#![allow(dead_code, deprecated, unused_variables, unused_mut)]
fn main() {
    let mut s: String = "123".to_string();
    let ptr: *mut u8 = s.as_mut_ptr();
    unsafe {
        assert_eq!('2', * ptr.add(1) as char);
        assert_eq!('3', * ptr.add(2) as char);
    }
}