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/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/BinaryOptions.kt

@@ -23,6 +23,8 @@ object BinaryOptions : BinaryOptionRegistry() {
     val sourceInfoType by option<SourceInfoType>()
 
     val androidProgramType by option<AndroidProgramType>()
+
+    val unitSuspendFunctionObjCExport by option<UnitSuspendFunctionObjCExport>()
 }
 
 open class BinaryOption<T : Any>(

kotlin-native/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/KonanCompilerFrontendServices.kt

@@ -38,6 +38,9 @@ internal fun StorageComponentContainer.initContainer(config: KonanConfig) {
 
             override val objcGenerics: Boolean
                 get() = config.configuration.getBoolean(KonanConfigKeys.OBJC_GENERICS)
+
+            override val unitSuspendFunctionExport: UnitSuspendFunctionObjCExport
+                get() = config.unitSuspendFunctionObjCExport
         })
     }
 }

kotlin-native/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/KonanConfig.kt

@@ -303,6 +303,9 @@ class KonanConfig(val project: Project, val configuration: CompilerConfiguration
         }
         "Konan_main"
     }
+
+    internal val unitSuspendFunctionObjCExport: UnitSuspendFunctionObjCExport
+        get() = configuration.get(BinaryOptions.unitSuspendFunctionObjCExport) ?: UnitSuspendFunctionObjCExport.LEGACY
 }
 
 fun CompilerConfiguration.report(priority: CompilerMessageSeverity, message: String)

kotlin-native/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/UnitSuspendFunctionObjCExport.kt

@@ -0,0 +1,26 @@
+/*
+ * Copyright 2010-2021 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package org.jetbrains.kotlin.backend.konan
+
+enum class UnitSuspendFunctionObjCExport {
+    /**
+     * In this mode suspend functions and methods with [Unit] return type are exported to Objective-C with an additional argument,
+     * continuation callback, with the following Objective-C signature: `(^)(KtKotlinUnit * _Nullable, NSError * _Nullable)`.
+     */
+    LEGACY,
+
+    /**
+     * In this mode suspend functions and methods with [Unit] return type are exported to Objective-C with an additional argument,
+     * continuation callback, with the following Objective-C signature: `(^)(NSError * _Nullable)`.
+     *
+     * Methods overriding superclass methods or implementing interface requirements narrowing down a more general return type
+     * to [Unit] are exported like in [LEGACY] mode.
+     *
+     * Note that in Swift 5.5 and higher suspend functions exported this way are transparently mapped to
+     * async functions with `Void` return type
+     */
+    PROPER,
+}

kotlin-native/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/llvm/ContextUtils.kt

@@ -503,6 +503,7 @@ internal class Llvm(val context: Context, val llvmModule: LLVMModuleRef) : Runti
     val Kotlin_ObjCExport_RethrowNSErrorAsException by lazyRtFunction
     val Kotlin_ObjCExport_AllocInstanceWithAssociatedObject by lazyRtFunction
     val Kotlin_ObjCExport_createContinuationArgument by lazyRtFunction
+    val Kotlin_ObjCExport_createUnitContinuationArgument by lazyRtFunction
     val Kotlin_ObjCExport_resumeContinuation by lazyRtFunction
 
     private val Kotlin_ObjCExport_NSIntegerTypeProvider by lazyRtFunction

kotlin-native/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/llvm/objcexport/ObjCExportCodeGenerator.kt

@@ -243,6 +243,10 @@ internal class ObjCExportCodeGenerator(
         generateContinuationToRetainedCompletionConverter(blockGenerator)
     }
 
