psci

> import X
> import Data.Lens
> :paste
… _x :: Lens' X Int
… _x = _Newtype
… 
(line 2, column 4):
unexpected =
expecting ::, qualifier, proper name, (, string literal, {, _, "forall", "\8704", identifier, type name, operator, number, char literal, "true", "false", [, "\\", data constructor name, "case", "if", "do", "let", hole literal or end of input

X.purs

module X where

import Data.Newtype
import Data.Lens (Lens')
import Data.Lens.Iso.Newtype (_Newtype)

newtype X = X Int

ten = X 10

derive instance newtypeX :: Newtype X _