I've been poking around with porting the Classpath implementation of Java's Collection Framework and have bumped up against the following linux bug:

interface Iterator(T) {}
interface Iterable(T) {
  Iterator!(T) foo();
}
class List(T) : Iterable!(T) {
  Iterator!(T) foo() {return new ListIterator!(T);}
}
class ListIterator(T) : Iterator!(T) {}
int main() {
  List!(int) x = new List!(int);
  return 0;
}

compile with dmd-0.95 on linux gives

gcc foo.o -o foo -lphobos -lpthread -lm foo.o(.gnu.linkonce.d._Class_3foo14ListIterator_i12ListIterator+0x3c): undefined reference to `_Interface_3foo10Iterator_i8Iterator' collect2: ld returned 1 exit status
--- errorlevel 1

I haven't tried on Windows. I haven't found any workarounds.

-Ben