perf(regular_expression): defer literal range dash allocation (#28511)

Allocate a literal dash only when a class range falls back to literal
class contents.

AI-assisted (Codex).

crates/oxc_regular_expression/src/parser/pattern_parser/pattern_parser_impl.rs

@@ -873,21 +873,21 @@ impl<'a> PatternParser<'a> {
                 continue;
             }
 
-            let dash = ast::CharacterClassContents::Character(ArenaBox::new_in(
-                ast::Character {
-                    span: self.span_factory.create(span_start, self.reader.offset()),
-                    kind: ast::CharacterKind::Symbol,
-                    value: '-' as u32,
-                },
-                self,
-            ));
+            let dash_span = self.span_factory.create(span_start, self.reader.offset());
 
             let Some(class_atom_to) = self.parse_class_atom()? else {
                 // ClassAtom[?UnicodeMode] NonemptyClassRangesNoDash[?UnicodeMode]
                 // => ClassAtom[?UnicodeMode] ClassAtom[?UnicodeMode]
                 // => ClassAtom[?UnicodeMode] -
                 body.push(class_atom);
-                body.push(dash);
+                body.push(ast::CharacterClassContents::Character(ArenaBox::new_in(
+                    ast::Character {
+                        span: dash_span,
+                        kind: ast::CharacterKind::Symbol,
+                        value: '-' as u32,
+                    },
+                    self,
+                )));
                 continue;
             };
 
@@ -937,7 +937,14 @@ impl<'a> PatternParser<'a> {
             }
 
             body.push(class_atom);
-            body.push(dash);
+            body.push(ast::CharacterClassContents::Character(ArenaBox::new_in(
+                ast::Character {
+                    span: dash_span,
+                    kind: ast::CharacterKind::Symbol,
+                    value: '-' as u32,
+                },
+                self,
+            )));
             body.push(class_atom_to);
         }
 

tasks/track_memory_allocations/allocs_minifier.yaml

@@ -51,7 +51,7 @@ antd.js:
   sys peak growth: 19934725 # 19.93 MB
   arena allocs: 175842
   arena reallocs: 34169
-  arena size: 43472344 # 43.47 MB
+  arena size: 43471240 # 43.47 MB
 
 binder.ts:
   file size: 193077 # 193.08 kB

tasks/track_memory_allocations/allocs_parser.yaml

@@ -5,7 +5,7 @@ checker.ts:
   sys deallocs: 19
   sys alloc bytes: 4820 # 4.82 kB
   sys peak growth: 2432 # 2.43 kB
-  arena allocs: 259312
+  arena allocs: 259307
   arena reallocs: 15233
   arena size: 12875504 # 12.88 MB
 
@@ -16,7 +16,7 @@ App.tsx:
   sys deallocs: 18
   sys alloc bytes: 4348 # 4.35 kB
   sys peak growth: 1868 # 1.87 kB
-  arena allocs: 43828
+  arena allocs: 43826
   arena reallocs: 2263
   arena size: 2228464 # 2.23 MB
 
@@ -38,7 +38,7 @@ pdf.mjs:
   sys deallocs: 61
   sys alloc bytes: 24020 # 24.02 kB
   sys peak growth: 12140 # 12.14 kB
-  arena allocs: 88940
+  arena allocs: 88912
   arena reallocs: 5904
   arena size: 4488040 # 4.49 MB
 
@@ -49,9 +49,9 @@ antd.js:
   sys deallocs: 183
   sys alloc bytes: 94120 # 94.12 kB
   sys peak growth: 38896 # 38.90 kB
-  arena allocs: 519986
+  arena allocs: 519914
   arena reallocs: 35629
-  arena size: 29903280 # 29.90 MB
+  arena size: 29902176 # 29.90 MB
 
 binder.ts:
   file size: 193077 # 193.08 kB
@@ -71,6 +71,6 @@ kitchen-sink.tsx:
   sys deallocs: 182
   sys alloc bytes: 34053 # 34.05 kB
   sys peak growth: 3892 # 3.89 kB
-  arena allocs: 135741
+  arena allocs: 135713
   arena reallocs: 8759
   arena size: 6398256 # 6.40 MB

tasks/track_memory_allocations/allocs_semantic.yaml

@@ -51,7 +51,7 @@ antd.js:
   sys peak growth: 5441278 # 5.44 MB
   arena allocs: 0
   arena reallocs: 0
-  arena size: 29903280 # 29.90 MB
+  arena size: 29902176 # 29.90 MB
 
 binder.ts:
   file size: 193077 # 193.08 kB

tasks/track_memory_allocations/allocs_transformer.yaml

@@ -51,7 +51,7 @@ antd.js:
   sys peak growth: 1611 # 1.61 kB
   arena allocs: 2
   arena reallocs: 0
-  arena size: 29903304 # 29.90 MB
+  arena size: 29902200 # 29.90 MB
 
 binder.ts:
   file size: 193077 # 193.08 kB