Now I finally see that deepDup/deepCopy/clone is not a (good)
solution, because it would be inefficient in a lot of situations.
This whole mess makes me wish that D was designed so that all
types had value semantics (by convention, since it's probably not
possible to enforce by the language).
That would mean:
1) No classes. Just duck-typing based polymorphism à la go
language.
2) Dynamic arrays of mutable types would have had to been
implemented as copy-on-write types à la Qt containers.
Don't know about the performance implications of COW though.
