| // 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 function can be a class type argument and |
| /// bound: test extends clause in the class declaration dynamically. |
| /// @Issue 45415 |
| /// @author iarkh@unipro.ru |
| |
| |
| import "../../Utils/expect.dart"; |
| |
| typedef exp1 = T Function<T>(T); |
| typedef exp2 = void Function<T>(); |
| typedef exp3 = T Function<T>(); |
| typedef exp4 = void Function<T>(T); |
| |
| class C1<X extends T Function<T>(T)> { |
| C1() { Expect.equals(exp1, X); } |
| } |
| |
| class C2<X extends void Function<T>()> { |
| C2() { Expect.equals(exp2, X); } |
| } |
| |
| class C3<X extends T Function<T>()> { |
| C3() { Expect.equals(exp3, X); } |
| } |
| |
| class C4<X extends void Function<T>(T)> { |
| C4() { Expect.equals(exp4, X); } |
| } |
| |
| main() { |
| C1 c1 = C1(); |
| C1 c2 = C1<T Function<T>(T)>(); |
| |
| C2 c3 = C2(); |
| C2 c4 = C2<void Function<int>()>(); |
| |
| C3 c5 = C3(); |
| C3 c6 = C3<T Function<T>()>(); |
| |
| C4 c7 = C4(); |
| C4 c8 = C4<void Function<T>(T)>(); |
| } |