remove `box_patterns` by cyrgani · Pull Request #156749 · rust-lang/rust

cyrgani · 2026-05-19T12:04:35Z

This PR removes the old feature box_patterns, tracked in #29641. As explained in #29641 (comment), this feature will not be stabilized since deref_patterns (#87121) is a better and more general version of this feature.

It was not possible to remove this feature until recently since the compiler itself still depended on this feature. This was changed with rust-lang/compiler-team#984.

This PR currently breaks crates that rely on box patterns using the incorrect pre-expansion feature gating (see #154045 for more details). Therefore, this needs a crater run.

Closes #29641.
Closes #105099.
Closes #156110.

rustbot · 2026-05-19T12:04:39Z

The parser was modified, potentially altering the grammar of (stable) Rust
which would be a breaking change.

cc @fmease

The Rustfmt subtree was changed

cc @rust-lang/rustfmt

The Clippy subtree was changed

cc @rust-lang/clippy

rustbot · 2026-05-19T12:04:43Z

r? @Kivooeo

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Kivooeo · 2026-05-19T23:25:26Z

Therefore, this needs a crater run

Which one? would check-only be sufficient for this?

tmandry · 2026-05-27T15:39:47Z

I don't expect the crater breakage to be significant; if it is, we should discuss again.

@rfcbot merge lang

rust-rfcbot · 2026-05-27T15:39:50Z

@tmandry has proposed to merge this. The next step is review by the rest of the tagged team members:

Concerns:

~~crater~~ resolved by remove box_patterns #156749 (comment)

Once a majority of reviewers approve (and at most 2 approvals are outstanding), this will enter its final comment period. If you spot a major issue that hasn't been raised at any point in this process, please speak up!

cc @rust-lang/lang-advisors: FCP proposed for lang, please feel free to register concerns.
See this document for info about what commands tagged team members can give me.

traviscross · 2026-05-27T23:10:24Z

Looks good to me pending crater results; thanks @cyrgani.

@rfcbot reviewed
@rfcbot concern crater

Kivooeo · 2026-05-29T08:56:21Z

About to run crater. In my opinion check-only should be sufficient for this, do folks have other opinion?

fmease · 2026-05-29T10:27:44Z

About to run crater. In my opinion check-only should be sufficient for this, do folks have other opinion?

Yes, it's absolutely sufficient. This PR rejects previously valid code in the frontend of the compiler, it removes syntax. The only things that don't show up in check builds are monomorphization and codegen changes.

IINM one thing which you miss out on in check-only crater runs are potential doctest regressions but that's just something you have to accept if you want to have "faster" crater runs, otherwise craterbot check would never be an option for anyone. In any case, the beta crater runs will run in build-and-test mode and exercise doctests anyway, so we'd still catch such regressions eventually and still have a bit of time to either revert the change or to send (more) downstream patches. Anyway, it's not super likely that anybody is using box patterns in doctests (without also using them in the main crater), I'd say.

fmease · 2026-05-29T10:27:53Z

@bors try

remove `box_patterns`

rust-bors · 2026-05-29T12:37:35Z

☀️ Try build successful (CI)
Build commit: 1639375 (163937523761cc0def32f1ba9ed63fdf65ad3478, parent: dc375db7d8df0aa450e622c529147c95eee756f5)

Kivooeo · 2026-05-29T12:39:11Z

@craterbot run mode=check-only

remove `box_patterns` This PR removes the old feature `box_patterns`, tracked in rust-lang#29641. As explained in rust-lang#29641 (comment), this feature will not be stabilized since `deref_patterns` (rust-lang#87121) is a better and more general version of this feature. It was not possible to remove this feature until recently since the compiler itself still depended on this feature. This was changed with rust-lang/compiler-team#984. This PR currently breaks crates that rely on box patterns using the incorrect pre-expansion feature gating (see rust-lang#154045 for more details). Therefore, this needs a crater run. Closes rust-lang#29641. Closes rust-lang#105099. Closes rust-lang#156110.

