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 }<!>
+}

compiler/testData/diagnostics/testsWithStdLib/PropertyDelegateWithPrivateSet.txt

@@ -0,0 +1,11 @@
+package
+
+public final class My {
+    public constructor My()
+    public final val another: kotlin.String
+    public final var delegate: kotlin.String
+    public final var delegateWithBackingField: kotlin.String
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}