Non-idempotent transformation of partly commented data definition

[mrkkrp]

This source code:

data Optimisation = PETransform | GeneralisedNatHack -- ^ partial eval and associated transforms
  deriving (Show, Eq, Generic)

gets first re-formatted as (1)

data Optimisation
  = PETransform | -- | partial eval and associated transforms
                  GeneralisedNatHack
  deriving (Show, Eq, Generic)

and then as (2)

data Optimisation
  = PETransform
  | -- | partial eval and associated transforms
    GeneralisedNatHack
  deriving (Show, Eq, Generic)

It should be printed as (2) right away.