Write syntactically incorrect constructions processing (light tree to FIR)

compiler/fir/lightTree/src/org/jetbrains/kotlin/fir/lightTree/converter/BaseConverter.kt

@@ -46,12 +46,12 @@ open class BaseConverter(
         return kidsRef.get()
     }
 
-    fun LighterASTNode.getExpressionInParentheses(): LighterASTNode {
+    fun LighterASTNode.getExpressionInParentheses(): LighterASTNode? {
         this.forEachChildren {
             if (it.isExpression()) return it
         }
 
-        throw Exception()
+        return null
     }
 
     protected inline fun LighterASTNode.forEachChildren(vararg skipTokens: KtToken, f: (LighterASTNode) -> Unit) {

compiler/fir/lightTree/src/org/jetbrains/kotlin/fir/lightTree/converter/ConverterUtil.kt

@@ -9,6 +9,7 @@ import com.intellij.lang.LighterASTNode
 import com.intellij.psi.tree.IElementType
 import org.jetbrains.kotlin.KtNodeType
 import org.jetbrains.kotlin.KtNodeTypes
+import org.jetbrains.kotlin.KtNodeTypes.*
 import org.jetbrains.kotlin.descriptors.Modality
 import org.jetbrains.kotlin.descriptors.Visibilities
 import org.jetbrains.kotlin.fir.FirFunctionTarget
@@ -43,10 +44,10 @@ import org.jetbrains.kotlin.types.Variance
 
 object ConverterUtil {
     private val expressionSet = listOf(
-        KtNodeTypes.REFERENCE_EXPRESSION,
-        KtNodeTypes.DOT_QUALIFIED_EXPRESSION,
-        KtNodeTypes.LAMBDA_EXPRESSION,
-        KtNodeTypes.FUN
+        REFERENCE_EXPRESSION,
+        DOT_QUALIFIED_EXPRESSION,
+        LAMBDA_EXPRESSION,
+        FUN
     )
 
     fun String?.nameAsSafeName(defaultName: String = ""): Name {
@@ -157,10 +158,20 @@ object ConverterUtil {
     inline fun isClassLocal(classNode: LighterASTNode, getParent: LighterASTNode.() -> LighterASTNode?): Boolean {
         var currentNode: LighterASTNode? = classNode
         while (currentNode != null) {
-            if (currentNode.tokenType == KtNodeTypes.BLOCK) {
+            val tokenType = currentNode.tokenType
+            val parent = currentNode.getParent()
+            if (tokenType == PROPERTY || tokenType == FUN) {
+                val grandParent = parent?.getParent()
+                when {
+                    parent?.tokenType == KT_FILE -> return true
+                    parent?.tokenType == CLASS_BODY && !(grandParent?.tokenType == OBJECT_DECLARATION && grandParent?.getParent()?.tokenType == OBJECT_LITERAL) -> return true
+                    parent?.tokenType == BLOCK && grandParent?.tokenType == SCRIPT -> return true
+                }
+            }
+            if (tokenType == BLOCK) {
                 return true
             }
-            currentNode = currentNode.getParent()
+            currentNode = parent
         }
         return false
     }

compiler/fir/lightTree/src/org/jetbrains/kotlin/fir/lightTree/converter/DeclarationsConverter.kt

@@ -6,6 +6,7 @@
 package org.jetbrains.kotlin.fir.lightTree.converter
 
 import com.intellij.lang.LighterASTNode
+import com.intellij.psi.TokenType
 import com.intellij.psi.tree.IFileElementType
 import com.intellij.util.diff.FlyweightCapableTreeStructure
 import org.jetbrains.kotlin.KtNodeTypes.*
@@ -49,6 +50,7 @@ import org.jetbrains.kotlin.fir.types.impl.*
 import org.jetbrains.kotlin.lexer.KtModifierKeywordToken
 import org.jetbrains.kotlin.lexer.KtTokens.*
 import org.jetbrains.kotlin.name.FqName
+import org.jetbrains.kotlin.name.Name
 import org.jetbrains.kotlin.name.SpecialNames
 
 class DeclarationsConverter(
@@ -141,15 +143,14 @@ class DeclarationsConverter(
         return packageName
     }
 
-    private fun convertImportAlias(importAlias: LighterASTNode): String {
+    private fun convertImportAlias(importAlias: LighterASTNode): String? {
         importAlias.forEachChildren {
             when (it.tokenType) {
                 IDENTIFIER -> return it.getAsString()
             }
         }
 
-        //TODO specify error
-        throw Exception()
+        return null
     }
 
     /**
@@ -178,7 +179,7 @@ class DeclarationsConverter(
             null,
             importedFqName,
             isAllUnder,
-            aliasName.nameAsSafeName()
+            aliasName?.let { Name.identifier(it) }
         )
     }
 
@@ -332,7 +333,7 @@ class DeclarationsConverter(
      */
     private fun convertClass(classNode: LighterASTNode): FirDeclaration {
         var modifiers = Modifier(session)
-        lateinit var classKind: ClassKind
+        var classKind: ClassKind = ClassKind.CLASS //TODO
         var identifier: String? = null
         val firTypeParameters = mutableListOf<FirTypeParameter>()
         var primaryConstructor: LighterASTNode? = null
@@ -360,17 +361,20 @@ class DeclarationsConverter(
             }
         }
 
-        classKind = when {
-            modifiers.isEnum() -> ClassKind.ENUM_CLASS
-            modifiers.isAnnotation() -> ClassKind.ANNOTATION_CLASS
-            else -> classKind
-        }
         val defaultDelegatedSuperTypeRef = when {
-            modifiers.isEnum() -> implicitEnumType
-            modifiers.isAnnotation() -> implicitAnnotationType
+            modifiers.isEnum() && (classKind == ClassKind.CLASS || classKind == ClassKind.INTERFACE) -> implicitEnumType
+            modifiers.isAnnotation() && (classKind == ClassKind.CLASS || classKind == ClassKind.INTERFACE) -> implicitAnnotationType
             else -> implicitAnyType
         }
 
+        if (classKind == ClassKind.CLASS) {
+            classKind = when {
+                modifiers.isEnum() -> ClassKind.ENUM_CLASS
+                modifiers.isAnnotation() -> ClassKind.ANNOTATION_CLASS
+                else -> classKind
+            }
+        }
+
         val className = identifier.nameAsSafeName(if (modifiers.isCompanion()) "Companion" else "")
         superTypeRefs.ifEmpty { superTypeRefs += defaultDelegatedSuperTypeRef }
         val isLocal = isClassLocal(classNode) { getParent() }
@@ -387,8 +391,8 @@ class DeclarationsConverter(
                 modifiers.hasActual(),
                 classKind,
                 isInner = modifiers.isInner(),
-                isCompanion = modifiers.isCompanion(),
-                isData = modifiers.isDataClass(),
+                isCompanion = modifiers.isCompanion() && classKind == ClassKind.OBJECT,
+                isData = modifiers.isDataClass() && classKind != ClassKind.OBJECT,
                 isInline = modifiers.hasInline()
             )
             firClass.annotations += modifiers.annotations
@@ -406,13 +410,16 @@ class DeclarationsConverter(
             val firPrimaryConstructor = convertPrimaryConstructor(primaryConstructor, classWrapper)
             firPrimaryConstructor?.let { firClass.declarations += it }
 
-            //parse properties
-            val properties = primaryConstructor
-                .getChildNodesByType(VALUE_PARAMETER_LIST)
-                .flatMap { convertValueParameters(it) }
-                .filter { it.hasValOrVar() }
-                .map { it.toFirProperty() }
-            firClass.addDeclarations(properties)
+            val properties = mutableListOf<FirProperty>()
+            if (primaryConstructor != null && firPrimaryConstructor != null) {
+                //parse properties
+                properties += primaryConstructor
+                    .getChildNodesByType(VALUE_PARAMETER_LIST)
+                    .flatMap { convertValueParameters(it) }
+                    .filter { it.hasValOrVar() }
+                    .map { it.toFirProperty() }
+                firClass.addDeclarations(properties)
+            }
 
             //parse declarations
             classBody?.let {
@@ -465,7 +472,7 @@ class DeclarationsConverter(
             val classWrapper = ClassWrapper(
                 this@DeclarationsConverter.session, SpecialNames.NO_NAME_PROVIDED, modifiers, ClassKind.OBJECT,
                 hasPrimaryConstructor = false,
-                hasSecondaryConstructor = false,
+                hasSecondaryConstructor = classBody.getChildNodesByType(SECONDARY_CONSTRUCTOR).isNotEmpty(),
                 delegatedSelfTypeRef = delegatedType,
                 delegatedSuperTypeRef = delegatedType,
                 superTypeCallEntry = superTypeCallEntry
@@ -490,6 +497,7 @@ class DeclarationsConverter(
         var hasInitializerList = false
         val enumSuperTypeCallEntry = mutableListOf<FirExpression>()
         val firDeclarations = mutableListOf<FirDeclaration>()
+        var classBodyNode: LighterASTNode? = null
         enumEntry.forEachChildren {
             when (it.tokenType) {
                 MODIFIER_LIST -> modifiers = convertModifierList(it)
@@ -498,7 +506,7 @@ class DeclarationsConverter(
                     hasInitializerList = true
                     enumSuperTypeCallEntry += convertInitializerList(it)
                 }
-                CLASS_BODY -> firDeclarations += convertClassBody(it, classWrapper)
+                CLASS_BODY -> classBodyNode = it
             }
         }
 
@@ -512,16 +520,23 @@ class DeclarationsConverter(
             )
             firEnumEntry.annotations += modifiers.annotations
 
+            val defaultDelegatedSuperTypeRef = when {
+                modifiers.isEnum() -> implicitEnumType
+                modifiers.isAnnotation() -> implicitAnnotationType
+                else -> implicitAnyType
+            }
+
             val enumClassWrapper = ClassWrapper(
                 session, enumEntryName, modifiers, ClassKind.ENUM_ENTRY,
-                hasPrimaryConstructor = true, hasSecondaryConstructor = false,
+                hasPrimaryConstructor = true,
+                hasSecondaryConstructor = classBodyNode.getChildNodesByType(SECONDARY_CONSTRUCTOR).isNotEmpty(),
                 delegatedSelfTypeRef = toDelegatedSelfType(firEnumEntry),
-                delegatedSuperTypeRef = if (hasInitializerList) classWrapper.getFirUserTypeFromClassName() else implicitAnyType,
+                delegatedSuperTypeRef = if (hasInitializerList) classWrapper.getFirUserTypeFromClassName() else defaultDelegatedSuperTypeRef,
                 superTypeCallEntry = enumSuperTypeCallEntry
             )
             firEnumEntry.superTypeRefs += enumClassWrapper.delegatedSuperTypeRef
-            val firEnumPrimaryConstructor = convertPrimaryConstructor(null, enumClassWrapper)!!
-            firEnumEntry.addDeclaration(firEnumPrimaryConstructor)
+            convertPrimaryConstructor(null, enumClassWrapper)?.let { firEnumEntry.addDeclaration(it) }
+            classBodyNode?.also { firDeclarations += convertClassBody(it, /*classWrapper*/enumClassWrapper) }
             firDeclarations.forEach { firEnumEntry.addDeclaration(it) }
 
             return@withChildClassName firEnumEntry
@@ -641,6 +656,10 @@ class DeclarationsConverter(
             }
         }
 
