Stabilize Ipv6Addr::to_ipv4_mapped

[tbu-]

CC #27709 (tracking issue for the ip feature which contains more
functions)

The function Ipv6Addr::to_ipv4 is bad because it also returns an IPv4
address for the IPv6 loopback address ::1. Stabilize
Ipv6Addr::to_ipv4_mapped so we can recommend that function instead.

[rust-highfive]

Hey! It looks like you've submitted a new PR for the library teams!

If this PR contains changes to any rust-lang/rust public library APIs then please comment with r? rust-lang/libs-api @rustbot label +T-libs-api -T-libs to request review from a libs-api team reviewer. If you're unsure where your change falls no worries, just leave it as is and the reviewer will take a look and make a decision to forward on if necessary.

Examples of T-libs-api changes:

• Stabilizing library features
• Introducing insta-stable changes such as new implementations of existing stable traits on existing stable types
• Introducing new or changing existing unstable library APIs (excluding permanently unstable features / features without a tracking issue)
• Changing public documentation in ways that create new stability guarantees
• Changing observable runtime behavior of library APIs

[rust-highfive]

r? @kennytm

(rust-highfive has picked a reviewer for you, use r? to override)

[tbu-]

r? rust-lang/libs-api @rustbot label +T-libs-api -T-libs

[dtolnay]

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

https://doc.rust-lang.org/std/net/struct.Ipv6Addr.html#method.to_ipv4_mapped

[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
• @yaahc

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. 🔔

[dtolnay]

@bors r+

[bors]

📌 Commit 813c5b0 has been approved by dtolnay

[bors]

⌛ Testing commit 813c5b0 with merge d125574...

[bors]

☀️ Test successful - checks-actions
Approved by: dtolnay
Pushing d125574 to master...

[rust-timer]

Finished benchmarking commit (d125574): comparison url.

Instruction count

This benchmark run did not return any relevant results for this metric.

Max RSS (memory usage)

Results

• Primary benchmarks: 🎉 relevant improvement found
• Secondary benchmarks: 🎉 relevant improvements found

	Regressions 😿 (primary)	Regressions 😿 (secondary)	Improvements 🎉 (primary)	Improvements 🎉 (secondary)	All 😿 🎉 (primary)
count1	0	0	1	2	1
mean2	N/A	N/A	-3.2%	-1.9%	-3.2%
max	N/A	N/A	-3.2%	-2.0%	-3.2%

Cycles

Results

• Primary benchmarks: mixed results
• Secondary benchmarks: no relevant changes found

	Regressions 😿 (primary)	Regressions 😿 (secondary)	Improvements 🎉 (primary)	Improvements 🎉 (secondary)	All 😿 🎉 (primary)
count1	1	0	1	0	2
mean2	2.4%	N/A	-1.6%	N/A	0.4%
max	2.4%	N/A	-1.6%	N/A	2.4%

If you disagree with this performance assessment, please file an issue in rust-lang/rustc-perf.

@rustbot label: -perf-regression

Footnotes

1. number of relevant changes ↩ ↩²

2. the arithmetic mean of the percent change ↩ ↩²