error[E0596]: cannot borrow `*buf` as mutable, as it is behind a `&` reference --> $DIR/issue-40823.rs:3:5 | LL | buf.iter_mut(); | ^^^ `buf` is a `&` reference, so the data it refers to cannot be borrowed as mutable | help: consider changing this to be a mutable reference | LL | let mut buf = &mut [1, 2, 3, 4]; | +++ error: aborting due to previous error For more information about this error, try `rustc --explain E0596`.