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<p class='location'>Crate quote</p><div class="sidebar-elems"><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>
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<h1 class='fqn'><span class='in-band'>Crate <a class="mod" href=''>quote</a></span><span class='out-of-band'><span id='render-detail'>
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[<span class='inner'>&#x2212;</span>]
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</span><a class='srclink' href='../src/quote/lib.rs.html#1-858' title='goto source code'>[src]</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
structures into tokens of source code.</p>
<p>Procedural macros in Rust receive a stream of tokens as input, execute
arbitrary Rust code to determine how to manipulate those tokens, and produce
a stream of tokens to hand back to the compiler to compile into the caller's
crate. Quasi-quoting is a solution to one piece of that -- producing tokens
to return to the compiler.</p>
<p>The idea of quasi-quoting is that we write <em>code</em> that we treat as <em>data</em>.
Within the <code>quote!</code> macro, we can write what looks like code to our text
editor or IDE. We get all the benefits of the editor's brace matching,
syntax highlighting, indentation, and maybe autocompletion. But rather than
compiling that as code into the current crate, we can treat it as data, pass
it around, mutate it, and eventually hand it back to the compiler as tokens
to compile into the macro caller's crate.</p>
<p>This crate is motivated by the procedural macro use case, but is a
general-purpose Rust quasi-quoting library and is not specific to procedural
macros.</p>
<p><em>Version requirement: Quote supports any compiler version back to Rust's
very first support for procedural macros in Rust 1.15.0.</em></p>
<pre><code class="language-toml">[dependencies]
quote = &quot;0.6&quot;
</code></pre>
<pre class="rust rust-example-rendered">
<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>;</pre>
<h1 id="example" class="section-header"><a href="#example">Example</a></h1>
<p>The following quasi-quoted block of code is something you might find in <a href="https://serde.rs/">a</a>
procedural macro having to do with data structure serialization. The <code>#var</code>
syntax performs interpolation of runtime variables into the quoted tokens.
Check out the documentation of the <a href="macro.quote.html"><code>quote!</code></a> macro for more detail about
the syntax. See also the <a href="macro.quote_spanned.html"><code>quote_spanned!</code></a> macro which is important for
implementing hygienic procedural macros.</p>
<pre class="rust rust-example-rendered">
<span class="kw">let</span> <span class="ident">tokens</span> <span class="op">=</span> <span class="macro">quote</span><span class="macro">!</span> {
<span class="kw">struct</span> <span class="ident">SerializeWith</span> #<span class="ident">generics</span> #<span class="ident">where_clause</span> {
<span class="ident">value</span>: <span class="kw-2">&amp;</span><span class="lifetime">&#39;a</span> #<span class="ident">field_ty</span>,
<span class="ident">phantom</span>: ::<span class="ident">std</span>::<span class="ident">marker</span>::<span class="ident">PhantomData</span><span class="op">&lt;</span>#<span class="ident">item_ty</span><span class="op">&gt;</span>,
}
<span class="kw">impl</span> #<span class="ident">generics</span> <span class="ident">serde</span>::<span class="ident">Serialize</span> <span class="kw">for</span> <span class="ident">SerializeWith</span> #<span class="ident">generics</span> #<span class="ident">where_clause</span> {
<span class="kw">fn</span> <span class="ident">serialize</span><span class="op">&lt;</span><span class="ident">S</span><span class="op">&gt;</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">serializer</span>: <span class="ident">S</span>) <span class="op">-&gt;</span> <span class="prelude-ty">Result</span><span class="op">&lt;</span><span class="ident">S</span>::<span class="prelude-val">Ok</span>, <span class="ident">S</span>::<span class="ident">Error</span><span class="op">&gt;</span>
<span class="kw">where</span>
<span class="ident">S</span>: <span class="ident">serde</span>::<span class="ident">Serializer</span>,
{
#<span class="ident">path</span>(<span class="self">self</span>.<span class="ident">value</span>, <span class="ident">serializer</span>)
}
}
<span class="ident">SerializeWith</span> {
<span class="ident">value</span>: #<span class="ident">value</span>,
<span class="ident">phantom</span>: ::<span class="ident">std</span>::<span class="ident">marker</span>::<span class="ident">PhantomData</span>::<span class="op">&lt;</span>#<span class="ident">item_ty</span><span class="op">&gt;</span>,
}
};</pre>
<h2 id="recursion-limit" class="section-header"><a href="#recursion-limit">Recursion limit</a></h2>
<p>The <code>quote!</code> macro relies on deep recursion so some large invocations may
fail with &quot;recursion limit reached&quot; when you compile. If it fails, bump up
the recursion limit by adding <code>#![recursion_limit = &quot;128&quot;]</code> to your crate.
An even higher limit may be necessary for especially large invocations.</p>
</div><h2 id='macros' class='section-header'><a href="#macros">Macros</a></h2>
<table>
<tr class=' module-item'>
<td><a class="macro" href="macro.quote.html"
title='macro quote::quote'>quote</a></td>
<td class='docblock-short'>
<p>The whole point.</p>
</td>
</tr>
<tr class=' module-item'>
<td><a class="macro" href="macro.quote_spanned.html"
title='macro quote::quote_spanned'>quote_spanned</a></td>
<td class='docblock-short'>
<p>Same as <code>quote!</code>, but applies a given span to all tokens originating within
the macro invocation.</p>
</td>
</tr></table><h2 id='traits' class='section-header'><a href="#traits">Traits</a></h2>
<table>
<tr class=' module-item'>
<td><a class="trait" href="trait.ToTokens.html"
title='trait quote::ToTokens'>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>
</td>
</tr>
<tr class=' module-item'>
<td><a class="trait" href="trait.TokenStreamExt.html"
title='trait quote::TokenStreamExt'>TokenStreamExt</a></td>
<td class='docblock-short'>
<p>TokenStream extension trait with methods for appending tokens.</p>
</td>
</tr></table></section>
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