RefCell alternative that is Send?

[Hyeonu]

@godmar

So you're proposing to pay the runtime overhead of double indirection (2 hash table lookups?) to avoid the sharing?

Indeed. It pays double lookup to remove aliasing.

@godmar

This is indeed what's happening. Specifically, I have a 'currentPerson' (to stay in your example) that is already mutably borrowed. Sometimes, an operation applies to the current person, and sometimes it applies to another.

For this case, consider to not store the current person in the hashtable. This would add additional branch to the lookup function to check current ssn first.

struct State {
    // boxed the person to minimize move cost, possibly premature optimization
    persons: HashMap<Ssn, Box<Person>>,
    ssns: HashMap<Name, Ssn>,
    current_ssn: Ssn,
    current_person: Box<Person>,
}

Also suggested by the discourse popup, it seems we're somewhat hijacking the thread at this stage. Feel free to open another thread and mention me if you have more questions.