python / python/mypy

false positive errors when calling operator override that returns `Never` from another function that returns `Never`

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bug
Dominant language
Python
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Description

from typing import Never

class Foo:
    def __mul__(self, value: float, /) -> Never:
        raise Exception("multiplication is banned")

    def __rmul__(self, value: float, /) -> Never: # error: Implicit return in function which does not return  [misc]
        self * value
    
    def __rmul_attempt_2__(self, value: float, /) -> Never:
        return self * value # error: Return statement in function which does not return  [misc]

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Research direction

Reproduce the diagnostics in the linked mypy playground using the two Never-returning operator examples. Then locate the relevant return and Never checking path and add a regression test showing that both calls are accepted; done when the false-positive errors disappear without weakening the intended Never checks.

Written by the indexing model from the issue text.

Assessment

Tech stack
python
Domain
compilers
Issue type
Bug
Difficulty
3/5
Estimated time
1-2 days
Activity status
Stale
Clarity
Clearly specified
Newbie friendliness
45/100

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