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    use std::any::Any;
    use std::fmt;
    use std::io;
    use std::sync::Mutex;

    cfg_rt! {
        /// Task failed to execute to completion.
        pub struct JoinError {
            repr: Repr,
        }
    }

    enum Repr {
        Cancelled,
        Panic(Mutex<Box<dyn Any + Send + 'static>>),
    }

    impl JoinError {
        pub(crate) fn cancelled() -> JoinError {
            JoinError {
                repr: Repr::Cancelled,
            }
        }

        pub(crate) fn panic(err: Box<dyn Any + Send + 'static>) -> JoinError {
            JoinError {
                repr: Repr::Panic(Mutex::new(err)),
            }
        }

        /// Returns true if the error was caused by the task being cancelled
        pub fn is_cancelled(&self) -> bool {
            matches!(&self.repr, Repr::Cancelled)
        }

        /// Returns true if the error was caused by the task panicking
        ///
        /// # Examples
        ///
        /// ```
        /// use std::panic;
        ///
        /// #[tokio::main]
        /// async fn main() {
        ///     let err = tokio::spawn(async {
        ///         panic!("boom");
        ///     }).await.unwrap_err();
        ///
        ///     assert!(err.is_panic());
        /// }
        /// ```
        pub fn is_panic(&self) -> bool {
            matches!(&self.repr, Repr::Panic(_))
        }

        /// Consumes the join error, returning the object with which the task panicked.
        ///
        /// # Panics
        ///
        /// `into_panic()` panics if the `Error` does not represent the underlying
        /// task terminating with a panic. Use `is_panic` to check the error reason
        /// or `try_into_panic` for a variant that does not panic.
        ///
        /// # Examples
        ///
        /// ```should_panic
        /// use std::panic;
        ///
        /// #[tokio::main]
        /// async fn main() {
        ///     let err = tokio::spawn(async {
        ///         panic!("boom");
        ///     }).await.unwrap_err();
        ///
        ///     if err.is_panic() {
        ///         // Resume the panic on the main task
        ///         panic::resume_unwind(err.into_panic());
        ///     }
        /// }
        /// ```
        pub fn into_panic(self) -> Box<dyn Any + Send + 'static> {
            self.try_into_panic()
                .expect("`JoinError` reason is not a panic.")
        }

        /// Consumes the join error, returning the object with which the task
        /// panicked if the task terminated due to a panic. Otherwise, `self` is
        /// returned.
        ///
        /// # Examples
        ///
        /// ```should_panic
        /// use std::panic;
        ///
        /// #[tokio::main]
        /// async fn main() {
        ///     let err = tokio::spawn(async {
        ///         panic!("boom");
        ///     }).await.unwrap_err();
        ///
        ///     if let Ok(reason) = err.try_into_panic() {
        ///         // Resume the panic on the main task
        ///         panic::resume_unwind(reason);
        ///     }
        /// }
        /// ```
        pub fn try_into_panic(self) -> Result<Box<dyn Any + Send + 'static>, JoinError> {
            match self.repr {
                Repr::Panic(p) => Ok(p.into_inner().expect("Extracting panic from mutex")),
                _ => Err(self),
            }
        }
    }

    impl fmt::Display for JoinError {
        fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
            match &self.repr {
                Repr::Cancelled => write!(fmt, "cancelled"),
                Repr::Panic(_) => write!(fmt, "panic"),
            }
        }
    }

    impl fmt::Debug for JoinError {
        fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
            match &self.repr {
                Repr::Cancelled => write!(fmt, "JoinError::Cancelled"),
                Repr::Panic(_) => write!(fmt, "JoinError::Panic(...)"),
            }
        }
    }

    impl std::error::Error for JoinError {}

    impl From<JoinError> for io::Error {
        fn from(src: JoinError) -> io::Error {
            io::Error::new(
                io::ErrorKind::Other,
                match src.repr {
                    Repr::Cancelled => "task was cancelled",
                    Repr::Panic(_) => "task panicked",
                },
            )
        }
    }