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{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE MultiParamTypeClasses, FlexibleInstances, FlexibleContexts #-}
type family Id x
type instance Id Int = Int
type instance Id Bool = Bool
class Convert x y where convert :: x -> y
instance Convert x x where convert = id
f :: Convert a (Id a) => a -> Id a
f x = convert x
g :: Convert a (Id a) => a -> Id a
g x = let x' = f x in x'
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