Document undesirable generator expression behavior in test and fix one case #20594
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michaelm-openai
commented
Jan 16, 2026
| take_iterable(reveal_type(1 for _ in [])) # N: Revealed type is "typing.Generator[builtins.int, None, None]" | ||
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| # NOTE: Type is revealed for every overload tried | ||
| # TODO: Overload shouldn't fail if expression contains an error that shouldn't affect the inferred type. |
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I guess this is not strictly true, since it could be that the overload adds contextual information that causes the expression to have an error. Maybe a better behavior is if every overload contains errors, then pick the one with a valid inferred expression type.
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According to mypy_primer, this change doesn't affect type check results on a corpus of open source code. ✅ |
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Adds a test case to explicitly demonstrate behavior which I believe has the same root cause as #18026
The short explanation is that if any get produced while inferring the type of a generator expression which is being passed to an overloaded function, the overload will be considered failed, even if the error has no effect on the inferred type of the generator expression.
One experiment to try that might address this could be to only fail the overload if the inferred type contains
AnyType(TypeOfAny.from_error).For now, only fix the specific case where the "error" is a
reveal_typenote.