anchor.diff:              listener(key, widget);
           }
         }
  -
         for (GlobalKey key in _removedKeys) {
           if (!_registry.containsKey(key) && _removeListeners.containsKey(key)) {
             Set<GlobalKeyRemoveListener> localListeners = new Set<GlobalKeyRemoveListener>.from(_removeListeners[key]);
  
positive.code:     if (_syncedKeys.isEmpty && _removedKeys.isEmpty)
        return;
      try {
  
        for (GlobalKey key in _syncedKeys) {
          Widget widget = _registry[key];
          if (widget != null && _syncListeners.containsKey(key)) {
  
negative.code:     _scheduleBuild();
    }
  
    void debugAddDetails(List<String> details) {
      super.debugAddDetails(details);
      details.add(_isStateInitialized ? 'stateful' : 'stateless');
    }
  }
  
  