+        val delegatedSelfTypeRef =
+            if (classWrapper.isObjectLiteral()) FirErrorTypeRefImpl(session, null, "Constructor in object")
+            else classWrapper.delegatedSelfTypeRef
+
         val firConstructor = FirConstructorImpl(
             session,
             null,
@@ -648,13 +667,13 @@ class DeclarationsConverter(
             modifiers.getVisibility(),
             modifiers.hasExpect(),
             modifiers.hasActual(),
-            classWrapper.delegatedSelfTypeRef,
+            delegatedSelfTypeRef,
             constructorDelegationCall
         )
 
         FunctionUtil.firFunctions += firConstructor
         firConstructor.annotations += modifiers.annotations
-        firConstructor.typeParameters += ConverterUtil.typeParametersFromSelfType(classWrapper.delegatedSelfTypeRef)
+        firConstructor.typeParameters += ConverterUtil.typeParametersFromSelfType(delegatedSelfTypeRef)
         firConstructor.valueParameters += firValueParameters.map { it.firValueParameter }
         firConstructor.body = convertFunctionBody(block, null)
         FunctionUtil.firFunctions.removeLast()
@@ -680,10 +699,15 @@ class DeclarationsConverter(
 
         val isImplicit = constructorDelegationCall.getAsString().isEmpty()
         val isThis = (isImplicit && classWrapper.hasPrimaryConstructor) || thisKeywordPresent
-        val delegatedType = when {
-            isThis -> classWrapper.delegatedSelfTypeRef
-            else -> classWrapper.delegatedSuperTypeRef
-        }
+        val delegatedType =
+            if (classWrapper.isObjectLiteral() || classWrapper.isInterface()) when {
+                isThis -> FirErrorTypeRefImpl(session, null, "Constructor in object")
+                else -> FirErrorTypeRefImpl(session, null, "No super type")
+            }
+            else when {
+                isThis -> classWrapper.delegatedSelfTypeRef
+                else -> classWrapper.delegatedSuperTypeRef
+            }
 
         return FirDelegatedConstructorCallImpl(
             session,
@@ -698,7 +722,7 @@ class DeclarationsConverter(
      */
     private fun convertTypeAlias(typeAlias: LighterASTNode): FirDeclaration {
         var modifiers = Modifier(session)
-        lateinit var identifier: String
+        var identifier: String? = null
         lateinit var firType: FirTypeRef
         val firTypeParameters = mutableListOf<FirTypeParameter>()
         typeAlias.forEachChildren {
@@ -733,10 +757,10 @@ class DeclarationsConverter(
      */
     fun convertPropertyDeclaration(property: LighterASTNode): FirDeclaration {
         var modifiers = Modifier(session)
-        lateinit var identifier: String
+        var identifier: String? = null
         val firTypeParameters = mutableListOf<FirTypeParameter>()
         var isReturnType = false
-        var firDelegateExpression: FirExpression? = null
+        var delegateExpression: LighterASTNode? = null
         var isVar = false
         var receiverType: FirTypeRef? = null
         var returnType: FirTypeRef = implicitType
@@ -752,13 +776,13 @@ class DeclarationsConverter(
                 COLON -> isReturnType = true
                 TYPE_REFERENCE -> if (isReturnType) returnType = convertType(it) else receiverType = convertType(it)
                 TYPE_CONSTRAINT_LIST -> typeConstraints += convertTypeConstraints(it)
-                PROPERTY_DELEGATE -> firDelegateExpression = expressionConverter.getAsFirExpression(it)
+                PROPERTY_DELEGATE -> delegateExpression = it
                 VAR_KEYWORD -> isVar = true
                 PROPERTY_ACCESSOR -> {
                     val propertyAccessor = convertGetterOrSetter(it, returnType)
                     if (propertyAccessor.isGetter) getter = propertyAccessor else setter = propertyAccessor
                 }
-                else -> if (it.isExpression()) firExpression = expressionConverter.getAsFirExpression(it)
+                else -> if (it.isExpression()) firExpression = expressionConverter.getAsFirExpression(it, "Should have initializer")
             }
         }
 
@@ -774,7 +798,7 @@ class DeclarationsConverter(
                 returnType,
                 isVar,
                 firExpression,
-                delegate = firDelegateExpression
+                delegate = delegateExpression?.let { expressionConverter.getAsFirExpression(it, "Incorrect delegate expression") }
             ).apply {
                 annotations += modifiers.annotations
             }
@@ -797,7 +821,7 @@ class DeclarationsConverter(
                 firExpression,
                 getter ?: FirDefaultPropertyGetter(session, null, returnType, modifiers.getVisibility()),
                 if (isVar) setter ?: FirDefaultPropertySetter(session, null, returnType, modifiers.getVisibility()) else null,
-                firDelegateExpression
+                delegateExpression?.let { expressionConverter.getAsFirExpression(it, "Should have delegate") }
             ).apply {
                 this.typeParameters += firTypeParameters
                 this.joinTypeParameters(typeConstraints)
@@ -812,12 +836,13 @@ class DeclarationsConverter(
     private fun convertDestructingDeclaration(destructingDeclaration: LighterASTNode): DestructuringDeclaration {
         var isVar = false
         val entries = mutableListOf<FirVariable<*>>()
-        var firExpression: FirExpression? = null
+        var firExpression: FirExpression = FirErrorExpressionImpl(session, null, "Destructuring declaration without initializer")
         destructingDeclaration.forEachChildren {
             when (it.tokenType) {
                 VAR_KEYWORD -> isVar = true
                 DESTRUCTURING_DECLARATION_ENTRY -> entries += convertDestructingDeclarationEntry(it)
-                else -> if (it.isExpression()) firExpression = expressionConverter.getAsFirExpression(it)
+                else -> if (it.isExpression()) firExpression =
+                    expressionConverter.getAsFirExpression(it, "Destructuring declaration without initializer")
             }
         }
 
@@ -829,7 +854,7 @@ class DeclarationsConverter(
      */
     private fun convertDestructingDeclarationEntry(entry: LighterASTNode): FirVariable<*> {
         var modifiers = Modifier(session)
-        lateinit var identifier: String
+        var identifier: String? = null
         var firType: FirTypeRef? = null
         entry.forEachChildren {
             when (it.tokenType) {
@@ -882,7 +907,7 @@ class DeclarationsConverter(
             firAccessor.valueParameters += firValueParameters
         }
 
-        firAccessor.body = convertFunctionBody(block, expression?.let { expressionConverter.getAsFirExpression(it) })
+        firAccessor.body = convertFunctionBody(block, expression)
         FunctionUtil.firFunctions.removeLast()
         return firAccessor
     }
@@ -909,11 +934,11 @@ class DeclarationsConverter(
             firValueParameter.name,
             if (firValueParameter.returnTypeRef == implicitType) propertyTypeRef else firValueParameter.returnTypeRef,
             firValueParameter.defaultValue,
-            isCrossinline = modifiers.hasCrossinline(),
-            isNoinline = modifiers.hasNoinline(),
-            isVararg = modifiers.hasVararg()
+            isCrossinline = modifiers.hasCrossinline() || firValueParameter.isCrossinline,
+            isNoinline = modifiers.hasNoinline() || firValueParameter.isNoinline,
+            isVararg = modifiers.hasVararg() || firValueParameter.isVararg
         ).apply {
-            annotations += modifiers.annotations
+            annotations += modifiers.annotations + firValueParameter.annotations
         }
     }
 
@@ -924,30 +949,32 @@ class DeclarationsConverter(
         var modifiers = Modifier(session)
         var identifier: String? = null
         val firTypeParameters = mutableListOf<FirTypeParameter>()
-        val valueParametersList = mutableListOf<ValueParameter>()
+        var valueParametersList: LighterASTNode? = null
         var isReturnType = false
         var receiverType: FirTypeRef? = null
         var returnType: FirTypeRef? = null
         val typeConstraints = mutableListOf<TypeConstraint>()
         var block: LighterASTNode? = null
         var expression: LighterASTNode? = null
+        var hasEqToken = false
         functionDeclaration.forEachChildren {
             when (it.tokenType) {
                 MODIFIER_LIST -> modifiers = convertModifierList(it)
                 IDENTIFIER -> identifier = it.getAsString()
                 TYPE_PARAMETER_LIST -> firTypeParameters += convertTypeParameters(it)
-                VALUE_PARAMETER_LIST -> valueParametersList += convertValueParameters(it)
+                VALUE_PARAMETER_LIST -> valueParametersList = it //must convert later, because it can contains "return"
                 COLON -> isReturnType = true
                 TYPE_REFERENCE -> if (isReturnType) returnType = convertType(it) else receiverType = convertType(it)
                 TYPE_CONSTRAINT_LIST -> typeConstraints += convertTypeConstraints(it)
                 BLOCK -> block = it
+                EQ -> hasEqToken = true
                 else -> if (it.isExpression()) expression = it
             }
         }
 
         if (returnType == null) {
             returnType =
-                if (block != null || (block == null && expression == null)) implicitUnitType
+                if (block != null || !hasEqToken) implicitUnitType
                 else implicitType
         }
 
@@ -986,8 +1013,8 @@ class DeclarationsConverter(
             firFunction.joinTypeParameters(typeConstraints)
         }
 
-        firFunction.valueParameters += valueParametersList.map { it.firValueParameter }
-        firFunction.body = convertFunctionBody(block, expression?.let { expressionConverter.getAsFirExpression(it) })
+        valueParametersList?.let { firFunction.valueParameters += convertValueParameters(it).map { it.firValueParameter } }
+        firFunction.body = convertFunctionBody(block, expression)
         FunctionUtil.firFunctions.removeLast()
         return firFunction
     }
@@ -996,10 +1023,13 @@ class DeclarationsConverter(
      * @see org.jetbrains.kotlin.parsing.KotlinParsing.parseFunctionBody
      * @see org.jetbrains.kotlin.fir.builder.RawFirBuilder.Visitor.buildFirBody
      */
-    private fun convertFunctionBody(blockNode: LighterASTNode?, firExpression: FirExpression?): FirBlock? {
+    private fun convertFunctionBody(blockNode: LighterASTNode?, expression: LighterASTNode?): FirBlock? {
         return when {
             blockNode != null -> return convertBlock(blockNode)
-            firExpression != null -> FirSingleExpressionBlock(session, firExpression.toReturn())
+            expression != null -> FirSingleExpressionBlock(
+                session,
+                expressionConverter.getAsFirExpression<FirExpression>(expression, "Function has no body (but should)").toReturn()
+            )
             else -> null
         }
     }
@@ -1081,11 +1111,11 @@ class DeclarationsConverter(
      */
     private fun convertExplicitDelegation(explicitDelegation: LighterASTNode): FirDelegatedTypeRef {
         lateinit var firTypeRef: FirTypeRef
-        var firExpression: FirExpression? = null
+        var firExpression: FirExpression? = FirErrorExpressionImpl(session, null, "Should have delegate")
         explicitDelegation.forEachChildren {
             when (it.tokenType) {
                 TYPE_REFERENCE -> firTypeRef = convertType(it)
-                else -> if (it.isExpression()) firExpression = expressionConverter.getAsFirExpression(it)
+                else -> if (it.isExpression()) firExpression = expressionConverter.getAsFirExpression(it, "Should have delegate")
             }
         }
 
