public function createArgNode($path, $node)
    {
        $v = trim($node);
        if (substr($v, 0, 1) == '?') {
            $conditional = true;
            $v = ltrim(substr($v, 1));
        } else {
            $conditional = false;
        }
        return new ArgNode(end($path), $this->exprcompiler->parse($v), $conditional);
    }