Gradient bug with ForwardDiff over Enzyme.Forward for size 1 only

[gdalle]

julia> import ForwardDiff, Enzyme

julia> using DifferentiationInterface

julia> b = SecondOrder(AutoForwardDiff(), AutoEnzyme(Enzyme.Forward));

julia> hessian(sum, b, [1.0, 2.0])
2×2 Matrix{Float64}:
 0.0  0.0
 0.0  0.0

julia> hessian(sum, b, [1.0])
ERROR: MethodError: no method matching EnzymeCore.Duplicated(::Vector{ForwardDiff.Dual{ForwardDiff.Tag{…}, Float64, 1}}, ::Tuple{Vector{ForwardDiff.Dual{…}}})

julia> show(err)
1-element ExceptionStack:
MethodError: no method matching EnzymeCore.Duplicated(::Vector{ForwardDiff.Dual{ForwardDiff.Tag{DifferentiationInterface.var"#inner_gradient_closure#24"{typeof(sum), SecondOrder{AutoForwardDiff{nothing, Nothing}, AutoEnzyme{EnzymeCore.ForwardMode{EnzymeCore.FFIABI}}}}, Float64}, Float64, 1}}, ::Tuple{Vector{ForwardDiff.Dual{ForwardDiff.Tag{DifferentiationInterface.var"#inner_gradient_closure#24"{typeof(sum), SecondOrder{AutoForwardDiff{nothing, Nothing}, AutoEnzyme{EnzymeCore.ForwardMode{EnzymeCore.FFIABI}}}}, Float64}, Float64, 1}}})

Closest candidates are:
  EnzymeCore.Duplicated(::T1, ::T1) where T1
   @ EnzymeCore ~/.julia/packages/EnzymeCore/MB3tJ/src/EnzymeCore.jl:64
  EnzymeCore.Duplicated(::T1, ::T1, ::Bool) where T1
   @ EnzymeCore ~/.julia/packages/EnzymeCore/MB3tJ/src/EnzymeCore.jl:64

