mcs/tests/gtest-variance-11.cs

   1 // Compiler options: -langversion:future
   2
   3 using System;
   4
   5 interface IContravariant<in T>
   6 {
   7 }
   8
   9 interface ICovariant<out T>
  10 {
  11 }
  12
  13 class D
  14 {
  15         public static bool Contra<T> (IContravariant<T> e1, IContravariant<T> e2)
  16         {
  17                 Console.WriteLine (typeof (T));
  18                 return typeof (T) == typeof (string);
  19         }
  20
  21         public static bool Covariant<T> (ICovariant<T> e1, ICovariant<T> e2)
  22         {
  23                 Console.WriteLine (typeof (T));
  24                 return typeof (T) == typeof (object);
  25         }
  26
  27         public static int Main ()
  28         {
  29                 ICovariant<object> a = null;
  30                 ICovariant<string> b = null;
  31                 if (!Covariant (a, b))
  32                         return 1;
  33
  34                 IContravariant<string> a_1 = null;
  35                 IContravariant<object> b_1 = null;
  36                 if (!Contra (a_1, b_1))
  37                         return 2;
  38
  39                 return 0;
  40         }
  41 }