Re: [Haskell-cafe] Dealing with GHC 7.10 prelude imports

You can use a custom Prelude. E.g., the "base-prelude" project takes care of this problem: http://hackage.haskell.org/package/base-prelude 2015-04-12 11:14 GMT+03:00 Alan & Kim Zimmerman :

See https://ghc.haskell.org/trac/ghc/wiki/Migration/7.10.

I have just solved one of these by doing

{-# LANGUAGE CPP #-} #if __GLASGOW_HASKELL__ < 709 import Data.Monoid hiding ((<>)) #endif

Alan

On Sun, Apr 12, 2015 at 9:55 AM, Brendan Hay wrote:

...

Hi,

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.

This then results in successful compilation on 7.10 and failure on earlier versions of GHC due to missing imports (ie. Data.Monoid (mappend, mempty)), which prior to my current workflow of manually building on multiple versions of GHC before releasing a new version, manifested once or twice only after uploading to Hackage.

Now this is all user/workflow error on my part, but I wondered if others have some kind of trick up their sleeve for avoiding these kind of issues? I could attempt to tailor the compiler's warning flags appropriately, but it bodes ill for spotting genuinely unused imports.

Cheers, Brendan

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