# Open this file for writing
	#
	# ~~~
	# var file = "bla.log".to_path.open_wo
	# file.write "Blabla\n"
	# file.close
	# ~~~
	#
	# Note that it is the user's responsibility to close the stream.
	# Therefore, for simple use case, look at `Writable::write_to_file`.
	#
	# ENSURE `last_error == result.last_error`
	fun open_wo: FileWriter
	do
		var res = new FileWriter.open(path)
		last_error = res.last_error
		return res
	end