From ce1e4f252f5a7f748b701b11b35223e1818155ce Mon Sep 17 00:00:00 2001
From: Ilya Kirillov <ilya.kirillov@jetbrains.com>
Date: Tue, 18 Jan 2022 12:23:56 +0300
Subject: [PATCH] FIR: make transformInplace to be thread safe if no
 transformation was done

^KT-50822 fixed
---
 .../jetbrains/kotlin/fir/visitors/FirTransformerUtil.kt   | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/compiler/fir/tree/src/org/jetbrains/kotlin/fir/visitors/FirTransformerUtil.kt b/compiler/fir/tree/src/org/jetbrains/kotlin/fir/visitors/FirTransformerUtil.kt
index cb5f3b98d17..fcd1d9ec662 100644
--- a/compiler/fir/tree/src/org/jetbrains/kotlin/fir/visitors/FirTransformerUtil.kt
+++ b/compiler/fir/tree/src/org/jetbrains/kotlin/fir/visitors/FirTransformerUtil.kt
@@ -17,7 +17,9 @@ fun <T : FirElement, D> MutableList<T>.transformInplace(transformer: FirTransfor
     while (iterator.hasNext()) {
         val next = iterator.next() as FirPureAbstractElement
         val result = next.transform<T, D>(transformer, data)
-        iterator.set(result)
+        if (result !== next) {
+            iterator.set(result)
+        }
     }
 }
 
@@ -36,7 +38,9 @@ inline fun <T : FirElement, D> MutableList<T>.transformInplace(transformer: FirT
             TransformData.Nothing -> continue
         }
         val result = next.transform<T, D>(transformer, data)
-        iterator.set(result)
+        if (result !== next) {
+            iterator.set(result)
+        }
     }
 }