protected function argValue(&$out)
    {
        $s = $this->count;

        $keyword = null;

        if (! $this->variable($keyword) || ! $this->matchChar(':')) {
            $this->seek($s);
            $keyword = null;
        }

        if ($this->genericList($value, 'expression')) {
            $out = [$keyword, $value, false];
            $s = $this->count;

            if ($this->literal('...', 3)) {
                $out[2] = true;
            } else {
                $this->seek($s);
            }

            return true;
        }

        return false;
    }