Make AnnotationsImpl internal, introduce Annotations.create

core/descriptors.jvm/src/org/jetbrains/kotlin/builtins/jvm/JvmBuiltInsSettings.kt

@@ -8,7 +8,7 @@ package org.jetbrains.kotlin.builtins.jvm
 import org.jetbrains.kotlin.builtins.BuiltInsInitializer
 import org.jetbrains.kotlin.builtins.KotlinBuiltIns
 import org.jetbrains.kotlin.descriptors.*
-import org.jetbrains.kotlin.descriptors.annotations.AnnotationsImpl
+import org.jetbrains.kotlin.descriptors.annotations.Annotations
 import org.jetbrains.kotlin.descriptors.annotations.createDeprecatedAnnotation
 import org.jetbrains.kotlin.descriptors.deserialization.AdditionalClassPartsProvider
 import org.jetbrains.kotlin.descriptors.deserialization.PLATFORM_DEPENDENT_ANNOTATION_FQ_NAME
@@ -64,9 +64,10 @@ open class JvmBuiltInsSettings(
 
     // Most this properties are lazy because they depends on KotlinBuiltIns initialization that depends on JvmBuiltInsSettings object
     private val notConsideredDeprecation by storageManager.createLazyValue {
-        moduleDescriptor.builtIns.createDeprecatedAnnotation(
+        val annotation = moduleDescriptor.builtIns.createDeprecatedAnnotation(
             "This member is not fully supported by Kotlin compiler, so it may be absent or have different signature in next major version"
-        ).let { AnnotationsImpl(listOf(it)) }
+        )
+        Annotations.create(listOf(annotation))
     }
 
     private fun StorageManager.createMockJavaIoSerializableType(): KotlinType {

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

@@ -10,7 +10,6 @@ import org.jetbrains.kotlin.builtins.functions.FunctionClassDescriptor
 import org.jetbrains.kotlin.descriptors.ClassDescriptor
 import org.jetbrains.kotlin.descriptors.DeclarationDescriptor
 import org.jetbrains.kotlin.descriptors.annotations.Annotations
-import org.jetbrains.kotlin.descriptors.annotations.AnnotationsImpl
 import org.jetbrains.kotlin.descriptors.annotations.BuiltInAnnotationDescriptor
 import org.jetbrains.kotlin.name.ClassId
 import org.jetbrains.kotlin.name.FqNameUnsafe
@@ -165,7 +164,7 @@ fun getFunctionTypeArgumentProjections(
                     KotlinBuiltIns.FQ_NAMES.parameterName,
                     mapOf(Name.identifier("name") to StringValue(name.asString()))
             )
-            type.replaceAnnotations(AnnotationsImpl(type.annotations + parameterNameAnnotation))
+            type.replaceAnnotations(Annotations.create(type.annotations + parameterNameAnnotation))
         }
         else {
             type
@@ -199,8 +198,9 @@ fun createFunctionType(
                 annotations
             }
             else {
-                AnnotationsImpl(annotations +
-                                BuiltInAnnotationDescriptor(builtIns, KotlinBuiltIns.FQ_NAMES.extensionFunctionType, emptyMap()))
+                Annotations.create(
+                    annotations + BuiltInAnnotationDescriptor(builtIns, KotlinBuiltIns.FQ_NAMES.extensionFunctionType, emptyMap())
+                )
             }
 
     return KotlinTypeFactory.simpleNotNullType(typeAnnotations, classDescriptor, arguments)

core/descriptors/src/org/jetbrains/kotlin/descriptors/annotations/Annotations.kt

@@ -41,6 +41,9 @@ interface Annotations : Iterable<AnnotationDescriptor> {
 
             override fun toString() = "EMPTY"
         }
+
+        fun create(annotations: List<AnnotationDescriptor>): Annotations =
+            if (annotations.isEmpty()) EMPTY else AnnotationsImpl(annotations)
     }
 }
 

core/descriptors/src/org/jetbrains/kotlin/descriptors/annotations/AnnotationsImpl.kt

@@ -16,7 +16,10 @@
 
 package org.jetbrains.kotlin.descriptors.annotations
 
-class AnnotationsImpl(private val annotations: List<AnnotationDescriptor>) : Annotations {
+/**
+ * Use [Annotations.create] to create an instance of this class if necessary.
+ */
+internal class AnnotationsImpl(private val annotations: List<AnnotationDescriptor>) : Annotations {
     override fun isEmpty(): Boolean = annotations.isEmpty()
 
     override fun iterator(): Iterator<AnnotationDescriptor> = annotations.iterator()

core/deserialization/src/org/jetbrains/kotlin/serialization/deserialization/MemberDeserializer.kt

@@ -8,7 +8,6 @@ package org.jetbrains.kotlin.serialization.deserialization
 import org.jetbrains.kotlin.builtins.isSuspendFunctionType
 import org.jetbrains.kotlin.descriptors.*
 import org.jetbrains.kotlin.descriptors.annotations.Annotations
-import org.jetbrains.kotlin.descriptors.annotations.AnnotationsImpl
 import org.jetbrains.kotlin.descriptors.impl.FieldDescriptorImpl
 import org.jetbrains.kotlin.descriptors.impl.PropertyGetterDescriptorImpl
 import org.jetbrains.kotlin.descriptors.impl.PropertySetterDescriptorImpl
@@ -291,7 +290,9 @@ class MemberDeserializer(private val c: DeserializationContext) {
     }
 
     fun loadTypeAlias(proto: ProtoBuf.TypeAlias): TypeAliasDescriptor {
-        val annotations = AnnotationsImpl(proto.annotationList.map { annotationDeserializer.deserializeAnnotation(it, c.nameResolver) })
+        val annotations = Annotations.create(
+            proto.annotationList.map { annotationDeserializer.deserializeAnnotation(it, c.nameResolver) }
+        )
 
         val visibility = ProtoEnumFlags.visibility(Flags.VISIBILITY.get(proto.flags))
         val typeAlias = DeserializedTypeAliasDescriptor(