# Pastebin 4aygJmq9
{-# LANGUAGE FunctionalDependencies, TypeFamilies, UndecidableInstances #-}

import Data.Kind (Type)

class Foo x y z | x y -> z where

class Foo x y (Foo' x y) => F x y where
  type Foo' x y :: Type

instance Foo x y z => F x y where
  type Foo' x y = z