| <!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="Formatting macro for constructing `Ident`s."><meta name="keywords" content="rust, rustlang, rust-lang, format_ident"><title>format_ident in quote - 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" href="../normalize.css"><link rel="stylesheet" href="../rustdoc.css" id="mainThemeStyle"><link rel="stylesheet" href="../ayu.css" disabled><link rel="stylesheet" href="../dark.css" disabled><link rel="stylesheet" href="../light.css" id="themeStyle"><script id="default-settings" ></script><script src="../storage.js"></script><script defer src="sidebar-items.js"></script><script defer src="../main.js"></script><noscript><link rel="stylesheet" href="../noscript.css"></noscript><link rel="alternate icon" type="image/png" href="../favicon-16x16.png"><link rel="alternate icon" type="image/png" href="../favicon-32x32.png"><link rel="icon" type="image/svg+xml" href="../favicon.svg"></head><body class="rustdoc macro"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="mobile-topbar"><button class="sidebar-menu-toggle">☰</button><a class="sidebar-logo" href="../quote/index.html"><div class="logo-container"><img class="rust-logo" src="../rust-logo.svg" alt="logo"></div></a><h2></h2></nav><nav class="sidebar"><a class="sidebar-logo" href="../quote/index.html"><div class="logo-container"><img class="rust-logo" src="../rust-logo.svg" alt="logo"></div></a><div class="sidebar-elems"><h2><a href="index.html">In quote</a></h2></div></nav><main><div class="width-limiter"><nav class="sub"><form class="search-form"><div class="search-container"><span></span><input class="search-input" name="search" autocomplete="off" spellcheck="false" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"><div id="help-button" title="help" tabindex="-1"><a href="../help.html">?</a></div><div id="settings-menu" tabindex="-1"><a href="../settings.html" title="settings"><img width="22" height="22" alt="Change settings" src="../wheel.svg"></a></div></div></form></nav><section id="main-content" class="content"><div class="main-heading"><h1 class="fqn">Macro <a href="index.html">quote</a>::<wbr><a class="macro" href="#">format_ident</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></h1><span class="out-of-band"><a class="srclink" href="../src/quote/format.rs.html#111-125">source</a> · <a id="toggle-all-docs" href="javascript:void(0)" title="collapse all docs">[<span class="inner">−</span>]</a></span></div><div class="item-decl"><div class="example-wrap"><pre class="rust macro"><code><span class="macro">macro_rules! </span>format_ident { |
| (<span class="macro-nonterminal">$fmt</span>:expr) => { ... }; |
| (<span class="macro-nonterminal">$fmt</span>:expr, $(<span class="macro-nonterminal">$rest</span>:tt)<span class="kw-2">*</span>) => { ... }; |
| }</code></pre></div> |
| </div><details class="rustdoc-toggle top-doc" open><summary class="hideme"><span>Expand description</span></summary><div class="docblock"><p>Formatting macro for constructing <code>Ident</code>s.</p> |
| <br> |
| <h2 id="syntax"><a href="#syntax">Syntax</a></h2> |
| <p>Syntax is copied from the <a href="https://doc.rust-lang.org/nightly/alloc/macro.format.html" title="format!"><code>format!</code></a> macro, supporting both positional and |
| named arguments.</p> |
| <p>Only a limited set of formatting traits are supported. The current mapping |
| of format types to traits is:</p> |
| <ul> |
| <li><code>{}</code> ⇒ <a href="trait.IdentFragment.html"><code>IdentFragment</code></a></li> |
| <li><code>{:o}</code> ⇒ <a href="https://doc.rust-lang.org/nightly/core/fmt/trait.Octal.html"><code>Octal</code></a></li> |
| <li><code>{:x}</code> ⇒ <a href="https://doc.rust-lang.org/nightly/core/fmt/trait.LowerHex.html"><code>LowerHex</code></a></li> |
| <li><code>{:X}</code> ⇒ <a href="https://doc.rust-lang.org/nightly/core/fmt/trait.UpperHex.html"><code>UpperHex</code></a></li> |
| <li><code>{:b}</code> ⇒ <a href="https://doc.rust-lang.org/nightly/core/fmt/trait.Binary.html"><code>Binary</code></a></li> |
| </ul> |
| <p>See <a href="https://doc.rust-lang.org/nightly/alloc/fmt/index.html" title="std::fmt"><code>std::fmt</code></a> for more information.</p> |
