Note that choose-completion-string-functions funcs take four args

* lisp/simple.el (choose-completion-string-functions): Functions in
  this list actually need to accept four arguments, though the fourth
  should be ignored.

diff --git a/lisp/simple.el b/lisp/simple.el
index 2646d7b02599e4fac5391d2d60387a093bbaca29..a0f2da7152c762a6baf45db922a3bfcc34bed7a7 100644 (file)
--- a/lisp/simple.el
+++ b/lisp/simple.el
@@ -8181,6 +8181,9 @@ CHOICE - the string to insert in the buffer,
 BUFFER - the buffer in which the choice should be inserted,
 BASE-POSITION - where to insert the completion.
 
+Functions should also accept and ignore a potential fourth
+argument, passed for backwards compatibility.
+
 If a function in the list returns non-nil, that function is supposed
 to have inserted the CHOICE in the BUFFER, and possibly exited
 the minibuffer; no further functions will be called.