shorter error messages?

[akrzemi1]

When I compile the example from the other issue:

#ifdef WITH_BOOST_SPIRIT
#include <boost/fusion/adapted/struct/adapt_struct.hpp>
#include <boost/spirit/include/qi.hpp>
namespace bp = boost::spirit::qi;
#else
#include <boost/parser/parser.hpp>
namespace bp = boost::parser;
#endif

int main()
{
#ifdef WITH_BOOST_SPIRIT
  auto alnum = bp::ascii::alnum;
  auto alpha = bp::alpha;
#else
  auto alnum = bp::ascii::alnum;
  auto alpha = bp::ascii::alpha;
#endif

  auto myParser  = (alpha >> alpha >> -alnum);

  std::string input = "MM2";
  std::string result;

#ifdef WITH_BOOST_SPIRIT
  auto begin = input.begin();
  bool b = bp::phrase_parse(begin, input.end(), myParser, bp::ascii::space, result);
#else
  auto b = bp::parse(input, myParser, bp::ws, result);
#endif

  if (b)
    std::cout << ":-) " << result << std::endl;
  else
    std::cout << ":-(" << std::endl;
}

I get the following error message. It is very long, and I am convinced that it could be made shorter with some metapprogramming tricks.

In file included from ../boost/boost/hana/functional/partial.hpp:13,
                 from ../boost/boost/hana/fold_left.hpp:19,
                 from ../boost/boost/hana/concept/foldable.hpp:19,
                 from ../boost/boost/hana/core/to.hpp:16,
                 from ../boost/boost/hana/bool.hpp:17,
                 from ../boost/boost/hana/string.hpp:15,
                 from ../boost/boost/hana/detail/struct_macros.hpp:28,
                 from ../boost/boost/hana/adapt_adt.hpp:15,
                 from ../boost/boost/hana.hpp:59,
                 from ../parser/include/boost/parser/tuple.hpp:27,
                 from ../parser/include/boost/parser/detail/printing.hpp:5,
                 from ../parser/include/boost/parser/error_handling.hpp:5,
                 from ../parser/include/boost/parser/parser.hpp:6,
                 from ./main.cpp:6:
../boost/boost/hana/basic_tuple.hpp: In instantiation of ‘constexpr decltype(auto) boost::hana::at_c(basic_tuple<Xs ...>&) [with long unsigned int n = 1; Xs = {std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >}]’:
../boost/boost/hana/tuple.hpp:287:29:   required from ‘constexpr decltype(auto) boost::hana::at_c(tuple<Xs ...>&) [with long unsigned int n = 1; Xs = {std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >}]’
../parser/include/boost/parser/tuple.hpp:161:33:   required from ‘constexpr decltype(auto) boost::parser::detail::tuple_get(boost::hana::tuple<Args ...>&, boost::parser::integral_constant<T, I>) [with T = long long int; T I = 1; Args = {std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >}; boost::parser::integral_constant<T, I> = boost::hana::integral_constant<long long int, 1>]’
../parser/include/boost/parser/tuple.hpp:331:37:   required from ‘constexpr decltype(auto) boost::parser::get(T&&, integral_constant<U, I>) [with T = boost::hana::tuple<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >&; U = long long int; U I = 1; integral_constant<U, I> = boost::hana::integral_constant<long long int, 1>]’
../parser/include/boost/parser/parser.hpp:3489:41:   required from ‘boost::parser::seq_parser<boost::hana::tuple<boost::parser::char_parser<boost::parser::detail::ascii_char_class<boost::parser::detail::ascii_char_class_t::alpha>, void>, boost::parser::char_parser<boost::parser::detail::ascii_char_class<boost::parser::detail::ascii_char_class_t::alpha>, void>, boost::parser::opt_parser<boost::parser::char_parser<boost::parser::detail::ascii_char_class<boost::parser::detail::ascii_char_class_t::alnum>, void> > >, boost::hana::tuple<std::integral_constant<bool, true>, std::integral_constant<bool, true>, std::integral_constant<bool, true> > >::call_impl<false, __gnu_cxx::__normal_iterator<const char*, std::__cxx11::basic_string<char> >, __gnu_cxx::__normal_iterator<const char*, std::__cxx11::basic_string<char> >, boost::parser::detail::parse_context<__gnu_cxx::__normal_iterator<const char*, std::__cxx11::basic_string<char> >, __gnu_cxx::__normal_iterator<const char*, std::__cxx11::basic_string<char> >, boost::parser::default_error_handler, const boost::parser::detail::nope, boost::parser::detail::nope, boost::parser::detail::nope, boost::parser::detail::nope, void, boost::parser::detail::nope, boost::parser::detail::nope, boost::parser::detail::nope>, boost::parser::parser_interface<boost::parser::ws_parser<false> >, boost::hana::tuple<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >, boost::hana::tuple<boost::hana::integral_constant<long long int, 0>, boost::hana::integral_constant<long long int, 1>, boost::hana::integral_constant<long long int, 2> >, boost::hana::tuple<std::integral_constant<bool, false>, std::integral_constant<bool, false>, std::integral_constant<bool, false> > >(std::bool_constant<false>, __gnu_cxx::__normal_iterator<const char*, std::__cxx11::basic_string<char> >&, __gnu_cxx::__normal_iterator<const char*, std::__cxx11::basic_string<char> >, const boost::parser::detail::parse_context<__gnu_cxx::__normal_iterator<const char*, std::__cxx11::basic_string<char> >, __gnu_cxx::__normal_iterator<const char*, std::__cxx11::basic_string<char> >, boost::parser::default_error_handler, const boost::parser::detail::nope, boost::parser::detail::nope, boost::parser::detail::nope, boost::parser::detail::nope, void, boost::parser::detail::nope, boost::parser::detail::nope, boost::parser::detail::nope>&, const boost::parser::parser_interface<boost::parser::ws_parser<false> >&, boost::parser::detail::flags, bool&, boost::hana::tuple<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >&, const boost::hana::tuple<boost::hana::integral_constant<long long int, 0>, boost::hana::integral_constant<long long int, 1>, boost::hana::integral_constant<long long int, 2> >&, const boost::hana::tuple<std::integral_constant<bool, false>, std::integral_constant<bool, false>, std::integral_constant<bool, false> >&) const::<lambda(const auto:38&)> [with auto:38 = boost::hana::tuple<boost::parser::char_parser<boost::parser::detail::ascii_char_class<boost::parser::detail::ascii_char_class_t::alpha>, void>, boost::hana::integral_constant<long long int, 1>, std::integral_constant<bool, false>, std::integral_constant<bool, true> >]’
