[Diagnostics] Support @_semantics("swiftui.requires_constant_range") #84679
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Xcode seems to have some code in `swiftc` that knows how to diagnose incorrect usages of APIs annotated with `@_semantics`. There is around half a dozen different `@_semantics` annotation in `SwiftUI`. The changes here deal with only `swiftui.requires_constant_range`. When the `ForEach` `struct` from `SwiftUI` is used with a `Range` (which conforms to `RandomAccessCollection`) the compiler seems to check for some extra details of the argument which cannot be expressed in the type system, one of them that it should be a compile-time "constant". It seems that part of the code to do so is part of the open source swift.org toolchain, but some other pieces are not. This PR implements to the best of my knowledge what I think the Xcode toolchain might be doing as close as I can. When one builds tooling on top of the open source toolchain one can find cases in which the tooling considers some code valid, while Xcode will consider it invalid, causing confusion. I provide this implementation in the hope that the actual Xcode implementation can be open sourced, because even if SwiftUI itself is not open source, it would be valuable that the `@_semantics` annotations produce the same output in the open source swift.org and the Xcode toolchains.
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@swift-ci please test |
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@swift-ci please test |
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@swift-ci please test macOS platform |
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Xcode seems to have some code in
swiftcthat knows how to diagnose incorrect usages of APIs annotated with@_semantics. There is around half a dozen different@_semanticsannotation inSwiftUI. The changes here deal with onlyswiftui.requires_constant_range.When the
ForEachstructfromSwiftUIis used with aRange(which conforms toRandomAccessCollection) the compiler seems to check for some extra details of the argument which cannot be expressed in the type system, one of them that it should be a compile-time "constant".It seems that part of the code to do so is part of the open source swift.org toolchain, but some other pieces are not. This PR implements to the best of my knowledge what I think the Xcode toolchain might be doing as close as I can.
When one builds tooling on top of the open source toolchain one can find cases in which the tooling considers some code valid, while Xcode will consider it invalid, causing confusion.
I provide this implementation in the hope that the actual Xcode implementation can be open sourced, because even if SwiftUI itself is not open source, it would be valuable that the
@_semanticsannotations produce the same output in the open source swift.org and the Xcode toolchains.