This allows more migration tool unit tests to be simplified so that
they don't have to refer to ConstraintVariable objects directly
anymore.
In order to make this work, a few other changes were also necessary:
- Make a derived class for NullabilityNodes that arise from
conditional expressions.
- Add a getter to reveal whether a NullabilityNode is known a priori
to be non-nullable.
Change-Id: I8a68b627ce9e807a50d371369985f52848903a2f
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/100922
Commit-Queue: Paul Berry <paulberry@google.com>
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Reviewed-by: Konstantin Shcheglov <scheglov@google.com>
Paul Berry
fa274ec059