From ae0423835d195f915b582ce7e5b25bca128142d0 Mon Sep 17 00:00:00 2001
From: Jim Blandy <jimb@red-bean.com>
Date: Wed, 20 Sep 2023 15:34:26 -0700
Subject: [PATCH] Introduce `FastIndexMap` type alias, and use it for
 NamedExpressions.

---
 src/lib.rs | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/src/lib.rs b/src/lib.rs
index 92a0ba2ce2..b220872dd0 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -310,12 +310,13 @@ pub type FastHashSet<K> = rustc_hash::FxHashSet<K>;
 pub type FastIndexSet<K> =
     indexmap::IndexSet<K, std::hash::BuildHasherDefault<rustc_hash::FxHasher>>;
 
+/// Insertion-order-preserving hash map (`IndexMap<K, V>`), but with the same
+/// hasher as `FastHashMap<K, V>` (faster but not resilient to DoS attacks).
+pub type FastIndexMap<K, V> =
+    indexmap::IndexMap<K, V, std::hash::BuildHasherDefault<rustc_hash::FxHasher>>;
+
 /// Map of expressions that have associated variable names
-pub(crate) type NamedExpressions = indexmap::IndexMap<
-    Handle<Expression>,
-    String,
-    std::hash::BuildHasherDefault<rustc_hash::FxHasher>,
->;
+pub(crate) type NamedExpressions = FastIndexMap<Handle<Expression>, String>;
 
 /// Early fragment tests.
 ///