https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100567
Bug ID: 100567
Summary: views::take and views::drop should conditionally use
_RangeAdaptor::operator()
Product: gcc
Version: 12.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: libstdc++
Assignee: unassigned at gcc dot gnu.org
Reporter: hewillk at gmail dot com
Target Milestone: ---
Hi, the re-implemented range adaptors use _RangeAdaptor to handle the arg of
the adaptors, but for views::take and views::drop, the constraint that this arg
can perfectly forward to range::range_difference_t<V> is lacking.
https://godbolt.org/z/j88q5Yn6Y
#include <ranges>
struct S {
operator int() { return 0; }
};
const S obj;
auto r = std::views::iota(0, 3);
auto d1 = r | std::views::drop(obj); // ok, should error
auto d2 = std::views::drop(r, obj); // error
auto f1 = r | std::views::take(obj); // ok, should error
auto f2 = std::views::take(r, obj); // error
