jni: Unify common methods using generic implementations

Package.swift

@@ -152,7 +152,7 @@ let package = Package(
     .library(
       name: "SwiftJava",
       type: .dynamic,
-      targets: ["SwiftJava"]
+      targets: ["SwiftJava", "SwiftJavaRuntimeSupport"]
     ),
 
     .library(
@@ -226,12 +226,6 @@ let package = Package(
       ]
     ),
 
-    // Support library written in Swift for SwiftKit "Java"
-    .library(
-      name: "SwiftJavaRuntimeSupport",
-      targets: ["SwiftJavaRuntimeSupport"]
-    ),
-
     .library(
       name: "SwiftRuntimeFunctions",
       type: .dynamic,
@@ -311,6 +305,7 @@ let package = Package(
       exclude: ["swift-java.config"],
       swiftSettings: [
         .swiftLanguageMode(.v5),
+        .enableUpcomingFeature("ImplicitOpenExistentials"),
         .unsafeFlags(
           ["-I\(javaIncludePath)", "-I\(javaPlatformIncludePath)"],
           .when(platforms: [.macOS, .linux, .windows])

Samples/SwiftJavaExtractJNISampleApp/Package.swift

@@ -110,7 +110,6 @@ let package = Package(
       dependencies: [
         .product(name: "SwiftJava", package: "swift-java"),
         .product(name: "CSwiftJavaJNI", package: "swift-java"),
-        .product(name: "SwiftJavaRuntimeSupport", package: "swift-java"),
       ],
       exclude: [
         "swift-java.config"

Samples/SwiftJavaExtractJNISampleApp/Sources/MySwiftLibrary/Benchmark.swift

@@ -0,0 +1,31 @@
+//===----------------------------------------------------------------------===//
+//
+// 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 struct BasicStruct {
+  public var value: Int
+  public init(value: Int) {
+    self.value = value
+  }
+}
+
+public struct GenericStruct<T> {
+  public var value: Int
+  public init(value: Int) {
+    self.value = value
+  }
+}
+
+public func makeGenericStruct(value: Int) -> GenericStruct<Int> {
+  GenericStruct(value: value)
+}

Samples/SwiftJavaExtractJNISampleApp/src/jmh/java/com/example/swift/GenericBenchmark.java

@@ -0,0 +1,71 @@
+//===----------------------------------------------------------------------===//
+//
+// 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.openjdk.jmh.annotations.*;
+import org.openjdk.jmh.infra.Blackhole;
+import org.swift.swiftkit.core.ClosableSwiftArena;
+import org.swift.swiftkit.core.ConfinedSwiftMemorySession;
+import org.swift.swiftkit.core.SwiftArena;
+
+import java.util.concurrent.TimeUnit;
+
+@BenchmarkMode(Mode.AverageTime)
+@Warmup(iterations = 5, time = 200, timeUnit = TimeUnit.MILLISECONDS)
+@Measurement(iterations = 10, time = 500, timeUnit = TimeUnit.MILLISECONDS)
+@OutputTimeUnit(TimeUnit.NANOSECONDS)
+@Fork(value = 3, jvmArgsAppend = { "--enable-native-access=ALL-UNNAMED" })
+public class GenericBenchmark {
+    @State(Scope.Benchmark)
+    public static class BenchmarkState {
+        ClosableSwiftArena arena;
+        BasicStruct basicStruct;
+        GenericStruct genericStruct;
+
+        @Setup(Level.Trial)
+        public void beforeAll() {
+            arena = SwiftArena.ofConfined();
+            basicStruct = BasicStruct.init(42, arena);
+            genericStruct = MySwiftLibrary.makeGenericStruct(42, arena);
+        }
+
+        @TearDown(Level.Trial)
+        public void afterAll() {
+            arena.close();
+        }
+    }
+
+    @Benchmark
+    public long basicStruct_basicGetter(BenchmarkState state, Blackhole bh) {
+        return state.basicStruct.getValue();
+    }
+
+    @Benchmark
+    public long genericStruct_basicGetter(BenchmarkState state, Blackhole bh) {
+        return state.genericStruct.getValue();
+    }
+
+    @Benchmark
+    public String basicStruct_toString(BenchmarkState state, Blackhole bh) {
+         // toString is internally implemented as a generic method in Swift
+        return state.basicStruct.toString();
+    }
+
+    @Benchmark
+    public String genericStruct_toString(BenchmarkState state, Blackhole bh) {
+         // toString is internally implemented as a generic method in Swift
+        return state.genericStruct.toString();
+    }
+}

