Trait Error 

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>) { ... }
}

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

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"),
    }
}

fn description(&self) -> &str

👎Deprecated since 1.42.0: use the Display impl or to_string()

if let Err(e) = "xc".parse::<u32>() {
    // Print `e` itself, no need for description().
    eprintln!("Error: {e}");
}

fn cause(&self) -> Option<&dyn Error>

👎Deprecated since 1.33.0: replaced by Error::source, which can support downcasting

fn provide<'a>(&'a self, request: &mut Request<'a>)

🔬This is a nightly-only experimental API. (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

impl dyn Error

pub fn is<T>(&self) -> bool

where T: Error + 'static,

Returns true if the inner type is the same as T.

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.

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.

impl dyn Error + Send

pub fn is<T>(&self) -> bool

where T: Error + 'static,

Forwards to the method defined on the type dyn Error.

pub fn downcast_ref<T>(&self) -> Option<&T>

where T: Error + 'static,

Forwards to the method defined on the type dyn Error.

pub fn downcast_mut<T>(&mut self) -> Option<&mut T>

where T: Error + 'static,

Forwards to the method defined on the type dyn Error.

impl dyn Error + Sync + Send

pub fn is<T>(&self) -> bool

where T: Error + 'static,

Forwards to the method defined on the type dyn Error.

pub fn downcast_ref<T>(&self) -> Option<&T>

where T: Error + 'static,

Forwards to the method defined on the type dyn Error.

pub fn downcast_mut<T>(&mut self) -> Option<&mut T>

where T: Error + 'static,

Forwards to the method defined on the type dyn Error.

impl dyn Error

pub fn sources(&self) -> Source<'_>

🔬This is a nightly-only experimental API. (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());

impl dyn Error

pub fn downcast<T>(self: Box<dyn Error>) -> Result<Box<T>, Box<dyn Error>>

where T: Error + 'static,

Attempts to downcast the box to a concrete type.

impl dyn Error + Send

pub fn downcast<T>( self: Box<dyn Error + Send>, ) -> Result<Box<T>, Box<dyn Error + Send>>

where T: Error + 'static,

Attempts to downcast the box to a concrete type.

impl dyn Error + Sync + Send

pub fn downcast<T>( self: Box<dyn Error + Sync + Send>, ) -> Result<Box<T>, Box<dyn Error + Sync + Send>>

where T: Error + 'static,

Attempts to downcast the box to a concrete type.

Trait Implementations

impl AsRef<dyn Error> for Error

fn as_ref(&self) -> &(dyn Error + 'static)

Converts this type into a shared reference of the (usually inferred) input type.

impl AsRef<dyn Error> for Error

fn as_ref(&self) -> &(dyn Error + 'static)

Converts this type into a shared reference of the (usually inferred) input type.

impl AsRef<dyn Error + Sync + Send> for Error

fn as_ref(&self) -> &(dyn Error + Sync + Send + 'static)

Converts this type into a shared reference of the (usually inferred) input type.

impl AsRef<dyn Error + Sync + Send> for Error

fn as_ref(&self) -> &(dyn Error + Sync + Send + 'static)

Converts this type into a shared reference of the (usually inferred) input type.

impl<'v, 'u> From<&'v &'u (dyn Error + 'static)> for ValueBag<'v>

where 'u: 'v,

fn from(v: &'v &'u (dyn Error + 'static)) -> ValueBag<'v>

Converts to this type from the input type.

impl<'v> From<&'v (dyn Error + 'static)> for ValueBag<'v>

fn from(v: &'v (dyn Error + 'static)) -> ValueBag<'v>

Converts to this type from the input type.

impl<'a> From<&str> for Box<dyn Error + 'a>

fn from(err: &str) -> Box<dyn Error + 'a>

Converts a str into a box of dyn Error.

Examples

use std::error::Error;

let a_str_error = "a str error";
let a_boxed_error = Box::<dyn Error>::from(a_str_error);
assert!(size_of::<Box<dyn Error>>() == size_of_val(&a_boxed_error))

impl<'a> From<&str> for Box<dyn Error + Sync + Send + 'a>

fn from(err: &str) -> Box<dyn Error + Sync + Send + 'a>

Converts a str into a box of dyn Error + Send + Sync.

Examples

use std::error::Error;

let a_str_error = "a str error";
let a_boxed_error = Box::<dyn Error + Send + Sync>::from(a_str_error);
assert!(
    size_of::<Box<dyn Error + Send + Sync>>() == size_of_val(&a_boxed_error))

impl<'a, 'b> From<Cow<'b, str>> for Box<dyn Error + 'a>

fn from(err: Cow<'b, str>) -> Box<dyn Error + 'a>

Converts a Cow into a box of dyn Error.

