根据这个注解，冻结不支持超类。最接近的解决方案，可能为您工作是这样的：

// create mixin with getter of properties that you would like to share between states
mixin TodoMixin {
  List<Todo> get todos;
}

@freezed
// add mixin to your class with state
class TodoState with TodoMixin, _$TodoState {
  const TodoState._(); // add private constructor

  //override getter with map function that will return data for each state
  @override
  List<Todo> get todos {
    return map(
      loading: (state) => state.todos,
      loaded: (state) => state.todos,
      error: (state) => state.todos,
    );
  }

  const factory TodoState.loading(List<Todo> todos) = TodoStateLoading;
  const factory TodoState.loaded(List<Todo> todos) = TodoStateLoaded;
  const factory TodoState.error(List<Todo> todos, String message) = TodoStateError;
}

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它将为state创建公共getter，当你引入新的state时，map方法将向你展示，你需要在getter中处理新的状态。在mixin中添加另一个属性，您也需要覆盖它。
要使用它，你可以用肘来称呼它：state.todos;或视图中：context.read<TodoCubit>().state.todos;个

这个用例现在似乎可以开箱即用（freezed: ^2.3.5，freezed_annotation: ^2.2.0）：

import 'package:freezed_annotation/freezed_annotation.dart';

part 'todo.freezed.dart';

class Todo {}

@freezed
class TodoState with _$TodoState {
  const factory TodoState.loading(List<Todo> noTodos) = TodoStateLoading;
  const factory TodoState.loaded(List<Todo> todos) = TodoStateLoaded;
  const factory TodoState.error(List<Todo> todos, String message) = TodoStateError;
}

void main(List<String> args) {
  const test = TodoState.loading(<Todo>[]);
  test.todos.first;
}

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Freezed将共享工厂参数（这里是List<Todo> todos）定义为_$TodoState mixin的成员。