From 8bd792792f257f55afdd7078a520e89cd3d45864 Mon Sep 17 00:00:00 2001
From: Mikhail Glukhikh <mikhail.glukhikh@jetbrains.com>
Date: Thu, 28 Sep 2023 11:42:53 +0200
Subject: [PATCH] K2: consider backing fields of vars as smartcast unstable

#KT-61974 Fixed
---
 .../jetbrains/kotlin/fir/resolve/dfa/VariableStorageImpl.kt | 5 ++---
 .../firProblems/elvisOnBackingFieldInGetter.fir.ir.txt      | 6 +++---
 .../firProblems/elvisOnBackingFieldInGetter.fir.kt.txt      | 2 +-
 3 files changed, 6 insertions(+), 7 deletions(-)

diff --git a/compiler/fir/semantics/src/org/jetbrains/kotlin/fir/resolve/dfa/VariableStorageImpl.kt b/compiler/fir/semantics/src/org/jetbrains/kotlin/fir/resolve/dfa/VariableStorageImpl.kt
index e627cc7c05e..7baa6efecca 100644
--- a/compiler/fir/semantics/src/org/jetbrains/kotlin/fir/resolve/dfa/VariableStorageImpl.kt
+++ b/compiler/fir/semantics/src/org/jetbrains/kotlin/fir/resolve/dfa/VariableStorageImpl.kt
@@ -161,9 +161,8 @@ class VariableStorageImpl(private val session: FirSession) : VariableStorage() {
         if (originalFir is FirThisReceiverExpression) return PropertyStability.STABLE_VALUE
         when (this) {
             is FirAnonymousObjectSymbol -> return null
-            is FirFunctionSymbol<*>,
-            is FirClassSymbol<*>,
-            is FirBackingFieldSymbol -> return PropertyStability.STABLE_VALUE
+            is FirFunctionSymbol<*>, is FirClassSymbol<*> -> return PropertyStability.STABLE_VALUE
+            is FirBackingFieldSymbol -> return if (isVal) PropertyStability.STABLE_VALUE else PropertyStability.MUTABLE_PROPERTY
         }
         if (this !is FirVariableSymbol<*>) return null
         if (this is FirFieldSymbol && !this.isFinal) return PropertyStability.MUTABLE_PROPERTY
diff --git a/compiler/testData/ir/irText/firProblems/elvisOnBackingFieldInGetter.fir.ir.txt b/compiler/testData/ir/irText/firProblems/elvisOnBackingFieldInGetter.fir.ir.txt
index 14274ae000a..66bd8b12f31 100644
--- a/compiler/testData/ir/irText/firProblems/elvisOnBackingFieldInGetter.fir.ir.txt
+++ b/compiler/testData/ir/irText/firProblems/elvisOnBackingFieldInGetter.fir.ir.txt
@@ -39,18 +39,18 @@ FILE fqName:<root> fileName:/elvisOnBackingFieldInGetter.kt
                   value: CONSTRUCTOR_CALL 'public constructor <init> () declared in <root>.ResourceTable' type=<root>.ResourceTable origin=null
           RETURN type=kotlin.Nothing from='public final fun <get-resourceTable> (): <root>.ResourceTable? declared in <root>.Test'
             BLOCK type=<root>.ResourceTable origin=ELVIS
-              VAR IR_TEMPORARY_VARIABLE name:tmp_0 type:kotlin.Nothing? [val]
+              VAR IR_TEMPORARY_VARIABLE name:tmp_0 type:<root>.ResourceTable? [val]
                 GET_FIELD 'FIELD PROPERTY_BACKING_FIELD name:resourceTable type:<root>.ResourceTable? visibility:private' type=<root>.ResourceTable? origin=GET_PROPERTY
                   receiver: GET_VAR '<this>: <root>.Test declared in <root>.Test.<get-resourceTable>' type=<root>.Test origin=null
               WHEN type=<root>.ResourceTable origin=null
                 BRANCH
                   if: CALL 'public final fun EQEQ (arg0: kotlin.Any?, arg1: kotlin.Any?): kotlin.Boolean declared in kotlin.internal.ir' type=kotlin.Boolean origin=EQEQ
-                    arg0: GET_VAR 'val tmp_0: kotlin.Nothing? declared in <root>.Test.<get-resourceTable>' type=kotlin.Nothing? origin=null
+                    arg0: GET_VAR 'val tmp_0: <root>.ResourceTable? declared in <root>.Test.<get-resourceTable>' type=<root>.ResourceTable? origin=null
                     arg1: CONST Null type=kotlin.Nothing? value=null
                   then: CONSTRUCTOR_CALL 'public constructor <init> () declared in <root>.ResourceTable' type=<root>.ResourceTable origin=null
                 BRANCH
                   if: CONST Boolean type=kotlin.Boolean value=true
-                  then: GET_VAR 'val tmp_0: kotlin.Nothing? declared in <root>.Test.<get-resourceTable>' type=kotlin.Nothing? origin=null
+                  then: GET_VAR 'val tmp_0: <root>.ResourceTable? declared in <root>.Test.<get-resourceTable>' type=<root>.ResourceTable? origin=null
       FUN DEFAULT_PROPERTY_ACCESSOR name:<set-resourceTable> visibility:public modality:FINAL <> ($this:<root>.Test, <set-?>:<root>.ResourceTable?) returnType:kotlin.Unit
         correspondingProperty: PROPERTY name:resourceTable visibility:public modality:FINAL [var]
         $this: VALUE_PARAMETER name:<this> type:<root>.Test
diff --git a/compiler/testData/ir/irText/firProblems/elvisOnBackingFieldInGetter.fir.kt.txt b/compiler/testData/ir/irText/firProblems/elvisOnBackingFieldInGetter.fir.kt.txt
index f93e6cf08a4..81366e83387 100644
--- a/compiler/testData/ir/irText/firProblems/elvisOnBackingFieldInGetter.fir.kt.txt
+++ b/compiler/testData/ir/irText/firProblems/elvisOnBackingFieldInGetter.fir.kt.txt
@@ -20,7 +20,7 @@ class Test {
         }
       }
       return { // BLOCK
-        val <elvis>: Nothing? = <this>.#resourceTable
+        val <elvis>: ResourceTable? = <this>.#resourceTable
         when {
           EQEQ(arg0 = <elvis>, arg1 = null) -> ResourceTable()
           else -> <elvis>