Merge pull request #2228 from dotty-staging/fix-#2218

Fix #2218: Add fullyDefinedType for class parent types

Author: odersky

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

@@ -843,7 +843,7 @@ class Namer { typer: Typer =>
           val targs1 = targs map (typedAheadType(_))
           val ptype = typedAheadType(tpt).tpe appliedTo targs1.tpes
           if (ptype.typeParams.isEmpty) ptype
-          else typedAheadExpr(parent).tpe
+          else fullyDefinedType(typedAheadExpr(parent).tpe, "class parent", parent.pos)
         }
 
       /* Check parent type tree `parent` for the following well-formedness conditions:

tests/pos/i2218.scala

@@ -0,0 +1,9 @@
+trait Rule[In]
+
+class C {
+  def ruleWithName[In](f: In => Int): Rule[In] = {
+     new DefaultRule(f) {}
+  }
+
+  class DefaultRule[In](f: In => Int) extends Rule[In]
+}