Don't register "def" as an autoload prefix (Bug#26412)

* lisp/emacs-lisp/autoload.el (autoload--make-defs-autoload): Don't
accept "def" as a prefix.

1 files changed, 3 insertions, 1 deletions

diff --git a/lisp/emacs-lisp/autoload.el b/lisp/emacs-lisp/autoload.el
index 90e6aec4e75..ca46f317677 100644
--- a/lisp/emacs-lisp/autoload.el
+++ b/lisp/emacs-lisp/autoload.el
@@ -547,7 +547,9 @@ Don't try to split prefixes that are already longer than that.")
     ;; "cc-helper" and "c-mode", you'll get "c" in the root prefixes.
     (dolist (pair (prog1 prefixes (setq prefixes nil)))
       (let ((s (car pair)))
-        (if (or (> (length s) 2)                  ;Long enough!
+        (if (or (and (> (length s) 2)   ; Long enough!
+                     ;; But don't use "def" from deffoo-pkg-thing.
+                     (not (string= "def" s)))
                 (string-match ".[[:punct:]]\\'" s) ;A real (tho short) prefix?
                 (radix-tree-lookup (cdr pair) "")) ;Nothing to expand!
             (push pair prefixes) ;Keep it as is.