FWIW the approach that swift-java takes in managing interop with Java (and potentially Kotlin) function calls means it is perfectly possible to to catch exceptions thrown by the JVM using wrappers that catch and rethrow them as Swift errors. So there would be a distinction here with bringing Swift calling into JVM-based code running on Android.

While Swift can use Objective-C's message sending to communicate with Objective-C libraries, that isn't its primary dispatch mechanism. In the case of the service described in the article, it isn't even available (since it runs on Linux, which does not have an Objective-C runtime implementation).

Instead, like Rust, Swift's primary dispatch is static by default (either directly on types, or via reified generics), with dynamic dispatch possible via any (which is similar to Rust's dyn). Swift also has vtable-based dispatch when using subclassing, but again this is opt-in like any/dyn is.

Swift and Rust also allow their protocols to be erased and dispatched dynamically (dyn in Rust, any in Swift). But in both languages that's more of a "when you need it" thing, generics are the preferred tool.

In particular:

> Even with the introduction of typed throws into Swift, the existing (untyped) throws remains the better default error-handling mechanism for most Swift code. The section "When to use typed throws" describes the circumstances in which typed throws should be used.