Compile time detection for unimplemented stl-style iterators

3 files changed, 27 insertions, 1 deletions

diff --git a/Eigen/src/Core/DenseBase.h b/Eigen/src/Core/DenseBase.h
index 0c34bce40..eedeacc94 100644
--- a/Eigen/src/Core/DenseBase.h
+++ b/Eigen/src/Core/DenseBase.h
@@ -583,11 +583,23 @@ template<typename Derived> class DenseBase
     typedef typename internal::conditional< (Flags&DirectAccessBit)==DirectAccessBit,
                                             internal::pointer_based_stl_iterator<Derived>,
                                             internal::generic_randaccess_stl_iterator<Derived>
-                                          >::type iterator;
+                                          >::type iterator_type;
 
     typedef typename internal::conditional< (Flags&DirectAccessBit)==DirectAccessBit,
                                             internal::pointer_based_stl_iterator<const Derived>,
                                             internal::generic_randaccess_stl_iterator<const Derived>
+                                          >::type const_iterator_type;
+
+    // Stl-style iterators are supported only for vectors.
+
+    typedef typename internal::conditional< IsVectorAtCompileTime,
+                                            iterator_type,
+                                            internal::not_an_iterator<const Derived>
+                                          >::type iterator;
+
+    typedef typename internal::conditional< IsVectorAtCompileTime,
+                                            const_iterator_type,
+                                            internal::not_an_iterator<const Derived>
                                           >::type const_iterator;
     #endif
 
diff --git a/Eigen/src/Core/StlIterators.h b/Eigen/src/Core/StlIterators.h
index 24eef1269..5f2edc4e6 100644
--- a/Eigen/src/Core/StlIterators.h
+++ b/Eigen/src/Core/StlIterators.h
@@ -11,6 +11,19 @@ namespace Eigen {
 
 namespace internal {
 
+// Iterator type for XprType that do not support stl-style iterators. Allows to
+// detect that expression does not support stl iterators at compile time.
+template<typename XprType>
+class not_an_iterator
+{
+  not_an_iterator() : mp_xpr(0), m_index(0) {}
+  not_an_iterator(XprType& xpr, Index index) : mp_xpr(&xpr), m_index(index) {}
+
+ protected:
+  XprType *mp_xpr;
+  Index m_index;
+};
+
 template<typename XprType,typename Derived>
 class indexed_based_stl_iterator_base
 {
diff --git a/Eigen/src/Core/util/ForwardDeclarations.h b/Eigen/src/Core/util/ForwardDeclarations.h
index 3ab3a5f50..49c4e0c31 100644
--- a/Eigen/src/Core/util/ForwardDeclarations.h
+++ b/Eigen/src/Core/util/ForwardDeclarations.h
@@ -135,6 +135,7 @@ template<typename Derived> class SolverBase;
 template<typename XprType> class InnerIterator;
 
 namespace internal {
+template<typename XprType> class not_an_iterator;
 template<typename XprType> class generic_randaccess_stl_iterator;
 template<typename XprType> class pointer_based_stl_iterator;
 template<typename XprType, DirectionType Direction> class subvector_stl_iterator;