Leafo\ScssPhp\Compiler::flattenSelectorSingle PHP Method

    protected function flattenSelectorSingle($single)
    {
        $joined = [];
        foreach ($single as $part) {
            if (empty($joined) || !is_string($part) || preg_match('/[\\[.:#%]/', $part)) {
                $joined[] = $part;
                continue;
            }
            if (is_array(end($joined))) {
                $joined[] = $part;
            } else {
                $joined[count($joined) - 1] .= $part;
            }
        }
        return $joined;
    }