My usage of imenu is broken.

[Alan Mackenzie <acm@muc.de>]

Hello, Emacs.

imenu no longer works for me.  The imenu page in the Emacs manual says

    the command [imenu] always displays the whole list of valid names.  

This is not true.  When I type C-c i (my binding for imenu) I see no
such list.  When I additionally type TAB I still see no such list.  All
I see is *Rescan*, Function, and Variable.  I think the manual should be
fixed.

The manual talks about "flatten"ing without explaining what this means.
The NEWS item doesn't explain it either.  I think this should be fixed.

On typing C-c i, I used to be able to type the first characters of a
function name and complete it with TAB in the minibuffer.  This no
longer works.  It doesn't work even if I set imenu-flatten to t.
Instead I've got to type boilerplate first.  This is unacceptable to me.

How do I get the old behaviour back, please?  Why doesn't the NEWS item
say how to get back the old behaviour?

What happened to Emacs's convention that new facilities are disabled by
default to begin with, and only made the default after positive
experience with their use?

-- 
Alan Mackenzie (Nuremberg, Germany).