<!DOCTYPE HTML>
<html lang="en" class="sidebar-visible no-js light">
<head>
<!-- Book generated using mdBook -->
<meta charset="UTF-8">
<title>Writing a library - chainerror</title>
<meta content="text/html; charset=utf-8" http-equiv="Content-Type">
<meta name="description" content="A tutorial for the chainerror rust crate.">
<meta name="viewport" content="width=device-width, initial-scale=1">
<meta name="theme-color" content="#ffffff" />
<link rel="shortcut icon" href="favicon.png">
<link rel="stylesheet" href="css/variables.css">
<link rel="stylesheet" href="css/general.css">
<link rel="stylesheet" href="css/chrome.css">
<link rel="stylesheet" href="css/print.css" media="print">
<!-- Fonts -->
<link rel="stylesheet" href="FontAwesome/css/font-awesome.css">
<link href="https://fonts.googleapis.com/css?family=Open+Sans:300italic,400italic,600italic,700italic,800italic,400,300,600,700,800" rel="stylesheet" type="text/css">
<link href="https://fonts.googleapis.com/css?family=Source+Code+Pro:500" rel="stylesheet" type="text/css">
<!-- Highlight.js Stylesheets -->
<link rel="stylesheet" href="highlight.css">
<link rel="stylesheet" href="tomorrow-night.css">
<link rel="stylesheet" href="ayu-highlight.css">
<!-- Custom theme stylesheets -->
</head>
<body>
<!-- Provide site root to javascript -->
<script type="text/javascript">
var path_to_root = "";
var default_theme = window.matchMedia("(prefers-color-scheme: dark)").matches ? "light" : "light";
</script>
<!-- Work around some values being stored in localStorage wrapped in quotes -->
<script type="text/javascript">
try {
var theme = localStorage.getItem('mdbook-theme');
var sidebar = localStorage.getItem('mdbook-sidebar');
if (theme.startsWith('"') && theme.endsWith('"')) {
localStorage.setItem('mdbook-theme', theme.slice(1, theme.length - 1));
}
if (sidebar.startsWith('"') && sidebar.endsWith('"')) {
localStorage.setItem('mdbook-sidebar', sidebar.slice(1, sidebar.length - 1));
}
} catch (e) { }
</script>
<!-- Set the theme before any content is loaded, prevents flash -->
<script type="text/javascript">
var theme;
try { theme = localStorage.getItem('mdbook-theme'); } catch(e) { }
if (theme === null || theme === undefined) { theme = default_theme; }
var html = document.querySelector('html');
html.classList.remove('no-js')
html.classList.remove('light')
html.classList.add(theme);
html.classList.add('js');
</script>
<!-- Hide / unhide sidebar before it is displayed -->
<script type="text/javascript">
var html = document.querySelector('html');
var sidebar = 'hidden';
if (document.body.clientWidth >= 1080) {
try { sidebar = localStorage.getItem('mdbook-sidebar'); } catch(e) { }
sidebar = sidebar || 'visible';
}
html.classList.remove('sidebar-visible');
html.classList.add("sidebar-" + sidebar);
</script>
<nav id="sidebar" class="sidebar" aria-label="Table of contents">
<div id="sidebar-scrollbox" class="sidebar-scrollbox">
<ol class="chapter"><li class="expanded affix "><a href="index.html">chainerror</a></li><li class="expanded "><a href="tutorial1.html"><strong aria-hidden="true">1.</strong> Simple String Errors</a></li><li class="expanded "><a href="tutorial2.html"><strong aria-hidden="true">2.</strong> Simple Chained String Errors</a></li><li class="expanded "><a href="tutorial3.html"><strong aria-hidden="true">3.</strong> Mapping Errors</a></li><li class="expanded "><a href="tutorial4.html"><strong aria-hidden="true">4.</strong> Saving coding chars</a></li><li class="expanded "><a href="tutorial5.html"><strong aria-hidden="true">5.</strong> The source() of Errors</a></li><li class="expanded "><a href="tutorial6.html"><strong aria-hidden="true">6.</strong> Downcast the Errors</a></li><li class="expanded "><a href="tutorial7.html"><strong aria-hidden="true">7.</strong> The root cause of all Errors</a></li><li class="expanded "><a href="tutorial8.html"><strong aria-hidden="true">8.</strong> Finding an Error cause</a></li><li class="expanded "><a href="tutorial9.html"><strong aria-hidden="true">9.</strong> Selective Error Handling</a></li><li class="expanded "><a href="tutorial10.html"><strong aria-hidden="true">10.</strong> ErrorKind to the rescue</a></li><li class="expanded "><a href="tutorial11.html"><strong aria-hidden="true">11.</strong> Debug for the ErrorKind</a></li><li class="expanded "><a href="tutorial12.html"><strong aria-hidden="true">12.</strong> Deref for the ErrorKind</a></li><li class="expanded "><a href="tutorial13.html" class="active"><strong aria-hidden="true">13.</strong> Writing a library</a></li><li class="expanded "><a href="tutorial14.html"><strong aria-hidden="true">14.</strong> Going back to std</a></li><li class="expanded affix "><a href="end.html">The End</a></li></ol>
</div>
<div id="sidebar-resize-handle" class="sidebar-resize-handle"></div>
</nav>
<div id="page-wrapper" class="page-wrapper">
<div class="page">
<div id="menu-bar" class="menu-bar">
<div id="menu-bar-sticky-container">
<div class="left-buttons">
<button id="sidebar-toggle" class="icon-button" type="button" title="Toggle Table of Contents" aria-label="Toggle Table of Contents" aria-controls="sidebar">
<i class="fa fa-bars"></i>
</button>
<button id="theme-toggle" class="icon-button" type="button" title="Change theme" aria-label="Change theme" aria-haspopup="true" aria-expanded="false" aria-controls="theme-list">
<i class="fa fa-paint-brush"></i>
</button>
<ul id="theme-list" class="theme-popup" aria-label="Themes" role="menu">
<li role="none"><button role="menuitem" class="theme" id="light">Light (default)</button></li>
<li role="none"><button role="menuitem" class="theme" id="rust">Rust</button></li>
<li role="none"><button role="menuitem" class="theme" id="coal">Coal</button></li>
<li role="none"><button role="menuitem" class="theme" id="navy">Navy</button></li>
<li role="none"><button role="menuitem" class="theme" id="ayu">Ayu</button></li>
</ul>
<button id="search-toggle" class="icon-button" type="button" title="Search. (Shortkey: s)" aria-label="Toggle Searchbar" aria-expanded="false" aria-keyshortcuts="S" aria-controls="searchbar">
<i class="fa fa-search"></i>
</button>
</div>
<h1 class="menu-title">chainerror</h1>
<div class="right-buttons">
<a href="print.html" title="Print this book" aria-label="Print this book">
<i id="print-button" class="fa fa-print"></i>
</a>
</div>
</div>
</div>
<div id="search-wrapper" class="hidden">
<form id="searchbar-outer" class="searchbar-outer">
<input type="search" name="search" id="searchbar" name="searchbar" placeholder="Search this book ..." aria-controls="searchresults-outer" aria-describedby="searchresults-header">
</form>
<div id="searchresults-outer" class="searchresults-outer hidden">
<div id="searchresults-header" class="searchresults-header"></div>
<ul id="searchresults">
</ul>
</div>
</div>
<!-- Apply ARIA attributes after the sidebar and the sidebar toggle button are added to the DOM -->
<script type="text/javascript">
document.getElementById('sidebar-toggle').setAttribute('aria-expanded', sidebar === 'visible');
document.getElementById('sidebar').setAttribute('aria-hidden', sidebar !== 'visible');
Array.from(document.querySelectorAll('#sidebar a')).forEach(function(link) {
link.setAttribute('tabIndex', sidebar === 'visible' ? 0 : -1);
});
</script>
<div id="content" class="content">
<main>
<h1><a class="header" href="#writing-a-library" id="writing-a-library">Writing a library</a></h1>
<p>I would advise to only expose an <code>mycrate::ErrorKind</code> and type alias <code>mycrate::Error</code> to <code>ChainError<mycrate::ErrorKind></code>
so you can tell your library users to use the <code>.kind()</code> method as <code>std::io::Error</code> does.</p>
<p>If you later decide to make your own <code>Error</code> implementation, your library users don't
have to change much or anything.</p>
<pre><pre class="playpen"><code class="language-rust"><span class="boring">#[allow(dead_code)]
</span><span class="boring">#[macro_use]
</span><span class="boring">pub mod chainerror {
</span><span class="boring">//! `chainerror` provides an error backtrace without doing a real backtrace, so even after you `strip` your
</span><span class="boring">//! binaries, you still have the error backtrace.
</span><span class="boring">//!
</span><span class="boring">//! `chainerror` has no dependencies!
</span><span class="boring">//!
</span><span class="boring">//! `chainerror` uses `.source()` of `std::error::Error` along with `line()!` and `file()!` to provide a nice debug error backtrace.
</span><span class="boring">//! It encapsulates all types, which have `Display + Debug` and can store the error cause internally.
</span><span class="boring">//!
</span><span class="boring">//! Along with the `ChainError<T>` struct, `chainerror` comes with some useful helper macros to save a lot of typing.
</span><span class="boring">//!
</span><span class="boring">//! ## Features
</span><span class="boring">//!
</span><span class="boring">//! `no-fileline`
</span><span class="boring">//! : completely turn off storing filename and line
</span><span class="boring">//!
</span><span class="boring">//! `display-cause`
</span><span class="boring">//! : turn on printing a backtrace of the errors in `Display`
</span><span class="boring">//!
</span><span class="boring">//! `no-debug-cause`
</span><span class="boring">//! : turn off printing a backtrace of the errors in `Debug`
</span><span class="boring">//!
