Language/Types/Function_Types/subtype_optional_args_t04.dart

// Copyright (c) 2011, 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 A function type (T1,...Tk,[Tk+1,...,Tn+m]) -> T is a subtype of
 * the function type (S1,...,Sk+j,[Sk+j+1,...,Sn]) -> S, if all of the following
 * conditions are met:
 * 1. Either
 *    • S is void, or
 *    • T <=> S.
 * 2. ∀i ∈ 1..n, Ti ⇐⇒ Si.
 * @description Checks that this statement is true for quite complex function
 * types: non-dynamic return type and a bunch of required and positional optional
 * parameters.
 * @author iefremov
 */
import "../../../Utils/expect.dart";

class A {}
class A1 {}
class A2 {}
class B implements A, A1, A2 {}
class C implements B {}
class D implements C {}

typedef B func(Object o);
typedef B t1(int i, B b, Map<int, num> m, var x, [var ox, B? ob, List<num>? ol, bool? obool]);

B f1(int i, B b, Map<int, num> m, var x, [var ox, D? ob, List<num>? ol, bool? obool]) => new B();
D f2(int i, D b, Map<int, int> m, func x, [func? ox, D? ob, List<int>? ol, bool? obool]) => new D();
C f3(num i, A b, Map<Object, Object> m, var x, [var ox, A2? ob, List? ol, Object? obool]) => new C();
C f4(num i, A b, Map<Object, Object> m, var x, [var ox, A2? ob, List? ol, bool? obool, A? xx, B? yy]) => new C();
A f5(num i, A b, Map<Object, Object> m, var x, [var ox, A2? ob, List? ol, Object? obool]) => new A();

main() {
  Expect.isFalse(f1 is t1);
  Expect.isFalse(f2 is t1);
  Expect.isTrue(f3 is t1);
  Expect.isTrue(f4 is t1);
  Expect.isFalse(f5 is t1);
}