Cleanup: Remove redundant asserts about dirty normals

These asserts basically just reiterated the way things work-- there's no
no way for them to trigger with the current code. And even if they did,
that sort of change wouldn't happen by mistake, so it's not worth
an assert.

source/blender/blenkernel/BKE_mesh.h

@@ -321,16 +321,10 @@ void BKE_mesh_recalc_looptri(const int *corner_verts,
 
 /* *** mesh_normals.cc *** */
 
-/**
- * Return true if the mesh vertex normals either are not stored or are dirty.
- * This can be used to help decide whether to transfer them when copying a mesh.
- */
+/** Return true if the mesh vertex normals either are not stored or are dirty. */
 bool BKE_mesh_vert_normals_are_dirty(const struct Mesh *mesh);
 
-/**
- * Return true if the mesh face normals either are not stored or are dirty.
- * This can be used to help decide whether to transfer them when copying a mesh.
- */
+/** Return true if the mesh face normals either are not stored or are dirty. */
 bool BKE_mesh_face_normals_are_dirty(const struct Mesh *mesh);
 
 /**

source/blender/blenkernel/intern/mesh.cc

@@ -1058,9 +1058,6 @@ Mesh *BKE_mesh_new_nomain_from_template_ex(const Mesh *me_src,
     CustomData_add_layer(&me_dst->fdata_legacy, CD_MFACE, CD_SET_DEFAULT, me_dst->totface_legacy);
   }
 
-  /* Expect that normals aren't copied at all, since the destination mesh is new. */
-  BLI_assert(BKE_mesh_vert_normals_are_dirty(me_dst));
-
   return me_dst;
 }
 

source/blender/blenkernel/intern/subdiv_mesh.cc

@@ -1196,6 +1196,11 @@ Mesh *BKE_subdiv_to_mesh(Subdiv *subdiv,
   BKE_subdiv_stats_end(&subdiv->stats, SUBDIV_STATS_SUBDIV_TO_MESH_GEOMETRY);
   Mesh *result = subdiv_context.subdiv_mesh;
 
+  /* NOTE: Using normals from the limit surface gives different results than Blender's vertex
+   * normal calculation. Since vertex normals are supposed to be a consistent cache, don't bother
+   * calculating them here. The work may have been pointless anyway if the mesh is deformed or
+   * changed afterwards. */
+
   /* Move the optimal display edge array to the final bit vector. */
   if (!subdiv_context.subdiv_display_edges.is_empty()) {
     const Span<bool> span = subdiv_context.subdiv_display_edges;
@@ -1224,12 +1229,6 @@ Mesh *BKE_subdiv_to_mesh(Subdiv *subdiv,
 
   // BKE_mesh_validate(result, true, true);
   BKE_subdiv_stats_end(&subdiv->stats, SUBDIV_STATS_SUBDIV_TO_MESH);
-  /* Using normals from the limit surface gives different results than Blender's vertex normal
-   * calculation. Since vertex normals are supposed to be a consistent cache, don't bother
-   * calculating them here. The work may have been pointless anyway if the mesh is deformed or
-   * changed afterwards. */
-  BLI_assert(BKE_mesh_vert_normals_are_dirty(result) || BKE_mesh_face_normals_are_dirty(result));
-  /* Free used memory. */
   subdiv_mesh_context_free(&subdiv_context);
   return result;
 }

source/blender/editors/mesh/editmesh_undo.cc

@@ -825,10 +825,6 @@ static void undomesh_to_editmesh(UndoMesh *um, Object *ob, BMEditMesh *em)
   em_tmp = BKE_editmesh_create(bm);
   *em = *em_tmp;
 
-  /* Normals should not be stored in the undo mesh, so recalculate them. The edit
-   * mesh is expected to have valid normals and there is no tracked dirty state. */
-  BLI_assert(BKE_mesh_vert_normals_are_dirty(&um->me));
-
   /* Calculate face normals and tessellation at once since it's multi-threaded. */
   BKE_editmesh_looptri_and_normals_calc(em);