anchor.diff:        }
       }
       if (wrapped) {
  -      assert(_faces4.length == w * h);
  +      assert(_faces4.length == w * h, "face4 length mismatch");
       }
     }
   
  
positive.code:     }
    }
  
    void AddVertex(VM.Vector3 v) {
      vertices.add(v.clone());
    }
  
negative.code:   void AddVerticesFace4(List<VM.Vector3> vs) {
      assert(vs.length == 4);
      int i = vertices.length;
      AddFace4(i + 0, i + 1, i + 2, i + 3);
      AddVertices(vs);
    }
  
    void AddVerticesFace4TakeOwnership(List<VM.Vector3> vs) {
      assert(vs.length == 4);
      int i = vertices.length;
      AddFace4(i + 0, i + 1, i + 2, i + 3);
      AddVerticesTakeOwnership(vs);
    }
  
    void AddFaces4Strip(List<VM.Vector3> top, List<VM.Vector3> bot, bool closed) {
  