Language/Types/Interface_Types/subtype_t30.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 type T is more specific than a type S, written T << S, if one
/// of the following conditions is met:
///  • T is S.
///  • T is ⊥
///  • S is dynamic.
///  • S is a direct supertype of T.
///  • T is a type parameter and S is the upper bound of T.
///  • T is a type parameter and S is Object.
///  • T is of the form I<T1, ..., Tn > and S is of the form I <S1, ..., Sn>
///    and Ti << Si 1 <= i <= n.
///  • T and S are both function types, and T << S under the rules of section
///    (Types/Function Types).
///  • T is a function type and S is Function.
///  • T << U and U << S.
/// << is a partial order on types. T is a subtype of S, written T <: S, iff
/// [⊥/Dynamic]T << S.
/// . . .
/// An interface type T may be assigned to a type S, written T <=> S, if either
/// T <: S or S <: T.
/// @description Checks that if type T is a subtype of S1 and S2 where
/// S1 <: S<G1> and S2 <: S<G2> then T is a subtype of S<G1> as well as S<G2>
/// and every other supertype of S.
/// @author iefremov

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

class S<Type> {}
class S1 extends S<int> {}
class S2 extends S<int> {}
class T implements S1, S2 {}

main() {
  Expect.isTrue(new T() is S<int>);
  Expect.isFalse(new T() is S<double>);
  Expect.isTrue(new T() is S<num>);
  Expect.isTrue(new T() is S<Object>);
  Expect.isTrue(new T() is S);
  Expect.runtimeIsType<S<int>>(new T());
  Expect.runtimeIsNotType<S<double>>(new T());
  Expect.runtimeIsType<S<num>>(new T());
  Expect.runtimeIsType<S<Object>>(new T());
  Expect.runtimeIsType<S>(new T());
}