pub trait Error: Debug + Display {
// Provided methods
fn source(&self) -> Option<&(dyn Error + 'static)> { ... }
fn description(&self) -> &str { ... }
fn cause(&self) -> Option<&dyn Error> { ... }
fn provide<'a>(&'a self, request: &mut Request<'a>) { ... }
}
Expand description
Error
is a trait representing the basic expectations for error values,
i.e., values of type E
in Result<T, E>
.
Errors must describe themselves through the Display
and Debug
traits. Error messages are typically concise lowercase sentences without
trailing punctuation:
let err = "NaN".parse::<u32>().unwrap_err();
assert_eq!(err.to_string(), "invalid digit found in string");
Errors may provide cause information. Error::source()
is generally
used when errors cross “abstraction boundaries”. If one module must report
an error that is caused by an error from a lower-level module, it can allow
accessing that error via Error::source()
. This makes it possible for the
high-level module to provide its own errors while also revealing some of the
implementation for debugging.
Provided Methods§
1.30.0 · Sourcefn source(&self) -> Option<&(dyn Error + 'static)>
fn source(&self) -> Option<&(dyn Error + 'static)>
Returns the lower-level source of this error, if any.
§Examples
use std::error::Error;
use std::fmt;
#[derive(Debug)]
struct SuperError {
source: SuperErrorSideKick,
}
impl fmt::Display for SuperError {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
write!(f, "SuperError is here!")
}
}
impl Error for SuperError {
fn source(&self) -> Option<&(dyn Error + 'static)> {
Some(&self.source)
}
}
#[derive(Debug)]
struct SuperErrorSideKick;
impl fmt::Display for SuperErrorSideKick {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
write!(f, "SuperErrorSideKick is here!")
}
}
impl Error for SuperErrorSideKick {}
fn get_super_error() -> Result<(), SuperError> {
Err(SuperError { source: SuperErrorSideKick })
}
fn main() {
match get_super_error() {
Err(e) => {
println!("Error: {e}");
println!("Caused by: {}", e.source().unwrap());
}
_ => println!("No error"),
}
}
1.0.0 · Sourcefn description(&self) -> &str
👎Deprecated since 1.42.0: use the Display impl or to_string()
fn description(&self) -> &str
if let Err(e) = "xc".parse::<u32>() {
// Print `e` itself, no need for description().
eprintln!("Error: {e}");
}
fn cause(&self) -> Option<&dyn Error>
Sourcefn provide<'a>(&'a self, request: &mut Request<'a>)
🔬This is a nightly-only experimental API. (error_generic_member_access
)
fn provide<'a>(&'a self, request: &mut Request<'a>)
error_generic_member_access
)Provides type-based access to context intended for error reports.
Used in conjunction with Request::provide_value
and Request::provide_ref
to extract
references to member variables from dyn Error
trait objects.
§Example
#![feature(error_generic_member_access)]
use core::fmt;
use core::error::{request_ref, Request};
#[derive(Debug)]
enum MyLittleTeaPot {
Empty,
}
#[derive(Debug)]
struct MyBacktrace {
// ...
}
impl MyBacktrace {
fn new() -> MyBacktrace {
// ...
}
}
#[derive(Debug)]
struct Error {
backtrace: MyBacktrace,
}
impl fmt::Display for Error {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
write!(f, "Example Error")
}
}
impl std::error::Error for Error {
fn provide<'a>(&'a self, request: &mut Request<'a>) {
request
.provide_ref::<MyBacktrace>(&self.backtrace);
}
}
fn main() {
let backtrace = MyBacktrace::new();
let error = Error { backtrace };
let dyn_error = &error as &dyn std::error::Error;
let backtrace_ref = request_ref::<MyBacktrace>(dyn_error).unwrap();
assert!(core::ptr::eq(&error.backtrace, backtrace_ref));
assert!(request_ref::<MyLittleTeaPot>(dyn_error).is_none());
}
Implementations§
Source§impl dyn Error
impl dyn Error
1.3.0 · Sourcepub fn is<T>(&self) -> boolwhere
T: Error + 'static,
pub fn is<T>(&self) -> boolwhere
T: Error + 'static,
Returns true
if the inner type is the same as T
.
