Mypy doesn't object to `cached_property` methods that don't exist

[tungol]

Bug Report

Mypy includes functools.cached_property on it's list of property-list types, but considers it to be too identical to property. It allows the use of cached_property.setter and cached_property.deleter without raising an error, despite the fact that neither of these are methods that exist on cached_property.

I discovered this while looking at permutations of property-like behavior for python/typeshed#13276.

Actually, I realized just now that it can be anything from any of the property types. See the second playground link. [Edit: this part fixed by #19313]

To Reproduce

Playground link showing : https://mypy-play.net/?mypy=latest&python=3.12&gist=f5336c7a8df8f028a565bab576b74062

This one shows that mypy doesn't object to non-existent methods of property used as a decorator:

https://mypy-play.net/?mypy=latest&python=3.12&gist=d91764177a604ba5640a1fe741718f52 [Edit: this part fixed by #19313]

Expected Behavior

I expect mypy to generate errors for methods that don't exist in the stubs, even with the special-cased behavior.

Actual Behavior

No errors are generated.

[tungol]

@sterliakov @ilevkivskyi This issue shouldn't be closed yet. #19313 solves the problem of arbitrary methods on property, but still accepts setter and deleter for functools.cached_property instances, as in the first playground link I provided. I don't have permissions to re-open the issue myself.

[tungol]

Thanks! I edited the title and first post to reflect the work done by #19313 .