FIR checker: report VIRTUAL_MEMBER_HIDDEN

compiler/fir/analysis-tests/testData/resolve/overrides/simple.kt

@@ -8,7 +8,7 @@ open class A {
 
 class B : A() {
     override fun foo(): B = this
-    fun bar(): B = this // Ambiguity, no override here (really it's just "missing override" and no ambiguity)
+    fun <!VIRTUAL_MEMBER_HIDDEN!>bar<!>(): B = this // Missing 'override'
     override fun buz(p: B): B = this //No override as B not :> A
 
     fun test() {

compiler/fir/analysis-tests/testData/resolve/properties/kotlinOverridesJavaComplex.kt

@@ -44,7 +44,7 @@ public <!ABSTRACT_MEMBER_NOT_IMPLEMENTED!>class LightClassWrapper<!> : Light(),
 }
 
 public abstract class Light : Field, TypeParametersOwner {
-    fun getTypeParameters() = listOf()
+    fun <!VIRTUAL_MEMBER_HIDDEN!>getTypeParameters<!>() = listOf()
 }
 
 public interface Field : Named

compiler/fir/analysis-tests/testData/resolveWithStdlib/j+k/OverrideWithJava.kt

@@ -14,7 +14,7 @@ public class A {
 
 class B : A() {
     override fun foo(): B = this
-    fun bar(): B = this // Here we should have "missing override" but no ambiguity
+    fun <!VIRTUAL_MEMBER_HIDDEN!>bar<!>(): B = this // Here we should have "missing override" but no ambiguity
 
     fun test() {
         foo()

compiler/fir/checkers/checkers-component-generator/src/org/jetbrains/kotlin/fir/checkers/generator/diagnostics/FirDiagnosticsList.kt

@@ -563,6 +563,10 @@ object DIAGNOSTICS_LIST : DiagnosticList("FirErrors") {
         }
         val NON_FINAL_MEMBER_IN_FINAL_CLASS by warning<KtNamedDeclaration>(PositioningStrategy.OPEN_MODIFIER)
         val NON_FINAL_MEMBER_IN_OBJECT by warning<KtNamedDeclaration>(PositioningStrategy.OPEN_MODIFIER)
+        val VIRTUAL_MEMBER_HIDDEN by error<KtNamedDeclaration>(PositioningStrategy.DECLARATION_NAME) {
+            parameter<FirMemberDeclaration>("declared")
+            parameter<FirRegularClass>("overriddenContainer")
+        }
     }
 
     val REDECLARATIONS by object : DiagnosticGroup("Redeclarations") {

compiler/fir/checkers/gen/org/jetbrains/kotlin/fir/analysis/diagnostics/FirErrors.kt

@@ -20,6 +20,7 @@ import org.jetbrains.kotlin.fir.declarations.FirClass
 import org.jetbrains.kotlin.fir.declarations.FirDeclaration
 import org.jetbrains.kotlin.fir.declarations.FirEnumEntry
 import org.jetbrains.kotlin.fir.declarations.FirMemberDeclaration
+import org.jetbrains.kotlin.fir.declarations.FirRegularClass
 import org.jetbrains.kotlin.fir.declarations.FirSimpleFunction
 import org.jetbrains.kotlin.fir.declarations.FirValueParameter
 import org.jetbrains.kotlin.fir.expressions.FirExpression
@@ -336,6 +337,7 @@ object FirErrors {
     val VAR_OVERRIDDEN_BY_VAL by error2<KtNamedDeclaration, FirMemberDeclaration, FirMemberDeclaration>(SourceElementPositioningStrategies.VAL_OR_VAR_NODE)
     val NON_FINAL_MEMBER_IN_FINAL_CLASS by warning0<KtNamedDeclaration>(SourceElementPositioningStrategies.OPEN_MODIFIER)
     val NON_FINAL_MEMBER_IN_OBJECT by warning0<KtNamedDeclaration>(SourceElementPositioningStrategies.OPEN_MODIFIER)
+    val VIRTUAL_MEMBER_HIDDEN by error2<KtNamedDeclaration, FirMemberDeclaration, FirRegularClass>(SourceElementPositioningStrategies.DECLARATION_NAME)
 
