<!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/borrow.rs`."> <meta name="keywords" content="rust, rustlang, rust-lang"> <title>borrow.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"> 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> </pre><pre class="rust "> <span class="comment">// Copyright 2014 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">//! A module for working with borrowed data.</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="doccomment">/// A trait for borrowing data.</span> <span class="doccomment">///</span> <span class="doccomment">/// In general, there may be several ways to "borrow" a piece of data. The</span> <span class="doccomment">/// typical ways of borrowing a type `T` are `&T` (a shared borrow) and `&mut T`</span> <span class="doccomment">/// (a mutable borrow). But types like `Vec<T>` provide additional kinds of</span> <span class="doccomment">/// borrows: the borrowed slices `&[T]` and `&mut [T]`.</span> <span class="doccomment">///</span> <span class="doccomment">/// When writing generic code, it is often desirable to abstract over all ways</span> <span class="doccomment">/// of borrowing data from a given type. That is the role of the `Borrow`</span> <span class="doccomment">/// trait: if `T: Borrow<U>`, then `&U` can be borrowed from `&T`. A given</span> <span class="doccomment">/// type can be borrowed as multiple different types. In particular, `Vec<T>:</span> <span class="doccomment">/// Borrow<Vec<T>>` and `Vec<T>: Borrow<[T]>`.</span> <span class="doccomment">///</span> <span class="doccomment">/// If you are implementing `Borrow` and both `Self` and `Borrowed` implement</span> <span class="doccomment">/// `Hash`, `Eq`, and/or `Ord`, they must produce the same result.</span> <span class="doccomment">///</span> <span class="doccomment">/// `Borrow` is very similar to, but different than, `AsRef`. See</span> <span class="doccomment">/// [the book][book] for more.</span> <span class="doccomment">///</span> <span class="doccomment">/// [book]: ../../book/first-edition/borrow-and-asref.html</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">Borrow</span><span class="op"><</span><span class="ident">Borrowed</span>: <span class="question-mark">?</span><span class="ident">Sized</span><span class="op">></span> { <span class="doccomment">/// Immutably borrows from an owned value.</span> <span class="doccomment">///</span> <span class="doccomment">/// # Examples</span> <span class="doccomment">///</span> <span class="doccomment">/// ```</span> <span class="doccomment">/// use std::borrow::Borrow;</span> <span class="doccomment">///</span> <span class="doccomment">/// fn check<T: Borrow<str>>(s: T) {</span> <span class="doccomment">/// assert_eq!("Hello", s.borrow());</span> <span class="doccomment">/// }</span> <span class="doccomment">///</span> <span class="doccomment">/// let s = "Hello".to_string();</span> <span class="doccomment">///</span> <span class="doccomment">/// check(s);</span> <span class="doccomment">///</span> <span class="doccomment">/// let s = "Hello";</span> <span class="doccomment">///</span> <span class="doccomment">/// check(s);</span> <span class="doccomment">/// ```</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">borrow</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="kw-2">&</span><span class="ident">Borrowed</span>; } <span class="doccomment">/// A trait for mutably borrowing data.</span> <span class="doccomment">///</span> <span class="doccomment">/// Similar to `Borrow`, but for mutable borrows.</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">BorrowMut</span><span class="op"><</span><span class="ident">Borrowed</span>: <span class="question-mark">?</span><span class="ident">Sized</span><span class="op">></span> : <span class="ident">Borrow</span><span class="op"><</span><span class="ident">Borrowed</span><span class="op">></span> { <span class="doccomment">/// Mutably borrows from an owned value.</span> <span class="doccomment">///</span> <span class="doccomment">/// # Examples</span> <span class="doccomment">///</span> <span class="doccomment">/// ```</span> <span class="doccomment">/// use std::borrow::BorrowMut;</span> <span class="doccomment">///</span> <span class="doccomment">/// fn check<T: BorrowMut<[i32]>>(mut v: T) {</span> <span class="doccomment">/// assert_eq!(&mut [1, 2, 3], v.borrow_mut());</span> <span class="doccomment">/// }</span> <span class="doccomment">///</span> <span class="doccomment">/// let v = vec![1, 2, 3];</span> <span class="doccomment">///</span> <span class="doccomment">/// check(v);</span> <span class="doccomment">/// ```</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">borrow_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">Borrowed</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="ident">T</span>: <span class="question-mark">?</span><span class="ident">Sized</span><span class="op">></span> <span class="ident">Borrow</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="kw">for</span> <span class="ident">T</span> { <span class="kw">fn</span> <span class="ident">borrow</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="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="ident">T</span>: <span class="question-mark">?</span><span class="ident">Sized</span><span class="op">></span> <span class="ident">BorrowMut</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="kw">for</span> <span class="ident">T</span> { <span class="kw">fn</span> <span class="ident">borrow_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="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">Borrow</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="kw">for</span> <span class="kw-2">&</span><span class="lifetime">'a</span> <span class="ident">T</span> { <span class="kw">fn</span> <span class="ident">borrow</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="kw-2">*</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">Borrow</span><span class="op"><</span><span class="ident">T</span><span class="op">></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">borrow</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="kw-2">*</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">BorrowMut</span><span class="op"><</span><span class="ident">T</span><span class="op">></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">borrow_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="kw-2">mut</span> <span class="kw-2">*</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 = "../../"; window.currentCrate = "core"; </script> <script src="../../main.js"></script> <script defer src="../../search-index.js"></script> </body> </html>