Dart Editor stops highlighting errors when using the "part"

Question

I'm not sure if this is a bug in the Darts Editor or a problem with the way I use part of, but given the following project structure:

myapp/
    pubspec.yaml
    pubspec.lock
    asset/
    packages/
    build/
    web/
        Fizz.dart
        Buzz.dart

Where Fizz.dart:

library fizz;

void herp() {
    print("Herp!");
}

and where Buzz.dart:

library buzz;

void derp() {
    String x = "Derp!";
    print(x);
}

If I change Buzz.dartto intentionally having a compiler error:

library buzz;

void derp() {
    djedString x = "Derp!";  // Produces "Undefined class 'djedString'" error
    print(x);
}

The Dart editor then underlines with a djedStringred line and gives the above compiler error:

Undefined class 'djedString'

But if I then change Buzz.dartas a part oflibrary fizz:

part of fizz;

void derp() {
    djedString x = "Derp!";  // Perfectly fine! No errors!
    print(x);
}

The Dart editor then removes the compiler error and actually stops looking for warnings / errors (inside the file).

Is this a mistake or am I using it incorrectly part of?

Answer 1

part of aaa; part "xxx";.

a.dart

library a;

part 'a1.dart';

a1.dart

part of a;

// content of the part