Prepare for computation of NewStructure in Resolution.

pkg/compiler/lib/src/resolution/class_members.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library dart2js.resolution.compute_members;
 
 import '../common/names.dart' show
     Identifiers;
 import '../compiler.dart' show
     Compiler;
@@ skipping 359 matching lines @@
         }
       }
 
       DartType declaredType = declared.functionType;
       for (Member inherited in superMember.declarations) {
         if (inherited.element == declared.element) {
           // TODO(ahe): For some reason, "call" elements are repeated in
           // superMember.declarations. Investigate why.
         } else if (cls == inherited.declarer.element) {
           // An error should already have been reported.
-          assert(invariant(declared.element, compiler.compilationFailed));
+          assert(invariant(declared.element, compiler.compilationFailed,
+              message: "Member $inherited inherited from its "
+                       "declaring class: ${cls}."));
           continue;
         }
 
         void reportError(MessageKind errorKind, MessageKind infoKind) {
           reportMessage(
               inherited.element, MessageKind.INVALID_OVERRIDE_METHOD, () {
             compiler.reportError(declared.element, errorKind,
                 {'name': declared.name.text,
                  'class': cls.thisType,
                  'inheritedClass': inherited.declarer});
@@ skipping 517 matching lines @@
         message: "Members have not been fully computed for $this."));
     if (interfaceMembersAreClassMembers) {
       classMembers.forEach((_, member) {
         if (!member.isStatic) f(member);
       });
     } else {
       interfaceMembers.forEach((_, member) => f(member));
     }
   }
 }