+    internal val unitContinuationToRetainedCompletionConverter: LLVMValueRef by lazy {
+        generateUnitContinuationToRetainedCompletionConverter(blockGenerator)
+    }
+
     fun meaningfulBridgeNameOrNull(irFunction: IrFunction?): String? {
         if (!context.config.configuration.getBoolean(KonanConfigKeys.MEANINGFUL_BRIDGE_NAMES)) {
             return null
@@ -771,7 +775,31 @@ private fun ObjCExportCodeGenerator.generateContinuationToRetainedCompletionConv
             invokeName = "invokeCompletion"
     ) { continuation, arguments ->
         check(arguments.size == 2)
-        callFromBridge(context.llvm.Kotlin_ObjCExport_resumeContinuation, listOf(continuation) + arguments)
+
+        val resultArgument = objCReferenceToKotlin(arguments[0], Lifetime.ARGUMENT)
+        val errorArgument = arguments[1]
+
+        callFromBridge(context.llvm.Kotlin_ObjCExport_resumeContinuation, listOf(continuation, resultArgument, errorArgument))
+        ret(null)
+    }
+}
+
+private fun ObjCExportCodeGenerator.generateUnitContinuationToRetainedCompletionConverter(
+        blockGenerator: BlockGenerator
+): LLVMValueRef = with(blockGenerator) {
+    generateWrapKotlinObjectToRetainedBlock(
+            BlockType(numberOfParameters = 1, returnsVoid = true),
+            convertName = "convertUnitContinuation",
+            invokeName = "invokeUnitCompletion"
+    ) { continuation, arguments ->
+        check(arguments.size == 1)
+
+        val errorArgument = arguments[0]
+        val resultArgument = ifThenElse(icmpNe(errorArgument, kNullInt8Ptr), kNullObjHeaderPtr) {
+            codegen.theUnitInstanceRef.llvm
+        }
+        
+        callFromBridge(context.llvm.Kotlin_ObjCExport_resumeContinuation, listOf(continuation, resultArgument, errorArgument))
         ret(null)
     }
 }
@@ -979,9 +1007,14 @@ private fun ObjCExportCodeGenerator.generateObjCImp(
                 null
             }
 
-            MethodBridgeValueParameter.SuspendCompletion -> {
+            is MethodBridgeValueParameter.SuspendCompletion -> {
+                val createContinuationArgument = if (paramBridge.useUnitCompletion) {
+                    context.llvm.Kotlin_ObjCExport_createUnitContinuationArgument
+                } else {
+                    context.llvm.Kotlin_ObjCExport_createContinuationArgument
+                }
                 callFromBridge(
-                        context.llvm.Kotlin_ObjCExport_createContinuationArgument,
+                        createContinuationArgument,
                         listOf(parameter, generateExceptionTypeInfoArray(baseMethod!!)),
                         Lifetime.ARGUMENT
                 ).also {
@@ -1187,7 +1220,7 @@ private fun ObjCExportCodeGenerator.generateKotlinToObjCBridge(
                         errorOutPtr = it
                     }
 
-                MethodBridgeValueParameter.SuspendCompletion -> {
+                is MethodBridgeValueParameter.SuspendCompletion -> {
                     val continuation = param(irFunction.allParametersCount) // The last argument.
                     // TODO: consider placing interception into the converter to reduce code size.
                     val intercepted = callFromBridge(
@@ -1195,7 +1228,13 @@ private fun ObjCExportCodeGenerator.generateKotlinToObjCBridge(
                             listOf(continuation),
                             Lifetime.ARGUMENT
                     )
-                    val retainedCompletion = callFromBridge(continuationToRetainedCompletionConverter, listOf(intercepted))
+
+                    val converter = if (bridge.useUnitCompletion) {
+                        unitContinuationToRetainedCompletionConverter
+                    } else {
+                        continuationToRetainedCompletionConverter
+                    }
+                    val retainedCompletion = callFromBridge(converter, listOf(intercepted))
                     callFromBridge(objcAutorelease, listOf(retainedCompletion)) // TODO: use stack-allocated block here instead.
                 }
             }
@@ -1771,7 +1810,7 @@ private fun MethodBridgeParameter.toLlvmParamType(): LlvmParamType = when (this)
     is MethodBridgeReceiver -> ReferenceBridge.toLlvmParamType()
     MethodBridgeSelector -> LlvmParamType(int8TypePtr)
     MethodBridgeValueParameter.ErrorOutParameter -> LlvmParamType(pointerType(ReferenceBridge.toLlvmParamType().llvmType))
-    MethodBridgeValueParameter.SuspendCompletion -> LlvmParamType(int8TypePtr)
+    is MethodBridgeValueParameter.SuspendCompletion -> LlvmParamType(int8TypePtr)
 }
 
