alt Hacker News fn f() {
let mut v = vec![1, 2, 3, 4, 5];
let (header, tail) = v.split_at_mut(1);
b(&header[0], &mut tail[0]);
} fn f() {
let mut v = vec![1, 2, 3, 4, 5];
let (header, tail) = v.split_at_mut(1);
b(&header[0], &mut tail[0]);
}
split_at_mut is just unsafe code (and sibling comment mentioned it hours before you did). The borrow checker doesn't natively understand that.