Override toString function in stdlib delegates

Co-authored-by: ilya-g <ilya.gorbunov@jetbrains.com>

compiler/util/src/org/jetbrains/kotlin/utils/threadLocal.kt

@@ -23,4 +23,7 @@ private class ThreadLocalDelegate<T>(private val initializer: () -> T) : ReadWri
     override operator fun setValue(thisRef: Any?, property: KProperty<*>, value: T) {
         map[Thread.currentThread()] = value
     }
+
+    override fun toString(): String =
+        "ThreadLocalDelegate(${map.entries.joinToString { "#${it.key.id}=>${it.value}" }})"
 }

libraries/stdlib/api/js-v1/kotlin.properties.kt

@@ -16,6 +16,8 @@ public abstract class ObservableProperty<V> : kotlin.properties.ReadWritePropert
     public open override operator fun getValue(thisRef: kotlin.Any?, property: kotlin.reflect.KProperty<*>): V
 
     public open override operator fun setValue(thisRef: kotlin.Any?, property: kotlin.reflect.KProperty<*>, value: V): kotlin.Unit
+
+    public open override fun toString(): kotlin.String
 }
 
 @kotlin.SinceKotlin(version = "1.4")

libraries/stdlib/api/js/kotlin.properties.kt

@@ -16,6 +16,8 @@ public abstract class ObservableProperty<V> : kotlin.properties.ReadWritePropert
     public open override operator fun getValue(thisRef: kotlin.Any?, property: kotlin.reflect.KProperty<*>): V
 
     public open override operator fun setValue(thisRef: kotlin.Any?, property: kotlin.reflect.KProperty<*>, value: V): kotlin.Unit
+
+    public open override fun toString(): kotlin.String
 }
 
 @kotlin.SinceKotlin(version = "1.4")

libraries/stdlib/src/kotlin/properties/Delegates.kt

@@ -65,5 +65,8 @@ private class NotNullVar<T : Any>() : ReadWriteProperty<Any?, T> {
     public override fun setValue(thisRef: Any?, property: KProperty<*>, value: T) {
         this.value = value
     }
+
+    public override fun toString(): String =
+        "NotNullProperty(${if (value != null) "value=$value" else "value not initialized yet"})"
 }
 

libraries/stdlib/src/kotlin/properties/ObservableProperty.kt

@@ -40,4 +40,6 @@ public abstract class ObservableProperty<V>(initialValue: V) : ReadWriteProperty
         this.value = value
         afterChange(property, oldValue, value)
     }
+
+    override fun toString(): String = "ObservableProperty(value=$value)"
 }

libraries/stdlib/test/properties/delegation/DelegationTest.kt

@@ -16,30 +16,36 @@ class NotNullVarTest() {
 
 private class NotNullVarTestGeneric<T : Any>(val a1: String, val b1: T) {
     var a: String by Delegates.notNull()
-    var b by Delegates.notNull<T>()
+    val bDelegate = Delegates.notNull<T>()
+    var b by bDelegate
 
     public fun doTest() {
+        assertEquals("NotNullProperty(value not initialized yet)", bDelegate.toString())
         a = a1
         b = b1
         assertTrue(a == "a", "fail: a should be a, but was $a")
         assertTrue(b == "b", "fail: b should be b, but was $b")
+        assertEquals("NotNullProperty(value=$b)", bDelegate.toString())
     }
 }
 
 class ObservablePropertyTest {
     var result = false
 
-    var b: Int by Delegates.observable(1, { property, old, new ->
+    val bDelegate = Delegates.observable(1) { property, old, new ->
         assertEquals("b", property.name)
         if (!result) assertEquals(1, old)
         result = true
         assertEquals(new, b, "New value has already been set")
-    })
+    }
+
+    var b: Int by bDelegate
 
     @Test fun doTest() {
         b = 4
         assertTrue(b == 4, "fail: b != 4")
         assertTrue(result, "fail: result should be true")
+        assertEquals("ObservableProperty(value=$b)", bDelegate.toString())
     }
 }
 

libraries/tools/binary-compatibility-validator/reference-public-api/kotlin-stdlib-runtime-merged.txt

@@ -4426,6 +4426,7 @@ public abstract class kotlin/properties/ObservableProperty : kotlin/properties/R
 	protected fun beforeChange (Lkotlin/reflect/KProperty;Ljava/lang/Object;Ljava/lang/Object;)Z
 	public fun getValue (Ljava/lang/Object;Lkotlin/reflect/KProperty;)Ljava/lang/Object;
 	public fun setValue (Ljava/lang/Object;Lkotlin/reflect/KProperty;Ljava/lang/Object;)V
+	public fun toString ()Ljava/lang/String;
 }
 
 public abstract interface class kotlin/properties/PropertyDelegateProvider {