python / python/mypy

__set_name__ isn't checked

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#8,057 1 comment 3 reactions 0 assignees View on GitHub

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feature priority-1-normal topic-descriptors
Dominant language
Python
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Description

from typing import Type

class Foo:
	def __set_name__(self, owner: Type['Bar'], name: str) -> None:
		...

class Bar:
	foo_bar = Foo() # correctly passes

class Baz:
	foo_baz = Foo() # should fail

mypy correctly accepts Bar.foo_var, but incorrectly accepts Baz.foo_baz

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First steps

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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 by reproducing the supplied example with mypy and inspect how descriptor set_name annotations are checked. The fix is done when Bar.foo_bar remains accepted while Baz.foo_baz is rejected, with coverage for both cases.

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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