tupleof.length of a class in a template return 0

["Michaël]

I've given a second chance to D after watching D videos from 
Lang.NEXT 2012. As a first look, I wanted to try generate 
serialization code at compile time.

Here's the class:
class MyObject
{
     public int m_id;
     public Data m_data;
     public bool AutoDelete;
     public int RefCount;

mixin(AddStreamSerialization!(MyObject));
}