protected function isRegexpLiteral()
    {
        if (strpos("\n{;(,=:[!&|?", $this->a) !== false) {
            return true;
        }
        if ($this->a === ' ') {
            $length = strlen($this->output);
            if ($length < 2) {
                return true;
            }
            if (preg_match('/(?:case|else|in|return|typeof)$/', $this->output, $m)) {
                if ($this->output === $m[0]) {
                    return true;
                }
                $charBeforeKeyword = substr($this->output, $length - strlen($m[0]) - 1, 1);
                if (!$this->isAlphaNum($charBeforeKeyword)) {
                    return true;
                }
            }
        }
        return false;
    }