Change underlying to superType in TypeEval

Author: odersky

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

@@ -18,7 +18,9 @@ object TypeEval:
           // final val one = 1
           // type Two = one.type + one.type
           // ```
-          case tp: TypeProxy if tp.underlying.isStable => tp.underlying.fixForEvaluation
+          case tp: TypeProxy =>
+            val tp1 = tp.superType
+            if tp1.isStable then tp1.fixForEvaluation else tp
           case tp => tp
 
       def constValue(tp: Type): Option[Any] = tp.fixForEvaluation match

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

@@ -33,7 +33,7 @@ trait Deriving {
       case tp: TypeRef if tp.symbol.isClass => tp
       case tp: TypeRef if tp.symbol.isAbstractType => NoType
       case tp: TermRef => NoType
-      case tp: TypeProxy => underlyingClassRef(tp.underlying)
+      case tp: TypeProxy => underlyingClassRef(tp.superType)
       case _ => NoType
     }