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madsodgaardktoso
madsodgaard
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ktoso
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jextract/jni: Add support for returning protocols (#814)
Co-authored-by: Konrad `ktoso` Malawski <ktoso@apple.com>
1 parent 05681e8 commit ba6de8c

17 files changed

Lines changed: 1276 additions & 100 deletions

‎Samples/SwiftJavaExtractJNISampleApp/Sources/MySwiftLibrary/ConcreteProtocolAB.swift‎

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@@ -30,3 +30,10 @@ public class ConcreteProtocolAB: ProtocolA, ProtocolB {
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MySwiftClass(x: 10, y: 50)
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}
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}
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/// Returns a **reference-type** (class) `ProtocolA` conformer boxed as `any
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/// ProtocolA`, to exercise existential-box setter write-back against a
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/// class conformer.
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public func makeProtocolAClass(constantA: Int64, constantB: Int64) -> any ProtocolA {
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ConcreteProtocolAB(constantA: constantA, constantB: constantB)
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}

‎Samples/SwiftJavaExtractJNISampleApp/Sources/MySwiftLibrary/ProtocolA.swift‎

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@@ -23,3 +23,27 @@ public protocol ProtocolA {
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public func takeProtocol(_ proto1: any ProtocolA, _ proto2: some ProtocolA) -> Int64 {
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proto1.constantA + proto2.constantA
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}
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/// A struct conformer to `ProtocolA`, used to prove that
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/// setter dispatch through a returned existential box
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public struct ConcreteProtocolAStruct: ProtocolA {
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public let constantA: Int64
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public var mutable: Int64 = 0
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public init(constantA: Int64) {
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self.constantA = constantA
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}
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public func name() -> String {
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"ConcreteProtocolAStruct"
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}
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public func makeClass() -> MySwiftClass {
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MySwiftClass(x: constantA, y: mutable)
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}
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}
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/// Returns a value-type `ProtocolA` conformer boxed as `any ProtocolA`.
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public func makeProtocolA(constantA: Int64) -> any ProtocolA {
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ConcreteProtocolAStruct(constantA: constantA)
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}

‎Samples/SwiftJavaExtractJNISampleApp/Sources/MySwiftLibrary/ProtocolC.swift‎

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@@ -24,3 +24,7 @@ public struct ConcreteProtocolC: ProtocolC {
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constantC = c
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}
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}
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public func makeProtocolC(b: Int64, c: Int64) -> any ProtocolC {
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ConcreteProtocolC(b: b, c: c)
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}

‎Samples/SwiftJavaExtractJNISampleApp/Sources/MySwiftLibrary/ProtocolWithStatic.swift‎

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@@ -23,6 +23,18 @@ public func useProtocolWithStatic(_ value: any ProtocolWithStatic) -> Int {
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return meta.myFunc()
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}
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public struct ConcreteProtocolWithStatic: ProtocolWithStatic {
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public init() {}
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public static func myFunc() -> Int {
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42
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}
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}
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public func makeProtocolWithStatic() -> any ProtocolWithStatic {
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ConcreteProtocolWithStatic()
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}
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public protocol ProtocolWithStaticProperty {
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static var value: Int { get }
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}

‎Samples/SwiftJavaExtractJNISampleApp/Sources/MySwiftLibrary/ReturnProtocol.swift‎

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//===----------------------------------------------------------------------===//
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//
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// This source file is part of the Swift.org open source project
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//
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// Copyright (c) 2026 Apple Inc. and the Swift.org project authors
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// Licensed under Apache License v2.0
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//
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// See LICENSE.txt for license information
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// See CONTRIBUTORS.txt for the list of Swift.org project authors
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//
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// SPDX-License-Identifier: Apache-2.0
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//
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//===----------------------------------------------------------------------===//
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public protocol Greeter {
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func greeting() -> String
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func repeated(count: Int64) -> String
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}
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public struct EnglishGreeter: Greeter {
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public let name: String
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public init(name: String) {
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self.name = name
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}
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public func greeting() -> String {
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"Hello, \(name)!"
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}
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public func repeated(count: Int64) -> String {
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Array(repeating: greeting(), count: Int(count)).joined(separator: " ")
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}
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}
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public struct DanishGreeter: Greeter {
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public let name: String
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public init(name: String) {
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self.name = name
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}
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public func greeting() -> String {
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"Hej, \(name)!"
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}
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public func repeated(count: Int64) -> String {
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Array(repeating: greeting(), count: Int(count)).joined(separator: " ")
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}
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}
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public func makeEnglishGreeter(name: String) -> any Greeter {
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EnglishGreeter(name: name)
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}
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public func makeDanishGreeter(name: String) -> any Greeter {
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DanishGreeter(name: name)
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}
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public func makeOpaqueGreeter(name: String) -> some Greeter {
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EnglishGreeter(name: name)
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}
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public func describeGreeter(_ greeter: any Greeter) -> String {
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greeter.greeting()
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}

