[Fir2Ir] Support rebuilding fake overrides over IR

^KT-61514

analysis/analysis-api-fir/src/org/jetbrains/kotlin/analysis/api/fir/components/KtFirCompilerFacility.kt

@@ -159,7 +159,8 @@ internal class KtFirCompilerFacility(
             Fir2IrJvmSpecialAnnotationSymbolProvider(),
             DefaultBuiltIns.Instance,
             Fir2IrCommonMemberStorage(signatureComposerForJvmFir2Ir(false), FirJvmKotlinMangler()),
-            initializedIrBuiltIns = null
+            initializedIrBuiltIns = null,
+            ::JvmIrTypeSystemContext,
         )
 
         patchCodeFragmentIr(fir2IrResult)

compiler/fir/entrypoint/src/org/jetbrains/kotlin/fir/pipeline/convertToIr.kt

@@ -19,6 +19,7 @@ import org.jetbrains.kotlin.fir.backend.jvm.Fir2IrJvmSpecialAnnotationSymbolProv
 import org.jetbrains.kotlin.fir.backend.jvm.FirJvmKotlinMangler
 import org.jetbrains.kotlin.fir.backend.jvm.FirJvmVisibilityConverter
 import org.jetbrains.kotlin.fir.declarations.FirFile
+import org.jetbrains.kotlin.fir.moduleData
 import org.jetbrains.kotlin.fir.resolve.ScopeSession
 import org.jetbrains.kotlin.ir.IrBuiltIns
 import org.jetbrains.kotlin.ir.backend.jvm.serialization.JvmDescriptorMangler
@@ -44,6 +45,7 @@ data class ModuleCompilerAnalyzedOutput(
         irMangler: KotlinMangler.IrMangler,
         visibilityConverter: Fir2IrVisibilityConverter,
         kotlinBuiltIns: KotlinBuiltIns,
+        typeContextProvider: (IrBuiltIns) -> IrTypeSystemContext,
     ): Fir2IrResult {
         return Fir2IrConverter.createIrModuleFragment(
             session, scopeSession, fir,
@@ -52,7 +54,8 @@ data class ModuleCompilerAnalyzedOutput(
             Fir2IrJvmSpecialAnnotationSymbolProvider(), // TODO KT-60526: replace with appropriate (probably empty) implementation for other backends.
             kotlinBuiltIns = kotlinBuiltIns,
             commonMemberStorage = commonMemberStorage,
-            initializedIrBuiltIns = irBuiltIns
+            initializedIrBuiltIns = irBuiltIns,
+            typeContextProvider = typeContextProvider
         )
     }
 }
@@ -117,6 +120,7 @@ fun FirResult.convertToIrAndActualize(
                 irMangler,
                 visibilityConverter,
                 kotlinBuiltIns,
+                actualizerTypeContextProvider,
             ).also { result ->
                 fir2IrResultPostCompute(result)
             }
@@ -129,12 +133,15 @@ fun FirResult.convertToIrAndActualize(
             val commonIrOutputs = commonOutputs.map {
                 it.convertToIr(
                     fir2IrExtensions,
-                    fir2IrConfiguration,
+                    // We need to build all modules before rebuilding fake overrides
+                    // to avoid fixing declaration storages
+                    fir2IrConfiguration.copy(useIrFakeOverrideBuilder = false),
                     commonMemberStorage = commonMemberStorage,
                     irBuiltIns = irBuiltIns,
                     irMangler,
                     visibilityConverter,
                     kotlinBuiltIns,
+                    actualizerTypeContextProvider,
                 ).also { result ->
                     fir2IrResultPostCompute(result)
                     if (irBuiltIns == null) {
@@ -150,6 +157,7 @@ fun FirResult.convertToIrAndActualize(
                 irMangler,
                 visibilityConverter,
                 kotlinBuiltIns,
+                actualizerTypeContextProvider,
             ).also {
                 fir2IrResultPostCompute(it)
             }
@@ -159,7 +167,11 @@ fun FirResult.convertToIrAndActualize(
                 commonIrOutputs.map { it.irModuleFragment },
                 fir2IrConfiguration.diagnosticReporter,
                 actualizerTypeContextProvider(fir2IrResult.irModuleFragment.irBuiltins),
-                fir2IrConfiguration.languageVersionSettings
+                fir2IrConfiguration.languageVersionSettings,
+                commonMemberStorage.symbolTable,
+                irMangler,
+                Fir2IrConverter.friendModulesMap(outputs.last().session),
+                fir2IrConfiguration.useIrFakeOverrideBuilder
             )
         }
     }

compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/Fir2IrConfiguration.kt

@@ -27,6 +27,8 @@ import org.jetbrains.kotlin.incremental.components.InlineConstTracker
  *  It means asking for an IR element of a non-cached declaration is a sign of inconsistent state.
  *  Code generation in the IDE is trickier, though, as declarations from any module can be potentially referenced.
  *  For such a scenario, there is a flag that relaxes consistency checks.
+ *
+ *  @param useIrFakeOverrideBuilder enables creation of fake-overrides using IR f/o generator instead of FIR2IR one. KT-61514
  */
 data class Fir2IrConfiguration(
     val languageVersionSettings: LanguageVersionSettings,
@@ -35,4 +37,5 @@ data class Fir2IrConfiguration(
     val evaluatedConstTracker: EvaluatedConstTracker,
     val inlineConstTracker: InlineConstTracker?,
     val allowNonCachedDeclarations: Boolean,
+    val useIrFakeOverrideBuilder: Boolean = false
 )

compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/Fir2IrConverter.kt

@@ -10,6 +10,7 @@ import org.jetbrains.kotlin.KtFakeSourceElementKind
 import org.jetbrains.kotlin.KtPsiSourceFileLinesMapping
 import org.jetbrains.kotlin.KtSourceFileLinesMappingFromLineStartOffsets
 import org.jetbrains.kotlin.backend.common.CommonBackendErrors
+import org.jetbrains.kotlin.backend.common.actualizer.FakeOverrideRebuilder
 import org.jetbrains.kotlin.backend.common.sourceElement
 import org.jetbrains.kotlin.builtins.KotlinBuiltIns
 import org.jetbrains.kotlin.config.LanguageFeature
@@ -30,6 +31,7 @@ import org.jetbrains.kotlin.fir.extensions.generatedNestedClassifiers
 import org.jetbrains.kotlin.fir.resolve.ScopeSession
 import org.jetbrains.kotlin.fir.symbols.lazyDeclarationResolver
 import org.jetbrains.kotlin.ir.PsiIrFileEntry
+import org.jetbrains.kotlin.ir.IrBuiltIns
 import org.jetbrains.kotlin.ir.UNDEFINED_OFFSET
 import org.jetbrains.kotlin.ir.declarations.*
 import org.jetbrains.kotlin.ir.declarations.impl.IrFileImpl
@@ -40,6 +42,7 @@ import org.jetbrains.kotlin.ir.interpreter.IrInterpreterConfiguration
 import org.jetbrains.kotlin.ir.interpreter.IrInterpreterEnvironment
 import org.jetbrains.kotlin.ir.interpreter.checker.EvaluationMode
 import org.jetbrains.kotlin.ir.interpreter.transformer.transformConst
+import org.jetbrains.kotlin.ir.types.IrTypeSystemContext
 import org.jetbrains.kotlin.ir.symbols.impl.IrConstructorPublicSymbolImpl
 import org.jetbrains.kotlin.ir.symbols.impl.IrSimpleFunctionPublicSymbolImpl
 import org.jetbrains.kotlin.ir.util.KotlinMangler
@@ -530,6 +533,13 @@ class Fir2IrConverter(
             }
         }
 
+        // TODO: drop this function in favor of using [IrModuleDescriptor::shouldSeeInternalsOf] in FakeOverrideBuilder KT-61384
+        fun friendModulesMap(session: FirSession) = mapOf(
+            session.moduleData.name.asStringStripSpecialMarkers() to session.moduleData.friendDependencies.map {
+                it.name.asStringStripSpecialMarkers()
+            }
+        )
+
         fun createIrModuleFragment(
             session: FirSession,
             scopeSession: ScopeSession,
@@ -542,7 +552,8 @@ class Fir2IrConverter(
             specialSymbolProvider: Fir2IrSpecialSymbolProvider,
             kotlinBuiltIns: KotlinBuiltIns,
             commonMemberStorage: Fir2IrCommonMemberStorage,
-            initializedIrBuiltIns: IrBuiltInsOverFir?
+            initializedIrBuiltIns: IrBuiltInsOverFir?,
+            typeContextProvider: (IrBuiltIns) -> IrTypeSystemContext
         ): Fir2IrResult {
             session.lazyDeclarationResolver.disableLazyResolveContractChecks()
             val moduleDescriptor = FirModuleDescriptor(session, kotlinBuiltIns)
@@ -564,6 +575,16 @@ class Fir2IrConverter(
                 allFirFiles, irModuleFragment, components.fir2IrVisitor, runPreCacheBuiltinClasses = initializedIrBuiltIns == null
             )
 
