When compiling with unordered-containers < 0.2.6 and base < 4.8, some CPP gets triggered that imports `sort` and `foldl'` from Data.List, seemingly from [this commit](https://github.com/bos/aeson/commit/c2def3b753269fe3d6603e5361584c486b10ed0d) 13 days ago. I'm suspecting that CI doesn't hit this case because I don't think it can work. I get the error: ``` Data/Aeson/Types/Internal.hs:401:28: Ambiguous occurrence ‘foldl'’ It could refer to either ‘Data.Foldable.foldl'’, imported from ‘Data.Foldable’ at Data/Aeson/Types/Internal.hs:88:23-34 or ‘Data.List.foldl'’, imported from ‘Data.List’ at Data/Aeson/Types/Internal.hs:94:19-24 ``` I can understand why we have the explicit imports of Foldable due to FTP, but Data.Foldable has had `foldl'` for many years and so would always conflict with the one from Data.List. You can test this by building this repo with: ``` cabal install --only-dependencies --enable-tests --enable-benchmarks --constraint='base==4.7.0.2' --constraint='unordered-containers==0.2.5.1' ``` Tagging in the author of the commit, @watashi to see if there was a reason for the explicit foldl' there.