Rollup merge of #144091 - thaliaarchi:stabilize-new-zeroed, r=Mark-Simulacrum

Stabilize `new_zeroed_alloc`

The corresponding `new_uninit` and `new_uninit_slice` functions were stabilized in rust-lang/rust#129401, but the zeroed counterparts were left for later out of a [desire](https://github.com/rust-lang/rust/issues/63291#issuecomment-2161039756) to stabilize only the minimal set. These functions are straightforward mirrors of the uninit functions and well-established. Since no blockers or design questions have surfaced in the past year, I think it's time to stabilize them.

Tracking issue: rust-lang/rust#129396

6 files changed, 9 insertions, 44 deletions

diff --git a/compiler/rustc_index/src/bit_set.rs b/compiler/rustc_index/src/bit_set.rs
index 684bd34f909..f7649c5f5c5 100644
--- a/compiler/rustc_index/src/bit_set.rs
+++ b/compiler/rustc_index/src/bit_set.rs
@@ -645,7 +645,7 @@ impl<T: Idx> ChunkedBitSet<T> {
                     };
                     #[cfg(not(feature = "nightly"))]
                     let mut words = {
-                        // FIXME: unconditionally use `Rc::new_zeroed` once it is stable (#63291).
+                        // FIXME: unconditionally use `Rc::new_zeroed` once it is stable (#129396).
                         let words = mem::MaybeUninit::<[Word; CHUNK_WORDS]>::zeroed();
                         // SAFETY: `words` can safely be all zeroes.
                         let words = unsafe { words.assume_init() };
@@ -708,7 +708,7 @@ impl<T: Idx> ChunkedBitSet<T> {
                     };
                     #[cfg(not(feature = "nightly"))]
                     let mut words = {
-                        // FIXME: unconditionally use `Rc::new_zeroed` once it is stable (#63291).
+                        // FIXME: unconditionally use `Rc::new_zeroed` once it is stable (#129396).
                         let words = mem::MaybeUninit::<[Word; CHUNK_WORDS]>::zeroed();
                         // SAFETY: `words` can safely be all zeroes.
                         let words = unsafe { words.assume_init() };
diff --git a/compiler/rustc_index/src/lib.rs b/compiler/rustc_index/src/lib.rs
index cc680838e7e..9d647209c6f 100644
--- a/compiler/rustc_index/src/lib.rs
+++ b/compiler/rustc_index/src/lib.rs
@@ -1,9 +1,9 @@
 // tidy-alphabetical-start
 #![cfg_attr(all(feature = "nightly", test), feature(stmt_expr_attributes))]
+#![cfg_attr(bootstrap, feature(new_zeroed_alloc))]
 #![cfg_attr(feature = "nightly", allow(internal_features))]
 #![cfg_attr(feature = "nightly", feature(extend_one, step_trait, test))]
 #![cfg_attr(feature = "nightly", feature(new_range_api))]
-#![cfg_attr(feature = "nightly", feature(new_zeroed_alloc))]
 // tidy-alphabetical-end
 
 pub mod bit_set;
diff --git a/library/alloc/src/boxed.rs b/library/alloc/src/boxed.rs
index 7d2dd12c6ea..1c549f7b6ba 100644
--- a/library/alloc/src/boxed.rs
+++ b/library/alloc/src/boxed.rs
@@ -290,8 +290,6 @@ impl<T> Box<T> {
     /// # Examples
     ///
     /// ```
-    /// #![feature(new_zeroed_alloc)]
-    ///
     /// let zero = Box::<u32>::new_zeroed();
