2018-12-20 14:55:19 +01:00
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2018-12-20 16:02:24 +01:00
< a class = "header" href = "#simple-string-errors" id = "simple-string-errors" > < h2 > Simple String Errors< / h2 > < / a >
2018-12-20 15:12:59 +01:00
< p > The most simplest of doing error handling in rust is by returning < code > String< / code > as a < code > Box< Error> < / code > .< / p >
< p > As you can see by running the example, this only prints out the last < code > Error< / code > .< / p >
< p > If the rust < code > main< / code > function returns an Err(), this Err() will be displayed with < code > std::fmt::Debug< / code > .< / p >
< pre > < pre class = "playpen" > < code class = "language-rust" > use std::error::Error;
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use std::result::Result;
fn do_some_io() -> Result< (), Box< Error> > {
Err(" do_some_io error" )?;
Ok(())
}
fn func2() -> Result< (), Box< Error> > {
if let Err(_) = do_some_io() {
Err(" func2 error" )?;
}
Ok(())
}
fn func1() -> Result< (), Box< Error> > {
if let Err(_) = func2() {
Err(" func1 error" )?;
}
Ok(())
}
fn main() -> Result< (), Box< Error> > {
func1()
}
< / code > < / pre > < / pre >
2018-12-20 16:02:24 +01:00
< a class = "header" href = "#simple-chained-string-errors" id = "simple-chained-string-errors" > < h2 > Simple Chained String Errors< / h2 > < / a >
2018-12-20 15:12:59 +01:00
< p > Now with the help of the < code > chainerror< / code > crate, we can have a nicer output.< / p >
< p > Press the play button in the upper right corner and see the nice debug output.< / p >
2018-12-20 14:55:19 +01:00
< pre > < pre class = "playpen" > < code class = "language-rust" > use crate::chainerror::*;
use std::error::Error;
use std::result::Result;
fn do_some_io() -> Result< (), Box< Error> > {
Err(" do_some_io error" )?;
Ok(())
}
fn func2() -> Result< (), Box< Error> > {
if let Err(e) = do_some_io() {
Err(cherr!(e, " func2 error" ))?;
}
Ok(())
}
fn func1() -> Result< (), Box< Error> > {
if let Err(e) = func2() {
Err(cherr!(e, " func1 error" ))?;
}
Ok(())
}
fn main() -> Result< (), Box< Error> > {
func1()
}
# #[allow(dead_code)]
# mod chainerror {
# use std::error::Error;
# use std::fmt::{Debug, Display, Formatter, Result};
# use std::result::Result as StdResult;
#
# pub struct ChainError< T> {
# #[cfg(not(feature = " no-fileline" ))]
# occurrence: Option< (u32, & 'static str)> ,
# kind: T,
# error_cause: Option< Box< dyn Error + 'static> > ,
# }
#
# pub type ChainResult< O, E> = StdResult< O, ChainError< E> > ;
#
# impl< T: 'static + Display + Debug> ChainError< T> {
# #[cfg(not(feature = " no-fileline" ))]
# 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" )]
# pub fn new(
# kind: T,
# error_cause: Option< Box< dyn Error + 'static> > ,
# _occurrence: Option< (u32, & 'static str)> ,
# ) -> Self {
# Self { kind, error_cause }
# }
#
# pub fn root_cause(& self) -> Option< & (dyn Error + 'static)> {
# let mut cause = self as & (dyn Error + 'static);
# while let Some(c) = cause.source() {
# cause = c;
# }
# Some(cause)
# }
#
# pub fn find_cause< U: Error + 'static> (& self) -> Option< & U> {
# let mut cause = self as & (dyn Error + 'static);
# loop {
# if cause.is::< U> () {
# return cause.downcast_ref::< U> ();
# }
#
# match cause.source() {
# Some(c) => cause = c,
# None => return None,
# }
# }
# }
#
# pub fn find_chain_cause< U: Error + 'static> (& self) -> Option< & ChainError< U> > {
# let mut cause = self as & (dyn Error + 'static);
# loop {
# if cause.is::< ChainError< U> > () {
# return cause.downcast_ref::< ChainError< U> > ();
# }
#
# match cause.source() {
# Some(c) => cause = c,
# None => return None,
# }
# }
# }
#
# pub fn kind< 'a> (& 'a self) -> & 'a T {
# & self.kind
# }
# }
#
# pub trait ChainErrorDown {
# fn is_chain< T: 'static + Display + Debug> (& self) -> bool;
# fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > ;
# fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > ;
# }
#
# use std::any::TypeId;
#
# 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> () {
# unsafe { Some(& *(self as *const dyn Error as *const & ChainError< T> )) }
# } else {
# None
# }
# }
#
# fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > {
# if self.is_chain::< T> () {
# unsafe { Some(& mut *(self as *mut dyn Error as *mut & mut ChainError< T> )) }
# } 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)> {
# if let Some(ref e) = self.error_cause {
# Some(e.as_ref())
# } else {
# None
# }
# }
# }
#
# impl< T: 'static + Display + Debug> Error for & ChainError< T> {
# fn source(& self) -> Option< & (dyn Error + 'static)> {
# if let Some(ref e) = self.error_cause {
# Some(e.as_ref())
# } else {
# None
# }
# }
# }
#
# impl< T: 'static + Display + Debug> Error for & mut ChainError< T> {
# fn source(& self) -> Option< & (dyn Error + 'static)> {
# if let Some(ref e) = self.error_cause {
# Some(e.as_ref())
# } else {
# None
# }
# }
# }
#
# 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)?;
# }
# }
#
# Debug::fmt(& self.kind, f)?;
#
# #[cfg(not(feature = " no-debug-cause" ))]
# {
# if let Some(e) = self.source() {
# writeln!(f, " \nCaused by:" )?;
# Debug::fmt(& e, f)?;
# }
# }
# Ok(())
# }
# }
#
# #[macro_export]
# macro_rules! cherr {
# ( $k:expr ) => {
# ChainError::< _> ::new($k, None, Some((line!(), file!())))
# };
# ( $e:expr, $k:expr ) => {
# ChainError::< _> ::new($k, Some(Box::from($e)), Some((line!(), file!())))
# };
# }
#
# #[macro_export]
# macro_rules! mstrerr {
# ( $t:ident, $v:expr $(, $more:expr)* ) => {
# |e| cherr!(e, $t (format!($v, $( $more , )* )))
# };
# ( $t:path, $v:expr $(, $more:expr)* ) => {
# |e| cherr!(e, $t (format!($v, $( $more , )* )))
# };
# ( $v:expr $(, $more:expr)* ) => {
# |e| cherr!(e, format!($v, $( $more , )* ))
# };
# }
#
# #[macro_export]
# macro_rules! derive_str_cherr {
# ($e:ident) => {
# struct $e(String);
# 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 {}
# };
# }
#
# #[macro_export]
# macro_rules! try_cherr_ref {
# ( $e:expr, $t:ident ) => {
# $e.downcast_ref::< ChainError< $t> > ()
# };
# ( $e:expr, $t:path ) => {
# $e.downcast_ref::< ChainError< $t> > ()
# };
# }
#
# #[macro_export]
# macro_rules! try_cherr_mut {
# ( $e:expr, $t:ident ) => {
# $e.downcast_mut::< ChainError< $t> > ()
# };
# ( $e:expr, $t:path ) => {
# $e.downcast_mut::< ChainError< $t> > ()
# };
# }
# }
< / code > < / pre > < / pre >
2018-12-20 16:02:24 +01:00
< a class = "header" href = "#what-did-we-do-here" id = "what-did-we-do-here" > < h3 > What did we do here?< / h3 > < / a >
