PHPStan\Rules\Classes\UnusedConstructorParametersRule::getUsedVariables PHP Method

    private function getUsedVariables($node) : array
    {
        $variableNames = [];
        if ($node instanceof Node) {
            if ($node instanceof Node\Expr\Variable && is_string($node->name) && $node->name !== 'this') {
                return [$node->name];
            }
            foreach ($node->getSubNodeNames() as $subNodeName) {
                $subNode = $node->{$subNodeName};
                $variableNames = array_merge($variableNames, $this->getUsedVariables($subNode));
            }
        } elseif (is_array($node)) {
            foreach ($node as $subNode) {
                $variableNames = array_merge($variableNames, $this->getUsedVariables($subNode));
            }
        }
        return $variableNames;
    }