Bug report

After some trial and error, it seems that the first branch (the one we are falling though) does not narrow the value type for follow up branches.

For example, if you swap lines 12-13 in the provided example, the warning changes to get_class expects object, IClass|string given (instead of IClass|null). Unless I'm missing something, this would be a bug, since other branches seem to work fine.

Note: for my current use-case, and in general, splitting the branches (without fall-throughs) is a good workaround.

Code snippet that reproduces the problem

https://phpstan.org/r/46475e6a-20c2-476c-860d-ff70a934b449

Expected output

There shouldn't be any warnings, since both types/branches are actually handled.

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