ObjCExport: remove KotlinUnit from suspend funs returning Unit (#4635)

With `unitSuspendFunctionObjCExport=proper` binary option,
for Unit-returning suspend functions ObjCExport now generates
completion handlers without redundant `KotlinUnit*` result parameter.

So Swift (5.5+) can import these functions as Void-returning async
functions.

^KT-47399 Fixed

kotlin-native/backend.native/tests/build.gradle

@@ -5321,7 +5321,7 @@ if (isAppleTarget(project)) {
         framework(frameworkName) {
             sources = ['objcexport']
             library = libraryName
-            opts = ["-Xemit-lazy-objc-header=$lazyHeader", "-Xexport-kdoc", "-Xbundle-id=foo.bar"]
+            opts = ["-Xemit-lazy-objc-header=$lazyHeader", "-Xexport-kdoc", "-Xbundle-id=foo.bar", "-Xbinary=unitSuspendFunctionObjCExport=proper"]
         }
         swiftSources = ['objcexport']
         if (isNoopGC) {
@@ -5375,7 +5375,7 @@ if (isAppleTarget(project)) {
             sources = ['objcexport']
             artifact = frameworkArtifactName
             library = libraryName
-            opts = ["-Xemit-lazy-objc-header=$lazyHeader", "-Xno-objc-generics"]
+            opts = ["-Xemit-lazy-objc-header=$lazyHeader", "-Xno-objc-generics", "-Xbinary=unitSuspendFunctionObjCExport=proper"]
         }
         swiftSources = ['objcexport']
         swiftExtraOpts = [ '-D', 'NO_GENERICS' ]
@@ -5384,6 +5384,61 @@ if (isAppleTarget(project)) {
         }
     }
 
+    frameworkTest('testObjCExportLegacySuspendUnit') {
+        final String frameworkName = 'KtLegacySuspendUnit'
+        final String frameworkArtifactName = 'Kt'
+        final String dir = "$testOutputFramework/testObjCExportLegacySuspendUnit"
+        final File lazyHeader = file("$dir/$target-lazy.h")
+
+        doLast {
+            final String expectedLazyHeaderName = "expectedLazyLegacySuspendUnit.h"
+            final String expectedLazyHeaderDir = file("objcexport/")
+            final File expectedLazyHeader = new File(expectedLazyHeaderDir, expectedLazyHeaderName)
+
+            if (expectedLazyHeader.readLines() != lazyHeader.readLines()) {
+                exec {
+                    commandLine 'diff', '-u', expectedLazyHeader, lazyHeader
+                    ignoreExitValue = true
+                }
+
+                copy {
+                    from(lazyHeader)
+                    into(expectedLazyHeaderDir)
+                    rename { expectedLazyHeaderName }
+                }
+
+                throw new Error("$expectedLazyHeader file patched;\nre-run the test and don't forget to commit the patch")
+            }
+
+        }
+
+        def libraryName = frameworkName + "Library"
+        konanArtifacts {
+            library(libraryName, targets: [target.name]) {
+                srcDir "objcexport/library"
+                artifactName "test-library"
+
+                if (!useCustomDist) {
+                    dependsOn ":${target.name}CrossDistRuntime", ':distCompiler'
+                }
+
+                extraOpts "-Xshort-module-name=MyLibrary"
+                extraOpts "-module-name", "org.jetbrains.kotlin.native.test-library"
+            }
+        }
+        framework(frameworkName) {
+            sources = ['objcexport']
+            artifact = frameworkArtifactName
+            library = libraryName
+            opts = ["-Xemit-lazy-objc-header=$lazyHeader"]
+        }
+        swiftSources = ['objcexport']
+        swiftExtraOpts = [ '-D', 'LEGACY_SUSPEND_UNIT_FUNCTION_EXPORT' ]
+        if (isNoopGC) {
+            swiftExtraOpts += ["-D", "NOOP_GC"]
+        }
+    }
+
     frameworkTest('testObjCExportStatic') {
         final String frameworkName = 'KtStatic'
         final String frameworkArtifactName = 'Kt'
@@ -5410,6 +5465,7 @@ if (isAppleTarget(project)) {
             artifact = frameworkArtifactName
             library = libraryName
             isStatic = true
+            opts = ["-Xbinary=unitSuspendFunctionObjCExport=proper"]
         }
         swiftSources = ['objcexport']
         if (isNoopGC) {

