League\CommonMark\Util\RegexHelper::getLinkDestinationRegex PHP Method

    public function getLinkDestinationRegex()
    {
        return '/^' . '(?:' . $this->regex[self::REG_CHAR] . '+|' . $this->regex[self::ESCAPED_CHAR] . '|\\\\|' . $this->regex[self::IN_PARENS_NOSP] . ')*' . '/';
    }