Correctly handle @Repeatable @SerialInfo annotations on classes

that were affected by deduplication of inherited serial info annotations.

Prohibit combination of @InheritableSerialInfo and @Repeatable.

Fixes https://github.com/Kotlin/kotlinx.serialization/issues/2099

plugins/kotlinx-serialization/kotlinx-serialization.k2/src/org/jetbrains/kotlinx/serialization/compiler/fir/checkers/FirSerializationErrors.kt

@@ -46,6 +46,7 @@ object FirSerializationErrors {
 
     val INCONSISTENT_INHERITABLE_SERIALINFO by error2<PsiElement, ConeKotlinType, ConeKotlinType>()
     val META_SERIALIZABLE_NOT_APPLICABLE by error0<PsiElement>()
+    val INHERITABLE_SERIALINFO_CANT_BE_REPEATABLE by error0<PsiElement>()
 
     val EXTERNAL_SERIALIZER_USELESS by warning1<PsiElement, FirClassSymbol<*>>()
     val EXTERNAL_CLASS_NOT_SERIALIZABLE by error2<PsiElement, FirClassSymbol<*>, ConeKotlinType>()

plugins/kotlinx-serialization/kotlinx-serialization.k2/src/org/jetbrains/kotlinx/serialization/compiler/fir/checkers/FirSerializationPluginClassChecker.kt

@@ -9,6 +9,7 @@ import org.jetbrains.kotlin.KtSourceElement
 import org.jetbrains.kotlin.config.KotlinCompilerVersion
 import org.jetbrains.kotlin.descriptors.ClassKind
 import org.jetbrains.kotlin.diagnostics.*
+import org.jetbrains.kotlin.fir.analysis.checkers.containsRepeatableAnnotation
 import org.jetbrains.kotlin.fir.analysis.checkers.context.CheckerContext
 import org.jetbrains.kotlin.fir.analysis.checkers.declaration.FirClassChecker
 import org.jetbrains.kotlin.fir.analysis.checkers.isSingleFieldValueClass
@@ -46,6 +47,7 @@ object FirSerializationPluginClassChecker : FirClassChecker() {
         with(context) {
             val classSymbol = declaration.symbol
             checkMetaSerializableApplicable(classSymbol, reporter)
+            checkInheritableSerialInfoNotRepeatable(classSymbol, reporter)
             checkEnum(classSymbol, reporter)
             checkExternalSerializer(classSymbol, reporter)
             if (!canBeSerializedInternally(classSymbol, reporter)) return
@@ -71,6 +73,16 @@ object FirSerializationPluginClassChecker : FirClassChecker() {
         reporter.reportOn(anno.source, FirSerializationErrors.META_SERIALIZABLE_NOT_APPLICABLE)
     }
 
+    context(CheckerContext)
+    private fun checkInheritableSerialInfoNotRepeatable(classSymbol: FirClassSymbol<out FirClass>, reporter: DiagnosticReporter) {
+        if (classSymbol.classKind != ClassKind.ANNOTATION_CLASS) return
+        if (!classSymbol.containsRepeatableAnnotation(session)) return
+        val anno = classSymbol.resolvedAnnotationsWithClassIds
+            .find { it.toAnnotationClassId(session) == SerializationAnnotations.inheritableSerialInfoClassId }
+            ?: return
+        reporter.reportOn(anno.source, FirSerializationErrors.INHERITABLE_SERIALINFO_CANT_BE_REPEATABLE)
+    }
+
     context(CheckerContext)
     @Suppress("IncorrectFormatting") // KTIJ-22227
     private fun checkExternalSerializer(classSymbol: FirClassSymbol<*>, reporter: DiagnosticReporter) {

plugins/kotlinx-serialization/kotlinx-serialization.k2/src/org/jetbrains/kotlinx/serialization/compiler/fir/checkers/KtDefaultErrorMessagesSerialization.kt

@@ -155,6 +155,10 @@ object KtDefaultErrorMessagesSerialization : BaseDiagnosticRendererFactory() {
             FirSerializationErrors.META_SERIALIZABLE_NOT_APPLICABLE,
             "@MetaSerializable annotation can be used only on top-level annotation classes."
         )
+        put(
+            FirSerializationErrors.INHERITABLE_SERIALINFO_CANT_BE_REPEATABLE,
+            "Repeatable serial info annotations can not be inheritable. Either remove @Repeatable or use a regular @SerialInfo annotation."
+        )
 
         put(
             FirSerializationErrors.EXTERNAL_SERIALIZER_USELESS,