Use cases for type lower bounds

[Tamas_Papp]

One use case was mentioned in

X::Vector{Union{Missing, Any}}

Indeed, since (as its name indicates) Any can be any value, including missing. In general, use ::AbstractArray{>:Missing} to define a method which should be called for any array which can contain missing. But note that in many cases you can just define a single generic method, knowing that the compiler will (often) optimize out ismissing(A[i]) calls when the array cannot contain missing.