mono/tests/iface-contravariant1.cs

   1 using System;
   2
   3 /* Test of constrained.callvirt resolution for contravariant interfaces */
   4
   5
   6 public interface I<in T>
   7 {
   8                 string F (T t);
   9 }
  10
  11 public class C : I<object>
  12 {
  13         public string F (object t)
  14         {
  15                 return t.GetType().Name;
  16         }
  17 }
  18
  19 /* U should be instantiated by a valuetype because we don't want the generic
  20  * sharing codepath */
  21 public class G<T, TI, U>
  22         where TI : I<T>
  23 {
  24         public G(TI i)
  25         {
  26                 _i = i;
  27         }
  28
  29         public string Do (T t)
  30         {
  31                 // we want to get this in IL:
  32                 //
  33                 // constrained. !1
  34                 // callvirt I`1<!T>::F(!0)
  35                 //
  36                 return _i.F (t);
  37         }
  38
  39         private readonly TI _i;
  40 }
  41
  42 public class Driver
  43 {
  44         public static int Main ()
  45         {
  46                 var c = new C();
  47                 // instantiate with: T=string because we want to be
  48                 // contravariant with object; U=int because we need a valuetype
  49                 // to not end up in the generic sharing codepath.
  50                 var h = new G<string, C, int>(c);
  51                 var s = h.Do ("abc");
  52                 var expected = typeof(string).Name;
  53                 if (s == expected)
  54                         return 0;
  55                 else {
  56                         Console.Error.WriteLine ("Got '{0}', expected '{1}'", s, expected);
  57                         return 1;
  58                 }
  59         }
  60 }