add Enabler template argument to range_iterator, range_const_iterator and range_mutable_iterator extension points.

doc/reference/synopsis.qbk

@@ -12,7 +12,7 @@ namespace boost
     // Single Pass Range metafunctions
     //
 
-    template< class T >
+    template< class T, class Enabler=void >
     struct range_iterator;
 
     template< class T >

include/boost/range/const_iterator.hpp

@@ -62,7 +62,7 @@ struct range_const_iterator< T[sz] >
 
     } // namespace range_detail
 
-template<typename C>
+template<typename C, typename Enabler=void>
 struct range_const_iterator
         : range_detail::range_const_iterator<
             BOOST_DEDUCED_TYPENAME remove_reference<C>::type

include/boost/range/iterator.hpp

@@ -47,7 +47,7 @@ namespace boost
     
 #endif  
 
-    template< typename C >
+    template< typename C, typename Enabler=void >
     struct range_iterator
     {
 #if BOOST_WORKAROUND(BOOST_MSVC, == 1310)

include/boost/range/mutable_iterator.hpp

@@ -31,37 +31,47 @@ namespace boost
     // default
     //////////////////////////////////////////////////////////////////////////
     
-    namespace range_detail {
+    namespace range_detail
-        BOOST_RANGE_EXTRACT_OPTIONAL_TYPE( iterator )
+    {
-    }
 
-    template< typename C >
+BOOST_RANGE_EXTRACT_OPTIONAL_TYPE( iterator )
-    struct range_mutable_iterator
+
+template< typename C >
+struct range_mutable_iterator
         : range_detail::extract_iterator<
             BOOST_DEDUCED_TYPENAME remove_reference<C>::type>
-    {};
+{};
 
-    //////////////////////////////////////////////////////////////////////////
+//////////////////////////////////////////////////////////////////////////
-    // pair
+// pair
-    //////////////////////////////////////////////////////////////////////////
+//////////////////////////////////////////////////////////////////////////
 
-    template< typename Iterator >
+template< typename Iterator >
-    struct range_mutable_iterator< std::pair<Iterator,Iterator> >
+struct range_mutable_iterator< std::pair<Iterator,Iterator> >
-    {
+{
     typedef Iterator type;
-    };
+};
 
-    //////////////////////////////////////////////////////////////////////////
+//////////////////////////////////////////////////////////////////////////
-    // array
+// array
-    //////////////////////////////////////////////////////////////////////////
+//////////////////////////////////////////////////////////////////////////
 
-    template< typename T, std::size_t sz >
+template< typename T, std::size_t sz >
-    struct range_mutable_iterator< T[sz] >
+struct range_mutable_iterator< T[sz] >
-    {
+{
     typedef T* type;
-    };
+};
+
+    } // namespace range_detail
+
+template<typename C, typename Enabler=void>
+struct range_mutable_iterator
+        : range_detail::range_mutable_iterator<
+            BOOST_DEDUCED_TYPENAME remove_reference<C>::type
+        >
+{
+};
 
 } // namespace boost
 
-
 #endif

test/Jamfile.v2

@@ -187,6 +187,7 @@ test-suite range :
     [ range-test irange ]
     [ range-test istream_range ]
     [ range-test iterator ]
+    [ range-test iterator_ext ]
     [ range-test iterator_pair ]
     [ range-test iterator_range ]
     [ range-test iterator_range_drop ]

test/iterator_ext.cpp

@@ -0,0 +1,153 @@
+// Boost.Range library
+//
+//  Copyright Neil Groves 2014. Use, modification and
+//  distribution is subject to the Boost Software License, Version
+//  1.0. (See accompanying file LICENSE_1_0.txt or copy at
+//  http://www.boost.org/LICENSE_1_0.txt)
+//
+// For more information, see http://www.boost.org/libs/range/
+//
+
+#include <boost/range/iterator.hpp>
+#include <boost/static_assert.hpp>
+#include <boost/type_traits/is_same.hpp>
+#include <boost/type_traits/is_base_of.hpp>
+#include <boost/type_traits/decay.hpp>
+
+#include <boost/test/test_tools.hpp>
+#include <boost/test/unit_test.hpp>
+
+#include <vector>
+
+namespace boost_range_test
+{
+
+struct point
+{
+    int x;
+    int y;
+};
+
+class shape
+{
+public:
+    virtual ~shape()
+    {
+    }
+
+    const std::vector<point>& points() const
+    {
+        return m_points;
+    }
+
+private:
+    std::vector<point> m_points;
+};
+
+class rectangle : public shape
+{
+};
+
+class circle : public shape
+{
+};
+
+class container
+{
+    typedef std::vector<point> impl_t;
+};
+
+} // namespace boost_range_test
+
+namespace boost
+{
+    template<typename T>
+    struct range_mutable_iterator<
+            T,
+            typename boost::enable_if<
+                boost::is_base_of<
+                    boost_range_test::shape,
+                    typename boost::remove_reference<
+                        typename boost::remove_cv<T>::type
+                    >::type
+                >
+            >::type
+        >
+    {
+        typedef std::vector<boost_range_test::point>::iterator type;
+    };
+
+    template<typename T>
+    struct range_const_iterator<
+            T,
+            typename boost::enable_if<
+                boost::is_base_of<
+                    boost_range_test::shape,
+                    typename boost::remove_reference<
+                        typename boost::remove_cv<T>::type
+                    >::type
+                >
+            >::type
+        >
+    {
+        typedef std::vector<boost_range_test::point>::const_iterator type;
+    };
+
+    template<>
+    struct range_mutable_iterator<boost_range_test::container>
+    {
+        typedef std::vector<boost_range_test::point>::iterator type;
+    };
+
+    template<>
+    struct range_const_iterator<boost_range_test::container>
+    {
+        typedef std::vector<boost_range_test::point>::const_iterator type;
+    };
+}
+
+namespace boost_range_test
+{
+    template<typename Shape>
+    void test_iterator_impl()
+    {
+        BOOST_STATIC_ASSERT((
+            boost::is_same<
+                std::vector<point>::iterator,
+                typename boost::range_iterator<Shape>::type
+            >::value));
+
+        BOOST_STATIC_ASSERT((
+            boost::is_same<
+                std::vector<point>::const_iterator,
+                typename boost::range_iterator<const Shape>::type
+            >::value));
+
+    #ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
+        BOOST_STATIC_ASSERT((
+            boost::is_same<
+                std::vector<point>::iterator,
+                typename boost::range_iterator<Shape&&>::type
+            >::value));
+    #endif
+    }
+
+    void test_iterator()
+    {
+        test_iterator_impl<shape>();
+        test_iterator_impl<rectangle>();
+        test_iterator_impl<circle>();
+
+        test_iterator_impl<container>();
+    }
+} // namespace boost_range_test
+
+boost::unit_test::test_suite* init_unit_test_suite( int argc, char* argv[] )
+{
+    boost::unit_test::test_suite* test =
+        BOOST_TEST_SUITE("Boost.Range range_iterator meta-function");
+
+    test->add(BOOST_TEST_CASE(&boost_range_test::test_iterator));
+
+    return test;
+}