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< title > ErrorKind to the rescue - chainerror< / title >
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< ol class = "chapter" > < li class = "affix" > < a href = "index.html" > chainerror< / a > < / li > < li > < a href = "tutorial1.html" > < strong aria-hidden = "true" > 1.< / strong > Simple String Errors< / a > < / li > < li > < a href = "tutorial2.html" > < strong aria-hidden = "true" > 2.< / strong > Simple Chained String Errors< / a > < / li > < li > < a href = "tutorial3.html" > < strong aria-hidden = "true" > 3.< / strong > Mapping Errors< / a > < / li > < li > < a href = "tutorial4.html" > < strong aria-hidden = "true" > 4.< / strong > Saving coding chars< / a > < / li > < li > < a href = "tutorial5.html" > < strong aria-hidden = "true" > 5.< / strong > The source() of Errors< / a > < / li > < li > < a href = "tutorial6.html" > < strong aria-hidden = "true" > 6.< / strong > Downcast the Errors< / a > < / li > < li > < a href = "tutorial7.html" > < strong aria-hidden = "true" > 7.< / strong > The root cause of all Errors< / a > < / li > < li > < a href = "tutorial8.html" > < strong aria-hidden = "true" > 8.< / strong > Finding an Error cause< / a > < / li > < li > < a href = "tutorial9.html" > < strong aria-hidden = "true" > 9.< / strong > Selective Error Handling< / a > < / li > < li > < a href = "tutorial10.html" class = "active" > < strong aria-hidden = "true" > 10.< / strong > ErrorKind to the rescue< / a > < / li > < li > < a href = "tutorial11.html" > < strong aria-hidden = "true" > 11.< / strong > Debug for the ErrorKind< / a > < / li > < li > < a href = "tutorial12.html" > < strong aria-hidden = "true" > 12.< / strong > Deref for the ErrorKind< / a > < / li > < li class = "affix" > < a href = "end.html" > The End< / a > < / li > < / ol >
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< a class = "header" href = "#errorkind-to-the-rescue" id = "errorkind-to-the-rescue" > < h1 > ErrorKind to the rescue< / h1 > < / a >
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< 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 >
< p > Only returning < code > Func1ErrorKind< / code > in < code > func1()< / code > now let us get rid of < code > Result< (), Box< Error> > < / code > and we can
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 >
< p > Also a nice < code > match< / code > on < code > ChainError< T> .kind()< / code > is now possible, which returns < code > & T< / code > , meaning
< code > & Func1ErrorKind< / code > here.< / p >
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< pre > < pre class = "playpen" > < code class = "language-rust" > use crate::chainerror::*;
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use std::error::Error;
use std::io;
use std::result::Result;
fn do_some_io() -> Result< (), Box< Error> > {
Err(io::Error::from(io::ErrorKind::NotFound))?;
Ok(())
}
derive_str_cherr!(Func2Error);
fn func2() -> Result< (), Box< Error> > {
let filename = " foo.txt" ;
do_some_io().map_err(mstrerr!(Func2Error, " Error reading '{}'" , filename))?;
Ok(())
}
#[derive(Debug)]
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enum Func1ErrorKind {
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Func2,
IO(String),
}
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impl ::std::fmt::Display for Func1ErrorKind {
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fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
match self {
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Func1ErrorKind::Func2 => write!(f, " func1 error calling func2" ),
Func1ErrorKind::IO(filename) => write!(f, " Error reading '{}'" , filename),
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}
}
}
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impl ::std::error::Error for Func1ErrorKind {}
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fn func1() -> ChainResult< (), Func1ErrorKind> {
func2().map_err(|e| cherr!(e, Func1ErrorKind::Func2))?;
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let filename = String::from(" bar.txt" );
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do_some_io().map_err(|e| cherr!(e, Func1ErrorKind::IO(filename)))?;
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Ok(())
}
fn main() -> Result< (), Box< Error> > {
if let Err(e) = func1() {
match e.kind() {
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Func1ErrorKind::Func2 => eprintln!(" Main Error Report: func1 error calling func2" ),
Func1ErrorKind::IO(filename) => {
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eprintln!(" Main Error Report: func1 error reading '{}'" , filename)
}
}
if let Some(e) = e.find_chain_cause::< Func2Error> () {
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eprintln!(" \nError reported by Func2Error: {}" , e)
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}
eprintln!(" \nDebug Error:\n{:?}" , e);
}
Ok(())
}
# #[allow(dead_code)]
# mod chainerror {
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# //! `chainerror` provides an error backtrace without doing a real backtrace, so even after you `strip` your
# //! binaries, you still have the error backtrace.
# //!
# //! `chainerror` has no dependencies!
# //!
# //! `chainerror` uses `.source()` of `std::error::Error` along with `line()!` and `file()!` to provide a nice debug error backtrace.
