1.0.0[−][src]Trait std::error::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, and may provide
cause chain information:
The cause method is generally used when errors cross "abstraction
boundaries", i.e.  when a one module must report an error that is "caused"
by an error from a lower-level module. This setup makes it possible for the
high-level module to provide its own errors that do not commit to any
particular implementation, but also reveal some of its implementation for
debugging via cause chains.
Provided Methods
fn description(&self) -> &str
This method is soft-deprecated.
Although using it won’t cause compilation warning,
new code should use Display instead
and new impls can omit it.
To obtain error description as a string, use to_string().
Examples
match "xc".parse::<u32>() { Err(e) => { // Print `e` itself, not `e.description()`. println!("Error: {}", e); } _ => println!("No error"), }Run
fn cause(&self) -> Option<&Error>
: replaced by Error::source, which can support downcasting
The lower-level cause 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 description(&self) -> &str { "I'm the superhero of errors" } fn cause(&self) -> Option<&Error> { 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 description(&self) -> &str { "I'm SuperError side kick" } } fn get_super_error() -> Result<(), SuperError> { Err(SuperError { side: SuperErrorSideKick }) } fn main() { match get_super_error() { Err(e) => { println!("Error: {}", e.description()); println!("Caused by: {}", e.cause().unwrap()); } _ => println!("No error"), } }Run
fn source(&self) -> Option<&(Error + 'static)>1.30.0
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 description(&self) -> &str { "I'm the superhero of errors" } 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 description(&self) -> &str { "I'm SuperError side kick" } } fn get_super_error() -> Result<(), SuperError> { Err(SuperError { side: SuperErrorSideKick }) } fn main() { match get_super_error() { Err(e) => { println!("Error: {}", e.description()); println!("Caused by: {}", e.source().unwrap()); } _ => println!("No error"), } }Run
Methods
impl Error + 'static[src] 
impl Error + 'staticpub fn is<T: Error + 'static>(&self) -> bool1.3.0[src] 
pub fn is<T: Error + 'static>(&self) -> boolReturns true if the boxed type is the same as T
pub fn downcast_ref<T: Error + 'static>(&self) -> Option<&T>1.3.0[src] 
pub fn downcast_ref<T: Error + 'static>(&self) -> Option<&T>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] 
pub fn downcast_mut<T: Error + 'static>(&mut self) -> Option<&mut T>Returns some mutable reference to the boxed value if it is of type T, or
None if it isn't.
impl Error + Send + 'static[src] 
impl Error + Send + 'staticpub fn is<T: Error + 'static>(&self) -> bool1.3.0[src] 
pub fn is<T: Error + 'static>(&self) -> boolForwards to the method defined on the type Any.
pub fn downcast_ref<T: Error + 'static>(&self) -> Option<&T>1.3.0[src] 
pub fn downcast_ref<T: Error + 'static>(&self) -> Option<&T>Forwards to the method defined on the type Any.
pub fn downcast_mut<T: Error + 'static>(&mut self) -> Option<&mut T>1.3.0[src] 
pub fn downcast_mut<T: Error + 'static>(&mut self) -> Option<&mut T>Forwards to the method defined on the type Any.
impl Error + Send + Sync + 'static[src] 
impl Error + Send + Sync + 'staticpub fn is<T: Error + 'static>(&self) -> bool1.3.0[src] 
pub fn is<T: Error + 'static>(&self) -> boolForwards to the method defined on the type Any.
pub fn downcast_ref<T: Error + 'static>(&self) -> Option<&T>1.3.0[src] 
pub fn downcast_ref<T: Error + 'static>(&self) -> Option<&T>Forwards to the method defined on the type Any.
pub fn downcast_mut<T: Error + 'static>(&mut self) -> Option<&mut T>1.3.0[src] 
pub fn downcast_mut<T: Error + 'static>(&mut self) -> Option<&mut T>Forwards to the method defined on the type Any.
impl Error[src] 
impl Errorpub fn downcast<T: Error + 'static>(
    self: Box<Self>
) -> Result<Box<T>, Box<Error>>1.3.0[src] 
pub fn downcast<T: Error + 'static>(
    self: Box<Self>
) -> Result<Box<T>, Box<Error>>Attempt to downcast the box to a concrete type.
