error[E0277]: expected a `FnMut(char)` closure, found `String` --> $DIR/issue-62843.rs:4:32 | LL | println!("{:?}", line.find(pattern)); | ---- ^^^^^^^ the trait `Pattern<'_>` is not implemented for `String` | | | required by a bound introduced by this call | = note: the trait bound `String: Pattern<'_>` is not satisfied = note: required for `String` to implement `Pattern<'_>` note: required by a bound in `core::str::::find` --> $SRC_DIR/core/src/str/mod.rs:LL:COL help: consider borrowing here | LL | println!("{:?}", line.find(&pattern)); | + error: aborting due to 1 previous error For more information about this error, try `rustc --explain E0277`.