Implement `IntoIterator` for `[&[mut]] Box<[T; N], A>` by WaffleLapkin · Pull Request #134021 · rust-lang/rust

WaffleLapkin · 2024-12-08T05:07:27Z

Revival of #124108

bors · 2025-02-06T00:52:13Z

☔ The latest upstream changes (presumably #136572) made this pull request unmergeable. Please resolve the merge conflicts.

WaffleLapkin · 2025-12-08T14:17:19Z

@scottmcm anything I can do to move this forward?

Mark-Simulacrum

I guess this also needs rebasing + FCP, maybe starting with the FCP makes sense since it's not obvious to me this is worth it (especially if it needs an edition change...)

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Mark-Simulacrum

r=me with FCP done

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Mark-Simulacrum · 2026-03-21T14:09:19Z

+
+    fn advance_by(&mut self, n: usize) -> Result<(), NonZero<usize>> {
+        self.inner.advance_by(n)
+    }


It looks like we're missing overrides for next_chunk, try_fold, and probably __iterator_get_unchecked? Those are 'just' perf optimizations though.

I think the best way to fix this long-term is the change to have a common iterator type rather than duplicating all the surface area.

programmerjake · 2026-04-21T10:36:24Z

+/// A by-value `Box<[T; N]>` iterator.
+#[stable(feature = "boxed_array_value_iter", since = "CURRENT_RUSTC_VERSION")]
+#[rustc_insignificant_dtor]
+pub struct BoxedArrayIntoIter<T, const N: usize, A: Allocator = Global> {


can you add Default for BoxedArrayIntoIter<...> that gives an empty iterator just like vec::IntoIter and array::IntoIter?

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I don't want to change what the FCP is about, so maybe this should be left as a follow up?

BurntSushi · 2026-06-09T01:28:20Z

Given the potential for breaking changes here, it seems prudent to do a crater run. I don't see that one has been done. Thoughts on doing so?

@rfcbot concern crater

…>` and `[T; N]` They'll be needed for `IntoIterator` impls.

Note: this removes warnings, as this breakage was deemed acceptable, see <rust-lang#124108 (comment)>

rustbot · 2026-06-09T12:36:13Z

This PR was rebased onto a different main 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.

WaffleLapkin · 2026-06-09T12:42:06Z

@BurntSushi doing a crater run seems reasonable to me. I'll start it once the try build completes.

@bors try

Implement `IntoIterator` for `[&[mut]] Box<[T; N], A>`

rust-log-analyzer · 2026-06-09T13:40:52Z

The job x86_64-gnu-tools failed! Check out the build log: (web) (plain enhanced) (plain)

Click to see the possible cause of the failure (guessed by this bot)

...............................F.................. (50/144)
.................................................. (100/144)
............................................       (144/144)

======== tests/rustdoc-gui/go-to-collapsed-elem.goml ========

[ERROR] line 40
    at `tests/rustdoc-gui/go-to-collapsed-elem.goml` line 21: Error: Node is detached from document: for command `click: "//*[@id='search']//a[@href='../test_docs/struct.Foo.html#method.must_use']"`
    at <file:///checkout/obj/build/x86_64-unknown-linux-gnu/test/rustdoc-gui/doc/test_docs/struct.Foo.html?search=t_use>


<= doc-ui tests done: 143 succeeded, 1 failed, 0 filtered out

Error: ()

rust-bors · 2026-06-09T14:52:25Z

☀️ Try build successful (CI)
Build commit: c37f0ee (c37f0eebe7e1f4c42e88bffc7961c6a7aa9c4d00, parent: 057ed8ba87418a77d5758f2d5e13f84b89b197e9)

WaffleLapkin · 2026-06-09T17:23:10Z

@craterbot check

craterbot · 2026-06-09T17:23:28Z

👌 Experiment pr-134021 created and queued.
🤖 Automatically detected try build c37f0ee
🔍 You can check out the queue and this experiment's details.

ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

theemathas · 2026-06-12T16:30:11Z

@craterbot cancel

See #157814

craterbot · 2026-06-12T16:30:26Z

🗑️ Experiment pr-134021 deleted!

ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

rustbot assigned scottmcm Dec 8, 2024

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 Dec 8, 2024

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WaffleLapkin force-pushed the box-arr-into-iter2 branch from 6f3a44b to 576e704 Compare December 10, 2024 01:04

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tgross35 added the T-libs-api Relevant to the library API team, which will review and decide on the PR/issue. label Dec 13, 2024

WaffleLapkin marked this pull request as ready for review December 16, 2024 19:24

tgross35 added the needs-fcp This change is insta-stable, or significant enough to need a team FCP to proceed. label Dec 19, 2024

scottmcm reviewed Feb 24, 2025

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Comment thread library/alloc/src/boxed/iter.rs

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rustbot assigned Mark-Simulacrum and unassigned scottmcm Feb 8, 2026

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Comment thread library/alloc/src/boxed/iter.rs Outdated

Comment thread library/alloc/src/boxed/iter.rs Outdated

Comment thread library/alloc/src/boxed/iter.rs Outdated

Comment thread tests/ui/iterators/into-iter-on-arrays-lint.stderr

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WaffleLapkin force-pushed the box-arr-into-iter2 branch from 6bcd9c3 to 72ea626 Compare March 10, 2026 11:02

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WaffleLapkin force-pushed the box-arr-into-iter2 branch 2 times, most recently from 33ce55c to a26c96f Compare March 10, 2026 15:10

rust-rfcbot added the disposition-merge This issue / PR is in PFCP or FCP with a disposition to merge it. label Mar 17, 2026

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WaffleLapkin force-pushed the box-arr-into-iter2 branch from f65b35f to 5d3dba6 Compare April 9, 2026 13:52

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WaffleLapkin mentioned this pull request Apr 21, 2026

&Box<[T; N]> doesn't impl IntoIterator #155577

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programmerjake reviewed Apr 21, 2026

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WaffleLapkin added 5 commits June 9, 2026 14:34

Add negative implementation of Iterator for `[&[mut]] Box<[T; N], A…

77e540a

…>` and `[T; N]` They'll be needed for `IntoIterator` impls.

Implement IntoIterator for &[mut] Box<[T; N], A>

7739c5a

drive-by: make NonDrop traits non-public

1dea9c2

Implement IntoIterator for Box<[T; N], A>

f1f16b5

Bless tests

6bf1d93

Note: this removes warnings, as this breakage was deemed acceptable, see <rust-lang#124108 (comment)>

WaffleLapkin force-pushed the box-arr-into-iter2 branch from 5d3dba6 to 6bf1d93 Compare June 9, 2026 12:36

rust-bors Bot pushed a commit that referenced this pull request Jun 9, 2026

Auto merge of #134021 - WaffleLapkin:box-arr-into-iter2, r=<try>

c37f0ee

Implement `IntoIterator` for `[&[mut]] Box<[T; N], A>`

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craterbot added S-waiting-on-crater Status: Waiting on a crater run to be completed. and removed S-waiting-on-fcp Status: PR is in FCP and is awaiting for FCP to complete. labels Jun 9, 2026

theemathas mentioned this pull request Jun 12, 2026

Crater rollup #157814

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craterbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-crater Status: Waiting on a crater run to be completed. labels Jun 12, 2026

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