I had a problem with the exception avaliable on the tutorial.
i32 calculate(1:i32 logid, 2:Work w) throws (1:InvalidOperation ouch),
It couldn't be thrown because initialization of numeric base types is done with 0 instead of null and the checks do compare against null.
I've made a patch that initializes the base types I16,I32, I64 and DOUBLE with null. This could probably solve other issues as well