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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="Support for checking the next token in a stream to decide how to parse."><meta name="keywords" content="rust, rustlang, rust-lang, Lookahead1"><title>Lookahead1 in syn::parse - 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 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 struct"><!--[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">&#9776;</button><a class="sidebar-logo" href="../../syn/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="../../syn/index.html"><div class="logo-container"><img class="rust-logo" src="../../rust-logo.svg" alt="logo"></div></a><h2 class="location"><a href="#">Lookahead1</a></h2><div class="sidebar-elems"><section><div class="block"><h3 class="sidebar-title"><a href="#implementations">Methods</a></h3><ul><li><a href="#method.error">error</a></li><li><a href="#method.peek">peek</a></li></ul></div><div class="block"><h3 class="sidebar-title"><a href="#synthetic-implementations">Auto Trait Implementations</a></h3><ul><li><a href="#impl-RefUnwindSafe-for-Lookahead1%3C%27a%3E">!RefUnwindSafe</a></li><li><a href="#impl-Send-for-Lookahead1%3C%27a%3E">!Send</a></li><li><a href="#impl-Sync-for-Lookahead1%3C%27a%3E">!Sync</a></li><li><a href="#impl-Unpin-for-Lookahead1%3C%27a%3E">Unpin</a></li><li><a href="#impl-UnwindSafe-for-Lookahead1%3C%27a%3E">UnwindSafe</a></li></ul></div><div class="block"><h3 class="sidebar-title"><a href="#blanket-implementations">Blanket Implementations</a></h3><ul><li><a href="#impl-Any-for-Lookahead1%3C%27a%3E">Any</a></li><li><a href="#impl-Borrow%3CT%3E-for-Lookahead1%3C%27a%3E">Borrow&lt;T&gt;</a></li><li><a href="#impl-BorrowMut%3CT%3E-for-Lookahead1%3C%27a%3E">BorrowMut&lt;T&gt;</a></li><li><a href="#impl-From%3CT%3E-for-Lookahead1%3C%27a%3E">From&lt;T&gt;</a></li><li><a href="#impl-Into%3CU%3E-for-Lookahead1%3C%27a%3E">Into&lt;U&gt;</a></li><li><a href="#impl-TryFrom%3CU%3E-for-Lookahead1%3C%27a%3E">TryFrom&lt;U&gt;</a></li><li><a href="#impl-TryInto%3CU%3E-for-Lookahead1%3C%27a%3E">TryInto&lt;U&gt;</a></li></ul></div></section><h2 class="location"><a href="index.html">In syn::parse</a></h2></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.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">Struct <a href="../index.html">syn</a>::<wbr><a href="index.html">parse</a>::<wbr><a class="struct" href="#">Lookahead1</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/lookahead.rs.html#62-66">source</a> · <a id="toggle-all-docs" href="javascript:void(0)" title="collapse all docs">[<span class="inner">&#x2212;</span>]</a></span></div><div class="docblock item-decl"><pre class="rust struct"><code>pub struct Lookahead1&lt;'a&gt; { /* private fields */ }</code></pre></div><details class="rustdoc-toggle top-doc" open><summary class="hideme"><span>Expand description</span></summary><div class="docblock"><p>Support for checking the next token in a stream to decide how to parse.</p>
<p>An important advantage over <a href="struct.ParseBuffer.html#method.peek"><code>ParseStream::peek</code></a> is that here we
automatically construct an appropriate error message based on the token
alternatives that get peeked. If you are producing your own error message,
go ahead and use <code>ParseStream::peek</code> instead.</p>
<p>Use <a href="struct.ParseBuffer.html#method.lookahead1"><code>ParseStream::lookahead1</code></a> to construct this object.</p>
<p>Consuming tokens from the source stream after constructing a lookahead
object does not also advance the lookahead object.</p>
