Collection.toString() should not throw if it contains itself

Merge-request: KT-MR-10591
Merged-by: Abduqodiri Qurbonzoda <abduqodiri.qurbonzoda@jetbrains.com>

kotlin-native/runtime/src/main/kotlin/kotlin/collections/ArrayUtil.kt

@@ -137,18 +137,3 @@ internal external fun arrayCopy(array: DoubleArray, fromIndex: Int, destination:
 @GCUnsafeCall("Kotlin_BooleanArray_copyImpl")
 internal external fun arrayCopy(array: BooleanArray, fromIndex: Int, destination: BooleanArray, toIndex: Int, count: Int)
 
-
-internal fun <E> Collection<E>.collectionToString(): String {
-    val sb = StringBuilder(2 + size * 3)
-    sb.append("[")
-    var i = 0
-    val it = iterator()
-    while (it.hasNext()) {
-        if (i > 0) sb.append(", ")
-        val next = it.next()
-        if (next == this) sb.append("(this Collection)") else sb.append(next)
-        i++
-    }
-    sb.append("]")
-    return sb.toString()
-}

libraries/stdlib/jvm/src/kotlin/collections/builders/ListBuilder.kt

@@ -174,7 +174,7 @@ internal class ListBuilder<E> private constructor(
     }
 
     override fun toString(): String {
-        return array.subarrayContentToString(offset, length)
+        return array.subarrayContentToString(offset, length, this)
     }
 
     // ---------------------------- private ----------------------------
@@ -359,13 +359,18 @@ internal fun <E> arrayOfUninitializedElements(size: Int): Array<E> {
     return arrayOfNulls<Any?>(size) as Array<E>
 }
 
-private fun <T> Array<out T>.subarrayContentToString(offset: Int, length: Int): String {
+private fun <T> Array<out T>.subarrayContentToString(offset: Int, length: Int, thisCollection: Collection<T>): String {
     val sb = StringBuilder(2 + length * 3)
     sb.append("[")
     var i = 0
     while (i < length) {
         if (i > 0) sb.append(", ")
-        sb.append(this[offset + i])
+        val nextElement = this[offset + i]
+        if (nextElement === thisCollection) {
+            sb.append("(this Collection)")
+        } else {
+            sb.append(nextElement)
+        }
         i++
     }
     sb.append("]")

libraries/stdlib/jvm/src/kotlin/collections/builders/MapBuilder.kt

@@ -571,10 +571,10 @@ internal class MapBuilder<K, V> private constructor(
             if (index >= map.length) throw NoSuchElementException()
             lastIndex = index++
             val key = map.keysArray[lastIndex]
-            if (key == map) sb.append("(this Map)") else sb.append(key)
+            if (key === map) sb.append("(this Map)") else sb.append(key)
             sb.append('=')
             val value = map.valuesArray!![lastIndex]
-            if (value == map) sb.append("(this Map)") else sb.append(value)
+            if (value === map) sb.append("(this Map)") else sb.append(value)
             initNext()
         }
     }

libraries/stdlib/native-wasm/src/kotlin/collections/ArrayList.kt

@@ -182,7 +182,7 @@ actual class ArrayList<E> private constructor(
     }
 
     override fun toString(): String {
-        return backingArray.subarrayContentToString(offset, length)
+        return backingArray.subarrayContentToString(offset, length, this)
     }
 
     @Suppress("UNCHECKED_CAST")

libraries/stdlib/native-wasm/src/kotlin/collections/Arrays.kt

@@ -23,13 +23,18 @@ internal fun checkCopyOfRangeArguments(fromIndex: Int, toIndex: Int, size: Int)
 /**
  * Returns a string representation of the contents of the subarray of the specified array as if it is [List].
  */
-internal inline fun <T> Array<out T>.subarrayContentToString(offset: Int, length: Int): String {
+internal inline fun <T> Array<out T>.subarrayContentToString(offset: Int, length: Int, thisCollection: Collection<T>): String {
     val sb = StringBuilder(2 + length * 3)
     sb.append("[")
     var i = 0
     while (i < length) {
         if (i > 0) sb.append(", ")
-        sb.append(this[offset + i])
+        val nextElement = this[offset + i]
+        if (nextElement === thisCollection) {
+            sb.append("(this Collection)")
+        } else {
+            sb.append(nextElement)
+        }
         i++
     }
     sb.append("]")

libraries/stdlib/native-wasm/src/kotlin/collections/HashMap.kt

@@ -634,10 +634,10 @@ actual class HashMap<K, V> private constructor(
             if (index >= map.length) throw NoSuchElementException()
             lastIndex = index++
             val key = map.keysArray[lastIndex]
-            if (key == map) sb.append("(this Map)") else sb.append(key)
+            if (key === map) sb.append("(this Map)") else sb.append(key)
             sb.append('=')
             val value = map.valuesArray!![lastIndex]
-            if (value == map) sb.append("(this Map)") else sb.append(value)
+            if (value === map) sb.append("(this Map)") else sb.append(value)
             initNext()
         }
     }

libraries/stdlib/test/collections/CollectionTest.kt

@@ -5,9 +5,7 @@
 
 package test.collections
 
-import test.assertIsNegativeZero
-import test.assertIsPositiveZero
-import test.assertStaticAndRuntimeTypeIs
+import test.*
 import kotlin.test.*
 import test.collections.behaviors.*
 import test.comparisons.STRING_CASE_INSENSITIVE_ORDER
@@ -1224,6 +1222,57 @@ class CollectionTest {
         assertEquals("[1, a, null, ${Long.MAX_VALUE.toString()}]", listOf(1, "a", null, Long.MAX_VALUE).toString())
     }
 
+    @Test fun toStringContainingThis() = testExceptOn(TestPlatform.Js) {
+        // resulting string is platform-dependent, but shouldn't throw
+        arrayOf<Any>("a", "b", "c").apply { this[1] = this }.toString()
+
+        assertEquals(
+            "[a, (this Collection), c]",
+            arrayListOf<Any>("a", "b", "c").apply { this[1] = this }.toString()
+        )
+        assertEquals(
+            "[a, (this Collection), c]",
+            buildList<Any> {
+                addAll(listOf("a", "b", "c"))
+                this[1] = this
+            }.toString()
+        )
+
+        assertEquals(
+            "[a, (this Collection), c]",
+            linkedSetOf<Any>().apply {
+                add("a")
+                add(this)
+                add("c")
+            }.toString()
+        )
+        assertEquals(
+            "[a, (this Collection), c]",
+            buildSet<Any> {
+                add("a")
+                add(this)
+                add("c")
+            }.toString()
+        )
+
+        assertEquals(
+            "{a=1, (this Map)=(this Map), c=3}",
+            linkedMapOf<Any, Any>().apply {
+                put("a", "1")
+                put(this, this)
+                put("c", "3")
+            }.toString()
+        )
+        assertEquals(
+            "{a=1, (this Map)=(this Map), c=3}",
+            buildMap<Any, Any> {
+                put("a", "1")
+                put(this, this)
+                put("c", "3")
+            }.toString()
+        )
+    }
+
     @Test fun randomAccess() {
         assertStaticAndRuntimeTypeIs<RandomAccess>(arrayListOf(1))
         assertTrue(listOf(1, 2) is RandomAccess, "Default read-only list implementation is RandomAccess")