Why is the product of Real numbers Any?

[Kakadus]

Consider the following code:

from numbers import Real

a: Real
b: Real
reveal_type(a * b)  # Any
reveal_type(a + b)  # Any
reveal_type(a - b)  # Any
reveal_type(a / b)  # Any

reveals Any during typechecking. Why is this the case? Even if b is typed as int or float, the result is still Any

From a mathematical perspective, this does not seem to make much sense.

I'm using latest mypy on python 3.11

[srittau]

Looking at the numbers module, while many arguments and return types are explicitly annotated using Any, I think most of those are actually unannotated. Many Anys were added in #4401, possibly to remove warnings about partially/unannotated methods. Maybe @erictraut remembers details.

[JelleZijlstra]

Note that the numbers module in general doesn't play well with type checking; see python/mypy#3186 for much background on why.

I don't see a reason why we can't annotate the return types of method like Real.__add__, though.

[erictraut]

@srittau, I don't remember the details of that PR. I think I was on a mission at that time to get all of the stdlib stubs to be "complete" with regard to return type annotations.

[srittau]

I've removed the Any annotations. Now at least we clearly mark the stubs as unannotated. Any PR to improve the situation welcome! I'm going to close the issue though, since we don't keep issues for unannotated stubs open. Thanks, for reporting this, @Kakadus!