Forward dereferencing operators in operator_brackets_proxy.

This allows for expressions like it[n]->foo() and (*it[n]).foo() to compile.

Author: Lastique

include/boost/iterator/iterator_facade.hpp

@@ -9,6 +9,7 @@
 
 #include <cstddef>
 #include <memory>
+#include <utility>
 #include <type_traits>
 
 #include <boost/config.hpp>
@@ -370,6 +371,19 @@ class operator_brackets_proxy
         return *this;
     }
 
+    // Provides it[n]->foo(). Leverages chaining of operator->.
+    reference operator->() const noexcept(noexcept(*m_iter))
+    {
+        return *m_iter;
+    }
+
+    // Provides (*it[n]).foo()
+    template< typename Ref = reference, typename Result = decltype(*std::declval< Ref >()) >
+    Result operator*() const noexcept(noexcept(**m_iter))
+    {
+        return **m_iter;
+    }
+
 private:
     Iterator m_iter;
 };

test/iterator_adaptor_test.cpp

@@ -189,6 +189,16 @@ main()
     boost::const_nonconst_iterator_test(i, ++j);
   }
 
+  // Test that operator_brackets_proxy forwards operator-> and operator*
+  {
+    dummyT* ptr_array[] = { array + 0, array + 1, array + 2,
+                            array + 3, array + 4, array + 5 };
+
+    ptr_iterator<dummyT*> i(ptr_array);
+    BOOST_TEST_EQ(i[2]->foo(), 2);
+    BOOST_TEST_EQ((*i[2]).foo(), 2);
+  }
+
   int test;
   // Test the iterator_traits
   {