invalid_use_of_internal_member

The member '{0}' can only be used within its package.

The analyzer produces this diagnostic when a reference to a declaration that is annotated with the internal annotation is found outside the package containing the declaration.

Given a package p that defines a library containing a declaration marked with the internal annotation:

import 'package:meta/meta.dart';
​
@internal
class C {}

The following code produces this diagnostic because it's referencing the class C, which isn't intended to be used outside the package p:

import 'package:p/src/p.dart';
​
void f(C c) {}

Remove the reference to the internal declaration.