Tracking Issue for fn unsigned_abs

[carbotaniuman]

This is a tracking issue for fn unsigned_abs on signed integral types.
The feature gate for the issue is #![feature(unsigned_abs)].

About tracking issues

Tracking issues are used to record the overall progress of implementation.
They are also uses as hubs connecting to other relevant issues, e.g., bugs or open design questions.
A tracking issue is however not meant for large scale discussion, questions, or bug reports about a feature.
Instead, open a dedicated issue for the specific matter and add the relevant feature gate label.

Steps

• Stabilization PR (see instructions on rustc-dev-guide)

Implementation history

First implemented in #74759

[jhpratt]

Are there any outstanding issues with this feature gate? It has a trivial implementation that is unquestionably correct, and it seemed quite clear in the RFC that it was desired.

[Kixunil]

One significant issue I see is currently the implementation for isize returns u64 instead of usize.

Documentation of the function
Playground proof that the implementation matches the documentation

Edit: I found the reason. The macro int_impl is called with u64 instead of usize as $UnsignedT. This was not a problem so far because $UnsignedT didn't appear in any function signature until now. So changing the call site for all pointer sizes should be enough.

[jhpratt]

Hmm…the behavior is different for different widths (16, 32, or 64). However, usize and u16/32/64 are not the same type. I'll make a modification locally and open a PR shortly.

[Kixunil]

Yes, exactly. Good job with the PR!

[AngelicosPhosphoros]

Why unsigned_abs of isize returns u64 instead of usize?
IMHO, it is not valid.
https://doc.rust-lang.org/std/primitive.isize.html#method.unsigned_abs

@carbotaniuman @jhpratt

[CryZe]

This is fixed on nightly (that you need anyway to use this for now)

[AngelicosPhosphoros]

Nice, thank you!