Stacktrace:
  [1] (::Enzyme.var"#81#82"{Tuple{Tuple{Vector{ForwardDiff.Dual{ForwardDiff.Tag{DifferentiationInterface.var"#inner_gradient_closure#24"{typeof(sum), SecondOrder{AutoForwardDiff{nothing, Nothing}, AutoEnzyme{EnzymeCore.ForwardMode{EnzymeCore.FFIABI}}}}, Float64}, Float64, 1}}}}, typeof(sum), Vector{ForwardDiff.Dual{ForwardDiff.Tag{DifferentiationInterface.var"#inner_gradient_closure#24"{typeof(sum), SecondOrder{AutoForwardDiff{nothing, Nothing}, AutoEnzyme{EnzymeCore.ForwardMode{EnzymeCore.FFIABI}}}}, Float64}, Float64, 1}}})(i::Int64)
    @ Enzyme ~/.julia/packages/Enzyme/l4FS0/src/Enzyme.jl:909
  [2] ntuple
    @ ./ntuple.jl:19 [inlined]
  [3] #gradient#80
    @ ~/.julia/packages/Enzyme/l4FS0/src/Enzyme.jl:908 [inlined]
  [4] gradient
    @ ~/.julia/packages/Enzyme/l4FS0/src/Enzyme.jl:907 [inlined]
  [5] gradient(f::Function, backend::AutoEnzyme{EnzymeCore.ForwardMode{EnzymeCore.FFIABI}}, x::Vector{ForwardDiff.Dual{ForwardDiff.Tag{DifferentiationInterface.var"#inner_gradient_closure#24"{typeof(sum), SecondOrder{AutoForwardDiff{nothing, Nothing}, AutoEnzyme{EnzymeCore.ForwardMode{EnzymeCore.FFIABI}}}}, Float64}, Float64, 1}}, extras::DifferentiationInterfaceEnzymeExt.EnzymeForwardGradientExtras{1, Tuple{Tuple{Vector{ForwardDiff.Dual{ForwardDiff.Tag{DifferentiationInterface.var"#inner_gradient_closure#24"{typeof(sum), SecondOrder{AutoForwardDiff{nothing, Nothing}, AutoEnzyme{EnzymeCore.ForwardMode{EnzymeCore.FFIABI}}}}, Float64}, Float64, 1}}}}})
    @ DifferentiationInterfaceEnzymeExt ~/Work/GitHub/Julia/DifferentiationInterface.jl/DifferentiationInterface/ext/DifferentiationInterfaceEnzymeExt/forward_onearg.jl:49
  [6] gradient(f::Function, backend::AutoEnzyme{EnzymeCore.ForwardMode{EnzymeCore.FFIABI}}, x::Vector{ForwardDiff.Dual{ForwardDiff.Tag{DifferentiationInterface.var"#inner_gradient_closure#24"{typeof(sum), SecondOrder{AutoForwardDiff{nothing, Nothing}, AutoEnzyme{EnzymeCore.ForwardMode{EnzymeCore.FFIABI}}}}, Float64}, Float64, 1}})
    @ DifferentiationInterface ~/Work/GitHub/Julia/DifferentiationInterface.jl/DifferentiationInterface/src/gradient.jl:73
  [7] inner_gradient_closure
    @ ~/Work/GitHub/Julia/DifferentiationInterface.jl/DifferentiationInterface/src/hvp.jl:69 [inlined]
  [8] value_and_pushforward(f::DifferentiationInterface.var"#inner_gradient_closure#24"{typeof(sum), SecondOrder{AutoForwardDiff{nothing, Nothing}, AutoEnzyme{EnzymeCore.ForwardMode{EnzymeCore.FFIABI}}}}, ::AutoForwardDiff{nothing, Nothing}, x::Vector{Float64}, dx::FillArrays.OneElement{Float64, 1, Tuple{Int64}, Tuple{Base.OneTo{Int64}}}, ::DifferentiationInterface.NoPushforwardExtras)
    @ DifferentiationInterfaceForwardDiffExt ~/Work/GitHub/Julia/DifferentiationInterface.jl/DifferentiationInterface/ext/DifferentiationInterfaceForwardDiffExt/onearg.jl:8
  [9] pushforward
    @ ~/Work/GitHub/Julia/DifferentiationInterface.jl/DifferentiationInterface/src/pushforward.jl:128 [inlined]
 [10] hvp_aux
    @ ~/Work/GitHub/Julia/DifferentiationInterface.jl/DifferentiationInterface/src/hvp.jl:120 [inlined]
 [11] hvp
    @ ~/Work/GitHub/Julia/DifferentiationInterface.jl/DifferentiationInterface/src/hvp.jl:115 [inlined]
 [12] (::DifferentiationInterface.var"#30#31"{typeof(sum), SecondOrder{AutoForwardDiff{nothing, Nothing}, AutoEnzyme{EnzymeCore.ForwardMode{EnzymeCore.FFIABI}}}, Vector{Float64}, DifferentiationInterface.HVPHessianExtras{DifferentiationInterface.ForwardOverForwardHVPExtras{DifferentiationInterface.var"#inner_gradient_closure#24"{typeof(sum), SecondOrder{AutoForwardDiff{nothing, Nothing}, AutoEnzyme{EnzymeCore.ForwardMode{EnzymeCore.FFIABI}}}}, DifferentiationInterface.NoPushforwardExtras}}})(j::CartesianIndex{1})
