I agree that would be nice; probably not near the top of our list right now (and not trivial to implement), but it makes sense. Thanks for the suggestion.

Nontrivial way to do it is dynamically scan the python 3.12 namespace, and add these warnings.

Is there any big downside to do it the boring way, hardcode a list and compare the error to the list?

This information is already maintained via `if sys.version_info >= (...):` conditionals in typeshed stubs. I don't think this is important enough to justify maintaining the same information in a duplicate way.