Haskell2020 Is Dead, but All Hope Is Not Lost (2019)(reasonablypolymorphic.com)

    module Main where
    
    import Rel8
    import Data.Int
    import Hasql.Statement
    import Hasql.Session
    import Hasql.Connection
    import Database.Postgres.Temp
    
    main = Database.Postgres.Temp.with $ \db -> do
      Right conn <- acquire (toConnectionString db)
    
      flip run conn $ statement () $ select $ do
        q1 <- many $ do
          r1 <- many (values [1 , 2 :: Expr Int16])
          r2 <- many (values [3 , 4 :: Expr Int16])
    
          values [(litExpr "one", r1), (litExpr "two", r2)]
    
        q2 <- many $ do
          r1 <- many (values [10 , 20 :: Expr Int16])
          r2 <- many (values [30 , 40 :: Expr Int16])
    
          values [(litExpr "ten", r1), (litExpr "twenty", r2)]
    
        values [(litExpr "X", q1), (litExpr "Y", q2)]
    

    > main
    Right (Right [("X",[("one",[1,2]),("two",[3,4])]),("Y",[("ten",[10,20]),("twenty",[30,40])])])