[FIR] Fix computing compatibility of expect and actual modality

analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/diagnostic/compiler/based/DiagnosisCompilerTestFE10TestdataTestGenerated.java

@@ -20000,6 +20000,12 @@ public class DiagnosisCompilerTestFE10TestdataTestGenerated extends AbstractDiag
                 runTest("compiler/testData/diagnostics/tests/multiplatform/expectInterfaceApplicability.kt");
             }
 
+            @Test
+            @TestMetadata("expectObjectWithAbstractMember.kt")
+            public void testExpectObjectWithAbstractMember() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/multiplatform/expectObjectWithAbstractMember.kt");
+            }
+
             @Test
             @TestMetadata("headerFunInNonHeaderClass.kt")
             public void testHeaderFunInNonHeaderClass() throws Exception {
@@ -20311,6 +20317,12 @@ public class DiagnosisCompilerTestFE10TestdataTestGenerated extends AbstractDiag
                     runTest("compiler/testData/diagnostics/tests/multiplatform/headerClass/dontOverrideMethodsFromInterfaceInCommonCode.kt");
                 }
 
+                @Test
+                @TestMetadata("equalsOverrideInActualInterface.kt")
+                public void testEqualsOverrideInActualInterface() throws Exception {
+                    runTest("compiler/testData/diagnostics/tests/multiplatform/headerClass/equalsOverrideInActualInterface.kt");
+                }
+
                 @Test
                 @TestMetadata("expectClassWithExplicitAbstractMember.kt")
                 public void testExpectClassWithExplicitAbstractMember() throws Exception {

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

@@ -20000,6 +20000,12 @@ public class FirOldFrontendDiagnosticsTestGenerated extends AbstractFirDiagnosti
                 runTest("compiler/testData/diagnostics/tests/multiplatform/expectInterfaceApplicability.kt");
             }
 
+            @Test
+            @TestMetadata("expectObjectWithAbstractMember.kt")
+            public void testExpectObjectWithAbstractMember() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/multiplatform/expectObjectWithAbstractMember.kt");
+            }
+
             @Test
             @TestMetadata("headerFunInNonHeaderClass.kt")
             public void testHeaderFunInNonHeaderClass() throws Exception {
@@ -20311,6 +20317,12 @@ public class FirOldFrontendDiagnosticsTestGenerated extends AbstractFirDiagnosti
                     runTest("compiler/testData/diagnostics/tests/multiplatform/headerClass/dontOverrideMethodsFromInterfaceInCommonCode.kt");
                 }
 
+                @Test
+                @TestMetadata("equalsOverrideInActualInterface.kt")
+                public void testEqualsOverrideInActualInterface() throws Exception {
+                    runTest("compiler/testData/diagnostics/tests/multiplatform/headerClass/equalsOverrideInActualInterface.kt");
+                }
+
                 @Test
                 @TestMetadata("expectClassWithExplicitAbstractMember.kt")
                 public void testExpectClassWithExplicitAbstractMember() throws Exception {

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

@@ -20000,6 +20000,12 @@ public class FirOldFrontendDiagnosticsWithLightTreeTestGenerated extends Abstrac
                 runTest("compiler/testData/diagnostics/tests/multiplatform/expectInterfaceApplicability.kt");
             }
 
+            @Test
+            @TestMetadata("expectObjectWithAbstractMember.kt")
+            public void testExpectObjectWithAbstractMember() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/multiplatform/expectObjectWithAbstractMember.kt");
+            }
+
             @Test
             @TestMetadata("headerFunInNonHeaderClass.kt")
             public void testHeaderFunInNonHeaderClass() throws Exception {
@@ -20311,6 +20317,12 @@ public class FirOldFrontendDiagnosticsWithLightTreeTestGenerated extends Abstrac
                     runTest("compiler/testData/diagnostics/tests/multiplatform/headerClass/dontOverrideMethodsFromInterfaceInCommonCode.kt");
                 }
 
+                @Test
+                @TestMetadata("equalsOverrideInActualInterface.kt")
+                public void testEqualsOverrideInActualInterface() throws Exception {
+                    runTest("compiler/testData/diagnostics/tests/multiplatform/headerClass/equalsOverrideInActualInterface.kt");
+                }
+
                 @Test
                 @TestMetadata("expectClassWithExplicitAbstractMember.kt")
                 public void testExpectClassWithExplicitAbstractMember() throws Exception {

