Ensure vararg copy behavior for specific case of arrayListOf in JS.

js/js.libraries/src/core/javautilCode.kt

@@ -16,13 +16,18 @@
 
 package java.util
 
-public fun HashSet<E>(c: Collection<E>): HashSet<E> = HashSet<E>(c.size()).apply { addAll(c) }
+public fun HashSet<E>(c: Collection<E>): HashSet<E>
+        = HashSet<E>(c.size()).apply { addAll(c) }
 
-public fun LinkedHashSet<E>(c: Collection<E>): HashSet<E> = LinkedHashSet<E>(c.size()).apply { addAll(c) }
+public fun LinkedHashSet<E>(c: Collection<E>): HashSet<E>
+        = LinkedHashSet<E>(c.size()).apply { addAll(c) }
 
-public fun HashMap<K, V>(m: Map<K, V>): HashMap<K, V> = HashMap<K, V>(m.size()).apply { putAll(m) }
+public fun HashMap<K, V>(m: Map<K, V>): HashMap<K, V>
+        = HashMap<K, V>(m.size()).apply { putAll(m) }
 
-public fun LinkedHashMap<K, V>(m: Map<K, V>): LinkedHashMap<K, V> = LinkedHashMap<K, V>(m.size()).apply { putAll(m) }
+public fun LinkedHashMap<K, V>(m: Map<K, V>): LinkedHashMap<K, V>
+        = LinkedHashMap<K, V>(m.size()).apply { putAll(m) }
 
-public fun ArrayList<E>(c: Collection<E>): ArrayList<E> = ArrayList<E>().apply { asDynamic().array = c.toTypedArray<Any?>() } // black dynamic magic
+public fun ArrayList<E>(c: Collection<E>): ArrayList<E>
+        = ArrayList<E>().apply { asDynamic().array = c.toTypedArray<Any?>() } // black dynamic magic
 

js/js.libraries/src/core/kotlin.kt

@@ -91,3 +91,7 @@ internal fun <T> arrayPlusCollection(array: dynamic, collection: Collection<T>):
     for (element in collection) result[index++] = element
     return result
 }
+
+// copies vararg array due to different spread vararg behavior in JS.
+// After fixing #KT-6491 may return `this`
+internal inline fun <T> Array<out T>.varargToArrayOfAny(): Array<out Any?> = this.copyOf()