kotlin-native/backend.native/tests/objcexport/coroutines.kt

@@ -15,6 +15,7 @@ import kotlin.test.*
 class CoroutineException : Throwable()
 
 suspend fun suspendFun() = 42
+suspend fun unitSuspendFun() = Unit
 
 @Throws(CoroutineException::class, CancellationException::class)
 suspend fun suspendFun(result: Any?, doSuspend: Boolean, doThrow: Boolean): Any? {
@@ -30,6 +31,18 @@ suspend fun suspendFun(result: Any?, doSuspend: Boolean, doThrow: Boolean): Any?
     return result
 }
 
+@Throws(CoroutineException::class, CancellationException::class)
+suspend fun unitSuspendFun(doSuspend: Boolean, doThrow: Boolean) {
+    if (doSuspend) {
+        suspendCoroutineUninterceptedOrReturn<Unit> {
+            it.resume(Unit)
+            COROUTINE_SUSPENDED
+        }
+    }
+
+    if (doThrow) throw CoroutineException()
+}
+
 class ContinuationHolder<T> {
     internal lateinit var continuation: Continuation<T>
 
@@ -96,6 +109,7 @@ interface SuspendBridge<T> {
 
     suspend fun unit(value: T): Unit
     suspend fun unitAsAny(value: T): Any?
+    suspend fun nullableUnit(value: T): Unit?
 
     @Throws(Throwable::class) suspend fun nothing(value: T): Nothing
     @Throws(Throwable::class) suspend fun nothingAsInt(value: T): Int
@@ -106,7 +120,9 @@ interface SuspendBridge<T> {
 abstract class AbstractSuspendBridge : SuspendBridge<Int> {
     override suspend fun intAsAny(value: Int): Int = TODO()
 
+    override suspend fun unit(value: Int): Unit = TODO()
     override suspend fun unitAsAny(value: Int): Unit = TODO()
+    override suspend fun nullableUnit(value: Int): Unit? = TODO()
 
     override suspend fun nothingAsInt(value: Int): Nothing = TODO()
     override suspend fun nothingAsAny(value: Int): Nothing = TODO()
@@ -116,21 +132,25 @@ abstract class AbstractSuspendBridge : SuspendBridge<Int> {
 private suspend fun callSuspendBridgeImpl(bridge: SuspendBridge<Int>) {
     assertEquals(1, bridge.intAsAny(1))
 
-    assertSame(Unit, bridge.unitAsAny(2))
+    assertSame(Unit, bridge.unit(2))
+    assertSame(Unit, bridge.unitAsAny(3))
+    assertSame(Unit, bridge.nullableUnit(4))
 
-    assertFailsWith<ObjCErrorException> { bridge.nothingAsInt(3) }
-    assertFailsWith<ObjCErrorException> { bridge.nothingAsAny(4) }
-    assertFailsWith<ObjCErrorException> { bridge.nothingAsUnit(5) }
+    assertFailsWith<ObjCErrorException> { bridge.nothingAsInt(5) }
+    assertFailsWith<ObjCErrorException> { bridge.nothingAsAny(6) }
+    assertFailsWith<ObjCErrorException> { bridge.nothingAsUnit(7) }
 }
 
 private suspend fun callAbstractSuspendBridgeImpl(bridge: AbstractSuspendBridge) {
-    assertEquals(6, bridge.intAsAny(6))
+    assertEquals(8, bridge.intAsAny(8))
 
-    assertSame(Unit, bridge.unitAsAny(7))
+    assertSame(Unit, bridge.unit(9))
+    assertSame(Unit, bridge.unitAsAny(10))
+    assertSame(Unit, bridge.nullableUnit(11))
 
-    assertFailsWith<ObjCErrorException> { bridge.nothingAsInt(8) }
-    assertFailsWith<ObjCErrorException> { bridge.nothingAsAny(9) }
-    assertFailsWith<ObjCErrorException> { bridge.nothingAsUnit(10) }
+    assertFailsWith<ObjCErrorException> { bridge.nothingAsInt(12) }
+    assertFailsWith<ObjCErrorException> { bridge.nothingAsAny(13) }
+    assertFailsWith<ObjCErrorException> { bridge.nothingAsUnit(14) }
 }
 