< pre > < code class = "language-rust ignore" > if let Err(e) = do_some_io() {
Err(cherr!(e, " func2 error" ))?;
}
< / code > < / pre >
< p > The macro < code > cherr!(cause, newerror)< / code > stores < code > cause< / code > as the source/cause of < code > newerror< / code > and returns
< code > newerror< / code > , along with the filename (< code > file!()< / code > ) and line number (< code > line!()< / code > ).< / p >
< p > < code > Err(e)?< / code > then returns the error < code > e< / code > applying < code > e.into()< / code > , so that we
again have a < code > Err(Box< Error> )< / code > as a result.< / p >
< p > The < code > Debug< / code > implementation of < code > ChainError< T> < / code > (which is returned by < code > cherr!()< / code > )
prints the < code > Debug< / code > of < code > T< / code > prefixed with the stored filename and line number.< / p >
< p > < code > ChainError< T> < / code > is in our case < code > ChainError< String> < / code > .< / p >
< a class = "header" href = "#mapping-errors" id = "mapping-errors" > < h2 > Mapping Errors< / h2 > < / a >
< p > Now let's get more rust idiomatic by using < code > .map_err()< / code > .< / p >
2018-12-20 14:55:19 +01:00
< pre > < pre class = "playpen" > < code class = "language-rust" > use crate::chainerror::*;
use std::error::Error;
use std::result::Result;
fn do_some_io() -> Result< (), Box< Error> > {
Err(" do_some_io error" )?;
Ok(())
}
fn func2() -> Result< (), Box< Error> > {
do_some_io().map_err(|e| cherr!(e, " func2 error" ))?;
Ok(())
}
fn func1() -> Result< (), Box< Error> > {
func2().map_err(|e| cherr!(e, " func1 error" ))?;
Ok(())
}
fn main() -> Result< (), Box< Error> > {
if let Err(e) = func1() {
eprintln!(" {:?}" , e);
}
Ok(())
}
# #[allow(dead_code)]
# mod chainerror {
# use std::error::Error;
# use std::fmt::{Debug, Display, Formatter, Result};
# use std::result::Result as StdResult;
#
# pub struct ChainError< T> {
# #[cfg(not(feature = " no-fileline" ))]
# occurrence: Option< (u32, & 'static str)> ,
# kind: T,
# error_cause: Option< Box< dyn Error + 'static> > ,
# }
#
# pub type ChainResult< O, E> = StdResult< O, ChainError< E> > ;
#
# impl< T: 'static + Display + Debug> ChainError< T> {
# #[cfg(not(feature = " no-fileline" ))]
# 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" )]
# pub fn new(
# kind: T,
# error_cause: Option< Box< dyn Error + 'static> > ,
# _occurrence: Option< (u32, & 'static str)> ,
# ) -> Self {
# Self { kind, error_cause }
# }
#
# pub fn root_cause(& self) -> Option< & (dyn Error + 'static)> {
# let mut cause = self as & (dyn Error + 'static);
# while let Some(c) = cause.source() {
# cause = c;
# }
# Some(cause)
# }
#
# pub fn find_cause< U: Error + 'static> (& self) -> Option< & U> {
# let mut cause = self as & (dyn Error + 'static);
# loop {
# if cause.is::< U> () {
# return cause.downcast_ref::< U> ();
# }
#
# match cause.source() {
# Some(c) => cause = c,
# None => return None,
# }
# }
# }
#
# pub fn find_chain_cause< U: Error + 'static> (& self) -> Option< & ChainError< U> > {
# let mut cause = self as & (dyn Error + 'static);
# loop {
# if cause.is::< ChainError< U> > () {
# return cause.downcast_ref::< ChainError< U> > ();
# }
#
# match cause.source() {
# Some(c) => cause = c,
# None => return None,
# }
# }
# }
#
# pub fn kind< 'a> (& 'a self) -> & 'a T {
# & self.kind
# }
# }
#
# pub trait ChainErrorDown {
# fn is_chain< T: 'static + Display + Debug> (& self) -> bool;
# fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > ;
# fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > ;
# }
#
# use std::any::TypeId;
#
# 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> () {
# unsafe { Some(& *(self as *const dyn Error as *const & ChainError< T> )) }
# } else {
# None
# }
# }
#
# fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > {
# if self.is_chain::< T> () {
# unsafe { Some(& mut *(self as *mut dyn Error as *mut & mut ChainError< T> )) }
# } 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)> {
# if let Some(ref e) = self.error_cause {
# Some(e.as_ref())
# } else {
# None
# }
# }
# }
#
# impl< T: 'static + Display + Debug> Error for & ChainError< T> {
# fn source(& self) -> Option< & (dyn Error + 'static)> {
# if let Some(ref e) = self.error_cause {
# Some(e.as_ref())
# } else {
# None
# }
# }
# }
#
# impl< T: 'static + Display + Debug> Error for & mut ChainError< T> {
# fn source(& self) -> Option< & (dyn Error + 'static)> {
# if let Some(ref e) = self.error_cause {
# Some(e.as_ref())
# } else {
# None
# }
# }
# }
#
# 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)?;
# }
# }
#
# Debug::fmt(& self.kind, f)?;
#
# #[cfg(not(feature = " no-debug-cause" ))]
# {
# if let Some(e) = self.source() {
# writeln!(f, " \nCaused by:" )?;
# Debug::fmt(& e, f)?;
# }
# }
# Ok(())
# }
# }
#
# #[macro_export]
# macro_rules! cherr {
# ( $k:expr ) => {
# ChainError::< _> ::new($k, None, Some((line!(), file!())))
# };
# ( $e:expr, $k:expr ) => {
# ChainError::< _> ::new($k, Some(Box::from($e)), Some((line!(), file!())))
# };
# }
#
# #[macro_export]
# macro_rules! mstrerr {
# ( $t:ident, $v:expr $(, $more:expr)* ) => {
# |e| cherr!(e, $t (format!($v, $( $more , )* )))
# };
# ( $t:path, $v:expr $(, $more:expr)* ) => {
# |e| cherr!(e, $t (format!($v, $( $more , )* )))
# };
# ( $v:expr $(, $more:expr)* ) => {
# |e| cherr!(e, format!($v, $( $more , )* ))
# };
# }
#
# #[macro_export]
# macro_rules! derive_str_cherr {
# ($e:ident) => {
# struct $e(String);
# 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 {}
# };
# }
#
# #[macro_export]
# macro_rules! try_cherr_ref {
# ( $e:expr, $t:ident ) => {
# $e.downcast_ref::< ChainError< $t> > ()
# };
# ( $e:expr, $t:path ) => {
# $e.downcast_ref::< ChainError< $t> > ()
# };
# }
#
# #[macro_export]
# macro_rules! try_cherr_mut {
# ( $e:expr, $t:ident ) => {
# $e.downcast_mut::< ChainError< $t> > ()
# };
# ( $e:expr, $t:path ) => {
# $e.downcast_mut::< ChainError< $t> > ()
# };
# }
# }
< / code > < / pre > < / pre >
2018-12-20 16:02:24 +01:00
< p > If you compare the output to the previous example, you will see,
that:< / p >
< pre > < code > Error: src/main.rs:19: " func1 error"
< / code > < / pre >
< p > changed to just:< / p >
< pre > < code > src/main.rs:16: " func1 error"
< / code > < / pre >
< p > This is, because we caught the error of < code > func1()< / code > in < code > main()< / code > and print it out ourselves.< / p >
< p > We can now control, whether to output in < code > Debug< / code > or < code > Display< / code > mode.
