Why can't I import Control.Monad.Writer while I have mtl-2.2.2 installed?

问题

I am trying to import Writer monad which is defined in mtl-2.2.2 package which I have installed as I checked with ghc-pkg list.

When I tried to do import Control.Monad.Writer in ghci it is giving me an error. I don't understand why?

Prelude> import Control.Monad.Writer  

<no location info>: error:
    Could not find module ‘Control.Monad.Writer’
    Perhaps you meant
      Control.Monad.Fail (from base-4.11.1.0)
      Control.Monad.Fix (from base-4.11.1.0)
      Control.Monad.Zip (from base-4.11.1.0)

来源：https://stackoverflow.com/questions/61500083/why-cant-i-import-control-monad-writer-while-i-have-mtl-2-2-2-installed