185 lines
8.9 KiB
HTML
185 lines
8.9 KiB
HTML
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<!DOCTYPE html>
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<meta name="description" content="API documentation for the Rust `quote` macro in crate `synstructure`.">
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<meta name="keywords" content="rust, rustlang, rust-lang, quote">
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<title>synstructure::quote - Rust</title>
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<div class="sidebar-menu">☰</div>
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<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>
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type="search">
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<section id='main' class="content">
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<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'>
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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></span></h1>
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<pre class="rust macro">
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<span class="macro">macro_rules</span><span class="macro">!</span> <span class="ident">quote</span> {
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( $ ( $ <span class="ident">tt</span> : <span class="ident">tt</span> ) <span class="op">*</span> ) <span class="op">=></span> { ... };
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}</pre>
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<div class='docblock'><p>The whole point.</p>
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<p>Performs variable interpolation against the input and produces it as
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<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
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<code>into()</code> to build a <code>TokenStream</code>.</p>
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<h1 id="interpolation" class="section-header"><a href="#interpolation">Interpolation</a></h1>
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<p>Variable interpolation is done with <code>#var</code> (similar to <code>$var</code> in
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<code>macro_rules!</code> macros). This grabs the <code>var</code> variable that is currently in
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scope and inserts it in that location in the output tokens. Any type
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implementing the <a href="trait.ToTokens.html"><code>ToTokens</code></a> trait can be interpolated. This includes most
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Rust primitive types as well as most of the syntax tree types from the <a href="https://github.com/dtolnay/syn">Syn</a>
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crate.</p>
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<p>Repetition is done using <code>#(...)*</code> or <code>#(...),*</code> again similar to
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<code>macro_rules!</code>. This iterates through the elements of any variable
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interpolated within the repetition and inserts a copy of the repetition body
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for each one. The variables in an interpolation may be anything that
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implements <code>IntoIterator</code>, including <code>Vec</code> or a pre-existing iterator.</p>
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<ul>
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<li><code>#(#var)*</code> — no separators</li>
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<li><code>#(#var),*</code> — the character before the asterisk is used as a separator</li>
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<li><code>#( struct #var; )*</code> — the repetition can contain other tokens</li>
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<li><code>#( #k => println!("{}", #v), )*</code> — even multiple interpolations</li>
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</ul>
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<h1 id="hygiene" class="section-header"><a href="#hygiene">Hygiene</a></h1>
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<p>Any interpolated tokens preserve the <code>Span</code> information provided by their
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<code>ToTokens</code> implementation. Tokens that originate within the <code>quote!</code>
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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>
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<p>A different span can be provided through the <a href="macro.quote_spanned.html"><code>quote_spanned!</code></a> macro.</p>
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<h1 id="example" class="section-header"><a href="#example">Example</a></h1>
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<pre class="rust rust-example-rendered">
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<span class="kw">extern</span> <span class="kw">crate</span> <span class="ident">proc_macro</span>;
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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>;
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<span class="kw">use</span> <span class="ident">proc_macro</span>::<span class="ident">TokenStream</span>;
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<span class="attribute">#[<span class="ident">proc_macro_derive</span>(<span class="ident">HeapSize</span>)]</span>
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<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">-></span> <span class="ident">TokenStream</span> {
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<span class="comment">// Parse the input and figure out what implementation to generate...</span>
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<span class="kw">let</span> <span class="ident">name</span> <span class="op">=</span> <span class="comment">/* ... */</span>;
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<span class="kw">let</span> <span class="ident">expr</span> <span class="op">=</span> <span class="comment">/* ... */</span>;
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<span class="kw">let</span> <span class="ident">expanded</span> <span class="op">=</span> <span class="macro">quote</span><span class="macro">!</span> {
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<span class="comment">// The generated impl.</span>
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<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> {
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<span class="kw">fn</span> <span class="ident">heap_size_of_children</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="ident">usize</span> {
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#<span class="ident">expr</span>
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}
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}
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};
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<span class="comment">// Hand the output tokens back to the compiler.</span>
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<span class="ident">expanded</span>.<span class="ident">into</span>()
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}</pre>
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</div></section>
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Accepted types are: <code>fn</code>, <code>mod</code>,
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