Maybe depending on < code > --debug< / code > as a CLI argument.< / p >
< a class = "header" href = "#saving-coding-chars" id = "saving-coding-chars" > < h2 > Saving coding chars< / h2 > < / a >
< p > Because decorating an error with more information should not
let you jump through hoops, < code > chainerror< / code > has a quick macro for that.< / p >
< p > < code > mstrerror!()< / code > fits right into < code > .map_err()< / code > letting you quickly add
more debug strings.< / p >
< p > < code > mstrerror!()< / code > even understands < code > format!()< / code > syntax like < code > println!()< / code > .< / p >
2018-12-20 14:55:19 +01:00
< pre > < pre class = "playpen" > < code class = "language-rust" > use crate::chainerror::*;
use std::error::Error;
use std::result::Result;
fn do_some_io() -> Result< (), Box< Error> > {
Err(" do_some_io error" )?;
Ok(())
}
fn func2() -> Result< (), Box< Error> > {
2018-12-20 16:02:24 +01:00
let filename = " foo.txt" ;
do_some_io().map_err(mstrerr!(" Error reading '{}'" , filename))?;
2018-12-20 14:55:19 +01:00
Ok(())
}
fn func1() -> Result< (), Box< Error> > {
func2().map_err(mstrerr!(" func1 error" ))?;
Ok(())
}
fn main() -> Result< (), Box< Error> > {
if let Err(e) = func1() {
eprintln!(" {:?}" , e);
}
Ok(())
}
# #[allow(dead_code)]
# mod chainerror {
# use std::error::Error;
# use std::fmt::{Debug, Display, Formatter, Result};
# use std::result::Result as StdResult;
#
# pub struct ChainError< T> {
# #[cfg(not(feature = " no-fileline" ))]
# occurrence: Option< (u32, & 'static str)> ,
# kind: T,
# error_cause: Option< Box< dyn Error + 'static> > ,
# }
#
# pub type ChainResult< O, E> = StdResult< O, ChainError< E> > ;
#
# impl< T: 'static + Display + Debug> ChainError< T> {
# #[cfg(not(feature = " no-fileline" ))]
# 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" )]
# pub fn new(
# kind: T,
# error_cause: Option< Box< dyn Error + 'static> > ,
# _occurrence: Option< (u32, & 'static str)> ,
# ) -> Self {
# Self { kind, error_cause }
# }
#
# pub fn root_cause(& self) -> Option< & (dyn Error + 'static)> {
# let mut cause = self as & (dyn Error + 'static);
# while let Some(c) = cause.source() {
# cause = c;
# }
# Some(cause)
# }
#
# pub fn find_cause< U: Error + 'static> (& self) -> Option< & U> {
# let mut cause = self as & (dyn Error + 'static);
# loop {
# if cause.is::< U> () {
# return cause.downcast_ref::< U> ();
# }
#
# match cause.source() {
# Some(c) => cause = c,
# None => return None,
# }
# }
# }
#
# pub fn find_chain_cause< U: Error + 'static> (& self) -> Option< & ChainError< U> > {
# let mut cause = self as & (dyn Error + 'static);
# loop {
# if cause.is::< ChainError< U> > () {
# return cause.downcast_ref::< ChainError< U> > ();
# }
#
# match cause.source() {
# Some(c) => cause = c,
# None => return None,
# }
# }
# }
#
# pub fn kind< 'a> (& 'a self) -> & 'a T {
# & self.kind
# }
# }
#
# pub trait ChainErrorDown {
# fn is_chain< T: 'static + Display + Debug> (& self) -> bool;
# fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > ;
# fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > ;
# }
#
# use std::any::TypeId;
#
# 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> () {
# unsafe { Some(& *(self as *const dyn Error as *const & ChainError< T> )) }
# } else {
# None
# }
# }
#
# fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > {
# if self.is_chain::< T> () {
# unsafe { Some(& mut *(self as *mut dyn Error as *mut & mut ChainError< T> )) }
# } 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)> {
# if let Some(ref e) = self.error_cause {
# Some(e.as_ref())
# } else {
# None
# }
# }
# }
#
# impl< T: 'static + Display + Debug> Error for & ChainError< T> {
# fn source(& self) -> Option< & (dyn Error + 'static)> {
# if let Some(ref e) = self.error_cause {
# Some(e.as_ref())
# } else {
# None
# }
# }
# }
#
# impl< T: 'static + Display + Debug> Error for & mut ChainError< T> {
# fn source(& self) -> Option< & (dyn Error + 'static)> {
# if let Some(ref e) = self.error_cause {
# Some(e.as_ref())
# } else {
# None
# }
# }
# }
#
# 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)?;
# }
# }
#
# Debug::fmt(& self.kind, f)?;
#
# #[cfg(not(feature = " no-debug-cause" ))]
# {
# if let Some(e) = self.source() {
# writeln!(f, " \nCaused by:" )?;
# Debug::fmt(& e, f)?;
# }
# }
# Ok(())
# }
# }
#
# #[macro_export]
# macro_rules! cherr {
# ( $k:expr ) => {
# ChainError::< _> ::new($k, None, Some((line!(), file!())))
# };
# ( $e:expr, $k:expr ) => {
# ChainError::< _> ::new($k, Some(Box::from($e)), Some((line!(), file!())))
# };
# }
#
# #[macro_export]
# macro_rules! mstrerr {
# ( $t:ident, $v:expr $(, $more:expr)* ) => {
# |e| cherr!(e, $t (format!($v, $( $more , )* )))
# };
# ( $t:path, $v:expr $(, $more:expr)* ) => {
# |e| cherr!(e, $t (format!($v, $( $more , )* )))
# };
# ( $v:expr $(, $more:expr)* ) => {
# |e| cherr!(e, format!($v, $( $more , )* ))
# };
# }
#
# #[macro_export]
# macro_rules! derive_str_cherr {
# ($e:ident) => {
# struct $e(String);
# 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 {}
# };
# }
#
# #[macro_export]
# macro_rules! try_cherr_ref {
# ( $e:expr, $t:ident ) => {
# $e.downcast_ref::< ChainError< $t> > ()
# };
# ( $e:expr, $t:path ) => {
# $e.downcast_ref::< ChainError< $t> > ()
# };
# }
#
# #[macro_export]
# macro_rules! try_cherr_mut {
# ( $e:expr, $t:ident ) => {
# $e.downcast_mut::< ChainError< $t> > ()
# };
# ( $e:expr, $t:path ) => {
# $e.downcast_mut::< ChainError< $t> > ()
# };
# }
# }
< / code > < / pre > < / pre >
2018-12-20 16:02:24 +01:00
< a class = "header" href = "#the-source-of-errors" id = "the-source-of-errors" > < h2 > The source() of Errors< / h2 > < / a >
< p > Sometimes you want to inspect the < code > source()< / code > of an < code > Error< / code > .
< code > chainerror< / code > implements < code > std::error::Error::source()< / code > , so you can get the cause of an error.< / p >
2018-12-20 14:55:19 +01:00
< pre > < pre class = "playpen" > < code class = "language-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> > {
if let Err(e) = func2() {
if let Some(s) = e.source() {
eprintln!(" func2 failed because of '{}'" , s);
Err(e).map_err(mstrerr!(" func1 error" ))?;
}
}
Ok(())
}
fn main() -> Result< (), Box< Error> > {
if let Err(e) = func1() {
eprintln!(" {}" , e);
}
Ok(())
}
