mypy 1.9.0: self check fails with Python 3.11 / 3.12

[mr-c]

Bug Report

mypy 1.9.0: self check fails with Python 3.11 / 3.12. This was found while updating the Debian packaging.

To Reproduce

# in a checkout of https://github.com/python/mypy/tree/1.9.0
PYTHONPATH=$PWD python3.11 -m mypy    --config-file mypy_self_check.ini -p mypy
# or
PYTHONPATH=$PWD python3.12 -m mypy    --config-file mypy_self_check.ini -p mypy

Expected Behavior

Success: no issues found in 179 source files or similar

Actual Behavior

mypy/checker.py:540: error: Parenthesized context managers are only supported in Python 3.9 and greater  [syntax]
                return True
                ^
mypy/checker.py:540: note: See https://mypy.rtfd.io/en/stable/_refs.html#code-syntax for more info
Found 1 error in 1 file (errors prevented further checking)

Your Environment

• Mypy version used: 1.9.0
• Mypy command-line flags: N/A
• Mypy configuration options from mypy.ini (and other config files):
• Python version used: 3.11.8-3 & 3.12.2-4

[JelleZijlstra]

This was fixed on master (#16949) but unfortunately not in the 1.9.0 branch.

[mr-c]

@JelleZijlstra No worries; thanks for the tip. That PR applies cleanly and I can confirm the fix. I've added that PR as a local patch for the Debian package. I don't think a 1.9.1 release is necessary for this issue, so I'll close it.

[JelleZijlstra]

Sounds good. I'll mention this on the release tracking issue, as it would be nice to cherry-pick the fix in if we do end up making a 1.9.1 release for other reasons.