bug #178: remove additional const on nested expression, and remove several const_cast.

Eigen/src/Core/ArrayWrapper.h

@@ -52,7 +52,7 @@ class ArrayWrapper : public ArrayBase<ArrayWrapper<ExpressionType> >
                        const Scalar
                      >::type ScalarWithConstIfNotLvalue;
 
-    typedef typename internal::ref_selector<ExpressionType>::type NestedExpressionType;
+    typedef typename internal::ref_selector<ExpressionType>::non_const_type NestedExpressionType;
 
     EIGEN_DEVICE_FUNC
     explicit EIGEN_STRONG_INLINE ArrayWrapper(ExpressionType& matrix) : m_expression(matrix) {}
@@ -67,7 +67,7 @@ class ArrayWrapper : public ArrayBase<ArrayWrapper<ExpressionType> >
     inline Index innerStride() const { return m_expression.innerStride(); }
 
     EIGEN_DEVICE_FUNC
-    inline ScalarWithConstIfNotLvalue* data() { return m_expression.const_cast_derived().data(); }
+    inline ScalarWithConstIfNotLvalue* data() { return m_expression.data(); }
     EIGEN_DEVICE_FUNC
     inline const Scalar* data() const { return m_expression.data(); }
 
@@ -80,13 +80,13 @@ class ArrayWrapper : public ArrayBase<ArrayWrapper<ExpressionType> >
     EIGEN_DEVICE_FUNC
     inline Scalar& coeffRef(Index rowId, Index colId)
     {
-      return m_expression.const_cast_derived().coeffRef(rowId, colId);
+      return m_expression.coeffRef(rowId, colId);
     }
 
     EIGEN_DEVICE_FUNC
     inline const Scalar& coeffRef(Index rowId, Index colId) const
     {
-      return m_expression.const_cast_derived().coeffRef(rowId, colId);
+      return m_expression.coeffRef(rowId, colId);
     }
 
     EIGEN_DEVICE_FUNC
@@ -98,13 +98,13 @@ class ArrayWrapper : public ArrayBase<ArrayWrapper<ExpressionType> >
     EIGEN_DEVICE_FUNC
     inline Scalar& coeffRef(Index index)
     {
-      return m_expression.const_cast_derived().coeffRef(index);
+      return m_expression.coeffRef(index);
     }
 
     EIGEN_DEVICE_FUNC
     inline const Scalar& coeffRef(Index index) const
     {
-      return m_expression.const_cast_derived().coeffRef(index);
+      return m_expression.coeffRef(index);
     }
 
     template<int LoadMode>
@@ -116,7 +116,7 @@ class ArrayWrapper : public ArrayBase<ArrayWrapper<ExpressionType> >
     template<int LoadMode>
     inline void writePacket(Index rowId, Index colId, const PacketScalar& val)
     {
-      m_expression.const_cast_derived().template writePacket<LoadMode>(rowId, colId, val);
+      m_expression.template writePacket<LoadMode>(rowId, colId, val);
     }
 
     template<int LoadMode>
@@ -128,7 +128,7 @@ class ArrayWrapper : public ArrayBase<ArrayWrapper<ExpressionType> >
     template<int LoadMode>
     inline void writePacket(Index index, const PacketScalar& val)
     {
-      m_expression.const_cast_derived().template writePacket<LoadMode>(index, val);
+      m_expression.template writePacket<LoadMode>(index, val);
     }
 
     template<typename Dest>
@@ -145,11 +145,11 @@ class ArrayWrapper : public ArrayBase<ArrayWrapper<ExpressionType> >
     /** Forwards the resizing request to the nested expression
       * \sa DenseBase::resize(Index)  */
     EIGEN_DEVICE_FUNC
-    void resize(Index newSize) { m_expression.const_cast_derived().resize(newSize); }
+    void resize(Index newSize) { m_expression.resize(newSize); }
     /** Forwards the resizing request to the nested expression
       * \sa DenseBase::resize(Index,Index)*/
     EIGEN_DEVICE_FUNC
-    void resize(Index rows, Index cols) { m_expression.const_cast_derived().resize(rows,cols); }
+    void resize(Index rows, Index cols) { m_expression.resize(rows,cols); }
 
   protected:
     NestedExpressionType m_expression;
@@ -195,7 +195,7 @@ class MatrixWrapper : public MatrixBase<MatrixWrapper<ExpressionType> >
                        const Scalar
                      >::type ScalarWithConstIfNotLvalue;
 
