Trait std::error::Error 1.0.0[−][src]
pub trait Error: Debug + Display { fn source(&self) -> Option<&(dyn Error + 'static)> { ... } fn backtrace(&self) -> Option<&Backtrace> { ... } fn description(&self) -> &str { ... } fn cause(&self) -> Option<&dyn Error> { ... } }
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");Run
Errors may provide cause chain 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 via source
chains.
Provided methods
fn source(&self) -> Option<&(dyn Error + 'static)>
1.30.0[src]
The lower-level source of this error, if any.
Examples
use std::error::Error; use std::fmt; #[derive(Debug)] struct SuperError { side: 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.side) } } #[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 { side: SuperErrorSideKick }) } fn main() { match get_super_error() { Err(e) => { println!("Error: {}", e); println!("Caused by: {}", e.source().unwrap()); } _ => println!("No error"), } }Run
fn backtrace(&self) -> Option<&Backtrace>
[src]
Returns a stack backtrace, if available, of where this error occurred.
This function allows inspecting the location, in code, of where an error
happened. The returned Backtrace
contains information about the stack
trace of the OS thread of execution of where the error originated from.
Note that not all errors contain a Backtrace
. Also note that a
Backtrace
may actually be empty. For more information consult the
Backtrace
type itself.
fn description(&self) -> &str
[src]
use the Display impl or to_string()
if let Err(e) = "xc".parse::<u32>() { // Print `e` itself, no need for description(). eprintln!("Error: {}", e); }Run
fn cause(&self) -> Option<&dyn Error>
[src]
replaced by Error::source, which can support downcasting
Implementations
impl dyn Error + 'static
[src]
impl dyn Error + 'static
[src]pub fn is<T: Error + 'static>(&self) -> bool
1.3.0[src]
Returns true
if the boxed type is the same as T
pub fn downcast_ref<T: Error + 'static>(&self) -> Option<&T>
1.3.0[src]
Returns some reference to the boxed value if it is of type T
, or
None
if it isn’t.
pub fn downcast_mut<T: Error + 'static>(&mut self) -> Option<&mut T>
1.3.0[src]
Returns some mutable reference to the boxed value if it is of type T
, or
None
if it isn’t.
impl dyn Error + Send + 'static
[src]
impl dyn Error + Send + 'static
[src]pub fn is<T: Error + 'static>(&self) -> bool
1.3.0[src]
Forwards to the method defined on the type dyn Error
.
pub fn downcast_ref<T: Error + 'static>(&self) -> Option<&T>
1.3.0[src]
Forwards to the method defined on the type dyn Error
.
pub fn downcast_mut<T: Error + 'static>(&mut self) -> Option<&mut T>
1.3.0[src]
Forwards to the method defined on the type dyn Error
.
impl dyn Error + Send + Sync + 'static
[src]
impl dyn Error + Send + Sync + 'static
[src]pub fn is<T: Error + 'static>(&self) -> bool
1.3.0[src]
Forwards to the method defined on the type dyn Error
.
pub fn downcast_ref<T: Error + 'static>(&self) -> Option<&T>
1.3.0[src]
Forwards to the method defined on the type dyn Error
.
pub fn downcast_mut<T: Error + 'static>(&mut self) -> Option<&mut T>
1.3.0[src]
Forwards to the method defined on the type dyn Error
.
impl dyn Error
[src]
impl dyn Error
[src]pub fn downcast<T: Error + 'static>(
self: Box<Self>
) -> Result<Box<T>, Box<dyn Error>>
1.3.0[src]
self: Box<Self>
) -> Result<Box<T>, Box<dyn Error>>
Attempts to downcast the box to a concrete type.
pub fn chain(&self) -> Chain<'_>ⓘ
[src]
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.chain(); 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());Run
impl dyn Error + Send
[src]
impl dyn Error + Send
[src]impl dyn Error + Send + Sync
[src]
impl dyn Error + Send + Sync
[src]Implementors
impl Error for TryReserveError
[src]
impl Error for Infallible
1.8.0[src]
impl Error for Infallible
1.8.0[src]fn description(&self) -> &str
[src]
impl Error for RecvTimeoutError
1.15.0[src]
impl Error for RecvTimeoutError
1.15.0[src]fn description(&self) -> &str
[src]
impl Error for TryRecvError
[src]
impl Error for TryRecvError
[src]fn description(&self) -> &str
[src]
impl Error for !
