LanguageFeatures/Set-literals/type_inference_A27_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 map, and at least one element must be a map, then e
/// is a map literal with static type Map<K, V> where K is the least upper bound
/// of the key types of the elements and V is the least upper bound of the value
/// types.
///
/// @description Checks that if all elements can be a map, and at least one
/// element must be a map, then e is a map literal with static type Map<K, V>
/// where K is the least upper bound of the key types of the elements and V is
/// the least upper bound of the value types.
/// @author sgrekhov@unipro.ru

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

main() {
  var n = null;
  var m1 = {...?n, 1: 2};
  Expect.isTrue(m1 is Map<Object?, Object?>);
  Expect.isFalse(m1 is Map<int, int>);
  Expect.isFalse(m1 is Map<Null, Null>);
  Expect.runtimeIsType<Map<Object?, Object?>>(m1);
  Expect.runtimeIsNotType<Map<int, int>>(m1);
  Expect.runtimeIsNotType<Map<Null, Null>>(m1);

  var m2 = {1: 2, ...?n};
  Expect.isTrue(m2 is Map<Object?, Object?>);
  Expect.isFalse(m2 is Map<int, int>);
  Expect.isFalse(m2 is Map<Null, Null>);
  Expect.runtimeIsType<Map<Object?, Object?>>(m2);
  Expect.runtimeIsNotType<Map<int, int>>(m2);
  Expect.runtimeIsNotType<Map<Null, Null>>(m2);
}