[FIR] Add FirBackingField

compiler/fir/java/src/org/jetbrains/kotlin/fir/java/declarations/FirJavaField.kt

@@ -55,6 +55,7 @@ class FirJavaField @FirImplementationDetail constructor(
     override val isVal: Boolean get() = !isVar
     override val getter: FirPropertyAccessor? get() = null
     override val setter: FirPropertyAccessor? get() = null
+    override val backingField: FirBackingField? = null
 
     override val origin: FirDeclarationOrigin
         get() = FirDeclarationOrigin.Java
@@ -78,6 +79,10 @@ class FirJavaField @FirImplementationDetail constructor(
         return this
     }
 
+    override fun <D> transformBackingField(transformer: FirTransformer<D>, data: D): FirField {
+        return this
+    }
+
     override fun <D> transformOtherChildren(transformer: FirTransformer<D>, data: D): FirField {
         transformAnnotations(transformer, data)
         initializer = initializer?.transformSingle(transformer, data)

compiler/fir/java/src/org/jetbrains/kotlin/fir/java/declarations/FirJavaValueParameter.kt

@@ -79,6 +79,9 @@ class FirJavaValueParameter @FirImplementationDetail constructor(
     override val setter: FirPropertyAccessor?
         get() = null
 
+    override val backingField: FirBackingField?
+        get() = null
+
     override val controlFlowGraphReference: FirControlFlowGraphReference?
         get() = null
 
@@ -131,6 +134,10 @@ class FirJavaValueParameter @FirImplementationDetail constructor(
         return this
     }
 
+    override fun <D> transformBackingField(transformer: FirTransformer<D>, data: D): FirValueParameter {
+        return this
+    }
+
     override fun <D> transformAnnotations(transformer: FirTransformer<D>, data: D): FirValueParameter {
         return this
     }

compiler/fir/tree/gen/org/jetbrains/kotlin/fir/declarations/FirBackingField.kt

@@ -0,0 +1,61 @@
+/*
+ * Copyright 2010-2021 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package org.jetbrains.kotlin.fir.declarations
+
+import org.jetbrains.kotlin.fir.FirElement
+import org.jetbrains.kotlin.fir.FirModuleData
+import org.jetbrains.kotlin.fir.FirSourceElement
+import org.jetbrains.kotlin.fir.expressions.FirAnnotationCall
+import org.jetbrains.kotlin.fir.expressions.FirExpression
+import org.jetbrains.kotlin.fir.expressions.FirStatement
+import org.jetbrains.kotlin.fir.symbols.impl.FirBackingFieldSymbol
+import org.jetbrains.kotlin.fir.symbols.impl.FirPropertyFieldDeclarationSymbol
+import org.jetbrains.kotlin.fir.symbols.impl.FirPropertySymbol
+import org.jetbrains.kotlin.fir.types.FirTypeRef
+import org.jetbrains.kotlin.fir.visitors.*
+
+/*
+ * This file was generated automatically
+ * DO NOT MODIFY IT MANUALLY
+ */
+
+abstract class FirBackingField : FirTypedDeclaration(), FirTypeParametersOwner, FirStatement {
+    abstract override val source: FirSourceElement?
+    abstract override val moduleData: FirModuleData
+    abstract override val resolvePhase: FirResolvePhase
+    abstract override val origin: FirDeclarationOrigin
+    abstract override val attributes: FirDeclarationAttributes
+    abstract override val returnTypeRef: FirTypeRef
+    abstract override val symbol: FirPropertyFieldDeclarationSymbol
+    abstract val backingFieldSymbol: FirBackingFieldSymbol?
+    abstract val propertySymbol: FirPropertySymbol?
+    abstract val initializer: FirExpression?
+    abstract override val annotations: List<FirAnnotationCall>
+    abstract override val typeParameters: List<FirTypeParameter>
+    abstract val status: FirDeclarationStatus
+
+    override fun <R, D> accept(visitor: FirVisitor<R, D>, data: D): R = visitor.visitBackingField(this, data)
+
+    @Suppress("UNCHECKED_CAST")
+    override fun <E: FirElement, D> transform(transformer: FirTransformer<D>, data: D): E = 
+        transformer.transformBackingField(this, data) as E
+
+    abstract override fun replaceResolvePhase(newResolvePhase: FirResolvePhase)
+
+    abstract override fun replaceReturnTypeRef(newReturnTypeRef: FirTypeRef)
+
+    abstract fun replaceInitializer(newInitializer: FirExpression?)
+
+    abstract override fun <D> transformReturnTypeRef(transformer: FirTransformer<D>, data: D): FirBackingField
+
+    abstract fun <D> transformInitializer(transformer: FirTransformer<D>, data: D): FirBackingField
+
+    abstract override fun <D> transformAnnotations(transformer: FirTransformer<D>, data: D): FirBackingField
+
+    abstract override fun <D> transformTypeParameters(transformer: FirTransformer<D>, data: D): FirBackingField
+
+    abstract fun <D> transformStatus(transformer: FirTransformer<D>, data: D): FirBackingField
+}

compiler/fir/tree/gen/org/jetbrains/kotlin/fir/declarations/FirEnumEntry.kt

@@ -42,6 +42,7 @@ abstract class FirEnumEntry : FirVariable() {
     abstract override val isVal: Boolean
     abstract override val getter: FirPropertyAccessor?
     abstract override val setter: FirPropertyAccessor?
+    abstract override val backingField: FirBackingField?
     abstract override val annotations: List<FirAnnotationCall>
     abstract override val symbol: FirEnumEntrySymbol
 
@@ -77,6 +78,8 @@ abstract class FirEnumEntry : FirVariable() {
 
     abstract override fun <D> transformSetter(transformer: FirTransformer<D>, data: D): FirEnumEntry
 
+    abstract override fun <D> transformBackingField(transformer: FirTransformer<D>, data: D): FirEnumEntry
+
     abstract override fun <D> transformAnnotations(transformer: FirTransformer<D>, data: D): FirEnumEntry
 
     abstract override fun <D> transformOtherChildren(transformer: FirTransformer<D>, data: D): FirEnumEntry

compiler/fir/tree/gen/org/jetbrains/kotlin/fir/declarations/FirErrorProperty.kt

@@ -44,6 +44,7 @@ abstract class FirErrorProperty : FirVariable(), FirDiagnosticHolder {
     abstract override val isVal: Boolean
     abstract override val getter: FirPropertyAccessor?
     abstract override val setter: FirPropertyAccessor?
+    abstract override val backingField: FirBackingField?
     abstract override val annotations: List<FirAnnotationCall>
     abstract override val diagnostic: ConeDiagnostic
     abstract override val symbol: FirErrorPropertySymbol
@@ -80,6 +81,8 @@ abstract class FirErrorProperty : FirVariable(), FirDiagnosticHolder {
 
     abstract override fun <D> transformSetter(transformer: FirTransformer<D>, data: D): FirErrorProperty
 
