[JExtract] Adopt SwiftFunctionSignature and the lowering mechanisms

* Utilize `SwiftFunctionSignature` and the cdecl-lowering  facilities
  throughout the code base.
  * `SwiftFunctionSignature` is created from the `DeclSyntax` in
    `Swift2JavaVisitor`.
  * `LoweredFunctionSignature` describing `@cdecl` thunk, is created
    from `SwiftFunctionSignature`.
  * `TranslatedFunctionSignature` describing generated Java API, is
    created from `LoweredFunctionSignature`.
    (Swift2JavaTranslator+JavaTranslation.swift)
  * `ImportedFunc` is now basically just a wrapper of
    `TranslatedFunctionSignature` with the `name`.

* Remove `ImportedVariable`, instead variables are described as
  `ImportedFunc` as accessors.
* Support APIs returning imported type values. E.g.
  `func factory(arg: Int) -> MyClass` such methods require `SwiftArena`
  parameter passed-in.
* Built-in lowerings (e.g. `toCString(String)` for `String` -> C string
  conversion) are now implemented in JavaKit.
* Stop emitting `MyClass::apiName$descriptor()` method etc. as they were
  not used.
* Use the `@cdecl` thunk name as the function descriptor class name, for
  simplicity.
* Getter and setter accessors are now completely separate API. No more
  `HANDLE_GET` and `HANDLE_SET` etc. Instead descriptor class is split
  to `$get` or `$set` suffixed name.

Author: rintaro

Samples/SwiftAndJavaJarSampleLib/src/test/java/com/example/swift/MySwiftLibraryTest.java

@@ -30,15 +30,11 @@ public class MySwiftLibraryTest {
     @Test
     void call_helloWorld() {
         MySwiftLibrary.helloWorld();
-
-        assertNotNull(MySwiftLibrary.helloWorld$address());
     }
 
     @Test
     void call_globalTakeInt() {
         MySwiftLibrary.globalTakeInt(12);
-
-        assertNotNull(MySwiftLibrary.globalTakeInt$address());
     }
 
     @Test

Samples/SwiftKitSampleApp/Sources/MySwiftLibrary/MySwiftClass.swift

@@ -34,6 +34,10 @@ public class MySwiftClass {
 
   public var counter: Int32 = 0
 
+  public static func factory(len: Int, cap: Int) -> MySwiftClass {
+    return MySwiftClass(len: len, cap: cap)
+  }
+
   public func voidMethod() {
     p("")
   }

Samples/SwiftKitSampleApp/build.gradle

@@ -81,7 +81,7 @@ def jextract = tasks.register("jextract", Exec) {
 
     workingDir = layout.projectDirectory
     commandLine "swift"
-    args("package", "jextract", "-v", "--log-level", "info") // TODO: pass log level from Gradle build
+    args("package", "jextract", "-v", "--log-level", "debug") // TODO: pass log level from Gradle build
 }
 
 // Add the java-swift generated Java sources

Samples/SwiftKitSampleApp/src/main/java/com/example/swift/HelloJava2Swift.java

@@ -16,13 +16,10 @@
 
 // Import swift-extract generated sources
 
-import com.example.swift.MySwiftLibrary;
-import com.example.swift.MySwiftClass;
-
 // Import javakit/swiftkit support libraries
+
 import org.swift.swiftkit.SwiftArena;
 import org.swift.swiftkit.SwiftKit;
-import org.swift.swiftkit.SwiftValueWitnessTable;
 
 public class HelloJava2Swift {
 
@@ -40,21 +37,33 @@ static void examples() {
 
         MySwiftLibrary.globalTakeInt(1337);
 
+        long cnt = MySwiftLibrary.globalWriteString("String from Java");
+
+        SwiftKit.trace("count = " + cnt);
+
+        MySwiftLibrary.globalCallMeRunnable(() -> {
+            SwiftKit.trace("running runnable");
+        });
+
         // Example of using an arena; MyClass.deinit is run at end of scope
         try (var arena = SwiftArena.ofConfined()) {
-             MySwiftClass obj = new MySwiftClass(2222, 7777, arena);
+            MySwiftClass obj = new MySwiftClass(2222, 7777, arena);
+
+            // just checking retains/releases work
+            SwiftKit.trace("retainCount = " + SwiftKit.retainCount(obj));
+            SwiftKit.retain(obj);
+            SwiftKit.trace("retainCount = " + SwiftKit.retainCount(obj));
+            SwiftKit.release(obj);
+            SwiftKit.trace("retainCount = " + SwiftKit.retainCount(obj));
 