# //! It encapsulates all types, which have `Display + Debug` and can store the error cause internally.
# //!
# //! Along with the `ChainError< T> ` struct, `chainerror` comes with some useful helper macros to save a lot of typing.
# //!
# //! ## Features
# //!
# //! `no-fileline`
# //! : completely turn off storing filename and line
# //!
# //! `display-cause`
# //! : turn on printing a backtrace of the errors in `Display`
# //!
# //! `no-debug-cause`
# //! : turn off printing a backtrace of the errors in `Debug`
# //!
# //!
# //! # Tutorial
# //!
# //! Read the [Tutorial](https://haraldh.github.io/chainerror/tutorial1.html)
# //!
# //! # Examples
# //!
# //! ~~~rust
# //! use chainerror::*;
# //! use std::error::Error;
# //! use std::io;
# //! use std::result::Result;
# //!
# //! fn do_some_io() -> Result< (), Box< Error> > {
# //! Err(io::Error::from(io::ErrorKind::NotFound))?;
# //! Ok(())
# //! }
# //!
# //! fn func2() -> Result< (), Box< Error> > {
# //! let filename = " foo.txt" ;
# //! do_some_io().map_err(mstrerr!(" Error reading '{}'" , filename))?;
# //! Ok(())
# //! }
# //!
# //! fn func1() -> Result< (), Box< Error> > {
# //! func2().map_err(mstrerr!(" func1 error" ))?;
# //! Ok(())
# //! }
# //!
# //! fn main() {
# //! if let Err(e) = func1() {
# //! #[cfg(not(windows))]
# //! assert_eq!(
# //! format!(" \n{:?}\n" , e), r#"
# //! src/lib.rs:20: func1 error
# //! Caused by:
# //! src/lib.rs:15: Error reading 'foo.txt'
# //! Caused by:
# //! Kind(NotFound)
# //! " #
# //! );
# //! }
# //! # else {
# //! # unreachable!();
# //! # }
# //! }
# //! ~~~
# //!
# //!
# //! ~~~rust
# //! use chainerror::*;
# //! use std::error::Error;
# //! use std::io;
# //! use std::result::Result;
# //!
# //! fn do_some_io() -> Result< (), Box< Error> > {
# //! Err(io::Error::from(io::ErrorKind::NotFound))?;
# //! Ok(())
# //! }
# //!
# //! fn func3() -> Result< (), Box< Error> > {
# //! let filename = " foo.txt" ;
# //! do_some_io().map_err(mstrerr!(" Error reading '{}'" , filename))?;
# //! Ok(())
# //! }
# //!
# //! derive_str_cherr!(Func2Error);
# //!
# //! fn func2() -> ChainResult< (), Func2Error> {
# //! func3().map_err(mstrerr!(Func2Error, " func2 error: calling func3" ))?;
# //! Ok(())
# //! }
# //!
# //! enum Func1Error {
# //! Func2,
# //! IO(String),
# //! }
# //!
# //! impl ::std::fmt::Display for Func1Error {
# //! fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
# //! match self {
# //! Func1Error::Func2 => write!(f, " func1 error calling func2" ),
# //! Func1Error::IO(filename) => write!(f, " Error reading '{}'" , filename),
# //! }
# //! }
# //! }
# //!
# //! impl ::std::fmt::Debug for Func1Error {
# //! fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
# //! write!(f, " {}" , self)
# //! }
# //! }
# //!
# //! fn func1() -> ChainResult< (), Func1Error> {
# //! func2().map_err(|e| cherr!(e, Func1Error::Func2))?;
# //! let filename = String::from(" bar.txt" );
# //! do_some_io().map_err(|e| cherr!(e, Func1Error::IO(filename)))?;
# //! Ok(())
# //! }
# //!
# //! fn main() {
# //! if let Err(e) = func1() {
# //! assert!(
# //! match e.kind() {
# //! Func1Error::Func2 => {
# //! eprintln!(" Main Error Report: func1 error calling func2" );
# //! true
# //! }
# //! Func1Error::IO(filename) => {
# //! eprintln!(" Main Error Report: func1 error reading '{}'" , filename);
# //! false
# //! }
# //! }
# //! );
# //!
# //! assert!(e.find_chain_cause::< Func2Error> ().is_some());
# //!
# //! if let Some(e) = e.find_chain_cause::< Func2Error> () {
# //! eprintln!(" \nError reported by Func2Error: {}" , e)
# //! }
# //!
# //!
# //! assert!(e.root_cause().is_some());
# //!
# //! if let Some(e) = e.root_cause() {
# //! let ioerror = e.downcast_ref::< io::Error> ().unwrap();
# //! eprintln!(" \nThe root cause was: std::io::Error: {:#?}" , ioerror);
# //! }
# //!
# //! #[cfg(not(windows))]
# //! assert_eq!(
# //! format!(" \n{:?}\n" , e), r#"
# //! src/lib.rs:47: func1 error calling func2
# //! Caused by:
# //! src/lib.rs:22: Func2Error(func2 error: calling func3)
# //! Caused by:
# //! src/lib.rs:15: Error reading 'foo.txt'
# //! Caused by:
# //! Kind(NotFound)
# //! " #
# //! );
# //! }
# //! # else {
# //! # unreachable!();
# //! # }
# //! }
# //! ~~~
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#
# use std::any::TypeId;
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# use std::error::Error;
# use std::fmt::{Debug, Display, Formatter, Result};
#
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# /// chains an inner error kind `T` with a causing error
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# pub struct ChainError< T> {
# #[cfg(not(feature = " no-fileline" ))]
# occurrence: Option< (u32, & 'static str)> ,
# kind: T,
# error_cause: Option< Box< dyn Error + 'static> > ,
# }
#
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# /// convenience type alias
