fix for http://tinyurl.com/zuohe

[SVN r35101]

include/boost/iterator/iterator_facade.hpp

@@ -293,17 +293,17 @@ namespace boost
 
     // operator->() needs special support for input iterators to strictly meet the
     // standard's requirements. If *i is not a reference type, we must still
-    // produce a (constant) lvalue to which a pointer can be formed. We do that by
+    // produce a lvalue to which a pointer can be formed. We do that by
     // returning an instantiation of this special proxy class template.
     template <class T>
     struct operator_arrow_proxy
     {
         operator_arrow_proxy(T const* px) : m_value(*px) {}
-        const T* operator->() const { return &m_value; }
+        T* operator->() const { return &m_value; }
         // This function is needed for MWCW and BCC, which won't call operator->
         // again automatically per 13.3.1.2 para 8
-        operator const T*() const { return &m_value; }
+        operator T*() const { return &m_value; }
-        T m_value;
+        mutable T m_value;
     };
 
     // A metafunction that gets the result type for operator->.  Also

test/iterator_facade.cpp

@@ -57,6 +57,34 @@ struct proxy
     int& state;
 };
     
+struct value { int x; };
+
+struct input_iter
+  : boost::iterator_facade<
+        input_iter
+      , value
+      , boost::single_pass_traversal_tag
+      , value
+    >
+{
+ public:
+    input_iter() {}
+
+    void increment()
+    {
+    }
+    value
+    dereference() const
+    {
+        return value();
+    }
+
+    bool equal(input_iter const& y) const
+    {
+        return false;
+    }
+};
+
 int main()
 {
     int state = 0;
@@ -65,5 +93,12 @@ int main()
     boost::readable_iterator_test(counter_iterator<proxy>(&state), 3);
     boost::writable_iterator_test(counter_iterator<proxy>(&state), 9, 7);
     BOOST_ASSERT(state == 8);
+
+    // test for a fix to http://tinyurl.com/zuohe
+    // These two lines should be equivalent (and both compile)
+    input_iter p;
+    (*p).x = 2;
+    p->x = 2;
+    
     return 0;
 }