I'd expect boost::is_convertible<int, int&>::value to be false, so I was surprised that it gives me "true" under g++ 4.7.1. Switch to std::is_convertible<int, int&> or using clang instead gives me the expected "false".

After some search, I found: https://svn.boost.org/trac/boost/ticket/7251

Any plan to fix it?

Yes, but it's tricky to do without breaking stuff, I will get back to this eventually though, John.