Align `ArrayWindows` trait impls with `Windows` #151613

cuviper · 2026-01-24T19:41:14Z

With slice::ArrayWindows getting ready to stabilize in 1.94, I noticed that it currently has some differences in trait implementations compared to slice::Windows, and I think we should align these.

Remove derive(Copy) -- we generally don't want Copy for iterators at all, as this is seen as a footgun (e.g. remove Copy impls from remaining iterators #21809). This is obviously a breaking change though, so we should only remove this if we also backport the removal before it's stable. Otherwise, it should at least be replaced by a manual impl without requiring T: Copy.
Manually impl Clone, simply to avoid requiring T: Clone.
impl FusedIterator, because it is trivially so. The since = "1.94.0" assumes we'll backport this, otherwise we should change that to the "current" placeholder.
impl TrustedLen, because we can trust our implementation.
impl TrustedRandomAccess, because the required __iterator_get_unchecked method is straightforward.

r? libs-api

@rustbot label beta-nominated
(at least for the Copy removal, but we could be more selective about the rest).

The derived `T: Copy` constraint is not appropriate for an iterator by reference, but we generally do not want `Copy` on iterators anyway.

This implementation doesn't need the derived `T: Clone`.

hkBst · 2026-01-27T16:21:17Z

The minimal fix would seem to be to backport an unstabling PR, then let these changes ride the train as normal.

cuviper · 2026-01-27T16:27:32Z

@hkBst "unstabling" is an option, but that comes with a lot of secondary effects, like needing to reverse the bootstrap-feature change in commit 3dc7a1f.

Backporting just the Copy removal would be simplest action. The rest can ride the train, no problem.

hkBst · 2026-01-28T14:39:01Z

Given the number of missed things, it seems clear that this feature did not receive enough attention before it was stabilized. That's why I think unstabilizing is the most principled solution. Beta is the least used/tested release channel so backporting like this feels awfully close to committing straight to stable ;P. These changes seem straightforward enough, but the changes that end up causing problems often seem so as well...

cuviper · 2026-02-05T19:35:33Z

r? Amanieu

Amanieu · 2026-02-09T12:00:10Z

@bors r+

rust-bors · 2026-02-09T12:00:14Z

📌 Commit 129d552 has been approved by Amanieu

It is now in the queue for this repository.

@rustbot

…anieu Align `ArrayWindows` trait impls with `Windows` With `slice::ArrayWindows` getting ready to stabilize in 1.94, I noticed that it currently has some differences in trait implementations compared to `slice::Windows`, and I think we should align these. - Remove `derive(Copy)` -- we generally don't want `Copy` for iterators at all, as this is seen as a footgun (e.g. rust-lang#21809). This is obviously a breaking change though, so we should only remove this if we also backport the removal before it's stable. Otherwise, it should at least be replaced by a manual impl without requiring `T: Copy`. - Manually `impl Clone`, simply to avoid requiring `T: Clone`. - `impl FusedIterator`, because it is trivially so. The `since = "1.94.0"` assumes we'll backport this, otherwise we should change that to the "current" placeholder. - `impl TrustedLen`, because we can trust our implementation. - `impl TrustedRandomAccess`, because the required `__iterator_get_unchecked` method is straightforward. r? libs-api @rustbot label beta-nominated (at least for the `Copy` removal, but we could be more selective about the rest).

@rustbot

…anieu Align `ArrayWindows` trait impls with `Windows` With `slice::ArrayWindows` getting ready to stabilize in 1.94, I noticed that it currently has some differences in trait implementations compared to `slice::Windows`, and I think we should align these. - Remove `derive(Copy)` -- we generally don't want `Copy` for iterators at all, as this is seen as a footgun (e.g. rust-lang#21809). This is obviously a breaking change though, so we should only remove this if we also backport the removal before it's stable. Otherwise, it should at least be replaced by a manual impl without requiring `T: Copy`. - Manually `impl Clone`, simply to avoid requiring `T: Clone`. - `impl FusedIterator`, because it is trivially so. The `since = "1.94.0"` assumes we'll backport this, otherwise we should change that to the "current" placeholder. - `impl TrustedLen`, because we can trust our implementation. - `impl TrustedRandomAccess`, because the required `__iterator_get_unchecked` method is straightforward. r? libs-api @rustbot label beta-nominated (at least for the `Copy` removal, but we could be more selective about the rest).

