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constify Index(Mut), Deref(Mut) for Vec #155054

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Merged
rust-bors merged 1 commit into from
Apr 20, 2026
+16 −20
Merged

constify Index(Mut), Deref(Mut) for Vec #155054

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1 change: 1 addition & 0 deletions library/alloc/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -106,6 +106,7 @@
#![feature(const_destruct)]
#![feature(const_eval_select)]
#![feature(const_heap)]
#![feature(const_index)]
#![feature(const_option_ops)]
#![feature(const_try)]
#![feature(copied_into_inner)]
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12 changes: 8 additions & 4 deletions library/alloc/src/vec/mod.rs
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Expand Up @@ -3747,7 +3747,8 @@ impl<T: TrivialClone, A: Allocator> ExtendFromWithinSpec for Vec<T, A> {
////////////////////////////////////////////////////////////////////////////////

#[stable(feature = "rust1", since = "1.0.0")]
impl<T, A: Allocator> ops::Deref for Vec<T, A> {
#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
impl<T, A: Allocator> const ops::Deref for Vec<T, A> {
type Target = [T];

#[inline]
Expand All @@ -3757,7 +3758,8 @@ impl<T, A: Allocator> ops::Deref for Vec<T, A> {
}

#[stable(feature = "rust1", since = "1.0.0")]
impl<T, A: Allocator> ops::DerefMut for Vec<T, A> {
#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
impl<T, A: Allocator> const ops::DerefMut for Vec<T, A> {
#[inline]
fn deref_mut(&mut self) -> &mut [T] {
self.as_mut_slice()
Expand Down Expand Up @@ -3822,7 +3824,8 @@ impl<T: Hash, A: Allocator> Hash for Vec<T, A> {
}

#[stable(feature = "rust1", since = "1.0.0")]
impl<T, I: SliceIndex<[T]>, A: Allocator> Index<I> for Vec<T, A> {
#[rustc_const_unstable(feature = "const_index", issue = "143775")]
impl<T, I: [const] SliceIndex<[T]>, A: Allocator> const Index<I> for Vec<T, A> {
type Output = I::Output;

#[inline]
Expand All @@ -3832,7 +3835,8 @@ impl<T, I: SliceIndex<[T]>, A: Allocator> Index<I> for Vec<T, A> {
}

#[stable(feature = "rust1", since = "1.0.0")]
impl<T, I: SliceIndex<[T]>, A: Allocator> IndexMut<I> for Vec<T, A> {
#[rustc_const_unstable(feature = "const_index", issue = "143775")]
impl<T, I: [const] SliceIndex<[T]>, A: Allocator> const IndexMut<I> for Vec<T, A> {
#[inline]
fn index_mut(&mut self, index: I) -> &mut Self::Output {
IndexMut::index_mut(&mut **self, index)
Expand Down
3 changes: 1 addition & 2 deletions tests/ui/consts/issue-94675.rs
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Expand Up @@ -9,8 +9,7 @@ struct Foo<'a> {
impl<'a> Foo<'a> {
const fn spam(&mut self, baz: &mut Vec<u32>) {
self.bar[0] = baz.len();
//~^ ERROR: `Vec<usize>: [const] Index<_>` is not satisfied
//~| ERROR: `Vec<usize>: [const] IndexMut<usize>` is not satisfied
//~^ ERROR: `IndexMut` is not yet stable as a const trait
}
}

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20 changes: 6 additions & 14 deletions tests/ui/consts/issue-94675.stderr
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@@ -1,21 +1,13 @@
error[E0277]: the trait bound `Vec<usize>: [const] Index<_>` is not satisfied
--> $DIR/issue-94675.rs:11:9
error: `IndexMut` is not yet stable as a const trait
--> $DIR/issue-94675.rs:11:17
|
LL | self.bar[0] = baz.len();
| ^^^^^^^^^^^
| ^^^
|
note: trait `Index` is implemented but not `const`
--> $SRC_DIR/alloc/src/vec/mod.rs:LL:COL

error[E0277]: the trait bound `Vec<usize>: [const] IndexMut<usize>` is not satisfied
--> $DIR/issue-94675.rs:11:9
help: add `#![feature(const_index)]` to the crate attributes to enable
|
LL | self.bar[0] = baz.len();
| ^^^^^^^^^^^
LL + #![feature(const_index)]
|
note: trait `IndexMut` is implemented but not `const`
--> $SRC_DIR/alloc/src/vec/mod.rs:LL:COL

error: aborting due to 2 previous errors
error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0277`.
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