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

error: aborting due to 1 previous error

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