Dispatching values to handlers, as in std.concurrency

["Luís]

I have a list of functions which receive values of different 
types, like in std.concurrency...

     // example from std.concurrency
     receive(
          (int i) { writeln("Received the number ", i);}
      );

...although in my case I can probably live by with only accepting 
objects.

I built a list of the handlers and the message classes they 
accept. My problem is that I don't know how to check if the 
message I have to dispatch is of the class the handler accepts 
*or a subclass*. I only managed to check for class equality:

     if(typeid(msg) == typeHandler.type)
     {
         typeHandler.handler(msg);
     }

How can I also accept subclasses?

Thanks,
Luís