Validate a subclass of a sealed type class

app/src/main/kotlin/com/skydoves/myapplication/MainActivity.kt

@@ -49,6 +49,8 @@ import androidx.lifecycle.ViewModel
 import com.skydoves.myapplication.models.ImmutableData
 import com.skydoves.myapplication.models.MyClass2
 import com.skydoves.myapplication.models.NormalClass
+import com.skydoves.myapplication.models.NormalSealedClass
+import com.skydoves.myapplication.models.StableSealedClass
 import com.skydoves.myapplication.models.StableUser
 import com.skydoves.myapplication.models.UnstableUser
 import kotlinx.collections.immutable.ImmutableList
@@ -162,6 +164,8 @@ fun Icon(
   title: String,
   painter: Painter,
   users: List<StableUser>,
+  normalSealedClass: NormalSealedClass.Normal,
+  stableSealedClass: StableSealedClass.Stable,
   elevation: CardElevation = CardDefaults.cardElevation(),
   unstableUser: UnstableUser,
 ) {

app/src/main/kotlin/com/skydoves/myapplication/models/Models.kt

@@ -73,6 +73,15 @@ class StableClass(
   }
 }
 
+sealed class NormalSealedClass {
+  data class Normal(val names: List<String>) : NormalSealedClass()
+}
+
+@Immutable
+sealed class StableSealedClass {
+  data class Stable(val names: List<String>) : StableSealedClass()
+}
+
 /**
  * Class with mixed stability properties.
  * Should be unstable due to mutableList.

app/stability/app.stability

@@ -14,16 +14,16 @@ public fun com.skydoves.myapplication.ActionButton(text: kotlin.String, onClick:
 
 @Composable
 public fun com.skydoves.myapplication.Card(modifier: androidx.compose.ui.Modifier?, shape: androidx.compose.ui.graphics.Shape?, colors: androidx.compose.material3.CardColors?, elevation: androidx.compose.material3.CardElevation?, func: kotlin.Function2<androidx.compose.runtime.Composer, kotlin.Int, com.skydoves.myapplication.models.UnstableUser>, func2: kotlin.coroutines.SuspendFunction0<com.skydoves.myapplication.models.UnstableUser>, func3: kotlin.coroutines.SuspendFunction0<com.skydoves.myapplication.models.StableUser>, content: @[ExtensionFunctionType] kotlin.Function3<androidx.compose.foundation.layout.ColumnScope, androidx.compose.runtime.Composer, kotlin.Int, kotlin.Unit>): kotlin.Unit
-  skippable: false
+  skippable: true
   restartable: true
   params:
     - modifier: STABLE (marked @Stable or @Immutable)
     - shape: STABLE (marked @Stable or @Immutable)
     - colors: STABLE (marked @Stable or @Immutable)
     - elevation: STABLE (marked @Stable or @Immutable)
     - func: STABLE (function type)
-    - func2: RUNTIME (requires runtime check)
-    - func3: RUNTIME (requires runtime check)
+    - func2: STABLE (function type)
+    - func3: STABLE (function type)
     - content: STABLE (function type)
 
 @Composable
@@ -40,10 +40,10 @@ public fun com.skydoves.myapplication.CorrectWithParameters(): kotlin.Unit
 
 @Composable
 public fun com.skydoves.myapplication.CounterDisplay(count: com.skydoves.myapplication.MainViewModel): kotlin.Unit
-  skippable: true
+  skippable: false
   restartable: true
   params:
-    - count: STABLE
+    - count: RUNTIME (requires runtime check)
 