+    abstract override fun <D> transformBackingField(transformer: FirTransformer<D>, data: D): FirErrorProperty
+
     abstract override fun <D> transformAnnotations(transformer: FirTransformer<D>, data: D): FirErrorProperty
 
     abstract override fun <D> transformOtherChildren(transformer: FirTransformer<D>, data: D): FirErrorProperty

compiler/fir/tree/gen/org/jetbrains/kotlin/fir/declarations/FirField.kt

@@ -42,6 +42,7 @@ abstract class FirField : FirVariable() {
     abstract override val isVal: Boolean
     abstract override val getter: FirPropertyAccessor?
     abstract override val setter: FirPropertyAccessor?
+    abstract override val backingField: FirBackingField?
     abstract override val annotations: List<FirAnnotationCall>
     abstract override val symbol: FirFieldSymbol
 
@@ -77,6 +78,8 @@ abstract class FirField : FirVariable() {
 
     abstract override fun <D> transformSetter(transformer: FirTransformer<D>, data: D): FirField
 
+    abstract override fun <D> transformBackingField(transformer: FirTransformer<D>, data: D): FirField
+
     abstract override fun <D> transformAnnotations(transformer: FirTransformer<D>, data: D): FirField
 
     abstract override fun <D> transformOtherChildren(transformer: FirTransformer<D>, data: D): FirField

compiler/fir/tree/gen/org/jetbrains/kotlin/fir/declarations/FirProperty.kt

@@ -44,6 +44,7 @@ abstract class FirProperty : FirVariable(), FirTypeParametersOwner, FirControlFl
     abstract override val isVal: Boolean
     abstract override val getter: FirPropertyAccessor?
     abstract override val setter: FirPropertyAccessor?
+    abstract override val backingField: FirBackingField?
     abstract override val annotations: List<FirAnnotationCall>
     abstract override val controlFlowGraphReference: FirControlFlowGraphReference?
     abstract override val symbol: FirPropertySymbol
@@ -87,6 +88,8 @@ abstract class FirProperty : FirVariable(), FirTypeParametersOwner, FirControlFl
 
     abstract override fun <D> transformSetter(transformer: FirTransformer<D>, data: D): FirProperty
 
+    abstract override fun <D> transformBackingField(transformer: FirTransformer<D>, data: D): FirProperty
+
     abstract override fun <D> transformAnnotations(transformer: FirTransformer<D>, data: D): FirProperty
 
     abstract override fun <D> transformTypeParameters(transformer: FirTransformer<D>, data: D): FirProperty

compiler/fir/tree/gen/org/jetbrains/kotlin/fir/declarations/FirValueParameter.kt

@@ -43,6 +43,7 @@ abstract class FirValueParameter : FirVariable(), FirControlFlowGraphOwner {
     abstract override val isVal: Boolean
     abstract override val getter: FirPropertyAccessor?
     abstract override val setter: FirPropertyAccessor?
+    abstract override val backingField: FirBackingField?
     abstract override val annotations: List<FirAnnotationCall>
     abstract override val controlFlowGraphReference: FirControlFlowGraphReference?
     abstract override val symbol: FirValueParameterSymbol
@@ -85,6 +86,8 @@ abstract class FirValueParameter : FirVariable(), FirControlFlowGraphOwner {
 
     abstract override fun <D> transformSetter(transformer: FirTransformer<D>, data: D): FirValueParameter
 
+    abstract override fun <D> transformBackingField(transformer: FirTransformer<D>, data: D): FirValueParameter
+
     abstract override fun <D> transformAnnotations(transformer: FirTransformer<D>, data: D): FirValueParameter
 
     abstract override fun <D> transformOtherChildren(transformer: FirTransformer<D>, data: D): FirValueParameter

compiler/fir/tree/gen/org/jetbrains/kotlin/fir/declarations/FirVariable.kt

@@ -44,6 +44,7 @@ sealed class FirVariable : FirCallableDeclaration(), FirStatement {
     abstract val isVal: Boolean
     abstract val getter: FirPropertyAccessor?
     abstract val setter: FirPropertyAccessor?
+    abstract val backingField: FirBackingField?
     abstract override val annotations: List<FirAnnotationCall>
 
     override fun <R, D> accept(visitor: FirVisitor<R, D>, data: D): R = visitor.visitVariable(this, data)
@@ -78,6 +79,8 @@ sealed class FirVariable : FirCallableDeclaration(), FirStatement {
 
     abstract fun <D> transformSetter(transformer: FirTransformer<D>, data: D): FirVariable
 
+    abstract fun <D> transformBackingField(transformer: FirTransformer<D>, data: D): FirVariable
+
     abstract override fun <D> transformAnnotations(transformer: FirTransformer<D>, data: D): FirVariable
 
     abstract fun <D> transformOtherChildren(transformer: FirTransformer<D>, data: D): FirVariable

compiler/fir/tree/gen/org/jetbrains/kotlin/fir/declarations/builder/FirBackingFieldBuilder.kt

