gistfile1.txt

> :set -XDeriveGeneric
> :set -XGeneralizedNewtypeDeriving
> import GHC.Generics

> data Bar = Bar { baz :: Int, qux :: Int } deriving (Generic, Eq, Show)
> instance ToJSON Bar
> instance FromJSON Bar
> toJSON $ Bar 1 2
Object (fromList [("baz",Number 1.0),("qux",Number 2.0)])

> newtype Foo = Foo Bar deriving (Generic, Eq, Show)
> instance ToJSON Foo
> instance FromJSON Foo
> toJSON . Foo $ Bar 1 2
Object (fromList [("baz",Number 1.0),("qux",Number 2.0)])

> :set -XDerivingStrategies
> :{
 newtype Zoo = Zoo Bar
   deriving stock Generic
   deriving newtype (Eq, Show)
 :}
> instance ToJSON Zoo
> instance FromJSON Zoo
> toJSON . Zoo $ Bar 1 2
Object (fromList [("baz",Number 1.0),("qux",Number 2.0)])