Provide protected toArray implementation in AbstractCollection.

Relates to #KT-13898

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

@@ -31,7 +31,14 @@ public abstract class AbstractCollection<out E> protected constructor() : Collec
         if (it === this) "(this Collection)" else it.toString()
     }
 
+    /**
+     * Returns new array of type `Array<Any?>` with the elements of this collection.
+     */
+    protected open fun toArray(): Array<Any?> = copyToArrayImpl(this)
 
+    /**
+     * Fills the provided [array] or creates new array of the same type
+     * and fills it with the elements of this collection.
+     */
+    protected open fun <T> toArray(array: Array<T>): Array<T> = copyToArrayImpl(this, array)
 }
-
-

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

@@ -182,6 +182,16 @@ internal fun <T> List<T>.optimizeReadOnlyList() = when (size) {
     else -> this
 }
 
+@JvmVersion
+@kotlin.internal.InlineOnly
+internal inline fun copyToArrayImpl(collection: Collection<*>): Array<Any?> =
+        kotlin.jvm.internal.CollectionToArray.toArray(collection)
+
+@JvmVersion
+@kotlin.internal.InlineOnly
+internal inline fun <T> copyToArrayImpl(collection: Collection<*>, array: Array<T>): Array<T> =
+        kotlin.jvm.internal.CollectionToArray.toArray(collection, array)
+
 // copies typed varargs array to array of objects
 @JvmVersion
 private fun <T> Array<out T>.copyToArrayOfAny(isVarargs: Boolean): Array<Any?> =