Repair and speed up safe-copy-tree and make it internal (bug#61962)

There is no particular requirement for safe-copy-tree so let's make it
internal for now.  The new implementation is faster and more correct.

* doc/lispref/lists.texi (Building Lists):
* etc/NEWS:  Remove doc and announcement.
* lisp/subr.el (safe-copy-tree--seen, safe-copy-tree--1)
(safe-copy-tree): Remove old version.
* lisp/emacs-lisp/bytecomp.el (bytecomp--copy-tree-seen)
(bytecomp--copy-tree-1, bytecomp--copy-tree): Add new version.
(byte-compile-initial-macro-environment): Use it.
* test/lisp/subr-tests.el (subr--safe-copy-tree):
* test/lisp/emacs-lisp/bytecomp-tests.el (bytecomp--copy-tree):
Move and improve tests.

1 files changed, 0 insertions, 55 deletions

diff --git a/lisp/subr.el b/lisp/subr.el
index 40bec544b73..8aedce934d1 100644
--- a/lisp/subr.el
+++ b/lisp/subr.el
@@ -846,61 +846,6 @@ argument VECP, this copies vectors as well as conses."
 	  tree)
       tree)))
 
-(defvar safe-copy-tree--seen nil
-  "A hash table for conses/vectors/records already seen by safe-copy-tree-1.
-Its key is a cons or vector/record seen by the algorithm, and its
-value is the corresponding cons/vector/record in the copy.")
-
-(defun safe-copy-tree--1 (tree &optional vecp)
-  "Make a copy of TREE, taking circular structure into account.
-If TREE is a cons cell, this recursively copies both its car and its cdr.
-Contrast to `copy-sequence', which copies only along the cdrs.  With second
-argument VECP, this copies vectors and records as well as conses."
-  (cond
-   ((gethash tree safe-copy-tree--seen))
-   ((consp tree)
-    (let* ((result (cons (car tree) (cdr tree)))
-	   (newcons result)
-	   hash)
-      (while (and (not hash) (consp tree))
-	(if (setq hash (gethash tree safe-copy-tree--seen))
-            (setq newcons hash)
-	  (puthash tree newcons safe-copy-tree--seen))
-        (setq tree newcons)
-        (unless hash
-	  (if (or (consp (car tree))
-                  (and vecp (or (vectorp (car tree)) (recordp (car tree)))))
-	      (let ((newcar (safe-copy-tree--1 (car tree) vecp)))
-	        (setcar tree newcar)))
-          (setq newcons (if (consp (cdr tree))
-                            (cons (cadr tree) (cddr tree))
-                          (cdr tree)))
-          (setcdr tree newcons)
-          (setq tree (cdr tree))))
-      (nconc result
-             (if (and vecp (or (vectorp tree) (recordp tree)))
-		 (safe-copy-tree--1 tree vecp) tree))))
-   ((and vecp (or (vectorp tree) (recordp tree)))
-    (let* ((newvec (copy-sequence tree))
-           (i (length newvec)))
-      (puthash tree newvec safe-copy-tree--seen)
-      (setq tree newvec)
-      (while (>= (setq i (1- i)) 0)
-	(aset tree i (safe-copy-tree--1 (aref tree i) vecp)))
-      tree))
-   (t tree)))
-
-(defun safe-copy-tree (tree &optional vecp)
-  "Make a copy of TREE, taking circular structure into account.
-If TREE is a cons cell, this recursively copies both its car and its cdr.
-Contrast to `copy-sequence', which copies only along the cdrs.  With second
-argument VECP, this copies vectors and records as well as conses."
-  (setq safe-copy-tree--seen (make-hash-table :test #'eq))
-  (unwind-protect
-      (safe-copy-tree--1 tree vecp)
-    (clrhash safe-copy-tree--seen)
-    (setq safe-copy-tree--seen nil)))
-
 
 ;;;; Various list-search functions.