jextract: Support Java Int & Long to Double func interfaces

Samples/SwiftAndJavaJarFFMSampleLib/Sources/MySwiftLibrary/MySwiftLibrary.swift

@@ -116,6 +116,14 @@ public func globalCallMeIntToLongFunction(run: (Int32) -> Int64) -> Int64 {
   run(1)
 }
 
+public func globalCallMeIntToDoubleFunction(run: (Int32) -> Double) -> Double {
+  run(1)
+}
+
+public func globalCallMeLongToDoubleFunction(run: (Int64) -> Double) -> Double {
+  run(1)
+}
+
 // ==== Internal helpers
 
 func p(_ msg: String, file: String = #fileID, line: UInt = #line, function: String = #function) {

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

@@ -168,4 +168,16 @@ void call_globalCallMeIntToLongFunction_noThrow() {
         long result = MySwiftLibrary.globalCallMeIntToLongFunction((int a) -> { return (long) a; });
         assertEquals(1L, result);
     }
+
+    @Test
+    void call_globalCallMeIntToDoubleFunction_noThrow() {
+        double result = MySwiftLibrary.globalCallMeIntToDoubleFunction((int a) -> { return (double) a; });
+        assertEquals(1.0, result);
+    }
+
+    @Test
+    void call_globalCallMeLongToDoubleFunction_noThrow() {
+        double result = MySwiftLibrary.globalCallMeLongToDoubleFunction((long a) -> { return (double) a; });
+        assertEquals(1.0, result);
+    }
 }

Samples/SwiftJavaExtractFFMSampleApp/Sources/MySwiftLibrary/MySwiftLibrary.swift

@@ -128,6 +128,14 @@ public func globalCallMeIntToLongFunction(run: (Int32) -> Int64) -> Int64 {
   run(1)
 }
 
+public func globalCallMeIntToDoubleFunction(run: (Int32) -> Double) -> Double {
+  run(1)
+}
+
+public func globalCallMeLongToDoubleFunction(run: (Int64) -> Double) -> Double {
+  run(1)
+}
+
 public func globalReceiveRawBuffer(buf: UnsafeRawBufferPointer) -> Int {
   buf.count
 }

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

@@ -280,4 +280,16 @@ void call_globalCallMeIntToLongFunction_noThrow() {
         long result = MySwiftLibrary.globalCallMeIntToLongFunction((int a) -> { return (long) a; });
         assertEquals(1L, result);
     }
+
+    @Test
+    void call_globalCallMeIntToDoubleFunction_noThrow() {
+        double result = MySwiftLibrary.globalCallMeIntToDoubleFunction((int a) -> { return (double) a; });
+        assertEquals(1.0, result);
+    }
+
+    @Test
+    void call_globalCallMeLongToDoubleFunction_noThrow() {
+        double result = MySwiftLibrary.globalCallMeLongToDoubleFunction((long a) -> { return (double) a; });
+        assertEquals(1.0, result);
+    }
 }

Samples/SwiftJavaExtractJNISampleApp/Sources/MySwiftLibrary/Closures.swift

@@ -101,6 +101,14 @@ public func globalCallMeIntToLongFunction(run: (Int32) -> Int64) -> Int64 {
   run(1)
 }
 
+public func globalCallMeIntToDoubleFunction(run: (Int32) -> Double) -> Double {
+  run(1)
+}
+
+public func globalCallMeLongToDoubleFunction(run: (Int64) -> Double) -> Double {
+  run(1)
+}
+
 public func closureMultipleArguments(
   input1: Int64,
   input2: Int64,

Samples/SwiftJavaExtractJNISampleApp/src/test/java/com/example/swift/ClosuresTest.java