<h2 id="example"><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">syn</span>::{<span class="ident">ConstParam</span>, <span class="ident">Ident</span>, <span class="ident">Lifetime</span>, <span class="ident">LifetimeDef</span>, <span class="prelude-ty">Result</span>, <span class="ident">Token</span>, <span class="ident">TypeParam</span>};
<span class="kw">use</span> <span class="ident">syn::parse</span>::{<span class="ident">Parse</span>, <span class="ident">ParseStream</span>};
<span class="comment">// A generic parameter, a single one of the comma-separated elements inside</span>
<span class="comment">// angle brackets in:</span>
<span class="comment">//</span>
<span class="comment">// fn f&lt;T: Clone, &#39;a, &#39;b: &#39;a, const N: usize&gt;() { ... }</span>
<span class="comment">//</span>
<span class="comment">// On invalid input, lookahead gives us a reasonable error message.</span>
<span class="comment">//</span>
<span class="comment">// error: expected one of: identifier, lifetime, `const`</span>
<span class="comment">// |</span>
<span class="comment">// 5 | fn f&lt;!Sized&gt;() {}</span>
<span class="comment">// | ^</span>
<span class="kw">enum</span> <span class="ident">GenericParam</span> {
<span class="ident">Type</span>(<span class="ident">TypeParam</span>),
<span class="ident">Lifetime</span>(<span class="ident">LifetimeDef</span>),
<span class="ident">Const</span>(<span class="ident">ConstParam</span>),
}
<span class="kw">impl</span> <span class="ident">Parse</span> <span class="kw">for</span> <span class="ident">GenericParam</span> {
<span class="kw">fn</span> <span class="ident">parse</span>(<span class="ident">input</span>: <span class="ident">ParseStream</span>) -&gt; <span class="prelude-ty">Result</span><span class="op">&lt;</span><span class="self">Self</span><span class="op">&gt;</span> {
<span class="kw">let</span> <span class="ident">lookahead</span> <span class="op">=</span> <span class="ident">input</span>.<span class="ident">lookahead1</span>();
<span class="kw">if</span> <span class="ident">lookahead</span>.<span class="ident">peek</span>(<span class="ident">Ident</span>) {
<span class="ident">input</span>.<span class="ident">parse</span>().<span class="ident">map</span>(<span class="ident">GenericParam::Type</span>)
} <span class="kw">else</span> <span class="kw">if</span> <span class="ident">lookahead</span>.<span class="ident">peek</span>(<span class="ident">Lifetime</span>) {
<span class="ident">input</span>.<span class="ident">parse</span>().<span class="ident">map</span>(<span class="ident">GenericParam::Lifetime</span>)
} <span class="kw">else</span> <span class="kw">if</span> <span class="ident">lookahead</span>.<span class="ident">peek</span>(<span class="macro">Token!</span>[<span class="kw">const</span>]) {
<span class="ident">input</span>.<span class="ident">parse</span>().<span class="ident">map</span>(<span class="ident">GenericParam::Const</span>)
} <span class="kw">else</span> {
<span class="prelude-val">Err</span>(<span class="ident">lookahead</span>.<span class="ident">error</span>())
}
}
}</code></pre></div>
</div></details><h2 id="implementations" class="small-section-header">Implementations<a href="#implementations" class="anchor"></a></h2><div id="implementations-list"><details class="rustdoc-toggle implementors-toggle" open><summary><section id="impl-Lookahead1%3C%27a%3E" class="impl has-srclink"><span class="rightside"><a class="srclink" href="../../src/syn/lookahead.rs.html#88-137">source</a></span><a href="#impl-Lookahead1%3C%27a%3E" class="anchor"></a><h3 class="code-header in-band">impl&lt;'a&gt; <a class="struct" href="struct.Lookahead1.html" title="struct syn::parse::Lookahead1">Lookahead1</a>&lt;'a&gt;</h3></section></summary><div