 private fun MethodBridge.ReturnValue.toLlvmRetType(
@@ -1827,7 +1866,7 @@ private val MethodBridgeParameter.objCEncoding: String get() = when (this) {
     is MethodBridgeReceiver -> ReferenceBridge.objCEncoding
     MethodBridgeSelector -> ":"
     MethodBridgeValueParameter.ErrorOutParameter -> "^${ReferenceBridge.objCEncoding}"
-    MethodBridgeValueParameter.SuspendCompletion -> "@"
+    is MethodBridgeValueParameter.SuspendCompletion -> "@"
 }
 
 private val TypeBridge.objCEncoding: String get() = when (this) {

kotlin-native/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/objcexport/MethodBridge.kt

@@ -35,7 +35,7 @@ internal object MethodBridgeSelector : MethodBridgeParameter()
 internal sealed class MethodBridgeValueParameter : MethodBridgeParameter() {
     data class Mapped(val bridge: TypeBridge) : MethodBridgeValueParameter()
     object ErrorOutParameter : MethodBridgeValueParameter()
-    object SuspendCompletion : MethodBridgeValueParameter()
+    data class SuspendCompletion(val useUnitCompletion: Boolean) : MethodBridgeValueParameter()
 }
 
 internal data class MethodBridge(
@@ -92,7 +92,7 @@ internal fun MethodBridge.valueParametersAssociated(
         when (it) {
             is MethodBridgeValueParameter.Mapped -> it to kotlinParameters.next()
 
-            MethodBridgeValueParameter.SuspendCompletion,
+            is MethodBridgeValueParameter.SuspendCompletion,
             is MethodBridgeValueParameter.ErrorOutParameter -> it to null
         }
     }.also { assert(!kotlinParameters.hasNext()) }
@@ -108,7 +108,7 @@ internal fun MethodBridge.parametersAssociated(
             is MethodBridgeValueParameter.Mapped, MethodBridgeReceiver.Instance ->
                 it to kotlinParameters.next()
 
-            MethodBridgeValueParameter.SuspendCompletion,
+            is MethodBridgeValueParameter.SuspendCompletion,
             MethodBridgeReceiver.Static, MethodBridgeSelector, MethodBridgeValueParameter.ErrorOutParameter ->
                 it to null
 

kotlin-native/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/objcexport/ObjCExport.kt

@@ -56,7 +56,8 @@ internal class ObjCExport(val context: Context, symbolTable: SymbolTable) {
         val produceFramework = context.config.produce == CompilerOutputKind.FRAMEWORK
 
         return if (produceFramework) {
-            val mapper = ObjCExportMapper(context.frontendServices.deprecationResolver)
+            val unitSuspendFunctionExport = context.config.unitSuspendFunctionObjCExport
+            val mapper = ObjCExportMapper(context.frontendServices.deprecationResolver, unitSuspendFunctionExport = unitSuspendFunctionExport)
             val moduleDescriptors = listOf(context.moduleDescriptor) + context.getExportedDependencies()
             val objcGenerics = context.configuration.getBoolean(KonanConfigKeys.OBJC_GENERICS)
             val namer = ObjCExportNamerImpl(
@@ -86,7 +87,7 @@ internal class ObjCExport(val context: Context, symbolTable: SymbolTable) {
 
         if (!context.config.produce.isFinalBinary) return // TODO: emit RTTI to the same modules as classes belong to.
 
-        val mapper = exportedInterface?.mapper ?: ObjCExportMapper()
+        val mapper = exportedInterface?.mapper ?: ObjCExportMapper(unitSuspendFunctionExport = context.config.unitSuspendFunctionObjCExport)
         namer = exportedInterface?.namer ?: ObjCExportNamerImpl(
                 setOf(codegen.context.moduleDescriptor),
                 context.moduleDescriptor.builtIns,

kotlin-native/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/objcexport/ObjCExportHeaderGenerator.kt

