Native Swift Set support for jextract/jni

Samples/SwiftJavaExtractJNISampleApp/Sources/MySwiftLibrary/Set.swift

@@ -0,0 +1,43 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2025 Apple Inc. and the Swift.org project authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of Swift.org project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+
+public func makeStringSet() -> Set<String> {
+  ["hello", "world"]
+}
+
+public func stringSet(set: Set<String>) -> Set<String> {
+  set
+}
+
+public func insertIntoStringSet(set: Set<String>, element: String) -> Set<String> {
+  var copy = set
+  copy.insert(element)
+  return copy
+}
+
+public func makeIntegerSet() -> Set<Int32> {
+  [1, 2, 3]
+}
+
+public func integerSet(set: Set<Int32>) -> Set<Int32> {
+  set
+}
+
+public func makeLongSet() -> Set<Int> {
+  [10, 20, 30]
+}
+
+public func longSet(set: Set<Int>) -> Set<Int> {
+  set
+}

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

@@ -0,0 +1,144 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2025 Apple Inc. and the Swift.org project authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of Swift.org project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+
+package com.example.swift;
+
+import java.util.HashSet;
+import java.util.Set;
+import org.junit.jupiter.api.Test;
+import org.swift.swiftkit.core.collections.SwiftSet;
+import org.swift.swiftkit.core.SwiftArena;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+public class SwiftSetTest {
+    @Test
+    void makeStringSet() {
+        try (var arena = SwiftArena.ofConfined()) {
+            SwiftSet<String> set = MySwiftLibrary.makeStringSet(arena);
+            assertEquals(2, set.size());
+            assertTrue(set.contains("hello"));
+            assertTrue(set.contains("world"));
+            assertFalse(set.contains("missing"));
+        }
+    }
+
+    @Test
+    void stringSetRoundtrip() {
+        try (var arena = SwiftArena.ofConfined()) {
+            SwiftSet<String> original = MySwiftLibrary.makeStringSet(arena);
+            SwiftSet<String> roundtripped = MySwiftLibrary.stringSet(original, arena);
+            assertEquals(original.size(), roundtripped.size());
+            assertTrue(roundtripped.contains("hello"));
+            assertTrue(roundtripped.contains("world"));
+        }
+    }
+
+    @Test
+    void insertIntoStringSet() {
+        try (var arena = SwiftArena.ofConfined()) {
+            SwiftSet<String> original = MySwiftLibrary.makeStringSet(arena);
+            assertEquals(2, original.size());
+
+            // Insert a new element by passing the set through Swift
+            SwiftSet<String> modified =
+                MySwiftLibrary.insertIntoStringSet(original, "swift", arena);
+
+            // The modified set has the new element
+            assertEquals(3, modified.size());
+            assertTrue(modified.contains("hello"));
+            assertTrue(modified.contains("world"));
+            assertTrue(modified.contains("swift"));
+
+            // The original set is unchanged (Swift value semantics — it's a copy)
+            assertEquals(2, original.size());
+            assertFalse(original.contains("swift"));
+        }
+    }
+
+    @Test
+    void toJavaSet() {
+        Set<String> javaSet;
+        try (var arena = SwiftArena.ofConfined()) {
+            SwiftSet<String> set = MySwiftLibrary.makeStringSet(arena);
+            javaSet = set.toJavaSet();
+
+            // The copy has the same contents as the original
+            assertEquals(2, javaSet.size());
+            assertTrue(javaSet.contains("hello"));
+            assertTrue(javaSet.contains("world"));
+            assertFalse(javaSet.contains("missing"));
+
+            // It's a plain HashSet, not the native-backed set
+            assertInstanceOf(HashSet.class, javaSet);
+        }
+
+        // The Java set copy survives arena closure
+        assertEquals(2, javaSet.size());
+        assertTrue(javaSet.contains("hello"));
+        assertTrue(javaSet.contains("world"));
+    }
+
+    // ==== Swift Set<Int32> -> Java Set<Integer> tests ====
+
+    @Test
+    void makeIntegerSet() {
+        try (var arena = SwiftArena.ofConfined()) {
+            SwiftSet<Integer> set = MySwiftLibrary.makeIntegerSet(arena);
+            assertEquals(3, set.size());
+            assertTrue(set.contains(1));
+            assertTrue(set.contains(2));
+            assertTrue(set.contains(3));
+            assertFalse(set.contains(42));
+        }
+    }
+
+    @Test
+    void integerSetRoundtrip() {
+        try (var arena = SwiftArena.ofConfined()) {
+            SwiftSet<Integer> original = MySwiftLibrary.makeIntegerSet(arena);
+            SwiftSet<Integer> roundtripped = MySwiftLibrary.integerSet(original, arena);
+            assertEquals(original.size(), roundtripped.size());
+            assertTrue(roundtripped.contains(1));
+            assertTrue(roundtripped.contains(2));
+            assertTrue(roundtripped.contains(3));
+        }
+    }
+
+    // ==== Swift Set<Int> -> Java Set<Long> tests ====
+
+    @Test
+    void makeLongSet() {
+        try (var arena = SwiftArena.ofConfined()) {
+            SwiftSet<Long> set = MySwiftLibrary.makeLongSet(arena);
+            assertEquals(3, set.size());
+            assertTrue(set.contains(10L));
+            assertTrue(set.contains(20L));
+            assertTrue(set.contains(30L));
+            assertFalse(set.contains(99L));
+        }
+    }
+
+    @Test
+    void longSetRoundtrip() {
+        try (var arena = SwiftArena.ofConfined()) {
+            SwiftSet<Long> original = MySwiftLibrary.makeLongSet(arena);
+            SwiftSet<Long> roundtripped = MySwiftLibrary.longSet(original, arena);
+            assertEquals(original.size(), roundtripped.size());
+            assertTrue(roundtripped.contains(10L));
+            assertTrue(roundtripped.contains(20L));
+            assertTrue(roundtripped.contains(30L));
+        }
+    }
+}

