| /* |
| * 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 At this location about an asynchronous non-generator function with |
| * future value type $T_v$, the text is changed as follows: |
| * |
| * It is a compile-time error if $s$ is \code{\RETURN{};}, |
| * unless $T_v$ |
| * is \VOID, \DYNAMIC, or \code{Null}. |
| * % |
| * It is a compile-time error if $s$ is \code{\RETURN{} $e$;}, |
| * $T_v$ is \VOID, |
| * and \flatten{S} is neither \VOID, \DYNAMIC, \code{Null}. |
| * % |
| * It is a compile-time error if $s$ is \code{\RETURN{} $e$;}, |
| * $T_v$ is neither \VOID{} nor \DYNAMIC, |
| * and \flatten{S} is \VOID. |
| * % |
| * It is a compile-time error if $s$ is \code{\RETURN{} $e$;}, |
| * \flatten{S} is not \VOID, |
| * $S$ is not assignable to $T_v$, |
| * and flatten{S} is not a subtype of $T_v$. |
| * Comparing to Dart before null-safety, this means that it is no longer |
| * allowed to return an expression whose flattened static type is void in an |
| * async function with future value type Null; nor is it allowed, in an async |
| * function with future value type void, to return an expression whose |
| * flattened static type is not void, void*, dynamic, or Null. Conversely, it |
| * is allowed to return a future when the future value type is a suitable |
| * future; for instance, we can have return Future<int>.value(42) in an async |
| * function with declared return type Future<Future<int>>. Finally, let S be |
| * Future<dynamic> or FutureOr<dynamic>; it is then no longer allowed to return |
| * an expression with static type S, unless the future value type is a |
| * supertype of S. This differs from Dart before null-safety in that it was |
| * allowed to return an expression of these types with a declared return type |
| * of the form Future<T> for any T. |
| * |
| * @description Check that it is a compile-time error to return a future |
| * when the future value type is not a suitable future |
| * @author sgrekhov@unipro.ru |
| */ |
| |
| Future<Future<int>> f1() async { |
| return new Future<num>.value(42); |
| // ^^^^^^^^^^^^^^^^^^^^^^^^^ |
| // [analyzer] unspecified |
| // [cfe] unspecified |
| } |
| |
| main() { |
| f1(); |
| } |
