Switch NonZero alias direction.

Author: reitermarkus

Diff for: library/core/src/num/nonzero.rs

@@ -3,7 +3,7 @@
 use crate::cmp::Ordering;
 use crate::fmt;
 use crate::hash::{Hash, Hasher};
-use crate::marker::StructuralPartialEq;
+use crate::marker::{StructuralEq, StructuralPartialEq};
 use crate::ops::{BitOr, BitOrAssign, Div, Neg, Rem};
 use crate::str::FromStr;
 
@@ -67,24 +67,40 @@ impl_zeroable_primitive!(NonZeroI64(i64));
 impl_zeroable_primitive!(NonZeroI128(i128));
 impl_zeroable_primitive!(NonZeroIsize(isize));
 
-#[unstable(
-    feature = "nonzero_internals",
-    reason = "implementation detail which may disappear or be replaced at any time",
-    issue = "none"
-)]
-pub(crate) type NonZero<T> = <T as ZeroablePrimitive>::NonZero;
+/// A value that is known not to equal zero.
+///
+/// This enables some memory layout optimization.
+/// For example, `Option<NonZero<u32>>` is the same size as `u32`:
+///
+/// ```rust
+/// #![feature(generic_nonzero)]
+///
+/// use core::mem::size_of;
+/// assert_eq!(size_of::<Option<core::num::NonZero<u32>>>(), size_of::<u32>());
+/// ```
+#[unstable(feature = "generic_nonzero", issue = "82363")]
+#[repr(transparent)]
+#[rustc_layout_scalar_valid_range_start(1)]
+#[rustc_nonnull_optimization_guaranteed]
+#[rustc_diagnostic_item = "NonZero"]
+pub struct NonZero<T: ZeroablePrimitive>(T);
 
 macro_rules! impl_nonzero_traits {
     (#[$stability:meta] $Ty:ty) => {
         #[$stability]
         impl Clone for $Ty {
             #[inline]
             fn clone(&self) -> Self {
+                let value = self.0;
+
                 // SAFETY: The contained value is non-zero.
-                unsafe { Self(self.0) }
+                unsafe { Self(value) }
             }
         }
 
+        #[$stability]
+        impl Copy for $Ty {}
+
         #[$stability]
         impl PartialEq for $Ty {
             #[inline]
@@ -101,6 +117,12 @@ macro_rules! impl_nonzero_traits {
         #[unstable(feature = "structural_match", issue = "31434")]
         impl StructuralPartialEq for $Ty {}
 
+        #[$stability]
+        impl Eq for $Ty {}
+
+        #[unstable(feature = "structural_match", issue = "31434")]
+        impl StructuralEq for $Ty {}
+
         #[$stability]
         impl PartialOrd for $Ty {
             #[inline]
@@ -225,12 +247,7 @@ macro_rules! nonzero_integer {
         ///
         /// [null pointer optimization]: crate::option#representation
         #[$stability]
-        #[derive(Copy, Eq)]
-        #[repr(transparent)]
-        #[rustc_layout_scalar_valid_range_start(1)]
-        #[rustc_nonnull_optimization_guaranteed]
-        #[rustc_diagnostic_item = stringify!($Ty)]
-        pub struct $Ty($Int);
+        pub type $Ty = NonZero<$Int>;
 
         impl_nonzero_traits!(#[$stability] $Ty);