[libc++][ranges] LWG3984: ranges::to's recursion branch may be ill-formed (#87964)
This pull request implements LWG3984: ranges::to's recursion branch
may be ill-formed.
In the current implementation, ranges::to's recursion branch pipes the
range into a `views::transform(/* lambda */)`, which is a __range_adaptor_closure
object. In libc++, the pipe operator of __range_adaptor_closure requires a
viewable_range, so the following code won't compile, as the type of lvalue
`r` doesn't model viewable_range:
#include <ranges>
#include <vector>
#include <list>
int main() {
std::vector<std::vector<int>> v;
auto r = std::views::all(std::move(v));
auto l = std::ranges::to<std::list<std::list<int>>>(r);
}
Co-authored-by: A. Jiang <de34@live.cn>
GitOrigin-RevId: e74be35c1abedf87cfaa141284cb730911211ee1
3 files changed
