Serialize type annotations in builtins

core/descriptors/src/org/jetbrains/kotlin/builtins/BuiltInsAnnotationAndConstantLoader.kt

@@ -68,8 +68,7 @@ class BuiltInsAnnotationAndConstantLoader(
     ): List<AnnotationDescriptor> = emptyList()
 
     override fun loadTypeAnnotations(proto: ProtoBuf.Type, nameResolver: NameResolver): List<AnnotationDescriptor> {
-        // TODO: support type annotations in built-ins
-        return listOf()
+        return proto.getExtension(BuiltInsProtoBuf.typeAnnotation).orEmpty().map { deserializer.deserializeAnnotation(it, nameResolver) }
     }
 
     override fun loadPropertyConstant(

core/deserialization/src/builtins.proto

@@ -51,3 +51,7 @@ extend Property {
 extend ValueParameter {
   repeated Annotation parameter_annotation = 150;
 }
+
+extend Type {
+  repeated Annotation type_annotation = 150;
+}

core/deserialization/src/org/jetbrains/kotlin/serialization/builtins/BuiltInsProtoBuf.java

@@ -16,6 +16,7 @@ public final class BuiltInsProtoBuf {
     registry.add(org.jetbrains.kotlin.serialization.builtins.BuiltInsProtoBuf.propertyAnnotation);
     registry.add(org.jetbrains.kotlin.serialization.builtins.BuiltInsProtoBuf.compileTimeValue);
     registry.add(org.jetbrains.kotlin.serialization.builtins.BuiltInsProtoBuf.parameterAnnotation);
+    registry.add(org.jetbrains.kotlin.serialization.builtins.BuiltInsProtoBuf.typeAnnotation);
   }
   public static final int CLASS_NAME_FIELD_NUMBER = 150;
   /**
@@ -152,6 +153,21 @@ public final class BuiltInsProtoBuf {
         150,
         com.google.protobuf.WireFormat.FieldType.MESSAGE,
         false);
+  public static final int TYPE_ANNOTATION_FIELD_NUMBER = 150;
+  /**
+   * <code>extend .org.jetbrains.kotlin.serialization.Type { ... }</code>
+   */
+  public static final
+    com.google.protobuf.GeneratedMessageLite.GeneratedExtension<
+      org.jetbrains.kotlin.serialization.ProtoBuf.Type,
+      java.util.List<org.jetbrains.kotlin.serialization.ProtoBuf.Annotation>> typeAnnotation = com.google.protobuf.GeneratedMessageLite
+          .newRepeatedGeneratedExtension(
+        org.jetbrains.kotlin.serialization.ProtoBuf.Type.getDefaultInstance(),
+        org.jetbrains.kotlin.serialization.ProtoBuf.Annotation.getDefaultInstance(),
+        null,
+        150,
+        com.google.protobuf.WireFormat.FieldType.MESSAGE,
+        false);
 
   static {
   }