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<!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="`VariantAccess` is a visitor that is created by the `Deserializer` and passed to the `Deserialize` to deserialize the content of a particular enum variant."><meta name="keywords" content="rust, rustlang, rust-lang, VariantAccess"><title>VariantAccess in serde::de - 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 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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="../../serde/index.html"><div class="logo-container"><img class="rust-logo" src="../../rust-logo.svg" alt="logo"></div></a><h2 class="location"></h2></nav><nav class="sidebar"><a class="sidebar-logo" href="../../serde/index.html"><div class="logo-container"><img class="rust-logo" src="../../rust-logo.svg" alt="logo"></div></a><h2 class="location"><a href="#">VariantAccess</a></h2><div class="sidebar-elems"><section><div class="block"><h3 class="sidebar-title"><a href="#required-associated-types">Required Associated Types</a></h3><ul><li><a href="#associatedtype.Error">Error</a></li></ul></div><div class="block"><h3 class="sidebar-title"><a href="#required-methods">Required Methods</a></h3><ul><li><a href="#tymethod.newtype_variant_seed">newtype_variant_seed</a></li><li><a href="#tymethod.struct_variant">struct_variant</a></li><li><a href="#tymethod.tuple_variant">tuple_variant</a></li><li><a href="#tymethod.unit_variant">unit_variant</a></li></ul></div><div class="block"><h3 class="sidebar-title"><a href="#provided-methods">Provided Methods</a></h3><ul><li><a href="#method.newtype_variant">newtype_variant</a></li></ul></div><div class="block"><h3 class="sidebar-title"><a href="#implementors">Implementors</a></h3></div></section><h2 class="location"><a href="index.html">In serde::de</a></h2></div></nav><main><div class="width-limiter"><div class="sub-container"><a class="sub-logo-container" href="../../serde/index.html"><img class="rust-logo" src="../../rust-logo.svg" alt="logo"></a><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"><button type="button">?</button></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></div><section id="main-content" class="content"><div class="main-heading"><h1 class="fqn"><span class="in-band">Trait <a href="../index.html">serde</a>::<wbr><a href="index.html">de</a>::<wbr><a class="trait" href="#">VariantAccess</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/serde/de/mod.rs.html#2028-2224">source</a> · <a id="toggle-all-docs" href="javascript:void(0)" title="collapse all docs">[<span class="inner">−</span>]</a></span></div><div class="docblock item-decl"><pre class="rust trait"><code>pub trait VariantAccess<'de>: <a class="trait" href="https://doc.rust-lang.org/1.64.0/core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a> {
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type <a href="#associatedtype.Error" class="associatedtype">Error</a>: <a class="trait" href="trait.Error.html" title="trait serde::de::Error">Error</a>;
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fn <a href="#tymethod.unit_variant" class="fnname">unit_variant</a>(self) -> <a class="enum" href="https://doc.rust-lang.org/1.64.0/core/result/enum.Result.html" title="enum core::result::Result">Result</a><<a class="primitive" href="https://doc.rust-lang.org/1.64.0/std/primitive.unit.html">()</a>, Self::<a class="associatedtype" href="trait.VariantAccess.html#associatedtype.Error" title="type serde::de::VariantAccess::Error">Error</a>>;
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<span class="item-spacer"></span> fn <a href="#tymethod.newtype_variant_seed" class="fnname">newtype_variant_seed</a><T>(self, seed: T) -> <a class="enum" href="https://doc.rust-lang.org/1.64.0/core/result/enum.Result.html" title="enum core::result::Result">Result</a><T::<a class="associatedtype" href="trait.DeserializeSeed.html#associatedtype.Value" title="type serde::de::DeserializeSeed::Value">Value</a>, Self::<a class="associatedtype" href="trait.VariantAccess.html#associatedtype.Error" title="type serde::de::VariantAccess::Error">Error</a>><br> <span class="where">where<br> T: <a class="trait" href="trait.DeserializeSeed.html" title="trait serde::de::DeserializeSeed">DeserializeSeed</a><'de></span>;
