restack errors on partially initialized structs

[maartenvd]

minimal working example:

julia> using Transducers

julia> struct test
       a
       b
       test(x) = new(x);
       end

julia> t =test(3)
test(3, #undef)

julia> Transducers.restack(t)
ERROR: UndefRefError: access to undefined reference
Stacktrace:
 [1] macro expansion
   @ ~/.julia/packages/Transducers/q4vZD/src/AutoObjectsReStacker.jl:37 [inlined]
 [2] restack(x::test)
   @ Transducers.AutoObjectsReStacker ~/.julia/packages/Transducers/q4vZD/src/AutoObjectsReStacker.jl:16
 [3] top-level scope
   @ REPL[8]:1

I think these kind of objects are 'proper' julia objects. It's probably only a matter of filtering out the fieldnames that are defined in restack.

[tkf]

Right, this shouldn't throw.