-    typedef typename internal::ref_selector<ExpressionType>::type NestedExpressionType;
+    typedef typename internal::ref_selector<ExpressionType>::non_const_type NestedExpressionType;
 
     EIGEN_DEVICE_FUNC
     explicit inline MatrixWrapper(ExpressionType& matrix) : m_expression(matrix) {}
@@ -210,7 +210,7 @@ class MatrixWrapper : public MatrixBase<MatrixWrapper<ExpressionType> >
     inline Index innerStride() const { return m_expression.innerStride(); }
 
     EIGEN_DEVICE_FUNC
-    inline ScalarWithConstIfNotLvalue* data() { return m_expression.const_cast_derived().data(); }
+    inline ScalarWithConstIfNotLvalue* data() { return m_expression.data(); }
     EIGEN_DEVICE_FUNC
     inline const Scalar* data() const { return m_expression.data(); }
 
@@ -223,7 +223,7 @@ class MatrixWrapper : public MatrixBase<MatrixWrapper<ExpressionType> >
     EIGEN_DEVICE_FUNC
     inline Scalar& coeffRef(Index rowId, Index colId)
     {
-      return m_expression.const_cast_derived().coeffRef(rowId, colId);
+      return m_expression.coeffRef(rowId, colId);
     }
 
     EIGEN_DEVICE_FUNC
@@ -241,13 +241,13 @@ class MatrixWrapper : public MatrixBase<MatrixWrapper<ExpressionType> >
     EIGEN_DEVICE_FUNC
     inline Scalar& coeffRef(Index index)
     {
-      return m_expression.const_cast_derived().coeffRef(index);
+      return m_expression.coeffRef(index);
     }
 
     EIGEN_DEVICE_FUNC
     inline const Scalar& coeffRef(Index index) const
     {
-      return m_expression.const_cast_derived().coeffRef(index);
+      return m_expression.coeffRef(index);
     }
 
     template<int LoadMode>
@@ -259,7 +259,7 @@ class MatrixWrapper : public MatrixBase<MatrixWrapper<ExpressionType> >
     template<int LoadMode>
     inline void writePacket(Index rowId, Index colId, const PacketScalar& val)
     {
-      m_expression.const_cast_derived().template writePacket<LoadMode>(rowId, colId, val);
+      m_expression.template writePacket<LoadMode>(rowId, colId, val);
     }
 
     template<int LoadMode>
@@ -271,7 +271,7 @@ class MatrixWrapper : public MatrixBase<MatrixWrapper<ExpressionType> >
     template<int LoadMode>
     inline void writePacket(Index index, const PacketScalar& val)
     {
-      m_expression.const_cast_derived().template writePacket<LoadMode>(index, val);
+      m_expression.template writePacket<LoadMode>(index, val);
     }
 
     EIGEN_DEVICE_FUNC
@@ -284,11 +284,11 @@ class MatrixWrapper : public MatrixBase<MatrixWrapper<ExpressionType> >
     /** Forwards the resizing request to the nested expression
       * \sa DenseBase::resize(Index)  */
     EIGEN_DEVICE_FUNC
-    void resize(Index newSize) { m_expression.const_cast_derived().resize(newSize); }
+    void resize(Index newSize) { m_expression.resize(newSize); }
     /** Forwards the resizing request to the nested expression
       * \sa DenseBase::resize(Index,Index)*/
     EIGEN_DEVICE_FUNC
-    void resize(Index rows, Index cols) { m_expression.const_cast_derived().resize(rows,cols); }
+    void resize(Index rows, Index cols) { m_expression.resize(rows,cols); }
 
   protected:
     NestedExpressionType m_expression;

Eigen/src/Core/Block.h

@@ -221,15 +221,13 @@ template<typename XprType, int BlockRows, int BlockCols, bool InnerPanel, bool H
     inline Scalar& coeffRef(Index rowId, Index colId)
     {
       EIGEN_STATIC_ASSERT_LVALUE(XprType)
-      return m_xpr.const_cast_derived()
+      return m_xpr.coeffRef(rowId + m_startRow.value(), colId + m_startCol.value());
-               .coeffRef(rowId + m_startRow.value(), colId + m_startCol.value());
     }
 
