[FIR] Use toFirRegularClassSymbol instead of toFirRegular in checkers

compiler/fir/checkers/checkers.jvm/src/org/jetbrains/kotlin/fir/analysis/jvm/FirJvmOverridesBackwardCompatibilityHelper.kt

@@ -20,7 +20,7 @@ import org.jetbrains.kotlin.fir.declarations.utils.isFinal
 import org.jetbrains.kotlin.fir.declarations.utils.isInterface
 import org.jetbrains.kotlin.fir.dispatchReceiverTypeOrNull
 import org.jetbrains.kotlin.fir.originalOrSelf
-import org.jetbrains.kotlin.fir.resolve.toFirRegularClass
+import org.jetbrains.kotlin.fir.resolve.toFirRegularClassSymbol
 import org.jetbrains.kotlin.fir.scopes.getDirectOverriddenFunctions
 import org.jetbrains.kotlin.fir.scopes.getDirectOverriddenProperties
 import org.jetbrains.kotlin.fir.symbols.SymbolInternals
@@ -77,9 +77,9 @@ object FirJvmOverridesBackwardCompatibilityHelper : FirOverridesBackwardCompatib
         if (JavaToKotlinClassMap.mapKotlinToJava(containingClassName) != null) {
             return true
         }
-        
+
         if (!originalMember.isAbstract) {
-            val containingClass = originalMember.containingClass()?.toFirRegularClass(context.session)
+            val containingClass = originalMember.containingClass()?.toFirRegularClassSymbol(context.session)
             if (containingClass?.isInterface == false) {
                 return false
             }

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

@@ -22,12 +22,12 @@ import org.jetbrains.kotlin.fir.declarations.utils.isInterface
 import org.jetbrains.kotlin.fir.declarations.utils.modality
 import org.jetbrains.kotlin.fir.expressions.FirAnnotationCall
 import org.jetbrains.kotlin.fir.java.jvmDefaultModeState
-import org.jetbrains.kotlin.fir.resolve.toFirRegularClass
 import org.jetbrains.kotlin.fir.resolve.toSymbol
 import org.jetbrains.kotlin.fir.scopes.getDirectOverriddenFunctions
 import org.jetbrains.kotlin.fir.scopes.impl.FirClassUseSiteMemberScope
 import org.jetbrains.kotlin.fir.symbols.impl.FirCallableSymbol
 import org.jetbrains.kotlin.fir.symbols.impl.FirIntersectionCallableSymbol
+import org.jetbrains.kotlin.fir.resolve.toFirRegularClassSymbol
 import org.jetbrains.kotlin.name.JvmNames.JVM_DEFAULT_CLASS_ID
 import org.jetbrains.kotlin.name.JvmNames.JVM_DEFAULT_NO_COMPATIBILITY_CLASS_ID
 

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

@@ -21,7 +21,7 @@ import org.jetbrains.kotlin.fir.declarations.utils.isExternal
 import org.jetbrains.kotlin.fir.declarations.utils.isInline
 import org.jetbrains.kotlin.fir.declarations.utils.isInterface
 import org.jetbrains.kotlin.fir.declarations.utils.modality
-import org.jetbrains.kotlin.fir.resolve.toFirRegularClass
+import org.jetbrains.kotlin.fir.resolve.toFirRegularClassSymbol
 import org.jetbrains.kotlin.lexer.KtTokens
 
 object FirJvmExternalDeclarationChecker : FirBasicDeclarationChecker() {
@@ -62,7 +62,7 @@ object FirJvmExternalDeclarationChecker : FirBasicDeclarationChecker() {
             return
         }
 
-        val containingClassSymbol = declaration.symbol.containingClass()?.toFirRegularClass(context.session)
+        val containingClassSymbol = declaration.symbol.containingClass()?.toFirRegularClassSymbol(context.session)
         if (containingClassSymbol != null) {
             if (containingClassSymbol.isInterface) {
                 reporter.reportOn(declaration.source, FirJvmErrors.EXTERNAL_DECLARATION_IN_INTERFACE, context)

