How generics work in C++/CX

Question

I couldn't find anything about this on the Internet, so I'm looking for someone with the insights into the way C++/CX is impemented. The Wikipedia article on C++/CX says that it supports runtime-based generics, wich would imply that you don't need a header file with full implementation in order to instantiate a generic type. I undertand how this works for .NET (assemblies contain IL code and JIT can just insert concrete types into it and compile it whenever there's a new instantiation), but in C++/CX (which is natively compiled) there is no JIT to edit the code at runtime (which I asume would be pretty hard for x86 machine code)

So what's the trick here, is it type erasure with boxing or some new contrived scheme?

(I know that the metadata about types is stored in .NET format, I'm after the code in the methods)