     EIGEN_DEVICE_FUNC
     inline const Scalar& coeffRef(Index rowId, Index colId) const
     {
-      return m_xpr.derived()
+      return m_xpr.derived().coeffRef(rowId + m_startRow.value(), colId + m_startCol.value());
-               .coeffRef(rowId + m_startRow.value(), colId + m_startCol.value());
     }
 
     EIGEN_DEVICE_FUNC
@@ -242,39 +240,34 @@ template<typename XprType, int BlockRows, int BlockCols, bool InnerPanel, bool H
     inline Scalar& coeffRef(Index index)
     {
       EIGEN_STATIC_ASSERT_LVALUE(XprType)
-      return m_xpr.const_cast_derived()
+      return m_xpr.coeffRef(m_startRow.value() + (RowsAtCompileTime == 1 ? 0 : index),
-             .coeffRef(m_startRow.value() + (RowsAtCompileTime == 1 ? 0 : index),
+                            m_startCol.value() + (RowsAtCompileTime == 1 ? index : 0));
-                       m_startCol.value() + (RowsAtCompileTime == 1 ? index : 0));
     }
 
     EIGEN_DEVICE_FUNC
     inline const Scalar& coeffRef(Index index) const
     {
-      return m_xpr.const_cast_derived()
+      return m_xpr.coeffRef(m_startRow.value() + (RowsAtCompileTime == 1 ? 0 : index),
-             .coeffRef(m_startRow.value() + (RowsAtCompileTime == 1 ? 0 : index),
+                            m_startCol.value() + (RowsAtCompileTime == 1 ? index : 0));
-                       m_startCol.value() + (RowsAtCompileTime == 1 ? index : 0));
     }
 
     EIGEN_DEVICE_FUNC
     inline const CoeffReturnType coeff(Index index) const
     {
-      return m_xpr
+      return m_xpr.coeff(m_startRow.value() + (RowsAtCompileTime == 1 ? 0 : index),
-             .coeff(m_startRow.value() + (RowsAtCompileTime == 1 ? 0 : index),
+                         m_startCol.value() + (RowsAtCompileTime == 1 ? index : 0));
-                    m_startCol.value() + (RowsAtCompileTime == 1 ? index : 0));
     }
 
     template<int LoadMode>
     inline PacketScalar packet(Index rowId, Index colId) const
     {
-      return m_xpr.template packet<Unaligned>
+      return m_xpr.template packet<Unaligned>(rowId + m_startRow.value(), colId + m_startCol.value());
-              (rowId + m_startRow.value(), colId + m_startCol.value());
     }
 
     template<int LoadMode>
     inline void writePacket(Index rowId, Index colId, const PacketScalar& val)
     {
-      m_xpr.const_cast_derived().template writePacket<Unaligned>
+      m_xpr.template writePacket<Unaligned>(rowId + m_startRow.value(), colId + m_startCol.value(), val);
-              (rowId + m_startRow.value(), colId + m_startCol.value(), val);
     }
 
     template<int LoadMode>
@@ -288,7 +281,7 @@ template<typename XprType, int BlockRows, int BlockCols, bool InnerPanel, bool H
     template<int LoadMode>
     inline void writePacket(Index index, const PacketScalar& val)
     {
-      m_xpr.const_cast_derived().template writePacket<Unaligned>
+      m_xpr.template writePacket<Unaligned>
          (m_startRow.value() + (RowsAtCompileTime == 1 ? 0 : index),
           m_startCol.value() + (RowsAtCompileTime == 1 ? index : 0), val);
     }
@@ -320,7 +313,7 @@ template<typename XprType, int BlockRows, int BlockCols, bool InnerPanel, bool H
 
   protected:
 
-    const typename XprType::Nested m_xpr;
+    typename XprType::Nested m_xpr;
     const internal::variable_if_dynamic<StorageIndex, XprType::RowsAtCompileTime == 1 ? 0 : Dynamic> m_startRow;
     const internal::variable_if_dynamic<StorageIndex, XprType::ColsAtCompileTime == 1 ? 0 : Dynamic> m_startCol;
     const internal::variable_if_dynamic<StorageIndex, RowsAtCompileTime> m_blockRows;

