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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 `parse_quote` macro in crate `syn`."><meta name="keywords" content="rust, rustlang, rust-lang, parse_quote"><title>syn::parse_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 macro"><!--[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='../syn/index.html'><div class='logo-container'><img src='../rust-logo.png' alt='logo'></div></a><div class="sidebar-elems"><p class='location'><a href='index.html'>syn</a></p><script>window.sidebarCurrent = {name: 'parse_quote', ty: 'macro', relpath: ''};</script><script defer src="sidebar-items.js"></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/syn/parse_quote.rs.html#69-73' title='goto source code'>[src]</a></span><span class='in-band'>Macro <a href='index.html'>syn</a>::<wbr><a class="macro" href=''>parse_quote</a></span></h1><div class="docblock type-decl hidden-by-usual-hider"><div class="example-wrap"><pre class="rust macro">
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<span class="macro">macro_rules</span><span class="macro">!</span> <span class="ident">parse_quote</span> {
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($(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">tt</span>:<span class="ident">tt</span>)<span class="kw-2">*</span>) <span class="op">=</span><span class="op">></span> { ... };
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}</pre></div>
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</div><div class='docblock'><p>Quasi-quotation macro that accepts input like the <a href="https://docs.rs/quote/0.6/quote/index.html"><code>quote!</code></a> macro but uses
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type inference to figure out a return type for those tokens.</p>
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<p>The return type can be any syntax tree node that implements the <a href="parse/trait.Parse.html"><code>Parse</code></a>
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trait.</p>
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<pre><code class="language-edition2018">use quote::quote;
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use syn::{parse_quote, Stmt};
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fn main() {
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let name = quote!(v);
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let ty = quote!(u8);
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let stmt: Stmt = parse_quote! {
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let #name: #ty = Default::default();
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};
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println!("{:#?}", stmt);
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}
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</code></pre>
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<p><em>This macro is available if Syn is built with the <code>"parsing"</code> feature,
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although interpolation of syntax tree nodes into the quoted tokens is only
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supported if Syn is built with the <code>"printing"</code> feature as well.</em></p>
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<h1 id="example" class="section-header"><a href="#example">Example</a></h1>
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<p>The following helper function adds a bound <code>T: HeapSize</code> to every type
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parameter <code>T</code> in the input generics.</p>
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<pre><code class="language-edition2018">use syn::{parse_quote, Generics, GenericParam};
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// Add a bound `T: HeapSize` to every type parameter T.
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fn add_trait_bounds(mut generics: Generics) -> Generics {
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for param in &mut generics.params {
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if let GenericParam::Type(type_param) = param {
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type_param.bounds.push(parse_quote!(HeapSize));
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}
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}
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generics
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}
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</code></pre>
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<h1 id="special-cases" class="section-header"><a href="#special-cases">Special cases</a></h1>
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<p>This macro can parse the following additional types as a special case even
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though they do not implement the <code>Parse</code> trait.</p>
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<ul>
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<li><a href="struct.Attribute.html"><code>Attribute</code></a> — parses one attribute, allowing either outer like <code>#[...]</code>
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or inner like <code>#![...]</code></li>
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<li><a href="punctuated/struct.Punctuated.html"><code>Punctuated<T, P></code></a> — parses zero or more <code>T</code> separated by punctuation
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<code>P</code> with optional trailing punctuation</li>
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</ul>
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<h1 id="panics" class="section-header"><a href="#panics">Panics</a></h1>
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<p>Panics if the tokens fail to parse as the expected syntax tree type. The
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caller is responsible for ensuring that the input tokens are syntactically
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valid.</p>
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