Stabilize {IpAddr, Ipv6Addr}::to_canonical

[tgross35]

Make IpAddr::to_canonical and IpV6Addr::to_canonical stable (+const), as well as const stabilize Ipv6Addr::to_ipv4_mapped.

Newly stable API:

impl IpAddr {
    // Newly stable under `ip_to_canonical`
    const fn to_canonical(&self) -> IpAddr;
}

impl Ipv6Addr {
    // Newly stable under `ip_to_canonical`
    const fn to_canonical(&self) -> IpAddr;

    // Already stable, this makes it const stable under
    // `const_ipv6_to_ipv4_mapped`
    const fn to_ipv4_mapped(&self) -> Option<Ipv4Addr>
}

These stabilize a subset of the following tracking issues:

• Tracking issue for Ipv{4,6}Addr convenience methods #27709
• Constify std::net::IpAddr, Ipv4Addr, and Ipv6Addr #76205

Stabilization of all methods under the ip gate was attempted once at #66584 then again at #76098. These were not successful because there are still unknowns about is_documentation is_benchmarking and similar; to_canonical is much more straightforward.

I have looked and could not find any known issues with to_canonical. These were added in 2021 in #87708

cc implementor @the8472

r? libs-api
@rustbot label +T-libs-api +needs-fcp

[dtolnay]

@rust-lang/libs-api:
@rfcbot fcp merge

[rfcbot]

Team member @dtolnay 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.

[rfcbot]

🔔 This is now entering its final comment period, as per the review above. 🔔

[rfcbot]

The final comment period, with a disposition to merge, as per the review above, is now complete.

As the automated representative of the governance process, I would like to thank the author for their work and everyone else who contributed.

This will be merged soon.

[dtolnay]

Thank you!

[dtolnay]

@bors r+

[bors]

📌 Commit 7381f9d has been approved by dtolnay

It is now in the queue for this repository.