     // Redeclarations
     val MANY_COMPANION_OBJECTS by error0<KtObjectDeclaration>(SourceElementPositioningStrategies.COMPANION_OBJECT)

compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/FirOverridesBackwardCompatibilityHelper.kt

@@ -0,0 +1,21 @@
+/*
+ * Copyright 2010-2021 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package org.jetbrains.kotlin.fir.analysis
+
+import org.jetbrains.kotlin.fir.FirSession
+import org.jetbrains.kotlin.fir.FirSessionComponent
+import org.jetbrains.kotlin.fir.analysis.checkers.context.CheckerContext
+import org.jetbrains.kotlin.fir.symbols.impl.FirCallableSymbol
+
+interface FirOverridesBackwardCompatibilityHelper : FirSessionComponent {
+    fun overrideCanBeOmitted(overriddenMemberSymbols: List<FirCallableSymbol<*>>, context: CheckerContext): Boolean
+
+    class Default : FirOverridesBackwardCompatibilityHelper {
+        override fun overrideCanBeOmitted(overriddenMemberSymbols: List<FirCallableSymbol<*>>, context: CheckerContext): Boolean = false
+    }
+}
+
+val FirSession.overridesBackwardCompatibilityHelper: FirOverridesBackwardCompatibilityHelper by FirSession.sessionComponentAccessor()

compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/FirHelpers.kt

@@ -49,7 +49,7 @@ import org.jetbrains.kotlin.utils.addToStdlib.safeAs
 
 private val INLINE_ONLY_ANNOTATION_CLASS_ID = ClassId.topLevel(FqName("kotlin.internal.InlineOnly"))
 
-internal fun FirClass<*>.unsubstitutedScope(context: CheckerContext) =
+fun FirClass<*>.unsubstitutedScope(context: CheckerContext) =
     this.unsubstitutedScope(context.sessionHolder.session, context.sessionHolder.scopeSession, withForcedTypeCalculator = false)
 
 /**

compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/declaration/FirOverrideChecker.kt

@@ -7,21 +7,22 @@ package org.jetbrains.kotlin.fir.analysis.checkers.declaration
 
 import org.jetbrains.kotlin.descriptors.Modality
 import org.jetbrains.kotlin.descriptors.Visibilities
+import org.jetbrains.kotlin.fir.*
 import org.jetbrains.kotlin.fir.analysis.checkers.context.CheckerContext
 import org.jetbrains.kotlin.fir.analysis.checkers.unsubstitutedScope
 import org.jetbrains.kotlin.fir.analysis.diagnostics.DiagnosticReporter
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors
 import org.jetbrains.kotlin.fir.analysis.diagnostics.reportOn
-import org.jetbrains.kotlin.fir.containingClass
+import org.jetbrains.kotlin.fir.analysis.overridesBackwardCompatibilityHelper
 import org.jetbrains.kotlin.fir.declarations.*
 import org.jetbrains.kotlin.fir.resolve.substitution.substitutorByMap
+import org.jetbrains.kotlin.fir.resolve.toFirRegularClass
 import org.jetbrains.kotlin.fir.scopes.FirTypeScope
 import org.jetbrains.kotlin.fir.scopes.getDirectOverriddenFunctions
 import org.jetbrains.kotlin.fir.scopes.getDirectOverriddenProperties
 import org.jetbrains.kotlin.fir.scopes.impl.toConeType
 import org.jetbrains.kotlin.fir.symbols.impl.FirCallableSymbol
 import org.jetbrains.kotlin.fir.symbols.impl.FirTypeParameterSymbol
-import org.jetbrains.kotlin.fir.typeContext
 import org.jetbrains.kotlin.fir.types.ConeKotlinErrorType
 import org.jetbrains.kotlin.fir.types.ConeKotlinType
 import org.jetbrains.kotlin.fir.types.coneType
@@ -172,12 +173,30 @@ object FirOverrideChecker : FirClassChecker() {
         firTypeScope: FirTypeScope,
         context: CheckerContext,
     ) {
+        val overriddenMemberSymbols = firTypeScope.retrieveDirectOverriddenOf(member)
+
         if (!member.isOverride) {
+            if (overriddenMemberSymbols.isEmpty() ||
+                context.session.overridesBackwardCompatibilityHelper.overrideCanBeOmitted(overriddenMemberSymbols, context)
+            ) {
+                return
+            }
+            val kind = member.source?.kind
+            // Only report if the current member has real source or it's a member property declared inside the primary constructor.
+            if (kind !is FirRealSourceElementKind && kind !is FirFakeSourceElementKind.PropertyFromParameter) return
+
+            val overridden = overriddenMemberSymbols.first().originalOrSelf()
+            val containingClass = overridden.containingClass()?.toFirRegularClass(context.session) ?: return
+            reporter.reportOn(
+                member.source,
+                FirErrors.VIRTUAL_MEMBER_HIDDEN,
+                member,
+                containingClass,
+                context
+            )
             return
         }
 