+            if (fir2IrConfiguration.useIrFakeOverrideBuilder) {
+                FakeOverrideRebuilder(
+                    commonMemberStorage.symbolTable,
+                    irMangler,
+                    typeContextProvider(components.irBuiltIns),
+                    irModuleFragment,
+                    friendModulesMap(session)
+                ).rebuildFakeOverrides()
+            }
+
             return Fir2IrResult(irModuleFragment, components, moduleDescriptor)
         }
     }

compiler/ir/backend.common/build.gradle.kts

@@ -9,6 +9,7 @@ dependencies {
     api(project(":compiler:backend-common"))
     api(project(":compiler:ir.tree"))
     api(project(":compiler:ir.interpreter"))
+    implementation(project(":compiler:ir.serialization.common"))
     compileOnly(intellijCore())
 }
 

compiler/ir/backend.common/src/org/jetbrains/kotlin/backend/common/actualizer/FakeOverrideRebuilder.kt

@@ -0,0 +1,251 @@
+/*
+ * Copyright 2010-2023 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.backend.common.actualizer
+
+import org.jetbrains.kotlin.backend.common.linkage.partial.PartialLinkageSupportForLinker
+import org.jetbrains.kotlin.backend.common.overrides.FakeOverrideBuilder
+import org.jetbrains.kotlin.backend.common.overrides.FileLocalAwareLinker
+import org.jetbrains.kotlin.backend.common.serialization.CompatibilityMode
+import org.jetbrains.kotlin.descriptors.ModuleDescriptor
+import org.jetbrains.kotlin.ir.IrElement
+import org.jetbrains.kotlin.ir.declarations.*
+import org.jetbrains.kotlin.ir.declarations.lazy.IrLazyDeclarationBase
+import org.jetbrains.kotlin.ir.expressions.IrCall
+import org.jetbrains.kotlin.ir.expressions.IrFunctionReference
+import org.jetbrains.kotlin.ir.expressions.IrLocalDelegatedPropertyReference
+import org.jetbrains.kotlin.ir.expressions.IrPropertyReference
+import org.jetbrains.kotlin.ir.symbols.*
+import org.jetbrains.kotlin.ir.symbols.impl.IrPropertySymbolImpl
+import org.jetbrains.kotlin.ir.symbols.impl.IrSimpleFunctionSymbolImpl
+import org.jetbrains.kotlin.ir.types.IrTypeSystemContext
+import org.jetbrains.kotlin.ir.types.getClass
+import org.jetbrains.kotlin.ir.util.*
+import org.jetbrains.kotlin.ir.visitors.IrElementVisitorVoid
+import org.jetbrains.kotlin.ir.visitors.acceptChildrenVoid
+import org.jetbrains.kotlin.ir.visitors.acceptVoid
+import org.jetbrains.kotlin.ir.visitors.transformChildrenVoid
+import org.jetbrains.kotlin.utils.addToStdlib.shouldNotBeCalled
+
+
+/**
+ * After actualization, fake overrides can be incorrect.
+ *
+ * Fake overrides can change even in classes, which don't have expect/actuals in their superclasses.
+ * And this change can be more untrivial than just substitute expect class with actual.
+ *
+ * For example, if an expect class is actualized to common class, or several expect classes are actualized to same class,
+ * several fake overrides can be merged with each other, or with real functions.
+ *
+ * To fix that, we are just rebuilding fake overrides from stretch, after actualization is done.
+ *
+ * This is done in 3 steps:
+ * 1. Remove all fake overrides from all classes
+ * 2. Build new fake overrides and map old one to some function now existing in class (possible real function, not fake override)
+ * 3. Remap callsites of all functions using the map collected on step 2.
+ *
+ * Steps 1 and 3 are kinda trivial, expect we should remove all fake overrides from symbol table.
+ *
+ * For matching in step 2, classes are processed in such order. That superclass is processed before class.
+ * That allows us to match using overridden symbols. In particular, f/o is mapped to only function
+ * overriding any of functions (possibly already mapped), which was overriden by initial fake override.
+ *
+ * Here we assume that functions can be only merged, not split, i.e. if the same fake override was overriding several
+ * super-functions, it's impossible to have different function overriding them after actualization.
+ */
+class FakeOverrideRebuilder(
+    val symbolTable: SymbolTable,
+    val mangler: KotlinMangler.IrMangler,
+    val typeSystemContext: IrTypeSystemContext,
+    val irModule: IrModuleFragment,
+    // TODO: drop this argument in favor of using [IrModuleDescriptor::shouldSeeInternalsOf] in FakeOverrideBuilder KT-61384
