A few years ago I checked swift, and the internals documentation was out of date, non existent, or wrong in some cases. Nor was there any other good way to interact with the swift compiler and get things like abi info, parameters info, field offsets or encoding information from the outside (without having to hack the compiler itself).
My question now is this: Has the situation been improved?
My goal is to be able to interact from non swift with swift libraries (like swiftui, or really any new libraries for osx/ios that are swift only).
You can find ABI related documentation under swift/docs/ABI at main · apple/swift · GitHub, but they're in different states... The mangling doc is generally kept up-to-date and register use doc should be easily verifiable in case it is out-of-date, whereas the type layout and type metadata docs are outdated...
You can get field offsets using MemoryLayout.offsetOf thanks to SE-0210.
Yep. That's pretty much the same state as it was in back then. I do have mangling covered already. But the swift compiler has so many undocumented rules that it becomes impossible to interact with:
most types use or extend some objc types, whose renaming doesn't match the documentation
some type parameter or associated type parameters in abi calls depend on if the body needs them
enums reuse bits in a way I can't figure out or find consistency in