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Add PF selector cast only after checking bound #11160

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Add PF selector cast only after checking bound #11160

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29 changes: 19 additions & 10 deletions src/compiler/scala/tools/nsc/typechecker/Typers.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -2790,21 +2790,30 @@ trait Typers extends Adaptations with Tags with TypersTracking with PatternTyper
val casesTrue = cases.map(deriveCaseDef(_)(x => atPos(x.pos.focus)(TRUE)).duplicate)

// must generate a new tree every time
def selector(paramSym: Symbol): Tree = gen.mkUnchecked(
def selector(paramSym: Symbol): Tree = gen.mkUnchecked {
if (sel != EmptyTree) sel.duplicate
else atPos(tree.pos.focusStart)(
else if (paramSym.info.upperBound =:= argTp)
atPos(tree.pos.focusStart) {
Typed(Ident(paramSym), TypeTree(argTp))
}
else
// scala/bug#6925: subsume type of the selector to `argTp`
// we don't want/need the match to see the `A1` type that we must use for variance reasons in the method signature
// we don't want/need the match to see the `A1` type that we must use
// for variance reasons in the method signature
//
// this failed: replace `selector` by `Typed(selector, TypeTree(argTp))` -- as it's an upcast, this should never fail,
// `(x: A1): A` doesn't always type check, even though `A1 <: A`, due to singleton types (test/files/pos/t4269.scala)
// this failed:
// replace `selector` by `Typed(selector, TypeTree(argTp))` -- as it's an upcast, this should never fail,
// `(x: A1): A` doesn't always type check, even though `A1 <: A`,
// due to singleton types (test/files/pos/t4269.scala)
// hence the cast, which will be erased in posterasure
// (the cast originally caused extremely weird types to show up
// in test/scaladoc/run/scala/bug#5933.scala because `variantToSkolem` was missing `tpSym.initialize`)
gen.mkCastPreservingAnnotations(Ident(paramSym), argTp)
))
atPos(tree.pos.focusStart) {
gen.mkCastPreservingAnnotations(Ident(paramSym), argTp)
}
}

def mkParam(methodSym: Symbol, tp: Type = argTp) =
def mkParam(methodSym: Symbol, tp: Type) =
methodSym.newValueParameter(paramName, paramPos.focus, SYNTHETIC) setInfo tp

def mkDefaultCase(body: Tree) =
Expand Down Expand Up @@ -2911,7 +2920,7 @@ trait Typers extends Adaptations with Tags with TypersTracking with PatternTyper
// `def isDefinedAt(x: $argTp): Boolean = ${`$selector match { $casesTrue; case default$ => false } }`
def isDefinedAtMethod = {
val methodSym = anonClass.newMethod(nme.isDefinedAt, tree.pos.makeTransparent, FINAL)
val paramSym = mkParam(methodSym)
val paramSym = mkParam(methodSym, argTp)

val methodBodyTyper = synthMethodTyper(methodSym) // should use the DefDef for the context's tree, but it doesn't exist yet (we need the typer we're creating to create it)
if (!paramSynthetic) methodBodyTyper.context.scope enter paramSym
Expand All @@ -2927,7 +2936,7 @@ trait Typers extends Adaptations with Tags with TypersTracking with PatternTyper
// `def apply(x: $argTp): $matchResTp = $selector match { $cases }`
def applyMethod = {
val methodSym = anonClass.newMethod(nme.apply, tree.pos, FINAL | OVERRIDE)
val paramSym = mkParam(methodSym)
val paramSym = mkParam(methodSym, argTp)

methodSym setInfo MethodType(List(paramSym), AnyTpe)

Expand Down
6 changes: 6 additions & 0 deletions test/files/pos/t13134.scala
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@@ -0,0 +1,6 @@
//> using options -Werror -Xlint

object Main {
def callFunction(function: PartialFunction[Unit, Unit]): Unit = function(???)
def main(arguments: Array[String]): Unit = callFunction { _ => }
}