These sounds like exceptions rather than errors to me. Difference being, exceptions truly are exceptional and not anticipated; like running out of memory. How do you even handle that? Would probably let it crash and restart (Erlang model). Errors is something you anticipate can happen, such as getting 4xx-5xx back from the server and know what to do in those cases.
Then it's fair to say that you definitely can't get an error by adding two numbers.
Then it's fair to say that you definitely can't get an error by adding two numbers.