From 36d194f5612852a6d4fcf9d5fae8e0fba942adfa Mon Sep 17 00:00:00 2001
From: Markus Reiter <me@reitermark.us>
Date: Mon, 19 Feb 2024 05:51:10 +0100
Subject: [PATCH] Use generic `NonZero` everywhere in `alloc`.

---
 library/alloc/src/ffi/c_str.rs   | 18 ++++++------
 library/alloc/src/vec/is_zero.rs | 49 ++++++++++++--------------------
 2 files changed, 27 insertions(+), 40 deletions(-)

diff --git a/library/alloc/src/ffi/c_str.rs b/library/alloc/src/ffi/c_str.rs
index 9419b0cfb24..61ec04a4849 100644
--- a/library/alloc/src/ffi/c_str.rs
+++ b/library/alloc/src/ffi/c_str.rs
@@ -11,7 +11,7 @@ use core::borrow::Borrow;
 use core::ffi::{c_char, CStr};
 use core::fmt;
 use core::mem;
-use core::num::NonZeroU8;
+use core::num::NonZero;
 use core::ops;
 use core::ptr;
 use core::slice;
@@ -795,22 +795,22 @@ impl From<Box<CStr>> for CString {
 }
 
 #[stable(feature = "cstring_from_vec_of_nonzerou8", since = "1.43.0")]
-impl From<Vec<NonZeroU8>> for CString {
-    /// Converts a <code>[Vec]<[NonZeroU8]></code> into a [`CString`] without
+impl From<Vec<NonZero<u8>>> for CString {
+    /// Converts a <code>[Vec]<[NonZero]<[u8]>></code> into a [`CString`] without
     /// copying nor checking for inner nul bytes.
     #[inline]
-    fn from(v: Vec<NonZeroU8>) -> CString {
+    fn from(v: Vec<NonZero<u8>>) -> CString {
         unsafe {
-            // Transmute `Vec<NonZeroU8>` to `Vec<u8>`.
+            // Transmute `Vec<NonZero<u8>>` to `Vec<u8>`.
             let v: Vec<u8> = {
                 // SAFETY:
-                //   - transmuting between `NonZeroU8` and `u8` is sound;
-                //   - `alloc::Layout<NonZeroU8> == alloc::Layout<u8>`.
-                let (ptr, len, cap): (*mut NonZeroU8, _, _) = Vec::into_raw_parts(v);
+                //   - transmuting between `NonZero<u8>` and `u8` is sound;
+                //   - `alloc::Layout<NonZero<u8>> == alloc::Layout<u8>`.
+                let (ptr, len, cap): (*mut NonZero<u8>, _, _) = Vec::into_raw_parts(v);
                 Vec::from_raw_parts(ptr.cast::<u8>(), len, cap)
             };
             // SAFETY: `v` cannot contain nul bytes, given the type-level
-            // invariant of `NonZeroU8`.
+            // invariant of `NonZero<u8>`.
             Self::_from_vec_unchecked(v)
         }
     }
diff --git a/library/alloc/src/vec/is_zero.rs b/library/alloc/src/vec/is_zero.rs
index cb9adf05c25..bcc5bf4d65b 100644
--- a/library/alloc/src/vec/is_zero.rs
+++ b/library/alloc/src/vec/is_zero.rs
@@ -1,4 +1,4 @@
-use core::num::{Saturating, Wrapping};
+use core::num::{NonZero, Saturating, Wrapping};
 
 use crate::boxed::Box;
 
@@ -69,7 +69,7 @@ unsafe impl<T: IsZero, const N: usize> IsZero for [T; N] {
 }
 
 // This is recursive macro.
-macro_rules! impl_for_tuples {
+macro_rules! impl_is_zero_tuples {
     // Stopper
     () => {
         // No use for implementing for empty tuple because it is ZST.
@@ -88,11 +88,11 @@ macro_rules! impl_for_tuples {
             }
         }
 
