Generate valid C# for specializations in default args

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

Author: ddobrev

src/Generator/Generators/CSharp/CSharpExpressionPrinter.cs

@@ -31,8 +31,19 @@ public string VisitParameter(Parameter parameter)
                 return $"({desugared.Visit(typePrinter)}) {expression}";
             var finalType = (desugared.GetFinalPointee() ?? desugared).Desugar();
             if (finalType.TryGetClass(out var @class) && @class.IsInterface)
-                return $@"({@class.Visit(typePrinter)}) ({
-                    @class.OriginalClass.Visit(typePrinter)}) {expression}";
+            {
+                string cast;
+                if (parameter.DefaultArgument.Declaration is Method method &&
+                    method.IsConstructor && method.Namespace == @class.OriginalClass)
+                {
+                    cast = string.Empty;
+                }
+                else
+                {
+                    cast = $"({@class.OriginalClass.Visit(typePrinter)}) ";
+                }
+                return cast + expression;
+            }
             return expression;
         }
 

src/Generator/Passes/ExpressionHelper.cs

@@ -237,7 +237,7 @@ private static bool CheckForDefaultPointer(BindingContext context, Type desugare
             var typePrinter = new CSharpTypePrinter(context);
             typePrinter.PushMarshalKind(MarshalKind.DefaultExpression);
 
-            var typePrinterResult = type.Visit(typePrinter).Type;
+            var typePrinterResult = type.Visit(typePrinter);
 
             TypeMap typeMap;
             if (context.TypeMaps.FindTypeMap(type, out typeMap))

tests/CSharp/CSharp.Tests.cs

@@ -341,6 +341,7 @@ public void TestDefaultArguments()
             methodsWithDefaultValues.DefaultWithCharFromInt();
             methodsWithDefaultValues.DefaultWithFreeConstantInNameSpace();
             methodsWithDefaultValues.DefaultWithStdNumericLimits(10, 5);
+            methodsWithDefaultValues.DefaultWithSpecialization();
             methodsWithDefaultValues.DefaultWithParamNamedSameAsMethod(5);
         }
     }

tests/CSharp/CSharp.cpp

@@ -818,6 +818,10 @@ void MethodsWithDefaultValues::defaultWithParamRequiringRename(_ClassWithLeading
 {
 }
 
+void MethodsWithDefaultValues::defaultWithSpecialization(IndependentFields<int> specialization)
+{
+}
+
 int MethodsWithDefaultValues::DefaultWithParamNamedSameAsMethod(int DefaultWithParamNamedSameAsMethod, const Foo& defaultArg)
 {
     return 1;

tests/CSharp/CSharp.h

@@ -482,6 +482,7 @@ class DLL_API MethodsWithDefaultValues : public Quux
     void defaultWithFreeConstantInNameSpace(int c = HasFreeConstant::FREE_CONSTANT_IN_NAMESPACE);
     void defaultWithStdNumericLimits(double d = 1.0, int i = std::numeric_limits<double>::infinity());
     void defaultWithParamRequiringRename(_ClassWithLeadingUnderscore* ptr = nullptr);
+    void defaultWithSpecialization(IndependentFields<int> specialization = IndependentFields<int>());
     int DefaultWithParamNamedSameAsMethod(int DefaultWithParamNamedSameAsMethod, const Foo& defaultArg = Foo());
     int getA();
 private: