Tweak `&mut self` suggestion span

```
error[E0596]: cannot borrow `*self.s` as mutable, as it is behind a `&` reference
  --> $DIR/issue-38147-1.rs:17:9
   |
LL |         self.s.push('x');
   |         ^^^^^^ `self` is a `&` reference, so the data it refers to cannot be borrowed as mutable
   |
help: consider changing this to be a mutable reference
   |
LL |     fn f(&mut self) {
   |           +++
```

Note the suggestion to add `mut` instead of replacing the entire `&self` with `&mut self`.

0 files changed, 0 insertions, 0 deletions