FIR: implement backing field references via 'field' synthetic variable

compiler/fir/tree/src/org/jetbrains/kotlin/fir/FirBackingFieldReference.kt

@@ -0,0 +1,26 @@
+/*
+ * Copyright 2010-2019 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
+
+import org.jetbrains.kotlin.fir.symbols.impl.FirBackingFieldSymbol
+import org.jetbrains.kotlin.fir.visitors.FirVisitor
+import org.jetbrains.kotlin.name.Name
+
+interface FirBackingFieldReference : FirResolvedCallableReference {
+
+    override val name: Name
+        get() = NAME
+
+    override val coneSymbol: FirBackingFieldSymbol
+
+    override fun <R, D> accept(visitor: FirVisitor<R, D>, data: D): R {
+        return visitor.visitBackingFieldReference(this, data)
+    }
+
+    companion object {
+        val NAME = Name.identifier("field")
+    }
+}

compiler/fir/tree/src/org/jetbrains/kotlin/fir/FirRenderer.kt

@@ -786,6 +786,12 @@ class FirRenderer(builder: StringBuilder) : FirVisitorVoid() {
         }
     }
 
+    override fun visitBackingFieldReference(backingFieldReference: FirBackingFieldReference) {
+        print("F|")
+        print(backingFieldReference.coneSymbol.callableId)
+        print("|")
+    }
+
     override fun visitResolvedCallableReference(resolvedCallableReference: FirResolvedCallableReference) {
         print("R|")
         val isFakeOverride = (resolvedCallableReference.coneSymbol as? FirFunctionSymbol)?.isFakeOverride == true

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

@@ -8,6 +8,8 @@ package org.jetbrains.kotlin.fir.declarations
 import org.jetbrains.kotlin.fir.BaseTransformedType
 import org.jetbrains.kotlin.fir.VisitedSupertype
 import org.jetbrains.kotlin.fir.expressions.FirVariable
+import org.jetbrains.kotlin.fir.symbols.impl.FirBackingFieldSymbol
+import org.jetbrains.kotlin.fir.visitors.FirTransformer
 import org.jetbrains.kotlin.fir.visitors.FirVisitor
 
 // May be should not inherit FirVariable
@@ -24,6 +26,10 @@ interface FirProperty : @VisitedSupertype FirDeclaration, FirCallableMemberDecla
 
     val setter: FirPropertyAccessor?
 
+    val backingFieldSymbol: FirBackingFieldSymbol
+
+    fun <D> transformChildrenWithoutAccessors(transformer: FirTransformer<D>, data: D)
+
     override fun <R, D> accept(visitor: FirVisitor<R, D>, data: D): R =
         visitor.visitProperty(this, data)
 

compiler/fir/tree/src/org/jetbrains/kotlin/fir/declarations/impl/FirMemberPropertyImpl.kt

@@ -13,7 +13,9 @@ import org.jetbrains.kotlin.fir.FirSession
 import org.jetbrains.kotlin.fir.declarations.FirProperty
 import org.jetbrains.kotlin.fir.declarations.FirPropertyAccessor
 import org.jetbrains.kotlin.fir.expressions.FirExpression
+import org.jetbrains.kotlin.fir.symbols.impl.FirBackingFieldSymbol
 import org.jetbrains.kotlin.fir.symbols.impl.FirPropertySymbol
+import org.jetbrains.kotlin.fir.transformInplace
 import org.jetbrains.kotlin.fir.transformSingle
 import org.jetbrains.kotlin.fir.types.FirTypeRef
 import org.jetbrains.kotlin.fir.visitors.FirTransformer
@@ -41,18 +43,30 @@ class FirMemberPropertyImpl(
 ) : FirAbstractCallableMember(
     session, psi, name, visibility, modality, isExpect, isActual, isOverride, receiverTypeRef, returnTypeRef
 ), FirProperty {
+    override val backingFieldSymbol = FirBackingFieldSymbol(symbol.callableId)
+
     init {
         symbol.bind(this)
+        backingFieldSymbol.bind(this)
         status.isConst = isConst
         status.isLateInit = isLateInit
     }
 
