rust - How to pass `Option<&mut ...>` to multiple function calls without causing move errors? -

since it's possible pass mutable reference vector around (without causing moves), how can option<reference> passed functions multiple times without causing borrow checking errors?

this simple example shows happens when option<&mut vec<usize>> passed multiple times function:

fn maybe_push(mut v_option: option<&mut vec<usize>>) -> usize {     let mut c = 0;     if let some(ref mut v) = v_option.as_mut() {         in 0..10 {             v.push(i);             c += i;         }     }      return c; }  fn maybe_push_multi(v_option: option<&mut vec<usize>>) -> usize {     let mut c = 0;     c += maybe_push(v_option);     c += maybe_push(v_option);     c += maybe_push(none);     return c; }  fn main() {     let mut v: vec<usize> = vec![];     let v_option = some(&mut v);     println!("{}", maybe_push_multi(v_option)); } 

(playground)

gives error:

error[e0382]: use of moved value: `v_option`   --> <anon>:17:21    | 16 |     c += maybe_push(v_option);    |                     -------- value moved here 17 |     c += maybe_push(v_option);    |                     ^^^^^^^^ value used here after move    |    = note: move occurs because `v_option` has type `std::option::option<&mut std::vec::vec<usize>>`, not implement `copy` trait 

you can pass option reference too, if don't want moved function.

fn maybe_push(mut v_option: &mut option<&mut vec<usize>>) -> usize  // ...  maybe_push_twice(&mut v_option); 

then replace:

maybe_push(none); 

with:

maybe_push(&mut none);