ACP: change as_{mut,const} on pointers to cast_{mut,const}

[Kixunil]

Proposal

Problem statement

The as_mut method on *const T may be confused with *mut T.

Motivation, use-cases

This confusion already broke the doc once. Also I believe cast_ is more clear, especially since a similar cast() method exists.

Solution sketches

Rename the method to use cast_ prefix

Links and related work

#92675
#98174

What happens now?

This issue is part of the libs-api team API change proposal process. Once this issue is filed the libs-api team will review open proposals in its weekly meeting. You should receive feedback within a week or two.

[yaahc]

This confusion already broke the doc once. Also I believe cast_ is more clear, especially since a similar cast() method exists.

can you link to the example you're referring to?

[cuviper]

I'm not sure what broke, but to be more explicit about the confusion, we have one that casts and one that forms a reference, which is an unresolved question on rust-lang/rust#92675.

• <*const T>::as_mut(self) -> *mut T (unstable)
• <*mut T>::as_mut<'a>(self) -> Option<&'a mut T> (stable 1.9)

[yaahc]

I'm not sure what broke, but to be more explicit about the confusion, we have one that casts and one that forms a reference, which is an unresolved question on rust-lang/rust#92675.

* `<*const T>::as_mut(self) -> *mut T` (unstable)

* `<*mut T>::as_mut<'a>(self) -> Option<&'a mut T>` (stable 1.9)

that seems to support the renaming being proposed here

[scottmcm]

👍 from me. Having the common prefix sounds good.

[yaahc]

Seconded

@rustbot label +initial-comment-period

[rustbot]

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[yaahc]

gosh dangit

[yaahc]

trying to fix it but, uuuh, github is having a moment... #52

just gonna add the label manually for now

[Kixunil]

There was also an interesting point that to_mut/to_const may be better: rust-lang/rust#98174 (comment)

Regarding breaking the docs, I meant this: rust-lang/rust#96327

[yaahc]

There was also an interesting point that to_mut/to_const may be better: rust-lang/rust#98174 (comment)

According to https://rust-lang.github.io/api-guidelines/naming.html#ad-hoc-conversions-follow-as_-to_-into_-conventions-c-conv that wouldn't be consistent with the ways we normally use as_ vs to_. Best alternative I can think up with that is consistent with the naming guidelines would be as_mut_ptr

[cuviper]

There is already <*mut [T]>::as_mut_ptr(self) -> *mut T too.

[joboet]

There was also an interesting point that to_mut/to_const may be better: rust-lang/rust#98174 (comment)

According to https://rust-lang.github.io/api-guidelines/naming.html#ad-hoc-conversions-follow-as_-to_-into_-conventions-c-conv that wouldn't be consistent with the ways we normally use as_ vs to_. Best alternative I can think up with that is consistent with the naming guidelines would be as_mut_ptr

Since this is a method of a Copy type which does not change the level of abstraction, to seems more fitting than as when following the API guidelines.

It would put the method in the same category as e.g. f32::to_bits or Cow::to_mut. I think it reads really well.

[joshtriplett]

We discussed this in today's libs-api meeting, and ended up settling on cast_*.