-        val overriddenMemberSymbols = firTypeScope.retrieveDirectOverriddenOf(member)
-
         if (overriddenMemberSymbols.isEmpty()) {
             reporter.reportNothingToOverride(member, context)
             return

compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/diagnostics/FirDefaultErrorMessages.kt

@@ -353,6 +353,7 @@ import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.VARIANCE_ON_TYPE_
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.VAR_ANNOTATION_PARAMETER
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.VAR_OVERRIDDEN_BY_VAL
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.VAR_TYPE_MISMATCH_ON_OVERRIDE
+import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.VIRTUAL_MEMBER_HIDDEN
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.WRONG_ANNOTATION_TARGET
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.WRONG_ANNOTATION_TARGET_WITH_USE_SITE_TARGET
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.WRONG_GETTER_RETURN_TYPE
@@ -818,6 +819,11 @@ class FirDefaultErrorMessages : DefaultErrorMessages.Extension {
             )
             map.put(NON_FINAL_MEMBER_IN_FINAL_CLASS, "'open' has no effect in a final class")
             map.put(NON_FINAL_MEMBER_IN_OBJECT, "'open' has no effect in an object")
+            map.put(
+                VIRTUAL_MEMBER_HIDDEN, "''{0}'' hides member of supertype ''{1}'' and needs ''override'' modifier", DECLARATION_NAME,
+                DECLARATION_NAME
+            )
+
             map.put(
                 GENERIC_THROWABLE_SUBCLASS,
                 "Subclass of 'Throwable' may not have type parameters"

compiler/fir/entrypoint/src/org/jetbrains/kotlin/fir/session/ComponentsContainers.kt

@@ -9,6 +9,7 @@ import com.intellij.psi.PsiFile
 import org.jetbrains.kotlin.config.LanguageVersionSettings
 import org.jetbrains.kotlin.fir.*
 import org.jetbrains.kotlin.fir.analysis.CheckersComponent
+import org.jetbrains.kotlin.fir.analysis.FirOverridesBackwardCompatibilityHelper
 import org.jetbrains.kotlin.fir.analysis.checkers.declaration.FirNameConflictsTracker
 import org.jetbrains.kotlin.fir.caches.FirCachesFactory
 import org.jetbrains.kotlin.fir.caches.FirThreadUnsafeCachesFactory
@@ -92,6 +93,7 @@ fun FirSession.registerJavaSpecificResolveComponents() {
     register(FirPlatformClassMapper::class, FirJavaClassMapper(this))
     register(FirSyntheticNamesProvider::class, FirJavaSyntheticNamesProvider)
     register(FirJsr305StateContainer::class, FirJsr305StateContainer.Default)
+    register(FirOverridesBackwardCompatibilityHelper::class, FirJvmOverridesBackwardCompatibilityHelper)
 }
 
 @OptIn(SessionConfiguration::class)

compiler/fir/entrypoint/src/org/jetbrains/kotlin/fir/session/FirJvmOverridesBackwardCompatibilityHelper.kt