@@ -1143,7 +1173,7 @@ class DeclarationsConverter(
      */
     private fun convertTypeParameter(typeParameter: LighterASTNode): FirTypeParameter {
         var typeParameterModifiers = TypeParameterModifier(session)
-        lateinit var identifier: String
+        var identifier: String? = null
         var firType: FirTypeRef? = null
         typeParameter.forEachChildren {
             when (it.tokenType) {
@@ -1171,16 +1201,22 @@ class DeclarationsConverter(
      * @see org.jetbrains.kotlin.parsing.KotlinParsing.parseTypeRef
      */
     fun convertType(type: LighterASTNode): FirTypeRef {
+        if (type.getAsString().isEmpty()) {
+            return FirErrorTypeRefImpl(session, null, "Unwrapped type is null")
+        }
         var typeModifiers = TypeModifier(session) //TODO what with suspend?
-        lateinit var firType: FirTypeRef
+        var firType: FirTypeRef = FirErrorTypeRefImpl(session, null, "Incomplete code")
+        var afterLPar = false
         type.forEachChildren {
             when (it.tokenType) {
+                LPAR -> afterLPar = true
                 TYPE_REFERENCE -> firType = convertType(it)
-                MODIFIER_LIST -> typeModifiers = convertTypeModifierList(it)
-                USER_TYPE -> firType = convertUserType(it).also { firUserType -> (firUserType as FirUserTypeRefImpl).qualifier.reverse() }
+                MODIFIER_LIST -> if (!afterLPar || typeModifiers.hasNoAnnotations()) typeModifiers = convertTypeModifierList(it)
+                USER_TYPE -> firType = convertUserType(it)
                 NULLABLE_TYPE -> firType = convertNullableType(it)
                 FUNCTION_TYPE -> firType = convertFunctionType(it)
                 DYNAMIC_TYPE -> firType = FirDynamicTypeRefImpl(session, null, false)
+                TokenType.ERROR_ELEMENT -> firType = FirErrorTypeRefImpl(session, null, "Unwrapped type is null")
             }
         }
 
@@ -1209,7 +1245,7 @@ class DeclarationsConverter(
         nullableType.forEachChildren {
             when (it.tokenType) {
                 USER_TYPE -> firType =
-                    convertUserType(it, true).also { firUserType -> (firUserType as FirUserTypeRefImpl).qualifier.reverse() }
+                    convertUserType(it, true)
                 FUNCTION_TYPE -> firType = convertFunctionType(it, true)
                 NULLABLE_TYPE -> firType = convertNullableType(it)
                 DYNAMIC_TYPE -> firType = FirDynamicTypeRefImpl(session, null, true)
@@ -1222,18 +1258,21 @@ class DeclarationsConverter(
     /**
      * @see org.jetbrains.kotlin.parsing.KotlinParsing.parseUserType
      */
-    private fun convertUserType(userType: LighterASTNode, isNullable: Boolean = false): FirUserTypeRef {
+    private fun convertUserType(userType: LighterASTNode, isNullable: Boolean = false): FirTypeRef {
         var simpleFirUserType: FirUserTypeRef? = null
-        lateinit var identifier: String
+        var identifier: String? = null
         val firTypeArguments = mutableListOf<FirTypeProjection>()
         userType.forEachChildren {
             when (it.tokenType) {
-                USER_TYPE -> simpleFirUserType = convertUserType(it) //simple user type
+                USER_TYPE -> simpleFirUserType = convertUserType(it) as? FirUserTypeRef //simple user type
                 REFERENCE_EXPRESSION -> identifier = it.getAsString()
                 TYPE_ARGUMENT_LIST -> firTypeArguments += convertTypeArguments(it)
             }
         }
 
+        if (identifier == null)
+            return FirErrorTypeRefImpl(session, null, "Incomplete user type")
+
         val qualifier = FirQualifierPartImpl(
             identifier.nameAsSafeName()
         ).apply { typeArguments += firTypeArguments }
@@ -1244,7 +1283,7 @@ class DeclarationsConverter(
             isNullable
         ).apply {
             this.qualifier.add(qualifier)
-            simpleFirUserType?.qualifier?.let { this@apply.qualifier.addAll(it) }
+            simpleFirUserType?.qualifier?.let { this@apply.qualifier.addAll(0, it) }
         }
     }
 
@@ -1338,7 +1377,7 @@ class DeclarationsConverter(
                 IDENTIFIER -> identifier = it.getAsString()
                 TYPE_REFERENCE -> firType = convertType(it)
                 DESTRUCTURING_DECLARATION -> destructuringDeclaration = convertDestructingDeclaration(it)
-                else -> if (it.isExpression()) firExpression = expressionConverter.getAsFirExpression(it)
+                else -> if (it.isExpression()) firExpression = expressionConverter.getAsFirExpression(it, "Should have default value")
             }
         }
 

compiler/fir/lightTree/src/org/jetbrains/kotlin/fir/lightTree/converter/ExpressionsConverter.kt

@@ -6,33 +6,31 @@
 package org.jetbrains.kotlin.fir.lightTree.converter
 
 import com.intellij.lang.LighterASTNode
+import com.intellij.psi.TokenType
 import com.intellij.psi.impl.source.tree.java.PsiForStatementImpl
 import com.intellij.util.diff.FlyweightCapableTreeStructure
 import org.jetbrains.kotlin.KtNodeTypes.*
-import org.jetbrains.kotlin.descriptors.ClassKind
 import org.jetbrains.kotlin.fir.*
 import org.jetbrains.kotlin.fir.builder.*
-import org.jetbrains.kotlin.fir.declarations.FirClass
 import org.jetbrains.kotlin.fir.declarations.impl.FirAnonymousFunctionImpl
-import org.jetbrains.kotlin.fir.declarations.impl.FirAnonymousObjectImpl
 import org.jetbrains.kotlin.fir.declarations.impl.FirErrorLoop
 import org.jetbrains.kotlin.fir.declarations.impl.FirValueParameterImpl
+import org.jetbrains.kotlin.fir.declarations.impl.FirVariableImpl
 import org.jetbrains.kotlin.fir.expressions.*
 import org.jetbrains.kotlin.fir.expressions.impl.*
 import org.jetbrains.kotlin.fir.labels.FirLabelImpl
 import org.jetbrains.kotlin.fir.lightTree.LightTree2Fir
 import org.jetbrains.kotlin.fir.lightTree.converter.ConverterUtil.extractArgumentsFrom
 import org.jetbrains.kotlin.fir.lightTree.converter.ConverterUtil.getAsString
+import org.jetbrains.kotlin.fir.lightTree.converter.ConverterUtil.getAsStringWithoutBacktick
 import org.jetbrains.kotlin.fir.lightTree.converter.ConverterUtil.isExpression
 import org.jetbrains.kotlin.fir.lightTree.converter.ConverterUtil.nameAsSafeName
 import org.jetbrains.kotlin.fir.lightTree.converter.ConverterUtil.toReturn
 import org.jetbrains.kotlin.fir.lightTree.converter.FunctionUtil.pop
 import org.jetbrains.kotlin.fir.lightTree.converter.FunctionUtil.removeLast
 import org.jetbrains.kotlin.fir.lightTree.converter.utils.*
-import org.jetbrains.kotlin.fir.lightTree.fir.ClassWrapper
 import org.jetbrains.kotlin.fir.lightTree.fir.ValueParameter
 import org.jetbrains.kotlin.fir.lightTree.fir.WhenEntry
-import org.jetbrains.kotlin.fir.lightTree.fir.modifier.Modifier
 import org.jetbrains.kotlin.fir.references.FirErrorNamedReference
 import org.jetbrains.kotlin.fir.references.FirExplicitSuperReference
 import org.jetbrains.kotlin.fir.references.FirExplicitThisReference
@@ -57,12 +55,12 @@ class ExpressionsConverter(
     private val declarationsConverter: DeclarationsConverter
 ) : BaseConverter(session, tree) {
 
-    inline fun <reified R : FirElement> getAsFirExpression(expression: LighterASTNode): R {
-        return convertExpression(expression) as R
+    inline fun <reified R : FirElement> getAsFirExpression(expression: LighterASTNode?, errorReason: String = ""): R {
+        return expression?.let { convertExpression(it, errorReason) } as? R ?: (FirErrorExpressionImpl(session, null, errorReason) as R)
     }
 
     /*****    EXPRESSIONS    *****/
-    fun convertExpression(expression: LighterASTNode): FirElement {
+    fun convertExpression(expression: LighterASTNode, errorReason: String): FirElement {
         if (!stubMode) {
             return when (expression.tokenType) {
                 LAMBDA_EXPRESSION -> {
@@ -93,22 +91,28 @@ class ExpressionsConverter(
                 BREAK, CONTINUE -> convertLoopJump(expression)
                 RETURN -> convertReturn(expression)
                 THROW -> convertThrow(expression)
-                PARENTHESIZED, PROPERTY_DELEGATE, INDICES -> convertExpression(expression.getExpressionInParentheses())
+                PARENTHESIZED -> getAsFirExpression(expression.getExpressionInParentheses(), "Empty parentheses")
+                PROPERTY_DELEGATE, INDICES, CONDITION, LOOP_RANGE ->
+                    getAsFirExpression(expression.getExpressionInParentheses(), errorReason)
                 THIS_EXPRESSION -> convertThisExpression(expression)
                 SUPER_EXPRESSION -> convertSuperExpression(expression)
 
