From 076a94f7f2804b9a5990f4c97b400b7635f63427 Mon Sep 17 00:00:00 2001
From: Ilya Gorbunov <ilya.gorbunov@jetbrains.com>
Date: Mon, 2 Jan 2017 07:16:53 +0300
Subject: [PATCH] Provide parameterless mutable collection factory functions.
 #KT-15630

---
 .../src/kotlin/collections/Collections.kt     | 10 ++++++++
 .../stdlib/src/kotlin/collections/Maps.kt     | 23 +++++++++++++++++++
 .../stdlib/src/kotlin/collections/Sets.kt     | 19 +++++++++++++++
 3 files changed, 52 insertions(+)

diff --git a/libraries/stdlib/src/kotlin/collections/Collections.kt b/libraries/stdlib/src/kotlin/collections/Collections.kt
index 96cb57725e4..1fd4b18facd 100644
--- a/libraries/stdlib/src/kotlin/collections/Collections.kt
+++ b/libraries/stdlib/src/kotlin/collections/Collections.kt
@@ -90,6 +90,16 @@ public inline fun <T> listOf(): List<T> = emptyList()
 @JvmVersion
 public fun <T> listOf(element: T): List<T> = java.util.Collections.singletonList(element)
 
+/** Returns an empty new [MutableList]. */
+@SinceKotlin("1.1")
+@kotlin.internal.InlineOnly
+public inline fun <T> mutableListOf(): MutableList<T> = ArrayList()
+
+/** Returns an empty new [ArrayList]. */
+@SinceKotlin("1.1")
+@kotlin.internal.InlineOnly
+public inline fun <T> arrayListOf(): ArrayList<T> = ArrayList()
+
 /** Returns a new [MutableList] with the given elements. */
 public fun <T> mutableListOf(vararg elements: T): MutableList<T>
         = if (elements.size == 0) ArrayList() else ArrayList(ArrayAsCollection(elements, isVarargs = true))
diff --git a/libraries/stdlib/src/kotlin/collections/Maps.kt b/libraries/stdlib/src/kotlin/collections/Maps.kt
index e52e65f4fd0..7908b311214 100644
--- a/libraries/stdlib/src/kotlin/collections/Maps.kt
+++ b/libraries/stdlib/src/kotlin/collections/Maps.kt
@@ -56,6 +56,16 @@ public inline fun <K, V> mapOf(): Map<K, V> = emptyMap()
 @JvmVersion
 public fun <K, V> mapOf(pair: Pair<K, V>): Map<K, V> = java.util.Collections.singletonMap(pair.first, pair.second)
 
+/**
+ * Returns an empty new [MutableMap].
+ *
+ * The returned map preserves the entry iteration order.
+ * @sample samples.collections.Maps.Instantiation.emptyMutableMap
+ */
+@SinceKotlin("1.1")
+@kotlin.internal.InlineOnly
+public inline fun <K, V> mutableMapOf(): MutableMap<K, V> = LinkedHashMap()
+
 /**
  * Returns a new [MutableMap] with the specified contents, given as a list of pairs
  * where the first component is the key and the second is the value. If multiple pairs have
@@ -67,6 +77,13 @@ public fun <K, V> mapOf(pair: Pair<K, V>): Map<K, V> = java.util.Collections.sin
 public fun <K, V> mutableMapOf(vararg pairs: Pair<K, V>): MutableMap<K, V>
         = LinkedHashMap<K, V>(mapCapacity(pairs.size)).apply { putAll(pairs) }
 
+/**
+ * Returns an empty new [HashMap].
+ */
+@SinceKotlin("1.1")
+@kotlin.internal.InlineOnly
+public inline fun <K, V> hashMapOf(): HashMap<K, V> = HashMap<K, V>()
+
 /**
  * Returns a new [HashMap] with the specified contents, given as a list of pairs
  * where the first component is the key and the second is the value.
@@ -76,6 +93,12 @@ public fun <K, V> mutableMapOf(vararg pairs: Pair<K, V>): MutableMap<K, V>
 public fun <K, V> hashMapOf(vararg pairs: Pair<K, V>): HashMap<K, V>
         = HashMap<K, V>(mapCapacity(pairs.size)).apply { putAll(pairs) }
 
+/**
+ * Returns an empty new [LinkedHashMap].
+ */
+@SinceKotlin("1.1")
+@kotlin.internal.InlineOnly
+public inline fun <K, V> linkedMapOf(): LinkedHashMap<K, V> = LinkedHashMap<K, V>()
 
 /**
  * Returns a new [LinkedHashMap] with the specified contents, given as a list of pairs
diff --git a/libraries/stdlib/src/kotlin/collections/Sets.kt b/libraries/stdlib/src/kotlin/collections/Sets.kt
index aaf5f3f0ab7..2f8c2ae3ff6 100644
--- a/libraries/stdlib/src/kotlin/collections/Sets.kt
+++ b/libraries/stdlib/src/kotlin/collections/Sets.kt
@@ -35,15 +35,34 @@ public fun <T> setOf(vararg elements: T): Set<T> = if (elements.size > 0) elemen
 @kotlin.internal.InlineOnly
 public inline fun <T> setOf(): Set<T> = emptySet()
 
+/**
+ * Returns an empty new [MutableSet].
+ *
+ * The returned set preserves the element iteration order.
+ */
+@SinceKotlin("1.1")
+@kotlin.internal.InlineOnly
+public inline fun <T> mutableSetOf(): MutableSet<T> = LinkedHashSet()
+
 /**
  * Returns a new [MutableSet] with the given elements.
  * Elements of the set are iterated in the order they were specified.
  */
 public fun <T> mutableSetOf(vararg elements: T): MutableSet<T> = elements.toCollection(LinkedHashSet(mapCapacity(elements.size)))
 
+/** Returns an empty new [HashSet]. */
+@SinceKotlin("1.1")
+@kotlin.internal.InlineOnly
+public inline fun <T> hashSetOf(): HashSet<T> = HashSet()
+
 /** Returns a new [HashSet] with the given elements. */
 public fun <T> hashSetOf(vararg elements: T): HashSet<T> = elements.toCollection(HashSet(mapCapacity(elements.size)))
 
+/** Returns an empty new [LinkedHashSet]. */
+@SinceKotlin("1.1")
+@kotlin.internal.InlineOnly
+public inline fun <T> linkedSetOf(): LinkedHashSet<T> = LinkedHashSet()
+
 /**
  * Returns a new [LinkedHashSet] with the given elements.
  * Elements of the set are iterated in the order they were specified.