Eigen/src/Core/CwiseUnaryOp.h

@@ -58,6 +58,7 @@ class CwiseUnaryOp : public CwiseUnaryOpImpl<UnaryOp, XprType, typename internal
 
     typedef typename CwiseUnaryOpImpl<UnaryOp, XprType,typename internal::traits<XprType>::StorageKind>::Base Base;
     EIGEN_GENERIC_PUBLIC_INTERFACE(CwiseUnaryOp)
+    typedef typename internal::ref_selector<XprType>::type XprTypeNested;
     typedef typename internal::remove_all<XprType>::type NestedExpression;
 
     EIGEN_DEVICE_FUNC
@@ -75,16 +76,16 @@ class CwiseUnaryOp : public CwiseUnaryOpImpl<UnaryOp, XprType, typename internal
 
     /** \returns the nested expression */
     EIGEN_DEVICE_FUNC
-    const typename internal::remove_all<typename XprType::Nested>::type&
+    const typename internal::remove_all<XprTypeNested>::type&
     nestedExpression() const { return m_xpr; }
 
     /** \returns the nested expression */
     EIGEN_DEVICE_FUNC
-    typename internal::remove_all<typename XprType::Nested>::type&
+    typename internal::remove_all<XprTypeNested>::type&
-    nestedExpression() { return m_xpr.const_cast_derived(); }
+    nestedExpression() { return m_xpr; }
 
   protected:
-    typename XprType::Nested m_xpr;
+    XprTypeNested m_xpr;
     const UnaryOp m_functor;
 };
 

Eigen/src/Core/CwiseUnaryView.h

@@ -61,6 +61,7 @@ class CwiseUnaryView : public CwiseUnaryViewImpl<ViewOp, MatrixType, typename in
 
     typedef typename CwiseUnaryViewImpl<ViewOp, MatrixType,typename internal::traits<MatrixType>::StorageKind>::Base Base;
     EIGEN_GENERIC_PUBLIC_INTERFACE(CwiseUnaryView)
+    typedef typename internal::ref_selector<MatrixType>::non_const_type MatrixTypeNested;
     typedef typename internal::remove_all<MatrixType>::type NestedExpression;
 
     explicit inline CwiseUnaryView(MatrixType& mat, const ViewOp& func = ViewOp())
@@ -75,15 +76,15 @@ class CwiseUnaryView : public CwiseUnaryViewImpl<ViewOp, MatrixType, typename in
     const ViewOp& functor() const { return m_functor; }
 
     /** \returns the nested expression */
-    const typename internal::remove_all<typename MatrixType::Nested>::type&
+    const typename internal::remove_all<MatrixTypeNested>::type&
     nestedExpression() const { return m_matrix; }
 
     /** \returns the nested expression */
-    typename internal::remove_all<typename MatrixType::Nested>::type&
+    typename internal::remove_reference<MatrixTypeNested>::type&
     nestedExpression() { return m_matrix.const_cast_derived(); }
 
   protected:
-    typename internal::ref_selector<MatrixType>::type m_matrix;
+    MatrixTypeNested m_matrix;
     ViewOp m_functor;
 };
 

Eigen/src/Core/Diagonal.h

@@ -103,21 +103,21 @@ template<typename MatrixType, int _DiagIndex> class Diagonal
                      >::type ScalarWithConstIfNotLvalue;
 
     EIGEN_DEVICE_FUNC
-    inline ScalarWithConstIfNotLvalue* data() { return &(m_matrix.const_cast_derived().coeffRef(rowOffset(), colOffset())); }
+    inline ScalarWithConstIfNotLvalue* data() { return &(m_matrix.coeffRef(rowOffset(), colOffset())); }
     EIGEN_DEVICE_FUNC
-    inline const Scalar* data() const { return &(m_matrix.const_cast_derived().coeffRef(rowOffset(), colOffset())); }
+    inline const Scalar* data() const { return &(m_matrix.coeffRef(rowOffset(), colOffset())); }
 
