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<!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="A synchronization primitive which can be used to run a one-time global initialization. Useful for one-time initialization for FFI or related functionality. This type can only be constructed with `Once::new()`."><title>Once in tracing_core - Rust</title><script> if (window.location.protocol !== "file:") document.write(`<link rel="preload" as="font" type="font/woff2" crossorigin href="../static.files/SourceSerif4-Regular-46f98efaafac5295.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../static.files/FiraSans-Regular-018c141bf0843ffd.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../static.files/FiraSans-Medium-8f9a781e4970d388.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../static.files/SourceCodePro-Regular-562dcc5011b6de7d.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../static.files/SourceCodePro-Semibold-d899c5a5c4aeb14a.ttf.woff2">`)</script><link rel="stylesheet" href="../static.files/normalize-76eba96aa4d2e634.css"><link rel="stylesheet" href="../static.files/rustdoc-e935ef01ae1c1829.css"><meta name="rustdoc-vars" data-root-path="../" data-static-root-path="../static.files/" data-current-crate="tracing_core" data-themes="" data-resource-suffix="" data-rustdoc-version="1.78.0 (9b00956e5 2024-04-29)" data-channel="1.78.0" data-search-js="search-42d8da7a6b9792c2.js" data-settings-js="settings-4313503d2e1961c2.js" ><script src="../static.files/storage-4c98445ec4002617.js"></script><script defer src="sidebar-items.js"></script><script defer src="../static.files/main-12cf3b4f4f9dc36d.js"></script><noscript><link rel="stylesheet" href="../static.files/noscript-04d5337699b92874.css"></noscript><link rel="alternate icon" type="image/png" href="../static.files/favicon-16x16-8b506e7a72182f1c.png"><link rel="alternate icon" type="image/png" href="../static.files/favicon-32x32-422f7d1d52889060.png"><link rel="icon" type="image/svg+xml" href="../static.files/favicon-2c020d218678b618.svg"></head><body class="rustdoc struct"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="mobile-topbar"><button class="sidebar-menu-toggle" title="show sidebar"></button><a class="logo-container" href="../tracing_core/index.html"><img src="https://raw.githubusercontent.com/tokio-rs/tracing/master/assets/logo-type.png" alt=""></a></nav><nav class="sidebar"><div class="sidebar-crate"><a class="logo-container" href="../tracing_core/index.html"><img src="https://raw.githubusercontent.com/tokio-rs/tracing/master/assets/logo-type.png" alt="logo"></a><h2><a href="../tracing_core/index.html">tracing_core</a><span class="version">0.1.32</span></h2></div><h2 class="location"><a href="#">Once</a></h2><div class="sidebar-elems"><section><h3><a href="#implementations">Methods</a></h3><ul class="block method"><li><a href="#method.call_once">call_once</a></li><li><a href="#method.call_once_force">call_once_force</a></li><li><a href="#method.is_completed">is_completed</a></li><li><a href="#method.new">new</a></li></ul><h3><a href="#trait-implementations">Trait Implementations</a></h3><ul class="block trait-implementation"><li><a href="#impl-Debug-for-Once">Debug</a></li><li><a href="#impl-RefUnwindSafe-for-Once">RefUnwindSafe</a></li><li><a href="#impl-UnwindSafe-for-Once">UnwindSafe</a></li></ul><h3><a href="#synthetic-implementations">Auto Trait Implementations</a></h3><ul class="block synthetic-implementation"><li><a href="#impl-Freeze-for-Once">!Freeze</a></li><li><a href="#impl-Send-for-Once">Send</a></li><li><a href="#impl-Sync-for-Once">Sync</a></li><li><a href="#impl-Unpin-for-Once">Unpin</a></li></ul><h3><a href="#blanket-implementations">Blanket Implementations</a></h3><ul class="block blanket-implementation"><li><a href="#impl-Any-for-T">Any</a></l
<main><div class="width-limiter"><nav class="sub"><form class="search-form"><span></span><div id="sidebar-button" tabindex="-1"><a href="../tracing_core/all.html" title="show sidebar"></a></div><input class="search-input" name="search" aria-label="Run search in the documentation" autocomplete="off" spellcheck="false" placeholder="Click or press S to search, ? for more options…" type="search"><div id="help-button" tabindex="-1"><a href="../help.html" title="help">?