Php $request>route() 在 laravel 中返​​回 null

我有以下代码:

class TotersProviderLoginController extends Controller
{

    private $oauthService;

    public function __construct(Request $request)
    {
        $provider = $request->route()->parameter('provider'); // error here
        if($provider == 'google')
            $this->oauthService = new GoogleOauthService();
        else
            throw new \Exception('Provider '.($provider ?? '').' not supported!');
    }

我定义了以下路由:

Route::get('login/toters/{provider}', 'Accounts\TotersProviderLoginController@redirectToProvider');
Route::get('login/toters/{provider}/redirect', 'Accounts\TotersProviderLoginController@handleProviderCallback');
Route::get('login/toters/{provider}/csrf', 'Accounts\TotersProviderLoginController@getCsrf');
Route::post('login/toters/{provider}/oauth', 'Accounts\TotersProviderLoginController@requestToken');
    

因为某种原因当我 run 的时候

php artisan route:list --verbose

我得到这个错误

In TotersProviderLoginController.php line 38:

  [Symfony\Component\Debug\Exception\FatalThrowableError]
  Call to a member function parameter() on null

所以很明显，$request->route()返回null.为什么会这样？