MUST_BE_INITIALIZED: take into account containingDeclaration's modality

^KT-58587 Fixed
Review: https://jetbrains.team/p/kt/reviews/10136

This commit is important in scope of KT-57553. It makes the migration
more smooth.

Other related tests:
- testUninitializedOrReassignedVariables
- testAugmentedAssignmentInInitializer

analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/diagnostic/compiler/based/DiagnosticCompilerTestFE10TestdataTestGenerated.java

@@ -2948,6 +2948,18 @@ public class DiagnosticCompilerTestFE10TestdataTestGenerated extends AbstractDia
                 runTest("compiler/testData/diagnostics/tests/backingField/LocalDeclarations.kt");
             }
 
+            @Test
+            @TestMetadata("MustBeInitializedEffectivelyFinalOff.kt")
+            public void testMustBeInitializedEffectivelyFinalOff() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/backingField/MustBeInitializedEffectivelyFinalOff.kt");
+            }
+
+            @Test
+            @TestMetadata("MustBeInitializedEffectivelyFinalOn.kt")
+            public void testMustBeInitializedEffectivelyFinalOn() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/backingField/MustBeInitializedEffectivelyFinalOn.kt");
+            }
+
             @Test
             @TestMetadata("SetterWithExplicitType.kt")
             public void testSetterWithExplicitType() throws Exception {

analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/diagnostic/compiler/based/LLFirPreresolvedReversedDiagnosticCompilerFE10TestDataTestGenerated.java

@@ -2948,6 +2948,18 @@ public class LLFirPreresolvedReversedDiagnosticCompilerFE10TestDataTestGenerated
                 runTest("compiler/testData/diagnostics/tests/backingField/LocalDeclarations.kt");
             }
 
+            @Test
+            @TestMetadata("MustBeInitializedEffectivelyFinalOff.kt")
+            public void testMustBeInitializedEffectivelyFinalOff() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/backingField/MustBeInitializedEffectivelyFinalOff.kt");
+            }
+
+            @Test
+            @TestMetadata("MustBeInitializedEffectivelyFinalOn.kt")
+            public void testMustBeInitializedEffectivelyFinalOn() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/backingField/MustBeInitializedEffectivelyFinalOn.kt");
+            }
+
             @Test
             @TestMetadata("SetterWithExplicitType.kt")
             public void testSetterWithExplicitType() throws Exception {

compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirLightTreeOldFrontendDiagnosticsTestGenerated.java

@@ -2948,6 +2948,18 @@ public class FirLightTreeOldFrontendDiagnosticsTestGenerated extends AbstractFir
                 runTest("compiler/testData/diagnostics/tests/backingField/LocalDeclarations.kt");
             }
 
+            @Test
+            @TestMetadata("MustBeInitializedEffectivelyFinalOff.kt")
+            public void testMustBeInitializedEffectivelyFinalOff() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/backingField/MustBeInitializedEffectivelyFinalOff.kt");
+            }
+
+            @Test
+            @TestMetadata("MustBeInitializedEffectivelyFinalOn.kt")
+            public void testMustBeInitializedEffectivelyFinalOn() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/backingField/MustBeInitializedEffectivelyFinalOn.kt");
+            }
+
             @Test
             @TestMetadata("SetterWithExplicitType.kt")
             public void testSetterWithExplicitType() throws Exception {

compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirPsiOldFrontendDiagnosticsTestGenerated.java

@@ -2954,6 +2954,18 @@ public class FirPsiOldFrontendDiagnosticsTestGenerated extends AbstractFirPsiDia
                 runTest("compiler/testData/diagnostics/tests/backingField/LocalDeclarations.kt");
             }
 
+            @Test
+            @TestMetadata("MustBeInitializedEffectivelyFinalOff.kt")
+            public void testMustBeInitializedEffectivelyFinalOff() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/backingField/MustBeInitializedEffectivelyFinalOff.kt");
+            }
+
+            @Test
+            @TestMetadata("MustBeInitializedEffectivelyFinalOn.kt")
+            public void testMustBeInitializedEffectivelyFinalOn() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/backingField/MustBeInitializedEffectivelyFinalOn.kt");
+            }
+
             @Test
             @TestMetadata("SetterWithExplicitType.kt")
             public void testSetterWithExplicitType() throws Exception {

compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/IrBuiltInsOverFir.kt

@@ -372,18 +372,29 @@ class IrBuiltInsOverFir(
     override val ieee754equalsFunByOperandType: MutableMap<IrClassifierSymbol, IrSimpleFunctionSymbol>
         get() = _ieee754equalsFunByOperandType
 