                 OBJECT_LITERAL -> declarationsConverter.convertObjectLiteral(expression)
                 FUN -> declarationsConverter.convertFunctionDeclaration(expression)
-                else -> FirExpressionStub(session, null)
+                else -> FirErrorExpressionImpl(session, null, errorReason)
             }
         }
 
         return FirExpressionStub(session, null)
     }
 
+    /**
+     * @see org.jetbrains.kotlin.parsing.KotlinExpressionParsing.parseFunctionLiteral
+     * @see org.jetbrains.kotlin.fir.builder.RawFirBuilder.Visitor.visitLambdaExpression
+     */
     private fun convertLambdaExpression(lambdaExpression: LighterASTNode): FirExpression {
         val valueParameterList = mutableListOf<ValueParameter>()
-        lateinit var block: LighterASTNode
+        var block: LighterASTNode? = null
         lambdaExpression.getChildNodesByType(FUNCTION_LITERAL).first().forEachChildren {
             when (it.tokenType) {
                 VALUE_PARAMETER_LIST -> valueParameterList += declarationsConverter.convertValueParameters(it)
@@ -141,7 +145,8 @@ class ExpressionsConverter(
             label = FunctionUtil.firLabels.pop() ?: FunctionUtil.firFunctionCalls.lastOrNull()?.calleeReference?.name?.let {
                 FirLabelImpl(this@ExpressionsConverter.session, null, it.asString())
             }
-            val bodyExpression = declarationsConverter.convertBlockExpression(block)
+            val bodyExpression = block?.let { declarationsConverter.convertBlockExpression(it) }
+                ?: FirErrorExpressionImpl(session, null, "Lambda has no body")
             body = if (bodyExpression is FirBlockImpl) {
                 if (bodyExpression.statements.isEmpty()) {
                     bodyExpression.statements.add(FirUnitExpression(this@ExpressionsConverter.session, null))
@@ -167,8 +172,8 @@ class ExpressionsConverter(
     private fun convertBinaryExpression(binaryExpression: LighterASTNode): FirStatement {
         var isLeftArgument = true
         lateinit var operationTokenName: String
-        lateinit var leftArgNode: LighterASTNode
-        lateinit var rightArgAsFir: FirExpression
+        var leftArgNode: LighterASTNode? = null
+        var rightArgAsFir: FirExpression = FirErrorExpressionImpl(session, null, "No right operand")
         binaryExpression.forEachChildren {
             when (it.tokenType) {
                 OPERATION_REFERENCE -> {
@@ -179,7 +184,7 @@ class ExpressionsConverter(
                     if (isLeftArgument) {
                         leftArgNode = it
                     } else {
-                        rightArgAsFir = getAsFirExpression(it)
+                        rightArgAsFir = getAsFirExpression(it, "No right operand")
                     }
                 }
             }
@@ -188,16 +193,16 @@ class ExpressionsConverter(
         val operationToken = operationTokenName.getOperationSymbol()
         when (operationToken) {
             ELVIS ->
-                return getAsFirExpression<FirExpression>(leftArgNode).generateNotNullOrOther(
+                return getAsFirExpression<FirExpression>(leftArgNode, "No left operand").generateNotNullOrOther(
                     session, rightArgAsFir, "elvis", null
                 )
             ANDAND, OROR ->
-                return getAsFirExpression<FirExpression>(leftArgNode).generateLazyLogicalOperation(
+                return getAsFirExpression<FirExpression>(leftArgNode, "No left operand").generateLazyLogicalOperation(
                     session, rightArgAsFir, operationToken == ANDAND, null
                 )
             in OperatorConventions.IN_OPERATIONS ->
                 return rightArgAsFir.generateContainsOperation(
-                    session, getAsFirExpression(leftArgNode), operationToken == NOT_IN, null, null
+                    session, getAsFirExpression(leftArgNode, "No left operand"), operationToken == NOT_IN, null, null
                 )
         }
         val conventionCallName = operationToken.toBinaryName()
@@ -207,7 +212,7 @@ class ExpressionsConverter(
                     this@ExpressionsConverter.session, null,
                     conventionCallName ?: operationTokenName.nameAsSafeName()
                 )
-                explicitReceiver = getAsFirExpression(leftArgNode)
+                explicitReceiver = getAsFirExpression(leftArgNode, "No left operand")
                 arguments += rightArgAsFir
             }
         } else {
@@ -216,7 +221,7 @@ class ExpressionsConverter(
                 return convertAssignment(leftArgNode, rightArgAsFir, firOperation)
             } else {
                 FirOperatorCallImpl(session, null, firOperation).apply {
-                    arguments += getAsFirExpression<FirExpression>(leftArgNode)
+                    arguments += getAsFirExpression<FirExpression>(leftArgNode, "No left operand")
                     arguments += rightArgAsFir
                 }
             }
@@ -229,13 +234,13 @@ class ExpressionsConverter(
      */
     private fun convertBinaryWithType(binaryExpression: LighterASTNode): FirTypeOperatorCall {
         lateinit var operationTokenName: String
-        lateinit var leftArgAsFir: FirExpression
+        var leftArgAsFir: FirExpression = FirErrorExpressionImpl(session, null, "No left operand")
         lateinit var firType: FirTypeRef
         binaryExpression.forEachChildren {
             when (it.tokenType) {
                 OPERATION_REFERENCE -> operationTokenName = it.getAsString()
                 TYPE_REFERENCE -> firType = declarationsConverter.convertType(it)
-                else -> if (it.isExpression()) leftArgAsFir = getAsFirExpression(it)
+                else -> if (it.isExpression()) leftArgAsFir = getAsFirExpression(it, "No left operand")
             }
         }
 
@@ -250,13 +255,13 @@ class ExpressionsConverter(
      */
     private fun convertIsExpression(isExpression: LighterASTNode): FirTypeOperatorCall {
         lateinit var operationTokenName: String
-        lateinit var leftArgAsFir: FirExpression
+        var leftArgAsFir: FirExpression = FirErrorExpressionImpl(session, null, "No left operand")
         lateinit var firType: FirTypeRef
         isExpression.forEachChildren {
             when (it.tokenType) {
                 OPERATION_REFERENCE -> operationTokenName = it.getAsString()
                 TYPE_REFERENCE -> firType = declarationsConverter.convertType(it)
-                else -> if (it.isExpression()) leftArgAsFir = getAsFirExpression(it)
+                else -> if (it.isExpression()) leftArgAsFir = getAsFirExpression(it, "No left operand")
             }
         }
 
@@ -276,6 +281,8 @@ class ExpressionsConverter(
         labeledExpression.forEachChildren {
             when (it.tokenType) {
                 LABEL_QUALIFIER -> FunctionUtil.firLabels += FirLabelImpl(session, null, it.toString().replace("@", ""))
+                BLOCK -> firExpression = declarationsConverter.convertBlock(it)
+                PROPERTY -> firExpression = declarationsConverter.convertPropertyDeclaration(it)
                 else -> if (it.isExpression()) firExpression = getAsFirExpression(it)
             }
         }
@@ -294,7 +301,7 @@ class ExpressionsConverter(
      */
     private fun convertUnaryExpression(unaryExpression: LighterASTNode): FirExpression {
         lateinit var operationTokenName: String
-        lateinit var argument: LighterASTNode
+        var argument: LighterASTNode? = null
         unaryExpression.forEachChildren {
             when (it.tokenType) {
                 OPERATION_REFERENCE -> operationTokenName = it.getAsString()
@@ -304,7 +311,7 @@ class ExpressionsConverter(
 
         val operationToken = operationTokenName.getOperationSymbol()
         if (operationToken == EXCLEXCL) {
-            return bangBangToWhen(session, getAsFirExpression(argument))
+            return bangBangToWhen(session, getAsFirExpression(argument, "No operand"))
         }
 
         val conventionCallName = operationToken.toUnaryName()
@@ -318,12 +325,12 @@ class ExpressionsConverter(
             }
             FirFunctionCallImpl(session, null).apply {
                 calleeReference = FirSimpleNamedReference(this@ExpressionsConverter.session, null, conventionCallName)
-                explicitReceiver = getAsFirExpression(argument)
+                explicitReceiver = getAsFirExpression(argument, "No operand")
             }
         } else {
             val firOperation = operationToken.toFirOperation()
             FirOperatorCallImpl(session, null, firOperation).apply {
-                arguments += getAsFirExpression<FirExpression>(argument)
+                arguments += getAsFirExpression<FirExpression>(argument, "No operand")
             }
         }
     }
@@ -353,9 +360,9 @@ class ExpressionsConverter(
      * @see org.jetbrains.kotlin.fir.builder.RawFirBuilder.Visitor.visitClassLiteralExpression
      */
     private fun convertClassLiteralExpression(classLiteralExpression: LighterASTNode): FirExpression {
-        lateinit var firReceiverExpression: FirExpression
+        var firReceiverExpression: FirExpression = FirErrorExpressionImpl(session, null, "No receiver in class literal")
         classLiteralExpression.forEachChildren {
-            if (it.isExpression()) firReceiverExpression = getAsFirExpression(it)
+            if (it.isExpression()) firReceiverExpression = getAsFirExpression(it, "No receiver in class literal")
         }
 
         return FirGetClassCallImpl(session, null).apply {
@@ -376,7 +383,7 @@ class ExpressionsConverter(
                 COLONCOLON -> isReceiver = false
                 else -> if (it.isExpression()) {
                     if (isReceiver) {
-                        firReceiverExpression = getAsFirExpression(it)
+                        firReceiverExpression = getAsFirExpression(it, "Incorrect receiver expression")
                     } else {
                         firCallableReference = convertSimpleNameExpression(it)
                     }
@@ -397,8 +404,8 @@ class ExpressionsConverter(
     private fun convertQualifiedExpression(dotQualifiedExpression: LighterASTNode): FirExpression {
         var isSelector = false
         var isSafe = false
-        var firSelector: FirExpression? = null //after dot
-        lateinit var firReceiver: FirExpression //before dot
+        var firSelector: FirExpression = FirErrorExpressionImpl(session, null, "Qualified expression without selector") //after dot
+        var firReceiver: FirExpression? = null //before dot
         dotQualifiedExpression.forEachChildren {
             when (it.tokenType) {
                 DOT -> isSelector = true
@@ -406,20 +413,21 @@ class ExpressionsConverter(
                     isSafe = true
                     isSelector = true
                 }
-                else -> if (isSelector) firSelector = getAsFirExpression(it) else firReceiver = getAsFirExpression(it)
+                else -> {
+                    if (isSelector && it.tokenType != TokenType.ERROR_ELEMENT)
+                        firSelector = getAsFirExpression(it, "Incorrect selector expression")
+                    else
+                        firReceiver = getAsFirExpression(it, "Incorrect receiver expression")
+                }
             }
         }
 
-        if (firSelector == null) {
-            return FirErrorExpressionImpl(session, null, "Qualified expression without selector")
-        }
-
         //TODO use contracts?
         if (firSelector is FirModifiableQualifiedAccess<*>) {
             (firSelector as FirModifiableQualifiedAccess<*>).safe = isSafe
             (firSelector as FirModifiableQualifiedAccess<*>).explicitReceiver = firReceiver
         }
-        return firSelector!!
+        return firSelector
     }
 
