error[E0277]: expected a `FnMut<(char,)>` closure, found `String`
  --> $DIR/issue-62843.rs:4:32
   |
LL |     println!("{:?}", line.find(pattern));
   |                                ^^^^^^^
   |                                |
   |                                expected an implementor of trait `Pattern<'_>`
   |                                help: consider borrowing here: `&pattern`
   |
   = note: the trait bound `String: Pattern<'_>` is not satisfied
   = note: required because of the requirements on the impl of `Pattern<'_>` for `String`

error: aborting due to previous error

For more information about this error, try `rustc --explain E0277`.