# pub type ChainResult< O, E> = std::result::Result< O, ChainError< E> > ;
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#
# impl< T: 'static + Display + Debug> ChainError< T> {
# #[cfg(not(feature = " no-fileline" ))]
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# /// Use the `cherr!()` or `mstrerr!()` macro instead of calling this directly
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# pub fn new(
# kind: T,
# error_cause: Option< Box< dyn Error + 'static> > ,
# occurrence: Option< (u32, & 'static str)> ,
# ) -> Self {
# Self {
# occurrence,
# kind,
# error_cause,
# }
# }
#
# #[cfg(feature = " no-fileline" )]
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# /// Use the `cherr!()` or `mstrerr!()` macro instead of calling this directly
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# pub fn new(
# kind: T,
# error_cause: Option< Box< dyn Error + 'static> > ,
# _occurrence: Option< (u32, & 'static str)> ,
# ) -> Self {
# Self { kind, error_cause }
# }
#
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# /// return the root cause of the error chain, if any exists
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# pub fn root_cause(& self) -> Option< & (dyn Error + 'static)> {
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# self.iter().last()
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# }
#
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# /// Find the first error cause of type U, if any exists
# ///
# /// # Examples
# ///
# /// ~~~rust
# /// # use crate::chainerror::*;
# /// # use std::error::Error;
# /// # use std::io;
# /// # use std::result::Result;
# /// #
# /// fn do_some_io() -> Result< (), Box< Error> > {
# /// Err(io::Error::from(io::ErrorKind::NotFound))?;
# /// Ok(())
# /// }
# ///
# /// derive_str_cherr!(Func2Error);
# ///
# /// fn func2() -> Result< (), Box< Error> > {
# /// let filename = " foo.txt" ;
# /// do_some_io().map_err(mstrerr!(Func2Error, " Error reading '{}'" , filename))?;
# /// Ok(())
# /// }
# ///
# /// derive_str_cherr!(Func1Error);
# ///
# /// fn func1() -> Result< (), Box< Error> > {
# /// func2().map_err(mstrerr!(Func1Error, " func1 error" ))?;
# /// Ok(())
# /// }
# ///
# /// fn main() {
# /// if let Err(e) = func1() {
# /// if let Some(f1err) = e.downcast_chain_ref::< Func1Error> () {
# ///
# /// assert!(f1err.find_cause::< io::Error> ().is_some());
# ///
# /// assert!(f1err.find_chain_cause::< Func2Error> ().is_some());
# /// }
# /// # else {
# /// # panic!();
# /// # }
# /// }
# /// # else {
# /// # unreachable!();
# /// # }
# /// }
# /// ~~~
# pub fn find_cause< U: Error + 'static> (& self) -> Option< & U> {
# self.iter().filter_map(Error::downcast_ref::< U> ).next()
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# }
#
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# /// Find the first error cause of type `ChainError< U> `, if any exists
# ///
# /// Same as `find_cause`, but hides the `ChainError< U> ` implementation internals
# ///
# /// # Examples
# ///
# /// ~~~rust,ignore
# /// // Instead of writing
# /// err.find_cause::< ChainError< FooError> > ();
# ///
# /// // leave out the ChainError< FooError> implementation detail
# /// err.find_chain_cause::< FooError> ();
# /// ~~~
# pub fn find_chain_cause< U: Error + 'static> (& self) -> Option< & ChainError< U> > {
# self.iter()
# .filter_map(Error::downcast_ref::< ChainError< U> > )
# .next()
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# }
#
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# /// Find the first error cause of type `ChainError< U> ` or `U`, if any exists and return `U`
# ///
# /// Same as `find_cause` and `find_chain_cause`, but hides the `ChainError< U> ` implementation internals
# ///
# /// # Examples
# ///
# /// ~~~rust,ignore
# /// // Instead of writing
# /// err.find_cause::< ChainError< FooErrorKind> > ();
# /// // and/or
# /// err.find_chain_cause::< FooErrorKind> ();
# /// // and/or
# /// err.find_cause::< FooErrorKind> ();
# ///
# /// // leave out the ChainError< FooErrorKind> implementation detail
# /// err.find_chain_or_kind::< FooErrorKind> ();
# /// ~~~
# pub fn find_kind_or_cause< U: Error + 'static> (& self) -> Option< & U> {
# self.iter()
# .filter_map(|e| {
# e.downcast_ref::< ChainError< U> > ()
# .map(|e| e.kind())
# .or_else(|| e.downcast_ref::< U> ())
# })
# .next()
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# }
#
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# /// Return a reference to T of `ChainError< T> `
