TypeSystem/upper-lower-bounds/up_A02_t03.dart

// Copyright (c) 2026, 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 We define the upper bound of two types `T1` and `T2` to be
/// UP(`T1`,`T2`) as follows.
/// ...
/// - UP(`T1`, `T2`) where TOP(`T1`) and TOP(`T2`) =
///   - `T1` if MORETOP(`T1`, `T2`)
///   - `T2` otherwise
///
/// @description Check that UP(`T1`, `T2`) = `T2` if `T1 != T2` and TOP(`T1`)
/// and TOP(`T2`) and MORETOP(`T1`, `T2`) == `false`. Test that `void` is more
/// top type than others.
/// @author sgrekhov22@gmail.com

import 'dart:async';

void getVoid() {}
void getFutureOrVoid() {}

void f1(dynamic y) {
  var v = (1 > 2) ? y : getVoid(); // MORETOP(dynamic, void) = false
  print(v); // Type void cannot be used
//      ^
// [analyzer] unspecified
// [cfe] unspecified
}

void f2(Object? y) {
  var v = (1 > 2) ? y : getVoid(); // MORETOP(Object?, void) = false
  print(v);
//      ^
// [analyzer] unspecified
// [cfe] unspecified
}

void f3(FutureOr<dynamic> y) {
  var v = (1 > 2) ? y: getVoid(); // MORETOP(FutureOr<dynamic>, void) = false
  print(v);
//      ^
// [analyzer] unspecified
// [cfe] unspecified
}

void f4(FutureOr<Object?> y) {
  var v = (1 > 2) ? y : getVoid(); // MORETOP(FutureOr<Object?>, void) = false
  print(v);
//      ^
// [analyzer] unspecified
// [cfe] unspecified
}

void f5() {
  var v = (1 > 2) ? getFutureOrVoid() : getVoid(); // MORETOP(FutureOr<void>, void) = false
  print(v); // Type void cannot be used
//      ^
// [analyzer] unspecified
// [cfe] unspecified
}

void main() {
  print(f1);
  print(f2);
  print(f3);
  print(f4);
  print(f5);
}