| <!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/anyhow-1.0.71/src/kind.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>kind.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="../../anyhow/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="../../anyhow/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="comment">// Tagged dispatch mechanism for resolving the behavior of `anyhow!($expr)`. |
| // |
| // When anyhow! is given a single expr argument to turn into anyhow::Error, we |
| // want the resulting Error to pick up the input's implementation of source() |
| // and backtrace() if it has a std::error::Error impl, otherwise require nothing |
| // more than Display and Debug. |
| // |
| // Expressed in terms of specialization, we want something like: |
| // |
| // trait AnyhowNew { |
| // fn new(self) -> Error; |
| // } |
| // |
| // impl<T> AnyhowNew for T |
| // where |
| // T: Display + Debug + Send + Sync + 'static, |
| // { |
| // default fn new(self) -> Error { |
| // /* no std error impl */ |
| // } |
| // } |
| // |
| // impl<T> AnyhowNew for T |
| // where |
| // T: std::error::Error + Send + Sync + 'static, |
| // { |
| // fn new(self) -> Error { |
| // /* use std error's source() and backtrace() */ |
| // } |
| // } |
| // |
| // Since specialization is not stable yet, instead we rely on autoref behavior |
| // of method resolution to perform tagged dispatch. Here we have two traits |
| // AdhocKind and TraitKind that both have an anyhow_kind() method. AdhocKind is |
| // implemented whether or not the caller's type has a std error impl, while |
| // TraitKind is implemented only when a std error impl does exist. The ambiguity |
| // is resolved by AdhocKind requiring an extra autoref so that it has lower |
| // precedence. |
| // |
| // The anyhow! macro will set up the call in this form: |
| // |
| // #[allow(unused_imports)] |
| // use $crate::__private::{AdhocKind, TraitKind}; |
| // let error = $msg; |
| // (&error).anyhow_kind().new(error) |
| |
| </span><span class="kw">use </span><span class="kw">crate</span>::Error; |
| <span class="kw">use </span>core::fmt::{Debug, Display}; |
| |
| <span class="attribute">#[cfg(feature = <span class="string">"std"</span>)] |
| </span><span class="kw">use </span><span class="kw">crate</span>::StdError; |
| |
| <span class="kw">pub struct </span>Adhoc; |
| |
| <span class="kw">pub trait </span>AdhocKind: Sized { |
| <span class="attribute">#[inline] |
| </span><span class="kw">fn </span>anyhow_kind(<span class="kw-2">&</span><span class="self">self</span>) -> Adhoc { |
| Adhoc |
| } |
| } |
| |
| <span class="kw">impl</span><T> AdhocKind <span class="kw">for </span><span class="kw-2">&</span>T <span class="kw">where </span>T: <span class="question-mark">?</span>Sized + Display + Debug + Send + Sync + <span class="lifetime">'static </span>{} |
| |
| <span class="kw">impl </span>Adhoc { |
| <span class="attribute">#[cold] |
| </span><span class="kw">pub fn </span>new<M>(<span class="self">self</span>, message: M) -> Error |
| <span class="kw">where |
| </span>M: Display + Debug + Send + Sync + <span class="lifetime">'static</span>, |
| { |
| Error::from_adhoc(message, <span class="macro">backtrace!</span>()) |
| } |
| } |
| |
| <span class="kw">pub struct </span>Trait; |
| |
| <span class="kw">pub trait </span>TraitKind: Sized { |
| <span class="attribute">#[inline] |
| </span><span class="kw">fn </span>anyhow_kind(<span class="kw-2">&</span><span class="self">self</span>) -> Trait { |
| Trait |
| } |
| } |
| |
| <span class="kw">impl</span><E> TraitKind <span class="kw">for </span>E <span class="kw">where </span>E: Into<Error> {} |
| |
| <span class="kw">impl </span>Trait { |
| <span class="attribute">#[cold] |
| </span><span class="kw">pub fn </span>new<E>(<span class="self">self</span>, error: E) -> Error |
| <span class="kw">where |
| </span>E: Into<Error>, |
| { |
| error.into() |
| } |
| } |
| |
| <span class="attribute">#[cfg(feature = <span class="string">"std"</span>)] |
| </span><span class="kw">pub struct </span>Boxed; |
| |
| <span class="attribute">#[cfg(feature = <span class="string">"std"</span>)] |
| </span><span class="kw">pub trait </span>BoxedKind: Sized { |
| <span class="attribute">#[inline] |
| </span><span class="kw">fn </span>anyhow_kind(<span class="kw-2">&</span><span class="self">self</span>) -> Boxed { |
| Boxed |
| } |
| } |
| |
| <span class="attribute">#[cfg(feature = <span class="string">"std"</span>)] |
| </span><span class="kw">impl </span>BoxedKind <span class="kw">for </span>Box<<span class="kw">dyn </span>StdError + Send + Sync> {} |
| |
| <span class="attribute">#[cfg(feature = <span class="string">"std"</span>)] |
| </span><span class="kw">impl </span>Boxed { |
| <span class="attribute">#[cold] |
| </span><span class="kw">pub fn </span>new(<span class="self">self</span>, error: Box<<span class="kw">dyn </span>StdError + Send + Sync>) -> Error { |
| <span class="kw">let </span>backtrace = <span class="macro">backtrace_if_absent!</span>(<span class="kw-2">&*</span>error); |
| Error::from_boxed(error, backtrace) |
| } |
| } |
| </code></pre></div> |
| </section></div></main><div id="rustdoc-vars" data-root-path="../../" data-current-crate="anyhow" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.66.0-nightly (5c8bff74b 2022-10-21)" ></div></body></html> |