# #[allow(dead_code)]
# mod chainerror {
# use std::error::Error;
# use std::fmt::{Debug, Display, Formatter, Result};
# use std::result::Result as StdResult;
#
# pub struct ChainError< T> {
# #[cfg(not(feature = " no-fileline" ))]
# occurrence: Option< (u32, & 'static str)> ,
# kind: T,
# error_cause: Option< Box< dyn Error + 'static> > ,
# }
#
# pub type ChainResult< O, E> = StdResult< O, ChainError< E> > ;
#
# impl< T: 'static + Display + Debug> ChainError< T> {
# #[cfg(not(feature = " no-fileline" ))]
# 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" )]
# pub fn new(
# kind: T,
# error_cause: Option< Box< dyn Error + 'static> > ,
# _occurrence: Option< (u32, & 'static str)> ,
# ) -> Self {
# Self { kind, error_cause }
# }
#
# pub fn root_cause(& self) -> Option< & (dyn Error + 'static)> {
# let mut cause = self as & (dyn Error + 'static);
# while let Some(c) = cause.source() {
# cause = c;
# }
# Some(cause)
# }
#
# pub fn find_cause< U: Error + 'static> (& self) -> Option< & U> {
# let mut cause = self as & (dyn Error + 'static);
# loop {
# if cause.is::< U> () {
# return cause.downcast_ref::< U> ();
# }
#
# match cause.source() {
# Some(c) => cause = c,
# None => return None,
# }
# }
# }
#
# pub fn find_chain_cause< U: Error + 'static> (& self) -> Option< & ChainError< U> > {
# let mut cause = self as & (dyn Error + 'static);
# loop {
# if cause.is::< ChainError< U> > () {
# return cause.downcast_ref::< ChainError< U> > ();
# }
#
# match cause.source() {
# Some(c) => cause = c,
# None => return None,
# }
# }
# }
#
# pub fn kind< 'a> (& 'a self) -> & 'a T {
# & self.kind
# }
# }
#
# pub trait ChainErrorDown {
# fn is_chain< T: 'static + Display + Debug> (& self) -> bool;
# fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > ;
# fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > ;
# }
#
# use std::any::TypeId;
#
# 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> () {
# unsafe { Some(& *(self as *const dyn Error as *const & ChainError< T> )) }
# } else {
# None
# }
# }
#
# fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > {
# if self.is_chain::< T> () {
# unsafe { Some(& mut *(self as *mut dyn Error as *mut & mut ChainError< T> )) }
# } 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)> {
# if let Some(ref e) = self.error_cause {
# Some(e.as_ref())
# } else {
# None
# }
# }
# }
#
# impl< T: 'static + Display + Debug> Error for & ChainError< T> {
# fn source(& self) -> Option< & (dyn Error + 'static)> {
# if let Some(ref e) = self.error_cause {
# Some(e.as_ref())
# } else {
# None
# }
# }
# }
#
# impl< T: 'static + Display + Debug> Error for & mut ChainError< T> {
# fn source(& self) -> Option< & (dyn Error + 'static)> {
# if let Some(ref e) = self.error_cause {
# Some(e.as_ref())
# } else {
# None
# }
# }
# }
#
# 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)?;
# }
# }
#
# Debug::fmt(& self.kind, f)?;
#
# #[cfg(not(feature = " no-debug-cause" ))]
# {
# if let Some(e) = self.source() {
# writeln!(f, " \nCaused by:" )?;
# Debug::fmt(& e, f)?;
# }
# }
# Ok(())
# }
# }
#
# #[macro_export]
# macro_rules! cherr {
# ( $k:expr ) => {
# ChainError::< _> ::new($k, None, Some((line!(), file!())))
# };
# ( $e:expr, $k:expr ) => {
# ChainError::< _> ::new($k, Some(Box::from($e)), Some((line!(), file!())))
# };
# }
#
# #[macro_export]
# macro_rules! mstrerr {
# ( $t:ident, $v:expr $(, $more:expr)* ) => {
# |e| cherr!(e, $t (format!($v, $( $more , )* )))
# };
# ( $t:path, $v:expr $(, $more:expr)* ) => {
# |e| cherr!(e, $t (format!($v, $( $more , )* )))
# };
# ( $v:expr $(, $more:expr)* ) => {
# |e| cherr!(e, format!($v, $( $more , )* ))
# };
# }
#
# #[macro_export]
# macro_rules! derive_str_cherr {
# ($e:ident) => {
# struct $e(String);
# 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 {}
# };
# }
#
# #[macro_export]
# macro_rules! try_cherr_ref {
# ( $e:expr, $t:ident ) => {
# $e.downcast_ref::< ChainError< $t> > ()
# };
# ( $e:expr, $t:path ) => {
# $e.downcast_ref::< ChainError< $t> > ()
# };
# }
#
# #[macro_export]
# macro_rules! try_cherr_mut {
# ( $e:expr, $t:ident ) => {
# $e.downcast_mut::< ChainError< $t> > ()
# };
# ( $e:expr, $t:path ) => {
# $e.downcast_mut::< ChainError< $t> > ()
# };
# }
# }
< / code > < / pre > < / pre >
2018-12-20 16:02:24 +01:00
< p > Note, that we changed the output of the error in < code > main()< / code > from < code > Debug< / code > to < code > Display< / code > , so we don't see
the error backtrace with filename and line number.< / p >
< p > To enable the < code > Display< / code > backtrace, you have to enable the feature < code > display-cause< / code > for < code > chainerror< / code > .< / p >
< a class = "header" href = "#downcast-the-errors" id = "downcast-the-errors" > < h2 > Downcast the Errors< / h2 > < / a >
< p > [TBD]< / p >
2018-12-20 14:55:19 +01:00
< pre > < pre class = "playpen" > < code class = "language-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() -> Result< (), Box< Error> > {
if let Err(e) = func1() {
eprintln!(" Error: {}" , e);
let mut s = e.as_ref();
while let Some(c) = s.source() {
if let Some(ioerror) = c.downcast_ref::< io::Error> () {
eprintln!(" caused by: std::io::Error: {}" , ioerror);
match ioerror.kind() {
io::ErrorKind::NotFound => eprintln!(" of kind: std::io::ErrorKind::NotFound" ),
_ => {}
}
} else {
eprintln!(" caused by: {}" , c);
}
s = c;
}
}
Ok(())
}
# #[allow(dead_code)]
# mod chainerror {
# use std::error::Error;
# use std::fmt::{Debug, Display, Formatter, Result};
# use std::result::Result as StdResult;
#
# pub struct ChainError< T> {
# #[cfg(not(feature = " no-fileline" ))]
# occurrence: Option< (u32, & 'static str)> ,
# kind: T,
# error_cause: Option< Box< dyn Error + 'static> > ,
# }
#
# pub type ChainResult< O, E> = StdResult< O, ChainError< E> > ;
#
# impl< T: 'static + Display + Debug> ChainError< T> {
# #[cfg(not(feature = " no-fileline" ))]
# 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" )]
# pub fn new(
# kind: T,
# error_cause: Option< Box< dyn Error + 'static> > ,
# _occurrence: Option< (u32, & 'static str)> ,
# ) -> Self {
# Self { kind, error_cause }
# }
#
# pub fn root_cause(& self) -> Option< & (dyn Error + 'static)> {
# let mut cause = self as & (dyn Error + 'static);
# while let Some(c) = cause.source() {
# cause = c;
# }
# Some(cause)
# }
#
# pub fn find_cause< U: Error + 'static> (& self) -> Option< & U> {
# let mut cause = self as & (dyn Error + 'static);
# loop {
# if cause.is::< U> () {
# return cause.downcast_ref::< U> ();
# }
#
# match cause.source() {
# Some(c) => cause = c,
# None => return None,
# }
# }
# }
#
# pub fn find_chain_cause< U: Error + 'static> (& self) -> Option< & ChainError< U> > {
# let mut cause = self as & (dyn Error + 'static);
# loop {
# if cause.is::< ChainError< U> > () {
# return cause.downcast_ref::< ChainError< U> > ();
# }
#
# match cause.source() {
# Some(c) => cause = c,
# None => return None,
# }
# }
# }
#
# pub fn kind< 'a> (& 'a self) -> & 'a T {
# & self.kind
# }
# }
#
# pub trait ChainErrorDown {
# fn is_chain< T: 'static + Display + Debug> (& self) -> bool;
# fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > ;
# fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > ;
# }
#
# use std::any::TypeId;
#
# 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> () {
# unsafe { Some(& *(self as *const dyn Error as *const & ChainError< T> )) }
# } else {
# None
# }
# }
#
# fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > {
# if self.is_chain::< T> () {
# unsafe { Some(& mut *(self as *mut dyn Error as *mut & mut ChainError< T> )) }
# } 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)> {
# if let Some(ref e) = self.error_cause {
# Some(e.as_ref())
# } else {
# None
# }
# }
# }
#
# impl< T: 'static + Display + Debug> Error for & ChainError< T> {
# fn source(& self) -> Option< & (dyn Error + 'static)> {
# if let Some(ref e) = self.error_cause {
# Some(e.as_ref())
# } else {
# None
# }
# }
# }
#
# impl< T: 'static + Display + Debug> Error for & mut ChainError< T> {
# fn source(& self) -> Option< & (dyn Error + 'static)> {
# if let Some(ref e) = self.error_cause {
# Some(e.as_ref())
# } else {
# None
# }
# }
# }
#
# 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)?;
# }
# }
#
# Debug::fmt(& self.kind, f)?;
#
# #[cfg(not(feature = " no-debug-cause" ))]
# {
# if let Some(e) = self.source() {
# writeln!