haskell - ¿Cómo consigo que funcione la extensión de lenguaje OverloadedStrings?

ghc overloaded-strings

Question

He habilitado cadenas sobrecargadas, pero no puedo hacer que funcionen:

$ cat overloadedstrings.hs 
{-# LANGUAGE OverloadedStrings #-}

import qualified Data.ByteString as B
import qualified Data.ByteString.Lazy as BL

lazy :: BL.ByteString
lazy = "I''m a lazy ByteString"

strict :: B.ByteString
strict = "I''m a strict ByteString"

$ ghci
GHCi, version 6.12.1: http://www.haskell.org/ghc/  :? for help
Loading package ghc-prim ... linking ... done.
Loading package integer-gmp ... linking ... done.
Loading package base ... linking ... done.
Prelude> :l overloadedstrings.hs 
[1 of 1] Compiling Main             ( overloadedstrings.hs, interpreted )

overloadedstrings.hs:7:7:
    No instance for (Data.String.IsString BL.ByteString)
      arising from the literal `"I''m a lazy ByteString"''
                   at overloadedstrings.hs:7:7-29
    Possible fix:
      add an instance declaration for
      (Data.String.IsString BL.ByteString)
    In the expression: "I''m a lazy ByteString"
    In the definition of `lazy'': lazy = "I''m a lazy ByteString"

overloadedstrings.hs:10:9:
    No instance for (Data.String.IsString B.ByteString)
      arising from the literal `"I''m a strict ByteString"''
                   at overloadedstrings.hs:10:9-33
    Possible fix:
      add an instance declaration for (Data.String.IsString B.ByteString)
    In the expression: "I''m a strict ByteString"
    In the definition of `strict'': strict = "I''m a strict ByteString"
Failed, modules loaded: none.

¿ IsString dónde importo las instancias de ByteString para ByteString ? ¿No debería esto suceder automáticamente? ¿Qué estoy haciendo mal?

Answer 1

.Char8 importar los módulos .Char8 , como Data.ByteString.Char8 y Data.ByteString.Lazy.Char8