pub trait StdError: 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)>
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"),
}
}
sourcefn description(&self) -> &str
fn description(&self) -> &str
if let Err(e) = "xc".parse::<u32>() {
// Print `e` itself, no need for description().
eprintln!("Error: {e}");
}
sourcefn cause(&self) -> Option<&dyn Error>
fn cause(&self) -> Option<&dyn Error>
sourcefn provide<'a>(&'a self, request: &mut Request<'a>)
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)]
#![feature(error_in_core)]
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§
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> From<Cow<'a, str>> for Box<dyn Error>
impl<'a> From<Cow<'a, str>> for Box<dyn Error>
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))
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))
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 From<String> for Box<dyn Error>
impl From<String> for Box<dyn Error>
source§impl From<String> for Box<dyn Error + Send + Sync>
impl From<String> for Box<dyn Error + Send + Sync>
source§fn from(err: String) -> Box<dyn Error + Send + Sync>
fn from(err: String) -> Box<dyn Error + Send + Sync>
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 geng::prelude::bincode::ErrorKind
impl Error for MatchesError
impl Error for geng::prelude::rand::distributions::BernoulliError
impl Error for geng::prelude::rand::distributions::WeightedError
impl Error for geng::prelude::ron::Error
impl Error for Infallible
impl Error for VarError
impl Error for std::sync::mpsc::RecvTimeoutError
impl Error for std::sync::mpsc::TryRecvError
impl Error for DistanceModelError
impl Error for gilrs::ff::Error
impl Error for gilrs::gamepad::Error
impl Error for MappingError
impl Error for url::parser::ParseError
impl Error for rand::distributions::bernoulli::BernoulliError
impl Error for rand::distributions::weighted::WeightedError
impl Error for !
impl Error for geng::prelude::fmt::Error
impl Error for geng::prelude::futures::channel::mpsc::SendError
impl Error for geng::prelude::futures::channel::mpsc::TryRecvError
impl Error for Canceled
impl Error for EnterError
impl Error for geng::prelude::futures::io::Error
impl Error for Aborted
impl Error for SpawnError
impl Error for geng::prelude::log::kv::Error
impl Error for geng::prelude::log::ParseLevelError
impl Error for SetLoggerError
impl Error for geng::prelude::rand::rngs::adapter::ReadError
impl Error for geng::prelude::rand::Error
impl Error for SpannedError
impl Error for geng::prelude::serde_json::Error
impl Error for geng::prelude::toml::de::Error
impl Error for geng::prelude::toml::ser::Error
impl Error for DatetimeParseError
impl Error for geng::prelude::serde::de::value::Error
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 FromBytesWithNulError
impl Error for core::net::parser::AddrParseError
impl Error for ParseFloatError
impl Error for ParseIntError
impl Error for TryFromIntError
impl Error for ParseBoolError
impl Error for Utf8Error
impl Error for TryFromFloatSecsError
impl Error for JoinPathsError
impl Error for WriterPanicked
impl Error for StripPrefixError
impl Error for ExitStatusError
impl Error for std::sync::mpsc::RecvError
impl Error for std::thread::local::AccessError
impl Error for SystemTimeError
impl Error for CompressError
impl Error for DecompressError
impl Error for getrandom::error::Error
impl Error for h2::error::Error
impl Error for LengthLimitError
impl Error for http::error::Error
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 indexmap::TryReserveError
impl Error for PrefixLenError
impl Error for ipnet::parser::AddrParseError
impl Error for FromStrError
impl Error for reqwest::error::Error
impl Error for ProgramLinkError
impl Error for ShaderCompilationError
impl Error for uuid::error::Error
impl Error for getrandom::error::Error
impl Error for rand::rngs::adapter::read::ReadError
impl Error for rand_core::error::Error
impl Error for AccessError
impl Error for AcquireError
impl Error for ActivateSlotError
impl Error for AddrParseError
impl Error for AnyDelimiterCodecError
impl Error for AudioReadError
impl Error for BackendSpecificError
impl Error for BadIcon
impl Error for BindError
impl Error for BuildError
impl Error for BuildError
impl Error for BuildError
impl Error for BuildError
impl Error for BuildError
impl Error for BuildStreamError
impl Error for CacheError
impl Error for CaseFoldError
impl Error for ChannelError
impl Error for ColorChoiceParseError
impl Error for ConnectError
impl Error for ConnectError
impl Error for ConnectionError
impl Error for CreateBufferError
impl Error for CreatePoolError
impl Error for DataOfferError
impl Error for DecodeError
impl Error for DecodeSliceError
impl Error for DecoderError
impl Error for DecodingError
impl Error for DecodingError
impl Error for DecodingError
impl Error for DecodingFormatError
impl Error for DefaultStreamConfigError
impl Error for DeserializeError
impl Error for DeviceNameError
impl Error for DevicesError
impl Error for DispatchError
impl Error for DlError
