slice: Mark `rotate_left`, `rotate_right` unstably const #143554

okaneco · 2025-07-07T00:50:38Z

Tracking issue #143812

Add the const unstable const_slice_rotate feature
Mark <[T]>::rotate_left and <[T]>::rotate_right as const unstable

The internal rotate functions use <*mut T>::replace and ptr::swap_nonoverlapping which were const-stabilized in 1.88.

Two changes were needed in the rotate.rs module to make these functions const:

A usage of cmp::min was replaced with a local function implementation of Ord::min.
A for start in 1..gcd loop was changed to a while loop with an increment variable.

This needs libs-api approval and cc-ing const-eval.

rustbot · 2025-07-07T00:50:42Z

r? @Mark-Simulacrum

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tgross35 · 2025-07-11T00:23:53Z

library/core/src/slice/mod.rs

+    #[rustc_const_unstable(feature = "const_slice_rotate", issue = "none")]
+    pub const fn rotate_left(&mut self, mid: usize) {


Please create a tracking issue

Created an issue and added it to the PR description.

tgross35 · 2025-07-11T00:24:28Z

library/core/src/slice/rotate.rs

@@ -265,3 +270,8 @@ unsafe fn ptr_rotate_swap<T>(mut left: usize, mut mid: *mut T, mut right: usize)
        }
    }
 }
+
+// FIXME(const-hack): Use cmp::min when available in const
+const fn min(left: usize, right: usize) -> usize {


Name this const_min to make it obvious where this is getting used

Addressed.
https://github.com/rust-lang/rust/compare/81d95ca36ce48ef06f5ce965794878ec1aa2aeff..3751e133bca55dbec521ccb36132fa0bdbf10b88

tgross35 · 2025-07-11T00:25:35Z

@rust-lang/libs-api this seems unproblematic, could it get a +1 from one of you?

Amanieu

LGTM

tgross35 · 2025-07-11T20:29:57Z

@bors r=Amanieu,tgross35 rollup

bors · 2025-07-11T20:30:00Z

📌 Commit 3751e13 has been approved by Amanieu,tgross35

It is now in the queue for this repository.

…ieu,tgross35 slice: Mark `rotate_left`, `rotate_right` unstably const Tracking issue rust-lang#143812 - Add the const unstable `const_slice_rotate` feature - Mark `<[T]>::rotate_left` and `<[T]>::rotate_right` as const unstable The internal rotate functions use [`<*mut T>::replace`](https://doc.rust-lang.org/stable/core/primitive.pointer.html#method.replace) and [`ptr::swap_nonoverlapping`](https://doc.rust-lang.org/stable/core/ptr/fn.swap_nonoverlapping.html) which were const-stabilized in 1.88. Two changes were needed in the `rotate.rs` module to make these functions const: 1. A usage of `cmp::min` was replaced with a local function implementation of [`Ord::min`](https://doc.rust-lang.org/1.88.0/src/core/cmp.rs.html#1048-1053). 2. A `for start in 1..gcd` loop was changed to a while loop with an increment variable. This needs libs-api approval and cc-ing const-eval.

Rollup of 9 pull requests Successful merges: - #143213 (de-duplicate condition scoping logic between AST→HIR lowering and `ScopeTree` construction) - #143461 (make `cfg_select` a builtin macro) - #143519 (Check assoc consts and tys later like assoc fns) - #143554 (slice: Mark `rotate_left`, `rotate_right` unstably const) - #143704 (Be a bit more careful around exotic cycles in in the inliner) - #143774 (constify `From` and `Into`) - #143786 (Fix fallback for CI_JOB_NAME) - #143796 (Fix ICE for parsed attributes with longer path not handled by CheckAttribute) - #143798 (Remove format short command trait) r? `@ghost` `@rustbot` modify labels: rollup

…ieu,tgross35 slice: Mark `rotate_left`, `rotate_right` unstably const Tracking issue rust-lang#143812 - Add the const unstable `const_slice_rotate` feature - Mark `<[T]>::rotate_left` and `<[T]>::rotate_right` as const unstable The internal rotate functions use [`<*mut T>::replace`](https://doc.rust-lang.org/stable/core/primitive.pointer.html#method.replace) and [`ptr::swap_nonoverlapping`](https://doc.rust-lang.org/stable/core/ptr/fn.swap_nonoverlapping.html) which were const-stabilized in 1.88. Two changes were needed in the `rotate.rs` module to make these functions const: 1. A usage of `cmp::min` was replaced with a local function implementation of [`Ord::min`](https://doc.rust-lang.org/1.88.0/src/core/cmp.rs.html#1048-1053). 2. A `for start in 1..gcd` loop was changed to a while loop with an increment variable. This needs libs-api approval and cc-ing const-eval.