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

@@ -14,15 +14,19 @@ import org.jetbrains.kotlin.descriptors.Modality
 import org.jetbrains.kotlin.descriptors.Visibilities
 import org.jetbrains.kotlin.fir.FirFakeSourceElementKind
 import org.jetbrains.kotlin.fir.FirSession
+import org.jetbrains.kotlin.fir.analysis.checkers.classKind
 import org.jetbrains.kotlin.fir.analysis.checkers.context.CheckerContext
 import org.jetbrains.kotlin.fir.analysis.checkers.context.findClosest
 import org.jetbrains.kotlin.fir.analysis.checkers.declaration.FirPropertyChecker
+import org.jetbrains.kotlin.fir.analysis.checkers.getContainingDeclarationSymbol
 import org.jetbrains.kotlin.fir.analysis.checkers.toRegularClassSymbol
 import org.jetbrains.kotlin.fir.analysis.diagnostics.DiagnosticReporter
 import org.jetbrains.kotlin.fir.analysis.diagnostics.jvm.FirJvmErrors
 import org.jetbrains.kotlin.fir.analysis.diagnostics.reportOn
 import org.jetbrains.kotlin.fir.containingClass
-import org.jetbrains.kotlin.fir.declarations.*
+import org.jetbrains.kotlin.fir.declarations.FirFile
+import org.jetbrains.kotlin.fir.declarations.FirProperty
+import org.jetbrains.kotlin.fir.declarations.getAnnotationByClassId
 import org.jetbrains.kotlin.fir.declarations.utils.*
 import org.jetbrains.kotlin.fir.languageVersionSettings
 import org.jetbrains.kotlin.fir.references.FirResolvedNamedReference
@@ -31,22 +35,18 @@ import org.jetbrains.kotlin.fir.symbols.impl.FirPropertySymbol
 import org.jetbrains.kotlin.fir.symbols.impl.FirRegularClassSymbol
 import org.jetbrains.kotlin.fir.types.FirTypeRef
 import org.jetbrains.kotlin.fir.types.coneType
-import org.jetbrains.kotlin.JvmFieldApplicabilityProblem.*
 import org.jetbrains.kotlin.load.java.JvmAbi.JVM_FIELD_ANNOTATION_CLASS_ID
-import org.jetbrains.kotlin.JvmNames.JVM_MULTIFILE_CLASS_SHORT
-import org.jetbrains.kotlin.fir.analysis.checkers.getContainingDeclarationSymbol
-import org.jetbrains.kotlin.psi.stubs.elements.KtParameterElementType
 
 object FirJvmFieldApplicabilityChecker : FirPropertyChecker() {
     override fun check(declaration: FirProperty, context: CheckerContext, reporter: DiagnosticReporter) {
         val annotation = declaration.getAnnotationByClassId(JVM_FIELD_ANNOTATION_CLASS_ID) ?: return
         val session = context.session
-        val containingClass = declaration.containingClass()?.toFirRegularClass(session)
+        val containingClassSymbol = declaration.containingClass()?.toFirRegularClassSymbol(session)
 
         val problem = when {
             declaration.delegate != null -> DELEGATE
             !declaration.hasBackingField -> return
-            declaration.isOverridable(containingClass) -> NOT_FINAL
+            declaration.isOverridable(containingClassSymbol) -> NOT_FINAL
             Visibilities.isPrivate(declaration.visibility) -> PRIVATE
             declaration.hasCustomAccessor() -> CUSTOM_ACCESSOR
             declaration.isOverride -> OVERRIDES
@@ -63,7 +63,7 @@ object FirJvmFieldApplicabilityChecker : FirPropertyChecker() {
                     }
                 }
             }
-            containingClass == null && isInsideJvmMultifileClassFile(context) ->
+            containingClassSymbol == null && isInsideJvmMultifileClassFile(context) ->
                 TOP_LEVEL_PROPERTY_OF_MULTIFILE_FACADE
             declaration.returnTypeRef.isInlineClassThatRequiresMangling(session) -> RETURN_TYPE_IS_INLINE_CLASS
             else -> return
@@ -89,7 +89,7 @@ object FirJvmFieldApplicabilityChecker : FirPropertyChecker() {
         return this.classId.relativeClassName.asString() == StandardNames.RESULT_FQ_NAME.asString()
     }
 
-    private fun FirProperty.isOverridable(containingClass: FirRegularClass?): Boolean {
+    private fun FirProperty.isOverridable(containingClass: FirRegularClassSymbol?): Boolean {
         return visibility != Visibilities.Private && modality != Modality.FINAL &&
                 containingClass?.isFinal != true
     }
@@ -104,7 +104,7 @@ object FirJvmFieldApplicabilityChecker : FirPropertyChecker() {
             return false
         }
 
-        val outerClassKind = (getContainingDeclarationSymbol(session) as? FirRegularClass)?.classKind
+        val outerClassKind = getContainingDeclarationSymbol(session)?.classKind
         return outerClassKind == ClassKind.INTERFACE || outerClassKind == ClassKind.ANNOTATION_CLASS
     }
 

