python / python/mypy

Generic function can't make function call with mapping unpacking

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#11,583 12 comments 8 reactions 0 assignees View on GitHub

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bug topic-calls
Dominant language
Python
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Description

from typing import Any, Optional, TypeVar

_T = TypeVar('_T')

def f(b: bool = True, **kwargs: Any) -> None:
    pass

def g(x: _T) -> _T:
    f(**{'x': x})
    return x

gives

a.py:9: error: Argument 1 to "f" has incompatible type "**Dict[str, _T]"; expected "bool"

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Research direction

The issue names no repository files, tests, or entry points. Start by running the supplied minimal reproducer through mypy and tracing the diagnostic for the generic function's mapping unpacking. Done means this example no longer reports the incompatible-type error.

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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