Minor, fix NonExistentClass name and format

compiler/backend/src/org/jetbrains/kotlin/codegen/serialization/JvmSerializerExtension.java

@@ -26,6 +26,7 @@ import org.jetbrains.kotlin.descriptors.annotations.AnnotationDescriptor;
 import org.jetbrains.kotlin.load.java.JvmAbi;
 import org.jetbrains.kotlin.load.java.lazy.types.RawTypeImpl;
 import org.jetbrains.kotlin.load.kotlin.JavaFlexibleTypeDeserializer;
+import org.jetbrains.kotlin.load.kotlin.TypeSignatureMappingKt;
 import org.jetbrains.kotlin.name.ClassId;
 import org.jetbrains.kotlin.serialization.AnnotationSerializer;
 import org.jetbrains.kotlin.serialization.ProtoBuf;
@@ -164,7 +165,7 @@ public class JvmSerializerExtension extends SerializerExtension {
     @Override
     public void serializeErrorType(@NotNull KotlinType type, @NotNull ProtoBuf.Type.Builder builder) {
         if (classBuilderMode == ClassBuilderMode.KAPT) {
-            builder.setClassName(stringTable.getStringIndex("error.NonExistingClass"));
+            builder.setClassName(stringTable.getStringIndex(TypeSignatureMappingKt.NON_EXISTENT_CLASS_NAME));
             return;
         }
 

core/descriptor.loader.java/src/org/jetbrains/kotlin/load/kotlin/typeSignatureMapping.kt

@@ -47,6 +47,8 @@ interface TypeMappingConfiguration<out T : Any> {
     fun processErrorType(kotlinType: KotlinType, descriptor: ClassDescriptor)
 }
 
+const val NON_EXISTENT_CLASS_NAME = "error/NonExistentClass"
+
 fun <T : Any> mapType(
         kotlinType: KotlinType,
         factory: JvmTypeFactory<T>,
@@ -81,7 +83,7 @@ fun <T : Any> mapType(
 
     when {
         ErrorUtils.isError(descriptor) -> {
-            val jvmType = factory.createObjectType("error/NonExistentClass")
+            val jvmType = factory.createObjectType(NON_EXISTENT_CLASS_NAME)
             typeMappingConfiguration.processErrorType(kotlinType, descriptor as ClassDescriptor)
             descriptorTypeWriter?.writeClass(jvmType)
             return jvmType