// Copyright (c) 2018, 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 T0 is a subtype of a type T1 (written T0 <: T1) when:
/// Positional Function Types: T0 is U0 Function<X0 extends B00, ... ,
/// Xk extends B0k>(V0 x0, ..., Vn xn, [Vn+1 xn+1, ..., Vm xm])
///
///  and T1 is U1 Function<Y0 extends B10, ..., Yk extends B1k>(S0 y0, ...,
///  Sp yp, [Sp+1 yp+1, ..., Sq yq])
///  and p >= n
///  and m >= q
///  and Si[Z0/Y0, ..., Zk/Yk] <: Vi[Z0/X0, ..., Zk/Xk] for i in 0...q
///  and U0[Z0/X0, ..., Zk/Xk] <: U1[Z0/Y0, ..., Zk/Yk]
///  and B0i[Z0/X0, ..., Zk/Xk] === B1i[Z0/Y0, ..., Zk/Yk] for i in 0...k
///  where the Zi are fresh type variables with bounds B0i[Z0/X0, ..., Zk/Xk]
/// @description Check that if T0 and T1 satisfies the rules above, then T0 is
/// subtype of T1. Test the case when p == n and m == q.
/// @author sgrekhov@unipro.ru
///
/// @description Check that if type T0 is a subtype of a type T1, then instance
/// of T0 can be be used as a return value of type T1
/// @author sgrekhov@unipro.ru
///
/// This test is generated from positional_function_types_A01.dart and 
/// return_value_x01.dart.
/// Don't modify it. If you want to change this test, change one of the files 
/// above and then run generator.dart to regenerate the tests.


class U0 extends U1 {}
class U1 {}
class V0 {}
class V1 {}
class V2 {}
class V3 {}
class S0 extends V0 {}
class S1 extends V1 {}
class S2 extends V2 {}
class S3 extends V3 {}

typedef T0 = U0 Function(V0 x0, V1 x1, [V2? x2, V3? x3]);
typedef T1 = U1 Function(S0 y0, S1 y1, [S2? y2, S3? y3]);

U0 t0Func(V0 x0, V1 x1, [V2? x2, V3? x3]) => new U0();
U1 t1Func(S0 y0, S1 y1, [S2? y2, S3? y3]) => new U1();

T0 t0Instance = t0Func;
T1 t1Instance = t1Func;

const t1Default = t1Func;


T1 returnValueFunc() => t0Instance;

class ReturnValueTest {
  static T1 staticTestMethod() => t0Instance;

  T1 testMethod() => t0Instance;

  T1 get testGetter => t0Instance;
}

main() {
  T1 returnValueLocalFunc() => t0Instance;

  returnValueFunc();
  returnValueLocalFunc();

  ReturnValueTest.staticTestMethod();

  new ReturnValueTest().testMethod();
  new ReturnValueTest().testGetter;

}