The problem you have seems the following (again, I'm not an expert and
have been using Xtext for a couple of weeks now) if someone else has
better ideas please let me also know about this!
Changing the grammer below makes it work for now!
TerminalArithmeticExpression returns LogicExpression:
// var=ID |
number=INT
// | BinaryArithmeticExpression
| UnaryArithmeticExpression
// | '(' TerminalArithmeticExpression ')'
;