# ///
# /// # Examples
# ///
# /// ~~~rust
# /// # use crate::chainerror::*;
# /// # use std::error::Error;
# /// # use std::io;
# /// # use std::result::Result;
# /// #
# /// fn do_some_io() -> Result< (), Box< Error> > {
# /// Err(io::Error::from(io::ErrorKind::NotFound))?;
# /// Ok(())
# /// }
# ///
# /// derive_str_cherr!(Func2Error);
# ///
# /// fn func2() -> Result< (), Box< Error> > {
# /// let filename = " foo.txt" ;
# /// do_some_io().map_err(mstrerr!(Func2Error, " Error reading '{}'" , filename))?;
# /// Ok(())
# /// }
# ///
# /// #[derive(Debug)]
# /// enum Func1ErrorKind {
# /// Func2,
# /// IO(String),
# /// }
# ///
# /// /// impl ::std::fmt::Display for Func1ErrorKind {…}
# /// # impl ::std::fmt::Display for Func1ErrorKind {
# /// # fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
# /// # match self {
# /// # Func1ErrorKind::Func2 => write!(f, " func1 error calling func2" ),
# /// # Func1ErrorKind::IO(filename) => write!(f, " Error reading '{}'" , filename),
# /// # }
# /// # }
# /// # }
# ///
# /// fn func1() -> ChainResult< (), Func1ErrorKind> {
# /// func2().map_err(|e| cherr!(e, Func1ErrorKind::Func2))?;
# /// do_some_io().map_err(|e| cherr!(e, Func1ErrorKind::IO(" bar.txt" .into())))?;
# /// Ok(())
# /// }
# ///
# /// fn main() {
# /// if let Err(e) = func1() {
# /// match e.kind() {
# /// Func1ErrorKind::Func2 => {},
# /// Func1ErrorKind::IO(filename) => panic!(),
# /// }
# /// }
# /// # else {
# /// # unreachable!();
# /// # }
# /// }
# /// ~~~
# pub fn kind(& self) -> & T {
# & self.kind
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# }
#
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# /// Returns an Iterator over all error causes/sources
# ///
# /// # Example
# ///
# ///
# pub fn iter(& self) -> impl Iterator< Item = & (dyn Error + 'static)> {
# ErrorIter {
# current: Some(self),
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# }
# }
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# }
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#
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# struct ErrorIter< 'a> {
# current: Option< & 'a (dyn Error + 'static)> ,
# }
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#
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# impl< 'a> Iterator for ErrorIter< 'a> {
# type Item = & 'a (dyn Error + 'static);
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#
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# fn next(& mut self) -> Option< Self::Item> {
# let current = self.current;
# self.current = self.current.and_then(Error::source);
# current
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# }
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# }
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#
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# impl< T: 'static + Display + Debug> std::ops::Deref for ChainError< T> {
# type Target = T;
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#
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# fn deref(& self) -> & Self::Target {
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# & self.kind
# }
# }
#
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# /// Convenience trait to hide the `ChainError< T> ` implementation internals
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# pub trait ChainErrorDown {
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# /// Test if of type `ChainError< T> `
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# fn is_chain< T: 'static + Display + Debug> (& self) -> bool;
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# /// Downcast to a reference of `ChainError< T> `
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# fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > ;
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# /// Downcast to a mutable reference of `ChainError< T> `
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# fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > ;
# }
#
# impl< U: 'static + Display + Debug> ChainErrorDown for ChainError< U> {
# fn is_chain< T: 'static + Display + Debug> (& self) -> bool {
# TypeId::of::< T> () == TypeId::of::< U> ()
# }
#
# fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > {
# if self.is_chain::< T> () {
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# #[allow(clippy::cast_ptr_alignment)]
# unsafe {
# Some(& *(self as *const dyn Error as *const & ChainError< T> ))
# }
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# } else {
# None
# }
# }
#
# fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > {
# if self.is_chain::< T> () {
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# #[allow(clippy::cast_ptr_alignment)]
# unsafe {
# Some(& mut *(self as *mut dyn Error as *mut & mut ChainError< T> ))
# }
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# } else {
