Juri Linkov <juri@jurta.org> writes:

>> `completion-all-sorted-completions' prefers recent input history.  Once
>> you have `gnus-read-ephemeral-emacs-bug-group' in the command history,
>> it is likely to be the first of the few completions which you can pick
>> with one or more C-s-es.
>>
>> One doesn't need to rely on traditional "C-r" exclusively to accomplish
>> the above work flow.
>
> IIUC, it matches only prefixes, whereas traditional Isearch `C-r'
> can also match in the middle of the command name in the history.
>
> When I tried now `icomplete-backward-completions' currently bound to `C-r',
> I discovered that it is broken.  It fails with the error:
>
> Debugger entered--Lisp error: (wrong-type-argument listp 0)
>   cdr(0)
>   (setcdr last-but-one (cdr last))
>
> The full test case:
>
> 0. emacs -Q
> 1. M-x icomplete-mode RET
> 2. M-x icomplete-m C-r