Also, now that I think about it, why couldn't you do this?
(it's equivalent):
auto serialize(T)(T a) {
auto c = cast(SerializerBase) new Serializer!T;
return c.serialize(a);
}
that won't work with my example:
class A{}
class B:A{int x;}
A a=new B;
auto c=serialize(a); => T is A, but we want B so that
serialization includes field x.