@@ -0,0 +1,78 @@
+/*
+ * Copyright 2010-2021 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package org.jetbrains.kotlin.fir.session
+
+import org.jetbrains.kotlin.builtins.jvm.JavaToKotlinClassMap
+import org.jetbrains.kotlin.fir.analysis.FirOverridesBackwardCompatibilityHelper
+import org.jetbrains.kotlin.fir.analysis.checkers.context.CheckerContext
+import org.jetbrains.kotlin.fir.analysis.checkers.toRegularClass
+import org.jetbrains.kotlin.fir.analysis.checkers.unsubstitutedScope
+import org.jetbrains.kotlin.fir.containingClass
+import org.jetbrains.kotlin.fir.declarations.*
+import org.jetbrains.kotlin.fir.dispatchReceiverTypeOrNull
+import org.jetbrains.kotlin.fir.originalOrSelf
+import org.jetbrains.kotlin.fir.scopes.getDirectOverriddenFunctions
+import org.jetbrains.kotlin.fir.scopes.getDirectOverriddenProperties
+import org.jetbrains.kotlin.fir.symbols.impl.FirCallableSymbol
+import org.jetbrains.kotlin.fir.types.ConeClassLikeType
+import org.jetbrains.kotlin.fir.types.classId
+import org.jetbrains.kotlin.fir.types.coneTypeSafe
+import org.jetbrains.kotlin.name.ClassId
+
+/**
+ * Helper that determines if `override` keyword can be omitted for certain overrides. In general it can be omitted if
+ *
+ * 1. the super member is annotated with `@kotlin.internal.PlatformDependent`, OR
+ * 2. the super member is declared in a Java class that has special Kotlin class mapping. For example, overriding members of
+ *    `kotlin.Throwable` does not require `override` keyword.
+ *
+ * Note that, in case of multi-override, if any super member requires `override`, then the `override` keyword cannot be omitted.
+ */
+object FirJvmOverridesBackwardCompatibilityHelper : FirOverridesBackwardCompatibilityHelper {
+    private val javaOrigin = setOf(FirDeclarationOrigin.Java, FirDeclarationOrigin.Enhancement)
+    private val platformDependentAnnotation = ClassId.fromString("kotlin/internal/PlatformDependent")
+
+    override fun overrideCanBeOmitted(
+        overriddenMemberSymbols: List<FirCallableSymbol<*>>,
+        context: CheckerContext
+    ): Boolean {
+        // Members could share the same common interface up in the hierarchy. Hence we track the visited members to avoid redundant work.
+        val visitedSymbols = hashSetOf<FirCallableSymbol<*>>()
+        return overriddenMemberSymbols.all { isPlatformSpecificSymbolThatCanBeImplicitlyOverridden(it, visitedSymbols, context) }
+    }
+
+    private fun isPlatformSpecificSymbolThatCanBeImplicitlyOverridden(
+        symbol: FirCallableSymbol<*>,
+        visitedSymbols: MutableSet<FirCallableSymbol<*>>,
+        context: CheckerContext
+    ): Boolean {
+        val fir = symbol.fir as? FirCallableMemberDeclaration<*> ?: return false
+        if (fir.isFinal) return false
+
+        if (symbol in visitedSymbols) return true
+        visitedSymbols += symbol
+
+        val originalMember = fir.originalOrSelf()
+        if (originalMember.annotations.any { it.annotationTypeRef.coneTypeSafe<ConeClassLikeType>()?.classId == platformDependentAnnotation }) {
+            return true
+        }
+
+        if (originalMember.origin !in javaOrigin) return false
+        val containingClassName = originalMember.containingClass()?.classId?.asSingleFqName()?.toUnsafe() ?: return false
+        // If the super class is mapped to a Kotlin built-in class, then we don't require `override` keyword.
+        if (JavaToKotlinClassMap.mapKotlinToJava(containingClassName) != null) return true
+
+        val scope =
+            symbol.dispatchReceiverTypeOrNull()?.toRegularClass(context.session)?.unsubstitutedScope(context) ?: return false
+        val overriddenSymbols = when (originalMember) {
+            is FirSimpleFunction -> scope.getDirectOverriddenFunctions(originalMember.symbol)
+            is FirProperty -> scope.getDirectOverriddenProperties(originalMember.symbol)
+            else -> return false
+        }
+        if (overriddenSymbols.isEmpty()) return false
+        return overriddenSymbols.all { isPlatformSpecificSymbolThatCanBeImplicitlyOverridden(it, visitedSymbols, context) }
+    }
+}

