问FatalErrorException Laravel 5社交名流Facebook登录

EN

<?php namespace App\Http\Controllers;
  use App\Http\Requests;
  use App\Http\Controllers\Controller;
  use Illuminate\Http\Request;
  use App\AuthenticateUser;

  class AuthController extends Controller {

  public function login(AuthenticateUser $authenticateUser, Request $request){
    return $authenticateUser->execute($request->has('code'));
  }// End function
}// End class

<?php namespace App;
 use Illuminate\Contracts\Auth\Authenticator;
 use Laravel\Socialite\Contracts\Factory as Socialite;
 use App\Data\UserData;

 class AuthenticateUser{
    private $socialite;
    private $auth;
    private $users;

    /* Constructor */
    public function _construct(UserData $users, Socialite $socialite, Authenticator $auth){
    $this->users = $users;
    $this->socialite = $socialite;
    $this->auth = $auth;

}// End constructor

/*  @hasCode : boolean 

*/
public function execute($hasCode){
    if(!$hasCode)
        return $this->getAuthorizationFirst();

    $user = $this->socialite->driver('facebook')->user();
    dd($user);
}

/* Método auxiliar para autorizar el login, si no se tiene el código de autorización */
private function getAuthorizationFirst(){
    return $this->socialite->driver('facebook')->redirect(); //line 34
  }
}

Route::get('/', function() {
    if (Auth::check()) {
        return 'Welcome back, ' . Auth::user()->username;
    } else {
        return 'Hi guest. ' . link_to('login', 'Login with facebook');
    }
});

Route::get('login','AuthController@login');