Language/Types/Interface_Types/subtype_t47.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 a generic interface type B that is a subtype of a
/// generic type A parameterized with type parameters of B is not assignable to
/// A parameterized with another, incompatible set of type parameters.
/// @author iefremov


class A<T, S, U, W> {}
class B<S, U> extends A<S, S, U, U>{}

B<int, double> checker() => new B<double>();
//                              ^
// [analyzer] unspecified
// [cfe] unspecified

main() {
  A<int, int, double, int> a = checker();
//                             ^
// [analyzer] unspecified
// [cfe] unspecified
}