[interop] C++ function returning NonCopyable type returns Never in Swift and is callable

[hyp]

This code:

struct NonCopyable {
    NonCopyable(const NonCopyable &) = delete;
    
    int x;
};

NonCopyable returnsNoncopyable();

Produces callable returnsNoncopyable function in Swift module interface that returns Never:

func returnsNoncopyable() -> Never

This function is callable, and doesn't result in an error unless the return value is attempted to be used.

[Rajveer100]

@hyp Could you give a hint on how one would go about this?

[Rajveer100]

@AnthonyLatsis Are there any resources I can go through to solve this?

[AnthonyLatsis]

My best guess would be that this is an issue with ClangImporter. My interoperability kung fu is pretty lame though, so take this with a grain of salt. That aside, C++ interop is an experimental feature. If I were to poke at this, I would skim through the manifesto first.

[Rajveer100]

Well, ok!
@egorzhdan What's your take on this! Please let me know!

[hyp]

Sorry for delay, I already have a PR that addresses on this issue: #65105 . Not yet merged to 5.9 though

[hyp]

Will work around it in a different way