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

@@ -993,14 +993,6 @@ extension LoweredFunctionSignature {
         .joined(separator: ", ")
       resultExpr = "\(callee)(\(raw: arguments))"
 
-    case .synthesizedFunction(let function):
-      switch function {
-      case .toString:
-        resultExpr = "String(describing: \(callee))"
-      case .toDebugString:
-        resultExpr = "String(reflecting: \(callee))"
-      }
-
     case .getter:
       assert(paramExprs.isEmpty)
       resultExpr = callee

Sources/JExtractSwiftLib/FFM/FFMSwift2JavaGenerator+JavaTranslation.swift

@@ -160,7 +160,7 @@ extension FFMSwift2JavaGenerator {
         switch decl.apiKind {
         case .getter, .subscriptGetter: decl.javaGetterName
         case .setter, .subscriptSetter: decl.javaSetterName
-        case .function, .synthesizedFunction, .initializer, .enumCase: decl.name
+        case .function, .initializer, .enumCase: decl.name
         }
 
       // Signature.

Sources/JExtractSwiftLib/ImportedDecls.swift

@@ -17,14 +17,8 @@ import SwiftSyntax
 /// Any imported (Swift) declaration
 protocol ImportedDecl: AnyObject {}
 
-package enum SynthesizedAPI: Equatable {
-  case toString
-  case toDebugString
-}
-
 package enum SwiftAPIKind: Equatable {
   case function
-  case synthesizedFunction(SynthesizedAPI)
   case initializer
   case getter
   case setter
@@ -178,7 +172,7 @@ public final class ImportedFunc: ImportedDecl, CustomStringConvertible {
       case .getter: "getter:"
       case .setter: "setter:"
       case .enumCase: "case:"
-      case .function, .synthesizedFunction, .initializer: ""
+      case .function, .initializer: ""
       case .subscriptGetter: "subscriptGetter:"
       case .subscriptSetter: "subscriptSetter:"
       }

Sources/JExtractSwiftLib/JNI/JNISwift2JavaGenerator+JavaBindingsPrinting.swift

@@ -295,6 +295,20 @@ extension JNISwift2JavaGenerator {
 
       printTypeMetadataAddressFunction(&printer, decl)
       printer.println()
+
+      printer.print(
+        """
+        public String toString() {
+          return SwiftObjects.toString(this.$memoryAddress(), this.$typeMetadataAddress());
+        }
+
+        public String toDebugString() {
+          return SwiftObjects.toDebugString(this.$memoryAddress(), this.$typeMetadataAddress());
+        }
+        """
+      )
+      printer.println()
+
       printDestroyFunction(&printer, decl)
     }
   }
@@ -394,17 +408,9 @@ extension JNISwift2JavaGenerator {
       )
     }
 
