Refactoring fixes in ParamTypeToInterfacePass.

src/Generator/Passes/ParamTypeToInterfacePass.cs

@@ -5,6 +5,10 @@ using CppSharp.AST.Extensions;
 
 namespace CppSharp.Passes
 {
+    /// <summary>
+    /// Replaces all references to secondary bases with their respective interface
+    /// type that is generated by MultipleInheritancePass.
+    /// </summary>
     public class ParamTypeToInterfacePass : TranslationUnitPass
     {
         public ParamTypeToInterfacePass()
@@ -29,7 +33,8 @@ namespace CppSharp.Passes
 
             // parameters and returns from a specialised interface
             // must not be replaced if the templated interface uses a template parameter
-            Function templateInterfaceFunction = GetTemplateInterfaceFunction(function);
+            var interfaceFunction = GetInterfaceFunction(function);
+            var templateInterfaceFunction = interfaceFunction?.InstantiatedFrom;
 
             if ((!function.IsOperator || function.Parameters.Count > 1) &&
                 (templateInterfaceFunction == null ||
@@ -53,11 +58,13 @@ namespace CppSharp.Passes
                         templateInterfaceFunction.Parameters.Where(
                             p => p.Kind != ParameterKind.OperatorParameter &&
                                 p.Kind != ParameterKind.IndirectReturnType));
+
                 for (int i = 0; i < parameters.Count; i++)
                 {
                     if (templateFunctionParameters.Any() &&
                         IsTemplateParameter(templateFunctionParameters[i].QualifiedType))
                         continue;
+
                     var qualifiedType = parameters[i].QualifiedType;
                     ChangeToInterfaceType(ref qualifiedType);
                     parameters[i].QualifiedType = qualifiedType;
@@ -84,14 +91,13 @@ namespace CppSharp.Passes
             return true;
         }
 
-        private static Function GetTemplateInterfaceFunction(Function function)
+        private static Function GetInterfaceFunction(Function function)
         {
-            Function templateInterfaceFunction = null;
-            Class @class = function.OriginalNamespace as Class;
-            if (@class != null && @class.IsInterface)
-                templateInterfaceFunction = @class.Methods.First(
-                   m => m.OriginalFunction == function.OriginalFunction).InstantiatedFrom;
-            return templateInterfaceFunction;
+            var @class = function.OriginalNamespace as Class;
+            if (@class == null || !@class.IsInterface)
+                return null;
+
+            return @class.Methods.First(m => m.OriginalFunction == function.OriginalFunction);
         }
 
         private static Property GetTemplateInterfaceProperty(Property property)