Laravel - Getting error after postLogin validate

Well, after validate, if my password is longer than 3 characters I get this error:

Argument 1 passed to Illuminate\Http\RedirectResponse::withInput() must be of the type array, object given, called in /home/vagrant/Code/stack-laravel/app/Http/Controllers/Admin/AuthController.php on line 50 and defined

And this is my AuthController:

<?php

namespace App\Http\Controllers\Admin;

use App\User;
use Illuminate\Http\Request;
use Illuminate\Support\Facades\Auth;
use Validator;
use App\Http\Controllers\Controller;
use Illuminate\Foundation\Auth\ThrottlesLogins;
use Illuminate\Foundation\Auth\AuthenticatesAndRegistersUsers;

class AuthController extends Controller
{
    use AuthenticatesAndRegistersUsers, ThrottlesLogins;

    protected $redirectPath = '/admin';

    public $loginPath = '/admin';

    public function __construct()
    {
        $this->middleware('guest', ['except' => 'getLogout']);
    }

    public function getLogin()
    {
        if (Auth::user()){
            return redirect('/admin');
        }

        return view('admin.pages.login.index');

    }

    public function postLogin(Request $request)
    {
        $this->validate($request, [
            'email' => 'required|email',
            'password' => 'required|min:3'
        ]);

        $credentials = $this->getCredentials($request);

        if (Auth::attempt($credentials, $request->has('remember'))) {
            return redirect()->intended($this->redirectPath());
        }

        return redirect($this->loginPath())
            ->withInput($request)
            ->withErrors();
    }
}

What is wrong?

via Chebli Mohamed