# None
# }
# }
# }
#
# impl ChainErrorDown for dyn Error + 'static {
# fn is_chain< T: 'static + Display + Debug> (& self) -> bool {
# self.is::< ChainError< T> > ()
# }
#
# fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > {
# self.downcast_ref::< ChainError< T> > ()
# }
#
# fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > {
# self.downcast_mut::< ChainError< T> > ()
# }
# }
#
# impl ChainErrorDown for dyn Error + 'static + Send {
# fn is_chain< T: 'static + Display + Debug> (& self) -> bool {
# self.is::< ChainError< T> > ()
# }
#
# fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > {
# self.downcast_ref::< ChainError< T> > ()
# }
#
# fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > {
# self.downcast_mut::< ChainError< T> > ()
# }
# }
#
# impl ChainErrorDown for dyn Error + 'static + Send + Sync {
# fn is_chain< T: 'static + Display + Debug> (& self) -> bool {
# self.is::< ChainError< T> > ()
# }
#
# fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > {
# self.downcast_ref::< ChainError< T> > ()
# }
#
# fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > {
# self.downcast_mut::< ChainError< T> > ()
# }
# }
#
# impl< T: 'static + Display + Debug> Error for ChainError< T> {
# fn source(& self) -> Option< & (dyn Error + 'static)> {
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# self.error_cause.as_ref().map(|e| e.as_ref())
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# }
# }
#
# impl< T: 'static + Display + Debug> Error for & ChainError< T> {
# fn source(& self) -> Option< & (dyn Error + 'static)> {
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# self.error_cause.as_ref().map(|e| e.as_ref())
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# }
# }
#
# impl< T: 'static + Display + Debug> Error for & mut ChainError< T> {
# fn source(& self) -> Option< & (dyn Error + 'static)> {
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# self.error_cause.as_ref().map(|e| e.as_ref())
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# }
# }
#
# impl< T: 'static + Display + Debug> Display for ChainError< T> {
# fn fmt(& self, f: & mut Formatter) -> Result {
# write!(f, " {}" , self.kind)?;
#
# #[cfg(feature = " display-cause" )]
# {
# if let Some(e) = self.source() {
# writeln!(f, " \nCaused by:" )?;
# Display::fmt(& e, f)?;
# }
# }
# Ok(())
# }
# }
#
# impl< T: 'static + Display + Debug> Debug for ChainError< T> {
# fn fmt(& self, f: & mut Formatter) -> Result {
# #[cfg(not(feature = " no-fileline" ))]
# {
# if let Some(o) = self.occurrence {
# write!(f, " {}:{}: " , o.1, o.0)?;
# }
# }
#
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# if self.is_chain::< String> () {
# Display::fmt(& self.kind, f)?;
# } else {
# Debug::fmt(& self.kind, f)?;
# }
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#
# #[cfg(not(feature = " no-debug-cause" ))]
# {
# if let Some(e) = self.source() {
# writeln!(f, " \nCaused by:" )?;
# Debug::fmt(& e, f)?;
# }
# }
# Ok(())
# }
# }
#
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# pub trait ChainErrorFrom< T> : Sized {
# fn chain_error_from(_: T, line_filename: Option< (u32, & 'static str)> ) -> ChainError< Self> ;
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# }
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#
# pub trait IntoChainError< T> : Sized {
# fn into_chain_error(self, line_filename: Option< (u32, & 'static str)> ) -> ChainError< T> ;
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# }
#
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# impl< T, U> IntoChainError< U> for T
# where
# U: ChainErrorFrom< T> ,
# {
# fn into_chain_error(self, line_filename: Option< (u32, & 'static str)> ) -> ChainError< U> {
# U::chain_error_from(self, line_filename)
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# }
# }
#
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# impl< T, U> ChainErrorFrom< T> for U
# where
# T: Into< U> ,
# U: 'static + Display + Debug,
# {
# fn chain_error_from(t: T, line_filename: Option< (u32, & 'static str)> ) -> ChainError< Self> {
# let e: U = t.into();
# ChainError::< _> ::new(e, None, line_filename)
# }
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# }
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#
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# #[macro_export]
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# macro_rules! minto_cherr {
# ( ) => {
# |e| e.into_chain_error(Some((line!(), file!())))
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# };
# }
#
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# #[macro_export]
# macro_rules! into_cherr {
# ( $t:expr ) => {
# $t.into_chain_error(Some((line!(), file!())))
# };
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# }
#
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# /// Creates a new `ChainError< T> `