</span><span class="boring">//!
</span><span class="boring">//! # Tutorial
</span><span class="boring">//!
</span><span class="boring">//! Read the [Tutorial](https://haraldh.github.io/chainerror/tutorial1.html)
</span><span class="boring">//!
</span><span class="boring">//! # Examples
</span><span class="boring">//!
</span><span class="boring">//! ```rust
</span><span class="boring">//! use chainerror::*;
</span><span class="boring">//! use std::error::Error;
</span><span class="boring">//! use std::io;
</span><span class="boring">//! use std::result::Result;
</span><span class="boring">//!
</span><span class="boring">//! fn do_some_io() -> Result<(), Box<dyn Error + Send + Sync>> {
</span><span class="boring">//! Err(io::Error::from(io::ErrorKind::NotFound))?;
</span><span class="boring">//! Ok(())
</span><span class="boring">//! }
</span><span class="boring">//!
</span><span class="boring">//! fn func2() -> Result<(), Box<dyn Error + Send + Sync>> {
</span><span class="boring">//! let filename = "foo.txt";
</span><span class="boring">//! do_some_io().map_err(mstrerr!("Error reading '{}'", filename))?;
</span><span class="boring">//! Ok(())
</span><span class="boring">//! }
</span><span class="boring">//!
</span><span class="boring">//! fn func1() -> Result<(), Box<dyn Error + Send + Sync>> {
</span><span class="boring">//! func2().map_err(mstrerr!("func1 error"))?;
</span><span class="boring">//! Ok(())
</span><span class="boring">//! }
</span><span class="boring">//!
</span><span class="boring">//! fn main() {
</span><span class="boring">//! if let Err(e) = func1() {
</span><span class="boring">//! #[cfg(not(windows))]
</span><span class="boring">//! assert_eq!(
</span><span class="boring">//! format!("\n{:?}\n", e), r#"
</span><span class="boring">//! src/lib.rs:20: func1 error
</span><span class="boring">//! Caused by:
</span><span class="boring">//! src/lib.rs:15: Error reading 'foo.txt'
</span><span class="boring">//! Caused by:
</span><span class="boring">//! Kind(NotFound)
</span><span class="boring">//! "#
</span><span class="boring">//! );
</span><span class="boring">//! }
</span><span class="boring">//! # else {
</span><span class="boring">//! # unreachable!();
</span><span class="boring">//! # }
</span><span class="boring">//! }
</span><span class="boring">//! ```
</span><span class="boring">//!
</span><span class="boring">//!
</span><span class="boring">//! ```rust
</span><span class="boring">//! use chainerror::*;
</span><span class="boring">//! use std::error::Error;
</span><span class="boring">//! use std::io;
</span><span class="boring">//! use std::result::Result;
</span><span class="boring">//!
</span><span class="boring">//! fn do_some_io() -> Result<(), Box<dyn Error + Send + Sync>> {
</span><span class="boring">//! Err(io::Error::from(io::ErrorKind::NotFound))?;
</span><span class="boring">//! Ok(())
</span><span class="boring">//! }
</span><span class="boring">//!
</span><span class="boring">//! fn func3() -> Result<(), Box<dyn Error + Send + Sync>> {
</span><span class="boring">//! let filename = "foo.txt";
</span><span class="boring">//! do_some_io().map_err(mstrerr!("Error reading '{}'", filename))?;
</span><span class="boring">//! Ok(())
</span><span class="boring">//! }
</span><span class="boring">//!
</span><span class="boring">//! derive_str_cherr!(Func2Error);
</span><span class="boring">//!
</span><span class="boring">//! fn func2() -> ChainResult<(), Func2Error> {
</span><span class="boring">//! func3().map_err(mstrerr!(Func2Error, "func2 error: calling func3"))?;
</span><span class="boring">//! Ok(())
</span><span class="boring">//! }
</span><span class="boring">//!
</span><span class="boring">//! enum Func1Error {
</span><span class="boring">//! Func2,
</span><span class="boring">//! IO(String),
</span><span class="boring">//! }
</span><span class="boring">//!
</span><span class="boring">//! impl ::std::fmt::Display for Func1Error {
</span><span class="boring">//! fn fmt(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
</span><span class="boring">//! match self {
</span><span class="boring">//! Func1Error::Func2 => write!(f, "func1 error calling func2"),
</span><span class="boring">//! Func1Error::IO(filename) => write!(f, "Error reading '{}'", filename),
</span><span class="boring">//! }
</span><span class="boring">//! }
</span><span class="boring">//! }
</span><span class="boring">//!
</span><span class="boring">//! impl ::std::fmt::Debug for Func1Error {
</span><span class="boring">//! fn fmt(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
</span><span class="boring">//! write!(f, "{}", self)
</span><span class="boring">//! }
</span><span class="boring">//! }
</span><span class="boring">//!
</span><span class="boring">//! fn func1() -> ChainResult<(), Func1Error> {
</span><span class="boring">//! func2().map_err(|e| cherr!(e, Func1Error::Func2))?;
</span><span class="boring">//! let filename = String::from("bar.txt");
</span><span class="boring">//! do_some_io().map_err(|e| cherr!(e, Func1Error::IO(filename)))?;
</span><span class="boring">//! Ok(())
</span><span class="boring">//! }
</span><span class="boring">//!
</span><span class="boring">//! fn main() {
</span><span class="boring">//! if let Err(e) = func1() {
</span><span class="boring">//! assert!(
</span><span class="boring">//! match e.kind() {
</span><span class="boring">//! Func1Error::Func2 => {
</span><span class="boring">//! eprintln!("Main Error Report: func1 error calling func2");
</span><span class="boring">//! true
</span><span class="boring">//! }
</span><span class="boring">//! Func1Error::IO(filename) => {
</span><span class="boring">//! eprintln!("Main Error Report: func1 error reading '{}'", filename);
</span><span class="boring">//! false
</span><span class="boring">//! }
</span><span class="boring">//! }
</span><span class="boring">//! );
</span><span class="boring">//!
</span><span class="boring">//! assert!(e.find_chain_cause::<Func2Error>().is_some());
</span><span class="boring">//!
</span><span class="boring">//! if let Some(e) = e.find_chain_cause::<Func2Error>() {
</span><span class="boring">//! eprintln!("\nError reported by Func2Error: {}", e)
</span><span class="boring">//! }
</span><span class="boring">//!
</span><span class="boring">//!
</span><span class="boring">//! assert!(e.root_cause().is_some());
</span><span class="boring">//!
</span><span class="boring">//! if let Some(e) = e.root_cause() {
</span><span class="boring">//! let io_error = e.downcast_ref::<io::Error>().unwrap();
</span><span class="boring">//! eprintln!("\nThe root cause was: std::io::Error: {:#?}", io_error);
</span><span class="boring">//! }
</span><span class="boring">//!