| <br> |
| <h2 id="identfragment"><a href="#identfragment">IdentFragment</a></h2> |
| <p>Unlike <code>format!</code>, this macro uses the <a href="trait.IdentFragment.html"><code>IdentFragment</code></a> formatting trait by |
| default. This trait is like <code>Display</code>, with a few differences:</p> |
| <ul> |
| <li><code>IdentFragment</code> is only implemented for a limited set of types, such as |
| unsigned integers and strings.</li> |
| <li><a href="../proc_macro2/struct.Ident.html"><code>Ident</code></a> arguments will have their <code>r#</code> prefixes stripped, if present.</li> |
| </ul> |
| <br> |
| <h2 id="hygiene"><a href="#hygiene">Hygiene</a></h2> |
| <p>The <a href="../proc_macro2/struct.Span.html"><code>Span</code></a> of the first <code>Ident</code> argument is used as the span of the final |
| identifier, falling back to <a href="../proc_macro2/struct.Span.html#method.call_site"><code>Span::call_site</code></a> when no identifiers are |
| provided.</p> |
| |
| <div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="comment">// If `ident` is an Ident, the span of `my_ident` will be inherited from it. |
| </span><span class="kw">let </span>my_ident = <span class="macro">format_ident!</span>(<span class="string">"My{}{}"</span>, ident, <span class="string">"IsCool"</span>); |
| <span class="macro">assert_eq!</span>(my_ident, <span class="string">"MyIdentIsCool"</span>);</code></pre></div> |
| <p>Alternatively, the span can be overridden by passing the <code>span</code> named |
| argument.</p> |
| |
| <div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">let </span>my_span = <span class="comment">/* ... */</span>; |
| <span class="macro">format_ident!</span>(<span class="string">"MyIdent"</span>, span = my_span);</code></pre></div> |
| <p><br></p> |
| <h2 id="panics"><a href="#panics">Panics</a></h2> |
| <p>This method will panic if the resulting formatted string is not a valid |
| identifier.</p> |
| <br> |
| <h2 id="examples"><a href="#examples">Examples</a></h2> |
| <p>Composing raw and non-raw identifiers:</p> |
| |
| <div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">let </span>my_ident = <span class="macro">format_ident!</span>(<span class="string">"My{}"</span>, <span class="string">"Ident"</span>); |
| <span class="macro">assert_eq!</span>(my_ident, <span class="string">"MyIdent"</span>); |
| |
| <span class="kw">let </span>raw = <span class="macro">format_ident!</span>(<span class="string">"r#Raw"</span>); |
| <span class="macro">assert_eq!</span>(raw, <span class="string">"r#Raw"</span>); |
| |
| <span class="kw">let </span>my_ident_raw = <span class="macro">format_ident!</span>(<span class="string">"{}Is{}"</span>, my_ident, raw); |
| <span class="macro">assert_eq!</span>(my_ident_raw, <span class="string">"MyIdentIsRaw"</span>);</code></pre></div> |
| <p>Integer formatting options:</p> |
| |
| <div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">let </span>num: u32 = <span class="number">10</span>; |
| |
| <span class="kw">let </span>decimal = <span class="macro">format_ident!</span>(<span class="string">"Id_{}"</span>, num); |
| <span class="macro">assert_eq!</span>(decimal, <span class="string">"Id_10"</span>); |
| |
| <span class="kw">let </span>octal = <span class="macro">format_ident!</span>(<span class="string">"Id_{:o}"</span>, num); |
| <span class="macro">assert_eq!</span>(octal, <span class="string">"Id_12"</span>); |
| |
| <span class="kw">let </span>binary = <span class="macro">format_ident!</span>(<span class="string">"Id_{:b}"</span>, num); |
| <span class="macro">assert_eq!</span>(binary, <span class="string">"Id_1010"</span>); |
| |
| <span class="kw">let </span>lower_hex = <span class="macro">format_ident!</span>(<span class="string">"Id_{:x}"</span>, num); |
| <span class="macro">assert_eq!</span>(lower_hex, <span class="string">"Id_a"</span>); |
| |
| <span class="kw">let </span>upper_hex = <span class="macro">format_ident!</span>(<span class="string">"Id_{:X}"</span>, num); |
| <span class="macro">assert_eq!</span>(upper_hex, <span class="string">"Id_A"</span>);</code></pre></div> |
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