Boost::accumulators [deprecated-copy] warnings GCC11.2

Hi,

I noticed that at least from Boost 1.79 with GCC 11.2 I get a lot of deprecated-copy warnings when using boost::accumlators library:
```

#include
#include
#include
#include
using namespace boost::accumulators;

int main()
{
accumulator_set > > acc;
return 0;
}
```

Output:

```
In file included from /opt/wandbox/boost-1.79.0-gcc-11.1.0/include/boost/accumulators/accumulators.hpp:12,
from prog.cc:1:
/opt/wandbox/boost-1.79.0-gcc-11.1.0/include/boost/accumulators/framework/accumulator_set.hpp: In instantiation of 'void boost::accumulators::accumulator_set::visit_if(const UnaryFunction&) [with FilterPred = boost::accumulators::detail::contains_feature_of_ > >; UnaryFunction = boost::accumulators::detail::add_ref_visitor > > > > >; Sample = double; Features = boost::accumulators::stats >; Weight = void]':
/opt/wandbox/boost-1.79.0-gcc-11.1.0/include/boost/accumulators/framework/accumulator_set.hpp:175:73: required from 'boost::accumulators::accumulator_set::accumulator_set() [with Sample = double; Features = boost::accumulators::stats >; Weight = void]'
prog.cc:9:65: required from here
/opt/wandbox/boost-1.79.0-gcc-11.1.0/include/boost/accumulators/framework/accumulator_set.hpp:314:25: warning: implicitly-declared 'constexpr boost::accumulators::detail::add_ref_visitor > > > > >::add_ref_visitor(const boost::accumulators::detail::add_ref_visitor > > > > >&)' is deprecated [-Wdeprecated-copy]
314 | fusion::for_each(filtered_accs, func);
| ~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~
In file included from /opt/wandbox/boost-1.79.0-gcc-11.1.0/include/boost/accumulators/framework/accumulator_set.hpp:35,
from /opt/wandbox/boost-1.79.0-gcc-11.1.0/include/boost/accumulators/accumulators.hpp:12,
from prog.cc:1:
/opt/wandbox/boost-1.79.0-gcc-11.1.0/include/boost/accumulators/framework/accumulators/droppable_accumulator.hpp:52:30: note: because 'boost::accumulators::detail::add_ref_visitor > > > > >' has user-provided 'boost::accumulators::detail::add_ref_visitor& boost::accumulators::detail::add_ref_visitor::operator=(const boost::accumulators::detail::add_ref_visitor&) [with Args = boost::parameter::aux::tagged_argument_list_of_1 > > > >]'
52 | add_ref_visitor &operator =(add_ref_visitor const &);
| ^~~~~~~~
In file included from /opt/wandbox/boost-1.79.0-gcc-11.1.0/include/boost/fusion/include/for_each.hpp:11,
from /opt/wandbox/boost-1.79.0-gcc-11.1.0/include/boost/accumulators/framework/accumulator_set.hpp:38,
from /opt/wandbox/boost-1.79.0-gcc-11.1.0/include/boost/accumulators/accumulators.hpp:12,
from prog.cc:1:
/opt/wandbox/boost-1.79.0-gcc-11.1.0/include/boost/fusion/algorithm/iteration/for_each.hpp:33:31: note: initializing argument 2 of 'constexpr typename boost::enable_if >::type boost::fusion::for_each(Sequence&, F) [with Sequence = boost::fusion::filter_view, boost::fusion::cons, boost::accumulators::tag::sum>, boost::fusion::cons, boost::accumulators::tag::mean>, boost::fusion::cons, double>, boost::accumulators::tag::moment<2> >, boost::fusion::nil_> > > >, boost::accumulators::detail::contains_feature_of_ > > >; F = boost::accumulators::detail::add_ref_visitor > > > > >; typename boost::enable_if >::type = void]'
33 | for_each(Sequence& seq, F f)
| ~~^
In file included from /opt/wandbox/boost-1.79.0-gcc-11.1.0/include/boost/accumulators/accumulators.hpp:12,
from prog.cc:1:
/opt/wandbox/boost-1.79.0-gcc-11.1.0/include/boost/accumulators/framework/accumulator_set.hpp: In instantiation of 'void boost::accumulators::accumulator_set::visit_if(const UnaryFunction&) [with FilterPred = boost::accumulators::detail::contains_feature_of_, 0>, 0> >; UnaryFunction = boost::accumulators::detail::add_ref_visitor > > > > >; Sample = double; Features = boost::accumulators::stats >; Weight = void]':
/opt/wandbox/boost-1.79.0-gcc-11.1.0/include/boost/accumulators/framework/accumulators/droppable_accumulator.hpp:46:74: required from 'void boost::accumulators::detail::add_ref_visitor::operator()(Accumulator&) const [with Accumulator = boost::accumulators::detail::accumulator_wrapper, boost::accumulators::tag::mean>; Args = boost::parameter::aux::tagged_argument_list_of_1 > > > >]'
/opt/wandbox/boost-1.79.0-gcc-11.1.0/include/boost/fusion/algorithm/iteration/detail/for_each.hpp:35:10: required from 'constexpr void boost::fusion::detail::for_each_linear(const First&, const Last&, F&, mpl_::false_) [with First = boost::fusion::filter_iterator, boost::fusion::cons, boost::accumulators::tag::sum>, boost::fusion::cons, boost::accumulators::tag::mean>, boost::fusion::cons, double>, boost::accumulators::tag::moment<2> >, boost::fusion::nil_> > > > >, boost::fusion::cons_iterator, boost::accumulators::detail::contains_feature_of_ > > >; Last = boost::fusion::filter_iterator, boost::fusion::cons_iterator, boost::accumulators::detail::contains_feature_of_ > > >; F = boost::accumulators::detail::add_ref_visitor > > > > >; mpl_::false_ = mpl_::bool_]'
/opt/wandbox/boost-1.79.0-gcc-11.1.0/include/boost/fusion/algorithm/iteration/detail/for_each.hpp:46:32: required from 'constexpr void boost::fusion::detail::for_each_dispatch(Sequence&, F&, Tag) [with Sequence = boost::fusion::filter_view, boost::fusion::cons, boost::accumulators::tag::sum>, boost::fusion::cons, boost::accumulators::tag::mean>, boost::fusion::cons, double>, boost::accumulators::tag::moment<2> >, boost::fusion::nil_> > > >, boost::accumulators::detail::contains_feature_of_ > > >; F = boost::accumulators::detail::add_ref_visitor > > > > >; Tag = boost::fusion::forward_traversal_tag]'
/opt/wandbox/boost-1.79.0-gcc-11.1.0/include/boost/fusion/algorithm/iteration/detail/for_each.hpp:143:34: required from 'constexpr void boost::fusion::detail::for_each(Sequence&, F&, mpl_::false_) [with Sequence = boost::fusion::filter_view, boost::fusion::cons, boost::accumulators::tag::sum>, boost::fusion::cons, boost::accumulators::tag::mean>, boost::fusion::cons, double>, boost::accumulators::tag::moment<2> >, boost::fusion::nil_> > > >, boost::accumulators::detail::contains_feature_of_ > > >; F = boost::accumulators::detail::add_ref_visitor > > > > >; mpl_::false_ = mpl_::bool_]'
/opt/wandbox/boost-1.79.0-gcc-11.1.0/include/boost/fusion/algorithm/iteration/for_each.hpp:35:25: required from 'constexpr typename boost::enable_if >::type boost::fusion::for_each(Sequence&, F) [with Sequence = boost::fusion::filter_view, boost::fusion::cons, boost::accumulators::tag::sum>, boost::fusion::cons, boost::accumulators::tag::mean>, boost::fusion::cons, double>, boost::accumulators::tag::moment<2> >, boost::fusion::nil_> > > >, boost::accumulators::detail::contains_feature_of_ > > >; F = boost::accumulators::detail::add_ref_visitor > > > > >; typename boost::enable_if >::type = void]'
/opt/wandbox/boost-1.79.0-gcc-11.1.0/include/boost/accumulators/framework/accumulator_set.hpp:314:25: required from 'void boost::accumulators::accumulator_set::visit_if(const UnaryFunction&) [with FilterPred = boost::accumulators::detail::contains_feature_of_ > >; UnaryFunction = boost::accumulators::detail::add_ref_visitor > > > > >; Sample = double; Features = boost::accumulators::stats >; Weight = void]'