-    override lateinit var eqeqeqSymbol: IrSimpleFunctionSymbol private set
+    @Suppress("RedundantModalityModifier") // Explicit `final` keyword can be dropped after bootstrap update
-    override lateinit var eqeqSymbol: IrSimpleFunctionSymbol private set
+    final override var eqeqeqSymbol: IrSimpleFunctionSymbol private set
-    override lateinit var throwCceSymbol: IrSimpleFunctionSymbol private set
+    @Suppress("RedundantModalityModifier") // Explicit `final` keyword can be dropped after bootstrap update
-    override lateinit var throwIseSymbol: IrSimpleFunctionSymbol private set
+    final override var eqeqSymbol: IrSimpleFunctionSymbol private set
-    override lateinit var andandSymbol: IrSimpleFunctionSymbol private set
+    @Suppress("RedundantModalityModifier") // Explicit `final` keyword can be dropped after bootstrap update
-    override lateinit var ororSymbol: IrSimpleFunctionSymbol private set
+    final override var throwCceSymbol: IrSimpleFunctionSymbol private set
-    override lateinit var noWhenBranchMatchedExceptionSymbol: IrSimpleFunctionSymbol private set
+    @Suppress("RedundantModalityModifier") // Explicit `final` keyword can be dropped after bootstrap update
-    override lateinit var illegalArgumentExceptionSymbol: IrSimpleFunctionSymbol private set
+    final override var throwIseSymbol: IrSimpleFunctionSymbol private set
-    override lateinit var dataClassArrayMemberHashCodeSymbol: IrSimpleFunctionSymbol private set
+    @Suppress("RedundantModalityModifier") // Explicit `final` keyword can be dropped after bootstrap update
-    override lateinit var dataClassArrayMemberToStringSymbol: IrSimpleFunctionSymbol private set
+    final override var andandSymbol: IrSimpleFunctionSymbol private set
+    @Suppress("RedundantModalityModifier") // Explicit `final` keyword can be dropped after bootstrap update
+    final override var ororSymbol: IrSimpleFunctionSymbol private set
+    @Suppress("RedundantModalityModifier") // Explicit `final` keyword can be dropped after bootstrap update
+    final override var noWhenBranchMatchedExceptionSymbol: IrSimpleFunctionSymbol private set
+    @Suppress("RedundantModalityModifier") // Explicit `final` keyword can be dropped after bootstrap update
+    final override var illegalArgumentExceptionSymbol: IrSimpleFunctionSymbol private set
+    @Suppress("RedundantModalityModifier") // Explicit `final` keyword can be dropped after bootstrap update
+    final override var dataClassArrayMemberHashCodeSymbol: IrSimpleFunctionSymbol private set
+    @Suppress("RedundantModalityModifier") // Explicit `final` keyword can be dropped after bootstrap update
+    final override var dataClassArrayMemberToStringSymbol: IrSimpleFunctionSymbol private set
 
-    override lateinit var checkNotNullSymbol: IrSimpleFunctionSymbol private set
+    @Suppress("RedundantModalityModifier") // Explicit `final` keyword can be dropped after bootstrap update
+    final override var checkNotNullSymbol: IrSimpleFunctionSymbol private set
     override val arrayOfNulls: IrSimpleFunctionSymbol by lazy {
         findFunctions(kotlinPackage, Name.identifier("arrayOfNulls")).first {
             it.owner.dispatchReceiverParameter == null && it.owner.valueParameters.size == 1 &&
@@ -394,10 +405,14 @@ class IrBuiltInsOverFir(
     override val linkageErrorSymbol: IrSimpleFunctionSymbol
         get() = TODO("Not yet implemented")
 
-    override lateinit var lessFunByOperandType: Map<IrClassifierSymbol, IrSimpleFunctionSymbol> private set
+    @Suppress("RedundantModalityModifier") // Explicit `final` keyword can be dropped after bootstrap update
-    override lateinit var lessOrEqualFunByOperandType: Map<IrClassifierSymbol, IrSimpleFunctionSymbol> private set
+    final override var lessFunByOperandType: Map<IrClassifierSymbol, IrSimpleFunctionSymbol> private set
-    override lateinit var greaterOrEqualFunByOperandType: Map<IrClassifierSymbol, IrSimpleFunctionSymbol> private set
+    @Suppress("RedundantModalityModifier") // Explicit `final` keyword can be dropped after bootstrap update
-    override lateinit var greaterFunByOperandType: Map<IrClassifierSymbol, IrSimpleFunctionSymbol> private set
+    final override var lessOrEqualFunByOperandType: Map<IrClassifierSymbol, IrSimpleFunctionSymbol> private set
+    @Suppress("RedundantModalityModifier") // Explicit `final` keyword can be dropped after bootstrap update
+    final override var greaterOrEqualFunByOperandType: Map<IrClassifierSymbol, IrSimpleFunctionSymbol> private set
+    @Suppress("RedundantModalityModifier") // Explicit `final` keyword can be dropped after bootstrap update
+    final override var greaterFunByOperandType: Map<IrClassifierSymbol, IrSimpleFunctionSymbol> private set
 
     init {
         with(this.operatorsPackageFragment) {

compiler/frontend/cfg/src/org/jetbrains/kotlin/cfg/ControlFlowInformationProviderImpl.kt

