<!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="API documentation for the Rust `Any` trait in crate `std`."> <meta name="keywords" content="rust, rustlang, rust-lang, Any"> <title>std::any::Any - Rust</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 trait"> <!--[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='../../std/index.html'><img src='https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png' alt='logo' width='100'></a> <p class='location'>Trait Any</p><div class="sidebar-elems"><div class="block items"><a class="sidebar-title" href="#required-methods">Required Methods</a><div class="sidebar-links"><a href="#tymethod.get_type_id">get_type_id</a></div><a class="sidebar-title" href="#implementors">Implementors</a><a class="sidebar-title" href="#methods">Methods</a><div class="sidebar-links"><a href="#method.is">is</a><a href="#method.downcast_ref">downcast_ref</a><a href="#method.downcast_mut">downcast_mut</a><a href="#method.is">is</a><a href="#method.downcast_ref">downcast_ref</a><a href="#method.downcast_mut">downcast_mut</a></div><a class="sidebar-title" href="#implementations">Trait Implementations</a><div class="sidebar-links"><a href="#impl-Debug">Debug</a></div></div><p class='location'><a href='../index.html'>std</a>::<wbr><a href='index.html'>any</a></p><script>window.sidebarCurrent = {name: 'Any', ty: 'trait', relpath: ''};</script><script defer src="sidebar-items.js"></script></div> </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"> <h1 class='fqn'><span class='in-band'>Trait <a href='../index.html'>std</a>::<wbr><a href='index.html'>any</a>::<wbr><a class="trait" href=''>Any</a></span><span class='out-of-band'><span class='since' title='Stable since Rust version 1.0.0'>1.0.0</span><span id='render-detail'> <a id="toggle-all-docs" href="javascript:void(0)" title="collapse all docs"> [<span class='inner'>−</span>] </a> </span><a class='srclink' href='../../src/core/any.rs.html#88-111' title='goto source code'>[src]</a></span></h1> <pre class='rust trait'>pub trait Any: 'static { fn <a href='#tymethod.get_type_id' class='fnname'>get_type_id</a>(&self) -> <a class="struct" href="../../std/any/struct.TypeId.html" title="struct std::any::TypeId">TypeId</a>; }</pre><div class='docblock'><p>A type to emulate dynamic typing.</p> <p>Most types implement <code>Any</code>. However, any type which contains a non-<code>'static</code> reference does not. See the <a href="index.html">module-level documentation</a> for more details.</p> </div> <h2 id='required-methods' class='small-section-header'> Required Methods<a href='#required-methods' class='anchor'></a> </h2> <div class='methods'> <h3 id='tymethod.get_type_id' class='method'><span id='get_type_id.v' class='invisible'><code>fn <a href='#tymethod.get_type_id' class='fnname'>get_type_id</a>(&self) -> <a class="struct" href="../../std/any/struct.TypeId.html" title="struct std::any::TypeId">TypeId</a></code></span></h3><div class='stability'><div class='stab unstable'><details><summary><span class=microscope>🔬</span> This is a nightly-only experimental API. (<code>get_type_id </code><a href="https://github.com/rust-lang/rust/issues/27745">#27745</a>)</summary><p>this method will likely be replaced by an associated static</p> </details></div></div><div class='docblock'><p>Gets the <code>TypeId</code> of <code>self</code>.</p> <h1 id="examples" class="section-header"><a href="#examples">Examples</a></h1> <pre class="rust rust-example-rendered"> <span class="attribute">#![<span class="ident">feature</span>(<span class="ident">get_type_id</span>)]</span> <span class="kw">use</span> <span class="ident">std</span>::<span class="ident">any</span>::{<span class="ident">Any</span>, <span class="ident">TypeId</span>}; <span class="kw">fn</span> <span class="ident">is_string</span>(<span class="ident">s</span>: <span class="kw-2">&</span><span class="ident">Any</span>) <span class="op">-></span> <span class="ident">bool</span> { <span class="ident">TypeId</span>::<span class="ident">of</span>::<span class="op"><</span><span class="ident">String</span><span class="op">></span>() <span class="op">==</span> <span class="ident">s</span>.