<!DOCTYPE html><htmllang="en"><head><metacharset="utf-8"><metaname="viewport"content="width=device-width, initial-scale=1.0"><metaname="generator"content="rustdoc"><metaname="description"content="A trait for visiting the high-level IR (HIR) in depth first order."><title>Visitor in regex_syntax::hir - Rust</title><linkrel="preload"as="font"type="font/woff2"crossoriginhref="../../static.files/SourceSerif4-Regular-46f98efaafac5295.ttf.woff2"><linkrel="preload"as="font"type="font/woff2"crossoriginhref="../../static.files/FiraSans-Regular-018c141bf0843ffd.woff2"><linkrel="preload"as="font"type="font/woff2"crossoriginhref="../../static.files/FiraSans-Medium-8f9a781e4970d388.woff2"><linkrel="preload"as="font"type="font/woff2"crossoriginhref="../../static.files/SourceCodePro-Regular-562dcc5011b6de7d.ttf.woff2"><linkrel="preload"as="font"type="font/woff2"crossoriginhref="../../static.files/SourceCodePro-Semibold-d899c5a5c4aeb14a.ttf.woff2"><linkrel="stylesheet"href="../../static.files/normalize-76eba96aa4d2e634.css"><linkrel="stylesheet"href="../../static.files/rustdoc-5bc39a1768837dd0.css"><metaname="rustdoc-vars"data-root-path="../../"data-static-root-path="../../static.files/"data-current-crate="regex_syntax"data-themes=""data-resource-suffix=""data-rustdoc-version="1.77.1 (7cf61ebde 2024-03-27)"data-channel="1.77.1"data-search-js="search-dd67cee4cfa65049.js"data-settings-js="settings-4313503d2e1961c2.js"><scriptsrc="../../static.files/storage-4c98445ec4002617.js"></script><scriptdefersrc="sidebar-items.js"></script><scriptdefersrc="../../static.files/main-48f368f3872407c8.js"></script><noscript><linkrel="stylesheet"href="../../static.files/noscript-04d5337699b92874.css"></noscript><linkrel="alternate icon"type="image/png"href="../../static.files/favicon-16x16-8b506e7a72182f1c.png"><linkrel="alternate icon"type="image/png"href="../../static.files/favicon-32x32-422f7d1d52889060.png"><linkrel="icon"type="image/svg+xml"href="../../static.files/favicon-2c020d218678b618.svg"></head><bodyclass="rustdoc trait"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><navclass="mobile-topbar"><buttonclass="sidebar-menu-toggle"title="show sidebar"></button></nav><navclass="sidebar"><divclass="sidebar-crate"><h2><ahref="../../regex_syntax/index.html">regex_syntax</a><spanclass="version">0.8.3</span></h2></div><h2class="location"><ahref="#">Visitor</a></h2><divclass="sidebar-elems"><section><h3><ahref="#required-associated-types">Required Associated Types</a></h3><ulclass="block"><li><ahref="#associatedtype.Err">Err</a></li><li><ahref="#associatedtype.Output">Output</a></li></ul><h3><ahref="#required-methods">Required Methods</a></h3><ulclass="block"><li><ahref="#tymethod.finish">finish</a></li></ul><h3><ahref="#provided-methods">Provided Methods</a></h3><ulclass="block"><li><ahref="#method.start">start</a></li><li><ahref="#method.visit_alternation_in">visit_alternation_in</a></li><li><ahref="#method.visit_concat_in">visit_concat_in</a></li><li><ahref="#method.visit_post">visit_post</a></li><li><ahref="#method.visit_pre">visit_pre</a></li></ul><h3><ahref="#implementors">Implementors</a></h3></section><h2><ahref="index.html">In regex_syntax::hir</a></h2></div></nav><divclass="sidebar-resizer"></div>
