Language/Types/Interface_Types/subtype_t23.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 GenericType<T> is a subtype of GenericType<S> where
 * T and S are simple functions.
 * @author iefremov
 */
import "../../../Utils/expect.dart";

class I0 {}
class I1 extends I0 {}
class I2 extends I1 {}
class I3 extends I2 {}
class I4 extends I2 {}

class G<T> {}

typedef t1();
typedef void t1_1(); // void <: Dynamic
typedef G<List<t1>> t1_2();

typedef I2 t2(I2 i, [I2 j]);
typedef I0 t2_1(I0 i, [I0 j]);
typedef I4 t2_2(I4 i, [I4 j]);
typedef I4 t2_3(I0 i, [I4 j]);
typedef I0 t2_4(I4 i, [I0 j]);

typedef t1 t3(t1 f1, [t1 f2]);
typedef t1_1 t3_1(t1_1 f1, [t1_1 f2]);
typedef t1_2 t3_2(t1_2 f1, [t1_2 f2]);

main() {
  Expect.isTrue(new List<t1>.empty() is List<t1>);
  Expect.isTrue(new List<t1_1>.empty() is List<t1>);
  Expect.isTrue(new List<t1_2>.empty() is List<t1>);

  Expect.isTrue(new List<t2>.empty() is List<t2>);
  Expect.isFalse(new List<t2_1>.empty() is List<t2>);
  Expect.isFalse(new List<t2_2>.empty() is List<t2>);
  Expect.isFalse(new List<t2_3>.empty() is List<t2>);
  Expect.isFalse(new List<t2_4>.empty() is List<t2>);

  Expect.isTrue(new List<t3>.empty() is List<t3>);
  Expect.isTrue(new List<t3_1>.empty() is List<t3>);
  Expect.isFalse(new List<t3_2>.empty() is List<t3>);
}