FIR: add helper to check if a smartcast expressioin is stable

compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/Fir2IrImplicitCastInserter.kt

@@ -271,7 +271,7 @@ class Fir2IrImplicitCastInserter(
     }
 
     override fun visitExpressionWithSmartcast(expressionWithSmartcast: FirExpressionWithSmartcast, data: IrElement): IrExpression {
-        return if (expressionWithSmartcast.smartcastStability == SmartcastStability.STABLE_VALUE) {
+        return if (expressionWithSmartcast.isStable) {
             implicitCastOrExpression(data as IrExpression, expressionWithSmartcast.typeRef)
         } else {
             data as IrExpression

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/ScopeUtils.kt

@@ -35,7 +35,7 @@ fun FirExpressionWithSmartcast.smartcastScope(
 ): FirTypeScope? {
     val smartcastType = smartcastType.coneType
     val smartcastScope = smartcastType.scope(useSiteSession, scopeSession, FakeOverrideTypeCalculator.DoNothing)
-    if (smartcastStability == SmartcastStability.STABLE_VALUE) {
+    if (isStable) {
         return smartcastScope
     }
     val originalScope = originalType.coneType.scope(useSiteSession, scopeSession, FakeOverrideTypeCalculator.DoNothing)

compiler/fir/tree/gen/org/jetbrains/kotlin/fir/expressions/FirExpressionWithSmartcast.kt

@@ -33,6 +33,7 @@ abstract class FirExpressionWithSmartcast : FirQualifiedAccessExpression() {
     abstract val typesFromSmartCast: Collection<ConeKotlinType>
     abstract val originalType: FirTypeRef
     abstract val smartcastType: FirTypeRef
+    abstract val isStable: Boolean
     abstract val smartcastStability: SmartcastStability
 
     override fun <R, D> accept(visitor: FirVisitor<R, D>, data: D): R = visitor.visitExpressionWithSmartcast(this, data)

compiler/fir/tree/gen/org/jetbrains/kotlin/fir/expressions/FirExpressionWithSmartcastToNull.kt

@@ -29,6 +29,7 @@ abstract class FirExpressionWithSmartcastToNull : FirExpressionWithSmartcast() {
     abstract override val explicitReceiver: FirExpression?
     abstract override val dispatchReceiver: FirExpression
     abstract override val extensionReceiver: FirExpression
+    abstract override val isStable: Boolean
     abstract override val originalExpression: FirQualifiedAccessExpression
     abstract override val typesFromSmartCast: Collection<ConeKotlinType>
     abstract override val originalType: FirTypeRef

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

@@ -39,10 +39,12 @@ internal class FirExpressionWithSmartcastImpl(
     override val extensionReceiver: FirExpression get() = originalExpression.extensionReceiver
     override val calleeReference: FirReference get() = originalExpression.calleeReference
     override val originalType: FirTypeRef get() = originalExpression.typeRef
+    override val isStable: Boolean get() = smartcastStability == SmartcastStability.STABLE_VALUE
+
     // A FirExpressionWithSmartcast is only an effective smartcast if `smartcastStability == SmartcastStability.STABLE_VALUE`. Otherwise,
     // it's the same as the `originalExpression` under the hood. The reason we still create such a smartcast expression is for diagnostics
     // purpose only.
-    override val typeRef: FirTypeRef get() = if (smartcastStability == SmartcastStability.STABLE_VALUE) smartcastType else originalType
+    override val typeRef: FirTypeRef get() = if (isStable) smartcastType else originalType
 
     override fun <D> transformChildren(transformer: FirTransformer<D>, data: D): FirExpressionWithSmartcast {
         originalExpression = originalExpression.transformSingle(transformer, data)

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

@@ -7,7 +7,10 @@ package org.jetbrains.kotlin.fir.expressions.impl
 
 import org.jetbrains.kotlin.fir.FirImplementationDetail
 import org.jetbrains.kotlin.fir.FirSourceElement
-import org.jetbrains.kotlin.fir.expressions.*
+import org.jetbrains.kotlin.fir.expressions.FirAnnotationCall
+import org.jetbrains.kotlin.fir.expressions.FirExpression
+import org.jetbrains.kotlin.fir.expressions.FirExpressionWithSmartcastToNull
+import org.jetbrains.kotlin.fir.expressions.FirQualifiedAccessExpression
 import org.jetbrains.kotlin.fir.references.FirReference
 import org.jetbrains.kotlin.fir.types.ConeKotlinType
 import org.jetbrains.kotlin.fir.types.FirResolvedTypeRef
@@ -34,12 +37,14 @@ class FirExpressionWithSmartcastToNullImpl(
     override val explicitReceiver: FirExpression? get() = originalExpression.explicitReceiver
     override val dispatchReceiver: FirExpression get() = originalExpression.dispatchReceiver
     override val extensionReceiver: FirExpression get() = originalExpression.extensionReceiver
+    override val isStable: Boolean get() = smartcastStability == SmartcastStability.STABLE_VALUE
     override val calleeReference: FirReference get() = originalExpression.calleeReference
     override val originalType: FirTypeRef get() = originalExpression.typeRef
+
     // A FirExpressionWithSmartcast is only an effective smartcast if `smartcastStability == SmartcastStability.STABLE_VALUE`. Otherwise,
     // it's the same as the `originalExpression` under the hood. The reason we still create such a smartcast expression is for diagnostics
     // purpose only.
-    override val typeRef: FirTypeRef get() = if (smartcastStability == SmartcastStability.STABLE_VALUE) smartcastType else originalType
+    override val typeRef: FirTypeRef get() = if (isStable) smartcastType else originalType
 
     override fun <D> transformChildren(transformer: FirTransformer<D>, data: D): FirExpressionWithSmartcastToNull {
         originalExpression = originalExpression.transformSingle(transformer, data)

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

@@ -464,6 +464,7 @@ object NodeConfigurator : AbstractFieldConfigurator<FirTreeBuilder>(FirTreeBuild
             +field("typesFromSmartCast", "Collection<ConeKotlinType>", null, customType = coneKotlinTypeType)
             +field("originalType", typeRef)
             +field("smartcastType", typeRef)
+            +booleanField("isStable")
             +smartcastStability
         }
 

compiler/tests-common-new/tests/org/jetbrains/kotlin/test/frontend/fir/handlers/FirDiagnosticsHandler.kt

@@ -176,7 +176,7 @@ class FirDiagnosticsHandler(testServices: TestServices) : FirAnalysisHandler(tes
         diagnosedRangesToDiagnosticNames: Map<IntRange, Set<String>>
     ): FirDiagnosticWithParameters1<FirSourceElement, String>? =
         DebugInfoDiagnosticFactory1.EXPRESSION_TYPE.createDebugInfoDiagnostic(element, diagnosedRangesToDiagnosticNames) {
-            element.typeRef.renderAsString((element as? FirExpressionWithSmartcast)?.takeIf { it.smartcastStability == SmartcastStability.STABLE_VALUE }?.originalType)
+            element.typeRef.renderAsString((element as? FirExpressionWithSmartcast)?.takeIf { it.isStable }?.originalType)
         }
 
     private fun FirTypeRef.renderAsString(originalTypeRef: FirTypeRef?): String {