public inbox for gcc-bugs@sourceware.org
help / color / mirror / Atom feed
From: "andrew.n.sutton at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/66092] [c++-concepts] Concept can't check variadic template arguments
Date: Tue, 19 May 2015 12:23:00 -0000	[thread overview]
Message-ID: <bug-66092-4-GCsJznU8Xx@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-66092-4@http.gcc.gnu.org/bugzilla/>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66092

Andrew Sutton <andrew.n.sutton at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |andrew.n.sutton at gmail dot com

--- Comment #2 from Andrew Sutton <andrew.n.sutton at gmail dot com> ---
I think that this should be ill-formed.

template <typename T, typename U, typename... Args>
  concept bool Same()
  {
    return decltype(check<T, U, Args...>())::value;
  }

template <typename... Args>
requires Same<Args...>()
  void foo( Args... args ) {}


Template constraint processing requires that flatten (inline) the check for
Same<Args...>(), but I don't see how we can substitute a dependent argument
pack into three distinct template parameters (T, U, and ...Args). 

The wording prohibiting this is missing in the TS.


  parent reply	other threads:[~2015-05-19 12:23 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <bug-66092-4@http.gcc.gnu.org/bugzilla/>
2015-05-13 20:22 ` yingpo.liao at gmail dot com
2015-05-19 12:23 ` andrew.n.sutton at gmail dot com [this message]
2015-07-10  7:26 ` jason at gcc dot gnu.org
2015-07-14  4:11 ` jason at gcc dot gnu.org
2015-07-17 17:43 ` jason at gcc dot gnu.org
2015-08-04 13:36 ` jason at gcc dot gnu.org

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=bug-66092-4-GCsJznU8Xx@http.gcc.gnu.org/bugzilla/ \
    --to=gcc-bugzilla@gcc.gnu.org \
    --cc=gcc-bugs@gcc.gnu.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).