(🐞) Narrower overload impl return included in union creates false error
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bug
topic-overloads
- Dominant language
- Python
- Stars
- 20.6k
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Description
related to: #12434
from typing import overload
@overload
def f(a: int) -> int: ...
@overload
def f(a: str) -> str: ...
def f(a: int | str) -> bool | str: ... # E: Overloaded function implementation cannot produce return type of signature 1
This impl can definitely produce the return type of signature 1.
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Research direction
Reproduce the overload example first, then trace mypy's overload implementation compatibility check. Done when the shown example no longer reports the false error and a regression test covers this narrower implementation return type.
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
- 38/100