stdlib: Fix variance for map and collection extensions

runtime/src/main/kotlin/kotlin/collections/Collections.kt

@@ -309,15 +309,6 @@ public fun CharArray.asList(): List<Char> {
     }
 }
 
-
-@FixmeVariance
-public fun <T, C : MutableCollection</*in */T>> Iterable<T>.toCollection(destination: C): C {
-    for (item in this) {
-        destination.add(item)
-    }
-    return destination
-}
-
 @Fixme
 internal fun <T> List<T>.optimizeReadOnlyList() = this
 

runtime/src/main/kotlin/kotlin/collections/HashMap.kt

@@ -45,7 +45,7 @@ class HashMap<K, V> private constructor(
             INITIAL_MAX_PROBE_DISTANCE,
             0)
 
-    constructor(m: Map<K, V>) : this(m.size) {
+    constructor(m: Map<out K, out V>) : this(m.size) {
         putAll(m)
     }
 

runtime/src/main/kotlin/kotlin/collections/Maps.kt

@@ -487,7 +487,8 @@ public fun <K, V, M : MutableMap<in K, in V>> Sequence<Pair<K, V>>.toMap(destina
  *
  * The returned map preserves the entry iteration order of the original map.
  */
-public fun <K, V> Map</* out */K, V>.toMap(): Map<K, V> = when (size) {
+@SinceKotlin("1.1")
+public fun <K, V> Map<out K, V>.toMap(): Map<K, V> = when (size) {
     0 -> emptyMap()
 //    1 -> toSingletonMap()
     else -> toMutableMap()
@@ -498,7 +499,8 @@ public fun <K, V> Map</* out */K, V>.toMap(): Map<K, V> = when (size) {
  *
  * The returned map preserves the entry iteration order of the original map.
  */
-public fun <K, V> Map</*out */K, V>.toMutableMap(): MutableMap<K, V> = HashMap(this)
+@SinceKotlin("1.1")
+public fun <K, V> Map<out K, V>.toMutableMap(): MutableMap<K, V> = HashMap<K, V>(this)
 
 /**
  * Populates and returns the [destination] mutable map with key-value pairs from the given map.
@@ -512,9 +514,8 @@ public fun <K, V, M : MutableMap<in K, in V>> Map<out K, V>.toMap(destination: M
  * The returned map preserves the entry iteration order of the original map.
  * The [pair] is iterated in the end if it has a unique key.
  */
-@FixmeVariance
-public operator fun <K, V> Map</*out */K, V>.plus(pair: Pair<K, V>): Map<K, V>
-        = if (this.isEmpty()) mapOf(pair) else HashMap(this).apply { put(pair.first, pair.second) }
+public operator fun <K, V> Map<out K, V>.plus(pair: Pair<K, V>): Map<K, V>
+        = if (this.isEmpty()) mapOf(pair) else HashMap<K, V>(this).apply { put(pair.first, pair.second) }
 
 /**
  * Creates a new read-only map by replacing or adding entries to this map from a given collection of key-value [pairs].
@@ -522,8 +523,7 @@ public operator fun <K, V> Map</*out */K, V>.plus(pair: Pair<K, V>): Map<K, V>
  * The returned map preserves the entry iteration order of the original map.
  * Those [pairs] with unique keys are iterated in the end in the order of [pairs] collection.
  */
-@FixmeVariance
-public operator fun <K, V> Map</*out */K, V>.plus(pairs: Iterable<Pair<K, V>>): Map<K, V>
+public operator fun <K, V> Map<out K, V>.plus(pairs: Iterable<Pair<K, V>>): Map<K, V>
         = if (this.isEmpty()) pairs.toMap() else HashMap(this).apply { putAll(pairs) }
 
 /**
@@ -532,8 +532,7 @@ public operator fun <K, V> Map</*out */K, V>.plus(pairs: Iterable<Pair<K, V>>):
  * The returned map preserves the entry iteration order of the original map.
  * Those [pairs] with unique keys are iterated in the end in the order of [pairs] array.
  */
-@FixmeVariance
-public operator fun <K, V> Map</*out */K, V>.plus(pairs: Array<out Pair<K, V>>): Map<K, V>
+public operator fun <K, V> Map<out K, V>.plus(pairs: Array<out Pair<K, V>>): Map<K, V>
         = if (this.isEmpty()) pairs.toMap() else HashMap(this).apply { putAll(pairs) }
 
 /**
@@ -542,7 +541,7 @@ public operator fun <K, V> Map</*out */K, V>.plus(pairs: Array<out Pair<K, V>>):
  * The returned map preserves the entry iteration order of the original map.
  * Those [pairs] with unique keys are iterated in the end in the order of [pairs] sequence.
  */
-public operator fun <K, V> Map</*out */K, V>.plus(pairs: Sequence<Pair<K, V>>): Map<K, V>
+public operator fun <K, V> Map<out K, V>.plus(pairs: Sequence<Pair<K, V>>): Map<K, V>
         = HashMap(this).apply { putAll(pairs) }.optimizeReadOnlyMap()
 
 /**
@@ -551,8 +550,7 @@ public operator fun <K, V> Map</*out */K, V>.plus(pairs: Sequence<Pair<K, V>>):
  * The returned map preserves the entry iteration order of the original map.
  * Those entries of another [map] that are missing in this map are iterated in the end in the order of that [map].
  */
-@FixmeVariance
-public operator fun <K, V> Map</*out */K, V>.plus(map: Map</*out */K, V>): Map<K, V>
+public operator fun <K, V> Map<out K, V>.plus(map: Map<out K, V>): Map<K, V>
         = HashMap(this).apply { putAll(map) }
 
 /**