<!DOCTYPE html> <html lang="en"> <head> <meta charset="utf-8"> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <meta name="generator" content="rustdoc"> <meta name="description" content="Source to the Rust file `libcore/ops/deref.rs`."> <meta name="keywords" content="rust, rustlang, rust-lang"> <title>deref.rs.html -- source</title> <link rel="stylesheet" type="text/css" href="../../../normalize.css"> <link rel="stylesheet" type="text/css" href="../../../rustdoc.css" id="mainThemeStyle"> <link rel="stylesheet" type="text/css" href="../../../dark.css"> <link rel="stylesheet" type="text/css" href="../../../main.css" id="themeStyle"> <script src="../../../storage.js"></script> <link rel="shortcut icon" href="https://doc.rust-lang.org/favicon.ico"> </head> <body class="rustdoc source"> <!--[if lte IE 8]> <div class="warning"> This old browser is unsupported and will most likely display funky things. </div> <![endif]--> <nav class="sidebar"> <div class="sidebar-menu">☰</div> <a href='../../../core/index.html'><img src='https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png' alt='logo' width='100'></a> </nav> <div class="theme-picker"> <button id="theme-picker" aria-label="Pick another theme!"> <img src="../../../brush.svg" width="18" alt="Pick another theme!"> </button> <div id="theme-choices"></div> </div> <script src="../../../theme.js"></script> <nav class="sub"> <form class="search-form js-only"> <div class="search-container"> <input class="search-input" name="search" autocomplete="off" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"> </div> </form> </nav> <section id='main' class="content"><pre class="line-numbers"><span id="1"> 1</span> <span id="2"> 2</span> <span id="3"> 3</span> <span id="4"> 4</span> <span id="5"> 5</span> <span id="6"> 6</span> <span id="7"> 7</span> <span id="8"> 8</span> <span id="9"> 9</span> <span id="10"> 10</span> <span id="11"> 11</span> <span id="12"> 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id="169">169</span> <span id="170">170</span> <span id="171">171</span> <span id="172">172</span> <span id="173">173</span> <span id="174">174</span> <span id="175">175</span> </pre><pre class="rust "> <span class="comment">// Copyright 2012 The Rust Project Developers. See the COPYRIGHT</span> <span class="comment">// file at the top-level directory of this distribution and at</span> <span class="comment">// http://rust-lang.org/COPYRIGHT.</span> <span class="comment">//</span> <span class="comment">// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or</span> <span class="comment">// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license</span> <span class="comment">// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your</span> <span class="comment">// option. This file may not be copied, modified, or distributed</span> <span class="comment">// except according to those terms.</span> <span class="doccomment">/// Used for immutable dereferencing operations, like `*v`.</span> <span class="doccomment">///</span> <span class="doccomment">/// In addition to being used for explicit dereferencing operations with the</span> <span class="doccomment">/// (unary) `*` operator in immutable contexts, `Deref` is also used implicitly</span> <span class="doccomment">/// by the compiler in many circumstances. This mechanism is called</span> <span class="doccomment">/// ['`Deref` coercion'][more]. In mutable contexts, [`DerefMut`] is used.</span> <span class="doccomment">///</span> <span class="doccomment">/// Implementing `Deref` for smart pointers makes accessing the data behind them</span> <span class="doccomment">/// convenient, which is why they implement `Deref`. On the other hand, the</span> <span class="doccomment">/// rules regarding `Deref` and [`DerefMut`] were designed specifically to</span> <span class="doccomment">/// accommodate smart pointers. Because of this, **`Deref` should only be</span> <span class="doccomment">/// implemented for smart pointers** to avoid confusion.</span> <span class="doccomment">///</span> <span class="doccomment">/// For similar reasons, **this trait should never fail**. Failure during</span> <span class="doccomment">/// dereferencing can be extremely confusing when `Deref` is invoked implicitly.</span> <span class="doccomment">///</span> <span class="doccomment">/// # More on `Deref` coercion</span> <span class="doccomment">///</span> <span class="doccomment">/// If `T` implements `Deref<Target = U>`, and `x` is a value of type `T`, then:</span> <span class="doccomment">///</span> <span class="doccomment">/// * In immutable contexts, `*x` on non-pointer types is equivalent to</span> <span class="doccomment">/// `*Deref::deref(&x)`.</span> <span class="doccomment">/// * Values of type `&T` are coerced to values of type `&U`</span> <span class="doccomment">/// * `T` implicitly implements all the (immutable) methods of the type `U`.</span> <span class="doccomment">///</span> <span class="doccomment">/// For more details, visit [the chapter in *The Rust Programming Language*]</span> <span class="doccomment">/// [book] as well as the reference sections on [the dereference operator]</span> <span class="doccomment">/// [ref-deref-op], [method resolution] and [type coercions].