class="impl-items"><details class="rustdoc-toggle method-toggle" open><summary><section id="method.peek" class="method has-srclink"><span class="rightside"><a class="srclink" href="../../src/syn/lookahead.rs.html#103-106">source</a></span><h4 class="code-header">pub fn <a href="#method.peek" class="fnname">peek</a>&lt;T:&nbsp;<a class="trait" href="trait.Peek.html" title="trait syn::parse::Peek">Peek</a>&gt;(&amp;self, token: T) -&gt; <a class="primitive" href="https://doc.rust-lang.org/1.64.0/std/primitive.bool.html">bool</a></h4></section></summary><div class="docblock"><p>Looks at the next token in the parse stream to determine whether it
matches the requested type of token.</p>
<h5 id="syntax"><a href="#syntax">Syntax</a></h5>
<p>Note that this method does not use turbofish syntax. Pass the peek type
inside of parentheses.</p>
<ul>
<li><code>input.peek(Token![struct])</code></li>
<li><code>input.peek(Token![==])</code></li>
<li><code>input.peek(Ident)</code><em>(does not accept keywords)</em></li>
<li><code>input.peek(Ident::peek_any)</code></li>
<li><code>input.peek(Lifetime)</code></li>
<li><code>input.peek(token::Brace)</code></li>
</ul>
</div></details><details class="rustdoc-toggle method-toggle" open><summary><section id="method.error" class="method has-srclink"><span class="rightside"><a class="srclink" href="../../src/syn/lookahead.rs.html#112-136">source</a></span><h4 class="code-header">pub fn <a href="#method.error" class="fnname">error</a>(self) -&gt; <a class="struct" href="struct.Error.html" title="struct syn::parse::Error">Error</a></h4></section></summary><div class="docblock"><p>Triggers an error at the current position of the parse stream.</p>
<p>The error message will identify all of the expected token types that
have been peeked against this lookahead instance.</p>
</div></details></div></details></div><h2 id="synthetic-implementations" class="small-section-header">Auto Trait Implementations<a href="#synthetic-implementations" class="anchor"></a></h2><div id="synthetic-implementations-list"><section id="impl-RefUnwindSafe-for-Lookahead1%3C%27a%3E" class="impl has-srclink"><a href="#impl-RefUnwindSafe-for-Lookahead1%3C%27a%3E" class="anchor"></a><h3 class="code-header in-band">impl&lt;'a&gt; !<a class="trait" href="https://doc.rust-lang.org/1.64.0/core/panic/unwind_safe/trait.RefUnwindSafe.html" title="trait core::panic::unwind_safe::RefUnwindSafe">RefUnwindSafe</a> for <a class="struct" href="struct.Lookahead1.html" title="struct syn::parse::Lookahead1">Lookahead1</a>&lt;'a&gt;</h3></section><section id="impl-Send-for-Lookahead1%3C%27a%3E" class="impl has-srclink"><a href="#impl-Send-for-Lookahead1%3C%27a%3E" class="anchor"></a><h3 class="code-header in-band">impl&lt;'a&gt; !<a class="trait" href="https://doc.rust-lang.org/1.64.0/core/marker/trait.Send.html" title="trait core::marker::Send">Send</a> for <a class="struct" href="struct.Lookahead1.html" title="struct syn::parse::Lookahead1">Lookahead1</a>&lt;'a&gt;</h3></section><section id="impl-Sync-for-Lookahead1%3C%27a%3E" class="impl has-srclink"><a href="#impl-Sync-for-Lookahead1%3C%27a%3E" class="anchor"></a><h3 class="code-header in-band">impl&lt;'a&gt; !