#![allow(dead_code, deprecated, unused_variables, unused_mut)]
fn main() {
    let a = ["1", "rust", "3"];
    let mut it = a.iter();
    let sum = it
        .by_ref()
        .map(|&s| s.parse::<i32>())
        .try_rfold(0, |acc, x| x.and_then(|y| Ok(acc + y)));
    assert!(sum.is_err());
    assert_eq!(it.next_back(), Some(& "1"));
}