Generator return type and send type are treated as None under allow-any-generics

[koogoro]

Bug Report
On the newest master, Generator is not the same as Generator[Any, Any, Any] with allow-any-generics enabled. This doesn't happen on 1.10.0.

To Reproduce
https://gist.github.com/mypy-play/16ab6e35d0fa38ee42cd9d40b3a7474d

Expected Behavior
No errors.

Actual Behavior

main.py:5: error: Incompatible types in assignment (expression has type "None", variable has type "str")  [assignment]
main.py:6: error: No return value expected  [return-value]

[hauntsaninja]

Looks like it bisects to #17246 . Generator now uses PEP 696, so Generator and Generator[Any, Any, Any] should be different

[JelleZijlstra]

This seems like an expected consequence of PEP 696; the two type parameters now default to None.

[koogoro]

Oh nice. Seems like it's not a bug after all!