未定义的属性: laravel \Auth\SessionGuard：：$Auth(在laravel 7.30.4中)

use Illuminate\Support\Facades\Auth;

// 登录
public function login(Request $request)
{
    $credentials = $request->only('email', 'password');

    if (Auth::attempt($credentials)) {
        // 登录成功
        return redirect()->intended('/dashboard');
    } else {
        // 登录失败
        return back()->withErrors(['email' => '登录失败，请检查邮箱和密码']);
    }
}

// 注销
public function logout()
{
    Auth::logout();
    return redirect('/login');
}

// 验证用户是否已登录
public function checkLogin()
{
    if (Auth::check()) {
        // 用户已登录
        return "用户已登录";
    } else {
        // 用户未登录
        return "用户未登录";
    }
}