pub trait ErrorTrait: 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");§Error source
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.
In error types that wrap an underlying error, the underlying error
should be either returned by the outer error’s Error::source(), or rendered
by the outer error’s Display implementation, but not both.
§Example
Implementing the Error trait only requires that Debug and Display are implemented too.
use std::error::Error;
use std::fmt;
use std::path::PathBuf;
#[derive(Debug)]
struct ReadConfigError {
path: PathBuf
}
impl fmt::Display for ReadConfigError {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
let path = self.path.display();
write!(f, "unable to read configuration at {path}")
}
}
impl Error for ReadConfigError {}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§
1.0.0 · 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::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!(
size_of::<Box<dyn Error + Send + Sync>>() == 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;
#[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 == size_of_val(&an_error));
let a_boxed_error = Box::<dyn Error>::from(an_error);
assert!(size_of::<Box<dyn Error>>() == 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;
#[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 == size_of_val(&an_error));
let a_boxed_error = Box::<dyn Error + Send + Sync>::from(an_error);
assert!(
size_of::<Box<dyn Error + Send + Sync>>() == 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§impl Pointee for dyn Error
impl Pointee for dyn Error
Source§type Metadata = DynMetadata<dyn Error>
type Metadata = DynMetadata<dyn Error>
Implementors§
impl !Error for &str
impl Error for Infallible
impl Error for FromBytesWithNulError
impl Error for core::slice::GetDisjointMutError
impl Error for VarError
impl Error for std::fs::TryLockError
impl Error for RecvTimeoutError
impl Error for std::sync::mpsc::TryRecvError
impl Error for arbitrary::error::Error
impl Error for base64::alphabet::ParseAlphabetError
impl Error for base64::alphabet::ParseAlphabetError
impl Error for base64::decode::DecodeError
impl Error for base64::decode::DecodeError
impl Error for base64::decode::DecodeSliceError
impl Error for base64::decode::DecodeSliceError
impl Error for base64::encode::EncodeSliceError
impl Error for base64::encode::EncodeSliceError
impl Error for BuiltinPluginBuilderError
impl Error for CardinalConfigBuilderError
impl Error for DestinationBuilderError
impl Error for HealthCheckBuilderError
impl Error for MiddlewareBuilderError
impl Error for RouteBuilderError
impl Error for ServerConfigBuilderError
impl Error for WasmPluginConfigBuilderError
impl Error for CardinalError
impl Error for CardinalInternalError
impl Error for CardinalProxyError
impl Error for MatchesError
impl Error for ConfigError
impl Error for DataValueCastFailure
impl Error for LookupError
impl Error for RegisterMappingError
impl Error for CodegenError
impl Error for cranelift_codegen::settings::SetError
impl Error for gimli::read::Error
impl Error for gimli::write::convert::ConvertError
impl Error for gimli::write::Error
impl Error for FromHexError
impl Error for httparse::Error
impl Error for indexmap::GetDisjointMutError
impl Error for json5::error::Error
impl Error for local_ip_address::error::Error
impl Error for InsertError
impl Error for matchit::error::MatchError
impl Error for DeError
impl Error for SerError
impl Error for WrappedError
impl Error for Errno
impl Error for prometheus::errors::Error
impl Error for ProtobufError
impl Error for Panic
impl Error for rand::distr::bernoulli::BernoulliError
impl Error for rand::distr::uniform::Error
impl Error for rand::distr::weighted::Error
impl Error for rand::distributions::bernoulli::BernoulliError
impl Error for WeightedError
impl Error for RegAllocError
impl Error for StartError
impl Error for regex_syntax::error::Error
impl Error for regex::error::Error
impl Error for region::error::Error
impl Error for rmp_serde::decode::Error
impl Error for rmp_serde::encode::Error
impl Error for BytesReadError
impl Error for NumValueReadError
impl Error for ValueReadError
impl Error for ron::error::Error
impl Error for ini::Error