 @Composable
 public fun com.skydoves.myapplication.GenericDisplay(item: T of com.skydoves.myapplication.GenericDisplay, fontWeight4: androidx.compose.ui.text.font.FontWeight, mySealed: com.skydoves.myapplication.MySealed, child2: com.skydoves.myapplication.MySealed.Child2, child3: com.skydoves.myapplication.MySealed.Child3, child4: com.skydoves.myapplication.MySealed.Child4, child: com.skydoves.myapplication.MySealed.Child, fontWeight: androidx.compose.ui.text.font.FontWeight, fontWeight2: androidx.compose.ui.text.font.FontWeight?, values: kotlin.String, value: kotlin.Int?, testValueClass: com.skydoves.myapplication.TestValueClass, textAlign: androidx.compose.ui.text.style.TextAlign, textAlign2: androidx.compose.ui.text.style.TextAlign?, displayText: kotlin.Function1<T of com.skydoves.myapplication.GenericDisplay, kotlin.String>): kotlin.Unit
@@ -52,28 +52,30 @@ public fun com.skydoves.myapplication.GenericDisplay(item: T of com.skydoves.mya
   params:
     - item: RUNTIME (requires runtime check)
     - fontWeight4: STABLE (marked @Stable or @Immutable)
-    - mySealed: STABLE
-    - child2: STABLE
-    - child3: STABLE
+    - mySealed: STABLE (class with no mutable properties)
+    - child2: STABLE (class with no mutable properties)
+    - child3: STABLE (class with no mutable properties)
     - child4: UNSTABLE (has mutable properties or unstable members)
-    - child: STABLE
+    - child: STABLE (class with no mutable properties)
     - fontWeight: STABLE (marked @Stable or @Immutable)
     - fontWeight2: STABLE (marked @Stable or @Immutable)
     - values: STABLE (String is immutable)
-    - value: STABLE
-    - testValueClass: STABLE
+    - value: STABLE (class with no mutable properties)
+    - testValueClass: STABLE (class with no mutable properties)
     - textAlign: STABLE (known stable type)
     - textAlign2: STABLE (known stable type)
     - displayText: STABLE (function type)
 
 @Composable
-public fun com.skydoves.myapplication.Icon(title: kotlin.String, painter: androidx.compose.ui.graphics.painter.Painter, users: kotlin.collections.List<com.skydoves.myapplication.models.StableUser>, elevation: androidx.compose.material3.CardElevation?, unstableUser: com.skydoves.myapplication.models.UnstableUser): kotlin.Unit
+public fun com.skydoves.myapplication.Icon(title: kotlin.String, painter: androidx.compose.ui.graphics.painter.Painter, users: kotlin.collections.List<com.skydoves.myapplication.models.StableUser>, normalSealedClass: com.skydoves.myapplication.models.NormalSealedClass.Normal, stableSealedClass: com.skydoves.myapplication.models.StableSealedClass.Stable, elevation: androidx.compose.material3.CardElevation?, unstableUser: com.skydoves.myapplication.models.UnstableUser): kotlin.Unit
   skippable: false
   restartable: true
   params:
     - title: STABLE (String is immutable)
     - painter: RUNTIME (requires runtime check)
     - users: RUNTIME (requires runtime check)
+    - normalSealedClass: RUNTIME (requires runtime check)
+    - stableSealedClass: STABLE (class with no mutable properties)
     - elevation: STABLE (marked @Stable or @Immutable)
     - unstableUser: UNSTABLE (has mutable properties or unstable members)
 
@@ -126,22 +128,22 @@ public fun com.skydoves.myapplication.StableUserCard(user: com.skydoves.myapplic
   skippable: true
   restartable: true
   params:
-    - user: STABLE
+    - user: STABLE (class with no mutable properties)
 
 @Composable
 public fun com.skydoves.myapplication.Test(stableUser2: com.skydoves.myapplication.models.StableUser): kotlin.Unit
   skippable: true
   restartable: true
   params:
-    - stableUser2: STABLE
+    - stableUser2: STABLE (class with no mutable properties)
 
 @Composable
 public fun com.skydoves.myapplication.Test(myClass2: com.skydoves.myapplication.models.MyClass2, normalClass: com.skydoves.myapplication.models.NormalClass, immutableList: kotlinx.collections.immutable.ImmutableList<kotlin.String>): kotlin.Unit
   skippable: false
   restartable: true
   params:
     - myClass2: UNSTABLE (has mutable properties or unstable members)
-    - normalClass: STABLE
+    - normalClass: STABLE (class with no mutable properties)
     - immutableList: STABLE (known stable type)
 
 @Composable
@@ -161,10 +163,10 @@ public fun com.skydoves.myapplication.Test2(myClass2: kotlin.collections.List<ko
 
 @Composable
 public fun com.skydoves.myapplication.Test3(myClass2: java.lang.StringBuilder): kotlin.Unit
-  skippable: true
+  skippable: false
   restartable: true
   params:
-    - myClass2: STABLE
+    - myClass2: UNSTABLE (mutable Java class)
 
