835317d7da
Basic support for the `sealed` keyword and added a few tests. Change-Id: I5adedda22b1e8ce6d4b61136ad8e6d38bdf05043 Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/268366 Commit-Queue: Kallen Tu <kallentu@google.com> Reviewed-by: Johnni Winther <johnniwinther@google.com> Reviewed-by: Konstantin Shcheglov <scheglov@google.com>