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Fix bounds of match type cases #14645

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Merged
merged 2 commits into from
Mar 28, 2022
Merged

Fix bounds of match type cases #14645

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3a00dc5
When assigning type cases, substitute any instances of type parameter…
dwijnand Mar 8, 2022
81cc6f1
Use substSym instead of mutating symbols
dwijnand Mar 8, 2022
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12 changes: 8 additions & 4 deletions compiler/src/dotty/tools/dotc/typer/TypeAssigner.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -401,15 +401,19 @@ trait TypeAssigner {
def assignType(tree: untpd.CaseDef, pat: Tree, body: Tree)(using Context): CaseDef = {
val ownType =
if (body.isType) {
val params = new TreeAccumulator[mutable.ListBuffer[TypeSymbol]] {
val getParams = new TreeAccumulator[mutable.ListBuffer[TypeSymbol]] {
def apply(ps: mutable.ListBuffer[TypeSymbol], t: Tree)(using Context) = t match {
case t: Bind if t.symbol.isType => foldOver(ps += t.symbol.asType, t)
case _ => foldOver(ps, t)
}
}
HKTypeLambda.fromParams(
params(new mutable.ListBuffer[TypeSymbol](), pat).toList,
defn.MatchCase(pat.tpe, body.tpe))
val params = getParams(new mutable.ListBuffer[TypeSymbol](), pat).toList
pat.tpe match
case AppliedType(tycon, args) =>
val tparams = tycon.typeParamSymbols
for param <- params do param.info = param.info.subst(tparams, args)
case _ =>
HKTypeLambda.fromParams(params, defn.MatchCase(pat.tpe, body.tpe))
}
else body.tpe
tree.withType(ownType)
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13 changes: 0 additions & 13 deletions tests/neg/6697.check
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This file was deleted.

0 tests/neg/6697.scala → tests/pos/6697.scala
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9 changes: 9 additions & 0 deletions tests/pos/i14477.scala
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Original file line number Diff line number Diff line change
@@ -0,0 +1,9 @@
sealed trait Foo[A, X <: A]

type FooX[F] = F match {
case Foo[a, x] => x
}

type MyFoo = Foo[String, "hello"]

val hello: FooX[MyFoo] = "hello"