../parser/include/boost/parser/detail/hl.hpp:67:25:   required from ‘constexpr void boost::parser::detail::hl::for_each_impl(const Tuple&, F&&, std::integer_sequence<long unsigned int, _Idx ...>) [with F = boost::parser::seq_parser<boost::hana::tuple<boost::parser::char_parser<boost::parser::detail::ascii_char_class<boost::parser::detail::ascii_char_class_t::alpha>, void>, boost::parser::char_parser<boost::parser::detail::ascii_char_class<boost::parser::detail::ascii_char_class_t::alpha>, void>, boost::parser::opt_parser<boost::parser::char_parser<boost::parser::detail::ascii_char_class<boost::parser::detail::ascii_char_class_t::alnum>, void> > >, boost::hana::tuple<std::integral_constant<bool, true>, std::integral_constant<bool, true>, std::integral_constant<bool, true> > >::call_impl<false, __gnu_cxx::__normal_iterator<const char*, std::__cxx11::basic_string<char> >, __gnu_cxx::__normal_iterator<const char*, std::__cxx11::basic_string<char> >, boost::parser::detail::parse_context<__gnu_cxx::__normal_iterator<const char*, std::__cxx11::basic_string<char> >, __gnu_cxx::__normal_iterator<const char*, std::__cxx11::basic_string<char> >, boost::parser::default_error_handler, const boost::parser::detail::nope, boost::parser::detail::nope, boost::parser::detail::nope, boost::parser::detail::nope, void, boost::parser::detail::nope, boost::parser::detail::nope, boost::parser::detail::nope>, boost::parser::parser_interface<boost::parser::ws_parser<false> >, boost::hana::tuple<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >, boost::hana::tuple<boost::hana::integral_constant<long long int, 0>, boost::hana::integral_constant<long long int, 1>, boost::hana::integral_constant<long long int, 2> >, boost::hana::tuple<std::integral_constant<bool, false>, std::integral_constant<bool, false>, std::integral_constant<bool, false> > >(std::bool_constant<false>, __gnu_cxx::__normal_iterator<const char*, std::__cxx11::basic_string<char> >&, __gnu_cxx::__normal_iterator<const char*, std::__cxx11::basic_string<char> >, const boost::parser::detail::parse_context<__gnu_cxx::__normal_iterator<const char*, std::__cxx11::basic_string<char> >, __gnu_cxx::__normal_iterator<const char*, std::__cxx11::basic_string<char> >, boost::parser::default_error_handler, const boost::parser::detail::nope, boost::parser::detail::nope, boost::parser::detail::nope, boost::parser::detail::nope, void, boost::parser::detail::nope, boost::parser::detail::nope, boost::parser::detail::nope>&, const boost::parser::parser_interface<boost::parser::ws_parser<false> >&, boost::parser::detail::flags, bool&, boost::hana::tuple<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >&, const boost::hana::tuple<boost::hana::integral_constant<long long int, 0>, boost::hana::integral_constant<long long int, 1>, boost::hana::integral_constant<long long int, 2> >&, const boost::hana::tuple<std::integral_constant<bool, false>, std::integral_constant<bool, false>, std::integral_constant<bool, false> >&) const::<lambda(const auto:38&)>&; Tuple = boost::hana::tuple<boost::hana::tuple<boost::parser::char_parser<boost::parser::detail::ascii_char_class<boost::parser::detail::ascii_char_class_t::alpha>, void>, boost::hana::integral_constant<long long int, 0>, std::integral_constant<bool, false>, std::integral_constant<bool, true> >, boost::hana::tuple<boost::parser::char_parser<boost::parser::detail::ascii_char_class<boost::parser::detail::ascii_char_class_t::alpha>, void>, boost::hana::integral_constant<long long int, 1>, std::integral_constant<bool, false>, std::integral_constant<bool, true> >, boost::hana::tuple<boost::parser::opt_parser<boost::parser::char_parser<boost::parser::detail::ascii_char_class<boost::parser::detail::ascii_char_class_t::alnum>, void> >, boost::hana::integral_constant<long long int, 2>, std::integral_constant<bool, false>, std::integral_constant<bool, true> > >; long unsigned int ...I = {0, 1, 2}]’
../parser/include/boost/parser/detail/hl.hpp:93:26:   [ skipping 2 instantiation contexts, use -ftemplate-backtrace-limit=0 to disable ]
../parser/include/boost/parser/parser.hpp:3403:26:   required from ‘void boost::parser::seq_parser<ParserTuple, BacktrackingTuple>::call(std::bool_constant<UseCallbacks>, Iter&, Sentinel, const Context&, const SkipParser&, boost::parser::detail::flags, bool&, Attribute&) const [with bool UseCallbacks = false; Iter = __gnu_cxx::__normal_iterator<const char*, std::__cxx11::basic_string<char> >; Sentinel = __gnu_cxx::__normal_iterator<const char*, std::__cxx11::basic_string<char> >; Context = boost::parser::detail::parse_context<__gnu_cxx::__normal_iterator<const char*, std::__cxx11::basic_string<char> >, __gnu_cxx::__normal_iterator<const char*, std::__cxx11::basic_string<char> >, boost::parser::default_error_handler, const boost::parser::detail::nope, boost::parser::detail::nope, boost::parser::detail::nope, boost::parser::detail::nope, void, boost::parser::detail::nope, boost::parser::detail::nope, boost::parser::detail::nope>; SkipParser = boost::parser::parser_interface<boost::parser::ws_parser<false> >; Attribute = std::__cxx11::basic_string<char>; ParserTuple = boost::hana::tuple<boost::parser::char_parser<boost::parser::detail::ascii_char_class<boost::parser::detail::ascii_char_class_t::alpha>, void>, boost::parser::char_parser<boost::parser::detail::ascii_char_class<boost::parser::detail::ascii_char_class_t::alpha>, void>, boost::parser::opt_parser<boost::parser::char_parser<boost::parser::detail::ascii_char_class<boost::parser::detail::ascii_char_class_t::alnum>, void> > >; BacktrackingTuple = boost::hana::tuple<std::integral_constant<bool, true>, std::integral_constant<bool, true>, std::integral_constant<bool, true> >; std::bool_constant<UseCallbacks> = std::integral_constant<bool, false>]’
