How to implement a friend/factory pattern in C++/WinRT

[amtopel]

I'm using C++/WinRT, and I'd like to make a class ("ClassB") instantiable only through another class ("ClassA"). I've already removed the default constructor from the Class B .idl declaration.

It seems that the general C++ approach to this is to make the constructor of ClassB private, and then to make ClassA a friend struct of ClassB. But it doesn't seem that be that straightforward in C++/WinRT, given the complex implementation class hierarchy and projection setup. I'll get this compiler error:

'winrt::impl::heap_implements<T>::heap_implements(void)': attempting to reference a deleted function

Or in other words, is there a way to make the call to winrt::make<implementation::ClassA>() exclusive to Class B?

Does anyone know how to do this? Thanks for any info.