I agree they made the right decision not to add custom move constructors, potentially throwing move constructors and unmovable types make life very, very diffic

I agree they made the right decision not to add custom move constructors, potentially throwing move constructors and unmovable types make life very, very difficult for certain things in c++. That said, an annotation on a field that it either always references part of the parent or may reference part of the parent (or better a defined range or expression from the parent) could provide enough information for an automatically generated move constructor to correctly update the parent referencing pointer or reference. It’s entirely machinable, we had to do a version of this for the OpenMP offload memory model. It’s not the simplest thing, but updating references based on known offsets from known bases isn’t itself all that hard. Getting the syntax for the user to provide enough information to do it to be ergonomic however, that’s hard.