../parser/include/boost/parser/parser.hpp:4681:25:   required from ‘void boost::parser::parser_interface<Parser, GlobalState, ErrorHandler>::operator()(std::bool_constant<UseCallbacks>, Iter&, Sentinel, const Context&, const SkipParserType&, boost::parser::detail::flags, bool&, Attribute&) const [with bool UseCallbacks = false; Iter = __gnu_cxx::__normal_iterator<const char*, std::__cxx11::basic_string<char> >; Sentinel = __gnu_cxx::__normal_iterator<const char*, std::__cxx11::basic_string<char> >; Context = boost::parser::detail::parse_context<__gnu_cxx::__normal_iterator<const char*, std::__cxx11::basic_string<char> >, __gnu_cxx::__normal_iterator<const char*, std::__cxx11::basic_string<char> >, boost::parser::default_error_handler, const boost::parser::detail::nope, boost::parser::detail::nope, boost::parser::detail::nope, boost::parser::detail::nope, void, boost::parser::detail::nope, boost::parser::detail::nope, boost::parser::detail::nope>; SkipParserType = boost::parser::parser_interface<boost::parser::ws_parser<false> >; Attribute = std::__cxx11::basic_string<char>; Parser = boost::parser::seq_parser<boost::hana::tuple<boost::parser::char_parser<boost::parser::detail::ascii_char_class<boost::parser::detail::ascii_char_class_t::alpha>, void>, boost::parser::char_parser<boost::parser::detail::ascii_char_class<boost::parser::detail::ascii_char_class_t::alpha>, void>, boost::parser::opt_parser<boost::parser::char_parser<boost::parser::detail::ascii_char_class<boost::parser::detail::ascii_char_class_t::alnum>, void> > >, boost::hana::tuple<std::integral_constant<bool, true>, std::integral_constant<bool, true>, std::integral_constant<bool, true> > >; GlobalState = boost::parser::detail::nope; ErrorHandler = boost::parser::default_error_handler; std::bool_constant<UseCallbacks> = std::integral_constant<bool, false>]’
../parser/include/boost/parser/parser.hpp:2142:23:   required from ‘bool boost::parser::detail::skip_parse_impl(Iter&, Sentinel, const Parser&, const SkipParser&, const ErrorHandler&, Attr&) [with bool Debug = true; Iter = __gnu_cxx::__normal_iterator<const char*, std::__cxx11::basic_string<char> >; Sentinel = __gnu_cxx::__normal_iterator<const char*, std::__cxx11::basic_string<char> >; Parser = boost::parser::parser_interface<boost::parser::seq_parser<boost::hana::tuple<boost::parser::char_parser<ascii_char_class<boost::parser::detail::ascii_char_class_t::alpha>, void>, boost::parser::char_parser<ascii_char_class<boost::parser::detail::ascii_char_class_t::alpha>, void>, boost::parser::opt_parser<boost::parser::char_parser<ascii_char_class<boost::parser::detail::ascii_char_class_t::alnum>, void> > >, boost::hana::tuple<std::integral_constant<bool, true>, std::integral_constant<bool, true>, std::integral_constant<bool, true> > >, nope, boost::parser::default_error_handler>; SkipParser = boost::parser::parser_interface<boost::parser::ws_parser<false> >; Attr = std::__cxx11::basic_string<char>; ErrorHandler = boost::parser::default_error_handler]’
../parser/include/boost/parser/parser.hpp:6912:53:   required from ‘bool boost::parser::prefix_parse(I&, S, const parser_interface<Parser, GlobalState, ErrorHandler>&, const parser_interface<SkipParser>&, Attr&, trace) [with I = __gnu_cxx::__normal_iterator<const char*, std::__cxx11::basic_string<char> >; S = __gnu_cxx::__normal_iterator<const char*, std::__cxx11::basic_string<char> >; Parser = seq_parser<boost::hana::tuple<char_parser<detail::ascii_char_class<boost::parser::detail::ascii_char_class_t::alpha>, void>, char_parser<detail::ascii_char_class<boost::parser::detail::ascii_char_class_t::alpha>, void>, opt_parser<char_parser<detail::ascii_char_class<boost::parser::detail::ascii_char_class_t::alnum>, void> > >, boost::hana::tuple<std::integral_constant<bool, true>, std::integral_constant<bool, true>, std::integral_constant<bool, true> > >; GlobalState = detail::nope; ErrorHandler = default_error_handler; SkipParser = ws_parser<false>; Attr = std::__cxx11::basic_string<char>; Enable = void]’
../parser/include/boost/parser/parser.hpp:6985:33:   required from ‘bool boost::parser::parse(const R&, const parser_interface<Parser, GlobalState, ErrorHandler>&, const parser_interface<SkipParser>&, Attr&, trace) [with R = std::__cxx11::basic_string<char>; Parser = seq_parser<boost::hana::tuple<char_parser<detail::ascii_char_class<boost::parser::detail::ascii_char_class_t::alpha>, void>, char_parser<detail::ascii_char_class<boost::parser::detail::ascii_char_class_t::alpha>, void>, opt_parser<char_parser<detail::ascii_char_class<boost::parser::detail::ascii_char_class_t::alnum>, void> > >, boost::hana::tuple<std::integral_constant<bool, true>, std::integral_constant<bool, true>, std::integral_constant<bool, true> > >; GlobalState = detail::nope; ErrorHandler = default_error_handler; SkipParser = ws_parser<false>; Attr = std::__cxx11::basic_string<char>; Enable = void]’
./main.cpp:29:21:   required from here
../boost/boost/hana/basic_tuple.hpp:225:47: error: no matching function for call to ‘ebo_get<boost::hana::detail::bti<1> >(boost::hana::basic_tuple<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >&)’
  225 |         return detail::ebo_get<detail::bti<n>>(xs);
      |                ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~
In file included from ../boost/boost/hana/pair.hpp:17,
                 from ../boost/boost/hana/detail/struct_macros.hpp:27:
../boost/boost/hana/detail/ebo.hpp:104:19: note: candidate: ‘template<class K, class V> constexpr V&& _hana::ebo_get(ebo<K, V, false>&&)’
  104 |     constexpr V&& ebo_get(ebo<K, V, false>&& x)
      |                   ^~~~~~~
../boost/boost/hana/detail/ebo.hpp:104:19: note:   template argument deduction/substitution failed:
../boost/boost/hana/basic_tuple.hpp:225:47: note:   template argument ‘0’ does not match ‘1’
  225 |         return detail::ebo_get<detail::bti<n>>(xs);
      |                ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~
