Make builder collection implementations serializable KT-39328

Collections returned by collection builders are now serializable in
their read-only state.
The builder mutable collections inside collection builder lambda,
however, are not.

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2010-2020 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Copyright 2010-2021 JetBrains s.r.o. and Kotlin Programming Language contributors.
  * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
  */
 
@@ -162,6 +162,8 @@ public inline fun <T> MutableList(size: Int, init: (index: Int) -> T): MutableLi
  * The list passed as a receiver to the [builderAction] is valid only inside that function.
  * Using it outside of the function produces an unspecified behavior.
  *
+ * The returned list is serializable (JVM).
+ *
  * @sample samples.collections.Builders.Lists.buildListSample
  */
 @SinceKotlin("1.3")
@@ -185,6 +187,8 @@ internal expect inline fun <E> buildListInternal(builderAction: MutableList<E>.(
  * The list passed as a receiver to the [builderAction] is valid only inside that function.
  * Using it outside of the function produces an unspecified behavior.
  *
+ * The returned list is serializable (JVM).
+ *
  * [capacity] is used to hint the expected number of elements added in the [builderAction].
  *
  * @throws IllegalArgumentException if the given [capacity] is negative.

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2010-2018 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Copyright 2010-2021 JetBrains s.r.o. and Kotlin Programming Language contributors.
  * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
  */
 
@@ -132,6 +132,8 @@ public fun <K, V> linkedMapOf(vararg pairs: Pair<K, V>): LinkedHashMap<K, V> = p
  *
  * Entries of the map are iterated in the order they were added by the [builderAction].
  *
+ * The returned map is serializable (JVM).
+ *
  * @sample samples.collections.Builders.Maps.buildMapSample
  */
 @SinceKotlin("1.3")
@@ -159,6 +161,8 @@ internal expect inline fun <K, V> buildMapInternal(builderAction: MutableMap<K,
  *
  * Entries of the map are iterated in the order they were added by the [builderAction].
  *
+ * The returned map is serializable (JVM).
+ *
  * @throws IllegalArgumentException if the given [capacity] is negative.
  *
  * @sample samples.collections.Builders.Maps.buildMapSample

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2010-2018 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Copyright 2010-2021 JetBrains s.r.o. and Kotlin Programming Language contributors.
  * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
  */
 
@@ -118,6 +118,8 @@ public fun <T : Any> setOfNotNull(vararg elements: T?): Set<T> {
  *
  * Elements of the set are iterated in the order they were added by the [builderAction].
  *
+ * The returned set is serializable (JVM).
+ *
  * @sample samples.collections.Builders.Sets.buildSetSample
  */
 @SinceKotlin("1.3")
@@ -145,6 +147,8 @@ internal expect inline fun <E> buildSetInternal(builderAction: MutableSet<E>.()
  *
  * Elements of the set are iterated in the order they were added by the [builderAction].
  *
+ * The returned set is serializable (JVM).
+ *
  * @throws IllegalArgumentException if the given [capacity] is negative.
  *
  * @sample samples.collections.Builders.Sets.buildSetSample