Tracking Issue for bound_as_ref

[glittershark]

Feature gate: #![feature(bound_as_ref)]

This is a tracking issue for providing as_ref and as_mut on bound. These methods mirror similar methods on the Option type.

Public API

impl<T> Bound<T> {
  pub fn as_ref(&self) -> Bound<&T>;
  pub fn as_mut(&mut self) -> Bound<&mut T>;
}

Steps / History

• Implementation: Add as_ref and as_mut methods for Bound #80444
• Final commenting period (FCP)
• Stabilization PR

Unresolved Questions

• None yet.

[tesuji]

Note: Please add ; after pub fn line in the API summary above. Without it, syntax highlighting broke.

[drmason13]

Hi, I just spotted that the docs have a typo and commented on the merge request. I hope that's ok, don't mean to be rude :)

[glittershark]

Hi, I just spotted that the docs have a typo and commented on the merge request. I hope that's ok, don't mean to be rude :)

not at all! good find :)

[glittershark]

That's fixed in #86101

[glittershark]

This has been unstable since Jan 14 and seems relatively uncontroversial, modulo that issue, so I'd love to get the stabilization process kicked off. @dtolnay you reviewed the original PR, any qualms with that?

[dtolnay]

as_ref seems well motivated to me and I would be prepared to propose FCP. Given that RangeBounds revolves around returning Bound<&T>, having an easy way to acquire them from non-borrowed data is compelling.

But does anybody so far have a real world use case for as_mut? Can we delete it?

[glittershark]

But does anybody so far have a real world use case for as_mut? Can we delete it?

it would seem weird to have as_ref and not as_mut, wouldn't it? especially since Option has both. I feel like that violates principle of least surprise.

[dtolnay]

Okay but Option::as_mut is widely used and useful.

[glittershark]

I guess my point is that if Option::as_mut is useful, then Bound::as_mut is reasonably likely to be useful as well, and I don't see a downside to including it - but that latter point is something that maintainers are much more likely to have opinions about than me 😄. Definitely not my hill to die on, though.

[dtolnay]

@rfcbot poll libs-api Delete core::ops::Bound::as_mut because it is useless as far as any of us can tell
@rfcbot poll libs-api Keep core::ops::Bound::as_mut because wherever a as_ref exists, so must as_mut, even if useless

[rfcbot]

Team member @dtolnay has asked teams: T-libs-api, for consensus on:

Delete core::ops::Bound::as_mut because it is useless as far as any of us can tell

• @Amanieu
• @BurntSushi
• @dtolnay
• @joshtriplett
• @m-ou-se
• @yaahc

[rfcbot]

Team member @dtolnay has asked teams: T-libs-api, for consensus on:

Keep core::ops::Bound::as_mut because wherever a as_ref exists, so must as_mut, even if useless

• @Amanieu
• @BurntSushi
• @dtolnay
• @joshtriplett
• @m-ou-se
• @yaahc