deref.rs

// 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/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/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 }
}