Create an Algebraic type at compile time and more

[uknys]

Hello,

I wanted to know if such code was possible :

alias Operation = Algebraic!(/* All type that implements X UDA */)

struct X
{
     int opcode;
     Operation h;
}

@X(0x01, Hello(3))
@X(0x02, Hello(4))
struct Hello
{
     int Hello;
}

@X(0x03, Toto(5))
@X(0x05, Toto(6))
struct Toto
{
    int A;
}


It has two problems, Operation not being defined while I use it 
in the UDA, and how to get back all the types that implements 
this UDA to give it to Algebraic.
I don't know if it's a good idea or not, but might as well try 
the dark side of meta programming.

Thanks a lot :)