1.0.0[−][src]Trait c3p0_mysql::mysql::r2d2::mysql::serde::de::StdError
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 source
method 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 access to that error via the
source
method. 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 description(&self) -> &str
This method is soft-deprecated.
Although using it won’t cause compilation warning,
new code should use Display
instead
and new impl
s 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"), }
fn cause(&self) -> Option<&dyn 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<&dyn 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"), } }
fn source(&self) -> Option<&(dyn 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"), } }
fn backtrace(&self) -> Option<&Backtrace>
backtrace
)Returns a stack backtrace, if available, of where this error ocurred.
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.
Methods
impl dyn Error + 'static
[src]
pub fn is<T>(&self) -> bool where
T: 'static + Error,
1.3.0[src]
T: 'static + Error,
Returns true
if the boxed type is the same as T
pub fn downcast_ref<T>(&self) -> Option<&T> where
T: 'static + Error,
1.3.0[src]
T: 'static + Error,
Returns some reference to the boxed 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: 'static + Error,
1.3.0[src]
T: 'static + Error,
Returns some mutable reference to the boxed value if it is of type T
, or
None
if it isn't.
impl dyn Error + 'static + Send
[src]
pub fn is<T>(&self) -> bool where
T: 'static + Error,
1.3.0[src]
T: 'static + Error,
Forwards to the method defined on the type dyn Error
.
pub fn downcast_ref<T>(&self) -> Option<&T> where
T: 'static + Error,
1.3.0[src]
T: 'static + Error,
Forwards to the method defined on the type dyn Error
.
pub fn downcast_mut<T>(&mut self) -> Option<&mut T> where
T: 'static + Error,
1.3.0[src]
T: 'static + Error,
Forwards to the method defined on the type dyn Error
.
impl dyn Error + 'static + Send + Sync
[src]
pub fn is<T>(&self) -> bool where
T: 'static + Error,
1.3.0[src]
T: 'static + Error,
Forwards to the method defined on the type dyn Error
.
pub fn downcast_ref<T>(&self) -> Option<&T> where
T: 'static + Error,
1.3.0[src]
T: 'static + Error,
Forwards to the method defined on the type dyn Error
.
pub fn downcast_mut<T>(&mut self) -> Option<&mut T> where
T: 'static + Error,
1.3.0[src]
T: 'static + Error,
Forwards to the method defined on the type dyn Error
.
impl dyn Error + 'static
[src]
pub fn downcast<T>(
self: Box<dyn Error + 'static>
) -> Result<Box<T>, Box<dyn Error + 'static>> where
T: 'static + Error,
1.3.0[src]
self: Box<dyn Error + 'static>
) -> Result<Box<T>, Box<dyn Error + 'static>> where
T: 'static + Error,
Attempts to downcast the box to a concrete type.
pub fn iter_chain(&self) -> ErrorIter
[src]
error_iter
)Returns an iterator starting with the current error and continuing with
recursively calling source
.
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.iter_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());
pub fn iter_sources(&self) -> ErrorIter
[src]
error_iter
)Returns an iterator starting with the source
of this error
and continuing with recursively calling source
.
Examples
#![feature(error_iter)] use std::error::Error; use std::fmt; #[derive(Debug)] struct A; #[derive(Debug)] struct B(Option<Box<dyn Error + 'static>>); #[derive(Debug)] struct C(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 fmt::Display for C { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { write!(f, "C") } } impl Error for A {} impl Error for B { fn source(&self) -> Option<&(dyn Error + 'static)> { self.0.as_ref().map(|e| e.as_ref()) } } impl Error for C { fn source(&self) -> Option<&(dyn Error + 'static)> { self.0.as_ref().map(|e| e.as_ref()) } } let b = B(Some(Box::new(A))); let c = C(Some(Box::new(b))); // let err : Box<Error> = c.into(); // or let err = &c as &(dyn Error); let mut iter = err.iter_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 + 'static + Send
[src]
pub fn downcast<T>(
self: Box<dyn Error + 'static + Send>
) -> Result<Box<T>, Box<dyn Error + 'static + Send>> where
T: 'static + Error,
1.3.0[src]
self: Box<dyn Error + 'static + Send>
) -> Result<Box<T>, Box<dyn Error + 'static + Send>> where
T: 'static + Error,
Attempts to downcast the box to a concrete type.
impl dyn Error + 'static + Send + Sync
[src]
pub fn downcast<T>(
self: Box<dyn Error + 'static + Send + Sync>
) -> Result<Box<T>, Box<dyn Error + 'static + Send + Sync>> where
T: 'static + Error,
1.3.0[src]
self: Box<dyn Error + 'static + Send + Sync>
) -> Result<Box<T>, Box<dyn Error + 'static + Send + Sync>> where
T: 'static + Error,
Attempts to downcast the box to a concrete type.
