protected function is_special_selector($type = null, $selector = null)
    {
        $selector = Phery::coalesce($selector, $this->last_selector);

        if ($selector && preg_match('/\{([\D]+)\d+\}/', $selector, $matches)) {
            if ($type === null) {
                return true;
            }

            return ($matches[1] === $type);
        }

        return false;
    }