@@ -164,4 +164,16 @@ void globalCallMeIntToLongFunction() {
         long result = MySwiftLibrary.globalCallMeIntToLongFunction((int a) -> { return (long) a; });
         assertEquals(1L, result);
     }
+
+    @Test
+    void globalCallMeIntToDoubleFunction() {
+        double result = MySwiftLibrary.globalCallMeIntToDoubleFunction((int a) -> { return (double) a; });
+        assertEquals(1.0, result);
+    }
+
+    @Test
+    void globalCallMeLongToDoubleFunction() {
+        double result = MySwiftLibrary.globalCallMeLongToDoubleFunction((long a) -> { return (double) a; });
+        assertEquals(1.0, result);
+    }
 }

Sources/ExampleSwiftLibrary/MySwiftLibrary.swift

@@ -123,6 +123,14 @@ public func globalCallMeIntToLongFunction(run: (Int32) -> Int64) -> Int64 {
   run(1)
 }
 
+public func globalCallMeIntToDoubleFunction(run: (Int32) -> Double) -> Double {
+  run(1)
+}
+
+public func globalCallMeLongToDoubleFunction(run: (Int64) -> Double) -> Double {
+  run(1)
+}
+
 public func globalReceiveRawBuffer(buf: UnsafeRawBufferPointer) -> Int {
   buf.count
 }

Sources/JExtractSwiftLib/JavaTypes/JavaType+JDK.swift

@@ -130,6 +130,16 @@ extension JavaType {
     .class(package: "java.util.function", name: "IntToLongFunction")
   }
 
+  /// The description of the type java.util.function.IntToDoubleFunction.
+  static var javaUtilFunctionIntToDoubleFunction: JavaType {
+    .class(package: "java.util.function", name: "IntToDoubleFunction")
+  }
+
+  /// The description of the type java.util.function.LongToDoubleFunction.
+  static var javaUtilFunctionLongToDoubleFunction: JavaType {
+    .class(package: "java.util.function", name: "LongToDoubleFunction")
+  }
+
   /// The description of the type java.lang.Class.
   static var javaLangClass: JavaType {
     .class(package: "java.lang", name: "Class")

Sources/JExtractSwiftLib/KnownFunctionalInterfaces.swift

@@ -169,6 +169,20 @@ struct KnownJavaFunctionalInterface: Sendable {
     result: .long
   )
 
+  static let intToDoubleFunction = KnownJavaFunctionalInterface(
+    JavaType.javaUtilFunctionIntToDoubleFunction,
+    method: "applyAsDouble",
+    parameters: [.int],
+    result: .double
+  )
+
+  static let longToDoubleFunction = KnownJavaFunctionalInterface(
+    JavaType.javaUtilFunctionLongToDoubleFunction,
+    method: "applyAsDouble",
+    parameters: [.long],
+    result: .double
+  )
+
   static let all: [KnownJavaFunctionalInterface] = [
     .runnable,
     .booleanSupplier,
@@ -191,6 +205,8 @@ struct KnownJavaFunctionalInterface: Sendable {
     .longToIntFunction,
     .doubleToLongFunction,
     .intToLongFunction,
+    .intToDoubleFunction,
+    .longToDoubleFunction,
   ]
 
   static func find(parameters: [JavaType], result: JavaType) -> KnownJavaFunctionalInterface? {
@@ -306,6 +322,19 @@ struct KnownJavaFunctionalInterface: Sendable {
       }
     }
 
+    // To double functions
+    if parameters.count == 1 && result.isDouble {
+      let parameter = parameters[0].type
+      return switch () {
+      case _ where parameter.isInt32:
+        intToDoubleFunction
+      case _ where parameter.isInt64:
+        longToDoubleFunction
+      default:
+        nil
+      }
+    }
+
     // Binary operators
     if parameters.count == 2 && parameters[0].type == result && parameters[1].type == result {
       let parameter = parameters[0].type

Tests/JExtractSwiftTests/FuncCallbackImportTests.swift

@@ -53,6 +53,9 @@ final class FuncCallbackImportTests {
     public func callMeDoubleToLongFunction(callback: (Double) -> Int64)
     public func callMeIntToLongFunction(callback: (Int32) -> Int64)
 
