Verify that the presence of an error type doesn't accidentally trigger
"unnecessary cast pattern" or "unnecessary wildcard pattern" warnings
(this verifies that `promoteForPattern` returns the proper value when
an error type is encountered).
Verify that the presence of an error type doesn't alter reachability
conclusions that were established by previous subpatterns (this
verifies that `promoteForPattern` uses the proper join to update
`_unmatched` when an error type is encountered).
Change-Id: I351c71574dff31602c40b257c28681b81fad2867
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/303260
Commit-Queue: Paul Berry <paulberry@google.com>
Reviewed-by: Konstantin Shcheglov <scheglov@google.com>
Paul Berry
5043c38d25