call of overloaded ‘ignore_unused_variable_warning(...)’ is ambiguous

Hello dear team of Boostorg/range.

I was already at boostorg/geometry, but now the the error continued to exist, and is triggered by `boost/range/concepts.hpp:19`.

The error is pretty much the same as in the closed issue [#9438](https://svn.boost.org/trac10/ticket/9438#no1), because there are ambigous declarations for `ignore_unused_variable_warning(...)` in `boost` and `lemon`.

In `boostorg/geometry` the method `ignore_unused_variable_warning(...)` was replaced, [this way in #514](https://github.com/boostorg/geometry/pull/514).

- OS: Ubuntu 18.04 Bionic Beaver
- clang: 6.0
- lemon: 1.3.1
- boost: happened under 1.63 and was reproduced with boost 1.68

```c++
#include
#include

namespace bg = boost::geometry;
namespace bgi = boost::geometry::index;

using Point = boost::geometry::model::point;
using Graph = lemon::ListDigraph;
using Node = lemon::ListDigraph::Node;
typedef std::pair Pair;
using BoostRTree = bgi::rtree>;
using BoostQueryResult = std::vector;

int main()
{
Point one = Point(10, 51);
Point two = Point(10, 51);
BoostRTree rtreePair = BoostRTree();
Graph graph;
Node dummy1 = graph.addNode();
Node dummy2 = graph.addNode();

rtreePair.insert(std::make_pair(one, dummy1));
return 0;
}

```

Here is the first error instance of the compiler output.
All output has ~200k characters... so not sure if you want to see it.

```shell
In file included from /usr/include/boost/range/concepts.hpp:19:0,
from /usr/include/boost/range/size_type.hpp:20,
from /usr/include/boost/range/size.hpp:21,
from /usr/include/boost/range/functions.hpp:20,
from /usr/include/boost/range/iterator_range_core.hpp:38,
from /usr/include/boost/lexical_cast.hpp:30,
from /usr/include/boost/math/tools/convert_from_string.hpp:15,
from /usr/include/boost/math/constants/constants.hpp:13,
from /usr/include/boost/geometry/util/math.hpp:28,
from /usr/include/boost/geometry/core/radian_access.hpp:33,
from /usr/include/boost/geometry/geometry.hpp:43,
from /usr/include/boost/geometry.hpp:17,
from test.cpp:1:
/usr/include/boost/concept_check.hpp: In instantiation of ‘boost::DefaultConstructible::~DefaultConstructible() [with TT = std::pair, lemon::ListDigraphBase::Node>*]’:
/usr/include/boost/iterator/iterator_concepts.hpp:143:3: required from ‘static void boost::concepts::requirement::failed() [with Model = boost_concepts::ForwardTraversal, lemon::ListDigraphBase::Node>*>]’
/usr/include/boost/geometry/index/detail/varray.hpp:288:9: required from ‘boost::geometry::index::detail::varray::varray(Iterator, Iterator) [with Iterator = std::pair, lemon::ListDigraphBase::Node>*; Value = std::pair, lemon::ListDigraphBase::Node>; long unsigned int Capacity = 17]’
/usr/include/boost/geometry/index/detail/rtree/quadratic/redistribute_elements.hpp:116:24: required from ‘static void boost::geometry::index::detail::rtree::redistribute_elements::apply(Node&, Node&, Box&, Box&, const parameters_type&, const Translator&, Allocators&) [with Node = boost::geometry::index::detail::rtree::variant_leaf, lemon::ListDigraphBase::Node>, boost::geometry::index::quadratic<16>, boost::geometry::model::box >, boost::geometry::index::detail::rtree::allocators, lemon::ListDigraphBase::Node> >, std::pair, lemon::ListDigraphBase::Node>, boost::geometry::index::quadratic<16>, boost::geometry::model::box >, boost::geometry::index::detail::rtree::node_variant_static_tag>, boost::geometry::index::detail::rtree::node_variant_static_tag>; Value = std::pair, lemon::ListDigraphBase::Node>; Options = boost::geometry::index::detail::rtree::options, boost::geometry::index::detail::rtree::insert_default_tag, boost::geometry::index::detail::rtree::choose_by_content_diff_tag, boost::geometry::index::detail::rtree::split_default_tag, boost::geometry::index::detail::rtree::quadratic_tag, boost::geometry::index::detail::rtree::node_variant_static_tag>; Translator = boost::geometry::index::detail::translator, lemon::ListDigraphBase::Node> >, boost::geometry::index::equal_to, lemon::ListDigraphBase::Node> > >; Box = boost::geometry::model::box >; Allocators = boost::geometry::index::detail::rtree::allocators, lemon::ListDigraphBase::Node> >, std::pair, lemon::ListDigraphBase::Node>, boost::geometry::index::quadratic<16>, boost::geometry::model::box >, boost::geometry::index::detail::rtree::node_variant_static_tag>; boost::geometry::index::detail::rtree::redistribute_elements::parameters_type = boost::geometry::index::quadratic<16>]’
/usr/include/boost/geometry/index/detail/rtree/visitors/insert.hpp:164:17: required from ‘static void boost::geometry::index::detail::rtree::split::apply(boost::geometry::index::detail::rtree::split::nodes_container_type&, Node&, Box&, const parameters_type&, const Translator&, Allocators&) [with Node = boost::geometry::index::detail::rtree::variant_leaf, lemon::ListDigraphBase::Node>, boost::geometry::index::quadratic<16>, boost::geometry::model::box >, boost::geometry::index::detail::rtree::allocators, lemon::ListDigraphBase::Node> >, std::pair, lemon::ListDigraphBase::Node>, boost::geometry::index::quadratic<16>, boost::geometry::model::box >, boost::geometry::index::detail::rtree::node_variant_static_tag>, boost::geometry::index::detail::rtree::node_variant_static_tag>; Value = std::pair, lemon::ListDigraphBase::Node>; Options = boost::geometry::index::detail::rtree::options, boost::geometry::index::detail::rtree::insert_default_tag, boost::geometry::index::detail::rtree::choose_by_content_diff_tag, boost::geometry::index::detail::rtree::split_default_tag, boost::geometry::index::detail::rtree::quadratic_tag, boost::geometry::index::detail::rtree::node_variant_static_tag>; Translator = boost::geometry::index::detail::translator, lemon::ListDigraphBase::Node> >, boost::geometry::index::equal_to, lemon::ListDigraphBase::Node> > >; Box = boost::geometry::model::box >; Allocators = boost::geometry::index::detail::rtree::allocators, lemon::ListDigraphBase::Node> >, std::pair, lemon::ListDigraphBase::Node>, boost::geometry::index::quadratic<16>, boost::geometry::model::box >, boost::geometry::index::detail::rtree::node_variant_static_tag>; boost::geometry::index::detail::rtree::split::nodes_container_type = boost::geometry::index::detail::varray >, boost::variant, lemon::ListDigraphBase::Node>, boost::geometry::index::quadratic<16>, boost::geometry::model::box >, boost::geometry::index::detail::rtree::allocators, lemon::ListDigraphBase::Node> >, std::pair, lemon::ListDigraphBase::Node>, boost::geometry::index::quadratic<16>, boost::geometry::model::box >, boost::geometry::index::detail::rtree::node_variant_static_tag>, boost::geometry::index::detail::rtree::node_variant_static_tag>, boost::geometry::index::detail::rtree::variant_internal_node, lemon::ListDigraphBase::Node>, boost::geometry::index::quadratic<16, 4>, boost::geometry::model::box >, boost::geometry::index::detail::rtree::allocators, lemon::ListDigraphBase::Node> >, std::pair, lemon::ListDigraphBase::Node>, boost::geometry::index::quadratic<16, 