Delegated properties never require backing field #KT-10107 Fixed

compiler/frontend/src/org/jetbrains/kotlin/resolve/BindingContext.java

@@ -174,6 +174,8 @@ public interface BindingContext {
                        backingFieldRequired; // this part is unused because we do not allow access to constructor parameters in member bodies
             }
             if (propertyDescriptor.getModality() == Modality.ABSTRACT) return false;
+            if (declarationPsiElement instanceof KtProperty &&
+                ((KtProperty) declarationPsiElement).hasDelegate()) return false;
             PropertyGetterDescriptor getter = propertyDescriptor.getGetter();
             PropertySetterDescriptor setter = propertyDescriptor.getSetter();
 

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
+}

compiler/tests/org/jetbrains/kotlin/checkers/DiagnosticsTestWithStdLibGenerated.java

@@ -95,6 +95,12 @@ public class DiagnosticsTestWithStdLibGenerated extends AbstractDiagnosticsTestW
         doTest(fileName);
     }
 
+    @TestMetadata("PropertyDelegateWithPrivateSet.kt")
+    public void testPropertyDelegateWithPrivateSet() throws Exception {
+        String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/testsWithStdLib/PropertyDelegateWithPrivateSet.kt");
+        doTest(fileName);
+    }
+
     @TestMetadata("RedeclarationMainInMultiFileClass.kt")
     public void testRedeclarationMainInMultiFileClass() throws Exception {
         String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/testsWithStdLib/RedeclarationMainInMultiFileClass.kt");