Leafo\ScssPhp\Parser::expression PHP Method

    protected function expression(&$out)
    {
        $s = $this->seek();
        if ($this->literal('(')) {
            if ($this->literal(')')) {
                $out = [Type::T_LIST, '', []];
                return true;
            }
            if ($this->valueList($out) && $this->literal(')') && $out[0] === Type::T_LIST) {
                return true;
            }
            $this->seek($s);
            if ($this->map($out)) {
                return true;
            }
            $this->seek($s);
        }
        if ($this->value($lhs)) {
            $out = $this->expHelper($lhs, 0);
            return true;
        }
        return false;
    }