Improve inspect stubs

[AlexWaygood]

No description provided.

[JelleZijlstra]

I'm not sure making the Signature class generic is really helpful, and the mypy-primer output agrees. It's usually used for introspection, and most code doing that probably doesn't benefit from precise types for the return annotation.

It's also not always correct: your code will infer something like Signature[int] for inspect.signature(lambda: 1), but in fact the signature that computes has no return_annotation.

[AlexWaygood]

It's also not always correct: your code will infer something like Signature[int] for inspect.signature(lambda: 1), but in fact the signature that computes has no return_annotation.

Good point -- I've reverted the changes making it generic. I've also removed the TODO comment, since, from what you're saying (and I agree), it sounds like we can't really be more specific here.

[JelleZijlstra]

It's either the empty marker or whatever the user put in an annotation. I don't think we can express that better in the current type system.

[AlexWaygood]

Yeah

[github-actions]

According to mypy_primer, this change has no effect on the checked open source code. 🤖🎉