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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 lightweight version of pin-project written with declarative macros."><meta name="keywords" content="rust, rustlang, rust-lang, pin_project_lite"><title>pin_project_lite - Rust</title><link rel="preload" as="font" type="font/woff2" crossorigin href="../SourceSerif4-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../FiraSans-Regular.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../FiraSans-Medium.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../SourceCodePro-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../SourceSerif4-Bold.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../SourceCodePro-Semibold.ttf.woff2"><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="../ayu.css" disabled><link rel="stylesheet" type="text/css" href="../dark.css" disabled><link rel="stylesheet" type="text/css" href="../light.css" id="themeStyle"><script id="default-settings" ></script><script src="../storage.js"></script><script src="../crates.js"></script><script defer src="../main.js"></script>
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</a><h2 class="location">Crate pin_project_lite</h2><div class="block version"><div class="narrow-helper"></div><p>Version 0.2.8</p></div><div class="sidebar-elems"><a id="all-types" href="all.html"><p>See all pin_project_lite's items</p></a><div class="block items"><ul><li><a href="#macros">Macros</a></li></ul></div><div id="sidebar-vars" data-name="pin_project_lite" data-ty="mod" data-relpath=""></div><script defer src="sidebar-items.js"></script></div></nav><main><div class="width-limiter"><div class="sub-container"><a class="sub-logo-container" href="../pin_project_lite/index.html"><img class="rust-logo" src="../rust-logo.png" alt="logo"></a><nav class="sub"><div class="theme-picker"><button id="theme-picker" aria-label="Pick another theme!" aria-haspopup="menu" title="themes"><img width="18" height="18" alt="Pick another theme!" src="../brush.svg"></button><div id="theme-choices" role="menu"></div></div><form class="search-form"><div class="search-container"><div><select id="crate-search"><option value="All crates">All crates</option></select><input class="search-input" name="search" autocomplete="off" spellcheck="false" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"></div><button type="button" id="help-button" title="help">?</button><a id="settings-menu" href="../settings.html" title="settings"><img width="18" height="18" alt="Change settings" src="../wheel.svg"></a></div></form></nav></div><section id="main-content" class="content"><h1 class="fqn"><span class="in-band">Crate <a class="mod" href="#">pin_project_lite</a><button id="copy-path" onclick="copy_path(this)" title="Copy item path to clipboard"><img src="../clipboard.svg" width="19" height="18" alt="Copy item path"></button></span><span class="out-of-band"><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/pin_project_lite/lib.rs.html#1-1558" title="goto source code">[src]</a></span></h1><details class="rustdoc-toggle top-doc" open><summary class="hideme"><span>Expand description</span></summary><div class="docblock"><p>A lightweight version of <a href="https://github.com/taiki-e/pin-project">pin-project</a> written with declarative macros.</p>
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<h2 id="examples" class="section-header"><a href="#examples">Examples</a></h2>
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<p><a href="macro.pin_project.html" title="pin_project!"><code>pin_project!</code></a> macro creates a projection type covering all the fields of struct.</p>
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<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use</span> <span class="ident">std::pin::Pin</span>;
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<span class="kw">use</span> <span class="ident">pin_project_lite::pin_project</span>;
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<span class="macro">pin_project!</span> {
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<span class="kw">struct</span> <span class="ident">Struct</span><span class="op"><</span><span class="ident">T</span>, <span class="ident">U</span><span class="op">></span> {
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<span class="attribute">#[<span class="ident">pin</span>]</span>
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<span class="ident">pinned</span>: <span class="ident">T</span>,
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<span class="ident">unpinned</span>: <span class="ident">U</span>,
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}
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}
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<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span>, <span class="ident">U</span><span class="op">></span> <span class="ident">Struct</span><span class="op"><</span><span class="ident">T</span>, <span class="ident">U</span><span class="op">></span> {
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<span class="kw">fn</span> <span class="ident">method</span>(<span class="self">self</span>: <span class="ident">Pin</span><span class="op"><</span><span class="kw-2">&mut</span> <span class="self">Self</span><span class="op">></span>) {
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<span class="kw">let</span> <span class="ident">this</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">project</span>();
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<span class="kw">let</span> <span class="kw">_</span>: <span class="ident">Pin</span><span class="op"><</span><span class="kw-2">&mut</span> <span class="ident">T</span><span class="op">></span> <span class="op">=</span> <span class="ident">this</span>.<span class="ident">pinned</span>; <span class="comment">// Pinned reference to the field</span>
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<span class="kw">let</span> <span class="kw">_</span>: <span class="kw-2">&mut</span> <span class="ident">U</span> <span class="op">=</span> <span class="ident">this</span>.<span class="ident">unpinned</span>; <span class="comment">// Normal reference to the field</span>
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}
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}</code></pre></div>
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<p>To use <a href="macro.pin_project.html" title="pin_project!"><code>pin_project!</code></a> on enums, you need to name the projection type
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returned from the method.</p>
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<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use</span> <span class="ident">std::pin::Pin</span>;
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<span class="kw">use</span> <span class="ident">pin_project_lite::pin_project</span>;
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<span class="macro">pin_project!</span> {
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<span class="attribute">#[<span class="ident">project</span> <span class="op">=</span> <span class="ident">EnumProj</span>]</span>