</span> <span class="doccomment">///</span> <span class="doccomment">/// [book]: ../../book/second-edition/ch15-02-deref.html</span> <span class="doccomment">/// [`DerefMut`]: trait.DerefMut.html</span> <span class="doccomment">/// [more]: #more-on-deref-coercion</span> <span class="doccomment">/// [ref-deref-op]: ../../reference/expressions/operator-expr.html#the-dereference-operator</span> <span class="doccomment">/// [method resolution]: ../../reference/expressions/method-call-expr.html</span> <span class="doccomment">/// [type coercions]: ../../reference/type-coercions.html</span> <span class="doccomment">///</span> <span class="doccomment">/// # Examples</span> <span class="doccomment">///</span> <span class="doccomment">/// A struct with a single field which is accessible by dereferencing the</span> <span class="doccomment">/// struct.</span> <span class="doccomment">///</span> <span class="doccomment">/// ```</span> <span class="doccomment">/// use std::ops::Deref;</span> <span class="doccomment">///</span> <span class="doccomment">/// struct DerefExample<T> {</span> <span class="doccomment">/// value: T</span> <span class="doccomment">/// }</span> <span class="doccomment">///</span> <span class="doccomment">/// impl<T> Deref for DerefExample<T> {</span> <span class="doccomment">/// type Target = T;</span> <span class="doccomment">///</span> <span class="doccomment">/// fn deref(&self) -> &T {</span> <span class="doccomment">/// &self.value</span> <span class="doccomment">/// }</span> <span class="doccomment">/// }</span> <span class="doccomment">///</span> <span class="doccomment">/// let x = DerefExample { value: 'a' };</span> <span class="doccomment">/// assert_eq!('a', *x);</span> <span class="doccomment">/// ```</span> <span class="attribute">#[<span class="ident">lang</span> <span class="op">=</span> <span class="string">"deref"</span>]</span> <span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span> <span class="kw">pub</span> <span class="kw">trait</span> <span class="ident">Deref</span> { <span class="doccomment">/// The resulting type after dereferencing.</span> <span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span> <span class="kw">type</span> <span class="ident">Target</span>: <span class="question-mark">?</span><span class="ident">Sized</span>; <span class="doccomment">/// Dereferences the value.</span> <span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span> <span class="kw">fn</span> <span class="ident">deref</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="kw-2">&</span><span class="self">Self</span>::<span class="ident">Target</span>; } <span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span> <span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">T</span>: <span class="question-mark">?</span><span class="ident">Sized</span><span class="op">></span> <span class="ident">Deref</span> <span class="kw">for</span> <span class="kw-2">&</span><span class="lifetime">'a</span> <span class="ident">T</span> { <span class="kw">type</span> <span class="ident">Target</span> <span class="op">=</span> <span class="ident">T</span>; <span class="kw">fn</span> <span class="ident">deref</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="kw-2">&</span><span class="ident">T</span> { <span class="kw-2">*</span><span class="self">self</span> } } <span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span> <span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">T</span>: <span class="question-mark">?</span><span class="ident">Sized</span><span class="op">></span> <span class="ident">Deref</span> <span class="kw">for</span> <span class="kw-2">&</span><span class="lifetime">'a</span> <span class="kw-2">mut</span> <span class="ident">T</span> { <span class="kw">type</span> <span class="ident">Target</span> <span class="op">=</span> <span class="ident">T</span>; <span class="kw">fn</span> <span class="ident">deref</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="kw-2">&</span><span class="ident">T</span> { <span class="kw-2">*</span><span class="self">self</span> } } <span class="doccomment">/// Used for mutable dereferencing operations, like in `*v = 1;`.</span> <span class="doccomment">///</span> <span class="doccomment">/// In addition to being used for explicit dereferencing operations with the</span> <span class="doccomment">/// (unary) `*` operator in mutable contexts, `DerefMut` is also used implicitly</span> <span class="doccomment">/// by the compiler in many circumstances. This mechanism is called</span> <span class="doccomment">/// ['`Deref` coercion'][more]. In immutable contexts, [`Deref`] is used.</span> <span class="doccomment">///</span> <span class="doccomment">/// Implementing `DerefMut` for smart pointers makes mutating the data behind</span> <span class="doccomment">/// them convenient, which is why they implement `DerefMut`. On the other hand,</span> <span class="doccomment">/// the rules regarding [`Deref`] and `DerefMut` were designed specifically to</span> <span class="doccomment">/// accommodate smart pointers. Because of this, **`DerefMut` should only be</span> <span class="doccomment">/// implemented for smart pointers** to avoid confusion.</span> <span class="doccomment">///</span> <span class="doccomment">/// For similar reasons, **this trait should never fail**. Failure during</span> <span class="doccomment">/// dereferencing can be extremely confusing when `DerefMut` is invoked</span> <span class="doccomment">/// implicitly.