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.

diff --git a/lisp/emacs-lisp/eieio-opt.el b/lisp/emacs-lisp/eieio-opt.el
index dbec48d038bdb57c5f58ecbcbb72e0032142e5a4..eeb0bc95d68a51fe8e3721197417def1d77d43c8 100644 (file)
--- 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 "'")))