I'll wait for reviews before doing a typeshed PR :)

What should we do for type aliases like this, in fractions.pyi?

_ComparableNum: TypeAlias = int | float | Decimal | Real

Strictly speaking we can "simplify" this union to float | Decimal | Real. But it's more explicit and clear as it is, imo. Should we exempt type aliases from this check?

https://github.com/python/typeshed/blob/7576805aee96fe091821d4c963c46645a1894052/stdlib/fractions.pyi#L8

I would maybe even consider to exempt return types. -> int | float, while redundant, makes it clear that not all values returned must be floats, a distinction that is meaningless for argument types. But I have no strong feelings either way.