| <!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="Source of the Rust file `/root/.cargo/registry/src/github.com-1ecc6299db9ec823/syn-2.0.18/src/parse_macro_input.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>parse_macro_input.rs - source</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="../../source-script.js"></script><script defer src="../../source-files.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 source"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><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></nav><main><div class="width-limiter"><nav class="sub"><a class="sub-logo-container" href="../../syn/index.html"><img class="rust-logo" src="../../rust-logo.svg" alt="logo"></a><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="example-wrap"><pre class="src-line-numbers"><span id="1">1</span> |
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| </pre><pre class="rust"><code><span class="doccomment">/// Parse the input TokenStream of a macro, triggering a compile error if the |
| /// tokens fail to parse. |
| /// |
| /// Refer to the [`parse` module] documentation for more details about parsing |
| /// in Syn. |
| /// |
| /// [`parse` module]: mod@crate::parse |
| /// |
| /// <br> |
| /// |
| /// # Intended usage |
| /// |
| /// This macro must be called from a function that returns |
| /// `proc_macro::TokenStream`. Usually this will be your proc macro entry point, |
| /// the function that has the #\[proc_macro\] / #\[proc_macro_derive\] / |
| /// #\[proc_macro_attribute\] attribute. |
| /// |
| /// ``` |
| /// # extern crate proc_macro; |
| /// # |
| /// use proc_macro::TokenStream; |
| /// use syn::{parse_macro_input, Result}; |
| /// use syn::parse::{Parse, ParseStream}; |
| /// |
| /// struct MyMacroInput { |
| /// /* ... */ |
| /// } |
| /// |
| /// impl Parse for MyMacroInput { |
| /// fn parse(input: ParseStream) -> Result<Self> { |
| /// /* ... */ |
| /// # Ok(MyMacroInput {}) |
| /// } |
| /// } |
| /// |
| /// # const IGNORE: &str = stringify! { |
| /// #[proc_macro] |
| /// # }; |
| /// pub fn my_macro(tokens: TokenStream) -> TokenStream { |
| /// let input = parse_macro_input!(tokens as MyMacroInput); |
| /// |
| /// /* ... */ |
| /// # TokenStream::new() |
| /// } |
| /// ``` |
| /// |
| /// <br> |
| /// |
| /// # Usage with Parser |
| /// |
| /// This macro can also be used with the [`Parser` trait] for types that have |
| /// multiple ways that they can be parsed. |
| /// |
| /// [`Parser` trait]: crate::parse::Parser |
| /// |
| /// ``` |
| /// # extern crate proc_macro; |
| /// # |
| /// # use proc_macro::TokenStream; |
| /// # use syn::{parse_macro_input, Result}; |
| /// # use syn::parse::ParseStream; |
| /// # |
| /// # struct MyMacroInput {} |
| /// # |
| /// impl MyMacroInput { |
| /// fn parse_alternate(input: ParseStream) -> Result<Self> { |
| /// /* ... */ |
| /// # Ok(MyMacroInput {}) |
| /// } |
| /// } |
| /// |
| /// # const IGNORE: &str = stringify! { |
| /// #[proc_macro] |
| /// # }; |
| /// pub fn my_macro(tokens: TokenStream) -> TokenStream { |
| /// let input = parse_macro_input!(tokens with MyMacroInput::parse_alternate); |
| /// |
| /// /* ... */ |
| /// # TokenStream::new() |
| /// } |
| /// ``` |
| /// |
| /// <br> |
| /// |
| /// # Expansion |
| /// |
| /// `parse_macro_input!($variable as $Type)` expands to something like: |
| /// |
| /// ```no_run |
| /// # extern crate proc_macro; |
| /// # |
| /// # macro_rules! doc_test { |
| /// # ($variable:ident as $Type:ty) => { |
| /// match syn::parse::<$Type>($variable) { |
| /// Ok(syntax_tree) => syntax_tree, |
| /// Err(err) => return proc_macro::TokenStream::from(err.to_compile_error()), |
| /// } |
| /// # }; |
| /// # } |
| /// # |
| /// # fn test(input: proc_macro::TokenStream) -> proc_macro::TokenStream { |
| /// # let _ = doc_test!(input as syn::Ident); |
| /// # proc_macro::TokenStream::new() |
| /// # } |
| /// ``` |
| </span><span class="attribute">#[macro_export] |
| #[cfg_attr(doc_cfg, doc(cfg(all(feature = <span class="string">"parsing"</span>, feature = <span class="string">"proc-macro"</span>))))] |
| </span><span class="macro">macro_rules! </span>parse_macro_input { |
| (<span class="macro-nonterminal">$tokenstream</span>:ident <span class="kw">as </span><span class="macro-nonterminal">$ty</span>:ty) => { |
| <span class="kw">match </span><span class="macro-nonterminal">$crate::parse</span>::<<span class="macro-nonterminal">$ty</span>>(<span class="macro-nonterminal">$tokenstream</span>) { |
| <span class="macro-nonterminal">$crate::__private::Ok</span>(data) => data, |
| <span class="macro-nonterminal">$crate::__private::Err</span>(err) => { |
| <span class="kw">return </span><span class="macro-nonterminal">$crate::__private::TokenStream::from</span>(err.to_compile_error()); |
| } |
| } |
| }; |
| (<span class="macro-nonterminal">$tokenstream</span>:ident with <span class="macro-nonterminal">$parser</span>:path) => { |
| <span class="kw">match </span><span class="macro-nonterminal">$crate::parse::Parser::parse</span>(<span class="macro-nonterminal">$parser</span>, <span class="macro-nonterminal">$tokenstream</span>) { |
| <span class="macro-nonterminal">$crate::__private::Ok</span>(data) => data, |
| <span class="macro-nonterminal">$crate::__private::Err</span>(err) => { |
| <span class="kw">return </span><span class="macro-nonterminal">$crate::__private::TokenStream::from</span>(err.to_compile_error()); |
| } |
| } |
| }; |
| (<span class="macro-nonterminal">$tokenstream</span>:ident) => { |
| <span class="macro-nonterminal">$</span><span class="macro">crate::parse_macro_input!</span>(<span class="macro-nonterminal">$tokenstream </span><span class="kw">as _</span>) |
| }; |
| } |
| </code></pre></div> |
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