anchor.diff:      List<Middleware<T>> middleware,
     })  : assert(preloadedState != null,
               'Expected the preloadedState to be non-null value.'),
  -        assert(pages != null, 'Expected the slots to be non-null value.'),
  +        assert(pages != null, 'Expected the pages to be non-null value.'),
           _store = createPageStore<T>(
             preloadedState,
             _createReducer<T>(pages, reducer),
  
positive.code:   }
  
    static Reducer<T> _createReducer<T>(
        Map<String, Dependent<T>> slots, Reducer<T> reducer) {
      final Map<String, SubReducer<T>> subReducerMap = slots.map((String path,
              Dependent<T> dependent) =>
          MapEntry<String, SubReducer<T>>(path, dependent.createSubReducer()));
  
  
negative.code: ///             AppRoutes<T>(
  ///               preloadedState: T(),
  ///               middleware:[],
  ///               pages: {
  ///                 'message': MsgConn() + MessageComponent(),
  ///                 'personal': PersonalConn() + PersonalComponent(),
  ///               },
  