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(🐞) false error: undefined-loop-variable when for loop has terminating else branch #5971

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KotlinIsland opened this issue Mar 25, 2022 · 2 comments · Fixed by #6480
Closed

(🐞) false error: undefined-loop-variable when for loop has terminating else branch #5971

KotlinIsland opened this issue Mar 25, 2022 · 2 comments · Fixed by #6480
Labels
Control flow Requires control flow understanding False Positive 🦟 A message is emitted but nothing is wrong with the code
Milestone
2.13.8

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@KotlinIsland
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KotlinIsland commented Mar 25, 2022 •
edited
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Bug description

def foo(l):
    for i in l:
        break
    else:
        return
    print(i)

Configuration

No response

Command used

pylint test.py

Pylint output

************* Module test
test.py:6:10: W0631: Using possibly undefined loop variable 'i' (undefined-loop-variable)

Expected behavior

no error

Pylint version

pylint 2.13.0
astroid 2.11.1
Python 3.10.2 (tags/v3.10.2:a58ebcc, Jan 17 2022, 14:12:15) [MSC v.1929 64 bit (AMD64)]

OS / Environment

No response

Additional dependencies

No response
@KotlinIsland KotlinIsland added the Needs triage 📥 Just created, needs acknowledgment, triage, and proper labelling label Mar 25, 2022
@KotlinIsland KotlinIsland changed the title false error: undefined-loop-variable when for loop has terminating else branch (🐞) false error: undefined-loop-variable when for loop has terminating else branch Mar 25, 2022
@Pierre-Sassoulas Pierre-Sassoulas added False Positive 🦟 A message is emitted but nothing is wrong with the code and removed Needs triage 📥 Just created, needs acknowledgment, triage, and proper labelling labels Mar 25, 2022
@DanielNoord
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Related are #5608, #5146.

@jacobtylerwalls Please help me remember, what was our conclusion about this message. Were you going to take a look at the larger problem with this message and these patterns for 2.14?

@jacobtylerwalls
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Were you going to take a look at the larger problem with this message and these patterns for 2.14?

I was just waiting for input on #5649 -- I'll update the PR itself, looks like most discussion happened on the issue.

But that said, I think this issue is a completely isolated control-flow issue. We just lack any logic to know that else: return means you can depend on i being defined.

@jacobtylerwalls jacobtylerwalls added the Control flow Requires control flow understanding label Mar 25, 2022
@jacobtylerwalls jacobtylerwalls mentioned this issue May 1, 2022
Merged
@jacobtylerwalls jacobtylerwalls added this to the 2.13.8 milestone May 1, 2022
@DetachHead DetachHead mentioned this issue Aug 16, 2022
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Labels
Control flow Requires control flow understanding False Positive 🦟 A message is emitted but nothing is wrong with the code
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Milestone
2.13.8
4 participants
@Pierre-Sassoulas @DanielNoord @jacobtylerwalls @KotlinIsland