/opt/wandbox/boost-1.79.0-gcc-11.1.0/include/boost/accumulators/framework/accumulator_set.hpp:175:73: required from 'boost::accumulators::accumulator_set::accumulator_set() [with Sample = double; Features = boost::accumulators::stats >; Weight = void]'
prog.cc:9:65: required from here
/opt/wandbox/boost-1.79.0-gcc-11.1.0/include/boost/accumulators/framework/accumulator_set.hpp:314:25: warning: implicitly-declared 'constexpr boost::accumulators::detail::add_ref_visitor > > > > >::add_ref_visitor(const boost::accumulators::detail::add_ref_visitor > > > > >&)' is deprecated [-Wdeprecated-copy]
314 | fusion::for_each(filtered_accs, func);
| ~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~
In file included from /opt/wandbox/boost-1.79.0-gcc-11.1.0/include/boost/accumulators/framework/accumulator_set.hpp:35,
from /opt/wandbox/boost-1.79.0-gcc-11.1.0/include/boost/accumulators/accumulators.hpp:12,
from prog.cc:1:
/opt/wandbox/boost-1.79.0-gcc-11.1.0/include/boost/accumulators/framework/accumulators/droppable_accumulator.hpp:52:30: note: because 'boost::accumulators::detail::add_ref_visitor > > > > >' has user-provided 'boost::accumulators::detail::add_ref_visitor& boost::accumulators::detail::add_ref_visitor::operator=(const boost::accumulators::detail::add_ref_visitor&) [with Args = boost::parameter::aux::tagged_argument_list_of_1 > > > >]'
52 | add_ref_visitor &operator =(add_ref_visitor const &);
| ^~~~~~~~
In file included from /opt/wandbox/boost-1.79.0-gcc-11.1.0/include/boost/fusion/include/for_each.hpp:11,
from /opt/wandbox/boost-1.79.0-gcc-11.1.0/include/boost/accumulators/framework/accumulator_set.hpp:38,
from /opt/wandbox/boost-1.79.0-gcc-11.1.0/include/boost/accumulators/accumulators.hpp:12,
from prog.cc:1:
/opt/wandbox/boost-1.79.0-gcc-11.1.0/include/boost/fusion/algorithm/iteration/for_each.hpp:33:31: note: initializing argument 2 of 'constexpr typename boost::enable_if >::type boost::fusion::for_each(Sequence&, F) [with Sequence = boost::fusion::filter_view, boost::fusion::cons, boost::accumulators::tag::sum>, boost::fusion::cons, boost::accumulators::tag::mean>, boost::fusion::cons, double>, boost::accumulators::tag::moment<2> >, boost::fusion::nil_> > > >, boost::accumulators::detail::contains_feature_of_, 0>, 0> > >; F = boost::accumulators::detail::add_ref_visitor > > > > >; typename boost::enable_if >::type = void]'
33 | for_each(Sequence& seq, F f)
| ~~^
In file included from /opt/wandbox/boost-1.79.0-gcc-11.1.0/include/boost/accumulators/accumulators.hpp:12,
from prog.cc:1:
/opt/wandbox/boost-1.79.0-gcc-11.1.0/include/boost/accumulators/framework/accumulator_set.hpp: In instantiation of 'void boost::accumulators::accumulator_set::visit_if(const UnaryFunction&) [with FilterPred = boost::accumulators::detail::contains_feature_of_, 0> >; UnaryFunction = boost::accumulators::detail::add_ref_visitor > > > > >; Sample = double; Features = boost::accumulators::stats >; Weight = void]':
/opt/wandbox/boost-1.79.0-gcc-11.1.0/include/boost/accumulators/framework/accumulators/droppable_accumulator.hpp:46:74: required from 'void boost::accumulators::detail::add_ref_visitor::operator()(Accumulator&) const [with Accumulator = boost::accumulators::detail::accumulator_wrapper, double>, boost::accumulators::tag::moment<2> >; Args = boost::parameter::aux::tagged_argument_list_of_1 > > > >]'
