LanguageFeatures/Patterns/relational_A06_t04.dart

// Copyright (c) 2022, 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 relationalPattern ::=
///   ( equalityOperator | relationalOperator) bitwiseOrExpression
///
/// A relational pattern lets you compare the matched value to a given constant
/// using any of the equality or relational operators: ==, !=, <, >, <=, and >=.
/// The pattern matches when calling the appropriate operator on the matched
/// value with the constant as an argument returns true.
///
/// It is a compile-time error if bitwiseOrExpression is not a valid constant
/// expression.
///
/// @description Checks the case when user-defined class with custom relational
/// operators is used in a relational pattern. Test a relational subpattern in a
/// switch statement
/// @author sgrekhov22@gmail.com

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

class C {
  final int value;
  const C(this.value);

  bool operator <(C other) => this.value < other.value;
  bool operator >(C other) => this.value > other.value;
  bool operator <=(C other) => this.value <= other.value;
  bool operator >=(C other) => this.value >= other.value;
  @override
  bool operator ==(Object other) => this.value == (other as C).value;
  @override
  int get hashCode => throw "Never used";
}

void test(List<C> list, String expected) {
  switch (list) {
    case [> const C(0) && <= const C(2)]:
      Expect.equals("case 1", expected);
      break;
    case [== const C(42)]:
      Expect.equals("case 2", expected);
      break;
    case [>= const C(10) && < const C(20)]:
      Expect.equals("case 3", expected);
      break;
    case [!= const C(100)]:
      Expect.equals("case 4", expected);
      break;
    default:
      Expect.equals("default", expected);
  }
}

main() {
  test([C(1)], "case 1");
  test([C(2)], "case 1");
  test([C(42)], "case 2");
  test([C(10)], "case 3");
  test([C(11)], "case 3");
  test([C(20)], "case 4");
  test([C(100)], "default");
}