-    // TODO: Consider whether all of these "utility" functions can be printed using our existing printing logic.
-    if decl.swiftNominal.isGeneric {
-      printer.printBraceBlock("public Discriminator getDiscriminator()") { printer in
-        printer.print("return Discriminator.values()[$getDiscriminator(this.$memoryAddress(), this.$typeMetadataAddress())];")
-      }
-      printer.print("private static native int $getDiscriminator(long selfPointer, long selfTypePointer);")
-    } else {
-      printer.printBraceBlock("public Discriminator getDiscriminator()") { printer in
-        printer.print("return Discriminator.values()[$getDiscriminator(this.$memoryAddress())];")
-      }
-      printer.print("private static native int $getDiscriminator(long selfPointer);")
+    printer.printBraceBlock("public Discriminator getDiscriminator()") { printer in
+      printer.print("var raw = SwiftObjects.getRawDiscriminator(this.$memoryAddress(), this.$typeMetadataAddress());")
+      printer.print("return Discriminator.values()[raw];")
     }
   }
 
@@ -717,42 +723,25 @@ extension JNISwift2JavaGenerator {
       }
     } else {
       printer.print("private static native long $typeMetadataAddressDowncall();")
-
-      let funcName = "$typeMetadataAddress"
       printer.print("@Override")
       printer.printBraceBlock("public long $typeMetadataAddress()") { printer in
-        printer.print(
-          """
-          long self$ = this.$memoryAddress();
-          if (CallTraces.TRACE_DOWNCALLS) {
-            CallTraces.traceDowncall("\(type.swiftNominal.name).\(funcName)",
-                "this", this,
-                "self", self$);
-          }
-          """
-        )
+        // INFO: We are omitting `CallTraces.traceDowncall` here.
+        // It internally calls `toString`, which in turn calls `$typeMetadataAddress`, creating an infinite loop.
         printer.print("return \(type.swiftNominal.name).$typeMetadataAddressDowncall();")
       }
     }
   }
 
   /// Prints the destroy function for a `JNISwiftInstance`
   private func printDestroyFunction(_ printer: inout CodePrinter, _ type: ImportedNominalType) {
-    let isGeneric = type.swiftNominal.isGeneric
-    if isGeneric {
-      printer.print("private static native void $destroy(long selfPointer, long selfTypePointer);")
-    } else {
-      printer.print("private static native void $destroy(long selfPointer);")
-    }
-
     let funcName = "$createDestroyFunction"
     printer.print("@Override")
     printer.printBraceBlock("public Runnable \(funcName)()") { printer in
       printer.print("long self$ = this.$memoryAddress();")
-      if isGeneric {
+      printer.print("long selfType$ = this.$typeMetadataAddress();")
+      if type.swiftNominal.isGeneric {
         printer.print(
           """
-          long selfType$ = this.$typeMetadataAddress();
           if (CallTraces.TRACE_DOWNCALLS) {
             CallTraces.traceDowncall("\(type.swiftNominal.name).\(funcName)",
                 "this", this,
@@ -765,7 +754,7 @@ extension JNISwift2JavaGenerator {
               if (CallTraces.TRACE_DOWNCALLS) {
                 CallTraces.traceDowncall("\(type.swiftNominal.name).$destroy", "self", self$, "selfType", selfType$);
               }
-              \(type.swiftNominal.name).$destroy(self$, selfType$);
+              SwiftObjects.destroy(self$, selfType$);
             }
           };
           """
@@ -784,7 +773,7 @@ extension JNISwift2JavaGenerator {
               if (CallTraces.TRACE_DOWNCALLS) {
                 CallTraces.traceDowncall("\(type.swiftNominal.name).$destroy", "self", self$);
               }
-              \(type.swiftNominal.name).$destroy(self$);
+              SwiftObjects.destroy(self$, selfType$);
             }
           };
           """

Sources/JExtractSwiftLib/JNI/JNISwift2JavaGenerator+JavaTranslation.swift

@@ -229,7 +229,7 @@ extension JNISwift2JavaGenerator {
         switch decl.apiKind {
         case .getter, .subscriptGetter: decl.javaGetterName
         case .setter, .subscriptSetter: decl.javaSetterName
-        case .function, .synthesizedFunction, .initializer, .enumCase: decl.name
+        case .function, .initializer, .enumCase: decl.name
         }
 
       // Swift -> Java