Array of unions of subtypes

[Gnimuc]

@hideakiv

So now my understanding is that Union{Nothing, Real} isn’t simply a union of type Nothing and abstract type Real , but also includes all concrete subtypes in the set.

julia> x = Array{T} where T<:Union{Nothing,S} where S <: Real
Array{T} where {S<:Real, T<:Union{Nothing, S}}

julia> y = Array{Union{Nothing, <:Real}} 
Array{Union{Nothing, Real}}

julia> x == y
false

julia> y <: x
true

julia> x <: y
false