[darioush]

this isn't what I would call an abstraction, that's creating a named type. named types are simple because their algebra is also simple and their maintenance cost is low.

problem is more when you have types that "do things" and "have responsibilities" (usually to "do things with other types they hold pointers to, but do not totally own"), such a type is very difficult to maintain because there's now:

- a boundary of its responsibilities that is subjective,

- responsibility of building collaborators and initializing the type

- dealing with test doubles for the collaborators.