$ cargo run
   Compiling rectangles v0.1.0 (file:///projects/rectangles)
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.61s
     Running `target/debug/rectangles`
[src/main.rs:10:16] 30 * scale = 60
[src/main.rs:14:5] &rect1 = Rectangle {
    width: 60,
    height: 50,
}