</a></div><div id="settings-menu" tabindex="-1"><a href="../settings.html" title="settings"><img width="22" height="22" alt="Change settings" src="../static.files/wheel-7b819b6101059cd0.svg"></a></div></form></nav><section id="main-content" class="content"><div class="main-heading"><h1>Struct <a href="index.html">tracing_core</a>::<wbr><a class="struct" href="#">Once</a><button id="copy-path" title="Copy item path to clipboard"><img src="../static.files/clipboard-7571035ce49a181d.svg" width="19" height="18" alt="Copy item path"></button></h1><span class="out-of-band"><span class="since" title="Stable since Rust version 1.0.0">1.0.0</span> · <a class="src" href="https://doc.rust-lang.org/1.78.0/src/std/sync/once.rs.html#29">source</a> · <button id="toggle-all-docs" title="collapse all docs">[<span>&#x2212;</span>]</button></span></div><pre class="rust item-decl"><code>pub struct Once { <span class="comment">/* private fields */</span> }</code></pre><details class="toggle top-doc" open><summary class="hideme"><span>Expand description</span></summary><div class="docblock"><p>A synchronization primitive which can be used to run a one-time global
initialization. Useful for one-time initialization for FFI or related
functionality. This type can only be constructed with <a href="struct.Once.html#method.new" title="associated function tracing_core::Once::new"><code>Once::new()</code></a>.</p>
<h2 id="examples"><a class="doc-anchor" href="#examples">§</a>Examples</h2>
<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use </span>std::sync::Once;
<span class="kw">static </span>START: Once = Once::new();
START.call_once(|| {
<span class="comment">// run initialization here
</span>});</code></pre></div>
</div></details><h2 id="implementations" class="section-header">Implementations<a href="#implementations" class="anchor">§</a></h2><div id="implementations-list"><details class="toggle implementors-toggle" open><summary><section id="impl-Once" class="impl"><a class="src rightside" href="https://doc.rust-lang.org/1.78.0/src/std/sync/once.rs.html#69">source</a><a href="#impl-Once" class="anchor">§</a><h3 class="code-header">impl <a class="struct" href="struct.Once.html" title="struct tracing_core::Once">Once</a></h3></section></summary><div class="impl-items"><details class="toggle method-toggle" open><summary><section id="method.new" class="method"><span class="rightside"><span class="since" title="Stable since Rust version 1.2.0, const since 1.32.0">1.2.0 (const: 1.32.0)</span> · <a class="src" href="https://doc.rust-lang.org/1.78.0/src/std/sync/once.rs.html#75">source</a></span><h4 class="code-header">pub const fn <a href="#method.new" class="fn">new</a>() -&gt; <a class="struct" href="struct.Once.html" title="struct tracing_core::Once">Once</a></h4></section></summary><div class="docblock"><p>Creates a new <code>Once</code> value.</p>
</div></details><details class="toggle method-toggle" open><summary><section id="method.call_once" class="method"><a class="src rightside" href="https://doc.rust-lang.org/1.78.0/src/std/sync/once.rs.html#139-141">source</a><h4 class="code-header">pub fn <a href="#method.call_once" class="fn">call_once</a>&lt;F&gt;(&amp;self, f: F)<div class="where">where
F: <a class="trait" href="https://doc.rust-lang.org/1.78.0/core/ops/function/trait.FnOnce.html" title="trait core::ops::function::FnOnce">FnOnce</a>(),</div></h4></section></summary><div class="docblock"><p>Performs an initialization routine once and only once. The given closure
will be executed if this is the first time <code>call_once</code> has been called,
and otherwise the routine will <em>not</em> be invoked.</p>
<p>This method will block the calling thread if another initialization
routine is currently running.</p>
<p>When this function returns, it is guaranteed that some initialization
has run and completed (it might not be the closure specified). It is also
guaranteed that any memory writes performed by the executed closure can
be reliably observed by other threads at this point (there is a
happens-before relation between the closure and code executing after the
return).</p>
<p>If the given closure recursively invokes <code>call_once</code> on the same <a href="struct.Once.html" title="struct tracing_core::Once"><code>Once</code></a>
instance, the exact behavior is not specified: allowed outcomes are
a panic or a deadlock.</p>
<h5 id="examples-1"><a class="doc-anchor" href="#examples-1">§</a>Examples</h5>
<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use </span>std::sync::Once;
<span class="kw">static </span><span class="kw-2">mut </span>VAL: usize = <span class="number">0</span>;
<span class="kw">static </span>INIT: Once = Once::new();
<span class="comment">// Accessing a `static mut` is unsafe much of the time, but if we do so
// in a synchronized fashion (e.g., write once or read all) then we're
// good to go!