 @Throws(Throwable::class)

kotlin-native/backend.native/tests/objcexport/coroutines.swift

@@ -21,6 +21,33 @@ private func testCallSimple() throws {
     try assertNil(error)
 }
 
+private func testUnitCallSimple() throws {
+#if LEGACY_SUSPEND_UNIT_FUNCTION_EXPORT
+    var result: KotlinUnit? = nil
+#endif
+    var error: Error? = nil
+    var completionCalled = 0
+
+#if LEGACY_SUSPEND_UNIT_FUNCTION_EXPORT
+    CoroutinesKt.unitSuspendFun { _result, _error in
+        completionCalled += 1
+        result = _result
+        error = _error
+    }
+#else
+    CoroutinesKt.unitSuspendFun { _error in
+        completionCalled += 1
+        error = _error
+    }
+#endif
+
+#if LEGACY_SUSPEND_UNIT_FUNCTION_EXPORT
+    try assertSame(actual: result, expected: KotlinUnit.shared)
+#endif
+    try assertEquals(actual: completionCalled, expected: 1)
+    try assertNil(error)
+}
+
 private func testCallSuspendFun(doSuspend: Bool, doThrow: Bool) throws {
     class C {}
     let expectedResult = C()
@@ -46,6 +73,39 @@ private func testCallSuspendFun(doSuspend: Bool, doThrow: Bool) throws {
     }
 }
 
+private func testCallUnitSuspendFun(doSuspend: Bool, doThrow: Bool) throws {
+    var completionCalled = 0
+    var result: AnyObject? = nil
+    var error: Error? = nil
+
+#if LEGACY_SUSPEND_UNIT_FUNCTION_EXPORT
+    CoroutinesKt.unitSuspendFun(doSuspend: doSuspend, doThrow: doThrow) { _result, _error in
+        completionCalled += 1
+        result = _result as AnyObject?
+        error = _error
+    }
+#else
+    CoroutinesKt.unitSuspendFun(doSuspend: doSuspend, doThrow: doThrow) { _error in
+        completionCalled += 1
+        error = _error
+    }
+#endif
+
+    try assertEquals(actual: completionCalled, expected: 1)
+
+    if doThrow {
+#if LEGACY_SUSPEND_UNIT_FUNCTION_EXPORT
+        try assertNil(result)
+#endif
+        try assertTrue(error?.kotlinException is CoroutineException)
+    } else {
+#if LEGACY_SUSPEND_UNIT_FUNCTION_EXPORT
+        try assertSame(actual: result, expected: KotlinUnit.shared)
+#endif
+        try assertNil(error)
+    }
+}
+
 private func testSuspendFuncAsync(doThrow: Bool) throws {
     var completionCalled = 0
     var result: AnyObject? = nil
@@ -91,6 +151,11 @@ private func testCall() throws {
     try testCallSuspendFun(doSuspend: true, doThrow: true)
     try testCallSuspendFun(doSuspend: false, doThrow: true)
 
+    try testCallUnitSuspendFun(doSuspend: true, doThrow: false)
+    try testCallUnitSuspendFun(doSuspend: false, doThrow: false)
+    try testCallUnitSuspendFun(doSuspend: true, doThrow: true)
+    try testCallUnitSuspendFun(doSuspend: false, doThrow: true)
+
     try testSuspendFuncAsync(doThrow: false)
     try testSuspendFuncAsync(doThrow: true)
 }
@@ -237,10 +302,24 @@ private class SwiftSuspendBridge : AbstractSuspendBridge {
         completionHandler(value, nil)
     }
 
+#if LEGACY_SUSPEND_UNIT_FUNCTION_EXPORT
+    override func unit(value: KotlinInt, completionHandler: @escaping (KotlinUnit?, Error?) -> Void) {
+        completionHandler(KotlinUnit(), nil)
+    }
+#else
+    override func unit(value: KotlinInt, completionHandler: @escaping (Error?) -> Void) {
+        completionHandler(nil)
+    }
+#endif
+
     override func unitAsAny(value: KotlinInt, completionHandler: @escaping (KotlinUnit?, Error?) -> Void) {
         completionHandler(KotlinUnit(), nil)
     }
 