1.3.0 · Sourcepub fn downcast_ref<T>(&self) -> Option<&T>where
T: Error + 'static,
pub fn downcast_ref<T>(&self) -> Option<&T>where
T: Error + 'static,
Returns some reference to the inner value if it is of type T
, or
None
if it isn’t.
1.3.0 · Sourcepub fn downcast_mut<T>(&mut self) -> Option<&mut T>where
T: Error + 'static,
pub fn downcast_mut<T>(&mut self) -> Option<&mut T>where
T: Error + 'static,
Returns some mutable reference to the inner value if it is of type T
, or
None
if it isn’t.
Source§impl dyn Error + Send
impl dyn Error + Send
1.3.0 · Sourcepub fn is<T>(&self) -> boolwhere
T: Error + 'static,
pub fn is<T>(&self) -> boolwhere
T: Error + 'static,
Forwards to the method defined on the type dyn Error
.
1.3.0 · Sourcepub fn downcast_ref<T>(&self) -> Option<&T>where
T: Error + 'static,
pub fn downcast_ref<T>(&self) -> Option<&T>where
T: Error + 'static,
Forwards to the method defined on the type dyn Error
.
1.3.0 · Sourcepub fn downcast_mut<T>(&mut self) -> Option<&mut T>where
T: Error + 'static,
pub fn downcast_mut<T>(&mut self) -> Option<&mut T>where
T: Error + 'static,
Forwards to the method defined on the type dyn Error
.
Source§impl dyn Error + Send + Sync
impl dyn Error + Send + Sync
1.3.0 · Sourcepub fn is<T>(&self) -> boolwhere
T: Error + 'static,
pub fn is<T>(&self) -> boolwhere
T: Error + 'static,
Forwards to the method defined on the type dyn Error
.
1.3.0 · Sourcepub fn downcast_ref<T>(&self) -> Option<&T>where
T: Error + 'static,
pub fn downcast_ref<T>(&self) -> Option<&T>where
T: Error + 'static,
Forwards to the method defined on the type dyn Error
.
1.3.0 · Sourcepub fn downcast_mut<T>(&mut self) -> Option<&mut T>where
T: Error + 'static,
pub fn downcast_mut<T>(&mut self) -> Option<&mut T>where
T: Error + 'static,
Forwards to the method defined on the type dyn Error
.
Source§impl dyn Error
impl dyn Error
Sourcepub fn sources(&self) -> Source<'_> ⓘ
🔬This is a nightly-only experimental API. (error_iter
)
pub fn sources(&self) -> Source<'_> ⓘ
error_iter
)Returns an iterator starting with the current error and continuing with
recursively calling Error::source
.
If you want to omit the current error and only use its sources,
use skip(1)
.
§Examples
#![feature(error_iter)]
use std::error::Error;
use std::fmt;
#[derive(Debug)]
struct A;
#[derive(Debug)]
struct B(Option<Box<dyn Error + 'static>>);
impl fmt::Display for A {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
write!(f, "A")
}
}
impl fmt::Display for B {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
write!(f, "B")
}
}
impl Error for A {}
impl Error for B {
fn source(&self) -> Option<&(dyn Error + 'static)> {
self.0.as_ref().map(|e| e.as_ref())
}
}
let b = B(Some(Box::new(A)));
// let err : Box<Error> = b.into(); // or
let err = &b as &(dyn Error);
let mut iter = err.sources();
assert_eq!("B".to_string(), iter.next().unwrap().to_string());
assert_eq!("A".to_string(), iter.next().unwrap().to_string());
assert!(iter.next().is_none());
assert!(iter.next().is_none());
Trait Implementations§
1.6.0 · Source§impl<'a> From<&str> for Box<dyn Error + 'a>
impl<'a> From<&str> for Box<dyn Error + 'a>
1.0.0 · Source§impl<'a> From<&str> for Box<dyn Error + Send + Sync + 'a>
impl<'a> From<&str> for Box<dyn Error + Send + Sync + 'a>
1.22.0 · Source§impl<'a, 'b> From<Cow<'b, str>> for Box<dyn Error + 'a>
impl<'a, 'b> From<Cow<'b, str>> for Box<dyn Error + 'a>
1.22.0 · Source§impl<'a, 'b> From<Cow<'b, str>> for Box<dyn Error + Send + Sync + 'a>
impl<'a, 'b> From<Cow<'b, str>> for Box<dyn Error + Send + Sync + 'a>
Source§fn from(err: Cow<'b, str>) -> Box<dyn Error + Send + Sync + 'a>
fn from(err: Cow<'b, str>) -> Box<dyn Error + Send + Sync + 'a>
Converts a Cow
into a box of dyn Error
+ Send
+ Sync
.
