boost variant order of parameters relevant in 1.78.0 ?

[allopislozano]

Some of our code broke after the 1.78.0 update. I finally managed to pinpoint the issue. It looks like for some reason a grammar that is a disjunction needs the same order of parameters in the variant to be synthesized. Was this something that should not have compiled in 1.77 or is it something that broke in 78?

The following code works in 77 but not in 78:
https://godbolt.org/z/MKMezMTqq

After switching the order of the parameters in the X variant from B,A to A,B it works in both versions:
https://godbolt.org/z/6e6sMKTYW

[Kojoley]

Pulling the repro from #722 here:

#include <boost/spirit/home/x3.hpp>
#include <boost/variant/variant.hpp>
#include <boost/fusion/include/std_pair.hpp>

int main()
{
    namespace x3 = boost::spirit::x3;
    using namespace x3;

    char const* s = "";

    struct A {};
    struct B {};
    struct C {};
    boost::variant<
        std::pair<int, boost::variant<B, A>>,
        C
    > target;

    x3::parse(s, s,

        attr(int{}) >> (attr(A{}) | attr(B{}))
      | attr(C{})

      , target);
}

[cppljevans]

Does this also solve #707 ?
Test case for 707 is located here:
https://github.com/cppljevans/spirit-experiments/blob/develop/test/x3/issue707.cpp

[cppljevans]

Does this also solve #707 ? Test case for 707 is located here: https://github.com/cppljevans/spirit-experiments/blob/develop/test/x3/issue707.cpp

Apparently it doesn't solve #707 because when I tried compiling the issue707.cpp test case, I got errors. The start of the error messages were:

clang++ -c -O0 -gdwarf-2 -g3 -ftemplate-backtrace-limit=0  -std=c++2b -ftemplate-backtrace-limit=0 -fdiagnostics-show-template-tree -fno-elide-type -fmacro-backtrace-limit=0 -fexceptions -fcxx-exceptions   -DBOOST_NO_CXX98_FUNCTION_BASE  -I../../include -I/home/evansl/prog_dev/boost.org/1_80_0download/download    -ftemplate-depth=200  issue707.cpp -MMD -o c:/msys64/tmp/build/clangxx14_0_3/boost.org/1_80_0download/download/sandbox/eido79/variant_substitute/test/x3-80/issue707.o 
In file included from issue707.cpp:8:
In file included from ../../include/boost/spirit/home/x3.hpp:62:
In file included from ../../include/boost/spirit/home/x3/auxiliary.hpp:11:
In file included from ../../include/boost/spirit/home/x3/auxiliary/any_parser.hpp:17:
../../include/boost/spirit/home/x3/support/traits/move_to.hpp:196:9: error: no matching function for call to 'move_to'
        detail::move_to(src, dest, typename attribute_category<Dest>::type());
        ^~~~~~~~~~~~~~~
../../include/boost/spirit/home/x3/auxiliary/attr.hpp:66:21: note: in instantiation of function template specialization 'boost::spirit::x3::traits::move_to<const issue707::D &, issue707::uda_data>' requested here
            traits::move_to(value_, attr_);
                    ^
../../include/boost/spirit/home/x3/core/detail/parse_into_container.hpp:97:25: note: in instantiation of function template specialization 'boost::spirit::x3::attr_parser<issue707::D>::parse<const char *, boost::spirit::x3::unused_type, const boost::spirit::x3::unused_type, issue707::uda_data>' requested here
            if (!parser.parse(first, last, context, rcontext, val))
                        ^
../../include/boost/spirit/home/x3/core/detail/parse_into_container.hpp:128:20: note: in instantiation of function template specialization 'boost::spirit::x3::detail::parse_into_container_base_impl<boost::spirit::x3::attr_parser<issue707::D>>::call_synthesize_x<const char *, boost::spirit::x3::unused_type, const boost::spirit::x3::unused_type, std::vector<issue707::uda_data>>' requested here
            return call_synthesize_x(parser, first, last, context, rcontext, attr
                   ^