Black magic to make cps-async compile

Author: odersky

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

@@ -489,10 +489,18 @@ object Denotations {
               || sym1.is(Method) && !sym2.is(Method)
               || sym1.info.isErroneous)
 
-          if preferMethod(sym1, sym2) then denot1
+          if sym1 eq sym2 then denot2
+            // black magic to make cps-async compile. The problem lies elsewhere: the compiler
+            // is not able to identify two types that should be the same. In
+            //
+            // trait ApplyTreeTransform[F[_],CT]:
+            //   thisTreeTransform: TreeTransformScope[F,CT] =>
+            // It does not see that the `F` instances in `ApplyTreeTransform` and `TreeTransformScope`
+            // are the same. It's actually not clear to me that they should be regarded as the same.
+          else if preferMethod(sym1, sym2) then denot1
           else if preferMethod(sym2, sym1) then denot2
           else
-            overload.println(i"overloaded with same signature: ${sym1.showLocated}: $info1 / ${sym2.showLocated}: $info2")
+            println(i"overloaded with same signature: ${sym1.showLocated}: $info1 / ${sym2.showLocated}: $info2")
             MultiDenotation(denot1, denot2)
         end handleConflict