My instinct is that this would end up being more costly than it's worth. You'd be essentially adding extra bookkeeping and logic for every single type that needs to remain alive as long as the type is still possible to reference.
Moreover, how would you deal with downstream usage by dependents? Should I be able to make my dependency's type implement Debug (which is at least in spirit a violation of the orphan rule, and would make the bookkeeping/extra logic described above explode for any non-trivial dependency tree)?
People already find the Rust compiler too slow. If there's budget for adding more expensive checks, I don't think I'd want it to be spent on something like this.
Moreover, how would you deal with downstream usage by dependents? Should I be able to make my dependency's type implement Debug (which is at least in spirit a violation of the orphan rule, and would make the bookkeeping/extra logic described above explode for any non-trivial dependency tree)?
People already find the Rust compiler too slow. If there's budget for adding more expensive checks, I don't think I'd want it to be spent on something like this.