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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 `quote` crate."><meta name="keywords" content="rust, rustlang, rust-lang, quote"><title>quote - 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="../dark.css"><link rel="stylesheet" type="text/css" href="../light.css" id="themeStyle"><script src="../storage.js"></script><noscript><link rel="stylesheet" href="../noscript.css"></noscript><link rel="shortcut icon" href="../favicon.ico"><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='../quote/index.html'><div class='logo-container'><img src='../rust-logo.png' alt='logo'></div></a><p class='location'>Crate quote</p><div class="sidebar-elems"><a id='all-types' href='all.html'><p>See all quote's items</p></a><div class="block items"><ul><li><a href="#macros">Macros</a></li><li><a href="#traits">Traits</a></li></ul></div><p class='location'></p><script>window.sidebarCurrent = {name: 'quote', ty: 'mod', relpath: '../'};</script></div></nav><div class="theme-picker"><button id="theme-picker" aria-label="Pick another theme!"><img src="../brush.svg" width="18" alt="Pick another theme!"></button><div id="theme-choices"></div></div><script src="../theme.js"></script><nav class="sub"><form class="search-form js-only"><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><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/quote/lib.rs.html#1-861' title='goto source code'>[src]</a></span><span class='in-band'>Crate <a class="mod" href=''>quote</a></span></h1><div class='docblock'><p>This crate provides the <a href="macro.quote.html"><code>quote!</code></a> macro for turning Rust syntax tree data
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structures into tokens of source code.</p>
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<p>Procedural macros in Rust receive a stream of tokens as input, execute
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arbitrary Rust code to determine how to manipulate those tokens, and produce
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a stream of tokens to hand back to the compiler to compile into the caller's
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crate. Quasi-quoting is a solution to one piece of that -- producing tokens
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to return to the compiler.</p>
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<p>The idea of quasi-quoting is that we write <em>code</em> that we treat as <em>data</em>.
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Within the <code>quote!</code> macro, we can write what looks like code to our text
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editor or IDE. We get all the benefits of the editor's brace matching,
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syntax highlighting, indentation, and maybe autocompletion. But rather than
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compiling that as code into the current crate, we can treat it as data, pass
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it around, mutate it, and eventually hand it back to the compiler as tokens
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to compile into the macro caller's crate.</p>
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<p>This crate is motivated by the procedural macro use case, but is a
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general-purpose Rust quasi-quoting library and is not specific to procedural
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macros.</p>
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<p><em>Version requirement: Quote supports any compiler version back to Rust's
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very first support for procedural macros in Rust 1.15.0.</em></p>
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<pre><code class="language-toml">[dependencies]
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quote = "0.6"
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</code></pre>
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<h1 id="example" class="section-header"><a href="#example">Example</a></h1>
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<p>The following quasi-quoted block of code is something you might find in <a href="https://serde.rs/">a</a>
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procedural macro having to do with data structure serialization. The <code>#var</code>
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syntax performs interpolation of runtime variables into the quoted tokens.
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Check out the documentation of the <a href="macro.quote.html"><code>quote!</code></a> macro for more detail about
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the syntax. See also the <a href="macro.quote_spanned.html"><code>quote_spanned!</code></a> macro which is important for
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implementing hygienic procedural macros.</p>
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<pre><code class="language-edition2018"># use quote::quote;
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#
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# let generics = "";
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# let where_clause = "";
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# let field_ty = "";
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# let item_ty = "";
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# let path = "";
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# let value = "";
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#
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let tokens = quote! {
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struct SerializeWith #generics #where_clause {
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value: &'a #field_ty,
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phantom: core::marker::PhantomData<#item_ty>,
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}
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impl #generics serde::Serialize for SerializeWith #generics #where_clause {
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fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
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where
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S: serde::Serializer,
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{
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#path(self.value, serializer)
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}
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}
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SerializeWith {
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value: #value,
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phantom: core::marker::PhantomData::<#item_ty>,
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}
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};
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</code></pre>
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<h1 id="recursion-limit" class="section-header"><a href="#recursion-limit">Recursion limit</a></h1>
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<p>The <code>quote!</code> macro relies on deep recursion so some large invocations may
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fail with "recursion limit reached" when you compile. If it fails, bump up
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the recursion limit by adding <code>#![recursion_limit = "128"]</code> to your crate.
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An even higher limit may be necessary for especially large invocations.</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.quote.html" title='quote::quote macro'>quote</a></td><td class='docblock-short'><p>The whole point.</p>
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</td></tr><tr class='module-item'><td><a class="macro" href="macro.quote_spanned.html" title='quote::quote_spanned macro'>quote_spanned</a></td><td class='docblock-short'><p>Same as <code>quote!</code>, but applies a given span to all tokens originating within
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the macro invocation.</p>
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</td></tr></table><h2 id='traits' class='section-header'><a href="#traits">Traits</a></h2>
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<table><tr class='module-item'><td><a class="trait" href="trait.ToTokens.html" title='quote::ToTokens trait'>ToTokens</a></td><td class='docblock-short'><p>Types that can be interpolated inside a <a href="macro.quote.html"><code>quote!</code></a> invocation.</p>
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</td></tr><tr class='module-item'><td><a class="trait" href="trait.TokenStreamExt.html" title='quote::TokenStreamExt trait'>TokenStreamExt</a></td><td class='docblock-short'><p>TokenStream extension trait with methods for appending tokens.</p>
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</td></tr></table></section><section id="search" class="content hidden"></section><section class="footer"></section><aside id="help" class="hidden"><div><h1 class="hidden">Help</h1><div class="shortcuts"><h2>Keyboard Shortcuts</h2><dl><dt><kbd>?</kbd></dt><dd>Show this help dialog</dd><dt><kbd>S</kbd></dt><dd>Focus the search field</dd><dt><kbd>↑</kbd></dt><dd>Move up in search results</dd><dt><kbd>↓</kbd></dt><dd>Move down in search results</dd><dt><kbd>↹</kbd></dt><dd>Switch tab</dd><dt><kbd>⏎</kbd></dt><dd>Go to active search result</dd><dt><kbd>+</kbd></dt><dd>Expand all sections</dd><dt><kbd>-</kbd></dt><dd>Collapse all sections</dd></dl></div><div class="infos"><h2>Search Tricks</h2><p>Prefix searches with a type followed by a colon (e.g., <code>fn:</code>) to restrict the search to a given type.</p><p>Accepted types are: <code>fn</code>, <code>mod</code>, <code>struct</code>, <code>enum</code>, <code>trait</code>, <code>type</code>, <code>macro</code>, and <code>const</code>.</p><p>Search functions by type signature (e.g., <code>vec -> usize</code> or <code>* -> vec</code>)</p><p>Search multiple things at once by splitting your query with comma (e.g., <code>str,u8</code> or <code>String,struct:Vec,test</code>)</p></div></div></aside><script>window.rootPath = "../";window.currentCrate = "quote";</script><script src="../aliases.js"></script><script src="../main.js"></script><script defer src="../search-index.js"></script></body></html>
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