dart_generics_issue.dart

dart_generics_issue.dart

mixin IModel {
  int get field1;
}

mixin IWidget<Model extends IModel> {
  ///
  Model get model;
}

mixin IState<W extends IWidget<M>, M extends IModel> {
  W get widget;

  // Access to model
  M get model => widget.model;

  void someMethod() {
    assert(model.field1 != null);
    print(model.runtimeType);
  }
}

class MyModel with IModel {
  @override
  int field1 = 42;
}

class MyWidget with IWidget<MyModel> {
  @override
  final MyModel model;

  MyWidget(this.model);
}

class MyState with IState<MyWidget, MyModel> {
  MyState(this.widget);

  @override
  final MyWidget widget;
}

class IStateConsumer<M extends IModel, W extends IWidget<M>,
    State extends IState<W, M>> {
  IStateConsumer(this.state);
  final State state;
}

void main() {
  final consumer = IStateConsumer(MyState(MyWidget(MyModel())));

  /// Works
  if (consumer is! IStateConsumer) print('fails for no type parameters');

  /// Works
  if (consumer is! IStateConsumer<IModel, IWidget, MyState>)
    print('fails when type parameters are  incomplete');

  /// Prints  IStateConsumer<IModel, IWidget, MyState>
  print(consumer.runtimeType);

  /// Fails
  if (consumer is! IStateConsumer<MyModel, MyWidget, MyState>)
    print('fails when all type parameters are specific');

  /// Works
  final IStateConsumer<MyModel, MyWidget, MyState> implicitTypeParameters =
      IStateConsumer(MyState(MyWidget(MyModel())));

  /// Prints IStateConsumer<MyModel, MyWidget, MyState>
  print(implicitTypeParameters.runtimeType);
}