Mypy subclass/intersection issue on 1.15.0

[gandhis1]

This code filters using an isinstance call to try to find objects that fit the profile of both Foo and Bar:

from abc import ABC
from collections.abc import Sequence

class Foo(ABC):
 pass

class Bar(ABC):
 pass

class Baz(ABC):
 pass

class FooBar(Foo, Bar):
 pass

class FooBaz(Foo, Baz):
 pass

def my_func(foos: list[Foo]) -> Sequence[Foo]:
 my_list = []
 for foo in foos:
 if not isinstance(foo, Bar):
 continue
 my_list.append(foo)
 return my_list

foos = [FooBar(), FooBaz()]
my_func(foos)

This code does not fail on Mypy 1.14.1:

https://mypy-play.net/?mypy=1.14.1&python=3.12&gist=7b5be66ab0fb3f04d15a99317ef21a7d

But it does fail on Mypy 1.15:

main.py:24: error: Argument 1 to "append" of "list" has incompatible type "__main__.<subclass of "Foo" and "Bar">1"; expected "__main__.<subclass of "Foo" and "Bar">" [arg-type]
Found 1 error in 1 file (checked 1 source file)

https://mypy-play.net/?mypy=1.15.0&python=3.12&gist=7b5be66ab0fb3f04d15a99317ef21a7d

Originally posted by @gandhis1 in python/typing#1968

[sterliakov]

This is the problem discussed in #18433 - pyodide false positive caused by incompatible pseudo-intersections.

[gandhis1]

I realized I did not check the master branch, and it appears this issue is fixed on master: https://mypy-play.net/?mypy=master&python=3.12&gist=7b5be66ab0fb3f04d15a99317ef21a7d