Analyzer shows warning of use_late_for_private_fields_and_variables in wrong file when part and part of are used

[Quijx]

The analyzer shows a warning of the use_late_for_private_fields_and_variables lint in wrong file when part and part of are used.

Steps to reproduce

1. Create a new dart project with dart create use_late_bug
2. Add the following to the analysis_options.yaml file:

linter:
  rules:
    - use_late_for_private_fields_and_variables

3. Create a file foo.dart in bin with the content:

part 'bar.dart';

class Foo {
  final String? _s;

  Foo(this._s);
}

4. Create a file bar.dart in bin with the content:

part of 'foo.dart';

void bar() {
  print('bar');
}

5. Run dart analyze. The output is:

Analyzing use_late_bug...              0.7s

   info • bin/bar.dart:4:13 • Use late for private members with non-nullable type. • use_late_for_private_fields_and_variables
   info • bin/foo.dart:4:17 • The value of the field '_s' isn't used. Try removing the field, or using it. • unused_field

2 issues found.

Expected Result

The warning for the lint use_late_for_private_fields_and_variables should be shown in the file foo.dart on the field _s.

Actual Result

The warning for the lint use_late_for_private_fields_and_variables is shown in the file bar.dart by the print.
Notably the warning is shown at index 46 of the bar.dart file and the field _s is also defined at index 46 in a string containing the foo.dart file.
So the warning is shown at the correct place, just in the wrong file.

---

Output of dart --version: Dart SDK version: 2.14.0-301.0.dev (dev) (Sat Jul 10 17:56:59 2021 -0700) on "linux_x64"

[pq]

FWIW, the issue here is that today we can only report lints on the file currently being analyzed. To fix this we'll need to take a performance hit and do a fresh (and redundant) run through all the constituent part files that define a library. For an example of how this is done, see PreferFinalFields.

/fyi @a14n

[FMorschel]

I'm not sure if this helps in any way for this issue to be solved, but I have a Flutter package and my latest commit is showing something similar. Here is the link to the latest commit where this is showing on my size_extension.dart file.

[srawlins]

Finally fixed with dart-lang/sdk@bca7663 ; thanks for the repros.