Downcast the Errors

std::error::Error comes with some helper methods to get to the original object of the &(dyn Error + 'static) returned by .source().

pub fn downcast_ref<T: Error + 'static>(&self) -> Option<&T>
pub fn downcast_mut<T: Error + 'static>(&mut self) -> Option<&mut T>

This is how it looks like, when using those:

use crate::chainerror::*;
{{#include ../examples/tutorial6.rs:2:}}
# #[allow(dead_code)]
# mod chainerror {
{{#includecomment ../src/lib.rs}}
# }