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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."><title>pin_project_lite - 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_project_lite" 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="../crates.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 mod crate"><!--[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_project_lite/index.html">pin_project_lite</a><span class="version">0.2.13</span></h2></div><div class="sidebar-elems"><ul class="block">
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<li><a id="all-types" href="all.html">All Items</a></li></ul><section><ul class="block"><li><a href="#macros">Macros</a></li></ul></section></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_project_lite/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>Crate <a class="mod" href="#">pin_project_lite</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_project_lite/lib.rs.html#1-1682">source</a> · <button id="toggle-all-docs" title="collapse all docs">[<span>−</span>]</button></span></div><details class="toggle top-doc" open><summary class="hideme"><span>Expand description</span></summary><div class="docblock"><!-- tidy:crate-doc:start -->
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<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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<h3 id="usage"><a href="#usage">Usage</a></h3>
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<p>Add this to your <code>Cargo.toml</code>:</p>
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<div class="example-wrap"><pre class="language-toml"><code>[dependencies]
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pin-project-lite = "0.2"
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</code></pre></div>
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<p><em>Compiler support: requires rustc 1.37+</em></p>
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<h3 id="examples"><a href="#examples">Examples</a></h3>
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<p><a href="macro.pin_project.html" title="macro pin_project_lite::pin_project"><code>pin_project!</code></a> macro creates a projection type covering all the fields of
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struct.</p>
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<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use </span>std::pin::Pin;
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<span class="kw">use </span>pin_project_lite::pin_project;
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<span class="macro">pin_project! </span>{
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<span class="kw">struct </span>Struct<T, U> {
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<span class="attr">#[pin]
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</span>pinned: T,
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unpinned: U,
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}
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}
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<span class="kw">impl</span><T, U> Struct<T, U> {
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<span class="kw">fn </span>method(<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>this = <span class="self">self</span>.project();
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<span class="kw">let _</span>: Pin<<span class="kw-2">&mut </span>T> = this.pinned; <span class="comment">// Pinned reference to the field
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</span><span class="kw">let _</span>: <span class="kw-2">&mut </span>U = this.unpinned; <span class="comment">// Normal reference to the field
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</span>}
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}</code></pre></div>
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<p>To use <a href="macro.pin_project.html" title="macro pin_project_lite::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>std::pin::Pin;
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<span class="kw">use </span>pin_project_lite::pin_project;
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<span class="macro">pin_project! </span>{
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<span class="attr">#[project = EnumProj]
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</span><span class="kw">enum </span>Enum<T, U> {
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Variant { <span class="attr">#[pin] </span>pinned: T, unpinned: U },
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}
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}
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<span class="kw">impl</span><T, U> Enum<T, U> {
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<span class="kw">fn </span>method(<span class="self">self</span>: Pin<<span class="kw-2">&mut </span><span class="self">Self</span>>) {
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<span class="kw">match </span><span class="self">self</span>.project() {
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EnumProj::Variant { pinned, unpinned } => {
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<span class="kw">let _</span>: Pin<<span class="kw-2">&mut </span>T> = pinned;
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<span class="kw">let _</span>: <span class="kw-2">&mut </span>U = unpinned;
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}
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}
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}
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}</code></pre></div>
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<h3 id="pin-project-vs-pin-project-lite"><a href="#pin-project-vs-pin-project-lite">pin-project vs pin-project-lite</a></h3>
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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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<h4 id="similar-safety"><a href="#similar-safety">Similar: Safety</a></h4>
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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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<h4 id="different-minimal-design"><a href="#different-minimal-design">Different: Minimal design</a></h4>
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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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<h4 id="different-no-proc-macro-related-dependencies"><a href="#different-no-proc-macro-related-dependencies">Different: No proc-macro related dependencies</a></h4>
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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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<h4 id="different-no-useful-error-messages"><a href="#different-no-useful-error-messages">Different: No useful error messages</a></h4>
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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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<h4 id="different-no-support-for-custom-unpin-implementation"><a href="#different-no-support-for-custom-unpin-implementation">Different: No support for custom Unpin implementation</a></h4>
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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>. (<code>!Unpin</code> is supported by both <a href="https://docs.rs/pin-project/1/pin_project/attr.pin_project.html#unpin">pin-project</a> and <a href="https://docs.rs/pin-project-lite/0.2/pin_project_lite/macro.pin_project.html#unpin">pin-project-lite</a>.)</p>
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<h4 id="different-no-support-for-tuple-structs-and-tuple-variants"><a href="#different-no-support-for-tuple-structs-and-tuple-variants">Different: No support for tuple structs and tuple variants</a></h4>
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<p>pin-project supports this.</p>
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<!-- tidy:crate-doc:end --></div></details><h2 id="macros" class="section-header"><a href="#macros">Macros</a></h2><ul class="item-table"><li><div class="item-name"><a class="macro" href="macro.pin_project.html" title="macro pin_project_lite::pin_project">pin_project</a></div><div class="desc docblock-short">A macro that creates a projection type covering all the fields of struct.</div></li></ul></section></div></main></body></html>
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