anchor.diff:  
     @override
     String toString() => '[${_value.runtimeType}(${_value.hashCode})]';
  -}
  +}
positive.code: }
  
  /// State for a [StoreWatcher] widget.
  class StoreWatcherState extends State<StoreWatcher>
      with StoreWatcherMixin<StoreWatcher> {
    // If you get these errors from the analyzer, then you need to add a file
    // analysis_options.yaml like you find in the root of this repo.
    // [error] The class 'StoreWatcherMixin' cannot be used as a mixin because it
    // extends a class other than Object.
    // [error] The class 'StoreWatcherMixin' cannot be used as a mixin because it
    // references 'super'
  
    final Map<StoreToken, Store> _storeTokens = <StoreToken, Store>{};
  
  
negative.code:   @protected
    Store listenToStore(StoreToken token, [ValueChanged<Store> onStoreChanged]) {
      final Store store = token._value;
      _streamSubscriptions[store] = store.listen(onStoreChanged ?? _handleStoreChanged);
      return store;
    }
  
  