+    friendModules: Map<String, List<String>>
+) {
+    private val removedFakeOverrides = mutableMapOf<IrClassSymbol, List<IrSymbol>>()
+    private val processedClasses = mutableSetOf<IrClass>()
+    private val fakeOverrideMap = mutableMapOf<IrSymbol, IrSymbol>()
+
+    private val fakeOverrideBuilder = FakeOverrideBuilder(
+        LocalFakeOverridesStorage(),
+        symbolTable,
+        mangler,
+        typeSystemContext,
+        friendModules,
+        PartialLinkageSupportForLinker.DISABLED
+    )
+
+    fun rebuildFakeOverrides() {
+        irModule.acceptVoid(RemoveFakeOverridesVisitor(removedFakeOverrides, symbolTable))
+        for (clazz in removedFakeOverrides.keys) {
+            rebuildClassFakeOverrides(clazz.owner)
+        }
+        irModule.acceptVoid(RemapFakeOverridesVisitor(fakeOverrideMap))
+    }
+
+    private fun collectOverriddenDeclarations(
+        member: IrOverridableDeclaration<*>,
+        result: MutableSet<IrOverridableDeclaration<*>>,
+        visited: MutableSet<IrOverridableDeclaration<*>>,
+        stopAtReal: Boolean,
+    ) {
+        if (!visited.add(member)) return
+        if (member.isReal) {
+            result.add(member)
+            if (stopAtReal) return
+        } else {
+            require(member.overriddenSymbols.isNotEmpty()) { "No overridden symbols found for (fake override) ${member.render()}" }
+        }
+        for (overridden in member.overriddenSymbols) {
+            collectOverriddenDeclarations(overridden.owner as IrOverridableDeclaration<*>, result, visited, stopAtReal)
+        }
+    }
+
+    private fun rebuildClassFakeOverrides(irClass: IrClass) {
+        if (irClass is IrLazyDeclarationBase) return
+        if (!processedClasses.add(irClass)) return
+        val oldList = removedFakeOverrides[irClass.symbol] ?: return
+        for (c in irClass.superTypes) {
+            c.getClass()?.let { rebuildClassFakeOverrides(it) }
+        }
+        fakeOverrideBuilder.provideFakeOverrides(irClass, CompatibilityMode.CURRENT)
+        val overriddenMap = mutableMapOf<IrSymbol, IrSymbol>()
+        irClass.properties
+            .forEach { prop ->
+                val allOverridden = mutableSetOf<IrOverridableDeclaration<*>>()
+                collectOverriddenDeclarations(prop, allOverridden, mutableSetOf(), false)
+                for (overridden in allOverridden) {
+                    require(overriddenMap.put(overridden.symbol, prop.symbol) == null) { "Multiple overrides for ${overridden.render()} "}
+                }
+            }
+        irClass.simpleFunctions()
+            .forEach { func ->
+                val allOverridden = mutableSetOf<IrOverridableDeclaration<*>>()
+                collectOverriddenDeclarations(func, allOverridden, mutableSetOf(), false)
+                for (overridden in allOverridden) {
+                    require(overriddenMap.put(overridden.symbol, func.symbol) == null) { "Multiple overrides for ${overridden.render()} "}
+                }
+            }
+        for (old in oldList) {
+            fakeOverrideMap[old] = mutableSetOf<IrOverridableDeclaration<*>>()
+                .apply { collectOverriddenDeclarations(old.owner as IrOverridableDeclaration<*>, this, mutableSetOf(), true) }
+                .map { overriddenMap[it.symbol] }
+                .distinct()
+                .single() ?: error("${old.owner.render()} is not overridden in ${irClass.render()}")
+        }
+    }
+}
+
+private class LocalFakeOverridesStorage : FileLocalAwareLinker {
+    val funStorage = mutableMapOf<Pair<IrDeclaration, IdSignature>, IrSimpleFunctionSymbolImpl>()
+    val propertyStorage = mutableMapOf<Pair<IrDeclaration, IdSignature>, IrPropertySymbol>()
+    override fun tryReferencingSimpleFunctionByLocalSignature(
+        parent: IrDeclaration,
+        idSignature: IdSignature,
+    ): IrSimpleFunctionSymbol? {
+        if (idSignature.isPubliclyVisible) return null
+        return funStorage.getOrPut(parent to idSignature) {
+            IrSimpleFunctionSymbolImpl()
+        }
+    }
+
+    override fun tryReferencingPropertyByLocalSignature(parent: IrDeclaration, idSignature: IdSignature): IrPropertySymbol? {
+        if (idSignature.isPubliclyVisible) return null