../boost/boost/hana/basic_tuple.hpp:225:47: note:   ‘boost::hana::basic_tuple<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >’ is not derived from ‘_hana::ebo<boost::hana::detail::bti<1>, V, false>’
../boost/boost/hana/detail/ebo.hpp:100:18: note: candidate: ‘template<class K, class V> constexpr V& _hana::ebo_get(ebo<K, V, false>&)’
  100 |     constexpr V& ebo_get(ebo<K, V, false>& x)
      |                  ^~~~~~~
../boost/boost/hana/detail/ebo.hpp:100:18: note:   template argument deduction/substitution failed:
../boost/boost/hana/basic_tuple.hpp:225:47: note:   template argument ‘0’ does not match ‘1’
  225 |         return detail::ebo_get<detail::bti<n>>(xs);
      |                ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~
../boost/boost/hana/basic_tuple.hpp:225:47: note:   ‘boost::hana::basic_tuple<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >’ is not derived from ‘_hana::ebo<boost::hana::detail::bti<1>, V, false>’
../boost/boost/hana/detail/ebo.hpp:96:24: note: candidate: ‘template<class K, class V> constexpr const V& _hana::ebo_get(const ebo<K, V, false>&)’
   96 |     constexpr V const& ebo_get(ebo<K, V, false> const& x)
      |                        ^~~~~~~
../boost/boost/hana/detail/ebo.hpp:96:24: note:   template argument deduction/substitution failed:
../boost/boost/hana/basic_tuple.hpp:225:47: note:   template argument ‘0’ does not match ‘1’
  225 |         return detail::ebo_get<detail::bti<n>>(xs);
      |                ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~
../boost/boost/hana/basic_tuple.hpp:225:47: note:   ‘boost::hana::basic_tuple<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >’ is not derived from ‘const _hana::ebo<boost::hana::detail::bti<1>, V, false>’
../boost/boost/hana/detail/ebo.hpp:91:19: note: candidate: ‘template<class K, class V> constexpr V&& _hana::ebo_get(ebo<K, V, true>&&)’
   91 |     constexpr V&& ebo_get(ebo<K, V, true>&& x)
      |                   ^~~~~~~
../boost/boost/hana/detail/ebo.hpp:91:19: note:   template argument deduction/substitution failed:
../boost/boost/hana/basic_tuple.hpp:225:47: note:   template argument ‘0’ does not match ‘1’
  225 |         return detail::ebo_get<detail::bti<n>>(xs);
      |                ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~
../boost/boost/hana/basic_tuple.hpp:225:47: note:   ‘boost::hana::basic_tuple<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >’ is not derived from ‘_hana::ebo<boost::hana::detail::bti<1>, V, true>’
../boost/boost/hana/detail/ebo.hpp:87:18: note: candidate: ‘template<class K, class V> constexpr V& _hana::ebo_get(ebo<K, V, true>&)’
   87 |     constexpr V& ebo_get(ebo<K, V, true>& x)
      |                  ^~~~~~~
../boost/boost/hana/detail/ebo.hpp:87:18: note:   template argument deduction/substitution failed:
../boost/boost/hana/basic_tuple.hpp:225:47: note:   template argument ‘0’ does not match ‘1’
  225 |         return detail::ebo_get<detail::bti<n>>(xs);
      |                ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~
../boost/boost/hana/basic_tuple.hpp:225:47: note:   ‘boost::hana::basic_tuple<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >’ is not derived from ‘_hana::ebo<boost::hana::detail::bti<1>, V, true>’
../boost/boost/hana/detail/ebo.hpp:83:24: note: candidate: ‘template<class K, class V> constexpr const V& _hana::ebo_get(const ebo<K, V, true>&)’
   83 |     constexpr V const& ebo_get(ebo<K, V, true> const& x)
      |                        ^~~~~~~
../boost/boost/hana/detail/ebo.hpp:83:24: note:   template argument deduction/substitution failed:
../boost/boost/hana/basic_tuple.hpp:225:47: note:   template argument ‘0’ does not match ‘1’
  225 |         return detail::ebo_get<detail::bti<n>>(xs);
      |                ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~
../boost/boost/hana/basic_tuple.hpp:225:47: note:   ‘boost::hana::basic_tuple<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >’ is not derived from ‘const _hana::ebo<boost::hana::detail::bti<1>, V, true>’
../boost/boost/hana/basic_tuple.hpp: In instantiation of ‘constexpr decltype(auto) boost::hana::at_c(basic_tuple<Xs ...>&) [with long unsigned int n = 2; Xs = {std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >}]’:
../boost/boost/hana/tuple.hpp:287:29:   required from ‘constexpr decltype(auto) boost::hana::at_c(tuple<Xs ...>&) [with long unsigned int n = 2; Xs = {std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >}]’
../parser/include/boost/parser/tuple.hpp:161:33:   required from ‘constexpr decltype(auto) boost::parser::detail::tuple_get(boost::hana::tuple<Args ...>&, boost::parser::integral_constant<T, I>) [with T = long long int; T I = 2; Args = {std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >}; boost::parser::integral_constant<T, I> = boost::hana::integral_constant<long long int, 2>]’
../parser/include/boost/parser/tuple.hpp:331:37:   required from ‘constexpr decltype(auto) boost::parser::get(T&&, integral_constant<U, I>) [with T = boost::hana::tuple<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >&; U = long long int; U I = 2; integral_constant<U, I> = boost::hana::integral_constant<long long int, 2>]’