Implementations on Foreign Types
impl Error for TryFromSliceError
[src]
fn description(&self) -> &str
[src]
impl Error for AllocErr
[src]
fn description(&self) -> &str
[src]
impl Error for StripPrefixError
[src]
fn description(&self) -> &str
[src]
impl Error for Error
[src]
fn description(&self) -> &str
[src]
impl<T> Error for SendError<T> where
T: Send,
[src]
T: Send,
impl Error for AccessError
[src]
impl Error for CharTryFromError
[src]
fn description(&self) -> &str
[src]
impl Error for RecvError
[src]
impl Error for SystemTimeError
[src]
fn description(&self) -> &str
[src]
impl<T> Error for TryLockError<T>
[src]
impl Error for FromBytesWithNulError
[src]
fn description(&self) -> &str
[src]
impl Error for ParseFloatError
[src]
fn description(&self) -> &str
[src]
impl Error for AddrParseError
[src]
fn description(&self) -> &str
[src]
impl Error for Infallible
[src]
fn description(&self) -> &str
[src]
impl Error for JoinPathsError
[src]
fn description(&self) -> &str
[src]
impl Error for FromUtf16Error
[src]
fn description(&self) -> &str
[src]
impl Error for ParseBoolError
[src]
fn description(&self) -> &str
[src]
impl Error for DecodeUtf16Error
[src]
fn description(&self) -> &str
[src]
impl Error for !
[src]
fn description(&self) -> &str
[src]
impl Error for Utf8Error
[src]
fn description(&self) -> &str
[src]
impl<T> Error for TrySendError<T> where
T: Send,
[src]
T: Send,
impl Error for Error
[src]
fn description(&self) -> &str
[src]
fn cause(&self) -> Option<&dyn Error>
[src]
fn source(&self) -> Option<&(dyn Error + 'static)>
[src]
impl Error for IntoStringError
[src]
impl<W> Error for IntoInnerError<W> where
W: Send + Debug,
[src]
W: Send + Debug,
fn description(&self) -> &str
[src]
impl Error for VarError
[src]
fn description(&self) -> &str
[src]
impl Error for TryFromIntError
[src]
fn description(&self) -> &str
[src]
impl Error for ParseCharError
[src]
fn description(&self) -> &str
[src]
impl Error for BorrowError
[src]
fn description(&self) -> &str
[src]
impl Error for LayoutErr
[src]
fn description(&self) -> &str
[src]
impl Error for BorrowMutError
[src]
fn description(&self) -> &str
[src]
impl Error for NulError
[src]
fn description(&self) -> &str
[src]
impl Error for FromUtf8Error
[src]
fn description(&self) -> &str
[src]
impl<T> Error for Box<T> where
T: Error,
[src]
T: Error,
fn description(&self) -> &str
[src]
fn cause(&self) -> Option<&dyn Error>
[src]
fn source(&self) -> Option<&(dyn Error + 'static)>
[src]
impl Error for TryRecvError
[src]
impl Error for CannotReallocInPlace
[src]
fn description(&self) -> &str
[src]
impl Error for RecvTimeoutError
[src]
impl Error for ParseIntError
[src]
fn description(&self) -> &str
[src]
impl<T> Error for PoisonError<T>
[src]
fn description(&self) -> &str
[src]
impl Error for ParseBigDecimalError
fn description(&self) -> &str
impl Error for ParseBigIntError
[src]
fn description(&self) -> &str
[src]
impl Error for Error
fn description(&self) -> &str
impl<E> Error for ParseComplexError<E> where
E: Error,
[src]
E: Error,
fn description(&self) -> &str
[src]
impl Error for ParseRatioError
[src]
fn description(&self) -> &str
[src]
impl Error for ReadError
[src]
impl Error for WeightedError
[src]
impl Error for Error
[src]
impl Error for Error
[src]
impl Error for DecodeError
fn description(&self) -> &str
fn cause(&self) -> Option<&dyn Error>
impl Error for Error
fn description(&self) -> &str
impl Error for Error
fn description(&self) -> &str
impl Error for Error
fn description(&self) -> &str
impl Error for CaseFoldError
impl Error for Error
fn description(&self) -> &str
impl Error for Error
fn description(&self) -> &str
impl Error for UnicodeWordError
impl Error for Error
fn description(&self) -> &str
fn cause(&self) -> Option<&dyn Error>
impl<T> Error for CapacityError<T> where
T: Any,
[src]
T: Any,
Requires features="std"
.
fn description(&self) -> &str
[src]
impl Error for InvalidOutputSize
fn description(&self) -> &str
impl Error for ParseError
[src]
fn description(&self) -> &str
[src]
impl<W> Error for IntoInnerError<W> where
W: Debug,
W: Debug,