@@ -644,7 +644,7 @@ internal class ObjCExportTranslatorImpl(
                         }
                     }
                     MethodBridgeValueParameter.ErrorOutParameter -> "error"
-                    MethodBridgeValueParameter.SuspendCompletion -> "completionHandler"
+                    is MethodBridgeValueParameter.SuspendCompletion -> "completionHandler"
                 }
 
                 val uniqueName = unifyName(candidateName, usedNames)
@@ -655,14 +655,18 @@ internal class ObjCExportTranslatorImpl(
                     MethodBridgeValueParameter.ErrorOutParameter ->
                         ObjCPointerType(ObjCNullableReferenceType(ObjCClassType("NSError")), nullable = true)
 
-                    MethodBridgeValueParameter.SuspendCompletion -> {
+                    is MethodBridgeValueParameter.SuspendCompletion -> {
-                        val resultType = when (val it = mapReferenceType(method.returnType!!, objCExportScope)) {
+                        val resultType = if (bridge.useUnitCompletion) {
-                            is ObjCNonNullReferenceType -> ObjCNullableReferenceType(it, isNullableResult = false)
+                            null
-                            is ObjCNullableReferenceType -> ObjCNullableReferenceType(it.nonNullType, isNullableResult = true)
+                        } else {
+                            when (val it = mapReferenceType(method.returnType!!, objCExportScope)) {
+                                is ObjCNonNullReferenceType -> ObjCNullableReferenceType(it, isNullableResult = false)
+                                is ObjCNullableReferenceType -> ObjCNullableReferenceType(it.nonNullType, isNullableResult = true)
+                            }
                         }
                         ObjCBlockPointerType(
                                 returnType = ObjCVoidType,
-                                parameterTypes = listOf(
+                                parameterTypes = listOfNotNull(
                                         resultType,
                                         ObjCNullableReferenceType(ObjCClassType("NSError"))
                                 )

kotlin-native/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/objcexport/ObjCExportLazy.kt

@@ -7,6 +7,7 @@ package org.jetbrains.kotlin.backend.konan.objcexport
 
 import com.intellij.psi.PsiElement
 import org.jetbrains.kotlin.analyzer.ModuleInfo
+import org.jetbrains.kotlin.backend.konan.UnitSuspendFunctionObjCExport
 import org.jetbrains.kotlin.descriptors.konan.isNativeStdlib
 import org.jetbrains.kotlin.builtins.KotlinBuiltIns
 import org.jetbrains.kotlin.descriptors.*
@@ -43,6 +44,7 @@ interface ObjCExportLazy {
         fun isIncluded(moduleInfo: ModuleInfo): Boolean
         fun getCompilerModuleName(moduleInfo: ModuleInfo): String
         val objcGenerics: Boolean
+        val unitSuspendFunctionExport: UnitSuspendFunctionObjCExport
     }
 
     fun generateBase(): List<ObjCTopLevel<*>>
@@ -86,7 +88,7 @@ internal class ObjCExportLazyImpl(
 
     private val nameTranslator: ObjCExportNameTranslator = ObjCExportNameTranslatorImpl(namerConfiguration)
 
-    private val mapper = ObjCExportMapper(deprecationResolver, local = true)
+    private val mapper = ObjCExportMapper(deprecationResolver, local = true, configuration.unitSuspendFunctionExport)
 
     private val namer = ObjCExportNamerImpl(namerConfiguration, builtIns, mapper, local = true)
 

kotlin-native/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/objcexport/ObjCExportMapper.kt

@@ -25,7 +25,8 @@ import org.jetbrains.kotlin.types.typeUtil.isUnit
 
 internal class ObjCExportMapper(
         internal val deprecationResolver: DeprecationResolver? = null,
-        private val local: Boolean = false
+        private val local: Boolean = false,
+        internal val unitSuspendFunctionExport: UnitSuspendFunctionObjCExport
 ) {
     fun getCustomTypeMapper(descriptor: ClassDescriptor): CustomTypeMapper? = CustomTypeMappers.getMapper(descriptor)
 