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<span class="kw">enum</span> <span class="ident">Enum</span><span class="op"><</span><span class="ident">T</span>, <span class="ident">U</span><span class="op">></span> {
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<span class="ident">Variant</span> { <span class="attribute">#[<span class="ident">pin</span>]</span> <span class="ident">pinned</span>: <span class="ident">T</span>, <span class="ident">unpinned</span>: <span class="ident">U</span> },
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}
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}
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<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span>, <span class="ident">U</span><span class="op">></span> <span class="ident">Enum</span><span class="op"><</span><span class="ident">T</span>, <span class="ident">U</span><span class="op">></span> {
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<span class="kw">fn</span> <span class="ident">method</span>(<span class="self">self</span>: <span class="ident">Pin</span><span class="op"><</span><span class="kw-2">&mut</span> <span class="self">Self</span><span class="op">></span>) {
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<span class="kw">match</span> <span class="self">self</span>.<span class="ident">project</span>() {
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<span class="ident">EnumProj::Variant</span> { <span class="ident">pinned</span>, <span class="ident">unpinned</span> } => {
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<span class="kw">let</span> <span class="kw">_</span>: <span class="ident">Pin</span><span class="op"><</span><span class="kw-2">&mut</span> <span class="ident">T</span><span class="op">></span> <span class="op">=</span> <span class="ident">pinned</span>;
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<span class="kw">let</span> <span class="kw">_</span>: <span class="kw-2">&mut</span> <span class="ident">U</span> <span class="op">=</span> <span class="ident">unpinned</span>;
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}
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}
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}
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}</code></pre></div>
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<h2 id="pin-project-vs-pin-project-lite" class="section-header"><a href="#pin-project-vs-pin-project-lite">pin-project vs pin-project-lite</a></h2>
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<p>Here are some similarities and differences compared to <a href="https://github.com/taiki-e/pin-project">pin-project</a>.</p>
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<h3 id="similar-safety" class="section-header"><a href="#similar-safety">Similar: Safety</a></h3>
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<p>pin-project-lite guarantees safety in much the same way as <a href="https://github.com/taiki-e/pin-project">pin-project</a>.
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Both are completely safe unless you write other unsafe code.</p>
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<h3 id="different-minimal-design" class="section-header"><a href="#different-minimal-design">Different: Minimal design</a></h3>
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<p>This library does not tackle as expansive of a range of use cases as
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<a href="https://github.com/taiki-e/pin-project">pin-project</a> does. If your use case is not already covered, please use
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<a href="https://github.com/taiki-e/pin-project">pin-project</a>.</p>
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<h3 id="different-no-proc-macro-related-dependencies" class="section-header"><a href="#different-no-proc-macro-related-dependencies">Different: No proc-macro related dependencies</a></h3>
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<p>This is the <strong>only</strong> reason to use this crate. However, <strong>if you already
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have proc-macro related dependencies in your crate’s dependency graph, there
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is no benefit from using this crate.</strong> (Note: There is almost no difference
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in the amount of code generated between <a href="https://github.com/taiki-e/pin-project">pin-project</a> and pin-project-lite.)</p>
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<h3 id="different-no-useful-error-messages" class="section-header"><a href="#different-no-useful-error-messages">Different: No useful error messages</a></h3>
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<p>This macro does not handle any invalid input. So error messages are not to
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be useful in most cases. If you do need useful error messages, then upon
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error you can pass the same input to <a href="https://github.com/taiki-e/pin-project">pin-project</a> to receive a helpful
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description of the compile error.</p>
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<h3 id="different-no-support-for-custom-unpin-implementation" class="section-header"><a href="#different-no-support-for-custom-unpin-implementation">Different: No support for custom Unpin implementation</a></h3>
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<p>pin-project supports this by <a href="https://docs.rs/pin-project/1/pin_project/attr.pin_project.html#unsafeunpin"><code>UnsafeUnpin</code></a> and <a href="https://docs.rs/pin-project/1/pin_project/attr.pin_project.html#unpin"><code>!Unpin</code></a>.</p>
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<h3 id="different-no-support-for-tuple-structs-and-tuple-variants" class="section-header"><a href="#different-no-support-for-tuple-structs-and-tuple-variants">Different: No support for tuple structs and tuple variants</a></h3>
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<p>pin-project supports this.</p>
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</div></details><h2 id="macros" class="small-section-header"><a href="#macros">Macros</a></h2>
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<div class="item-table"><div class="item-row"><div class="item-left module-item"><a class="macro" href="macro.pin_project.html" title="pin_project_lite::pin_project macro">pin_project</a></div><div class="item-right docblock-short"><p>A macro that creates a projection type covering all the fields of struct.</p>
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</div></div></div></section><section id="search" class="content hidden"></section></div></main><div id="rustdoc-vars" data-root-path="../" data-current-crate="pin_project_lite" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.59.0 (9d1b2106e 2022-02-23)" ></div>
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