[Haskell-cafe] Dealing with GHC 7.10 prelude imports

Benno Fünfstück benno.fuenfstueck at gmail.com
Sun Apr 12 10:37:44 UTC 2015

> I've run into a couple of cases when attempting to support multiple GHC
versions in my libraries (7.6.3 -> 7.10) where I've repeatedly made
mistakes due to being warned about unused imports for various modules that
are now part of the Prelude such as Data.Monoid, Data.Foldable, etc. which
I subsequently remove either manually or via editor automation sufficiently
indistinguishable from magic.

A trick is to import Prelude at the very end, like:

import Control.Applicative
import Data.Monoid
import Prelude

Since the unused import check is done from top to bottom, and you almost
always use *something* from the Prelude, this will suppress the warning.

There are some problems with qualified/explicit import lists if I recall
correctly though. But it works for me most of the time.

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