pub trait Widget<'a> {
    fn addChild(&mut self, child: &'a Widget<'a>);
}

pub struct WidgetImpl<'a> {
    pub children: Vec<&'a Widget<'a>>
}

impl<'a> WidgetImpl<'a> {
    pub fn new() -> Self {
        let children: Vec<&'a Widget<'a>> = Vec::new();
        WidgetImpl {
            children
        }
    }
}

impl<'a> Widget<'a> for WidgetImpl<'a> {
    fn addChild(&mut self, child: &'a Widget<'a>) {
        self.children.push(child);
    }

}



fn main() {
    println!("Hello, world!");
}