@@ -0,0 +1,75 @@
+/*
+ * Copyright 2010-2021 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package org.jetbrains.kotlin.fir.declarations.builder
+
+import kotlin.contracts.*
+import org.jetbrains.kotlin.fir.FirModuleData
+import org.jetbrains.kotlin.fir.FirSourceElement
+import org.jetbrains.kotlin.fir.builder.FirAnnotationContainerBuilder
+import org.jetbrains.kotlin.fir.builder.FirBuilderDsl
+import org.jetbrains.kotlin.fir.declarations.FirBackingField
+import org.jetbrains.kotlin.fir.declarations.FirDeclarationAttributes
+import org.jetbrains.kotlin.fir.declarations.FirDeclarationOrigin
+import org.jetbrains.kotlin.fir.declarations.FirDeclarationStatus
+import org.jetbrains.kotlin.fir.declarations.FirResolvePhase
+import org.jetbrains.kotlin.fir.declarations.FirTypeParameter
+import org.jetbrains.kotlin.fir.declarations.impl.FirBackingFieldImpl
+import org.jetbrains.kotlin.fir.expressions.FirAnnotationCall
+import org.jetbrains.kotlin.fir.expressions.FirExpression
+import org.jetbrains.kotlin.fir.symbols.impl.FirBackingFieldSymbol
+import org.jetbrains.kotlin.fir.symbols.impl.FirPropertyFieldDeclarationSymbol
+import org.jetbrains.kotlin.fir.symbols.impl.FirPropertySymbol
+import org.jetbrains.kotlin.fir.types.FirTypeRef
+import org.jetbrains.kotlin.fir.visitors.*
+
+/*
+ * This file was generated automatically
+ * DO NOT MODIFY IT MANUALLY
+ */
+
+@FirBuilderDsl
+class FirBackingFieldBuilder : FirAnnotationContainerBuilder {
+    override var source: FirSourceElement? = null
+    lateinit var moduleData: FirModuleData
+    var resolvePhase: FirResolvePhase = FirResolvePhase.RAW_FIR
+    lateinit var origin: FirDeclarationOrigin
+    var attributes: FirDeclarationAttributes = FirDeclarationAttributes()
+    lateinit var returnTypeRef: FirTypeRef
+    lateinit var symbol: FirPropertyFieldDeclarationSymbol
+    var backingFieldSymbol: FirBackingFieldSymbol? = null
+    var propertySymbol: FirPropertySymbol? = null
+    var initializer: FirExpression? = null
+    override val annotations: MutableList<FirAnnotationCall> = mutableListOf()
+    val typeParameters: MutableList<FirTypeParameter> = mutableListOf()
+    lateinit var status: FirDeclarationStatus
+
+    override fun build(): FirBackingField {
+        return FirBackingFieldImpl(
+            source,
+            moduleData,
+            resolvePhase,
+            origin,
+            attributes,
+            returnTypeRef,
+            symbol,
+            backingFieldSymbol,
+            propertySymbol,
+            initializer,
+            annotations,
+            typeParameters,
+            status,
+        )
+    }
+
+}
+
+@OptIn(ExperimentalContracts::class)
+inline fun buildBackingField(init: FirBackingFieldBuilder.() -> Unit): FirBackingField {
+    contract {
+        callsInPlace(init, kotlin.contracts.InvocationKind.EXACTLY_ONCE)
+    }
+    return FirBackingFieldBuilder().apply(init).build()
+}

compiler/fir/tree/gen/org/jetbrains/kotlin/fir/declarations/builder/FirDefaultSetterValueParameterBuilder.kt

@@ -11,6 +11,7 @@ import org.jetbrains.kotlin.fir.FirSourceElement
 import org.jetbrains.kotlin.fir.builder.FirAnnotationContainerBuilder
 import org.jetbrains.kotlin.fir.builder.FirBuilderDsl
 import org.jetbrains.kotlin.fir.declarations.DeprecationsPerUseSite
+import org.jetbrains.kotlin.fir.declarations.FirBackingField
 import org.jetbrains.kotlin.fir.declarations.FirDeclarationAttributes
 import org.jetbrains.kotlin.fir.declarations.FirDeclarationOrigin
 import org.jetbrains.kotlin.fir.declarations.FirDeclarationStatus
@@ -53,6 +54,7 @@ class FirDefaultSetterValueParameterBuilder : FirAnnotationContainerBuilder {
     var isVal: Boolean = true
     var getter: FirPropertyAccessor? = null
     var setter: FirPropertyAccessor? = null
+    var backingField: FirBackingField? = null
     override val annotations: MutableList<FirAnnotationCall> = mutableListOf()
     lateinit var symbol: FirValueParameterSymbol
     var defaultValue: FirExpression? = null
@@ -78,6 +80,7 @@ class FirDefaultSetterValueParameterBuilder : FirAnnotationContainerBuilder {
             isVal,
             getter,
             setter,
+            backingField,
             annotations,
             symbol,
             defaultValue,

compiler/fir/tree/gen/org/jetbrains/kotlin/fir/declarations/builder/FirEnumEntryBuilder.kt

@@ -11,6 +11,7 @@ import org.jetbrains.kotlin.fir.FirSourceElement
 import org.jetbrains.kotlin.fir.builder.FirAnnotationContainerBuilder
 import org.jetbrains.kotlin.fir.builder.FirBuilderDsl
 import org.jetbrains.kotlin.fir.declarations.DeprecationsPerUseSite
+import org.jetbrains.kotlin.fir.declarations.FirBackingField
 import org.jetbrains.kotlin.fir.declarations.FirDeclarationAttributes
 import org.jetbrains.kotlin.fir.declarations.FirDeclarationOrigin
 import org.jetbrains.kotlin.fir.declarations.FirDeclarationStatus
@@ -48,6 +49,7 @@ class FirEnumEntryBuilder : FirAnnotationContainerBuilder {
     var dispatchReceiverType: ConeKotlinType? = null
     lateinit var name: Name
     var initializer: FirExpression? = null
+    var backingField: FirBackingField? = null
     override val annotations: MutableList<FirAnnotationCall> = mutableListOf()
     lateinit var symbol: FirEnumEntrySymbol
 
@@ -66,6 +68,7 @@ class FirEnumEntryBuilder : FirAnnotationContainerBuilder {
             dispatchReceiverType,
             name,
             initializer,
+            backingField,
             annotations,
             symbol,
         )

compiler/fir/tree/gen/org/jetbrains/kotlin/fir/declarations/builder/FirErrorPropertyBuilder.kt

@@ -11,6 +11,7 @@ import org.jetbrains.kotlin.fir.FirSourceElement
 import org.jetbrains.kotlin.fir.builder.FirAnnotationContainerBuilder
 import org.jetbrains.kotlin.fir.builder.FirBuilderDsl
 import org.jetbrains.kotlin.fir.declarations.DeprecationsPerUseSite
+import org.jetbrains.kotlin.fir.declarations.FirBackingField
 import org.jetbrains.kotlin.fir.declarations.FirDeclarationAttributes
 import org.jetbrains.kotlin.fir.declarations.FirDeclarationOrigin
 import org.jetbrains.kotlin.fir.declarations.FirDeclarationStatus
@@ -47,6 +48,7 @@ class FirErrorPropertyBuilder : FirAnnotationContainerBuilder {
     var containerSource: DeserializedContainerSource? = null
     var dispatchReceiverType: ConeKotlinType? = null
     lateinit var name: Name
+    var backingField: FirBackingField? = null
     override val annotations: MutableList<FirAnnotationCall> = mutableListOf()
     lateinit var diagnostic: ConeDiagnostic
     lateinit var symbol: FirErrorPropertySymbol
@@ -62,6 +64,7 @@ class FirErrorPropertyBuilder : FirAnnotationContainerBuilder {
             containerSource,
             dispatchReceiverType,
             name,
+            backingField,
             annotations,
             diagnostic,
             symbol,

compiler/fir/tree/gen/org/jetbrains/kotlin/fir/declarations/builder/FirFieldBuilder.kt