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<span class="item-spacer"></span> fn <a href="#tymethod.tuple_variant" class="fnname">tuple_variant</a><V>(<br> self,<br> len: <a class="primitive" href="https://doc.rust-lang.org/1.64.0/std/primitive.usize.html">usize</a>,<br> visitor: V<br> ) -> <a class="enum" href="https://doc.rust-lang.org/1.64.0/core/result/enum.Result.html" title="enum core::result::Result">Result</a><V::<a class="associatedtype" href="trait.Visitor.html#associatedtype.Value" title="type serde::de::Visitor::Value">Value</a>, Self::<a class="associatedtype" href="trait.VariantAccess.html#associatedtype.Error" title="type serde::de::VariantAccess::Error">Error</a>><br> <span class="where">where<br> V: <a class="trait" href="trait.Visitor.html" title="trait serde::de::Visitor">Visitor</a><'de></span>;
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<span class="item-spacer"></span> fn <a href="#tymethod.struct_variant" class="fnname">struct_variant</a><V>(<br> self,<br> fields: &'static [&'static <a class="primitive" href="https://doc.rust-lang.org/1.64.0/std/primitive.str.html">str</a>],<br> visitor: V<br> ) -> <a class="enum" href="https://doc.rust-lang.org/1.64.0/core/result/enum.Result.html" title="enum core::result::Result">Result</a><V::<a class="associatedtype" href="trait.Visitor.html#associatedtype.Value" title="type serde::de::Visitor::Value">Value</a>, Self::<a class="associatedtype" href="trait.VariantAccess.html#associatedtype.Error" title="type serde::de::VariantAccess::Error">Error</a>><br> <span class="where">where<br> V: <a class="trait" href="trait.Visitor.html" title="trait serde::de::Visitor">Visitor</a><'de></span>;
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fn <a href="#method.newtype_variant" class="fnname">newtype_variant</a><T>(self) -> <a class="enum" href="https://doc.rust-lang.org/1.64.0/core/result/enum.Result.html" title="enum core::result::Result">Result</a><T, Self::<a class="associatedtype" href="trait.VariantAccess.html#associatedtype.Error" title="type serde::de::VariantAccess::Error">Error</a>><br> <span class="where">where<br> T: <a class="trait" href="../trait.Deserialize.html" title="trait serde::Deserialize">Deserialize</a><'de></span>,
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{ ... }
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}</code></pre></div><details class="rustdoc-toggle top-doc" open><summary class="hideme"><span>Expand description</span></summary><div class="docblock"><p><code>VariantAccess</code> is a visitor that is created by the <code>Deserializer</code> and
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passed to the <code>Deserialize</code> to deserialize the content of a particular enum
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variant.</p>
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<h2 id="lifetime"><a href="#lifetime">Lifetime</a></h2>
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<p>The <code>'de</code> lifetime of this trait is the lifetime of data that may be
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borrowed by the deserialized enum variant. See the page <a href="https://serde.rs/lifetimes.html">Understanding
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deserializer lifetimes</a> for a more detailed explanation of these lifetimes.</p>
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<h2 id="example-implementation"><a href="#example-implementation">Example implementation</a></h2>
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<p>The <a href="https://serde.rs/data-format.html">example data format</a> presented on the website demonstrates an
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implementation of <code>VariantAccess</code> for a basic JSON data format.</p>
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</div></details><h2 id="required-associated-types" class="small-section-header">Required Associated Types<a href="#required-associated-types" class="anchor"></a></h2><div class="methods"><details class="rustdoc-toggle" open><summary><div id="associatedtype.Error" class="method has-srclink"><div class="rightside"><a class="srclink" href="../../src/serde/de/mod.rs.html#2031">source</a></div><h4 class="code-header">type <a href="#associatedtype.Error" class="associatedtype">Error</a>: <a class="trait" href="trait.Error.html" title="trait serde::de::Error">Error</a></h4></div></summary><div class="docblock"><p>The error type that can be returned if some error occurs during
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deserialization. Must match the error type of our <code>EnumAccess</code>.</p>
