Invalid file referenceDRT-W1701
The analyzer produces this diagnostic when an import, export, or part directive is found where the URI refers to a file that doesn't exist.
Example
If the file lib.dart
doesn't exist, the following code produces this
diagnostic:
import 'lib.dart';
Common fixes
If the URI was mistyped or invalid, then correct the URI.
If the URI is correct, then create the file.