<format>: Cannot format a long value with formatter

[cpplearner]

Describe the bug
From https://stackoverflow.com/questions/72510490/stdformat-with-custom-types

Formatting a long value with formatter fails because long is not convertible to basic_format_arg.

With int it works as expected.

Command-line test case

D:\>type repro.cpp
#include <format>
#include <iostream>

template<class T>
struct Box {
    T value;
};

template<class T, class CharT>
struct std::formatter<Box<T>, CharT> : std::formatter<T, CharT> {
    template<class FormatContext>
    auto format(Box<T> t, FormatContext& fc) const {
        return std::formatter<T, CharT>::format(t.value, fc);
    }
};

int main() {
    Box<long> v = { 42 };
    std::cout << std::format("{:#x}", v);
}


D:\>cl /std:c++20 /EHsc repro.cpp
Microsoft (R) C/C++ Optimizing Compiler Version 19.33.31424 for x64
Copyright (C) Microsoft Corporation.  All rights reserved.

repro.cpp
D:\Program Files\Microsoft Visual Studio\2022\Preview\VC\Tools\MSVC\14.33.31424\include\format(2900): error C2440: '<function-style-cast>': cannot convert from 'initializer list' to 'std::basic_format_arg<_Context>'
        with
        [
            _Context=std::format_context
        ]
D:\Program Files\Microsoft Visual Studio\2022\Preview\VC\Tools\MSVC\14.33.31424\include\format(2900): note: No constructor could take the source type, or constructor overload resolution was ambiguous
repro.cpp(13): note: see reference to function template instantiation 'std::back_insert_iterator<std::_Fmt_buffer<char>> std::_Formatter_base<long,_CharT,std::_Basic_format_arg_type::_Int_type>::format<FormatContext>(const _Ty &,_FormatContext &) const' being compiled
        with
        [
            _CharT=char,
            FormatContext=std::format_context,
            _Ty=long,
            _FormatContext=std::format_context
        ]
repro.cpp(13): note: see reference to function template instantiation 'std::back_insert_iterator<std::_Fmt_buffer<char>> std::_Formatter_base<long,_CharT,std::_Basic_format_arg_type::_Int_type>::format<FormatContext>(const _Ty &,_FormatContext &) const' being compiled
        with
        [
            _CharT=char,
            FormatContext=std::format_context,
            _Ty=long,
            _FormatContext=std::format_context
        ]
D:\Program Files\Microsoft Visual Studio\2022\Preview\VC\Tools\MSVC\14.33.31424\include\format(173): note: see reference to function template instantiation 'std::back_insert_iterator<std::_Fmt_buffer<char>> std::formatter<Box<long>,_CharT>::format<_Context>(Box<long>,FormatContext &) const' being compiled
        with
        [
            _CharT=char,
            _Context=std::format_context,
            FormatContext=std::format_context
        ]
D:\Program Files\Microsoft Visual Studio\2022\Preview\VC\Tools\MSVC\14.33.31424\include\format(1449): note: see reference to variable template 'bool _Has_formatter<Box<long> &,std::basic_format_context<std::back_insert_iterator<std::_Fmt_buffer<char> >,char> >' being compiled
D:\Program Files\Microsoft Visual Studio\2022\Preview\VC\Tools\MSVC\14.33.31424\include\format(1499): note: see reference to alias template instantiation 'std::_Format_arg_traits<_Context>::_Storage_type<_Ty>' being compiled
        with
        [
            _Context=std::format_context,
            _Ty=Box<long> &
        ]
D:\Program Files\Microsoft Visual Studio\2022\Preview\VC\Tools\MSVC\14.33.31424\include\format(1534): note: see reference to variable template 'const size_t std::_Format_arg_traits<std::basic_format_context<std::back_insert_iterator<std::_Fmt_buffer<char> >,char> >::_Storage_size<Box<long> &>' being compiled
D:\Program Files\Microsoft Visual Studio\2022\Preview\VC\Tools\MSVC\14.33.31424\include\format(2980): note: see reference to class template instantiation 'std::_Format_arg_store<std::format_context,Box<long> &>' being compiled
D:\Program Files\Microsoft Visual Studio\2022\Preview\VC\Tools\MSVC\14.33.31424\include\format(3098): note: see reference to function template instantiation 'std::_Format_arg_store<std::format_context,Box<long> &> std::make_format_args<std::format_context,Box<long>&>(Box<long> &)' being compiled
repro.cpp(19): note: see reference to function template instantiation 'std::string std::format<Box<long>&>(const std::_Basic_format_string<char,Box<long> &>,Box<long> &)' being compiled
D:\Program Files\Microsoft Visual Studio\2022\Preview\VC\Tools\MSVC\14.33.31424\include\format(2897): error C2672: 'std::visit_format_arg': no matching overloaded function found
D:\Program Files\Microsoft Visual Studio\2022\Preview\VC\Tools\MSVC\14.33.31424\include\format(2900): error C2780: 'decltype(auto) std::visit_format_arg(_Visitor &&,std::basic_format_arg<_Context>)': expects 2 arguments - 1 provided
D:\Program Files\Microsoft Visual Studio\2022\Preview\VC\Tools\MSVC\14.33.31424\include\format(349): note: see declaration of 'std::visit_format_arg'

Expected behavior
Should compile

STL version

Microsoft Visual Studio Community 2022 Preview
Version 17.3.0 Preview 1.0

[cpplearner]

The culprit is

STL/stl/inc/format

Line 3292 in 17fde2c

basic_format_arg<_FormatContext>{_Val});

the argument _Val should probably be cast to _Format_arg_traits<_FormatContext>::_Storage_type<_Ty>.