8000 Replace topoSortDistinctsBy with topoSortDistinctsWith by gzm0 · Pull Request #4462 · scala-js/scala-js · GitHub
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Replace topoSortDistinctsBy with topoSortDistinctsWith #4462

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Merged
merged 1 commit into from
Apr 6, 2021
Merged

Replace topoSortDistinctsBy with topoSortDistinctsWith #4462

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55 changes: 19 additions & 36 deletions compiler/src/main/scala/org/scalajs/nscplugin/GenJSExports.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -525,8 +525,22 @@ trait GenJSExports[G <: Global with Singleton] extends SubComponent {
} else {
// Sort them so that, e.g., isInstanceOf[String]
// comes before isInstanceOf[Object]
val sortedAltsByTypeTest = topoSortDistinctsBy(
altsByTypeTest)(_._1)(RTTypeTest.Ordering)
val sortedAltsByTypeTest = topoSortDistinctsWith(altsByTypeTest) { (lhs, rhs) =>
(lhs._1, rhs._1) match {
// NoTypeTest is always last
case (_, NoTypeTest) => true
case (NoTypeTest, _) => false

case (PrimitiveTypeTest(_, rank1), PrimitiveTypeTest(_, rank2)) =>
rank1 <= rank2

case (InstanceOfTypeTest(t1), InstanceOfTypeTest(t2)) =>
t1 <:< t2

case (_: PrimitiveTypeTest, _: InstanceOfTypeTest) => true
case (_: InstanceOfTypeTest, _: PrimitiveTypeTest) => false
}
}

val defaultCase = genThrowTypeError()

Expand Down Expand Up @@ -946,47 +960,16 @@ trait GenJSExports[G <: Global with Singleton] extends SubComponent {

private case object NoTypeTest extends RTTypeTest

private object RTTypeTest {
implicit object Ordering extends PartialOrdering[RTTypeTest] {
override def tryCompare(lhs: RTTypeTest, rhs: RTTypeTest): Option[Int] = {
if (lteq(lhs, rhs)) if (lteq(rhs, lhs)) Some(0) else Some(-1)
else if (lteq(rhs, lhs)) Some(1) else None
}

override def lteq(lhs: RTTypeTest, rhs: RTTypeTest): Boolean = {
(lhs, rhs) match {
// NoTypeTest is always last
case (_, NoTypeTest) => true
case (NoTypeTest, _) => false

case (PrimitiveTypeTest(_, rank1), PrimitiveTypeTest(_, rank2)) =>
rank1 <= rank2

case (InstanceOfTypeTest(t1), InstanceOfTypeTest(t2)) =>
t1 <:< t2

case (_: PrimitiveTypeTest, _: InstanceOfTypeTest) => true
case (_: InstanceOfTypeTest, _: PrimitiveTypeTest) => false
}
}

override def equiv(lhs: RTTypeTest, rhs: RTTypeTest): Boolean = {
lhs == rhs
}
}
}

// Very simple O(n²) topological sort for elements assumed to be distinct
private def topoSortDistinctsBy[A <: AnyRef, B](coll: List[A])(f: A => B)(
implicit ord: PartialOrdering[B]): List[A] = {

private def topoSortDistinctsWith[A <: AnyRef](coll: List[A])(
lteq: (A, A) => Boolean): List[A] = {
@scala.annotation.tailrec
def loop(coll: List[A], acc: List[A]): List[A] = {
if (coll.isEmpty) acc
else if (coll.tail.isEmpty) coll.head :: acc
else {
val (lhs, rhs) = coll.span(x => !coll.forall(
y => (x eq y) || !ord.lteq(f(x), f(y))))
y => (x eq y) || !lteq(x, y)))
assert(!rhs.isEmpty, s"cycle while ordering $coll")
loop(lhs ::: rhs.tail, rhs.head :: acc)
}
Expand Down
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