impl Error for Elapsed
impl Error for EncodeSliceError
impl Error for EncodingError
impl Error for EncodingError
impl Error for EncodingError
impl Error for Errno
impl Error for Errno
impl Error for Errno
impl Error for Errno
impl Error for Errno
impl Error for Error
impl Error for Error
impl Error for Error
impl Error for Error
impl Error for Error
impl Error for Error
impl Error for Error
impl Error for Error
impl Error for Error
impl Error for Error
impl Error for Error
impl Error for Error
impl Error for Error
impl Error for Error
impl Error for Error
impl Error for Error
impl Error for Error
impl Error for Error
impl Error for Error
impl Error for Error
impl Error for Error
impl Error for Error
impl Error for Error
impl Error for Error
impl Error for Error
impl Error for Error
impl Error for Error
impl Error for Error
impl Error for Error
impl Error for Error
impl Error for ErrorKind
impl Error for Errors
impl Error for EventLoopError
impl Error for ExternalError
impl Error for FaceParsingError
impl Error for GlobalError
impl Error for GlobalError
impl Error for GroupInfoError
impl Error for HandleError
impl Error for HandleError
impl Error for HeaderReadError
impl Error for IdsExhausted
impl Error for ImageError
impl Error for InitError
impl Error for InvalidDnsNameError
impl Error for InvalidDnsNameError
impl Error for InvalidFont
impl Error for InvalidId
impl Error for InvalidId
impl Error for InvalidNameError
impl Error for InvalidOutputSize
impl Error for JoinError
impl Error for LengthDelimitedCodecError
impl Error for LibxcbLoadError
impl Error for LimitError
impl Error for LinesCodecError
impl Error for LzwError
impl Error for MatchError
impl Error for MatchError
impl Error for NoWaylandLib
impl Error for NotSupportedError
impl Error for OggReadError
impl Error for OpenError
impl Error for OsError
impl Error for ParameterError
impl Error for ParseAlphabetError
impl Error for ParseColorError
impl Error for ParseError
impl Error for ParseError
impl Error for ParseError
impl Error for ParseError
impl Error for ParseLevelError
impl Error for ParseLevelFilterError
impl Error for PatternIDError
impl Error for PatternIDError
impl Error for PatternSetInsertError
impl Error for PauseStreamError
impl Error for PingError
impl Error for PlayError
impl Error for PlayStreamError
impl Error for PointerThemeError
impl Error for PoolError
impl Error for PopError
impl Error for ProtocolError
impl Error for RecvError
impl Error for RecvError
impl Error for RecvError
impl Error for RecvError
impl Error for RecvError
impl Error for RecvError
impl Error for RecvError
impl Error for RecvError
impl Error for RecvTimeoutError
impl Error for RecvTimeoutError
impl Error for ReplyError
impl Error for ReplyOrIdError
impl Error for ReuniteError
impl Error for ReuniteError
impl Error for SeatError
impl Error for SelectTimeoutError
impl Error for SerializeError
impl Error for SetGlobalDefaultError
impl Error for SignError
impl Error for SmallIndexError
impl Error for StartError
impl Error for StateIDError
impl Error for StateIDError
impl Error for StrSimError
impl Error for StreamError
impl Error for StreamError
impl Error for SupportedStreamConfigsError
impl Error for ThreadPoolBuildError
impl Error for TiffError
impl Error for TimeoutError
impl Error for TomlError
impl Error for TryAcquireError
impl Error for TryCurrentError
impl Error for TryLockError
impl Error for TryRecvError
impl Error for TryRecvError
impl Error for TryRecvError
impl Error for TryRecvError
impl Error for TryRecvError
impl Error for TryRecvError
impl Error for TryRecvError
impl Error for TryRecvError
impl Error for TrySelectError
impl Error for UnicodeWordBoundaryError
impl Error for UnicodeWordError
impl Error for UnknownLayer
impl Error for UnsupportedError
impl Error for VorbisError
impl Error for WEnumError
impl Error for WaylandError
impl Error for XNotSupported
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<E> Error for Err<E>where
E: Debug,
impl<Enum> Error for TryFromPrimitiveError<Enum>where
Enum: TryFromPrimitive,
impl<F> Error for geng::prelude::cli::prelude::clap::error::Error<F>where
F: ErrorFormatter,
impl<I> Error for geng::prelude::itertools::ExactlyOneError<I>
impl<I> Error for itertools::exactly_one_err::ExactlyOneError<I>
impl<I> Error for Error<I>
impl<I> Error for InputError<I>
impl<I> Error for VerboseError<I>
impl<I, C> Error for TreeError<I, C>
impl<I, C> Error for VerboseError<I, C>
impl<K> Error for BufferSlot<K>
impl<L, R> Error for Either<L, R>
Either
implements Error
if both L
and R
implement it.
impl<T> Error for std::sync::mpsc::TrySendError<T>
impl<T> Error for std::sync::poison::TryLockError<T>
impl<T> Error for geng::prelude::futures::channel::mpsc::TrySendError<T>where
T: Any,
impl<T> Error for geng::prelude::futures::io::ReuniteError<T>where
T: Any,
impl<T> Error for Arc<T>
impl<T> Error for Box<T>where
T: Error,
impl<T> Error for ThinBox<T>
impl<T> Error for std::sync::mpsc::SendError<T>
impl<T> Error for PoisonError<T>
impl<T> Error for CapacityError<T>where
T: Any,
Requires features="std"
.