<a class="trait" href="https://doc.rust-lang.org/1.64.0/core/marker/trait.Sync.html" title="trait core::marker::Sync">Sync</a> for <a class="struct" href="struct.Lookahead1.html" title="struct syn::parse::Lookahead1">Lookahead1</a>&lt;'a&gt;</h3></section><section id="impl-Unpin-for-Lookahead1%3C%27a%3E" class="impl has-srclink"><a href="#impl-Unpin-for-Lookahead1%3C%27a%3E" class="anchor"></a><h3 class="code-header in-band">impl&lt;'a&gt; <a class="trait" href="https://doc.rust-lang.org/1.64.0/core/marker/trait.Unpin.html" title="trait core::marker::Unpin">Unpin</a> for <a class="struct" href="struct.Lookahead1.html" title="struct syn::parse::Lookahead1">Lookahead1</a>&lt;'a&gt;</h3></section><section id="impl-UnwindSafe-for-Lookahead1%3C%27a%3E" class="impl has-srclink"><a href="#impl-UnwindSafe-for-Lookahead1%3C%27a%3E" class="anchor"></a><h3 class="code-header in-band">impl&lt;'a&gt; <a class="trait" href="https://doc.rust-lang.org/1.64.0/core/panic/unwind_safe/trait.UnwindSafe.html" title="trait core::panic::unwind_safe::UnwindSafe">UnwindSafe</a> for <a class="struct" href="struct.Lookahead1.html" title="struct syn::parse::Lookahead1">Lookahead1</a>&lt;'a&gt;</h3></section></div><h2 id="blanket-implementations" class="small-section-header">Blanket Implementations<a href="#blanket-implementations" class="anchor"></a></h2><div id="blanket-implementations-list"><details class="rustdoc-toggle implementors-toggle"><summary><section id="impl-Any-for-Lookahead1%3C%27a%3E" class="impl has-srclink"><span class="rightside"><a class="srclink" href="https://doc.rust-lang.org/1.64.0/src/core/any.rs.html#203">source</a></span><a href="#impl-Any-for-Lookahead1%3C%27a%3E" class="anchor"></a><h3 class="code-header in-band">impl&lt;T&gt; <a class="trait" href="https://doc.rust-lang.org/1.64.0/core/any/trait.Any.html" title="trait core::any::Any">Any</a> for T <span class="where fmt-newline">where<br>&nbsp;&nbsp;&nbsp;&nbsp;T: 'static + ?<a class="trait" href="https://doc.rust-lang.org/1.64.0/core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a>,&nbsp;</span></h3></section></summary><div class="impl-items"><details class="rustdoc-toggle method-toggle" open><summary><section id="method.type_id" class="method trait-impl has-srclink"><span class="rightside"><a class="srclink" href="https://doc.rust-lang.org/1.64.0/src/core/any.rs.html#204">source</a></span><a href="#method.type_id" class="anchor"></a><h4 class="code-header">fn <a href="https://doc.rust-lang.org/1.64.0/core/any/trait.Any.html#tymethod.type_id" class="fnname">type_id</a>(&amp;self) -&gt; <a class="struct" href="https://doc.rust-lang.org/1.64.0/core/any/struct.TypeId.html" title="struct core::any::TypeId">TypeId</a></h4></section></summary><div class='docblock'><p>Gets the <code>TypeId</code> of <code>self</code>. <a href="https://doc.rust-lang.org/1.64.0/core/any/trait.Any.html#tymethod.type_id">Read more</a></p>
</div></details></div></details><details class="rustdoc-toggle implementors-toggle"><summary><section id="impl-Borrow%3CT%3E-for-Lookahead1%3C%27a%3E" class="impl has-srclink"><span class="rightside"><a class="srclink" href="https://doc.rust-lang.org/1.64.0/src/core/borrow.rs.html#209">source</a></span><a href="#impl-Borrow%3CT%3E-for-Lookahead1%3C%27a%3E" class="anchor"></a><h3 class="code-header in-band">impl&lt;T&gt; <a class="trait" href="https://doc.rust-lang.org/1.64.0/core/borrow/trait.Borrow.html" title="trait core::borrow::Borrow">Borrow</a>&lt;T&gt; for T <span class="where fmt-newline">where<br>&nbsp;&nbsp;&nbsp;&nbsp;T: ?<a class="trait" href="https://doc.rust-lang.org/1.64.0/core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a>,&nbsp;</span></h3></section></summary><div class="impl-items"><details class="rustdoc-toggle method-toggle" open><summary><section id="method.borrow" class="method trait-impl has-srclink"><span class="rightside"><span class="since" title="const unstable">const: <a href="https://github.com/rust-lang/rust/issues/91522" title="Tracking issue for const_borrow">unstable</a></span> · <a class="srclink" href="https://doc.rust-lang.org/1.64.0/src/core/borrow.rs.html#211">source</a></span><a href="#method.borrow" class="anchor"></a><h4 class="code-header">fn <a href="https://doc.rust-lang.org/1.64.0/core/borrow/trait.Borrow.html#tymethod.borrow" class="fnname">borrow</a>(&amp;self) -&gt; <a class="primitive" href="https://doc.rust-lang.org/1.64.0/std/primitive.reference.html">&amp;</a>T</h4></section></summary><div class='docblock'><p>Immutably borrows from an owned value. <a href="https://doc.rust-lang.org/1.64.0/core/borrow/trait.Borrow.html#tymethod.borrow">Read more</a></p>
