Fix collision only map iterator initialization crash (#57)

Author: Abduqodiri Qurbonzoda

core/commonMain/src/implementations/immutableMap/PersistentHashMapContentIterators.kt

@@ -105,7 +105,11 @@ internal abstract class PersistentHashMapBaseIterator<K, V, T>(node: TrieNode<K,
     private var hasNext = true
 
     init {
-        path[0].reset(node.buffer, ENTRY_SIZE * node.entryCount())
+        if (node.isCollision()) {
+            path[0].reset(node.buffer, node.buffer.size)
+        } else {
+            path[0].reset(node.buffer, ENTRY_SIZE * node.entryCount())
+        }
         pathLastIndex = 0
         ensureNextEntryIsReady()
     }

core/commonTest/src/stress/map/PersistentHashMapTest.kt

@@ -109,6 +109,22 @@ class PersistentHashMapTest : ExecutionTimeMeasuringTest() {
         }
     }
 
+    @Test
+    fun iteratorTests() {
+        val emptyIterator = persistentHashMapOf<Int, String>().iterator()
+        assertFalse(emptyIterator.hasNext())
+        assertFails { emptyIterator.next() }
+
+        val collisionIterator = persistentHashMapOf<IntWrapper, String>().put(IntWrapper(1, 1), "a").put(IntWrapper(2, 1), "b").iterator()
+        var aFlag = false
+        var bFlag = false
+        for (entry in collisionIterator) {
+            aFlag = aFlag || entry.value == "a"
+            bFlag = bFlag || entry.value == "b"
+        }
+        assertTrue(aFlag && bFlag)
+    }
+
     @Test
     fun removeTests() {
         var map = persistentHashMapOf<Int, String>()