if t, dup := nameToConcreteType.LoadOrStore(name, reflect.TypeOf(value)); dup && t != ut.user {
		panic(fmt.Sprintf("gob: registering duplicate types for %q: %s != %s", name, t, ut.user))
	}

	// but the flattened type in the type table, since that's what decode needs.
	if n, dup := concreteTypeToName.LoadOrStore(ut.base, name); dup && n != name {
		nameToConcreteType.Delete(name)