Generational-indices also help to secure system boundaries. The memory is always owned and manipulated by a system, and the system only hands out generational-i

Generational-indices also help to secure system boundaries. The memory is always owned and manipulated by a system, and the system only hands out generational-index-handles as "object references". Arguably that's even a good idea in memory safe languages, it avoids tricky borrow checker issues, and also prevents the outside world to directly manipulate objects. Everything happens under control of the system.