‎Samples/SwiftJavaExtractJNISampleApp/Sources/MySwiftLibrary/RichGreeter.swift‎

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//===----------------------------------------------------------------------===//
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//
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// This source file is part of the Swift.org open source project
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//
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// Copyright (c) 2026 Apple Inc. and the Swift.org project authors
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// Licensed under Apache License v2.0
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//
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// See LICENSE.txt for license information
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// See CONTRIBUTORS.txt for the list of Swift.org project authors
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//
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// SPDX-License-Identifier: Apache-2.0
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//
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//===----------------------------------------------------------------------===//
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public struct GreeterError: Error {}
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public protocol RichGreeter {
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func nickname() -> String?
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func aliases() -> [String]
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func decorate(_ object: MySwiftClass) -> MySwiftClass
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func greetOrThrow(shouldThrow: Bool) throws -> String
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func recordGreeting()
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func count() -> Int64
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}
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public final class RichGreeterImpl: RichGreeter {
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private var greetings: Int64 = 0
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private let base: String
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public init(base: String) {
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self.base = base
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}
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public func nickname() -> String? {
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base.isEmpty ? nil : "Mr. \(base)"
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}
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public func aliases() -> [String] {
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[base, base + base]
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}
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public func decorate(_ object: MySwiftClass) -> MySwiftClass {
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MySwiftClass(x: object.x + 1, y: object.y + 1)
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}
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public func greetOrThrow(shouldThrow: Bool) throws -> String {
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if shouldThrow {
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throw GreeterError()
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}
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return "Hi \(base)"
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}
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public func recordGreeting() {
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greetings += 1
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}
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public func count() -> Int64 {
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greetings
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}
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}
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public func makeRichGreeter(base: String) -> any RichGreeter {
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RichGreeterImpl(base: base)
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}

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

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//===----------------------------------------------------------------------===//
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//
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// This source file is part of the Swift.org open source project
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//
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// Copyright (c) 2026 Apple Inc. and the Swift.org project authors
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// Licensed under Apache License v2.0
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//
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// See LICENSE.txt for license information
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// See CONTRIBUTORS.txt for the list of Swift.org project authors
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//
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// SPDX-License-Identifier: Apache-2.0
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//
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//===----------------------------------------------------------------------===//
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package com.example.swift;
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import org.junit.jupiter.api.Test;
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import org.swift.swiftkit.core.JNISwiftInstance;
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import org.swift.swiftkit.core.SwiftArena;
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import static org.junit.jupiter.api.Assertions.*;
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public class ReturnInheritedProtocolTest {
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@Test
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void returnedRefinedProtocolExposesOwnAndInheritedRequirements() {
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try (var arena = SwiftArena.ofConfined()) {
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ProtocolC protoC = MySwiftLibrary.makeProtocolC(7, 11, arena);
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// Own requirement, declared directly on ProtocolC.
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assertEquals(11, protoC.getConstantC());
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// Inherited requirement, declared on ProtocolB, which ProtocolC refines.
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assertEquals(7, protoC.getConstantB());
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}
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}
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@Test
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void returnedRefinedProtocolIsAlsoUsableAsParentProtocol() {
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try (var arena = SwiftArena.ofConfined()) {
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ProtocolC protoC = MySwiftLibrary.makeProtocolC(7, 11, arena);
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ProtocolB protoB = protoC;
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assertEquals(7, protoB.getConstantB());
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assertEquals(7, MySwiftLibrary.takeProtocolB(protoB));
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}
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}
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@Test
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void returnedRefinedProtocolIsABackingSwiftInstance() {
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try (var arena = SwiftArena.ofConfined()) {
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ProtocolC protoC = MySwiftLibrary.makeProtocolC(7, 11, arena);
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assertInstanceOf(JNISwiftInstance.class, protoC);
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}
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}
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@Test
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void returnedProtocolBoxSetterWritesBackToValueTypeStorage() {
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try (var arena = SwiftArena.ofConfined()) {
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// ConcreteProtocolAStruct is a *value type* (struct) conformer to
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// ProtocolA. Opening the existential returned by makeProtocolA
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// yields a copy of the struct, so if setMutable merely mutated the
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// opened copy without writing it back into the box's storage, the
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// new value would be silently lost and getMutable() would still
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// read 0.
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ProtocolA proto = MySwiftLibrary.makeProtocolA(10, arena);
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assertEquals(10, proto.getConstantA());
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assertEquals(0, proto.getMutable());
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proto.setMutable(42);
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assertEquals(42, proto.getMutable());
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}
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}
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@Test
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void returnedProtocolBoxSetterWritesBackToReferenceTypeStorage() {
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try (var arena = SwiftArena.ofConfined()) {
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// ConcreteProtocolAB is a *reference type* (class) conformer to
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// ProtocolA, exercising the same write-back path against a class
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// conformer boxed as any ProtocolA.
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ProtocolA proto = MySwiftLibrary.makeProtocolAClass(10, 5, arena);
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assertEquals(10, proto.getConstantA());
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assertEquals(0, proto.getMutable());
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proto.setMutable(7);
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assertEquals(7, proto.getMutable());
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}
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}
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@Test
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void returnedProtocolWithUnsupportedStaticRequirementIsStillUsable() {
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try (var arena = SwiftArena.ofConfined()) {
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// ProtocolWithStatic declares a static func and an init(), neither of which
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// are supported requirements for existential boxing, so ProtocolWithStaticBox
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// simply omits them. The box/interface should still come back usable as a
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// JNISwiftInstance-backed reference.
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ProtocolWithStatic protoWithStatic = MySwiftLibrary.makeProtocolWithStatic(arena);
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assertInstanceOf(JNISwiftInstance.class, protoWithStatic);
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}
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}
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}