compiler/fir/tree/src/org/jetbrains/kotlin/fir/ClassMembers.kt

@@ -71,6 +71,16 @@ inline fun <reified D : FirCallableDeclaration<*>> D.originalIfFakeOverride(): D
 inline fun <reified S : FirCallableSymbol<*>> S.originalIfFakeOverride(): S? =
     fir.originalIfFakeOverride()?.symbol as S?
 
+inline fun <reified D : FirCallableDeclaration<*>> D.originalOrSelf(): D {
+    var result = this
+    while (result.isSubstitutionOrIntersectionOverride) {
+        result = result.originalIfFakeOverride() ?: break
+    }
+    return result
+}
+
+inline fun <reified S : FirCallableSymbol<*>> S.originalOrSelf(): S = fir.originalOrSelf().symbol as S
+
 inline fun <reified D : FirCallableDeclaration<*>> D.unwrapFakeOverrides(): D {
     var current = this
 

compiler/testData/diagnostics/tests/java8Overrides/hidingMethodOfAny.fir.kt

@@ -1,5 +0,0 @@
-interface IA {
-    fun toString(): String = "IB"
-
-    override fun equals(other: Any?): Boolean
-}

compiler/testData/diagnostics/tests/java8Overrides/hidingMethodOfAny.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 interface IA {
     fun <!VIRTUAL_MEMBER_HIDDEN!>toString<!>(): String = "IB"
 

compiler/testData/diagnostics/tests/override/MultipleDefaultParametersInSupertypesNoOverride.fir.kt

@@ -1,15 +0,0 @@
-interface X {
-    fun foo(a : Int = 1)
-}
-
-interface Y {
-    fun foo(a : Int = 1)
-}
-
-class Z : X, Y {
-    fun foo(a : Int) {}
-}
-
-object ZO : X, Y {
-    fun foo(a : Int) {}
-}

compiler/testData/diagnostics/tests/override/MultipleDefaultParametersInSupertypesNoOverride.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 interface X {
     fun foo(a : Int = 1)
 }

compiler/testData/diagnostics/tests/override/NonGenerics.fir.kt

@@ -36,8 +36,8 @@ class MyChildClass() : MyClass() {}
 }
 
 <!ABSTRACT_CLASS_MEMBER_NOT_IMPLEMENTED!>class MyIllegalClass4<!>() : MyTrait, MyAbstractClass() {
-    fun foo() {}
-    <!MUST_BE_INITIALIZED_OR_BE_ABSTRACT!>val pr : Unit<!>
+    fun <!VIRTUAL_MEMBER_HIDDEN!>foo<!>() {}
+    <!MUST_BE_INITIALIZED_OR_BE_ABSTRACT!>val <!VIRTUAL_MEMBER_HIDDEN!>pr<!> : Unit<!>
     override fun other() {}
     override val otherPr : Int = 1
 }

compiler/testData/diagnostics/tests/scopes/inheritance/methodsPriority.fir.kt

@@ -25,7 +25,7 @@ fun test() {
 }
 
 class E: A() {
-    fun foo() = A()
+    fun <!VIRTUAL_MEMBER_HIDDEN!>foo<!>() = A()
 
     init {
         val a: A = foo() // todo: discuss

compiler/testData/diagnostics/tests/targetedBuiltIns/backwardCompatibility/basic.fir.kt