     /**
@@ -435,12 +443,13 @@ class ExpressionsConverter(
                 REFERENCE_EXPRESSION -> name = it.getAsString()
                 TYPE_ARGUMENT_LIST -> firTypeArguments += declarationsConverter.convertTypeArguments(it)
                 VALUE_ARGUMENT_LIST, LAMBDA_ARGUMENT -> valueArguments += it
-                else -> additionalArgument = getAsFirExpression(it)
+                else -> if (it.tokenType != TokenType.ERROR_ELEMENT) additionalArgument =
+                    getAsFirExpression(it, "Incorrect invoke receiver")
             }
         }
 
         return FirFunctionCallImpl(session, null).apply {
-            val calleeReference = when {
+            this.calleeReference = when {
                 name != null -> FirSimpleNamedReference(this@ExpressionsConverter.session, null, name.nameAsSafeName())
                 additionalArgument != null -> {
                     arguments += additionalArgument!!
@@ -448,7 +457,7 @@ class ExpressionsConverter(
                 }
                 else -> FirErrorNamedReference(this@ExpressionsConverter.session, null, "Call has no callee")
             }
-            this.calleeReference = calleeReference
+
             FunctionUtil.firFunctionCalls += this
             this.extractArgumentsFrom(valueArguments.flatMap { convertValueArguments(it) }, stubMode)
             typeArguments += firTypeArguments
@@ -472,8 +481,11 @@ class ExpressionsConverter(
                     FirConstExpressionImpl(session, null, IrConstKind.String, it.getAsString())
                 }
                 ESCAPE_STRING_TEMPLATE_ENTRY -> {
-                    sb.append(escapedStringToCharacter(it.getAsString()))
-                    FirConstExpressionImpl(session, null, IrConstKind.String, escapedStringToCharacter(it.getAsString())?.toString() ?: "")
+                    val escape = it.getAsString()
+                    val unescaped = escapedStringToCharacter(escape)?.toString()
+                        ?: escape.replace("\\", "").replace("u", "\\u")
+                    sb.append(unescaped)
+                    FirConstExpressionImpl(session, null, IrConstKind.String, unescaped)
                 }
                 SHORT_STRING_TEMPLATE_ENTRY, LONG_STRING_TEMPLATE_ENTRY -> {
                     hasExpressions = true
@@ -503,9 +515,9 @@ class ExpressionsConverter(
     }
 
     private fun convertShortOrLongStringTemplate(shortOrLongString: LighterASTNode): FirExpression {
-        lateinit var firExpression: FirExpression
+        var firExpression: FirExpression = FirErrorExpressionImpl(session, null, "Incorrect template argument")
         shortOrLongString.forEachChildren(LONG_TEMPLATE_ENTRY_START, LONG_TEMPLATE_ENTRY_END) {
-            firExpression = getAsFirExpression(it)
+            firExpression = getAsFirExpression(it, "Incorrect template argument")
         }
         return firExpression
     }
@@ -571,22 +583,24 @@ class ExpressionsConverter(
         val whenEntries = mutableListOf<WhenEntry>()
         whenExpression.forEachChildren {
             when (it.tokenType) {
-                PROPERTY -> subjectVariable = declarationsConverter.convertPropertyDeclaration(it) as FirVariable<*>
-                DESTRUCTURING_DECLARATION -> subjectExpression = getAsFirExpression(it)
+                PROPERTY -> subjectVariable = (declarationsConverter.convertPropertyDeclaration(it) as FirVariable<*>).let { variable ->
+                    FirVariableImpl(
+                        session, null, variable.name, variable.returnTypeRef,
+                        isVar = false, initializer = variable.initializer
+                    )
+                }
+                DESTRUCTURING_DECLARATION -> subjectExpression =
+                    getAsFirExpression(it, "Incorrect when subject expression: ${whenExpression.getAsString()}")
                 WHEN_ENTRY -> whenEntries += convertWhenEntry(it)
-                else -> if (it.isExpression()) subjectExpression = getAsFirExpression(it)
+                else -> if (it.isExpression()) subjectExpression =
+                    getAsFirExpression(it, "Incorrect when subject expression: ${whenExpression.getAsString()}")
             }
         }
 
         subjectExpression = subjectVariable?.initializer ?: subjectExpression
         val hasSubject = subjectExpression != null
         val subject = FirWhenSubject()
-        return FirWhenExpressionImpl(
-            session,
-            null,
-            subjectExpression,
-            subjectVariable
-        ).apply {
+        return FirWhenExpressionImpl(session, null, subjectExpression, subjectVariable).apply {
             if (hasSubject) {
                 subject.bind(this)
             }
@@ -615,7 +629,7 @@ class ExpressionsConverter(
      */
     private fun convertWhenEntry(whenEntry: LighterASTNode): WhenEntry {
         var isElse = false
-        lateinit var firBlock: FirBlock
+        var firBlock: FirBlock = FirEmptyExpressionBlock(session)
         val conditions = mutableListOf<FirExpression>()
         whenEntry.forEachChildren {
             when (it.tokenType) {
@@ -632,10 +646,10 @@ class ExpressionsConverter(
     }
 
     private fun convertWhenConditionExpression(whenCondition: LighterASTNode): FirExpression {
-        lateinit var firExpression: FirExpression
+        var firExpression: FirExpression = FirErrorExpressionImpl(session, null, "No expression in condition with expression")
         whenCondition.forEachChildren {
             when (it.tokenType) {
-                else -> if (it.isExpression()) firExpression = getAsFirExpression(it)
+                else -> if (it.isExpression()) firExpression = getAsFirExpression(it, "No expression in condition with expression")
             }
         }
 
@@ -646,7 +660,7 @@ class ExpressionsConverter(
 
     private fun convertWhenConditionInRange(whenCondition: LighterASTNode): FirExpression {
         var isNegate = false
-        lateinit var firExpression: FirExpression
+        var firExpression: FirExpression = FirErrorExpressionImpl(session, null, "No range in condition with range")
         whenCondition.forEachChildren {
             when (it.tokenType) {
                 NOT_IN -> isNegate = true
@@ -680,12 +694,12 @@ class ExpressionsConverter(
      * @see org.jetbrains.kotlin.fir.builder.RawFirBuilder.Visitor.visitArrayAccessExpression
      */
     private fun convertArrayAccessExpression(arrayAccess: LighterASTNode): FirFunctionCall {
-        lateinit var firExpression: FirExpression
+        var firExpression: FirExpression = FirErrorExpressionImpl(session, null, "No array expression")
         val indices: MutableList<FirExpression> = mutableListOf()
         arrayAccess.forEachChildren {
             when (it.tokenType) {
                 INDICES -> indices += convertIndices(it)
-                else -> if (it.isExpression()) firExpression = getAsFirExpression(it)
+                else -> if (it.isExpression()) firExpression = getAsFirExpression(it, "No array expression")
             }
         }
         return FirFunctionCallImpl(session, null).apply {
@@ -701,7 +715,7 @@ class ExpressionsConverter(
     private fun convertCollectionLiteralExpresion(expression: LighterASTNode): FirExpression {
         val firExpressionList = mutableListOf<FirExpression>()
         expression.forEachChildren {
-            if (it.isExpression()) firExpressionList += getAsFirExpression<FirExpression>(it)
+            if (it.isExpression()) firExpressionList += getAsFirExpression<FirExpression>(it, "Incorrect collection literal argument")
         }
 
         return FirArrayOfCallImpl(session, null).apply {
@@ -715,7 +729,7 @@ class ExpressionsConverter(
     private fun convertIndices(indices: LighterASTNode): List<FirExpression> {
         val firExpressionList: MutableList<FirExpression> = mutableListOf()
         indices.forEachChildren {
-            if (it.isExpression()) firExpressionList += getAsFirExpression<FirExpression>(it)
+            if (it.isExpression()) firExpressionList += getAsFirExpression<FirExpression>(it, "Incorrect index expression")
         }
 
         return firExpressionList
@@ -738,17 +752,15 @@ class ExpressionsConverter(
      */
     private fun convertDoWhile(doWhileLoop: LighterASTNode): FirElement {
         var block: LighterASTNode? = null
-        var condition: FirExpression? = null
+        var firCondition: FirExpression = FirErrorExpressionImpl(session, null, "No condition in do-while loop")
         doWhileLoop.forEachChildren {
             when (it.tokenType) {
                 BODY -> block = it
-                CONDITION -> condition = convertCondition(it)
+                CONDITION -> firCondition = getAsFirExpression(it, "No condition in do-while loop")
             }
         }
 
-        return FirDoWhileLoopImpl(
-            session, null, condition ?: FirErrorExpressionImpl(session, null, "No condition in do-while loop")
-        ).configure { convertLoopBody(block) }
+        return FirDoWhileLoopImpl(session, null, firCondition).configure { convertLoopBody(block) }
     }
 
     /**
@@ -757,17 +769,15 @@ class ExpressionsConverter(
      */
     private fun convertWhile(whileLoop: LighterASTNode): FirElement {
         var block: LighterASTNode? = null
-        var condition: FirExpression? = null
+        var firCondition: FirExpression = FirErrorExpressionImpl(session, null, "No condition in while loop")
         whileLoop.forEachChildren {
             when (it.tokenType) {
                 BODY -> block = it
-                CONDITION -> condition = convertCondition(it)
+                CONDITION -> firCondition = getAsFirExpression(it, "No condition in while loop")
             }
         }
 
-        return FirWhileLoopImpl(
-            session, null, condition ?: FirErrorExpressionImpl(session, null, "No condition in while loop")
-        ).configure { convertLoopBody(block) }
+        return FirWhileLoopImpl(session, null, firCondition).configure { convertLoopBody(block) }
     }
 
     /**
@@ -781,7 +791,7 @@ class ExpressionsConverter(
         forLoop.forEachChildren {
             when (it.tokenType) {
                 VALUE_PARAMETER -> parameter = declarationsConverter.convertValueParameter(it)
-                LOOP_RANGE -> convertCondition(it)?.apply { rangeExpression = this }
+                LOOP_RANGE -> rangeExpression = getAsFirExpression(it, "No range in for loop")
                 BODY -> blockNode = it
             }
         }
@@ -873,7 +883,7 @@ class ExpressionsConverter(
         tryExpression.forEachChildren {
             when (it.tokenType) {
                 BLOCK -> tryBlock = declarationsConverter.convertBlock(it)
-                CATCH -> catchClauses += convertCatchClause(it)
+                CATCH -> convertCatchClause(it)?.also { oneClause -> catchClauses += oneClause }
                 FINALLY -> finallyBlock = convertFinally(it)
             }
         }
@@ -888,12 +898,12 @@ class ExpressionsConverter(
     /**
      * @see org.jetbrains.kotlin.parsing.KotlinExpressionParsing.parseTry
      */
-    private fun convertCatchClause(catchClause: LighterASTNode): Pair<ValueParameter?, FirBlock> {
+    private fun convertCatchClause(catchClause: LighterASTNode): Pair<ValueParameter?, FirBlock>? {
         var valueParameter: ValueParameter? = null
         var blockNode: LighterASTNode? = null
         catchClause.forEachChildren {
             when (it.tokenType) {
-                VALUE_PARAMETER_LIST -> valueParameter = declarationsConverter.convertValueParameters(it).first()
+                VALUE_PARAMETER_LIST -> valueParameter = declarationsConverter.convertValueParameters(it).firstOrNull() ?: return null
                 BLOCK -> blockNode = it
             }
         }
@@ -920,20 +930,18 @@ class ExpressionsConverter(
      * @see org.jetbrains.kotlin.fir.builder.RawFirBuilder.Visitor.visitIfExpression
      */
     private fun convertIfExpression(ifExpression: LighterASTNode): FirExpression {
-        var condition: FirExpression? = null
+        var firCondition: FirExpression = FirErrorExpressionImpl(session, null, "If statement should have condition")
         var thenBlock: LighterASTNode? = null
         var elseBlock: LighterASTNode? = null
         ifExpression.forEachChildren {
             when (it.tokenType) {
-                CONDITION -> condition = convertCondition(it)
+                CONDITION -> firCondition = getAsFirExpression(it, "If statement should have condition")
                 THEN -> thenBlock = it
                 ELSE -> elseBlock = it
             }
         }
 
         return FirWhenExpressionImpl(session, null).apply {
-            val firCondition =
-                condition ?: FirErrorExpressionImpl(this@ExpressionsConverter.session, null, "If statement should have condition")
             val trueBranch = convertLoopBody(thenBlock)
             branches += FirWhenBranchImpl(this@ExpressionsConverter.session, null, firCondition, trueBranch)
             val elseBranch = convertLoopBody(elseBlock)
@@ -943,17 +951,6 @@ class ExpressionsConverter(
         }
     }
 
