LanguageFeatures/Spread-collections/TypeInference_A05_t05.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.

/// @assertion From the Unified collections Spec:
/// We require that at least one component unambiguously determine the literal
/// form, otherwise it is a compile-time error. So, given:
///    dynamic x = <int, int>{};
///    Iterable l = [];
///    Map m = {};
///    Then:
///    {...x}       // Static error, because it is ambiguous.
///    {...x, ...l} // Statically a set, runtime error when spreading x.
///    {...x, ...m} // Statically a map, no runtime error.
///    {...l, ...m} // Static error, because it must be both a set and a map.
/// @description Checks that if one of the spreadable element is [Map], result
/// is statically [Map]
/// @author iarkh@unipro.ru


import "../../Utils/expect.dart";

main() {
  dynamic map = <int, int>{};
  dynamic set = <int>{};
  Map m = {};

  Map res;
  Expect.throws(() =>  res = {...m, ...set});
  Expect.throws(() =>  res = {...set, ...m});

  Expect.isTrue({...map, ...m} is Map);
  Expect.isTrue({...m, ...map} is Map);
}