Once the samplers that require higher order derivatives (such as SMMALA, MMALA, RMHMC) have been ported, the autodiff-related parameter constructors need to be updated to allow calculating the required higher order derivatives via forward mode autodiff.
Sorted from v0.8.0 onwards, at least for SMMALA. On the other hand, MMALA and RMHMC require third order derivatives, which are not supported by ForwardDiff.
Once the samplers that require higher order derivatives (such as SMMALA, MMALA, RMHMC) have been ported, the autodiff-related parameter constructors need to be updated to allow calculating the required higher order derivatives via forward mode autodiff.