get rid of a bunch of unnecessary rustc_const_unstable

alloc/src/collections/binary_heap/mod.rs

@@ -486,7 +486,6 @@ impl<T: Ord, A: Allocator> BinaryHeap<T, A> {
     /// heap.push(4);
     /// ```
     #[unstable(feature = "allocator_api", issue = "32838")]
-    #[rustc_const_unstable(feature = "const_binary_heap_new_in", issue = "125961")]
     #[must_use]
     pub const fn new_in(alloc: A) -> BinaryHeap<T, A> {
         BinaryHeap { data: Vec::new_in(alloc) }

core/src/cell.rs

@@ -713,7 +713,6 @@ impl<T, const N: usize> Cell<[T; N]> {
     /// let array_cell: &[Cell<i32>; 3] = cell_array.as_array_of_cells();
     /// ```
     #[unstable(feature = "as_array_of_cells", issue = "88248")]
-    #[rustc_const_unstable(feature = "as_array_of_cells", issue = "88248")]
     pub const fn as_array_of_cells(&self) -> &[Cell<T>; N] {
         // SAFETY: `Cell<T>` has the same memory layout as `T`.
         unsafe { &*(self as *const Cell<[T; N]> as *const [Cell<T>; N]) }

core/src/num/nonzero.rs

@@ -614,7 +614,6 @@ macro_rules! nonzero_integer {
             /// ```
             ///
             #[unstable(feature = "non_zero_count_ones", issue = "120287")]
-            #[rustc_const_unstable(feature = "non_zero_count_ones", issue = "120287")]
             #[doc(alias = "popcount")]
             #[doc(alias = "popcnt")]
             #[must_use = "this returns the result of the operation, \

core/src/num/uint_macros.rs

@@ -3162,7 +3162,6 @@ macro_rules! uint_impl {
         #[inline]
         #[unstable(feature = "wrapping_next_power_of_two", issue = "32463",
                    reason = "needs decision on wrapping behavior")]
-        #[rustc_const_unstable(feature = "wrapping_next_power_of_two", issue = "32463")]
         #[must_use = "this returns the result of the operation, \
                       without modifying the original"]
         pub const fn wrapping_next_power_of_two(self) -> Self {

core/src/ptr/const_ptr.rs

@@ -346,7 +346,6 @@ impl<T: ?Sized> *const T {
     /// ```
     #[inline]
     #[unstable(feature = "ptr_as_uninit", issue = "75402")]
-    #[rustc_const_unstable(feature = "ptr_as_uninit", issue = "75402")]
     pub const unsafe fn as_uninit_ref<'a>(self) -> Option<&'a MaybeUninit<T>>
     where
         T: Sized,
@@ -1528,7 +1527,6 @@ impl<T> *const [T] {
     ///
     /// If `N` is not exactly equal to the length of `self`, then this method returns `None`.
     #[unstable(feature = "slice_as_array", issue = "133508")]
-    #[rustc_const_unstable(feature = "slice_as_array", issue = "133508")]
     #[inline]
     #[must_use]
     pub const fn as_array<const N: usize>(self) -> Option<*const [T; N]> {
@@ -1608,7 +1606,6 @@ impl<T> *const [T] {
     /// [allocated object]: crate::ptr#allocated-object
     #[inline]
     #[unstable(feature = "ptr_as_uninit", issue = "75402")]
-    #[rustc_const_unstable(feature = "ptr_as_uninit", issue = "75402")]
     pub const unsafe fn as_uninit_slice<'a>(self) -> Option<&'a [MaybeUninit<T>]> {
         if self.is_null() {
             None

core/src/ptr/mut_ptr.rs

@@ -342,7 +342,6 @@ impl<T: ?Sized> *mut T {
     /// ```
     #[inline]
     #[unstable(feature = "ptr_as_uninit", issue = "75402")]
-    #[rustc_const_unstable(feature = "ptr_as_uninit", issue = "75402")]
     pub const unsafe fn as_uninit_ref<'a>(self) -> Option<&'a MaybeUninit<T>>
     where
         T: Sized,
@@ -676,7 +675,6 @@ impl<T: ?Sized> *mut T {
     /// the pointer is [convertible to a reference](crate::ptr#pointer-to-reference-conversion).
     #[inline]
     #[unstable(feature = "ptr_as_uninit", issue = "75402")]
-    #[rustc_const_unstable(feature = "ptr_as_uninit", issue = "75402")]
     pub const unsafe fn as_uninit_mut<'a>(self) -> Option<&'a mut MaybeUninit<T>>
     where
         T: Sized,
@@ -1762,7 +1760,6 @@ impl<T> *mut [T] {
     ///
     /// If `N` is not exactly equal to the length of `self`, then this method returns `None`.
     #[unstable(feature = "slice_as_array", issue = "133508")]
-    #[rustc_const_unstable(feature = "slice_as_array", issue = "133508")]
     #[inline]
     #[must_use]
     pub const fn as_mut_array<const N: usize>(self) -> Option<*mut [T; N]> {
@@ -1963,7 +1960,6 @@ impl<T> *mut [T] {
     /// [allocated object]: crate::ptr#allocated-object
     #[inline]
     #[unstable(feature = "ptr_as_uninit", issue = "75402")]
-    #[rustc_const_unstable(feature = "ptr_as_uninit", issue = "75402")]
     pub const unsafe fn as_uninit_slice<'a>(self) -> Option<&'a [MaybeUninit<T>]> {
         if self.is_null() {
             None
@@ -2015,7 +2011,6 @@ impl<T> *mut [T] {
     /// [allocated object]: crate::ptr#allocated-object
     #[inline]
     #[unstable(feature = "ptr_as_uninit", issue = "75402")]
-    #[rustc_const_unstable(feature = "ptr_as_uninit", issue = "75402")]
     pub const unsafe fn as_uninit_slice_mut<'a>(self) -> Option<&'a mut [MaybeUninit<T>]> {
         if self.is_null() {
             None

core/src/ptr/unique.rs

@@ -92,6 +92,7 @@ impl<T: ?Sized> Unique<T> {
 
     /// Creates a new `Unique` if `ptr` is non-null.
     #[inline]
+    // rustc_const_unstable attribute can be removed when `const_nonnull_new` is stable
     #[rustc_const_unstable(feature = "ptr_internals", issue = "none")]
     pub const fn new(ptr: *mut T) -> Option<Self> {
         if let Some(pointer) = NonNull::new(ptr) {

core/src/slice/mod.rs

@@ -860,7 +860,6 @@ impl<T> [T] {
     ///
     /// If `N` is not exactly equal to slice's the length of `self`, then this method returns `None`.
     #[unstable(feature = "slice_as_array", issue = "133508")]
-    #[rustc_const_unstable(feature = "slice_as_array", issue = "133508")]
     #[inline]
     #[must_use]
     pub const fn as_array<const N: usize>(&self) -> Option<&[T; N]> {
@@ -879,7 +878,6 @@ impl<T> [T] {
     ///
     /// If `N` is not exactly equal to the length of `self`, then this method returns `None`.
     #[unstable(feature = "slice_as_array", issue = "133508")]
-    #[rustc_const_unstable(feature = "slice_as_array", issue = "133508")]
     #[inline]
     #[must_use]
     pub const fn as_mut_array<const N: usize>(&mut self) -> Option<&mut [T; N]> {