sincos errors for ComplexF64 forward-mode

[sethaxen]

When the argument type is ComplexF64, forward-mode autodiff raises an error:

using Enzyme

x, ∂x = randn(ComplexF64, 2)
autodiff(Forward, sincos, Duplicated, Duplicated(x, ∂x))

dump.txt

[vchuravy]

Looks like it is missing a custom rule for cos we end up in flipsign and that does bit twiddling

[wsmoses]

Yeah simply autodiff(Forward, cos, Duplicated, Duplicated(x, ∂x)) fails.

Interestingly sin(complex) doesn't have the flipsign call inside that cos(complex) does.