jextract/jni: Support optional tuple return values

Samples/SwiftJavaExtractJNISampleApp/Sources/MySwiftLibrary/Optionals.swift

@@ -91,3 +91,11 @@ public func multipleOptionals(
 ) -> Int64? {
   1
 }
+
+public func optionalTuple() -> (Int64, String)? {
+  (42, "hello")
+}
+
+public func optionalTuple2() -> (Int64?, Alignment?)? {
+  (42, .horizontal)
+}

Samples/SwiftJavaExtractJNISampleApp/Sources/MySwiftLibrary/Tuples.swift

@@ -45,3 +45,7 @@ public func makeBigTuple() -> (
 public func namedByteArrayTuple() -> (name: [UInt8], another: [UInt8]) {
   (name: [1, 2, 3], another: [4, 5])
 }
+
+public func genericTypeTuple() -> (MyID<Double>, Alignment) {
+  (MyID(1.23), .horizontal)
+}

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

@@ -143,4 +143,30 @@ void optionalThrows() {
             assertEquals("swiftError", exception.getMessage());
         }
     }
-}
+
+    @Test
+    void optionalTuple() {
+        var result = MySwiftLibrary.optionalTuple();
+        assertDoesNotThrow(() -> {
+            var resultUnwrapped = result.orElseThrow();
+            assertEquals(42, resultUnwrapped.$0);
+            assertEquals("hello", resultUnwrapped.$1);
+        });
+    }
+
+    @Test
+    void optionalTuple2() {
+        try (var arena = SwiftArena.ofConfined()) {
+            var result = MySwiftLibrary.optionalTuple2(arena);
+            assertDoesNotThrow(() -> {
+                var resultUnwrapped = result.orElseThrow();
+                assertDoesNotThrow(() -> {
+                    assertEquals(42, resultUnwrapped.$0.orElseThrow());
+                });
+                assertDoesNotThrow(() -> {
+                    assertEquals(Alignment.Discriminator.HORIZONTAL, resultUnwrapped.$1.orElseThrow().getDiscriminator());
+                });
+            });
+        }
+    }
+}

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

@@ -15,6 +15,7 @@
 package com.example.swift;
 
 import org.junit.jupiter.api.Test;
+import org.swift.swiftkit.core.SwiftArena;
 import org.swift.swiftkit.core.tuple.Tuple2;
 import org.swift.swiftkit.core.tuple.Tuple3;
 import org.swift.swiftkit.core.tuple.Tuple16;
@@ -95,4 +96,13 @@ void namedByteArrayTuple() {
         assertArrayEquals(new byte[] { 1, 2, 3 }, (byte[]) result.$0);
         assertArrayEquals(new byte[] { 4, 5 }, (byte[]) result.$1);
     }
+
+    @Test
+    void genericTypeTuple() {
+        try (var arena = SwiftArena.ofConfined()) {
+            var result = MySwiftLibrary.genericTypeTuple(arena);
+            assertEquals("1.23", result.$0.getDescription());
+            assertEquals(Alignment.Discriminator.HORIZONTAL, result.$1.getDiscriminator());
+        }
+    }
 }