struct Some[T](value: T) {}

struct None() {}

sumtype Option[T] = Some[T] | None;

pub fun main() ! Io -> Unit {
    printOption!(Some[String]("hello, world!"));
    printOption!(None());
}

fun printOption(option: Option[String]) !Io -> Unit {
    when (option) {
        is Some[String] {
            print!("Some(");
            print!(option.value);
            print!(")\n");
        }
        is None {
            print!("None\n");
        }
    }
}