From 24f8fdeb4635d0f81bfb87a7eb049e8ce72346f4 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Antonio=20S=C3=A1nchez?= <cantonios@google.com>
Date: Thu, 14 Mar 2024 21:04:49 +0000
Subject: [PATCH] Fix CwiseUnaryView const access (Attempt 2).

---
 Eigen/src/Core/CwiseUnaryView.h | 86 +++++++++++++++++++--------------
 1 file changed, 51 insertions(+), 35 deletions(-)

diff --git a/Eigen/src/Core/CwiseUnaryView.h b/Eigen/src/Core/CwiseUnaryView.h
index f1653c87a..6bd838b4d 100644
--- a/Eigen/src/Core/CwiseUnaryView.h
+++ b/Eigen/src/Core/CwiseUnaryView.h
@@ -20,9 +20,7 @@ template <typename ViewOp, typename MatrixType, typename StrideType>
 struct traits<CwiseUnaryView<ViewOp, MatrixType, StrideType> > : traits<MatrixType> {
   typedef typename result_of<ViewOp(typename traits<MatrixType>::Scalar&)>::type1 ScalarRef;
   static_assert(std::is_reference<ScalarRef>::value, "Views must return a reference type.");
-  typedef remove_all_t<ScalarRef> MutableScalar;
-  // Ensure const matrices stay const.
-  typedef std::conditional_t<std::is_const<MatrixType>::value, const MutableScalar, MutableScalar> Scalar;
+  typedef remove_all_t<ScalarRef> Scalar;
   typedef typename MatrixType::Nested MatrixTypeNested;
   typedef remove_all_t<MatrixTypeNested> MatrixTypeNested_;
   enum {
@@ -48,11 +46,13 @@ struct traits<CwiseUnaryView<ViewOp, MatrixType, StrideType> > : traits<MatrixTy
                                    : int(StrideType::OuterStrideAtCompileTime)
   };
 };
-}  // namespace internal
 
-template <typename ViewOp, typename MatrixType, typename StrideType, typename StorageKind>
+template <typename ViewOp, typename MatrixType, typename StrideType, typename StorageKind,
+          bool Mutable = !std::is_const<MatrixType>::value>
 class CwiseUnaryViewImpl;
 
+}  // namespace internal
+
 /** \class CwiseUnaryView
  * \ingroup Core_Module
  *
@@ -67,11 +67,11 @@ class CwiseUnaryViewImpl;
  * \sa MatrixBase::unaryViewExpr(const CustomUnaryOp &) const, class CwiseUnaryOp
  */
 template <typename ViewOp, typename MatrixType, typename StrideType>
-class CwiseUnaryView
-    : public CwiseUnaryViewImpl<ViewOp, MatrixType, StrideType, typename internal::traits<MatrixType>::StorageKind> {
+class CwiseUnaryView : public internal::CwiseUnaryViewImpl<ViewOp, MatrixType, StrideType,
+                                                           typename internal::traits<MatrixType>::StorageKind> {
  public:
-  typedef typename CwiseUnaryViewImpl<ViewOp, MatrixType, StrideType,
-                                      typename internal::traits<MatrixType>::StorageKind>::Base Base;
+  typedef typename internal::CwiseUnaryViewImpl<ViewOp, MatrixType, StrideType,
+                                                typename internal::traits<MatrixType>::StorageKind>::Base Base;
   EIGEN_GENERIC_PUBLIC_INTERFACE(CwiseUnaryView)
   typedef typename internal::ref_selector<MatrixType>::non_const_type MatrixTypeNested;
   typedef internal::remove_all_t<MatrixType> NestedExpression;
@@ -98,40 +98,63 @@ class CwiseUnaryView
   ViewOp m_functor;
 };
 
+namespace internal {
+
 // Generic API dispatcher
-template <typename ViewOp, typename XprType, typename StrideType, typename StorageKind>
-class CwiseUnaryViewImpl : public internal::generic_xpr_base<CwiseUnaryView<ViewOp, XprType, StrideType> >::type {
+template <typename ViewOp, typename XprType, typename StrideType, typename StorageKind, bool Mutable>
+class CwiseUnaryViewImpl : public generic_xpr_base<CwiseUnaryView<ViewOp, XprType, StrideType> >::type {
  public:
-  typedef typename internal::generic_xpr_base<CwiseUnaryView<ViewOp, XprType, StrideType> >::type Base;
+  typedef typename generic_xpr_base<CwiseUnaryView<ViewOp, XprType, StrideType> >::type Base;
 };
 
 template <typename ViewOp, typename MatrixType, typename StrideType>
-class CwiseUnaryViewImpl<ViewOp, MatrixType, StrideType, Dense>
-    : public internal::dense_xpr_base<CwiseUnaryView<ViewOp, MatrixType, StrideType> >::type {
+class CwiseUnaryViewImpl<ViewOp, MatrixType, StrideType, Dense, false>
+    : public dense_xpr_base<CwiseUnaryView<ViewOp, MatrixType, StrideType> >::type {
  public:
   typedef CwiseUnaryView<ViewOp, MatrixType, StrideType> Derived;
-  typedef typename internal::dense_xpr_base<CwiseUnaryView<ViewOp, MatrixType, StrideType> >::type Base;
-
+  typedef typename dense_xpr_base<CwiseUnaryView<ViewOp, MatrixType, StrideType> >::type Base;
   EIGEN_DENSE_PUBLIC_INTERFACE(Derived)
   EIGEN_INHERIT_ASSIGNMENT_OPERATORS(CwiseUnaryViewImpl)
 