</span><span class="boring">//! #[cfg(not(windows))]
</span><span class="boring">//! assert_eq!(
</span><span class="boring">//! format!("\n{:?}\n", e), r#"
</span><span class="boring">//! src/lib.rs:47: func1 error calling func2
</span><span class="boring">//! Caused by:
</span><span class="boring">//! src/lib.rs:22: Func2Error(func2 error: calling func3)
</span><span class="boring">//! Caused by:
</span><span class="boring">//! src/lib.rs:15: Error reading 'foo.txt'
</span><span class="boring">//! Caused by:
</span><span class="boring">//! Kind(NotFound)
</span><span class="boring">//! "#
</span><span class="boring">//! );
</span><span class="boring">//! }
</span><span class="boring">//! # else {
</span><span class="boring">//! # unreachable!();
</span><span class="boring">//! # }
</span><span class="boring">//! }
</span><span class="boring">//! ```
</span><span class="boring">
</span><span class="boring">#![deny(
</span><span class="boring"> warnings,
</span><span class="boring"> absolute_paths_not_starting_with_crate,
</span><span class="boring"> deprecated_in_future,
</span><span class="boring"> keyword_idents,
</span><span class="boring"> macro_use_extern_crate,
</span><span class="boring"> missing_debug_implementations,
</span><span class="boring"> trivial_numeric_casts,
</span><span class="boring"> unused_extern_crates,
</span><span class="boring"> unused_import_braces,
</span><span class="boring"> unused_qualifications,
</span><span class="boring"> unused_results,
</span><span class="boring"> unused_labels,
</span><span class="boring"> unused_lifetimes,
</span><span class="boring"> unstable_features,
</span><span class="boring"> unreachable_pub,
</span><span class="boring"> future_incompatible,
</span><span class="boring"> missing_copy_implementations,
</span><span class="boring"> missing_doc_code_examples,
</span><span class="boring"> rust_2018_idioms,
</span><span class="boring"> rust_2018_compatibility
</span><span class="boring">)]
</span><span class="boring">
</span><span class="boring">use std::any::TypeId;
</span><span class="boring">use std::error::Error;
</span><span class="boring">use std::fmt::{Debug, Display, Formatter, Result};
</span><span class="boring">
</span><span class="boring">/// chains an inner error kind `T` with a causing error
</span><span class="boring">pub struct ChainError<T> {
</span><span class="boring"> #[cfg(not(feature = "no-fileline"))]
</span><span class="boring"> occurrence: Option<&'static str>,
</span><span class="boring"> kind: T,
</span><span class="boring"> error_cause: Option<Box<dyn Error + 'static + Send + Sync>>,
</span><span class="boring">}
</span><span class="boring">
</span><span class="boring">/// convenience type alias
</span><span class="boring">pub type ChainResult<O, E> = std::result::Result<O, ChainError<E>>;
</span><span class="boring">
</span><span class="boring">impl<T: 'static + Display + Debug> ChainError<T> {
</span><span class="boring"> #[cfg(not(feature = "no-fileline"))]
</span><span class="boring"> /// Use the `cherr!()` or `mstrerr!()` macro instead of calling this directly
</span><span class="boring"> #[inline]
</span><span class="boring"> pub fn new(
</span><span class="boring"> kind: T,
</span><span class="boring"> error_cause: Option<Box<dyn Error + 'static + Send + Sync>>,
</span><span class="boring"> occurrence: Option<&'static str>,
</span><span class="boring"> ) -> Self {
</span><span class="boring"> Self {
</span><span class="boring"> occurrence,
</span><span class="boring"> kind,
</span><span class="boring"> error_cause,
</span><span class="boring"> }
</span><span class="boring"> }
</span><span class="boring">
</span><span class="boring"> #[cfg(feature = "no-fileline")]
</span><span class="boring"> /// Use the `cherr!()` or `mstrerr!()` macro instead of calling this directly
</span><span class="boring"> #[inline]
</span><span class="boring"> pub fn new(
</span><span class="boring"> kind: T,
</span><span class="boring"> error_cause: Option<Box<dyn Error + 'static + Send + Sync>>,
</span><span class="boring"> _occurrence: Option<&'static str>,
</span><span class="boring"> ) -> Self {
</span><span class="boring"> Self { kind, error_cause }
</span><span class="boring"> }
</span><span class="boring">
</span><span class="boring"> /// return the root cause of the error chain, if any exists
</span><span class="boring"> pub fn root_cause(&self) -> Option<&(dyn Error + 'static)> {
</span><span class="boring"> self.iter().last()
</span><span class="boring"> }
</span><span class="boring">
</span><span class="boring"> /// Find the first error cause of type U, if any exists
</span><span class="boring"> ///
</span><span class="boring"> /// # Examples
</span><span class="boring"> ///
</span><span class="boring"> /// ```rust
</span><span class="boring"> /// use chainerror::*;
</span><span class="boring"> /// use std::error::Error;
</span><span class="boring"> /// use std::io;
</span><span class="boring"> ///
</span><span class="boring"> /// fn do_some_io() -> Result<(), Box<dyn Error + Send + Sync>> {
</span><span class="boring"> /// Err(io::Error::from(io::ErrorKind::NotFound))?;
</span><span class="boring"> /// Ok(())
</span><span class="boring"> /// }
</span><span class="boring"> ///
</span><span class="boring"> /// derive_str_cherr!(Func2Error);
</span><span class="boring"> ///
</span><span class="boring"> /// fn func2() -> Result<(), Box<dyn Error + Send + Sync>> {
</span><span class="boring"> /// let filename = "foo.txt";
</span><span class="boring"> /// do_some_io().map_err(mstrerr!(Func2Error, "Error reading '{}'", filename))?;
</span><span class="boring"> /// Ok(())
</span><span class="boring"> /// }
</span><span class="boring"> ///
</span><span class="boring"> /// derive_str_cherr!(Func1Error);
</span><span class="boring"> ///
</span><span class="boring"> /// fn func1() -> Result<(), Box<dyn Error + Send + Sync>> {
</span><span class="boring"> /// func2().map_err(mstrerr!(Func1Error, "func1 error"))?;
</span><span class="boring"> /// Ok(())
</span><span class="boring"> /// }
</span><span class="boring"> ///
</span><span class="boring"> /// fn main() {
</span><span class="boring"> /// if let Err(e) = func1() {
</span><span class="boring"> /// if let Some(f1err) = e.downcast_chain_ref::<Func1Error>() {
</span><span class="boring"> ///
</span><span class="boring"> /// assert!(f1err.find_cause::<io::Error>().is_some());
</span><span class="boring"> ///
</span><span class="boring"> /// assert!(f1err.find_chain_cause::<Func2Error>().is_some());
</span><span class="boring"> /// }
</span><span class="boring"> /// # else {
</span><span class="boring"> /// # panic!();
</span><span class="boring"> /// # }
</span><span class="boring"> /// }
</span><span class="boring"> /// # else {
</span><span class="boring"> /// # unreachable!();
</span><span class="boring"> /// # }
</span><span class="boring"> /// }
</span><span class="boring"> /// ```
</span><span class="boring"> #[inline]
</span><span class="boring"> pub fn find_cause<U: Error + 'static>(&self) -> Option<&U> {
</span><span class="boring"> self.iter().filter_map(Error::downcast_ref::<U>).next()
</span><span class="boring"> }
</span><span class="boring">
</span><span class="boring"> /// Find the first error cause of type `ChainError<U>`, if any exists
</span><span class="boring"> ///
</span><span class="boring"> /// Same as `find_cause`, but hides the `ChainError<U>` implementation internals
</span><span class="boring"> ///
</span><span class="boring"> /// # Examples
</span><span class="boring"> ///
</span><span class="boring"> /// ```rust
</span><span class="boring"> /// # use chainerror::*;
</span><span class="boring"> /// # derive_str_cherr!(FooError);
</span><span class="boring"> /// # let err = ChainError::new(String::new(), None, None);
</span><span class="boring"> /// // Instead of writing
</span><span class="boring"> /// err.find_cause::<ChainError<FooError>>();
</span><span class="boring"> ///
</span><span class="boring"> /// // leave out the ChainError<FooError> implementation detail
</span><span class="boring"> /// err.find_chain_cause::<FooError>();
</span><span class="boring"> /// ```
</span><span class="boring"> #[inline]
</span><span class="boring"> pub fn find_chain_cause<U: Error + 'static>(&self) -> Option<&ChainError<U>> {
</span><span class="boring"> self.iter()
</span><span class="boring"> .filter_map(Error::downcast_ref::<ChainError<U>>)
</span><span class="boring"> .next()
</span><span class="boring"> }
</span><span class="boring">
</span><span class="boring"> /// Find the first error cause of type `ChainError<U>` or `U`, if any exists and return `U`
</span><span class="boring"> ///
</span><span class="boring"> /// Same as `find_cause` and `find_chain_cause`, but hides the `ChainError<U>` implementation internals
</span><span class="boring"> ///
</span><span class="boring"> /// # Examples
</span><span class="boring"> ///
</span><span class="boring"> /// ```rust
</span><span class="boring"> /// # use chainerror::*;
</span><span class="boring"> /// # derive_str_cherr!(FooErrorKind);
</span><span class="boring"> /// # let err = ChainError::new(String::new(), None, None);
</span><span class="boring"> /// // Instead of writing
</span><span class="boring"> /// err.find_cause::<ChainError<FooErrorKind>>();
</span><span class="boring"> /// // and/or
</span><span class="boring"> /// err.find_chain_cause::<FooErrorKind>();
</span><span class="boring"> /// // and/or
</span><span class="boring"> /// err.find_cause::<FooErrorKind>();
</span><span class="boring"> ///
</span><span class="boring"> /// // leave out the ChainError<FooErrorKind> implementation detail
</span><span class="boring"> /// err.find_kind_or_cause::<FooErrorKind>();
</span><span class="boring"> /// ```
</span><span class="boring"> #[inline]
</span><span class="boring"> pub fn find_kind_or_cause<U: Error + 'static>(&self) -> Option<&U> {
</span><span class="boring"> self.iter()
</span><span class="boring"> .filter_map(|e| {
</span><span class="boring"> e.downcast_ref::<ChainError<U>>()
</span><span class="boring"> .map(|e| e.kind())
</span><span class="boring"> .or_else(|| e.downcast_ref::<U>())
</span><span class="boring"> })
</span><span class="boring"> .next()
</span><span class="boring"> }
</span><span class="boring">
</span><span class="boring"> /// Return a reference to T of `ChainError<T>`
</span><span class="boring"> ///
</span><span class="boring"> /// # Examples
</span><span class="boring"> ///
