| <!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="Define a type that supports parsing and printing a multi-character symbol as if it were a punctuation token."><meta name="keywords" content="rust, rustlang, rust-lang, custom_punctuation"><title>custom_punctuation in syn - Rust</title><link rel="preload" as="font" type="font/woff2" crossorigin href="../SourceSerif4-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../FiraSans-Regular.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../FiraSans-Medium.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../SourceCodePro-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../SourceSerif4-Bold.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../SourceCodePro-Semibold.ttf.woff2"><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="../ayu.css" disabled><link rel="stylesheet" type="text/css" href="../dark.css" disabled><link rel="stylesheet" type="text/css" href="../light.css" id="themeStyle"><script id="default-settings" ></script><script src="../storage.js"></script><script src="../crates.js"></script><script defer src="../main.js"></script> |
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| </a><div class="sidebar-elems"><h2 class="location">Other items in<br><a href="index.html">syn</a></h2><div id="sidebar-vars" data-name="custom_punctuation" data-ty="macro" data-relpath=""></div><script defer src="sidebar-items.js"></script></div></nav><main><div class="width-limiter"><div class="sub-container"><a class="sub-logo-container" href="../syn/index.html"><img class="rust-logo" src="../rust-logo.png" alt="logo"></a><nav class="sub"><div class="theme-picker"><button id="theme-picker" aria-label="Pick another theme!" aria-haspopup="menu" title="themes"><img width="18" height="18" alt="Pick another theme!" src="../brush.svg"></button><div id="theme-choices" role="menu"></div></div><form class="search-form"><div class="search-container"><div> |
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| <h1 class="fqn"><span class="in-band">Macro <a href="index.html">syn</a>::<wbr><a class="macro" href="#">custom_punctuation</a><button id="copy-path" onclick="copy_path(this)" title="Copy item path to clipboard"><img src="../clipboard.svg" width="19" height="18" alt="Copy item path"></button></span></h1><span class="out-of-band"> |
| <a class="srclink" href="../src/syn/custom_punctuation.rs.html#78-106" title="goto source code">source</a> · |
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| <div class="docblock item-decl"><div class="example-wrap"><pre class="rust macro"><code><span class="macro">macro_rules!</span> <span class="ident">custom_punctuation</span> { |
| (<span class="macro-nonterminal">$</span><span class="macro-nonterminal">ident</span> : <span class="ident">ident</span>, $(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">tt</span> : <span class="ident">tt</span>) <span class="op">+</span>) => { ... }; |
| }</code></pre></div> |
| </div><details class="rustdoc-toggle top-doc" open><summary class="hideme"><span>Expand description</span></summary><div class="docblock"><p>Define a type that supports parsing and printing a multi-character symbol |
| as if it were a punctuation token.</p> |
| <h2 id="usage" class="section-header"><a href="#usage">Usage</a></h2> |
| <div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="macro">syn::custom_punctuation!</span>(<span class="ident">LeftRightArrow</span>, <span class="op"><</span>=>);</code></pre></div> |
| <p>The generated syntax tree node supports the following operations just like |
| any built-in punctuation token.</p> |
| <ul> |
| <li> |
| <p><a href="parse/struct.ParseBuffer.html#method.peek">Peeking</a> — <code>input.peek(LeftRightArrow)</code></p> |
| </li> |
| <li> |
| <p><a href="parse/struct.ParseBuffer.html#method.parse">Parsing</a> — <code>input.parse::<LeftRightArrow>()?</code></p> |
| </li> |
| <li> |
| <p><a href="../quote/to_tokens/trait.ToTokens.html">Printing</a> — <code>quote!( ... #lrarrow ... )</code></p> |
| </li> |
| <li> |
| <p>Construction from a <a href="../proc_macro2/struct.Span.html"><code>Span</code></a> — <code>let lrarrow = LeftRightArrow(sp)</code></p> |
| </li> |
| <li> |
| <p>Construction from multiple <a href="../proc_macro2/struct.Span.html"><code>Span</code></a> — <code>let lrarrow = LeftRightArrow([sp, sp, sp])</code></p> |
| </li> |
| <li> |
| <p>Field access to its spans — <code>let spans = lrarrow.spans</code></p> |
| </li> |
| </ul> |
| <h2 id="example" class="section-header"><a href="#example">Example</a></h2> |
| <div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use</span> <span class="ident">proc_macro2</span>::{<span class="ident">TokenStream</span>, <span class="ident">TokenTree</span>}; |
