Fix regression in TypeComparer

So we could not delete the two lines that never returned a result. It turns out
they were necessary for their effect on the constraint. If they are removed, i3422.scala fails.

Author: odersky

compiler/src/dotty/tools/dotc/core/TypeComparer.scala

@@ -379,6 +379,8 @@ class TypeComparer(initctx: Context) extends DotClass with ConstraintHandling {
         if (cls2.isClass) {
           if (cls2 eq AnyKindClass)
             return true
+          else if (cls2.typeParams.nonEmpty && tp1.isHK)
+            return recur(tp1, EtaExpansion(cls2.typeRef))
           else {
             val base = tp1.baseType(cls2)
             if (base.exists) {