Denis Mikhailov

Needs more informative error message in core17_generated.hpp

@apolukhin i'm finished

``` /usr/bin/../lib/gcc/x86_64-linux-gnu/5.5.0/../../../../include/c++/5.5.0/tuple:807:33: error: implicit instantiation of undefined template 'std::tuple_size' : integral_constant { }; ^ ./boost/pfr/detail/core17_generated.hpp:57:9: note: in instantiation of template class 'std::tuple_size' requested here auto& [a,b,c] = val; // ====================>...

> ``` > /usr/bin/../lib/gcc/x86_64-linux-gnu/5.5.0/../../../../include/c++/5.5.0/tuple:807:33: error: implicit instantiation of undefined template 'std::tuple_size' > : integral_constant { }; > ^ > ./boost/pfr/detail/core17_generated.hpp:57:9: note: in instantiation of template class 'std::tuple_size' requested here >...

This may help to resolve this issue: https://github.com/boostorg/pfr/issues/62 BUT i unfortunately do not know how to make `get_memptr` constexpr((

> Something must be done with the default constructor 1. `template struct declval_helper { static T value; };` But it not for clang and msvc https://godbolt.org/z/nYz6M61YT 2. What if we...

> Something must be done with the default constructor 3. Why don't we use the already checked `offset_based_getter`? In my opinion it solves this problem good. https://godbolt.org/z/hfxbnvqrE This works on...

@schaumb interesting. Unfortunatelly, `refl` cannot be passed as template parameter, only `orig` can.

@schaumb I created clang ticket here: https://github.com/llvm/llvm-project/issues/56541 Let's see where the answer will be faster :)

Hi. In progress there: https://github.com/boostorg/fusion/pull/241