It is a macro that just helps you define a type that implements the appropriate traits so of course it works with the rest of the world. No-one outside the crate that uses it even needs to notice, as one could just write out the definition by hand.
This is correct. Technically the backtrace functionality and ErrorChainIter implementation come from the error-chain crate (the former as a re-export of the backtrace crate) so your linker will notice.
