tuple_size does not work on clang

[egorpugin]

Works both for gcc and msvc, but not clang.

https://godbolt.org/z/bcochYz5P

#include <variant>
#include <optional>
#include <vector>
#include <memory>
#include <boost/pfr.hpp>

using Boolean = bool;
using Integer = std::int64_t;
using Float = double;
using String = std::string;

template <typename T>
using Optional = std::optional<T>;
template <typename ... Args>
using Ptr = std::unique_ptr<Args...>;
template <typename ... Args>
using Variant = std::variant<Args...>;
template <typename ... Args>
using Vector = std::vector<Args...>;

// This object represents one button of the reply keyboard. For simple text buttons, String can be used instead of this object to specify the button text. The optional fields web_app, request_users, request_chat, request_contact, request_location, and request_poll are mutually exclusive.
struct KeyboardButton
{
    // Text of the button. If none of the optional fields are used, it will be sent as a message when the button is pressed
    String text;
    // Optional. If True, the user's phone number will be sent as a contact when the button is pressed. Available in private chats only.
    Optional<Boolean> request_contact;
    // Optional. If True, the user's current location will be sent when the button is pressed. Available in private chats only.
    Optional<Boolean> request_location;
};

// This object represents a custom keyboard with reply options (see Introduction to bots for details and examples).
struct ReplyKeyboardMarkup
{
    // Array of button rows, each represented by an Array of KeyboardButton objects
    Vector<Vector<Ptr<KeyboardButton>>> keyboard;
};

struct sendAnimationRequest
{
    // Additional interface options. A JSON-serialized object for an inline keyboard, custom reply keyboard, instructions to remove a reply keyboard or to force a reply from the user. Not supported for messages sent on behalf of a business account
    Optional<Variant<ReplyKeyboardMarkup>> reply_markup;
};

