Leafo\ScssPhp\Compiler::compileSelectorPart PHP Method

    protected function compileSelectorPart($piece)
    {
        foreach ($piece as &$p) {
            if (!is_array($p)) {
                continue;
            }
            switch ($p[0]) {
                case Type::T_SELF:
                    $p = '&';
                    break;
                default:
                    $p = $this->compileValue($p);
                    break;
            }
        }
        return implode($piece);
    }