LanguageFeatures/Spread-collections/StaticSemantic_A01_t01.dart

// 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.

// @dart = 2.9

/// @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.
/// @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";

main() {
  var numbers = <num>[1, 2, 3];
  Expect.listEquals([1, 2, 3], <int>[...numbers]);

  var objects = <Object>[2, 7, 9];
  Expect.listEquals([2, 7, 9], <int>[...objects]);

  var a;
  Expect.throws(() => a = <String>[...objects]);

  var numbers1 = <num>[1.1, 2, 3];
  Expect.throws(() => a = <int>[...numbers1]);


  numbers = <num>[1, 2, 3];
  Expect.listEquals([1, 2, 3], <int>[...?numbers]);

  objects = <Object>[2, 7, 9];
  Expect.listEquals([2, 7, 9], <int>[...?objects]);

  Expect.throws(() => a = <String>[...?objects]);

  numbers1 = <num>[1.1, 2, 3];
  Expect.throws(() => a = <int>[...?numbers1]);

}