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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 pinned projection of a struct field."><title>unsafe_pinned in pin_utils - Rust</title><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"><link rel="stylesheet" href="../static.files/normalize-76eba96aa4d2e634.css"><link rel="stylesheet" href="../static.files/rustdoc-ac92e1bbe349e143.css"><meta name="rustdoc-vars" data-root-path="../" data-static-root-path="../static.files/" data-current-crate="pin_utils" data-themes="" data-resource-suffix="" data-rustdoc-version="1.76.0 (07dca489a 2024-02-04)" data-channel="1.76.0" data-search-js="search-2b6ce74ff89ae146.js" data-settings-js="settings-4313503d2e1961c2.js" ><script src="../static.files/storage-f2adc0d6ca4d09fb.js"></script><script defer src="sidebar-items.js"></script><script defer src="../static.files/main-305769736d49e732.js"></script><noscript><link rel="stylesheet" href="../static.files/noscript-feafe1bb7466e4bd.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 macro"><!--[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">☰</button></nav><nav class="sidebar"><div class="sidebar-crate"><h2><a href="../pin_utils/index.html">pin_utils</a><span class="version">0.1.0</span></h2></div><div class="sidebar-elems"></div></nav><div class="sidebar-resizer"></div>
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<main><div class="width-limiter"><nav class="sub"><form class="search-form"><span></span><div id="sidebar-button" tabindex="-1"><a href="../pin_utils/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>Macro <a href="index.html">pin_utils</a>::<wbr><a class="macro" href="#">unsafe_pinned</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"><a class="src" href="../src/pin_utils/projection.rs.html#40-53">source</a> · <button id="toggle-all-docs" title="collapse all docs">[<span>−</span>]</button></span></div><pre class="rust item-decl"><span class="macro">macro_rules! </span>unsafe_pinned {
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(<span class="macro-nonterminal">$f</span>:tt: <span class="macro-nonterminal">$t</span>:ty) => { ... };
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}</pre><details class="toggle top-doc" open><summary class="hideme"><span>Expand description</span></summary><div class="docblock"><p>A pinned projection of a struct field.</p>
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<h2 id="safety"><a href="#safety">Safety</a></h2>
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<p>To make using this macro safe, three things need to be ensured:</p>
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<ul>
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<li>If the struct implements <a href="https://doc.rust-lang.org/1.76.0/core/ops/drop/trait.Drop.html#tymethod.drop" title="method core::ops::drop::Drop::drop"><code>Drop</code></a>, the <a href="https://doc.rust-lang.org/1.76.0/core/ops/drop/trait.Drop.html#tymethod.drop" title="method core::ops::drop::Drop::drop"><code>drop</code></a> method is not allowed to
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move the value of the field.</li>
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<li>If the struct wants to implement <a href="https://doc.rust-lang.org/1.76.0/core/marker/trait.Unpin.html" title="trait core::marker::Unpin"><code>Unpin</code></a>, it has to do so conditionally:
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The struct can only implement <a href="https://doc.rust-lang.org/1.76.0/core/marker/trait.Unpin.html" title="trait core::marker::Unpin"><code>Unpin</code></a> if the field’s type is <a href="https://doc.rust-lang.org/1.76.0/core/marker/trait.Unpin.html" title="trait core::marker::Unpin"><code>Unpin</code></a>.</li>
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<li>The struct must not be <code>#[repr(packed)]</code>.</li>
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</ul>
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<h2 id="example"><a href="#example">Example</a></h2>
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<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use </span>pin_utils::unsafe_pinned;
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<span class="kw">use </span>std::marker::Unpin;
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<span class="kw">use </span>std::pin::Pin;
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<span class="kw">struct </span>Foo<T> {
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field: T,
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}
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<span class="kw">impl</span><T> Foo<T> {
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<span class="macro">unsafe_pinned!</span>(field: T);
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<span class="kw">fn </span>baz(<span class="kw-2">mut </span><span class="self">self</span>: Pin<<span class="kw-2">&mut </span><span class="self">Self</span>>) {
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<span class="kw">let _</span>: Pin<<span class="kw-2">&mut </span>T> = <span class="self">self</span>.field(); <span class="comment">// Pinned reference to the field
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</span>}
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}
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<span class="kw">impl</span><T: Unpin> Unpin <span class="kw">for </span>Foo<T> {} <span class="comment">// Conditional Unpin impl</span></code></pre></div>
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<p>Note: borrowing the field multiple times requires using <code>.as_mut()</code> to
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avoid consuming the <code>Pin</code>.</p>
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