LanguageFeatures/Set-literals/type_inference_A26_t03.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 Finally, we define inference on a setOrMapLiteral collection as
/// follows:
/// ...
/// Otherwise, collection is still ambiguous, the downwards context for the
/// elements of collection is ?, and the disambiguation is done using the
/// immediate elements of collection as follows:
///
/// If all elements can be a set, and at least one element must be a set, then
/// collection is a set literal with static type Set<T> where T is the least
/// upper bound of the set element types of the elements.
///
/// @description Checks that if all elements can be a set, and at least one
/// element must be a set, then collection is a set literal with static type
/// Set<T> where T is the least upper bound of the set element types of the
/// elements
/// @author sgrekhov@unipro.ru

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

main() {
  var n = null;
  var s1 = {...?n, 1};
  Expect.isTrue(s1 is Set<Object?>);
  Expect.isFalse(s1 is Set<int>);
  Expect.isFalse(s1 is Set<Null>);
  Expect.runtimeIsType<Set<Object?>>(s1);
  Expect.runtimeIsNotType<Set<int>>(s1);
  Expect.runtimeIsNotType<Set<Null>>(s1);

  var s2 = {1, ...?n};
  Expect.isTrue(s2 is Set<Object?>);
  Expect.isFalse(s2 is Set<int>);
  Expect.isFalse(s2 is Set<Null>);
  Expect.runtimeIsType<Set<Object?>>(s2);
  Expect.runtimeIsNotType<Set<int>>(s2);
  Expect.runtimeIsNotType<Set<Null>>(s2);
}