Make `PeekMut` generic over the allocator #146621

cammeresi · 2025-09-16T04:20:53Z

plumb in allocator generic
additional testing

rustbot · 2025-09-16T04:20:58Z

rustbot has assigned @tgross35.
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library/alloc/src/vec/peek_mut.rs

library/alloc/src/vec/mod.rs

library/alloc/src/vec/peek_mut.rs

joboet · 2025-09-18T12:00:31Z

r? libs-api

library/alloc/src/vec/peek_mut.rs

joboet

Looks great! This needs approval from someone in T-libs-api though, so it can't be merged just yet.

View changes since this review

tgross35 · 2025-09-18T18:23:50Z

@rust-lang/libs-api anybody willing to give a quick thumbs up here? Straightforward extension to unstable API.

@cammeresi please squash when you get the chance

Amanieu · 2025-09-19T00:11:07Z

library/alloc/src/vec/peek_mut.rs

 #[unstable(feature = "vec_peek_mut", issue = "122742")]
-pub struct PeekMut<'a, T> {
-    vec: &'a mut Vec<T>,
+pub struct PeekMut<'a, T, A: Allocator> {


The allocator parameter should be unstable and default to Global, just like that of Vec,

Thanks, I was going to ask. I wasn't sure since there's no public entry point by which to create one directly. I guess the point is to be defensive against such an accidental change?

Does that mean that std::collections::btree_map::IntoKeys is incorrectly missing the attribute?

It's sort of indirectly gated because there is nothing stable implementing Allocator that you could specify in that position. But yeah, I think IntoKeys should technically have the same unstable attribute. Feel free to put up a PR if you're interested.

Amanieu · 2025-09-19T00:11:46Z

r=me once the generic parameter is fixed.

cammeresi · 2025-09-20T00:12:47Z

@tgross35 Am I supposed to ping now that I've updated? (Also, if you can answer my review question, I'd appreciate it.)

Amanieu · 2025-09-20T00:52:08Z

@bors r+

bors · 2025-09-20T00:52:10Z

📌 Commit 934ee04 has been approved by Amanieu

It is now in the queue for this repository.

bors · 2025-09-20T04:43:22Z

⌛ Testing commit 934ee04 with merge e4b5219...

bors · 2025-09-20T07:46:48Z

☀️ Test successful - checks-actions
Approved by: Amanieu
Pushing e4b5219 to master...

github-actions · 2025-09-20T07:49:28Z

What is this?

This is an experimental post-merge analysis report that shows differences in test outcomes between the merged PR and its parent PR.

Comparing ec38671 (parent) -> e4b5219 (this PR)

Test differences

Show 200 test diffs

200 doctest diffs were found. These are ignored, as they are noisy.

Test dashboard

Run

cargo run --manifest-path src/ci/citool/Cargo.toml -- \
    test-dashboard e4b521903b3b1a671e26a70b9475bcff385767e5 --output-dir test-dashboard

And then open test-dashboard/index.html in your browser to see an overview of all executed tests.

Job duration changes

dist-apple-various: 5142.9s -> 3455.3s (-32.8%)
dist-aarch64-windows-gnullvm: 5398.6s -> 4631.9s (-14.2%)
dist-aarch64-apple: 6123.4s -> 6750.9s (10.2%)
dist-x86_64-windows-gnullvm: 4688.0s -> 5054.6s (7.8%)
dist-x86_64-apple: 7693.0s -> 7129.6s (-7.3%)
x86_64-gnu-aux: 6373.1s -> 6800.4s (6.7%)
dist-arm-linux-musl: 5440.5s -> 5803.0s (6.7%)
dist-powerpc64le-linux-gnu: 5567.0s -> 5222.7s (-6.2%)
dist-powerpc64-linux: 5029.0s -> 5323.5s (5.9%)
x86_64-msvc-ext3: 6339.9s -> 6699.7s (5.7%)

How to interpret the job duration changes?

Job durations can vary a lot, based on the actual runner instance
that executed the job, system noise, invalidated caches, etc. The table above is provided
mostly for t-infra members, for simpler debugging of potential CI slow-downs.

rust-timer · 2025-09-20T08:57:23Z

Finished benchmarking commit (e4b5219): 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)

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

Cycles

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

Binary size

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

Bootstrap: 470.599s -> 472.018s (0.30%)
Artifact size: 389.97 MiB -> 389.98 MiB (0.00%)

Make `PeekMut` generic over the allocator - plumb in allocator generic - additional testing Related: rust-lang#122742

rustbot added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Sep 16, 2025

rustbot assigned tgross35 Sep 16, 2025

rustbot added the T-libs Relevant to the library team, which will review and decide on the PR/issue. label Sep 16, 2025

joboet requested changes Sep 18, 2025

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library/alloc/src/vec/peek_mut.rs Show resolved Hide resolved

rustbot added the T-libs-api Relevant to the library API team, which will review and decide on the PR/issue. label Sep 18, 2025

rustbot assigned BurntSushi and unassigned tgross35 Sep 18, 2025

joboet changed the title ~~Minor improvements to Vec::peek_mut~~ Make PeekMut generic over the allocator Sep 18, 2025

cammeresi force-pushed the peek-20250915 branch from c2c526d to 7dd447e Compare September 18, 2025 14:46

joboet reviewed Sep 18, 2025

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cammeresi force-pushed the peek-20250915 branch from 7dd447e to cc0a3d4 Compare September 18, 2025 15:21

joboet approved these changes Sep 18, 2025

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Amanieu reviewed Sep 19, 2025

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Plumb Allocator generic into std::vec::PeekMut

934ee04

cammeresi force-pushed the peek-20250915 branch from cc0a3d4 to 934ee04 Compare September 19, 2025 00:30

bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Sep 20, 2025

bors added the merged-by-bors This PR was explicitly merged by bors. label Sep 20, 2025

bors merged commit e4b5219 into rust-lang:master Sep 20, 2025
11 checks passed

rustbot added this to the 1.92.0 milestone Sep 20, 2025

cammeresi deleted the peek-20250915 branch September 20, 2025 15:28

Muscraft pushed a commit to Muscraft/rust that referenced this pull request Sep 24, 2025

Auto merge of rust-lang#146621 - cammeresi:peek-20250915, r=Amanieu

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Make `PeekMut` generic over the allocator - plumb in allocator generic - additional testing Related: rust-lang#122742

Make PeekMut generic over the allocator #146621

Make PeekMut generic over the allocator #146621

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Overall result: no relevant changes - no action needed

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Make `PeekMut` generic over the allocator #146621

Make `PeekMut` generic over the allocator #146621

cammeresi commented Sep 16, 2025 •

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tgross35 commented Sep 18, 2025 •

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Amanieu commented Sep 19, 2025 •

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