fix(parser): avoid duplicate index signature modifier diagnostic (#27190)

## Summary

- Report TS1071 once for invalid modifiers on class index signatures, while retaining TS1031 for other class members.
- Update the TypeScript parser snapshot for `parserIndexMemberDeclaration9.ts`.

crates/oxc_parser/src/js/class.rs

@@ -257,6 +257,18 @@ impl<'a, C: Config> ParserImpl<'a, C> {
     }
 
     fn parse_class_element_impl(&mut self) -> ClassElement<'a> {
+        fn verify_class_element_modifiers<C: Config>(
+            parser: &mut ParserImpl<'_, C>,
+            modifiers: &Modifiers,
+        ) {
+            parser.verify_modifiers(
+                modifiers,
+                ModifierKinds::all_except([ModifierKind::Export]),
+                false,
+                diagnostics::cannot_appear_on_class_elements,
+            );
+        }
+
         let start = self.cur_start();
 
         let decorators = self.parse_decorators();
@@ -279,13 +291,6 @@ impl<'a, C: Config> ParserImpl<'a, C> {
             return self.parse_class_static_block(start);
         }
 
-        self.verify_modifiers(
-            &modifiers,
-            ModifierKinds::all_except([ModifierKind::Export]),
-            false,
-            diagnostics::cannot_appear_on_class_elements,
-        );
-
         let r#abstract = modifiers.contains(ModifierKind::Abstract);
 
         let r#type = if r#abstract {
@@ -295,6 +300,7 @@ impl<'a, C: Config> ParserImpl<'a, C> {
         };
 
         if self.parse_contextual_modifier(Kind::Get) {
+            verify_class_element_modifiers(self, &modifiers);
             return self.parse_accessor_declaration(
                 start,
                 r#type,
@@ -305,6 +311,7 @@ impl<'a, C: Config> ParserImpl<'a, C> {
         }
 
         if self.parse_contextual_modifier(Kind::Set) {
+            verify_class_element_modifiers(self, &modifiers);
             return self.parse_accessor_declaration(
                 start,
                 r#type,
@@ -318,6 +325,7 @@ impl<'a, C: Config> ParserImpl<'a, C> {
             && !modifiers.contains(ModifierKind::Static)
             && let Some(name) = self.parse_constructor_name()
         {
+            verify_class_element_modifiers(self, &modifiers);
             return self.parse_constructor_declaration(start, r#type, name, &modifiers, decorators);
         }
 
@@ -339,6 +347,7 @@ impl<'a, C: Config> ParserImpl<'a, C> {
             );
         }
 
+        verify_class_element_modifiers(self, &modifiers);
         let kind = self.cur_kind();
         if kind.is_identifier_or_keyword() || kind == Kind::Star || kind == Kind::LBrack {
             let is_ambient = modifiers.contains(ModifierKind::Declare);

tasks/coverage/snapshots/parser_typescript.snap

@@ -27400,14 +27400,6 @@ Expect to Parse: tasks/coverage/typescript/tsc/testdata/tests/cases/conformance/
    ╰────
   help: Allowed modifiers are: static, readonly
 
-  × TS(1031): 'export' modifier cannot appear on class elements of this kind.
-   ╭─[typescript/tsc/testdata/tests/cases/conformance/parser/ecmascript5/IndexMemberDeclarations/parserIndexMemberDeclaration9.ts:2:4]
- 1 │ class C {
- 2 │    export [x: string]: string;
-   ·    ──────
- 3 │ }
-   ╰────
-
   × TS(1071): 'export' modifier cannot appear on an index signature.
    ╭─[typescript/tsc/testdata/tests/cases/conformance/parser/ecmascript5/IndexMemberDeclarations/parserIndexMemberDeclaration9.ts:2:4]
  1 │ class C {