#[derive(Debug)]
struct XBuilder{
    val1: Option<i32>,
    val2: Option<i32>,
}

impl XBuilder {
    fn new() -> XBuilder {
        XBuilder {
            val1: None,
            val2: None,
        }
    }
    fn val1(self, x: i32) -> XBuilder {
        XBuilder {
            val1: Some(x),
            ..self
        }
    }

    fn val2(self, x: i32) -> XBuilder {
        XBuilder {
            val2: Some(x),
            ..self
        }
    }
}

fn main() {
    let xb = XBuilder::new();
    let xb = xb.val1(1);

    println!("{:?}", xb);
}