enum.IntFlag now unpickles incorrectly on Python 3.11.4

[da-woods]

Bug report

Follow up to #105332

Following the changes to fix that issue enum.IntFlag appears to pickle correctly on the latest Python 3.12 commit (dd36656ada05731c069ecd5b1878380294fb1f3e) but fail on Python 3.11.4 (where on 3.11.2 it worked)

Code to reproduce

import enum
import pickle

class PxdEnum(enum.IntFlag):
    RANK_0 = 11
    RANK_1 = 37
    RANK_2 = 389

pickled = pickle.dumps(PxdEnum.RANK_2)

print(pickle.loads(pickled))

error output:

Traceback (most recent call last):
  File "<path>/enumtest.py", line 11, in <module>
    print(pickle.loads(pickled))
          ^^^^^^^^^^^^^^^^^^^^^
TypeError: unsupported operand type(s) for |: 'PxdEnum' and 'NoneType'

Your environment

64 bit Linux, Python 3.11.4

[da-woods]

Just as background for this, in Cython we're converting C enums in enum.IntFlags when they're passed back to Python. One of the tests we have is that our converted enums can be pickled and unpickled, and this test is now failing. (Although it can be easily demonstrated outside Cython, as in the reproducible example above)

[sobolevn]

This was solved in #105348

Can you please verify?

[da-woods]

Sorry - I think you're right. I'd thought that the fix was in 3.11.4 but looking at the commit history the fix was just after 3.11.4.

I'll double check later today, but I suspect this is a false alarm caused by me not realising what has included in the release

[da-woods]

Yes - sorry - it's fixed on the Python 3.11 branch. I'd got slightly confused about what was in the 3.11.4 release.

I'll close this issue. Sorry for the noise.