core::sync: rename `Exclusive` to `SyncView` and make improvements by pthariensflame · Pull Request #153038 · rust-lang/rust

pthariensflame · 2026-02-24T07:33:55Z

This PR implements the renaming of core::sync::Exclusive to SyncView as decided in #98407. To preserve the ability to search for the old name, it adds Exclusive as a doc_alias.

It also makes the following additional changes:

Converting the get_mut method to being an instance of AsMut::as_mut. In the process, it makes both the new impl AsMut and the existing impl AsRef const, and it also renames get_pin_mut to as_pin_mut for consistency. This direction follows a suggestion from Tracking Issue for Exclusive #98407.
Adding an as_pin method that can only be used when the wrapped type implements Sync, to complete the square of access methods.
Making as many of the existing impls const as possible; this involved making the existing impl Default no longer derived.
Adding impls for AsyncFnOnce, AsyncFnMut, and AsyncFn, akin to the existing impls for FnOnce, FnMut, and Fn.

It does not yet do the following, which may be desirable:

Fixing/improving the documentation to address the concern pointed out in Example for std::sync::Exclusive is dubious #146245.

It previously did the following, but this was removed after discussion:

Adding an impl for (const) Iterator, which felt in line with the existing impls for Future and Coroutine.

rustbot · 2026-02-24T07:34:01Z

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joboet · 2026-02-24T11:42:54Z

library/core/src/sync/sync_view.rs

+#[rustc_const_unstable(feature = "const_iter", issue = "92476")]
+impl<T> const Iterator for SyncView<T>
+where
+    T: [const] Iterator + ?Sized,


This needs to be bounded on Sync – size_hint takes &self.

We figured this was similar to the case with Debug, which doesn’t need Sync despite taking &self because it doesn’t inspect self in any way. The default definition for size_hint is used here (so giving no information about the underlying iterator) instead of delegating through (which would require T: Sync).

pthariensflame · 2026-02-26T16:50:22Z

Since you’re already here and reviewing it anyway, may as well make it official:

r? @joboet

joboet · 2026-02-28T13:18:06Z

r? libs-api
This will need oversight from libs-api (and I'm not sure whether it is a good idea to do all these things in a single PR).

Amanieu · 2026-04-06T23:00:04Z

This mostly LGTM, except for the Iterator impl which feels suspicious for the reasons @joboet mentioned. I would prefer if that impl was removed for now.

pthariensflame · 2026-04-07T00:57:00Z

This mostly LGTM, except for the Iterator impl which feels suspicious for the reasons @joboet mentioned. I would prefer if that impl was removed for now.

We will remove it, then; what would be the best way for us to bring up the impl for a closer look/discussion, since this PR seems like the wrong place for it?

This moves the inherent `get_mut` method to be `AsMut::as_mut`, and renames `get_pin_mut` to `as_pin_mut` accordingly. It also constifies the `AsRef` (and `AsMut`) implementations, preserving the `const` status of the original `get_mut`, albeit only unstably.

This completes the existing suite of `as_ref`, `as_mut`, and `as_pin_mut` methods.

rustbot · 2026-04-07T01:15:18Z

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.

Amanieu · 2026-04-09T06:29:30Z

We will remove it, then; what would be the best way for us to bring up the impl for a closer look/discussion, since this PR seems like the wrong place for it?

This should probably be an ACP. You would also need to demonstrate that this impl is useful in practice.

Amanieu · 2026-04-09T06:29:35Z

@bors r+

rust-bors · 2026-04-09T06:29:38Z

📌 Commit 57d4965 has been approved by Amanieu

It is now in the queue for this repository.

rust-bors · 2026-04-09T06:30:38Z

⌛ Testing commit 57d4965 with merge 7654d3b...

Workflow: https://github.com/rust-lang/rust/actions/runs/24176039890

core::sync: rename `Exclusive` to `SyncView` and make improvements This PR implements the renaming of `core::sync::Exclusive` to `SyncView` as decided in #98407. To preserve the ability to search for the old name, it adds `Exclusive` as a `doc_alias`. It also makes the following additional changes: - Converting the `get_mut` method to being an instance of `AsMut::as_mut`. In the process, it makes both the new `impl AsMut` and the existing `impl AsRef` `const`, and it also renames `get_pin_mut` to `as_pin_mut` for consistency. This direction follows a suggestion from #98407. - Adding an `as_pin` method that can only be used when the wrapped type implements `Sync`, to complete the square of access methods. - Making as many of the existing `impl`s `const` as possible; this involved making the existing `impl Default` no longer derived. - Adding `impl`s for `AsyncFnOnce`, `AsyncFnMut`, and `AsyncFn`, akin to the existing `impls` for `FnOnce`, `FnMut`, and `Fn`. It does not yet do the following, which may be desirable: - Fixing/improving the documentation to address the concern pointed out in #146245. It previously did the following, but this was removed after discussion: - Adding an `impl` for (`const`) `Iterator`, which felt in line with the existing `impl`s for `Future` and `Coroutine`.