int main() {
    return boost::pfr::tuple_size<sendAnimationRequest>::value;
}

In file included from <source>:1:
In file included from /opt/compiler-explorer/gcc-13.2.0/lib/gcc/x86_64-linux-gnu/13.2.0/../../../../include/c++/13.2.0/string:42:
In file included from /opt/compiler-explorer/gcc-13.2.0/lib/gcc/x86_64-linux-gnu/13.2.0/../../../../include/c++/13.2.0/bits/char_traits.h:57:
/opt/compiler-explorer/gcc-13.2.0/lib/gcc/x86_64-linux-gnu/13.2.0/../../../../include/c++/13.2.0/bits/stl_construct.h:115:4: error: no matching function for call to 'construct_at'
  115 |           std::construct_at(__p, std::forward<_Args>(__args)...);
      |           ^~~~~~~~~~~~~~~~~
/opt/compiler-explorer/gcc-13.2.0/lib/gcc/x86_64-linux-gnu/13.2.0/../../../../include/c++/13.2.0/bits/stl_uninitialized.h:120:11: note: in instantiation of function template specialization 'std::_Construct<std::unique_ptr<KeyboardButton>, const std::unique_ptr<KeyboardButton> &>' requested here
  120 |             std::_Construct(std::__addressof(*__cur), *__first);
      |                  ^
/opt/compiler-explorer/gcc-13.2.0/lib/gcc/x86_64-linux-gnu/13.2.0/../../../../include/c++/13.2.0/bits/stl_uninitialized.h:371:14: note: in instantiation of function template specialization 'std::__do_uninit_copy<__gnu_cxx::__normal_iterator<const std::unique_ptr<KeyboardButton> *, std::vector<std::unique_ptr<KeyboardButton>>>, std::unique_ptr<KeyboardButton> *>' requested here
  371 |         return std::__do_uninit_copy(__first, __last, __result);
      |                     ^
/opt/compiler-explorer/gcc-13.2.0/lib/gcc/x86_64-linux-gnu/13.2.0/../../../../include/c++/13.2.0/bits/stl_vector.h:603:9: note: in instantiation of function template specialization 'std::__uninitialized_copy_a<__gnu_cxx::__normal_iterator<const std::unique_ptr<KeyboardButton> *, std::vector<std::unique_ptr<KeyboardButton>>>, std::unique_ptr<KeyboardButton> *, std::unique_ptr<KeyboardButton>>' requested here
  603 |           std::__uninitialized_copy_a(__x.begin(), __x.end(),
      |                ^
/opt/compiler-explorer/gcc-13.2.0/lib/gcc/x86_64-linux-gnu/13.2.0/../../../../include/c++/13.2.0/bits/stl_construct.h:97:39: note: in instantiation of member function 'std::vector<std::unique_ptr<KeyboardButton>>::vector' requested here
   97 |     { return ::new((void*)__location) _Tp(std::forward<_Args>(__args)...); }
      |                                       ^
/opt/compiler-explorer/gcc-13.2.0/lib/gcc/x86_64-linux-gnu/13.2.0/../../../../include/c++/13.2.0/bits/stl_construct.h:115:9: note: in instantiation of function template specialization 'std::construct_at<std::vector<std::unique_ptr<KeyboardButton>>, const std::vector<std::unique_ptr<KeyboardButton>> &>' requested here
  115 |           std::construct_at(__p, std::forward<_Args>(__args)...);
      |                ^
/opt/compiler-explorer/gcc-13.2.0/lib/gcc/x86_64-linux-gnu/13.2.0/../../../../include/c++/13.2.0/bits/stl_uninitialized.h:120:11: note: (skipping 23 contexts in backtrace; use -ftemplate-backtrace-limit=0 to see all)
  120 |             std::_Construct(std::__addressof(*__cur), *__first);
      |                  ^
/opt/compiler-explorer/libs/boost_1_84_0/boost/pfr/detail/fields_count.hpp:183:11: note: in instantiation of default argument for 'enable_if_constructible_helper_t<sendAnimationRequest, 161UL>' required here
  183 | constexpr auto detect_fields_count(detail::multi_element_range, long) noexcept
      |           ^~~~
/opt/compiler-explorer/libs/boost_1_84_0/boost/pfr/detail/fields_count.hpp:246:12: note: while substituting explicitly-specified template arguments into function template 'detect_fields_count' 
  246 |     return detail::detect_fields_count<T, 0, middle>(detail::multi_element_range{}, 1L);
      |            ^
/opt/compiler-explorer/libs/boost_1_84_0/boost/pfr/detail/fields_count.hpp:305:44: note: in instantiation of function template specialization 'boost::pfr::detail::detect_fields_count_dispatch<sendAnimationRequest, 320UL>' requested here
  305 |     constexpr std::size_t result = detail::detect_fields_count_dispatch<type>(size_t_<max_fields_count>{}, 1L, 1L);
      |                                            ^
/opt/compiler-explorer/libs/boost_1_84_0/boost/pfr/tuple_size.hpp:33:57: note: in instantiation of function template specialization 'boost::pfr::detail::fields_count<sendAnimationRequest>' requested here
   33 | using tuple_size = detail::size_t_< boost::pfr::detail::fields_count<T>() >;
      |                                                         ^
<source>:47:24: note: in instantiation of template type alias 'tuple_size' requested here
   47 |     return boost::pfr::tuple_size<sendAnimationRequest>::value;
      |                        ^
/opt/compiler-explorer/gcc-13.2.0/lib/gcc/x86_64-linux-gnu/13.2.0/../../../../include/c++/13.2.0/bits/stl_construct.h:94:5: note: candidate template ignored: substitution failure [with _Tp = std::unique_ptr<KeyboardButton>, _Args = <const std::unique_ptr<KeyboardButton> &>]: call to deleted constructor of 'std::unique_ptr<KeyboardButton>'
   94 |     construct_at(_Tp* __location, _Args&&... __args)
      |     ^
   95 |     noexcept(noexcept(::new((void*)0) _Tp(std::declval<_Args>()...)))
   96 |     -> decltype(::new((void*)0) _Tp(std::declval<_Args>()...))
      |                                 ~~~
/opt/compiler-explorer/gcc-13.2.0/lib/gcc/x86_64-linux-gnu/13.2.0/../../../../include/c++/13.2.0/bits/stl_construct.h:119:25: error: call to deleted constructor of 'std::unique_ptr<KeyboardButton>'
  119 |       ::new((void*)__p) _Tp(std::forward<_Args>(__args)...);
      |                         ^   ~~~~~~~~~~~~~~~~~~~~~~~~~~~
/opt/compiler-explorer/gcc-13.2.0/lib/gcc/x86_64-linux-gnu/13.2.0/../../../../include/c++/13.2.0/bits/unique_ptr.h:522:7: note: 'unique_ptr' has been explicitly marked deleted here
  522 |       unique_ptr(const unique_ptr&) = delete;
      |       ^
In file included from <source>:4:
In file included from /opt/compiler-explorer/gcc-13.2.0/lib/gcc/x86_64-linux-gnu/13.2.0/../../../../include/c++/13.2.0/vector:65:
/opt/compiler-explorer/gcc-13.2.0/lib/gcc/x86_64-linux-gnu/13.2.0/../../../../include/c++/13.2.0/bits/stl_uninitialized.h:90:21: error: static assertion failed due to requirement 'is_constructible<std::unique_ptr<KeyboardButton, std::default_delete<KeyboardButton>>, const std::unique_ptr<KeyboardButton, std::default_delete<KeyboardButton>> &>::value': result type must be constructible from input type
   90 |       static_assert(is_constructible<_ValueType, _Tp>::value,
      |                     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/opt/compiler-explorer/gcc-13.2.0/lib/gcc/x86_64-linux-gnu/13.2.0/../../../../include/c++/13.2.0/bits/stl_uninitialized.h:182:4: note: in instantiation of function template specialization 'std::__check_constructible<std::unique_ptr<KeyboardButton>, const std::unique_ptr<KeyboardButton> &>' requested here
  182 |         = _GLIBCXX_USE_ASSIGN_FOR_INIT(_ValueType2, _From);
      |           ^
/opt/compiler-explorer/gcc-13.2.0/lib/gcc/x86_64-linux-gnu/13.2.0/../../../../include/c++/13.2.0/bits/stl_uninitialized.h:101:13: note: expanded from macro '_GLIBCXX_USE_ASSIGN_FOR_INIT'
  101 |     && std::__check_constructible<T, U>()
      |             ^
/opt/compiler-explorer/gcc-13.2.0/lib/gcc/x86_64-linux-gnu/13.2.0/../../../../include/c++/13.2.0/bits/stl_uninitialized.h:373:19: note: in instantiation of function template specialization 'std::uninitialized_copy<__gnu_cxx::__normal_iterator<const std::unique_ptr<KeyboardButton> *, std::vector<std::unique_ptr<KeyboardButton>>>, std::unique_ptr<KeyboardButton> *>' requested here
  373 |       return std::uninitialized_copy(__first, __last, __result);
      |                   ^
3 errors generated.
Compiler returned: 1