impl Error + Send[src] 
impl Error + Sendpub fn downcast<T: Error + 'static>(
    self: Box<Self>
) -> Result<Box<T>, Box<Error + Send>>1.3.0[src] 
pub fn downcast<T: Error + 'static>(
    self: Box<Self>
) -> Result<Box<T>, Box<Error + Send>>Attempt to downcast the box to a concrete type.
impl Error + Send + Sync[src] 
impl Error + Send + Syncpub fn downcast<T: Error + 'static>(
    self: Box<Self>
) -> Result<Box<T>, Box<Self>>1.3.0[src] 
pub fn downcast<T: Error + 'static>(
    self: Box<Self>
) -> Result<Box<T>, Box<Self>>Attempt to downcast the box to a concrete type.
Implementations on Foreign Types
impl Error for TryFromSliceError[src] 
impl Error for TryFromSliceErrorfn description(&self) -> &str[src] 
fn description(&self) -> &strfn cause(&self) -> Option<&Error>1.0.0[src] 
fn cause(&self) -> Option<&Error>: replaced by Error::source, which can support downcasting
fn source(&self) -> Option<&(Error + 'static)>1.30.0[src] 
fn source(&self) -> Option<&(Error + 'static)>Implementors
impl Error for VarError[src] 
impl Error for VarErrorfn description(&self) -> &str[src] 
fn description(&self) -> &strfn cause(&self) -> Option<&Error>[src] 
fn cause(&self) -> Option<&Error>: replaced by Error::source, which can support downcasting
fn source(&self) -> Option<&(Error + 'static)>1.30.0[src] 
fn source(&self) -> Option<&(Error + 'static)>impl Error for ParseError[src] 
impl Error for ParseErrorfn description(&self) -> &str[src] 
fn description(&self) -> &strfn cause(&self) -> Option<&Error>1.0.0[src] 
fn cause(&self) -> Option<&Error>: replaced by Error::source, which can support downcasting
fn source(&self) -> Option<&(Error + 'static)>1.30.0[src] 
fn source(&self) -> Option<&(Error + 'static)>impl Error for RecvTimeoutError[src] 
impl Error for RecvTimeoutErrorfn description(&self) -> &str[src] 
fn description(&self) -> &strfn cause(&self) -> Option<&Error>[src] 
fn cause(&self) -> Option<&Error>: replaced by Error::source, which can support downcasting
fn source(&self) -> Option<&(Error + 'static)>1.30.0[src] 
fn source(&self) -> Option<&(Error + 'static)>impl Error for TryRecvError[src] 
impl Error for TryRecvErrorfn description(&self) -> &str[src] 
fn description(&self) -> &strfn cause(&self) -> Option<&Error>[src] 
fn cause(&self) -> Option<&Error>: replaced by Error::source, which can support downcasting
fn source(&self) -> Option<&(Error + 'static)>1.30.0[src] 
fn source(&self) -> Option<&(Error + 'static)>impl Error for ![src] 
impl Error for !fn description(&self) -> &str[src] 
fn description(&self) -> &strfn cause(&self) -> Option<&Error>1.0.0[src] 
fn cause(&self) -> Option<&Error>: replaced by Error::source, which can support downcasting
fn source(&self) -> Option<&(Error + 'static)>1.30.0[src] 
fn source(&self) -> Option<&(Error + 'static)>impl Error for AllocErr[src] 
impl Error for AllocErrfn description(&self) -> &str[src] 
fn description(&self) -> &strfn cause(&self) -> Option<&Error>1.0.0[src] 
fn cause(&self) -> Option<&Error>: replaced by Error::source, which can support downcasting
fn source(&self) -> Option<&(Error + 'static)>1.30.0[src] 
fn source(&self) -> Option<&(Error + 'static)>impl Error for CannotReallocInPlace[src] 
impl Error for CannotReallocInPlacefn description(&self) -> &str[src] 
fn description(&self) -> &strfn cause(&self) -> Option<&Error>1.0.0[src] 
fn cause(&self) -> Option<&Error>: replaced by Error::source, which can support downcasting
fn source(&self) -> Option<&(Error + 'static)>1.30.0[src] 
