Export: true should cascade on transitive calls

[cando]

Hello,
it would be nice if transitive calls starting from a root function marked as "@export: true" are not maked as unused.
E.g.

defmodule Foo do
  @doc export: true
  def exported do
    used_only_externally()
  end

  def used_only_externally do
    foo()
    bar()
  end

  def foo, do: :ok

  def bar, do: :ok
end

Right now, used_only_externally is marked as unused, but it is not.

Thanks a lot.