jhpratt · 2026-04-09T06:31:31Z

Yielding to encompassing rollup

@bors yield

rust-bors · 2026-04-09T06:31:35Z

Auto build was cancelled. Cancelled workflows:

https://github.com/rust-lang/rust/actions/runs/24176039890

The next pull request likely to be tested is #155029.

Rollup of 3 pull requests Successful merges: - #153038 (core::sync: rename `Exclusive` to `SyncView` and make improvements) - #154955 (Fix pattern types rendering in rustdoc) - #155026 (Move `maybe_loop_headers` out of `rustc_middle`.)

Rollup merge of #153038 - pthariensflame:syncview-rename, r=Amanieu core::sync: rename `Exclusive` to `SyncView` and make improvements This PR implements the renaming of `core::sync::Exclusive` to `SyncView` as decided in #98407. To preserve the ability to search for the old name, it adds `Exclusive` as a `doc_alias`. It also makes the following additional changes: - Converting the `get_mut` method to being an instance of `AsMut::as_mut`. In the process, it makes both the new `impl AsMut` and the existing `impl AsRef` `const`, and it also renames `get_pin_mut` to `as_pin_mut` for consistency. This direction follows a suggestion from #98407. - Adding an `as_pin` method that can only be used when the wrapped type implements `Sync`, to complete the square of access methods. - Making as many of the existing `impl`s `const` as possible; this involved making the existing `impl Default` no longer derived. - Adding `impl`s for `AsyncFnOnce`, `AsyncFnMut`, and `AsyncFn`, akin to the existing `impls` for `FnOnce`, `FnMut`, and `Fn`. It does not yet do the following, which may be desirable: - Fixing/improving the documentation to address the concern pointed out in #146245. It previously did the following, but this was removed after discussion: - Adding an `impl` for (`const`) `Iterator`, which felt in line with the existing `impl`s for `Future` and `Coroutine`.

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 Feb 24, 2026

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pthariensflame force-pushed the syncview-rename branch from 0967996 to b5f2783 Compare February 24, 2026 09:14

rustbot added F-explicit_tail_calls `#![feature(explicit_tail_calls)]` WG-trait-system-refactor The Rustc Trait System Refactor Initiative (-Znext-solver) labels Feb 24, 2026

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joboet reviewed Feb 24, 2026

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WaffleLapkin removed the F-explicit_tail_calls `#![feature(explicit_tail_calls)]` label Feb 25, 2026

pthariensflame requested a review from joboet February 25, 2026 18:24

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pthariensflame force-pushed the syncview-rename branch from b5f2783 to ef2873c Compare February 27, 2026 00:33

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rustbot added the T-libs-api Relevant to the library API team, which will review and decide on the PR/issue. label Feb 28, 2026

rustbot assigned Amanieu and unassigned joboet Feb 28, 2026

pthariensflame force-pushed the syncview-rename branch from ef2873c to e39d61b Compare March 6, 2026 05:09

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pthariensflame force-pushed the syncview-rename branch from 7900ef4 to e2f838b Compare April 2, 2026 20:44

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pthariensflame added 7 commits April 6, 2026 18:00

core::sync: Rename Exclusive to SyncView

5adc031

core::sync::SyncView: constify all the impls

b360620

Add core::sync::SyncView<T: Sync>::as_pin

4b35912

This completes the existing suite of `as_ref`, `as_mut`, and `as_pin_mut` methods.

core::sync::SyncView: minor doc nits

f5830a7

impl AsyncFn{,Mut,Once} for core::sync::SyncView

99d0986

Update UI tests for SyncView rename

57d4965

pthariensflame force-pushed the syncview-rename branch from e2f838b to 57d4965 Compare April 7, 2026 01:15

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 Apr 9, 2026

jhpratt mentioned this pull request Apr 9, 2026

Rollup of 3 pull requests #155029

Merged

rust-bors bot merged commit 9ebe418 into rust-lang:main Apr 9, 2026
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rustbot added this to the 1.96.0 milestone Apr 9, 2026

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