Parcelable: Parcelize overrides describeContents despite being already implemented (KT-20026)

plugins/android-extensions/android-extensions-compiler/src/org/jetbrains/kotlin/android/parcel/ParcelableResolveExtension.kt

@@ -93,6 +93,7 @@ open class ParcelableResolveExtension : SyntheticResolveExtension {
                 && clazz.isParcelize
                 && isExperimental()
                 && result.none { it.isDescribeContents() }
+                && fromSupertypes.none { it.isDescribeContents() }
         ) {
             result += createMethod(clazz, DESCRIBE_CONTENTS, clazz.builtIns.intType)
         } else if (name.asString() == WRITE_TO_PARCEL.methodName
@@ -107,7 +108,9 @@ open class ParcelableResolveExtension : SyntheticResolveExtension {
     }
 
     private fun SimpleFunctionDescriptor.isDescribeContents(): Boolean {
-        return typeParameters.isEmpty()
+        return this.kind != CallableMemberDescriptor.Kind.FAKE_OVERRIDE
+               && modality != Modality.ABSTRACT
+               && typeParameters.isEmpty()
                && valueParameters.isEmpty()
                && returnType?.let { type -> KotlinBuiltIns.isInt(type) } == true
     }

plugins/android-extensions/android-extensions-compiler/testData/parcel/codegen/describeContentsFromSuperType.kt

@@ -0,0 +1,11 @@
+// CURIOUS_ABOUT describeContents
+
+import kotlinx.android.parcel.*
+import android.os.Parcelable
+
+abstract class AbstractUser : Parcelable {
+    override fun describeContents() = 100
+}
+
+@Parcelize
+class User(val firstName: String, val lastName: String, val age: Int, val isProUser: Boolean) : AbstractUser()

plugins/android-extensions/android-extensions-compiler/testData/parcel/codegen/describeContentsFromSuperType.txt

@@ -0,0 +1,53 @@
+public abstract class AbstractUser : java/lang/Object, android/os/Parcelable {
+    public void <init>()
+
+    public int describeContents() {
+        LABEL (L0)
+        LINENUMBER (7)
+          BIPUSH (100)
+          IRETURN
+        LABEL (L1)
+    }
+}
+
+public final class User$Companion : java/lang/Object {
+    private void <init>()
+
+    public void <init>(kotlin.jvm.internal.DefaultConstructorMarker p0)
+}
+
+public static class User$Creator : java/lang/Object, android/os/Parcelable$Creator {
+    public void <init>()
+
+    public final java.lang.Object createFromParcel(android.os.Parcel p0)
+
+    public final User[] newArray(int p0)
+}
+
+public final class User : AbstractUser {
+    public final static User$Creator CREATOR
+
+    public final static User$Companion Companion
+
+    private final int age
+
+    private final java.lang.String firstName
+
+    private final boolean isProUser
+
+    private final java.lang.String lastName
+
+    static void <clinit>()
+
+    public void <init>(java.lang.String p0, java.lang.String p1, int p2, boolean p3)
+
+    public final int getAge()
+
+    public final java.lang.String getFirstName()
+
+    public final java.lang.String getLastName()
+
+    public final boolean isProUser()
+
+    public final void writeToParcel(android.os.Parcel p0, int p1)
+}

plugins/plugins-tests/tests/org/jetbrains/kotlin/android/parcel/ParcelBytecodeListingTestGenerated.java

@@ -54,6 +54,12 @@ public class ParcelBytecodeListingTestGenerated extends AbstractParcelBytecodeLi
         doTest(fileName);
     }
 
+    @TestMetadata("describeContentsFromSuperType.kt")
+    public void testDescribeContentsFromSuperType() throws Exception {
+        String fileName = KotlinTestUtils.navigationMetadata("plugins/android-extensions/android-extensions-compiler/testData/parcel/codegen/describeContentsFromSuperType.kt");
+        doTest(fileName);
+    }
+
     @TestMetadata("duplicatingClinit.kt")
     public void testDuplicatingClinit() throws Exception {
         String fileName = KotlinTestUtils.navigationMetadata("plugins/android-extensions/android-extensions-compiler/testData/parcel/codegen/duplicatingClinit.kt");