@rustbot

…anieu Align `ArrayWindows` trait impls with `Windows` With `slice::ArrayWindows` getting ready to stabilize in 1.94, I noticed that it currently has some differences in trait implementations compared to `slice::Windows`, and I think we should align these. - Remove `derive(Copy)` -- we generally don't want `Copy` for iterators at all, as this is seen as a footgun (e.g. rust-lang#21809). This is obviously a breaking change though, so we should only remove this if we also backport the removal before it's stable. Otherwise, it should at least be replaced by a manual impl without requiring `T: Copy`. - Manually `impl Clone`, simply to avoid requiring `T: Clone`. - `impl FusedIterator`, because it is trivially so. The `since = "1.94.0"` assumes we'll backport this, otherwise we should change that to the "current" placeholder. - `impl TrustedLen`, because we can trust our implementation. - `impl TrustedRandomAccess`, because the required `__iterator_get_unchecked` method is straightforward. r? libs-api @rustbot label beta-nominated (at least for the `Copy` removal, but we could be more selective about the rest).

@rustbot

…anieu Align `ArrayWindows` trait impls with `Windows` With `slice::ArrayWindows` getting ready to stabilize in 1.94, I noticed that it currently has some differences in trait implementations compared to `slice::Windows`, and I think we should align these. - Remove `derive(Copy)` -- we generally don't want `Copy` for iterators at all, as this is seen as a footgun (e.g. rust-lang#21809). This is obviously a breaking change though, so we should only remove this if we also backport the removal before it's stable. Otherwise, it should at least be replaced by a manual impl without requiring `T: Copy`. - Manually `impl Clone`, simply to avoid requiring `T: Clone`. - `impl FusedIterator`, because it is trivially so. The `since = "1.94.0"` assumes we'll backport this, otherwise we should change that to the "current" placeholder. - `impl TrustedLen`, because we can trust our implementation. - `impl TrustedRandomAccess`, because the required `__iterator_get_unchecked` method is straightforward. r? libs-api @rustbot label beta-nominated (at least for the `Copy` removal, but we could be more selective about the rest).

@rustbot

…anieu Align `ArrayWindows` trait impls with `Windows` With `slice::ArrayWindows` getting ready to stabilize in 1.94, I noticed that it currently has some differences in trait implementations compared to `slice::Windows`, and I think we should align these. - Remove `derive(Copy)` -- we generally don't want `Copy` for iterators at all, as this is seen as a footgun (e.g. rust-lang#21809). This is obviously a breaking change though, so we should only remove this if we also backport the removal before it's stable. Otherwise, it should at least be replaced by a manual impl without requiring `T: Copy`. - Manually `impl Clone`, simply to avoid requiring `T: Clone`. - `impl FusedIterator`, because it is trivially so. The `since = "1.94.0"` assumes we'll backport this, otherwise we should change that to the "current" placeholder. - `impl TrustedLen`, because we can trust our implementation. - `impl TrustedRandomAccess`, because the required `__iterator_get_unchecked` method is straightforward. r? libs-api @rustbot label beta-nominated (at least for the `Copy` removal, but we could be more selective about the rest).

