diff --git a/compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/Fir2IrDeclarationStorage.kt b/compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/Fir2IrDeclarationStorage.kt
index 28bbaa403fb..375eb97435f 100644
--- a/compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/Fir2IrDeclarationStorage.kt
+++ b/compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/Fir2IrDeclarationStorage.kt
@@ -32,6 +32,7 @@ import org.jetbrains.kotlin.fir.symbols.ConeClassLikeLookupTag
 import org.jetbrains.kotlin.fir.symbols.FirBasedSymbol
 import org.jetbrains.kotlin.fir.symbols.impl.*
 import org.jetbrains.kotlin.fir.types.*
+import org.jetbrains.kotlin.ir.IrImplementationDetail
 import org.jetbrains.kotlin.ir.UNDEFINED_OFFSET
 import org.jetbrains.kotlin.ir.builders.declarations.UNDEFINED_PARAMETER_INDEX
 import org.jetbrains.kotlin.ir.declarations.*
@@ -229,6 +230,7 @@ class Fir2IrDeclarationStorage(
         return fileCache[firFile]!!
     }
 
+    @OptIn(IrImplementationDetail::class)
     internal class NonCachedSourceFileFacadeClass(
         origin: IrDeclarationOrigin,
         name: Name,
diff --git a/compiler/ir/backend.jvm/lower/src/org/jetbrains/kotlin/backend/jvm/lower/FileClassLowering.kt b/compiler/ir/backend.jvm/lower/src/org/jetbrains/kotlin/backend/jvm/lower/FileClassLowering.kt
index f81e77107a9..1bcd8a1aa20 100644
--- a/compiler/ir/backend.jvm/lower/src/org/jetbrains/kotlin/backend/jvm/lower/FileClassLowering.kt
+++ b/compiler/ir/backend.jvm/lower/src/org/jetbrains/kotlin/backend/jvm/lower/FileClassLowering.kt
@@ -31,7 +31,6 @@ import org.jetbrains.kotlin.fileClasses.JvmMultifileClassPartInfo
 import org.jetbrains.kotlin.fileClasses.JvmSimpleFileClassInfo
 import org.jetbrains.kotlin.ir.PsiIrFileEntry
 import org.jetbrains.kotlin.ir.declarations.*
-import org.jetbrains.kotlin.ir.declarations.impl.IrClassImpl
 import org.jetbrains.kotlin.ir.expressions.IrConst
 import org.jetbrains.kotlin.ir.expressions.IrConstKind
 import org.jetbrains.kotlin.ir.expressions.IrConstructorCall
@@ -98,17 +97,18 @@ private class FileClassLowering(val context: JvmBackendContext) : FileLoweringPa
                 IrDeclarationOrigin.FILE_CLASS
             else
                 IrDeclarationOrigin.SYNTHETIC_FILE_CLASS
-        return IrClassImpl(
-            0, fileEntry.maxOffset,
-            fileClassOrigin,
-            symbol = IrClassSymbolImpl(),
+        return context.irFactory.createClass(
+            startOffset = 0,
+            endOffset = fileEntry.maxOffset,
+            origin = fileClassOrigin,
             name = fileClassInfo.fileClassFqName.shortName(),
-            kind = ClassKind.CLASS,
             visibility = if (isMultifilePart || onlyPrivateDeclarationsAndFeatureIsEnabled)
                 JavaDescriptorVisibilities.PACKAGE_VISIBILITY
             else
                 DescriptorVisibilities.PUBLIC,
-            modality = Modality.FINAL
+            symbol = IrClassSymbolImpl(),
+            kind = ClassKind.CLASS,
+            modality = Modality.FINAL,
         ).apply {
             superTypes = listOf(context.irBuiltIns.anyType)
             parent = irFile
diff --git a/compiler/ir/backend.jvm/src/org/jetbrains/kotlin/backend/jvm/JvmFileFacadeClass.kt b/compiler/ir/backend.jvm/src/org/jetbrains/kotlin/backend/jvm/JvmFileFacadeClass.kt
index 2962b86d15f..2c7ef5896df 100644
--- a/compiler/ir/backend.jvm/src/org/jetbrains/kotlin/backend/jvm/JvmFileFacadeClass.kt
+++ b/compiler/ir/backend.jvm/src/org/jetbrains/kotlin/backend/jvm/JvmFileFacadeClass.kt
@@ -6,6 +6,7 @@
 package org.jetbrains.kotlin.backend.jvm
 
