<!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 `proc_macro` crate."><meta name="keywords" content="rust, rustlang, rust-lang, proc_macro"><title>proc_macro - 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><link rel="shortcut icon" href="https://doc.rust-lang.org/favicon.ico"></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='../proc_macro/index.html'><img src='https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png' alt='logo' width='100'></a><p class='location'>Crate proc_macro</p><div class='block version'><p>Version 1.28.0</p></div>
<a id='all-types' href='all.html'><p>See all proc_macro's items</p></a><div class="sidebar-elems"><div class="block items"><ul><li><a href="#modules">Modules</a></li><li><a href="#macros">Macros</a></li><li><a href="#structs">Structs</a></li><li><a href="#enums">Enums</a></li><li><a href="#functions">Functions</a></li></ul></div><p class='location'></p><script>window.sidebarCurrent = {name: 'proc_macro', 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"><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'>Crate <a class="mod" href=''>proc_macro</a></span><span class='out-of-band'><span class='since' title='Stable since Rust version 1.15.0'>1.15.0</span><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/proc_macro/lib.rs.html#11-1457' title='goto source code'>[src]</a></span></h1><div class='docblock'><p>A support library for macro authors when defining new macros.</p>
<p>This library, provided by the standard distribution, provides the types
consumed in the interfaces of procedurally defined macro definitions such as
function-like macros <code>#[proc_macro]</code>, macro attribures <code>#[proc_macro_attribute]</code> and
custom derive attributes<code>#[proc_macro_derive]</code>.</p>
<p>Note that this crate is intentionally bare-bones currently.
This functionality is intended to be expanded over time as more surface
area for macro authors is stabilized.</p>
<p>See <a href="../book/first-edition/procedural-macros.html">the book</a> for more.</p>
</div><h2 id='modules' class='section-header'><a href="#modules">Modules</a></h2>
<table>
<tr class='unstable module-item'>
<td><a class="mod" href="token_stream/index.html"
title='mod proc_macro::token_stream'>token_stream</a></td>
<td class='docblock-short'>
[<div class='stab unstable'>Experimental</div>] <p>Public implementation details for the <code>TokenStream</code> type, such as iterators.</p>
</td>
</tr></table><h2 id='macros' class='section-header'><a href="#macros">Macros</a></h2>
<table>
<tr class='unstable module-item'>
<td><a class="macro" href="macro.quote.html"
title='macro proc_macro::quote'>quote</a></td>
<td class='docblock-short'>
[<div class='stab unstable'>Experimental</div>] <p><code>quote!(..)</code> accepts arbitrary tokens and expands into a <code>TokenStream</code> describing the input.
For example, <code>quote!(a + b)</code> will produce a expression, that, when evaluated, constructs
the <code>TokenStream</code> <code>[Ident("a"), Punct('+', Alone), Ident("b")]</code>.</p>
</td>
</tr></table><h2 id='structs' class='section-header'><a href="#structs">Structs</a></h2>
<table>
<tr class=' module-item'>
<td><a class="struct" href="struct.LexError.html"
title='struct proc_macro::LexError'>LexError</a></td>
<td class='docblock-short'>
<p>Error returned from <code>TokenStream::from_str</code>.</p>
</td>
</tr>
<tr class=' module-item'>
<td><a class="struct" href="struct.TokenStream.html"
title='struct proc_macro::TokenStream'>TokenStream</a></td>
<td class='docblock-short'>
<p>The main type provided by this crate, representing an abstract stream of
tokens, or, more specifically, a sequence of token trees.
