Cannot obtain a mutable reference when iterating a recursive structure: cannot borrow as mutable more than once at a time

Question

I\'m trying to navigate a recursive data structure iteratively in order to insert elements at a certain position. To my limited understanding, this means taking a mutable re

Answer 1

You can use recursion to satisfy the borrow checker. This has the disadvantage of creating a stack frame for every item in your list. If your list is long, this will definitely run into a stack overflow. LLVM will optimize the Node::back method into a loop (see the LLVM IR generated on the playground)

impl Node {
    fn back(&mut self) -> &mut Link {
        match self.next {
            Some(ref mut node) => node.back(),
            None => &mut self.next,
        }
    }
}

impl Recursive {
    fn back(&mut self) -> Option<&mut Link> {
        self.root.as_mut().map(|node| node.back())
    }
}