I have a question regarding the macro or metaprogramming system:
I have seen that it seems to at least have not been possible some years ago but
it might have changed so the question is..

 Is it possible to get all types at compile-time in order to generate code
based on them
 Is it possible to mark specific types and get them at compile-time to generate
code based on them
 Is it possible to get all types of a subset of the program e.g. module or
other representations to again generate code based on them

The general idea behind this would be for example generating a packet handler
mediator or  in a more simplistic manner a switch case based on an op code.