Sources/JExtractSwiftLib/FFM/CDeclLowering/CRepresentation.swift

@@ -70,7 +70,7 @@ extension CType {
     case .optional(let wrapped) where wrapped.isPointer:
       try self.init(cdeclType: wrapped)
 
-    case .genericParameter, .metatype, .optional, .tuple, .opaque, .existential, .composite, .array, .dictionary:
+    case .genericParameter, .metatype, .optional, .tuple, .opaque, .existential, .composite, .array, .dictionary, .set:
       throw CDeclToCLoweringError.invalidCDeclType(cdeclType)
     }
   }

Sources/JExtractSwiftLib/FFM/CDeclLowering/FFMSwift2JavaGenerator+FunctionLowering.swift

@@ -438,6 +438,9 @@ struct CdeclLowering {
 
     case .dictionary:
       throw LoweringError.unhandledType(type)
+
+    case .set:
+      throw LoweringError.unhandledType(type)
     }
   }
 
@@ -530,7 +533,7 @@ struct CdeclLowering {
       }
       throw LoweringError.unhandledType(.optional(wrappedType))
 
-    case .function, .metatype, .optional, .composite, .array, .dictionary:
+    case .function, .metatype, .optional, .composite, .array, .dictionary, .set:
       throw LoweringError.unhandledType(.optional(wrappedType))
     }
   }
@@ -632,7 +635,7 @@ struct CdeclLowering {
       // Custom types are not supported yet.
       throw LoweringError.unhandledType(type)
 
-    case .genericParameter, .function, .metatype, .optional, .tuple, .existential, .opaque, .composite, .array, .dictionary:
+    case .genericParameter, .function, .metatype, .optional, .tuple, .existential, .opaque, .composite, .array, .dictionary, .set:
       // TODO: Implement
       throw LoweringError.unhandledType(type)
     }
@@ -835,7 +838,7 @@ struct CdeclLowering {
         )
       )
 
-    case .genericParameter, .function, .optional, .existential, .opaque, .composite, .array, .dictionary:
+    case .genericParameter, .function, .optional, .existential, .opaque, .composite, .array, .dictionary, .set:
       throw LoweringError.unhandledType(type)
     }
   }