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>::from(a_cow_str_error);
assert!(size_of::<Box<dyn Error>>() == size_of_val(&a_boxed_error))

impl<'a, 'b> From<Cow<'b, str>> for Box<dyn Error + Sync + Send + 'a>

fn from(err: Cow<'b, str>) -> Box<dyn Error + Sync + Send + '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))

impl<'a, E> From<E> for Box<dyn Error + 'a>

where E: 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))

impl<'a, E> From<E> for Box<dyn Error + Sync + Send + 'a>

where E: Error + Send + Sync + 'a,

fn from(err: E) -> Box<dyn Error + Sync + Send + '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))

impl From<Error> for Box<dyn Error>

fn from(error: Error) -> Box<dyn Error>

Converts to this type from the input type.

impl From<Error> for Box<dyn Error>

fn from(error: Error) -> Box<dyn Error>

Converts to this type from the input type.

impl From<Error> for Box<dyn Error + Send>

fn from(error: Error) -> Box<dyn Error + Send>

Converts to this type from the input type.

impl From<Error> for Box<dyn Error + Sync + Send>

fn from(error: Error) -> Box<dyn Error + Sync + Send>

Converts to this type from the input type.

impl From<Error> for Box<dyn Error + Sync + Send>

fn from(error: Error) -> Box<dyn Error + Sync + Send>

Converts to this type from the input type.

impl<'a> From<String> for Box<dyn Error + 'a>

fn from(str_err: String) -> Box<dyn Error + 'a>

Converts a String into a box of dyn Error.

Examples

use std::error::Error;

let a_string_error = "a string error".to_string();
let a_boxed_error = Box::<dyn Error>::from(a_string_error);
assert!(size_of::<Box<dyn Error>>() == size_of_val(&a_boxed_error))

impl<'a> From<String> for Box<dyn Error + Sync + Send + 'a>

fn from(err: String) -> Box<dyn Error + Sync + Send + 'a>

Converts a String into a box of dyn Error + Send + Sync.

Examples

use std::error::Error;

let a_string_error = "a string error".to_string();
let a_boxed_error = Box::<dyn Error + Send + Sync>::from(a_string_error);
assert!(
    size_of::<Box<dyn Error + Send + Sync>>() == size_of_val(&a_boxed_error))

impl<'v> TryFrom<ValueBag<'v>> for &'v (dyn Error + 'static)

type Error = Error

The type returned in the event of a conversion error.

fn try_from( v: ValueBag<'v>, ) -> Result<&'v (dyn Error + 'static), <&'v (dyn Error + 'static) as TryFrom<ValueBag<'v>>>::Error>

Performs the conversion.

Implementors

impl !Error for &str

impl Error for rosetta_server::crypto::bip39::Error

impl Error for Infallible

impl Error for FromBytesWithNulError

impl Error for rosetta_server::crypto::bip39::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 async_channel::TryRecvError

impl Error for async_channel::TryRecvError

impl Error for DecodeError

impl Error for base64ct::errors::Error

impl Error for bech32::Error

impl Error for bitcoin_hashes::error::Error

impl Error for bitcoin_hashes::hex::Error

impl Error for bs58::alphabet::Error

impl Error for bs58::decode::Error

impl Error for bs58::encode::Error

impl Error for MatchesError

impl Error for PopError

impl Error for cookie::parse::ParseError

impl Error for FromHexError

impl Error for httparse::Error

impl Error for icu_collections::codepointtrie::error::Error

impl Error for icu_locale_core::parser::errors::ParseError

impl Error for PreferencesParseError

impl Error for pkcs8::error::Error

impl Error for rand::distributions::bernoulli::BernoulliError

impl Error for rand::distributions::bernoulli::BernoulliError

impl Error for rand::distributions::weighted::WeightedError

impl Error for rand::distributions::weighted_index::WeightedError

impl Error for sec1::error::Error

impl Error for serde_qs::error::Error

impl Error for serde_urlencoded::ser::Error

impl Error for slab::GetDisjointMutError

impl Error for sled::result::Error

impl Error for UnabortableTransactionError

impl Error for spki::error::Error

impl Error for StrSimError

impl Error for time::error::Error

impl Error for Format

impl Error for time::format::parse::Error

impl Error for tinystr::error::ParseError

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 url::parser::ParseError

impl Error for ZeroTrieBuildError

impl Error for UleError

impl Error for !

