Rollup merge of rust-lang#80959 - jhpratt:unsigned_abs-stabilization, r=m-ou-se

Stabilize `unsigned_abs`

Resolves rust-lang#74913.

This PR stabilizes the `i*::unsigned_abs()` method, which returns the absolute value of an integer _as its unsigned equivalent_. This has the advantage that it does not overflow on `i*::MIN`.

I have gone ahead and used this in a couple locations throughout the repository.

Author: JohnTitor

core/src/num/dec2flt/mod.rs

@@ -332,7 +332,7 @@ fn bound_intermediate_digits(decimal: &Decimal<'_>, e: i64) -> u64 {
         // It tries to find a positive number k such that `f << k / 10^e` is an in-range
         // significand. This will result in about `2^53 * f * 10^e` < `10^17 * f * 10^e`.
         // One input that triggers this is 0.33...33 (375 x 3).
-        f_len + (e.abs() as u64) + 17
+        f_len + e.unsigned_abs() + 17
     }
 }
 

core/src/num/int_macros.rs

@@ -1158,12 +1158,12 @@ macro_rules! int_impl {
         /// Basic usage:
         ///
         /// ```
-        /// #![feature(unsigned_abs)]
         #[doc = concat!("assert_eq!(100", stringify!($SelfT), ".unsigned_abs(), 100", stringify!($UnsignedT), ");")]
         #[doc = concat!("assert_eq!((-100", stringify!($SelfT), ").unsigned_abs(), 100", stringify!($UnsignedT), ");")]
         /// assert_eq!((-128i8).unsigned_abs(), 128u8);
         /// ```
-        #[unstable(feature = "unsigned_abs", issue = "74913")]
+        #[stable(feature = "unsigned_abs", since = "1.51.0")]
+        #[rustc_const_stable(feature = "unsigned_abs", since = "1.51.0")]
         #[inline]
         pub const fn unsigned_abs(self) -> $UnsignedT {
              self.wrapping_abs() as $UnsignedT