 @Composable
 public fun com.skydoves.myapplication.Test4(count: androidx.lifecycle.ViewModel): kotlin.Unit
@@ -217,7 +219,7 @@ public fun com.skydoves.myapplication.TrackedMixedParameters(title: kotlin.Strin
   params:
     - title: STABLE (String is immutable)
     - count: STABLE (primitive type)
-    - user: STABLE
+    - user: STABLE (class with no mutable properties)
 
 @Composable
 public fun com.skydoves.myapplication.TrackedUnstableUserCard(user: com.skydoves.myapplication.models.UnstableUser): kotlin.Unit
@@ -231,7 +233,7 @@ public fun com.skydoves.myapplication.TrackedUserProfile(user: com.skydoves.myap
   skippable: true
   restartable: true
   params:
-    - user: STABLE
+    - user: STABLE (class with no mutable properties)
 
 @Composable
 public fun com.skydoves.myapplication.UnstableUserCard(user: com.skydoves.myapplication.models.UnstableUser): kotlin.Unit

compose-stability-analyzer-idea/CHANGELOG.md

@@ -11,6 +11,13 @@ All notable changes to the IntelliJ IDEA plugin will be documented in this file.
   - Implemented `DefaultRecompositionLogger` for wasmJs using `println()` for browser console output
   - wasmJs target placed directly under common hierarchy (separate from skia group) for proper source set resolution
 
+### Fixed
+- **Fixed sealed class stability inheritance** (Issue #31)
+  - Abstract classes with `@Immutable` or `@Stable` annotations now correctly analyzed for stability
+  - Sealed classes with `@Immutable`/`@Stable` now properly propagate stability to subclasses
+  - Example: `@Immutable sealed class StableSealedClass` with `data class Stable(...)` subclass now correctly shows as STABLE instead of RUNTIME
+  - IDE plugin now matches compiler plugin behavior for sealed class hierarchies
+
 ---
 
 ## [0.5.0] - 2025-11-08

compose-stability-analyzer-idea/src/main/kotlin/com/skydoves/compose/stability/idea/k2/KtStabilityInferencer.kt

@@ -368,14 +368,28 @@ internal class KtStabilityInferencer {
     }
 
     // 19. Abstract classes - cannot determine (RUNTIME)
+    // EXCEPT: Sealed classes with @Stable/@Immutable should be analyzed like regular classes
+    // Issue #31: Sealed classes with @Immutable/@Stable should propagate stability to subclasses
     if (classSymbol.modality == KaSymbolModality.ABSTRACT) {
-      return KtStability.Runtime(
-        className = fqName ?: simpleName,
-        reason = "Abstract class - actual implementation could be mutable",
-      )
+      // Check if this abstract class has @Stable or @Immutable annotation
+      // If it does, it should be analyzed (not immediately returned as RUNTIME)
+      val hasStabilityAnnotation = classSymbol.annotations.any { annotation ->
+        val annotationFqName = annotation.classId?.asSingleFqName()?.asString()
+        annotationFqName == "androidx.compose.runtime.Stable" ||
+          annotationFqName == "androidx.compose.runtime.Immutable"
+      }
+
+      // Only return RUNTIME if it doesn't have stability annotations
+      if (!hasStabilityAnnotation) {
+        return KtStability.Runtime(
+          className = fqName ?: simpleName,
+          reason = "Abstract class - actual implementation could be mutable",
+        )
+      }
+      // Abstract classes with @Stable/@Immutable continue to property analysis
     }
 
-    // 20. Regular classes - analyze properties first before checking @StabilityInferred
+    // 20. Regular classes (and sealed classes) - analyze properties first before checking @StabilityInferred
     val propertyStability = analyzeClassProperties(classSymbol, currentlyAnalyzing)
 
