From 448d9d943c3996f6d74cebad457865d005248ddd Mon Sep 17 00:00:00 2001
From: Gael Guennebaud <g.gael@free.fr>
Date: Wed, 18 May 2016 16:00:11 +0200
Subject: [PATCH] bug #1222: fix compilation in AutoDiffScalar and add
 respective unit test

---
 unsupported/Eigen/src/AutoDiff/AutoDiffScalar.h |  2 +-
 unsupported/test/autodiff.cpp                   | 11 ++++++++++-
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/unsupported/Eigen/src/AutoDiff/AutoDiffScalar.h b/unsupported/Eigen/src/AutoDiff/AutoDiffScalar.h
index 481dfa91a..dfc08f751 100755
--- a/unsupported/Eigen/src/AutoDiff/AutoDiffScalar.h
+++ b/unsupported/Eigen/src/AutoDiff/AutoDiffScalar.h
@@ -101,7 +101,7 @@ class AutoDiffScalar
     template<typename OtherDerType>
     AutoDiffScalar(const AutoDiffScalar<OtherDerType>& other
 #ifndef EIGEN_PARSED_BY_DOXYGEN
-    , typename internal::enable_if<internal::is_same<Scalar,typename OtherDerType::Scalar>::value,void*>::type = 0
+    , typename internal::enable_if<internal::is_same<Scalar, typename internal::traits<typename internal::remove_all<OtherDerType>::type>::Scalar>::value,void*>::type = 0
 #endif
     )
       : m_value(other.value()), m_derivatives(other.derivatives())
diff --git a/unsupported/test/autodiff.cpp b/unsupported/test/autodiff.cpp
index c4606cd17..ad3f83d4e 100644
--- a/unsupported/test/autodiff.cpp
+++ b/unsupported/test/autodiff.cpp
@@ -207,7 +207,14 @@ void test_autodiff_hessian()
   VERIFY_IS_APPROX(y.derivatives()(1).derivatives(),  -std::sin(s1*s3+s2*s4)*Vector2d(s3*s4,s4*s4));
 }
 
-
+double bug_1222() {
+  typedef Eigen::AutoDiffScalar<Eigen::Vector3d> AD;
+  const double _cv1_3 = 1.0;
+  const AD chi_3 = 1.0;
+  // this line did not work, because operator+ returns ADS<DerType&>, which then cannot be converted to ADS<DerType>
+  const AD denom = chi_3 + _cv1_3;
+  return denom.value();
+}
 
 void test_autodiff()
 {
@@ -217,5 +224,7 @@ void test_autodiff()
     CALL_SUBTEST_3( test_autodiff_jacobian<1>() );
     CALL_SUBTEST_4( test_autodiff_hessian<1>() );
   }
+
+  bug_1222();
 }