Miracles

gistfile1.txt

data Never
data Once = Once

miracle :: (Never -> a) -> (a -> Once) -> Once
miracle = undefined -- let's keep the mystery...


*Main> miracle miracle

<interactive>:1:9:
    Couldn't match expected type `Never' with actual type `Never -> a0'
    Expected type: Never -> a1
      Actual type: (Never -> a0) -> (a0 -> Once) -> Once
    In the first argument of `miracle', namely `miracle'
    In the expression: miracle miracle