| /* |
| * 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 The requirement that satisfaction of the bounds on the formal type |
| * parameters of a generic type alias [D] must imply satisfaction of all bounds |
| * pertaining to every type that occurs in the body of [D] limits the expressive |
| * power of generic type aliases. However, it would require the constraints on |
| * formal type parameters to be expressed in a much more powerful language if we |
| * were to allow a significantly larger set of types to be expressed using a |
| * generic type alias. |
| * For example, consider the following code: |
| * class A<X extends void Function(num)> {} |
| * typedef F<Y> = A<void Function(Y)> Function(); // compile-time error |
| * There is no way to specify a bound on [Y] in the declaration of [F] which |
| * will ensure that all bounds on the right hand side are respected. This is |
| * because the actual requirement is that [Y] must be a supertype of [num], but |
| * Dart does not support lower bounds for type parameters. The type [A<void |
| * Function(U)> Function()] can still be specified explicitly for every [U] |
| * which satisfies the bounds declared by [A]. So the types can be expressed, |
| * they just cannot be abbreviated using a generic type alias. |
| * @description Checks that example from the Spec throws compile error as |
| * expected. |
| * @compile-error |
| * @author iarkh@unipro.ru |
| */ |
| // SharedOptions=--enable-experiment=nonfunction-type-aliases |
| |
| class A<X extends void Function(num)> {} |
| typedef AAlias<Y> = A<Y>; |
| |
| main() { |
| } |
