[flake8-bugbear] Avoid false positive for usage after continue (B031)

[yt2b]

Summary

#10337
I've fixed the code to count usage of variable.
Usage count inside the block is reset when there is a following statement.

• continue
• break
• return

Test Plan

Add test case.

[github-actions]

ruff-ecosystem results

Linter (stable)

✅ ecosystem check detected no linter changes.

Linter (preview)

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[charliermarsh]

Looks good, thanks!

[dhruvmanila]

I don't think this is the correct solution as it will not work for nested for loops. This is when the continue/break/return is without an if condition as there isn't any dedicated counter value in the stack for the for loop. For example:

for _, group in itertools.groupby(...):
	use_group(group)
	for _ in range(5):
		use_group(group)  # B031
		continue
	use_group(group)  # B031

This PR stops highlighting the second B031 in the above snippet which is incorrect. The continue is only for the inner for loop. For return, it would be different as it actually exits the loop.

[charliermarsh]

@dhruvmanila - It seems like we're fixing a common false positive but introducing a less common false negative, so it seems like the right tradeoff, unless you disagree? Feel free to file an issue if so.