Unused.hs

-- Copyright (c) 2017 Uber Technologies, Inc.
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{-# LANGUAGE DeriveDataTypeable #-}
{-# LANGUAGE DeriveFunctor #-}
{-# LANGUAGE DeriveFoldable #-}
{-# LANGUAGE DeriveGeneric #-}
{-# LANGUAGE DeriveTraversable #-}

module Database.Sql.Type.Unused where

import Data.Aeson
import Data.Data (Data)
import GHC.Generics (Generic)
import Test.QuickCheck

data Unused a = Unused
                deriving (Data, Generic, Eq, Ord, Show, Functor, Foldable, Traversable)

instance ToJSON (Unused a) where
    toJSON Unused = object [("tag", "Unused")]

instance FromJSON (Unused a) where
    parseJSON (Object o) = do
        String "Unused" <- o .: "tag"
        return Unused

    parseJSON v = fail $ unwords
        [ "don't know how to parse as Unused:"
        , show v
        ]

instance Arbitrary (Unused a) where
    arbitrary = pure Unused