I cant’s seem to make this kind of code work with ForwardDiff2

```
function gaussian(f,N)
a=-8.38149 # exp(-x^2/2)/sqrt(2π) == eps(1.0)
b=8.38149
dx=(b-a)/(N)
Δ=(b-a)/(2N)
x=a+Δ
I=(exp(-x*x/2).*f(x)).*dx
for i in 2:N
x=a+Δ*(2i-1)
I=I.+(exp(-x*x/2).*f(x)).*dx
end
I/sqrt(2*π)
end
using ForwardDiff2: DI
f(α) = gaussian(x->tanh(x+α),100)
f(2.0) # 0.8646647167633871
DI(f)(2.0)
using StaticArrays
g(α) = gaussian(x->@SVector([tanh(2x+α),tanh(x+α)]),100)
g(2.0) # [0.6389517914690043, 0.8646647167633871]
DI(g)(2.0)
```

the error message it gives is about type promotion from Float64 to Dual

is there a known workaround?

thank you guys!

EDIT.

altough immensely inelegant, i managed to get excellent performance via manually using ForwardDiff Dual type.