Patterns
https://doc.rust-lang.org/book/patterns.html
構造体のmatchもできるのが便利。
struct Point { x: i32, y: i32, } let origin = Point { x: 2, y: 4 }; match origin { Point { x, y } => println!("({},{})", x, y), } // -> (2,4) match origin { Point { x, .. } => println!("x is {}", x), } // -> x is 2 match origin { Point { y, .. } => println!("y is {}", y), } // -> y is 4