#[derive(Debug)]
enum Shape { Circle { r: f64 }, Rect { w: f64, h: f64 }, Dot }

fn main() {

let mut shapes: Vec<Shape> = Vec::new();
shapes.push(Shape::Circle { r: 1.0 });
shapes.push(Shape::Rect { w: 2.0, h: 3.0 });
shapes.push(Shape::Dot);
shapes[2] = Shape::Rect { w: 1.0, h: 1.0 };

assert!(matches!(shapes[2],Shape::Rect {w:1.0,h:1.0}));
}