https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94674
Bug ID: 94674
Summary: std::ranges::basic_istream_view::iterator is missing
std::iterator_traits entries
Product: gcc
Version: 10.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: gcc-bugs at marehr dot dialup.fu-berlin.de
Target Milestone: ---
Hi gcc-team,
I'm not sure if I should have named the issue `std::iterator_traits is missing
default values for an iterator` (https://eel.is/c++draft/iterator.traits#3.2).
Maybe I misunderstood this, but I thought that I can query every iterator for
it's traits.
The following code does not work:
```c++
#include <ranges>
#include <istream>
#include <string_view>
int main()
{
// std::string_view view; // does work
auto && view = std::ranges::basic_istream_view<int, char,
std::char_traits<char>>{}; // does not work
// auto && view = std::ranges::take_view<std::string_view>{}; // does work
using iterator_t = std::ranges::iterator_t<decltype(view)>;
using iter_value1_t = std::iter_value_t<iterator_t>;
using iter_value2_t = typename
std::iterator_traits<iterator_t>::value_type;
static_assert(std::same_as<iter_value1_t, iter_value2_t>);
return 0;
}
```
with `g++-10 -std=c++2a`
https://godbolt.org/z/QAfdml
