Move std::io::util to core::io

[bushrat011899]

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ACP: rust-lang/libs-team#755
Tracking issue: #154046
Subset of: #154684

Description

Moves utility types and functions from std::io::util and std::io to core::io, leaving any IO trait implementations behind. They will be moved along with the traits themselves. Certain documentation links had to be amended.

• Chain
• Empty
• Repeat
• Sink
• Take
• empty
• repeat
• sink

---

Notes

• This can be reviewed independently of the other PRs tracked in Tracking Issue for alloc::io and core::io #154046.
• Chain and Take were previously in the main mod.rs file for std::io, but I've chosen to move them into the util.rs file in core::io instead. I think they make more sense in that file, but I'm happy to move them into mod.rs if that's a controversial decision.
• No AI tooling of any kind was used during the creation of this PR.

[rustbot]

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The reviewer was selected based on:

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[nia-e]

Requested a few small changes, but overall looks great ^^ ty!

View changes since this review

[rustbot]

Reminder, once the PR becomes ready for a review, use @rustbot ready.

[bushrat011899]

@rustbot ready

Pending CI passing, which I expect it to due to the minor nature of the changes involved.

[nia-e]

@bors r+

[rust-bors]

📌 Commit 5cbf9f8 has been approved by nia-e

It is now in the queue for this repository.

🌲 The tree is currently closed for pull requests below priority 1000. This pull request will be tested once the tree is reopened.

[Mark-Simulacrum]

@rust-timer build 7a40b5e

cc #156506 (comment)

[rust-timer]

Finished benchmarking commit (7a40b5e): comparison URL.

Overall result: ❌✅ regressions and improvements - please read:

Benchmarking means the PR may be perf-sensitive. It's automatically marked not fit for rolling up. Overriding is possible but disadvised: it risks changing compiler perf.

Next, please: If you can, justify the regressions found in this try perf run in writing along with @rustbot label: +perf-regression-triaged. If not, fix the regressions and do another perf run. Neutral or positive results will clear the label automatically.

@bors rollup=never
@rustbot label: -S-waiting-on-perf +perf-regression

Instruction count

Our most reliable metric. Used to determine the overall result above. However, even this metric can be noisy.

	mean	range	count
Regressions ❌ (primary)	1.3%	[1.3%, 1.3%]	1
Regressions ❌ (secondary)	0.1%	[0.0%, 0.1%]	3
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.6%	[-1.0%, -0.1%]	9
All ❌✅ (primary)	1.3%	[1.3%, 1.3%]	1

Max RSS (memory usage)

Results (primary -2.7%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	1.4%	[1.4%, 1.4%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-6.8%	[-6.8%, -6.8%]	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-2.7%	[-6.8%, 1.4%]	2

Cycles

Results (primary -2.1%, secondary 4.2%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	4.2%	[3.4%, 5.6%]	3
Improvements ✅ (primary)	-2.1%	[-2.1%, -2.1%]	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-2.1%	[-2.1%, -2.1%]	1

Binary size

Results (primary 4.4%, secondary 0.1%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	4.4%	[4.4%, 4.4%]	1
Regressions ❌ (secondary)	0.1%	[0.1%, 0.1%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	4.4%	[4.4%, 4.4%]	1

Bootstrap: 510.527s -> 523.299s (2.50%)
Artifact size: 400.06 MiB -> 398.07 MiB (-0.50%)