@@ -1,18 +0,0 @@
-// !DIAGNOSTICS: -UNUSED_PARAMETER -PLATFORM_CLASS_MAPPED_TO_KOTLIN
-
-abstract class Test1 : Map<String, String> {
-    fun containsKey(key: String): Boolean = TODO()
-
-    fun getOrDefault(key: String, defaultValue: String): String = TODO()
-}
-
-abstract class Test2 : MutableMap<String, String> {
-    fun replace(key: String, value: String): String? = TODO()
-}
-
-abstract class Test3 : java.util.AbstractMap<String, String>() {
-    fun containsKey(key: String): Boolean = TODO()
-
-    fun replace(key: String, value: String): String? = TODO()
-}
-

compiler/testData/diagnostics/tests/targetedBuiltIns/backwardCompatibility/basic.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 // !DIAGNOSTICS: -UNUSED_PARAMETER -PLATFORM_CLASS_MAPPED_TO_KOTLIN
 
 abstract class Test1 : Map<String, String> {

compiler/testData/diagnostics/tests/targetedBuiltIns/backwardCompatibility/delegation.fir.kt

@@ -1,32 +0,0 @@
-// !DIAGNOSTICS: -UNUSED_PARAMETER -PLATFORM_CLASS_MAPPED_TO_KOTLIN
-
-
-// Default methods from Java interfaces are NOT overridden by delegation.
-// So, in the example below 'TestNoDelegationToDefaultMethods#replace' implicitly overrides a method from 'java.util.Map' (which is ok),
-// but not a method from 'WithDelegation' (would be an error).
-open class WithDelegation(val m: Map<String, String>) : Map<String, String> by m
-
-class TestNoDelegationToDefaultMethods(m: Map<String, String>): WithDelegation(m) {
-    fun containsKey(key: String): Boolean = TODO()
-
-    fun getOrDefault(key: String, defaultValue: String): String = TODO()
-
-    fun replace(key: String, value: String): String? = TODO()
-}
-
-
-
-interface IBaseWithKotlinDeclaration : Map<String, String> {
-    fun replace(key: String, value: String): String?
-}
-
-abstract class WithDelegation2(val m: Map<String, String>) : Map<String, String> by m, IBaseWithKotlinDeclaration
-
-abstract class TestNoDelegationToDefaultMethods2(m: Map<String, String>): WithDelegation2(m) {
-    fun containsKey(key: String): Boolean = TODO()
-
-    fun getOrDefault(key: String, defaultValue: String): String = TODO()
-
-    // VIRTUAL_MEMBER_HIDDEN: hides member declaration inherited from a Kotlin interface
-    fun replace(key: String, value: String): String? = TODO()
-}

compiler/testData/diagnostics/tests/targetedBuiltIns/backwardCompatibility/delegation.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 // !DIAGNOSTICS: -UNUSED_PARAMETER -PLATFORM_CLASS_MAPPED_TO_KOTLIN
 
 

compiler/testData/diagnostics/tests/targetedBuiltIns/backwardCompatibility/derivedInterfacesWithKotlinFun.fir.kt

@@ -1,15 +0,0 @@
-// !DIAGNOSTICS: -UNUSED_PARAMETER -PLATFORM_CLASS_MAPPED_TO_KOTLIN
-
-interface IBaseWithKotlinDeclaration : Map<String, String> {
-    fun replace(key: String, value: String): String?
-}
-
-interface TestDerivedInterfaceHidingWithKotlinDeclaration : IBaseWithKotlinDeclaration {
-    // VIRTUAL_MEMBER_HIDDEN: hides member declaration inherited from a Kotlin interface
-    fun replace(key: String, value: String): String?
-}
-
-interface TestDerivedInterfaceDefaultWithKotlinDeclaration : IBaseWithKotlinDeclaration {
-    // VIRTUAL_MEMBER_HIDDEN: hides member declaration inherited from a Kotlin interface
-    fun replace(key: String, value: String): String? = TODO()
-}

compiler/testData/diagnostics/tests/targetedBuiltIns/backwardCompatibility/derivedInterfacesWithKotlinFun.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 // !DIAGNOSTICS: -UNUSED_PARAMETER -PLATFORM_CLASS_MAPPED_TO_KOTLIN
 
 interface IBaseWithKotlinDeclaration : Map<String, String> {

compiler/testData/diagnostics/testsWithStdLib/targetedBuiltIns/unsupportedFeature.fir.kt

