Make non-hash an external lib

Cargo.lock

@@ -1054,6 +1054,10 @@ dependencies = [
  "static_assertions",
 ]
 
+[[package]]
+name = "non-hash"
+version = "0.1.0"
+
 [[package]]
 name = "notify"
 version = "5.1.0"
@@ -1693,6 +1697,7 @@ dependencies = [
  "backtrace",
  "libc",
  "miow",
+ "non-hash",
  "winapi",
 ]
 

crates/stdx/Cargo.toml

@@ -15,6 +15,7 @@ doctest = false
 libc = "0.2.135"
 backtrace = { version = "0.3.65", optional = true }
 always-assert = { version = "0.1.2", features = ["log"] }
+non-hash = { version = "0.1.0", path = "../../lib/non-hash" }
 # Think twice before adding anything here
 
 [target.'cfg(windows)'.dependencies]

crates/stdx/src/lib.rs

@@ -7,13 +7,13 @@ use std::process::Command;
 use std::{cmp::Ordering, ops, time::Instant};
 
 mod macros;
-pub mod hash;
 pub mod process;
 pub mod panic_context;
 pub mod non_empty_vec;
 pub mod rand;
 
 pub use always_assert::{always, never};
+pub use non_hash as hash;
 
 #[inline(always)]
 pub fn is_ci() -> bool {

lib/non-hash/Cargo.toml

@@ -0,0 +1,7 @@
+[package]
+name = "non-hash"
+version = "0.1.0"
+description = "A non-hashing `Hasher` implementation."
+license = "MIT OR Apache-2.0"
+repository = "https://github.com/rust-lang/rust-analyzer/tree/master/lib/non-hash"
+edition = "2021"

lib/non-hash/src/lib.rs

@@ -1,25 +1,49 @@
-//! A none hashing [`Hasher`] implementation.
+//! A non-hashing [`Hasher`] implementation.
+
+#![deny(clippy::pedantic, missing_debug_implementations, missing_docs, rust_2018_idioms)]
+
 use std::{
     hash::{BuildHasher, Hasher},
     marker::PhantomData,
 };
 
+/// A [`std::collections::HashMap`] with [`NoHashHasherBuilder`].
 pub type NoHashHashMap<K, V> = std::collections::HashMap<K, V, NoHashHasherBuilder<K>>;
+
+/// A [`std::collections::HashSet`] with [`NoHashHasherBuilder`].
 pub type NoHashHashSet<K> = std::collections::HashSet<K, NoHashHasherBuilder<K>>;
 
+/// A hasher builder for [`NoHashHasher`].
 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
 pub struct NoHashHasherBuilder<T>(PhantomData<T>);
 
 impl<T> Default for NoHashHasherBuilder<T> {
     fn default() -> Self {
-        Self(Default::default())
+        Self(PhantomData)
     }
 }
 
+/// Types for which an acceptable hash function is to return itself.
+///
+/// This trait is implemented by sufficiently-small integer types. It should only be implemented for
+/// foreign types that are newtypes of these types. If it is implemented on more complex types,
+/// hashing will panic.
 pub trait NoHashHashable {}
-impl NoHashHashable for usize {}
-impl NoHashHashable for u32 {}
 
+impl NoHashHashable for u8 {}
+impl NoHashHashable for u16 {}
+impl NoHashHashable for u32 {}
+impl NoHashHashable for u64 {}
+impl NoHashHashable for usize {}
+
+impl NoHashHashable for i8 {}
+impl NoHashHashable for i16 {}
+impl NoHashHashable for i32 {}
+impl NoHashHashable for i64 {}
+impl NoHashHashable for isize {}
+
+/// A hasher for [`NoHashHashable`] types.
+#[derive(Debug)]
 pub struct NoHashHasher(u64);
 
 impl<T: NoHashHashable> BuildHasher for NoHashHasherBuilder<T> {
@@ -35,7 +59,7 @@ impl Hasher for NoHashHasher {
     }
 
     fn write(&mut self, _: &[u8]) {
-        unimplemented!("NoHashHasher should only be used for hashing primitive integers")
+        unimplemented!("NoHashHasher should only be used for hashing sufficiently-small integer types and their newtypes")
     }
 
     fn write_u8(&mut self, i: u8) {