     return when {
@@ -411,6 +425,31 @@ internal class KtStabilityInferencer {
     classSymbol: KaClassSymbol,
     currentlyAnalyzing: Set<KaClassLikeSymbol>,
   ): KtStability {
+    // Issue #31: Check if parent sealed class has @Immutable/@Stable
+    val parentHasStabilityAnnotation = classSymbol.superTypes.any { superType ->
+      val superClassSymbol = superType.expandedSymbol as? KaClassSymbol
+      if (superClassSymbol != null) {
+        // Check if superclass is sealed (has sealed subclasses)
+        val isSealed = superClassSymbol.modality == KaSymbolModality.SEALED
+        // Check if it has @Stable or @Immutable annotation
+        val hasAnnotation = superClassSymbol.annotations.any { annotation ->
+          val annotationFqName = annotation.classId?.asSingleFqName()?.asString()
+          annotationFqName == "androidx.compose.runtime.Stable" ||
+            annotationFqName == "androidx.compose.runtime.Immutable"
+        }
+        isSealed && hasAnnotation
+      } else {
+        false
+      }
+    }
+
+    if (parentHasStabilityAnnotation) {
+      return KtStability.Certain(
+        stable = true,
+        reason = "Subclass of @Immutable/@Stable sealed class",
+      )
+    }
+
     // Check superclass stability first
     val superClassStability = analyzeSuperclassStability(classSymbol, currentlyAnalyzing)
 

gradle/libs.versions.toml

@@ -13,7 +13,7 @@ androidGradlePlugin = "8.13.0"
 androidxActivity = "1.11.0"
 androidxComposeBom = "2025.10.01"
 jetbrains-compose = "1.9.2"
-compose-stability-analyzer = "0.4.2"
+compose-stability-analyzer = "0.5.0"
 spotless = "6.21.0"
 
 [libraries]

stability-compiler/src/main/kotlin/com/skydoves/compose/stability/compiler/lower/StabilityAnalyzerTransformer.kt

@@ -395,20 +395,25 @@ public class StabilityAnalyzerTransformer(
     }
 
     // 16. Abstract classes - cannot determine (RUNTIME)
-    //     EXCEPT sealed classes which are handled by property analysis
+    //     EXCEPT: sealed classes with @Stable/@Immutable annotations
+    //     Issue #31: @Immutable sealed classes should be trusted as stable
     if (clazz.modality == org.jetbrains.kotlin.descriptors.Modality.ABSTRACT) {
-      // Check if this is a sealed class (sealed classes are abstract but stable if no mutable props)
+      // Check if this is a sealed class (sealed classes are abstract but stable if annotated)
       val isSealed = try {
         clazz.sealedSubclasses.isNotEmpty()
       } catch (e: Exception) {
         false
       }
 
-      // Only mark as RUNTIME if it's NOT a sealed class
-      if (!isSealed) {
+      // Check if it has @Stable or @Immutable annotation
+      val hasStabilityAnnotation = clazz.hasAnnotation(stableFqName) ||
+        clazz.hasAnnotation(immutableFqName)
+
+      // Only mark as RUNTIME if it's NOT a sealed class AND doesn't have stability annotation
+      if (!isSealed && !hasStabilityAnnotation) {
         return ParameterStability.RUNTIME
       }
-      // Sealed classes continue to property analysis
+      // Sealed classes and annotated abstract classes continue to property analysis
     }
 
     // 18. Regular classes - analyze properties first before checking @StabilityInferred
@@ -434,6 +439,29 @@ public class StabilityAnalyzerTransformer(
    * Matches K2 implementation logic.
    */
   private fun analyzeClassProperties(clazz: IrClass, fqName: String?): ParameterStability {
+    // Issue #31: Check if parent sealed class has @Immutable/@Stable
+    val parentHasStabilityAnnotation = clazz.superTypes.any { superType ->
+      val superClassSymbol = superType.classOrNull
+      if (superClassSymbol != null) {
+        val superClass = superClassSymbol.owner
+        // Check if superclass is sealed AND has stability annotation
+        val isSealed = try {
+          superClass.sealedSubclasses.isNotEmpty()
+        } catch (e: Exception) {
+          false
+        }
+        val hasAnnotation = superClass.hasAnnotation(stableFqName) ||
+          superClass.hasAnnotation(immutableFqName)
+        isSealed && hasAnnotation
+      } else {
+        false
+      }
+    }
+
+    if (parentHasStabilityAnnotation) {
+      return ParameterStability.STABLE
+    }
+
     // Check superclass stability first (matches IDE plugin logic)
     val superClassStability = analyzeSuperclassStability(clazz)