I get a method error with ForwardDiff.jacobian that I fails to understand. Below a MWE.

```
function fooworks(cvec,xmesh)
residual = cvec
return residual
end
function foofails(cvec,xmesh)
residual = zeros(length(cvec))
N = length(cvec)
for i=1:N
residual[i] = cvec[i]
end
return residual
end
# generate the mesh with N elements (intervals) and N+1 nodes
N = 10; h = 1/N; Np1 = N+1;
xmesh = Vector(0:h:1)
cvec = ones(size(xmesh))
h = cvec->fooworks(cvec,xmesh);
h = cvec->foofails(cvec,xmesh)
ForwardDiff.jacobian(h,cvec)
```

The error message is:

MethodError: no method matching Float64(::ForwardDiff.Dual{ForwardDiff.Tag{var"#127#128", Float64}, Float64, 11})

Closest candidates are:

(::Type{T})(::Real, ::RoundingMode) where T<:AbstractFloat at rounding.jl:200

(::Type{T})(::T) where T<:Number at boot.jl:772

(::Type{T})(::AbstractChar) where T<:Union{AbstractChar, Number} at char.jl:50

Help is much appreciated.