/opt/wandbox/boost-1.79.0-gcc-11.1.0/include/boost/fusion/algorithm/iteration/detail/for_each.hpp:35:10: required from 'constexpr void boost::fusion::detail::for_each_linear(const First&, const Last&, F&, mpl_::false_) [with First = boost::fusion::filter_iterator, double>, boost::accumulators::tag::moment<2> >, boost::fusion::nil_> >, boost::fusion::cons_iterator, boost::accumulators::detail::contains_feature_of_ > > >; Last = boost::fusion::filter_iterator, boost::fusion::cons_iterator, boost::accumulators::detail::contains_feature_of_ > > >; F = boost::accumulators::detail::add_ref_visitor > > > > >; mpl_::false_ = mpl_::bool_]'
/opt/wandbox/boost-1.79.0-gcc-11.1.0/include/boost/fusion/algorithm/iteration/detail/for_each.hpp:36:32: required from 'constexpr void boost::fusion::detail::for_each_linear(const First&, const Last&, F&, mpl_::false_) [with First = boost::fusion::filter_iterator, boost::fusion::cons, boost::accumulators::tag::sum>, boost::fusion::cons, boost::accumulators::tag::mean>, boost::fusion::cons, double>, boost::accumulators::tag::moment<2> >, boost::fusion::nil_> > > > >, boost::fusion::cons_iterator, boost::accumulators::detail::contains_feature_of_ > > >; Last = boost::fusion::filter_iterator, boost::fusion::cons_iterator, boost::accumulators::detail::contains_feature_of_ > > >; F = boost::accumulators::detail::add_ref_visitor > > > > >; mpl_::false_ = mpl_::bool_]'
/opt/wandbox/boost-1.79.0-gcc-11.1.0/include/boost/fusion/algorithm/iteration/detail/for_each.hpp:46:32: required from 'constexpr void boost::fusion::detail::for_each_dispatch(Sequence&, F&, Tag) [with Sequence = boost::fusion::filter_view, boost::fusion::cons, boost::accumulators::tag::sum>, boost::fusion::cons, boost::accumulators::tag::mean>, boost::fusion::cons, double>, boost::accumulators::tag::moment<2> >, boost::fusion::nil_> > > >, boost::accumulators::detail::contains_feature_of_ > > >; F = boost::accumulators::detail::add_ref_visitor > > > > >; Tag = boost::fusion::forward_traversal_tag]'
/opt/wandbox/boost-1.79.0-gcc-11.1.0/include/boost/fusion/algorithm/iteration/detail/for_each.hpp:143:34: required from 'constexpr void boost::fusion::detail::for_each(Sequence&, F&, mpl_::false_) [with Sequence = boost::fusion::filter_view, boost::fusion::cons, boost::accumulators::tag::sum>, boost::fusion::cons, boost::accumulators::tag::mean>, boost::fusion::cons, double>, boost::accumulators::tag::moment<2> >, boost::fusion::nil_> > > >, boost::accumulators::detail::contains_feature_of_ > > >; F = boost::accumulators::detail::add_ref_visitor > > > > >; mpl_::false_ = mpl_::bool_]'
/opt/wandbox/boost-1.79.0-gcc-11.1.0/include/boost/fusion/algorithm/iteration/for_each.hpp:35:25: required from 'constexpr typename boost::enable_if >::type boost::fusion::for_each(Sequence&, F) [with Sequence = boost::fusion::filter_view, boost::fusion::cons, boost::accumulators::tag::sum>, boost::fusion::cons, boost::accumulators::tag::mean>, boost::fusion::cons, double>, boost::accumulators::tag::moment<2> >, boost::fusion::nil_> > > >, boost::accumulators::detail::contains_feature_of_ > > >; F = boost::accumulators::detail::add_ref_visitor > > > > >; typename boost::enable_if >::type = void]'
/opt/wandbox/boost-1.79.0-gcc-11.1.0/include/boost/accumulators/framework/accumulator_set.hpp:314:25: required from 'void boost::accumulators::accumulator_set::visit_if(const UnaryFunction&) [with FilterPred = boost::accumulators::detail::contains_feature_of_ > >; UnaryFunction = boost::accumulators::detail::add_ref_visitor > > > > >; Sample = double; Features = boost::accumulators::stats >; Weight = void]'
