failtest: a new cmake-based test suite for testing stuff that should fail to build. This first batch imports some const correctness checks from bug #54.

failtest/diagonal_nonconst_ctor_on_const_xpr.cpp

@@ -0,0 +1,15 @@
+#include "../Eigen/Core"
+
+#ifdef EIGEN_SHOULD_FAIL_TO_BUILD
+#define CV_QUALIFIER const
+#else
+#define CV_QUALIFIER
+#endif
+
+using namespace Eigen;
+
+void foo(CV_QUALIFIER Matrix3d &m){
+    Diagonal<Matrix3d> d(m);
+}
+
+int main() {}