2009-02-16 Marek Safar <marek.safar@gmail.com>

[mono.git] / mcs / mcs / generic.cs

diff --git a/mcs/mcs/generic.cs b/mcs/mcs/generic.cs
index ad97e41002437a8fe63a925edff1e108bc307b7c..9bdcc1d77fc33725dde6203eae64c7e32a2ca3c8 100644 (file)
--- a/mcs/mcs/generic.cs
+++ b/mcs/mcs/generic.cs
@@ -1303,6 +1303,42 @@ namespace Mono.CSharp {
                        return ConstraintChecker.CheckConstraints (ec, open_type, gen_params, args.Arguments, loc);
                }
 
+               static bool IsVariant (Type type)
+               {
+                       return (type.GenericParameterAttributes & GenericParameterAttributes.VarianceMask) != 0;
+               }
+       
+               static bool IsCovariant (Type type)
+               {
+                       return (type.GenericParameterAttributes & GenericParameterAttributes.Covariant) != 0;
+               }
+       
+               static bool IsContravariant (Type type)
+               {
+                       return (type.GenericParameterAttributes & GenericParameterAttributes.Contravariant) != 0;
+               }
+       
+               public bool VerifyVariantTypeParameters ()
+               {
+                       for (int i = 0; i < args.Count; i++) {
+                               Type argument = args.Arguments[i];
+                               if (argument.IsGenericParameter && IsVariant (argument)) {
+                                       if (IsContravariant (argument) && !IsContravariant (gen_params[i])) {
+                                               Report.Error (-34, loc, "Contravariant type parameters can only be used " +
+                                             "as type arguments in contravariant positions");
+                                               return false;
+                                       }
+                                       else if (IsCovariant (argument) && !IsCovariant (gen_params[i])) {
+                                               Report.Error (-35, loc, "Covariant type parameters can only be used " +
+                                             "as type arguments in covariant positions");
+                                               return false;
+                                       }
+                               }
+                       }
+                       return true;
+               }
+
+               
                public override bool CheckAccessLevel (DeclSpace ds)
                {
                        return ds.CheckAccessLevel (open_type);