//
// This function will only call `expensive_computation` once, and will
// otherwise always return the value returned from the first invocation.
</span><span class="kw">fn </span>get_cached_val() -&gt; usize {
<span class="kw">unsafe </span>{
INIT.call_once(|| {
VAL = expensive_computation();
});
VAL
}
}
<span class="kw">fn </span>expensive_computation() -&gt; usize {
<span class="comment">// ...
</span>}</code></pre></div>
<h5 id="panics"><a class="doc-anchor" href="#panics">§</a>Panics</h5>
<p>The closure <code>f</code> will only be executed once even if this is called
concurrently amongst many threads. If that closure panics, however, then
it will <em>poison</em> this <a href="struct.Once.html" title="struct tracing_core::Once"><code>Once</code></a> instance, causing all future invocations of
<code>call_once</code> to also panic.</p>
<p>This is similar to <a href="struct.Mutex.html#poisoning">poisoning with mutexes</a>.</p>
</div></details><details class="toggle method-toggle" open><summary><section id="method.call_once_force" class="method"><span class="rightside"><span class="since" title="Stable since Rust version 1.51.0">1.51.0</span> · <a class="src" href="https://doc.rust-lang.org/1.78.0/src/std/sync/once.rs.html#198-200">source</a></span><h4 class="code-header">pub fn <a href="#method.call_once_force" class="fn">call_once_force</a>&lt;F&gt;(&amp;self, f: F)<div class="where">where
F: <a class="trait" href="https://doc.rust-lang.org/1.78.0/core/ops/function/trait.FnOnce.html" title="trait core::ops::function::FnOnce">FnOnce</a>(&amp;<a class="struct" href="https://doc.rust-lang.org/1.78.0/std/sync/once/struct.OnceState.html" title="struct std::sync::once::OnceState">OnceState</a>),</div></h4></section></summary><div class="docblock"><p>Performs the same function as <a href="struct.Once.html#method.call_once" title="method tracing_core::Once::call_once"><code>call_once()</code></a> except ignores poisoning.</p>
<p>Unlike <a href="struct.Once.html#method.call_once" title="method tracing_core::Once::call_once"><code>call_once()</code></a>, if this <a href="struct.Once.html" title="struct tracing_core::Once"><code>Once</code></a> has been poisoned (i.e., a previous
call to <a href="struct.Once.html#method.call_once" title="method tracing_core::Once::call_once"><code>call_once()</code></a> or <a href="struct.Once.html#method.call_once_force" title="method tracing_core::Once::call_once_force"><code>call_once_force()</code></a> caused a panic), calling
<a href="struct.Once.html#method.call_once_force" title="method tracing_core::Once::call_once_force"><code>call_once_force()</code></a> will still invoke the closure <code>f</code> and will <em>not</em>
result in an immediate panic. If <code>f</code> panics, the <a href="struct.Once.html" title="struct tracing_core::Once"><code>Once</code></a> will remain
in a poison state. If <code>f</code> does <em>not</em> panic, the <a href="struct.Once.html" title="struct tracing_core::Once"><code>Once</code></a> will no
longer be in a poison state and all future calls to <a href="struct.Once.html#method.call_once" title="method tracing_core::Once::call_once"><code>call_once()</code></a> or
<a href="struct.Once.html#method.call_once_force" title="method tracing_core::Once::call_once_force"><code>call_once_force()</code></a> will be no-ops.</p>
<p>The closure <code>f</code> is yielded a <a href="https://doc.rust-lang.org/1.78.0/std/sync/once/struct.OnceState.html" title="struct std::sync::once::OnceState"><code>OnceState</code></a> structure which can be used
to query the poison status of the <a href="struct.Once.html" title="struct tracing_core::Once"><code>Once</code></a>.</p>
<h5 id="examples-2"><a class="doc-anchor" href="#examples-2">§</a>Examples</h5>
