Method downcast

crates/core/src/error/error.rs:992–1017

Downcast this error into an `E`, taking ownership. If this error is an `E`, then `Ok(E)` is returned. Otherwise, `Err(self)` is returned. If there are multiple instances of `E` in this error's chain, then the first (as encountered by [`Error::chain`]'s iteration order) is returned. # Example ``` # use wasmtime_internal_core as wasmtime; use wasmtime::error::{Error, OutOfMemory}; let error = E

(self)

    /// );
    /// ```
    pub fn downcast<E>(self) -> Result<E, Self>
    where
        E: fmt::Display + fmt::Debug + Send + Sync + 'static,
    {
        self.error_ext_zip(|e| {
            let result = e.inner.downcast::<E>().map_err(|inner| Self { inner });

            #[cfg(feature = "anyhow")]
            let result = result.or_else(|e| {
                if e.inner
                    .downcast_ref::<anyhow::Error>()
                    .is_some_and(|e| e.is::<E>())
                {
                    let anyhow = match e.inner.downcast::<anyhow::Error>() {
                        Ok(e) => e,
                        Err(_) => unreachable!(),
                    };
                    Ok(anyhow.downcast::<E>().unwrap())
                } else {
                    Err(e)
                }
            });

            result
        })
    }

    /// Downcast this error into a shared `&E` borrow.
    ///