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

@@ -21,11 +21,8 @@ import org.jetbrains.kotlin.fir.expressions.FirFunctionCall
 import org.jetbrains.kotlin.fir.expressions.FirVariableAssignment
 import org.jetbrains.kotlin.fir.expressions.impl.FirEmptyExpressionBlock
 import org.jetbrains.kotlin.fir.expressions.toResolvedCallableSymbol
-import org.jetbrains.kotlin.fir.resolve.SessionHolder
-import org.jetbrains.kotlin.fir.resolve.fullyExpandedType
+import org.jetbrains.kotlin.fir.resolve.*
 import org.jetbrains.kotlin.fir.resolve.inference.isBuiltinFunctionalType
-import org.jetbrains.kotlin.fir.resolve.symbolProvider
-import org.jetbrains.kotlin.fir.resolve.toSymbol
 import org.jetbrains.kotlin.fir.scopes.FirTypeScope
 import org.jetbrains.kotlin.fir.scopes.ProcessorAction
 import org.jetbrains.kotlin.fir.scopes.impl.multipleDelegatesWithTheSameSignature
@@ -135,6 +132,21 @@ fun FirClassLikeSymbol<*>.outerClassSymbol(context: CheckerContext): FirClassLik
     return context.session.symbolProvider.getClassLikeSymbolByClassId(outerClassId)
 }
 
+@OptIn(SymbolInternals::class)
+fun FirClassSymbol<*>.getContainingDeclarationSymbol(session: FirSession): FirClassLikeSymbol<*>? {
+    if (isLocal) {
+        return (this as FirRegularClassSymbol).fir.containingClassForLocalAttr?.toFirRegularClassSymbol(session)
+    } else {
+        val parentId = classId.relativeClassName.parent()
+        if (!parentId.isRoot) {
+            val containingDeclarationId = ClassId(classId.packageFqName, parentId, false)
+            return session.symbolProvider.getClassLikeSymbolByClassId(containingDeclarationId)
+        }
+    }
+
+    return null
+}
+
 /**
  * Returns the FirClassLikeDeclaration that the
  * sequence of FirTypeAlias'es points to starting
@@ -171,7 +183,7 @@ fun CheckerContext.findClosestClassOrObject(): FirClass? {
  * Returns the list of functions that overridden by given
  */
 fun FirSimpleFunction.overriddenFunctions(
-    containingClass: FirClass,
+    containingClass: FirClassSymbol<*>,
     context: CheckerContext
 ): List<FirFunctionSymbol<*>> {
     val firTypeScope = containingClass.unsubstitutedScope(

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

@@ -28,7 +28,7 @@ import org.jetbrains.kotlin.fir.analysis.diagnostics.reportOn
 import org.jetbrains.kotlin.fir.containingClass
 import org.jetbrains.kotlin.fir.declarations.FirSimpleFunction
 import org.jetbrains.kotlin.fir.declarations.utils.isOperator
-import org.jetbrains.kotlin.fir.resolve.toFirRegularClass
+import org.jetbrains.kotlin.fir.resolve.toFirRegularClassSymbol
 import org.jetbrains.kotlin.fir.symbols.impl.ConeClassLikeLookupTagImpl
 import org.jetbrains.kotlin.fir.typeContext
 import org.jetbrains.kotlin.fir.types.*
@@ -62,7 +62,7 @@ object FirOperatorModifierChecker : FirSimpleFunctionChecker() {
         if (!declaration.isOperator) return
         //we are not interested in implicit operators from override
         if (!declaration.hasModifier(KtTokens.OPERATOR_KEYWORD)) return
-        
+
         val checks = OperatorFunctionChecks.checksByName.getOrElse(declaration.name) {
             OperatorFunctionChecks.regexChecks.find { it.first.matches(declaration.name.asString()) }?.second
         }
@@ -185,8 +185,8 @@ private object OperatorFunctionChecks {
             EQUALS,
             member,
             Checks.full("must override ''equals()'' in Any") { ctx, function ->
-                val containingClass = function.containingClass()?.toFirRegularClass(ctx.session) ?: return@full true
-                function.overriddenFunctions(containingClass, ctx).any {
+                val containingClassSymbol = function.containingClass()?.toFirRegularClassSymbol(ctx.session) ?: return@full true
+                function.overriddenFunctions(containingClassSymbol, ctx).any {
                     it.containingClass()?.classId?.asSingleFqName() == StandardNames.FqNames.any.toSafe()
                 }
             }

compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/expression/FirEqualityCompatibilityChecker.kt

@@ -19,7 +19,7 @@ import org.jetbrains.kotlin.fir.expressions.FirEqualityOperatorCall
 import org.jetbrains.kotlin.fir.expressions.FirOperation
 import org.jetbrains.kotlin.fir.render
 import org.jetbrains.kotlin.fir.resolve.inference.inferenceComponents
-import org.jetbrains.kotlin.fir.resolve.toFirRegularClass
+ import org.jetbrains.kotlin.fir.resolve.toFirRegularClassSymbol
 import org.jetbrains.kotlin.fir.typeContext
 import org.jetbrains.kotlin.fir.types.*
 