<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use </span>std::sync::Once;
<span class="kw">use </span>std::thread;
<span class="kw">static </span>INIT: Once = Once::new();
<span class="comment">// poison the once
</span><span class="kw">let </span>handle = thread::spawn(|| {
INIT.call_once(|| <span class="macro">panic!</span>());
});
<span class="macro">assert!</span>(handle.join().is_err());
<span class="comment">// poisoning propagates
</span><span class="kw">let </span>handle = thread::spawn(|| {
INIT.call_once(|| {});
});
<span class="macro">assert!</span>(handle.join().is_err());
<span class="comment">// call_once_force will still run and reset the poisoned state
</span>INIT.call_once_force(|state| {
<span class="macro">assert!</span>(state.is_poisoned());
});
<span class="comment">// once any success happens, we stop propagating the poison
</span>INIT.call_once(|| {});</code></pre></div>
</div></details><details class="toggle method-toggle" open><summary><section id="method.is_completed" class="method"><span class="rightside"><span class="since" title="Stable since Rust version 1.43.0">1.43.0</span> · <a class="src" href="https://doc.rust-lang.org/1.78.0/src/std/sync/once.rs.html#254">source</a></span><h4 class="code-header">pub fn <a href="#method.is_completed" class="fn">is_completed</a>(&amp;self) -&gt; <a class="primitive" href="https://doc.rust-lang.org/1.78.0/std/primitive.bool.html">bool</a></h4></section></summary><div class="docblock"><p>Returns <code>true</code> if some <a href="struct.Once.html#method.call_once" title="method tracing_core::Once::call_once"><code>call_once()</code></a> call has completed
successfully. Specifically, <code>is_completed</code> will return false in
the following situations:</p>
<ul>
<li><a href="struct.Once.html#method.call_once" title="method tracing_core::Once::call_once"><code>call_once()</code></a> was not called at all,</li>
<li><a href="struct.Once.html#method.call_once" title="method tracing_core::Once::call_once"><code>call_once()</code></a> was called, but has not yet completed,</li>
<li>the <a href="struct.Once.html" title="struct tracing_core::Once"><code>Once</code></a> instance is poisoned</li>
</ul>
<p>This function returning <code>false</code> does not mean that <a href="struct.Once.html" title="struct tracing_core::Once"><code>Once</code></a> has not been
executed. For example, it may have been executed in the time between
when <code>is_completed</code> starts executing and when it returns, in which case
the <code>false</code> return value would be stale (but still permissible).</p>
<h5 id="examples-3"><a class="doc-anchor" href="#examples-3">§</a>Examples</h5>
<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use </span>std::sync::Once;
<span class="kw">static </span>INIT: Once = Once::new();
<span class="macro">assert_eq!</span>(INIT.is_completed(), <span class="bool-val">false</span>);
INIT.call_once(|| {
<span class="macro">assert_eq!</span>(INIT.is_completed(), <span class="bool-val">false</span>);
});
<span class="macro">assert_eq!</span>(INIT.is_completed(), <span class="bool-val">true</span>);</code></pre></div>
<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use </span>std::sync::Once;
<span class="kw">use </span>std::thread;
<span class="kw">static </span>INIT: Once = Once::new();
<span class="macro">assert_eq!</span>(INIT.is_completed(), <span class="bool-val">false</span>);
<span class="kw">let </span>handle = thread::spawn(|| {
INIT.call_once(|| <span class="macro">panic!</span>());
});
<span class="macro">assert!</span>(handle.join().is_err());
<span class="macro">assert_eq!</span>(INIT.is_completed(), <span class="bool-val">false</span>);</code></pre></div>
