perf(parser): optimize code around parsing delimited list and object (#11755)

parse_object_expression:
- remove unnecessary `bump(Kind::Comma)`

parse_delimited_list:
- avoid `first` variable and related check by unrolling first iteration
of loop
- avoid `trailing_separator` variable by restructuring code
- avoid mostly wasted call to `start_span()` (only possible if
`separator` is always one character)

parse_object_literal_element
- avoid redundant kind check when parsing getter and setter

Author: ulrichstark

crates/oxc_parser/src/cursor.rs

@@ -346,25 +346,21 @@ impl<'a> ParserImpl<'a> {
         F: Fn(&mut Self) -> T,
     {
         let mut list = self.ast.vec();
-        let mut first = true;
-        let mut trailing_separator = None;
+        if self.at(close) || self.has_fatal_error() {
+            return (list, None);
+        }
+        list.push(f(self));
         loop {
-            if self.cur_kind() == close || self.has_fatal_error() {
-                break;
+            if self.at(close) || self.has_fatal_error() {
+                return (list, None);
             }
-            if first {
-                first = false;
-            } else {
-                let separator_span = self.start_span();
-                self.expect(separator);
-                if self.at(close) {
-                    trailing_separator = Some(separator_span);
-                    break;
-                }
+            self.expect(separator);
+            if self.at(close) {
+                let trailing_separator = self.prev_token_end - 1;
+                return (list, Some(trailing_separator));
             }
             list.push(f(self));
         }
-        (list, trailing_separator)
     }
 
     pub(crate) fn parse_delimited_list_with_rest<E, A, D>(

crates/oxc_parser/src/js/object.rs

@@ -26,7 +26,6 @@ impl<'a> ParserImpl<'a> {
                 Self::parse_object_expression_property,
             )
         });
-        self.bump(Kind::Comma); // Trailing Comma
         self.expect(Kind::RCurly);
         self.ast.alloc_object_expression(self.end_span(span), object_expression_properties)
     }
@@ -47,13 +46,12 @@ impl<'a> ParserImpl<'a> {
             /* stop_on_start_of_class_static_block */ false,
         );
 
-        let kind = self.cur_kind();
-        if self.parse_contextual_modifier(Kind::Get) || self.parse_contextual_modifier(Kind::Set) {
-            return match kind {
-                Kind::Get => self.parse_method_getter_setter(span, PropertyKind::Get, &modifiers),
-                Kind::Set => self.parse_method_getter_setter(span, PropertyKind::Set, &modifiers),
-                _ => unreachable!(),
-            };
+        if self.parse_contextual_modifier(Kind::Get) {
+            return self.parse_method_getter_setter(span, PropertyKind::Get, &modifiers);
+        }
+
+        if self.parse_contextual_modifier(Kind::Set) {
+            return self.parse_method_getter_setter(span, PropertyKind::Set, &modifiers);
         }
 
         let asterisk_token = self.eat(Kind::Star);