../parser/include/boost/parser/parser.hpp:3489:41:   required from ‘boost::parser::seq_parser<boost::hana::tuple<boost::parser::char_parser<boost::parser::detail::ascii_char_class<boost::parser::detail::ascii_char_class_t::alpha>, void>, boost::parser::char_parser<boost::parser::detail::ascii_char_class<boost::parser::detail::ascii_char_class_t::alpha>, void>, boost::parser::opt_parser<boost::parser::char_parser<boost::parser::detail::ascii_char_class<boost::parser::detail::ascii_char_class_t::alnum>, void> > >, boost::hana::tuple<std::integral_constant<bool, true>, std::integral_constant<bool, true>, std::integral_constant<bool, true> > >::call_impl<false, __gnu_cxx::__normal_iterator<const char*, std::__cxx11::basic_string<char> >, __gnu_cxx::__normal_iterator<const char*, std::__cxx11::basic_string<char> >, boost::parser::detail::parse_context<__gnu_cxx::__normal_iterator<const char*, std::__cxx11::basic_string<char> >, __gnu_cxx::__normal_iterator<const char*, std::__cxx11::basic_string<char> >, boost::parser::default_error_handler, const boost::parser::detail::nope, boost::parser::detail::nope, boost::parser::detail::nope, boost::parser::detail::nope, void, boost::parser::detail::nope, boost::parser::detail::nope, boost::parser::detail::nope>, boost::parser::parser_interface<boost::parser::ws_parser<false> >, boost::hana::tuple<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >, boost::hana::tuple<boost::hana::integral_constant<long long int, 0>, boost::hana::integral_constant<long long int, 1>, boost::hana::integral_constant<long long int, 2> >, boost::hana::tuple<std::integral_constant<bool, false>, std::integral_constant<bool, false>, std::integral_constant<bool, false> > >(std::bool_constant<false>, __gnu_cxx::__normal_iterator<const char*, std::__cxx11::basic_string<char> >&, __gnu_cxx::__normal_iterator<const char*, std::__cxx11::basic_string<char> >, const boost::parser::detail::parse_context<__gnu_cxx::__normal_iterator<const char*, std::__cxx11::basic_string<char> >, __gnu_cxx::__normal_iterator<const char*, std::__cxx11::basic_string<char> >, boost::parser::default_error_handler, const boost::parser::detail::nope, boost::parser::detail::nope, boost::parser::detail::nope, boost::parser::detail::nope, void, boost::parser::detail::nope, boost::parser::detail::nope, boost::parser::detail::nope>&, const boost::parser::parser_interface<boost::parser::ws_parser<false> >&, boost::parser::detail::flags, bool&, boost::hana::tuple<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >&, const boost::hana::tuple<boost::hana::integral_constant<long long int, 0>, boost::hana::integral_constant<long long int, 1>, boost::hana::integral_constant<long long int, 2> >&, const boost::hana::tuple<std::integral_constant<bool, false>, std::integral_constant<bool, false>, std::integral_constant<bool, false> >&) const::<lambda(const auto:38&)> [with auto:38 = boost::hana::tuple<boost::parser::opt_parser<boost::parser::char_parser<boost::parser::detail::ascii_char_class<boost::parser::detail::ascii_char_class_t::alnum>, void> >, boost::hana::integral_constant<long long int, 2>, std::integral_constant<bool, false>, std::integral_constant<bool, true> >]’
../parser/include/boost/parser/detail/hl.hpp:67:25:   required from ‘constexpr void boost::parser::detail::hl::for_each_impl(const Tuple&, F&&, std::integer_sequence<long unsigned int, _Idx ...>) [with F = boost::parser::seq_parser<boost::hana::tuple<boost::parser::char_parser<boost::parser::detail::ascii_char_class<boost::parser::detail::ascii_char_class_t::alpha>, void>, boost::parser::char_parser<boost::parser::detail::ascii_char_class<boost::parser::detail::ascii_char_class_t::alpha>, void>, boost::parser::opt_parser<boost::parser::char_parser<boost::parser::detail::ascii_char_class<boost::parser::detail::ascii_char_class_t::alnum>, void> > >, boost::hana::tuple<std::integral_constant<bool, true>, std::integral_constant<bool, true>, std::integral_constant<bool, true> > >::call_impl<false, __gnu_cxx::__normal_iterator<const char*, std::__cxx11::basic_string<char> >, __gnu_cxx::__normal_iterator<const char*, std::__cxx11::basic_string<char> >, boost::parser::detail::parse_context<__gnu_cxx::__normal_iterator<const char*, std::__cxx11::basic_string<char> >, __gnu_cxx::__normal_iterator<const char*, std::__cxx11::basic_string<char> >, boost::parser::default_error_handler, const boost::parser::detail::nope, boost::parser::detail::nope, boost::parser::detail::nope, boost::parser::detail::nope, void, boost::parser::detail::nope, boost::parser::detail::nope, boost::parser::detail::nope>, boost::parser::parser_interface<boost::parser::ws_parser<false> >, boost::hana::tuple<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >, boost::hana::tuple<boost::hana::integral_constant<long long int, 0>, boost::hana::integral_constant<long long int, 1>, boost::hana::integral_constant<long long int, 2> >, boost::hana::tuple<std::integral_constant<bool, false>, std::integral_constant<bool, false>, std::integral_constant<bool, false> > >(std::bool_constant<false>, __gnu_cxx::__normal_iterator<const char*, std::__cxx11::basic_string<char> >&, __gnu_cxx::__normal_iterator<const char*, std::__cxx11::basic_string<char> >, const boost::parser::detail::parse_context<__gnu_cxx::__normal_iterator<const char*, std::__cxx11::basic_string<char> >, __gnu_cxx::__normal_iterator<const char*, std::__cxx11::basic_string<char> >, boost::parser::default_error_handler, const boost::parser::detail::nope, boost::parser::detail::nope, boost::parser::detail::nope, boost::parser::detail::nope, void, boost::parser::detail::nope, boost::parser::detail::nope, boost::parser::detail::nope>&, const boost::parser::parser_interface<boost::parser::ws_parser<false> >&, boost::parser::detail::flags, bool&, boost::hana::tuple<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >&, const boost::hana::tuple<boost::hana::integral_constant<long long int, 0>, boost::hana::integral_constant<long long int, 1>, boost::hana::integral_constant<long long int, 2> >&, const boost::hana::tuple<std::integral_constant<bool, false>, std::integral_constant<bool, false>, std::integral_constant<bool, false> >&) const::<lambda(const auto:38&)>&; Tuple = boost::hana::tuple<boost::hana::tuple<boost::parser::char_parser<boost::parser::detail::ascii_char_class<boost::parser::detail::ascii_char_class_t::alpha>, void>, boost::hana::integral_constant<long long int, 0>, std::integral_constant<bool, false>, std::integral_constant<bool, true> >, boost::hana::tuple<boost::parser::char_parser<boost::parser::detail::ascii_char_class<boost::parser::detail::ascii_char_class_t::alpha>, void>, boost::hana::integral_constant<long long int, 1>, std::integral_constant<bool, false>, std::integral_constant<bool, true> >, boost::hana::tuple<boost::parser::opt_parser<boost::parser::char_parser<boost::parser::detail::ascii_char_class<boost::parser::detail::ascii_char_class_t::alnum>, void> >, boost::hana::integral_constant<long long int, 2>, std::integral_constant<bool, false>, std::integral_constant<bool, true> > >; long unsigned int ...I = {0, 1, 2}]’
