julia> using Unzip

julia> function unstable(x)
           if x == 2
               (x, x + 0.0, x, x + 0.0)
           else
               (x, x + 0.0)
           end
       end
unstable (generic function with 1 method)

julia> unzip(Iterators.map(unstable, 1:3))
ERROR: TypeError: in typeassert, expected AbstractVector{<:Tuple{Int64, Float64, Vararg{Real}}}, got a value of type Unzip.Rows{Tuple{Int64, Float64, Union{Missing, Int64}, Union{Missing, Float64}}, 1, Tuple{Vector{Int64}, Vector{Float64}, Vector{Union{Missing, Int64}}, Vector{Union{Missing, Float64}}}}
Stacktrace:
 [1] _collect(c::Unzip.Rows{Tuple{}, 1, Tuple{}}, itr::Base.Generator{UnitRange{Int64}, typeof(unstable)}, #unused#::Base.EltypeUnknown, isz::Base.HasShape{1})
   @ Base .\array.jl:754
 [2] unzip(rows::Base.Generator{UnitRange{Int64}, typeof(unstable)})
   @ Unzip C:\Users\brand\.julia\dev\Unzip\src\Unzip.jl:282
 [3] top-level scope
   @ REPL[14]:1

unzip([(1, 'a'), (2,), (3, 'b')] = ([1, 2, 3], [1, missing, 'b'])