FIR. Refactor smart-cast representation in FIR tree

Make smart-casts non-transparent expression without delegation
to underlying FirQualifiedAccessExpression, as children delegation in
fir tree has unclear semantics
Remove two different kinds of tree nodes for smart-casts

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

@@ -310,6 +310,9 @@ object BuilderConfigurator : AbstractBuilderConfigurator<FirTreeBuilder>(FirTree
             withCopy()
         }
 
+        builder(smartCastExpression) {
+        }
+
         builder(tryExpression) {
             default("calleeReference", "FirStubReference")
             useTypes(stubReferenceType)

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

@@ -120,10 +120,8 @@ object FirTreeBuilder : AbstractFirTreeBuilder() {
     val componentCall by element(Expression, functionCall)
     val callableReferenceAccess by element(Expression, qualifiedAccessExpression)
     val thisReceiverExpression by element(Expression, qualifiedAccessExpression)
-    val wrappedExpressionWithSmartcast by element(Expression)
-    val wrappedExpressionWithSmartcastToNothing by element(Expression, wrappedExpressionWithSmartcast)
-    val expressionWithSmartcast by element(Expression, qualifiedAccessExpression, wrappedExpressionWithSmartcast)
-    val expressionWithSmartcastToNothing by element(Expression, expressionWithSmartcast, wrappedExpressionWithSmartcastToNothing)
+
+    val smartCastExpression by element(Expression, expression)
     val safeCallExpression by element(Expression, expression)
     val checkedSafeCallSubject by element(Expression, expression)
     val getClassCall by element(Expression, expression, call)
@@ -142,8 +140,6 @@ object FirTreeBuilder : AbstractFirTreeBuilder() {
     val throwExpression by element(Expression, expression)
     val variableAssignment by element(Expression, qualifiedAccess)
     val whenSubjectExpression by element(Expression, expression)
-    val whenSubjectExpressionWithSmartcast by element(Expression, whenSubjectExpression, wrappedExpressionWithSmartcast)
-    val whenSubjectExpressionWithSmartcastToNothing by element(Expression, whenSubjectExpression, wrappedExpressionWithSmartcastToNothing)
 
     val wrappedDelegateExpression by element(Expression, wrappedExpression)
 

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

@@ -189,12 +189,6 @@ object ImplementationConfigurator : AbstractFirTreeImplementationConfigurator()
             publicImplementation()
         }
 
-        noImpl(expressionWithSmartcast)
-        noImpl(expressionWithSmartcastToNothing)
-
-        noImpl(whenSubjectExpressionWithSmartcast)
-        noImpl(whenSubjectExpressionWithSmartcastToNothing)
-
         impl(getClassCall) {
             default("argument") {
                 value = "argumentList.arguments.first()"
@@ -360,6 +354,13 @@ object ImplementationConfigurator : AbstractFirTreeImplementationConfigurator()
             }
         }
 
+        impl(smartCastExpression) {
+            default("isStable") {
+                value = "smartcastStability == SmartcastStability.STABLE_VALUE"
+                withGetter = true
+            }
+        }
+
         impl(resolvedNamedReference) {
             defaultNull("candidateSymbol", withGetter = true)
         }
@@ -562,7 +563,8 @@ object ImplementationConfigurator : AbstractFirTreeImplementationConfigurator()
             "FirIntegerLiteralOperatorCallImpl",
             "FirContextReceiverImpl",
             "FirClassReferenceExpressionImpl",
-            "FirGetClassCallImpl"
+            "FirGetClassCallImpl",
+            "FirSmartCastExpressionImpl"
         )
         configureFieldInAllImplementations(
             field = "typeRef",

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

@@ -490,31 +490,16 @@ object NodeConfigurator : AbstractFieldConfigurator<FirTreeBuilder>(FirTreeBuild
             +intField("componentIndex")
         }
 
-        wrappedExpressionWithSmartcast.configure {
-            withArg("E", expression)
+        smartCastExpression.configure {
             +typeRefField
-            +field("originalExpression", "E", packageName = null)
+            +field("originalExpression", expression).withTransform()
             +field("typesFromSmartCast", "Collection<ConeKotlinType>", null, customType = coneKotlinTypeType)
-            +field("originalType", typeRef)
             +field("smartcastType", typeRef)
+            +field("smartcastTypeWithoutNullableNothing", typeRef, nullable = true)
             +booleanField("isStable")
             +smartcastStability
         }
 
-        wrappedExpressionWithSmartcastToNothing.configure {
-            withArg("E", expression)
-            parentArg(wrappedExpressionWithSmartcast, "E", "E")
-            +field("smartcastTypeWithoutNullableNothing", typeRef)
-        }
-
-        expressionWithSmartcast.configure {
-            parentArg(wrappedExpressionWithSmartcast, "E", qualifiedAccessExpression)
-        }
-
-        expressionWithSmartcastToNothing.configure {
-            parentArg(wrappedExpressionWithSmartcastToNothing, "E", qualifiedAccessExpression)
-        }
-
         safeCallExpression.configure {
             +field("receiver", expression).withTransform()
             // Special node that might be used as a reference to receiver of a safe call after null check
@@ -581,14 +566,6 @@ object NodeConfigurator : AbstractFieldConfigurator<FirTreeBuilder>(FirTreeBuild
             +field("whenRef", whenRefType)
         }
 
-        whenSubjectExpressionWithSmartcast.configure {
-            parentArg(wrappedExpressionWithSmartcast, "E", whenSubjectExpression)
-        }
-
-        whenSubjectExpressionWithSmartcastToNothing.configure {
-            parentArg(wrappedExpressionWithSmartcastToNothing, "E", whenSubjectExpression)
-        }
-
         wrappedExpression.configure {
             +field(expression).withReplace()
         }