It’s strange. First of all, before writing here, I tried to type without looking to autocomplete, but got an error. But now, I retry and it’s ok… May be it’s because there was nothing in input side at the first time.
@orth if you didn’t have any input data yet, that would be why. FYI: in a future phase we plan to add not only expression errors but warnings. So once that’s added, you’d get a more specific warning that it could be due to no input data.