<span class="ident">get_type_id</span>() } <span class="kw">fn</span> <span class="ident">main</span>() { <span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">is_string</span>(<span class="kw-2">&</span><span class="number">0</span>), <span class="bool-val">false</span>); <span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">is_string</span>(<span class="kw-2">&</span><span class="string">"cookie monster"</span>.<span class="ident">to_string</span>()), <span class="bool-val">true</span>); }<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0A%23!%5Bfeature(get_type_id)%5D%0A%0Ause%20std%3A%3Aany%3A%3A%7BAny%2C%20TypeId%7D%3B%0A%0Afn%20is_string(s%3A%20%26Any)%20-%3E%20bool%20%7B%0A%20%20%20%20TypeId%3A%3Aof%3A%3A%3CString%3E()%20%3D%3D%20s.get_type_id()%0A%7D%0A%0Afn%20main()%20%7B%0A%20%20%20%20assert_eq!(is_string(%260)%2C%20false)%3B%0A%20%20%20%20assert_eq!(is_string(%26%22cookie%20monster%22.to_string())%2C%20true)%3B%0A%7D%0A&version=nightly">Run</a></pre> </div></div> <h2 id='methods' class='small-section-header'> Methods<a href='#methods' class='anchor'></a> </h2> <h3 id='impl' class='impl'><span class='in-band'><code>impl <a class="trait" href="../../std/any/trait.Any.html" title="trait std::any::Any">Any</a> + 'static</code><a href='#impl' class='anchor'></a></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/any.rs.html#139-242' title='goto source code'>[src]</a></span></h3> <div class='impl-items'><h4 id='method.is' class="method"><span id='is.v' class='invisible'><code>pub fn <a href='#method.is' class='fnname'>is</a><T>(&self) -> <a class="primitive" href="../primitive.bool.html">bool</a> <span class="where fmt-newline">where<br> T: <a class="trait" href="../../std/any/trait.Any.html" title="trait std::any::Any">Any</a>, </span></code></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/any.rs.html#162-171' title='goto source code'>[src]</a></span></h4> <div class='docblock'><p>Returns <code>true</code> if the boxed type is the same as <code>T</code>.</p> <h1 id="examples-1" class="section-header"><a href="#examples-1">Examples</a></h1> <pre class="rust rust-example-rendered"> <span class="kw">use</span> <span class="ident">std</span>::<span class="ident">any</span>::<span class="ident">Any</span>; <span class="kw">fn</span> <span class="ident">is_string</span>(<span class="ident">s</span>: <span class="kw-2">&</span><span class="ident">Any</span>) { <span class="kw">if</span> <span class="ident">s</span>.<span class="ident">is</span>::<span class="op"><</span><span class="ident">String</span><span class="op">></span>() { <span class="macro">println</span><span class="macro">!</span>(<span class="string">"It's a string!"</span>); } <span class="kw">else</span> { <span class="macro">println</span><span class="macro">!</span>(<span class="string">"Not a string..."</span>); } } <span class="kw">fn</span> <span class="ident">main</span>() { <span class="ident">is_string</span>(<span class="kw-2">&</span><span class="number">0</span>); <span class="ident">is_string</span>(<span class="kw-2">&</span><span class="string">"cookie monster"</span>.<span class="ident">to_string</span>()); }<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Ause%20std%3A%3Aany%3A%3AAny%3B%0A%0Afn%20is_string(s%3A%20%26Any)%20%7B%0A%20%20%20%20if%20s.is%3A%3A%3CString%3E()%20%7B%0A%20%20%20%20%20%20%20%20println!(%22It's%20a%20string!%22)%3B%0A%20%20%20%20%7D%20else%20%7B%0A%20%20%20%20%20%20%20%20println!(%22Not%20a%20string...%22)%3B%0A%20%20%20%20%7D%0A%7D%0A%0Afn%20main()%20%7B%0A%20%20%20%20is_string(%260)%3B%0A%20%20%20%20is_string(%26%22cookie%20monster%22.to_string())%3B%0A%7D%0A">Run</a></pre> </div><h4 id='method.downcast_ref' class="method"><span id='downcast_ref.v' class='invisible'><code>pub fn <a href='#method.downcast_ref' class='fnname'>downcast_ref</a><T>(&self) -> <a class="enum" href="../../std/option/enum.Option.html" title="enum std::option::Option">Option</a><<a class="primitive" href="../primitive.reference.html">&</a>T> <span class="where fmt-newline">where<br> T: <a class="trait" href="../../std/any/trait.Any.html" title="trait std::any::Any">Any</a>, </span></code></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/any.rs.html#196-204' title='goto source code'>[src]</a></span></h4> <div class='docblock'><p>Returns some reference to the boxed value if it is of type <code>T</code>, or <code>None</code> if it isn't.