+        return propertyStorage.getOrPut(parent to idSignature) {
+            IrPropertySymbolImpl()
+        }
+    }
+}
+
+private class RemoveFakeOverridesVisitor(
+    val removedOverrides: MutableMap<IrClassSymbol, List<IrSymbol>>,
+    val symbolTable: SymbolTable
+) : IrElementVisitorVoid {
+
+    override fun visitElement(element: IrElement) {
+        element.acceptChildrenVoid(this)
+    }
+
+    @OptIn(DelicateSymbolTableApi::class)
+    override fun visitClass(declaration: IrClass) {
+        val curList = mutableListOf<IrSymbol>()
+        declaration.declarations.removeIf {
+            if (it is IrOverridableDeclaration<*> && it.isFakeOverride) {
+                when (it) {
+                    is IrProperty -> {
+                        curList.add(it.symbol)
+                        symbolTable.removeProperty(it.symbol)
+                        it.getter?.symbol?.let { getter ->
+                            curList.add(getter)
+                            symbolTable.removeSimpleFunction(getter)
+                        }
+                        it.setter?.symbol?.let { setter ->
+                            curList.add(setter)
+                            symbolTable.removeSimpleFunction(setter)
+                        }
+                    }
+                    is IrSimpleFunction -> {
+                        curList.add(it.symbol)
+                        symbolTable.removeSimpleFunction(it.symbol)
+                    }
+                    else -> shouldNotBeCalled("Only simple functions and properties can be overridden")
+                }
+                true
+            } else {
+                false
+            }
+        }
+        if (curList.isNotEmpty()) {
+            removedOverrides[declaration.symbol] = curList
+        }
+        declaration.acceptChildrenVoid(this)
+    }
+}
+
+
+// TODO: KT-61561 it seams, this class is too generic to be here.
+// By some reason, we don't have utility class doing that, but we probably should, as we have DeepCopy util classes
+// Probably, it should also be generated, to avoid missing some plaves, where symbols can happen.
+private class RemapFakeOverridesVisitor(val fakeOverridesMap: Map<IrSymbol, IrSymbol>) : IrElementVisitorVoid {
+    override fun visitElement(element: IrElement) {
+        element.acceptChildrenVoid(this)
+    }
+
+    override fun visitSimpleFunction(declaration: IrSimpleFunction) {
+        declaration.overriddenSymbols = declaration.overriddenSymbols.map {
+            (fakeOverridesMap[it] as? IrSimpleFunctionSymbol) ?: it
+        }
+        declaration.acceptChildrenVoid(this)
+    }
+
+    override fun visitProperty(declaration: IrProperty) {
+        declaration.overriddenSymbols = declaration.overriddenSymbols.map {
+            (fakeOverridesMap[it] as? IrPropertySymbol) ?: it
+        }
+        declaration.acceptChildrenVoid(this)
+    }
+
+    override fun visitCall(expression: IrCall) {
+        expression.symbol = (fakeOverridesMap[expression.symbol] as? IrSimpleFunctionSymbol) ?: expression.symbol
+        expression.acceptChildrenVoid(this)
+    }
+
+    override fun visitFunctionReference(expression: IrFunctionReference) {
+        expression.symbol = (fakeOverridesMap[expression.symbol] as? IrSimpleFunctionSymbol) ?: expression.symbol
+        expression.acceptChildrenVoid(this)
+    }
+
+    override fun visitPropertyReference(expression: IrPropertyReference) {
+        expression.symbol = (fakeOverridesMap[expression.symbol] as? IrPropertySymbol) ?: expression.symbol
+        expression.getter = (expression.getter?.let { fakeOverridesMap[it] } as? IrSimpleFunctionSymbol) ?: expression.getter
+        expression.setter = (expression.setter?.let { fakeOverridesMap[it] } as? IrSimpleFunctionSymbol) ?: expression.setter
+        expression.acceptChildrenVoid(this)
+    }
+
+    override fun visitLocalDelegatedPropertyReference(expression: IrLocalDelegatedPropertyReference) {
+        expression.getter = (fakeOverridesMap[expression.getter] as? IrSimpleFunctionSymbol) ?: expression.getter
+        expression.setter = (expression.setter?.let { fakeOverridesMap[it] } as? IrSimpleFunctionSymbol) ?: expression.setter
+        expression.acceptChildrenVoid(this)
+    }
+}

