When I first implemented this I thought that checking exports wasn't
needed, since it's not allowed for a migrated library to re-export
symbols defined in an unmigtated library. But it turns out we still
do need to include exports in the check, since there might be migrated
libraries that are only reachable in the transitive dependency graph
via an export, and we need to check that *those* libraries don't
import unmigrated code.
Bug: https://github.com/dart-lang/sdk/issues/44061
Change-Id: I280b4117373a3320fc1efe65abe24e344199754c
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/170840
Reviewed-by: Samuel Rawlins <srawlins@google.com>
Commit-Queue: Paul Berry <paulberry@google.com>
Paul Berry
f4001df118