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</div></details></div><h2 id="required-methods" class="small-section-header">Required Methods<a href="#required-methods" class="anchor"></a></h2><div class="methods"><details class="rustdoc-toggle" open><summary><div id="tymethod.unit_variant" class="method has-srclink"><div class="rightside"><a class="srclink" href="../../src/serde/de/mod.rs.html#2068">source</a></div><h4 class="code-header">fn <a href="#tymethod.unit_variant" class="fnname">unit_variant</a>(self) -> <a class="enum" href="https://doc.rust-lang.org/1.64.0/core/result/enum.Result.html" title="enum core::result::Result">Result</a><<a class="primitive" href="https://doc.rust-lang.org/1.64.0/std/primitive.unit.html">()</a>, Self::<a class="associatedtype" href="trait.VariantAccess.html#associatedtype.Error" title="type serde::de::VariantAccess::Error">Error</a>></h4></div></summary><div class="docblock"><p>Called when deserializing a variant with no values.</p>
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<p>If the data contains a different type of variant, the following
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<code>invalid_type</code> error should be constructed:</p>
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<div class='information'><div class='tooltip edition' data-edition="2018">ⓘ</div></div><div class="example-wrap"><pre class="rust rust-example-rendered edition"><code><span class="kw">fn</span> <span class="ident">unit_variant</span>(<span class="self">self</span>) -> <span class="prelude-ty">Result</span><span class="op"><</span>(), <span class="ident"><span class="self">Self</span>::Error</span><span class="op">></span> {
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<span class="comment">// What the data actually contained; suppose it is a tuple variant.</span>
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<span class="kw">let</span> <span class="ident">unexp</span> <span class="op">=</span> <span class="ident">Unexpected::TupleVariant</span>;
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<span class="prelude-val">Err</span>(<span class="ident">de::Error::invalid_type</span>(<span class="ident">unexp</span>, <span class="kw-2">&</span><span class="string">"unit variant"</span>))
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}</code></pre></div>
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</div></details><details class="rustdoc-toggle" open><summary><div id="tymethod.newtype_variant_seed" class="method has-srclink"><div class="rightside"><a class="srclink" href="../../src/serde/de/mod.rs.html#2110-2112">source</a></div><h4 class="code-header">fn <a href="#tymethod.newtype_variant_seed" class="fnname">newtype_variant_seed</a><T>(self, seed: T) -> <a class="enum" href="https://doc.rust-lang.org/1.64.0/core/result/enum.Result.html" title="enum core::result::Result">Result</a><T::<a class="associatedtype" href="trait.DeserializeSeed.html#associatedtype.Value" title="type serde::de::DeserializeSeed::Value">Value</a>, Self::<a class="associatedtype" href="trait.VariantAccess.html#associatedtype.Error" title="type serde::de::VariantAccess::Error">Error</a>> <span class="where fmt-newline">where<br> T: <a class="trait" href="trait.DeserializeSeed.html" title="trait serde::de::DeserializeSeed">DeserializeSeed</a><'de>, </span></h4></div></summary><div class="docblock"><p>Called when deserializing a variant with a single value.</p>
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<p><code>Deserialize</code> implementations should typically use
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<code>VariantAccess::newtype_variant</code> instead.</p>
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<p>If the data contains a different type of variant, the following
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<code>invalid_type</code> error should be constructed:</p>
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<div class='information'><div class='tooltip edition' data-edition="2018">ⓘ</div></div><div class="example-wrap"><pre class="rust rust-example-rendered edition"><code><span class="kw">fn</span> <span class="ident">newtype_variant_seed</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>(<span class="self">self</span>, <span class="ident">_seed</span>: <span class="ident">T</span>) -> <span class="prelude-ty">Result</span><span class="op"><</span><span class="ident">T::Value</span>, <span class="ident"><span class="self">Self</span>::Error</span><span class="op">></span>
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<span class="kw">where</span>
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<span class="ident">T</span>: <span class="ident">DeserializeSeed</span><span class="op"><</span><span class="lifetime">'de</span><span class="op">></span>,
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{
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<span class="comment">// What the data actually contained; suppose it is a unit variant.</span>
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<span class="kw">let</span> <span class="ident">unexp</span> <span class="op">=</span> <span class="ident">Unexpected::UnitVariant</span>;