</p> <h1 id="examples-2" class="section-header"><a href="#examples-2">Examples</a></h1> <pre class="rust rust-example-rendered"> <span class="kw">use</span> <span class="ident">std</span>::<span class="ident">any</span>::<span class="ident">Any</span>; <span class="kw">fn</span> <span class="ident">print_if_string</span>(<span class="ident">s</span>: <span class="kw-2">&</span><span class="ident">Any</span>) { <span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Some</span>(<span class="ident">string</span>) <span class="op">=</span> <span class="ident">s</span>.<span class="ident">downcast_ref</span>::<span class="op"><</span><span class="ident">String</span><span class="op">></span>() { <span class="macro">println</span><span class="macro">!</span>(<span class="string">"It's a string({}): '{}'"</span>, <span class="ident">string</span>.<span class="ident">len</span>(), <span class="ident">string</span>); } <span class="kw">else</span> { <span class="macro">println</span><span class="macro">!</span>(<span class="string">"Not a string..."</span>); } } <span class="kw">fn</span> <span class="ident">main</span>() { <span class="ident">print_if_string</span>(<span class="kw-2">&</span><span class="number">0</span>); <span class="ident">print_if_string</span>(<span class="kw-2">&</span><span class="string">"cookie monster"</span>.<span class="ident">to_string</span>()); }<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Ause%20std%3A%3Aany%3A%3AAny%3B%0A%0Afn%20print_if_string(s%3A%20%26Any)%20%7B%0A%20%20%20%20if%20let%20Some(string)%20%3D%20s.downcast_ref%3A%3A%3CString%3E()%20%7B%0A%20%20%20%20%20%20%20%20println!(%22It's%20a%20string(%7B%7D)%3A%20'%7B%7D'%22%2C%20string.len()%2C%20string)%3B%0A%20%20%20%20%7D%20else%20%7B%0A%20%20%20%20%20%20%20%20println!(%22Not%20a%20string...%22)%3B%0A%20%20%20%20%7D%0A%7D%0A%0Afn%20main()%20%7B%0A%20%20%20%20print_if_string(%260)%3B%0A%20%20%20%20print_if_string(%26%22cookie%20monster%22.to_string())%3B%0A%7D%0A">Run</a></pre> </div><h4 id='method.downcast_mut' class="method"><span id='downcast_mut.v' class='invisible'><code>pub fn <a href='#method.downcast_mut' class='fnname'>downcast_mut</a><T>(&mut self) -> <a class="enum" href="../../std/option/enum.Option.html" title="enum std::option::Option">Option</a><<a class="primitive" href="../primitive.reference.html">&mut </a>T> <span class="where fmt-newline">where<br> T: <a class="trait" href="../../std/any/trait.Any.html" title="trait std::any::Any">Any</a>, </span></code></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/any.rs.html#233-241' title='goto source code'>[src]</a></span></h4> <div class='docblock'><p>Returns some mutable reference to the boxed value if it is of type <code>T</code>, or <code>None</code> if it isn't.</p> <h1 id="examples-3" class="section-header"><a href="#examples-3">Examples</a></h1> <pre class="rust rust-example-rendered"> <span class="kw">use</span> <span class="ident">std</span>::<span class="ident">any</span>::<span class="ident">Any</span>; <span class="kw">fn</span> <span class="ident">modify_if_u32</span>(<span class="ident">s</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">Any</span>) { <span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Some</span>(<span class="ident">num</span>) <span class="op">=</span> <span class="ident">s</span>.<span class="ident">downcast_mut</span>::<span class="op"><</span><span class="ident">u32</span><span class="op">></span>() { <span class="kw-2">*</span><span class="ident">num</span> <span class="op">=</span> <span class="number">42</span>; } } <span class="kw">fn</span> <span class="ident">main</span>() { <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">x</span> <span class="op">=</span> <span class="number">10u32</span>; <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">s</span> <span class="op">=</span> <span class="string">"starlord"</span>.<span class="ident">to_string</span>(); <span class="ident">modify_if_u32</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">x</span>); <span class="ident">modify_if_u32</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">s</span>); <span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>, <span class="number">42</span>); <span class="macro">assert_eq</span><span class="macro">!