haskell error

{-# LANGUAGE OverloadedStrings #-}
import Control.Applicative
import Database.SQLite.Simple
import Database.SQLite.Simple.FromRow

data TestField = TestField Int String deriving (Show)

instance FromRow TestField where
  fromRow = TestField <$> field <*> field


main :: IO()
main = do
  conn <- open "db1.sqlite"
  execute conn "DROP TABLE tabela"
  close conn