If it works like Emacs paredit, the default for just hitting `(` would be

  let y = f()(2, 3)

but there should be a different command to do (`alt-(` in paredit)

  let y = f((2, 3))

There should of course also be "slurp" and "barf" commands to add or remove items from the parentheses if you do the wrong thing first (or want to wrap multiple things in the parentheses)