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()

libraries/stdlib/src/kotlin/collections/JUtil.kt

@@ -50,8 +50,8 @@ private class ArrayAsCollection<T>(val values: Array<out T>): Collection<T> {
     override fun contains(o: T): Boolean = values.contains(o)
     override fun containsAll(c: Collection<T>): Boolean = c.all { contains(it) }
     override fun iterator(): Iterator<T> = values.iterator()
-    // override of hidden toArray method implementation to prevent copying of values array
-    public fun toArray(): Array<out Any?> = values
+    // override hidden toArray implementation to prevent copying of values array
+    public fun toArray(): Array<out Any?> = values.varargToArrayOfAny()
 }
 
 /** Returns an empty read-only list.  The returned list is serializable (JVM). */
@@ -72,10 +72,12 @@ public fun <T> listOf(value: T): List<T> = Collections.singletonList(value)
 
 /** Returns a new [LinkedList] with the given elements. */
 @JvmVersion
-public fun <T> linkedListOf(vararg values: T): LinkedList<T> = LinkedList(ArrayAsCollection(values))
+public fun <T> linkedListOf(vararg values: T): LinkedList<T>
+        = if (values.size() == 0) LinkedList() else LinkedList(ArrayAsCollection(values))
 
 /** Returns a new [ArrayList] with the given elements. */
-public fun <T> arrayListOf(vararg values: T): ArrayList<T> = ArrayList(ArrayAsCollection(values))
+public fun <T> arrayListOf(vararg values: T): ArrayList<T>
+        = if (values.size() == 0) ArrayList() else ArrayList(ArrayAsCollection(values))
 
 /** Returns a new read-only list either of single given element, if it is not null, or empty list it the element is null. The returned list is serializable (JVM). */
 public fun <T : Any> listOfNotNull(value: T?): List<T> = if (value != null) listOf(value) else emptyList()
@@ -146,6 +148,11 @@ internal fun <T> Iterable<T>.convertToSetForSetOperation(): Collection<T> =
             else -> toHashSet()
         }
 
+// copies typed varargs array to array of objects
+@JvmVersion
+private fun <T> Array<out T>.varargToArrayOfAny(): Array<Any?>
+        = Arrays.copyOf(this, this.size(), Array<Any?>::class.java)
+
 /**
  * Searches this list or its range for the provided [element] index using binary search algorithm.
  * The list is expected to be sorted into ascending order according to the Comparable natural ordering of its elements.

libraries/stdlib/test/js/javautilCollectionsTest.kt

@@ -34,4 +34,18 @@ class JavautilCollectionsTest {
         val array = TEST_LIST.toTypedArray()
         assertEquals(array.toList(), TEST_LIST)
     }
+
+    @test fun arrayListDoesNotCreateArrayView() {
+        val array = arrayOf(1)
+        val list = arrayListOf(*array)
+        assertEquals(1, list[0])
+        array[0] = 2
+        assertEquals(1, list[0])
+
+        val arrayOfAny = arrayOf<Any>("first")
+        val listOfAny = arrayListOf(*arrayOfAny)
+        assertEquals("first", listOfAny[0])
+        arrayOfAny[0] = "last"
+        assertEquals("first", listOfAny[0])
+    }
 }