Comment by afavour
2 days ago
One of the genius things about Swift is its interop with Objective C. Made the switch over considerably easier for developers. I’m not sure what that looks like in a Rust world.
Rust is also just a more complex language. I’m not convinced the benefits would have been worth it.
Not just interoperability with Objective C but with C (full) and C++ (increasingly better but not full) as well.
Swift is also interoperable with different versions of itself courtesy of the Swift stable ABI (Application Binary Interface)[0], which they invested a significant amount of time into at the expense of adding other new features to the language, which have come along later.
Rust offers a different approach: recompile everything and static linking.
[0] https://faultlore.com/blah/swift-abi/
C compatibility comes via Objective-C, because contrary to C++, Objective-C extends C, instead of being based on a C subset.
You missed Java as well.