[Haskell-cafe] aeson: instance FromJSON IntMap

Dear Cafe, why is Aeson's instance FromJSON IntMap so different from the instance of Map? Apparently the Map instance expects an Object (the dictionary) while the IntMap instance [1] is implemented using IntMap.fromList, so it expects an array. I can of course decode the JSON as (Map Int) and then use IntMap.fromAscList . Map.assocs but how efficient is that? And it also relies on Map.assocs producing the list in the order expected by fromAscList which (unlikely) could be broken in a future version of containers. Thanks Olaf [1] https://hackage.haskell.org/package/aeson-1.5.6.0/docs/src/Data.Aeson.Types....