala
index 5bf34ae492..6d64b1bbbd 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/WasmContext.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/WasmContext.scala
@@ -19,6 +19,7 @@ import scala.collection.mutable.LinkedHashMap
 
 import org.scalajs.ir.ClassKind
 import org.scalajs.ir.Names._
+import org.scalajs.ir.OriginalName
 import org.scalajs.ir.OriginalName.NoOriginalName
 import org.scalajs.ir.Trees.{FieldDef, ParamDef, JSNativeLoadSpec}
 import org.scalajs.ir.Types._
@@ -38,8 +39,8 @@ import org.scalajs.linker.backend.webassembly.{Types => watpe}
 
 import org.scalajs.linker.backend.javascript.{Trees => js}
 
+import EmbeddedConstants._
 import VarGen._
-import org.scalajs.ir.OriginalName
 
 final class WasmContext(
     val coreSpec: CoreSpec,
@@ -77,7 +78,7 @@ final class WasmContext(
     val id = CustomJSHelperFunctionID(customJSHelpers.size)
     moduleBuilder.addImport(
       wamod.Import(
-        "__scalaJSCustomHelpers",
+        CustomHelpersModule,
         id.importName,
         wamod.ImportDesc.Func(
           id,
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/TextWriter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/TextWriter.scala
index d8adec9b9f..4bdf39d011 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/TextWriter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/TextWriter.scala
@@ -595,7 +595,7 @@ object TextWriter {
         str.charAt(i) match {
           case '"'                        => builder.append("\\\"")
           case '\\'                       => builder.append("\\\\")
-          case c if c < 0x20 || c == 0x7f => builder.append("\\%02x".format(c))
+          case c if c < 0x20 || c == 0x7f => builder.append("\\%02x".format(c.toInt))
           case c                          => builder.append(c)
         }
         i += 1

From b5e27004f95216715e122be2cc5be9e4a2a5690c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Wed, 26 Mar 2025 13:37:40 +0100
Subject: [PATCH 276/298] Wasm: Implement fmod on the Scala side.

This avoids the JS call overhead for that "primitive" operation.

As can be seen in the implementation, `fmod` is far from a
primitive, though. It requires an involved algorithm in software.

We took an MIT implemention of `fmod` written in Rust, generic
in the bit-width, and translated it to Scala. The "generic"
aspect is turned into a big copy-pasted blob between the `Float`
and `Double` versions, with some "configuration" at the top.

We put that implementation in the linker private library, in a
new object `WasmRuntime`. The Wasm backend compiles `Float_%` and
`Double_%` as calls to those runtime functions.

Since our new implementation is sensitive to the normal/subnormal
distinction, we add new tests for subnormal values.
---
 .../scalajs/linker/runtime/WasmRuntime.scala  | 455 ++++++++++++++++++
 .../backend/emitter/PrivateLibHolder.scala    |   2 +
 .../backend/wasmemitter/CoreWasmLib.scala     |   2 -
 .../linker/backend/wasmemitter/Emitter.scala  |   6 +-
 .../backend/wasmemitter/FunctionEmitter.scala |  30 +-
 .../backend/wasmemitter/LoaderContent.scala   |   3 -
 .../backend/wasmemitter/SpecialNames.scala    |   6 +
 .../linker/backend/wasmemitter/VarGen.scala   |   2 -
 .../testsuite/compiler/DoubleTest.scala       |  39 +-
 .../testsuite/compiler/FloatTest.scala        |  39 +-
 10 files changed, 549 insertions(+), 35 deletions(-)
 create mode 100644 linker-private-library/src/main/scala/org/scalajs/linker/runtime/WasmRuntime.scala

diff --git a/linker-private-library/src/main/scala/org/scalajs/linker/runtime/WasmRuntime.scala b/linker-private-library/src/main/scala/org/scalajs/linker/runtime/WasmRuntime.scala
new file mode 100644
index 0000000000..4f62a64213
--- /dev/null
+++ b/linker-private-library/src/main/scala/org/scalajs/linker/runtime/WasmRuntime.scala
@@ -0,0 +1,455 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package org.scalajs.linker.runtime
+
+object WasmRuntime {
+  /** `fmod` for `Double`s, the implementation of `Double_%`.
+   *
+   *  Floating point remainders are specified by
+   *  https://262.ecma-international.org/#sec-numeric-types-number-remainder
+   *  which says that it is equivalent to the C library function `fmod`.
+   *
+   *  This method is a translation to Scala of the Rust generic implementation,
+   *  which can be found at
+   *  https://github.com/rust-lang/libm/blob/c9672e5a1a75bfa82981b6240b7bc3ed3524b8b3/src/math/generic/fmod.rs
+   *  under the MIT license
+   *
+   *  (The naive function `x - trunc(x / y) * y` that we can find on the
+   *  Web does not work.)
+   */
+  @inline // inline into the static forwarder, which will be the entry point
+  def fmodd(x: Double, y: Double): Double = {
+    // Configuration that depends on the floating-point type and its corresponding integer type
+
+    type FType = Double
+    type IType = Long
+
+    val mbits = 52
+    val ebits = 11
+    val fZero = 0.0
+    val iZero = 0L
+    val iOne = 1L
+
+    /* TODO Use doubleToRawLongBits when we add support for it. Either is
+     * correct in this context, but the raw variant would be more efficient.
+     */
+    @inline def toBits(v: FType): IType = java.lang.Double.doubleToLongBits(v)
+    @inline def fromBits(v: IType): FType = java.lang.Double.longBitsToDouble(v)
+    @inline def leadingZeros(v: IType): Int = java.lang.Long.numberOfLeadingZeros(v)
+    @inline def extendFromInt(v: Int): IType = v.toLong
+    @inline def wrapToInt(v: IType): Int = v.toInt
+
+    /* Usually we use an @inline def to specialize code like this. Here,
+     * copy-pasting is (unfortunately) better. There are lot of primitive
+     * numeric operations (arithmetics, shifts, comparisons) that are correctly
+     * resolved because they have the same name, which works with the
+     * copy-paste. They don't have a common abstraction, though, so the @inline
+     * def would not work.
+     */
+
+    // --- BEGIN COPY-PASTE wrt. fmodf ----------------------------------------
+
+    // scalastyle:off return
+
+    // --- BEGIN MIT license
+
+    // derived constants
+    val mmask: IType = (iOne << mbits) - iOne
+    val emask: Int = (1 << ebits) - 1
+    val SignBit: IType = iOne << (mbits + ebits)
+
+    /* let mut ix = x.to_bits();
+     * let mut iy = y.to_bits();
+     */
+    var ix: IType = toBits(x)
+    var iy: IType = toBits(y)
+
+    /* let sx = ix & F::SIGN_MASK;
+     * The Rust implementation does this after initializing ex and ey. We must
+     * do it now, *before* masking off the sign bits.
+     */
+    val sx: IType = ix & SignBit
+
+    /* The Rust implementation exploits the unsinged semantics of `ix` and
+     * `iy`. In Scala, this is a bit awkward to do. Instead, we mask off the
+     * sign bit of both now, so we have less work to do later.
+     */
+    ix &= ~SignBit
+    iy &= ~SignBit
+
+    /* let mut ex = x.ex().signed();
+     * let mut ey = y.ex().signed();
+     * -> wrapToInt(ix >>> mbits) & emask
+     *    but `& emask` is redundant since the sign bit is already 0 for us
+     */
+    var ex: Int = wrapToInt(ix >>> mbits)
+    var ey: Int = wrapToInt(iy >>> mbits)
+
+    /* if iy << 1 == zero || y.is_nan() || ex == F::EXP_SAT as i32 {
+     *     return (x * y) / (x * y);
+     * }
+     *
+     * `iy << 1 == zero` is the same as `iy == zero` for us, since we masked
+     * off the sign bit.
+     */
+    if (iy == iZero || y != y || ex == emask)
+      return (x * y) / (x * y)
+
+    /* if ix << 1 <= iy << 1 {
+     *     if ix << 1 == iy << 1 {
+     *         return F::ZERO * x;
+     *     }
+     *     return x;
+     * }
+     * Since we masked off the sign bit already, all the `<< 1` above are not
+     * necessary. That also means that our signed comparison does the right
+     * thing.
+     */
+    if (ix <= iy) { // semantically, this tests whether abs(x) <= abs(y) at this point
+      if (ix == iy)
+        return fZero * x
+      return x
+    }
+
+    /* if ex == 0 {
+     *     let i = ix << (F::EXP_BITS + 1);
+     *     ex -= i.leading_zeros() as i32;
+     *     ix <<= -ex + 1;
+     * } else {
+     *     ix &= F::Int::MAX >> (F::EXP_BITS + 1); // this is mmask
+     *     ix |= one << F::SIG_BITS;
+     * }
+     * and same for y
+     *
+     * Note that the two `F::EXP_BITS + 1` do *not* have the `+ 1` in the
+     * original Rust implementation. The `+ 1`s I added account for the sign
+     * bit, in addition to the exponent bits.
+     *
+     * I believe the first one is just wrong, and fails to correctly handle
+     * subnormal values. Removing that one causes the tests for subnormals to
+     * fail.
+     *
+     * The second one makes no actual difference, since the bit that is
+     * affected is anyway or'ed back to 1 on the last line. However to me it
+     * makes more sense to have it, as it then really corresponds to `mmask`,
+     * and we use it to mask mantissa bits.
+     */
+    if (ex == 0) {
+      // subnormal
+      ex -= leadingZeros(ix << (ebits + 1))
+      ix <<= -ex + 1
+    } else {
+      // normal form
+      ix = (ix & mmask) | (iOne << mbits)
+    }
+    if (ey == 0) {
+      // subnormal
+      ey -= leadingZeros(iy << (ebits + 1))
+      iy <<= -ey + 1
+    } else {
+      // normal form
+      iy = (iy & mmask) | (iOne << mbits)
+    }
+
+    // x mod y
+
+    /* while ex > ey {
+     *     let i = ix.wrapping_sub(iy);
+     *     if i >> (F::BITS - 1) == zero { // i.e., i >= 0 with signed semantics
+     *         if i == zero {
+     *             return F::ZERO * x;
+     *         }
+     *         ix = i;
+     *     }
+     *
+     *     ix <<= 1;
+     *     ex -= 1;
+     * }
+     *
+     * let i = ix.wrapping_sub(iy);
+     * if i >> (F::BITS - 1) == zero {
+     *     if i == zero {
+     *         return F::ZERO * x;
+     *     }
+     *     ix = i;
+     * }
+     *
+     * but we factor out the duplicate block inside the loop, taking
+     * advantage of a funny-looking "while loop with condition in the middle".
+     */
+    while ({
+      val i = ix - iy
+      if (i >= iZero) {
+        if (i == iZero)
+          return fZero * x
+        ix = i
+      }
+
+      ex > ey // the actual condition of the while loop
+    }) {
+      ix <<= 1
+      ex -= 1
+    }
+
+    // re-normalize the result in ix
+
+    /* let shift = ix.leading_zeros().saturating_sub(F::EXP_BITS);
+     * ix <<= shift;
+     * ex -= shift as i32;
+     */
+    val shift = leadingZeros(ix) - ebits
+    ix <<= shift
+    ex -= shift
+
+    // scale result
+
+    /* if ex > 0 {
+     *     ix -= one << F::SIG_BITS;
+     *     ix |= F::Int::cast_from(ex) << F::SIG_BITS;
+     * } else {
+     *     ix >>= -ex + 1;
+     * }
+     */
+    if (ex > 0) {
+      // normal form
+      ix = (ix - (iOne << mbits)) | (extendFromInt(ex) << mbits)
+    } else {
+      // subnormal
+      ix >>>= -ex + 1
+    }
+
+    // integrate the sign bit and return
+
+    /* ix |= sx;
+     * F::from_bits(ix)
+     */
+    fromBits(ix | sx)
+
+    // --- END MIT license
+
+    // scalastyle:on return
+
+    // --- END COPY-PASTE wrt. fmodf ------------------------------------------
+  }
+
+  /** `fmod` for `Float`s, the implementation of `Float_%`.
+   *
+   *  See `fmodd` for details.
+   */
+  @inline // inline into the static forwarder, which will be the entry point
+  def fmodf(x: Float, y: Float): Float = {
+    // Configuration that depends on the floating-point type and its corresponding integer type
+
+    type FType = Float
+    type IType = Int
+
+    val mbits = 23
+    val ebits = 8
+    val fZero = 0.0f
+    val iZero = 0
+    val iOne = 1
+
+    /* TODO Use floatToRawIntBits when we add support for it. Either is
+     * correct in this context, but the raw variant would be more efficient.
+     */
+    @inline def toBits(v: FType): IType = java.lang.Float.floatToIntBits(v)
+    @inline def fromBits(v: IType): FType = java.lang.Float.intBitsToFloat(v)
+    @inline def leadingZeros(v: IType): Int = java.lang.Integer.numberOfLeadingZeros(v)
+    @inline def extendFromInt(v: Int): IType = v
+    @inline def wrapToInt(v: IType): Int = v
+
+    // --- BEGIN COPY-PASTE wrt. fmodd ----------------------------------------
+
+    // scalastyle:off return
+
+    // --- BEGIN MIT license
+
+    // derived constants
+    val mmask: IType = (iOne << mbits) - iOne
+    val emask: Int = (1 << ebits) - 1
+    val SignBit: IType = iOne << (mbits + ebits)
+
+    /* let mut ix = x.to_bits();
+     * let mut iy = y.to_bits();
+     */
+    var ix: IType = toBits(x)
+    var iy: IType = toBits(y)
+
+    /* let sx = ix & F::SIGN_MASK;
+     * The Rust implementation does this after initializing ex and ey. We must
+     * do it now, *before* masking off the sign bits.
+     */
+    val sx: IType = ix & SignBit
+
+    /* The Rust implementation exploits the unsinged semantics of `ix` and
+     * `iy`. In Scala, this is a bit awkward to do. Instead, we mask off the
+     * sign bit of both now, so we have less work to do later.
+     */
+    ix &= ~SignBit
+    iy &= ~SignBit
+
+    /* let mut ex = x.ex().signed();
+     * let mut ey = y.ex().signed();
+     * -> wrapToInt(ix >>> mbits) & emask
+     *    but `& emask` is redundant since the sign bit is already 0 for us
+     */
+    var ex: Int = wrapToInt(ix >>> mbits)
+    var ey: Int = wrapToInt(iy >>> mbits)
+
+    /* if iy << 1 == zero || y.is_nan() || ex == F::EXP_SAT as i32 {
+     *     return (x * y) / (x * y);
+     * }
+     *
+     * `iy << 1 == zero` is the same as `iy == zero` for us, since we masked
+     * off the sign bit.
+     */
+    if (iy == iZero || y != y || ex == emask)
+      return (x * y) / (x * y)
+
+    /* if ix << 1 <= iy << 1 {
+     *     if ix << 1 == iy << 1 {
+     *         return F::ZERO * x;
+     *     }
+     *     return x;
+     * }
+     * Since we masked off the sign bit already, all the `<< 1` above are not
+     * necessary. That also means that our signed comparison does the right
+     * thing.
+     */
+    if (ix <= iy) { // semantically, this tests whether abs(x) <= abs(y) at this point
+      if (ix == iy)
+        return fZero * x
+      return x
+    }
+
+    /* if ex == 0 {
+     *     let i = ix << (F::EXP_BITS + 1);
+     *     ex -= i.leading_zeros() as i32;
+     *     ix <<= -ex + 1;
+     * } else {
+     *     ix &= F::Int::MAX >> (F::EXP_BITS + 1); // this is mmask
+     *     ix |= one << F::SIG_BITS;
+     * }
+     * and same for y
+     *
+     * Note that the two `F::EXP_BITS + 1` do *not* have the `+ 1` in the
+     * original Rust implementation. The `+ 1`s I added account for the sign
+     * bit, in addition to the exponent bits.
+     *
+     * I believe the first one is just wrong, and fails to correctly handle
+     * subnormal values. Removing that one causes the tests for subnormals to
+     * fail.
+     *
+     * The second one makes no actual difference, since the bit that is
+     * affected is anyway or'ed back to 1 on the last line. However to me it
+     * makes more sense to have it, as it then really corresponds to `mmask`,
+     * and we use it to mask mantissa bits.
+     */
+    if (ex == 0) {
+      // subnormal
+      ex -= leadingZeros(ix << (ebits + 1))
+      ix <<= -ex + 1
+    } else {
+      // normal form
+      ix = (ix & mmask) | (iOne << mbits)
+    }
+    if (ey == 0) {
+      // subnormal
+      ey -= leadingZeros(iy << (ebits + 1))
+      iy <<= -ey + 1
+    } else {
+      // normal form
+      iy = (iy & mmask) | (iOne << mbits)
+    }
+
+    // x mod y
+
+    /* while ex > ey {
+     *     let i = ix.wrapping_sub(iy);
+     *     if i >> (F::BITS - 1) == zero { // i.e., i >= 0 with signed semantics
+     *         if i == zero {
+     *             return F::ZERO * x;
+     *         }
+     *         ix = i;
+     *     }
+     *
+     *     ix <<= 1;
+     *     ex -= 1;
+     * }
+     *
+     * let i = ix.wrapping_sub(iy);
+     * if i >> (F::BITS - 1) == zero {
+     *     if i == zero {
+     *         return F::ZERO * x;
+     *     }
+     *     ix = i;
+     * }
+     *
+     * but we factor out the duplicate block inside the loop, taking
+     * advantage of a funny-looking "while loop with condition in the middle".
+     */
+    while ({
+      val i = ix - iy
+      if (i >= iZero) {
+        if (i == iZero)
+          return fZero * x
+        ix = i
+      }
+
+      ex > ey // the actual condition of the while loop
+    }) {
+      ix <<= 1
+      ex -= 1
+    }
+
+    // re-normalize the result in ix
+
+    /* let shift = ix.leading_zeros().saturating_sub(F::EXP_BITS);
+     * ix <<= shift;
+     * ex -= shift as i32;
+     */
+    val shift = leadingZeros(ix) - ebits
+    ix <<= shift
+    ex -= shift
+
+    // scale result
+
+    /* if ex > 0 {
+     *     ix -= one << F::SIG_BITS;
+     *     ix |= F::Int::cast_from(ex) << F::SIG_BITS;
+     * } else {
+     *     ix >>= -ex + 1;
+     * }
+     */
+    if (ex > 0) {
+      // normal form
+      ix = (ix - (iOne << mbits)) | (extendFromInt(ex) << mbits)
+    } else {
+      // subnormal
+      ix >>>= -ex + 1
+    }
+
+    // integrate the sign bit and return
+
+    /* ix |= sx;
+     * F::from_bits(ix)
+     */
+    fromBits(ix | sx)
+
+    // --- END MIT license
+
+    // scalastyle:on return
+
+    // --- END COPY-PASTE wrt. fmodd ------------------------------------------
+  }
+}
diff --git a/linker/jvm/src/main/scala/org/scalajs/linker/backend/emitter/PrivateLibHolder.scala b/linker/jvm/src/main/scala/org/scalajs/linker/backend/emitter/PrivateLibHolder.scala
index 44801549e7..d668c26e25 100644
--- a/linker/jvm/src/main/scala/org/scalajs/linker/backend/emitter/PrivateLibHolder.scala
+++ b/linker/jvm/src/main/scala/org/scalajs/linker/backend/emitter/PrivateLibHolder.scala
@@ -27,6 +27,8 @@ object PrivateLibHolder {
       "org/scalajs/linker/runtime/RuntimeLong.sjsir",
       "org/scalajs/linker/runtime/RuntimeLong$.sjsir",
       "org/scalajs/linker/runtime/UndefinedBehaviorError.sjsir",
+      "org/scalajs/linker/runtime/WasmRuntime.sjsir",
+      "org/scalajs/linker/runtime/WasmRuntime$.sjsir",
       "scala/scalajs/js/JavaScriptException.sjsir"
   )
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
index 68b14c51c2..8fd45218f5 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
@@ -377,8 +377,6 @@ final class CoreWasmLib(coreSpec: CoreSpec, globalInfo: LinkedGlobalInfo) {
     addHelperImport(genFunctionID.uIFallback, List(anyref), List(Int32))
     addHelperImport(genFunctionID.typeTest(IntRef), List(anyref), List(Int32))
 
-    addHelperImport(genFunctionID.fmod, List(Float64, Float64), List(Float64))
-
     addHelperImport(genFunctionID.jsValueToString, List(RefType.any), List(RefType.extern))
     addHelperImport(genFunctionID.jsValueToStringForConcat, List(anyref), List(RefType.extern))
     addHelperImport(genFunctionID.booleanToString, List(Int32), List(RefType.extern))
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala
index 6c78b14fa3..137c99bec3 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala
@@ -446,7 +446,11 @@ object Emitter {
 
       // See genIdentityHashCode in HelperFunctions
       callMethodStatically(BoxedDoubleClass, hashCodeMethodName),
-      callMethodStatically(BoxedStringClass, hashCodeMethodName)
+      callMethodStatically(BoxedStringClass, hashCodeMethodName),
+
+      // Implementation of Float_% and Double_%
+      callStaticMethod(WasmRuntimeClass, fmodfMethodName),
+      callStaticMethod(WasmRuntimeClass, fmoddMethodName)
     )
   }
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
index d0275d97fc..13956310e3 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
@@ -1721,31 +1721,6 @@ private class FunctionEmitter private (
       case Long_>> =>
         genLongShiftOp(wa.I64ShrS)
 
-      /* Floating point remainders are specified by
-       * https://262.ecma-international.org/#sec-numeric-types-number-remainder
-       * which says that it is equivalent to the C library function `fmod`.
-       * For `Float`s, we promote and demote to `Double`s.
-       * `fmod` seems quite hard to correctly implement, so we delegate to a
-       * JavaScript Helper.
-       * (The naive function `x - trunc(x / y) * y` that we can find on the
-       * Web does not work.)
-       */
-      case Float_% =>
-        genTree(lhs, FloatType)
-        fb += wa.F64PromoteF32
-        genTree(rhs, FloatType)
-        fb += wa.F64PromoteF32
-        markPosition(tree)
-        fb += wa.Call(genFunctionID.fmod)
-        fb += wa.F32DemoteF64
-        FloatType
-      case Double_% =>
-        genTree(lhs, DoubleType)
-        genTree(rhs, DoubleType)
-        markPosition(tree)
-        fb += wa.Call(genFunctionID.fmod)
-        DoubleType
-
       case String_charAt =>
         genTree(lhs, StringType)
         genTree(rhs, IntType)
@@ -1884,6 +1859,9 @@ private class FunctionEmitter private (
   private def getElementaryBinaryOpInstr(op: BinaryOp.Code): wa.Instr = {
     import BinaryOp._
 
+    def fmodFunctionID(methodName: MethodName): wanme.FunctionID =
+      genFunctionID.forMethod(MemberNamespace.PublicStatic, SpecialNames.WasmRuntimeClass, methodName)
+
     (op: @switch) match {
       case Boolean_== => wa.I32Eq
       case Boolean_!= => wa.I32Ne
@@ -1924,11 +1902,13 @@ private class FunctionEmitter private (
       case Float_- => wa.F32Sub
       case Float_* => wa.F32Mul
       case Float_/ => wa.F32Div
+      case Float_% => wa.Call(fmodFunctionID(SpecialNames.fmodfMethodName))
 
       case Double_+ => wa.F64Add
       case Double_- => wa.F64Sub
       case Double_* => wa.F64Mul
       case Double_/ => wa.F64Div
+      case Double_% => wa.Call(fmodFunctionID(SpecialNames.fmoddMethodName))
 
       case Double_== => wa.F64Eq
       case Double_!= => wa.F64Ne
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala
index 271894e7f5..0b35cdbab0 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/LoaderContent.scala
@@ -100,9 +100,6 @@ const scalaJSHelpers = {
   tF: (x) => typeof x === 'number' && (Math.fround(x) === x || x !== x),
   tD: (x) => typeof x === 'number',
 
-  // fmod, to implement Float_% and Double_% (it is apparently quite hard to implement fmod otherwise)
-  fmod: (x, y) => x % y,
-
   // Strings
   emptyString: "",
   jsValueToString: (x) => (x === void 0) ? "undefined" : x.toString(),
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/SpecialNames.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/SpecialNames.scala
index 6e5887ddda..fcf63e8d11 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/SpecialNames.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/SpecialNames.scala
@@ -37,6 +37,9 @@ object SpecialNames {
   val UndefinedBehaviorErrorClass =
     ClassName("org.scalajs.linker.runtime.UndefinedBehaviorError")
 
+  val WasmRuntimeClass =
+    ClassName("org.scalajs.linker.runtime.WasmRuntime")
+
   // Field names
 
   val valueFieldSimpleName = SimpleFieldName("value")
@@ -52,6 +55,9 @@ object SpecialNames {
 
   val hashCodeMethodName = MethodName("hashCode", Nil, IntRef)
 
+  val fmodfMethodName = MethodName("fmodf", List(FloatRef, FloatRef), FloatRef)
+  val fmoddMethodName = MethodName("fmodd", List(DoubleRef, DoubleRef), DoubleRef)
+
   /** A unique simple method name to map all method *signatures* into `MethodName`s. */
   val normalizedSimpleMethodName = SimpleMethodName("m")
 }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
index c007314c9d..80da606d6d 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
@@ -130,8 +130,6 @@ object VarGen {
     case object bIFallback extends JSHelperFunctionID
     case object uIFallback extends JSHelperFunctionID
 
-    case object fmod extends JSHelperFunctionID
-
     case object jsValueToString extends JSHelperFunctionID // for actual toString() call
     case object jsValueToStringForConcat extends JSHelperFunctionID
     case object booleanToString extends JSHelperFunctionID
diff --git a/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/DoubleTest.scala b/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/DoubleTest.scala
index f7b7d2005d..900212675b 100644
--- a/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/DoubleTest.scala
+++ b/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/DoubleTest.scala
@@ -221,6 +221,8 @@ class DoubleTest {
     test(Double.NaN, Double.NaN, 2.1)
     test(Double.NaN, Double.NaN, 5.5)
     test(Double.NaN, Double.NaN, -151.189)
+    test(Double.NaN, Double.NaN, 3.123e-320)
+    test(Double.NaN, Double.NaN, 2.253547e-318)
 
     // If d is NaN, return NaN
     test(Double.NaN, Double.NaN, Double.NaN)
@@ -231,6 +233,8 @@ class DoubleTest {
     test(Double.NaN, 2.1, Double.NaN)
     test(Double.NaN, 5.5, Double.NaN)
     test(Double.NaN, -151.189, Double.NaN)
+    test(Double.NaN, 3.123e-320, Double.NaN)
+    test(Double.NaN, 2.253547e-318, Double.NaN)
 
     // If n is PositiveInfinity, return NaN
     test(Double.NaN, Double.PositiveInfinity, Double.PositiveInfinity)
@@ -240,6 +244,8 @@ class DoubleTest {
     test(Double.NaN, Double.PositiveInfinity, 2.1)
     test(Double.NaN, Double.PositiveInfinity, 5.5)
     test(Double.NaN, Double.PositiveInfinity, -151.189)
+    test(Double.NaN, Double.PositiveInfinity, 3.123e-320)
+    test(Double.NaN, Double.PositiveInfinity, 2.253547e-318)
 
     // If n is NegativeInfinity, return NaN
     test(Double.NaN, Double.NegativeInfinity, Double.PositiveInfinity)
@@ -249,6 +255,8 @@ class DoubleTest {
     test(Double.NaN, Double.NegativeInfinity, 2.1)
     test(Double.NaN, Double.NegativeInfinity, 5.5)
     test(Double.NaN, Double.NegativeInfinity, -151.189)
+    test(Double.NaN, Double.NegativeInfinity, 3.123e-320)
+    test(Double.NaN, Double.NegativeInfinity, 2.253547e-318)
 
     // If d is PositiveInfinity, return n
     test(+0.0, +0.0, Double.PositiveInfinity)
@@ -256,6 +264,8 @@ class DoubleTest {
     test(2.1, 2.1, Double.PositiveInfinity)
     test(5.5, 5.5, Double.PositiveInfinity)
     test(-151.189, -151.189, Double.PositiveInfinity)
+    test(3.123e-320, 3.123e-320, Double.PositiveInfinity)
+    test(2.253547e-318, 2.253547e-318, Double.PositiveInfinity)
 
     // If d is NegativeInfinity, return n
     test(+0.0, +0.0, Double.NegativeInfinity)
@@ -263,6 +273,8 @@ class DoubleTest {
     test(2.1, 2.1, Double.NegativeInfinity)
     test(5.5, 5.5, Double.NegativeInfinity)
     test(-151.189, -151.189, Double.NegativeInfinity)
+    test(3.123e-320, 3.123e-320, Double.NegativeInfinity)
+    test(2.253547e-318, 2.253547e-318, Double.NegativeInfinity)
 
     // If d is +0.0, return NaN
     test(Double.NaN, +0.0, +0.0)
@@ -270,6 +282,8 @@ class DoubleTest {
     test(Double.NaN, 2.1, +0.0)
     test(Double.NaN, 5.5, +0.0)
     test(Double.NaN, -151.189, +0.0)
+    test(Double.NaN, 3.123e-320, +0.0)
+    test(Double.NaN, 2.253547e-318, +0.0)
 
     // If d is -0.0, return NaN
     test(Double.NaN, +0.0, -0.0)
@@ -277,28 +291,51 @@ class DoubleTest {
     test(Double.NaN, 2.1, -0.0)
     test(Double.NaN, 5.5, -0.0)
     test(Double.NaN, -151.189, -0.0)
+    test(Double.NaN, 3.123e-320, -0.0)
+    test(Double.NaN, 2.253547e-318, -0.0)
 
     // If n is +0.0, return n
     test(+0.0, +0.0, 2.1)
     test(+0.0, +0.0, 5.5)
     test(+0.0, +0.0, -151.189)
+    test(+0.0, +0.0, 3.123e-320)
+    test(+0.0, +0.0, 2.253547e-318)
 
     // If n is -0.0, return n
     test(-0.0, -0.0, 2.1)
     test(-0.0, -0.0, 5.5)
     test(-0.0, -0.0, -151.189)
+    test(-0.0, -0.0, 3.123e-320)
+    test(-0.0, -0.0, 2.253547e-318)
 
     // Non-special values
-    // { val l = List(2.1, 5.5, -151.189); for (n <- l; d <- l) println(s"    test(${n % d}, $n, $d)") }
+    // { val l = List(2.1, 5.5, -151.189, 3.123e-320, 2.253547e-318);
+    //   for (n <- l; d <- l) println(s"    test(${n % d}, $n, $d)".toLowerCase()) }
     test(0.0, 2.1, 2.1)
     test(2.1, 2.1, 5.5)
     test(2.1, 2.1, -151.189)
+    test(2.0696e-320, 2.1, 3.123e-320)
+    test(1.772535e-318, 2.1, 2.253547e-318)
     test(1.2999999999999998, 5.5, 2.1)
     test(0.0, 5.5, 5.5)
     test(5.5, 5.5, -151.189)
+    test(3.607e-321, 5.5, 3.123e-320)
+    test(6.8103e-319, 5.5, 2.253547e-318)
     test(-2.0889999999999866, -151.189, 2.1)
     test(-2.688999999999993, -151.189, 5.5)
     test(-0.0, -151.189, -151.189)
+    test(-1.94e-320, -151.189, 3.123e-320)
+    test(-4.1349e-319, -151.189, 2.253547e-318)
+    test(3.123e-320, 3.123e-320, 2.1)
+    test(3.123e-320, 3.123e-320, 5.5)
+    test(3.123e-320, 3.123e-320, -151.189)
+    test(0.0, 3.123e-320, 3.123e-320)
+    test(3.123e-320, 3.123e-320, 2.253547e-318)
+    test(2.253547e-318, 2.253547e-318, 2.1)
+    test(2.253547e-318, 2.253547e-318, 5.5)
+    test(2.253547e-318, 2.253547e-318, -151.189)
+    test(4.995e-321, 2.253547e-318, 3.123e-320)
+    test(0.0, 2.253547e-318, 2.253547e-318)
   }
 
   @Test
diff --git a/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/FloatTest.scala b/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/FloatTest.scala
index 60a4e40060..e7b96a7324 100644
--- a/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/FloatTest.scala
+++ b/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/FloatTest.scala
@@ -73,6 +73,8 @@ class FloatTest {
     test(Float.NaN, Float.NaN, 2.1f)
     test(Float.NaN, Float.NaN, 5.5f)
     test(Float.NaN, Float.NaN, -151.189f)
+    test(Float.NaN, Float.NaN, 8.858e-42f)
+    test(Float.NaN, Float.NaN, 6.39164e-40f)
 
     // If d is NaN, return NaN
     test(Float.NaN, Float.NaN, Float.NaN)
@@ -83,6 +85,8 @@ class FloatTest {
     test(Float.NaN, 2.1f, Float.NaN)
     test(Float.NaN, 5.5f, Float.NaN)
     test(Float.NaN, -151.189f, Float.NaN)
+    test(Float.NaN, 8.858e-42f, Float.NaN)
+    test(Float.NaN, 6.39164e-40f, Float.NaN)
 
     // If n is PositiveInfinity, return NaN
     test(Float.NaN, Float.PositiveInfinity, Float.PositiveInfinity)
@@ -92,6 +96,8 @@ class FloatTest {
     test(Float.NaN, Float.PositiveInfinity, 2.1f)
     test(Float.NaN, Float.PositiveInfinity, 5.5f)
     test(Float.NaN, Float.PositiveInfinity, -151.189f)
+    test(Float.NaN, Float.PositiveInfinity, 8.858e-42f)
+    test(Float.NaN, Float.PositiveInfinity, 6.39164e-40f)
 
     // If n is NegativeInfinity, return NaN
     test(Float.NaN, Float.NegativeInfinity, Float.PositiveInfinity)
@@ -101,6 +107,8 @@ class FloatTest {
     test(Float.NaN, Float.NegativeInfinity, 2.1f)
     test(Float.NaN, Float.NegativeInfinity, 5.5f)
     test(Float.NaN, Float.NegativeInfinity, -151.189f)
+    test(Float.NaN, Float.NegativeInfinity, 8.858e-42f)
+    test(Float.NaN, Float.NegativeInfinity, 6.39164e-40f)
 
     // If d is PositiveInfinity, return n
     test(+0.0f, +0.0f, Float.PositiveInfinity)
@@ -108,6 +116,8 @@ class FloatTest {
     test(2.1f, 2.1f, Float.PositiveInfinity)
     test(5.5f, 5.5f, Float.PositiveInfinity)
     test(-151.189f, -151.189f, Float.PositiveInfinity)
+    test(8.858e-42f, 8.858e-42f, Float.PositiveInfinity)
+    test(6.39164e-40f, 6.39164e-40f, Float.PositiveInfinity)
 
     // If d is NegativeInfinity, return n
     test(+0.0f, +0.0f, Float.NegativeInfinity)
@@ -115,6 +125,8 @@ class FloatTest {
     test(2.1f, 2.1f, Float.NegativeInfinity)
     test(5.5f, 5.5f, Float.NegativeInfinity)
     test(-151.189f, -151.189f, Float.NegativeInfinity)
+    test(8.858e-42f, 8.858e-42f, Float.NegativeInfinity)
+    test(6.39164e-40f, 6.39164e-40f, Float.NegativeInfinity)
 
     // If d is +0.0, return NaN
     test(Float.NaN, +0.0f, +0.0f)
@@ -122,6 +134,8 @@ class FloatTest {
     test(Float.NaN, 2.1f, +0.0f)
     test(Float.NaN, 5.5f, +0.0f)
     test(Float.NaN, -151.189f, +0.0f)
+    test(Float.NaN, 8.858e-42f, +0.0f)
+    test(Float.NaN, 6.39164e-40f, +0.0f)
 
     // If d is -0.0, return NaN
     test(Float.NaN, +0.0f, -0.0f)
@@ -129,28 +143,51 @@ class FloatTest {
     test(Float.NaN, 2.1f, -0.0f)
     test(Float.NaN, 5.5f, -0.0f)
     test(Float.NaN, -151.189f, -0.0f)
+    test(Float.NaN, 8.858e-42f, -0.0f)
+    test(Float.NaN, 6.39164e-40f, -0.0f)
 
     // If n is +0.0, return n
     test(+0.0f, +0.0f, 2.1f)
     test(+0.0f, +0.0f, 5.5f)
     test(+0.0f, +0.0f, -151.189f)
+    test(+0.0f, +0.0f, 8.858e-42f)
+    test(+0.0f, +0.0f, 6.39164e-40f)
 
     // If n is -0.0, return n
     test(-0.0f, -0.0f, 2.1f)
     test(-0.0f, -0.0f, 5.5f)
     test(-0.0f, -0.0f, -151.189f)
+    test(-0.0f, -0.0f, 8.858e-42f)
+    test(-0.0f, -0.0f, 6.39164e-40f)
 
     // Non-special values
-    // { val l = List(2.1f, 5.5f, -151.189f); for (n <- l; d <- l) println(s"      test(${n % d}f, ${n}f, ${d}f)") }
+    // { val l = List(2.1f, 5.5f, -151.189f, 8.858e-42f, 6.39164e-40f);
+    //   for (n <- l; d <- l) println(s"    test(${n % d}f, ${n}f, ${d}f)".toLowerCase()) }
     test(0.0f, 2.1f, 2.1f)
     test(2.1f, 2.1f, 5.5f)
     test(2.1f, 2.1f, -151.189f)
+    test(8.085e-42f, 2.1f, 8.858e-42f)
+    test(6.1636e-40f, 2.1f, 6.39164e-40f)
     test(1.3000002f, 5.5f, 2.1f)
     test(0.0f, 5.5f, 5.5f)
     test(5.5f, 5.5f, -151.189f)
+    test(5.11e-43f, 5.5f, 8.858e-42f)
+    test(4.77036e-40f, 5.5f, 6.39164e-40f)
     test(-2.0890021f, -151.189f, 2.1f)
     test(-2.6889954f, -151.189f, 5.5f)
     test(-0.0f, -151.189f, -151.189f)
+    test(-1.139e-42f, -151.189f, 8.858e-42f)
+    test(-5.64734e-40f, -151.189f, 6.39164e-40f)
+    test(8.858e-42f, 8.858e-42f, 2.1f)
+    test(8.858e-42f, 8.858e-42f, 5.5f)
+    test(8.858e-42f, 8.858e-42f, -151.189f)
+    test(0.0f, 8.858e-42f, 8.858e-42f)
+    test(8.858e-42f, 8.858e-42f, 6.39164e-40f)
+    test(6.39164e-40f, 6.39164e-40f, 2.1f)
+    test(6.39164e-40f, 6.39164e-40f, 5.5f)
+    test(6.39164e-40f, 6.39164e-40f, -151.189f)
+    test(1.417e-42f, 6.39164e-40f, 8.858e-42f)
+    test(0.0f, 6.39164e-40f, 6.39164e-40f)
   }
 
   @Test

From 1b989f249659c7878595afbbe94a5d4aa62bc929 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Thu, 3 Apr 2025 17:28:29 +0200
Subject: [PATCH 277/298] Merge the itables into the corresponding vtables.

This is a trade-off on memory and code size.

The big advantage is that run-time instances of our classes use
one fewer word each, since we do not have an `itables` field
anymore. There could be some execution time improvements as a
side effect, since we have one fewer word to initialize.

There are two disadvantages, but IMO they are comparatively minor:

* We cannot use the "one empty itables to rule them all" trick
  anymore. Classes that implement no interfaces need to list their
  N `null` values. This has both a code size impact and a constant
  run-time memory cost.
* We cannot share the itables of array classes either. This has no
  impact on code size (there is a single place in the code where
  we initialize those fields), but it does add run-time footprint
  to the vtables of each array type that gets created.

Interface method calls are not impacted, neither in the code we
generate, nor in their run-time performance. Virtual method calls
are only impacted insofar as the index of virtual method pointers
is bumped up by the number of itable slots. This can add one more
byte to some calls, due to the var-length encoding. If we get very
unlucky, it could also push some vtable method pointers past a
pre-fetch boundary, slowing down the calls at run-time. But I
don't really think that's plausible.
---
 .../backend/wasmemitter/ClassEmitter.scala    | 139 +++++++-----------
 .../backend/wasmemitter/CoreWasmLib.scala     |  48 +-----
 .../linker/backend/wasmemitter/Emitter.scala  |   1 -
 .../backend/wasmemitter/FunctionEmitter.scala |   9 +-
 .../backend/wasmemitter/Preprocessor.scala    |   7 -
 .../linker/backend/wasmemitter/README.md      |  48 +++---
 .../linker/backend/wasmemitter/SWasmGen.scala |  11 +-
 .../linker/backend/wasmemitter/VarGen.scala   |  14 +-
 .../backend/wasmemitter/WasmContext.scala     |   3 +-
 9 files changed, 97 insertions(+), 183 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/ClassEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/ClassEmitter.scala
index 88cdbdbae8..645974dfa0 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/ClassEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/ClassEmitter.scala
@@ -49,7 +49,7 @@ class ClassEmitter(coreSpec: CoreSpec) {
     if (classInfo.hasRuntimeTypeInfo && !(clazz.kind.isClass && clazz.hasDirectInstances)) {
       // Gen typeData -- for concrete Scala classes, we do it as part of the vtable generation instead
       val typeDataFieldValues = genTypeDataFieldValues(clazz, Nil)
-      genTypeDataGlobal(clazz.className, genTypeID.typeData, typeDataFieldValues, Nil)
+      genTypeDataGlobal(clazz.className, genTypeID.typeData, typeDataFieldValues, Nil, Nil)
     }
 
     // Declare static fields
@@ -138,15 +138,6 @@ class ClassEmitter(coreSpec: CoreSpec) {
     }
   }
 
-  /** Generate common itable global for all array classes. */
-  def genGlobalArrayClassItable()(implicit ctx: WasmContext): Unit = {
-    genGlobalClassItable(
-      genGlobalID.arrayClassITable, ctx.getClassInfo(ObjectClass),
-      List(SerializableClass, CloneableClass),
-      OriginalName(genGlobalID.arrayClassITable.toString())
-    )
-  }
-
   private def genIsJSClassInstanceFunction(clazz: LinkedClass)(
       implicit ctx: WasmContext): Option[wanme.FunctionID] = {
     implicit val noPos: Position = Position.NoPosition
@@ -330,10 +321,11 @@ class ClassEmitter(coreSpec: CoreSpec) {
   }
 
   private def genTypeDataGlobal(className: ClassName, typeDataTypeID: wanme.TypeID,
-      typeDataFieldValues: List[wa.Instr], vtableElems: List[wa.RefFunc])(
+      typeDataFieldValues: List[wa.Instr], itableSlots: List[wa.Instr],
+      vtableElems: List[wa.RefFunc])(
       implicit ctx: WasmContext): Unit = {
     val instrs: List[wa.Instr] =
-      typeDataFieldValues ::: vtableElems ::: wa.StructNew(typeDataTypeID) :: Nil
+      typeDataFieldValues ::: itableSlots ::: vtableElems ::: wa.StructNew(typeDataTypeID) :: Nil
     ctx.addGlobal(
       wamod.Global(
         genGlobalID.forVTable(className),
@@ -356,19 +348,17 @@ class ClassEmitter(coreSpec: CoreSpec) {
 
     val isAbstractClass = !clazz.hasDirectInstances
 
-    // Generate the vtable and itable for concrete classes
+    // Generate the vtable for concrete classes
     if (!isAbstractClass) {
       // Generate an actual vtable, which we integrate into the typeData
       val reflectiveProxies =
         classInfo.resolvedMethodInfos.valuesIterator.filter(_.methodName.isReflectiveProxy).toList
       val typeDataFieldValues = genTypeDataFieldValues(clazz, reflectiveProxies)
+      val itableSlots = genItableSlots(classInfo, clazz.ancestors)
       val vtableElems = classInfo.tableEntries.map { methodName =>
         wa.RefFunc(classInfo.resolvedMethodInfos(methodName).tableEntryID)
       }
-      genTypeDataGlobal(className, vtableTypeID, typeDataFieldValues, vtableElems)
-
-      // Generate the itable
-      genGlobalClassItable(clazz)
+      genTypeDataGlobal(className, vtableTypeID, typeDataFieldValues, itableSlots, vtableElems)
     }
 
     // Declare the struct type for the class
@@ -378,12 +368,6 @@ class ClassEmitter(coreSpec: CoreSpec) {
       watpe.RefType(vtableTypeID),
       isMutable = false
     )
-    val itablesField = watpe.StructField(
-      genFieldID.objStruct.itables,
-      itablesOriginalName,
-      watpe.RefType(genTypeID.itables),
-      isMutable = false
-    )
     val fields = classInfo.allFieldDefs.map { field =>
       watpe.StructField(
         genFieldID.forClassInstanceField(field.name.name),
@@ -405,7 +389,7 @@ class ClassEmitter(coreSpec: CoreSpec) {
     }
     val structTypeID = genTypeID.forClass(className)
     val superType = clazz.superClass.map(s => genTypeID.forClass(s.name))
-    val structType = watpe.StructType(vtableField :: itablesField :: fields ::: jlClassDataField)
+    val structType = watpe.StructType(vtableField :: fields ::: jlClassDataField)
     val subType = watpe.SubType(
       structTypeID,
       makeDebugName(ns.ClassInstance, className),
@@ -461,6 +445,14 @@ class ClassEmitter(coreSpec: CoreSpec) {
       implicit ctx: WasmContext): wanme.TypeID = {
     val className = classInfo.name
     val typeID = genTypeID.forVTable(className)
+    val itableSlotFields = (0 until ctx.itablesLength).map { i =>
+      watpe.StructField(
+        genFieldID.vtableStruct.itableSlot(i),
+        OriginalName.NoOriginalName,
+        watpe.RefType.nullable(watpe.HeapType.Struct),
+        isMutable = false
+      )
+    }.toList
     val vtableFields =
       classInfo.tableEntries.map { methodName =>
         watpe.StructField(
@@ -474,7 +466,7 @@ class ClassEmitter(coreSpec: CoreSpec) {
       case None    => genTypeID.typeData
       case Some(s) => genTypeID.forVTable(s.name)
     }
-    val structType = watpe.StructType(ctx.coreLib.typeDataStructFields ::: vtableFields)
+    val structType = watpe.StructType(ctx.coreLib.typeDataStructFields ::: itableSlotFields ::: vtableFields)
     val subType = watpe.SubType(
       typeID,
       makeDebugName(ns.VTable, className),
@@ -525,10 +517,10 @@ class ClassEmitter(coreSpec: CoreSpec) {
         /* Test whether the itable at the target interface's slot is indeed an
          * instance of that interface's itable struct type.
          */
-        fb += wa.StructGet(genTypeID.ObjectStruct, genFieldID.objStruct.itables)
+        fb += wa.StructGet(genTypeID.ObjectStruct, genFieldID.objStruct.vtable)
         fb += wa.StructGet(
-          genTypeID.itables,
-          genFieldID.itablesStruct.itableSlot(classInfo.itableIdx)
+          genTypeID.ObjectVTable,
+          genFieldID.vtableStruct.itableSlot(classInfo.itableIdx)
         )
         fb += wa.RefTest(watpe.RefType(genTypeID.forITable(className)))
         fb += wa.Return
@@ -642,12 +634,6 @@ class ClassEmitter(coreSpec: CoreSpec) {
     fb.setResultType(watpe.RefType(structTypeID))
 
     fb += wa.GlobalGet(genGlobalID.forVTable(className))
-
-    if (classInfo.classImplementsAnyInterface)
-      fb += wa.GlobalGet(genGlobalID.forITable(className))
-    else
-      fb += wa.GlobalGet(genGlobalID.emptyITable)
-
     classInfo.allFieldDefs.foreach { f =>
       fb += genZeroOf(f.ftpe)
     }
@@ -689,9 +675,8 @@ class ClassEmitter(coreSpec: CoreSpec) {
     fb += wa.RefCast(structRefType)
     fb += wa.LocalSet(fromTypedLocal)
 
-    // Push vtable and itables on the stack (there is at least Cloneable in the itables)
+    // Push the vtable on the stack
     fb += wa.GlobalGet(genGlobalID.forVTable(className))
-    fb += wa.GlobalGet(genGlobalID.forITable(className))
 
     // Push every field of `fromTyped` on the stack
     info.allFieldDefs.foreach { field =>
@@ -822,55 +807,6 @@ class ClassEmitter(coreSpec: CoreSpec) {
     fb.buildAndAddToModule()
   }
 
-  /** Generates the global instance of the class itable.
-   *
-   *  If the class implements no interface at all, we skip this step. Instead,
-   *  we will use the unique `emptyITable` as itable for this class.
-   */
-  private def genGlobalClassItable(clazz: LinkedClass)(implicit ctx: WasmContext): Unit = {
-    val className = clazz.className
-    val classInfo = ctx.getClassInfo(className)
-    if (classInfo.classImplementsAnyInterface) {
-      genGlobalClassItable(
-        genGlobalID.forITable(className),
-        classInfo,
-        clazz.ancestors,
-        makeDebugName(ns.ITable, classInfo.name)
-      )
-    }
-  }
-
-  private def genGlobalClassItable(classITableGlobalID: wanme.GlobalID,
-      classInfoForResolving: WasmContext.ClassInfo, ancestors: List[ClassName],
-      originalName: OriginalName)(
-      implicit ctx: WasmContext): Unit = {
-    val itablesInit = Array.fill[List[wa.Instr]](ctx.itablesLength) {
-      List(wa.RefNull(watpe.HeapType.Struct))
-    }
-    val resolvedMethodInfos = classInfoForResolving.resolvedMethodInfos
-
-    for {
-      ancestor <- ancestors
-      // Use getClassInfoOption in case the reachability analysis got rid of those interfaces
-      interfaceInfo <- ctx.getClassInfoOption(ancestor)
-      if interfaceInfo.isInterface
-    } {
-      val init = interfaceInfo.tableEntries.map { method =>
-        wa.RefFunc(resolvedMethodInfos(method).tableEntryID)
-      } :+ wa.StructNew(genTypeID.forITable(ancestor))
-      itablesInit(interfaceInfo.itableIdx) = init
-    }
-
-    val global = wamod.Global(
-      classITableGlobalID,
-      originalName,
-      isMutable = false,
-      watpe.RefType(genTypeID.itables),
-      wa.Expr(itablesInit.flatten.toList :+ wa.StructNew(genTypeID.itables))
-    )
-    ctx.addGlobal(global)
-  }
-
   private def genInterface(clazz: LinkedClass)(implicit ctx: WasmContext): Unit = {
     assert(clazz.kind == ClassKind.Interface)
     // gen itable type
@@ -1563,5 +1499,36 @@ object ClassEmitter {
 
   private val thisOriginalName: OriginalName = OriginalName("this")
   private val vtableOriginalName: OriginalName = OriginalName("vtable")
-  private val itablesOriginalName: OriginalName = OriginalName("itables")
+
+  /** Generates the itable slots of a class.
+   *
+   *  @param classInfoForResolving
+   *    The `ClassInfo` from which to resolve methods. This is normally the
+   *    class info of the class for which we are generating the itable slots.
+   *    For the itable slots of array classes, it must be the info of `jl.Object`.
+   *  @param ancestors
+   *    The list of ancestors of the target class.
+   */
+  def genItableSlots(classInfoForResolving: WasmContext.ClassInfo,
+      ancestors: List[ClassName])(
+      implicit ctx: WasmContext): List[wa.Instr] = {
+    val itablesInit = Array.fill[List[wa.Instr]](ctx.itablesLength) {
+      List(wa.RefNull(watpe.HeapType.Struct))
+    }
+    val resolvedMethodInfos = classInfoForResolving.resolvedMethodInfos
+
+    for {
+      ancestor <- ancestors
+      // Use getClassInfoOption in case the reachability analysis got rid of those interfaces
+      interfaceInfo <- ctx.getClassInfoOption(ancestor)
+      if interfaceInfo.isInterface
+    } {
+      val init = interfaceInfo.tableEntries.map { method =>
+        wa.RefFunc(resolvedMethodInfos(method).tableEntryID)
+      } :+ wa.StructNew(genTypeID.forITable(ancestor))
+      itablesInit(interfaceInfo.itableIdx) = init
+    }
+
+    itablesInit.flatten.toList
+  }
 }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
index 50d9ac0dff..cc5fb760ea 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/CoreWasmLib.scala
@@ -117,7 +117,6 @@ final class CoreWasmLib(coreSpec: CoreSpec, globalInfo: LinkedGlobalInfo) {
 
     genImports()
 
-    genEmptyITable()
     genPrimitiveTypeDataGlobals()
 
     genHelperDefinitions()
@@ -175,20 +174,6 @@ final class CoreWasmLib(coreSpec: CoreSpec, globalInfo: LinkedGlobalInfo) {
       ArrayType(FieldType(RefType(genTypeID.typeData), isMutable = false))
     )
 
-    genCoreType(
-      genTypeID.itables,
-      StructType(
-        (0 until ctx.itablesLength).map { i =>
-          StructField(
-            genFieldID.itablesStruct.itableSlot(i),
-            OriginalName.NoOriginalName,
-            RefType.nullable(HeapType.Struct),
-            isMutable = false
-          )
-        }.toList
-      )
-    )
-
     genCoreType(
       genTypeID.reflectiveProxies,
       ArrayType(FieldType(RefType(genTypeID.reflectiveProxy), isMutable = false))
@@ -234,12 +219,6 @@ final class CoreWasmLib(coreSpec: CoreSpec, globalInfo: LinkedGlobalInfo) {
       RefType(vtableTypeID),
       isMutable = false
     )
-    val itablesField = StructField(
-      genFieldID.objStruct.itables,
-      OriginalName(genFieldID.objStruct.itables.toString()),
-      RefType(genTypeID.itables),
-      isMutable = false
-    )
 
     val typeRefsWithArrays: List[(TypeID, TypeID)] =
       List(
@@ -266,7 +245,7 @@ final class CoreWasmLib(coreSpec: CoreSpec, globalInfo: LinkedGlobalInfo) {
 
       val superType = genTypeID.ObjectStruct
       val structType = StructType(
-        List(vtableField, itablesField, underlyingArrayField)
+        List(vtableField, underlyingArrayField)
       )
       val subType = SubType(structTypeID, origName, isFinal = true, Some(superType), structType)
       ctx.mainRecType.addSubType(subType)
@@ -431,18 +410,6 @@ final class CoreWasmLib(coreSpec: CoreSpec, globalInfo: LinkedGlobalInfo) {
 
   // --- Global definitions ---
 
-  private def genEmptyITable()(implicit ctx: WasmContext): Unit = {
-    ctx.addGlobal(
-      Global(
-        genGlobalID.emptyITable,
-        OriginalName(genGlobalID.emptyITable.toString()),
-        isMutable = false,
-        RefType(genTypeID.itables),
-        Expr(List(StructNewDefault(genTypeID.itables)))
-      )
-    )
-  }
-
   private def genPrimitiveTypeDataGlobals()(implicit ctx: WasmContext): Unit = {
     import genFieldID.typeData._
 
@@ -498,7 +465,6 @@ final class CoreWasmLib(coreSpec: CoreSpec, globalInfo: LinkedGlobalInfo) {
       val boxStruct = genTypeID.forClass(boxClassName)
       val instrs: List[Instr] = List(
         GlobalGet(genGlobalID.forVTable(boxClassName)),
-        GlobalGet(genGlobalID.forITable(boxClassName)),
         zeroValueInstr,
         StructNew(boxStruct)
       )
@@ -1566,7 +1532,11 @@ final class CoreWasmLib(coreSpec: CoreSpec, globalInfo: LinkedGlobalInfo) {
         // reflectiveProxies, empty since all methods of array classes exist in jl.Object
         fb += ArrayNewFixed(genTypeID.reflectiveProxies, 0)
 
+        // itable slots
         val objectClassInfo = ctx.getClassInfo(ObjectClass)
+        fb ++= ClassEmitter.genItableSlots(objectClassInfo, List(SerializableClass, CloneableClass))
+
+        // vtable items
         fb ++= objectClassInfo.tableEntries.map { methodName =>
           ctx.refFuncWithDeclaration(objectClassInfo.resolvedMethodInfos(methodName).tableEntryID)
         }
@@ -2256,17 +2226,16 @@ final class CoreWasmLib(coreSpec: CoreSpec, globalInfo: LinkedGlobalInfo) {
     fb += StructGet(genTypeID.ClassStruct, genFieldID.classData)
     fb += LocalTee(componentTypeDataLocal)
 
-    // Load the vtable and itables of the ArrayClass instance we will create
+    // Load the vtable of the ArrayClass instance we will create
     fb += I32Const(1)
-    fb += Call(genFunctionID.arrayTypeData) // vtable
-    fb += GlobalGet(genGlobalID.arrayClassITable) // itables
+    fb += Call(genFunctionID.arrayTypeData)
 
     // Load the length
     fb += LocalGet(lengthParam)
 
     // switch (componentTypeData.kind)
     val switchClauseSig = FunctionType(
-      List(arrayTypeDataType, RefType(genTypeID.itables), Int32),
+      List(arrayTypeDataType, Int32),
       List(RefType(genTypeID.ObjectStruct))
     )
     fb.switch(switchClauseSig) { () =>
@@ -2807,7 +2776,6 @@ final class CoreWasmLib(coreSpec: CoreSpec, globalInfo: LinkedGlobalInfo) {
     // Build the result arrayStruct
     fb += LocalGet(fromLocal)
     fb += StructGet(arrayStructTypeID, genFieldID.objStruct.vtable) // vtable
-    fb += GlobalGet(genGlobalID.arrayClassITable) // itable
     fb += LocalGet(resultUnderlyingLocal)
     fb += StructNew(arrayStructTypeID)
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala
index ec913fe9cb..58facb4619 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Emitter.scala
@@ -90,7 +90,6 @@ final class Emitter(config: Emitter.Config) {
     coreLib.genPreClasses()
     sortedClasses.foreach(classEmitter.genClassDef(_))
     topLevelExports.foreach(classEmitter.genTopLevelExport(_))
-    classEmitter.genGlobalArrayClassItable()
     coreLib.genPostClasses()
 
     genStartFunction(sortedClasses, moduleInitializers, topLevelExports)
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
index 9ff845757f..12a4913928 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
@@ -1190,10 +1190,10 @@ private class FunctionEmitter private (
     // Generates an itable-based dispatch.
     def genITableDispatch(): Unit = {
       fb += wa.LocalGet(receiverLocalForDispatch)
-      fb += wa.StructGet(genTypeID.ObjectStruct, genFieldID.objStruct.itables)
+      fb += wa.StructGet(genTypeID.ObjectStruct, genFieldID.objStruct.vtable)
       fb += wa.StructGet(
-        genTypeID.itables,
-        genFieldID.itablesStruct.itableSlot(receiverClassInfo.itableIdx)
+        genTypeID.ObjectVTable,
+        genFieldID.vtableStruct.itableSlot(receiverClassInfo.itableIdx)
       )
       fb += wa.RefCast(watpe.RefType(genTypeID.forITable(receiverClassInfo.name)))
       fb += wa.StructGet(
@@ -2722,7 +2722,6 @@ private class FunctionEmitter private (
 
     fb += wa.LocalSet(primLocal)
     fb += wa.GlobalGet(genGlobalID.forVTable(boxClassName))
-    fb += wa.GlobalGet(genGlobalID.forITable(boxClassName))
     fb += wa.LocalGet(primLocal)
     fb += wa.StructNew(genTypeID.forClass(boxClassName))
 
@@ -3001,7 +3000,7 @@ private class FunctionEmitter private (
 
     markPosition(tree)
 
-    genLoadVTableAndITableForArray(fb, arrayTypeRef)
+    genLoadArrayTypeData(fb, arrayTypeRef) // vtable
 
     // Create the underlying array
     genTree(length, IntType)
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Preprocessor.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Preprocessor.scala
index 7221cab491..34e5f44f9a 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Preprocessor.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/Preprocessor.scala
@@ -140,12 +140,6 @@ object Preprocessor {
       }
     }
 
-    // Does this Scala class implement any interface?
-    val classImplementsAnyInterface = {
-      (kind.isClass || kind == ClassKind.HijackedClass) &&
-      (clazz.interfaces.nonEmpty || superClass.exists(_.classImplementsAnyInterface))
-    }
-
     /* Should we emit a vtable/typeData global for this class?
      *
      * There are essentially three reasons for which we need them:
@@ -215,7 +209,6 @@ object Preprocessor {
       kind,
       clazz.jsClassCaptures,
       allFieldDefs,
-      classImplementsAnyInterface,
       clazz.hasInstances,
       !clazz.hasDirectInstances,
       hasRuntimeTypeInfo,
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/README.md b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/README.md
index a565099a88..d1830d355e 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/README.md
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/README.md
@@ -77,10 +77,10 @@ Our "type representation" for `nothing` is therefore to make sure that we are in
 ### Basic structure
 
 We use GC `struct`s to represent instances of classes.
-The structs start with a `vtable` reference and an `itables` reference, which are followed by user-defined fields.
+The structs start with a `vtable` reference, which is followed by user-defined fields.
 The declared supertypes of those `struct`s follow the *class* hierarchy (ignoring interfaces).
 