-  EIGEN_DEVICE_FUNC inline Scalar* data() { return &(this->coeffRef(0)); }
   EIGEN_DEVICE_FUNC inline const Scalar* data() const { return &(this->coeffRef(0)); }
 
   EIGEN_DEVICE_FUNC EIGEN_CONSTEXPR inline Index innerStride() const {
-    return StrideType::InnerStrideAtCompileTime != 0
-               ? int(StrideType::InnerStrideAtCompileTime)
-               : derived().nestedExpression().innerStride() * sizeof(typename internal::traits<MatrixType>::Scalar) /
-                     sizeof(Scalar);
+    return StrideType::InnerStrideAtCompileTime != 0 ? int(StrideType::InnerStrideAtCompileTime)
+                                                     : derived().nestedExpression().innerStride() *
+                                                           sizeof(typename traits<MatrixType>::Scalar) / sizeof(Scalar);
   }
 
   EIGEN_DEVICE_FUNC EIGEN_CONSTEXPR inline Index outerStride() const {
-    return StrideType::OuterStrideAtCompileTime != 0
-               ? int(StrideType::OuterStrideAtCompileTime)
-               : derived().nestedExpression().outerStride() * sizeof(typename internal::traits<MatrixType>::Scalar) /
-                     sizeof(Scalar);
+    return StrideType::OuterStrideAtCompileTime != 0 ? int(StrideType::OuterStrideAtCompileTime)
+                                                     : derived().nestedExpression().outerStride() *
+                                                           sizeof(typename traits<MatrixType>::Scalar) / sizeof(Scalar);
   }
 
+ protected:
+  EIGEN_DEFAULT_EMPTY_CONSTRUCTOR_AND_DESTRUCTOR(CwiseUnaryViewImpl)
+
+  // Allow const access to coeffRef for the case of direct access being enabled.
+  EIGEN_DEVICE_FUNC inline const Scalar& coeffRef(Index index) const {
+    return internal::evaluator<Derived>(derived()).coeffRef(index);
+  }
+
+  EIGEN_DEVICE_FUNC inline const Scalar& coeffRef(Index row, Index col) const {
+    return internal::evaluator<Derived>(derived()).coeffRef(row, col);
+  }
+};
+
+template <typename ViewOp, typename MatrixType, typename StrideType>
+class CwiseUnaryViewImpl<ViewOp, MatrixType, StrideType, Dense, true>
+    : public CwiseUnaryViewImpl<ViewOp, MatrixType, StrideType, Dense, false> {
+ public:
+  typedef CwiseUnaryViewImpl<ViewOp, MatrixType, StrideType, Dense, false> Base;
+  typedef CwiseUnaryView<ViewOp, MatrixType, StrideType> Derived;
+  EIGEN_DENSE_PUBLIC_INTERFACE(Derived)
+  EIGEN_INHERIT_ASSIGNMENT_OPERATORS(CwiseUnaryViewImpl)
+
+  using Base::data;
+  EIGEN_DEVICE_FUNC inline Scalar* data() { return &(this->coeffRef(0)); }
+
   EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE Scalar& coeffRef(Index row, Index col) {
     return internal::evaluator<Derived>(derived()).coeffRef(row, col);
   }
@@ -142,17 +165,10 @@ class CwiseUnaryViewImpl<ViewOp, MatrixType, StrideType, Dense>
 
  protected:
   EIGEN_DEFAULT_EMPTY_CONSTRUCTOR_AND_DESTRUCTOR(CwiseUnaryViewImpl)
-
-  // Allow const access to coeffRef for the case of direct access being enabled.
-  EIGEN_DEVICE_FUNC inline const Scalar& coeffRef(Index index) const {
-    return const_cast<CwiseUnaryViewImpl*>(this)->coeffRef(index);
-  }
-
-  EIGEN_DEVICE_FUNC inline const Scalar& coeffRef(Index row, Index col) const {
-    return const_cast<CwiseUnaryViewImpl*>(this)->coeffRef(row, col);
-  }
 };
 
-}  // end namespace Eigen
+}  // namespace internal
+
+}  // namespace Eigen
 
 #endif  // EIGEN_CWISE_UNARY_VIEW_H