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Check variance of RHS of opaque type #14058

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Merged
merged 1 commit into from
Dec 7, 2021
Merged

Check variance of RHS of opaque type #14058

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2 changes: 2 additions & 0 deletions compiler/src/dotty/tools/dotc/transform/PostTyper.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -378,6 +378,8 @@ class PostTyper extends MacroTransform with IdentityDenotTransformer { thisPhase
else (tree.rhs, sym.info) match
case (rhs: LambdaTypeTree, bounds: TypeBounds) =>
VarianceChecker.checkLambda(rhs, bounds)
if sym.isOpaqueAlias then
VarianceChecker.checkLambda(rhs, TypeBounds.upper(sym.opaqueAlias))
case _ =>
processMemberDef(super.transform(tree))
case tree: New if isCheckable(tree) =>
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10 changes: 10 additions & 0 deletions tests/neg/i13997.scala
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Original file line number Diff line number Diff line change
@@ -0,0 +1,10 @@
opaque type CovariantArray[+A] = Array[A] // error

object CovariantArray:
def crash() =
val stringArray: CovariantArray[String] = Array("foo", "bar")
val anyArray: CovariantArray[Any] = stringArray
anyArray(0) = 42
stringArray(0).length

@main def Test = CovariantArray.crash()