insert an error when an operator doesn't get found - note the comment...

parser.c

@@ -1898,8 +1898,13 @@ static ast_expression* parse_expression_leave(parser_t *parser, bool stopatcomma
                 }
             }
             if (o == operator_count) {
+                compile_error(parser_ctx(parser), "unknown operator: %s", parser_tokval(parser));
+                goto onerr;
+#if 0
+Are there any expressions which actually end with an operator?
                 /* no operator found... must be the end of the statement */
                 break;
+#endif
             }
             /* found an operator */
             op = &operators[o];