impl Error for rosetta_server::types::Error

impl Error for rosetta_server::crypto::bip39::serde::de::value::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 FromBytesUntilNulError

impl Error for rosetta_server::crypto::bip39::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 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 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 std::thread::local::AccessError

impl Error for SystemTimeError

impl Error for async_channel::RecvError

impl Error for async_channel::RecvError

impl Error for async_std::future::timeout::TimeoutError

impl Error for async_std::stream::stream::timeout::TimeoutError

impl Error for async_std::task::task_local::AccessError

impl Error for InvalidEncodingError

impl Error for InvalidLengthError

impl Error for bitflags::parser::ParseError

impl Error for TryGetError

impl Error for InvalidLength

impl Error for der::error::Error

impl Error for digest::errors::InvalidOutputSize

impl Error for MacError

impl Error for InvalidBufferSize

impl Error for digest::InvalidOutputSize

impl Error for elliptic_curve::error::Error

impl Error for erased_serde::error::Error

impl Error for SpawnError

impl Error for Aborted

impl Error for getrandom::error::Error

impl Error for getrandom::error::Error

impl Error for DataError

impl Error for Errors

impl Error for log::kv::error::Error

impl Error for ParseLevelError

impl Error for SetLoggerError

impl Error for num_format::error::Error

impl Error for rand::rngs::adapter::read::ReadError

impl Error for rand::rngs::adapter::read::ReadError

impl Error for rand_core::error::Error

impl Error for rand_core::error::Error

impl Error for rustix::backend::io::errno::Errno

impl Error for rustix::backend::io::errno::Errno

impl Error for serde_json::error::Error

impl Error for signature::error::Error

impl Error for signature::error::Error

impl Error for CompareAndSwapError

impl Error for ss58_registry::error::ParseError

impl Error for ComponentRange

impl Error for ConversionRange

impl Error for IndeterminateOffset

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 Elapsed

impl Error for tokio::time::error::Error

impl Error for value_bag::error::Error

impl<'a, K, V> Error for alloc::collections::btree::map::entry::OccupiedError<'a, K, V>

where K: Debug + Ord, V: Debug,

impl<'a, K, V> Error for std::collections::hash::map::OccupiedError<'a, K, V>

where K: Debug, V: Debug,

impl<'a, T> Error for &'a T

where T: Error + ?Sized,

impl<A, S, V> Error for ConvertError<A, S, V>

where A: Display + Debug, S: Display + Debug, V: Display + Debug,

impl<E> Error for ConflictableTransactionError<E>

where E: Error,

impl<E> Error for TransactionError<E>

where E: Error,

impl<E> Error for Box<E>

where E: Error,

impl<F> Error for clap_builder::error::Error<F>

where F: ErrorFormatter,

impl<Src, Dst> Error for AlignmentError<Src, Dst>

where Src: Deref, Dst: KnownLayout + ?Sized,

impl<Src, Dst> Error for SizeError<Src, Dst>

where Src: Deref, Dst: KnownLayout + ?Sized,

impl<Src, Dst> Error for ValidityError<Src, Dst>

where Dst: KnownLayout + TryFromBytes + ?Sized,

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 async_channel::TrySendError<T>

impl<T> Error for async_channel::TrySendError<T>

impl<T> Error for PushError<T>

where T: Debug,

impl<T> Error for tokio::sync::mpsc::error::SendTimeoutError<T>

impl<T> Error for tokio::sync::mpsc::error::TrySendError<T>

impl<T> Error for SetError<T>

where T: Debug,

impl<T> Error for ThinBox<T>

where T: Error + ?Sized,

impl<T> Error for Arc<T>

where T: Error + ?Sized,

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".

impl<T> Error for async_channel::SendError<T>

impl<T> Error for async_channel::SendError<T>

impl<T> Error for ForcePushError<T>

where T: Debug,

impl<T> Error for AsyncFdTryNewError<T>

impl<T> Error for tokio::sync::broadcast::error::SendError<T>

where T: Debug,

impl<T> Error for tokio::sync::mpsc::error::SendError<T>

impl<T> Error for SetOnceError<T>

where T: Debug,

impl<T> Error for tokio::sync::watch::error::SendError<T>

impl<T, E> Error for TryChunksError<T, E>

where E: Debug + Display,

impl<T, E> Error for TryReadyChunksError<T, E>

where E: Debug + Display,

impl<W> Error for IntoInnerError<W>

where W: Send + Debug,