bug#47388: 27.1; eldoc-documentation-function is ignore in updated eldoc

[Stefan Monnier]

>>>   (when (function-equal #'ignore eldoc-documentation-function)
>>>         (setq-local eldoc-documentation-function
>>> #'eldoc-documentation-default|compose|whatever))))
>>
>> BTW, using code like the one above is tolerable, usually for historical
>> reasons, but new APIs should aim not to need such things: comparing
>> functions is fundamentally always a hack.
>
> So is run-time version checking, the risk is mostly the same.

I just wanted to make sure that it's only needed for backward
compatibility reasons.


        Stefan