SE-0384: Importing Forward Declared Objective-C Interfaces and Protocols

Regardless of one's stance on if the existing debt should be increased via this proposal, I agree that the ClangImporter and its interactions with the rest of the system have some existing fundamental issues that need addressing before compiler - debugger parity is achievable.

With respect to the issue you've linked, I'm aware of this issue and have recently made a rough attempt at fixing it (the compiler part of it): [ClangImporter] Swift Implemented ObjC Forward Declarations by NuriAmari · Pull Request #62983 · apple/swift · GitHub. Though decidedly related, unless the community feels otherwise I'd rather not stray too far with this proposal's discussion. A solution to that problem relies upon a resolution of the issues raised in this discussion anyhow.

This proposal has been accepted. Thanks to all who participated in the review!