import_of_non_library

The imported library '{0}' can't have a part-of directive.

The analyzer produces this diagnostic when a part file is imported into a library.

Given a part file named part.dart containing the following:

part of lib;

The following code produces this diagnostic because imported files can't have a part-of directive:

library lib;

import 'part.dart';

Import the library that contains the part file rather than the part file itself.