Trait boolean_enums::lstd::error::Error

pub trait Error: Debug + Display {
    fn description(&self) -> &str { ... }
    fn cause(&self) -> Option<&dyn Error> { ... }
    fn source(&self) -> Option<&(dyn Error + 'static)> { ... }
}

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"),
}

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

Deprecated since 1.33.0:

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"),
    }
}

fn source(&self) -> Option<&(dyn Error + 'static)>

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"),
    }
}

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Methods

impl dyn Error + 'static

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

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,

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

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

Forwards to the method defined on the type Any.

pub fn downcast_ref<T>(&self) -> Option<&T> where     T: 'static + Error,

Forwards to the method defined on the type Any.

pub fn downcast_mut<T>(&mut self) -> Option<&mut T> where     T: 'static + Error,

Forwards to the method defined on the type Any.

impl dyn Error + 'static + Send + Sync

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

Forwards to the method defined on the type Any.

pub fn downcast_ref<T>(&self) -> Option<&T> where     T: 'static + Error,

Forwards to the method defined on the type Any.

pub fn downcast_mut<T>(&mut self) -> Option<&mut T> where     T: 'static + Error,

Forwards to the method defined on the type Any.

impl dyn Error + 'static

pub fn downcast<T>(     self: Box<dyn Error + 'static> ) -> Result<Box<T>, Box<dyn Error + 'static>> where     T: 'static + Error,

Attempt to downcast the box to a concrete type.

impl dyn Error + 'static + Send

pub fn downcast<T>(     self: Box<dyn Error + 'static + Send> ) -> Result<Box<T>, Box<dyn Error + 'static + Send>> where     T: 'static + Error,

Attempt to downcast the box to a concrete type.

impl dyn Error + 'static + Send + Sync

pub fn downcast<T>(     self: Box<dyn Error + 'static + Send + Sync> ) -> Result<Box<T>, Box<dyn Error + 'static + Send + Sync>> where     T: 'static + Error,

Attempt to downcast the box to a concrete type.

Implementations on Foreign Types

impl Error for !

fn description(&self) -> &str

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

Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

fn source(&self) -> Option<&(dyn Error + 'static)>

impl Error for TryFromSliceError

fn description(&self) -> &str

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

Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

fn source(&self) -> Option<&(dyn Error + 'static)>

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Implementors

impl Error for VarError

fn description(&self) -> &str

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

Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

fn source(&self) -> Option<&(dyn Error + 'static)>

impl Error for ParseError

fn description(&self) -> &str

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

Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

fn source(&self) -> Option<&(dyn Error + 'static)>

impl Error for RecvTimeoutError

fn description(&self) -> &str

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

Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

fn source(&self) -> Option<&(dyn Error + 'static)>

impl Error for TryRecvError

fn description(&self) -> &str

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

Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

fn source(&self) -> Option<&(dyn Error + 'static)>

impl Error for AllocErr

fn description(&self) -> &str

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

Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

fn source(&self) -> Option<&(dyn Error + 'static)>

impl Error for CannotReallocInPlace

fn description(&self) -> &str

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

Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

fn source(&self) -> Option<&(dyn Error + 'static)>

impl Error for LayoutErr

fn description(&self) -> &str

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

Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

fn source(&self) -> Option<&(dyn Error + 'static)>

impl Error for BorrowError

fn description(&self) -> &str

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

Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

fn source(&self) -> Option<&(dyn Error + 'static)>

impl Error for BorrowMutError

fn description(&self) -> &str

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

Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

fn source(&self) -> Option<&(dyn Error + 'static)>

impl Error for CharTryFromError

fn description(&self) -> &str

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

Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

fn source(&self) -> Option<&(dyn Error + 'static)>

impl Error for DecodeUtf16Error

fn description(&self) -> &str

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

Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

fn source(&self) -> Option<&(dyn Error + 'static)>

impl Error for ParseCharError

fn description(&self) -> &str

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

Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

fn source(&self) -> Option<&(dyn Error + 'static)>

impl Error for JoinPathsError

fn description(&self) -> &str

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

Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

fn source(&self) -> Option<&(dyn Error + 'static)>

impl Error for FromBytesWithNulError

fn description(&self) -> &str

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

Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

fn source(&self) -> Option<&(dyn Error + 'static)>

impl Error for IntoStringError

fn description(&self) -> &str

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

Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

fn source(&self) -> Option<&(dyn Error + 'static)>

impl Error for NulError

fn description(&self) -> &str

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

Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

fn source(&self) -> Option<&(dyn Error + 'static)>

impl Error for boolean_enums::lstd::fmt::Error

fn description(&self) -> &str

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

Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

fn source(&self) -> Option<&(dyn Error + 'static)>

impl Error for boolean_enums::lstd::io::Error

fn description(&self) -> &str

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

Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

fn source(&self) -> Option<&(dyn Error + 'static)>

impl Error for AddrParseError

fn description(&self) -> &str

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

Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

fn source(&self) -> Option<&(dyn Error + 'static)>

impl Error for ParseFloatError

fn description(&self) -> &str

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

Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

fn source(&self) -> Option<&(dyn Error + 'static)>

impl Error for ParseIntError

fn description(&self) -> &str

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

Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

fn source(&self) -> Option<&(dyn Error + 'static)>

impl Error for TryFromIntError

fn description(&self) -> &str

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

Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

fn source(&self) -> Option<&(dyn Error + 'static)>

impl Error for StripPrefixError

fn description(&self) -> &str

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

Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

fn source(&self) -> Option<&(dyn Error + 'static)>

impl Error for ParseBoolError

fn description(&self) -> &str

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

Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

fn source(&self) -> Option<&(dyn Error + 'static)>

impl Error for Utf8Error

fn description(&self) -> &str

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

Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

fn source(&self) -> Option<&(dyn Error + 'static)>

impl Error for FromUtf16Error

fn description(&self) -> &str

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

Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

fn source(&self) -> Option<&(dyn Error + 'static)>

impl Error for FromUtf8Error

fn description(&self) -> &str

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

Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

fn source(&self) -> Option<&(dyn Error + 'static)>

impl Error for RecvError

fn description(&self) -> &str

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

Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

fn source(&self) -> Option<&(dyn Error + 'static)>

impl Error for SystemTimeError

fn description(&self) -> &str

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

Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

fn source(&self) -> Option<&(dyn Error + 'static)>

impl<T> Error for TryLockError<T>

fn description(&self) -> &str

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

Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

fn source(&self) -> Option<&(dyn Error + 'static)>

impl<T> Error for TrySendError<T> where     T: Send,

fn description(&self) -> &str

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

Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

fn source(&self) -> Option<&(dyn Error + 'static)>

impl<T> Error for Box<T> where     T: Error,

fn description(&self) -> &str

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

Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

fn source(&self) -> Option<&(dyn Error + 'static)>

impl<T> Error for SendError<T> where     T: Send,

fn description(&self) -> &str

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

Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

fn source(&self) -> Option<&(dyn Error + 'static)>

impl<T> Error for PoisonError<T>

fn description(&self) -> &str

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

Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

fn source(&self) -> Option<&(dyn Error + 'static)>

impl<W> Error for IntoInnerError<W> where     W: Send + Debug,

fn description(&self) -> &str

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

Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

fn source(&self) -> Option<&(dyn Error + 'static)>

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