     /// let zero = unsafe { zero.assume_init() };
     ///
@@ -301,7 +299,7 @@ impl<T> Box<T> {
     /// [zeroed]: mem::MaybeUninit::zeroed
     #[cfg(not(no_global_oom_handling))]
     #[inline]
-    #[unstable(feature = "new_zeroed_alloc", issue = "129396")]
+    #[stable(feature = "new_zeroed_alloc", since = "CURRENT_RUSTC_VERSION")]
     #[must_use]
     pub fn new_zeroed() -> Box<mem::MaybeUninit<T>> {
         Self::new_zeroed_in(Global)
@@ -358,7 +356,6 @@ impl<T> Box<T> {
     /// # Ok::<(), std::alloc::AllocError>(())
     /// ```
     #[unstable(feature = "allocator_api", issue = "32838")]
-    // #[unstable(feature = "new_uninit", issue = "63291")]
     #[inline]
     pub fn try_new_uninit() -> Result<Box<mem::MaybeUninit<T>>, AllocError> {
         Box::try_new_uninit_in(Global)
@@ -384,7 +381,6 @@ impl<T> Box<T> {
     ///
     /// [zeroed]: mem::MaybeUninit::zeroed
     #[unstable(feature = "allocator_api", issue = "32838")]
-    // #[unstable(feature = "new_uninit", issue = "63291")]
     #[inline]
     pub fn try_new_zeroed() -> Result<Box<mem::MaybeUninit<T>>, AllocError> {
         Box::try_new_zeroed_in(Global)
@@ -463,7 +459,6 @@ impl<T, A: Allocator> Box<T, A> {
     #[unstable(feature = "allocator_api", issue = "32838")]
     #[cfg(not(no_global_oom_handling))]
     #[must_use]
-    // #[unstable(feature = "new_uninit", issue = "63291")]
     pub fn new_uninit_in(alloc: A) -> Box<mem::MaybeUninit<T>, A>
     where
         A: Allocator,
@@ -496,7 +491,6 @@ impl<T, A: Allocator> Box<T, A> {
     /// # Ok::<(), std::alloc::AllocError>(())
     /// ```
     #[unstable(feature = "allocator_api", issue = "32838")]
-    // #[unstable(feature = "new_uninit", issue = "63291")]
     pub fn try_new_uninit_in(alloc: A) -> Result<Box<mem::MaybeUninit<T>, A>, AllocError>
     where
         A: Allocator,
@@ -532,7 +526,6 @@ impl<T, A: Allocator> Box<T, A> {
     /// [zeroed]: mem::MaybeUninit::zeroed
     #[unstable(feature = "allocator_api", issue = "32838")]
     #[cfg(not(no_global_oom_handling))]
-    // #[unstable(feature = "new_uninit", issue = "63291")]
     #[must_use]
     pub fn new_zeroed_in(alloc: A) -> Box<mem::MaybeUninit<T>, A>
     where
@@ -570,7 +563,6 @@ impl<T, A: Allocator> Box<T, A> {
     ///
     /// [zeroed]: mem::MaybeUninit::zeroed
     #[unstable(feature = "allocator_api", issue = "32838")]
-    // #[unstable(feature = "new_uninit", issue = "63291")]
     pub fn try_new_zeroed_in(alloc: A) -> Result<Box<mem::MaybeUninit<T>, A>, AllocError>
     where
         A: Allocator,
@@ -660,8 +652,6 @@ impl<T> Box<[T]> {
     /// # Examples
     ///
     /// ```
-    /// #![feature(new_zeroed_alloc)]
-    ///
     /// let values = Box::<[u32]>::new_zeroed_slice(3);
     /// let values = unsafe { values.assume_init() };
     ///
@@ -670,7 +660,7 @@ impl<T> Box<[T]> {
     ///
     /// [zeroed]: mem::MaybeUninit::zeroed
     #[cfg(not(no_global_oom_handling))]
-    #[unstable(feature = "new_zeroed_alloc", issue = "129396")]
+    #[stable(feature = "new_zeroed_alloc", since = "CURRENT_RUSTC_VERSION")]
