std.concurrency.send

[japplegame]

Multithreading in D confuses me more and more.

import std.concurrency;
import std.stdio;
shared Tid tid;
void main() {
   send(cast(Tid)tid, "Hello, World");
}
void worker() {
    writeln(receiveOnly!string);
}
shared static this() {
   tid = cast(shared)spawn(&worker);
}

I hate these explicit casts. It is impossible sharing anything 
between threads without these ugly casts from/to shared. Seems 
like something wrong in program design when I'm forced to use 
explicit casts. But I don't understand what is it exactly.

For example. I need create mutable object in one thread and send 
to another. I don't need to share this object, just create, send 
and forget. But I have no idea how make this without using shared 
attribute and casting to/from it.