[FIR] Do not smartcast class delegation implemented properties

When a property is implemented via class delegation, it should be
considered unstable for smart-casting. This is because it is unknown
what kind of stability the underlying class delegate property has. It
could be a stable property, or it could be implemented via a custom
getter and unstable.

^KT-57417 Fixed

analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/diagnostic/compiler/based/DiagnosticCompilerTestFE10TestdataTestGenerated.java

@@ -36967,6 +36967,12 @@ public class DiagnosticCompilerTestFE10TestdataTestGenerated extends AbstractDia
                     runTest("compiler/testData/diagnostics/tests/smartCasts/varnotnull/capturedInlineModifiedBefore.kt");
                 }
 
+                @Test
+                @TestMetadata("classDelegation.kt")
+                public void testClassDelegation() throws Exception {
+                    runTest("compiler/testData/diagnostics/tests/smartCasts/varnotnull/classDelegation.kt");
+                }
+
                 @Test
                 @TestMetadata("doWhileWithBreak.kt")
                 public void testDoWhileWithBreak() throws Exception {

analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/diagnostic/compiler/based/LLFirPreresolvedReversedDiagnosticCompilerFE10TestDataTestGenerated.java

@@ -36967,6 +36967,12 @@ public class LLFirPreresolvedReversedDiagnosticCompilerFE10TestDataTestGenerated
                     runTest("compiler/testData/diagnostics/tests/smartCasts/varnotnull/capturedInlineModifiedBefore.kt");
                 }
 
+                @Test
+                @TestMetadata("classDelegation.kt")
+                public void testClassDelegation() throws Exception {
+                    runTest("compiler/testData/diagnostics/tests/smartCasts/varnotnull/classDelegation.kt");
+                }
+
                 @Test
                 @TestMetadata("doWhileWithBreak.kt")
                 public void testDoWhileWithBreak() throws Exception {

compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirLightTreeOldFrontendDiagnosticsTestGenerated.java

@@ -34635,6 +34635,12 @@ public class FirLightTreeOldFrontendDiagnosticsTestGenerated extends AbstractFir
                     runTest("compiler/testData/diagnostics/tests/smartCasts/varnotnull/capturedInlineModifiedBefore.kt");
                 }
 
+                @Test
+                @TestMetadata("classDelegation.kt")
+                public void testClassDelegation() throws Exception {
+                    runTest("compiler/testData/diagnostics/tests/smartCasts/varnotnull/classDelegation.kt");
+                }
+
                 @Test
                 @TestMetadata("doWhileWithBreak.kt")
                 public void testDoWhileWithBreak() throws Exception {

compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirPsiOldFrontendDiagnosticsTestGenerated.java

@@ -34761,6 +34761,12 @@ public class FirPsiOldFrontendDiagnosticsTestGenerated extends AbstractFirPsiDia
                     runTest("compiler/testData/diagnostics/tests/smartCasts/varnotnull/capturedInlineModifiedBefore.kt");
                 }
 
+                @Test
+                @TestMetadata("classDelegation.kt")
+                public void testClassDelegation() throws Exception {
+                    runTest("compiler/testData/diagnostics/tests/smartCasts/varnotnull/classDelegation.kt");
+                }
+
                 @Test
                 @TestMetadata("doWhileWithBreak.kt")
                 public void testDoWhileWithBreak() throws Exception {

compiler/fir/semantics/src/org/jetbrains/kotlin/fir/resolve/dfa/VariableStorageImpl.kt

@@ -7,8 +7,7 @@ package org.jetbrains.kotlin.fir.resolve.dfa
 
 import org.jetbrains.kotlin.descriptors.Modality
 import org.jetbrains.kotlin.descriptors.Visibilities
-import org.jetbrains.kotlin.fir.FirElement
+import org.jetbrains.kotlin.fir.*
-import org.jetbrains.kotlin.fir.FirSession
 import org.jetbrains.kotlin.fir.declarations.FirAnonymousObject
 import org.jetbrains.kotlin.fir.declarations.FirProperty
 import org.jetbrains.kotlin.fir.declarations.FirRegularClass
@@ -18,8 +17,6 @@ import org.jetbrains.kotlin.fir.declarations.utils.isFinal
 import org.jetbrains.kotlin.fir.declarations.utils.modality
 import org.jetbrains.kotlin.fir.declarations.utils.visibility
 import org.jetbrains.kotlin.fir.expressions.*
-import org.jetbrains.kotlin.fir.moduleData
-import org.jetbrains.kotlin.fir.originalOrSelf
 import org.jetbrains.kotlin.fir.references.FirThisReference
 import org.jetbrains.kotlin.fir.resolve.fullyExpandedType
 import org.jetbrains.kotlin.fir.resolve.toSymbol
@@ -173,7 +170,7 @@ class VariableStorageImpl(private val session: FirSession) : VariableStorage() {
         val property = this.fir as? FirProperty ?: return PropertyStability.STABLE_VALUE
 
         return when {
-            property.delegate != null -> PropertyStability.DELEGATED_PROPERTY
+            property.delegate != null || property.isDelegated -> PropertyStability.DELEGATED_PROPERTY
             property.isLocal -> if (property.isVal) PropertyStability.STABLE_VALUE else PropertyStability.LOCAL_VAR
             property.isVar -> PropertyStability.MUTABLE_PROPERTY
             property.receiverParameter != null -> PropertyStability.PROPERTY_WITH_GETTER

compiler/testData/diagnostics/tests/smartCasts/varnotnull/classDelegation.fir.kt

@@ -0,0 +1,11 @@
+// ISSUE: KT-57417
+
+interface HasProperty {
+    val property: Int?
+}
+
+class Test(delegate: HasProperty) : HasProperty by delegate
+
+fun test(a: Test) {
+    if (a.property != null) <!SMARTCAST_IMPOSSIBLE!>a.property<!> + 1
+}

compiler/testData/diagnostics/tests/smartCasts/varnotnull/classDelegation.kt

@@ -0,0 +1,11 @@
+// ISSUE: KT-57417
+
+interface HasProperty {
+    val property: Int?
+}
+
+class Test(delegate: HasProperty) : HasProperty by delegate
+
+fun test(a: Test) {
+    if (a.property != null) <!DEBUG_INFO_SMARTCAST!>a.property<!> + 1
+}

compiler/tests-common-new/tests-gen/org/jetbrains/kotlin/test/runners/DiagnosticTestGenerated.java

@@ -36967,6 +36967,12 @@ public class DiagnosticTestGenerated extends AbstractDiagnosticTest {
                     runTest("compiler/testData/diagnostics/tests/smartCasts/varnotnull/capturedInlineModifiedBefore.kt");
                 }
 
+                @Test
+                @TestMetadata("classDelegation.kt")
+                public void testClassDelegation() throws Exception {
+                    runTest("compiler/testData/diagnostics/tests/smartCasts/varnotnull/classDelegation.kt");
+                }
+
                 @Test
                 @TestMetadata("doWhileWithBreak.kt")
                 public void testDoWhileWithBreak() throws Exception {