-    /**
-     * @see org.jetbrains.kotlin.parsing.KotlinExpressionParsing.parseCondition
-     */
-    private fun convertCondition(condition: LighterASTNode): FirExpression? {
-        condition.forEachChildren {
-            if (it.isExpression()) return getAsFirExpression(it)
-        }
-
-        return null
-    }
-
     /**
      * @see org.jetbrains.kotlin.parsing.KotlinExpressionParsing.parseJump
      * @see org.jetbrains.kotlin.fir.builder.RawFirBuilder.Visitor.visitBreakExpression
@@ -997,16 +994,15 @@ class ExpressionsConverter(
      */
     private fun convertReturn(returnExpression: LighterASTNode): FirExpression {
         var labelName: String? = null
-        var firExpression: FirExpression? = null
+        var firExpression: FirExpression = FirUnitExpression(session, null)
         returnExpression.forEachChildren {
             when (it.tokenType) {
-                LABEL_QUALIFIER -> labelName = it.getAsString().replace("@", "")
-                else -> if (it.isExpression()) firExpression = getAsFirExpression(it)
+                LABEL_QUALIFIER -> labelName = it.getAsStringWithoutBacktick().replace("@", "")
+                else -> if (it.isExpression()) firExpression = getAsFirExpression(it, "Incorrect return expression")
             }
         }
 
-        val result = firExpression ?: FirUnitExpression(session, null)
-        return result.toReturn(labelName)
+        return firExpression.toReturn(labelName)
     }
 
     /**
@@ -1014,12 +1010,12 @@ class ExpressionsConverter(
      * @see org.jetbrains.kotlin.fir.builder.RawFirBuilder.Visitor.visitThrowExpression
      */
     private fun convertThrow(throwExpression: LighterASTNode): FirExpression {
-        var firExpression: FirExpression? = null
+        var firExpression: FirExpression = FirErrorExpressionImpl(session, null, "Nothing to throw")
         throwExpression.forEachChildren {
-            if (it.isExpression()) firExpression = getAsFirExpression(it)
+            if (it.isExpression()) firExpression = getAsFirExpression(it, "Nothing to throw")
         }
 
-        return FirThrowExpressionImpl(session, null, firExpression ?: FirErrorExpressionImpl(session, null, "Nothing to throw"))
+        return FirThrowExpressionImpl(session, null, firExpression)
     }
 
     /**
@@ -1077,14 +1073,14 @@ class ExpressionsConverter(
     private fun convertValueArgument(valueArgument: LighterASTNode): FirExpression {
         var identifier: String? = null
         var isSpread = false
-        lateinit var firExpression: FirExpression
+        var firExpression: FirExpression = FirErrorExpressionImpl(session, null, "Argument is absent")
         valueArgument.forEachChildren {
             when (it.tokenType) {
                 VALUE_ARGUMENT_NAME -> identifier = it.getAsString()
                 MUL -> isSpread = true
                 STRING_TEMPLATE -> firExpression = convertStringTemplate(it)
                 is KtConstantExpressionElementType -> firExpression = convertConstantExpression(it)
-                else -> if (it.isExpression()) firExpression = getAsFirExpression(it)
+                else -> if (it.isExpression()) firExpression = getAsFirExpression(it, "Argument is absent")
             }
         }
         return when {
@@ -1097,15 +1093,16 @@ class ExpressionsConverter(
     /**
      * @see org.jetbrains.kotlin.fir.builder.ConversionUtilsKt.initializeLValue
      */
-    fun convertLValue(leftArgNode: LighterASTNode, container: FirModifiableQualifiedAccess<*>): FirReference {
-        return when (leftArgNode.tokenType) {
+    fun convertLValue(leftArgNode: LighterASTNode?, container: FirModifiableQualifiedAccess<*>): FirReference {
+        return when (leftArgNode?.tokenType) {
+            null -> FirErrorNamedReference(session, null, "Unsupported LValue: ${leftArgNode?.tokenType}")
             THIS_EXPRESSION -> convertThisExpression(leftArgNode).calleeReference
             REFERENCE_EXPRESSION -> FirSimpleNamedReference(session, null, leftArgNode.getAsString().nameAsSafeName())
-            in qualifiedAccessTokens -> (getAsFirExpression(leftArgNode) as FirQualifiedAccess).let { firQualifiedAccess ->
+            in qualifiedAccessTokens -> (getAsFirExpression<FirExpression>(leftArgNode) as? FirQualifiedAccess)?.let { firQualifiedAccess ->
                 container.explicitReceiver = firQualifiedAccess.explicitReceiver
                 container.safe = firQualifiedAccess.safe
                 return@let firQualifiedAccess.calleeReference
-            }
+            } ?: FirErrorNamedReference(session, null, "Unsupported qualified LValue: ${leftArgNode.getAsString()}")
             PARENTHESIZED -> convertLValue(leftArgNode.getExpressionInParentheses(), container)
             else -> FirErrorNamedReference(session, null, "Unsupported LValue: ${leftArgNode.tokenType}")
         }

compiler/fir/lightTree/src/org/jetbrains/kotlin/fir/lightTree/converter/utils/ExpressionUtil.kt

@@ -16,16 +16,14 @@ import org.jetbrains.kotlin.fir.expressions.*
 import org.jetbrains.kotlin.fir.expressions.impl.*
 import org.jetbrains.kotlin.fir.lightTree.converter.ConverterUtil.getAsString
 import org.jetbrains.kotlin.fir.lightTree.converter.ConverterUtil.nameAsSafeName
-import org.jetbrains.kotlin.fir.lightTree.converter.FunctionUtil.pop
-import org.jetbrains.kotlin.fir.lightTree.converter.FunctionUtil.removeLast
 import org.jetbrains.kotlin.fir.lightTree.converter.ExpressionsConverter
 import org.jetbrains.kotlin.fir.lightTree.converter.FunctionUtil
+import org.jetbrains.kotlin.fir.lightTree.converter.FunctionUtil.pop
+import org.jetbrains.kotlin.fir.lightTree.converter.FunctionUtil.removeLast
 import org.jetbrains.kotlin.fir.lightTree.fir.DestructuringDeclaration
 import org.jetbrains.kotlin.fir.references.FirSimpleNamedReference
 import org.jetbrains.kotlin.fir.symbols.impl.FirVariableSymbol
-import org.jetbrains.kotlin.fir.types.FirTypeRef
 import org.jetbrains.kotlin.lexer.KtSingleValueToken
-import org.jetbrains.kotlin.lexer.KtTokens
 import org.jetbrains.kotlin.lexer.KtTokens.*
 import org.jetbrains.kotlin.name.Name
 import org.jetbrains.kotlin.parsing.KotlinExpressionParsing
@@ -42,16 +40,17 @@ fun String.getOperationSymbol(): IElementType {
 }
 
 fun ExpressionsConverter.convertAssignment(
-    leftArgNode: LighterASTNode,
+    leftArgNode: LighterASTNode?,
     rightArgAsFir: FirExpression,
     operation: FirOperation
 ): FirStatement {
-    if (leftArgNode.tokenType == PARENTHESIZED) {
+    if (leftArgNode != null && leftArgNode.tokenType == PARENTHESIZED) {
         return convertAssignment(leftArgNode.getExpressionInParentheses(), rightArgAsFir, operation)
     }
-    if (leftArgNode.tokenType == ARRAY_ACCESS_EXPRESSION) {
+    if (leftArgNode != null && leftArgNode.tokenType == ARRAY_ACCESS_EXPRESSION) {
         val arrayAccessFunctionCall = getAsFirExpression(leftArgNode) as FirFunctionCall
-        val firArrayExpression = arrayAccessFunctionCall.explicitReceiver!!
+        val firArrayExpression = arrayAccessFunctionCall.explicitReceiver
+            ?: FirErrorExpressionImpl(session, null, "No array expression")
         val arraySet = if (operation != FirOperation.ASSIGN) {
             FirArraySetCallImpl(session, null, rightArgAsFir, operation).apply {
                 indexes += arrayAccessFunctionCall.arguments
@@ -76,12 +75,14 @@ fun ExpressionsConverter.convertAssignment(
         }
     }
     if (operation != FirOperation.ASSIGN &&
-        leftArgNode.tokenType != REFERENCE_EXPRESSION && leftArgNode.tokenType != THIS_EXPRESSION &&
-        (leftArgNode.tokenType !in qualifiedAccessTokens || getSelectorType(leftArgNode.getChildrenAsArray()) != REFERENCE_EXPRESSION)
+        leftArgNode?.tokenType != REFERENCE_EXPRESSION && leftArgNode?.tokenType != THIS_EXPRESSION &&
+        (leftArgNode?.tokenType !in qualifiedAccessTokens || getSelectorType(leftArgNode.getChildrenAsArray()) != REFERENCE_EXPRESSION)
     ) {
         return FirBlockImpl(session, null).apply {
             val name = Name.special("<complex-set>")
-            statements += generateTemporaryVariable(this@convertAssignment.session, null, name, getAsFirExpression(leftArgNode))
+            statements += generateTemporaryVariable(
+                this@convertAssignment.session, null, name, getAsFirExpression(leftArgNode, "No LValue in assignment")
+            )
             statements += FirVariableAssignmentImpl(this@convertAssignment.session, null, rightArgAsFir, operation).apply {
                 lValue = FirSimpleNamedReference(this@convertAssignment.session, null, name)
             }
@@ -104,7 +105,7 @@ fun ExpressionsConverter.generateIncrementOrDecrementBlock(
     return FirBlockImpl(session, null).apply {
         val tempName = Name.special("<unary>")
         val temporaryVariable = generateTemporaryVariable(
-            this@generateIncrementOrDecrementBlock.session, null, tempName, getAsFirExpression(argument)
+            this@generateIncrementOrDecrementBlock.session, null, tempName, getAsFirExpression(argument, "Incorrect expression inside inc/dec")
         )
         statements += temporaryVariable
         val resultName = Name.special("<unary-result>")

compiler/fir/lightTree/src/org/jetbrains/kotlin/fir/lightTree/fir/ClassWrapper.kt