(f, " \nCaused by:" )?;
# Debug::fmt(& e, f)?;
# }
# }
# Ok(())
# }
# }
#
# #[macro_export]
# macro_rules! cherr {
# ( $k:expr ) => {
# ChainError::< _> ::new($k, None, Some((line!(), file!())))
# };
# ( $e:expr, $k:expr ) => {
# ChainError::< _> ::new($k, Some(Box::from($e)), Some((line!(), file!())))
# };
# }
#
# #[macro_export]
# macro_rules! mstrerr {
# ( $t:ident, $v:expr $(, $more:expr)* ) => {
# |e| cherr!(e, $t (format!($v, $( $more , )* )))
# };
# ( $t:path, $v:expr $(, $more:expr)* ) => {
# |e| cherr!(e, $t (format!($v, $( $more , )* )))
# };
# ( $v:expr $(, $more:expr)* ) => {
# |e| cherr!(e, format!($v, $( $more , )* ))
# };
# }
#
# #[macro_export]
# macro_rules! derive_str_cherr {
# ($e:ident) => {
# struct $e(String);
# 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 {}
# };
# }
#
# #[macro_export]
# macro_rules! try_cherr_ref {
# ( $e:expr, $t:ident ) => {
# $e.downcast_ref::< ChainError< $t> > ()
# };
# ( $e:expr, $t:path ) => {
# $e.downcast_ref::< ChainError< $t> > ()
# };
# }
#
# #[macro_export]
# macro_rules! try_cherr_mut {
# ( $e:expr, $t:ident ) => {
# $e.downcast_mut::< ChainError< $t> > ()
# };
# ( $e:expr, $t:path ) => {
# $e.downcast_mut::< ChainError< $t> > ()
# };
# }
# }
< / code > < / pre > < / pre >
2018-12-20 16:02:24 +01:00
< a class = "header" href = "#the-root-cause-of-all-errors" id = "the-root-cause-of-all-errors" > < h2 > The root cause of all Errors< / h2 > < / a >
< p > [TBD]< / p >
2018-12-20 14:55:19 +01:00
< pre > < pre class = "playpen" > < code class = "language-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() -> Result< (), Box< Error> > {
if let Err(e) = func1() {
eprintln!(" Error: {}" , e);
if let Some(s) = e.downcast_chain_ref::< String> () {
if let Some(ioerror) = s.find_cause::< io::Error> () {
eprintln!(" caused by: std::io::Error: {}" , ioerror);
match ioerror.kind() {
io::ErrorKind::NotFound => eprintln!(" of kind: std::io::ErrorKind::NotFound" ),
_ => {}
}
}
if let Some(e) = s.root_cause() {
let ioerror = e.downcast_ref::< io::Error> ().unwrap();
eprintln!(" The root cause was: std::io::Error: {:#?}" , ioerror);
}
}
}
Ok(())
}
# #[allow(dead_code)]
# mod chainerror {
# use std::error::Error;
# use std::fmt::{Debug, Display, Formatter, Result};
# use std::result::Result as StdResult;
#
# pub struct ChainError< T> {
# #[cfg(not(feature = " no-fileline" ))]
# occurrence: Option< (u32, & 'static str)> ,
# kind: T,
# error_cause: Option< Box< dyn Error + 'static> > ,
# }
#
# pub type ChainResult< O, E> = StdResult< O, ChainError< E> > ;
#
# impl< T: 'static + Display + Debug> ChainError< T> {
# #[cfg(not(feature = " no-fileline" ))]
# 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" )]
# pub fn new(
# kind: T,
# error_cause: Option< Box< dyn Error + 'static> > ,
# _occurrence: Option< (u32, & 'static str)> ,
# ) -> Self {
# Self { kind, error_cause }
# }
#
# pub fn root_cause(& self) -> Option< & (dyn Error + 'static)> {
# let mut cause = self as & (dyn Error + 'static);
# while let Some(c) = cause.source() {
# cause = c;
# }
# Some(cause)
# }
#
# pub fn find_cause< U: Error + 'static> (& self) -> Option< & U> {
# let mut cause = self as & (dyn Error + 'static);
# loop {
# if cause.is::< U> () {
# return cause.downcast_ref::< U> ();
# }
#
# match cause.source() {
# Some(c) => cause = c,
# None => return None,
# }
# }
# }
#
# pub fn find_chain_cause< U: Error + 'static> (& self) -> Option< & ChainError< U> > {
# let mut cause = self as & (dyn Error + 'static);
# loop {
# if cause.is::< ChainError< U> > () {
# return cause.downcast_ref::< ChainError< U> > ();
# }
#
# match cause.source() {
# Some(c) => cause = c,
# None => return None,
# }
# }
# }
#
# pub fn kind< 'a> (& 'a self) -> & 'a T {
# & self.kind
# }
# }
#
# pub trait ChainErrorDown {
# fn is_chain< T: 'static + Display + Debug> (& self) -> bool;
# fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > ;
# fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > ;
# }
#
# use std::any::TypeId;
#
# 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> () {
# unsafe { Some(& *(self as *const dyn Error as *const & ChainError< T> )) }
# } else {
# None
# }
# }
#
# fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > {
# if self.is_chain::< T> () {
# unsafe { Some(& mut *(self as *mut dyn Error as *mut & mut ChainError< T> )) }
# } 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)> {
# if let Some(ref e) = self.error_cause {
# Some(e.as_ref())
# } else {
# None
# }
# }
# }
#
# impl< T: 'static + Display + Debug> Error for & ChainError< T> {
# fn source(& self) -> Option< & (dyn Error + 'static)> {
# if let Some(ref e) = self.error_cause {
# Some(e.as_ref())
# } else {
# None
# }
# }
# }
#
# impl< T: 'static + Display + Debug> Error for & mut ChainError< T> {
# fn source(& self) -> Option< & (dyn Error + 'static)> {
# if let Some(ref e) = self.error_cause {
# Some(e.as_ref())
# } else {
# None
# }
# }
# }
#
# 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)?;
# }
# }
#
# Debug::fmt(& self.kind, f)?;
#
# #[cfg(not(feature = " no-debug-cause" ))]
# {
# if let Some(e) = self.source() {
# writeln!(f, " \nCaused by:" )?;
# Debug::fmt(& e, f)?;
# }
# }
# Ok(())
# }
# }
#
# #[macro_export]
# macro_rules! cherr {
# ( $k:expr ) => {
# ChainError::< _> ::new($k, None, Some((line!(), file!())))
# };
# ( $e:expr, $k:expr ) => {
# ChainError::< _> ::new($k, Some(Box::from($e)), Some((line!(), file!())))
# };
# }
#
# #[macro_export]
# macro_rules! mstrerr {
# ( $t:ident, $v:expr $(, $more:expr)* ) => {
# |e| cherr!(e, $t (format!($v, $( $more , )* )))
# };
# ( $t:path, $v:expr $(, $more:expr)* ) => {
# |e| cherr!(e, $t (format!($v, $( $more , )* )))
# };
# ( $v:expr $(, $more:expr)* ) => {
# |e| cherr!(e, format!($v, $( $more , )* ))
# };
# }
#
# #[macro_export]
# macro_rules! derive_str_cherr {
# ($e:ident) => {
# struct $e(String);
# 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 {}
# };
# }
#
# #[macro_export]
# macro_rules! try_cherr_ref {
# ( $e:expr, $t:ident ) => {
# $e.downcast_ref::< ChainError< $t> > ()
# };
# ( $e:expr, $t:path ) => {
# $e.downcast_ref::< ChainError< $t> > ()
# };
# }
#
# #[macro_export]
# macro_rules! try_cherr_mut {
# ( $e:expr, $t:ident ) => {
# $e.downcast_mut::< ChainError< $t> > ()
# };
# ( $e:expr, $t:path ) => {
# $e.downcast_mut::< ChainError< $t> > ()
# };
# }
# }
< / code > < / pre > < / pre >
2018-12-20 16:02:24 +01:00
< a class = "header" href = "#finding-an-error-cause" id = "finding-an-error-cause" > < h2 > Finding an Error cause< / h2 > < / a >