@@ -331,7 +332,8 @@ private fun ObjCExportMapper.bridgeMethodImpl(descriptor: FunctionDescriptor): M
     val returnBridge = bridgeReturnType(descriptor, convertExceptionsToErrors)
 
     if (descriptor.isSuspend) {
-        valueParameters += MethodBridgeValueParameter.SuspendCompletion
+        val useUnitCompletion = (unitSuspendFunctionExport == UnitSuspendFunctionObjCExport.PROPER) && (descriptor.returnType!!.isUnit())
+        valueParameters += MethodBridgeValueParameter.SuspendCompletion(useUnitCompletion)
     } else if (convertExceptionsToErrors) {
         // Add error out parameter before tail block parameters. The convention allows this.
         // Placing it after would trigger https://bugs.swift.org/browse/SR-12201
@@ -349,7 +351,7 @@ private fun MethodBridgeValueParameter.isBlockPointer(): Boolean = when (this) {
         is BlockPointerBridge -> true
     }
     MethodBridgeValueParameter.ErrorOutParameter -> false
-    MethodBridgeValueParameter.SuspendCompletion -> true
+    is MethodBridgeValueParameter.SuspendCompletion -> true
 }
 
 internal fun ObjCExportMapper.bridgePropertyType(descriptor: PropertyDescriptor): TypeBridge {

kotlin-native/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/objcexport/ObjCExportNamer.kt

@@ -7,6 +7,7 @@ package org.jetbrains.kotlin.backend.konan.objcexport
 
 import org.jetbrains.kotlin.backend.common.serialization.findSourceFile
 import org.jetbrains.kotlin.backend.konan.Context
+import org.jetbrains.kotlin.backend.konan.UnitSuspendFunctionObjCExport
 import org.jetbrains.kotlin.backend.konan.cKeywords
 import org.jetbrains.kotlin.backend.konan.descriptors.isArray
 import org.jetbrains.kotlin.backend.konan.descriptors.isInterface
@@ -89,7 +90,7 @@ fun createNamer(
 ): ObjCExportNamer = ObjCExportNamerImpl(
         (exportedDependencies + moduleDescriptor).toSet(),
         moduleDescriptor.builtIns,
-        ObjCExportMapper(local = true),
+        ObjCExportMapper(local = true, unitSuspendFunctionExport = UnitSuspendFunctionObjCExport.LEGACY),
         topLevelNamePrefix,
         local = true
 )
@@ -472,7 +473,7 @@ internal class ObjCExportNamerImpl(
                         else -> it!!.name.asString().toIdentifier()
                     }
                     MethodBridgeValueParameter.ErrorOutParameter -> "error"
-                    MethodBridgeValueParameter.SuspendCompletion -> "completionHandler"
+                    is MethodBridgeValueParameter.SuspendCompletion -> "completionHandler"
                 }
 
                 if (index == 0) {
@@ -525,7 +526,7 @@ internal class ObjCExportNamerImpl(
                         else -> it!!.name.asString().toIdentifier()
                     }
                     MethodBridgeValueParameter.ErrorOutParameter -> continue@parameters
-                    MethodBridgeValueParameter.SuspendCompletion -> "completionHandler"
+                    is MethodBridgeValueParameter.SuspendCompletion -> "completionHandler"
                 }
 
                 append(label)

kotlin-native/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/objcexport/ObjCExportTranslatorMobile.kt

@@ -10,9 +10,9 @@ import org.jetbrains.kotlin.descriptors.FunctionDescriptor
 
 class ObjCExportTranslatorMobile internal constructor(private val delegate: ObjCExportTranslatorImpl) : ObjCExportTranslator by delegate {
     companion object {
-        fun create(namer: ObjCExportNamer): ObjCExportTranslatorMobile {
+        fun create(namer: ObjCExportNamer, configuration: ObjCExportLazy.Configuration): ObjCExportTranslatorMobile {
-            val mapper = ObjCExportMapper(local = true)
+            val mapper = ObjCExportMapper(local = true, unitSuspendFunctionExport = configuration.unitSuspendFunctionExport)
-            return ObjCExportTranslatorMobile(ObjCExportTranslatorImpl(null, mapper, namer, ObjCExportProblemCollector.SILENT, false))
+            return ObjCExportTranslatorMobile(ObjCExportTranslatorImpl(null, mapper, namer, ObjCExportProblemCollector.SILENT, configuration.objcGenerics))
         }
     }
 

kotlin-native/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/objcexport/ObjcExportHeaderGeneratorMobile.kt

