Manually implement derived NonZero traits.

Author: reitermarkus

library/core/src/num/nonzero.rs

@@ -1,6 +1,9 @@
 //! Definitions of integer that is known not to equal zero.
 
+use crate::cmp::Ordering;
 use crate::fmt;
+use crate::hash::{Hash, Hasher};
+use crate::marker::StructuralPartialEq;
 use crate::ops::{BitOr, BitOrAssign, Div, Neg, Rem};
 use crate::str::FromStr;
 
@@ -31,13 +34,6 @@ pub trait ZeroablePrimitive: Sized + Copy + private::Sealed {
     type NonZero;
 }
 
-#[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;
-
 macro_rules! impl_zeroable_primitive {
     ($NonZero:ident ( $primitive:ty )) => {
         #[unstable(
@@ -71,6 +67,174 @@ impl_zeroable_primitive!(NonZeroI64(i64));
 impl_zeroable_primitive!(NonZeroI128(i128));
 impl_zeroable_primitive!(NonZeroIsize(isize));
 
+/// 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")]
+#[derive(Clone, Copy)]
+#[repr(transparent)]
+#[rustc_layout_scalar_valid_range_start(1)]
+#[rustc_nonnull_optimization_guaranteed]
+#[rustc_diagnostic_item = "NonZero"]
+pub struct NonZero2<T: ZeroablePrimitive>(T);
+
+#[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;
+
+macro_rules! impl_nonzero_traits {
+    (#[$stability:meta] $Ty:ty) => {
+        #[$stability]
+        impl Clone for $Ty {
+            #[inline]
+            fn clone(&self) -> Self {
+                #[allow(unused_unsafe)]
+                // SAFETY: A `NonZero` is guaranteed to only contain primitive non-zero values.
+                unsafe {
+                    Self(self.0)
+                }
+            }
+        }
+
+        #[$stability]
+        impl PartialEq for $Ty {
+            #[inline]
+            fn eq(&self, other: &Self) -> bool {
+                #[allow(unused_unsafe)]
+                // SAFETY: A `NonZero` is guaranteed to only contain primitive non-zero values.
+                unsafe {
+                    self.0 == other.0
+                }
+            }
+
+            #[inline]
+            fn ne(&self, other: &Self) -> bool {
+                #[allow(unused_unsafe)]
+                // SAFETY: A `NonZero` is guaranteed to only contain primitive non-zero values.
+                unsafe {
+                    self.0 != other.0
+                }
+            }
+        }
+
+        #[$stability]
+        #[rustc_const_unstable(feature = "const_ops", issue = "90080")]
+        impl StructuralPartialEq for $Ty {}
+
+        #[$stability]
+        impl PartialOrd for $Ty {
+            #[inline]
+            fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+                #[allow(unused_unsafe)]
+                // SAFETY: A `NonZero` is guaranteed to only contain primitive non-zero values.
+                unsafe {
+                    self.0.partial_cmp(&other.0)
+                }
+            }
+
+            #[inline]
+            fn lt(&self, other: &Self) -> bool {
+                #[allow(unused_unsafe)]
+                // SAFETY: A `NonZero` is guaranteed to only contain primitive non-zero values.
+                unsafe {
+                    self.0 < other.0
+                }
+            }
+
+            #[inline]
+            fn le(&self, other: &Self) -> bool {
+                #[allow(unused_unsafe)]
+                // SAFETY: A `NonZero` is guaranteed to only contain primitive non-zero values.
+                unsafe {
+                    self.0 <= other.0
+                }
+            }
+
+            #[inline]
+            fn gt(&self, other: &Self) -> bool {
+                #[allow(unused_unsafe)]
+                // SAFETY: A `NonZero` is guaranteed to only contain primitive non-zero values.
+                unsafe {
+                    self.0 > other.0
+                }
+            }
+
+            #[inline]
+            fn ge(&self, other: &Self) -> bool {
+                #[allow(unused_unsafe)]
+                // SAFETY: A `NonZero` is guaranteed to only contain primitive non-zero values.
+                unsafe {
+                    self.0 >= other.0
+                }
+            }
+        }
+
+        #[$stability]
+        impl Ord for $Ty {
+            fn cmp(&self, other: &Self) -> Ordering {
+                #[allow(unused_unsafe)]
+                // SAFETY: A `NonZero` is guaranteed to only contain primitive non-zero values.
+                unsafe {
+                    self.0.cmp(&other.0)
+                }
+            }
+
+            fn max(self, other: Self) -> Self {
+                #[allow(unused_unsafe)]
+                // SAFETY: A `NonZero` is guaranteed to only contain primitive non-zero values,
+                //         and the maximum of two non-zero values is still non-zero.
+                unsafe {
+                    Self(self.0.max(other.0))
+                }
+            }
+
+            fn min(self, other: Self) -> Self {
+                #[allow(unused_unsafe)]
+                // SAFETY: A `NonZero` is guaranteed to only contain primitive non-zero values,
+                //         and the minimum of two non-zero values is still non-zero.
+                unsafe {
+                    Self(self.0.min(other.0))
+                }
+            }
+
+            fn clamp(self, min: Self, max: Self) -> Self {
+                #[allow(unused_unsafe)]
+                // SAFETY: A `NonZero` is guaranteed to only contain primitive non-zero values, and
+                //         a non-zero value clamped between two non-zero values is still non-zero.
+                unsafe {
+                    Self(self.0.clamp(min.0, max.0))
+                }
+            }
+        }
+
+        #[$stability]
+        impl Hash for $Ty {
+            #[inline]
+            fn hash<H>(&self, state: &mut H)
+            where
+                H: Hasher,
+            {
+                // SAFETY: A `NonZero` is guaranteed to only contain primitive non-zero values.
+                #[allow(unused_unsafe)]
+                unsafe {
+                    self.0.hash(state)
+                }
+            }
+        }
+    };
+}
+
 macro_rules! impl_nonzero_fmt {
     ( #[$stability: meta] ( $( $Trait: ident ),+ ) for $Ty: ident ) => {
         $(
@@ -128,13 +292,15 @@ macro_rules! nonzero_integer {
         ///
         /// [null pointer optimization]: crate::option#representation
         #[$stability]
-        #[derive(Copy, Clone, Eq, PartialEq, Ord, PartialOrd, Hash)]
+        #[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);
 
+        impl_nonzero_traits!(#[$stability] $Ty);
+
         impl $Ty {
             /// Creates a non-zero without checking whether the value is non-zero.
             /// This results in undefined behaviour if the value is zero.

tests/ui/unsafe/ranged_ints3.rs

@@ -5,6 +5,7 @@ use std::cell::Cell;
 #[rustc_layout_scalar_valid_range_start(1)]
 #[repr(transparent)]
 pub(crate) struct NonZero<T>(pub(crate) T);
+
 fn main() {
     let mut x = unsafe { NonZero(Cell::new(1)) };
     let y = &x.0; //~ ERROR borrow of layout constrained field with interior mutability

tests/ui/unsafe/ranged_ints3_match.rs

@@ -5,6 +5,7 @@ use std::cell::Cell;
 #[rustc_layout_scalar_valid_range_start(1)]
 #[repr(transparent)]
 pub(crate) struct NonZero<T>(pub(crate) T);
+
 fn main() {
     let mut x = unsafe { NonZero(Cell::new(1)) };
     match x {