diff --git a/compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/lazy/Fir2IrLazyClass.kt b/compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/lazy/Fir2IrLazyClass.kt
index 81312d40a38..4a460ea09ed 100644
--- a/compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/lazy/Fir2IrLazyClass.kt
+++ b/compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/lazy/Fir2IrLazyClass.kt
@@ -6,8 +6,9 @@
 package org.jetbrains.kotlin.fir.lazy
 
 import org.jetbrains.kotlin.descriptors.*
-import org.jetbrains.kotlin.fir.backend.*
+import org.jetbrains.kotlin.fir.backend.Fir2IrComponents
 import org.jetbrains.kotlin.fir.backend.declareThisReceiverParameter
+import org.jetbrains.kotlin.fir.backend.toIrType
 import org.jetbrains.kotlin.fir.declarations.*
 import org.jetbrains.kotlin.fir.resolve.buildUseSiteMemberScope
 import org.jetbrains.kotlin.fir.symbols.Fir2IrClassSymbol
@@ -19,8 +20,8 @@ import org.jetbrains.kotlin.ir.declarations.*
 import org.jetbrains.kotlin.ir.declarations.lazy.lazyVar
 import org.jetbrains.kotlin.ir.types.IrType
 import org.jetbrains.kotlin.ir.types.impl.IrSimpleTypeImpl
-import org.jetbrains.kotlin.ir.util.mapOptimized
 import org.jetbrains.kotlin.ir.util.transform
+import org.jetbrains.kotlin.ir.util.transformIfNeeded
 import org.jetbrains.kotlin.ir.visitors.IrElementTransformer
 import org.jetbrains.kotlin.ir.visitors.IrElementVisitor
 import org.jetbrains.kotlin.name.Name
@@ -190,7 +191,7 @@ class Fir2IrLazyClass(
 
     override fun <D> transformChildren(transformer: IrElementTransformer<D>, data: D) {
         thisReceiver = thisReceiver?.transform(transformer, data)
-        typeParameters = typeParameters.mapOptimized { it.transform(transformer, data) }
+        typeParameters = typeParameters.transformIfNeeded(transformer, data)
         declarations.transform { it.transform(transformer, data) }
     }
 }
\ No newline at end of file
diff --git a/compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/lazy/Fir2IrLazyConstructor.kt b/compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/lazy/Fir2IrLazyConstructor.kt
index 77242fe8de8..de749bc62ee 100644
--- a/compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/lazy/Fir2IrLazyConstructor.kt
+++ b/compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/lazy/Fir2IrLazyConstructor.kt
@@ -20,8 +20,8 @@ import org.jetbrains.kotlin.ir.declarations.IrValueParameter
 import org.jetbrains.kotlin.ir.declarations.lazy.lazyVar
 import org.jetbrains.kotlin.ir.expressions.IrBody
 import org.jetbrains.kotlin.ir.types.IrType
-import org.jetbrains.kotlin.ir.util.mapOptimized
 import org.jetbrains.kotlin.ir.util.parentClassOrNull
+import org.jetbrains.kotlin.ir.util.transformIfNeeded
 import org.jetbrains.kotlin.ir.visitors.IrElementTransformer
 import org.jetbrains.kotlin.ir.visitors.IrElementVisitor
 import org.jetbrains.kotlin.name.Name
@@ -125,11 +125,11 @@ class Fir2IrLazyConstructor(
     }
 
     override fun <D> transformChildren(transformer: IrElementTransformer<D>, data: D) {
-        typeParameters = typeParameters.mapOptimized { it.transform(transformer, data) }
+        typeParameters = typeParameters.transformIfNeeded(transformer, data)
 
         dispatchReceiverParameter = dispatchReceiverParameter?.transform(transformer, data)
         extensionReceiverParameter = extensionReceiverParameter?.transform(transformer, data)
-        valueParameters = valueParameters.mapOptimized { it.transform(transformer, data) }
+        valueParameters = valueParameters.transformIfNeeded(transformer, data)
 
