Debugging mypy segmentation faults

[jace]

Some code I was working on last night is causing mypy to segfault. I tried retracing my steps to find the change that broke mypy, without luck. How do I debug it?

Config:

• Platform: macOS 12.4 on M1
• Arch: arm64
• Python: 3.9.13
• mypy: 0.971

mypy --tb and mypy --pdb are segfaulting without any info. gdb is not available on arm64. I get a bit more info using faulthandler, but all it indicates is the file:

$ python -X faulthandler -m mypy -v .
…
LOG:  Processing SCC singleton (coaster.views.classview) as inherently stale with stale deps (__future__ asyncio builtins coaster coaster.auth coaster.sqlalchemy coaster.typing coaster.utils coaster.views.misc flask flask.blueprints flask.typing functools sqlalchemy.orm.attributes sqlalchemy.orm.descriptor_props sqlalchemy.orm.mapper sqlalchemy.orm.properties sqlalchemy.orm.query types typing typing_extensions werkzeug.local werkzeug.routing werkzeug.wrappers)
Fatal Python error: Segmentation fault

Current thread 0x0000000102f10580 (most recent call first):
  File "/Users/jace/.virtualenvs/hasgeek/lib/python3.9/site-packages/mypy/__main__.py", line 12 in console_entry
  File "/Users/jace/.virtualenvs/hasgeek/lib/python3.9/site-packages/mypy/__main__.py", line 34 in <module>
  File "/opt/homebrew/Cellar/[email protected]/3.9.13_2/Frameworks/Python.framework/Versions/3.9/lib/python3.9/runpy.py", line 87 in _run_code
  File "/opt/homebrew/Cellar/[email protected]/3.9.13_2/Frameworks/Python.framework/Versions/3.9/lib/python3.9/runpy.py", line 197 in _run_module_as_main
[1]    44130 segmentation fault  python -X faulthandler -m mypy -v .

The file in question is located at https://github.com/hasgeek/coaster/blob/369ce391f11850f10fc0ab42a52c196188436a50/coaster/views/classview.py

[JukkaL]

@jace Can you file this in the mypy issues tracker (https://github.com/python/mypy/issues)?

[jace]

Sorry this took a while. Reported here: python/mypy#13431