impl Error for LiteralsSectionParseError
impl Error for SequencesHeaderParseError
impl Error for GetBitsError
impl Error for BlockHeaderReadError
impl Error for BlockSizeError
impl Error for BlockTypeError
impl Error for DecodeBlockContentError
impl Error for DecompressBlockError
impl Error for DecodebufferError
impl Error for DictionaryDecodeError
impl Error for DecompressLiteralsError
impl Error for ExecuteSequencesError
impl Error for DecodeSequenceError
impl Error for FrameDescriptorError
impl Error for FrameHeaderError
impl Error for ReadFrameHeaderError
impl Error for FrameDecoderError
impl Error for FSEDecoderError
impl Error for FSETableError
impl Error for HuffmanDecoderError
impl Error for HuffmanTableError
impl Error for MmapError
impl Error for slab::GetDisjointMutError
impl Error for StrSimError
impl Error for strum::ParseError
impl Error for AnyDelimiterCodecError
impl Error for LinesCodecError
impl Error for TryAcquireError
impl Error for tokio::sync::broadcast::error::RecvError
impl Error for tokio::sync::broadcast::error::TryRecvError
impl Error for tokio::sync::mpsc::error::TryRecvError
impl Error for tokio::sync::oneshot::error::TryRecvError
impl Error for SerializerError
impl Error for ucd_trie::owned::Error
impl Error for wasmer_compiler::engine::error::InstantiationError
impl Error for wasmer_compiler::engine::error::LinkError
impl Error for ObjectError
impl Error for CompileError
impl Error for wasmer_types::error::DeserializeError
impl Error for ImportError
impl Error for MemoryError
impl Error for ParseCpuFeatureError
impl Error for PreInstantiationError
impl Error for wasmer_types::error::SerializeError
impl Error for WasmError
impl Error for TrapCode
impl Error for WaiterError
impl Error for Trap
impl Error for ExportError
impl Error for IoCompileError
impl Error for BackendTrap
impl Error for AtomicsError
impl Error for wasmer::error::InstantiationError
impl Error for wasmer::error::LinkError
impl Error for MemoryAccessError
impl Error for yaml_rust2::emitter::EmitError
impl Error for yaml_rust::emitter::EmitError
impl Error for !
impl Error for UnorderedKeyError
impl Error for alloc::collections::TryReserveError
impl Error for FromVecWithNulError
impl Error for IntoStringError
impl Error for NulError
impl Error for FromUtf8Error
impl Error for FromUtf16Error
impl Error for LayoutError
impl Error for AllocError
impl Error for TryFromSliceError
impl Error for BorrowError
impl Error for BorrowMutError
impl Error for CharTryFromError
impl Error for ParseCharError
impl Error for DecodeUtf16Error
impl Error for TryFromCharError
impl Error for FromBytesUntilNulError
impl Error for core::fmt::Error
impl Error for AddrParseError
impl Error for ParseFloatError
impl Error for ParseIntError
impl Error for TryFromIntError
impl Error for ParseBoolError
impl Error for core::str::error::Utf8Error
impl Error for TryFromFloatSecsError
impl Error for JoinPathsError
impl Error for WriterPanicked
impl Error for std::io::error::Error
impl Error for NormalizeError
impl Error for StripPrefixError
impl Error for ExitStatusError
impl Error for std::sync::mpsc::RecvError
impl Error for AccessError
impl Error for SystemTimeError
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 MaxRecursionReached
impl Error for TryGetError
impl Error for cf_rustracing::error::Error
impl Error for clap::error::Error
impl Error for VerifierError
impl Error for VerifierErrors
impl Error for InvalidLength
impl Error for daemonize::error::Error
impl Error for UninitializedFieldError
impl Error for MacError
impl Error for InvalidBufferSize
impl Error for InvalidOutputSize
impl Error for erased_serde::error::Error
impl Error for CompressError
impl Error for DecompressError
impl Error for futures_channel::mpsc::SendError
impl Error for futures_channel::mpsc::TryRecvError
impl Error for Canceled
impl Error for EnterError
impl Error for SpawnError
impl Error for Aborted
impl Error for getrandom::error::Error
impl Error for getrandom::error::Error
impl Error for h2::error::Error
impl Error for http::error::Error
impl Error for MaxSizeReached
impl Error for InvalidHeaderName
impl Error for InvalidHeaderValue
impl Error for ToStrError
impl Error for InvalidMethod
impl Error for InvalidStatusCode
impl Error for InvalidUri
