how.rs

fn mount<T, P, B: FnMut(&mut P)>(
    component: fn(this: Option<T>, props: P, block: B) -> T,
    props: P,
    block: B,
) {
    component(None, props, block);
}

struct Props<T: FnMut()> {
    on_click: T,
}

fn component<B: FnMut(&mut Props<T>), T: FnMut()>(a: Option<u32>, mut props: Props<T>, mut block: B) -> u32 {
    block(&mut props);
    a.or_else(|| Some(0)).unwrap()
}

fn main() {
    let mut x = 0;

    mount(
        component,
        Props {
            on_click: || x += 10,
        },
        |props| {
          (props.on_click)();
          print!("A");
      },
    );

    mount(
        component,
        Props {
            on_click: || x += 10,
        },
        |props| {
            (props.on_click)();
            print!("A");
        },
    );

    println!("{}", x);
}