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