§Examples
use std::error::Error;
use std::mem;
use std::borrow::Cow;
let a_cow_str_error = Cow::from("a str error");
let a_boxed_error = Box::<dyn Error + Send + Sync>::from(a_cow_str_error);
assert!(
mem::size_of::<Box<dyn Error + Send + Sync>>() == mem::size_of_val(&a_boxed_error))
1.0.0 · Source§impl<'a, E> From<E> for Box<dyn Error + 'a>where
E: Error + 'a,
impl<'a, E> From<E> for Box<dyn Error + 'a>where
E: Error + 'a,
Source§fn from(err: E) -> Box<dyn Error + 'a>
fn from(err: E) -> Box<dyn Error + 'a>
Converts a type of Error
into a box of dyn Error
.
§Examples
use std::error::Error;
use std::fmt;
use std::mem;
#[derive(Debug)]
struct AnError;
impl fmt::Display for AnError {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
write!(f, "An error")
}
}
impl Error for AnError {}
let an_error = AnError;
assert!(0 == mem::size_of_val(&an_error));
let a_boxed_error = Box::<dyn Error>::from(an_error);
assert!(mem::size_of::<Box<dyn Error>>() == mem::size_of_val(&a_boxed_error))
1.0.0 · Source§impl<'a, E> From<E> for Box<dyn Error + Send + Sync + 'a>
impl<'a, E> From<E> for Box<dyn Error + Send + Sync + 'a>
Source§fn from(err: E) -> Box<dyn Error + Send + Sync + 'a>
fn from(err: E) -> Box<dyn Error + Send + Sync + 'a>
Converts a type of Error
+ Send
+ Sync
into a box of
dyn Error
+ Send
+ Sync
.
§Examples
use std::error::Error;
use std::fmt;
use std::mem;
#[derive(Debug)]
struct AnError;
impl fmt::Display for AnError {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
write!(f, "An error")
}
}
impl Error for AnError {}
unsafe impl Send for AnError {}
unsafe impl Sync for AnError {}
let an_error = AnError;
assert!(0 == mem::size_of_val(&an_error));
let a_boxed_error = Box::<dyn Error + Send + Sync>::from(an_error);
assert!(
mem::size_of::<Box<dyn Error + Send + Sync>>() == mem::size_of_val(&a_boxed_error))
1.6.0 · Source§impl<'a> From<String> for Box<dyn Error + 'a>
impl<'a> From<String> for Box<dyn Error + 'a>
1.0.0 · Source§impl<'a> From<String> for Box<dyn Error + Send + Sync + 'a>
impl<'a> From<String> for Box<dyn Error + Send + Sync + 'a>
Source§fn from(err: String) -> Box<dyn Error + Send + Sync + 'a>
fn from(err: String) -> Box<dyn Error + Send + Sync + 'a>
Converts a String
into a box of dyn Error
+ Send
+ Sync
.
