Also handle refinements in joins with AndTypes

Author: odersky

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

@@ -198,23 +198,26 @@ trait TypeOps { this: Context => // TODO: Make standalone object.
 
     def mergeRefinedOrApplied(tp1: Type, tp2: Type): Type = {
       def fail = throw new AssertionError(i"Failure to join alternatives $tp1 and $tp2")
+      def fallback = tp2 match
+        case AndType(tp21, tp22) =>
+          mergeRefinedOrApplied(tp1, tp21) & mergeRefinedOrApplied(tp1, tp22)
+        case _ =>
+          fail
       tp1 match {
         case tp1 @ RefinedType(parent1, name1, rinfo1) =>
           tp2 match {
             case RefinedType(parent2, `name1`, rinfo2) =>
               tp1.derivedRefinedType(
                 mergeRefinedOrApplied(parent1, parent2), name1, rinfo1 | rinfo2)
-            case _ => fail
+            case _ => fallback
           }
         case tp1 @ AppliedType(tycon1, args1) =>
           tp2 match {
             case AppliedType(tycon2, args2) =>
               tp1.derivedAppliedType(
                 mergeRefinedOrApplied(tycon1, tycon2),
                 ctx.typeComparer.lubArgs(args1, args2, tycon1.typeParams))
-            case AndType(tp21, tp22) =>
-              mergeRefinedOrApplied(tp1, tp21) & mergeRefinedOrApplied(tp1, tp22)
-            case _ => fail
+            case _ => fallback
           }
         case tp1 @ TypeRef(pre1, _) =>
           tp2 match {