Hi @Filipewelton there are no differences in either compile time or runtime performance.

I can swear the word “performance” was not in the title when I posted my answer which now looks awfully out of place, lol.

Consider this:

defmodule Project.Module
  def function(arg) do
    IO.inspect(arg, label: "function")
  end

  def another_function(arg) do
    IO.inspect(arg, label: "another_function")
  end
end

So then let’s use it:

defmodule User1 do
  import Project.Module

  def do_stuff() do
    function()
    another_function()
  end
end

Both work because when you do import Project.Module you include all its functions in your current scope so you don’t have to prefix them.

But if you do this:

defmodule User2 do
  import Project.Module, only: [function: 1]

  def do_stuff() do
    function() # works.
    another_function() # compile error, `another_function` not found.
    Project.Module.another_function() # full scoping works.
  end
end

Link to docs.