+    override func nullableUnit(value: KotlinInt, completionHandler: @escaping (KotlinUnit?, Error?) -> Void) {
+        completionHandler(KotlinUnit(), nil)
+    }
+
     override func nothingAsInt(value: KotlinInt, completionHandler: @escaping (KotlinNothing?, Error?) -> Void) {
         completionHandler(nil, E())
     }
@@ -249,9 +328,15 @@ private class SwiftSuspendBridge : AbstractSuspendBridge {
         completionHandler(nil, E())
     }
 
+#if LEGACY_SUSPEND_UNIT_FUNCTION_EXPORT
     override func nothingAsUnit(value: KotlinInt, completionHandler: @escaping (KotlinNothing?, Error?) -> Void) {
         completionHandler(nil, E())
     }
+#else
+    override func nothingAsUnit(value: KotlinInt, completionHandler: @escaping (Error?) -> Void) {
+        completionHandler(E())
+    }
+#endif
 }
 
 private func testBridges() throws {
@@ -268,34 +353,52 @@ private func testBridges() throws {
 }
 
 private func testImplicitThrows1() throws {
-    var result: KotlinUnit? = nil
     var error: Error? = nil
     var completionCalled = 0
 
+#if LEGACY_SUSPEND_UNIT_FUNCTION_EXPORT
+    var result: KotlinUnit? = nil
+
     CoroutinesKt.throwCancellationException { _result, _error in
         completionCalled += 1
         result = _result
         error = _error
     }
 
-    try assertEquals(actual: completionCalled, expected: 1)
     try assertNil(result)
+#else
+    CoroutinesKt.throwCancellationException { _error in
+        completionCalled += 1
+        error = _error
+    }
+#endif
+
+    try assertEquals(actual: completionCalled, expected: 1)
     try assertTrue(error?.kotlinException is KotlinCancellationException)
 }
 
 private func testImplicitThrows2() throws {
-    var result: KotlinUnit? = nil
     var error: Error? = nil
     var completionCalled = 0
 
+#if LEGACY_SUSPEND_UNIT_FUNCTION_EXPORT
+    var result: KotlinUnit? = nil
+
     ThrowCancellationExceptionImpl().throwCancellationException { _result, _error in
-        completionCalled += 1
-        result = _result
-        error = _error
+            completionCalled += 1
+            result = _result
+            error = _error
     }
 
-    try assertEquals(actual: completionCalled, expected: 1)
     try assertNil(result)
+#else
+    ThrowCancellationExceptionImpl().throwCancellationException { _error in
+        completionCalled += 1
+        error = _error
+    }
+#endif
+
+    try assertEquals(actual: completionCalled, expected: 1)
     try assertTrue(error?.kotlinException is KotlinCancellationException)
 }
 
@@ -369,6 +472,7 @@ class CoroutinesTests : SimpleTestProvider {
         super.init()
 
         test("TestCallSimple", testCallSimple)
+        test("TestCallUnitSimple", testUnitCallSimple)
         test("TestCall", testCall)
         test("TestCallChain", testCallChain)
         test("TestOverride", testOverride)

kotlin-native/backend.native/tests/objcexport/expectedLazy.h

@@ -180,7 +180,7 @@ __attribute__((swift_name("SuspendBridge")))
  @note This method converts instances of CancellationException to errors.
  Other uncaught Kotlin exceptions are fatal.
 */
-- (void)unitValue:(id _Nullable)value completionHandler:(void (^)(KtKotlinUnit * _Nullable, NSError * _Nullable))completionHandler __attribute__((swift_name("unit(value:completionHandler:)")));
+- (void)unitValue:(id _Nullable)value completionHandler:(void (^)(NSError * _Nullable))completionHandler __attribute__((swift_name("unit(value:completionHandler:)")));
 
 /**
  @note This method converts instances of CancellationException to errors.
@@ -188,6 +188,12 @@ __attribute__((swift_name("SuspendBridge")))
 */
 - (void)unitAsAnyValue:(id _Nullable)value completionHandler:(void (^)(id _Nullable_result, NSError * _Nullable))completionHandler __attribute__((swift_name("unitAsAny(value:completionHandler:)")));
 
