[boost] [thread] locks.hpp double declaration of unique_lock(unique_lock&& other)

Subject: [boost] [thread] locks.hpp double declaration of unique_lock(unique_lock&& other)
From: vicente.botet (vicente.botet_at_[hidden])
Date: 2009-01-21 12:06:29

Hi in lines  248-255 of the file boost/thread/locks.hpp we found the unique_lock(unique_lock&& other) declaration twice one withoth explicit and defined and the other with explicit an undefined.

#ifdef BOOST_HAS_RVALUE_REFS
        unique_lock(unique_lock&& other):
            m(other.m),is_locked(other.is_locked)
        {
            other.is_locked=false;
            other.m=0;
        }
        explicit unique_lock(upgrade_lock<Mutex>&& other);

Could you say me why this is nesded? 
_____________________
Vicente Juan Botet Escribá