/opt/wandbox/boost-1.79.0-gcc-11.1.0/include/boost/accumulators/framework/accumulator_set.hpp:175:73: required from 'boost::accumulators::accumulator_set::accumulator_set() [with Sample = double; Features = boost::accumulators::stats >; Weight = void]'
prog.cc:9:65: required from here
/opt/wandbox/boost-1.79.0-gcc-11.1.0/include/boost/accumulators/framework/accumulator_set.hpp:314:25: warning: implicitly-declared 'constexpr boost::accumulators::detail::add_ref_visitor > > > > >::add_ref_visitor(const boost::accumulators::detail::add_ref_visitor > > > > >&)' is deprecated [-Wdeprecated-copy]
314 | fusion::for_each(filtered_accs, func);
| ~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~
In file included from /opt/wandbox/boost-1.79.0-gcc-11.1.0/include/boost/accumulators/framework/accumulator_set.hpp:35,
from /opt/wandbox/boost-1.79.0-gcc-11.1.0/include/boost/accumulators/accumulators.hpp:12,
from prog.cc:1:
/opt/wandbox/boost-1.79.0-gcc-11.1.0/include/boost/accumulators/framework/accumulators/droppable_accumulator.hpp:52:30: note: because 'boost::accumulators::detail::add_ref_visitor > > > > >' has user-provided 'boost::accumulators::detail::add_ref_visitor& boost::accumulators::detail::add_ref_visitor::operator=(const boost::accumulators::detail::add_ref_visitor&) [with Args = boost::parameter::aux::tagged_argument_list_of_1 > > > >]'
52 | add_ref_visitor &operator =(add_ref_visitor const &);
| ^~~~~~~~
In file included from /opt/wandbox/boost-1.79.0-gcc-11.1.0/include/boost/fusion/include/for_each.hpp:11,
from /opt/wandbox/boost-1.79.0-gcc-11.1.0/include/boost/accumulators/framework/accumulator_set.hpp:38,
from /opt/wandbox/boost-1.79.0-gcc-11.1.0/include/boost/accumulators/accumulators.hpp:12,
from prog.cc:1:
/opt/wandbox/boost-1.79.0-gcc-11.1.0/include/boost/fusion/algorithm/iteration/for_each.hpp:33:31: note: initializing argument 2 of 'constexpr typename boost::enable_if >::type boost::fusion::for_each(Sequence&, F) [with Sequence = boost::fusion::filter_view, boost::fusion::cons, boost::accumulators::tag::sum>, boost::fusion::cons, boost::accumulators::tag::mean>, boost::fusion::cons, double>, boost::accumulators::tag::moment<2> >, boost::fusion::nil_> > > >, boost::accumulators::detail::contains_feature_of_, 0> > >; F = boost::accumulators::detail::add_ref_visitor > > > > >; typename boost::enable_if >::type = void]'
33 | for_each(Sequence& seq, F f)
| ~~^
In file included from /opt/wandbox/boost-1.79.0-gcc-11.1.0/include/boost/accumulators/accumulators.hpp:12,
from prog.cc:1:
/opt/wandbox/boost-1.79.0-gcc-11.1.0/include/boost/accumulators/framework/accumulator_set.hpp: In instantiation of 'void boost::accumulators::accumulator_set::visit_if(const UnaryFunction&) [with FilterPred = boost::accumulators::detail::contains_feature_of_ >; UnaryFunction = boost::accumulators::detail::add_ref_visitor > > > > >; Sample = double; Features = boost::accumulators::stats >; Weight = void]':
/opt/wandbox/boost-1.79.0-gcc-11.1.0/include/boost/accumulators/framework/accumulators/droppable_accumulator.hpp:46:74: required from 'void boost::accumulators::detail::add_ref_visitor::operator()(Accumulator&) const [with Accumulator = boost::accumulators::detail::accumulator_wrapper; Args = boost::parameter::aux::tagged_argument_list_of_1 > > > >]'
