B909 false positive when directly returning mutation

[TeamSpen210]

Summary

The B909 rule checks for mutations to loop iterables, but permits cases where return/break would prevent further iterations. However if the return and the mutation are the same statement it flags the value.

Example:

def fail_map(mapping):
    for key in mapping:
        return mapping.pop(key)  # false positive

def success_map(mapping):
    for key in mapping:
        ret = mapping.pop(key)  # passes
        return ret

def fail_list(seq):
    for val in seq:
        return seq.pop(4)  # also false positive

Used ruff check --preview --isolated --select B909 iter_mut_bug.py.

Version

ruff 0.11.11 (0397682 2025-05-22)

[ntBre]

Thanks for the report! Without looking at the code this seems like a pretty straightforward fix since we already handle the second case here.