Backward compatibility with pre-existing struct instances.scratch/record

* lisp/emacs-lisp/cl-lib.el (cl--old-struct-type-of): New function.
(cl-old-struct-compat-mode): New minor mode.

* lisp/emacs-lisp/cl-macs.el (cl-defstruct): Pass `record' to
cl-struct-define to signal use of record objects.

* lisp/emacs-lisp/cl-preloaded.el (cl--struct-get-class,
cl-struct-define): Enable legacy defstruct compatibility.

* test/lisp/emacs-lisp/cl-lib-tests.el (cl-lib-old-struct,
old-struct): New tests.

* doc/lispref/elisp.texi, doc/lispref/records.texi: Document
`old-struct-compat'.

1 files changed, 1 insertions, 0 deletions

diff --git a/doc/lispref/elisp.texi b/doc/lispref/elisp.texi
index 0f7efb6f187..3a348aae98e 100644
--- a/doc/lispref/elisp.texi
+++ b/doc/lispref/elisp.texi
@@ -423,6 +423,7 @@ Sequences, Arrays, and Vectors
 Records
 
 * Record Functions::        Functions for records.
+* Backward Compatibility::  Compatibility for cl-defstruct.
 
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