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use Fail;
use std::error::Error;
use std::fmt::{self, Debug, Display};
use std::sync::Mutex;
/// Wrapper for `std` errors to make them `Sync`.
///
/// This exists to coerce existing types that are only `Error + Send +
/// 'static` into a `Fail`-compatible representation, most notably for
/// types generated by `error-chain`.
///
/// Unfortunately, this requires wrapping the error in a `Mutex`, which must
/// be locked for every `Debug`/`Display`. Therefore, this should be
/// something of a last resort in making the error work with `failure`.
///
pub struct SyncFailure<T> {
inner: Mutex<T>,
}
impl<E: Error + Send + 'static> SyncFailure<E> {
/// Wraps a non-`Sync` `Error` in order to make it implement `Fail`.
///
/// # Example
///
/// ```rust
/// extern crate failure;
///
/// # use std::error::Error as StdError;
/// # use std::fmt::{self, Display};
/// use failure::{Error, SyncFailure};
/// use std::cell::RefCell;
///
/// #[derive(Debug)]
/// struct NonSyncError {
/// // RefCells are non-Sync, so structs containing them will be
/// // non-Sync as well.
/// count: RefCell<usize>,
/// }
///
/// // implement Display/Error for NonSyncError...
/// #
/// # impl StdError for NonSyncError {
/// # fn description(&self) -> &str {
/// # "oops!"
/// # }
/// # }
/// #
/// # impl Display for NonSyncError {
/// # fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
/// # write!(f, "oops!")
/// # }
/// # }
///
/// fn returns_error() -> Result<(), NonSyncError> {
/// // Do stuff
/// # Ok(())
/// }
///
/// fn my_function() -> Result<(), Error> {
/// // without the map_err here, we end up with a compile error
/// // complaining that NonSyncError doesn't implement Sync.
/// returns_error().map_err(SyncFailure::new)?;
/// // Do more stuff
/// # Ok(())
/// }
/// #
/// # fn main() {
/// # my_function().unwrap();
/// # }
/// ```
///
pub fn new(err: E) -> Self {
SyncFailure {
inner: Mutex::new(err),
}
}
}
impl<T> Display for SyncFailure<T>
where
T: Display,
{
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
self.inner.lock().unwrap().fmt(f)
}
}
impl<T> Debug for SyncFailure<T>
where
T: Debug,
{
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
(*self.inner.lock().unwrap()).fmt(f)
}
}
impl<E: Error + Send + 'static> Fail for SyncFailure<E> {}
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