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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><script>if(window.location.protocol!=="file:")document.head.insertAdjacentHTML("beforeend","SourceSerif4-Regular-46f98efaafac5295.ttf.woff2,FiraSans-Regular-018c141bf0843ffd.woff2,FiraSans-Medium-8f9a781e4970d388.woff2,SourceCodePro-Regular-562dcc5011b6de7d.ttf.woff2,SourceCodePro-Semibold-d899c5a5c4aeb14a.ttf.woff2".split(",").map(f=>`<link rel="preload" as="font" type="font/woff2" crossorigin href="../static.files/${f}">`).join(""))</script><link rel="stylesheet" href="../static.files/normalize-76eba96aa4d2e634.css"><link rel="stylesheet" href="../static.files/rustdoc-492a78a4a87dcc01.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="1.82.0 (f6e511eec 2024-10-15)" data-channel="1.82.0" data-search-js="search-a99f1315e7cc5121.js" data-settings-js="settings-4313503d2e1961c2.js" ><script src="../static.files/storage-118b08c4c78b968e.js"></script><script defer src="../crates.js"></script><script defer src="../static.files/main-921df33f47b8780c.js"></script><noscript><link rel="stylesheet" href="../static.files/noscript-3b12f09e550e0385.css"></noscript><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" title="show sidebar"></button></nav><nav class="sidebar"><div class="sidebar-crate"><h2><a href="../pin_project_lite/index.html">pin_<wbr>project_<wbr>lite</a><span class="version">0.2.14</span></h2></div><div class="sidebar-elems"><ul class="block"><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><main><div class="width-limiter"><rustdoc-search></rustdoc-search><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">Copy item path</button></h1><span class="out-of-band"><a class="src" href="../src/pin_project_lite/lib.rs.html#3-1729">source</a> · <button id="toggle-all-docs" title="collapse all docs">[<span>&#x2212;</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 -->
<p>A lightweight version of <a href="https://github.com/taiki-e/pin-project">pin-project</a> written with declarative macros.</p>
<h3 id="usage"><a class="doc-anchor" href="#usage">§</a>Usage</h3>
<p>Add this to your <code>Cargo.toml</code>:</p>
<div class="example-wrap"><pre class="language-toml"><code>[dependencies]
pin-project-lite = &quot;0.2&quot;
</code></pre></div>
<p><em>Compiler support: requires rustc 1.37+</em></p>
<h3 id="examples"><a class="doc-anchor" href="#examples">§</a>Examples</h3>
<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
struct.</p>
<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use </span>std::pin::Pin;
<span class="kw">use </span>pin_project_lite::pin_project;
<span class="macro">pin_project!</span> {
<span class="kw">struct </span>Struct&lt;T, U&gt; {
<span class="attr">#[pin]
</span>pinned: T,
unpinned: U,
}
}
<span class="kw">impl</span>&lt;T, U&gt; Struct&lt;T, U&gt; {
<span class="kw">fn </span>method(<span class="self">self</span>: Pin&lt;<span class="kw-2">&amp;mut </span><span class="self">Self</span>&gt;) {
<span class="kw">let </span>this = <span class="self">self</span>.project();
<span class="kw">let _</span>: Pin&lt;<span class="kw-2">&amp;mut </span>T&gt; = this.pinned; <span class="comment">// Pinned reference to the field
</span><span class="kw">let _</span>: <span class="kw-2">&amp;mut </span>U = this.unpinned; <span class="comment">// Normal reference to the field
</span>}
}</code></pre></div>
<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
returned from the method.</p>
<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use </span>std::pin::Pin;
<span class="kw">use </span>pin_project_lite::pin_project;
<span class="macro">pin_project!</span> {
<span class="attr">#[project = EnumProj]
</span><span class="kw">enum </span>Enum&lt;T, U&gt; {
Variant { <span class="attr">#[pin] </span>pinned: T, unpinned: U },
}
}
<span class="kw">impl</span>&lt;T, U&gt; Enum&lt;T, U&gt; {
<span class="kw">fn </span>method(<span class="self">self</span>: Pin&lt;<span class="kw-2">&amp;mut </span><span class="self">Self</span>&gt;) {
<span class="kw">match </span><span class="self">self</span>.project() {
EnumProj::Variant { pinned, unpinned } =&gt; {
<span class="kw">let _</span>: Pin&lt;<span class="kw-2">&amp;mut </span>T&gt; = pinned;
<span class="kw">let _</span>: <span class="kw-2">&amp;mut </span>U = unpinned;
}
}
}
}</code></pre></div>
<h3 id="pin-project-vs-pin-project-lite"><a class="doc-anchor" href="#pin-project-vs-pin-project-lite">§</a><a href="https://github.com/taiki-e/pin-project">pin-project</a> vs pin-project-lite</h3>
<p>Here are some similarities and differences compared to <a href="https://github.com/taiki-e/pin-project">pin-project</a>.</p>
<h4 id="similar-safety"><a class="doc-anchor" href="#similar-safety">§</a>Similar: Safety</h4>
<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>
<h4 id="different-minimal-design"><a class="doc-anchor" href="#different-minimal-design">§</a>Different: Minimal design</h4>
<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>
<h4 id="different-no-proc-macro-related-dependencies"><a class="doc-anchor" href="#different-no-proc-macro-related-dependencies">§</a>Different: No proc-macro related dependencies</h4>
<p>This is the <strong>only</strong> reason to use this crate. However, <strong>if you already
have proc-macro related dependencies in your crates 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>
<h4 id="different-no-useful-error-messages"><a class="doc-anchor" href="#different-no-useful-error-messages">§</a>Different: No useful error messages</h4>
<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>
<h4 id="different-no-support-for-custom-unpin-implementation"><a class="doc-anchor" href="#different-no-support-for-custom-unpin-implementation">§</a>Different: No support for custom Unpin implementation</h4>
<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>
<h4 id="different-no-support-for-tuple-structs-and-tuple-variants"><a class="doc-anchor" href="#different-no-support-for-tuple-structs-and-tuple-variants">§</a>Different: No support for tuple structs and tuple variants</h4>
<p>pin-project supports this.</p>
<!-- tidy:crate-doc:end --></div></details><h2 id="macros" class="section-header">Macros<a href="#macros" class="anchor">§</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_<wbr>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>