| // 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 covariant function can be a type argument |
| * and bound for List. |
| * @author iarkh@unipro.ru |
| */ |
| // SharedOptions=--enable-experiment=generic-metadata |
| |
| import "../../Utils/expect.dart"; |
| |
| T test1<T>(T i) => i; |
| void test2<T>() {} |
| T test3<T>() => 0 as T; |
| void test4<T>(T i) {} |
| |
| void testme() {} |
| |
| main() { |
| List<void Function<T>()> l2 = <void Function<T>()>[]; |
| l2.add(test2); |
| Expect.equals(test2, l2[0]); |
| l2.add(test3); |
| Expect.equals(test3, l2[1]); |
| |
| Expect.throws(() { l2.add(1 as dynamic); }); |
| Expect.throws(() { l2.add(test1 as dynamic); }); |
| Expect.throws(() { l2.add(test4 as dynamic); }); |
| Expect.throws(() { l2.add(testme as dynamic); }); |
| } |