Sequence-reference variables with &map can't be recursive

[okamsn]

This a problem with the upstream implementation of the setf support for
map-elt. It currently passes through the map value instead of treating it
like a reference.

For example,

(let ((arr (vector 0 1 2 3 4 5 6)))
  (setf (map-elt (cl-subseq arr 3) 0)
        27)
  arr)

expands to

(let ((arr (vector 0 1 2 3 4 5 6)))
  (let* ((v arr))
    (condition-case nil
        (with-no-warnings
          (map-put! (cl-subseq v 3) 0 27 nil))
      (map-not-inplace
       (let* ((new (map-insert (cl-subseq v 3) 0 27)))
         (progn
           (cl-replace v new :start1 3 :end1 nil)
           new))
       27)))
  arr)

See how map-put! is being used instead of expanding into something more.

[okamsn]

This might also be a problem with cl-subseq, or some interaction of multiple
things.

elt also has this problem

;; = > [0 1 2 3 4 5 6]
(let ((arr (vector 0 1 2 3 4 5 6)))
  (setf (elt (cl-subseq arr 3) 0)
        27)
  arr)

but using the hash-table functions does not

;; => [27 1 2]
(let ((map (make-hash-table)))
  (puthash 3 (vector 0 1 2) map)
  (setf (elt (gethash 3 map) 0) 27)
  (gethash 3 map))