test_types_in_equals false positive

[Hixie]

This code:

  @override
  bool operator ==(dynamic other) {
    if (other.runtimeType != runtimeType)
      return false;
    final AvatarImage typedOther = other as AvatarImage; // line 465
    return username == typedOther.username
        && photoManager == typedOther.photoManager
        && twitarr == typedOther.twitarr;
  }

Led to this message from the analyzer:

[info] Test type arguments in operator ==(Object other) (/home/ianh/dev/cruisemonkey/lib/src/logic/cruise.dart:465:36)

...which is wrong. The type is checked, in the first line. The advice on the Web page (http://dart-lang.github.io/linter/lints/test_types_in_equals.html) is actually bad, because it does a check using "is" which doesn't guarantee equality, and leads to asymmetric equality, where a == b but b != a if a is an instance of a superclass of b.

[Hixie]

See also #35522 which is about the lint's wording being unclear. This specific issue is about the heuristics of the lint being bad.

[pq]

This issue was moved to #57891