[Boost-bugs] [Boost C++ Libraries] #11932: [1.60 regression] [C++11] Binary MPL transform on empty fusion vectors does not work

Subject: [Boost-bugs] [Boost C++ Libraries] #11932: [1.60 regression] [C++11] Binary MPL transform on empty fusion vectors does not work
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2016-01-22 00:24:07

#11932: [1.60 regression] [C++11] Binary MPL transform on empty fusion vectors does
not work
------------------------------+---------------------
 Reporter:  zeratul976@…      |      Owner:  djowel
     Type:  Bugs              |     Status:  new
Milestone:  To Be Determined  |  Component:  fusion
  Version:  Boost 1.60.0      |   Severity:  Problem
 Keywords:  regression        |
------------------------------+---------------------
 The following code does not compile with Boost 1.60 in C++11 mode. Tested
 with recent gcc and clang.


 {{{
 #include <boost/mpl/transform.hpp>
 #include <boost/fusion/container/vector.hpp>
 #include <boost/fusion/mpl.hpp>

 struct predicate {
     template <typename T, typename U>
     struct apply {
         typedef T type;
     };
 };

 typedef
     boost::mpl::transform<
         boost::fusion::vector<>,
         boost::fusion::vector<>,
         predicate>
     ::type
 Result;
 }}}

 The error is:


 {{{
 In file included from test.cpp:2:
 In file included from boost/include/boost/fusion/container/vector.hpp:12:
 In file included from
 boost/include/boost/fusion/container/vector/vector.hpp:28:
 In file included from
 boost/include/boost/fusion/container/vector/detail/at_impl.hpp:12:
 boost/include/boost/fusion/container/vector/detail/value_at_impl.hpp:50:57:
 error: no matching function for call to 'value_at_impl'
                 typedef typename mpl::identity<decltype(seq::template
 value_at_impl<N::value>(boost::declval<seq*>()))>::type::type type;
 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 boost/include/boost/fusion/container/vector/detail/value_of_impl.hpp:30:61:
 note: in instantiation of template class
 'boost::fusion::extension::value_at_impl<boost::fusion::vector_tag>::apply<boost::fusion::vector<>,
 mpl_::int_<0>>' requested here
                 typedef typename value_at_impl<vector_tag>::template
 apply<vector, index>::type type;
                                                             ^
 boost/include/boost/fusion/iterator/value_of.hpp:52:15: note: in
 instantiation of template class
 'boost::fusion::extension::value_of_impl<boost::fusion::vector_iterator_tag>::apply<boost::fusion::vector_iterator<boost::fusion::vector<>,
 0>>' requested here
             : extension::value_of_impl<typename
 detail::tag_of<Iterator>::type>::
               ^
 boost/include/boost/fusion/iterator/mpl/fusion_iterator.hpp:47:45: note:
 in instantiation of template class
 'boost::fusion::result_of::value_of<boost::fusion::vector_iterator<boost::fusion::vector<>,
 0>>' requested here
         typedef typename fusion::result_of::value_of<Iterator>::type type;
                                             ^
 boost/include/boost/mpl/iterator_category.hpp:27:22: note: in
 instantiation of template class
 'boost::mpl::fusion_iterator<boost::fusion::vector_iterator<boost::fusion::vector<>,
 0>>' requested here
     typedef typename Iterator::category type;
                      ^
 boost/include/boost/mpl/pair_view.hpp:152:20: note: in instantiation of
 template class
 'boost::mpl::iterator_category<boost::mpl::fusion_iterator<boost::fusion::vector_iterator<boost::fusion::vector<>,
 0>>>' requested here
           typename iterator_category<iter1_>::type
                    ^
 boost/include/boost/mpl/aux_/has_tag.hpp:20:1: note: in instantiation of
 template class 'boost::mpl::pair_view<boost::fusion::vector<>,
 boost::fusion::vector<>>'
       requested here
 BOOST_MPL_HAS_XXX_TRAIT_NAMED_DEF(has_tag, tag, false)
 ^
 boost/include/boost/mpl/has_xxx.hpp:245:65: note: expanded from macro
 'BOOST_MPL_HAS_XXX_TRAIT_NAMED_DEF'
             , boost::mpl::aux::type_wrapper<BOOST_MSVC_TYPENAME U::name>*
 = 0 \
                                                                 ^
 boost/include/boost/mpl/aux_/has_tag.hpp:20:1: note: while substituting
 deduced template arguments into function template 'test' [with U =
       boost::mpl::pair_view<boost::fusion::vector<>,
 boost::fusion::vector<>>]
 BOOST_MPL_HAS_XXX_TRAIT_NAMED_DEF(has_tag, tag, false)
 ^
 boost/include/boost/mpl/has_xxx.hpp:253:18: note: expanded from macro
 'BOOST_MPL_HAS_XXX_TRAIT_NAMED_DEF'
           sizeof(gcc_3_2_wknd::test(static_cast<t_*>(0))) \
                  ^
 boost/include/boost/config/suffix.hpp:394:72: note: expanded from macro
 'BOOST_STATIC_CONSTANT'
 #     define BOOST_STATIC_CONSTANT(type, assignment) static const type
 assignment
                                                                        ^
 boost/include/boost/mpl/sequence_tag.hpp:112:30: note: in instantiation of
 template class
 'boost::mpl::aux::has_tag<boost::mpl::pair_view<boost::fusion::vector<>,
       boost::fusion::vector<>>, mpl_::bool_<false>>' requested here
           ::boost::mpl::aux::has_tag<Sequence>::value
                              ^
 boost/include/boost/mpl/O1_size.hpp:30:30: note: in instantiation of
 template class
 'boost::mpl::sequence_tag<boost::mpl::pair_view<boost::fusion::vector<>,
       boost::fusion::vector<>>>' requested here
     : O1_size_impl< typename sequence_tag<Sequence>::type>
                              ^
 boost/include/boost/mpl/fold.hpp:34:25: note: in instantiation of template
 class 'boost::mpl::O1_size<boost::mpl::pair_view<boost::fusion::vector<>,
       boost::fusion::vector<>>>' requested here
           ::boost::mpl::O1_size<Sequence>::value
                         ^
 boost/include/boost/mpl/transform.hpp:75:7: note: in instantiation of
 template class
 'boost::mpl::fold<boost::mpl::pair_view<boost::fusion::vector<>,
       boost::fusion::vector<>>, boost::fusion::vector<>,
 boost::mpl::bind2<boost::mpl::push_back<mpl_::na, mpl_::na>, mpl_::arg<1>,
 boost::mpl::bind2<predicate,
       boost::mpl::bind1<boost::mpl::first<mpl_::na>, mpl_::arg<2>>,
 boost::mpl::bind1<boost::mpl::second<mpl_::na>, mpl_::arg<2>>>>>'
 requested here
     : fold<
       ^
 boost/include/boost/mpl/transform.hpp:114:1: note: in instantiation of
 template class 'boost::mpl::aux::transform2_impl<boost::fusion::vector<>,
       boost::fusion::vector<>, predicate,
 boost::mpl::back_inserter<boost::fusion::vector<>>>' requested here
 BOOST_MPL_AUX_INSERTER_ALGORITHM_DEF(4, transform2)
 ^
 boost/include/boost/mpl/aux_/inserter_algorithm.hpp:52:7: note: expanded
 from macro 'BOOST_MPL_AUX_INSERTER_ALGORITHM_DEF'
     : if_< has_push_back< typename clear<P1>::type> \
       ^
 boost/include/boost/mpl/eval_if.hpp:38:22: note: in instantiation of
 template class 'boost::mpl::transform2<boost::fusion::vector<>,
 boost::fusion::vector<>, predicate,
       mpl_::na>' requested here
     typedef typename f_::type type;
                      ^
 boost/include/boost/mpl/transform.hpp:138:1: note: in instantiation of
 template class
 'boost::mpl::eval_if<boost::mpl::or_<boost::mpl::is_na<predicate>,
       boost::mpl::is_lambda_expression<boost::fusion::vector<>>,
 boost::mpl::not_<boost::mpl::is_sequence<boost::fusion::vector<>>>,
 mpl_::bool_<false>, mpl_::bool_<false>>,
       boost::mpl::transform1<boost::fusion::vector<>,
 boost::fusion::vector<>, predicate>,
 boost::mpl::transform2<boost::fusion::vector<>, boost::fusion::vector<>,
 predicate, mpl_::na>>'
       requested here
 AUX778076_TRANSFORM_DEF(transform)
 ^
 boost/include/boost/mpl/transform.hpp:125:22: note: expanded from macro
 'AUX778076_TRANSFORM_DEF'
     typedef typename eval_if<                                           \
                      ^
 test.cpp:13:17: note: in instantiation of template class
 'boost::mpl::transform<boost::fusion::vector<>, boost::fusion::vector<>,
 predicate, mpl_::na>' requested here
     boost::mpl::transform<
                 ^
 boost/include/boost/fusion/container/vector/vector.hpp:275:30: note:
 candidate template ignored: could not match 'store' against 'vector'
             mpl::identity<U> value_at_impl(store<N, U>*);
                              ^
 }}}

 Kohei has indicated on the mailing list [1] that this affects C++11 mode
 only, and seems to be a regression in 1.60.

 [1] http://boost.2283326.n4.nabble.com/fusion-mpl-binary-MPL-transform-on-

 empty-fusion-vectors-tp4682832p4682837.html

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/11932>
Boost C++ Libraries <http://www.boost.org/>
Boost provides free peer-reviewed portable C++ source libraries.