From: Andrea Corallo <akrl@sdf.org>
Date: Sat, 7 Nov 2020 20:00:14 +0000 (+0100)
Subject: * lisp/emacs-lisp/comp.el (comp-common-supertype-2): Fix null intersection
X-Git-Tag: emacs-28.0.90~2727^2~340
X-Git-Url: http://git.eshelyaron.com/gitweb/?a=commitdiff_plain;h=a5408d5715de5ee9b6858c6eb0638043f4cdb136;p=emacs.git

* lisp/emacs-lisp/comp.el (comp-common-supertype-2): Fix null intersection
---

diff --git a/lisp/emacs-lisp/comp.el b/lisp/emacs-lisp/comp.el
index 9fbf60c96c2..c837e020603 100644
--- a/lisp/emacs-lisp/comp.el
+++ b/lisp/emacs-lisp/comp.el
@@ -2155,14 +2155,13 @@ PRE-LAMBDA and POST-LAMBDA are called in pre or post-order if non-nil."
 
 (defun comp-common-supertype-2 (type1 type2)
   "Return the first common supertype of TYPE1 TYPE2."
-  (car (cl-reduce (lambda (x y)
-                    (if (> (cdr x) (cdr y))
-                        x
-                      y))
-                  (cl-intersection
-                   (comp-supertypes type1)
-                   (comp-supertypes type2)
-                   :key #'car))))
+  (when-let ((types (cl-intersection
+                     (comp-supertypes type1)
+                     (comp-supertypes type2)
+                     :key #'car)))
+    (car (cl-reduce (lambda (x y)
+                      (if (> (cdr x) (cdr y)) x y))
+                    types))))
 
 (defun comp-common-supertype (&rest types)
   "Return the first common supertype of TYPES."