Stabilize `local_key_cell_update` by tgross35 · Pull Request #157734 · rust-lang/rust

tgross35 · 2026-06-11T02:00:34Z

Newly stable API:

impl<T: 'static> LocalKey<Cell<T>> {
    pub fn update(&'static self, f: impl FnOnce(T) -> T)
    where
        T: Copy;
}

This matches the signature on Cell.

Closes: https://www.github.com/rust-lang/rust/issues/143989 (Tracking issue)

The disclaimers relevant for other `LocalKey` methods are relevant for `update`, so add them to the documentation.

Newly stable API: impl<T: 'static> LocalKey<Cell<T>> { pub fn update(&'static self, f: impl FnOnce(T) -> T) where T: Copy; } This matches the signature on `Cell`. Tracking issue: RUST-143989

rustbot · 2026-06-11T02:00:39Z

r? @jhpratt

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Owners of files modified in this PR: @ChrisDenton, libs
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tgross35 · 2026-06-11T02:02:05Z

This has been around for close to a year and is pretty straightforward, similar to existing stable methods on LocalKey<Cell<T>> that predate the stability of Cell::update.

@rustbot label +I-libs-api-nominated

jhpratt

r=me after FCP completion

View changes since this review

joshtriplett · 2026-06-23T17:03:49Z

Seems reasonable, and consistent with other methods.

@rfcbot merge libs-api

rust-rfcbot · 2026-06-23T17:03:52Z

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

No concerns currently listed.

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!

See this document for info about what commands tagged team members can give me.

tgross35 · 2026-06-23T17:16:27Z

@joshtriplett there's a FCP proposal at #143989 (comment). If votes are merged then that's enough to start :)

Amanieu · 2026-06-30T15:47:06Z

@rfcbot cancel

rust-rfcbot · 2026-06-30T15:47:08Z

@Amanieu proposal cancelled.

Amanieu · 2026-06-30T15:47:42Z

Cancelling in favor of the FCP in the tracking issue.

tgross35 · 2026-07-05T22:03:43Z

FCP complete at #143989 (comment),

@bors r=jhpratt rollup

rust-bors · 2026-07-05T22:03:46Z

📋 This PR cannot be approved because it currently has the following label: S-waiting-on-t-libs-api.

tgross35 · 2026-07-05T22:04:02Z

@bors r=jhpratt rollup

rust-bors · 2026-07-05T22:04:06Z

📌 Commit ef5968d has been approved by jhpratt

It is now in the queue for this repository.

🌲 The tree is currently closed for pull requests below priority 2. This pull request will be tested once the tree is reopened.

…update, r=jhpratt Stabilize `local_key_cell_update` Newly stable API: ```rust impl<T: 'static> LocalKey<Cell<T>> { pub fn update(&'static self, f: impl FnOnce(T) -> T) where T: Copy; } ``` This matches the signature on `Cell`. Closes: https://www.github.com/rust-lang/rust/issues/143989 (Tracking issue)

Rollup of 20 pull requests Successful merges: - #158377 (add `-Zforce-intrinsic-fallback` flag) - #158642 (Clarify some interning details) - #158743 (Look for cdb location in the registry first) - #158775 (bootstrap: only encode RUSTFLAGS when a flag contains a space) - #158782 (Add and use cfg(target_has_threads) to enforce no_thread impl usage) - #158785 (hook intrinsic-test into aarch64-gnu) - #157734 (Stabilize `local_key_cell_update`) - #158183 (std: allocate less memory in `current_exe` for OpenBSD) - #158671 (Move tests batch 17) - #158730 (Update `FIXME(static_mut_refs)` comments) - #158752 (Reorganize `tests/ui/issues` [18/N]) - #158755 (Use `ThinVec` more in the AST) - #158757 (Fix incorrect tracking issue for `read_le`/`read_be`) - #158765 (Fix ICE on non-ident path in `doc(auto_cfg values)`) - #158771 (library: expand HashSet::extract_if coverage) - #158772 (rustc-dev-guide subtree update) - #158776 (fix: emit diagnostic for AVR target without target-cpu) - #158786 (Add regression test for builtin attr macro values) - #158807 (Add regression test for CString::clone_into unwind safety) - #158825 (Fix typo)

