A hacky way to create Dart enum's with associated values

LoadingState.dart

// Models an enum with three mutually exclusive states:
//  - loading
//  - success (with an object of some type)
//  - error (with an Error object)

abstract class LoadingStatus<T> {
  static const loading = const LoadingStatusLoading();
  factory LoadingStatus.success(T object) = LoadingStatusSuccess;
  factory LoadingStatus.error(Error error) = LoadingStatusError;
}

class LoadingStatusLoading implements LoadingStatus {
  const LoadingStatusLoading();
}

class LoadingStatusSuccess<T> implements LoadingStatus<T> {
  final T object;
  const LoadingStatusSuccess(this.object);
}

class LoadingStatusError<T> implements LoadingStatus<T> {
  final Error error;

  LoadingStatusError(this.error);
}