Как создать собственную монаду синтаксического анализатора для SimpleJSON в PureScript?

У меня есть следующее, которое работает до тех пор, пока я не пытаюсь определить readJSON':

newtype JSONWithErr a = JSONWithErr (Writer (Array Foreign.ForeignError) a)

derive newtype instance jsonWithErrApply :: Apply JSONWithErr
derive newtype instance jsonWithErrApplicative :: Applicative JSONWithErr
derive newtype instance jsonWithErrFunctor :: Functor JSONWithErr
derive newtype instance jsonWithErrBind :: Bind JSONWithErr
derive newtype instance jsonWithErrMonad :: Monad JSONWithErr
derive newtype instance jsonWithErrTell :: MonadTell (Array Foreign.ForeignError) JSONWithErr
derive newtype instance jsonWithErrWriter :: MonadWriter (Array Foreign.ForeignError) JSONWithErr

newtype JSONParse a = JSONParse (ExceptT (NonEmptyList ForeignError) JSONWithErr a)

derive newtype instance jsonParseApply :: Apply JSONParse
derive newtype instance jsonParseApplicative :: Applicative JSONParse
derive newtype instance jsonParseFunctor :: Functor JSONParse
derive newtype instance jsonParseBind :: Bind JSONParse
derive newtype instance jsonParseMonad :: Monad JSONParse
derive newtype instance jsonParseTell :: MonadTell (Array Foreign.ForeignError) JSONParse
derive newtype instance jsonParseWriter :: MonadWriter (Array Foreign.ForeignError) JSONParse
derive newtype instance jsonParseThrow :: MonadThrow (NonEmptyList ForeignError) JSONParse

generalize :: forall m a. Monad m => Identity a -> m a
generalize = unwrap >>> pure

-- type Except e = ExceptT e Identity
genExcept :: forall m e a. Monad m => ExceptT e Identity a -> ExceptT e m a
genExcept = unwrap >>> generalize >>> ExceptT

readJSON' :: forall a. JSON.ReadForeign a => String -> JSONParse a
readJSON' s = JSONParse $ genExcept $ (pure >>> JSONWithErr) <$> (JSON.readJSON' s) -}

Ошибка здесь, которая охватывает все определение readJSON', такова:

Could not match type

    JSONWithErr t2

  with type

    a0


while trying to match type JSONParse t1
  with type JSONParse a0
while checking that expression (apply JSONParse) ((apply genExcept) ((map (...)) (readJSON' s)))
  has type JSONParse a0
in value declaration readJSON'

where a0 is a rigid type variable
        bound at (line 0, column 0 - line 0, column 0)
      t1 is an unknown type
      t2 is an unknown type

Я попытался немного упростить его, но, похоже, у меня возникли проблемы с ограничениями; в следующем упрощении типизированная дыра не работает из-за более ранней ошибки:

tmp :: forall a. JSON.ReadForeign a => String -> ExceptT (NonEmptyList ForeignError) JSONWithErr a
tmp s = ?help (JSON.readJSON' s)

И ошибка:

  No type class instance was found for

    Simple.JSON.ReadForeign t0

  The instance head contains unknown type variables. Consider adding a type annotation.

while applying a function readJSON'
  of type ReadForeign t0 => String -> ExceptT (NonEmptyList ForeignError) Identity t0
  to argument s
while inferring the type of readJSON' s
in value declaration tmp