@@ -106,8 +106,8 @@ object FirEqualityCompatibilityChecker : FirEqualityOperatorCallChecker() {
         context: CheckerContext
     ): Boolean {
         if (isEnum) return true
-        val firRegularClass = (this as? ConeClassLikeType)?.lookupTag?.toFirRegularClass(context.session) ?: return false
-        return firRegularClass.isEnumClass
+        val firRegularClassSymbol = (this as? ConeClassLikeType)?.lookupTag?.toFirRegularClassSymbol(context.session) ?: return false
+        return firRegularClassSymbol.isEnumClass
     }
 
     private fun checkSensibleness(

compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/expression/FirOptInUsageBaseChecker.kt

@@ -22,7 +22,7 @@ import org.jetbrains.kotlin.fir.expressions.FirConstExpression
 import org.jetbrains.kotlin.fir.expressions.FirQualifiedAccessExpression
 import org.jetbrains.kotlin.fir.references.FirResolvedNamedReference
 import org.jetbrains.kotlin.fir.resolve.fullyExpandedType
-import org.jetbrains.kotlin.fir.resolve.toFirRegularClass
+import org.jetbrains.kotlin.fir.resolve.toFirRegularClassSymbol
 import org.jetbrains.kotlin.fir.resolve.toSymbol
 import org.jetbrains.kotlin.fir.scopes.ProcessorAction
 import org.jetbrains.kotlin.fir.scopes.processDirectlyOverriddenFunctions
@@ -132,7 +132,7 @@ object FirOptInUsageBaseChecker {
             val annotationType = annotation.annotationTypeRef.coneTypeSafe<ConeClassLikeType>()
             if (annotation.useSiteTarget != AnnotationUseSiteTarget.PROPERTY_SETTER || fromSetter) {
                 result.addIfNotNull(
-                    annotationType?.lookupTag?.toFirRegularClass(
+                    annotationType?.lookupTag?.toFirRegularClassSymbol(
                         session
                     )?.loadExperimentalityForMarkerAnnotation()
                 )

compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/expression/FirSuspendCallChecker.kt

@@ -15,13 +15,15 @@ import org.jetbrains.kotlin.fir.analysis.diagnostics.reportOn
 import org.jetbrains.kotlin.fir.analysis.getChild
 import org.jetbrains.kotlin.fir.declarations.*
 import org.jetbrains.kotlin.fir.declarations.utils.isSuspend
+import org.jetbrains.kotlin.fir.declarations.utils.superConeTypes
 import org.jetbrains.kotlin.fir.expressions.*
 import org.jetbrains.kotlin.fir.expressions.impl.FirNoReceiverExpression
 import org.jetbrains.kotlin.fir.references.FirResolvedCallableReference
 import org.jetbrains.kotlin.fir.references.FirResolvedNamedReference
 import org.jetbrains.kotlin.fir.resolve.fullyExpandedType
 import org.jetbrains.kotlin.fir.resolve.inference.isSuspendFunctionType
-import org.jetbrains.kotlin.fir.resolve.toFirRegularClass
+import org.jetbrains.kotlin.fir.resolve.toFirRegularClassSymbol
+import org.jetbrains.kotlin.fir.symbols.FirBasedSymbol
 import org.jetbrains.kotlin.fir.symbols.impl.FirCallableSymbol
 import org.jetbrains.kotlin.fir.symbols.impl.FirNamedFunctionSymbol
 import org.jetbrains.kotlin.fir.symbols.impl.FirPropertySymbol
@@ -145,25 +147,25 @@ object FirSuspendCallChecker : FirQualifiedAccessExpressionChecker() {
         context: CheckerContext
     ): Boolean {
         val session = context.session
-        val enclosingSuspendFunctionDispatchReceiverOwner =
-            (enclosingSuspendFunction.dispatchReceiverType as? ConeClassLikeType)?.lookupTag?.toFirRegularClass(session)
-        val enclosingSuspendFunctionExtensionReceiverOwner = enclosingSuspendFunction.takeIf { it.receiverTypeRef != null }
+        val enclosingSuspendFunctionDispatchReceiverOwnerSymbol =
+            (enclosingSuspendFunction.dispatchReceiverType as? ConeClassLikeType)?.lookupTag?.toFirRegularClassSymbol(session)
+        val enclosingSuspendFunctionExtensionReceiverOwnerSymbol = enclosingSuspendFunction.takeIf { it.receiverTypeRef != null }?.symbol
         val dispatchReceiverExpression = expression.dispatchReceiver.takeIf { it !is FirNoReceiverExpression }
         val extensionReceiverExpression = expression.extensionReceiver.takeIf { it !is FirNoReceiverExpression }
         for (receiverExpression in listOfNotNull(dispatchReceiverExpression, extensionReceiverExpression)) {
             if (!receiverExpression.typeRef.coneType.isRestrictSuspensionReceiver(session)) continue
-            if (sameInstanceOfReceiver(receiverExpression, enclosingSuspendFunctionDispatchReceiverOwner)) continue
-            if (sameInstanceOfReceiver(receiverExpression, enclosingSuspendFunctionExtensionReceiverOwner)) continue
+            if (sameInstanceOfReceiver(receiverExpression, enclosingSuspendFunctionDispatchReceiverOwnerSymbol)) continue
+            if (sameInstanceOfReceiver(receiverExpression, enclosingSuspendFunctionExtensionReceiverOwnerSymbol)) continue
 