</span><span class="boring"> /// ```rust
</span><span class="boring"> /// use chainerror::*;
</span><span class="boring"> /// use std::error::Error;
</span><span class="boring"> /// use std::io;
</span><span class="boring"> ///
</span><span class="boring"> /// fn do_some_io() -> Result<(), Box<dyn Error + Send + Sync>> {
</span><span class="boring"> /// Err(io::Error::from(io::ErrorKind::NotFound))?;
</span><span class="boring"> /// Ok(())
</span><span class="boring"> /// }
</span><span class="boring"> ///
</span><span class="boring"> /// derive_str_cherr!(Func2Error);
</span><span class="boring"> ///
</span><span class="boring"> /// fn func2() -> Result<(), Box<dyn Error + Send + Sync>> {
</span><span class="boring"> /// let filename = "foo.txt";
</span><span class="boring"> /// do_some_io().map_err(mstrerr!(Func2Error, "Error reading '{}'", filename))?;
</span><span class="boring"> /// Ok(())
</span><span class="boring"> /// }
</span><span class="boring"> ///
</span><span class="boring"> /// #[derive(Debug)]
</span><span class="boring"> /// enum Func1ErrorKind {
</span><span class="boring"> /// Func2,
</span><span class="boring"> /// IO(String),
</span><span class="boring"> /// }
</span><span class="boring"> ///
</span><span class="boring"> /// /// impl ::std::fmt::Display for Func1ErrorKind {…}
</span><span class="boring"> /// # impl ::std::fmt::Display for Func1ErrorKind {
</span><span class="boring"> /// # fn fmt(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
</span><span class="boring"> /// # match self {
</span><span class="boring"> /// # Func1ErrorKind::Func2 => write!(f, "func1 error calling func2"),
</span><span class="boring"> /// # Func1ErrorKind::IO(filename) => write!(f, "Error reading '{}'", filename),
</span><span class="boring"> /// # }
</span><span class="boring"> /// # }
</span><span class="boring"> /// # }
</span><span class="boring"> ///
</span><span class="boring"> /// fn func1() -> ChainResult<(), Func1ErrorKind> {
</span><span class="boring"> /// func2().map_err(|e| cherr!(e, Func1ErrorKind::Func2))?;
</span><span class="boring"> /// do_some_io().map_err(|e| cherr!(e, Func1ErrorKind::IO("bar.txt".into())))?;
</span><span class="boring"> /// Ok(())
</span><span class="boring"> /// }
</span><span class="boring"> ///
</span><span class="boring"> /// fn main() {
</span><span class="boring"> /// if let Err(e) = func1() {
</span><span class="boring"> /// match e.kind() {
</span><span class="boring"> /// Func1ErrorKind::Func2 => {}
</span><span class="boring"> /// Func1ErrorKind::IO(filename) => panic!(),
</span><span class="boring"> /// }
</span><span class="boring"> /// }
</span><span class="boring"> /// # else {
</span><span class="boring"> /// # unreachable!();
</span><span class="boring"> /// # }
</span><span class="boring"> /// }
</span><span class="boring"> /// ```
</span><span class="boring"> #[inline]
</span><span class="boring"> pub fn kind(&self) -> &T {
</span><span class="boring"> &self.kind
</span><span class="boring"> }
</span><span class="boring">
</span><span class="boring"> /// Returns an Iterator over all error causes/sources
</span><span class="boring"> ///
</span><span class="boring"> /// # Example
</span><span class="boring"> ///
</span><span class="boring"> ///
</span><span class="boring"> #[inline]
</span><span class="boring"> pub fn iter(&self) -> impl Iterator<Item = &(dyn Error + 'static)> {
</span><span class="boring"> ErrorIter {
</span><span class="boring"> current: Some(self),
</span><span class="boring"> }
</span><span class="boring"> }
</span><span class="boring">}
</span><span class="boring">
</span><span class="boring">struct ErrorIter<'a> {
</span><span class="boring"> current: Option<&'a (dyn Error + 'static)>,
</span><span class="boring">}
</span><span class="boring">
</span><span class="boring">impl<'a> Iterator for ErrorIter<'a> {
</span><span class="boring"> type Item = &'a (dyn Error + 'static);
</span><span class="boring">
</span><span class="boring"> #[inline]
</span><span class="boring"> fn next(&mut self) -> Option<Self::Item> {
</span><span class="boring"> let current = self.current;
</span><span class="boring"> self.current = self.current.and_then(Error::source);
</span><span class="boring"> current
</span><span class="boring"> }
</span><span class="boring">}
</span><span class="boring">
</span><span class="boring">impl<T: 'static + Display + Debug> std::ops::Deref for ChainError<T> {
</span><span class="boring"> type Target = T;
</span><span class="boring">
</span><span class="boring"> #[inline]
</span><span class="boring"> fn deref(&self) -> &Self::Target {
</span><span class="boring"> &self.kind
</span><span class="boring"> }
</span><span class="boring">}
</span><span class="boring">
</span><span class="boring">/// Convenience trait to hide the `ChainError<T>` implementation internals
</span><span class="boring">pub trait ChainErrorDown {
</span><span class="boring"> /// Test if of type `ChainError<T>`
</span><span class="boring"> fn is_chain<T: 'static + Display + Debug>(&self) -> bool;
</span><span class="boring"> /// Downcast to a reference of `ChainError<T>`
</span><span class="boring"> fn downcast_chain_ref<T: 'static + Display + Debug>(&self) -> Option<&ChainError<T>>;
</span><span class="boring"> /// Downcast to a mutable reference of `ChainError<T>`
</span><span class="boring"> fn downcast_chain_mut<T: 'static + Display + Debug>(&mut self) -> Option<&mut ChainError<T>>;
</span><span class="boring"> /// Downcast to T of `ChainError<T>`
</span><span class="boring"> fn downcast_inner_ref<T: 'static + Error>(&self) -> Option<&T>;
</span><span class="boring"> /// Downcast to T mutable reference of `ChainError<T>`
</span><span class="boring"> fn downcast_inner_mut<T: 'static + Error>(&mut self) -> Option<&mut T>;
</span><span class="boring">}
</span><span class="boring">
</span><span class="boring">impl<U: 'static + Display + Debug> ChainErrorDown for ChainError<U> {
</span><span class="boring"> #[inline]
</span><span class="boring"> fn is_chain<T: 'static + Display + Debug>(&self) -> bool {
</span><span class="boring"> TypeId::of::<T>() == TypeId::of::<U>()
</span><span class="boring"> }
</span><span class="boring">
</span><span class="boring"> #[inline]
</span><span class="boring"> fn downcast_chain_ref<T: 'static + Display + Debug>(&self) -> Option<&ChainError<T>> {
</span><span class="boring"> if self.is_chain::<T>() {
</span><span class="boring"> #[allow(clippy::cast_ptr_alignment)]
</span><span class="boring"> unsafe {
</span><span class="boring"> #[allow(trivial_casts)]
</span><span class="boring"> Some(&*(self as *const dyn Error as *const &ChainError<T>))
</span><span class="boring"> }
</span><span class="boring"> } else {
</span><span class="boring"> None
</span><span class="boring"> }
</span><span class="boring"> }
</span><span class="boring">
</span><span class="boring"> #[inline]
</span><span class="boring"> fn downcast_chain_mut<T: 'static + Display + Debug>(&mut self) -> Option<&mut ChainError<T>> {
</span><span class="boring"> if self.is_chain::<T>() {
</span><span class="boring"> #[allow(clippy::cast_ptr_alignment)]
</span><span class="boring"> unsafe {
</span><span class="boring"> #[allow(trivial_casts)]
</span><span class="boring"> Some(&mut *(self as *mut dyn Error as *mut &mut ChainError<T>))
</span><span class="boring"> }
</span><span class="boring"> } else {
</span><span class="boring"> None
</span><span class="boring"> }
</span><span class="boring"> }
</span><span class="boring"> #[inline]
</span><span class="boring"> fn downcast_inner_ref<T: 'static + Error>(&self) -> Option<&T> {
</span><span class="boring"> if self.is_chain::<T>() {
</span><span class="boring"> #[allow(clippy::cast_ptr_alignment)]
</span><span class="boring"> unsafe {
</span><span class="boring"> #[allow(trivial_casts)]
</span><span class="boring"> Some(&(*(self as *const dyn Error as *const &ChainError<T>)).kind)
</span><span class="boring"> }
</span><span class="boring"> } else {
</span><span class="boring"> None
</span><span class="boring"> }
</span><span class="boring"> }
</span><span class="boring">
</span><span class="boring"> #[inline]
</span><span class="boring"> fn downcast_inner_mut<T: 'static + Error>(&mut self) -> Option<&mut T> {
</span><span class="boring"> if self.is_chain::<T>() {
</span><span class="boring"> #[allow(clippy::cast_ptr_alignment)]
</span><span class="boring"> unsafe {
</span><span class="boring"> #[allow(trivial_casts)]
</span><span class="boring"> Some(&mut (*(self as *mut dyn Error as *mut &mut ChainError<T>)).kind)
</span><span class="boring"> }
</span><span class="boring"> } else {
</span><span class="boring"> None
</span><span class="boring"> }
</span><span class="boring"> }
</span><span class="boring">}
</span><span class="boring">
</span><span class="boring">impl ChainErrorDown for dyn Error + 'static {
</span><span class="boring"> #[inline]
</span><span class="boring"> fn is_chain<T: 'static + Display + Debug>(&self) -> bool {
</span><span class="boring"> self.is::<ChainError<T>>()
</span><span class="boring"> }
</span><span class="boring">
</span><span class="boring"> #[inline]
</span><span class="boring"> fn downcast_chain_ref<T: 'static + Display + Debug>(&self) -> Option<&ChainError<T>> {
</span><span class="boring"> self.downcast_ref::<ChainError<T>>()
</span><span class="boring"> }
</span><span class="boring">
</span><span class="boring"> #[inline]
</span><span class="boring"> fn downcast_chain_mut<T: 'static + Display + Debug>(&mut self) -> Option<&mut ChainError<T>> {
</span><span class="boring"> self.downcast_mut::<ChainError<T>>()
</span><span class="boring"> }
</span><span class="boring">
</span><span class="boring"> #[inline]
</span><span class="boring"> fn downcast_inner_ref<T: 'static + Error>(&self) -> Option<&T> {
</span><span class="boring"> self.downcast_ref::<T>()
</span><span class="boring"> .or_else(|| self.downcast_ref::<ChainError<T>>().map(|e| e.kind()))
</span><span class="boring"> }
</span><span class="boring">
</span><span class="boring"> #[inline]
</span><span class="boring"> fn downcast_inner_mut<T: 'static + Error>(&mut self) -> Option<&mut T> {
</span><span class="boring"> if self.is::<T>() {
</span><span class="boring"> return self.downcast_mut::<T>();
</span><span class="boring"> }
</span><span class="boring">
</span><span class="boring"> self.downcast_mut::<ChainError<T>>()
</span><span class="boring"> .and_then(|e| e.downcast_inner_mut::<T>())
