Fixes dart-lang#3063. Add additional "correct member overrides" test

Language/Interfaces/Superinterfaces/Correct_Member_Overrides/correct_member_overrides_A03_t29.dart

@@ -0,0 +1,38 @@
+// Copyright (c) 2025, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+/// @assertion Let `m` and `m′` be member signatures with the same name `id`.
+/// Then `m` is a correct override of `m′` iff the following criteria are all
+/// satisfied:
+/// ...
+/// • If `m` and `m′` are both methods or both setters: Let F be the function
+///   type of `m` except that the parameter type is the built-in class `Object`
+///   for each parameter of `m` which is covariant-by-declaration. Let `F′` be
+///   the function type of `m′`. `F` must then be a subtype of `F′`.
+///
+/// Note that a parameter which is covariant-by-declaration must have a type
+/// which satisfies one more requirement, relative to the corresponding
+/// parameters in all superinterfaces, both direct and indirect
+///
+/// @description Checks that it is a compile-time error if `m` and `m′` are both
+/// generic methods and a function type of `m` is not a subtype of `m′.
+/// @author [email protected]
+/// @issue 60011
+
+class A<T extends num> {
+  X foo<X extends T>(X x) => x;
+}
+
+class C<T extends num> extends A<num> {
+  int v;
+  C(this.v);
+  X foo<X extends T>(X x) => x + v as X;
+//  ^^^
+// [analyzer] unspecified
+// [cfe] unspecified
+}
+
+void main() {
+  C<int>(1);
+}