</span>(<span class="kw-2">&</span><span class="ident">s</span>, <span class="string">"starlord"</span>); }<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Ause%20std%3A%3Aany%3A%3AAny%3B%0A%0Afn%20modify_if_u32(s%3A%20%26mut%20Any)%20%7B%0A%20%20%20%20if%20let%20Some(num)%20%3D%20s.downcast_mut%3A%3A%3Cu32%3E()%20%7B%0A%20%20%20%20%20%20%20%20*num%20%3D%2042%3B%0A%20%20%20%20%7D%0A%7D%0A%0Afn%20main()%20%7B%0A%20%20%20%20let%20mut%20x%20%3D%2010u32%3B%0A%20%20%20%20let%20mut%20s%20%3D%20%22starlord%22.to_string()%3B%0A%0A%20%20%20%20modify_if_u32(%26mut%20x)%3B%0A%20%20%20%20modify_if_u32(%26mut%20s)%3B%0A%0A%20%20%20%20assert_eq!(x%2C%2042)%3B%0A%20%20%20%20assert_eq!(%26s%2C%20%22starlord%22)%3B%0A%7D%0A">Run</a></pre> </div></div><h3 id='impl-1' class='impl'><span class='in-band'><code>impl <a class="trait" href="../../std/any/trait.Any.html" title="trait std::any::Any">Any</a> + 'static + <a class="trait" href="../../std/marker/trait.Send.html" title="trait std::marker::Send">Send</a></code><a href='#impl-1' class='anchor'></a></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/any.rs.html#244-326' title='goto source code'>[src]</a></span></h3> <div class='impl-items'><h4 id='method.is-1' class="method"><span id='is.v-1' class='invisible'><code>pub fn <a href='#method.is-1' class='fnname'>is</a><T>(&self) -> <a class="primitive" href="../primitive.bool.html">bool</a> <span class="where fmt-newline">where<br> T: <a class="trait" href="../../std/any/trait.Any.html" title="trait std::any::Any">Any</a>, </span></code></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/any.rs.html#267-269' title='goto source code'>[src]</a></span></h4> <div class='docblock'><p>Forwards to the method defined on the type <code>Any</code>.</p> <h1 id="examples-4" class="section-header"><a href="#examples-4">Examples</a></h1> <pre class="rust rust-example-rendered"> <span class="kw">use</span> <span class="ident">std</span>::<span class="ident">any</span>::<span class="ident">Any</span>; <span class="kw">fn</span> <span class="ident">is_string</span>(<span class="ident">s</span>: <span class="kw-2">&</span>(<span class="ident">Any</span> <span class="op">+</span> <span class="ident">Send</span>)) { <span class="kw">if</span> <span class="ident">s</span>.<span class="ident">is</span>::<span class="op"><</span><span class="ident">String</span><span class="op">></span>() { <span class="macro">println</span><span class="macro">!</span>(<span class="string">"It's a string!"</span>); } <span class="kw">else</span> { <span class="macro">println</span><span class="macro">!</span>(<span class="string">"Not a string..."</span>); } } <span class="kw">fn</span> <span class="ident">main</span>() { <span class="ident">is_string</span>(<span class="kw-2">&</span><span class="number">0</span>); <span class="ident">is_string</span>(<span class="kw-2">&</span><span class="string">"cookie monster"</span>.<span class="ident">to_string</span>()); }<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Ause%20std%3A%3Aany%3A%3AAny%3B%0A%0Afn%20is_string(s%3A%20%26(Any%20%2B%20Send))%20%7B%0A%20%20%20%20if%20s.is%3A%3A%3CString%3E()%20%7B%0A%20%20%20%20%20%20%20%20println!(%22It's%20a%20string!%22)%3B%0A%20%20%20%20%7D%20else%20%7B%0A%20%20%20%20%20%20%20%20println!(%22Not%20a%20string...%22)%3B%0A%20%20%20%20%7D%0A%7D%0A%0Afn%20main()%20%7B%0A%20%20%20%20is_string(%260)%3B%0A%20%20%20%20is_string(%26%22cookie%20monster%22.to_string())%3B%0A%7D%0A">Run</a></pre> </div><h4 id='method.downcast_ref-1' class="method"><span id='downcast_ref.v-1' class='invisible'><code>pub fn <a href='#method.downcast_ref-1' class='fnname'>downcast_ref</a><T>(&self) -> <a class="enum" href="../../std/option/enum.Option.html" title="enum std::option::Option">Option</a><<a class="primitive" href="../primitive.reference.html">&</a>T> <span class="where fmt-newline">where<br> T: <a class="trait" href="../../std/any/trait.Any.html" title="trait std::any::Any">Any</a>, </span></code></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/any.rs.html#293-295' title='goto source code'>[src]</a></span></h4> <div class='docblock'><p>Forwards to the method defined on the type <code>Any</code>.