anchor.diff:      for (var superclass in superclasses.reversed) {
         _breadHelper(superclass);
       }
  +    for (var interface in interfaces) {
  +      _breadHelper(interface);
  +    }
     }
   
     /** Returns all superclasses of this class. */
  
positive.code:   for (var library in libraries.values) {
      library.invalidate();
    }
    var library = new LibraryElement(json.parse(data), null);
    libraries[library.id] = library;
  }
  
  void loadPackageJson(String data) {
  
negative.code:   }
  
    /** Returns all interfaces implemented by this class. */
    List<ClassElement> get interfaces {
      if (_interfaces == null) {
        final allInterfaces = new Set<ClassElement>();
        final superclassSet = superclasses.toSet();
       
        addInterface(ClassElement ref) {
          if (!superclassSet.contains(ref)) {
            allInterfaces.add(ref);
          }
        }
        addInterfaces(Iterable<ClassElement> refs) {
          for(var ref in refs) {
            addInterface(ref);
          }
  