From 9357838f94d2907996adadc7e5200376f3561ed4 Mon Sep 17 00:00:00 2001
From: Gael Guennebaud <g.gael@free.fr>
Date: Tue, 10 Jul 2018 09:10:15 +0200
Subject: [PATCH] bug #1543: improve linear indexing for general block
 expressions

---
 Eigen/src/Core/CoreEvaluators.h | 6 +++---
 test/block.cpp                  | 2 ++
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/Eigen/src/Core/CoreEvaluators.h b/Eigen/src/Core/CoreEvaluators.h
index 6231f2edd..b65ec4ffb 100644
--- a/Eigen/src/Core/CoreEvaluators.h
+++ b/Eigen/src/Core/CoreEvaluators.h
@@ -1080,7 +1080,7 @@ struct unary_evaluator<Block<ArgType, BlockRows, BlockCols, InnerPanel>, IndexBa
     : m_argImpl(block.nestedExpression()), 
       m_startRow(block.startRow()), 
       m_startCol(block.startCol()),
-      m_linear_offset(InnerPanel?(XprType::IsRowMajor ? block.startRow()*block.cols() : block.startCol()*block.rows()):0)
+      m_linear_offset((InnerPanel|| XprType::IsVectorAtCompileTime)?(XprType::IsRowMajor ? block.startRow()*block.cols() + block.startCol() : block.startCol()*block.rows() + block.startRow()):0)
   { }
  
   typedef typename XprType::Scalar Scalar;
@@ -1088,7 +1088,7 @@ struct unary_evaluator<Block<ArgType, BlockRows, BlockCols, InnerPanel>, IndexBa
 
   enum {
     RowsAtCompileTime = XprType::RowsAtCompileTime,
-    ForwardLinearAccess = InnerPanel && bool(evaluator<ArgType>::Flags&LinearAccessBit)
+    ForwardLinearAccess = (InnerPanel || XprType::IsVectorAtCompileTime) && bool(evaluator<ArgType>::Flags&LinearAccessBit)
   };
  
   EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE
@@ -1162,7 +1162,7 @@ protected:
   evaluator<ArgType> m_argImpl;
   const variable_if_dynamic<Index, (ArgType::RowsAtCompileTime == 1 && BlockRows==1) ? 0 : Dynamic> m_startRow;
   const variable_if_dynamic<Index, (ArgType::ColsAtCompileTime == 1 && BlockCols==1) ? 0 : Dynamic> m_startCol;
-  const variable_if_dynamic<Index, InnerPanel ? Dynamic : 0> m_linear_offset;
+  const variable_if_dynamic<Index, (InnerPanel || XprType::IsVectorAtCompileTime) ? Dynamic : 0> m_linear_offset;
 };
 
 // TODO: This evaluator does not actually use the child evaluator; 
diff --git a/test/block.cpp b/test/block.cpp
index 8c4dd87be..9c2424662 100644
--- a/test/block.cpp
+++ b/test/block.cpp
@@ -162,9 +162,11 @@ template<typename MatrixType> void block(const MatrixType& m)
   // expressions without direct access
   VERIFY_IS_APPROX( ((m1+m2).block(r1,c1,rows-r1,cols-c1).block(r2-r1,c2-c1,rows-r2,cols-c2)) , ((m1+m2).block(r2,c2,rows-r2,cols-c2)) );
   VERIFY_IS_APPROX( ((m1+m2).block(r1,c1,r2-r1+1,c2-c1+1).row(0)) , ((m1+m2).row(r1).segment(c1,c2-c1+1)) );
+  VERIFY_IS_APPROX( ((m1+m2).block(r1,c1,r2-r1+1,c2-c1+1).row(0)) , ((m1+m2).eval().row(r1).segment(c1,c2-c1+1)) );
   VERIFY_IS_APPROX( ((m1+m2).block(r1,c1,r2-r1+1,c2-c1+1).col(0)) , ((m1+m2).col(c1).segment(r1,r2-r1+1)) );
   VERIFY_IS_APPROX( ((m1+m2).block(r1,c1,r2-r1+1,c2-c1+1).transpose().col(0)) , ((m1+m2).row(r1).segment(c1,c2-c1+1)).transpose() );
   VERIFY_IS_APPROX( ((m1+m2).transpose().block(c1,r1,c2-c1+1,r2-r1+1).col(0)) , ((m1+m2).row(r1).segment(c1,c2-c1+1)).transpose() );
+  VERIFY_IS_APPROX( ((m1+m2).template block<1,Dynamic>(r1,c1,1,c2-c1+1)) , ((m1+m2).eval().row(r1).segment(c1,c2-c1+1)) );
 
   VERIFY_IS_APPROX( (m1*1).topRows(r1),  m1.topRows(r1) );
   VERIFY_IS_APPROX( (m1*1).leftCols(c1), m1.leftCols(c1) );