For those who are interested, I think that arena allocation is an underrated approach to managing lifetimes of interconnected objects that works well with borrow checking.
I was previously excited about this project which proposed to support arena allocation in the language in a more fundamental way: https://www.sophiajt.com/search-for-easier-safe-systems-prog...
That effort was focused primarily on learnability and teachability, but it seems like more fundamental arena support could help even for experienced devs if it made patterns like linked lists fundamentally easier to work with.
Yes, because it defeats borrow checking.
Unsafe Rust, used directly, works too
That is if we are talking about the same thing!
All the borrow checker knows is there is a chunk of memory (the arena) in scope.
It works, no memory safety in the sense that you must manage your own garbage and you can reference uninitialized parts of the arena
I have found myself using arenas in Rust for managing circular references (networks with cycles) and if I were to do it again I think I would write that bit in C or unsafe Rust.