diff --git a/compiler/fir/tree/src/org/jetbrains/kotlin/fir/Utils.kt b/compiler/fir/tree/src/org/jetbrains/kotlin/fir/Utils.kt
index fffb09993e2..b7e62020ba2 100644
--- a/compiler/fir/tree/src/org/jetbrains/kotlin/fir/Utils.kt
+++ b/compiler/fir/tree/src/org/jetbrains/kotlin/fir/Utils.kt
@@ -30,31 +30,6 @@ fun <T : FirElement, D> MutableList<T>.transformInplace(transformer: FirTransfor
     }
 }
 
-fun <T : FirElement, D> MutableList<T>.transformInplaceWithBeforeOperation(
-    transformer: FirTransformer<D>, data: D, operation: (T, Int) -> Unit
-) {
-    val iterator = this.listIterator()
-    var index = 0
-    while (iterator.hasNext()) {
-        val next = iterator.next()
-        operation(next, index++)
-        val result = next.transform<T, D>(transformer, data)
-        if (result.isSingle) {
-            iterator.set(result.single)
-        } else {
-            val resultIterator = result.list.listIterator()
-            if (!resultIterator.hasNext()) {
-                iterator.remove()
-            } else {
-                iterator.set(resultIterator.next())
-            }
-            while (resultIterator.hasNext()) {
-                iterator.add(resultIterator.next())
-            }
-        }
-    }
-}
-
 fun <T : FirElement, D> T.transformSingle(transformer: FirTransformer<D>, data: D): T {
     return (this as FirPureAbstractElement).transform<T, D>(transformer, data).single
 }