Optimizations in listOf and arrayListOf constructor functions.

Remove linkedListOf() from JS.
#KT-5703 Fixed
#KT-8519 Fixed

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

@@ -16,34 +16,13 @@
 
 package java.util
 
-public fun HashSet<E>(c: Collection<E>): HashSet<E> {
-    val set: HashSet<E> = HashSet(c.size())
-    set.addAll(c)
-    return set
-}
+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> {
-    val set: LinkedHashSet<E> = LinkedHashSet(c.size())
-    set.addAll(c)
-    return set
-}
+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> {
-    val map: HashMap<K, V> = HashMap(m.size())
-    map.putAll(m)
-    return map
-}
+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> {
-    val map: LinkedHashMap<K, V> = LinkedHashMap(m.size())
-    map.putAll(m)
-    return map
-}
+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> {
-    val result = ArrayList<E>()
-    for (element in c) {
-        result.add(element)
-    }
-    return result
-}

js/js.translator/testData/kotlin_lib.js

@@ -1018,6 +1018,8 @@
     };
 
     Kotlin.copyToArray = function (collection) {
+        if (typeof collection.toArray !== "undefined") return collection.toArray();
+
         var array = [];
         var it = collection.iterator();
         while (it.hasNext()) {

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

@@ -44,29 +44,38 @@ internal object EmptyList : List<Nothing>, Serializable {
     private fun readResolve(): Any = EmptyList
 }
 
-
+private class ArrayAsCollection<T>(val values: Array<out T>): Collection<T> {
+    override val size: Int get() = values.size()
+    override fun isEmpty(): Boolean = values.isEmpty()
+    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
+}
 
 /** Returns an empty read-only list.  The returned list is serializable (JVM). */
-public fun emptyList<T>(): List<T> = EmptyList
+public fun <T> emptyList(): List<T> = EmptyList
 
 /** Returns a new read-only list of given elements.  The returned list is serializable (JVM). */
-public fun listOf<T>(vararg values: T): List<T> = if (values.size() > 0) arrayListOf(*values) else emptyList()
+public fun <T> listOf(vararg values: T): List<T> = if (values.size() > 0) values.asList() else emptyList()
 
 /** Returns an empty read-only list.  The returned list is serializable (JVM). */
-public fun listOf<T>(): List<T> = emptyList()
+public fun <T> listOf(): List<T> = emptyList()
 
 /**
  * Returns an immutable list containing only the specified object [value].
  * The returned list is serializable.
  */
 @JvmVersion
-public fun listOf<T>(value: T): List<T> = Collections.singletonList(value)
+public fun <T> listOf(value: T): List<T> = Collections.singletonList(value)
 
 /** Returns a new [LinkedList] with the given elements. */
-public fun linkedListOf<T>(vararg values: T): LinkedList<T> = values.toCollection(LinkedList<T>())
+@JvmVersion
+public fun <T> linkedListOf(vararg values: T): LinkedList<T> = LinkedList(ArrayAsCollection(values))
 
 /** Returns a new [ArrayList] with the given elements. */
-public fun arrayListOf<T>(vararg values: T): ArrayList<T> = values.toCollection(ArrayList(values.size()))
+public fun <T> arrayListOf(vararg values: T): ArrayList<T> = 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()