Rollup of 12 pull requests Successful merges: - #152388 (`rust-analyzer` subtree update) - #151613 (Align `ArrayWindows` trait impls with `Windows`) - #152134 (Set crt_static_allow_dylibs to true for Emscripten target) - #152166 (cleanup some more things in `proc_macro::bridge`) - #152236 (compiletest: `-Zunstable-options` for json targets) - #152287 (Fix an ICE in the vtable iteration for a trait reference in const eval when a supertrait not implemented) - #142957 (std: introduce path normalize methods at top of `std::path`) - #145504 (Add some conversion trait impls) - #152131 (Port rustc_no_implicit_bounds attribute to parser.) - #152315 (fix: rhs_span to rhs_span_new) - #152327 (Check stalled coroutine obligations eagerly) - #152377 (Rename the query system's `JobOwner` to `ActiveJobGuard`, and include `key_hash`)

@rustbot

Rollup merge of #151613 - cuviper:array-windows-parity, r=Amanieu Align `ArrayWindows` trait impls with `Windows` With `slice::ArrayWindows` getting ready to stabilize in 1.94, I noticed that it currently has some differences in trait implementations compared to `slice::Windows`, and I think we should align these. - Remove `derive(Copy)` -- we generally don't want `Copy` for iterators at all, as this is seen as a footgun (e.g. #21809). This is obviously a breaking change though, so we should only remove this if we also backport the removal before it's stable. Otherwise, it should at least be replaced by a manual impl without requiring `T: Copy`. - Manually `impl Clone`, simply to avoid requiring `T: Clone`. - `impl FusedIterator`, because it is trivially so. The `since = "1.94.0"` assumes we'll backport this, otherwise we should change that to the "current" placeholder. - `impl TrustedLen`, because we can trust our implementation. - `impl TrustedRandomAccess`, because the required `__iterator_get_unchecked` method is straightforward. r? libs-api @rustbot label beta-nominated (at least for the `Copy` removal, but we could be more selective about the rest).

cuviper added 5 commits January 24, 2026 11:06

Remove derive(Copy) on ArrayWindows

2bae85e

The derived `T: Copy` constraint is not appropriate for an iterator by reference, but we generally do not want `Copy` on iterators anyway.

Manually impl Clone for ArrayWindows

9052155

This implementation doesn't need the derived `T: Clone`.

impl FusedIterator for ArrayWindows

08cd2ac

impl TrustedLen for ArrayWindows

8f7d556

impl TrustedRandomAccess for ArrayWindows

129d552

rustbot assigned dtolnay Jan 24, 2026

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. beta-nominated Nominated for backporting to the compiler in the beta channel. labels Jan 24, 2026

cuviper added the T-libs-api Relevant to the library API team, which will review and decide on the PR/issue. label Jan 25, 2026

Amanieu added the beta-accepted Accepted for backporting to the compiler in the beta channel. label Jan 28, 2026

rustbot assigned Amanieu and unassigned dtolnay Feb 5, 2026

rust-bors bot 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 Feb 9, 2026

JonathanBrouwer mentioned this pull request Feb 9, 2026

Rollup of 3 pull requests #152386

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Rollup of 8 pull requests #152390

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Rollup of 12 pull requests #152391

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Rollup of 12 pull requests #152395

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matthiaskrgr mentioned this pull request Feb 9, 2026

Rollup of 12 pull requests #152399

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Rollup of 17 pull requests #152400

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rust-bors bot merged commit 144b77a into rust-lang:main Feb 9, 2026
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rustbot added this to the 1.95.0 milestone Feb 9, 2026

cuviper mentioned this pull request Feb 10, 2026

[beta] backports, plus stable versions in stdarch #152187

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cuviper removed the beta-nominated Nominated for backporting to the compiler in the beta channel. label Feb 10, 2026

cuviper modified the milestones: 1.95.0, 1.94.0 Feb 10, 2026

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Align `ArrayWindows` trait impls with `Windows` #151613

Align `ArrayWindows` trait impls with `Windows` #151613

cuviper commented Jan 24, 2026 •

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Align `ArrayWindows` trait impls with `Windows` #151613

Align `ArrayWindows` trait impls with `Windows` #151613

cuviper commented Jan 24, 2026 •

edited by rustbot

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