 import org.jetbrains.kotlin.descriptors.*
+import org.jetbrains.kotlin.ir.IrImplementationDetail
 import org.jetbrains.kotlin.ir.UNDEFINED_OFFSET
 import org.jetbrains.kotlin.ir.declarations.IrClass
 import org.jetbrains.kotlin.ir.declarations.IrDeclarationOrigin
@@ -14,6 +15,7 @@ import org.jetbrains.kotlin.ir.symbols.impl.IrClassSymbolImpl
 import org.jetbrains.kotlin.ir.util.DeserializableClass
 import org.jetbrains.kotlin.name.Name
 
+@OptIn(IrImplementationDetail::class)
 class JvmFileFacadeClass(
     origin: IrDeclarationOrigin,
     name: Name,
diff --git a/compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/declarations/impl/IrClassImpl.kt b/compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/declarations/impl/IrClassImpl.kt
index 336f20fe2a1..e7251be6632 100644
--- a/compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/declarations/impl/IrClassImpl.kt
+++ b/compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/declarations/impl/IrClassImpl.kt
@@ -6,6 +6,7 @@
 package org.jetbrains.kotlin.ir.declarations.impl
 
 import org.jetbrains.kotlin.descriptors.*
+import org.jetbrains.kotlin.ir.IrImplementationDetail
 import org.jetbrains.kotlin.ir.ObsoleteDescriptorBasedAPI
 import org.jetbrains.kotlin.ir.declarations.*
 import org.jetbrains.kotlin.ir.expressions.IrConstructorCall
@@ -15,7 +16,7 @@ import org.jetbrains.kotlin.ir.types.IrSimpleType
 import org.jetbrains.kotlin.ir.types.IrType
 import org.jetbrains.kotlin.name.Name
 
-open class IrClassImpl(
+open class IrClassImpl @IrImplementationDetail constructor(
     override val startOffset: Int,
     override val endOffset: Int,
     override var origin: IrDeclarationOrigin,
diff --git a/compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/types/impl/IrErrorClassImpl.kt b/compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/types/impl/IrErrorClassImpl.kt
index 1e8daa404a3..ad29d680ca2 100644
--- a/compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/types/impl/IrErrorClassImpl.kt
+++ b/compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/types/impl/IrErrorClassImpl.kt
@@ -7,6 +7,7 @@ package org.jetbrains.kotlin.ir.types.impl
 
 import org.jetbrains.kotlin.descriptors.*
 import org.jetbrains.kotlin.ir.IrFileEntry
+import org.jetbrains.kotlin.ir.IrImplementationDetail
 import org.jetbrains.kotlin.ir.ObsoleteDescriptorBasedAPI
 import org.jetbrains.kotlin.ir.UNDEFINED_OFFSET
 import org.jetbrains.kotlin.ir.declarations.*
@@ -19,6 +20,8 @@ import org.jetbrains.kotlin.name.FqName
 import org.jetbrains.kotlin.name.Name
 import org.jetbrains.kotlin.utils.addToStdlib.shouldNotBeCalled
 
+
+@OptIn(IrImplementationDetail::class)
 object IrErrorClassImpl : IrClassImpl(
     UNDEFINED_OFFSET, UNDEFINED_OFFSET, IrDeclarationOrigin.ERROR_CLASS, IrClassSymbolImpl(),
     Name.special("<error>"), ClassKind.CLASS, DescriptorVisibilities.DEFAULT_VISIBILITY, Modality.FINAL
diff --git a/kotlin-native/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/cgen/CBridgeGen.kt b/kotlin-native/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/cgen/CBridgeGen.kt
index da2e58796fc..7c2c74cbf88 100644
--- a/kotlin-native/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/cgen/CBridgeGen.kt
+++ b/kotlin-native/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/cgen/CBridgeGen.kt
@@ -1114,13 +1114,15 @@ private class ObjCBlockPointerValuePassing(
     private fun IrBuilderWithScope.generateKotlinFunctionClass(): IrConstructor {
         val symbols = stubs.symbols
 
