hh.php

<?php

declare(strict_types=1);

namespace Rost\Rules;

use PhpParser\Node;
use PHPStan\Analyser\Scope;
use PHPStan\Rules\Rule;

class DetectCopyOnWrite implements Rule
{
    public function getNodeType(): string
    {
        return Node\Expr\Assign::class;
    }

    public function processNode(Node $node, Scope $scope): array
    {
        $messages = [];

        /** @var Node\Expr\Assign $node */
        $assignAcceptor = $node->var;

        if ($assignAcceptor instanceof Node\Expr\ArrayDimFetch) {
            /** @var Node\Expr\Variable $variable */
            $variable = $assignAcceptor->var;
            $currentFunctionParameters = $this->getCurrentFunctionParameters($scope);

            if (in_array($variable->name, $currentFunctionParameters)) {
                $messages[] = 'Function argument mutation found. It can cause memory problems, because of copy on write principle';
            }
        }

        return $messages;
    }

    private function getCurrentFunctionParameters(Scope $scope): array
    {
        $parameters = [];
        if ($scope->isInAnonymousFunction()) {
            $functionParameters = $scope->getAnonymousFunctionReflection()->getParameters();
            foreach ($functionParameters as $parameter) {
                $parameters[] = $parameter->getName();
            }
        } else {
            $functionVariants = $scope->getFunction()->getVariants();
            foreach ($functionVariants as $functionVariant) {
                foreach ($functionVariant->getParameters() as $functionParameter) {
                    $parameters[] = $functionParameter->getName();
                }
            }
        }

        return $parameters;
    }
}