Cannot generate mock for a class that extends GetxController

[jimbengtsson92]

When generating a mock for a class that extends GetxController, the generated file contains the following error:

'MockTestControllerToMock.addListener' ('void Function(void Function()?)') isn't a valid override of 'ListNotifierMixin.addListener' ('void Function() Function(void Function())')

Minimal GitHub repo that shows the error.

[srawlins]

Here's the type hierarchy:

class Listenable {
  void addListener(VoidCallback listener) { /*...*/ }
}

mixin ListenableMixin implements Listenable {}
mixin ListNotifierMixin on ListenableMixin {
  @override
  Disposer addListener(GetStateUpdate listener) { /*...*/ }
}

abstract class GetxController extends DisposableInterface
    with ListenableMixin, ListNotifierMixin { /*...*/ }

Mockito appears to be going for the overridden signature, instead of the proper signature.