| /* |
| * 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 Allow generic function types as type arguments and bounds |
| * |
| * The language disallows generic function types as type arguments and bounds. |
| * |
| * late List<T Function<T>(T)> idFunctions; // INVALID. |
| * var callback = [foo<T>(T value) => value]; // Inferred as above, then invalid. |
| * late S Function<S extends T Function<T>(T)>(S) f; // INVALID. |
| * |
| * We remove that restriction, so a type argument and a bound can be a generic |
| * function type. |
| * |
| * This requires no new syntax, and in some cases only the removal of a single |
| * check. There might be some platforms where the implementation currently |
| * assumes that generic function types cannot occur as the value of type |
| * variables (an proof-of-concept attempt hit an assert in the VM). Such |
| * assumptions will need to be flushed out with tests and fixed. |
| * |
| * Because we already infer List<T Function<T>(T)> in the code above, this |
| * change will not affect type inference, it will just make the inferred type |
| * not be an error afterwards. |
| * |
| * We do not expect the removal of this restriction to affect the feasibility of |
| * type inference. After all, it's already possible to have a generic function |
| * type occurring covariantly in a type argument, like List<T Function<T>(T) |
| * Function()>. |
| * @description Checks that generic invariant function can be a type argument |
| * and bound of FutureOr. |
| * @author iarkh@unipro.ru |
| */ |
| // SharedOptions=--enable-experiment=generic-metadata |
| |
| import "dart:async"; |
| import "../../Utils/expect.dart"; |
| |
| T test1<T>(T i) => i; |
| void test2<T>() {} |
| T test3<T>() => 0 as T; |
| void test4<T>(T i) {} |
| |
| main() { |
| FutureOr<void Function<T>(T)> f = test4; |
| f = test1; |
| Expect.throws(() { f = 1 as dynamic; }); |
| Expect.throws(() { f = test2 as dynamic; }); |
| Expect.throws(() { f = test3 as dynamic; }); |
| } |