@@ -12,6 +12,7 @@ import org.jetbrains.kotlin.fir.FirSourceElement
 import org.jetbrains.kotlin.fir.builder.FirAnnotationContainerBuilder
 import org.jetbrains.kotlin.fir.builder.FirBuilderDsl
 import org.jetbrains.kotlin.fir.declarations.DeprecationsPerUseSite
+import org.jetbrains.kotlin.fir.declarations.FirBackingField
 import org.jetbrains.kotlin.fir.declarations.FirDeclarationAttributes
 import org.jetbrains.kotlin.fir.declarations.FirDeclarationOrigin
 import org.jetbrains.kotlin.fir.declarations.FirDeclarationStatus
@@ -51,6 +52,7 @@ open class FirFieldBuilder : FirDeclarationBuilder, FirAnnotationContainerBuilde
     open lateinit var name: Name
     open var initializer: FirExpression? = null
     open var isVar: Boolean by kotlin.properties.Delegates.notNull<Boolean>()
+    open var backingField: FirBackingField? = null
     override val annotations: MutableList<FirAnnotationCall> = mutableListOf()
     open lateinit var symbol: FirFieldSymbol
 
@@ -71,6 +73,7 @@ open class FirFieldBuilder : FirDeclarationBuilder, FirAnnotationContainerBuilde
             name,
             initializer,
             isVar,
+            backingField,
             annotations,
             symbol,
         )

compiler/fir/tree/gen/org/jetbrains/kotlin/fir/declarations/builder/FirPropertyBuilder.kt

@@ -11,6 +11,7 @@ import org.jetbrains.kotlin.fir.FirSourceElement
 import org.jetbrains.kotlin.fir.builder.FirAnnotationContainerBuilder
 import org.jetbrains.kotlin.fir.builder.FirBuilderDsl
 import org.jetbrains.kotlin.fir.declarations.DeprecationsPerUseSite
+import org.jetbrains.kotlin.fir.declarations.FirBackingField
 import org.jetbrains.kotlin.fir.declarations.FirDeclarationAttributes
 import org.jetbrains.kotlin.fir.declarations.FirDeclarationOrigin
 import org.jetbrains.kotlin.fir.declarations.FirDeclarationStatus
@@ -58,6 +59,7 @@ class FirPropertyBuilder : FirDeclarationBuilder, FirTypeParametersOwnerBuilder,
     var isVar: Boolean by kotlin.properties.Delegates.notNull<Boolean>()
     var getter: FirPropertyAccessor? = null
     var setter: FirPropertyAccessor? = null
+    var backingField: FirBackingField? = null
     override val annotations: MutableList<FirAnnotationCall> = mutableListOf()
     lateinit var symbol: FirPropertySymbol
     var delegateFieldSymbol: FirDelegateFieldSymbol? = null
@@ -84,6 +86,7 @@ class FirPropertyBuilder : FirDeclarationBuilder, FirTypeParametersOwnerBuilder,
             isVar,
             getter,
             setter,
+            backingField,
             annotations,
             symbol,
             delegateFieldSymbol,
@@ -126,6 +129,7 @@ inline fun buildPropertyCopy(original: FirProperty, init: FirPropertyBuilder.()
     copyBuilder.isVar = original.isVar
     copyBuilder.getter = original.getter
     copyBuilder.setter = original.setter
+    copyBuilder.backingField = original.backingField
     copyBuilder.annotations.addAll(original.annotations)
     copyBuilder.symbol = original.symbol
     copyBuilder.delegateFieldSymbol = original.delegateFieldSymbol

compiler/fir/tree/gen/org/jetbrains/kotlin/fir/declarations/builder/FirValueParameterBuilder.kt

@@ -11,6 +11,7 @@ import org.jetbrains.kotlin.fir.FirSourceElement
 import org.jetbrains.kotlin.fir.builder.FirAnnotationContainerBuilder
 import org.jetbrains.kotlin.fir.builder.FirBuilderDsl
 import org.jetbrains.kotlin.fir.declarations.DeprecationsPerUseSite
+import org.jetbrains.kotlin.fir.declarations.FirBackingField
 import org.jetbrains.kotlin.fir.declarations.FirDeclarationAttributes
 import org.jetbrains.kotlin.fir.declarations.FirDeclarationOrigin
 import org.jetbrains.kotlin.fir.declarations.FirDeclarationStatus
@@ -47,6 +48,7 @@ open class FirValueParameterBuilder : FirAnnotationContainerBuilder {
     open var containerSource: DeserializedContainerSource? = null
     open var dispatchReceiverType: ConeKotlinType? = null
     open lateinit var name: Name
+    open var backingField: FirBackingField? = null
     override val annotations: MutableList<FirAnnotationCall> = mutableListOf()
     open lateinit var symbol: FirValueParameterSymbol
     open var defaultValue: FirExpression? = null
@@ -66,6 +68,7 @@ open class FirValueParameterBuilder : FirAnnotationContainerBuilder {
             containerSource,
             dispatchReceiverType,
             name,
+            backingField,
             annotations,
             symbol,
             defaultValue,
@@ -101,6 +104,7 @@ inline fun buildValueParameterCopy(original: FirValueParameter, init: FirValuePa
     copyBuilder.containerSource = original.containerSource
     copyBuilder.dispatchReceiverType = original.dispatchReceiverType
     copyBuilder.name = original.name
+    copyBuilder.backingField = original.backingField
     copyBuilder.annotations.addAll(original.annotations)
     copyBuilder.symbol = original.symbol
     copyBuilder.defaultValue = original.defaultValue

compiler/fir/tree/gen/org/jetbrains/kotlin/fir/declarations/impl/FirBackingFieldImpl.kt

