dmypy + torch: second run produces different results (Final name must be initialized with a value)

[randolf-scholz]

Today I tried using dmypy for the first time and noticed a really strange bug: the second run produced different results than the first run!
More specifically (and even stranger) the error message "Final name must be initialized with a value" spreads from a known false positive (#5608) to other cases.

To Reproduce

I created a repository with complete repro: https://github.com/randolf-scholz/dmypy_bug
It seems 3 things are relevant:

1. Using python 3.12.
   (I believe this is because the 3.12 wheel of torch==2.4.0 ships with the py.typed marker, but the 3.11 wheel doesn't)
2. torch must be imported.
3. A dataclass using a Final annotation is defined.

minimal working example

__all__ = ["ImmutablePoint", "MyDataClass"]

from typing import Final
from dataclasses import dataclass

import torch

@dataclass
class MyDataClass:
    foo: Final[int]
    bar: Final[int]


class ImmutablePoint:
    x: Final[int]
    y: Final[int]

    def __init__(self, x: int, y: int) -> None:
        super().__init__()
        self.x = x
        self.y = y

Expected Behavior

Subsequent runs should yield the same results.

Actual Behavior

Subsequent spread the error from cases where it is expected to cases where it is not.

$ dmypy start
Daemon started
$ dmypy check src
src/dmypy_final_bug/__init__.py:10: error: Final name must be initialized with a value  [misc]
src/dmypy_final_bug/__init__.py:11: error: Final name must be initialized with a value  [misc]
Found 2 errors in 1 file (checked 1 source file)
$ dmypy check src
src/dmypy_final_bug/__init__.py:10: error: Final name must be initialized with a value  [misc]
src/dmypy_final_bug/__init__.py:11: error: Final name must be initialized with a value  [misc]
src/dmypy_final_bug/__init__.py:15: error: Final name must be initialized with a value  [misc]
src/dmypy_final_bug/__init__.py:16: error: Final name must be initialized with a value  [misc]
Found 4 errors in 1 file (checked 1 source file)

Your Environment

• python==3.12.4
• mypy==1.11.1
• torch==2.4.0