80b48195b1
Improve comments and test, report errors. Follow-up to https://dart-review.googlesource.com/c/sdk/+/49040. Change-Id: Ie02dae1c0edfcb54e3cd7333641e2c5eface1412 Reviewed-on: https://dart-review.googlesource.com/56030 Reviewed-by: Siva Annamalai <asiva@google.com> Commit-Queue: Alexander Aprelev <aam@google.com>