[afavour]

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.

[inkyoto]

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/

[pjmlp]

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.