@@ -0,0 +1,102 @@
+/*
+ * Copyright 2010-2021 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package org.jetbrains.kotlin.fir.declarations.impl
+
+import org.jetbrains.kotlin.fir.FirModuleData
+import org.jetbrains.kotlin.fir.FirSourceElement
+import org.jetbrains.kotlin.fir.declarations.FirBackingField
+import org.jetbrains.kotlin.fir.declarations.FirDeclarationAttributes
+import org.jetbrains.kotlin.fir.declarations.FirDeclarationOrigin
+import org.jetbrains.kotlin.fir.declarations.FirDeclarationStatus
+import org.jetbrains.kotlin.fir.declarations.FirResolvePhase
+import org.jetbrains.kotlin.fir.declarations.FirTypeParameter
+import org.jetbrains.kotlin.fir.expressions.FirAnnotationCall
+import org.jetbrains.kotlin.fir.expressions.FirExpression
+import org.jetbrains.kotlin.fir.symbols.impl.FirBackingFieldSymbol
+import org.jetbrains.kotlin.fir.symbols.impl.FirPropertyFieldDeclarationSymbol
+import org.jetbrains.kotlin.fir.symbols.impl.FirPropertySymbol
+import org.jetbrains.kotlin.fir.types.FirTypeRef
+import org.jetbrains.kotlin.fir.visitors.*
+
+/*
+ * This file was generated automatically
+ * DO NOT MODIFY IT MANUALLY
+ */
+
+internal class FirBackingFieldImpl(
+    override val source: FirSourceElement?,
+    override val moduleData: FirModuleData,
+    @Volatile
+    override var resolvePhase: FirResolvePhase,
+    override val origin: FirDeclarationOrigin,
+    override val attributes: FirDeclarationAttributes,
+    override var returnTypeRef: FirTypeRef,
+    override val symbol: FirPropertyFieldDeclarationSymbol,
+    override val backingFieldSymbol: FirBackingFieldSymbol?,
+    override val propertySymbol: FirPropertySymbol?,
+    override var initializer: FirExpression?,
+    override val annotations: MutableList<FirAnnotationCall>,
+    override val typeParameters: MutableList<FirTypeParameter>,
+    override var status: FirDeclarationStatus,
+) : FirBackingField() {
+    init {
+        symbol.bind(this)
+    }
+
+    override fun <R, D> acceptChildren(visitor: FirVisitor<R, D>, data: D) {
+        returnTypeRef.accept(visitor, data)
+        initializer?.accept(visitor, data)
+        annotations.forEach { it.accept(visitor, data) }
+        typeParameters.forEach { it.accept(visitor, data) }
+        status.accept(visitor, data)
+    }
+
+    override fun <D> transformChildren(transformer: FirTransformer<D>, data: D): FirBackingFieldImpl {
+        transformReturnTypeRef(transformer, data)
+        transformInitializer(transformer, data)
+        transformAnnotations(transformer, data)
+        transformTypeParameters(transformer, data)
+        transformStatus(transformer, data)
+        return this
+    }
+
+    override fun <D> transformReturnTypeRef(transformer: FirTransformer<D>, data: D): FirBackingFieldImpl {
+        returnTypeRef = returnTypeRef.transform(transformer, data)
+        return this
+    }
+
+    override fun <D> transformInitializer(transformer: FirTransformer<D>, data: D): FirBackingFieldImpl {
+        initializer = initializer?.transform(transformer, data)
+        return this
+    }
+
+    override fun <D> transformAnnotations(transformer: FirTransformer<D>, data: D): FirBackingFieldImpl {
+        annotations.transformInplace(transformer, data)
+        return this
+    }
+
+    override fun <D> transformTypeParameters(transformer: FirTransformer<D>, data: D): FirBackingFieldImpl {
+        typeParameters.transformInplace(transformer, data)
+        return this
+    }
+
+    override fun <D> transformStatus(transformer: FirTransformer<D>, data: D): FirBackingFieldImpl {
+        status = status.transform(transformer, data)
+        return this
+    }
+
+    override fun replaceResolvePhase(newResolvePhase: FirResolvePhase) {
+        resolvePhase = newResolvePhase
+    }
+
+    override fun replaceReturnTypeRef(newReturnTypeRef: FirTypeRef) {
+        returnTypeRef = newReturnTypeRef
+    }
+
+    override fun replaceInitializer(newInitializer: FirExpression?) {
+        initializer = newInitializer
+    }
+}

compiler/fir/tree/gen/org/jetbrains/kotlin/fir/declarations/impl/FirDefaultSetterValueParameter.kt

@@ -8,6 +8,7 @@ package org.jetbrains.kotlin.fir.declarations.impl
 import org.jetbrains.kotlin.fir.FirModuleData
 import org.jetbrains.kotlin.fir.FirSourceElement
 import org.jetbrains.kotlin.fir.declarations.DeprecationsPerUseSite
+import org.jetbrains.kotlin.fir.declarations.FirBackingField
 import org.jetbrains.kotlin.fir.declarations.FirDeclarationAttributes
 import org.jetbrains.kotlin.fir.declarations.FirDeclarationOrigin
 import org.jetbrains.kotlin.fir.declarations.FirDeclarationStatus
@@ -49,6 +50,7 @@ internal class FirDefaultSetterValueParameter(
     override val isVal: Boolean,
     override var getter: FirPropertyAccessor?,
     override var setter: FirPropertyAccessor?,
+    override var backingField: FirBackingField?,
     override val annotations: MutableList<FirAnnotationCall>,
     override val symbol: FirValueParameterSymbol,
     override var defaultValue: FirExpression?,
@@ -73,6 +75,7 @@ internal class FirDefaultSetterValueParameter(
         delegate?.accept(visitor, data)
         getter?.accept(visitor, data)
         setter?.accept(visitor, data)
+        backingField?.accept(visitor, data)
         annotations.forEach { it.accept(visitor, data) }
         controlFlowGraphReference?.accept(visitor, data)
         defaultValue?.accept(visitor, data)
@@ -86,6 +89,7 @@ internal class FirDefaultSetterValueParameter(
         transformDelegate(transformer, data)
         transformGetter(transformer, data)
         transformSetter(transformer, data)
+        transformBackingField(transformer, data)
         transformOtherChildren(transformer, data)
         return this
     }
@@ -129,6 +133,11 @@ internal class FirDefaultSetterValueParameter(
         return this
     }
 
+    override fun <D> transformBackingField(transformer: FirTransformer<D>, data: D): FirDefaultSetterValueParameter {
+        backingField = backingField?.transform(transformer, data)
+        return this
+    }
+
     override fun <D> transformAnnotations(transformer: FirTransformer<D>, data: D): FirDefaultSetterValueParameter {
         annotations.transformInplace(transformer, data)
         return this

compiler/fir/tree/gen/org/jetbrains/kotlin/fir/declarations/impl/FirEnumEntryImpl.kt