# ///
# /// # Examples
# ///
# /// Create a new ChainError< FooError> , where `FooError` must implement `Display` and `Debug`.
# /// ~~~rust
# /// # use chainerror::*;
# /// #
# /// # #[derive(Debug)]
# /// enum FooError {
# /// Bar,
# /// Baz(& 'static str),
# /// }
# /// #
# /// # impl ::std::fmt::Display for FooError {
# /// # fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
# /// # match self {
# /// # FooError::Bar => write!(f, " Bar Error" ),
# /// # FooError::Baz(s) => write!(f, " Baz Error: '{}'" , s),
# /// # }
# /// # }
# /// # }
# ///
# /// // impl ::std::fmt::Display for FooError
# ///
# /// fn do_some_stuff() -> bool {
# /// false
# /// }
# ///
# /// fn func() -> ChainResult< (), FooError> {
# /// if ! do_some_stuff() {
# /// Err(cherr!(FooError::Baz(" Error" )))?;
# /// }
# /// Ok(())
# /// }
# /// #
# /// # pub fn main() {
# /// # match func().unwrap_err().kind() {
# /// # FooError::Baz(s) if s == & " Error" => {},
# /// # _ => panic!(),
# /// # }
# /// # }
# /// ~~~
# ///
# /// Additionally an error cause can be added.
# ///
# /// ~~~rust
# /// # use chainerror::*;
# /// # use std::io;
# /// # use std::error::Error;
# /// #
# /// # #[derive(Debug)]
# /// # enum FooError {
# /// # Bar,
# /// # Baz(& 'static str),
# /// # }
# /// #
# /// # impl ::std::fmt::Display for FooError {
# /// # fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
# /// # match self {
# /// # FooError::Bar => write!(f, " Bar Error" ),
# /// # FooError::Baz(s) => write!(f, " Baz Error: '{}'" , s),
# /// # }
# /// # }
# /// # }
# /// #
# /// fn do_some_stuff() -> Result< (), Box< Error> > {
# /// Err(io::Error::from(io::ErrorKind::NotFound))?;
# /// Ok(())
# /// }
# ///
# /// fn func() -> ChainResult< (), FooError> {
# /// do_some_stuff().map_err(
# /// |e| cherr!(e, FooError::Baz(" Error" ))
# /// )?;
# /// Ok(())
# /// }
# /// #
# /// # pub fn main() {
# /// # match func().unwrap_err().kind() {
# /// # FooError::Baz(s) if s == & " Error" => {},
# /// # _ => panic!(),
# /// # }
# /// # }
# /// ~~~
# #[macro_export]
# macro_rules! cherr {
# ( $k:expr ) => ({
# ChainError::< _> ::new($k, None, Some((line!(), file!())))
# });
# ( None, $k:expr ) => ({
# ChainError::< _> ::new($k, None, Some((line!(), file!())))
# });
# ( None, $fmt:expr, $($arg:tt)+ ) => ({
# cherr!(None, format!($fmt, $($arg)+ ))
# });
# ( None, $fmt:expr, $($arg:tt)+ ) => ({
# cherr!(None, format!($fmt, $($arg)+ ))
# });
# ( $e:ident, $k:expr ) => ({
# ChainError::< _> ::new($k, Some(Box::from($e)), Some((line!(), file!())))
# });
# ( $e:path, $k:expr ) => ({
# ChainError::< _> ::new($k, Some(Box::from($e)), Some((line!(), file!())))
# });
# ( $e:ident, $fmt:expr, $($arg:tt)+ ) => ({
# cherr!($e, format!($fmt, $($arg)+ ))
# });
# ( $e:path, $fmt:expr, $($arg:tt)+ ) => ({
# cherr!($e, format!($fmt, $($arg)+ ))
# });
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#
# }
#
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# /// Convenience macro for `|e| cherr!(e, format!(…))`
