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

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 https://github.com/python/typeshed/pull/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.

まず、リンク先の mypy playground で Python 3.12 を使って動作を再現します。次に、property に似た型に対する mypy の特別扱いを調べ、cached_property が setter と deleter を受け入れる理由に焦点を当てます。cached_property に存在しないメソッドについて mypy がエラーを報告しつつ、cached_property の有効な動作が維持されれば完了です。