Sorry, I edited my comment and added a part about recursion. So you are right that not all of Haskell is compileable using Clash. But that also isn't the goal.

Sorry, I edited my comment and added a part about recursion. So you are right that not all of Haskell is compileable using Clash. But that also isn't the goal. You are using Haskell to describe your digital circuit. That generally is very different from writing a normal Haskell program. It just so happens that Haskell is good at both.