<main><divclass="width-limiter"><navclass="sub"><formclass="search-form"><span></span><divid="sidebar-button"tabindex="-1"><ahref="../../regex_syntax/all.html"title="show sidebar"></a></div><inputclass="search-input"name="search"aria-label="Run search in the documentation"autocomplete="off"spellcheck="false"placeholder="Click or press ‘S’ to search, ‘?’ for more options…"type="search"><divid="help-button"tabindex="-1"><ahref="../../help.html"title="help">?</a></div><divid="settings-menu"tabindex="-1"><ahref="../../settings.html"title="settings"><imgwidth="22"height="22"alt="Change settings"src="../../static.files/wheel-7b819b6101059cd0.svg"></a></div></form></nav><sectionid="main-content"class="content"><divclass="main-heading"><h1>Trait <ahref="../index.html">regex_syntax</a>::<wbr><ahref="index.html">hir</a>::<wbr><aclass="trait"href="#">Visitor</a><buttonid="copy-path"title="Copy item path to clipboard"><imgsrc="../../static.files/clipboard-7571035ce49a181d.svg"width="19"height="18"alt="Copy item path"></button></h1><spanclass="out-of-band"><aclass="src"href="../../src/regex_syntax/hir/visitor.rs.html#15-49">source</a> · <buttonid="toggle-all-docs"title="collapse all docs">[<span>−</span>]</button></span></div><preclass="rust item-decl"><code>pub trait Visitor {
type <ahref="#associatedtype.Output"class="associatedtype">Output</a>;
type <ahref="#associatedtype.Err"class="associatedtype">Err</a>;
}</code></pre><detailsclass="toggle top-doc"open><summaryclass="hideme"><span>Expand description</span></summary><divclass="docblock"><p>A trait for visiting the high-level IR (HIR) in depth first order.</p>
<p>The principle aim of this trait is to enable callers to perform case
analysis on a high-level intermediate representation of a regular
expression without necessarily using recursion. In particular, this permits
callers to do case analysis with constant stack usage, which can be
important since the size of an HIR may be proportional to end user input.</p>
<p>Typical usage of this trait involves providing an implementation and then
running it using the <ahref="fn.visit.html"title="fn regex_syntax::hir::visit"><code>visit</code></a> function.</p>
</div></details><h2id="required-associated-types"class="section-header">Required Associated Types<ahref="#required-associated-types"class="anchor">§</a></h2><divclass="methods"><detailsclass="toggle"open><summary><sectionid="associatedtype.Output"class="method"><aclass="src rightside"href="../../src/regex_syntax/hir/visitor.rs.html#17">source</a><h4class="code-header">type <ahref="#associatedtype.Output"class="associatedtype">Output</a></h4></section></summary><divclass="docblock"><p>The result of visiting an HIR.</p>
</div></details><detailsclass="toggle"open><summary><sectionid="associatedtype.Err"class="method"><aclass="src rightside"href="../../src/regex_syntax/hir/visitor.rs.html#19">source</a><h4class="code-header">type <ahref="#associatedtype.Err"class="associatedtype">Err</a></h4></section></summary><divclass="docblock"><p>An error that visiting an HIR might return.</p>
</div></details></div><h2id="required-methods"class="section-header">Required Methods<ahref="#required-methods"class="anchor">§</a></h2><divclass="methods"><detailsclass="toggle method-toggle"open><summary><sectionid="tymethod.finish"class="method"><aclass="src rightside"href="../../src/regex_syntax/hir/visitor.rs.html#23">source</a><h4class="code-header">fn <ahref="#tymethod.finish"class="fn">finish</a>(self) -><aclass="enum"href="https://doc.rust-lang.org/1.77.1/core/result/enum.Result.html"title="enum core::result::Result">Result</a><Self::<aclass="associatedtype"href="trait.Visitor.html#associatedtype.Output"title="type regex_syntax::hir::Visitor::Output">Output</a>, Self::<aclass="associatedtype"href="trait.Visitor.html#associatedtype.Err"title="type regex_syntax::hir::Visitor::Err">Err</a>></h4></section></summary><divclass="docblock"><p>All implementors of <code>Visitor</code> must provide a <code>finish</code> method, which
yields the result of visiting the HIR or an error.</p>