</span><span class="boring"> }
</span><span class="boring">}
</span><span class="boring">
</span><span class="boring">impl ChainErrorDown for dyn Error + 'static + Send {
</span><span class="boring"> #[inline]
</span><span class="boring"> fn is_chain<T: 'static + Display + Debug>(&self) -> bool {
</span><span class="boring"> self.is::<ChainError<T>>()
</span><span class="boring"> }
</span><span class="boring">
</span><span class="boring"> #[inline]
</span><span class="boring"> fn downcast_chain_ref<T: 'static + Display + Debug>(&self) -> Option<&ChainError<T>> {
</span><span class="boring"> self.downcast_ref::<ChainError<T>>()
</span><span class="boring"> }
</span><span class="boring">
</span><span class="boring"> #[inline]
</span><span class="boring"> fn downcast_chain_mut<T: 'static + Display + Debug>(&mut self) -> Option<&mut ChainError<T>> {
</span><span class="boring"> self.downcast_mut::<ChainError<T>>()
</span><span class="boring"> }
</span><span class="boring">
</span><span class="boring"> #[inline]
</span><span class="boring"> fn downcast_inner_ref<T: 'static + Error>(&self) -> Option<&T> {
</span><span class="boring"> self.downcast_ref::<T>()
</span><span class="boring"> .or_else(|| self.downcast_ref::<ChainError<T>>().map(|e| e.kind()))
</span><span class="boring"> }
</span><span class="boring">
</span><span class="boring"> #[inline]
</span><span class="boring"> fn downcast_inner_mut<T: 'static + Error>(&mut self) -> Option<&mut T> {
</span><span class="boring"> if self.is::<T>() {
</span><span class="boring"> return self.downcast_mut::<T>();
</span><span class="boring"> }
</span><span class="boring">
</span><span class="boring"> self.downcast_mut::<ChainError<T>>()
</span><span class="boring"> .and_then(|e| e.downcast_inner_mut::<T>())
</span><span class="boring"> }
</span><span class="boring">}
</span><span class="boring">
</span><span class="boring">impl ChainErrorDown for dyn Error + 'static + Send + Sync {
</span><span class="boring"> #[inline]
</span><span class="boring"> fn is_chain<T: 'static + Display + Debug>(&self) -> bool {
</span><span class="boring"> self.is::<ChainError<T>>()
</span><span class="boring"> }
</span><span class="boring">
</span><span class="boring"> #[inline]
</span><span class="boring"> fn downcast_chain_ref<T: 'static + Display + Debug>(&self) -> Option<&ChainError<T>> {
</span><span class="boring"> self.downcast_ref::<ChainError<T>>()
</span><span class="boring"> }
</span><span class="boring">
</span><span class="boring"> #[inline]
</span><span class="boring"> fn downcast_chain_mut<T: 'static + Display + Debug>(&mut self) -> Option<&mut ChainError<T>> {
</span><span class="boring"> self.downcast_mut::<ChainError<T>>()
</span><span class="boring"> }
</span><span class="boring">
</span><span class="boring"> #[inline]
</span><span class="boring"> fn downcast_inner_ref<T: 'static + Error>(&self) -> Option<&T> {
</span><span class="boring"> self.downcast_ref::<T>()
</span><span class="boring"> .or_else(|| self.downcast_ref::<ChainError<T>>().map(|e| e.kind()))
</span><span class="boring"> }
</span><span class="boring">
</span><span class="boring"> #[inline]
</span><span class="boring"> fn downcast_inner_mut<T: 'static + Error>(&mut self) -> Option<&mut T> {
</span><span class="boring"> if self.is::<T>() {
</span><span class="boring"> return self.downcast_mut::<T>();
</span><span class="boring"> }
</span><span class="boring">
</span><span class="boring"> self.downcast_mut::<ChainError<T>>()
</span><span class="boring"> .and_then(|e| e.downcast_inner_mut::<T>())
</span><span class="boring"> }
</span><span class="boring">}
</span><span class="boring">
</span><span class="boring">impl<T: 'static + Display + Debug> Error for ChainError<T> {
</span><span class="boring"> #[inline]
</span><span class="boring"> fn source(&self) -> Option<&(dyn Error + 'static)> {
</span><span class="boring"> self.error_cause
</span><span class="boring"> .as_ref()
</span><span class="boring"> .map(|e| e.as_ref() as &(dyn Error + 'static))
</span><span class="boring"> }
</span><span class="boring">}
</span><span class="boring">
</span><span class="boring">impl<T: 'static + Display + Debug> Error for &ChainError<T> {
</span><span class="boring"> #[inline]
</span><span class="boring"> fn source(&self) -> Option<&(dyn Error + 'static)> {
</span><span class="boring"> self.error_cause
</span><span class="boring"> .as_ref()
</span><span class="boring"> .map(|e| e.as_ref() as &(dyn Error + 'static))
</span><span class="boring"> }
</span><span class="boring">}
</span><span class="boring">
</span><span class="boring">impl<T: 'static + Display + Debug> Error for &mut ChainError<T> {
</span><span class="boring"> #[inline]
</span><span class="boring"> fn source(&self) -> Option<&(dyn Error + 'static)> {
</span><span class="boring"> self.error_cause
</span><span class="boring"> .as_ref()
</span><span class="boring"> .map(|e| e.as_ref() as &(dyn Error + 'static))
</span><span class="boring"> }
</span><span class="boring">}
</span><span class="boring">
</span><span class="boring">impl<T: 'static + Display + Debug> Display for ChainError<T> {
</span><span class="boring"> #[inline]
</span><span class="boring"> fn fmt(&self, f: &mut Formatter<'_>) -> Result {
</span><span class="boring"> write!(f, "{}", self.kind)?;
</span><span class="boring">
</span><span class="boring"> #[cfg(feature = "display-cause")]
</span><span class="boring"> {
</span><span class="boring"> if let Some(e) = self.source() {
</span><span class="boring"> writeln!(f, "\nCaused by:")?;
</span><span class="boring"> Display::fmt(&e, f)?;
</span><span class="boring"> }
</span><span class="boring"> }
</span><span class="boring"> Ok(())
</span><span class="boring"> }
</span><span class="boring">}
</span><span class="boring">
</span><span class="boring">impl<T: 'static + Display + Debug> Debug for ChainError<T> {
</span><span class="boring"> #[inline]
</span><span class="boring"> fn fmt(&self, f: &mut Formatter<'_>) -> Result {
</span><span class="boring"> #[cfg(not(feature = "no-fileline"))]
</span><span class="boring"> {
</span><span class="boring"> if let Some(ref o) = self.occurrence {
</span><span class="boring"> Display::fmt(o, f)?;
</span><span class="boring"> }
</span><span class="boring"> }
</span><span class="boring">
</span><span class="boring"> if self.is_chain::<String>() {
</span><span class="boring"> Display::fmt(&self.kind, f)?;
</span><span class="boring"> } else {
</span><span class="boring"> Debug::fmt(&self.kind, f)?;
</span><span class="boring"> }
</span><span class="boring">
</span><span class="boring"> #[cfg(not(feature = "no-debug-cause"))]
</span><span class="boring"> {
</span><span class="boring"> if let Some(e) = self.source() {
</span><span class="boring"> writeln!(f, "\nCaused by:")?;
</span><span class="boring"> Debug::fmt(&e, f)?;
</span><span class="boring"> }
</span><span class="boring"> }
</span><span class="boring"> Ok(())
</span><span class="boring"> }
</span><span class="boring">}
</span><span class="boring">
</span><span class="boring">/// `ChainErrorFrom<T>` is similar to `From<T>`
</span><span class="boring">pub trait ChainErrorFrom<T>: Sized {
</span><span class="boring"> /// similar to From<T>::from()
</span><span class="boring"> fn chain_error_from(from: T, line_filename: Option<&'static str>) -> ChainError<Self>;
</span><span class="boring">}
</span><span class="boring">
</span><span class="boring">/// `IntoChainError<T>` is similar to `Into<T>`
</span><span class="boring">pub trait IntoChainError<T>: Sized {
</span><span class="boring"> /// similar to Into<T>::into()
</span><span class="boring"> fn into_chain_error(self, line_filename: Option<&'static str>) -> ChainError<T>;
</span><span class="boring">}
</span><span class="boring">
</span><span class="boring">impl<T, U> IntoChainError<U> for T
</span><span class="boring">where
</span><span class="boring"> U: ChainErrorFrom<T>,
</span><span class="boring">{
</span><span class="boring"> #[inline]
</span><span class="boring"> fn into_chain_error(self, line_filename: Option<&'static str>) -> ChainError<U> {
</span><span class="boring"> U::chain_error_from(self, line_filename)
</span><span class="boring"> }
</span><span class="boring">}
</span><span class="boring">
</span><span class="boring">impl<T, U> ChainErrorFrom<T> for U
</span><span class="boring">where
</span><span class="boring"> T: Into<U>,
</span><span class="boring"> U: 'static + Display + Debug,
</span><span class="boring">{
</span><span class="boring"> #[inline]
</span><span class="boring"> fn chain_error_from(t: T, line_filename: Option<&'static str>) -> ChainError<Self> {
</span><span class="boring"> let e: U = t.into();
</span><span class="boring"> ChainError::new(e, None, line_filename)
</span><span class="boring"> }
</span><span class="boring">}
</span><span class="boring">
</span><span class="boring">/*
</span><span class="boring">impl<T, U> ChainErrorFrom<T> for U
</span><span class="boring"> where
</span><span class="boring"> T: 'static + Error + Into<Box<T>> + Clone,
</span><span class="boring"> U: 'static + Display + Debug + From<T>,
</span><span class="boring">{
</span><span class="boring"> #[inline]
</span><span class="boring"> fn chain_error_from(t: T, line_filename: Option<&'static str>) -> ChainError<Self> {
</span><span class="boring"> ChainError::new(U::from(t.clone()), Some(Box::from(t)), line_filename)
</span><span class="boring"> }
</span><span class="boring">}
</span><span class="boring">*/
</span><span class="boring">
</span><span class="boring">/// map into `ChainError<T>` with `T::from(err)`
</span><span class="boring">///
</span><span class="boring">/// adds `line!()` and `file!()` information
</span><span class="boring">#[macro_export]
</span><span class="boring">macro_rules! minto_cherr {
</span><span class="boring"> ( $k:ident ) => (
</span><span class="boring"> |e| $crate::cherr!(e, $k::from(&e))
</span><span class="boring"> );
</span><span class="boring"> ( $enum:ident $(:: $enum_path:ident)* ) => (
</span><span class="boring"> |e| $crate::cherr!(e, $enum $(:: $enum_path)*::from(&e))
</span><span class="boring"> );
</span><span class="boring">}
</span><span class="boring">
</span><span class="boring">/// Creates a new `ChainError<T>`
</span><span class="boring">///
</span><span class="boring">/// # Examples
</span><span class="boring">///
</span><span class="boring">/// Create a new ChainError<FooError>, where `FooError` must implement `Display` and `Debug`.
