Add an rvalue-qualified overload of closure::operator(). This makes

forwarding work properly in cases such as r | foo(std::string("foo")), where
foo is an adaptor.  Without this, the std::string temporary dangles.

include/boost/stl_interfaces/view_adaptor.hpp

@@ -242,11 +242,24 @@ namespace boost { namespace stl_interfaces {
             typename Enable =
                 std::enable_if_t<detail::is_invocable_v<F const &, T>>>
 #endif
-        constexpr decltype(auto) operator()(T && t) const
+        constexpr decltype(auto) operator()(T && t) const &
         {
             return f_((T &&) t);
         }
 
+#if BOOST_STL_INTERFACES_USE_CONCEPTS
+        template<typename T>
+        requires std::invocable<F &&, T>
+#else
+        template<
+            typename T,
+            typename Enable = std::enable_if_t<detail::is_invocable_v<F &&, T>>>
+#endif
+        constexpr decltype(auto) operator()(T && t) &&
+        {
+            return std::move(f_)((T &&) t);
+        }
+
     private:
         F f_;
     };