44 lines
1.1 KiB
Rust
44 lines
1.1 KiB
Rust
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// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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#![feature(untagged_unions)]
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union MaybeItem<T: Iterator> {
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elem: T::Item,
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none: (),
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}
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union U<A, B> {
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a: A,
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b: B,
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}
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unsafe fn union_transmute<A, B>(a: A) -> B {
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U { a: a }.b
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}
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fn main() {
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unsafe {
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let u = U::<String, Vec<u8>> { a: String::from("abcd") };
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assert_eq!(u.b.len(), 4);
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assert_eq!(u.b[0], b'a');
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let b = union_transmute::<(u8, u8), u16>((1, 1));
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assert_eq!(b, (1 << 8) + 1);
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let v: Vec<u8> = vec![1, 2, 3];
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let mut i = v.iter();
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i.next();
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let mi = MaybeItem::<std::slice::Iter<_>> { elem: i.next().unwrap() };
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assert_eq!(*mi.elem, 2);
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}
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}
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