LanguageFeatures/Extension-methods/syntax_covariant_t01.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 an extension declaration is a top-level declaration with a grammar
 * similar to:
 * <extension> ::=
 *   `extension' <identifier>? <typeParameters>? `on' <type> `?'? `{'
 *     memberDeclaration*
 *   `}'
 * Instance member declaration parameters must not be marked covariant
 *
 * @description Check that instance member declaration parameters must not be
 * marked covariant
 * @author sgrekhov@unipro.ru
 */


class A {}

class C extends A {
}

extension on C {
  addChild(covariant A child) {}
  //       ^^^^^^^^^
  // [analyzer] SYNTACTIC_ERROR.INVALID_USE_OF_COVARIANT_IN_EXTENSION
  // [cfe] Can't have modifier 'covariant' in an extension.
  addChild2(A c, [covariant A child]) {}
// [error line 31, column 0]
// [analyzer] unspecified
// [cfe] unspecified
  addChild3(A c, {covariant A child}) {}
// [error line 35, column 0]
// [analyzer] unspecified
// [cfe] unspecified
  void set setter (covariant A value) {}
  //               ^^^^^^^^^
  // [analyzer] SYNTACTIC_ERROR.INVALID_USE_OF_COVARIANT_IN_EXTENSION
  // [cfe] Can't have modifier 'covariant' in an extension.
  C operator+(covariant A other) => this;
  //          ^^^^^^^^^
  // [analyzer] SYNTACTIC_ERROR.INVALID_USE_OF_COVARIANT_IN_EXTENSION
  // [cfe] Can't have modifier 'covariant' in an extension.
}

main() {
  new C();
}