</div></details></div></details><details class="rustdoc-toggle implementors-toggle"><summary><section id="impl-BorrowMut%3CT%3E-for-Lookahead1%3C%27a%3E" class="impl has-srclink"><span class="rightside"><a class="srclink" href="https://doc.rust-lang.org/1.64.0/src/core/borrow.rs.html#218">source</a></span><a href="#impl-BorrowMut%3CT%3E-for-Lookahead1%3C%27a%3E" class="anchor"></a><h3 class="code-header in-band">impl&lt;T&gt; <a class="trait" href="https://doc.rust-lang.org/1.64.0/core/borrow/trait.BorrowMut.html" title="trait core::borrow::BorrowMut">BorrowMut</a>&lt;T&gt; for T <span class="where fmt-newline">where<br>&nbsp;&nbsp;&nbsp;&nbsp;T: ?<a class="trait" href="https://doc.rust-lang.org/1.64.0/core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a>,&nbsp;</span></h3></section></summary><div class="impl-items"><details class="rustdoc-toggle method-toggle" open><summary><section id="method.borrow_mut" class="method trait-impl has-srclink"><span class="rightside"><span class="since" title="const unstable">const: <a href="https://github.com/rust-lang/rust/issues/91522" title="Tracking issue for const_borrow">unstable</a></span> · <a class="srclink" href="https://doc.rust-lang.org/1.64.0/src/core/borrow.rs.html#219">source</a></span><a href="#method.borrow_mut" class="anchor"></a><h4 class="code-header">fn <a href="https://doc.rust-lang.org/1.64.0/core/borrow/trait.BorrowMut.html#tymethod.borrow_mut" class="fnname">borrow_mut</a>(&amp;mut self) -&gt; <a class="primitive" href="https://doc.rust-lang.org/1.64.0/std/primitive.reference.html">&amp;mut </a>T</h4></section></summary><div class='docblock'><p>Mutably borrows from an owned value. <a href="https://doc.rust-lang.org/1.64.0/core/borrow/trait.BorrowMut.html#tymethod.borrow_mut">Read more</a></p>
</div></details></div></details><details class="rustdoc-toggle implementors-toggle"><summary><section id="impl-From%3CT%3E-for-Lookahead1%3C%27a%3E" class="impl has-srclink"><span class="rightside"><a class="srclink" href="https://doc.rust-lang.org/1.64.0/src/core/convert/mod.rs.html#557">source</a></span><a href="#impl-From%3CT%3E-for-Lookahead1%3C%27a%3E" class="anchor"></a><h3 class="code-header in-band">impl&lt;T&gt; <a class="trait" href="https://doc.rust-lang.org/1.64.0/core/convert/trait.From.html" title="trait core::convert::From">From</a>&lt;T&gt; for T</h3></section></summary><div class="impl-items"><details class="rustdoc-toggle method-toggle" open><summary><section id="method.from" class="method trait-impl has-srclink"><span class="rightside"><span class="since" title="const unstable">const: <a href="https://github.com/rust-lang/rust/issues/88674" title="Tracking issue for const_convert">unstable</a></span> · <a class="srclink" href="https://doc.rust-lang.org/1.64.0/src/core/convert/mod.rs.html#559">source</a></span><a href="#method.from" class="anchor"></a><h4 class="code-header">fn <a href="https://doc.rust-lang.org/1.64.0/core/convert/trait.From.html#tymethod.from" class="fnname">from</a>(t: T) -&gt; T</h4></section></summary><div class="docblock"><p>Returns the argument unchanged.</p>
