Built-in macros expanding to invalid code

output.txt

case(:condition) do
  x when x in [false, nil] ->
    nil
  _ ->
    :ok
end
case(:condition) do
  x when Enum.member?([false, nil], x) ->
    nil
  _ ->
    :ok
end

# cannot invoke remote function Enum.member?/2 inside guard

test.ex

block = quote do
  if :condition do :ok end
end

block
|> Macro.expand_once(__ENV__)
|> Macro.to_string
|> IO.puts

block
|> Macro.prewalk(&Macro.expand(&1, __ENV__))
|> Macro.to_string
|> IO.puts