+/**
+ @note This method converts instances of CancellationException to errors.
+ Other uncaught Kotlin exceptions are fatal.
+*/
+- (void)nullableUnitValue:(id _Nullable)value completionHandler:(void (^)(KtKotlinUnit * _Nullable_result, NSError * _Nullable))completionHandler __attribute__((swift_name("nullableUnit(value:completionHandler:)")));
+
 /**
  @note This method converts all Kotlin exceptions to errors.
 */
@@ -206,7 +212,7 @@ __attribute__((swift_name("SuspendBridge")))
 /**
  @note This method converts all Kotlin exceptions to errors.
 */
-- (void)nothingAsUnitValue:(id _Nullable)value completionHandler:(void (^)(KtKotlinUnit * _Nullable, NSError * _Nullable))completionHandler __attribute__((swift_name("nothingAsUnit(value:completionHandler:)")));
+- (void)nothingAsUnitValue:(id _Nullable)value completionHandler:(void (^)(NSError * _Nullable))completionHandler __attribute__((swift_name("nothingAsUnit(value:completionHandler:)")));
 @end;
 
 __attribute__((swift_name("AbstractSuspendBridge")))
@@ -220,12 +226,24 @@ __attribute__((swift_name("AbstractSuspendBridge")))
 */
 - (void)intAsAnyValue:(KtInt *)value completionHandler:(void (^)(KtInt * _Nullable, NSError * _Nullable))completionHandler __attribute__((swift_name("intAsAny(value:completionHandler:)")));
 
+/**
+ @note This method converts instances of CancellationException to errors.
+ Other uncaught Kotlin exceptions are fatal.
+*/
+- (void)unitValue:(KtInt *)value completionHandler:(void (^)(NSError * _Nullable))completionHandler __attribute__((swift_name("unit(value:completionHandler:)")));
+
 /**
  @note This method converts instances of CancellationException to errors.
  Other uncaught Kotlin exceptions are fatal.
 */
 - (void)unitAsAnyValue:(KtInt *)value completionHandler:(void (^)(KtKotlinUnit * _Nullable, NSError * _Nullable))completionHandler __attribute__((swift_name("unitAsAny(value:completionHandler:)")));
 
+/**
+ @note This method converts instances of CancellationException to errors.
+ Other uncaught Kotlin exceptions are fatal.
+*/
+- (void)nullableUnitValue:(KtInt *)value completionHandler:(void (^)(KtKotlinUnit * _Nullable_result, NSError * _Nullable))completionHandler __attribute__((swift_name("nullableUnit(value:completionHandler:)")));
+
 /**
  @note This method converts all Kotlin exceptions to errors.
 */
@@ -239,7 +257,7 @@ __attribute__((swift_name("AbstractSuspendBridge")))
 /**
  @note This method converts all Kotlin exceptions to errors.
 */
-- (void)nothingAsUnitValue:(KtInt *)value completionHandler:(void (^)(KtKotlinNothing * _Nullable, NSError * _Nullable))completionHandler __attribute__((swift_name("nothingAsUnit(value:completionHandler:)")));
+- (void)nothingAsUnitValue:(KtInt *)value completionHandler:(void (^)(NSError * _Nullable))completionHandler __attribute__((swift_name("nothingAsUnit(value:completionHandler:)")));
 @end;
 
 __attribute__((swift_name("ThrowCancellationException")))
@@ -258,7 +276,7 @@ __attribute__((swift_name("ThrowCancellationExceptionImpl")))
  @note This method converts instances of CancellationException to errors.
  Other uncaught Kotlin exceptions are fatal.
 */
-- (void)throwCancellationExceptionWithCompletionHandler:(void (^)(KtKotlinUnit * _Nullable, NSError * _Nullable))completionHandler __attribute__((swift_name("throwCancellationException(completionHandler:)")));
+- (void)throwCancellationExceptionWithCompletionHandler:(void (^)(NSError * _Nullable))completionHandler __attribute__((swift_name("throwCancellationException(completionHandler:)")));
 @end;
 
