Laravel选项路由参数不起作用

I'm using laravel 5.2 and having problems with regards to routing. Supposed I have this route: http://example.com/out/parameter1/parameter2/

Parameter1 should be required while Parameter2 should be optional. When user enter this url: http://example.com/out/parameter1/ or this http://example.com/out/parameter1/parameter2/, they should be able to proceed. By when this is entered, http://example.com/out/ they will be redirected to the homepage.

Here's my route:

Route::get('out/{param1}/{param2?}', 'MyController@out']);
Route::get('out/', 'MyController@redirect']);

The controller:

public function out($param1, $param2 = '', Request $request) {
    // logic here
}

The error that I'm getting is this: Argument 3 passed to App\Http\Controllers\MyController::out() must be an instance of Illuminate\Http\Request, none given

I already specify a default value for param2 on the method.

Request instance must be the first one

public function out(Request $request, $param1, $param2 = '') 
{
    // logic here
}

Docs: https://laravel.com/docs/5.2/controllers under Method Injection