@@ -628,7 +628,7 @@ class ControlFlowInformationProviderImpl private constructor(
         val property = DescriptorToSourceUtils.descriptorToDeclaration(variableDescriptor) as? KtProperty
             ?: throw AssertionError("$variableDescriptor is not related to KtProperty")
         val setter = property.setter
-        if (variableDescriptor.modality == Modality.FINAL && (setter == null || !setter.hasBody())) {
+        if (variableDescriptor.getEffectiveModality(languageVersionSettings) == Modality.FINAL && (setter == null || !setter.hasBody())) {
             return false
         }
 
@@ -1472,3 +1472,10 @@ class ControlFlowInformationProviderImpl private constructor(
             return result
         }
 }
+
+private fun PropertyDescriptor.getEffectiveModality(languageVersionSettings: LanguageVersionSettings): Modality =
+    when (languageVersionSettings.supportsFeature(LanguageFeature.TakeIntoAccountEffectivelyFinalInMustBeInitializedCheck) &&
+            modality == Modality.OPEN && (containingDeclaration as? ClassDescriptor)?.modality == Modality.FINAL) {
+        true -> Modality.FINAL
+        false -> modality
+    }

compiler/testData/diagnostics/tests/backingField/MustBeInitializedEffectivelyFinalOff.fir.kt

@@ -0,0 +1,12 @@
+// !LANGUAGE:-TakeIntoAccountEffectivelyFinalInMustBeInitializedCheck
+open class Base {
+    open var x: String = ""
+}
+
+class Foo : Base() {
+    override var x: String
+
+    init {
+        x = ""
+    }
+}

compiler/testData/diagnostics/tests/backingField/MustBeInitializedEffectivelyFinalOff.kt

@@ -0,0 +1,12 @@
+// !LANGUAGE:-TakeIntoAccountEffectivelyFinalInMustBeInitializedCheck
+open class Base {
+    open var x: String = ""
+}
+
+class Foo : Base() {
+    <!MUST_BE_INITIALIZED_OR_BE_ABSTRACT!>override var x: String<!>
+
+    init {
+        x = ""
+    }
+}

compiler/testData/diagnostics/tests/backingField/MustBeInitializedEffectivelyFinalOn.kt

@@ -0,0 +1,13 @@
+// FIR_IDENTICAL
+// !LANGUAGE:+TakeIntoAccountEffectivelyFinalInMustBeInitializedCheck
+open class Base {
+    open var x: String = ""
+}
+
+class Foo : Base() {
+    override var x: String
+
+    init {
+        x = ""
+    }
+}

compiler/tests-common-new/tests-gen/org/jetbrains/kotlin/test/runners/DiagnosticTestGenerated.java

@@ -2954,6 +2954,18 @@ public class DiagnosticTestGenerated extends AbstractDiagnosticTest {
                 runTest("compiler/testData/diagnostics/tests/backingField/LocalDeclarations.kt");
             }
 
+            @Test
+            @TestMetadata("MustBeInitializedEffectivelyFinalOff.kt")
+            public void testMustBeInitializedEffectivelyFinalOff() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/backingField/MustBeInitializedEffectivelyFinalOff.kt");
+            }
+
+            @Test
+            @TestMetadata("MustBeInitializedEffectivelyFinalOn.kt")
+            public void testMustBeInitializedEffectivelyFinalOn() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/backingField/MustBeInitializedEffectivelyFinalOn.kt");
+            }
+
             @Test
             @TestMetadata("SetterWithExplicitType.kt")
             public void testSetterWithExplicitType() throws Exception {

compiler/util/src/org/jetbrains/kotlin/config/LanguageVersionSettings.kt

@@ -275,6 +275,7 @@ enum class LanguageFeature(
     RefineTypeCheckingOnAssignmentsToJavaFields(KOTLIN_1_9, kind = BUG_FIX), // KT-46727
     ValueClassesSecondaryConstructorWithBody(sinceVersion = KOTLIN_1_9, kind = UNSTABLE_FEATURE), // KT-55333
     NativeJsProhibitLateinitIsInitializedIntrinsicWithoutPrivateAccess(KOTLIN_1_9, kind = BUG_FIX), // KT-27002
+    TakeIntoAccountEffectivelyFinalInMustBeInitializedCheck(KOTLIN_1_9, kind = OTHER), // KT-58587
 
     // End of 1.* language features --------------------------------------------------