[Haskell-cafe] Newtype derivation understanding problem

[Konstantine Rybnikov]

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/Internal/Types.hs#L260
[1]:
https://github.com/snapframework/snap/blob/0.13.2.8/src/Snap/Snaplet/Internal/Lensed.hs#L20
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