-        val irClass = IrClassImpl(
-                startOffset, endOffset,
-                OBJC_BLOCK_FUNCTION_IMPL, IrClassSymbolImpl(),
+        val irClass = context.irFactory.createClass(
+                startOffset,
+                endOffset,
+                OBJC_BLOCK_FUNCTION_IMPL,
                 Name.identifier(stubs.getUniqueKotlinFunctionReferenceClassName("BlockFunctionImpl")),
-                ClassKind.CLASS, DescriptorVisibilities.PRIVATE, Modality.FINAL,
-                isCompanion = false, isInner = false, isData = false, isExternal = false,
-                isValue = false, isExpect = false, isFun = false
+                DescriptorVisibilities.PRIVATE,
+                IrClassSymbolImpl(),
+                ClassKind.CLASS,
+                Modality.FINAL,
         )
         irClass.createParameterDeclarations()
 
diff --git a/kotlin-native/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/lower/TestProcessor.kt b/kotlin-native/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/lower/TestProcessor.kt
index 3840faa8e22..ed812f86b1d 100644
--- a/kotlin-native/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/lower/TestProcessor.kt
+++ b/kotlin-native/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/lower/TestProcessor.kt
@@ -21,7 +21,6 @@ import org.jetbrains.kotlin.ir.IrStatement
 import org.jetbrains.kotlin.ir.builders.*
 import org.jetbrains.kotlin.ir.builders.declarations.buildField
 import org.jetbrains.kotlin.ir.declarations.*
-import org.jetbrains.kotlin.ir.declarations.impl.IrClassImpl
 import org.jetbrains.kotlin.ir.declarations.impl.IrConstructorImpl
 import org.jetbrains.kotlin.ir.declarations.impl.IrFunctionImpl
 import org.jetbrains.kotlin.ir.expressions.IrExpression
@@ -34,15 +33,12 @@ import org.jetbrains.kotlin.ir.symbols.impl.IrConstructorSymbolImpl
 import org.jetbrains.kotlin.ir.symbols.impl.IrSimpleFunctionSymbolImpl
 import org.jetbrains.kotlin.ir.types.*
 import org.jetbrains.kotlin.ir.util.*
-import org.jetbrains.kotlin.ir.util.SetDeclarationsParentVisitor
-import org.jetbrains.kotlin.ir.util.addChild
 import org.jetbrains.kotlin.ir.visitors.IrElementVisitorVoid
 import org.jetbrains.kotlin.ir.visitors.acceptChildrenVoid
 import org.jetbrains.kotlin.load.kotlin.PackagePartClassUtils
 import org.jetbrains.kotlin.name.ClassId
 import org.jetbrains.kotlin.name.FqName
 import org.jetbrains.kotlin.name.Name
-import org.jetbrains.kotlin.resolve.descriptorUtil.module
 
 internal class TestProcessor (val context: Context) {
     companion object {
@@ -479,21 +475,15 @@ internal class TestProcessor (val context: Context) {
             functions: Collection<TestFunction>,
             irFile: IrFile
     ): IrClass {
-        return IrClassImpl(
-                testClass.startOffset, testClass.endOffset,
+        return context.irFactory.createClass(
+                testClass.startOffset,
+                testClass.endOffset,
                 TEST_SUITE_CLASS,
-                IrClassSymbolImpl(),
                 testClass.name.synthesizeSuiteClassName(),
-                ClassKind.CLASS,
                 DescriptorVisibilities.PRIVATE,
+                IrClassSymbolImpl(),
+                ClassKind.CLASS,
                 Modality.FINAL,
-                isCompanion = false,
-                isInner = false,
-                isData = false,
-                isExternal = false,
-                isValue = false,
-                isExpect = false,
-                isFun = false
         ).apply {
             irFile.addChild(this)
             createParameterDeclarations()