Trait std::error::Error

pub trait Error: Debug + Display {
    fn description(&self) -> &str;

    fn cause(&self) -> Option<&Error> { ... }
}

Base functionality for all errors in Rust.

Required Methods

fn description(&self) -> &str

A short description of the error.

The description should only be used for a simple message. It should not contain newlines or sentence-ending punctuation, to facilitate embedding in larger user-facing strings. For showing formatted error messages with more information see Display.

Examples

use std::error::Error;

match "xc".parse::<u32>() {
    Err(e) => {
        println!("Error: {}", e.description());
    }
    _ => println!("No error"),
}

Provided Methods

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

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"),
    }
}

Methods

impl Error + 'static

pub fn is<T: Error + 'static>(&self) -> bool

Returns true if the boxed type is the same as T

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>

Returns some mutable reference to the boxed value if it is of type T, or None if it isn't.

impl Error + Send + 'static

pub fn is<T: Error + 'static>(&self) -> bool

Forwards to the method defined on the type Any.

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>

Forwards to the method defined on the type Any.

impl Error + Send + Sync + 'static

pub fn is<T: Error + 'static>(&self) -> bool

Forwards to the method defined on the type Any.

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>

Forwards to the method defined on the type Any.

impl Error

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

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

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

fn description(&self) -> &str

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

Implementors

• impl Error for VarError
• impl Error for JoinPathsError
• impl Error for !
• impl Error for AllocErr
• impl Error for CannotReallocInPlace
• impl Error for ParseBoolError
• impl Error for Utf8Error
• impl Error for ParseIntError
• impl Error for TryFromIntError
• impl Error for ParseFloatError
• impl Error for FromUtf8Error
• impl Error for FromUtf16Error
• impl Error for ParseError
• impl Error for DecodeUtf16Error
• impl<T: Error> Error for Box<T>
• impl Error for std::fmt::Error
• impl Error for BorrowError
• impl Error for BorrowMutError
• impl Error for CharTryFromError
• impl Error for ParseCharError
• impl Error for Infallible
• impl Error for NulError
• impl Error for FromBytesWithNulError
• impl Error for IntoStringError
• impl<W: Send + Debug> Error for IntoInnerError<W>
• impl Error for std::io::Error
• impl Error for CharsError
• impl Error for AddrParseError
• impl Error for StripPrefixError
• impl<T: Send> Error for SendError<T>
• impl<T: Send> Error for TrySendError<T>
• impl Error for RecvError
• impl Error for TryRecvError
• impl Error for RecvTimeoutError
• impl Error for SystemTimeError
• impl<T> Error for PoisonError<T>
• impl<T> Error for TryLockError<T>