Code shared from the Rust Playground

playground.rs

macro_rules! run {
    ($a:expr) => {{
        println!("{:?}", $a);
    }};
}

#[derive(Debug)]
enum UiNode<'a> {
    Window { content: &'a UiNode<'a> },
    Column { content: Vec<UiNode<'a>> },
    Label { text: &'a str },
    Button { text: &'a str, on_click: fn() -> () },
}

fn main() {
    fn on_button_click() {}

    run! {
        UiNode::Window {
            content: &UiNode::Column {
                content: vec![
                    UiNode::Label {
                        text: "Hello World"
                    },
                    UiNode::Button {
                        text: "Say Hi!",
                        on_click: on_button_click
                    }
                ]
            }
        }
    }
}