This adds `LookupResult.isInvalidLookup` to the handle invalid lookup
results and uses this to avoid a lot of cascading error messages.
This is a step towards removing ProblemBuilder, AmbiguousBuilder and
reliance on `NamedBuilder.isDuplicate` in lookups.
Change-Id: Ia9d558ce55b45567607282295dd1e54e6187f9c5
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/441880
Reviewed-by: Chloe Stefantsova <cstefantsova@google.com>
Commit-Queue: Johnni Winther <johnniwinther@google.com>
Reviewed-by: Erik Ernst <eernst@google.com>
Johnni Winther
f49d92aba9