How to pass a class by (const) reference to C++

[Jan]

In D I have an extern(C++) class:

```cpp
extern(C++) class A
{
     ~this();

     // other stuff
}
```

An a function that takes A by const reference:

```cpp
void CppFunc(const A& arg);
```

But how do I bind this in D ?

```cpp
extern(C++) void CppFunc(A arg); // tries to pass as 'A*'
extern(C++) void CppFunc(ref const(A) arg); // tries to pass as 
'A const * const &'
```

I have solved similar problems with other classes by declaring 
them as struct in D, but that only works for classes that have no 
virtual functions. I now have a class where I do need to use a 
class on the D side, and now I have problems passing these 
objects to C++.