use superstruct::superstruct;
#[superstruct(variants(V1, V2))]
pub struct Request {
pub start: u16,
#[superstruct(only(V2))]
pub end: u16,
}
#[cfg_attr(test, test)]
fn main() {
let r1 = Request::V1(RequestV1 { start: 0 });
let r2 = Request::V2(RequestV2 { start: 0, end: 10 });
assert_eq!(r1.start(), r2.start());
assert_eq!(r1.end(), Err(()));
assert_eq!(r2.end(), Ok(&10));
}