diff --git a/runtime/src/main/kotlin/kotlin/collections/HashMap.kt b/runtime/src/main/kotlin/kotlin/collections/HashMap.kt
index 7d56b7a517e..534f2134b20 100644
--- a/runtime/src/main/kotlin/kotlin/collections/HashMap.kt
+++ b/runtime/src/main/kotlin/kotlin/collections/HashMap.kt
@@ -13,9 +13,9 @@ class HashMap<K, V> private constructor(
     override var size: Int = 0
         private set
 
-    // private var keysView: HashSet<K>? = null
-    // private var valuesView: HashMapValues<V>? = null
-    // private var entriesView: HashMapEntrySet<K, V>? = null
+    private var keysView: HashSet<K>? = null
+    private var valuesView: HashMapValues<V>? = null
+    private var entriesView: HashMapEntrySet<K, V>? = null
 
     // ---------------------------- functions ----------------------------
 
@@ -90,45 +90,30 @@ class HashMap<K, V> private constructor(
     }
 
     override val keys: MutableSet<K> get() {
-        return HashSet(this)
-
-        // Caching creates a reference cycle and thus leads to memory leaks;
-        // TODO: fix and enable.
-
-        // val cur = keysView
-        // return if (cur == null) {
-        //     val new = HashSet(this)
-        //     keysView = new
-        //     new
-        // } else cur
+        val cur = keysView
+        return if (cur == null) {
+            val new = HashSet(this)
+            keysView = new
+            new
+        } else cur
     }
 
     override val values: MutableCollection<V> get() {
-        return HashMapValues(this)
-
-        // Caching creates a reference cycle and thus leads to memory leaks;
-        // TODO: fix and enable.
-
-        // val cur = valuesView
-        // return if (cur == null) {
-        //     val new = HashMapValues(this)
-        //     valuesView = new
-        //     new
-        // } else cur
+        val cur = valuesView
+        return if (cur == null) {
+            val new = HashMapValues(this)
+            valuesView = new
+            new
+        } else cur
     }
 
     override val entries: MutableSet<MutableMap.MutableEntry<K, V>> get() {
-        return HashMapEntrySet(this)
-
-        // Caching creates a reference cycle and thus leads to memory leaks;
-        // TODO: fix and enable.
-
-        // val cur = entriesView
-        // return if (cur == null) {
-        //     val new = HashMapEntrySet(this)
-        //     entriesView = new
-        //     return new
-        // } else cur
+        val cur = entriesView
+        return if (cur == null) {
+            val new = HashMapEntrySet(this)
+            entriesView = new
+            return new
+        } else cur
     }
 
     override fun equals(other: Any?): Boolean {
@@ -246,7 +231,7 @@ class HashMap<K, V> private constructor(
     private fun findKey(key: K): Int {
         var hash = hash(key)
         var probesLeft = maxProbeDistance
-        while (true)  {
+        while (true) {
             val index = hashArray[hash]
             if (index == 0) return TOMBSTONE
             if (index > 0 && keysArray[index - 1] == key) return index - 1
@@ -265,7 +250,7 @@ class HashMap<K, V> private constructor(
     }
 
     internal fun addKey(key: K): Int {
-            retry@ while (true) {
+        retry@ while (true) {
             var hash = hash(key)
             // put is allowed to grow maxProbeDistance with some limits (resize hash on reaching limits)
             val tentativeMaxProbeDistance = (maxProbeDistance * 2).coerceAtMost(hashSize / 2)
diff --git a/runtime/src/main/kotlin/kotlin/collections/Maps.kt b/runtime/src/main/kotlin/kotlin/collections/Maps.kt
index 997c502162d..ccb7bcb9bbf 100644
--- a/runtime/src/main/kotlin/kotlin/collections/Maps.kt
+++ b/runtime/src/main/kotlin/kotlin/collections/Maps.kt
@@ -417,14 +417,8 @@ public fun <K, V> Iterable<Pair<K, V>>.toMap(): Map<K, V> {
 /**
  * Populates and returns the [destination] mutable map with key-value pairs from the given collection of pairs.
  */
-@Fixme
-public fun <K, V, M : MutableMap<in K, in V>> Iterable<Pair<K, V>>.toMap(destination: M): M {
-    for (pair in this) {
-        destination.put(pair.first, pair.second)
-    }
-    return destination
-}
-//        = destination.apply { putAll(this@toMap) }
+public fun <K, V, M : MutableMap<in K, in V>> Iterable<Pair<K, V>>.toMap(destination: M): M
+        = destination.apply { putAll(this@toMap) }
 
