Andreas Fabri

Do you agree that [here](https://github.com/CGAL/cgal/blob/7570ad8a43994b2890f0172293f48e69ca803672/Surface_mesh_deformation/include/CGAL/Surface_mesh_deformation.h#L568) we cannot replace because it is something that can happen ?

Does it make sense to have an assertion in [`TDS_3::is_valid()`](https://github.com/CGAL/cgal/blob/7570ad8a43994b2890f0172293f48e69ca803672/TDS_3/include/CGAL/Triangulation_data_structure_3.h#L3595)?

Shall we make [here](https://github.com/CGAL/cgal/blob/7570ad8a43994b2890f0172293f48e69ca803672/Tetrahedral_remeshing/include/CGAL/Tetrahedral_remeshing/internal/tetrahedral_adaptive_remeshing_impl.h#L503) the last `case` to `default` and then we don't need an assert or unreachable statement.

> > Do you agree that [here](https://github.com/CGAL/cgal/blob/7570ad8a43994b2890f0172293f48e69ca803672/Surface_mesh_deformation/include/CGAL/Surface_mesh_deformation.h#L568) we cannot replace because it is something that can happen ? > > assertion should be removed So _unreachable_ means that one may...

> > > > Do you agree that [here](https://github.com/CGAL/cgal/blob/7570ad8a43994b2890f0172293f48e69ca803672/Surface_mesh_deformation/include/CGAL/Surface_mesh_deformation.h#L568) we cannot replace because it is something that can happen ? > > > > > > > > > assertion...

Shall we declare [this](https://github.com/CGAL/cgal/blob/418b00e27469c6ed8b2539242e5158d5ece072ca/Mesh_3/include/CGAL/Mesh_3/C3T3_helpers.h#L76) copy constructor private instead?

Would this also compile if the static function [here ](https://github.com/CGAL/cgal/blob/418b00e27469c6ed8b2539242e5158d5ece072ca/Surface_mesh_topology/include/CGAL/Surface_mesh_topology/internal/Functors_for_face_graph_wrapper.h#L42) was just removed? After all we need the class only because of the offered specializations.

> > Would this also compile if the static function [here ](https://github.com/CGAL/cgal/blob/418b00e27469c6ed8b2539242e5158d5ece072ca/Surface_mesh_topology/include/CGAL/Surface_mesh_topology/internal/Functors_for_face_graph_wrapper.h#L42) was just removed? After all we need the class only because of the offered specializations. > > Indeed,...

[Here](https://github.com/CGAL/cgal/blob/50219fc33bc53b5846e9a4257befc6baef3f395a/Convex_decomposition_3/include/CGAL/Convex_decomposition_3/Single_wall_creator.h#L257) we have the assertion as first line of a function.

Is there a subtlety I miss here which makes that there is a `CGAL_assertion(false)` at the end, while before we have several `CGAL_unreachable()` @sloriot