readFail039.hs:9:14: error: [GHC-82023]
    • Can't make a derived instance of ‘C Foo’:
        ‘C’ is not a stock derivable class (Eq, Show, etc.)
    • In the newtype declaration for ‘Foo’
    Suggested fix:
      Perhaps you intended to use GeneralizedNewtypeDeriving
      for GHC's newtype-deriving extension