Deprecate smart cast on alien derived property #KT-48101 Fixed

compiler/frontend/src/org/jetbrains/kotlin/resolve/calls/smartcasts/DataFlowValue.kt

@@ -41,25 +41,37 @@ class DataFlowValue(
         // or protected / public member value from the same module without open / custom getter
         // Smart casts are completely safe
         STABLE_VALUE("stable val"),
+
         // Block, or if / else, or when
         STABLE_COMPLEX_EXPRESSION("complex expression", ""),
+
         // Should be unstable, but can be used as stable with deprecation warning
         LEGACY_STABLE_LOCAL_DELEGATED_PROPERTY("local delegated property"),
+
         // Member value with open / custom getter
         // Smart casts are not safe
         PROPERTY_WITH_GETTER("custom getter", "property that has open or custom getter"),
+
+        // Protected / public member value from derived class from another module
+        // Should be unstable, but can be used as stable with deprecation warning
+        LEGACY_ALIEN_BASE_PROPERTY("alien derived", "property declared in base class from different module"),
+
         // Protected / public member value from another module
         // Smart casts are not safe
         ALIEN_PUBLIC_PROPERTY("alien public", "public API property declared in different module"),
+
         // Local variable not yet captured by a changing closure
         // Smart casts are safe but possible changes in loops / closures ahead must be taken into account
         STABLE_VARIABLE("stable var", "local variable that can be changed since the check in a loop"),
+
         // Local variable already captured by a changing closure
         // Smart casts are not safe
         CAPTURED_VARIABLE("captured var", "local variable that is captured by a changing closure"),
+
         // Member variable regardless of its visibility
         // Smart casts are not safe
         MUTABLE_PROPERTY("member", "mutable property that could have been changed by this time"),
+
         // Some complex expression
         // Smart casts are not safe
         OTHER("other", "complex expression");
@@ -74,7 +86,8 @@ class DataFlowValue(
     val isStable = kind == Kind.STABLE_VALUE ||
             kind == Kind.STABLE_VARIABLE ||
             kind == Kind.STABLE_COMPLEX_EXPRESSION ||
-            kind == Kind.LEGACY_STABLE_LOCAL_DELEGATED_PROPERTY
+            kind == Kind.LEGACY_STABLE_LOCAL_DELEGATED_PROPERTY ||
+            kind == Kind.LEGACY_ALIEN_BASE_PROPERTY
 
     val canBeBound get() = identifierInfo.canBeBound
 

compiler/frontend/src/org/jetbrains/kotlin/resolve/calls/smartcasts/DataFlowValueKindUtils.kt

@@ -19,7 +19,10 @@ import org.jetbrains.kotlin.resolve.DescriptorUtils
 import org.jetbrains.kotlin.types.expressions.AssignedVariablesSearcher
 import org.jetbrains.kotlin.types.expressions.PreliminaryDeclarationVisitor
 
-internal fun PropertyDescriptor.propertyKind(usageModule: ModuleDescriptor?): DataFlowValue.Kind {
+internal fun PropertyDescriptor.propertyKind(
+    usageModule: ModuleDescriptor?,
+    languageVersionSettings: LanguageVersionSettings
+): DataFlowValue.Kind {
     if (isVar) return DataFlowValue.Kind.MUTABLE_PROPERTY
     if (isOverridable) return DataFlowValue.Kind.PROPERTY_WITH_GETTER
     if (!hasDefaultGetter()) return DataFlowValue.Kind.PROPERTY_WITH_GETTER
@@ -28,11 +31,30 @@ internal fun PropertyDescriptor.propertyKind(usageModule: ModuleDescriptor?): Da
         if (!areCompiledTogether(usageModule, declarationModule)) {
             return DataFlowValue.Kind.ALIEN_PUBLIC_PROPERTY
         }
+        if (kind == CallableMemberDescriptor.Kind.FAKE_OVERRIDE) {
+            if (overriddenDescriptors.any { isDeclaredInAnotherModule(usageModule) }) {
+                return if (!languageVersionSettings.supportsFeature(LanguageFeature.ProhibitSmartcastsOnPropertyFromAlienBaseClass)) {
+                    DataFlowValue.Kind.LEGACY_ALIEN_BASE_PROPERTY
+                } else {
+                    DataFlowValue.Kind.ALIEN_PUBLIC_PROPERTY
+                }
+            }
+        }
     }
     return DataFlowValue.Kind.STABLE_VALUE
 }
 
-internal fun areCompiledTogether(
+private fun PropertyDescriptor.isDeclaredInAnotherModule(usageModule: ModuleDescriptor?): Boolean {
+    if (!areCompiledTogether(usageModule, DescriptorUtils.getContainingModule(this))) {
+        return true
+    }
+    if (kind == CallableMemberDescriptor.Kind.FAKE_OVERRIDE) {
+        return overriddenDescriptors.any { it.isDeclaredInAnotherModule(usageModule) }
+    }
+    return false
+}
+
+private fun areCompiledTogether(
     usageModule: ModuleDescriptor?,
     declarationModule: ModuleDescriptor,
 ): Boolean {
@@ -49,7 +71,7 @@ internal fun VariableDescriptor.variableKind(
     languageVersionSettings: LanguageVersionSettings
 ): DataFlowValue.Kind {
     if (this is PropertyDescriptor) {
-        return propertyKind(usageModule)
+        return propertyKind(usageModule, languageVersionSettings)
     }
 
     if (this is LocalVariableDescriptor && this.isDelegated) {

compiler/frontend/src/org/jetbrains/kotlin/resolve/calls/smartcasts/SmartCastManager.kt

@@ -226,7 +226,9 @@ class SmartCastManager(private val argumentTypeResolver: ArgumentTypeResolver) {
         ) {
             if (KotlinBuiltIns.isNullableNothing(type)) return
             if (dataFlowValue.isStable) {
-                if (dataFlowValue.kind == DataFlowValue.Kind.LEGACY_STABLE_LOCAL_DELEGATED_PROPERTY) {
+                if (dataFlowValue.kind == DataFlowValue.Kind.LEGACY_ALIEN_BASE_PROPERTY ||
+                    dataFlowValue.kind == DataFlowValue.Kind.LEGACY_STABLE_LOCAL_DELEGATED_PROPERTY
+                ) {
                     trace.report(Errors.DEPRECATED_SMARTCAST.on(expression, type, expression.text, dataFlowValue.kind.description))
                 }