From 55a8763d6ea606eddcf11eeaf919ca19449056fc Mon Sep 17 00:00:00 2001
From: overlookmotel <557937+overlookmotel@users.noreply.github.com>
Date: Wed, 31 Jul 2024 03:33:08 +0000
Subject: [PATCH] perf(parser): faster decoding unicode escapes in identifiers
 (#4579)

Replace `next_char` and `peek_char` with `peek_byte` when decoding unicode escape sequences in identifiers.
---
 crates/oxc_parser/src/lexer/unicode.rs | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/crates/oxc_parser/src/lexer/unicode.rs b/crates/oxc_parser/src/lexer/unicode.rs
index 1f5f598af..d67508ec7 100644
--- a/crates/oxc_parser/src/lexer/unicode.rs
+++ b/crates/oxc_parser/src/lexer/unicode.rs
@@ -54,14 +54,17 @@ impl<'a> Lexer<'a> {
         check_identifier_start: bool,
     ) {
         let start = self.offset();
-        if self.next_char() != Some('u') {
+        if self.peek_byte() == Some(b'u') {
+            self.consume_char();
+        } else {
+            self.next_char();
             let range = Span::new(start, self.offset());
             self.error(diagnostics::unicode_escape_sequence(range));
             return;
         }
 
-        let value = match self.peek_char() {
-            Some('{') => self.unicode_code_point(),
+        let value = match self.peek_byte() {
+            Some(b'{') => self.unicode_code_point(),
             _ => self.surrogate_pair(),
         };