compiler/ir/backend.common/src/org/jetbrains/kotlin/backend/common/actualizer/IrActualizer.kt

@@ -11,7 +11,7 @@ import org.jetbrains.kotlin.diagnostics.DiagnosticReporter
 import org.jetbrains.kotlin.ir.declarations.*
 import org.jetbrains.kotlin.ir.symbols.IrSymbol
 import org.jetbrains.kotlin.ir.types.IrTypeSystemContext
-import org.jetbrains.kotlin.ir.util.DeepCopyTypeRemapper
+import org.jetbrains.kotlin.ir.util.*
 
 data class IrActualizedResult(val actualizedExpectDeclarations: List<IrDeclaration>)
 
@@ -21,7 +21,12 @@ object IrActualizer {
         dependentFragments: List<IrModuleFragment>,
         diagnosticReporter: DiagnosticReporter,
         typeSystemContext: IrTypeSystemContext,
-        languageVersionSettings: LanguageVersionSettings
+        languageVersionSettings: LanguageVersionSettings,
+        symbolTable: SymbolTable,
+        mangler: KotlinMangler.IrMangler,
+        // TODO: drop this argument in favor of using [IrModuleDescriptor::shouldSeeInternalsOf] in FakeOverrideBuilder KT-61384
+        friendModules: Map<String, List<String>>,
+        useIrFakeOverrideBuilder: Boolean
     ): IrActualizedResult {
         val ktDiagnosticReporter = KtDiagnosticReporterWithImplicitIrBasedContext(diagnosticReporter, languageVersionSettings)
 
@@ -40,18 +45,20 @@ object IrActualizer {
         //      Also, it doesn't remove unactualized expect declarations marked with @OptionalExpectation
         val removedExpectDeclarations = removeExpectDeclarations(dependentFragments, expectActualMap)
 
-        //   3. Actualize expect fake overrides in non-expect classes inside common or multi-platform module.
-        //      It's probably important to run FakeOverridesActualizer before ActualFakeOverridesAdder
-        FakeOverridesActualizer(expectActualMap).apply { dependentFragments.forEach { visitModuleFragment(it) } }
+        if (!useIrFakeOverrideBuilder) {
+            //   3. Actualize expect fake overrides in non-expect classes inside common or multi-platform module.
+            //      It's probably important to run FakeOverridesActualizer before ActualFakeOverridesAdder
+            FakeOverridesActualizer(expectActualMap).apply { dependentFragments.forEach { visitModuleFragment(it) } }
 