@@ -8,6 +8,7 @@ package org.jetbrains.kotlin.fir.declarations.impl
 import org.jetbrains.kotlin.fir.FirModuleData
 import org.jetbrains.kotlin.fir.FirSourceElement
 import org.jetbrains.kotlin.fir.declarations.DeprecationsPerUseSite
+import org.jetbrains.kotlin.fir.declarations.FirBackingField
 import org.jetbrains.kotlin.fir.declarations.FirDeclarationAttributes
 import org.jetbrains.kotlin.fir.declarations.FirDeclarationOrigin
 import org.jetbrains.kotlin.fir.declarations.FirDeclarationStatus
@@ -44,6 +45,7 @@ internal class FirEnumEntryImpl(
     override val dispatchReceiverType: ConeKotlinType?,
     override val name: Name,
     override var initializer: FirExpression?,
+    override var backingField: FirBackingField?,
     override val annotations: MutableList<FirAnnotationCall>,
     override val symbol: FirEnumEntrySymbol,
 ) : FirEnumEntry() {
@@ -63,6 +65,7 @@ internal class FirEnumEntryImpl(
         typeParameters.forEach { it.accept(visitor, data) }
         status.accept(visitor, data)
         initializer?.accept(visitor, data)
+        backingField?.accept(visitor, data)
         annotations.forEach { it.accept(visitor, data) }
     }
 
@@ -71,6 +74,7 @@ internal class FirEnumEntryImpl(
         transformTypeParameters(transformer, data)
         transformStatus(transformer, data)
         transformInitializer(transformer, data)
+        transformBackingField(transformer, data)
         transformOtherChildren(transformer, data)
         return this
     }
@@ -111,6 +115,11 @@ internal class FirEnumEntryImpl(
         return this
     }
 
+    override fun <D> transformBackingField(transformer: FirTransformer<D>, data: D): FirEnumEntryImpl {
+        backingField = backingField?.transform(transformer, data)
+        return this
+    }
+
     override fun <D> transformAnnotations(transformer: FirTransformer<D>, data: D): FirEnumEntryImpl {
         annotations.transformInplace(transformer, data)
         return this

compiler/fir/tree/gen/org/jetbrains/kotlin/fir/declarations/impl/FirErrorPropertyImpl.kt

@@ -8,6 +8,7 @@ package org.jetbrains.kotlin.fir.declarations.impl
 import org.jetbrains.kotlin.fir.FirModuleData
 import org.jetbrains.kotlin.fir.FirSourceElement
 import org.jetbrains.kotlin.fir.declarations.DeprecationsPerUseSite
+import org.jetbrains.kotlin.fir.declarations.FirBackingField
 import org.jetbrains.kotlin.fir.declarations.FirDeclarationAttributes
 import org.jetbrains.kotlin.fir.declarations.FirDeclarationOrigin
 import org.jetbrains.kotlin.fir.declarations.FirDeclarationStatus
@@ -43,6 +44,7 @@ internal class FirErrorPropertyImpl(
     override val containerSource: DeserializedContainerSource?,
     override val dispatchReceiverType: ConeKotlinType?,
     override val name: Name,
+    override var backingField: FirBackingField?,
     override val annotations: MutableList<FirAnnotationCall>,
     override val diagnostic: ConeDiagnostic,
     override val symbol: FirErrorPropertySymbol,
@@ -65,12 +67,14 @@ internal class FirErrorPropertyImpl(
     override fun <R, D> acceptChildren(visitor: FirVisitor<R, D>, data: D) {
         returnTypeRef.accept(visitor, data)
         status.accept(visitor, data)
+        backingField?.accept(visitor, data)
         annotations.forEach { it.accept(visitor, data) }
     }
 
     override fun <D> transformChildren(transformer: FirTransformer<D>, data: D): FirErrorPropertyImpl {
         transformReturnTypeRef(transformer, data)
         transformStatus(transformer, data)
+        transformBackingField(transformer, data)
         transformOtherChildren(transformer, data)
         return this
     }
@@ -109,6 +113,11 @@ internal class FirErrorPropertyImpl(
         return this
     }
 
+    override fun <D> transformBackingField(transformer: FirTransformer<D>, data: D): FirErrorPropertyImpl {
+        backingField = backingField?.transform(transformer, data)
+        return this
+    }
+
     override fun <D> transformAnnotations(transformer: FirTransformer<D>, data: D): FirErrorPropertyImpl {
         annotations.transformInplace(transformer, data)
         return this

compiler/fir/tree/gen/org/jetbrains/kotlin/fir/declarations/impl/FirFieldImpl.kt

@@ -9,6 +9,7 @@ import org.jetbrains.kotlin.fir.FirImplementationDetail
 import org.jetbrains.kotlin.fir.FirModuleData
 import org.jetbrains.kotlin.fir.FirSourceElement
 import org.jetbrains.kotlin.fir.declarations.DeprecationsPerUseSite
+import org.jetbrains.kotlin.fir.declarations.FirBackingField
 import org.jetbrains.kotlin.fir.declarations.FirDeclarationAttributes
 import org.jetbrains.kotlin.fir.declarations.FirDeclarationOrigin
 import org.jetbrains.kotlin.fir.declarations.FirDeclarationStatus
@@ -46,6 +47,7 @@ class FirFieldImpl @FirImplementationDetail constructor(
     override val name: Name,
     override var initializer: FirExpression?,
     override val isVar: Boolean,
+    override var backingField: FirBackingField?,
     override val annotations: MutableList<FirAnnotationCall>,
     override val symbol: FirFieldSymbol,
 ) : FirField() {
@@ -64,6 +66,7 @@ class FirFieldImpl @FirImplementationDetail constructor(
         typeParameters.forEach { it.accept(visitor, data) }
         status.accept(visitor, data)
         initializer?.accept(visitor, data)
+        backingField?.accept(visitor, data)
         annotations.forEach { it.accept(visitor, data) }
     }
 
@@ -72,6 +75,7 @@ class FirFieldImpl @FirImplementationDetail constructor(
         transformTypeParameters(transformer, data)
         transformStatus(transformer, data)
         transformInitializer(transformer, data)
+        transformBackingField(transformer, data)
         transformOtherChildren(transformer, data)
         return this
     }
@@ -112,6 +116,11 @@ class FirFieldImpl @FirImplementationDetail constructor(
         return this
     }
 
+    override fun <D> transformBackingField(transformer: FirTransformer<D>, data: D): FirFieldImpl {
+        backingField = backingField?.transform(transformer, data)
+        return this
+    }
+
     override fun <D> transformAnnotations(transformer: FirTransformer<D>, data: D): FirFieldImpl {
         annotations.transformInplace(transformer, data)
         return this

compiler/fir/tree/gen/org/jetbrains/kotlin/fir/declarations/impl/FirPropertyImpl.kt

