Mypy crashes with 1.11.1 version and Pydantic 1.10.11

[OmerFI]

Crash Report

Updated mypy to 1.11.1 version. Run mypy and faced with error.
It doesn't crash with mypy 1.10.1

Traceback

❯ mypy xxx/ --show-traceback
/home/omerfi/xxx/.venv/lib/python3.10/site-packages/pydantic/env_settings.py:23: error: INTERNAL ERROR -- Please try using mypy master on GitHub:
https://mypy.readthedocs.io/en/stable/common_issues.html#using-a-development-mypy-build
Please report a bug at https://github.com/python/mypy/issues
version: 1.11.1
Traceback (most recent call last):
  File "mypy/semanal.py", line 7092, in accept
  File "mypy/nodes.py", line 1183, in accept
  File "mypy/semanal.py", line 1700, in visit_class_def
  File "mypy/semanal.py", line 1891, in analyze_class
  File "mypy/semanal.py", line 1925, in analyze_class_body_common
  File "mypy/semanal.py", line 2010, in apply_class_plugin_hooks
  File "pydantic/mypy.py", line 154, in pydantic.mypy.PydanticPlugin._pydantic_model_class_maker_callback
  File "pydantic/mypy.py", line 317, in pydantic.mypy.PydanticModelTransformer.transform
  File "pydantic/mypy.py", line 497, in pydantic.mypy.PydanticModelTransformer.add_construct_method
  File "mypy/types.py", line 607, in __init__
TypeError: mypy.types.TypeVarId object expected; got int
/home/omerfi/xxx/.venv/lib/python3.10/site-packages/pydantic/env_settings.py:23: : note: use --pdb to drop into pdb

To Reproduce

I created a POC repository. You can follow the instructions in the README and face the error yourself: https://github.com/OmerFI/mypyfailproject

Your Environment

• Mypy version used: 1.11.1
• Mypy command-line flags: -
• Mypy configuration options from mypy.ini (and other config files): https://github.com/OmerFI/mypyfailproject/blob/main/mypy.ini
• Python version used: 3.10.13
• Operating system and version: Ubuntu 22.04.2 LTS (WSL)

[ilevkivskyi]

This should be reported to pydantic instead: plain integers as type variable IDs are not supported anymore (plain integers are kind of private API anyway).

[OmerFI]

Interesting,
it works with mypy 1.10 and you publish a release, everything breaks and you say its pydantic's issue.
you should change the description btw it points to mypy issues:

❯ mypy xxx/ --show-traceback
/home/omerfi/xxx/.venv/lib/python3.10/site-packages/pydantic/env_settings.py:23: error: INTERNAL ERROR -- Please try using mypy master on GitHub:
https://mypy.readthedocs.io/en/stable/common_issues.html#using-a-development-mypy-build
Please report a bug at https://github.com/python/mypy/issues

[JukkaL]

The plugin is run within the mypy process, so each traceback that has entries related to plugins needs to be investigated to determine the correct root cause.

In this case it seems clear that mypy changed an internal API, and the plugin may need to switch to the new API (i.e. using TypeVarId). This was changed in #17311. Replacing integer ids with TypeVarId(id) could be enough to avoid the crash, but additional adjustments may be required to avoid type variable conflicts. Refer to #17311 for more details. This PR fixed some long-standing issues with how mypy deals with type variables, and this required dropping support for integer ids.

As the plugin system doesn't guarantee backward compatibility, my suggestion would be to test plugins using mypy master in addition to the most recent release to catch issue like this earlier. Also, we could document internal changes in #6617 more widely, but it's hard to predict which internal changes could impact plugins.