allow check-structures-sanity to check the size of the value explicitly specified in a lua expression rather than just its descendants.

print an error if getting the type identity fails.

plugins/devel/check-structures-sanity.cpp

@@ -165,12 +165,14 @@ static command_result command(color_ostream & out, std::vector<std::string> & pa
 
         ToCheck ref;
         ref.path.push_back(parameters.at(0));
+        ref.path.push_back(""); // tell check_struct that it is a pointer
         ref.ptr = get_object_ref(State, -1);
         lua_getfield(State, -1, "_type");
         lua_getfield(State, -1, "_identity");
         ref.identity = reinterpret_cast<type_identity *>(lua_touserdata(State, -1));
         if (!ref.identity)
         {
+            out.printerr("could not determine type identity\n");
             return CR_FAILURE;
         }