<!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="../../../light.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"><a id="settings-menu" href="../../../settings.html"><img src="../../../wheel.svg" width="18" alt="Change settings"></a></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"> 12</span>
<span id="13"> 13</span>
<span id="14"> 14</span>
<span id="15"> 15</span>
<span id="16"> 16</span>
<span id="17"> 17</span>
<span id="18"> 18</span>
<span id="19"> 19</span>
<span id="20"> 20</span>
<span id="21"> 21</span>
<span id="22"> 22</span>
<span id="23"> 23</span>
<span id="24"> 24</span>
<span id="25"> 25</span>
<span id="26"> 26</span>
<span id="27"> 27</span>
<span id="28"> 28</span>
<span id="29"> 29</span>
<span id="30"> 30</span>
<span id="31"> 31</span>
<span id="32"> 32</span>
<span id="33"> 33</span>
<span id="34"> 34</span>
<span id="35"> 35</span>
<span id="36"> 36</span>
<span id="37"> 37</span>
<span id="38"> 38</span>
<span id="39"> 39</span>
<span id="40"> 40</span>
<span id="41"> 41</span>
<span id="42"> 42</span>
<span id="43"> 43</span>
<span id="44"> 44</span>
<span id="45"> 45</span>
<span id="46"> 46</span>
<span id="47"> 47</span>
<span id="48"> 48</span>
<span id="49"> 49</span>
<span id="50"> 50</span>
<span id="51"> 51</span>
<span id="52"> 52</span>
<span id="53"> 53</span>
<span id="54"> 54</span>
<span id="55"> 55</span>
<span id="56"> 56</span>
<span id="57"> 57</span>
<span id="58"> 58</span>
<span id="59"> 59</span>
<span id="60"> 60</span>
<span id="61"> 61</span>
<span id="62"> 62</span>
<span id="63"> 63</span>
<span id="64"> 64</span>
<span id="65"> 65</span>
<span id="66"> 66</span>
<span id="67"> 67</span>
<span id="68"> 68</span>
<span id="69"> 69</span>
<span id="70"> 70</span>
<span id="71"> 71</span>
<span id="72"> 72</span>
<span id="73"> 73</span>
<span id="74"> 74</span>
<span id="75"> 75</span>
<span id="76"> 76</span>
<span id="77"> 77</span>
<span id="78"> 78</span>
<span id="79"> 79</span>
<span id="80"> 80</span>
<span id="81"> 81</span>
<span id="82"> 82</span>
<span id="83"> 83</span>
<span id="84"> 84</span>
<span id="85"> 85</span>
<span id="86"> 86</span>
<span id="87"> 87</span>
<span id="88"> 88</span>
<span id="89"> 89</span>
<span id="90"> 90</span>
<span id="91"> 91</span>
<span id="92"> 92</span>
<span id="93"> 93</span>
<span id="94"> 94</span>
<span id="95"> 95</span>
<span id="96"> 96</span>
<span id="97"> 97</span>
<span id="98"> 98</span>
<span id="99"> 99</span>
<span id="100">100</span>
<span id="101">101</span>
<span id="102">102</span>
<span id="103">103</span>
<span id="104">104</span>
<span id="105">105</span>
<span id="106">106</span>
<span id="107">107</span>
<span id="108">108</span>
<span id="109">109</span>
<span id="110">110</span>
<span id="111">111</span>
<span id="112">112</span>
<span id="113">113</span>
<span id="114">114</span>
<span id="115">115</span>
<span id="116">116</span>
<span id="117">117</span>
<span id="118">118</span>
<span id="119">119</span>
<span id="120">120</span>
<span id="121">121</span>
<span id="122">122</span>
<span id="123">123</span>
<span id="124">124</span>
<span id="125">125</span>
<span id="126">126</span>
<span id="127">127</span>
<span id="128">128</span>
<span id="129">129</span>
<span id="130">130</span>
<span id="131">131</span>
<span id="132">132</span>
<span id="133">133</span>
<span id="134">134</span>
<span id="135">135</span>
<span id="136">136</span>
<span id="137">137</span>
<span id="138">138</span>
<span id="139">139</span>
<span id="140">140</span>
<span id="141">141</span>
<span id="142">142</span>
<span id="143">143</span>
<span id="144">144</span>
<span id="145">145</span>
<span id="146">146</span>
<span id="147">147</span>
<span id="148">148</span>
<span id="149">149</span>
<span id="150">150</span>
<span id="151">151</span>
<span id="152">152</span>
<span id="153">153</span>
<span id="154">154</span>
<span id="155">155</span>
<span id="156">156</span>
<span id="157">157</span>
<span id="158">158</span>
<span id="159">159</span>
<span id="160">160</span>
<span id="161">161</span>
<span id="162">162</span>
<span id="163">163</span>
<span id="164">164</span>
<span id="165">165</span>
<span id="166">166</span>
<span id="167">167</span>
<span id="168">168</span>
<span 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>
<span id="176">176</span>
<span id="177">177</span>
<span id="178">178</span>
<span id="179">179</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">doc</span>(<span class="ident">alias</span> <span class="op">=</span> <span class="string">"*"</span>)]</span>
<span class="attribute">#[<span class="ident">doc</span>(<span class="ident">alias</span> <span class="op">=</span> <span class="string">"&*"</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">must_use</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">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">doc</span>(<span class="ident">alias</span> <span class="op">=</span> <span class="string">"*"</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><p>Search multiple things at once by splitting your query with comma (e.g. <code>str,u8</code> or <code>String,struct:Vec,test</code>)</p></div></div></aside><script>window.rootPath = "../../../";window.currentCrate = "core";</script><script src="../../../aliases.js"></script><script src="../../../main.js"></script><script defer src="../../../search-index.js"></script></body></html>