fn source(&self) -> Option<&(Error + 'static)>impl Error for LayoutErr[src] 
impl Error for LayoutErrfn description(&self) -> &str[src] 
fn description(&self) -> &strfn cause(&self) -> Option<&Error>1.0.0[src] 
fn cause(&self) -> Option<&Error>: replaced by Error::source, which can support downcasting
fn source(&self) -> Option<&(Error + 'static)>1.30.0[src] 
fn source(&self) -> Option<&(Error + 'static)>impl Error for BorrowError[src] 
impl Error for BorrowErrorfn description(&self) -> &str[src] 
fn description(&self) -> &strfn cause(&self) -> Option<&Error>1.0.0[src] 
fn cause(&self) -> Option<&Error>: replaced by Error::source, which can support downcasting
fn source(&self) -> Option<&(Error + 'static)>1.30.0[src] 
fn source(&self) -> Option<&(Error + 'static)>impl Error for BorrowMutError[src] 
impl Error for BorrowMutErrorfn description(&self) -> &str[src] 
fn description(&self) -> &strfn cause(&self) -> Option<&Error>1.0.0[src] 
fn cause(&self) -> Option<&Error>: replaced by Error::source, which can support downcasting
fn source(&self) -> Option<&(Error + 'static)>1.30.0[src] 
fn source(&self) -> Option<&(Error + 'static)>impl Error for CharTryFromError[src] 
impl Error for CharTryFromErrorfn description(&self) -> &str[src] 
fn description(&self) -> &strfn cause(&self) -> Option<&Error>1.0.0[src] 
fn cause(&self) -> Option<&Error>: replaced by Error::source, which can support downcasting
fn source(&self) -> Option<&(Error + 'static)>1.30.0[src] 
fn source(&self) -> Option<&(Error + 'static)>impl Error for DecodeUtf16Error[src] 
impl Error for DecodeUtf16Errorfn description(&self) -> &str[src] 
fn description(&self) -> &strfn cause(&self) -> Option<&Error>1.0.0[src] 
fn cause(&self) -> Option<&Error>: replaced by Error::source, which can support downcasting
fn source(&self) -> Option<&(Error + 'static)>1.30.0[src] 
fn source(&self) -> Option<&(Error + 'static)>impl Error for ParseCharError[src] 
impl Error for ParseCharErrorfn description(&self) -> &str[src] 
fn description(&self) -> &strfn cause(&self) -> Option<&Error>1.0.0[src] 
fn cause(&self) -> Option<&Error>: replaced by Error::source, which can support downcasting
fn source(&self) -> Option<&(Error + 'static)>1.30.0[src] 
fn source(&self) -> Option<&(Error + 'static)>impl Error for JoinPathsError[src] 
impl Error for JoinPathsErrorfn description(&self) -> &str[src] 
fn description(&self) -> &strfn cause(&self) -> Option<&Error>[src] 
fn cause(&self) -> Option<&Error>: replaced by Error::source, which can support downcasting
fn source(&self) -> Option<&(Error + 'static)>1.30.0[src] 
fn source(&self) -> Option<&(Error + 'static)>impl Error for FromBytesWithNulError[src] 
impl Error for FromBytesWithNulErrorfn description(&self) -> &str[src] 
fn description(&self) -> &strfn cause(&self) -> Option<&Error>1.0.0[src] 
fn cause(&self) -> Option<&Error>: replaced by Error::source, which can support downcasting
fn source(&self) -> Option<&(Error + 'static)>1.30.0[src] 
fn source(&self) -> Option<&(Error + 'static)>impl Error for IntoStringError[src] 
impl Error for IntoStringErrorfn description(&self) -> &str[src] 
fn description(&self) -> &strfn cause(&self) -> Option<&Error>[src] 
fn cause(&self) -> Option<&Error>: replaced by Error::source, which can support downcasting
fn source(&self) -> Option<&(Error + 'static)>1.30.0[src] 
fn source(&self) -> Option<&(Error + 'static)>impl Error for NulError[src] 
impl Error for NulErrorfn description(&self) -> &str[src] 
