Egor Zhdan 3791ccb6e6 [cxx-interop] Allow AppKit & UIKit to be rebuilt with C++ interop enabled ...

This removes a workaround from the module interface loader, which was forcing AppKit and UIKit to be rebuilt from their textual interfaces with C++ interop disabled, even if the current compilation explicitly enables it.

The workaround was previously put in place because of a compiler error:
```
error: type 'AttributeScopes.AppKitAttributes.StrikethroughStyleAttribute' does not conform to protocol 'AttributedStringKey'
note: possibly intended match 'AttributeScopes.AppKitAttributes.StrikethroughStyleAttribute.Value' (aka 'NSUnderlineStyle') does not conform to 'Hashable'
```

`NSUnderlineStyle` is a C/C++ type from AppKit that is declared using `NS_OPTIONS` macro. `NS_OPTIONS`/`CF_OPTIONS` macros have different expansions in C vs C++ language modes. The C++ expansions weren't handled correctly by ClangImporter, resulting in two distinct Swift types being created: a `typealias NSUnderlineStyle` which was marked as unavailable in Swift, and `enum NSUnderlineStyle`. This mostly worked fine, since the lookup logic was picking the enum during regular name lookup. However, this silently broke down when rebuilding the explicit conformance from `AppKit.swiftinterface`:
```
extension AppKit.NSUnderlineStyle : Swift.Hashable {}
```
Swift was picking the (unavailable) typealias when rebuilding this extension, which means the (available) enum wasn't getting the conformance.

This is verified by an existing test (`test/Interop/Cxx/objc-correctness/appkit-uikit.swift`).

rdar://142961112

2025-03-07 13:27:11 +00:00

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