error[E0596]: cannot borrow `v` as mutable, as it is not declared as mutable --> $DIR/borrowck-mut-slice-of-imm-vec.rs:7:11 | LL | write(&mut v); | ^^^^^^ cannot borrow as mutable | help: consider changing this to be mutable | LL | let mut v = vec![1, 2, 3]; | +++ error: aborting due to previous error For more information about this error, try `rustc --explain E0596`.