anchor.diff:        }
       }
   
  -    _initialize2(_infoFor.keys, 0);
  +    _initializeTopologicallySortedClasses(_infoFor.keys, 0);
     }
   
     /// - Build index of direct children.
  
positive.code:       for (var supertype in class_.implementedTypes) {
          _infoFor[supertype.classNode].directImplementers.add(info);
        }
        _topDownVisitClass(class_);
  
        if (class_.supertype != null) {
          _recordSuperTypes(info, class_.supertype);
  
negative.code:     }
    }
  
    /// Build lists of super types and super classes.
    /// Note that the super class and super types of the class must already have
    /// had their supers collected.
    void _collectSupersForClass(Class class_) {
      _ClassInfo info = _infoFor[class_];
  
      var superclassSetBuilder = new _IntervalListBuilder()
  