[Bug libstdc++/108362] New: views::istream is SFINAE-unfriendly

[Bug libstdc++/108362] New: views::istream is SFINAE-unfriendly

[hewillk at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108362

            Bug ID: 108362
           Summary: views::istream is SFINAE-unfriendly
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: hewillk at gmail dot com
  Target Milestone: ---

Similar issue with https://github.com/microsoft/STL/pull/3335.

#include <ranges>
#include <iostream>

template<class T>
concept can_istream_view = requires {
  std::views::istream<T>(std::cin);
};

struct S { };
static_assert(!can_istream_view<S>);

https://godbolt.org/z/b3W1KsPWd

[Bug libstdc++/108362] views::istream is SFINAE-unfriendly

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108362

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2023-01-13

[Bug libstdc++/108362] views::istream is SFINAE-unfriendly

[ppalka at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108362

Patrick Palka <ppalka at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
                 CC|                            |ppalka at gcc dot gnu.org
           Assignee|unassigned at gcc dot gnu.org      |ppalka at gcc dot gnu.org

--- Comment #1 from Patrick Palka <ppalka at gcc dot gnu.org> ---
views::iota and views::single too

[Bug libstdc++/108362] views::istream is SFINAE-unfriendly

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108362

--- Comment #2 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Patrick Palka <ppalka@gcc.gnu.org>:

https://gcc.gnu.org/g:95827e1b9f7d5dd5a697bd60292e3876a7e8c15c

commit r13-6560-g95827e1b9f7d5dd5a697bd60292e3876a7e8c15c
Author: Patrick Palka <ppalka@redhat.com>
Date:   Thu Mar 9 13:35:04 2023 -0500

    libstdc++: Make views::single/iota/istream SFINAE-friendly [PR108362]

            PR libstdc++/108362

    libstdc++-v3/ChangeLog:

            * include/std/ranges (__detail::__can_single_view): New concept.
            (_Single::operator()): Constrain it.  Move [[nodiscard]] to the
            end of the function declarator.
            (__detail::__can_iota_view): New concept.
            (_Iota::operator()): Constrain it.  Move [[nodiscard]] to the
            end of the function declarator.
            (__detail::__can_istream_view): New concept.
            (_Istream::operator()): Constrain it.  Move [[nodiscard]] to the
            end of the function declarator.
            * testsuite/std/ranges/iota/iota_view.cc (test07): New test.
            * testsuite/std/ranges/istream_view.cc (test08): New test.
            * testsuite/std/ranges/single_view.cc (test07): New test.

[Bug libstdc++/108362] views::istream is SFINAE-unfriendly

[ppalka at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108362

Patrick Palka <ppalka at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |12.3

--- Comment #3 from Patrick Palka <ppalka at gcc dot gnu.org> ---
Fixed for GCC 13 so far

[Bug libstdc++/108362] views::istream is SFINAE-unfriendly

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108362

--- Comment #4 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-12 branch has been updated by Patrick Palka
<ppalka@gcc.gnu.org>:

https://gcc.gnu.org/g:7d0cddced0ff101f5f59ceb2a45e7f145ff973ac

commit r12-9496-g7d0cddced0ff101f5f59ceb2a45e7f145ff973ac
Author: Patrick Palka <ppalka@redhat.com>
Date:   Thu Mar 9 13:35:04 2023 -0500

    libstdc++: Make views::single/iota/istream SFINAE-friendly [PR108362]

            PR libstdc++/108362

    libstdc++-v3/ChangeLog:

            * include/std/ranges (__detail::__can_single_view): New concept.
            (_Single::operator()): Constrain it.  Move [[nodiscard]] to the
            end of the function declarator.
            (__detail::__can_iota_view): New concept.
            (_Iota::operator()): Constrain it.  Move [[nodiscard]] to the
            end of the function declarator.
            (__detail::__can_istream_view): New concept.
            (_Istream::operator()): Constrain it.  Move [[nodiscard]] to the
            end of the function declarator.
            * testsuite/std/ranges/iota/lwg3292_neg.cc: Prune "in
            requirements" diagnostic.
            * testsuite/std/ranges/iota/iota_view.cc (test07): New test.
            * testsuite/std/ranges/istream_view.cc (test08): New test.
            * testsuite/std/ranges/single_view.cc (test07): New test.

    (cherry picked from commit 95827e1b9f7d5dd5a697bd60292e3876a7e8c15c)

[Bug libstdc++/108362] views::istream is SFINAE-unfriendly

[ppalka at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108362

Patrick Palka <ppalka at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|---                         |FIXED

--- Comment #5 from Patrick Palka <ppalka at gcc dot gnu.org> ---
Fixed for GCC 12.3+