</span> <span class="doccomment">///</span> <span class="doccomment">/// # More on `Deref` coercion</span> <span class="doccomment">///</span> <span class="doccomment">/// If `T` implements `DerefMut<Target = U>`, and `x` is a value of type `T`,</span> <span class="doccomment">/// then:</span> <span class="doccomment">///</span> <span class="doccomment">/// * In mutable contexts, `*x` on non-pointer types is equivalent to</span> <span class="doccomment">/// `*Deref::deref(&x)`.</span> <span class="doccomment">/// * Values of type `&mut T` are coerced to values of type `&mut U`</span> <span class="doccomment">/// * `T` implicitly implements all the (mutable) methods of the type `U`.</span> <span class="doccomment">///</span> <span class="doccomment">/// For more details, visit [the chapter in *The Rust Programming Language*]</span> <span class="doccomment">/// [book] as well as the reference sections on [the dereference operator]</span> <span class="doccomment">/// [ref-deref-op], [method resolution] and [type coercions].</span> <span class="doccomment">///</span> <span class="doccomment">/// [book]: ../../book/second-edition/ch15-02-deref.html</span> <span class="doccomment">/// [`Deref`]: trait.Deref.html</span> <span class="doccomment">/// [more]: #more-on-deref-coercion</span> <span class="doccomment">/// [ref-deref-op]: ../../reference/expressions/operator-expr.html#the-dereference-operator</span> <span class="doccomment">/// [method resolution]: ../../reference/expressions/method-call-expr.html</span> <span class="doccomment">/// [type coercions]: ../../reference/type-coercions.html</span> <span class="doccomment">///</span> <span class="doccomment">/// # Examples</span> <span class="doccomment">///</span> <span class="doccomment">/// A struct with a single field which is modifiable by dereferencing the</span> <span class="doccomment">/// struct.</span> <span class="doccomment">///</span> <span class="doccomment">/// ```</span> <span class="doccomment">/// use std::ops::{Deref, DerefMut};</span> <span class="doccomment">///</span> <span class="doccomment">/// struct DerefMutExample<T> {</span> <span class="doccomment">/// value: T</span> <span class="doccomment">/// }</span> <span class="doccomment">///</span> <span class="doccomment">/// impl<T> Deref for DerefMutExample<T> {</span> <span class="doccomment">/// type Target = T;</span> <span class="doccomment">///</span> <span class="doccomment">/// fn deref(&self) -> &T {</span> <span class="doccomment">/// &self.value</span> <span class="doccomment">/// }</span> <span class="doccomment">/// }</span> <span class="doccomment">///</span> <span class="doccomment">/// impl<T> DerefMut for DerefMutExample<T> {</span> <span class="doccomment">/// fn deref_mut(&mut self) -> &mut T {</span> <span class="doccomment">/// &mut self.value</span> <span class="doccomment">/// }</span> <span class="doccomment">/// }</span> <span class="doccomment">///</span> <span class="doccomment">/// let mut x = DerefMutExample { value: 'a' };</span> <span class="doccomment">/// *x = 'b';</span> <span class="doccomment">/// assert_eq!('b', *x);</span> <span class="doccomment">/// ```</span> <span class="attribute">#[<span class="ident">lang</span> <span class="op">=</span> <span class="string">"deref_mut"</span>]</span> <span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span> <span class="kw">pub</span> <span class="kw">trait</span> <span class="ident">DerefMut</span>: <span class="ident">Deref</span> { <span class="doccomment">/// Mutably dereferences the value.</span> <span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span> <span class="kw">fn</span> <span class="ident">deref_mut</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">Self</span>::<span class="ident">Target</span>; } <span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span> <span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">T</span>: <span class="question-mark">?</span><span class="ident">Sized</span><span class="op">></span> <span class="ident">DerefMut</span> <span class="kw">for</span> <span class="kw-2">&</span><span class="lifetime">'a</span> <span class="kw-2">mut</span> <span class="ident">T</span> { <span class="kw">fn</span> <span class="ident">deref_mut</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">T</span> { <span class="kw-2">*</span><span class="self">self</span> } } </pre> </section> <section id='search' class="content hidden"></section> <section class="footer"></section> <aside id="help" class="hidden"> <div> <h1 class="hidden">Help</h1> <div class="shortcuts"> <h2>Keyboard Shortcuts</h2> <dl> <dt><kbd>?</kbd></dt> <dd>Show this help dialog</dd> <dt><kbd>S</kbd></dt> <dd>Focus the search field</dd> <dt><kbd>↑</kbd></dt> <dd>Move up in search results</dd> <dt><kbd>↓</kbd></dt> <dd>Move down in search results</dd> <dt><kbd>↹</kbd></dt> <dd>Switch tab</dd> <dt><kbd>⏎</kbd></dt> <dd>Go to active search result</dd> <dt><kbd>+</kbd></dt> <dd>Expand all sections</dd> <dt><kbd>-</kbd></dt> <dd>Collapse all sections</dd> </dl> </div> <div class="infos"> <h2>Search Tricks</h2> <p> Prefix searches with a type followed by a colon (e.g. <code>fn:</code>) to restrict the search to a given type. </p> <p> Accepted types are: <code>fn</code>, <code>mod</code>, <code>struct</code>, <code>enum</code>, <code>trait</code>, <code>type</code>, <code>macro</code>, and <code>const</code>. </p> <p> Search functions by type signature (e.g. <code>vec -> usize</code> or <code>* -> vec</code>) </p> </div> </div> </aside> <script> window.rootPath = "../../../"; 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