@@ -24,7 +24,7 @@ class ObjcExportHeaderGeneratorMobile internal constructor(
                 deprecationResolver: DeprecationResolver? = null,
                 local: Boolean = false,
                 restrictToLocalModules: Boolean = false): ObjCExportHeaderGenerator {
-            val mapper = ObjCExportMapper(deprecationResolver, local)
+            val mapper = ObjCExportMapper(deprecationResolver, local, configuration.unitSuspendFunctionExport)
             val namerConfiguration = createNamerConfiguration(configuration)
             val namer = ObjCExportNamerImpl(namerConfiguration, builtIns, mapper, local)
 

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.nothingAsInt(5) }
-    assertFailsWith<ObjCErrorException> { bridge.nothingAsAny(4) }
+    assertFailsWith<ObjCErrorException> { bridge.nothingAsAny(6) }
-    assertFailsWith<ObjCErrorException> { bridge.nothingAsUnit(5) }
+    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.nothingAsInt(12) }
-    assertFailsWith<ObjCErrorException> { bridge.nothingAsAny(9) }
+    assertFailsWith<ObjCErrorException> { bridge.nothingAsAny(13) }
-    assertFailsWith<ObjCErrorException> { bridge.nothingAsUnit(10) }
+    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
+            completionCalled += 1
-        result = _result
+            result = _result
-        error = _error
+            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 {

kotlin-native/runtime/src/main/cpp/ObjCExportCoroutines.mm

@@ -48,12 +48,21 @@ extern "C" OBJ_GETTER(Kotlin_ObjCExport_createContinuationArgument, id completio
   RETURN_RESULT_OF(Kotlin_ObjCExport_createContinuationArgumentImpl, completionHolder, exceptionTypes);
 }
 
+extern "C" OBJ_GETTER(Kotlin_ObjCExport_createUnitContinuationArgument, id completion, const TypeInfo** exceptionTypes) {
+  void (^typedCompletion)(NSError * _Nullable) = completion;
+  Completion twoArgumentCompletion = ^(_Nullable id result, NSError* _Nullable error) {
+    // typedCompletion will be retained by the containing block when the latter is copied
+    // from stack to heap via objc_retainBlock.
+    typedCompletion(error);
+  };
+
+  RETURN_RESULT_OF(Kotlin_ObjCExport_createContinuationArgument, twoArgumentCompletion, exceptionTypes);
+}
+
 extern "C" void Kotlin_ObjCExport_resumeContinuationSuccess(KRef continuation, KRef result);
 extern "C" void Kotlin_ObjCExport_resumeContinuationFailure(KRef continuation, KRef exception);
 
-extern "C" void Kotlin_ObjCExport_resumeContinuation(KRef continuation, id result, id error) {
+extern "C" void Kotlin_ObjCExport_resumeContinuation(KRef continuation, KRef result, id error) {
-  ObjHolder holder;
-
   if (error != nullptr) {
     if (result != nullptr) {
       [NSException raise:NSGenericException
@@ -61,11 +70,12 @@ extern "C" void Kotlin_ObjCExport_resumeContinuation(KRef continuation, id resul
           result, error];
     }
 
+    ObjHolder holder;
+
     KRef exception = Kotlin_ObjCExport_NSErrorAsException(error, holder.slot());
     Kotlin_ObjCExport_resumeContinuationFailure(continuation, exception);
   } else {
-    KRef kotlinResult = Kotlin_ObjCExport_refFromObjC(result, holder.slot());
+    Kotlin_ObjCExport_resumeContinuationSuccess(continuation, result);
-    Kotlin_ObjCExport_resumeContinuationSuccess(continuation, kotlinResult);
   }
 }
 

kotlin-native/runtime/src/mm/cpp/CallsChecker.cpp

@@ -185,6 +185,7 @@ extern "C" const char* Kotlin_callsCheckerGoodFunctionNames[] = {
         "CFStringCreateCopy",
         "CFStringGetCharacters",
         "CFStringGetLength",
+        "_Block_object_assign",
         "class_addIvar",
         "class_addMethod",
         "class_addProtocol",