error[E0277]: the trait bound `&[u8]: std::io::Write` is not satisfied --> $DIR/issue-105645.rs:4:9 | LL | foo(&mut bref); | --- ^^^^^^^^^ the trait `std::io::Write` is not implemented for `&[u8]` | | | required by a bound introduced by this call | = help: the trait `std::io::Write` is implemented for `&mut [u8]` note: required by a bound in `foo` --> $DIR/issue-105645.rs:8:21 | LL | fn foo(_: &mut impl std::io::Write) {} | ^^^^^^^^^^^^^^ required by this bound in `foo` error: aborting due to previous error For more information about this error, try `rustc --explain E0277`.