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Defend against AliasingBounds #23668

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Defend against AliasingBounds #23668

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8d36681
test
som-snytt Aug 5, 2025
36dba58
Defend against AliasingBounds
som-snytt Aug 5, 2025
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4 changes: 3 additions & 1 deletion compiler/src/dotty/tools/dotc/typer/RefChecks.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -1166,7 +1166,9 @@ object RefChecks {
def targetOfHiddenExtension: Symbol =
val target =
val target0 = explicitInfo.firstParamTypes.head // required for extension method, the putative receiver
target0.dealiasKeepOpaques.typeSymbol.info
target0.dealiasKeepOpaques.typeSymbol.info match
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This is kind of weird since dealias does skip aliasing bounds. It would be good to get an explanation what exactly goes wrong here. What's the type of target0.dealiasKeepOpaques in the failing test? What is its info? Is there an opaque type involved?

case tb: AliasingBounds => tb.alias
case tp => tp
val member = target.nonPrivateMember(sym.name)
.filterWithPredicate: member =>
member.symbol.isPublic && memberHidesMethod(member)
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14 changes: 14 additions & 0 deletions tests/pos/i23666.scala
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@@ -0,0 +1,14 @@

type Tuple = scala.Tuple
type Any = scala.Any

infix type =:= [A, B] = A => B

object `=:=` :
given [A] => A =:= A = a => a

extension [T <: Tuple] (tuple: T)

def reverse[A, B](using ev: T =:= (A, B)): (B, A) =
val ab = ev(tuple)
(ab._2, ab._1)
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