message: Check that the diag policy is `DIAG_ONE` when FA.
diff: @@ -975,6 +975,9 @@ void FABilinearFormExtension::RAP(OperatorHandle &A)
  void FABilinearFormExtension::EliminateBC(const Array<int> &ess_dofs,
  OperatorHandle &A)
  {
  + MFEM_VERIFY(a->diag_policy == DiagonalPolicy::DIAG_ONE,
  + "Only DiagonalPolicy::DIAG_ONE supported with"
  + " FABilinearFormExtension.");
  #ifdef MFEM_USE_MPI
  if ( dynamic_cast<ParBilinearForm*>(a) )
  {
  