Rollup of 9 pull requests Successful merges: - #161689 (bootstrap: don't LTO C dependencies on aarch64) - #161553 (rustdoc: fix issue preventing "read more" links from generating.) - #161670 (Pass LargeDataThreshold to LLVM module IR) - #146529 (rustdoc: Nuke `--passes=list` and defossilize the passes infrastructure) - #156009 (Check `redundant_explicit_links` against generated URLs) - #159583 (Add new `invalid_markdown_table` rustdoc lint) - #161098 (PassWrapper: handle LLVM 24 change in function types) - #161641 (Check for missing rustfmt in the stdarch intrinsic test step sooner) - #161661 (Don't treat slashes as path seps after drive letters in verbatim paths) Failed merges: - #156749 (remove `box_patterns`)

fmease · 2026-08-25T08:46:11Z

@bors r=Kivooeo,fmease

rust-bors · 2026-08-25T08:46:14Z

📌 Commit 9609b96 has been approved by Kivooeo,fmease

It is now in the queue for this repository.

Rollup of 5 pull requests Successful merges: - #156749 (remove `box_patterns`) - #161411 (avoid overlapping const suggestions) - #161484 (Discard `.pdr` in the PSP linker script) - #161663 (Reduce dependency on implicit paths in bootstrap) - #161720 (rename rust_target_features query to make it clear that these are *all* target features)

Rollup merge of #156749 - cyrgani:unbox-full, r=Kivooeo,fmease remove `box_patterns` This PR removes the old feature `box_patterns`, tracked in #29641. As explained in #29641 (comment), this feature will not be stabilized since `deref_patterns` (#87121) is a better and more general version of this feature. It was not possible to remove this feature until recently since the compiler itself still depended on this feature. This was changed with rust-lang/compiler-team#984. This PR currently breaks crates that rely on box patterns using the incorrect pre-expansion feature gating (see #154045 for more details). Therefore, this needs a crater run. Closes #29641. Closes #105099. Closes #156110.

rustbot assigned Kivooeo May 19, 2026

cyrgani changed the title ~~remove box_patterrns~~ remove box_patterns May 19, 2026

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jakubadamw reviewed May 20, 2026

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Comment thread tests/ui/match/issue-42679.rs

traviscross added the P-lang-drag-1 Lang team prioritization drag level 1. https://rust-lang.zulipchat.com/#narrow/channel/410516-t-lang label May 27, 2026

tmandry added the T-lang Relevant to the language team label May 27, 2026

rust-rfcbot added proposed-final-comment-period Proposed to merge/close by relevant subteam, see T-<team> label. Will enter FCP once signed off. disposition-merge This issue / PR is in PFCP or FCP with a disposition to merge it. labels May 27, 2026

traviscross added the I-lang-radar Items that are on lang's radar and will need eventual work or consideration. label May 27, 2026

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rust-bors Bot pushed a commit that referenced this pull request May 29, 2026

Auto merge of #156749 - cyrgani:unbox-full, r=<try>

1639375

remove `box_patterns`

rust-bors Bot removed the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Aug 24, 2026

JonathanBrouwer mentioned this pull request Aug 24, 2026

Rollup of 6 pull requests #161696

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JonathanBrouwer mentioned this pull request Aug 24, 2026

Rollup of 8 pull requests #161700

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This was referenced Aug 24, 2026

Rollup of 10 pull requests #161704

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Rollup of 9 pull requests #161706

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cyrgani added 4 commits August 25, 2026 07:50

remove box_patterns feature

9caab26

remove box_patterns from remaining tests

d86e422

clippy: replace box_patterns usage with deref_patterns

dea89f8

also remove hir::PatKind::Box

9609b96

rust-cloud-vms Bot force-pushed the unbox-full branch from 0a78bac to 9609b96 Compare August 25, 2026 08:04

cyrgani added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Aug 25, 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 Aug 25, 2026

jhpratt mentioned this pull request Aug 25, 2026

Rollup of 5 pull requests #161731

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rust-bors Bot merged commit a7ace5d into rust-lang:main Aug 25, 2026
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rustbot added this to the 1.100.0 milestone Aug 25, 2026

cyrgani deleted the unbox-full branch August 25, 2026 11:59

fmease mentioned this pull request Aug 25, 2026

Tracking issue for MCP 984: replace box_patterns in the compiler with deref_patterns #156110

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