Avoid testing with eq

Author: odersky

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

@@ -344,7 +344,8 @@ object TypeOps:
     tp match {
       case tp: OrType =>
         (tp.tp1.dealias, tp.tp2.dealias) match
-          case (tp1 @ AppliedType(tycon1, args1), tp2 @ AppliedType(tycon2, args2)) if tycon1 eq tycon2 =>
+          case (tp1 @ AppliedType(tycon1, args1), tp2 @ AppliedType(tycon2, args2))
+          if tycon1.typeSymbol == tycon2.typeSymbol && (tycon1 =:= tycon2) =>
             mergeRefinedOrApplied(tp1, tp2)
           case (tp1, tp2) =>
             approximateOr(tp1, tp2)