Need better documentation/examples/error messages for using HessianConfig with DiffResult API

The following works for gradient!():

using DiffBase, ReverseDiff

f(x) = sum(sin, x)+prod(tan, x)*sum(sqrt, x);

x = rand(4);

result = DiffBase.GradientResult(x);

rcfg = ReverseDiff.GradientConfig(x);

ReverseDiff.gradient!(result, f, x, rcfg);

DiffBase.value(result)

DiffBase.gradient(result)

However, the Hessian analogue of the above fails:

using DiffBase, ReverseDiff

f(x) = sum(sin, x)+prod(tan, x)*sum(sqrt, x);

x = rand(4);

result = DiffBase.HessianResult(x);

rcfg = ReverseDiff.HessianConfig(x);

ReverseDiff.hessian!(result, f, x, rcfg);

DiffBase.value(result)

DiffBase.gradient(result)

DiffBase.hessian(result)

Start by reproducing the working GradientResult example and the failing HessianResult example using DiffBase and ReverseDiff, then inspect the documentation or examples covering HessianConfig and the DiffResult API. Done means the Hessian usage and resulting error behavior are clearly documented, with examples or error messages that explain the difference.