The FA1.2 standard specifies that the NotEnoughAllowance error should contain a nat: required, nat: present pair. How do I attach this kind of data to a failwith call?
I am writing the token contract in PascaLIGO.
Currently, LIGO does not support failing with an arbitrary type like a tuple or record. However you can embed Michelson to fail with the tuple.
failwith("NotEnoughAllowance: required: 100, present: 0");