| <!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/pin-project-internal-1.1.0/src/pin_project/attribute.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>attribute.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="../../../pin_project_internal/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="../../../pin_project_internal/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="kw">use </span>proc_macro2::TokenStream; |
| <span class="kw">use </span>quote::quote; |
| <span class="kw">use </span>syn::{ |
| parse::{Parse, ParseStream}, |
| Attribute, <span class="prelude-ty">Result</span>, Token, Visibility, |
| }; |
| |
| <span class="kw">use </span><span class="kw">super</span>::PIN; |
| <span class="kw">use </span><span class="kw">crate</span>::utils::SliceExt; |
| |
| <span class="comment">// To generate the correct `Unpin` implementation and the projection methods, |
| // we need to collect the types of the pinned fields. |
| // However, since proc-macro-attribute is applied before `cfg` and `cfg_attr` |
| // on fields, we cannot be collecting field types properly at this timing. |
| // So instead of generating the `Unpin` implementation and the projection |
| // methods here, delegate their processing to proc-macro-derive. |
| // |
| // At this stage, only attributes are parsed and the following attributes are |
| // added to the attributes of the item. |
| // - `#[derive(InternalDerive)]` - An internal helper macro that does the above |
| // processing. |
| // - `#[pin(__private(#args))]` - Pass the argument of `#[pin_project]` to |
| // proc-macro-derive (`InternalDerive`). |
| |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>parse_attribute(args: <span class="kw-2">&</span>TokenStream, input: TokenStream) -> <span class="prelude-ty">Result</span><TokenStream> { |
| <span class="kw">let </span>Input { attrs, body } = syn::parse2(input)<span class="question-mark">?</span>; |
| |
| <span class="prelude-val">Ok</span>(<span class="macro">quote! </span>{ |
| #(#attrs)* |
| <span class="attribute">#[derive(::pin_project::__private::__PinProjectInternalDerive)] |
| </span><span class="comment">// Use `__private` to prevent users from trying to control `InternalDerive` |
| // manually. `__private` does not guarantee compatibility between patch |
| // versions, so it should be sufficient for this purpose in most cases. |
| </span><span class="attribute">#[pin(__private(#args))] |
| </span>#body |
| }) |
| } |
| |
| <span class="attribute">#[allow(dead_code)] </span><span class="comment">// false positive that fixed in Rust 1.39 |
| </span><span class="kw">struct </span>Input { |
| attrs: Vec<Attribute>, |
| body: TokenStream, |
| } |
| |
| <span class="kw">impl </span>Parse <span class="kw">for </span>Input { |
| <span class="kw">fn </span>parse(input: ParseStream<<span class="lifetime">'_</span>>) -> <span class="prelude-ty">Result</span><<span class="self">Self</span>> { |
| <span class="kw">let </span>attrs = input.call(Attribute::parse_outer)<span class="question-mark">?</span>; |
| |
| <span class="kw">let </span>ahead = input.fork(); |
| <span class="kw">let </span>_vis: Visibility = ahead.parse()<span class="question-mark">?</span>; |
| <span class="kw">if </span>!ahead.peek(<span class="macro">Token!</span>[<span class="kw">struct</span>]) && !ahead.peek(<span class="macro">Token!</span>[<span class="kw">enum</span>]) { |
| <span class="comment">// If we check this only on proc-macro-derive, it may generate unhelpful error |
| // messages. So it is preferable to be able to detect it here. |
| </span><span class="macro">bail!</span>( |
| input.parse::<TokenStream>()<span class="question-mark">?</span>, |
| <span class="string">"#[pin_project] attribute may only be used on structs or enums" |
| </span>); |
| } <span class="kw">else if let </span><span class="prelude-val">Some</span>(attr) = attrs.find(PIN) { |
| <span class="macro">bail!</span>(attr, <span class="string">"#[pin] attribute may only be used on fields of structs or variants"</span>); |
| } <span class="kw">else if let </span><span class="prelude-val">Some</span>(attr) = attrs.find(<span class="string">"pin_project"</span>) { |
| <span class="macro">bail!</span>(attr, <span class="string">"duplicate #[pin_project] attribute"</span>); |
| } |
| <span class="prelude-val">Ok</span>(<span class="self">Self </span>{ attrs, body: input.parse()<span class="question-mark">? </span>}) |
| } |
| } |
| </code></pre></div> |
| </section></div></main><div id="rustdoc-vars" data-root-path="../../../" data-current-crate="pin_project_internal" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.66.0-nightly (5c8bff74b 2022-10-21)" ></div></body></html> |