+    override fun <D> transformChildrenWithoutAccessors(transformer: FirTransformer<D>, data: D) {
+        initializer = initializer?.transformSingle(transformer, data)
+        delegate = delegate?.transformSingle(transformer, data)
+        receiverTypeRef = receiverTypeRef?.transformSingle(transformer, data)
+        returnTypeRef = returnTypeRef.transformSingle(transformer, data)
+        typeParameters.transformInplace(transformer, data)
+        status = status.transformSingle(transformer, data)
+        annotations.transformInplace(transformer, data)
+    }
+
     override fun <D> transformChildren(transformer: FirTransformer<D>, data: D): FirElement {
         getter = getter.transformSingle(transformer, data)
         setter = setter?.transformSingle(transformer, data)
-        initializer = initializer?.transformSingle(transformer, data)
-        delegate = delegate?.transformSingle(transformer, data)
-
-        return super<FirAbstractCallableMember>.transformChildren(transformer, data)
+        transformChildrenWithoutAccessors(transformer, data)
+        // Everything other (annotations, etc.) is done above
+        return this
     }
 }

compiler/fir/tree/src/org/jetbrains/kotlin/fir/references/FirBackingFieldReferenceImpl.kt

@@ -0,0 +1,18 @@
+/*
+ * Copyright 2010-2019 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.references
+
+import com.intellij.psi.PsiElement
+import org.jetbrains.kotlin.fir.FirAbstractElement
+import org.jetbrains.kotlin.fir.FirBackingFieldReference
+import org.jetbrains.kotlin.fir.FirSession
+import org.jetbrains.kotlin.fir.symbols.impl.FirBackingFieldSymbol
+
+class FirBackingFieldReferenceImpl(
+    session: FirSession,
+    psi: PsiElement?,
+    override val coneSymbol: FirBackingFieldSymbol
+) : FirAbstractElement(session, psi), FirBackingFieldReference

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

@@ -12,6 +12,8 @@ import org.jetbrains.kotlin.name.Name
 
 open class FirPropertySymbol(callableId: CallableId) : FirVariableSymbol(callableId), ConePropertySymbol
 
+class FirBackingFieldSymbol(callableId: CallableId) : FirVariableSymbol(callableId)
+
 open class FirVariableSymbol(override val callableId: CallableId) : ConeVariableSymbol, FirCallableSymbol() {
 
     @Deprecated("TODO: Better solution for local vars?")

compiler/fir/tree/visitors/org/jetbrains/kotlin/fir/visitors/FirTransformerGenerated.kt

@@ -160,6 +160,10 @@ abstract class FirTransformer<in D> : FirVisitor<CompositeTransformResult<FirEle
         return transformNamedReference(resolvedCallableReference, data)
     }
 
+    open fun transformBackingFieldReference(backingFieldReference: FirBackingFieldReference, data: D): CompositeTransformResult<FirNamedReference> {
+        return transformResolvedCallableReference(backingFieldReference, data)
+    }
+
     open fun <E : FirReference> transformSuperReference(superReference: E, data: D): CompositeTransformResult<E> {
         return transformReference(superReference, data)
     }
@@ -464,6 +468,10 @@ abstract class FirTransformer<in D> : FirVisitor<CompositeTransformResult<FirEle
         return transformAssignment(assignment, data)
     }
 
+    final override fun visitBackingFieldReference(backingFieldReference: FirBackingFieldReference, data: D): CompositeTransformResult<FirElement> {
+        return transformBackingFieldReference(backingFieldReference, data)
+    }
+
     final override fun visitBlock(block: FirBlock, data: D): CompositeTransformResult<FirElement> {
         return transformBlock(block, data)
     }

compiler/fir/tree/visitors/org/jetbrains/kotlin/fir/visitors/FirVisitorGenerated.kt

@@ -160,6 +160,10 @@ abstract class FirVisitor<out R, in D> {
         return visitNamedReference(resolvedCallableReference, data)
     }
 
+    open fun visitBackingFieldReference(backingFieldReference: FirBackingFieldReference, data: D): R {
+        return visitResolvedCallableReference(backingFieldReference, data)
+    }
+
     open fun visitSuperReference(superReference: FirSuperReference, data: D): R {
         return visitReference(superReference, data)
     }

compiler/fir/tree/visitors/org/jetbrains/kotlin/fir/visitors/FirVisitorVoidGenerated.kt

@@ -160,6 +160,10 @@ abstract class FirVisitorVoid : FirVisitor<Unit, Nothing?>() {
         visitNamedReference(resolvedCallableReference, null)
     }
 
+    open fun visitBackingFieldReference(backingFieldReference: FirBackingFieldReference) {
+        visitResolvedCallableReference(backingFieldReference, null)
+    }
+
     open fun visitSuperReference(superReference: FirSuperReference) {
         visitReference(superReference, null)
     }
@@ -464,6 +468,10 @@ abstract class FirVisitorVoid : FirVisitor<Unit, Nothing?>() {
         visitAssignment(assignment)
     }
 
+    final override fun visitBackingFieldReference(backingFieldReference: FirBackingFieldReference, data: Nothing?) {
+        visitBackingFieldReference(backingFieldReference)
+    }
+
     final override fun visitBlock(block: FirBlock, data: Nothing?) {
         visitBlock(block)
     }