             return false
         }
-        if (enclosingSuspendFunctionExtensionReceiverOwner?.receiverTypeRef?.coneType?.isRestrictSuspensionReceiver(session) != true) {
+        if (enclosingSuspendFunctionExtensionReceiverOwnerSymbol?.resolvedReceiverTypeRef?.coneType?.isRestrictSuspensionReceiver(session) != true) {
             return true
         }
-        if (sameInstanceOfReceiver(dispatchReceiverExpression, enclosingSuspendFunctionExtensionReceiverOwner)) {
+        if (sameInstanceOfReceiver(dispatchReceiverExpression, enclosingSuspendFunctionExtensionReceiverOwnerSymbol)) {
             return true
         }
-        if (sameInstanceOfReceiver(extensionReceiverExpression, enclosingSuspendFunctionExtensionReceiverOwner)) {
+        if (sameInstanceOfReceiver(extensionReceiverExpression, enclosingSuspendFunctionExtensionReceiverOwnerSymbol)) {
             if (calledDeclarationSymbol.resolvedReceiverTypeRef?.coneType?.isRestrictSuspensionReceiver(session) == true) {
                 return true
             }
@@ -174,11 +176,11 @@ object FirSuspendCallChecker : FirQualifiedAccessExpressionChecker() {
     private fun ConeKotlinType.isRestrictSuspensionReceiver(session: FirSession): Boolean {
         when (this) {
             is ConeClassLikeType -> {
-                val regularClass = fullyExpandedType(session).lookupTag.toFirRegularClass(session) ?: return false
-                if (regularClass.hasAnnotation(RESTRICTS_SUSPENSION_CLASS_ID)) {
+                val regularClassSymbol = fullyExpandedType(session).lookupTag.toFirRegularClassSymbol(session) ?: return false
+                if (regularClassSymbol.getAnnotationByClassId(RESTRICTS_SUSPENSION_CLASS_ID) != null) {
                     return true
                 }
-                return regularClass.superTypeRefs.any { it.coneType.isRestrictSuspensionReceiver(session) }
+                return regularClassSymbol.superConeTypes.any { it.isRestrictSuspensionReceiver(session) }
             }
             is ConeTypeParameterType -> {
                 return lookupTag.typeParameterSymbol.resolvedBounds.any { it.coneType.isRestrictSuspensionReceiver(session) }
@@ -187,10 +189,13 @@ object FirSuspendCallChecker : FirQualifiedAccessExpressionChecker() {
         }
     }
 
-    private fun sameInstanceOfReceiver(useSiteReceiverExpression: FirExpression?, declarationSiteReceiverOwner: FirDeclaration?): Boolean {
-        if (declarationSiteReceiverOwner == null || useSiteReceiverExpression == null) return false
+    private fun sameInstanceOfReceiver(
+        useSiteReceiverExpression: FirExpression?,
+        declarationSiteReceiverOwnerSymbol: FirBasedSymbol<*>?
+    ): Boolean {
+        if (declarationSiteReceiverOwnerSymbol == null || useSiteReceiverExpression == null) return false
         if (useSiteReceiverExpression is FirThisReceiverExpression) {
-            return useSiteReceiverExpression.calleeReference.boundSymbol == declarationSiteReceiverOwner.symbol
+            return useSiteReceiverExpression.calleeReference.boundSymbol == declarationSiteReceiverOwnerSymbol
         }
         return false
     }

compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/extended/RedundantVisibilityModifierSyntaxChecker.kt