[src]
impl Error for AllocError
[src]
impl Error for LayoutError
1.28.0[src]
impl Error for TryFromSliceError
1.34.0[src]
impl Error for TryFromSliceError
1.34.0[src]fn description(&self) -> &str
[src]
impl Error for BorrowError
1.13.0[src]
impl Error for BorrowError
1.13.0[src]fn description(&self) -> &str
[src]
impl Error for BorrowMutError
1.13.0[src]
impl Error for BorrowMutError
1.13.0[src]fn description(&self) -> &str
[src]
impl Error for CharTryFromError
1.34.0[src]
impl Error for CharTryFromError
1.34.0[src]fn description(&self) -> &str
[src]
impl Error for DecodeUtf16Error
1.9.0[src]
impl Error for DecodeUtf16Error
1.9.0[src]fn description(&self) -> &str
[src]
impl Error for ParseCharError
1.20.0[src]
impl Error for ParseCharError
1.20.0[src]fn description(&self) -> &str
[src]
impl Error for JoinPathsError
[src]
impl Error for JoinPathsError
[src]fn description(&self) -> &str
[src]
impl Error for FromBytesWithNulError
1.17.0[src]
impl Error for FromBytesWithNulError
1.17.0[src]fn description(&self) -> &str
[src]
impl Error for FromVecWithNulError
[src]
impl Error for IntoStringError
1.7.0[src]
impl Error for IntoStringError
1.7.0[src]impl Error for AddrParseError
1.4.0[src]
impl Error for AddrParseError
1.4.0[src]fn description(&self) -> &str
[src]
impl Error for ParseFloatError
[src]
impl Error for ParseFloatError
[src]fn description(&self) -> &str
[src]
impl Error for ParseIntError
[src]
impl Error for ParseIntError
[src]fn description(&self) -> &str
[src]
impl Error for TryFromIntError
1.34.0[src]
impl Error for TryFromIntError
1.34.0[src]fn description(&self) -> &str
[src]
impl Error for StripPrefixError
1.7.0[src]
impl Error for StripPrefixError
1.7.0[src]fn description(&self) -> &str
[src]
impl Error for ParseBoolError
[src]
impl Error for ParseBoolError
[src]fn description(&self) -> &str
[src]
impl Error for FromUtf8Error
[src]
impl Error for FromUtf8Error
[src]fn description(&self) -> &str
[src]
impl Error for FromUtf16Error
[src]
impl Error for FromUtf16Error
[src]fn description(&self) -> &str
[src]
impl Error for AccessError
1.26.0[src]
impl Error for SystemTimeError
1.8.0[src]
impl Error for SystemTimeError
1.8.0[src]fn description(&self) -> &str
[src]
impl<'a, K: Debug + Ord, V: Debug> Error for std::collections::btree_map::OccupiedError<'a, K, V>
[src]
impl<'a, K: Debug + Ord, V: Debug> Error for std::collections::btree_map::OccupiedError<'a, K, V>
[src]fn description(&self) -> &str
[src]
impl<'a, K: Debug, V: Debug> Error for std::collections::hash_map::OccupiedError<'a, K, V>
[src]
impl<'a, K: Debug, V: Debug> Error for std::collections::hash_map::OccupiedError<'a, K, V>
[src]fn description(&self) -> &str
[src]
impl<T> Error for TryLockError<T>
[src]
impl<T> Error for TryLockError<T>
[src]impl<T> Error for PoisonError<T>
[src]
impl<T> Error for PoisonError<T>
[src]fn description(&self) -> &str
[src]
impl<T: Send> Error for TrySendError<T>
[src]
impl<T: Send> Error for TrySendError<T>
[src]fn description(&self) -> &str
[src]
impl<W: Send + Debug> Error for IntoInnerError<W>
[src]
impl<W: Send + Debug> Error for IntoInnerError<W>
[src]