LanguageFeatures/Patterns/matching_variable_A01_t01.dart

// Copyright (c) 2023, 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 At runtime, a pattern is matched against a value. This determines
/// whether or not the match fails and the pattern refutes the value. If the
/// match succeeds, the pattern may also destructure data from the object or
/// bind variables.
///
/// Refutable patterns usually occur in a context where match refutation causes
/// execution to skip over the body of code where any variables bound by the
/// pattern are in scope. If a pattern match failure occurs in an irrefutable
/// context, a runtime error is thrown.
///
/// To match a pattern p against a value v:
/// ...
/// Variable:
/// i. Let T be the static type of the variable p declares or assigns to.
/// ii. If the runtime type of v is not a subtype of T then the match fails.
/// iii. Otherwise, store v in p's variable and the match succeeds.
///
/// @description Checks that if the runtime type of `v` is not a subtype of the
/// static type of the variable `p` declares or assigns to, then the match fails
/// @author sgrekhov22@gmail.com

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

String test1(Object? o) {
  switch (o) {
    case int v1:
      return "match-1";
    case final String v2:
      return "match-2";
    case num? _:
      return "match-3";
    default:
      return "no match";
  }
}

String test2(Object? o) {
  if (o case int v1) {
    return "match-1";
  }
  if (o case final String _) {
    return "match-2";
  }
  if (o case num? v3) {
    return "match-3";
  }
  return "no match";
}

String test3(Object? o) =>
  switch (o) {
    int _ => "match-1",
    final String v2 => "match-2",
    num? v3 => "match-3",
    _ => "no match"
  };

main() {
  int? answer = 42;
  Expect.equals("match-1", test1(1));
  Expect.equals("match-1", test1(1 as dynamic));
  Expect.equals("match-2", test1("1"));
  Expect.equals("match-2", test1("1" as dynamic));
  Expect.equals("match-1", test1(answer));
  Expect.equals("match-3", test1(null));
  Expect.equals("match-3", test1(3.14));
  Expect.equals("no match", test1(true));

  Expect.equals("match-1", test2(1));
  Expect.equals("match-1", test2(1 as dynamic));
  Expect.equals("match-2", test2("1"));
  Expect.equals("match-2", test2("1" as dynamic));
  Expect.equals("match-1", test2(answer));
  Expect.equals("match-3", test2(null));
  Expect.equals("match-3", test2(3.14));
  Expect.equals("no match", test2(true));

  Expect.equals("match-1", test3(1));
  Expect.equals("match-1", test3(1 as dynamic));
  Expect.equals("match-2", test3("1"));
  Expect.equals("match-2", test3("1" as dynamic));
  Expect.equals("match-1", test3(answer));
  Expect.equals("match-3", test3(null));
  Expect.equals("match-3", test3(3.14));
  Expect.equals("no match", test3(true));

  Expect.throws(() {
    var <dynamic>[int v] = ["42"] as dynamic;
  });
  Expect.throws(() {
    final <dynamic>[String v] = [42] as dynamic;
  });
  Expect.throws(() {
    var <dynamic>[int v] = [null] as dynamic;
  });
}