</div></details></div></details><details class="rustdoc-toggle implementors-toggle"><summary><section id="impl-Into%3CU%3E-for-Lookahead1%3C%27a%3E" class="impl has-srclink"><span class="rightside"><a class="srclink" href="https://doc.rust-lang.org/1.64.0/src/core/convert/mod.rs.html#541">source</a></span><a href="#impl-Into%3CU%3E-for-Lookahead1%3C%27a%3E" class="anchor"></a><h3 class="code-header in-band">impl&lt;T, U&gt; <a class="trait" href="https://doc.rust-lang.org/1.64.0/core/convert/trait.Into.html" title="trait core::convert::Into">Into</a>&lt;U&gt; for T <span class="where fmt-newline">where<br>&nbsp;&nbsp;&nbsp;&nbsp;U: <a class="trait" href="https://doc.rust-lang.org/1.64.0/core/convert/trait.From.html" title="trait core::convert::From">From</a>&lt;T&gt;,&nbsp;</span></h3></section></summary><div class="impl-items"><details class="rustdoc-toggle method-toggle" open><summary><section id="method.into" class="method trait-impl has-srclink"><span class="rightside"><span class="since" title="const unstable">const: <a href="https://github.com/rust-lang/rust/issues/88674" title="Tracking issue for const_convert">unstable</a></span> · <a class="srclink" href="https://doc.rust-lang.org/1.64.0/src/core/convert/mod.rs.html#549">source</a></span><a href="#method.into" class="anchor"></a><h4 class="code-header">fn <a href="https://doc.rust-lang.org/1.64.0/core/convert/trait.Into.html#tymethod.into" class="fnname">into</a>(self) -&gt; U</h4></section></summary><div class="docblock"><p>Calls <code>U::from(self)</code>.</p>
<p>That is, this conversion is whatever the implementation of
<code><a href="https://doc.rust-lang.org/1.64.0/core/convert/trait.From.html" title="From">From</a>&lt;T&gt; for U</code> chooses to do.</p>
</div></details></div></details><details class="rustdoc-toggle implementors-toggle"><summary><section id="impl-TryFrom%3CU%3E-for-Lookahead1%3C%27a%3E" class="impl has-srclink"><span class="rightside"><a class="srclink" href="https://doc.rust-lang.org/1.64.0/src/core/convert/mod.rs.html#598">source</a></span><a href="#impl-TryFrom%3CU%3E-for-Lookahead1%3C%27a%3E" class="anchor"></a><h3 class="code-header in-band">impl&lt;T, U&gt; <a class="trait" href="https://doc.rust-lang.org/1.64.0/core/convert/trait.TryFrom.html" title="trait core::convert::TryFrom">TryFrom</a>&lt;U&gt; for T <span class="where fmt-newline">where<br>&nbsp;&nbsp;&nbsp;&nbsp;U: <a class="trait" href="https://doc.rust-lang.org/1.64.0/core/convert/trait.Into.html" title="trait core::convert::Into">Into</a>&lt;T&gt;,&nbsp;</span></h3></section></summary><div class="impl-items"><details class="rustdoc-toggle" open><summary><section id="associatedtype.Error" class="associatedtype trait-impl has-srclink"><a href="#associatedtype.Error" class="anchor"></a><h4 class="code-header">type <a href="https://doc.rust-lang.org/1.64.0/core/convert/trait.TryFrom.html#associatedtype.Error" class="associatedtype">Error</a> = <a class="enum" href="https://doc.rust-lang.org/1.64.0/core/convert/enum.Infallible.html" title="enum core::convert::Infallible">Infallible</a></h4></section></summary><div class='docblock'><p>The type returned in the event of a conversion error.</p>
</div></details><details class="rustdoc-toggle method-toggle" open><summary><section id="method.try_from" class="method trait-impl has-srclink"><span class="rightside"><span class="since" title="const unstable">const: <a href="https://github.com/rust-lang/rust/issues/88674" title="Tracking issue for const_convert">unstable</a></span> · <a class="srclink" href="https://doc.rust-lang.org/1.64.0/src/core/convert/mod.rs.html#604">source</a></span><a href="#method.try_from" class="anchor"></a><h4 class="code-header">fn <a