is_subclass_of is giving a wrong prediction when call on mixed or object. #6891
Description
Bug report
Code snippet that reproduces the problem
https://phpstan.org/r/ad0c77fa-c1a6-4893-bbaf-bb051911009a
Expected output
No errors
Did PHPStan help you today? Did it make you happy in any way?
Sure, it detected a bug today :)