If you don't use complicated compiler extensions (which, to be fair, many people do), then Haskell's complexity is more compositional. There are not a lot of fundamental concepts you need to understand; it's just their combination that creates the complexity (such as typeclasses like Monad).

Swift's complexity feels much less compositional. There are still a lot of situations where I won't really know how certain features interact (especially when it comes to generics, associated types, etc.). Also, the documentation on some edge-cases is basically non-existant.