When mixin is applied, its instance members are cloned and copies
of the members would override original members.
This change fixes bugs and improved usability of extendable mixins with
private members:
- All instance members of extendable mixins and mixin classes are
marked as can-be-overridden to allow overriding by cloned members
when mixin is applied.
- TFA no longer takes privacy into account, as private members of
mixins can be overridden by their clones in other libraries.
- Dynamic module validator always unwraps cloned members to originals
before verifying if overriding is allowed. This eliminates overriding
errors between clone(s) and original members of mixins.
TEST=pkg/dynamic_modules/test/data/mixin_private_member1,
pkg/dynamic_modules/test/data/mixin_private_member2
Fixes b/470461203
Fixes b/469094721
Change-Id: If369c42c58e5ea4d707be83b1e7078ee9a8cc3ce
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/470803
Reviewed-by: Slava Egorov <vegorov@google.com>
Commit-Queue: Alexander Markov <alexmarkov@google.com>
Reviewed-by: Sigmund Cherem <sigmund@google.com>
Alexander Markov
d95e527aab