@@ -14,11 +14,11 @@ class A : java.util.ArrayList<String>() {
 }
 
 class A1 : java.util.ArrayList<String>() {
-    // `stream` is defined in ArrayList, so it was possible to declare it in 1.0 without an 'override' keyword
+    // `stream` is defined in Collection, so it was possible to declare it in 1.0 without an 'override' keyword
     fun stream(): java.util.stream.Stream<String> = super.stream()
 
     // `sort` is defined in ArrayList, so it was impossible to declare it in 1.0 without an 'override' keyword
-    fun sort(c: Comparator<in String>?) {
+    fun <!VIRTUAL_MEMBER_HIDDEN!>sort<!>(c: Comparator<in String>?) {
         super.sort(c)
     }
 }

compiler/testData/diagnostics/testsWithStdLib/targetedBuiltIns/unsupportedFeature.kt

@@ -14,7 +14,7 @@ class A : java.util.ArrayList<String>() {
 }
 
 class A1 : java.util.ArrayList<String>() {
-    // `stream` is defined in ArrayList, so it was possible to declare it in 1.0 without an 'override' keyword
+    // `stream` is defined in Collection, so it was possible to declare it in 1.0 without an 'override' keyword
     fun stream(): java.util.stream.Stream<String> = super.<!UNRESOLVED_REFERENCE!>stream<!>()
 
     // `sort` is defined in ArrayList, so it was impossible to declare it in 1.0 without an 'override' keyword

idea/idea-frontend-fir/idea-frontend-fir-generator/src/org/jetbrains/kotlin/idea/frontend/api/fir/generator/HLDiagnosticConverter.kt

@@ -144,6 +144,14 @@ private object FirToKtConversionCreator {
             "firSymbolBuilder.classifierBuilder.buildClassLikeSymbol({0})",
             KtClassLikeSymbol::class.createType()
         ),
+        FirRegularClass::class to HLFunctionCallConversion(
+            "firSymbolBuilder.classifierBuilder.buildClassLikeSymbol({0}) as KtNamedClassOrObjectSymbol",
+            KtNamedClassOrObjectSymbol::class.createType(),
+            importsToAdd = listOf(
+                "org.jetbrains.kotlin.fir.declarations.FirRegularClass",
+                "org.jetbrains.kotlin.idea.frontend.api.symbols.KtNamedClassOrObjectSymbol"
+            )
+        ),
         FirExpression::class to HLFunctionCallConversion(
             "{0}.source!!.psi as KtExpression",
             KtExpression::class.createType(),

idea/idea-frontend-fir/src/org/jetbrains/kotlin/idea/frontend/api/fir/diagnostics/KtFirDataClassConverters.kt

@@ -20,6 +20,7 @@ import org.jetbrains.kotlin.fir.declarations.FirSimpleFunction
 import org.jetbrains.kotlin.fir.declarations.FirTypeParameter
 import org.jetbrains.kotlin.fir.declarations.FirVariable
 import org.jetbrains.kotlin.fir.psi
+import org.jetbrains.kotlin.idea.frontend.api.symbols.KtNamedClassOrObjectSymbol
 import org.jetbrains.kotlin.psi.KtAnnotation
 import org.jetbrains.kotlin.psi.KtAnnotationEntry
 import org.jetbrains.kotlin.psi.KtArrayAccessExpression
@@ -1589,6 +1590,14 @@ internal val KT_DIAGNOSTIC_CONVERTER = KtDiagnosticConverterBuilder.buildConvert
             token,
         )
     }
+    add(FirErrors.VIRTUAL_MEMBER_HIDDEN) { firDiagnostic ->
+        VirtualMemberHiddenImpl(
+            firSymbolBuilder.buildSymbol(firDiagnostic.a as FirDeclaration),
+            firSymbolBuilder.classifierBuilder.buildClassLikeSymbol(firDiagnostic.b) as KtNamedClassOrObjectSymbol,
+            firDiagnostic as FirPsiDiagnostic<*>,
+            token,
+        )
+    }
     add(FirErrors.MANY_COMPANION_OBJECTS) { firDiagnostic ->
         ManyCompanionObjectsImpl(
             firDiagnostic as FirPsiDiagnostic<*>,

idea/idea-frontend-fir/src/org/jetbrains/kotlin/idea/frontend/api/fir/diagnostics/KtFirDiagnostics.kt