< p > [TBD]< / p >
2018-12-20 14:55:19 +01:00
< pre > < pre class = "playpen" > < code class = "language-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() -> Result< (), Box< Error> > {
if let Err(e) = func1() {
if let Some(f1err) = e.downcast_chain_ref::< Func1Error> () {
eprintln!(" Func1Error: {}" , f1err);
if let Some(f2err) = f1err.find_cause::< ChainError< Func2Error> > () {
eprintln!(" Func2Error: {}" , f2err);
}
if let Some(f2err) = f1err.find_chain_cause::< Func2Error> () {
eprintln!(" Debug Func2Error:\n{:?}" , f2err);
}
}
}
Ok(())
}
# #[allow(dead_code)]
# mod chainerror {
# use std::error::Error;
# use std::fmt::{Debug, Display, Formatter, Result};
# use std::result::Result as StdResult;
#
# pub struct ChainError< T> {
# #[cfg(not(feature = " no-fileline" ))]
# occurrence: Option< (u32, & 'static str)> ,
# kind: T,
# error_cause: Option< Box< dyn Error + 'static> > ,
# }
#
# pub type ChainResult< O, E> = StdResult< O, ChainError< E> > ;
#
# impl< T: 'static + Display + Debug> ChainError< T> {
# #[cfg(not(feature = " no-fileline" ))]
# 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" )]
# pub fn new(
# kind: T,
# error_cause: Option< Box< dyn Error + 'static> > ,
# _occurrence: Option< (u32, & 'static str)> ,
# ) -> Self {
# Self { kind, error_cause }
# }
#
# pub fn root_cause(& self) -> Option< & (dyn Error + 'static)> {
# let mut cause = self as & (dyn Error + 'static);
# while let Some(c) = cause.source() {
# cause = c;
# }
# Some(cause)
# }
#
# pub fn find_cause< U: Error + 'static> (& self) -> Option< & U> {
# let mut cause = self as & (dyn Error + 'static);
# loop {
# if cause.is::< U> () {
# return cause.downcast_ref::< U> ();
# }
#
# match cause.source() {
# Some(c) => cause = c,
# None => return None,
# }
# }
# }
#
# pub fn find_chain_cause< U: Error + 'static> (& self) -> Option< & ChainError< U> > {
# let mut cause = self as & (dyn Error + 'static);
# loop {
# if cause.is::< ChainError< U> > () {
# return cause.downcast_ref::< ChainError< U> > ();
# }
#
# match cause.source() {
# Some(c) => cause = c,
# None => return None,
# }
# }
# }
#
# pub fn kind< 'a> (& 'a self) -> & 'a T {
# & self.kind
# }
# }
#
# pub trait ChainErrorDown {
# fn is_chain< T: 'static + Display + Debug> (& self) -> bool;
# fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > ;
# fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > ;
# }
#
# use std::any::TypeId;
#
# 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> () {
# unsafe { Some(& *(self as *const dyn Error as *const & ChainError< T> )) }
# } else {
# None
# }
# }
#
# fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > {
# if self.is_chain::< T> () {
# unsafe { Some(& mut *(self as *mut dyn Error as *mut & mut ChainError< T> )) }
# } 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)> {
# if let Some(ref e) = self.error_cause {
# Some(e.as_ref())
# } else {
# None
# }
# }
# }
#
# impl< T: 'static + Display + Debug> Error for & ChainError< T> {
# fn source(& self) -> Option< & (dyn Error + 'static)> {
# if let Some(ref e) = self.error_cause {
# Some(e.as_ref())
# } else {
# None
# }
# }
# }
#
# impl< T: 'static + Display + Debug> Error for & mut ChainError< T> {
# fn source(& self) -> Option< & (dyn Error + 'static)> {
# if let Some(ref e) = self.error_cause {
# Some(e.as_ref())
# } else {
# None
# }
# }
# }
#
# 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)?;
# }
# }
#
# Debug::fmt(& self.kind, f)?;
#
# #[cfg(not(feature = " no-debug-cause" ))]
# {
# if let Some(e) = self.source() {
# writeln!(f, " \nCaused by:" )?;
# Debug::fmt(& e, f)?;
# }
# }
# Ok(())
# }
# }
#
# #[macro_export]
# macro_rules! cherr {
# ( $k:expr ) => {
# ChainError::< _> ::new($k, None, Some((line!(), file!())))
# };
# ( $e:expr, $k:expr ) => {
# ChainError::< _> ::new($k, Some(Box::from($e)), Some((line!(), file!())))
# };
# }
#
# #[macro_export]
# macro_rules! mstrerr {
# ( $t:ident, $v:expr $(, $more:expr)* ) => {
# |e| cherr!(e, $t (format!($v, $( $more , )* )))
# };
# ( $t:path, $v:expr $(, $more:expr)* ) => {
# |e| cherr!(e, $t (format!($v, $( $more , )* )))
# };
# ( $v:expr $(, $more:expr)* ) => {
# |e| cherr!(e, format!($v, $( $more , )* ))
# };
# }
#
# #[macro_export]
# macro_rules! derive_str_cherr {
# ($e:ident) => {
# struct $e(String);
# 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 {}
# };
# }
#
# #[macro_export]
# macro_rules! try_cherr_ref {
# ( $e:expr, $t:ident ) => {
# $e.downcast_ref::< ChainError< $t> > ()
# };
# ( $e:expr, $t:path ) => {
# $e.downcast_ref::< ChainError< $t> > ()
# };
# }
#
# #[macro_export]
# macro_rules! try_cherr_mut {
# ( $e:expr, $t:ident ) => {
# $e.downcast_mut::< ChainError< $t> > ()
# };
# ( $e:expr, $t:path ) => {
# $e.downcast_mut::< ChainError< $t> > ()
# };
# }
# }
< / code > < / pre > < / pre >
2018-12-20 16:02:24 +01:00
< a class = "header" href = "#selective-error-handling" id = "selective-error-handling" > < h2 > Selective Error Handling< / h2 > < / a >
< p > [TBD]< / p >
2018-12-20 14:55:19 +01:00
< pre > < pre class = "playpen" > < code class = "language-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!(Func1ErrorFunc2);
derive_str_cherr!(Func1ErrorIO);
fn func1() -> Result< (), Box< Error> > {
func2().map_err(mstrerr!(Func1ErrorFunc2, " func1 error calling func2" ))?;
let filename = " bar.txt" ;
do_some_io().map_err(mstrerr!(Func1ErrorIO, " Error reading '{}'" , filename))?;
Ok(())
}
fn main() -> Result< (), Box< Error> > {
if let Err(e) = func1() {
if let Some(s) = e.downcast_ref::< ChainError< Func1ErrorIO> > () {
eprintln!(" Func1ErrorIO:\n{:?}" , s);
}
if let Some(s) = try_cherr_ref!(e, Func1ErrorFunc2) {
eprintln!(" Func1ErrorFunc2:\n{:?}" , s);
}
}
Ok(())
}
# #[allow(dead_code)]
# mod chainerror {
# use std::error::Error;
# use std::fmt::{Debug, Display, Formatter, Result};
# use std::result::Result as StdResult;
#
# pub struct ChainError< T> {
# #[cfg(not(feature = " no-fileline" ))]
# occurrence: Option< (u32, & 'static str)> ,
# kind: T,
# error_cause: Option< Box< dyn Error + 'static> > ,
# }
#
# pub type ChainResult< O, E> = StdResult< O, ChainError< E> > ;
#
# impl< T: 'static + Display + Debug> ChainError< T> {
# #[cfg(not(feature = " no-fileline" ))]
# 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" )]
# pub fn new(
# kind: T,
# error_cause: Option< Box< dyn Error + 'static> > ,
# _occurrence: Option< (u32, & 'static str)> ,
# ) -> Self {
# Self { kind, error_cause }
# }
#
# pub fn root_cause(& self) -> Option< & (dyn Error + 'static)> {
# let mut cause = self as & (dyn Error + 'static);
# while let Some(c) = cause.source() {
# cause = c;
# }
# Some(cause)
# }
#
# pub fn find_cause< U: Error + 'static> (& self) -> Option< & U> {
# let mut cause = self as & (dyn Error + 'static);
# loop {
# if cause.is::< U> () {
# return cause.downcast_ref::< U> ();
# }
#
# match cause.source() {
# Some(c) => cause = c,
# None => return None,
# }
# }
# }
#
# pub fn find_chain_cause< U: Error + 'static> (& self) -> Option< & ChainError< U> > {
