Define cl-type-definition button type as needed (Bug#28899)

* lisp/emacs-lisp/eieio-opt.el (eieio-help-constructor): Require
`cl-extra' before using the `cl-type-definition' button type.

1 files changed, 4 insertions, 1 deletions

diff --git a/lisp/emacs-lisp/eieio-opt.el b/lisp/emacs-lisp/eieio-opt.el
index dbec48d038b..eeb0bc95d68 100644
--- a/lisp/emacs-lisp/eieio-opt.el
+++ b/lisp/emacs-lisp/eieio-opt.el
@@ -142,7 +142,10 @@ are not abstract."
               (find-lisp-object-file-name ctr def)))
       (when location
         (insert (substitute-command-keys " in `"))
-        (help-insert-xref-button
+        ;; The `cl-type-definition' button type can't be autoloaded
+        ;; due to circularity during bootstrap (Bug#28899).
+        (require 'cl-extra)
+        (help-insert-xref-button
          (help-fns-short-filename location)
          'cl-type-definition ctr location 'define-type)
         (insert (substitute-command-keys "'")))