Lastindex not defined for CartesianIndex

Hi all,

I get a method error on the following on v1.1:

julia> i = CartesianIndex{2}(2, 3)
CartesianIndex(2, 3)

julia> lastindex(i)
ERROR: MethodError: no method matching lastindex(::CartesianIndex{2})

I know that you’re not supposed to be able to iterate over a CartesianIndex directly, but does the same logic apply to lastindex, or should I file this as an issue?