§Examples
use std::error::Error;
use std::mem;
let a_string_error = "a string error".to_string();
let a_boxed_error = Box::<dyn Error + Send + Sync>::from(a_string_error);
assert!(
mem::size_of::<Box<dyn Error + Send + Sync>>() == mem::size_of_val(&a_boxed_error))
Implementors§
impl !Error for &str
impl Error for codespan_reporting::files::Error
impl Error for AdditionError
impl Error for CreationError
impl Error for RecordError
impl Error for SubtractionError
impl Error for httparse::Error
impl Error for humantime::date::Error
impl Error for humantime::duration::Error
impl Error for GetTimezoneError
impl Error for ignore::Error
impl Error for libloading::error::Error
impl Error for InsertError
impl Error for matchit::error::MatchError
impl Error for nix::errno::consts::Errno
impl Error for rand::distributions::bernoulli::BernoulliError
impl Error for WeightedError
impl Error for StartError
impl Error for regex_syntax::error::Error
impl Error for rustls_pki_types::pem::Error
impl Error for rusty_fork::error::Error
impl Error for serde_urlencoded::ser::Error
impl Error for QuoteError
impl Error for StrSimError
impl Error for AnyDelimiterCodecError
impl Error for LinesCodecError
impl Error for toml_edit::ser::Error
impl Error for ucd_trie::owned::Error
impl Error for ErrorKind
impl Error for BytesRejection
impl Error for ExtensionRejection
impl Error for FailedToBufferBody
impl Error for FormRejection
impl Error for JsonRejection
impl Error for MatchedPathRejection
impl Error for PathRejection
impl Error for QueryRejection
impl Error for RawFormRejection
impl Error for RawPathParamsRejection
impl Error for StringRejection
impl Error for ParseAlphabetError
impl Error for DecodeError
impl Error for DecodeSliceError
impl Error for EncodeSliceError
impl Error for BindgenError
impl Error for RoundingError
impl Error for MatchesError
impl Error for rustmax::crossbeam::channel::RecvTimeoutError
impl Error for rustmax::crossbeam::channel::TryRecvError
impl Error for rustmax::ctrlc::Error
impl Error for BinaryError
impl Error for FromHexError
impl Error for rustmax::json5::Error
impl Error for rustmax::proptest::string::Error
impl Error for rustmax::rand::distr::BernoulliError
impl Error for rustmax::rand::distr::uniform::Error
impl Error for rustmax::rand::seq::WeightError
impl Error for rustmax::regex::Error
impl Error for ReadlineError
impl Error for rustmax::tokio::sync::broadcast::error::RecvError
impl Error for rustmax::tokio::sync::broadcast::error::TryRecvError
impl Error for TryAcquireError
impl Error for rustmax::tokio::sync::mpsc::error::TryRecvError
impl Error for rustmax::tokio::sync::oneshot::error::TryRecvError
impl Error for rustmax::url::ParseError
impl Error for Infallible
impl Error for VarError
impl Error for rustmax::std::sync::mpsc::RecvTimeoutError
impl Error for rustmax::std::sync::mpsc::TryRecvError
impl Error for !