-The `vtable` and `itables` references are immutable.
+The `vtable` reference is immutable.
 User-defined fields are always mutable as the WebAssembly level, since they are mutated in the constructors.
 
 For example, given the following IR classes:
@@ -100,13 +100,11 @@ We define the following GC structs:
 ```wat
 (type $c.A (sub $c.java.lang.Object (struct
   (field $vtable (ref $v.A))
-  (field $itables (ref $itables))
   (field $f.A.x (mut i32)))
 ))
 
 (type $c.B (sub $c.A (struct
   (field $vtable (ref $v.B))
-  (field $itables (ref $itables))
   (field $f.A.x (mut i32))
   (field $f.B.y (mut f64)))
 ))
@@ -197,6 +195,7 @@ Documentation for the meaning of each field can be found in `VarGen.genFieldID.t
 The vtable of our object model follows a standard layout:
 
 * The class meta data, then
+* Slots for itable pointers (see below for interface method calls), then
 * Function pointers for the virtual methods, from `jl.Object` down to the current class.
 
 vtable structs form a subtyping hierarchy that mirrors the class hierarchy, so that `$v.B` is a subtype of `$v.A`.
@@ -229,12 +228,14 @@ we get
 ```wat
 (type $v.A (sub $v.java.lang.Object (struct
   ;; ... class metadata
+  ;; ... itable slots
   ;; ... methods of jl.Object
   (field $m.foo_I_I (ref $4))
 )))
 
 (type $v.helloworld.B (sub $v.A (struct
   ;; ... class metadata
+  ;; ... itable slots
   ;; ... methods of jl.Object
   (field $m.foo_I_I (ref $4))
   (field $m.bar_D_D (ref $6))
@@ -278,17 +279,24 @@ A virtual call to `a.foo(1)` is compiled as you would expect: lookup the functio
 
 ### itables and interface method calls
 
-The itables field contains the method tables for interface call dispatch.
-It is an instance of the following struct type:
+Before the function pointers for virtual call dispatch, each vtable contains the method tables for interface call dispatch.
+They have one more level of indirection than for virtual calls.
+There are `N` immutable fields of type `structref`, which are the *itable slots*:
 
 ```wat
-(type $itables (struct (field $slot1 structref) ... (field $slotN structref)))
+(type $v.A (sub $v.java.lang.Object (struct
+  ;; ... class metadata
+  (field $itableSlot1 structref)
+  ...
+  (field $itableSlotN structref)
+  ;; ... virtual method pointers
+)))
 ```
 
 As a first approximation, we assign a distinct index to every interface in the program.
-The index maps to a slot of the itables struct of the instance.
+The index maps to an itable slot.
 At the index of a given interface `Intf`, we find a `(ref $it.Intf)` whose fields are the method table entries of `Intf`.
-Like for vtables, we use the "table entry bridges" in the itables, i.e., the functions where the receiver is of type `(ref any)`.
+Like for virtual calls, we use the "table entry bridges" in the itables, i.e., the functions where the receiver is of type `(ref any)`.
 
 For example, given
 
@@ -323,7 +331,7 @@ This slot allocation is implemented in `Preprocessor.assignBuckets`.
 Since Wasm structs only support single inheritance in their subtyping relationships, we have to transform every interface type as `(ref null jl.Object)` (the common supertype of all interfaces).
 This does not turn out to be a problem for interface method calls, since they pass through the `itables` struct anyway, and use the table entry bridges which take `(ref any)` as argument.
 
-Given the above structure, an interface method call to `intf.foo(1)` is compiled as expected: lookup the function reference in the appropriate slot of the `itables` struct, then call it.
+Given the above structure, an interface method call to `intf.foo(1)` is compiled as expected: lookup the function reference in the appropriate itable slot of the vtable, then call it.
 
 ### Reflective calls
 
@@ -476,9 +484,10 @@ All array "classes" follow the same structure:
 
 * They actually extend `jl.Object`
 * Their vtable type is the same as `jl.Object`
-* They each have their own vtable value for the differing metadata, although the method table entries are the same as in `jl.Object`
+* They each have their own vtable value for the differing metadata, although their method table entries are all the same
   * This is also true for reference types: the vtables are dynamically created at run-time on first use (they are values and share the same type, so that we can do)
-* Their `itables` field points to a common itables struct with entries for `jl.Cloneable` and `j.io.Serializable`
+* Their virtual method pointers are the same as in `jl.Object`
+* Their itable slots are all the same, with entries for `jl.Cloneable` and `j.io.Serializable`
 * They have a unique "user-land" field `$underlyingArray`, which is a Wasm array of its values:
   * For primitives, they are primitive arrays, such as `(array mut i32)`
   * For references, they are all the same type `(array mut anyref)`
@@ -496,18 +505,15 @@ Concretely, here are the relevant Wasm definitions:
 
