Tracking Issue for `core::iter::chain`

[rossmacarthur]

Feature gate: #![feature(iter_chain)]

This is a tracking issue for the core::iter::chain function that combines two IntoIterator arguments together into a Chain iterator.

Public API

// core::iter
pub fn chain<A, B>(a: A, b: B) -> Chain<A::IntoIter, B::IntoIter>
where
    A: IntoIterator,
    B: IntoIterator<Item = A::Item>;

Steps / History

• Approved ACP Add core::iter::chain method libs-team#154
• Implementation: Add function core::iter::chain #106186
• Final comment period (FCP)¹
• Stabilization PR: Stabilize core::iter::chain #144963

Unresolved Questions

• None yet.

Footnotes

1. https://std-dev-guide.rust-lang.org/feature-lifecycle/stabilization.html ↩

[scottmcm]

I was reminded of this by it showing up on URLO: https://users.rust-lang.org/t/iterator-extension-allthesame/117972/3?u=scottmcm

Can we just stabilize it? Having both sides be IntoIterator is nice.

Only other choice I could come up with for the signature would be

pub fn chain<A, B>(a: impl IntoIterator<IntoIter = A>, b: impl IntoIterator<IntoIter = B>) -> Chain<A, B>
where
    A: Iterator,
    B: Iterator<Item = A::Item>;

but that really doesn't seem materially better, so as it is seems good.

[japm48]

Hi, any news on this?
I'm unfamiliar with the process, but is there any reason why the FCP has not yet started?

[rossmacarthur]

@rust-lang/libs-api can we start an FCP for this?

[rossmacarthur]

@Mark-Simulacrum / @workingjubilee / @jhpratt can we start an FCP for this?

[jhpratt]

Unsure why I'm being pinged; I have nothing to do with FCPs, nor have I ever. Maybe try asking on Zulip?

[Amanieu]

@rfcbot merge

[rfcbot]

Team member @Amanieu has proposed to merge this. The next step is review by the rest of the tagged team members:

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

No concerns currently listed.

Once a majority of reviewers approve (and at most 2 approvals are outstanding), this will enter its final comment period. If you spot a major issue that hasn't been raised at any point in this process, please speak up!

See this document for info about what commands tagged team members can give me.