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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="API documentation for the Rust `pin_project_lite` crate."><meta name="keywords" content="rust, rustlang, rust-lang, pin_project_lite"><title>pin_project_lite - 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="../light.css" id="themeStyle"><link rel="stylesheet" type="text/css" href="../dark.css" disabled ><link rel="stylesheet" type="text/css" href="../ayu.css" disabled ><script id="default-settings"></script><script src="../storage.js"></script><noscript><link rel="stylesheet" href="../noscript.css"></noscript><link rel="icon" type="image/svg+xml" href="../favicon.svg">
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<link rel="alternate icon" type="image/png" href="../favicon-32x32.png"><style type="text/css">#crate-search{background-image:url("../down-arrow.svg");}</style></head><body class="rustdoc mod"><!--[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='../pin_project_lite/index.html'><div class='logo-container rust-logo'><img src='../rust-logo.png' alt='logo'></div></a><p class="location">Crate pin_project_lite</p><div class="block version"><p>Version 0.2.0</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><p class="location"></p><script>window.sidebarCurrent = {name: "pin_project_lite", ty: "mod", relpath: "../"};</script></div></nav><div class="theme-picker"><button id="theme-picker" aria-label="Pick another theme!" aria-haspopup="menu"><img src="../brush.svg" width="18" alt="Pick another theme!"></button><div id="theme-choices" role="menu"></div></div><script src="../theme.js"></script><nav class="sub"><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" disabled autocomplete="off" spellcheck="false" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"></div><span class="help-button">?</span>
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<a id="settings-menu" href="../settings.html"><img src="../wheel.svg" width="18" alt="Change settings"></a></div></form></nav><section id="main" class="content"><h1 class="fqn"><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#1-1273" title="goto source code">[src]</a></span><span class="in-band">Crate <a class="mod" href="">pin_project_lite</a></span></h1><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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<h1 id="examples" class="section-header"><a href="#examples">Examples</a></h1>
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<p><a href="../pin_project_lite/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">
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<span class="kw">use</span> <span class="ident">pin_project_lite</span>::<span class="ident">pin_project</span>;
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<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">pin</span>::<span class="ident">Pin</span>;
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<span class="macro">pin_project</span><span class="macro">!</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">&</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">&</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">&</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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}</pre></div>
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<p>To use <a href="../pin_project_lite/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">
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<span class="kw">use</span> <span class="ident">pin_project_lite</span>::<span class="ident">pin_project</span>;
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<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">pin</span>::<span class="ident">Pin</span>;
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<span class="macro">pin_project</span><span class="macro">!</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">&</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</span>::<span class="ident">Variant</span> { <span class="ident">pinned</span>, <span class="ident">unpinned</span> } <span class="op">=</span><span class="op">></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">&</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">&</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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}</pre></div>
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<h1 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></h1>
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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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<h2 id="similar-safety" class="section-header"><a href="#similar-safety">Similar: Safety</a></h2>
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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>. Both are completely safe unless you write other unsafe code.</p>
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<h2 id="different-minimal-design" class="section-header"><a href="#different-minimal-design">Different: Minimal design</a></h2>
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<p>This library does not tackle as expansive of a range of use cases as <a href="https://github.com/taiki-e/pin-project">pin-project</a> does. If your use case is not already covered, please use <a href="https://github.com/taiki-e/pin-project">pin-project</a>.</p>
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<h2 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></h2>
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<p>This is the <strong>only</strong> reason to use this crate. However, <strong>if you already have proc-macro related dependencies in your crate's dependency graph, there is no benefit from using this crate.</strong> (Note: There is almost no difference 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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<h2 id="different-no-useful-error-messages" class="section-header"><a href="#different-no-useful-error-messages">Different: No useful error messages</a></h2>
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<p>This macro does not handle any invalid input. So error messages are not to be useful in most cases. If you do need useful error messages, then upon error you can pass the same input to <a href="https://github.com/taiki-e/pin-project">pin-project</a> to receive a helpful description of the compile error.</p>
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<h2 id="different-no-support-for-custom-drop-implementation" class="section-header"><a href="#different-no-support-for-custom-drop-implementation">Different: No support for custom Drop implementation</a></h2>
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<p>pin-project supports this by <a href="https://docs.rs/pin-project/1/pin_project/attr.pin_project.html#pinned_drop"><code>#[pinned_drop]</code></a>.</p>
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<h2 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></h2>
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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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<h2 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></h2>
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<p>pin-project supports this.</p>
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</div><h2 id="macros" class="section-header"><a href="#macros">Macros</a></h2>
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<table><tr class="module-item"><td><a class="macro" href="macro.pin_project.html" title="pin_project_lite::pin_project macro">pin_project</a></td><td class="docblock-short"><p>A macro that creates a projection type covering all the fields of struct.</p>
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</td></tr></table></section><section id="search" class="content hidden"></section><section class="footer"></section><script>window.rootPath = "../";window.currentCrate = "pin_project_lite";</script><script src="../main.js"></script><script defer src="../search-index.js"></script></body></html>
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