 (type $BooleanArray (sub final $c.java.lang.Object (struct
   (field $vtable (ref $v.java.lang.Object))
-  (field $itables (ref $itables))
   (field $arrayUnderlying (ref $i8Array))
 )))
 (type $CharArray (sub final $c.java.lang.Object (struct
   (field $vtable (ref $v.java.lang.Object))
-  (field $itables (ref $itables))
   (field $arrayUnderlying (ref $i16Array))
 )))
 ...
 (type $ObjectArray (sub final $c.java.lang.Object (struct
   (field $vtable (ref $v.java.lang.Object))
-  (field $itables (ref $itables))
   (field $arrayUnderlying (ref $anyArray))
 )))
 ```
@@ -550,18 +556,15 @@ For type definitions, we use the following ordering:
 
 For global definitions, we use the following ordering:
 
-1. A unique "empty" itables global for classes that do not implement any interface (`$emptyITable`)
-2. The typeData of the primitive types (e.g., `$d.I`)
-3. For each linked class, in the same ancestor count-based order:
+1. The typeData of the primitive types (e.g., `$d.I`)
+2. For each linked class, in the same ancestor count-based order:
    1. In no particular order, if applicable:
       * Its typeData/vtable global (e.g., `$d.java.lang.Object`), which may refer to the typeData of ancestors, so the order between classes is important
-      * Its itables global (e.g., `$it.java.lang.Class`)
       * Static field definitions
       * Definitions of `Symbol`s for the "names" of private JS fields
       * The module instance
       * The cached JS class value
-4. Cached values of boxed zero values (such as `$bZeroChar`), which refer to the vtable and itables globals of the box classes
-5. The itables global of array classes (namely, `$arrayClassITable`)
+3. Cached values of boxed zero values (such as `$bZeroChar`), which refer to the vtable globals of the box classes
 
 ## Miscellaneous
 
@@ -581,7 +584,6 @@ It looks like the following:
   (result (ref $c.C))
 
   global.get $d.C  ;; the global vtable for class C
-  global.get $it.C ;; the global itables for class C
   i32.const 0      ;; zero of type int
   f64.const 0.0    ;; zero of type double
   struct.new $c.C  ;; allocate a $c.C initialized with all of the above
@@ -591,7 +593,7 @@ It looks like the following:
 It would be nice to do the following instead:
 
 1. Allocate a `$c.C` entirely initialized with zeros, using `struct.new_default`
-2. Set the `$vtable` and `$itables` fields
+2. Set the `$vtable` field
 
 This would have a constant code size cost, irrespective of the amount of fields in `C`.
 Unfortunately, we cannot do this because the `$vtable` field is immutable.
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/SWasmGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/SWasmGen.scala
index 7ac01cf64d..02ee2ca7ba 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/SWasmGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/SWasmGen.scala
@@ -62,18 +62,9 @@ object SWasmGen {
     fb += Call(genFunctionID.arrayTypeData)
   }
 
-  /** Gen code to load the vtable and the itable of the given array type. */
-  def genLoadVTableAndITableForArray(fb: FunctionBuilder, arrayTypeRef: ArrayTypeRef): Unit = {
-    // Load the typeData of the resulting array type. It is the vtable of the resulting object.
-    genLoadArrayTypeData(fb, arrayTypeRef)
-
-    // Load the itables for the array type
-    fb += GlobalGet(genGlobalID.arrayClassITable)
-  }
-
   def genArrayValue(fb: FunctionBuilder, arrayTypeRef: ArrayTypeRef, length: Int)(
       genElems: => Unit): Unit = {
-    genLoadVTableAndITableForArray(fb, arrayTypeRef)
+    genLoadArrayTypeData(fb, arrayTypeRef) // vtable
 
     // Create the underlying array
     genElems
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
index e9416b3071..09dacde150 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/VarGen.scala
@@ -37,7 +37,6 @@ object VarGen {
         forVTable(ClassRef(className))
     }
 
-    final case class forITable(className: ClassName) extends GlobalID
     final case class forStaticField(fieldName: FieldName) extends GlobalID
     final case class forJSPrivateField(fieldName: FieldName) extends GlobalID
 
@@ -45,8 +44,6 @@ object VarGen {
 
     case object bZeroChar extends GlobalID
     case object bZeroLong extends GlobalID
-    case object emptyITable extends GlobalID
-    case object arrayClassITable extends GlobalID
     case object lastIDHashCode extends GlobalID
 
     /** A `GlobalID` for a JS helper global.
@@ -231,14 +228,9 @@ object VarGen {
 
     object objStruct {
       case object vtable extends FieldID
-      case object itables extends FieldID
       case object arrayUnderlying extends FieldID
     }
 
-    object itablesStruct {
-      final case class itableSlot(i: Int) extends FieldID
-    }
-
     object reflectiveProxy {
       case object methodID extends FieldID
       case object funcRef extends FieldID
@@ -343,6 +335,11 @@ object VarGen {
       case object reflectiveProxies extends FieldID
     }
 
+    /** Extension of `typeData` for vtables, starting with `jl.Object`. */
+    object vtableStruct {
+      final case class itableSlot(i: Int) extends FieldID
+    }
+
     /** The magic `data` field of type `(ref typeData)`, injected into `jl.Class`. */
     case object classData extends FieldID
 
@@ -405,7 +402,6 @@ object VarGen {
     }
 
     case object typeDataArray extends TypeID
-    case object itables extends TypeID
     case object reflectiveProxies extends TypeID
 
     // primitive array types, underlying the Array[T] classes
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/WasmContext.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/WasmContext.scala
index 6d64b1bbbd..6f0551921a 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/WasmContext.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/WasmContext.scala
@@ -256,7 +256,6 @@ object WasmContext {
       val kind: ClassKind,
       val jsClassCaptures: Option[List[ParamDef]],
       val allFieldDefs: List[FieldDef],
-      val classImplementsAnyInterface: Boolean,
       val hasInstances: Boolean,
       val isAbstract: Boolean,
       val hasRuntimeTypeInfo: Boolean,
@@ -271,7 +270,7 @@ object WasmContext {
     override def toString(): String =
       s"ClassInfo(${name.nameString})"
 
-    /** Returns the index of this interface's itable in the classes' interface tables.
+    /** Returns the index of this interface's itable in the classes' vtables.
      *
      *  Only interfaces that have instances get an itable index.
      */

From 9481522bcd4251bda3ccee0cc57863826b7738f1 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Thu, 30 Jan 2025 15:43:20 +0100
Subject: [PATCH 278/298] Rewrite old IR with `AnonFunctionN` references to use
 `NewLambda`.

We change the definition of `AnonFunctionN`s from `final class`es
with concrete `apply` methods to `sealed abstract` classes. We
rewrite `New` nodes to them to use `NewLambda` instead.

See comments in the IR deserializer for more details on the
performed rewrites.

The rewritten `NewLambda` must target classes with the same
identity (and not directly `AbstractFunctionN`) because the class
names can be used in *types* somewhere else in the IR. The result
of the `NewLambda` nodes must stay compatible with those types.

This change ensures that even old libraries benefit from all the
new optimizations for lambdas on Wasm, and that they can
participate in a call chain between `js.async` and an orphan
`js.await`.
---
 .../scala/org/scalajs/ir/Serializers.scala    | 269 +++++++++++++++++-
 .../scala/scalajs/runtime/AnonFunctions.scala | 135 +++------
 project/BinaryIncompatibilities.scala         |   4 +
 .../linker/anonfunction-compat/build.sbt      |  61 ++++
 .../project/build.properties                  |   1 +
 .../anonfunction-compat/project/build.sbt     |   5 +
 .../scala2-old-compiler-new-lib/Main.scala    |   9 +
 .../scala2-old-compiler-old-lib/Main.scala    |   9 +
 .../scala3-old-compiler-new-lib/Main.scala    |  18 ++
 .../scala3-old-compiler-old-lib/Main.scala    |  18 ++
 .../sbt-test/linker/anonfunction-compat/test  |  25 ++
 11 files changed, 455 insertions(+), 99 deletions(-)
 create mode 100644 sbt-plugin/src/sbt-test/linker/anonfunction-compat/build.sbt
 create mode 100644 sbt-plugin/src/sbt-test/linker/anonfunction-compat/project/build.properties
 create mode 100644 sbt-plugin/src/sbt-test/linker/anonfunction-compat/project/build.sbt
 create mode 100644 sbt-plugin/src/sbt-test/linker/anonfunction-compat/scala2-old-compiler-new-lib/Main.scala
 create mode 100644 sbt-plugin/src/sbt-test/linker/anonfunction-compat/scala2-old-compiler-old-lib/Main.scala
 create mode 100644 sbt-plugin/src/sbt-test/linker/anonfunction-compat/scala3-old-compiler-new-lib/Main.scala
 create mode 100644 sbt-plugin/src/sbt-test/linker/anonfunction-compat/scala3-old-compiler-old-lib/Main.scala
 create mode 100644 sbt-plugin/src/sbt-test/linker/anonfunction-compat/test

diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
index 43abb124ae..7cc64e28e1 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
@@ -1226,8 +1226,15 @@ object Serializers {
 
         case TagDebugger => Debugger()
 
-        case TagNew          => New(readClassName(), readMethodIdent(), readTrees())
-        case TagLoadModule   => LoadModule(readClassName())
+        case TagNew =>
+          val tree = New(readClassName(), readMethodIdent(), readTrees())
+          if (hacks.useBelow(19))
+            anonFunctionNewNodeHackBelow19(tree)
+          else
+            tree
+
+        case TagLoadModule =>
+          LoadModule(readClassName())
 
         case TagStoreModule =>
           if (hacks.useBelow(16)) {
@@ -1542,6 +1549,129 @@ object Serializers {
         UnaryOp(UnaryOp.CheckNotNull, expr)
     }
 
+    /** Rewrites `New` nodes of `AnonFunctionN`s coming from before 1.19 into `NewLambda` nodes.
+     *
+     *  Before 1.19, the codegen for `scala.FunctionN` lambda was of the following shape:
+     *  {{{
+     *  new scala.scalajs.runtime.AnonFunctionN(arrow-lambda<...captures>(...args: any): any = {
+     *    body
+     *  })
+     *  }}}
+     *
+     *  This function rewrites such calls to `NewLambda` nodes, using the new
+     *  definition of these classes:
+     *  {{{
+     *  <newLambda>(scala.scalajs.runtime.AnonFunctionN,
+     *     apply;Ljava.lang.Object;...;Ljava.lang.Object,
+     *     any, any, (typed-lambda<...captures>(...args: any): any = {
+     *    body
+     *  }))
+     *  }}}
+     *
+     *  The rewrite ensures that previously published lambdas get the same
+     *  optimizations on Wasm as those recompiled with 1.19+.
+     *
+     *  The rewrite also applies to Scala 3's `AnonFunctionXXL` classes, with
+     *  an additional adaptation of the parameter's type. It rewrites
+     *  {{{
+     *  new scala.scalajs.runtime.AnonFunctionXXL(arrow-lambda<...captures>(argArray: any): any = {
+     *    body
+     *  })
+     *  }}}
+     *  to
+     *  {{{
+     *  <newLambda>(scala.scalajs.runtime.AnonFunctionXXL,
+     *     apply;Ljava.lang.Object[];Ljava.lang.Object,
+     *     any, any, (typed-lambda<...captures>(argArray: jl.Object[]): any = {
+     *    newBody
+     *  }))
+     *  }}}
+     *  where `newBody` is `body` transformed to adapt the type of `argArray`
+     *  everywhere.
+     *
+     *  Tests are in `sbt-plugin/src/sbt-test/linker/anonfunction-compat/`.
+     *
+     *  ---
+     *
+     *  In case the argument is not an arrow-lambda of the expected shape, we
+     *  use a fallback. This never happens for our published codegens, but
+     *  could happen for other valid IR. We rewrite
+     *  {{{
+     *  new scala.scalajs.runtime.AnonFunctionN(jsFunctionArg)
+     *  }}}
+     *  to
+     *  {{{
+     *  <newLambda>(scala.scalajs.runtime.AnonFunctionN,
+     *     apply;Ljava.lang.Object;...;Ljava.lang.Object,
+     *     any, any, (typed-lambda<f: any = jsFunctionArg>(...args: any): any = {
+     *    f(...args)
+     *  }))
+     *  }}}
+     *
+     *  This code path is not tested in the CI, but can be locally tested by
+     *  commenting out the `case Closure(...) =>`.
+     */
+    private def anonFunctionNewNodeHackBelow19(tree: New): Tree = {
+      tree match {
+        case New(cls, _, funArg :: Nil) =>
+          def makeFallbackTypedClosure(paramTypes: List[Type]): Closure = {
+            implicit val pos = funArg.pos
+            val fParamDef = ParamDef(LocalIdent(LocalName("f")), NoOriginalName, AnyType, mutable = false)
+            val xParamDefs = paramTypes.zipWithIndex.map { case (ptpe, i) =>
+              ParamDef(LocalIdent(LocalName(s"x$i")), NoOriginalName, ptpe, mutable = false)
+            }
+            Closure(ClosureFlags.typed, List(fParamDef), xParamDefs, None, AnyType,
+                JSFunctionApply(fParamDef.ref, xParamDefs.map(_.ref)),
+                List(funArg))
+          }
+
+          cls match {
+            case HackNames.AnonFunctionClass(arity) =>
+              val typedClosure = funArg match {
+                // The shape produced by our earlier compilers, which we can optimally rewrite
+                case Closure(ClosureFlags.arrow, captureParams, params, None, AnyType, body, captureValues)
+                    if params.lengthCompare(arity) == 0 =>
+                  Closure(ClosureFlags.typed, captureParams, params, None, AnyType,
+                      body, captureValues)(funArg.pos)
+
+                // Fallback for other shapes (theoretically required; dead code in practice)
+                case _ =>
+                  makeFallbackTypedClosure(List.fill(arity)(AnyType))
+              }
+
+              NewLambda(HackNames.anonFunctionDescriptors(arity), typedClosure)(tree.tpe)(tree.pos)
+
+            case HackNames.AnonFunctionXXLClass =>
+              val typedClosure = funArg match {
+                // The shape produced by our earlier compilers, which we can optimally rewrite
+                case Closure(ClosureFlags.arrow, captureParams, oldParam :: Nil, None, AnyType, body, captureValues) =>
+                  // Here we need to adapt the type of the parameter from `any` to `jl.Object[]`.
+                  val newParam = oldParam.copy(ptpe = HackNames.ObjectArrayType)(oldParam.pos)
+                  val newBody = new Transformers.LocalScopeTransformer {
+                    override def transform(tree: Tree): Tree = tree match {
+                      case tree @ VarRef(newParam.name.name) => tree.copy()(newParam.ptpe)(tree.pos)
+                      case _                                 => super.transform(tree)
+                    }
+                  }.transform(body)
+                  Closure(ClosureFlags.typed, captureParams, List(newParam), None, AnyType,
+                      newBody, captureValues)(funArg.pos)
+
+                // Fallback for other shapes (theoretically required; dead code in practice)
+                case _ =>
+                  makeFallbackTypedClosure(List(HackNames.ObjectArrayType))
+              }
+
+              NewLambda(HackNames.anonFunctionXXLDescriptor, typedClosure)(tree.tpe)(tree.pos)
+
+            case _ =>
+              tree
+          }
+
+        case _ =>
+          tree
+      }
+    }
+
     def readTrees(): List[Tree] =
       List.fill(readInt())(readTree())
 
@@ -1641,10 +1771,15 @@ object Serializers {
 
       val jsNativeMembers = jsNativeMembersBuilder.result()
 
-      ClassDef(name, originalName, kind, jsClassCaptures, superClass, parents,
+      val classDef = ClassDef(name, originalName, kind, jsClassCaptures, superClass, parents,
           jsSuperClass, jsNativeLoadSpec, fields, methods, jsConstructor,
           jsMethodProps, jsNativeMembers, topLevelExportDefs)(
           optimizerHints)
+
+      if (hacks.useBelow(19))
+        anonFunctionClassDefHackBelow19(classDef)
+      else
+        classDef
     }
 
     private def jlClassMethodsHackBelow17(methods: List[MethodDef]): List[MethodDef] = {
@@ -1931,6 +2066,88 @@ object Serializers {
       (jsConstructorBuilder.result(), jsMethodPropsBuilder.result())
     }
 
+    /** Rewrites `scala.scalajs.runtime.AnonFunctionN`s from before 1.19.
+     *
+     *  Before 1.19, these classes were defined as
+     *  {{{
+     *  // final in source code
+     *  class AnonFunctionN extends AbstractFunctionN {
+     *    val f: any
+     *    def this(f: any) = {
+     *      this.f = f;
+     *      super()
+     *    }
+     *    def apply(...args: any): any = f(...args)
+     *  }
+     *  }}}
+     *
+     *  Starting with 1.19, they were rewritten to be used as SAM classes for
+     *  `NewLambda` nodes. The new IR shape is
+     *  {{{
+     *  // sealed abstract in source code
+     *  class AnonFunctionN extends AbstractFunctionN {
+     *    def this() = super()
+     *  }
+     *  }}}
+     *
+     *  This function rewrites those classes to the new shape.
+     *
+     *  The rewrite also applies to Scala 3's `AnonFunctionXXL`.
+     *
+     *  Tests are in `sbt-plugin/src/sbt-test/linker/anonfunction-compat/`.
+     */
+    private def anonFunctionClassDefHackBelow19(classDef: ClassDef): ClassDef = {
+      import classDef._
+
+      if (!HackNames.allAnonFunctionClasses.contains(className)) {
+        classDef
+      } else {
+        val newCtor: MethodDef = {
+          // Find the old constructor to get its position and version
+          val oldCtor = methods.find(_.methodName.isConstructor).getOrElse {
+            throw new InvalidIRException(classDef,
+                s"Did not find a constructor in ${className.nameString}")
+          }
+          implicit val pos = oldCtor.pos
+
+          // constructor def <init>() = this.superClass::<init>()
+          MethodDef(
+            MemberFlags.empty.withNamespace(MemberNamespace.Constructor),
+            MethodIdent(NoArgConstructorName),
+            NoOriginalName,
+            Nil,
+            VoidType,
+            Some {
+              ApplyStatically(
+                ApplyFlags.empty.withConstructor(true),
+                This()(ClassType(className, nullable = false)),
+                superClass.get.name,
+                MethodIdent(NoArgConstructorName),
+                Nil
+              )(VoidType)
+            }
+          )(OptimizerHints.empty, oldCtor.version)
+        }
+
+        ClassDef(
+          name,
+          originalName,
+          kind,
+          jsClassCaptures,
+          superClass,
+          interfaces,
+          jsSuperClass,
+          jsNativeLoadSpec,
+          fields = Nil, // throws away the `f` field
+          methods = List(newCtor), // throws away the old constructor and `apply` method
+          jsConstructor,
+          jsMethodProps,
+          jsNativeMembers,
+          topLevelExportDefs
+        )(OptimizerHints.empty)(pos) // throws away the `@inline`
+      }
+    }
+
     private def readFieldDef()(implicit pos: Position): FieldDef = {
       val flags = MemberFlags.fromBits(readInt())
       val name = readFieldIdentForEnclosingClass()
@@ -2602,6 +2819,8 @@ object Serializers {
 
   /** Names needed for hacks. */
   private object HackNames {
+    val AnonFunctionXXLClass =
+      ClassName("scala.scalajs.runtime.AnonFunctionXXL") // from the Scala 3 library
     val CloneNotSupportedExceptionClass =
       ClassName("java.lang.CloneNotSupportedException")
     val SystemModule: ClassName =
@@ -2611,14 +2830,50 @@ object Serializers {
     val ReflectArrayModClass =
       ClassName("java.lang.reflect.Array$")
 
+    val ObjectArrayType = ArrayType(ArrayTypeRef(ObjectRef, 1), nullable = true)
+
+    private val applySimpleName = SimpleMethodName("apply")
+
     val cloneName: MethodName =
-      MethodName("clone", Nil, ClassRef(ObjectClass))
+      MethodName("clone", Nil, ObjectRef)
     val identityHashCodeName: MethodName =
-      MethodName("identityHashCode", List(ClassRef(ObjectClass)), IntRef)
+      MethodName("identityHashCode", List(ObjectRef), IntRef)
     val newInstanceSingleName: MethodName =
-      MethodName("newInstance", List(ClassRef(ClassClass), IntRef), ClassRef(ObjectClass))
+      MethodName("newInstance", List(ClassRef(ClassClass), IntRef), ObjectRef)
     val newInstanceMultiName: MethodName =
-      MethodName("newInstance", List(ClassRef(ClassClass), ArrayTypeRef(IntRef, 1)), ClassRef(ObjectClass))
+      MethodName("newInstance", List(ClassRef(ClassClass), ArrayTypeRef(IntRef, 1)), ObjectRef)
+
+    private val anonFunctionArities: Map[ClassName, Int] =
+      (0 to 22).map(arity => ClassName(s"scala.scalajs.runtime.AnonFunction$arity") -> arity).toMap
+    val allAnonFunctionClasses: Set[ClassName] =
+      anonFunctionArities.keySet + AnonFunctionXXLClass
+
+    object AnonFunctionClass {
+      def unapply(cls: ClassName): Option[Int] =
+        anonFunctionArities.get(cls)
+    }
+
+    lazy val anonFunctionDescriptors: IndexedSeq[NewLambda.Descriptor] = {
+      anonFunctionArities.toIndexedSeq.sortBy(_._2).map { case (className, arity) =>
+        NewLambda.Descriptor(
+          superClass = className,
+          interfaces = Nil,
+          methodName = MethodName(applySimpleName, List.fill(arity)(ObjectRef), ObjectRef),
+          paramTypes = List.fill(arity)(AnyType),
+          resultType = AnyType
+        )
+      }
+    }
+
+    lazy val anonFunctionXXLDescriptor: NewLambda.Descriptor = {
+      NewLambda.Descriptor(
+        superClass = AnonFunctionXXLClass,
+        interfaces = Nil,
+        methodName = MethodName(applySimpleName, List(ObjectArrayType.arrayTypeRef), ObjectRef),
+        paramTypes = List(ObjectArrayType),
+        resultType = AnyType
+      )
+    }
   }
 
   private class OptionBuilder[T] {
diff --git a/library/src/main/scala/scala/scalajs/runtime/AnonFunctions.scala b/library/src/main/scala/scala/scalajs/runtime/AnonFunctions.scala
index 6441a5ee23..dd83d20a1a 100644
--- a/library/src/main/scala/scala/scalajs/runtime/AnonFunctions.scala
+++ b/library/src/main/scala/scala/scalajs/runtime/AnonFunctions.scala
@@ -17,142 +17,93 @@ import scala.runtime._
 
 // scalastyle:off line.size.limit
 
+/* Before 1.19, these classes were concrete. They had a 1-argument constructor
+ * taking a js.FunctionN, and their `apply()` method called that function.
+ *
+ * In 1.19, we introduced `NewLambda` nodes, which superseded these specialized
+ * classes with a compilation mode that is more efficient on Wasm.
+ * However, libraries compiled with earlier versions still contain references
+ * to `AnonFunctionN`.
+ *
+ * The IR deserializer patches allocations of the form
+ *   New(AnonFunctionN, ctor, closure :: Nil)
+ * into
+ *   NewLambda(AnonFunctionN, ..., (...xs) => closure(...xs))
+ *
+ * When the `closure` is directly a JS `Closure` with the right number of
+ * arguments (which is supposed to be always, as far as our codegens were
+ * concerned), it rewrites that as
+ *   NewLambda(AnonFunctionN, ..., (...closureParams) => closureBody)
+ * which provides the best performance for old code.
+ */
+
 @deprecated("used by the codegen before 1.19", since = "1.19.0")
-@inline
-final class AnonFunction0[+R](f: js.Function0[R]) extends AbstractFunction0[R] {
-  override def apply(): R = f()
-}
+sealed abstract class AnonFunction0[+R] extends AbstractFunction0[R]
 
 @deprecated("used by the codegen before 1.19", since = "1.19.0")
-@inline
-final class AnonFunction1[-T1, +R](f: js.Function1[T1, R]) extends AbstractFunction1[T1, R] {
-  override def apply(arg1: T1): R = f(arg1)
-}
+sealed abstract class AnonFunction1[-T1, +R] extends AbstractFunction1[T1, R]
 
 @deprecated("used by the codegen before 1.19", since = "1.19.0")
-@inline
-final class AnonFunction2[-T1, -T2, +R](f: js.Function2[T1, T2, R]) extends AbstractFunction2[T1, T2, R] {
-  override def apply(arg1: T1, arg2: T2): R = f(arg1, arg2)
-}
+sealed abstract class AnonFunction2[-T1, -T2, +R] extends AbstractFunction2[T1, T2, R]
 
 @deprecated("used by the codegen before 1.19", since = "1.19.0")
-@inline
-final class AnonFunction3[-T1, -T2, -T3, +R](f: js.Function3[T1, T2, T3, R]) extends AbstractFunction3[T1, T2, T3, R] {
-  override def apply(arg1: T1, arg2: T2, arg3: T3): R = f(arg1, arg2, arg3)
-}
+sealed abstract class AnonFunction3[-T1, -T2, -T3, +R] extends AbstractFunction3[T1, T2, T3, R]
 
 @deprecated("used by the codegen before 1.19", since = "1.19.0")
-@inline
-final class AnonFunction4[-T1, -T2, -T3, -T4, +R](f: js.Function4[T1, T2, T3, T4, R]) extends AbstractFunction4[T1, T2, T3, T4, R] {
-  override def apply(arg1: T1, arg2: T2, arg3: T3, arg4: T4): R = f(arg1, arg2, arg3, arg4)
-}
+sealed abstract class AnonFunction4[-T1, -T2, -T3, -T4, +R] extends AbstractFunction4[T1, T2, T3, T4, R]
 
 @deprecated("used by the codegen before 1.19", since = "1.19.0")
-@inline
-final class AnonFunction5[-T1, -T2, -T3, -T4, -T5, +R](f: js.Function5[T1, T2, T3, T4, T5, R]) extends AbstractFunction5[T1, T2, T3, T4, T5, R] {
-  override def apply(arg1: T1, arg2: T2, arg3: T3, arg4: T4, arg5: T5): R = f(arg1, arg2, arg3, arg4, arg5)
-}
+sealed abstract class AnonFunction5[-T1, -T2, -T3, -T4, -T5, +R] extends AbstractFunction5[T1, T2, T3, T4, T5, R]
 
 @deprecated("used by the codegen before 1.19", since = "1.19.0")
-@inline
-final class AnonFunction6[-T1, -T2, -T3, -T4, -T5, -T6, +R](f: js.Function6[T1, T2, T3, T4, T5, T6, R]) extends AbstractFunction6[T1, T2, T3, T4, T5, T6, R] {
-  override def apply(arg1: T1, arg2: T2, arg3: T3, arg4: T4, arg5: T5, arg6: T6): R = f(arg1, arg2, arg3, arg4, arg5, arg6)
-}
+sealed abstract class AnonFunction6[-T1, -T2, -T3, -T4, -T5, -T6, +R] extends AbstractFunction6[T1, T2, T3, T4, T5, T6, R]
 
 @deprecated("used by the codegen before 1.19", since = "1.19.0")
-@inline
-final class AnonFunction7[-T1, -T2, -T3, -T4, -T5, -T6, -T7, +R](f: js.Function7[T1, T2, T3, T4, T5, T6, T7, R]) extends AbstractFunction7[T1, T2, T3, T4, T5, T6, T7, R] {
-  override def apply(arg1: T1, arg2: T2, arg3: T3, arg4: T4, arg5: T5, arg6: T6, arg7: T7): R = f(arg1, arg2, arg3, arg4, arg5, arg6, arg7)
-}
+sealed abstract class AnonFunction7[-T1, -T2, -T3, -T4, -T5, -T6, -T7, +R] extends AbstractFunction7[T1, T2, T3, T4, T5, T6, T7, R]
 
 @deprecated("used by the codegen before 1.19", since = "1.19.0")
-@inline
-final class AnonFunction8[-T1, -T2, -T3, -T4, -T5, -T6, -T7, -T8, +R](f: js.Function8[T1, T2, T3, T4, T5, T6, T7, T8, R]) extends AbstractFunction8[T1, T2, T3, T4, T5, T6, T7, T8, R] {
-  override def apply(arg1: T1, arg2: T2, arg3: T3, arg4: T4, arg5: T5, arg6: T6, arg7: T7, arg8: T8): R = f(arg1, arg2, arg3, arg4, arg5, arg6, arg7, arg8)
-}
+sealed abstract class AnonFunction8[-T1, -T2, -T3, -T4, -T5, -T6, -T7, -T8, +R] extends AbstractFunction8[T1, T2, T3, T4, T5, T6, T7, T8, R]
 
 @deprecated("used by the codegen before 1.19", since = "1.19.0")
-@inline
-final class AnonFunction9[-T1, -T2, -T3, -T4, -T5, -T6, -T7, -T8, -T9, +R](f: js.Function9[T1, T2, T3, T4, T5, T6, T7, T8, T9, R]) extends AbstractFunction9[T1, T2, T3, T4, T5, T6, T7, T8, T9, R] {
-  override def apply(arg1: T1, arg2: T2, arg3: T3, arg4: T4, arg5: T5, arg6: T6, arg7: T7, arg8: T8, arg9: T9): R = f(arg1, arg2, arg3, arg4, arg5, arg6, arg7, arg8, arg9)
-}
+sealed abstract class AnonFunction9[-T1, -T2, -T3, -T4, -T5, -T6, -T7, -T8, -T9, +R] extends AbstractFunction9[T1, T2, T3, T4, T5, T6, T7, T8, T9, R]
 
 @deprecated("used by the codegen before 1.19", since = "1.19.0")
-@inline
-final class AnonFunction10[-T1, -T2, -T3, -T4, -T5, -T6, -T7, -T8, -T9, -T10, +R](f: js.Function10[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, R]) extends AbstractFunction10[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, R] {
-  override def apply(arg1: T1, arg2: T2, arg3: T3, arg4: T4, arg5: T5, arg6: T6, arg7: T7, arg8: T8, arg9: T9, arg10: T10): R = f(arg1, arg2, arg3, arg4, arg5, arg6, arg7, arg8, arg9, arg10)
-}
+sealed abstract class AnonFunction10[-T1, -T2, -T3, -T4, -T5, -T6, -T7, -T8, -T9, -T10, +R] extends AbstractFunction10[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, R]
 
 @deprecated("used by the codegen before 1.19", since = "1.19.0")
-@inline
-final class AnonFunction11[-T1, -T2, -T3, -T4, -T5, -T6, -T7, -T8, -T9, -T10, -T11, +R](f: js.Function11[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, R]) extends AbstractFunction11[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, R] {
-  override def apply(arg1: T1, arg2: T2, arg3: T3, arg4: T4, arg5: T5, arg6: T6, arg7: T7, arg8: T8, arg9: T9, arg10: T10, arg11: T11): R = f(arg1, arg2, arg3, arg4, arg5, arg6, arg7, arg8, arg9, arg10, arg11)
-}
+sealed abstract class AnonFunction11[-T1, -T2, -T3, -T4, -T5, -T6, -T7, -T8, -T9, -T10, -T11, +R] extends AbstractFunction11[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, R]
 
 @deprecated("used by the codegen before 1.19", since = "1.19.0")
-@inline
-final class AnonFunction12[-T1, -T2, -T3, -T4, -T5, -T6, -T7, -T8, -T9, -T10, -T11, -T12, +R](f: js.Function12[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, R]) extends AbstractFunction12[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, R] {
-  override def apply(arg1: T1, arg2: T2, arg3: T3, arg4: T4, arg5: T5, arg6: T6, arg7: T7, arg8: T8, arg9: T9, arg10: T10, arg11: T11, arg12: T12): R = f(arg1, arg2, arg3, arg4, arg5, arg6, arg7, arg8, arg9, arg10, arg11, arg12)
-}
+sealed abstract class AnonFunction12[-T1, -T2, -T3, -T4, -T5, -T6, -T7, -T8, -T9, -T10, -T11, -T12, +R] extends AbstractFunction12[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, R]
 
 @deprecated("used by the codegen before 1.19", since = "1.19.0")
-@inline
-final class AnonFunction13[-T1, -T2, -T3, -T4, -T5, -T6, -T7, -T8, -T9, -T10, -T11, -T12, -T13, +R](f: js.Function13[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, R]) extends AbstractFunction13[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, R] {
-  override def apply(arg1: T1, arg2: T2, arg3: T3, arg4: T4, arg5: T5, arg6: T6, arg7: T7, arg8: T8, arg9: T9, arg10: T10, arg11: T11, arg12: T12, arg13: T13): R = f(arg1, arg2, arg3, arg4, arg5, arg6, arg7, arg8, arg9, arg10, arg11, arg12, arg13)
-}
+sealed abstract class AnonFunction13[-T1, -T2, -T3, -T4, -T5, -T6, -T7, -T8, -T9, -T10, -T11, -T12, -T13, +R] extends AbstractFunction13[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, R]
 
 @deprecated("used by the codegen before 1.19", since = "1.19.0")
-@inline
-final class AnonFunction14[-T1, -T2, -T3, -T4, -T5, -T6, -T7, -T8, -T9, -T10, -T11, -T12, -T13, -T14, +R](f: js.Function14[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, R]) extends AbstractFunction14[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, R] {
-  override def apply(arg1: T1, arg2: T2, arg3: T3, arg4: T4, arg5: T5, arg6: T6, arg7: T7, arg8: T8, arg9: T9, arg10: T10, arg11: T11, arg12: T12, arg13: T13, arg14: T14): R = f(arg1, arg2, arg3, arg4, arg5, arg6, arg7, arg8, arg9, arg10, arg11, arg12, arg13, arg14)
-}
+sealed abstract class AnonFunction14[-T1, -T2, -T3, -T4, -T5, -T6, -T7, -T8, -T9, -T10, -T11, -T12, -T13, -T14, +R] extends AbstractFunction14[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, R]
 
 @deprecated("used by the codegen before 1.19", since = "1.19.0")
-@inline
-final class AnonFunction15[-T1, -T2, -T3, -T4, -T5, -T6, -T7, -T8, -T9, -T10, -T11, -T12, -T13, -T14, -T15, +R](f: js.Function15[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, R]) extends AbstractFunction15[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, R] {
-  override def apply(arg1: T1, arg2: T2, arg3: T3, arg4: T4, arg5: T5, arg6: T6, arg7: T7, arg8: T8, arg9: T9, arg10: T10, arg11: T11, arg12: T12, arg13: T13, arg14: T14, arg15: T15): R = f(arg1, arg2, arg3, arg4, arg5, arg6, arg7, arg8, arg9, arg10, arg11, arg12, arg13, arg14, arg15)
-}
+sealed abstract class AnonFunction15[-T1, -T2, -T3, -T4, -T5, -T6, -T7, -T8, -T9, -T10, -T11, -T12, -T13, -T14, -T15, +R] extends AbstractFunction15[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, R]
 
 @deprecated("used by the codegen before 1.19", since = "1.19.0")
-@inline
-final class AnonFunction16[-T1, -T2, -T3, -T4, -T5, -T6, -T7, -T8, -T9, -T10, -T11, -T12, -T13, -T14, -T15, -T16, +R](f: js.Function16[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, R]) extends AbstractFunction16[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, R] {
-  override def apply(arg1: T1, arg2: T2, arg3: T3, arg4: T4, arg5: T5, arg6: T6, arg7: T7, arg8: T8, arg9: T9, arg10: T10, arg11: T11, arg12: T12, arg13: T13, arg14: T14, arg15: T15, arg16: T16): R = f(arg1, arg2, arg3, arg4, arg5, arg6, arg7, arg8, arg9, arg10, arg11, arg12, arg13, arg14, arg15, arg16)
-}
+sealed abstract class AnonFunction16[-T1, -T2, -T3, -T4, -T5, -T6, -T7, -T8, -T9, -T10, -T11, -T12, -T13, -T14, -T15, -T16, +R] extends AbstractFunction16[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, R]
 
 @deprecated("used by the codegen before 1.19", since = "1.19.0")
-@inline
-final class AnonFunction17[-T1, -T2, -T3, -T4, -T5, -T6, -T7, -T8, -T9, -T10, -T11, -T12, -T13, -T14, -T15, -T16, -T17, +R](f: js.Function17[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, R]) extends AbstractFunction17[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, R] {
-  override def apply(arg1: T1, arg2: T2, arg3: T3, arg4: T4, arg5: T5, arg6: T6, arg7: T7, arg8: T8, arg9: T9, arg10: T10, arg11: T11, arg12: T12, arg13: T13, arg14: T14, arg15: T15, arg16: T16, arg17: T17): R = f(arg1, arg2, arg3, arg4, arg5, arg6, arg7, arg8, arg9, arg10, arg11, arg12, arg13, arg14, arg15, arg16, arg17)
-}
+sealed abstract class AnonFunction17[-T1, -T2, -T3, -T4, -T5, -T6, -T7, -T8, -T9, -T10, -T11, -T12, -T13, -T14, -T15, -T16, -T17, +R] extends AbstractFunction17[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, R]
 
 @deprecated("used by the codegen before 1.19", since = "1.19.0")
-@inline
-final class AnonFunction18[-T1, -T2, -T3, -T4, -T5, -T6, -T7, -T8, -T9, -T10, -T11, -T12, -T13, -T14, -T15, -T16, -T17, -T18, +R](f: js.Function18[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, T18, R]) extends AbstractFunction18[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, T18, R] {
-  override def apply(arg1: T1, arg2: T2, arg3: T3, arg4: T4, arg5: T5, arg6: T6, arg7: T7, arg8: T8, arg9: T9, arg10: T10, arg11: T11, arg12: T12, arg13: T13, arg14: T14, arg15: T15, arg16: T16, arg17: T17, arg18: T18): R = f(arg1, arg2, arg3, arg4, arg5, arg6, arg7, arg8, arg9, arg10, arg11, arg12, arg13, arg14, arg15, arg16, arg17, arg18)
-}
+sealed abstract class AnonFunction18[-T1, -T2, -T3, -T4, -T5, -T6, -T7, -T8, -T9, -T10, -T11, -T12, -T13, -T14, -T15, -T16, -T17, -T18, +R] extends AbstractFunction18[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, T18, R]
 
 @deprecated("used by the codegen before 1.19", since = "1.19.0")
-@inline
-final class AnonFunction19[-T1, -T2, -T3, -T4, -T5, -T6, -T7, -T8, -T9, -T10, -T11, -T12, -T13, -T14, -T15, -T16, -T17, -T18, -T19, +R](f: js.Function19[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, T18, T19, R]) extends AbstractFunction19[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, T18, T19, R] {
-  override def apply(arg1: T1, arg2: T2, arg3: T3, arg4: T4, arg5: T5, arg6: T6, arg7: T7, arg8: T8, arg9: T9, arg10: T10, arg11: T11, arg12: T12, arg13: T13, arg14: T14, arg15: T15, arg16: T16, arg17: T17, arg18: T18, arg19: T19): R = f(arg1, arg2, arg3, arg4, arg5, arg6, arg7, arg8, arg9, arg10, arg11, arg12, arg13, arg14, arg15, arg16, arg17, arg18, arg19)
-}
+sealed abstract class AnonFunction19[-T1, -T2, -T3, -T4, -T5, -T6, -T7, -T8, -T9, -T10, -T11, -T12, -T13, -T14, -T15, -T16, -T17, -T18, -T19, +R] extends AbstractFunction19[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, T18, T19, R]
 
 @deprecated("used by the codegen before 1.19", since = "1.19.0")
-@inline
-final class AnonFunction20[-T1, -T2, -T3, -T4, -T5, -T6, -T7, -T8, -T9, -T10, -T11, -T12, -T13, -T14, -T15, -T16, -T17, -T18, -T19, -T20, +R](f: js.Function20[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, T18, T19, T20, R]) extends AbstractFunction20[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, T18, T19, T20, R] {
-  override def apply(arg1: T1, arg2: T2, arg3: T3, arg4: T4, arg5: T5, arg6: T6, arg7: T7, arg8: T8, arg9: T9, arg10: T10, arg11: T11, arg12: T12, arg13: T13, arg14: T14, arg15: T15, arg16: T16, arg17: T17, arg18: T18, arg19: T19, arg20: T20): R = f(arg1, arg2, arg3, arg4, arg5, arg6, arg7, arg8, arg9, arg10, arg11, arg12, arg13, arg14, arg15, arg16, arg17, arg18, arg19, arg20)
-}
+sealed abstract class AnonFunction20[-T1, -T2, -T3, -T4, -T5, -T6, -T7, -T8, -T9, -T10, -T11, -T12, -T13, -T14, -T15, -T16, -T17, -T18, -T19, -T20, +R] extends AbstractFunction20[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, T18, T19, T20, R]
 
 @deprecated("used by the codegen before 1.19", since = "1.19.0")
-@inline
-final class AnonFunction21[-T1, -T2, -T3, -T4, -T5, -T6, -T7, -T8, -T9, -T10, -T11, -T12, -T13, -T14, -T15, -T16, -T17, -T18, -T19, -T20, -T21, +R](f: js.Function21[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, T18, T19, T20, T21, R]) extends AbstractFunction21[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, T18, T19, T20, T21, R] {
-  override def apply(arg1: T1, arg2: T2, arg3: T3, arg4: T4, arg5: T5, arg6: T6, arg7: T7, arg8: T8, arg9: T9, arg10: T10, arg11: T11, arg12: T12, arg13: T13, arg14: T14, arg15: T15, arg16: T16, arg17: T17, arg18: T18, arg19: T19, arg20: T20, arg21: T21): R = f(arg1, arg2, arg3, arg4, arg5, arg6, arg7, arg8, arg9, arg10, arg11, arg12, arg13, arg14, arg15, arg16, arg17, arg18, arg19, arg20, arg21)
-}
+sealed abstract class AnonFunction21[-T1, -T2, -T3, -T4, -T5, -T6, -T7, -T8, -T9, -T10, -T11, -T12, -T13, -T14, -T15, -T16, -T17, -T18, -T19, -T20, -T21, +R] extends AbstractFunction21[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, T18, T19, T20, T21, R]
 
 @deprecated("used by the codegen before 1.19", since = "1.19.0")
-@inline
-final class AnonFunction22[-T1, -T2, -T3, -T4, -T5, -T6, -T7, -T8, -T9, -T10, -T11, -T12, -T13, -T14, -T15, -T16, -T17, -T18, -T19, -T20, -T21, -T22, +R](f: js.Function22[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, T18, T19, T20, T21, T22, R]) extends AbstractFunction22[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, T18, T19, T20, T21, T22, R] {
-  override def apply(arg1: T1, arg2: T2, arg3: T3, arg4: T4, arg5: T5, arg6: T6, arg7: T7, arg8: T8, arg9: T9, arg10: T10, arg11: T11, arg12: T12, arg13: T13, arg14: T14, arg15: T15, arg16: T16, arg17: T17, arg18: T18, arg19: T19, arg20: T20, arg21: T21, arg22: T22): R = f(arg1, arg2, arg3, arg4, arg5, arg6, arg7, arg8, arg9, arg10, arg11, arg12, arg13, arg14, arg15, arg16, arg17, arg18, arg19, arg20, arg21, arg22)
-}
+sealed abstract class AnonFunction22[-T1, -T2, -T3, -T4, -T5, -T6, -T7, -T8, -T9, -T10, -T11, -T12, -T13, -T14, -T15, -T16, -T17, -T18, -T19, -T20, -T21, -T22, +R] extends AbstractFunction22[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, T18, T19, T20, T21, T22, R]
 
 // scalastyle:on line.size.limit
diff --git a/project/BinaryIncompatibilities.scala b/project/BinaryIncompatibilities.scala
index b361c1701b..5435860a02 100644
--- a/project/BinaryIncompatibilities.scala
+++ b/project/BinaryIncompatibilities.scala
@@ -64,6 +64,10 @@ object BinaryIncompatibilities {
   )
 
   val Library = Seq(
+    // Changes covered by a deserialization hack (and the code cannot be used on the JVM, such as in macros)
+    ProblemFilters.exclude[AbstractClassProblem]("scala.scalajs.runtime.AnonFunction*"),
+    ProblemFilters.exclude[DirectMissingMethodProblem]("scala.scalajs.runtime.AnonFunction*.this"),
+    ProblemFilters.exclude[DirectMissingMethodProblem]("scala.scalajs.runtime.AnonFunction*.apply"),
   )
 
   val TestInterface = Seq(
diff --git a/sbt-plugin/src/sbt-test/linker/anonfunction-compat/build.sbt b/sbt-plugin/src/sbt-test/linker/anonfunction-compat/build.sbt
new file mode 100644
index 0000000000..4ada232e79
--- /dev/null
+++ b/sbt-plugin/src/sbt-test/linker/anonfunction-compat/build.sbt
@@ -0,0 +1,61 @@
+val scala2Version = "2.12.20"
+
+ThisBuild / version := scalaJSVersion
+ThisBuild / scalaVersion := scala2Version
+
+ThisBuild / scalaJSLinkerConfig ~= { _.withCheckIR(true) }
+
+val ScalaJSVersionBeforeTypedClosures = "1.18.2"
+
+/** In libraryDependencies, replace the dependency whose `name` starts with
+ *  `artifactNamePrefix` by the given `newModuleID`.
+ */
+def replaceDependency(artifactNamePrefix: String, newModuleID: ModuleID): Setting[_] = {
+  libraryDependencies := {
+    libraryDependencies.value.map { dep =>
+      if (dep.name.startsWith(artifactNamePrefix))
+        newModuleID
+      else
+        dep
+    }
+  }
+}
+
+def scalaJSCompilerPlugin(v: String): ModuleID =
+  compilerPlugin("org.scala-js" % "scalajs-compiler" % v cross CrossVersion.full)
+
+lazy val scala2OldCompilerOldLib = project.in(file("scala2-old-compiler-old-lib"))
+  .enablePlugins(ScalaJSPlugin)
+  .settings(
+    replaceDependency("scalajs-compiler",
+        scalaJSCompilerPlugin(ScalaJSVersionBeforeTypedClosures)),
+    replaceDependency("scalajs-library",
+        "org.scala-js" %% "scalajs-library" % ScalaJSVersionBeforeTypedClosures),
+    replaceDependency("scalajs-scalalib",
+        "org.scala-js" %% "scalajs-scalalib" % s"$scala2Version+$ScalaJSVersionBeforeTypedClosures"),
+    scalaJSUseMainModuleInitializer := true
+  )
+
+lazy val scala2OldCompilerNewLib = project.in(file("scala2-old-compiler-new-lib"))
+  .enablePlugins(ScalaJSPlugin)
+  .settings(
+    replaceDependency("scalajs-compiler",
+        scalaJSCompilerPlugin(ScalaJSVersionBeforeTypedClosures)),
+    scalaJSUseMainModuleInitializer := true
+  )
+
+lazy val scala3OldCompilerOldLib = project.in(file("scala3-old-compiler-old-lib"))
+  .enablePlugins(ScalaJSPlugin)
+  .settings(
+    scalaVersion := "3.6.3",
+    replaceDependency("scalajs-library",
+        "org.scala-js" % "scalajs-library_2.13" % ScalaJSVersionBeforeTypedClosures),
+    scalaJSUseMainModuleInitializer := true
+  )
+
+lazy val scala3OldCompilerNewLib = project.in(file("scala3-old-compiler-new-lib"))
+  .enablePlugins(ScalaJSPlugin)
+  .settings(
+    scalaVersion := "3.6.3",
+    scalaJSUseMainModuleInitializer := true
+  )
diff --git a/sbt-plugin/src/sbt-test/linker/anonfunction-compat/project/build.properties b/sbt-plugin/src/sbt-test/linker/anonfunction-compat/project/build.properties
new file mode 100644
index 0000000000..40b3b8e7b6
--- /dev/null
+++ b/sbt-plugin/src/sbt-test/linker/anonfunction-compat/project/build.properties
@@ -0,0 +1 @@
+sbt.version=1.9.0
diff --git a/sbt-plugin/src/sbt-test/linker/anonfunction-compat/project/build.sbt b/sbt-plugin/src/sbt-test/linker/anonfunction-compat/project/build.sbt
new file mode 100644
index 0000000000..4465f18281
--- /dev/null
+++ b/sbt-plugin/src/sbt-test/linker/anonfunction-compat/project/build.sbt
@@ -0,0 +1,5 @@
+val scalaJSVersion = sys.props("plugin.version")
+
+addSbtPlugin("org.scala-js" % "sbt-scalajs" % scalaJSVersion)
+
+libraryDependencies += "org.scala-js" %% "scalajs-linker" % scalaJSVersion
diff --git a/sbt-plugin/src/sbt-test/linker/anonfunction-compat/scala2-old-compiler-new-lib/Main.scala b/sbt-plugin/src/sbt-test/linker/anonfunction-compat/scala2-old-compiler-new-lib/Main.scala
new file mode 100644
index 0000000000..358d46f21b
--- /dev/null
+++ b/sbt-plugin/src/sbt-test/linker/anonfunction-compat/scala2-old-compiler-new-lib/Main.scala
@@ -0,0 +1,9 @@
+package org.scalajs.sbtplugin.test
+
+object Main {
+  def main(args: Array[String]): Unit = {
+    val xs = List(2, 3, 5, 7, 11)
+    xs.foreach(println(_))
+    xs.map(i => i * 2).foreach(println(_))
+  }
+}
diff --git a/sbt-plugin/src/sbt-test/linker/anonfunction-compat/scala2-old-compiler-old-lib/Main.scala b/sbt-plugin/src/sbt-test/linker/anonfunction-compat/scala2-old-compiler-old-lib/Main.scala
new file mode 100644
index 0000000000..358d46f21b
--- /dev/null
+++ b/sbt-plugin/src/sbt-test/linker/anonfunction-compat/scala2-old-compiler-old-lib/Main.scala
@@ -0,0 +1,9 @@
+package org.scalajs.sbtplugin.test
+
+object Main {
+  def main(args: Array[String]): Unit = {
+    val xs = List(2, 3, 5, 7, 11)
+    xs.foreach(println(_))
+    xs.map(i => i * 2).foreach(println(_))
+  }
+}
diff --git a/sbt-plugin/src/sbt-test/linker/anonfunction-compat/scala3-old-compiler-new-lib/Main.scala b/sbt-plugin/src/sbt-test/linker/anonfunction-compat/scala3-old-compiler-new-lib/Main.scala
new file mode 100644
index 0000000000..ca1337ac22
--- /dev/null
+++ b/sbt-plugin/src/sbt-test/linker/anonfunction-compat/scala3-old-compiler-new-lib/Main.scala
@@ -0,0 +1,18 @@
+package org.scalajs.sbtplugin.test
+
+object Main {
+  def foo(f: (Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int,
+      Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int) => Int): Int = {
+    f(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25)
+  }
+
+  def main(args: Array[String]): Unit = {
+    val xs = List(2, 3, 5, 7, 11)
+    xs.foreach(println(_))
+    xs.map(i => i * 2).foreach(println(_))
+
+    println(foo { (x1, x2, x3, x4, x5, x6, x7, x8, x9, x10, x11, x12, x13, x14, x15, x16, x17, x18, x19, x20, x21, x22, x23, x24, x25) =>
+      x1 + x2 + x3 + x4 + x5 + x6 + x7 + x8 + x9 + x10 + x11 + x12 + x13 + x14 + x15 + x16 + x17 + x18 + x19 + x20 + x21 + x22 + x23 + x24 + x25
+    })
+  }
+}
diff --git a/sbt-plugin/src/sbt-test/linker/anonfunction-compat/scala3-old-compiler-old-lib/Main.scala b/sbt-plugin/src/sbt-test/linker/anonfunction-compat/scala3-old-compiler-old-lib/Main.scala
new file mode 100644
index 0000000000..ca1337ac22
--- /dev/null
+++ b/sbt-plugin/src/sbt-test/linker/anonfunction-compat/scala3-old-compiler-old-lib/Main.scala
@@ -0,0 +1,18 @@
+package org.scalajs.sbtplugin.test
+
+object Main {
+  def foo(f: (Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int,
+      Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int) => Int): Int = {
+    f(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25)
+  }
+
+  def main(args: Array[String]): Unit = {
+    val xs = List(2, 3, 5, 7, 11)
+    xs.foreach(println(_))
+    xs.map(i => i * 2).foreach(println(_))
+
+    println(foo { (x1, x2, x3, x4, x5, x6, x7, x8, x9, x10, x11, x12, x13, x14, x15, x16, x17, x18, x19, x20, x21, x22, x23, x24, x25) =>
+      x1 + x2 + x3 + x4 + x5 + x6 + x7 + x8 + x9 + x10 + x11 + x12 + x13 + x14 + x15 + x16 + x17 + x18 + x19 + x20 + x21 + x22 + x23 + x24 + x25
+    })
+  }
+}
diff --git a/sbt-plugin/src/sbt-test/linker/anonfunction-compat/test b/sbt-plugin/src/sbt-test/linker/anonfunction-compat/test
new file mode 100644
index 0000000000..2621440f32
--- /dev/null
+++ b/sbt-plugin/src/sbt-test/linker/anonfunction-compat/test
@@ -0,0 +1,25 @@
+> show scala2OldCompilerOldLib/libraryDependencies
+> show scala2OldCompilerOldLib/Compile/fullClasspath
+> scala2OldCompilerOldLib/scalajsp scala.scalajs.runtime.AnonFunction2
+> scala2OldCompilerOldLib/scalajsp org.scalajs.sbtplugin.test.Main$
+> scala2OldCompilerOldLib/run
+
+> show scala2OldCompilerNewLib/libraryDependencies
+> show scala2OldCompilerNewLib/Compile/fullClasspath
+> scala2OldCompilerNewLib/scalajsp scala.scalajs.runtime.AnonFunction2
+> scala2OldCompilerNewLib/scalajsp org.scalajs.sbtplugin.test.Main$
+> scala2OldCompilerNewLib/run
+
+> show scala3OldCompilerOldLib/libraryDependencies
+> show scala3OldCompilerOldLib/Compile/fullClasspath
+> scala3OldCompilerOldLib/scalajsp scala.scalajs.runtime.AnonFunction2
+> scala3OldCompilerOldLib/scalajsp scala.scalajs.runtime.AnonFunctionXXL
+> scala3OldCompilerOldLib/scalajsp org.scalajs.sbtplugin.test.Main$
+> scala3OldCompilerOldLib/run
+
+> show scala3OldCompilerNewLib/libraryDependencies
+> show scala3OldCompilerNewLib/Compile/fullClasspath
+> scala3OldCompilerNewLib/scalajsp scala.scalajs.runtime.AnonFunction2
+> scala3OldCompilerNewLib/scalajsp scala.scalajs.runtime.AnonFunctionXXL
+> scala3OldCompilerNewLib/scalajsp org.scalajs.sbtplugin.test.Main$
+> scala3OldCompilerNewLib/run

From 151d3d67ed32c5e6d3753321fa020988d04a30f1 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Sun, 20 Apr 2025 17:30:16 +0200
Subject: [PATCH 279/298] Version 1.19.0.

---
 ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala b/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala
index 03bf83efcd..7ad9ee3876 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala
@@ -17,8 +17,8 @@ import java.util.concurrent.ConcurrentHashMap
 import scala.util.matching.Regex
 
 object ScalaJSVersions extends VersionChecks(
-    current = "1.19.0-SNAPSHOT",
-    binaryEmitted = "1.19-SNAPSHOT"
+    current = "1.19.0",
+    binaryEmitted = "1.19"
 )
 
 /** Helper class to allow for testing of logic. */

From b53a090206eb72be2c94893394297503106d0f04 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Mon, 21 Apr 2025 11:41:44 +0200
Subject: [PATCH 280/298] Towards 1.19.1.

---
 .../org/scalajs/ir/ScalaJSVersions.scala      |  2 +-
 project/BinaryIncompatibilities.scala         | 48 -------------------
 project/Build.scala                           |  2 +-
 3 files changed, 2 insertions(+), 50 deletions(-)

diff --git a/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala b/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala
index 7ad9ee3876..4de34d7f0b 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala
@@ -17,7 +17,7 @@ import java.util.concurrent.ConcurrentHashMap
 import scala.util.matching.Regex
 
 object ScalaJSVersions extends VersionChecks(
-    current = "1.19.0",
+    current = "1.19.1-SNAPSHOT",
     binaryEmitted = "1.19"
 )
 
diff --git a/project/BinaryIncompatibilities.scala b/project/BinaryIncompatibilities.scala
index 5435860a02..4713fe6bf8 100644
--- a/project/BinaryIncompatibilities.scala
+++ b/project/BinaryIncompatibilities.scala
@@ -5,56 +5,12 @@ import com.typesafe.tools.mima.core.ProblemFilters._
 
 object BinaryIncompatibilities {
   val IR = Seq(
-    // !!! Breaking, OK in minor release
-    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Names.*Class"),
-    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Names.ClassInitializerName"),
-    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Names.DefaultModuleID"),
-    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Names.HijackedClasses"),
-    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Names.NoArgConstructorName"),
-    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Names.ObjectArgConstructorName"),
-    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Names.StaticInitializerName"),
-    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Types.BoxedClassToPrimType"),
-    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Types.PrimTypeToBoxedClass"),
-
-    // !!! Breaking, OK in minor release
-    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.InvalidIRException.tree"),
-    ProblemFilters.exclude[Problem]("org.scalajs.ir.Trees#Closure.*"),
-
-    // !!! Breaking, PrimRef is not a case class anymore
-    ProblemFilters.exclude[MissingTypesProblem]("org.scalajs.ir.Types$PrimRef"),
-    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Types#PrimRef.canEqual"),
-    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Types#PrimRef.productArity"),
-    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Types#PrimRef.productElement"),
-    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Types#PrimRef.productElementName"),
-    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Types#PrimRef.productElementNames"),
-    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Types#PrimRef.productIterator"),
-    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Types#PrimRef.productPrefix"),
-    ProblemFilters.exclude[IncompatibleResultTypeProblem]("org.scalajs.ir.Types#PrimRef.unapply"),
-
-    // !!! Breaking I guess ... we used to leak public things out of a `case class` with a private[ir] constructor
-    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Types#PrimRef.this"),
-    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Types#PrimRef.apply"),
-    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Types#PrimRef.copy"),
-    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Types#PrimRef.copy$default$1"),
-    ProblemFilters.exclude[MissingTypesProblem]("org.scalajs.ir.Types$PrimRef$"),
-
-    // constructor of a sealed abstract class, not an issue
-    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Types#PrimTypeWithRef.this"),
-
-    // private, not an issue
-    ProblemFilters.exclude[MissingClassProblem]("org.scalajs.ir.Serializers$Deserializer$BodyHack5Transformer$"),
-    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.ir.Serializers#Hacks.use*"),
   )
 
   val Linker = Seq(
-    // !!! Breaking, OK in minor release
-    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.linker.standard.LinkedClass.this"),
-    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.linker.standard.LinkedTopLevelExport.this"),
   )
 
   val LinkerInterface = Seq(
-    // private, not an issue
-    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.linker.interface.Semantics.this"),
   )
 
   val SbtPlugin = Seq(
@@ -64,10 +20,6 @@ object BinaryIncompatibilities {
   )
 
   val Library = Seq(
-    // Changes covered by a deserialization hack (and the code cannot be used on the JVM, such as in macros)
-    ProblemFilters.exclude[AbstractClassProblem]("scala.scalajs.runtime.AnonFunction*"),
-    ProblemFilters.exclude[DirectMissingMethodProblem]("scala.scalajs.runtime.AnonFunction*.this"),
-    ProblemFilters.exclude[DirectMissingMethodProblem]("scala.scalajs.runtime.AnonFunction*.apply"),
   )
 
   val TestInterface = Seq(
diff --git a/project/Build.scala b/project/Build.scala
index eb8b6b9f2f..80bfe9792c 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -396,7 +396,7 @@ object Build {
       "1.3.0", "1.3.1", "1.4.0", "1.5.0", "1.5.1", "1.6.0", "1.7.0", "1.7.1",
       "1.8.0", "1.9.0", "1.10.0", "1.10.1", "1.11.0", "1.12.0", "1.13.0",
       "1.13.1", "1.13.2", "1.14.0", "1.15.0", "1.16.0", "1.17.0", "1.18.0",
-      "1.18.1", "1.18.2")
+      "1.18.1", "1.18.2", "1.19.0")
   val previousVersion = previousVersions.last
 
   val previousBinaryCrossVersion = CrossVersion.binaryWith("sjs1_", "")

From 1e6540a60cc3f1bf7737c3ff1318ae10e8b9b026 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Mon, 28 Apr 2025 20:04:28 +0200
Subject: [PATCH 281/298] Fix #5159: Register static module dependency on used
 lambda classes.

When we use a lambda class, we implicitly instantiate it. That
constitutes a static dependency, which we previously failed to
register.
---
 Jenkinsfile                                                  | 5 +++++
 .../main/scala/org/scalajs/linker/analyzer/Analyzer.scala    | 1 +
 2 files changed, 6 insertions(+)

diff --git a/Jenkinsfile b/Jenkinsfile
index 165dec8254..c1a4c70069 100644
--- a/Jenkinsfile
+++ b/Jenkinsfile
@@ -263,6 +263,11 @@ def Tasks = [
         'set scalaJSLinkerConfig in $testSuite.v$v ~= (_.withModuleSplitStyle(ModuleSplitStyle.SmallestModules))' \
         'set scalaJSLinkerConfig in $testSuite.v$v ~= (_.withModuleKind(ModuleKind.ESModule))' \
         $testSuite$v/test &&
+    sbtretry ++$scala 'set Global/enableMinifyEverywhere := $testMinify' \
+        'set scalaJSLinkerConfig in $testSuite.v$v ~= (_.withModuleSplitStyle(ModuleSplitStyle.SmallestModules))' \
+        'set scalaJSLinkerConfig in $testSuite.v$v ~= (_.withModuleKind(ModuleKind.ESModule))' \
+        'set scalaJSLinkerConfig in $testSuite.v$v ~= (_.withOptimizer(false))' \
+        $testSuite$v/test &&
     sbtretry ++$scala 'set Global/enableMinifyEverywhere := $testMinify' \
         'set scalaJSLinkerConfig in $testSuite.v$v ~= (_.withModuleSplitStyle(ModuleSplitStyle.SmallModulesFor(List("org.scalajs.testsuite"))))' \
         'set scalaJSLinkerConfig in $testSuite.v$v ~= (_.withModuleKind(ModuleKind.ESModule))' \
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala
index 9a80ac96a2..2379ca00c6 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala
@@ -1488,6 +1488,7 @@ private class AnalyzerRun(config: CommonPhaseConfig, initial: Boolean,
         lookupOrSynthesizeClass(className, SyntheticClassKind.Lambda(descriptor)) { lambdaClassInfo =>
           lambdaClassInfo.instantiated()
           lambdaClassInfo.callMethodStatically(MemberNamespace.Constructor, ctorName)
+          moduleUnit.addStaticDependency(lambdaClassInfo.className)
         }
       }
     }

From fd90409ff6bee7702b9a23bc540df4ef1d875d75 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Sun, 4 May 2025 17:46:18 +0200
Subject: [PATCH 282/298] Reorganize LinkTimeProperties.

* Move it to `frontend`.
* Make it public.
* Move the logic of `validate` and `transformLinkTimeProperty` to
  their respective call sites.
* Construct them from a CoreSpec, rather than being contained by CoreSpec.

These changes better isolate the data (`LinkTimeProperties`) from the
transformations we apply to that data (the logic in `Analyzer` and `Desugarer`).
---
 .../scalajs/linker/analyzer/Analyzer.scala    | 13 +++--
 .../scalajs/linker/frontend/Desugarer.scala   | 19 +++++--
 .../LinkTimeProperties.scala                  | 52 ++++++++-----------
 .../scalajs/linker/standard/CoreSpec.scala    |  3 --
 project/BinaryIncompatibilities.scala         |  3 ++
 5 files changed, 50 insertions(+), 40 deletions(-)
 rename linker/shared/src/main/scala/org/scalajs/linker/{standard => frontend}/LinkTimeProperties.scala (50%)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala
index 2379ca00c6..22d3752fd4 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala
@@ -31,7 +31,7 @@ import org.scalajs.ir.WellKnownNames._
 
 import org.scalajs.linker._
 import org.scalajs.linker.checker.CheckingPhase
-import org.scalajs.linker.frontend.{IRLoader, LambdaSynthesizer, SyntheticClassKind}
+import org.scalajs.linker.frontend.{IRLoader, LambdaSynthesizer, LinkTimeProperties, SyntheticClassKind}
 import org.scalajs.linker.interface._
 import org.scalajs.linker.interface.unstable.ModuleInitializerImpl
 import org.scalajs.linker.standard._
@@ -47,6 +47,8 @@ import Infos.{NamespacedMethodName, ReachabilityInfo, ReachabilityInfoInClass}
 final class Analyzer(config: CommonPhaseConfig, initial: Boolean,
     checkIRFor: Option[CheckingPhase], failOnError: Boolean, irLoader: IRLoader) {
 
+  private val linkTimeProperties = LinkTimeProperties.fromCoreSpec(config.coreSpec)
+
   private val infoLoader: InfoLoader =
     new InfoLoader(irLoader, checkIRFor)
 
@@ -55,7 +57,7 @@ final class Analyzer(config: CommonPhaseConfig, initial: Boolean,
 
     infoLoader.update(logger)
 
-    val run = new AnalyzerRun(config, initial, infoLoader)(
+    val run = new AnalyzerRun(config, initial, infoLoader, linkTimeProperties)(
         adjustExecutionContextForParallelism(ec, config.parallel))
 
     run
@@ -99,7 +101,10 @@ final class Analyzer(config: CommonPhaseConfig, initial: Boolean,
 }
 
 private class AnalyzerRun(config: CommonPhaseConfig, initial: Boolean,
