fix(parser): do not double-parse modifiers of ts index signature in c…

…lass

crates/oxc_parser/src/js/class.rs

@@ -229,9 +229,9 @@ impl<'a> ParserImpl<'a> {
         }
 
         if self.is_at_ts_index_signature_member() {
-            if let TSSignature::TSIndexSignature(sig) = self.parse_ts_index_signature_member()? {
-                return Ok(Some(ClassElement::TSIndexSignature(sig)));
-            }
+            return Ok(Some(self.ast.class_element_from_ts_index_signature(
+                self.parse_ts_index_signature_member(span, &modifiers)?,
+            )));
         }
 
         // * ...

crates/oxc_parser/src/lib.rs

@@ -696,6 +696,23 @@ mod test {
         assert_eq!(ret.errors.first().unwrap().to_string(), "Source length exceeds 4 GiB limit");
     }
 
+    #[test]
+    fn class_index_signature_modifiers() {
+        use oxc_ast::ast::*;
+        let allocator = Allocator::default();
+        let source_type = SourceType::ts();
+        let source = "class Foo { readonly [a: string]: string }";
+        let ret = Parser::new(&allocator, source, source_type).parse();
+        let Statement::ClassDeclaration(class_decl) = &ret.program.body[0] else {
+            panic!("expected Statement::ClassDeclaration");
+        };
+        let ClassElement::TSIndexSignature(index_sig) = &class_decl.body.body[0] else {
+            panic!("expected ClassElement::TSIndexSignature");
+        };
+        assert!(index_sig.readonly);
+        assert_eq!(index_sig.span.start as usize, source.find("readonly").unwrap());
+    }
+
     // Source with length MAX_LEN parses OK.
     // This test takes over 1 minute on an M1 Macbook Pro unless compiled in release mode.
     // `not(debug_assertions)` is a proxy for detecting release mode.

crates/oxc_parser/src/ts/statement.rs

@@ -206,7 +206,7 @@ impl<'a> ParserImpl<'a> {
 
     pub(crate) fn parse_ts_type_signature(&mut self) -> Result<Option<TSSignature<'a>>> {
         if self.is_at_ts_index_signature_member() {
-            return self.parse_ts_index_signature_member().map(Some);
+            return self.parse_ts_index_signature_member_with_modifiers().map(Some);
         }
 
         match self.cur_kind() {

crates/oxc_parser/src/ts/types.rs

@@ -1267,12 +1267,24 @@ impl<'a> ParserImpl<'a> {
         ))
     }
 
-    pub(crate) fn parse_ts_index_signature_member(&mut self) -> Result<TSSignature<'a>> {
-        let span = self.start_span();
+    pub(crate) fn parse_ts_index_signature_member_with_modifiers(
+        &mut self,
+    ) -> Result<TSSignature<'a>> {
+        let start_span = self.start_span();
 
         let modifiers = self.parse_class_element_modifiers(false);
+        Ok(self.ast.ts_signature_from_ts_index_signature(
+            self.parse_ts_index_signature_member(start_span, &modifiers)?,
+        ))
+    }
+
+    pub(crate) fn parse_ts_index_signature_member(
+        &mut self,
+        start_span: Span,
+        modifiers: &Modifiers<'a>,
+    ) -> Result<TSIndexSignature<'a>> {
         self.verify_modifiers(
-            &modifiers,
+            modifiers,
             ModifierFlags::READONLY,
             diagnostics::cannot_appear_on_an_index_signature,
         );
@@ -1288,8 +1300,8 @@ impl<'a> ParserImpl<'a> {
         if let Some(type_annotation) = type_annotation {
             self.bump(Kind::Comma);
             self.bump(Kind::Semicolon);
-            Ok(self.ast.ts_signature_index_signature(
-                self.end_span(span),
+            Ok(self.ast.ts_index_signature(
+                self.end_span(start_span),
                 parameters,
                 type_annotation,
                 readonly,