Recently I've encountered a problem, when I wanted to return a slice of bytes in an integer:

fn to_bytes(num: &u32) -> &[u8] {
    &u32::to_le_bytes(*num)
}

(This is an oversimplification of the original code, which is generic over every integer type along with other stuff)

Obviously, since to_le_bytes(*num) is dropped when the function returns, this piece of code failed the borrow check. Hence my need for as_le_bytes(num), as num is actually alive all this time!