bug#31052: 26.0.91; Improve documentation of inline-letevals

[Stefan Monnier <monnier@iro.umontreal.ca>]

>> Also, while looking at inline-letevals in inline.el, I noticed that the
>> preceeding macros inline--leteval and inline--letlisteval mention the
>> wrong symbol name in their error messages:
>> 
>> (defmacro inline--leteval (_var-exp &rest _body)
>>   (declare (indent 1) (debug (sexp &rest body)))
>>   (error "inline-letevals can only be used within define-inline"))
>> 
>> (defmacro inline--letlisteval (_list &rest _body)
>>   (declare (indent 1) (debug (sexp &rest body)))
>>   (error "inline-letevals can only be used within define-inline"))
>> 
>> Perhaps these typos can be fixed before the release.
>
> It's not too late for that, but I'm not sure this is a typo.  It could
> be deliberate.
>
> Stefan, can you comment on this, please?

Good catch: these aren't typos!

The inline-letevals macro expands to calls to inline--leteval and
inline--letlisteval and it's easier to have those signal the error than
to make inline-letevals check whether we're within a define-inline.

The user is not supposed to use  inline--leteval or inline--letlisteval
manually anywhere at all (as indicated by the "--" in their name), so if
those occur it's (presumably) because of an incorrect use of
inline-letevals.

I'll add a comment about it, to stop other people from trying to "fix" it.


        Stefan