         body = body?.transform(transformer, data)
     }
diff --git a/compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/lazy/Fir2IrLazySimpleFunction.kt b/compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/lazy/Fir2IrLazySimpleFunction.kt
index 567d1f71f00..fe92501c7e4 100644
--- a/compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/lazy/Fir2IrLazySimpleFunction.kt
+++ b/compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/lazy/Fir2IrLazySimpleFunction.kt
@@ -21,7 +21,7 @@ import org.jetbrains.kotlin.ir.expressions.IrBody
 import org.jetbrains.kotlin.ir.symbols.IrPropertySymbol
 import org.jetbrains.kotlin.ir.symbols.IrSimpleFunctionSymbol
 import org.jetbrains.kotlin.ir.types.IrType
-import org.jetbrains.kotlin.ir.util.mapOptimized
+import org.jetbrains.kotlin.ir.util.transformIfNeeded
 import org.jetbrains.kotlin.ir.visitors.IrElementTransformer
 import org.jetbrains.kotlin.ir.visitors.IrElementVisitor
 import org.jetbrains.kotlin.name.Name
@@ -147,11 +147,11 @@ class Fir2IrLazySimpleFunction(
     }
 
     override fun <D> transformChildren(transformer: IrElementTransformer<D>, data: D) {
-        typeParameters = typeParameters.mapOptimized { it.transform(transformer, data) }
+        typeParameters = typeParameters.transformIfNeeded(transformer, data)
 
         dispatchReceiverParameter = dispatchReceiverParameter?.transform(transformer, data)
         extensionReceiverParameter = extensionReceiverParameter?.transform(transformer, data)
-        valueParameters = valueParameters.mapOptimized { it.transform(transformer, data) }
+        valueParameters = valueParameters.transformIfNeeded(transformer, data)
 
         body = body?.transform(transformer, data)
     }
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 c73d8044f1a..c22d17ede5e 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
@@ -23,7 +23,7 @@ import org.jetbrains.kotlin.ir.declarations.impl.carriers.ClassCarrier
 import org.jetbrains.kotlin.ir.symbols.IrClassSymbol
 import org.jetbrains.kotlin.ir.types.IrType
 import org.jetbrains.kotlin.ir.util.transform
-import org.jetbrains.kotlin.ir.util.mapOptimized
+import org.jetbrains.kotlin.ir.util.transformIfNeeded
 import org.jetbrains.kotlin.ir.visitors.IrElementTransformer
 import org.jetbrains.kotlin.ir.visitors.IrElementVisitor
 import org.jetbrains.kotlin.name.Name
@@ -177,7 +177,7 @@ class IrClassImpl(
 
     override fun <D> transformChildren(transformer: IrElementTransformer<D>, data: D) {
         thisReceiver = thisReceiver?.transform(transformer, data)
-        typeParameters = typeParameters.mapOptimized { it.transform(transformer, data) }
+        typeParameters = typeParameters.transformIfNeeded(transformer, data)
         declarations.transform { it.transform(transformer, data) }
     }
 }
diff --git a/compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/declarations/impl/IrFunctionBase.kt b/compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/declarations/impl/IrFunctionBase.kt
index 54cbbd35fd4..582d6171d8d 100644
--- a/compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/declarations/impl/IrFunctionBase.kt
+++ b/compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/declarations/impl/IrFunctionBase.kt
@@ -22,7 +22,7 @@ import org.jetbrains.kotlin.ir.declarations.impl.carriers.FunctionBaseCarrier
 import org.jetbrains.kotlin.ir.expressions.IrBody
 import org.jetbrains.kotlin.ir.types.IrType
 import org.jetbrains.kotlin.ir.types.impl.IrUninitializedType
-import org.jetbrains.kotlin.ir.util.mapOptimized
+import org.jetbrains.kotlin.ir.util.transformIfNeeded
 import org.jetbrains.kotlin.ir.visitors.IrElementTransformer
 import org.jetbrains.kotlin.ir.visitors.IrElementVisitor
 import org.jetbrains.kotlin.name.Name
@@ -144,12 +144,11 @@ abstract class IrFunctionBase<T : FunctionBaseCarrier<T>>(
     }
 
     override fun <D> transformChildren(transformer: IrElementTransformer<D>, data: D) {
-
-        typeParameters = typeParameters.mapOptimized { it.transform(transformer, data) }
+        typeParameters = typeParameters.transformIfNeeded(transformer, data)
 