     #[must_use]
     pub fn new_zeroed_slice(len: usize) -> Box<[mem::MaybeUninit<T>]> {
         unsafe { RawVec::with_capacity_zeroed(len).into_box(len) }
@@ -785,7 +775,6 @@ impl<T, A: Allocator> Box<[T], A> {
     /// ```
     #[cfg(not(no_global_oom_handling))]
     #[unstable(feature = "allocator_api", issue = "32838")]
-    // #[unstable(feature = "new_uninit", issue = "63291")]
     #[must_use]
     pub fn new_uninit_slice_in(len: usize, alloc: A) -> Box<[mem::MaybeUninit<T>], A> {
         unsafe { RawVec::with_capacity_in(len, alloc).into_box(len) }
@@ -813,7 +802,6 @@ impl<T, A: Allocator> Box<[T], A> {
     /// [zeroed]: mem::MaybeUninit::zeroed
     #[cfg(not(no_global_oom_handling))]
     #[unstable(feature = "allocator_api", issue = "32838")]
-    // #[unstable(feature = "new_uninit", issue = "63291")]
     #[must_use]
     pub fn new_zeroed_slice_in(len: usize, alloc: A) -> Box<[mem::MaybeUninit<T>], A> {
         unsafe { RawVec::with_capacity_zeroed_in(len, alloc).into_box(len) }
diff --git a/library/alloc/src/rc.rs b/library/alloc/src/rc.rs
index 529b583cdd2..fcb466778a3 100644
--- a/library/alloc/src/rc.rs
+++ b/library/alloc/src/rc.rs
@@ -515,8 +515,6 @@ impl<T> Rc<T> {
     /// # Examples
     ///
     /// ```
-    /// #![feature(new_zeroed_alloc)]
-    ///
     /// use std::rc::Rc;
     ///
     /// let zero = Rc::<u32>::new_zeroed();
@@ -527,7 +525,7 @@ impl<T> Rc<T> {
     ///
     /// [zeroed]: mem::MaybeUninit::zeroed
     #[cfg(not(no_global_oom_handling))]
-    #[unstable(feature = "new_zeroed_alloc", issue = "129396")]
+    #[stable(feature = "new_zeroed_alloc", since = "CURRENT_RUSTC_VERSION")]
     #[must_use]
     pub fn new_zeroed() -> Rc<mem::MaybeUninit<T>> {
         unsafe {
@@ -589,7 +587,6 @@ impl<T> Rc<T> {
     /// # Ok::<(), std::alloc::AllocError>(())
     /// ```
     #[unstable(feature = "allocator_api", issue = "32838")]
-    // #[unstable(feature = "new_uninit", issue = "63291")]
     pub fn try_new_uninit() -> Result<Rc<mem::MaybeUninit<T>>, AllocError> {
         unsafe {
             Ok(Rc::from_ptr(Rc::try_allocate_for_layout(
@@ -622,7 +619,6 @@ impl<T> Rc<T> {
     ///
     /// [zeroed]: mem::MaybeUninit::zeroed
     #[unstable(feature = "allocator_api", issue = "32838")]
-    //#[unstable(feature = "new_uninit", issue = "63291")]
     pub fn try_new_zeroed() -> Result<Rc<mem::MaybeUninit<T>>, AllocError> {
         unsafe {
             Ok(Rc::from_ptr(Rc::try_allocate_for_layout(
@@ -690,7 +686,6 @@ impl<T, A: Allocator> Rc<T, A> {
     /// ```
     #[cfg(not(no_global_oom_handling))]
     #[unstable(feature = "allocator_api", issue = "32838")]
-    // #[unstable(feature = "new_uninit", issue = "63291")]
     #[inline]
     pub fn new_uninit_in(alloc: A) -> Rc<mem::MaybeUninit<T>, A> {
         unsafe {
@@ -728,7 +723,6 @@ impl<T, A: Allocator> Rc<T, A> {
     /// [zeroed]: mem::MaybeUninit::zeroed
     #[cfg(not(no_global_oom_handling))]
     #[unstable(feature = "allocator_api", issue = "32838")]
-    // #[unstable(feature = "new_uninit", issue = "63291")]
