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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` fn in crate `syn`."><meta name="keywords" content="rust, rustlang, rust-lang, parse"><title>syn::parse - 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></head><body class="rustdoc fn"><!--[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><div class="sidebar-elems"><p class='location'><a href='index.html'>syn</a></p><script>window.sidebarCurrent = {name: 'parse', ty: 'fn', 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"><input class="search-input" name="search" autocomplete="off" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"><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='in-band'>Function <a href='index.html'>syn</a>::<wbr><a class="fn" href=''>parse</a></span><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/lib.rs.html#637-642' title='goto source code'>[src]</a></span></h1><pre class='rust fn'>pub fn parse<T>(tokens: <a class="struct" href="https://doc.rust-lang.org/nightly/proc_macro/struct.TokenStream.html" title="struct proc_macro::TokenStream">TokenStream</a>) -> <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a><T, <a class="struct" href="../syn/synom/struct.ParseError.html" title="struct syn::synom::ParseError">ParseError</a>> <span class="where fmt-newline">where<br> T: <a class="trait" href="../syn/synom/trait.Synom.html" title="trait syn::synom::Synom">Synom</a>, </span></pre><div class='docblock'><p>Parse tokens of source code into the chosen syntax tree node.</p>
- <p>This is preferred over parsing a string because tokens are able to preserve
- information about where in the user's code they were originally written (the
- "span" of the token), possibly allowing the compiler to produce better error
- messages.</p>
- <p>This function parses a <code>proc_macro::TokenStream</code> which is the type used for
- interop with the compiler in a procedural macro. To parse a
- <code>proc_macro2::TokenStream</code>, use <a href="fn.parse2.html"><code>syn::parse2</code></a> instead.</p>
- <p><em>This function is available if Syn is built with both the <code>"parsing"</code> and
- <code>"proc-macro"</code> features.</em></p>
- <h1 id="examples" class="section-header"><a href="#examples">Examples</a></h1>
- <pre class="rust rust-example-rendered">
- <span class="kw">extern</span> <span class="kw">crate</span> <span class="ident">proc_macro</span>;
- <span class="kw">use</span> <span class="ident">proc_macro</span>::<span class="ident">TokenStream</span>;
- <span class="kw">extern</span> <span class="kw">crate</span> <span class="ident">syn</span>;
- <span class="attribute">#[<span class="ident">macro_use</span>]</span>
- <span class="kw">extern</span> <span class="kw">crate</span> <span class="ident">quote</span>;
- <span class="kw">use</span> <span class="ident">syn</span>::<span class="ident">DeriveInput</span>;
- <span class="attribute">#[<span class="ident">proc_macro_derive</span>(<span class="ident">MyMacro</span>)]</span>
- <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">my_macro</span>(<span class="ident">input</span>: <span class="ident">TokenStream</span>) <span class="op">-></span> <span class="ident">TokenStream</span> {
- <span class="comment">// Parse the tokens into a syntax tree</span>
- <span class="kw">let</span> <span class="ident">ast</span>: <span class="ident">DeriveInput</span> <span class="op">=</span> <span class="ident">syn</span>::<span class="ident">parse</span>(<span class="ident">input</span>).<span class="ident">unwrap</span>();
- <span class="comment">// Build the output, possibly using quasi-quotation</span>
- <span class="kw">let</span> <span class="ident">expanded</span> <span class="op">=</span> <span class="macro">quote</span><span class="macro">!</span> {
- <span class="comment">/* ... */</span>
- };
- <span class="comment">// Convert into a token stream and return it</span>
- <span class="ident">expanded</span>.<span class="ident">into</span>()
- }</pre>
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