blob: 9ad30538bc25b3ed4b16499e5d7f891a59f33642 [file] [log] [blame]
// Copyright (c) 2021, 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’s currently a compile-time error for a class to implement,
/// extend or mix-in the Enum class.
/// Because we want to allow interfaces and mixins that are intended to be
/// applied to enum declarations, and therefore to assume Enum to be a
/// superclass, we loosen that restriction to:
/// It’s a compile-time error if a non-abstract class implements Enum unless it
/// is the implicit class of an enum declaration.
/// It is a compile-time error if a class implements, extends or mixes-in a
/// class declared by an enum declaration.
/// That allows abstract classes (interfaces) which implements Enum in order to
/// have the int index; getter member available, and it allows mixin
/// declarations to use Enum as an on type because mixin declarations cannot be
/// instantiated directly.
/// This restriction still ensure enum values are the only object instances
/// which implements Enum, while making it valid to declare abstract class
/// MyInterface implements Enum and mixin MyMixin on Enum for interfaces and
/// mixins intended to be used in declaring enum classes.
/// @description Check that abstract classes may implement enum
/// @author
// SharedOptions=--enable-experiment=enhanced-enums
import "../../Utils/expect.dart";
abstract class C implements Enum {
int foo();
enum E implements C {
int foo() => this.index;
main() {