I was solving 203. Remove Linked List Elements and thought that I easily figured out the solution:

#[derive(PartialEq, Eq, Clone, Debug)]
pub struct ListNode {
    pub val: i32,
    pub next: Option<Box<ListNode>>,
}

impl ListNode {
    #[inline]
    pub fn new(val: i32, next: Option<Box<ListNode>>) -> Self {
        ListNode { val, next }
    }
}

pub struct Solution;

impl Solution {
    pub fn remove_elements(mut head: Option<Box<ListNode>>, val: i32) -> Option<Box<ListNode>> {
        let mut current = &mut head;
        while let Some(current_node) = current {
            if current_node.val == val {
                *current = current_node.next.take();
            } else {
                current = &mut current_node.next;
            }
        }
        head
    }
}

But unfortunately I ran into a problem:

error[E0506]: cannot assign to `*current` because it is borrowed
  --> src/solutions/p0203.rs:21:17
   |
19 |         while let Some(current_node) = current {
   |                        ------------ `*current` is borrowed here
20 |             if current_node.val == val {
21 |                 *current = current_node.next.take();
   |                 ^^^^^^^^
   |                 |
   |                 `*current` is assigned to here but it was already borrowed
   |                 borrow later used here

Also after this issue I wandered how to solve it, so I look thru the solutions and found this guy, and his code has no errors.

pub fn remove_elements(mut head: Option<Box<ListNode>>, val: i32) -> Option<Box<ListNode>> {
   let mut pp = &mut head;
   while( (*pp).is_some() ){
    if( (*pp).as_ref().unwrap().val == val ){
        *pp = (*pp).as_mut().unwrap().next.take();
    }else{
        pp = &mut ((*pp).as_mut().unwrap().next);
    }
   }
   head
}

I kinda feel that the problem is with Some(_) = value, where the value is borrowed. But I like the look of while let with Some(_) in this situation, while we deal with Option, because in my opinion it feels much cleaner.

So the question is: how to fix this problem?