gradients of hessians with divisions

[simonbyrne]

I can't figure this one out. When I try in the debugger or with --inline=no, it works correctly!

julia> using ForwardDiff

julia> ForwardDiff.gradient([1.0]) do s
           ForwardDiff.hessian(u -> u[1]/s[1], [1.0])[1]
       end
ERROR: MethodError: Cannot `convert` an object of type ForwardDiff.Dual{ForwardDiff.Tag{##1#3,Float64},Float64,1} to an object of type Float64
This may have arisen from a call to the constructor Float64(...),
since type constructors fall back to convert methods.
Stacktrace:
 [1] convert(::Type{ForwardDiff.Dual{ForwardDiff.Tag{##1#3,Float64},ForwardDiff.Dual{ForwardDiff.Tag{##2#4{Array{ForwardDiff.Dual{ForwardDiff.Tag{##1#3,Float64},Float64,1},1}},Float64},Float64,1},1}}, ::ForwardDiff.Dual{ForwardDiff.Tag{##2#4{Array{ForwardDiff.Dual{ForwardDiff.Tag{##1#3,Float64},Float64,1},1}},Float64},ForwardDiff.Dual{ForwardDiff.Tag{##1#3,Float64},Float64,1},1}) at /Users/simon/.julia/v0.6/ForwardDiff/src/dual.jl:314
 [2] convert(::Type{Tuple{ForwardDiff.Dual{ForwardDiff.Tag{##1#3,Float64},ForwardDiff.Dual{ForwardDiff.Tag{##2#4{Array{ForwardDiff.Dual{ForwardDiff.Tag{##1#3,Float64},Float64,1},1}},Float64},Float64,1},1}}}, ::Tuple{ForwardDiff.Dual{ForwardDiff.Tag{##2#4{Array{ForwardDiff.Dual{ForwardDiff.Tag{##1#3,Float64},Float64,1},1}},Float64},ForwardDiff.Dual{ForwardDiff.Tag{##1#3,Float64},Float64,1},1}}) at ./essentials.jl:135
 [3] / at /Users/simon/.julia/v0.6/ForwardDiff/src/dual.jl:99 [inlined]
...

[simonbyrne]

apparently it is fixed on 0.7 (thanks @YingboMa), so must be some sort of lowering bug

[simonbyrne]

To simplify the stack trace, the top-level traceback is

 [1] convert(::Type{ForwardDiff.Dual{ForwardDiff.Tag{AAA,Float64},ForwardDiff.Dual{BBB,Float64,1},1}}, ::ForwardDiff.Dual{BBB,ForwardDiff.Dual{ForwardDiff.Tag{AAA,Float64},Float64,1},1})

Here the AAA tag is generated by the gradient, and BBB is generate by the hessian. It (correctly) has the BBB tag on the outside, but wants to convert it to the other way around. No idea why.

[KristofferC]

This seems to work now.