Created originally on Bitbucket by nbtaylor (Nathan Taylor)
Was already merged in Bitbucket before import, marked as merged by the import user
Source changeset not longer availableat the time of import. Commit listwill look empty
The current error when the EBNF parser is given a rule production that can evaluate to the empty string can be improved - the text I found rather hard to understand, and it currently doesn't specify the rule that is causing the problem, so I at first had a hard time understanding what I had done wrong. I added explicit mention of the offending rule and modified the text to explicitly mention 'repetitions' in the exception.
Example: for the invalid rule "foo: expr?"
Before: "AssertionError: currently an expansion needs at least onesymbol that always has to occur" After: "AssertionError: Rule 'foo''s expansion needs at least one symbol with >0 repetitions"