# let mut cause = self as & (dyn Error + 'static);
# loop {
# if cause.is::< ChainError< U> > () {
# return cause.downcast_ref::< ChainError< U> > ();
# }
#
# match cause.source() {
# Some(c) => cause = c,
# None => return None,
# }
# }
# }
#
# pub fn kind< 'a> (& 'a self) -> & 'a T {
# & self.kind
# }
# }
#
# pub trait ChainErrorDown {
# fn is_chain< T: 'static + Display + Debug> (& self) -> bool;
# fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > ;
# fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > ;
# }
#
# use std::any::TypeId;
#
# 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> () {
# unsafe { Some(& *(self as *const dyn Error as *const & ChainError< T> )) }
# } else {
# None
# }
# }
#
# fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > {
# if self.is_chain::< T> () {
# unsafe { Some(& mut *(self as *mut dyn Error as *mut & mut ChainError< T> )) }
# } 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)> {
# if let Some(ref e) = self.error_cause {
# Some(e.as_ref())
# } else {
# None
# }
# }
# }
#
# impl< T: 'static + Display + Debug> Error for & ChainError< T> {
# fn source(& self) -> Option< & (dyn Error + 'static)> {
# if let Some(ref e) = self.error_cause {
# Some(e.as_ref())
# } else {
# None
# }
# }
# }
#
# impl< T: 'static + Display + Debug> Error for & mut ChainError< T> {
# fn source(& self) -> Option< & (dyn Error + 'static)> {
# if let Some(ref e) = self.error_cause {
# Some(e.as_ref())
# } else {
# None
# }
# }
# }
#
# 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)?;
# }
# }
#
# Debug::fmt(& self.kind, f)?;
#
# #[cfg(not(feature = " no-debug-cause" ))]
# {
# if let Some(e) = self.source() {
# writeln!(f, " \nCaused by:" )?;
# Debug::fmt(& e, f)?;
# }
# }
# Ok(())
# }
# }
#
# #[macro_export]
# macro_rules! cherr {
# ( $k:expr ) => {
# ChainError::< _> ::new($k, None, Some((line!(), file!())))
# };
# ( $e:expr, $k:expr ) => {
# ChainError::< _> ::new($k, Some(Box::from($e)), Some((line!(), file!())))
# };
# }
#
# #[macro_export]
# macro_rules! mstrerr {
# ( $t:ident, $v:expr $(, $more:expr)* ) => {
# |e| cherr!(e, $t (format!($v, $( $more , )* )))
# };
# ( $t:path, $v:expr $(, $more:expr)* ) => {
# |e| cherr!(e, $t (format!($v, $( $more , )* )))
# };
# ( $v:expr $(, $more:expr)* ) => {
# |e| cherr!(e, format!($v, $( $more , )* ))
# };
# }
#
# #[macro_export]
# macro_rules! derive_str_cherr {
# ($e:ident) => {
# struct $e(String);
# 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 {}
# };
# }
#
# #[macro_export]
# macro_rules! try_cherr_ref {
# ( $e:expr, $t:ident ) => {
# $e.downcast_ref::< ChainError< $t> > ()
# };
# ( $e:expr, $t:path ) => {
# $e.downcast_ref::< ChainError< $t> > ()
# };
# }
#
# #[macro_export]
# macro_rules! try_cherr_mut {
# ( $e:expr, $t:ident ) => {
# $e.downcast_mut::< ChainError< $t> > ()
# };
# ( $e:expr, $t:path ) => {
# $e.downcast_mut::< ChainError< $t> > ()
# };
# }
# }
< / code > < / pre > < / pre >
2018-12-20 16:02:24 +01:00
< a class = "header" href = "#errorkind-to-the-rescue" id = "errorkind-to-the-rescue" > < h2 > ErrorKind to the rescue< / h2 > < / a >
< p > [TBD]< / p >
2018-12-20 14:55:19 +01:00
< pre > < pre class = "playpen" > < code class = "language-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 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),
}
}
}
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() -> Result< (), Box< Error> > {
if let Err(e) = func1() {
match e.kind() {
Func1Error::Func2 => eprintln!(" Main Error Report: func1 error calling func2" ),
Func1Error::IO(filename) => {
eprintln!(" Main Error Report: func1 error reading '{}'" , filename)
}
}
if let Some(e) = e.find_chain_cause::< Func2Error> () {
eprintln!(" Error reported by Func2Error: {}" , e)
}
eprintln!(" \nDebug Error:\n{:?}" , e);
}
Ok(())
}
# #[allow(dead_code)]
# mod chainerror {
# use std::error::Error;
# use std::fmt::{Debug, Display, Formatter, Result};
# use std::result::Result as StdResult;
#
# pub struct ChainError< T> {
# #[cfg(not(feature = " no-fileline" ))]
# occurrence: Option< (u32, & 'static str)> ,
# kind: T,
# error_cause: Option< Box< dyn Error + 'static> > ,
# }
#
# pub type ChainResult< O, E> = StdResult< O, ChainError< E> > ;
#
# impl< T: 'static + Display + Debug> ChainError< T> {
# #[cfg(not(feature = " no-fileline" ))]
# 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" )]
# pub fn new(
# kind: T,
# error_cause: Option< Box< dyn Error + 'static> > ,
# _occurrence: Option< (u32, & 'static str)> ,
# ) -> Self {
# Self { kind, error_cause }
# }
#
# pub fn root_cause(& self) -> Option< & (dyn Error + 'static)> {
# let mut cause = self as & (dyn Error + 'static);
# while let Some(c) = cause.source() {
# cause = c;
# }
# Some(cause)
# }
#
# pub fn find_cause< U: Error + 'static> (& self) -> Option< & U> {
# let mut cause = self as & (dyn Error + 'static);
# loop {
# if cause.is::< U> () {
# return cause.downcast_ref::< U> ();
# }
#
# match cause.source() {
# Some(c) => cause = c,
# None => return None,
# }
# }
# }
#
# pub fn find_chain_cause< U: Error + 'static> (& self) -> Option< & ChainError< U> > {
# let mut cause = self as & (dyn Error + 'static);
# loop {
# if cause.is::< ChainError< U> > () {
# return cause.downcast_ref::< ChainError< U> > ();
# }
#
# match cause.source() {
# Some(c) => cause = c,
# None => return None,
# }
# }
# }
#
# pub fn kind< 'a> (& 'a self) -> & 'a T {
# & self.kind
# }
# }
#
# pub trait ChainErrorDown {
# fn is_chain< T: 'static + Display + Debug> (& self) -> bool;
# fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > ;
# fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > ;
# }
#
# use std::any::TypeId;
#
# 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> () {
# unsafe { Some(& *(self as *const dyn Error as *const & ChainError< T> )) }
# } else {
# None
# }
# }
#
# fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > {
# if self.is_chain::< T> () {
# unsafe { Some(& mut *(self as *mut dyn Error as *mut & mut ChainError< T> )) }
# } 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)> {
# if let Some(ref e) = self.error_cause {
# Some(e.as_ref())
# } else {
# None
# }
# }
# }
#
# impl< T: 'static + Display + Debug> Error for & ChainError< T> {
# fn source(& self) -> Option< & (dyn Error + 'static)> {
# if let Some(ref e) = self.error_cause {
# Some(e.as_ref())
# } else {
# None
# }
# }
# }
#
# impl< T: 'static + Display + Debug> Error for & mut ChainError< T> {
# fn source(& self) -> Option< & (dyn Error + 'static)> {
# if let Some(ref e) = self.error_cause {
# Some(e.as_ref())
# } else {
# None
# }
# }
# }
#
# 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)?;
# }
# }
#
# Debug::fmt(& self.kind, f)?;
#
# #[cfg(not(feature = " no-debug-cause" ))]
# {
# if let Some(e) = self.source() {
# writeln!(f, " \nCaused by:" )?;
# Debug::fmt(& e, f)?;
# }
# }
# Ok(())
# }
# }
#
# #[macro_export]
# macro_rules! cherr {
# ( $k:expr ) => {
# ChainError::< _> ::new($k, None, Some((line!(), file!())))
# };
# ( $e:expr, $k:expr ) => {
# ChainError::< _> ::new($k, Some(Box::from($e)), Some((line!(), file!())))
# };
# }
#
# #[macro_export]
# macro_rules! mstrerr {
# ( $t:ident, $v:expr $(, $more:expr)* ) => {
# |e| cherr!(e, $t (format!($v, $( $more , )* )))
# };
# ( $t:path, $v:expr $(, $more:expr)* ) => {
# |e| cherr!(e, $t (format!($v, $( $more , )* )))
# };
# ( $v:expr $(, $more:expr)* ) => {
# |e| cherr!(e, format!($v, $( $more , )* ))
# };
# }
#
# #[macro_export]
# macro_rules! derive_str_cherr {
# ($e:ident) => {
# struct $e(String);
# 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 {}
# };
# }
#
# #[macro_export]
# macro_rules! try_cherr_ref {
# ( $e:expr, $t:ident ) => {
# $e.downcast_ref::< ChainError< $t> > ()
# };
# ( $e:expr, $t:path ) => {
# $e.downcast_ref::< ChainError< $t> > ()
# };
# }
#
# #[macro_export]
# macro_rules! try_cherr_mut {
# ( $e:expr, $t:ident ) => {
# $e.downcast_mut::< ChainError< $t> > ()
# };
# ( $e:expr, $t:path ) => {
# $e.downcast_mut::< ChainError< $t> > ()
# };
# }
# }
< / code > < / pre > < / pre >