     EIGEN_DEVICE_FUNC
     inline Scalar& coeffRef(Index row, Index)
     {
       EIGEN_STATIC_ASSERT_LVALUE(MatrixType)
-      return m_matrix.const_cast_derived().coeffRef(row+rowOffset(), row+colOffset());
+      return m_matrix.coeffRef(row+rowOffset(), row+colOffset());
     }
 
     EIGEN_DEVICE_FUNC
     inline const Scalar& coeffRef(Index row, Index) const
     {
-      return m_matrix.const_cast_derived().coeffRef(row+rowOffset(), row+colOffset());
+      return m_matrix.coeffRef(row+rowOffset(), row+colOffset());
     }
 
     EIGEN_DEVICE_FUNC
@@ -130,13 +130,13 @@ template<typename MatrixType, int _DiagIndex> class Diagonal
     inline Scalar& coeffRef(Index idx)
     {
       EIGEN_STATIC_ASSERT_LVALUE(MatrixType)
-      return m_matrix.const_cast_derived().coeffRef(idx+rowOffset(), idx+colOffset());
+      return m_matrix.coeffRef(idx+rowOffset(), idx+colOffset());
     }
 
     EIGEN_DEVICE_FUNC
     inline const Scalar& coeffRef(Index idx) const
     {
-      return m_matrix.const_cast_derived().coeffRef(idx+rowOffset(), idx+colOffset());
+      return m_matrix.coeffRef(idx+rowOffset(), idx+colOffset());
     }
 
     EIGEN_DEVICE_FUNC
@@ -159,7 +159,7 @@ template<typename MatrixType, int _DiagIndex> class Diagonal
     }
 
   protected:
-    typename MatrixType::Nested m_matrix;
+    typename internal::ref_selector<MatrixType>::non_const_type m_matrix;
     const internal::variable_if_dynamicindex<Index, DiagIndex> m_index;
 
   private:

Eigen/src/Core/SelfAdjointView.h

@@ -32,7 +32,7 @@ namespace internal {
 template<typename MatrixType, unsigned int UpLo>
 struct traits<SelfAdjointView<MatrixType, UpLo> > : traits<MatrixType>
 {
-  typedef typename ref_selector<MatrixType>::type MatrixTypeNested;
+  typedef typename ref_selector<MatrixType>::non_const_type MatrixTypeNested;
   typedef typename remove_all<MatrixTypeNested>::type MatrixTypeNestedCleaned;
   typedef MatrixType ExpressionType;
   typedef typename MatrixType::PlainObject FullMatrixType;
@@ -97,7 +97,7 @@ template<typename _MatrixType, unsigned int UpLo> class SelfAdjointView
     {
       EIGEN_STATIC_ASSERT_LVALUE(SelfAdjointView);
       Base::check_coordinates_internal(row, col);
-      return m_matrix.const_cast_derived().coeffRef(row, col);
+      return m_matrix.coeffRef(row, col);
     }
 
     /** \internal */
@@ -107,7 +107,7 @@ template<typename _MatrixType, unsigned int UpLo> class SelfAdjointView
     EIGEN_DEVICE_FUNC
     const MatrixTypeNestedCleaned& nestedExpression() const { return m_matrix; }
     EIGEN_DEVICE_FUNC
-    MatrixTypeNestedCleaned& nestedExpression() { return *const_cast<MatrixTypeNestedCleaned*>(&m_matrix); }
+    MatrixTypeNestedCleaned& nestedExpression() { return m_matrix; }
 
     /** Efficient triangular matrix times vector/matrix product */
     template<typename OtherDerived>

Eigen/src/Core/Transpose.h

@@ -54,6 +54,8 @@ template<typename MatrixType> class Transpose
 {
   public:
 
+    typedef typename internal::ref_selector<MatrixType>::non_const_type MatrixTypeNested;
+
     typedef typename TransposeImpl<MatrixType,typename internal::traits<MatrixType>::StorageKind>::Base Base;
     EIGEN_GENERIC_PUBLIC_INTERFACE(Transpose)
     typedef typename internal::remove_all<MatrixType>::type NestedExpression;
@@ -68,16 +70,16 @@ template<typename MatrixType> class Transpose
 
