Laravel 5.2重定向(）->；back(）->；withErrors$errors为空

我正在尝试在我的身份验证表单中应用验证。一切都很好，直到我返回$this->sendFailedLoginResponse（$request）；，其中重定向（）->back（）->withErrors（）没有将错误存储在MessageBag中（使视图中的$errors变量为空）。

laravel.blad.php

<!-- BEGIN LOGIN FORM -->
        <form class="login-form" action="{{ url('/login') }}" method="post">
            {!! csrf_field() !!}
            <h3 class="form-title font-green">Iniciar sesión</h3>
                @if (count($errors) > 0) // Here is where i check and my $errors variable is empty
                    @foreach ($errors->all() as $error)
                        <div class="alert alert-danger">
                            <button class="close" data-close="alert"></button>
                            <span>{{ $error }}</span>
                        </div>
                    @endforeach
                @endif
            <div class="form-group">
                <!--ie8, ie9 does not support html5 placeholder, so we just show field title for that-->
                <label class="control-label visible-ie8 visible-ie9">Username</label>
                <input class="form-control form-control-solid placeholder-no-fix" type="text" autocomplete="on" placeholder="Usuario" name="email" value="{{ (isset($email) ? $email : '' ) }}" /> </div>
            <div class="form-group">
                <label class="control-label visible-ie8 visible-ie9">Password</label>
                <input class="form-control form-control-solid placeholder-no-fix" type="password" autocomplete="off" placeholder="Contraseña" name="password" /> </div>
            <div class="form-actions">
                <button type="submit" class="btn green uppercase">Iniciar sesión</button>
            </div>
        </form>
        <!-- END LOGIN FORM -->

AuthenticatesUsers.php

public function login(Request $request)
{
    $this->validateLogin($request);
    // If the class is using the ThrottlesLogins trait, we can automatically throttle
    // the login attempts for this application. We'll key this by the username and
    // the IP address of the client making these requests into this application.
    $throttles = $this->isUsingThrottlesLoginsTrait();
    if ($throttles && $lockedOut = $this->hasTooManyLoginAttempts($request)) {
        $this->fireLockoutEvent($request);
        return $this->sendLockoutResponse($request);
    }
    $credentials = $this->getCredentials($request);
    if (Auth::guard($this->getGuard())->attempt($credentials, $request->has('remember'))) {
        return $this->handleUserWasAuthenticated($request, $throttles);
    }
    // If the login attempt was unsuccessful we will increment the number of attempts
    // to login and redirect the user back to the login form. Of course, when this
    // user surpasses their maximum number of attempts they will get locked out.
    if ($throttles && ! $lockedOut) {
        $this->incrementLoginAttempts($request);
    }
    return $this->sendFailedLoginResponse($request);
}
/**
 * Validate the user login request.
 *
 * @param  'Illuminate'Http'Request  $request
 * @return void
 */
protected function validateLogin(Request $request)
{
    $this->validate($request, [
        $this->loginUsername() => 'required', 'password' => 'required',
    ]);
}
/**
 * Get the failed login response instance.
 *
 * @param 'Illuminate'Http'Request  $request
 * @return 'Illuminate'Http'Response
 */
protected function sendFailedLoginResponse(Request $request)
{
    return redirect()->back()
        ->withInput($request->only($this->loginUsername(), 'remember'))
        ->withErrors([
            $this->loginUsername() => $this->getFailedLoginMessage(),
        ]);
}
/**
 * Get the failed login message.
 *
 * @return string
 */
protected function getFailedLoginMessage()
{
    return Lang::has('auth.failed')
            ? Lang::get('auth.failed')
            : 'These credentials do not match our records.';
}