-    infoLoader: InfoLoader)(implicit ec: ExecutionContext) extends Analysis {
+    infoLoader: InfoLoader, linkTimeProperties: LinkTimeProperties)(
+    implicit ec: ExecutionContext)
+    extends Analysis {
+
   import AnalyzerRun._
 
   private val allowAddingSyntheticMethods = initial
@@ -1539,7 +1544,7 @@ private class AnalyzerRun(config: CommonPhaseConfig, initial: Boolean,
 
     if (data.referencedLinkTimeProperties.nonEmpty) {
       for ((name, tpe) <- data.referencedLinkTimeProperties) {
-        if (!config.coreSpec.linkTimeProperties.validate(name, tpe)) {
+        if (!linkTimeProperties.get(name).exists(_.tpe == tpe)) {
           _errors ::= InvalidLinkTimeProperty(name, tpe, from)
         }
       }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/Desugarer.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/Desugarer.scala
index 44e2f66d09..57f8eeb366 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/Desugarer.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/Desugarer.scala
@@ -28,7 +28,9 @@ import org.scalajs.ir.{Position, Version}
 final class Desugarer(config: CommonPhaseConfig, checkIR: Boolean) {
   import Desugarer._
 
-  private val desugarTransformer = new DesugarTransformer(config.coreSpec)
+  private val linkTimeProperties = LinkTimeProperties.fromCoreSpec(config.coreSpec)
+
+  private val desugarTransformer = new DesugarTransformer(linkTimeProperties)
 
   def desugar(unit: LinkingUnit, logger: Logger): LinkingUnit = {
     val result = logger.time("Desugarer: Desugar") {
@@ -118,7 +120,7 @@ final class Desugarer(config: CommonPhaseConfig, checkIR: Boolean) {
 
 private[linker] object Desugarer {
 
-  private final class DesugarTransformer(coreSpec: CoreSpec)
+  private final class DesugarTransformer(linkTimeProperties: LinkTimeProperties)
       extends ClassTransformer {
 
     /* Cache the names generated for lambda classes because computing their
@@ -135,8 +137,17 @@ private[linker] object Desugarer {
 
     override def transform(tree: Tree): Tree = {
       tree match {
-        case prop: LinkTimeProperty =>
-          coreSpec.linkTimeProperties.transformLinkTimeProperty(prop)
+        case LinkTimeProperty(name) =>
+          implicit val pos = tree.pos
+          val value = linkTimeProperties.get(name).getOrElse {
+            throw new IllegalArgumentException(
+                s"link time property not found: '$name' of type ${tree.tpe}")
+          }
+          value match {
+            case LinkTimeProperties.LinkTimeBoolean(value) => BooleanLiteral(value)
+            case LinkTimeProperties.LinkTimeInt(value)     => IntLiteral(value)
+            case LinkTimeProperties.LinkTimeString(value)  => StringLiteral(value)
+          }
 
         case NewLambda(descriptor, fun) =>
           implicit val pos = tree.pos
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/standard/LinkTimeProperties.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/LinkTimeProperties.scala
similarity index 50%
rename from linker/shared/src/main/scala/org/scalajs/linker/standard/LinkTimeProperties.scala
rename to linker/shared/src/main/scala/org/scalajs/linker/frontend/LinkTimeProperties.scala
index 875196c736..d2c12c67d0 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/standard/LinkTimeProperties.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/LinkTimeProperties.scala
@@ -10,15 +10,16 @@
  * additional information regarding copyright ownership.
  */
 
-package org.scalajs.linker.standard
+package org.scalajs.linker.frontend
 
-import org.scalajs.ir.{Types => jstpe, Trees => js}
 import org.scalajs.ir.Trees.LinkTimeProperty._
+import org.scalajs.ir.Types._
 import org.scalajs.ir.ScalaJSVersions
-import org.scalajs.ir.Position.NoPosition
-import org.scalajs.linker.interface.{Semantics, ESFeatures}
 
-private[linker] final class LinkTimeProperties (
+import org.scalajs.linker.interface.{ESVersion => _, _}
+import org.scalajs.linker.standard.CoreSpec
+
+final class LinkTimeProperties private (
   semantics: Semantics,
   esFeatures: ESFeatures,
   targetIsWebAssembly: Boolean
@@ -38,31 +39,24 @@ private[linker] final class LinkTimeProperties (
       LinkTimeString(ScalaJSVersions.current)
   )
 
-  def validate(name: String, tpe: jstpe.Type): Boolean = {
-    linkTimeProperties.get(name).exists {
-      case _: LinkTimeBoolean => tpe == jstpe.BooleanType
-      case _: LinkTimeInt     => tpe == jstpe.IntType
-      case _: LinkTimeString  => tpe == jstpe.StringType
-    }
-  }
+  def get(name: String): Option[LinkTimeValue] =
+    linkTimeProperties.get(name)
+}
+
+object LinkTimeProperties {
+  sealed abstract class LinkTimeValue(val tpe: Type)
 
-  def transformLinkTimeProperty(prop: js.LinkTimeProperty): js.Literal = {
-    val value = linkTimeProperties.getOrElse(prop.name,
-        throw new IllegalArgumentException(s"link time property not found: '${prop.name}' of type ${prop.tpe}"))
-    value match {
-      case LinkTimeBoolean(value) =>
-        js.BooleanLiteral(value)(prop.pos)
-      case LinkTimeInt(value) =>
-        js.IntLiteral(value)(prop.pos)
-      case LinkTimeString(value) =>
-        js.StringLiteral(value)(prop.pos)
-    }
+  final case class LinkTimeInt(value: Int) extends LinkTimeValue(IntType)
+
+  final case class LinkTimeBoolean(value: Boolean) extends LinkTimeValue(BooleanType)
+
+  final case class LinkTimeString(value: String) extends LinkTimeValue(StringType) {
+    // Being extra careful
+    require(value != null, "LinkTimeString requires a non-null value.")
   }
-}
 
-private[linker] object LinkTimeProperties {
-  sealed abstract class LinkTimeValue
-  final case class LinkTimeInt(value: Int) extends LinkTimeValue
-  final case class LinkTimeBoolean(value: Boolean) extends LinkTimeValue
-  final case class LinkTimeString(value: String) extends LinkTimeValue
+  def fromCoreSpec(coreSpec: CoreSpec): LinkTimeProperties = {
+    new LinkTimeProperties(coreSpec.semantics, coreSpec.esFeatures,
+        coreSpec.targetIsWebAssembly)
+  }
 }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/standard/CoreSpec.scala b/linker/shared/src/main/scala/org/scalajs/linker/standard/CoreSpec.scala
index e5e285268f..3c4c979adc 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/standard/CoreSpec.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/standard/CoreSpec.scala
@@ -96,9 +96,6 @@ final class CoreSpec private (
       targetIsWebAssembly
     )
   }
-
-  private[linker] lazy val linkTimeProperties = new LinkTimeProperties(
-      semantics, esFeatures, targetIsWebAssembly)
 }
 
 private[linker] object CoreSpec {
diff --git a/project/BinaryIncompatibilities.scala b/project/BinaryIncompatibilities.scala
index 4713fe6bf8..2e94162e72 100644
--- a/project/BinaryIncompatibilities.scala
+++ b/project/BinaryIncompatibilities.scala
@@ -8,6 +8,9 @@ object BinaryIncompatibilities {
   )
 
   val Linker = Seq(
+    // private[linker], not an issue
+    ProblemFilters.exclude[DirectMissingMethodProblem]("org.scalajs.linker.standard.CoreSpec.linkTimeProperties"),
+    ProblemFilters.exclude[MissingClassProblem]("org.scalajs.linker.standard.LinkTimeProperties*"),
   )
 
   val LinkerInterface = Seq(

From 4913fc9661fc39681221412a94577f57d30ebe1d Mon Sep 17 00:00:00 2001
From: Rikito Taniguchi <rikiriki1238@gmail.com>
Date: Mon, 5 May 2025 15:51:05 +0900
Subject: [PATCH 283/298] Check index on bounds in ArrayList addAll and
 removeRange.

removeRange should throws an `IndexOutOfBoundsException` if
fromIndex or toIndex is out of range. addAll should also throw
when the index is not within bounds.
---
 .../src/main/scala/java/util/ArrayList.scala  |  7 +-
 .../javalib/util/ArrayListTest.scala          | 66 +++++++++++++++++++
 .../testsuite/javalib/util/ListTest.scala     | 13 ++++
 3 files changed, 84 insertions(+), 2 deletions(-)

diff --git a/javalib/src/main/scala/java/util/ArrayList.scala b/javalib/src/main/scala/java/util/ArrayList.scala
index 68b9705f62..62de296cab 100644
--- a/javalib/src/main/scala/java/util/ArrayList.scala
+++ b/javalib/src/main/scala/java/util/ArrayList.scala
@@ -81,13 +81,16 @@ class ArrayList[E] private (private[ArrayList] val inner: js.Array[E])
   override def addAll(index: Int, c: Collection[_ <: E]): Boolean = {
     c match {
       case other: ArrayList[_] =>
+        checkIndexOnBounds(index)
         inner.splice(index, 0, other.inner.toSeq: _*)
         other.size() > 0
       case _ => super.addAll(index, c)
     }
   }
 
-  override protected def removeRange(fromIndex: Int, toIndex: Int): Unit =
+  override protected def removeRange(fromIndex: Int, toIndex: Int): Unit = {
+    if (fromIndex < 0 || toIndex > size() || toIndex < fromIndex)
+      throw new IndexOutOfBoundsException()
     inner.splice(fromIndex, toIndex - fromIndex)
-
+  }
 }
diff --git a/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/util/ArrayListTest.scala b/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/util/ArrayListTest.scala
index 9b9812f93c..25d9bbb7de 100644
--- a/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/util/ArrayListTest.scala
+++ b/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/util/ArrayListTest.scala
@@ -13,6 +13,9 @@
 package org.scalajs.testsuite.javalib.util
 
 import org.junit.Test
+import org.junit.Assert._
+
+import org.scalajs.testsuite.utils.AssertThrows.assertThrows
 
 import java.{util => ju}
 
@@ -29,6 +32,60 @@ class ArrayListTest extends AbstractListTest {
     al.ensureCapacity(34)
     al.trimToSize()
   }
+
+  @Test def removeRangeFromIdenticalIndices(): Unit = {
+    val al = new ArrayListRangeRemovable[Int](
+        TrivialImmutableCollection(-175, 24, 7, 44))
+    val expected = Array[Int](-175, 24, 7, 44)
+    al.removeRangeList(0, 0)
+    assertTrue(al.toArray().sameElements(expected))
+    al.removeRangeList(1, 1)
+    assertTrue(al.toArray().sameElements(expected))
+    al.removeRangeList(al.size, al.size) // no op
+    assertTrue(al.toArray().sameElements(expected))
+  }
+
+  @Test def removeRangeFromToInvalidIndices(): Unit = {
+    val al = new ArrayListRangeRemovable[Int](
+        TrivialImmutableCollection(175, -24, -7, -44))
+
+    assertThrows(
+      classOf[java.lang.IndexOutOfBoundsException],
+      al.removeRangeList(-1, 2)
+    ) // fromIndex < 0
+    assertThrows(
+      classOf[java.lang.IndexOutOfBoundsException],
+      al.removeRangeList(0, al.size + 1)
+    ) // toIndex > size
+    assertThrows(
+      classOf[java.lang.IndexOutOfBoundsException],
+      al.removeRangeList(2, -1)
+    ) // toIndex < fromIndex
+  }
+
+  @Test def removeRangeFromToFirstTwoElements(): Unit = {
+    val al = new ArrayListRangeRemovable[Int](
+        TrivialImmutableCollection(284, -27, 995, 500, 267, 904))
+    val expected = Array[Int](995, 500, 267, 904)
+    al.removeRangeList(0, 2)
+    assertTrue(al.toArray().sameElements(expected))
+  }
+
+  @Test def removeRangeFromToTwoElementsFromMiddle(): Unit = {
+    val al = new ArrayListRangeRemovable[Int](
+        TrivialImmutableCollection(7, 9, -1, 20))
+    val expected = Array[Int](7, 20)
+    al.removeRangeList(1, 3)
+    assertTrue(al.toArray().sameElements(expected))
+  }
+
+  @Test def removeRangeFromToLastTwoElementsAtTail(): Unit = {
+    val al = new ArrayListRangeRemovable[Int](
+        TrivialImmutableCollection(50, 72, 650, 12, 7, 28, 3))
+    val expected = Array[Int](50, 72, 650, 12, 7)
+    al.removeRangeList(al.size - 2, al.size)
+    assertTrue(al.toArray().sameElements(expected))
+  }
 }
 
 class ArrayListFactory extends AbstractListFactory {
@@ -37,4 +94,13 @@ class ArrayListFactory extends AbstractListFactory {
 
   override def empty[E: ClassTag]: ju.ArrayList[E] =
     new ju.ArrayList[E]
+
+  override def fromElements[E: ClassTag](coll: E*): ju.ArrayList[E] =
+    new ju.ArrayList[E](TrivialImmutableCollection(coll: _*))
+}
+
+class ArrayListRangeRemovable[E](c: ju.Collection[_ <: E]) extends ju.ArrayList[E](c) {
+  def removeRangeList(fromIndex: Int, toIndex: Int): Unit = {
+    removeRange(fromIndex, toIndex)
+  }
 }
diff --git a/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/util/ListTest.scala b/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/util/ListTest.scala
index 8835696b00..98773fef7a 100644
--- a/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/util/ListTest.scala
+++ b/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/util/ListTest.scala
@@ -96,6 +96,19 @@ trait ListTest extends CollectionTest with CollectionsTestBase {
     assertThrows(classOf[IndexOutOfBoundsException], lst.get(lst.size))
   }
 
+  @Test def addAllIndexBounds(): Unit = {
+    val al = factory.fromElements[String]("one", "two", "three")
+
+    val coll = factory.fromElements[String]("foo")
+    assertThrows(classOf[IndexOutOfBoundsException], al.addAll(-1, coll))
+    assertThrows(classOf[IndexOutOfBoundsException], al.addAll(al.size + 1, coll))
+
+    assertThrows(classOf[IndexOutOfBoundsException],
+        al.addAll(-1, TrivialImmutableCollection("foo")))
+    assertThrows(classOf[IndexOutOfBoundsException],
+        al.addAll(al.size + 1, TrivialImmutableCollection("foo")))
+  }
+
   @Test def removeStringRemoveIndex(): Unit = {
     val lst = factory.empty[String]
 

From a088ec4b5f3e22f1f287365ef84bf6ec9ced3adb Mon Sep 17 00:00:00 2001
From: Rikito Taniguchi <rikiriki1238@gmail.com>
Date: Fri, 2 May 2025 10:03:33 +0900
Subject: [PATCH 284/298] Wasm: Implement ju.ArrayList without js.Array.

The original implementation of ju.ArrayList uses js.Array as its
internal data structure. When compiling to Wasm, operations on
ju.ArrayList require JS interop calls to access the underlying
js.Array, which causes a slow performance.

This commit introduces an implementation of ju.ArrayList for the
Wasm backend. This version uses Scala's Array instead of js.Array
for better performance.
---
 .../src/main/scala/java/util/ArrayList.scala  | 140 +++++++++++++++---
 .../javalib/util/ArrayListTest.scala          |  30 +++-
 .../javalib/util/CollectionTest.scala         |  10 ++
 3 files changed, 158 insertions(+), 22 deletions(-)

diff --git a/javalib/src/main/scala/java/util/ArrayList.scala b/javalib/src/main/scala/java/util/ArrayList.scala
index 62de296cab..1c67de682b 100644
--- a/javalib/src/main/scala/java/util/ArrayList.scala
+++ b/javalib/src/main/scala/java/util/ArrayList.scala
@@ -14,75 +14,154 @@ package java.util
 
 import java.lang.Cloneable
 import java.lang.Utils._
+import java.util.ScalaOps._
 
 import scala.scalajs._
+import scala.scalajs.LinkingInfo.isWebAssembly
 
-class ArrayList[E] private (private[ArrayList] val inner: js.Array[E])
+class ArrayList[E] private (innerInit: AnyRef, private var _size: Int)
     extends AbstractList[E] with RandomAccess with Cloneable with Serializable {
   self =>
 
+  /* This class has two different implementations for handling the
+   * internal data storage, depending on whether we are on Wasm or JS.
+   * On JS, we utilize `js.Array`. On Wasm, for performance reasons,
+   * we avoid JS interop and use a scala.Array.
+   * The `_size` field (unused in JS) keeps track of the effective size
+   * of the underlying Array for the Wasm implementation.
+   */
+
+  private val innerJS: js.Array[E] =
+    if (isWebAssembly) null
+    else innerInit.asInstanceOf[js.Array[E]]
+
+  private var innerWasm: Array[AnyRef] =
+    if (!isWebAssembly) null
+    else innerInit.asInstanceOf[Array[AnyRef]]
+
   def this(initialCapacity: Int) = {
-    this(new js.Array[E])
-    if (initialCapacity < 0)
-      throw new IllegalArgumentException
+    this(
+      {
+        if (initialCapacity < 0)
+          throw new IllegalArgumentException
+        if (isWebAssembly) new Array[AnyRef](initialCapacity)
+        else new js.Array[E]
+      },
+      0
+    )
   }
 
-  def this() =
-    this(new js.Array[E])
+  def this() = this(16)
 
   def this(c: Collection[_ <: E]) = {
-    this()
+    this(c.size())
     addAll(c)
   }
 
   def trimToSize(): Unit = {
-    // We ignore this as js.Array doesn't support explicit pre-allocation
+    if (isWebAssembly)
+      resizeTo(size())
+    // We ignore this in JS as js.Array doesn't support explicit pre-allocation
   }
 
   def ensureCapacity(minCapacity: Int): Unit = {
-    // We ignore this as js.Array doesn't support explicit pre-allocation
+    if (isWebAssembly) {
+      if (innerWasm.length < minCapacity) {
+        if (minCapacity > (1 << 30))
+          resizeTo(minCapacity)
+        else
+          resizeTo(((1 << 31) >>> (Integer.numberOfLeadingZeros(minCapacity - 1)) - 1))
+      }
+    }
+    // We ignore this in JS as js.Array doesn't support explicit pre-allocation
   }
 
   def size(): Int =
-    inner.length
-
-  override def clone(): AnyRef =
-    new ArrayList(inner.jsSlice(0))
+    if (isWebAssembly) _size
+    else innerJS.length
+
+  override def clone(): AnyRef = {
+    if (isWebAssembly)
+      new ArrayList(innerWasm.clone(), size())
+    else
+      new ArrayList(innerJS.jsSlice(0), 0)
+  }
 
   def get(index: Int): E = {
     checkIndexInBounds(index)
-    inner(index)
+    if (isWebAssembly)
+      innerWasm(index).asInstanceOf[E]
+    else
+      innerJS(index)
   }
 
   override def set(index: Int, element: E): E = {
     val e = get(index)
-    inner(index) = element
+    if (isWebAssembly)
+      innerWasm(index) = element.asInstanceOf[AnyRef]
+    else
+      innerJS(index) = element
     e
   }
 
   override def add(e: E): Boolean = {
-    inner.push(e)
+    if (isWebAssembly) {
+      if (size() >= innerWasm.length)
+        expand()
+      innerWasm(size()) = e.asInstanceOf[AnyRef]
+      _size += 1
+    } else {
+      innerJS.push(e)
+    }
     true
   }
 
   override def add(index: Int, element: E): Unit = {
     checkIndexOnBounds(index)
-    inner.splice(index, 0, element)
+    if (isWebAssembly) {
+      if (size() >= innerWasm.length)
+        expand()
+      System.arraycopy(innerWasm, index, innerWasm, index + 1, size() - index)
+      innerWasm(index) = element.asInstanceOf[AnyRef]
+      _size += 1
+    } else {
+      innerJS.splice(index, 0, element)
+    }
   }
 
   override def remove(index: Int): E = {
     checkIndexInBounds(index)
-    arrayRemoveAndGet(inner, index)
+    if (isWebAssembly) {
+      val removed = innerWasm(index).asInstanceOf[E]
+      System.arraycopy(innerWasm, index + 1, innerWasm, index, size() - index - 1)
+      innerWasm(size - 1) = null // free reference for GC
+      _size -= 1
+      removed
+    } else {
+      arrayRemoveAndGet(innerJS, index)
+    }
   }
 
   override def clear(): Unit =
-    inner.length = 0
+    if (isWebAssembly) {
+      Arrays.fill(innerWasm, null) // free references for GC
+      _size = 0
+    } else {
+      innerJS.length = 0
+    }
 
   override def addAll(index: Int, c: Collection[_ <: E]): Boolean = {
     c match {
       case other: ArrayList[_] =>
         checkIndexOnBounds(index)
-        inner.splice(index, 0, other.inner.toSeq: _*)
+        if (isWebAssembly) {
+          ensureCapacity(size() + other.size())
+          System.arraycopy(innerWasm, index, innerWasm, index + other.size(), size() - index)
+          System.arraycopy(other.innerWasm, 0, innerWasm, index, other.size())
+          _size += c.size()
+        } else {
+          innerJS.splice(index, 0, other.innerJS.toSeq: _*)
+        }
         other.size() > 0
       case _ => super.addAll(index, c)
     }
@@ -91,6 +170,25 @@ class ArrayList[E] private (private[ArrayList] val inner: js.Array[E])
   override protected def removeRange(fromIndex: Int, toIndex: Int): Unit = {
     if (fromIndex < 0 || toIndex > size() || toIndex < fromIndex)
       throw new IndexOutOfBoundsException()
-    inner.splice(fromIndex, toIndex - fromIndex)
+    if (isWebAssembly) {
+      if (fromIndex != toIndex) {
+        System.arraycopy(innerWasm, toIndex, innerWasm, fromIndex, size() - toIndex)
+        val newSize = size() - toIndex + fromIndex
+        Arrays.fill(innerWasm, newSize, size(), null) // free references for GC
+        _size = newSize
+      }
+    } else {
+      innerJS.splice(fromIndex, toIndex - fromIndex)
+    }
+  }
+
+  // Wasm only
+  private def expand(): Unit = {
+    resizeTo(Math.max(innerWasm.length * 2, 16))
+  }
+
+  // Wasm only
+  private def resizeTo(newCapacity: Int): Unit = {
+    innerWasm = Arrays.copyOf(innerWasm, newCapacity)
   }
 }
diff --git a/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/util/ArrayListTest.scala b/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/util/ArrayListTest.scala
index 25d9bbb7de..400da32882 100644
--- a/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/util/ArrayListTest.scala
+++ b/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/util/ArrayListTest.scala
@@ -14,8 +14,10 @@ package org.scalajs.testsuite.javalib.util
 
 import org.junit.Test
 import org.junit.Assert._
+import org.junit.Assume._
 
 import org.scalajs.testsuite.utils.AssertThrows.assertThrows
+import org.scalajs.testsuite.utils.Platform
 
 import java.{util => ju}
 
@@ -23,7 +25,7 @@ import scala.reflect.ClassTag
 
 class ArrayListTest extends AbstractListTest {
 
-  override def factory: AbstractListFactory = new ArrayListFactory
+  override def factory: ArrayListFactory = new ArrayListFactory
 
   @Test def ensureCapacity(): Unit = {
     // note that these methods become no ops in js
@@ -33,6 +35,32 @@ class ArrayListTest extends AbstractListTest {
     al.trimToSize()
   }
 
+  @Test def constructorInitialCapacity(): Unit = {
+    val al1 = new ju.ArrayList(0)
+    assertTrue(al1.size() == 0)
+    assertTrue(al1.isEmpty())
+
+    val al2 = new ju.ArrayList(2)
+    assertTrue(al2.size() == 0)
+    assertTrue(al2.isEmpty())
+
+    assertThrows(classOf[IllegalArgumentException], new ju.ArrayList(-1))
+  }
+
+  @Test def constructorNullThrowsNullPointerException(): Unit = {
+    assumeTrue("assumed compliant NPEs", Platform.hasCompliantNullPointers)
+    assertThrows(classOf[NullPointerException], new ju.ArrayList(null))
+  }
+
+  @Test def testClone(): Unit = {
+    val al1 = factory.fromElements[Int](1, 2)
+    val al2 = al1.clone().asInstanceOf[ju.ArrayList[Int]]
+    al1.add(100)
+    al2.add(200)
+    assertTrue(Array[Int](1, 2, 100).sameElements(al1.toArray()))
+    assertTrue(Array[Int](1, 2, 200).sameElements(al2.toArray()))
+  }
+
   @Test def removeRangeFromIdenticalIndices(): Unit = {
     val al = new ArrayListRangeRemovable[Int](
         TrivialImmutableCollection(-175, 24, 7, 44))
diff --git a/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/util/CollectionTest.scala b/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/util/CollectionTest.scala
index 787d88a4c3..c73e6acccd 100644
--- a/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/util/CollectionTest.scala
+++ b/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/util/CollectionTest.scala
@@ -117,6 +117,16 @@ trait CollectionTest extends IterableTest {
     assertFalse(coll.contains(TestObj(200)))
   }
 
+  @Test def isEmpty(): Unit = {
+    val coll = factory.empty[Int]
+    assertTrue(coll.size() == 0)
+    assertTrue(coll.isEmpty())
+
+    val nonEmpty = factory.fromElements[Int](1)
+    assertTrue(nonEmpty.size() == 1)
+    assertFalse(nonEmpty.isEmpty())
+  }
+
   @Test def removeString(): Unit = {
     val coll = factory.empty[String]
 

From c399a080a86503a67dd235a02561feb8b8d96c65 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Tue, 22 Apr 2025 10:02:38 +0200
Subject: [PATCH 285/298] Bump the version to 1.20.0-SNAPSHOT for the upcoming
 changes.

As well as the IR version to 1.20-SNAPSHOT.
---
 ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala b/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala
index 4de34d7f0b..23292cbcdc 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/ScalaJSVersions.scala
@@ -17,8 +17,8 @@ import java.util.concurrent.ConcurrentHashMap
 import scala.util.matching.Regex
 
 object ScalaJSVersions extends VersionChecks(
-    current = "1.19.1-SNAPSHOT",
-    binaryEmitted = "1.19"
+    current = "1.20.0-SNAPSHOT",
+    binaryEmitted = "1.20-SNAPSHOT"
 )
 
 /** Helper class to allow for testing of logic. */

From 5e842d868dd16c0f15bfbb4c583e6f8eac24c87e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Fri, 3 Jan 2025 17:22:15 +0100
Subject: [PATCH 286/298] Fix #4997: Add `linkTimeIf` for link-time conditional
 branching.

Thanks to our optimizer's ability to inline, constant-fold, and
then eliminate dead code, we have been able to write link-time
conditional branches for a long time. Typical examples include
polyfills, as illustrated in the documentation of `LinkingInfo`:

    if (esVersion >= ESVersion.ES2018 || featureTest())
      useES2018Feature()
    else
      usePolyfill()

which gets folded away to nothing but

    useES2018Feature()

when linking for ES2018+.

However, this only works because both branches can *link* during
the initial reachability analysis. We cannot use the same technique
when one of the branches would refuse to link in the first place.
The canonical example is the usage of the JS `**` operator, which
does not link below ES2016. The following snippet produces good
code when linking for ES2016+, but does not link at all for ES2015:

    def pow(x: Double, y: Double): Double = {
      if (esVersion >= ESVersion.ES2016) {
        (x.asInstanceOf[js.Dynamic] ** y.asInstanceOf[js.Dynamic])
          .asInstanceOf[Double]
      } {
        Math.pow(x, y)
      }
    }

---

This commit introduces `LinkingInfo.linkTimeIf`, a conditional
branch that is guaranteed by spec to be resolved at link-time.
Using a `linkTimeIf` instead of the `if` in `def pow`, we can
successfully link the fallback branch on ES2015, because the then
branch is not even followed by the reachability analysis.

In order to provide that guarantee, the corresponding `LinkTimeIf`
IR node has strong requirements on its condition. It must be a
"link-time expression", which is guaranteed to be resolved at
link-time. A link-time expression tree must be of the form:

* A `Literal` (of type `int`, `boolean` or `string`, although
  `string`s are not actually usable here).
* A `LinkTimeProperty`.
* One of the boolean operators.
* One of the int comparison operators.
* A nested `LinkTimeIf` (used to encode short-circuiting boolean
  `&&` and `||`).

The `ClassDefChecker` validates the above property, and ensures
that link-time expression trees are *well-typed*. Normally that is
the job of the IR checker. Here we *can* do in `ClassDefChecker`
because we only have the 3 primitive types to deal with; and we
*must* do it then, because the reachability analysis itself is only
sound if all link-time expression trees are well-typed.

The reachability analysis algorithm itself is not affected by
`LinkTimeIf`. Instead, we resolve link-time branches when building
the `Infos` of methods. We follow only the branch that is taken.
This means that `Infos` builders now require access to the
`linkTimeProperties` derived from the `coreSpec`, but that is the
only additional piece of complexity in that area.

`LinkTimeIf`s nodes are later removed from the trees during
desugaring.

---

At the language and compiler level, we introduce
`LinkingInfo.linkTimeIf` as a primitive for `LinkTimeIf`. We need
a dedicated method to compile link-time expression trees, which
does incur some duplication, unfortunately. Other than that,
`linkTimeIf` is straightforward, by itself.

The problem is that the whole point of `linkTimeIf` is that we can
refer to *link-time properties*, and not just literals. However,
our link-time properties are all hidden behind regular method calls,
such as `LinkInfo.esVersion`. For optimizer-based branching with
`if`s, that is fine, as the method is always inlined, and the
optimizer can then see the constant. However, for `linkTimeIf`,
that does not work, as it does not follow the requirements of a
link-time expression tree.

If we were on Scala 3 only, we could declare `esVersion` and its
friends as an `inline def`, as follows:

    inline def esVersion: Int =
      linkTimePropertyInt("core/esVersion")

The `inline` keyword is guaranteed by the language to be resolved
at *compile*-time. Since the `linkTimePropertyInt` method is itself
a primitive replaced by a `LinkTimeProperty`, by the time we reach
our backend, we would see the latter, and all would be well.
The same cannot be said for the `@inline` optimizer hint, which is
all we have.

We therefore add another language-level feature:
`@linkTimeProperty`. This annotation can (currently) only be used
in our own library. By contract, it must only be used on a method
whose body is the corresponding `linkTimePropertyX` primitive.
With it, we can define `esVersion` as:

    @inline @linkTimeProperty("core/esVersion")
    def esVersion: Int =
      linkTimePropertyInt("core/esVersion")

That annotation makes the body public, in a way. That means the
compiler back-end can now replace *call sites* to `esVersion` by
the `LinkTimeProperty`.

Semantically, `@linkTimeProperty` does nothing more than guaranteed
inlining (with strong restrictions on the shape of body).

Co-authored-by: Rikito Taniguchi <rikiriki1238@gmail.com>
---
 .../org/scalajs/nscplugin/GenJSCode.scala     |  87 ++++++++++
 .../org/scalajs/nscplugin/JSDefinitions.scala |   3 +
 .../org/scalajs/nscplugin/JSPrimitives.scala  |   4 +-
 .../nscplugin/test/LinkTimeIfTest.scala       | 109 +++++++++++++
 .../main/scala/org/scalajs/ir/Hashers.scala   |   7 +
 .../main/scala/org/scalajs/ir/Printers.scala  |   9 ++
 .../scala/org/scalajs/ir/Serializers.scala    |  16 +-
 .../src/main/scala/org/scalajs/ir/Tags.scala  |   3 +
 .../scala/org/scalajs/ir/Transformers.scala   |   3 +
 .../scala/org/scalajs/ir/Traversers.scala     |   5 +
 .../src/main/scala/org/scalajs/ir/Trees.scala |  32 ++++
 .../scala/org/scalajs/ir/PrintersTest.scala   |  55 +++++++
 .../scala/scala/scalajs/LinkingInfo.scala     |  47 +++++-
 .../scalajs/annotation/linkTimeProperty.scala |  33 ++++
 .../scalajs/linker/analyzer/Analyzer.scala    |   2 +-
 .../scalajs/linker/analyzer/InfoLoader.scala  |  39 +++--
 .../org/scalajs/linker/analyzer/Infos.scala   | 150 +++++++++++-------
 .../backend/wasmemitter/FunctionEmitter.scala |   3 +-
 .../linker/checker/ClassDefChecker.scala      |  70 +++++++-
 .../scalajs/linker/checker/FeatureSet.scala   |   6 +-
 .../scalajs/linker/checker/IRChecker.scala    |  35 +++-
 .../scalajs/linker/frontend/BaseLinker.scala  |   5 +-
 .../scalajs/linker/frontend/Desugarer.scala   |  18 ++-
 .../linker/frontend/LinkTimeEvaluator.scala   | 129 +++++++++++++++
 .../org/scalajs/linker/frontend/Refiner.scala |   5 +-
 .../frontend/optimizer/OptimizerCore.scala    |   3 +-
 .../org/scalajs/linker/AnalyzerTest.scala     | 125 ++++++++++++++-
 .../org/scalajs/linker/IRCheckerTest.scala    |   1 +
 .../linker/checker/ClassDefCheckerTest.scala  |  78 +++++++++
 .../LinkTimeEvaluatorTest.scala               | 102 ++++++++++++
 .../linker/testutils/TestIRBuilder.scala      |   1 +
 .../testsuite/library/LinkTimeIfTest.scala    |  95 +++++++++++
 32 files changed, 1178 insertions(+), 102 deletions(-)
 create mode 100644 compiler/src/test/scala/org/scalajs/nscplugin/test/LinkTimeIfTest.scala
 create mode 100644 library/src/main/scala/scala/scalajs/annotation/linkTimeProperty.scala
 create mode 100644 linker/shared/src/main/scala/org/scalajs/linker/frontend/LinkTimeEvaluator.scala
 create mode 100644 linker/shared/src/test/scala/org/scalajs/linker/frontend/modulesplitter/LinkTimeEvaluatorTest.scala
 create mode 100644 test-suite/js/src/test/scala/org/scalajs/testsuite/library/LinkTimeIfTest.scala

diff --git a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
index e46b1dc14f..dc1348ea22 100644
--- a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
+++ b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
@@ -5511,6 +5511,16 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
           js.UnaryOp(js.UnaryOp.UnwrapFromThrowable,
               js.UnaryOp(js.UnaryOp.CheckNotNull, genArgs1))
 
+        case LINKTIME_IF =>
+          // LinkingInfo.linkTimeIf(cond, thenp, elsep)
+          val cond = genLinkTimeExpr(args(0))
+          val thenp = genExpr(args(1))
+          val elsep = genExpr(args(2))
+          val tpe =
+            if (isStat) jstpe.VoidType
+            else toIRType(tree.tpe)
+          js.LinkTimeIf(cond, thenp, elsep)(tpe)
+
         case LINKTIME_PROPERTY =>
           // LinkingInfo.linkTimePropertyXXX("...")
           val arg = genArgs1
@@ -5529,6 +5539,83 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
       }
     }
 
+    private def genLinkTimeExpr(tree: Tree): js.Tree = {
+      import scalaPrimitives._
+
+      implicit val pos = tree.pos
+
+      def invalid(): js.Tree = {
+        reporter.error(tree.pos,
+            "Illegal expression in the condition of a linkTimeIf. " +
+            "Valid expressions are: boolean and int primitives; " +
+            "references to link-time properties; " +
+            "primitive operations on booleans; " +
+            "and comparisons on ints.")
+        js.BooleanLiteral(false)
+      }
+
+      tree match {
+        case Literal(c) =>
+          c.tag match {
+            case BooleanTag => js.BooleanLiteral(c.booleanValue)
+            case IntTag     => js.IntLiteral(c.intValue)
+            case _          => invalid()
+          }
+
+        case Apply(fun @ Select(receiver, _), args) =>
+          fun.symbol.getAnnotation(LinkTimePropertyAnnotation) match {
+            case Some(annotation) =>
+              val propName = annotation.constantAtIndex(0).get.stringValue
+              js.LinkTimeProperty(propName)(toIRType(tree.tpe))
+
+            case None if isPrimitive(fun.symbol) =>
+              val code = getPrimitive(fun.symbol)
+
+              def genLhs: js.Tree = genLinkTimeExpr(receiver)
+              def genRhs: js.Tree = genLinkTimeExpr(args.head)
+
+              def unaryOp(op: js.UnaryOp.Code): js.Tree =
+                js.UnaryOp(op, genLhs)
+              def binaryOp(op: js.BinaryOp.Code): js.Tree =
+                js.BinaryOp(op, genLhs, genRhs)
+
+              toIRType(receiver.tpe) match {
+                case jstpe.BooleanType =>
+                  (code: @switch) match {
+                    case ZNOT     => unaryOp(js.UnaryOp.Boolean_!)
+                    case EQ       => binaryOp(js.BinaryOp.Boolean_==)
+                    case NE | XOR => binaryOp(js.BinaryOp.Boolean_!=)
+                    case OR       => binaryOp(js.BinaryOp.Boolean_|)
+                    case AND      => binaryOp(js.BinaryOp.Boolean_&)
+                    case ZOR      => js.LinkTimeIf(genLhs, js.BooleanLiteral(true), genRhs)(jstpe.BooleanType)
+                    case ZAND     => js.LinkTimeIf(genLhs, genRhs, js.BooleanLiteral(false))(jstpe.BooleanType)
+                    case _        => invalid()
+                  }
+
+                case jstpe.IntType =>
+                  (code: @switch) match {
+                    case EQ => binaryOp(js.BinaryOp.Int_==)
+                    case NE => binaryOp(js.BinaryOp.Int_!=)
+                    case LT => binaryOp(js.BinaryOp.Int_<)
+                    case LE => binaryOp(js.BinaryOp.Int_<=)
+                    case GT => binaryOp(js.BinaryOp.Int_>)
+                    case GE => binaryOp(js.BinaryOp.Int_>=)
+                    case _  => invalid()
+                  }
+
+                case _ =>
+                  invalid()
+              }
+
+            case None => // if !isPrimitive
+              invalid()
+          }
+
+        case _ =>
+          invalid()
+      }
+    }
+
     /** Gen JS code for a primitive JS call (to a method of a subclass of js.Any)
      *  This is the typed Scala.js to JS bridge feature. Basically it boils
      *  down to calling the method without name mangling. But other aspects
diff --git a/compiler/src/main/scala/org/scalajs/nscplugin/JSDefinitions.scala b/compiler/src/main/scala/org/scalajs/nscplugin/JSDefinitions.scala
index 2b0c5590d9..58c4910233 100644
--- a/compiler/src/main/scala/org/scalajs/nscplugin/JSDefinitions.scala
+++ b/compiler/src/main/scala/org/scalajs/nscplugin/JSDefinitions.scala
@@ -135,10 +135,13 @@ trait JSDefinitions {
       lazy val Runtime_dynamicImport              = getMemberMethod(RuntimePackageModule, newTermName("dynamicImport"))
 
     lazy val LinkingInfoModule = getRequiredModule("scala.scalajs.LinkingInfo")
+      lazy val LinkingInfo_linkTimeIf = getMemberMethod(LinkingInfoModule, newTermName("linkTimeIf"))
       lazy val LinkingInfo_linkTimePropertyBoolean = getMemberMethod(LinkingInfoModule, newTermName("linkTimePropertyBoolean"))
       lazy val LinkingInfo_linkTimePropertyInt = getMemberMethod(LinkingInfoModule, newTermName("linkTimePropertyInt"))
       lazy val LinkingInfo_linkTimePropertyString = getMemberMethod(LinkingInfoModule, newTermName("linkTimePropertyString"))
 
+    lazy val LinkTimePropertyAnnotation = getRequiredClass("scala.scalajs.annotation.linkTimeProperty")
+
     lazy val DynamicImportThunkClass = getRequiredClass("scala.scalajs.runtime.DynamicImportThunk")
       lazy val DynamicImportThunkClass_apply = getMemberMethod(DynamicImportThunkClass, nme.apply)
 
diff --git a/compiler/src/main/scala/org/scalajs/nscplugin/JSPrimitives.scala b/compiler/src/main/scala/org/scalajs/nscplugin/JSPrimitives.scala
index 90aa1b1513..cf6f896453 100644
--- a/compiler/src/main/scala/org/scalajs/nscplugin/JSPrimitives.scala
+++ b/compiler/src/main/scala/org/scalajs/nscplugin/JSPrimitives.scala
@@ -71,7 +71,8 @@ abstract class JSPrimitives {
   final val WRAP_AS_THROWABLE = JS_TRY_CATCH + 1          // js.special.wrapAsThrowable
   final val UNWRAP_FROM_THROWABLE = WRAP_AS_THROWABLE + 1 // js.special.unwrapFromThrowable
   final val DEBUGGER = UNWRAP_FROM_THROWABLE + 1          // js.special.debugger
-  final val LINKTIME_PROPERTY = DEBUGGER + 1              // LinkingInfo.linkTimePropertyXXX
+  final val LINKTIME_IF = DEBUGGER + 1                    // LinkingInfo.linkTimeIf
+  final val LINKTIME_PROPERTY = LINKTIME_IF + 1           // LinkingInfo.linkTimePropertyXXX
 
   final val LastJSPrimitiveCode = LINKTIME_PROPERTY
 
@@ -128,6 +129,7 @@ abstract class JSPrimitives {
     addPrimitive(Special_unwrapFromThrowable, UNWRAP_FROM_THROWABLE)
     addPrimitive(Special_debugger, DEBUGGER)
 
+    addPrimitive(LinkingInfo_linkTimeIf, LINKTIME_IF)
     addPrimitive(LinkingInfo_linkTimePropertyBoolean, LINKTIME_PROPERTY)
     addPrimitive(LinkingInfo_linkTimePropertyInt, LINKTIME_PROPERTY)
     addPrimitive(LinkingInfo_linkTimePropertyString, LINKTIME_PROPERTY)
diff --git a/compiler/src/test/scala/org/scalajs/nscplugin/test/LinkTimeIfTest.scala b/compiler/src/test/scala/org/scalajs/nscplugin/test/LinkTimeIfTest.scala
new file mode 100644
index 0000000000..881c0e9a2f
--- /dev/null
+++ b/compiler/src/test/scala/org/scalajs/nscplugin/test/LinkTimeIfTest.scala
@@ -0,0 +1,109 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package org.scalajs.nscplugin.test
+
+import util._
+
+import org.junit.Test
+import org.junit.Assert._
+
+// scalastyle:off line.size.limit
+
+class LinkTimeIfTest extends TestHelpers {
+  override def preamble: String = "import scala.scalajs.LinkingInfo._"
+
+  private final val IllegalLinkTimeIfArgMessage = {
+    "Illegal expression in the condition of a linkTimeIf. " +
+    "Valid expressions are: boolean and int primitives; " +
+    "references to link-time properties; " +
+    "primitive operations on booleans; " +
+    "and comparisons on ints."
+  }
+
+  @Test
+  def linkTimeErrorInvalidOp(): Unit = {
+    """
+    object A {
+      def foo =
+        linkTimeIf((esVersion + 1) < ESVersion.ES2015) { } { }
+    }
+    """ hasErrors
+    s"""
+      |newSource1.scala:4: error: $IllegalLinkTimeIfArgMessage
+      |        linkTimeIf((esVersion + 1) < ESVersion.ES2015) { } { }
+      |                              ^
+    """
+  }
+
+  @Test
+  def linkTimeErrorInvalidEntities(): Unit = {
+    """
+    object A {
+      def foo(x: String) = {
+        val bar = 1
+        linkTimeIf(bar == 0) { } { }
+      }
+    }
+    """ hasErrors
+    s"""
+      |newSource1.scala:5: error: $IllegalLinkTimeIfArgMessage
+      |        linkTimeIf(bar == 0) { } { }
+      |                   ^
+    """
+
+    // String comparison is a `BinaryOp.===`, which is not allowed
+    """
+    object A {
+      def foo(x: String) =
+        linkTimeIf("foo" == x) { } { }
+    }
+    """ hasErrors
+    s"""
+      |newSource1.scala:4: error: $IllegalLinkTimeIfArgMessage
+      |        linkTimeIf("foo" == x) { } { }
+      |                         ^
+    """
+
+    """
+    object A {
+      def bar = true
+      def foo(x: String) =
+        linkTimeIf(bar || !bar) { } { }
+    }
+    """ hasErrors
+    s"""
+      |newSource1.scala:5: error: $IllegalLinkTimeIfArgMessage
+      |        linkTimeIf(bar || !bar) { } { }
+      |                   ^
+      |newSource1.scala:5: error: $IllegalLinkTimeIfArgMessage
+      |        linkTimeIf(bar || !bar) { } { }
+      |                           ^
+    """
+  }
+
+  @Test
+  def linkTimeCondInvalidTree(): Unit = {
+    """
+    object A {
+      def bar = true
+      def foo(x: String) =
+        linkTimeIf(if (bar) true else false) { } { }
+    }
+    """ hasErrors
+    s"""
+      |newSource1.scala:5: error: $IllegalLinkTimeIfArgMessage
+      |        linkTimeIf(if (bar) true else false) { } { }
+      |                   ^
+    """
+  }
+}
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Hashers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Hashers.scala
index ad94d65549..599e9e8c1c 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Hashers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Hashers.scala
@@ -206,6 +206,13 @@ object Hashers {
           mixTree(elsep)
           mixType(tree.tpe)
 
+        case LinkTimeIf(cond, thenp, elsep) =>
+          mixTag(TagLinkTimeIf)
+          mixTree(cond)
+          mixTree(thenp)
+          mixTree(elsep)
+          mixType(tree.tpe)
+
         case While(cond, body) =>
           mixTag(TagWhile)
           mixTree(cond)
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala
index c69ad1447c..9a05ed7788 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala
@@ -93,6 +93,7 @@ object Printers {
     protected def printBlock(tree: Tree): Unit = {
       val trees = tree match {
         case Block(trees) => trees
+        case Skip()       => Nil
         case _            => tree :: Nil
       }
       printBlock(trees)
@@ -232,6 +233,14 @@ object Printers {
               printBlock(elsep)
           }
 
+        case LinkTimeIf(cond, thenp, elsep) =>
+          print("link-time-if (")
+          print(cond)
+          print(") ")
+          printBlock(thenp)
+          print(" else ")
+          printBlock(elsep)
+
         case While(cond, body) =>
           print("while (")
           print(cond)
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
index 7cc64e28e1..628630dfa1 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Serializers.scala
@@ -297,6 +297,11 @@ object Serializers {
           writeTree(cond); writeTree(thenp); writeTree(elsep)
           writeType(tree.tpe)
 
+        case LinkTimeIf(cond, thenp, elsep) =>
+          writeTagAndPos(TagLinkTimeIf)
+          writeTree(cond); writeTree(thenp); writeTree(elsep)
+          writeType(tree.tpe)
+
         case While(cond, body) =>
           writeTagAndPos(TagWhile)
           writeTree(cond); writeTree(body)
@@ -1196,9 +1201,14 @@ object Serializers {
 
           Assign(lhs.asInstanceOf[AssignLhs], rhs)
 
-        case TagReturn  => Return(readTree(), readLabelName())
-        case TagIf      => If(readTree(), readTree(), readTree())(readType())
-        case TagWhile   => While(readTree(), readTree())
+        case TagReturn =>
+          Return(readTree(), readLabelName())
+        case TagIf =>
+          If(readTree(), readTree(), readTree())(readType())
+        case TagLinkTimeIf =>
+          LinkTimeIf(readTree(), readTree(), readTree())(readType())
+        case TagWhile =>
+          While(readTree(), readTree())
 
         case TagDoWhile =>
           if (!hacks.useBelow(13))
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Tags.scala b/ir/shared/src/main/scala/org/scalajs/ir/Tags.scala
index bc7d2982b0..dc2862b7ec 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Tags.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Tags.scala
@@ -135,6 +135,9 @@ private[ir] object Tags {
   final val TagNewLambda = TagApplyTypedClosure + 1
   final val TagJSAwait = TagNewLambda + 1
 
+  // New in 1.20
+  final val TagLinkTimeIf = TagJSAwait + 1
+
   // Tags for member defs
 
   final val TagFieldDef = 1
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Transformers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Transformers.scala
index 27d9086435..e95a154e1c 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Transformers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Transformers.scala
@@ -60,6 +60,9 @@ object Transformers {
         case If(cond, thenp, elsep) =>
           If(transform(cond), transform(thenp), transform(elsep))(tree.tpe)
 
+        case LinkTimeIf(cond, thenp, elsep) =>
+          LinkTimeIf(transform(cond), transform(thenp), transform(elsep))(tree.tpe)
+
         case While(cond, body) =>
           While(transform(cond), transform(body))
 
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Traversers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Traversers.scala
index d5782da074..15c9da9093 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Traversers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Traversers.scala
@@ -48,6 +48,11 @@ object Traversers {
         traverse(thenp)
         traverse(elsep)
 
+      case LinkTimeIf(cond, thenp, elsep) =>
+        traverse(cond)
+        traverse(thenp)
+        traverse(elsep)
+
       case While(cond, body) =>
         traverse(cond)
         traverse(body)
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala b/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
index ccc3b56196..23a2eb7118 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
@@ -168,6 +168,38 @@ object Trees {
   sealed case class If(cond: Tree, thenp: Tree, elsep: Tree)(val tpe: Type)(
       implicit val pos: Position) extends Tree
 
+  /** Link-time `if` expression.
+   *
+   *  The `cond` must be a well-typed link-time tree of type `boolean`.
+   *
+   *  A link-time tree is a `Tree` matching the following sub-grammar:
+   *
+   *  {{{
+   *  link-time-tree ::=
+   *      BooleanLiteral
+   *    | IntLiteral
+   *    | StringLiteral
+   *    | LinkTimeProperty
+   *    | UnaryOp(link-time-unary-op, link-time-tree)
+   *    | BinaryOp(link-time-binary-op, link-time-tree, link-time-tree)
+   *    | LinkTimeIf(link-time-tree, link-time-tree, link-time-tree)
+   *
+   *  link-time-unary-op ::=
+   *      Boolean_!
+   *
+   *  link-time-binary-op ::=
+   *      Boolean_== | Boolean_!= | Boolean_| | Boolean_&
+   *    | Int_== | Int_!= | Int_< | Int_<= | Int_> | Int_>=
+   *  }}}
+   *
+   *  Note: nested `LinkTimeIf` nodes in the `cond` are used to encode
+   *  short-circuiting boolean `&&` and `||`, just like we do with regular
+   *  `If` nodes.
+   */
+  sealed case class LinkTimeIf(cond: Tree, thenp: Tree, elsep: Tree)(
+      val tpe: Type)(implicit val pos: Position)
+      extends Tree
+
   sealed case class While(cond: Tree, body: Tree)(
       implicit val pos: Position) extends Tree {
     val tpe = cond match {
diff --git a/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala b/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala
index 060bf4fdb8..fd49eb406e 100644
--- a/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala
+++ b/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala
@@ -202,6 +202,61 @@ class PrintersTest {
         If(ref("x", BooleanType), ref("y", BooleanType), b(false))(BooleanType))
   }
 
+  @Test def printLinkTimeIf(): Unit = {
+    assertPrintEquals(
+        """
+          |link-time-if (true) {
+          |  5
+          |} else {
+          |  6
+          |}
+        """,
+        LinkTimeIf(b(true), i(5), i(6))(IntType))
+
+    assertPrintEquals(
+        """
+          |link-time-if (true) {
+          |  5
+          |} else {
+          |}
+        """,
+        LinkTimeIf(b(true), i(5), Skip())(VoidType))
+
+    assertPrintEquals(
+        """
+          |link-time-if (true) {
+          |  5
+          |} else {
+          |  link-time-if (false) {
+          |    6
+          |  } else {
+          |    7
+          |  }
+          |}
+        """,
+        LinkTimeIf(b(true), i(5), LinkTimeIf(b(false), i(6), i(7))(IntType))(IntType))
+
+    assertPrintEquals(
+        """
+          |link-time-if (x) {
+          |  true
+          |} else {
+          |  y
+          |}
+        """,
+        LinkTimeIf(ref("x", BooleanType), b(true), ref("y", BooleanType))(BooleanType))
+
+    assertPrintEquals(
+        """
+          |link-time-if (x) {
+          |  y
+          |} else {
+          |  false
+          |}
+        """,
+        LinkTimeIf(ref("x", BooleanType), ref("y", BooleanType), b(false))(BooleanType))
+  }
+
   @Test def printWhile(): Unit = {
     assertPrintEquals(
         """
diff --git a/library/src/main/scala/scala/scalajs/LinkingInfo.scala b/library/src/main/scala/scala/scalajs/LinkingInfo.scala
index ea9d6c1a2f..0a7218fb44 100644
--- a/library/src/main/scala/scala/scalajs/LinkingInfo.scala
+++ b/library/src/main/scala/scala/scalajs/LinkingInfo.scala
@@ -12,6 +12,8 @@
 
 package scala.scalajs
 
+import scala.scalajs.annotation.linkTimeProperty
+
 object LinkingInfo {
 
   /** Returns true if we are linking for production, false otherwise.
@@ -42,7 +44,7 @@ object LinkingInfo {
    *
    *  @see [[developmentMode]]
    */
-  @inline
+  @inline @linkTimeProperty("core/productionMode")
   def productionMode: Boolean =
     linkTimePropertyBoolean("core/productionMode")
 
@@ -120,7 +122,7 @@ object LinkingInfo {
    *  useES2018Feature()
    *  }}}
    */
-  @inline
+  @inline @linkTimeProperty("core/esVersion")
   def esVersion: Int =
     linkTimePropertyInt("core/esVersion")
 
@@ -218,7 +220,7 @@ object LinkingInfo {
    *  implementationWithoutES2015Semantics()
    *  }}}
    */
-  @inline
+  @inline @linkTimeProperty("core/useECMAScript2015Semantics")
   def useECMAScript2015Semantics: Boolean =
     linkTimePropertyBoolean("core/useECMAScript2015Semantics")
 
@@ -252,15 +254,50 @@ object LinkingInfo {
    *  implementationOptimizedForJavaScript()
    *  }}}
    */
-  @inline
+  @inline @linkTimeProperty("core/isWebAssembly")
   def isWebAssembly: Boolean =
     linkTimePropertyBoolean("core/isWebAssembly")
 
   /** Version of the linker. */
-  @inline
+  @inline @linkTimeProperty("core/linkerVersion")
   def linkerVersion: String =
     linkTimePropertyString("core/linkerVersion")
 
+  /** Link-time conditional branching.
+   *
+   *  A `linkTimeIf` expression behaves like an `if`, but it is guaranteed to
+   *  be resolved at link-time. This prevents the unused branch to be linked at
+   *  all. It can therefore reference APIs or language features that would
+   *  otherwise fail to link.
+   *
+   *  The condition `cond` can be constructed using:
+   *
+   *  - Calls to methods annotated with `@linkTimeProperty`
+   *  - Integer or boolean constants
+   *  - Binary operators that return a boolean value
+   *
+   *  A typical use case is to leverage the `**` operator on JavaScript
+   *  `bigint`s if it is available, and otherwise fall back on using Scala
+   *  `BigInt`s. Indeed, the `**` operator refuses to link when the target
+   *  `esVersion` is too low.
+   *
+   *  {{{
+   *  // Returns true iff 2^x < 10^y, for x and y positive integers
+   *  def compareTwoPowTenPow(x: Int, y: Int): Boolean = {
+   *    import scala.scalajs.LinkingInfo._
+   *    linkTimeIf(esVersion >= ESVersion.ES2020) {
+   *      // JS bigints are available, and a fortiori their ** operator
+   *      (js.BigInt(2) ** js.BigInt(x)) < (js.BigInt(10) ** js.BigInt(y))
+   *    } {
+   *      // Fall back on Scala's BigInt's, which use a lot more code size
+   *      BigInt(2).pow(x) < BigInt(10).pow(y)
+   *    }
+   *  }
+   *  }}}
+   */
+  def linkTimeIf[T](cond: Boolean)(thenp: T)(elsep: T): T =
+    throw new Error("stub")
+
   /** Constants for the value of `esVersion`. */
   object ESVersion {
     /** ECMAScrîpt 5.1. */
diff --git a/library/src/main/scala/scala/scalajs/annotation/linkTimeProperty.scala b/library/src/main/scala/scala/scalajs/annotation/linkTimeProperty.scala
new file mode 100644
index 0000000000..6b93167c88
--- /dev/null
+++ b/library/src/main/scala/scala/scalajs/annotation/linkTimeProperty.scala
@@ -0,0 +1,33 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package scala.scalajs.annotation
+
+/** Publicly marks the annotated method as being a link-time property.
+ *
+ *  When an entity is annotated with `@linkTimeProperty`, its body must be a
+ *  link-time property with the same `name`. The annotation makes that body
+ *  "public", and it can therefore be inlined at call site at compile-time.
+ *
+ *  From a user perspective, we can treat the presence of that annotation as if
+ *  it were the `inline` keyword of Scala 3: it forces the inlining to happen
+ *  at compile-time.
+ *
+ *  This is necessary for the target method to be used in the condition of a
+ *  `LinkingInfo.linkTimeIf`.
+ *
+ *  @param name The name used to resolve the link-time value.
+ *
+ *  @see [[LinkingInfo.linkTimeIf]]
+ */
+private[scalajs] final class linkTimeProperty(name: String)
+    extends scala.annotation.StaticAnnotation
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala
index 22d3752fd4..c3b428dbeb 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Analyzer.scala
@@ -50,7 +50,7 @@ final class Analyzer(config: CommonPhaseConfig, initial: Boolean,
   private val linkTimeProperties = LinkTimeProperties.fromCoreSpec(config.coreSpec)
 
   private val infoLoader: InfoLoader =
-    new InfoLoader(irLoader, checkIRFor)
+    new InfoLoader(irLoader, checkIRFor, linkTimeProperties)
 
   def computeReachability(moduleInitializers: Seq[ModuleInitializer],
       symbolRequirements: SymbolRequirement, logger: Logger)(implicit ec: ExecutionContext): Future[Analysis] = {
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/InfoLoader.scala b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/InfoLoader.scala
index 83003e6be5..c791727110 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/InfoLoader.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/InfoLoader.scala
@@ -23,13 +23,16 @@ import org.scalajs.ir.Trees._
 import org.scalajs.logging._
 
 import org.scalajs.linker.checker._
-import org.scalajs.linker.frontend.IRLoader
+import org.scalajs.linker.frontend.{IRLoader, LinkTimeProperties}
 import org.scalajs.linker.interface.LinkingException
 import org.scalajs.linker.CollectionsCompat.MutableMapCompatOps
 
 import Platform.emptyThreadSafeMap
 
-private[analyzer] final class InfoLoader(irLoader: IRLoader, checkIRFor: Option[CheckingPhase]) {
+private[analyzer] final class InfoLoader(irLoader: IRLoader,
+    checkIRFor: Option[CheckingPhase], linkTimeProperties: LinkTimeProperties) {
+
+  private val generator = new Infos.InfoGenerator(linkTimeProperties)
   private var logger: Logger = _
   private val cache = emptyThreadSafeMap[ClassName, InfoLoader.ClassInfoCache]
 
@@ -44,7 +47,7 @@ private[analyzer] final class InfoLoader(irLoader: IRLoader, checkIRFor: Option[
       implicit ec: ExecutionContext): Option[Future[Infos.ClassInfo]] = {
     if (irLoader.classExists(className)) {
       val infoCache = cache.getOrElseUpdate(className,
-          new InfoLoader.ClassInfoCache(className, irLoader, checkIRFor))
+          new InfoLoader.ClassInfoCache(className, irLoader, checkIRFor, generator))
       Some(infoCache.loadInfo(logger))
     } else {
       None
@@ -60,7 +63,9 @@ private[analyzer] final class InfoLoader(irLoader: IRLoader, checkIRFor: Option[
 private[analyzer] object InfoLoader {
   private type MethodInfos = Array[Map[MethodName, Infos.MethodInfo]]
 
-  private class ClassInfoCache(className: ClassName, irLoader: IRLoader, checkIRFor: Option[CheckingPhase]) {
+  private class ClassInfoCache(className: ClassName, irLoader: IRLoader,
+      checkIRFor: Option[CheckingPhase], generator: Infos.InfoGenerator) {
+
     private var cacheUsed: Boolean = false
     private var version: Version = Version.Unversioned
     private var info: Future[Infos.ClassInfo] = _
@@ -103,12 +108,12 @@ private[analyzer] object InfoLoader {
     }
 
     private def generateInfos(classDef: ClassDef): Infos.ClassInfo =  {
-      val referencedFieldClasses = Infos.genReferencedFieldClasses(classDef.fields)
+      val referencedFieldClasses = generator.genReferencedFieldClasses(classDef.fields)
 
-      prevMethodInfos = genMethodInfos(classDef.methods, prevMethodInfos)
-      prevJSCtorInfo = genJSCtorInfo(classDef.jsConstructor, prevJSCtorInfo)
+      prevMethodInfos = genMethodInfos(classDef.methods, prevMethodInfos, generator)
+      prevJSCtorInfo = genJSCtorInfo(classDef.jsConstructor, prevJSCtorInfo, generator)
       prevJSMethodPropDefInfos =
-        genJSMethodPropDefInfos(classDef.jsMethodProps, prevJSMethodPropDefInfos)
+        genJSMethodPropDefInfos(classDef.jsMethodProps, prevJSMethodPropDefInfos, generator)
 
       val exportedMembers = prevJSCtorInfo.toList ::: prevJSMethodPropDefInfos
 
@@ -116,7 +121,7 @@ private[analyzer] object InfoLoader {
        * and usually quite small when they exist.
        */
       val topLevelExports = classDef.topLevelExportDefs
-        .map(Infos.generateTopLevelExportInfo(classDef.name.name, _))
+        .map(generator.generateTopLevelExportInfo(classDef.name.name, _))
 
       val jsNativeMembers = classDef.jsNativeMembers
         .map(m => m.name.name -> m.jsNativeLoadSpec).toMap
@@ -136,7 +141,7 @@ private[analyzer] object InfoLoader {
   }
 
   private def genMethodInfos(methods: List[MethodDef],
-      prevMethodInfos: MethodInfos): MethodInfos = {
+      prevMethodInfos: MethodInfos, generator: Infos.InfoGenerator): MethodInfos = {
 
     val builders = Array.fill(MemberNamespace.Count)(Map.newBuilder[MethodName, Infos.MethodInfo])
 
@@ -144,7 +149,7 @@ private[analyzer] object InfoLoader {
       val info = prevMethodInfos(method.flags.namespace.ordinal)
         .get(method.methodName)
         .filter(_.version.sameVersion(method.version))
-        .getOrElse(Infos.generateMethodInfo(method))
+        .getOrElse(generator.generateMethodInfo(method))
 
       builders(method.flags.namespace.ordinal) += method.methodName -> info
     }
@@ -153,16 +158,18 @@ private[analyzer] object InfoLoader {
   }
 
   private def genJSCtorInfo(jsCtor: Option[JSConstructorDef],