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<span class="prelude-val">Err</span>(<span class="ident">de::Error::invalid_type</span>(<span class="ident">unexp</span>, <span class="kw-2">&</span><span class="string">"newtype variant"</span>))
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}</code></pre></div>
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</div></details><details class="rustdoc-toggle" open><summary><div id="tymethod.tuple_variant" class="method has-srclink"><div class="rightside"><a class="srclink" href="../../src/serde/de/mod.rs.html#2170-2172">source</a></div><h4 class="code-header">fn <a href="#tymethod.tuple_variant" class="fnname">tuple_variant</a><V>(self, len: <a class="primitive" href="https://doc.rust-lang.org/1.64.0/std/primitive.usize.html">usize</a>, visitor: V) -> <a class="enum" href="https://doc.rust-lang.org/1.64.0/core/result/enum.Result.html" title="enum core::result::Result">Result</a><V::<a class="associatedtype" href="trait.Visitor.html#associatedtype.Value" title="type serde::de::Visitor::Value">Value</a>, Self::<a class="associatedtype" href="trait.VariantAccess.html#associatedtype.Error" title="type serde::de::VariantAccess::Error">Error</a>> <span class="where fmt-newline">where<br> V: <a class="trait" href="trait.Visitor.html" title="trait serde::de::Visitor">Visitor</a><'de>, </span></h4></div></summary><div class="docblock"><p>Called when deserializing a tuple-like variant.</p>
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<p>The <code>len</code> is the number of fields expected in the tuple variant.</p>
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<p>If the data contains a different type of variant, the following
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<code>invalid_type</code> error should be constructed:</p>
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<div class='information'><div class='tooltip edition' data-edition="2018">ⓘ</div></div><div class="example-wrap"><pre class="rust rust-example-rendered edition"><code><span class="kw">fn</span> <span class="ident">tuple_variant</span><span class="op"><</span><span class="ident">V</span><span class="op">></span>(
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<span class="self">self</span>,
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<span class="ident">_len</span>: <span class="ident">usize</span>,
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<span class="ident">_visitor</span>: <span class="ident">V</span>,
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) -> <span class="prelude-ty">Result</span><span class="op"><</span><span class="ident">V::Value</span>, <span class="ident"><span class="self">Self</span>::Error</span><span class="op">></span>
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<span class="kw">where</span>
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<span class="ident">V</span>: <span class="ident">Visitor</span><span class="op"><</span><span class="lifetime">'de</span><span class="op">></span>,
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{
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<span class="comment">// What the data actually contained; suppose it is a unit variant.</span>
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<span class="kw">let</span> <span class="ident">unexp</span> <span class="op">=</span> <span class="ident">Unexpected::UnitVariant</span>;
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<span class="prelude-val">Err</span>(<span class="ident">de::Error::invalid_type</span>(<span class="ident">unexp</span>, <span class="kw-2">&</span><span class="string">"tuple variant"</span>))
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}</code></pre></div>
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</div></details><details class="rustdoc-toggle" open><summary><div id="tymethod.struct_variant" class="method has-srclink"><div class="rightside"><a class="srclink" href="../../src/serde/de/mod.rs.html#2217-2223">source</a></div><h4 class="code-header">fn <a href="#tymethod.struct_variant" class="fnname">struct_variant</a><V>(<br> self,<br> fields: &'static [&'static <a class="primitive" href="https://doc.rust-lang.org/1.64.0/std/primitive.str.html">str</a>],<br> visitor: V<br>) -> <a class="enum" href="https://doc.rust-lang.org/1.64.0/core/result/enum.Result.html" title="enum core::result::Result">Result</a><V::<a class="associatedtype" href="trait.Visitor.html#associatedtype.Value" title="type serde::de::Visitor::Value">Value</a>, Self::<a class="associatedtype" href="trait.VariantAccess.html#associatedtype.Error" title="type serde::de::VariantAccess::Error">Error</a>> <span class="where fmt-newline">where<br> V: <a class="trait" href="trait.Visitor.html" title="trait serde::de::Visitor">Visitor</a><'de>, </span></h4></div></summary><div class="docblock"><p>Called when deserializing a struct-like variant.</p>
