Bug report

Only happens in lvl 9. The issue lies basically in this snippet:

if (isset($array['mightExist']) && !is_string($array['mightExist'])) {
    throw new Exception('Has to be string if set');
}

PHPStan still assumes that $array['mightExist'] is mixed, even though it can only be unset or string after that point. Interestingly, it does not complain if the key is used without null coalesce, even though it can still be unset

Code snippet that reproduces the problem

https://phpstan.org/r/4d0bc609-96f0-4eec-a029-5926d67f9370

Expected output

No error reported