8a5ddecfb3
Adds a new TargetKind for extension types and adds it to `@optionalTypeArgs`. Change-Id: I7254c1299c296451b9adc5d1f8eceb50af66f039 Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/324769 Commit-Queue: Phil Quitslund <pquitslund@google.com> Reviewed-by: Samuel Rawlins <srawlins@google.com> Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>