[][src]Struct failure::Error

pub struct Error { /* fields omitted */ }

The Error type, which can contain any failure.

Functions which accumulate many kinds of errors should return this type. All failures can be converted into it, so functions which catch those errors can be tried with ? inside of a function that returns this kind of error.

In addition to implementing Debug and Display, this type carries Backtrace information, and can be downcast into the failure that underlies it for more detailed inspection.

Methods

impl Error
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Creates an Error from Box<std::error::Error>.

This method is useful for comparability with code, which does not use the Fail trait.

Example

use std::error::Error as StdError;
use failure::Error;

fn app_fn() -> Result<i32, Error> {
    let x = library_fn().map_err(Error::from_boxed_compat)?;
    Ok(x * 2)
}

fn library_fn() -> Result<i32, Box<StdError + Sync + Send + 'static>> {
    Ok(92)
}

Return a reference to the underlying failure that this Error contains.

Returns the name of the underlying fail.

Deprecated since 0.1.2

: please use 'as_fail()' method instead

Returns a reference to the underlying cause of this Error. Unlike the method on Fail, this does not return an Option. The Error type always has an underlying failure.

This method has been deprecated in favor of the Error::as_fail method, which does the same thing.

Gets a reference to the Backtrace for this Error.

If the failure this wrapped carried a backtrace, that backtrace will be returned. Otherwise, the backtrace will have been constructed at the point that failure was cast into the Error type.

Provides context for this Error.

This can provide additional information about this error, appropriate to the semantics of the current layer. That is, if you have a lower-level error, such as an IO error, you can provide additional context about what that error means in the context of your function. This gives users of this function more information about what has gone wrong.

This takes any type that implements Display, as well as Send/Sync/'static. In practice, this means it can take a String or a string literal, or a failure, or some other custom context-carrying type.

Wraps Error in a compatibility type.

This type implements the Error trait from std::error. If you need to pass failure's Error to an interface that takes any Error, you can use this method to get a compatible type.

Attempts to downcast this Error to a particular Fail type.

This downcasts by value, returning an owned T if the underlying failure is of the type T. For this reason it returns a Result - in the case that the underlying error is of a different type, the original Error is returned.

Returns the "root cause" of this error - the last value in the cause chain which does not return an underlying cause.

Important traits for Causes<'f>

Returns a iterator over the causes of this error with the cause of the fail as the first item and the root_cause as the final item.

Use iter_chain to also include the fail of this error itself.

Important traits for Causes<'f>

Returns a iterator over all fails up the chain from the current as the first item up to the root_cause as the final item.

This means that the chain also includes the fail itself which means that it does not start with cause. To skip the outermost fail use iter_causes instead.

Attempts to downcast this Error to a particular Fail type by reference.

If the underlying error is not of type T, this will return None.

Attempts to downcast this Error to a particular Fail type by mutable reference.

If the underlying error is not of type T, this will return None.

Deprecated since 0.1.2

: please use the 'find_root_cause()' method instead

Deprecated alias to find_root_cause.

Important traits for Causes<'f>

Deprecated since 0.1.2

: please use the 'iter_chain()' method instead

Deprecated alias to iter_causes.

Trait Implementations

impl AsFail for Error
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impl<T> ResultExt<T, Error> for Result<T, Error>
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impl From<Error> for Box<dyn StdError>
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impl From<Error> for Box<dyn StdError + Send + Sync>
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impl<F: Fail> From<F> for Error
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impl AsRef<dyn Fail + 'static> for Error
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impl Display for Error
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impl Debug for Error
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Auto Trait Implementations

impl Send for Error

impl Sync for Error

Blanket Implementations

impl<T> From for T
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impl<T, U> Into for T where
    U: From<T>, 
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impl<T> ToString for T where
    T: Display + ?Sized
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impl<T, U> TryFrom for T where
    T: From<U>, 
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🔬 This is a nightly-only experimental API. (try_from)

The type returned in the event of a conversion error.

impl<T> Borrow for T where
    T: ?Sized
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impl<T> BorrowMut for T where
    T: ?Sized
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impl<T, U> TryInto for T where
    U: TryFrom<T>, 
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🔬 This is a nightly-only experimental API. (try_from)

The type returned in the event of a conversion error.

impl<T> Any for T where
    T: 'static + ?Sized
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