What is the easiest way to deeply clone (copy) a mutable Scala object?
Since you want the easiest way to deep copy a Scala object and not the fastest, you can always serialize the object, provided that it's serializable, and then deserialize it back. The following code only runs when compiled, not in REPL.
def deepCopy[A](a: A)(implicit m: reflect.Manifest[A]): A =
util.Marshal.load[A](util.Marshal.dump(a))
val o1 = new Something(...) // "Something" has to be serializable
val o2 = deepCopy(o1)