[jondwillis]

Why can’t provenance of throws be traced with certainty? It is possible to trace the return type of functions.

Even if it were an opt-in/progressive adoption keyword like “throws” that enforced some compiler guardrails, I think that could be a huge win for reducing unexpected runtime exceptions.

[tgv]

Take the following function:

    function arrmin<T extends {field: number}>(a: T[]): number {
        let m = a[0].field;
        for (let i = 1; i < a.length; i++) {
            if (a[i].field < m) {
                m = a[i].field;
            }
        }
        return m;
    }

Now call arrmin([]). There's no way to avoid a throw. You would have to annotate every function that uses field selection on an array element (and a bunch of other conditions) as "throws", or enforce error checking code (if (0 <= i < a.length) {...}).

Rust didn't solve that either, does it? It just panics.