[Bug c++/96704] New: begin() and end() iterators of views::values_view have different type

[Bug c++/96704] New: begin() and end() iterators of views::values_view have different type

[gleb at scylladb dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96704

            Bug ID: 96704
           Summary: begin() and end() iterators of views::values_view have
                    different type
           Product: gcc
           Version: 10.2.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: gleb at scylladb dot com
  Target Milestone: ---

The following program fail on the second assert.

#include <ranges>
#include <unordered_map>

int main() {
  std::unordered_map<int, int> x;
  auto r = std::views::values(x);
  static_assert(std::is_same_v<decltype(x.begin()), decltype(x.end())>);
  static_assert(std::is_same_v<decltype(r.begin()), decltype(r.end())>);
}

It means functions like:

template<typename I> foo(I it1, I it2);

cannot be called with:

foo(r.begin(), r.end());

[Bug c++/96704] begin() and end() iterators of views::values_view have different type

[gleb at scylladb dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96704

--- Comment #1 from Gleb Natapov <gleb at scylladb dot com> ---
Ah, those appears to be sentinel iterators.

[Bug c++/96704] begin() and end() iterators of views::values_view have different type

[gleb at scylladb dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96704

Gleb Natapov <gleb at scylladb dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|---                         |INVALID

--- Comment #2 from Gleb Natapov <gleb at scylladb dot com> ---
Closing.

[Bug c++/96704] begin() and end() iterators of views::values_view have different type

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96704

--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Right, it's incorrect to assume begin and end return the same type for a range.

Use std::common_iterator if you need to turn an iterator and its sentinel into
a single type:

  using CI = std::common_iterator<decltype(r.begin()), decltype(r.end())>;
  foo(CI(r.begin()), CI(r.end()));