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Fix #7392: Interpolate all wildcards in the resulttype of a closure #7396

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Merged
merged 3 commits into from
Oct 10, 2019
Merged

Fix #7392: Interpolate all wildcards in the resulttype of a closure #7396

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35b05c5
Fix #7392: Interpolate all wildcards in the result prototype of a clo…
odersky Oct 9, 2019
4cf3a1a
Replace wildcard types by TypeVars in decomposeProto
odersky Oct 9, 2019
4800aec
Recursively interpolate bounds in interpolateWildcards
odersky Oct 9, 2019
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9 changes: 7 additions & 2 deletions compiler/src/dotty/tools/dotc/typer/Typer.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -833,12 +833,18 @@ class Typer extends Namer
case _: WildcardType => untpd.TypeTree()
case _ => untpd.TypeTree(tp)
}
def interpolateWildcards = new TypeMap {
def apply(t: Type) = t match
case WildcardType => newTypeVar(TypeBounds.empty)
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newTypeVar will call constrained(poly, untpd.EmptyTree, ...) but we do actually have an owning tree that we could use here I think.

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It does not actually change anything. We need an owning tree only to set the position of a TypeVarBinder tree. But in this case we throw the TypeVarBinder away anyway and just keep the type.

case WildcardType(bounds: TypeBounds) => newTypeVar(bounds)
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Could there be WildcardTypes in the bounds themselves that need to be replaced recursively ?

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Maybe. Better to be on the safe side.

case _ => mapOver(t)
}
pt.stripTypeVar.dealias match {
case pt1 if defn.isNonRefinedFunction(pt1) =>
// if expected parameter type(s) are wildcards, approximate from below.
// if expected result type is a wildcard, approximate from above.
// this can type the greatest set of admissible closures.
(pt1.argTypesLo.init, typeTree(pt1.argTypesHi.last))
(pt1.argTypesLo.init, typeTree(interpolateWildcards(pt1.argTypesHi.last)))
case SAMType(sam @ MethodTpe(_, formals, restpe)) =>
(formals,
if (sam.isResultDependent)
Expand Down Expand Up @@ -1900,7 +1906,6 @@ class Typer extends Namer
else tree1
}


def typedAsFunction(tree: untpd.PostfixOp, pt: Type)(implicit ctx: Context): Tree = {
val untpd.PostfixOp(qual, Ident(nme.WILDCARD)) = tree
val pt1 = if (defn.isFunctionType(pt)) pt else AnyFunctionProto
Expand Down
16 changes: 16 additions & 0 deletions tests/pos/i7392.scala
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@@ -0,0 +1,16 @@
object Test {

trait ZStream[-R, +E, +A]

object ZStream {
def empty: ZStream[Any, Nothing, Nothing] =
???
}

trait Gen[-R, +A](sample: ZStream[R, Nothing, A])

def fromIterable[R, A](
as: Iterable[A],
shrinker: (A => ZStream[R, Nothing, A]) = (_: A) => ZStream.empty
): Gen[R, A] = ???
}