gh-104050: Argument clinic: enable mypy's --warn-return-any setting - #107405
gh-104050: Argument clinic: enable mypy's --warn-return-any setting#107405AlexWaygood merged 4 commits into
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Good sleuthing! |
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| filename: str = '-' | ||
| ) -> FunctionType: | ||
| ) -> Any: |
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Should we add a comment as to why Any is the correct annotation here?
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You weren't going to make finally closing that issue easy, were you? ;)
Let me know if a5103be is too verbose...!
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Hmm, actually, now that I look at it again, the comment feels like it duplicates the docstring a little bit... not sure if it's worth it? I'll defer to you on whether it's helpful or not!
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Sorry, you're right. The docstring should be enough!
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Okay -- removed the comment again and tweaked the docstring slightly! How's it look now?
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erlend-aasland
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Yay!
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Mypy's --warn-return-any check flags when a function is declared to return a specific type, but mypy can't verify whether it's actually returning that type or not -- it can only infer a vague, unsafe Any type as the returned type. This can often lead to bugs slipping beneath the radar.
In the case of argument clinic, the check only flags a single function. But, turns out that it's a true positive! The function is incorrectly annotated at the moment -- the annotation says that it returns a FunctionType, but that's not true. The function creates a FunctionType instance fn, and then returns whatever calling fn returns returns. Therefore, the proper return annotation for this function is -> Any, not -> FunctionType.
Closes #104050!