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    // Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
    // file at the top-level directory of this distribution and at
    // http://rust-lang.org/COPYRIGHT.
    //
    // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
    // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
    // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
    // option. This file may not be copied, modified, or distributed
    // except according to those terms.

    //! Exposes the NonZero lang item which provides optimization hints.
    #![unstable(feature = "nonzero",
                reason = "needs an RFC to flesh out the design",
                issue = "27730")]

    use marker::Sized;
    use ops::{CoerceUnsized, Deref};

    /// Unsafe trait to indicate what types are usable with the NonZero struct
    pub unsafe trait Zeroable {}

    unsafe impl<T:?Sized> Zeroable for *const T {}
    unsafe impl<T:?Sized> Zeroable for *mut T {}
    unsafe impl Zeroable for isize {}
    unsafe impl Zeroable for usize {}
    unsafe impl Zeroable for i8 {}
    unsafe impl Zeroable for u8 {}
    unsafe impl Zeroable for i16 {}
    unsafe impl Zeroable for u16 {}
    unsafe impl Zeroable for i32 {}
    unsafe impl Zeroable for u32 {}
    unsafe impl Zeroable for i64 {}
    unsafe impl Zeroable for u64 {}

    /// A wrapper type for raw pointers and integers that will never be
    /// NULL or 0 that might allow certain optimizations.
    #[lang = "non_zero"]
    #[derive(Copy, Clone, Eq, PartialEq, Ord, PartialOrd, Debug, Hash)]
    pub struct NonZero<T: Zeroable>(T);

    impl<T: Zeroable> NonZero<T> {
        /// Creates an instance of NonZero with the provided value.
        /// You must indeed ensure that the value is actually "non-zero".
        #[inline(always)]
        pub const unsafe fn new(inner: T) -> NonZero<T> {
            NonZero(inner)
        }
    }

    impl<T: Zeroable> Deref for NonZero<T> {
        type Target = T;

        #[inline]
        fn deref(&self) -> &T {
            let NonZero(ref inner) = *self;
            inner
        }
    }

    impl<T: Zeroable+CoerceUnsized<U>, U: Zeroable> CoerceUnsized<NonZero<U>> for NonZero<T> {}

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