[edgarrmondragon]

When the return type is a bare type variable (or an optional one) and the type context is a union mixing literals (or sentinels, or enums) with other types, the context was used to solve the type variable before looking at the arguments. This could produce a spurious error if an argument was wider than the context:

def none_if_one[T](value: T | Literal[1]) -> T | None: ...

x: str | Literal[1] | None = 1
x = none_if_one(x)  # error: expected "str | Literal[1]"

Now, if using the literal context produces errors, retry inference from the arguments only, and use that if it type checks and the result is compatible with the context.

Fixes #22334

[ilevkivskyi]

Sorry, but I think this is (very) wrong. IMO this issue should be solved by removing None-related special-casing in infer_function_type_arguments_using_context() after #22286 (and its equivalent for second pass) is merged. Only if that doesn't work for some reasons we can consider some hacks.

(FWIW I verified my idea locally and it works, but there is also primer...)

[github-actions]

According to mypy_primer, this change doesn't affect type check results on a corpus of open source code. ✅

[edgarrmondragon]

Sorry, but I think this is (very) wrong [...]

Ok, thanks for taking a look 🙇‍♂️. Removing the is_overlapping_none checks in your branch does make the tests in this PR pass and I couldn't find any obvious regression related to generics and literals/enums/sentinels.