impl Error for aho_corasick::util::error::BuildError
impl Error for aho_corasick::util::error::MatchError
impl Error for aho_corasick::util::primitives::PatternIDError
impl Error for aho_corasick::util::primitives::StateIDError
impl Error for bstr::ext_vec::FromUtf8Error
impl Error for bstr::utf8::Utf8Error
impl Error for chrono_tz::timezones::ParseError
impl Error for env_filter::parser::ParseError
impl Error for getrandom::error::Error
impl Error for getrandom::error::Error
impl Error for glob::GlobError
impl Error for PatternError
impl Error for globset::Error
impl Error for globwalk::GlobError
impl Error for h2::error::Error
impl Error for UsizeTypeTooSmall
impl Error for http_body_util::limited::LengthLimitError
impl Error for httpdate::Error
impl Error for hyper_util::client::legacy::client::Error
impl Error for InvalidNameError
impl Error for Errors
impl Error for indexmap::TryReserveError
impl Error for PrefixLenError
impl Error for ipnet::parser::AddrParseError
impl Error for native_tls::Error
impl Error for object::read::Error
impl Error for openssl::error::Error
impl Error for ErrorStack
impl Error for openssl::ssl::error::Error
impl Error for X509VerifyResult
impl Error for ReadError
impl Error for rand_core::error::Error
impl Error for regex_automata::dfa::onepass::BuildError
impl Error for regex_automata::hybrid::error::BuildError
impl Error for CacheError
impl Error for regex_automata::meta::error::BuildError
impl Error for regex_automata::nfa::thompson::error::BuildError
impl Error for GroupInfoError
impl Error for UnicodeWordBoundaryError
impl Error for regex_automata::util::primitives::PatternIDError
impl Error for SmallIndexError
impl Error for regex_automata::util::primitives::StateIDError
impl Error for regex_automata::util::search::MatchError
impl Error for PatternSetInsertError
impl Error for DeserializeError
impl Error for SerializeError
impl Error for regex_syntax::ast::Error
impl Error for regex_syntax::hir::Error
impl Error for CaseFoldError
impl Error for UnicodeWordError
impl Error for rustix::backend::io::errno::Errno
impl Error for rustls_pki_types::server_name::AddrParseError
impl Error for InvalidDnsNameError
impl Error for LengthDelimitedCodecError
impl Error for toml_edit::de::Error
impl Error for TomlError
impl Error for SetGlobalDefaultError
impl Error for tracing_core::metadata::ParseLevelError
impl Error for ParseLevelFilterError
impl Error for FailedToDeserializeForm
impl Error for FailedToDeserializeFormBody
impl Error for FailedToDeserializePathParams
impl Error for FailedToDeserializeQueryString
impl Error for InvalidFormContentType
impl Error for InvalidUtf8
impl Error for InvalidUtf8InPathParam
impl Error for JsonDataError
impl Error for JsonSyntaxError
impl Error for rustmax::axum::extract::rejection::LengthLimitError
impl Error for MatchedPathMissing
impl Error for MissingExtension
impl Error for MissingJsonContentType
impl Error for MissingPathParams
impl Error for NestedPathRejection
impl Error for UnknownBodyError
impl Error for rustmax::axum::Error
impl Error for rustmax::bitflags::parser::ParseError
impl Error for HexError
impl Error for rustmax::cc::Error
impl Error for OutOfRange
impl Error for OutOfRangeError
impl Error for rustmax::chrono::ParseError
impl Error for ParseMonthError
impl Error for ParseWeekdayError
impl Error for rustmax::crossbeam::channel::RecvError
impl Error for SelectTimeoutError
impl Error for TrySelectError
impl Error for Exception
impl Error for rustmax::derive_more::FromStrError
impl Error for UnitError
impl Error for WrongVariantError
impl Error for rustmax::futures::channel::mpsc::SendError
impl Error for rustmax::futures::channel::mpsc::TryRecvError
impl Error for Canceled
impl Error for EnterError
impl Error for Aborted
impl Error for SpawnError
impl Error for InvalidMethod
impl Error for InvalidStatusCode
impl Error for rustmax::hyper::http::Error
impl Error for InvalidUri
impl Error for InvalidUriParts
impl Error for rustmax::hyper::Error
impl Error for rustmax::jiff::Error
