error[E0596]: cannot borrow immutable argument `arg` as mutable
  --> $DIR/mut-suggestion.rs:12:5
   |
LL | fn func(arg: S) {
   |         --- help: make this binding mutable: `mut arg`
...
LL |     arg.mutate();
   |     ^^^ cannot borrow mutably

error[E0596]: cannot borrow immutable local variable `local` as mutable
  --> $DIR/mut-suggestion.rs:21:5
   |
LL |     let local = S;
   |         ----- help: make this binding mutable: `mut local`
...
LL |     local.mutate();
   |     ^^^^^ cannot borrow mutably

error: aborting due to 2 previous errors

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