Sources/JExtractSwiftLib/FFM/FFMSwift2JavaGenerator+JavaTranslation.swift

@@ -511,6 +511,9 @@ extension FFMSwift2JavaGenerator {
 
       case .dictionary:
         throw JavaTranslationError.unhandledType(swiftType)
+
+      case .set:
+        throw JavaTranslationError.unhandledType(swiftType)
       }
     }
 
@@ -742,7 +745,7 @@ extension FFMSwift2JavaGenerator {
           )
         )
 
-      case .genericParameter, .optional, .function, .existential, .opaque, .composite, .array, .dictionary:
+      case .genericParameter, .optional, .function, .existential, .opaque, .composite, .array, .dictionary, .set:
         throw JavaTranslationError.unhandledType(swiftType)
       }
 

Sources/JExtractSwiftLib/JNI/JNIJavaTypeTranslator.swift

@@ -50,6 +50,7 @@ enum JNIJavaTypeTranslator {
       .essentialsData, .essentialsDataProtocol,
       .array,
       .dictionary,
+      .set,
       .foundationDate, .essentialsDate,
       .foundationUUID, .essentialsUUID:
       return nil
@@ -75,6 +76,7 @@ enum JNIJavaTypeTranslator {
       .essentialsData, .essentialsDataProtocol,
       .array,
       .dictionary,
+      .set,
       .foundationDate, .essentialsDate,
       .foundationUUID, .essentialsUUID:
       nil
@@ -100,6 +102,7 @@ enum JNIJavaTypeTranslator {
       .essentialsData, .essentialsDataProtocol,
       .array,
       .dictionary,
+      .set,
       .foundationDate, .essentialsDate,
       .foundationUUID, .essentialsUUID:
       nil

Sources/JExtractSwiftLib/JNI/JNISwift2JavaGenerator+InterfaceWrapperGeneration.swift

@@ -241,6 +241,9 @@ extension JNISwift2JavaGenerator {
       case .dictionary:
         throw JavaTranslationError.unsupportedSwiftType(type)
 
+      case .set:
+        throw JavaTranslationError.unsupportedSwiftType(type)
+
       case .genericParameter, .function, .metatype, .tuple, .existential, .opaque, .composite:
         throw JavaTranslationError.unsupportedSwiftType(type)
       }
@@ -259,7 +262,7 @@ extension JNISwift2JavaGenerator {
           )
         )
 
-      case .array, .dictionary, .composite, .existential, .function, .genericParameter, .metatype, .opaque, .optional, .tuple:
+      case .array, .dictionary, .set, .composite, .existential, .function, .genericParameter, .metatype, .opaque, .optional, .tuple:
         throw JavaTranslationError.unsupportedSwiftType(.array(elementType))
       }
     }
@@ -330,6 +333,9 @@ extension JNISwift2JavaGenerator {
       case .dictionary:
         throw JavaTranslationError.unsupportedSwiftType(type)
 
+      case .set:
+        throw JavaTranslationError.unsupportedSwiftType(type)
+
       case .genericParameter, .function, .metatype, .tuple, .existential, .opaque, .composite:
         throw JavaTranslationError.unsupportedSwiftType(type)
       }
@@ -348,7 +354,7 @@ extension JNISwift2JavaGenerator {
           )
         )
 
-      case .array, .dictionary, .composite, .existential, .function, .genericParameter, .metatype, .opaque, .optional, .tuple:
+      case .array, .dictionary, .set, .composite, .existential, .function, .genericParameter, .metatype, .opaque, .optional, .tuple:
         throw JavaTranslationError.unsupportedSwiftType(.array(elementType))
       }
     }
@@ -484,7 +490,7 @@ extension SwiftType {
     case .array(let elementType):
       return elementType.isDirectlyTranslatedToWrapJava
 
-    case .genericParameter, .function, .metatype, .optional, .tuple, .existential, .opaque, .composite, .dictionary:
+    case .genericParameter, .function, .metatype, .optional, .tuple, .existential, .opaque, .composite, .dictionary, .set:
       return false
     }
   }