[Haskell-cafe] Newtype derivation understanding problem

Excuse me if the question is silly. Thought this MonadCatchIO will be removed in next version of snap, current version has it and I can't understand this derivation: [0] L.Lensed seems like just a newtype wrapper around a function [1], and there is no instance of MonadCatchIO for a function. How is it derived? [0]: https://github.com/snapframework/snap/blob/0.13.2.8/src/Snap/Snaplet/Interna... [1]: https://github.com/snapframework/snap/blob/0.13.2.8/src/Snap/Snaplet/Interna...