FIR: add new qualified access implementation (FirThisReceiverExpression)

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

@@ -896,10 +896,7 @@ class ExpressionsConverter(
      */
     private fun convertThisExpression(thisExpression: LighterASTNode): FirQualifiedAccessExpression {
         val label: String? = thisExpression.getLabelName()
-
-        return FirQualifiedAccessExpressionImpl(null).apply {
-            calleeReference = FirExplicitThisReference(null, label)
-        }
+        return FirThisReceiverExpressionImpl(null, FirExplicitThisReference(null, label))
     }
 
     /**

compiler/fir/psi2fir/src/org/jetbrains/kotlin/fir/builder/RawFirBuilder.kt

@@ -1182,9 +1182,7 @@ class RawFirBuilder(session: FirSession, val stubMode: Boolean) : BaseFirBuilder
 
         override fun visitThisExpression(expression: KtThisExpression, data: Unit): FirElement {
             val labelName = expression.getLabelName()
-            return FirQualifiedAccessExpressionImpl(expression).apply {
-                calleeReference = FirExplicitThisReference(expression, labelName)
-            }
+            return FirThisReceiverExpressionImpl(expression, FirExplicitThisReference(expression, labelName))
         }
 
         override fun visitSuperExpression(expression: KtSuperExpression, data: Unit): FirElement {

compiler/fir/tree/src/org/jetbrains/kotlin/fir/expressions/impl/FirThisReceiverExpressionImpl.kt

@@ -0,0 +1,31 @@
+/*
+ * 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.expressions.impl
+
+import com.intellij.psi.PsiElement
+import org.jetbrains.kotlin.fir.FirElement
+import org.jetbrains.kotlin.fir.FirThisReference
+import org.jetbrains.kotlin.fir.expressions.FirExpression
+import org.jetbrains.kotlin.fir.expressions.FirQualifiedAccessExpression
+import org.jetbrains.kotlin.fir.transformSingle
+import org.jetbrains.kotlin.fir.visitors.FirTransformer
+
+class FirThisReceiverExpressionImpl(
+    psi: PsiElement?,
+    override var calleeReference: FirThisReference
+) : FirModifiableQualifiedAccess<FirThisReference>, FirQualifiedAccessExpression(psi) {
+    override var explicitReceiver: FirExpression?
+        get() = null
+        set(_) {}
+
+    override fun <D> transformChildren(transformer: FirTransformer<D>, data: D): FirElement {
+        calleeReference = calleeReference.transformSingle(transformer, data)
+        dispatchReceiver.transformSingle(transformer, data)
+        extensionReceiver.transformSingle(transformer, data)
+
+        return super<FirQualifiedAccessExpression>.transformChildren(transformer, data)
+    }
+}