     #[inline]
     pub fn new_zeroed_in(alloc: A) -> Rc<mem::MaybeUninit<T>, A> {
         unsafe {
@@ -873,7 +867,6 @@ impl<T, A: Allocator> Rc<T, A> {
     /// # Ok::<(), std::alloc::AllocError>(())
     /// ```
     #[unstable(feature = "allocator_api", issue = "32838")]
-    // #[unstable(feature = "new_uninit", issue = "63291")]
     #[inline]
     pub fn try_new_uninit_in(alloc: A) -> Result<Rc<mem::MaybeUninit<T>, A>, AllocError> {
         unsafe {
@@ -912,7 +905,6 @@ impl<T, A: Allocator> Rc<T, A> {
     ///
     /// [zeroed]: mem::MaybeUninit::zeroed
     #[unstable(feature = "allocator_api", issue = "32838")]
-    //#[unstable(feature = "new_uninit", issue = "63291")]
     #[inline]
     pub fn try_new_zeroed_in(alloc: A) -> Result<Rc<mem::MaybeUninit<T>, A>, AllocError> {
         unsafe {
@@ -1054,8 +1046,6 @@ impl<T> Rc<[T]> {
     /// # Examples
     ///
     /// ```
-    /// #![feature(new_zeroed_alloc)]
-    ///
     /// use std::rc::Rc;
     ///
     /// let values = Rc::<[u32]>::new_zeroed_slice(3);
@@ -1066,7 +1056,7 @@ impl<T> Rc<[T]> {
     ///
     /// [zeroed]: mem::MaybeUninit::zeroed
     #[cfg(not(no_global_oom_handling))]
-    #[unstable(feature = "new_zeroed_alloc", issue = "129396")]
+    #[stable(feature = "new_zeroed_alloc", since = "CURRENT_RUSTC_VERSION")]
     #[must_use]
     pub fn new_zeroed_slice(len: usize) -> Rc<[mem::MaybeUninit<T>]> {
         unsafe {
@@ -1129,7 +1119,6 @@ impl<T, A: Allocator> Rc<[T], A> {
     /// ```
     #[cfg(not(no_global_oom_handling))]
     #[unstable(feature = "allocator_api", issue = "32838")]
-    // #[unstable(feature = "new_uninit", issue = "63291")]
     #[inline]
     pub fn new_uninit_slice_in(len: usize, alloc: A) -> Rc<[mem::MaybeUninit<T>], A> {
         unsafe { Rc::from_ptr_in(Rc::allocate_for_slice_in(len, &alloc), alloc) }
@@ -1158,7 +1147,6 @@ impl<T, A: Allocator> Rc<[T], A> {
     /// [zeroed]: mem::MaybeUninit::zeroed
     #[cfg(not(no_global_oom_handling))]
     #[unstable(feature = "allocator_api", issue = "32838")]
-    // #[unstable(feature = "new_uninit", issue = "63291")]
     #[inline]
     pub fn new_zeroed_slice_in(len: usize, alloc: A) -> Rc<[mem::MaybeUninit<T>], A> {
         unsafe {
diff --git a/library/alloc/src/sync.rs b/library/alloc/src/sync.rs
index a21b6880674..32396cccb8f 100644
--- a/library/alloc/src/sync.rs
+++ b/library/alloc/src/sync.rs
@@ -516,8 +516,6 @@ impl<T> Arc<T> {
     /// # Examples
     ///
     /// ```
-    /// #![feature(new_zeroed_alloc)]
-    ///
     /// use std::sync::Arc;
     ///
     /// let zero = Arc::<u32>::new_zeroed();
@@ -529,7 +527,7 @@ impl<T> Arc<T> {
     /// [zeroed]: mem::MaybeUninit::zeroed
     #[cfg(not(no_global_oom_handling))]
     #[inline]
-    #[unstable(feature = "new_zeroed_alloc", issue = "129396")]
+    #[stable(feature = "new_zeroed_alloc", since = "CURRENT_RUSTC_VERSION")]
     #[must_use]
     pub fn new_zeroed() -> Arc<mem::MaybeUninit<T>> {
         unsafe {
@@ -603,7 +601,6 @@ impl<T> Arc<T> {
     /// # Ok::<(), std::alloc::AllocError>(())
