Skip to content

add #[rustc_no_writable] to slice::get_unchecked_mut #157202

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
quiode wants to merge 1 commit into
base: main
Choose a base branch
from
+1 −0
Open

add #[rustc_no_writable] to slice::get_unchecked_mut #157202

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
1 change: 1 addition & 0 deletions library/core/src/slice/mod.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -681,6 +681,7 @@ impl<T> [T] {
#[must_use]
#[track_caller]
#[rustc_const_unstable(feature = "const_index", issue = "143775")]
#[rustc_no_writable]
Copy link
Copy Markdown
Member

@Mark-Simulacrum Mark-Simulacrum May 31, 2026 •
edited by rustbot
Loading

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Should this get an annotation of some kind (e.g., "FIXME: #xxx")? I assume the intent is not to guarantee that we don't have compiler-added writes of the full slice, maybe with the long-term intent being that users move to using raw pointer functions where they need that (https://doc.rust-lang.org/nightly/std/primitive.pointer.html#method.get_unchecked_mut)?

View changes since the review

Copy link
Copy Markdown
Member

@RalfJung RalfJung Jun 1, 2026

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Personally I think this is fine to guarantee. But for now the attribute is experimental anyway.

Copy link
Copy Markdown
Member

@RalfJung RalfJung Jun 1, 2026 •
edited by rustbot
Loading

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Please add a Miri test that relies on this attribute. Something like https://rust.godbolt.org/z/TreEYqfW8, I assume?

View changes since the review

pub const unsafe fn get_unchecked_mut<I>(&mut self, index: I) -> &mut I::Output
where
I: [const] SliceIndex<Self>,
Expand Down
Loading