Leafo\ScssPhp\Compiler::mergeDirectRelationships PHP Method

    protected function mergeDirectRelationships($selectors1, $selectors2)
    {
        if (empty($selectors1) || empty($selectors2)) {
            return array_merge($selectors1, $selectors2);
        }
        $part1 = end($selectors1);
        $part2 = end($selectors2);
        if (!$this->isImmediateRelationshipCombinator($part1[0]) || $part1 !== $part2) {
            return array_merge($selectors1, $selectors2);
        }
        $merged = [];
        do {
            $part1 = array_pop($selectors1);
            $part2 = array_pop($selectors2);
            if ($this->isImmediateRelationshipCombinator($part1[0]) && $part1 !== $part2) {
                $merged = array_merge($selectors1, [$part1], $selectors2, [$part2], $merged);
                break;
            }
            array_unshift($merged, $part1);
            array_unshift($merged, [array_pop($selectors1)[0] . array_pop($selectors2)[0]]);
        } while (!empty($selectors1) && !empty($selectors2));
        return $merged;
    }