</span><span class="boring">/// ```rust
</span><span class="boring">/// # use chainerror::*;
</span><span class="boring">/// # #[derive(Debug)]
</span><span class="boring">/// enum FooError {
</span><span class="boring">/// Bar,
</span><span class="boring">/// Baz(&'static str),
</span><span class="boring">/// }
</span><span class="boring">/// # impl ::std::fmt::Display for FooError {
</span><span class="boring">/// # fn fmt(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
</span><span class="boring">/// # match self {
</span><span class="boring">/// # FooError::Bar => write!(f, "Bar Error"),
</span><span class="boring">/// # FooError::Baz(s) => write!(f, "Baz Error: '{}'", s),
</span><span class="boring">/// # }
</span><span class="boring">/// # }
</span><span class="boring">/// # }
</span><span class="boring">///
</span><span class="boring">/// // impl ::std::fmt::Display for FooError
</span><span class="boring">///
</span><span class="boring">/// fn do_some_stuff() -> bool {
</span><span class="boring">/// false
</span><span class="boring">/// }
</span><span class="boring">///
</span><span class="boring">/// fn func() -> ChainResult<(), FooError> {
</span><span class="boring">/// if ! do_some_stuff() {
</span><span class="boring">/// Err(cherr!(FooError::Baz("Error")))?;
</span><span class="boring">/// }
</span><span class="boring">/// Ok(())
</span><span class="boring">/// }
</span><span class="boring">/// # pub fn main() {
</span><span class="boring">/// # match func().unwrap_err().kind() {
</span><span class="boring">/// # FooError::Baz(s) if s == &"Error" => {}
</span><span class="boring">/// # _ => panic!(),
</span><span class="boring">/// # }
</span><span class="boring">/// # }
</span><span class="boring">/// ```
</span><span class="boring">///
</span><span class="boring">/// Additionally an error cause can be added.
</span><span class="boring">///
</span><span class="boring">/// ```rust
</span><span class="boring">/// # use chainerror::*;
</span><span class="boring">/// # use std::io;
</span><span class="boring">/// # use std::error::Error;
</span><span class="boring">/// # #[derive(Debug)]
</span><span class="boring">/// # enum FooError {
</span><span class="boring">/// # Bar,
</span><span class="boring">/// # Baz(&'static str),
</span><span class="boring">/// # }
</span><span class="boring">/// # impl ::std::fmt::Display for FooError {
</span><span class="boring">/// # fn fmt(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
</span><span class="boring">/// # match self {
</span><span class="boring">/// # FooError::Bar => write!(f, "Bar Error"),
</span><span class="boring">/// # FooError::Baz(s) => write!(f, "Baz Error: '{}'", s),
</span><span class="boring">/// # }
</span><span class="boring">/// # }
</span><span class="boring">/// # }
</span><span class="boring">/// fn do_some_stuff() -> Result<(), Box<dyn Error + Send + Sync>> {
</span><span class="boring">/// Err(io::Error::from(io::ErrorKind::NotFound))?;
</span><span class="boring">/// Ok(())
</span><span class="boring">/// }
</span><span class="boring">///
</span><span class="boring">/// fn func() -> ChainResult<(), FooError> {
</span><span class="boring">/// do_some_stuff().map_err(
</span><span class="boring">/// |e| cherr!(e, FooError::Baz("Error"))
</span><span class="boring">/// )?;
</span><span class="boring">/// Ok(())
</span><span class="boring">/// }
</span><span class="boring">/// # pub fn main() {
</span><span class="boring">/// # match func().unwrap_err().kind() {
</span><span class="boring">/// # FooError::Baz(s) if s == &"Error" => {}
</span><span class="boring">/// # _ => panic!(),
</span><span class="boring">/// # }
</span><span class="boring">/// # }
</span><span class="boring">/// ```
</span><span class="boring">#[macro_export]
</span><span class="boring">macro_rules! cherr {
</span><span class="boring"> ( $k:expr ) => ({
</span><span class="boring"> $crate::ChainError::new($k, None, Some(concat!(file!(), ":", line!(), ": ")))
</span><span class="boring"> });
</span><span class="boring"> ( None, $k:expr ) => ({
</span><span class="boring"> $crate::ChainError::new($k, None, Some(concat!(file!(), ":", line!(), ": ")))
</span><span class="boring"> });
</span><span class="boring"> ( None, $fmt:expr, $($arg:tt)+ ) => ({
</span><span class="boring"> $crate::cherr!(None, format!($fmt, $($arg)+ ))
</span><span class="boring"> });
</span><span class="boring"> ( None, $fmt:expr, $($arg:tt)+ ) => ({
</span><span class="boring"> $crate::cherr!(None, format!($fmt, $($arg)+ ))
</span><span class="boring"> });
</span><span class="boring"> ( $e:path, $k:expr ) => ({
</span><span class="boring"> $crate::ChainError::new($k, Some(Box::from($e)), Some(concat!(file!(), ":", line!(), ": ")))
</span><span class="boring"> });
</span><span class="boring"> ( $e:path, $fmt:expr, $($arg:tt)+ ) => ({
</span><span class="boring"> $crate::cherr!($e, format!($fmt, $($arg)+ ))
</span><span class="boring"> });
</span><span class="boring">}
</span><span class="boring">
</span><span class="boring">/// Convenience macro for `|e| cherr!(e, format!(…))`
</span><span class="boring">///
</span><span class="boring">/// # Examples
</span><span class="boring">///
</span><span class="boring">/// ```rust
</span><span class="boring">/// # use crate::chainerror::*;
</span><span class="boring">/// # use std::error::Error;
</span><span class="boring">/// # use std::io;
</span><span class="boring">/// # use std::result::Result;
</span><span class="boring">/// # fn do_some_io() -> Result<(), Box<dyn Error + Send + Sync>> {
</span><span class="boring">/// # Err(io::Error::from(io::ErrorKind::NotFound))?;
</span><span class="boring">/// # Ok(())
</span><span class="boring">/// # }
</span><span class="boring">/// fn func2() -> Result<(), Box<dyn Error + Send + Sync>> {
</span><span class="boring">/// let filename = "foo.txt";
</span><span class="boring">/// do_some_io().map_err(mstrerr!("Error reading '{}'", filename))?;
</span><span class="boring">/// Ok(())
</span><span class="boring">/// }
</span><span class="boring">///
</span><span class="boring">/// fn func1() -> Result<(), Box<dyn Error + Send + Sync>> {
</span><span class="boring">/// func2().map_err(mstrerr!("func1 error"))?;
</span><span class="boring">/// Ok(())
</span><span class="boring">/// }
</span><span class="boring">///
</span><span class="boring">/// # fn main() {
</span><span class="boring">/// # if let Err(e) = func1() {
</span><span class="boring">/// # #[cfg(not(windows))]
</span><span class="boring">/// # assert_eq!(
</span><span class="boring">/// # format!("\n{:?}\n", e), r#"
</span><span class="boring">/// # src/lib.rs:18: func1 error
</span><span class="boring">/// # Caused by:
</span><span class="boring">/// # src/lib.rs:13: Error reading 'foo.txt'
</span><span class="boring">/// # Caused by:
</span><span class="boring">/// # Kind(NotFound)
</span><span class="boring">/// # "#
</span><span class="boring">/// # );
</span><span class="boring">/// # } else {
</span><span class="boring">/// # unreachable!();
</span><span class="boring">/// # }
</span><span class="boring">/// # }
</span><span class="boring">/// ```
</span><span class="boring">///
</span><span class="boring">/// `mstrerr!()` can also be used to map a new `ChainError<T>`, where T was defined with
</span><span class="boring">/// `derive_str_cherr!(T)`
</span><span class="boring">///
</span><span class="boring">/// ```rust
</span><span class="boring">/// # use crate::chainerror::*;
</span><span class="boring">/// # use std::error::Error;
</span><span class="boring">/// # use std::io;
</span><span class="boring">/// # use std::result::Result;
</span><span class="boring">/// # fn do_some_io() -> Result<(), Box<dyn Error + Send + Sync>> {
</span><span class="boring">/// # Err(io::Error::from(io::ErrorKind::NotFound))?;
</span><span class="boring">/// # Ok(())
</span><span class="boring">/// # }
</span><span class="boring">/// derive_str_cherr!(Func2Error);
</span><span class="boring">///
</span><span class="boring">/// fn func2() -> Result<(), Box<dyn Error + Send + Sync>> {
</span><span class="boring">/// let filename = "foo.txt";
</span><span class="boring">/// do_some_io().map_err(mstrerr!(Func2Error, "Error reading '{}'", filename))?;
</span><span class="boring">/// Ok(())
</span><span class="boring">/// }
</span><span class="boring">///
</span><span class="boring">/// derive_str_cherr!(Func1Error);
</span><span class="boring">///