/opt/wandbox/boost-1.79.0-gcc-11.1.0/include/boost/fusion/algorithm/iteration/detail/for_each.hpp:35:10: required from 'constexpr void boost::fusion::detail::for_each_linear(const First&, const Last&, F&, mpl_::false_) [with First = boost::fusion::filter_iterator, boost::fusion::cons, boost::accumulators::tag::sum>, boost::fusion::cons, boost::accumulators::tag::mean>, boost::fusion::cons, double>, boost::accumulators::tag::moment<2> >, boost::fusion::nil_> > > > >, boost::fusion::cons_iterator, boost::accumulators::detail::contains_feature_of_, 0>, 0> > >; Last = boost::fusion::filter_iterator, boost::fusion::cons_iterator, boost::accumulators::detail::contains_feature_of_, 0>, 0> > >; F = boost::accumulators::detail::add_ref_visitor > > > > >; mpl_::false_ = mpl_::bool_]'
/opt/wandbox/boost-1.79.0-gcc-11.1.0/include/boost/fusion/algorithm/iteration/detail/for_each.hpp:46:32: required from 'constexpr void boost::fusion::detail::for_each_dispatch(Sequence&, F&, Tag) [with Sequence = boost::fusion::filter_view, boost::fusion::cons, boost::accumulators::tag::sum>, boost::fusion::cons, boost::accumulators::tag::mean>, boost::fusion::cons, double>, boost::accumulators::tag::moment<2> >, boost::fusion::nil_> > > >, boost::accumulators::detail::contains_feature_of_, 0>, 0> > >; F = boost::accumulators::detail::add_ref_visitor > > > > >; Tag = boost::fusion::forward_traversal_tag]'
/opt/wandbox/boost-1.79.0-gcc-11.1.0/include/boost/fusion/algorithm/iteration/detail/for_each.hpp:143:34: required from 'constexpr void boost::fusion::detail::for_each(Sequence&, F&, mpl_::false_) [with Sequence = boost::fusion::filter_view, boost::fusion::cons, boost::accumulators::tag::sum>, boost::fusion::cons, boost::accumulators::tag::mean>, boost::fusion::cons, double>, boost::accumulators::tag::moment<2> >, boost::fusion::nil_> > > >, boost::accumulators::detail::contains_feature_of_, 0>, 0> > >; F = boost::accumulators::detail::add_ref_visitor > > > > >; mpl_::false_ = mpl_::bool_]'
/opt/wandbox/boost-1.79.0-gcc-11.1.0/include/boost/fusion/algorithm/iteration/for_each.hpp:35:25: required from 'constexpr typename boost::enable_if >::type boost::fusion::for_each(Sequence&, F) [with Sequence = boost::fusion::filter_view, boost::fusion::cons, boost::accumulators::tag::sum>, boost::fusion::cons, boost::accumulators::tag::mean>, boost::fusion::cons, double>, boost::accumulators::tag::moment<2> >, boost::fusion::nil_> > > >, boost::accumulators::detail::contains_feature_of_, 0>, 0> > >; F = boost::accumulators::detail::add_ref_visitor > > > > >; typename boost::enable_if >::type = void]'
/opt/wandbox/boost-1.79.0-gcc-11.1.0/include/boost/accumulators/framework/accumulator_set.hpp:314:25: [ skipping 3 instantiation contexts, use -ftemplate-backtrace-limit=0 to disable ]
/opt/wandbox/boost-1.79.0-gcc-11.1.0/include/boost/fusion/algorithm/iteration/detail/for_each.hpp:46:32: required from 'constexpr void boost::fusion::detail::for_each_dispatch(Sequence&, F&, Tag) [with Sequence = boost::fusion::filter_view, boost::fusion::cons, boost::accumulators::tag::sum>, boost::fusion::cons, boost::accumulators::tag::mean>, boost::fusion::cons, double>, boost::accumulators::tag::moment<2> >, boost::fusion::nil_> > > >, boost::accumulators::detail::contains_feature_of_ > > >; F = boost::accumulators::detail::add_ref_visitor > > > > >; Tag = boost::fusion::forward_traversal_tag]'
/opt/wandbox/boost-1.79.0-gcc-11.1.0/include/boost/fusion/algorithm/iteration/detail/for_each.hpp:143:34: required from 'constexpr void boost::fusion::detail::for_each(Sequence&, F&, mpl_::false_) [with Sequence = boost::fusion::filter_view, boost::fusion::cons, boost::accumulators::tag::sum>, boost::fusion::cons, boost::accumulators::tag::mean>, boost::fusion::cons, double>, boost::accumulators::tag::moment<2> >, boost::fusion::nil_> > > >, boost::accumulators::detail::contains_feature_of_ > > >; F = boost::accumulators::detail::add_ref_visitor > > > > >; mpl_::false_ = mpl_::bool_]'
