make-pathname fails to sanitize :directory string components

I'll add that the sanitization problem exists for other component parameters than :DIRECTORY:

--
* (make-pathname :name "a/b")
#P"a/b"
* (namestring (make-pathname :name "a/b"))
"a/b"
--

And it exists for characters other than slash, e.g.,

--
(let* ((string (make-array 3 :element-type 'character
                           :initial-contents '(#\a #\nul #\b)))
       (pathname (make-pathname :name string :defaults #p"/tmp/foo.lisp")))
  (with-open-file (file pathname :direction :output :if-exists :supersede)
    (write-line "foo" file)
    (close file)
    (probe-file file)))
#P"/tmp/a"
--

While I'm at it, PARSE-NAMESTRING also doesn't catch #\NUL:

--
* (parse-namestring (coerce '(#\a #\nul #\b) 'string))
#P"a^@b" ;; that's a rendering, it's actually "a\0b"
3
--

I'd bet, but haven't investigated, that PATTERNs don't get sanitized either, and there might be observable anomalies that could result.

Reproduced under SBCL 2.0.0.