I'd like to use an arena allocator to allocate `ref object` s (for spatial locality). Is it possible get `ref object` s to allocate on my specific memory region? I'm thinking something like `emplace` in D: <https://dlang.org/phobos/core_lifetime.html#.emplace.3>.
I'd also like to explore freeing the arena all at once but I'm assuming that'd break the ARC. I can do what I have mind with plain `object` s and getters returning `var T` but I lose the ability to that with library types.
