On Wed, Nov 20, 2024 at 11:36 PM mauro russo <ing.russomauro_at_[hidden]>
wrote:

>
> > I'm not seeing what the problem is. The existing text disallows the
> second `auto`.
> > [dcl.spec.auto.general]/4 contains the "declares a function" restriction.
> > Consequently there is no case in [dcl.spec.auto.general] that allows the
> > second `auto` and it is therefore ill-formed by
> [dcl.spec.auto.general]/8.
>
> I agree with you p4 is not problematic.
>
> I see problematic p3 that allows the second auto, whereas p4 does not
> state it is ill-formed.
>
> p4 adds legal options, it does not 'erase' any option from p3,
> whereas p3 formally allows that second 'auto' for the example
> auto (*p)() -> auto;
>

No, p3 doesn't allow the second `auto`. I'm not sure how you can read it
that way. Each of p2-p7 defines a *context* in which placeholders are
legal; it doesn't define the legality of the entire construct in which the
placeholder appears. The context that is made legal by p3 is the one
occupied by the first `auto`, namely the decl-specifier-seq, so it says
nothing about the legality of the second `auto`. It only means that, if
there's no trailing return type present at all, then p3 doesn't give any
permission for a placeholder to appear in the decl-specifier-seq.


>
> p3 states legal some options in case of trailing-return-type is present,
> whereas p4 adds other legal options regardless of the presence
> of the trailing-return-type.
>
> Thank you for the answer, I hope you may also provide answers
> on the other 2 side points of the original post
> https://lists.isocpp.org/std-discussion/2024/11/2710.php.
>
>
As to your second point, I'm not sure which p1 you're referring to. The
text you quote, "or as one of the type-specifiers in a
trailing-return-type", does not appear in [dcl.spec.auto.general]/1
<https://eel.is/c++draft/dcl.spec.auto.general#1>.

As to your third point, are you suggesting that in that one comment we
should use the hyphenated spelling? Or do you want to change other comments
to say "trailing return type"?

-- 
*Brian Bi*