[KT-48068] Add opt-in support for NSEnum for Kotlin Native iOS via an annotation

[stefanhaustein]

Basically implementing the feature suggested here: https://youtrack.jetbrains.com/issue/KT-48068

[SvyatoslavScherbina]

/test-private

[kotlin-safe-merge]

Failed to process command due to an unexpected exception.

[SvyatoslavScherbina]

The K2 (Analysis API, aka AA) implementation is missing, which makes the new test fail in this mode.
Run

./gradlew :native:objcexport-header-generator:testAnalysisApi --tests "org.jetbrains.kotlin.backend.konan.tests.ObjCExportHeaderGeneratorTest"

to reproduce.

Related code:

kotlin/native/objcexport-header-generator/impl/analysis-api/src/org/jetbrains/kotlin/objcexport/translateToObjCClass.kt

Line 54 in f90cbf3

this += translateEnumMembers(symbol)

[SvyatoslavScherbina]

Another thing to fix: adding a declaration to stdlib requires updating the ABI dump.
Run the following command to do that:

./gradlew :tools:binary-compatibility-validator:cleanTest :tools:binary-compatibility-validator:test --tests "*" -Poverwrite.output=true

[stefanhaustein]

The K2 (Analysis API, aka AA) implementation is missing, which makes the new test fail in this mode. Run

I have added this, but AA emits the a comment about the annotation whereas K1 does not... Any suggestions how to resolve this? Current state is the AA output

[SvyatoslavScherbina]

Now, that's a bit tricky.
IIRC, the dump generated here is used for some additional DCE: if the Objective-C/Swift code doesn't use certain generated method, using this dump we can find the original Kotlin declaration that doesn't need to be exposed then.

The problem with this implementation is therefore the following: if the generated nsEnum property of a class is not used, the compiler will be instructed to hide Enum.ordinal, which is not exactly intended.

See these changes for more details:

• 6473bc5
• 9ef93a1

[stefanhaustein]

I have changed the return value to null, does this make sense?