[Haskell] Re: indirectly recursive dictionaries

Ralf wrote:

class C1 x where m1 :: x -> () m1 = const undefined

instance (C1 x, C1 y) => C1 (x,y) instance C1 Bool instance (C2 x y, C1 (y,Bool)) => C1 x

class C2 x y | x -> y instance C2 Int Int

bar :: () bar = m1 (1::Int)

I believe it works very well (meaning bar typechecks and even runs) if we either add an instance instance C1 Int or change the instance of C2 to instance C2 Int Bool Otherwise, the problem really has no solution, and looping is an indication. I used GHC 6.8.3....