impl Error for rustmax::log::ParseLevelError
impl Error for SetLoggerError
impl Error for rustmax::mime::FromStrError
impl Error for ParseBigIntError
impl Error for rustmax::proc_macro2::LexError
impl Error for ExpandError
impl Error for rustmax::proc_macro::LexError
impl Error for Empty
impl Error for OsError
impl Error for ThreadPoolBuildError
impl Error for InvalidHeaderName
impl Error for InvalidHeaderValue
impl Error for MaxSizeReached
impl Error for ToStrError
impl Error for rustmax::reqwest::Error
impl Error for rustmax::semver::Error
impl Error for rustmax::serde::de::value::Error
impl Error for rustmax::serde_json::Error
impl Error for InvalidLength
impl Error for InvalidBufferSize
impl Error for InvalidOutputSize
impl Error for rustmax::syn::Error
impl Error for PathPersistError
impl Error for rustmax::tera::Error
impl Error for ColorChoiceParseError
impl Error for ParseColorError
impl Error for rustmax::tokio::net::tcp::ReuniteError
impl Error for rustmax::tokio::net::unix::ReuniteError
impl Error for TryCurrentError
impl Error for rustmax::tokio::sync::oneshot::error::RecvError
impl Error for AcquireError
impl Error for rustmax::tokio::sync::TryLockError
impl Error for rustmax::tokio::sync::watch::error::RecvError
impl Error for JoinError
impl Error for rustmax::tokio::time::error::Elapsed
impl Error for rustmax::tokio::time::error::Error
impl Error for rustmax::toml::de::Error
impl Error for rustmax::toml::ser::Error
impl Error for DatetimeParseError
impl Error for Discover
impl Error for Closed
impl Error for ServiceError
impl Error for Overloaded
impl Error for InvalidBackoff
impl Error for rustmax::tower::timeout::error::Elapsed
impl Error for None
impl Error for rustmax::walkdir::Error
impl Error for rustmax::xshell::Error
impl Error for AllocError
impl Error for LayoutError
impl Error for TryFromSliceError
impl Error for BorrowError
impl Error for BorrowMutError
impl Error for CharTryFromError
impl Error for DecodeUtf16Error
impl Error for ParseCharError
impl Error for TryFromCharError
impl Error for UnorderedKeyError
impl Error for rustmax::std::collections::TryReserveError
impl Error for JoinPathsError
impl Error for FromBytesUntilNulError
impl Error for FromBytesWithNulError
impl Error for FromVecWithNulError
impl Error for IntoStringError
impl Error for NulError
impl Error for rustmax::std::fmt::Error
impl Error for rustmax::std::io::Error
impl Error for WriterPanicked
impl Error for rustmax::std::net::AddrParseError
impl Error for ParseFloatError
impl Error for ParseIntError
impl Error for TryFromIntError
impl Error for StripPrefixError
impl Error for ExitStatusError
impl Error for ParseBoolError
impl Error for rustmax::std::str::Utf8Error
impl Error for rustmax::std::string::FromUtf8Error
impl Error for FromUtf16Error
impl Error for rustmax::std::sync::mpsc::RecvError
impl Error for AccessError
impl Error for SystemTimeError
impl Error for TryFromFloatSecsError
impl<'a, K, V> Error for rustmax::std::collections::btree_map::OccupiedError<'a, K, V>
impl<'a, K, V> Error for rustmax::std::collections::hash_map::OccupiedError<'a, K, V>
impl<'a, T> Error for &'a T
impl<A, S, V> Error for ConvertError<A, S, V>
impl<E> Error for nom::internal::Err<E>where
E: Debug,
impl<E> Error for rustmax::nom::Err<E>where
E: Debug,
impl<E> Error for serde_path_to_error::Error<E>where
E: Error,
impl<E> Error for Box<E>where
E: Error,
impl<Enum> Error for TryFromPrimitiveError<Enum>where
Enum: TryFromPrimitive,
impl<F> Error for rustmax::clap::error::Error<F>where
F: ErrorFormatter,
impl<F> Error for PersistError<F>
impl<I> Error for nom::error::Error<I>
impl<I> Error for VerboseError<I>
impl<I> Error for InputError<I>
impl<I> Error for ExactlyOneError<I>
impl<I> Error for rustmax::nom::error::Error<I>
impl<I, C> Error for TreeError<I, C>
impl<K> Error for Failed<K>where
K: Debug,
impl<K, V> Error for TryIntoHeaderError<K, V>
impl<L, R> Error for Either<L, R>
Either
implements Error
if both L
and R
implement it.
Requires crate feature "use_std"