-      prevJSCtorInfo: Option[Infos.ReachabilityInfo]): Option[Infos.ReachabilityInfo] = {
+      prevJSCtorInfo: Option[Infos.ReachabilityInfo],
+      generator: Infos.InfoGenerator): Option[Infos.ReachabilityInfo] = {
     jsCtor.map { ctor =>
       prevJSCtorInfo
         .filter(_.version.sameVersion(ctor.version))
-        .getOrElse(Infos.generateJSConstructorInfo(ctor))
+        .getOrElse(generator.generateJSConstructorInfo(ctor))
     }
   }
 
   private def genJSMethodPropDefInfos(jsMethodProps: List[JSMethodPropDef],
-      prevJSMethodPropDefInfos: List[Infos.ReachabilityInfo]): List[Infos.ReachabilityInfo] = {
+      prevJSMethodPropDefInfos: List[Infos.ReachabilityInfo],
+      generator: Infos.InfoGenerator): List[Infos.ReachabilityInfo] = {
     /* For JS method and property definitions, we use their index in the list of
      * `linkedClass.exportedMembers` as their identity. We cannot use their name
      * because the name itself is a `Tree`.
@@ -176,13 +183,13 @@ private[analyzer] object InfoLoader {
 
     if (prevJSMethodPropDefInfos.size != jsMethodProps.size) {
       // Regenerate everything.
-      jsMethodProps.map(Infos.generateJSMethodPropDefInfo(_))
+      jsMethodProps.map(generator.generateJSMethodPropDefInfo(_))
     } else {
       for {
         (prevInfo, member) <- prevJSMethodPropDefInfos.zip(jsMethodProps)
       } yield {
         if (prevInfo.version.sameVersion(member.version)) prevInfo
-        else Infos.generateJSMethodPropDefInfo(member)
+        else generator.generateJSMethodPropDefInfo(member)
       }
     }
   }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala
index fe957ca837..00b40402fe 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala
@@ -22,8 +22,7 @@ import org.scalajs.ir.Types._
 import org.scalajs.ir.Version
 import org.scalajs.ir.WellKnownNames._
 
-import org.scalajs.linker.backend.emitter.Transients._
-import org.scalajs.linker.standard.LinkedTopLevelExport
+import org.scalajs.linker.frontend.{LinkTimeEvaluator, LinkTimeProperties}
 import org.scalajs.linker.standard.ModuleSet.ModuleID
 
 object Infos {
@@ -184,27 +183,6 @@ object Infos {
     val methodName: MethodName
   ) extends MemberReachabilityInfo
 
-  def genReferencedFieldClasses(fields: List[AnyFieldDef]): Map[FieldName, ClassName] = {
-    val builder = Map.newBuilder[FieldName, ClassName]
-
-    fields.foreach {
-      case FieldDef(flags, FieldIdent(name), _, ftpe) =>
-        if (!flags.namespace.isStatic) {
-          ftpe match {
-            case ClassType(cls, _) =>
-              builder += name -> cls
-            case ArrayType(ArrayTypeRef(ClassRef(cls), _), _) =>
-              builder += name -> cls
-            case _ =>
-          }
-        }
-      case _: JSFieldDef =>
-        // Nothing to do.
-    }
-
-    builder.result()
-  }
-
   final class ReachabilityInfoBuilder(version: Version) {
     import ReachabilityInfoBuilder._
     private val byClass = mutable.Map.empty[ClassName, ReachabilityInfoInClassBuilder]
@@ -415,8 +393,11 @@ object Infos {
     def addUsedClassSuperClass(): this.type =
       setFlag(ReachabilityInfo.FlagUsedClassSuperClass)
 
-    def addReferencedLinkTimeProperty(linkTimeProperty: LinkTimeProperty): this.type = {
+    def markNeedsDesugaring(): this.type =
       setFlag(ReachabilityInfo.FlagNeedsDesugaring)
+
+    def addReferencedLinkTimeProperty(linkTimeProperty: LinkTimeProperty): this.type = {
+      markNeedsDesugaring()
       linkTimeProperties.append((linkTimeProperty.name, linkTimeProperty.tpe))
       this
     }
@@ -539,46 +520,71 @@ object Infos {
     }
   }
 
-  /** Generates the [[MethodInfo]] of a
-   *  [[org.scalajs.ir.Trees.MethodDef Trees.MethodDef]].
-   */
-  def generateMethodInfo(methodDef: MethodDef): MethodInfo =
-    new GenInfoTraverser(methodDef.version).generateMethodInfo(methodDef)
+  final class InfoGenerator(linkTimeProperties: LinkTimeProperties) {
+    def genReferencedFieldClasses(fields: List[AnyFieldDef]): Map[FieldName, ClassName] = {
+      val builder = Map.newBuilder[FieldName, ClassName]
+
+      fields.foreach {
+        case FieldDef(flags, FieldIdent(name), _, ftpe) =>
+          if (!flags.namespace.isStatic) {
+            ftpe match {
+              case ClassType(cls, _) =>
+                builder += name -> cls
+              case ArrayType(ArrayTypeRef(ClassRef(cls), _), _) =>
+                builder += name -> cls
+              case _ =>
+            }
+          }
+        case _: JSFieldDef =>
+          // Nothing to do.
+      }
 
-  /** Generates the [[ReachabilityInfo]] of a
-   *  [[org.scalajs.ir.Trees.JSConstructorDef Trees.JSConstructorDef]].
-   */
-  def generateJSConstructorInfo(ctorDef: JSConstructorDef): ReachabilityInfo =
-    new GenInfoTraverser(ctorDef.version).generateJSConstructorInfo(ctorDef)
+      builder.result()
+    }
 
-  /** Generates the [[ReachabilityInfo]] of a
-   *  [[org.scalajs.ir.Trees.JSMethodDef Trees.JSMethodDef]].
-   */
-  def generateJSMethodInfo(methodDef: JSMethodDef): ReachabilityInfo =
-    new GenInfoTraverser(methodDef.version).generateJSMethodInfo(methodDef)
+    /** Generates the [[MethodInfo]] of a
+     *  [[org.scalajs.ir.Trees.MethodDef Trees.MethodDef]].
+     */
+    def generateMethodInfo(methodDef: MethodDef): MethodInfo =
+      new GenInfoTraverser(methodDef.version, linkTimeProperties).generateMethodInfo(methodDef)
 
-  /** Generates the [[ReachabilityInfo]] of a
-   *  [[org.scalajs.ir.Trees.JSPropertyDef Trees.JSPropertyDef]].
-   */
-  def generateJSPropertyInfo(propertyDef: JSPropertyDef): ReachabilityInfo =
-    new GenInfoTraverser(propertyDef.version).generateJSPropertyInfo(propertyDef)
+    /** Generates the [[ReachabilityInfo]] of a
+     *  [[org.scalajs.ir.Trees.JSConstructorDef Trees.JSConstructorDef]].
+     */
+    def generateJSConstructorInfo(ctorDef: JSConstructorDef): ReachabilityInfo =
+      new GenInfoTraverser(ctorDef.version, linkTimeProperties).generateJSConstructorInfo(ctorDef)
 
-  def generateJSMethodPropDefInfo(member: JSMethodPropDef): ReachabilityInfo = member match {
-    case methodDef: JSMethodDef     => generateJSMethodInfo(methodDef)
-    case propertyDef: JSPropertyDef => generateJSPropertyInfo(propertyDef)
-  }
+    /** Generates the [[ReachabilityInfo]] of a
+     *  [[org.scalajs.ir.Trees.JSMethodDef Trees.JSMethodDef]].
+     */
+    def generateJSMethodInfo(methodDef: JSMethodDef): ReachabilityInfo =
+      new GenInfoTraverser(methodDef.version, linkTimeProperties).generateJSMethodInfo(methodDef)
+
+    /** Generates the [[ReachabilityInfo]] of a
+     *  [[org.scalajs.ir.Trees.JSPropertyDef Trees.JSPropertyDef]].
+     */
+    def generateJSPropertyInfo(propertyDef: JSPropertyDef): ReachabilityInfo =
+      new GenInfoTraverser(propertyDef.version, linkTimeProperties).generateJSPropertyInfo(propertyDef)
 
-  /** Generates the [[MethodInfo]] for the top-level exports. */
-  def generateTopLevelExportInfo(enclosingClass: ClassName,
-      topLevelExportDef: TopLevelExportDef): TopLevelExportInfo = {
-    val info = new GenInfoTraverser(Version.Unversioned)
-        .generateTopLevelExportInfo(enclosingClass, topLevelExportDef)
-    new TopLevelExportInfo(info,
-        ModuleID(topLevelExportDef.moduleID),
-        topLevelExportDef.topLevelExportName)
+    def generateJSMethodPropDefInfo(member: JSMethodPropDef): ReachabilityInfo = member match {
+      case methodDef: JSMethodDef     => generateJSMethodInfo(methodDef)
+      case propertyDef: JSPropertyDef => generateJSPropertyInfo(propertyDef)
+    }
+
+    /** Generates the [[MethodInfo]] for the top-level exports. */
+    def generateTopLevelExportInfo(enclosingClass: ClassName,
+        topLevelExportDef: TopLevelExportDef): TopLevelExportInfo = {
+      val info = new GenInfoTraverser(Version.Unversioned, linkTimeProperties)
+          .generateTopLevelExportInfo(enclosingClass, topLevelExportDef)
+      new TopLevelExportInfo(info,
+          ModuleID(topLevelExportDef.moduleID),
+          topLevelExportDef.topLevelExportName)
+    }
   }
 
-  private final class GenInfoTraverser(version: Version) extends Traverser {
+  private final class GenInfoTraverser(version: Version,
+      linkTimeProperties: LinkTimeProperties) extends Traverser {
+
     private val builder = new ReachabilityInfoBuilder(version)
 
     /** Whether we are currently in the body of an `async` closure.
@@ -684,6 +690,36 @@ object Infos {
           // Capture values are in the enclosing scope; not the scope of the closure
           captureValues.foreach(traverse(_))
 
+        // Do not call super.traverse(), as we must follow a single branch
+        case LinkTimeIf(cond, thenp, elsep) =>
+          builder.markNeedsDesugaring()
+          traverse(cond)
+          LinkTimeEvaluator.tryEvalLinkTimeBooleanExpr(linkTimeProperties, cond) match {
+            case Some(result) =>
+              if (result)
+                traverse(thenp)
+              else
+                traverse(elsep)
+            case None =>
+              /* Ignore. Recall that we *assume* here that the ClassDef is
+               * valid on its own, i.e., it would pass the ClassDefChecker
+               * (irrespective of whether we actually run that checker).
+               *
+               * Under that assumption, the only failure mode for evaluating
+               * the `cond` is that it refers to a  `LinkTimeProperty` that
+               * does not exist or has the wrong type. In that case, the
+               * analyzer will report a linking error at least for that
+               * `LinkTimeProperty` inside the `cond` (which we always
+               * traverse).
+               *
+               * If the assumption is broken and the evaluation failure was
+               * due to an ill-formed or ill-typed `cond`, then Desugar will
+               * eventually crash (with a message suggesting to enable checking
+               * the IR).
+               */
+              ()
+          }
+
         // In all other cases, we'll have to call super.traverse()
         case _ =>
           tree match {
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
index a86c55909e..7cf164c228 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
@@ -634,7 +634,8 @@ private class FunctionEmitter private (
       // Transients (only generated by the optimizer)
       case t: Transient => genTransient(t)
 
-      case _:JSSuperConstructorCall | _:LinkTimeProperty | _:NewLambda =>
+      case _:JSSuperConstructorCall | _:LinkTimeProperty | _:LinkTimeIf |
+          _:NewLambda =>
         throw new AssertionError(s"Invalid tree: $tree")
     }
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala b/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
index a1c9f6363d..2d1437ee5f 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/checker/ClassDefChecker.scala
@@ -761,6 +761,13 @@ private final class ClassDefChecker(classDef: ClassDef,
         checkTree(thenp, env)
         checkTree(elsep, env)
 
+      case LinkTimeIf(cond, thenp, elsep) =>
+        if (!featureSet.supports(FeatureSet.LinkTimeNodes))
+          reportError(i"Illegal link-time if after desugaring")
+        checkLinkTimeTree(cond, BooleanType)
+        checkTree(thenp, env)
+        checkTree(elsep, env)
+
       case While(cond, body) =>
         checkTree(cond, env)
         checkTree(body, env)
@@ -923,9 +930,16 @@ private final class ClassDefChecker(classDef: ClassDef,
         }
 
       case LinkTimeProperty(name) =>
-        if (!featureSet.supports(FeatureSet.LinkTimeProperty))
+        if (!featureSet.supports(FeatureSet.LinkTimeNodes))
           reportError(i"Illegal link-time property '$name' after desugaring")
 
+        tree.tpe match {
+          case BooleanType | IntType | StringType =>
+            () // ok
+          case tpe =>
+            reportError(i"$tpe is not a valid type for LinkTimeProperty")
+        }
+
       // JavaScript expressions
 
       case JSNew(ctor, args) =>
@@ -1091,6 +1105,60 @@ private final class ClassDefChecker(classDef: ClassDef,
     }
   }
 
+  private def checkLinkTimeTree(tree: Tree, expectedType: PrimType): Unit = {
+    implicit val ctx = ErrorContext(tree)
+
+    /* For link-time trees, we need to check the types. Having a well-typed
+     * condition is required for `LinkTimeIf` to be resolved, and that happens
+     * before IR checking. Fortunately, only trivial primitive types can appear
+     * in link-time trees, and it is therefore possible to check them now.
+     */
+    if (tree.tpe != expectedType)
+      reportError(i"$expectedType expected but ${tree.tpe} found in link-time tree")
+
+    /* Unlike the evaluation algorithm, at this time we allow LinkTimeProperty's
+     * that are not actually available. We only check that their declared type
+     * matches the expected type. If it does not exist or does not have the
+     * type it was declared with, that constitutes a *linking error*, but it
+     * does not make the ClassDef invalid.
+     */
+
+    tree match {
+      case _:IntLiteral | _:BooleanLiteral | _:StringLiteral | _:LinkTimeProperty =>
+        () // ok
+
+      case UnaryOp(op, lhs) =>
+        import UnaryOp._
+        op match {
+          case Boolean_! =>
+            checkLinkTimeTree(lhs, BooleanType)
+          case _ =>
+            reportError(i"illegal unary op $op in link-time tree")
+        }
+
+      case BinaryOp(op, lhs, rhs) =>
+        import BinaryOp._
+        op match {
+          case Boolean_== | Boolean_!= | Boolean_| | Boolean_& =>
+            checkLinkTimeTree(lhs, BooleanType)
+            checkLinkTimeTree(rhs, BooleanType)
+          case Int_== | Int_!= | Int_< | Int_<= | Int_> | Int_>= =>
+            checkLinkTimeTree(lhs, IntType)
+            checkLinkTimeTree(rhs, IntType)
+          case _ =>
+            reportError(i"illegal binary op $op in link-time tree")
+        }
+
+      case LinkTimeIf(cond, thenp, elsep) =>
+        checkLinkTimeTree(cond, BooleanType)
+        checkLinkTimeTree(thenp, expectedType)
+        checkLinkTimeTree(elsep, expectedType)
+
+      case _ =>
+        reportError(i"illegal tree of class ${tree.getClass().getName()} in link-time tree")
+    }
+  }
+
   private def checkArrayType(tpe: ArrayType)(
       implicit ctx: ErrorContext): Unit = {
     checkArrayTypeRef(tpe.arrayTypeRef)
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/checker/FeatureSet.scala b/linker/shared/src/main/scala/org/scalajs/linker/checker/FeatureSet.scala
index 33cbeaa135..94aabffff1 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/checker/FeatureSet.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/checker/FeatureSet.scala
@@ -36,8 +36,8 @@ private[checker] object FeatureSet {
 
   // Individual features
 
-  /** The `LinkTimeProperty` IR node. */
-  val LinkTimeProperty = new FeatureSet(1 << 0)
+  /** Link-time IR nodes: `LinkTimeProperty` and `LinkTimeIf`. */
+  val LinkTimeNodes = new FeatureSet(1 << 0)
 
   /** The `NewLambda` IR node. */
   val NewLambda = new FeatureSet(1 << 1)
@@ -84,7 +84,7 @@ private[checker] object FeatureSet {
 
   /** Features that must be desugared away. */
   private val NeedsDesugaring =
-    LinkTimeProperty | NewLambda
+    LinkTimeNodes | NewLambda
 
   /** IR that is only the result of desugaring (currently empty). */
   private val Desugared =
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala b/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
index b66dfeea1f..3f87f8be04 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
@@ -24,13 +24,13 @@ import org.scalajs.ir.WellKnownNames._
 
 import org.scalajs.logging._
 
-import org.scalajs.linker.frontend.LinkingUnit
+import org.scalajs.linker.frontend.{LinkingUnit, LinkTimeEvaluator, LinkTimeProperties}
 import org.scalajs.linker.standard.LinkedClass
 import org.scalajs.linker.checker.ErrorReporter._
 
 /** Checker for the validity of the IR. */
-private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter,
-    previousPhase: CheckingPhase) {
+private final class IRChecker(linkTimeProperties: LinkTimeProperties,
+    unit: LinkingUnit, reporter: ErrorReporter, previousPhase: CheckingPhase) {
 
   import IRChecker._
   import reporter.reportError
@@ -315,6 +315,26 @@ private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter,
         typecheckExpect(thenp, env, tpe)
         typecheckExpect(elsep, env, tpe)
 
+      case LinkTimeIf(cond, thenp, elsep) if featureSet.supports(FeatureSet.LinkTimeNodes) =>
+        /* The `cond` is entirely checked in ClassDefChecker.
+         *
+         * We must only check the branch that is actually selected.
+         * We *cannot* check the dropped branch, because it may refer to types
+         * that are dropped by the reachability analysis (which is the whole
+         * point of LinkTimeIf). It is OK to have ill-typed IR in the dropped
+         * branch, because it is guaranteed to disappear during desugaring,
+         * before types are relied upon for any optimization or emission.
+         */
+        LinkTimeEvaluator.tryEvalLinkTimeBooleanExpr(linkTimeProperties, cond) match {
+          case Some(value) =>
+            if (value)
+              typecheckExpect(thenp, env, tree.tpe)
+            else
+              typecheckExpect(elsep, env, tree.tpe)
+          case None =>
+            reportError(i"could not evaluate link-time condition: $cond")
+        }
+
       case While(cond, body) =>
         typecheckExpect(cond, env, BooleanType)
         typecheck(body, env)
@@ -609,7 +629,7 @@ private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter,
         typecheckAny(expr, env)
         checkIsAsInstanceTargetType(tpe)
 
-      case LinkTimeProperty(name) if featureSet.supports(FeatureSet.LinkTimeProperty) =>
+      case LinkTimeProperty(name) if featureSet.supports(FeatureSet.LinkTimeNodes) =>
 
       // JavaScript expressions
 
@@ -793,7 +813,7 @@ private final class IRChecker(unit: LinkingUnit, reporter: ErrorReporter,
         }
 
       case _:RecordSelect | _:RecordValue | _:Transient |
-          _:JSSuperConstructorCall | _:LinkTimeProperty |
+          _:JSSuperConstructorCall | _:LinkTimeProperty | _:LinkTimeIf |
           _:ApplyTypedClosure | _:NewLambda =>
         reportError("invalid tree")
     }
@@ -963,9 +983,10 @@ object IRChecker {
    *
    *  @return Count of IR checking errors (0 in case of success)
    */
-  def check(unit: LinkingUnit, logger: Logger, previousPhase: CheckingPhase): Int = {
+  def check(linkTimeProperties: LinkTimeProperties, unit: LinkingUnit,
+      logger: Logger, previousPhase: CheckingPhase): Int = {
     val reporter = new LoggerErrorReporter(logger)
-    new IRChecker(unit, reporter, previousPhase).check()
+    new IRChecker(linkTimeProperties, unit, reporter, previousPhase).check()
     reporter.errorCount
   }
 }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/BaseLinker.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/BaseLinker.scala
index 62d05ff87e..b88ea4fd55 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/BaseLinker.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/BaseLinker.scala
@@ -35,6 +35,8 @@ import Analysis._
 final class BaseLinker(config: CommonPhaseConfig, checkIR: Boolean) {
   import BaseLinker._
 
+  private val linkTimeProperties = LinkTimeProperties.fromCoreSpec(config.coreSpec)
+
   private val irLoader = new FileIRLoader
   private val analyzer = {
     val checkIRFor = if (checkIR) Some(CheckingPhase.Compiler) else None
@@ -58,7 +60,8 @@ final class BaseLinker(config: CommonPhaseConfig, checkIR: Boolean) {
     } yield {
       if (checkIR) {
         logger.time("Linker: Check IR") {
-          val errorCount = IRChecker.check(linkResult, logger, CheckingPhase.BaseLinker)
+          val errorCount = IRChecker.check(linkTimeProperties, linkResult,
+              logger, CheckingPhase.BaseLinker)
           if (errorCount != 0) {
             throw new LinkingException(
                 s"There were $errorCount IR checking errors.")
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/Desugarer.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/Desugarer.scala
index 57f8eeb366..b97423440d 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/Desugarer.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/Desugarer.scala
@@ -43,7 +43,8 @@ final class Desugarer(config: CommonPhaseConfig, checkIR: Boolean) {
 
     if (checkIR) {
       logger.time("Desugarer: Check IR") {
-        val errorCount = IRChecker.check(result, logger, CheckingPhase.Desugarer)
+        val errorCount = IRChecker.check(linkTimeProperties, result, logger,
+            CheckingPhase.Desugarer)
         if (errorCount != 0) {
           throw new AssertionError(
               s"There were $errorCount IR checking errors after desugaring (this is a Scala.js bug)")
@@ -149,6 +150,21 @@ private[linker] object Desugarer {
             case LinkTimeProperties.LinkTimeString(value)  => StringLiteral(value)
           }
 
+        case LinkTimeIf(cond, thenp, elsep) =>
+          LinkTimeEvaluator.tryEvalLinkTimeBooleanExpr(linkTimeProperties, cond) match {
+            case Some(result) =>
+              if (result)
+                transform(thenp)
+              else
+                transform(elsep)
+            case None =>
+              throw new AssertionError(
+                  s"Invalid link-time condition should not have passed the reachability analysis:\n" +
+                  s"${tree.show}\n" +
+                  s"at ${tree.pos}.\n" +
+                  "Consider running the linker with `withCheckIR(true)` before submitting a bug report.")
+          }
+
         case NewLambda(descriptor, fun) =>
           implicit val pos = tree.pos
           val (className, ctorName) = syntheticLambdaNamesFor(descriptor)
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/LinkTimeEvaluator.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/LinkTimeEvaluator.scala
new file mode 100644
index 0000000000..3ab224306f
--- /dev/null
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/LinkTimeEvaluator.scala
@@ -0,0 +1,129 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package org.scalajs.linker.frontend
+
+import org.scalajs.ir.Position
+import org.scalajs.ir.Trees._
+import org.scalajs.ir.Trees.LinkTimeProperty._
+
+import org.scalajs.linker.frontend.LinkTimeProperties._
+import org.scalajs.linker.interface.LinkingException
+
+private[linker] object LinkTimeEvaluator {
+
+  /** Try and evaluate a link-time expression tree as a boolean value.
+   *
+   *  This method assumes that the given `tree` is valid according to the
+   *  `ClassDefChecker` and that its `tpe` is `BooleanType`.
+   *  If that is not the case, it may throw or return an arbitrary result.
+   *
+   *  Returns `None` if any subtree that needed evaluation was a missing
+   *  `LinkTimeProperty` or one with the wrong type (i.e., one that would not
+   *  pass the reachability analysis).
+   */
+  def tryEvalLinkTimeBooleanExpr(
+      linkTimeProperties: LinkTimeProperties, tree: Tree): Option[Boolean] = {
+    implicit val pos = tree.pos
+
+    tryEvalLinkTimeExpr(linkTimeProperties, tree).map(booleanValue(_))
+  }
+
+  /** Try and evaluate a link-time expression tree.
+   *
+   *  This method assumes that the given `tree` is valid according to the
+   *  `ClassDefChecker`.
+   *  If that is not the case, it may throw or return an arbitrary result.
+   *
+   *  Returns `None` if any subtree that needed evaluation was a missing
+   *  `LinkTimeProperty` or one with the wrong type (i.e., one that would not
+   *  pass the reachability analysis).
+   */
+  private def tryEvalLinkTimeExpr(
+      props: LinkTimeProperties, tree: Tree): Option[LinkTimeValue] = {
+    implicit val pos = tree.pos
+
+    tree match {
+      case IntLiteral(value)     => Some(LinkTimeInt(value))
+      case BooleanLiteral(value) => Some(LinkTimeBoolean(value))
+      case StringLiteral(value)  => Some(LinkTimeString(value))
+
+      case LinkTimeProperty(name) =>
+        props.get(name).filter(_.tpe == tree.tpe)
+
+      case UnaryOp(op, lhs) =>
+        import UnaryOp._
+        for {
+          l <- tryEvalLinkTimeExpr(props, lhs)
+        } yield {
+          op match {
+            case Boolean_! => LinkTimeBoolean(!booleanValue(l))
+
+            case _ =>
+              throw new LinkingException(
+                  s"Illegal unary op $op in link-time tree at $pos")
+          }
+        }
+
+      case BinaryOp(op, lhs, rhs) =>
+        import BinaryOp._
+        for {
+          l <- tryEvalLinkTimeExpr(props, lhs)
+          r <- tryEvalLinkTimeExpr(props, rhs)
+        } yield {
+          op match {
+            case Boolean_== => LinkTimeBoolean(booleanValue(l) == booleanValue(r))
+            case Boolean_!= => LinkTimeBoolean(booleanValue(l) != booleanValue(r))
+            case Boolean_|  => LinkTimeBoolean(booleanValue(l) | booleanValue(r))
+            case Boolean_&  => LinkTimeBoolean(booleanValue(l) & booleanValue(r))
+
+            case Int_== => LinkTimeBoolean(intValue(l) == intValue(r))
+            case Int_!= => LinkTimeBoolean(intValue(l) != intValue(r))
+            case Int_<  => LinkTimeBoolean(intValue(l) < intValue(r))
+            case Int_<= => LinkTimeBoolean(intValue(l) <= intValue(r))
+            case Int_>  => LinkTimeBoolean(intValue(l) > intValue(r))
+            case Int_>= => LinkTimeBoolean(intValue(l) >= intValue(r))
+
+            case _ =>
+              throw new LinkingException(
+                  s"Illegal binary op $op in link-time tree at $pos")
+          }
+        }
+
+      case LinkTimeIf(cond, thenp, elsep) =>
+        tryEvalLinkTimeExpr(props, cond).flatMap { c =>
+          if (booleanValue(c))
+            tryEvalLinkTimeExpr(props, thenp)
+          else
+            tryEvalLinkTimeExpr(props, elsep)
+        }
+
+      case _ =>
+        throw new LinkingException(
+            s"Illegal tree of class ${tree.getClass().getName()} in link-time tree at $pos")
+    }
+  }
+
+  private def intValue(value: LinkTimeValue)(implicit pos: Position): Int = value match {
+    case LinkTimeInt(value) =>
+      value
+    case _ =>
+      throw new LinkingException(s"Value of type int expected but got $value at $pos")
+  }
+
+  private def booleanValue(value: LinkTimeValue)(implicit pos: Position): Boolean = value match {
+    case LinkTimeBoolean(value) =>
+      value
+    case _ =>
+      throw new LinkingException(s"Value of type boolean expected but got $value at $pos")
+  }
+}
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/Refiner.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/Refiner.scala
index 0f074adf55..4f778351ba 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/Refiner.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/Refiner.scala
@@ -30,6 +30,8 @@ import org.scalajs.linker.analyzer._
 final class Refiner(config: CommonPhaseConfig, checkIR: Boolean) {
   import Refiner._
 
+  private val linkTimeProperties = LinkTimeProperties.fromCoreSpec(config.coreSpec)
+
   private val irLoader = new ClassDefIRLoader
   private val analyzer = {
     val checkIRFor = if (checkIR) Some(CheckingPhase.Optimizer) else None
@@ -81,7 +83,8 @@ final class Refiner(config: CommonPhaseConfig, checkIR: Boolean) {
 
       if (shouldRunIRChecker) {
         logger.time("Refiner: Check IR") {
-          val errorCount = IRChecker.check(result, logger, CheckingPhase.Optimizer)
+          val errorCount = IRChecker.check(linkTimeProperties, result, logger,
+              CheckingPhase.Optimizer)
           if (errorCount != 0) {
             throw new AssertionError(
                 s"There were $errorCount IR checking errors after optimization (this is a Scala.js bug)")
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
index 51cebcdcca..9f7fe1aa95 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
@@ -689,7 +689,8 @@ private[optimizer] abstract class OptimizerCore(
           _:JSGlobalRef | _:JSTypeOfGlobalRef | _:Literal =>
         tree
 
-      case _:LinkTimeProperty | _:NewLambda | _:RecordSelect | _:Transient =>
+      case _:LinkTimeProperty | _:LinkTimeIf | _:NewLambda | _:RecordSelect |
+          _:Transient =>
         throw new IllegalArgumentException(
             s"Invalid tree in transform of class ${tree.getClass.getName}: $tree")
     }
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/AnalyzerTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/AnalyzerTest.scala
index 4eb535144d..c543be0f2b 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/AnalyzerTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/AnalyzerTest.scala
@@ -874,6 +874,114 @@ class AnalyzerTest {
     )
     Future.sequence(results)
   }
+
+  @Test
+  def linkTimeIfReachable(): AsyncResult = await {
+    val mainMethodName = m("main", Nil, IntRef)
+    val fooMethodName = m("foo", Nil, IntRef)
+    val barMethodName = m("bar", Nil, IntRef)
+
+    val thisType = ClassType("A", nullable = false)
+
+    val productionMode = true
+
+    /* linkTimeIf(productionMode) {
+     *   this.foo()
+     * } {
+     *   this.bar()
+     * }
+     */
+    val mainBody = LinkTimeIf(
+      BinaryOp(BinaryOp.Boolean_==,
+          LinkTimeProperty("core/productionMode")(BooleanType),
+          BooleanLiteral(productionMode)),
+      Apply(EAF, This()(thisType), fooMethodName, Nil)(IntType),
+      Apply(EAF, This()(thisType), barMethodName, Nil)(IntType)
+    )(IntType)
+
+    val classDefs = Seq(
+      classDef("A", superClass = Some(ObjectClass),
+        methods = List(
+          trivialCtor("A"),
+          MethodDef(EMF, mainMethodName, NON, Nil, IntType, Some(mainBody))(EOH, UNV),
+          MethodDef(EMF, fooMethodName, NON, Nil, IntType, Some(int(1)))(EOH, UNV),
+          MethodDef(EMF, barMethodName, NON, Nil, IntType, Some(int(2)))(EOH, UNV)
+        )
+      )
+    )
+
+    val requirements = {
+      reqsFactory.instantiateClass("A", NoArgConstructorName) ++
+      reqsFactory.callMethod("A", mainMethodName)
+    }
+
+    val analysisFuture = computeAnalysis(classDefs, requirements,
+        config = StandardConfig().withSemantics(_.withProductionMode(productionMode)))
+
+    for (analysis <- analysisFuture) yield {
+      assertNoError(analysis)
+
+      val AfooMethodInfo = analysis.classInfos("A")
+        .methodInfos(MemberNamespace.Public)(fooMethodName)
+      assertTrue(AfooMethodInfo.isReachable)
+
+      val AbarMethodInfo = analysis.classInfos("A")
+        .methodInfos(MemberNamespace.Public)(barMethodName)
+      assertFalse(AbarMethodInfo.isReachable)
+    }
+  }
+
+  @Test
+  def linkTimeIfError(): AsyncResult = await {
+    val mainMethodName = m("main", Nil, IntRef)
+    val fooMethodName = m("foo", Nil, IntRef)
+
+    val thisType = ClassType("A", nullable = false)
+
+    val productionMode = true
+
+    /* linkTimeIf(unknownProperty) {
+     *   this.foo()
+     * } {
+     *   this.bar()
+     * }
+     */
+    val mainBody = LinkTimeIf(
+      BinaryOp(BinaryOp.Boolean_==,
+          LinkTimeProperty("core/unknownProperty")(BooleanType),
+          BooleanLiteral(productionMode)),
+      Apply(EAF, This()(thisType), fooMethodName, Nil)(IntType),
+      Apply(EAF, This()(thisType), fooMethodName, Nil)(IntType)
+    )(IntType)
+
+    val classDefs = Seq(
+      classDef("A", superClass = Some(ObjectClass),
+        methods = List(
+          trivialCtor("A"),
+          MethodDef(EMF, mainMethodName, NON, Nil, IntType, Some(mainBody))(EOH, UNV)
+        )
+      )
+    )
+
+    val requirements = {
+      reqsFactory.instantiateClass("A", NoArgConstructorName) ++
+      reqsFactory.callMethod("A", mainMethodName)
+    }
+
+    val analysisFuture = computeAnalysis(classDefs, requirements,
+        config = StandardConfig().withSemantics(_.withProductionMode(productionMode)))
+
+    for (analysis <- analysisFuture) yield {
+      assertContainsError(s"InvalidLinkTimeProperty(core/unknownProperty)", analysis) {
+        case InvalidLinkTimeProperty("core/unknownProperty", BooleanType, _) => true
+      }
+
+      // Branches are not taken, so there is no error for linking `foo`
+      assertNotContainsError(s"any MissingMethod", analysis) {
+        case MissingMethod(_, _) => true
+      }
+    }
+  }
 }
 
 object AnalyzerTest {
@@ -962,10 +1070,21 @@ object AnalyzerTest {
 
   private def assertContainsError(msg: String, analysis: Analysis)(
       pf: PartialFunction[Error, Boolean]): Unit = {
-    val fullMessage = s"Expected $msg, got ${analysis.errors}"
-    assertTrue(fullMessage, analysis.errors.exists {
+    assertTrue(s"Expected $msg, got ${analysis.errors}",
+        containsError(analysis)(pf))
+  }
+
+  private def assertNotContainsError(msg: String, analysis: Analysis)(
+      pf: PartialFunction[Error, Boolean]): Unit = {
+    assertFalse(s"Did not expect $msg, got ${analysis.errors}",
+        containsError(analysis)(pf))
+  }
+
+  private def containsError(analysis: Analysis)(
+      pf: PartialFunction[Error, Boolean]): Boolean = {
+    analysis.errors.exists {
       e => pf.applyOrElse(e, (_: Error) => false)
-    })
+    }
   }
 
   object ClsInfo {
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/IRCheckerTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/IRCheckerTest.scala
index 73dce25631..1c6ae731b1 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/IRCheckerTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/IRCheckerTest.scala
@@ -446,6 +446,7 @@ object IRCheckerTest {
           new ClassTransformer {
             override def transform(tree: Tree): Tree = tree match {
               case tree: LinkTimeProperty => zeroOf(tree.tpe)
+              case tree: LinkTimeIf       => zeroOf(tree.tpe)
               case tree: NewLambda        => UnaryOp(UnaryOp.Throw, Null())
               case _                      => super.transform(tree)
             }
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/checker/ClassDefCheckerTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/checker/ClassDefCheckerTest.scala
index 6441fd0c48..309cc5d7a1 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/checker/ClassDefCheckerTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/checker/ClassDefCheckerTest.scala
@@ -834,6 +834,84 @@ class ClassDefCheckerTest {
         "Assignment to RecordSelect of illegal tree: org.scalajs.ir.Trees$IntLiteral",
         previousPhase = CheckingPhase.Optimizer)
   }
+
+  @Test
+  def linkTimePropertyTest(): Unit = {
+    // Test that some illegal types are rejected
+    for (tpe <- List(FloatType, NullType, NothingType, ClassType(BoxedStringClass, nullable = false))) {
+      assertError(
+          mainTestClassDef(LinkTimeProperty("foo")(tpe)),
+          s"${tpe.show()} is not a valid type for LinkTimeProperty")
+    }
+
+    // Some error also gets reported if used in link-time-tree position
+    assertError(
+        mainTestClassDef {
+          LinkTimeIf(LinkTimeProperty("foo")(NothingType), int(5), int(6))(IntType)
+        },
+        s"boolean expected but nothing found in link-time tree")
+
+    // LinkTimeProperty is rejected after desugaring
+    assertError(
+        mainTestClassDef(LinkTimeProperty("foo")(IntType)),
+        "Illegal link-time property 'foo' after desugaring",
+        previousPhase = CheckingPhase.Optimizer)
+  }
+
+  @Test
+  def linkTimeIfTest(): Unit = {
+    def makeTestClassDef(cond: Tree): ClassDef = {
+      classDef(
+        "Foo",
+        superClass = Some(ObjectClass),
+        methods = List(
+          trivialCtor("Foo"),
+          MethodDef(EMF, MethodName("foo", Nil, VoidRef), NON, Nil, VoidType, Some {
+            LinkTimeIf(
+              cond,
+              consoleLog(StringLiteral("foo")),
+              consoleLog(StringLiteral("bar"))
+            )(VoidType)
+          })(EOH, UNV)
+        )
+      )
+    }
+
+    assertError(
+      makeTestClassDef(
+        UnaryOp(UnaryOp.Boolean_!, int(0))
+      ),
+      "boolean expected but int found in link-time tree"
+    )
+
+    assertError(
+      makeTestClassDef(
+        BinaryOp(BinaryOp.Int_==, int(0), LinkTimeProperty("core/productionMode")(BooleanType))
+      ),
+      "int expected but boolean found in link-time tree"
+    )
+
+    assertError(
+      makeTestClassDef(
+        BinaryOp(BinaryOp.Boolean_==, int(0), LinkTimeProperty("core/productionMode")(BooleanType))
+      ),
+      "boolean expected but int found in link-time tree"
+    )
+
+    assertError(
+      makeTestClassDef(
+        BinaryOp(BinaryOp.===, int(0), int(1))
+      ),
+      "illegal binary op 1 in link-time tree"
+    )
+
+    assertError(
+      makeTestClassDef(
+        If(BooleanLiteral(true), BooleanLiteral(true), BooleanLiteral(false))(BooleanType)
+      ),
+      "illegal tree of class org.scalajs.ir.Trees$If in link-time tree"
+    )
+  }
 }
 
 private object ClassDefCheckerTest {
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/frontend/modulesplitter/LinkTimeEvaluatorTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/frontend/modulesplitter/LinkTimeEvaluatorTest.scala
new file mode 100644
index 0000000000..79e8d36ff6
--- /dev/null
+++ b/linker/shared/src/test/scala/org/scalajs/linker/frontend/modulesplitter/LinkTimeEvaluatorTest.scala
@@ -0,0 +1,102 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package org.scalajs.linker.frontend
+
+import org.junit.Test
+import org.junit.Assert._
+
+import org.scalajs.ir.Trees._
+import org.scalajs.ir.Types._
+
+import org.scalajs.linker.interface.{ESFeatures, ESVersion, Semantics, StandardConfig}
+import org.scalajs.linker.standard.CoreSpec
+import org.scalajs.linker.testutils.TestIRBuilder._
+
+class LinkTimeEvaluatorTest {
+  /** Convenience builder for `LinkTimeProperties` with mostly-default configs. */
+  private def make(
+    semantics: Semantics => Semantics = identity,
+    esFeatures: ESFeatures => ESFeatures = identity,
+    isWebAssembly: Boolean = false
+  ): LinkTimeProperties = {
+    val config = StandardConfig()
+      .withSemantics(semantics)
+      .withESFeatures(esFeatures)
+      .withExperimentalUseWebAssembly(isWebAssembly)
+    LinkTimeProperties.fromCoreSpec(CoreSpec.fromStandardConfig(config))
+  }
+
+  @Test
+  def testTryEvalLinkTimeBooleanExpr(): Unit = {
+    val defaults = make()
+
+    def test(expected: Option[Boolean], tree: Tree, config: LinkTimeProperties = defaults): Unit =
+      assertEquals(expected, LinkTimeEvaluator.tryEvalLinkTimeBooleanExpr(config, tree))
+
+    def testTrue(tree: Tree, config: LinkTimeProperties = defaults): Unit =
+      test(Some(true), tree, config)
+
+    def testFalse(tree: Tree, config: LinkTimeProperties = defaults): Unit =
+      test(Some(false), tree, config)
+
+    def testFail(tree: Tree, config: LinkTimeProperties = defaults): Unit =
+      test(None, tree, config)
+
+    // Boolean literal
+    testTrue(bool(true))
+    testFalse(bool(false))
+
+    // Boolean link-time property
+    testFalse(LinkTimeProperty("core/isWebAssembly")(BooleanType))
+    testTrue(LinkTimeProperty("core/isWebAssembly")(BooleanType), make(isWebAssembly = true))
+    testFail(LinkTimeProperty("core/missing")(BooleanType))
+    testFail(LinkTimeProperty("core/esVersion")(BooleanType))
+
+    // Int comparison
+    for (l <- List(3, 5, 7); r <- List(3, 5, 7)) {
+      test(Some(l == r), BinaryOp(BinaryOp.Int_==, int(l), int(r)))
+      test(Some(l != r), BinaryOp(BinaryOp.Int_!=, int(l), int(r)))
+      test(Some(l < r), BinaryOp(BinaryOp.Int_<, int(l), int(r)))
+      test(Some(l <= r), BinaryOp(BinaryOp.Int_<=, int(l), int(r)))
+      test(Some(l > r), BinaryOp(BinaryOp.Int_>, int(l), int(r)))
+      test(Some(l >= r), BinaryOp(BinaryOp.Int_>=, int(l), int(r)))
+    }
+
+    // Boolean operator
+    testTrue(UnaryOp(UnaryOp.Boolean_!, bool(false)))
+    testFalse(UnaryOp(UnaryOp.Boolean_!, bool(true)))
+
+    // Comparison with link-time property
+    val esVersionProp = LinkTimeProperty("core/esVersion")(IntType)
+    testTrue(BinaryOp(BinaryOp.Int_>=, esVersionProp, int(ESVersion.ES2015.edition)))
+    testFalse(BinaryOp(BinaryOp.Int_>=, esVersionProp, int(ESVersion.ES2019.edition)))
+    testTrue(BinaryOp(BinaryOp.Int_>=, esVersionProp, int(ESVersion.ES2019.edition)),
+        make(esFeatures = _.withESVersion(ESVersion.ES2021)))
+
+    // LinkTimeIf
+    testTrue(LinkTimeIf(bool(true), bool(true), bool(false))(BooleanType))
+    testFalse(LinkTimeIf(bool(true), bool(false), bool(true))(BooleanType))
+    testFalse(LinkTimeIf(bool(false), bool(true), bool(false))(BooleanType))
+
+    // Complex expression: esVersion >= ES2016 && esVersion <= ES2019
+    val complexExpr = LinkTimeIf(
+        BinaryOp(BinaryOp.Int_>=, esVersionProp, int(ESVersion.ES2016.edition)),
+        BinaryOp(BinaryOp.Int_<=, esVersionProp, int(ESVersion.ES2019.edition)),
+        bool(false))(
+        BooleanType)
+    testTrue(complexExpr, make(esFeatures = _.withESVersion(ESVersion.ES2017)))
+    testTrue(complexExpr, make(esFeatures = _.withESVersion(ESVersion.ES2019)))
+    testFalse(complexExpr, make(esFeatures = _.withESVersion(ESVersion.ES2015)))
+    testFalse(complexExpr, make(esFeatures = _.withESVersion(ESVersion.ES2021)))
+  }
+}
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/testutils/TestIRBuilder.scala b/linker/shared/src/test/scala/org/scalajs/linker/testutils/TestIRBuilder.scala
index 7d022a5123..a4284ec897 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/testutils/TestIRBuilder.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/testutils/TestIRBuilder.scala
@@ -196,6 +196,7 @@ object TestIRBuilder {
   implicit def methodName2MethodIdent(name: MethodName): MethodIdent =
     MethodIdent(name)
 
+  def bool(x: Boolean): BooleanLiteral = BooleanLiteral(x)
   def int(x: Int): IntLiteral = IntLiteral(x)
   def str(x: String): StringLiteral = StringLiteral(x)
 }
diff --git a/test-suite/js/src/test/scala/org/scalajs/testsuite/library/LinkTimeIfTest.scala b/test-suite/js/src/test/scala/org/scalajs/testsuite/library/LinkTimeIfTest.scala
new file mode 100644
index 0000000000..1cca641fbf
--- /dev/null
+++ b/test-suite/js/src/test/scala/org/scalajs/testsuite/library/LinkTimeIfTest.scala
@@ -0,0 +1,95 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package org.scalajs.testsuite.library
+
+import scala.scalajs.js
+import scala.scalajs.LinkingInfo._
+
+import org.junit.Test
+import org.junit.Assert._
+import org.junit.Assume._
+
+import org.scalajs.testsuite.utils.Platform
+
+class LinkTimeIfTest {
+  @Test def linkTimeIfConst(): Unit = {
+    // boolean const
+    assertEquals(1, linkTimeIf(true) { 1 } { 2 })
+    assertEquals(2, linkTimeIf(false) { 1 } { 2 })
+  }
+
+  @Test def linkTimeIfProp(): Unit = {
+    locally {
+      val cond = Platform.isInProductionMode
+      assertEquals(cond, linkTimeIf(productionMode) { true } { false })
+    }
+
+    locally {
+      val cond = !Platform.isInProductionMode
+      assertEquals(cond, linkTimeIf(!productionMode) { true } { false })
+    }
+  }
+
+  @Test def linkTimIfIntProp(): Unit = {
+    locally {
+      val cond = Platform.assumedESVersion >= ESVersion.ES2015
+      assertEquals(cond, linkTimeIf(esVersion >= ESVersion.ES2015) { true } { false })
+    }
+
+    locally {
+      val cond = !(Platform.assumedESVersion < ESVersion.ES2015)
+      assertEquals(cond, linkTimeIf(!(esVersion < ESVersion.ES2015)) { true } { false })
+    }
+  }
+
+  @Test def linkTimeIfNested(): Unit = {
+    locally {
+      val cond = {
+        Platform.isInProductionMode &&
+        Platform.assumedESVersion >= ESVersion.ES2015
+      }
+      assertEquals(if (cond) 53 else 78,
+          linkTimeIf(productionMode && esVersion >= ESVersion.ES2015) { 53 } { 78 })
+    }
+
+    locally {
+      val cond = {
+        Platform.assumedESVersion >= ESVersion.ES2015 &&
+        Platform.assumedESVersion < ESVersion.ES2019 &&
+        Platform.isInProductionMode
+      }
+      val result = linkTimeIf(esVersion >= ESVersion.ES2015 &&
+          esVersion < ESVersion.ES2019 && productionMode) {
+        53
+      } {
+        78
+      }
+      assertEquals(if (cond) 53 else 78, result)
+    }
+  }
+
+  @Test def exponentOp(): Unit = {
+    def pow(x: Double, y: Double): Double = {
+      linkTimeIf(esVersion >= ESVersion.ES2016) {
+        assertTrue("Took the wrong branch of linkTimeIf when linking for ES 2016+",
+            esVersion >= ESVersion.ES2016)
+        (x.asInstanceOf[js.Dynamic] ** y.asInstanceOf[js.Dynamic]).asInstanceOf[Double]
+      } {
+        assertFalse("Took the wrong branch of linkTimeIf when linking for ES 2015-",
+            esVersion >= ESVersion.ES2016)
+        Math.pow(x, y)
+      }
+    }
+    assertEquals(pow(2.0, 8.0), 256.0, 0)
+  }
+}

From f0e7a337b03584b0bb2e7868153509fbd60a409b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Sun, 5 Jan 2025 19:19:20 +0100
Subject: [PATCH 287/298] Use JS bigint's if possible inside the `parseFloat`
 algorithm.

We use a `linkTimeIf` to select a `bigint`-based implementation of
`parseFloatDecimalCorrection` when they are supported. We need a
`linkTimeIf` in this case because it uses the JS `**` operator,
which does not link below ES 2016.

The `bigint`-based implementation avoids bringing in the entire
`BigInteger` implementation, which is a major code size win if that
was the only reason `BigInteger` was needed.
---
 javalib/src/main/scala/java/lang/Float.scala | 82 ++++++++++++++++----
 1 file changed, 69 insertions(+), 13 deletions(-)

diff --git a/javalib/src/main/scala/java/lang/Float.scala b/javalib/src/main/scala/java/lang/Float.scala
index 8fa4ce3070..a2d54c77fd 100644
--- a/javalib/src/main/scala/java/lang/Float.scala
+++ b/javalib/src/main/scala/java/lang/Float.scala
@@ -13,9 +13,9 @@
 package java.lang
 
 import java.lang.constant.{Constable, ConstantDesc}
-import java.math.BigInteger
 
 import scala.scalajs.js
+import scala.scalajs.LinkingInfo._
 
 /* This is a hijacked class. Its instances are primitive numbers.
  * Constructors are not emitted.
@@ -226,9 +226,23 @@ object Float {
       fractionalPartStr: String, exponentStr: String,
       zDown: scala.Float, zUp: scala.Float, mid: scala.Double): scala.Float = {
 
+    /* Get the best available implementation of big integers for the given platform.
+     *
+     * If JS bigint's are supported, use them. Otherwise fall back on
+     * `java.math.BigInteger`.
+     *
+     * We need a `linkTimeIf` here because the JS bigint implementation uses
+     * the `**` operator, which does not link when `esVersion < ESVersion.ES2016`.
+     */
+    val bigIntImpl = linkTimeIf[BigIntImpl](esVersion >= ESVersion.ES2020) {
+      BigIntImpl.JSBigInt
+    } {
+      BigIntImpl.JBigInteger
+    }
+
     // 1. Accurately parse the string with the representation f × 10ᵉ
 
-    val f: BigInteger = new BigInteger(integralPartStr + fractionalPartStr)
+    val f: bigIntImpl.Repr = bigIntImpl.fromString(integralPartStr + fractionalPartStr)
     val e: Int = Integer.parseInt(exponentStr) - fractionalPartStr.length()
 
     /* Note: we know that `e` is "reasonable" (in the range [-324, +308]). If
@@ -261,24 +275,23 @@ object Float {
 
     val mExplicitBits = midBits & ((1L << mbits) - 1)
     val mImplicit1Bit = 1L << mbits // the implicit '1' bit of a normalized floating-point number
-    val m = BigInteger.valueOf(mExplicitBits | mImplicit1Bit)
+    val m = bigIntImpl.fromUnsignedLong53(mExplicitBits | mImplicit1Bit)
     val k = biasedK - bias - mbits
 
     // 3. Accurately compare f × 10ᵉ to m × 2ᵏ
 
-    @inline def compare(x: BigInteger, y: BigInteger): Int =
-      x.compareTo(y)
+    import bigIntImpl.{multiplyBy2Pow, multiplyBy10Pow}
 
     val cmp = if (e >= 0) {
       if (k >= 0)
-        compare(multiplyBy10Pow(f, e), multiplyBy2Pow(m, k))
+        bigIntImpl.compare(multiplyBy10Pow(f, e), multiplyBy2Pow(m, k))
       else
-        compare(multiplyBy2Pow(multiplyBy10Pow(f, e), -k), m) // this branch may be dead code in practice
+        bigIntImpl.compare(multiplyBy2Pow(multiplyBy10Pow(f, e), -k), m) // this branch may be dead code in practice
     } else {
       if (k >= 0)
-        compare(f, multiplyBy2Pow(multiplyBy10Pow(m, -e), k))
+        bigIntImpl.compare(f, multiplyBy2Pow(multiplyBy10Pow(m, -e), k))
       else
-        compare(multiplyBy2Pow(f, -k), multiplyBy10Pow(m, -e))
+        bigIntImpl.compare(multiplyBy2Pow(f, -k), multiplyBy10Pow(m, -e))
     }
 
     // 4. Choose zDown or zUp depending on the result of the comparison
@@ -293,11 +306,54 @@ object Float {
       zUp
   }
 
-  @inline private def multiplyBy10Pow(v: BigInteger, e: Int): BigInteger =
-    v.multiply(BigInteger.TEN.pow(e))
+  /** An implementation of big integer arithmetics that we need in the above method. */
+  private sealed abstract class BigIntImpl {
+    type Repr
+
+    def fromString(str: String): Repr
+
+    /** Creates a big integer from a `Long` that needs at most 53 bits (unsigned). */
+    def fromUnsignedLong53(x: scala.Long): Repr
+
+    def multiplyBy2Pow(v: Repr, e: Int): Repr
+    def multiplyBy10Pow(v: Repr, e: Int): Repr
+
+    def compare(x: Repr, y: Repr): Int
+  }
+
+  private object BigIntImpl {
+    object JSBigInt extends BigIntImpl {
+      type Repr = js.BigInt
+
+      @inline def fromString(str: String): Repr = js.BigInt(str)
 
-  @inline private def multiplyBy2Pow(v: BigInteger, e: Int): BigInteger =
-    v.shiftLeft(e)
+      // The 53-bit restriction guarantees that the conversion to `Double` is lossless.
+      @inline def fromUnsignedLong53(x: scala.Long): Repr = js.BigInt(x.toDouble)
+
+      @inline def multiplyBy2Pow(v: Repr, e: Int): Repr = v << js.BigInt(e)
+      @inline def multiplyBy10Pow(v: Repr, e: Int): Repr = v * (js.BigInt(10) ** js.BigInt(e))
+
+      @inline def compare(x: Repr, y: Repr): Int = {
+        if (x < y) -1
+        else if (x > y) 1
+        else 0
+      }
+    }
+
+    object JBigInteger extends BigIntImpl {
+      import java.math.BigInteger
+
+      type Repr = BigInteger
+
+      @inline def fromString(str: String): Repr = new BigInteger(str)
+      @inline def fromUnsignedLong53(x: scala.Long): Repr = BigInteger.valueOf(x)
+
+      @inline def multiplyBy2Pow(v: Repr, e: Int): Repr = v.shiftLeft(e)
+      @inline def multiplyBy10Pow(v: Repr, e: Int): Repr = v.multiply(BigInteger.TEN.pow(e))
+
+      @inline def compare(x: Repr, y: Repr): Int = x.compareTo(y)
+    }
+  }
 
   private def parseFloatHexadecimal(integralPartStr: String,
       fractionalPartStr: String, binaryExpStr: String): scala.Float = {

From 5c3184396b9a0fe83b10c2662093491d092df064 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Fri, 16 May 2025 13:51:39 +0200
Subject: [PATCH 288/298] Refactoring: Isolate handling of javalib methods with
 special bodies.

A number of methods from the javalib are special-cased by the
compiler, which replaces their body with a dedicated `UnaryOp` or
`BinaryOp`.

This commit refactors that handling to isolate it better from the
handling of regular methods. We also make it a bit more flexible,
so that we can more easily add further such methods in the future.
---
 .../org/scalajs/nscplugin/GenJSCode.scala     | 179 +++++++++++-------
 1 file changed, 106 insertions(+), 73 deletions(-)

diff --git a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
index dc1348ea22..6696ce90c2 100644
--- a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
+++ b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
@@ -2298,50 +2298,17 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
           isJSFunctionDef(currentClassSym)) {
         val flags = js.MemberFlags.empty.withNamespace(namespace)
         val body = {
-          def genAsUnaryOp(op: js.UnaryOp.Code): js.Tree =
-            js.UnaryOp(op, genThis())
-          def genAsBinaryOp(op: js.BinaryOp.Code): js.Tree =
-            js.BinaryOp(op, genThis(), jsParams.head.ref)
-          def genAsBinaryOpRhsNotNull(op: js.BinaryOp.Code): js.Tree =
-            js.BinaryOp(op, genThis(), js.UnaryOp(js.UnaryOp.CheckNotNull, jsParams.head.ref))
-
-          if (currentClassSym.get == HackedStringClass) {
-            /* Hijack the bodies of String.length and String.charAt and replace
-             * them with String_length and String_charAt operations, respectively.
-             */
-            methodName.name match {
-              case `lengthMethodName` => genAsUnaryOp(js.UnaryOp.String_length)
-              case `charAtMethodName` => genAsBinaryOp(js.BinaryOp.String_charAt)
-              case _                  => genBody()
-            }
-          } else if (currentClassSym.get == ClassClass) {
-            // Similar, for the Class_x operations
-            methodName.name match {
-              case `getNameMethodName`          => genAsUnaryOp(js.UnaryOp.Class_name)
-              case `isPrimitiveMethodName`      => genAsUnaryOp(js.UnaryOp.Class_isPrimitive)
-              case `isInterfaceMethodName`      => genAsUnaryOp(js.UnaryOp.Class_isInterface)
-              case `isArrayMethodName`          => genAsUnaryOp(js.UnaryOp.Class_isArray)
-              case `getComponentTypeMethodName` => genAsUnaryOp(js.UnaryOp.Class_componentType)
-              case `getSuperclassMethodName`    => genAsUnaryOp(js.UnaryOp.Class_superClass)
-
-              case `isInstanceMethodName`       => genAsBinaryOp(js.BinaryOp.Class_isInstance)
-              case `isAssignableFromMethodName` => genAsBinaryOpRhsNotNull(js.BinaryOp.Class_isAssignableFrom)
-              case `castMethodName`             => genAsBinaryOp(js.BinaryOp.Class_cast)
-
-              case _ => genBody()
-            }
-          } else if (currentClassSym.get == JavaLangReflectArrayModClass) {
-            methodName.name match {
-              case `arrayNewInstanceMethodName` =>
-                val List(jlClassParam, lengthParam) = jsParams
-                js.BinaryOp(js.BinaryOp.Class_newArray,
-                    js.UnaryOp(js.UnaryOp.CheckNotNull, jlClassParam.ref),
-                    lengthParam.ref)
-              case _ =>
+          val classOwner = currentClassSym.owner
+          if (classOwner != JavaLangPackageClass && classOwner.owner != JavaLangPackageClass) {
+            // Fast path; it cannot be any of the special methods of the javalib
+            genBody()
+          } else {
+            JavalibMethodsWithOpBody.get((encodeClassName(currentClassSym), methodName.name)) match {
+              case None =>
                 genBody()
+              case Some(javalibOpBody) =>
+                javalibOpBody.generate(genThis(), jsParams.map(_.ref))
             }
-          } else {
-            genBody()
           }
         }
         js.MethodDef(flags, methodName, originalName, jsParams, resultIRType,
@@ -7379,37 +7346,6 @@ private object GenJSCode {
   private val ObjectArgConstructorName =
     MethodName.constructor(List(jswkn.ObjectRef))
 
-  private val lengthMethodName =
-    MethodName("length", Nil, jstpe.IntRef)
-  private val charAtMethodName =
-    MethodName("charAt", List(jstpe.IntRef), jstpe.CharRef)
-
-  private val getNameMethodName =
-    MethodName("getName", Nil, jstpe.ClassRef(jswkn.BoxedStringClass))
-  private val isPrimitiveMethodName =
-    MethodName("isPrimitive", Nil, jstpe.BooleanRef)
-  private val isInterfaceMethodName =
-    MethodName("isInterface", Nil, jstpe.BooleanRef)
-  private val isArrayMethodName =
-    MethodName("isArray", Nil, jstpe.BooleanRef)
-  private val getComponentTypeMethodName =
-    MethodName("getComponentType", Nil, jstpe.ClassRef(jswkn.ClassClass))
-  private val getSuperclassMethodName =
-    MethodName("getSuperclass", Nil, jstpe.ClassRef(jswkn.ClassClass))
-
-  private val isInstanceMethodName =
-    MethodName("isInstance", List(jstpe.ClassRef(jswkn.ObjectClass)), jstpe.BooleanRef)
-  private val isAssignableFromMethodName =
-    MethodName("isAssignableFrom", List(jstpe.ClassRef(jswkn.ClassClass)), jstpe.BooleanRef)
-  private val castMethodName =
-    MethodName("cast", List(jstpe.ClassRef(jswkn.ObjectClass)), jstpe.ClassRef(jswkn.ObjectClass))
-
-  private val arrayNewInstanceMethodName = {
-    MethodName("newInstance",
-        List(jstpe.ClassRef(jswkn.ClassClass), jstpe.IntRef),
-        jstpe.ClassRef(jswkn.ObjectClass))
-  }
-
   private val thisOriginalName = OriginalName("this")
 
   private object BlockOrAlone {
@@ -7425,4 +7361,101 @@ private object GenJSCode {
       case _               => Some((tree, Nil))
     }
   }
+
+  private abstract class JavalibOpBody {
+    /** Generates the body of this special method, given references to the receiver and parameters. */
+    def generate(receiver: js.Tree, args: List[js.Tree])(implicit pos: ir.Position): js.Tree
+  }
+
+  private object JavalibOpBody {
+    private def checkNotNullIf(arg: js.Tree, checkNulls: Boolean)(implicit pos: ir.Position): js.Tree =
+      if (checkNulls && arg.tpe.isNullable) js.UnaryOp(js.UnaryOp.CheckNotNull, arg)
+      else arg
+
+    /* These are case classes for convenience (for the apply method).
+     * They are not intended for pattern matching.
+     */
+
+    /** UnaryOp applying to the `this` parameter. */
+    final case class ThisUnaryOp(op: js.UnaryOp.Code) extends JavalibOpBody {
+      def generate(receiver: js.Tree, args: List[js.Tree])(implicit pos: ir.Position): js.Tree = {
+        assert(args.isEmpty)
+        js.UnaryOp(op, receiver)
+      }
+    }
+
+    /** BinaryOp applying to the `this` parameter and the regular parameter. */
+    final case class ThisBinaryOp(op: js.BinaryOp.Code, checkNulls: Boolean = false) extends JavalibOpBody {
+      def generate(receiver: js.Tree, args: List[js.Tree])(implicit pos: ir.Position): js.Tree = {
+        val List(rhs) = args: @unchecked
+        js.BinaryOp(op, receiver, checkNotNullIf(rhs, checkNulls))
+      }
+    }
+
+    /** UnaryOp applying to the only regular parameter (`this` is ignored). */
+    final case class ArgUnaryOp(op: js.UnaryOp.Code, checkNulls: Boolean = false) extends JavalibOpBody {
+      def generate(receiver: js.Tree, args: List[js.Tree])(implicit pos: ir.Position): js.Tree = {
+        val List(arg) = args: @unchecked
+        js.UnaryOp(op, checkNotNullIf(arg, checkNulls))
+      }
+    }
+
+    /** BinaryOp applying to the two regular paramters (`this` is ignored). */
+    final case class ArgBinaryOp(op: js.BinaryOp.Code, checkNulls: Boolean = false) extends JavalibOpBody {
+      def generate(receiver: js.Tree, args: List[js.Tree])(implicit pos: ir.Position): js.Tree = {
+        val List(lhs, rhs) = args: @unchecked
+        js.BinaryOp(op, checkNotNullIf(lhs, checkNulls), checkNotNullIf(rhs, checkNulls))
+      }
+    }
+  }
+
+  /** Methods of the javalib whose body must be replaced by a dedicated
+   *  UnaryOp or BinaryOp.
+   *
+   *  We use IR encoded names to identify them, rather than scalac Symbols.