         dispatchReceiverParameter = dispatchReceiverParameter?.transform(transformer, data)
         extensionReceiverParameter = extensionReceiverParameter?.transform(transformer, data)
-        valueParameters = valueParameters.mapOptimized { it.transform(transformer, data) }
+        valueParameters = valueParameters.transformIfNeeded(transformer, data)
 
         body = body?.transform(transformer, data)
     }
diff --git a/compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/declarations/impl/IrTypeAliasImpl.kt b/compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/declarations/impl/IrTypeAliasImpl.kt
index 66506a80b5e..f23df27e301 100644
--- a/compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/declarations/impl/IrTypeAliasImpl.kt
+++ b/compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/declarations/impl/IrTypeAliasImpl.kt
@@ -14,7 +14,7 @@ import org.jetbrains.kotlin.ir.declarations.IrTypeParameter
 import org.jetbrains.kotlin.ir.declarations.impl.carriers.TypeAliasCarrier
 import org.jetbrains.kotlin.ir.symbols.IrTypeAliasSymbol
 import org.jetbrains.kotlin.ir.types.IrType
-import org.jetbrains.kotlin.ir.util.mapOptimized
+import org.jetbrains.kotlin.ir.util.transformIfNeeded
 import org.jetbrains.kotlin.ir.visitors.IrElementTransformer
 import org.jetbrains.kotlin.ir.visitors.IrElementVisitor
 import org.jetbrains.kotlin.name.Name
@@ -59,7 +59,7 @@ class IrTypeAliasImpl(
     }
 
     override fun <D> transformChildren(transformer: IrElementTransformer<D>, data: D) {
-        typeParameters = typeParameters.mapOptimized { it.transform(transformer, data) }
+        typeParameters = typeParameters.transformIfNeeded(transformer, data)
     }
 
     companion object {
@@ -81,4 +81,4 @@ class IrTypeAliasImpl(
                 origin
             )
     }
-}
\ No newline at end of file
+}
diff --git a/compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/declarations/lazy/IrLazyClass.kt b/compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/declarations/lazy/IrLazyClass.kt
index e7c83052c62..ff79b9a047e 100644
--- a/compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/declarations/lazy/IrLazyClass.kt
+++ b/compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/declarations/lazy/IrLazyClass.kt
@@ -13,7 +13,7 @@ import org.jetbrains.kotlin.ir.types.IrType
 import org.jetbrains.kotlin.ir.util.DeclarationStubGenerator
 import org.jetbrains.kotlin.ir.util.TypeTranslator
 import org.jetbrains.kotlin.ir.util.transform
-import org.jetbrains.kotlin.ir.util.mapOptimized
+import org.jetbrains.kotlin.ir.util.transformIfNeeded
 import org.jetbrains.kotlin.ir.visitors.IrElementTransformer
 import org.jetbrains.kotlin.ir.visitors.IrElementVisitor
 import org.jetbrains.kotlin.metadata.ProtoBuf
@@ -102,7 +102,7 @@ class IrLazyClass(
 
     override fun <D> transformChildren(transformer: IrElementTransformer<D>, data: D) {
         thisReceiver = thisReceiver?.transform(transformer, data)
-        typeParameters = typeParameters.mapOptimized { it.transform(transformer, data) }
+        typeParameters = typeParameters.transformIfNeeded(transformer, data)
         declarations.transform { it.transform(transformer, data) }
     }
 }
diff --git a/compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/declarations/lazy/IrLazyFunctionBase.kt b/compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/declarations/lazy/IrLazyFunctionBase.kt
index 0db10584cde..b1919549944 100644
--- a/compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/declarations/lazy/IrLazyFunctionBase.kt
+++ b/compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/declarations/lazy/IrLazyFunctionBase.kt
@@ -14,7 +14,7 @@ import org.jetbrains.kotlin.ir.expressions.IrBody
 import org.jetbrains.kotlin.ir.types.IrType
 import org.jetbrains.kotlin.ir.util.DeclarationStubGenerator
 import org.jetbrains.kotlin.ir.util.TypeTranslator
-import org.jetbrains.kotlin.ir.util.mapOptimized
+import org.jetbrains.kotlin.ir.util.transformIfNeeded
 import org.jetbrains.kotlin.ir.visitors.IrElementTransformer
 import org.jetbrains.kotlin.ir.visitors.IrElementVisitor
 import org.jetbrains.kotlin.name.Name
@@ -77,12 +77,12 @@ abstract class IrLazyFunctionBase(
     }
 
