Replace wildcard types by TypeVars in decomposeProto

odersky · odersky · commit 4cf3a1a5a161 · 2019-10-09T14:46:08.000+02:00
Approximating wildcard types loses too much information. it's better
to replace them by fresh typevars instead.
diff --git a/compiler/src/dotty/tools/dotc/typer/Typer.scala b/compiler/src/dotty/tools/dotc/typer/Typer.scala
@@ -833,10 +833,10 @@ class Typer extends Namer
       case _: WildcardType => untpd.TypeTree()
       case _ => untpd.TypeTree(tp)
     }
-    def interpolateWildcards = new ApproximatingTypeMap {
+    def interpolateWildcards = new TypeMap {
       def apply(t: Type) = t match
-        case WildcardType => emptyRange
-        case WildcardType(bounds: TypeBounds) => range(bounds.lo, bounds.hi)
+        case WildcardType => newTypeVar(TypeBounds.empty)
+        case WildcardType(bounds: TypeBounds) => newTypeVar(bounds)
         case _ => mapOver(t)
     }
     pt.stripTypeVar.dealias match {

Original file line number	Diff line number	Diff line change
`@@ -833,10 +833,10 @@ class Typer extends Namer`
`833`	`833`	`case _: WildcardType => untpd.TypeTree()`
`834`	`834`	`case _ => untpd.TypeTree(tp)`
`835`	`835`	`}`
`836`		`- def interpolateWildcards = new ApproximatingTypeMap {`
	`836`	`+ def interpolateWildcards = new TypeMap {`
`837`	`837`	`def apply(t: Type) = t match`
`838`		`- case WildcardType => emptyRange`
`839`		`- case WildcardType(bounds: TypeBounds) => range(bounds.lo, bounds.hi)`
	`838`	`+ case WildcardType => newTypeVar(TypeBounds.empty)`
	`839`	`+ case WildcardType(bounds: TypeBounds) => newTypeVar(bounds)`
`840`	`840`	`case _ => mapOver(t)`
`841`	`841`	`}`
`842`	`842`	`pt.stripTypeVar.dealias match {`