ErrorKind to the rescue

To cope with different kind of errors, we introduce the kind of an error Func1ErrorKind with an enum.

Because we derive Debug and implement Display our Func1ErrorKind enum, this enum can be used as a std::error::Error.

Not using String errors anymore, the cherr!() macro seen in the beginning of the tutorial has to be used again.

Only returning Func1ErrorKind in func1() now let us get rid of Result<(), Box<Error>> and we can use ChainResult<(), Func1ErrorKind>.

In main we can now directly use the methods of ChainError<T> without downcasting the error first.

Also a nice match on ChainError<T>.kind() is now possible, which returns &T, meaning &Func1ErrorKind here.

{{#include ../examples/tutorial10.rs}}
# #[allow(dead_code)]
# mod chainerror {
{{#includecomment ../src/lib.rs}}
# }