test_typeddict_errors fails on python3.11

[mweinelt]

Heads up, we're seeing a test failure with python 3.11.0rc2 and mypy_extensions. Python 3.11 will be released in October.

======================================================================
FAIL: test_typeddict_errors (testextensions.TypedDictTests.test_typeddict_errors)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/build/source/tests/testextensions.py", line 91, in test_typeddict_errors
    with self.assertRaises(TypeError):
AssertionError: TypeError not raised

----------------------------------------------------------------------
Ran 7 tests in 0.003s

FAILED (failures=1)

[gvanrossum]

I cannot repro this yet. Which version of Python 3.11 did you use? rc2? What platform? What version of mypy? Accelerated through mypyc or not?

[mweinelt]

• NixOS unstable (x86_64-linux)
• Python 3.11.0rc2
• mypy 0.961
  • built using MYPYC_OPT_LEVEL=1
• mypy_extensions 0.4.3

I'm in the process of updating to mypy 0.971 and can retest if that helps. Except mypy is not part of the environment during testing, so that seems pointless.

[gvanrossum]

Ah, I was confused. I've confirmed your report on macOS. I didn't try earlier versions of Python 3.11, but the tests pass with 3.10.

Do you have time to debug this further? I'm guessing something in the stdlib typing.py module changed, but I don't have time to investigate further.

[mweinelt]

Works on 3.11.0a6, broke on 3.11.0a7. I'm not too familiar with the cpython codebase and I don't have a setup ready to bisect this any further.

[gvanrossum]

@JelleZijlstra -- what could have broken this? It seems to be this code at L91-92 that no longer raises TypeError:

        with self.assertRaises(TypeError):
            TypedDict('Hi', x=1)

A lot of stuff went in between a6 and a7, including PEP 646, and a bunch of refactoring by Serhiy.

[JelleZijlstra]

I think that's because of 870b22b9c442d035190d2b8fb82256cd9a03da48 (python/cpython#31151).

[gvanrossum]

So the test should just be fixed.