fn description(&self) -> &strfn cause(&self) -> Option<&Error>[src] 
fn cause(&self) -> Option<&Error>: replaced by Error::source, which can support downcasting
fn source(&self) -> Option<&(Error + 'static)>1.30.0[src] 
fn source(&self) -> Option<&(Error + 'static)>impl Error for std::fmt::Error[src] 
impl Error for std::fmt::Errorfn description(&self) -> &str[src] 
fn description(&self) -> &strfn cause(&self) -> Option<&Error>1.0.0[src] 
fn cause(&self) -> Option<&Error>: replaced by Error::source, which can support downcasting
fn source(&self) -> Option<&(Error + 'static)>1.30.0[src] 
fn source(&self) -> Option<&(Error + 'static)>impl Error for std::io::Error[src] 
impl Error for std::io::Errorfn description(&self) -> &str[src] 
fn description(&self) -> &strfn cause(&self) -> Option<&Error>[src] 
fn cause(&self) -> Option<&Error>: replaced by Error::source, which can support downcasting
fn source(&self) -> Option<&(Error + 'static)>1.30.0[src] 
fn source(&self) -> Option<&(Error + 'static)>impl Error for AddrParseError[src] 
impl Error for AddrParseErrorfn description(&self) -> &str[src] 
fn description(&self) -> &strfn cause(&self) -> Option<&Error>1.0.0[src] 
fn cause(&self) -> Option<&Error>: replaced by Error::source, which can support downcasting
fn source(&self) -> Option<&(Error + 'static)>1.30.0[src] 
fn source(&self) -> Option<&(Error + 'static)>impl Error for ParseFloatError[src] 
impl Error for ParseFloatErrorfn description(&self) -> &str[src] 
fn description(&self) -> &strfn cause(&self) -> Option<&Error>[src] 
fn cause(&self) -> Option<&Error>: replaced by Error::source, which can support downcasting
fn source(&self) -> Option<&(Error + 'static)>1.30.0[src] 
fn source(&self) -> Option<&(Error + 'static)>impl Error for ParseIntError[src] 
impl Error for ParseIntErrorfn description(&self) -> &str[src] 
fn description(&self) -> &strfn cause(&self) -> Option<&Error>[src] 
fn cause(&self) -> Option<&Error>: replaced by Error::source, which can support downcasting
fn source(&self) -> Option<&(Error + 'static)>1.30.0[src] 
fn source(&self) -> Option<&(Error + 'static)>impl Error for TryFromIntError[src] 
impl Error for TryFromIntErrorfn description(&self) -> &str[src] 
fn description(&self) -> &strfn cause(&self) -> Option<&Error>1.0.0[src] 
fn cause(&self) -> Option<&Error>: replaced by Error::source, which can support downcasting
fn source(&self) -> Option<&(Error + 'static)>1.30.0[src] 
fn source(&self) -> Option<&(Error + 'static)>impl Error for StripPrefixError[src] 
impl Error for StripPrefixErrorfn description(&self) -> &str[src] 
fn description(&self) -> &strfn cause(&self) -> Option<&Error>1.0.0[src] 
fn cause(&self) -> Option<&Error>: replaced by Error::source, which can support downcasting
fn source(&self) -> Option<&(Error + 'static)>1.30.0[src] 
fn source(&self) -> Option<&(Error + 'static)>impl Error for ParseBoolError[src] 
impl Error for ParseBoolErrorfn description(&self) -> &str[src] 
fn description(&self) -> &strfn cause(&self) -> Option<&Error>[src] 
fn cause(&self) -> Option<&Error>: replaced by Error::source, which can support downcasting
fn source(&self) -> Option<&(Error + 'static)>1.30.0[src] 
fn source(&self) -> Option<&(Error + 'static)>impl Error for Utf8Error[src] 
impl Error for Utf8Errorfn description(&self) -> &str[src] 
fn description(&self) -> &strfn cause(&self) -> Option<&Error>[src] 
fn cause(&self) -> Option<&Error>: replaced by Error::source, which can support downcasting
fn source(&self) -> Option<&(Error + 'static)>1.30.0[src] 
