问“Class”的返回类型不是用户

EN

import 'package:firebase_auth/firebase_auth.dart';

import 'package:flutter_user_profile/model/user.dart';

class AuthService {

  final FirebaseAuth _auth = FirebaseAuth.instance;

  //creating a user object based on Firebase user
  Client? _userFromCredUser(User? user) {
    return user != null ? Client(uid: user.uid) : null;
  }
  //for authenticate user stream
  Stream<User?> get user {
    return _auth.authStateChanges().map((User? user) => _userFromCredUser(user!));
  }

  //sign in anonymously
  Future signInAnon() async {
    try {
      UserCredential result =  await _auth.signInAnonymously();
      User? user = result.user;
      return _userFromCredUser(user!);
    } 
    catch(e){
      print(e.toString());
      return null;
    }
  }
}