../parser/include/boost/parser/detail/hl.hpp:93:26:   [ skipping 2 instantiation contexts, use -ftemplate-backtrace-limit=0 to disable ]
../parser/include/boost/parser/parser.hpp:3403:26:   required from ‘void boost::parser::seq_parser<ParserTuple, BacktrackingTuple>::call(std::bool_constant<UseCallbacks>, Iter&, Sentinel, const Context&, const SkipParser&, boost::parser::detail::flags, bool&, Attribute&) const [with bool UseCallbacks = false; Iter = __gnu_cxx::__normal_iterator<const char*, std::__cxx11::basic_string<char> >; Sentinel = __gnu_cxx::__normal_iterator<const char*, std::__cxx11::basic_string<char> >; Context = boost::parser::detail::parse_context<__gnu_cxx::__normal_iterator<const char*, std::__cxx11::basic_string<char> >, __gnu_cxx::__normal_iterator<const char*, std::__cxx11::basic_string<char> >, boost::parser::default_error_handler, const boost::parser::detail::nope, boost::parser::detail::nope, boost::parser::detail::nope, boost::parser::detail::nope, void, boost::parser::detail::nope, boost::parser::detail::nope, boost::parser::detail::nope>; SkipParser = boost::parser::parser_interface<boost::parser::ws_parser<false> >; Attribute = std::__cxx11::basic_string<char>; ParserTuple = boost::hana::tuple<boost::parser::char_parser<boost::parser::detail::ascii_char_class<boost::parser::detail::ascii_char_class_t::alpha>, void>, boost::parser::char_parser<boost::parser::detail::ascii_char_class<boost::parser::detail::ascii_char_class_t::alpha>, void>, boost::parser::opt_parser<boost::parser::char_parser<boost::parser::detail::ascii_char_class<boost::parser::detail::ascii_char_class_t::alnum>, void> > >; BacktrackingTuple = boost::hana::tuple<std::integral_constant<bool, true>, std::integral_constant<bool, true>, std::integral_constant<bool, true> >; std::bool_constant<UseCallbacks> = std::integral_constant<bool, false>]’
../parser/include/boost/parser/parser.hpp:4681:25:   required from ‘void boost::parser::parser_interface<Parser, GlobalState, ErrorHandler>::operator()(std::bool_constant<UseCallbacks>, Iter&, Sentinel, const Context&, const SkipParserType&, boost::parser::detail::flags, bool&, Attribute&) const [with bool UseCallbacks = false; Iter = __gnu_cxx::__normal_iterator<const char*, std::__cxx11::basic_string<char> >; Sentinel = __gnu_cxx::__normal_iterator<const char*, std::__cxx11::basic_string<char> >; Context = boost::parser::detail::parse_context<__gnu_cxx::__normal_iterator<const char*, std::__cxx11::basic_string<char> >, __gnu_cxx::__normal_iterator<const char*, std::__cxx11::basic_string<char> >, boost::parser::default_error_handler, const boost::parser::detail::nope, boost::parser::detail::nope, boost::parser::detail::nope, boost::parser::detail::nope, void, boost::parser::detail::nope, boost::parser::detail::nope, boost::parser::detail::nope>; SkipParserType = boost::parser::parser_interface<boost::parser::ws_parser<false> >; Attribute = std::__cxx11::basic_string<char>; Parser = boost::parser::seq_parser<boost::hana::tuple<boost::parser::char_parser<boost::parser::detail::ascii_char_class<boost::parser::detail::ascii_char_class_t::alpha>, void>, boost::parser::char_parser<boost::parser::detail::ascii_char_class<boost::parser::detail::ascii_char_class_t::alpha>, void>, boost::parser::opt_parser<boost::parser::char_parser<boost::parser::detail::ascii_char_class<boost::parser::detail::ascii_char_class_t::alnum>, void> > >, boost::hana::tuple<std::integral_constant<bool, true>, std::integral_constant<bool, true>, std::integral_constant<bool, true> > >; GlobalState = boost::parser::detail::nope; ErrorHandler = boost::parser::default_error_handler; std::bool_constant<UseCallbacks> = std::integral_constant<bool, false>]’
../parser/include/boost/parser/parser.hpp:2142:23:   required from ‘bool boost::parser::detail::skip_parse_impl(Iter&, Sentinel, const Parser&, const SkipParser&, const ErrorHandler&, Attr&) [with bool Debug = true; Iter = __gnu_cxx::__normal_iterator<const char*, std::__cxx11::basic_string<char> >; Sentinel = __gnu_cxx::__normal_iterator<const char*, std::__cxx11::basic_string<char> >; Parser = boost::parser::parser_interface<boost::parser::seq_parser<boost::hana::tuple<boost::parser::char_parser<ascii_char_class<boost::parser::detail::ascii_char_class_t::alpha>, void>, boost::parser::char_parser<ascii_char_class<boost::parser::detail::ascii_char_class_t::alpha>, void>, boost::parser::opt_parser<boost::parser::char_parser<ascii_char_class<boost::parser::detail::ascii_char_class_t::alnum>, void> > >, boost::hana::tuple<std::integral_constant<bool, true>, std::integral_constant<bool, true>, std::integral_constant<bool, true> > >, nope, boost::parser::default_error_handler>; SkipParser = boost::parser::parser_interface<boost::parser::ws_parser<false> >; Attr = std::__cxx11::basic_string<char>; ErrorHandler = boost::parser::default_error_handler]’
../parser/include/boost/parser/parser.hpp:6912:53:   required from ‘bool boost::parser::prefix_parse(I&, S, const parser_interface<Parser, GlobalState, ErrorHandler>&, const parser_interface<SkipParser>&, Attr&, trace) [with I = __gnu_cxx::__normal_iterator<const char*, std::__cxx11::basic_string<char> >; S = __gnu_cxx::__normal_iterator<const char*, std::__cxx11::basic_string<char> >; Parser = seq_parser<boost::hana::tuple<char_parser<detail::ascii_char_class<boost::parser::detail::ascii_char_class_t::alpha>, void>, char_parser<detail::ascii_char_class<boost::parser::detail::ascii_char_class_t::alpha>, void>, opt_parser<char_parser<detail::ascii_char_class<boost::parser::detail::ascii_char_class_t::alnum>, void> > >, boost::hana::tuple<std::integral_constant<bool, true>, std::integral_constant<bool, true>, std::integral_constant<bool, true> > >; GlobalState = detail::nope; ErrorHandler = default_error_handler; SkipParser = ws_parser<false>; Attr = std::__cxx11::basic_string<char>; Enable = void]’