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

@@ -7,6 +7,7 @@ package org.jetbrains.kotlin.fir.analysis.checkers.declaration
 
 import org.jetbrains.kotlin.descriptors.ClassKind
 import org.jetbrains.kotlin.descriptors.Modality
+import org.jetbrains.kotlin.descriptors.Modality.*
 import org.jetbrains.kotlin.descriptors.Visibilities
 import org.jetbrains.kotlin.fir.FirSession
 import org.jetbrains.kotlin.fir.analysis.checkers.collectEnumEntries
@@ -31,7 +32,10 @@ import org.jetbrains.kotlin.types.AbstractTypeChecker
 import org.jetbrains.kotlin.types.model.TypeConstructorMarker
 import org.jetbrains.kotlin.utils.SmartList
 import org.jetbrains.kotlin.utils.addIfNotNull
+import org.jetbrains.kotlin.utils.addToStdlib.enumMapOf
+import org.jetbrains.kotlin.utils.addToStdlib.enumSetOf
 import org.jetbrains.kotlin.utils.keysToMap
+import java.util.*
 
 object FirExpectActualResolver {
     @OptIn(ExperimentalStdlibApi::class)
@@ -330,11 +334,13 @@ object FirExpectActualResolver {
             !areCompatibleModalities(
                 expectDeclaration.modality,
                 actualDeclaration.modality,
-                (expectDeclaration.dispatchReceiverType?.toSymbol(expectSession) as? FirRegularClassSymbol)?.modality,
+                expectContainingClass?.modality,
                 actualContainingClass?.modality
             )
         ) {
-            return ExpectActualCompatibility.Incompatible.Modality
+            if (expectDeclaration.dispatchReceiverType?.isAny != true) {
+                return ExpectActualCompatibility.Incompatible.Modality
+            }
         }
 
         if (!areDeclarationsWithCompatibleVisibilities(expectDeclaration.resolvedStatus, actualDeclaration.resolvedStatus)) {
@@ -460,19 +466,39 @@ object FirExpectActualResolver {
         expectContainingClassModality: Modality? = null,
         actualContainingClassModality: Modality? = null
     ): Boolean {
-        val result = (expectModality == actualModality) ||
+        val expectEffectiveModality = effectiveModality(expectModality, expectContainingClassModality)
-                (expectModality == Modality.FINAL && (actualModality == Modality.OPEN || actualModality == Modality.ABSTRACT))
+        val actualEffectiveModality = effectiveModality(actualModality, actualContainingClassModality)
-        if (result) return true
+
-        if (expectContainingClassModality == null || actualContainingClassModality == null) return result
+        val result = actualEffectiveModality in compatibleModalityMap.getValue(expectEffectiveModality)
-        return expectModality == expectContainingClassModality && actualModality == actualContainingClassModality
+        return result
     }
 
+    /*
+     * If containing class is final then all declarations in it effectively final
+     */
+    private fun effectiveModality(declarationModality: Modality?, containingClassModality: Modality?): Modality? {
+        return when (containingClassModality) {
+            FINAL -> FINAL
+            else -> declarationModality
+        }
+    }
+
+    /*
+     * Key is expect modality, value is a set of compatible actual modalities
+     */
+    private val compatibleModalityMap: EnumMap<Modality, EnumSet<Modality>> = enumMapOf(
+        ABSTRACT to enumSetOf(ABSTRACT, OPEN),
+        OPEN to enumSetOf(OPEN),
+        FINAL to enumSetOf(ABSTRACT, OPEN, FINAL),
+        SEALED to enumSetOf(SEALED),
+    )
+
     private fun areDeclarationsWithCompatibleVisibilities(
         expectStatus: FirDeclarationStatus,
         actualStatus: FirDeclarationStatus
     ): Boolean {
         val compare = Visibilities.compare(expectStatus.visibility, actualStatus.visibility)
-        return if (expectStatus.modality != Modality.FINAL) {
+        return if (expectStatus.modality != FINAL) {
             // For overridable declarations visibility should match precisely, see KT-19664
             compare == 0
         } else {

compiler/testData/diagnostics/tests/multiplatform/expectObjectWithAbstractMember.kt