@@ -95,8 +95,8 @@ object RedundantVisibilityModifierSyntaxChecker : FirDeclarationSyntaxChecker<Fi
     }
 
     private fun findFunctionVisibility(function: FirSimpleFunction, context: CheckerContext): Visibility {
-        val currentClass = context.findClosestClassOrObject() ?: return Visibilities.Unknown
-        val overriddenFunctions = function.overriddenFunctions(currentClass, context)
+        val currentClassSymbol = context.findClosestClassOrObject()?.symbol ?: return Visibilities.Unknown
+        val overriddenFunctions = function.overriddenFunctions(currentClassSymbol, context)
         var visibility: Visibility = Visibilities.Private
         for (func in overriddenFunctions) {
             val currentVisibility = func.visibility

compiler/fir/fir2ir/jvm-backend/src/org/jetbrains/kotlin/fir/backend/jvm/FirJvmSerializerExtension.kt

@@ -21,7 +21,7 @@ import org.jetbrains.kotlin.fir.expressions.FirAnnotationCall
 import org.jetbrains.kotlin.fir.render
 import org.jetbrains.kotlin.fir.resolve.firProvider
 import org.jetbrains.kotlin.fir.resolve.inference.isBuiltinFunctionalType
-import org.jetbrains.kotlin.fir.resolve.toFirRegularClass
+import org.jetbrains.kotlin.fir.resolve.toFirRegularClassSymbol
 import org.jetbrains.kotlin.fir.serialization.FirElementSerializer
 import org.jetbrains.kotlin.fir.serialization.FirSerializerExtension
 import org.jetbrains.kotlin.fir.types.*
@@ -260,14 +260,14 @@ class FirJvmSerializerExtension(
     private fun FirProperty.isJvmFieldPropertyInInterfaceCompanion(): Boolean {
         if (!hasJvmFieldAnnotation) return false
 
-        val container = (dispatchReceiverType as? ConeClassLikeType)?.lookupTag?.toFirRegularClass(session)
+        val containerSymbol = (dispatchReceiverType as? ConeClassLikeType)?.lookupTag?.toFirRegularClassSymbol(session)
         // Note: companions are anyway forbidden in local classes
-        if (container == null || !container.isCompanion || container.isLocal) {
+        if (containerSymbol == null || !containerSymbol.isCompanion || containerSymbol.isLocal) {
             return false
         }
 
         val grandParent =
-            container.classId.outerClassId?.let {
+            containerSymbol.classId.outerClassId?.let {
                 session.firProvider.getFirClassifierByFqName(it) as? FirRegularClass
             }
         return grandParent != null &&

compiler/fir/java/src/org/jetbrains/kotlin/fir/java/JavaTypeConversion.kt

@@ -13,9 +13,10 @@ import org.jetbrains.kotlin.fir.diagnostics.ConeIntermediateDiagnostic
 import org.jetbrains.kotlin.fir.diagnostics.ConeSimpleDiagnostic
 import org.jetbrains.kotlin.fir.diagnostics.DiagnosticKind
 import org.jetbrains.kotlin.fir.java.enhancement.readOnlyToMutable
-import org.jetbrains.kotlin.fir.resolve.toFirRegularClass
+import org.jetbrains.kotlin.fir.resolve.toFirRegularClassSymbol
 import org.jetbrains.kotlin.fir.symbols.ConeClassLikeLookupTag
 import org.jetbrains.kotlin.fir.symbols.impl.ConeClassLikeLookupTagImpl
+import org.jetbrains.kotlin.fir.symbols.impl.FirTypeParameterSymbol
 import org.jetbrains.kotlin.fir.typeContext
 import org.jetbrains.kotlin.fir.types.*
 import org.jetbrains.kotlin.fir.types.builder.buildResolvedTypeRef
@@ -166,19 +167,19 @@ private fun JavaClassifierType.toConeKotlinTypeForFlexibleBound(
             // When converting type parameter bounds we should not attempt to load any classes, as this may trigger
             // enhancement of type parameter bounds on some other class that depends on this one. Also, in case of raw
             // types specifically there could be an infinite recursion on the type parameter itself.
-            val typeParameters = lookupTag.takeIf { mode != FirJavaTypeConversionMode.TYPE_PARAMETER_BOUND }
-                ?.toFirRegularClass(session)?.typeParameters
+            val typeParameterSymbols = lookupTag.takeIf { mode != FirJavaTypeConversionMode.TYPE_PARAMETER_BOUND }
+                ?.toFirRegularClassSymbol(session)?.typeParameterSymbols
             val mappedTypeArguments = when {
                 isRaw ->
                     // Given `C<T : X>`, `C` -> `C<X>..C<*>?`.
-                    typeParameters.takeIf { lowerBound == null }?.eraseToUpperBounds(session)
+                    typeParameterSymbols.takeIf { lowerBound == null }?.eraseToUpperBounds(session)
                         ?: Array(classifier.typeParameters.size) { ConeStarProjection }
                 lookupTag != lowerBound?.lookupTag ->
                     Array(typeArguments.size) { index ->
                         // TODO: check this
                         val newMode = if (mode == FirJavaTypeConversionMode.ANNOTATION_MEMBER) FirJavaTypeConversionMode.DEFAULT else mode
                         val argument = typeArguments[index]
-                        val variance = typeParameters?.getOrNull(index)?.symbol?.fir?.variance ?: Variance.INVARIANT
+                        val variance = typeParameterSymbols?.getOrNull(index)?.fir?.variance ?: Variance.INVARIANT
                         argument.toConeTypeProjection(session, javaTypeParameterStack, variance, newMode)
                     }
                 else -> lowerBound.typeArguments
@@ -211,15 +212,15 @@ private fun JavaClassifierType.argumentsMakeSenseOnlyForMutableContainer(
 
