[Bug libstdc++/97935] New: Missing subsumption in iterator category detection

[Bug libstdc++/97935] New: Missing subsumption in iterator category detection

[rs2740 at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97935

            Bug ID: 97935
           Summary: Missing subsumption in iterator category detection
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: rs2740 at gmail dot com
  Target Milestone: ---

In <bits/iterator_concepts.h>:

      template<typename _Iter>
        requires (!requires { typename _Iter::iterator_category; }
                  && __detail::__cpp17_randacc_iterator<_Iter>)
        struct __cat<_Iter>
        { using type = random_access_iterator_tag; };

      template<typename _Iter>
        requires (!requires { typename _Iter::iterator_category; }
                  && __detail::__cpp17_bidi_iterator<_Iter>)
        struct __cat<_Iter>
        { using type = bidirectional_iterator_tag; };

      template<typename _Iter>
        requires (!requires { typename _Iter::iterator_category; }
                  && __detail::__cpp17_fwd_iterator<_Iter>)
        struct __cat<_Iter>
        { using type = forward_iterator_tag; };

The !requires part of the constraints do not subsume each other, so any
iterator that is a __cpp17_bidi_iterator or stronger causes an ambiguity. It
needs to be extracted into a concept.

[Bug libstdc++/97935] Missing subsumption in iterator category detection

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97935

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever confirmed|0                           |1
   Target Milestone|---                         |10.3
   Last reconfirmed|                            |2020-11-22

[Bug libstdc++/97935] Missing subsumption in iterator category detection

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97935

--- Comment #1 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Jonathan Wakely <redi@gcc.gnu.org>:

https://gcc.gnu.org/g:9d908b7fc475b351622fa5630d4874068c789d70

commit r11-5381-g9d908b7fc475b351622fa5630d4874068c789d70
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Wed Nov 25 17:18:44 2020 +0000

    libstdc++: Fix missing subsumption in std::iterator_traits [PR 97935]

    libstdc++-v3/ChangeLog:

            PR libstdc++/97935
            * include/bits/iterator_concepts.h
(__detail::__iter_without_category):
            New helper concept.
            (__iterator_traits::__cat): Use __detail::__iter_without_category.
            * testsuite/24_iterators/associated_types/iterator.traits.cc: New
test.

[Bug libstdc++/97935] Missing subsumption in iterator category detection

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97935

--- Comment #2 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-10 branch has been updated by Jonathan Wakely
<redi@gcc.gnu.org>:

https://gcc.gnu.org/g:f89ba6e9a5da5506cb72235f500b152d4d365f3f

commit r10-9081-gf89ba6e9a5da5506cb72235f500b152d4d365f3f
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Wed Nov 25 17:18:44 2020 +0000

    libstdc++: Fix missing subsumption in std::iterator_traits [PR 97935]

    libstdc++-v3/ChangeLog:

            PR libstdc++/97935
            * include/bits/iterator_concepts.h
(__detail::__iter_without_category):
            New helper concept.
            (__iterator_traits::__cat): Use __detail::__iter_without_category.
            * testsuite/24_iterators/associated_types/iterator.traits.cc: New
test.

    (cherry picked from commit 9d908b7fc475b351622fa5630d4874068c789d70)

[Bug libstdc++/97935] Missing subsumption in iterator category detection

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97935

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

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

--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Fix for 10.3, thanks.