@@ -8,6 +8,7 @@ package org.jetbrains.kotlin.fir.declarations.impl
 import org.jetbrains.kotlin.fir.FirModuleData
 import org.jetbrains.kotlin.fir.FirSourceElement
 import org.jetbrains.kotlin.fir.declarations.DeprecationsPerUseSite
+import org.jetbrains.kotlin.fir.declarations.FirBackingField
 import org.jetbrains.kotlin.fir.declarations.FirDeclarationAttributes
 import org.jetbrains.kotlin.fir.declarations.FirDeclarationOrigin
 import org.jetbrains.kotlin.fir.declarations.FirDeclarationStatus
@@ -52,6 +53,7 @@ internal class FirPropertyImpl(
     override val isVar: Boolean,
     override var getter: FirPropertyAccessor?,
     override var setter: FirPropertyAccessor?,
+    override var backingField: FirBackingField?,
     override val annotations: MutableList<FirAnnotationCall>,
     override val symbol: FirPropertySymbol,
     override val delegateFieldSymbol: FirDelegateFieldSymbol?,
@@ -77,6 +79,7 @@ internal class FirPropertyImpl(
         delegate?.accept(visitor, data)
         getter?.accept(visitor, data)
         setter?.accept(visitor, data)
+        backingField?.accept(visitor, data)
         annotations.forEach { it.accept(visitor, data) }
         controlFlowGraphReference?.accept(visitor, data)
         typeParameters.forEach { it.accept(visitor, data) }
@@ -90,6 +93,7 @@ internal class FirPropertyImpl(
         transformDelegate(transformer, data)
         transformGetter(transformer, data)
         transformSetter(transformer, data)
+        transformBackingField(transformer, data)
         transformTypeParameters(transformer, data)
         transformOtherChildren(transformer, data)
         return this
@@ -130,6 +134,11 @@ internal class FirPropertyImpl(
         return this
     }
 
+    override fun <D> transformBackingField(transformer: FirTransformer<D>, data: D): FirPropertyImpl {
+        backingField = backingField?.transform(transformer, data)
+        return this
+    }
+
     override fun <D> transformAnnotations(transformer: FirTransformer<D>, data: D): FirPropertyImpl {
         annotations.transformInplace(transformer, data)
         return this

compiler/fir/tree/gen/org/jetbrains/kotlin/fir/declarations/impl/FirValueParameterImpl.kt

@@ -8,6 +8,7 @@ package org.jetbrains.kotlin.fir.declarations.impl
 import org.jetbrains.kotlin.fir.FirModuleData
 import org.jetbrains.kotlin.fir.FirSourceElement
 import org.jetbrains.kotlin.fir.declarations.DeprecationsPerUseSite
+import org.jetbrains.kotlin.fir.declarations.FirBackingField
 import org.jetbrains.kotlin.fir.declarations.FirDeclarationAttributes
 import org.jetbrains.kotlin.fir.declarations.FirDeclarationOrigin
 import org.jetbrains.kotlin.fir.declarations.FirDeclarationStatus
@@ -43,6 +44,7 @@ internal class FirValueParameterImpl(
     override val containerSource: DeserializedContainerSource?,
     override val dispatchReceiverType: ConeKotlinType?,
     override val name: Name,
+    override var backingField: FirBackingField?,
     override val annotations: MutableList<FirAnnotationCall>,
     override val symbol: FirValueParameterSymbol,
     override var defaultValue: FirExpression?,
@@ -68,6 +70,7 @@ internal class FirValueParameterImpl(
     override fun <R, D> acceptChildren(visitor: FirVisitor<R, D>, data: D) {
         returnTypeRef.accept(visitor, data)
         status.accept(visitor, data)
+        backingField?.accept(visitor, data)
         annotations.forEach { it.accept(visitor, data) }
         controlFlowGraphReference?.accept(visitor, data)
         defaultValue?.accept(visitor, data)
@@ -76,6 +79,7 @@ internal class FirValueParameterImpl(
     override fun <D> transformChildren(transformer: FirTransformer<D>, data: D): FirValueParameterImpl {
         transformReturnTypeRef(transformer, data)
         transformStatus(transformer, data)
+        transformBackingField(transformer, data)
         transformOtherChildren(transformer, data)
         return this
     }
@@ -114,6 +118,11 @@ internal class FirValueParameterImpl(
         return this
     }
 
+    override fun <D> transformBackingField(transformer: FirTransformer<D>, data: D): FirValueParameterImpl {
+        backingField = backingField?.transform(transformer, data)
+        return this
+    }
+
     override fun <D> transformAnnotations(transformer: FirTransformer<D>, data: D): FirValueParameterImpl {
         annotations.transformInplace(transformer, data)
         return this

compiler/fir/tree/gen/org/jetbrains/kotlin/fir/visitors/FirTransformer.kt

@@ -40,6 +40,7 @@ import org.jetbrains.kotlin.fir.declarations.FirFunction
 import org.jetbrains.kotlin.fir.declarations.FirContractDescriptionOwner
 import org.jetbrains.kotlin.fir.declarations.FirSimpleFunction
 import org.jetbrains.kotlin.fir.declarations.FirPropertyAccessor
+import org.jetbrains.kotlin.fir.declarations.FirBackingField
 import org.jetbrains.kotlin.fir.declarations.FirConstructor
 import org.jetbrains.kotlin.fir.declarations.FirFile
 import org.jetbrains.kotlin.fir.FirPackageDirective
@@ -280,6 +281,10 @@ abstract class FirTransformer<in D> : FirVisitor<FirElement, D>() {
         return transformElement(propertyAccessor, data)
     }
 
+    open fun transformBackingField(backingField: FirBackingField, data: D): FirStatement {
+        return transformElement(backingField, data)
+    }
+
     open fun transformConstructor(constructor: FirConstructor, data: D): FirStatement {
         return transformElement(constructor, data)
     }
@@ -796,6 +801,10 @@ abstract class FirTransformer<in D> : FirVisitor<FirElement, D>() {
         return transformPropertyAccessor(propertyAccessor, data)
     }
 
+    final override fun visitBackingField(backingField: FirBackingField, data: D): FirStatement {
+        return transformBackingField(backingField, data)
+    }
+
     final override fun visitConstructor(constructor: FirConstructor, data: D): FirStatement {
         return transformConstructor(constructor, data)
     }

compiler/fir/tree/gen/org/jetbrains/kotlin/fir/visitors/FirVisitor.kt

@@ -40,6 +40,7 @@ import org.jetbrains.kotlin.fir.declarations.FirFunction
 import org.jetbrains.kotlin.fir.declarations.FirContractDescriptionOwner
 import org.jetbrains.kotlin.fir.declarations.FirSimpleFunction
 import org.jetbrains.kotlin.fir.declarations.FirPropertyAccessor
+import org.jetbrains.kotlin.fir.declarations.FirBackingField
 import org.jetbrains.kotlin.fir.declarations.FirConstructor
 import org.jetbrains.kotlin.fir.declarations.FirFile
 import org.jetbrains.kotlin.fir.FirPackageDirective
@@ -211,6 +212,8 @@ abstract class FirVisitor<out R, in D> {
 
     open fun visitPropertyAccessor(propertyAccessor: FirPropertyAccessor, data: D): R  = visitElement(propertyAccessor, data)
 
