error[E0507]: cannot move out of borrowed content
  --> $DIR/issue-51415.rs:16:42
   |
LL |     let opt = a.iter().enumerate().find(|(_, &s)| {
   |                                          ^^^^^-^
   |                                          |    |
   |                                          |    data moved here
   |                                          |    help: to prevent move, use ref or ref mut: `ref s`
   |                                          cannot move out of borrowed content

error: aborting due to previous error

For more information about this error, try `rustc --explain E0507`.