From d8a3dacdc519492f014ffd487fda0524e5cd9493 Mon Sep 17 00:00:00 2001
From: Ilya Kirillov <ilya.kirillov@jetbrains.com>
Date: Mon, 22 Feb 2021 16:00:54 +0100
Subject: [PATCH] FIR: return back supertypeRefs list recreation

---
 .../resolve/transformers/FirSupertypesResolution.kt    | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/transformers/FirSupertypesResolution.kt b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/transformers/FirSupertypesResolution.kt
index 4f4ba4a93f1..18f26cff764 100644
--- a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/transformers/FirSupertypesResolution.kt
+++ b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/transformers/FirSupertypesResolution.kt
@@ -284,7 +284,13 @@ private class FirSupertypeResolverVisitor(
         supertypeRefs: List<FirTypeRef>
     ): List<FirTypeRef> {
         return resolveSpecificClassLikeSupertypes(classLikeDeclaration) { transformer, scope ->
-            supertypeRefs.mapTo(mutableListOf()) {
+            /*
+              This list is backed by mutable list and during iterating on it we can resolve supertypes of that class via IDE light classes
+              as IJ Java resolve may resolve a lot of stuff by light classes
+              this causes ConcurrentModificationException
+              So we create a copy of supertypeRefs to avoid it
+             */
+            supertypeRefs.createCopy().mapTo(mutableListOf()) {
                 val superTypeRef = transformer.transformTypeRef(it, scope).single
                 val typeParameterType = superTypeRef.coneTypeSafe<ConeTypeParameterType>()
                 when {
@@ -304,6 +310,8 @@ private class FirSupertypeResolverVisitor(
         }
     }
 
+    private fun <T> List<T>.createCopy(): List<T> = ArrayList(this)
+
     private fun addSupertypesFromExtensions(klass: FirClassLikeDeclaration<*>, supertypeRefs: MutableList<FirResolvedTypeRef>) {
         if (supertypeGenerationExtensions.isEmpty()) return
         val provider = session.predicateBasedProvider