-        //   4. Add fake overrides to non-expect classes inside common or multi-platform module,
-        //      taken from these non-expect classes actualized super classes.
-        ActualFakeOverridesAdder(
-            expectActualMap,
-            actualDeclarations.actualClasses,
-            ktDiagnosticReporter,
-            typeSystemContext
-        ).apply { dependentFragments.forEach { visitModuleFragment(it) } }
+            //   4. Add fake overrides to non-expect classes inside common or multi-platform module,
+            //      taken from these non-expect classes actualized super classes.
+            ActualFakeOverridesAdder(
+                expectActualMap,
+                actualDeclarations.actualClasses,
+                ktDiagnosticReporter,
+                typeSystemContext
+            ).apply { dependentFragments.forEach { visitModuleFragment(it) } }
+        }
 
         //   5. Copy and actualize function parameter default values from expect functions
         val symbolRemapper = ActualizerSymbolRemapper(expectActualMap)
@@ -65,6 +72,11 @@ object IrActualizer {
         //   7. Merge dependent fragments into the main one
         mergeIrFragments(mainFragment, dependentFragments)
 
+        if (useIrFakeOverrideBuilder) {
+            //   8. Rebuild fake overrides from stretch, as they could become invalid during actualization
+            FakeOverrideRebuilder(symbolTable, mangler, typeSystemContext, mainFragment, friendModules).rebuildFakeOverrides()
+        }
+
         return IrActualizedResult(removedExpectDeclarations)
     }
 
@@ -98,3 +110,4 @@ object IrActualizer {
         mainFragment.files.addAll(0, dependentFragments.flatMap { it.files })
     }
 }
+

compiler/tests-common-new/tests/org/jetbrains/kotlin/test/backend/ir/IrActualizerAndPluginsFacade.kt

@@ -12,7 +12,9 @@ import org.jetbrains.kotlin.config.LanguageFeature
 import org.jetbrains.kotlin.config.languageVersionSettings
 import org.jetbrains.kotlin.fir.pipeline.applyIrGenerationExtensions
 import org.jetbrains.kotlin.ir.types.IrTypeSystemContextImpl
+import org.jetbrains.kotlin.ir.util.SymbolTable
 import org.jetbrains.kotlin.platform.jvm.isJvm
+import org.jetbrains.kotlin.test.directives.CodegenTestDirectives
 import org.jetbrains.kotlin.test.model.*
 import org.jetbrains.kotlin.test.services.TestServices
 import org.jetbrains.kotlin.test.services.compilerConfigurationProvider
@@ -33,7 +35,11 @@ class IrActualizerAndPluginsFacade(
                 inputArtifact.dependentIrModuleFragments,
                 inputArtifact.diagnosticReporter,
                 typeSystemContext,
-                testServices.compilerConfigurationProvider.getCompilerConfiguration(module).languageVersionSettings
+                testServices.compilerConfigurationProvider.getCompilerConfiguration(module).languageVersionSettings,
+                inputArtifact.irPluginContext.symbolTable as SymbolTable, // TODO: it's strange place to get it.
+                inputArtifact.irMangler,
+                mapOf(module.name to module.friendDependencies.map { it.moduleName }),
+                useIrFakeOverrideBuilder = false,
             )
             inputArtifact.irActualizerResult = result
         }

compiler/tests-common-new/tests/org/jetbrains/kotlin/test/frontend/fir/Fir2IrJsResultsConverter.kt

@@ -34,6 +34,7 @@ import org.jetbrains.kotlin.ir.backend.js.incrementalDataProvider
 import org.jetbrains.kotlin.ir.backend.js.lower.serialization.ir.JsManglerDesc
 import org.jetbrains.kotlin.ir.backend.js.lower.serialization.ir.JsManglerIr
 import org.jetbrains.kotlin.ir.declarations.IrModuleFragment
+import org.jetbrains.kotlin.ir.types.IrTypeSystemContextImpl
 import org.jetbrains.kotlin.library.metadata.resolver.KotlinResolvedLibrary
 import org.jetbrains.kotlin.library.unresolvedDependencies
 import org.jetbrains.kotlin.storage.LockBasedStorageManager
@@ -180,7 +181,8 @@ fun ModuleCompilerAnalyzedOutput.convertToJsIr(
         irBuiltIns,
         JsManglerIr,
         Fir2IrVisibilityConverter.Default,
-        builtIns ?: DefaultBuiltIns.Instance // TODO: consider passing externally,
+        builtIns ?: DefaultBuiltIns.Instance, // TODO: consider passing externally,
+        ::IrTypeSystemContextImpl
     ).also {
         (it.irModuleFragment.descriptor as? FirModuleDescriptor)?.let { it.allDependencyModules = dependencies }
     }

compiler/tests-common-new/tests/org/jetbrains/kotlin/test/frontend/fir/Fir2IrJvmResultsConverter.kt

