Laravel 5 Form 对象报错

{!! Form::open(['route' => 'register_path']) !!}aa
    <!--- Username Field --->
    <div class="form-group">
        {!! Form::label('username', 'Username:') !!}
        {!! Form::text('username', null, ['class' => 'form-control', 'required' => 'required']) !!}
    </div>

    <!--- Email Field --->
    <div class="form-group">
        {!! Form::label('email', 'Email:') !!}
        {!! Form::email('email', null, ['class' => 'form-control', 'required' => 'required']) !!}
    </div>

    <!--- Password Field --->
    <div class="form-group">
        {!! Form::label('password', 'Password:') !!}
        {!! Form::password('password', ['class' => 'form-control', 'required' => 'required']) !!}
    </div>

    <!--- Password Confirmation Field --->
    <div class="form-group">
        {!! Form::label('password_confirmation', 'Password Confirmation:') !!}
        {!! Form::password('password_confirmation', ['class' => 'form-control', 'required' => 'required']) !!}
    </div>

    <!--- Sign Up Field --->
    <div class="form-group">
        {!! Form::submit('Sign Up', ['class' => 'btn btn-primary']) !!}
    </div>
{!! Form::close() !!}Copy