Fix doc typo in Vec::into_array and convert Arc/Box/Rc::into_arry to -> Result
Hello 🪼,
the first commit fixes a documentation mistake added in the recent PR rust-lang/rust#156234
The second commit addresses three function signature changes as defined by the tracking issue rust-lang/rust#148082
It converts all `.into_array() -> Option<>` into `.into_array() -> Result<>`
The third commit is a fixup for the second. The change is needed as calling `unwrap()` on `Err(E)` requires `E` to implement `Debug`. I thought `Vec<T, A> where T: Debug` is not an acceptable solution, so I tried to come up with my own. I am *NOT* confident in my `unsafe {}` code due to lack of expierence, please check extra carefully.
Appreciating feedback & greetings from the RustWeek,
Thanks!
Add unstable Share trait
Tracking issue: rust-lang/rust#156756
This adds an initial unstable `Share` trait for clone-as-alias types, as part of the 2026 ergonomic ref-counting project goal.
```rust
pub trait Share: Clone {
fn share(&self) -> Self {
Clone::clone(self)
}
}
```
This PR adds a separate unstable feature gate:
```rust
#![feature(share_trait)]
```
and places the trait next to `Clone` in `core::clone`.
Implemented initial impls:
- `impl<T: ?Sized> Share for &T`
- `impl<T: ?Sized, A: Allocator + Clone> Share for Rc<T, A>`
- `impl<T: ?Sized, A: Allocator + Clone> Share for Arc<T, A>`
- `impl<T> Share for std::sync::mpsc::Sender<T>`
- `impl<T> Share for std::sync::mpsc::SyncSender<T>`
The PR deliberately does not add `Share` to the prelude.
r? @nikomatsakis
@rustbot label F-ergonomic_clones
Add `str::word_to_titlecase()` to `alloc`
A small addition to https://github.com/rust-lang/rust/issues/153892.
Hasn't gone through ACP, so needs libs-API signoff.
@rustbot label A-Unicode T-libs-api
`BufWriter`: Make the soundness of `BorrowedBuf` usage clearer.
The previous safety comment was outdated as it was written before `BorrowedBuf::set_init` was changed to be a boolean. It also failed to address the possibility that `flush_buf` invalidated the assumption.
std: implement `clear` via `truncate`
This gets rid of some `unsafe`. `truncate(0)` is even documented to be equivalent to `clear`, this makes that equivalence even more obvious.
The previous safety comment was outdated as it was written before
`BorrowedBuf::set_init` was changed to be a boolean. It also failed
to address the possibility that `flush_buf` invalidated the
assumption.
Simplify the implementation of `flush_buf` to more obviously preserve
the spare capacity, and document the need to preserve the spare
capacity where necessary.
`slice::join`: borrow only once during length calc
This ensures the length calculation will always be self-consistent even if the real length changes when we actually come to use them.
This is a follow up to rust-lang/rust#155708
Don't reload length in String::push
Same as in `Vec::push_mut`, we get `.len()` once at the start since it won't change in the `reserve()` call.
Saves reloading the length after the allocation: https://godbolt.org/z/W3G165Gd7
Fix heap overflow in slice::join caused by misbehaving Borrow
This code allocates a buffer using lengths calculated by calling `.borrow()` on some slices, and then copies them over after again calling `.borrow()`. There is no safety-reliable guarantee that these will return the same slices.
While this code calls `.borrow()` three times, only one of them is problematic: the others already use checked indexing.
I made the test a normal library test, but let me know if it should go elsewhere.
Bug discovered by Rust Foundation Security using AI. I'm just helping with the patch as a member of wg-security-response. We do not believe this bug needs embargo, it is a soundness fix for hard-to-trigger unsoundness.
Make Rcs and Arcs use pointer comparison for unsized types
`Rc` and `Arc`s have an `Eq` implementation that first attempt to compare the pointers as an optimization. This, however, was not extended to DSTs, which is what this PR fixes.
Fixesrust-lang/rust#154998.
Same as in Vec::push_mut, we get `.len()` once at the start since
it won't change in the `reserve()` call.
Saves reloading the length after the allocation: https://godbolt.org/z/W3G165Gd7
fix: add aliasing rules for Box
This is a new revised version for the PR [139857](https://github.com/rust-lang/rust/pull/139857), sorry for the delayed reply. I've rewritten the sentence to closely mirror the wording from `Vec::from_raw_parts`, which clearly states the transfer of ownership and its consequences. This should make the aliasing requirements much clearer.
I opted not to include a note about `mem::forget` by default to keep the documentation focused on the primary contract, similar to `Vec`.
Documenting the case of `Weak::upgrade` returning `None` when the value behind the reference is missing
Adds a clause to the documentation of `Weak` for `Arc` which was discussed in rust-lang/rust#154936.
Adds the same clause to the documentation of `Weak` for `Rc`, because the behavior is the same.
Make `convert_while_ascii` unsafe
`convert_while_ascii` assumes `convert` only returns ASCII to ensure the output remains valid UTF-8. This adds that requirement as a safety precondition.
Make Box/Rc/Arc::into_array allocator-aware (and add doctest)
Tracking issue for `alloc_slice_into_array`: https://github.com/rust-lang/rust/issues/148082
Tracking issue for `allocator_api`: https://github.com/rust-lang/rust/issues/32838
Make the `into_array` methods on `Box`, `Rc`, and `Arc` allocator-aware.
I think the allocator-aware-ness should not be observable on stable, so these should not be additionally (comment-)gated behind `feature(allocator_api)`, just like e.g. `Box::leak` and `Vec::into_boxed_slice`. The added doctests do not use `feature(allocator_api)`.
@rustbot label T-libs-api
* Extend `core::char`'s documentation of casing issues
* Fix typos
* Fix typo
Co-authored-by: GrigorenkoPV <GrigorenkoPV+github@yandex.ru>
* Document maximum 3x character expansion
This is guaranteed by Unicode.
* Fix error in `str` casing method docs
Jacob Pratt