LanguageFeatures/Extension-methods/explicit_extension_member_invocation_A20_t04.dart

/*
 * Copyright (c) 2019, 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 It is a compile-time error if an extension application occurs in a
 * place where it is not the target expression of a simple or composite member
 * invocation. That is, the only valid use of an extension application is to
 * invoke members on it. This is similar to how prefix names can also only be
 * used as member invocation targets. The main difference is that extensions can
 * also declare operators.
 *
 * @description Check that it is no compile-time error if null-aware member
 * access like E(o)?[v] is used for explicit extension invocation
 * @issue 39326
 * https://github.com/dart-lang/language/issues/677
 * @author sgrekhov@unipro.ru
 * @static-warning
 * @issue 43217
 */

import "../../Utils/expect.dart";

class C {
}

extension Ext on C {
  int operator [](int index) => index;
}

main() {
  C c = C();
  Expect.equals(42, Ext(c)?[42]); /// static type warning
}