|
|
<!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="API documentation for the Rust `custom_keyword` macro in crate `syn`."><meta name="keywords" content="rust, rustlang, rust-lang, custom_keyword"><title>syn::custom_keyword - Rust</title><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="../dark.css"><link rel="stylesheet" type="text/css" href="../light.css" id="themeStyle"><script src="../storage.js"></script><noscript><link rel="stylesheet" href="../noscript.css"></noscript><link rel="shortcut icon" href="../favicon.ico"><style type="text/css">#crate-search{background-image:url("../down-arrow.svg");}</style></head><body class="rustdoc macro"><!--[if lte IE 8]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="sidebar"><div class="sidebar-menu">☰</div><a href='../syn/index.html'><div class='logo-container'><img src='../rust-logo.png' alt='logo'></div></a><div class="sidebar-elems"><p class='location'><a href='index.html'>syn</a></p><script>window.sidebarCurrent = {name: 'custom_keyword', ty: 'macro', relpath: ''};</script><script defer src="sidebar-items.js"></script></div></nav><div class="theme-picker"><button id="theme-picker" aria-label="Pick another theme!"><img src="../brush.svg" width="18" alt="Pick another theme!"></button><div id="theme-choices"></div></div><script src="../theme.js"></script><nav class="sub"><form class="search-form js-only"><div class="search-container"><div><select id="crate-search"><option value="All crates">All crates</option></select><input class="search-input" name="search" autocomplete="off" spellcheck="false" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"></div><a id="settings-menu" href="../settings.html"><img src="../wheel.svg" width="18" alt="Change settings"></a></div></form></nav><section id="main" class="content"><h1 class='fqn'><span class='out-of-band'><span id='render-detail'><a id="toggle-all-docs" href="javascript:void(0)" title="collapse all docs">[<span class='inner'>−</span>]</a></span><a class='srclink' href='../src/syn/custom_keyword.rs.html#90-120' title='goto source code'>[src]</a></span><span class='in-band'>Macro <a href='index.html'>syn</a>::<wbr><a class="macro" href=''>custom_keyword</a></span></h1><div class="docblock type-decl hidden-by-usual-hider"><div class="example-wrap"><pre class="rust macro">
|
|
|
<span class="macro">macro_rules</span><span class="macro">!</span> <span class="ident">custom_keyword</span> {
|
|
|
(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">ident</span>:<span class="ident">ident</span>) <span class="op">=</span><span class="op">></span> { ... };
|
|
|
}</pre></div>
|
|
|
</div><div class='docblock'><p>Define a type that supports parsing and printing a given identifier as if it
|
|
|
were a keyword.</p>
|
|
|
<h1 id="usage" class="section-header"><a href="#usage">Usage</a></h1>
|
|
|
<p>As a convention, it is recommended that this macro be invoked within a
|
|
|
module called <code>kw</code> or <code>keyword</code> and that the resulting parser be invoked
|
|
|
with a <code>kw::</code> or <code>keyword::</code> prefix.</p>
|
|
|
<pre><code class="language-edition2018">mod kw {
|
|
|
syn::custom_keyword!(whatever);
|
|
|
}
|
|
|
</code></pre>
|
|
|
<p>The generated syntax tree node supports the following operations just like
|
|
|
any built-in keyword token.</p>
|
|
|
<ul>
|
|
|
<li>
|
|
|
<p><a href="parse/struct.ParseBuffer.html#method.peek">Peeking</a> — <code>input.peek(kw::whatever)</code></p>
|
|
|
</li>
|
|
|
<li>
|
|
|
<p><a href="parse/struct.ParseBuffer.html#method.parse">Parsing</a> — <code>input.parse::<kw::whatever>()?</code></p>
|
|
|
</li>
|
|
|
<li>
|
|
|
<p><a href="https://docs.rs/quote/0.6/quote/trait.ToTokens.html">Printing</a> — <code>quote!( ... #whatever_token ... )</code></p>
|
|
|
</li>
|
|
|
<li>
|
|
|
<p>Construction from a <a href="https://docs.rs/proc-macro2/0.4/proc_macro2/struct.Span.html"><code>Span</code></a> — <code>let whatever_token = kw::whatever(sp)</code></p>
|
|
|
</li>
|
|
|
<li>
|
|
|
<p>Field access to its span — <code>let sp = whatever_token.span</code></p>
|
|
|
</li>
|
|
|
</ul>
|
|
|
<h1 id="example" class="section-header"><a href="#example">Example</a></h1>
|
|
|
<p>This example parses input that looks like <code>bool = true</code> or <code>str = "value"</code>.