 __attribute__((objc_subclassing_restricted))
@@ -271,12 +289,24 @@ __attribute__((swift_name("CoroutinesKt")))
 */
 + (void)suspendFunWithCompletionHandler:(void (^)(KtInt * _Nullable, NSError * _Nullable))completionHandler __attribute__((swift_name("suspendFun(completionHandler:)")));
 
+/**
+ @note This method converts instances of CancellationException to errors.
+ Other uncaught Kotlin exceptions are fatal.
+*/
++ (void)unitSuspendFunWithCompletionHandler:(void (^)(NSError * _Nullable))completionHandler __attribute__((swift_name("unitSuspendFun(completionHandler:)")));
+
 /**
  @note This method converts instances of CoroutineException, CancellationException to errors.
  Other uncaught Kotlin exceptions are fatal.
 */
 + (void)suspendFunResult:(id _Nullable)result doSuspend:(BOOL)doSuspend doThrow:(BOOL)doThrow completionHandler:(void (^)(id _Nullable_result, NSError * _Nullable))completionHandler __attribute__((swift_name("suspendFun(result:doSuspend:doThrow:completionHandler:)")));
 
+/**
+ @note This method converts instances of CoroutineException, CancellationException to errors.
+ Other uncaught Kotlin exceptions are fatal.
+*/
++ (void)unitSuspendFunDoSuspend:(BOOL)doSuspend doThrow:(BOOL)doThrow completionHandler:(void (^)(NSError * _Nullable))completionHandler __attribute__((swift_name("unitSuspendFun(doSuspend:doThrow:completionHandler:)")));
+
 /**
  @note This method converts instances of CoroutineException, CancellationException to errors.
  Other uncaught Kotlin exceptions are fatal.
@@ -305,7 +335,7 @@ __attribute__((swift_name("CoroutinesKt")))
  @note This method converts instances of CancellationException to errors.
  Other uncaught Kotlin exceptions are fatal.
 */
-+ (void)throwCancellationExceptionWithCompletionHandler:(void (^)(KtKotlinUnit * _Nullable, NSError * _Nullable))completionHandler __attribute__((swift_name("throwCancellationException(completionHandler:)")));
++ (void)throwCancellationExceptionWithCompletionHandler:(void (^)(NSError * _Nullable))completionHandler __attribute__((swift_name("throwCancellationException(completionHandler:)")));
 + (id<KtKotlinSuspendFunction0>)getSuspendLambda0 __attribute__((swift_name("getSuspendLambda0()")));
 + (id<KtKotlinSuspendFunction0>)getSuspendCallableReference0 __attribute__((swift_name("getSuspendCallableReference0()")));
 + (id<KtKotlinSuspendFunction1>)getSuspendLambda1 __attribute__((swift_name("getSuspendLambda1()")));
@@ -1191,7 +1221,7 @@ __attribute__((swift_name("ThrowsThrowableAsErrorSuspend")))
  @note This method converts instances of CancellationException to errors.
  Other uncaught Kotlin exceptions are fatal.
 */
-- (void)throwErrorWithCompletionHandler:(void (^)(KtKotlinUnit * _Nullable, NSError * _Nullable))completionHandler __attribute__((swift_name("throwError(completionHandler:)")));
+- (void)throwErrorWithCompletionHandler:(void (^)(NSError * _Nullable))completionHandler __attribute__((swift_name("throwError(completionHandler:)")));
 @end;
 
 __attribute__((objc_subclassing_restricted))

kotlin-native/backend.native/tests/objcexport/expectedLazyNoGenerics.h

@@ -180,7 +180,7 @@ __attribute__((swift_name("SuspendBridge")))
  @note This method converts instances of CancellationException to errors.
  Other uncaught Kotlin exceptions are fatal.
 */
-- (void)unitValue:(id _Nullable)value completionHandler:(void (^)(KtKotlinUnit * _Nullable, NSError * _Nullable))completionHandler __attribute__((swift_name("unit(value:completionHandler:)")));
+- (void)unitValue:(id _Nullable)value completionHandler:(void (^)(NSError * _Nullable))completionHandler __attribute__((swift_name("unit(value:completionHandler:)")));
 