 /**
  * Returns a new map containing all key-value pairs from the given array of pairs.
@@ -440,14 +434,8 @@ public fun <K, V> Array<out Pair<K, V>>.toMap(): Map<K, V> = when(size) {
 /**
  *  Populates and returns the [destination] mutable map with key-value pairs from the given array of pairs.
  */
-@Fixme
-public fun <K, V, M : MutableMap<in K, in V>> Array<out Pair<K, V>>.toMap(destination: M): M {
-//        = destination.apply { putAll(this@toMap) }
-    for (pair in this) {
-        destination.put(pair.first, pair.second)
-    }
-    return destination
-}
+public fun <K, V, M : MutableMap<in K, in V>> Array<out Pair<K, V>>.toMap(destination: M): M
+        = destination.apply { putAll(this@toMap) }
 
 /**
  * Returns a new map containing all key-value pairs from the given sequence of pairs.
@@ -459,14 +447,8 @@ public fun <K, V> Sequence<Pair<K, V>>.toMap(): Map<K, V> = toMap(HashMap<K, V>(
 /**
  * Populates and returns the [destination] mutable map with key-value pairs from the given sequence of pairs.
  */
-@Fixme
-public fun <K, V, M : MutableMap<in K, in V>> Sequence<Pair<K, V>>.toMap(destination: M): M {
-    for (pair in this) {
-        destination.put(pair.first, pair.second)
-    }
-    return destination
-}
-//        = destination.apply { putAll(this@toMap) }
+public fun <K, V, M : MutableMap<in K, in V>> Sequence<Pair<K, V>>.toMap(destination: M): M
+        = destination.apply { putAll(this@toMap) }
 
 /**
  * Returns a new read-only map containing all key-value pairs from the original map.
diff --git a/samples/csvparser/CsvParser.kt b/samples/csvparser/CsvParser.kt
index b6035bfb08f..2e195b1e72c 100644
--- a/samples/csvparser/CsvParser.kt
+++ b/samples/csvparser/CsvParser.kt
@@ -3,7 +3,7 @@ import stdio.*
 
 fun parseLine(line: String, separator: Char) : List<String> {
     val result = mutableListOf<String>()
-    var builder = StringBuilder()
+    val builder = StringBuilder()
     var quotes = 0
     for (ch in line) {
         when {
@@ -14,7 +14,7 @@ fun parseLine(line: String, separator: Char) : List<String> {
             (ch == '\n') || (ch ==  '\r') -> {}
             (ch == separator) && (quotes % 2 == 0) -> {
                 result.add(builder.toString())
-                builder = StringBuilder()
+                builder.length = 0
             }
             else -> builder.append(ch)
         }
@@ -37,6 +37,8 @@ fun main(args: Array<String>) {
         return
     }
 
+    val keyValue = mutableMapOf<String, Int>()
+
     try {
         memScoped {
             val bufferLength = 64 * 1024
@@ -47,10 +49,16 @@ fun main(args: Array<String>) {
                 if (nextLine == null || nextLine.isEmpty()) break
 
                 val records = parseLine(nextLine, ',')
-                println(records[column])
+                val key = records[column]
+                val current = keyValue[key] ?: 0
+                keyValue[key] = current + 1
             }
         }
     } finally {
         fclose(file)
     }
-}
\ No newline at end of file
+
+    keyValue.forEach {
+        println("${it.key} -> ${it.value}")
+    }
+}
diff --git a/samples/csvparser/README.md b/samples/csvparser/README.md
index 83d6ce628df..1305efecff6 100644
--- a/samples/csvparser/README.md
+++ b/samples/csvparser/README.md
@@ -10,4 +10,5 @@ To run use
 
     ./CsvParser.kexe ./European_Mammals_Red_List_Nov_2009.csv 4 100
 
-It will print fifth column (Family, zero-based index) in first 100 rows of the CSV file.
+It will print number of all unique entries in fifth column
+(Family, zero-based index) in first 100 rows of the CSV file.