../parser/include/boost/parser/parser.hpp:6985:33:   required from ‘bool boost::parser::parse(const R&, const parser_interface<Parser, GlobalState, ErrorHandler>&, const parser_interface<SkipParser>&, Attr&, trace) [with R = std::__cxx11::basic_string<char>; Parser = seq_parser<boost::hana::tuple<char_parser<detail::ascii_char_class<boost::parser::detail::ascii_char_class_t::alpha>, void>, char_parser<detail::ascii_char_class<boost::parser::detail::ascii_char_class_t::alpha>, void>, opt_parser<char_parser<detail::ascii_char_class<boost::parser::detail::ascii_char_class_t::alnum>, void> > >, boost::hana::tuple<std::integral_constant<bool, true>, std::integral_constant<bool, true>, std::integral_constant<bool, true> > >; GlobalState = detail::nope; ErrorHandler = default_error_handler; SkipParser = ws_parser<false>; Attr = std::__cxx11::basic_string<char>; Enable = void]’
./main.cpp:29:21:   required from here
../boost/boost/hana/basic_tuple.hpp:225:47: error: no matching function for call to ‘ebo_get<boost::hana::detail::bti<2> >(boost::hana::basic_tuple<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >&)’
../boost/boost/hana/detail/ebo.hpp:104:19: note: candidate: ‘template<class K, class V> constexpr V&& _hana::ebo_get(ebo<K, V, false>&&)’
  104 |     constexpr V&& ebo_get(ebo<K, V, false>&& x)
      |                   ^~~~~~~
../boost/boost/hana/detail/ebo.hpp:104:19: note:   template argument deduction/substitution failed:
../boost/boost/hana/basic_tuple.hpp:225:47: note:   template argument ‘0’ does not match ‘2’
  225 |         return detail::ebo_get<detail::bti<n>>(xs);
      |                ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~
../boost/boost/hana/basic_tuple.hpp:225:47: note:   ‘boost::hana::basic_tuple<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >’ is not derived from ‘_hana::ebo<boost::hana::detail::bti<2>, V, false>’
../boost/boost/hana/detail/ebo.hpp:100:18: note: candidate: ‘template<class K, class V> constexpr V& _hana::ebo_get(ebo<K, V, false>&)’
  100 |     constexpr V& ebo_get(ebo<K, V, false>& x)
      |                  ^~~~~~~
../boost/boost/hana/detail/ebo.hpp:100:18: note:   template argument deduction/substitution failed:
../boost/boost/hana/basic_tuple.hpp:225:47: note:   template argument ‘0’ does not match ‘2’
  225 |         return detail::ebo_get<detail::bti<n>>(xs);
      |                ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~
../boost/boost/hana/basic_tuple.hpp:225:47: note:   ‘boost::hana::basic_tuple<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >’ is not derived from ‘_hana::ebo<boost::hana::detail::bti<2>, V, false>’
../boost/boost/hana/detail/ebo.hpp:96:24: note: candidate: ‘template<class K, class V> constexpr const V& _hana::ebo_get(const ebo<K, V, false>&)’
   96 |     constexpr V const& ebo_get(ebo<K, V, false> const& x)
      |                        ^~~~~~~
../boost/boost/hana/detail/ebo.hpp:96:24: note:   template argument deduction/substitution failed:
../boost/boost/hana/basic_tuple.hpp:225:47: note:   template argument ‘0’ does not match ‘2’
  225 |         return detail::ebo_get<detail::bti<n>>(xs);
      |                ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~
../boost/boost/hana/basic_tuple.hpp:225:47: note:   ‘boost::hana::basic_tuple<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >’ is not derived from ‘const _hana::ebo<boost::hana::detail::bti<2>, V, false>’
../boost/boost/hana/detail/ebo.hpp:91:19: note: candidate: ‘template<class K, class V> constexpr V&& _hana::ebo_get(ebo<K, V, true>&&)’
   91 |     constexpr V&& ebo_get(ebo<K, V, true>&& x)
      |                   ^~~~~~~
../boost/boost/hana/detail/ebo.hpp:91:19: note:   template argument deduction/substitution failed:
../boost/boost/hana/basic_tuple.hpp:225:47: note:   template argument ‘0’ does not match ‘2’
  225 |         return detail::ebo_get<detail::bti<n>>(xs);
      |                ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~
../boost/boost/hana/basic_tuple.hpp:225:47: note:   ‘boost::hana::basic_tuple<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >’ is not derived from ‘_hana::ebo<boost::hana::detail::bti<2>, V, true>’
../boost/boost/hana/detail/ebo.hpp:87:18: note: candidate: ‘template<class K, class V> constexpr V& _hana::ebo_get(ebo<K, V, true>&)’
   87 |     constexpr V& ebo_get(ebo<K, V, true>& x)
      |                  ^~~~~~~
../boost/boost/hana/detail/ebo.hpp:87:18: note:   template argument deduction/substitution failed:
../boost/boost/hana/basic_tuple.hpp:225:47: note:   template argument ‘0’ does not match ‘2’
  225 |         return detail::ebo_get<detail::bti<n>>(xs);
      |                ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~
../boost/boost/hana/basic_tuple.hpp:225:47: note:   ‘boost::hana::basic_tuple<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >’ is not derived from ‘_hana::ebo<boost::hana::detail::bti<2>, V, true>’
../boost/boost/hana/detail/ebo.hpp:83:24: note: candidate: ‘template<class K, class V> constexpr const V& _hana::ebo_get(const ebo<K, V, true>&)’
   83 |     constexpr V const& ebo_get(ebo<K, V, true> const& x)
      |                        ^~~~~~~
../boost/boost/hana/detail/ebo.hpp:83:24: note:   template argument deduction/substitution failed:
../boost/boost/hana/basic_tuple.hpp:225:47: note:   template argument ‘0’ does not match ‘2’
  225 |         return detail::ebo_get<detail::bti<n>>(xs);
      |                ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~
../boost/boost/hana/basic_tuple.hpp:225:47: note:   ‘boost::hana::basic_tuple<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >’ is not derived from ‘const _hana::ebo<boost::hana::detail::bti<2>, V, true>’

