All well and good when the shared superclass is Functor. But is the below program valid, and if so, what does it print? If it is invalid due to overlapping instances, is there going to be a special case that recognizes Functor-derived classes like Monad and Traversable as not conflicting?
class Alpha a where
alpha :: a -> String
class Bravo a where
bravo :: a -> a -> String
implication instance Bravo a => Alpha a where
alpha a = bravo a a
class Charlie a where
charlie :: [a] -> String
implication instance Charlie a => Alpha a where
alpha a = charlie [a]
data Foo = Foo
instance Bravo Foo where
bravo _ _ = "bravo"
instance Charlie Foo where
charlie _ = "charlie"
-- What does this print?
main :: IO ()
main = putStrLn $ alpha Foo