Rollup of 15 pull requests Successful merges: - #143554 (slice: Mark `rotate_left`, `rotate_right` unstably const) - #143634 (interpret/allocation: expose init + write_wildcards on a range) - #143710 (Updates to random number generation APIs) - #143774 (constify `From` and `Into`) - #143776 (std: move NuttX to use arc4random for random number generation) - #143778 (Some const_trait_impl test cleanups) - #143782 (Disambiguate between rustc vs std having debug assertions in `run-make-support` and `run-make` tests) - #143791 (Update sysinfo version to `0.36.0`) - #143796 (Fix ICE for parsed attributes with longer path not handled by CheckAttribute) - #143798 (Remove format short command trait) - #143803 (New tracking issues for const_ops and const_cmp) - #143814 (htmldocck: better error messages for some negative directives) - #143817 (Access `wasi_sdk_path` instead of reading environment variable in bootstrap) - #143822 (./x test miri: fix cleaning the miri_ui directory) - #143823 ([COMPILETEST-UNTANGLE 5/N] Test mode adjustments and other assorted cleanups) r? `@ghost` `@rustbot` modify labels: rollup

…ieu,tgross35 slice: Mark `rotate_left`, `rotate_right` unstably const Tracking issue rust-lang#143812 - Add the const unstable `const_slice_rotate` feature - Mark `<[T]>::rotate_left` and `<[T]>::rotate_right` as const unstable The internal rotate functions use [`<*mut T>::replace`](https://doc.rust-lang.org/stable/core/primitive.pointer.html#method.replace) and [`ptr::swap_nonoverlapping`](https://doc.rust-lang.org/stable/core/ptr/fn.swap_nonoverlapping.html) which were const-stabilized in 1.88. Two changes were needed in the `rotate.rs` module to make these functions const: 1. A usage of `cmp::min` was replaced with a local function implementation of [`Ord::min`](https://doc.rust-lang.org/1.88.0/src/core/cmp.rs.html#1048-1053). 2. A `for start in 1..gcd` loop was changed to a while loop with an increment variable. This needs libs-api approval and cc-ing const-eval.

Rollup of 14 pull requests Successful merges: - #143301 (`tests/ui`: A New Order [26/N]) - #143461 (make `cfg_select` a builtin macro) - #143519 (Check assoc consts and tys later like assoc fns) - #143554 (slice: Mark `rotate_left`, `rotate_right` unstably const) - #143634 (interpret/allocation: expose init + write_wildcards on a range) - #143679 (Preserve the .debug_gdb_scripts section) - #143685 (Resolve: merge `source_bindings` and `target_bindings` into `bindings`) - #143704 (Be a bit more careful around exotic cycles in in the inliner) - #143734 (Refactor resolve resolution bindings) - #143774 (constify `From` and `Into`) - #143785 (Add --compile-time-deps argument for x check) - #143786 (Fix fallback for CI_JOB_NAME) - #143825 (clippy: fix test filtering when TESTNAME is empty) - #143826 (Fix command trace) r? `@ghost` `@rustbot` modify labels: rollup

…ieu,tgross35 slice: Mark `rotate_left`, `rotate_right` unstably const Tracking issue rust-lang#143812 - Add the const unstable `const_slice_rotate` feature - Mark `<[T]>::rotate_left` and `<[T]>::rotate_right` as const unstable The internal rotate functions use [`<*mut T>::replace`](https://doc.rust-lang.org/stable/core/primitive.pointer.html#method.replace) and [`ptr::swap_nonoverlapping`](https://doc.rust-lang.org/stable/core/ptr/fn.swap_nonoverlapping.html) which were const-stabilized in 1.88. Two changes were needed in the `rotate.rs` module to make these functions const: 1. A usage of `cmp::min` was replaced with a local function implementation of [`Ord::min`](https://doc.rust-lang.org/1.88.0/src/core/cmp.rs.html#1048-1053). 2. A `for start in 1..gcd` loop was changed to a while loop with an increment variable. This needs libs-api approval and cc-ing const-eval.

