Implement operator-is for interfaces' supertypes and String's supertypes. Also, improve stack trace…

dart/frog/leg/resolver.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.
 
 interface TreeElements {
   Element operator[](Node node);
   Selector getSelector(Send send);
 }
 
 class TreeElementMapping implements TreeElements {
@@ skipping 245 matching lines @@
       Link<Type> superSupertypes =
         getOrCalculateAllSupertypes(supertype.element, seen);
       Link<Type> supertypes = new Link<Type>(supertype, superSupertypes);
       for (Link<Type> interfaces = classElement.interfaces;
            !interfaces.isEmpty();
            interfaces = interfaces.tail) {
         Element element = interfaces.head.element;
         Link<Type> interfaceSupertypes =
             getOrCalculateAllSupertypes(element, seen);
         supertypes = supertypes.reversePrependAll(interfaceSupertypes);
+        supertypes = supertypes.prepend(interfaces.head);
       }
       seen.remove(classElement);
       classElement.allSupertypes = supertypes;
     } else {
       classElement.allSupertypes = const EmptyLink<Type>();
     }
   }
 
   error(Node node, MessageKind kind, [arguments = const []]) {
     ResolutionError message = new ResolutionError(kind, arguments);
@@ skipping 1149 matching lines @@
 class TopScope extends Scope {
   LibraryElement get library() => element;
 
   TopScope(LibraryElement library) : super(null, library);
   Element lookup(SourceString name) => library.find(name);
 
   Element add(Element element) {
     throw "Cannot add an element in the top scope";
   }
 }