What if you do: my_fn(|| { db.store(42); }); db.drop(); (Assuming you can just drop the database object, the semantics don’t really matter

What if you do: my_fn(|| { db.store(42); }); db.drop(); (Assuming you can just drop the database object, the semantics don’t really matter but the idea is the same.) The OP wants an easy way to do this but this is just not an easy thing to do. How can the closure guarantee that the database object will exist if my_fn decides to sleep for a couple seconds? Most languages do not have this problem because either: they use a garbage collector (Java and it’s cousins, Python, Go) or they are not safe (C, C++). Rust is in a particularly difficult (and ambitious and exciting!) intersection where this problem is tricky.