Haskell's type system works best for me in allowing fearless changes, even significant ones to the core of a code base. The compiler won't let me overlook somet

Haskell's type system works best for me in allowing fearless changes, even significant ones to the core of a code base. The compiler won't let me overlook something. A comprehensive test suite would achieve the same thing, but I'm rarely confident that my test suites are truly comprehensive.