One thing I don&#x27;t see in this list (though maybe I&#x27;m missing it) is the ability to expose a Swift function as a function compatible with the C ABI. Something like extern &quot;C&quot; in C++ or no_mangle in Rust.<p>You can pass @convention(c) blocks around as C function pointers, but you can&#x27;t currently call directly into a Swift library from C code. That makes it difficult to do things like expose platform-specific functionality to a shared C library using Swift.<p>Right now you have to implement the C function inside an Objective-C file, and then have your Objective-C code call your Swift code, or you have to change all your interfaces to allow injection of function pointers for all external dependencies.<p>It&#x27;s the kind of thing that makes staying with Objective-C attractive for that type of stuff, but Swift in general has been a solid improvement, and I&#x27;d like to not have to give that up.