</div></details></div></details></div><h2 id="trait-implementations" class="section-header">Trait Implementations<a href="#trait-implementations" class="anchor">§</a></h2><div id="trait-implementations-list"><details class="toggle implementors-toggle" open><summary><section id="impl-Debug-for-Once" class="impl"><span class="rightside"><span class="since" title="Stable since Rust version 1.16.0">1.16.0</span> · <a class="src" href="https://doc.rust-lang.org/1.78.0/src/std/sync/once.rs.html#270">source</a></span><a href="#impl-Debug-for-Once" class="anchor">§</a><h3 class="code-header">impl <a class="trait" href="https://doc.rust-lang.org/1.78.0/core/fmt/trait.Debug.html" title="trait core::fmt::Debug">Debug</a> for <a class="struct" href="struct.Once.html" title="struct tracing_core::Once">Once</a></h3></section></summary><div class="impl-items"><details class="toggle method-toggle" open><summary><section id="method.fmt" class="method trait-impl"><a class="src rightside" href="https://doc.rust-lang.org/1.78.0/src/std/sync/once.rs.html#271">source</a><a href="#method.fmt" class="anchor">§</a><h4 class="code-header">fn <a href="https://doc.rust-lang.org/1.78.0/core/fmt/trait.Debug.html#tymethod.fmt" class="fn">fmt</a>(&amp;self, f: &amp;mut <a class="struct" href="https://doc.rust-lang.org/1.78.0/core/fmt/struct.Formatter.html" title="struct core::fmt::Formatter">Formatter</a>&lt;'_&gt;) -&gt; <a class="enum" href="https://doc.rust-lang.org/1.78.0/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/1.78.0/std/primitive.unit.html">()</a>, <a class="struct" href="https://doc.rust-lang.org/1.78.0/core/fmt/struct.Error.html" title="struct core::fmt::Error">Error</a>&gt;</h4></section></summary><div class='docblock'>Formats the value using the given formatter. <a href="https://doc.rust-lang.org/1.78.0/core/fmt/trait.Debug.html#tymethod.fmt">Read more</a></div></details></div></details><section id="impl-RefUnwindSafe-for-Once" class="impl"><span class="rightside"><span class="since" title="Stable since Rust version 1.59.0">1.59.0</span> · <a class="src" href="https://doc.rust-lang.org/1.78.0/src/std/sync/once.rs.html#37">source</a></span><a href="#impl-RefUnwindSafe-for-Once" class="anchor">§</a><h3 class="code-header">impl <a class="trait" href="https://doc.rust-lang.org/1.78.0/core/panic/unwind_safe/trait.RefUnwindSafe.html" title="trait core::panic::unwind_safe::RefUnwindSafe">RefUnwindSafe</a> for <a class="struct" href="struct.Once.html" title="struct tracing_core::Once">Once</a></h3></section><section id="impl-UnwindSafe-for-Once" class="impl"><span class="rightside"><span class="since" title="Stable since Rust version 1.59.0">1.59.0</span> · <a class="src" href="https://doc.rust-lang.org/1.78.0/src/std/sync/once.rs.html#34">source</a></span><a href="#impl-UnwindSafe-for-Once" class="anchor">§</a><h3 class="code-header">impl <a class="trait" href="https://doc.rust-lang.org/1.78.0/core/panic/unwind_safe/trait.UnwindSafe.html" title="trait core::panic::unwind_safe::UnwindSafe">UnwindSafe</a> for <a class="struct" href="struct.Once.html" title="struct tracing_core::Once">Once</a></h3></section></div><h2 id="synthetic-implementations" class="section-header">Auto Trait Implementations<a href="#synthetic-implementations" class="anchor">§</a></h2><div id="synthetic-implementations-list"><section id="impl-Freeze-for-Once" class="impl"><a href="#impl-Freeze-for-Once" class="anchor">§</a><h3 class="code-header">impl !<a class="trait" href="https://doc.rust-lang.org/1.78.0/core/marker/trait.Freeze.html" title="trait core::marker::Freeze">Freeze</a> for <a class="struct" href="struct.Once.html" title="struct tracing_core::Once">Once</a></h3></section><section id="impl-Send-for-Once" class="impl"><a href="#impl-Send-for-Once" class="anchor">§</a><h3 class="code-header">impl <a class="trait" href="https://doc.rust-lang.org/1.78.0/core/marker/trait.Send.html" title="trait core::marker::Send">Send</a> for <a class="struct" href="struct.Once.html" tit
