T5217.hs:(6,3)-(9,53): Splicing declarations
    [d| data T a b
          where
            T1 :: Int -> T Int Char
            T2 :: a -> T a a
            T3 :: a -> T [a] a
            T4 :: a -> b -> T b [a] |]
  ======>
    data T a b
      where
        T1 :: Int -> T Int Char
        T2 :: forall a. a -> T a a
        T3 :: forall a. a -> T [a] a
        T4 :: forall a b. a -> b -> T b [a]