is that the following instance exists (and is not just undefined):
-- Infinite sequences
data InfSeq a = InfSeq a (InfSeq a)
-- Crazy instance
instance Eq y => Eq (InfSeq Bool -> y)

is that the following instance exists (and is not just undefined):
-- Infinite sequences
data InfSeq a = InfSeq a (InfSeq a)
-- Crazy instance
instance Eq y => Eq (InfSeq Bool -> y)