8000 Short circuit type comparisons of type refs when eta-expansion is futile · scala/scala@babf510 · GitHub
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Short circuit type comparisons of type refs when eta-expansion is futile
If the initial comparison of a pair of higher kinded type refs yield false, there is no point eta expanding them both to poly types to repeat the comparison (in an more expensive fashion!)
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lines changed

2 files changed

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‎src/reflect/scala/reflect/internal/Symbols.scala

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -3067,7 +3067,7 @@ trait Symbols extends api.Symbols { self: SymbolTable =>
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override def tpeHK: Type = typeConstructor
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private def tyconCacheNeedsUpdate = (tyconCache eq null) || tyconRunId != currentRunId
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private def setTyconCache(tycon: Type) {
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private[Symbols] def setTyconCache(tycon: Type) {
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tyconCache = tycon
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tyconRunId = currentRunId
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assert(tyconCache ne null, this)

‎src/reflect/scala/reflect/internal/tpe/TypeComparers.scala

Lines changed: 14 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -180,7 +180,11 @@ trait TypeComparers {
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!settings.isScala211 || methodHigherOrderTypeParamsSameVariance(low, high) || low.variance.isInvariant
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def isSameType2(tp1: Type, tp2: Type): Boolean = {
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def retry(lhs: Type, rhs: Type) = ((lhs ne tp1) || (rhs ne tp2)) && isSameType(lhs, rhs)
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def retry(lhs: Type, rhs: Type) = ((lhs ne tp1) || (rhs ne tp2)) && {
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def sameSyms(tp1: Type, tp2: Type) = tp1.typeSymbolDirect eq tp2.typeSymbolDirect
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val skipRetry = lhs.isInstanceOf[PolyType] && rhs.isInstanceOf[PolyType] && sameSyms(tp1, lhs) && sameSyms(tp2, rhs)
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!skipRetry && isSameType(lhs, rhs)
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}
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/* Here we highlight those unfortunate type-like constructs which
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* are hidden bundles of mutable state, cruising the type system picking
@@ -360,10 +364,18 @@ trait TypeComparers {
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devWarning(s"HK subtype check on $tp1 and $tp2, but both don't normalize to polytypes:\n tp1=${tp_s(ntp1)}\n tp2=${tp_s(ntp2)}")
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false
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}
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def isTrivialTypeRef(tp: Type) = tp match {
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case TypeRef(pre, sym, Nil) if pre.isTrivial && !sym.isAliasType => true
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case _ => false
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}
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( (tp1.typeSymbol eq NothingClass) // @M Nothing is subtype of every well-kinded type
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|| (tp2.typeSymbol eq AnyClass) // @M Any is supertype of every well-kinded type (@PP: is it? What about continuations plugin?)
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|| isSub(tp1.normalize, tp2.normalize) && annotationsConform(tp1, tp2) // @M! normalize reduces higher-kinded case to PolyType's
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|| (if (isTrivialTypeRef(tp1) && isTrivialTypeRef(tp2)) {
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tp1.typeSymbolDirect.isNonBottomSubClass(tp2.typeSymbolDirect) // OPT faster than comparing eta-expanded types
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} else
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isSub(tp1.normalize, tp2.normalize) && annotationsConform(tp1, tp2) // @M! normalize reduces higher-kinded case to PolyType's
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)
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)
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}
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