The following code works well (incl. your mentioned cases) both in C++03 and C++11 on gcc. <snip> static bool const rval_to_nonconst_lval_ref_conv = ::boost::type_traits::ice_and< !(::boost::is_function<From>::value) // Note: an rvalue ref to function type is an lvalue , !(::boost::is_reference<From>::value) , ::boost::is_reference<To>::value , !(::boost::is_const<typename ::boost::remove_reference<To>::type>::value) >::value;
Sorry, the above code is wrong. It does not detect binding const volatile reference to an rvalue. Here is a right code:
static bool const rval_to_nonconst_lval_ref_conv = ::boost::type_traits::ice_and< !(::boost::is_function<From>::value) // Note: an rvalue ref to function type is an lvalue , !(::boost::is_reference<From>::value) , ::boost::is_reference<To>::value , ::boost::type_traits::ice_or< !::boost::is_const<typename ::boost::remove_reference<To>::type>::value , ::boost::type_traits::ice_and< ::boost::is_const<typename ::boost::remove_reference<To>::type>::value , ::boost::is_volatile<typename ::boost::remove_reference<To>::type>::value >::value >::value
::value;
Michel, Apologies for the delay, as I have no time right now, can you please let me have this as a patch, and verify our test suite passes? Any changes should also probably be dependent upon BOOST_NO_SFINAE_EXPR as well as I believe the technique depends upon that. Sorry for the abundance of caution, but something somewhere usually breaks when we mess with a header like that, and there's a limit to how many folks I'm willing to annoy to fix a corner case! ;-) Cheers, John.