2018-12-20 16:02:24 +01:00
< a class = "header" href = "#debug-for-the-errorkind" id = "debug-for-the-errorkind" > < h2 > Debug for the ErrorKind< / h2 > < / a >
< p > [TBD]< / p >
2018-12-20 14:55:19 +01:00
< pre > < pre class = "playpen" > < code class = "language-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(())
}
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() -> Result< (), Box< Error> > {
if let Err(e) = func1() {
match e.kind() {
Func1Error::Func2 => eprintln!(" Main Error Report: func1 error calling func2" ),
Func1Error::IO(filename) => {
eprintln!(" Main Error Report: func1 error reading '{}'" , filename)
}
}
if let Some(e) = e.find_chain_cause::< Func2Error> () {
eprintln!(" Error reported by Func2Error: {}" , e)
}
eprintln!(" \nDebug Error:\n{:?}" , e);
}
Ok(())
}
# #[allow(dead_code)]
# mod chainerror {
# use std::error::Error;
# use std::fmt::{Debug, Display, Formatter, Result};
# use std::result::Result as StdResult;
#
# pub struct ChainError< T> {
# #[cfg(not(feature = " no-fileline" ))]
# occurrence: Option< (u32, & 'static str)> ,
# kind: T,
# error_cause: Option< Box< dyn Error + 'static> > ,
# }
#
# pub type ChainResult< O, E> = StdResult< O, ChainError< E> > ;
#
# impl< T: 'static + Display + Debug> ChainError< T> {
# #[cfg(not(feature = " no-fileline" ))]
# 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" )]
# pub fn new(
# kind: T,
# error_cause: Option< Box< dyn Error + 'static> > ,
# _occurrence: Option< (u32, & 'static str)> ,
# ) -> Self {
# Self { kind, error_cause }
# }
#
# pub fn root_cause(& self) -> Option< & (dyn Error + 'static)> {
# let mut cause = self as & (dyn Error + 'static);
# while let Some(c) = cause.source() {
# cause = c;
# }
# Some(cause)
# }
#
# pub fn find_cause< U: Error + 'static> (& self) -> Option< & U> {
# let mut cause = self as & (dyn Error + 'static);
# loop {
# if cause.is::< U> () {
# return cause.downcast_ref::< U> ();
# }
#
# match cause.source() {
# Some(c) => cause = c,
# None => return None,
# }
# }
# }
#
# pub fn find_chain_cause< U: Error + 'static> (& self) -> Option< & ChainError< U> > {
# let mut cause = self as & (dyn Error + 'static);
# loop {
# if cause.is::< ChainError< U> > () {
# return cause.downcast_ref::< ChainError< U> > ();
# }
#
# match cause.source() {
# Some(c) => cause = c,
# None => return None,
# }
# }
# }
#
# pub fn kind< 'a> (& 'a self) -> & 'a T {
# & self.kind
# }
# }
#
# pub trait ChainErrorDown {
# fn is_chain< T: 'static + Display + Debug> (& self) -> bool;
# fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > ;
# fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > ;
# }
#
# use std::any::TypeId;
#
# 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> () {
# unsafe { Some(& *(self as *const dyn Error as *const & ChainError< T> )) }
# } else {
# None
# }
# }
#
# fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > {
# if self.is_chain::< T> () {
# unsafe { Some(& mut *(self as *mut dyn Error as *mut & mut ChainError< T> )) }
# } 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)> {
# if let Some(ref e) = self.error_cause {
# Some(e.as_ref())
# } else {
# None
# }
# }
# }
#
# impl< T: 'static + Display + Debug> Error for & ChainError< T> {
# fn source(& self) -> Option< & (dyn Error + 'static)> {
# if let Some(ref e) = self.error_cause {
# Some(e.as_ref())
# } else {
# None
# }
# }
# }
#
# impl< T: 'static + Display + Debug> Error for & mut ChainError< T> {
# fn source(& self) -> Option< & (dyn Error + 'static)> {
# if let Some(ref e) = self.error_cause {
# Some(e.as_ref())
# } else {
# None
# }
# }
# }
#
# 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)?;
# }
# }
#
# Debug::fmt(& self.kind, f)?;
#
# #[cfg(not(feature = " no-debug-cause" ))]
# {
# if let Some(e) = self.source() {
# writeln!(f, " \nCaused by:" )?;
# Debug::fmt(& e, f)?;
# }
# }
# Ok(())
# }
# }
#
# #[macro_export]
# macro_rules! cherr {
# ( $k:expr ) => {
# ChainError::< _> ::new($k, None, Some((line!(), file!())))
# };
# ( $e:expr, $k:expr ) => {
# ChainError::< _> ::new($k, Some(Box::from($e)), Some((line!(), file!())))
# };
# }
#
# #[macro_export]
# macro_rules! mstrerr {
# ( $t:ident, $v:expr $(, $more:expr)* ) => {
# |e| cherr!(e, $t (format!($v, $( $more , )* )))
# };
# ( $t:path, $v:expr $(, $more:expr)* ) => {
# |e| cherr!(e, $t (format!($v, $( $more , )* )))
# };
# ( $v:expr $(, $more:expr)* ) => {
# |e| cherr!(e, format!($v, $( $more , )* ))
# };
# }
#
# #[macro_export]
# macro_rules! derive_str_cherr {
# ($e:ident) => {
# struct $e(String);
# 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 {}
# };
# }
#
# #[macro_export]
# macro_rules! try_cherr_ref {
# ( $e:expr, $t:ident ) => {
# $e.downcast_ref::< ChainError< $t> > ()
# };
# ( $e:expr, $t:path ) => {
# $e.downcast_ref::< ChainError< $t> > ()
# };
# }
#
# #[macro_export]
# macro_rules! try_cherr_mut {
# ( $e:expr, $t:ident ) => {
# $e.downcast_mut::< ChainError< $t> > ()
# };
# ( $e:expr, $t:path ) => {
# $e.downcast_mut::< ChainError< $t> > ()
# };
# }
# }
< / code > < / pre > < / pre >
< / main >
< nav class = "nav-wrapper" aria-label = "Page navigation" >
<!-- Mobile navigation buttons -->
< div style = "clear: both" > < / div >
< / nav >
< / div >
< / div >
< nav class = "nav-wide-wrapper" aria-label = "Page navigation" >
< / nav >
< / div >
< script src = "ace.js" type = "text/javascript" charset = "utf-8" > < / script >
< script src = "editor.js" type = "text/javascript" charset = "utf-8" > < / script >
< script src = "mode-rust.js" type = "text/javascript" charset = "utf-8" > < / script >
< script src = "theme-dawn.js" type = "text/javascript" charset = "utf-8" > < / script >
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< script src = "mark.min.js" type = "text/javascript" charset = "utf-8" > < / script >
< script src = "searcher.js" type = "text/javascript" charset = "utf-8" > < / script >
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window.addEventListener('load', function() {
window.setTimeout(window.print, 100);
});
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