     if (!typeArguments.lastOrNull().isSuperWildcard()) return false
     val mutableLastParameterVariance =
-        mutableClassId.toLookupTag().toFirRegularClass(session)?.typeParameters?.lastOrNull()?.symbol?.fir?.variance
+        mutableClassId.toLookupTag().toFirRegularClassSymbol(session)?.typeParameterSymbols?.lastOrNull()?.variance
             ?: return false
 
     return mutableLastParameterVariance != Variance.OUT_VARIANCE
 }
 
-private fun List<FirTypeParameterRef>.eraseToUpperBounds(session: FirSession): Array<ConeTypeProjection> {
+private fun List<FirTypeParameterSymbol>.eraseToUpperBounds(session: FirSession): Array<ConeTypeProjection> {
     val cache = mutableMapOf<FirTypeParameter, ConeKotlinType>()
-    return Array(size) { index -> this[index].symbol.fir.eraseToUpperBound(session, cache) }
+    return Array(size) { index -> this[index].fir.eraseToUpperBound(session, cache) }
 }
 
 private fun FirTypeParameter.eraseToUpperBound(session: FirSession, cache: MutableMap<FirTypeParameter, ConeKotlinType>): ConeKotlinType {

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/LookupTagUtils.kt

@@ -39,15 +39,19 @@ fun ConeClassLikeLookupTag.toSymbolOrError(useSiteSession: FirSession): FirClass
     toSymbol(useSiteSession)
         ?: error("Class symbol with classId $classId was not found")
 
-
-fun ConeClassLikeLookupTag.toFirRegularClass(session: FirSession): FirRegularClass? =
-    session.symbolProvider.getSymbolByLookupTag(this)?.fir as? FirRegularClass
+@OptIn(LookupTagInternals::class)
+fun ConeClassLikeLookupTag.toFirRegularClassSymbol(session: FirSession): FirRegularClassSymbol? =
+    session.symbolProvider.getSymbolByLookupTag(this) as? FirRegularClassSymbol
 
 @OptIn(LookupTagInternals::class)
 fun ConeClassLikeLookupTagImpl.bindSymbolToLookupTag(session: FirSession, symbol: FirClassLikeSymbol<*>?) {
     boundSymbol = WeakPair(session, symbol)
 }
 
+@LookupTagInternals
+fun ConeClassLikeLookupTag.toFirRegularClass(session: FirSession): FirRegularClass? =
+    session.symbolProvider.getSymbolByLookupTag(this)?.fir as? FirRegularClass
+
 fun FirSymbolProvider.getSymbolByLookupTag(lookupTag: ConeClassifierLookupTag): FirClassifierSymbol<*>? {
     return lookupTag.toSymbol(session)
 }

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/ResolveUtils.kt

@@ -505,6 +505,7 @@ fun FirRegularClass.getActualTypeParametersCount(session: FirSession): Int {
 
 fun FirClassLikeDeclaration.getContainingDeclaration(session: FirSession): FirClassLikeDeclaration? {
     if (isLocal) {
+        @OptIn(LookupTagInternals::class)
         return (this as? FirRegularClass)?.containingClassForLocalAttr?.toFirRegularClass(session)
     } else {
         val classId = symbol.classId

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/SamResolution.kt

@@ -69,6 +69,7 @@ class FirSamResolverImpl(
     }
 
     private fun getFunctionTypeForPossibleSamType(type: ConeClassLikeType): ConeLookupTagBasedType? {
+        @OptIn(LookupTagInternals::class)
         val firRegularClass = type.lookupTag.toFirRegularClass(session) ?: return null
 
         val unsubstitutedFunctionType = resolveFunctionTypeIfSamInterface(firRegularClass) ?: return null

compiler/visualizer/render-fir/src/org/jetbrains/kotlin/compiler/visualizer/FirVisualizer.kt

