Do not use spread-operator when it causes excessive array copying

(cherry picked from commit ddf6599)
JetBrains · May 19, 2017 · 6a15981 · 6a15981
1 parent 10c85a6
commit 6a15981
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Showing 2 changed files with 8 additions and 3 deletions.
diff --git a/libraries/stdlib/src/kotlin/collections/Maps.kt b/libraries/stdlib/src/kotlin/collections/Maps.kt
@@ -43,7 +43,7 @@ public fun <K, V> emptyMap(): Map<K, V> = @Suppress("UNCHECKED_CAST") (EmptyMap
  *
  * @sample samples.collections.Maps.Instantiation.mapFromPairs
  */
-public fun <K, V> mapOf(vararg pairs: Pair<K, V>): Map<K, V> = if (pairs.size > 0) linkedMapOf(*pairs) else emptyMap()
+public fun <K, V> mapOf(vararg pairs: Pair<K, V>): Map<K, V> = if (pairs.size > 0) pairs.toMap(LinkedHashMap(mapCapacity(pairs.size))) else emptyMap()
 
 /**
  * Returns an empty read-only map.
@@ -123,7 +123,7 @@ public inline fun <K, V> linkedMapOf(): LinkedHashMap<K, V> = LinkedHashMap<K, V
  * @sample samples.collections.Maps.Instantiation.linkedMapFromPairs
  */
 public fun <K, V> linkedMapOf(vararg pairs: Pair<K, V>): LinkedHashMap<K, V>
-        = LinkedHashMap<K, V>(mapCapacity(pairs.size)).apply { putAll(pairs) }
+        = pairs.toMap(LinkedHashMap(mapCapacity(pairs.size)))
 
 /**
  * Calculate the initial capacity of a map, based on Guava's com.google.common.collect.Maps approach. This is equivalent

diff --git a/libraries/stdlib/src/kotlin/comparisons/Comparisons.kt b/libraries/stdlib/src/kotlin/comparisons/Comparisons.kt
@@ -26,6 +26,10 @@ package kotlin.comparisons
  */
 public fun <T> compareValuesBy(a: T, b: T, vararg selectors: (T) -> Comparable<*>?): Int {
     require(selectors.size > 0)
+    return compareValuesByImpl(a, b, selectors)
+}
+
+private fun <T> compareValuesByImpl(a: T, b: T, selectors: Array<out (T)->Comparable<*>?>): Int {
     for (fn in selectors) {
         val v1 = fn(a)
         val v2 = fn(b)
@@ -84,8 +88,9 @@ public fun <T : Comparable<*>> compareValues(a: T?, b: T?): Int {
  * compare as equal, the result of that comparison is returned from the [Comparator].
  */
 public fun <T> compareBy(vararg selectors: (T) -> Comparable<*>?): Comparator<T> {
+    require(selectors.size > 0)
     return object : Comparator<T> {
-        public override fun compare(a: T, b: T): Int = compareValuesBy(a, b, *selectors)
+        public override fun compare(a: T, b: T): Int = compareValuesByImpl(a, b, selectors)
     }
 }