Language/Types/Function_Types/subtype_optional_args_t12.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 Assertion means that as long function type t1 has no more
/// required parameters and no less total positional parameters than function
/// type t2, types of extra positional parameters of t1 do not matter for subtype
/// relation. Under this condition, checks that t1 is subtype of t2 if their
/// parameter types are assignable on t2 parameters set range, and t1 has extra
/// optional positional parameters of some arbitary type.
/// @author ilya

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

typedef t1(int x);
typedef t2(int x, int y);

class Whatever {}

main() {
  Expect.isTrue(([int x = 0, Whatever? w]) {} is t1);
  Expect.isTrue(([var x, Whatever? w, Whatever? w2]) {} is t1);
  Expect.isTrue((int x, [int y = 0, Whatever? w]) {} is t2);
  Expect.isTrue((int x, [int y = 0, Whatever? w, Whatever? w2]) {} is t2);
  Expect.isTrue(([int x = 42, int y = 0, Whatever? w, Whatever? w2]) {} is t2);
  Expect.runtimeIsType<t1>(([int x = 0, Whatever? w]) {});
  Expect.runtimeIsType<t1>(([var x, Whatever? w, Whatever? w2]) {});
  Expect.runtimeIsType<t1>((int x, [int y = 0, Whatever? w]) {});
  Expect.runtimeIsType<t1>((int x, [int y = 0, Whatever? w, Whatever? w2]) {});
  Expect.runtimeIsType<t1>(
      ([int x = 42, int y = 0, Whatever? w, Whatever? w2]) {});
}