os::copy_file makes a funny smell?

gistfile1.rs

fn copy_warn(src: str, dest: str) {
  if !os::copy_file(src, dest) {
      io::println(#fmt["Copying %s to %s failed", src, dest]);
  }
}

fn main() {
   // EDIT: not so bad, I just wasn't paying attention
   copy_warn("./dir/a", "./dir2"  );
   copy_warn("./dir/a", "./dir2/a");                 // THIS ONE IS OK
}