    @ DifferentiationInterface ~/Work/GitHub/Julia/DifferentiationInterface.jl/DifferentiationInterface/src/hessian.jl:55
 [13] #186
    @ ./generator.jl:0 [inlined]
 [14] iterate
    @ ./generator.jl:47 [inlined]
 [15] collect(itr::Base.Generator{CartesianIndices{1, Tuple{Base.OneTo{Int64}}}, Base.var"#186#187"{DifferentiationInterface.var"#30#31"{typeof(sum), SecondOrder{AutoForwardDiff{nothing, Nothing}, AutoEnzyme{EnzymeCore.ForwardMode{EnzymeCore.FFIABI}}}, Vector{Float64}, DifferentiationInterface.HVPHessianExtras{DifferentiationInterface.ForwardOverForwardHVPExtras{DifferentiationInterface.var"#inner_gradient_closure#24"{typeof(sum), SecondOrder{AutoForwardDiff{nothing, Nothing}, AutoEnzyme{EnzymeCore.ForwardMode{EnzymeCore.FFIABI}}}}, DifferentiationInterface.NoPushforwardExtras}}}}})
    @ Base ./array.jl:834
 [16] _stack(dims::Function, ::Base.HasShape{1}, iter::Base.Generator{CartesianIndices{1, Tuple{Base.OneTo{Int64}}}, Base.var"#186#187"{DifferentiationInterface.var"#30#31"{typeof(sum), SecondOrder{AutoForwardDiff{nothing, Nothing}, AutoEnzyme{EnzymeCore.ForwardMode{EnzymeCore.FFIABI}}}, Vector{Float64}, DifferentiationInterface.HVPHessianExtras{DifferentiationInterface.ForwardOverForwardHVPExtras{DifferentiationInterface.var"#inner_gradient_closure#24"{typeof(sum), SecondOrder{AutoForwardDiff{nothing, Nothing}, AutoEnzyme{EnzymeCore.ForwardMode{EnzymeCore.FFIABI}}}}, DifferentiationInterface.NoPushforwardExtras}}}}})
    @ Base ./abstractarray.jl:2809
 [17] _stack
    @ ./abstractarray.jl:2799 [inlined]
 [18] stack(f::DifferentiationInterface.var"#30#31"{typeof(sum), SecondOrder{AutoForwardDiff{nothing, Nothing}, AutoEnzyme{EnzymeCore.ForwardMode{EnzymeCore.FFIABI}}}, Vector{Float64}, DifferentiationInterface.HVPHessianExtras{DifferentiationInterface.ForwardOverForwardHVPExtras{DifferentiationInterface.var"#inner_gradient_closure#24"{typeof(sum), SecondOrder{AutoForwardDiff{nothing, Nothing}, AutoEnzyme{EnzymeCore.ForwardMode{EnzymeCore.FFIABI}}}}, DifferentiationInterface.NoPushforwardExtras}}}, iter::CartesianIndices{1, Tuple{Base.OneTo{Int64}}}; dims::Function)
    @ Base ./abstractarray.jl:2796
 [19] hessian
    @ ~/Work/GitHub/Julia/DifferentiationInterface.jl/DifferentiationInterface/src/hessian.jl:54 [inlined]
 [20] hessian(f::Function, backend::SecondOrder{AutoForwardDiff{nothing, Nothing}, AutoEnzyme{EnzymeCore.ForwardMode{EnzymeCore.FFIABI}}}, x::Vector{Float64})
    @ DifferentiationInterface ~/Work/GitHub/Julia/DifferentiationInterface.jl/DifferentiationInterface/src/hessian.jl:54
 [21] top-level scope
    @ REPL[6]:1
 [22] eval
    @ ./boot.jl:385 [inlined]
 [23] eval
    @ ./Base.jl:88 [inlined]
 [24] repleval(m::Module, code::Expr, ::String)
    @ VSCodeServer ~/.vscode/extensions/julialang.language-julia-1.76.2/scripts/packages/VSCodeServer/src/repl.jl:229
 [25] (::VSCodeServer.var"#112#114"{Module, Expr, REPL.LineEditREPL, REPL.LineEdit.Prompt})()
    @ VSCodeServer ~/.vscode/extensions/julialang.language-julia-1.76.2/scripts/packages/VSCodeServer/src/repl.jl:192
 [26] with_logstate(f::Function, logstate::Any)
    @ Base.CoreLogging ./logging.jl:515
 [27] with_logger
    @ ./logging.jl:627 [inlined]
 [28] (::VSCodeServer.var"#111#113"{Module, Expr, REPL.LineEditREPL, REPL.LineEdit.Prompt})()
    @ VSCodeServer ~/.vscode/extensions/julialang.language-julia-1.76.2/scripts/packages/VSCodeServer/src/repl.jl:193
 [29] #invokelatest#2
    @ ./essentials.jl:892 [inlined]
 [30] invokelatest(::Any)
    @ Base ./essentials.jl:889
 [31] (::VSCodeServer.var"#64#65")()
    @ VSCodeServer ~/.vscode/extensions/julialang.language-julia-1.76.2/scripts/packages/VSCodeServer/src/eval.jl:34

[gdalle]

Error no longer occurs with current release