Re: master 431f8ff1e38: * lisp/imenu.el: Support more values for imenu-flatten (bug#70846)

[Juri Linkov <juri@linkov.net>]

>>> What I would suggest is to ensure completion candidates are unambiguous
>>> as strings rather than relying on text properties.  Namely:
>> Unfortunately, that'd be a step back.  Maybe at least we could document
>> limitations that annotations work only by selection.
>
> How about we make them unambiguous by adding text *at the end* (and
> only if there's ambiguity)?
>
> The completion code assumes in all kinds of places that the same text
> means the same thing, so using the same text to mean different
> completion choices will get you in trouble in all kinds of corner (and
> not so corner) cases.

Ok, this patch adds the suffix only to ambiguous items.

At least it helps to get the right item for the case when not selecting
candidates from the completions list.

OTOH, it still doesn't solve the original issue of using `M-<down> M-<down> M-RET`
where `completion--replace` keeps properties of previous completion strings
by using `insert-and-inherit`.

```
diff --git a/lisp/imenu.el b/lisp/imenu.el
index 8f1b1f22a67..e151a685ce5 100644
--- a/lisp/imenu.el
+++ b/lisp/imenu.el
@@ -740,6 +740,24 @@ imenu--completion-buffer
 
 Return one of the entries in index-alist or nil."
   ;; Create a list for this buffer only when needed.
+  (when (eq imenu-flatten 'annotation)
+    (let ((hash (make-hash-table :test 'equal)))
+      (dolist (item index-alist)
+        (puthash (car item) (1+ (gethash (car item) hash 0)) hash))
+      (setq index-alist
+            (mapcar (lambda (item)
+                      (if (> (gethash (car item) hash) 1)
+                          (cons (let ((ann (get-text-property
+                                            0 'imenu-section (car item))))
+                                  (if ann
+                                      (concat (propertize (car item)
+                                                          'imenu-section nil)
+                                              imenu-level-separator
+                                              (substring ann 1))
+                                    (car item)))
+                                (cdr item))
+                        item))
+                    index-alist))))
   (let ((name (thing-at-point 'symbol))
 	choice
 	(prepared-index-alist
```