System Information
Operating system: Windows-10-10.0.18362 64 Bits
Graphics card: Quadro K3000M/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 416.78

Blender Version
Broken: version: 2.80 (sub 74), branch: master, commit date: 2019-07-01 15:48, hash: rBdcf520cdad79
Worked: 2.79

Short description of error
When the target has a Follow Path constraint, the Set Inverse function of the Child Of bone gives unexpected results, it repositions the Child Of bone, but not to it's Rest Position.

Exact steps for others to reproduce the error
Create a Curve object.
Attach curves vertices to "hook" bones to deform.
Add a bone at world origin, and add Follow Path constraint using the above curve as the target.
Add another bone at it's intended rest position, add a Child of constraint with the target being the Follow Path bone.
Child Of bone is offset from its rest position/rotation.
Set Inverse, Child of bone moves, but not to its rest position/rotation.
All bones are in the same armature.