+   *  There is no fundamental reason for that. It makes it easier to define
+   *  this map in a declarative way, especially when overloaded methods are
+   *  concerned (Array.newInstance). It also allows to define it independently
+   *  of the Global instance, but that is marginal.
+   */
+  private lazy val JavalibMethodsWithOpBody: Map[(ClassName, MethodName), JavalibOpBody] = {
+    import JavalibOpBody._
+    import js.{UnaryOp => unop, BinaryOp => binop}
+    import jstpe.{BooleanRef => Z, CharRef => C, IntRef => I}
+    import MethodName.{apply => m}
+
+    val O = jswkn.ObjectRef
+    val CC = jstpe.ClassRef(jswkn.ClassClass)
+    val T = jstpe.ClassRef(jswkn.BoxedStringClass)
+
+    val byClass: Map[ClassName, Map[MethodName, JavalibOpBody]] = Map(
+      jswkn.BoxedStringClass -> Map(
+        m("length", Nil, I)     -> ThisUnaryOp(unop.String_length),
+        m("charAt", List(I), C) -> ThisBinaryOp(binop.String_charAt)
+      ),
+      jswkn.ClassClass -> Map(
+        // Unary operators
+        m("getName", Nil, T)           -> ThisUnaryOp(unop.Class_name),
+        m("isPrimitive", Nil, Z)       -> ThisUnaryOp(unop.Class_isPrimitive),
+        m("isInterface", Nil, Z)       -> ThisUnaryOp(unop.Class_isInterface),
+        m("isArray", Nil, Z)           -> ThisUnaryOp(unop.Class_isArray),
+        m("getComponentType", Nil, CC) -> ThisUnaryOp(unop.Class_componentType),
+        m("getSuperclass", Nil, CC)    -> ThisUnaryOp(unop.Class_superClass),
+        // Binary operators
+        m("isInstance", List(O), Z)        -> ThisBinaryOp(binop.Class_isInstance),
+        m("isAssignableFrom", List(CC), Z) -> ThisBinaryOp(binop.Class_isAssignableFrom, checkNulls = true),
+        m("cast", List(O), O)              -> ThisBinaryOp(binop.Class_cast)
+      ),
+      ClassName("java.lang.reflect.Array$") -> Map(
+        m("newInstance", List(CC, I), O) -> ArgBinaryOp(binop.Class_newArray, checkNulls = true)
+      )
+    )
+
+    for {
+      (cls, methods) <- byClass
+      (methodName, body) <- methods
+    } yield {
+      (cls, methodName) -> body
+    }
+  }
 }

From 7516f1abdb0f0529578867e46f1b083446b6d93c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Mon, 19 May 2025 12:11:21 +0200
Subject: [PATCH 289/298] Switch to GitHub Actions for the Windows CI.

AppVeyor has become increasingly unstable recently.

While we're there, upgrade to Node.js 24.x.
---
 .github/workflows/windows-ci.yml | 51 ++++++++++++++++++++++++++++++++
 appveyor.yml                     | 23 --------------
 project/Build.scala              |  9 ------
 3 files changed, 51 insertions(+), 32 deletions(-)
 create mode 100644 .github/workflows/windows-ci.yml
 delete mode 100644 appveyor.yml

diff --git a/.github/workflows/windows-ci.yml b/.github/workflows/windows-ci.yml
new file mode 100644
index 0000000000..9b8170126d
--- /dev/null
+++ b/.github/workflows/windows-ci.yml
@@ -0,0 +1,51 @@
+name: Windows CI
+
+on:
+  push:
+    branches: [ main ]
+  pull_request:
+    branches: [ main ]
+
+env:
+  SBT_OPTS: '-Xmx6g -Xms1g -Xss4m'
+
+jobs:
+  build:
+    strategy:
+      matrix:
+        java: [ '8' ]
+
+    # Use the latest supported version. We will be less affected by ambient changes
+    # due to the lack of pinning than by breakages because of changing version support.
+    runs-on: windows-latest
+
+    steps:
+    - name: Set up git to use LF
+      run: |
+        git config --global core.autocrlf false
+        git config --global core.eol lf
+    - uses: actions/checkout@v3
+    - name: Set up JDK ${{ matrix.java }}
+      uses: coursier/setup-action@v1
+      with:
+        jvm: temurin:1.${{ matrix.java }}
+        apps: sbt
+    - uses: actions/setup-node@v4
+      with:
+        node-version: '24.x'
+        cache: 'npm'
+    - name: npm install
+      run: npm install
+
+    # Very far from testing everything, but at least it is a good sanity check
+    - name: Test suite
+      run: sbt testSuite2_12/test
+    - name: Linker test suite
+      run: sbt linker2_12/test
+    # partest is slow; only execute one test as a smoke test
+    - name: partest smoke test
+      run: sbt "partestSuite2_12/testOnly -- --fastOpt run/option-fold.scala"
+    # Module splitting has some logic for case-insensitive filesystems, which we must test on Windows
+    - name: Test suite with module splitting
+      run: sbt 'set testSuite.v2_12/scalaJSLinkerConfig ~= (_.withModuleKind(ModuleKind.ESModule).withModuleSplitStyle(ModuleSplitStyle.SmallModulesFor(List("org.scalajs.testsuite"))))' testSuite2_12/test
+      shell: bash # for the special characters in the command
diff --git a/appveyor.yml b/appveyor.yml
deleted file mode 100644
index 4f0c93e14c..0000000000
--- a/appveyor.yml
+++ /dev/null
@@ -1,23 +0,0 @@
-version: '{build}'
-image: Visual Studio 2015
-environment:
-  global:
-    NODEJS_VERSION: "16"
-    JAVA_HOME: C:\Program Files\Java\jdk1.8.0
-install:
-  - ps: Install-Product node $env:NODEJS_VERSION
-  - npm install
-  - cmd: choco install sbt --version 1.3.12 -ia "INSTALLDIR=""C:\sbt"""
-  - cmd: SET PATH=C:\sbt\bin;%JAVA_HOME%\bin;%PATH%
-  - cmd: SET "SBT_OPTS=-Xmx4g -Xms4m"
-build: off
-test_script:
-  # Very far from testing everything, but at least it is a good sanity check
-  # For slow things (partest and scripted), we execute only one test
-  - cmd: sbt ";clean;testSuite2_12/test;linker2_12/test;partestSuite2_12/testOnly -- --fastOpt run/option-fold.scala"
-  # Module splitting has some logic for case-insensitive filesystems, which we must test on Windows
-  - cmd: sbt ";setSmallESModulesForAppVeyorCI;testSuite2_12/test"
-cache:
-  - C:\sbt
-  - C:\Users\appveyor\.ivy2\cache
-  - C:\Users\appveyor\.sbt
diff --git a/project/Build.scala b/project/Build.scala
index 80bfe9792c..a365701850 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -205,15 +205,6 @@ object MyScalaJSPlugin extends AutoPlugin {
             }
         }
       },
-
-      /* The AppVeyor CI build definition is very sensitive to weird characthers
-       * in its command lines, so we cannot directly spell out the correct
-       * incantation. Instead, we define this alias.
-       */
-      addCommandAlias(
-        "setSmallESModulesForAppVeyorCI",
-        "set testSuite.v2_12 / scalaJSLinkerConfig ~= (_.withModuleKind(ModuleKind.ESModule).withModuleSplitStyle(ModuleSplitStyle.SmallModulesFor(List(\"org.scalajs.testsuite\"))))"
-      ),
   )
 
   override def projectSettings: Seq[Setting[_]] = Def.settings(

From e33a2129133a065a9de276b420104e76dc9197bd Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Tue, 22 Apr 2025 13:27:28 +0200
Subject: [PATCH 290/298] Use a DataView in FloatingPointBits.

Previously, we used several typed arrays pointing to the same
`ArrayBuffer`. Now, we use a single `DataView`. Since we can (must)
force a specific endianness with `DataView`, we get rid of the
`highOffset` and `lowOffset` fields, which further streamlines the
code.

The assembly produced by V8 is now better. Since it knows that it
manipulates a single buffer, it needs fewer loads and type tests
internally. I expect the same would be true for other optimizing
engines.
---
 .../scala/java/lang/FloatingPointBits.scala   | 114 +++++++-----------
 .../org/scalajs/linker/LibrarySizeTest.scala  |   6 +-
 project/Build.scala                           |   6 +-
 project/NodeJSEnvForcePolyfills.scala         |   1 +
 4 files changed, 48 insertions(+), 79 deletions(-)

diff --git a/javalib/src/main/scala/java/lang/FloatingPointBits.scala b/javalib/src/main/scala/java/lang/FloatingPointBits.scala
index 96e1c8f64c..3b03975c3e 100644
--- a/javalib/src/main/scala/java/lang/FloatingPointBits.scala
+++ b/javalib/src/main/scala/java/lang/FloatingPointBits.scala
@@ -20,65 +20,33 @@ import scala.scalajs.LinkingInfo.ESVersion
 /** Manipulating the bits of floating point numbers. */
 private[lang] object FloatingPointBits {
 
-  import scala.scalajs.LinkingInfo
-
-  private[this] val _areTypedArraysSupported = {
-    // Here we use the `esVersion` test to dce the 4 subsequent tests
-    LinkingInfo.esVersion >= ESVersion.ES2015 || {
-      js.typeOf(global.ArrayBuffer) != "undefined" &&
-      js.typeOf(global.Int32Array) != "undefined" &&
-      js.typeOf(global.Float32Array) != "undefined" &&
-      js.typeOf(global.Float64Array) != "undefined"
-    }
-  }
-
+  /** Are typed arrays known to be supported at link time?
+   *
+   *  If yes, we can dce polyfills away.
+   */
   @inline
-  private def areTypedArraysSupported: scala.Boolean = {
-    /* We have a forwarder to the internal `val _areTypedArraysSupported` to
-     * be able to inline it. This achieves the following:
-     * * If we emit ES2015+, dce `|| _areTypedArraysSupported` and replace
-     *   `areTypedArraysSupported` by `true` in the calling code, allowing
-     *   polyfills in the calling code to be dce'ed in turn.
-     * * If we emit ES5, replace `areTypedArraysSupported` by
-     *   `_areTypedArraysSupported` so we do not calculate it multiple times.
-     */
-    LinkingInfo.esVersion >= ESVersion.ES2015 || _areTypedArraysSupported
-  }
-
-  private val arrayBuffer =
-    if (areTypedArraysSupported) new typedarray.ArrayBuffer(8)
-    else null
+  private def areTypedArraysKnownSupported: scala.Boolean =
+    scala.scalajs.LinkingInfo.esVersion >= ESVersion.ES2015
 
-  private val int32Array =
-    if (areTypedArraysSupported) new typedarray.Int32Array(arrayBuffer, 0, 2)
-    else null
-
-  private val float32Array =
-    if (areTypedArraysSupported) new typedarray.Float32Array(arrayBuffer, 0, 2)
-    else null
-
-  private val float64Array =
-    if (areTypedArraysSupported) new typedarray.Float64Array(arrayBuffer, 0, 1)
-    else null
-
-  private val areTypedArraysBigEndian = {
-    if (areTypedArraysSupported) {
-      int32Array(0) = 0x01020304
-      (new typedarray.Int8Array(arrayBuffer, 0, 8))(0) == 0x01
-    } else {
-      true // as good a value as any
-    }
+  /** The DataView we use when typed arrays are supported; null if they are not supported.
+   *
+   *  We always use it in `littleEndian` mode. Major architectures are all
+   *  little endian these days.
+   */
+  private val dataView: typedarray.DataView = {
+    // If DataView exists, ArrayBuffer must exist as well. There is no need to test both.
+    if (areTypedArraysKnownSupported || js.typeOf(global.DataView) != "undefined")
+      new typedarray.DataView(new typedarray.ArrayBuffer(8))
+    else
+      null
   }
 
-  private val highOffset = if (areTypedArraysBigEndian) 0 else 1
-  private val lowOffset  = if (areTypedArraysBigEndian) 1 else 0
-
   private val floatPowsOf2: js.Array[scala.Double] =
-    if (areTypedArraysSupported) null
+    if (areTypedArraysKnownSupported || (dataView != null)) null
     else makePowsOf2(len = 1 << 8, java.lang.Float.MIN_NORMAL.toDouble)
 
   private val doublePowsOf2: js.Array[scala.Double] =
-    if (areTypedArraysSupported) null
+    if (areTypedArraysKnownSupported || (dataView != null)) null
     else makePowsOf2(len = 1 << 11, java.lang.Double.MIN_NORMAL)
 
   private def makePowsOf2(len: Int, minNormal: scala.Double): js.Array[scala.Double] = {
@@ -116,15 +84,11 @@ private[lang] object FloatingPointBits {
       /* Basically an inlined version of `Long.hashCode(doubleToLongBits(value))`,
        * so that we never allocate a RuntimeLong instance (or anything, for
        * that matter).
-       *
-       * In addition, in the happy path where typed arrays are supported, since
-       * we xor together the two Ints, it doesn't matter which one comes first
-       * or second, and hence we can use constants 0 and 1 instead of having an
-       * indirection through `highOffset` and `lowOffset`.
        */
-      if (areTypedArraysSupported) {
-        float64Array(0) = value
-        int32Array(0) ^ int32Array(1)
+      val dataView = this.dataView // local copy
+      if (areTypedArraysKnownSupported || (dataView != null)) {
+        dataView.setFloat64(0, value, littleEndian = true)
+        dataView.getInt32(0, littleEndian = true) ^ dataView.getInt32(4, littleEndian = true)
       } else {
         doubleHashCodePolyfill(value)
       }
@@ -136,38 +100,42 @@ private[lang] object FloatingPointBits {
     Long.hashCode(doubleToLongBitsPolyfillInline(value))
 
   def intBitsToFloat(bits: Int): scala.Float = {
-    if (areTypedArraysSupported) {
-      int32Array(0) = bits
-      float32Array(0)
+    val dataView = this.dataView // local copy
+    if (areTypedArraysKnownSupported || (dataView != null)) {
+      dataView.setInt32(0, bits, littleEndian = true)
+      dataView.getFloat32(0, littleEndian = true)
     } else {
       intBitsToFloatPolyfill(bits).toFloat
     }
   }
 
   def floatToIntBits(value: scala.Float): Int = {
-    if (areTypedArraysSupported) {
-      float32Array(0) = value
-      int32Array(0)
+    val dataView = this.dataView // local copy
+    if (areTypedArraysKnownSupported || (dataView != null)) {
+      dataView.setFloat32(0, value, littleEndian = true)
+      dataView.getInt32(0, littleEndian = true)
     } else {
       floatToIntBitsPolyfill(value)
     }
   }
 
   def longBitsToDouble(bits: scala.Long): scala.Double = {
-    if (areTypedArraysSupported) {
-      int32Array(highOffset) = (bits >>> 32).toInt
-      int32Array(lowOffset) = bits.toInt
-      float64Array(0)
+    val dataView = this.dataView // local copy
+    if (areTypedArraysKnownSupported || (dataView != null)) {
+      dataView.setInt32(0, bits.toInt, littleEndian = true)
+      dataView.setInt32(4, (bits >>> 32).toInt, littleEndian = true)
+      dataView.getFloat64(0, littleEndian = true)
     } else {
       longBitsToDoublePolyfill(bits)
     }
   }
 
   def doubleToLongBits(value: scala.Double): scala.Long = {
-    if (areTypedArraysSupported) {
-      float64Array(0) = value
-      ((int32Array(highOffset).toLong << 32) |
-          (int32Array(lowOffset).toLong & 0xffffffffL))
+    val dataView = this.dataView // local copy
+    if (areTypedArraysKnownSupported || (dataView != null)) {
+      dataView.setFloat64(0, value, littleEndian = true)
+      ((dataView.getInt32(0, littleEndian = true).toLong & 0xffffffffL) |
+          (dataView.getInt32(4, littleEndian = true).toLong << 32))
     } else {
       doubleToLongBitsPolyfill(value)
     }
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/LibrarySizeTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/LibrarySizeTest.scala
index 137d8e7400..5b8f6dba4b 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/LibrarySizeTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/LibrarySizeTest.scala
@@ -70,9 +70,9 @@ class LibrarySizeTest {
     )
 
     testLinkedSizes(
-      expectedFastLinkSize = 147046,
-      expectedFullLinkSizeWithoutClosure = 85355,
-      expectedFullLinkSizeWithClosure = 21492,
+      expectedFastLinkSize = 145795,
+      expectedFullLinkSizeWithoutClosure = 84996,
+      expectedFullLinkSizeWithClosure = 21364,
       classDefs,
       moduleInitializers = MainTestModuleInitializers
     )
diff --git a/project/Build.scala b/project/Build.scala
index a365701850..60a245b05b 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -2041,7 +2041,7 @@ object Build {
           case `default212Version` =>
             if (!useMinifySizes) {
               Some(ExpectedSizes(
-                  fastLink = 624000 to 625000,
+                  fastLink = 623000 to 624000,
                   fullLink = 96000 to 97000,
                   fastLinkGz = 75000 to 79000,
                   fullLinkGz = 25000 to 26000,
@@ -2058,8 +2058,8 @@ object Build {
           case `default213Version` =>
             if (!useMinifySizes) {
               Some(ExpectedSizes(
-                  fastLink = 442000 to 443000,
-                  fullLink = 93000 to 94000,
+                  fastLink = 441000 to 442000,
+                  fullLink = 92000 to 93000,
                   fastLinkGz = 57000 to 58000,
                   fullLinkGz = 25000 to 26000,
               ))
diff --git a/project/NodeJSEnvForcePolyfills.scala b/project/NodeJSEnvForcePolyfills.scala
index 6859a3aa7b..899bd79c7d 100644
--- a/project/NodeJSEnvForcePolyfills.scala
+++ b/project/NodeJSEnvForcePolyfills.scala
@@ -66,6 +66,7 @@ final class NodeJSEnvForcePolyfills(esVersion: ESVersion, config: NodeJSEnv.Conf
         |delete global.Set;
         |delete global.Symbol;
         |
+        |delete global.DataView;
         |delete global.Int8Array;
         |delete global.Int16Array;
         |delete global.Int32Array;

From f84fa2ed357bacbaa68acacff8110d088e838b08 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Sat, 10 May 2025 11:41:24 +0200
Subject: [PATCH 291/298] Add copies of the run/finally.scala partest into our
 own test suite.

The compilation scheme for `finally` is a beast on Wasm. It's good
to have direct feedback on it without having to wait for the full
partest.
---
 .../testsuite/compiler/TryFinallyTest.scala   | 232 ++++++++++++++++++
 1 file changed, 232 insertions(+)
 create mode 100644 test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/TryFinallyTest.scala

diff --git a/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/TryFinallyTest.scala b/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/TryFinallyTest.scala
new file mode 100644
index 0000000000..ffce227e01
--- /dev/null
+++ b/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/TryFinallyTest.scala
@@ -0,0 +1,232 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package org.scalajs.testsuite.compiler
+
+import scala.collection.mutable
+
+import org.junit.Test
+import org.junit.Assert._
+
+// Much of the point of this test class is to test `return`s inside `try..finally`s
+// scalastyle:off return
+
+class TryFinallyTest {
+
+  /* Some of these tests are ported from the partest run/finally.scala.
+   * We have copies of them in our own test suite to more quickly identify
+   * any issues with our compilation scheme for try..finally. On JS it is
+   * straightforward, but it is a huge beast in Wasm.
+   */
+
+  type SideEffect = Any => Unit
+
+  @noinline
+  def test(body: SideEffect => Unit)(expectedSideEffects: String*): Unit = {
+    val sideEffects = mutable.ListBuffer.empty[String]
+
+    try {
+      body(x => sideEffects += ("" + x))
+    } catch {
+      case e: Throwable =>
+        sideEffects += ("CAUGHT: " + e)
+    }
+
+    if (!sideEffects.sameElements(expectedSideEffects)) {
+      // Custom message for easier debugging
+      fail(
+          "Expected side effects:" +
+          expectedSideEffects.mkString("\n* ", "\n* ", "\n") +
+          "but got:" +
+          sideEffects.mkString("\n* ", "\n* ", "\n"))
+    }
+  }
+
+  // test that finally is not covered by any exception handlers.
+  @Test
+  def throwCatchFinally(): Unit = {
+    test { println =>
+      def bar(): Unit = {
+        try {
+          println("hi")
+        } catch {
+          case e: Throwable => println("SHOULD NOT GET HERE")
+        } finally {
+          println("In Finally")
+          throw new RuntimeException("ouch")
+        }
+      }
+
+      try {
+        bar()
+      } catch {
+        case e: Throwable => println(e)
+      }
+    } (
+      "hi",
+      "In Finally",
+      "java.lang.RuntimeException: ouch"
+    )
+  }
+
+  // test that finally is not covered by any exception handlers.
+  // return in catch (finally is executed)
+  @Test
+  def retCatch(): Unit = {
+    test { println =>
+      def retCatchInner(): Unit = {
+        try {
+          throw new Exception
+        } catch {
+          case e: Throwable =>
+            println(e)
+            return
+        } finally {
+          println("in finally")
+        }
+      }
+
+      retCatchInner()
+    } (
+      "java.lang.Exception",
+      "in finally"
+    )
+  }
+
+  // throw in catch (finally is executed, exception propagated)
+  @Test
+  def throwCatch(): Unit = {
+    test { println =>
+      try {
+        throw new Exception
+      } catch {
+        case e: Throwable =>
+          println(e)
+          throw e
+      } finally {
+        println("in finally")
+      }
+    } (
+      "java.lang.Exception",
+      "in finally",
+      "CAUGHT: java.lang.Exception"
+    )
+  }
+
+  // return inside body (finally is executed)
+  @Test
+  def retBody(): Unit = {
+    test { println =>
+      def retBodyInner(): Unit = {
+        try {
+          return
+        } catch {
+          case e: Throwable =>
+            println(e)
+            throw e
+        } finally println("in finally")
+      }
+
+      retBodyInner()
+    } (
+      "in finally"
+    )
+  }
+
+  // throw inside body (finally and catch are executed)
+  @Test
+  def throwBody(): Unit = {
+    test { println =>
+      try {
+        throw new Exception
+      } catch {
+        case e: Throwable =>
+          println(e)
+      } finally {
+        println("in finally")
+      }
+    } (
+      "java.lang.Exception",
+      "in finally"
+    )
+  }
+
+  // return inside finally (each finally is executed once)
+  @Test
+  def retFinally(): Unit = {
+    test { println =>
+      def retFinallyInner(): Unit = {
+        try {
+          try {
+            println("body")
+          } finally {
+            println("in finally 1")
+            return
+          }
+        } finally {
+          println("in finally 2")
+        }
+      }
+
+      retFinallyInner()
+    } (
+      "body",
+      "in finally 1",
+      "in finally 2"
+    )
+  }
+
+  // throw inside finally (finally is executed once, exception is propagated)
+  @Test
+  def throwFinally(): Unit = {
+    test { println =>
+      try {
+        try {
+          println("body")
+        } finally {
+          println("in finally")
+          throw new Exception
+        }
+      } catch {
+        case e: Throwable => println(e)
+      }
+    } (
+      "body",
+      "in finally",
+      "java.lang.Exception"
+    )
+  }
+
+  // nested finally blocks with return value
+  @Test
+  def nestedFinallyBlocks(): Unit = {
+    test { println =>
+      def nestedFinallyBlocksInner(): Int = {
+        try {
+          try {
+            return 10
+          } finally {
+            try { () } catch { case _: Throwable => () }
+            println("in finally 1")
+          }
+        } finally {
+          println("in finally 2")
+        }
+      }
+
+      assertEquals(10, nestedFinallyBlocksInner())
+    } (
+      "in finally 1",
+      "in finally 2"
+    )
+  }
+}

From a7b99e99bca75060c24b5972b65887767414e3af Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Fri, 16 May 2025 14:00:22 +0200
Subject: [PATCH 292/298] Handle System.identityHashCode as a method with a
 special body.

Instead of having it call a primitive whose sole purpose was to
be called from `System.identityHashCode()`.
---
 .../src/main/scala/org/scalajs/nscplugin/GenJSCode.scala  | 8 +++-----
 .../main/scala/org/scalajs/nscplugin/JSDefinitions.scala  | 1 -
 .../main/scala/org/scalajs/nscplugin/JSPrimitives.scala   | 4 +---
 javalib/src/main/scala/java/lang/System.scala             | 2 +-
 .../src/main/scala/scala/scalajs/runtime/package.scala    | 4 +++-
 5 files changed, 8 insertions(+), 11 deletions(-)

diff --git a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
index 6696ce90c2..e5b205179e 100644
--- a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
+++ b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
@@ -5254,11 +5254,6 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
             genStatOrExpr(args(1), isStat)
           }
 
-        case IDENTITY_HASH_CODE =>
-          // runtime.identityHashCode(arg)
-          val arg = genArgs1
-          js.UnaryOp(js.UnaryOp.IdentityHashCode, arg)
-
         case DEBUGGER =>
           // js.special.debugger()
           js.Debugger()
@@ -7446,6 +7441,9 @@ private object GenJSCode {
         m("isAssignableFrom", List(CC), Z) -> ThisBinaryOp(binop.Class_isAssignableFrom, checkNulls = true),
         m("cast", List(O), O)              -> ThisBinaryOp(binop.Class_cast)
       ),
+      ClassName("java.lang.System$") -> Map(
+        m("identityHashCode", List(O), I) -> ArgUnaryOp(unop.IdentityHashCode)
+      ),
       ClassName("java.lang.reflect.Array$") -> Map(
         m("newInstance", List(CC, I), O) -> ArgBinaryOp(binop.Class_newArray, checkNulls = true)
       )
diff --git a/compiler/src/main/scala/org/scalajs/nscplugin/JSDefinitions.scala b/compiler/src/main/scala/org/scalajs/nscplugin/JSDefinitions.scala
index 58c4910233..e91b74d4ff 100644
--- a/compiler/src/main/scala/org/scalajs/nscplugin/JSDefinitions.scala
+++ b/compiler/src/main/scala/org/scalajs/nscplugin/JSDefinitions.scala
@@ -131,7 +131,6 @@ trait JSDefinitions {
       lazy val Runtime_withContextualJSClassValue = getMemberMethod(RuntimePackageModule, newTermName("withContextualJSClassValue"))
       lazy val Runtime_privateFieldsSymbol        = getMemberMethod(RuntimePackageModule, newTermName("privateFieldsSymbol"))
       lazy val Runtime_linkingInfo                = getMemberMethod(RuntimePackageModule, newTermName("linkingInfo"))
-      lazy val Runtime_identityHashCode           = getMemberMethod(RuntimePackageModule, newTermName("identityHashCode"))
       lazy val Runtime_dynamicImport              = getMemberMethod(RuntimePackageModule, newTermName("dynamicImport"))
 
     lazy val LinkingInfoModule = getRequiredModule("scala.scalajs.LinkingInfo")
diff --git a/compiler/src/main/scala/org/scalajs/nscplugin/JSPrimitives.scala b/compiler/src/main/scala/org/scalajs/nscplugin/JSPrimitives.scala
index cf6f896453..a199b87f98 100644
--- a/compiler/src/main/scala/org/scalajs/nscplugin/JSPrimitives.scala
+++ b/compiler/src/main/scala/org/scalajs/nscplugin/JSPrimitives.scala
@@ -58,8 +58,7 @@ abstract class JSPrimitives {
   final val CREATE_INNER_JS_CLASS = CONSTRUCTOROF + 1                  // runtime.createInnerJSClass
   final val CREATE_LOCAL_JS_CLASS = CREATE_INNER_JS_CLASS + 1          // runtime.createLocalJSClass
   final val WITH_CONTEXTUAL_JS_CLASS_VALUE = CREATE_LOCAL_JS_CLASS + 1 // runtime.withContextualJSClassValue
-  final val IDENTITY_HASH_CODE = WITH_CONTEXTUAL_JS_CLASS_VALUE + 1    // runtime.identityHashCode
-  final val DYNAMIC_IMPORT = IDENTITY_HASH_CODE + 1                    // runtime.dynamicImport
+  final val DYNAMIC_IMPORT = WITH_CONTEXTUAL_JS_CLASS_VALUE + 1        // runtime.dynamicImport
 
   final val STRICT_EQ = DYNAMIC_IMPORT + 1                // js.special.strictEquals
   final val IN = STRICT_EQ + 1                            // js.special.in
@@ -115,7 +114,6 @@ abstract class JSPrimitives {
     addPrimitive(Runtime_createLocalJSClass, CREATE_LOCAL_JS_CLASS)
     addPrimitive(Runtime_withContextualJSClassValue,
         WITH_CONTEXTUAL_JS_CLASS_VALUE)
-    addPrimitive(Runtime_identityHashCode, IDENTITY_HASH_CODE)
     addPrimitive(Runtime_dynamicImport, DYNAMIC_IMPORT)
 
     addPrimitive(Special_strictEquals, STRICT_EQ)
diff --git a/javalib/src/main/scala/java/lang/System.scala b/javalib/src/main/scala/java/lang/System.scala
index 976ea7ff15..d6ee87996f 100644
--- a/javalib/src/main/scala/java/lang/System.scala
+++ b/javalib/src/main/scala/java/lang/System.scala
@@ -184,7 +184,7 @@ object System {
 
   @inline
   def identityHashCode(x: Any): scala.Int =
-    scala.scalajs.runtime.identityHashCode(x.asInstanceOf[AnyRef])
+    throw new Error("stub") // body replaced by the compiler back-end
 
   // System properties --------------------------------------------------------
 
diff --git a/library/src/main/scala/scala/scalajs/runtime/package.scala b/library/src/main/scala/scala/scalajs/runtime/package.scala
index d3ba4f766f..342081817d 100644
--- a/library/src/main/scala/scala/scalajs/runtime/package.scala
+++ b/library/src/main/scala/scala/scalajs/runtime/package.scala
@@ -111,7 +111,9 @@ package object runtime {
   }
 
   /** Identity hash code of an object. */
-  def identityHashCode(x: Object): Int = throw new Error("stub")
+  @deprecated("Unused; use System.identityHashCode(x) instead.", since = "1.20.0")
+  def identityHashCode(x: Object): Int =
+    System.identityHashCode(x)
 
   def dynamicImport[A](thunk: DynamicImportThunk): js.Promise[A] =
     throw new Error("stub")

From 12918186cb190c558a9fd1219352d59d4ae22594 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Sat, 10 May 2025 12:27:06 +0200
Subject: [PATCH 293/298] Fix #5165: Use defaultable types for the locals of
 `TryFinally`s.

As well as for the locals of `Labeled` blocks whose `Return`s cross
a `try..finally` boundary.

If their original type was not defaultable, we cast away
nullability when reading them back.
---
 .../backend/wasmemitter/FunctionEmitter.scala | 26 ++++++++++--
 .../linker/backend/webassembly/Types.scala    | 19 ++++++++-
 .../testsuite/compiler/TryFinallyTest.scala   | 40 +++++++++++++++++++
 3 files changed, 80 insertions(+), 5 deletions(-)

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
index 7cf164c228..7196e8a075 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
@@ -1040,6 +1040,13 @@ private class FunctionEmitter private (
          * not need to store the receiver in a local at all.
          * For the case with the args, it does not hurt either way. We could
          * move it out, but that would make for a less consistent codegen.
+         *
+         * Loading the arguments and storing them in locals inside the block
+         * only works if their type is defaultable. Currently, for instance
+         * methods, parameter types are always defaultable, so this is fine.
+         * We may need to revisit this strategy if that invariant changes.
+         * If we do, it may be better to use different code paths for the
+         * no-args case and the with-args case. See #5165 for more context.
          */
         val argsLocals = fb.block(watpe.RefType.any) { labelNotOurObject =>
           // Load receiver and arguments and store them in temporary variables
@@ -3623,6 +3630,11 @@ private class FunctionEmitter private (
    * we cannot use the stack for the `try_table` itself: each label has a
    * dedicated local for its result if it comes from such a crossing `return`.
    *
+   * Those locals must have defaultable types, because they are read outside of
+   * the block where they are first ininitialized. If their natural type is not
+   * defaultable, we make it defaultable, and cast away nullability when we
+   * read them back. See #5165.
+   *
    * Two more complications:
    *
    * - If the `finally` block itself contains another `try..finally`, they may
@@ -3850,7 +3862,7 @@ private class FunctionEmitter private (
         _crossInfo.getOrElse {
           val destinationTag = allocateDestinationTag()
           val resultTypes = transformResultType(expectedType)
-          val resultLocals = resultTypes.map(addSyntheticLocal(_))
+          val resultLocals = resultTypes.map(tpe => addSyntheticLocal(tpe.toDefaultableType))
           val crossLabel = fb.genLabel()
           val info = CrossInfo(destinationTag, resultLocals, crossLabel)
           _crossInfo = Some(info)
@@ -3941,8 +3953,11 @@ private class FunctionEmitter private (
         // Add the `br`, `end` and `local.get` at the current position, as usual
         fb += wa.Br(entry.regularWasmLabel)
         fb += wa.End
-        for (local <- resultLocals)
+        for ((local, origType) <- resultLocals.zip(ty)) {
           fb += wa.LocalGet(local)
+          if (!origType.isDefaultable)
+            fb += wa.RefAsNonNull
+        }
       }
 
       fb += wa.End
@@ -3959,7 +3974,7 @@ private class FunctionEmitter private (
       val entry = new TryFinallyEntry(currentUnwindingStackDepth)
 
       val resultType = transformResultType(expectedType)
-      val resultLocals = resultType.map(addSyntheticLocal(_))
+      val resultLocals = resultType.map(tpe => addSyntheticLocal(tpe.toDefaultableType))
 
       markPosition(tree)
 
@@ -4074,8 +4089,11 @@ private class FunctionEmitter private (
       } // end block $done
 
       // reload the result onto the stack
-      for (resultLocal <- resultLocals)
+      for ((resultLocal, origType) <- resultLocals.zip(resultType)) {
         fb += wa.LocalGet(resultLocal)
+        if (!origType.isDefaultable)
+          fb += wa.RefAsNonNull
+      }
 
       if (expectedType == NothingType)
         fb += wa.Unreachable
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/Types.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/Types.scala
index 58f07eba99..62b3be1849 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/Types.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/webassembly/Types.scala
@@ -33,7 +33,24 @@ object Types {
    *  typing" point of view. It is also the kind of type we manipulate the most
    *  across the backend, so it also makes sense for it to be the "default".
    */
-  sealed abstract class Type extends StorageType
+  sealed abstract class Type extends StorageType {
+    /** Returns true if and only if this type is defaultable. */
+    final def isDefaultable: Boolean = this match {
+      case RefType(nullable, _) => nullable
+      case _                    => true
+    }
+
+    /** Returns a defaultable supertype of this type.
+     *
+     *  If this type is already defaultable, return `this`. Otherwise, this
+     *  type must be a non-nullable reference type, and this method returns the
+     *  nullable variant.
+     */
+    final def toDefaultableType: Type = this match {
+      case RefType(false, heapType) => RefType.nullable(heapType)
+      case _                        => this
+    }
+  }
 
   /** Convenience superclass for `Type`s that are encoded with a simple opcode. */
   sealed abstract class SimpleType(val textName: String, val binaryCode: Byte) extends Type
diff --git a/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/TryFinallyTest.scala b/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/TryFinallyTest.scala
index ffce227e01..57d6119aa4 100644
--- a/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/TryFinallyTest.scala
+++ b/test-suite/shared/src/test/scala/org/scalajs/testsuite/compiler/TryFinallyTest.scala
@@ -229,4 +229,44 @@ class TryFinallyTest {
       "in finally 2"
     )
   }
+
+  @Test
+  def nonDefaultableTryResultType_Issue5165(): Unit = {
+    test { println =>
+      // after the optimizer, some has type Some! (a non-nullable reference type)
+      val some = try {
+        println("in try")
+        Some(1)
+      } finally {
+        println("in finally")
+      }
+      assertEquals(1, some.value)
+    } (
+      "in try",
+      "in finally"
+    )
+  }
+
+  @Test
+  def nonDefaultableLabeledResultType_Issue5165(): Unit = {
+    test { println =>
+      /* After the optimizer, the result type of the Labeled block that gets
+       * inlined is a Some! (a non-nullable reference type).
+       */
+      @inline def nonDefaultableLabeledResultTypeInner(): Some[Int] = {
+        try {
+          println("in try")
+          return Some(1)
+        } finally {
+          println("in finally")
+        }
+      }
+
+      val some = nonDefaultableLabeledResultTypeInner()
+      assertEquals(1, some.value)
+    } (
+      "in try",
+      "in finally"
+    )
+  }
 }

From d97f4e43d83a4c9e62b9d3370081ec6a4d4d4645 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Thu, 24 Apr 2025 15:26:08 +0200
Subject: [PATCH 294/298] Support reading jar files in the IR cleaner.

That allows the IR cleaner to see the JS type definitions from
the library when it appears as a jar on the classpath. This is
the case for the linker private library. Adding that support will
allow the linker private library to use JS type definitions from
the Scala.js library, as long as the references can be erased
away.
---
 project/Build.scala            | 14 ++++++++++-
 project/JavalibIRCleaner.scala | 45 ++++++++++++++++++++++++++++++----
 2 files changed, 53 insertions(+), 6 deletions(-)

diff --git a/project/Build.scala b/project/Build.scala
index 60a245b05b..3b57fe3a24 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -750,9 +750,21 @@ object Build {
         val libFileMappings = (PathFinder(prevProducts) ** "*.sjsir")
           .pair(Path.rebase(prevProducts, outputDir))
 
+        /* Note: we cannot use `linkerImpl` here to load `IRFile`s. That would
+         * create the circular dependency
+         *   linkerPrivateLibrary/products
+         *     -> linkerImpl
+         *     -> linker/fullClasspath
+         *     -> linkerPrivateLibrary/products
+         */
         val dependencyFiles = {
           val cp = Attributed.data((internalDependencyClasspath in Compile).value)
-          (PathFinder(cp) ** "*.sjsir").get
+          cp.flatMap { entry =>
+            if (entry.getName().endsWith(".jar"))
+              Seq(entry)
+            else
+              (PathFinder(entry) ** "*.sjsir").get
+          }
         }
 
         FileFunction.cached(s.cacheDirectory / "cleaned-sjsir",
diff --git a/project/JavalibIRCleaner.scala b/project/JavalibIRCleaner.scala
index be6103d72c..3ec8d081c8 100644
--- a/project/JavalibIRCleaner.scala
+++ b/project/JavalibIRCleaner.scala
@@ -10,7 +10,9 @@ import org.scalajs.ir.WellKnownNames._
 
 import java.io._
 import java.net.URI
-import java.nio.file.Files
+import java.nio._
+import java.nio.file._
+import java.nio.file.attribute._
 
 import scala.collection.immutable.IndexedSeq
 import scala.collection.mutable
@@ -53,7 +55,12 @@ final class JavalibIRCleaner(baseDirectoryURI: URI) {
     }
 
     val jsTypes = {
-      val dependencyIR = dependencyFiles.iterator.map(readIR(_))
+      val dependencyIR = dependencyFiles.iterator.flatMap { file =>
+        if (file.getName().endsWith(".jar"))
+          readIRJar(file)
+        else
+          List(readIR(file))
+      }
       val libIR = libIRMappings.iterator.map(_._1)
       getJSTypes(dependencyIR ++ libIR)
     }
@@ -107,14 +114,42 @@ final class JavalibIRCleaner(baseDirectoryURI: URI) {
     def errorCount: Int = _errorCount
   }
 
-  private def readIR(file: File): ClassDef = {
-    import java.nio.ByteBuffer
+  private def readIR(file: File): ClassDef =
+    readIR(file.toPath())
 
-    val bytes = Files.readAllBytes(file.toPath())
+  private def readIR(path: Path): ClassDef = {
+    val bytes = Files.readAllBytes(path)
     val buffer = ByteBuffer.wrap(bytes)
     Serializers.deserialize(buffer)
   }
 
+  private def readIRJar(jar: File): List[ClassDef] = {
+    // Similar to PathIRContainer.JarIRContainer and its walkIR helper
+
+    val classDefs = List.newBuilder[ClassDef]
+
+    val dirVisitor = new SimpleFileVisitor[Path] {
+      override def visitFile(path: Path, attrs: BasicFileAttributes): FileVisitResult = {
+        if (path.getFileName().toString().endsWith(".sjsir"))
+          classDefs += readIR(path)
+        super.visitFile(path, attrs)
+      }
+    }
+
+    // Open zip/jar file as filesystem.
+    // The type ascription is necessary on JDK 13+.
+    val fs = FileSystems.newFileSystem(jar.toPath(), null: ClassLoader)
+    try {
+      val iter = fs.getRootDirectories().iterator()
+      while (iter.hasNext())
+        Files.walkFileTree(iter.next(), dirVisitor)
+    } finally {
+      fs.close()
+    }
+
+    classDefs.result()
+  }
+
   private def writeIRFile(file: File, tree: ClassDef): Unit = {
     Files.createDirectories(file.toPath().getParent())
     val outputStream =

From b49cff92db67e67c0cd509fba4f96d8b2dd1d3dc Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Wed, 23 Apr 2025 22:11:37 +0200
Subject: [PATCH 295/298] Introduce IR UnaryOps for floating point bit
 manipulation.

Previously, our floating point bit manipulation methods were
implemented in user space. This commit instead introduces dedicated
IR `UnaryOp`s for them.

On Wasm, the implementations are straightforward opcodes. In
JavaScript, we use the same strategies as before, but moved to the
linker world.

In most cases, we use a unique scratch `DataView` to perform the
manipulations. It is now allocated as a `globalVar` in the emitter,
rather than in user space. The functions for `Float`/`Int`
conversions are straightforward, as well as those for
`Double`/`Long` when we use `bigint`s for `Long`s. When we use
`RuntimeLong`s, the conversions are implemented in `RuntimeLong`,
but require the scratch `DataView` as an argument, which the
linker injects.

This new strategy brings several benefits:

* For JavaScript, the generated code is basically optimal now.
  It produces tight sequences of Assembly instructions that do not
  allocate anything.
* For Wasm, the implementation does not rely on JS interop anymore,
  even when the optimizer does not run. This property will be
  required when we target Wasm outside of a JS host.
* We open a path to adding support for the "raw" variants
  `floatToRawIntBits`/`doubleToRawLongBits` in Wasm in the future,
  should we need it.
---
 .../org/scalajs/nscplugin/GenJSCode.scala     |  10 +-
 .../main/scala/org/scalajs/ir/Printers.scala  |   5 +
 .../src/main/scala/org/scalajs/ir/Trees.scala |  16 +-
 .../scala/org/scalajs/ir/PrintersTest.scala   |   5 +
 javalib/src/main/scala/java/lang/Double.scala |  33 +-
 javalib/src/main/scala/java/lang/Float.scala  |   6 +-
 .../scala/java/lang/FloatingPointBits.scala   | 294 ------------------
 .../runtime/FloatingPointBitsPolyfills.scala  | 190 +++++++++++
 .../scalajs/linker/runtime/RuntimeLong.scala  |  28 ++
 .../backend/emitter/PrivateLibHolder.scala    |   2 +
 .../linker/backend/emitter/CoreJSLib.scala    |  90 +++++-
 .../linker/backend/emitter/Emitter.scala      |  10 +
 .../linker/backend/emitter/EmitterNames.scala |   8 +
 .../backend/emitter/FunctionEmitter.scala     |  18 +-
 .../linker/backend/emitter/LongImpl.scala     |  12 +-
 .../linker/backend/emitter/Transients.scala   |  16 +
 .../linker/backend/emitter/VarField.scala     |   8 +
 .../backend/wasmemitter/FunctionEmitter.scala |  40 +++
 .../backend/wasmemitter/WasmTransients.scala  |  18 +-
 .../scalajs/linker/checker/IRChecker.scala    |   8 +-
 .../frontend/optimizer/OptimizerCore.scala    | 100 +++---
 .../org/scalajs/linker/LibrarySizeTest.scala  |   6 +-
 project/Build.scala                           |  12 +-
 project/MiniLib.scala                         |   2 -
 24 files changed, 539 insertions(+), 398 deletions(-)
 delete mode 100644 javalib/src/main/scala/java/lang/FloatingPointBits.scala
 create mode 100644 linker-private-library/src/main/scala/org/scalajs/linker/runtime/FloatingPointBitsPolyfills.scala

diff --git a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
index 6696ce90c2..77c2e66d7f 100644
--- a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
+++ b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
@@ -7421,7 +7421,7 @@ private object GenJSCode {
   private lazy val JavalibMethodsWithOpBody: Map[(ClassName, MethodName), JavalibOpBody] = {
     import JavalibOpBody._
     import js.{UnaryOp => unop, BinaryOp => binop}
-    import jstpe.{BooleanRef => Z, CharRef => C, IntRef => I}
+    import jstpe.{BooleanRef => Z, CharRef => C, IntRef => I, LongRef => J, FloatRef => F, DoubleRef => D}
     import MethodName.{apply => m}
 
     val O = jswkn.ObjectRef
@@ -7429,6 +7429,14 @@ private object GenJSCode {
     val T = jstpe.ClassRef(jswkn.BoxedStringClass)
 
     val byClass: Map[ClassName, Map[MethodName, JavalibOpBody]] = Map(
+      jswkn.BoxedFloatClass.withSuffix("$") -> Map(
+        m("floatToIntBits", List(F), I) -> ArgUnaryOp(unop.Float_toBits),
+        m("intBitsToFloat", List(I), F) -> ArgUnaryOp(unop.Float_fromBits)
+      ),
+      jswkn.BoxedDoubleClass.withSuffix("$") -> Map(
+        m("doubleToLongBits", List(D), J) -> ArgUnaryOp(unop.Double_toBits),
+        m("longBitsToDouble", List(J), D) -> ArgUnaryOp(unop.Double_fromBits)
+      ),
       jswkn.BoxedStringClass -> Map(
         m("length", Nil, I)     -> ThisUnaryOp(unop.String_length),
         m("charAt", List(I), C) -> ThisBinaryOp(binop.String_charAt)
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala
index 9a05ed7788..c7f66671fd 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala
@@ -445,6 +445,11 @@ object Printers {
             case UnwrapFromThrowable => p("<unwrapFromThrowable>(", ")")
 
             case Throw => p("throw ", "")
+
+            case Float_toBits    => p("<floatToBits>(", ")")
+            case Float_fromBits  => p("<floatFromBits>(", ")")
+            case Double_toBits   => p("<doubleToBits>(", ")")
+            case Double_fromBits => p("<doubleFromBits>(", ")")
           }
 
         case BinaryOp(BinaryOp.Int_-, IntLiteral(0), rhs) =>
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala b/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
index 23a2eb7118..f463279933 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
@@ -509,6 +509,14 @@ object Trees {
     final val UnwrapFromThrowable = 30
     final val Throw = 31
 
+    // Floating point bit manipulation, introduced in 1.20
+    final val Float_toBits = 32
+    // final val Float_toRawBits = 33 // Reserved
+    final val Float_fromBits = 34
+    final val Double_toBits = 35
+    // final val Double_toRawBits = 36 // Reserved
+    final val Double_fromBits = 37
+
     def isClassOp(op: Code): Boolean =
       op >= Class_name && op <= Class_superClass
 
@@ -530,13 +538,13 @@ object Trees {
       case IntToShort =>
         ShortType
       case CharToInt | ByteToInt | ShortToInt | LongToInt | DoubleToInt |
-          String_length | Array_length | IdentityHashCode =>
+          String_length | Array_length | IdentityHashCode | Float_toBits =>
         IntType
-      case IntToLong | DoubleToLong =>
+      case IntToLong | DoubleToLong | Double_toBits =>
         LongType
-      case DoubleToFloat | LongToFloat =>
+      case DoubleToFloat | LongToFloat | Float_fromBits =>
         FloatType
-      case IntToDouble | LongToDouble | FloatToDouble =>
+      case IntToDouble | LongToDouble | FloatToDouble | Double_fromBits =>
         DoubleType
       case CheckNotNull | Clone =>
         argType.toNonNullable
diff --git a/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala b/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala
index fd49eb406e..6ce589756e 100644
--- a/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala
+++ b/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala
@@ -514,6 +514,11 @@ class PrintersTest {
     assertPrintEquals("<wrapAsThrowable>(e)", UnaryOp(WrapAsThrowable, ref("e", AnyType)))
     assertPrintEquals("<unwrapFromThrowable>(e)",
         UnaryOp(UnwrapFromThrowable, ref("e", ClassType(ThrowableClass, nullable = true))))
+
+    assertPrintEquals("<floatToBits>(x)", UnaryOp(Float_toBits, ref("x", FloatType)))
+    assertPrintEquals("<floatFromBits>(x)", UnaryOp(Float_fromBits, ref("x", IntType)))
+    assertPrintEquals("<doubleToBits>(x)", UnaryOp(Double_toBits, ref("x", DoubleType)))
+    assertPrintEquals("<doubleFromBits>(x)", UnaryOp(Double_fromBits, ref("x", LongType)))
   }
 
   @Test def printPseudoUnaryOp(): Unit = {
diff --git a/javalib/src/main/scala/java/lang/Double.scala b/javalib/src/main/scala/java/lang/Double.scala
index aa6e3bc8d9..b8c1ffc779 100644
--- a/javalib/src/main/scala/java/lang/Double.scala
+++ b/javalib/src/main/scala/java/lang/Double.scala
@@ -364,14 +364,28 @@ object Double {
   @inline def isFinite(d: scala.Double): scala.Boolean =
     !isNaN(d) && !isInfinite(d)
 
+  /** Hash code of a number (excluding Longs).
+   *
+   *  Because of the common encoding for integer and floating point values,
+   *  the hashCode of Floats and Doubles must align with that of Ints for the
+   *  common values.
+   *
+   *  For other values, we use the hashCode specified by the JavaDoc for
+   *  *Doubles*, even for values which are valid Float values. Because of the
+   *  previous point, we cannot align completely with the Java specification,
+   *  so there is no point trying to be a bit more aligned here. Always using
+   *  the Double version requires fewer branches.
+   *
+   *  We use different code paths in JS and Wasm for performance reasons.
+   *  The two implementations compute the same results.
+   */
   @inline def hashCode(value: scala.Double): Int = {
     if (LinkingInfo.isWebAssembly)
       hashCodeForWasm(value)
     else
-      FloatingPointBits.numberHashCode(value)
+      hashCodeForJS(value)
   }
 
-  // See FloatingPointBits for the spec of this computation
   @inline
   private def hashCodeForWasm(value: scala.Double): Int = {
     val bits = doubleToLongBits(value)
@@ -382,13 +396,20 @@ object Double {
       Long.hashCode(bits)
   }
 
-  // Wasm intrinsic
+  @inline
+  private def hashCodeForJS(value: scala.Double): Int = {
+    val valueInt = (value.asInstanceOf[js.Dynamic] | 0.asInstanceOf[js.Dynamic]).asInstanceOf[Int]
+    if (valueInt.toDouble == value && 1.0/value != scala.Double.NegativeInfinity)
+      valueInt
+    else
+      Long.hashCode(doubleToLongBits(value))
+  }
+
   @inline def longBitsToDouble(bits: scala.Long): scala.Double =
-    FloatingPointBits.longBitsToDouble(bits)
+    throw new Error("stub") // body replaced by the compiler back-end
 
-  // Wasm intrinsic
   @inline def doubleToLongBits(value: scala.Double): scala.Long =
-    FloatingPointBits.doubleToLongBits(value)
+    throw new Error("stub") // body replaced by the compiler back-end
 
   @inline def sum(a: scala.Double, b: scala.Double): scala.Double =
     a + b
diff --git a/javalib/src/main/scala/java/lang/Float.scala b/javalib/src/main/scala/java/lang/Float.scala
index a2d54c77fd..279d8ed1a8 100644
--- a/javalib/src/main/scala/java/lang/Float.scala
+++ b/javalib/src/main/scala/java/lang/Float.scala
@@ -427,13 +427,11 @@ object Float {
   @inline def hashCode(value: scala.Float): Int =
     Double.hashCode(value.toDouble)
 
-  // Wasm intrinsic
   @inline def intBitsToFloat(bits: scala.Int): scala.Float =
-    FloatingPointBits.intBitsToFloat(bits)
+    throw new Error("stub") // body replaced by the compiler back-end
 
-  // Wasm intrinsic
   @inline def floatToIntBits(value: scala.Float): scala.Int =
-    FloatingPointBits.floatToIntBits(value)
+    throw new Error("stub") // body replaced by the compiler back-end
 
   @inline def sum(a: scala.Float, b: scala.Float): scala.Float =
     a + b
diff --git a/javalib/src/main/scala/java/lang/FloatingPointBits.scala b/javalib/src/main/scala/java/lang/FloatingPointBits.scala
deleted file mode 100644
index 3b03975c3e..0000000000
--- a/javalib/src/main/scala/java/lang/FloatingPointBits.scala
+++ /dev/null
@@ -1,294 +0,0 @@
-/*
- * Scala.js (https://www.scala-js.org/)
- *
- * Copyright EPFL.
- *
- * Licensed under Apache License 2.0
- * (https://www.apache.org/licenses/LICENSE-2.0).
- *
- * See the NOTICE file distributed with this work for
- * additional information regarding copyright ownership.
- */
-
-package java.lang
-
-import scala.scalajs.js
-import scala.scalajs.js.Dynamic.global
-import scala.scalajs.js.typedarray
-import scala.scalajs.LinkingInfo.ESVersion
-
-/** Manipulating the bits of floating point numbers. */
-private[lang] object FloatingPointBits {
-
-  /** Are typed arrays known to be supported at link time?
-   *
-   *  If yes, we can dce polyfills away.
-   */
-  @inline
-  private def areTypedArraysKnownSupported: scala.Boolean =
-    scala.scalajs.LinkingInfo.esVersion >= ESVersion.ES2015
-
-  /** The DataView we use when typed arrays are supported; null if they are not supported.
-   *
-   *  We always use it in `littleEndian` mode. Major architectures are all
-   *  little endian these days.
-   */
-  private val dataView: typedarray.DataView = {
-    // If DataView exists, ArrayBuffer must exist as well. There is no need to test both.
-    if (areTypedArraysKnownSupported || js.typeOf(global.DataView) != "undefined")
-      new typedarray.DataView(new typedarray.ArrayBuffer(8))
-    else
-      null
-  }
-
-  private val floatPowsOf2: js.Array[scala.Double] =
-    if (areTypedArraysKnownSupported || (dataView != null)) null
-    else makePowsOf2(len = 1 << 8, java.lang.Float.MIN_NORMAL.toDouble)
-
-  private val doublePowsOf2: js.Array[scala.Double] =
-    if (areTypedArraysKnownSupported || (dataView != null)) null
-    else makePowsOf2(len = 1 << 11, java.lang.Double.MIN_NORMAL)
-
-  private def makePowsOf2(len: Int, minNormal: scala.Double): js.Array[scala.Double] = {
-    val r = new js.Array[scala.Double](len)
-    r(0) = 0.0
-    var i = 1
-    var next = minNormal
-    while (i != len - 1) {
-      r(i) = next
-      i += 1
-      next *= 2
-    }
-    r(len - 1) = scala.Double.PositiveInfinity
-    r
-  }
-
-  /** Hash code of a number (excluding Longs).
-   *
-   *  Because of the common encoding for integer and floating point values,
-   *  the hashCode of Floats and Doubles must align with that of Ints for the
-   *  common values.
-   *
-   *  For other values, we use the hashCode specified by the JavaDoc for
-   *  *Doubles*, even for values which are valid Float values. Because of the
-   *  previous point, we cannot align completely with the Java specification,
-   *  so there is no point trying to be a bit more aligned here. Always using
-   *  the Double version should typically be faster on VMs without fround
-   *  support because we avoid several fround operations.
-   */
-  def numberHashCode(value: scala.Double): Int = {
-    val iv = rawToInt(value)
-    if (iv == value && 1.0/value != scala.Double.NegativeInfinity) {
-      iv
-    } else {
-      /* Basically an inlined version of `Long.hashCode(doubleToLongBits(value))`,
-       * so that we never allocate a RuntimeLong instance (or anything, for
-       * that matter).
-       */
-      val dataView = this.dataView // local copy
-      if (areTypedArraysKnownSupported || (dataView != null)) {
-        dataView.setFloat64(0, value, littleEndian = true)
-        dataView.getInt32(0, littleEndian = true) ^ dataView.getInt32(4, littleEndian = true)
-      } else {
-        doubleHashCodePolyfill(value)
-      }
-    }
-  }
-
-  @noinline
-  private def doubleHashCodePolyfill(value: scala.Double): Int =
-    Long.hashCode(doubleToLongBitsPolyfillInline(value))
-
-  def intBitsToFloat(bits: Int): scala.Float = {
-    val dataView = this.dataView // local copy
-    if (areTypedArraysKnownSupported || (dataView != null)) {
-      dataView.setInt32(0, bits, littleEndian = true)
-      dataView.getFloat32(0, littleEndian = true)
-    } else {
-      intBitsToFloatPolyfill(bits).toFloat
-    }
-  }
-
-  def floatToIntBits(value: scala.Float): Int = {
-    val dataView = this.dataView // local copy
-    if (areTypedArraysKnownSupported || (dataView != null)) {
-      dataView.setFloat32(0, value, littleEndian = true)
-      dataView.getInt32(0, littleEndian = true)
-    } else {
-      floatToIntBitsPolyfill(value)
-    }
-  }
-
-  def longBitsToDouble(bits: scala.Long): scala.Double = {
-    val dataView = this.dataView // local copy
-    if (areTypedArraysKnownSupported || (dataView != null)) {
-      dataView.setInt32(0, bits.toInt, littleEndian = true)
-      dataView.setInt32(4, (bits >>> 32).toInt, littleEndian = true)
-      dataView.getFloat64(0, littleEndian = true)
-    } else {
-      longBitsToDoublePolyfill(bits)
-    }
-  }
-
-  def doubleToLongBits(value: scala.Double): scala.Long = {
-    val dataView = this.dataView // local copy
-    if (areTypedArraysKnownSupported || (dataView != null)) {
-      dataView.setFloat64(0, value, littleEndian = true)
-      ((dataView.getInt32(0, littleEndian = true).toLong & 0xffffffffL) |
-          (dataView.getInt32(4, littleEndian = true).toLong << 32))
-    } else {
-      doubleToLongBitsPolyfill(value)
-    }
-  }
-
-  /* --- Polyfills for floating point bit manipulations ---
-   *
-   * Originally inspired by
-   * https://github.com/inexorabletash/polyfill/blob/3447582628b6e3ea81959c4d5987aa332c22d1ca/typedarray.js#L150-L264
-   *
-   * Note that if typed arrays are not supported, it is almost certain that
-   * fround is not supported natively, so Float operations are extremely slow.
-   *
-   * We therefore do all computations in Doubles here.
-   */
-
-  private def intBitsToFloatPolyfill(bits: Int): scala.Double = {
-    val ebits = 8
-    val fbits = 23
-    val sign = (bits >> 31) | 1 // -1 or 1
-    val e = (bits >> fbits) & ((1 << ebits) - 1)
-    val f = bits & ((1 << fbits) - 1)
-    decodeIEEE754(ebits, fbits, floatPowsOf2, scala.Float.MinPositiveValue, sign, e, f)
-  }
-
-  private def floatToIntBitsPolyfill(floatValue: scala.Float): Int = {
-    // Some constants
-    val ebits = 8
-    val fbits = 23
-
-    // Force computations to be on Doubles
-    val value = floatValue.toDouble
-
-    // Determine sign bit and compute the absolute value av
-    val sign = if (value < 0.0 || (value == 0.0 && 1.0 / value < 0.0)) -1 else 1
-    val s = sign & scala.Int.MinValue
-    val av = sign * value
-
-    // Compute e and f
-    val powsOf2 = this.floatPowsOf2 // local cache
-    val e = encodeIEEE754Exponent(ebits, powsOf2, av)
-    val f = encodeIEEE754MantissaBits(ebits, fbits, powsOf2, scala.Float.MinPositiveValue.toDouble, av, e)
-
-    // Encode
-    s | (e << fbits) | rawToInt(f)
-  }
-
-  private def longBitsToDoublePolyfill(bits: scala.Long): scala.Double = {
-    val ebits = 11
-    val fbits = 52
-    val hifbits = fbits - 32
-    val hi = (bits >>> 32).toInt
-    val lo = Utils.toUint(bits.toInt)
-    val sign = (hi >> 31) | 1 // -1 or 1
-    val e = (hi >> hifbits) & ((1 << ebits) - 1)
-    val f = (hi & ((1 << hifbits) - 1)).toDouble * 0x100000000L.toDouble + lo
-    decodeIEEE754(ebits, fbits, doublePowsOf2, scala.Double.MinPositiveValue, sign, e, f)
-  }
-
-  @noinline
-  private def doubleToLongBitsPolyfill(value: scala.Double): scala.Long =
-    doubleToLongBitsPolyfillInline(value)
-
-  @inline
-  private def doubleToLongBitsPolyfillInline(value: scala.Double): scala.Long = {
-    // Some constants
-    val ebits = 11
-    val fbits = 52
-    val hifbits = fbits - 32
-
-    // Determine sign bit and compute the absolute value av
-    val sign = if (value < 0.0 || (value == 0.0 && 1.0 / value < 0.0)) -1 else 1
-    val s = sign & scala.Int.MinValue
-    val av = sign * value
-
-    // Compute e and f
-    val powsOf2 = this.doublePowsOf2 // local cache
-    val e = encodeIEEE754Exponent(ebits, powsOf2, av)
-    val f = encodeIEEE754MantissaBits(ebits, fbits, powsOf2, scala.Double.MinPositiveValue, av, e)
-
-    // Encode
-    val hi = s | (e << hifbits) | rawToInt(f / 0x100000000L.toDouble)
-    val lo = rawToInt(f)
-    (hi.toLong << 32) | (lo.toLong & 0xffffffffL)
-  }
-
-  @inline
-  private def decodeIEEE754(ebits: Int, fbits: Int,
-      powsOf2: js.Array[scala.Double], minPositiveValue: scala.Double,
-      sign: scala.Int, e: Int, f: scala.Double): scala.Double = {
-
-    // Some constants
-    val specialExponent = (1 << ebits) - 1
-    val twoPowFbits = (1L << fbits).toDouble