-             // just checking retains/releases work
-             SwiftKit.trace("retainCount = " + SwiftKit.retainCount(obj));
-             SwiftKit.retain(obj);
-             SwiftKit.trace("retainCount = " + SwiftKit.retainCount(obj));
-             SwiftKit.release(obj);
-             SwiftKit.trace("retainCount = " + SwiftKit.retainCount(obj));
+            obj.setCounter(12);
+            SwiftKit.trace("obj.counter = " + obj.getCounter());
 
-             obj.voidMethod();
-             obj.takeIntMethod(42);
+            obj.voidMethod();
+            obj.takeIntMethod(42);
 
             MySwiftStruct swiftValue = new MySwiftStruct(2222, 1111, arena);
+            SwiftKit.trace("swiftValue.capacity = " + swiftValue.getCapacity());
         }
 
         System.out.println("DONE.");

Samples/SwiftKitSampleApp/src/test/java/com/example/swift/MySwiftLibraryTest.java

@@ -35,15 +35,11 @@ public class MySwiftLibraryTest {
     @Test
     void call_helloWorld() {
         MySwiftLibrary.helloWorld();
-
-        assertNotNull(MySwiftLibrary.helloWorld$address());
     }
 
     @Test
     void call_globalTakeInt() {
         MySwiftLibrary.globalTakeInt(12);
-
-        assertNotNull(MySwiftLibrary.globalTakeInt$address());
     }
 
     @Test

Sources/JExtractSwift/CDeclLowering/Swift2JavaTranslator+FunctionLowering.swift

@@ -619,14 +619,7 @@ extension LoweredFunctionSignature {
 
   @_spi(Testing)
   public func cFunctionDecl(cName: String) throws -> CFunction {
-    return CFunction(
-      resultType: try CType(cdeclType: self.result.cdeclResultType),
-      name: cName,
-      parameters: try self.allLoweredParameters.map {
-        try CParameter(name: $0.parameterName, type: CType(cdeclType: $0.type).parameterDecay)
-      },
-      isVariadic: false
-    )
+    try CFunction(cdeclSignature: self.cdeclSignature, cName: cName)
   }
 }
 

Sources/JExtractSwift/CTypes/CType.swift

@@ -298,3 +298,12 @@ extension CType {
     }
   }
 }
+
+extension CType {
+  var isVoid: Bool {
+    return switch self {
+    case .void: true
+    default: false
+    }
+  }
+}

Sources/JExtractSwift/CodePrinter.swift

@@ -68,16 +68,16 @@ public struct CodePrinter {
     }
   }
 
-  public mutating func printTypeDecl(
-    _ text: Any,
+  public mutating func printBraceBlock(
+    _ header: Any,
     function: String = #function,
     file: String = #fileID,
     line: UInt = #line,
-    body: (inout CodePrinter) -> ()
-  ) {
-    print("\(text) {")
+    body: (inout CodePrinter) throws -> ()
+  ) rethrows {
+    print("\(header) {")
     indent()
-    body(&self)
+    try body(&self)
     outdent()
     print("}", .sloc, function: function, file: file, line: line)
   }
@@ -145,9 +145,10 @@ public struct CodePrinter {
 
   // TODO: remove this in real mode, this just helps visually while working on it
   public mutating func printSeparator(_ text: String) {
-    // TODO: actually use the indentationDepth
+    assert(!text.contains(where: \.isNewline))
     print(
       """
+
       // ==== --------------------------------------------------
       // \(text)
 

Sources/JExtractSwift/Convenience/SwiftSyntax+Extensions.swift

@@ -36,39 +36,6 @@ extension ImplicitlyUnwrappedOptionalTypeSyntax {
   }
 }
 
-extension SyntaxProtocol {
-
-  var asNominalTypeKind: NominalTypeKind {
-    if isClass {
-      .class
-    } else if isActor {
-      .actor
-    } else if isStruct {
-      .struct
-    } else if isEnum {
-      .enum
-    } else {
-      fatalError("Unknown nominal kind: \(self)")
-    }
-  }
-
-  var isClass: Bool {
-    return self.is(ClassDeclSyntax.self)
-  }
-
-  var isActor: Bool {
-    return self.is(ActorDeclSyntax.self)
-  }
-
-  var isEnum: Bool {
-    return self.is(EnumDeclSyntax.self)
-  }
-
-  var isStruct: Bool {
-    return self.is(StructDeclSyntax.self)
-  }
-}
-
 extension DeclModifierSyntax {
   var isAccessControl: Bool {
     switch self.name.tokenKind {