https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103951
--- Comment #2 from 康桓瑋 <hewillk at gmail dot com> ---
Here is the reduced version without the header:
template<class T>
T&& declval() noexcept;
struct true_type {
static constexpr bool value = true;
};
template<typename _From, typename _To>
class is_convertible {
template<typename _To1>
static void __test_aux(_To1) noexcept;
template<typename _From1, typename _To1,
typename = decltype(__test_aux<_To1>(declval<_From1>()))>
static true_type __test(int);
public:
static constexpr bool value = decltype(__test<_From, _To>(0))::value;
};
template<typename _Tp>
void __decay_copy(_Tp) noexcept(is_convertible<_Tp, _Tp>::value);
template<class _Tp>
concept range = requires(_Tp& __t) {
__decay_copy(__t.begin());
};
struct string_view {
template<range R>
string_view(R&&);
};
struct Iter {
Iter(string_view);
Iter begin() const { return *this; }
};
https://godbolt.org/z/nrcq84dno