Rollup of 24 pull requests Successful merges: - #158377 (add `-Zforce-intrinsic-fallback` flag) - #158642 (Clarify some interning details) - #158694 (Positive test for closures needing expectations) - #158743 (Look for cdb location in the registry first) - #158775 (bootstrap: only encode RUSTFLAGS when a flag contains a space) - #158782 (Add and use cfg(target_has_threads) to enforce no_thread impl usage) - #158785 (hook intrinsic-test into aarch64-gnu) - #158819 (Put `InhabitedPredicate::NotInModule` earlier in disjunction since it can be a lot faster) - #157734 (Stabilize `local_key_cell_update`) - #158183 (std: allocate less memory in `current_exe` for OpenBSD) - #158310 (Remove unexpected usage of Unambig in non-infer variants) - #158671 (Move tests batch 17) - #158730 (Update `FIXME(static_mut_refs)` comments) - #158752 (Reorganize `tests/ui/issues` [18/N]) - #158755 (Use `ThinVec` more in the AST) - #158757 (Fix incorrect tracking issue for `read_le`/`read_be`) - #158765 (Fix ICE on non-ident path in `doc(auto_cfg values)`) - #158771 (library: expand HashSet::extract_if coverage) - #158772 (rustc-dev-guide subtree update) - #158776 (fix: emit diagnostic for AVR target without target-cpu) - #158786 (Add regression test for builtin attr macro values) - #158810 (Add supplementary information for get_unchecked(mut)) - #158825 (Fix typo) - #158838 (tidy: Use `empty_alternate = true` for triagebot mention glob check)

tgross35 added 2 commits June 10, 2026 20:35

std: Update documentation for LocalKey<Cell<T>>::update

88c0724

The disclaimers relevant for other `LocalKey` methods are relevant for `update`, so add them to the documentation.

Stabilize local_key_cell_update

ef5968d

Newly stable API: impl<T: 'static> LocalKey<Cell<T>> { pub fn update(&'static self, f: impl FnOnce(T) -> T) where T: Copy; } This matches the signature on `Cell`. Tracking issue: RUST-143989

rustbot assigned jhpratt Jun 11, 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. labels Jun 11, 2026

tgross35 mentioned this pull request Jun 11, 2026

Tracking Issue for LocalKey<Cell>::update #143989

Closed

3 tasks

rustbot added the I-libs-api-nominated Nominated for discussion during a libs-api team meeting. label Jun 11, 2026

jhpratt linked an issue Jun 11, 2026 that may be closed by this pull request

Tracking Issue for LocalKey<Cell>::update #143989

Closed

3 tasks

Mark-Simulacrum mentioned this pull request Jun 11, 2026

Should libs-reviewers kick off FCP where they think it reasonable? rust-lang/libs-team#813

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jhpratt approved these changes Jun 11, 2026

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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 Jun 23, 2026

rust-rfcbot removed 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 Jun 30, 2026

Amanieu removed the I-libs-api-nominated Nominated for discussion during a libs-api team meeting. label Jun 30, 2026

tgross35 removed the S-waiting-on-t-libs-api Status: Awaiting decision from T-libs-api label Jul 5, 2026

rust-bors Bot added the S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. label Jul 5, 2026

jhpratt mentioned this pull request Jul 6, 2026

Rollup of 20 pull requests #158837

Closed

jhpratt mentioned this pull request Jul 6, 2026

Rollup of 24 pull requests #158847

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rust-bors Bot merged commit 04b47ed into rust-lang:main Jul 6, 2026
12 checks passed

rustbot added this to the 1.99.0 milestone Jul 6, 2026

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