PEP 695 type annotations with lambdas produce false F401

[rijenkii]

Minimal reproduction:

from typing import Annotated
import re

type X = Annotated[int, lambda: re.compile("x")]

Result:

$ ruff repro.py --isolated
repro.py:2:8: F401 [*] `re` imported but unused
Found 1 error.
[*] 1 fixable with the `--fix` option.

Settings:

[tool.ruff.lint]
select = ["F", "E"]

Version 0.1.8

[charliermarsh]

Thanks! Agree that we should probably fix this, although I admittedly don't understand how Annotated is supposed to work here. For example:

from typing import Annotated

type X = Annotated[int, lambda: re.compile("x")]
print(X.__metadata__)

Yields:

Traceback (most recent call last):
  File "/Users/crmarsh/workspace/foo.py", line 10, in <module>
    print(X.__metadata__)
          ^^^^^^^^^^^^^^
AttributeError: 'typing.TypeAliasType' object has no attribute '__metadata__'. Did you mean: '__getstate__'?

[charliermarsh]

On the other hand, Ruff correctly does not flag F401 here:

from typing import Annotated

X = Annotated[int, lambda: re.compile("x")]
print(X.__metadata__)

So I suspect our treatment right be correct.

[rijenkii]

Thanks! Agree that we should probably fix this, although I admittedly don't understand how Annotated is supposed to work here

Here:

>>> from typing import Annotated
>>> import re
>>> type X = Annotated[int, lambda: re.compile("x")]
>>> print(X.__value__.__metadata__)
(<function X.<locals>.<lambda> at 0x7f4df0747f60>,)

[charliermarsh]

Huh, ok. I will admit that I find Annotated very strange but I agree that this is a false positive. Thanks.

[rijenkii]

This example also produces an F401 and has no Annotation. I have not used it in the OP because according to pyright it is just wrong, but it works at runtime:

import re
type X = lambda: re.compile("x")

$ ruff repro.py --isolated
repro.py:1:8: F401 [*] `re` imported but unused
Found 1 error.
[*] 1 fixable with the `--fix` option.

>>> import re
>>> type X = lambda: re.compile("x")
>>> X.__value__
<function X.<locals>.<lambda> at 0x7f6d4cb30040>
>>> X.__value__()
re.compile('x')