类型系统高级特性 #

type Kilometers = i32;
type Thunk = Box<dyn Fn() + Send + 'static>;

fn main() {
    let distance: Kilometers = 100;
    println!("{}", distance);
}

fn bar() -> ! {
    loop {
        // 永不返回
    }
}

fn main() {
    let s1: &str = "hello";
    let s2: &str = "world";
}

struct Millimeters(u32);
struct Meters(u32);

impl Millimeters {
    fn from_meters(m: Meters) -> Self {
        Millimeters(m.0 * 1000)
    }
}