On Tue, Jan 27, 2015 at 3:18 PM, Eric Mertens
I can certainly see the reasoning in wanting Data.List.foldr to actually be the list-specific one, and this would be consistent with other cases like Data.Map. Changing this might break some code, but it might be a more reasonable situation in the end. If we're going to consider this it would probably be better in its own thread so that it doesn't get drowned out by the rest of the BBP discussion.
The main reason this wasn't done is that we ran quick trial balloon to see which style broke less code. Looking through hackage for usage of Data.List, quite a bit of it is done unqualified. Monomorphizing Data.List combinators would break code that is written as import Data.List foo = ... foldr ... Removing them would break code that is written as import qualified Data.List as List foo = ... List.foldr ... Both of these styles were fairly common, though the former more so. In an ideal world we'd have never put them in Data.List in the first place, same with mapM etc. in Control.Monad, etc. and then something like Lennart's proposal here would have been viable. The main thing we can learn from this is that having modules that "conveniently" re-export stuff is a dangerous thing in terms of long term API design.