fn source(&self) -> Option<&(Error + 'static)>impl Error for FromUtf16Error[src] 
impl Error for FromUtf16Errorfn description(&self) -> &str[src] 
fn description(&self) -> &strfn cause(&self) -> Option<&Error>[src] 
fn cause(&self) -> Option<&Error>: replaced by Error::source, which can support downcasting
fn source(&self) -> Option<&(Error + 'static)>1.30.0[src] 
fn source(&self) -> Option<&(Error + 'static)>impl Error for FromUtf8Error[src] 
impl Error for FromUtf8Errorfn description(&self) -> &str[src] 
fn description(&self) -> &strfn cause(&self) -> Option<&Error>[src] 
fn cause(&self) -> Option<&Error>: replaced by Error::source, which can support downcasting
fn source(&self) -> Option<&(Error + 'static)>1.30.0[src] 
fn source(&self) -> Option<&(Error + 'static)>impl Error for RecvError[src] 
impl Error for RecvErrorfn description(&self) -> &str[src] 
fn description(&self) -> &strfn cause(&self) -> Option<&Error>[src] 
fn cause(&self) -> Option<&Error>: replaced by Error::source, which can support downcasting
fn source(&self) -> Option<&(Error + 'static)>1.30.0[src] 
fn source(&self) -> Option<&(Error + 'static)>impl Error for SystemTimeError[src] 
impl Error for SystemTimeErrorfn description(&self) -> &str[src] 
fn description(&self) -> &strfn cause(&self) -> Option<&Error>1.0.0[src] 
fn cause(&self) -> Option<&Error>: replaced by Error::source, which can support downcasting
fn source(&self) -> Option<&(Error + 'static)>1.30.0[src] 
fn source(&self) -> Option<&(Error + 'static)>impl<T> Error for TryLockError<T>[src] 
impl<T> Error for TryLockError<T>fn description(&self) -> &str[src] 
fn description(&self) -> &strfn cause(&self) -> Option<&Error>[src] 
fn cause(&self) -> Option<&Error>: replaced by Error::source, which can support downcasting
fn source(&self) -> Option<&(Error + 'static)>1.30.0[src] 
fn source(&self) -> Option<&(Error + 'static)>impl<T> Error for PoisonError<T>[src] 
impl<T> Error for PoisonError<T>fn description(&self) -> &str[src] 
fn description(&self) -> &strfn cause(&self) -> Option<&Error>[src] 
fn cause(&self) -> Option<&Error>: replaced by Error::source, which can support downcasting
fn source(&self) -> Option<&(Error + 'static)>1.30.0[src] 
fn source(&self) -> Option<&(Error + 'static)>impl<T: Error> Error for Box<T>[src] 
impl<T: Error> Error for Box<T>fn description(&self) -> &str[src] 
fn description(&self) -> &strfn cause(&self) -> Option<&Error>[src] 
fn cause(&self) -> Option<&Error>: replaced by Error::source, which can support downcasting
fn source(&self) -> Option<&(Error + 'static)>1.30.0[src] 
fn source(&self) -> Option<&(Error + 'static)>impl<T: Send> Error for TrySendError<T>[src] 
impl<T: Send> Error for TrySendError<T>fn description(&self) -> &str[src] 
fn description(&self) -> &strfn cause(&self) -> Option<&Error>[src] 
fn cause(&self) -> Option<&Error>: replaced by Error::source, which can support downcasting
fn source(&self) -> Option<&(Error + 'static)>1.30.0[src] 
fn source(&self) -> Option<&(Error + 'static)>impl<T: Send> Error for SendError<T>[src] 
impl<T: Send> Error for SendError<T>fn description(&self) -> &str[src] 
fn description(&self) -> &strfn cause(&self) -> Option<&Error>[src] 
fn cause(&self) -> Option<&Error>: replaced by Error::source, which can support downcasting
fn source(&self) -> Option<&(Error + 'static)>1.30.0[src] 
fn source(&self) -> Option<&(Error + 'static)>impl<W: Send + Debug> Error for IntoInnerError<W>[src] 
impl<W: Send + Debug> Error for IntoInnerError<W>