From b69e465d7ab3cfc922f8ae363398d83c5e341920 Mon Sep 17 00:00:00 2001
From: Gael Guennebaud <g.gael@free.fr>
Date: Fri, 9 Jun 2017 13:13:03 +0200
Subject: [PATCH] bug #1410: fix lvalue propagation of Array/Matrix-Wrapper
 with a const nested expression. (grafted from
 fb1ee04087f6d5cfe9009941c1a1eb25b3133a04 )

---
 Eigen/src/Core/ArrayWrapper.h |  6 ++++--
 test/array_for_matrix.cpp     | 22 +++++++++++++++++++++-
 2 files changed, 25 insertions(+), 3 deletions(-)

diff --git a/Eigen/src/Core/ArrayWrapper.h b/Eigen/src/Core/ArrayWrapper.h
index a04521a16..688aadd62 100644
--- a/Eigen/src/Core/ArrayWrapper.h
+++ b/Eigen/src/Core/ArrayWrapper.h
@@ -32,7 +32,8 @@ struct traits<ArrayWrapper<ExpressionType> >
   // Let's remove NestByRefBit
   enum {
     Flags0 = traits<typename remove_all<typename ExpressionType::Nested>::type >::Flags,
-    Flags = Flags0 & ~NestByRefBit
+    LvalueBitFlag = is_lvalue<ExpressionType>::value ? LvalueBit : 0,
+    Flags = (Flags0 & ~(NestByRefBit | LvalueBit)) | LvalueBitFlag
   };
 };
 }
@@ -129,7 +130,8 @@ struct traits<MatrixWrapper<ExpressionType> >
   // Let's remove NestByRefBit
   enum {
     Flags0 = traits<typename remove_all<typename ExpressionType::Nested>::type >::Flags,
-    Flags = Flags0 & ~NestByRefBit
+    LvalueBitFlag = is_lvalue<ExpressionType>::value ? LvalueBit : 0,
+    Flags = (Flags0 & ~(NestByRefBit | LvalueBit)) | LvalueBitFlag
   };
 };
 }
diff --git a/test/array_for_matrix.cpp b/test/array_for_matrix.cpp
index c1501947b..b8721391f 100644
--- a/test/array_for_matrix.cpp
+++ b/test/array_for_matrix.cpp
@@ -235,12 +235,31 @@ template<typename MatrixTraits> void resize(const MatrixTraits& t)
   VERIFY(a1.size()==cols);
 }
 
+template<int>
 void regression_bug_654()
 {
   ArrayXf a = RowVectorXf(3);
   VectorXf v = Array<float,1,Dynamic>(3);
 }
 
+// Check propagation of LvalueBit through Array/Matrix-Wrapper
+template<int>
+void regrrssion_bug_1410()
+{
+  const Matrix4i M;
+  const Array4i A;
+  ArrayWrapper<const Matrix4i> MA = M.array();
+  MA.row(0);
+  MatrixWrapper<const Array4i> AM = A.matrix();
+  AM.row(0);
+
+  VERIFY((internal::traits<ArrayWrapper<const Matrix4i> >::Flags&LvalueBit)==0);
+  VERIFY((internal::traits<MatrixWrapper<const Array4i> >::Flags&LvalueBit)==0);
+
+  VERIFY((internal::traits<ArrayWrapper<Matrix4i> >::Flags&LvalueBit)==LvalueBit);
+  VERIFY((internal::traits<MatrixWrapper<Array4i> >::Flags&LvalueBit)==LvalueBit);
+}
+
 void test_array_for_matrix()
 {
   for(int i = 0; i < g_repeat; i++) {
@@ -280,5 +299,6 @@ void test_array_for_matrix()
     CALL_SUBTEST_5( resize(MatrixXf(internal::random<int>(1,EIGEN_TEST_MAX_SIZE), internal::random<int>(1,EIGEN_TEST_MAX_SIZE))) );
     CALL_SUBTEST_6( resize(MatrixXi(internal::random<int>(1,EIGEN_TEST_MAX_SIZE), internal::random<int>(1,EIGEN_TEST_MAX_SIZE))) );
   }
-  CALL_SUBTEST_6( regression_bug_654() );
+  CALL_SUBTEST_6( regression_bug_654<0>() );
+  CALL_SUBTEST_6( regrrssion_bug_1410<0>() );
 }