Can someone help me understand this grammar?

Question

I can't understand these grammar rules, and what the "returns" and "current" keywords means ?

WhereEntry returns WhereEntry:
AndWhereEntry ({OrWhereEntry.entries+=current} 
    ("OR" entries+=AndWhereEntry)+)?
;

Answer 1

1. returns means: the result of the rule will be of type WhereEntry.
2. current means: the object parsed so far.

In sum this will mean

• AndWhereEntry is a Subclass of WhereEntry.
• if there is an OR then the AndWhereEntry parsed before will be added to the OrWhereEntry entries list.