error[E0277]: expected a `FnMut(char)` closure, found `u8` --> $DIR/assoc-fn-bound-root-obligation.rs:2:7 | LL | s.strip_suffix(b'\n').unwrap_or(s) | ^^^^^^^^^^^^ expected an `FnMut(char)` closure, found `u8` | = help: the trait `FnMut<(char,)>` is not implemented for `u8` = help: the following other types implement trait `Pattern<'a>`: char [char; N] &'b String &'b [char; N] &'b [char] &'c &'b str &'b str = note: required for `u8` to implement `Pattern<'_>` error: aborting due to previous error For more information about this error, try `rustc --explain E0277`.