| // 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 non-function typedef type |
| * argument and bound: test extends clause in the typedef declaration |
| * dynamically. |
| * @author iarkh@unipro.ru |
| */ |
| // SharedOptions=--enable-experiment=generic-metadata,nonfunction-type-aliases |
| |
| 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 C<T> { |
| C(expected) { Expect.equals(expected, T); } |
| } |
| |
| typedef C1<X extends exp1> = C<X>; |
| typedef C2<X extends exp2> = C<X>; |
| typedef C3<X extends exp3> = C<X>; |
| typedef C4<X extends exp4> = C<X>; |
| |
| main() { |
| C1 c1 = C1(exp1); |
| C2 c3 = C2(exp2); |
| C3 c5 = C3(exp3); |
| C4 c7 = C4(exp4); |
| } |