href="https://doc.rust-lang.org/1.64.0/core/convert/trait.TryFrom.html#tymethod.try_from" class="fnname">try_from</a>(value: U) -&gt; <a class="enum" href="https://doc.rust-lang.org/1.64.0/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;T, &lt;T as <a class="trait" href="https://doc.rust-lang.org/1.64.0/core/convert/trait.TryFrom.html" title="trait core::convert::TryFrom">TryFrom</a>&lt;U&gt;&gt;::<a class="associatedtype" href="https://doc.rust-lang.org/1.64.0/core/convert/trait.TryFrom.html#associatedtype.Error" title="type core::convert::TryFrom::Error">Error</a>&gt;</h4></section></summary><div class='docblock'><p>Performs the conversion.</p>
</div></details></div></details><details class="rustdoc-toggle implementors-toggle"><summary><section id="impl-TryInto%3CU%3E-for-Lookahead1%3C%27a%3E" class="impl has-srclink"><span class="rightside"><a class="srclink" href="https://doc.rust-lang.org/1.64.0/src/core/convert/mod.rs.html#583">source</a></span><a href="#impl-TryInto%3CU%3E-for-Lookahead1%3C%27a%3E" class="anchor"></a><h3 class="code-header in-band">impl&lt;T, U&gt; <a class="trait" href="https://doc.rust-lang.org/1.64.0/core/convert/trait.TryInto.html" title="trait core::convert::TryInto">TryInto</a>&lt;U&gt; for T <span class="where fmt-newline">where<br>&nbsp;&nbsp;&nbsp;&nbsp;U: <a class="trait" href="https://doc.rust-lang.org/1.64.0/core/convert/trait.TryFrom.html" title="trait core::convert::TryFrom">TryFrom</a>&lt;T&gt;,&nbsp;</span></h3></section></summary><div class="impl-items"><details class="rustdoc-toggle" open><summary><section id="associatedtype.Error-1" class="associatedtype trait-impl has-srclink"><a href="#associatedtype.Error-1" class="anchor"></a><h4 class="code-header">type <a href="https://doc.rust-lang.org/1.64.0/core/convert/trait.TryInto.html#associatedtype.Error" class="associatedtype">Error</a> = &lt;U as <a class="trait" href="https://doc.rust-lang.org/1.64.0/core/convert/trait.TryFrom.html" title="trait core::convert::TryFrom">TryFrom</a>&lt;T&gt;&gt;::<a class="associatedtype" href="https://doc.rust-lang.org/1.64.0/core/convert/trait.TryFrom.html#associatedtype.Error" title="type core::convert::TryFrom::Error">Error</a></h4></section></summary><div class='docblock'><p>The type returned in the event of a conversion error.</p>
</div></details><details class="rustdoc-toggle method-toggle" open><summary><section id="method.try_into" class="method trait-impl has-srclink"><span class="rightside"><span class="since" title="const unstable">const: <a href="https://github.com/rust-lang/rust/issues/88674" title="Tracking issue for const_convert">unstable</a></span> · <a class="srclink" href="https://doc.rust-lang.org/1.64.0/src/core/convert/mod.rs.html#589">source</a></span><a href="#method.try_into" class="anchor"></a><h4 class="code-header">fn <a href="https://doc.rust-lang.org/1.64.0/core/convert/trait.TryInto.html#tymethod.try_into" class="fnname">try_into</a>(self) -&gt; <a class="enum" href="https://doc.rust-lang.org/1.64.0/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;U, &lt;U as <a class="trait" href="https://doc.rust-lang.org/1.64.0/core/convert/trait.TryFrom.html" title="trait core::convert::TryFrom">TryFrom</a>&lt;T&gt;&gt;::<a class="associatedtype" href="https://doc.rust-lang.org/1.64.0/core/convert/trait.TryFrom.html#associatedtype.Error" title="type core::convert::TryFrom::Error">Error</a>&gt;</h4></section></summary><div class='docblock'><p>Performs the conversion.</p>
</div></details></div></details></div></section></div></main><div id="rustdoc-vars" data-root-path="../../" data-current-crate="syn" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.64.0 (a55dd71d5 2022-09-19)" ></div></body></html>