`ParameterBag::keys()` stub not applied for Symfony ≥ 7.4 → false-positive `is_string()` `alwaysNarrowedType`

[laszlomezzei]

phpstan-symfony ships a stub correcting Symfony\Component\HttpFoundation\ParameterBag::keys() to @return list<array-key>, but StubFilesExtensionLoader only loads it for symfony/http-foundation < 7.4:

// src/Stubs/Symfony/StubFilesExtensionLoader.php
if ($this->isInstalledVersionBelow('symfony/http-foundation', '7.4.0.0')) {
    $files[] = $stubsDir . '/Symfony/Component/HttpFoundation/ParameterBag.stub';
}

From Symfony 7.4 on, Symfony declares its own @return list<string> on keys(), so PHPStan uses that instead. But that PHPDoc is inaccurate: PHP normalises numeric-string array keys to integers, so keys are int|string at runtime (e.g. ?0[]=x produces the int key 0). Symfony declined to correct it (symfony/symfony#60411).

The result is a false positive: a correct runtime guard over ->keys() is reported as always-true, and removing it reintroduces a real TypeError (a numeric param name → int key passed to a string parameter). This is a regression — the stub made this correct for < 7.4.

Code snippet that reproduces the problem

Not reproducible on phpstan.org/r — it needs the phpstan-symfony extension and symfony/http-foundation >= 7.4. Minimal case:

<?php declare(strict_types=1);

use Symfony\Component\HttpFoundation\Request;

function coreField(string $name): bool { return false; }

function f(Request $request): void
{
    foreach ($request->query->keys() as $key) {
        if (!is_string($key)) {
            continue;
        }
        coreField($key);
    }
}

Run PHPStan (level 8, phpstan-symfony enabled) with symfony/http-foundation >= 7.4.

Expected output

No error — keys() returns list<int|string> at runtime, so is_string($key) is a valid narrowing (as it is on symfony/http-foundation < 7.4, where the stub is applied).

Actual output

Call to function is_string() with string will always evaluate to true.    function.alreadyNarrowedType

Environment

• phpstan/phpstan-symfony: 2.0.20 (also reproduced on 2.0.x-dev)
• phpstan/phpstan: 2.2.x — level 8, bleedingEdge (treatPhpDocTypesAsCertain)
• symfony/http-foundation: 7.4.x and 8.1.x
• PHP 8.x

Suggested fix

The ParameterBag.stub is still accurate for 7.4+, so keep applying it — e.g. bump the gate from < 7.4.0.0 to < 8.3.0.0 (8.2 still ships the inaccurate PHPDoc). Related: #439 (original report), #443 (the stub).