/opt/wandbox/boost-1.79.0-gcc-11.1.0/include/boost/fusion/algorithm/iteration/for_each.hpp:35:25: required from 'constexpr typename boost::enable_if >::type boost::fusion::for_each(Sequence&, F) [with Sequence = boost::fusion::filter_view, boost::fusion::cons, boost::accumulators::tag::sum>, boost::fusion::cons, boost::accumulators::tag::mean>, boost::fusion::cons, double>, boost::accumulators::tag::moment<2> >, boost::fusion::nil_> > > >, boost::accumulators::detail::contains_feature_of_ > > >; F = boost::accumulators::detail::add_ref_visitor > > > > >; typename boost::enable_if >::type = void]'
/opt/wandbox/boost-1.79.0-gcc-11.1.0/include/boost/accumulators/framework/accumulator_set.hpp:314:25: required from 'void boost::accumulators::accumulator_set::visit_if(const UnaryFunction&) [with FilterPred = boost::accumulators::detail::contains_feature_of_ > >; UnaryFunction = boost::accumulators::detail::add_ref_visitor > > > > >; Sample = double; Features = boost::accumulators::stats >; Weight = void]'
/opt/wandbox/boost-1.79.0-gcc-11.1.0/include/boost/accumulators/framework/accumulator_set.hpp:175:73: required from 'boost::accumulators::accumulator_set::accumulator_set() [with Sample = double; Features = boost::accumulators::stats >; Weight = void]'
prog.cc:9:65: required from here
/opt/wandbox/boost-1.79.0-gcc-11.1.0/include/boost/accumulators/framework/accumulator_set.hpp:314:25: warning: implicitly-declared 'constexpr boost::accumulators::detail::add_ref_visitor > > > > >::add_ref_visitor(const boost::accumulators::detail::add_ref_visitor > > > > >&)' is deprecated [-Wdeprecated-copy]
314 | fusion::for_each(filtered_accs, func);
| ~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~
In file included from /opt/wandbox/boost-1.79.0-gcc-11.1.0/include/boost/accumulators/framework/accumulator_set.hpp:35,
from /opt/wandbox/boost-1.79.0-gcc-11.1.0/include/boost/accumulators/accumulators.hpp:12,
from prog.cc:1:
/opt/wandbox/boost-1.79.0-gcc-11.1.0/include/boost/accumulators/framework/accumulators/droppable_accumulator.hpp:52:30: note: because 'boost::accumulators::detail::add_ref_visitor > > > > >' has user-provided 'boost::accumulators::detail::add_ref_visitor& boost::accumulators::detail::add_ref_visitor::operator=(const boost::accumulators::detail::add_ref_visitor&) [with Args = boost::parameter::aux::tagged_argument_list_of_1 > > > >]'
52 | add_ref_visitor &operator =(add_ref_visitor const &);
| ^~~~~~~~
In file included from /opt/wandbox/boost-1.79.0-gcc-11.1.0/include/boost/fusion/include/for_each.hpp:11,
from /opt/wandbox/boost-1.79.0-gcc-11.1.0/include/boost/accumulators/framework/accumulator_set.hpp:38,
from /opt/wandbox/boost-1.79.0-gcc-11.1.0/include/boost/accumulators/accumulators.hpp:12,
from prog.cc:1:
/opt/wandbox/boost-1.79.0-gcc-11.1.0/include/boost/fusion/algorithm/iteration/for_each.hpp:33:31: note: initializing argument 2 of 'constexpr typename boost::enable_if >::type boost::fusion::for_each(Sequence&, F) [with Sequence = boost::fusion::filter_view, boost::fusion::cons, boost::accumulators::tag::sum>, boost::fusion::cons, boost::accumulators::tag::mean>, boost::fusion::cons, double>, boost::accumulators::tag::moment<2> >, boost::fusion::nil_> > > >, boost::accumulators::detail::contains_feature_of_ > >; F = boost::accumulators::detail::add_ref_visitor > > > > >; typename boost::enable_if >::type = void]'
33 | for_each(Sequence& seq, F f)
| ~~^

```

Link to test it: https://wandbox.org/permlink/mpeDCpAenEJcQKnW

Any idea who to fix this?

Thanks