# Return the directory part of the path.
	#
	# ~~~
	# var path = "/foo/bar/baz".to_path
	# assert path.dir.to_s == "/foo/bar"
	# assert path.dir.dir.to_s == "/foo"
	# assert path.dir.dir.dir.to_s == "/"
	# ~~~
	#
	# See `String:dirname` for details.
	#
	# The result does not depend of the file system, thus is cached for efficiency.
	var dir: Path is lazy do
		return path.dirname.to_path
	end