jextract/jni: Implement generic equals method

Samples/SwiftJavaExtractJNISampleApp/Sources/MySwiftLibrary/EquatableClass.swift

@@ -0,0 +1,30 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2026 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 class EquatableClass: Equatable {
+  public let value: Int
+  public init(value: Int) {
+    self.value = value
+  }
+
+  public static func == (lhs: EquatableClass, rhs: EquatableClass) -> Bool {
+    lhs.value == rhs.value
+  }
+}
+
+public class EquatableSubclass: EquatableClass {
+  public override init(value: Int) {
+    super.init(value: value)
+  }
+}

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

@@ -0,0 +1,52 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2026 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 org.junit.jupiter.api.Test;
+import org.swift.swiftkit.core.SwiftArena;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+@SuppressWarnings({"AssertBetweenInconvertibleTypes", "EqualsWithItself"})
+public class EquatableTest {
+    @Test
+    void genericStructType() {
+        try (var arena = SwiftArena.ofConfined()) {
+            var a = MyIDs.makeIntID(42, arena);
+            var b = MyIDs.makeIntID(42, arena);
+            var c = MyIDs.makeIntID(0, arena);
+            var d = MyIDs.makeStringID("42", arena);
+            assertEquals(a, a);
+            assertEquals(a, b);
+            assertNotEquals(a, c);
+            assertNotEquals(a, d);
+            assertNotEquals("foo", a);
+        }
+    }
+
+    @Test
+    void classType() {
+        try (var arena = SwiftArena.ofConfined()) {
+            var a = EquatableClass.init(42, arena);
+            var b = EquatableSubclass.init(42, arena);
+            var c = EquatableSubclass.init(0, arena);
+            assertEquals(a, b);
+            assertEquals(b, a);
+            assertEquals(b, b);
+            assertNotEquals(a, c);
+            assertNotEquals(b, c);
+        }
+    }
+}

Sources/JExtractSwiftLib/JNI/JNISwift2JavaGenerator+JavaBindingsPrinting.swift

@@ -373,6 +373,13 @@ extension JNISwift2JavaGenerator {
 
       printer.print(
         """
+        public boolean equals(Object obj) {
+          if (obj instanceof JNISwiftInstance rhs) {
+            return SwiftObjects.equals(this.$memoryAddress(), this.$typeMetadataAddress(), rhs.$memoryAddress(), rhs.$typeMetadataAddress());
+          }
+          return false;
+        }
+
         public java.lang.String toString() {
           return SwiftObjects.toString(this.$memoryAddress(), this.$typeMetadataAddress());
         }

Sources/SwiftJava/SwiftObjects.swift

@@ -98,4 +98,41 @@ extension SwiftObjects {
     let typeMetadata = unsafeBitCast(selfType$, to: Any.Type.self)
     return String(describing: typeMetadata)
   }
+
+  @JavaMethod
+  public static func equals(environment: UnsafeMutablePointer<JNIEnv?>!, lhsPointer: Int64, lhsTypePointer: Int64, rhsPointer: Int64, rhsTypePointer: Int64) -> Bool {
+    guard let lhsType$ = UnsafeRawPointer(bitPattern: Int(lhsTypePointer)) else {
+      fatalError("lhsType metadata address was null")
+    }
+    let lhsMetatype = unsafeBitCast(lhsType$, to: Any.Type.self)
+    guard let lhsMetatype = lhsMetatype as? (any Equatable.Type) else {
+      return false
+    }
+
+    guard let rhsType$ = UnsafeRawPointer(bitPattern: Int(rhsTypePointer)) else {
+      fatalError("rhsType metadata address was null")
+    }
+    let rhsMetatype = unsafeBitCast(rhsType$, to: Any.Type.self)
+    guard let rhsMetatype = rhsMetatype as? (any Equatable.Type) else {
+      return false
+    }
+
+    func perform<L: Equatable, R: Equatable>(lhsType: L.Type, rhsType: R.Type) -> Bool {
+      guard let lhs$ = UnsafeMutablePointer<L>(bitPattern: Int(lhsPointer)) else {
+        fatalError("lhs memory address was null")
+      }
+      guard let rhs$ = UnsafeMutablePointer<R>(bitPattern: Int(rhsPointer)) else {
+        fatalError("rhs memory address was null")
+      }
+      if lhsType == rhsType {
+        return lhs$.pointee == rhs$.pointee as! L
+      } else if let lhs = lhs$.pointee as? R {
+        return lhs == rhs$.pointee
+      } else if let rhs = rhs$.pointee as? L {
+        return lhs$.pointee == rhs
+      }
+      return false
+    }
+    return perform(lhsType: lhsMetatype, rhsType: rhsMetatype)
+  }
 }

SwiftKitCore/src/main/java/org/swift/swiftkit/core/SwiftObjects.java

@@ -29,4 +29,5 @@ public static void requireNonZero(long number, String name) {
     public static native String toDebugString(long selfPointer, long selfTypePointer);
     public static native void destroy(long selfPointer, long selfTypePointer);
     public static native String typeDescription(long selfTypePointer);
+    public static native boolean equals(long lhsPointer, long lhsTypePointer, long rhsPointer, long rhsTypePointer);
 }