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)>
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 gsdk::result::Error
impl Error for TxError
impl Error for gclient::Error
impl Error for gclient::errors::ModuleError
impl Error for DeriveError
impl Error for SecretStringError
impl Error for TransactionValidityError
impl Error for gclient::ext::sp_core::crypto::AddressUriError
impl Error for PublicError
impl Error for Infallible
impl Error for RecvTimeoutError
impl Error for gclient::ext::sp_core::sp_std::sync::mpsc::TryRecvError
impl Error for VarError
impl Error for ErrorKind
impl Error for hex::error::FromHexError
impl Error for url::parser::ParseError
impl Error for BernoulliError
impl Error for WeightedError
impl Error for !
impl Error for gclient::ext::sp_runtime::codec::Error
impl Error for SystemTimeError
impl Error for TryFromFloatSecsError
impl Error for UnorderedKeyError
impl Error for gclient::ext::sp_core::bounded::alloc::collections::TryReserveError
impl Error for FromVecWithNulError
impl Error for IntoStringError
impl Error for NulError
impl Error for ParseBoolError
impl Error for Utf8Error
impl Error for FromUtf8Error
impl Error for FromUtf16Error
impl Error for AllocError
impl Error for LayoutError
impl Error for BorrowError
impl Error for BorrowMutError
impl Error for ParseFloatError
impl Error for gclient::ext::sp_core::sp_std::num::ParseIntError
impl Error for gclient::ext::sp_core::sp_std::num::TryFromIntError
impl Error for gclient::ext::sp_core::sp_std::sync::mpsc::RecvError
impl Error for gclient::ext::sp_core::serde::de::value::Error
impl Error for TryFromSliceError
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::fmt::Error
impl Error for core::net::parser::AddrParseError
impl Error for JoinPathsError
impl Error for WriterPanicked
impl Error for std::io::error::Error
impl Error for StripPrefixError
impl Error for ExitStatusError
impl Error for AccessError
impl Error for getrandom::error::Error
impl Error for http::error::Error
impl Error for http::header::name::InvalidHeaderName
impl Error for http::header::value::InvalidHeaderValue
impl Error for http::header::value::ToStrError
impl Error for http::method::InvalidMethod
impl Error for http::status::InvalidStatusCode
impl Error for http::uri::InvalidUri
impl Error for http::uri::InvalidUriParts
impl Error for log::ParseLevelError
impl Error for SetLoggerError
impl Error for ParseBigIntError
impl Error for num_format::error::Error
impl Error for ParseRatioError
impl Error for serde_json::error::Error
impl Error for ReadError
impl Error for rand_core::error::Error
impl Error for Aborted
impl Error for AcquireError
impl Error for AddrParseError
impl Error for AlreadyStoppedError
impl Error for AnyDelimiterCodecError
impl Error for ArithmeticError
impl Error for AuthorityError
impl Error for BadName
impl Error for BinaryReaderError
impl Error for BinaryReaderError
impl Error for BlockError
impl Error for BlockError
impl Error for BroadcastStreamRecvError
impl Error for BuildError
impl Error for BuildError
impl Error for BuildError
impl Error for BuildError
impl Error for BuildError
impl Error for CacheError
impl Error for Canceled
impl Error for CaseFoldError
impl Error for CaseFoldError
impl Error for ColorChoiceParseError
impl Error for CompileError
impl Error for ComponentRange
impl Error for ConversionRange
impl Error for ConvertError
impl Error for DecodeError
impl Error for DecodeError
impl Error for DecodeError
impl Error for DecodeError
impl Error for DecodeSliceError
impl Error for DecodeSliceError
impl Error for DeserializeError
impl Error for DeserializerError
impl Error for DifferentVariant
impl Error for DisconnectError
impl Error for DispatchError
impl Error for EarlyDataError
impl Error for Elapsed
impl Error for Elapsed
impl Error for EmptyBatchRequest
impl Error for EmptyBatchRequest
impl Error for EncodeError
impl Error for EncodeSliceError
impl Error for EncodeSliceError
impl Error for EncryptError
impl Error for EnterError
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 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 Error
impl Error for Error
impl Error for ErrorCode
impl Error for ErrorCode
impl Error for Errors
impl Error for ExecutionError
impl Error for ExtrinsicParamsError
impl Error for FetchChainspecError
impl Error for Format
