From 963a2d1b850fac2ab6fd779b2876547ec6545f05 Mon Sep 17 00:00:00 2001
From: Dunqing <29533304+Dunqing@users.noreply.github.com>
Date: Sat, 27 Jul 2024 10:55:49 +0000
Subject: [PATCH] perf(mangler): reduce unnecessary allocation (#4498)

There seems to be no noticeable change in performance.
---
 crates/oxc_mangler/src/lib.rs | 13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)

diff --git a/crates/oxc_mangler/src/lib.rs b/crates/oxc_mangler/src/lib.rs
index 68457e1d16f66..041bd1ed2acb3 100644
--- a/crates/oxc_mangler/src/lib.rs
+++ b/crates/oxc_mangler/src/lib.rs
@@ -105,8 +105,8 @@ impl ManglerBuilder {
 
             if !bindings.is_empty() {
                 // `bindings` are stored in order, traverse and increment slot
-                for symbol_id in bindings.values() {
-                    slots[*symbol_id] = slot;
+                for symbol_id in bindings.values().copied() {
+                    slots[symbol_id] = slot;
                     slot += 1;
                 }
             }
@@ -121,9 +121,6 @@ impl ManglerBuilder {
         let frequencies =
             Self::tally_slot_frequencies(&symbol_table, total_number_of_slots, &slots);
 
-        let unresolved_references =
-            scope_tree.root_unresolved_references().keys().collect::<Vec<_>>();
-
         let mut names = Vec::with_capacity(total_number_of_slots);
 
         let generate_name = if self.debug { debug_name } else { base54 };
@@ -133,7 +130,9 @@ impl ManglerBuilder {
                 let name = generate_name(count);
                 count += 1;
                 // Do not mangle keywords and unresolved references
-                if !is_keyword(&name) && !unresolved_references.iter().any(|n| **n == name) {
+                if !is_keyword(&name)
+                    && !scope_tree.root_unresolved_references().contains_key(name.as_str())
+                {
                     break name;
                 }
             });
@@ -169,7 +168,7 @@ impl ManglerBuilder {
             // sorting by slot enables us to sort by the order at which the vars first appear in the source
             // (this is possible because the slots are discovered currently in a DFS method which is the same order
             //  as variables appear in the source code)
-            symbols_renamed_in_this_batch.sort_by(|a, b| a.slot.cmp(&b.slot.clone()));
+            symbols_renamed_in_this_batch.sort_by(|a, b| a.slot.cmp(&b.slot));
 
             // here we just zip the iterator of symbols to rename with the iterator of new names for the next for loop
             let symbols_to_rename_with_new_names =