It’s just the compiler assuming you know what you’re doing. You’re building this data structure on the stack, so it’ll point out where you’re not sufficiently e

It’s just the compiler assuming you know what you’re doing. You’re building this data structure on the stack, so it’ll point out where you’re not sufficiently explaining to it how the lifetimes of your code are safe. And even if you build it on the heap (using Box) you’ll still need to get the ownership right (using e.g. Rc). There’s only so many variations that work for something like trees (especially with doubly linked nodes) in any language, without either inherently unsafe lifetimes (because the particular language can’t express them as part of the API) or some kind of indirection (such as ECS style indices). Or garbage collection or ref counting, but one probably uses Rust to be able to control that kind of overhead instead of having to use whatever the language creators picked. If you want to learn about this, instead of using a ‘blessed’ implementation, read “too many linked lists” https://rust-unofficial.github.io/too-many-lists/ https://rust-unofficial.github.io/too-many-lists/. As for the front-loading comment: yes, Rust requires you to get some things right from the start, particularly ownership and lifetimes. If you want to work in Rust like in a scripting language, you can just use Box, Rc and clone() everywhere. But getting it right without those might require a significantly different API. Which isn’t that much different with your rough C implementation. To get any kind of safe API there will require just as many changes (if not more).