DartType.== implementations ignore nullability if the flag is not true.
TypeSystem APIs eliminate nullability from types before doing anything.
Internally analyzer continues using actual nullability for types.
Package nnbd_migration opted into NullSafetyUnderstandingFlag.
Bug: https://github.com/dart-lang/sdk/issues/40500
Change-Id: Ifeea28c01adf1dc59ed2da675b4a62c6334d529a
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/134865
Reviewed-by: Paul Berry <paulberry@google.com>
Commit-Queue: Konstantin Shcheglov <scheglov@google.com>
Konstantin Shcheglov
6f6797e745