From 1dbe7d12a2b3c4fd2686df776d4fd117196ea648 Mon Sep 17 00:00:00 2001
From: Shagen Ogandzhanian <shagen.ogandzhanian@jetbrains.com>
Date: Fri, 8 Jan 2021 18:38:23 +0100
Subject: [PATCH] Simplify concatElements resolution for size=0 and size=1
 cases

^KT-40689 fixed
---
 .../ir/backend/js/transformers/irToJs/jsAstUtils.kt      | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/jsAstUtils.kt b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/jsAstUtils.kt
index fae36a97a9e..2b818a75e87 100644
--- a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/jsAstUtils.kt
+++ b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/jsAstUtils.kt
@@ -240,15 +240,18 @@ fun argumentsWithVarargAsSingleArray(
             }
         }
 
-    if (arraysForConcat.isNotEmpty() || concatElements.isEmpty()) {
+    if (arraysForConcat.isNotEmpty()) {
         concatElements.add(JsArrayLiteral(arraysForConcat))
     }
 
-    return concatElements.singleOrNull()
-        ?: JsInvocation(
+    return when (concatElements.size) {
+        0 -> JsArrayLiteral()
+        1 -> concatElements[0]
+        else -> JsInvocation(
             JsNameRef("concat", concatElements.first()),
             concatElements.drop(1)
         )
+    }
 }
 
 fun IrFunction.varargParameterIndex() = valueParameters.indexOfFirst { it.varargElementType != null }