refactor(resolver): remove the identity-hash crate

Cargo.lock

@@ -931,12 +931,6 @@ version = "2.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "9a3a5bfb195931eeb336b2a7b4d761daec841b97f947d34394601737a7bba5e4"
 
-[[package]]
-name = "identity-hash"
-version = "0.1.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "dfdd7caa900436d8f13b2346fe10257e0c05c1f1f9e351f4f5d57c03bd5f45da"
-
 [[package]]
 name = "idna"
 version = "0.4.0"
@@ -1751,7 +1745,6 @@ dependencies = [
  "criterion",
  "dashmap",
  "dunce",
- "identity-hash",
  "indexmap 2.0.0",
  "jemallocator",
  "mimalloc",

crates/oxc_resolver/Cargo.toml

@@ -19,7 +19,6 @@ serde_json    = { workspace = true }
 rustc-hash    = { workspace = true }
 indexmap      = { workspace = true, features = ["serde"] }
 dunce         = "1.0.4"
-identity-hash = "0.1.0"
 # Use `std::sync::OnceLock::get_or_try_init` when it is stable.
 once_cell     = "1.18.0"
 

crates/oxc_resolver/src/cache.rs

@@ -1,14 +1,13 @@
 use once_cell::sync::OnceCell as OnceLock;
 use std::{
     convert::AsRef,
-    hash::{Hash, Hasher},
+    hash::{BuildHasherDefault, Hash, Hasher},
     ops::Deref,
     path::{Path, PathBuf},
     sync::Arc,
 };
 
 use dashmap::DashMap;
-use identity_hash::BuildIdentityHasher;
 use rustc_hash::FxHasher;
 
 use crate::{package_json::PackageJson, FileMetadata, FileSystem, ResolveError};
@@ -16,7 +15,22 @@ use crate::{package_json::PackageJson, FileMetadata, FileSystem, ResolveError};
 pub struct Cache<Fs> {
     pub(crate) fs: Fs,
     // Using IdentityHasher to avoid double hashing in the `get` + `insert` case.
-    cache: DashMap<u64, CachedPath, BuildIdentityHasher<u64>>,
+    cache: DashMap<u64, CachedPath, BuildHasherDefault<IdentityHasher>>,
+}
+
+#[derive(Default)]
+struct IdentityHasher(u64);
+
+impl Hasher for IdentityHasher {
+    fn write(&mut self, _: &[u8]) {
+        panic!("Invalid use of IdentityHasher")
+    }
+    fn write_u64(&mut self, n: u64) {
+        self.0 = n;
+    }
+    fn finish(&self) -> u64 {
+        self.0
+    }
 }
 
 impl<Fs: FileSystem> Default for Cache<Fs> {