Heterogeneous records in PureScript using existential row variables

Hetero.js

// module Hetero

exports.mkExists = function(fa) {
    return fa;
};

exports.runExists = function(f) {
  return function(fa) {
    return f(fa);
  };
};

Hetero.purs

module Hetero where

import Prelude
import Control.Monad.Eff
import Control.Monad.Eff.Console

foreign import data Exists :: (# * -> *) -> *
foreign import mkExists :: forall f a. f a -> Exists f
foreign import runExists :: forall f r. (forall a. f a -> r) -> Exists f -> r

newtype HasNameF r = HasNameF { name :: String | r }

type HasName = Exists HasNameF

hasName :: forall r. { name :: String | r } -> HasName
hasName o = mkExists (HasNameF o)

brian :: HasName
brian = hasName { name: "Brian", age: 25 }

josh :: HasName
josh = hasName { name: "Josh", legs: 4 }

things :: Array HasName
things = [ brian, josh ]

names :: Array String
names = runExists (\(HasNameF o) -> o.name) <$> things

main :: Eff (console :: CONSOLE) Unit
main = print names