impl Error for FromDecStrErr
impl Error for FromEnvError
impl Error for FromHexError
impl Error for FromHexError
impl Error for FromStrRadixErr
impl Error for GroupInfoError
impl Error for HttpError
impl Error for InvalidBufferSize
impl Error for InvalidDnsNameError
impl Error for InvalidEncodingError
impl Error for InvalidFormatDescription
impl Error for InvalidHeaderName
impl Error for InvalidHeaderValue
impl Error for InvalidLength
impl Error for InvalidLengthError
impl Error for InvalidMethod
impl Error for InvalidNameError
impl Error for InvalidOutputSize
impl Error for InvalidOutputSize
impl Error for InvalidParityValue
impl Error for InvalidPath
impl Error for InvalidRequestId
impl Error for InvalidRequestId
impl Error for InvalidStatusCode
impl Error for InvalidUri
impl Error for InvalidUriParts
impl Error for InvalidValue
impl Error for InvalidVariant
impl Error for JoinError
impl Error for LengthDelimitedCodecError
impl Error for LengthLimitError
impl Error for LinesCodecError
impl Error for MacError
impl Error for MatchError
impl Error for MatchError
impl Error for MaxSizeReached
impl Error for MemoryAccessError
impl Error for MetadataError
impl Error for MethodsError
impl Error for ModuleError
impl Error for None
impl Error for OtherError
impl Error for OtherError
impl Error for OutOfRangeError
impl Error for ParseAlphabetError
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 ParseError
impl Error for ParseHexError
impl Error for ParseIntError
impl Error for ParseLevelError
impl Error for ParseLevelFilterError
impl Error for PatternIDError
impl Error for PatternIDError
impl Error for PatternSetInsertError
impl Error for PendingSubscriptionAcceptError
impl Error for RecvError
impl Error for RecvError
impl Error for RecvError
impl Error for RegisterMethodError
impl Error for RegisterMethodError
impl Error for ReuniteError
impl Error for ReuniteError
impl Error for RpcError
impl Error for SendError
impl Error for SendTimeoutError
impl Error for SerializeError
impl Error for SerializerError
impl Error for SetGlobalDefaultError
impl Error for SliceTooLarge
impl Error for SliceTooLarge
impl Error for SmallIndexError
impl Error for SpawnError
impl Error for StartError
impl Error for StateIDError
impl Error for StateIDError
impl Error for StorageAddressError
impl Error for ToStrError
impl Error for TokenError
impl Error for TransactionError
impl Error for TransactionalError
impl Error for Trap
impl Error for Trap
impl Error for TryAcquireError
impl Error for TryCurrentError
impl Error for TryFromError
impl Error for TryFromIntError
impl Error for TryInitError
impl Error for TryLockError
impl Error for TryRecvError
impl Error for TryRecvError
impl Error for TryRecvError
impl Error for TryRecvError
impl Error for TryReserveError
impl Error for TrySendError
impl Error for UnicodeWordBoundaryError
impl Error for UnicodeWordError
impl Error for UnicodeWordError
impl Error for UnknownImportError
impl Error for UnknownOpCode
impl Error for UnknownOpCode
impl Error for UnsupportedOperationError
impl Error for UnsupportedOperationError
impl Error for VerifierBuilderError
impl Error for VerifierBuilderError
impl Error for WasmError
impl Error for WsError
impl Error for WsError
impl Error for WsHandshakeError
impl Error for WsHandshakeError
impl<'a> Error for ErrorObject<'a>
impl<'a> Error for ErrorObject<'a>
impl<'a, K, V> Error for gclient::ext::sp_core::bounded::alloc::collections::btree_map::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<Ctx> Error for TraceDecodingError<Value<Ctx>>where
Ctx: Debug,
impl<H> Error for Error<H>
impl<H, CodecError> Error for Error<H, CodecError>
impl<HO, CE> Error for Error<HO, CE>
impl<I> Error for ExactlyOneError<I>
impl<L, R> Error for Either<L, R>
Either
implements Error
if both L
and R
implement it.
Requires crate feature "use_std"
impl<R> Error for BitIdxError<R>where
R: BitRegister,
impl<T> Error for gclient::ext::sp_core::sp_std::sync::TryLockError<T>
impl<T> Error for gclient::ext::sp_core::sp_std::sync::mpsc::TrySendError<T>
impl<T> Error for ThinBox<T>
impl<T> Error for Box<T>where
T: Error,
impl<T> Error for gclient::ext::sp_core::sp_std::sync::mpsc::SendError<T>
impl<T> Error for Arc<T>
impl<T> Error for PoisonError<T>
impl<T> Error for CapacityError<T>where
T: Any,
Requires features="std"
.