JS: serialize/deserialize type annotations similarly to JVM

No new tests added because there are some on extension functions, which soon
will depend on type annotations to be preserved to work correctly

js/js.serializer/src/js.proto

@@ -34,6 +34,10 @@ extend Callable.ValueParameter {
   repeated Annotation parameter_annotation = 130;
 }
 
+extend Type {
+  repeated Annotation type_annotation = 130;
+}
+
 message Classes {
   // id in StringTable
   repeated int32 class_name = 1 [packed = true];

js/js.serializer/src/org/jetbrains/kotlin/serialization/js/KotlinJavascriptAnnotationAndConstantLoader.kt

@@ -58,8 +58,8 @@ class KotlinJavascriptAnnotationAndConstantLoader(
     }
 
     override fun loadTypeAnnotations(proto: ProtoBuf.Type, nameResolver: NameResolver): List<AnnotationDescriptor> {
-        // TODO: support type annotations for js descriptors
-        return listOf()
+        val annotations = proto.getExtension(JsProtoBuf.typeAnnotation).orEmpty()
+        return annotations.map { proto -> deserializer.deserializeAnnotation(proto, nameResolver) }
     }
 
     override fun loadPropertyConstant(

js/js.serializer/src/org/jetbrains/kotlin/serialization/js/KotlinJavascriptSerializerExtension.kt

@@ -16,11 +16,17 @@
 
 package org.jetbrains.kotlin.serialization.js
 
-import org.jetbrains.kotlin.descriptors.*
+import org.jetbrains.kotlin.descriptors.CallableMemberDescriptor
+import org.jetbrains.kotlin.descriptors.ClassDescriptor
+import org.jetbrains.kotlin.descriptors.PropertyDescriptor
+import org.jetbrains.kotlin.descriptors.ValueParameterDescriptor
 import org.jetbrains.kotlin.resolve.constants.NullValue
 import org.jetbrains.kotlin.resolve.descriptorUtil.builtIns
-import org.jetbrains.kotlin.resolve.scopes.DescriptorKindFilter
-import org.jetbrains.kotlin.serialization.*
+import org.jetbrains.kotlin.serialization.AnnotationSerializer
+import org.jetbrains.kotlin.serialization.ProtoBuf
+import org.jetbrains.kotlin.serialization.SerializerExtension
+import org.jetbrains.kotlin.serialization.StringTable
+import org.jetbrains.kotlin.types.JetType
 
 public object KotlinJavascriptSerializerExtension : SerializerExtension() {
     override fun serializeClass(descriptor: ClassDescriptor, proto: ProtoBuf.Class.Builder, stringTable: StringTable) {
@@ -54,4 +60,10 @@ public object KotlinJavascriptSerializerExtension : SerializerExtension() {
             proto.addExtension(JsProtoBuf.parameterAnnotation, AnnotationSerializer.serializeAnnotation(annotation, stringTable))
         }
     }
-}
+
+    override fun serializeType(type: JetType, proto: ProtoBuf.Type.Builder, stringTable: StringTable) {
+        for (annotation in type.getAnnotations()) {
+            proto.addExtension(JsProtoBuf.typeAnnotation, AnnotationSerializer.serializeAnnotation(annotation, stringTable))
+        }
+    }
+}