Thank you for explanation!
Actually, I’ve started thinking about it when I had to replace a structure with a named tuple as a field inside another structure (didn’t want to declare additional nested structures somewhere), and found that I need a long string like NamedTuple{(:pos, :val),Tuple{Int64,Float64}}. Do you think that at least changing it to NamedTuple{pos::Int64, val::Float64} is not possible eighter?