That's been considered, but for now @johnmyleswhite preferred to go with the simpler solution of applying standard lifting semantics to all functions (see #166 (comment), #144). This might change in the future once we have more experience.

Is there any reason why you cannot/don't want to use isnull(x)?

I wanted to use this kind of syntax: x[isnull.(x)].

Mmm, I thought isnull(x::NullableArray) was defined as the vectorized version of isnull, but apparently it isn't (which is consistent with isnull retuning false when the argument isn't a Nullable). So there's no correct way of doing this currently except for x.isnull, which should be discouraged.

I guess we should add a special lift method then.

(Though note that your example doesn't make much sense AFAICT, since it will return a vector of null values...)

You´re right... That´s why I considered isnull.(x) returning Array{Bool} instead of nullables.
If that´s the case, I would think that isnull.(lift(x)) should work.
I put up a very simple module with this kind of lift function at https://github.com/felipenoris/Lifting.jl , obviously not the same kind of solution discussed at JuliaLang/julia#18758

update: missing dots