# ///
# /// # Examples
# ///
# /// ~~~rust
# /// # use crate::chainerror::*;
# /// # use std::error::Error;
# /// # use std::io;
# /// # use std::result::Result;
# /// #
# /// # fn do_some_io() -> Result< (), Box< Error> > {
# /// # Err(io::Error::from(io::ErrorKind::NotFound))?;
# /// # Ok(())
# /// # }
# /// #
# /// fn func2() -> Result< (), Box< Error> > {
# /// let filename = " foo.txt" ;
# /// do_some_io().map_err(mstrerr!(" Error reading '{}'" , filename))?;
# /// Ok(())
# /// }
# ///
# /// fn func1() -> Result< (), Box< Error> > {
# /// func2().map_err(mstrerr!(" func1 error" ))?;
# /// Ok(())
# /// }
# ///
# /// # fn main() {
# /// # if let Err(e) = func1() {
# /// # #[cfg(not(windows))]
# /// # assert_eq!(
# /// # format!(" \n{:?}\n" , e), r#"
# /// # src/lib.rs:20: func1 error
# /// # Caused by:
# /// # src/lib.rs:15: Error reading 'foo.txt'
# /// # Caused by:
# /// # Kind(NotFound)
# /// # " #
# /// # );
# /// # } else {
# /// # unreachable!();
# /// # }
# /// # }
# /// ~~~
# ///
# /// `mstrerr!()` can also be used to map a new `ChainError< T> `, where T was defined with
# /// `derive_str_cherr!(T)`
# ///
# /// ~~~rust
# /// # use crate::chainerror::*;
# /// # use std::error::Error;
# /// # use std::io;
# /// # use std::result::Result;
# /// #
# /// # fn do_some_io() -> Result< (), Box< Error> > {
# /// # Err(io::Error::from(io::ErrorKind::NotFound))?;
# /// # Ok(())
# /// # }
# /// #
# /// derive_str_cherr!(Func2Error);
# ///
# /// fn func2() -> Result< (), Box< Error> > {
# /// let filename = " foo.txt" ;
# /// do_some_io().map_err(mstrerr!(Func2Error, " Error reading '{}'" , filename))?;
# /// Ok(())
# /// }
# ///
# /// derive_str_cherr!(Func1Error);
# ///
# /// fn func1() -> Result< (), Box< Error> > {
# /// func2().map_err(mstrerr!(Func1Error, " func1 error" ))?;
# /// Ok(())
# /// }
# /// #
# /// # fn main() {
# /// # if let Err(e) = func1() {
# /// # if let Some(f1err) = e.downcast_chain_ref::< Func1Error> () {
# /// # assert!(f1err.find_cause::< ChainError< Func2Error> > ().is_some());
# /// # assert!(f1err.find_chain_cause::< Func2Error> ().is_some());
# /// # } else {
# /// # panic!();
# /// # }
# /// # } else {
# /// # unreachable!();
# /// # }
# /// # }
# /// ~~~
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# #[macro_export]
# macro_rules! mstrerr {
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# ( $t:ident, $msg:expr ) => ({
# |e| cherr!(e, $t ($msg.to_string()))
# });
# ( $t:path, $msg:expr ) => ({
# |e| cherr!(e, $t ($msg.to_string()))
# });
# ( $t:ident, $msg:expr, ) => ({
# |e| cherr!(e, $t ($msg.to_string()))
# });
# ( $t:path, $msg:expr, ) => ({
# |e| cherr!(e, $t ($msg.to_string()))
# });
# ( $t:ident, $fmt:expr, $($arg:tt)+ ) => ({
# |e| cherr!(e, $t (format!($fmt, $($arg)+ )))
# });
# ( $t:path, $fmt:expr, $($arg:tt)+ ) => ({
# |e| cherr!(e, $t (format!($fmt, $($arg)+ )))
# });
# ($msg:expr) => ({
# |e| cherr!(e, $msg.to_string())
# });
# ($msg:expr, ) => ({
# |e| cherr!(e, $msg.to_string())
# });
# ($fmt:expr, $($arg:tt)+) => ({
# |e| cherr!(e, format!($fmt, $($arg)+ ))
# });
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# }
#
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# /// Convenience macro for `cherr!(T(format!(…)))` where `T(String)`
