error[E0596]: cannot borrow `*inner` as mutable, as it is behind a `&` reference
  --> $DIR/issue-91206.rs:13:5
   |
LL |     let inner = client.get_inner_ref();
   |         ----- consider changing this binding's type to be: `&mut Vec<usize>`
LL |
LL |     inner.clear();
   |     ^^^^^^^^^^^^^ `inner` is a `&` reference, so the data it refers to cannot be borrowed as mutable

error: aborting due to previous error

For more information about this error, try `rustc --explain E0596`.