 /**
  @note This method converts instances of CancellationException to errors.
@@ -188,6 +188,12 @@ __attribute__((swift_name("SuspendBridge")))
 */
 - (void)unitAsAnyValue:(id _Nullable)value completionHandler:(void (^)(id _Nullable_result, NSError * _Nullable))completionHandler __attribute__((swift_name("unitAsAny(value:completionHandler:)")));
 
+/**
+ @note This method converts instances of CancellationException to errors.
+ Other uncaught Kotlin exceptions are fatal.
+*/
+- (void)nullableUnitValue:(id _Nullable)value completionHandler:(void (^)(KtKotlinUnit * _Nullable_result, NSError * _Nullable))completionHandler __attribute__((swift_name("nullableUnit(value:completionHandler:)")));
+
 /**
  @note This method converts all Kotlin exceptions to errors.
 */
@@ -206,7 +212,7 @@ __attribute__((swift_name("SuspendBridge")))
 /**
  @note This method converts all Kotlin exceptions to errors.
 */
-- (void)nothingAsUnitValue:(id _Nullable)value completionHandler:(void (^)(KtKotlinUnit * _Nullable, NSError * _Nullable))completionHandler __attribute__((swift_name("nothingAsUnit(value:completionHandler:)")));
+- (void)nothingAsUnitValue:(id _Nullable)value completionHandler:(void (^)(NSError * _Nullable))completionHandler __attribute__((swift_name("nothingAsUnit(value:completionHandler:)")));
 @end;
 
 __attribute__((swift_name("AbstractSuspendBridge")))
@@ -220,12 +226,24 @@ __attribute__((swift_name("AbstractSuspendBridge")))
 */
 - (void)intAsAnyValue:(KtInt *)value completionHandler:(void (^)(KtInt * _Nullable, NSError * _Nullable))completionHandler __attribute__((swift_name("intAsAny(value:completionHandler:)")));
 
+/**
+ @note This method converts instances of CancellationException to errors.
+ Other uncaught Kotlin exceptions are fatal.
+*/
+- (void)unitValue:(KtInt *)value completionHandler:(void (^)(NSError * _Nullable))completionHandler __attribute__((swift_name("unit(value:completionHandler:)")));
+
 /**
  @note This method converts instances of CancellationException to errors.
  Other uncaught Kotlin exceptions are fatal.
 */
 - (void)unitAsAnyValue:(KtInt *)value completionHandler:(void (^)(KtKotlinUnit * _Nullable, NSError * _Nullable))completionHandler __attribute__((swift_name("unitAsAny(value:completionHandler:)")));
 
+/**
+ @note This method converts instances of CancellationException to errors.
+ Other uncaught Kotlin exceptions are fatal.
+*/
+- (void)nullableUnitValue:(KtInt *)value completionHandler:(void (^)(KtKotlinUnit * _Nullable_result, NSError * _Nullable))completionHandler __attribute__((swift_name("nullableUnit(value:completionHandler:)")));
+
 /**
  @note This method converts all Kotlin exceptions to errors.
 */
@@ -239,7 +257,7 @@ __attribute__((swift_name("AbstractSuspendBridge")))
 /**
  @note This method converts all Kotlin exceptions to errors.
 */
-- (void)nothingAsUnitValue:(KtInt *)value completionHandler:(void (^)(KtKotlinNothing * _Nullable, NSError * _Nullable))completionHandler __attribute__((swift_name("nothingAsUnit(value:completionHandler:)")));
+- (void)nothingAsUnitValue:(KtInt *)value completionHandler:(void (^)(NSError * _Nullable))completionHandler __attribute__((swift_name("nothingAsUnit(value:completionHandler:)")));
 @end;
 
 __attribute__((swift_name("ThrowCancellationException")))
@@ -258,7 +276,7 @@ __attribute__((swift_name("ThrowCancellationExceptionImpl")))
  @note This method converts instances of CancellationException to errors.
  Other uncaught Kotlin exceptions are fatal.
 */
-- (void)throwCancellationExceptionWithCompletionHandler:(void (^)(KtKotlinUnit * _Nullable, NSError * _Nullable))completionHandler __attribute__((swift_name("throwCancellationException(completionHandler:)")));
+- (void)throwCancellationExceptionWithCompletionHandler:(void (^)(NSError * _Nullable))completionHandler __attribute__((swift_name("throwCancellationException(completionHandler:)")));
 @end;
 
