[IR] Mark IrAnonymousInitializerImpl with an opt-in annotation

KT-59318

compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/IrImplementationDetail.kt

@@ -0,0 +1,17 @@
+/*
+ * 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.ir
+
+import org.jetbrains.kotlin.ir.declarations.IrFactory
+
+/**
+ * IR implementation classes annotated with this annotation are not expected to be used directly.
+ *
+ * [IrFactory] should be the preferred way to create instances of such classes.
+ */
+@RequiresOptIn("Use IrFactory instead of creating IR nodes directly", level = RequiresOptIn.Level.ERROR)
+@Target(AnnotationTarget.CONSTRUCTOR)
+annotation class IrImplementationDetail

compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/declarations/impl/IrAnonymousInitializerImpl.kt

@@ -6,6 +6,7 @@
 package org.jetbrains.kotlin.ir.declarations.impl
 
 import org.jetbrains.kotlin.descriptors.ClassDescriptor
+import org.jetbrains.kotlin.ir.IrImplementationDetail
 import org.jetbrains.kotlin.ir.ObsoleteDescriptorBasedAPI
 import org.jetbrains.kotlin.ir.declarations.IrAnonymousInitializer
 import org.jetbrains.kotlin.ir.declarations.IrFactory
@@ -15,7 +16,7 @@ import org.jetbrains.kotlin.ir.expressions.IrBlockBody
 import org.jetbrains.kotlin.ir.expressions.IrConstructorCall
 import org.jetbrains.kotlin.ir.symbols.IrAnonymousInitializerSymbol
 
-class IrAnonymousInitializerImpl(
+class IrAnonymousInitializerImpl @IrImplementationDetail constructor(
     override val startOffset: Int,
     override val endOffset: Int,
     override var origin: IrDeclarationOrigin,

compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/declarations/impl/IrFactoryImpl.kt

@@ -6,7 +6,7 @@
 package org.jetbrains.kotlin.ir.declarations.impl
 
 import org.jetbrains.kotlin.descriptors.*
-import org.jetbrains.kotlin.ir.IrStatement
+import org.jetbrains.kotlin.ir.IrImplementationDetail
 import org.jetbrains.kotlin.ir.declarations.*
 import org.jetbrains.kotlin.ir.expressions.IrBlockBody
 import org.jetbrains.kotlin.ir.expressions.IrExpression
@@ -23,6 +23,7 @@ object IrFactoryImpl : AbstractIrFactoryImpl() {
     override val stageController: StageController = StageController()
 }
 
+@OptIn(IrImplementationDetail::class)
 abstract class AbstractIrFactoryImpl : IrFactory {
 
     override fun createAnonymousInitializer(