python
warn unused ignores flag does not respect TYPE_CHECKING
Bug Report
With pandas-stubs, we are using pyright and mypy. We have code that we want to test with pyright, but not mypy because of a mypy bug. We are using the always-true option, but the issue here can be shown using TYPE_CHECKING.
If you include the flag --warn-unused-ignores, then the warnings will occur on code that should not be checked if looking at constants like TYPE_CHECKING or those set by always-true.
To Reproduce
from typing import TYPE_CHECKING
if not TYPE_CHECKING:
x: int = "abc" # type: ignore[assignment]
Using mypy --no-incremental --warn-unused-ignores ignoretst.py, you get the error:
ignoretst.py:4: error: Unused "type: ignore" comment
Expected Behavior
No warning reported.
Actual Behavior
See above - even though the code should NOT be type checked, you are getting a warning.
Your Environment
- Mypy version used: 0.991
- Mypy command-line flags:
--no-incremental --warn-unused-ignores - Mypy configuration options from
mypy.ini(and other config files): None - Python version used: 3.9
The underlying problem is the same as #8823: mypy reports that type: ignore comments are "unused" if they appear in code blocks that it detects are unreachable. (To an extent, that's a logical conclusion: you "obviously" can't be "using" the type: ignore comment if it's in a section of code that you can't ever get to!)
