This moves the logic for detecting the patterns `variable == null` and
`null == variable` into flow analysis, so that they don't need to be
replicated in each client. It also opens the door to potential future
improvements (e.g. allowing `x == expr` to promote `x` to non-nullable
if expr has a non-nullable type).
Change-Id: I51fd9df822e3df1eb8bad5884f767c8b61c496ef
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/120934
Reviewed-by: Konstantin Shcheglov <scheglov@google.com>
Commit-Queue: Paul Berry <paulberry@google.com>
Paul Berry
fd60a3eeba