test.exs

defmodule Foo do
  def bar() do
    """
    x = 10
    IO.inspect({x, y})
    """
    |> Code.string_to_quoted!()
    |> Macro.traverse(
      %{vars: [], unbound: []},
      fn
        {:=, _, [{new_var, _, nil} | _]} = ast, acc ->
          {ast, %{acc | vars: [new_var | acc.vars]}}

        {var, _, nil} = ast, acc ->
          if var in acc.vars do
            {ast, acc}
          else
            {ast, %{acc | unbound: [var | acc.unbound]}}
          end

        ast, acc ->
          {ast, acc}
      end,
      fn ast, acc -> {ast, acc} end
    )
    |> elem(1)
    |> IO.inspect()
  end
end

Foo.bar()