bug#74090: 31.0.50; Problems with dabbrev-expand

[Juri Linkov <juri@linkov.net>]

>>> The attached patch fixes these problems, according to my tests.
>>
>> Maybe your patch also fixes bug#36516
>> where we failed to find a solution.
>> Or maybe these are separate cases.
>
> I was unaware of that bug, thanks for the pointer.  But unfortunately,
> my patch does not fix it.  My changes only affect cases where the buffer
> in which dabbrev-expand is called is different from the buffer where it
> finds the expected expansion (at least I only tried to fix such cases
> and not alter the behavior of the same buffer cases).  I'll try taking a
> closer look at this case, but judging by the discussion in that bug
> thread, it doesn't look related, or easy to fix.  But as was noted in
> that thread, at least you can get the expected expected by repeatedly
> typing `M-/', while in the cases I tried (hopefully successfully) to
> fix, without my patch either you cannot get the expected expansion or
> you get an error, so bug#36516 seems less serious.

Indeed, bug#36516 reports just a logical inconsistency,
whereas your patch fixes a plain bug.  I've looked at your patch,
and everything looks right, and the comprehensive test coverage
will ensure no breakages, thanks.