[tzlaine]

Hm. How exactly? I'm interested, but I don't see how. The usual techniques -- SFINAE/concept constraints and static_asserts won't really work very well here, because of the loose matching of attribute types. If I pass in a U instead of a T for the attribute, that should work under many circumstances. However, it's pretty hard to write the constraint/static_assert for a failure like the one above.

[tzlaine]

Well, I did actually find a place to put a static_assert that gives a likely-useful hint at the kind of error above.

So, Let's keep this issue open; please post more examples as they come up.

[akrzemi1]

From my experience, static_assert alone is not enough, as it doesn't stop the compilation. A static_assert followed by an enable-if trick, or a tricky template specializaiton does the job.

[tzlaine]

I don't know of any snippet of code guaranteed to stop the compile on any implementation, and I tried putting a constraint on the use of the bad index after the static assert, and it did not stop the build, or produce any fewer diagnostics. I'm open to suggestions though.

[akrzemi1]

257dcd3#r136667439

[akrzemi1]

Also, maybe after the new assert, use some redundant template instantiation that would display (as error message) the type of the default attribute and the type of the struct that I wanted to parse into.

In a nested parser it is far from obvious what structure is being parsed into.

[akrzemi1]

another example with huge error messages in GCC:

#include <boost/parser/parser.hpp>
namespace bp = boost::parser;

int main()
{
  auto myParser  = (bp::lower >> bp::lower >> -bp::digi);

  std::string input = "MM2";
  int result;

  auto b = bp::parse(input, myParser, bp::ws, result);

  if (b)
    std::cout << ":-) " << result << std::endl;
  else
    std::cout << ":-(" << std::endl;
}