python / python/mypy

no error when setting property defined without decorator to incorrect type

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#13,128 0 comments 2 reactions 0 assignees View on GitHub

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Dominant language
Python
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Description

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

a = A()

a.foo = "" # no error

playground
related: #13127

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  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 property example and its mypy-play reproduction, then compare the behavior with related issue #13127. Trace how mypy infers the setter type for a property created without a decorator. Done means the shown assignment to a property whose setter expects int is reported as a type error, with appropriate regression coverage.

Written by the indexing model from the issue text.

Assessment

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

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