use std::collections::HashMap;

struct S {
  id: i32,
  value: i32,
}

fn main() {
  let v1 = vec![
    S { id: 0, value: 0 },
    S { id: 1, value: 1 },
    S { id: 2, value: 2 },
    S { id: 3, value: 3 },
  ];
  let v2 = vec![
    S { id: 3, value: 3 },
    S { id: 0, value: 0 },
    S { id: 2, value: 2 },
    S { id: 1, value: 1 },
  ];

  // this works
  {
    let mut m1 = HashMap::new();
    let mut m2 = HashMap::new();

    assert_eq!(v1.len(), v2.len());

    for i in 0..v1.len() {
      m1.insert(v1[i].id, v1[i].value);
      m2.insert(v2[i].id, v2[i].value);
    }

    for (id1, val1) in m1 {
      let val2 = m2.get(&id1).unwrap().clone();
      assert_eq!(val1, val2);
    }
  }

  // this doesn't work
  {
    for (item1, item2) in v1.iter().zip(v2) {
      assert_eq!(item1.value, item2.value);
    }
  }
}