bug #1222: fix compilation in AutoDiffScalar and add respective unit test

1 files changed, 10 insertions, 1 deletions

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();
 }