@@ -30,12 +30,16 @@ class ClassWrapper(
     val delegatedSuperTypeRef: FirTypeRef,
     val superTypeCallEntry: MutableList<FirExpression>
 ) {
+    fun isObjectLiteral(): Boolean {
+        return className == SpecialNames.NO_NAME_PROVIDED && isObject()
+    }
+
     private fun isObject(): Boolean {
         return classKind == ClassKind.OBJECT
     }
 
     private fun isSealed(): Boolean {
-        return modifiers.getModality() == Modality.SEALED
+        return modifiers.hasModality(Modality.SEALED)
     }
 
     private fun isEnum(): Boolean {

compiler/fir/lightTree/src/org/jetbrains/kotlin/fir/lightTree/fir/DestructuringDeclaration.kt

@@ -16,18 +16,10 @@ import org.jetbrains.kotlin.fir.lightTree.converter.utils.generateDestructuringB
 data class DestructuringDeclaration(
     val isVar: Boolean,
     val entries: List<FirVariable<*>>,
-    val initializer: FirExpression?
+    val initializer: FirExpression
 ) {
     fun toFirDestructingDeclaration(session: FirSession): FirExpression {
-        val baseVariable = generateTemporaryVariable(
-            session, null, "destruct",
-            initializer ?: FirErrorExpressionImpl(session, null, "Destructuring declaration without initializer")
-        )
-        return generateDestructuringBlock(
-            session,
-            this,
-            baseVariable,
-            tmpVariable = true
-        )
+        val baseVariable = generateTemporaryVariable(session, null, "destruct", initializer)
+        return generateDestructuringBlock(session, this, baseVariable, tmpVariable = true)
     }
 }

compiler/fir/lightTree/src/org/jetbrains/kotlin/fir/lightTree/fir/ValueParameter.kt

@@ -17,6 +17,9 @@ import org.jetbrains.kotlin.fir.lightTree.converter.ClassNameUtil
 import org.jetbrains.kotlin.fir.lightTree.fir.modifier.Modifier
 import org.jetbrains.kotlin.fir.references.FirPropertyFromParameterCallableReference
 import org.jetbrains.kotlin.fir.symbols.impl.FirPropertySymbol
+import org.jetbrains.kotlin.fir.types.FirErrorTypeRef
+import org.jetbrains.kotlin.fir.types.FirImplicitTypeRef
+import org.jetbrains.kotlin.fir.types.impl.FirErrorTypeRefImpl
 
 class ValueParameter(
     private val isVal: Boolean,
@@ -31,7 +34,10 @@ class ValueParameter(
 
     fun toFirProperty(): FirProperty {
         val name = this.firValueParameter.name
-        val type = this.firValueParameter.returnTypeRef
+        var type = this.firValueParameter.returnTypeRef
+        if (type is FirImplicitTypeRef) {
+            type = FirErrorTypeRefImpl(this.firValueParameter.session, null, "Incomplete code")
+        }
 
         return FirMemberPropertyImpl(
             this.firValueParameter.session,

compiler/fir/lightTree/src/org/jetbrains/kotlin/fir/lightTree/fir/WhenEntry.kt

@@ -64,9 +64,9 @@ data class WhenEntry(
         val condition = conditions.first()
         return when (condition) {
             is FirOperatorCallImpl -> condition.arguments.first()
-            is FirFunctionCall -> condition.explicitReceiver!!
-            is FirTypeOperatorCallImpl -> condition
-            else -> FirErrorExpressionImpl(session, null, "Unsupported when condition: ${condition.javaClass}")
+            //is FirFunctionCall -> condition.explicitReceiver!!
+            //is FirTypeOperatorCallImpl -> condition
+            else -> FirErrorExpressionImpl(session, null, "No expression in condition with expression")
         }
     }
 }

compiler/fir/lightTree/src/org/jetbrains/kotlin/fir/lightTree/fir/modifier/Modifier.kt

@@ -8,6 +8,7 @@ package org.jetbrains.kotlin.fir.lightTree.fir.modifier
 import com.intellij.lang.LighterASTNode
 import com.intellij.psi.PsiElement
 import org.jetbrains.kotlin.descriptors.Modality
+import org.jetbrains.kotlin.descriptors.Visibilities
 import org.jetbrains.kotlin.descriptors.Visibility
 import org.jetbrains.kotlin.fir.FirSession
 import org.jetbrains.kotlin.fir.expressions.impl.FirAbstractAnnotatedElement
@@ -24,49 +25,49 @@ class Modifier(
     session: FirSession,
     psi: PsiElement? = null,
 
-    private var classModifier: ClassModifier? = null,
+    private val classModifiers: MutableList<ClassModifier> = mutableListOf(),
     private val memberModifiers: MutableList<MemberModifier> = mutableListOf(),
-    private var visibilityModifier: VisibilityModifier = VisibilityModifier.UNKNOWN,
+    private val visibilityModifiers: MutableList<VisibilityModifier> = mutableListOf(),
     private val functionModifiers: MutableList<FunctionModifier> = mutableListOf(),
     private var propertyModifier: PropertyModifier? = null,
-    private var inheritanceModifier: InheritanceModifier? = null,
-    private var parameterModifier: ParameterModifier? = null,
-    private var platformModifier: PlatformModifier? = null
+    private val inheritanceModifiers: MutableList<InheritanceModifier> = mutableListOf(),
+    private val parameterModifiers: MutableList<ParameterModifier> = mutableListOf(),
+    private val platformModifiers: MutableList<PlatformModifier> = mutableListOf()
 ) : FirAbstractAnnotatedElement(session, psi) {
     fun addModifier(modifier: LighterASTNode) {
         val tokenType = modifier.tokenType
         when {
-            CLASS_MODIFIER.contains(tokenType) -> this.classModifier = ClassModifier.valueOf(modifier.toString().toUpperCase())
+            CLASS_MODIFIER.contains(tokenType) -> this.classModifiers += ClassModifier.valueOf(modifier.toString().toUpperCase())
             MEMBER_MODIFIER.contains(tokenType) -> this.memberModifiers += MemberModifier.valueOf(modifier.toString().toUpperCase())
-            VISIBILITY_MODIFIER.contains(tokenType) -> this.visibilityModifier =
+            VISIBILITY_MODIFIER.contains(tokenType) -> this.visibilityModifiers +=
                 VisibilityModifier.valueOf(modifier.toString().toUpperCase())
             FUNCTION_MODIFIER.contains(tokenType) -> this.functionModifiers += FunctionModifier.valueOf(modifier.toString().toUpperCase())
             PROPERTY_MODIFIER.contains(tokenType) -> this.propertyModifier = PropertyModifier.valueOf(modifier.toString().toUpperCase())
-            INHERITANCE_MODIFIER.contains(tokenType) -> this.inheritanceModifier =
+            INHERITANCE_MODIFIER.contains(tokenType) -> this.inheritanceModifiers +=
                 InheritanceModifier.valueOf(modifier.toString().toUpperCase())
-            PARAMETER_MODIFIER.contains(tokenType) -> this.parameterModifier = ParameterModifier.valueOf(modifier.toString().toUpperCase())
-            PLATFORM_MODIFIER.contains(tokenType) -> this.platformModifier = PlatformModifier.valueOf(modifier.toString().toUpperCase())
+            PARAMETER_MODIFIER.contains(tokenType) -> this.parameterModifiers += ParameterModifier.valueOf(modifier.toString().toUpperCase())
+            PLATFORM_MODIFIER.contains(tokenType) -> this.platformModifiers += PlatformModifier.valueOf(modifier.toString().toUpperCase())
         }
     }
 
     fun isEnum(): Boolean {
-        return classModifier == ClassModifier.ENUM
+        return classModifiers.contains(ClassModifier.ENUM)
     }
 
     fun isAnnotation(): Boolean {
-        return classModifier == ClassModifier.ANNOTATION
+        return classModifiers.contains(ClassModifier.ANNOTATION)
     }
 
     fun isDataClass(): Boolean {
-        return classModifier == ClassModifier.DATA
+        return classModifiers.contains(ClassModifier.DATA)
     }
 
     fun isInner(): Boolean {
-        return classModifier == ClassModifier.INNER
+        return classModifiers.contains(ClassModifier.INNER)
     }
 
     fun isCompanion(): Boolean {
-        return classModifier == ClassModifier.COMPANION
+        return classModifiers.contains(ClassModifier.COMPANION)
     }
 
     fun hasOverride(): Boolean {
@@ -78,7 +79,13 @@ class Modifier(
     }
 
     fun getVisibility(): Visibility {
-        return visibilityModifier.toVisibility()
+        return when {
+            visibilityModifiers.contains(VisibilityModifier.PRIVATE) -> Visibilities.PRIVATE
+            visibilityModifiers.contains(VisibilityModifier.PUBLIC) -> Visibilities.PUBLIC
+            visibilityModifiers.contains(VisibilityModifier.PROTECTED) -> Visibilities.PROTECTED
+            visibilityModifiers.contains(VisibilityModifier.INTERNAL) -> Visibilities.INTERNAL
+            else -> Visibilities.UNKNOWN
+        }
     }
 
     fun hasTailrec(): Boolean {
@@ -109,27 +116,43 @@ class Modifier(
         return propertyModifier == PropertyModifier.CONST
     }
 
+    fun hasModality(modality: Modality): Boolean {
+        return when {
+            modality == Modality.FINAL && inheritanceModifiers.contains(InheritanceModifier.FINAL) -> true
+            modality == Modality.SEALED && inheritanceModifiers.contains(InheritanceModifier.SEALED) -> true
+            modality == Modality.ABSTRACT && inheritanceModifiers.contains(InheritanceModifier.ABSTRACT) -> true
+            modality == Modality.OPEN && inheritanceModifiers.contains(InheritanceModifier.OPEN) -> true
+            else -> false
+        }
+    }
+
     fun getModality(): Modality? {
-        return inheritanceModifier?.toModality()
+        return when {
+            inheritanceModifiers.contains(InheritanceModifier.FINAL) -> Modality.FINAL
+            inheritanceModifiers.contains(InheritanceModifier.SEALED) -> Modality.SEALED
+            inheritanceModifiers.contains(InheritanceModifier.ABSTRACT) -> Modality.ABSTRACT
+            inheritanceModifiers.contains(InheritanceModifier.OPEN) -> Modality.OPEN
+            else -> null
+        }
     }
 
     fun hasVararg(): Boolean {
-        return parameterModifier == ParameterModifier.VARARG
+        return parameterModifiers.contains(ParameterModifier.VARARG)
     }
 
     fun hasNoinline(): Boolean {
-        return parameterModifier == ParameterModifier.NOINLINE
+        return parameterModifiers.contains(ParameterModifier.NOINLINE)
     }
 
     fun hasCrossinline(): Boolean {
-        return parameterModifier == ParameterModifier.CROSSINLINE
+        return parameterModifiers.contains(ParameterModifier.CROSSINLINE)
     }
 
     fun hasExpect(): Boolean {
-        return platformModifier == PlatformModifier.EXPECT
+        return platformModifiers.contains(PlatformModifier.EXPECT) || platformModifiers.contains(PlatformModifier.HEADER)
     }
 
     fun hasActual(): Boolean {
-        return platformModifier == PlatformModifier.ACTUAL
+        return platformModifiers.contains(PlatformModifier.ACTUAL) || platformModifiers.contains(PlatformModifier.IMPL)
     }
 }

compiler/fir/lightTree/src/org/jetbrains/kotlin/fir/lightTree/fir/modifier/ModifierSets.kt