4>, boost::geometry::model::box >, boost::geometry::index::detail::rtree::node_variant_static_tag>, boost::geometry::index::detail::rtree::node_variant_static_tag> >*>, 1>; typename boost::geometry::index::detail::rtree::elements_type::type>::type::value_type = boost::geometry::index::detail::rtree::ptr_pair >, boost::variant, lemon::ListDigraphBase::Node>, boost::geometry::index::quadratic<16>, boost::geometry::model::box >, boost::geometry::index::detail::rtree::allocators, lemon::ListDigraphBase::Node> >, std::pair, lemon::ListDigraphBase::Node>, boost::geometry::index::quadratic<16>, boost::geometry::model::box >, boost::geometry::index::detail::rtree::node_variant_static_tag>, boost::geometry::index::detail::rtree::node_variant_static_tag>, boost::geometry::index::detail::rtree::variant_internal_node, lemon::ListDigraphBase::Node>, boost::geometry::index::quadratic<16, 4>, boost::geometry::model::box >, boost::geometry::index::detail::rtree::allocators, lemon::ListDigraphBase::Node> >, std::pair, lemon::ListDigraphBase::Node>, boost::geometry::index::quadratic<16, 4>, boost::geometry::model::box >, boost::geometry::index::detail::rtree::node_variant_static_tag>, boost::geometry::index::detail::rtree::node_variant_static_tag> >*>; boost::geometry::index::detail::rtree::split::parameters_type = boost::geometry::index::quadratic<16>]’
/usr/include/boost/geometry/index/detail/rtree/visitors/insert.hpp:357:26: required from ‘void boost::geometry::index::detail::rtree::visitors::detail::insert::split(Node&) const [with Node = boost::geometry::index::detail::rtree::variant_leaf, lemon::ListDigraphBase::Node>, boost::geometry::index::quadratic<16>, boost::geometry::model::box >, boost::geometry::index::detail::rtree::allocators, lemon::ListDigraphBase::Node> >, std::pair, lemon::ListDigraphBase::Node>, boost::geometry::index::quadratic<16>, boost::geometry::model::box >, boost::geometry::index::detail::rtree::node_variant_static_tag>, boost::geometry::index::detail::rtree::node_variant_static_tag>; Element = std::pair, lemon::ListDigraphBase::Node>; Value = std::pair, lemon::ListDigraphBase::Node>; Options = boost::geometry::index::detail::rtree::options, boost::geometry::index::detail::rtree::insert_default_tag, boost::geometry::index::detail::rtree::choose_by_content_diff_tag, boost::geometry::index::detail::rtree::split_default_tag, boost::geometry::index::detail::rtree::quadratic_tag, boost::geometry::index::detail::rtree::node_variant_static_tag>; Translator = boost::geometry::index::detail::translator, lemon::ListDigraphBase::Node> >, boost::geometry::index::equal_to, lemon::ListDigraphBase::Node> > >; Box = boost::geometry::model::box >; Allocators = boost::geometry::index::detail::rtree::allocators, lemon::ListDigraphBase::Node> >, std::pair, lemon::ListDigraphBase::Node>, boost::geometry::index::quadratic<16>, boost::geometry::model::box >, boost::geometry::index::detail::rtree::node_variant_static_tag>]’
/usr/include/boost/geometry/index/detail/rtree/visitors/insert.hpp:326:18: [ skipping 8 instantiation contexts, use -ftemplate-backtrace-limit=0 to disable ]