+    open fun visitBackingField(backingField: FirBackingField, data: D): R  = visitElement(backingField, data)
+
     open fun visitConstructor(constructor: FirConstructor, data: D): R  = visitElement(constructor, data)
 
     open fun visitFile(file: FirFile, data: D): R  = visitElement(file, data)

compiler/fir/tree/gen/org/jetbrains/kotlin/fir/visitors/FirVisitorVoid.kt

@@ -40,6 +40,7 @@ import org.jetbrains.kotlin.fir.declarations.FirFunction
 import org.jetbrains.kotlin.fir.declarations.FirContractDescriptionOwner
 import org.jetbrains.kotlin.fir.declarations.FirSimpleFunction
 import org.jetbrains.kotlin.fir.declarations.FirPropertyAccessor
+import org.jetbrains.kotlin.fir.declarations.FirBackingField
 import org.jetbrains.kotlin.fir.declarations.FirConstructor
 import org.jetbrains.kotlin.fir.declarations.FirFile
 import org.jetbrains.kotlin.fir.FirPackageDirective
@@ -279,6 +280,10 @@ abstract class FirVisitorVoid : FirVisitor<Unit, Nothing?>() {
         visitElement(propertyAccessor)
     }
 
+    open fun visitBackingField(backingField: FirBackingField) {
+        visitElement(backingField)
+    }
+
     open fun visitConstructor(constructor: FirConstructor) {
         visitElement(constructor)
     }
@@ -795,6 +800,10 @@ abstract class FirVisitorVoid : FirVisitor<Unit, Nothing?>() {
         visitPropertyAccessor(propertyAccessor)
     }
 
+    final override fun visitBackingField(backingField: FirBackingField, data: Nothing?) {
+        visitBackingField(backingField)
+    }
+
     final override fun visitConstructor(constructor: FirConstructor, data: Nothing?) {
         visitConstructor(constructor)
     }

compiler/fir/tree/src/org/jetbrains/kotlin/fir/declarations/synthetic/FirSyntheticProperty.kt

@@ -30,6 +30,7 @@ class FirSyntheticProperty(
     override var resolvePhase: FirResolvePhase,
     override val getter: FirSyntheticPropertyAccessor,
     override val setter: FirSyntheticPropertyAccessor? = null,
+    override val backingField: FirBackingField? = null,
     override val deprecation: DeprecationsPerUseSite? = null
 ) : FirProperty() {
     init {
@@ -122,6 +123,10 @@ class FirSyntheticProperty(
         throw AssertionError("Transformation of synthetic property isn't supported")
     }
 
+    override fun <D> transformBackingField(transformer: FirTransformer<D>, data: D): FirSyntheticProperty {
+        throw AssertionError("Transformation of synthetic property isn't supported")
+    }
+
     override fun <D> transformDelegate(transformer: FirTransformer<D>, data: D): FirProperty {
         throw AssertionError("Transformation of synthetic property isn't supported")
     }

compiler/fir/tree/src/org/jetbrains/kotlin/fir/symbols/impl/FirFunctionSymbol.kt

@@ -9,6 +9,7 @@ import org.jetbrains.kotlin.fir.FirLabel
 import org.jetbrains.kotlin.fir.contracts.FirResolvedContractDescription
 import org.jetbrains.kotlin.fir.declarations.*
 import org.jetbrains.kotlin.fir.symbols.AccessorSymbol
+import org.jetbrains.kotlin.fir.symbols.FirBasedSymbol
 import org.jetbrains.kotlin.fir.symbols.ensureResolved
 import org.jetbrains.kotlin.name.CallableId
 import org.jetbrains.kotlin.name.FqName
@@ -70,4 +71,6 @@ class FirAnonymousFunctionSymbol : FirFunctionWithoutNameSymbol<FirAnonymousFunc
 
 class FirPropertyAccessorSymbol : FirFunctionWithoutNameSymbol<FirPropertyAccessor>(Name.identifier("accessor"))
 
+class FirPropertyFieldDeclarationSymbol() : FirBasedSymbol<FirBackingField>()
+
 class FirErrorFunctionSymbol : FirFunctionWithoutNameSymbol<FirErrorFunction>(Name.identifier("error"))

compiler/fir/tree/tree-generator/src/org/jetbrains/kotlin/fir/tree/generator/FirTreeBuilder.kt

@@ -53,6 +53,7 @@ object FirTreeBuilder : AbstractFirTreeBuilder() {
     val contractDescriptionOwner = sealedElement("ContractDescriptionOwner", Declaration)
     val simpleFunction = element("SimpleFunction", Declaration, function, contractDescriptionOwner, typeParametersOwner)
     val propertyAccessor = element("PropertyAccessor", Declaration, function, contractDescriptionOwner, typeParametersOwner)
+    val backingField = element("BackingField", Declaration, typedDeclaration, typeParametersOwner, statement)
     val constructor = element("Constructor", Declaration, function, typeParameterRefsOwner)
     val file = element("File", Declaration, annotatedDeclaration)
     val packageDirective = element("PackageDirective", Other)

compiler/fir/tree/tree-generator/src/org/jetbrains/kotlin/fir/tree/generator/NodeConfigurator.kt

@@ -333,6 +333,20 @@ object NodeConfigurator : AbstractFieldConfigurator<FirTreeBuilder>(FirTreeBuild
             +typeParameters
         }
 
+        backingField.configure {
+            +symbol("FirPropertyFieldDeclarationSymbol")
+            +field("backingFieldSymbol", backingFieldSymbolType, nullable = true).apply {
+                withBindThis = false
+            }
+            +field("propertySymbol", firPropertySymbolType, nullable = true).apply {
+                withBindThis = false
+            }
+            +initializer.withTransform().withReplace()
+            +annotations
+            +typeParameters
+            +status.withTransform()
+        }
+
         declarationStatus.configure {
             +visibility
             +modality
@@ -377,6 +391,7 @@ object NodeConfigurator : AbstractFieldConfigurator<FirTreeBuilder>(FirTreeBuild
             generateBooleanFields("var", "val")
             +field("getter", propertyAccessor, nullable = true).withTransform()
             +field("setter", propertyAccessor, nullable = true).withTransform()
+            +field("backingField", backingField, nullable = true).withTransform()
             +annotations
             needTransformOtherChildren()
         }