T: 'static + ?<a class="trait" href="https://doc.rust-lang.org/1.78.0/core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a>,</div></h3></section></summary><div class="impl-items"><details class="toggle method-toggle" open><summary><section id="method.type_id" class="method trait-impl"><a class="src rightside" href="https://doc.rust-lang.org/1.78.0/src/core/any.rs.html#141">source</a><a href="#method.type_id" class="anchor">§</a><h4 class="code-header">fn <a href="https://doc.rust-lang.org/1.78.0/core/any/trait.Any.html#tymethod.type_id" class="fn">type_id</a>(&amp;self) -&gt; <a class="struct" href="https://doc.rust-lang.org/1.78.0/core/any/struct.TypeId.html" title="struct core::any::TypeId">TypeId</a></h4></section></summary><div class='docblock'>Gets the <code>TypeId</code> of <code>self</code>. <a href="https://doc.rust-lang.org/1.78.0/core/any/trait.Any.html#tymethod.type_id">Read more</a></div></details></div></details><details class="toggle implementors-toggle"><summary><section id="impl-Borrow%3CT%3E-for-T" class="impl"><a class="src rightside" href="https://doc.rust-lang.org/1.78.0/src/core/borrow.rs.html#208">source</a><a href="#impl-Borrow%3CT%3E-for-T" class="anchor">§</a><h3 class="code-header">impl&lt;T&gt; <a class="trait" href="https://doc.rust-lang.org/1.78.0/core/borrow/trait.Borrow.html" title="trait core::borrow::Borrow">Borrow</a>&lt;T&gt; for T<div class="where">where
T: ?<a class="trait" href="https://doc.rust-lang.org/1.78.0/core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a>,</div></h3></section></summary><div class="impl-items"><details class="toggle method-toggle" open><summary><section id="method.borrow" class="method trait-impl"><a class="src rightside" href="https://doc.rust-lang.org/1.78.0/src/core/borrow.rs.html#210">source</a><a href="#method.borrow" class="anchor">§</a><h4 class="code-header">fn <a href="https://doc.rust-lang.org/1.78.0/core/borrow/trait.Borrow.html#tymethod.borrow" class="fn">borrow</a>(&amp;self) -&gt; <a class="primitive" href="https://doc.rust-lang.org/1.78.0/std/primitive.reference.html">&amp;T</a></h4></section></summary><div class='docblock'>Immutably borrows from an owned value. <a href="https://doc.rust-lang.org/1.78.0/core/borrow/trait.Borrow.html#tymethod.borrow">Read more</a></div></details></div></details><details class="toggle implementors-toggle"><summary><section id="impl-BorrowMut%3CT%3E-for-T" class="impl"><a class="src rightside" href="https://doc.rust-lang.org/1.78.0/src/core/borrow.rs.html#216">source</a><a href="#impl-BorrowMut%3CT%3E-for-T" class="anchor">§</a><h3 class="code-header">impl&lt;T&gt; <a class="trait" href="https://doc.rust-lang.org/1.78.0/core/borrow/trait.BorrowMut.html" title="trait core::borrow::BorrowMut">BorrowMut</a>&lt;T&gt; for T<div class="where">where
T: ?<a class="trait" href="https://doc.rust-lang.org/1.78.0/core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a>,</div></h3></section></summary><div class="impl-items"><details class="toggle method-toggle" open><summary><section id="method.borrow_mut" class="method trait-impl"><a class="src rightside" href="https://doc.rust-lang.org/1.78.0/src/core/borrow.rs.html#217">source</a><a href="#method.borrow_mut" class="anchor">§</a><h4 class="code-header">fn <a href="https://doc.rust-lang.org/1.78.0/core/borrow/trait.BorrowMut.html#tymethod.borrow_mut" class="fn">borrow_mut</a>(&amp;mut self) -&gt; <a