Boo.Lang.Parser.BooParserBase.sum C# (CSharp) Method

        protected Expression sum()
        {
            Expression e;

            IToken  add = null;
            IToken  sub = null;
            IToken  bitor = null;
            IToken  eo = null;

                e = null;
                Expression r = null;
                IToken op = null;
                BinaryOperatorType bOperator = BinaryOperatorType.None;

            try {      // for error handling
            e=term();
            {    // ( ... )*
                for (;;)
                {
                    if ((tokenSet_116_.member(LA(1))) && (tokenSet_114_.member(LA(2))))
                    {
                        {
                            switch ( LA(1) )
                            {
                            case ADD:
                            {
                                add = LT(1);
                                match(ADD);
                                if (0==inputState.guessing)
                                {
                                    op=add; bOperator = BinaryOperatorType.Addition;
                                }
                                break;
                            }
                            case SUBTRACT:
                            {
                                sub = LT(1);
                                match(SUBTRACT);
                                if (0==inputState.guessing)
                                {
                                    op=sub; bOperator = BinaryOperatorType.Subtraction;
                                }
                                break;
                            }
                            case BITWISE_OR:
                            {
                                bitor = LT(1);
                                match(BITWISE_OR);
                                if (0==inputState.guessing)
                                {
                                    op=bitor; bOperator = BinaryOperatorType.BitwiseOr;
                                }
                                break;
                            }
                            case EXCLUSIVE_OR:
                            {
                                eo = LT(1);
                                match(EXCLUSIVE_OR);
                                if (0==inputState.guessing)
                                {
                                    op=eo; bOperator = BinaryOperatorType.ExclusiveOr;
                                }
                                break;
                            }
                            default:
                            {
                                throw new NoViableAltException(LT(1), getFilename());
                            }
                             }
                        }
                        r=term();
                        if (0==inputState.guessing)
                        {

                                        BinaryExpression be = new BinaryExpression(ToLexicalInfo(op));
                                        be.Operator = bOperator;
                                        be.Left = e;
                                        be.Right = r;
                                        e = be;

                        }
                    }
                    else
                    {
                        goto _loop527_breakloop;
                    }

                }
            _loop527_breakloop:				;
            }    // ( ... )*
            }
            catch (RecognitionException ex)
            {
            if (0 == inputState.guessing)
            {
                reportError(ex, "sum");
                recover(ex,tokenSet_117_);
            }
            else
            {
                throw ex;
            }
            }
            return e;
        }