# Struct failure::Error [−] [src]

    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`
[src]

#### `pub fn cause(&self) -> &Fail`
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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.

#### `pub fn backtrace(&self) -> &Backtrace`
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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.

#### `pub fn context<D: Display + Send + Sync + 'static>(
self,
context: D
) -> Context<D>`
[src]

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.

#### `pub fn compat(self) -> Compat<Error>`
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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.

#### `pub fn downcast<T: Fail>(self) -> Result<T, Error>`
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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.

#### `pub fn root_cause(&self) -> &Fail`
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Returns the "root cause" of this error - the last value in the cause chain which does not return an underlying `cause`.

#### `pub fn downcast_ref<T: Fail>(&self) -> Option<&T>`
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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`.

#### `pub fn downcast_mut<T: Fail>(&mut self) -> Option<&mut T>`
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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`.

####
ⓘImportant traits for Causes<'f>

### Important traits for Causes<'f>

`impl<'f> Iterator for Causes<'f> type Item = &'f Fail;`
`pub fn causes(&self) -> Causes`
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Returns a iterator over the causes of the `Error`, beginning with the failure returned by the `cause` method and ending with the failure returned by `root_cause`.

## Trait Implementations

### `impl From<Error> for Box<StdError>`
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####
ⓘImportant traits for Box<R>

### Important traits for Box<R>

`impl<R> Read for Box<R> where
R: Read + ?Sized, impl<W> Write for Box<W> where
W: Write + ?Sized, impl<I> Iterator for Box<I> where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;`
`fn from(error: Error) -> Box<StdError>`
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Performs the conversion.

### `impl<T> ResultExt<T, Error> for Result<T, Error>`
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#### `fn compat(self) -> Result<T, Compat<Error>>`
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Wraps the error in `Compat` to make it compatible with older error handling APIs that expect `std::error::Error`. Read more

#### `fn context<D>(self, context: D) -> Result<T, Context<D>> where
D: Display + Send + Sync + 'static,`
[src]

Wraps the error type in a context type.

#### `fn with_context<F, D>(self, f: F) -> Result<T, Context<D>> where
F: FnOnce(&Error) -> D,
D: Display + Send + Sync + 'static,`
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Wraps the error type in a context type generated by looking at the error value. Read more

### `impl<F: Fail> From<F> for Error`
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#### `fn from(failure: F) -> Error`
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Performs the conversion.

### `impl Display for Error`
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#### `fn fmt(&self, f: &mut Formatter) -> Result`
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Formats the value using the given formatter. Read more

### `impl Debug for Error`
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#### `fn fmt(&self, f: &mut Formatter) -> Result`
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Formats the value using the given formatter. Read more

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