Implementations are allowed to diverge in their handling of attributes too,
so if =delete("message") isn't good enough that's a problem that can be
fixed in the implementation.

On Tue, Mar 18, 2025 at 4:14 AM Samuel Alonso Rodríguez via Std-Proposals <
std-proposals_at_[hidden]> wrote:

> The fixed message stating that the function is unimplemented is the
> divergence from raw = delete, and sure, since C++26, users could simply do
> something like = delete(“unimplemented function!”), but the compiler
> outcome could differ and tools inspecting the compiler output may not be
> able to easily detect that
>
> > On 18 Mar 2025, at 10:08, Giuseppe D'Angelo via Std-Proposals <
> std-proposals_at_[hidden]> wrote:
> >
> > Il 18/03/25 10:47, Samuel Alonso Rodríguez via Std-Proposals ha scritto:
> >> This attribute is meant to be used in function (member or free, static
> or non-static, template or non-template) declarations to indicate that the
> function declaration is left unimplemented (without a definition) with an
> additional diagnostic message that can be fixed or opt-in thru an
> unevaluated string literal.
> >> The interesting bit comes from its behaviour: defining any function
> marked with such attribute, lleads to an ill-formed program (preferably
> with a diagnostic message), making calls to it be always diagnosable in
> non-linking time, because no TU can ever define this.
> >> The only catch so far is: redeclarations w/o this attribute would break
> that assumption. I thought of straight banning redeclarations but I think
> that’s too much. Maybe forcing redeclarations to have this attribute
> aswell, once the former declaration has it, could be an interesting idea to
> explore.
> >
> > Could you please elaborate a bit more on what's your use case for
> something like this? For instance, how is this different from just
> `=delete` the function?
> >
> > Thank you,
> > --
> > Giuseppe D'Angelo
> > --
> > Std-Proposals mailing list
> > Std-Proposals_at_[hidden]
> > https://lists.isocpp.org/mailman/listinfo.cgi/std-proposals
>
> --
> Std-Proposals mailing list
> Std-Proposals_at_[hidden]
> https://lists.isocpp.org/mailman/listinfo.cgi/std-proposals
>