python / python/mypy

no error when getter and setter types don't match in `property.__init__`

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#13,127 2 comments 2 reactions 0 assignees View on GitHub

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feature topic-descriptors
Dominant language
Python
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Description

class A:
    def _get_foo(self) -> int:
        ...
    def _set_foo(self, value: str) -> None:
        ...
    foo = property(fget=_get_foo, fset=_set_foo)

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Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  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 provided Python reproduction and trace mypy's handling of property.init when checking the getter and setter annotations. Run mypy on the snippet to confirm the missing diagnostic; done means incompatible getter and setter types produce an error.

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
38/100

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