is_subclass_of is giving a wrong prediction when call on mixed or object.

[VincentLanglet]

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 :)

[ondrejmirtes]

Because we can't represent "subclass of HelloWorld" in the typesystem, I think that is_subclass_of extension shouldn't assume anything about the falsy context. //cc @herndlm

[herndlm]

weird error, there are a couple of other is_subclass_of bugs too. looks like someone needs to do a is_subclass_of bugfix session.. was on my list, but I couldn't motivate myself yet, will try to soon :)

[github-actions]

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