object_is: object_is::<E>,

            object_is: object_is::<M>,

            object_is: object_is::<M>,

            object_is: context_is::<C, E>,

            object_is: context_chain_is::<C>,

        let target = TypeId::of::<E>();
        unsafe { (self.inner.vtable.object_is)(&self.inner, target) }

        self.downcast_ref::<E>().is_some()

    object_is: unsafe fn(&ErrorImpl<()>, TypeId) -> bool,

}
unsafe fn object_is<E>(e: &ErrorImpl<()>, target: TypeId) -> bool
where
    E: 'static,
{
    let _ = e;
    TypeId::of::<E>() == target

unsafe fn context_is<C, E>(e: &ErrorImpl<()>, target: TypeId) -> bool
where
    C: 'static,
    E: 'static,
{
    let _ = e;
    TypeId::of::<C>() == target || TypeId::of::<E>() == target
}

unsafe fn context_chain_is<C>(e: &ErrorImpl<()>, target: TypeId) -> bool
where
    C: 'static,
{
    if TypeId::of::<C>() == target {
        true
    } else {
        let unerased = e as *const ErrorImpl<()> as *const ErrorImpl<ContextError<C, Error>>;
        let source = &(*unerased)._object.error;
        (source.inner.vtable.object_is)(&source.inner, target)
    }
}