     /** \returns the nested expression */
     EIGEN_DEVICE_FUNC
-    const typename internal::remove_all<typename MatrixType::Nested>::type&
+    const typename internal::remove_all<MatrixTypeNested>::type&
     nestedExpression() const { return m_matrix; }
 
     /** \returns the nested expression */
     EIGEN_DEVICE_FUNC
-    typename internal::remove_all<typename MatrixType::Nested>::type&
+    typename internal::remove_reference<MatrixTypeNested>::type&
-    nestedExpression() { return m_matrix.const_cast_derived(); }
+    nestedExpression() { return m_matrix; }
 
   protected:
-    typename MatrixType::Nested m_matrix;
+    typename internal::ref_selector<MatrixType>::non_const_type m_matrix;
 };
 
 namespace internal {

Eigen/src/Core/Transpositions.h

@@ -325,7 +325,7 @@ class TranspositionsWrapper
 
   protected:
 
-    const typename IndicesType::Nested m_indices;
+    typename IndicesType::Nested m_indices;
 };
 
 

Eigen/src/Core/TriangularMatrix.h

@@ -168,7 +168,7 @@ namespace internal {
 template<typename MatrixType, unsigned int _Mode>
 struct traits<TriangularView<MatrixType, _Mode> > : traits<MatrixType>
 {
-  typedef typename ref_selector<MatrixType>::type MatrixTypeNested;
+  typedef typename ref_selector<MatrixType>::non_const_type MatrixTypeNested;
   typedef typename remove_reference<MatrixTypeNested>::type MatrixTypeNestedNonRef;
   typedef typename remove_all<MatrixTypeNested>::type MatrixTypeNestedCleaned;
   typedef typename MatrixType::PlainObject FullMatrixType;
@@ -213,7 +213,6 @@ template<typename _MatrixType, unsigned int _Mode> class TriangularView
       IsVectorAtCompileTime = false
     };
 
-    // FIXME This, combined with const_cast_derived in transpose() leads to a const-correctness loophole
     EIGEN_DEVICE_FUNC
     explicit inline TriangularView(MatrixType& matrix) : m_matrix(matrix)
     {}
@@ -235,7 +234,7 @@ template<typename _MatrixType, unsigned int _Mode> class TriangularView
 
     /** \returns a reference to the nested expression */
     EIGEN_DEVICE_FUNC
-    NestedExpression& nestedExpression() { return *const_cast<NestedExpression*>(&m_matrix); }
+    NestedExpression& nestedExpression() { return m_matrix; }
     
     typedef TriangularView<const MatrixConjugateReturnType,Mode> ConjugateReturnType;
     /** \sa MatrixBase::conjugate() const */
@@ -255,7 +254,7 @@ template<typename _MatrixType, unsigned int _Mode> class TriangularView
     inline TransposeReturnType transpose()
     {
       EIGEN_STATIC_ASSERT_LVALUE(MatrixType)
-      typename MatrixType::TransposeReturnType tmp(m_matrix.const_cast_derived());
+      typename MatrixType::TransposeReturnType tmp(m_matrix);
       return TransposeReturnType(tmp);
     }
     
@@ -418,7 +417,7 @@ template<typename _MatrixType, unsigned int _Mode> class TriangularViewImpl<_Mat
     {
       EIGEN_STATIC_ASSERT_LVALUE(TriangularViewType);
       Base::check_coordinates_internal(row, col);
-      return derived().nestedExpression().const_cast_derived().coeffRef(row, col);
+      return derived().nestedExpression().coeffRef(row, col);
     }
 
     /** Assigns a triangular matrix to a triangular part of a dense matrix */

Eigen/src/Core/util/XprHelper.h

@@ -466,17 +466,17 @@ struct special_scalar_op_base : public BaseType
 template<typename Derived,typename Scalar,typename OtherScalar, typename BaseType>
 struct special_scalar_op_base<Derived,Scalar,OtherScalar,BaseType,true>  : public BaseType
 {
-  const CwiseUnaryOp<scalar_multiple2_op<Scalar,OtherScalar>, Derived>
+  const CwiseUnaryOp<scalar_multiple2_op<Scalar,OtherScalar>, const Derived>
   operator*(const OtherScalar& scalar) const
   {
 #ifdef EIGEN_SPECIAL_SCALAR_MULTIPLE_PLUGIN
     EIGEN_SPECIAL_SCALAR_MULTIPLE_PLUGIN
 #endif
-    return CwiseUnaryOp<scalar_multiple2_op<Scalar,OtherScalar>, Derived>
+    return CwiseUnaryOp<scalar_multiple2_op<Scalar,OtherScalar>, const Derived>
       (*static_cast<const Derived*>(this), scalar_multiple2_op<Scalar,OtherScalar>(scalar));
   }
 
