Fix #5326: Fix false positive for unused-variable for a comprehension variable matching a type annotation

[jacobtylerwalls]

Type of Changes

	Type
✓	🐛 Bug fix

Description

Fixes the regression described in #5326 where undefined-variable is emitted when a comprehension variable matches a type annotation.

One test result is edited to show that after these changes we will need better detection of walrus operators.

Fixes #5326

[coveralls]

Pull Request Test Coverage Report for Build 1672085133

• 1 of 1 (100.0%) changed or added relevant line in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 93.704%

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Totals
Change from base Build 1663696938:	0.0%
Covered Lines:	14363
Relevant Lines:	15328

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💛 - Coveralls

[DanielNoord]

Knowing you you have probably already investigated this, but it was impossible to fix this without creating the false negative?

[jacobtylerwalls]

Knowing you you have probably already investigated this, but it was impossible to fix this without creating the false negative?

Ha. So my thought there was that it was wrong to make _is_only_type_assignment() responsible for finding undefined variables in self-referencing walrus operator expressions. Pylint already has trouble with that, and it has nothing to do with with type annotations at all. I'll open a new issue.

$ cat test.py
'''Should raise undefined-variable'''
if (var := var):
    print(var)
$ pylint test.py

-------------------------------------------------------------------
Your code has been rated at 10.00/10 (previous run: 5.00/10, +5.00)

I'm assuming that's the false negative you meant, since it was "created" instead of "left alone." (But "created" only insofar as we were getting lucky 🎲 .)

If you meant the false negative I started to describe in #5326 (comment), then to keep things sane I'll just break that out into a new issue. I think they can be addressed separately.

[Pierre-Sassoulas]

Thanks a lot @jacobtylerwalls, very elegant fix !

[Pierre-Sassoulas]

I like the small optimization to save a "not" on top of the clever fix !