Use generic `NonZero` everywhere in `std`.

library/std/src/io/error/repr_bitpacked.rs

@@ -73,7 +73,7 @@
 //! union Repr {
 //!     // holds integer (Simple/Os) variants, and
 //!     // provides access to the tag bits.
-//!     bits: NonZeroU64,
+//!     bits: NonZero<u64>,
 //!     // Tag is 0, so this is stored untagged.
 //!     msg: &'static SimpleMessage,
 //!     // Tagged (offset) `Box<Custom>` pointer.
@@ -93,7 +93,7 @@
 //!    `io::Result<()>` and `io::Result<usize>` larger, which defeats part of
 //!    the motivation of this bitpacking.
 //!
-//! Storing everything in a `NonZeroUsize` (or some other integer) would be a
+//! Storing everything in a `NonZero<usize>` (or some other integer) would be a
 //! bit more traditional for pointer tagging, but it would lose provenance
 //! information, couldn't be constructed from a `const fn`, and would probably
 //! run into other issues as well.

library/std/src/process.rs

@@ -111,7 +111,7 @@ use crate::ffi::OsStr;
 use crate::fmt;
 use crate::fs;
 use crate::io::{self, BorrowedCursor, IoSlice, IoSliceMut};
-use crate::num::NonZeroI32;
+use crate::num::NonZero;
 use crate::path::Path;
 use crate::str;
 use crate::sys::pipe::{read2, AnonPipe};
@@ -1775,9 +1775,9 @@ impl ExitStatusError {
         self.code_nonzero().map(Into::into)
     }
 
-    /// Reports the exit code, if applicable, from an `ExitStatusError`, as a `NonZero`
+    /// Reports the exit code, if applicable, from an `ExitStatusError`, as a [`NonZero`].
     ///
-    /// This is exactly like [`code()`](Self::code), except that it returns a `NonZeroI32`.
+    /// This is exactly like [`code()`](Self::code), except that it returns a <code>[NonZero]<[i32]></code>.
     ///
     /// Plain `code`, returning a plain integer, is provided because it is often more convenient.
     /// The returned value from `code()` is indeed also nonzero; use `code_nonzero()` when you want
@@ -1786,17 +1786,17 @@ impl ExitStatusError {
     /// # Examples
     ///
     /// ```
-    /// #![feature(exit_status_error)]
+    /// #![feature(exit_status_error, generic_nonzero)]
     /// # if cfg!(unix) {
-    /// use std::num::NonZeroI32;
+    /// use std::num::NonZero;
     /// use std::process::Command;
     ///
     /// let bad = Command::new("false").status().unwrap().exit_ok().unwrap_err();
-    /// assert_eq!(bad.code_nonzero().unwrap(), NonZeroI32::try_from(1).unwrap());
+    /// assert_eq!(bad.code_nonzero().unwrap(), NonZero::new(1).unwrap());
     /// # } // cfg!(unix)
     /// ```
     #[must_use]
-    pub fn code_nonzero(&self) -> Option<NonZeroI32> {
+    pub fn code_nonzero(&self) -> Option<NonZero<i32>> {
         self.0.code()
     }
 

library/std/src/thread/mod.rs

@@ -165,7 +165,7 @@ use crate::fmt;
 use crate::io;
 use crate::marker::PhantomData;
 use crate::mem::{self, forget};
-use crate::num::{NonZero, NonZeroU64, NonZeroUsize};
+use crate::num::NonZero;
 use crate::panic;
 use crate::panicking;
 use crate::pin::Pin;
@@ -1222,7 +1222,7 @@ impl ThreadId {
     /// change across Rust versions.
     #[must_use]
     #[unstable(feature = "thread_id_value", issue = "67939")]
-    pub fn as_u64(&self) -> NonZeroU64 {
+    pub fn as_u64(&self) -> NonZero<u64> {
         self.0
     }
 }
@@ -1784,6 +1784,6 @@ fn _assert_sync_and_send() {
 #[doc(alias = "hardware_concurrency")] // Alias for C++ `std::thread::hardware_concurrency`.
 #[doc(alias = "num_cpus")] // Alias for a popular ecosystem crate which provides similar functionality.
 #[stable(feature = "available_parallelism", since = "1.59.0")]
-pub fn available_parallelism() -> io::Result<NonZeroUsize> {
+pub fn available_parallelism() -> io::Result<NonZero<usize>> {
     imp::available_parallelism()
 }