-  inline friend const CwiseUnaryOp<scalar_multiple2_op<Scalar,OtherScalar>, Derived>
+  inline friend const CwiseUnaryOp<scalar_multiple2_op<Scalar,OtherScalar>, const Derived>
   operator*(const OtherScalar& scalar, const Derived& matrix)
   {
 #ifdef EIGEN_SPECIAL_SCALAR_MULTIPLE_PLUGIN
@@ -485,13 +485,13 @@ struct special_scalar_op_base<Derived,Scalar,OtherScalar,BaseType,true>  : publi
     return static_cast<const special_scalar_op_base&>(matrix).operator*(scalar);
   }
   
-  const CwiseUnaryOp<scalar_quotient2_op<Scalar,OtherScalar>, Derived>
+  const CwiseUnaryOp<scalar_quotient2_op<Scalar,OtherScalar>, const Derived>
   operator/(const OtherScalar& scalar) const
   {
 #ifdef EIGEN_SPECIAL_SCALAR_MULTIPLE_PLUGIN
     EIGEN_SPECIAL_SCALAR_MULTIPLE_PLUGIN
 #endif
-    return CwiseUnaryOp<scalar_quotient2_op<Scalar,OtherScalar>, Derived>
+    return CwiseUnaryOp<scalar_quotient2_op<Scalar,OtherScalar>, const Derived>
       (*static_cast<const Derived*>(this), scalar_quotient2_op<Scalar,OtherScalar>(scalar));
   }
 };

test/array_for_matrix.cpp

@@ -68,6 +68,16 @@ template<typename MatrixType> void array_for_matrix(const MatrixType& m)
   const Scalar& ref_a2 = m.array().matrix().coeffRef(0,0);
   VERIFY(&ref_a1 == &ref_m1);
   VERIFY(&ref_a2 == &ref_m2);
+
+  // Check write accessors:
+  m1.array().coeffRef(0,0) = 1;
+  VERIFY_IS_APPROX(m1(0,0),Scalar(1));
+  m1.array()(0,0) = 2;
+  VERIFY_IS_APPROX(m1(0,0),Scalar(2));
+  m1.array().matrix().coeffRef(0,0) = 3;
+  VERIFY_IS_APPROX(m1(0,0),Scalar(3));
+  m1.array().matrix()(0,0) = 4;
+  VERIFY_IS_APPROX(m1(0,0),Scalar(4));
 }
 
 template<typename MatrixType> void comparisons(const MatrixType& m)

test/diagonal.cpp

@@ -20,6 +20,8 @@ template<typename MatrixType> void diagonal(const MatrixType& m)
   MatrixType m1 = MatrixType::Random(rows, cols),
              m2 = MatrixType::Random(rows, cols);
 
+  Scalar s1 = internal::random<Scalar>();
+
   //check diagonal()
   VERIFY_IS_APPROX(m1.diagonal(), m1.transpose().diagonal());
   m2.diagonal() = 2 * m1.diagonal();
@@ -58,6 +60,11 @@ template<typename MatrixType> void diagonal(const MatrixType& m)
     VERIFY_IS_APPROX(m2.template diagonal<N2>(), static_cast<Scalar>(2) * m1.diagonal(N2));
     m2.diagonal(N2)[0] *= 3;
     VERIFY_IS_APPROX(m2.diagonal(N2)[0], static_cast<Scalar>(6) * m1.diagonal(N2)[0]);
+
+    m2.diagonal(N2).x() = s1;
+    VERIFY_IS_APPROX(m2.diagonal(N2).x(), s1);
+    m2.diagonal(N2).coeffRef(0) = Scalar(2)*s1;
+    VERIFY_IS_APPROX(m2.diagonal(N2).coeff(0), Scalar(2)*s1);
   }
 }