Fix: Store private props in FxIndexMap

crates/oxc_transformer/src/es2022/class_properties.rs

@@ -70,7 +70,10 @@
 //!   * <https://github.com/babel/babel/blob/v7.26.2/packages/babel-helper-create-class-features-plugin/src/fields.ts>
 //! * Class properties TC39 proposal: <https://github.com/tc39/proposal-class-fields>
 
-use rustc_hash::FxHashMap;
+use std::hash::BuildHasherDefault;
+
+use indexmap::IndexMap;
+use rustc_hash::FxHasher;
 use serde::Deserialize;
 
 use oxc_allocator::{Address, Box as ArenaBox, GetAddress};
@@ -89,6 +92,8 @@ use crate::{common::helper_loader::Helper, CompilerAssumptions, TransformCtx};
 
 use super::ClassStaticBlock;
 
+type FxIndexMap<K, V> = IndexMap<K, V, BuildHasherDefault<FxHasher>>;
+
 #[derive(Debug, Default, Clone, Copy, Deserialize)]
 #[serde(default, rename_all = "camelCase")]
 pub struct ClassPropertiesOptions {
@@ -113,7 +118,8 @@ pub struct ClassProperties<'a, 'ctx> {
     // then stack will get out of sync.
     // TODO: Should push to the stack only when entering class body, because `#x` in class `extends`
     // clause resolves to `#x` in *outer* class, not the current class.
-    private_props_stack: SparseStack<FxHashMap<Atom<'a>, PrivateProp<'a>>>,
+    // TODO(improve-on-babel): Order that temp vars are created in is not important. Use `FxHashMap` instead.
+    private_props_stack: SparseStack<FxIndexMap<Atom<'a>, PrivateProp<'a>>>,
     /// Addresses of class expressions being processed, to prevent same class being visited twice.
     /// Have to use a stack because the revisit doesn't necessarily happen straight after the first visit.
     /// e.g. `c = class C { [class D {}] = 1; }` -> `c = (_D = class D {}, class C { ... })`
@@ -455,8 +461,8 @@ impl<'a, 'ctx> ClassProperties<'a, 'ctx> {
         // Check if class has any properties and get index and `ScopeId` of constructor (if class has one)
         let mut instance_prop_count = 0;
         let mut has_static_prop_or_static_block = false;
-        // TODO: Store `FxHashMap`s in a pool and re-use them
-        let mut private_props = FxHashMap::default();
+        // TODO: Store `FxIndexMap`s in a pool and re-use them
+        let mut private_props = FxIndexMap::default();
         let mut constructor = None;
         let mut index_not_including_removed = 0;
         for element in &class.body.body {