Fixed the generated C# for templates with optional arguments.

Signed-off-by: Dimitar Dobrev <dpldobrev@protonmail.com>

src/Generator/Generators/CSharp/CSharpTypePrinter.cs

@@ -356,8 +356,14 @@ namespace CppSharp.Generators.CSharp
                 if (ContextKind == TypePrinterContextKind.Managed &&
                     decl == template.Template.TemplatedDecl &&
                     template.Arguments.All(IsValid))
+                {
+                    List<TemplateArgument> args = template.Arguments;
+                    var @class = (Class) template.Template.TemplatedDecl;
+                    TemplateArgument lastArg = args.Last();
                     return $@"{VisitDeclaration(decl)}<{string.Join(", ",
-                        template.Arguments.Select(VisitTemplateArgument))}>";
+                       args.Concat(Enumerable.Range(0, @class.TemplateParameters.Count - args.Count).Select(
+                           i => lastArg)).Select(this.VisitTemplateArgument))}>";
+                }
 
                 if (ContextKind == TypePrinterContextKind.Native)
                     return template.Desugared.Visit(this);

tests/CSharp/CSharpTemplates.h

@@ -374,11 +374,18 @@ T& TemplateWithIndexer<T>::operator[](const char* string)
     return t[0];
 }
 
+template <typename T1 = void, typename T2 = void, typename T3 = void, typename T4 = void,
+          typename T5 = void, typename T6 = void, typename T7 = void, typename T8 = void>
+class OptionalTemplateArgs
+{
+};
+
 template <typename T>
 class VirtualTemplate
 {
 public:
     VirtualTemplate();
+    VirtualTemplate(OptionalTemplateArgs<T> optionalTemplateArgs);
     virtual ~VirtualTemplate();
     virtual int function();
 };
@@ -388,6 +395,11 @@ VirtualTemplate<T>::VirtualTemplate()
 {
 }
 
+template <typename T>
+VirtualTemplate<T>::VirtualTemplate(OptionalTemplateArgs<T> optionalTemplateArgs)
+{
+}
+
 template <typename T>
 VirtualTemplate<T>::~VirtualTemplate()
 {