AppState appReducer(AppState state, action) => AppState(toDoListReducer(state.toDos, action), listStateReducer(state.listState, action));

final Reducer<List<ToDoItem>> toDoListReducer = // Boilerplate ignored
final Reducer<ListState> listStateReducer = combineReducers<ListState>([
  TypedReducer<ListState, DisplayListOnlyAction>(_displayListOnly),
  TypedReducer<ListState, DisplayListWithNewItemAction>(_displayListWithNewItem),
]);

ListState _displayListOnly(ListState listState, DisplayListOnlyAction action) => ListState.listOnly;

ListState _displayListWithNewItem(ListState listState, DisplayListWithNewItemAction action) => ListState.listWithNewItem;