chainerror/booksrc/tutorial8.md

Finding an Error cause

To distinguish the errors occurring in various places, we can define named string errors with the "new type" pattern.

chainerror::str_context!(Func2Error);
chainerror::str_context!(Func1Error);

Instead of chainerror::Error<String> we now have struct Func1Error(String) and chainerror::Error<Func1Error>.

In the main function you can see, how we can match the different errors.

Also see:

            if let Some(f2err) = f1err.find_chain_cause::<Func2Error>() {

as a shortcut to

            if let Some(f2err) = f1err.find_cause::<chainerror::Error<Func2Error>>() {

hiding the chainerror::Error<T> implementation detail.

{{#include ../examples/tutorial8.rs}}
# #[allow(dead_code)]
# mod chainerror {
{{#rustdoc_include ../src/lib.rs:-1}}
# }