prepare_jacobian error for OOP function with type unspecified output

[ErikQQY]

MWE from https://juliadiff.org/DifferentiationInterface.jl/DifferentiationInterface/stable/tutorials/advanced/#Sparsity-speedup, not sure if this is intended or a bug

using DifferentiationInterface, SparseConnectivityTracer, SparseMatrixColorings
dense_first_order_backend = AutoForwardDiff()
sparse_first_order_backend = AutoSparse(
    dense_first_order_backend;
    sparsity_detector=SparseConnectivityTracer.TracerLocalSparsityDetector(),
    coloring_algorithm=GreedyColoringAlgorithm(LargestFirst()),
)
function f_sparse_vector(x::AbstractVector)
	n = length(x)
    ret = []
    for i in 1:n-1
        append!(ret, abs2(x[i + 1]) - abs2(x[i]) + abs2(x[n - i]) - abs2(x[n - i + 1]))
    end
    return ret
end
xbig = rand(1000)
jac_prep_sparse_nonallocating = prepare_jacobian(f_sparse_vector, sparse_first_order_backend, zero(xbig))

ERROR: MethodError: no method matching jacobian_pattern_to_mat(::Vector{SparseConnectivityTracer.Dual{Float64, SparseConnectivityTracer.GradientTracer{…}}}, ::Vector{Any})

Closest candidates are:
  jacobian_pattern_to_mat(::AbstractArray{D}, ::AbstractArray{<:Real}) where {P, T<:SparseConnectivityTracer.GradientTracer, D<:SparseConnectivityTracer.Dual{P, T}}
   @ SparseConnectivityTracer ~/.julia/packages/SparseConnectivityTracer/4CmIb/src/trace_functions.jl:122

Stacktrace:
 [1] _local_jacobian_sparsity(f::Function, x::Vector{Float64}, ::Type{SparseConnectivityTracer.GradientTracer{SparseConnectivityTracer.IndexSetGradientPattern{Int64, BitSet}}})
   @ SparseConnectivityTracer ~/.julia/packages/SparseConnectivityTracer/4CmIb/src/trace_functions.jl:91
 [2] jacobian_sparsity(f::Function, x::Vector{Float64}, ::TracerLocalSparsityDetector{SparseConnectivityTracer.GradientTracer{…}, SparseConnectivityTracer.HessianTracer{…}})
   @ SparseConnectivityTracer ~/.julia/packages/SparseConnectivityTracer/4CmIb/src/adtypes_interface.jl:149
 [3] _prepare_sparse_jacobian_aux(::DifferentiationInterface.PushforwardFast, ::Vector{…}, ::Tuple{…}, ::AutoSparse{…}, ::Vector{…})
   @ DifferentiationInterfaceSparseMatrixColoringsExt ~/.julia/packages/DifferentiationInterface/gSdHF/ext/DifferentiationInterfaceSparseMatrixColoringsExt/jacobian.jl:61
 [4] prepare_jacobian(::typeof(f_sparse_vector), ::AutoSparse{AutoForwardDiff{…}, TracerLocalSparsityDetector{…}, GreedyColoringAlgorithm{…}}, ::Vector{Float64})
   @ DifferentiationInterfaceSparseMatrixColoringsExt ~/.julia/packages/DifferentiationInterface/gSdHF/ext/DifferentiationInterfaceSparseMatrixColoringsExt/jacobian.jl:41
 [5] top-level scope
   @ REPL[19]:1
Some type information was truncated. Use `show(err)` to see complete types.

[adrhill]

Looks like an SCT error. Could you reopen in there?

[adrhill]

Closing in favor of adrhill/SparseConnectivityTracer.jl#216.

[adrhill]

Fixed in SCT v0.6.9.