Introduce final field in SynchronizedLazyImpl to enable safe publication.

libraries/stdlib/src/kotlin/util/Lazy.kt

@@ -54,11 +54,10 @@ public enum class LazyThreadSafetyMode {
 
 private object UNINITIALIZED_VALUE
 
-internal open class LazyImpl<out T>(initializer: () -> T) : Lazy<T>(), Serializable {
+internal class SynchronizedLazyImpl<out T>(initializer: () -> T, lock: Any? = null) : Lazy<T>(), Serializable {
     private var initializer: (() -> T)? = initializer
     @Volatile private var _value: Any? = UNINITIALIZED_VALUE
-    protected open val lock: Any
-        get() = this
+    private val lock = lock ?: this
 
     override val value: T
         get() {
@@ -88,8 +87,6 @@ internal open class LazyImpl<out T>(initializer: () -> T) : Lazy<T>(), Serializa
     private fun writeReplace(): Any = InitializedLazyImpl(value)
 }
 
-internal class ExternallySynchronizedLazyImpl<out T>(override val lock: Any, initializer: () -> T): LazyImpl<T>(initializer)
-
 internal class UnsafeLazyImpl<out T>(initializer: () -> T) : Lazy<T>(), Serializable {
     private var initializer: (() -> T)? = initializer
     private var _value: Any? = UNINITIALIZED_VALUE

libraries/stdlib/src/kotlin/util/LazyJVM.kt

@@ -13,7 +13,7 @@ package kotlin
  * Note that the returned instance uses itself to synchronize on. Do not synchronize from external code on
  * the returned instance as it may cause accidental deadlock. Also this behavior can be changed in the future.
  */
-public fun lazy<T>(initializer: () -> T): Lazy<T> = LazyImpl(initializer)
+public fun lazy<T>(initializer: () -> T): Lazy<T> = SynchronizedLazyImpl(initializer)
 
 /**
  * Creates a new instance of the [Lazy] that uses the specified initialization function [initializer]
@@ -27,7 +27,7 @@ public fun lazy<T>(initializer: () -> T): Lazy<T> = LazyImpl(initializer)
  */
 public fun lazy<T>(mode: LazyThreadSafetyMode, initializer: () -> T): Lazy<T> =
     when (mode) {
-        LazyThreadSafetyMode.SYNCHRONIZED -> LazyImpl(initializer)
+        LazyThreadSafetyMode.SYNCHRONIZED -> SynchronizedLazyImpl(initializer)
         LazyThreadSafetyMode.NONE -> UnsafeLazyImpl(initializer)
     }
 
@@ -42,8 +42,4 @@ public fun lazy<T>(mode: LazyThreadSafetyMode, initializer: () -> T): Lazy<T> =
  * in this case do not synchronize from external code on the returned instance as it may cause accidental deadlock.
  * Also this behavior can be changed in the future.
  */
-public fun lazy<T>(lock: Any?, initializer: () -> T): Lazy<T> =
-    if (lock != null)
-        ExternallySynchronizedLazyImpl(lock, initializer)
-    else
-        LazyImpl(initializer)
+public fun lazy<T>(lock: Any?, initializer: () -> T): Lazy<T> = SynchronizedLazyImpl(initializer, lock)