Enum snafu::guide::examples::basic::Error

pub enum Error {
    Leaf {
        user_id: i32,
    },
    Intermediate {
        source: Error,
    },
}

An enumeration of possible errors.

This will create a number of context selectors:

• LeafSnafu
• IntermediateSnafu

Leaf errors

Context selectors for error variants without a source, such as LeafSnafu, have methods to construct them, such as LeafSnafu::build or LeafSnafu::fail. The ensure macro also accepts these kinds of context selectors.

use snafu::prelude::*;

fn always_fails() -> Result<(), Error> {
    LeafSnafu { user_id: 42 }.fail()
}

fn sometimes_fails(user_id: i32) -> Result<(), Error> {
    ensure!(user_id > 0, LeafSnafu { user_id });
    Ok(())
}

Intermediate errors

Context selectors for error variants with a source, such as IntermediateSnafu, are intended to be used with the ResultExt::context family of methods.

use snafu::prelude::*;

fn load_config_file() -> Result<usize, Error> {
    let config = std::fs::read_to_string("/path/to/my/config/file").context(IntermediateSnafu)?;
    Ok(config.len())
}

Variants

Leaf

Fields

user_id: i32

Intermediate

Fields

source: Error

Trait Implementations

impl Debug for Error

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Display for Error

fn fmt(&self, __snafu_display_formatter: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Error for Errorwhere
    Self: Debug + Display,

fn description(&self) -> &str

👎Deprecated since 1.42.0:

use the Display impl or to_string()

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)>

The lower-level source of this error, if any.

fn provide(&'a self, demand: &mut Demand<'a>)

🔬This is a nightly-only experimental API. (error_generic_member_access)

Provides type based access to context intended for error reports.

impl ErrorCompat for Error

fn backtrace(&self) -> Option<&Backtrace>

Returns a Backtrace that may be printed.

fn iter_chain(&self) -> ChainCompat<'_>where
    Self: AsErrorSource,

Returns an iterator for traversing the chain of errors, starting with the current error and continuing with recursive calls to Error::source.

impl IntoError<Error> for IntermediateSnafuwhere
    Error: Error + ErrorCompat,

type Source = Error

The underlying error

fn into_error(self, error: Self::Source) -> Error

Combine the information to produce the error

impl<__T0> IntoError<Error> for LeafSnafu<__T0>where
    Error: Error + ErrorCompat,
    __T0: Into<i32>,

type Source = NoneError

The underlying error

fn into_error(self, error: Self::Source) -> Error

Combine the information to produce the error