Move-assign the contents of the specified rhs map into this map.
Declared in <bslstl_map.h>
map<KEY, VALUE, COMPARATOR, ALLOCATOR>&
operator=(BloombergLP::bslmf::MovableRef<map> rhs) noexcept(/* see-below */);This function is potentially-throwing unless AllocatorTraits::is_always_equal::value && std::is_nothrow_move_assignable<COMPARATOR>::value.