public inbox for gcc-bugs@sourceware.org
help / color / mirror / Atom feed
From: "danakj at orodu dot net" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/99599] [11/12/13/14 Regression] Concepts requirement falsely reporting cyclic dependency, breaks tag_invoke pattern
Date: Wed, 07 Jun 2023 18:41:34 +0000	[thread overview]
Message-ID: <bug-99599-4-wS4YFIiTWD@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-99599-4@http.gcc.gnu.org/bugzilla/>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99599

--- Comment #15 from danakj at orodu dot net ---
The workaround listed in Comment #6 does not work for templated types,
unfortunately, making Clang and MSVC more expressive here than GCC.

https://godbolt.org/z/obhsqhrbx

```
#include <concepts>
#include <sstream>
#include <string>

#if defined(__GNUC__) && !defined(__clang__)
#define COMPILER_IS_GCC 1
#else
#define COMPILER_IS_GCC 0
#endif

namespace sus::string::__private {
template <class A, class B>
A& format_to_stream(A&, B);

template <class T, class Char>
concept StreamCanReceiveString = requires(T& t, std::basic_string<Char> s) {
    { operator<<(t, s) };
};

/// Consumes the string `s` and streams it to the output stream `os`.
template <class Char, StreamCanReceiveString<Char> S>
S& format_to_stream(S& os, const std::basic_string<Char>& s) {
    os << s;
    return os;
}

}  // namespace sus::string::__private

namespace sus::option {
template <class T>
class Option {};

using namespace ::sus::string::__private;
template <
    class T, 
#if COMPILER_IS_GCC
    std::same_as<Option<T> > Sus_ValueType,  // Does not deduce T.  *****
#endif
    StreamCanReceiveString<char> Sus_StreamType
>
inline Sus_StreamType& operator<<(
    Sus_StreamType& stream,
#if COMPILER_IS_GCC
    const Sus_ValueType& value
#else
    const ::sus::option::Option<T>& value  // Does deduce T.   ****
#endif
) {
    return format_to_stream(stream, std::string());
}

}  // namespace sus::option

int main() {
    std::stringstream s;
    s << sus::option::Option<int>();
}
```

  parent reply	other threads:[~2023-06-07 18:41 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-15 13:24 [Bug c++/99599] New: Concepts requirement falsely reporting recursion, " the_gamester28 at msn dot com
2021-03-15 13:49 ` [Bug c++/99599] [11 Regression] Concepts requirement falsely reporting cyclic dependency, " rguenth at gcc dot gnu.org
2021-03-15 14:20 ` redi at gcc dot gnu.org
2021-04-01 22:04 ` jason at gcc dot gnu.org
2021-04-02 12:47 ` gcc-bugs at marehr dot dialup.fu-berlin.de
2021-04-05 19:49 ` the_gamester28 at msn dot com
2021-04-27 11:40 ` [Bug c++/99599] [11/12 " jakub at gcc dot gnu.org
2021-05-01 17:38 ` ppalka at gcc dot gnu.org
2021-07-28  7:06 ` rguenth at gcc dot gnu.org
2021-08-25 14:44 ` ppalka at gcc dot gnu.org
2022-04-21  7:48 ` rguenth at gcc dot gnu.org
2022-08-08 15:06 ` [Bug c++/99599] [11/12/13 " ppalka at gcc dot gnu.org
2022-10-27 12:42 ` ppalka at gcc dot gnu.org
2023-04-04  5:33 ` catsith at me dot com
2023-05-29 10:04 ` [Bug c++/99599] [11/12/13/14 " jakub at gcc dot gnu.org
2023-06-07 18:25 ` danakj at orodu dot net
2023-06-07 18:41 ` danakj at orodu dot net [this message]
2023-06-07 20:03 ` danakj at orodu dot net
2023-08-01 18:16 ` ppalka at gcc dot gnu.org
2023-09-08 16:03 ` cvs-commit at gcc dot gnu.org
2024-02-02 18:02 ` [Bug c++/99599] [11/12/13 " ppalka at gcc dot gnu.org
2024-03-09 15:37 ` ppalka at gcc dot gnu.org
2024-03-21 21:40 ` redi at gcc dot gnu.org
2024-03-21 21:43 ` redi at gcc dot gnu.org
2024-03-22 14:08 ` ppalka at gcc dot gnu.org
2024-03-22 15:58 ` redi at gcc dot gnu.org
2024-03-27 23:16 ` redi at gcc dot gnu.org
2024-03-27 23:18 ` redi 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-99599-4-wS4YFIiTWD@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).