Merge pull request #334 from olhotak/pr-annotatedtypevars

fix TypeMap.mapOver to not drop type annotations

Author: DarkDimius

src/dotty/tools/dotc/core/Types.scala

@@ -2727,7 +2727,7 @@ object Types {
 
         case tp @ AnnotatedType(annot, underlying) =>
           val underlying1 = this(underlying)
-          if (underlying1 eq underlying) tp else underlying1
+          if (underlying1 eq underlying) tp else tp.derivedAnnotatedType(mapOver(annot), underlying1)
 
         case tp @ WildcardType =>
           tp.derivedWildcardType(mapOver(tp.optBounds))

src/dotty/tools/dotc/typer/Inferencing.scala

@@ -99,6 +99,7 @@ trait Inferencing { this: Checking =>
   /** Recursively widen and also follow type declarations and type aliases. */
   def widenForMatchSelector(tp: Type)(implicit ctx: Context): Type = tp.widen match {
     case tp: TypeRef if !tp.symbol.isClass => widenForMatchSelector(tp.info.bounds.hi)
+    case tp: AnnotatedType => tp.derivedAnnotatedType(tp.annot, widenForMatchSelector(tp.tpe))
     case tp => tp
   }