[#197] Fix small issues caused by rebase
Problem: 'Buildable ()' still exists but not used. It's caused by wrong rebase. Also, 'ConstantScope' doesn't have to be used outside of morley package.
Solution: fix these two issues.
Problem: 'Buildable ()' still exists but not used. It's caused by wrong rebase. Also, 'ConstantScope' doesn't have to be used outside of morley package.
Solution: fix these two issues.