Foo.hs

{-# LANGUAGE NamedFieldPuns #-}

module Foo where

newtype MyData = MyData {myField :: Integer}

f :: MyData -> Integer
f MyData {myField} = myField

-- I want to ensure that f is called only with a variable named myField
-- this does work but too verbose
-- something like "f {myField}" would be better
-- "f MyData {otherField}" shows a syntax error and that is the purpose
foo =
  let myField = 1; otherField = 2
   in f MyData {myField}