[K/N] KT-56464: implementation of HiddenFromObjC for classes in backend

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

@@ -596,9 +596,36 @@ private class BackendChecker(
         if (declaration.isKotlinObjCClass()) {
             checkKotlinObjCClass(declaration)
         }
+        checkHiddenFromObjCRestrictions(declaration)
         super.visitClass(declaration)
 
     }
+
+    private fun IrClass.isHiddenFromObjC(): Boolean {
+        return annotations.any { annotationCall ->
+            val annotationClass = annotationCall.symbol.owner.parentAsClass
+            annotationClass.annotations.hasAnnotation(KonanFqNames.hidesFromObjC)
+        }
+    }
+
+    private fun checkHiddenFromObjCRestrictions(declaration: IrClass) {
+        // If declaration itself. is marked as hidden, we don't need to do anything
+        if (declaration.isHiddenFromObjC()) return
+        // Enum entries inherit from their classes, so if enum class is marked as hidden, there is no need to
+        // produce additional errors.
+        if (declaration.kind == ClassKind.ENUM_ENTRY) return
+        // Private and local classes does not leak to Objective-C API surface, so it is OK for them
+        // to inherit from hidden types.
+        if (DescriptorVisibilities.isPrivate(declaration.visibility) || declaration.isLocal) return
+        if (declaration.superClass?.isHiddenFromObjC() == true) {
+            reportError(declaration, "Only @HiddenFromObjC declaration can inherit from class annotated with @HiddenFromObjC")
+        }
+        declaration.getSuperInterfaces().forEach {
+            if (it.isHiddenFromObjC()) {
+                reportError(declaration, "Only @HiddenFromObjC declaration can implement interface annotated with @HiddenFromObjC")
+            }
+        }
+    }
 }
 
 private fun BackendChecker.checkCanGenerateCCall(expression: IrCall, isInvoke: Boolean) {

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

@@ -108,6 +108,16 @@ private fun CallableMemberDescriptor.isHiddenFromObjC(): Boolean = when {
     }
 }
 
+/**
+ * Check if the given class or its enclosing declaration is marked as @HiddenFromObjC.
+ */
+internal fun ClassDescriptor.isHiddenFromObjC(): Boolean = when {
+    (this.containingDeclaration as? ClassDescriptor)?.isHiddenFromObjC() == true -> true
+    else -> annotations.any { annotation ->
+        annotation.annotationClass?.annotations?.any { it.fqName == KonanFqNames.hidesFromObjC } == true
+    }
+}
+
 internal fun ObjCExportMapper.shouldBeExposed(descriptor: ClassDescriptor): Boolean =
         shouldBeVisible(descriptor) && !isSpecialMapped(descriptor) && !descriptor.defaultType.isObjCObjectType()
 
@@ -175,7 +185,7 @@ internal fun ObjCExportMapper.shouldBeVisible(descriptor: ClassDescriptor): Bool
         descriptor.isEffectivelyPublicApi && when (descriptor.kind) {
         ClassKind.CLASS, ClassKind.INTERFACE, ClassKind.ENUM_CLASS, ClassKind.OBJECT -> true
         ClassKind.ENUM_ENTRY, ClassKind.ANNOTATION_CLASS -> false
-    } && !descriptor.isExpect && !descriptor.isInlined() && !isHiddenByDeprecation(descriptor)
+    } && !descriptor.isExpect && !descriptor.isInlined() && !isHiddenByDeprecation(descriptor) && !descriptor.isHiddenFromObjC()
 
 private fun ObjCExportMapper.isBase(descriptor: CallableMemberDescriptor): Boolean =
         descriptor.overriddenDescriptors.all { !shouldBeExposed(it) }