Flutter Riverpod 2.0如何使用FutureOr和AutoDisposeSyncNotificationer处理api状态代码

我只是在学习Riverpod，我不确定如何处理来自API请求的状态代码.我还没有找到任何优雅地处理这一问题的好例子.我正在开发一个简化的登录测试来解决这个问题:

final LoginAsyncProvider = AsyncNotifierProvider.autoDispose<LoginProvider, User>(() {
  return LoginProvider();
});

class LoginProvider extends AutoDisposeAsyncNotifier<User> {

  FutureOr<User> login({required String userName, required String password}) async {
    final response = await http.post(Uri.https(Api.mainDomain, Api.login));
    final json = jsonDecode(response.body) as Map<String, dynamic>;
    User _user = User.fromJson(json);
    state = AsyncData(_user);
    return _user;
  }

  @override
  FutureOr<User> build() async {
    return login(userName: "someUser", password: "somePass");  }
}

我想在用户界面的Switch语句中使用它:

...
    child: switch (userAsyncValue) { 
      AsyncData(:final value) => Text(text: userAsyncValue.userName),
      AsyncError() => const Text('Some Error happened'),
      _ => const CircularProgressIndicator(),
    },
...

显然，当response.statusCode!=200与不在response.body中返回数据时，这在语句final json = jsonDecode(response.body) as Map<String, dynamic>;上失败.

处理API请求失败的正确方法是什么？