   """
   @spec extname(t) :: binary
   def extname(path) do
-    FN.extension(IO.chardata_to_string(path))
+    :filename.extension(IO.chardata_to_string(path))
   end
 
   @doc """

  def split(""), do: []

  def split(path) do
    FN.split(IO.chardata_to_string(path))
  end

  defmodule Wildcard do

  that require it (like `wildcard/2` and `expand/1`).
  """

  @type t :: :unicode.chardata()

  @doc """
