Slice iter cleanup#146436

hkBst · 2025-09-11T11:07:26Z

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rustbot · 2025-09-11T11:07:30Z

rustbot has assigned @scottmcm.
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hkBst · 2025-10-10T08:54:45Z

r? libs

ibraheemdev · 2025-10-22T22:29:37Z

Going to pass this one along. r? libs

library/core/src/slice/iter.rs

hkBst · 2025-11-01T22:28:00Z

@rustbot ready

Perhaps a perf run to see if I haven't regressed anything unwittingly?

library/core/src/slice/iter.rs

joboet · 2025-11-03T11:30:53Z

library/core/src/slice/iter.rs

-            // SAFETY: Nothing else points to or will point to the contents of this slice.
-            Some(unsafe { &mut *head })
-        }
+        // SAFETY: we have `&mut self`, so are allowed to temporarily materialize a mut slice


I'd add that next must not be called if __get_unchecked was called, so invalidating previously returned items does not conflict with TrustedRandomAccess.

While that is true, I don't see how this particular next method is special in that regard. So would you then like all next methods of iterators that impl TrustedRandomAccess to get such a comment?

rustbot · 2025-11-04T07:39:49Z

This PR was rebased onto a different master commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.

hkBst · 2025-11-04T07:43:39Z

@joboet Thanks for reviewing so far; your comments have been very helpful!

I've removed all uses of overflowing_* and also switched all remaining conditions like if n >= len { code } else { code that needs the condition to be correct } to if n < len { code that needs the condition to be correct } else { code }.

library/core/src/slice/iter.rs

joboet · 2025-11-06T10:55:01Z

library/core/src/slice/iter.rs

        if self.v.is_empty() {
            (0, Some(0))
        } else {
-            let n = self.v.len() / self.chunk_size;
-            let rem = self.v.len() % self.chunk_size;
-            let n = if rem > 0 { n + 1 } else { n };
+            let n = (self.v.len() - 1) / self.chunk_size + 1;
            (n, Some(n))
        }


I changed 4 cases of this manual div_ceil to the real thing..

…t code close

joboet · 2025-12-02T16:27:12Z

@bors r+

bors · 2025-12-02T16:27:15Z

📌 Commit b60788e has been approved by joboet

It is now in the queue for this repository.

Slice iter cleanup

Rollup of 4 pull requests Successful merges: - #141980 (Rework `c_variadic`) - #146436 (Slice iter cleanup) - #148250 (array_chunks: slightly improve docs) - #149520 (also introduce Peekable::next_if_map_mut next to next_if_map) r? `@ghost` `@rustbot` modify labels: rollup

Rollup of 5 pull requests Successful merges: - #146436 (Slice iter cleanup) - #148250 (array_chunks: slightly improve docs) - #148678 (Merge E0412 into E0425) - #149520 (also introduce Peekable::next_if_map_mut next to next_if_map) - #149538 (std: sys: fs: uefi: Make time in FileAttr optional) r? `@ghost` `@rustbot` modify labels: rollup

bors · 2025-12-03T00:35:43Z

⌛ Testing commit b60788e with merge a4cfac7...

Rollup merge of #146436 - hkBst:slice-iter-1, r=joboet Slice iter cleanup

slice iter cleanup: replace checked_sub with saturating_sub Continuation of rust-lang#146436 r? `@joboet`

slice iter cleanup: replace checked_sub with saturating_sub Continuation of rust-lang#146436 r? ``@joboet``

Rollup merge of #150262 - hkBst:slice-iter-2, r=joboet slice iter cleanup: replace checked_sub with saturating_sub Continuation of #146436 r? `@joboet`

slice iter cleanup: replace checked_sub with saturating_sub Continuation of rust-lang/rust#146436 r? `@joboet`

rustbot assigned scottmcm Sep 11, 2025

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-libs Relevant to the library team, which will review and decide on the PR/issue. labels Sep 11, 2025

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rustbot assigned ibraheemdev and unassigned scottmcm Oct 10, 2025

rustbot assigned joboet and unassigned ibraheemdev Oct 22, 2025

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hkBst added 2 commits November 3, 2025 11:50

slice iter: replace manual saturating_sub

786cca8

slice iter: cleanup and make similar Chunks[Mut]::nth

c62abb6

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hkBst added 2 commits November 14, 2025 17:45

slice iter: more cleanup

a7ee7c8

slice iter: rm all overflowing_* and switch conditions to mv dependen…

b60788e

…t code close

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This was referenced Nov 28, 2025

Don't delegate to default implementations of ExactSizeIterator #149384

Open

Use usize::div_ceil instead of open-coding it #149383

Closed

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 Dec 2, 2025

matthiaskrgr added a commit to matthiaskrgr/rust that referenced this pull request Dec 2, 2025

Rollup merge of rust-lang#146436 - hkBst:slice-iter-1, r=joboet

b8338e9

Slice iter cleanup

matthiaskrgr mentioned this pull request Dec 2, 2025

Rollup of 4 pull requests #149552

Closed

matthiaskrgr mentioned this pull request Dec 2, 2025

Rollup of 5 pull requests #149560

Merged

bors merged commit 38d5d28 into rust-lang:main Dec 3, 2025
11 checks passed

rustbot added this to the 1.93.0 milestone Dec 3, 2025

rust-timer added a commit that referenced this pull request Dec 3, 2025

Unrolled build for #146436

0311eec

Rollup merge of #146436 - hkBst:slice-iter-1, r=joboet Slice iter cleanup

hkBst mentioned this pull request Dec 23, 2025

slice iter cleanup: replace checked_sub with saturating_sub #150262

Merged

matthiaskrgr added a commit to matthiaskrgr/rust that referenced this pull request Dec 29, 2025

Rollup merge of rust-lang#150262 - hkBst:slice-iter-2, r=joboet

9de01a8

slice iter cleanup: replace checked_sub with saturating_sub Continuation of rust-lang#146436 r? `@joboet`

JonathanBrouwer added a commit to JonathanBrouwer/rust that referenced this pull request Dec 29, 2025

Rollup merge of rust-lang#150262 - hkBst:slice-iter-2, r=joboet

523a023

slice iter cleanup: replace checked_sub with saturating_sub Continuation of rust-lang#146436 r? ``@joboet``

rust-timer added a commit that referenced this pull request Dec 29, 2025

Unrolled build for #150262

9024e0a

Rollup merge of #150262 - hkBst:slice-iter-2, r=joboet slice iter cleanup: replace checked_sub with saturating_sub Continuation of #146436 r? `@joboet`

github-actions bot pushed a commit to rust-lang/rustc-dev-guide that referenced this pull request Jan 2, 2026

Rollup merge of #150262 - hkBst:slice-iter-2, r=joboet

86df091

slice iter cleanup: replace checked_sub with saturating_sub Continuation of rust-lang/rust#146436 r? `@joboet`

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