Some initial experimentation with finally tagless sums for JS primitives in Purescript

Primitive.purs

module Primitive (class Primitive) where

class OnlyPrimitive a
instance intOnlyPrimitive ∷ OnlyPrimitive Int
instance boolOnlyPrimitive ∷ OnlyPrimitive Boolean
instance stringOnlyPrimitive ∷ OnlyPrimitive String

class OnlyPrimitive a ⇐ Primitive a
instance intPrimitive ∷ Primitive Int
instance boolPrimitive ∷ Primitive Boolean
instance stringPrimitive ∷ Primitive String