Changed the site to add cast.

Author: genuinelucifer

src/Generator/Generators/CSharp/CSharpTextTemplate.cs

@@ -2202,9 +2202,11 @@ public void GenerateMethod(Method method, Class @class)
 
         private string OverloadParamNameWithDefValue(Parameter p, ref int index)
         {
+            Class @class;
             return p.Type.IsPointerToPrimitiveType() && p.Usage == ParameterUsage.InOut && p.HasDefaultValue
                 ? "ref param" + index++
-                : ExpressionPrinter.VisitExpression(p.DefaultArgument).Value;
+                : (( p.Type.TryGetClass(out @class) && @class.IsInterface) ? "param" + index++ 
+                     : ExpressionPrinter.VisitExpression(p.DefaultArgument).Value);
         }
 
         private void GenerateOverloadCall(Function function)
@@ -2221,6 +2223,14 @@ private void GenerateOverloadCall(Function function)
                     WriteLine("{0} param{1} = {2};", pointeeType, j++,
                         primitiveType == PrimitiveType.Bool ? "false" : "0");
                 }
+                Class @class;
+                if(parameter.Kind == ParameterKind.Regular && parameter.Ignore &&
+                    parameter.Type.Desugar().TryGetClass(out @class) && @class.IsInterface &&
+                    parameter.HasDefaultValue)
+                {
+                    WriteLine("var param{0} = ({1}) {2};",  j++, @class.OriginalClass.OriginalName,
+                        ExpressionPrinter.VisitExpression(parameter.DefaultArgument).Value);
+                }
             }
 
             GenerateManagedCall(function);

src/Generator/Passes/HandleDefaultParamValuesPass.cs

@@ -243,7 +243,7 @@ private bool CheckForEnumValue(Type desugared, Statement statement,
             if (enumItem != null)
             {
                 result = string.Format("{0}{1}.{2}",
-                    desugared.IsPrimitiveType() ? "(int) " : "(" + desugared.CSharpType(new CSharpTypePrinter(Driver)) + ") ",
+                    desugared.IsPrimitiveType() ? "(int) " : string.Empty,
                     new CSharpTypePrinter(Driver).VisitEnumDecl(
                         (Enumeration) enumItem.Namespace), enumItem.Name);
                 return true;