@@ -16,7 +16,7 @@ import org.jetbrains.kotlin.fir.expressions.impl.FirNoReceiverExpression
 import org.jetbrains.kotlin.fir.references.*
 import org.jetbrains.kotlin.fir.resolve.defaultType
 import org.jetbrains.kotlin.fir.resolve.fullyExpandedType
-import org.jetbrains.kotlin.fir.resolve.toFirRegularClass
+import org.jetbrains.kotlin.fir.resolve.toFirRegularClassSymbol
 import org.jetbrains.kotlin.fir.resolve.transformers.body.resolve.firUnsafe
 import org.jetbrains.kotlin.fir.scopes.impl.delegatedWrapperData
 import org.jetbrains.kotlin.fir.symbols.FirBasedSymbol
@@ -844,7 +844,7 @@ class FirVisualizer(private val firFile: FirFile) : BaseRenderer() {
             return when (val fir = this.fir) {
                 is FirConstructor -> fir.returnTypeRef.coneType.isLocal()
                 is FirCallableDeclaration -> {
-                    fir.dispatchReceiverClassOrNull()?.toFirRegularClass(session)?.isLocal ?: false
+                    fir.dispatchReceiverClassOrNull()?.toFirRegularClassSymbol(session)?.isLocal ?: false
                 }
                 else -> false
             }
@@ -852,7 +852,7 @@ class FirVisualizer(private val firFile: FirFile) : BaseRenderer() {
 
         private fun ConeKotlinType.isLocal(): Boolean {
             if (this !is ConeClassLikeType) return false
-            return this.lookupTag.toFirRegularClass(session)?.isLocal == true
+            return this.lookupTag.toFirRegularClassSymbol(session)?.isLocal == true
         }
 
         // id == packageName + className

idea/idea-frontend-fir/idea-fir-low-level-api/src/org/jetbrains/kotlin/idea/fir/low/level/api/api/FirDeclarationDesignation.kt

@@ -14,6 +14,7 @@ import org.jetbrains.kotlin.fir.render
 import org.jetbrains.kotlin.fir.renderWithType
 import org.jetbrains.kotlin.fir.resolve.firProvider
 import org.jetbrains.kotlin.fir.resolve.toFirRegularClass
+import org.jetbrains.kotlin.fir.symbols.impl.LookupTagInternals
 import org.jetbrains.kotlin.idea.fir.low.level.api.util.getContainingFile
 
 class FirDeclarationDesignationWithFile(
@@ -63,6 +64,7 @@ private fun collectDesignationPath(declaration: FirDeclaration): List<FirDeclara
                 is FirSimpleFunction, is FirProperty, is FirField, is FirConstructor -> {
                     val klass = declaration.containingClass() ?: return emptyList()
                     if (klass.classId.isLocal) return null
+                    @OptIn(LookupTagInternals::class)
                     klass.toFirRegularClass(declaration.moduleData.session)
                 }
                 else -> return null

idea/idea-frontend-fir/src/org/jetbrains/kotlin/idea/frontend/api/fir/renderer/ConeTypeIdeRenderer.kt

@@ -18,6 +18,7 @@ import org.jetbrains.kotlin.fir.resolve.inference.*
 import org.jetbrains.kotlin.fir.resolve.toFirRegularClass
 import org.jetbrains.kotlin.fir.resolve.toSymbol
 import org.jetbrains.kotlin.fir.symbols.impl.FirRegularClassSymbol
+import org.jetbrains.kotlin.fir.symbols.impl.LookupTagInternals
 import org.jetbrains.kotlin.fir.types.*
 import org.jetbrains.kotlin.idea.fir.low.level.api.api.tryCollectDesignation
 import org.jetbrains.kotlin.idea.frontend.api.components.KtTypeRendererOptions
@@ -183,6 +184,7 @@ internal class ConeTypeIdeRenderer(
         require(isLocal)
         var containingClassLookUp = containingClassForLocal()
         val designation = mutableListOf<FirClassLikeDeclaration>(this)
+        @OptIn(LookupTagInternals::class)
         while (containingClassLookUp != null && containingClassLookUp.classId.isLocal) {
             val currentClass = containingClassLookUp.toFirRegularClass(moduleData.session) ?: break
             designation.add(currentClass)
@@ -192,6 +194,7 @@ internal class ConeTypeIdeRenderer(
     }
 
     private fun collectDesignationPathForLocal(declaration: FirDeclaration): List<FirDeclaration>? {
+        @OptIn(LookupTagInternals::class)
         val containingClass = when (declaration) {
             is FirCallableDeclaration -> declaration.containingClass()?.toFirRegularClass(declaration.moduleData.session)
             is FirAnonymousObject -> return listOf(declaration)