>>> I hope that in a more general case we could use something similar, 
>>> since every definition of a function should start from "defun " 
>>> followed by some part of its name, right?
>>
>> Not always, I can imagine functions defined with fset for example.
>>
>> What about the attached patch?  It seems to work well.
>
> SGTM.  With which cases did you test this?
>
> Adding Stefan, in case he has any comments.
>

Mainly with the original recipe and some variants of it.

I attach a slightly improved version of the patch.