Check keyword arguments in class definitions

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#2,653 1 comment 0 reactions 0 assignees View on GitHub

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Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
35/100
Issue type
Bug
Clarity
Mostly clear
Activity status
Stale
Tech stack
python
Domain
compilers

Research direction

Start with the reproducer in the issue and trace mypy's handling of class definitions and custom class keyword arguments. Inspect how new and init_subclass signatures are checked, then add regression coverage for invalid and accepted keywords. Done means mypy rejects unsupported class-definition keyword arguments while preserving valid cases.

Written by the indexing model from the issue text.

Description

feature priority-2-low topic-metaclasses topic-runtime-semantics

Currently, this incorrect code passes mypy:

class C(a=3):
    pass

It should check that __new__/__init_subclass__ accepts these keyword arguments.

This doesn't seem high-priority to fix since custom class kwargs are rarely used and this should usually cause import-time errors anyway when running the code, but I'm reporting it so it can be tracked.

Dominant language
Python
Stars
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Forks
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Avg merge
1d 18h
Merged PRs (30d)
54

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