Invalid suggestion to consider borrowing `Option`'s content in tuple

[camsteffen]

Given the following code: (playground)

fn foo(a: &Option<String>, b: &Option<String>) {
    match (a, b) {
        (None, &c) | (&c, None) => &c.unwrap(),
        (&Some(ref c), _) => c,
    };
}

The current output is:

error[E0507]: cannot move out of a shared reference
 --> src/lib.rs:2:11
  |
2 |     match (a, b) {
  |           ^^^^^^ help: consider borrowing the `Option`'s content: `(a, b).as_ref()`
3 |         (None, &c) | (&c, None) => &c.unwrap(),
  |                 -
  |                 |
  |                 data moved here
  |                 move occurs because `c` has type `Option<String>`, which does not implement the `Copy` trait

The suggestion does not compile. Presumably it should suggest (a.as_ref(), b.as_ref()).