2018-12-20 14:55:19 +01:00
<!DOCTYPE HTML>
2020-03-03 15:08:09 +01:00
< html lang = "en" class = "sidebar-visible no-js light" >
2018-12-20 14:55:19 +01:00
< head >
<!-- Book generated using mdBook -->
< meta charset = "UTF-8" >
2018-12-21 13:55:46 +01:00
< title > ErrorKind to the rescue - chainerror< / title >
2020-03-03 15:08:09 +01:00
2018-12-20 14:55:19 +01:00
< meta content = "text/html; charset=utf-8" http-equiv = "Content-Type" >
2018-12-21 13:55:46 +01:00
< meta name = "description" content = "A tutorial for the chainerror rust crate." >
2018-12-20 14:55:19 +01:00
< 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 >
2020-03-03 15:08:09 +01:00
< body >
2018-12-20 14:55:19 +01:00
<!-- Provide site root to javascript -->
< script type = "text/javascript" >
var path_to_root = "";
2020-03-03 15:08:09 +01:00
var default_theme = window.matchMedia("(prefers-color-scheme: dark)").matches ? "light" : "light";
2018-12-20 14:55:19 +01:00
< / 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;
2020-03-03 15:08:09 +01:00
try { theme = localStorage.getItem('mdbook-theme'); } catch(e) { }
2018-12-20 14:55:19 +01:00
if (theme === null || theme === undefined) { theme = default_theme; }
2020-03-03 15:08:09 +01:00
var html = document.querySelector('html');
html.classList.remove('no-js')
html.classList.remove('light')
html.classList.add(theme);
html.classList.add('js');
2018-12-20 14:55:19 +01:00
< / 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" >
2020-03-03 15:08:09 +01:00
< 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" class = "active" > < 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" > < 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 >
2018-12-20 14:55:19 +01:00
< / 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 >
2020-03-03 15:08:09 +01:00
< h1 class = "menu-title" > chainerror< / h1 >
2018-12-20 14:55:19 +01:00
< 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 >
2020-03-03 15:08:09 +01:00
< h1 > < a class = "header" href = "#errorkind-to-the-rescue" id = "errorkind-to-the-rescue" > ErrorKind to the rescue< / a > < / h1 >
2018-12-21 13:55:46 +01:00
< p > To cope with different kind of errors, we introduce the kind of an error < code > Func1ErrorKind< / code > with an enum.< / p >
< p > Because we derive < code > Debug< / code > and implement < code > Display< / code > our < code > Func1ErrorKind< / code > enum, this enum can be used as
a < code > std::error::Error< / code > .< / p >
< p > Not using < code > String< / code > errors anymore, the < code > cherr!()< / code > macro seen in the beginning of
the tutorial has to be used again.< / p >
2020-03-03 15:08:09 +01:00
< p > Only returning < code > Func1ErrorKind< / code > in < code > func1()< / code > now let us get rid of < code > Result< (), Box< Error + Send + Sync> > < / code > and we can
2018-12-21 13:55:46 +01:00
use < code > ChainResult< (), Func1ErrorKind> < / code > .< / p >
< p > In < code > main< / code > we can now directly use the methods of < code > ChainError< T> < / code > without downcasting the error first.< / p >
2020-03-03 15:08:09 +01:00
< p > Also a nice < code > match< / code > on < code > ChainError< T> .kind()< / code > is now possible, which returns < code > & T< / code > , meaning
2018-12-21 13:55:46 +01:00
< code > & Func1ErrorKind< / code > here.< / p >
2019-03-04 11:46:17 +01:00
< pre > < pre class = "playpen" > < code class = "language-rust" > use chainerror::*;
2018-12-20 14:55:19 +01:00
use std::error::Error;
use std::io;
use std::result::Result;
2020-03-03 15:16:51 +01:00
fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
2018-12-20 14:55:19 +01:00
Err(io::Error::from(io::ErrorKind::NotFound))?;
Ok(())
}
derive_str_cherr!(Func2Error);
2020-03-03 15:16:51 +01:00
fn func2() -> Result< (), Box< dyn Error + Send + Sync> > {
2018-12-20 14:55:19 +01:00
let filename = " foo.txt" ;
do_some_io().map_err(mstrerr!(Func2Error, " Error reading '{}'" , filename))?;
Ok(())
}
#[derive(Debug)]
2018-12-21 13:55:46 +01:00
enum Func1ErrorKind {
2018-12-20 14:55:19 +01:00
Func2,
IO(String),
}
2018-12-21 13:55:46 +01:00
impl ::std::fmt::Display for Func1ErrorKind {
2018-12-20 14:55:19 +01:00
fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
match self {
2018-12-21 13:55:46 +01:00
Func1ErrorKind::Func2 => write!(f, " func1 error calling func2" ),
Func1ErrorKind::IO(filename) => write!(f, " Error reading '{}'" , filename),
2018-12-20 14:55:19 +01:00
}
}
}
2019-02-07 09:02:01 +01:00
impl ::std::error::Error for Func1ErrorKind {}
2018-12-20 14:55:19 +01:00
2018-12-21 13:55:46 +01:00
fn func1() -> ChainResult< (), Func1ErrorKind> {
func2().map_err(|e| cherr!(e, Func1ErrorKind::Func2))?;
2018-12-20 14:55:19 +01:00
let filename = String::from(" bar.txt" );
2018-12-21 13:55:46 +01:00
do_some_io().map_err(|e| cherr!(e, Func1ErrorKind::IO(filename)))?;
2018-12-20 14:55:19 +01:00
Ok(())
}
2020-03-03 15:16:51 +01:00
fn main() -> Result< (), Box< dyn Error + Send + Sync> > {
2018-12-20 14:55:19 +01:00
if let Err(e) = func1() {
match e.kind() {
2018-12-21 13:55:46 +01:00
Func1ErrorKind::Func2 => eprintln!(" Main Error Report: func1 error calling func2" ),
Func1ErrorKind::IO(filename) => {
2018-12-20 14:55:19 +01:00
eprintln!(" Main Error Report: func1 error reading '{}'" , filename)
}
}
if let Some(e) = e.find_chain_cause::< Func2Error> () {
2018-12-21 13:55:46 +01:00
eprintln!(" \nError reported by Func2Error: {}" , e)
2018-12-20 14:55:19 +01:00
}
eprintln!(" \nDebug Error:\n{:?}" , e);
}
Ok(())
}
2020-03-03 15:08:09 +01:00
< span class = "boring" > #[allow(dead_code)]
< / span > < span class = "boring" > mod chainerror {
2020-03-03 15:16:51 +01:00
< / 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" > }
2020-03-03 15:08:09 +01:00
< / span > < / code > < / pre > < / pre >
2018-12-20 14:55:19 +01:00
< / main >
< nav class = "nav-wrapper" aria-label = "Page navigation" >
<!-- Mobile navigation buttons -->
< a rel = "prev" href = "tutorial9.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 = "tutorial11.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 = "tutorial9.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 = "tutorial11.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 >
2020-03-03 15:08:09 +01:00
< script type = "text/javascript" >
window.playpen_copyable = true;
< / script >
2018-12-20 14:55:19 +01:00
< 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 >