+    public func callMeIntToDoubleFunction(callback: (Int32) -> Double)
+    public func callMeLongToDoubleFunction(callback: (Int64) -> Double)
+
     public func callMeIntUnaryOperator(callback: (Int32) -> Int32)
     public func callMeLongUnaryOperator(callback: (Int64) -> Int64)
     public func callMeDoubleUnaryOperator(callback: (Double) -> Double)
@@ -1032,6 +1035,92 @@ final class FuncCallbackImportTests {
     )
   }
 
+  @Test("Import: public func callMeIntToDoubleFunction(callback: (Int32) -> Double)")
+  func func_callMecallMeIntToDoubleFunctionFunc_callback() throws {
+    var config = Configuration()
+    config.swiftModule = "__FakeModule"
+    let st = makeSwiftJavaAnalyzer(config: config)
+    st.log.logLevel = .error
+
+    try st.analyze(path: "Fake.swift", text: Self.class_interfaceFile)
+
+    let funcDecl = st.extractedGlobalFuncs.first { $0.name == "callMeIntToDoubleFunction" }!
+
+    let generator = FFMSwift2JavaGenerator(
+      config: config,
+      translator: st,
+      javaPackage: "com.example.swift",
+      swiftOutputDirectory: "/fake",
+      javaOutputDirectory: "/fake"
+    )
+
+    let output = JavaPrinter.toString { printer in
+      generator.printFunctionDowncallMethods(&printer, funcDecl)
+    }
+
+    assertOutput(
+      output,
+      expectedChunks: [
+        """
+        /**
+         * Downcall to Swift:
+         * {@snippet lang=swift :
+         * public func callMeIntToDoubleFunction(callback: (Int32) -> Double)
+         * }
+         */
+        public static void callMeIntToDoubleFunction(java.util.function.IntToDoubleFunction callback) {
+          try(var arena$ = Arena.ofConfined()) {
+            swiftjava___FakeModule_callMeIntToDoubleFunction_callback.call(callMeIntToDoubleFunction.$toUpcallStub(callback, arena$));
+          }
+        }
+        """
+      ]
+    )
+  }
+
+  @Test("Import: public func callMeLongToDoubleFunction(callback: (Int64) -> Double)")
+  func func_callMecallMeLongToDoubleFunctionFunc_callback() throws {
+    var config = Configuration()
+    config.swiftModule = "__FakeModule"
+    let st = makeSwiftJavaAnalyzer(config: config)
+    st.log.logLevel = .error
+
+    try st.analyze(path: "Fake.swift", text: Self.class_interfaceFile)
+
+    let funcDecl = st.extractedGlobalFuncs.first { $0.name == "callMeLongToDoubleFunction" }!
+
+    let generator = FFMSwift2JavaGenerator(
+      config: config,
+      translator: st,
+      javaPackage: "com.example.swift",
+      swiftOutputDirectory: "/fake",
+      javaOutputDirectory: "/fake"
+    )
+
+    let output = JavaPrinter.toString { printer in
+      generator.printFunctionDowncallMethods(&printer, funcDecl)
+    }
+
+    assertOutput(
+      output,
+      expectedChunks: [
+        """
+        /**
+         * Downcall to Swift:
+         * {@snippet lang=swift :
+         * public func callMeLongToDoubleFunction(callback: (Int64) -> Double)
+         * }
+         */
+        public static void callMeLongToDoubleFunction(java.util.function.LongToDoubleFunction callback) {
+          try(var arena$ = Arena.ofConfined()) {
+            swiftjava___FakeModule_callMeLongToDoubleFunction_callback.call(callMeLongToDoubleFunction.$toUpcallStub(callback, arena$));
+          }
+        }
+        """
+      ]
+    )
+  }
+
   @Test("Import: public func callMecallMeIntBinaryOperatorFunc(callback: (Int32, Int32) -> Int32)")
   func func_callMecallMeIntBinaryOperatorFunc_callback() throws {
     var config = Configuration()