|
|
|
The key must be either the identifier <code>bool</code> or the identifier <code>str</code>. If
|
|
|
<code>bool</code>, the value may be either <code>true</code> or <code>false</code>. If <code>str</code>, the value may
|
|
|
be any string literal.</p>
|
|
|
<p>The symbols <code>bool</code> and <code>str</code> are not reserved keywords in Rust so these are
|
|
|
not considered keywords in the <code>syn::token</code> module. Like any other
|
|
|
identifier that is not a keyword, these can be declared as custom keywords
|
|
|
by crates that need to use them as such.</p>
|
|
|
<pre><code class="language-edition2018">use syn::{LitBool, LitStr, Result, Token};
|
|
|
use syn::parse::{Parse, ParseStream};
|
|
|
|
|
|
mod kw {
|
|
|
syn::custom_keyword!(bool);
|
|
|
syn::custom_keyword!(str);
|
|
|
}
|
|
|
|
|
|
enum Argument {
|
|
|
Bool {
|
|
|
bool_token: kw::bool,
|
|
|
eq_token: Token![=],
|
|
|
value: LitBool,
|
|
|
},
|
|
|
Str {
|
|
|
str_token: kw::str,
|
|
|
eq_token: Token![=],
|
|
|
value: LitStr,
|
|
|
},
|
|
|
}
|
|
|
|
|
|
impl Parse for Argument {
|
|
|
fn parse(input: ParseStream) -> Result<Self> {
|
|
|
let lookahead = input.lookahead1();
|
|
|
if lookahead.peek(kw::bool) {
|
|
|
Ok(Argument::Bool {
|
|
|
bool_token: input.parse::<kw::bool>()?,
|
|
|
eq_token: input.parse()?,
|
|
|
value: input.parse()?,
|
|
|
})
|
|
|
} else if lookahead.peek(kw::str) {
|
|
|
Ok(Argument::Str {
|
|
|
str_token: input.parse::<kw::str>()?,
|
|
|
eq_token: input.parse()?,
|
|
|
value: input.parse()?,
|
|
|
})
|
|
|
} else {
|
|
|
Err(lookahead.error())
|
|
|
}
|
|
|
}
|
|
|
}
|
|
|
</code></pre>
|
|
|
</div></section><section id="search" class="content hidden"></section><section class="footer"></section><aside id="help" class="hidden"><div><h1 class="hidden">Help</h1><div class="shortcuts"><h2>Keyboard Shortcuts</h2><dl><dt><kbd>?</kbd></dt><dd>Show this help dialog</dd><dt><kbd>S</kbd></dt><dd>Focus the search field</dd><dt><kbd>↑</kbd></dt><dd>Move up in search results</dd><dt><kbd>↓</kbd></dt><dd>Move down in search results</dd><dt><kbd>↹</kbd></dt><dd>Switch tab</dd><dt><kbd>⏎</kbd></dt><dd>Go to active search result</dd><dt><kbd>+</kbd></dt><dd>Expand all sections</dd><dt><kbd>-</kbd></dt><dd>Collapse all sections</dd></dl></div><div class="infos"><h2>Search Tricks</h2><p>Prefix searches with a type followed by a colon (e.g., <code>fn:</code>) to restrict the search to a given type.</p><p>Accepted types are: <code>fn</code>, <code>mod</code>, <code>struct</code>, <code>enum</code>, <code>trait</code>, <code>type</code>, <code>macro</code>, and <code>const</code>.</p><p>Search functions by type signature (e.g., <code>vec -> usize</code> or <code>* -> vec</code>)</p><p>Search multiple things at once by splitting your query with comma (e.g., <code>str,u8</code> or <code>String,struct:Vec,test</code>)</p></div></div></aside><script>window.rootPath = "../";window.currentCrate = "syn";</script><script src="../aliases.js"></script><script src="../main.js"></script><script defer src="../search-index.js"></script></body></html> |
