Global counter.rs

use std::collections::HashMap;

static GLOBAL_COUNTER: std::sync::atomic::AtomicUsize = std::sync::atomic::AtomicUsize::new(0);

#[derive(Hash, Eq, PartialEq, Debug)]
struct TypeA {
    a: usize,
    id: usize,
}

impl TypeA {
    fn new(a: usize) -> Self {
        let id:usize = {
            GLOBAL_COUNTER.fetch_add(1, std::sync::atomic::Ordering::SeqCst);
            GLOBAL_COUNTER
                .load(std::sync::atomic::Ordering::SeqCst)
                .into()
        };
        Self { id, a }
    }
}

#[derive(Hash, Eq, PartialEq, Debug)]
struct TypeB {
    b: usize,
}

fn main() {
    let mut map: HashMap<&TypeA, &TypeB> = HashMap::new();
    let a0 = TypeA::new(1);
    let b0 = TypeB { b: 111 };
    map.insert(&a0, &b0);

    let a1 = TypeA::new(1);
    let b1 = TypeB { b: 222 };
    map.insert(&a1, &b1);

    let b_for_a0 = map.get(&a0);
    println!("{:?}", b_for_a0); // gives Some(TypeB { b: 222 }) - not the expected Some(TypeB { b: 111 })...
}