LanguageFeatures/Spread-collections/TypeInference_A05_t06.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
 */
// SharedOptions=--enable-experiment=constant-update-2018

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

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

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

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

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