Adding an append method to a singly linked list

I was looking through the singly linked list example on rustbyexample.com and I noticed the implementation had no append method, so I decided to try and implement it:

fn append(self, elem: u32) -> List {
    let mut node = &self;
    loop { 
        match *node {
            Cons(_, ref tail) => {
                node = tail;
            },
            Nil => {
                node.prepend(elem);
                break;
            },
        }
    }
    return self;
}

The above is one of many different attempts, but I cannot seem to find a way to iterate down to the tail and modify it, then somehow return the head, without upsetting the borrow checker in some way.

I am trying to figure out a solution that doesn't involve copying data or doing additional bookkeeping outside the append method.