Delegated properties never require backing field #KT-10107 Fixed

compiler/testData/diagnostics/testsWithStdLib/PropertyDelegateWithPrivateSet.kt

@@ -0,0 +1,12 @@
+// See KT-10107: 'Variable must be initialized' for delegate with private set
+
+class My {
+    var delegate: String by kotlin.properties.Delegates.notNull()
+        private set
+
+    // Error: Variable 'delegate' must be initialized
+    val another: String = delegate
+
+    var delegateWithBackingField: String by kotlin.properties.Delegates.notNull()
+        <!ACCESSOR_FOR_DELEGATED_PROPERTY!>private set(arg) { field = arg }<!>
+}