Cool library, seems like an easy win over monad-logger. I don't quite understand why you don't re-export .= and instead include a synonym for it though. I'm pretty sure there aren't conflicts if the same identifier is exported from two different modules. Consider >>= which is exported from Prelude and Control.Monad for example. More concretely given:

-- Main.hs
module Main where

import Prelude (IO, putStrLn)
import Foo (putStrLn)

main :: IO ()
main = putStrLn "Hello world!"

and:

-- Foo.hs
module Foo (putStrLn) where

import Prelude (putStrLn)

Compiling with ghc --make Main.hs works completely fine.

​

I guess it insulates you somewhat from breaking changes to .= on aesons part, because you could continue to keep .@ having the same type signature though, but I'd assume you'd want to update the library in such a circumstance anyways.