Extract the function parameter marshal logic into its own method.

src/Generator/Generators/CLI/CLISourcesTemplate.cs

@@ -348,13 +348,20 @@ namespace Cxxi.Generators.CLI
             for (var i = 0; i < function.Parameters.Count; ++i)
             {
                 var param = function.Parameters[i];
+                GenerateFunctionParamMarshal(function, param, @params, i);
+            }
+
+            return @params;
+        }
 
+        private void GenerateFunctionParamMarshal(Function function, Parameter param, List<ParamMarshal> @params, int i)
+        {
             if (param.Type is BuiltinType)
             {
                 @params.Add(new ParamMarshal {Name = param.Name, Param = param});
+                return;
             }
-                else
-                {
+
             var argName = "arg" + i.ToString(CultureInfo.InvariantCulture);
 
             var ctx = new MarshalContext()
@@ -384,10 +391,6 @@ namespace Cxxi.Generators.CLI
             var argText = marshal.ArgumentPrefix + argName;
             @params.Add(new ParamMarshal {Name = argText, Param = param});
         }
-            }
-
-            return @params;
-        }
 
         public void GenerateFunctionParams(Function function, List<ParamMarshal> @params)
         {