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<p>The <code>fields</code> are the names of the fields of the struct variant.</p>
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<p>If the data contains a different type of variant, the following
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<code>invalid_type</code> error should be constructed:</p>
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<div class='information'><div class='tooltip edition' data-edition="2018">ⓘ</div></div><div class="example-wrap"><pre class="rust rust-example-rendered edition"><code><span class="kw">fn</span> <span class="ident">struct_variant</span><span class="op"><</span><span class="ident">V</span><span class="op">></span>(
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<span class="self">self</span>,
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<span class="ident">_fields</span>: <span class="kw-2">&</span><span class="lifetime">'static</span> [<span class="kw-2">&</span><span class="lifetime">'static</span> <span class="ident">str</span>],
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<span class="ident">_visitor</span>: <span class="ident">V</span>,
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) -> <span class="prelude-ty">Result</span><span class="op"><</span><span class="ident">V::Value</span>, <span class="ident"><span class="self">Self</span>::Error</span><span class="op">></span>
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<span class="kw">where</span>
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<span class="ident">V</span>: <span class="ident">Visitor</span><span class="op"><</span><span class="lifetime">'de</span><span class="op">></span>,
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{
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<span class="comment">// What the data actually contained; suppose it is a unit variant.</span>
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<span class="kw">let</span> <span class="ident">unexp</span> <span class="op">=</span> <span class="ident">Unexpected::UnitVariant</span>;
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<span class="prelude-val">Err</span>(<span class="ident">de::Error::invalid_type</span>(<span class="ident">unexp</span>, <span class="kw-2">&</span><span class="string">"struct variant"</span>))
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}</code></pre></div>
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</div></details></div><h2 id="provided-methods" class="small-section-header">Provided Methods<a href="#provided-methods" class="anchor"></a></h2><div class="methods"><details class="rustdoc-toggle" open><summary><div id="method.newtype_variant" class="method has-srclink"><div class="rightside"><a class="srclink" href="../../src/serde/de/mod.rs.html#2120-2125">source</a></div><h4 class="code-header">fn <a href="#method.newtype_variant" class="fnname">newtype_variant</a><T>(self) -> <a class="enum" href="https://doc.rust-lang.org/1.64.0/core/result/enum.Result.html" title="enum core::result::Result">Result</a><T, Self::<a class="associatedtype" href="trait.VariantAccess.html#associatedtype.Error" title="type serde::de::VariantAccess::Error">Error</a>> <span class="where fmt-newline">where<br> T: <a class="trait" href="../trait.Deserialize.html" title="trait serde::Deserialize">Deserialize</a><'de>, </span></h4></div></summary><div class="docblock"><p>Called when deserializing a variant with a single value.</p>
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<p>This method exists as a convenience for <code>Deserialize</code> implementations.
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<code>VariantAccess</code> implementations should not override the default
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behavior.</p>
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</div></details></div><h2 id="implementors" class="small-section-header">Implementors<a href="#implementors" class="anchor"></a></h2><div class="item-list" id="implementors-list"></div><script type="text/javascript" src="../../implementors/serde/de/trait.VariantAccess.js" data-ignore-extern-crates="" async></script></section></div></main><div id="rustdoc-vars" data-root-path="../../" data-current-crate="serde" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.64.0 (a55dd71d5 2022-09-19)" ></div></body></html> |