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Rollup merge of #138540 - okaneco:const_split_off_first_last, r=m-ou-se

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core/slice: Mark some `split_off` variants unstably const

Tracking issue: #138539

Add feature gate `#![feature(const_split_off_first_last)]`
Mark `split_off_first`, `split_off_first_mut`, `split_off_last`, and `split_off_last_mut` slice methods unstably const
This commit is contained in:
Matthias Krüger
2025-03-19 16:52:55 +01:00
committed by GitHub
parent 2ab69b898a e1388bfb03
commit 2df731d586
1 changed files with 18 additions and 8 deletions
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26
library/core/src/slice/mod.rs
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@@ -4445,8 +4445,10 @@ impl<T> [T] {
/// ``` /// ```
#[inline] #[inline]
#[stable(feature = "slice_take", since = "CURRENT_RUSTC_VERSION")] #[stable(feature = "slice_take", since = "CURRENT_RUSTC_VERSION")]
pub fn split_off_first<'a>(self: &mut &'a Self) -> Option<&'a T> { #[rustc_const_unstable(feature = "const_split_off_first_last", issue = "138539")]
let (first, rem) = self.split_first()?; pub const fn split_off_first<'a>(self: &mut &'a Self) -> Option<&'a T> {
// FIXME(const-hack): Use `?` when available in const instead of `let-else`.
let Some((first, rem)) = self.split_first() else { return None };
*self = rem; *self = rem;
Some(first) Some(first)
} }
@@ -4468,8 +4470,11 @@ impl<T> [T] {
/// ``` /// ```
#[inline] #[inline]
#[stable(feature = "slice_take", since = "CURRENT_RUSTC_VERSION")] #[stable(feature = "slice_take", since = "CURRENT_RUSTC_VERSION")]
pub fn split_off_first_mut<'a>(self: &mut &'a mut Self) -> Option<&'a mut T> { #[rustc_const_unstable(feature = "const_split_off_first_last", issue = "138539")]
let (first, rem) = mem::take(self).split_first_mut()?; pub const fn split_off_first_mut<'a>(self: &mut &'a mut Self) -> Option<&'a mut T> {
// FIXME(const-hack): Use `mem::take` and `?` when available in const.
// Original: `mem::take(self).split_first_mut()?`
let Some((first, rem)) = mem::replace(self, &mut []).split_first_mut() else { return None };
*self = rem; *self = rem;
Some(first) Some(first)
} }
@@ -4490,8 +4495,10 @@ impl<T> [T] {
/// ``` /// ```
#[inline] #[inline]
#[stable(feature = "slice_take", since = "CURRENT_RUSTC_VERSION")] #[stable(feature = "slice_take", since = "CURRENT_RUSTC_VERSION")]
pub fn split_off_last<'a>(self: &mut &'a Self) -> Option<&'a T> { #[rustc_const_unstable(feature = "const_split_off_first_last", issue = "138539")]
let (last, rem) = self.split_last()?; pub const fn split_off_last<'a>(self: &mut &'a Self) -> Option<&'a T> {
// FIXME(const-hack): Use `?` when available in const instead of `let-else`.
let Some((last, rem)) = self.split_last() else { return None };
*self = rem; *self = rem;
Some(last) Some(last)
} }
@@ -4513,8 +4520,11 @@ impl<T> [T] {
/// ``` /// ```
#[inline] #[inline]
#[stable(feature = "slice_take", since = "CURRENT_RUSTC_VERSION")] #[stable(feature = "slice_take", since = "CURRENT_RUSTC_VERSION")]
pub fn split_off_last_mut<'a>(self: &mut &'a mut Self) -> Option<&'a mut T> { #[rustc_const_unstable(feature = "const_split_off_first_last", issue = "138539")]
let (last, rem) = mem::take(self).split_last_mut()?; pub const fn split_off_last_mut<'a>(self: &mut &'a mut Self) -> Option<&'a mut T> {
// FIXME(const-hack): Use `mem::take` and `?` when available in const.
// Original: `mem::take(self).split_last_mut()?`
let Some((last, rem)) = mem::replace(self, &mut []).split_last_mut() else { return None };
*self = rem; *self = rem;
Some(last) Some(last)
} }