[bug] F401 false positive for imports inside functions

[smackesey]

Contrived example, but ruff 0.0.271 flags the below import inside of fn with F401 (unused import) and auto-deletes it, but this results in a runtime error when you execute the code, because the first argument to cast doesn't get a deferred annotation like a function parameter:

from __future__ import annotations

from typing import TYPE_CHECKING, cast

if TYPE_CHECKING:
    from threading import Thread


def fn(thread: Thread):
    from threading import Thread  # Flagged as F401

    casted_thread = cast(Thread, thread)
    return casted_thread

print(fn(1))

You can work around it by quoting the cast argument, but still a bug.

[charliermarsh]

Oops, thanks. I’ll fix this tonight. I need to cut a new release anyway.