[Analyzer] FFI verifier applies lints to mixin following a Struct

[ds84182]

final class Foo extends Struct {
  external Pointer<Void> field;
}

mixin Bar {
  // Analyzer says "Struct fields must be marked external" on this line:
  late final field = 123;
}

Currently seeing this on an SDK build from last week (3.1.0-48.0.dev). Reordering the declarations or adding a non-struct class between the two makes the issue go away.

[bwilkerson]

@dcharkes

[dcharkes]

Thanks for the report!

Fix underway: https://dart-review.googlesource.com/c/sdk/+/301980