Thank you.

@ondrejmirtes, I recently encounter an issue related to this stub change.
You can see symfony/symfony#46698 for more information.

This is a lot related to the fact that array-key like '1' are automatically cast to int by php.
It seems like Symfony often use such name as key.

An exemple, code like

foreach ($form as $name => $child) {
     $form->remove($name);
}

fail with strict types because the $name is sometimes an int and remove expects a string.

So I start to wonder if it's not better to keep

\Traversable<string|int, \Symfony\Component\Form\FormInterface>

in order to prevent people "You might need to cast keys to string".

WDYT if I revert this PR with a comment ?

Will be solved in 6.2 by symfony/symfony#46813