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<meta name="generator" content="rustdoc">
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<meta name="description" content="API documentation for the Rust `quote` crate.">
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<meta name="keywords" content="rust, rustlang, rust-lang, quote">
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<title>quote - Rust</title>
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<!--[if lte IE 8]>
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This old browser is unsupported and will most likely display funky
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things.
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<![endif]-->
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<nav class="sidebar">
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<div class="sidebar-menu">☰</div>
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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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autocomplete="off"
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placeholder="Click or press ‘S’ to search, ‘?’ for more options…"
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type="search">
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</div>
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</form>
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</nav>
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<section id='main' class="content">
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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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<a id="toggle-all-docs" href="javascript:void(0)" title="collapse all docs">
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[<span class='inner'>−</span>]
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</a>
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</span><a class='srclink' href='../src/quote/lib.rs.html#1-858' title='goto source code'>[src]</a></span></h1>
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<div class='docblock'><p>This crate provides the <a href="macro.quote.html"><code>quote!</code></a> macro for turning Rust syntax tree data
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structures into tokens of source code.</p>
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<p>Procedural macros in Rust receive a stream of tokens as input, execute
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arbitrary Rust code to determine how to manipulate those tokens, and produce
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a stream of tokens to hand back to the compiler to compile into the caller's
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crate. Quasi-quoting is a solution to one piece of that -- producing tokens
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to return to the compiler.</p>
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<p>The idea of quasi-quoting is that we write <em>code</em> that we treat as <em>data</em>.
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Within the <code>quote!</code> macro, we can write what looks like code to our text
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editor or IDE. We get all the benefits of the editor's brace matching,
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syntax highlighting, indentation, and maybe autocompletion. But rather than
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compiling that as code into the current crate, we can treat it as data, pass
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it around, mutate it, and eventually hand it back to the compiler as tokens
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to compile into the macro caller's crate.</p>
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<p>This crate is motivated by the procedural macro use case, but is a
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general-purpose Rust quasi-quoting library and is not specific to procedural
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macros.</p>
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<p><em>Version requirement: Quote supports any compiler version back to Rust's
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very first support for procedural macros in Rust 1.15.0.</em></p>
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<pre><code class="language-toml">[dependencies]
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quote = "0.6"
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</code></pre>
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<pre class="rust rust-example-rendered">
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<span class="attribute">#[<span class="ident">macro_use</span>]</span>
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<span class="kw">extern</span> <span class="kw">crate</span> <span class="ident">quote</span>;</pre>
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<h1 id="example" class="section-header"><a href="#example">Example</a></h1>
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<p>The following quasi-quoted block of code is something you might find in <a href="https://serde.rs/">a</a>
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procedural macro having to do with data structure serialization. The <code>#var</code>
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syntax performs interpolation of runtime variables into the quoted tokens.
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Check out the documentation of the <a href="macro.quote.html"><code>quote!</code></a> macro for more detail about
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the syntax. See also the <a href="macro.quote_spanned.html"><code>quote_spanned!</code></a> macro which is important for
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implementing hygienic procedural macros.</p>
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<pre class="rust rust-example-rendered">
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<span class="kw">let</span> <span class="ident">tokens</span> <span class="op">=</span> <span class="macro">quote</span><span class="macro">!</span> {
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<span class="kw">struct</span> <span class="ident">SerializeWith</span> #<span class="ident">generics</span> #<span class="ident">where_clause</span> {
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<span class="ident">value</span>: <span class="kw-2">&</span><span class="lifetime">'a</span> #<span class="ident">field_ty</span>,
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<span class="ident">phantom</span>: ::<span class="ident">std</span>::<span class="ident">marker</span>::<span class="ident">PhantomData</span><span class="op"><</span>#<span class="ident">item_ty</span><span class="op">></span>,
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}
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<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> {
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<span class="kw">fn</span> <span class="ident">serialize</span><span class="op"><</span><span class="ident">S</span><span class="op">></span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">serializer</span>: <span class="ident">S</span>) <span class="op">-></span> <span class="prelude-ty">Result</span><span class="op"><</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">></span>
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<span class="kw">where</span>
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<span class="ident">S</span>: <span class="ident">serde</span>::<span class="ident">Serializer</span>,
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{
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#<span class="ident">path</span>(<span class="self">self</span>.<span class="ident">value</span>, <span class="ident">serializer</span>)
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}
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}
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<span class="ident">SerializeWith</span> {
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<span class="ident">value</span>: #<span class="ident">value</span>,
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<span class="ident">phantom</span>: ::<span class="ident">std</span>::<span class="ident">marker</span>::<span class="ident">PhantomData</span>::<span class="op"><</span>#<span class="ident">item_ty</span><span class="op">></span>,
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}
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};</pre>
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<h2 id="recursion-limit" class="section-header"><a href="#recursion-limit">Recursion limit</a></h2>
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<p>The <code>quote!</code> macro relies on deep recursion so some large invocations may
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fail with "recursion limit reached" when you compile. If it fails, bump up
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the recursion limit by adding <code>#![recursion_limit = "128"]</code> to your crate.
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An even higher limit may be necessary for especially large invocations.</p>
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</div><h2 id='macros' class='section-header'><a href="#macros">Macros</a></h2>
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<table>
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<tr class=' module-item'>
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<td><a class="macro" href="macro.quote.html"
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title='macro quote::quote'>quote</a></td>
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<td class='docblock-short'>
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<p>The whole point.</p>
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</td>
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</tr>
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<tr class=' module-item'>
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<td><a class="macro" href="macro.quote_spanned.html"
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title='macro quote::quote_spanned'>quote_spanned</a></td>
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<td class='docblock-short'>
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<p>Same as <code>quote!</code>, but applies a given span to all tokens originating within
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the macro invocation.</p>
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</td>
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</tr></table><h2 id='traits' class='section-header'><a href="#traits">Traits</a></h2>
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<table>
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<tr class=' module-item'>
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<td><a class="trait" href="trait.ToTokens.html"
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title='trait quote::ToTokens'>ToTokens</a></td>
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<td class='docblock-short'>
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<p>Types that can be interpolated inside a <a href="macro.quote.html"><code>quote!</code></a> invocation.</p>
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</td>
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</tr>
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<tr class=' module-item'>
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<td><a class="trait" href="trait.TokenStreamExt.html"
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title='trait quote::TokenStreamExt'>TokenStreamExt</a></td>
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<td class='docblock-short'>
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<p>TokenStream extension trait with methods for appending tokens.</p>
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</td>
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</tr></table></section>
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