https://hackage.haskell.org/package/first-class-instances

main.hs

-- Breaking first-class-instances
{-#
LANGUAGE
  TemplateHaskell,
  RankNTypes,
  TypeFamilies,
  KindSignatures,
  FlexibleInstances,
  ConstraintKinds
#-}
module Main where

import FCI

class Foo a where
  foo :: a -> String

mkInst ''Foo

instance Foo String where
  foo = ("top:" ++)

main :: IO ()
main = do
  putStrLn $
    Foo ("outer:" ++) ==> Foo ("inner:" ++) ==> foo (foo "")
  putStrLn $
    Foo ("outer:" ++) ==>
      (let f = Foo ("inner:" ++) ==> foo . foo in f "")