functools.partial false negative with higher order functions
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bug
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- Python
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Description
See https://github.com/python/mypy/pull/17425 , in particular this comment https://github.com/python/mypy/pull/17425#discussion_r1650028681 from ilevkivskyi
[case testFunctoolsPartialHigherOrder]
from functools import partial
from typing import Callable
def fn(a: int, b: str, c: bytes) -> int: ...
def callback1(fn: Callable[[str, bytes], int]) -> None: ...
def callback2(fn: Callable[[str, int], int]) -> None: ...
callback1(partial(fn, 1))
# TODO: false negative
callback2(partial(fn, 1))
[builtins fixtures/tuple.pyi]
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start with the testFunctoolsPartialHigherOrder case in the referenced pull request and read the linked discussion comment for the intended behavior. Verify that callback1(partial(fn, 1)) remains accepted while callback2(partial(fn, 1)) is rejected, then run the relevant mypy test suite.
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