Merge pull request #4844 from Medowhill/issue4653

Fix #4653: check method return type is value type

Author: liufengyun

compiler/src/dotty/tools/dotc/typer/Namer.scala

@@ -1153,7 +1153,7 @@ class Namer { typer: Typer =>
       case _ =>
         WildcardType
     }
-    paramFn(typedAheadType(mdef.tpt, tptProto).tpe)
+    paramFn(checkSimpleKinded(typedAheadType(mdef.tpt, tptProto)).tpe)
   }
 
   /** The type signature of a DefDef with given symbol */

tests/neg/i4653.scala

@@ -0,0 +1,14 @@
+trait T {
+  type S
+}
+
+class C {
+  class D[X](val t: T) {
+     def bar: t.S = ???
+  }
+
+  def fooD: D = ??? // error
+  fooD.bar
+
+  def f(fooV: => D): Any = fooV.bar // error
+}