Fix Objective-C block to kotlin.Function* dynamic conversion (#3499)

after migrating to synthetic function classes.

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

@@ -487,6 +487,9 @@ private fun ObjCExportCodeGenerator.setObjCExportTypeInfo(
 private val ObjCExportCodeGenerator.kotlinToObjCFunctionType: LLVMTypeRef
     get() = functionType(int8TypePtr, false, codegen.kObjHeaderPtr)
 
+private val ObjCExportCodeGenerator.objCToKotlinFunctionType: LLVMTypeRef
+    get() = functionType(codegen.kObjHeaderPtr, false, int8TypePtr, codegen.kObjHeaderPtrPtr)
+
 private fun ObjCExportCodeGenerator.emitBoxConverters() {
     val irBuiltIns = context.irBuiltIns
 
@@ -537,22 +540,38 @@ private fun ObjCExportCodeGenerator.emitFunctionConverters() {
 }
 
 private fun ObjCExportCodeGenerator.emitBlockToKotlinFunctionConverters() {
-    val converters = context.ir.symbols.functionIrClassFactory.builtFunctionNClasses.map {
-        val bridge = BlockPointerBridge(numberOfParameters = it.arity, returnsVoid = false)
-        constPointer(blockToKotlinFunctionConverter(bridge))
+    val functionClassesByArity =
+            context.ir.symbols.functionIrClassFactory.builtFunctionNClasses.associateBy { it.arity }
+
+    val count = (functionClassesByArity.keys.max() ?: -1) + 1
+
+    val converters = (0 until count).map { arity ->
+        val functionClass = functionClassesByArity[arity]
+        if (functionClass != null) {
+            val bridge = BlockPointerBridge(numberOfParameters = functionClass.arity, returnsVoid = false)
+            constPointer(blockToKotlinFunctionConverter(bridge))
+        } else {
+            NullPointer(objCToKotlinFunctionType)
+        }
     }
+
     val ptr = staticData.placeGlobalArray(
             "",
-            converters.first().llvmType,
+            pointerType(objCToKotlinFunctionType),
             converters
     ).pointer.getElementPtr(0)
 
-    // Note: this global replaces the weak global defined in runtime.
+    // Note: replacing weak globals defined in runtime.
     replaceExternalWeakOrCommonGlobal(
             "Kotlin_ObjCExport_blockToFunctionConverters",
             ptr,
             context.standardLlvmSymbolsOrigin
     )
+    replaceExternalWeakOrCommonGlobal(
+            "Kotlin_ObjCExport_blockToFunctionConverters_size",
+            Int32(count),
+            context.standardLlvmSymbolsOrigin
+    )
 }
 
 private fun ObjCExportCodeGenerator.emitSpecialClassesConvertions() {

backend.native/tests/framework/values/values.kt

@@ -16,6 +16,9 @@ import kotlin.reflect.KClass
 import kotlin.reflect.KProperty
 import kotlinx.cinterop.*
 
+// Ensure loaded function IR classes aren't ordered by arity:
+internal fun referenceFunction1(block: (Any?) -> Unit) {}
+
 // Constants
 const val dbl: Double = 3.14
 const val flt: Float = 2.73F

backend.native/tests/framework/values/values.swift

@@ -392,6 +392,13 @@ func testLambda() throws {
     try assertTrue(ValuesKt.isFunction0(obj: blockMustBeFunction0))
     try assertFalse(ValuesKt.isFunction(obj: NSObject()))
     try assertFalse(ValuesKt.isFunction0(obj: NSObject()))
+
+    // Test no function class for dynamic conversion:
+    let blockAsMissingFunction: @convention(block) (AnyObject?, AnyObject?, AnyObject?, AnyObject?, AnyObject?) -> AnyObject?
+            = { return $0 ?? $1 ?? $2 ?? $3 ?? $4 }
+
+    try assertTrue(ValuesKt.isFunction(obj: blockAsMissingFunction))
+    try assertFalse(ValuesKt.isFunction0(obj: blockAsMissingFunction))
 }
 
 // -------- Tests for classes and interfaces -------

runtime/src/main/cpp/ObjCExport.mm

@@ -440,6 +440,9 @@ static const char* getBlockEncoding(id block) {
 
 // Note: replaced by compiler in appropriate compilation modes.
 __attribute__((weak)) convertReferenceFromObjC* Kotlin_ObjCExport_blockToFunctionConverters = nullptr;
+__attribute__((weak)) int Kotlin_ObjCExport_blockToFunctionConverters_size = 0;
+
+extern "C" id objc_retainBlock(id self);
 
 static OBJ_GETTER(blockToKotlinImp, id block, SEL cmd) {
   const char* encoding = getBlockEncoding(block);
@@ -448,10 +451,6 @@ static OBJ_GETTER(blockToKotlinImp, id block, SEL cmd) {
   NSMethodSignature *signature = [NSMethodSignature signatureWithObjCTypes:encoding];
   int parameterCount = signature.numberOfArguments - 1; // 1 for the block itself.
 
-  if (parameterCount > 22) {
-    [NSException raise:NSGenericException format:@"Blocks with %d (>22) parameters aren't supported", parameterCount];
-  }
-
   for (int i = 1; i <= parameterCount; ++i) {
     const char* argEncoding = [signature getArgumentTypeAtIndex:i];
     if (argEncoding[0] != '@') {
@@ -466,7 +465,17 @@ static OBJ_GETTER(blockToKotlinImp, id block, SEL cmd) {
           format:@"Blocks with non-reference-typed return value aren't supported (%s)", returnTypeEncoding];
   }
 
-  RETURN_RESULT_OF(Kotlin_ObjCExport_blockToFunctionConverters[parameterCount], block);
+  auto converter = parameterCount < Kotlin_ObjCExport_blockToFunctionConverters_size
+          ? Kotlin_ObjCExport_blockToFunctionConverters[parameterCount]
+          : nullptr;
+
+  if (converter != nullptr) {
+    RETURN_RESULT_OF(converter, block);
+  } else {
+    // There is no function class for this arity, so resulting object will not be cast to FunctionN class,
+    // and it is enough to convert block to arbitrary object conforming Function.
+    RETURN_RESULT_OF(AllocInstanceWithAssociatedObject, theOpaqueFunctionTypeInfo, objc_retainBlock(block));
+  }
 }
 
 static id Kotlin_ObjCExport_refToObjC_slowpath(ObjHeader* obj);

runtime/src/main/cpp/Types.h

@@ -96,6 +96,7 @@ extern const TypeInfo* theFloatArrayTypeInfo;
 extern const TypeInfo* theForeignObjCObjectTypeInfo;
 extern const TypeInfo* theFreezableAtomicReferenceTypeInfo;
 extern const TypeInfo* theObjCObjectWrapperTypeInfo;
+extern const TypeInfo* theOpaqueFunctionTypeInfo;
 extern const TypeInfo* theShortArrayTypeInfo;
 extern const TypeInfo* theStringTypeInfo;
 extern const TypeInfo* theThrowableTypeInfo;

runtime/src/main/kotlin/kotlin/native/internal/ObjCExportUtils.kt

@@ -295,3 +295,7 @@ private fun Kotlin_Throwable_getMessage(throwable: Throwable): String? = throwab
 @ExportForCppRuntime
 private fun Kotlin_ObjCExport_getWrappedError(throwable: Throwable): Any? =
         (throwable as? ObjCErrorException)?.error
+
+@ExportTypeInfo("theOpaqueFunctionTypeInfo")
+@PublishedApi
+internal class OpaqueFunction : Function<Any?>