Currently, because ScrollableState.setCanDrag doesn't check whether it complies with ScrollPhysics.shouldAcceptUserOffset, it's possible that user of ScrollableState doesn't check whether it can be set to true or false and thus ignores scroll physics by mistake - which is what happens to NestedScrollView, which forgets to do exactly this #45619

I propose that we force users of the ScrollableState to check the physics before they apply their own conditions with such assert (or something similar)

assert(
  _physics == null || newCanDrag == _physics!.shouldAcceptUserOffset(position),
  'When scrollable has physics, canDrag should be equal to shouldAcceptUserOffset result',
);

cc @Hixie