</div></details></div><h2id="provided-methods"class="section-header">Provided Methods<ahref="#provided-methods"class="anchor">§</a></h2><divclass="methods"><detailsclass="toggle method-toggle"open><summary><sectionid="method.start"class="method"><aclass="src rightside"href="../../src/regex_syntax/hir/visitor.rs.html#26">source</a><h4class="code-header">fn <ahref="#method.start"class="fn">start</a>(&mut self)</h4></section></summary><divclass="docblock"><p>This method is called before beginning traversal of the HIR.</p>
</div></details><detailsclass="toggle method-toggle"open><summary><sectionid="method.visit_pre"class="method"><aclass="src rightside"href="../../src/regex_syntax/hir/visitor.rs.html#30-32">source</a><h4class="code-header">fn <ahref="#method.visit_pre"class="fn">visit_pre</a>(&mut self, _hir: &<aclass="struct"href="struct.Hir.html"title="struct regex_syntax::hir::Hir">Hir</a>) -><aclass="enum"href="https://doc.rust-lang.org/1.77.1/core/result/enum.Result.html"title="enum core::result::Result">Result</a><<aclass="primitive"href="https://doc.rust-lang.org/1.77.1/std/primitive.unit.html">()</a>, Self::<aclass="associatedtype"href="trait.Visitor.html#associatedtype.Err"title="type regex_syntax::hir::Visitor::Err">Err</a>></h4></section></summary><divclass="docblock"><p>This method is called on an <code>Hir</code> before descending into child <code>Hir</code>
</div></details><detailsclass="toggle method-toggle"open><summary><sectionid="method.visit_post"class="method"><aclass="src rightside"href="../../src/regex_syntax/hir/visitor.rs.html#36-38">source</a><h4class="code-header">fn <ahref="#method.visit_post"class="fn">visit_post</a>(&mut self, _hir: &<aclass="struct"href="struct.Hir.html"title="struct regex_syntax::hir::Hir">Hir</a>) -><aclass="enum"href="https://doc.rust-lang.org/1.77.1/core/result/enum.Result.html"title="enum core::result::Result">Result</a><<aclass="primitive"href="https://doc.rust-lang.org/1.77.1/std/primitive.unit.html">()</a>, Self::<aclass="associatedtype"href="trait.Visitor.html#associatedtype.Err"title="type regex_syntax::hir::Visitor::Err">Err</a>></h4></section></summary><divclass="docblock"><p>This method is called on an <code>Hir</code> after descending all of its child
</div></details><detailsclass="toggle method-toggle"open><summary><sectionid="method.visit_alternation_in"class="method"><aclass="src rightside"href="../../src/regex_syntax/hir/visitor.rs.html#41-43">source</a><h4class="code-header">fn <ahref="#method.visit_alternation_in"class="fn">visit_alternation_in</a>(&mut self) -><aclass="enum"href="https://doc.rust-lang.org/1.77.1/core/result/enum.Result.html"title="enum core::result::Result">Result</a><<aclass="primitive"href="https://doc.rust-lang.org/1.77.1/std/primitive.unit.html">()</a>, Self::<aclass="associatedtype"href="trait.Visitor.html#associatedtype.Err"title="type regex_syntax::hir::Visitor::Err">Err</a>></h4></section></summary><divclass="docblock"><p>This method is called between child nodes of an alternation.</p>
</div></details><detailsclass="toggle method-toggle"open><summary><sectionid="method.visit_concat_in"class="method"><aclass="src rightside"href="../../src/regex_syntax/hir/visitor.rs.html#46-48">source</a><h4class="code-header">fn <ahref="#method.visit_concat_in"class="fn">visit_concat_in</a>(&mut self) -><aclass="enum"href="https://doc.rust-lang.org/1.77.1/core/result/enum.Result.html"title="enum core::result::Result">Result</a><<aclass="primitive"href="https://doc.rust-lang.org/1.77.1/std/primitive.unit.html">()</a>, Self::<aclass="associatedtype"href="trait.Visitor.html#associatedtype.Err"title="type regex_syntax::hir::Visitor::Err">Err</a>></h4></section></summary><divclass="docblock"><p>This method is called between child nodes of a concatenation.</p>
