Hid null from Foldable

[luke-clifton]

In Data/Rope/Internal.hs. It was clashing with Data.FingerTree.null.

[adinapoli]

Is this needed though only with version of GHC >= 7.8.x?
Data.Foldable.null was added in base-4.8.0.0:

http://hackage.haskell.org/package/base-4.7.0.0/docs/Data-Foldable.html
http://hackage.haskell.org/package/base-4.8.0.0/docs/Data-Foldable.html

IMHO a better fix would be to import qualified Data.Foldable and Data.FingerTree with different names (not using F for both). This will work across all the versions of GHC & base.

What Mr. @ekmett reckon?

[luke-clifton]

It is OK to hide identifiers that don't exist. And it was the easier option :lazy:

[adinapoli]

Ok, wasn't 100% sure on top of my mind if GHC would have barked at us in trying to hide identifiers which don't exist. In that case I will go on and merge.

[ekmett]

It is OK to hide identifiers that don't exist.

Only on newer GHCs.

Doing so shuts off access to old versions of GHC.

[adinapoli]

@ekmett Damn, I was right. @luke-clifton Could you send us another PR to amend the changes and roll out my proposed fix?

[luke-clifton]

@adinapoli Oh, damn, sorry. I didn't realize that was a new feature. I will do so.