@@ -41,7 +41,7 @@ object ModifierSets {
         SEALED_KEYWORD
     )
     val PARAMETER_MODIFIER = TokenSet.create(VARARG_KEYWORD, NOINLINE_KEYWORD, CROSSINLINE_KEYWORD)
-    val PLATFORM_MODIFIER = TokenSet.create(EXPECT_KEYWORD, ACTUAL_KEYWORD)
+    val PLATFORM_MODIFIER = TokenSet.create(EXPECT_KEYWORD, ACTUAL_KEYWORD, HEADER_KEYWORD, IMPL_KEYWORD)
     val VARIANCE_MODIFIER = TokenSet.create(IN_KEYWORD, OUT_KEYWORD)
     val REIFICATION_MODIFIER = TokenSet.create(REIFIED_KEYWORD)
 }

compiler/fir/lightTree/src/org/jetbrains/kotlin/fir/lightTree/fir/modifier/ModifiersEnumSet.kt

@@ -24,33 +24,11 @@ enum class MemberModifier {
 }
 
 enum class VisibilityModifier {
-    PUBLIC {
-        override fun toVisibility(): Visibility {
-            return Visibilities.PUBLIC
-        }
-    },
-    PRIVATE {
-        override fun toVisibility(): Visibility {
-            return Visibilities.PRIVATE
-        }
-    },
-    INTERNAL {
-        override fun toVisibility(): Visibility {
-            return Visibilities.INTERNAL
-        }
-    },
-    PROTECTED {
-        override fun toVisibility(): Visibility {
-            return Visibilities.PROTECTED
-        }
-    },
-    UNKNOWN {
-        override fun toVisibility(): Visibility {
-            return Visibilities.UNKNOWN
-        }
-    };
-
-    abstract fun toVisibility(): Visibility
+    PUBLIC,
+    PRIVATE,
+    INTERNAL,
+    PROTECTED,
+    UNKNOWN
 }
 
 enum class FunctionModifier {
@@ -67,28 +45,10 @@ enum class PropertyModifier {
 }
 
 enum class InheritanceModifier {
-    ABSTRACT {
-        override fun toModality(): Modality {
-            return Modality.ABSTRACT
-        }
-    },
-    FINAL {
-        override fun toModality(): Modality {
-            return Modality.FINAL
-        }
-    },
-    OPEN {
-        override fun toModality(): Modality {
-            return Modality.OPEN
-        }
-    },
-    SEALED {
-        override fun toModality(): Modality {
-            return Modality.SEALED
-        }
-    };
-
-    abstract fun toModality(): Modality
+    ABSTRACT,
+    FINAL,
+    OPEN,
+    SEALED
 }
 
 enum class ParameterModifier {
@@ -99,27 +59,15 @@ enum class ParameterModifier {
 
 enum class PlatformModifier {
     EXPECT,
-    ACTUAL
+    ACTUAL,
+    HEADER,
+    IMPL
 }
 
 enum class VarianceModifier {
-    IN {
-        override fun toVariance(): Variance {
-            return Variance.IN_VARIANCE
-        }
-    },
-    OUT {
-        override fun toVariance(): Variance {
-            return Variance.OUT_VARIANCE
-        }
-    },
-    INVARIANT {
-        override fun toVariance(): Variance {
-            return Variance.INVARIANT
-        }
-    };
-
-    abstract fun toVariance(): Variance
+    IN,
+    OUT,
+    INVARIANT
 }
 
 enum class ReificationModifier {

compiler/fir/lightTree/src/org/jetbrains/kotlin/fir/lightTree/fir/modifier/TypeModifier.kt

@@ -22,4 +22,8 @@ class TypeModifier(
             KtTokens.SUSPEND_KEYWORD -> this.hasSuspend = true
         }
     }
+
+    fun hasNoAnnotations(): Boolean {
+        return annotations.isEmpty()
+    }
 }

compiler/fir/lightTree/src/org/jetbrains/kotlin/fir/lightTree/fir/modifier/TypeParameterModifier.kt

@@ -17,19 +17,24 @@ class TypeParameterModifier(
     session: FirSession,
     psi: PsiElement? = null,
 
-    private var varianceModifier: VarianceModifier = VarianceModifier.INVARIANT,
+    private val varianceModifiers: MutableList<VarianceModifier> = mutableListOf(),
     private var reificationModifier: ReificationModifier? = null
 ) : FirAbstractAnnotatedElement(session, psi) {
     fun addModifier(modifier: LighterASTNode) {
         val tokenType = modifier.tokenType
         when {
-            VARIANCE_MODIFIER.contains(tokenType) -> this.varianceModifier = VarianceModifier.valueOf(modifier.toString().toUpperCase())
-            REIFICATION_MODIFIER.contains(tokenType) -> this.reificationModifier = ReificationModifier.valueOf(modifier.toString().toUpperCase())
+            VARIANCE_MODIFIER.contains(tokenType) -> this.varianceModifiers += VarianceModifier.valueOf(modifier.toString().toUpperCase())
+            REIFICATION_MODIFIER.contains(tokenType) -> this.reificationModifier =
+                ReificationModifier.valueOf(modifier.toString().toUpperCase())
         }
     }
 
     fun getVariance(): Variance {
-        return varianceModifier.toVariance()
+        return when {
+            varianceModifiers.contains(VarianceModifier.OUT) -> Variance.OUT_VARIANCE
+            varianceModifiers.contains(VarianceModifier.IN) -> Variance.IN_VARIANCE
+            else -> Variance.INVARIANT
+        }
     }
 
     fun hasReified(): Boolean {

compiler/fir/lightTree/src/org/jetbrains/kotlin/fir/lightTree/fir/modifier/TypeProjectionModifier.kt

@@ -16,16 +16,20 @@ class TypeProjectionModifier(
     session: FirSession,
     psi: PsiElement? = null,
 
-    private var varianceModifier: VarianceModifier = VarianceModifier.INVARIANT
+    private val varianceModifiers: MutableList<VarianceModifier> = mutableListOf()
 ) : FirAbstractAnnotatedElement(session, psi) {
     fun addModifier(modifier: LighterASTNode) {
         val tokenType = modifier.tokenType
         when {
-            VARIANCE_MODIFIER.contains(tokenType) -> this.varianceModifier = VarianceModifier.valueOf(modifier.toString().toUpperCase())
+            VARIANCE_MODIFIER.contains(tokenType) -> this.varianceModifiers += VarianceModifier.valueOf(modifier.toString().toUpperCase())
         }
     }
 
     fun getVariance(): Variance {
-        return varianceModifier.toVariance()
+        return when {
+            varianceModifiers.contains(VarianceModifier.IN) -> Variance.IN_VARIANCE
+            varianceModifiers.contains(VarianceModifier.OUT) -> Variance.OUT_VARIANCE
+            else -> Variance.INVARIANT
+        }
     }
 }

compiler/fir/lightTree/tests/org/jetbrains/kotlin/fir/lightTree/compare/TreesCompareTest.kt

@@ -27,37 +27,56 @@ class TreesCompareTest : AbstractRawFirBuilderTestCase() {
         var counter = 0
         var errorCounter = 0
 
+        val onEachFile: (File) -> Unit = { file ->
+            if (!compareFir(file)) errorCounter++
+            counter++
+        }
         println("BASE PATH: $path")
         if (!withTestData) {
-            path.walkTopDown { file ->
-                if (!compareFir(file)) errorCounter++
-                counter++
-            }
+            path.walkTopDown(onEachFile)
         } else {
-            path.walkTopDownWithTestData { file ->
-                if (!compareFir(file)) errorCounter++
-                counter++
-            }
+            path.walkTopDownWithTestData(onEachFile)
         }
         println("All scanned files: $counter")
         println("Files that aren't equal to FIR: $errorCounter")
         TestCase.assertEquals(0, errorCounter)
     }
 
-    private fun compareAll(stubMode: Boolean, path: String = System.getProperty("user.dir"), withTestData: Boolean = false) {
+    private fun compareAll(stubMode: Boolean) {
         val lightTreeConverter = LightTree2Fir(stubMode, myProject)
-        compareBase(path, withTestData) { file ->
+        compareBase(System.getProperty("user.dir"), withTestData = false) { file ->
             val text = FileUtil.loadFile(file, CharsetToolkit.UTF8, true).trim()
 
-            //light tree
-            val firFileFromLightTree = lightTreeConverter.buildFirFile(text, file.name)
-            val treeFromLightTree = StringBuilder().also { FirRenderer(it).visitFile(firFileFromLightTree) }.toString()
-
             //psi
             val ktFile = createPsiFile(FileUtil.getNameWithoutExtension(PathUtil.getFileName(file.path)), text) as KtFile
             val firFileFromPsi = ktFile.toFirFile(stubMode)
             val treeFromPsi = StringBuilder().also { FirRenderer(it).visitFile(firFileFromPsi) }.toString()
 
+            //light tree
+            val firFileFromLightTree = lightTreeConverter.buildFirFile(text, file.name)
+            val treeFromLightTree = StringBuilder().also { FirRenderer(it).visitFile(firFileFromLightTree) }.toString()
+
+            return@compareBase treeFromLightTree == treeFromPsi
+        }
+    }
+
+    fun testCompareDiagnostics() {
+        val lightTreeConverter = LightTree2Fir(false, myProject)
+        compareBase("compiler/testData/diagnostics/tests", withTestData = true) { file ->
+            val notEditedText = FileUtil.loadFile(file, CharsetToolkit.UTF8, true).trim()
+            val text = notEditedText.replace("(<!>)|(<!.*?!>)".toRegex(), "").replaceAfter(".java", "")
+
+            //psi
+            val ktFile = createPsiFile(FileUtil.getNameWithoutExtension(PathUtil.getFileName(file.path)), text) as KtFile
+            val firFileFromPsi = ktFile.toFirFile(stubMode = false)
+            val treeFromPsi = StringBuilder().also { FirRenderer(it).visitFile(firFileFromPsi) }.toString()
+                .replace("<Unsupported LValue.*?>".toRegex(), "<Unsupported LValue>")
+
+            //light tree
+            val firFileFromLightTree = lightTreeConverter.buildFirFile(text, file.name)
+            val treeFromLightTree = StringBuilder().also { FirRenderer(it).visitFile(firFileFromLightTree) }.toString()
+                .replace("<Unsupported LValue.*?>".toRegex(), "<Unsupported LValue>")
+
             return@compareBase treeFromLightTree == treeFromPsi
         }
     }
@@ -366,8 +385,4 @@ class TreesCompareTest : AbstractRawFirBuilderTestCase() {
             visitAnonymousObject = true
         )
     }
-
-    fun testDiagnostics() {
-        compareAll(false, "compiler/testData/diagnostics/tests", withTestData = true)
-    }
 }