graphql-engine/server/src-lib/Control/Monad/Unique.hs

-- | A tiny mtl-style wrapper around 'U.newUnique'.
module Control.Monad.Unique
  ( U.Unique,
    MonadUnique (..),
  )
where

import Data.Unique qualified as U
import Hasura.Prelude

class (Monad m) => MonadUnique m where
  newUnique :: m U.Unique

instance MonadUnique IO where
  newUnique = U.newUnique

instance (MonadUnique m) => MonadUnique (ExceptT e m) where
  newUnique = lift newUnique

instance (MonadUnique m) => MonadUnique (ReaderT r m) where
  newUnique = lift newUnique

instance (MonadUnique m) => MonadUnique (StateT s m) where
  newUnique = lift newUnique

instance (Monoid w, MonadUnique m) => MonadUnique (WriterT w m) where
  newUnique = lift newUnique