LanguageFeatures/Set-literals/type_inference_A07_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.

/// @assertion To infer the type of element:
/// ...
/// If element is a spreadElement with expression e1:
///
/// If P is ? then let S be the inferred type of e1 in context ?:
///
/// If S is a non-Null subtype of Iterable<Object>, then the inferred set element
/// type of element is T where T is the type such that Iterable<T> is a
/// superinterface of S (the result of constraint matching for X using the
/// constraint S <: Iterable<X>).
///
/// @description Checks that if S is a non-Null subtype of Iterable<Object?>,
/// then the inferred set element type of element is T where T is the type such
/// that Iterable<T> is a superinterface of S
/// @author sgrekhov@unipro.ru

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

void test1<T extends Iterable<num>>(T t) {
  var s1 = {...t};
  var s2 = {...?t};
//          ^^^^
// [analyzer] STATIC_WARNING.INVALID_NULL_AWARE_OPERATOR
//              ^
// [cfe] Operand of null-aware operation '...?' has type 'T' which excludes null.
  Expect.isTrue(s1 is Set<num>);
  Expect.isFalse(s1 is Set<int>);
  Expect.isTrue(s2 is Set<num>);
  Expect.isFalse(s2 is Set<int>);
}

void test2<T extends Iterable<Object>>(T t) {
  var s1 = {...t};
  var s2 = {...?t};
//          ^^^^
// [analyzer] STATIC_WARNING.INVALID_NULL_AWARE_OPERATOR
//              ^
// [cfe] Operand of null-aware operation '...?' has type 'T' which excludes null.
  Expect.isTrue(s1 is Set<Object>);
  Expect.isFalse(s1 is Set<num>);
  Expect.isTrue(s2 is Set<Object>);
  Expect.isFalse(s2 is Set<num>);
}

main() {
  int x = 2;
  test1([1, x, 3, 4]);
  test2([1.0, 2.0, x, 4]);
}