     /// ```
     #[unstable(feature = "allocator_api", issue = "32838")]
-    // #[unstable(feature = "new_uninit", issue = "63291")]
     pub fn try_new_uninit() -> Result<Arc<mem::MaybeUninit<T>>, AllocError> {
         unsafe {
             Ok(Arc::from_ptr(Arc::try_allocate_for_layout(
@@ -636,7 +633,6 @@ impl<T> Arc<T> {
     ///
     /// [zeroed]: mem::MaybeUninit::zeroed
     #[unstable(feature = "allocator_api", issue = "32838")]
-    // #[unstable(feature = "new_uninit", issue = "63291")]
     pub fn try_new_zeroed() -> Result<Arc<mem::MaybeUninit<T>>, AllocError> {
         unsafe {
             Ok(Arc::from_ptr(Arc::try_allocate_for_layout(
@@ -703,7 +699,6 @@ impl<T, A: Allocator> Arc<T, A> {
     /// ```
     #[cfg(not(no_global_oom_handling))]
     #[unstable(feature = "allocator_api", issue = "32838")]
-    // #[unstable(feature = "new_uninit", issue = "63291")]
     #[inline]
     pub fn new_uninit_in(alloc: A) -> Arc<mem::MaybeUninit<T>, A> {
         unsafe {
@@ -741,7 +736,6 @@ impl<T, A: Allocator> Arc<T, A> {
     /// [zeroed]: mem::MaybeUninit::zeroed
     #[cfg(not(no_global_oom_handling))]
     #[unstable(feature = "allocator_api", issue = "32838")]
-    // #[unstable(feature = "new_uninit", issue = "63291")]
     #[inline]
     pub fn new_zeroed_in(alloc: A) -> Arc<mem::MaybeUninit<T>, A> {
         unsafe {
@@ -927,7 +921,6 @@ impl<T, A: Allocator> Arc<T, A> {
     /// # Ok::<(), std::alloc::AllocError>(())
     /// ```
     #[unstable(feature = "allocator_api", issue = "32838")]
-    // #[unstable(feature = "new_uninit", issue = "63291")]
     #[inline]
     pub fn try_new_uninit_in(alloc: A) -> Result<Arc<mem::MaybeUninit<T>, A>, AllocError> {
         unsafe {
@@ -966,7 +959,6 @@ impl<T, A: Allocator> Arc<T, A> {
     ///
     /// [zeroed]: mem::MaybeUninit::zeroed
     #[unstable(feature = "allocator_api", issue = "32838")]
-    // #[unstable(feature = "new_uninit", issue = "63291")]
     #[inline]
     pub fn try_new_zeroed_in(alloc: A) -> Result<Arc<mem::MaybeUninit<T>, A>, AllocError> {
         unsafe {
@@ -1197,8 +1189,6 @@ impl<T> Arc<[T]> {
     /// # Examples
     ///
     /// ```
-    /// #![feature(new_zeroed_alloc)]
-    ///
     /// use std::sync::Arc;
     ///
     /// let values = Arc::<[u32]>::new_zeroed_slice(3);
@@ -1210,7 +1200,7 @@ impl<T> Arc<[T]> {
     /// [zeroed]: mem::MaybeUninit::zeroed
     #[cfg(not(no_global_oom_handling))]
     #[inline]
-    #[unstable(feature = "new_zeroed_alloc", issue = "129396")]
+    #[stable(feature = "new_zeroed_alloc", since = "CURRENT_RUSTC_VERSION")]
     #[must_use]
     pub fn new_zeroed_slice(len: usize) -> Arc<[mem::MaybeUninit<T>]> {
         unsafe {
diff --git a/library/std/src/lib.rs b/library/std/src/lib.rs
index 33e3bf0c085..45abd6bca8a 100644
--- a/library/std/src/lib.rs
+++ b/library/std/src/lib.rs
@@ -381,7 +381,6 @@
 #![feature(allocator_api)]
 #![feature(get_mut_unchecked)]
 #![feature(map_try_insert)]
-#![feature(new_zeroed_alloc)]
 #![feature(slice_concat_trait)]
 #![feature(thin_box)]
 #![feature(try_reserve_kind)]