Try to compile using boost 1.80 fails in boost.json

[RoyBellingan]

Maybe just add a check that 1.81 (or whatever required version) is present ?

If you want I can downgrade to report the actual error while compiling the example, but I think is just requiring a recent version as it was accessing nonexistent element.

It also fails using 1.81 using Opensuse tumbleweed, GCC 12.2.1 using C++11 mode with

In file included from /usr/include/boost/json/value_from.hpp:15,
                 from ../untitled/mustache/include/boost/mustache/renderer.hpp:15,
                 from ../untitled/mustache/include/boost/mustache/render.hpp:8,
                 from ../untitled/mustache/include/boost/mustache.hpp:8,
                 from ../untitled/main1.cpp:4:
/usr/include/boost/json/detail/value_from.hpp: In instantiation of ‘void boost::json::detail::value_from_helper(boost::json::value&, T&&, no_conversion_tag) [with T = const reference&]’:
/usr/include/boost/json/value_from.hpp:65:30:   required from ‘void boost::json::value_from(T&&, value&) [with T = const reference&]’
/usr/include/boost/json/value_from.hpp:120:21:   required from ‘boost::json::value boost::json::value_from(T&&, storage_ptr) [with T = const reference&]’
../untitled/mustache/include/boost/mustache/renderer.hpp:134:35:   required from ‘boost::mustache::renderer::renderer(const T1&, const T2&, boost::json::storage_ptr) [with T1 = reference; T2 = boost::json::object]’
../untitled/mustache/include/boost/mustache/render.hpp:17:24:   required from ‘void boost::mustache::render(boost::core::string_view, output_ref, const T1&, const T2&, boost::json::storage_ptr) [with T1 = reference; T2 = boost::json::object; boost::core::string_view = boost::core::basic_string_view<char>]’
../untitled/main1.cpp:85:25:   required from here
/usr/include/boost/json/detail/value_from.hpp:152:30: error: static assertion failed: No suitable tag_invoke overload found for the type
  152 |         !std::is_same<T, T>::value,
      |                              ^~~~~
/usr/include/boost/json/detail/value_from.hpp:152:30: note: ‘!(bool)std::integral_constant<bool, true>::value’ evaluates to false

[pdimov]

It's not going to work with 1.80, because the necessary Boost.JSON features have only been added in 1.81.

[RoyBellingan]

Yes it will of course make sense once is mainlined to skip the check, but maybe during this initial / testing could help to inform the user to update ?