Improve defface error message

* lisp/cus-face.el (custom-declare-face): Improve the error
message when there's a missing doc string (bug#51576).

diff --git a/lisp/cus-face.el b/lisp/cus-face.el
index 6c0052bf86046bca7ef678ddb0cf58981947b339..5037ee77c7cf8cb98c490ee1c4f8c84382fb73bc 100644 (file)
--- a/lisp/cus-face.el
+++ b/lisp/cus-face.el
@@ -31,6 +31,9 @@
 
 (defun custom-declare-face (face spec doc &rest args)
   "Like `defface', but with FACE evaluated as a normal argument."
+  (when (and doc
+             (not (stringp doc)))
+    (error "Invalid (or missing) doc string %S" doc))
   (unless (get face 'face-defface-spec)
     (face-spec-set face (purecopy spec) 'face-defface-spec)
     (push (cons 'defface face) current-load-list)