-
-    if (e == specialExponent) {
-      // Special
-      if (f == 0.0)
-        sign * scala.Double.PositiveInfinity
-      else
-        scala.Double.NaN
-    } else if (e > 0) {
-      // Normalized
-      sign * powsOf2(e) * (1 + f / twoPowFbits)
-    } else {
-      // Subnormal
-      sign * f * minPositiveValue
-    }
-  }
-
-  private def encodeIEEE754Exponent(ebits: Int,
-      powsOf2: js.Array[scala.Double], av: scala.Double): Int = {
-
-    /* Binary search of `av` inside `powsOf2`.
-     * There are exactly `ebits` iterations of this loop (11 for Double, 8 for Float).
-     */
-    var eMin = 0
-    var eMax = 1 << ebits
-    while (eMin + 1 < eMax) {
-      val e = (eMin + eMax) >> 1
-      if (av < powsOf2(e)) // false when av is NaN
-        eMax = e
-      else
-        eMin = e
-    }
-    eMin
-  }
-
-  @inline
-  private def encodeIEEE754MantissaBits(ebits: Int, fbits: Int,
-      powsOf2: js.Array[scala.Double], minPositiveValue: scala.Double,
-      av: scala.Double, e: Int): scala.Double = {
-
-    // Some constants
-    val specialExponent = (1 << ebits) - 1
-    val twoPowFbits = (1L << fbits).toDouble
-
-    if (e == specialExponent) {
-      if (av != av)
-        (1L << (fbits - 1)).toDouble // NaN
-      else
-        0.0 // Infinity
-    } else {
-      if (e == 0)
-        av / minPositiveValue // Subnormal
-      else
-        ((av / powsOf2(e)) - 1.0) * twoPowFbits // Normal
-    }
-  }
-
-  @inline private def rawToInt(x: scala.Double): Int = {
-    import scala.scalajs.js.DynamicImplicits.number2dynamic
-    (x | 0).asInstanceOf[Int]
-  }
-
-}
diff --git a/linker-private-library/src/main/scala/org/scalajs/linker/runtime/FloatingPointBitsPolyfills.scala b/linker-private-library/src/main/scala/org/scalajs/linker/runtime/FloatingPointBitsPolyfills.scala
new file mode 100644
index 0000000000..693b4f4136
--- /dev/null
+++ b/linker-private-library/src/main/scala/org/scalajs/linker/runtime/FloatingPointBitsPolyfills.scala
@@ -0,0 +1,190 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package org.scalajs.linker.runtime
+
+import scala.scalajs.js
+
+/** Polyfills for manipulating the bits of floating point numbers without DataView.
+ *
+ *  These polyfills are only used when targeting ECMAScript 5.1.
+ *
+ *  Originally inspired by
+ *  https://github.com/inexorabletash/polyfill/blob/3447582628b6e3ea81959c4d5987aa332c22d1ca/typedarray.js#L150-L264
+ *
+ *  Note that if typed arrays are not supported, it is almost certain that
+ *  fround is not supported natively, so Float operations are extremely slow.
+ *
+ *  We therefore do all computations in Doubles here.
+ */
+object FloatingPointBitsPolyfills {
+  private val floatPowsOf2: js.Array[Double] =
+    makePowsOf2(len = 1 << 8, java.lang.Float.MIN_NORMAL.toDouble)
+
+  private val doublePowsOf2: js.Array[Double] =
+    makePowsOf2(len = 1 << 11, java.lang.Double.MIN_NORMAL)
+
+  private def makePowsOf2(len: Int, minNormal: Double): js.Array[Double] = {
+    val r = new js.Array[Double](len)
+    r(0) = 0.0
+    var i = 1
+    var next = minNormal
+    while (i != len - 1) {
+      r(i) = next
+      i += 1
+      next *= 2
+    }
+    r(len - 1) = Double.PositiveInfinity
+    r
+  }
+
+  @inline // inline into the static forwarder, which will be the entry point
+  def floatFromBits(bits: Int): Double = {
+    val ebits = 8
+    val fbits = 23
+    val sign = (bits >> 31) | 1 // -1 or 1
+    val e = (bits >> fbits) & ((1 << ebits) - 1)
+    val f = bits & ((1 << fbits) - 1)
+    decodeIEEE754(ebits, fbits, floatPowsOf2, Float.MinPositiveValue, sign, e, f)
+  }
+
+  @inline // inline into the static forwarder, which will be the entry point
+  def floatToBits(floatValue: Float): Int = {
+    // Some constants
+    val ebits = 8
+    val fbits = 23
+
+    // Force computations to be on Doubles
+    val value = floatValue.toDouble
+
+    // Determine sign bit and compute the absolute value av
+    val sign = if (value < 0.0 || (value == 0.0 && 1.0 / value < 0.0)) -1 else 1
+    val s = sign & Int.MinValue
+    val av = sign * value
+
+    // Compute e and f
+    val powsOf2 = this.floatPowsOf2 // local cache
+    val e = encodeIEEE754Exponent(ebits, powsOf2, av)
+    val f = encodeIEEE754MantissaBits(ebits, fbits, powsOf2, Float.MinPositiveValue.toDouble, av, e)
+
+    // Encode
+    s | (e << fbits) | rawToInt(f)
+  }
+
+  @inline // inline into the static forwarder, which will be the entry point
+  def doubleFromBits(bits: Long): Double = {
+    val ebits = 11
+    val fbits = 52
+    val hifbits = fbits - 32
+    val hi = (bits >>> 32).toInt
+    val lo = toUint(bits.toInt)
+    val sign = (hi >> 31) | 1 // -1 or 1
+    val e = (hi >> hifbits) & ((1 << ebits) - 1)
+    val f = (hi & ((1 << hifbits) - 1)).toDouble * 0x100000000L.toDouble + lo
+    decodeIEEE754(ebits, fbits, doublePowsOf2, Double.MinPositiveValue, sign, e, f)
+  }
+
+  @inline // inline into the static forwarder, which will be the entry point
+  def doubleToBits(value: Double): Long = {
+    // Some constants
+    val ebits = 11
+    val fbits = 52
+    val hifbits = fbits - 32
+
+    // Determine sign bit and compute the absolute value av
+    val sign = if (value < 0.0 || (value == 0.0 && 1.0 / value < 0.0)) -1 else 1
+    val s = sign & Int.MinValue
+    val av = sign * value
+
+    // Compute e and f
+    val powsOf2 = this.doublePowsOf2 // local cache
+    val e = encodeIEEE754Exponent(ebits, powsOf2, av)
+    val f = encodeIEEE754MantissaBits(ebits, fbits, powsOf2, Double.MinPositiveValue, av, e)
+
+    // Encode
+    val hi = s | (e << hifbits) | rawToInt(f / 0x100000000L.toDouble)
+    val lo = rawToInt(f)
+    (hi.toLong << 32) | (lo.toLong & 0xffffffffL)
+  }
+
+  @inline
+  private def decodeIEEE754(ebits: Int, fbits: Int,
+      powsOf2: js.Array[Double], minPositiveValue: Double,
+      sign: Int, e: Int, f: Double): Double = {
+
+    // Some constants
+    val specialExponent = (1 << ebits) - 1
+    val twoPowFbits = (1L << fbits).toDouble
+
+    if (e == specialExponent) {
+      // Special
+      if (f == 0.0)
+        sign * Double.PositiveInfinity
+      else
+        Double.NaN
+    } else if (e > 0) {
+      // Normalized
+      sign * powsOf2(e) * (1 + f / twoPowFbits)
+    } else {
+      // Subnormal
+      sign * f * minPositiveValue
+    }
+  }
+
+  @inline
+  private def encodeIEEE754Exponent(ebits: Int,
+      powsOf2: js.Array[Double], av: Double): Int = {
+
+    /* Binary search of `av` inside `powsOf2`.
+     * There are exactly `ebits` iterations of this loop (11 for Double, 8 for Float).
+     */
+    var eMin = 0
+    var eMax = 1 << ebits
+    while (eMin + 1 < eMax) {
+      val e = (eMin + eMax) >> 1
+      if (av < powsOf2(e)) // false when av is NaN
+        eMax = e
+      else
+        eMin = e
+    }
+    eMin
+  }
+
+  @inline
+  private def encodeIEEE754MantissaBits(ebits: Int, fbits: Int,
+      powsOf2: js.Array[Double], minPositiveValue: Double,
+      av: Double, e: Int): Double = {
+
+    // Some constants
+    val specialExponent = (1 << ebits) - 1
+    val twoPowFbits = (1L << fbits).toDouble
+
+    if (e == specialExponent) {
+      if (av != av)
+        (1L << (fbits - 1)).toDouble // NaN
+      else
+        0.0 // Infinity
+    } else {
+      if (e == 0)
+        av / minPositiveValue // Subnormal
+      else
+        ((av / powsOf2(e)) - 1.0) * twoPowFbits // Normal
+    }
+  }
+
+  @inline private def toUint(x: Int): Double =
+    (x.asInstanceOf[js.Dynamic] >>> 0.asInstanceOf[js.Dynamic]).asInstanceOf[Double]
+
+  @inline private def rawToInt(x: Double): Int =
+    (x.asInstanceOf[js.Dynamic] | 0.asInstanceOf[js.Dynamic]).asInstanceOf[Int]
+
+}
diff --git a/linker-private-library/src/main/scala/org/scalajs/linker/runtime/RuntimeLong.scala b/linker-private-library/src/main/scala/org/scalajs/linker/runtime/RuntimeLong.scala
index 7a90e2a9e1..7e4e256beb 100644
--- a/linker-private-library/src/main/scala/org/scalajs/linker/runtime/RuntimeLong.scala
+++ b/linker-private-library/src/main/scala/org/scalajs/linker/runtime/RuntimeLong.scala
@@ -541,6 +541,18 @@ final class RuntimeLong(val lo: Int, val hi: Int) {
   def remainderUnsigned(b: RuntimeLong): RuntimeLong =
     RuntimeLong.remainderUnsigned(a, b)
 
+  /** Computes `longBitsToDouble(this)`.
+   *
+   *  `fpBitsDataView` must be a scratch `js.typedarray.DataView` whose
+   *  underlying buffer is at least 8 bytes long.
+   */
+  @inline
+  def bitsToDouble(fpBitsDataView: scala.scalajs.js.typedarray.DataView): Double = {
+    fpBitsDataView.setInt32(0, lo, littleEndian = true)
+    fpBitsDataView.setInt32(4, hi, littleEndian = true)
+    fpBitsDataView.getFloat64(0, littleEndian = true)
+  }
+
 }
 
 object RuntimeLong {
@@ -728,6 +740,22 @@ object RuntimeLong {
     }
   }
 
+  /** Computes `doubleToLongBits(value)`.
+   *
+   *  `fpBitsDataView` must be a scratch `js.typedarray.DataView` whose
+   *  underlying buffer is at least 8 bytes long.
+   */
+  @inline
+  def fromDoubleBits(value: Double,
+      fpBitsDataView: scala.scalajs.js.typedarray.DataView): RuntimeLong = {
+
+    fpBitsDataView.setFloat64(0, value, littleEndian = true)
+    new RuntimeLong(
+      fpBitsDataView.getInt32(0, littleEndian = true),
+      fpBitsDataView.getInt32(4, littleEndian = true)
+    )
+  }
+
   private def compare(alo: Int, ahi: Int, blo: Int, bhi: Int): Int = {
     if (ahi == bhi) {
       if (alo == blo) 0
diff --git a/linker/jvm/src/main/scala/org/scalajs/linker/backend/emitter/PrivateLibHolder.scala b/linker/jvm/src/main/scala/org/scalajs/linker/backend/emitter/PrivateLibHolder.scala
index d668c26e25..c4849c8955 100644
--- a/linker/jvm/src/main/scala/org/scalajs/linker/backend/emitter/PrivateLibHolder.scala
+++ b/linker/jvm/src/main/scala/org/scalajs/linker/backend/emitter/PrivateLibHolder.scala
@@ -24,6 +24,8 @@ object PrivateLibHolder {
   private val stableVersion = ir.Version.fromInt(0) // never changes
 
   private val sjsirPaths = Seq(
+      "org/scalajs/linker/runtime/FloatingPointBitsPolyfills.sjsir",
+      "org/scalajs/linker/runtime/FloatingPointBitsPolyfills$.sjsir",
       "org/scalajs/linker/runtime/RuntimeLong.sjsir",
       "org/scalajs/linker/runtime/RuntimeLong$.sjsir",
       "org/scalajs/linker/runtime/UndefinedBehaviorError.sjsir",
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
index 6fb37ce343..6b1eb65103 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
@@ -101,6 +101,8 @@ private[emitter] object CoreJSLib {
     private val StringRef = globalRef("String")
     private val MathRef = globalRef("Math")
     private val NumberRef = globalRef("Number")
+    private val DataViewRef = globalRef("DataView")
+    private val ArrayBufferRef = globalRef("ArrayBuffer")
     private val TypeErrorRef = globalRef("TypeError")
     private def BigIntRef = globalRef("BigInt")
     private val SymbolRef = globalRef("Symbol")
@@ -874,6 +876,48 @@ private[emitter] object CoreJSLib {
       def wrapBigInt64(tree: Tree): Tree =
         Apply(genIdentBracketSelect(BigIntRef, "asIntN"), 64 :: tree :: Nil)
 
+      /* Defines a core function of 1 argument `x` that uses the `fpBitsDataView`
+       * global var. When linking for ES 2015+, the provided body is always
+       * used, as `fpBitsDataView` is known to exist. When linking for 5.1,
+       * a polyfill from `org.scalajs.linker.runtime.FloatingPointBitsPolyfills`
+       * is used when `fpBitsDataView` is `null`.
+       *
+       * The `body` function receives `x` and `fpBitsDataView` as arguments,
+       * in that order.
+       */
+      def defineFloatingPointBitsFunctionOrPolyfill(name: VarField,
+          polyfillMethod: MethodName)(body: (VarRef, VarRef) => Tree): List[Tree] = {
+
+        val dataView = varRef("dataView")
+        val dataViewConst = const(dataView, globalVar(VarField.fpBitsDataView, CoreVar))
+
+        if (esVersion >= ESVersion.ES2015) {
+          defineFunction1(name) { x =>
+            Block(
+              dataViewConst,
+              body(x, dataView)
+            )
+          }
+        } else {
+          val x = varRef("x")
+
+          extractWithGlobals(globalVarDef(name, CoreVar, {
+            If(globalVar(VarField.fpBitsDataView, CoreVar) !== Null(), {
+              genArrowFunction(paramList(x), {
+                Block(
+                  dataViewConst,
+                  body(x, dataView)
+                )
+              })
+            }, {
+              genArrowFunction(paramList(x), {
+                Return(Apply(globalVar(VarField.s, (FloatingPointBitsPolyfillsClass, polyfillMethod)), List(x)))
+              })
+            })
+          }))
+        }
+      }
+
       condDefs(shouldDefineIntLongDivModFunctions)(
         defineFunction2(VarField.intDiv) { (x, y) =>
           If(y === 0, throwDivByZero, {
@@ -956,7 +1000,51 @@ private[emitter] object CoreJSLib {
             Return(genCallPolyfillableBuiltin(FroundBuiltin, If(x < bigInt(0L), -absR, absR)))
           )
         }
-      )
+      ) :::
+      extractWithGlobals(globalVarDef(VarField.fpBitsDataView, CoreVar, {
+        val newDataView = New(DataViewRef, List(New(ArrayBufferRef, List(8))))
+        if (esVersion >= ESVersion.ES2015) {
+          newDataView
+        } else {
+          If(typeof(DataViewRef) !== str("undefined"), {
+            newDataView
+          }, {
+            Null()
+          })
+        }
+      })) :::
+      defineFloatingPointBitsFunctionOrPolyfill(VarField.floatToBits, floatToBits) { (x, fpBitsDataView) =>
+        Block(
+          Apply(genIdentBracketSelect(fpBitsDataView, "setFloat32"), List(0, x, bool(true))),
+          Return(Apply(genIdentBracketSelect(fpBitsDataView, "getInt32"), List(0, bool(true))))
+        )
+      } :::
+      defineFloatingPointBitsFunctionOrPolyfill(VarField.floatFromBits, floatFromBits) { (x, fpBitsDataView) =>
+        Block(
+          Apply(genIdentBracketSelect(fpBitsDataView, "setInt32"), List(0, x, bool(true))),
+          Return(Apply(genIdentBracketSelect(fpBitsDataView, "getFloat32"), List(0, bool(true))))
+        )
+      } :::
+      defineFloatingPointBitsFunctionOrPolyfill(VarField.doubleToBits, doubleToBits) { (x, fpBitsDataView) =>
+        if (allowBigIntsForLongs) {
+          Block(
+            Apply(genIdentBracketSelect(fpBitsDataView, "setFloat64"), List(0, x, bool(true))),
+            Return(Apply(genIdentBracketSelect(fpBitsDataView, "getBigInt64"), List(0, bool(true))))
+          )
+        } else {
+          Return(genLongModuleApply(LongImpl.fromDoubleBits, x, fpBitsDataView))
+        }
+      } :::
+      defineFloatingPointBitsFunctionOrPolyfill(VarField.doubleFromBits, doubleFromBits) { (x, fpBitsDataView) =>
+        if (allowBigIntsForLongs) {
+          Block(
+            Apply(genIdentBracketSelect(fpBitsDataView, "setBigInt64"), List(0, x, bool(true))),
+            Return(Apply(genIdentBracketSelect(fpBitsDataView, "getFloat64"), List(0, bool(true))))
+          )
+        } else {
+          Return(genApply(x, LongImpl.bitsToDouble, fpBitsDataView))
+        }
+      }
     }
 
     private def defineES2015LikeHelpers(): List[Tree] = (
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala
index b625c51c12..e96103fd08 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Emitter.scala
@@ -1440,6 +1440,16 @@ object Emitter {
               callMethods(LongImpl.RuntimeLongClass, LongImpl.AllMethods.toList),
               callOnModule(LongImpl.RuntimeLongModuleClass, LongImpl.AllModuleMethods.toList)
           )
+        },
+
+        cond(config.coreSpec.esFeatures.esVersion < ESVersion.ES2015) {
+          val cls = FloatingPointBitsPolyfillsClass
+          multiple(
+            callStaticMethod(cls, floatToBits),
+            callStaticMethod(cls, floatFromBits),
+            callStaticMethod(cls, doubleToBits),
+            callStaticMethod(cls, doubleFromBits)
+          )
         }
     )
   }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/EmitterNames.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/EmitterNames.scala
index 02e46fd548..3bf4e8984a 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/EmitterNames.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/EmitterNames.scala
@@ -25,6 +25,9 @@ private[emitter] object EmitterNames {
   val UndefinedBehaviorErrorClass =
     ClassName("org.scalajs.linker.runtime.UndefinedBehaviorError")
 
+  val FloatingPointBitsPolyfillsClass =
+    ClassName("org.scalajs.linker.runtime.FloatingPointBitsPolyfills")
+
   // Field names
 
   val exceptionFieldName = FieldName(JavaScriptExceptionClass, SimpleFieldName("exception"))
@@ -43,4 +46,9 @@ private[emitter] object EmitterNames {
 
   val getNameMethodName = MethodName("getName", Nil, ClassRef(BoxedStringClass))
   val getSuperclassMethodName = MethodName("getSuperclass", Nil, ClassRef(ClassClass))
+
+  val floatToBits = MethodName("floatToBits", List(FloatRef), IntRef)
+  val floatFromBits = MethodName("floatFromBits", List(IntRef), DoubleRef) // yes, Double
+  val doubleToBits = MethodName("doubleToBits", List(DoubleRef), LongRef)
+  val doubleFromBits = MethodName("doubleFromBits", List(LongRef), DoubleRef)
 }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
index e5c444e342..2fbd0eecd0 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
@@ -1266,8 +1266,9 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
 
       def test(tree: Tree): Boolean = tree match {
         // Atomic expressions
-        case _: Literal     => true
-        case _: JSNewTarget => true
+        case _: Literal                   => true
+        case _: JSNewTarget               => true
+        case Transient(GetFPBitsDataView) => true
 
         // Vars (side-effect free, pure if immutable)
         case VarRef(name) =>
@@ -2515,6 +2516,16 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
                   genIsInstanceOfClass(newLhs, JavaScriptExceptionClass),
                   genSelect(newLhs, FieldIdent(exceptionFieldName)),
                   newLhs)
+
+            // Floating point bit manipulation
+            case Float_toBits =>
+              genCallHelper(VarField.floatToBits, newLhs)
+            case Float_fromBits =>
+              genCallHelper(VarField.floatFromBits, newLhs)
+            case Double_toBits =>
+              genCallHelper(VarField.doubleToBits, newLhs)
+            case Double_fromBits =>
+              genCallHelper(VarField.doubleFromBits, newLhs)
           }
 
         case BinaryOp(op, lhs, rhs) =>
@@ -2879,6 +2890,9 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
         case Transient(ObjectClassName(obj)) =>
           genCallHelper(VarField.objectClassName, transformExprNoChar(obj))
 
+        case Transient(GetFPBitsDataView) =>
+          globalVar(VarField.fpBitsDataView, CoreVar)
+
         case Transient(ArrayToTypedArray(expr, primRef)) =>
           val value = transformExprNoChar(checkNotNull(expr))
           val valueUnderlying = genSyntheticPropSelect(value, SyntheticProperty.u)
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/LongImpl.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/LongImpl.scala
index e4059324e0..2c93e5e358 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/LongImpl.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/LongImpl.scala
@@ -62,9 +62,10 @@ private[linker] object LongImpl {
   final val >   = compareOp("$greater")
   final val >=  = compareOp("$greater$eq")
 
-  final val toInt    = MethodName("toInt", Nil, IntRef)
-  final val toFloat  = MethodName("toFloat", Nil, FloatRef)
+  final val toInt = MethodName("toInt", Nil, IntRef)
+  final val toFloat = MethodName("toFloat", Nil, FloatRef)
   final val toDouble = MethodName("toDouble", Nil, DoubleRef)
+  final val bitsToDouble = MethodName("bitsToDouble", List(ObjectRef), DoubleRef)
 
   final val byteValue   = MethodName("byteValue", Nil, ByteRef)
   final val shortValue  = MethodName("shortValue", Nil, ShortRef)
@@ -81,7 +82,7 @@ private[linker] object LongImpl {
 
   private val OperatorMethods = Set(
       UNARY_-, UNARY_~, this.+, this.-, *, /, %, |, &, ^, <<, >>>, >>,
-      ===, !==, <, <=, >, >=, toInt, toFloat, toDouble)
+      ===, !==, <, <=, >, >=, toInt, toFloat, toDouble, bitsToDouble)
 
   private val BoxedLongMethods = Set(
       byteValue, shortValue, intValue, longValue, floatValue, doubleValue,
@@ -107,11 +108,12 @@ private[linker] object LongImpl {
 
   // Methods on the companion
 
-  final val fromInt    = MethodName("fromInt", List(IntRef), RTLongRef)
+  final val fromInt = MethodName("fromInt", List(IntRef), RTLongRef)
   final val fromDouble = MethodName("fromDouble", List(DoubleRef), RTLongRef)
+  final val fromDoubleBits = MethodName("fromDoubleBits", List(DoubleRef, ObjectRef), RTLongRef)
 
   val AllModuleMethods = Set(
-      fromInt, fromDouble)
+      fromInt, fromDouble, fromDoubleBits)
 
   // Extract the parts to give to the initFromParts constructor
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Transients.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Transients.scala
index 00301771cc..b1ac1c10a6 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Transients.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/Transients.scala
@@ -156,6 +156,22 @@ object Transients {
     }
   }
 
+  /** Gets the unique instance of `DataView` used for floating point bit manipulation.
+   *
+   *  When linking for ES 5.1, the resulting value can be `null`.
+   */
+  final case object GetFPBitsDataView extends Transient.Value {
+    val tpe: Type = AnyType
+
+    def traverse(traverser: Traverser): Unit = ()
+
+    def transform(transformer: Transformer)(implicit pos: Position): Tree =
+      Transient(this)
+
+    def printIR(out: IRTreePrinter): Unit =
+      out.print("$fpBitsDataView")
+  }
+
   /** Copies a primitive `Array` into a new appropriate `TypedArray`.
    *
    *  This node accepts `null` values for `expr`. Its implementation takes care
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/VarField.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/VarField.scala
index 44193542b9..ba3355e54a 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/VarField.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/VarField.scala
@@ -146,6 +146,9 @@ private[emitter] object VarField {
   /** Long zero. */
   final val L0 = mk("$L0")
 
+  /** DataView for floating point bit manipulation. */
+  final val fpBitsDataView = mk("$fpBitsDataView")
+
   /** Dispatchers. */
   final val dp = mk("$dp")
 
@@ -270,6 +273,11 @@ private[emitter] object VarField {
 
   final val doubleToInt = mk("$doubleToInt")
 
+  final val floatToBits = mk("$floatToBits")
+  final val floatFromBits = mk("$floatFromBits")
+  final val doubleToBits = mk("$doubleToBits")
+  final val doubleFromBits = mk("$doubleFromBits")
+
   // Polyfills
 
   final val imul = mk("$imul")
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
index 7cf164c228..2cf8d2682c 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
@@ -1638,6 +1638,46 @@ private class FunctionEmitter private (
       case Throw =>
         fb += wa.ExternConvertAny
         fb += wa.Throw(genTagID.exception)
+
+      // Floating point bit manipulation
+      case Float_toBits =>
+        val bitsLocal = addSyntheticLocal(watpe.Int32)
+        // bits := toRawBits(arg)
+        fb += wa.I32ReinterpretF32
+        fb += wa.LocalTee(bitsLocal)
+        // if ((bits & ~SignBit) > bit pattern of Infinity)
+        fb += wa.I32Const(~Int.MinValue)
+        fb += wa.I32And
+        fb += wa.I32Const(java.lang.Float.floatToIntBits(Float.PositiveInfinity))
+        fb += wa.I32GtU
+        fb.ifThen() { // there is a good chance that this branch is predictably false, so don't use wa.Select
+          // then it's NaN; replace with the canonical bit pattern
+          fb += wa.I32Const(java.lang.Float.floatToIntBits(Float.NaN))
+          fb += wa.LocalSet(bitsLocal)
+        }
+        // result is in bits
+        fb += wa.LocalGet(bitsLocal)
+      case Float_fromBits =>
+        fb += wa.F32ReinterpretI32
+      case Double_toBits =>
+        val bitsLocal = addSyntheticLocal(watpe.Int64)
+        // bits := toRawBits(arg)
+        fb += wa.I64ReinterpretF64
+        fb += wa.LocalTee(bitsLocal)
+        // if ((bits & ~SignBit) > bit pattern of Infinity)
+        fb += wa.I64Const(~Long.MinValue)
+        fb += wa.I64And
+        fb += wa.I64Const(java.lang.Double.doubleToLongBits(Double.PositiveInfinity))
+        fb += wa.I64GtU
+        fb.ifThen() { // there is a good chance that this branch is predictably false, so don't use wa.Select
+          // then it's NaN; replace with the canonical bit pattern
+          fb += wa.I64Const(java.lang.Double.doubleToLongBits(Double.NaN))
+          fb += wa.LocalSet(bitsLocal)
+        }
+        // result is in bits
+        fb += wa.LocalGet(bitsLocal)
+      case Double_fromBits =>
+        fb += wa.F64ReinterpretI64
     }
 
     tree.tpe
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/WasmTransients.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/WasmTransients.scala
index bf41838a98..3d3f12fdb8 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/WasmTransients.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/WasmTransients.scala
@@ -62,11 +62,6 @@ object WasmTransients {
       case F64Floor   => wa.F64Floor
       case F64Nearest => wa.F64Nearest
       case F64Sqrt    => wa.F64Sqrt
-
-      case I32ReinterpretF32 => wa.I32ReinterpretF32
-      case I64ReinterpretF64 => wa.I64ReinterpretF64
-      case F32ReinterpretI32 => wa.F32ReinterpretI32
-      case F64ReinterpretI64 => wa.F64ReinterpretI64
     }
 
     def printIR(out: IRTreePrinter): Unit = {
@@ -96,22 +91,17 @@ object WasmTransients {
     final val F64Nearest = 11
     final val F64Sqrt = 12
 
-    final val I32ReinterpretF32 = 13
-    final val I64ReinterpretF64 = 14
-    final val F32ReinterpretI32 = 15
-    final val F64ReinterpretI64 = 16
-
     def resultTypeOf(op: Code): Type = (op: @switch) match {
-      case I32Clz | I32Ctz | I32Popcnt | I32ReinterpretF32 =>
+      case I32Clz | I32Ctz | I32Popcnt =>
         IntType
 
-      case I64Clz | I64Ctz | I64Popcnt | I64ReinterpretF64 =>
+      case I64Clz | I64Ctz | I64Popcnt =>
         LongType
 
-      case F32Abs | F32ReinterpretI32 =>
+      case F32Abs =>
         FloatType
 
-      case F64Abs | F64Ceil | F64Floor | F64Nearest | F64Sqrt | F64ReinterpretI64 =>
+      case F64Abs | F64Ceil | F64Floor | F64Nearest | F64Sqrt =>
         DoubleType
     }
   }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala b/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
index 3f87f8be04..b744dd380a 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
@@ -538,13 +538,13 @@ private final class IRChecker(linkTimeProperties: LinkTimeProperties,
             ByteType
           case ShortToInt =>
             ShortType
-          case IntToLong | IntToDouble | IntToChar | IntToByte | IntToShort =>
+          case IntToLong | IntToDouble | IntToChar | IntToByte | IntToShort | Float_fromBits =>
             IntType
-          case LongToInt | LongToDouble | LongToFloat =>
+          case LongToInt | LongToDouble | LongToFloat | Double_fromBits =>
             LongType
-          case FloatToDouble =>
+          case FloatToDouble | Float_toBits =>
             FloatType
-          case DoubleToInt | DoubleToFloat | DoubleToLong =>
+          case DoubleToInt | DoubleToFloat | DoubleToLong | Double_toBits =>
             DoubleType
           case String_length =>
             StringType
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
index 9f7fe1aa95..422831e52e 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
@@ -1649,6 +1649,9 @@ private[optimizer] abstract class OptimizerCore(
       else
         Block(exprSideEffects, Transient(Cast(Null(), tpe)))
 
+    case Transient(GetFPBitsDataView) =>
+      Skip()(stat.pos)
+
     case _ =>
       stat
   }
@@ -1901,6 +1904,8 @@ private[optimizer] abstract class OptimizerCore(
 
         case _: Literal =>
           NotFoundPureSoFar
+        case Transient(GetFPBitsDataView) =>
+          NotFoundPureSoFar
 
         case Closure(flags, captureParams, params, restParam, resultType, body, captureValues) =>
           recs(captureValues).mapOrKeepGoing { newCaptureValues =>
@@ -2979,41 +2984,6 @@ private[optimizer] abstract class OptimizerCore(
               cont)
         }
 
-      // java.lang.Float
-
-      case FloatToIntBits =>
-        // The Wasm I32ReinterpretF32 is the *raw* version; we need to normalize NaNs
-        withNewTempLocalDefs(targs) { (localDefs, cont1) =>
-          val argLocalDef = localDefs.head
-          def argToDouble = UnaryOp(UnaryOp.FloatToDouble, argLocalDef.newReplacement)
-          cont1 {
-            If(BinaryOp(BinaryOp.Double_!=, argToDouble, argToDouble),
-                IntLiteral(java.lang.Float.floatToIntBits(Float.NaN)),
-                wasmUnaryOp(WasmUnaryOp.I32ReinterpretF32, argLocalDef.toPreTransform))(
-                IntType).toPreTransform
-          }
-        } (cont)
-
-      case IntBitsToFloat =>
-        contTree(wasmUnaryOp(WasmUnaryOp.F32ReinterpretI32, targs.head))
-
-      // java.lang.Double
-
-      case DoubleToLongBits =>
-        // The Wasm I64ReinterpretF64 is the *raw* version; we need to normalize NaNs
-        withNewTempLocalDefs(targs) { (localDefs, cont1) =>
-          val argLocalDef = localDefs.head
-          cont1 {
-            If(BinaryOp(BinaryOp.Double_!=, argLocalDef.newReplacement, argLocalDef.newReplacement),
-                LongLiteral(java.lang.Double.doubleToLongBits(Double.NaN)),
-                wasmUnaryOp(WasmUnaryOp.I64ReinterpretF64, argLocalDef.toPreTransform))(
-                LongType).toPreTransform
-          }
-        } (cont)
-
-      case LongBitsToDouble =>
-        contTree(wasmUnaryOp(WasmUnaryOp.F64ReinterpretI64, targs.head))
-
       // java.lang.Character
 
       case CharacterCodePointToString =>
@@ -3586,12 +3556,12 @@ private[optimizer] abstract class OptimizerCore(
     def rtLongClassType = ClassType(LongImpl.RuntimeLongClass, nullable = true)
 
     def expandLongModuleOp(methodName: MethodName,
-        arg: PreTransform): TailRec[Tree] = {
+        args: PreTransform*): TailRec[Tree] = {
       import LongImpl.{RuntimeLongModuleClass => modCls}
       val receiver =
         makeCast(LoadModule(modCls), ClassType(modCls, nullable = false)).toPreTransform
       pretransformApply(ApplyFlags.empty, receiver, MethodIdent(methodName),
-          arg :: Nil, rtLongClassType, isStat = false,
+          args.toList, rtLongClassType, isStat = false,
           usePreTransform = true)(
           cont)
     }
@@ -3631,6 +3601,15 @@ private[optimizer] abstract class OptimizerCore(
           case LongToFloat =>
             expandUnaryOp(LongImpl.toFloat, arg, FloatType)
 
+          case Double_toBits if config.coreSpec.esFeatures.esVersion >= ESVersion.ES2015 =>
+            expandLongModuleOp(LongImpl.fromDoubleBits,
+                arg, PreTransTree(Transient(GetFPBitsDataView)))
+
+          case Double_fromBits if config.coreSpec.esFeatures.esVersion >= ESVersion.ES2015 =>
+            // It's a bit of a hack to use expandBinaryOp here, but it's fine.
+            expandBinaryOp(LongImpl.bitsToDouble,
+                arg, PreTransTree(Transient(GetFPBitsDataView)))
+
           case _ =>
             cont(pretrans)
         }
@@ -3940,6 +3919,37 @@ private[optimizer] abstract class OptimizerCore(
             foldCast(default, ClassType(ClassClass, nullable = false))
         }
 
+      // Floating point bit manipulation
+
+      case Float_toBits =>
+        arg match {
+          case PreTransLit(FloatLiteral(v)) =>
+            PreTransLit(IntLiteral(java.lang.Float.floatToIntBits(v)))
+          case _ =>
+            default
+        }
+      case Float_fromBits =>
+        arg match {
+          case PreTransLit(IntLiteral(v)) =>
+            PreTransLit(FloatLiteral(java.lang.Float.intBitsToFloat(v)))
+          case _ =>
+            default
+        }
+      case Double_toBits =>
+        arg match {
+          case PreTransLit(DoubleLiteral(v)) =>
+            PreTransLit(LongLiteral(java.lang.Double.doubleToLongBits(v)))
+          case _ =>
+            default
+        }
+      case Double_fromBits =>
+        arg match {
+          case PreTransLit(LongLiteral(v)) =>
+            PreTransLit(DoubleLiteral(java.lang.Double.longBitsToDouble(v)))
+          case _ =>
+            default
+        }
+
       case _ =>
         default
     }
@@ -6492,13 +6502,7 @@ private[optimizer] object OptimizerCore {
     final val LongDivideUnsigned = LongCompare + 1
     final val LongRemainderUnsigned = LongDivideUnsigned + 1
 
-    final val FloatToIntBits = LongRemainderUnsigned + 1
-    final val IntBitsToFloat = FloatToIntBits + 1
-
-    final val DoubleToLongBits = IntBitsToFloat + 1
-    final val LongBitsToDouble = DoubleToLongBits + 1
-
-    final val CharacterCodePointToString = LongBitsToDouble + 1
+    final val CharacterCodePointToString = LongRemainderUnsigned + 1
 
     final val StringCodePointAt = CharacterCodePointToString + 1
     final val StringSubstringStart = StringCodePointAt + 1
@@ -6631,14 +6635,6 @@ private[optimizer] object OptimizerCore {
             m("divideUnsigned", List(J, J), J) -> LongDivideUnsigned,
             m("remainderUnsigned", List(J, J), J) -> LongRemainderUnsigned
         ),
-        ClassName("java.lang.Float$") -> List(
-            m("floatToIntBits", List(F), I) -> FloatToIntBits,
-            m("intBitsToFloat", List(I), F) -> IntBitsToFloat
-        ),
-        ClassName("java.lang.Double$") -> List(
-            m("doubleToLongBits", List(D), J) -> DoubleToLongBits,
-            m("longBitsToDouble", List(J), D) -> LongBitsToDouble
-        ),
         ClassName("java.lang.Character$") -> List(
             m("toString", List(I), StringClassRef) -> CharacterCodePointToString
         ),
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/LibrarySizeTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/LibrarySizeTest.scala
index 5b8f6dba4b..9fb1213758 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/LibrarySizeTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/LibrarySizeTest.scala
@@ -70,9 +70,9 @@ class LibrarySizeTest {
     )
 
     testLinkedSizes(
-      expectedFastLinkSize = 145795,
-      expectedFullLinkSizeWithoutClosure = 84996,
-      expectedFullLinkSizeWithClosure = 21364,
+      expectedFastLinkSize = 146044,
+      expectedFullLinkSizeWithoutClosure = 85435,
+      expectedFullLinkSizeWithClosure = 21197,
       classDefs,
       moduleInitializers = MainTestModuleInitializers
     )
diff --git a/project/Build.scala b/project/Build.scala
index 3b57fe3a24..a383ebf1ac 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -2053,16 +2053,16 @@ object Build {
           case `default212Version` =>
             if (!useMinifySizes) {
               Some(ExpectedSizes(
-                  fastLink = 623000 to 624000,
+                  fastLink = 624000 to 625000,
                   fullLink = 96000 to 97000,
                   fastLinkGz = 75000 to 79000,
                   fullLinkGz = 25000 to 26000,
               ))
             } else {
               Some(ExpectedSizes(
-                  fastLink = 424000 to 425000,
-                  fullLink = 281000 to 282000,
-                  fastLinkGz = 60000 to 61000,
+                  fastLink = 425000 to 426000,
+                  fullLink = 282000 to 283000,
+                  fastLinkGz = 61000 to 62000,
                   fullLinkGz = 43000 to 44000,
               ))
             }
@@ -2077,8 +2077,8 @@ object Build {
               ))
             } else {
               Some(ExpectedSizes(
-                  fastLink = 299000 to 300000,
-                  fullLink = 257000 to 258000,
+                  fastLink = 300000 to 301000,
+                  fullLink = 258000 to 259000,
                   fastLinkGz = 47000 to 48000,
                   fullLinkGz = 42000 to 43000,
               ))
diff --git a/project/MiniLib.scala b/project/MiniLib.scala
index 0d447e4e30..69f5a08ca9 100644
--- a/project/MiniLib.scala
+++ b/project/MiniLib.scala
@@ -22,8 +22,6 @@ object MiniLib {
         "Double",
         "String",
 
-        "FloatingPointBits",
-
         "Throwable",
         "StackTrace",
         "Error",

From 6d0475759f17070655693d2c7cae8382ebe917fe Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Sat, 3 May 2025 13:41:11 +0200
Subject: [PATCH 296/298] Introduce IR BinaryOps for unsigned division and
 remainder.

This allows to better mutualize their implementation with the
signed divisions.

Moreover, our 3 implementation strategies (JS with `RuntimeLong`,
JS with `bigint` and Wasm) have different efficient implementations
of those operations. Using IR BinaryOps for them allows each backend
to use the most appropriate implementation, while letting the
optimizer generically manipulate their mathematical properties.
---
 .../org/scalajs/nscplugin/GenJSCode.scala     |   8 +
 .../main/scala/org/scalajs/ir/Printers.scala  |   5 +
 .../src/main/scala/org/scalajs/ir/Trees.scala |  12 +-
 .../scala/org/scalajs/ir/PrintersTest.scala   |   9 +
 .../src/main/scala/java/lang/Integer.scala    |   8 +-
 javalib/src/main/scala/java/lang/Long.scala   |  44 +----
 .../org/scalajs/linker/analyzer/Infos.scala   |   4 +-
 .../linker/backend/emitter/CoreJSLib.scala    |  24 +--
 .../backend/emitter/FunctionEmitter.scala     |  66 +++----
 .../linker/backend/emitter/LongImpl.scala     |  13 +-
 .../linker/backend/emitter/VarField.scala     |   8 +-
 .../backend/wasmemitter/FunctionEmitter.scala |  53 +++---
 .../backend/wasmemitter/WasmTransients.scala  |  12 +-
 .../scalajs/linker/checker/IRChecker.scala    |   6 +-
 .../frontend/optimizer/OptimizerCore.scala    | 166 +++++++++---------
 .../org/scalajs/linker/LibrarySizeTest.scala  |   4 +-
 project/Build.scala                           |   8 +-
 .../testsuite/javalib/lang/LongTest.scala     |  18 +-
 18 files changed, 221 insertions(+), 247 deletions(-)

diff --git a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
index 2fc15c4dd8..2c39124753 100644
--- a/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
+++ b/compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala
@@ -7424,6 +7424,14 @@ private object GenJSCode {
     val T = jstpe.ClassRef(jswkn.BoxedStringClass)
 
     val byClass: Map[ClassName, Map[MethodName, JavalibOpBody]] = Map(
+      jswkn.BoxedIntegerClass.withSuffix("$") -> Map(
+        m("divideUnsigned", List(I, I), I)    -> ArgBinaryOp(binop.Int_unsigned_/),
+        m("remainderUnsigned", List(I, I), I) -> ArgBinaryOp(binop.Int_unsigned_%)
+      ),
+      jswkn.BoxedLongClass.withSuffix("$") -> Map(
+        m("divideUnsigned", List(J, J), J)    -> ArgBinaryOp(binop.Long_unsigned_/),
+        m("remainderUnsigned", List(J, J), J) -> ArgBinaryOp(binop.Long_unsigned_%)
+      ),
       jswkn.BoxedFloatClass.withSuffix("$") -> Map(
         m("floatToIntBits", List(F), I) -> ArgUnaryOp(unop.Float_toBits),
         m("intBitsToFloat", List(I), F) -> ArgUnaryOp(unop.Float_fromBits)
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala
index c7f66671fd..facd69b122 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala
@@ -576,6 +576,11 @@ object Printers {
             case Double_<= => "<=[double]"
             case Double_>  => ">[double]"
             case Double_>= => ">=[double]"
+
+            case Int_unsigned_/  => "unsigned_/[int]"
+            case Int_unsigned_%  => "unsigned_%[int]"
+            case Long_unsigned_/ => "unsigned_/[long]"
+            case Long_unsigned_% => "unsigned_%[long]"
           })
           print(' ')
           print(rhs)
diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala b/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
index f463279933..d0cc772980 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Trees.scala
@@ -679,6 +679,12 @@ object Trees {
     final val Class_cast = 61
     final val Class_newArray = 62
 
+    // New in 1.20
+    final val Int_unsigned_/ = 63
+    final val Int_unsigned_% = 64
+    final val Long_unsigned_/ = 65
+    final val Long_unsigned_% = 66
+
     def isClassOp(op: Code): Boolean =
       op >= Class_isInstance && op <= Class_newArray
 
@@ -693,10 +699,12 @@ object Trees {
       case String_+ =>
         StringType
       case Int_+ | Int_- | Int_* | Int_/ | Int_% |
-          Int_| | Int_& | Int_^ | Int_<< | Int_>>> | Int_>> =>
+          Int_| | Int_& | Int_^ | Int_<< | Int_>>> | Int_>> |
+          Int_unsigned_/ | Int_unsigned_% =>
         IntType
       case Long_+ | Long_- | Long_* | Long_/ | Long_% |
-          Long_| | Long_& | Long_^ | Long_<< | Long_>>> | Long_>> =>
+          Long_| | Long_& | Long_^ | Long_<< | Long_>>> | Long_>> |
+          Long_unsigned_/ | Long_unsigned_% =>
         LongType
       case Float_+ | Float_- | Float_* | Float_/ | Float_% =>
         FloatType
diff --git a/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala b/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala
index 6ce589756e..d570445fc8 100644
--- a/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala
+++ b/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala
@@ -671,6 +671,15 @@ class PrintersTest {
         BinaryOp(Class_isAssignableFrom, classVarRef, ref("y", ClassType(ClassClass, nullable = false))))
     assertPrintEquals("cast(x, y)", BinaryOp(Class_cast, classVarRef, ref("y", AnyType)))
     assertPrintEquals("newArray(x, y)", BinaryOp(Class_newArray, classVarRef, ref("y", IntType)))
+
+    assertPrintEquals("(x unsigned_/[int] y)",
+        BinaryOp(Int_unsigned_/, ref("x", IntType), ref("y", IntType)))
+    assertPrintEquals("(x unsigned_%[int] y)",
+        BinaryOp(Int_unsigned_%, ref("x", IntType), ref("y", IntType)))
+    assertPrintEquals("(x unsigned_/[long] y)",
+        BinaryOp(Long_unsigned_/, ref("x", LongType), ref("y", LongType)))
+    assertPrintEquals("(x unsigned_%[long] y)",
+        BinaryOp(Long_unsigned_%, ref("x", LongType), ref("y", LongType)))
   }
 
   @Test def printNewArray(): Unit = {
diff --git a/javalib/src/main/scala/java/lang/Integer.scala b/javalib/src/main/scala/java/lang/Integer.scala
index a4c2694365..0bf5d3561f 100644
--- a/javalib/src/main/scala/java/lang/Integer.scala
+++ b/javalib/src/main/scala/java/lang/Integer.scala
@@ -221,15 +221,11 @@ object Integer {
     (((t2 + (t2 >> 4)) & 0xF0F0F0F) * 0x1010101) >> 24
   }
 
-  // Wasm intrinsic
   @inline def divideUnsigned(dividend: Int, divisor: Int): Int =
-    if (divisor == 0) 0 / 0
-    else asInt(asUint(dividend) / asUint(divisor))
+    throw new Error("stub") // body replaced by the compiler back-end
 
-  // Wasm intrinsic
   @inline def remainderUnsigned(dividend: Int, divisor: Int): Int =
-    if (divisor == 0) 0 % 0
-    else asInt(asUint(dividend) % asUint(divisor))
+    throw new Error("stub") // body replaced by the compiler back-end
 
   @inline def highestOneBit(i: Int): Int = {
     /* The natural way of implementing this is:
diff --git a/javalib/src/main/scala/java/lang/Long.scala b/javalib/src/main/scala/java/lang/Long.scala
index 0413372acf..faa69bc6d9 100644
--- a/javalib/src/main/scala/java/lang/Long.scala
+++ b/javalib/src/main/scala/java/lang/Long.scala
@@ -348,47 +348,11 @@ object Long {
   @inline def compareUnsigned(x: scala.Long, y: scala.Long): scala.Int =
     compare(x ^ SignBit, y ^ SignBit)
 
-  // Intrinsic, except for JS when using bigint's for longs
-  def divideUnsigned(dividend: scala.Long, divisor: scala.Long): scala.Long =
-    divModUnsigned(dividend, divisor, isDivide = true)
-
-  // Intrinsic, except for JS when using bigint's for longs
-  def remainderUnsigned(dividend: scala.Long, divisor: scala.Long): scala.Long =
-    divModUnsigned(dividend, divisor, isDivide = false)
-
-  private def divModUnsigned(a: scala.Long, b: scala.Long,
-      isDivide: scala.Boolean): scala.Long = {
-    /* This is a much simplified (and slow) version of
-     * RuntimeLong.unsignedDivModHelper.
-     */
-
-    if (b == 0L)
-      throw new ArithmeticException("/ by zero")
-
-    var shift = numberOfLeadingZeros(b) - numberOfLeadingZeros(a)
-    var bShift = b << shift
-
-    var rem = a
-    var quot = 0L
-
-    /* Invariants:
-     *   bShift == b << shift == b * 2^shift
-     *   quot >= 0
-     *   0 <= rem < 2 * bShift
-     *   quot * b + rem == a
-     */
-    while (shift >= 0 && rem != 0) {
-      if ((rem ^ SignBit) >= (bShift ^ SignBit)) {
-        rem -= bShift
-        quot |= (1L << shift)
-      }
-      shift -= 1
-      bShift >>>= 1
-    }
+  @inline def divideUnsigned(dividend: scala.Long, divisor: scala.Long): scala.Long =
+    throw new Error("stub") // body replaced by the compiler back-end
 
-    if (isDivide) quot
-    else rem
-  }
+  @inline def remainderUnsigned(dividend: scala.Long, divisor: scala.Long): scala.Long =
+    throw new Error("stub") // body replaced by the compiler back-end
 
   @inline
   def highestOneBit(i: scala.Long): scala.Long = {
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala
index 00b40402fe..90fe76ca07 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/analyzer/Infos.scala
@@ -789,12 +789,12 @@ object Infos {
               import BinaryOp._
 
               op match {
-                case Int_/ | Int_% =>
+                case Int_/ | Int_% | Int_unsigned_/ | Int_unsigned_% =>
                   rhs match {
                     case IntLiteral(r) if r != 0 =>
                     case _                       => builder.addUsedIntLongDivModByMaybeZero()
                   }
-                case Long_/ | Long_% =>
+                case Long_/ | Long_% | Long_unsigned_/ | Long_unsigned_% =>
                   rhs match {
                     case LongLiteral(r) if r != 0L =>
                     case _                         => builder.addUsedIntLongDivModByMaybeZero()
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
index 6b1eb65103..b2b64aee66 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
@@ -919,17 +919,11 @@ private[emitter] object CoreJSLib {
       }
 
       condDefs(shouldDefineIntLongDivModFunctions)(
-        defineFunction2(VarField.intDiv) { (x, y) =>
+        defineFunction1(VarField.checkIntDivisor) { y =>
           If(y === 0, throwDivByZero, {
-            Return((x / y) | 0)
+            Return(y)
           })
-        } :::
-        defineFunction2(VarField.intMod) { (x, y) =>
-          If(y === 0, throwDivByZero, {
-            Return((x % y) | 0)
-          })
-        } :::
-        Nil
+        }
       ) :::
       defineFunction1(VarField.doubleToInt) { x =>
         Return(If(x > 2147483647, 2147483647, If(x < -2147483648, -2147483648, x | 0)))
@@ -953,17 +947,11 @@ private[emitter] object CoreJSLib {
         }
       ) :::
       condDefs(allowBigIntsForLongs && shouldDefineIntLongDivModFunctions)(
-        defineFunction2(VarField.longDiv) { (x, y) =>
+        defineFunction1(VarField.checkLongDivisor) { y =>
           If(y === bigInt(0), throwDivByZero, {
-            Return(wrapBigInt64(x / y))
+            Return(y)
           })
-        } :::
-        defineFunction2(VarField.longMod) { (x, y) =>
-          If(y === bigInt(0), throwDivByZero, {
-            Return(wrapBigInt64(x % y))
-          })
-        } :::
-        Nil
+        }
       ) :::
       condDefs(allowBigIntsForLongs)(
         defineFunction1(VarField.doubleToLong)(x => Return {
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
index 2fbd0eecd0..fc766eb527 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
@@ -1287,12 +1287,14 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
             allowSideEffects && test(lhs)
 
         // Division and modulo, preserve pureness unless they can divide by 0
-        case BinaryOp(BinaryOp.Int_/ | BinaryOp.Int_%, lhs, rhs) if !allowSideEffects =>
+        case BinaryOp(BinaryOp.Int_/ | BinaryOp.Int_% | BinaryOp.Int_unsigned_/ | BinaryOp.Int_unsigned_%, lhs, rhs)
+            if !allowSideEffects =>
           rhs match {
             case IntLiteral(r) if r != 0 => test(lhs)
             case _                       => false
           }
-        case BinaryOp(BinaryOp.Long_/ | BinaryOp.Long_%, lhs, rhs) if !allowSideEffects =>
+        case BinaryOp(BinaryOp.Long_/ | BinaryOp.Long_% | BinaryOp.Long_unsigned_/ | BinaryOp.Long_unsigned_%, lhs, rhs)
+            if !allowSideEffects =>
           rhs match {
             case LongLiteral(r) if r != 0L => test(lhs)
             case _                         => false
@@ -2206,6 +2208,9 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
       def or0(tree: js.Tree): js.Tree =
         js.BinaryOp(JSBinaryOp.|, tree, js.IntLiteral(0))
 
+      def shr0(tree: js.Tree): js.Tree =
+        js.BinaryOp(JSBinaryOp.>>>, tree, js.IntLiteral(0))
+
       def bigIntShiftRhs(tree: js.Tree): js.Tree = {
         tree match {
           case js.IntLiteral(v) =>
@@ -2631,20 +2636,17 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
               }
             case Int_* =>
               genCallPolyfillableBuiltin(ImulBuiltin, newLhs, newRhs)
-            case Int_/ =>
-              rhs match {
-                case IntLiteral(r) if r != 0 =>
-                  or0(js.BinaryOp(JSBinaryOp./, newLhs, newRhs))
-                case _ =>
-                  genCallHelper(VarField.intDiv, newLhs, newRhs)
-              }
-            case Int_% =>
-              rhs match {
-                case IntLiteral(r) if r != 0 =>
-                  or0(js.BinaryOp(JSBinaryOp.%, newLhs, newRhs))
-                case _ =>
-                  genCallHelper(VarField.intMod, newLhs, newRhs)
+            case Int_/ | Int_% | Int_unsigned_/ | Int_unsigned_% =>
+              val newRhs1 = rhs match {
+                case IntLiteral(r) if r != 0 => newRhs
+                case _                       => genCallHelper(VarField.checkIntDivisor, newRhs)
               }
+              or0((op: @switch) match {
+                case Int_/          => js.BinaryOp(JSBinaryOp./, newLhs, newRhs1)
+                case Int_%          => js.BinaryOp(JSBinaryOp.%, newLhs, newRhs1)
+                case Int_unsigned_/ => js.BinaryOp(JSBinaryOp./, shr0(newLhs), shr0(newRhs1))
+                case Int_unsigned_% => js.BinaryOp(JSBinaryOp.%, shr0(newLhs), shr0(newRhs1))
+              })
 
             case Int_|   => js.BinaryOp(JSBinaryOp.|, newLhs, newRhs)
             case Int_&   => js.BinaryOp(JSBinaryOp.&, newLhs, newRhs)
@@ -2685,27 +2687,27 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
                 wrapBigInt64(js.BinaryOp(JSBinaryOp.*, newLhs, newRhs))
               else
                 genApply(newLhs, LongImpl.*, newRhs)
-            case Long_/ =>
+            case Long_/ | Long_% | Long_unsigned_/ | Long_unsigned_% =>
               if (useBigIntForLongs) {
-                rhs match {
-                  case LongLiteral(r) if r != 0L =>
-                    wrapBigInt64(js.BinaryOp(JSBinaryOp./, newLhs, newRhs))
-                  case _ =>
-                    genCallHelper(VarField.longDiv, newLhs, newRhs)
+                val newRhs1 = rhs match {
+                  case LongLiteral(r) if r != 0L => newRhs
+                  case _                         => genCallHelper(VarField.checkLongDivisor, newRhs)
                 }
+                wrapBigInt64((op: @switch) match {
+                  case Long_/          => js.BinaryOp(JSBinaryOp./, newLhs, newRhs1)
+                  case Long_%          => js.BinaryOp(JSBinaryOp.%, newLhs, newRhs1)
+                  case Long_unsigned_/ => js.BinaryOp(JSBinaryOp./, wrapBigIntU64(newLhs), wrapBigIntU64(newRhs1))
+                  case Long_unsigned_% => js.BinaryOp(JSBinaryOp.%, wrapBigIntU64(newLhs), wrapBigIntU64(newRhs1))
+                })
               } else {
-                genApply(newLhs, LongImpl./, newRhs)
-              }
-            case Long_% =>
-              if (useBigIntForLongs) {
-                rhs match {
-                  case LongLiteral(r) if r != 0L =>
-                    wrapBigInt64(js.BinaryOp(JSBinaryOp.%, newLhs, newRhs))
-                  case _ =>
-                    genCallHelper(VarField.longMod, newLhs, newRhs)
+                // The zero divisor check is performed by the implementation methods
+                val implMethodName = (op: @switch) match {
+                  case Long_/          => LongImpl./
+                  case Long_%          => LongImpl.%
+                  case Long_unsigned_/ => LongImpl.divideUnsigned
+                  case Long_unsigned_% => LongImpl.remainderUnsigned
                 }
-              } else {
-                genApply(newLhs, LongImpl.%, newRhs)
+                genApply(newLhs, implMethodName, newRhs)
               }
 
             case Long_| =>
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/LongImpl.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/LongImpl.scala
index 2c93e5e358..1e1c6b8305 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/LongImpl.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/LongImpl.scala
@@ -47,6 +47,9 @@ private[linker] object LongImpl {
   final val / = binaryOp("$div")
   final val % = binaryOp("$percent")
 
+  final val divideUnsigned = binaryOp("divideUnsigned")
+  final val remainderUnsigned = binaryOp("remainderUnsigned")
+
   final val | = binaryOp("$bar")
   final val & = binaryOp("$amp")
   final val ^ = binaryOp("$up")
@@ -81,8 +84,8 @@ private[linker] object LongImpl {
   final val compareToO = MethodName("compareTo", List(ClassRef(ObjectClass)), IntRef)
 
   private val OperatorMethods = Set(
-      UNARY_-, UNARY_~, this.+, this.-, *, /, %, |, &, ^, <<, >>>, >>,
-      ===, !==, <, <=, >, >=, toInt, toFloat, toDouble, bitsToDouble)
+      UNARY_-, UNARY_~, this.+, this.-, *, /, %, divideUnsigned, remainderUnsigned,
+      |, &, ^, <<, >>>, >>, ===, !==, <, <=, >, >=, toInt, toFloat, toDouble, bitsToDouble)
 
   private val BoxedLongMethods = Set(
       byteValue, shortValue, intValue, longValue, floatValue, doubleValue,
@@ -92,12 +95,10 @@ private[linker] object LongImpl {
 
   // Methods used for intrinsics
 
-  final val compareToRTLong   = MethodName("compareTo", List(RTLongRef), IntRef)
-  final val divideUnsigned    = binaryOp("divideUnsigned")
-  final val remainderUnsigned = binaryOp("remainderUnsigned")
+  final val compareToRTLong = MethodName("compareTo", List(RTLongRef), IntRef)
 
   val AllIntrinsicMethods = Set(
-      compareToRTLong, divideUnsigned, remainderUnsigned)
+      compareToRTLong)
 
   // Constructors
 
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/VarField.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/VarField.scala
index ba3355e54a..98b3171e05 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/VarField.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/VarField.scala
@@ -259,16 +259,12 @@ private[emitter] object VarField {
 
   // Arithmetic Call Helpers
 
-  final val intDiv = mk("$intDiv")
+  final val checkIntDivisor = mk("$checkIntDivisor")
 
-  final val intMod = mk("$intMod")
+  final val checkLongDivisor = mk("$checkLongDivisor")
 
   final val longToFloat = mk("$longToFloat")
 
-  final val longDiv = mk("$longDiv")
-
-  final val longMod = mk("$longMod")
-
   final val doubleToLong = mk("$doubleToLong")
 
   final val doubleToInt = mk("$doubleToInt")
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
index 21de9d63ed..7fbdeef29e 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/FunctionEmitter.scala
@@ -1734,33 +1734,34 @@ private class FunctionEmitter private (
       case String_+ =>
         genStringConcat(tree)
 
-      case Int_/ =>
-        rhs match {
-          case IntLiteral(rhsValue) =>
-            genDivModByConstant(tree, isDiv = true, rhsValue, wa.I32Const(_), wa.I32Sub, wa.I32DivS)
-          case _ =>
-            genDivMod(tree, isDiv = true, wa.I32Const(_), wa.I32Eqz, wa.I32Eq, wa.I32Sub, wa.I32DivS)
+      case Int_/ | Int_% | Int_unsigned_/ | Int_unsigned_% =>
+        val isSignedDiv = op == Int_/
+        val mainOp = (op: @switch) match {
+          case Int_/          => wa.I32DivS
+          case Int_%          => wa.I32RemS
+          case Int_unsigned_/ => wa.I32DivU
+          case Int_unsigned_% => wa.I32RemU
         }
-      case Int_% =>
         rhs match {
           case IntLiteral(rhsValue) =>
-            genDivModByConstant(tree, isDiv = false, rhsValue, wa.I32Const(_), wa.I32Sub, wa.I32RemS)
+            genDivModByConstant(tree, isSignedDiv, rhsValue, wa.I32Const(_), wa.I32Sub, mainOp)
           case _ =>
-            genDivMod(tree, isDiv = false, wa.I32Const(_), wa.I32Eqz, wa.I32Eq, wa.I32Sub, wa.I32RemS)
+            genDivMod(tree, isSignedDiv, wa.I32Const(_), wa.I32Eqz, wa.I32Eq, wa.I32Sub, mainOp)
         }
-      case Long_/ =>
-        rhs match {
-          case LongLiteral(rhsValue) =>
-            genDivModByConstant(tree, isDiv = true, rhsValue, wa.I64Const(_), wa.I64Sub, wa.I64DivS)
-          case _ =>
-            genDivMod(tree, isDiv = true, wa.I64Const(_), wa.I64Eqz, wa.I64Eq, wa.I64Sub, wa.I64DivS)
+
+      case Long_/ | Long_% | Long_unsigned_/ | Long_unsigned_% =>
+        val isSignedDiv = op == Long_/
+        val mainOp = (op: @switch) match {
+          case Long_/          => wa.I64DivS
+          case Long_%          => wa.I64RemS
+          case Long_unsigned_/ => wa.I64DivU
+          case Long_unsigned_% => wa.I64RemU
         }
-      case Long_% =>
         rhs match {
           case LongLiteral(rhsValue) =>
-            genDivModByConstant(tree, isDiv = false, rhsValue, wa.I64Const(_), wa.I64Sub, wa.I64RemS)
+            genDivModByConstant(tree, isSignedDiv, rhsValue, wa.I64Const(_), wa.I64Sub, mainOp)
           case _ =>
-            genDivMod(tree, isDiv = false, wa.I64Const(_), wa.I64Eqz, wa.I64Eq, wa.I64Sub, wa.I64RemS)
+            genDivMod(tree, isSignedDiv, wa.I64Const(_), wa.I64Eqz, wa.I64Eq, wa.I64Sub, mainOp)
         }
 
       case Long_<< =>
@@ -2136,7 +2137,7 @@ private class FunctionEmitter private (
     }
   }
 
-  private def genDivModByConstant[T](tree: BinaryOp, isDiv: Boolean,
+  private def genDivModByConstant[T](tree: BinaryOp, isSignedDiv: Boolean,
       rhsValue: T, const: T => wa.Instr, sub: wa.Instr, mainOp: wa.Instr)(
       implicit num: Numeric[T]): Type = {
     /* When we statically know the value of the rhs, we can avoid the
@@ -2146,8 +2147,7 @@ private class FunctionEmitter private (
 
     import BinaryOp._
 
-    val BinaryOp(op, lhs, rhs) = tree
-    assert(op == Int_/ || op == Int_% || op == Long_/ || op == Long_%)
+    val BinaryOp(_, lhs, rhs) = tree
 
     val tpe = tree.tpe
 
@@ -2156,7 +2156,7 @@ private class FunctionEmitter private (