</p> <h1 id="examples-5" class="section-header"><a href="#examples-5">Examples</a></h1> <pre class="rust rust-example-rendered"> <span class="kw">use</span> <span class="ident">std</span>::<span class="ident">any</span>::<span class="ident">Any</span>; <span class="kw">fn</span> <span class="ident">print_if_string</span>(<span class="ident">s</span>: <span class="kw-2">&</span>(<span class="ident">Any</span> <span class="op">+</span> <span class="ident">Send</span>)) { <span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Some</span>(<span class="ident">string</span>) <span class="op">=</span> <span class="ident">s</span>.<span class="ident">downcast_ref</span>::<span class="op"><</span><span class="ident">String</span><span class="op">></span>() { <span class="macro">println</span><span class="macro">!</span>(<span class="string">"It's a string({}): '{}'"</span>, <span class="ident">string</span>.<span class="ident">len</span>(), <span class="ident">string</span>); } <span class="kw">else</span> { <span class="macro">println</span><span class="macro">!</span>(<span class="string">"Not a string..."</span>); } } <span class="kw">fn</span> <span class="ident">main</span>() { <span class="ident">print_if_string</span>(<span class="kw-2">&</span><span class="number">0</span>); <span class="ident">print_if_string</span>(<span class="kw-2">&</span><span class="string">"cookie monster"</span>.<span class="ident">to_string</span>()); }<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Ause%20std%3A%3Aany%3A%3AAny%3B%0A%0Afn%20print_if_string(s%3A%20%26(Any%20%2B%20Send))%20%7B%0A%20%20%20%20if%20let%20Some(string)%20%3D%20s.downcast_ref%3A%3A%3CString%3E()%20%7B%0A%20%20%20%20%20%20%20%20println!(%22It's%20a%20string(%7B%7D)%3A%20'%7B%7D'%22%2C%20string.len()%2C%20string)%3B%0A%20%20%20%20%7D%20else%20%7B%0A%20%20%20%20%20%20%20%20println!(%22Not%20a%20string...%22)%3B%0A%20%20%20%20%7D%0A%7D%0A%0Afn%20main()%20%7B%0A%20%20%20%20print_if_string(%260)%3B%0A%20%20%20%20print_if_string(%26%22cookie%20monster%22.to_string())%3B%0A%7D%0A">Run</a></pre> </div><h4 id='method.downcast_mut-1' class="method"><span id='downcast_mut.v-1' class='invisible'><code>pub fn <a href='#method.downcast_mut-1' class='fnname'>downcast_mut</a><T>(&mut self) -> <a class="enum" href="../../std/option/enum.Option.html" title="enum std::option::Option">Option</a><<a class="primitive" href="../primitive.reference.html">&mut </a>T> <span class="where fmt-newline">where<br> T: <a class="trait" href="../../std/any/trait.Any.html" title="trait std::any::Any">Any</a>, </span></code></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/any.rs.html#323-325' title='goto source code'>[src]</a></span></h4> <div class='docblock'><p>Forwards to the method defined on the type <code>Any</code>.</p> <h1 id="examples-6" class="section-header"><a href="#examples-6">Examples</a></h1> <pre class="rust rust-example-rendered"> <span class="kw">use</span> <span class="ident">std</span>::<span class="ident">any</span>::<span class="ident">Any</span>; <span class="kw">fn</span> <span class="ident">modify_if_u32</span>(<span class="ident">s</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> (<span class="ident">Any</span><span class="op">+</span> <span class="ident">Send</span>)) { <span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Some</span>(<span class="ident">num</span>) <span class="op">=</span> <span class="ident">s</span>.<span class="ident">downcast_mut</span>::<span class="op"><</span><span class="ident">u32</span><span class="op">></span>() { <span class="kw-2">*</span><span class="ident">num</span> <span class="op">=</span> <span class="number">42</span>; } } <span class="kw">fn</span> <span class="ident">main</span>() { <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">x</span> <span class="op">=</span> <span class="number">10u32</span>; <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">s</span> <span class="op">=</span> <span class="string">"starlord"</span>.<span class="ident">to_string</span>(); <span class="ident">modify_if_u32</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">x</span>); <span class="ident">modify_if_u32</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">s</span>); <span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>, <span class="number">42</span>); <span class="macro">assert_eq</span><span class="macro">!