fix(parser): reject readonly modifier on constructors (#26612)

The parser accepted `class C { readonly constructor() {} }` and silently discarded `readonly`. Report TS1024 on the modifier instead, matching TypeScript and the existing validation for ordinary methods.

crates/oxc_parser/src/js/class.rs

@@ -525,6 +525,12 @@ impl<'a, C: Config> ParserImpl<'a, C> {
         if let Some(modifier) = modifiers.get(ModifierKind::Declare) {
             self.error(diagnostics::declare_constructor(modifier.span()));
         }
+        self.verify_modifiers(
+            modifiers,
+            ModifierKinds::all_except([ModifierKind::Readonly]),
+            false,
+            diagnostics::modifier_only_on_property_declaration_or_index_signature,
+        );
 
         let value = self.parse_method(
             modifiers.contains(ModifierKind::Async),

tasks/coverage/misc/fail/readonly-constructor-ambient.ts

@@ -0,0 +1 @@
+declare class C { readonly constructor(); }

tasks/coverage/misc/fail/readonly-constructor-overload.ts

@@ -0,0 +1,4 @@
+class C {
+  readonly constructor(value: number);
+  constructor(value: number) {}
+}

tasks/coverage/misc/fail/readonly-constructor-quoted.ts

@@ -0,0 +1 @@
+class C { public readonly "constructor"() {} }

tasks/coverage/misc/fail/readonly-constructor.ts

@@ -0,0 +1 @@
+class C { readonly constructor() {} }

tasks/coverage/misc/pass/readonly-constructor.ts

@@ -0,0 +1,15 @@
+class C {
+  readonly field = 1;
+  constructor(value: number);
+  constructor(public readonly value: number) {}
+}
+
+class D {
+  protected constructor() {}
+  readonly = 1;
+}
+
+declare class E {
+  readonly field: number;
+  constructor();
+}

tasks/coverage/snapshots/codegen_misc.snap

@@ -1,3 +1,3 @@
 codegen_misc Summary:
-AST Parsed     : 108/108 (100.00%)
-Positive Passed: 108/108 (100.00%)
+AST Parsed     : 109/109 (100.00%)
+Positive Passed: 109/109 (100.00%)

tasks/coverage/snapshots/formatter_misc.snap

@@ -1,3 +1,3 @@
 formatter_misc Summary:
-AST Parsed     : 108/108 (100.00%)
-Positive Passed: 108/108 (100.00%)
+AST Parsed     : 109/109 (100.00%)
+Positive Passed: 109/109 (100.00%)

tasks/coverage/snapshots/lexer_misc.snap

@@ -1,3 +1,3 @@
 lexer_misc Summary:
-AST Parsed     : 326/326 (100.00%)
-Positive Passed: 326/326 (100.00%)
+AST Parsed     : 331/331 (100.00%)
+Positive Passed: 331/331 (100.00%)

tasks/coverage/snapshots/parser_misc.snap

@@ -1,7 +1,7 @@
 parser_misc Summary:
-AST Parsed     : 108/108 (100.00%)
-Positive Passed: 108/108 (100.00%)
-Negative Passed: 218/218 (100.00%)
+AST Parsed     : 109/109 (100.00%)
+Positive Passed: 109/109 (100.00%)
+Negative Passed: 222/222 (100.00%)
 
   × Cannot assign to 'arguments' in strict mode
    ╭─[misc/fail/arguments-eval-ambient.ts:2:13]
@@ -4765,6 +4765,32 @@ Negative Passed: 218/218 (100.00%)
    ·                               ───────────
    ╰────
 
+  × TS(1024): 'readonly' modifier can only appear on a property declaration or index signature.
+   ╭─[misc/fail/readonly-constructor-ambient.ts:1:19]
+ 1 │ declare class C { readonly constructor(); }
+   ·                   ────────
+   ╰────
+
+  × TS(1024): 'readonly' modifier can only appear on a property declaration or index signature.
+   ╭─[misc/fail/readonly-constructor-overload.ts:2:3]
+ 1 │ class C {
+ 2 │   readonly constructor(value: number);
+   ·   ────────
+ 3 │   constructor(value: number) {}
+   ╰────
+
+  × TS(1024): 'readonly' modifier can only appear on a property declaration or index signature.
+   ╭─[misc/fail/readonly-constructor-quoted.ts:1:18]
+ 1 │ class C { public readonly "constructor"() {} }
+   ·                  ────────
+   ╰────
+
+  × TS(1024): 'readonly' modifier can only appear on a property declaration or index signature.
+   ╭─[misc/fail/readonly-constructor.ts:1:11]
+ 1 │ class C { readonly constructor() {} }
+   ·           ────────
+   ╰────
+
   × Invalid rest element target in destructuring assignment
    ╭─[misc/fail/rest-assignment-target.js:1:6]
  1 │ ({...[]} = {});

tasks/coverage/snapshots/semantic_misc.snap

@@ -1,6 +1,6 @@
 semantic_misc Summary:
-AST Parsed     : 108/108 (100.00%)
-Positive Passed: 104/108 (96.30%)
+AST Parsed     : 109/109 (100.00%)
+Positive Passed: 104/109 (95.41%)
 semantic Error: tasks/coverage/misc/pass/declare-let-private.ts
 Bindings mismatch:
 after transform: ScopeId(0): ["private"]
@@ -85,6 +85,11 @@ Unresolved reference IDs mismatch for "Object":
 after transform: [ReferenceId(166), ReferenceId(170), ReferenceId(174), ReferenceId(185), ReferenceId(226), ReferenceId(228), ReferenceId(265), ReferenceId(267), ReferenceId(304), ReferenceId(306), ReferenceId(343), ReferenceId(345), ReferenceId(382), ReferenceId(386), ReferenceId(425), ReferenceId(427), ReferenceId(464), ReferenceId(468), ReferenceId(507), ReferenceId(509), ReferenceId(546), ReferenceId(550), ReferenceId(589), ReferenceId(591), ReferenceId(628), ReferenceId(632), ReferenceId(671), ReferenceId(673), ReferenceId(839), ReferenceId(843), ReferenceId(876), ReferenceId(880), ReferenceId(891), ReferenceId(895)]
 rebuilt        : [ReferenceId(169), ReferenceId(173), ReferenceId(177), ReferenceId(182), ReferenceId(291), ReferenceId(295), ReferenceId(364), ReferenceId(368), ReferenceId(437), ReferenceId(441), ReferenceId(625), ReferenceId(632), ReferenceId(777), ReferenceId(781), ReferenceId(810), ReferenceId(814), ReferenceId(819), ReferenceId(823)]
 
+semantic Error: tasks/coverage/misc/pass/readonly-constructor.ts
+Bindings mismatch:
+after transform: ScopeId(0): ["C", "D", "E", "_defineProperty"]
+rebuilt        : ScopeId(0): ["C", "D", "_defineProperty"]
+
 semantic Error: tasks/coverage/misc/pass/reserved-kw-ambient-context.ts
 Bindings mismatch:
 after transform: ScopeId(0): ["C", "C2", "f", "f2"]

tasks/coverage/snapshots/transformer_misc.snap

@@ -1,3 +1,3 @@
 transformer_misc Summary:
-AST Parsed     : 108/108 (100.00%)
-Positive Passed: 108/108 (100.00%)
+AST Parsed     : 109/109 (100.00%)
+Positive Passed: 109/109 (100.00%)