class="primitive" href="https://doc.rust-lang.org/1.78.0/std/primitive.reference.html">&amp;mut T</a></h4></section></summary><div class='docblock'>Mutably borrows from an owned value. <a href="https://doc.rust-lang.org/1.78.0/core/borrow/trait.BorrowMut.html#tymethod.borrow_mut">Read more</a></div></details></div></details><details class="toggle implementors-toggle"><summary><section id="impl-From%3CT%3E-for-T" class="impl"><a class="src rightside" href="https://doc.rust-lang.org/1.78.0/src/core/convert/mod.rs.html#765">source</a><a href="#impl-From%3CT%3E-for-T" class="anchor">§</a><h3 class="code-header">impl&lt;T&gt; <a class="trait" href="https://doc.rust-lang.org/1.78.0/core/convert/trait.From.html" title="trait core::convert::From">From</a>&lt;T&gt; for T</h3></section></summary><div class="impl-items"><details class="toggle method-toggle" open><summary><section id="method.from" class="method trait-impl"><a class="src rightside" href="https://doc.rust-lang.org/1.78.0/src/core/convert/mod.rs.html#768">source</a><a href="#method.from" class="anchor">§</a><h4 class="code-header">fn <a href="https://doc.rust-lang.org/1.78.0/core/convert/trait.From.html#tymethod.from" class="fn">from</a>(t: T) -&gt; T</h4></section></summary><div class="docblock"><p>Returns the argument unchanged.</p>
</div></details></div></details><details class="toggle implementors-toggle"><summary><section id="impl-Into%3CU%3E-for-T" class="impl"><a class="src rightside" href="https://doc.rust-lang.org/1.78.0/src/core/convert/mod.rs.html#748-750">source</a><a href="#impl-Into%3CU%3E-for-T" class="anchor">§</a><h3 class="code-header">impl&lt;T, U&gt; <a class="trait" href="https://doc.rust-lang.org/1.78.0/core/convert/trait.Into.html" title="trait core::convert::Into">Into</a>&lt;U&gt; for T<div class="where">where
U: <a class="trait" href="https://doc.rust-lang.org/1.78.0/core/convert/trait.From.html" title="trait core::convert::From">From</a>&lt;T&gt;,</div></h3></section></summary><div class="impl-items"><details class="toggle method-toggle" open><summary><section id="method.into" class="method trait-impl"><a class="src rightside" href="https://doc.rust-lang.org/1.78.0/src/core/convert/mod.rs.html#758">source</a><a href="#method.into" class="anchor">§</a><h4 class="code-header">fn <a href="https://doc.rust-lang.org/1.78.0/core/convert/trait.Into.html#tymethod.into" class="fn">into</a>(self) -&gt; U</h4></section></summary><div class="docblock"><p>Calls <code>U::from(self)</code>.</p>
<p>That is, this conversion is whatever the implementation of
<code><a href="https://doc.rust-lang.org/1.78.0/core/convert/trait.From.html" title="trait core::convert::From">From</a>&lt;T&gt; for U</code> chooses to do.</p>
</div></details></div></details><details class="toggle implementors-toggle"><summary><section id="impl-TryFrom%3CU%3E-for-T" class="impl"><a class="src rightside" href="https://doc.rust-lang.org/1.78.0/src/core/convert/mod.rs.html#805-807">source</a><a href="#impl-TryFrom%3CU%3E-for-T" class="anchor">§</a><h3 class="code-header">impl&lt;T, U&gt; <a class="trait" href="https://doc.rust-lang.org/1.78.0/core/convert/trait.TryFrom.html" title="trait core::convert::TryFrom">TryFrom</a>&lt;U&gt; for T<div class="where">where
