Is it possible to validate a FormRequest without dependency injection?

I am using a FormRequest to validate a delete request, but I do not need to access the request inside of my controller. I just need it for validation.

I find the unused variable annoying, but I can't see anything in the docs that suggests I can call anything on the class to validate it.

Form request:

class DeleteList extends FormRequest
{
    protected $errorBag = 'delete_list';

    /**
     * Determine if the user is authorized to make this request.
     *
     * @return bool
     */
    public function authorize()
    {
        return true;
    }

    /**
     * Get the validation rules that apply to the request.
     *
     * @return array
     */
    public function rules()
    {
        return [
            'confirm' => 'required|accepted'
        ];
    }
}

Controller:

public function postDelete(DeleteList $request, ListService $listService, $site, $list)
{
    $listService->delete($site, $list);
    return redirect()->route('site.lists', ['site' => $site]);
}

via Chebli Mohamed