Fixes dart-lang#2491. Add test that an extension type cannot implemen…

…t type `Never`

LanguageFeatures/Extension-types/static_analysis_extension_types_A10_t16.dart

@@ -0,0 +1,32 @@
+// Copyright (c) 2024, 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 A compile-time error occurs if an extension type has a
+/// non-extension superinterface whose transitive alias expansion is a type
+/// variable, a deferred type, any top type (including dynamic and void), the
+/// type Null, any function type, the type Function, any record type, the type
+/// Record, or any type of the form T? or FutureOr<T> for any type T.
+///
+/// @description Checks that it is a compile-time error if an extension type has
+/// a non-extension superinterface whose transitive alias expansion is a type
+/// `Never`
+/// @author sgrekhov22@gmail.com
+
+// SharedOptions=--enable-experiment=inline-class
+
+typedef NeverAlias = Never;
+
+extension type NeverET1(Object? _) implements Never {}
+//                                            ^^^^^
+// [analyzer] unspecified
+// [cfe] unspecified
+extension type NeverET2(Object? _) implements NeverAlias {}
+//                                            ^^^^^^^^^^
+// [analyzer] unspecified
+// [cfe] unspecified
+
+main() {
+  print(NeverET1);
+  print(NeverET2);
+}