Coalton, being a strictly typed language within Common Lisp, addresses type errors showing up at runtime and not having certain useful abstractions. Since it’s not practical to rewrite an entire compiler, we opted to implement a significant new feature of quilc in Coalton called discrete compilation. In this post, we’ll walk through what discrete compilation is, how Coalton made it simpler to implement (compared to Common Lisp), and how we tested that such a complicated feature actually works.