</span>(<span class="kw-2">&</span><span class="ident">s</span>, <span class="string">"starlord"</span>); }<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Ause%20std%3A%3Aany%3A%3AAny%3B%0A%0Afn%20modify_if_u32(s%3A%20%26mut%20(Any%2B%20Send))%20%7B%0A%20%20%20%20if%20let%20Some(num)%20%3D%20s.downcast_mut%3A%3A%3Cu32%3E()%20%7B%0A%20%20%20%20%20%20%20%20*num%20%3D%2042%3B%0A%20%20%20%20%7D%0A%7D%0A%0Afn%20main()%20%7B%0A%20%20%20%20let%20mut%20x%20%3D%2010u32%3B%0A%20%20%20%20let%20mut%20s%20%3D%20%22starlord%22.to_string()%3B%0A%0A%20%20%20%20modify_if_u32(%26mut%20x)%3B%0A%20%20%20%20modify_if_u32(%26mut%20s)%3B%0A%0A%20%20%20%20assert_eq!(x%2C%2042)%3B%0A%20%20%20%20assert_eq!(%26s%2C%20%22starlord%22)%3B%0A%7D%0A">Run</a></pre> </div></div> <h2 id='implementations' class='small-section-header'> Trait Implementations<a href='#implementations' class='anchor'></a> </h2> <h3 id='impl-Debug' class='impl'><span class='in-band'><code>impl <a class="trait" href="../../std/fmt/trait.Debug.html" title="trait std::fmt::Debug">Debug</a> for <a class="trait" href="../../std/any/trait.Any.html" title="trait std::any::Any">Any</a> + 'static</code><a href='#impl-Debug' class='anchor'></a></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/any.rs.html#123-127' title='goto source code'>[src]</a></span></h3> <div class='impl-items'><h4 id='method.fmt' class="method"><span id='fmt.v' class='invisible'><code>fn <a href='../../std/fmt/trait.Debug.html#tymethod.fmt' class='fnname'>fmt</a>(&self, f: &mut <a class="struct" href="../../std/fmt/struct.Formatter.html" title="struct std::fmt::Formatter">Formatter</a>) -> <a class="enum" href="../../std/result/enum.Result.html" title="enum std::result::Result">Result</a><<a class="primitive" href="../primitive.unit.html">()</a>, <a class="struct" href="../../std/fmt/struct.Error.html" title="struct std::fmt::Error">Error</a>></code></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/any.rs.html#124-126' title='goto source code'>[src]</a></span></h4> <div class='docblock'><p>Formats the value using the given formatter. <a href="../../std/fmt/trait.Debug.html#tymethod.fmt">Read more</a></p> </div></div><h3 id='impl-Debug-1' class='impl'><span class='in-band'><code>impl <a class="trait" href="../../std/fmt/trait.Debug.html" title="trait std::fmt::Debug">Debug</a> for <a class="trait" href="../../std/any/trait.Any.html" title="trait std::any::Any">Any</a> + 'static + <a class="trait" href="../../std/marker/trait.Send.html" title="trait std::marker::Send">Send</a></code><a href='#impl-Debug-1' class='anchor'></a></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/any.rs.html#133-137' title='goto source code'>[src]</a></span></h3> <div class='impl-items'><h4 id='method.fmt-1' class="method"><span id='fmt.v-1' class='invisible'><code>fn <a href='../../std/fmt/trait.Debug.html#tymethod.fmt' class='fnname'>fmt</a>(&self, f: &mut <a class="struct" href="../../std/fmt/struct.Formatter.html" title="struct std::fmt::Formatter">Formatter</a>) -> <a class="enum" href="../../std/result/enum.Result.html" title="enum std::result::Result">Result</a><<a class="primitive" href="../primitive.unit.html">()</a>, <a class="struct" href="../../std/fmt/struct.Error.html" title="struct std::fmt::Error">Error</a>></code></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/any.rs.html#134-136' title='goto source code'>[src]</a></span></h4> <div class='docblock'><p>Formats the value using the given formatter. <a href="../../std/fmt/trait.Debug.html#tymethod.fmt">Read more</a></p> </div></div> <h2 id='implementors' class='small-section-header'> Implementors<a href='#implementors' class='anchor'></a> </h2> <ul class='item-list' id='implementors-list'> <li><div class='out-of-band'><a class='srclink' href='../../src/core/any.rs.html#114-116' title='goto source code'>[src]</a></div><code>impl<T> Any for T <span class="where fmt-newline">where<br> T: 'static + ?<a class="trait" href="../../std/marker/trait.Sized.html" title="trait std::marker::Sized">Sized</a>, </span></code></li> </ul><script type="text/javascript" async src="../../implementors/core/any/trait.Any.js"> </script></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 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