/usr/include/boost/variant/variant.hpp:2431:52: required from ‘typename Visitor::result_type boost::variant::apply_visitor(Visitor&) [with Visitor = boost::geometry::index::detail::rtree::visitors::insert, lemon::ListDigraphBase::Node>, std::pair, lemon::ListDigraphBase::Node>, boost::geometry::index::detail::rtree::options, boost::geometry::index::detail::rtree::insert_default_tag, boost::geometry::index::detail::rtree::choose_by_content_diff_tag, boost::geometry::index::detail::rtree::split_default_tag, boost::geometry::index::detail::rtree::quadratic_tag, boost::geometry::index::detail::rtree::node_variant_static_tag>, boost::geometry::index::detail::translator, lemon::ListDigraphBase::Node> >, boost::geometry::index::equal_to, lemon::ListDigraphBase::Node> > >, boost::geometry::model::box >, boost::geometry::index::detail::rtree::allocators, lemon::ListDigraphBase::Node> >, std::pair, lemon::ListDigraphBase::Node>, boost::geometry::index::quadratic<16>, boost::geometry::model::box >, boost::geometry::index::detail::rtree::node_variant_static_tag>, boost::geometry::index::detail::rtree::insert_default_tag>; T0_ = boost::geometry::index::detail::rtree::variant_leaf, lemon::ListDigraphBase::Node>, boost::geometry::index::quadratic<16>, boost::geometry::model::box >, boost::geometry::index::detail::rtree::allocators, lemon::ListDigraphBase::Node> >, std::pair, lemon::ListDigraphBase::Node>, boost::geometry::index::quadratic<16>, boost::geometry::model::box >, boost::geometry::index::detail::rtree::node_variant_static_tag>, boost::geometry::index::detail::rtree::node_variant_static_tag>; TN = {boost::geometry::index::detail::rtree::variant_internal_node, lemon::ListDigraphBase::Node>, boost::geometry::index::quadratic<16, 4>, boost::geometry::model::box >, boost::geometry::index::detail::rtree::allocators, lemon::ListDigraphBase::Node> >, std::pair, lemon::ListDigraphBase::Node>, boost::geometry::index::quadratic<16, 4>, boost::geometry::model::box >, boost::geometry::index::detail::rtree::node_variant_static_tag>, boost::geometry::index::detail::rtree::node_variant_static_tag>}; typename Visitor::result_type = void]’
/usr/include/boost/variant/detail/apply_visitor_unary.hpp:70:43: required from ‘typename Visitor::result_type boost::apply_visitor(Visitor&, Visitable&) [with Visitor = boost::geometry::index::detail::rtree::visitors::insert, lemon::ListDigraphBase::Node>, std::pair, lemon::ListDigraphBase::Node>, boost::geometry::index::detail::rtree::options, boost::geometry::index::detail::rtree::insert_default_tag, boost::geometry::index::detail::rtree::choose_by_content_diff_tag, boost::geometry::index::detail::rtree::split_default_tag, boost::geometry::index::detail::rtree::quadratic_tag, boost::geometry::index::detail::rtree::node_variant_static_tag>, boost::geometry::index::detail::translator, lemon::ListDigraphBase::Node> >, boost::geometry::index::equal_to, lemon::ListDigraphBase::Node> > >, boost::geometry::model::box >, boost::geometry::index::detail::rtree::allocators, lemon::ListDigraphBase::Node> >, std::pair, lemon::ListDigraphBase::Node>, boost::geometry::index::quadratic<16>, boost::geometry::model::box >, boost::geometry::index::detail::rtree::node_variant_static_tag>, boost::geometry::index::detail::rtree::insert_default_tag>; Visitable = boost::variant, lemon::ListDigraphBase::Node>, boost::geometry::index::quadratic<16>, boost::geometry::model::box >, boost::geometry::index::detail::rtree::allocators, lemon::ListDigraphBase::Node> >, std::pair, lemon::ListDigraphBase::Node>, boost::geometry::index::quadratic<16>, boost::geometry::model::box >, boost::geometry::index::detail::rtree::node_variant_static_tag>, boost::geometry::index::detail::rtree::node_variant_static_tag>, boost::geometry::index::detail::rtree::variant_internal_node, lemon::ListDigraphBase::Node>, boost::geometry::index::quadratic<16, 4>, boost::geometry::model::box >, boost::geometry::index::detail::rtree::allocators, lemon::ListDigraphBase::Node> >, std::pair, lemon::ListDigraphBase::Node>, boost::geometry::index::quadratic<16, 4>, boost::geometry::model::box >, boost::geometry::index::detail::rtree::node_variant_static_tag>, boost::geometry::index::detail::rtree::node_variant_static_tag> >; typename Visitor::result_type = void]’