Rollup of 13 pull requests Successful merges: - #143301 (`tests/ui`: A New Order [26/N]) - #143461 (make `cfg_select` a builtin macro) - #143519 (Check assoc consts and tys later like assoc fns) - #143554 (slice: Mark `rotate_left`, `rotate_right` unstably const) - #143634 (interpret/allocation: expose init + write_wildcards on a range) - #143679 (Preserve the .debug_gdb_scripts section) - #143685 (Resolve: merge `source_bindings` and `target_bindings` into `bindings`) - #143734 (Refactor resolve resolution bindings) - #143774 (constify `From` and `Into`) - #143785 (Add --compile-time-deps argument for x check) - #143786 (Fix fallback for CI_JOB_NAME) - #143825 (clippy: fix test filtering when TESTNAME is empty) - #143826 (Fix command trace) r? `@ghost` `@rustbot` modify labels: rollup

…ieu,tgross35 slice: Mark `rotate_left`, `rotate_right` unstably const Tracking issue rust-lang#143812 - Add the const unstable `const_slice_rotate` feature - Mark `<[T]>::rotate_left` and `<[T]>::rotate_right` as const unstable The internal rotate functions use [`<*mut T>::replace`](https://doc.rust-lang.org/stable/core/primitive.pointer.html#method.replace) and [`ptr::swap_nonoverlapping`](https://doc.rust-lang.org/stable/core/ptr/fn.swap_nonoverlapping.html) which were const-stabilized in 1.88. Two changes were needed in the `rotate.rs` module to make these functions const: 1. A usage of `cmp::min` was replaced with a local function implementation of [`Ord::min`](https://doc.rust-lang.org/1.88.0/src/core/cmp.rs.html#1048-1053). 2. A `for start in 1..gcd` loop was changed to a while loop with an increment variable. This needs libs-api approval and cc-ing const-eval.

Rollup of 11 pull requests Successful merges: - #143301 (`tests/ui`: A New Order [26/N]) - #143519 (Check assoc consts and tys later like assoc fns) - #143554 (slice: Mark `rotate_left`, `rotate_right` unstably const) - #143634 (interpret/allocation: expose init + write_wildcards on a range) - #143685 (Resolve: merge `source_bindings` and `target_bindings` into `bindings`) - #143734 (Refactor resolve resolution bindings) - #143774 (constify `From` and `Into`) - #143785 (Add --compile-time-deps argument for x check) - #143786 (Fix fallback for CI_JOB_NAME) - #143825 (clippy: fix test filtering when TESTNAME is empty) - #143826 (Fix command trace) r? `@ghost` `@rustbot` modify labels: rollup

rustbot assigned Mark-Simulacrum Jul 7, 2025

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 Jul 7, 2025

tgross35 requested changes Jul 11, 2025

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Amanieu approved these changes Jul 11, 2025

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okaneco mentioned this pull request Jul 11, 2025

Tracking Issue for const_slice_rotate #143812

Open

3 tasks

slice: Mark rotate_left, rotate_right unstably const

3751e13

okaneco force-pushed the const_slice_rotate branch from 81d95ca to 3751e13 Compare July 11, 2025 18:47

tgross35 assigned tgross35 and unassigned Mark-Simulacrum Jul 11, 2025

bors 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 Jul 11, 2025

matthiaskrgr mentioned this pull request Jul 12, 2025

Rollup of 9 pull requests #143840

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jhpratt mentioned this pull request Jul 12, 2025

Rollup of 15 pull requests #143853

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fmease mentioned this pull request Jul 13, 2025

Rollup of 14 pull requests #143866

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Rollup of 13 pull requests #143876

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Rollup of 12 pull requests #143886

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Rollup of 11 pull requests #143888

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slice: Mark `rotate_left`, `rotate_right` unstably const #143554

slice: Mark `rotate_left`, `rotate_right` unstably const #143554

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		#[rustc_const_unstable(feature = "const_slice_rotate", issue = "none")]
		pub const fn rotate_left(&mut self, mid: usize) {

slice: Mark rotate_left, rotate_right unstably const #143554

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slice: Mark rotate_left, rotate_right unstably const #143554

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slice: Mark `rotate_left`, `rotate_right` unstably const #143554

slice: Mark `rotate_left`, `rotate_right` unstably const #143554

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