# ///
# /// # Examples
# ///
# /// ~~~rust
# /// # use crate::chainerror::*;
# /// # use std::error::Error;
# /// # use std::result::Result;
# /// #
# /// derive_str_cherr!(Func2Error);
# ///
# /// fn func2() -> ChainResult< (), Func2Error> {
# /// let filename = " foo.txt" ;
# /// Err(strerr!(Func2Error, " Error reading '{}'" , filename))
# /// }
# ///
# /// derive_str_cherr!(Func1Error);
# ///
# /// fn func1() -> Result< (), Box< Error> > {
# /// func2().map_err(mstrerr!(Func1Error, " func1 error" ))?;
# /// Ok(())
# /// }
# /// #
# /// # fn main() {
# /// # if let Err(e) = func1() {
# /// # if let Some(f1err) = e.downcast_chain_ref::< Func1Error> () {
# /// # assert!(f1err.find_cause::< ChainError< Func2Error> > ().is_some());
# /// # assert!(f1err.find_chain_cause::< Func2Error> ().is_some());
# /// # } else {
# /// # panic!();
# /// # }
# /// # } else {
# /// # unreachable!();
# /// # }
# /// # }
# /// ~~~
# #[macro_export]
# macro_rules! strerr {
# ( $t:ident, $msg:expr ) => ({
# cherr!($t ($msg.to_string()))
# });
# ( $t:path, $msg:expr ) => ({
# cherr!($t ($msg.to_string()))
# });
# ( $t:ident, $msg:expr, ) => ({
# cherr!($t ($msg.to_string()))
# });
# ( $t:path, $msg:expr, ) => ({
# cherr!($t ($msg.to_string()))
# });
# ( $t:ident, $fmt:expr, $($arg:tt)+ ) => ({
# cherr!($t (format!($fmt, $($arg)+ )))
# });
# ( $t:path, $fmt:expr, $($arg:tt)+ ) => ({
# cherr!($t (format!($fmt, $($arg)+ )))
# });
# ($msg:expr) => ({
# cherr!($msg.to_string())
# });
# ($msg:expr, ) => ({
# cherr!($msg.to_string())
# });
# ($fmt:expr, $($arg:tt)+) => ({
# cherr!(format!($fmt, $($arg)+ ))
# });
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# }
#
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# /// Convenience macro to create a " new type" T(String) and implement Display + Debug for T
# ///
# /// # Examples
# ///
# /// ~~~rust
# /// # use crate::chainerror::*;
# /// # use std::error::Error;
# /// # use std::io;
# /// # use std::result::Result;
# /// #
# /// # fn do_some_io() -> Result< (), Box< Error> > {
# /// # Err(io::Error::from(io::ErrorKind::NotFound))?;
# /// # Ok(())
# /// # }
# /// #
# /// derive_str_cherr!(Func2Error);
# ///
# /// fn func2() -> ChainResult< (), Func2Error> {
# /// let filename = " foo.txt" ;
# /// do_some_io().map_err(mstrerr!(Func2Error, " Error reading '{}'" , filename))?;
# /// Ok(())
# /// }
# ///
# /// derive_str_cherr!(Func1Error);
# ///
# /// fn func1() -> Result< (), Box< Error> > {
# /// func2().map_err(mstrerr!(Func1Error, " func1 error" ))?;
# /// Ok(())
# /// }
# /// #
# /// # fn main() {
# /// # if let Err(e) = func1() {
# /// # if let Some(f1err) = e.downcast_chain_ref::< Func1Error> () {
# /// # assert!(f1err.find_cause::< ChainError< Func2Error> > ().is_some());
# /// # assert!(f1err.find_chain_cause::< Func2Error> ().is_some());
# /// # } else {
# /// # panic!();
# /// # }
# /// # } else {
# /// # unreachable!();
# /// # }
# /// # }
# /// ~~~
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# #[macro_export]
# macro_rules! derive_str_cherr {
# ($e:ident) => {
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# pub struct $e(pub String);
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# impl ::std::fmt::Display for $e {
# fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
# write!(f, " {}" , self.0)
# }
# }
# impl ::std::fmt::Debug for $e {
# fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
# write!(f, " {}({})" , stringify!($e), self.0)
# }
# }
# impl ::std::error::Error for $e {}
# };
# }
# }
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