/usr/include/boost/geometry/index/detail/rtree/node/variant_visitor.hpp:51:25: required from ‘void boost::geometry::index::detail::rtree::apply_visitor(Visitor&, boost::variant, boost::geometry::index::detail::rtree::variant_internal_node >&) [with Visitor = boost::geometry::index::detail::rtree::visitors::insert, lemon::ListDigraphBase::Node>, std::pair, lemon::ListDigraphBase::Node>, boost::geometry::index::detail::rtree::options, boost::geometry::index::detail::rtree::insert_default_tag, boost::geometry::index::detail::rtree::choose_by_content_diff_tag, boost::geometry::index::detail::rtree::split_default_tag, boost::geometry::index::detail::rtree::quadratic_tag, boost::geometry::index::detail::rtree::node_variant_static_tag>, boost::geometry::index::detail::translator, lemon::ListDigraphBase::Node> >, boost::geometry::index::equal_to, lemon::ListDigraphBase::Node> > >, boost::geometry::model::box >, boost::geometry::index::detail::rtree::allocators, lemon::ListDigraphBase::Node> >, std::pair, lemon::ListDigraphBase::Node>, boost::geometry::index::quadratic<16>, boost::geometry::model::box >, boost::geometry::index::detail::rtree::node_variant_static_tag>, boost::geometry::index::detail::rtree::insert_default_tag>; Value = std::pair, lemon::ListDigraphBase::Node>; Parameters = boost::geometry::index::quadratic<16>; Box = boost::geometry::model::box >; Allocators = boost::geometry::index::detail::rtree::allocators, lemon::ListDigraphBase::Node> >, std::pair, lemon::ListDigraphBase::Node>, boost::geometry::index::quadratic<16>, boost::geometry::model::box >, boost::geometry::index::detail::rtree::node_variant_static_tag>; Tag = boost::geometry::index::detail::rtree::node_variant_static_tag]’
/usr/include/boost/geometry/index/rtree.hpp:1454:37: required from ‘void boost::geometry::index::rtree::raw_insert(const value_type&) [with Value = std::pair, lemon::ListDigraphBase::Node>; Parameters = boost::geometry::index::quadratic<16>; IndexableGetter = boost::geometry::index::indexable, lemon::ListDigraphBase::Node> >; EqualTo = boost::geometry::index::equal_to, lemon::ListDigraphBase::Node> >; Allocator = std::allocator, lemon::ListDigraphBase::Node> >; boost::geometry::index::rtree::value_type = std::pair, lemon::ListDigraphBase::Node>]’
/usr/include/boost/geometry/index/rtree.hpp:582:15: required from ‘void boost::geometry::index::rtree::insert(const value_type&) [with Value = std::pair, lemon::ListDigraphBase::Node>; Parameters = boost::geometry::index::quadratic<16>; IndexableGetter = boost::geometry::index::indexable, lemon::ListDigraphBase::Node> >; EqualTo = boost::geometry::index::equal_to, lemon::ListDigraphBase::Node> >; Allocator = std::allocator, lemon::ListDigraphBase::Node> >; boost::geometry::index::rtree::value_type = std::pair, lemon::ListDigraphBase::Node>]’
test.cpp:23:49: required from here
/usr/include/boost/concept_check.hpp:139:37: error: call of overloaded ‘ignore_unused_variable_warning(std::pair, lemon::ListDigraphBase::Node>*&)’ is ambiguous
ignore_unused_variable_warning(a);
```