`F821 Undefined name` when definition is after usage

[samuelcolvin]

Ruff looks great, congratulations. I'd love to use it one day on pydantic instead of flake8.

---

The following code is valid python and runs fine

def main():
    foo()

def foo():
    print('this is foo')

main()

However ruff returns:

test.py:2:5: F821 Undefined name `foo`

Found 1 error(s).

Running ruff on pydantic's code base is currently returning 151 F821 errors, so it's a fairly common problem.

[charliermarsh]

Thank you! Really flattered by the interest.

This is a legit bug. We have to defer checking function scopes until we've parsed the rest of the module. It's known but unhandled. Gonna use this issue for tracking.

[samuelcolvin]

great, thanks so much.