Send VecDeque::from_iter via Vec::from_iter

[scottmcm]

Since it's O(1) to convert between them now, might as well reuse the logic.

Mostly for the various specializations it does, but might also save some monomorphization work if, say, people collect slice iterators into both Vecs and VecDeques.

[rustbot]

r? @Mark-Simulacrum

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[rustbot]

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 @rustbot label +T-libs-api -T-libs to tag it appropriately. If this PR contains changes to any unstable APIs please edit the PR description to add a link to the relevant API Change Proposal or create one if you haven't already. 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

[scottmcm]

@bors try @rust-timer queue

[bors]

⌛ Trying commit a964a37 with merge f7ad2ffb3732d494ee97cfd8458a0ab47bc56d4c...

[the8472]

That should be better than using Extend but there is room for further improvement. VecDeque could do a few things better than Vec can: Collecting from vec_deq::IntoIter, from a partially consumed vec::IntoIter and VecDeque -> VecDeque in-place iteration (sadly the vec in-place iteration code wouldn't work for vec-deque without making the source contiguous first).

[bors]

☀️ Try build successful - checks-actions
Build commit: f7ad2ffb3732d494ee97cfd8458a0ab47bc56d4c (f7ad2ffb3732d494ee97cfd8458a0ab47bc56d4c)

[scottmcm]

@the8472 Would you want to see that as part of this PR, or would it be fine to do this as-is and add the further specializations later?

(I do like the observation that vec::IntoIter -> VecDeque can be O(1) now too, without even needing data movement!)

[the8472]

I was just airing some thoughts, can totally be a separate PR.

[rust-timer]

Finished benchmarking commit (f7ad2ffb3732d494ee97cfd8458a0ab47bc56d4c): comparison URL.

Overall result: ❌✅ regressions and improvements - ACTION NEEDED

Benchmarking this pull request likely means that it is perf-sensitive, so we're automatically marking it as not fit for rolling up. While you can manually mark this PR as fit for rollup, we strongly recommend not doing so since this PR may lead to changes in compiler perf.

Next Steps: If you can justify the regressions found in this try perf run, please indicate this with @rustbot label: +perf-regression-triaged along with sufficient written justification. If you cannot justify the regressions please fix the regressions and do another perf run. If the next run shows neutral or positive results, the label will be automatically removed.

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

Instruction count

This is a highly reliable metric that was used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	0.6%	[0.5%, 0.9%]	7
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.9%	[-0.9%, -0.8%]	2
Improvements ✅ (secondary)	-2.4%	[-2.7%, -2.1%]	6
All ❌✅ (primary)	0.3%	[-0.9%, 0.9%]	9

Max RSS (memory usage)

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

Cycles

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.9%	[-4.0%, -1.5%]	10
All ❌✅ (primary)	-	-	0

[Mark-Simulacrum]

perf regressions look spurious to me (mostly in noisy benchmarks).

@bors r+

[bors]

📌 Commit a964a37 has been approved by Mark-Simulacrum

It is now in the queue for this repository.

[bors]

⌛ Testing commit a964a37 with merge 203c876...

[bors]

☀️ Test successful - checks-actions
Approved by: Mark-Simulacrum
Pushing 203c876 to master...

[bors]

☀️ Test successful - checks-actions
Approved by: Mark-Simulacrum
Pushing 203c876 to master...

[rust-timer]

Finished benchmarking commit (203c876): comparison URL.

Overall result: no relevant changes - no action needed

@rustbot label: -perf-regression

Instruction count

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

Max RSS (memory usage)

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	1.1%	[1.1%, 1.1%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-3.7%	[-3.7%, -3.7%]	1
Improvements ✅ (secondary)	-6.1%	[-6.1%, -6.1%]	1
All ❌✅ (primary)	-1.3%	[-3.7%, 1.1%]	2

Cycles

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.3%	[-2.5%, -2.0%]	2
All ❌✅ (primary)	-	-	0