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

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//===----------------------------------------------------------------------===//
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//
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// This source file is part of the Swift.org open source project
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//
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// Copyright (c) 2026 Apple Inc. and the Swift.org project authors
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// Licensed under Apache License v2.0
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//
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// See LICENSE.txt for license information
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// See CONTRIBUTORS.txt for the list of Swift.org project authors
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//
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// SPDX-License-Identifier: Apache-2.0
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//
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//===----------------------------------------------------------------------===//
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package com.example.swift;
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import org.junit.jupiter.api.Test;
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import org.swift.swiftkit.core.SwiftArena;
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import static org.junit.jupiter.api.Assertions.*;
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public class ReturnProtocolDispatchTest {
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@Test
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void boxMethodReturningJextractedClass() {
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try (var arena = SwiftArena.ofConfined()) {
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ProtocolA proto = MySwiftLibrary.makeProtocolA(10, arena);
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assertEquals(10, proto.makeClass(arena).getX());
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}
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}
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@Test
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void boxSetterWriteBackObservableThroughSecondRequirement() {
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try (var arena = SwiftArena.ofConfined()) {
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// ConcreteProtocolAStruct.makeClass() returns
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// MySwiftClass(x: constantA, y: mutable), so observing the
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// write-back of setMutable through makeClass()'s y (rather than
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// through getMutable() itself) proves the setter thunk wrote the
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// new value into the box's actual backing storage: makeClass()
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// is a *different* requirement that independently reads that
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// storage.
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ProtocolA proto = MySwiftLibrary.makeProtocolA(10, arena);
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proto.setMutable(42);
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assertEquals(42, proto.makeClass(arena).getY());
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}
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}
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@Test
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void returnedBoxesRoundTripIntoProtocolParameter() {
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try (var arena = SwiftArena.ofConfined()) {
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assertEquals(
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30,
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MySwiftLibrary.takeProtocol(
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MySwiftLibrary.makeProtocolA(10, arena),
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MySwiftLibrary.makeProtocolA(20, arena)
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)
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);
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}
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}
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@Test
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void returnedBoxesRoundTripIntoGenericProtocolParameters() {
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try (var arena = SwiftArena.ofConfined()) {
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// A ProtocolA box and a ProtocolC box (whose protocol refines
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// ProtocolB) fed into takeGenericProtocol<First: ProtocolA,
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// Second: ProtocolB>; the ProtocolC box must satisfy the
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// ProtocolB generic bound.
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assertEquals(
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17,
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MySwiftLibrary.takeGenericProtocol(
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MySwiftLibrary.makeProtocolA(10, arena),
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MySwiftLibrary.makeProtocolC(7, 11, arena)
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)
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);
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}
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}
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}

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