-        impl_for_tuples!($($rest),*);
+        impl_is_zero_tuples!($($rest),*);
     }
 }
 
-impl_for_tuples!(A, B, C, D, E, F, G, H);
+impl_is_zero_tuples!(A, B, C, D, E, F, G, H);
 
 // `Option<&T>` and `Option<Box<T>>` are guaranteed to represent `None` as null.
 // For fat pointers, the bytes that would be the pointer metadata in the `Some`
@@ -115,16 +115,15 @@ unsafe impl<T: ?Sized> IsZero for Option<Box<T>> {
     }
 }
 
-// `Option<num::NonZeroU32>` and similar have a representation guarantee that
+// `Option<NonZero<u32>>` and similar have a representation guarantee that
 // they're the same size as the corresponding `u32` type, as well as a guarantee
-// that transmuting between `NonZeroU32` and `Option<num::NonZeroU32>` works.
+// that transmuting between `NonZero<u32>` and `Option<NonZero<u32>>` works.
 // While the documentation officially makes it UB to transmute from `None`,
 // we're the standard library so we can make extra inferences, and we know that
 // the only niche available to represent `None` is the one that's all zeros.
-
-macro_rules! impl_is_zero_option_of_nonzero {
-    ($($t:ident,)+) => {$(
-        unsafe impl IsZero for Option<core::num::$t> {
+macro_rules! impl_is_zero_option_of_nonzero_int {
+    ($($t:ty),+ $(,)?) => {$(
+        unsafe impl IsZero for Option<NonZero<$t>> {
             #[inline]
             fn is_zero(&self) -> bool {
                 self.is_none()
@@ -133,23 +132,10 @@ macro_rules! impl_is_zero_option_of_nonzero {
     )+};
 }
 
-impl_is_zero_option_of_nonzero!(
-    NonZeroU8,
-    NonZeroU16,
-    NonZeroU32,
-    NonZeroU64,
-    NonZeroU128,
-    NonZeroI8,
-    NonZeroI16,
-    NonZeroI32,
-    NonZeroI64,
-    NonZeroI128,
-    NonZeroUsize,
-    NonZeroIsize,
-);
+impl_is_zero_option_of_nonzero_int!(u8, u16, u32, u64, u128, usize, i8, i16, i32, i64, i128, isize);
 
-macro_rules! impl_is_zero_option_of_num {
-    ($($t:ty,)+) => {$(
+macro_rules! impl_is_zero_option_of_int {
+    ($($t:ty),+ $(,)?) => {$(
         unsafe impl IsZero for Option<$t> {
             #[inline]
             fn is_zero(&self) -> bool {
@@ -163,7 +149,7 @@ macro_rules! impl_is_zero_option_of_num {
     )+};
 }
 
-impl_is_zero_option_of_num!(u8, u16, u32, u64, u128, i8, i16, i32, i64, i128, usize, isize,);
+impl_is_zero_option_of_int!(u8, u16, u32, u64, u128, i8, i16, i32, i64, i128, usize, isize);
 
 unsafe impl<T: IsZero> IsZero for Wrapping<T> {
     #[inline]
@@ -179,8 +165,8 @@ unsafe impl<T: IsZero> IsZero for Saturating<T> {
     }
 }
 
-macro_rules! impl_for_optional_bool {
-    ($($t:ty,)+) => {$(
+macro_rules! impl_is_zero_option_of_bool {
+    ($($t:ty),+ $(,)?) => {$(
         unsafe impl IsZero for $t {
             #[inline]
             fn is_zero(&self) -> bool {
@@ -194,9 +180,10 @@ macro_rules! impl_for_optional_bool {
         }
     )+};
 }
-impl_for_optional_bool! {
+
+impl_is_zero_option_of_bool! {
     Option<bool>,
     Option<Option<bool>>,
     Option<Option<Option<bool>>>,
-    // Could go further, but not worth the metadata overhead
+    // Could go further, but not worth the metadata overhead.
 }