Currently there is no way to remove a spec from the registry. During interactive development, particularly when working on complicated or recursive specs, it would be useful to have this ability.
Proposed: Make s/def take nil as a way to "clear" a spec:
Moving to 1.9 so it will get looked at, may not be added.
Updated patch to apply to spec.alpha
Update s/def docstring as well in -4 patch.