U: <a class="trait" href="https://doc.rust-lang.org/1.78.0/core/convert/trait.Into.html" title="trait core::convert::Into">Into</a>&lt;T&gt;,</div></h3></section></summary><div class="impl-items"><details class="toggle" open><summary><section id="associatedtype.Error-1" class="associatedtype trait-impl"><a href="#associatedtype.Error-1" class="anchor">§</a><h4 class="code-header">type <a href="https://doc.rust-lang.org/1.78.0/core/convert/trait.TryFrom.html#associatedtype.Error" class="associatedtype">Error</a> = <a class="enum" href="https://doc.rust-lang.org/1.78.0/core/convert/enum.Infallible.html" title="enum core::convert::Infallible">Infallible</a></h4></section></summary><div class='docblock'>The type returned in the event of a conversion error.</div></details><details class="toggle method-toggle" open><summary><section id="method.try_from" class="method trait-impl"><a class="src rightside" href="https://doc.rust-lang.org/1.78.0/src/core/convert/mod.rs.html#812">source</a><a href="#method.try_from" class="anchor">§</a><h4 class="code-header">fn <a href="https://doc.rust-lang.org/1.78.0/core/convert/trait.TryFrom.html#tymethod.try_from" class="fn">try_from</a>(value: U) -&gt; <a class="enum" href="https://doc.rust-lang.org/1.78.0/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;T, &lt;T as <a class="trait" href="https://doc.rust-lang.org/1.78.0/core/convert/trait.TryFrom.html" title="trait core::convert::TryFrom">TryFrom</a>&lt;U&gt;&gt;::<a class="associatedtype" href="https://doc.rust-lang.org/1.78.0/core/convert/trait.TryFrom.html#associatedtype.Error" title="type core::convert::TryFrom::Error">Error</a>&gt;</h4></section></summary><div class='docblock'>Performs the conversion.</div></details></div></details><details class="toggle implementors-toggle"><summary><section id="impl-TryInto%3CU%3E-for-T" class="impl"><a class="src rightside" href="https://doc.rust-lang.org/1.78.0/src/core/convert/mod.rs.html#790-792">source</a><a href="#impl-TryInto%3CU%3E-for-T" class="anchor">§</a><h3 class="code-header">impl&lt;T, U&gt; <a class="trait" href="https://doc.rust-lang.org/1.78.0/core/convert/trait.TryInto.html" title="trait core::convert::TryInto">TryInto</a>&lt;U&gt; for T<div class="where">where
U: <a class="trait" href="https://doc.rust-lang.org/1.78.0/core/convert/trait.TryFrom.html" title="trait core::convert::TryFrom">TryFrom</a>&lt;T&gt;,</div></h3></section></summary><div class="impl-items"><details class="toggle" open><summary><section id="associatedtype.Error" class="associatedtype trait-impl"><a href="#associatedtype.Error" class="anchor">§</a><h4 class="code-header">type <a href="https://doc.rust-lang.org/1.78.0/core/convert/trait.TryInto.html#associatedtype.Error" class="associatedtype">Error</a> = &lt;U as <a class="trait" href="https://doc.rust-lang.org/1.78.0/core/convert/trait.TryFrom.html" title="trait core::convert::TryFrom">TryFrom</a>&lt;T&gt;&gt;::<a class="associatedtype" href="https://doc.rust-lang.org/1.78.0/core/convert/trait.TryFrom.html#associatedtype.Error" title="type core::convert::TryFrom::Error">Error</a></h4></section></summary><div class='docblock'>The type returned in the event of a conversion error.</div></details><details class="toggle method-toggle" open><summary><section id="method.try_into" class="method trait-impl"><a class="src rightside" href="https://doc.rust-lang.org/1.78.0/src/core/convert/mod.rs.html#797">source</a><a href="#method.try_into" class="anchor">§</a><h4 class="code-header">fn <a href="https://doc.rust-lang.org/1.78.0/core/convert/trait.TryInto.html#tymethod.try_into" class="fn">try_into</a>(self) -&gt; <a class="enum" href="https://doc.rust-lang.org/1.78.0/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;U, &lt;U as <a class="trait" href="https://doc.rust-lang.org/1.78.0/core/convert/trait.TryFrom.html" title="trait core::convert::TryFrom">TryFrom</a>&lt;T&gt;&gt;::<a class="associatedtype" href="https://doc.rust-lang.org/1.78.0/core/convert/trait.TryFrom.html#associatedtype.Error" title="type core::convert::TryFrom::Error">Error</a>&gt;</h4></section></summary><div class='docblock'>Performs the conversion.</div></details></div></details></div></section></div></main></body></html>