Bug report

Code snippet that reproduces the problem

https://phpstan.org/r/4d1f3604-dd44-458a-813c-c043822c4b00

Expected output

I would expect no error here since it seems like the object has always a data property and a datalen property according to the doc:
https://www.php.net/manual/fr/function.stream-bucket-make-writeable.php#refsect1-function.stream-bucket-make-writeable-returnvalues

Is there a way to tell this to phpstan even if the stub is saying it's returning an object @ondrejmirtes ?