ObjCExport: fix replacing Kotlin class methods by Swift extensions

^KT-49937 Fixed

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

@@ -958,6 +958,14 @@ __attribute__((swift_name("Kt46431Kt")))
 + (id<KtHost>)createAbstractHost __attribute__((swift_name("createAbstractHost()")));
 @end;
 
+__attribute__((objc_subclassing_restricted))
+__attribute__((swift_name("KT49937")))
+@interface KtKT49937 : KtBase
+- (instancetype)init __attribute__((swift_name("init()"))) __attribute__((objc_designated_initializer));
++ (instancetype)new __attribute__((availability(swift, unavailable, message="use object initializers instead")));
+- (NSString *)description __attribute__((swift_name("description()")));
+@end;
+
 __attribute__((objc_subclassing_restricted))
 __attribute__((swift_name("LibraryKt")))
 @interface KtLibraryKt : KtBase

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

@@ -900,6 +900,14 @@ __attribute__((swift_name("Kt46431Kt")))
 + (id<KtHost>)createAbstractHost __attribute__((swift_name("createAbstractHost()")));
 @end;
 
+__attribute__((objc_subclassing_restricted))
+__attribute__((swift_name("KT49937")))
+@interface KtKT49937 : KtBase
+- (instancetype)init __attribute__((swift_name("init()"))) __attribute__((objc_designated_initializer));
++ (instancetype)new __attribute__((availability(swift, unavailable, message="use object initializers instead")));
+- (NSString *)description __attribute__((swift_name("description()")));
+@end;
+
 __attribute__((objc_subclassing_restricted))
 __attribute__((swift_name("LibraryKt")))
 @interface KtLibraryKt : KtBase

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

@@ -900,6 +900,14 @@ __attribute__((swift_name("Kt46431Kt")))
 + (id<KtHost>)createAbstractHost __attribute__((swift_name("createAbstractHost()")));
 @end;
 
+__attribute__((objc_subclassing_restricted))
+__attribute__((swift_name("KT49937")))
+@interface KtKT49937 : KtBase
+- (instancetype)init __attribute__((swift_name("init()"))) __attribute__((objc_designated_initializer));
++ (instancetype)new __attribute__((availability(swift, unavailable, message="use object initializers instead")));
+- (NSString *)description __attribute__((swift_name("description()")));
+@end;
+
 __attribute__((objc_subclassing_restricted))
 __attribute__((swift_name("LibraryKt")))
 @interface KtLibraryKt : KtBase

kotlin-native/backend.native/tests/objcexport/kt49937.kt

@@ -0,0 +1,14 @@
+/*
+ * Copyright 2010-2021 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license
+ * that can be found in the LICENSE file.
+ */
+
+package kt49937
+
+// Based on https://youtrack.jetbrains.com/issue/KT-49937
+
+final class KT49937 {
+    override fun toString(): String {
+        return "KT49937"
+    }
+}

kotlin-native/backend.native/tests/objcexport/kt49937.swift

@@ -0,0 +1,27 @@
+/*
+ * Copyright 2010-2021 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license
+ * that can be found in the LICENSE file.
+ */
+
+import Kt
+
+// Based on https://youtrack.jetbrains.com/issue/KT-49937.
+
+public extension KT49937 {
+    override var description: String { "KT49937Swift" }
+}
+
+private func test1() throws {
+    try assertEquals(actual: KT49937().description, expected: "KT49937Swift")
+
+    let nsObject: NSObject = KT49937()
+    try assertEquals(actual: nsObject.description, expected: "KT49937Swift")
+}
+
+class Kt49937Tests : SimpleTestProvider {
+    override init() {
+        super.init()
+
+        test("Test1", test1)
+    }
+}

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

@@ -307,15 +307,15 @@ extern "C" void Kotlin_ObjCExport_initializeClass(Class clazz) {
   for (int i = 0; i < typeAdapter->directAdapterNum; ++i) {
     const ObjCToKotlinMethodAdapter* adapter = typeAdapter->directAdapters + i;
     SEL selector = sel_registerName(adapter->selector);
-    BOOL added = class_addMethod(clazz, selector, adapter->imp, adapter->encoding);
+    class_addMethod(clazz, selector, adapter->imp, adapter->encoding);
-    RuntimeAssert(added, "Unexpected selector clash");
+    // The method above may fail if there is a matching Swift/Obj-C extension method for this Kotlin class.
+    // This is pretty much ok, and we shouldn't replace that method with our own.
   }
 
   for (int i = 0; i < typeAdapter->classAdapterNum; ++i) {
     const ObjCToKotlinMethodAdapter* adapter = typeAdapter->classAdapters + i;
     SEL selector = sel_registerName(adapter->selector);
-    BOOL added = class_addMethod(object_getClass(clazz), selector, adapter->imp, adapter->encoding);
+    class_addMethod(object_getClass(clazz), selector, adapter->imp, adapter->encoding);
-    RuntimeAssert(added, "Unexpected selector clash");
   }
 
   if (isClassForPackage) return;