How to get BOOST_FOREACH working with noncopyable rvalues? - c++

Question

The following code https://godbolt.org/z/X0na5H fails to compile the rvalue version of the following code. I've used the BOOST_FOREACH extensibility guidelines I found here
In short I can't seem to get boost_foreach working with noncopyabe rvalues. Is this even possible?
#include <boost/optional.hpp>
#include <boost/foreach.hpp>
#include <vector>
struct IdentityOp : std::vector<int>, boost::noncopyable {
IdentityOp(std::vector<int> && v):std::vector<int>(std::move(v)){}
};
namespace boost { namespace foreach
{
template <>
struct is_noncopyable< IdentityOp >
: mpl::true_
{
};
}}
#define BGS_TEST_LVALUE
// At global scope...
inline boost::mpl::true_ *
boost_foreach_is_noncopyable( IdentityOp *&, boost::foreach::tag )
{
return 0;
}
int main(){
std::vector<int> v;
#ifdef BGS_TEST_LVALUE
// LVALUE VERSION
IdentityOp op(std::move(v));
BOOST_FOREACH(const auto & a, op)
#else
// RVALUE VERSION
BOOST_FOREACH(const auto & a, IdentityOp(std::move(v)))
#endif
{}
}
shows the problem. If I define BGS_TEST_LVALUE then the code compiles. If I don't define it I get the error.
In file included from <source>:2:
/celibs/boost_1_70_0/boost/foreach.hpp: In instantiation of 'boost::foreach_detail_::auto_any<T> boost::foreach_detail_::contain(const T&, mpl_::true_*) [with T = IdentityOp; mpl_::true_ = mpl_::bool_<true>]':
<source>:34:5: required from here
/celibs/boost_1_70_0/boost/foreach.hpp:632:25: error: use of deleted function 'boost::foreach_detail_::auto_any<IdentityOp>::auto_any(boost::foreach_detail_::auto_any<IdentityOp>&&)'
632 | return auto_any<T>(t);
| ^
/celibs/boost_1_70_0/boost/foreach.hpp:253:8: note: 'boost::foreach_detail_::auto_any<IdentityOp>::auto_any(boost::foreach_detail_::auto_any<IdentityOp>&&)' is implicitly deleted because the default definition would be ill-formed:
253 | struct auto_any : auto_any_base
| ^~~~~~~~
/celibs/boost_1_70_0/boost/foreach.hpp:253:8: error: call of overloaded 'IdentityOp(IdentityOp)' is ambiguous
<source>:8:5: note: candidate: 'IdentityOp::IdentityOp(std::vector<int>&&)'
8 | IdentityOp(std::vector<int> && v):std::vector<int>(std::move(v)){}
| ^~~~~~~~~~
<source>:7:9: note: candidate: 'IdentityOp::IdentityOp(const IdentityOp&)' <deleted>
7 | struct IdentityOp : std::vector<int>, boost::noncopyable {
| ^~~~~~~~~~
<source>:7:9: note: candidate: 'IdentityOp::IdentityOp(IdentityOp&&)' <deleted>
In file included from <source>:2:
/celibs/boost_1_70_0/boost/foreach.hpp: In instantiation of 'boost::foreach_detail_::auto_any<T>::auto_any(const T&) [with T = IdentityOp]':
/celibs/boost_1_70_0/boost/foreach.hpp:632:12: required from 'boost::foreach_detail_::auto_any<T> boost::foreach_detail_::contain(const T&, mpl_::true_*) [with T = IdentityOp; mpl_::true_ = mpl_::bool_<true>]'
<source>:34:5: required from here
/celibs/boost_1_70_0/boost/foreach.hpp:256:15: error: use of deleted function 'IdentityOp::IdentityOp(const IdentityOp&)'
256 | : item(t)
| ^
<source>:7:9: note: 'IdentityOp::IdentityOp(const IdentityOp&)' is implicitly deleted because the default definition would be ill-formed:
7 | struct IdentityOp : std::vector<int>, boost::noncopyable {
| ^~~~~~~~~~
<source>:7:9: error: use of deleted function 'boost::noncopyable_::noncopyable::noncopyable(const boost::noncopyable_::noncopyable&)'
In file included from /celibs/boost_1_70_0/boost/noncopyable.hpp:15,
from /celibs/boost_1_70_0/boost/foreach.hpp:72,
from <source>:2:
/celibs/boost_1_70_0/boost/core/noncopyable.hpp:49:7: note: declared here
49 | noncopyable( const noncopyable& ) = delete;
| ^~~~~~~~~~~
Compiler returned: 1
https://godbolt.org/z/X0na5H