python / python/mypy

(🐞) Invalid error when inplace operator is an instance, not 'function'

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Dominant language
Python
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Description

Based on testGenericOperatorMethodOverlapping

class B:
    def __init__(self, _): ...
    def __call__(self, x: object) -> object: ...

class A:
    @B
    def __or__(self) -> None: ...
    def __ior__(self, x: object) -> object: ...  # error: Signatures of "__ior__" and "__or__" are incompatible  [misc]

Contributor guide

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First steps

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  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start with the testGenericOperatorMethodOverlapping case mentioned in the report and trace how mypy checks the relationship between or and ior when or is decorated with an instance. Reproduce the example, then verify that the erroneous incompatible-signatures diagnostic is no longer emitted while valid operator checks remain covered.

Written by the indexing model from the issue text.

Assessment

Tech stack
python
Domain
devtools
Issue type
Bug
Difficulty
3/5
Estimated time
1-2 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
45/100

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