ext/boost/range/concepts.hpp in passenger-3.0.21 vs ext/boost/range/concepts.hpp in passenger-3.9.1.beta

@@ -96,12 +96,13 @@
 
         // Rationale for the inclusion of redefined iterator concept
         // classes:
         //
         // The Range algorithms often do not require that the iterators are
-        // Assignable, but the correct standard conformant iterators
-        // do require the iterators to be a model of the Assignable concept.
+        // Assignable or default constructable, but the correct standard
+        // conformant iterators do require the iterators to be a model of the
+        // Assignable concept.
         // Iterators that contains a functor that is not assignable therefore
         // are not correct models of the standard iterator concepts,
         // despite being adequate for most algorithms. An example of this
         // use case is the combination of the boost::adaptors::filtered
         // class with a boost::lambda::bind generated functor.
@@ -139,10 +140,30 @@
             BOOST_RANGE_CONCEPT_ASSERT((
                 Convertible<
                     BOOST_DEDUCED_TYPENAME SinglePassIteratorConcept::traversal_category,
                     single_pass_traversal_tag
                 >));
+
+            BOOST_CONCEPT_USAGE(SinglePassIteratorConcept)
+            {
+                Iterator i2(++i);
+                boost::ignore_unused_variable_warning(i2);
+
+                // deliberately we are loose with the postfix version for the single pass
+                // iterator due to the commonly poor adherence to the specification means that
+                // many algorithms would be unusable, whereas actually without the check they
+                // work
+                (void)(i++);
+
+                BOOST_DEDUCED_TYPENAME boost::detail::iterator_traits<Iterator>::reference r1(*i);
+                boost::ignore_unused_variable_warning(r1);
+
+                BOOST_DEDUCED_TYPENAME boost::detail::iterator_traits<Iterator>::reference r2(*(++i));
+                boost::ignore_unused_variable_warning(r2);
+            }
+        private:
+            Iterator i;
 #endif
         };
 
         template<class Iterator>
         struct ForwardIteratorConcept
@@ -158,9 +179,23 @@
             BOOST_RANGE_CONCEPT_ASSERT((
                 Convertible<
                     BOOST_DEDUCED_TYPENAME ForwardIteratorConcept::traversal_category,
                     forward_traversal_tag
                 >));
+
+            BOOST_CONCEPT_USAGE(ForwardIteratorConcept)
+            {
+                // See the above note in the SinglePassIteratorConcept about the handling of the
+                // postfix increment. Since with forward and better iterators there is no need
+                // for a proxy, we can sensibly require that the dereference result
+                // is convertible to reference.
+                Iterator i2(i++);
+                boost::ignore_unused_variable_warning(i2);
+                BOOST_DEDUCED_TYPENAME boost::detail::iterator_traits<Iterator>::reference r(*(i++));
+                boost::ignore_unused_variable_warning(r);
+            }
+        private:
+            Iterator i;
 #endif
          };
 
          template<class Iterator>
          struct BidirectionalIteratorConcept