 __attribute__((objc_subclassing_restricted))
@@ -271,12 +289,24 @@ __attribute__((swift_name("CoroutinesKt")))
 */
 + (void)suspendFunWithCompletionHandler:(void (^)(KtInt * _Nullable, NSError * _Nullable))completionHandler __attribute__((swift_name("suspendFun(completionHandler:)")));
 
+/**
+ @note This method converts instances of CancellationException to errors.
+ Other uncaught Kotlin exceptions are fatal.
+*/
++ (void)unitSuspendFunWithCompletionHandler:(void (^)(NSError * _Nullable))completionHandler __attribute__((swift_name("unitSuspendFun(completionHandler:)")));
+
 /**
  @note This method converts instances of CoroutineException, CancellationException to errors.
  Other uncaught Kotlin exceptions are fatal.
 */
 + (void)suspendFunResult:(id _Nullable)result doSuspend:(BOOL)doSuspend doThrow:(BOOL)doThrow completionHandler:(void (^)(id _Nullable_result, NSError * _Nullable))completionHandler __attribute__((swift_name("suspendFun(result:doSuspend:doThrow:completionHandler:)")));
 
+/**
+ @note This method converts instances of CoroutineException, CancellationException to errors.
+ Other uncaught Kotlin exceptions are fatal.
+*/
++ (void)unitSuspendFunDoSuspend:(BOOL)doSuspend doThrow:(BOOL)doThrow completionHandler:(void (^)(NSError * _Nullable))completionHandler __attribute__((swift_name("unitSuspendFun(doSuspend:doThrow:completionHandler:)")));
+
 /**
  @note This method converts instances of CoroutineException, CancellationException to errors.
  Other uncaught Kotlin exceptions are fatal.
@@ -305,7 +335,7 @@ __attribute__((swift_name("CoroutinesKt")))
  @note This method converts instances of CancellationException to errors.
  Other uncaught Kotlin exceptions are fatal.
 */
-+ (void)throwCancellationExceptionWithCompletionHandler:(void (^)(KtKotlinUnit * _Nullable, NSError * _Nullable))completionHandler __attribute__((swift_name("throwCancellationException(completionHandler:)")));
++ (void)throwCancellationExceptionWithCompletionHandler:(void (^)(NSError * _Nullable))completionHandler __attribute__((swift_name("throwCancellationException(completionHandler:)")));
 + (id<KtKotlinSuspendFunction0>)getSuspendLambda0 __attribute__((swift_name("getSuspendLambda0()")));
 + (id<KtKotlinSuspendFunction0>)getSuspendCallableReference0 __attribute__((swift_name("getSuspendCallableReference0()")));
 + (id<KtKotlinSuspendFunction1>)getSuspendLambda1 __attribute__((swift_name("getSuspendLambda1()")));
@@ -1133,7 +1163,7 @@ __attribute__((swift_name("ThrowsThrowableAsErrorSuspend")))
  @note This method converts instances of CancellationException to errors.
  Other uncaught Kotlin exceptions are fatal.
 */
-- (void)throwErrorWithCompletionHandler:(void (^)(KtKotlinUnit * _Nullable, NSError * _Nullable))completionHandler __attribute__((swift_name("throwError(completionHandler:)")));
+- (void)throwErrorWithCompletionHandler:(void (^)(NSError * _Nullable))completionHandler __attribute__((swift_name("throwError(completionHandler:)")));
 @end;
 
 __attribute__((objc_subclassing_restricted))

kotlin-native/backend.native/tests/objcexport/throwableAsError.swift

@@ -38,9 +38,15 @@ private class ThrowsThrowableAsErrorSuspendImpl : ThrowsThrowableAsErrorSuspend
         self.throwable = throwable
     }
 
+#if LEGACY_SUSPEND_UNIT_FUNCTION_EXPORT
     func throwError(completionHandler: @escaping (KotlinUnit?, Error?) -> Void) {
         completionHandler(nil, throwable.asError())
     }
+#else
+    func throwError(completionHandler: @escaping (Error?) -> Void) {
+        completionHandler(throwable.asError())
+    }
+#endif
 }
 
 class ThrowableAsErrorTests : SimpleTestProvider {