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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` macro in crate `synstructure`."><meta name="keywords" content="rust, rustlang, rust-lang, quote"><title>synstructure::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></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">&#9776;</div><div class="sidebar-elems"><p class='location'><a href='index.html'>synstructure</a></p><script>window.sidebarCurrent = {name: '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"><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'>Macro <a href='index.html'>synstructure</a>::<wbr><a class="macro" href=''>quote</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'>&#x2212;</span>]</a></span><a class='srclink' href='../src/quote/lib.rs.html#321-323' title='goto source code'>[src]</a></span></h1><div class="docblock type-decl"><pre class="rust macro">
<span class="macro">macro_rules</span><span class="macro">!</span> <span class="ident">quote</span> {
    ( $ ( $ <span class="ident">tt</span> : <span class="ident">tt</span> ) <span class="op">*</span> ) <span class="op">=&gt;</span> { ... };
}</pre>
</div><div class='docblock'><p>The whole point.</p>
<p>Performs variable interpolation against the input and produces it as
<a href="https://docs.rs/proc-macro2/0.4/proc_macro2/struct.TokenStream.html"><code>TokenStream</code></a>. For returning tokens to the compiler in a procedural macro, use
<code>into()</code> to build a <code>TokenStream</code>.</p>
<h1 id="interpolation" class="section-header"><a href="#interpolation">Interpolation</a></h1>
<p>Variable interpolation is done with <code>#var</code> (similar to <code>$var</code> in
<code>macro_rules!</code> macros). This grabs the <code>var</code> variable that is currently in
scope and inserts it in that location in the output tokens. Any type
implementing the <a href="trait.ToTokens.html"><code>ToTokens</code></a> trait can be interpolated. This includes most
Rust primitive types as well as most of the syntax tree types from the <a href="https://github.com/dtolnay/syn">Syn</a>
crate.</p>
<p>Repetition is done using <code>#(...)*</code> or <code>#(...),*</code> again similar to
<code>macro_rules!</code>. This iterates through the elements of any variable
interpolated within the repetition and inserts a copy of the repetition body
for each one. The variables in an interpolation may be anything that
implements <code>IntoIterator</code>, including <code>Vec</code> or a pre-existing iterator.</p>
<ul>
<li><code>#(#var)*</code> — no separators</li>
<li><code>#(#var),*</code> — the character before the asterisk is used as a separator</li>
<li><code>#( struct #var; )*</code> — the repetition can contain other tokens</li>
<li><code>#( #k =&gt; println!(&quot;{}&quot;, #v), )*</code> — even multiple interpolations</li>
</ul>
<h1 id="hygiene" class="section-header"><a href="#hygiene">Hygiene</a></h1>
<p>Any interpolated tokens preserve the <code>Span</code> information provided by their
<code>ToTokens</code> implementation. Tokens that originate within the <code>quote!</code>
invocation are spanned with <a href="https://docs.rs/proc-macro2/0.4/proc_macro2/struct.Span.html#method.call_site"><code>Span::call_site()</code></a>.</p>
<p>A different span can be provided through the <a href="macro.quote_spanned.html"><code>quote_spanned!</code></a> macro.</p>
<h1 id="example" class="section-header"><a href="#example">Example</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="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">proc_macro</span>::<span class="ident">TokenStream</span>;

<span class="attribute">#[<span class="ident">proc_macro_derive</span>(<span class="ident">HeapSize</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">derive_heap_size</span>(<span class="ident">input</span>: <span class="ident">TokenStream</span>) <span class="op">-&gt;</span> <span class="ident">TokenStream</span> {
    <span class="comment">// Parse the input and figure out what implementation to generate...</span>
    <span class="kw">let</span> <span class="ident">name</span> <span class="op">=</span> <span class="comment">/* ... */</span>;
    <span class="kw">let</span> <span class="ident">expr</span> <span class="op">=</span> <span class="comment">/* ... */</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">// The generated impl.</span>
        <span class="kw">impl</span> ::<span class="ident">heapsize</span>::<span class="ident">HeapSize</span> <span class="kw">for</span> #<span class="ident">name</span> {
            <span class="kw">fn</span> <span class="ident">heap_size_of_children</span>(<span class="kw-2">&amp;</span><span class="self">self</span>) <span class="op">-&gt;</span> <span class="ident">usize</span> {
                #<span class="ident">expr</span>
            }
        }
    };

    <span class="comment">// Hand the output tokens back to the compiler.</span>
    <span class="ident">expanded</span>.<span class="ident">into</span>()
}</pre>
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