@@ -7,6 +7,7 @@ package org.jetbrains.kotlin.test.frontend.fir
 
 import org.jetbrains.kotlin.backend.jvm.JvmIrCodegenFactory
 import org.jetbrains.kotlin.backend.jvm.JvmIrDeserializerImpl
+import org.jetbrains.kotlin.backend.jvm.JvmIrTypeSystemContext
 import org.jetbrains.kotlin.builtins.DefaultBuiltIns
 import org.jetbrains.kotlin.cli.common.CLIConfigurationKeys
 import org.jetbrains.kotlin.cli.jvm.compiler.NoScopeRecordCliBindingTrace
@@ -113,8 +114,9 @@ class Fir2IrJvmResultsConverter(
                 irBuiltIns,
                 irMangler,
                 FirJvmVisibilityConverter,
-                DefaultBuiltIns.Instance
-            )
+                DefaultBuiltIns.Instance,
+                typeContextProvider = ::JvmIrTypeSystemContext,
+                )
             irBuiltIns = components.irBuiltIns
 
             if (index < inputArtifact.partsForDependsOnModules.size - 1) {

compiler/tests-common-new/tests/org/jetbrains/kotlin/test/frontend/fir/Fir2IrWasmResultsConverter.kt

@@ -34,6 +34,7 @@ import org.jetbrains.kotlin.ir.backend.js.incrementalDataProvider
 import org.jetbrains.kotlin.ir.backend.js.lower.serialization.ir.JsManglerDesc
 import org.jetbrains.kotlin.ir.backend.js.lower.serialization.ir.JsManglerIr
 import org.jetbrains.kotlin.ir.declarations.IrModuleFragment
+import org.jetbrains.kotlin.ir.types.IrTypeSystemContextImpl
 import org.jetbrains.kotlin.library.metadata.resolver.KotlinResolvedLibrary
 import org.jetbrains.kotlin.library.unresolvedDependencies
 import org.jetbrains.kotlin.storage.LockBasedStorageManager
@@ -176,7 +177,8 @@ fun ModuleCompilerAnalyzedOutput.convertToWasmIr(
         irBuiltIns,
         JsManglerIr,
         Fir2IrVisibilityConverter.Default,
-        builtIns ?: DefaultBuiltIns.Instance // TODO: consider passing externally,
+        builtIns ?: DefaultBuiltIns.Instance, // TODO: consider passing externally
+        typeContextProvider = ::IrTypeSystemContextImpl,
     ).also {
         (it.irModuleFragment.descriptor as? FirModuleDescriptor)?.let { it.allDependencyModules = dependencies }
     }

compiler/tests-compiler-utils/tests/org/jetbrains/kotlin/codegen/GenerationUtils.kt

@@ -15,6 +15,7 @@ import org.jetbrains.kotlin.analyzer.AnalysisResult
 import org.jetbrains.kotlin.asJava.finder.JavaElementFinder
 import org.jetbrains.kotlin.backend.jvm.JvmIrCodegenFactory
 import org.jetbrains.kotlin.backend.jvm.JvmIrDeserializerImpl
+import org.jetbrains.kotlin.backend.jvm.JvmIrTypeSystemContext
 import org.jetbrains.kotlin.builtins.DefaultBuiltIns
 import org.jetbrains.kotlin.cli.common.CLIConfigurationKeys
 import org.jetbrains.kotlin.cli.common.messages.CompilerMessageSeverity
@@ -149,7 +150,8 @@ object GenerationUtils {
             irBuiltIns = null,
             JvmIrMangler,
             FirJvmVisibilityConverter,
-            DefaultBuiltIns.Instance
+            DefaultBuiltIns.Instance,
+            ::JvmIrTypeSystemContext
         )
         val dummyBindingContext = NoScopeRecordCliBindingTrace().bindingContext