Bug report

Following #12467, it is not possible to avoid an issue with ReflectionClass::isSubclassOf in the following code:

function getPictureFqn(string $pictureType): ?string
{
    $fqn = 'App\\Entity\\' . $pictureType;
    if ($fqn === Picture::class) {
        return Picture::class;
    }
    $refl = new \ReflectionClass($fqn);
    if (!$refl->isSubclassOf(Picture::class)) {
        return null;
    }

    return $fqn;
}

Phpstan says:

Call to method ReflectionClass<object>::isSubclassOf() with 'App\\Entity\\Picture' will always evaluate to false.

If I force the variable type:

    /** @var class-string<Picture> $fqn */
    $fqn = 'App\\Entity\\' . $pictureType;

The error is:

Call to method ReflectionClass<Picture>::isSubclassOf() with 'App\\Entity\\Picture' will always evaluate to true.

Notice the output says "will evaluate to true" instead of false.

When I type:

    /** @var class-string<Picture|object> $fqn */
    $fqn = 'App\\Entity\\' . $pictureType;

The error reverts to:

Call to method ReflectionClass<object>::isSubclassOf() with 'App\\Entity\\Picture' will always evaluate to false.

This issue is related to php 8.4 (see #12459).

Code snippet that reproduces the problem

https://phpstan.org/r/cd85b227-3d67-4f14-8eb5-ad501398686f

Expected output

The result is not always false when applied on ReflectionClass<object>. Some objects are descendants of the class and other aren't.

I expect no issue with that function.

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