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    // Copyright 2012 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.

    /// The `Deref` trait is used to specify the functionality of dereferencing
    /// operations, like `*v`.
    ///
    /// `Deref` also enables ['`Deref` coercions'][coercions].
    ///
    /// [coercions]: ../../book/first-edition/deref-coercions.html
    ///
    /// # Examples
    ///
    /// A struct with a single field which is accessible via dereferencing the
    /// struct.
    ///
    /// ```
    /// use std::ops::Deref;
    ///
    /// struct DerefExample<T> {
    ///     value: T
    /// }
    ///
    /// impl<T> Deref for DerefExample<T> {
    ///     type Target = T;
    ///
    ///     fn deref(&self) -> &T {
    ///         &self.value
    ///     }
    /// }
    ///
    /// fn main() {
    ///     let x = DerefExample { value: 'a' };
    ///     assert_eq!('a', *x);
    /// }
    /// ```
    #[lang = "deref"]
    #[stable(feature = "rust1", since = "1.0.0")]
    pub trait Deref {
        /// The resulting type after dereferencing
        #[stable(feature = "rust1", since = "1.0.0")]
        type Target: ?Sized;

        /// The method called to dereference a value
        #[stable(feature = "rust1", since = "1.0.0")]
        fn deref(&self) -> &Self::Target;
    }

    #[stable(feature = "rust1", since = "1.0.0")]
    impl<'a, T: ?Sized> Deref for &'a T {
        type Target = T;

        fn deref(&self) -> &T { *self }
    }

    #[stable(feature = "rust1", since = "1.0.0")]
    impl<'a, T: ?Sized> Deref for &'a mut T {
        type Target = T;

        fn deref(&self) -> &T { *self }
    }

    /// The `DerefMut` trait is used to specify the functionality of dereferencing
    /// mutably like `*v = 1;`
    ///
    /// `DerefMut` also enables ['`Deref` coercions'][coercions].
    ///
    /// [coercions]: ../../book/first-edition/deref-coercions.html
    ///
    /// # Examples
    ///
    /// A struct with a single field which is modifiable via dereferencing the
    /// struct.
    ///
    /// ```
    /// use std::ops::{Deref, DerefMut};
    ///
    /// struct DerefMutExample<T> {
    ///     value: T
    /// }
    ///
    /// impl<T> Deref for DerefMutExample<T> {
    ///     type Target = T;
    ///
    ///     fn deref(&self) -> &T {
    ///         &self.value
    ///     }
    /// }
    ///
    /// impl<T> DerefMut for DerefMutExample<T> {
    ///     fn deref_mut(&mut self) -> &mut T {
    ///         &mut self.value
    ///     }
    /// }
    ///
    /// fn main() {
    ///     let mut x = DerefMutExample { value: 'a' };
    ///     *x = 'b';
    ///     assert_eq!('b', *x);
    /// }
    /// ```
    #[lang = "deref_mut"]
    #[stable(feature = "rust1", since = "1.0.0")]
    pub trait DerefMut: Deref {
        /// The method called to mutably dereference a value
        #[stable(feature = "rust1", since = "1.0.0")]
        fn deref_mut(&mut self) -> &mut Self::Target;
    }

    #[stable(feature = "rust1", since = "1.0.0")]
    impl<'a, T: ?Sized> DerefMut for &'a mut T {
        fn deref_mut(&mut self) -> &mut T { *self }
    }

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