@@ -0,0 +1,18 @@
+// FIR_IDENTICAL
+// MODULE: m1-common
+// FILE: common.kt
+
+interface Base {
+    fun foo()
+}
+
+expect object Implementation : Base
+
+// MODULE: m1-jvm()()(m1-common)
+// FILE: jvm.kt
+
+abstract class RealImplementation : Base {
+    override fun foo() {}
+}
+
+actual object Implementation : RealImplementation(), Base

compiler/testData/diagnostics/tests/multiplatform/expectObjectWithAbstractMember.txt

@@ -0,0 +1,43 @@
+// -- Module: <m1-common> --
+package
+
+public interface Base {
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public abstract fun foo(): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public expect object Implementation : Base {
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public final override /*1*/ /*fake_override*/ fun foo(): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+// -- Module: <m1-jvm> --
+package
+
+public interface Base {
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public abstract fun foo(): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public actual object Implementation : RealImplementation, Base {
+    private constructor Implementation()
+    public open override /*2*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*2*/ /*fake_override*/ fun foo(): kotlin.Unit
+    public open override /*2*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*2*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public abstract class RealImplementation : Base {
+    public constructor RealImplementation()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ fun foo(): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+

compiler/testData/diagnostics/tests/multiplatform/headerClass/equalsOverrideInActualInterface.kt

@@ -0,0 +1,8 @@
+// FIR_IDENTICAL
+// MODULE: m1-common
+expect interface Base
+
+// MODULE: m1-jvm()()(m1-common)
+actual interface Base {
+    override fun equals(other: Any?): Boolean
+}

compiler/testData/diagnostics/tests/multiplatform/headerClass/equalsOverrideInActualInterface.txt

@@ -0,0 +1,18 @@
+// -- Module: <m1-common> --
+package
+
+public expect interface Base {
+    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
+}
+
+// -- Module: <m1-jvm> --
+package
+
+public actual interface Base {
+    public abstract override /*1*/ 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-common-new/tests-gen/org/jetbrains/kotlin/test/runners/DiagnosticTestGenerated.java

@@ -20006,6 +20006,12 @@ public class DiagnosticTestGenerated extends AbstractDiagnosticTest {
                 runTest("compiler/testData/diagnostics/tests/multiplatform/expectInterfaceApplicability.kt");
             }
 
+            @Test
+            @TestMetadata("expectObjectWithAbstractMember.kt")
+            public void testExpectObjectWithAbstractMember() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/multiplatform/expectObjectWithAbstractMember.kt");
+            }
+
             @Test
             @TestMetadata("headerFunInNonHeaderClass.kt")
             public void testHeaderFunInNonHeaderClass() throws Exception {
@@ -20317,6 +20323,12 @@ public class DiagnosticTestGenerated extends AbstractDiagnosticTest {
                     runTest("compiler/testData/diagnostics/tests/multiplatform/headerClass/dontOverrideMethodsFromInterfaceInCommonCode.kt");
                 }
 
+                @Test
+                @TestMetadata("equalsOverrideInActualInterface.kt")
+                public void testEqualsOverrideInActualInterface() throws Exception {
+                    runTest("compiler/testData/diagnostics/tests/multiplatform/headerClass/equalsOverrideInActualInterface.kt");
+                }
+
                 @Test
                 @TestMetadata("expectClassWithExplicitAbstractMember.kt")
                 public void testExpectClassWithExplicitAbstractMember() throws Exception {

core/util.runtime/src/org/jetbrains/kotlin/utils/addToStdlib.kt

@@ -256,3 +256,6 @@ inline fun <T, U, K, V> List<T>.flatGroupBy(
 }
 
 fun <E> MutableList<E>.popLast(): E = removeAt(lastIndex)
+
+fun <K : Enum<K>, V> enumMapOf(vararg pairs: Pair<K, V>): EnumMap<K, V> = EnumMap(mapOf(*pairs))
+fun <T : Enum<T>> enumSetOf(element: T, vararg elements: T): EnumSet<T> = EnumSet.of(element, *elements)