[K2] Add version requirement for definitely non-null types to metadata.

compiler/fir/fir-serialization/src/org/jetbrains/kotlin/fir/serialization/FirElementSerializer.kt

@@ -68,6 +68,8 @@ class FirElementSerializer private constructor(
     private val contractSerializer = FirContractSerializer()
     private val providedDeclarationsService = session.providedDeclarationsForMetadataService
 
+    private var metDefinitelyNotNullType: Boolean = false
+
     fun packagePartProto(
         packageFqName: FqName,
         files: List<FirFile>,
@@ -247,6 +249,12 @@ class FirElementSerializer private constructor(
 
         writeVersionRequirementForInlineClasses(klass, builder, versionRequirementTable)
 
+        if (metDefinitelyNotNullType) {
+            builder.addVersionRequirement(
+                writeLanguageVersionRequirement(LanguageFeature.DefinitelyNonNullableTypes, versionRequirementTable)
+            )
+        }
+
         typeTable.serialize()?.let { builder.typeTable = it }
         versionRequirementTable.serialize()?.let { builder.versionRequirementTable = it }
 
@@ -412,6 +420,10 @@ class FirElementSerializer private constructor(
             if (property.hasInlineClassTypesInSignature()) {
                 builder.addVersionRequirement(writeVersionRequirement(LanguageFeature.InlineClasses))
             }
+
+            if (local.metDefinitelyNotNullType) {
+                builder.addVersionRequirement(writeVersionRequirement(LanguageFeature.DefinitelyNonNullableTypes))
+            }
         }
 
         extension.serializeProperty(property, builder, versionRequirementTable, local)
@@ -507,6 +519,10 @@ class FirElementSerializer private constructor(
             if (function.hasInlineClassTypesInSignature()) {
                 builder.addVersionRequirement(writeVersionRequirement(LanguageFeature.InlineClasses))
             }
+
+            if (local.metDefinitelyNotNullType) {
+                builder.addVersionRequirement(writeVersionRequirement(LanguageFeature.DefinitelyNonNullableTypes))
+            }
         }
 
         return builder
@@ -521,7 +537,7 @@ class FirElementSerializer private constructor(
         }
     }
 
-    private fun typeAliasProto(typeAlias: FirTypeAlias): ProtoBuf.TypeAlias.Builder? = whileAnalysing(session, typeAlias) {
+    private fun typeAliasProto(typeAlias: FirTypeAlias): ProtoBuf.TypeAlias.Builder? = whileAnalysing<ProtoBuf.TypeAlias.Builder?>(session, typeAlias) {
         val builder = ProtoBuf.TypeAlias.newBuilder()
         val local = createChildSerializer(typeAlias)
 
@@ -555,6 +571,11 @@ class FirElementSerializer private constructor(
 
         versionRequirementTable?.run {
             builder.addAllVersionRequirement(serializeVersionRequirements(typeAlias))
+            if (local.metDefinitelyNotNullType) {
+                builder.addVersionRequirement(
+                    writeLanguageVersionRequirement(LanguageFeature.DefinitelyNonNullableTypes, versionRequirementTable)
+                )
+            }
         }
 
         extension.serializeTypeAlias(typeAlias, builder)
@@ -598,6 +619,10 @@ class FirElementSerializer private constructor(
             if (constructor.hasInlineClassTypesInSignature()) {
                 builder.addVersionRequirement(writeVersionRequirement(LanguageFeature.InlineClasses))
             }
+
+            if (local.metDefinitelyNotNullType) {
+                builder.addVersionRequirement(writeVersionRequirement(LanguageFeature.DefinitelyNonNullableTypes))
+            }
         }
 
         extension.serializeConstructor(constructor, builder, local)
@@ -769,6 +794,7 @@ class FirElementSerializer private constructor(
                 }
 
                 if (isDefinitelyNotNullType) {
+                    metDefinitelyNotNullType = true
                     builder.flags = Flags.getTypeFlags(false, isDefinitelyNotNullType)
                 }
             }

compiler/serialization/src/org/jetbrains/kotlin/serialization/DescriptorSerializer.kt

@@ -58,12 +58,7 @@ class DescriptorSerializer private constructor(
 ) {
     private val contractSerializer = ContractSerializer()
 
-    private var metDefinitelyNotNullTypeStack: MutableList<Boolean> = mutableListOf(false)
-    private var metDefinitelyNotNullType: Boolean
-        get() = metDefinitelyNotNullTypeStack.last()
-        set(value) {
-            metDefinitelyNotNullTypeStack[metDefinitelyNotNullTypeStack.lastIndex] = value
-        }
+    private var metDefinitelyNotNullType: Boolean = false
 
     private fun createChildSerializer(descriptor: DeclarationDescriptor): DescriptorSerializer =
         DescriptorSerializer(
@@ -78,16 +73,7 @@ class DescriptorSerializer private constructor(
 
     private fun useTypeTable(): Boolean = extension.shouldUseTypeTable()
 
-    private inline fun <T> withNewMetDefinitelyNotNullType(block: () -> T): T {
-        metDefinitelyNotNullTypeStack.add(false)
-        return try {
-            block()
-        } finally {
-            metDefinitelyNotNullTypeStack.removeAt(metDefinitelyNotNullTypeStack.lastIndex)
-        }
-    }
-
-    fun classProto(classDescriptor: ClassDescriptor): ProtoBuf.Class.Builder = withNewMetDefinitelyNotNullType {
+    fun classProto(classDescriptor: ClassDescriptor): ProtoBuf.Class.Builder {
         val builder = ProtoBuf.Class.newBuilder()
 
         val hasEnumEntries = classDescriptor.kind == ClassKind.ENUM_CLASS &&
@@ -507,7 +493,7 @@ class DescriptorSerializer private constructor(
         )
     }
 
-    private fun typeAliasProto(descriptor: TypeAliasDescriptor): ProtoBuf.TypeAlias.Builder? = withNewMetDefinitelyNotNullType {
+    private fun typeAliasProto(descriptor: TypeAliasDescriptor): ProtoBuf.TypeAlias.Builder? {
         val builder = ProtoBuf.TypeAlias.newBuilder()
         val local = createChildSerializer(descriptor)