bug#72787: 31.0.50; Invalid describe-function completion candidates

[Eshel Yaron via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

Hi,

I've stumbled upon an issue with C-h f completions, both on the release
branch and on the master branch:

1. emacs -Q
2. C-h f string-edit- TAB

In Emacs 29, this pops up the *Completions* buffer, with 3 completion
candidates, string-edit-{abort,done,mode}.  That's the expected
behavior, because "string-edit-" is not itself a valid candidate.

However, in the release and master branches I get a minibuffer message
saying "Complete, but not unique".  This is incorrect, because the input
is not complete.  Another TAB pops up the *Completions* buffer, which is
now showing 4 candidates: the expected 3 plus "string-edit-" itself.
Typing RET exits the minibuffer without asking for confirmation, and
yields an error: "Symbol’s function definition is void: string-edit-".

So it seems like "string-edit-" is being considered as a valid
completion candidate, while it shouldn't be.


Thanks,

Eshel