Add new `cl-struct' and `eieio' pcase patterns.

* lisp/emacs-lisp/cl-macs.el (cl-struct): New pcase pattern.
* lisp/emacs-lisp/eieio.el (eieio-pcase-slot-index-table)
(eieio-pcase-slot-index-from-index-table): New functions.
(eieio): New pcase pattern.
* lisp/emacs-lisp/pcase.el (pcase--make-docstring): New function.
(pcase): Use it to build the docstring.
(pcase-defmacro): Make sure the macro is lazy-loaded.
(\`): Move its docstring from `pcase'.

1 files changed, 22 insertions, 0 deletions

diff --git a/lisp/emacs-lisp/cl-macs.el b/lisp/emacs-lisp/cl-macs.el
index 75c6a5687c4..a81d217e4ee 100644
--- a/lisp/emacs-lisp/cl-macs.el
+++ b/lisp/emacs-lisp/cl-macs.el
@@ -2768,6 +2768,28 @@ non-nil value, that slot cannot be set via `setf'.
                            ',print-auto))
        ',name)))
 
+;;; Add cl-struct support to pcase
+
+;;;###autoload
+(pcase-defmacro cl-struct (type &rest fields)
+  "Pcase patterns to match cl-structs.
+Elements of FIELDS can be of the form (NAME UPAT) in which case the contents of
+field NAME is matched against UPAT, or they can be of the form NAME which
+is a shorthand for (NAME NAME)."
+  ;; FIXME: This works well for a destructuring pcase-let, but for straight
+  ;; pcase, it suffers seriously from a lack of support for cl-typep in
+  ;; pcase--mutually-exclusive-p.
+  `(and (pred (pcase--swap cl-typep ',type))
+        ,@(mapcar
+           (lambda (field)
+             (let* ((name (if (consp field) (car field) field))
+                    (pat (if (consp field) (cadr field) field)))
+               `(app ,(if (eq (cl-struct-sequence-type type) 'list)
+                          `(nth ,(cl-struct-slot-offset type name))
+                        `(pcase--flip aref ,(cl-struct-slot-offset type name)))
+                     ,pat)))
+           fields)))
+
 (defun cl-struct-sequence-type (struct-type)
   "Return the sequence used to build STRUCT-TYPE.
 STRUCT-TYPE is a symbol naming a struct type.  Return 'vector or