| // run-pass |
| #![allow(dead_code)] |
| #![allow(unions_with_drop_fields)] |
| |
| #![feature(untagged_unions)] |
| |
| union MaybeItem<T: Iterator> { |
| elem: T::Item, |
| none: (), |
| } |
| |
| union U<A, B> { |
| a: A, |
| b: B, |
| } |
| |
| unsafe fn union_transmute<A, B>(a: A) -> B { |
| U { a: a }.b |
| } |
| |
| fn main() { |
| unsafe { |
| let u = U::<String, Vec<u8>> { a: String::from("abcd") }; |
| |
| assert_eq!(u.b.len(), 4); |
| assert_eq!(u.b[0], b'a'); |
| |
| let b = union_transmute::<(u8, u8), u16>((1, 1)); |
| assert_eq!(b, (1 << 8) + 1); |
| |
| let v: Vec<u8> = vec![1, 2, 3]; |
| let mut i = v.iter(); |
| i.next(); |
| let mi = MaybeItem::<std::slice::Iter<_>> { elem: i.next().unwrap() }; |
| assert_eq!(*mi.elem, 2); |
| } |
| } |