Don't emit CAST_NEVER_SUCCEEDS when casting to a forward declaration type

^KT-58929

native/frontend/src/org/jetbrains/kotlin/resolve/konan/diagnostics/NativePlatformSpecificCastChecker.kt

@@ -0,0 +1,28 @@
+/*
+ * Copyright 2010-2023 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.resolve.konan.diagnostics
+
+import org.jetbrains.kotlin.builtins.PlatformSpecificCastChecker
+import org.jetbrains.kotlin.descriptors.ClassDescriptor
+import org.jetbrains.kotlin.descriptors.konan.getForwardDeclarationKindOrNull
+import org.jetbrains.kotlin.types.KotlinType
+
+object NativePlatformSpecificCastChecker : PlatformSpecificCastChecker {
+    override fun isCastPossible(fromType: KotlinType, toType: KotlinType): Boolean {
+        return isCastToAForwardDeclaration(toType)
+    }
+
+    /**
+     * Here, we only check that we are casting to a forward declaration to suppress a CAST_NEVER_SUCCEEDS warning. The cast is further
+     * checked in NativeForwardDeclarationRttiChecker.
+     */
+    private fun isCastToAForwardDeclaration(forwardDeclarationType: KotlinType): Boolean {
+        val forwardDeclarationClassDescriptor = forwardDeclarationType.constructor.declarationDescriptor
+        if (forwardDeclarationClassDescriptor !is ClassDescriptor) return false
+        return forwardDeclarationClassDescriptor.getForwardDeclarationKindOrNull() != null
+    }
+
+}

native/frontend/src/org/jetbrains/kotlin/resolve/konan/platform/NativePlatformConfigurator.kt

@@ -30,7 +30,8 @@ object NativePlatformConfigurator : PlatformConfiguratorBase(
         NativeObjCNameChecker, NativeObjCNameOverridesChecker,
         NativeObjCRefinementChecker, NativeObjCRefinementAnnotationChecker,
         NativeObjCRefinementOverridesChecker, NativeHiddenFromObjCInheritanceChecker,
-    )
+    ),
+    platformSpecificCastChecker = NativePlatformSpecificCastChecker
 ) {
     override fun configureModuleComponents(container: StorageComponentContainer) {
         container.useInstance(NativeInliningRule)