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.
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.
Thanks for those links. Have you tried using arenas that give out handles (sometimes indexes) instead of mutable references? It's less convenient and you're not leveraging borrow checking but I would imagine it supports Send well.
The borrow checker knows nothing about your arena allocations.
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.
The popular Bumpalo only returns references with the lifetime of the allocator. Not sure what you mean by manage your own garbage, an arena allocator deallocates everything when it goes out of scope. You definitely can't reference uninitialized parts of an arena.
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.