jextract: Translate Swift () -> () to java Runnable

[AmrDeveloper]

Translate the Swift function parameter type () -> () to the Java Runnable interface

Issue: #811

[ktoso]

So this only does the FFM mode, could you also please do the JNI mode?

Then also please make sure we have a runtime test -- i.e. a test in Samples/SwiftJavaExtractJNISampleApp/Sources/MySwiftLibrary and Samples/SwiftJavaExtractJNISampleApp/src/test/java/com/example/swift that covers this so we didn't regress anythign and run end to end?

[ktoso]

Yeah samples broke:

/__w/swift-java/swift-java/Samples/SwiftAndJavaJarFFMSampleLib/.build/plugins/outputs/swiftandjavajarffmsamplelib/MySwiftLibrary/destination/JExtractSwiftPlugin/src/generated/java/com/example/swift/MySwiftLibrary.java:240: error: incompatible types: Runnable cannot be converted to run
      swiftjava_MySwiftLibrary_globalCallMeRunnable_run.call(globalCallMeRunnable.$toUpcallStub(run, arena$));
                                                                                                ^
Note: Some messages have been simplified; recompile with -Xdiags:verbose to get full output
1 error

You can run them by

  cd Samples/SwiftAndJavaJarFFMSampleLib
  ./ci-validate.sh

[AmrDeveloper]

So this only does the FFM mode, could you also please do the JNI mode?

Then also please make sure we have a runtime test -- i.e. a test in Samples/SwiftJavaExtractJNISampleApp/Sources/MySwiftLibrary and Samples/SwiftJavaExtractJNISampleApp/src/test/java/com/example/swift that covers this so we didn't regress anythign and run end to end?

I think we already have a test for Closures

swift-java/Samples/SwiftJavaExtractJNISampleApp/Sources/MySwiftLibrary/Closures.swift

Line 15 in c235a0f

public func emptyClosure(closure: () -> Void) {

https://github.com/swiftlang/swift-java/blob/main/Samples/SwiftJavaExtractJNISampleApp/src/test/java/com/example/swift/ClosuresTest.java

[AmrDeveloper]

I am still thinking of having a map to hold all names for functional interfaces 🤔

[ktoso]

Let's make a file with KnownFunctionalInterfaces.swift and cases on there; they should all have case ...(JavaType, method: ...) since they all have a single method and then we can take the name off off that

[ktoso]

I'd really welcome a follow up PR fixing this up so it's less random method names in here like that

[ktoso]

Good Yeap!