id	summary	reporter	owner	description	type	status	milestone	component	version	severity	resolution	keywords	cc
13037	<boost/variant/polymorphic_get.hpp> is missing include <boost/type_traits/is_const.hpp>	Adam Badura <adam.f.badura@…>	Antony Polukhin	"Trivial demonstration can be made by preparing a source file containing nothing but an inclusion of the `polymorphic_get.hpp`:
{{{#!c++
#include <boost/variant/polymorphic_get.hpp>
}}}
on GCC 6.3 with options `-Wall -Wextra -std=c++14` compiling such file produces errors:
{{{
In file included from Test.cpp:1:0:
/cygdrive/c/Programming/boost_1_64_0/boost/variant/polymorphic_get.hpp: In member function ‘boost::detail::variant::get_polymorphic_visitor<Base>::pointer boost::detail::variant::get_polymorphic_visitor<Base>::operator()(U&) const’:
/cygdrive/c/Programming/boost_1_64_0/boost/variant/polymorphic_get.hpp:121:18: error: ‘is_const’ is not a member of ‘boost’
                 (boost::is_const<base_t>::value || !boost::is_const<U>::value)
                  ^~~~~
/cygdrive/c/Programming/boost_1_64_0/boost/variant/polymorphic_get.hpp:121:18: note: suggested alternative:
In file included from /usr/lib/gcc/x86_64-pc-cygwin/6.3.0/include/c++/bits/move.h:57:0,
                 from /usr/lib/gcc/x86_64-pc-cygwin/6.3.0/include/c++/bits/nested_exception.h:40,
                 from /usr/lib/gcc/x86_64-pc-cygwin/6.3.0/include/c++/exception:171,
                 from /cygdrive/c/Programming/boost_1_64_0/boost/variant/polymorphic_get.hpp:15,
                 from Test.cpp:1:
/usr/lib/gcc/x86_64-pc-cygwin/6.3.0/include/c++/type_traits:652:12: note:   ‘std::is_const’
     struct is_const
            ^~~~~~~~
In file included from Test.cpp:1:0:
/cygdrive/c/Programming/boost_1_64_0/boost/variant/polymorphic_get.hpp:121:41: error: ‘::value’ has not been declared
                 (boost::is_const<base_t>::value || !boost::is_const<U>::value)
                                         ^~
/cygdrive/c/Programming/boost_1_64_0/boost/variant/polymorphic_get.hpp:121:53: error: ‘is_const’ is not a member of ‘boost’
                 (boost::is_const<base_t>::value || !boost::is_const<U>::value)
                                                     ^~~~~
/cygdrive/c/Programming/boost_1_64_0/boost/variant/polymorphic_get.hpp:121:53: note: suggested alternative:
In file included from /usr/lib/gcc/x86_64-pc-cygwin/6.3.0/include/c++/bits/move.h:57:0,
                 from /usr/lib/gcc/x86_64-pc-cygwin/6.3.0/include/c++/bits/nested_exception.h:40,
                 from /usr/lib/gcc/x86_64-pc-cygwin/6.3.0/include/c++/exception:171,
                 from /cygdrive/c/Programming/boost_1_64_0/boost/variant/polymorphic_get.hpp:15,
                 from Test.cpp:1:
/usr/lib/gcc/x86_64-pc-cygwin/6.3.0/include/c++/type_traits:652:12: note:   ‘std::is_const’
     struct is_const
            ^~~~~~~~
In file included from Test.cpp:1:0:
/cygdrive/c/Programming/boost_1_64_0/boost/variant/polymorphic_get.hpp:121:68: warning: logical not is only applied to the left hand side of comparison [-Wlogical-not-parentheses]
                 (boost::is_const<base_t>::value || !boost::is_const<U>::value)
                                                                    ^
/cygdrive/c/Programming/boost_1_64_0/boost/variant/polymorphic_get.hpp:121:71: error: ‘::value’ has not been declared
                 (boost::is_const<base_t>::value || !boost::is_const<U>::value)
                                                                       ^~
/cygdrive/c/Programming/boost_1_64_0/boost/variant/polymorphic_get.hpp:125:9: error: template argument 2 is invalid
         > tag_t;
         ^

}}}

Workaround it trivial - one needs to include `is_const.hpp` before including `polymorphic_get.hpp`:
{{{#!c++
#include <boost/type_traits/is_const.hpp>
#include <boost/variant/polymorphic_get.hpp>
}}}"	Bugs	closed	Boost 1.65.0	variant	Boost 1.64.0	Problem	fixed	variant