Cleanup of RefinedType subtype comparison.

Author: odersky

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

@@ -338,25 +338,23 @@ class TypeComparer(initctx: Context) extends DotClass with ConstraintHandling {
         isSubType(tp1, tp2.parent) &&
           (name2 == nme.WILDCARD || hasMatchingMember(name2, tp1, tp2))
       }
+      def etaExpandedSubType(tp1: Type) =
+        isSubType(tp1.typeConstructor.EtaExpand(tp2.typeParams), tp2)
       def compareRefined: Boolean = {
         val tp1w = tp1.widen
         val skipped2 = skipMatching(tp1w, tp2)
-        if ((skipped2 eq tp2) || !Config.fastPathForRefinedSubtype) {
-          val normalPath = tp1 match {
+        if ((skipped2 eq tp2) || !Config.fastPathForRefinedSubtype)
+          tp1 match {
             case tp1: AndType =>
               // Delay calling `compareRefinedSlow` because looking up a member
               // of an `AndType` can lead to a cascade of subtyping checks
               // This twist is needed to make collection/generic/ParFactory.scala compile
               fourthTry(tp1, tp2) || compareRefinedSlow
             case _ =>
-              compareRefinedSlow || fourthTry(tp1, tp2)
+              compareRefinedSlow ||
+              fourthTry(tp1, tp2) ||
+              needsEtaLift(tp1, tp2) && testLifted(tp1, tp2, tp2.typeParams, etaExpandedSubType)
           }
-          def etaExpandedSubType(tp1: Type) =
-            isSubType(tp1.typeConstructor.EtaExpand(tp2.typeParams), tp2)
-          normalPath ||
-            needsEtaLift(tp1, tp2) &&
-            testLifted(tp1, tp2, tp2.typeParams, etaExpandedSubType)
-        }
         else // fast path, in particular for refinements resulting from parameterization.
           isSubType(tp1, skipped2) &&
           isSubRefinements(tp1w.asInstanceOf[RefinedType], tp2, skipped2)