Description
InternalImportsByDefault is a feature flag which can be opt-in since Swift 5.9.
And I just noticed it has some strange bug behavior occurring on Swift 6.0 toolchain.
Description
If you enable InternalImportsByDefault as a upcoming feature, you will be able to use other package's package API even you are not in the same package.
Example 1:
We have Demo and DemoKit package, and Demo has a dependency on DemoKit.
Both Demo and DemoKit is build by Swift 6.0 compiler with Swift 5/6 mode does not matter.
It will be buildable that Demo use DemoKit's package API if we are using Xcode 16.0 with Swift 6.0 compiler.
Example 2:
The same thing applies for the system framework.
SwiftUI.framework & SwiftUICore.framework has some @inlinable package API in its public interface.
We can also call it directly on Demo package if we enable InternalImportsByDefault and compile it under Xcode 16.0 with Swift 6.0 compiiler.
// SwiftUICore.swiftmodule
extension CoreFoundation.CGSize {
@available(iOS 18.0, macOS 15.0, tvOS 18.0, watchOS 11.0, visionOS 2.0, *)
@inlinable package var hasZero: Swift.Bool {
get { width == 0.0 || height == 0.0 }
}
}
import SwiftUI
let size = CGSize()
print(size.hasZero)
Reproduction
See Demo package in the attachment.
Expected behavior
Not able to call package API in other package and fail to compile.
Environment
swiftc -version
swift-driver version: 1.115 Apple Swift version 6.0 (swiftlang-6.0.0.9.10 clang-1600.0.26.2)
Target: arm64-apple-macosx15.0
Additional information
The bug seem to be fixed on Swift 6.1 / Xcode 16.3.
But I did not find any existing issue or test case covering it in the Swift repo.
cc @xymus