Trait fvm_ipld_encoding::de::StdError
1.0.0 · source · 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"),
}
}
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());
Implementors§
impl !Error for &str
impl Error for arbitrary::error::Error
impl Error for cid::error::Error
impl Error for multibase::error::Error
impl Error for BernoulliError
impl Error for WeightedError
impl Error for regex::error::Error
impl Error for StartError
impl Error for regex_syntax::error::Error
impl Error for unsigned_varint::decode::Error
Only available when the feature std
is present.
impl Error for unsigned_varint::io::ReadError
impl Error for Infallible
impl Error for VarError
impl Error for RecvTimeoutError
impl Error for 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 InvalidLength
impl Error for data_encoding::DecodeError
impl Error for SpecificationError
impl Error for MacError
impl Error for InvalidBufferSize
impl Error for InvalidOutputSize
impl Error for getrandom::error::Error
impl Error for ParseLevelError
impl Error for SetLoggerError
impl Error for rand::rngs::adapter::read::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 fvm_ipld_encoding::Error
impl Error for UnorderedKeyError
impl Error for 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::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 Utf8Error
impl Error for TryFromFloatSecsError
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 RecvError
impl Error for AccessError
impl Error for SystemTimeError
impl Error for fvm_ipld_encoding::de::value::Error
impl Error for Error
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 cbor4ii::error::DecodeError<E>where
E: Error + 'static,
impl<E> Error for cbor4ii::error::EncodeError<E>where
E: Error + 'static,
impl<E> Error for serde_ipld_dagcbor::error::DecodeError<E>where
E: Error + 'static,
impl<E> Error for serde_ipld_dagcbor::error::EncodeError<E>where
E: Error + 'static,
impl<T> Error for TrySendError<T>
impl<T> Error for TryLockError<T>
impl<T> Error for CapacityError<T>where
T: Any,
Requires features="std"
.