Look into promotion issue

[quinnj]

JuliaStats/DataArrays.jl#280 (comment)

[quinnj]

@nalimilan @andreasnoack, do we still need some extra promote definitions in Nulls for DataArrays?

[nalimilan]

Indeed, see https://github.com/JuliaStats/DataArrays.jl/pull/288/files#r141439438. I haven't tried defining more specific methods to fix the stack overflow.

[andreasnoack]

I think so. We still have the not too general definitions https://github.com/JuliaStats/DataArrays.jl/blob/8b9e89617ca3539440a9a1b2fc75fc44f86ec850/src/natype.jl#L41-L52. I tried to make some changes to Base's promotion mechanisms to handle these kinds of promotions but it is really brittle and I didn't manage to get it working.