| <span class="kw">use</span> <span class="ident">syn::parse</span>::{<span class="ident">Parse</span>, <span class="ident">ParseStream</span>, <span class="ident">Peek</span>, <span class="prelude-ty">Result</span>}; |
| <span class="kw">use</span> <span class="ident">syn::punctuated::Punctuated</span>; |
| <span class="kw">use</span> <span class="ident">syn::Expr</span>; |
| |
| <span class="macro">syn::custom_punctuation!</span>(<span class="ident">PathSeparator</span>, <span class="op"><</span><span class="op">/</span><span class="op">></span>); |
| |
| <span class="comment">// expr </> expr </> expr ...</span> |
| <span class="kw">struct</span> <span class="ident">PathSegments</span> { |
| <span class="ident">segments</span>: <span class="ident">Punctuated</span><span class="op"><</span><span class="ident">Expr</span>, <span class="ident">PathSeparator</span><span class="op">></span>, |
| } |
| |
| <span class="kw">impl</span> <span class="ident">Parse</span> <span class="kw">for</span> <span class="ident">PathSegments</span> { |
| <span class="kw">fn</span> <span class="ident">parse</span>(<span class="ident">input</span>: <span class="ident">ParseStream</span>) -> <span class="prelude-ty">Result</span><span class="op"><</span><span class="self">Self</span><span class="op">></span> { |
| <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">segments</span> <span class="op">=</span> <span class="ident">Punctuated::new</span>(); |
| |
| <span class="kw">let</span> <span class="ident">first</span> <span class="op">=</span> <span class="ident">parse_until</span>(<span class="ident">input</span>, <span class="ident">PathSeparator</span>)<span class="question-mark">?</span>; |
| <span class="ident">segments</span>.<span class="ident">push_value</span>(<span class="ident">syn::parse2</span>(<span class="ident">first</span>)<span class="question-mark">?</span>); |
| |
| <span class="kw">while</span> <span class="ident">input</span>.<span class="ident">peek</span>(<span class="ident">PathSeparator</span>) { |
| <span class="ident">segments</span>.<span class="ident">push_punct</span>(<span class="ident">input</span>.<span class="ident">parse</span>()<span class="question-mark">?</span>); |
| |
| <span class="kw">let</span> <span class="ident">next</span> <span class="op">=</span> <span class="ident">parse_until</span>(<span class="ident">input</span>, <span class="ident">PathSeparator</span>)<span class="question-mark">?</span>; |
| <span class="ident">segments</span>.<span class="ident">push_value</span>(<span class="ident">syn::parse2</span>(<span class="ident">next</span>)<span class="question-mark">?</span>); |
| } |
| |
| <span class="prelude-val">Ok</span>(<span class="ident">PathSegments</span> { <span class="ident">segments</span> }) |
| } |
| } |
| |
| <span class="kw">fn</span> <span class="ident">parse_until</span><span class="op"><</span><span class="ident">E</span>: <span class="ident">Peek</span><span class="op">></span>(<span class="ident">input</span>: <span class="ident">ParseStream</span>, <span class="ident">end</span>: <span class="ident">E</span>) -> <span class="prelude-ty">Result</span><span class="op"><</span><span class="ident">TokenStream</span><span class="op">></span> { |
| <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">tokens</span> <span class="op">=</span> <span class="ident">TokenStream::new</span>(); |
| <span class="kw">while</span> <span class="op">!</span><span class="ident">input</span>.<span class="ident">is_empty</span>() <span class="op">&&</span> <span class="op">!</span><span class="ident">input</span>.<span class="ident">peek</span>(<span class="ident">end</span>) { |
| <span class="kw">let</span> <span class="ident">next</span>: <span class="ident">TokenTree</span> <span class="op">=</span> <span class="ident">input</span>.<span class="ident">parse</span>()<span class="question-mark">?</span>; |
| <span class="ident">tokens</span>.<span class="ident">extend</span>(<span class="prelude-val">Some</span>(<span class="ident">next</span>)); |
| } |
| <span class="prelude-val">Ok</span>(<span class="ident">tokens</span>) |
| } |
| |
| <span class="kw">fn</span> <span class="ident">main</span>() { |
| <span class="kw">let</span> <span class="ident">input</span> <span class="op">=</span> <span class="string">r#" a::b </> c::d::e "#</span>; |
| <span class="kw">let</span> <span class="kw">_</span>: <span class="ident">PathSegments</span> <span class="op">=</span> <span class="ident">syn::parse_str</span>(<span class="ident">input</span>).<span class="ident">unwrap</span>(); |
| }</code></pre></div> |
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