       markPosition(tree)
       genThrowArithmeticException()(tree.pos)
       NothingType
-    } else if (isDiv && rhsValue == num.fromInt(-1)) {
+    } else if (isSignedDiv && rhsValue == num.fromInt(-1)) {
       /* MinValue / -1 overflows; it traps in Wasm but we need to wrap.
        * We rewrite as `0 - lhs` so that we do not need any test.
        */
@@ -2176,7 +2176,7 @@ private class FunctionEmitter private (
     }
   }
 
-  private def genDivMod[T](tree: BinaryOp, isDiv: Boolean, const: T => wa.Instr,
+  private def genDivMod[T](tree: BinaryOp, isSignedDiv: Boolean, const: T => wa.Instr,
       eqz: wa.Instr, eqInstr: wa.Instr, sub: wa.Instr, mainOp: wa.Instr)(
       implicit num: Numeric[T]): Type = {
     /* Here we perform the same steps as in the static case, but using
@@ -2185,8 +2185,7 @@ private class FunctionEmitter private (
 
     import BinaryOp._
 
-    val BinaryOp(op, lhs, rhs) = tree
-    assert(op == Int_/ || op == Int_% || op == Long_/ || op == Long_%)
+    val BinaryOp(_, lhs, rhs) = tree
 
     val tpe = tree.tpe.asInstanceOf[PrimType]
     val wasmType = transformPrimType(tpe)
@@ -2204,7 +2203,7 @@ private class FunctionEmitter private (
     fb.ifThen() {
       genThrowArithmeticException()(tree.pos)
     }
-    if (isDiv) {
+    if (isSignedDiv) {
       // Handle the MinValue / -1 corner case
       fb += wa.LocalGet(rhsLocal)
       fb += const(num.fromInt(-1))
@@ -2221,7 +2220,7 @@ private class FunctionEmitter private (
         fb += mainOp
       }
     } else {
-      // lhs % rhs
+      // lhs mainOp rhs
       fb += wa.LocalGet(lhsLocal)
       fb += wa.LocalGet(rhsLocal)
       fb += mainOp
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/WasmTransients.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/WasmTransients.scala
index 3d3f12fdb8..2ec686a081 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/WasmTransients.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/wasmemitter/WasmTransients.scala
@@ -137,13 +137,9 @@ object WasmTransients {
     def wasmInstr: wa.SimpleInstr = (op: @switch) match {
       case I32GtU => wa.I32GtU
 
-      case I32DivU => wa.I32DivU
-      case I32RemU => wa.I32RemU
       case I32Rotl => wa.I32Rotl
       case I32Rotr => wa.I32Rotr
 
-      case I64DivU => wa.I64DivU
-      case I64RemU => wa.I64RemU
       case I64Rotl => wa.I64Rotl
       case I64Rotr => wa.I64Rotr
 
@@ -167,13 +163,9 @@ object WasmTransients {
 
     final val I32GtU = 1
 
-    final val I32DivU = 2
-    final val I32RemU = 3
     final val I32Rotl = 4
     final val I32Rotr = 5
 
-    final val I64DivU = 6
-    final val I64RemU = 7
     final val I64Rotl = 8
     final val I64Rotr = 9
 
@@ -187,10 +179,10 @@ object WasmTransients {
       case I32GtU =>
         BooleanType
 
-      case I32DivU | I32RemU | I32Rotl | I32Rotr =>
+      case I32Rotl | I32Rotr =>
         IntType
 
-      case I64DivU | I64RemU | I64Rotl | I64Rotr =>
+      case I64Rotl | I64Rotr =>
         LongType
 
       case F32Min | F32Max =>
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala b/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
index b744dd380a..c4e0ff7d68 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/checker/IRChecker.scala
@@ -571,11 +571,13 @@ private final class IRChecker(linkTimeProperties: LinkTimeProperties,
             BooleanType
           case Int_+ | Int_- | Int_* | Int_/ | Int_% |
               Int_| | Int_& | Int_^ | Int_<< | Int_>>> | Int_>> |
-              Int_== | Int_!= | Int_< | Int_<= | Int_> | Int_>= =>
+              Int_== | Int_!= | Int_< | Int_<= | Int_> | Int_>= |
+              Int_unsigned_/ | Int_unsigned_% =>
             IntType
           case Long_+ | Long_- | Long_* | Long_/ | Long_% |
               Long_| | Long_& | Long_^ | Long_<< | Long_>>> | Long_>> |
-              Long_== | Long_!= | Long_< | Long_<= | Long_> | Long_>= =>
+              Long_== | Long_!= | Long_< | Long_<= | Long_> | Long_>= |
+              Long_unsigned_/ | Long_unsigned_% =>
             LongType
           case Float_+ | Float_- | Float_* | Float_/ | Float_% =>
             FloatType
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
index 422831e52e..2c0fa4ec70 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
@@ -1505,14 +1505,14 @@ private[optimizer] abstract class OptimizerCore(
         BinaryOp(op, finishTransformExpr(lhs), finishTransformExpr(rhs))
 
       (op: @switch) match {
-        case Int_/ | Int_% =>
+        case Int_/ | Int_% | Int_unsigned_/ | Int_unsigned_% =>
           rhs match {
             case PreTransLit(IntLiteral(r)) if r != 0 =>
               finishNoSideEffects
             case _ =>
               Block(newLhs, BinaryOp(op, IntLiteral(0), finishTransformExpr(rhs)))
           }
-        case Long_/ | Long_% =>
+        case Long_/ | Long_% | Long_unsigned_/ | Long_unsigned_% =>
           rhs match {
             case PreTransLit(LongLiteral(r)) if r != 0L =>
               finishNoSideEffects
@@ -1838,8 +1838,9 @@ private[optimizer] abstract class OptimizerCore(
             case NotFoundPureSoFar =>
               rec(rhs).mapOrKeepGoingIf(BinaryOp(op, lhs, _)) {
                 (op: @switch) match {
-                  case Int_/ | Int_% | Long_/ | Long_% | String_+ | String_charAt |
-                      Class_cast | Class_newArray =>
+                  case Int_/ | Int_% | Int_unsigned_/ | Int_unsigned_% |
+                      Long_/ | Long_% | Long_unsigned_/ | Long_unsigned_% |
+                      String_+ | String_charAt | Class_cast | Class_newArray =>
                     false
                   case _ =>
                     true
@@ -2734,28 +2735,6 @@ private[optimizer] abstract class OptimizerCore(
     def wasmBinaryOp(op: WasmBinaryOp.Code, lhs: PreTransform, rhs: PreTransform): Tree =
       Transient(WasmBinaryOp(op, finishTransformExpr(lhs), finishTransformExpr(rhs)))
 
-    def genericWasmDivModUnsigned(wasmOp: WasmBinaryOp.Code, signedOp: BinaryOp.Code,
-        equalsOp: BinaryOp.Code, zeroLiteral: Literal): TailRec[Tree] = {
-      targs(1) match {
-        case PreTransLit(IntLiteral(r)) if r != 0 =>
-          contTree(wasmBinaryOp(wasmOp, targs(0), targs(1)))
-        case PreTransLit(LongLiteral(r)) if r != 0L =>
-          contTree(wasmBinaryOp(wasmOp, targs(0), targs(1)))
-        case _ =>
-          withNewTempLocalDefs(targs) { (localDefs, cont1) =>
-            val List(lhsLocalDef, rhsLocalDef) = localDefs
-            cont1 {
-              If(BinaryOp(equalsOp, rhsLocalDef.newReplacement, zeroLiteral), {
-                // trigger the appropriate ArithmeticException
-                BinaryOp(signedOp, zeroLiteral, zeroLiteral)
-              }, {
-                wasmBinaryOp(wasmOp, lhsLocalDef.toPreTransform, rhsLocalDef.toPreTransform)
-              })(zeroLiteral.tpe).toPreTransform
-            }
-          } (cont)
-      }
-    }
-
     (intrinsicCode: @switch) match {
       // Not an intrisic
 
@@ -2897,13 +2876,6 @@ private[optimizer] abstract class OptimizerCore(
             contTree(wasmBinaryOp(WasmBinaryOp.I32Rotr, tvalue, tdistance))
         }
 
-      case IntegerDivideUnsigned =>
-        genericWasmDivModUnsigned(WasmBinaryOp.I32DivU, BinaryOp.Int_/,
-            BinaryOp.Int_==, IntLiteral(0))
-      case IntegerRemainderUnsigned =>
-        genericWasmDivModUnsigned(WasmBinaryOp.I32RemU, BinaryOp.Int_%,
-            BinaryOp.Int_==, IntLiteral(0))
-
       // java.lang.Long
 
       case LongNLZ =>
@@ -2961,29 +2933,6 @@ private[optimizer] abstract class OptimizerCore(
             isStat, usePreTransform)(
             cont)
 
-      case LongDivideUnsigned =>
-        if (isWasm) {
-          genericWasmDivModUnsigned(WasmBinaryOp.I64DivU, BinaryOp.Long_/,
-              BinaryOp.Long_==, LongLiteral(0L))
-        } else {
-          pretransformApply(ApplyFlags.empty, targs.head,
-              MethodIdent(LongImpl.divideUnsigned), targs.tail,
-              ClassType(LongImpl.RuntimeLongClass, nullable = true), isStat,
-              usePreTransform)(
-              cont)
-        }
-      case LongRemainderUnsigned =>
-        if (isWasm) {
-          genericWasmDivModUnsigned(WasmBinaryOp.I64RemU, BinaryOp.Long_%,
-              BinaryOp.Long_==, LongLiteral(0L))
-        } else {
-          pretransformApply(ApplyFlags.empty, targs.head,
-              MethodIdent(LongImpl.remainderUnsigned), targs.tail,
-              ClassType(LongImpl.RuntimeLongClass, nullable = true), isStat,
-              usePreTransform)(
-              cont)
-        }
-
       // java.lang.Character
 
       case CharacterCodePointToString =>
@@ -3647,6 +3596,9 @@ private[optimizer] abstract class OptimizerCore(
           case Long_>  => expandBinaryOp(LongImpl.>, lhs, rhs)
           case Long_>= => expandBinaryOp(LongImpl.>=, lhs, rhs)
 
+          case Long_unsigned_/ => expandBinaryOp(LongImpl.divideUnsigned, lhs, rhs)
+          case Long_unsigned_% => expandBinaryOp(LongImpl.remainderUnsigned, lhs, rhs)
+
           case _ =>
             cont(pretrans)
         }
@@ -4228,12 +4180,8 @@ private[optimizer] abstract class OptimizerCore(
               case 1  => rhs
 
               // Exact power of 2
-              case _ if (x & (x - 1)) == 0 =>
-                /* Note that this would match 0, but 0 is handled above.
-                 * It will also match Int.MinValue, but that is not a problem
-                 * as the optimization also works (if you need convincing,
-                 * simply interpret the multiplication as unsigned).
-                 */
+              case _ if isUnsignedPowerOf2(x) =>
+                // Interpret the multiplication as unsigned and turn it into a shift.
                 foldBinaryOp(Int_<<, rhs,
                     PreTransLit(IntLiteral(Integer.numberOfTrailingZeros(x))))
 
@@ -4258,6 +4206,33 @@ private[optimizer] abstract class OptimizerCore(
           case _ => default
         }
 
+      case Int_unsigned_/ =>
+        (lhs, rhs) match {
+          case (_, PreTransLit(IntLiteral(0))) =>
+            default
+          case (PreTransLit(IntLiteral(l)), PreTransLit(IntLiteral(r))) =>
+            intLit(java.lang.Integer.divideUnsigned(l, r))
+
+          case (_, PreTransLit(IntLiteral(r))) if isUnsignedPowerOf2(r) =>
+            foldBinaryOp(BinaryOp.Int_>>>, lhs,
+                PreTransLit(IntLiteral(java.lang.Integer.numberOfTrailingZeros(r))))
+
+          case _ => default
+        }
+
+      case Int_unsigned_% =>
+        (lhs, rhs) match {
+          case (_, PreTransLit(IntLiteral(0))) =>
+            default
+          case (PreTransLit(IntLiteral(l)), PreTransLit(IntLiteral(r))) =>
+            intLit(java.lang.Integer.remainderUnsigned(l, r))
+
+          case (_, PreTransLit(IntLiteral(r))) if isUnsignedPowerOf2(r) =>
+            foldBinaryOp(BinaryOp.Int_&, PreTransLit(IntLiteral(r - 1)), lhs)
+
+          case _ => default
+        }
+
       case Int_% =>
         (lhs, rhs) match {
           case (_, PreTransLit(IntLiteral(0))) =>
@@ -4536,12 +4511,8 @@ private[optimizer] abstract class OptimizerCore(
               case 1L  => rhs
 
               // Exact power of 2
-              case _ if (x & (x - 1L)) == 0L =>
-                /* Note that this would match 0L, but 0L is handled above.
-                 * It will also match Long.MinValue, but that is not a problem
-                 * as the optimization also works (if you need convincing,
-                 * simply interpret the multiplication as unsigned).
-                 */
+              case _ if isUnsignedPowerOf2(x) =>
+                // Interpret the multiplication as unsigned and turn it into a shift.
                 foldBinaryOp(Long_<<, rhs, PreTransLit(
                     IntLiteral(java.lang.Long.numberOfTrailingZeros(x))))
 
@@ -4558,10 +4529,10 @@ private[optimizer] abstract class OptimizerCore(
           case (PreTransLit(LongLiteral(l)), PreTransLit(LongLiteral(r))) =>
             longLit(l / r)
 
-          case (_, PreTransLit(LongLiteral(1))) =>
+          case (_, PreTransLit(LongLiteral(1L))) =>
             lhs
-          case (_, PreTransLit(LongLiteral(-1))) =>
-            foldBinaryOp(Long_-, PreTransLit(LongLiteral(0)), lhs)
+          case (_, PreTransLit(LongLiteral(-1L))) =>
+            foldBinaryOp(Long_-, PreTransLit(LongLiteral(0L)), lhs)
 
           case (LongFromInt(x), LongFromInt(PreTransLit(y: IntLiteral)))
               if y.value != -1 =>
@@ -4586,6 +4557,33 @@ private[optimizer] abstract class OptimizerCore(
           case _ => default
         }
 
+      case Long_unsigned_/ =>
+        (lhs, rhs) match {
+          case (_, PreTransLit(LongLiteral(0L))) =>
+            default
+          case (PreTransLit(LongLiteral(l)), PreTransLit(LongLiteral(r))) =>
+            longLit(java.lang.Long.divideUnsigned(l, r))
+
+          case (_, PreTransLit(LongLiteral(r))) if isUnsignedPowerOf2(r) =>
+            foldBinaryOp(BinaryOp.Long_>>>, lhs,
+                PreTransLit(IntLiteral(java.lang.Long.numberOfTrailingZeros(r))))
+
+          case _ => default
+        }
+
+      case Long_unsigned_% =>
+        (lhs, rhs) match {
+          case (_, PreTransLit(LongLiteral(0L))) =>
+            default
+          case (PreTransLit(LongLiteral(l)), PreTransLit(LongLiteral(r))) =>
+            longLit(java.lang.Long.remainderUnsigned(l, r))
+
+          case (_, PreTransLit(LongLiteral(r))) if isUnsignedPowerOf2(r) =>
+            foldBinaryOp(BinaryOp.Long_&, PreTransLit(LongLiteral(r - 1L)), lhs)
+
+          case _ => default
+        }
+
       case Long_| =>
         (lhs, rhs) match {
           case (PreTransLit(LongLiteral(l)), PreTransLit(LongLiteral(r))) =>
@@ -5677,6 +5675,12 @@ private[optimizer] object OptimizerCore {
   private val ClassTagApplyMethodName =
     MethodName("apply", List(ClassRef(ClassClass)), ClassRef(ClassName("scala.reflect.ClassTag")))
 
+  def isUnsignedPowerOf2(x: Int): Boolean =
+    (x & (x - 1)) == 0 && x != 0
+
+  def isUnsignedPowerOf2(x: Long): Boolean =
+    (x & (x - 1L)) == 0L && x != 0L
+
   final class InlineableClassStructure(val className: ClassName, private val allFields: List[FieldDef]) {
     private[OptimizerCore] val refinedType: RefinedType =
       RefinedType(ClassType(className, nullable = false), isExact = true)
@@ -6489,20 +6493,16 @@ private[optimizer] object OptimizerCore {
     final val IntegerBitCount = IntegerNTZ + 1
     final val IntegerRotateLeft = IntegerBitCount + 1
     final val IntegerRotateRight = IntegerRotateLeft + 1
-    final val IntegerDivideUnsigned = IntegerRotateRight + 1
-    final val IntegerRemainderUnsigned = IntegerDivideUnsigned + 1
 
-    final val LongNLZ = IntegerRemainderUnsigned + 1
+    final val LongNLZ = IntegerRotateRight + 1
     final val LongNTZ = LongNLZ + 1
     final val LongBitCount = LongNTZ + 1
     final val LongRotateLeft = LongBitCount + 1
     final val LongRotateRight = LongRotateLeft + 1
     final val LongToString = LongRotateRight + 1
     final val LongCompare = LongToString + 1
-    final val LongDivideUnsigned = LongCompare + 1
-    final val LongRemainderUnsigned = LongDivideUnsigned + 1
 
-    final val CharacterCodePointToString = LongRemainderUnsigned + 1
+    final val CharacterCodePointToString = LongCompare + 1
 
     final val StringCodePointAt = CharacterCodePointToString + 1
     final val StringSubstringStart = StringCodePointAt + 1
@@ -6610,9 +6610,7 @@ private[optimizer] object OptimizerCore {
     private val runtimeLongIntrinsics: List[(ClassName, List[(MethodName, Int)])] = List(
         ClassName("java.lang.Long$") -> List(
             m("toString", List(J), ClassRef(BoxedStringClass)) -> LongToString,
-            m("compare", List(J, J), I) -> LongCompare,
-            m("divideUnsigned", List(J, J), J) -> LongDivideUnsigned,
-            m("remainderUnsigned", List(J, J), J) -> LongRemainderUnsigned
+            m("compare", List(J, J), I) -> LongCompare
         )
     )
 
@@ -6622,18 +6620,14 @@ private[optimizer] object OptimizerCore {
             m("numberOfTrailingZeros", List(I), I) -> IntegerNTZ,
             m("bitCount", List(I), I) -> IntegerBitCount,
             m("rotateLeft", List(I, I), I) -> IntegerRotateLeft,
-            m("rotateRight", List(I, I), I) -> IntegerRotateRight,
-            m("divideUnsigned", List(I, I), I) -> IntegerDivideUnsigned,
-            m("remainderUnsigned", List(I, I), I) -> IntegerRemainderUnsigned
+            m("rotateRight", List(I, I), I) -> IntegerRotateRight
         ),
         ClassName("java.lang.Long$") -> List(
             m("numberOfLeadingZeros", List(J), I) -> LongNLZ,
             m("numberOfTrailingZeros", List(J), I) -> LongNTZ,
             m("bitCount", List(J), I) -> LongBitCount,
             m("rotateLeft", List(J, I), J) -> LongRotateLeft,
-            m("rotateRight", List(J, I), J) -> LongRotateRight,
-            m("divideUnsigned", List(J, J), J) -> LongDivideUnsigned,
-            m("remainderUnsigned", List(J, J), J) -> LongRemainderUnsigned
+            m("rotateRight", List(J, I), J) -> LongRotateRight
         ),
         ClassName("java.lang.Character$") -> List(
             m("toString", List(I), StringClassRef) -> CharacterCodePointToString
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/LibrarySizeTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/LibrarySizeTest.scala
index 9fb1213758..4bbe92a6b0 100644
--- a/linker/shared/src/test/scala/org/scalajs/linker/LibrarySizeTest.scala
+++ b/linker/shared/src/test/scala/org/scalajs/linker/LibrarySizeTest.scala
@@ -70,8 +70,8 @@ class LibrarySizeTest {
     )
 
     testLinkedSizes(
-      expectedFastLinkSize = 146044,
-      expectedFullLinkSizeWithoutClosure = 85435,
+      expectedFastLinkSize = 147727,
+      expectedFullLinkSizeWithoutClosure = 86377,
       expectedFullLinkSizeWithClosure = 21197,
       classDefs,
       moduleInitializers = MainTestModuleInitializers
diff --git a/project/Build.scala b/project/Build.scala
index a383ebf1ac..7209200769 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -2053,7 +2053,7 @@ object Build {
           case `default212Version` =>
             if (!useMinifySizes) {
               Some(ExpectedSizes(
-                  fastLink = 624000 to 625000,
+                  fastLink = 626000 to 627000,
                   fullLink = 96000 to 97000,
                   fastLinkGz = 75000 to 79000,
                   fullLinkGz = 25000 to 26000,
@@ -2061,7 +2061,7 @@ object Build {
             } else {
               Some(ExpectedSizes(
                   fastLink = 425000 to 426000,
-                  fullLink = 282000 to 283000,
+                  fullLink = 283000 to 284000,
                   fastLinkGz = 61000 to 62000,
                   fullLinkGz = 43000 to 44000,
               ))
@@ -2070,14 +2070,14 @@ object Build {
           case `default213Version` =>
             if (!useMinifySizes) {
               Some(ExpectedSizes(
-                  fastLink = 441000 to 442000,
+                  fastLink = 443000 to 444000,
                   fullLink = 92000 to 93000,
                   fastLinkGz = 57000 to 58000,
                   fullLinkGz = 25000 to 26000,
               ))
             } else {
               Some(ExpectedSizes(
-                  fastLink = 300000 to 301000,
+                  fastLink = 301000 to 302000,
                   fullLink = 258000 to 259000,
                   fastLinkGz = 47000 to 48000,
                   fullLinkGz = 42000 to 43000,
diff --git a/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/lang/LongTest.scala b/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/lang/LongTest.scala
index 8566a378a2..f9cb9c3e26 100644
--- a/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/lang/LongTest.scala
+++ b/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/lang/LongTest.scala
@@ -27,6 +27,8 @@ class LongTest {
   final val MinRadix = Character.MIN_RADIX
   final val MaxRadix = Character.MAX_RADIX
 
+  @noinline def hideFromOptimizer(x: Long): Long = x
+
   @Test def reverseBytes(): Unit = {
     assertEquals(0x14ff01d49c68abf5L, JLong.reverseBytes(0xf5ab689cd401ff14L))
     assertEquals(0x780176af73b18fc7L, JLong.reverseBytes(0xc78fb173af760178L))
@@ -659,8 +661,12 @@ class LongTest {
   }
 
   @Test def divideUnsigned(): Unit = {
-    def test(dividend: Long, divisor: Long, result: Long): Unit =
-      assertEquals(result, JLong.divideUnsigned(dividend, divisor))
+    @inline def test(x: Long, y: Long, result: Long): Unit = {
+      assertEquals(result, JLong.divideUnsigned(x, y))
+      assertEquals(result, JLong.divideUnsigned(hideFromOptimizer(x), y))
+      assertEquals(result, JLong.divideUnsigned(x, hideFromOptimizer(y)))
+      assertEquals(result, JLong.divideUnsigned(hideFromOptimizer(x), hideFromOptimizer(y)))
+    }
 
     test(-9223372034182170740L, 53886L, 171164533265177L)
     test(-9223372036854775807L, 1L, -9223372036854775807L)
@@ -721,8 +727,12 @@ class LongTest {
   }
 
   @Test def remainderUnsigned(): Unit = {
-    def test(dividend: Long, divisor: Long, result: Long): Unit =
-      assertEquals(result, JLong.remainderUnsigned(dividend, divisor))
+    @inline def test(x: Long, y: Long, result: Long): Unit = {
+      assertEquals(result, JLong.remainderUnsigned(x, y))
+      assertEquals(result, JLong.remainderUnsigned(hideFromOptimizer(x), y))
+      assertEquals(result, JLong.remainderUnsigned(x, hideFromOptimizer(y)))
+      assertEquals(result, JLong.remainderUnsigned(hideFromOptimizer(x), hideFromOptimizer(y)))
+    }
 
     test(97062081516L, 772L, 668L)
     test(-9223372036854775472L, 49L, 43L)

From 8a885adaeb7f958bca74fdf908fbedc89c9be0f0 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Mon, 19 May 2025 15:26:27 +0200
Subject: [PATCH 297/298] Move the require-jdk15 tests to require-jdk17.

This way, we only have `require-jdk*` directories for JDK versions
that we actually test in our CI. They also correspond to JDK LTS
versions, so they are not arbitrary.
---
 project/Build.scala                                             | 1 -
 .../scalajs/testsuite/javalib/io/InputStreamTestOnJDK17.scala}  | 2 +-
 .../org/scalajs/testsuite/javalib/lang/ConstableTest.scala      | 0
 .../org/scalajs/testsuite/javalib/lang/ConstantDescTest.scala   | 0
 .../org/scalajs/testsuite/javalib/lang/StringTestOnJDK17.scala} | 2 +-
 5 files changed, 2 insertions(+), 3 deletions(-)
 rename test-suite/shared/src/test/{require-jdk15/org/scalajs/testsuite/javalib/io/InputStreamTestOnJDK15.scala => require-jdk17/org/scalajs/testsuite/javalib/io/InputStreamTestOnJDK17.scala} (98%)
 rename test-suite/shared/src/test/{require-jdk15 => require-jdk17}/org/scalajs/testsuite/javalib/lang/ConstableTest.scala (100%)
 rename test-suite/shared/src/test/{require-jdk15 => require-jdk17}/org/scalajs/testsuite/javalib/lang/ConstantDescTest.scala (100%)
 rename test-suite/shared/src/test/{require-jdk15/org/scalajs/testsuite/javalib/lang/StringTestOnJDK15.scala => require-jdk17/org/scalajs/testsuite/javalib/lang/StringTestOnJDK17.scala} (99%)

diff --git a/project/Build.scala b/project/Build.scala
index 7209200769..c1337508a2 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -2138,7 +2138,6 @@ object Build {
         List(sharedTestDir / "scala", sharedTestDir / "require-scala2") :::
         collectionsEraDependentDirectory(scalaV, sharedTestDir) ::
         includeIf(sharedTestDir / "require-jdk11", javaV >= 11) :::
-        includeIf(sharedTestDir / "require-jdk15", javaV >= 15) :::
         includeIf(sharedTestDir / "require-jdk17", javaV >= 17) :::
         includeIf(sharedTestDir / "require-jdk21", javaV >= 21) :::
         includeIf(testDir / "require-scala2", isJSTest)
diff --git a/test-suite/shared/src/test/require-jdk15/org/scalajs/testsuite/javalib/io/InputStreamTestOnJDK15.scala b/test-suite/shared/src/test/require-jdk17/org/scalajs/testsuite/javalib/io/InputStreamTestOnJDK17.scala
similarity index 98%
rename from test-suite/shared/src/test/require-jdk15/org/scalajs/testsuite/javalib/io/InputStreamTestOnJDK15.scala
rename to test-suite/shared/src/test/require-jdk17/org/scalajs/testsuite/javalib/io/InputStreamTestOnJDK17.scala
index 5bda94aa7a..181f15cccf 100644
--- a/test-suite/shared/src/test/require-jdk15/org/scalajs/testsuite/javalib/io/InputStreamTestOnJDK15.scala
+++ b/test-suite/shared/src/test/require-jdk17/org/scalajs/testsuite/javalib/io/InputStreamTestOnJDK17.scala
@@ -21,7 +21,7 @@ import org.junit.Assume._
 import org.scalajs.testsuite.utils.AssertThrows.assertThrows
 import org.scalajs.testsuite.utils.Platform
 
-class InputStreamTestOnJDK15 {
+class InputStreamTestOnJDK17 {
   /** InputStream that only ever skips max bytes at once */
   def lowSkipStream(max: Int, seq: Seq[Int]): InputStream = new SeqInputStreamForTest(seq) {
     require(max > 0)
diff --git a/test-suite/shared/src/test/require-jdk15/org/scalajs/testsuite/javalib/lang/ConstableTest.scala b/test-suite/shared/src/test/require-jdk17/org/scalajs/testsuite/javalib/lang/ConstableTest.scala
similarity index 100%
rename from test-suite/shared/src/test/require-jdk15/org/scalajs/testsuite/javalib/lang/ConstableTest.scala
rename to test-suite/shared/src/test/require-jdk17/org/scalajs/testsuite/javalib/lang/ConstableTest.scala
diff --git a/test-suite/shared/src/test/require-jdk15/org/scalajs/testsuite/javalib/lang/ConstantDescTest.scala b/test-suite/shared/src/test/require-jdk17/org/scalajs/testsuite/javalib/lang/ConstantDescTest.scala
similarity index 100%
rename from test-suite/shared/src/test/require-jdk15/org/scalajs/testsuite/javalib/lang/ConstantDescTest.scala
rename to test-suite/shared/src/test/require-jdk17/org/scalajs/testsuite/javalib/lang/ConstantDescTest.scala
diff --git a/test-suite/shared/src/test/require-jdk15/org/scalajs/testsuite/javalib/lang/StringTestOnJDK15.scala b/test-suite/shared/src/test/require-jdk17/org/scalajs/testsuite/javalib/lang/StringTestOnJDK17.scala
similarity index 99%
rename from test-suite/shared/src/test/require-jdk15/org/scalajs/testsuite/javalib/lang/StringTestOnJDK15.scala
rename to test-suite/shared/src/test/require-jdk17/org/scalajs/testsuite/javalib/lang/StringTestOnJDK17.scala
index 25ed53f386..21ffe9cf1d 100644
--- a/test-suite/shared/src/test/require-jdk15/org/scalajs/testsuite/javalib/lang/StringTestOnJDK15.scala
+++ b/test-suite/shared/src/test/require-jdk17/org/scalajs/testsuite/javalib/lang/StringTestOnJDK17.scala
@@ -17,7 +17,7 @@ import org.junit.Assert._
 
 import org.scalajs.testsuite.utils.AssertThrows.assertThrows
 
-class StringTestOnJDK15 {
+class StringTestOnJDK17 {
 
   // indent and transform are available since JDK 12 but we're not testing them separately
 

From 4c128da9a1fd25c2776a8d0be57f17117026bc42 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Doeraene?= <sjrdoeraene@gmail.com>
Date: Mon, 19 May 2025 17:13:58 +0200
Subject: [PATCH 298/298] Implement jl.Math.{multiplyFull, multiplyHigh,
 unsignedMultiplyHigh}.

---
 javalib/src/main/scala/java/lang/Math.scala   |  37 +++
 .../scalajs/linker/runtime/RuntimeLong.scala  |  41 +++
 .../linker/backend/emitter/LongImpl.scala     |   7 +
 .../frontend/optimizer/IncOptimizer.scala     |   5 +-
 .../frontend/optimizer/OptimizerCore.scala    |  40 ++-
 .../javalib/lang/MathTestOnJDK11.scala        | 242 ++++++++++++++++++
 .../javalib/lang/MathTestOnJDK21.scala        | 129 ++++++++++
 7 files changed, 499 insertions(+), 2 deletions(-)
 create mode 100644 test-suite/shared/src/test/require-jdk11/org/scalajs/testsuite/javalib/lang/MathTestOnJDK11.scala
 create mode 100644 test-suite/shared/src/test/require-jdk21/org/scalajs/testsuite/javalib/lang/MathTestOnJDK21.scala

diff --git a/javalib/src/main/scala/java/lang/Math.scala b/javalib/src/main/scala/java/lang/Math.scala
index 7d77391990..7fe386b7a7 100644
--- a/javalib/src/main/scala/java/lang/Math.scala
+++ b/javalib/src/main/scala/java/lang/Math.scala
@@ -462,6 +462,43 @@ object Math {
     if (a >= Integer.MIN_VALUE && a <= Integer.MAX_VALUE) a.toInt
     else throw new ArithmeticException("Integer overflow")
 
+  // RuntimeLong intrinsic
+  @inline
+  def multiplyFull(x: scala.Int, y: scala.Int): scala.Long =
+    x.toLong * y.toLong
+
+  @inline
+  def multiplyHigh(x: scala.Long, y: scala.Long): scala.Long = {
+    /* Hacker's Delight, Section 8-2, Figure 8-2,
+     * where we have "inlined" all the variables used only once to help our
+     * optimizer perform simplifications.
+     */
+
+    val x0 = x & 0xffffffffL
+    val x1 = x >> 32
+    val y0 = y & 0xffffffffL
+    val y1 = y >> 32
+
+    val t = x1 * y0 + ((x0 * y0) >>> 32)
+    x1 * y1 + (t >> 32) + (((t & 0xffffffffL) + x0 * y1) >> 32)
+  }
+
+  @inline
+  def unsignedMultiplyHigh(x: scala.Long, y: scala.Long): scala.Long = {
+    /* Hacker's Delight, Section 8-2:
+     * > For an unsigned version, simply change all the int declarations to unsigned.
+     * In Scala, that means changing all the >> into >>>.
+     */
+
+    val x0 = x & 0xffffffffL
+    val x1 = x >>> 32
+    val y0 = y & 0xffffffffL
+    val y1 = y >>> 32
+
+    val t = x1 * y0 + ((x0 * y0) >>> 32)
+    x1 * y1 + (t >>> 32) + (((t & 0xffffffffL) + x0 * y1) >>> 32)
+  }
+
   def floorDiv(a: scala.Int, b: scala.Int): scala.Int = {
     val quot = a / b
     if ((a < 0) == (b < 0) || quot * b == a) quot
diff --git a/linker-private-library/src/main/scala/org/scalajs/linker/runtime/RuntimeLong.scala b/linker-private-library/src/main/scala/org/scalajs/linker/runtime/RuntimeLong.scala
index 7e4e256beb..f570defbe6 100644
--- a/linker-private-library/src/main/scala/org/scalajs/linker/runtime/RuntimeLong.scala
+++ b/linker-private-library/src/main/scala/org/scalajs/linker/runtime/RuntimeLong.scala
@@ -767,6 +767,47 @@ object RuntimeLong {
     }
   }
 
+  /** Intrinsic for Math.multiplyFull.
+   *
+   *  Compared to the regular expansion of `x.toLong * y.toLong`, this
+   *  intrinsic avoids 2 int multiplications.
+   */
+  @inline
+  def multiplyFull(a: Int, b: Int): RuntimeLong = {
+    /* We use Hacker's Delight, Section 8-2, Figure 8-2, to compute the hi
+     * word of the result. We reuse intermediate products to compute the lo
+     * word, like we do in `RuntimeLong.*`.
+     *
+     * We swap the role of a1b0 and a0b1 compared to Hacker's Delight, to
+     * optimize for the case where a1b0 collapses to 0, like we do in
+     * `RuntimeLong.*`. The optimizer normalizes constants in multiplyFull to
+     * be on the left-hand-side (when it cannot do constant-folding to begin
+     * with). Therefore, `b` is never constant in practice.
+     */
+
+    val a0 = a & 0xffff
+    val a1 = a >> 16
+    val b0 = b & 0xffff
+    val b1 = b >> 16
+
+    val a0b0 = a0 * b0
+    val a1b0 = a1 * b0 // collapses to 0 when a is constant and 0 <= a <= 0xffff
+    val a0b1 = a0 * b1
+
+    /* lo = a * b, but we compute the above 3 subproducts for hi anyway,
+     * so we reuse them to compute lo too, trading a * for 2 +'s and 1 <<.
+     */
+    val lo = a0b0 + ((a1b0 + a0b1) << 16)
+
+    val t = a0b1 + (a0b0 >>> 16)
+    val hi = {
+      a1 * b1 + (t >> 16) +
+      (((t & 0xffff) + a1b0) >> 16) // collapses to 0 when a1b0 = 0
+    }
+
+    new RuntimeLong(lo, hi)
+  }
+
   @inline
   def divide(a: RuntimeLong, b: RuntimeLong): RuntimeLong = {
     val lo = divideImpl(a.lo, a.hi, b.lo, b.hi)
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/LongImpl.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/LongImpl.scala
index 1e1c6b8305..b554c83d8a 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/LongImpl.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/LongImpl.scala
@@ -116,6 +116,13 @@ private[linker] object LongImpl {
   val AllModuleMethods = Set(
       fromInt, fromDouble, fromDoubleBits)
 
+  // Methods on the companion used for intrinsics
+
+  final val multiplyFull = MethodName("multiplyFull", List(IntRef, IntRef), RTLongRef)
+
+  val AllIntrinsicModuleMethods = Set(
+      multiplyFull)
+
   // Extract the parts to give to the initFromParts constructor
 
   def extractParts(value: Long): (Int, Int) =
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
index 38bdb804c3..7aea1cd466 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/IncOptimizer.scala
@@ -75,7 +75,10 @@ final class IncOptimizer private[optimizer] (config: CommonPhaseConfig, collOps:
     multiple(
       cond(!targetIsWebAssembly && !esFeatures.allowBigIntsForLongs) {
         // Required by the intrinsics manipulating Longs
-        callMethods(LongImpl.RuntimeLongClass, LongImpl.AllIntrinsicMethods.toList)
+        multiple(
+          callMethods(LongImpl.RuntimeLongClass, LongImpl.AllIntrinsicMethods.toList),
+          callMethods(LongImpl.RuntimeLongModuleClass, LongImpl.AllIntrinsicModuleMethods.toList)
+        )
       },
       cond(targetIsWebAssembly) {
         // Required by the intrinsic CharacterCodePointToString
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
index 2c0fa4ec70..93a8cbbdfc 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
@@ -2993,6 +2993,32 @@ private[optimizer] abstract class OptimizerCore(
       case MathMaxDouble =>
         contTree(wasmBinaryOp(WasmBinaryOp.F64Max, targs.head, targs.tail.head))
 
+      case MathMultiplyFull =>
+        def expand(targs: List[PreTransform]): TailRec[Tree] = {
+          import LongImpl.{RuntimeLongModuleClass => modCls}
+          val receiver =
+            makeCast(LoadModule(modCls), ClassType(modCls, nullable = false)).toPreTransform
+
+          pretransformApply(ApplyFlags.empty,
+              receiver,
+              MethodIdent(LongImpl.multiplyFull),
+              targs,
+              ClassType(LongImpl.RuntimeLongClass, nullable = true),
+              isStat, usePreTransform)(
+              cont)
+        }
+
+        targs match {
+          case List(PreTransLit(IntLiteral(x)), PreTransLit(IntLiteral(y))) =>
+            // cannot actually call multiplyHigh to constant-fold because it is JDK9+
+            contTree(LongLiteral(x.toLong * y.toLong))
+          case List(tlhs, trhs @ PreTransLit(_)) =>
+            // normalize a single constant on the left; the implementation is optimized for that case
+            expand(trhs :: tlhs :: Nil)
+          case _ =>
+            expand(targs)
+        }
+
       // scala.collection.mutable.ArrayBuilder
 
       case GenericArrayBuilderResult =>
@@ -4374,6 +4400,14 @@ private[optimizer] abstract class OptimizerCore(
               PreTransLit(IntLiteral(_))) if (y & 31) != 0 =>
             foldBinaryOp(Int_>>>, lhs, rhs)
 
+          case (PreTransBinaryOp(op @ (Int_| | Int_& | Int_^),
+              PreTransLit(IntLiteral(x)), y),
+              z @ PreTransLit(IntLiteral(zValue))) =>
+            foldBinaryOp(
+                op,
+                PreTransLit(IntLiteral(x >> zValue)),
+                foldBinaryOp(Int_>>, y, z))
+
           case (_, PreTransLit(IntLiteral(y))) =>
             val dist = y & 31
             if (dist == 0)
@@ -6518,8 +6552,9 @@ private[optimizer] object OptimizerCore {
     final val MathMinDouble = MathMinFloat + 1
     final val MathMaxFloat = MathMinDouble + 1
     final val MathMaxDouble = MathMaxFloat + 1
+    final val MathMultiplyFull = MathMaxDouble + 1
 
-    final val ArrayBuilderZeroOf = MathMaxDouble + 1
+    final val ArrayBuilderZeroOf = MathMultiplyFull + 1
     final val GenericArrayBuilderResult = ArrayBuilderZeroOf + 1
 
     final val ClassGetName = GenericArrayBuilderResult + 1
@@ -6611,6 +6646,9 @@ private[optimizer] object OptimizerCore {
         ClassName("java.lang.Long$") -> List(
             m("toString", List(J), ClassRef(BoxedStringClass)) -> LongToString,
             m("compare", List(J, J), I) -> LongCompare
+        ),
+        ClassName("java.lang.Math$") -> List(
+            m("multiplyFull", List(I, I), J) -> MathMultiplyFull
         )
     )
 
diff --git a/test-suite/shared/src/test/require-jdk11/org/scalajs/testsuite/javalib/lang/MathTestOnJDK11.scala b/test-suite/shared/src/test/require-jdk11/org/scalajs/testsuite/javalib/lang/MathTestOnJDK11.scala
new file mode 100644
index 0000000000..a94c198e9e
--- /dev/null
+++ b/test-suite/shared/src/test/require-jdk11/org/scalajs/testsuite/javalib/lang/MathTestOnJDK11.scala
@@ -0,0 +1,242 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package org.scalajs.testsuite.javalib.lang
+
+import java.math.BigInteger
+import java.util.SplittableRandom
+
+import org.junit.Test
+import org.junit.Assert._
+
+class MathTestOnJDK11 {
+
+  @noinline
+  private def hideFromOptimizer(x: Int): Int = x
+
+  @Test def testMultiplyFull(): Unit = {
+    @inline def test(expected: Long, x: Int, y: Int): Unit = {
+      assertEquals(expected, Math.multiplyFull(x, y))
+      assertEquals(expected, Math.multiplyFull(x, hideFromOptimizer(y)))
+      assertEquals(expected, Math.multiplyFull(hideFromOptimizer(x), y))
+      assertEquals(expected, Math.multiplyFull(hideFromOptimizer(x), hideFromOptimizer(y)))
+    }
+
+    test(2641928036408725662L, 1942041231, 1360387202)
+    test(54843908448922272L, 1565939409, 35023008)
+    test(510471553407128558L, 1283300489, 397780222)
+    test(-1211162085735907941L, -1990140693, 608581137)
+    test(-1197265696701533712L, -584098468, 2049766884)
+    test(203152587796496856L, -1809591416, -112264341)
+    test(-1869763755321108598L, 1235591906, -1513253483)
+    test(-737954189546644064L, 675415792, -1092592442)
+    test(-2570904460570261986L, 1639253754, -1568338309)
+    test(1106623967126000400L, 2088029790, 529984760)
+    test(1407516248272451352L, -869881054, -1618055988)
+    test(-2120367337662071940L, -1558894530, 1360173698)
+    test(-1464086284066637244L, -1417313902, 1033000722)
+    test(36729253163312334L, -1673852034, -21942951)
+    test(-3197007331876781046L, 1876799847, -1703435418)
+    test(461794994386945009L, -246001091, -1877207099)
+    test(-1206231192496917804L, 867896526, -1389832954)
+    test(-1739671893103255929L, -1083992841, 1604873969)
+    test(-409626127116780624L, 240101424, -1706054551)
+    test(-3083566560548370936L, -1568530113, 1965895672)
+    test(-1205028798380605000L, -1201743532, 1002733750)
+    test(-1328689065035027168L, 929349664, -1429697687)
+    test(-124212693522020684L, 80893862, -1535502082)
+    test(-82341860111074830L, -243230690, 338534007)
+    test(-846837059701860202L, 1959770926, -432110227)
+    test(335728245390354432L, 506816728, 662425344)
+    test(745294755971022170L, 1521993302, 489683335)
+    test(-2370525755201631608L, 2023520366, -1171485988)
+    test(-1039854583047715776L, 593162592, -1753068378)
+    test(-152985384388127808L, -635946432, 240563319)
+    test(-678107568956539050L, 649113254, -1044667575)
+    test(-3064094283703186444L, -1890896836, 1620444979)
+    test(1240687269228318870L, -1080325230, -1148438669)
+    test(-46551523496333580L, 27167878, -1713476610)
+    test(-2500430606368427103L, 2023288183, -1235825241)
+    test(92963399778762084L, 896198732, 103730787)
+    test(2469065794894324667L, 2105111101, 1172890967)
+    test(172558569988357136L, -142945148, -1207166332)
+    test(335684786634110970L, -1647598405, -203741874)
+    test(2406859843746696240L, 2049365815, 1174441296)
+    test(3100973294006114952L, 1991928152, 1556769651)
+    test(-335912134649077352L, 866240524, -387781598)
+    test(84303320581066207L, 75666091, 1114149277)
+    test(-2623126349572207976L, 1426933667, -1838295928)
+    test(59139945163750590L, 149344270, 395997417)
+    test(-105764175098643999L, 68726447, -1538915217)
+    test(8595303129864000L, 726092025, 11837760)
+    test(-2958527843471399088L, 1536412078, -1925608296)
+    test(1532625839159904477L, 867021537, 1767690621)
+    test(384402376484481316L, 1207235521, 318415396)
+    test(-219376614576542698L, 1816299166, -120782203)
+    test(-672138807810988440L, 531516745, -1264567512)
+    test(-193351903065245331L, 170858169, -1131651499)
+    test(71263251057597648L, 51058196, 1395725988)
+    test(-774312974742971385L, 1958551603, -395349795)
+    test(-1846593638370672048L, 1190143097, -1551572784)
+    test(240083094242536384L, 1404614968, 170924488)
+    test(-130950827889833280L, -115480554, 1133964320)
+    test(128954457719585228L, 735993884, 175211317)
+    test(364779990580792000L, -668489125, -545678272)
+    test(107252402494512045L, 759517757, 141211185)
+    test(3038084150893069044L, -1924640913, -1578519988)
+    test(760804294233336624L, -728394552, -1044494762)
+    test(1171051779605774913L, 848233701, 1380576813)
+    test(-1805862307837393080L, -1385644986, 1303264780)
+    test(172227703288618734L, -104999826, -1640266559)
+    test(150448013961014407L, 163398103, 920745169)
+    test(-671469201380991232L, 650262784, -1032612073)
+    test(-1325861126942924945L, -1773644581, 747534845)
+    test(987406376890116568L, -1626507773, -607071416)
+    test(2918138947401192144L, 1695881208, 1720721318)
+    test(-2590993826910153940L, -1397240042, 1854365570)
+    test(954644624447419276L, -1516139806, -629654746)
+    test(407510452326678620L, -384747652, -1059162935)
+    test(149866317537821404L, 1530355444, 97929091)
+    test(922044716091910632L, 968149268, 952378674)
+    test(-3508732521573808284L, 1825364562, -1922209182)
+    test(1701723136959404304L, 894776752, 1901841027)
+    test(-2435876799625512705L, -1276062909, 1908900245)
+    test(-516933170985379201L, 657063047, -786732983)
+    test(123334479976750576L, 313765817, 393078128)
+    test(-1072624004420456775L, -894199299, 1199535725)
+    test(301682711612188737L, 330918981, 911651277)
+    test(1790992996470651507L, -1115945231, -1604911197)
+    test(-2750453268538140155L, 1878389719, -1464261245)
+    test(758285757353272504L, 1259684942, 601964612)
+    test(-218581674312137400L, -161533394, 1353167100)
+    test(-1824007072461951836L, -1244277844, 1465916219)
+    test(-92753167730460334L, -65368843, 1418920138)
+    test(-2326636630979491248L, 1124395877, -2069232624)
+    test(-7380586257943446L, 29715454, -248375349)
+    test(31319707234597638L, 491995506, 63658523)
+    test(-1196559502630778250L, -1752963990, 682592175)
+    test(166065559841839548L, -911521074, -182185102)
+    test(-1222260378510810100L, 1071539812, -1140657925)
+    test(57800571165871464L, -257569032, -224408077)
+    test(332444627169725608L, 1247224172, 266547614)
+    test(217903869180130650L, 1069161915, 203808110)
+    test(920425054266935850L, -901689546, -1020778225)
+    test(-507632632656614388L, 864632142, -587108214)
+  }
+
+  @Test def testMultiplyHigh(): Unit = {
+    def test(expected: Long, x: Long, y: Long): Unit =
+      assertEquals(expected, Math.multiplyHigh(x, y))
+
+    test(-2514789262281153376L, 8217931296694472096L, -5644933286224084859L)
+    test(-298247406641127011L, -8034902747807161194L, 684724352445702293L)
+    test(242644198957550459L, 717019025263929004L, 6242505821226454837L)
+    test(-1089698470915011537L, -7558081430876177893L, 2659588811568490384L)
+    test(138675986327040026L, 2362930226177876193L, 1082605148727562445L)
+    test(-1260260349245855816L, -3350308785473442797L, 6938972380570262589L)
+    test(-1799534229489533301L, -4097805274432763180L, 8100811327075225922L)
+    test(437623091041087696L, -2968271773754119013L, -2719670493975918294L)
+    test(-107841114219899514L, 2013609532543228156L, -987936043452088475L)
+    test(2757621741022067854L, -7005993850636185311L, -7260803191272031988L)
+    test(-187671345159116030L, 1781219534362173574L, -1943570237881252419L)
+    test(-515018730942796014L, 6085558843030314089L, -1561141543105626636L)
+    test(-119091959391883575L, 7423442237814967910L, -295935339127164155L)
+    test(18351865713513547L, -1886460125362775846L, -179453657960126825L)
+    test(3928100041033091765L, 8449838094261471293L, 8575389888485029447L)
+    test(-7404756889594137L, -89549316594063561L, 1525345591296625693L)
+    test(714591873345926311L, -2929853068304815970L, -4499165349746322236L)
+    test(1305977852854305585L, -5568549492657237090L, -4326268312655360053L)
+    test(-2435010516398991446L, 6443930667478151719L, -6970592660082469124L)
+    test(2031324595328562735L, 5390460907312723801L, 6951413911530987604L)
+    test(34713245667458599L, -535353692461820541L, -1196118319182197181L)
+    test(255381044848343425L, -3176530727082196631L, -1483048388428836603L)
+    test(6566871520624982L, -33326351213089011L, -3634883324950494373L)
+    test(156130078476475485L, 687410849583778615L, 4189767446364284457L)
+    test(1647679448547038188L, 4460502251200507739L, 6814102850116870938L)
+    test(-2241611115434343963L, 5633894511267143863L, -7339581257068946568L)
+    test(-93572860194426351L, -1075368508503119813L, 1605137764964203383L)
+    test(1663347345126188661L, -6330756750592024018L, -4846710115399342760L)
+    test(-1686630202076061136L, 5124142056960069542L, -6071813649745693328L)
+    test(728105493712673843L, -8079843401135830331L, -1662306437683128283L)
+    test(-2030727779883712688L, 4452689522888653156L, -8412963770845872378L)
+    test(734253555387491804L, 5835084770836409518L, 2321232330529258387L)
+    test(2018627311798804222L, -7211950082779933827L, -5163250018863045382L)
+    test(-1244560006523295051L, -7326211205612788508L, 3133690700470219958L)
+    test(-492070935033321215L, 1614944457187625808L, -5620692751550184667L)
+    test(319340972880203566L, 2310036532484690677L, 2550090059672932009L)
+    test(1766280783448332865L, 5949345770128658249L, 5476590340096838859L)
+    test(2757208297958468913L, -5707089944199929572L, -8911987777945981523L)
+    test(408328069441815717L, 1242541635079749093L, 6062028975489127199L)
+    test(-77985829287979398L, -7943526433115400350L, 181101510313367840L)
+    test(-230121117022373017L, -780391911062895469L, 5439555807140802418L)
+    test(2588662639521587653L, 7451684432618227097L, 6408268846625040081L)
+    test(861249002493118404L, 1744344496585548181L, 9107856827493957233L)
+    test(-2703044944335540474L, 8052570526613861366L, -6192106997771248181L)
+    test(-2975059248415970510L, 6503508572335523474L, -8438546047759521035L)
+    test(-370291189062632935L, -8722964233277178137L, 783067156383574516L)
+    test(-90473002639507852L, 852694261922564555L, -1957245873225555126L)
+    test(-218977334338454381L, -1819563432425194345L, 2219993418476586419L)
+    test(-1087231185918604076L, -2941838679159182506L, 6817462690146034563L)
+    test(-1170480051005916145L, -2771463765488827700L, 7790665067735548924L)
+    test(-371145713487913188L, 3224241917397787909L, -2123423169279885562L)
+    test(-502492608136209963L, 1568228348895174267L, -5910716094215359887L)
+    test(1445926343733049503L, -7706328512722939071L, -3461133686196008644L)
+    test(-1374053009197983052L, -8787832166727089323L, 2884306814637966447L)
+    test(-1910150305525172307L, 8663815092401732543L, -4067036686787486282L)
+    test(2074971709256543740L, 8092193156887080609L, 4730049238662438083L)
+    test(953725989108917020L, 8492699833366153401L, 2071560232049848145L)
+    test(334989155711573307L, 1093268576921704206L, 5652279186765632978L)
+    test(129011196343964709L, 1000276763122669782L, 2379178052852915387L)
+    test(239042793587178901L, 3208737625070847213L, 1374235525371105170L)
+    test(127809344420152430L, -7696730067895344868L, -306320508313194466L)
+    test(-2506455997163955037L, -5731747797284935902L, 8066641092198683254L)
+    test(3016086034985660469L, -6992699346126002928L, -7956436339922591224L)
+    test(-1527917483534567268L, -8938885845855254814L, 3153089016969294968L)
+    test(-1268939936756528050L, 5537112727075101653L, -4227439716695399205L)
+    test(-37535014067603004L, -8605247800544091240L, 80462389271855887L)
+    test(-2710920384572235679L, -7926242046619125682L, 6309125338878172023L)
+    test(-3331830886924716794L, 6823617049086893513L, -9007163096323738999L)
+    test(1854911433578401793L, -4644835313936852982L, -7366693150982113934L)
+    test(-3840461794042836575L, 8006480391435326631L, -8848334396141248546L)
+    test(-1212641710132993432L, -7017377545321262459L, 3187699555205380404L)
+    test(946047090630044138L, -5829622550331878687L, -2993588077419595837L)
+    test(3518955178043574292L, -7909090733489625033L, -8207424565425867851L)
+    test(1231895337081111773L, 2841977238766797132L, 7996002817598962425L)
+    test(-1649686524869089287L, -3558405071306300052L, 8551962049372852642L)
+    test(1156466789444347220L, -8077807627762096372L, -2640945152160624636L)
+    test(-284428196958678125L, 7604654143237097972L, -689942508603024688L)
+    test(24530734973246035L, -4976536915346383672L, -90929133590073966L)
+    test(915668791878818L, -4915702564252847L, -3436153355352311231L)
+    test(-59487608720960501L, 2234272329433906652L, -491145452224512365L)
+    test(-935777346233643464L, 2234022931260640741L, -7726888105936443458L)
+    test(-539196324963981948L, 1233384294780865907L, -8064328899098291942L)
+    test(-302740552339519239L, 1652272762436229815L, -3379936785683182277L)
+    test(-1602328337662720444L, -5891195966699023422L, 5017273391344774367L)
+    test(1971437877011804292L, 6123334000940359947L, 5939021122948580484L)
+    test(3518273874050862283L, -7935043146462869940L, -8178997459486413381L)
+    test(989386049294028022L, 3631504400505165814L, 5025727419987895939L)
+    test(1075600553777136761L, 8162668046881939535L, 2430740540606242760L)
+    test(555876997051543592L, -1422006546765159905L, -7211022146415941068L)
+    test(1442987791832810570L, 3172003226122803882L, 8391676993961733131L)
+    test(122174343239443206L, 592078109511582332L, 3806455273225175653L)
+    test(-555975358284841098L, -2610695041141095892L, 3928430928909536969L)
+    test(1217820260754824228L, -2566343358431797989L, -8753629401971345682L)
+    test(-843540703271762806L, 2010390971620435041L, -7740076278033066915L)
+    test(28227414827282063L, 1691814723551530731L, 307778322255183098L)
+    test(-3487482743675782331L, 8885183126228404590L, -7240447464066348779L)
+    test(-641218088086423374L, -5793475349478143447L, 2041673650588512538L)
+    test(491218135799199820L, -3483174304311045377L, -2601470510458659970L)
+    test(-61083956648009538L, -331097881159246733L, 3403223576515274855L)
+    test(-1760654512150512675L, -6642702867806073297L, 4889326503714183951L)
+  }
+
+}
diff --git a/test-suite/shared/src/test/require-jdk21/org/scalajs/testsuite/javalib/lang/MathTestOnJDK21.scala b/test-suite/shared/src/test/require-jdk21/org/scalajs/testsuite/javalib/lang/MathTestOnJDK21.scala
new file mode 100644
index 0000000000..b57216847d
--- /dev/null
+++ b/test-suite/shared/src/test/require-jdk21/org/scalajs/testsuite/javalib/lang/MathTestOnJDK21.scala
@@ -0,0 +1,129 @@
+/*
+ * Scala.js (https://www.scala-js.org/)
+ *
+ * Copyright EPFL.
+ *
+ * Licensed under Apache License 2.0
+ * (https://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package org.scalajs.testsuite.javalib.lang
+
+import java.math.BigInteger
+import java.util.SplittableRandom
+
+import org.junit.Test
+import org.junit.Assert._
+
+class MathTestOnJDK21 {
+
+  @Test def testUnsignedMultiplyHigh(): Unit = {
+    def test(expected: Long, x: Long, y: Long): Unit =
+      assertEquals(expected, Math.unsignedMultiplyHigh(x, y))
+
+    test(-4655528149793241951L, -3491544249150011246L, -1435735621922138183L)
+    test(4723475310515791226L, -5748086171833985033L, 6861570794713764439L)
+    test(1844940925490449716L, 2113050876768271470L, -2340575756699630680L)
+    test(702124944283937448L, 2364425117167296916L, 5477830133394302018L)
+    test(8604154842195983318L, -765591305295706482L, 8976713476968422536L)
+    test(721433542721114290L, 2866411935332571322L, 4642772995997153672L)
+    test(198977852337409286L, 901957528446724377L, 4069474895038101365L)
+    test(763163907759431674L, 5160783458443768226L, 2727858939653224648L)
+    test(3387911794594526182L, 4369265381816556396L, -4143208729009548760L)
+    test(7271333002323704409L, -1757891743212949508L, 8037246439257825352L)
+    test(2439931237179080842L, -6474169961931828112L, 3759324157819640760L)
+    test(6061120068222317095L, -2837073725411217492L, 7162734907512678039L)
+    test(34351029958289581L, 2814331433271609755L, 225156373132738607L)
+    test(5537345867541993285L, -1010313517008906026L, 5858194527486398591L)
+    test(-5335982525234939944L, -2717969804981747482L, -3070411578621565733L)
+    test(8785453866123381013L, -8027031729027070236L, -2893241858030230601L)
+    test(846995399721837047L, 8016550578873635720L, 1949006273527852101L)
+    test(4706098605093773886L, -8117794498444021304L, 8404745896106734176L)
+    test(8161884790484487335L, -1014727160850354519L, 8636992531719324619L)
+    test(-8513922914337796266L, -7911312134726022659L, -1055125873522512866L)
+    test(5454317624646219097L, -5009725974720812208L, 7487851886286018345L)
+    test(2492015203153257923L, 5501297108904060131L, 8356132339400095318L)
+    test(251150029847529372L, 2825249782885673228L, 1639819725946463245L)
+    test(701745563060384928L, -862030064654873400L, 736146223360275347L)
+    test(-7730043035170177278L, -81403377518056314L, -7682541838496528017L)
+    test(7236963176581899295L, -5477193291802744595L, -8153526534093331950L)
+    test(626928141670112235L, 1514687386182852255L, 7635095589684134756L)
+    test(413586791425617421L, 2206621030247415833L, 3457471667819472989L)
+    test(5275688490004831530L, 5303665000787184389L, -97305454699880484L)
+    test(-4547690235532216689L, -4468474298913285824L, -104539126294685679L)
+    test(366277061497431976L, 2447428253923437996L, 2760701647814215009L)
+    test(6869979725009155017L, -6471585201942397935L, -7864107205517734491L)
+    test(3791302630224081431L, -3133537597544878918L, 4567115935815546723L)
+    test(1740958585965607218L, -1557363676960182057L, 1901491749479209603L)
+    test(1523197267704952893L, 6322993002648583029L, 4443786377646975729L)
+    test(-5259964406327079828L, -1435127053681489364L, -4147506711722433774L)
+    test(461442857371067152L, -3905080403415491898L, 585360691015982209L)
+    test(-5941004277830287560L, -823789104926622437L, -5356420579401640852L)
+    test(-8706994437197957328L, -7948824177902058651L, -1332242280026816373L)
+    test(-5824918531825640540L, -1108632841430213984L, -5017854248578702419L)
+    test(-8207168723011034838L, -6116459797997975723L, -3127808865551126328L)
+    test(73145162458483087L, 984457260399802488L, 1370592860022769137L)
+    test(1646786118016093153L, 1899627239649590099L, -2455268783649962915L)
+    test(3040972539165017704L, -1806601545829941920L, 3371127505138255794L)
+    test(-7035139036718491109L, -5137998055321179172L, -2629554588180521105L)
+    test(3814121656202007379L, 6827719277638332778L, -8141966856464601543L)
+    test(846533671710128614L, 928822269112330348L, -1634281118080467412L)
+    test(2465515036079121285L, -6936668916098982255L, 3951383831786888133L)
+    test(-8705991089541820518L, -4627352440152123018L, -5444349891042507930L)
+    test(-1725081446201736077L, -102123348177150214L, -1631993003537285149L)
+    test(3162229868737586796L, -3928062681119615377L, 4017778440996329527L)
+    test(-5644865433298065278L, -1848848427461824206L, -4218857359905179258L)
+    test(8602545182711575119L, -7248610265558893317L, -4275726644671484627L)
+    test(574312046131959731L, 3094727123103690882L, 3423302576293014745L)
+    test(1498569573726223576L, -7522287153787738568L, 2530444268837256898L)
+    test(9201094795447111684L, -7474596509362715910L, -2977553571653290816L)
+    test(3390173448745695247L, 4278016163532080543L, -3828364997071413384L)
+    test(1203823557488246474L, 7917135674481131658L, 2804881208044173681L)
+    test(78424886362034171L, 980323435081771015L, 1475720926338487149L)
+    test(2441060259411459766L, 5798689165809470750L, 7765481574589679868L)
+    test(1218713916031010010L, 1847981405952407601L, -6281414035388066866L)
+    test(3425204597140630L, 23488433971625858L, 2689999370748729443L)
+    test(1973267136565988242L, -1929721405614247783L, 2203808433804858703L)
+    test(68657367104675341L, 1589652507076814732L, 796718071475649415L)
+    test(3001541031524236691L, 8704517430100436852L, 6360910835079676298L)
+    test(681950840803061472L, 4077993211593106210L, 3084794892591474962L)
+    test(-8032203953933386693L, -1297027813828962384L, -7244555458827535130L)
+    test(1705455955228875706L, 7677829613973803154L, 4097526399626386343L)
+    test(-7072562212974300041L, -4950443113989053629L, -2900512372222814349L)
+    test(1553202529265923923L, -5818129186601545240L, 2268778469225152008L)
+    test(468774576517241981L, 4408923425379013709L, 1961332463044936276L)
+    test(3713249757582606154L, 3805244009484784339L, -445962050491898861L)
+    test(-6492270872661604844L, -3676904101986751446L, -3516243262736404968L)
+    test(-1570352970576497130L, -498180996573724276L, -1101931219921881504L)
+    test(5938952698782807216L, -2212548245883761340L, 6748368792775950262L)
+    test(6965609214550264138L, -44143931286210318L, 6982318232414802091L)
+    test(5427827011873507182L, -6210411243958046988L, 8182658739140523648L)
+    test(-4010444622072654726L, -2893048189377704445L, -1325236533881556505L)
+    test(-751397756032611136L, -297794630894262553L, -461046011882216476L)
+    test(547299415238293930L, 4622152711521934473L, 2184240304182297561L)
+    test(378891801518625290L, -4298572905176069751L, 494008731657528393L)
+    test(1743296278846509964L, 2577934180605703203L, -5972360304541326595L)
+    test(1039517173945592548L, 5277562622670643081L, 3633440025065309218L)
+    test(2800417145934889950L, 4637163034857372585L, -7306618526608114613L)
+    test(1678445276921448048L, 4821090766475680470L, 6422167091396679498L)
+    test(6227359204013573541L, -4999273910373625291L, 8542461897755272268L)
+    test(-5499015746244333303L, -1511897164914852634L, -4343077705835106861L)
+    test(2697793722365988629L, 6211672456183761935L, 8011612123978580051L)
+    test(1911468969140043410L, -5555150943474614346L, 2735145185110353700L)
+    test(2743615826392469850L, 6136958276954783995L, 8246883342207528968L)
+    test(1464762398133852646L, -6115223270905044522L, 2191140697019557187L)
+    test(457204414584490485L, -5068587596916665104L, 630425637481565869L)
+    test(-6229688730810143122L, -4425525343688714952L, -2373612516159392266L)
+    test(388393998755070731L, 797622384306174158L, 8982451891732844522L)
+    test(5110014275194731110L, 8574583813914626477L, -7453426194589668982L)
+    test(6332629791985833635L, -6221980493997883829L, -8891025443683788065L)
+    test(1100817927132096284L, -5992086725542985450L, 1630434784827422367L)
+    test(-6893218526017086868L, -566288691658266700L, -6527308893032530287L)
+    test(6838523840226613906L, 7591397219780968602L, -1829447485155925067L)
+    test(2870893831454164280L, 3649310365003545712L, -3934784696536939433L)
+  }
+
+}