BOOST_HANA_CONFIG_HAS_CONSTEXPR_LAMBDA and BOOST_HANA_CONSTEXPR_CHECK

I tried to enable BOOST_HANA_CONFIG_HAS_CONSTEXPR_LAMBDA once and see some errors when building with MSVC and /std:c++17.

I only investigated several failures and one of them seems to be source issue:

test\assert\constexpr.cpp
BOOST_HANA_CONSTEXPR_ASSERT(runtime_bool());

runtime_bool isn't a constexpr function.

Looks that this macro is deliberately left as undefined, so this issue is just a FYI.

Start with test\assert\constexpr.cpp and the BOOST_HANA_CONSTEXPR_ASSERT(runtime_bool()) case under MSVC with /std:c++17. Determine whether the reported non-constexpr runtime_bool use is an actual source issue related to BOOST_HANA_CONFIG_HAS_CONSTEXPR_LAMBDA and define what correction or confirmation would close the issue.

Written by the indexing model from the issue text.