Haskell does not have OOP style inheritance. If you define a new type, it is impossible to use it where you were expected a value from a concrete old type. The

Haskell does not have OOP style inheritance. If you define a new type, it is impossible to use it where you were expected a value from a concrete old type. The way around this is typeclasses, which are essentially interfaces. But this would require that the functions you are calling (which may be written by a third party) be written against a generic typeclass instead of the concrete List type. Haskell is improving in this regard, but there is still many places that are written expecting a List. Also, if the function needs any beyond simple iteration, the typeclass it would use would have a scary name like Semigroup (even iteration uses Foldable, which might not be clear to beginners) There is the IsList typeclass. But the intended use for that is to enable a list-like datatype to be represented with list literals in source code. Even with all of these difficulties, the worst case scenario is to spam your code with NonEmpty.toList and NonEmpty.fromList (or its safe sister NonEmpty.nonEmpty which returns an error value instead of throwing when given an empty list.