anchor.diff:        }
       }
   
  -    _initialize2(_infoFor.keys, 0);
  +    _initializeTopologicallySortedClasses(_infoFor.keys, 0);
     }
   
     /// - Build index of direct children.
  
positive.code:   void forEachOverridePair(Class class_,
        callback(Member declaredMember, Member interfaceMember, bool isSetter));
  
    /// This method is invoked by the client after a change: removal, adding, or
    /// modified classes. For modified classes specify a class as both removed and
    /// added: Some of the information that this hierarchy might have cached,
    /// is not valid anymore.
    /// Note, that it is the clients responsibility to mark all subclasses as
    /// changed too.
    ClassHierarchy applyTreeChanges(
  
negative.code:       for (var supertype in class_.implementedTypes) {
          _infoFor[supertype.classNode].directImplementers.add(info);
        }
        _collectSupersForClass(class_);
  
        if (class_.supertype != null) {
          _recordSuperTypes(info, class_.supertype);
  