From 30a869ead27d5d31b999492130e2f17da8a6b07f Mon Sep 17 00:00:00 2001
From: overlookmotel <557937+overlookmotel@users.noreply.github.com>
Date: Thu, 16 Jan 2025 23:29:57 +0000
Subject: [PATCH] perf(semantic): use `oxc_allocator::HashMap` in `ScopeTree`
 (#8554)

Use `oxc_allocator::HashMap` in `ScopeTree`, replacing `hashbrown::HashMap`. `oxc_allocator::HashMap` is non-drop, so it may reduce drop time of `ScopeTree` a little.
---
 Cargo.lock                         |  1 -
 crates/oxc_semantic/Cargo.toml     |  1 -
 crates/oxc_semantic/src/builder.rs |  3 +--
 crates/oxc_semantic/src/scope.rs   | 16 +++++-----------
 4 files changed, 6 insertions(+), 15 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index ce7ed0c069e14..2fa54cd0f76bd 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -2034,7 +2034,6 @@ name = "oxc_semantic"
 version = "0.46.0"
 dependencies = [
  "assert-unchecked",
- "hashbrown 0.15.2",
  "insta",
  "itertools",
  "oxc_allocator",
diff --git a/crates/oxc_semantic/Cargo.toml b/crates/oxc_semantic/Cargo.toml
index c2381f31888de..101c96d6d1cde 100644
--- a/crates/oxc_semantic/Cargo.toml
+++ b/crates/oxc_semantic/Cargo.toml
@@ -30,7 +30,6 @@ oxc_span = { workspace = true }
 oxc_syntax = { workspace = true }
 
 assert-unchecked = { workspace = true }
-hashbrown = { workspace = true, features = ["allocator-api2"] }
 itertools = { workspace = true }
 phf = { workspace = true, features = ["macros"] }
 rustc-hash = { workspace = true }
diff --git a/crates/oxc_semantic/src/builder.rs b/crates/oxc_semantic/src/builder.rs
index dfe5a4b892d8b..81b9e211b7a21 100644
--- a/crates/oxc_semantic/src/builder.rs
+++ b/crates/oxc_semantic/src/builder.rs
@@ -712,8 +712,7 @@ impl<'a> Visit<'a> for SemanticBuilder<'a> {
         if self.scope.get_flags(parent_scope_id).is_catch_clause() {
             self.scope.cell.with_dependent_mut(|allocator, inner| {
                 if !inner.bindings[parent_scope_id].is_empty() {
-                    let mut parent_bindings =
-                        Bindings::with_hasher_in(rustc_hash::FxBuildHasher, allocator);
+                    let mut parent_bindings = Bindings::new_in(allocator);
                     mem::swap(&mut inner.bindings[parent_scope_id], &mut parent_bindings);
                     for &symbol_id in parent_bindings.values() {
                         self.symbols.set_scope_id(symbol_id, self.current_scope_id);
diff --git a/crates/oxc_semantic/src/scope.rs b/crates/oxc_semantic/src/scope.rs
index 3edc5ff6b405f..a2bdffb519e74 100644
--- a/crates/oxc_semantic/src/scope.rs
+++ b/crates/oxc_semantic/src/scope.rs
@@ -1,8 +1,6 @@
 use std::{fmt, mem};
 
-use rustc_hash::FxBuildHasher;
-
-use oxc_allocator::{Allocator, Vec as ArenaVec};
+use oxc_allocator::{Allocator, HashMap as ArenaHashMap, Vec as ArenaVec};
 use oxc_index::{Idx, IndexVec};
 use oxc_syntax::{
     node::NodeId,
@@ -13,9 +11,8 @@ use oxc_syntax::{
 
 use crate::SymbolTable;
 
-pub(crate) type Bindings<'a> = hashbrown::HashMap<&'a str, SymbolId, FxBuildHasher, &'a Allocator>;
-pub type UnresolvedReferences<'a> =
-    hashbrown::HashMap<&'a str, ArenaVec<'a, ReferenceId>, FxBuildHasher, &'a Allocator>;
+pub(crate) type Bindings<'a> = ArenaHashMap<'a, &'a str, SymbolId>;
+pub type UnresolvedReferences<'a> = ArenaHashMap<'a, &'a str, ArenaVec<'a, ReferenceId>>;
 
 /// Scope Tree
 ///
@@ -58,10 +55,7 @@ impl Default for ScopeTree {
             cell: ScopeTreeCell::new(Allocator::default(), |allocator| ScopeTreeInner {
                 bindings: IndexVec::new(),
                 child_ids: ArenaVec::new_in(allocator),
-                root_unresolved_references: UnresolvedReferences::with_hasher_in(
-                    FxBuildHasher,
-                    allocator,
-                ),
+                root_unresolved_references: UnresolvedReferences::new_in(allocator),
             }),
         }
     }
@@ -384,7 +378,7 @@ impl ScopeTree {
         let scope_id = self.parent_ids.push(parent_id);
         self.flags.push(flags);
         self.cell.with_dependent_mut(|allocator, inner| {
-            inner.bindings.push(Bindings::with_hasher_in(FxBuildHasher, allocator));
+            inner.bindings.push(Bindings::new_in(allocator));
         });
         self.node_ids.push(node_id);
         if self.build_child_ids {