     override fun <D> transformChildren(transformer: IrElementTransformer<D>, data: D) {
-        typeParameters = typeParameters.mapOptimized { it.transform(transformer, data) }
+        typeParameters = typeParameters.transformIfNeeded(transformer, data)
 
         dispatchReceiverParameter = dispatchReceiverParameter?.transform(transformer, data)
         extensionReceiverParameter = extensionReceiverParameter?.transform(transformer, data)
-        valueParameters = valueParameters.mapOptimized { it.transform(transformer, data) }
+        valueParameters = valueParameters.transformIfNeeded(transformer, data)
 
         body = body?.transform(transformer, data)
     }
-}
\ No newline at end of file
+}
diff --git a/compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/declarations/lazy/IrLazyTypeAlias.kt b/compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/declarations/lazy/IrLazyTypeAlias.kt
index d6835bce796..b9b10f4935d 100644
--- a/compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/declarations/lazy/IrLazyTypeAlias.kt
+++ b/compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/declarations/lazy/IrLazyTypeAlias.kt
@@ -16,7 +16,7 @@ import org.jetbrains.kotlin.ir.symbols.IrTypeAliasSymbol
 import org.jetbrains.kotlin.ir.types.IrType
 import org.jetbrains.kotlin.ir.util.DeclarationStubGenerator
 import org.jetbrains.kotlin.ir.util.TypeTranslator
-import org.jetbrains.kotlin.ir.util.mapOptimized
+import org.jetbrains.kotlin.ir.util.transformIfNeeded
 import org.jetbrains.kotlin.ir.visitors.IrElementTransformer
 import org.jetbrains.kotlin.ir.visitors.IrElementVisitor
 import org.jetbrains.kotlin.name.Name
@@ -63,6 +63,6 @@ class IrLazyTypeAlias(
     }
 
     override fun <D> transformChildren(transformer: IrElementTransformer<D>, data: D) {
-        typeParameters = typeParameters.mapOptimized { it.transform(transformer, data) }
+        typeParameters = typeParameters.transformIfNeeded(transformer, data)
     }
-}
\ No newline at end of file
+}
diff --git a/compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/util/transform.kt b/compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/util/transform.kt
index a9193e92429..8f9aca58b26 100644
--- a/compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/util/transform.kt
+++ b/compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/util/transform.kt
@@ -19,6 +19,7 @@ package org.jetbrains.kotlin.ir.util
 import org.jetbrains.kotlin.ir.IrElement
 import org.jetbrains.kotlin.ir.declarations.IrDeclaration
 import org.jetbrains.kotlin.ir.declarations.IrDeclarationContainer
+import org.jetbrains.kotlin.ir.visitors.IrElementTransformer
 
 inline fun <reified T : IrElement> MutableList<T>.transform(transformation: (T) -> IrElement) {
     forEachIndexed { i, item ->
@@ -65,16 +66,17 @@ fun IrDeclarationContainer.transformDeclarationsFlat(transformation: (IrDeclarat
 }
 
 /**
- * Similar to `map`. Return the same List instance if no element instances have changed.
+ * Transforms the list of elements with the given transformer. Return the same List instance if no element instances have changed.
  */
-inline fun <reified T : IrElement> List<T>.mapOptimized(transformation: (T) -> IrElement): List<T> {
+fun <T : IrElement, D> List<T>.transformIfNeeded(transformer: IrElementTransformer<D>, data: D): List<T> {
     var result: ArrayList<T>? = null
     for ((i, item) in withIndex()) {
-        val transformed = transformation(item) as T
+        @Suppress("UNCHECKED_CAST")
+        val transformed = item.transform(transformer, data) as T
         if (transformed !== item && result == null) {
             result = ArrayList(this)
         }
         result?.set(i, transformed)
     }
     return result ?: this
-}
\ No newline at end of file
+}