</span><span class="boring">/// fn func1() -> Result<(), Box<dyn Error + Send + Sync>> {
</span><span class="boring">/// func2().map_err(mstrerr!(Func1Error, "func1 error"))?;
</span><span class="boring">/// Ok(())
</span><span class="boring">/// }
</span><span class="boring">/// # fn main() {
</span><span class="boring">/// # if let Err(e) = func1() {
</span><span class="boring">/// # if let Some(f1err) = e.downcast_chain_ref::<Func1Error>() {
</span><span class="boring">/// # assert!(f1err.find_cause::<ChainError<Func2Error>>().is_some());
</span><span class="boring">/// # assert!(f1err.find_chain_cause::<Func2Error>().is_some());
</span><span class="boring">/// # } else {
</span><span class="boring">/// # panic!();
</span><span class="boring">/// # }
</span><span class="boring">/// # } else {
</span><span class="boring">/// # unreachable!();
</span><span class="boring">/// # }
</span><span class="boring">/// # }
</span><span class="boring">/// ```
</span><span class="boring">#[macro_export]
</span><span class="boring">macro_rules! mstrerr {
</span><span class="boring"> ( $t:path, $msg:expr ) => ({
</span><span class="boring"> |e| $crate::cherr!(e, $t ($msg.to_string()))
</span><span class="boring"> });
</span><span class="boring"> ( $t:path, $msg:expr, ) => ({
</span><span class="boring"> |e| $crate::cherr!(e, $t ($msg.to_string()))
</span><span class="boring"> });
</span><span class="boring"> ( $t:path, $fmt:expr, $($arg:tt)+ ) => ({
</span><span class="boring"> |e| $crate::cherr!(e, $t (format!($fmt, $($arg)+ )))
</span><span class="boring"> });
</span><span class="boring"> ($msg:expr) => ({
</span><span class="boring"> |e| $crate::cherr!(e, $msg.to_string())
</span><span class="boring"> });
</span><span class="boring"> ($msg:expr, ) => ({
</span><span class="boring"> |e| $crate::cherr!(e, $msg.to_string())
</span><span class="boring"> });
</span><span class="boring"> ($fmt:expr, $($arg:tt)+) => ({
</span><span class="boring"> |e| $crate::cherr!(e, format!($fmt, $($arg)+ ))
</span><span class="boring"> });
</span><span class="boring">}
</span><span class="boring">
</span><span class="boring">/// Convenience macro for `cherr!(T(format!(…)))` where `T(String)`
</span><span class="boring">///
</span><span class="boring">/// # Examples
</span><span class="boring">///
</span><span class="boring">/// ```rust
</span><span class="boring">/// # use crate::chainerror::*;
</span><span class="boring">/// # use std::error::Error;
</span><span class="boring">/// # use std::result::Result;
</span><span class="boring">/// derive_str_cherr!(Func2Error);
</span><span class="boring">///
</span><span class="boring">/// fn func2() -> ChainResult<(), Func2Error> {
</span><span class="boring">/// let filename = "foo.txt";
</span><span class="boring">/// Err(strerr!(Func2Error, "Error reading '{}'", filename))
</span><span class="boring">/// }
</span><span class="boring">///
</span><span class="boring">/// derive_str_cherr!(Func1Error);
</span><span class="boring">///
</span><span class="boring">/// fn func1() -> Result<(), Box<dyn Error>> {
</span><span class="boring">/// func2().map_err(mstrerr!(Func1Error, "func1 error"))?;
</span><span class="boring">/// Ok(())
</span><span class="boring">/// }
</span><span class="boring">/// # fn main() {
</span><span class="boring">/// # if let Err(e) = func1() {
</span><span class="boring">/// # if let Some(f1err) = e.downcast_chain_ref::<Func1Error>() {
</span><span class="boring">/// # assert!(f1err.find_cause::<ChainError<Func2Error>>().is_some());
</span><span class="boring">/// # assert!(f1err.find_chain_cause::<Func2Error>().is_some());
</span><span class="boring">/// # } else {
</span><span class="boring">/// # panic!();
</span><span class="boring">/// # }
</span><span class="boring">/// # } else {
</span><span class="boring">/// # unreachable!();
</span><span class="boring">/// # }
</span><span class="boring">/// # }
</span><span class="boring">/// ```
</span><span class="boring">#[macro_export]
</span><span class="boring">macro_rules! strerr {
</span><span class="boring"> ( $t:path, $msg:expr ) => ({
</span><span class="boring"> $crate::cherr!($t ($msg.to_string()))
</span><span class="boring"> });
</span><span class="boring"> ( $t:path, $msg:expr, ) => ({
</span><span class="boring"> $crate::cherr!($t ($msg.to_string()))
</span><span class="boring"> });
</span><span class="boring"> ( $t:path, $fmt:expr, $($arg:tt)+ ) => ({
</span><span class="boring"> $crate::cherr!($t (format!($fmt, $($arg)+ )))
</span><span class="boring"> });
</span><span class="boring"> ($msg:expr) => ({
</span><span class="boring"> $crate::cherr!($msg.to_string())
</span><span class="boring"> });
</span><span class="boring"> ($msg:expr, ) => ({
</span><span class="boring"> $crate::cherr!($msg.to_string())
</span><span class="boring"> });
</span><span class="boring"> ($fmt:expr, $($arg:tt)+) => ({
</span><span class="boring"> $crate::cherr!(format!($fmt, $($arg)+ ))
</span><span class="boring"> });
</span><span class="boring">}
</span><span class="boring">
</span><span class="boring">/// Convenience macro to create a "new type" T(String) and implement Display + Debug for T
</span><span class="boring">///
</span><span class="boring">/// # Examples
</span><span class="boring">///
</span><span class="boring">/// ```rust
</span><span class="boring">/// # use crate::chainerror::*;
</span><span class="boring">/// # use std::error::Error;
</span><span class="boring">/// # use std::io;
</span><span class="boring">/// # use std::result::Result;
</span><span class="boring">/// # fn do_some_io() -> Result<(), Box<dyn Error + Send + Sync>> {
</span><span class="boring">/// # Err(io::Error::from(io::ErrorKind::NotFound))?;
</span><span class="boring">/// # Ok(())
</span><span class="boring">/// # }
</span><span class="boring">/// derive_str_cherr!(Func2Error);
</span><span class="boring">///
</span><span class="boring">/// fn func2() -> ChainResult<(), Func2Error> {
</span><span class="boring">/// let filename = "foo.txt";
</span><span class="boring">/// do_some_io().map_err(mstrerr!(Func2Error, "Error reading '{}'", filename))?;
</span><span class="boring">/// Ok(())
</span><span class="boring">/// }
</span><span class="boring">///
</span><span class="boring">/// derive_str_cherr!(Func1Error);
</span><span class="boring">///
</span><span class="boring">/// fn func1() -> Result<(), Box<dyn Error>> {
</span><span class="boring">/// func2().map_err(mstrerr!(Func1Error, "func1 error"))?;
</span><span class="boring">/// Ok(())
</span><span class="boring">/// }
</span><span class="boring">/// # fn main() {
</span><span class="boring">/// # if let Err(e) = func1() {
</span><span class="boring">/// # if let Some(f1err) = e.downcast_chain_ref::<Func1Error>() {
</span><span class="boring">/// # assert!(f1err.find_cause::<ChainError<Func2Error>>().is_some());
</span><span class="boring">/// # assert!(f1err.find_chain_cause::<Func2Error>().is_some());
</span><span class="boring">/// # } else {
</span><span class="boring">/// # panic!();
</span><span class="boring">/// # }
</span><span class="boring">/// # } else {
</span><span class="boring">/// # unreachable!();
</span><span class="boring">/// # }
</span><span class="boring">/// # }
</span><span class="boring">/// ```
</span><span class="boring">#[macro_export]
</span><span class="boring">macro_rules! derive_str_cherr {
</span><span class="boring"> ($e:ident) => {
</span><span class="boring"> #[derive(Clone)]
</span><span class="boring"> pub struct $e(pub String);
</span><span class="boring"> impl ::std::fmt::Display for $e {
</span><span class="boring"> fn fmt(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
</span><span class="boring"> write!(f, "{}", self.0)
</span><span class="boring"> }
</span><span class="boring"> }
</span><span class="boring"> impl ::std::fmt::Debug for $e {
</span><span class="boring"> fn fmt(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
</span><span class="boring"> write!(f, "{}({})", stringify!($e), self.0)
</span><span class="boring"> }
</span><span class="boring"> }
</span><span class="boring"> impl ::std::error::Error for $e {}
</span><span class="boring"> };
</span><span class="boring">}
</span><span class="boring">
</span><span class="boring">/// Derive an Error for an ErrorKind, which wraps a `ChainError` and implements a `kind()` method
</span><span class="boring">///
</span><span class="boring">/// It basically hides `ChainError` to the outside and only exposes the `kind()`
</span><span class="boring">/// method.
