Migrate helix-event to foldhash

This is following `hashbrown`'s switch in v0.15 from ahash to foldhash
for its `default-haster` feature, applied only to helix-event for now.

I don't have a strong preference between the two. Benchmarks in
Spellbook, which is particularly sensitive to hashers and hash table
performance, show no perceptible difference. Foldhash is dependency-free
though.

Once we migrate to the new tree-sitter bindings and highlighter we
should be able to eliminate the remaining dependencies on ahash.

Cargo.lock

@@ -1310,6 +1310,8 @@ version = "0.15.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "bf151400ff0baff5465007dd2f3e717f3fe502074ca563069ce3a6629d07b289"
 dependencies = [
+ "allocator-api2",
+ "equivalent",
  "foldhash",
 ]
 
@@ -1371,10 +1373,10 @@ dependencies = [
 name = "helix-event"
 version = "25.1.1"
 dependencies = [
- "ahash",
  "anyhow",
+ "foldhash",
  "futures-executor",
- "hashbrown 0.14.5",
+ "hashbrown 0.15.2",
  "log",
  "once_cell",
  "parking_lot",

Cargo.toml

@@ -45,6 +45,7 @@ tempfile = "3.16.0"
 bitflags = "2.8"
 unicode-segmentation = "1.2"
 ropey = { version = "1.6.1", default-features = false, features = ["simd"] }
+foldhash = "0.1"
 
 [workspace.package]
 version = "25.1.1"

helix-event/Cargo.toml

@@ -12,8 +12,8 @@ homepage.workspace = true
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
-ahash = "0.8.11"
-hashbrown = "0.14.5"
+foldhash.workspace = true
+hashbrown = "0.15"
 tokio = { version = "1", features = ["rt", "rt-multi-thread", "time", "sync", "parking_lot", "macros"] }
 # the event registry is essentially read only but must be an rwlock so we can
 # setup new events on initialization, hardware-lock-elision hugely benefits this case

helix-event/src/registry.rs

@@ -14,8 +14,8 @@ use crate::hook::ErasedHook;
 use crate::runtime_local;
 
 pub struct Registry {
-    events: HashMap<&'static str, TypeId, ahash::RandomState>,
-    handlers: HashMap<&'static str, Vec<ErasedHook>, ahash::RandomState>,
+    events: HashMap<&'static str, TypeId, foldhash::fast::FixedState>,
+    handlers: HashMap<&'static str, Vec<ErasedHook>, foldhash::fast::FixedState>,
 }
 
 impl Registry {
@@ -105,8 +105,8 @@ runtime_local! {
     static REGISTRY: RwLock<Registry> = RwLock::new(Registry {
         // hardcoded random number is good enough here we don't care about DOS resistance
         // and avoids the additional complexity of `Option<Registry>`
-        events: HashMap::with_hasher(ahash::RandomState::with_seeds(423, 9978, 38322, 3280080)),
-        handlers: HashMap::with_hasher(ahash::RandomState::with_seeds(423, 99078, 382322, 3282938)),
+        events: HashMap::with_hasher(foldhash::fast::FixedState::with_seed(72536814787)),
+        handlers: HashMap::with_hasher(foldhash::fast::FixedState::with_seed(72536814787)),
     });
 }
 

helix-event/src/runtime.rs

@@ -41,8 +41,9 @@ macro_rules! runtime_local {
 
 #[cfg(feature = "integration_test")]
 pub struct RuntimeLocal<T: 'static> {
-    data:
-        parking_lot::RwLock<hashbrown::HashMap<tokio::runtime::Id, &'static T, ahash::RandomState>>,
+    data: parking_lot::RwLock<
+        hashbrown::HashMap<tokio::runtime::Id, &'static T, foldhash::fast::FixedState>,
+    >,
     init: fn() -> T,
 }
 
@@ -53,7 +54,7 @@ impl<T> RuntimeLocal<T> {
     pub const fn __new(init: fn() -> T) -> Self {
         Self {
             data: parking_lot::RwLock::new(hashbrown::HashMap::with_hasher(
-                ahash::RandomState::with_seeds(423, 9978, 38322, 3280080),
+                foldhash::fast::FixedState::with_seed(12345678910),
             )),
             init,
         }