Rollup merge of rust-lang#81727 - m-ou-se:unstabilize-bits, r=Mark-Simulacrum

Revert stabilizing integer::BITS.

We agreed in the libs meeting just now to revert stablization, since the [breakage](rust-lang#81654) is significant throughout the ecosystem, through `lexical-core`.

cc rust-lang#76904

Fixes rust-lang#81654

Author: m-ou-se

alloc/src/lib.rs

@@ -102,6 +102,7 @@
 #![feature(fn_traits)]
 #![feature(fundamental)]
 #![feature(inplace_iteration)]
+#![feature(int_bits_const)]
 #![feature(lang_items)]
 #![feature(layout_for_ptr)]
 #![feature(maybe_uninit_ref)]

alloc/tests/lib.rs

@@ -17,6 +17,7 @@
 #![feature(binary_heap_retain)]
 #![feature(inplace_iteration)]
 #![feature(iter_map_while)]
+#![feature(int_bits_const)]
 #![feature(vecdeque_binary_search)]
 #![feature(slice_group_by)]
 #![feature(vec_extend_from_within)]

core/src/num/int_macros.rs

@@ -32,9 +32,10 @@ macro_rules! int_impl {
         /// # Examples
         ///
         /// ```
+        /// #![feature(int_bits_const)]
         #[doc = concat!("assert_eq!(", stringify!($SelfT), "::BITS, ", stringify!($BITS), ");")]
         /// ```
-        #[stable(feature = "int_bits_const", since = "1.51.0")]
+        #[unstable(feature = "int_bits_const", issue = "76904")]
         pub const BITS: u32 = $BITS;
 
         /// Converts a string slice in a given base to an integer.

core/src/num/uint_macros.rs

@@ -32,9 +32,10 @@ macro_rules! uint_impl {
         /// # Examples
         ///
         /// ```
+        /// #![feature(int_bits_const)]
         #[doc = concat!("assert_eq!(", stringify!($SelfT), "::BITS, ", stringify!($BITS), ");")]
         /// ```
-        #[stable(feature = "int_bits_const", since = "1.51.0")]
+        #[unstable(feature = "int_bits_const", issue = "76904")]
         pub const BITS: u32 = $BITS;
 
         /// Converts a string slice in a given base to an integer.

core/tests/lib.rs

@@ -70,6 +70,7 @@
 #![feature(partition_point)]
 #![feature(once_cell)]
 #![feature(unsafe_block_in_unsafe_fn)]
+#![feature(int_bits_const)]
 #![feature(nonzero_leading_trailing_zeros)]
 #![feature(const_option)]
 #![feature(integer_atomics)]

panic_unwind/src/lib.rs

@@ -18,6 +18,7 @@
     issue_tracker_base_url = "https://github.com/rust-lang/rust/issues/"
 )]
 #![feature(core_intrinsics)]
+#![feature(int_bits_const)]
 #![feature(lang_items)]
 #![feature(nll)]
 #![feature(panic_unwind)]