@@ -18,6 +18,7 @@ import org.jetbrains.kotlin.idea.frontend.api.diagnostics.KtDiagnosticWithPsi
 import org.jetbrains.kotlin.idea.frontend.api.symbols.KtCallableSymbol
 import org.jetbrains.kotlin.idea.frontend.api.symbols.KtClassLikeSymbol
 import org.jetbrains.kotlin.idea.frontend.api.symbols.KtFunctionLikeSymbol
+import org.jetbrains.kotlin.idea.frontend.api.symbols.KtNamedClassOrObjectSymbol
 import org.jetbrains.kotlin.idea.frontend.api.symbols.KtSymbol
 import org.jetbrains.kotlin.idea.frontend.api.symbols.KtTypeParameterSymbol
 import org.jetbrains.kotlin.idea.frontend.api.symbols.KtVariableLikeSymbol
@@ -1129,6 +1130,12 @@ sealed class KtFirDiagnostic<PSI: PsiElement> : KtDiagnosticWithPsi<PSI> {
         override val diagnosticClass get() = NonFinalMemberInObject::class
     }
 
+    abstract class VirtualMemberHidden : KtFirDiagnostic<KtNamedDeclaration>() {
+        override val diagnosticClass get() = VirtualMemberHidden::class
+        abstract val declared: KtSymbol
+        abstract val overriddenContainer: KtNamedClassOrObjectSymbol
+    }
+
     abstract class ManyCompanionObjects : KtFirDiagnostic<KtObjectDeclaration>() {
         override val diagnosticClass get() = ManyCompanionObjects::class
     }

idea/idea-frontend-fir/src/org/jetbrains/kotlin/idea/frontend/api/fir/diagnostics/KtFirDiagnosticsImpl.kt

@@ -19,6 +19,7 @@ import org.jetbrains.kotlin.idea.frontend.api.fir.utils.weakRef
 import org.jetbrains.kotlin.idea.frontend.api.symbols.KtCallableSymbol
 import org.jetbrains.kotlin.idea.frontend.api.symbols.KtClassLikeSymbol
 import org.jetbrains.kotlin.idea.frontend.api.symbols.KtFunctionLikeSymbol
+import org.jetbrains.kotlin.idea.frontend.api.symbols.KtNamedClassOrObjectSymbol
 import org.jetbrains.kotlin.idea.frontend.api.symbols.KtSymbol
 import org.jetbrains.kotlin.idea.frontend.api.symbols.KtTypeParameterSymbol
 import org.jetbrains.kotlin.idea.frontend.api.symbols.KtVariableLikeSymbol
@@ -1814,6 +1815,15 @@ internal class NonFinalMemberInObjectImpl(
     override val firDiagnostic: FirPsiDiagnostic<*> by weakRef(firDiagnostic)
 }
 
+internal class VirtualMemberHiddenImpl(
+    override val declared: KtSymbol,
+    override val overriddenContainer: KtNamedClassOrObjectSymbol,
+    firDiagnostic: FirPsiDiagnostic<*>,
+    override val token: ValidityToken,
+) : KtFirDiagnostic.VirtualMemberHidden(), KtAbstractFirDiagnostic<KtNamedDeclaration> {
+    override val firDiagnostic: FirPsiDiagnostic<*> by weakRef(firDiagnostic)
+}
+
 internal class ManyCompanionObjectsImpl(
     firDiagnostic: FirPsiDiagnostic<*>,
     override val token: ValidityToken,