python / python/mypy

(🐞) double partial handled incorrectly

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bug
Dominant language
Python
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Description

a = None
a = []
a.append("")
a = None  # incompatible, expected list[str], found None

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First steps

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  4. Open a pull request that references the issue number.

Research direction

The issue provides only a Python reproducer and names no files or tests. Start by running the snippet through mypy and tracing the partial-type handling that produces the diagnostic. Before changing behavior, establish the intended result for the second assignment and add a focused regression test showing the corrected diagnostic.

Written by the indexing model from the issue text.

Assessment

Tech stack
python
Domain
tooling
Issue type
Bug
Difficulty
3/5
Estimated time
1-2 days
Activity status
Stale
Clarity
Needs clarification
Newbie friendliness
32/100

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