</span><span class="boring">///
</span><span class="boring">/// Error::kind() returns the ErrorKind
</span><span class="boring">/// Error::source() returns the parent error
</span><span class="boring">///
</span><span class="boring">/// # Examples
</span><span class="boring">///
</span><span class="boring">/// ```rust
</span><span class="boring">/// use std::io;
</span><span class="boring">/// use chainerror::*;
</span><span class="boring">///
</span><span class="boring">/// fn do_some_io(_f: &str) -> std::result::Result<(), io::Error> {
</span><span class="boring">/// return Err(io::Error::from(io::ErrorKind::NotFound));
</span><span class="boring">/// }
</span><span class="boring">///
</span><span class="boring">/// #[derive(Debug, Clone)]
</span><span class="boring">/// pub enum ErrorKind {
</span><span class="boring">/// IO(String),
</span><span class="boring">/// FatalError(String),
</span><span class="boring">/// Unknown,
</span><span class="boring">/// }
</span><span class="boring">///
</span><span class="boring">/// derive_err_kind!(Error, ErrorKind);
</span><span class="boring">///
</span><span class="boring">/// impl std::fmt::Display for ErrorKind {
</span><span class="boring">/// fn fmt(&self, f: &mut ::std::fmt::Formatter) -> std::fmt::Result {
</span><span class="boring">/// match self {
</span><span class="boring">/// ErrorKind::FatalError(e) => write!(f, "fatal error {}", e),
</span><span class="boring">/// ErrorKind::Unknown => write!(f, "unknown error"),
</span><span class="boring">/// ErrorKind::IO(filename) => write!(f, "Error reading '{}'", filename),
</span><span class="boring">/// }
</span><span class="boring">/// }
</span><span class="boring">/// }
</span><span class="boring">///
</span><span class="boring">/// impl ErrorKind {
</span><span class="boring">/// fn from_io_error(e: &io::Error, f: String) -> Self {
</span><span class="boring">/// match e.kind() {
</span><span class="boring">/// io::ErrorKind::BrokenPipe => panic!("Should not happen"),
</span><span class="boring">/// io::ErrorKind::ConnectionReset => {
</span><span class="boring">/// ErrorKind::FatalError(format!("While reading `{}`: {}", f, e))
</span><span class="boring">/// }
</span><span class="boring">/// _ => ErrorKind::IO(f),
</span><span class="boring">/// }
</span><span class="boring">/// }
</span><span class="boring">/// }
</span><span class="boring">///
</span><span class="boring">/// impl From<&io::Error> for ErrorKind {
</span><span class="boring">/// fn from(e: &io::Error) -> Self {
</span><span class="boring">/// ErrorKind::IO(format!("{}", e))
</span><span class="boring">/// }
</span><span class="boring">/// }
</span><span class="boring">///
</span><span class="boring">/// pub fn func1() -> std::result::Result<(), Error> {
</span><span class="boring">/// let filename = "bar.txt";
</span><span class="boring">///
</span><span class="boring">/// do_some_io(filename)
</span><span class="boring">/// .map_err(|e| cherr!(e, ErrorKind::from_io_error(&e, filename.into())))?;
</span><span class="boring">/// do_some_io(filename).map_err(|e| cherr!(e, ErrorKind::IO(filename.into())))?;
</span><span class="boring">/// do_some_io(filename).map_err(|e| cherr!(e, ErrorKind::from(&e)))?;
</span><span class="boring">/// do_some_io(filename).map_err(minto_cherr!(ErrorKind))?;
</span><span class="boring">/// Ok(())
</span><span class="boring">/// }
</span><span class="boring">/// ```
</span><span class="boring">#[macro_export]
</span><span class="boring">macro_rules! derive_err_kind {
</span><span class="boring"> ($e:ident, $k:ident) => {
</span><span class="boring"> pub struct $e($crate::ChainError<$k>);
</span><span class="boring">
</span><span class="boring"> impl $e {
</span><span class="boring"> pub fn kind(&self) -> &$k {
</span><span class="boring"> self.0.kind()
</span><span class="boring"> }
</span><span class="boring"> }
</span><span class="boring">
</span><span class="boring"> impl From<$k> for $e {
</span><span class="boring"> fn from(e: $k) -> Self {
</span><span class="boring"> $e($crate::ChainError::new(e, None, None))
</span><span class="boring"> }
</span><span class="boring"> }
</span><span class="boring">
</span><span class="boring"> impl From<ChainError<$k>> for $e {
</span><span class="boring"> fn from(e: $crate::ChainError<$k>) -> Self {
</span><span class="boring"> $e(e)
</span><span class="boring"> }
</span><span class="boring"> }
</span><span class="boring">
</span><span class="boring"> impl From<&$e> for $k
</span><span class="boring"> where
</span><span class="boring"> $k: Clone,
</span><span class="boring"> {
</span><span class="boring"> fn from(e: &$e) -> Self {
</span><span class="boring"> e.kind().clone()
</span><span class="boring"> }
</span><span class="boring"> }
</span><span class="boring">
</span><span class="boring"> impl $crate::ChainErrorFrom<$e> for $k
</span><span class="boring"> where
</span><span class="boring"> $k: Clone,
</span><span class="boring"> {
</span><span class="boring"> #[inline]
</span><span class="boring"> fn chain_error_from(
</span><span class="boring"> t: $e,
</span><span class="boring"> line_filename: Option<&'static str>,
</span><span class="boring"> ) -> $crate::ChainError<$k> {
</span><span class="boring"> $crate::ChainError::new((*t.kind()).clone(), Some(Box::from(t)), line_filename)
</span><span class="boring"> }
</span><span class="boring"> }
</span><span class="boring">
</span><span class="boring"> impl std::error::Error for $e {
</span><span class="boring"> fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
</span><span class="boring"> self.0.source()
</span><span class="boring"> }
</span><span class="boring"> }
</span><span class="boring">
</span><span class="boring"> impl std::fmt::Display for $e {
</span><span class="boring"> fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
</span><span class="boring"> std::fmt::Display::fmt(&self.0, f)
</span><span class="boring"> }
</span><span class="boring"> }
</span><span class="boring">
</span><span class="boring"> impl std::fmt::Debug for $e {
</span><span class="boring"> fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
</span><span class="boring"> std::fmt::Debug::fmt(&self.0, f)
</span><span class="boring"> }
</span><span class="boring"> }
</span><span class="boring"> };
</span><span class="boring">}
</span><span class="boring">}
</span>pub mod mycrate {
use crate::chainerror::*; // omit the `crate::` part
use std::io;
fn do_some_io() -> std::result::Result<(), Box<dyn std::error::Error + Send + Sync>> {
Err(io::Error::from(io::ErrorKind::NotFound))?;
Ok(())
}
derive_str_cherr!(Func2Error);
fn func2() -> std::result::Result<(), Box<dyn std::error::Error + Send + Sync>> {
let filename = "foo.txt";
do_some_io().map_err(mstrerr!(Func2Error, "Error reading '{}'", filename))?;
Ok(())
}
#[derive(Debug, Clone)]
pub enum ErrorKind {
Func2,
IO(String),
}
derive_err_kind!(Error, ErrorKind);
pub type Result<T> = std::result::Result<T, Error>;
impl std::fmt::Display for ErrorKind {
fn fmt(&self, f: &mut ::std::fmt::Formatter) -> std::fmt::Result {
match self {
ErrorKind::Func2 => write!(f, "func1 error calling func2"),
ErrorKind::IO(filename) => write!(f, "Error reading '{}'", filename),
}
}
}
pub fn func1() -> Result<()> {
func2().map_err(|e| cherr!(e, ErrorKind::Func2))?;
let filename = String::from("bar.txt");
do_some_io().map_err(|e| cherr!(e, ErrorKind::IO(filename)))?;
Ok(())
}
}
fn main() -> Result<(), Box<dyn std::error::Error + Send + Sync>> {
use mycrate::func1;
use mycrate::ErrorKind;
use std::error::Error;
use std::io;
if let Err(e) = func1() {
match e.kind() {
ErrorKind::Func2 => eprintln!("Main Error Report: func1 error calling func2"),
ErrorKind::IO(ref filename) => {
eprintln!("Main Error Report: func1 error reading '{}'", filename)
}
}
eprintln!();
let mut s: &dyn Error = &e;
while let Some(c) = s.source() {
if let Some(ioerror) = c.downcast_ref::<io::Error>() {
eprintln!("caused by: std::io::Error: {}", ioerror);
match ioerror.kind() {
io::ErrorKind::NotFound => eprintln!("of kind: std::io::ErrorKind::NotFound"),
_ => {}
}
} else {
eprintln!("caused by: {}", c);
}
s = c;
}
eprintln!("\nDebug Error:\n{:?}", e);
}
Ok(())
}
</code></pre></pre>
</main>
<nav class="nav-wrapper" aria-label="Page navigation">
<!-- Mobile navigation buttons -->
<a rel="prev" href="tutorial12.html" class="mobile-nav-chapters previous" title="Previous chapter" aria-label="Previous chapter" aria-keyshortcuts="Left">
<i class="fa fa-angle-left"></i>
</a>
<a rel="next" href="tutorial14.html" class="mobile-nav-chapters next" title="Next chapter" aria-label="Next chapter" aria-keyshortcuts="Right">
<i class="fa fa-angle-right"></i>
</a>
<div style="clear: both"></div>
</nav>
</div>
</div>
<nav class="nav-wide-wrapper" aria-label="Page navigation">
<a href="tutorial12.html" class="nav-chapters previous" title="Previous chapter" aria-label="Previous chapter" aria-keyshortcuts="Left">
<i class="fa fa-angle-left"></i>
</a>
<a href="tutorial14.html" class="nav-chapters next" title="Next chapter" aria-label="Next chapter" aria-keyshortcuts="Right">
<i class="fa fa-angle-right"></i>
</a>
</nav>
</div>
<script type="text/javascript">
window.playpen_copyable = true;
</script>
<script src="elasticlunr.min.js" type="text/javascript" charset="utf-8"></script>
<script src="mark.min.js" type="text/javascript" charset="utf-8"></script>
<script src="searcher.js" type="text/javascript" charset="utf-8"></script>
<script src="clipboard.min.js" type="text/javascript" charset="utf-8"></script>
<script src="highlight.js" type="text/javascript" charset="utf-8"></script>
<script src="book.js" type="text/javascript" charset="utf-8"></script>
<!-- Custom JS scripts -->
</body>
</html>