impl Error for InvalidUriParts
impl Error for httpdate::Error
impl Error for indexmap::TryReserveError
impl Error for MergeError
impl Error for ClearEnvError
impl Error for object::read::Error
impl Error for object::read::Error
impl Error for object::write::Error
impl Error for EncodingError
impl Error for BoxedError
impl Error for rancor::Error
impl Error for rancor::Failure
impl Error for Empty
impl Error for ReadError
impl Error for rand_core::error::Error
impl Error for OsError
impl Error for ThreadPoolBuildError
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 regex_automata::util::wire::DeserializeError
impl Error for regex_automata::util::wire::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 IteratorLengthMismatch
impl Error for SpannedError
impl Error for ini::ParseError
impl Error for serde_untagged::error::Error
impl Error for serde_core::de::value::Error
impl Error for serde_json::error::Error
impl Error for serde_yaml::error::Error
impl Error for simdutf8::basic::Utf8Error
impl Error for simdutf8::compat::Utf8Error
impl Error for ColorChoiceParseError
impl Error for ParseColorError
impl Error for thrift_codec::error::Error
impl Error for tokio_stream::stream_ext::timeout::Elapsed
impl Error for LengthDelimitedCodecError
impl Error for tokio::net::tcp::split_owned::ReuniteError
impl Error for tokio::net::unix::split_owned::ReuniteError
impl Error for TryCurrentError
impl Error for JoinError
impl Error for AcquireError
impl Error for tokio::sync::mutex::TryLockError
impl Error for tokio::sync::oneshot::error::RecvError
impl Error for tokio::sync::watch::error::RecvError
impl Error for tokio::time::error::Elapsed
impl Error for tokio::time::error::Error
impl Error for toml::de::error::Error
impl Error for toml::ser::error::Error
impl Error for DatetimeParseError
impl Error for SetGlobalDefaultError
impl Error for ParseLevelError
impl Error for ParseLevelFilterError
impl Error for trackable::error::Failure
impl Error for IoError
impl Error for TopLevelError
impl Error for walkdir::error::Error
impl Error for MiddlewareError
impl Error for PageCountOutOfRange
impl Error for RuntimeError
impl Error for BinaryReaderError
impl Error for wast::error::Error
impl Error for wat::Error
impl Error for yaml_rust2::scanner::ScanError
impl Error for yaml_rust::scanner::ScanError
impl Error for cardinal_proxy::pingora::prelude::Elapsed
impl Error for ConnectProxyError
impl Error for cardinal_proxy::pingora::Error
impl Error for cardinal_proxy::pingora::tls::error::Error
impl Error for ErrorStack
impl Error for cardinal_proxy::pingora::tls::ssl::Error
impl Error for X509VerifyResult
impl<'a, E> Error for DecodeStringError<'a, E>where
E: RmpReadErr,
impl<'a, K, V> Error for alloc::collections::btree::map::entry::OccupiedError<'a, K, V>
impl<'a, K, V> Error for std::collections::hash::map::OccupiedError<'a, K, V>
impl<'a, T> Error for &'a T
impl<A, S, V> Error for zerocopy::error::ConvertError<A, S, V>
impl<E> Error for ValueWriteError<E>where
E: RmpWriteErr,
impl<E> Error for Box<E>where
E: Error,
impl<I> Error for ExactlyOneError<I>
impl<I> Error for InputError<I>
impl<I, C> Error for TreeError<I, C>
impl<K> Error for TrackableError<K>where
K: ErrorKind,
impl<L, R> Error for Either<L, R>
Either implements Error if both L and R implement it.
Requires crate feature "std"
impl<R> Error for ErrorVariant<R>
impl<R> Error for pest::error::Error<R>
impl<S> Error for HandshakeError<S>where
S: Debug,
impl<Src, Dst> Error for AlignmentError<Src, Dst>
impl<Src, Dst> Error for SizeError<Src, Dst>
impl<Src, Dst> Error for ValidityError<Src, Dst>
impl<T> Error for std::sync::mpmc::error::SendTimeoutError<T>
impl<T> Error for std::sync::mpsc::TrySendError<T>
impl<T> Error for std::sync::poison::TryLockError<T>
impl<T> Error for tokio::sync::mpsc::error::SendTimeoutError<T>
impl<T> Error for tokio::sync::mpsc::error::TrySendError<T>
impl<T> Error for tokio::sync::once_cell::SetError<T>where
T: Debug,
impl<T> Error for ThinBox<T>
impl<T> Error for Arc<T>
impl<T> Error for std::sync::mpsc::SendError<T>
impl<T> Error for PoisonError<T>
impl<T> Error for arraydeque::error::CapacityError<T>
impl<T> Error for arrayvec::errors::CapacityError<T>where
T: Any,
Requires features="std".