| // Copyright (c) 2019, 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 Since the spread is unpacked and its individual elements added to |
| /// the containing collection, we don't require the spread expression itself to |
| /// be assignable to the collection's type. For example, this is allowed: |
| /// |
| /// var numbers = <num>[1, 2, 3]; |
| /// var ints = <int>[...numbers]; |
| /// |
| /// This works because the individual elements in numbers do happen to have the |
| /// right type even though the list that contains them does not. As long as the |
| /// spread object is "spreadable" — it implements [Iterable] — there is no |
| /// static error. |
| /// @note That's an error with null-safety to assign List<num> to List<int>, see |
| /// https://github.com/dart-lang/language/blob/471a98ca0dd5b02d194ffad0dc128065771253a0/specification/dartLangSpec.tex#L8245, |
| /// because `num` isn't assignable to `int`. |
| /// @description Checks that for lists it's possible to have the spread |
| /// expression which is not assignable to the result collection type, no static |
| /// error in this case. |
| /// @author iarkh@unipro.ru |
| |
| |
| import "../../Utils/expect.dart"; |
| |
| List<dynamic> integers = <num>[1, 2, 3]; |
| List<dynamic?> objects = <Object>[2, 7, 9]; |
| List<dynamic> numbers1 = <num>[1.1, 2, 3]; |
| |
| List<dynamic>? nullableNums = <num>[1, 2, 3]; |
| List<dynamic>? nullableObjects = <Object>[2, 7, 9]; |
| List<dynamic>? nullableNums1 = <num>[1.1, 2, 3]; |
| |
| main() { |
| Expect.listEquals([1, 2, 3], <int>[...integers]); |
| Expect.listEquals([2, 7, 9], <int>[...objects]); |
| var a; |
| Expect.throws(() => a = <String>[...objects]); |
| |
| Expect.throws(() => a = <int>[...numbers1]); |
| |
| Expect.listEquals([1, 2, 3], <int>[...?nullableNums]); |
| |
| Expect.listEquals([2, 7, 9], <int>[...?nullableObjects]); |
| |
| Expect.throws(() => a = <String>[...?nullableObjects]); |
| |
| Expect.throws(() => a = <int>[...?nullableNums1]); |
| |
| } |