The type provide interfaces for iterating over those token trees and, conversely,
collecting a number of token trees into one stream.</p>
</td>
</tr>
<tr class='unstable module-item'>
<td><a class="struct" href="struct.Diagnostic.html"
title='struct proc_macro::Diagnostic'>Diagnostic</a></td>
<td class='docblock-short'>
[<div class='stab unstable'>Experimental</div>] <p>A structure representing a diagnostic message and associated children
messages.</p>
</td>
</tr>
<tr class='unstable module-item'>
<td><a class="struct" href="struct.Group.html"
title='struct proc_macro::Group'>Group</a></td>
<td class='docblock-short'>
[<div class='stab unstable'>Experimental</div>] <p>A delimited token stream.</p>
</td>
</tr>
<tr class='unstable module-item'>
<td><a class="struct" href="struct.Ident.html"
title='struct proc_macro::Ident'>Ident</a></td>
<td class='docblock-short'>
[<div class='stab unstable'>Experimental</div>] <p>An identifier (<code>ident</code>).</p>
</td>
</tr>
<tr class='unstable module-item'>
<td><a class="struct" href="struct.LineColumn.html"
title='struct proc_macro::LineColumn'>LineColumn</a></td>
<td class='docblock-short'>
[<div class='stab unstable'>Experimental</div>] <p>A line-column pair representing the start or end of a <code>Span</code>.</p>
</td>
</tr>
<tr class='unstable module-item'>
<td><a class="struct" href="struct.Literal.html"
title='struct proc_macro::Literal'>Literal</a></td>
<td class='docblock-short'>
[<div class='stab unstable'>Experimental</div>] <p>A literal string (<code>"hello"</code>), byte string (<code>b"hello"</code>),
character (<code>'a'</code>), byte character (<code>b'a'</code>), an integer or floating point number
with or without a suffix (<code>1</code>, <code>1u8</code>, <code>2.3</code>, <code>2.3f32</code>).
Boolean literals like <code>true</code> and <code>false</code> do not belong here, they are <code>Ident</code>s.</p>
</td>
</tr>
<tr class='unstable module-item'>
<td><a class="struct" href="struct.Punct.html"
title='struct proc_macro::Punct'>Punct</a></td>
<td class='docblock-short'>
[<div class='stab unstable'>Experimental</div>] <p>An <code>Punct</code> is an single punctuation character like <code>+</code>, <code>-</code> or <code>#</code>.</p>
</td>
</tr>
<tr class='unstable module-item'>
<td><a class="struct" href="struct.SourceFile.html"
title='struct proc_macro::SourceFile'>SourceFile</a></td>
<td class='docblock-short'>
[<div class='stab unstable'>Experimental</div>] <p>The source file of a given <code>Span</code>.</p>
</td>
</tr>
<tr class='unstable module-item'>
<td><a class="struct" href="struct.Span.html"
title='struct proc_macro::Span'>Span</a></td>
<td class='docblock-short'>
[<div class='stab unstable'>Experimental</div>] <p>A region of source code, along with macro expansion information.</p>
</td>
</tr></table><h2 id='enums' class='section-header'><a href="#enums">Enums</a></h2>
<table>
<tr class='unstable module-item'>
<td><a class="enum" href="enum.Delimiter.html"
title='enum proc_macro::Delimiter'>Delimiter</a></td>
<td class='docblock-short'>
[<div class='stab unstable'>Experimental</div>] <p>Describes how a sequence of token trees is delimited.</p>
</td>
</tr>
<tr class='unstable module-item'>
<td><a class="enum" href="enum.Level.html"
title='enum proc_macro::Level'>Level</a></td>
<td class='docblock-short'>
[<div class='stab unstable'>Experimental</div>] <p>An enum representing a diagnostic level.</p>
</td>
</tr>
<tr class='unstable module-item'>
<td><a class="enum" href="enum.Spacing.html"
title='enum proc_macro::Spacing'>Spacing</a></td>
<td class='docblock-short'>
[<div class='stab unstable'>Experimental</div>] <p>Whether an <code>Punct</code> is followed immediately by another <code>Punct</code> or
followed by another token or whitespace.</p>
</td>
</tr>
<tr class='unstable module-item'>
<td><a class="enum" href="enum.TokenTree.html"
title='enum proc_macro::TokenTree'>TokenTree</a></td>
<td class='docblock-short'>
[<div class='stab unstable'>Experimental</div>] <p>A single token or a delimited sequence of token trees (e.g. <code>[1, (), ..]</code>).</p>
</td>
</tr></table><h2 id='functions' class='section-header'><a href="#functions">Functions</a></h2>
<table>
<tr class='unstable module-item'>
<td><a class="fn" href="fn.quote_span.html"
title='fn proc_macro::quote_span'>quote_span</a></td>
<td class='docblock-short'>
[<div class='stab unstable'>Experimental</div>] <p>Quote a <code>Span</code> into a <code>TokenStream</code>.
This is needed to implement a custom quoter.</p>
</td>
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