The arena, a fast but limited type of allocator.
Arenas are a type of allocator that destroy the objects within, all at once, once the arena itself is destroyed. They do not support deallocation of individual objects while the arena itself is still alive. The benefit of an arena is very fast allocation; just a pointer bump.
This crate implements several kinds of arena.
Arena containing one dropless arena and many typed arenas (the
types of the typed arenas are specified by the arguments).
An arena that can hold objects of multiple different types that impl
An arena that can hold objects of only one type.